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Nov 2010

Volume 28, Issue 6, pp. L61-C6S27

Issue Cover Spotlight Figure

J. Vac. Sci. Technol. B 28, C6C6 (2010); http://dx.doi.org/10.1116/1.3511436 (8 pages)

Paul Petric, Chris Bevis, Mark McCord, Allen Carroll, Alan Brodie, Upendra Ummethala, Luca Grella, Anthony Cheung, and Regina Freed
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Sputtering of (001)AlN thin films: Control of polarity by a seed layer

E. Milyutin, S. Harada, D. Martin, J. F. Carlin, N. Grandjean, V. Savu, O. Vaszquez-Mena, J. Brugger, and P. Muralt

J. Vac. Sci. Technol. B 28, L61 (2010); http://dx.doi.org/10.1116/1.3501117 (3 pages)

Online Publication Date: 30 November 2010

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The authors report on the ability to control the polarity of sputter deposited AlN(001) thin films using seed layers. Reactive sputter deposition leads to N-polarity on any substrate hitherto applied, i.e., Si(111), sapphire, SiO2, and polycrystalline metals such as Pt(111), Mo(110), and W(110). A site-controlled polarity allows for an efficient excitation of shear modes of surface, bulk, and Lamb waves by interdigitated electrodes. The authors were able to introduce the Al-polarity through a metal-organic chemical-vapor deposition seed layer. By subsequently patterning the substrate surface, it was possible to define the desired film polarity of sputter deposited AlN film. Polarities were determined by selective etching with KOH solutions and by piezoresponse force microscopy.
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81.15.Cd Deposition by sputtering
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Ea III-V semiconductors
68.55.ag Semiconductors
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Editorial

Gerry Lucovsky, Editor “Emeritus”

J. Vac. Sci. Technol. B 28, P1 (2010); http://dx.doi.org/10.1116/1.3511696 (1 page)

Online Publication Date: 30 November 2010

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01.30.Ww Editorials
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
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Different growth mechanisms of vertical carbon nanotubes by rf- or dc-plasma enhanced chemical vapor deposition at low temperature

Huiyao Wang and John J. Moore

J. Vac. Sci. Technol. B 28, 1081 (2010); http://dx.doi.org/10.1116/1.3497030 (5 pages)

Online Publication Date: 12 October 2010

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Vertically aligned carbon nanotubes (CNTs) were synthesized using FeNi or Fe sputtered catalyst layers on glass substrates by radio frequency or direct current plasma enhanced chemical vapor deposition (rf- or dc-PECVD). This article compared the growth mechanisms of CNTs synthesized by rf- and dc-PECVD, based on gas flow rate, plasma power, and catalysts. Tip growth CNTs were produced at 180 °C, 10 SCCM (SCCM denotes cubic centimeter per minute at STP) CH4, and 30 W by rf-PECVD using 8 or 4 nm FeNi or 4 nm Fe island films sputtered onto glass substrates. CNTs could not grow using dc-PECVD under the same deposition conditions; tip growth of CNTs occurred at 180 °C, 15 SCCM CH4, and 50 W using dc-PECVD with sputtered FeNi island catalysts on increasing the plasma power and CH4 flow rate. This article explained why rf-PECVD provided more efficient decomposition of gas molecules than dc-PECVD by plasma theory. The major difference between rf- and dc-PECVD was the higher concentration of reactive radicals in the former. However, in dc-PECVD, the CNT growth was well aligned vertically. FeNi thin film catalysts exhibited higher activity and better wetting ability than the Fe island thin film catalysts.
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81.07.De Nanotubes
81.16.Hc Catalytic methods
52.77.Dq Plasma-based ion implantation and deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Influence of the tip work function on scanning tunneling microscopy and spectroscopy on zinc doped GaAs

A. P. Wijnheijmer, J. K. Garleff, M. A. v. d. Heijden, and P. M. Koenraad

J. Vac. Sci. Technol. B 28, 1086 (2010); http://dx.doi.org/10.1116/1.3498739 (7 pages)

Online Publication Date: 12 October 2010

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The authors investigated the influence of the tip work function on the signatures of zinc in gallium arsenide with scanning tunneling microscopy and spectroscopy. By deliberately inducing tip modifications, the authors can change the tip work function between 3.9 and 5.5 eV, which corresponds to the expected range for tungsten of 3.5–6 eV. The related change in flatband voltage has a drastic effect on both the dI/dV spectra and on the voltage where the typical triangular contrast appears in the topography images. The authors propose a model to explain the differences in the dI/dV spectra for the different tip work functions. By linking the topography images to the spectroscopy data, the authors confirm the generally believed idea that the triangles appear when tunneling into the conduction band is mainly suppressed.
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73.40.Gk Tunneling
71.55.Eq III-V semiconductors
81.05.Ea III-V semiconductors
73.30.+y Surface double layers, Schottky barriers, and work functions
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.35.bg Semiconductors

Field-emission of TiSi2 thin film deposited by an in situ chloride-generated route

Yemin Hu, Ying Li, Mingyuan Zhu, Zheng Hu, and Leshu Yu

J. Vac. Sci. Technol. B 28, 1093 (2010); http://dx.doi.org/10.1116/1.3498742 (4 pages)

Online Publication Date: 12 October 2010

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Titanium disilicide (TiSi2) is a high-melting compound with excellent conductivity, which appears to have potential applications in field-emission. In the present article, TiSi2 thin film was successfully synthesized on a silicon wafer through an in situ chloride-generated strategy by atmospheric-pressure chemical-vapor deposition. The required titanium chloride-precursor vapor was in situ produced at an elevated temperature by preloading NiCl2⋅6H2O onto Ti powder with anhydrous ethanol. This synthetic strategy avoided inconvenience with the direct usage of titanium halide or titanium powder as delivering gaseous precursors. The field-emission behavior of the sample shows a turn-on field of 7.2 V/μm and agrees well with the conventional Fowler–Nordheim theory. No obvious degradation was observed in a life-stability experiment period for over 100 min. The convenient and low-cost preparation of the TiSi2 thin film and its fine field-emission performance suggest that it can serve as a good candidate for a field emitter.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
79.70.+q Field emission, ionization, evaporation, and desorption
73.61.Ng Insulators
68.55.A- Nucleation and growth

Characterization of electrodeposited Ni–Fe–SiC alloys for microelectromechanical applications

Xiaohu Zheng, Xing Chen, Feng Gu, YuanWei Liu, and Dong-Weon Lee

J. Vac. Sci. Technol. B 28, 1097 (2010); http://dx.doi.org/10.1116/1.3498740 (3 pages)

Online Publication Date: 13 October 2010

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Ni–Fe–SiC alloy is a promising material for the fabrication of microactuators. In this article, the electrolytic codeposition technique is used to deposit the Ni–Fe–SiC composite onto stainless-steel substrates, where nickel becomes alloyed with iron as the binder phase, and SiC becomes alloyed as dispersed particles. Analysis of the morphology indicates that the deposited SiC nanoparticles are compact, with the orientation of the deposited crystal planes indexed as (111), (200), (220), (311), and (222). The resistivity of the deposited SiC nanoparticles is about 30×10−8 Ω m. When the loading of Fe (wt %) ranges from 10% to 50% in the deposit, the electrodeposit shows a strong paramagnetism with a lowest value of coercivity of 2.75×10−2 A/m. In addition, the remanence shows a monotonic decrease with an increasing iron content in the deposit. It is demonstrated that the electroformed Ni–Fe–SiC alloy has better electromagnetic properties and a higher corrosion resistance (with a corrosion rate of 0.17 mg/dm2 h 2M HCl) than the electroformed Ni–Fe alloy (with a corrosion rate of 0.23 mg/dm2 h).
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81.07.-b Nanoscale materials and structures: fabrication and characterization
82.45.Qr Electrodeposition and electrodissolution
82.45.Bb Corrosion and passivation
73.40.-c Electronic transport in interface structures
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)

UV ozone passivation of the metal/dielectric interface for HfO2-based organic thin film transistors

W. M. Tang, W. T. Ng, M. G. Helander, M. T. Greiner, and Z. H. Lu

J. Vac. Sci. Technol. B 28, 1100 (2010); http://dx.doi.org/10.1116/1.3498744 (4 pages)

Online Publication Date: 13 October 2010

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Ultraviolet (UV) ozone passivation of the metal/dielectric interface was investigated in HfO2-based devices. It is found that the passivation of Al gate reduces the gate leakage current by two orders of magnitude and increases the breakdown field strength by 14%. A thicker wide-band gap Al2O3 interlayer formed on the Al gate during UV ozone treatment improves the interface quality and suppresses the leakage associated with the high-k material. Copper phthalocyanine-based organic thin-film transistors with HfO2 as gate dielectric were fabricated on glass. UV ozone passivated devices exhibited a low threshold voltage of −0.29 V and a low subthreshold slope of 0.38 V/decade, demonstrating the advantage of UV ozone passivation.
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85.30.Tv Field effect devices
81.65.Rv Passivation
77.22.Jp Dielectric breakdown and space-charge effects
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Surface and near-surface modifications of ultralow dielectric constant materials exposed to plasmas under sidewall-like conditions

Ming-Shu Kuo and G. S. Oehrlein

J. Vac. Sci. Technol. B 28, 1104 (2010); http://dx.doi.org/10.1116/1.3499271 (7 pages) | Cited 1 time

Online Publication Date: 13 October 2010

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The authors describe the temporal evolution of the surface and near-surface regions of a porous SiCOH ultralow k (ULK) dielectric during exposure under sidewall-like exposure conditions to various plasma processing environments. The authors studied the exposure of the ULK material to Ar plasma, C4F8/Ar-based etching plasma, and O2 or CO2 ashing plasmas, as well as various sequences of these processes. Real-time monitoring of the ULK surfaces during plasma processing was performed by in situ ellipsometry employing a novel gap structure. Additionally, changes in ULK surface properties were characterized by x-ray photoelectron spectroscopy and selective dilute hydrofluoric acid wet etching in combination with ex situ ellipsometry measurements. Pristine ULK material exposed to O2 plasma without ion bombardment shows the formation of a near-surface porous layer. For exposure of the ULK to CO2 plasma operated at comparable plasma operation conditions, the modification depth for a given exposure time is reduced relative to O2, but otherwise an identical ellipsometric trajectory is followed. This is indicative of a similar ULK damage mechanism for the two discharges, although at different rates. Energetic ( ∼ 400 eV) ion bombardment on the surface of ULK with line-of-sight Ar plasma exposure introduced a ∼ 12 nm thick SiO2-like densified layer on the ULK surface meanwhile sputtering off the ULK material. The sidewall-like modifications of ULK due to metastable Ar, if present, were too subtle to be measurable in this article. For ULK exposed under sidewall-like geometry to C4F8/Ar-based etching plasma, fluorocarbon quickly permeated into the subsurface region and showed saturation at a mixed layer thickness of about 14 nm. For additional exposure to O2 or CO2 discharges, a strong decrease of the CO2 plasma induced ULK surface modifications with increasing fluorocarbon (FC) film thickness was found, indicative of surface protection by FC surface deposition along with pore-sealing by the FC material. Attempts to increase the protective nature of the FC film by additional plasma processing, e.g., by exposure to Ar or He plasma after FC plasma etching, did not reduce CO2 plasma induced ULK surface modifications further.
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81.65.Cf Surface cleaning, etching, patterning
77.22.Ch Permittivity (dielectric function)
61.43.Gt Powders, porous materials
77.55.Bh Low-permittivity dielectric films
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
61.80.Jh Ion radiation effects

Growth of size and density controlled GaAs/InxGa1−xAs/GaAs (x = 0.10) nanowires on anodic alumina membrane-assisted etching of nanopatterned GaAs

Aloysius A. Gunawan, S. Jha, and T. F. Kuech

J. Vac. Sci. Technol. B 28, 1111 (2010); http://dx.doi.org/10.1116/1.3498753 (9 pages)

Online Publication Date: 13 October 2010

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Electrochemical anodization using anodic alumina membrane-assisted etching of GaAs(111)B produced nanopatterned GaAs surfaces, which served as substrates for the growth of GaAs/InxGa1−xAs/GaAs quantum well (QW) nanowires with controllable size and density. The nanodepressions created on the anodized GaAs surface minimize the migration of Au nanodots during thermal annealing. The Au nanodots were used in vapor-liquid-solid based growth of the nanostructures. The thickness of the evaporated Au islands, the anodization voltage, and the duration of the etching are the most important parameters used to tailor the size distribution and density of the Au catalysts and hence the diameter of nanowires. Transmission electron microscopy (TEM) reveals that the QW nanowires are single crystals with the 〈111〉 main axis direction, similar to nanowires synthesized using conventional methods on bare GaAs substrates and other patterning mechanisms. Z-contrast high-angle annular dark-field scanning TEM confirmed the presence of the InGaAs layer having widths of 70–100 nm. Photoluminescence spectroscopy on the QW nanowires showed consistent peaks at 1.375 eV indicative of the first electron–heavy hole recombination from the InGaAs QW layer. This transition energy corresponds to a 0.10 In composition, in disagreement with the value obtained from energy-dispersive x rays in scanning TEM (xEDX = 0.05).
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81.07.Gf Nanowires
81.05.Ea III-V semiconductors
78.67.Uh Nanowires
78.55.Cr III-V semiconductors
73.63.Nm Quantum wires
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Complex dielectric function and refractive index spectra of epitaxial CdO thin film grown on r-plane sapphire from 0.74 to 6.45 eV

S. G. Choi, J. Zúñiga-Pérez, V. Muñoz-Sanjosé, A. G. Norman, C. L. Perkins, and D. H. Levi

J. Vac. Sci. Technol. B 28, 1120 (2010); http://dx.doi.org/10.1116/1.3498755 (5 pages) | Cited 2 times

Online Publication Date: 13 October 2010

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The authors report ellipsometrically determined optical properties of epitaxial cadmium oxide thin film grown by metal-organic vapor phase epitaxy on r-plane sapphire substrate. The ellipsometric data were collected from 0.74 to 6.45 eV with the sample at room temperature. Artifacts from the surface overlayers were reduced as far as possible by the premeasurement surface treatment procedures. Complex dielectric function ε = ε1+iε2 and refractive index N = n+ik spectra were extracted from multilayer modeling of the data with the B-spline functions.
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78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
42.70.-a Optical materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons

Formation of three-dimensional and nanowall structures on silicon using a hydrogen-assisted high aspect ratio etching

S. Azimi, M. Mehran, A. Amini, A. Vali, S. Mohajerzadeh, and M. Fathipour

J. Vac. Sci. Technol. B 28, 1125 (2010); http://dx.doi.org/10.1116/1.3497033 (7 pages)

Online Publication Date: 19 October 2010

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The authors report the realization of highly featured three-dimensional structures on silicon substrates with a single masking layer using a hydrogen-assisted deep reactive ion etching process. Oxygen, hydrogen, and SF6 are used in a sequential passivation and etching process to achieve high aspect ratio features. By controlling the flows of these gases and the power and timing of each subsequence, it is possible to achieve desired deep vertical etching, controlled underetching, and recovery, yielding three-dimensional features directly on silicon substrates. Etch rates up to 0.75 μm/min have been achieved with a low plasma power density of 1 W/cm2. In addition, features with a controllable underetching and recovery with more than 8 μm in sidewall recession have been achieved. Furthermore, values of aspect ratio higher than 40 can be obtained. The formation of three-dimensional features with nanowall structures is reported.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
68.47.Fg Semiconductor surfaces
81.05.Cy Elemental semiconductors
81.07.Bc Nanocrystalline materials
81.16.Nd Micro- and nanolithography
81.65.Rv Passivation

Statistical-noise effect on discrete power spectrum of line-edge and line-width roughness

Atsushi Hiraiwa (平岩篤) and Akio Nishida (西田彰男)

J. Vac. Sci. Technol. B 28, 1132 (2010); http://dx.doi.org/10.1116/1.3499647 (6 pages) | Cited 1 time

Online Publication Date: 19 October 2010

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The control of line-edge roughness (LER) and line-width roughness (LWR) is a key issue in addressing the growing challenge of device variability in large-scale integrations. The accurate characterization of LER and LWR forms a basis for this effort and mostly hinges on reducing the effects of noise inherent in experimental results. This article reports how a power spectral density (PSD) is affected by a statistical noise that originates from the finiteness of the number NL of available samples. To achieve this, the authors numerically generated line-width data using the Monte Carlo (MC) method and assuming an exponential autocorrelation function (ACF). By analyzing the pseudoexperimental PSDs obtained using the MC data, they found that the standard deviation η of normalized analysis errors was determined by the total number NALL of width data used in each analysis, regardless of NL and the number N of width data in each line segment. The authors found that η decreased with NALL approximately in inverse proportion to NALL3/4. It is noteworthy that they could obtain accurate results even in the case of NL = 1 as long as NALL was sufficiently large, although the distribution of PSDs was large due to a large statistical noise. This resulted from the fact that the PSD distribution was not completely irregular, but centered at the true value and that the best-fitted PSD accordingly approached the true one with an increasing N. On the other hand, η at a fixed NALL decreased with the ratio Δy/ξ of an interval Δy of width data to a correlation length ξ, approximately in inverse proportion to (Δy/ξ)3/8. As a result, NALL at a specified η decreased with Δy/ξ in inverse proportion to the square root of Δy/ξ in the case when Δy/ξ was 0.3 or smaller. Beyond this threshold of Δy/ξ, the authors needed to increase NALL markedly to achieve the same accuracy of analyses. This comes from a decrease in the range of the PSD with an increasing Δy/ξ and a subsequent loss of sensitivity of the PSD to the change of ξ. Based on these results, they established guidelines for accurate analyses as follows: Δy/ξ ≤ 0.3 and NALL ≥ Aη−4/3(Δy/ξ)−1/2, where A is 1.8×102 for ξ and 7.2×101 for the variance of widths, respectively. Equivalently in terms of the total measurement length LALL, instead of NALL, the guidelines are given in Δy/ξ ≤ 0.3 and LALL/ξ ≥ Aη−4/3(Δy/ξ)1/2 using the same A’s as those of NALL. Being expressed in universal forms like these, the guidelines of this study can be applied to many practical problems beyond LER and LWR to accurately analyze PSDs, as long as the stochastic processes have exponential ACFs.
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85.30.De Semiconductor-device characterization, design, and modeling
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
05.10.Ln Monte Carlo methods

Defect-free etching process for GaAs/AlGaAs hetero-nanostructure using chlorine/argon mixed neutral beam

Xuan-Yu Wang, Chi-Hsien Huang, Yuzo Ohno, Mokoto Igarashi, Akihiro Murayama, and Seiji Samukawa

J. Vac. Sci. Technol. B 28, 1138 (2010); http://dx.doi.org/10.1116/1.3499716 (5 pages)

Online Publication Date: 19 October 2010

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The authors studied a GaAs/Al0.3Ga0.7As hetero-nanostructure etching process, neutral beam (NB) etching with chlorine (Cl2) and argon (Ar) mix gas. The effect of different mixing ratios of chlorine and argon has been investigated. The results showed that when pure chlorine NB (Cl-NB) was used, the pillar formation problem was observed on the etched surface. By increasing the Ar/(Cl2+Ar) gas mixing ratio, the pillar can be eliminated and the roughness of etched surface smoothed. As an Ar/(Cl2+Ar) gas mixing ratio of 78% was used, the root-mean-square roughness of etched surfaces of both GaAs and Al0.3Ga0.7As is about 0.6 nm, which is almost the same as those of as-received samples. Meanwhile, the etching selectivity of GaAs/Al0.3Ga0.7As can be kept close to 1, which would help to etch a clear and smooth profile. Additionally, the high-resolution transmission-electron microscopy image of the GaAs etch profile shows that no crystalline defect was observed on the etched surface.
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81.65.Cf Surface cleaning, etching, patterning
68.35.bg Semiconductors
68.37.Lp Transmission electron microscopy (TEM)

Effect of Al doping on resistive switching behavior of NiOx films for nonvolatile memory application

Jonggi Kim, Heedo Na, Jinho Oh, Dae-Hong Ko, and Hyunchul Sohn

J. Vac. Sci. Technol. B 28, 1143 (2010); http://dx.doi.org/10.1116/1.3501109 (5 pages)

Online Publication Date: 19 October 2010

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In this work, the authors investigated the effect of Al doping on the resistance switching characteristics of sputtered NiOx films. Pt/NiOx/Pt metal-insulator-metal (MIM) stacks were fabricated by reactive dc magnetron sputtering with various Al contents in NiOx films and the resistance switching behavior of the MIM stack was characterized in conjunction with physical property, such as chemical bonding of NiOx. Al doping into NiOx films improved the endurance of SET/RESET operations, the distribution of VSET, and the memory window compared to the undoped NiOx films. X-ray photoemission spectroscopy showed that the Al doping caused the density of metallic nickel (Ni0) to be increased with the reduction of Ni3+ concentration. It was considered that the increase of metallic nickel (Ni0) in Al-doped NiOx films enhanced the repeated formation and rupture of conductive filaments during resistive switching operation, resulting in the enhanced endurance and the narrowed VSET distribution.
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73.40.Rw Metal-insulator-metal structures
84.30.Sk Pulse and digital circuits
61.72.up Other materials
81.15.Cd Deposition by sputtering

Mechanical and electronic characteristics of scanning probe microscopy probes based on coaxial palladium nanowire/carbon nanotube hybrid structures

Ian Thomas Clark, Gemma Rius, Yuki Matsuoka, and Masamichi Yoshimura

J. Vac. Sci. Technol. B 28, 1148 (2010); http://dx.doi.org/10.1116/1.3501131 (5 pages) | Cited 1 time

Online Publication Date: 19 October 2010

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The authors present the mechanical and electronic characterization of a novel kind of scanning probe microscopy probe fabricated by the microwave plasma-enhanced chemical vapor deposition growth of carbon nanotubes using a catalytic palladium film deposited only near the apices of commercial tapping mode atomic force microscopy (AFM) cantilevers with the use of a newly developed controlled-area electroplating method. This process is shown to result in the growth of coaxial palladium nanowire/carbon nanotube composite structures (PdNWCNTs). The authors demonstrate that neither the cantilever quality factor nor the cantilever spring constant is significantly degraded by PdNWCNT growth, and show that PdNWCNT probes are adequate for standard tapping mode AFM imaging. Low resistance Ohmic contact between PdNWCNT probes and metal surfaces is demonstrated. Importantly, repeated surface contact and current flow is shown to not damage the PdNWCNTs, indicating that the probes are appropriate for multiprobe conductivity measurements. A brief overview of the fabrication process is also provided.
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81.07.De Nanotubes
07.79.Lh Atomic force microscopes
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.07.Gf Nanowires

CO2 laser treatment for stabilization of the superhydrophobicity of carbon nanotube surfaces

S. C. Ramos, G. Vasconcelos, E. F. Antunes, A. O. Lobo, V. J. Trava-Airoldi, and E. J. Corat

J. Vac. Sci. Technol. B 28, 1153 (2010); http://dx.doi.org/10.1116/1.3502024 (5 pages)

Online Publication Date: 19 October 2010

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In this work, the authors demonstrate the formation of stable superhydrophobic vertically aligned multiwalled carbon nanotube (VACNT) surfaces through CO2 laser irradiance, in which the contact angle value reached 161°. VACNT arrays were synthesized by microwave plasma chemical vapor deposition using N2/H2/CH4 [10/90/14 SCCM (SCCM denotes cubic centimeter per minute at STP)]. CO2 laser technique was applied on VACNT surfaces with irradiance at different laser powers to promote the great stability of superhydrophobic surfaces. Contact angle measurement reveals that irradiated VACNT surface is superhydrophobic at all irradiances tested. Unlike as-grown VACNT, the samples treated with CO2 laser show no sign of water seepage even after a prolonged period of time ( ∼ 24 h). This characteristic is very interesting and has various possible functional applications in micro- and nanomaterials and devices.
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81.65.-b Surface treatments
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.48.De Structure of carbon nanotubes, boron nanotubes, and other related systems
81.07.De Nanotubes
68.03.Cd Surface tension and related phenomena
42.62.-b Laser applications

Dose loss of phosphorus due to interface segregation in silicon-on-insulator substrates

Ruey-Dar Chang, Chia-Chi Ma, and Jung-Ruey Tsai

J. Vac. Sci. Technol. B 28, 1158 (2010); http://dx.doi.org/10.1116/1.3499648 (6 pages)

Online Publication Date: 20 October 2010

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The dose loss of phosphorus due to interface segregation in silicon-on-insulator (SOI) substrates was characterized by using sheet resistance. Bulk silicon and SOI wafers were implanted with phosphorus at a dose of 5×1014 cm−2, followed by annealing at 900 °C to produce phosphorus segregation at the SiO2–Si interface. The effectiveness of the mobility model for calculating sheet resistance and the reliability of parameters in interface segregation models were verified based on the sheet resistance data and the secondary ion mass spectrometry profiles of phosphorus in bulk silicon samples. The sheet resistance in SOI substrates was then simulated using the verified mobility model and interface segregation parameters. Simulation results indicate that the equilibrium segregation behavior at the interfaces in SOI samples is similar to that in bulk silicon samples. Moreover, the dose loss in SOI substrates is more significant than that in bulk silicon wafers owing to a larger interface area in the SOI substrates.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
68.35.Dv Composition, segregation; defects and impurities
61.72.U- Doping and impurity implantation
61.72.Cc Kinetics of defect formation and annealing
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Influence of surface treatment and interface layers on electrical spin injection efficiency and transport in InAs

L. Zhu and E. T. Yu

J. Vac. Sci. Technol. B 28, 1164 (2010); http://dx.doi.org/10.1116/1.3502674 (5 pages) | Cited 1 time

Online Publication Date: 20 October 2010

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Spin-valve, weak localization/antilocalization, and scanned probe microscopy measurements are used to investigate the influence of sulfur-based surface treatments and electrically insulating barrier layers on spin injection into, and spin transport within, the two-dimensional electron layer at the surface of p-type InAs at 4.2 K. An electrically insulating barrier layer is found to be required to achieve nonzero spin injection efficiency, with a 3 nm Al2O3 electrically insulating barrier providing a spin injection efficiency of 5±2%. Conductive atomic force microscopy suggests that localized leakage through the InAs native oxide is sufficient to suppress spin-polarized current injection in the absence of a more highly insulating barrier layer. Spin scattering lengths are determined experimentally from both weak localization/antilocalization and spin-valve measurements. Spin and elastic scattering lengths of 230±20 and 85±5 nm, respectively, are measured, with a sulfur-based surface treatment increasing the spin scattering length to 250±20 nm and decreasing the elastic scattering length to 65±5 nm.
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85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields

Electron detection performance of diamond avalanche diode

Hideo Morishita, Takashi Ohshima, Michio Hatano, Yoko Iwakaji, Osamu Maida, and Toshimichi Ito

J. Vac. Sci. Technol. B 28, 1169 (2010); http://dx.doi.org/10.1116/1.3497031 (4 pages)

Online Publication Date: 21 October 2010

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The authors evaluated the electron detection performance of a diamond avalanche diode (DAD) detector. In the electrode region, the gain was uniformly about 103 with little noise. Meanwhile, an avalanche multiplication occurred locally. In the avalanche region, a total gain of 5×104 was obtained. In some regions where the electric field is regarded to be intensified, the avalanche multiplication gain was estimated to be approximately 100–300, and the signal-to-noise ratio (S/N) was nearly equal to 1. The DAD can be applied to an electron detector for a scanning electron microscope due to its high gain and small dark current. However, it is necessary to improve the S/N and homogenize the gain to use the DAD detector as an electron detector.
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85.30.Kk Junction diodes
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Thin film transistors with a ZnO channel and gate dielectric layers of HfO2 by atomic layer deposition

