JVB Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 
Search Issue | RSS Feeds RSS
Previous Issue

Nov 2004

Volume 22, Issue 6, pp. L35-3584

back to top
RSS Feeds

Fabrication and evaluation of highly manufacturable nanoscale flow-through parallel electrode structures

Wook Jun Nam, Stephen J. Fonash, and Joseph D. Cuiffi

J. Vac. Sci. Technol. B 22, L35 (2004); http://dx.doi.org/10.1116/1.1808748 (3 pages)

Online Publication Date: 10 November 2004

Full Text: | Download PDF

Show Abstract
A unique nanoscale gap configuration having parallel-plate electrodes and an integrated flow structure was designed, developed, and fabricated using micro- and nanomachining techniques. This structure is highly manufacturable and shows an excellent fabrication yield (more than 90%). Applications data are presented for 30 and 50 nm gap spacing structures used to monitor the formation of a 6-mercapto-1-hexanol self-assembled monolayer on the device electrode surfaces. The structure was found to be very robust in a high, inter-electrode electric-field environment (∼6×106 V∕cm in air).
Show PACS
81.16.-c Methods of micro- and nanofabrication and processing
81.07.-b Nanoscale materials and structures: fabrication and characterization

Analytical study on small contact hole process for sub-65 nm node generation

Hyun-Woo Kim, Jin-Young Yoon, Jung-Hwan Hah, Sang-Gyun Woo, Han-Ku Cho, and Joo-Tae Moon

J. Vac. Sci. Technol. B 22, L38 (2004); http://dx.doi.org/10.1116/1.1815315 (6 pages) | Cited 2 times

Online Publication Date: 24 November 2004

Full Text: | Download PDF

Abstract Unavailable
Show PACS
85.40.Hp Lithography, masks and pattern transfer

Reversible nanochemical conversion

Hiroyuki Sugimura, Sun-Hyung Lee, Nagahiro Saito, and Osamu Takai

J. Vac. Sci. Technol. B 22, L44 (2004); http://dx.doi.org/10.1116/1.1825020 (3 pages) | Cited 4 times

Online Publication Date: 24 November 2004

Full Text: | Download PDF

Show Abstract
Local chemical conversion of an organic surface that consists of a surface-confined monolayer is demonstrated in a reversible manner based on electrochemical reactions induced beneath a conductive probe tip of an atomic force microscope. The monolayer was prepared by a self-assembling technique from the precursor, p-aminophenyltrimethoxysilane. The chemical state of this self-assembled monolayer was regulated by probe-tip scanning with a bias voltage applied between the tip and substrate. With a positive substrate bias scanning, the monolayer surface was oxidized to be nitroso-terminated. With a negative bias scanning, this monolayer could be amino-terminated. These oxidation and reduction processes could be reversibly repeated.
Show PACS
82.45.Mp Thin layers, films, monolayers, membranes
82.30.-b Specific chemical reactions; reaction mechanisms
68.37.Ps Atomic force microscopy (AFM)
68.47.Pe Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces
81.16.Pr Micro- and nano-oxidation
back to top
RSS Feeds

Thermally actuated probe array for parallel dip-pen nanolithography

Xuefeng Wang, David A. Bullen, Jun Zou, Chang Liu, and Chad A. Mirkin

J. Vac. Sci. Technol. B 22, 2563 (2004); http://dx.doi.org/10.1116/1.1805544 (5 pages) | Cited 13 times

Online Publication Date: 25 October 2004

Full Text: | Download PDF

Show Abstract
Dip-pen nanolithography (DPN) uses scanning probes to directly deposit chemical and biological materials on a solid substrate. It offers the advantages of nanometer resolution and flexibility in pattern generation. Conventional DPN uses a single probe and its throughput is limited due to the serial nature of the process. This article reports the development of a linear silicon probe array that enables parallel DPN writing with improved throughput. The probe array has ten probes with tips with 100 nm radius of curvature. Each probe in the array is individually controllable by a bimorph thermal actuator on its cantilever. DPN writing tests with octadecanethiol (ODT) as ink on gold surface have been conducted on an atomic force microscope. Simultaneous generation of ten different ODT patterns has been achieved with an average linewidth of 40 nm.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography
81.05.Cy Elemental semiconductors

Effect of spontaneous and piezoelectric polarization on intersubband transition in AlxGa1−xN–GaN quantum well

J. M. Li, Y. W. Lü, D. B. Li, X. X. Han, Q. S. Zhu, X. L. Liu, and Z. G. Wang

J. Vac. Sci. Technol. B 22, 2568 (2004); http://dx.doi.org/10.1116/1.1805543 (6 pages) | Cited 6 times

Online Publication Date: 27 October 2004

Full Text: | Download PDF

Show Abstract
A self-consistent solution of conduction band profile and subband energies for AlxGa1−xN–GaN quantum well is presented by solving the Schrödinger and Poisson equations. A new method is introduced to deal with the accumulation of the immobile charges at the AlxGa1−xN–GaN interface caused by spontaneous and piezoelectric polarization in the process of solving the Poisson equation. The effect of spontaneous and piezoelectric polarization is taken into account in the calculation. It also includes the effect of exchange-correlation to the one electron potential on the Coulomb interaction. Our analysis is based on the one electron effective-mass approximation and charge conservation condition. Based on this model, the electron wave functions and the conduction band structure are derived. We calculate the intersubband transition wavelength λ21 for different Al molar fraction of barrier and thickness of well. The calculated result can fit to the experimental data well. The dependence of the absorption coefficient α on the well width and the doping density is also investigated theoretically.
Show PACS
77.22.Ej Polarization and depolarization
77.65.-j Piezoelectricity and electromechanical effects
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.20.-b Electron density of states and band structure of crystalline solids
73.20.At Surface states, band structure, electron density of states
73.21.Fg Quantum wells
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
61.72.up Other materials

Modeling of electronic transport in GaN n-i-p junctions

A. Mayer, N. M. Miskovsky, and P. H. Cutler

J. Vac. Sci. Technol. B 22, 2574 (2004); http://dx.doi.org/10.1116/1.1805547 (6 pages) | Cited 1 time

Online Publication Date: 28 October 2004

Full Text: | Download PDF

Show Abstract
We propose a model and an algorithm for computing the transport properties of GaN n-i-p devices. The formalism yields the band diagram and I–V characteristics of these systems, and accounts for the effects of an external resistance in series with the diode and the generator. For the conditions considered, the device obeys essentially the ideal diode equation with deviations due to the external resistance and the transfer of charges between the different layers. Compared to n-p devices, the isolating layer enables one to decrease the external resistance and obtain more diode current for the same voltage. The external resistance allows one also to control and reduce appreciably the height of the barrier that characterizes the n-i interface. This barrier may serve as an energy discriminator, which can be important in applications for thermal management.
Show PACS
85.30.De Semiconductor-device characterization, design, and modeling
85.30.Kk Junction diodes
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.Ey III-V semiconductors

Redeposition of etch products on sidewalls during SiO2 etching in a fluorocarbon plasma. V. Effects of C∕F ratio in plasma gases

Jae-Ho Min, Gyeo-Re Lee, Jin-Kwan Lee, and Sang Heup Moon

J. Vac. Sci. Technol. B 22, 2580 (2004); http://dx.doi.org/10.1116/1.1808746 (9 pages) | Cited 5 times

Online Publication Date: 28 October 2004

Full Text: | Download PDF

Show Abstract
The effects of C∕F ratio in fluorocarbon gases, used in the plasma etching of SiO2, on the properties of sidewalls of etched trenches, as affected particularly by the redeposition of particles emitted from the bottom, were investigated using three different plasma gases, CF4, CHF3, and C4F8. The use of a Faraday cage and step-shaped substrates permitted an effective analysis of the chemical and physical properties of the sidewall surface in a scale larger than that for micro-patterns. The step-shaped substrates consisted of one bottom and two sidewalls: One of the sidewalls was affected by bottom-emitted particles, designated as sidewall (A), and the other was unaffected by the particles, designated as sidewall (B). Comparison of the surface properties of the two sidewalls allowed us to observe the redeposition effect, independently from other complicated phenomena involved in the plasma etching. For all cases of CF4, CHF3, and C4F8, the rate of film deposition on sidewall (A) was larger than that on sidewall (B), which indicated that the formation of a passivation layer on the sidewall was accelerated by the redeposition of bottom-emitted particles. The contribution of redeposition to the formation of a sidewall passivation layer rapidly decreased with an increase in C∕F ratio, in the order CF4>CHF3>C4F8 approaching zero for C4F8. The change in the surface roughness of sidewall (A) with C∕F ratio was correlated with the contribution of redeposition particles, instead of the thickness and carbon content of the polymer film formed on the sidewall. The chemical composition of carbon-containing polymer layer of sidewall (A) and the extent of chemical etching of the SiO2 layer beneath the polymer layer were distinctly different for the three plasma gases.
Show PACS
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
81.65.Rv Passivation
68.47.Gh Oxide surfaces

Fabrication of ordered array of tungsten nanoparticles on anodic porous alumina by electron-beam-induced selective deposition

Guoqiang Xie, Minghui Song, Kazutaka Mitsuishi, and Kazuo Furuya

J. Vac. Sci. Technol. B 22, 2589 (2004); http://dx.doi.org/10.1116/1.1814108 (5 pages) | Cited 2 times

Online Publication Date: 28 October 2004

Full Text: | Download PDF

Show Abstract
Using an ordered nanopore array of anodic porous alumina membrane obtained by a two-step anodization process, ordered array of tungsten nanoparticles was fabricated using an electron-beam-induced selective deposition process. The nanoparticles were preferentially formed in the pores in the electron-beam irradiated area. The microstructure and composition of as-deposited nanoparticles were characterized. The as-deposited nanoparticles contain many nanocrystallites. The nanocrystallites were identified to be the equilibrium phase of bcc structure metal W at room temperature.
Show PACS
61.46.-w Structure of nanoscale materials
61.82.Rx Nanocrystalline materials
61.80.Fe Electron and positron radiation effects
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Investigation of surface modifications of 193 and 248 nm photoresist materials during low-pressure plasma etching

L. Ling, X. Hua, X. Li, G. S. Oehrlein, E. A. Hudson, P. Lazzeri, and M. Anderle

J. Vac. Sci. Technol. B 22, 2594 (2004); http://dx.doi.org/10.1116/1.1805545 (10 pages) | Cited 22 times

Online Publication Date: 4 November 2004

Full Text: | Download PDF

Show Abstract
Plasma-based pattern transfer of lithographically produced nanoscale patterns in advanced photoresist materials is often accompanied by photoresist surface roughening and line edge roughening due to factors which are not well understood. We have studied the evolution of surface roughening in prototypical 193 and 248 nm photoresist materials during plasma processing as a function of plasma operating parameters. We used real-time ellipsometry and mass spectrometry, along with atomic force microscopy, x-ray photoemission spectroscopy and time-of-flight secondary ion mass spectrometry in an effort to understand the morphological and chemical changes of the photoresist materials as a function of plasma–surface interactions parameters, e.g., maximum ion energy, total energy flux, and plasma chemistry, and photoresist material. A comparison of 248 nm photoresist with 193 nm photoresist shows that significantly more surface roughness is introduced in the 193 nm photoresist for most plasma processing conditions investigated. We also find a dramatic dependence of surface roughening on the chemistry of the plasma process, e.g., for Ar–C4F8 a modified photoresist surface layer with an extent of about 50 nm is produced in 193 nm photoresist, whereas for C4F8 discharges the surface modification is much less for otherwise similar conditions. We show that one important reason for these differences may be ion-enhanced selective volatilization of carbonyl groups of the 193 nm photoresist polymer backbone which is absent for the 248 nm material, along with modulation of the ion-interaction with the photoresist material by fluorocarbon surface passivation.
Show PACS
81.16.Nd Micro- and nanolithography
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
81.65.Rv Passivation
52.80.-s Electric discharges

Influence of molecular weight of resist polymers on surface roughness and line-edge roughness

T. Yamaguchi, K. Yamazaki, and H. Namatsu

J. Vac. Sci. Technol. B 22, 2604 (2004); http://dx.doi.org/10.1116/1.1805546 (7 pages) | Cited 16 times

Online Publication Date: 4 November 2004

Full Text: | Download PDF

Show Abstract
The effect of molecular weight on the roughness of the dissolution front (surface roughness) and line-edge roughness (LER) was investigated in a chain-scission-type of positive-tone electron-beam resist. Surface roughness and LER were measured by directly observing the surface of flood-exposed resists after development and the sidewall of patterns, respectively, with an atomic force microscope. It was clarified that the molecular weight dependencies of surface roughness and LER are quite different. Surface roughness was found to increase with molecular weight. This is because the size of aggregates protruding from the surface as a result of the development process becomes larger as the molecular weight increases. In contrast, LER was found to be larger in a low-molecular-weight resist than in a high-molecular-weight resist. Moreover, the dependence of LER on the latent-image profile is different for low- and high-molecular-weight resists. For low-molecular-weight resist, LER is independent of the steepness of the latent image; whereas, for high-molecular-weight resist, it increases rapidly as the steepness decreases. These results can be explained by the relationship between the size of aggregates and the width of the transition zone between low- and high-dose regions of the latent-image profile. This strongly suggests that low-molecular-weight resists are not necessarily advantageous in reducing LER.
Show PACS
85.40.Hp Lithography, masks and pattern transfer

Mechanism of Cu oxidation in ashing process

Akihiro Kojima, Takayuki Sakai, and Tokuhisa Ohiwa

J. Vac. Sci. Technol. B 22, 2611 (2004); http://dx.doi.org/10.1116/1.1808745 (4 pages) | Cited 2 times

Online Publication Date: 4 November 2004

Full Text: | Download PDF

Show Abstract
Because Cu is easily oxidized and its oxidation reaction proceeds without stopping, the oxygen ashing process causes unacceptable oxidation of the Cu surface. We investigated the chemical state and morphology of the Cu surface after the oxygen ashing process using x-ray photoelectron spectroscopy∕Auger electron spectroscopy and scanning electron microscopy, and then considered the oxidation mechanism of the Cu surface under the oxygen downstream and the oxygen reactive ion etch (RIE) ashing processes in the substrate temperature range of 35 °C to 260 °C. The Cu surface treated by an oxygen RIE ashing process at temperatures below 150 °C was found to have chiefly CuO bonds, whereas the Cu surface treated by the oxygen downstream ashing process consisted mostly of Cu2O bonds. The oxidized Cu thickness after the oxygen downstream process was thicker than that formed by the oxygen RIE ashing process. The Cu surface treated with the oxygen RIE ashing process at under 150 °C is less prone to oxidization because the Cu surface with CuO formation has a smooth surface that suppresses further oxidation.
Show PACS
81.65.Mq Oxidation
81.65.Cf Surface cleaning, etching, patterning
79.60.Bm Clean metal, semiconductor, and insulator surfaces
81.05.Bx Metals, semimetals, and alloys

Dielectric properties of highly (100) oriented (Pb0.5,Sr0.5)TiO3 thin films grown on Si with MgO buffer layer

Kyoung-Tae Kim and Chang-II Kim

J. Vac. Sci. Technol. B 22, 2615 (2004); http://dx.doi.org/10.1116/1.1809613 (5 pages) | Cited 1 time

Online Publication Date: 4 November 2004

Full Text: | Download PDF

Show Abstract
Pb0.5,Sr0.5TiO3 (PST) thin films were deposited on Si with MgO (100) buffer layer by the alkoxide-based sol-gel method. Structural and dielectric properties of PST thin films for the tunable microwave device applications were investigated. For the MgO∕Si buffer layer, the PST thin films exhibited highly (100) orientation. The MgO buffer layer affects the stress state of the (100)-oriented PST thin films. The dielectric constant, tunability, and figure of merit of the highly (100)-oriented PST thin film increased with increasing annealing temperature due to the decrease in lattice distortion. The differences in dielectric properties may be attributed to the change in the film stress. The dielectric constants, dielectric loss and tunability of the PST thin films deposited on the MgO∕Si substrates measured at 10 kHz were 822, 0.025, and 80.1%, respectively.
Show PACS
77.55.-g Dielectric thin films
77.22.Gm Dielectric loss and relaxation
77.22.Ch Permittivity (dielectric function)
81.40.Gh Other heat and thermomechanical treatments
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Mechanisms of nano-hole drilling due to nano-probe intense electron beam irradiation on a stainless steel

S. Bysakh, M. Shimojo, K. Mitsuishi, and K. Furuya

J. Vac. Sci. Technol. B 22, 2620 (2004); http://dx.doi.org/10.1116/1.1811626 (8 pages) | Cited 11 times

Online Publication Date: 4 November 2004

Full Text: | Download PDF

Show Abstract
Holes with diameters of a few nanometers were drilled in a stainless steel foil using intense electron beams of 2.4 nm nominal probe size from a field-emission electron gun in a high-resolution transmission electron microscope. Drilling experiments were carried out at regions of different foil thicknesses for different durations using three different condenser lens apertures. A better understanding of the mechanisms of nano-hole drilling by nano-probe electron beams has been achieved in this article. It was observed that the drilling process initiates from the bottom surface of a thin region while it initiates from the top surface for a thick region. It is concluded that material removal during nano-hole drilling is mainly by localized vaporization within the foil and drilling progresses through the formation of a row of interconnected nano-voids along the irradiated volume across the foil thickness.
Show PACS
61.80.Fe Electron and positron radiation effects
61.82.Bg Metals and alloys
61.46.-w Structure of nanoscale materials
81.20.Wk Machining, milling
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing

Pt nanostructured electrode encapsulated by a tantalum oxide for thin-film fuel cell

Kyung-Won Park and Yung-Eun Sung

J. Vac. Sci. Technol. B 22, 2628 (2004); http://dx.doi.org/10.1116/1.1814109 (4 pages) | Cited 2 times

Online Publication Date: 4 November 2004

Full Text: | Download PDF

Show Abstract
A nanostructured electrode, fabricated by means of a co-sputtering method, consisting of Pt nanophases of polycrystalline structure and amorphous tantalum oxide was characterized by transmission electron microscopy, x-ray diffraction, and x-ray photoelectron spectra analysis. The Pt nanostructured electrode showed excellent performance, that is, much higher current density of methanol electro-oxidation, compared to a typical Pt thin-film electrode. The origin of the enhanced performance in the nanostructured electrode appears to be due to an increased surface area of Pt catalyst in the porous oxide matrix, used as a support for the Pt nanophases and a pathway for transporting methanol as a fuel and protons.
Show PACS
81.15.Cd Deposition by sputtering
82.47.-a Applied electrochemistry
79.60.-i Photoemission and photoelectron spectra
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.45.Fk Electrodes
61.46.-w Structure of nanoscale materials

Surface flatness of polycrystalline copper after argon ion etching followed by annealing

T. Hino, T. Taguchi, Y. Yamauchi, Y. Hirohata, and M. Nishikawa

J. Vac. Sci. Technol. B 22, 2632 (2004); http://dx.doi.org/10.1116/1.1814110 (3 pages) | Cited 1 time

Online Publication Date: 4 November 2004

Full Text: | Download PDF

Show Abstract
Oblique injection of argon ions with energy of 1 keV was conducted for etching of polycrystalline copper. The surface became rough owing to the formation of blisters. The average diameter and height of blisters was approximately 150 and 20–30 nm, respectively. The polycrystalline copper irradiated by argon ions was annealed to rupture the blisters. The retained argon desorbed in the temperature range from 500 to 800 K. The height of blisters significantly reduced to 10–15 nm although the diameter and surface density of blisters roughly remained the same.
Show PACS
81.65.Cf Surface cleaning, etching, patterning
68.47.De Metallic surfaces
81.40.Gh Other heat and thermomechanical treatments
68.43.Mn Adsorption kinetics
52.77.Bn Etching and cleaning

Annealing temperature stability of Ir and Ni-based Ohmic contacts on AlGaN∕GaN high electron mobility transistors

B. S. Kang, S. Kim, J. R. La Roche, F. Ren, R. C. Fitch, J. K. Gillespie, N. Moser, T. Jenkins, J. Sewell, D. Via, A. Crespo, A. M. Dabiran, P. P. Chow, A. Osinsky, and S. J. Pearton

J. Vac. Sci. Technol. B 22, 2635 (2004); http://dx.doi.org/10.1116/1.1814111 (5 pages) | Cited 3 times

Online Publication Date: 4 November 2004

Full Text: | Download PDF

Show Abstract
Ti∕Al∕Ir∕Au Ohmic contacts on AlGaN∕GaN high electron mobility transistors (HEMTs) show promising electrical performance, with lower specific contact resistance than obtained with the more conventional Ti∕Al∕Ni∕Au metallization. HEMTs with both types of metallization have been measured up to 550 °C. We find that the dc performance of devices with Ir-based contacts is significantly better at each temperature up to this maximum value, with higher transconductance (gm), saturated drain-source current (IDSS), and more stable threshold voltage (Vth). These contacts look very promising for HEMT power amplifier applications involving high temperature operation.
Show PACS
85.40.Ls Metallization, contacts, interconnects; device isolation
81.40.Gh Other heat and thermomechanical treatments
73.40.Ns Metal-nonmetal contacts
85.30.Tv Field effect devices

High resolution and aspect ratio two-dimensional photonic band-gap crystal

Selin H. G. Teo, A. Q. Liu, J. Singh, and M. B. Yu

J. Vac. Sci. Technol. B 22, 2640 (2004); http://dx.doi.org/10.1116/1.1819900 (9 pages) | Cited 7 times

Online Publication Date: 4 November 2004

Full Text: | Download PDF

Show Abstract
This paper reports the challenges resolved to realize high aspect ratio pillar-type two-dimensional photonic band-gap crystal (PhC), designed for application at the optical communication wavelengths. Specifically, the issue of a drastically reduced process window of deep UV lithography and deep reactive ion etching, for a super dense array of submicron size pillars with a diameter of 230 nm and a spacing of 340 nm is treated. A rigorous design of experiments yielded high-resolution PhCs with precise lattice dimensions even near regions of “defect structures” designed for device operations. At the same time, in the etching process, the stringent requirement of an etch angle needed for successful realization of such a super dense array of submicron size PhC lattice was also satisfied to yield sidewalls of high verticality, aspect ratios greater than 50, and scallop-depths of 12 nm.
Show PACS
42.70.Qs Photonic bandgap materials
81.65.Cf Surface cleaning, etching, patterning

Damascene Cu electrodeposition on metal organic chemical vapor deposition-grown Ru thin film barrier

Sung Ki Cho, Soo-Kil Kim, Hee Han, Jae Jeong Kim, and Seung Mo Oh

J. Vac. Sci. Technol. B 22, 2649 (2004); http://dx.doi.org/10.1116/1.1819911 (5 pages) | Cited 13 times

Online Publication Date: 4 November 2004

Full Text: | Download PDF

Show Abstract
Ru thin film grown by metal organic chemical vapor deposition (MOCVD) was applied in this study as a substrate for superconformal Cu electrodeposition as well as a Cu diffusion barrier at a Cu∕Ru∕SiO2∕Si multilayer system for microelectronics. Bis (ethyl-π-cyclopentadienyl) Ru-based MOCVD Ru thin film had a roughness of about 12% of its thickness and well-developed textures with high purity. It also showed good step coverage in damascene trench structure. Pd catalyst-mediated Cu electrodeposition on Ru surface accomplished formation of continuous Cu film. For gap filling in single damascene structure, bumps indicative of bottom-up acceleration and superfilling were observed during two-step Cu electrodeposition on Ru substrate which involved seeding and filling with conventional three additives system. 30 nm-thick Ru film effectively worked as a barrier for interdiffusion and∕or reaction between layers even after annealing at 800 °C for 30 min. With the exception of slight agglomeration of Cu at elevated temperature, no silicidation or AES-profile broadening was observed in a Cu∕Ru∕SiO2∕Si system.
Show PACS
81.15.Pq Electrodeposition, electroplating
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Low temperature growth of amorphous Si nanoparticles in oxide matrix for efficient visible photoluminescence

L. B. Ma, A. L. Ji, C. Liu, Y. Q. Wang, and Z. X. Cao

J. Vac. Sci. Technol. B 22, 2654 (2004); http://dx.doi.org/10.1116/1.1819925 (4 pages) | Cited 3 times

Online Publication Date: 4 November 2004

Full Text: | Download PDF

Show Abstract
We report a low temperature procedure for the fabrication of highly luminescent silicon nanoparticles in silicon-rich oxide films. A number density over 1012∕cm2 has been achieved for silicon particles of about 3 nm in size by plasma-enhanced chemical vapor deposition at a substrate temperature of 30 °C. Such deposits, when post-annealed at 500 °C for 2 min, manifested a photoluminescence two orders of magnitude more intense than those samples grown at 250 °C. Strong photoluminescence in the whole visible light range has been measured in samples prepared with this low-temperature procedure. The present results indicate the feasibility of fabricating silicon-based light-emitting devices with moderate processing temperatures.
Show PACS
61.46.-w Structure of nanoscale materials
61.43.Dq Amorphous semiconductors, metals, and alloys
78.55.-m Photoluminescence, properties and materials

Dielectric function of thin-film titanium oxide with a granular nanostructure

R. S. Sorbello, J. D. DeLoach, C. R. Aita, and P. Fejes

J. Vac. Sci. Technol. B 22, 2658 (2004); http://dx.doi.org/10.1116/1.1808743 (5 pages) | Cited 4 times

Online Publication Date: 4 November 2004

Full Text: | Download PDF

Show Abstract
It is shown here that a simple weighted average dielectric function describes the experimental infrared reflection∕absorption spectra of titanium oxide films with a granular nanostructure. The films were grown on unheated substrates by reactive sputter deposition using a Ti metal target and a 10 mTorr pure O2 discharge. The films’ average dielectric function is derivable from a Maxwell-Garnett model in which randomly oriented nanograins with anatase short-range atomic order are embedded in a conducting background. In contrast, dielectric functions calculated using effective-medium and Maxwell–Garnett theories that do not consider the background fail to adequately account for the experimental absorption peak positions. High-resolution transmission electron microscopy confirmed the films’ granular nanostructure and the presence of Ti suboxides as a minority constituent. We associate the anatase-like constituent with the model’s embedded grains, and the Ti suboxide constituent with the model’s background medium. The formalism that is developed here is applicable to any composite system consisting of grains embedded in a medium whose dielectric function is much larger than that of the grains.
Show PACS
77.22.Ch Permittivity (dielectric function)
77.55.-g Dielectric thin films
78.30.Hv Other nonmetallic inorganics
81.15.Cd Deposition by sputtering
68.55.A- Nucleation and growth

Molecular-beam-epitaxy growth of high-quality InGaAsN∕GaAs quantum well lasers emitting at 1.3 μm

J. S. Wang, R. S. Hsiao, G. Lin, K. F. Lin, H. Y. Liu, C. M. Lai, L. Wei, C. Y. Liang, J. Y. Chi, A. R. Kovsh, N. A. Maleev, D. A. Livshits, J. F. Chen, H. C. Yu, and V. M. Ustinov

J. Vac. Sci. Technol. B 22, 2663 (2004); http://dx.doi.org/10.1116/1.1807839 (5 pages) | Cited 6 times

Online Publication Date: 5 November 2004

Full Text: | Download PDF

Show Abstract
Molecular-beam-epitaxy growth of high structural and optical-quality InGaAsN∕GaAs quantum wells (QW) has been investigated. The material quality can be improved significantly by using low-temperature growth to suppress the phase separation. High-performance ridge-waveguide InGaAsN∕GaAs single QW lasers emitting at 1.3 μm have been demonstrated. Infinite-cavity-length threshold-current density of 400 A∕cm2, internal quantum efficiency of 96%, and a slope efficiency of 0.67 W∕A for a cavity length L=1 mm were obtained. A TO46 packaging laser shows single lateral-mode kink-free output power of more than 200 mW with a maximum total wallplug efficiency of 29% at room temperature under continuous wave (cw) operation. Moreover, 1.3 μm InGaAsN∕GaAs QW vertical-cavity surface-emitting lasers with a threshold current density lower than 2 KA∕cm2 at room temperature have been achieved. We obtained multimode cw output power and slope efficiency in excess of 1 mW and 0.15 W∕A, respectively.
Show PACS
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
85.40.Sz Deposition technology
64.75.-g Phase equilibria
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
84.40.Az Waveguides, transmission lines, striplines
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
81.05.Ea III-V semiconductors

Optical study of spin injection dynamics in InGaN∕GaN quantum wells with GaMnN injection layers

I. A. Buyanova, J. P. Bergman, W. M. Chen, G. Thaler, R. Frazier, C. R. Abernathy, S. J. Pearton, Jihyun Kim, F. Ren, F. V. Kyrychenko, C. J. Stanton, C.-C. Pan, G.-T. Chen, J.-I. Chyi, and J. M. Zavada

J. Vac. Sci. Technol. B 22, 2668 (2004); http://dx.doi.org/10.1116/1.1819897 (5 pages) | Cited 7 times

Online Publication Date: 5 November 2004

Full Text: | Download PDF

Show Abstract
The spin injection dynamics of GaMnN∕InGaN multiquantum well (MQW) light emitting diodes (LEDs) grown by molecular beam epitaxy were examined using picosecond-transient and circularly polarized photoluminescence (PL) measurements. Even with the presence of a room temperature ferromagnetic GaMnN spin injector, the LEDs are shown to exhibit very low efficiency of spin injection. Based on resonant optical orientation spectroscopy, the spin loss in the structures is shown to be largely due to fast spin relaxation within the InGaN MQW, which itself destroys any spin polarization generated by optical spin orientation or electrical spin injection. Typical photoluminescence decay times were 20–40 ns in both commercial GaN MQW LEDs with emission wavelengths between 420–470 nm and in the GaMnN∕InGaN multi-quantum well MQW LEDs. In the wurtzite InGaN∕GaN system, biaxial strain at the interfaces give rise to large piezoelectric fields directed along the growth axis. This built-in piezofield breaks the reflection symmetry of confining potential leading to the presence of a large Rashba term in the conduction band Hamiltonian which is responsible for the short spin relaxation times.
Show PACS
78.67.De Quantum wells
78.55.Cr III-V semiconductors
85.60.Jb Light-emitting devices
77.65.-j Piezoelectricity and electromechanical effects
81.05.Ea III-V semiconductors
73.20.At Surface states, band structure, electron density of states

Evaluation of atomic exchange in GaAs∕GaP interfaces by tetragonal distortion measurements

J. C. Ferrer, F. Peiró, A. Cornet, and G. Armelles

J. Vac. Sci. Technol. B 22, 2673 (2004); http://dx.doi.org/10.1116/1.1819924 (7 pages)

Online Publication Date: 5 November 2004

Full Text: | Download PDF

Show Abstract
The quantification of interdiffusion processes in the interfaces of GaAs quantum wells, with thickness ranging from one to six atomic layers, grown by atomic layer molecular beam epitaxy in a GaP matrix is addressed. The atomic row positions have been determined from high resolution transmission electron microscopy images. The distortion of distances and angles between neighboring rows with respect to those expected in the strained structure has been related to changes in chemical composition. This method appears more efficient for this system than other methods based on the analysis of the atomic row contrast. Results show that interdiffusion occurred at the GaAs∕GaP interfaces. The arsenic profiles in the quantum well suggest that the main contribution of interdiffusion comes from atomic exchange. The experimental profiles have been fitted to a simple model of segregation giving segregation coefficients around 0.45. The results are compared to simulations based on Raman measurements performed on the same samples.
Show PACS
68.35.Fx Diffusion; interface formation
68.37.Lp Transmission electron microscopy (TEM)

Fabrication of diamond-like amorphous carbon cantilever resonators

Daniel H. C. Chua, W. I. Milne, D. Sheeja, B. K. Tay, and D. Schneider

J. Vac. Sci. Technol. B 22, 2680 (2004); http://dx.doi.org/10.1116/1.1824042 (5 pages) | Cited 3 times

Online Publication Date: 5 November 2004

Full Text: | Download PDF

Show Abstract
Amorphous carbon (a-C) films were deposited by an off-plane double bend filtered cathodic vacuum arc technique fitted with a plasma immersion ion implantation system. High resolution XPS measurements showed these films have an sp3 content of about 60%. Laser-surface acoustic wave measurements have shown such films to have a Young’s modulus and density of 310 GPa and 2.33 g∕cm3. 1.2 μm thick a-C films were grown and subsequently patterned into 150 μm×50 μm cantilevers using standard photolithography. Residual stress measurements were obtained from the curvature of bend of the cantilever. An accurate knowledge of the microstructural properties will in turn give accurate modeling results. Simulation results showed that such free-standing cantilevers fabricated with amorphous carbon films have resonant frequency much higher than standard polysilicon cantilevers. As such, free-standing diamond-like amorphous carbon cantilevers had been fabricated. The resonant frequency of these cantilevers was measured by laser vibrometer to be ∼108 MHz, in very good agreement with simulation results.
Show PACS
68.60.Bs Mechanical and acoustical properties
68.35.Iv Acoustical properties
79.60.Bm Clean metal, semiconductor, and insulator surfaces
79.20.Ds Laser-beam impact phenomena
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
52.77.Dq Plasma-based ion implantation and deposition
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Fabrication of masters for nanoimprint, step and flash, and soft lithography using hydrogen silsesquioxane and x-ray lithography

