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Nov 2004

Volume 22, Issue 6, pp. L35-3584

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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

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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).
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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

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Abstract Unavailable
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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

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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.
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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
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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 14 times

Online Publication Date: 25 October 2004

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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.
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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 8 times

Online Publication Date: 27 October 2004

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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.
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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

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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.
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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

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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.
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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

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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.
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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 25 times

Online Publication Date: 4 November 2004

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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.
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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 17 times

Online Publication Date: 4 November 2004

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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.
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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

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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.
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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

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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.
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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

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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.
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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 3 times

Online Publication Date: 4 November 2004

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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.
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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

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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.
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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

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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.
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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

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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.
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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

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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.
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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 4 times

Online Publication Date: 4 November 2004

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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.
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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

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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.
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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

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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.
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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

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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.
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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

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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.
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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

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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.
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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

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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).
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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

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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.
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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 15 times

Online Publication Date: 10 November 2004

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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.
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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

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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.
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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

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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.
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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

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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.
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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 8 times

Online Publication Date: 11 November 2004

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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.
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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

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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.
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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

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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.
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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 3 times

Online Publication Date: 15 November 2004

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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.
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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

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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.
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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

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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.
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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

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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.
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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

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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.
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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

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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.
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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 19 times

Online Publication Date: 17 November 2004

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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.
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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 30 times

Online Publication Date: 17 November 2004

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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.
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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

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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.
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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

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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.
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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

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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.
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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 8 times

Online Publication Date: 24 November 2004

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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.
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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 11 times

Online Publication Date: 24 November 2004

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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.
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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

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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.
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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 10 times

Online Publication Date: 24 November 2004

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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.
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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 12 times

Online Publication Date: 7 December 2004

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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.
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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 2 times

Online Publication Date: 9 December 2004

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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.
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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
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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

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Abstract Unavailable
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79.70.+q Field emission, ionization, evaporation, and desorption
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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

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Abstract Unavailable
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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
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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 16 times

Online Publication Date: 10 December 2004

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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.
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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

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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.
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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

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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.
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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

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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.
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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

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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.
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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,