Ronald Grundbacher, Kiran Chikkadi, and Christofer Hierold

J. Vac. Sci. Technol. B 28, 1173 (2010); http://dx.doi.org/10.1116/1.3501338 (6 pages)

Online Publication Date: 21 October 2010

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Thin film transistors (TFTs) have been fabricated with a zinc oxide (ZnO) channel layer and a hafnium dioxide (HfO2) gate dielectric layer. The oxide layers were deposited using an atomic layer deposition (ALD) system. The use of ALD for ZnO deposition allows subnanometer thickness control of the deposited layer, and thereby provides a means to vary TFT threshold voltage by controlling the carrier density in the ZnO channel: the carrier density is dependent on the layer thickness because band structure changes result in charge depletion in thinner layers. Enhancement-mode devices have been fabricated and have an on-off current ratio above 106. The enhancement-mode devices of the inverted (gate down) TFT structure were realized by decreasing the ZnO channel layer thickness to 15 nm and below, thereby reducing the carrier density of the as-deposited n-type ZnO layer. An important aspect of the fabrication of the inverted TFTs was the use of either an aluminum sacrificial layer or a thin HfO2 cap layer to eliminate the etching of the ZnO during the photolithography process. The results demonstrate that enhancement-mode TFTs with as-deposited n-type ZnO channels can be produced by tailoring the thickness of the ZnO channel by ALD and are the first reported TFTs in which both the ZnO channel and HfO2 gate dielectric are deposited by ALD to the authors’ knowledge.
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85.30.Tv Field effect devices
82.45.Un Dielectric materials in electrochemistry
81.16.Nd Micro- and nanolithography

Silicon nitride hardmask fabrication using a cyclic CHF3-based reactive ion etching process for vertical profile nanostructures

Peter Kaspar, Yogesh Jeyaram, Heinz Jäckel, Annette Foelske, Rüdiger Kötz, and Sandro Bellini

J. Vac. Sci. Technol. B 28, 1179 (2010); http://dx.doi.org/10.1116/1.3501120 (8 pages)

Online Publication Date: 22 October 2010

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A cyclic approach to silicon nitride dry-etching is presented, which differs in concept from most established high aspect ratio etching processes. Alternating steps of CHF3 etching and oxygen plasma treatment are applied to form vertical sidewalls. During the CHF3 etching step, an etch-inhibiting fluorocarbon film gradually forms on silicon nitride surfaces, whereas the oxygen plasma step removes the fluorocarbon layer and restores the bare nitride surface. By adjusting the timing between the two steps, the etch-inhibition by the fluorocarbon film can be controlled to yield vertical sidewalls. Using x-ray photoelectron spectroscopy, the formation and removal of the fluorocarbon film are confirmed, and its chemical composition is analyzed. The authors show the influence of cycle step duration on etched sidewall angles and present the results of an optimized set of etching parameters for smooth and vertical sidewalls. By feeding only one gas at a time to the plasma reactor, they avoid having to control the delicate balance between the fluxes of species that deposit and etch the fluorocarbon film. This makes their process very robust and removes the highly variable effects of reactor wall conditions. Finally, the authors comment on the feasibility of implementing a process for etching silicon dioxide in a similar fashion.
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81.16.Be Chemical synthesis methods
81.07.Bc Nanocrystalline materials
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning

Hydrogen etching and cutting of multiwall carbon nanotubes

Michael J. Behr, E. Ashley Gaulding, K. Andre Mkhoyan, and Eray S. Aydil

J. Vac. Sci. Technol. B 28, 1187 (2010); http://dx.doi.org/10.1116/1.3498737 (8 pages)

Online Publication Date: 25 October 2010

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The interaction of H atoms with the curved concentric graphene walls of a multiwall carbon nanotube and the stacked planar graphene sheets of graphite was investigated using a combination of high resolution transmission electron microscopy (HRTEM) in conjunction with electron energy-loss and Raman spectroscopies. Continuous cylindrical graphene walls of a nanotube are etched and amorphized by the H atoms. Etching is not uniform across the length of the CNT but rather, small etch pits form at defective sites on the CNT walls along the entire nanotube length. Once an etch pit is formed, etching proceeds rapidly, and the remainder of the CNT is quickly etched away. The carbon K core-loss edge spectra collected from etch pits do not differ from the spectra collected from pristine CNT walls, indicating that reactions occur exclusively at the exposed graphene edges. Similar observations were made when sheets of planar graphite were exposed to H atoms. Confocal Raman spectroscopic measurements revealed that H etching occurs preferentially at the graphite edges. Eventually, large holes appear in the graphite, as observed under HRTEM. Etched holes in planar graphite are similar to the etch pits that form when a graphene layer is rolled up to form the cylindrical walls of a CNT. Once a hole or an etch pit is formed, the edges of the planar graphene sheets or cylindrical CNT walls become exposed, and H etching proceeds quickly from these edges.
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81.65.Cf Surface cleaning, etching, patterning
78.67.Ch Nanotubes
79.20.Uv Electron energy loss spectroscopy
78.30.Na Fullerenes and related materials
61.43.Er Other amorphous solids

Controlled sacrificial sidewall surface micromachining for the release of high length-to-thickness aspect ratio bridges

Christopher R. Raum, R. Niall Tait, and Robert Gauthier

J. Vac. Sci. Technol. B 28, 1195 (2010); http://dx.doi.org/10.1116/1.3503612 (7 pages)

Online Publication Date: 25 October 2010

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A surface micromachining technique for the release of high length-to-thickness aspect ratio (800:1) bridge structures is presented. During a timed etch release, the remaining side wall geometry of the sacrificial layer provides intrinsic support for the structural layer. The micromachining process itself is an equipment limited procedure in which the wet etchant for the sacrificial layer is replaced in solution (i.e., in situ) with a supportive photoresist layer. Once in solid form, the photoresist is removed via ashing in an oxygen plasma. This combination of controlling the sidewall etch profile of the sacrificial layer and its removal technique results in the successful release of bridge structures, which are 4000 μm long and 5 μm thick, with a 2 μm suspension gap.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning

Field emission stability and properties of simultaneously grown microcrystalline diamond and carbon nanostructure films

Kishore Uppireddi, Brad R. Weiner, and Gerardo Morell

J. Vac. Sci. Technol. B 28, 1202 (2010); http://dx.doi.org/10.1116/1.3503619 (4 pages)

Online Publication Date: 26 October 2010

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The temporal stability and electron field emission characteristics of simultaneously grown microcrystalline diamond and carbon nanostructures were investigated. The films were prepared by hot filament chemical vapor deposition using typical diamond deposition parameters, and iron oxide nanoparticles on the molybdenum substrate were employed as catalyst for their induction. The hybrid system presented better emission characteristics compared with microcrystalline diamond with turn-on fields as low as 2.45 V/μm (at 1 μA/cm2), and a current density of up to 0.24 mA/cm2 was achieved. The films showed relatively stable emission behavior for a period of 24 h.
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68.55.A- Nucleation and growth
81.16.Hc Catalytic methods
79.70.+q Field emission, ionization, evaporation, and desorption
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
81.05.ug Diamond

Electron beam induced etching of silicon with SF6

N. Vanhove, P. Lievens, and W. Vandervorst

J. Vac. Sci. Technol. B 28, 1206 (2010); http://dx.doi.org/10.1116/1.3504594 (4 pages)

Online Publication Date: 26 October 2010

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Electron beam induced etching (EBIE) with SF6 precursor molecules has been demonstrated as an approach to induce localized etching of Si with an etch yield of approximately 0.003 atoms/incoming electron. Further understanding of the EBIE mechanisms is presented through an analysis of the influence of the different electron beam parameters (beam energy and electron flux) and the effect of the sample bias on the EBIE rate. It is demonstrated that the etch rate increases with decreasing beam energy and with increasing electron flux to a saturation value. The latter is explained by a transition from an electron flux density limited process (at low current densities) to a gas supply limited process (at high current densities). The authors also demonstrate that a large etch rate enhancement is obtained by applying a positive sample bias. This is explained within the frame of a model outlining the role of the low secondary energy electrons in the electron stimulated etching process.
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81.65.Cf Surface cleaning, etching, patterning

Simultaneous observation of surface topography and elasticity at atomic scale by multifrequency frequency modulation atomic force microscopy

Yoshitaka Naitoh, Zongmin Ma, Yan Jun Li, Masami Kageshima, and Yasuhiro Sugawara

J. Vac. Sci. Technol. B 28, 1210 (2010); http://dx.doi.org/10.1116/1.3503611 (5 pages) | Cited 2 times

Online Publication Date: 28 October 2010

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The authors integrated the frequency modulation (FM) technique into multifrequency atomic force microscopy (AFM). Based on theoretical considerations, simultaneous excitation of the cantilever oscillation at the first and second flexural modes allows us to acquire the surface topography and surface elasticity simultaneously. The authors performed multifrequency FM-AFM observation using a tungsten-coated silicon cantilever on a Ge(001) surface exhibiting a dimer structure at room temperature. The topography and the elasticity of the surface were successfully obtained at the atomic scale. The authors found that the dimer atoms around a missing dimer defect have higher elasticity than the other dimer atoms. This suggests that stiffer atomic bonding of the dimer atoms occurred as a result of the additional tensile strain field from the defect. Therefore, the multifrequency FM-AFM described in the present study is expected to be useful for the investigation of the surface elasticity at the atomic scale.
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68.35.bg Semiconductors
68.47.Fg Semiconductor surfaces
81.40.Jj Elasticity and anelasticity, stress-strain relations
81.40.Lm Deformation, plasticity, and creep
68.35.Gy Mechanical properties; surface strains
68.37.Ps Atomic force microscopy (AFM)

Nonlinearities in depth profiling nanometer layers

M. P. Seah, C. P. A. Mulcahy, and S. Biswas

J. Vac. Sci. Technol. B 28, 1215 (2010); http://dx.doi.org/10.1116/1.3504592 (7 pages)

Online Publication Date: 28 October 2010

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An analysis is made of the sputter depth profiling of ultrathin silicon dioxide layers on silicon to evaluate the variation in the sputtering rate in the first few nanometers. Such changes in sputtering rate are important for the development of the analysis of nanoparticles. Cs+ ions are chosen as an example of a metal ion popular in secondary ion mass spectrometry (SIMS) studies that provide excellent depth resolution. It is found that, if it is assumed that the signal is linear with oxygen content, the sputtering rate falls rapidly by a factor of 4.8, with an exponential decay near 1.2 nm when using 600 eV Cs+ ions at 60° incidence angle. The interface may be described by the integral of the response function of Dowsett et al. developed for SIMS depth profiling of delta layers with λu = 0.5 nm, λd = 0.7 nm, and σ = 0.4 nm, showing the excellent depth resolution. However, if published data for the nonlinearity of the signal with oxygen content are used, the rapid change is still seen but with an initial sputtering rate that is reduced from the above 4.8 to 3.5 times that at equilibrium.
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68.55.A- Nucleation and growth
81.07.Bc Nanocrystalline materials
81.15.Cd Deposition by sputtering
81.16.-c Methods of micro- and nanofabrication and processing
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)

Challenges in the fabrication of an optical frequency ground plane cloak consisting of silicon nanorod arrays

J. Blair, D. Brown, V. A. Tamma, W. Park, and C. Summers

J. Vac. Sci. Technol. B 28, 1222 (2010); http://dx.doi.org/10.1116/1.3504595 (9 pages) | Cited 1 time

Online Publication Date: 28 October 2010

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The application of transformation optical techniques to photonic crystal-like dielectric structures has facilitated the creation of invisibility cloaks that operate at optical wavelengths. In this article, the authors present the fabrication processes for an all-dielectric ground plane cloak structure that consists of multiple silicon nanorod arrays connected by input and output waveguides. An advantage of this particular design is that it does not use metals to obtain metamaterial-like device behavior. The structure consists only of dielectrics that can be processed by the use of electron beam nanofabrication technologies and is designed to operate in the 1400–1600 nm wavelength range.
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81.16.-c Methods of micro- and nanofabrication and processing
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.66.Db Elemental semiconductors and insulators
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)

Ni full-filling into Al2O3/Al film with etched tunnels using a polyethylene glycol solution bath in electroless-plating

Joo-Hee Jang, Chang-Hyoung Lee, Woo-Sung Choi, Nam-Jeong Kim, Taek-You Kim, Tae-Yoo Kim, Jang-Hyun Kim, Chan Park, and Su-Jeong Suh

J. Vac. Sci. Technol. B 28, 1231 (2010); http://dx.doi.org/10.1116/1.3506105 (4 pages)

Online Publication Date: 1 November 2010

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Ni/Al2O3/Al film was fabricated for a high performance capacitor using electrochemical etching, anodizing, and electroless-plating. The focus of this study was to form seamless and void-free Ni electrodes on Al2O3/Al with etched tunnels. The conventional deposition method of metal was limited to full-fill for the Al tunnel pits with a high aspect ratio, a depth of about 40 μm, and diameters of about 0.5–1 μm. Nevertheless, Ni filling in tunnel pits was achieved through electroless-plating for the first time, producing a seamless and void-free electrode. The authors used a polyethylene glycol solution bath to block the Pd on top of the tunnel prior to electroless-plating, which enabled the Ni to deposit preferentially at the bottom, leading to a filling from the bottom to the top. Finally, the capacitance density for the etched and Ni electroless plated films was 220 nF/cm2 while that for a film without any etch tunnel was 12.5 nF/cm2.
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81.15.Pq Electrodeposition, electroplating
82.45.Fk Electrodes
84.32.Tt Capacitors
81.65.Cf Surface cleaning, etching, patterning

Antimonide-based depletion-mode metal-oxide-semiconductor field-effect transistors using small-bandgap InAs channel layers

H.-K. Lin, G.-Y. Liau, and H.-K. Liu

J. Vac. Sci. Technol. B 28, 1235 (2010); http://dx.doi.org/10.1116/1.3506111 (4 pages)

Online Publication Date: 1 November 2010

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Antimonide-based depletion-mode InAs channel metal-oxide-semiconductor field-effect transistors showing complete pinch-off characteristics are successfully demonstrated. The epitaxial antimonide materials are grown by molecular beam epitaxy and gate dielectrics are deposited by plasma-enhanced chemical vapor deposition. A device with a 2.0 μm gate length shows a drain current density of 600 mA/mm at VGS = 0 V and a peak transconductance of 380 mS/mm at VDS = 1.5 V. Charge trapping at the dielectric-semiconductor interface is observed using pulsed ID−VDS measurements and is explained as a primary cause for the degradation of frequency performance of the device.
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85.30.Tv Field effect devices

Impact of exposure doses on demolding process in UV nanoimprint lithography

Toshiaki Tanabe, Noriyoshi Fujii, Masato Matsue, Hiroaki Kawata, and Yoshihiko Hirai

J. Vac. Sci. Technol. B 28, 1239 (2010); http://dx.doi.org/10.1116/1.3501126 (3 pages)

Online Publication Date: 5 November 2010

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The impact of exposure doses on the demolding process in UV nanoimprint lithography (UV NIL) was studied. The PAK-01 resist was examined to investigate the dependence of the conversion ratio and elastic modulus on the adhesion force between the mold and the resist for various UV dosages. Also, adhesion forces between the resist and SiO2/Si mold were measured in various dosages. The results show that the adhesion force is unstable until the elastic modulus of the resist is enlarged enough even if the chemical conversion is completed by UV exposure. On the other hand, the demolding in the actual UV NIL experiment is not successful at lower dosages. Based on these evaluations, a suitable exposure dosage is suggested for successful demolding to realize a high throughput UV NIL process without demolding defects.
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81.16.Nd Micro- and nanolithography
81.16.Rf Micro- and nanoscale pattern formation
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.de Elastic moduli
85.40.Hp Lithography, masks and pattern transfer

Statistical-noise effect on autocorrelation function of line-edge and line-width roughness

Atsushi Hiraiwa (平岩篤) and Akio Nishida (西田彰男)

J. Vac. Sci. Technol. B 28, 1242 (2010); http://dx.doi.org/10.1116/1.3514206 (9 pages) | Cited 1 time

Online Publication Date: 10 November 2010

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Accurate characterization of line-edge roughness (LER) and line-width roughness (LWR) is essential to cope with the growing challenge of device variability in large-scale integrations. The accuracy is affected markedly by statistical noise, which is caused by the finiteness of a number of samples. The statistical noise produces random oscillatory fluctuations of autocorrelation function (ACF) of LER/LWR. These fluctuations are obstacles to estimating LWR statistics by comparing experimental and theoretical ACFs. Using the Monte Carlo (MC) method to prepare pseudoexperimental ACFs (MC-ACFs), the authors found that an error η of the estimates is minimized in the case when a ratio of a fitting-window size to a correlation length is 0.3 or smaller, being less affected by the statistical noise. η under a fixed sampling interval is determined by the total number Nall of width data used to obtain the MC-ACF. This comes from the fact that the MC-ACF is obtained after averaging approximately for Nall times. The authors also investigated the case when LWR consisted of two components that had different correlation lengths. They confirmed that η of both components increase with a decrease in their occupancies in the entire LWR. This, together with a large correlation length, makes it difficult to accurately characterize the longer-correlation component, which is mostly minor (small occupancy) in actual cases. This difficulty is also an obstacle to estimating the shorter-correlation component, because the statistics of the former are mostly the prerequisites for analyzing the latter. These facts make a stark contrast to a power-spectral-density (PSD) fitting method, where at least the shorter-correlation component is estimated with almost the same accuracy as in the case of a single component. Based on these results, the authors propose to investigate PSDs, rather than ACFs, in the case of multicomponent LWR.
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05.40.Ca Noise
05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion
02.50.-r Probability theory, stochastic processes, and statistics

Thin polymer films viscosity measurements from nanopatterning method

Tanguy Leveder, Stefan Landis, Nicolas Chaix, and Laurent Davoust

J. Vac. Sci. Technol. B 28, 1251 (2010); http://dx.doi.org/10.1116/1.3504591 (8 pages) | Cited 1 time

Online Publication Date: 11 November 2010

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Polystyrene films, with thickness ranging from a few tens of nanometers up to several hundreds of nanometers and molecular weight of 27.5 kg mol−1, were patterned with nanoimprint lithography (NIL) technique. A rigid silicon stamp containing nanoscale features was printed into a thin spin coated polystyrene film. Then these patterns were annealed above the glass transition temperature in order to characterize the viscous reflow of the topography. Special attention was paid to provide, at initial times, imprinted nanoscale patterns with a very small aspect ratio and amplitude/wavelength as well as to avoid the nucleation of holes during imprinting or during the course of the reflow. This allowed the authors to process topography data with a high degree of accuracy from a linear viscous stability model. Atomic force microscopy measurements, with a spatial resolution lower than 1 nm, were used to characterize smooth or steep shapes. The mechanical measurements of earlier stages of pattern reflow were directly accessible without any assumption, contrary to the diffraction method usually employed. Our results clearly demonstrate that even the earliest stages of pattern reflow are driven by simple viscous effects and that relaxation dynamics, which is usually considered as following exponential laws, could be more complex. This article also demonstrates that the NIL process can be used for viscosity measurements for ultrathin resist film.
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66.20.-d Viscosity of liquids; diffusive momentum transport
81.16.Rf Micro- and nanoscale pattern formation
81.16.Nd Micro- and nanolithography
81.40.Gh Other heat and thermomechanical treatments
64.70.P- Glass transitions of specific systems

Effect of resist on the transfer of line-edge roughness spatial metrics from mask to wafer

Patrick P. Naulleau and Gregg M. Gallatin

J. Vac. Sci. Technol. B 28, 1259 (2010); http://dx.doi.org/10.1116/1.3509437 (8 pages)

Online Publication Date: 11 November 2010

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Mask contributors to line-edge roughness (LER) have recently been shown to be an issue of concern for extreme ultraviolet lithography both in terms of the accuracy of current resist evaluation tests and in terms of the ultimate LER requirements for the 22 nm production node and beyond. More recently, it has been shown that the power spectral density of the mask-induced roughness is markedly different from that of intrinsic resist roughness and thus potentially serves as a mechanism for distinguishing mask effects from resist effects in experimental results. However, the evaluation of stochastic effects in the resist itself demonstrates that such a test would only be viable in cases where the resist effects are negligible in terms of their contribution to the total LER compared with the mask effects. Moreover, the results presented here lead the authors to the surprising conclusion that it is indeed possible for mask contributors to be the dominant source of LER while the spatial characteristics of the LER remain indistinguishable from the fractal characteristics of resist-induced LER.
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81.16.Nd Micro- and nanolithography

Performance and reliability analysis of p-type metal-oxide-semiconductor field effect transistors with various combinations of Ru and Al gate metal

Hong Bae Park, Chang Seo Park, Chang Yong Kang, Seung-Chul Song, Byoung Hun Lee, Tea Wan Kim, Tae-Young Jang, Dong-Hyoub Kim, Jae Kyeong Jeong, and Rino Choi

J. Vac. Sci. Technol. B 28, 1267 (2010); http://dx.doi.org/10.1116/1.3514103 (4 pages) | Cited 1 time

Online Publication Date: 11 November 2010

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Device performance and reliability characteristics of various types of Ru–Al-based metal gates on HfSiO gate dielectrics were investigated for p-type metal-oxide-semiconductor field effect transistor (pMOSFET) applications. Using the high work function of Ru and a dipole formed by Al atoms in a gate dielectric, the threshold voltage of the pMOSFET could be controlled successfully. However, the excessive diffusion of Al atoms generated more interface states and bulk trapping in the high-k dielectric layer and degraded the device performances and reliability characteristics. It was also found that the carefully tailored sequence of deposition and composition of Ru and Al metals can be used to prevent the excessive diffusion of Al atoms.
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85.30.Tv Field effect devices

Structural and optical properties of self-assembled InAs quantum dot molecules on GaAs substrates

Peng Tian, Lirong Huang, Yi Yu, and Dexiu Huang

J. Vac. Sci. Technol. B 28, 1271 (2010); http://dx.doi.org/10.1116/1.3516010 (3 pages)

Online Publication Date: 12 November 2010

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Self-assembled laterally aligned InAs quantum dot molecules (QDMs) were grown on GaAs substrates by metal-organic chemical vapor deposition. The effects of growth temperature and InAs coverage on the structural and optical properties of QDMs are investigated by using atomic force microscopy and photoluminescence. It is found that through appropriately selecting growth parameters, QDMs composed of two closely spaced InAs quantum dots (QDs) are formed, and the distance between the two QDs can be controlled. Moreover, a redshift of emission wavelength attributed to the formation of QDMs is observed.
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78.67.Hc Quantum dots
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors

Fabrication and field emission of carbon nanotubes/TiO2/Ti composite nanostructures

Jian-Biao Chen, Cheng-Wei Wang, Rui-Sheng Guo, Lin-Qing Wang, Wei-Dong Zhu, Feng Zhou, and Wei-Min Liu

J. Vac. Sci. Technol. B 28, 1274 (2010); http://dx.doi.org/10.1116/1.3516017 (5 pages)

Online Publication Date: 12 November 2010

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Well-aligned TiO2/Ti nanotube arrays were fabricated by anodic oxidation, then carbon nanotubes (CNTs) were grown into TiO2/Ti nanotube arrays to form CNTs/TiO2/Ti composite nanostructures by catalytic chemical-vapor deposition for different deposition times. The morphology and quality of samples were assessed by field-emission scanning-electron microscopy and Raman spectroscopy. The field emission (FE) results indicate that the FE properties of CNTs/TiO2/Ti composite nanostructures were dramatically improved compared with bare TiO2/Ti nanotube arrays, and when the growth time of CNTs was 60 min, the composite nanostructures possessed the lowest turn-on field of 1.3 V/μm, the highest emission-current density of 10 mA/cm2 was easily gained at 5.6 V/μm, and there was good FE stability.
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81.07.De Nanotubes
81.16.Hc Catalytic methods
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.65.Mq Oxidation
79.70.+q Field emission, ionization, evaporation, and desorption
78.30.-j Infrared and Raman spectra

Atomic resolution force microscopy imaging on a strongly ionic surface with differently functionalized tips

T. Arai, S. Gritschneder, L. Tröger, and M. Reichling

J. Vac. Sci. Technol. B 28, 1279 (2010); http://dx.doi.org/10.1116/1.3511505 (5 pages)

Online Publication Date: 15 November 2010

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Three types of tips for noncontact atomic force microscopy imaging, namely, a silicon nanopillar tip, a carbon nanopillar tip, and a fluoride cluster tip, are prepared for atomic resolution imaging on the CaF2(111) surface. The most enhanced atomic corrugation is obtained with the fluoride cluster tip prepared by gently touching the fluorite surface. Atom resolved images are much harder to obtain with the other tips. This demonstrates the importance of having a polar tip for atomic resolution imaging of an ionic surface and supports the general notion that a surface is best imaged with a tip of the same material.
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68.35.B- Structure of clean surfaces (and surface reconstruction)

Electron field emission from well-aligned GaP nanotips

Hung-Chun Lo, Jeff T. H. Tsai, Jih-Perng Leu, and Chia-Fu Chen

J. Vac. Sci. Technol. B 28, 1284 (2010); http://dx.doi.org/10.1116/1.3506089 (3 pages)

Online Publication Date: 18 November 2010

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Field emission of electrons from single crystal gallium phosphide (GaP) nanotips has been investigated. GaP nanotip arrays were fabricated using silane-methane-argon-hydrogen based plasma using the self-masking dry etching technique in an electron-cyclotron-resonance microwave plasma enhanced chemical vapor deposition system. These nanotips have an average of 2 and 80 nm in apex and bottom diameters, respectively. They are 900 nm in height, which makes them the perfect electron emission source for their high aspect ratio topography. A nanosized silicon carbide (SiC) cap on each GaP nanotip in the array has been found. The SiC core has a heterointerface with GaP crystal that was observed using a high resolution transmission electron microscope. Field emission analysis shows low turn-on fields of 8.5–9 V/μm. Cold electron emissions in Fowler–Nordheim type current-voltage were observed from such GaP nanotip arrays.
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79.70.+q Field emission, ionization, evaporation, and desorption
81.07.Bc Nanocrystalline materials
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Sputtering behavior and evolution of depth resolution upon low energy ion irradiation of GaAs

M. J. P. Hopstaken, M. S. Gordon, D. Pfeiffer, D. K. Sadana, T. Topuria, P. M. Rice, C. Gerl, M. Richter, and C. Marchiori

J. Vac. Sci. Technol. B 28, 1287 (2010); http://dx.doi.org/10.1116/1.3514117 (11 pages)

Online Publication Date: 18 November 2010

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The authors have investigated the sputtering behavior and evolution of depth resolution upon low energy ion irradiation during secondary ion mass spectrometry (SIMS) depth profiling of GaAs. They presented a systematic and quantitative study of the impact of ion species, primary ion impact energy, and incident angle on (evolution of) depth resolution using a well-characterized dedicated InGaAs/GaAs multilayer structure with nearly atomically abrupt heterointerfaces. They demonstrated that for low energy O2+ ion beam irradiation, the SIMS depth resolution is severely degraded by (transient) incorporation of high surface O-concentration into the altered layer, leading to detrimental ion beam induced formation of topography. They provided evidence that topography formation is primarily invoked by the strong angular dependence of the sputter yield on (local) incident angle. In the case of low energy, oblique Cs+ ion beam irradiation, the sputtering behavior of GaAs is well-behaved with no significant transient yield changes and a constant depth resolution. This enables SIMS depth profiling of sharp heteroepitaxial III–V multilayer structures and shallow dopant profiles with sufficiently good depth resolution and good detection efficiency.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)
61.80.Jh Ion radiation effects
61.72.uj III-V and II-VI semiconductors

Relaxation of misfit strain in silicon-germanium (Si1−xGex) films during dry oxidation

Jung-Ho Yoo, Sun-Wook Kim, Byoung-Gi Min, Hyunchul Sohn, Dae-Hong Ko, and Mann-Ho Cho