Ivan Junarsa and Paul F. Nealey

J. Vac. Sci. Technol. B 22, 2685 (2004); http://dx.doi.org/10.1116/1.1807838 (6 pages) | Cited 11 times

Online Publication Date: 9 November 2004

Full Text: | Download PDF

Show Abstract
A technique for fabricating masters for nanoimprint lithography, step and flash lithography, and soft lithography has been demonstrated through direct patterning of hydrogen silsesquioxane (HSQ) using x-ray lithography. Patterns that are replicated by nanoimprint, step and flash, and other soft lithographic strategies are often originally written on masters with electron beam lithography. In this article we demonstrate that if the original pattern is written with electron beam lithography to make an x-ray mask, then masters with very well-defined three-dimensional relief structures can be easily produced by direct patterning of hydrogen silsesquioxane using x-ray lithography. Direct patterning of HSQ eliminates silicon or oxide etches associated with the current fabrication techniques, providing better critical dimension and aspect ratio control of the structures on the masters. A low surface energy release agent, tridecafluoro-1,1,2,2-tetrahydrooctyl trichlorosilane, can also be applied onto the patterned HSQ to prevent the imprinted substrates from sticking to the masters. Thousands of masters can be produced from a single x-ray mask, and the x-ray mask pattern can be stepped to make large masters from a single small patterned area on the x-ray mask. The HSQ masters were successfully applied to imprint structures onto a polymeric resist substrate and poly(dimethylsiloxane).
Show PACS
85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

Strain and electrical characterization of metal-oxide-semiconductor field-effect transistor fabricated on mechanically and thermally transferred silicon on insulator films

F. Lu, J. Bickford, C. Novotny, P. K. L. Yu, S. S. Lau, K. Henttinen, T. Suni, and I. Suni

J. Vac. Sci. Technol. B 22, 2691 (2004); http://dx.doi.org/10.1116/1.1819926 (7 pages) | Cited 1 time

Online Publication Date: 9 November 2004

Full Text: | Download PDF

Show Abstract
Silicon-on-insulator (SOI) substrates were created from two methods of ion cutting: thermal exfoliation (TE) and mechanical exfoliation (ME). These SOI films are characterized to discern the differences in electrical and other properties induced by the ME and TE processes. p-metal-oxide-semiconductor field-effect transistor were fabricated on these SOI substrates as well as on bulk silicon and their I-V characteristics measured and compared to point out materials differences created by the two methods. X-ray diffraction measurements were also performed to supplement the exploration of the TE and ME material properties. Overall the FETs fabricated from the ME SOI outperformed those made from the TE SOI and had similar Ion∕Ioff ratios and off-state drain-source leakage currents to the FETs fabricated from bulk Si.
Show PACS
85.30.Tv Field effect devices
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Effect of the deposition temperature on temperature coefficient of resistance in CuNi thin film resistors

Sung-Gi Hur, Dong-Jin Kim, Byoung-Don Kang, and Soon-Gil Yoon

J. Vac. Sci. Technol. B 22, 2698 (2004); http://dx.doi.org/10.1116/1.1815313 (4 pages) | Cited 12 times

Online Publication Date: 10 November 2004

Full Text: | Download PDF

Show Abstract
A constantan composition of Cu54Ni46 showing an near zero TCR value was obtained using a Ni power of 100 W and a Cu power of 50 W by dc magnetron cosputtering. The grain size increases and resistivity of the films decreases with increasing deposition temperature. The crystallinity of the films definitely influences the TCR value, which is an important parameter in resistor devices. The films deposited at 100 °C exhibited a near zero TCR value of approximately 5 ppm∕°C and the positive TCR values increased with increasing deposition temperature. The films deposited above 100 °C do not exhibit irreversibility of the resistance with increasing deposition temperature.
Show PACS
73.61.At Metal and metallic alloys
81.15.Cd Deposition by sputtering
81.40.-z Treatment of materials and its effects on microstructure, nanostructure, and properties
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.05.Bx Metals, semimetals, and alloys

Effects of postannealing on the bulk and interfacial characteristics of ZrO2 gate dielectrics prepared on Si by metalorganic chemical vapor deposition

Shih-Sian Huang and Tai-Bor Wu

J. Vac. Sci. Technol. B 22, 2702 (2004); http://dx.doi.org/10.1116/1.1811627 (7 pages) | Cited 3 times

Online Publication Date: 11 November 2004

Full Text: | Download PDF

Show Abstract
This work investigates the effects of postannealing on the bulk and interfacial characteristics of ultrathin ZrO2 films on Si substrates. The films were prepared by metalorganic chemical-vapor deposition and were subsequently annealed in N2 or O2 ambient at 500–900 °C. Partial crystallization of the ZrO2 film and growth of an interfacial layer (IL) were found by the increase of the annealing temperature. The IL is mainly composed of Zr–silicate for annealing in N2, but it is mostly SiO2 for annealing in O2. The annealing also effectively reduces the oxide trapped-charge density in ZrO2, as demonstrated by the reduction of hysteresis in the capacitance–voltage relation, but not for the specimen annealed in O2 at 900 °C, in which excessive oxygen diffused into the film and IL was found. Lower leakage current from substrate injection in association with the reduction of depletion layer, which provides less generation current, was found due to the growth of Zr–silicate IL in N2 annealing, but the leakage from gate injection increased in conjunction with the crystallization of the ZrO2 layer. In contrast, the relatively thick SiO2 IL formed in O2 annealing reduces the leakage for both substrate and gate injection. There is also a significant shift of the turn-around voltage in the current–voltage relation with voltage swept from inversion to accumulation, but not with voltage swept back.
Show PACS
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.55.-g Dielectric thin films
68.35.Ct Interface structure and roughness
81.40.Gh Other heat and thermomechanical treatments
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.A- Nucleation and growth
68.35.Fx Diffusion; interface formation

Synthesis of tin-incorporated nanocomposite diamond like carbon films by plasma enhanced chemical vapor deposition and their characterization

S. Kundoo, P. Saha, and K. K. Chattopadhyay

J. Vac. Sci. Technol. B 22, 2709 (2004); http://dx.doi.org/10.1116/1.1815318 (6 pages) | Cited 6 times

Online Publication Date: 11 November 2004

Full Text: | Download PDF

Show Abstract
Sn-incorporated nanocomposite diamond like carbon (DLC) films were synthesized using direct current plasma enhanced chemical vapor deposition method. The precursor gas used was acetylene. For Sn incorporation, SnCl2⋅2H2O dissolved in methanol was used. Fourier-transform infrared spectroscopy measurements showed different vibrational modes of tetrahedrally bonded carbon and also some small peaks due to Sn�C bonding vibrations. Transmission electron microscopy image and electron diffraction patterns also confirmed the incorporation of nanocrystalline Sn particles into the amorphous DLC matrix. Due to the presence of Sn clusters, the Tauc gap of the films decreased sharply, compared to the intrinsic material. It was found that the resistivity of Sn-incorporated DLC films decreased drastically (by eight orders of magnitude) compared to the undoped DLC film. Also, the films exhibited good field emission properties at a lower turn-on field.
Show PACS
81.05.ub Fullerenes and related materials
81.05.U- Carbon/carbon-based materials
78.30.Na Fullerenes and related materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology

Microstructure and resistivity characterization of CuAu I superlattice formed in Cu∕Au thin films

W. Zhang, S. H. Brongersma, O. Richard, B. Brijs, R. Palmans, L. Froyen, and K. Maex

J. Vac. Sci. Technol. B 22, 2715 (2004); http://dx.doi.org/10.1116/1.1819899 (4 pages) | Cited 1 time

Online Publication Date: 11 November 2004

Full Text: | Download PDF

Show Abstract
Stoichiometric AuCu alloy has been well studied in bulk form, but the resistivity of very thin films has rarely been reported. In fact, thin copper and gold films show a strong deviation from bulk resistivity due to the size effect, which motivates us to study CuAu I thin films and understand the properties of nanoscale metallization in more details. Very thin films of ordered CuAu I phase were formed by interdiffusion of Cu∕Au bilayers, in which the intermetallic phase formation was characterized by glancing angle x-ray diffraction and transmission electron microscopy. It was found that Kirkendall voids were created during the interdiffusion. Also, as it turned out, the resistivity of such thin CuAu I films changed only slightly with decreasing film thickness, which was different from pure copper and gold thin films.
Show PACS
73.61.At Metal and metallic alloys
73.63.-b Electronic transport in nanoscale materials and structures
61.72.-y Defects and impurities in crystals; microstructure
85.40.Ls Metallization, contacts, interconnects; device isolation
68.35.Fx Diffusion; interface formation
66.30.Ny Chemical interdiffusion; diffusion barriers
61.46.-w Structure of nanoscale materials
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Hydrogen in Si–Si bond center and platelet-like defect configurations in amorphous hydrogenated silicon

Sumit Agarwal, Bram Hoex, M.C.M. van de Sanden, Dimitrios Maroudas, and Eray S. Aydil

J. Vac. Sci. Technol. B 22, 2719 (2004); http://dx.doi.org/10.1116/1.1824191 (8 pages) | Cited 6 times

Online Publication Date: 11 November 2004

Full Text: | Download PDF

Show Abstract
Hydrogen and deuterium in bond-centered (BC) and platelet-like configurations were detected in hydrogenated (and deuterated) amorphous silicon thin films deposited from SiH4 and SiD4 plasmas. Infrared absorptions due to these configurations were measured using in situ multiple total internal reflection Fourier transform infrared spectroscopy in a differential mode, where changes in the as-deposited a-Si:H(D) films were observed during D2(H2) plasma exposure. This method coupled with preferential replacement of H(D) by D(H) in BC and platelet-like configurations over the isolated bulk SiH(SiD) configurations enabled detection of these modes without interference from the strong SiH(SiD) absorptions. The Si–H(D) stretching modes for BC hydrogen and BC deuterium were observed at ∼1950 and ∼1420 cm−1, respectively, while those for platelet-like hydrogen and deuterium were detected at ∼2033 and ∼1480 cm−1, respectively.
Show PACS
78.66.Jg Amorphous semiconductors; glasses
78.30.Am Elemental semiconductors and insulators
61.43.Dq Amorphous semiconductors, metals, and alloys
81.05.Cy Elemental semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Temperature-dependent dc characteristics of an InGaAs∕InGaAsP heterojunction bipolar transistor with an InGaAsP spacer and a composite-collector structure

Jing-Yuh Chen, Chun-Yuan Chen, Kuan-Ming Lee, Chih-Hung Yen, Sheng-Fu Tsai, Shiou-Ying Cheng, and Wen-Chau Liu

J. Vac. Sci. Technol. B 22, 2727 (2004); http://dx.doi.org/10.1116/1.1807840 (7 pages) | Cited 5 times

Online Publication Date: 15 November 2004

Full Text: | Download PDF

Show Abstract
The temperature-dependent dc characteristics of an interesting heterojunction bipolar transistor with an InGaAsP spacer and an InGaAs∕InGaAsP composite-collector structure are studied and demonstrated. By employing the intermediate band-gap In0.72Ga0.28As0.61P0.39 material at the emitter-base and base-collector heterojunction, the electron blocking effect is effectively eliminated. The studied device gives the promising dc performances including the small offset and saturation voltages without degrading the breakdown behaviors. The typical incremental current gain of 114 and the maximum dc current gain of 118 are obtained. It is worthwhile to note that the desired current amplification over 11 decades of the magnitude of collector current IC is obtained in the studied device. Moreover, the switching or hysteresis phenomenon usually observed in InP-based devices is not seen in the studied device.
Show PACS
85.30.Pq Bipolar transistors
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Chemically enhanced physical vapor deposition of tantalum nitride-based films for ultra-large-scale integrated devices

Ning Li, D. N. Ruzic, and R. A. Powell

J. Vac. Sci. Technol. B 22, 2734 (2004); http://dx.doi.org/10.1116/1.1808744 (9 pages) | Cited 1 time

Online Publication Date: 15 November 2004

Full Text: | Download PDF

Show Abstract
Physical vapor deposition (PVD) using ionized metal plasmas (ionized PVD or IPVD) is widely used to deposit conducting diffusion barriers and liners such as Ta and TaN for use in ultra-large-scale integrated (ULSI) interconnect stacks. Ionized PVD films exhibit the low resistivity, high density, and good adhesion to underlying dielectric desired for this application. On the other hand, extending PVD beyond the 45 nm technology node is problematic since IPVD may not provide sufficient step coverage to reliably coat features having high aspect ratio and sub-100 nm dimensions. Alternatively, chemical vapor deposition (CVD) and atomic layer deposition (ALD) can be used to deposit highly conformal metal films, but the electrical performance and interfacial quality may not equal that of PVD. To address future ULSI barrier∕liner deposition needs, a method providing PVD-like film quality and CVD-like step coverage would be highly attractive. We have recently reported a hybrid approach to film deposition, referred to as chemically enhanced physical vapor deposition (CEPVD), in which a chemical precursor is introduced at the substrate during IPVD to provide a CVD component to the overall deposition process. The isotropic precursor flux is intended to provide film deposition on surfaces that are not impacted by the directional ions, such as the lower sidewall of a narrow via or trench. Conversely, the kinetic energy delivered to the surface by the flux of ionized metal may serve to enhance the desorption of CVD byproducts, reduce incorporation of impurities, and increase film density. In order to investigate the potential of CEPVD to deposit barrier∕liner films, we have focused on the Ta-N material system since Ta∕TaN is widely used as a diffusion barrier in Cu damascene processing. IPVD TaN films were deposited by reactive sputtering of a Ta target in Ar∕N2 using a planar magnetron and internal rf coils to provide a secondary ionization plasma for the sputtered neutrals. CEPVD was carried out by introducing a Ta-containing, organometallic precursor [tert-butylimino tris(diethylamino) tantalum] in the vicinity of the substrate surface during IPVD. Film thickness and step coverage were determined by cross-sectional scanning electron microscopy (SEM). Film composition, chemical state, and crystal structure were characterized using Auger electron spectroscopy, x-ray photoelectron spectroscopy, and x-ray diffraction, respectively. Resistivity was measured by four-point probe. Cross-sectional SEM showed improved step coverage over IPVD TaN. CEPVD film properties were highly process dependent; however, unlike IPVD TaNx films that vary in stoichiometry but not purity, CEPVD “TaN” films contained relatively large amounts of carbon (∼30%–60%) and could best be described as TaCxNy. Resistivity as low as ∼370 μΩ cm was obtained for planar films of approximately 90 nm in thickness.
Show PACS
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
52.77.Dq Plasma-based ion implantation and deposition
68.35.Fx Diffusion; interface formation
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
79.60.Dp Adsorbed layers and thin films
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
73.61.At Metal and metallic alloys
85.40.Ls Metallization, contacts, interconnects; device isolation
61.72.S- Impurities in crystals

Experimental relationship between work function and dipole moment on ErO∕W(100) and LuO∕W(100) emitter surfaces

Y. Saito, K. Yada, K. Minami, H. Nakane, and H. Adachi

J. Vac. Sci. Technol. B 22, 2743 (2004); http://dx.doi.org/10.1116/1.1811625 (5 pages) | Cited 2 times

Online Publication Date: 15 November 2004

Full Text: | Download PDF

Show Abstract
A sharp reduction of work function occurs on a tungsten (100) surface after modifying of the surface with Er or Lu and oxygen and lasts for several hours. The fabricating process is similar to that of the standard ZrO∕W(100) Schottky emitter. The calculated work functions with the aid of Fowler–Nordheim plot are 1.8 eV for ErO∕W(100) and 2.3 eV for LuO∕W(100). These work functions are extremely low in comparison with both 4.6 eV for bare W(100) and 2.9 eV for ZrO∕W(100). The electrical dipole moments of complex pairs ErO and LuO are evaluated to be about 6.3 and 4.5 D, respectively.
Show PACS
73.30.+y Surface double layers, Schottky barriers, and work functions

Formation of silicon on plasma synthesized aluminum nitride structure by ion cutting

Ming Zhu, Peng Chen, Ricky K. Y. Fu, Weili Liu, Chenglu Lin, and Paul K. Chu

J. Vac. Sci. Technol. B 22, 2748 (2004); http://dx.doi.org/10.1116/1.1811629 (6 pages) | Cited 1 time

Online Publication Date: 15 November 2004

Full Text: | Download PDF

Show Abstract
The application of silicon-on-insulator (SOI) substrates to high-power integrated circuits is hampered by self-heating effects due to the poor thermal conductivity of the buried SiO2 layer. We propose to replace the buried SiO2 layer in SOI with a plasma synthesized AlN thin film to mitigate the self-heating penalty. The AlN films synthesized on silicon by metal plasma immersion ion implantation and deposition exhibit outstanding surface topography and excellent insulating characteristics. Using a modified direct bonding process in conjunction with hydrogen-induced layer transfer, a silicon-on-AlN structure has been successfully fabricated. Cross-sectional high-resolution transmission electron microscopy, x-ray photoelectron spectroscopy, and spreading resistance profiling results reveal a uniform buried AlN layer beneath a single crystal Si overlayer. The interfaces between the top Si layer, buried AlN layer, and Si substrate are smooth and sharp. Moreover, the use of relatively thick buried AlN layer bodes well for SOI wafers in high voltage and high power applications.
Show PACS
52.77.Dq Plasma-based ion implantation and deposition
61.72.uf Ge and Si
81.15.Jj Ion and electron beam-assisted deposition; ion plating
68.35.Ct Interface structure and roughness
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.05.Cy Elemental semiconductors
79.60.Jv Interfaces; heterostructures; nanostructures
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves

Effects of applied voltages on planarization efficiency of Cu electropolishing

Shih-Chieh Chang and Ying-Lang Wang

J. Vac. Sci. Technol. B 22, 2754 (2004); http://dx.doi.org/10.1116/1.1819898 (4 pages) | Cited 3 times

Online Publication Date: 15 November 2004

Full Text: | Download PDF

Show Abstract
Copper electropolishing (Cu-EP) was recently investigated to be a next generation technology for planarizing damascene copper interconnections. In this study, effects of applied voltages on microscaled planarization efficiency (PE) of Cu-EP are discussed. It was found that the initial polishing rate and the formation time of a viscous layer were crucial for the PE of Cu-EP because only a thin copper film should be removed. A higher polishing rate outside of a feature and a more resistive diffusion layer covered inside of a feature resulted in a higher step-height reduction on a copper film.
Show PACS
81.65.Ps Polishing, grinding, surface finishing
85.40.Ls Metallization, contacts, interconnects; device isolation

Optical and electrical properties of AlCrN films grown by molecular beam epitaxy

A. Y. Polyakov, N. B. Smirnov, A. V. Govorkov, R. M. Frazier, J. Y. Liefer, G. T. Thaler, C. R. Abernathy, S. J Pearton, and J. M. Zavada

J. Vac. Sci. Technol. B 22, 2758 (2004); http://dx.doi.org/10.1116/1.1819927 (6 pages) | Cited 4 times

Online Publication Date: 15 November 2004

Full Text: | Download PDF

Show Abstract
Doping of AlN with Cr at percent level concentrations produces ferromagnetism persisting to above 300 K. We have examined the electrical and optical properties of Cr-doped AlN grown by molecular beam epitaxy under conditions that produce single-phase or multiple phase material, as measured by x-ray diffraction. The band gap of single-phase AlN decreases from 6.2 to 6.1 eV for a Cr concentration of 2 at. %. This change originates from the Franz-Keldysh broadening of the band edge due to potential fluctuations caused by heavy Cr doping. The effect was more pronounced in multiple-phase samples (the secondary phases are Cr2N and AlxCry), producing an apparent band gap of 5.8 eV. Two strong defect absorption bands with thresholds of 3 and 5 eV are introduced by the Cr doping. The resistivity of single-phase AlCrN samples is higher than the resistivity of similarly grown undoped AlN films. Multiple-phase AlCrN samples show a high conductivity of the hopping type. The optical transmission spectra of multiphase AlCrN indicates appreciable absorption by free carriers and strong scattering, both most likely due to the presence of conducting inclusions.
Show PACS
78.66.Fd III-V semiconductors
73.61.Ey III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
71.55.Eq III-V semiconductors
61.72.uj III-V and II-VI semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
75.50.Pp Magnetic semiconductors

High aspect ratio pattern transfer in imprint lithography using a hybrid mold

Wen-Chang Liao and Steve Lien-Chung Hsu

J. Vac. Sci. Technol. B 22, 2764 (2004); http://dx.doi.org/10.1116/1.1824044 (4 pages) | Cited 6 times

Online Publication Date: 15 November 2004

Full Text: | Download PDF

Show Abstract
A new method has been developed to obtain high aspect ratio patterns transfer by using a combination of imprint lithography and photolithography through a hybrid mold on a flexible transparent plastic substrate. The hybrid mold was fabricated by optical lithography and wet etching of a commercial blank template containing photoresist, chromium and transparent glass. Etching barrier used in this method was a negative photoresist with a low softening point to achieve the pattern transfer on a flexible plastic substrate. After imprinting and the following development by an aqueous Na2CO3 solution, high aspect ratio patterns contributed by imprint and mask were successfully transferred. Using this method, we were able to obtain the desired high aspect ratio patterns on the plastic substrate without using expensive or specific photoresists. It was also easy to remove the residual layer that usually has to be treated by reactive ion etching (RIE) in conventional imprinting process.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
81.65.Cf Surface cleaning, etching, patterning

Fabrication of metallic nanostructures by atomic force microscopy nanomachining and lift-off process

Ju-Hung Hsu, Chun-Yu Lin, and Heh-Nan Lin

J. Vac. Sci. Technol. B 22, 2768 (2004); http://dx.doi.org/10.1116/1.1815314 (4 pages) | Cited 10 times

Online Publication Date: 17 November 2004

Full Text: | Download PDF

Show Abstract
We report the fabrication of metallic nanostructures by atomic force microscopy nanomachining on a thin resist and subsequent metal coating and lift-off. Nanodots with a size of 70 nm, nanowires with a width of 120 nm, and nanoelectrodes with a gap of 50 nm have been successfully created. Theoretical estimates of the minimum force for a satisfactory lift-off are also given and found to be consistent with the experimental value. The present work demonstrates the feasibility and effectiveness of using a single-layer resist in comparison with a two-layer resist.
Show PACS
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.Nd Micro- and nanolithography

Etching of porous SiOCH materials in fluorocarbon-based plasmas

N. Posseme, T. Chevolleau, O. Joubert, L. Vallier, and N. Rochat

J. Vac. Sci. Technol. B 22, 2772 (2004); http://dx.doi.org/10.1116/1.1815316 (13 pages) | Cited 17 times

Online Publication Date: 17 November 2004

Full Text: | Download PDF

Show Abstract
This work focuses on the etching of different porous methylsilsesquioxane materials (spin on SiOCH, k=2.2) with different porosity (30%, 40% and 50%) in fluorocarbon-based plasmas (CF4∕Ar). The etching of these materials is performed on blanket wafers in a magnetically enhanced reactive ion etcher. The surface and bulk modification after partial etching are studied using different surface analysis techniques such as quasi-in-situ x-ray photoelectron spectroscopy (XPS), infrared spectroscopy (FTIR), and attenuated total reflection spectroscopy (FTIR-ATR). Similar to nonporous SiOCH materials, a decrease in etch rate of porous SiOCH films is observed with either increasing Ar dilution or polymerizing gas addition (CH2F2), which can lead in this last case to an etch stop phenomenon. The etch rate increases with higher porosity in the SiOCH film, since less material per unit thickness needs to be removed as the porosity increases. The XPS results show that a fluorocarbon layer is formed at the surface of the porous material and complementary angle resolved XPS analyses reveal that fluorocarbon species diffuse through the pores into the material. After partial etching, FTIR and ATR analyses reveal a carbon depletion in the remaining film, which indicates that the porous material is altered during plasma exposure. The film degradation is more important as the porosity increases. The etch rate evolution and film degradation are discussed and interpreted in terms of etching mechanisms and plasma surface interaction.
Show PACS
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
79.60.Bm Clean metal, semiconductor, and insulator surfaces
78.30.Hv Other nonmetallic inorganics
77.55.-g Dielectric thin films
52.40.Hf Plasma-material interactions; boundary layer effects

Detection of bacterial cells and antibodies using surface micromachined thin silicon cantilever resonators

Amit Gupta, Demir Akin, and Rashid Bashir

J. Vac. Sci. Technol. B 22, 2785 (2004); http://dx.doi.org/10.1116/1.1824047 (7 pages) | Cited 28 times

Online Publication Date: 17 November 2004

Full Text: | Download PDF

Show Abstract
This article describes a surface micromachined cantilever beam-based resonator for biological sensing applications. The study used a novel microfabrication technique of merged epitaxial lateral overgrowth (MELO) and chemical mechanical polishing (CMP) to fabricate thin, low stress, single-crystal silicon cantilever beams. The vibration spectra of the cantilever beams, excited by thermal and ambient noise, was measured in air using a Dimension 3100 Series scanning probe microscope (SPM), and in certain cases, a Polytec MSV300 laser Doppler vibrometer. The sensors were used to detect the mass of Listeria innocua bacteria by applying increasing concentration of bacteria suspension on the same cantilever beams and measuring the resonant frequency changes in air. Cantilever beams were also used to detect the mass of proteins such as Bovine Serum Albumin (BSA) and antibodies for Listeria that were attached to the cantilever’s surfaces by physical adsorption; following which they were used to capture and detect the mass of the bacterial cells on the functionalized cantilever beam surfaces’. The effects of critical point drying of the proteins were evaluated and the results indicate that the functionality of the antibodies was not reduced once rehydrated after critical point drying. The developed biosensor is capable of rapid and ultrasensitive detection of bacteria and promises significant potential for the enhancement of microbiological research and diagnostics.
Show PACS
87.80.-y Biophysical techniques (research methods)
87.17.-d Cell processes
07.10.Cm Micromechanical devices and systems

Formation of density controlled Cr-filled carbon nanotubes on Au–Cr solid solution

K. Kamide, H. Araki, S. Hiwatashi, K. Yoshino, T. Sakata, J-Goo Lee, and H. Mori

J. Vac. Sci. Technol. B 22, 2792 (2004); http://dx.doi.org/10.1116/1.1808747 (7 pages)

Online Publication Date: 24 November 2004

Full Text: | Download PDF

Show Abstract
Whisker-like carbon nanotubes with a controlled density (∼8.5×107 tubes∕cm2) can be prepared on Au–Cr solid solution films with Cr concentration of 22.5–30.0 atomic %, by thermal chemical vapor deposition using Ni-phthalocyanine as precursor. An inner hollow of the nanotube is filled with a single crystalline nanowire composed of Cr atoms. Crystal structure of those nanowires mostly agrees with that of the fcc type Au–Cr solid solution, and rarely takes a metastable structure such as A15 type of Cr as well as oxide (Cr3O4) or carbide (Cr3C2). It is suggested that Ni catalysis does not contribute in the form of nanoparticles to the growth processes of those nanotubes, but in the form of ultra-thin Ni film having many nanoholes. Those films play an important role to dissolve both Cr atoms and C atoms, and offer a stage for active surface diffusion of those atoms precipitated on those films.
Show PACS
81.07.De Nanotubes
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.46.-w Structure of nanoscale materials
68.70.+w Whiskers and dendrites (growth, structure, and nonelectronic properties)
68.35.Fx Diffusion; interface formation

Nanocomposite low-k SiCOH films by plasma-enhanced chemical vapor deposition using vinyltrimethylsilane and CO2

Ki-Hun Jeong, Sung-Gyu Park, and Shi-Woo Rhee

J. Vac. Sci. Technol. B 22, 2799 (2004); http://dx.doi.org/10.1116/1.1811628 (5 pages) | Cited 6 times

Online Publication Date: 24 November 2004

Full Text: | Download PDF

Show Abstract
SiCOH films were deposited with plasma-enhanced chemical vapor deposition using vinyltrimethylsilane (VTMS) as a precursor and CO2 as an oxidant. The properties of the films were compared with those films deposited with VTMS and O2. As-deposited films and the films annealed at 360 °C have been characterized. The growth rate decreased with increasing substrate temperature and increased with increasing CO2∕precursor ratio and plasma power. The dielectric constant was inversely proportional to the relative carbon content and the films deposited with CO2 had a higher carbon content than those deposited with O2. It was confirmed that CO2 was more effective to increase the carbon content. The refractive index of the as-deposited films was about 1.48–1.49 and decreased to 1.46 after annealing. The reduction of the refractive index was due to the lower density and increased porosity of the film. After annealing, the SiCOH films showed a low dielectric constant of 1.9 at optimum condition.
Show PACS
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.77.Dq Plasma-based ion implantation and deposition
77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)
68.55.-a Thin film structure and morphology
68.55.A- Nucleation and growth
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.40.Gh Other heat and thermomechanical treatments

Ag metallization on silicides with nitride barriers

M. M. Mitan, H. C. Kim, T. L. Alford, J. W. Mayer, G. F. Malgas, and Daniel Adams

J. Vac. Sci. Technol. B 22, 2804 (2004); http://dx.doi.org/10.1116/1.1815312 (7 pages)

Online Publication Date: 24 November 2004

Full Text: | Download PDF

Show Abstract
The thermal stability of Ag thin films on Ti–O–N/silicides (CoSi2 and NiSi) is investigated with various characterization techniques in this study. A Ti–O–N film was used as a diffusion barrier for Ag metallization. Silicide thin films are prepared by solid phase reactions utilizing metal/silicon bilayer structure. Rutherford backscattering spectrometry (RBS) of annealed films reveals Ag film changes to occur at 650 °C. Optical microscopy shows voids in the Ag film on the Ti–O–N diffusion barrier for temperature above 600 °C. Increasing anneal temperature up to 700 °C produces high density of voids in Ag films. Atomic force microscopy (AFM) shows the morphology of the voids that occur in the Ag film on the Ti–O–N barrier. RBS indicates some amount of Ag loss from the annealed samples at high temperatures. Secondary ion mass spectroscopy (SIMS) depth profiling reveals Ag diffusions to Ti–O–N/silicides/Si structures. We discuss the thermal stability and failure mechanism of Ag films on Ti–O–N/silicides/Si annealed at various temperatures.
Show PACS
68.60.Dv Thermal stability; thermal effects
66.30.Ny Chemical interdiffusion; diffusion barriers
85.40.Ls Metallization, contacts, interconnects; device isolation
68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.60.Bs Mechanical and acoustical properties
68.60.Wm Other nonelectronic physical properties
68.35.Fx Diffusion; interface formation
81.40.Gh Other heat and thermomechanical treatments

Fabrication and properties of ultranano, nano, and microcrystalline diamond membranes and sheets

D. K. Reinhard, T. A. Grotjohn, M. Becker, M. K. Yaran, T. Schuelke, and J. Asmussen

J. Vac. Sci. Technol. B 22, 2811 (2004); http://dx.doi.org/10.1116/1.1819928 (7 pages) | Cited 7 times

Online Publication Date: 24 November 2004

Full Text: | Download PDF

Show Abstract
Thin diamond membranes and free-standing sheets are of interest for a variety of potential applications. This article describes the film nucleation, microwave plasma-assisted chemical-vapor-deposition synthesis, and subsequent processing steps required to make free-standing strong and flexible diamond foils of several cm2. Films are initially deposited on silicon wafers as ultrananocyrstalline, nanocrystalline, or microcrystalline diamond by varying selected deposition parameters including gas composition, nucleation, power, substrate temperature, and pressure. Subsequently the diamond is separated from the original substrate and applied either to new substrates or to frames. Diamond membranes and sheets with thickness between 1 and 3 μm have been fabricated from each of these film types. The sheets are drapable and can be applied to curved surfaces and wrapped around cylinders. Properties of the films including optical transmission, Young’s modulus and fracture strength are described. Several examples of foils and associated frames and substrates are given.
Show PACS
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.A- Nucleation and growth
81.05.Cy Elemental semiconductors
81.07.Bc Nanocrystalline materials
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.D- Elasticity
62.20.M- Structural failure of materials
78.66.Db Elemental semiconductors and insulators

