bluuebunny/crossref_metadata_2025 huggingface dataset:
Abstract: High-rate physical vapor deposition of refractory metals
Authors: Sherman Max A. , Bunshah Rointan F. , Beale Harry A.
Published: July 2002

Molybdenum, niobium, and vanadium bulk deposits produced by high-rate physical-vapor-deposition techniques (HRPVD) were characterized by impurity content, grain size and morphology, yield strength, hardness, and bend ductility. Yield strengths of molybdenum and niobium were comparable to those of wrought material having equivalent grain sizes, when the yield strength of vapor-deposited vanadium was superior to that of wrought vanadium because of its ultrafine (0.7 μ) grain size. Ultrafine-grained refractory metals, such as the vanadium deposits produced in this study, may greatly reduce void formation and growth which causes dimensional changes and degradation of mechanical properties in reactor structural components, by removing excess vacancies (produced by the neutron irradiation). For the vanadium of this study, at a typical operating temperature of a controlled thermonuclear reactor first wall (973 K), calculations show that up to 92% of the excess vacancies can be trapped at the boundaries for a dislocation density of 108 cm−2. It is suggested that HRPVD techniques may be used to prepare fine-grained materials having superior resistance to swelling induced by fast-neutron irradiation.
Properties of carriers at the Si-SiO2 interface in MOSFET structures
Authors: Stiles P. J.
Published: July 2002

A description of the electrical properties of carriers in inversion layers in a Si-SiO2 system at low temperatures is given. An attempt is made to relate the observed properties to the properties of the host interface.
Overlay evaluation of proximity x-ray lithography in 100 nm device fabrication
Authors: Aoyama H. , Taguchi T. , Matsui Y. , Fukuda M. , Deguchi K. , Morita H. , Oda M. , Matsuda T. , Kumasaka F. , Iba Y. , Horiuchi K.
Published: July 2002

In the semiconductor manufacturing of below 100 nm devices, overlay accuracy is a critical issue for high resolution on proximity x-ray lithography (PXL). We applied PXL for five layers (mark, isolation, gate, contact, and wiring) to fabricate a 100 nm n-type metal–oxide–semiconductor field effect transistor and evaluated the accuracy. Alignment exposure was done with optical heterodyne alignment and magnification correction. The overall overlay accuracy (mean±3σ) was 25–45 nm, and the best was about 25 nm for the contact layer. The overlay error was classified into several components to estimate the error budget. The analysis revealed that the alignment error of the x-ray stepper is less than 20 nm under various conditions in device fabrication. Individual x and y scaling errors caused by mask image placement and the difference of wafer-to-mask gap was from 18–35 nm: the error of common in-plane deformation was about 20 nm. The present accuracy may make it possible to fabricate devices with a 100 nm ground rule.
Estimation of the TEOS dissociation coefficient by electron impact
Authors: Vallée C. , Rhallabi A. , Granier A. , Goullet A. , Turban G.
Published: July 2002

SiO 2 -like films are deposited in a low-pressure rf helicon reactor using oxygen-rich O2/TEOS (tetraethoxysilane) mixtures. A model based on the deposition rate variation with the distance to the TEOS injection is used to estimate the TEOS electron-impact dissociation coefficient ke and the effective sticking coefficient of reactive fragments s. In the helicon diffusion chamber where the electron temperature and density are about 4 eV and 1010 cm−3, respectively, ke and s are found to be 1.82×10−7 cm3 s−1 and 0.035, respectively. Under these low-pressure plasma conditions, the TEOS dissociation by electron impact is dominant over dissociation by oxygen atoms.
Determination of resist exposure parameters in helium ion beam lithography: Absorbed energy gradient, contrast, and critical dose
Authors: Ruchhoeft P. , Wolfe J. C.
Published: July 2002