J. Vac. Sci. Technol. B 28, 1298 (2010); http://dx.doi.org/10.1116/1.3516014 (6 pages) | Cited 2 times

Online Publication Date: 18 November 2010

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The effects of oxidation on strain relaxation in Si1−xGex layers on silicon substrates were investigated. Si1−xGex layers, with different Ge fractions (x = 0.15 and 0.3), were grown on chemically cleaned silicon substrates by an ultrahigh vacuum chemical vapor deposition process. Oxidation at 800 and 900 °C under O2 ambient in a tube furnace resulted in the production of silicon oxide layers on top and a Ge-rich region in the Si1−xGex films. It was observed that the oxidation of Si0.85Ge0.15 films at 900 °C produced the relaxation of the misfit strain in the remnant Si1−xGex layer and the increase in strain in the Ge pile-up layer with increasing oxidation time, while the oxidation at 800 °C produced no changes in the misfit strain in the Si1−xGex layers. The oxidation of Si0.70Ge0.30 films at 800 °C showed the relaxation of the misfit strain in the remnant Si1−xGex layer with the accumulation of stain in the Ge pile-up layer. However, the oxidation of Si0.70Ge0.30 layers at 900 °C exhibited the strain relaxation in the Ge pile-up layer after the Ge pile-up was extended into the remaining Si1−xGex layer, with the formation of misfit dislocations at the interface between the remaining Si1−xGex and Si substrate.
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68.55.A- Nucleation and growth
81.65.Mq Oxidation
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Quantifying reaction spread and x-ray exposure sensitivity in hydrogen silsesquioxane latent resist patterns with x-ray spectromicroscopy

Allison G. Caster, Stefan Kowarik, Adam M. Schwartzberg, Stephen R. Leone, Alexei Tivanski, and Mary K. Gilles

J. Vac. Sci. Technol. B 28, 1304 (2010); http://dx.doi.org/10.1116/1.3514124 (10 pages) | Cited 2 times

Online Publication Date: 29 November 2010

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Direct-write soft x-ray lithography with an ∼ 50 nm diameter beam is used to pattern features in hydrogen silsesquioxane (HSQ) thin films. Scanning transmission x-ray microscopy of the undeveloped patterns (latent patterns) at the oxygen K-edge reveals a two-stage cross-linking mechanism. Oxygen and silicon near edge x-ray absorption fine structure spectra of latent patterns show an increase in oxygen content and no change in silicon content within exposed regions. A dose and thickness dependent spatial spread of the cross-linking reaction beyond the exposure boundaries is observed and quantified in detail. Strong area-dependent exposure sensitivity (attributed to cross-linking beyond the exposed region) is observed in latent patterns. A lateral spread in the cross-linking of >70 nm (full width at half maximum) is observed on both sides of the lines created with 580 eV x-rays (λ = 2.14 nm) in 330±50 nm thick HSQ films at low dose (0.6±0.3 MGy, 27±12 mJ/cm2) (1 MGy = 106 J/kg absorbed energy). At a higher dose (111±29 MGy, 5143±1027 mJ/cm2), this spread increased to 150 nm. Preliminary results indicate that latent line widths increased with increasing delay between film spin-coating and exposure. Sharper lines are observed after room temperature development of the latent HSQ patterns in NaOH/NaCl solution (onset dose of 3.9±1.0 MGy, 181±36 mJ/cm2) due to the removal of material below a critical degree of cross-linking. Given the short range of low energy secondary electrons in condensed media (<10 nm at ≤ 580 eV), the observed spread is likely due to the propagation of reactive ions or radicals beyond the exposed regions.
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82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
81.16.Nd Micro- and nanolithography
73.61.Ph Polymers; organic compounds
78.70.Dm X-ray absorption spectra
07.85.Tt X-ray microscopes
68.37.Yz X-ray microscopy

Reduction of spin-flip scattering in metallic nonlocal spin valves

H. Zou, X. J. Wang, and Y. Ji

J. Vac. Sci. Technol. B 28, 1314 (2010); http://dx.doi.org/10.1116/1.3514204 (4 pages)

Online Publication Date: 29 November 2010

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Cobalt-copper nonlocal spin valves are fabricated by shadow evaporation through nanoscale masks. The thickness of Co electrodes is varied and the spin diffusion length of the Cu channel is determined. Short spin diffusion lengths are found in devices with thick (>20 nm) Co layers. Co impurities are introduced into the Cu channel in the shadow evaporation process during the fabrication, and the impurities cause spin-flip scattering. The amount of Co impurities can be reduced by decreasing the thicknesses of Co electrodes. Spin diffusion lengths of ∼ 400 nm at 295 K and ∼ 800 nm at 4.2 K are measured in devices with thin (<10 nm) Co layers.
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85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Single-walled carbon nanotube alignment by grating-guided electrostatic self-assembly

Huifeng Li, Dazhi Sun, Hung-Jue Sue, and Xing Cheng

J. Vac. Sci. Technol. B 28, 1318 (2010); http://dx.doi.org/10.1116/1.3514205 (4 pages)

Online Publication Date: 30 November 2010

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Single-walled carbon nanotube (SWNT) has attracted widespread attention due to their exceptional electrical, thermal, and mechanical properties. Many applications require SWNT alignment and placement with good controllability to achieve the expected performance. The authors report here a simple but effective approach for SWNT alignment, which is based on grating-guided electrostatic self-assembly (ESA) in a polymer template patterned by nanoimprint. SWNT stripes can be obtained by removing the polymer template after ESA. The SWNT stripes on the substrate show strong polarized Raman signal, which is indicative of a high-level alignment of the SWNTs in the stripes. The effect of surfactants on the guided ESA process is discussed. The advantages of this SWNT alignment technique are flexibility and scalability. As an easy-to-process approach, the SWNT alignment by grating-guided ESA may advance the practical applications of SWNTs in integrated microelectronic systems.
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81.07.De Nanotubes
81.16.Dn Self-assembly
78.67.Ch Nanotubes
78.30.Na Fullerenes and related materials
61.46.Fg Nanotubes
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Moisture effect on electromigration characteristics for copper dual damascene interconnection

Yi-Lung Cheng, Wei-Yuan Chang, and Ying-Lang Wang

J. Vac. Sci. Technol. B 28, 1322 (2010); http://dx.doi.org/10.1116/1.3501127 (4 pages)

Online Publication Date: 1 December 2010

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The influence of moisture on Cu line electromigration (EM) behavior of dual damascene interconnection is reported. The authors have found that moisture has a negative influence on EM behavior, but it depends on the seal-ring structure located along the peripheral of the test pattern. The reduced Cu lifetime, observed for tested samples without seal-ring structure, was due to lateral moisture penetration. Lateral moisture diffusion was considered an effective mechanism for deteriorating the Cu interface during the die-sawing processing for structures without seal-ring layout. As a result, the seal-ring layout is effective and essential in Cu/low-dielectric (low-k) material integrity to prevent moisture penetration during the package procedures.
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85.40.Ls Metallization, contacts, interconnects; device isolation
66.30.Qa Electromigration
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Simple derivation of the formula for Sommerfeld supply density used in electron-emission physics and limitations on its use

Richard G. Forbes

J. Vac. Sci. Technol. B 28, 1326 (2010); http://dx.doi.org/10.1116/1.3501118 (4 pages)

Online Publication Date: 2 December 2010

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In a free-electron model, an electron crossing a mathematical plane inside a conductor can be characterized by the energy components associated with its motion normal and parallel to the plane. These components define a two-dimensional “energy-space.” The “supply density” is defined as the electron current crossing the plane, per unit area of the plane, per unit area in energy-space, when the relevant electron states are fully occupied. For a bulk free-electron conductor, the supply density is the same at all points in energy-space and has been called the “Sommerfeld supply density” (zS). This is given by zS = 4πeme/hP3, where e is the elementary positive charge, me is the electron mass, and hP is Planck’s constant. This result is often a convenient starting point for developing basic theories of electron emission. A simple proof of it is recorded here. For small electron emitters, it can be a poor approximation to assume that the supply density is constant in energy-space. Consequently, if an emitter is sufficiently small, then the emission will not be well described by the usual basic emission equations. Criteria for assessing what counts as “sufficiently small” are discussed.
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79.90.+b Other topics in electron and ion emission by liquids and solids and impact phenomena (restricted to new topics in section 79)
73.20.At Surface states, band structure, electron density of states
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Preface

Martin Feldman, Program Chair, EIPBN 2010

J. Vac. Sci. Technol. B 28, C6a1 (2010); http://dx.doi.org/10.1116/1.3522593 (1 page)

Online Publication Date: 30 November 2010

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01.30.-y Physics literature and publications
81.16.Rf Micro- and nanoscale pattern formation
back to top Plenary

To charge or not to charge: 50 years of lithographic choices

R. Fabian Pease

J. Vac. Sci. Technol. B 28, C6A1 (2010); http://dx.doi.org/10.1116/1.3517607 (6 pages)

Online Publication Date: 2 December 2010

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The first integrated circuits were manufactured in about 1960 (year 1 of Moore’s law) and were patterned using optical lithography. Almost immediately, electron beam lithography was pursued as a high-resolution alternative and has been ever since, but optical lithography is still the preferred technique. However, after 40 years of optical lithography for the manufacture of integrated circuits, we may finally have reached the point where the cost of further pushing optical technology is no longer economically attractive. So now many lithographic techniques are considered as candidates. These techniques range from various forms of charged-particle lithography to various forms of uncharged-particle lithography and even to simple localized mechanical contact (nanoimprinting). It may be that a combination of techniques is chosen in some applications or that three-dimensional integration will keep Moore’s law valid without further shrinking of devices.
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85.40.Hp Lithography, masks and pattern transfer
42.82.Cr Fabrication techniques; lithography, pattern transfer
81.16.Nd Micro- and nanolithography
back to top Directed Assembly

Argon ion multibeam nanopatterning of Ni–Cu inserts for injection molding

Anton Koeck, Roman Bruck, Markus Wellenzohn, Rainer Hainberger, Elmar Platzgummer, Hans Loeschner, Peter Joechl, Stefan Eder-Kapl, Christoph Ebm, Peter Czepl, Kurt Kaiblinger, Friedrich Pipelka, Florian Letzkus, Mathias Irmscher, and Bernd Heitkamp

J. Vac. Sci. Technol. B 28, C6B1 (2010); http://dx.doi.org/10.1116/1.3517643 (6 pages)

Online Publication Date: 29 November 2010

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The authors have successfully employed the charged particle nanopatterning (CHARPAN) technology for nanostructuring of a metal mold insert for a conventional injection molding machine. High-precision diamond-milled Ni–Cu mold inserts have been nanopatterned with 10 keV argon ion multibeam milling with feature sizes as small as 50 nm. A variety of structures such as circles, hexagons, and lines in different dimensions, with positive and negative shapes, have been fabricated in the metal mold. These structures have been successfully replicated in polymethylpentene samples by injection molding. To the authors’ best knowledge, the CHARPAN technology is one of the very few technologies that allow for resistless nanostructuring a field size of 25×25 μm2 into a metal mold in a single shot. This is of high importance for the practical injection molding fabrication of nanostructured polymer devices such as optical biosensors.
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81.16.Rf Micro- and nanoscale pattern formation
81.10.Fq Growth from melts; zone melting and refining
81.07.Bc Nanocrystalline materials
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials

Directed assembly of solution processed single-walled carbon nanotubes via dielectrophoresis: From aligned array to individual nanotube devices

Paul Stokes and Saiful I. Khondaker

J. Vac. Sci. Technol. B 28, C6B7 (2010); http://dx.doi.org/10.1116/1.3501347 (6 pages)

Online Publication Date: 29 November 2010

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The authors demonstrate directed assembly of high quality solution processed single-walled carbon nanotube (SWNT) devices via ac dielectrophoresis using commercially available SWNT solutions. By controlling the shape of the electrodes, concentration of the solution, and assembly time, the authors are able to control the assembly of SWNTs from dense arrays down to individual SWNT devices. Electronic transport studies of individual SWNT devices show field effect mobilities of up to 1380 cm2/V s for semiconducting SWNTs and saturation currents of up to ∼ 15 μA for metallic SWNTs. The field effect mobilities are more than an order of magnitude improvement over previous solution processed individual SWNT devices and close to the theoretical limit. Field effect transistors (FET) fabricated from aligned two-dimensional arrays of SWNT show field effect mobility as high as 123 cm2/V s, which is three orders of magnitude higher than the solution processed organic FET devices. This study shows promise for commercially available SWNT solution for the parallel fabrication of high quality nanoelectronic devices.
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85.35.Kt Nanotube devices
85.30.Tv Field effect devices

Mechanism and dynamics of block copolymer directed assembly with density multiplication on chemically patterned surfaces

Guoliang Liu, Sean P. Delcambre, Karl O. Stuen, Gordon S. W. Craig, Juan J. de Pablo, Paul F. Nealey, Kim Nygård, Dillip K. Satapathy, Oliver Bunk, and Harun H. Solak

J. Vac. Sci. Technol. B 28, C6B13 (2010); http://dx.doi.org/10.1116/1.3518918 (7 pages) | Cited 2 times

Online Publication Date: 29 November 2010

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In this work, we used scanning electron microscopy (SEM), in situ coherent small angle x-ray scattering (SAXS), and Monte Carlo molecular simulation to gain insights into the dynamics of block copolymer directed assembly with density multiplication on chemically patterned surfaces. During directed assembly, it was observed with SEM that poly(styrene-block-methyl methacrylate) initially formed discrete polystyrene domains that lacked long-range order at the free surface. After further annealing, the polystyrene domains gradually coalesced into linear domains that were not registered fully with the underlying chemical pattern. The linear domains could be trapped in metastable morphologies. Finally, the linear polystyrene domains formed perpendicular lamellae in full registration with the underlying chemical pattern. It was revealed with SAXS that scattering peaks characteristic of the period of the chemical pattern appeared and disappeared at the early stages of assembly. Finally, the morphological evolution of directed assembly of block copolymer on chemically patterned surfaces was modeled by molecular simulations.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
61.41.+e Polymers, elastomers, and plastics
78.70.Ck X-ray scattering
61.43.Bn Structural modeling: serial-addition models, computer simulation
81.40.Gh Other heat and thermomechanical treatments

Nanostructure fabrication by self-assembly of block copolymers on three-dimensional diamondlike carbon structures

Hiroyuki Mino, Reo Kometani, Shin-ichi Warisawa, and Sunao Ishihara

J. Vac. Sci. Technol. B 28, C6B20 (2010); http://dx.doi.org/10.1116/1.3518462 (4 pages)

Online Publication Date: 30 November 2010

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The block copolymer self-assembly has the potential to form nanoscale periodic patterns on three-dimensional (3D) nanostructures and nanomaterials. However, block copolymer self-assembly processes have only been examined on two-dimensional flat plane substrates. Forming copolymer nanostructures onto 3D structures would extend the applicability of these nanoscale patterns to 3D wiring for electric circuits and 3D nanomechanical devices. Herein, we investigate the formation process of nanopatterns of block copolymers onto 3D structures. A “dip-coating process” enables the block copolymer to self-assemble onto 3D structures. In addition, treatment with materials possessing a large surface energy effectively forms regular and dense nanoscale patterns onto a 3D diamondlike carbon structure. Moreover, self-assembled patterns are formed even if the angle of the slope of the 3D structure is changed.
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81.16.Dn Self-assembly
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
68.35.Md Surface thermodynamics, surface energies

Shape control and density multiplication of cylinder-forming ternary block copolymer-homopolymer blend thin films on chemical patterns

Huiman Kang, Francois Detcheverry, Karl O. Stuen, Gordon S. W. Craig, Juan J. de Pablo, Padma Gopalan, and Paul F. Nealey

J. Vac. Sci. Technol. B 28, C6B24 (2010); http://dx.doi.org/10.1116/1.3518910 (6 pages)

Online Publication Date: 30 November 2010

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The effect of the chemical pattern spot size, the spacing on the size, and the shape of the cylindrical domains in thin films of a ternary block copolymer/homopolymer/homopolymer blend was investigated over a range of homopolymer volume fractions. Cylinder-forming ternary blends were composed of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA), and the corresponding PS and PMMA homopolymers were directed to assemble on chemical patterns that had density multiplication ratios ranging from 1:1 to 4:1. By increasing the homopolymer fraction in the blends, the dimensions of the domains were expanded. When the size of the spots on the chemical pattern was not matched with the size of the domain of the blend in the bulk, the dimensions of the domains at the free surface of the assembled films differed from those at the interface with the chemical pattern.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
68.55.am Polymers and organics

Integration of block copolymer directed assembly with 193 immersion lithography

Chi-Chun Liu, Paul F. Nealey, Alex K. Raub, Philip J. Hakeem, Steve R. J. Brueck, Eungnak Han, and Padma Gopalan

J. Vac. Sci. Technol. B 28, C6B30 (2010); http://dx.doi.org/10.1116/1.3501348 (5 pages) | Cited 2 times

Online Publication Date: 30 November 2010

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An integration scheme of block copolymer directed assembly with 193 nm immersion lithography is presented. It is experimentally shown that a thin silicon nitride film can be used as an antireflective coating (ARC). With such an ARC, directed assembly of a block copolymer (BCP) to triple the feature density of a chemical pattern was demonstrated. A high quality of assembly was obtained over a large area, and pattern transfer feasibility was illustrated. The integration of feature density multiplication via directed assembly of a BCP with 193 nm immersion lithography provided a pattern quality that was comparable with existing double patterning techniques, suggesting that the process could be a promising candidate for extending the use of current 193 immersion lithography tools to higher pattern densities.
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81.20.-n Methods of materials synthesis and materials processing
68.55.A- Nucleation and growth
61.41.+e Polymers, elastomers, and plastics
back to top Electron Beams

High-current electron optical design for reflective electron beam lithography direct write lithography

Mark McCord, Shinichi Kojima, Paul Petric, Alan Brodie, and Jeff Sun

J. Vac. Sci. Technol. B 28, C6C1 (2010); http://dx.doi.org/10.1116/1.3505130 (5 pages) | Cited 2 times

Online Publication Date: 1 November 2010

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The authors present the latest design and results for the second generation column used in the reflective electron beam lithography program. The previous magnetic prism based concept to separate the illumination and projection beams has been replaced with a Wien filter that allows the column to be shrunk in size by a factor of 3, resulting in reduced Coulomb blur and energy spread. Experimental data from the column are presented and compared to simulation. The authors also discuss design considerations for this and future columns, including beam voltage, numerical aperture selection, and cathode optimization.
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85.40.Hp Lithography, masks and pattern transfer

Reflective electron beam lithography: A maskless ebeam direct write lithography approach using the reflective electron beam lithography concept

Paul Petric, Chris Bevis, Mark McCord, Allen Carroll, Alan Brodie, Upendra Ummethala, Luca Grella, Anthony Cheung, and Regina Freed

J. Vac. Sci. Technol. B 28, C6C6 (2010); http://dx.doi.org/10.1116/1.3511436 (8 pages) | Cited 1 time

Online Publication Date: 15 November 2010

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Reflective electron beam litography (REBL) utilizes several novel technologies to generate and expose lithographic patterns at throughputs that could make ebeam maskless lithography feasible for high volume manufacturing. The REBL program was described in a previous article [ P. Petric et al., J. Vac. Sci. Technol. B 27, 161 (2009) ] 2 years ago. This article will review the system architecture and the progress of REBL in the past 2 years. The main technologies making REBL unique are the reflective electron optics, the rotary stage, and the dynamic pattern generator (DPG). Changes in how these concepts have been implemented in a new design will be discussed. The main disadvantage of today’s electron beam direct write is low throughput; it takes many tens of hours to expose a 300 mm wafer today using ebeam lithography. The projected system throughput performance with the integrated technology of the reflective optics, DPG, and a multiple wafer rotary stage will be shown incorporating the performance data for the new column design.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
85.40.Hp Lithography, masks and pattern transfer

5 kV multielectron beam lithography: MAPPER tool and resist process characterization

D. Rio, C. Constancias, M. Martin, B. Icard, J. van Nieuwstadt, J. Vijverberg, and L. Pain

J. Vac. Sci. Technol. B 28, C6C14 (2010); http://dx.doi.org/10.1116/1.3517664 (7 pages) | Cited 3 times

Online Publication Date: 29 November 2010

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A multielectron beam tool from MAPPER lithography was installed in LETI premises in July 2009. It is based on low voltage lithography. In order to prepare acceptance tests, a preliminary study was carried out with a Leica VB6 HR at 5 kV in order to define 5 kV suitable resist processes. Results obtained at higher voltages are compared, since this tool has the capability to accelerate electrons up to 50 kV. The dependence of the deposition of backscattered energy on voltage is also evaluated. The 5 kV results are compared with those obtained on the MAPPER tool. Its spot size is measured, while a 32 nm half pitch resolution is reached.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

Excitation and imaging of resonant optical modes of Au triangular nanoantennas using cathodoluminescence spectroscopy

Anil Kumar, Kin-Hung Fung, James C. Mabon, Edmond Chow, and Nicholas X. Fang

J. Vac. Sci. Technol. B 28, C6C21 (2010); http://dx.doi.org/10.1116/1.3504566 (5 pages) | Cited 1 time

Online Publication Date: 29 November 2010

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Cathodoluminescence (CL) imaging spectroscopy is an important technique to understand the resonant behavior of optical nanoantennas. The authors report high-resolution CL spectroscopy of triangular gold nanoantennas designed with near-vacuum effective index and very small metal-substrate interface. This design helped in addressing issues related to background luminescence and shifting of dipole modes beyond visible spectrum. Spatial and spectral investigations of various plasmonic modes are reported. Out-of-plane dipole modes excited with a vertically illuminated electron beam showed high-contrast tip illumination in panchromatic imaging. By tilting the nanostructures during fabrication, in-plane dipole modes of antennas were excited. Finite-difference time-domain simulations for electron and optical excitations of different modes showed excellent agreement with experimental results. Their approach of efficiently exciting antenna modes by using low index substrates is confirmed both with experiments and numerical simulations. This should provide further insights into a better understanding of optical antennas for various applications.
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78.60.Hk Cathodoluminescence, ionoluminescence
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
81.07.Bc Nanocrystalline materials

Field induced shape and work function modification for the ZrO/W(100) Schottky cathode

K. Liu, G. A. Schwind, L. W. Swanson, and J. A. Campbell

J. Vac. Sci. Technol. B 28, C6C26 (2010); http://dx.doi.org/10.1116/1.3501362 (8 pages) | Cited 1 time

Online Publication Date: 29 November 2010

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The origin of the frequently observed long and short term current drifts after a change in the extractor voltage for the ZrO/W(100) Schottky cathode has been investigated. It has been found that a reversible, field dependent change in the equilibrium work function and shape of the cathode end form occurs at the typical operating temperature of 1800 K. The shape change results in three distinct geometric end form shapes. Although these end forms have been observed previously [ L. W. Swanson and G. A. Schwind, in Handbook of Charged Particle Optics, 2nd ed., edited by J. Orloff (CRC, New York, 2008), Chap. 1, p. 1 ; S. Fujita, T. R. Wells, W. Ushio, H. Sato, and M. M. El-Gomati, J. Microsc. 235, 215 (2010) ; M. S. Bronsgeest and P. Kruit, J. Vac. Sci. Technol. B 27, 2524 (2009) ], the purpose of this study is to elucidate the operating conditions under which these changes occur and the associated changes in emission properties. Emitters in the radii range 200–900 nm were investigated over the typical current density operating range employed in most electron probe forming systems. A correlation between work function and electric field has been found, which can be explained by a reversible, field induced change in the ZrO equilibrium coverage in the high field region of the emitter, thereby causing a change in the work function. It is believed that these field induced changes in the equilibrium work function and emitter shape at 1800 K explain the short and long term drifts observed after a change in extractor voltage.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts

Performance characterization of negative resists for sub-10-nm electron beam lithography

R. Bonam, P. Verhagen, A. Munder, and J. Hartley

J. Vac. Sci. Technol. B 28, C6C34 (2010); http://dx.doi.org/10.1116/1.3517721 (7 pages) | Cited 2 times

Online Publication Date: 1 December 2010

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As scaling continues, the need for reliable sub-10-nm electron beam lithography is apparent. Throughput is a major drawback and complex test structure fabrication would be constrained by practical limits on writing time. A major challenge for sub-10-nm patterning with electron beam lithography is tool and process efficiency especially for high sensitivity resists. This article presents current work done at the College of Nanoscale Science and Engineering where the authors investigated three different commercially available resist systems, namely, SU-8, NEB-31, and HSQ, which have a range of sensitivity from close to the shot noise limit to slow material with high resolution. The authors present the results obtained from these resists with their respective critical dimension, line edge roughness (LER), and line width roughness (LWR) values that correlate with sensitivity and are consistent with the well known resolution, line edge roughness, sensitivity trade-off. Due to the inability of tools to deliver low doses at step sizes close to grid size limit of the tool, the ultimate resolution limit of SU-8 and NEB-31 with acceptable LER and LWR is yet to be determined.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

Simulation of scanning electron microscope images taking into account local and global electromagnetic fields

Sergey Babin, Sergey S. Borisov, Hiroyuki Ito, Andrei Ivanchikov, and Makoto Suzuki

J. Vac. Sci. Technol. B 28, C6C41 (2010); http://dx.doi.org/10.1116/1.3518917 (7 pages)

Online Publication Date: 1 December 2010

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The authors report the development of a simulation tool with unique capabilities to comprehensively model a scanning electron microscope (SEM) signal. This includes electron scattering, charging, and detector settings, as well as modeling of the local and global electromagnetic fields and electron trajectories in these fields. Experimental and simulated results were compared for SEM imaging of carbon nanofibers embedded into bulk material in the presence of significant charging as well as for samples with applied potential on metal electrodes. The effect of the potentials applied to electrodes on the secondary emission was studied; the resulting SEM images were simulated. The image contrast depends strongly on the sign and the value of the potential. SEM imaging of nanofibers embedded into silicon dioxide resulted in the considerable change in the apparent dimensions of the fibers as well as tone reversal when the beam voltage was varied. The results of the simulations are in agreement with experimental results.
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61.46.-w Structure of nanoscale materials
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
41.20.-q Applied classical electromagnetism
68.49.-h Surface characterization by particle-surface scattering
79.20.-m Impact phenomena (including electron spectra and sputtering)
61.43.Bn Structural modeling: serial-addition models, computer simulation

Simulation of electron beam lithography of nanostructures

M. Stepanova, T. Fito, Zs. Szabó, K. Alti, A. P. Adeyenuwo, K. Koshelev, M. Aktary, and S. K. Dew

J. Vac. Sci. Technol. B 28, C6C48 (2010); http://dx.doi.org/10.1116/1.3497019 (10 pages) | Cited 4 times

Online Publication Date: 1 December 2010

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The authors report a numeric simulation tool that they developed for the modeling and analysis of electron beam lithography (EBL) of nanostructures employing a popular positive tone resist polymethylmethacrylate (PMMA). Modeling and process design for EBL fabrication of 5–50 nm PMMA structures on solid substrates is the target purpose of the simulator. The simulator is functional for exposure energies from 1 to 50 keV with arbitrary writing geometries. The authors employ a suite of kinetic models for the traveling of primary, secondary, and backscattered electrons in the resist, compute three-dimensional (3D) distributions of the yield of main-chain scission in PMMA, and convert these into the local volume fractions of fragments of various sizes. The kinetic process of development is described by the movement of the resist-developer interface with the rate derived from the mean-field theory of polymer diffusion. The EBL simulator allows the computation of detailed 3D distributions of the yield of main-chain scission in PMMA for various conditions of exposure, the corresponding volume fractions of small fragments, and the clearance profiles as functions of the development in time and temperature. This article describes the models employed to simulate the EBL exposure and development, reports examples of the computations, and presents comparisons of the predicted development profiles with experimental cross-sectional resist profiles in dense gratings.
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81.16.Nd Micro- and nanolithography
61.80.Fe Electron and positron radiation effects
81.07.Bc Nanocrystalline materials
66.30.-h Diffusion in solids
79.20.Kz Other electron-impact emission phenomena