Ultraviolet-induced damage in fluorocarbon plasma and its reduction by pulse-time-modulated plasma in charge coupled device image sensor wafer processes

Mitsuru Okigawa, Yasushi Ishikawa, Yoshinari Ichihashi, and Seiji Samukawa

J. Vac. Sci. Technol. B 22, 2818 (2004); http://dx.doi.org/10.1116/1.1827219 (5 pages) | Cited 7 times

Online Publication Date: 24 November 2004

Full Text: | Download PDF

Show Abstract
Highly sensitive charge coupled device (CCD) image sensors present a number of serious problems, such as increased dark current and interface states induced by plasma etching processes. In particular, irradiation with ultraviolet (UV) photons (200 to 310 nm) generates this damage. UV absorption at the Si∕SiO2 interface may contribute to increasing the density of the interface states. To solve this problem we investigated optimum fluorocarbon gas chemistries and the effect of pulse-time-modulated (TM) plasma. We found that selecting appropriate gas chemistries and using TM plasma drastically reduced the dark current in CCDs.
Show PACS
42.79.Pw Imaging detectors and sensors
85.60.Gz Photodetectors (including infrared and CCD detectors)
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning

Nanostructures produced by ultraviolet laser irradiation of silicon. I. Rippled structures

A. J. Pedraza, Y. F. Guan, J. D. Fowlkes, and D. A. Smith

J. Vac. Sci. Technol. B 22, 2823 (2004); http://dx.doi.org/10.1116/1.1821575 (13 pages) | Cited 22 times

Online Publication Date: 24 November 2004

Full Text: | Download PDF

Show Abstract
One- and two-dimensional (1D and 2D) nanorippled structures produced in silicon by ultraviolet laser irradiation were investigated using atomic force and scanning electron microscopy. One- and two-beam illumination of the substrate was used to generate the nanostructures. Single-beam irradiation was done using p-polarized laser light, while the two-beam incidence was achieved employing a Lloyd’s mirror arrangement to reflect part of the beam onto the substrate. The structures were characterized by direct measurement of the ripple spacing or by measurements done on the fast Fourier transform of their atomic force microscopy (AFM) images. Under single-beam illumination, only 1D gratings were generated on the substrate surface. The grating lines were perpendicular to the projection of the electric field of the incident light on the substrate surface. For the two-beam illumination, it was very difficult to obtain the Lloyd’s mirror characteristic interference pattern due to the poor coherency of the laser employed. Nonetheless, the use of a Lloyd’s mirror not only enhanced the production of rippled structures strongly but also produced 2D gratings. The gratings generated with this arrangement are many millimeters long and cover the entire laser illuminated area. In contrast with one-beam illumination, linearly polarized light was not required to promote the rippled structures. Experimental evidence strongly suggests the following: (1) the p component of the laser light is responsible for ripple formation; (2) ripples can propagate with increasing number of pulses; and (3) the ripple structure is produced while the silicon is melted. The occurrence of melting is further supported by a computer simulation of the thermal field during the laser pulse. An estimate done using the lubrication approximation indicates that liquid is displaced from the hotter into the cooler regions by the gradient of surface tension. At angles of incidence equal or larger that 50°, the ripple spacing data indicate that incident laser light promotes the generation of plasma oscillation in the liquid silicon. These surface electromagnetic waves are responsible for the formation of ripples with lines that run parallel to the projection of the wave vector of the incident wave on the substrate surface. The simple irradiation procedure used to produce these nanostructures opens the possibility of using them as a template for ordering other nanostructures on a vast scale.
Show PACS
61.82.Fk Semiconductors
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
68.47.Fg Semiconductor surfaces
61.46.-w Structure of nanoscale materials
68.03.Cd Surface tension and related phenomena
81.07.-b Nanoscale materials and structures: fabrication and characterization
68.37.Ps Atomic force microscopy (AFM)

Nanostructures produced by ultraviolet laser irradiation of silicon. II. Nanoprotrusions and nanoparticles

Y. F. Guan, A. J. Pedraza, J. D. Fowlkes, and D. A. Joy

J. Vac. Sci. Technol. B 22, 2836 (2004); http://dx.doi.org/10.1116/1.1821576 (8 pages) | Cited 9 times

Online Publication Date: 24 November 2004

Full Text: | Download PDF

Show Abstract
Two-dimensional ordered nanoprotrusion arrays were produced at silicon surface substrates by nanosecond ultraviolet laser irradiation using a Lloyd’s mirror set up. These protrusions are 40 to 70 nm high and have a diameter of ∼60 to 100 nm at their base, and in many cases display a regular rectangular lattice. Their origin and evolution were studied using scanning electron microscopy and atomic force microscopy. Nanoprotrusions originate from a subjacent laser-induced periodic surface structure upon continuing irradiation, under the same processing conditions that produced these ripples. Their evolution is discussed in terms of fingering instabilities of melted silicon consistent with a gradient of surface tension due to a temperature gradient. The temperature gradient is produced by the same mechanism responsible for the ripple formation. At slightly higher laser fluences, nanoparticles were observed to form using a single beam of nonpolarized laser light. The nanoparticles also span a linear ordered array, with line spacing that conforms to the grating equation. Their formation mechanism has been described previously as a result of ablation and redeposition, and thus is widely different from the formation of nanoprotrusions. The differences and similarities of nanoprotrusions and nanoparticles, and their connection with nanoripples, were studied in detail. In particular, when the ripple structure was still seen, nanoprotrusions were observed to form on ripple crests while nanoparticles were located in ripple valleys. Nanoprotrusions remained stable under a 2 h thermal annealing at 1073 K. By contrast, the aligned nanoparticle arrays became disordered as a result of a 2 h anneal at a temperature as low as 423 K, as nanoparticles moved on the surface.
Show PACS
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Ps Atomic force microscopy (AFM)
61.46.-w Structure of nanoscale materials
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
81.40.Gh Other heat and thermomechanical treatments

Particle adhesion and removal mechanisms during brush scrubber cleaning

K. Xu, R. Vos, G. Vereecke, G. Doumen, W. Fyen, P. W. Mertens, M. M. Heyns, C. Vinckier, and J. Fransaer

J. Vac. Sci. Technol. B 22, 2844 (2004); http://dx.doi.org/10.1116/1.1815319 (9 pages) | Cited 11 times

Online Publication Date: 7 December 2004

Full Text: | Download PDF

Show Abstract
Brush scrubbers are among the most commonly used instruments for wafer-cleaning applications nowadays. However, the removal mechanisms of nanosized particles are far from clear, especially because no direct experimental data are available to backup theoretical models in the literature. This study combines a theoretical approach based on a force analysis with an experimental study of the removal of nanosized slurry particles. In the theoretical part, all forces affecting the adhesion and the removal of particles are evaluated to determine which are dominant in two extreme removal mechanisms: lifting and rolling. In the experimental part, the removal efficiency of 34 nm SiO2 particles is investigated by using the haze approach. Based on a study of the aging of contaminated wafers, conditions are selected where no chemical bonds are formed between a particle and a substrate. Force analysis and experimental observations both show that nanosized particles cannot be lifted directly by a brush. Instead, rolling should be the main particle-removal mechanism. The average fluid film thickness between brush and wafer surface is determined based on power measurements of the brush motor and a friction analysis, indicating that the system is in a hydrodynamic lubrication regime across a wafer in average. In this frame, results also show that the hydrodynamic drag force is the dominant removal force for nanosized particles.
Show PACS
81.65.Cf Surface cleaning, etching, patterning
81.40.Pq Friction, lubrication, and wear
81.40.Gh Other heat and thermomechanical treatments
82.70.Kj Emulsions and suspensions
68.35.Np Adhesion

Application of ion beam etching technique to the direct fabrication of silicon microtip arrays

Xinyu Zhang, Qingle Tang, and Junming Tang

J. Vac. Sci. Technol. B 22, 2853 (2004); http://dx.doi.org/10.1116/1.1826061 (7 pages) | Cited 1 time

Online Publication Date: 9 December 2004

Full Text: | Download PDF

Show Abstract
A relatively simple and effective method to directly fabricate large-area field emission microtip arrays on n-type silicon wafers is proposed. The presented fabrication approach of silicon microtip devices mainly involves photolithography, thermal shaping and consolidation, argon ion beam etching and sputtering deposition. The measurements show that the silicon field emission microtip devices fabricated have good structural uniformity and electrical characteristics. The center-to-center spacing of microtips fabricated is 50 μm and the typical microtip height about 11 μm. The scanning electron microscope analysis and the surface style measurements are carried out for the surface morphologies of silicon microtips, such as square-bottom pyramid-shaped microtips, cone-shaped microtips, square-bottom circle-microtips, and circle-bottom circle-microtips. Electrical measurements are performed to obtain the typical field emission properties of the devices. The experiment results show that the method utilized can be applied to fabricate silicon field emission microtip arrays and circle-microtip arrays of larger area.
Show PACS
85.45.Db Field emitters and arrays, cold electron emitters
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
85.40.Hp Lithography, masks and pattern transfer
81.15.Cd Deposition by sputtering
42.82.Cr Fabrication techniques; lithography, pattern transfer
85.40.Sz Deposition technology
68.47.Fg Semiconductor surfaces
back to top
RSS Feeds

Cold-field-emission tips aging study using surface potential measurements

H. Dongmo, C. Guasch, and J. Bonnet

J. Vac. Sci. Technol. B 22, 2860 (2004); http://dx.doi.org/10.1116/1.1815317 (3 pages)

Online Publication Date: 9 December 2004

Full Text: | Download PDF

Abstract Unavailable
Show PACS
79.70.+q Field emission, ionization, evaporation, and desorption
back to top
RSS Feeds

Erratum: Nanofabrication using structure controlled hydrogenated Si clusters deposited on Si surfaces [J. Vac. Sci. Technol. B 18, 3497 (2000)]

Toshihiko Kanayama, Miyoko O. Watanabe, Lonid Bolotov, and Noriyuki Uchida

J. Vac. Sci. Technol. B 22, 2863 (2004); http://dx.doi.org/10.1116/1.1825021 (1 page)

Online Publication Date: 9 December 2004

Full Text: | Download PDF

Abstract Unavailable
Show PACS
99.10.Cd Errata
81.15.Jj Ion and electron beam-assisted deposition; ion plating
81.05.Cy Elemental semiconductors
81.16.-c Methods of micro- and nanofabrication and processing
81.07.-b Nanoscale materials and structures: fabrication and characterization
back to top
RSS Feeds
back to top Plenary

Liquid immersion lithography: Why, how, and when?

M. Rothschild, T. M. Bloomstein, R. R. Kunz, V. Liberman, M. Switkes, S. T. Palmacci, J. H. C. Sedlacek, D. Hardy, and A. Grenville

J. Vac. Sci. Technol. B 22, 2877 (2004); http://dx.doi.org/10.1116/1.1802955 (5 pages) | Cited 15 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Liquid immersion lithography, especially at 193 nm, is a serious candidate for extending projection optical lithography to the 65 nm node and beyond. This article reviews the status of this technology, the potential pitfalls that it may still encounter, and also the potential to extend it to 157 nm and to higher-index liquids. At 193 nm, no fundamental obstacles have been found yet, although defect control and materials compatibility must still be worked out. At 157 nm, significant progress has been made in developing suitable liquids. The next hurdle is to increase their refractive index, in order to make the transition in wavelengths cost-effective.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
01.30.Rr Surveys and tutorial papers; resource letters

Reaching for the bottom: The evolution of EIPBN

Henry I. Smith and R. Fabian Pease

J. Vac. Sci. Technol. B 22, 2882 (2004); http://dx.doi.org/10.1116/1.1828088 (3 pages)

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
The International Conference on Electron, Ion, and Photon Beam Technology and Nanofabrication (EIPBN) had its origins 45 years ago in electron-beam welding, but the focus soon shifted to microfabrication techniques. Since the early 1960’s, EIPBN has been the premier conference for reporting innovations in micro- and nanofabrication techniques, with a consistent goal of pushing to finer features and practical applications in research and industry. The conference name has evolved to reflect the changes in technology. With the exception of a few years, when some of the conferences were managed by the Electrochemical Society, the conference has been run by volunteers who are also active researchers. This has been one of its strengths, ensuring annual renewal of objectives and directions. In this article we identify some highlights in the history of EIPBN and suggest a direction for the conference in this era of nanotechnology.
Show PACS
01.60.+q Biographies, tributes, personal notes, and obituaries
01.10.Fv Conferences, lectures, and institutes
back to top Electron Beam Lithography

Full-field exposure performance of electron projection lithography tool

Kazuaki Suzuki, Noriyuki Hirayanagi, Tomoharu Fujiwara, Atsushi Yamada, Junji Ikeda, Takehisa Yahiro, Shinichi Kojima, Jin Udagawa, Hajime Yamamoto, Norihiro Katakura, Motoko Suzuki, Takashi Aoyama, Hidekazu Takekoshi, Takaaki Umemoto, Hiroyasu Shimizu, et al.

J. Vac. Sci. Technol. B 22, 2885 (2004); http://dx.doi.org/10.1116/1.1808715 (6 pages) | Cited 3 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Electron projection lithography (EPL) is a realistic technology for the 65 nm node and below, as a complementary technology of optical lithography especially for contacts and gate layers because of its high resolution and large process margin. Nikon has developed an EPL exposure tool as an electron-beam (EB) stepper and the first generation EB stepper; NSR-EB1A is now almost completed as an R&D tool for the 65 nm technology node. Using a ϕ200 mm reticle, a 20 mm×25 mm exposure field is realized. Full-field exposure performance of NSR-EB1A is shown. A 70 nm isolated line and 1:1 nested lines are simultaneously resolved, as are 50 nm 1:2 nested lines. 60 nm contact holes are resolved with a depth of focus over a 10 μm range and dosage window over ±6%. Stitching accuracy is about 20 nm (3σ) and the single machine overlay is about 30 nm (mean+3σ). These data mean sufficient performance for device manufacturing of the 65 nm technology node. The concept of a large subfield is one candidate for resolution and throughput enhancement in EPL production tool. The Coulomb blur is directly measured by an aerial image sensor for a large subfield and small beam half-angle, and the data show good agreement with simulations. It is shown that throughput over 20 wafers per hour (ϕ300 mm) is realistic and achievable in a production tool of a 45 nm technology node.
Show PACS
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer

Influence of Coulomb effects on electron projection lithography process

Jiro Yamamoto, Hiroshi Yamashita, Masaki Yamabe, and Hiroshi Arimoto

J. Vac. Sci. Technol. B 22, 2891 (2004); http://dx.doi.org/10.1116/1.1821571 (6 pages) | Cited 3 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Electron projection lithography (EPL) is an attractive candidate for next-generation lithography. In EPL, Coulomb effects consisting of a global space charge and stochastic Coulomb effect are a concern because of the huge beam current exposure required. We discuss the influence of the Coulomb effects in EPL. Proximity and Coulomb effects are known to degrade resolution and dose margin. To discriminate between the influence of Coulomb effects on exposure results from those of the proximity effect, we used complementary exposures. We found that a resolution of 1:1 L&S at a 6.9 μA beam current on a wafer was 100 nm and at a 1.3 μA beam current was 65–70 nm. These results roughly met specifications of the EPL system, NSR-EB1A. We found, however, that the beam blur varied within a subfield, and the difference between CD at 0.5 and 6.4 μA at 100 nm was 12 nm due to the different beam blur, even if the space-charge effect was corrected by refocusing. To achieve accurate CD control, the proximity effect must thus be corrected considering beam blur distribution in the subfield.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

Probe shape measurement in an electron beam lithography system

J. Alexander Liddle, Patrick Naulleau, and Gerard Schmid

J. Vac. Sci. Technol. B 22, 2897 (2004); http://dx.doi.org/10.1116/1.1821579 (5 pages) | Cited 6 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
We have devised a method of quantifying the size and shape of the probe in a Gaussian-beam lithography system. The technique is robust, being insensitive to noise, but is sensitive to changes in the probe size of as little as ±0.5 nm. We have determined that the probe shape of our system is indeed well fit by a Gaussian, with a best-focus full-width half-maximum of 6.5±1 nm. We are able readily to quantify the effects of astigmatism on the system. In addition, the approach we describe can be extended to deal with arbitrary point-spread functions.
Show PACS
41.85.Gy Chromatic and geometrical aberrations
85.40.Hp Lithography, masks and pattern transfer

Electron-beam-based photomask repair

Klaus Edinger, Hans Becht, Johannes Bihr, Volker Boegli, Michael Budach, Thorsten Hofmann, Hans W. P. Koops, Peter Kuschnerus, Jens Oster, Petra Spies, and Bernd Weyrauch

J. Vac. Sci. Technol. B 22, 2902 (2004); http://dx.doi.org/10.1116/1.1808711 (5 pages) | Cited 22 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
High-resolution electron-beam-assisted deposition and etching is an enabling technology for current and future generation photomask repair. NaWoTec in collaboration with Carl Zeiss NTS (formerly LEO Electron Microscopy) has developed a mask repair tool capable of processing a wide variety of mask types, such as quartz binary masks, phase shift masks, extreme ultraviolet masks, and e-beam projection stencil masks. Specifications currently meet the 65 nm device node requirements, and tool performance is extendible to 45 nm and below. The tool combines LEO’s ultra-high-resolution Supra scanning electron microscope platform with NaWoTec’s proprietary e-beam deposition and etching technology, gas delivery system, and mask repair software. In this article, we focus on tool performance results; that is, the reproducibility and accuracy of repair of clear and opaque programmed defects on Cr binary and MoSi phase shift masks. These masks have in the past been difficult to repair due to beam position instability caused by charging of the insulating quartz areas. We have found and implemented a solution to this charging problem and have demonstrated in spec repair of various defect types. The extendibility of e-beam-based repair technology to future lithography nodes, both in terms of the required resolution and the ability to repair next generation lithography mask types, will also be addressed.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

Electron beam induced conductivity in polymethyl methacrylate, polyimide, and SiO2 thin films

Min Bai and Fabian Pease

J. Vac. Sci. Technol. B 22, 2907 (2004); http://dx.doi.org/10.1116/1.1826062 (5 pages) | Cited 5 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Electron beam induced conductivity (EBIC) is one sensitive parameter that controls the charging of insulating materials under electron beam irradiation. In an earlier work [J. Vac. Sci. Technol. B 21, 2638 (2003)], we reported the measurement of EBIC in polymethyl methacrylate (PMMA) and thermal SiO2 thin films using an external bias method. The thin films under test were sandwiched between a silicon substrate and a metal electrode. One important observation is that the exposed region in the PMMA resist is ohmic regardless of the bias polarity. However, the EBIC in the metal-thermal oxide-silicon structure is highly asymmetric under opposite bias polarities. A model involving the internal emission of secondary electrons was proposed to interpret the asymmetric EBIC in thermal oxide. In this study, we extend the EBIC measurements to deposited SiO2 thin film and another polymeric material, polyimide. By putting the deposited oxide between symmetric metal electrodes, we validated the conjecture of the internal secondary electron emission from silicon substrate into thermal oxide when silicon is used as the bottom electrode. The results on deposited oxide also implicate the close dependence of EBIC in oxide on the property of Si∕SiO2 interface. On the other hand, under the same exposure condition, polyimide thin film is 50 times more conductive than PMMA, probably as a result of their different molecular structures.
Show PACS
73.61.Ph Polymers; organic compounds
73.61.Ng Insulators
61.80.Fe Electron and positron radiation effects
79.20.Hx Electron impact: secondary emission
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Full MEMS monolithic microcolumn for wafer-level arrayal

Hak Kim, Changho Han, Jinkwang Kim, Hoseob Kim, and Kukjin Chun

J. Vac. Sci. Technol. B 22, 2912 (2004); http://dx.doi.org/10.1116/1.1824952 (5 pages) | Cited 3 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Recently, an advanced microcolumn concept for improved throughput was proposed. However, due to the complexity of the approach, the miniaturization was limited. In addition, microcolumns must run under ultrahigh vacuum conditions in order to obtain stable electron emission at the field-emission tip. Both signal and power lines need to be connected through the ultrahigh vacuum chamber. Therefore, increases in the number of microcolumn arrays necessitate more wiring from the external control unit to the internal units, and the number of wires can become prohibitive. To solve this problem, a new concept, exploiting the possibility of an arrayed microcolumn which uses microelectromechanical systems (MEMS) technology has been developed. This paper describes a monolithic (3×3 arrayed) microcolumn, which consists of a cold field-emission tip, an input lens, an einzel lens, and novel deflectors for multiple-arrayed microcolumns. We also describe its fabrication process, which relies on improved microfabrication and MEMS technology, most notably multiwafer anodic bonding techniques and copper electroplating for the double metallization process. This paper describes an electro-optical analysis and an optimization using an equivalent circuit and a newly proposed simulation tool. We focus on the production possibilities for microcolumns constructed using MEMS technology. The emission current of the fabricated tungsten and molybdenum cold field-emission tip was several microamperes for an applied gate voltage of 100 V. The probe current, which was measured in the sample grid of the wafer stage, was about 1 nA. The amount of electron-beam deflection was proportional to the applied voltage at the deflector, and operated at about 1 μm∕V.
Show PACS
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
85.45.Db Field emitters and arrays, cold electron emitters
85.40.Ls Metallization, contacts, interconnects; device isolation

Variable cell projection as an advance in electron-beam cell projection system

Akio Yamada and Takayuki Yabe

J. Vac. Sci. Technol. B 22, 2917 (2004); http://dx.doi.org/10.1116/1.1808741 (6 pages) | Cited 5 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
As an advance in the electron-beam cell projection system, we have developed a deflection control and correction unit of the variable cell projection (VCP) system, which can increase the variety of projected images through a block of patterns on a CP mask. We estimate the extent of the minimum spacing between two patterns distinguished by partial illumination to be 58 nm on a wafer, which is due to the beam blur of 28 nm and the illuminating beam edge rotation of 6 mrad relative to the CP mask patterns. Exposure results show that the VCP can actually distinguish the patterns separated by 80 nm on a wafer. We also show that the VCP can improve the uniformity of linewidths of exposed patterns by about 5 nm compared with the simple VSB method.
Show PACS
85.40.Hp Lithography, masks and pattern transfer

3D proximity effect correction based on the simplified electron energy flux model in electron-beam lithography

Morimi Osawa, Kozo Ogino, Hiromi Hoshino, Yasuhide Machida, and Hiroshi Arimoto

J. Vac. Sci. Technol. B 22, 2923 (2004); http://dx.doi.org/10.1116/1.1824201 (6 pages) | Cited 2 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
We have confirmed the adequacy of simplified electron energy flux (SEEF) model which can be used in proximity effect correction (PEC) in electron beam lithography. The SEEF model enables calculation of the backscattering energy in a multiwiring structure by obtaining a transmission and reflection energy flux map. We prepared a substrate which contained three pairs of W-plug layers and inter-metal dielectric (IMD) layers, and obtained parameters for correction. The extracted transmittance and reflectance were 1 and 0 for the dielectrics, and 0 and 1.7 for the W plugs. The backscattering energies calculated by using these parameters corresponded with experimental data under the various conditions. We also extracted the scattering range of incident and reflected electrons in dielectrics. We found that the ranges of the reflected electrons were greater than those of the incident electrons because of a wider spread of angle. PEC based on the SEEF model enabled high CD accuracy even at the end of the W-plug area. We thus confirmed that the SEEF model can accommodate complex effects, such as scattering in a multiwiring structure or the screening effect, by following the electron’s path.
Show PACS
85.40.Hp Lithography, masks and pattern transfer

Representation of nonrectangular features for exposure estimation and proximity effect correction in electron-beam lithography

S.-Y. Lee, F. Hu, and J. Ji

J. Vac. Sci. Technol. B 22, 2929 (2004); http://dx.doi.org/10.1116/1.1824058 (7 pages) | Cited 1 time

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
In most proximity effect correction schemes, circuit features are assumed to be rectangular. However, there are many circuit patterns which contain nonrectangular shapes of features such as circles, circular arcs, polygons, etc. In this article, efficient ways to handle such features for exposure estimation required in proximity effect correction are proposed. A hierarchical approach, where a nonrectangular feature is partitioned into correction shapes first, and then each correction shape may be further decomposed into exposure shapes if necessary, is taken in order to develop efficient and generally applicable schemes. Specifically, for exposure estimation, four schemes (direct, slicing, hybrid, and coordinate transformation methods) are described, of which performances have been analyzed through an extensive simulation.
Show PACS
85.40.Hp Lithography, masks and pattern transfer

Electron beam lithography for data storage: Quantifying the proximity effect as a function of CAD design and thin metal layers

Andrew Eckert and Keith Mountfield

J. Vac. Sci. Technol. B 22, 2936 (2004); http://dx.doi.org/10.1116/1.1815297 (7 pages) | Cited 2 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
We have characterized the e-beam proximity effect as it applies to the write pole break-point angle of magnetic recording heads. These narrow isolated negative resist lines have been measured using an automated CD-SEM. The CD data allows us to quantify the e-beam proximity effect on silicon wafers with thin metallic films of varying thickness. Nickel and tantalum have atomic numbers of 28 and 73, respectively, and this difference is quantified by the increase in the CD of the Ta films compared to Ni. The CD was found to change at a rate of 0.17 nm per degree of break-point angle for the Ni films, and 0.25 nm per degree for Ta. We have analyzed the experimental data by comparing it to two relevant models. First, we compare the data to the traditional expression used to describe e-beam exposure, a double Gaussian. From both the CD data and the double Gaussian, we calculate a proximity effect term we refer to as the dose fraction. This dose fraction has a linear relationship with the “eta” parameter, which also relates the contribution of forward to back scattered electrons in the final exposure profile. We determine both a dose fraction, and the “eta” parameter, for each substrate material and thickness. Second, we compare this dose fraction term to a simple Rutherford elastic scattering model. The final outcome of this work is a quantifiable measure of how the break-point angle contributes to the final CD of the write pole when employing e-beam lithography. This work also demonstrates a practical way to quantify the e-beam proximity effect by the calculation of dose fraction and “eta” as a metric of metal layer material and thickness.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography
75.50.Ss Magnetic recording materials
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Experimental and simulation comparison of electron-beam proximity correction

L. H. A. Leunissen, R. Jonckheere, U. Hofmann, N. Ünal, and C. Kalus

J. Vac. Sci. Technol. B 22, 2943 (2004); http://dx.doi.org/10.1116/1.1808742 (5 pages)

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
In electron-beam lithography, electron scattering in the resist, and underlying substrate limits the control over feature sizes [M. Parikh, J. Vac. Sci. Technol. 19, 1275 (1981)]. To correct for this effect, one applies the so-called “proximity correction” that adjusts the beam dose of each individual feature. The algorithms that are commonly used to calculate this correction model the electron scattering as a double-Gaussian function. However, a point-spread function (PSF) describes the scattering process more accurately. Therefore, we have investigated whether the use of the PSF in the proximity correction algorithm leads to an increase in feature size control; as compared to the double-Gaussian PSF. In order to compare the two PSFs directly, we have performed a proximity correction on a pattern of contact holes, using each of the approximations. Our measurements show that the algorithm using the PSF performs a substantially better proximity correction, leading to a more accurate control over the contact hole sizes. Moreover, we have developed a method to assess the proximity correction’s success using the SELID [M. Bohn et al., Proc. SPIE 5256, 695 (2003)] simulation program. This strongly reduces the need for costly and time-consuming experiments.
Show PACS
85.40.Hp Lithography, masks and pattern transfer

Optimum dose for shot noise limited CD uniformity in electron-beam lithography

P. Kruit, S. Steenbrink, R. Jager, and M. Wieland

J. Vac. Sci. Technol. B 22, 2948 (2004); http://dx.doi.org/10.1116/1.1821577 (8 pages) | Cited 9 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
To maximize the performance of an electron-beam lithography system the resist sensitivity must be chosen carefully. Very sensitive resists require only a low illumination dose, thus increasing the throughput. However, shot noise effects may give rise to unacceptable line edge roughness and variations in critical dimension (CD). In this study, the physical parameters which influence the effect of shot noise statistics on CD uniformity (CD-u) and linewidth roughness (LWR) are determined and an analytical model for CD-u and LWR is derived. It is found that the CD-u and LWR depend on the dose, the Gaussian beam probe size, the diffusion length dr of secondary electrons and acids in resist. The influence of background dose and non-shot-noise dose variations must also be taken into account. Monte Carlo simulations are performed to obtain the statistical variation of the two-dimensional solubility distribution of illuminated resist in a developer. The results of this simulation are used to validate the model. For the CD-u and the LWR, different expressions were found for describing the effect of the shot noise because, to describe the LWR, an extra factor must be incorporated to include the effect that spatial frequencies lower than 2 CDs do not have a contribution. Also, the area over which the dose must be integrated for the shot noise calculation is different for CD-u and LWR. For CD-u this area depends on dr⋅CD, for LWR on dr2. From the model it can be concluded that shot noise has a significant effect on both the CD uniformity and the LWR and cannot be neglected in the optimization of the dose for high-throughput electron-beam lithography. With the specific relation between the current and the resolution of an e-beam tool, an expression for CD uniformity is found from which the throughput can be maximized for the required CD-u by optimizing the dose, probe size, and diffusion parameter. The background dose and the other dose variations are input parameters for such an optimization. For electron-beam systems with a typical resolution of 30 nm and a required CD uniformity contribution of 3.5 nm (3σ) due to all dose variations, a dose of 30 μC∕cm2 is needed if 20% background and 3% (3σ) non-shot-noise dose variations are taken into account.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
back to top EUV Lithography

At-wavelength alignment and testing of the 0.3 NA MET optic

Kenneth A. Goldberg, Patrick P. Naulleau, Paul E. Denham, Senajith B. Rekawa, Keith Jackson, Erik H. Anderson, and J. Alexander Liddle

J. Vac. Sci. Technol. B 22, 2956 (2004); http://dx.doi.org/10.1116/1.1815303 (6 pages) | Cited 17 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Extreme ultraviolet (EUV) interferometry has been successfully performed for the first time at 0.3 numerical aperture (NA). Extensive EUV “at-wavelength” testing including alignment, was performed on a newly created Micro Exposure Tool (MET) optic designed for sub-50-nm EUV lithographic imaging experiments. The two-mirror, 0.3 NA MET is among the highest resolution light-projection lithography tools ever made. Using both lateral shearing and phase-shifting point-diffraction interferometry, the wavefront was measured across the field of view, and the alignment was optimized in preparation for imaging. The wavefront quality reached 0.55 nm RMS (λEUV∕24.5) in a 37-term annular Zernike polynomial series, dominated by higher-order spherical aberration. Measurements included calibrations of the interferometer accuracy, assessment of repeatability, and cross-comparisons of visible and EUV interferometric measurements.
Show PACS
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.87.Bg Phase shifting interferometry
42.79.Bh Lenses, prisms and mirrors
42.15.Fr Aberrations

Extreme ultraviolet microexposures at the Advanced Light Source using the 0.3 numerical aperture micro-exposure tool optic

Patrick P. Naulleau, Kenneth A. Goldberg, Erik Anderson, Jason P. Cain, Paul Denham, Keith Jackson, Anne-Sophie Morlens, Seno Rekawa, and Farhad Salmassi

J. Vac. Sci. Technol. B 22, 2962 (2004); http://dx.doi.org/10.1116/1.1802851 (4 pages) | Cited 17 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
In an effort to continue the rapid pace of extreme ultraviolet (EUV) learning, the focus of developmental EUV lithography has shifted from low numerical aperture (NA) tools such as the 0.1 NA engineering test stand to higher NA tools such as the 0.3 NA micro-exposure tool (MET). To support this generation of lithographic optics, a static printing station has been developed at the Advanced Light Source. This synchrotron-based printing system relies on a scanning illuminator to provide real-time coherence (pupil-fill) control. Here, we describe a MET printing station and present early printing results obtained with the Sematech Set-2 MET optic. The resolution limit of baseline EUV resist is presented as well as 30 nm equal-line-space printing in an experimental resist.
Show PACS
42.82.Cr Fabrication techniques; lithography, pattern transfer
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer

Effects of flare in extreme ultraviolet lithography: Learning from the engineering test stand