We study the relationship between the true resist contrast (γtrue) and the apparent contrast (γHD), as determined by the slope of the Hurter–Driffield (HD) curve, in He+ ion beam lithography. These parameters can differ significantly because the absorbed energy density is a function of depth in the resist. We formulate an analytical model, using a linear approximation to the deposited energy distribution, that permits the extraction of the absorbed energy gradient, the true resist contrast, and the critical dose from experimental HD curves. The model accurately describes both experimental and simulation results. We show that the contrast for poly(methylmethacrylate) resist is 2.9 for various He+ ion energies even though the apparent contrast can be as low as unity at 50 keV.
Analytical-based solutions for SCALPEL wafer heating
Authors: Fares N. , Stanton S. , Liddle J. , Gallatin G.
Published: July 2002

When operating in high-throughput conditions, SCALPELs 100 keV electron beam causes significant dynamic wafer deformation. To complement extensive finite element analysis, we have undertaken an analytical solution to the governing heat transfer and elastic strain equations and boundary conditions. This efficient, Green’s function-based computational approach is able to support a robust and versatile image-placement correction strategy.
Micromask-induced surface defects inside Si trench isolation
Authors: Rho Kyeonglan
Published: July 2002

A 20-nm-thick pad oxide layer is thermally grown on a 6-in. p-type 〈100〉 Si wafer, and is followed by the deposition of a 315-nm-thick low pressure chemical vapor deposition nitride layer for the trench isolation formation. Nitride and oxide layers are etched and Si is then etched away for trench formation. Initially, CF4/Ar was used to etch the 20 nm/315-nm-thick oxide/nitride layers, after which the wafers were transferred to a different etcher, AME5000 MXP polysilicon etcher, for the Si etch. The Si etch consists of two steps: first, the breakthrough step was performed to remove either the remaining oxide layer from the previous step or the native oxide layer using 35 sccm of CF4 for 15 s. In a second step, the main etch was performed to etch Si using 90 sccm of HBr, 30 sccm of Cl2, and 7 sccm of He–O2 for 250 s. After the Si etch, surface defects on the order of 1000–1600/wafer were observed on the Si surfaces using the Tencor AIT pattern inspection tool. The surface defects are caused by polymer-related micromasking. Instead of employing CF4/Ar for the removal of the oxide/nitride layers, 30 sccm of NF3 and 5 sccm of O2 were used for the main etch step, and 10 sccm of CHF3 and 40 sccm of N2 were used for the overetch step. The Si etch was continued in the AME5000 MXP polysilicon etcher using the original parameters. The use of NF3/O2, which does not polymerize the Si surface, resulted in an almost defect-free surface. More experiments were conducted for the overetch step after the removal of nitride layer because NF3 etches the Si surface quickly once it is exposed. The combination of the NF3/O2 main etch step by endpoint algorithm and the 25 s CHF3/N2 overetch step, resulted in fewer surface defects than using CF4/Ar for both main and overetch steps.
Optimized bilayer hexamethyldisiloxane film as bottom antireflective coating for both KrF and ArF lithographies
Authors: Lin C. H. , Wang L. A. , Chen H. L.
Published: July 2002

A new bilayer bottom antireflective coating (BARC) layer composed of hexamethyldisiloxane film stack is demonstrated for both KrF and ArF lithographies. By simply adjusting the gas flow rate ratio, the materials of the bilayer can be varied to have suitable optical constants as BARC materials working at both 248 and 193 nm wavelengths. The swing effect is experimentally shown to be reduced significantly on both silicon and Al–Si substrates. The bilayer scheme is also demonstrated to be capable of providing large thickness-controlled tolerance.
1 kV resist technology for microcolumn-based electron-beam lithography
Authors: Lee K. Y. , Hsu Y. , Le P. , Tan Z. C. H. , Chang T. H. P. , Elian K.
Published: July 2002