Sub-10-nm half-pitch electron-beam lithography by using poly(methyl methacrylate) as a negative resist

Huigao Duan, Donald Winston, Joel K. W. Yang, Bryan M. Cord, Vitor R. Manfrinato, and Karl K. Berggren

J. Vac. Sci. Technol. B 28, C6C58 (2010); http://dx.doi.org/10.1116/1.3501353 (5 pages) | Cited 4 times

Online Publication Date: 1 December 2010

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Developing high-resolution resists and processes for electron-beam lithography is of great importance for high-density magnetic storage, integrated circuits, and nanoelectronic and nanophotonic devices. Until now, hydrogen silsesquioxane (HSQ) and calixarene were the only two reported negative resists that could approach sub-10-nm half-pitch resolution for electron-beam lithography. Here, the authors report that 10-nm half-pitch dense nanostructures can also be readily fabricated using the well known poly(methyl methacrylate) (PMMA) resist operating in negative tone, even at exposure energies as low as 2 keV. In addition to scanning electron microscopy metrology, transmission electron microscopy metrology was done to confirm the high-resolution capability of negative-tone PMMA. This process was compared to HSQ with salty development and showed similar ultimate resolution, so it could be used as an alternative for applications incompatible with HSQ.
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81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer

Analysis of surface electromagnetic wave resonant structures for potential application in an array of compact photoelectron sources

Heon J. Choi and Timothy R. Groves

J. Vac. Sci. Technol. B 28, C6C63 (2010); http://dx.doi.org/10.1116/1.3504590 (6 pages)

Online Publication Date: 1 December 2010

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Two different surface electromagnetic wave assisted light concentrators are analyzed that can, in principle, be integrated into an array with each concentrator delivering optical power to a photoelectron emitting metal nanodot. Such arrays could be used as a source for multiple electron-beam lithography and inspection systems. The optical power concentrators, composed of metal structures embedded onto the surface of a quartz substrate, can, in principle, be tuned to any wavelength from UV to IR, capturing and enhancing broad area optical excitation and focusing it to subwavelength dimensions. Results of the finite difference time domain computer simulations of the structures are presented, and the optical power density enhancement factors at the focal spot are calculated to be over an order of magnitude for both structures. General methods for manipulating the spectral response are proposed and analyzed.
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81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Inspection of open defects in a thin film transistor-liquid crystal display panel by using a low-energy electron microcolumn

Tae Sik Oh, Dae-Wook Kim, Young Chul Kim, Seungjoon Ahn, Gun-hee Lee, and Ho Seob Kim

J. Vac. Sci. Technol. B 28, C6C69 (2010); http://dx.doi.org/10.1116/1.3502658 (5 pages)

Online Publication Date: 1 December 2010

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The demand on the electron beam (e-beam) for the inspection of semiconductor devices or display panel is rapidly increasing since e-beam cannot only monitor the small structures but also has the potential of detecting electrical troubles or repairing the defects. However, the merit of e-beam is limited because of the high cost, low throughput, and the possible damage due to the high e-beam energy. A microcolumn is a strong candidate to solve these limitations as its size is extremely miniaturized (both column diameter and height can be reduced down to a few millimeters) and the output e-beam energy is as low as 100–1000 eV. In this work, the authors tried to test the inspection of defects by applying a low voltage microcolumn to liquid crystal display panel. In order to demonstrate the authors’ inspection method, they extracted a 7’’ thin film transistor-liquid crystal display (TFT-LCD) panel from the production line just after completing the pixel structures and used this panel as a test sample. On the selected panel, the authors intentionally made some defects such as open data or gate lines by cutting some points using a laser beam. They operated their microcolumn with a beam energy of 300 eV and obtained the scanning images of the panel while operating the panel with specific operation conditions. The operation parameters for the test TFT-LCD panel such as the voltages applied to the gate lines, data lines, and storage capacitors was fixed at two specific sets of values. Then, the image obtained by the secondary electron reflects the information on the electrical state of the pixels as well as the geometrical ones. By combining the two sets of data, the authors could explain the correlation between the irregular behavior in the image contrast and the open defects and the detailed results will be discussed.
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85.60.Pg Display systems
42.79.Kr Display devices, liquid-crystal devices
85.30.Tv Field effect devices

Brightness limitations of cold field emitters caused by Coulomb interactions

B. Cook, T. Verduin, C. W. Hagen, and P. Kruit

J. Vac. Sci. Technol. B 28, C6C74 (2010); http://dx.doi.org/10.1116/1.3502642 (6 pages) | Cited 1 time

Online Publication Date: 1 December 2010

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Emission theory predicts that high brightness cold field emitters can enhance imaging in the electron microscope. This (neglecting chromatic aberration) is because of the large (coherent) probe current available from a high brightness source and is based on theoretically determined values of reduced brightnesses up to 1014 A/(m2 sr V). However, in their analysis, the authors find that statistical Coulomb interactions limit the reduced brightness of even atomically sharp cold field emitters to 1011 A/(m2 sr V) and regular tungsten cold field emitters to around 2×108 A/(m2 sr V). The authors also find that for tip radii in the range from 5 nm to 1 μm, cold field emitters do not outperform larger Schottky (thermal field) emitters. Although this is applied to only one geometry, they expect that similar results will occur for most other cases due to a distinct difference in the behavior of different beam regimes.
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85.45.Db Field emitters and arrays, cold electron emitters
back to top Emerging Technologies

Direct transformation of a resist pattern into a graphene field effect transistor through interfacial graphitization of liquid gallium

Jun-ichi Fujita, Yosuke Miyazawa, Ryuichi Ueki, Mio Sasaki, and Takeshi Saito

J. Vac. Sci. Technol. B 28, C6D1 (2010); http://dx.doi.org/10.1116/1.3511511 (4 pages) | Cited 1 time

Online Publication Date: 10 November 2010

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The authors found that an extremely thin resist pattern on a silicon dioxide can be directly transformed into a graphene channel through interfacial graphitization of liquid gallium. These patterned graphene field effect transistors show p-type field effect conductance characteristics and a maximum conductance modulation of 100% against an applied gate voltage range from −50 to +50 V at room temperature, which is almost identical to the on/off ratio of 2. These conductance modulation ratios improved with decreasing the initial resist thickness below 2 nm; however, the absolute value of the channel conductance also deteriorated with decreasing the resist thickness, suggesting that electron scattering at the domain boundary dominates the channel conductance.
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85.30.Tv Field effect devices

Fabrication of metal patterns on freestanding graphenoid nanomembranes

André Beyer, Andrey Turchanin, Christoph T. Nottbohm, Nils Mellech, Mark Schnietz, and Armin Gölzhäuser

J. Vac. Sci. Technol. B 28, C6D5 (2010); http://dx.doi.org/10.1116/1.3511475 (6 pages)

Online Publication Date: 11 November 2010

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Metallic patterns on freestanding ultrathin supports are desirable for many applications in modern optics or nanomechanics. The authors present four fabrication paths to create gold patterns that are supported by 1 nm thick freestanding graphenoid nanomembranes from self-assembled monolayers. Two fabrication schemes apply resist based lithographic processes to define gold structures on nanosheets. The gold/nanomembrane hybrids are then released from their substrates to form a freestanding structure. In two further fabrication schemes, the direct metal deposition of metal onto a freestanding graphenoid is performed. All four schemes are capable of producing gold patterns on two-dimensional nanomaterials, thus resembling new paths for the routine fabrication of free-floating metallic structures.
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81.16.Rf Micro- and nanoscale pattern formation
81.16.Nd Micro- and nanolithography
81.16.Dn Self-assembly
82.45.Mp Thin layers, films, monolayers, membranes

Study of transport properties in graphene monolayer flakes on SiO2 substrates

J. M. Tirado, D. Nezich, X. Zhao, J. W. Chung, J. Kong, and T. Palacios

J. Vac. Sci. Technol. B 28, C6D11 (2010); http://dx.doi.org/10.1116/1.3516649 (4 pages)

Online Publication Date: 12 November 2010

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This work studies the transport properties of field effect transistors fabricated on graphene single monolayer flakes. In particular, carrier mobilities in graphene for electrons and holes as a function of the vertical electric field are presented and compared with universal mobility curves in silicon. The graphene device shows excellent transport properties, especially at low electric fields due to the lack of Coulomb scattering. At higher electric fields, the phonon scattering dominates and makes the electron mobility similar to the one in silicon. The effect of defects and traps by charged impurities in the transport properties has also been studied, and it has been shown that an initial high temperature annealing significantly improves the transport properties and stability of these devices.
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85.30.Tv Field effect devices
back to top Extreme Ultraviolet Lithography

Wavelength-specific reflections: A decade of extreme ultraviolet actinic mask inspection research

K. A. Goldberg and I. Mochi

J. Vac. Sci. Technol. B 28, C6E1 (2010); http://dx.doi.org/10.1116/1.3498757 (10 pages) | Cited 2 times

Online Publication Date: 18 November 2010

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Mask inspection is essential for the success of any pattern transfer lithography technology, and extreme ultraviolet lithography (EUVL), in particular, faces unique challenges. EUV masks’ resonant-reflective multilayer coatings have a narrow, wavelength-specific response that dramatically affects the way that defects appear, or disappear, at various illuminating wavelengths. Furthermore, the ever-shrinking size of “critical” defects limits the potential effectiveness of deep ultraviolet inspection techniques over time. Researchers pursuing numerous ways of finding and characterizing defects on extreme ultraviolet (EUV) masks and have met with varying degrees of success. Their lessons inform the current, urgent exploration to select the most effective techniques for high-volume manufacturing. Ranging from basic research and demonstration experiments to commercial inspection tool prototypes, the authors survey the recent history of work in this area, including sixteen projects in Europe, Asia, and America. Solutions range from scanning beams to microscopy, darkfield imaging to pattern transfer.
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85.40.Hp Lithography, masks and pattern transfer

Actinic imaging and evaluation of phase structures on extreme ultraviolet lithography masks

Iacopo Mochi, Kenneth A. Goldberg, and Sungmin Huh

J. Vac. Sci. Technol. B 28, C6E11 (2010); http://dx.doi.org/10.1116/1.3498756 (6 pages) | Cited 3 times

Online Publication Date: 18 November 2010

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The authors describe the implementation of a phase-retrieval algorithm to reconstruct the phase and complex amplitude of structures on extreme ultraviolet (EUV) lithography masks. Many native defects commonly found on EUV reticles are difficult to detect and review accurately because they have a strong phase component. Understanding the complex amplitude of mask features is essential for predictive modeling of defect printability and defect repair. Besides printing in a stepper, the most accurate way to characterize such defects is with actinic inspection, performed at the design, EUV wavelength. Phase defect and phase structures show a distinct through-focus behavior that enables qualitative evaluation of the object phase from two or more high-resolution intensity measurements. For the first time, the phase of structures and defects on EUV masks were quantitatively reconstructed based on aerial image measurements, using a modified version of a phase-retrieval algorithm developed to test optical phase shifting reticles.
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85.40.Hp Lithography, masks and pattern transfer
42.30.Wb Image reconstruction; tomography

Assessing the mask clamping ability of a low thermal expansion material chuck

J. R. Zeuske, P. Vukkadala, R. L. Engelstad, A. R. Mikkelson, G. Kalkowski, S. Risse, and S. Mueller

J. Vac. Sci. Technol. B 28, C6E17 (2010); http://dx.doi.org/10.1116/1.3502449 (6 pages)

Online Publication Date: 18 November 2010

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The successful implementation of extreme ultraviolet lithography (EUVL) for patterning in the sub-32 nm regime will require significant improvements in image placement (IP) accuracy over the next few years. The IP error budget for the mask system is extremely stringent; consequently, the reduction or elimination of all sources of error is essential. One potential source of IP error is the effect of the residual nonflatness of the patterned surface of the mask during exposure scanning. The focus of this article is to characterize the clamping ability of a Coulombic electrostatic pin-type chuck and to assess its ability to adequately flatten an EUVL mask. The chuck was fabricated from low thermal expansion material, with a nonflatness over the pin area of approximately 74 nm. Experimental results illustrate that a highly bowed substrate (1149 and 1047 nm for the frontside and backside nonflatness, respectively) could be chucked flat to less than 100 nm. Numerical models were also used to simulate electrostatic chucking and to predict the final nonflatness of the pattern surface of the mask. Excellent agreement was found between the experimental and numerical results. In addition, the modeling tools developed here can be used to optimize the chuck design parameters and to establish the requirements on nonflatness of both the EUVL substrate and the surface of the chuck.
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85.40.Hp Lithography, masks and pattern transfer

Extreme ultraviolet mask substrate surface roughness effects on lithographic patterning

Simi A. George, Patrick P. Naulleau, Iacopo Mochi, Farhad Salmassi, Eric M. Gullikson, Kenneth A. Goldberg, and Erik H. Anderson

J. Vac. Sci. Technol. B 28, C6E23 (2010); http://dx.doi.org/10.1116/1.3502436 (8 pages)

Online Publication Date: 19 November 2010

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In extreme ultraviolet lithography exposure systems, mask substrate roughness-induced scatter contributes to line edge roughness (LER) at the image plane. In this article, the impact of mask substrate roughness on image plane speckle is explicitly evaluated. A programed roughness mask was used to study the correlation between mask roughness metrics and wafer plane aerial image inspection. The authors find that the roughness measurements by the top surface topography profile do not provide complete information on the scatter related speckle that leads to LER at the image plane. They suggest at-wavelength characterization by imaging and/or scatter measurements into different frequencies as an alternative for a more comprehensive metrology of the mask substrate/multilayer roughness effects.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
68.65.Ac Multilayers

Extreme ultraviolet mask surface cleaning effects on lithography process performance

Simi A. George, Lorie Mae Baclea-an, Patrick P. Naulleau, Robert J. Chen, and Ted Liang

J. Vac. Sci. Technol. B 28, C6E31 (2010); http://dx.doi.org/10.1116/1.3501344 (5 pages) | Cited 1 time

Online Publication Date: 19 November 2010

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Extreme UV (EUV) masks are expected to undergo cleaning processes in order to maintain the lifetimes necessary for high volume manufacturing. For this study, the impact of repetitive cleaning of EUV masks on imaging performance is evaluated. Two high quality industry standard EUV masks are used, with one of the masks undergoing repeated cleaning and the other one kept as a reference. Lithographic performance, in terms of process window analysis and line edge roughness, was monitored after every two cleans and was compared to the reference mask performance. Surface analysis by atomic force microscopy did not show changes in the midspatial frequency roughness measured after each clean. After a total of eight cleans, minimal degradation is observed in the lithographic performance of the mask. From these observations, the authors conclude that the cleaning cycles completed thus far did not damage the mask multilayer or the absorber structures. The cleaning cycles will be continued until significant loss in imaging fidelity is found.
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85.40.Hp Lithography, masks and pattern transfer
81.65.Cf Surface cleaning, etching, patterning
68.37.Ps Atomic force microscopy (AFM)
68.35.B- Structure of clean surfaces (and surface reconstruction)

High transmission pellicles for extreme ultraviolet lithography reticle protection

Yashesh A. Shroff, Michael Leeson, Pei-Yang Yan, Eric Gullikson, and Farhad Salmassi

J. Vac. Sci. Technol. B 28, C6E36 (2010); http://dx.doi.org/10.1116/1.3505126 (6 pages) | Cited 1 time

Online Publication Date: 30 November 2010

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The authors present the results of a full-field extreme ultraviolet (EUV) pellicle for reticle protection and defect mitigation. Based on novel microelectromechanical systems based fabrication, it comprises a 50 nm Si membrane attached to a wire-grid. Two types of pellicle fabrication techniques are described. The authors present the first actinic results of extreme ultraviolet lithography reticle with pellicle exposed on IMEC Advanced Demo Tool. The impact of different pellicle types on imaging is evaluated as a function of pellicle standoff distance and mesh geometry. A new prototype pellicle has been developed with a measured transmission of 82% in EUV. Actinic exposures are complemented with aerial image modeling, thermal analysis, vacuum cycling, resist outgas tests, and >5 g repeated scan cycle robustness tests.
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85.40.Hp Lithography, masks and pattern transfer
back to top Focused Ion Beams

Focused chromium ion beam

A. V. Steele, B. Knuffman, J. J. McClelland, and J. Orloff

J. Vac. Sci. Technol. B 28, C6F1 (2010); http://dx.doi.org/10.1116/1.3502668 (5 pages) | Cited 2 times

Online Publication Date: 21 October 2010

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With the goal of expanding the capabilities of focused ion beam microscopy and milling systems, the authors have demonstrated nanoscale focusing of chromium ions produced in a magneto-optical trap ion source. Neutral chromium atoms are captured into a magneto-optical trap and cooled to 100 μK with laser light at 425 nm. The atoms are subsequently photoionized and accelerated to energies between 0.5 and 3 keV. The accelerated ion beam is scanned with a dipolar deflector and focused onto a sample by an einzel lens. Secondary electron images are collected and analyzed, and from these, a beam diameter is inferred. The result is a focused probe with a 1 standard-deviation radius as small as 205±10 nm. While this probe size is in the useful range for nanoscale applications, it is almost three times larger than is predicted by ray-tracing simulations. Possible explanations for this discrepancy are discussed.
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41.75.Ak Positive-ion beams
32.80.Fb Photoionization of atoms and ions
37.10.Ty Ion trapping
42.15.Dp Wave fronts and ray tracing

Analysis of subsurface beam spread and its impact on the image resolution of the helium ion microscope

Sybren Sijbrandij, John Notte, Colin Sanford, and Ray Hill

J. Vac. Sci. Technol. B 28, C6F6 (2010); http://dx.doi.org/10.1116/1.3497012 (4 pages)

Online Publication Date: 21 October 2010

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By virtue of its extremely bright gaseous field ion source, the ORION™ helium ion microscope has demonstrated a probe size smaller than 0.3 nm, when operating the microscope in its (typical) high-resolution imaging mode, i.e., surface imaging with secondary electron signal. The authors combined SRIM-models of beam spread in the sample with models for secondary electron signal generation and escape, for a wide range of beam energies and sample materials, in order to calculate the effect of beam spread on image resolution. It was found that the effect on resolution is larger for sample materials with higher atomic numbers, and that the effect is inversely proportional to beam energy. The magnitude of the calculated effect on image resolution ranges from 0.005 to 0.08 nm, which is typically an order of magnitude smaller than the currently experimentally measured image resolution of the helium ion microscope.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Design of a parallel mass spectrometer for focused ion beam columns

A. Khursheed, K. H. Cheong, and H. Q. Hoang

J. Vac. Sci. Technol. B 28, C6F10 (2010); http://dx.doi.org/10.1116/1.3497021 (5 pages)

Online Publication Date: 21 October 2010

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This article describes a parallel mass spectrometer design suitable for use as an add-on attachment for focused ion beam instruments. It consists of an acceleration transfer lens, an electric sector deflector, and a variable field strength magnetic sector deflector. The magnetic sector is designed to deflect and focus ions having a wide range of charge-to-mass ratios onto a flat plate detector. The size of an aperture inside the acceleration transfer lens can be used to change the spectrometer mass resolution. The simulation results presented in this article predict that it should be possible to perform secondary ion mass spectroscopy analysis on the nanoscale range with the proposed mass spectrometer attachment.
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07.75.+h Mass spectrometers

Gas field ion source and liquid metal ion source charged particle material interaction study for semiconductor nanomachining applications

Shida Tan, Richard Livengood, Darryl Shima, John Notte, and Shawn McVey

J. Vac. Sci. Technol. B 28, C6F15 (2010); http://dx.doi.org/10.1116/1.3511509 (7 pages) | Cited 1 time

Online Publication Date: 1 December 2010

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Semiconductor manufacturing technology nodes will evolve to the 22, 15, and 11 nm generations in the next few years. For semiconductor nanomachining applications, further beam spot size scaling is required beyond what is capable by present generation Ga+ focused ion beam technology. As a result, continued Ga+ beam scaling and/or alternative beam technology innovations will be required. In this work, several alternative ion beam technologies are explored and compared to Ga+ beam for key nanomachining and substrate interaction attributes. First, thorough Monte Carlo simulations were conducted with various ion species incident on silicon and copper. Additionally, silicon and copper substrates were experimentally exposed to ion beams of helium, neon, and gallium. These substrates were subsequently analyzed to determine the sputter yields and subsurface damage.
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81.16.-c Methods of micro- and nanofabrication and processing
61.80.Jh Ion radiation effects

Model for nanopillar growth by focused helium ion-beam-induced deposition

Paul F. A. Alkemade, Ping Chen, Emile van Veldhoven, and Diederik Maas

J. Vac. Sci. Technol. B 28, C6F22 (2010); http://dx.doi.org/10.1116/1.3517536 (4 pages) | Cited 3 times

Online Publication Date: 1 December 2010

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An analytical model for the growth of nanopillars by helium ion-beam-induced deposition is presented and compared to experimental data. This model describes the competition between pillar growth in vertical and lateral directions. It assumes that vertical growth is induced by incident primary ions and type-1 secondary electrons, whereas lateral growth is induced by scattered ions and type-2 secondary ions. An essential element of the model is the notion that depletion of adsorbed precursor molecules occurs only at the pillars’ apex. Depletion impedes vertical growth at the apex, allowing more time for lateral outgrowth of the pillar’s sidewalls. The model describes qualitatively the trends in measured vertical, lateral, and volumetric growth rates of PtC pillars as functions of the ion-beam current. It can be used to design growth experiments and Monte Carlo simulations.
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81.07.Bc Nanocrystalline materials
81.15.Jj Ion and electron beam-assisted deposition; ion plating
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.16.-c Methods of micro- and nanofabrication and processing

Ga+ beam lithography for suspended lateral beams and nanowires

M. David Henry, Michael Shearn, and Axel Scherer

J. Vac. Sci. Technol. B 28, C6F26 (2010); http://dx.doi.org/10.1116/1.3497013 (5 pages)

Online Publication Date: 1 December 2010

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The authors demonstrate the fabrication of suspended nanowires and doubly clamped beams by using a focused ion beam implanted Ga etch mask followed by an inductively coupled plasma reactive ion etching of silicon. This method will demonstrate how a two-step, completely dry fabrication sequence can be tuned to generate nanomechanical structures on either silicon substrates or silicon on insulator (SOI). This method was used to generate lateral nanowires suspended between 2 μm scaled structures with lengths up to 16 μm and widths down to 40 nm on a silicon substrate. The authors also fabricate 10 μm long doubly clamped beams on SOIs that are 20 nm thick and a minimum of 150 nm wide. In situ electrical measurements of the beams demonstrate a reduction of resistivity from >37.5 Ω cm down to 0.25 Ω cm. Transmission electron microscopy for quantifying both surface roughness and crystallinity of the suspended nanowires was performed. Finally, a dose array for repeatable fabrication of a desired beam width was also experimentally determined.
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81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
68.35.bg Semiconductors
07.10.Cm Micromechanical devices and systems
81.07.Oj Nanoelectromechanical systems (NEMS)
81.07.Gf Nanowires
52.77.Bn Etching and cleaning

Transmission electron microscopy study of damage layer formed through ion beam induced deposition of platinum on silicon substrate

Byong Chon Park, Yun Chang Park, Hwack Joo Lee, and Young Heon Kim

J. Vac. Sci. Technol. B 28, C6F31 (2010); http://dx.doi.org/10.1116/1.3516651 (7 pages)

Online Publication Date: 1 December 2010

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Ion beam induced deposition is used for nanofabrication operations (e.g., transmission electron microscopy sample preparation) but is still not perfectly understood. Here, the authors describe the use of a wide variety of analytical instruments to develop such an understanding. Pt-films were deposited on native oxide films on silicon (Si) by decomposing trimethyl platinum C5H4CH3Pt(CH3)3 with focused electron or gallium ion beams. Unlike electron beam induced deposition, ion beam induced deposition produces a deep and complex damage layer below the deposition. It is revealed that the damaged area can be divided into three layers: (1) a “white-band” with a lower Pt-concentration and concurrent higher carbon (C)-concentration; (2) a-Pt–Si region where amorphized silicon crystal is mixed with Pt, and Pt-particle formation starts somewhere in the middle area; and (3) a-Si, which is silicon amorphized by Ga ions. The change in the diffusion rate of platinum into the amorphized silicon layer plays a crucial role in the formation of the distinct layers. The diffusions are affected by interatomic chemical affinity as well as by concentration, so that the Pt–Si combination initially dominates Pt agglomeration and the combination of C–Si, resulting in the creation of the novel white-band.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
66.30.Fq Self-diffusion in metals, semimetals, and alloys

Piezoresistive effect in the three-dimensional diamondlike carbon nanostructure fabricated by focused-ion-beam chemical vapor deposition

Reo Kometani, Kouki Yusa, Shin’ichi Warisawa, and Sunao Ishihara

J. Vac. Sci. Technol. B 28, C6F38 (2010); http://dx.doi.org/10.1116/1.3504584 (4 pages) | Cited 2 times

Online Publication Date: 1 December 2010

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In this study, the electrical material characteristics of a three-dimensional (3D) diamondlike carbon (DLC) structure fabricated by focused-ion-beam chemical vapor deposition (FIB-CVD) were evaluated to realize functional 3D nano- and micromechanical devices based on the piezoresistive material. However, the DLC cantilever structure fabricated by FIB-CVD did not exhibit piezoresistive properties due to the incorporated gallium (Ga), which was implanted by Ga+ FIB irradiation. Therefore, a method for the modification of material characteristics was examined to introduce piezoresistive properties in the 3D DLC structure fabricated by FIB-CVD. Long-time annealing (12 h or more) at a low temperature (300 °C) was found to be an effective method to realize a 3D DLC structure with piezoresistive properties. Long-time annealing at low temperatures caused Ga elimination from the DLC without any change in the sp2/(sp2+sp3) ratio. The values of the gauge factor were in the range of 2–34. 3D nano- and microstructures with piezoresistive properties could be realized by FIB-CVD and annealing treatment.
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81.05.ug Diamond
81.15.Jj Ion and electron beam-assisted deposition; ion plating
73.50.Dn Low-field transport and mobility; piezoresistance
back to top Masks and Maskless Lithography

Blanking characteristics of a miniature electron beam column

C. S. Silver, J. P. Spallas, and L. P. Muray

J. Vac. Sci. Technol. B 28, C6G1 (2010); http://dx.doi.org/10.1116/1.3502437 (4 pages)

Online Publication Date: 27 October 2010

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A commercial field emission scanning electron microscopy (SEM) based around a miniature electron beam column includes an integrated electrostatic blanker, making the system well-suited for lithography. A previous version of the miniature column design demonstrated direct-write lithography with 70 nm lines and spaces written into resist. That column also demonstrated an 85 MHz blanking speed and a 6 nA beam current using a condenser lens. This article presents a study of the field emission SEM’s integrated blanking system, including measurements and simulations of the electron beam optics. Rise and settle times are discussed, as well as beam extinction ratios under various operating conditions. The column’s conjugate blanking optics are described, and measurements are presented, which suggest that the column may be used in a conjugate blanking mode for lithography. Finally, this article discusses how these results will feedback into the system design in order to improve the SEM’s existing lithography capabilities.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Multibeam scanning electron microscope: Experimental results