Manish Chandhok, Sang H. Lee, and Terence Bacuita

J. Vac. Sci. Technol. B 22, 2966 (2004); http://dx.doi.org/10.1116/1.1824068 (4 pages) | Cited 20 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
One of the technical challenges for introducing extreme ultraviolet lithography (13.5 nm) into high volume manufacturing is flare. Flare reduces aerial image contrast and creates critical dimension (CD) variations across the die due to local chrome density dependent flare variations. Therefore, it is important to experimentally characterize flare on a full-field stepper and develop methods to mitigate and compensate for its effects. In this article, the impact of flare on depth of focus and exposure latitude are experimentally quantified using the engineering test stand. In addition, we report a marked increase in line width roughness due to high levels of flare in the optical system. A technique for the extraction of the point spread function due to scatter using density dependent CD data has been demonstrated for more accurate flare variation compensation.
Show PACS
85.40.Hp Lithography, masks and pattern transfer

Phase measurement of reflection of EUV multilayer mirror using EUV standing waves

Akira Miyake, Mitsuaki Amemiya, Fumitaro Masaki, and Yutaka Watanabe

J. Vac. Sci. Technol. B 22, 2970 (2004); http://dx.doi.org/10.1116/1.1815302 (5 pages) | Cited 5 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Projection optics of an EUV lithography system consists of multilayer mirrors. Phase of the incident beam is shifted on reflection at the multilayer mirror [Y. Watanabe et al., Jpn. J. Appl. Phys. 30, 3053 (1991)]. If the phase shift at reflection of a multilayer is not well controlled, it becomes the cause of wavefront aberration. The phase shift depends on the incident angle and the wavelength of the beam. The phase shift is also dependent on the structure of the multilayer. Certain kinds of structural change cause non-negligible variation of the phase shift with very little change of wavelength dependency of reflectivity. Therefore, not only reflectivity measurement but also measurement of phase shift is essential to manufacture multilayer mirrors for projection optics. X-ray standing wave technique has been used to characterize multilayer structure [B. Lai et al., Nucl. Instrum. Methods Phys. Res. A 266, 684 (1988); T. Kawamura and H. Takenaka, J. Appl. Phys. 75, 3806 (1996)]. Intensity of electric field, which generates photoelectrons, near a multilayer surface depends not only on the intensity of incident beam but also on the phase shift and the reflectivity. EUV reflectivity and photo-yield of Mo∕Si multilayer samples were measured using a laser produced plasma source (LPP) based EUV reflectometer [A. Miyake, Proc. SPIE 5037, 647 (2003)]. Thickness ratio Γ is the ratio of the thickness of molybdenum layer to the multilayer period. Γ of each sample is changed by 2% step. According to a simulation, it corresponds to variation of phase shift by 0.02πstep, in other words, variation of wavefront by 10 mλstep. Measured wavelength dependencies of photo-yield for each sample are clearly separated. From the results of this experiment, it is shown that phase shift on multilayer reflection can be detected at a resolution of 0.02π rad.
Show PACS
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.79.Bh Lenses, prisms and mirrors
42.15.Fr Aberrations

Development of projection optics set-3 for high-numerical-aperture extreme ultraviolet exposure tool (HiNA)

Tetsuya Oshino, Shinichi Takahashi, Takahiro Yamamoto, Tatsuya Miyoshi, Masayuki Shiraishi, Takaharu Komiya, Noriaki Kandaka, Hiroyuki Kondo, Kiyoto Mashima, Kazushi Nomura, Katsuhiko Murakami, Takeshi Okuyama, Hiroaki Oizumi, Iwao Nishiyama, and Shinji Okazaki

J. Vac. Sci. Technol. B 22, 2975 (2004); http://dx.doi.org/10.1116/1.1808734 (5 pages) | Cited 7 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
We have developed a high-numerical-aperture extreme ultraviolet exposure tool (HiNA). HiNA is equipped with an illumination system, projection optics, a mask stage, and a wafer stage in the vacuum chamber. The projection optics consist of two aspherical mirrors (M1 and M2). The numerical aperture of the optics is 0.3. Thus far, we fabricated two sets of projection optics (set-1 and set-2). The wave-front errors of set-1 and set-2 were 7.5 and 1.9 nm rms, respectively. We developed a third set of projection optics (set-3), the target wave-front error of which was less than 1 nm rms. In set-3, we also attempted to reduce flare. We completed the mirror polishing, coating, and mirror adjustment of set-3. By using a recently developed polishing method, we reduced low-spatial-frequency roughness (LSFR), mid-spatial-frequency roughness (MSFR), and high-spatial-frequency roughness, simultaneously. The predicted wave-front error calculated from the LSFR number was 0.69 nm rms. MSFR, which strongly affects the flare of the optics, was significantly reduced to less than 0.2 nm rms. The estimated flare was 7%, which is significantly reduced to one-forth that of set-2. The wave-front error of set-3 was measured with the visible-light point diffraction interferometer after coating and assembly. The wave-front error measured after adjustment was 0.85 nm rms, which is less than one-half the wave-front error of set-2. Set-3 will be completed after the cramping of the adjustment system, which is performed to prevent mirror displacement during transportation.
Show PACS
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.79.Bh Lenses, prisms and mirrors
81.65.Ps Polishing, grinding, surface finishing

Astigmatism measurement by lateral shearing interferometer

Zhiqiang Liu, Kasumi Sugisaki, Mikihiko Ishii, Yucong Zhu, Jun Saito, Akiyosi Suzuki, Masanobu Hasegawa, and Katsuhiko Murakami

J. Vac. Sci. Technol. B 22, 2980 (2004); http://dx.doi.org/10.1116/1.1815307 (4 pages)

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
In the lateral shearing interferometer for EUVL PO at-wavelength measurement, a grating is used to separate and shear the test wavefront. Normally, the astigmatism component of the test wavefront is difficult to be measured from the phase distribution tilt because the grating position influences it also. We found the grating position influences the tilt component of the interferogram phase distribution along the shear direction only. A part of the astigmatism can be measured from the tilt component perpendicular to the shear direction. To measure the other part of astigmatism, we perform a measurement with the shear direction in 45°. From the tilt component of the phase distribution in 135°, the other part of the astigmatism can be measured. By these two measurements, the whole astigmatism can be measured. We analyzed the measurement errors and showed the conditions for high accuracy astigmatism measurement.
Show PACS
07.60.Ly Interferometers
42.15.Fr Aberrations
42.79.Dj Gratings
42.15.Dp Wave fronts and ray tracing

Angular dependency of off-axis illumination on 100-nm-width pattern printability for extreme ultraviolet lithography: Ru/Mo/Si reflector system

In-Yong Kang, Yong-Chae Chung, Jinho Ahn, Hye-Keun Oh, Takeo Watanabe, and Hiroo Kinoshita

J. Vac. Sci. Technol. B 22, 2984 (2004); http://dx.doi.org/10.1116/1.1824056 (3 pages)

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
The pattern printability of the Ru/Mo/Si system was quantitatively investigated by two successive schemes, reflectivity of the mask, and aerial image intensity transferred through the system. The reflectivity of a Ru/Mo/Si reflector was calculated and compared with the value of Mo/Si reflector for various incident angles (0°–5°) using Fresnel equation. In order to verify angular dependency of aerial image intensity in a Ru/Mo/Si reflector, we employed SOLID-EUV, which is capable of rigorous electromagnetic field computation. In the calculation, 100 nm line and space pattern was generated by 2D mask geometry with perfect absorber of opaque material. Through the investigation of the angular dependency on the pattern printability of Ru/Mo/Si and Mo/Si reflectors, we could suggest the optimal reflector system for specific condition of incident angle, i.e., Ru/Mo/Si system for ≲3° and Mo/Si system for ≳4° for maximizing optical performance of the EUVL system.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
back to top Ion Beam Lithography

Conductive nanostructure fabrication by focused ion beam direct-writing of silver nanoparticles

David S. Kong, Jonathan S. Varsanik, Saul Griffith, and Joseph M. Jacobson

J. Vac. Sci. Technol. B 22, 2987 (2004); http://dx.doi.org/10.1116/1.1825015 (5 pages)

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
A focused ion beam has been used to directly pattern thin films of organometallic silver nanoparticles down to a resolution of 100 nm. The unexposed regions were washed in hexane leaving the desired pattern, and subsequent annealing formed conductive, metallic features. Multiple-layer structures were also fabricated by spin-coating and exposing additional films of silver nanoparticles on top of already patterned structures. The sensitivity of the nanoparticles to 30 keV Ga+ ions was measured to be approximately 5 μC∕cm2. Using this technique test structures were fabricated in two and three dimensions with resistivities as low as 288 μΩ cm and 13 μΩ cm for single- and multiple-layer structures, respectively, as compared to a value of 1.589 μΩ cm for bulk silver. To our knowledge, this is the highest demonstrated throughput for any electron or ion beam direct-write process utilizing metal-organic precursors.
Show PACS
81.07.Bc Nanocrystalline materials
61.80.Jh Ion radiation effects
61.46.-w Structure of nanoscale materials
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
81.40.Gh Other heat and thermomechanical treatments

Single ion implantation with scanning probe alignment

A. Persaud, F. I. Allen, F. Gicquel, S. J. Park, J. A. Liddle, T. Schenkel, Tzv. Ivanov, K. Ivanova, I. W. Rangelow, and J. Bokor

J. Vac. Sci. Technol. B 22, 2992 (2004); http://dx.doi.org/10.1116/1.1802891 (3 pages) | Cited 7 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
We present results from our development of a single ion implantation technique integrated with a scanning force microscope. Accurate alignment at the 5 nm level is a crucial requirement for reliable single ion placement. We address this through integration of the ion beam with a scanning probe tip containing an aperture. Single ion registration is based on detection of secondary electron bursts from single, high charge state ions. We describe formation of scanning probe tips with holes and sensing poles by focused ion and electron beam processing (drilling and thin film deposition). Ion transport studies through apertures show stable transmission for >10 h with 1 nA scale beam intensities on precollimators.
Show PACS
07.79.Lh Atomic force microscopes
61.80.Jh Ion radiation effects

Advanced nanoscale material processing with focused ion beams

A. Lugstein, B. Basnar, J. Smoliner, E. Bertagnolli, and M. Weil

J. Vac. Sci. Technol. B 22, 2995 (2004); http://dx.doi.org/10.1116/1.1813467 (5 pages) | Cited 4 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
We present an approach for the generation of metallic Ga dots and In nano-crystallites which, in contrast to conventional bottom-up or top-down processes, is based on a subtractive self-organization process relying on material decomposition induced by focused ion beam exposure. The diameters of the Ga dots range from 120 to 850 nm with an aspect ratio of about 0.4 at a dot density of up to 7×107∕cm2. Two-dimensional ordered arrays of freestanding dots were fabricated by a site control technique relying on prepatterned holes and an irradiation mediated migration and agglomeration. By the analogous technique we generated indium nanocrystallites on the (100) InAs surface with sizes ranging from about 50 nm to a few microns obviously due to a preferential loss of arsenic atoms during Ga+ focused ion beam irradiation. The influence of the ion dose, the beam energy, and the dose rate on the surface evolution was investigated by atomic force microscopy, scanning electron microscopy, Auger electron spectroscopy, and x-ray diffraction measurements.
Show PACS
81.07.Ta Quantum dots
81.07.Bc Nanocrystalline materials
61.80.Jh Ion radiation effects
81.16.Dn Self-assembly

Focused ion beam induced deposition of low-resistivity copper material

Thomas J. Gannon, George Gu, J. David Casey, Chuong Huynh, Neil Bassom, and Nicholas Antoniou

J. Vac. Sci. Technol. B 22, 3000 (2004); http://dx.doi.org/10.1116/1.1826065 (4 pages) | Cited 4 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Focused ion beam (FIB) induced processes for material etching and deposition have proven successful in integrated circuit device modification applications. Current FIB metal deposition processes are typically limited to resistivities in the range of 150–200 μΩ cm due to included impurities; however, today’s high-frequency devices require very low interconnect resistivity. The organometallic precursor material copper (I) hexafluoroacetylacetonate trimethylvinylsilane, or Cu(hfac)TMVS for FIB-assisted metal deposition was investigated. 50 kV Ga+ ions were scanned over a defined area of an Al∕SiO2 resistivity test substrate in the presence of the precursor vapor, using two different 50 kV FIB column designs with beam currents from 49 to 2070 pA and current densities of 13–36 A cm−2. Resistivity was measured by the four-point probe method. This study verifies prior reported resistivities of ⩽50 μΩ cm at room T across all deposition parameters for film growth yields ⩽0.18 μm3 nC−1 ion dose. Depositing on a heated substrate yields considerably lower film resistivity at temperatures near 100 °C; resistivities as low as 18.8 μΩ cm were achieved at the high growth yield of 0.32 μm3 nC−1 ion dose. At room temperature, the resistivity varied inversely but nonlinearly with growth yield across all depositions. Auger electron spectroscopy revealed Cu content of ∼60 at. % in the lowest resistivity films at all substrate temperatures. Via filling with aspect ratios >9:1 is demonstrated.
Show PACS
73.61.At Metal and metallic alloys
81.15.Jj Ion and electron beam-assisted deposition; ion plating
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
79.20.Fv Electron impact: Auger emission

Optimum mode of operation for a low energy focused ion beam system

Michael Rauscher and Erich Plies

J. Vac. Sci. Technol. B 22, 3004 (2004); http://dx.doi.org/10.1116/1.1809630 (4 pages) | Cited 2 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
The system design and mode of operation for a dedicated low energy focused ion beam system based on immersion optics is presented. The ion beam is accelerated using a gun lens and the intermediate lens space is set on high potential. Beam retarding to the landing energy is accomplished within the objective lens. With this design the target is field free and can be kept on ground potential. As all voltage levels are comparatively low, both gun as well as objective lens can be operated in accel mode, thus improving system performance. The influence of Coulomb interactions is also taken into account. Calculations predict a spot size of approximately 80 nm and a corresponding probe current density of 1 A∕cm2 at a working distance of 15 mm and a final beam energy of 3 keV, respectively.
Show PACS
41.85.Ne Electrostatic lenses, septa
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Gas delivery and virtual process chamber concept for gas-assisted material processing in a focused ion beam system

Valery Ray

J. Vac. Sci. Technol. B 22, 3008 (2004); http://dx.doi.org/10.1116/1.1815306 (4 pages) | Cited 1 time

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Gas-assisted etching and material deposition using gaseous precursors have become a critical part of integrated circuit modification and other applications of focused ion beam (FIB) systems. Widely used methods of gas injection in FIB systems are either needle-type or shroud-type gas delivery nozzles. Each of these methods of gas delivery has significant drawbacks. Release of the gas from the needle-type nozzles is detrimental for the vacuum level in the main chamber of the system, as the gas quickly dissipates from the process area. Insertion of shroud concentrators into the primary ion beam path and the path of secondary electrons leads to a significant decline in the signal-to-noise ratio of the FIB image. Proposed “CUPOLA” geometry of the gas delivery nozzle could allow one to effectively concentrate process gas in the area of interest, as is currently done by shroud concentrators, and, according to secondary-electron trajectory simulations, would significantly improve the signal level of the secondary-electron image, as compared to the shroud concentrators.
Show PACS
81.65.Cf Surface cleaning, etching, patterning
07.30.-t Vacuum apparatus

Formation of GaN films by Ga ion direct deposition under nitrogen radical atmosphere

Masaya Toda, Junichi Yanagisawa, Kenji Gamo, and Yoichi Akasaka

J. Vac. Sci. Technol. B 22, 3012 (2004); http://dx.doi.org/10.1116/1.1808733 (4 pages) | Cited 6 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Formation of hydrogen-free gallium nitride (GaN) thin layers by ion beam direct deposition method under nitrogen ambient was investigated. After a Ga ion beam at an energy of 100 eV was irradiated on a chip of a Si(111) wafer under a nitrogen gas pressure of 2×10−4 Torr using a tungsten hot filament, the composition and the chemical bonding nature of the deposited materials were investigated by x-ray photoelectron spectroscopy (XPS). Although the deposited material using a filament power of 250 W showed almost the metallic gallium nature, the XPS spectra of the deposited Ga using the hot filament at a power of 300 W was very similar to that of an epitaxially grown GaN reference, indicating the possibility of the formation of GaN thin layer using the present method. Because the pure N2 gas was used as the nitrogen source, no impurity fragments should be incorporated in the deposited materials. As a result, it is shown that the formation of hydrogen-free GaN layers is possible by Ga ion beam direct deposition under nitrogen atmosphere using N2 gas and the hot filament.
Show PACS
68.55.A- Nucleation and growth
81.15.Jj Ion and electron beam-assisted deposition; ion plating
79.60.Bm Clean metal, semiconductor, and insulator surfaces
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors

Investigations of the Ga+ focused-ion-beam implantation in resist films for nanometer lithography applications

Khalil Arshak, Miroslav Mihov, Shohei Nakahara, Arous Arshak, and Declan McDonagh

J. Vac. Sci. Technol. B 22, 3016 (2004); http://dx.doi.org/10.1116/1.1813451 (5 pages) | Cited 1 time

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
A focused-ion-beam (FIB) machine is a versatile tool used extensively in the IC industry for conducting failure analysis, prototype fabrication, and device repair. Lithography can also be performed by the FIB technique for direct patterning of photoresists, followed by wet or dry development. We studied how the property of resist regions changes during oxygen dry development in the NERIME (the negative-resist-image-by-dry-etching) process after subjecting to FIB-assisted gallium implantation. The NERIME process is a single-layer scheme, in which DNQ/Novolak-based resists are exposed by gallium ions with FIB, followed by near-ultraviolet flood exposure, silylation, and oxygen dry etching. This process can yield both positive and negative resist images. In addition, the NERIME technique can achieve a nanometer resolution down to 80 nm and a high aspect ratio for the processed patterns. A scanning-transmission-electron-microscope (STEM) analysis of the resist regions FIB-implanted with gallium ions has revealed that there is a ∼15-nm-thick gallium oxide (Ga2O3) layer on the surface. The presence of the gallium oxide layer was found to provide an increased resistance against subsequent oxygen dry development. It was concluded that the NERIME process could be used for a specific CMOS processing task, such as high-resolution lithography over resist surfaces with complex topography.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
61.80.Jh Ion radiation effects
42.82.Cr Fabrication techniques; lithography, pattern transfer
85.40.Ry Impurity doping, diffusion and ion implantation technology
81.16.Nd Micro- and nanolithography
81.65.Cf Surface cleaning, etching, patterning
68.37.Lp Transmission electron microscopy (TEM)
back to top Maskless Lithography

Initial lithography results from the digital electrostatic e-beam array lithography concept

L. R. Baylor, W. L. Gardner, X. Yang, R. J. Kasica, M. A. Guillorn, B. Blalock, H. Cui, D. K. Hensley, S. Islam, D. H. Lowndes, A. V. Melechko, V. I. Merkulov, D. C. Joy, P. D. Rack, M. L. Simpson, et al.

J. Vac. Sci. Technol. B 22, 3021 (2004); http://dx.doi.org/10.1116/1.1824060 (4 pages) | Cited 15 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
The Digital Electrostatically focused e-beam Array direct-write Lithography (DEAL) concept is currently under development at Oak Ridge National Laboratory (ORNL). This concept incorporates a digitally addressable field-emission array (DAFEA) built into a logic and control integrated circuit to function as the write head for an e-beam lithography tool. The electrostatic focusing is integrated on the DAFEA and consists of additional grids lithographically aligned above the emitters and extraction grid, each separated by a dielectric (nominally low-temperature SiO2) layer. Prototypes of the DAFEA have been fabricated and used to test the focusing of the electron beams and to pattern lines in PMMA resist. First lithography tests have used electron energies of 500 eV to pattern lines less than 1 μm wide at a working distance of 500 μm which extrapolates to <300 nm at the nominal DEAL design working distance of 100 μm. Aspects of the DEAL lithography testing and further development are discussed.
Show PACS
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer

Cs halide photocathode for multi-electron-beam pattern generator

Juan R. Maldonado, Steven T. Coyle, Bassam Shamoun, Ming Yu, Mark Gesley, and Piero Pianetta

J. Vac. Sci. Technol. B 22, 3025 (2004); http://dx.doi.org/10.1116/1.1823433 (7 pages) | Cited 7 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
A unique approach to photocathode operation is described in this article. We utilize a relatively large bandgap CsBr photocathode material that under normal conditions would not photoemit with radiation energy less than the bandgap plus the work function. However, the material can be activated by proper UV illumination to obtain photoemission at wavelengths as long as 532 nm. Photoyields as high as several hundred nA∕mW and current densities greater than 100 A∕cm2 have been routinely obtained with lifetimes (50% degradation) well in excess of 200 h at 257 nm. The performance of the photocathode meeting all the requirements for a multi-electron-beam pattern generator will be presented.
Show PACS
85.60.Ha Photomultipliers; phototubes and photocathodes

Alpha-prototype system for zone-plate-array lithography

Rajesh Menon, Amil Patel, Euclid E. Moon, and Henry I. Smith

J. Vac. Sci. Technol. B 22, 3032 (2004); http://dx.doi.org/10.1116/1.1813464 (6 pages) | Cited 8 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
In this article, we present lithography results from a continuous-scan zone-plate-array lithography (ZPAL) system using the grating light valve (GLV) as the multiplexing element. ZPAL is an optical-maskless-lithography technique, in which an array of diffractive lenses (e.g., zone plates) focuses incident light into an array of spots on a photoresist-coated substrate. The intensity of the light incident on each lens is controlled by the GLV. By scanning the wafer and appropriately modulating the incident light, patterns are written in a “dot-matrix” fashion. We have incorporated the elements of ZPAL into an alpha-prototype system. We describe this system and characterize its lithographic performance.
Show PACS
85.40.Hp Lithography, masks and pattern transfer

Comparison of tilting and piston mirror elements for 65 nm node spatial light modulator optical maskless lithography

G. P. Watson, V. Aksyuk, D. M. Tennant, and R. A. Cirelli

J. Vac. Sci. Technol. B 22, 3038 (2004); http://dx.doi.org/10.1116/1.1824063 (5 pages) | Cited 5 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Spatial light modulator (SLM) maskless lithography, an optical technology that replaces photomasks with an adjustable array of microelectromechanical mirrors can potentially complement conventional, mask-based, lithography. The usefulness of this technology depends on whether it can print features at least as well as conventional tools and can keep pace with the International Technology Roadmap for Semiconductors. In particular, any SLM-based tool developed now must be capable of printing 50 nm or smaller gates and 130 nm pitch lines and spaces using 193 nm light as is being planned for the 65 nm half-pitch node. SLM mirrors may be designed to tilt or shift in depth (piston). Aerial image simulations presented here show that 65 nm node features formed by piston mirrors have the same process latitude as tilt mirrors with a numerical aperture (NA) of 1.1. In addition, piston mirrors exhibit the added benefit that they may be arranged to mimic alternating aperture phase shift photomasks. Isolated and dense features of 65 nm node dimensions can be printed with a reduced NA of 0.90. This form of phase shifting may be required at the 65 nm ITRS node both for conventional and maskless lithography applications.
Show PACS
42.79.Bh Lenses, prisms and mirrors
42.79.Hp Optical processors, correlators, and modulators
42.82.Cr Fabrication techniques; lithography, pattern transfer
85.40.Hp Lithography, masks and pattern transfer
back to top Masks

Effect of electrostatic chucking and substrate thickness uniformity on extreme ultraviolet lithography mask flatness

A. Mikkelson, R. Engelstad, J. Sohn, and E. Lovell

J. Vac. Sci. Technol. B 22, 3043 (2004); http://dx.doi.org/10.1116/1.1808738 (6 pages) | Cited 1 time

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Extreme ultraviolet lithography (EUVL) is one of the leading candidates for next-generation lithography in the sub-45 nm regime. Successful implementation of this technology will depend upon advancements in many areas, including the quality of the mask system to control image placement errors. Such errors will occur at the wafer as a result of height variations of the patterned (frontside) mask surface (i.e., its nonflatness). The Semiconductor Equipment and Materials International EUVL Mask Standard (SEMI P37) specifies that the mask frontside and backside nonflatness be no more than 50 nm peak-to-valley (P-V). Currently, the lowest level of freestanding flatness of EUVL mask substrates from production-level polishing and finishing techniques is about 200 nm P-V. The frontside and backside of typical (and representative) EUVL substrates were measured for flatness and these surfaces were represented mathematically using Legendre polynomials. The Legendre coefficients were then utilized in a finite element model to predict the effect of chucking on the flatness of these substrates. One of the significant conclusions of this research is that the substrate thickness nonuniformity has a dominant effect on the flatness of the patterned surface after chucking.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
42.82.Cr Fabrication techniques; lithography, pattern transfer

High reflectance of reflective-type attenuated-phase-shifting masks for extreme ultraviolet lithography with high inspection contrast in deep ultraviolet regimes

H. L. Chen, H. C. Cheng, T. S. Ko, F. H. Ko, and T. C. Chu

J. Vac. Sci. Technol. B 22, 3049 (2004); http://dx.doi.org/10.1116/1.1813450 (4 pages) | Cited 2 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Phase-shifting masks are a vital resolution enhance technique that will be used in extreme ultraviolet (EUV) lithography beyond the 20 nm node. In this article, we demonstrate a structure for a reflective-type attenuated phase-shifting mask, which is based on a Fabry–Perot structure with common materials in EUV masks. The mask structure not only performs 180° phase shift with high reflectance at EUV wavelength, but also has high inspection contrast at deep ultraviolet (DUV) wavelength. The top layer of mask structures exhibits good conductivity, which can alleviate the charging effect during electron-beam patterning. The reflectance ratio of the absorber stack could be tuned from 32.6% (TaN∕SiO2∕Mo) to 4.4% (TaN∕SiO2∕TaN) by choosing different bottom layers and thickness. The inspection contrast could be raised to 99% with large thickness-control tolerance.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
42.82.Cr Fabrication techniques; lithography, pattern transfer
81.16.Nd Micro- and nanolithography

Effect of mask pattern correction for off-axis incident light in extreme ultraviolet lithography

Minoru Sugawara, Iwao Nishiyama, and Mikio Takai

J. Vac. Sci. Technol. B 22, 3053 (2004); http://dx.doi.org/10.1116/1.1809616 (6 pages) | Cited 4 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
The effect of mask pattern correction for off-axis incident light on the pattern fidelity of a model pattern with 22 nm wide lines and spaces was investigated. Corrections were made to the edges of mask patterns, because off-axis incident light produces an asymmetric aerial image. The corrections were found to compensate effectively for the degradation in pattern fidelity due to the influence of off-axis incident light and optical proximity effects. Off-axis incident light causes asymmetry in the positions of pattern edges, the mask error enhancement factor, and pattern edge contrast, even when a symmetric mask pattern layout is designed. It was found that these asymmetries could be suppressed by employing thin buffer and absorber films and a large numerical aperature of projection optics.
Show PACS
85.40.Hp Lithography, masks and pattern transfer

Characterization of extreme ultraviolet masks by extreme ultraviolet scatterometry

J. Perlich, F.-M. Kamm, J. Rau, F. Scholze, and G. Ulm

J. Vac. Sci. Technol. B 22, 3059 (2004); http://dx.doi.org/10.1116/1.1809615 (4 pages) | Cited 7 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
The applicability of scatterometry for mask critical dimension (CD) metrology at extreme ultraviolet (EUV) wavelengths is investigated. Two different mask absorber stacks, a Cr∕SiO2 mask and a TaN∕Cr mask are patterned with periodic lines and spaces pattern and measured at EUV wavelengths in the range of λ=13.35–13.57 nm. All measurements are performed by the Physikalisch-Technische-Bundesanstalt at the BESSY II storage ring. The intensity of the diffracted light is measured as a function of diffraction angle 2Θ∕2 in the range between −0.5° and 10°. The measured results are compared to simulations in the Fourier domain, using the difference method. For the Cr∕SiO2 mask, the comparison between measured and simulated results shows good agreement for nominally 800 nm lines with 400 nm spaces (mask level). No arbitrary scaling has to be applied for the simulated intensity of the diffraction signal. A best-fit CD value of 742 nm at an absorber and buffer sidewall angle of 80° is obtained. This result is in excellent agreement with mechanical measurements using a surface nanoprofiler. Compared to a scanning electron microscope measurement, an offset of 16 nm is observed. For the TaN∕Cr mask, this offset is found to be only 9 nm, which can be attributed to the smaller stack thickness.
Show PACS
85.40.Hp Lithography, masks and pattern transfer

Influence of glass substrate surface roughness on extreme ultraviolet reflectivity of Mo∕Si multilayer

Shinji Miyagaki, Hiromasa Yamanashi, Atsuko Yamaguchi, and Iwao Nishiyama

J. Vac. Sci. Technol. B 22, 3063 (2004); http://dx.doi.org/10.1116/1.1808731 (4 pages) | Cited 7 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
The influence of the surface roughness of a glass substrate on the extreme ultraviolet (EUV) reflectivity of Mo∕Si multilayer deposited on it by ASET’s helicon sputtering system was investigated. Deposition by helicon sputtering was found to produce a smoothing effect on the multilayer. That is, surface roughness with a spatial period below 100 nm is smoothed out, but that with a spatial period longer than 100 nm is not. The result is that the rms roughness of a Mo∕Si multilayer is slightly smaller than that of the substrate. The EUV reflectivity of the multilayer improved as the rms roughness decreased down to 0.30 nm, and than leveled off at about 65% below that value, indicating that the EUV reflectivity is limited by some factor(s) other than surface roughness. However, a relatively high EUV reflectivity of 65% was obtained, even for an rms roughness of about 0.30 nm.
Show PACS
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Cd Deposition by sputtering
42.82.Cr Fabrication techniques; lithography, pattern transfer
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer

Lithographic performance of diamond-like carbon membrane mask in electron projection lithography

Hiroshi Yamashita, Isao Amemiya, Masaki Yamabe, and Hiroshi Arimoto

J. Vac. Sci. Technol. B 22, 3067 (2004); http://dx.doi.org/10.1116/1.1808714 (5 pages) | Cited 1 time

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
We have studied the lithographic performance of high-performance diamond-like carbon (DLC) membrane masks by demonstrating exposure experiments using Nikon’s electron beam stepper, NSR-EB1A. We estimated the inelastic mean free path of 100 keV electrons in a membrane analytically using the measurement results of zero-loss electron transmittance and found it to be about 50 nm. We then used this value to find the relationship between membrane thickness and zero-loss electron transmittance. The resolution for high-performance membrane masks is equivalent to that of a stencil mask and was not deteriorated by chromatic aberration due to inelastic electron scattering. Electrons undergoing inelastic scattering did not appear to affect resolution. The nominal exposure dose was proportional to the inverse of zero-loss electron transmittance. We also discussed the optimum membrane thickness in terms of throughput and electron inelastic scattering, focusing on plasmon excitation.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

Ultrathin membrane masks for electron projection lithography

O. R. Wood, W. J. Trybula, J. Greschner, S. Kalt, T. Bayer, S. Shimizu, H. Yamamoto, K. Suzuki, M. S. Gordon, C. F. Robinson, R. S. Dhaliwal, C. W. Thiel, N. Caldwell, M. S. Lawliss, and C. Huang

J. Vac. Sci. Technol. B 22, 3072 (2004); http://dx.doi.org/10.1116/1.1802911 (5 pages)

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Electron projection lithography (EPL) is one of the leading candidates for next-generation lithography at the 65-nm lithography node, particularly for contact levels. EPL has traditionally employed either an open stencil mask with a single patterned (perforated) scattering layer or a continuous membrane mask with a patterned scattering layer supported by an un-perforated membrane. This article reports on an experimental study of a type of EPL mask developed by Team Nanotec that employs a continuous ultrathin membrane (UTM) comprised of a trilayer of carbon, silicon nitride, and carbon. These UTM masks combine all of the benefits of continuous membrane masks with the higher energy throughput (and the smaller chromatic aberration) of an open stencil mask.
Show PACS
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer

Assessment of image placement errors induced in electron projection lithography masks by chucking

J. Chang, R. L. Engelstad, E. G. Lovell, W. J. Trybula, and O. R. Wood

J. Vac. Sci. Technol. B 22, 3077 (2004); http://dx.doi.org/10.1116/1.1808737 (5 pages)

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Electron projection lithography (EPL) is under active development, with potential applications at the sub 65 nm nodes. In order to meet the stringent error budgets in this regime, image placement (IP) errors induced by chucking the mask during e-beam patterning, metrology, and exposure must be characterized and minimized. The focus of this study is to assess the distortions induced in200-mm-diam EPL stencil masks by chucking during e-beam patterning and EPL exposure. High-throughput test masks (with 3.39 mm square membrane windows) were evaluated, to assess IP errors throughout a typical mask process flow. Finite element structural models were developed to simulate the response of the test mask during each processing step. Finally, the results of the analysis were used to identify and characterize the sources of IP errors.
Show PACS
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
85.40.Bh Computer-aided design of microcircuits; layout and modeling

Thermal analysis of diamondlike carbon membrane masks in projection electron-beam lithography