The objective of this article is to evaluate low-voltage electron-beam (e-beam) resists suitable for direct write on wafer and mask fabrication in the sub-100 nm regime. Low kV exposure provides the advantages of high sensitivity, reduced charging, and a lack of proximity and heating effects. However, a major concern is whether a low-voltage e-beam is capable of patterning sub-100 nm features in resist with a thickness substantially greater than the penetration range of the electrons. At 1–2 kV, the penetration range is between 30 and 100 nm, while typical resist thickness is >200 nm. In an effort to overcome this limitation, thin film layer techniques are evaluated for low kV e-beam exposure. Preliminary 1 kV results on two thin imaging schemes, the bilayer CARL process and top surface imaging with NTS-4 resist, are reported here. Important results achieved are high sensitivity (1–2 μC/cm2), high contrast (γ>10), high resolution (70 nm in ∼300 nm thick resist), good critical dimension (CD) linearity (range=7 nm, mean=8 nm), large exposure latitude (ΔCD/Δdose=0.5 nm/% change in dose), and absence of proximity effects.
Modeling influence of structural changes in photoacid generators on 193 nm single layer resist imaging
Authors: Croffie Ebo , Yuan Lei , Cheng Mosong , Neureuther Andrew , Houlihan Frank , Cirelli Ray , Watson Pat , Nalamasu Om , Gabor Allen
Published: July 2002

We present recent modeling work aimed at understanding the influence of structural changes in photoacid generators (PAGs) on acid generation efficiency, deprotection efficiency, and photoacid diffusion in 193 nm chemically amplified resists. An analytical model for the postexposure bake process is used to study the reaction and diffusion properties of the various acids generated by the PAGs. Fourier transfer infrared spectroscopy is used to monitor the generation of photoacid during exposure. Resist thickness loss after PEB as a function of exposure dose is related to the deprotection extent to extract the reaction rate parameters. The effects of the acid size and boiling point on process latitude, line end shortening, and line edge roughness are presented. Analytical model predictions of process latitude and line end shortening are also presented and compared to experimental data. In this study, the photogenerated acid with the smallest molar volume and highest boiling point temperature gave the best overall lithographic performance.
High resolution inductively coupled plasma etching of 30 nm lines and spaces in tungsten and silicon
Authors: Goodyear Andrew L. , Mackenzie Sinclair , Olynick Deirdre L. , Anderson Erik H.
Published: July 2002

Dry etching of 30 nm features was investigated for x-ray and integrated electronics applications. These typically require etching of either a tungsten absorber layer or a silicon mold. Through the use of an inductively coupled plasma source and accurate control over substrate temperature it was possible to achieve highly anisotropic patterning of tungsten and silicon. Densely patterned features as small as 30 nm and at pitches of 70 nm were etched in tungsten and silicon, to depths of 100 and 200 nm, respectively.
Nitridation of thermal SiO2 films by radio-frequency plasma assisted electron cyclotron resonance: Layer structure and composition
Authors: Raveh A. , Brewer J. , Irene E. A.
Published: July 2002

Thermally grown silicon dioxide (SiO2) films were nitrided using dual-frequency electron cyclotron resonance (ECR) and rf discharges. The structure and composition of the layers were studied by atomic force microscopy, spectroscopic ellipsometry, Fourier transform infrared spectroscopy, and Auger electron spectroscopy. A two-layer structure consisting of a silicon oxynitride (SiOxNy) outer layer and a SiO2 inner layer was found. The Si–SiO2 interface was found to be a suboxide (SiOx, x<2). The ECR/rf plasma mode enabled production of a more thermally stable structure and composition, when compared to rf plasma alone, due to incorporation of more bonded nitrogen.
Measurements of viscosity, velocity slip coefficients, and tangential momentum accommodation coefficients using a modified spinning rotor gauge
Authors: Bentz J. A. , Tompson R. V. , Loyalka S. K.
Published: July 2002