A. Mohammadi-Gheidari, C. W. Hagen, and P. Kruit

J. Vac. Sci. Technol. B 28, C6G5 (2010); http://dx.doi.org/10.1116/1.3498749 (6 pages) | Cited 1 time

Online Publication Date: 5 November 2010

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The authors present the first results obtained with their multibeam scanning electron microscope. For the first time, they were able to image 196 (array of 14×14) focused beams of a multielectron beam source on a specimen using single beam scanning electron microscope (SEM) optics. The system consists of an FEI Novanano 200 SEM optics column equipped with a multielectron beam source module. The source module consists of the multibeam source and an accelerator lens. In the multibeam source, the wide angle beam of a high brightness Schottky source is divided into 196 beamlets and focused by an aperture lens array. The accelerator lens is positioned on the image plane of the multibeam source to direct the beams toward the SEM column. The array of source images is further imaged by the SEM magnetic lenses, and the beam opening angle is defined at the variable aperture of the SEM. The system is designed to deliver 14×14 arrays of beamlets with a minimum probe size of 1 nm. In this article, the performance of the system is examined for a fixed magnification case.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
back to top Metrology and Imaging

Application of analytic scanning electron microscopy to critical dimensions metrology at nanometer scale

Sergey Babin, Konstantin Bay, and Justin J. Hwu

J. Vac. Sci. Technol. B 28, C6H1 (2010); http://dx.doi.org/10.1116/1.3504476 (5 pages)

Online Publication Date: 5 November 2010

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Scanning electron microscopy (SEM) metrology involves significant uncertainty of the linewidth measurement because the SEM image brightness is a complex function of SEM setup, pattern materials, and shape. In this work, the authors used an analytical SEM for critical dimensions metrology applications on a quartz nanoimprint template. The SEM was tuned to find the best condition for consistent operation. Beam characterization was done using BEAMETR beam measurement technique. SEM images of templates were taken at optimum conditions. The measurements were done using two methods: regular imaging processing software based on brightness threshold and using physical model based processing tool myCD. The quartz template was then measured using transmission electron microscopy cross sections at selected sites to reveal profile information as metrology comparison reference. The metrology capability and limitations of analytical SEM with regular image processing were identified. The considerable improvement of accuracy using the physics based image processing was found.
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06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
07.05.Pj Image processing
42.30.Va Image forming and processing

Linewidth metrology for sub-10-nm lithography

S. Thoms and D. S. Macintyre

J. Vac. Sci. Technol. B 28, C6H6 (2010); http://dx.doi.org/10.1116/1.3505129 (5 pages) | Cited 1 time

Online Publication Date: 22 November 2010

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As optical lithography advances toward the 10 nm mark, much effort is being expended to push electron beam lithography into the deep sub-10-nm regime. A significant issue at this length scale is the ability to accurately measure and compare linewidths. Measurements using secondary electron micrographs have a bias of a few nanometers and are therefore difficult to interpret in the sub-10-nm regime. Transmission electron microscopy can give greater accuracy but requires significant effort. This article shows that the use of a backscattered electron image together with a metal coating where appropriate can yield better measurement results than by using secondary electrons. With the use of a suitable model, linewidths for sub-10-nm hydrogen silsesquioxane lines were extracted with an estimated error of 1 nm.
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06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
79.20.Kz Other electron-impact emission phenomena
81.16.Nd Micro- and nanolithography
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Metrology for electron-beam lithography and resist contrast at the sub-10 nm scale

Huigao Duan, Vitor R. Manfrinato, Joel K. W. Yang, Donald Winston, Bryan M. Cord, and Karl K. Berggren

J. Vac. Sci. Technol. B 28, C6H11 (2010); http://dx.doi.org/10.1116/1.3501359 (7 pages) | Cited 1 time

Online Publication Date: 22 November 2010

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Exploring the resolution limit of electron-beam lithography is of great interest both scientifically and technologically. However, when electron-beam lithography approaches its resolution limit, imaging and metrology of the fabricated structures by using standard scanning electron microscopy become difficult. In this work, the authors adopted transmission-electron and atomic-force microscopies to improve the metrological accuracy and to analyze the resolution limit of electron-beam lithography. With these metrological methods, the authors found that sub-5 nm sparse features could be readily fabricated by electron-beam lithography, but dense 16 nm pitch structures were difficult to yield. Measurements of point- and line-spread functions suggested that the resolution in fabricating sub-10 nm half-pitch structures was primarily limited by the resist-development processes, meaning that the development rates depended on pattern density and/or length scale.
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85.40.Hp Lithography, masks and pattern transfer

Robust estimation of line width roughness parameters

Kedar Patel, Soumendra N. Lahiri, and Costas J. Spanos

J. Vac. Sci. Technol. B 28, C6H18 (2010); http://dx.doi.org/10.1116/1.3517718 (16 pages)

Online Publication Date: 29 November 2010

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Estimation of line width roughness (LWR) parameters is necessary for semiconductor process optimization, comparison of next-generation lithography processes as well as device performance simulation. According to previous studies [ V. Constantoudis et al., J. Vac. Sci. Technol. B 21, 1019 (2003) ; J. Vac. Sci. Technol. B 22, 1974 (2004) ], a complete description of LWR can be provided by three parameters: root-mean square roughness (σ), correlation length (ξ), and roughness exponent (α). However, the primary challenge in the estimation of the aforementioned LWR parameters is the limited availability of data in the scanning electron micrograph (SEM) image. A typical SEM image consists of 8–20 lines of 300–1500 nm length. It has been recognized that for a given line, in the presence of correlation between line widths at a given separation, the estimate of σ for a finite length of line can be significantly biased. Furthermore, for next-generation lithography (NGL) technologies such as double patterning, the number of lines available to estimate each lithography step is cut in half since alternate lines are produced from different processes. Thus, there is a need for an estimation procedure that performs robustly for arbitrarily shorter and fewer numbers of lines. Using a vectorized block or block of blocks bootstrap technique for dependent data and a weighted least-squares (WLS) fitting procedure, the authors fit a specific form of a variogram model. Block of blocks bootstrap is used to estimate the variance of a variogram, which in turn provides the WLS weights. Additionally, the bootstrap approach also allows us to estimate the error in the estimated LWR parameters, a vital requirement that has not been addressed by any of the previously reported procedures on this subject. The authors’ procedure works even in the presence of some unknown local critical dimension (CD) variation or if there is a systematic difference in CD (by design or otherwise) between the lines. The authors validate their procedure with simulated roughness profiles with deterministic LWR parameters. Lastly, as an application of their procedure, they evaluate actual profiles from a variety of different mainstream NGL processes such as litho-freeze-litho-etch double patterning lithography, self-aligned double patterning, and extreme ultraviolet, as well as alternatives such as directed self-assembly and nanoimprint lithography. It was shown that σ can be overestimated by over two times if local variation is not treated properly.
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81.16.Nd Micro- and nanolithography
81.16.Rf Micro- and nanoscale pattern formation
02.70.Rr General statistical methods
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
81.16.Dn Self-assembly

Understanding the relationship between true and measured resist feature critical dimension and line edge roughness using a detailed scanning electron microscopy simulator

Richard A. Lawson and Clifford L. Henderson

J. Vac. Sci. Technol. B 28, C6H34 (2010); http://dx.doi.org/10.1116/1.3517717 (6 pages)

Online Publication Date: 30 November 2010

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Top-down critical dimension scanning electron microscopy (SEM) is still the workhorse metrology tool used for nanoscale structure analysis, such as measurement of photoresist features, during integrated circuit manufacturing. However, the degree to which top-down SEM imaging can accurately be used to quantitatively determine the size, shape, and roughness characteristics of three-dimensional structures such as photoresist features has not been carefully characterized. A rigorous Monte Carlo simulation of scanning electron microscopy has been developed to probe the relationship between the roughness of a three-dimensional feature and the line edge roughness (LER) as measured by SEM. The model uses the differential Mott cross section to compute elastic scattering, while inelastic scattering and secondary electron generation are handled using dielectric function theory. The model can calculate the electron scattering for any arbitrary three-dimensional geometry. Experimental SEM measurements of photoresist nanostructures show good agreement with the simulation output. The critical dimension of the resist determined from SEM best matches the true resist feature width when the line edge is defined using a high image threshold because the roughness on the outer edge of the resist tends to cause an increase in SEM signal that is nonproportional to the amount of material on the outer edge of the feature. LER determined from SEM was found to be significantly smaller than the true resist feature sidewall roughness. The measured LER is typically greater than 50% smaller than the actual sidewall roughness.
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85.40.Hp Lithography, masks and pattern transfer
02.70.Uu Applications of Monte Carlo methods
back to top Microfluidics

Three-dimensional microfluidic mixers using ion beam lithography and micromachining

E. Palacios, L. E. Ocola, A. Joshi-Imre, S. Bauerdick, M. Berse, and L. Peto

J. Vac. Sci. Technol. B 28, C6I1 (2010); http://dx.doi.org/10.1116/1.3505128 (6 pages)

Online Publication Date: 5 November 2010

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In this article, the authors present microfluidic mixers containing three-dimensional (3D) geometries used to decrease mixing lengths in passive microfluidic systems. In order to create these 3D geometries, the authors use ion beam lithography and micromachining and address charging, redeposition, and stitching error effects that follow this type of fabrication. Prior to mixer fabrication, simulations were run and results were compared between a common straight mixer and two other mixers designed by the authors. The simulation results have shown that 3D geometries can generate lateral velocities and lower mixing lengths down to approximately 70 μm.
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07.10.Cm Micromechanical devices and systems
47.11.-j Computational methods in fluid dynamics
47.27.wj Turbulent mixing layers

Fabricating millimeter to nanometer sized cavities concurrently for nanofluidic devices

Nicole R. Devlin and Devin K. Brown

J. Vac. Sci. Technol. B 28, C6I7 (2010); http://dx.doi.org/10.1116/1.3517701 (4 pages)

Online Publication Date: 29 November 2010

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In this study, nanofluidic devices were fabricated using Unity® 4671E, a decomposable, negative tone resist. Cavities as large as 2.5 mm and channels as small as 30 nm were fabricated with the same process. Water was successfully flowed through the devices and the flow was characterized for a 500 nm channel.
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81.07.Oj Nanoelectromechanical systems (NEMS)
81.16.Nd Micro- and nanolithography
47.85.Np Fluidics
47.61.Fg Flows in micro-electromechanical systems (MEMS) and nano-electromechanical systems (NEMS)

Nanofluidic channels fabricated by e-beam lithography and polymer reflow sealing

Mina Fouad, Mustafa Yavuz, and Bo Cui

J. Vac. Sci. Technol. B 28, C6I11 (2010); http://dx.doi.org/10.1116/1.3517620 (3 pages)

Online Publication Date: 29 November 2010

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The authors developed a facile approach for creating nanofluidic channels by electron beam lithography that used a bilayer e-beam resist consisting of poly(methyl methacrylate) (PMMA) on top of poly(dimethyl glutarimide) (PMGI). In the process, the more sensitive PMGI was fully exposed with channel patterns, and the less sensitive PMMA was only fully exposed with a chain of dot patterns right above the channel patterns. PMMA was then developed to form a chain of holes through which PMGI channels were developed. After closing the holes by thermal reflowing PMMA, channels in PMGI were sealed with PMMA. The current method is capable of fabricating simultaneously channels with different channel widths.
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47.61.Fg Flows in micro-electromechanical systems (MEMS) and nano-electromechanical systems (NEMS)
47.85.Np Fluidics
07.10.Cm Micromechanical devices and systems

Rotation speed control of Janus particles by dielectrophoresis in a microfluidic channel

T. Honegger, O. Lecarme, K. Berton, and D. Peyrade

J. Vac. Sci. Technol. B 28, C6I14 (2010); http://dx.doi.org/10.1116/1.3502670 (6 pages) | Cited 1 time

Online Publication Date: 30 November 2010

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In this work, Janus particles (Au/fluorescent polystyrene) are fabricated and their flip/flop rotational effect is studied in a microfluidic channel thanks to dielectrophoresis, providing a new type of local light switch. A method for producing large amounts (more than 106 particles/ml) of Janus particles is first presented. Those particles were then injected in an electromicrofluidic chip and stabilized in the fluid by a dielectrophoretic trap. The spanning frequency of this trap allowed performing a “flip-flop” effect of the Janus particles by recording their fluorescent intensities. Flip (Au top side) and flop (PS top side) frequencies are identified. Finally, experiments were performed on the time triggered commutations between flip and flop frequencies to define the capability of each Janus particle to sustain speed control of their flip-flop.
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47.85.Np Fluidics
82.45.-h Electrochemistry and electrophoresis
47.61.Jd Multiphase flows
47.60.Dx Flows in ducts and channels
47.32.Ef Rotating and swirling flows
back to top Modeling

Mask-topography-induced phase effects and wave aberrations in optical and extreme ultraviolet lithography

A. Erdmann, F. Shao, P. Evanschitzky, and T. Fühner

J. Vac. Sci. Technol. B 28, C6J1 (2010); http://dx.doi.org/10.1116/1.3497024 (7 pages) | Cited 1 time

Online Publication Date: 19 October 2010

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Rigorous electromagnetic field simulations are applied to investigate phase effects in the light diffraction from masks for advanced optical and extreme ultraviolet lithography. Analogies of these phase effects with wave aberrations of the projection lens and their impact on the lithographic process performance are discussed.
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85.40.Hp Lithography, masks and pattern transfer

High accuracy electron beam model development in MICHELLE: eBEAM

Serguei G. Ovtchinnikov, Simon J. Cooke, Roman Shtokhamer, Alexander N. Vlasov, Masis M. Mkrtchyan, Christopher Kostas, John J. Petillo, and Baruch Levush

J. Vac. Sci. Technol. B 28, C6J8 (2010); http://dx.doi.org/10.1116/1.3503899 (5 pages) | Cited 1 time

Online Publication Date: 5 November 2010

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The authors present a new software tool (eBEAM) for high accuracy simulations of electron beams with stochastic space charge effects as a module of the SAIC/NRL MICHELLE particle simulation code. In modeling low current electron beam systems such as in electron beam lithography and electron microscopy, it is necessary to simulate ensembles of individual electrons to account correctly for the statistical effects of interparticle interactions. This article demonstrates the use of CPU/GPU hybrid techniques that run on multiple platforms to accomplish the simulation task within the MICHELLE/eBEAM framework.
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41.75.Fr Electron and positron beams
02.50.Ey Stochastic processes

Monte Carlo modeling of electron backscattering from carbon nanotube forests

M. K. Alam, P. Yaghoobi, and A. Nojeh

J. Vac. Sci. Technol. B 28, C6J13 (2010); http://dx.doi.org/10.1116/1.3511506 (6 pages) | Cited 3 times

Online Publication Date: 9 November 2010

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The authors present a new Monte Carlo tool capable of simulating electron trajectories in nanotube forests, taking into account the underlying nanoscale nature of the material. The scattering angle distribution is adaptively modified at each step of the simulation according to the local environment (how the nanotubes are positioned, their diameters, and internanotube distances). This provides additional degrees of freedom in the Monte Carlo simulation that are directly related to the internal structure of the nanotube forest, allowing the model to closely match experimental data.
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61.43.Bn Structural modeling: serial-addition models, computer simulation
79.20.Kz Other electron-impact emission phenomena
61.48.De Structure of carbon nanotubes, boron nanotubes, and other related systems

Reducing the pattern redundancy in optical proximity correction modeling by analyzing the pattern linearity

Jianliang Li, Lin Zhang, Qiliang Yan, Lawrence S. Melvin, III, Chadwick Lin, Eason Su, and Nail Tang

J. Vac. Sci. Technol. B 28, C6J19 (2010); http://dx.doi.org/10.1116/1.3511510 (6 pages)

Online Publication Date: 1 December 2010

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In modern photolithography, optical proximity correction (OPC) has been widely adopted to improve the image fidelity of the mask on silicon wafer and, hence, improve the yield and the performance of integrated circuits. In recent years, model based optical proximity correction (MBOPC) has evolved from a nice-to-have feature to a must-have feature, especially, for the advanced nodes, 90 nm and beyond. The purpose of MBOPC is to adjust the designed pattern on the photomask to introduce mask perturbations, such that the layout printed on the wafer is as close as possible to the drawn layout. Before MBOPC is conducted on the full chip, a high quality and yet compact OPC model must be built, which simulates the photolithography process accurately. A high quality OPC model apparently relies on the quality of the empirical critical-dimension data in terms of both metrology noisiness and layout representativeness. Although more measurements on a large number of patterns will keep overall noise at lower levels and provide better input to OPC modeling, it is crucial to choose the representative patterns wisely and minimize the redundancy of gauges due to the limited metrology budget and the requirement of shortening turnaround time. In this article, the authors propose a method that checks the linear response of the optical signal on the one-dimensional (1D) patterns and selects the most representative patterns among all possible 1D structures.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Rf Micro- and nanoscale pattern formation
42.82.Cr Fabrication techniques; lithography, pattern transfer
81.16.Nd Micro- and nanolithography
back to top Nanobiology

Fabrication of three-dimensional structures for the assessment of cell mechanical interactions within cell monolayers

David Fuard, Michel Moussus, Caterina Tomba, David Peyrade, and Alice Nicolas

J. Vac. Sci. Technol. B 28, C6K1 (2010); http://dx.doi.org/10.1116/1.3511435 (7 pages)

Online Publication Date: 10 November 2010

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The measurement of the forces at play in cell/cell adhesion uses a cell monolayer plated onto two-dimensional substrate like arrays of elastomeric microfabricated pillars. Unfortunately, the few attempts that have been done in this direction do not mimic the extracellular environment and lack knowledge on the correlation between the various types of cellular adhesions. Here, the authors suggest using a new experimental setup that more accurately simulates the three-dimensional (3D) environment of cells in tissues, using stretchable hexagonal monocellular 3D structures. The present article shows a way of fabricating these hexagonal biosensors, which are open structures made of biocompatible elastomeric polydimethylsiloxane (PDMS). The novelty of the whole fabrication process of these 3D PDMS structures consists in the use of a sacrificial silicon mold. An original mechanical PDMS planarization process is proposed. This article also describes a strategy for a selective functionalization of the 3D structure sidewalls where the cells must adhere.
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87.80.-y Biophysical techniques (research methods)
87.85.J- Biomaterials
87.17.Rt Cell adhesion and cell mechanics
87.16.-b Subcellular structure and processes

Texturing of silicon using a microporous polymer etch mask

N. S. Korivi, J. Hoffpauir, and P. K. Ajmera

J. Vac. Sci. Technol. B 28, C6K8 (2010); http://dx.doi.org/10.1116/1.3507890 (5 pages)

Online Publication Date: 10 November 2010

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This article reports on the texturing of silicon surface in microscale dimensions based on the formation of a polymeric layer on a silicon surface. The polymer layer is made porous by initially incorporating foreign material within it, followed by removal of the foreign material to leave behind pores. The pores in the polymer are of microscale dimensions having an interconnected structure, allowing the polymer layer to function as a chemical etch mask. The interconnected pores allow an etchant to access and etch the underlying silicon, resulting in texturing of the silicon surface. The texturing of silicon can be controlled, among other factors, by adjusting porosity in the polymer layer.
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81.65.Cf Surface cleaning, etching, patterning
68.35.bg Semiconductors

Gelatin/glycerol coating to preserve mechanically compliant nanowire electrodes from damage during brain implantation

Jolanda A. Witteveen, Dmitry B. Suyatin, Lina Gällentoft, Jens Schouenborg, Nils Danielsen, and Christelle N. Prinz

J. Vac. Sci. Technol. B 28, C6K13 (2010); http://dx.doi.org/10.1116/1.3498764 (4 pages)

Online Publication Date: 11 November 2010

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Chronically implanted neural implants are of clinical importance. However, currently used electrodes have several drawbacks. Some weeks after implantation in the brain, a glial scar forms around the electrode, causing decreased electrode functionality. Nanostructures, and in particular nanowires, are good candidates to overcome these drawbacks and reduce glial scar formation. Using a mechanically compliant substrate with protruding nanowires could further decrease the glial scar formation by reducing the mechanical mismatch between the tissue and the electrode. However, flexible substrates require strengthening upon brain implantation. One solution consists of embedding the implant in a gelatin-based matrix, which is resorbable. In the case where nanostructures are present at the surface of the implant, it is crucial that the embedding matrix also preserves the nanostructures, which can be challenging considering the forces involved during the drying phase of gelatin. Here, the authors show that freestanding gallium phosphide nanowires coated with hafnium oxide (HfO2), titanium (Ti), and gold (Au) were preserved in a gelatin-glycerol embedding matrix with subsequent implantation in 1% agar, which is a model for brain implantation.
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87.85.E- Neural prosthetics
87.85.Wc Neural engineering
87.85.Rs Nanotechnologies-applications
87.85.J- Biomaterials
87.19.L- Neuroscience
82.70.Gg Gels and sols

Microfluidics-assisted photo nanoimprint lithography for the formation of cellular bioimprints

V. Nock, L. Murray, F. Samsuri, M. M. Alkaisi, and J. J. Evans

J. Vac. Sci. Technol. B 28, C6K17 (2010); http://dx.doi.org/10.1116/1.3501342 (6 pages)

Online Publication Date: 11 November 2010

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Morphology and surface features provide important markers for cell development and reaction to external stimuli. Bioimprint offers a technique for the permanent capture of these features into an UV-curing, biocompatible, methacrylate biopolymer. This material shows excellent replication fidelity and fast setting times. However, the minimum reproducible feature size depends on the skillful application of the liquid prepolymer. To enable the repeatable formation of high-resolution, structurally bioactive cellular bioimprints, a modified process based on the use of microfluidics for integrated cell culture and polymer delivery has been developed. In this article, the authors introduce the process and demonstrate its use for the culture and imaging of Ishikawa endometrial cancer cells. Transfer of a 100 nm thick Cr test pattern with micrometer-scale features into the biopolymer is demonstrated. Replication and atomic force microscopy imaging of imprinted cellular surface features with sub-50 nm resolution is shown. The process has applications in disease diagnostics, in drug discovery, and for the creation of biomimetic cell culture scaffolds.
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87.85.Rs Nanotechnologies-applications
87.85.jf Bio-based materials
87.64.Dz Scanning tunneling and atomic force microscopy
87.17.Uv Biotechnology of cell processes
87.19.xj Cancer
81.16.Nd Micro- and nanolithography
back to top Nanoelectronics

Low damage fully self-aligned replacement gate process for fabricating deep sub-100 nm gate length GaAs metal-oxide-semiconductor field-effect transistors

X. Li, S. Bentley, H. McLelland, M. C. Holland, H. Zhou, S. Thoms, D. S. Macintyre, and I. G. Thayne

J. Vac. Sci. Technol. B 28, C6L1 (2010); http://dx.doi.org/10.1116/1.3501355 (5 pages)

Online Publication Date: 22 October 2010

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This article describes a process flow which has enabled the first demonstration of functional, fully self-aligned, 40 nm gate length replacement gate enhancement mode GaAs metal-oxide-semiconductor field-effect transistors (MOSFETs) with GaxGdyOz as high-κ dielectric, Pt/Au metal gate stack, and SiN sidewall spacers. The flow uses blanket metal and dielectric deposition and low damage dry etch modules. As a consequence, no critical dimension lift-off processes are required. As a gate replacement approach has been developed, the process is suitable for easily incorporating different gate metals, opening the way to work function engineering to control threshold voltage and so is a significant step forward to the demonstration of high performance “siliconlike” III-V MOSFETs.
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85.30.Tv Field effect devices

Platinum single-electron transistors with tunnel barriers made by atomic layer deposition

Hubert C. George, Alexei O. Orlov, and Gregory L. Snider

J. Vac. Sci. Technol. B 28, C6L6 (2010); http://dx.doi.org/10.1116/1.3511432 (3 pages)

Online Publication Date: 5 November 2010

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The fabrication and measurements of platinum single-electron transistors (SETs) employing high quality insulating barriers produced by atomic layer deposition (ALD) of alumina (Al2O3) are reported. The G-Vds, Coulomb blockade oscillations, and the charging diagram of the SET at 300 mK were successfully measured. The ALD technique provides atomic accuracy and precise control of the tunnel barriers and greatly expands the choice of materials suitable for SET fabrication (both electrodes and island materials as well as barrier dielectrics). This fabrication method is targeted toward large scale production of SETs, which will accelerate their adoption into practical applications.
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85.35.Gv Single electron devices
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Si single electron transistor fabricated by chemical mechanical polishing

Yen-Chun Lee, Vishwanath Joshi, Alexei O. Orlov, and Gregory L. Snider

J. Vac. Sci. Technol. B 28, C6L9 (2010); http://dx.doi.org/10.1116/1.3498748 (5 pages) | Cited 1 time

Online Publication Date: 5 November 2010

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The authors report the results of a novel single electron transistor (SET) fabrication technique that combines the unique advantages of chemical mechanical polishing and the versatility and scalability of silicon processing. A thin ( ∼ 15 nm) line of degenerately doped silicon on insulator is embedded in a planarized plasma enhanced chemical vapor deposition oxide through nanoencapsulation. A pit in this line is formed by a highly selective silicon dry etch, and the tunnel oxide is grown on the sidewalls of the pit using rapid thermal oxidation. Degenerately doped amorphous silicon is deposited into the pit to form the SET island, the overburden of silicon is removed, and the structure is thinned down by chemical mechanical polishing. The SET’s charging diagram indicates a charging energy of around 20 meV, credited to its small tunnel junction size as well as possible “puddle” formation from the dopant distribution within the island and the leads. The observed anomalies, such as missing and split diamonds in the charging plots and random telegraph signals, suggest that the donor sites play an important role in the device operation. Several fabricated SETs show a similar Coulomb blockade at 4 K, demonstrating reasonable yield for the process.
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85.35.Gv Single electron devices
81.65.Ps Polishing, grinding, surface finishing
73.23.Hk Coulomb blockade; single-electron tunneling
back to top Nanoimprint

Aspects of hybrid pattern definition while combining thermal nanoimprint with optical lithography

H.-C. Scheer, S. Möllenbeck, A. Mayer, and K. Dhima

J. Vac. Sci. Technol. B 28, C6M1 (2010); http://dx.doi.org/10.1116/1.3498750 (6 pages) | Cited 2 times

Online Publication Date: 19 October 2010

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Thermal nanoimprint (T-NIL) is uniquely suitable for combinational lithography because it proceeds without cross-linking and does not rely on changes in properties of the imprint material. Most typical are combinations with other lithography techniques. Combinations with optical lithography may help to circumvent the pattern size dependence of nanoimprint and help to remove the residual layer by a simple development step. This work focuses on a hybrid processing combining T-NIL with optical lithography by using a single resist layer. Critical issues are the imprintability of typical photoresists and the fact that lithography has to be performed over a prepatterned topography. A well-known positive tone photoresist, AZ 1500, is compared with a previously investigated negative tone resist, SU-8. Gel permeation chromatography reveals typical differences of these photoresists compared to typical imprint polymers. The results demonstrate that molecular mobility is a more important indicator for viscosity of photoresists than molecular weight. Additionally, a simple construction method was found to allow prediction of features typically encountered during hybrid patterning.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

Defect analysis for patterned media

Zhengmao Ye, John Fretwell, Kang Luo, Steven Ha, Gerard Schmid, Dwayne LaBrake, Douglas J. Resnick, and S. V. Sreenivasan

J. Vac. Sci. Technol. B 28, C6M7 (2010); http://dx.doi.org/10.1116/1.3498752 (5 pages) | Cited 2 times

Online Publication Date: 19 October 2010

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Imprint lithography has been shown to be an effective technique for the replication of nanoscale features. Acceptance of imprint lithography for manufacturing will require a demonstration of defect levels commensurate with cost-effective device production. This article summarizes the results of defect inspections of hard disks patterned using jet and flash imprint lithography (J-FIL™). This work presents a methodology for automated pattern inspection and defect classification for imprint-patterned media. Candela CS20 and 6120 tools from KLA-Tencor map the optical properties of the disk surface, producing high-resolution grayscale images of surface reflectivity and scattered light. Defects that have been identified in this manner are further characterized according to the morphology. The imprint process was tested after optimizing both the disk cleaning and adhesion layer processes that precede imprinting. Two extended imprint runs were performed and both the defect types and trends are reported.
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85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)