S. Babin, V. Butomo, I. Yu. Kuzmin, H. Yamashita, and M. Yamabe

J. Vac. Sci. Technol. B 22, 3082 (2004); http://dx.doi.org/10.1116/1.1826059 (5 pages)

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Diamondlike carbon (DLC) membrane masks for high-throughput projection electron-beam lithography have an important advantage over stencil masks: a single mask can be used to print donut-shaped patterns. At a membrane thickness on the order of a few tens of nanometers, thermal problems could occur. The temperature rise of a membrane mask was simulated with various exposure parameters. Membrane and scatterer thickness, resist sensitivity, and pattern coverage were varied. It was found that global temperature rise after exposure of a chip is on the order of 0.005 °C, while temperature rise in a membrane area under exposure reaches 2.54 °C. Simulation results were compared to those on a silicon stencil mask. It was found that the global heating is less on a DLC membrane mask.
Show PACS
85.40.Hp Lithography, masks and pattern transfer

Stress and image-placement distortions of 200 mm low-energy electron projection lithography masks

H. Eguchi, T. Susa, T. Sumida, T. Kurosu, T. Yoshii, K. Yotsui, K. Itoh, A. Tamura, R. L. Engelstad, E. G. Lovell, X. Azkorra, A. Mikkelson, J. Chang, and S. M. Janowski

J. Vac. Sci. Technol. B 22, 3087 (2004); http://dx.doi.org/10.1116/1.1824054 (5 pages)

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Low-energy electron projection lithography (LEEPL) is a candidate for next generation lithography and thus the 1× LEEPL mask requires a stringent local image placement (IP) error budget. Applying a doping method with silicon-on-insulator substrates, 700-nm-thick membranes were investigated for stress control and in-plane distortion (IPD), which are the main contributors to local IP errors. Stress control results show that at a dopant concentration of 6.74×1019∕cm3, the membrane stress in a 10 mm test structure is 8.4 MPa. Also stress variation is excellent at 0.3 MPa across a 200 mm complementary stencil mask on support strut-type LEEPL mask. The IPD results indicate that small membrane window size, low void fraction, as well as low membrane stress is the proper strategy to allow a stencil mask with dense stencil patterns to meet required IPD. Additionally, the local IP errors of large scale integrated 90 nm hole pattern were demonstrated.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

Approach to full-chip simulation and correction of stencil mask distortion for proximity electron lithography

J. Sawamura, K. Suzuki, S. Omori, I. Ashida, and H. Ohnuma

J. Vac. Sci. Technol. B 22, 3092 (2004); http://dx.doi.org/10.1116/1.1821503 (5 pages)

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
An approach for simulating the in-plane displacements of mask patterns induced by pattern-density gradients over thin membranes of a stencil mask as used for proximity electron lithography (PEL) has been proposed and demonstrated for the contact layer of a real device in the 65 nm node. The comparison of simulation and experiment shows that full-chip analysis is feasible if the method for tuning the boundary condition for the simulation to match with the experiment is established.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
85.40.Bh Computer-aided design of microcircuits; layout and modeling

Optimized HT-AttPSM blanks using Al2O3/TiO2 multilayer films for the 65 nm technology node

Fu-Der Lai

J. Vac. Sci. Technol. B 22, 3097 (2004); http://dx.doi.org/10.1116/1.1805541 (5 pages) | Cited 1 time

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
The optical properties of (Al2O3mathx(TiO2)1−x superlattice films have been shown to satisfy the effective medium approximation theory and, therefore, can be tunable. It is found that (Al2O3)x∕(TiO2)1−x superlattice films with x=79%–84% as π-phase shifters can be used as high-transmittance attenuated phase-shift mask (HT-AttPSM) blanks at a wavelength of 193 nm. Lower transmittance at an inspection wavelength of 257 nm is desirable for a better inspection. Due to the fact that the transmittance is less than 25% at a wavelength of 257 nm, this means that these layers allow for good inspection. Lower reflectance at an exposure wavelength of 193 nm is desirable, as this leads to better aerial images. To achieve a better aerial image, it is best to select a four-stack (Al2O3mathx(TiO2)1−x film as the HT-AttPSM blank layer because a four-stack film has the lower reflectance than others. The thickness fraction range of Al2O3 in the four-stack (Al2O3mathx(TiO2)1−x films used for the HT-AttPSM blanks at a wavelength of 193 nm is found to be between about 79% and about 85%. We fabricate a four-stack (Al2O3mathx(TiO2)1−x film sample for HT-AttPSM that has the optimized optical properties, which include a transmittance of 19.9% and a lower reflectance (3.2%) at a wavelength of 193 nm and a good inspection transmittance (less than 20%) at a wavelength of 257 nm. The four-stack (Al2O3mathx(TiO2)1−x film can be used to design a desirable HT-AttPSM at the exposure wavelength of 193 nm.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
42.82.Cr Fabrication techniques; lithography, pattern transfer
81.16.Nd Micro- and nanolithography
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
42.70.-a Optical materials
42.79.Wc Optical coatings

Pattern transferring technique using reversal mask process

Hirokazu Kato, Junko Abe, and Yasunobu Onishi

J. Vac. Sci. Technol. B 22, 3102 (2004); http://dx.doi.org/10.1116/1.1821574 (5 pages)

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
In the reversal mask process, the mask material film is deposited over the resist patterns. There is a problem in that the film step height at the surface of the mask material reduces the etch-back margin of the mask material. This is inevitable as long as the mask material film is deposited by spin-coating and no planarization process is used. In this article, the dependence of film step height on the half-pitches (periodic feature) or the widths (isolated feature) of the resist patterns is measured by means of both experiment and calculation. As a solution to avoid the effect of the film step height, a pattern transferring technique which makes use of a multiple exposure process and the reversal mask process is proposed and the fabrication of dense contact hole patterns was demonstrated. This technique is proven to be one of the practical applications of the reversal mask process and at the same time to be an effective method of fabricating the kind of patterns which a conventional single-exposure process is not able to fabricate due to insufficient lithography margin.
Show PACS
81.65.Cf Surface cleaning, etching, patterning
85.40.Hp Lithography, masks and pattern transfer
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
back to top Nanodevices

Assembly and electrical characterization of DNA-wrapped carbon nanotube devices

A. A. Talin, P. M. Dentinger, F. E. Jones, S. Pathak, L. Hunter, F. Léonard, and A. M. Morales

J. Vac. Sci. Technol. B 22, 3107 (2004); http://dx.doi.org/10.1116/1.1815304 (5 pages) | Cited 7 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
In this article we report on the electrical characteristics of single wall carbon nanotubes (SWCNTs) wrapped with single-stranded deoxyribonucleic acid (ssDNA). We fabricate these devices using a solution-based method whereby SWCNTs are dispersed in aqueous solution using 20-mer ssDNA, and are placed across pairs of Au electrodes using alternating current dielectrophoresis (ACDEP). In addition to current voltage characteristics, we evaluate our devices using scanning electron microscopy and atomic force microscopy. We find that ACDEP with ssDNA based suspensions results in individual SWCNTs bridging metal electrodes, free of carbon debris, while similar devices prepared using the Triton X-100 surfactant yield nanotube bundles, and frequently have carbon debris attached to the nanotubes. Furthermore, the presence of ssDNA around the nanotubes does not appear to appreciably affect the overall electrical characteristics of the devices. In addition to comparing the properties of several devices prepared on nominally clean Au electrodes, we also investigate the effects of self-assembled monolayers of C14H29-SH alkyl thiol and benzyl mercaptan on the adhesion and electrical transport across the metal/SWCNT/metal devices.
Show PACS
85.35.Kt Nanotube devices
81.07.De Nanotubes

Silicon nitride gate dielectric for top-gated carbon nanotube field effect transistors

Shengdong Li, Zhen Yu, and Peter J. Burke

J. Vac. Sci. Technol. B 22, 3112 (2004); http://dx.doi.org/10.1116/1.1824048 (3 pages) | Cited 6 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
We develop and demonstrate a process to fabricate top-gated carbon nanotube transistors using silicon nitride as the gate dielectric. I‐V curves of these silicon nitride gated nanotube transistors are measured.
Show PACS
85.35.Kt Nanotube devices
81.07.De Nanotubes
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Formation of 15 nm scale Coulomb blockade structures in silicon by electron beam lithography with a bilayer resist process

S.-J. Park, J. A. Liddle, A. Persaud, F. I. Allen, T. Schenkel, and J. Bokor

J. Vac. Sci. Technol. B 22, 3115 (2004); http://dx.doi.org/10.1116/1.1825012 (4 pages) | Cited 5 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
We have formed Coulomb blockade structures with widths of 15–30 nm in silicon-on-insulator (SOI) by electron beam lithography (EBL) in a bilayer resist process. The bilayer structure consisted of HSQ (hydrogen silsesquioxane) and AZ organic resist. The organic resist protects the buried oxide and allows removal of exposed HSQ features with hydrofluoric acid (HF). Measurements at 4.2 K show pronounced Coulomb blockade signatures for 15 nm wide wires. This bilayer resist process provides direct lithographic access to 15 nm level features in SOI without the need for size reduction by oxidation.
Show PACS
73.23.Hk Coulomb blockade; single-electron tunneling
85.35.Ds Quantum interference devices
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
81.07.Vb Quantum wires
85.35.Gv Single electron devices

Single electron memory devices utilizing Al2O3 tunnel oxide barriers

Kameshwar K. Yadavalli, Nicolas R. Anderson, Tatiana A. Orlova, Alexei O. Orlov, Gregory L. Snider, and Jeffrey Elam

J. Vac. Sci. Technol. B 22, 3119 (2004); http://dx.doi.org/10.1116/1.1821506 (5 pages) | Cited 3 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
We report experiments on single electron memory devices where the charging of a floating gate, which serves as a memory node, is done through aluminum oxide tunnel barriers and detected by a single electron transistor (SET) electrometer. The aluminum oxide tunnel barriers are fabricated through two different approaches. In one, the oxygen plasma oxidation of an as-deposited aluminum floating gate is used to grow aluminum oxide. In the other method, aluminum oxide is deposited on a titanium/gold floating gate by means of atomic layer deposition (ALD). Measurements performed on these devices at a temperature of 300 mK indicate the presence of a definite threshold for charging through the tunnel oxide barriers. A nonvolatile memory behavior is observed with each bit represented by about 15 electrons.
Show PACS
85.35.Gv Single electron devices
81.65.Mq Oxidation
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Electron beam stimulated field-emission from single-walled carbon nanotubes

Alireza Nojeh, Wai-Kin Wong, Eric Yieh, R. Fabian Pease, and Hongjie Dai

J. Vac. Sci. Technol. B 22, 3124 (2004); http://dx.doi.org/10.1116/1.1809628 (4 pages) | Cited 6 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Carbon nanotubes are good candidates for electron field- and photo-emitters at the nanoscale since their sharp geometries lead to significant external field enhancement. Also, their mechanical strength and structural completeness alleviate issues related to stability and lifetime that may be present in small-scale emitters that have loose atoms at their tips. Here, we demonstrate how an external electron beam can stimulate electron emission from the tip of a nanotube that is lying on an insulating surface and is subject to an external electric field, thus making it act as an electron bombardment source.
Show PACS
79.70.+q Field emission, ionization, evaporation, and desorption
79.20.Hx Electron impact: secondary emission

Fabrication and characterization of Au island single-electron transistors with CrOx step edge junctions

Xiangning Luo, Alexei O. Orlov, and Gregory L. Snider

J. Vac. Sci. Technol. B 22, 3128 (2004); http://dx.doi.org/10.1116/1.1815310 (5 pages) | Cited 3 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Single-electron transistors fabricated using Au islands and CrOx resistive microstrips are reported. To investigate the occurrence of Coulomb blockade in these devices, three types of device designs have been tested. Typical single-electron behavior, conductance modulation by the gate, is observed in the devices which had small overlap area with the gold island. Electron transport mechanism of CrOx resistors is discussed and a hypothesis of the formation of step edge junctions at the edges of granular metal microstrips is given as the explanation for the experimental results.
Show PACS
73.23.Hk Coulomb blockade; single-electron tunneling
85.35.Ds Quantum interference devices
85.35.Gv Single electron devices

Wavelength tuning of an antenna-coupled infrared microbolometer

Michael A. Gritz, Meredith Metzler, Donald Malocha, Mohamed Abdel-Rahman, Brian Monacelli, Guy Zummo, and Glenn D. Boreman

J. Vac. Sci. Technol. B 22, 3133 (2004); http://dx.doi.org/10.1116/1.1813465 (4 pages) | Cited 3 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Wavelength tuning is demonstrated in an antenna-coupled infrared microbolometer. With a 300-mV control voltage, we observed a tuning range of 0.15 μm near 10 μm. A metal-oxide-semiconductor capacitor underneath the antenna arms causes the shift of resonance wavelength with applied voltage. We develop a device model that agrees with measured results.
Show PACS
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
84.40.Ba Antennas: theory, components and accessories
85.60.Gz Photodetectors (including infrared and CCD detectors)
84.32.Tt Capacitors

Nanomechanical switch fabrication by focused-ion-beam chemical vapor deposition

Takahiko Morita, Ken-ichiro Nakamatsu, Kazuhiro Kanda, Yuichi Haruyama, Kazushige Kondo, Takayuki Hoshino, Takashi Kaito, Jun-ichi Fujita, Toshinari Ichihashi, Masahiko Ishida, Yukinori Ochiai, Tsutomu Tajima, and Shinji Matsui

J. Vac. Sci. Technol. B 22, 3137 (2004); http://dx.doi.org/10.1116/1.1826063 (6 pages) | Cited 7 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Focused-ion-beam chemical vapor deposition (FIB-CVD) is an excellent technology to form three-dimensional nanostructures. Various three-dimensional nanostructures such as an inductance, a capacitor, a resistance, and a filter-circuit have been demonstrated by applying FIB-CVD with phenanthrene (C14H10) source gas using a computer-controlled pattern generator (CPG). The electrical resistivity measurement of the free-space-nanowiring was carried out by two terminal electrode method. The resistivity was 1×102 Ω cm in the case of using C14H10. To reduce the electrical resistivity, tungsten hexacarbonyl [W(CO)6] is added to C14H10 as a source gas. Increasing content of W(CO)6, the electrical resistivity becomes lower from 1×102 to 2×10−2 Ω cm at room temperature. By using free-space-nanowiring fabrication technology, the world smallest nanomechanical switch composed of a coil and a nanowiring has been fabricated and confirmed the switching operation by applying a voltage.
Show PACS
85.35.-p Nanoelectronic devices
81.07.Lk Nanocontacts
81.07.Vb Quantum wires
84.32.Tt Capacitors
84.32.Hh Inductors and coils; wiring
85.40.Sz Deposition technology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.63.Nm Quantum wires
84.32.Ff Conductors, resistors (including thermistors, varistors, and photoresistors)
85.40.Ls Metallization, contacts, interconnects; device isolation

Fatigue life of a microcantilever beam in bending

H. Hocheng, K. S. Kao, and W. Fang

J. Vac. Sci. Technol. B 22, 3143 (2004); http://dx.doi.org/10.1116/1.1821502 (4 pages) | Cited 4 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
The fatigue behavior of a microcantilever beam loaded by various magnetic forces is investigated. The MEMS fabrication techniques, such as exposure, lithography, etching, etc., are applied to construct the micro structures on a silicon wafer. FEM and SEM are employed to study the relations between fractographies, stresses, and strains. The experimental results indicate that the deformation, stress and strain increase as the magnetic force increases, while the fatigue cycle time decreases with the load. The fatigue life lies in the range of 1–5×107 cycles at 12–15 MPa produced by the magnetic flux. Fracture occurs at the location of the maximum stress as predicted by an analytical approach.
Show PACS
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
81.40.Lm Deformation, plasticity, and creep
62.20.M- Structural failure of materials
62.20.F- Deformation and plasticity

Compliant pin chuck for minimizing the effect of backside particles on wafer planarity

Pawan Kumar Nimmakayala and S. V. Sreenivasan

J. Vac. Sci. Technol. B 22, 3147 (2004); http://dx.doi.org/10.1116/1.1825017 (4 pages)

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
A wafer chuck referred to as the compliant pin chuck (CPC) that can minimize the nonplanarity effect of backside particles on semiconductor wafers is presented in this article. The demand for flatter semiconductor substrates has been increasing as the size of the features that can be transferred onto a wafer surface becomes smaller. There are a number of factors affecting wafer planarity, most of which can be corrected by conventional wafer chucks. However, the problem of backside particles (particles affect a large portion of wafer real estate by causing out-of-plane distortion when they get lodged between a wafer and a wafer chuck) has not been adequately addressed by the current wafer chuck technology. The compliant pin chuck was designed to address this concern and fabricated from silicon using lithography based microfabrication techniques. The chuck consists of an array of microflexure mechanisms that react to the presence of backside particles so as to minimize the nonplanarity caused otherwise. It is also shown through experimental results that the fabricated chuck has a planarity of 120 nm (standard deviation −3σ) over an area of 30 mm×30 mm and is less sensitive to backside particles than a conventional wafer chuck.
Show PACS
81.65.-b Surface treatments
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
85.40.Hp Lithography, masks and pattern transfer

Piezoelectric projective displays

Bong Mo Park, Sang Woon Ha, Gil Sik Lee, Hoi-Yee Wong, Martin Feldman, and Sang Kyeong Yun

J. Vac. Sci. Technol. B 22, 3151 (2004); http://dx.doi.org/10.1116/1.1809629 (3 pages)

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
We report the fabrication of monolithic phase grating modulators in single crystal 0.67PMN-0.33PT. Diffraction was observed for a period (b) to thickness (T) ratio >2.5. Very strong diffraction was obtained at a period of 250 μm, electrode width of 100 μm, and a substrate thickness of 50 μm. Under these conditions, the overall diffraction efficiency into the first orders at optimal voltage applied to the modulator was about 57%. Modulators containing linear arrays of elements are attractive alternatives to acousto-optic modulators, and rectangular arrays may be used for image projection.
Show PACS
42.79.Hp Optical processors, correlators, and modulators
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
42.79.Kr Display devices, liquid-crystal devices
77.80.-e Ferroelectricity and antiferroelectricity

Nanoflash device with self-aligned double floating gates using scanning probe lithography and tetramethylammonium hydroxide wet etching

J. T. Sheu, C. C. Chen, K. S. You, and S. T. Tsai

J. Vac. Sci. Technol. B 22, 3154 (2004); http://dx.doi.org/10.1116/1.1826060 (4 pages) | Cited 2 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
We report a self-aligned technology for nanoflash devices with double floating gates using scanning probe lithography (SPL) technology and anisotropic wet etching. On a (110) SOI silicon wafer, along [001] and [111] directions, a silicon nanowire was generated through local oxidation with SPL followed by wet etching with tetramethylammonium hydroxide solution. Silicon nanowires (SiNW) with profiles of sidewall either sloped or vertical were formed after anisotropic etching in the [001] or [111] direction respectively. After deposition of a polysilicon film on the SiNW with low pressure chemical vapor deposition, nanostructures of a nanoflash device with polysilicon double-floating side gates were obtained along the [111] part of SiNW after reactive ion etching spacer etching. The silicon nanowire channel has a width of 20 nm and a height of 200 nm; the width of the self-aligned floating gate is approximately 40 nm. Silicon nitride was deposited to serve as gate dielectric. The top gate and source-drain aluminum pads were defined by photolithography. Electrical properties of such a nanoflash device with double-floating side gates are discussed.
Show PACS
84.30.Sk Pulse and digital circuits
42.82.Cr Fabrication techniques; lithography, pattern transfer
81.16.Nd Micro- and nanolithography
81.07.Vb Quantum wires
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.40.Hp Lithography, masks and pattern transfer
81.16.Pr Micro- and nano-oxidation
81.65.Mq Oxidation
81.65.Cf Surface cleaning, etching, patterning
85.30.-z Semiconductor devices
back to top Nanofabrication

Three-dimensional and multimaterial microfabrication using focused-ion-beam chemical-vapor deposition and its application to processing nerve electrodes

T. Hoshino, M. Kawamori, T. Suzuki, S. Matsui, and K. Mabuchi

J. Vac. Sci. Technol. B 22, 3158 (2004); http://dx.doi.org/10.1116/1.1821581 (5 pages) | Cited 3 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
One of the ways to interface electrodes to neurons is a regenerative electrode. The electrode is between the two cut end of a nerve. The cut nerve fiber regenerates through a metalized hold electrode in a two-dimensional (2D) planar of regenerative electrode. As this type of electrode has advantages enabling both the recording of signals of a single nerve fiber and the stimulation of a single nerve fiber, attempts have been made to develop it using traditional 2D microfabrication techniques. However, these traditional 2D techniques have made it difficult to process such electrodes, in particular, electrical wires that have a high density and an integrated structure. In this study, we developed a novel microfabrication method that enables three-dimensional (3D) micro∕nanostructures to be fabricated that are made of several kinds of materials with focused-ion-beam chemical-vapor deposition (FIB-CVD). To demonstrate the feasibility of this technique, we designed and fabricated a modified type of regenerative nerve electrode composed of a number of microtubes, each of which worked as both the guide for nerve regeneration and the electrode channel. The 3D structures with this method were fabricated by depositing either diamondlike carbon (DLC, nonconductor) or tungsten (conductor) using a scanning 30 keV Ga+ ion beam in an atmosphere of phenanthrene (C14H10) or tungsten hexacarbonyl (W(CO)6). The prototype for the electrode was fabricated with the following process. First, tungsten pillars, which worked as the electrical wiring, were deposited on the substrate by scanning the FIB in W(CO)6 gas. Next, carbon microtubes, which were used to guide the regenerated nerve fiber(s), were built up to be attached to each of the tungsten pillars by depositing DLC with a scanning FIB in C14H10 gas. These carbon microtubes (CMTs) were designed to be curved and to be spread so that they did not contact other wiring pillars, and they were gathered into one at both ends. Our FIB-CVD method made it possible to fabricate complicated 3D structures such as regenerative nerve electrodes made of several kinds of materials.
Show PACS
87.85.Qr Nanotechnologies-design
87.85.Rs Nanotechnologies-applications
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
87.80.-y Biophysical techniques (research methods)
87.19.R- Mechanical and electrical properties of tissues and organs

Biological lithography: Improvements in DNA synthesis methods

C. Kim, M. Li, M. Rodesch, A. Lowe, K. Richmond, and F. Cerrina

J. Vac. Sci. Technol. B 22, 3163 (2004); http://dx.doi.org/10.1116/1.1824066 (5 pages) | Cited 2 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
We have recently succeeded in synthesizing long oligonucleotides (90-mers) with high yield. This synthesis requires 360 virtual masks, and thus puts challenges on image placement and local contrast. We have updated our DNA synthesis modeling to Monte Carlo simulation from numerical approach. We also devised a method, called “Inverted Capping,” to remove sequence errors from edge scattering of light, which provides a large error reduction and the possibility of fabrication of higher resolutions. Finally, we have also implemented an image locking method to eliminate image drifts.
Show PACS
87.80.-y Biophysical techniques (research methods)
87.10.-e General theory and mathematical aspects
87.14.G- Nucleic acids
81.16.Nd Micro- and nanolithography
85.65.+h Molecular electronic devices

Assembled micro-electromechanical-systems microcolumn from a single layer silicon process

R. Saini, Z. Jandric, K. Tsui, T. Udeshi, and D. Tuggle

J. Vac. Sci. Technol. B 22, 3168 (2004); http://dx.doi.org/10.1116/1.1815311 (6 pages) | Cited 4 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
We report a novel microcolumn fabrication method using automated micro-electro-mechanical-systems (MEMS) assembly. Different microcolumn components, including deflectors, lens elements, and apertures, are fabricated on a highly doped 50 μm thick silicon-on-insulator (SOI) wafer. These components with compliant connectors are then assembled onto compliant MEMS sockets fabricated on the same wafer using MEMS NanoEffectors™ and automated assembly. The self-aligning nature of MEMS sockets yields submicron lateral alignment and less than 0.1° angular misalignment. The measured resonant frequency is 593 Hz for first generation assembled components; the footprint of the microcolumn is less than 1 cm2. We have successfully built a mechanical prototype microcolumn for technology demonstration and as a proof of concept. Second generation design is under development.
Show PACS
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.10.Cm Micromechanical devices and systems

Deep-ultraviolet–microelectromechanical systems stencils for high-throughput resistless patterning of mesoscopic structures

M. A. F. van den Boogaart, G. M. Kim, R. Pellens, J.-P. van den Heuvel, and J. Brugger

J. Vac. Sci. Technol. B 22, 3174 (2004); http://dx.doi.org/10.1116/1.1802931 (4 pages) | Cited 20 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
We describe a combination of 100-mm wafer scale deep-ultraviolet (DUV) exposure and a microelectromechanical systems (MEMS) process to fabricate silicon nitride membranes with submicrometer apertures to be used as miniature shadow masks or nanostencils. Apertures down to a lateral resolution of 200 nm were made in a 500-nm-thick membrane by DUV exposure and dry plasma etching. The membranes were released by a combination of wet silicon etching using potassium hydroxide (KOH) and dry silicon etching using a plasma process. The millimeter-size stencils were used for single-step, local deposition of metal micro- and nano-patterns without the need for photoresist process steps. We have performed stencil deposition on full wafer scale for micro- and nano-patterns in a variety of metals (e.g. Al, Au, Ni, etc.). Dry under-etching of the nanowires resulted in free-standing cantilevered nanoelectromechanical systems (NEMS) structures with resonance frequencies in the megahertz range. The resistless method allows us to pattern micrometer and nanometer scale patterns in a single step without any further processing. It is promising for the surface processing of MEMS/NEMS devices having sensitive or fragile surfaces, such as biochips, organic polymer layers, and self-assembled monolayers.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
81.16.Nd Micro- and nanolithography
81.65.Cf Surface cleaning, etching, patterning

Fabrication of sub-5 nm gaps between metallic electrodes using conventional lithographic techniques

Philipp Steinmann and J. M. R. Weaver

J. Vac. Sci. Technol. B 22, 3178 (2004); http://dx.doi.org/10.1116/1.1808712 (4 pages) | Cited 9 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
The reproducible fabrication of nanoscale gaps below 5 nm between metallic electrodes is key to the study of the electronic characteristics of individual molecules, but is hampered by the resolution limit and mechanical instabilities of commonly used electron-sensitive resists. We describe a fabrication process for the creation of nanoscale gaps between metallic electrodes based on conventional lithographic techniques. The process involves the patterning of a lithographic gap of 5–∼20 nm between metallic electrodes on an oxidized silicon substrate. The SiO2 not covered by the electrodes is undercut and another metal film is thermally evaporated onto the substrate. Due to the slow buildup of material at the edges of the patterned electrode, the gap size can be reduced in a controllable way, and the final gap size is determined by the thickness of the evaporated metal film. This batch fabrication process is suitable for high-density fabrication of nanoscale gaps with the attractive feature that a self-aligned gate can be formed underneath the gap. We have investigated the effect of annealing samples for a short period at 125 °C in air. Scanning electron microscopy data of a batch of identical gaps is presented which illustrates the variation in gap size and morphology after annealing. Gaps down to 1–∼2 nm can be resolved directly using a scanning electron microscope. For gaps below 1 nm, the separation between the two metallic electrodes cannot be resolved. To determine whether a tunnel gap is present, electrical measurements are required. Use of the Simmons tunnel model to fit an analytical curve to the measured IV characteristics of a gap gives a separation of 1.2±0.2 nm and also verifies the consistency of parameters such as the effective barrier height in air indicating the presence of contaminants on the electrodes.
Show PACS
81.16.Nd Micro- and nanolithography
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
85.40.Hp Lithography, masks and pattern transfer
81.40.Gh Other heat and thermomechanical treatments
68.55.-a Thin film structure and morphology
81.05.Bx Metals, semimetals, and alloys

Nanoscale electronics based on two-dimensional dopant patterns in silicon

T.-C. Shen, J. S. Kline, T. Schenkel, S. J. Robinson, J.-Y. Ji, C. Yang, R.-R. Du, and J. R. Tucker

J. Vac. Sci. Technol. B 22, 3182 (2004); http://dx.doi.org/10.1116/1.1813466 (4 pages) | Cited 22 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
A nanoscale fabrication process compatible with present Si technology is reported. Preimplanted contact arrays provide external leads for scanning tunneling microscope (STM)-defined dopant patterns. The STM’s low energy electron beam removes hydrogen from H terminated Si(100) surfaces for selective adsorption of PH3 precursor molecules, followed by room temperature Si overgrowth and 500 °C rapid thermal anneal to create activated P-donor patterns in contact with As+-implanted lines. Electrical and magnetoresistance measurements are reported here on 50 and 95 nm-wide P-donor lines, along with Ga-acceptor wires created by focused ion beams, as a means for extending Si device fabrication toward atomic dimensions.
Show PACS
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
85.35.-p Nanoelectronic devices
81.05.Cy Elemental semiconductors
61.82.Fk Semiconductors
68.47.Fg Semiconductor surfaces
72.20.My Galvanomagnetic and other magnetotransport effects
61.72.uf Ge and Si
85.40.Ry Impurity doping, diffusion and ion implantation technology

25 nm mechanically buttressed high aspect ratio zone plates: Fabrication and performance

Deirdre L. Olynick, Bruce D. Harteneck, Eugene Veklerov, Mihir Tendulkar, J. Alexander Liddle, A. L. David Kilcoyne, and Tolek Tyliszczak

J. Vac. Sci. Technol. B 22, 3186 (2004); http://dx.doi.org/10.1116/1.1815298 (5 pages) | Cited 16 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
High performance zone plates are critical for advancing the state-of-the-art in x-ray microscopy, both in terms of spatial and energy resolution. Improved resolution, increased energy bandwidth, and enhanced efficiency can be achieved through the fabrication of smaller, higher aspect ratio outer zones. Using electron beam lithography, we have fabricated and obtained initial performance data from a 25 nm outer zone width zone plate, with a 7:1 aspect ratio, using a hydrogen silsesquioxane (HSQ)/cross-linked polymer bilayer process. We investigated the effectiveness of buttresses, i.e., mechanical supports perpendicular to the zones, on our ability to achieve higher aspect ratios which conventionally would be unreachable due to resist collapse. Optimum buttress spacing is affected by film thickness, linewidth, collapse mechanisms, and resist modulus. For 25 nm zones, etched into 150 nm cross-linked polymer (AZPN114), buttress spacings of approximately two times the resist thickness or ten times the zone width are sufficient to prevent collapse during plating. We find that high aspect ratio features not only have to be able to withstand collapse during liquid immersion, but also during dry etching processes. In addition, we show that a 50% feature bias and longer development times (8 min in 1% TMAH based solutions) allow smaller dense feature sizes by eliminating resist webbing frequently observed in electron-beam imaging of HSQ.
Show PACS
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
81.65.Cf Surface cleaning, etching, patterning
07.85.Tt X-ray microscopes
42.79.Ci Filters, zone plates, and polarizers

Patterned grafting of polymer brushes onto flexible polymer substrates

Celestino Padeste, Harun H. Solak, Hans-Peter Brack, Michal Slaski, Selmiye Alkan Gürsel, and Günther G. Scherer

J. Vac. Sci. Technol. B 22, 3191 (2004); http://dx.doi.org/10.1116/1.1805542 (5 pages) | Cited 9 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Selective exposure of polymer substrates to extreme ultraviolet (EUV) radiation followed by graft polymerization of a second polymer is used to create patterns of polymer brushes. A key feature of this additive structuring process is the possibility to combine the properties of a polymer substrate in precisely predefined regions with the properties of the grafted material. Styrene brushes were grafted onto poly(ethylene-alt-tetrafluoroethylene) (ETFE) substrates after exposure to synchrotron EUV radiation in an interference lithographic setup. The grafted chains are covalently bound to the surface, which allows physical or chemical post-processing without deterioration of the grafted structures.
Show PACS
61.41.+e Polymers, elastomers, and plastics
82.35.-x Polymers: properties; reactions; polymerization
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Pv Polymers, organic compounds

Structure quality of high aspect ratio sub-micron polymer structures patterned at the electron storage ring ANKA