A selection of experimental viscosity and slip measurements are reported for He and Ar. The measured values have been made with a modified spinning rotor gauge (SRG-2; MKS Instruments, Inc.) where the sphere is coaxially rotated in the cylindrical tube housing. All of the experiments were conducted in the slip regime in accordance with the theory previously developed [S. K. Loyalka, J. Vac. Sci. Technol. A 14, 2940 (1996)]. The theoretical results from this previous article allow one to extract values of the viscosity, the velocity slip coefficient, and the tangential momentum accommodation coefficient from the experimentally obtained angular retardation data for each gas without a need for calibration of the system against a known gas viscosity. Since the existing manufactured SRGs mount horizontally with the rotor angular momentum vector oriented vertically, the required SRG modifications were necessarily limited to the interior of the mounting tube. Here, an insert was developed for the mounting tube in which was bored a short, vertically oriented, cylindrical hole in which the rotor could turn coaxially. Measurements made with this modified version of the SRG are compared with previous experimental results and a discussion of the errors associated with both wall and end effects is included.
Tribological performance of a novel high wear resistant high Si Al–Si alloy weld overlay
Authors: Ott R. D. , Blue C. A. , Santella M. L. , Blau P. J.
Published: July 2002

A novel process has been developed at Oak Ridge National Laboratory for the production of high silicon (Si) containing aluminum–silicon (Al–Si) alloy weld overlay on Al alloys. The main purpose of the overlay is to improve the wear resistance of the underlying alloy. The process is versatile enough to place the overlay only in critical areas, thus, greatly reducing the cost of a component. Instead of manufacturing a component from expensive high Si content 390 Al alloy, the component could be manufactured from an inexpensive alloy, such as 319 Al alloy, and the high Si, Al–Si alloy overlay could be placed in essential areas where high wear resistance was required. Test specimens comprised of the high Si, Al–Si alloy overlays on 319 Al alloy have been processed to mimic the wear resistance of bulk 390 Al alloys. Pin-on-disk wear tests have been performed, following ASTM standards, to quantify the wear resistance of the high Si, Al–Si alloy overlay with that of bulk 390 Al alloy. Wear tests have also been performed on bulk 319 Al alloy as a baseline. Lubricated and nonlubricated pin-on-disk wear tests were conducted utilizing 440 C stainless steel and 52 100 steel balls as the pin material. Also evaluated were the frictional forces during the wear tests, scratch hardness, microhardness, and the Hertzian contact pressures. From the tests conducted, the high Si, Al–Si alloy overlay shows potential as a replacement of bulk 390 Al alloy for high wear resistant applications.
Negative cesium sputter ion source for generating cluster primary ion beams for secondary ion mass spectrometry analysis
Authors: Gillen Greg , King Lance , Freibaum Brian , Lareau Richard , Bennett Joe , Chmara Frank
Published: July 2002

A cesium sputter ion source has been used to generate novel cluster and monoatomic primary ion beams for secondary ion mass spectrometry (SIMS). The source produces a variety of primary ion beam species with sufficient flux to be usable for both organic surface analysis and semiconductor depth profiling. The primary focus of this work is on the generation and use of carbon and carbon-containing cluster primary ion beams for SIMS. Stability of the sputter ion source is a few percent over 20 min, has useful lifetimes of weeks to months, and produces total primary ion beam currents for C2− ions, measured at the sample, of >1 μA at an extraction voltage of 10 kV. Larger cluster ions (Cx−x=4–10 and CsCx−x=2–8) are produced with tens of nA of beam current. Due to the divergence of the source, focused beam operation gives current densities under optimal conditions of 0.4–0.5 mA/cm2. Cluster bombardment studies of organic films using carbon clusters Cx−x=1–10 indicate that large enhancements (up to a factor of 800) in the secondary ion yield for characteristic molecular ions from organic samples can be obtained with the larger cluster ions. The signal enhancement can also be utilized in microfocus operation of the source for organic secondary ion imaging studies. For favorable organic samples, cluster bombardment with Cx−, x>6 shows little evidence of degradation of the sample from the accumulation of primary beam-induced damage. This effect can be potentially utilized for depth profiling of organic thin films and for further enhancements in sensitivity for organic SIMS analysis. Depth profiling of low energy As implants in silicon with the CsC6− primary ion demonstrates that as much as a factor of 6 improvement in apparent depth resolution can be obtained compared to profiles obtained under standard conditions using Cs+ bombardment. The flexibility of the source to produce monoatomic primary ion beams from virtually any target material is also being exploited to prepare low energy in situ ion implant standards for quantitative SIMS analysis.
Selective-area chemical-vapor deposition of Si using a bilayer dielectric mask patterned by proximal probe oxidation
Authors: Gwo S. , Yasuda T. , Yamasaki S.
Published: July 2002