45 nm hp line/space patterning into a thin spin coat film by UV nanoimprint based on condensation

Hiroshi Hiroshima, Qing Wang, and Sung-Won Youn

J. Vac. Sci. Technol. B 28, C6M12 (2010); http://dx.doi.org/10.1116/1.3507882 (5 pages) | Cited 2 times

Online Publication Date: 8 November 2010

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Applicability of UV nanoimprint based on gas condensation to 45 nm line and space (L/S) patterning using a spin-coat UV curable resin was evaluated. Although high capillary pressure is generated in such fine L/S patterns when UV curable resin liquid comes in contact with the groove surface, the trapped air in those grooves is not completely compressed and results in the formation of bubble defects. Bubbles much larger than the pattern size were generated at the middle of the L/S patterns for a 108 nm thick, UV curable resin film, and incomplete filling may occur on a large area of the L/S patterns for a 19 nm thick film. Since nearly bubble-free L/S patterns have been fabricated for 48 nm thick, UV curable resin film, it might be possible to make bubble-free UV nanoimprint by prolonging the imprinting time. On the contrary, when UV nanoimprint was carried out in pentafluoropropane (PFP), no bubbles were created for all thicknesses of the UV curable resin films. Uniformity of residual layer looked quite good judging from the color uniformity of the area around the L/S patterns. It was found, from the residual layer measurement by a reflective thickness monitor, that bubble-free UV nanoimprint was carried out with a residual layer thickness of 15.2 nm. UV nanoimprinted samples were inspected with a scanning electron microscope and it was verified that UV nanoimprint using PFP is viable for the fabrication 45 nm L/S patterns.
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81.16.Rf Micro- and nanoscale pattern formation
81.16.Nd Micro- and nanolithography
68.60.Wm Other nonelectronic physical properties
68.55.jd Thickness
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Evaluation of oxygen inhibition for UV-curable resins by adhesion force measurement using scanning probe microscope

Makoto Okada, Masayuki Iwasa, Hiroto Miyake, Takeshi Ohsaki, Yuichi Haruyama, Kazuhiro Kanda, and Shinji Matsui

J. Vac. Sci. Technol. B 28, C6M17 (2010); http://dx.doi.org/10.1116/1.3517511 (6 pages)

Online Publication Date: 30 November 2010

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UV nanoimprint lithography is used to fabricate nanostructure devices with high throughput, low cost, and high resolution. UV-curable resins are one important factor in UV nanoimprinting and they are mainly categorized into two reaction types: radical and cationic curing systems. A drawback of the radical curing system is curing inhibition by oxygen. To evaluate the oxygen inhibition for UV-curable resins, the authors measured the force curve transition by scanning probe microscopy with an UV irradiation system. With this system, the authors are able to measure in situ the UV dose dependence of the force curve transition on the same UV-curable resin. Measurements showed that the curing speed of radical UV-curable resin in vacuum became 800 times higher than that in air due to oxygen inhibition. Furthermore, for a cationic UV-curable resin, although the curing reaction of a cationic UV-curable resin is not affected by oxygen, the authors observed that the curing speed in vacuum at about 15 Pa became 4.5 times higher compared to that in air. The curing reaction of a cationic UV-curable resin may be inhibited by alkali.
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81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer

Assessment of release properties in UV nanoimprint lithography using high-aspect-ratio nanoscale molds

Junki Takahashi, Jun Taniguchi, and Yasuhiro Kamiya

J. Vac. Sci. Technol. B 28, C6M23 (2010); http://dx.doi.org/10.1116/1.3503896 (5 pages)

Online Publication Date: 30 November 2010

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Ultraviolet nanoimprint lithography (UV-NIL) is a potentially powerful tool for nanofabrication. However, the strong force required during the release step degrades the release coating layer, which leads to defects in pattern replication and eventual breakage of the mold. Therefore, optimal conditions for release coating are required. In addition, the recommended 1000 imprints for assessing the release properties in UV-NIL are extremely time consuming. The authors believed that the durability of the release layer could be varied by using a mold with a large surface area and previously fabricated such a mold to successfully transfer a high-aspect-ratio (>15) nanoscale pattern. In the present study, the authors used this method to investigate the optimal conditions for release coating and to assess the release properties in UV-NIL according to the measured release force and number of replication times. As a result, the conditions for release coating were optimized as follows: dipping time of 24 h, postrinsing bake temperature of 100 °C, and baking time of 3 min in a high-aspect-ratio mold with a 1300 nm pattern height. Low release force led to extended lifetime of the release coating layer in an accelerated durability test using a large-surface-area mold.
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81.16.Nd Micro- and nanolithography
81.15.Dj E-beam and hot filament evaporation deposition
85.40.Hp Lithography, masks and pattern transfer

Characterizations of nanoembossed Pb(Zr0.3,Ti0.7)O3 ferroelectric films

Zhenkui Shen, Zhihui Chen, Qian Lu, Anquan Jiang, Zhijun Qiu, Xinping Qu, Yifang Chen, and Ran Liu

J. Vac. Sci. Technol. B 28, C6M28 (2010); http://dx.doi.org/10.1116/1.3497018 (4 pages) | Cited 1 time

Online Publication Date: 30 November 2010

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Ferroelectric thin films may find potential applications in a broad range of ferroelectronic devices such as mass-storage memories. In this article, arrays of Pb(Zr0.3,Ti0.7)O3 (PZT) ferroelectric cells with minimum lateral size down to 500 nm were fabricated by nanoembossing technique. Structural characterizations of embossed PZT film were carried out by Raman spectroscopy and x-ray diffraction. Ferroelectronic properties of embossed PZT film were investigated by using piezoresponse force microscopy and Radiant Technologies precision material analyzer. Excellent ferroelectric and piezoelectric characteristics observed in the embossed PZT films suggest that the nanoembossing process proposed in this article is promising to become a new manufacturing approach for high density PZT based memory devices at significantly lower cost than the existing technique.
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77.84.Cg PZT ceramics and other titanates
81.07.Bc Nanocrystalline materials
81.16.-c Methods of micro- and nanofabrication and processing
78.30.Hv Other nonmetallic inorganics
77.55.H- Piezoelectric and electrostrictive films
77.80.-e Ferroelectricity and antiferroelectricity

Electrical properties of transferred metal nanopattern using metal oxide release layer

Noriyuki Unno, Jun Taniguchi, and Shouichi Ide

J. Vac. Sci. Technol. B 28, C6M32 (2010); http://dx.doi.org/10.1116/1.3501352 (5 pages)

Online Publication Date: 30 November 2010

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There is a growing demand for fine metal patterning techniques for the fabrication of next-generation devices such as patterned media, plasmon photonic devices, and nanoscale electrodes. Moreover, plastic substrate has become increasingly popular due to its many advantages that include transparency, flexibility, lightness, and low cost. The authors have developed a technique for transferring three-dimensional metal patterns onto poly(ethylene terephthalate) (PET) substrate by nanoimprint lithography using a metal oxide release layer. In this study, the authors examined the transfer characteristics of gold with a chromium oxide layer. The authors also studied the electrical properties of the transferred gold layer. The results revealed that the release force during the transfer process is independent of the thickness of the chromium oxide release layer and a higher temperature causes a larger release force. Furthermore, the obtained nanogap gold pattern on the PET substrate has low resistivity and can be applied to a nanoscale electrode.
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81.07.Bc Nanocrystalline materials
81.16.Rf Micro- and nanoscale pattern formation

Fabrication of mesas with micro- and nanopatterned surface relief used as working stamps for step and stamp imprint lithography

Arne Schleunitz, Christian Spreu, Tomi Haatainen, Anna Klukowska, and Helmut Schift

J. Vac. Sci. Technol. B 28, C6M37 (2010); http://dx.doi.org/10.1116/1.3497022 (4 pages)

Online Publication Date: 30 November 2010

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A manufacturing concept to fabricate working stamps with defined mesa structures using combined nanoimprint and photolithography is presented. OrmoStamp, an UV-curable organic-inorganic hybrid polymer, was used as mold material. 30 μm high large mesa structures (4×4 mm2) with sharp borders and almost vertical sidewalls were manufactured. On top they featured nanograting patterns with 200 nm height and lateral size as a surface relief. The good thermal decoupling of stamp body and imprinted substrate and the high planarity (divergence <50 nm) make the stamp very suitable for thermal step and repeat nanoimprint lithography of confined patterns with low stitching errors. Up to 210 imprints were performed with a single mesa into a 325 nm thin layer of mr-I 7030E.
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81.16.Rf Micro- and nanoscale pattern formation
81.16.Nd Micro- and nanolithography

Fabrication of ordered nanospheres using a combination of nanoimprint lithography and controlled dewetting

Arne Schleunitz, Christian Spreu, JaeJong Lee, and Helmut Schift

J. Vac. Sci. Technol. B 28, C6M41 (2010); http://dx.doi.org/10.1116/1.3498762 (4 pages)

Online Publication Date: 30 November 2010

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Arrays with hemispherical dots were produced from nanoimprinted line structures by thermal reflow and coagulation. By adding local nodes into 100 nm wide line cavities of the nanoimprint stamp, the coagulation was controlled and a self-ordered, highly regular dot matrix with almost totally dewetted lines was obtained. The forming of dots of almost equal sizes and distances along the line’s location shows that this coagulation effect is probably only restricted by geometry and surface energy. Simple resist preforms can be transformed into a more complex pattern by thermal-postprocessing in a controlled way.
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81.16.Nd Micro- and nanolithography
68.08.Bc Wetting
82.70.-y Disperse systems; complex fluids
61.46.-w Structure of nanoscale materials

Fabrication of seamless three-dimensional roll mold using direct electron-beam writing on rotating cylindrical substrate

Jun Taniguchi, Shintaro Tsuji, and Masao Aratani

J. Vac. Sci. Technol. B 28, C6M45 (2010); http://dx.doi.org/10.1116/1.3511474 (5 pages) | Cited 1 time

Online Publication Date: 1 December 2010

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A three-dimensional (3D) seamless roll mold is difficult to fabricate because of its cylindrical shape. However, seamless 3D nanoscale patterns are in great demand for optical film applications and printed electronics. The authors have therefore developed a method for producing a 3D seamless roll mold by direct electron-beam (EB) writing onto a layer of resist material coated on a cylindrical substrate that is rotating in a vacuum. In addition, the 3D shape is produced by using the EB dose change method and the controlled-acceleration-voltage electron beam lithography (CAV-EBL) method developed by the authors. In the case of the EB dose change method, hydrogen silsesquioxane (HSQ), which is a negative-type EB resist, was used for the 3D roll mold. In the case of CAV-EBL, spin on glass, which is a positive-type EB resist, was used for the 3D roll mold. As a result, the developed HSQ height can be controlled by changing the EB dose; however, the dose change also causes a line width change. On the other hand, in the CAV-EBL method, the EB dose and acceleration voltage can be used to control the line width and depth independently; therefore, this method can successfully fabricate the coveted 3D roll mold.
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85.40.Hp Lithography, masks and pattern transfer

Facile wide-scale defect detection of UV-nanoimprinted resist patterns by fluorescent microscopy

Kei Kobayashi, Shoichi Kubo, Shinji Matsui, and Masaru Nakagawa

J. Vac. Sci. Technol. B 28, C6M50 (2010); http://dx.doi.org/10.1116/1.3507440 (7 pages)

Online Publication Date: 1 December 2010

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The occurrence of resist pattern defects in UV nanoimprinting with a spincoated resin thin film on a silicon wafer was studied by fluorescent microscopy using a fluorescent UV-curable liquid resin causing radical photopolymerization. The generation of nonfill defects with a surface-modified silica mold with submicrometer line cavities was compared between UV nanoimprinting atmospheres of air and pentafluoropropane. It was visualized in a rapid and nondestructive manner that nonfill defects were hardly induced by UV nanoimprinting under easily condensable pentafluoropropane atmosphere, while nonfill defects owing to bubble trap and resin adhesion to a mold surface were observed in the case of UV nanoimprinting under air atmosphere. The fluorescent microscopy using the fluorescent UV-curable resin was useful for mold inspection whether or not the submicrometer-scale mold cavities were partially filled with the resin. To investigate a resolution limit to nonfill defect, the authors examined a pattern pitch and a space width for convex resist line patterns in the line width range of 80–3000 nm with various ratios of space width to line width. Linear analysis of fluorescence intensity using fluorescent microscope images revealed that line pattern pitches with a space width of 0.30 μm could be detected by fluorescent microscopy. The 0.30 μm space width was almost consistent with a value calculated according to a Sparrow resolution limit.
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81.16.Nd Micro- and nanolithography
82.35.-x Polymers: properties; reactions; polymerization
81.16.Rf Micro- and nanoscale pattern formation

High accuracy UV-nanoimprint lithography step-and-repeat master stamp fabrication for wafer level camera application

G. Kreindl, T. Glinsner, R. Miller, D. Treiblmayr, and R. Födisch

J. Vac. Sci. Technol. B 28, C6M57 (2010); http://dx.doi.org/10.1116/1.3518914 (6 pages)

Online Publication Date: 1 December 2010

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Herein, the authors demonstrate the use of step-and-repeat nanoimprint lithography for the fabrication of wafer level lens master. Thereby, the authors will focus on so far unmet needs in regard to lateral lens to lens positioning, residual layer uniformities, as well as optic axis tilt control to enable the fabrication of high-end megapixel camera modules.
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81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
42.82.Cr Fabrication techniques; lithography, pattern transfer

Hole mobility enhancement by chain alignment in nanoimprinted poly(3-hexylthiophene) nanogratings for organic electronics

Min Zhou, Mukti Aryal, Kamil Mielczarek, Anvar Zakhidov, and Walter Hu

J. Vac. Sci. Technol. B 28, C6M63 (2010); http://dx.doi.org/10.1116/1.3501343 (5 pages)

Online Publication Date: 1 December 2010

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The authors report that the poly(3-hexylthiophene-2,5-diyl) (P3HT) nanogratings shaped by nanoimprint lithography show enhanced hole mobility and strong anisotropy of conductance due to nanoimprint-induced three-dimensional polymer chain alignment. Field effect transistors were fabricated using these nanogratings and device measurements show a hole mobility of 0.03 cm2/V s along the grating direction, which is about 60 times higher than that of nonoptimized thin film transistors. Organic photovoltaic devices (OPV) were made using the P3HT nanograting with infiltration of [6,6]-phenyl-C61-butyric acid methyl ester. Compared to similar bilayer and bulk heterojunction devices, the nanoimprinted OPV shows improved device performance.
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85.30.Tv Field effect devices
85.35.-p Nanoelectronic devices
88.40.jr Organic photovoltaics
88.40.H- Solar cells (photovoltaics)
85.40.Hp Lithography, masks and pattern transfer

Impact of molecular size on resist filling process in nanoimprint lithography: Molecular dynamics study

Akihiro Taga, Masaaki Yasuda, Hiroaki Kawata, and Yoshihiko Hirai

J. Vac. Sci. Technol. B 28, C6M68 (2010); http://dx.doi.org/10.1116/1.3511434 (4 pages) | Cited 1 time

Online Publication Date: 1 December 2010

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The molecular size effects on resist filling process in nanoimprint lithography are studied by molecular dynamics simulation. Poly(methyl methacrylate) is selected as a resist model. The press force required to fill the resist into the mold cavity is calculated by the simulation. The press force increases with decreasing mold cavity size. When the cavity size goes below the molecular size of the resist polymer chain, the required press force increases sharply. This polymer size effect is not seen in the continuum mechanics simulation. The mold sidewall roughness effect on required press force also depends on the polymer size in molecular dynamics simulation.
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81.16.Nd Micro- and nanolithography
61.43.Bn Structural modeling: serial-addition models, computer simulation
68.35.bm Polymers, organics

Impact of the resist properties on the antisticking layer degradation in UV nanoimprint lithography

A. Francone, C. Iojoiu, C. Poulain, C. Lombard, B. Pépin-Donat, J. Boussey, and M. Zelsmann

J. Vac. Sci. Technol. B 28, C6M72 (2010); http://dx.doi.org/10.1116/1.3501339 (5 pages) | Cited 1 time

Online Publication Date: 1 December 2010

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In this work, the authors evaluate the impact of chemical and mechanical properties of UV nanoimprint lithography resists on the durability of antisticking treatments applied on the quartz mold surface. To do this, three acrylate-based resists were formulated and characterized. Fourier transform infrared spectroscopy was used to investigate the degree of conversion of each formulation as a function of the exposure dose and electron spin resonance was used to investigate the chemical reactivity of each formulation with respect to a fluorinated antisticking layer (Optool DSX from Daikin Chemicals). The impact of resist mechanical properties on the mold surface treatment degradation was also studied. Elastic modulus and hardness were measured by nanoindentation as a function of the polymerization degree. Then, these resists were imprinted with a dummy quartz template treated beforehand with the antisticking layer. The release properties of the molds were monitored by measuring their free surface energy as a function of the chemical and mechanical properties of the imprinted resists. A detailed comparative study has shown that release properties degradation is more governed by a mechanical than by a chemical interaction.
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81.16.Nd Micro- and nanolithography
78.30.Jw Organic compounds, polymers
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.de Elastic moduli
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
62.20.Qp Friction, tribology, and hardness

Impact of substrate deformation on demolding force for thermal imprint process

H. Kawata, Y. Watanabe, N. Fujikawa, M. Yasuda, and Y. Hirai

J. Vac. Sci. Technol. B 28, C6M77 (2010); http://dx.doi.org/10.1116/1.3517537 (6 pages) | Cited 1 time

Online Publication Date: 1 December 2010

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The impact of deformation on the demolding force is investigated both experimentally and by simulation for the thermal imprint process. The effects of substrate thickness are the focus of this article. In experiments, one mold is used throughout all experiments in order to exclude any effects of the mold fabrication process. The mold pattern is transferred to a polymethylmethacrylate (PMMA) film by the thermal imprint. The PMMA surface height is measured by a commercial height profiler after the imprint, and it agrees with lateral variations in residual layer thickness. Demolding force increases as substrate thickness increases. Substrate deformation is simulated by simplifying a model to assume the presence of large cavities. Substrate deformation in the simulation agrees with the PMMA surface height profile in the experiment. The normal force to the PMMA side wall by the mold pattern is important for estimating the demolding force. Since the normal force during the pressing process is simulated, the normal force is induced by both the lateral expansion of PMMA resin and substrate deformation. The normal force from substrate deformation is selected based on a detailed analysis of the simulated normal force. The obtained normal force agrees with the demolding force in the experiment.
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81.10.Fq Growth from melts; zone melting and refining
89.20.Kk Engineering
42.82.Cr Fabrication techniques; lithography, pattern transfer
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer

Imprinted quarter wave plate at terahertz frequency

Shimul C. Saha, Yong Ma, James P. Grant, A. Khalid, and David R. S. Cumming

J. Vac. Sci. Technol. B 28, C6M83 (2010); http://dx.doi.org/10.1116/1.3497023 (5 pages)

Online Publication Date: 1 December 2010

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The authors have imprinted high aspect ratio artificial dielectric quarter wave plates (QWPs) on polymers for use at 2.6, 3.2, and 3.8 THz. The QWPs are imprinted on high density polyethylene using silicon masters. The grating period for the quarter wave plates is 60 μm. Deep gratings of 330, 280, and 230 μm are used to obtain a π/2 phase retardance between TE and TM polarizations propagating through the QWPs. An inductively coupled plasma etch process was used to create the silicon masters for the imprint. A combination of heat and pressure was used for the imprinting process. Two plates, fixed in a back-to-back configuration, were used for each QWP. A highest aspect ratio (grating height/grating width) of 7 was obtained using the imprint technology.
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42.79.Ci Filters, zone plates, and polarizers
42.79.Dj Gratings
52.77.Bn Etching and cleaning
42.25.Ja Polarization
42.25.Lc Birefringence

Long-range ordered aluminum oxide nanotubes by nanoimprint-assisted aluminum film surface engineering

Kunbae Noh, Chulmin Choi, Jin-Yeol Kim, Young Oh, Karla S. Brammer, Mariana C. Loya, and Sungho Jin

J. Vac. Sci. Technol. B 28, C6M88 (2010); http://dx.doi.org/10.1116/1.3498759 (5 pages) | Cited 1 time

Online Publication Date: 1 December 2010

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The authors present successful fabrications of hexagonally ordered and vertically aligned anodic aluminum oxide (AAO) nanotube array patterns over a large area (at least ∼ 6×6 mm2) by utilizing nanoimprint-guided anodization on sputter deposited Al thin films. Perfectly periodic nanotube arrays with no domain boundaries are obtained. Nanoindented patterns comprising hexagonal pillar arrays having a periodically absent pillar in the center of each hexagon were pattern transferred onto a poly(methyl methacrylate) coated Al film surface via reactive ion etch (RIE) followed by a subsequent guided anodization to produce long-range ordered vertical pore arrays. Upon further anodization, a self-assembled extra pore was formed in the center of each hexagon in addition to the regular pores formed at the impression location, thus leading to a pattern increase by 50%. Interestingly, it is seen that the resultant AAO structure can be altered via RIE process time duration, i.e., Al surface topographic modification prior to anodization. Similarly, a pattern-tripling phenomenon was observed when a triangular-patterned nanoimprint stamp was used by producing self-assembled central pores in the center of all triangles as well as guided pores at the impressed location, thus increasing the total number of pores by a factor of 3.
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81.07.De Nanotubes
61.46.Fg Nanotubes
81.65.Cf Surface cleaning, etching, patterning
81.16.Dn Self-assembly

Nanofabrication of surface-enhanced Raman scattering device by an integrated block-copolymer and nanoimprint lithography method

E. L. Yang, C. C. Liu, C. Y. P. Yang, C. A. Steinhaus, P. F. Nealey, and J. L. Skinner

J. Vac. Sci. Technol. B 28, C6M93 (2010); http://dx.doi.org/10.1116/1.3501341 (5 pages) | Cited 1 time

Online Publication Date: 1 December 2010

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The integration of block-copolymers (BCPs) and nanoimprint lithography (NIL) presents a novel and cost-effective approach to achieving nanoscale patterning capabilities. The authors demonstrate the fabrication of a surface-enhanced Raman scattering device using templates created by the BCP-NIL integrated method. The method utilizes a poly(styrene-block-methyl methacrylate) cylindrical-forming diblock-copolymer as a masking material to create a Si template, which is then used to perform a thermal imprint of a poly(methyl methacrylate) (PMMA) layer on a Si substrate. Au with a Cr adhesion layer was evaporated onto the patterned PMMA and the subsequent lift-off resulted in an array of nanodots. Raman spectra collected for samples of R6G on Si substrates with and without patterned nanodots showed enhancement of peak intensities due to the presence of the nanodot array. The demonstrated BCP-NIL fabrication method shows promise for cost-effective nanoscale fabrication of plasmonic and nanoelectronic devices.
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81.16.Nd Micro- and nanolithography
81.16.Rf Micro- and nanoscale pattern formation
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
85.40.Hp Lithography, masks and pattern transfer
78.30.Jw Organic compounds, polymers

Nanoimprinting for diffractive light trapping in solar cells

Dirk N. Weiss, Hao-Chih Yuan, Benjamin G. Lee, Howard M. Branz, Stephen T. Meyers, Andrew Grenville, and Douglas A. Keszler

J. Vac. Sci. Technol. B 28, C6M98 (2010); http://dx.doi.org/10.1116/1.3498754 (6 pages) | Cited 2 times

Online Publication Date: 1 December 2010

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The authors investigate the light-trapping efficiency of nanoimprinted ceramic grating reflectors for crystal silicon photovoltaic cells. Using 25 μm silicon wafers as a model system and hemispherical reflection measurements, they demonstrate a 4%–6% increase in AM 1.5 solar-photon absorption for one-dimensional square and sinusoidal gratings compared to flat reflectors. The extrapolated increase in a short-circuit current for a 2 μm thick silicon film cell due to diffractive light trapping is 20%.
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88.40.jj Silicon solar cells
88.40.H- Solar cells (photovoltaics)
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
81.16.Ta Atom manipulation

Nanoimprinted P3HT/C60 solar cells optimized by oblique deposition of C60

Yi Yang, Mukti Aryal, Kamil Mielczarek, Walter Hu, and Anvar Zakhidov

J. Vac. Sci. Technol. B 28, C6M104 (2010); http://dx.doi.org/10.1116/1.3517513 (4 pages)

Online Publication Date: 1 December 2010

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Poly(3-hexylthiophene) (P3HT)-C60 organic photovoltaic devices with interpenetrating donor-acceptor interfaces were fabricated by oblique thermal deposition of C60 into the P3HT nanogratings. The uniformity and step coverage of C60 infiltration into the P3HT nanostructures, which can determine the device performance, were dependent on the C60 evaporation angle. It was also observed that the C60 deposition rate and thickness determine the efficiency. A 50% improvement in power conversion efficiency is observed due to the increased exciton dissociation rate at the larger area P3HT-C60 interface at optimal C60 deposition filling. With the proposed technique, a highly efficient organic solar cell using an insoluble acceptor has been fabricated.
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88.40.hj Efficiency and performance of solar cells
81.16.Nd Micro- and nanolithography
85.65.+h Molecular electronic devices

Process-simulation system for UV-nanoimprint lithography

Mayuko Shibata, Akira Horiba, Yoshinori Nagaoka, Hiroaki Kawata, Masaaki Yasuda, and Yoshihiko Hirai

J. Vac. Sci. Technol. B 28, C6M108 (2010); http://dx.doi.org/10.1116/1.3511789 (6 pages) | Cited 1 time

Online Publication Date: 1 December 2010

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Process-simulation systems for ultraviolet (UV) nanoimprint lithography are newly proposed to investigate process physics and resist profiles. The system consists of four modules, which simulate fluid dynamics in the resist-filling process into a pattern, the optical-intensity distribution in the UV exposure process, the mechanical properties in UV curing, and the resist profiles by UV shrinkage. Each module is independent, but shares physical parameters and resist profiles. Simulations on resist profiles by the UV curing process are demonstrated, taking the optical-intensity distribution into account. Also, a database model is newly introduced to simulate the resist profile due to shrinkage by UV curing.
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81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
82.35.-x Polymers: properties; reactions; polymerization
47.10.ad Navier-Stokes equations

Rapid patterning of spin-on-glass using ultrasonic nanoimprint

Harutaka Mekaru and Masaharu Takahashi

J. Vac. Sci. Technol. B 28, C6M114 (2010); http://dx.doi.org/10.1116/1.3501361 (8 pages)

Online Publication Date: 1 December 2010

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The authors succeeded in room-temperature patterning on a spin-on-glass (SOG) coated Si substrate by an ultrasonic nanoimprinting in a short duration of 1 min. Typically, at a room-temperature it takes a large press pressure and a long contact time to nanoimprint without a thermal pretreatment. In our ultrasonic nanoimprinting, a mold is attached directly to an ultrasonic generator, and mold patterns are set in motion at a high-speed in a direction aligned with the direction of the contact force applied. By this movement of mold patterns, plastic deformation and thermal deformation caused by the initial pressure and frictional heat generated by the ultrasonic vibration are combined to achieve precise structures. The authors had already confirmed the assisting effect of ultrasonic vibration at room-temperature nanoimprinting on various engineering plastics and baked SOG without any heating of mold. They then experimented to apply the ultrasonic nanoimprint method on nonbaked SOG coated substrates. They prepared an organic SOG and an inorganic SOG as molding materials, and executed ultrasonic nanoimprinting under various experimental conditions based on the optimized conditions for polyethylene terephthalate (frequency of ultrasonic vibration = 10 kHz, contact force = 500 N, and contact time = 60 s). Moreover, the relationship between the amplitude of ultrasonic vibration and the imprinted depth was investigated, and the influence that the ultrasonic vibration exerted on the transfer accuracy of mold patterns was also determined.
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81.16.Nd Micro- and nanolithography
81.16.Rf Micro- and nanoscale pattern formation
81.40.Lm Deformation, plasticity, and creep
62.20.fq Plasticity and superplasticity
62.65.+k Acoustical properties of solids
81.05.Kf Glasses (including metallic glasses)