S. Achenbach, T. Mappes, and J. Mohr

J. Vac. Sci. Technol. B 22, 3196 (2004); http://dx.doi.org/10.1116/1.1824910 (6 pages) | Cited 4 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
We describe the fabrication of polymer structures with lateral dimensions in the sub-micron regime using hard x rays (λ≈0.4 nm) from the electron storage ring ANKA. PMMA and Novolak resists have been analyzed with respect to development rates and contrast. Films with a thickness from 2 μm to 11 μm have been patterned using a high resolution x-ray mask consisting of 2 μm thick gold absorbers on a suspended silicon nitride membrane. The fabrication of those sub-micron x-ray lithography structures is confined by the mask absorber sizes of down to 400 nm and by the process conditions. The yield of resist structures with aspect ratios of 9 and above is limited by bending of the structures. An intermediate buffer layer of polyimide enhances the resist adhesion and reduces cracking in the microstructures. Diffraction at mask absorber edges biases the resist feature size on the order of tens of nanometers. It may also result in surface attack of periodic resist structures if the proximity gap between mask and resist chosen is too high. Resist surfaces are subject to rounding which can locally diminish the sidewall verticality. PMMA structures have been successfully used as a template for electroplating of 1 μm thick gold to demonstrate the fabrication capability of sub-micron scale metal parts.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
42.82.Cr Fabrication techniques; lithography, pattern transfer
81.16.Nd Micro- and nanolithography
61.41.+e Polymers, elastomers, and plastics
82.35.Gh Polymers on surfaces; adhesion
68.35.Np Adhesion

Direct metal pattern writing by VUV photodissociation

Jianxun Yan and Mool C. Gupta

J. Vac. Sci. Technol. B 22, 3202 (2004); http://dx.doi.org/10.1116/1.1802871 (4 pages)

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
An efficient process for direct pattern writing of thin metallic films has been developed using a 121.6 nm vacuum ultraviolet source by photodissociation of metalorganic materials. The optical reflection, crystal structure, and surface morphology of photodissociated palladium thin films were studied using a spectrophotometer, x-ray diffraction, and scanning electron microscopy. A pattern of 5 μm palladium lines separated by 5 μm spaces was produced on glass substrate by contact printing lithography.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
82.50.Hp Processes caused by visible and UV light
78.30.Er Solid metals and alloys
78.66.Bz Metals and metallic alloys
68.55.-a Thin film structure and morphology

Assessment of lithographic process variation effects in InGaAsP annular Bragg resonator lasers

William M. J. Green, Jacob Scheuer, Guy A. DeRose, Amnon Yariv, and Axel Scherer

J. Vac. Sci. Technol. B 22, 3206 (2004); http://dx.doi.org/10.1116/1.1808740 (4 pages) | Cited 2 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Optical microresonators based on an annular geometry of radial Bragg reflectors have been designed and fabricated by electron-beam lithography, reactive ion etching, and an epitaxial transfer process. Unlike conventional ring resonators that are based on total internal reflection of light, the annular structure described here is designed to support optical modes with very small azimuthal propagation coefficient and correspondingly large free spectral range. The effect of lithographic process variation upon device performance is studied. Laser emission wavelength and threshold optical pump power are found to vary between similar devices given different electron doses during electron-beam lithography. As the resonance wavelength and quality factor of these resonators are very sensitive to environmental changes, these resonators make ideal active light sources that can be integrated into large arrays for gas and liquid sensing applications and are easily interrogated.
Show PACS
42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.82.Cr Fabrication techniques; lithography, pattern transfer
81.05.Ea III-V semiconductors
78.66.Fd III-V semiconductors
81.65.Cf Surface cleaning, etching, patterning
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Plasma doping technology for fabrication of nanoscale metal-oxide-semiconductor devices

Won-ju Cho, Kiju Im, Chang-Geun Ahn, Jong-Heon Yang, Jihun Oh, In-Bok Baek, and Seongjae Lee

J. Vac. Sci. Technol. B 22, 3210 (2004); http://dx.doi.org/10.1116/1.1813461 (4 pages) | Cited 6 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
We developed a plasma doping (PLAD) technique which is appropriate for the nanoscale metal-oxide-semiconductor field effect transistors (MOSFETs) fabrications. Silicon-on-insulator (SOI) n-MOSFETs with a 50-nm-length metal gate and a 100-nm-channel width were successfully fabricated. The source and drain extensions (SDE) of SOI n-MOSFETs were formed using a plasma doping technique. The advantage of this process is the exclusion of additional activation annealing after introduction of impurity in SDE, which resulted in a laterally abrupt source/drain (S/D) junction profile. We can obtain a low sheet resistance by the PLAD technique and low damaged shallow junctions. A trigate structure SOI n-MOSFET with a gate length of 50 nm fabricated by high-temperature plasma doping revealed suppressed short-channel effects.
Show PACS
85.30.Tv Field effect devices
52.77.Dq Plasma-based ion implantation and deposition
61.72.uf Ge and Si
81.05.Cy Elemental semiconductors
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Towards intersubband quantum box lasers: Electron-beam lithography update

G. Tsvid, M. D’Souza, D. Botez, B. Hawkins, A. Khandekar, T. Kuech, and P. Zory

J. Vac. Sci. Technol. B 22, 3214 (2004); http://dx.doi.org/10.1116/1.1824055 (3 pages) | Cited 2 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
We report on the progress in the patterning and fabrication of the intersubband quantum-box (QB) laser structure. From a patterning point of view our goal is to make 30-nm-diameter SiO2 and/or hydrogen silsesquioxane (HSQ) disks on 60–80 nm centers on a GaAs surface to serve as masks for in situ etch and regrowth of QBs. Electron-beam lithography with high-resolution negative resist HSQ was used, and two processes have been investigated. The first process is to pattern HSQ directly on the GaAs surface, while the second one involves putting down an intermediate oxide layer first, followed by the e-beam lithography and the transfer of the pattern into the oxide. Problems were encountered with the e-beam patterning of HSQ directly on the GaAs surface because of the broad scattering from the substrate and not very good adhesion. Excellent patterning was demonstrated when the intermediate oxide layer was present between the GaAs substrate and the HSQ resist.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
81.07.St Quantum wells
85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

Scanning thermal lithography: Maskless, submicron thermochemical patterning of photoresist by ultracompliant probes

Amar S. Basu, Shamus McNamara, and Yogesh B. Gianchandani

J. Vac. Sci. Technol. B 22, 3217 (2004); http://dx.doi.org/10.1116/1.1808732 (4 pages) | Cited 9 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
This article introduces a scanning probe lithography technique in which ultracompliant thermal probes are used in the selective thermochemical patterning of commercially available photoresist. The micromachined single-probe and multiprobe arrays include a thin-film metal resistive heater and sensor sandwiched between two layers of polyimide. The low spring constant (<0.1 N∕m) and high thermal isolation provided by the polyimide shank is suitable for contact mode scanning across soft resists without force feedback control. The probes provide what is effectively a spatially localized postexposure bake that crosslinks the photoresist in the desired pattern, rendering it insoluble in developer. For 450-nm–1400-nm-thick AZ5214E (Clariant Corp.), line and dot features with sizes of 450 –1800 nm can be printed using probe powers of 13.5–18 mW, and durations of 1–60 s per pixel. Variation of feature sizes with process parameters is described.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

In situ observation of carbon-nanopillar tubulization process

Toshinari Ichihashi, Masahiko Ishida, Yukinori Ochiai, and Jun-ichi Fujita

J. Vac. Sci. Technol. B 22, 3221 (2004); http://dx.doi.org/10.1116/1.1808713 (3 pages) | Cited 6 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
We observed the tubulization process of amorphous carbon nanopillars using an in situ transmission electron microscopy. Amorphous carbon nanopillars were grown by electron-beam-induced chemical vapor deposition on an iron-doped carbon foundation. Amorphous carbon nanopillars were transformed into graphitic tubules by annealing at about 650 °C in the presence of iron nanoparticles supplied from the iron-doped carbon foundation. A molten catalyst nanoparticle penetrated an amorphous carbon nanopillar, dissolving it and leaving a graphite track behind. This graphitic nanotube synthesis technique using nanofabrication promises to bring about a great advance in nanotube electronic devices.
Show PACS
81.07.De Nanotubes
81.40.Gh Other heat and thermomechanical treatments
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.07.Bc Nanocrystalline materials
back to top Nanoimprint Components and Processes

Impact of residual layer uniformity on UV stabilization after embossing

M. Wissen, H. Schulz, N. Bogdanski, H.-C. Scheer, Y. Hirai, H. Kikuta, G. Ahrens, F. Reuther, and T. Glinsner

J. Vac. Sci. Technol. B 22, 3224 (2004); http://dx.doi.org/10.1116/1.1808716 (5 pages) | Cited 2 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
A low-Tg resist material, mr-L 6000XP, was investigated for low-temperature imprint. Its stabilization requires UV exposure and a postexposure bake. To approach the UV-induced crosslinking process, the local distribution of light intensity within the imprinted pattern was simulated. To account for a nonuniformity of the residual layer caused by pattern size and pattern density effects during imprint, different residual layer heights were adopted. The simulations show that not only the residual layer height but also the pattern size influences the resulting local intensity distribution. Experiments performed for selected residual layer heights (50, 100, 150, and 200 nm) document that in fact the residual layer height affects the pattern quality obtained after stabilization. The effects identified are different for differing pattern sizes. Beyond stabilization, the results have consequences for mix and match of nanoimprint with UV lithography.
Show PACS
42.82.Cr Fabrication techniques; lithography, pattern transfer
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer

High resolution lithography with PDMS molds

M. Bender, U. Plachetka, J. Ran, A. Fuchs, B. Vratzov, H. Kurz, T. Glinsner, and F. Lindner

J. Vac. Sci. Technol. B 22, 3229 (2004); http://dx.doi.org/10.1116/1.1824057 (4 pages) | Cited 22 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
The resolution, dimension stability, and reproducibility of the Soft UV-Nanoimprint is investigated. The potential for imprinting nanostructures with flexible molds in UV-curable resists in the 100 nm regime are explored and the limitations analyzed. The dimensional stability of imprinted patterns is determined by the deformation of the mold that in term depends on the geometry of the structures and the imprint pressure applied.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

Effect of fluoroalkyl substituents on the reactions of alkylchlorosilanes with mold surfaces for nanoimprint lithography

Jem-Kun Chen, Fu-Hsiang Ko, Kuen-Fong Hsieh, Cheng-Tung Chou, and Feng-Chih Chang

J. Vac. Sci. Technol. B 22, 3233 (2004); http://dx.doi.org/10.1116/1.1815305 (9 pages) | Cited 12 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
We have applied trichloro(3,3,3-trifluoropropyl)silane (FPTS) and trichloro(1H,1H,2H, 2H-perfluorooctyl)silane (FOTS) for the preparation of self-assembled film on a silicon mold for use as releasing, antisticking layers for nanoimprint lithography. From contact angle measurements, we have determined the surface energies of the molds in terms of their Lewis acid, Lewis base, and van der Waals components. The surface energies of the FPTS- and FOTS-derived film decreased as the annealing temperature and immersion time increased. Suitable self-assembled films were prepared by annealing at 150 °C for at least 1 h. The surface roughnesses of the self-assembled film formed from FPTS and FOTS were 0.468 and 0.189 nm, respectively. The lower surface energy and roughness of the FOTS-derived film on the silicon mold prevent both the adhesion and defect-formation problems from occurring during resist imprinting. The self-assembled films prepared on the mold are resistant to immersion in acid and base, but treatment with oxygen plasma has an adverse effect on these molds’ stabilities.
Show PACS
81.16.Nd Micro- and nanolithography
68.55.-a Thin film structure and morphology
68.47.Pe Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces
81.16.Dn Self-assembly
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.40.Gh Other heat and thermomechanical treatments
68.35.Md Surface thermodynamics, surface energies
81.10.Fq Growth from melts; zone melting and refining

Interferometric in situ alignment for UV-based nanoimprint

A. Fuchs, B. Vratzov, T. Wahlbrink, Y. Georgiev, and H. Kurz

J. Vac. Sci. Technol. B 22, 3242 (2004); http://dx.doi.org/10.1116/1.1808735 (4 pages) | Cited 7 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
A high precision alignment concept is evaluated for suitability in UV-based nanoimprint lithography. Through three consecutive alignment steps an overlay accuracy of 50 nm is obtained with ample room for further improvements.
Show PACS
07.60.Ly Interferometers
81.16.Nd Micro- and nanolithography
42.82.Cr Fabrication techniques; lithography, pattern transfer

Stamps for nanoimprint lithography by extreme ultraviolet interference lithography

Sunggook Park, Helmut Schift, Harun H. Solak, and Jens Gobrecht

J. Vac. Sci. Technol. B 22, 3246 (2004); http://dx.doi.org/10.1116/1.1828087 (5 pages) | Cited 11 times

Online Publication Date: 10 December 2004

Full Text: | Download PDF

Show Abstract
Extreme ultraviolet interference lithography (EUV-IL) was employed to fabricate large area stamps with patterns of sub-50 nm half pitch for nanoimprint lithography (NIL). The resist patterns exposed by EUV-IL were transferred into underlying Si or SiO2∕Si substrates by reactive ion etching. With this method, NIL stamps with feature sizes as small as 25 nm and patterned areas as large as 1×1 mm2 were successfully produced. Using those stamps in NIL, the patterns with aspect ratio up to 2 were replicated with good replication fidelity. Increasing aspect ratio for the stamp patterns first results in distortion and discontinuity and then, the ripping of partial structures in the imprinted patterns.
Show PACS
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
81.65.Cf Surface cleaning, etching, patterning
back to top Nanoimprint Fabrication

Duo-mold imprinting of three-dimensional polymeric structures

Y. P. Kong, H. Y. Low, S. W. Pang, and A. F. Yee

J. Vac. Sci. Technol. B 22, 3251 (2004); http://dx.doi.org/10.1116/1.1813459 (6 pages) | Cited 15 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
We present a new method of imprinting three dimensional (3D) polymeric micro- and nanostructures using a duo-mold process. In this method, two patterned Si molds are surface treated to have different surface energies. A polymer solution is spin-coated onto one of the molds, forming a planarized thin film on the mold. The two molds are pressed together at an appropriate temperature and pressure and then released. The patterned thin film adhering to one of the molds is then pressed onto a substrate at an appropriate temperature and pressure to form supported 3D structures. Alternatively, the patterned thin film on the mold may be released to form freestanding 3D structures. A key success factor in this process is the silane-based surface treatments to enable the patterning of the thin polymer film and final release from the mold to form 3D structures. We demonstrate various polymethyl methacrylate 3D structures with combinations of grating, circular-, and square-patterned molds. The duo-mold process is a potentially low-cost and high-throughput method to fabricate 3D polymeric micro- and nanostructures.
Show PACS
81.10.Fq Growth from melts; zone melting and refining
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.16.Nd Micro- and nanolithography
81.65.Cf Surface cleaning, etching, patterning
85.40.Hp Lithography, masks and pattern transfer
68.55.A- Nucleation and growth
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
68.35.Md Surface thermodynamics, surface energies

Direct imprint of sub-10 nm features into metal using diamond and SiC stamps

K. A. Lister, S. Thoms, D. S. Macintyre, C. D. W. Wilkinson, J. M. R. Weaver, and B. G. Casey

J. Vac. Sci. Technol. B 22, 3257 (2004); http://dx.doi.org/10.1116/1.1825010 (3 pages) | Cited 13 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
We demonstrate the transfer of sub-10 nm features into nickel using a hard stamp. Nanostructures were transferred directly from diamond and SiC in a single step by pressing the stamp into nickel at room temperature. The patterns were generated using ultrahigh resolution electron beam lithography. Patterns were transferred to the diamond and SiC using RIE etching with an O2 plasma used for the diamond and a SF6+O2 mixture used for the SiC. Hydrogen Silsesquioxane was used as a resist and served as a mask in the plasma etching.
Show PACS
81.65.Cf Surface cleaning, etching, patterning
85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

High fidelity blazed grating replication using nanoimprint lithography

Chih-Hao Chang, J. C. Montoya, M. Akilian, A. Lapsa, R. K. Heilmann, M. L. Schattenburg, M. Li, K. A. Flanagan, A. P. Rasmussen, J. F. Seely, J. M. Laming, B. Kjornrattanawanich, and L. I. Goray

J. Vac. Sci. Technol. B 22, 3260 (2004); http://dx.doi.org/10.1116/1.1809614 (5 pages) | Cited 6 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
We report progress in using nanoimprint lithography to fabricate high fidelity blazed diffraction gratings. Anisotropically etched silicon gratings with 200 nm period and 7.5° blaze angle were successfully replicated onto 100 mm diameter wafers with subnanometer roughness and excellent profile conformity. Out-of-plane distortion induced by residual stress from polymer films was also analyzed and found to be extremely low. The replicated blazed gratings were tested and demonstrated high x-ray diffraction efficiencies. This process was developed for fabricating blazed diffraction gratings for the NASA Constellation-X x-ray telescope.
Show PACS
42.79.Dj Gratings
42.82.Cr Fabrication techniques; lithography, pattern transfer
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer

Fabrication of a surface acoustic wave-based correlator using step-and-flash imprint lithography

G. F. Cardinale, J. L. Skinner, A. A. Talin, R. W. Brocato, D. W. Palmer, D. P. Mancini, W. J. Dauksher, K. Gehoski, N. Le, K. J. Nordquist, and D. J. Resnick

J. Vac. Sci. Technol. B 22, 3265 (2004); http://dx.doi.org/10.1116/1.1821508 (6 pages) | Cited 5 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
We report the surface acoustic wave (SAW) correlator devices fabricated using nanoimprint lithography. Using step-and-flash imprint lithography (S-FIL), we produced SAW correlator devices on 100 mm diameter z-cut LiNbO3 devices and an aluminum metal etch process. On the same chip layout, we fabricated SAW filters and compared both the filters and correlators to similar devices fabricated using electron-beam lithography (EBL). Both S-FIL- and EBL-patterned correlators and SAW filters were analyzed using a bit-error rate tester to generate the signal and a parametric signal analyzer to evaluate the output. The NIL filters had an average center frequency of 2.38 GHz with a standard deviation of 10 MHz. The measured insertion loss averaged −31 dB. In comparison, SAW filters fabricated using EBL exhibited a center frequency of 2.39 GHz and a standard deviation of 100 kHz. Based on our preliminary results, we believe that S-FIL is an efficient and entirely viable fabrication method to produce quality SAW filters and correlators.
Show PACS
84.30.Vn Filters
85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

Imprint lithography issues in the fabrication of high electron mobility transistors

S. Thoms, D. S. Macintyre, D. Moran, and I. Thayne

J. Vac. Sci. Technol. B 22, 3271 (2004); http://dx.doi.org/10.1116/1.1821504 (4 pages) | Cited 1 time

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
In earlier work we described procedures for the fabrication of High Electron Mobility Transistors (HEMTs) using nanoimprint lithography to produce T-shaped resist profiles for gate metallization. For reliable liftoff the T-gate process requires a clear undercut in resist, and this is intrinsically impossible with imprint lithography. In addition, the imprinting process resulted in fracture defects in the resist unless release was carried out at elevated temperatures. Both these problems required improvement. In this article we describe an improved method for obtaining metallized imprinted T-gates by creating resist undercut using a double angled evaporation. HEMTs with self-aligned gate structures were fabricated using this procedure. Multilayer resist stacks were used to investigate resist flow during imprinting and we show that such stacks are not suitable for liftoff enhancement of T-gates. We further show how resist fracture defects can be minimized by increasing the pattern density on the die.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
85.30.Tv Field effect devices
81.16.Nd Micro- and nanolithography
85.40.Ls Metallization, contacts, interconnects; device isolation

DNA nanopatterning with self-organization by using nanoimprint

Toshihito Ohtake, Ken-ichiro Nakamatsu, Shinji Matsui, Hitoshi Tabata, and Tomoji Kawai

J. Vac. Sci. Technol. B 22, 3275 (2004); http://dx.doi.org/10.1116/1.1823438 (4 pages) | Cited 8 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
Recently, DNA properties have been investigated to realize new functional biodevices. However, there are few reports on DNA nanopatterning to make bionanodevices. Therefore, we have attempted DNA nanopatterning by using a nanoimprint method. On a glass substrate coated with poly-L-lysine, which is known as a material for DNA immobilization by UV radiation, about 100 μl of a 1 μg∕μl DNA solution was applied and was dried at 60 °C for an hour, and was irradiated by UV for 2 min. Further 4% polyvinyl alcohol (PVA) solution was coated on the substrate. The substrate was imprinted at 100 °C and 6 MPa for 5 min, and a mold was applied with a SiO2 on Si substrate fabricated by electron-beam lithography and dry etching. Etching of the DNA substrate was done by reactive ion etching in O2 atmosphere. Finally, the PVA layer washed down by water, and the DNA nanopatterning was obtained.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
87.80.-y Biophysical techniques (research methods)
81.65.Cf Surface cleaning, etching, patterning
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Pv Polymers, organic compounds
back to top Nanoimprint Materials

Predicting the fluid behavior during the dispensing process for step-and-flash imprint lithography

A. Abdo, S. Schuetter, G. Nellis, A. Wei, R. Engelstad, and V. Truskett

J. Vac. Sci. Technol. B 22, 3279 (2004); http://dx.doi.org/10.1116/1.1825016 (4 pages) | Cited 1 time

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
In this article, the polymer dispense process in the step-and-flash imprint lithography is investigated with computational fluid dynamics (CFD) models. The dispense process is a function of the fluid properties and the system parameters such as the geometry and the details of the actuation motion. Physical arguments show that this functional dependence can be reduced to two dimensionless numbers: the Weber number which represents the ratio of inertia to surface tension forces, and the capillary number which represents the ratio of viscous to surface tension forces. A parametric study showed that there is a clear optimal regime for the dispensing process in which a single, clearly-defined drop forms. The CFD model was verified experimentally by comparing the predicted fluid dispense behavior with photographs of a dispense process.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

Process development and characterization of antisticking layers on nickel-based stamps designed for nanoimprint lithography

M. Keil, M. Beck, G. Frennesson, E. Theander, E. Bolmsjö, L. Montelius, and B. Heidari

J. Vac. Sci. Technol. B 22, 3283 (2004); http://dx.doi.org/10.1116/1.1824051 (5 pages) | Cited 5 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
Thin films of different derivatives of fluorinated alkyl phosphoric acids have been deposited from aqueous solutions onto surfaces of oxidized polycrystalline nickel stamps, which are commonly used in several industrial applications of nanoimprint lithography (NIL). The films have been established in order to increase the antiadhesion tendencies at the stamp polymer interface. Thicknesses, chemical compositions, and purities of the films as well as binding mechanisms to the stamp surfaces have been determined by photoelectron spectroscopy (XPS). The results demonstrate the adsorption of highly pure films having thicknesses in the monomolecular region, whose chemical compositions are characterized by large ratios of fluorinated to nonfluorinated carbon species. The high ionic nature of Ni-oxide benefits strong ionic linkages between the phosphate groups of the fluorinated antisticking film and the stamp surface, allowing a large-scale production of imprints with patterned stamps having feature sizes down to 100 nm.
Show PACS
81.16.Nd Micro- and nanolithography
68.35.Np Adhesion
68.43.Mn Adsorption kinetics
85.40.Hp Lithography, masks and pattern transfer

Simulation and experimental study of polymer deformation in nanoimprint lithography

Yoshihiko Hirai, Takaaki Konishi, Takashi Yoshikawa, and Satoshi Yoshida

J. Vac. Sci. Technol. B 22, 3288 (2004); http://dx.doi.org/10.1116/1.1826058 (6 pages) | Cited 46 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
A polymer deformation process is studied by numerical simulations and the results are compared with the related experimental results in nanoimprint lithography. The imprint pressures required for successful imprinting and the filling rate into the mold grooves are studied as the aspect ratio of the pattern, initial thickness of the polymer, and the duty ratio of the pattern are changed. The required pressure increases not only for high aspect ratio pattern but also low aspect ratio pattern. Also, the pressure increases when the initial thickness of the polymer decreases to less than about two times that of the groove depth of the mold. These results are explained by the deformation mechanism of the polymer and agree well with the related experimental results. Based on these theoretical and experimental studies, fabrication of a high aspect ratio pattern having 100 nm width and 860 nm height is successfully demonstrated using thick polymer by nanoimprint lithography.
Show PACS
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer

Stability of functional polymers after plasticizer-assisted imprint lithography

R. M. Reano, Y. P. Kong, H. Y. Low, L. Tan, F. Wang, S. W. Pang, and A. F. Yee

J. Vac. Sci. Technol. B 22, 3294 (2004); http://dx.doi.org/10.1116/1.1825013 (6 pages) | Cited 1 time

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
Poly(3,4-ethylenedioxythiophene) (PEDOT) and chitosan structures on Si, patterned by plasticizer-assisted imprint lithography (PAIL), are examined under a variety of imprinting conditions. The stabilities of pattern dimension and chemical functionality of these polymers are presented. Thermal annealing for 5 min at 80 °C is found to be an effective method to stabilize imprinted PEDOT patterns. Biofunctionality in chitosan as a function of imprint temperature and pressure is examined through fluorescence spectroscopy. The accessibility of the amine group of chitosan is observed to decrease for imprint temperatures above 80 °C, whereas the chemical functionality is not affected by pressure up to 1 MPa. Fluorescence spectra of the chitosan are observed to be strong functions of exposure time to O2 plasma.
Show PACS
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.40.Gh Other heat and thermomechanical treatments
78.55.Kz Solid organic materials
back to top Nanoimprint Templates

Inspection of templates for imprint lithography

Harald F. Hess, Don Pettibone, David Adler, Kirk Bertsche, Kevin J. Nordquist, David P. Mancini, William J. Dauksher, and Douglas J. Resnick

J. Vac. Sci. Technol. B 22, 3300 (2004); http://dx.doi.org/10.1116/1.1813456 (6 pages) | Cited 4 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
Masks of any next generation lithography (NGL), such as imprint lithography, must eventually achieve and maintain the very low defect counts of current production masks. This requires typically fewer than 10 or even no defects over the entire field. We describe an inspection methodology and how it can be applied to the imprint template. Special test patterns etched onto the template enable both a die to die comparison, to find nuisance defects, and also calibration of sensitivity to different types of preprogrammed defects. A state of the art deep ultraviolet photomask inspection system (KLA-Tencor model 526) can detect these rare events with about 70 nm threshold for imprint masks with reflection mode contrast. Initial scans are made at various stages of the imprint process: the newly processed mask, after dicing, and after several imprints. The scans show mostly isolated point defects at a density of ∼10–100 per mm2. This is an encouraging start for a new NGL, and reductions are expected from better processes, equipment, and handling. In the future viable mask inspection at the 45–22 nm node will be very demanding for these 1× masks and will require sensitivities approaching 10–20 nm defect size. To this end, special masks suitable for electron (e)-beam inspection are being made and show good contrast and immunity to e-beam charging.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography
81.65.Cf Surface cleaning, etching, patterning
42.82.Cr Fabrication techniques; lithography, pattern transfer

Repair of step and flash imprint lithography templates

W. J. Dauksher, K. J. Nordquist, N. V. Le, K. A. Gehoski, D. P. Mancini, D. J. Resnick, L. Casoose, R. Bozak, R. White, J. Csuy, and D. Lee

J. Vac. Sci. Technol. B 22, 3306 (2004); http://dx.doi.org/10.1116/1.1815300 (6 pages) | Cited 1 time

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
In order for step and flash imprint lithography (S-FIL) to become a truly viable manufacturing technology, infrastructure including template repair must be commercially available. Extensive template repair studies were undertaken using RAVE’s nm 650 tool which is predicated on an AFM platform and relies upon a nanomachining technique for opaque defect removal. On S-FIL templates, the standard deviation for depth repairs in quartz from the target depth was found to be 3.1 nm (1σ). At 21.5 nm (1σ), the analogous spread in edge placement data for opaque line protrusions was somewhat higher. Trench cuts through lines were successfully created with a minimum size of about 55 nm. The effectiveness of the repairs on the template was verified by imprinting experiments. The range of depth offsets studied (−15 to +15 nm) had no bearing on the imprinting process. The edge placement on wafers virtually mirrored the edge placement of the repaired templates. Connections between features which were created by trench cuts on the template were filled with the imprint monomer and measured slightly larger than the minimum gap size. Finally, imprinted wafers were used to pattern transfer features into 100 nm of oxide.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
81.16.-c Methods of micro- and nanofabrication and processing
81.20.Wk Machining, milling
81.05.-t Specific materials: fabrication, treatment, testing, and analysis

Controlling imprint distortions in step-and-flash imprint lithography

S. D. Schuetter, G. A. Dicks, G. F. Nellis, R. L. Engelstad, and E. G. Lovell

J. Vac. Sci. Technol. B 22, 3312 (2004); http://dx.doi.org/10.1116/1.1825011 (6 pages)

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
Step-and-Flash Imprint Lithography (S-FIL™) is a one-to-one imprinting process in which features are transferred from a template by lowering it onto a low-viscosity, photocurable, monomer solution that conforms to the template surface and is subsequently cured. The potential exists for both low cost and high throughput, making S-FIL a promising candidate for Next-Generation Lithography. However, there are many challenges that must be overcome in order to ensure the future viability of S-FIL. Mechanical distortion control is one of the principal challenges, and is addressed in this article. During the imprinting process, the viscous flow of the monomer liquid causes a significant pressure elevation within the fluid as it is forced to flow outwards through a small gap. These pressures cause out-of-plane distortions and in-plane distortions (OPD and IPD) of the template, which may be manifested as errors in the replicated pattern. A fluid-structure model was developed to predict the template distortion associated with the imprinting process. The model consists of two parts. The Reynolds Equation Module (REM) is a two-dimensional finite-difference model that solves the Reynolds equation, which describes the laminar flow of an incompressible constant-viscosity fluid through a small gap. The pressure distribution predicted by the REM is applied as a structural load, together with vacuum chucking and gravity, to a finite-element model of the template developed using ANSYS®. This model, called the Structural Distortion Model, calculates the resulting OPD and IPD of the template. The process is iterated in time for a continually decreasing gap height that corresponds to lowering the template. This article presents the details of the fluid-structure model, the results of the analysis at nominal conditions, and a parametric study of the effects of the operating conditions and fluid properties on the template distortion.
Show PACS
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer

Mold deformation in nanoimprint lithography

F. Lazzarino, C. Gourgon, P. Schiavone, and C. Perret

J. Vac. Sci. Technol. B 22, 3318 (2004); http://dx.doi.org/10.1116/1.1815299 (5 pages) | Cited 25 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
In nanoimprint lithography (NIL), one of the key points to be addressed is the printing uniformity on large area. During the process, the silicon mold undergoes significant mechanical stress of different kinds (tension, compression, flexion, and torsion). These stresses are function of the mold design and appear under the concurrent influence of both the applied pressure on the backside of the mold and an opposite force due to the polymer viscoelastic behavior. This translates into non-negligible deformations within patterned or unpatterned zones. This is a major issue because it causes nonuniformity of the printing, mold pattern break and degradation of the polymer surface. In this article, we demonstrate that during the imprint process mold deformations really occur at the local scale of the patterns but also at a larger scale.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
81.40.Lm Deformation, plasticity, and creep
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.10.Fq Growth from melts; zone melting and refining
62.20.F- Deformation and plasticity
81.05.Cy Elemental semiconductors
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials

Polyvinyl alcohol templates for low cost, high resolution, complex printing

Charles D. Schaper and Alan Miahnahri

J. Vac. Sci. Technol. B 22, 3323 (2004); http://dx.doi.org/10.1116/1.1827218 (4 pages) | Cited 12 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
Templates for imprint lithography and MxL (molecular transfer lithography) are generated by adhesion of a spin-cast film of polyvinyl alcohol (PVA) to a carrier comprised of materials selected for conformability or distortion reduction. Template formation using both polymeric carrier materials and rigid materials, including quartz and glass carrier materials, is demonstrated. The absence of a carrier material altogether to form a suspended thin film is shown to be feasible. The rigid template material is formed by bonding the PVA patterned film to a rigid carrier while still connected to the master pattern, and it is demonstrated that separation occurs at the PVA-silicon master pattern interface. Form factors for the templates include a 25 mm×25 mm patterned film attached to a 65 mm×65 mm glass substrate, a full 100 mm pattern bonded to a quartz substrate, and a 100 mm mask of Mylar™ bonded with a patterned PVA film for MxL applications. These carrier materials are developed in a form factor compatible with commercial nanoimprint lithography tools, and for standard contact aligners adapted to perform MxL processing.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
back to top Nanomagnetics and Nanophotonics

Fabrication of 1D and 2D vertical nanomagnetic resonators

Shuang Zhang, Wenjun Fan, B. K. Minhas, A. Frauenglass, K. J. Malloy, and S. R. J. Brueck