Silicon nitride (Si3N4) is a very robust material against oxidation and is typically used as an oxidation mask. Here, we report atomic-force microscope (AFM)-based local oxidation of Si3N4 and its applications in selective-area epitaxial growth using chemical-vapor deposition. High growth selectivity is accomplished in this work by employing a SiO2/Si3N4 bilayer mask structure, which is formed by locally oxidizing the Si3N4 surface (for defining the growth windows), depositing a blanket SiO2 layer, and then selectively removing SiO2 in the growth windows. High-resolution transmission electron microscopy images reveal that the selectively deposited Si structures can be grown with a high degree of crystalline perfection, while excellent size uniformity is confirmed by large-area AFM images.
Investigation of the W–TiN metal gate for metal–oxide–semiconductor devices
Authors: Youn Sunpil , Roh Kwanchong , Yang Sungwoo , Roh Yonghan , Kim Ki-Su , Jang Young-Chul , Lee Nae-Eung
Published: July 2002

We have characterized the physical and electrical properties of a W–TiN stacked gate in metal–oxide–semiconductor devices. The degree of tungsten crystallization was enhanced when the N2/Ar ratio was increased during TiN sputtering deposition and/or if the annealing temperature for W–TiN films was raised over 600 °C. However, the lowest resistivity was observed from W–TiN films annealed at 600 °C. We suggest that the TiOx intermediate layer was formed between the TiN gate electrode and SiO2 if the annealing temperature increases to more than 600 °C. In addition, we found that TiN effectively suppresses the fluorine diffusion into SiO2, and that the N2/Ar ratio determines the flatband voltage shift of the W–TiN/SiO2/Si capacitors.
Fabrication of ideally ordered anodic porous alumina with 63 nm hole periodicity using sulfuric acid
Authors: Asoh Hidetaka , Nishio Kazuyuki , Nakao Masashi , Yokoo Atsushi , Tamamura Toshiaki , Masuda Hideki
Published: July 2002

Nanochannel arrays with an ideally ordered hole configuration with a 63 nm hole periodicity and 15–40 nm hole diameter were fabricated using anodization of the pretextured Al in sulfuric acid solution. The SiC mold with an array of convexes, which was prepared by electron beam lithography, was used for the nanoindentation of the Al. The periodicity of convexes was adjusted to the self-organized periodicity in sulfuric acid solution. The obtained concaves on Al initiated the hole development during the anodization and generated the ideally ordered hole configuration with a 63 nm period. Under the appropriate anodization conditions, anodic porous alumina with an aspect ratio of over 20 was obtained.
Effects of gas-flow structures on radical and etch-product density distributions on wafers in magnetomicrowave plasma etching reactors
Authors: Ikegawa Masato , Kobayashi Jun’ichi , Fukuyama Ryoji
Published: July 2002

To achieve high etch rate, uniformity, good selectivity, and etch profile control across large diameter wafers, the distributions of ions, radicals, and etch products in magnetomicrowave high-etch-rate plasma etching reactors must be accurately controlled. In this work the effects of chamber heights, a focus ring around the wafer, and gas supply structures (or gas flow structures) on the radicals and etch products flux distribution onto the wafer were examined using the direct simulation Monte Carlo method and used to determine the optimal reactor geometry. The pressure uniformity on the wafer was less than ±1% when the chamber height was taller than 60 mm. The focus ring around the wafer produced uniform radical and etch-product fluxes but increased the etch-product flux on the wafer. A downward-flow gas-supply structure (type II) produced a more uniform radical distribution than that produced by a radial gas-supply structure (type I). The impact flow of the type II structure removed etch products from the wafer effectively and produced a uniform etch-product distribution even without the focus ring. Thus the downward-flow gas-supply structure (type II) was adopted in the design for the second-generation of a magnetomicrowave plasma etching reactor with a higher etching rate.
Epitaxial growth of Al2O3 thin films on Si(100) using ionized beam deposition
Authors: Whangbo S. W. , Choi Y. K. , Chung K. B. , Jang H. K. , Whang C. N.
Published: July 2002