Rapid thermal imprinting of high-aspect-ratio nanostructures with dynamic heating of mold surface

Keisuke Nagato, Shuntaro Hattori, Tetsuya Hamaguchi, and Masayuki Nakao

J. Vac. Sci. Technol. B 28, C6M122 (2010); http://dx.doi.org/10.1116/1.3517608 (3 pages) | Cited 1 time

Online Publication Date: 1 December 2010

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High-aspect-ratio nanostructures are thermally imprinted with dynamic heating of the mold surface. A thin-film current heater located at the back of the mold realized rapid heating, and an upper punch and a heater substrate as coolants make the cooling time short. This heater is applied to stamping-type imprinting and injection molding. The authors demonstrated imprinting nanostructures with aspect ratios of 2–3 in the cycle time of 15 s. This equipment concept is practical for high-throughput and low-energy thermal nanoimprinting.
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81.16.Nd Micro- and nanolithography
81.40.Gh Other heat and thermomechanical treatments

Residual layer uniformity using complementary patterns to compensate for pattern density variation in UV nanoimprint lithography

Qing Wang, Hiroshi Hiroshima, Hidemasa Atobe, and Sung-Won Youn

J. Vac. Sci. Technol. B 28, C6M125 (2010); http://dx.doi.org/10.1116/1.3497015 (5 pages) | Cited 1 time

Online Publication Date: 1 December 2010

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How to form a thin and uniform residual layer, which is difficult to be created for a feature with nonuniform pattern densities, is of critical importance in nanoimprint lithography since residual layer removal by a reactive ion etching process will result in poor pattern transfer fidelity for nonuniform residual layers. A capacity-equalized mold using complementary cavity patterns to balance the imprinted volume of the feature with pattern density variation was verified to be a good method against pattern density variation for producing a uniform residual layer. To obtain an insight into the validity of the capacity-equalized mold, the effects of the introduced complementary patterns for capacity equalization on the residual layer, at locations that were not only at a distance away from the introduced complementary patterns but also the ones that were very close to the introduced complementary patterns, were carefully studied. It was found that a capacity-equalized mold with even very coarse complementary patterns as large as 10 times the minimum width of original patterns could result in a good uniform residual layer. It showed that the residual layer thickness was mainly determined by the volume of the capacity of the pattern trench with varied depths per unit area, but not by the size of the complementary patterns. Furthermore, the local nonuniformity induced by the complementary patterns themselves was also studied. The authors found that this local nonuniformity had little influence on producing a uniform residual layer that contributed to the low viscosity of the UV-curable resin. The authors also found that the nonuniformity of the residual layer was produced even by using a capacity-equalized mold due to the presence of air bubbles.
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81.16.Nd Micro- and nanolithography

Spectroscopic ellipsometry optical critical dimension measurements of templates and imprinted resist for patterned magnetic media applications

Zhaoning Yu, Justin Hwu, Yongdong Liu, Zhenpeng Su, Henry Yang, Hongying Wang, Wei Hu, Yuan Xu, Nobuo Kurataka, Yautzong Hsu, Shifu Lee, Gene Gauzner, Kim Lee, and David Kuo

J. Vac. Sci. Technol. B 28, C6M130 (2010); http://dx.doi.org/10.1116/1.3507888 (6 pages) | Cited 1 time

Online Publication Date: 1 December 2010

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The authors have applied spectroscopic ellipsometry optical critical dimension (SE-OCD) measurement to grating templates and imprinted resist patterns with a pitch of 72.6 nm, corresponding to a track density of 350 ktpi (kilotracks per inch) for discreet track recording media. Their experiments indicate that SE-OCD is sensitive in detecting topography features in template profiles. The measurement of imprinted resist pattern is complicated by parameter correlation. Comparison of SE-OCD reported template and imprinted resist profiles can be used to study imprint pattern fidelity.
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81.16.Nd Micro- and nanolithography
81.16.Rf Micro- and nanoscale pattern formation

Sputtering with an etch-free lift-off in thermal nanoimprint lithography

Andre Mayer, Nicolas Bogdanski, Saskia Möllenbeck, Khalid Dhima, Marc Papenheim, and Hella-Christin Scheer

J. Vac. Sci. Technol. B 28, C6M136 (2010); http://dx.doi.org/10.1116/1.3507879 (4 pages)

Online Publication Date: 1 December 2010

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Two low-cost techniques suitable for large area processing are combined to define submicrometer metal structures, thermal nanoimprint lithography, and sputtering. With very low residual layers after thermal nanoimprint, as obtained under partial cavity filling conditions, it is possible to skip the etching step for residual layer removal before sputtering. As imprinted structures typically feature a positive sidewall angle, the authors investigate the morphology of sputtered layers on sloped sidewalls. Independent from inclination, the sputtered layers exhibit a columnar structure with only a slight taper, where the crystallites extend perpendicular to the substrate through the whole layer thickness. This structure allows penetration of the solvent, swelling of the polymer, and lifting of the top layer as long as the adhesion to the substrate within the contact area is sufficiently high, thus enabling successful lift-off.
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81.16.Nd Micro- and nanolithography
81.15.Cd Deposition by sputtering
68.55.A- Nucleation and growth
back to top Nanomechanics

Microelectromechanical systems for biomimetical applications

Rhonira Latif, Enrico Mastropaolo, Andy Bunting, Rebecca Cheung, Thomas Koickal, Alister Hamilton, Michael Newton, and Leslie Smith

J. Vac. Sci. Technol. B 28, C6N1 (2010); http://dx.doi.org/10.1116/1.3504892 (6 pages) | Cited 1 time

Online Publication Date: 10 November 2010

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An etch release process capable of releasing long resonant gate transistor bridges from a sacrificial layer has been studied as a step towards developing a system to mimic the cochlear mechanism inside the human ear. The developed etch release process involves the use of a gentle etch tool that is capable of a clean and damage-free etch release. The influence of temperature and oxygen/nitrogen gas flow rates on the undercut etch rates and the profiles of photoresist and polyimide sacrificial layers have been investigated. An array of aluminum bridges of length 0.278–1.618 mm, which cover the frequencies from 1 to 33.86 kHz, has been designed and released from a sacrificial layer. The resonating beams have been measured.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
85.30.Tv Field effect devices

Microfabricated resistive high-sensitivity nanoprobe for scanning thermal microscopy

G. Wielgoszewski, P. Sulecki, T. Gotszalk, P. Janus, D. Szmigiel, P. Grabiec, and E. Zschech

J. Vac. Sci. Technol. B 28, C6N7 (2010); http://dx.doi.org/10.1116/1.3502614 (5 pages)

Online Publication Date: 10 November 2010

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In this article, a novel microfabricated thermoresistive scanning thermal microscopy probe is presented. It is a V-shaped silicon nitride cantilever with platinum lines and a sharp off-plane nanotip. The cantilever fabrication sequence incorporates standard complementary metal oxide semiconductor technology processes and therefore provides high reproducibility, while the tip is additionally processed by focused ion beam, enabling high-sensitivity and high-resolution thermal sensing. The nanoprobe is designed for scanning thermal microscopes, operating in standard atomic force microscope setup with an optical detection system. The measurement setup, which is also presented, takes advantage of the four-point design of the probe by inclusion of a Thomson bridge and a modified Wheatstone bridge measurement electronics.
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81.07.Bc Nanocrystalline materials
66.30.Pa Diffusion in nanoscale solids
68.37.Ps Atomic force microscopy (AFM)

Micromachined scanning proximal probes with integrated piezoresistive readout and bimetal actuator for high eigenmode operation

Mirosław Woszczyna, Paweł Zawierucha, Piotr Pałetko, Michał Zielony, Teodor Gotszalk, Yanko Sarov, Tzvetan Ivanov, Andreas Frank, Jens-Peter Zöllner, and Ivo W. Rangelow

J. Vac. Sci. Technol. B 28, C6N12 (2010); http://dx.doi.org/10.1116/1.3518465 (6 pages)

Online Publication Date: 29 November 2010

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The fabrication process, application, and properties of a novel piezoresistive multiprobe with an integrated thermal tip deflection actuator are described in this article. The optimized fabrication process of the microprobe enables high-frequency sensor operation and integration of a high sharp conical tip, which was additionally covered with titanium using atomic layer deposition to improve mechanical endurance and ensure electrical conductivity. This microprobe was applied in high-resolution self-assembled monolayer surface investigations in which the piezoresistive cantilever with the integrated thermal deflection actuator was excited at two of its flexural-resonant eigenmodes. The excited second eigenmode and phase show different contrasts com-pared with images recorded at the first eigenmode.
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07.79.Lh Atomic force microscopes
68.37.Ps Atomic force microscopy (AFM)
81.16.Dn Self-assembly
81.20.Wk Machining, milling

Piezoelectrically driven silicon carbide resonators

Enrico Mastropaolo, Isaac Gual, Graham Wood, Andrew Bunting, and Rebecca Cheung

J. Vac. Sci. Technol. B 28, C6N18 (2010); http://dx.doi.org/10.1116/1.3498760 (6 pages)

Online Publication Date: 29 November 2010

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Silicon carbide cantilever beam resonators have been designed with top electrodes made of piezoelectric lead zirconium titanate (PZT). The devices have been simulated, fabricated, and tested. Piezoelectric actuation has been performed by applying an alternating actuation voltage to the PZT electrodes, thus inducing vertical displacements. The devices have been fabricated with a beam length of 150 and 200 μm, and driven into resonance at frequencies in the kilohertz range. The devices’ resonance has been detected by monitoring the impedance of the actuating electrode. Simulations and measurements have shown that the electrode length on top of the beam influences the magnitude of the deflection and the resonant frequency of the devices. Furthermore, the electrical feedthrough capacitance presented by the piezoelectric electrode has been observed to strongly influence the output impedance of the resonators. The obtained results show the importance of the electrode design for the optimization of the performance and reliability of piezoelectrically driven resonators.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
back to top Nanophotonics

On the fabrication of three-dimensional silicon-on-insulator based optical phased array for agile and large angle laser beam steering systems

Amir Hosseini, David Kwong, Yang Zhang, Saurabh A. Chandorkar, Filip Crnogorac, Andrew Carlson, Babak Fallah, Seth Bank, Emanuel Tutuc, John Rogers, R. Fabian W. Pease, and Ray T. Chen

J. Vac. Sci. Technol. B 28, C6O1 (2010); http://dx.doi.org/10.1116/1.3511508 (7 pages)

Online Publication Date: 9 November 2010

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In this article, the authors present and discuss the fabrication of three-dimensional (3D) optical phased array (OPA) devices for large angle, two-dimensional optical beam steering. Fabrication of a single layer (one-dimensional) OPA prototype for one-dimensional beam steering on silicon nanomembrane is presented. The authors present different approaches, such as nanoimprint lithography, optical lithography, and self-aligned patterning of multibonded silicon-on-insulator wafers, for the realization of 3D OPA devices in particular and 3D photonic circuits in general. At the end, the authors discuss the challenges and potential solutions.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
42.82.Et Waveguides, couplers, and arrays
81.16.Nd Micro- and nanolithography
81.16.Rf Micro- and nanoscale pattern formation

Tunable optofluidic nano-Bragg microcavity filter

A. S. Jugessur, J. Dou, and J. S. Aitchison

J. Vac. Sci. Technol. B 28, C6O8 (2010); http://dx.doi.org/10.1116/1.3498763 (3 pages)

Online Publication Date: 9 November 2010

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An optofluidic nano-Bragg microcavity filter is designed using three-dimensional finite difference time domain technique and fabricated using electron-beam lithography and reactive ion etching techniques on a silicon-on-insulator (SOI) material. Continuous filter tuning is possible via small refractive index changes by introducing different fluids. An index change of 0.03 corresponds to a peak resonance wavelength shift of approximately 1 nm. The SOI chip is also integrated with a polydimethlysiloxane microfluidic chip for the fluid delivery.
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42.79.Ci Filters, zone plates, and polarizers
47.85.Np Fluidics
81.65.Cf Surface cleaning, etching, patterning
85.40.Hp Lithography, masks and pattern transfer
42.82.Cr Fabrication techniques; lithography, pattern transfer
02.70.Bf Finite-difference methods

Colloidal optical waveguides with integrated local light sources built by capillary force assembly

O. Lecarme, T. Pinedo Rivera, L. Arbez, T. Honegger, K. Berton, and D. Peyrade

J. Vac. Sci. Technol. B 28, C6O11 (2010); http://dx.doi.org/10.1116/1.3503897 (5 pages) | Cited 2 times

Online Publication Date: 9 November 2010

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Colloidal waveguide fabrication based on the convective assisted capillary force assembly technique and their optical properties is presented in this work. A large variety in shape of colloidal waveguides is built with their own integrated local light sources. It is highlighted that these structures exhibit propagation of the visible light at the micrometric scale. Finally, the onset of the integration of a colloidal emitter on a classical photonic system is developed using a stamping method.
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42.82.Et Waveguides, couplers, and arrays
42.82.Cr Fabrication techniques; lithography, pattern transfer

Resonant coupling to a dipole absorber inside a metamaterial: Anticrossing of the negative index response

Svyatoslav Smolev, Zahyun Ku, S. R. J Brueck, Igal Brener, Michael B. Sinclair, Gregory A. Ten Eyck, W. L. Langston, and Lorena I. Basilio

J. Vac. Sci. Technol. B 28, C6O16 (2010); http://dx.doi.org/10.1116/1.3503898 (5 pages)

Online Publication Date: 9 November 2010

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The authors experimentally demonstrate a resonant hybridization between the magnetic dipole structural resonance in the permeability of a fishnet metamaterial and an electric dipole material resonance in the permittivity of the dielectric spacer layer. The hybrid resonances in the permeability and the negative index response exhibit an anticrossing behavior. A simple analytic model and numerical simulations using a rigorous coupled-wave analysis are in excellent qualitative agreement with the experiment.
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75.30.Cr Saturation moments and magnetic susceptibilities
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
02.60.-x Numerical approximation and analysis
77.22.Ch Permittivity (dielectric function)
42.70.-a Optical materials

Fabrication and characterization of coupled metal-dielectric-metal nanoantennas

Bhuwan Joshi, Xuejin Wen, Kai Sun, Wu Lu, and Qi-Huo Wei

J. Vac. Sci. Technol. B 28, C6O21 (2010); http://dx.doi.org/10.1116/1.3501349 (5 pages)

Online Publication Date: 10 November 2010

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The authors fabricated two dimensional arrays of metal-dielectric-metal nanoantennas consisting of a thin layer of light-emitting polymers sandwiched between two Ag parallel cuboids and characterized them by measuring the optical transmission through the antenna arrays. The measured transmission spectra show two resonant dips. Numerical simulations reproduce the experimental results and show that the left dip is due to a cavity resonance mode and the right dip is due to the absorption of the polymer. With this vertical antenna design, the dielectric gap can be made much smaller with an extremely small mode volume, making it a potential candidate for single molecule studies using surface enhanced Raman scattering and for various other optoelectronic applications.
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81.16.-c Methods of micro- and nanofabrication and processing
78.30.-j Infrared and Raman spectra
78.40.-q Absorption and reflection spectra: visible and ultraviolet
81.07.Bc Nanocrystalline materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters

Fabrication of nanostar arrays by nanoimprint lithography

Teodor Veres, Bo Cui, and Liviu Clime

J. Vac. Sci. Technol. B 28, C6O26 (2010); http://dx.doi.org/10.1116/1.3504890 (4 pages)

Online Publication Date: 10 November 2010

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Using a low-cost and high-throughput process, this work demonstrates the fabrication of nanostar arrays over a large surface area, which would be an efficient substrate for surface enhanced Raman scattering applications. In the method, the nanostar is defined by the gap between four nanoholes “touching” each other. The two-dimensional periodic hole array was fabricated by nanoimprint lithography, and then the array pattern was transferred into a polymer layer sandwiched between two hard mask layers. Next, the holes in the polymer layer were enlarged by oxygen reactive ion etching (RIE) until its diameter was equal to the array period. The nanostar array was formed in the bottom hard layer after RIE, or it can be further transferred into a noble metal layer by lift-off steps. The authors fabricated a nanostar array with 200 nm tip-tip distance (equal to array period) and down to sub-10-nm apex and gap between adjacent stars. Numerical simulation confirmed the great enhancement of electromagnetic field near the star apexes.
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81.16.Nd Micro- and nanolithography
52.77.Bn Etching and cleaning
78.30.-j Infrared and Raman spectra
81.07.Bc Nanocrystalline materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters

Fabrication techniques for three-dimensional metamaterials in the midinfrared

J. R. Wendt, D. B. Burckel, G. A. Ten Eyck, A. R. Ellis, I. Brener, and M. B. Sinclair

J. Vac. Sci. Technol. B 28, C6O30 (2010); http://dx.doi.org/10.1116/1.3504586 (4 pages) | Cited 1 time

Online Publication Date: 11 November 2010

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The authors have developed two versions of a flexible fabrication technique known as membrane projection lithography that can produce nearly arbitrary patterns in “2½ D” and fully three-dimensional (3D) structures. The authors have applied this new technique to the fabrication of split ring resonator-based metamaterials in the midinfrared. The technique utilizes electron beam lithography for resolution, pattern design flexibility, and alignment. The resulting structures are nearly three orders of magnitude smaller than equivalent microwave structures that were first used to demonstrate a negative index material. The fully 3D structures are highly isotropic and exhibit both electrically and magnetically excited resonances for incident transverse electromagnetic waves.
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84.40.Az Waveguides, transmission lines, striplines
81.16.Nd Micro- and nanolithography

Self-aligned gold nanocone probe tips

B. Zeeb, S. Jäger, C. Schäfer, P. Nill, A. J. Meixner, D. P. Kern, and M. Fleischer

J. Vac. Sci. Technol. B 28, C6O34 (2010); http://dx.doi.org/10.1116/1.3518461 (4 pages)

Online Publication Date: 29 November 2010

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Spatial resolution and optical near-field enhancement of scanning probes for apertureless near-field scanning optical microscopy depend strongly on the properties and geometry of the scanning probe. A new approach for very sharp probes with well-defined geometry based on gold nanocones is described and demonstrated on planar substrates. The fabrication involves a combination of thin-film deposition, electron beam lithography, and reactive ion etching or ion-milling, respectively. Well-defined gold nanocones with a tip radius of 10 nm and less on silica and bismuth pillars are obtained in a self-aligned process. The numerical simulations of the field distribution near the tip apex and the experimental verification via a photoluminescence intensity measurement are given, showing that these novel probes are suitable for performing optical measurements.
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81.16.-c Methods of micro- and nanofabrication and processing
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.66.Bz Metals and metallic alloys
78.55.Hx Other solid inorganic materials
61.46.-w Structure of nanoscale materials

Large area three-dimensional photonic crystals with embedded waveguides

Alex K. Raub and S. R. J. Brueck

J. Vac. Sci. Technol. B 28, C6O38 (2010); http://dx.doi.org/10.1116/1.3507887 (7 pages) | Cited 2 times

Online Publication Date: 29 November 2010

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Three-dimensional photonic crystals are attractive for very compact waveguide devices. A novel interferometric lithography technique for fabricating three-dimensional photonic crystals is presented, which allows for independent dimensional control of each axis of the crystal. Previous interferometric approaches using 3, 4, 5, or more beams have inherent constraints between the lattice constants and the exposure wavelength. With this new technique, it is possible to control each individual crystal lattice constant largely independent of the exposure wavelength, vastly increasing the available parameter space. Both mathematical models and experimentally realized three-dimensional photonic crystals, over 2 cm2 in size and up to 12 μm, are presented. Photonic crystals with integrated waveguides are of particular significance. A new approach to fabricating waveguides embedded in a three-dimensional photonic crystal is also presented. This approach uses multiple-exposure wavelengths, with one longer wavelength propagating throughout the photoresist for the photonic crystal fabrication and another shorter highly absorptive wavelength for the waveguide fabrication. This new approach to waveguide fabrication leads itself to scalable manufacturing using standard semiconductor lithography equipment.
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42.70.Qs Photonic bandgap materials
07.60.Ly Interferometers
42.82.Et Waveguides, couplers, and arrays
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.79.Gn Optical waveguides and couplers

Sub-10 nm patterning of gold nanostructures on silicon-nitride membranes for plasmon mapping with electron energy-loss spectroscopy

Ai Leen Koh, David W. McComb, Stefan A. Maier, H. Y. Low, and Joel K. W. Yang

J. Vac. Sci. Technol. B 28, C6O45 (2010); http://dx.doi.org/10.1116/1.3501351 (5 pages) | Cited 2 times

Online Publication Date: 29 November 2010

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Using high-resolution electron-beam lithography and lift-off, Au structures with sub-10 nm dimensions or spacings were fabricated on 30-nm-thick silicon-nitride (SiN) membranes. Fabricating metal nanostructures on electron-transparent SiN membranes permitted their surface plasmon resonances to be measured using electron energy-loss spectroscopy in a scanning transmission electron microscope (STEM). The surface plasmons that were excited by the 300 keV electron beam exhibited spatially and spectrally distinct longitudinal and transverse modes in elongated Au nanostructures. As the plasmonic response of the nanoparticle was dependent on the point of excitation of the STEM beam, a surface plasmon map could be obtained with nanometer resolution for nanostructures with various geometries. This combination of high-resolution lithography and microscopy will facilitate the design and systematic study of plasmonic nanostructures.
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81.16.Rf Micro- and nanoscale pattern formation
73.22.Lp Collective excitations

Geometry enhanced asymmetric rectifying tunneling diodes

Kwangsik Choi, Geunmin Ryu, Filiz Yesilkoy, Athanasios Chryssis, Neil Goldsman, Mario Dagenais, and Martin Peckerar

J. Vac. Sci. Technol. B 28, C6O50 (2010); http://dx.doi.org/10.1116/1.3501350 (6 pages)

Online Publication Date: 29 November 2010

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In this article, the authors show that geometric asymmetry in the layout of tunnel diodes yields asymmetry in the current-voltage (I-V) relationships associated with these diodes. Asymmetry improves diode performance. This effect is demonstrated for polysilicon–SiO2–Ti/Au and for Ni–NiO–Ni tunneling structures. For a polysilicon–SiO2–Ti/Au asymmetric tunneling diode (ATD), sensitivity and I-V curvature improvements of 71% and 350% are achieved, respectively. For a Ni–NiO–Ni asymmetric diode, sensitivity and I-V curvature improvements of 15% and 39% are observed. The authors further demonstrate that this asymmetry enhances the microwave radiation detection sensitivity of these diodes at 900 MHz. Superior rectifying performance of a Ni ATD is observed due to smaller band-edge offsets in this material compared to that of a polysilicon ATD. The resulting structure can be further optimized using plasmonic field enhancement.
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85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
29.40.-n Radiation detectors

Waveguide-plasmon resonances in gold-capped silicon-nitride disk photonic crystal slabs

Jia-Hong Shyu, Huang-Ming Lee, Jui-Hsing Chien, and Jong-Ching Wu

J. Vac. Sci. Technol. B 28, C6O56 (2010); http://dx.doi.org/10.1116/1.3518460 (4 pages)

Online Publication Date: 2 December 2010

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Waveguide-plasmon resonances of gold-capped silicon-nitride (SiN) disk photonic crystal slabs (PCSs) were investigated experimentally and numerically. The waveguide couplings were supported by the freestanding SiN membrane and the SiN-disk PCS. A tunable waveguide-plasmon resonance was modified by the SiN-disk height. When the SiN-disk height increased, the waveguide-plasmon resonances were enhanced and were blueshifted in optical-transmission spectra. The SiN-disk PCS was also fabricated to distinguish the presence of the waveguide-plasmon resonance in the gold-capped SiN-disk PCS from the guided resonance in the SiN-disk PCS. The finite-element method was used to calculate the optical transmittance of the gold disk array-coated SiN membranes, the gold-capped SiN-disk PCSs, and the SiN-disk PCSs. They were all in good agreement with the experiments.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
42.79.Gn Optical waveguides and couplers
42.70.Qs Photonic bandgap materials

Multilayer pattern transfer for plasmonic color filter applications

Alex F. Kaplan, Ting Xu, Yi-Kuei Wu, and L. Jay Guo

J. Vac. Sci. Technol. B 28, C6O60 (2010); http://dx.doi.org/10.1116/1.3511430 (4 pages) | Cited 1 time

Online Publication Date: 2 December 2010

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Contact printing involves transferring a material deposited on a prepatterned mold directly to a substrate with the application of uniform pressure and temperature. This process has traditionally been used to transfer metal layers to act as electrodes or masks for subsequent etch steps. In this work, the authors propose that devices with multiple layers, such as metal-insulator-metal (MIM) structures, can be transferred over using similar processing techniques. Using a SiO2 grating mold, the authors demonstrate the transfer of a MIM pattern to a flexible polycarbonate substrate in order to create a thin film, reflective color filter. This method could be optimized for roll-to-roll nanoimprint lithography and could be used to efficiently fabricate large-area structures on various substrates for display applications.
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85.40.Hp Lithography, masks and pattern transfer
42.79.Ci Filters, zone plates, and polarizers
81.16.Rf Micro- and nanoscale pattern formation
back to top Nanostructures

Batch wafer scale fabrication of passivated carbon nanotube transistors for electrochemical sensing applications

I. Martin-Fernandez, X. Borrisé, E. Lora-Tamayo, P. Godignon, and F. Perez-Murano

J. Vac. Sci. Technol. B 28, C6P1 (2010); http://dx.doi.org/10.1116/1.3504527 (5 pages)

Online Publication Date: 28 October 2010

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A technological process for batch wafer scale fabrication of electrochemical sensors based on single-walled carbon nanotube (SWCNT) field effect transistors (FETs) is presented. The fabrication of the carbon nanotube (CNT)-FETs is based on the chemical vapor deposition synthesis of the SWCNTs on predefined catalytic areas combined with standard microelectronic processes. Optical lithography is the only patterning method to be used. A fabrication yield close to 20% is achieved, which allows delivering thousands of CNT-FETs per wafer. An additional process to passivate the CNT-FETs is introduced to enable electrochemical sensing applications.
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82.47.Rs Electrochemical sensors
85.40.Hp Lithography, masks and pattern transfer
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.30.Tv Field effect devices
81.65.Rv Passivation
85.35.Kt Nanotube devices

Copper-plated 50 nm T-gate fabrication

Richard K. Oxland, Xu Li, Susan Ferguson, Steven Bentley, and Iain G. Thayne

J. Vac. Sci. Technol. B 28, C6P6 (2010); http://dx.doi.org/10.1116/1.3501346 (5 pages)

Online Publication Date: 28 October 2010

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In this article, the authors report for the first time a route to the realization of scalable sub-100 nm Cu-based T-gates using a fully subtractive, “silicon-compatible” process flow. High resolution electron beam lithography and a low-damage RIE etch process are used to transfer a 50 nm line into ICP-CVD silicon nitride. This pattern forms the T-gate foot. A single blanket metallization is then used to form the Schottky contact, the seed layer for the copper electroplating and a barrier to prevent diffusion of the copper once deposited. A constant potential copper electroplating process has been developed for a Ti/Pt seed layer. Copper films have been deposited with bulk sheet resistance ρsh ∼ 0.1 Ω/◻ (for a 300 nm film) and resistivity ρ = 1.8×10−6 Ω cm. The head dimensions of the T-gate are realized by patterning resist on top of the seed prior to electroplating. Heads of width 500 nm were fabricated and shown to have a total gate resistance of Rg = 150 Ω mm.
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81.15.Pq Electrodeposition, electroplating
68.55.-a Thin film structure and morphology
81.65.Cf Surface cleaning, etching, patterning
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.30.+y Surface double layers, Schottky barriers, and work functions