J. Vac. Sci. Technol. B 22, 3327 (2004); http://dx.doi.org/10.1116/1.1824067 (4 pages) | Cited 3 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
We have successfully fabricated the first resonant magnetic nanostructures exhibiting a negative permeability in the midinfrared. These metal-dielectric structures exhibit local resonances based on metallic inductive-capacitive effects that are controlled by the dimensions of the individual nanostructures and are independent of the periodicity, which is much smaller than the resonance wavelengths. Compared to other commonly used structures for obtaining negative permeability in the microwave and THz regions which are based on a planar fabrication paradigm, this structure is oriented vertically so that the smallest features are controlled by deposition rather than by lithography.
Show PACS
07.10.Cm Micromechanical devices and systems
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
77.22.Ch Permittivity (dielectric function)

Nanoscopic templates using self-assembled cylindrical diblock copolymers for patterned media

XiaoMin Yang, Shuaigang Xiao, Chao Liu, Kalman Pelhos, and Kevin Minor

J. Vac. Sci. Technol. B 22, 3331 (2004); http://dx.doi.org/10.1116/1.1815301 (4 pages) | Cited 13 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
We demonstrated a process to create nanoscopic templates for the nanofabrication of patterned media using thin films of diblock copolymers. The self-assembled monolayers (SAMs) technique is used as a means to chemically modify the topographically confined trench surfaces to manipulate the wetting behavior of cylindrical diblock copolymers and perpendicularly oriented cylindrical poly (styrene-block-methyl methacrylate) (PS-b-PMMA) copolymers are obtained. Through optimizing the annealing conditions, long-range ordering in trenches is achieved after annealing at 170 °C for about 24 h. The ordering is strongly dependent on the line-edge-roughness (LER) of the trenches and the number of defects in the copolymer films inside the trenches. Efforts to decrease the various defects in the copolymer films and improve the trench LER are still in progress. With our approach, a negative phase 20 nm nanoporous SiO2 template and a positive phase 20 nm Ta nanodot template based on the self-assembled cylindrical PS-b-PMMA block copolymers are feasible for following pattern transfer to make patterned media.
Show PACS
81.16.Dn Self-assembly
81.40.Gh Other heat and thermomechanical treatments
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.07.-b Nanoscale materials and structures: fabrication and characterization

Elliptical-ring magnetic arrays fabricated using zone-plate-array lithography

Wonjoon Jung, F. J. Castaño, C. A. Ross, Rajesh Menon, Amil Patel, Euclid E. Moon, and Henry I. Smith

J. Vac. Sci. Technol. B 22, 3335 (2004); http://dx.doi.org/10.1116/1.1809624 (4 pages) | Cited 6 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
Zone-plate-array lithography and lift-off processing were employed to fabricate large arrays of elliptical-ring thin film magnets with widths of 600 nm and above. An undercut profile was created using WiDE™ antireflection coating spun underneath a PFI-88 resist layer. The process allowed for up to 60-nm-thick sputtered magnetic multilayered structures. The magnetic properties of the elliptical ring arrays clearly show that the shape anisotropy induced by the ellipticity of the ring creates different magnetization reversal depending on the applied field direction. Magnetic force microscopy shows that the rings display magnetic states characteristic of ring structures, as well as sharp transitions between them. A fabrication process to produce magnetic memory prototypes based on these elliptical rings is presented.
Show PACS
75.70.Ak Magnetic properties of monolayers and thin films
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
85.40.Hp Lithography, masks and pattern transfer
75.60.Jk Magnetization reversal mechanisms
85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)

Electron-beam SAFIER™ process and its application for magnetic thin-film heads

XiaoMin Yang, Harold Gentile, Andrew Eckert, and Stanko R. Brankovic

J. Vac. Sci. Technol. B 22, 3339 (2004); http://dx.doi.org/10.1116/1.1815309 (5 pages) | Cited 9 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
We have coupled the SAFIER™ (shrink assist film for enhanced resolution) process with electron-beam lithography for the fabrication of the write top pole structures for thin-film heads. The SAFIER™ process is designed to physically shrink trench patterns and contact holes with very little deterioration of the resist profile. In this article, we will present the experimental results of the SAFIER™ process for the fabrication of the write top pole. We investigate the SAFIER™ process concerning several key processing issues, including shrink resolution capability, repetition of the SAFIER™ process, shrink-sensitive baking conditions, resist sidewall profile, and line edge roughness (LER) after shrinking of the trench. The experimental results show that this process not only shrinks the size of resist trenches and contact holes, but also improves LER and critical dimension variation. We demonstrate the capability of printing top pole structures with pole widths of sub-20 nm in a 0.30-μm-thick resist (aspect ratio>15:1), and electroplated top pole structures of 50 nm in a 0.50-μm-thick resist (aspect ratio=10:1).
Show PACS
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

GaAs-based 1.3 μm microlasers with photonic crystal mirrors

H. Scherer, D. Gollub, M. Kamp, and A. Forchel

J. Vac. Sci. Technol. B 22, 3344 (2004); http://dx.doi.org/10.1116/1.1823434 (4 pages) | Cited 2 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
We present results of GaAs-based microlasers with photonic crystal mirrors. The lasers are fabricated from GaAs∕AlGaAs layer structures with a doub1e GaInNAs quantum well emitting at 1.3 μm wavelength. The devices are realized as ridge waveguide lasers with two coupled cavities and a total length between 175 and 600 μm. Photonic crystals are used to define the front and back mirrors of the lasers. Threshold currents around 40 mA and output power levels of 80 mW were achieved. Single-mode emission with 30 dB side-mode suppression ratio is obtained due to mode interference between the two cavities.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
81.05.Ea III-V semiconductors
42.79.Bh Lenses, prisms and mirrors
42.55.Sa Microcavity and microdisk lasers
42.70.Qs Photonic bandgap materials

Photonic crystals in polymers by direct electron-beam lithography presenting a photonic band gap

Roberto R. Panepucci, Bryan H. Kim, Vilson R. Almeida, and Matthew D. Jones

J. Vac. Sci. Technol. B 22, 3348 (2004); http://dx.doi.org/10.1116/1.1813457 (4 pages) | Cited 7 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
Direct lithography in electron-beam sensitive polymers was investigated to fabricate 2D-slab polymer-based photonic crystal structures. Polymethyl-methacrylate (PMMA) doped with azo dye Disperse Red 1 (DR1) chromophores was used as a test material to produce optimized low-index contrast photonic crystals presenting a photonic band gap for TE polarization. Extensive computational simulations of the full 3D-slab modes guided the design and fabrication strategy through optimization of the lattice structure, lattice parameter, hole size, and slab thickness. An exposure strategy that takes advantage of 100 kV beam energy for deep lithography, and exposure control for multilevel pattern definition is presented, resulting in the high aspect ratio and verticality required to achieve a strong band gap effect. Finally, a method that enables a high-quality air-clad PMMA-DR1 to be fabricated and integrated with optical waveguides for characterization is presented, enabling successful observation of a photonic bandgap in a 2D-slab polymer photonic crystal.
Show PACS
42.70.Qs Photonic bandgap materials
78.30.Jw Organic compounds, polymers
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
42.79.Gn Optical waveguides and couplers
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.70.Jk Polymers and organics

Large-area patterning for photonic crystals via coherent diffraction lithography

Christel Zanke, Minghao Qi, and Henry I. Smith

J. Vac. Sci. Technol. B 22, 3352 (2004); http://dx.doi.org/10.1116/1.1813448 (4 pages) | Cited 10 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
A new method for lithographically patterning a large-area hexagonal lattice of circular holes is proposed, which is particularly suitable for the fabrication of 2D and 3D photonic crystals (PhC). The method, which we call coherent diffraction lithography (CDL), is based on the interference of beams diffracted from a mask containing a periodic pattern, often referred to as the Talbot effect. We demonstrate the replication of large-area hexagonal lattices using CDL, and investigate the most critical parameters of this technique.
Show PACS
42.70.Qs Photonic bandgap materials
42.82.Cr Fabrication techniques; lithography, pattern transfer
85.40.Hp Lithography, masks and pattern transfer

Photonic crystal waveguides with propagation losses in the 1 dB∕mm range

J. Zimmermann, H. Scherer, M. Kamp, S. Deubert, J. P. Reithmaier, A. Forchel, R. März, and S. Anand

J. Vac. Sci. Technol. B 22, 3356 (2004); http://dx.doi.org/10.1116/1.1824053 (3 pages) | Cited 5 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
High-quality photonic crystal waveguides have been fabricated in the InGaAsP∕InP and GaAs∕AlGaAs material systems aimed at the communication wavelengths of 1.55 and 1.31 μm. The waveguides consist of omitted rows of holes in a triangular lattice of air holes etched into the semiconductor heterostructures by electron cyclotron resonance reactive ion etching. Efficient waveguiding has been observed in optical transmission measurements, with waveguide losses ranging from 1.5 dB∕mm for a waveguide with three missing row of holes (W3) to 0.2 dB∕mm for seven missing rows (W7).
Show PACS
42.79.Gn Optical waveguides and couplers
42.70.Qs Photonic bandgap materials
78.30.Hv Other nonmetallic inorganics
76.40.+b Diamagnetic and cyclotron resonances
81.65.Cf Surface cleaning, etching, patterning

Fabrication of autocloned photonic crystals by using high-density-plasma chemical vapor deposition

H. L. Chen, H. F. Lee, W. C. Chao, C. I. Hsieh, F. H. Ko, and T. C. Chu

J. Vac. Sci. Technol. B 22, 3359 (2004); http://dx.doi.org/10.1116/1.1824059 (4 pages) | Cited 3 times

Online Publication Date: 17 December 2004

Full Text: | Download PDF

Show Abstract
The high-density-plasma chemical vapor deposition (HDP-CVD) method was demonstrated as an alternative to radio-frequency (rf) bias sputtering method for fabrication of “autocloned” photonic crystals. We successfully preserved periodic surface corrugation after deposition of multilayer stacks under appropriate chemical vapor deposition conditions. Freedom of the shaping process was increased by simply raising the bias power of the autocloning process, and thus created autocloned structures having a strong modulation of the effective refractive index in the lateral direction. The method allows photonic bands of autocloned photonic crystals to be designed with greater controllability and a simpler fabrication process. Furthermore, the HDP-CVD method has better step-coverage than the sputtering method and can be used to fabricate autocloning structures with small feature-sizes.
Show PACS
42.70.Qs Photonic bandgap materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Fabrication of photonic crystal waveguides composed of a square lattice of dielectric rods

Solomon Assefa, G. S. Petrich, L. A. Kolodziejski, M. K. Mondol, and H. I. Smith

J. Vac. Sci. Technol. B 22, 3363 (2004); http://dx.doi.org/10.1116/1.1821573 (3 pages) | Cited 2 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
The use of a negative resist, hydrogen silsesquioxane (HSQ), combined with electron-beam lithography, was found to greatly simplify the fabrication of photonic crystal structures having submicron-sized features. Two methods of fabrication were compared for the creation of photonic crystals; in this example, the structures were composed of a square lattice of dielectric rods. One method utilized positive resist PMMA, whereas another method used a negative resist HSQ. The process sequence using PMMA required a lift-off step and a hard mask in order to convert the hole-patterned PMMA into high-aspect-ratio dielectric rods through reactive ion etching. Alternatively, the electron-beam exposure and development of HSQ resist resulted in the formation of SiO2-like posts which then served as a hard mask for subsequent etches. The use of HSQ eliminated the need for the SiO2 deposition and nickel lift-off, thereby reducing the required number of steps in the process sequence and greatly simplified the fabrication.
Show PACS
42.82.Et Waveguides, couplers, and arrays
77.84.Jd Polymers; organic compounds
85.40.Hp Lithography, masks and pattern transfer
42.79.Gn Optical waveguides and couplers
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.70.Qs Photonic bandgap materials
81.65.Cf Surface cleaning, etching, patterning
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
back to top Nanometrology, Inspection and Alignment

Optical inspection of next generation lithography masks

Don Pettibone and Stan Stokowski

J. Vac. Sci. Technol. B 22, 3366 (2004); http://dx.doi.org/10.1116/1.1809619 (7 pages)

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
For the last 5 years a joint venture has pursued a research program studying and enhancing the ability of optical inspection tools to meet the inspection needs of extreme ultraviolet (EUV) and other next generation lithographies (NGLs). In this article we present a survey of results we have obtained for patterned inspection of NGL masks. The NGL technologies that we have studied include two electron projection lithographies, EUV, and step and flash imprint lithography (SFIL). We discuss the sensitivity of the inspection tools and mask design factors that affect tool sensitivity. In contrast to conventional photomask inspection, which primarily utilizes transmitted light for inspection, almost all NGL mask inspections are performed in reflected light. Much of the work has been directed towards EUV mask inspection and how to optimize the mask to facilitate inspection. Early EUV masks had an optical contrast of 40% or lower. Our partners have succeeded in making high contrast EUV masks ranging in contrast from 70% to 98%. Die to die and die to database inspections, at a wavelength of 257 nm, of EUV masks have been achieved with a sensitivity that is comparable to what can be achieved with conventional photomasks, with a minimum detected defect size of 80 nm square defects. We have inspected scattering with angular limitation projection electron-beam masks successfully. Electron-beam stencil masks, such as that used in projection reduction exposure with variable axis immersion lenses, pose a problem in that their high aspect ratio of mask thickness to minimum feature width results in low resolution transmission images. Reflected light images provide high-resolution images suitable for inspection, but will not be sensitive to defects below the inspection surface. We have run inspections on SFIL masks in die to die, reflected light in an effort to provide information concerning possible cumulative damage due to imprinting and to provide feedback on defect densities, types and sizes to improve the masks. Our defect sensitivity on SFIL masks is approximately 100 nm, though we cannot run at the highest sensitivity due to large numbers of nonprogrammed defects. We have also used an inspection system, at a wavelength of 364 nm, to inspect both unpatterned EUV substrates (no coatings) and blanks (with EUV multilayer coatings), and demonstrated a sensitivity of approximately 100 nm to polystyrene latex spheres. This information has helped drive down the defect densities on EUV blanks and substrates by some three orders of magnitude. Extensions of conventional optical lithography have pushed out the introduction of NGL technology to the 33 nm or possibly the 22 nm node. Mask inspection technology will need substantial improvements in resolution to meet the NGL inspection requirements below the 45 nm node.
Show PACS
85.40.Hp Lithography, masks and pattern transfer

Dynamic self-inspection of integrated circuit pattern defects

Hanying Feng, Jun Ye, and R. Fabian W. Pease

J. Vac. Sci. Technol. B 22, 3373 (2004); http://dx.doi.org/10.1116/1.1824049 (5 pages) | Cited 3 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
At various steps of integrated circuit manufacturing, defects need to be inspected to ensure process integrity. Based on the observation that good patterns usually repeat many times while defective patterns are different from others, we here propose an inspection methodology called dynamic self-inspection (DSI). We present a generic and systematic algorithm of DSI based on relative characteristic code space and code vectors. We also present a few specific examples of its implementations, using Euclidian distance between edge traces as relative characteristics.
Show PACS
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
85.40.Qx Microcircuit quality, noise, performance, and failure analysis

Nanometer gap measurement and verification via the chirped-Talbot effect

Euclid E. Moon, Lynn Chen, Patrick N. Everett, Mark K. Mondol, and Henry I. Smith

J. Vac. Sci. Technol. B 22, 3378 (2004); http://dx.doi.org/10.1116/1.1808739 (4 pages) | Cited 6 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
We describe a noncontact, optical method of measuring, with nanometer-level sensitivity, the gap between two planar objects in close proximity, such as a substrate and either a proximity-lithography mask or an imprint template. Interference fringes from a chirped-checkerboard mark on one object are observed using a nonexposing wavelength with long-working-distance, oblique-incidence microscopes. The gap is determined from the spatial frequency and phase of the fringes. We verify the gap measurement using a variation of the Talbot effect with the chirped-checkerboard mark. The two forms of gap measurement are complementary since one is suited to measuring and setting gap prior to exposure, and the other is ideal for confirmation of the gap that existed during exposure.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography
42.82.Cr Fabrication techniques; lithography, pattern transfer
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)

Scanning-spatial-phase alignment for zone-plate-array lithography

Rajesh Menon, Euclid E. Moon, Mark K. Mondol, Fernando J. Castaño, and Henry I. Smith

J. Vac. Sci. Technol. B 22, 3382 (2004); http://dx.doi.org/10.1116/1.1809631 (4 pages) | Cited 4 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
In this article, we describe a technique for level-to-level alignment in zone-plate-array lithography that does not require an external microscope, yet provides overlay superior to conventional microscopes.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
42.82.Cr Fabrication techniques; lithography, pattern transfer

Self-inspection of IC pattern defects

Hanying Feng, Jun Ye, and R. Fabian W. Pease

J. Vac. Sci. Technol. B 22, 3386 (2004); http://dx.doi.org/10.1116/1.1809627 (4 pages) | Cited 3 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
At various steps of IC manufacturing, defects need to be inspected to ensure process integrity. In this article, we describe a new methodology for defect inspection: defect self-inspection, i.e., defect detection based on a captured optical image itself without comparing to a reference image, where the reference image is a database image or an optical image from another die. Through intuitive understanding of human intelligence in detecting defects, we propose a systematic methodology of self-inspection based on pattern code space and code vectors. We describe the general methodology and present its implementations for two common types of defects as specific examples: detection of edge intrusion and protrusion (also known as mouse-bite) and detection of particle or contamination (also known as pinhole/pin-dot).
Show PACS
85.30.De Semiconductor-device characterization, design, and modeling

Stress estimation of patterned films using a high-energy electron beam

Fumio Mizuno and Takumi Toshinawa

J. Vac. Sci. Technol. B 22, 3390 (2004); http://dx.doi.org/10.1116/1.1813460 (4 pages)

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
A scanning electron microscope using an electron beam with energy more than several tens of keV enables us to observe features that are concealed under the specimen surface. By use of this method, nondestructive and in-line stress estimation of patterned films on a production wafer can be made. This method has been applied to a photoresist pattern, and the results showed mechanical properties of the patterned resist film.
Show PACS
68.60.Bs Mechanical and acoustical properties
85.40.Hp Lithography, masks and pattern transfer

Impacts of probe-tip tilt on scanning probe microscopy

Fumio Mizuno, Ichiko Misumi, Satoshi Gonda, and Tomizo Kurosawa

J. Vac. Sci. Technol. B 22, 3394 (2004); http://dx.doi.org/10.1116/1.1813458 (5 pages) | Cited 1 time

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
The effects of tip tilt on measurement uncertainty in scanning probe microscopy and tip-shape calibration for inclined tip have been discussed. Uncertainty of the untouchable region is the essential component of measurement uncertainty. Tip tilt is one of the most important parameters to determine the uncertainty of the untouchable region. The presence of tip tilt deteriorates fidelity of images and precision of critical-dimension measurements. It is necessary to use equivalent tip for calibrating the dilation of feature by inclined tip.
Show PACS
07.79.-v Scanning probe microscopes and components
06.20.F- Units and standards

Three-dimensional simulation of top down scanning electron microscopy images

Luca Grella, Gian Lorusso, Paul Lee, Fan Frank, and David L. Adler

J. Vac. Sci. Technol. B 22, 3399 (2004); http://dx.doi.org/10.1116/1.1825019 (6 pages) | Cited 5 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
Low voltage scanning electron microscopy (SEM) metrology and inspection are performed by immersing the sample in an electric field; under this condition, when a scanning electron beam images a sample containing insulating features (like oxides and resist), a surface global charge builds up to offset the applied field and a transverse local field will form as a result of the scanning beam. The surface global charge is responsible for the voltage contrast and imaging properties, while local fields degrade image resolution. In this article we describe a simulation approach able to explain the imaging properties of charged surfaces and how resolution is affected by local fields. Using electron ray tracing in the column, the simulation follows both the emitted and primary electron trajectories outside the sample. In addition, Monte Carlo scattering simulation calculates the electron trajectory and charge deposition inside the sample. The resulting charge density is used to calculate the field inside and outside the sample by solving the Poisson equation with the proper boundary conditions. Ray tracing, Monte Carlo scattering simulation; and field equation are then integrated in a self-consistent fashion to form a simulation algorithm capable of explaining SEM imaging and charging. The simulation is applied to a variety of cases regarding both inspection and metrology. The results are compared with experiments. Furthermore a method to calculate surface charging will be given for both insulating surfaces and patterned insulating surfaces on a grounded substrate.
Show PACS
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
02.50.Ng Distribution theory and Monte Carlo studies
02.60.Lj Ordinary and partial differential equations; boundary value problems

Technique for separately viewing multiple levels

L. Jiang and M. Feldman

J. Vac. Sci. Technol. B 22, 3405 (2004); http://dx.doi.org/10.1116/1.1802852 (4 pages) | Cited 4 times

Online Publication Date: 13 December 2004

Full Text: | Download PDF

Show Abstract
It is often desired to measure the accuracy of image placement in an integrated circuit, as well as the overlay between two levels printed on the same wafer. Such measurements yield information not only about alignment, but also about wafer, mask, and imaging distortions. Image placement measurements require state-of-the-art equipment. Overlay measurements are difficult to make if the patterns overlap each other, since one pattern may obscure parts of the other. In addition, the presence of an edge in one pattern may produce an error in the location of a nearby edge in the other pattern. This article describes a method of patterning that permits optical separation of the two levels so that they can be viewed independently. The method is based on the use of a resist containing a dye, such that the resist has a high contrast at one wavelength, but is completely transparent at another. In addition, the use of a precision grating for one of the levels provides a simple way to obtain highly accurate absolute image placement measurements.
Show PACS
85.30.De Semiconductor-device characterization, design, and modeling
85.40.Hp Lithography, masks and pattern transfer
back to top Nanotechnology-Directed Assembly

Lithographically directed self-assembly of nanostructures

J. Alexander Liddle, Yi Cui, and Paul Alivisatos

J. Vac. Sci. Technol. B 22, 3409 (2004); http://dx.doi.org/10.1116/1.1821572 (6 pages) | Cited 25 times

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
The combination of lithography and self-assembly provides a powerful means of organizing solution-synthesized nanostructures for a wide variety of applications. We have developed a fluidic assembly method that relies on the local pinning of a moving liquid contact line by lithographically produced topographic features to concentrate nanoparticles at those features. The final stages of the assembly process are controlled first by long-range immersion capillary forces and then by the short-range electrostatic and van der Waals interactions. We have successfully assembled nanoparticles from 50 to 2 nm in size using this technique and have also demonstrated the controlled positioning of more complex nanotetrapod structures. We have used this process to assemble Au nanoparticles into prepatterned electrode structures and have performed preliminary electrical characterization of the devices so formed. The fluidic assembly method is capable of very high yield, in terms of positioning nanostructures at each lithographically defined location, and of excellent specificity, with essentially no particle deposition between features.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
47.85.Np Fluidics
81.16.Nd Micro- and nanolithography
81.07.Bc Nanocrystalline materials

Lithographically directed deposition of silica nanoparticles using spin coating

Deying Xia and S. R. J. Brueck

J. Vac. Sci. Technol. B 22, 3415 (2004); http://dx.doi.org/10.1116/1.1821582 (6 pages) | Cited 10 times

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
Directed self-assembly is an important direction for the extension of patterning to the nanoscale regime and below. Here, examples are given of both individual particle placement and composite structure formation involving assemblies of many nanometer scale particles, both on patterned surfaces and on planar surfaces where the photoresist is used as a sacrificial layer to define the pattern and is subsequently removed. The underlying technologies employed in these experiments include interferometric lithography to define large-area, nanometer-scale patterns and directed self-assembly by spin coating to control particle placement. Three sizes of silica nanoparticles (mean diameters: 78, 50, and 15 nm) were employed for spin-coating processes. Single linear silica particle chain patterns and isolated two-dimensional particle patterns were easily formed on patterned surfaces. Silica particle rows, cross networks, and isolated posts with controllable thickness could be formed on flat surfaces using this approach. Directed self-assembly using nanoscale lithography and spin coating is a facile approach to the extension of lithographic techniques to the nanoscale.
Show PACS
81.16.Rf Micro- and nanoscale pattern formation
81.16.Nd Micro- and nanolithography
81.16.Dn Self-assembly
81.07.-b Nanoscale materials and structures: fabrication and characterization

Electric-field-directed growth of carbon nanotubes in two dimensions

Alireza Nojeh, Ant Ural, R. Fabian Pease, and Hongjie Dai

J. Vac. Sci. Technol. B 22, 3421 (2004); http://dx.doi.org/10.1116/1.1821578 (5 pages) | Cited 17 times

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
The interplay between mechanical and electronic properties in carbon nanotubes leads to interesting characteristics in devices such as a nanotube cross structure. The fabrication of nanotube devices has often been based on random growth or deposition of nanotubes and subsequently searching for those in desired locations with proper orientations. Obviously we want to be able to make such devices controllably. We present data on extending the technique of one-dimensional alignment of nanotubes using electric field to two dimensions in order to make more complicated structures such as nanotube crosses. It appears that nanotubes assemble in the regions of the most intense electric field. Also, they tend to follow the local field lines, even in nonuniform fields. Furthermore, they tend to grow away from negative toward positive polarities.
Show PACS
81.07.De Nanotubes
81.16.-c Methods of micro- and nanofabrication and processing
85.35.Kt Nanotube devices

Selective growth of sculptured nanowires on microlithographic lattices

Mark W. Horn, Matthew D. Pickett, Russell Messier, and Akhlesh Lakhtakia

J. Vac. Sci. Technol. B 22, 3426 (2004); http://dx.doi.org/10.1116/1.1824052 (5 pages) | Cited 5 times

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
We have grown helicoidal nanowire assemblies on a variety of topographic substrates with regular microlithographic patterns, thereby demonstrating that sculptured thin films with transversely latticed architecture can be grown by physical vapor deposition. The transverse feature-separations are as low as 100–300 nm, and mesa regions are circular posts as small as 60 nm in diameter. The initial as well as the subsequent stages of growth on topographic substrates can be understood using simple geometric shadowing arguments.
Show PACS
68.65.La Quantum wires (patterned in quantum wells)
85.40.Hp Lithography, masks and pattern transfer
68.55.A- Nucleation and growth
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
back to top Optical Lithography

Immersion lithography: New opportunities for semiconductor manufacturing

Darío Gil, Timothy A. Brunner, Carlos Fonseca, Nakgeuon Seong, Bob Streefkerk, Christian Wagner, and Marco Stavenga

J. Vac. Sci. Technol. B 22, 3431 (2004); http://dx.doi.org/10.1116/1.1823431 (8 pages) | Cited 5 times

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
Immersion lithography has recently emerged as the preferred lithography solution for manufacturing the next generation of semiconductor devices (likely to address the 65, 45, and possibly the 32 nm nodes). Full-field immersion scanners operating at λ=193 nm with de-ionized water as the immersion fluid have been recently demonstrated. In this article we report imaging results from the AT1150i prototype, a 0.75 numerical-aperture full-field scanner from ASML. We experimentally confirm the depth-of-focus improvements that immersion enables, and explore the implications of this gain for semiconductor manufacturing. This article also highlights the challenges the technology faces before it can be successfully introduced for semiconductor manufacturing. We pay particular attention to defects, in the form of particles, bubbles, and other processing residues, and highlight evaporation as a key mechanism underpinning these challenges.
Show PACS
85.40.Hp Lithography, masks and pattern transfer

Hyper NA water immersion lithography at 193 nm and 248 nm

Bruce W. Smith, Yongfa Fan, Jianming Zhou, Anatoly Bourov, Lena Zavyalova, Neal Lafferty, Frank Cropanese, and Andrew Estroff

J. Vac. Sci. Technol. B 22, 3439 (2004); http://dx.doi.org/10.1116/1.1825018 (5 pages) | Cited 3 times

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
Immersion lithography can allow for theoretical imaging to λ∕4n (where n is the refractive index of imaging fluid). As 193 nm and 248 nm technology is pushed toward this limit, experimental data becomes increasingly important. This paper describes research carried out to explore the limitations of water immersion lithography and its extension to higher numerical aperture values using modifications to the imaging fluid. Resist imaging to 38 nm is demonstrated using water as an imaging fluid. Several alternative fluids are presented including phosphates, sulfates, and halides, which are shown to increase the refractive index of water.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

Predicting air entrainment due to topography during the filling and scanning process for immersion lithography

A. Wei, M. El-Morsi, G. Nellis, A. Abdo, and R. Engelstad

J. Vac. Sci. Technol. B 22, 3444 (2004); http://dx.doi.org/10.1116/1.1808736 (6 pages) | Cited 2 times

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
Current optical lithography methods are nearing theoretical limits that prevent their use in the production of circuits for future nodes. A proposed solution is to increase the index of refraction of the transmission medium between the final lens of the exposure system and the wafer. When a liquid is used in this lens–wafer gap, the process is known as immersion lithography. A major concern is air bubbles in the liquid, since they are sources of index discontinuities. This article investigates the potential for trapping air as the free surface of the fluid front moves over features associated with wafer topography during the filling and scanning process. Optical simulations have shown that even very small bubbles located near or on the resist can significantly impact the imaging process. Therefore, the ability to predict the characteristics of the flow, liquid, and features that lead to air entrainment during filling is important. Modeling techniques were developed in order to create models that were capable of resolving the flow characteristics over 100 nm scale features without the need to simulate the entire macroscopic flow through the lens–wafer gap. Results of these models show that bubble formation occurs only for extreme geometries and flow conditions. In actual production the velocities, contact angles, and feature profiles are well out of these extreme ranges, and will not cause bubble formation.
Show PACS
47.55.Hd Stratified flows
47.55.D- Drops and bubbles
68.03.Cd Surface tension and related phenomena
42.82.Cr Fabrication techniques; lithography, pattern transfer
47.11.-j Computational methods in fluid dynamics
42.79.Bh Lenses, prisms and mirrors
42.25.Gy Edge and boundary effects; reflection and refraction

Fluid refractive index measurements using rough surface and prism minimum deviation techniques

R. A. Synowicki, Greg K. Pribil, Gerry Cooney, Craig M. Herzinger, Steven E. Green, Roger H. French, Min K. Yang, John H. Burnett, and Simon Kaplan

J. Vac. Sci. Technol. B 22, 3450 (2004); http://dx.doi.org/10.1116/1.1813455 (4 pages) | Cited 15 times

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
Two techniques are presented for measuring the refractive index of fluids. The first is a reflective technique where liquid is applied to a rough surface to hold the liquid during measurement. Ellipsometric psi and delta data are acquired and analyzed to determine the fluid refractive index. The second technique is refractive and uses a hollow prism cell to contain the liquid. The fluid index is then determined using the prism minimum deviation technique. Both techniques have been applied over a very wide spectral range from the vacuum ultraviolet to the infrared and have been implemented on a research spectroscopic ellipsometer system (VUV-VASE®) with continuously variable angle of incidence. The refractive index of several candidate immersion fluids for 157 and 193 nm immersion lithography are reported over the spectral range from 156 to 1700 nm in a nitrogen-purged environment. The advantages and disadvantages of both techniques are discussed. Results were checked against values measured on very accurate prism minimum deviation equipment at NIST, and agreement with NIST has been found to be good on all fluids measured.
Show PACS
07.60.Fs Polarimeters and ellipsometers
07.60.Hv Refractometers and reflectometers
07.60.Rd Visible and ultraviolet spectrometers
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
42.79.Bh Lenses, prisms and mirrors

Optimizing the fluid dispensing process for immersion lithography

A. Abdo, G. Nellis, A. Wei, M. El-Morsi, R. Engelstad, S. R. J. Brueck, and A. Neumann

J. Vac. Sci. Technol. B 22, 3454 (2004); http://dx.doi.org/10.1116/1.1824065 (5 pages) | Cited 3 times

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
The concept behind immersion lithography is the insertion of a high refractive index liquid in the space between the final projection lens of an exposure system and the device wafer to improve the overall resolution of the exposure process. Computational fluid dynamics (CFD) simulations were performed in order to investigate the process of initially filling the lens-wafer gap with immersion fluid. The CFD models were used to investigate the effects of dispense velocity, gap height, and fluid dispense angle on the fill process; specifically on the possibility of air entrainment. The simulations revealed that there is an optimal region in the parameter space of gap height and dispense velocity for which the gap fills completely. Outside of this region, either excessive inertial or surface tension forces cause an undesirable, incomplete filling process. The optimal region was found to shift somewhat based on the fluid dispense angle. Finally, experiments were performed to verify the CFD models. The CFD simulations and the experimental results were in good agreement, both qualitatively with regard to the shape and evolution of the free surface and quantitatively with regard to the velocity of the contact line.
Show PACS
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer

Imaging capabilities of resist in deep ultraviolet liquid immersion interferometric lithography

Alex K. Raub, A. Frauenglass, S. R. J. Brueck, Will Conley, Ralph Dammel, Andy Romano, Mitsuru Sato, and William Hinsberg

J. Vac. Sci. Technol. B 22, 3459 (2004); http://dx.doi.org/10.1116/1.1824951 (6 pages) | Cited 8 times

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
Liquid immersion lithography (LIL) extends the resolution of optical lithography to meet industry demands into the next decade. Through the use of exposure media such as purified water (n of 1.44 at 193 nm), it is possible to reduce minimum pitches compared with traditional air∕vacuum exposures media by a factor of as much as 44%—a full technology node. Beyond this simple observation, there is a good deal of work necessary to fully understand the impact of LIL immersion lithography on a lithography processes. This article addresses the impact of water immersion on the imaging capabilities of different resist formulations. All resists were evaluated by imaging dense line-space structures at a 65‐nm half-pitch both in air and with water immersion. Studies of dense 65‐nm lines made by immersion imaging in HPLC grade water with controlled variations in resist components were performed. Significant differences were observed and will be discussed.
Show PACS
42.82.Cr Fabrication techniques; lithography, pattern transfer
85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

244-nm imaging interferometric lithography

A. Frauenglass, S. Smolev, A. Biswas, and S. R. J. Brueck

J. Vac. Sci. Technol. B 22, 3465 (2004); http://dx.doi.org/10.1116/1.1821505 (5 pages) | Cited 2 times

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
Imaging interferometric lithography, combining off-axis illumination, multiple exposures covering different regions of spatial frequency space, and pupil plane filters to ensure uniform frequency-space coverage, is a relatively new imaging concept that provides an approach to accessing the fundamental, linear-systems-resolution limits of optics. With an air medium between the lens and the wafer, the highest spatial frequency available with 244-nm exposure tool with a numerical aperture of 0.9 corresponds to a half-pitch of 68-nm. Allowing for ∼10% subbands above this central frequency, this suggests that ∼75-nm half-pitch patterns should be accessible. A 22× reduction imaging interferometric lithography testbed demonstration of printing a non-periodic (arbitrary) 86-nm half-pitch pattern is reported. This result was achieved with a simple chrome-on-glass mask without the use of any mask-based resolution-enhancement techniques such as phase-shift or optical proximity correction. Scaling this result to a 193 nm wavelength and an immersion numerical aperture of 1.3 directly addresses the 45-nm half-pitch node.
Show PACS
85.40.Hp Lithography, masks and pattern transfer

Near-field optical lithography using a planar silver lens

David O. S. Melville and Richard J. Blaikie

J. Vac. Sci. Technol. B 22, 3470 (2004); http://dx.doi.org/10.1116/1.1813462 (5 pages) | Cited 13 times

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
A variation of proximity lithography has been proposed using a planar metallic film in a near-field configuration, where metal acts as a near-field “superlens.” We report here on experimental evidence of such optical lithography with a planar silver lens. Silver layers of varying thickness (85–120 nm) placed at specific distances (40–60 nm) below a patterned mask were able to image the mask’s features onto a photoresist located after a gap (26–60 nm) below the silver. The entire structure was exposed from above with a mercury lamp. Feature sizes as small as 250 nm (at a 500 nm period) were imaged, demonstrating the lensing ability of the planar silver slab.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

Sub-100 nm lithography using ultrashort wavelength of surface plasmons

W. Srituravanich, N. Fang, S. Durant, M. Ambati, C. Sun, and X. Zhang

J. Vac. Sci. Technol. B 22, 3475 (2004); http://dx.doi.org/10.1116/1.1823437 (4 pages) | Cited 17 times

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
The development of a nanolithography technique utilizing ultrashort wavelength of surface plasmons (SPs) is presented in this article. The mask consists of silver thin film perforated with two-dimensional hole arrays exhibiting superior confinement due to SPs with a wavelength equal to ¼ of that of the illuminating light (365 nm). This short wavelength of SPs can confine the field on an area much smaller compared to the excitation light wavelength, leading to the higher resolution lithography than conventional photolithography methods. Finite-difference time-domain simulations show significantly enhanced electric field and tight confinement of the near-field profile obtained from silver plasmonic masks, where features as small as 30 nm can be resolved. Furthermore, the lithography experiments have been performed with demonstration of sub-100 nm spatial resolution.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
back to top Resists

Sub-50 nm half-pitch imaging with a low activation energy chemically amplified photoresist

G. M. Wallraff, D. R. Medeiros, M. Sanchez, K. Petrillo, W.-S. Huang, C. Rettner, B. Davis, C. E. Larson, L. Sundberg, P. J. Brock, W. D. Hinsberg, F. A. Houle, J. A. Hoffnagle, D. Goldfarb, K. Temple, et al.