Al 2 O 3 thin films were epitaxially grown on Si(001) substrates by using reactive ionized beam deposition. The substrate temperature dependence of crystallinity of Al2O3 films were investigated by in situ reflection high-energy electron diffraction. The epitaxial γ-Al2O3 stacked structure was formed at above 850 °C, and below this temperature the films were polycrystal. Film compositions and interface states were investigated by x-ray photoelectron spectroscopy and transmission electron microscopy measurements. From these results, stoichiometric Al2O3 films with sharp interface were confirmed. The rms surface roughness of the epitaxially grown Al2O3 film was 0.46 nm, and as the substrate temperatures increased, the crystalline quality and the surface flatness were improved.
Technology for the fabrication of ultrashort channel metal–oxide–semiconductor field-effect transistors
Authors: Knoch J. , Appenzeller J. , Lengeler B. , Martel R. , Solomon P. , Avouris Ph. , Dieker Ch. , Lu Y. , Wang K. L. , Scholvin J. , del Alamo J. A.
Published: July 2002

We present the experimental details for the preparation of an ultrashort channel metal–oxide–semiconductor field-effect transistor (MOSFET) using a V-groove approach. This new fabrication process allows a definition of the channel with a resolution that exceeds the limit of the lithography used. The approach is based on the combination of electron beam lithography and anisotropic etching of an epitaxial silicon layered structure based on ultrathin silicon on insulator (SOI). A self-limiting etching process forms a “V” shaped groove into the silicon stack and the region at the tip of the V groove becomes the channel. The definition of the channel can be as small as 10 nm in length but it depends strongly on the anisotropic etching behavior, the quality of the molecular beam epitaxy grown layers, and the definition of the mask formed by the lithography. Here we discuss the fabrication of V-groove openings with the appropriate dimensions and quality required to fabricate nanoscale devices. The control of the V-groove process is discussed for making MOSFETs with good output characteristics.
Effects of the field emission display panel sealing process on the cathodoluminescence properties of phosphor screen
Authors: Park Z. M. , Jeon D. Y. , Jin Y. W. , Cha S. N. , Kim J. M.
Published: July 2002

The degradation of the cathodoluminescence (CL) brightness of the phosphor screen during the panel sealing process with frit glass as a sealing material was investigated. A simplified outgassing process, which could offer the same environment as the standard panel sealing process to the phosphor screen, was designed to investigate the searched effects with ease and accuracy. Commercially available red, green, and blue phosphors, i.e., Y2O2S:Eu, ZnS:Cu,Al, and ZnS:Ag,Cl phosphors were used in this study, and the characteristics of CL degradation varied with the phosphor. It was found that the CL brightness of the phosphor screen decreased after experiencing frit outgassing during the standard panel sealing process and the simplified outgassing process. From the surface analyses on the phosphor screen, it was found that the CL brightness of the phosphor screen decreased because of the surface contamination due to PbO and CO2 released from the frit.
Structure control of pulsed laser deposited ZrO2/Y2O3 films
Authors: Voevodin A. A. , Jones J. G. , Zabinski J. S.
Published: July 2002