Direct synthesis of vertical α-Fe2O3 nanowires from sputtered Fe thin film

Keisuke Nagato, Masaki Furubayashi, Tetsuya Hamaguchi, and Masayuki Nakao

J. Vac. Sci. Technol. B 28, C6P11 (2010); http://dx.doi.org/10.1116/1.3501363 (3 pages)

Online Publication Date: 28 October 2010

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α-Fe2O3 (hematite) nanowires were synthesized from Fe thin films. The bladelike nanowires were synthesized by the simple annealing of a sputtered Fe thin film in a furnace with the annealing time varied between 0 and 100 min. The length of the nanowires was proportional to the logarithm of the annealing time. The number density of nanowires was saturated within an annealing time of 0–1 min. The Fe thin film may have been oxidized during annealing and the iron oxide molecules may have diffused to the roots of nanowires in accordance with the solid-phase growth model or they may have vaporized and then have been deposited on the surface of nanowires in accordance with the vapor-liquid-solid model. The authors characterized the nanowires by Raman spectroscopy and transmission electron microscopy (TEM). The Raman shift and the results of TEM indicated that the nanowires consisted of trigonal α-Fe2O3.
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81.07.Gf Nanowires
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
78.30.Hv Other nonmetallic inorganics

Pyrolysis of two-dimensional and three-dimensional interferometrically patterned resist structures

D. B. Burckel, C. M. Washburn, D. D. Koleske, and R. Polsky

J. Vac. Sci. Technol. B 28, C6P14 (2010); http://dx.doi.org/10.1116/1.3495756 (4 pages)

Online Publication Date: 28 October 2010

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Interferometric lithography was used to create a wide variety of two-dimensional and three-dimensional patterns in standard photoresist. The patterns were then converted to amorphous carbon structures through pyrolysis in a reducing atmosphere. The structures maintain their fundamental in-plane morphology despite undergoing significant shrinkage. As an indication of their functionality, the authors highlight their use in two diverse applications: (1) as a defect reduction mask in metal-organic chemical vapor deposition growth of gallium nitride (GaN) on sapphire and (2) as a nanoparticle decorated electrode for catalytic oxidation of methanol.
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82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
82.45.Fk Electrodes
61.43.Er Other amorphous solids

Fabrication and initial characterization of ultrahigh aspect ratio vias in gold using the helium ion microscope

Larry Scipioni, David C. Ferranti, Vincent S. Smentkowski, and Radislav A. Potyrailo

J. Vac. Sci. Technol. B 28, C6P18 (2010); http://dx.doi.org/10.1116/1.3517514 (6 pages) | Cited 2 times

Online Publication Date: 18 November 2010

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Toward the end goal of creating transducers with nanometer scale sensing features, the helium ion microscope (HIM) has been employed to create and characterize high aspect ratio features in gold films. The HIM has a spot size less than 1 nm, uses a chemically inert noble gas (He), which does not deposit/implant any species that may contaminate the material being patterned, and is able to rapidly generate arrays of vias in Au. Hence, the HIM is an ideal tool to generate these ultrahigh aspect ratio features. The authors characterize the vias, also using HIM, by measurements of feature size, lateral milling resolution, sidewall angle, and fabrication speed. Two novel methods were employed to enable the characterization due to the very small size of the features. A significant reduction in via width is achieved, as compared with traditional focused ion beam milling.
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81.16.Rf Micro- and nanoscale pattern formation
68.55.-a Thin film structure and morphology

Fabrication of poly(ethylene glycol) hydrogel structures for pharmaceutical applications using electron beam and optical lithography

Misuk Bae, Richard A. Gemeinhart, Ralu Divan, Kamlesh J. Suthar, and Derrick C. Mancini

J. Vac. Sci. Technol. B 28, C6P24 (2010); http://dx.doi.org/10.1116/1.3517716 (6 pages)

Online Publication Date: 29 November 2010

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Soft-polymer based microparticles are currently being applied in many biomedical applications, ranging from bioimaging and bioassays to drug delivery carriers. As one class of soft polymers, hydrogels are materials that can be used for delivering drug cargoes and can be fabricated in controlled sizes. Among the various hydrogel-forming polymers, poly(ethylene glycol) (PEG) based hydrogel systems are widely used due to their negligible toxicity and limited immunogenic recognition. Physical and chemical properties of particles (i.e., particle size, shape, surface charge, and hydrophobicity) are known to play an important role in cell-particle recognition and response. To understand the role of physicochemical properties of PEG-based hydrogel structures on cells, it is important to have geometrically precise and uniform hydrogel structures. To fabricate geometrically uniform structures, the authors have employed electron beam lithography and ultraviolet optical lithography using PEG or PEG diacrylate polymers. These hydrogel structures have been characterized by scanning electron microscopy, atomic force microscopy, optical microscopy, and attenuated total reflection Fourier transform infrared spectroscopy, confirming control of chemistry, size, and shape.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
82.70.Gg Gels and sols
87.85.J- Biomaterials
78.30.Jw Organic compounds, polymers
61.41.+e Polymers, elastomers, and plastics

Nanofabrication of x-ray zone plates using ultrananocrystalline diamond molds and electroforming

Michael J. Wojcik, Vishwanath Joshi, Anirudha V. Sumant, Ralu Divan, Leonidas E. Ocola, Ming Lu, and Derrick C. Mancini

J. Vac. Sci. Technol. B 28, C6P30 (2010); http://dx.doi.org/10.1116/1.3501357 (6 pages)

Online Publication Date: 29 November 2010

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X-ray zone plates are diffractive focusing optics composed of concentric rings of phase-shifting material with a changing period along their radii. Hard x-ray zone plates operate primarily in a range of photon energies from 3 to 30 keV. In order to achieve needed resolution and efficiency, high-aspect-ratio structures are typically patterned and fabricated by gold electroforming into a dielectric mold. Ideally, the molds would be mechanically stable and radiation resistant. Ultrananocrystalline diamond offers a solution with a set of physical properties that suggests that the material can be fabricated to desired requirements. The authors present here the first results for the fabrication of hard x-ray zone plates using an ultrananocrystalline diamond mold for electroforming gold and discuss future developments for creating an optimized focusing optic.
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81.16.Rf Micro- and nanoscale pattern formation
81.10.Fq Growth from melts; zone melting and refining
82.45.-h Electrochemistry and electrophoresis

Nanomachining and clamping point optimization of silicon carbon nitride resonators using low voltage electron beam lithography and cold development

M. A. Mohammad, C. Guthy, S. Evoy, S. K. Dew, and M. Stepanova

J. Vac. Sci. Technol. B 28, C6P36 (2010); http://dx.doi.org/10.1116/1.3517683 (6 pages)

Online Publication Date: 2 December 2010

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The authors report the nanomachining of sub-20-nm wide doubly clamped silicon carbon nitride resonators using low keV electron beam lithography with polymethyl methacrylate resist and cold development. Methodologies are developed for precisely controlling the resonator widths in the ultranarrow regime of 11–20 nm. Resonators with lengths of 1–20 μm and widths of 16–280 nm are characterized at room temperature in vacuum using piezoelectric actuation and optical interferometry. Clamping and surface losses are identified as the dominant energy loss mechanisms for a range of resonator widths. The resonator clamping points are optimized using an original electron beam lithography simulator. Various alternative clamping point designs are also modeled and fabricated in order to reduce the clamping losses.
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07.10.Cm Micromechanical devices and systems
81.16.Nd Micro- and nanolithography
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.60.Ly Interferometers

Nanoporous ultrananocrystalline diamond membranes

Olga Makarova, Ralu Divan, Nicolaie Moldovan, Daniel Rosenmann, and Cha-Mei Tang

J. Vac. Sci. Technol. B 28, C6P42 (2010); http://dx.doi.org/10.1116/1.3501345 (6 pages)

Online Publication Date: 2 December 2010

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Micro- and nanoporous membranes have a wide range of applications in many fields, including medical diagnostics, drug delivery, and hemodialysis. Ultrananocrystalline diamond coatings are becoming more and more significant in medical applications because of the highest degree of biocompatibility, unmatched by other materials. The pores ranging in diameter from 100 to 2000 nm have been fabricated in a 1-μm-thick ultrananocrystalline diamond film on silicon wafers using e-beam and optical lithography, reactive ion etching, and laser writing.
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81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
61.43.Gt Powders, porous materials
81.05.Rm Porous materials; granular materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.65.Cf Surface cleaning, etching, patterning

Nanostructured silicon membranes for control of molecular transport

Bernadeta R. Srijanto, Scott T. Retterer, Jason D. Fowlkes, and Mitchel J. Doktycz

J. Vac. Sci. Technol. B 28, C6P48 (2010); http://dx.doi.org/10.1116/1.3518911 (5 pages)

Online Publication Date: 2 December 2010

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A membrane that allows selective transport of molecular species requires precise engineering on the nanoscale. Membrane permeability can be tuned by controlling the physical structure and surface chemistry of the pores. Here, a combination of electron beam and optical lithography, along with cryogenic deep reactive ion etching, has been used to fabricate silicon membranes that are physically robust, have uniform pore sizes, and are directly integrated into a microfluidic network. Additional reductions in pore size were achieved using plasma enhanced chemical vapor deposition and atomic layer deposition of silicon dioxide to coat membrane surfaces. Cross sectioning of the membranes using focused ion beam milling was used to determine the physical shape of the membrane pores before and after coating. Functional characterization of the membranes was performed by using quantitative fluorescence microscopy to document the transport of molecular species across the membrane.
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81.05.Cy Elemental semiconductors
81.05.Rm Porous materials; granular materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.Nd Micro- and nanolithography
81.65.Cf Surface cleaning, etching, patterning
78.67.Rb Nanoporous materials

Semiconductor crystal islands for three-dimensional integration

F. Crnogorac, S. Wong, and R. F. W. Pease

J. Vac. Sci. Technol. B 28, C6P53 (2010); http://dx.doi.org/10.1116/1.3511473 (6 pages)

Online Publication Date: 2 December 2010

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The critical operation needed to achieve monolithic three-dimensional integrated circuits is obtaining single-crystal, device-quality semiconductor material for upper layer active circuits without exceeding the thermal budget of underlying devices. Previous attempts at using pulsed laser crystallization of amorphous films for upper layer devices failed to provide large enough single crystals at a low enough temperature. Here, the authors demonstrate a more direct approach to realizing high-quality, single-crystal Si (100) and Ge (100) islands (3–3000 μm across) on amorphous SiO2 substrates. The technique is a form of hydrophilic fusion bonding featuring low temperatures ( ≤ 400 °C), chemical mechanical polishing, and chemical surface activation (using NH4OH). The bonds are strong enough (>1 J/m2) to withstand SmartCut® removal of the donor wafer. By bonding arrays of islands rather than one large contiguous layer, the authors effectively avoided the formation of thermally induced voids at the bonding interface, and so dramatically improved yield.
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85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
81.65.Ps Polishing, grinding, surface finishing

Structure and properties of polymer core-shell systems: Helium ion microscopy and electrical conductivity studies

Valery Bliznyuk, Alexander Pud, Larry Scipioni, Chuong Huynh, Nikolay Ogurtsov, and David Ferranti

J. Vac. Sci. Technol. B 28, C6P59 (2010); http://dx.doi.org/10.1116/1.3504589 (7 pages)

Online Publication Date: 2 December 2010

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Peculiarities of the structural organization and electrical properties of two core-shell polymer systems under different fabrication protocols have been studied with a combination of helium ion microscopy (HIM) and current-voltage characterization. The systems under study included a submicrometer core of a ferroelectric polymer polyvinylidene fluoride and a shell of intrinsically conducting or semiconducting polymer polyaniline (PANI) or poly(3-methylthiophene) (P3MT). Application of HIM allowed identification of the polymer components, visualization of the electrically conductive percolation network of PANI or P3MT, and its variation due to thermal annealing and/or interaction with the environment. HIM is proved to be a powerful tool for characterization of not only the morphology but also of the charge distribution and conductivity properties on the nanoscale. The specific contrast formation in HIM imaging is due to differences in local electrical conductivity of the components. The authors have demonstrated that the polymer core-shell systems under study can serve as a universal platform for development of nanostructured multifunctional materials. Specifically, it is shown that they can be used for preparation of conducting and semiconducting polymer films or layers having promising nonlinear electrical and sensor properties.
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73.61.Ph Polymers; organic compounds
73.63.-b Electronic transport in nanoscale materials and structures
81.40.Gh Other heat and thermomechanical treatments
61.46.-w Structure of nanoscale materials
68.55.-a Thin film structure and morphology

Noise analysis of carbon nanotube field effect transistors irradiated by electron beam

Jack Chan, Deborah Kidd, Brian Burke, Lloyd Harriott, and Keith Williams

J. Vac. Sci. Technol. B 28, C6P66 (2010); http://dx.doi.org/10.1116/1.3517517 (4 pages)

Online Publication Date: 2 December 2010

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Using current noise measurement techniques, the authors have studied the effects of electron beam exposure on field effect transistors based on carbon nanotube channels. In the case of p-type semiconducting nanotubes, the authors find that high doses induce a potential barrier along the channel, and transport is dominated by the tunneling events across this barrier. The authors suggest that the barrier is induced by charges trapped in the underlying SiO2 barrier. Complementary studies on metallic nanotubes do not exhibit this behavior.
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85.35.Kt Nanotube devices
85.30.Tv Field effect devices
85.75.Hh Spin polarized field effect transistors
73.63.Fg Nanotubes
61.80.Fe Electron and positron radiation effects
81.07.De Nanotubes

Plasma etch fabrication of 60:1 aspect ratio silicon nanogratings with 200 nm pitch

Pran Mukherjee, Alexander Bruccoleri, Ralf K. Heilmann, Mark L. Schattenburg, Alex F. Kaplan, and L. Jay Guo

J. Vac. Sci. Technol. B 28, C6P70 (2010); http://dx.doi.org/10.1116/1.3507427 (6 pages)

Online Publication Date: 2 December 2010

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The authors present a breakthrough multistage dry-etch process to create 100 nm half-pitch gratings in silicon with depths up to 6 μm. Interference lithography was used to pattern gratings in an optically matched stack of materials to form a 400-nm-thick silicon oxide hard-mask. The oxide was then used to mask the subsequent deep reactive-ion etching of silicon. In this article, the authors describe their grating patterning, pattern transfer, and deep etch processes, and present progress toward combining this technique with coarser scale lithography steps designed to form an integrated mechanical support structure to produce freestanding x-ray diffraction gratings.
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81.65.Cf Surface cleaning, etching, patterning
81.16.Rf Micro- and nanoscale pattern formation
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
42.82.Cr Fabrication techniques; lithography, pattern transfer
52.77.Bn Etching and cleaning
back to top Novel Imaging-Optical Lithography

Optical and computed evaluation of keyhole diffractive imaging for lensless x-ray microscopy

Bing Dai, Diling Zhu, Ronnachai Jaroensri, Kanokwan Kulalert, Piero Pianetta, and R. Fabian W. Pease

J. Vac. Sci. Technol. B 28, C6Q1 (2010); http://dx.doi.org/10.1116/1.3501340 (5 pages)

Online Publication Date: 19 October 2010

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X-ray microscopy without the need to focus the x-rays is obviously desirable. Thus, various ways of reconstructing the image from the far-field diffraction pattern have been demonstrated during the last decade. Here, the authors describe a variant of keyhole diffractive imaging in which the knowledge of the illuminating wavefront is used in the reconstruction. Unlike prior work in keyhole imaging in which a diverging beam was used, the authors employ a collimated beam such as emerges from a free electron x-ray source. From both computer simulations and scaled optical experiments, the authors found that the reconstruction is best when the shape is a right-angled triangle. For the authors’ samples, the best size of the triangle is one that covers about half of a rectangle 3000×3000 wavelengths. If the area is smaller, then the time to cover the entire sample is too long; if larger, then the reconstruction takes far longer and results in a noisy image. From the authors’ scaled experiment conducted under blind conditions (no a prior knowledge of the sample), it appears that a resolution of 10 nm should be readily achievable at an x-ray wavelength of 0.18 nm.
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42.30.Wb Image reconstruction; tomography
68.37.Yz X-ray microscopy

Customized illumination for process window optimization and yield improvement in mask aligner lithography systems

Michael Hornung, Uwe Vogler, and Reinhard Voelkel

J. Vac. Sci. Technol. B 28, C6Q6 (2010); http://dx.doi.org/10.1116/1.3518920 (6 pages) | Cited 1 time

Online Publication Date: 2 December 2010

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A novel illumination system for mask aligners will be described. The illumination system provides improved exposure light uniformity and customized illumination. It is based on two consecutive Köhler integrators and an exchangeable illumination filter plate. It allows a free choice of illumination settings, e.g., ring-illumination, quadrupole, multipole, Maltese cross, and free-forms in a standard mask aligner. The so-called micro optical exposure optics significantly increases the field of applications for mask aligners. The well defined illumination allows optical proximity correction (OPC) of the mask pattern to compensate for the remaining image errors due to diffraction or process effects. Customized illumination and OPC-like structures introduce well-known tools of projection lithography for mask aligners for the first time. Lithography process simulations as well as experimental results will be shown.
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85.40.Hp Lithography, masks and pattern transfer

Projection lithography below lambda/7 through deep-ultraviolet evanescent optical imaging

P. Xie and B. W. Smith

J. Vac. Sci. Technol. B 28, C6Q12 (2010); http://dx.doi.org/10.1116/1.3504550 (8 pages)

Online Publication Date: 2 December 2010

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An approach is presented to allow for imaging down to 26 nm using 193 nm projection reduction lithography together with evanescent wave optical effects at the imaging plane. The physical limitations of imaging imposed by the refractive indices of the materials were surpassed through the interference of evanescent waves at near fields. This has allowed for the imaging into photoresist of half-pitch resolution below lambda/7. A special situation where imaging at a system numerical aperture above the resist refractive index is discussed. Lithography results are shown using image media including air, water, and a high refractive index fluid together with a systematic gauge control to determine gap requirements and tolerances to achieve adequate image contrast into the resist. Gauging methods include both optical and mechanical approaches to achieve nanometer level gap control. It is found that gap depths as large as 50 nm can be tolerated using this approach, well beyond the levels associated with alternative high resolution approaches such as those using surface plasmons.
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81.16.Nd Micro- and nanolithography
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Development of a simple, compact, low-cost interference lithography system

Hasan Korre, Corey P. Fucetola, Jeremy A. Johnson, and Karl K. Berggren

J. Vac. Sci. Technol. B 28, C6Q20 (2010); http://dx.doi.org/10.1116/1.3504498 (5 pages)

Online Publication Date: 2 December 2010

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Interference lithography (IL) has proven itself to be an enabling technology for nanofabrication. Within IL, issues of spatial phase distortion, fringe stability, and substrate development have been explored and addressed. However, IL tools are still unnecessarily expensive, large, and complex. To address these issues, the authors previously built a simple IL tool that used a blue laser diode to produce ∼ 300 nm pitch structures. The resulting patterned areas ( ∼ mm2) were limited by both the temporal and spatial coherence of the laser. Here, the authors report on the advancement of their low-cost interference lithography tool that makes use of newly available blue laser diodes and a simplified spatial filter to print larger-area ( ∼ cm2) patterns. With this configuration, the authors have designed and implemented a small-footprint ( ∼ 0.2 m2) Lloyd’s mirror IL tool that can be assembled for less than ∼ 6000 USD.
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81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
81.16.Rf Micro- and nanoscale pattern formation
42.79.Ci Filters, zone plates, and polarizers
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.82.Cr Fabrication techniques; lithography, pattern transfer

Nondestructive detection of deviation in integrated circuits

Leili Baghaei, Bing Dai, Piero Pianetta, and R. Fabian W. Pease

J. Vac. Sci. Technol. B 28, C6Q25 (2010); http://dx.doi.org/10.1116/1.3518464 (3 pages)

Online Publication Date: 2 December 2010

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There exists a clear need for an inspection microscope that features suboptical resolution and high penetration but requires no ambient vacuum for the sample. The most prominent application of such microscope is the nondestructive examination of fabricated integrated circuits. Current semiconductor fabrication processes would require a resolution of approximately 10 nm to a penetration depth of 100 μm. These requirements are expected to increase over time due to process shrinks. The coherent x-ray diffraction microscope is a recent development where highly coherent x-ray sources are used without focusing optics. Instead, the diffraction pattern of the beam is recorded, and reconstruction of the sample image is achieved by recovering the phase information using computational algorithms.
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85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
back to top Resists

Impact of development chemistry on extreme ultraviolet resist performance

Roel Gronheid

J. Vac. Sci. Technol. B 28, C6S1 (2010); http://dx.doi.org/10.1116/1.3498751 (5 pages) | Cited 1 time

Online Publication Date: 19 October 2010

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Tetrabutyl ammonium hydroxide (TBAH) has recently been identified as a promising material for aqueous base development of extreme ultraviolet (EUV) photoresists. In this article, the merits and applicability of this new material are being further investigated. In general, TBAH has no impact on line width roughness or sensitivity performance when compared to conventional tetramethyl ammonium hydroxide. It does, however, improve the pattern collapse performance of several resists. Since pattern collapse is an important failure mechanism for EUV, TBAH also improves ultimate resolution of these materials and allows overexposure to target smaller critical dimensions. In contrast, several other resist platforms show no impact of TBAH on their pattern collapse behavior. A mechanism is proposed to explain this observation based on modification of the chemical surface properties during development. This mechanism is supported by independent contact angle measurements.
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85.40.Hp Lithography, masks and pattern transfer

Comparison of positive tone versus negative tone resist pattern collapse behavior

Wei-Ming Yeh, David E. Noga, Richard A. Lawson, Laren M. Tolbert, and Clifford L. Henderson

J. Vac. Sci. Technol. B 28, C6S6 (2010); http://dx.doi.org/10.1116/1.3518136 (6 pages) | Cited 2 times

Online Publication Date: 30 November 2010

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In this work, e-beam lithography patterns have been specifically designed and fabricated which provide the opportunity to probe the collapse behavior of both positive and negative tone systems. The pattern layout includes adjacent parallel line structures that both vary in the line size and also in the distance by which they are separated by the space between them. This type of structure allows for the control and modulation of the capillary forces, and ultimately the stresses, experienced by the photoresist line pairs during the final rinse and drying steps of the development process. Using such structures, it is possible to determine the critical stress, i.e., the maximum stress experienced by the photoresist lines before collapse, as a function of a variety of parameters including: material type, substrate preparation conditions, resist film thickness, and resist feature width. In this article, such a modular approach has been used to compare the pattern collapse behavior of a prototypical positive tone resist formulated using a protected hydroxystyrene-based copolymer and a prototypical negative tone epoxide-based molecular photoresist (4-EP). It was found that the critical stress at the point of pattern collapse decreased both as the thickness and the feature width of the resist lines decreased, though this trend was observed to a much lesser extent in the negative tone 4-EP material. It is observed that the negative tone resist, whose imaging mechanism involves cross-linking, shows far superior pattern collapse performance as compared to the positive tone deprotection based resist and is in general able to achieve significantly higher aspect ratio patterning at equivalent feature linewidths.
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85.40.Hp Lithography, masks and pattern transfer

High sensitivity nonchemically amplified molecular resists based on photosensitive dissolution inhibitors

Richard A. Lawson, Laren M. Tolbert, and Clifford L. Henderson

J. Vac. Sci. Technol. B 28, C6S12 (2010); http://dx.doi.org/10.1116/1.3511790 (7 pages)

Online Publication Date: 30 November 2010

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A new class of nonchemically amplified molecular resists has been made based on the use of photosensitive protecting groups. The deprotection during exposure converts a dissolution inhibiting compound into a dissolution promoter. The key benefit of the use of molecular resists in this application is that they can exhibit a sharp solubility transition with relatively low levels of deprotection. Two different inhibiting compounds were made that use a 2-nitrobenzyl protecting group; NBnDCh, an aliphatic molecular resist based on deoxycholic acid, and NBnHPF, based on an aromatic molecular resist containing two phenol groups. Blending these compounds with a calixarene dissolution promoter allowed the contrast and sensitivity of the resist formulations to be tuned. Contrast ratios as high as 27 and deep ultraviolet (DUV) sensitivities between 150 and 400 mJ/cm2 were obtained using NBnDCh. NBnHPF based systems not only showed somewhat lower contrasts but also exhibited much lower clearing doses of only 60 mJ/cm2 and smaller. One particular NBnHPF formulation possessed a sensitivity of 10 mJ/cm2 and a contrast of 8.3, and it was even possible to formulate one resist with an extremely low dose-to-clear value of only 1 mJ/cm2. Such low dose-to-clear values in nonchemically amplified resists have, to the authors’ knowledge, not been reported before. The Dill C parameter for each of the two systems was quantified using Fourier transform infrared spectroscopy. The sensitivity of the NBnHPF systems was found to be very good because they undergo a solubility transition at 75 mol % inhibitor; this means that some formulations only need 0.5% photoconversion to pattern. Despite the excellent DUV sensitivity of these systems, it was found that they do not possess high sensitivity when exposed using extreme ultraviolet or e-beam exposure sources.
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81.20.-n Methods of materials synthesis and materials processing
78.40.Me Organic compounds and polymers
78.30.Jw Organic compounds, polymers
64.75.Bc Solubility

Photopatternable inorganic hardmask

Alan Telecky, Peng Xie, Jason Stowers, Andrew Grenville, Bruce Smith, and Douglas A. Keszler

J. Vac. Sci. Technol. B 28, C6S19 (2010); http://dx.doi.org/10.1116/1.3507889 (4 pages)

Online Publication Date: 30 November 2010

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The authors present a directly photopatternable inorganic hardmask for 193 nm lithography based on the solution-deposited dielectric metal oxide sulfate (MSOx) system. To demonstrate pattern fidelity, 18 nm half-pitch features were written at a dose near 240 μC/cm2 (30 keV) with line width roughness values between 1.6 and 1.8 nm. Well-resolved and uniform 30 nm contact holes were fabricated via a litho-freeze-litho-etch process employing electron beam exposure and a simple thermal freeze. ZircSOx has a high index of refraction approaching 1.9 at 193 nm, and the extinction coefficient, k, can be varied by an order of magnitude by substituting Zr with Hf. Optical interference lithography at 193 nm was used to realize 60 nm half-pitch lines in MSOx at a dose of 25 mJ/cm2.
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81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Effects of salty-developer temperature on electron-beam-exposed hydrogen silsesquioxane resist for ultradense pattern transfer

M. Yan, J. Lee, B. Ofuonye, S. Choi, J. H. Jang, and I. Adesida

J. Vac. Sci. Technol. B 28, C6S23 (2010); http://dx.doi.org/10.1116/1.3504497 (5 pages) | Cited 2 times

Online Publication Date: 30 November 2010

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The characteristics of salty developers, TMAH/NaCl and NaOH/NaCl, on the processing of hydrogen silsesquioxane (HSQ) resist at elevated temperatures were investigated. The TMAH/NaCl developer demonstrated better contrast than the NaOH/NaCl developer at the temperatures (20–35 °C) investigated for both the unbaked and prebaked HSQ resists. The higher contrast developer was utilized to investigate the fabrication of ultradense gratings. Better reproducibility of the gratings was obtained from prebaked HSQ resist even though unbaked HSQ exhibited higher contrast. The ultradense grating patterns realized in HSQ resist was successfully transferred into a Si substrate. By employing the TMAH/NaCl development process at an elevated temperature and the inductively coupled plasma reactive ion etching process, 20-nm-pitch silicon nanowire arrays were demonstrated.
Show PACS
85.40.Hp Lithography, masks and pattern transfer
81.65.Cf Surface cleaning, etching, patterning
81.16.Rf Micro- and nanoscale pattern formation
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