J. Vac. Sci. Technol. B 22, 3479 (2004); http://dx.doi.org/10.1116/1.1813463 (6 pages) | Cited 5 times

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
Critical lithographic dimensions are rapidly approaching the sub-50 nm regime where there is a concern that image blur due to acid diffusion will impose a practical limit to the resolution of chemically amplified (CA) resists. Although recent EUV and 193- and 157 nm immersion interferometric experiments have reportedly resolved line-space arrays with individual dimensions on the order of ∼40 nm, smaller nested features are likely to prove problematic. Numerous reports suggest that conventional photoresist performance degrades rapidly at half-pitch dimensions in this range. New approaches to processing and materials development of photoresists will likely be required if the concept of chemical amplification is to be extended to the 32 nm node and beyond. In this article we show that through materials choice and proper processing, image blur can be controlled to an extent where dense features below 40 nm can routinely be resolved in CA resists. We describe our studies on high-sensitivity resists of differing activation energies and demonstrate the effect of postexposure bake conditions on the ultimate resolution. Most notably, electron-beam exposure of a CA resist that requires no postexpose bake has demonstrated half-pitch resolution down to 30 nm with reasonable process latitude. Acid diffusion measurements performed on the same systems using a 193 nm top surface-imaging-technique correlate with the observed resolution of the different resists and processing conditions. Additionally, this system has been probed to explore the effect of humidity on the rate of the resist deprotection reactions in order to determine the impact this might have on resolution.
Show PACS
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer

High resolution electron beam lithography using a chemically amplified calix[4]arene based resist

H. Sailer, A. Ruderisch, W. Henschel, V. Schurig, and D. P. Kern

J. Vac. Sci. Technol. B 22, 3485 (2004); http://dx.doi.org/10.1116/1.1809618 (4 pages) | Cited 3 times

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
The calix[4]arene based resist tetrakis(oxiran-2-ylmethoxy)-tetra-tert-butylcalix[4]arene is presented. The well known chemical amplification techniques can be applied to the nonpolymeric class of calixarenes resulting in area doses below 100 μC∕cm2 at 30 keV beam energy. This is achieved by application of the concept of cationic polymerization to a calix[4]arene derivative bearing four epoxide residues together with a photoacid generating triarylsulfonium salt. The high resolution capabilities of this calixarene based resist remain mainly intact under optimized bake parameters.
Show PACS
85.40.Hp Lithography, masks and pattern transfer

Modeling and simulation of chemically amplified electron beam, x-ray, and EUV resist processes

Takahiro Kozawa, Akinori Saeki, and Seiichi Tagawa

J. Vac. Sci. Technol. B 22, 3489 (2004); http://dx.doi.org/10.1116/1.1823435 (4 pages) | Cited 72 times

Online Publication Date: 15 December 2004

Full Text: | Download PDF

Show Abstract
With the shrinkage of feature sizes, ever precise accuracy has been required for process simulators because of the importance of nanoscale resist topography such as line edge roughness. Formation processes of latent images in chemically amplified electron beam (EB), x-ray, and EUV resists are different from both chemically amplified photoresists used in optical lithography and conventional, nonchemically amplified EB resists. A new simulation scheme precisely based on reaction mechanisms is necessary to reproduce resist patterns for the postoptical lithographies. We proposed a method to simulate electron dynamics in chemically amplified resists and to calculate the acid distribution around an ionization point with a typical parameter set.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
42.82.Cr Fabrication techniques; lithography, pattern transfer
81.16.Nd Micro- and nanolithography

Lithographic patterning of a highly metallized polymer resist system and pyrolytic or plasma treatment to afford ferromagnetic ceramics

Scott B. Clendenning and I. Manners

J. Vac. Sci. Technol. B 22, 3493 (2004); http://dx.doi.org/10.1116/1.1821507 (4 pages)

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
The highly metallized polymer cobalt-clusterized polyferrocenylsilane (Co-PFS) has been shown to act as a negative-tone resist for electron-beam lithography and UV-photolithography. Ferromagnetic ceramics containing Fe∕Co alloy nanoparticles result from subsequent pyrolysis or reactive ion etching in a secondary magnetic field.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
42.82.Cr Fabrication techniques; lithography, pattern transfer
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
75.50.Bb Fe and its alloys
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Nonaqueous development of silsesquioxane electron beam resist

Gerard M. Schmid, Leslie E. Carpenter, and J. Alexander Liddle

J. Vac. Sci. Technol. B 22, 3497 (2004); http://dx.doi.org/10.1116/1.1825014 (6 pages) | Cited 12 times

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
While the primary use of hydrogen silsesquioxane (HSQ) is as a dielectric in microelectronics fabrication, this material is also capable of forming high resolution, negative-tone features with low roughness when patterned with an electron beam. Unfortunately, under common processing conditions HSQ is relatively insensitive to electron beam exposure; poor reproducibility has also been observed. HSQ postexposure processing typically consists of development via immersion in an industry-standard aqueous solution of base, followed by rinsing with water or isopropanol. While other resist materials have been specifically designed for compatibility with aqueous base processing, HSQ is known to be chemically unstable in the presence of base. We report that several organic solvents that are not reactive towards HSQ are less aggressive at removing the exposed regions of the film. As a result, it is possible to successfully image HSQ with markedly reduced exposure dose. The considerable difference in exposure dose can be largely attributed to the difference in reactivity toward HSQ between organic solvents and aqueous base, but other factors must also be considered. For example, HSQ structures can be formed at low doses when developed with isopropanol, but the structures are very rough and irregular. This paper reports an alternative approach to HSQ processing that provides insight into mechanistic phenomena while offering certain advantages over standard processing techniques.
Show PACS
85.40.Hp Lithography, masks and pattern transfer

Patterning via surface monolayer initiated polymerization: A study of surface initiator photoreaction kinetics

Kendra McCoy, Dennis W. Hess, Clifford L. Henderson, and Laren M. Tolbert

J. Vac. Sci. Technol. B 22, 3503 (2004); http://dx.doi.org/10.1116/1.1824061 (6 pages)

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
Surface monolayer initiated polymerization (SMIP) is a potential method for achieving high resolution patterning of surfaces and materials that could be used as an alternative to conventional lithographic methods based on photoresist thin films. This article reports on the photochemical kinetic rate constants of two candidate azo-type surface bound photoradical initiator molecules. X-ray photoelectron spectroscopy was utilized to monitor the relative concentration of azo initiator on a silicon surface as a function of exposure dose to 248 nm radiation. This photochemical decomposition data showed that the photoreaction for both initiators followed first order kinetics with photoreaction rate constants in the range of 4.5×10−3 cm2∕mJ to 9.7×10−3 cm2∕mJ. The difference in the observed rate constants for the two azo initiators was attributed primarily to differences in their quantum efficiencies. These differences in quantum efficiency were attributed to the size of the nontethered fragment that would be produced from the initiator, with larger fragments producing slower photochemical decomposition kinetics. Thus, photoradical initiators with small non-surface bound fragments are desirable in terms of increasing the photosensitivity of such SMIP processes. For successful positive tone imaging using a SMIP process with photoradical initiators, it was estimated that approximately 99% of the monolayer must be decomposed in order to produce images in the resulting polymer layers. Using this information in conjunction with the photochemical reaction rate constants for the azo initiators, exposure doses on the order of 400 mJ∕cm2 and larger would be required for the present initiators.
Show PACS
81.16.Nd Micro- and nanolithography

Dissolution behavior of main-chain-fluorinated polymers for 157 nm lithography

T. Kodani, T. Ishikawa, T. Yoshida, T. Hayami, M. Koh, T. Moriya, T. Yamashita, M. Toriumi, T. Araki, H. Aoyama, T. Hagiwara, T. Furukawa, T. Itani, and K. Fujii

J. Vac. Sci. Technol. B 22, 3509 (2004); http://dx.doi.org/10.1116/1.1826064 (4 pages) | Cited 1 time

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
Tetrafluoroethylene-based copolymers with functionalized norbornenes are synthesized by using a fluorocarbon initiator. The effect of molecular weight on the dissolution behavior of five fluoropolymers in a standard alkaline developer is studied using the quartz crystal microbalance method and surface free energy measurements. It is observed that the dissolution rate decreases exponentially with increasing molecular weight for molecular weights under approximately 5000. Swelling is observed in the two polymers that have low surface free energy.
Show PACS
64.75.-g Phase equilibria
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
68.35.Md Surface thermodynamics, surface energies
85.40.Hp Lithography, masks and pattern transfer

Evaluation of outgassing from a fluorinated resist for 157 nm lithography

Shigeo Irie, Takuya Hagiwara, Kiyoshi Fujii, Yasuo Itakura, Youichi Kawasa, Keiji Egawa, Ikuo Uchino, Akira Sumitani, and Toshiro Itani

J. Vac. Sci. Technol. B 22, 3513 (2004); http://dx.doi.org/10.1116/1.1821580 (5 pages) | Cited 1 time

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
We have evaluated the outgassing products and the in situ transmittance of a contaminated CaF2 substrate for monocyclic fluoropolymers with four protecting groups: methoxymethyl (MOM), tert-butoxycarbonyl (t-BOC), menthoxymethyl, and 2-cyclohexylcyclohexyloxymethyl. We found little correlation between the total amount of outgassing from the polymer and the decreasing rate of the CaF2 substrate transmittance caused by outgassing adhesion. Although the MOM protecting group generated the largest amount of outgassing products, the most substantial decrease in the transmittance was observed for the t-BOC protecting group. Therefore, the absorption coefficient of the outgassing-contaminated CaF2 substrate appears to be more sensitive to the type of protecting group, especially the t-BOC protecting group including a t-butyl unit. We conclude that in terms of material design of the fluoropolymer resist for 157 nm lithography, we need to pay attention to the protecting group of polymers, especially the protecting group including a t-butyl unit, which generates isobutene product during 157 nm irradiation.
Show PACS
85.40.Hp Lithography, masks and pattern transfer

Impacts of 30-nm-thick resist on improving resolution performance of low-energy electron beam lithography

Masaki Yoshizawa, Shigeru Moriya, Kumiko Oguni, Hiroyuki Nakano, Shinji Omori, Tetsuya Kitagawa, Masatoshi Kotera, and Hirohisa Niu

J. Vac. Sci. Technol. B 22, 3518 (2004); http://dx.doi.org/10.1116/1.1815308 (4 pages)

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
Exploring the resolution performance of various electron beam lithography with the acceleration voltage of 2–100 kV showed that line edge roughness (LER) and resolution limit of resist patterns was in linear relation with blur of latent image profile. Reducing resist thickness is effective in decreasing the blur of low-energy electron-beam proximity projection lithography (LEEPL) because 47% of the blur is due to scattering of 2 keV electrons in 70-nm-thick resist film. The impact of thinning the resist thickness on the LER and the exposure latitude in LEEPL was investigated by simulation and experiment. A Monte Carlo simulation shows that the LER of a 100-nm-width space pattern decreases to 5.5 from 10.4 nm with reducing the resist thickness to 20 from 70 nm. Exposing the photosensitive polyorganosilazane resists (Clariant (Japan) K.K.) by LEEPL-3000 underpinned that latent image quality was improved by thinning the resist. The exposure latitude of 80-nm-diameter dense contact holes increased to 25 from 16% with reducing the resist thickness to 30 from 50 nm. It is necessary for taking an advantage of the improved latent image of the 30-nm-thick resist in resolving the 90-nm-pitch patterns to mitigate the edge roughness probably caused by the properties of a highly interfacial resist.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography
02.70.Uu Applications of Monte Carlo methods

Dependence of acid generation efficiency on the protection ratio of hydroxyl groups in chemically amplified electron beam, x-ray and EUV resists

Hiroki Yamamoto, Takahiro Kozawa, Atsuro Nakano, Kazumasa Okamoto, Seiichi Tagawa, Tomoyuki Ando, Mitsuru Sato, and Hiroji Komano

J. Vac. Sci. Technol. B 22, 3522 (2004); http://dx.doi.org/10.1116/1.1813452 (3 pages) | Cited 14 times

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
In chemically amplified resists for ionizing radiation such as an electron beam, protons of acids come from not acid generators but base polymers. This means that the modification of base polymers has a great effect on the acid generation efficiency. The relation between relative acid yield and protecting groups of poly(4-hydroxystyrene) was examined. The selection of protecting groups is important for the acid generation efficiency and the acid distribution uniformity.
Show PACS
85.40.Hp Lithography, masks and pattern transfer

Pinning effect of microliquid drop on geometrical complex substrates composed with different surface energy materials

Masaki Yamanaka, Akira Okada, and Akira Kawai

J. Vac. Sci. Technol. B 22, 3525 (2004); http://dx.doi.org/10.1116/1.1823432 (3 pages)

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
Wetting behavior of microliquid drop on a geometrical complex substrate is analyzed quantitatively. In order to analyze pinning effect in liquid spreading, the array of isolated square patterns is formed by the photolithography. The square patterns on flat substrate are composed with the combination of higher and lower surface energy materials. Two types of complex substrates, isolated polar and continuous polar patterns, are fabricated. The test liquids, de-ionized water, ethylene glycol and diiodomethane, are sessile dropped on the complex substrate. Particularly, the isolated polar pattern acts to pin the polar liquid spreading. The combination of a polar liquid and an isolated polar substrate has strong interaction on each other. However, in the case of the continuous polar pattern, the wetting behavior of liquid drop can be explained due to Cassie’s equation. The contribution of the polar material to the wetting property on geometrical complex substrate can be clarified.
Show PACS
68.08.Bc Wetting
68.03.Cd Surface tension and related phenomena
back to top Sources and Optics

Miniaturized finger-size electron-beam column with ceramic-type lenses for scanning electron microscopy

M. Miyoshi, K. Okumura, S. Awata, Y. Okada, T. Maeda, H. Yamaguchi, and S. Amano

J. Vac. Sci. Technol. B 22, 3528 (2004); http://dx.doi.org/10.1116/1.1824062 (6 pages) | Cited 1 time

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
A miniaturized electron-beam column has been developed for portable scanning electron microscope, which has greatly reduced size and weight compared with those of conventional electron-beam column, in order to satisfy the demands of new applications in surface analysis, inspection and metrology, electrical testing. For column miniaturization and high precision lens fabrication, we have constructed a ceramic lens integrated column system, in which all of the electro-optical elements are integrated in one ceramics body. In this trial production, we use a newly developed alumina-based high resistive conductive ceramics for the optimization of this electro-static lens operation. All the lens electrodes are metalized and patterned on the inner surface of the cylindrical high resistivity conductive ceramic whose volume resistivity is 1010 Ω cm. As the ceramic lens integrated column used here integrates all the lens electrodes and manufactured in a consecutive process, the mechanical alignment error can be reduced, resulting in the concentricity of 0.7 μm, in whole column fabrication. The initial images demonstrate the basic operation of the ceramic lens integrated column system.
Show PACS
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
41.85.Ne Electrostatic lenses, septa

Low energy large scan field electron beam column for wafer inspection

X. Liu, X. Zhang, Y. Zhao, A. Desai, and Z. W. Chen

J. Vac. Sci. Technol. B 22, 3534 (2004); http://dx.doi.org/10.1116/1.1827629 (5 pages)

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
A swing objective retarding immersion lens (SORIL) column for wafer inspection is designed and constructed based on SOIL concept. The column consists of a compound retarding electrostatic and magnetic immersion lens and five electrostatic deflectors. The retarding electrostatic and magnetic immersion lens has small spherical and chromatic aberration coefficients for low landing energy. All electrostatic deflectors have a cylindrical duodecapole structure. One deflector is accommodated between the polepiece of the magnetic lens and the specimen surface, and operated at high voltage to fulfill SOIL condition. An on-axis annular semiconductor detector with a small opening in the center is employed to collect signal electrons. The annular detector achieves high collection efficiency over a large scan field. Experimental results show that the SORIL column has accomplished a 600 μm×600 μm scan field with 0.1 μm maximum spot size in a wide landing energy range (from 200 to 2000 eV) without dynamic aberration correction or dynamic focusing. Resolution of 15 nm is achieved in a 50 μm×50 μm scan field. The probe beam current delivered by the SORIL column is from a few nA to more than 100 nA because of the specially designed bright electron gun. The SORIL column has been installed onto HMI’s electron beam wafer inspection tool, eScan™ 300. The SORIL’s optical performances enable eScan™ 300 to be a powerful electron beam wafer inspection and in-line process monitoring tool.
Show PACS
41.85.Gy Chromatic and geometrical aberrations
42.15.Eq Optical system design
42.79.Fm Reflectors, beam splitters, and deflectors

Addressable field emitter array: A tool for designing field emitters and a multibeam electron source

S. Bauerdick, C. Burkhardt, D. P. Kern, and W. Nisch

J. Vac. Sci. Technol. B 22, 3539 (2004); http://dx.doi.org/10.1116/1.1824050 (4 pages) | Cited 4 times

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
We have developed an array of 25 electrically addressable field emitters. This device is a very suitable tool for experimentally designing miniaturized electron sources with improved emission characteristics. The field emission tip itself is fabricated by a combination of electron beam induced deposition and physical vapor deposition. Thus it is possible to vary the geometrical setup of tip and extraction electrode easily and also to define the emitter material exactly. The influence of most important parameters on the tip shape has been examined and deposition of three-dimensional structures is shown. Analysis of Fowler–Nordheim-plots indicates that during first operation and increased exposure to argon, nitrogen, and oxygen a change in tip radius is the predominant effect. Two arrays of field emitters with different tip heights have been examined to show the variation in emission pattern and current distribution.
Show PACS
85.45.Db Field emitters and arrays, cold electron emitters
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Writing strategy and electron-beam system with an arbitrarily shaped beam

Sergey Babin

J. Vac. Sci. Technol. B 22, 3543 (2004); http://dx.doi.org/10.1116/1.1826057 (4 pages)

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
The greatly increased complexity of modern masks has in turn led to increased write times and cost of the masks. Any opportunity to decrease write time while providing the required accuracy of the fabricated pattern is highly beneficial. A writing strategy using an arbitrarily shaped beam (ASB) results in a considerably smaller number of flashes to write a complex pattern compared to other strategies. The design of an ASB system is proposed. The ASB electron-beam column is similar to that of a variable-shaped beam system, except for a modified beam-shaping block. This suggests the relatively easy integration of an ASB column. The throughput of an ASB system is higher than the throughput of other systems, except for patterns with low coverage or simple geometries. In addition to the throughput advantages, an ASB system enables higher accuracy, including the feasibility of writing features according to “ideal” optical proximity correction.
Show PACS
85.40.Hp Lithography, masks and pattern transfer

Gated photocathode arrays as sources for multibeam electron nanolithography

Jack McCarthy and Ron Simonson

J. Vac. Sci. Technol. B 22, 3547 (2004); http://dx.doi.org/10.1116/1.1824064 (5 pages)

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
Multiple electron beams will need to expose large areas of resist in parallel rapidly if maskless electron lithography of high-density nanoscale structures is to become a production tool. This will require large arrays of gated submicron scale sources for multiple beams with gate changeable currents. In this research and development a small 3×3 array was fabricated using a computer controlled focused ion beam milling machine (FIB). This gated array electron source was tested first in a vacuum chamber without optics to test the operation of the gates in preparation for installation in a column with electrostatic lenses, stigmation, steering, scanning and secondary electron imaging. A primary goal for the project is the exposure of nanoscale lines in resist. The fabrication of a 3×3 test array used a combination of sputter deposition, FIB microforming and micromachining of the necessary metals and insulators. The photoemitting film for each of the gated sources was a FIB deposited 15 nm thick layer of Pt. The initial tests on these gated photocathodes are encouraging, by changing the gate voltage we can change the photoemission current. In addition to the work on the fabrication of the gated arrays, blanket thin film materials are being tested for stability and photoyield for possible use in the gated arrays. In this work a range of thicknesses of glow discharge carbon was deposited on the Ti coated substrates. The 20 nm thick carbon film produced the best performance, a stable 7 nA∕mW photoyield. Carbon photocathodes 15 nm, 30 nm, and 60 nm thicknesses were stable but lower at 3.7, 3.6, and 1.3 nA∕mW, respectively. A new experimental chamber is currently under construction to allow us to investigate the feasibility of using our gated photocathode arrays to expose PMMA or other suitable electron sensitive resist materials. The photoelectron column is made from a modified FEI 600 series FIB column.
Show PACS
81.16.Nd Micro- and nanolithography
85.60.Ha Photomultipliers; phototubes and photocathodes
81.15.Cd Deposition by sputtering

Preliminary evaluation of surface plasmon enhanced light transmission with a scanning 257 nm ultraviolet microscope

Juan R. Maldonado, Steven T. Coyle, Jeffery K. Varner, Richard C. Moore, P. R. H. Stark, and D. N. Larson

J. Vac. Sci. Technol. B 22, 3552 (2004); http://dx.doi.org/10.1116/1.1809617 (5 pages) | Cited 1 time

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
Surface plasmon enhanced illumination (SPEI) devices could be useful in multielectron beam lithography systems to meet the roadmap requirements for mask- and direct write applications by creating arrays of light beams, or in conjunction with a photoemitter to produce a very stable array of electron beams from a patterned photocathode. Preliminary experiments were performed with a scanning 257 nm UV transmission microscope to evaluate the performance of SPEI devices. Light transmission enhancement relative to simple apertures greater than 200× were obtained with these devices utilizing apertures as small as 60 nm diameter. The results will be presented in this article together with other possible advantages for e-beam applications.
Show PACS
42.72.Bj Visible and ultraviolet sources

High-speed and high-precision deflectors applied in electron beam lithography system based on scanning electron microscopy

Zhuming Liu and Wenqi Gu

J. Vac. Sci. Technol. B 22, 3557 (2004); http://dx.doi.org/10.1116/1.1813454 (3 pages)

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
To develop a nano-lithography system based on scanning electron microscopy, a high-speed and high-precision deflection system including two prelens magnetic deflectors is introduced in this article. Best length ratio between two deflectors is achieved, which attributes to high sensitivity without loss of resolution. Some trade-off has been taken between aberrations and landing angle to get optimum performance of deflection system. The art of wire electron discharge machining is used to guarantee geometric accuracy and lower inductance. Frequency response test and lithographic experiments confirm the design.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

Direct spherical and chromatic aberration correction for charged particle optical systems

William Turnbull

J. Vac. Sci. Technol. B 22, 3560 (2004); http://dx.doi.org/10.1116/1.1813449 (5 pages)

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
A method to correct spherical and chromatic aberrations is described. The system provides complete physical and optical separation between first the first-order optics and higher order correctors. Calculations indicate subangstrom beams may be realized.
Show PACS
41.85.Gy Chromatic and geometrical aberrations

Negative electron affinity group III-nitride photocathode demonstrated as a high performance electron source

Francisco Machuca, Zhi Liu, J. R. Maldonado, S. T. Coyle, P. Pianetta, and R. F. W. Pease

J. Vac. Sci. Technol. B 22, 3565 (2004); http://dx.doi.org/10.1116/1.1813453 (5 pages) | Cited 6 times

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
The need for a high performance (low energy spread <0.5 eV, long lifetime >3 months per spot, emission stability <1%∕h) electron source continues as part of the development of new e-beam writing and inspection tools. We present measurements from a group III-nitride (indium gallium nitride) photocathode in a demountable vacuum system to measure energy spread, lifetime, and preliminary blanking effects. We show the results of cathodes operating in ultrahigh vacuum (UHV), high vacuum (HV), and oxygen-rich backpressures. Our results show InGaN has a longitudinal energy spread of <300 meV in reflection mode, flat lifetimes of 60 h per illuminated spot where the yield changes by <10%, and stable emission with typical recoveries within 99% of original photocurrent for all blanking periods and vacuum conditions tested (0.5 to 10 min periods).
Show PACS
85.60.Ha Photomultipliers; phototubes and photocathodes
back to top X-ray Lithography

Minimal zone plates for x-ray lithography

D. Amy, L. Jiang, R. Zheng, M. Feldman, F. Cerrina, S. Dhuey, Q. Leonard, and D. Thielman

J. Vac. Sci. Technol. B 22, 3570 (2004); http://dx.doi.org/10.1116/1.1809625 (5 pages) | Cited 1 time

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
As feature widths in integrated circuits continue to decrease, patterning the smallest features has become more and more challenging. This is especially true for contact levels, where vias less than 50 nm diameter will be extremely difficult to print. However, since vias are typically well separated, they are readily patterned by using zone plates to focus x rays. Although zone plates have been used to focus x rays to small spots for many years, it has generally been considered necessary to have more than about 10 zones to produce clean images, i.e., with minimal energy in the side lobes. However, we have found that zone plates useful for x-ray lithography may have small numerical apertures and as few as two zones, and still produce very small and clean images.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
42.79.Ci Filters, zone plates, and polarizers

Modeling, fabrication, and experimental application of clear x-ray phase masks

Daniel H. Malueg, James W. Taylor, Don Thielman, Quinn Leonard, Scott Dhuey, and Franco Cerrina

J. Vac. Sci. Technol. B 22, 3575 (2004); http://dx.doi.org/10.1116/1.1809626 (6 pages) | Cited 1 time

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
Phase-shifting masks are widely used in optical lithography, and the question is whether the technology can be extended to much shorter wavelengths. We have extensively modeled the use of clear phase-mask materials as absorbers for x-ray exposures. Similar to the optical domain, the imaging from x-ray phase masks is highly nonlinear, and thus can be used to produce a feature reduction of 3–5× compared to the mask pattern. This observation suggests that mask fabrication might be easier, but the technique is most suited for less dense pattern requirements. In this article we review some of the salient modeling, examine the requirements for effective fabrication of the masks, and provide some experimental verification of this approach to reach the sub-50 nm region. It is not essential to have exactly a 180° phase shift in the clear material, because mask feature reductions can be achieved with 45, 90, 180, and 270° shifts by choosing the appropriate thicknesses of the clear material. A mask with a 235 nm feature and a 45° thickness is transformed into a 134 nm aerial feature, but the same dose for a 180° thickness results in an 86 nm feature. The best resolution is obtained in the so-called bright peak enhanced x-ray phase mask (BPEXPM) mode with thicknesses appropriate to 180° or greater. Previous modeling of the clear phase feature indicated a strong dependence on the wall slope, and fabrication processes are being pursued to verify the modeling and demonstrate the slope dependence on the feature profile. Silicon nitride with a phase shift of 126° is currently employed, but other materials could also be used in the mask fabrication. Experimentally, we are pursuing the feature width reduction achieved from correctly fabricated masks to produce gate width structures at the sub-50 nm region.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
42.82.Cr Fabrication techniques; lithography, pattern transfer

Temperature distributions to correct distortions in membrane masks

L. Jiang and M. Feldman

J. Vac. Sci. Technol. B 22, 3581 (2004); http://dx.doi.org/10.1116/1.1821500 (4 pages)

Online Publication Date: 14 December 2004

Full Text: | Download PDF

Show Abstract
Adaptive membrane masks have recently been reported for the correction of distortions in integrated circuit masks and wafers. In these masks radiative heating is selectively applied to portions of the mask membranes. By controlling local heating, dimensional changes are made to the membrane which correct overlay errors between the mask and the wafer. The method is applicable to almost all of the next generation lithographies, and can correct distortions arising from the mask, the wafer, or the exposure tool. In previous work it was assumed that in-plane heat flow through the thin membranes was negligible, and that the local temperature rise was proportional to the heat input. The present work demonstrates that although there is substantial in-plane heat flow, its effects may be accounted for and a very wide range of temperature distributions may be generated on the membrane. These temperature distributions can then be used to correct almost arbitrary distortions.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
Close

Your Recent History Recent History Help

Recently Viewed

  1. Atomic layer deposition of metal and nitride thin films: Current research efforts and applications f...
  2. Metal contacts on semiconductors: The adsorption of Sb, Sn, and Ga on InP(110) cleaved surfaces
  3. Classical stochastic diffusion theory for thermal desorption from solid surfaces
  4. Single cell detection with micromechanical oscillators
  5. Step and flash imprint lithography: Template surface treatment and defect analysis
© 2012 AVS Science & Technology of Materials, Interfaces, and Processing Help | Contact
close