Structure control in the laser ablation deposition of yttria stabilized zirconia (YSZ) films is explored. A focus was given to a low temperature growth of tetragonal and cubic YSZ films with [001] growth orientation, using surface ion bombardment. Unlike an ion-beam assisted pulsed laser deposition, the ion bombardment was achieved by the acceleration of zirconium ions from the ablation plumes themselves with a negative substrate bias. The large degree of zirconium ionization was obtained by using low pressure Ar backgrounds. Correlation between substrate bias, film lattice parameters, orientation, surface microtopography, stress, and hardness are discussed. Film structural change from nearly amorphous and predominantly (111) oriented to distorted tetragonal and to cubic with (002) orientation were observed as the bias was increased from zero to −300 V in 0.2 Pa Ar environment. The technique was used to produce single-axis oriented YSZ films with a smooth (002) surface and 30 GPa hardness on a number of single and polycrystalline substrates at 100 °C deposition temperature.
Controlled coordination and oxidation states of copper and manganese cations in complex nickel–copper–cobalt–manganese oxide thin films
Authors: Kukuruznyak Dmitry A. , Han Sang-Wook , Lee Moon-Hwan , Omland Kimberly A. , Gregg Michael C. , Stern Edward A. , Ohuchi Fumio S.
Published: July 2002

Thin thermistor films of Ni0.48Co0.24CuxMn2.28−xO4 (x=0.6 and 1.2) were prepared by the deposition of metalorganic solutions followed by furnace annealing at temperatures between 600 and 800 °C. Annealing temperatures are decisive factors to control the electrical properties and electronic structure. X-ray photoelectron spectroscopy revealed that the specimens contained a mixture of Cu1+ and Cu2+ cations, and the annealing caused the change of the oxidation state from Cu1+ to Cu2+, which was accompanied by the reduction of manganese cations from Mn4+ to Mn3+. The Cu 2p core level from the Cu1+ state along with Cu 3d levels showed unusually large negative binding energy shifts (2p3/2 at 930.8 eV and 2p1/2 at 950.6 eV). Extended x-ray absorption fine structure showed that all manganese ions were located in octahedral sites of the spinel lattice, and both Cu1+ and Cu2+ cations occupy the tetrahedral sites regardless of the annealing temperature. X-ray absorption near edge structure spectra of the Mn K edge confirmed the reduction of manganese at high temperature. Cu K-edge spectra confirmed the presence of the cations with anomalous position in the 3d states, thus the negative shift of the Cu1+ core was attributed to the tetrahedral coordination of these cations in the spinel structure.
Synthesis and structural, electrochromic characterization of pulsed laser deposited vanadium oxide thin films
Authors: Fang Guo Jia , Liu Z. L. , Wang Yu , Liu Y. H. , Yao K. L.
Published: July 2002

Vanadium oxide thin films with different stoichiometry have been deposited on In2O3:SnO2 (ITO) glass and Si wafer by pulsed laser deposition technique at different substrate heating or annealing temperatures and oxygen pressure. The structural properties of as-deposited and annealed VOx thin films were analyzed by using a scanning accessory of transmission electron microscope, x-ray diffraction, Fourier transform infrared spectrum, and Raman spectrum. The as-deposited thin film on the Si(111) wafer showed lower orientation with polycrystalline structure but those annealed at 300 °C above showed highly c-axis oriented growth. Highly c-axis oriented growth nanocrystalline V2O5 thin films with orthorhombic polycrystalline structure were successfully synthesized on ITO glass by using the scanning laser ablation technique at deposition temperature as low as 200 °C. Cyclic voltammograms at sweep rate of 50 mV/s shows that the no-long-term degradation was noticed at least up to 1000 cycles, and durability was verified to 8000 cycles in the voltage range between −1.2 and 1.4 V. It is demonstrated that these c-axis oriented V2O5 thin films on ITO are good candidates for cathode thin films for rechargeable batteries and electrochromic devices.
Adsorption of hydrogen on clean and potassium modified low index copper surfaces: Cu(100) and Cu(110)
Authors: Thomsen L. , Onsgaard J. , Godowski P. J. , Møller P. , Hoffmann S. V.
Published: July 2002

The adsorption of atomic hydrogen has been studied on clean and potassium modified Cu(110) and Cu(100) surfaces. Two hydrogen induced states in the valence band have been found on the clean Cu(110) surface, an α state receding in the subsurface and a β state in the surface of the crystal. Upon annealing, hydrogen in the subsurface both diffuses to the surface and desorbs at 330 K, and diffuses into the bulk. Two states, αK and βK, have also been observed on the potassium modified surfaces, with the αK state assigned to a potassium-hydrogen bond and the βK state assigned to a Cu–hydrogen bond. The Cu(110) surface is significantly more reactive than the Cu(100) surface.
The application of in situ monitor of extremely rarefied particle clouds grown thermally above wafers by using laser light scattering method to the development of the mass-production condition of the tungsten thermal chemical vapor deposition
Authors: Ito Natsuko , Moriya Tsuyoshi , Uesugi Fumihiko , Moriya Shuji , Aomori Masaru , Kato Yoshinori , Tachibana Mitsuhiro
Published: July 2002

It has been successfully demonstrated that the scattered-light intensity of thermally grown particle clouds consisting of particles of less than 20 nm in size above wafers in a real tungsten (W) chemical vapor deposition (CVD) chamber correlate well with both the surface roughness of the W-CVD film measured by atomic force microscopy and with the gas-flow ratio SiH4/WF6. In addition, we can observe the appearance and motion of particle clouds corresponding to the transient variation of the ratio SiH4/WF6 at the conversion of gases and at the change of the flow ratio. These features of our in situ particle monitor enable us to achieve the mass-production conditions for particle-free and smooth surfaces of W films with short cycle time. Moreover, our particle monitor is sensitive enough to adopt in the development of process conditions as the reduction of design rules for large-scale integrated circuit proceeds. Therefore, applying our in situ particle monitor above wafers for developing mass-production conditions is a notable method to minimize the monitor wafers and to realize short cycle time.
Resonances in electron-stimulated desorption of Eu atoms
Authors: Ageev V. N. , Kuznetsov Yu. A. , Madey T. E.
Published: July 2002

The electron-stimulated desorption of europium (Eu) atoms has been detected for the first time from Eu layers adsorbed on an oxygen-covered tungsten surface. The dependence of Eu atom yield on electron energy has a pronounced resonance form. As a function of Eu coverage, there appear to be two different types of resonant processes associated with both Eu core excitations and W core excitations.
Molecular dynamics simulations of the trapping of ethane on Si(100)-(2×1): Effect of rotational energy and surface temperature
Authors: Reeves C. T. , Stiehl J. D. , Mullins C. B. , Sitz G. O.
Published: July 2002

Classical molecular dynamics simulations have been used to investigate the effect of rotational energy and surface temperature on the trapping probability of ethane on Si(100)-2×1. At all translational energies studied, the trapping probability remains constant as the rotational state of the incident molecule is increased to the equivalent of J=20, then decreases as the rotational energy is further increased. Over the range of incident translational energies (0.1–0.6 eV) and angles (0° to 60°) studied, when J=40, the trapping probability has decreased by about 30% relative to the probability at low J values. Computed trajectories also indicate that surface temperature can affect trapping probabilities. Simulations indicate that for trajectories with 0.3 eV of translational energy at normal incidence, increasing the surface temperature from 65 to 200 K will not significantly change the trapping probability. However, if the surface temperature is raised to 600 K, the trapping probability falls to about half of the trapping probability at 65 K.
Fluorocarbon polymer formation, characterization, and reduction in polycrystalline–silicon etching with CF4-added plasma
Authors: Xu Songlin , Sun Zhiwen , Chen Arthur , Qian Xueyu , Podlesnik Dragan
Published: July 2002

Addition of CF4 into HBr-based plasma for polycrystalline–silicon gate etching reduces the deposition of an etch byproduct, silicon oxide, onto the chamber wall but tends to generate organic polymer. In this work, a detailed study has been carried out to analyze the mechanism of polymerization and to characterize the polymer composition and quantity. The study has shown that the polymer formation is due to the F-radical depletion by H atoms dissociated from HBr. The composition of the polymer changes significantly with CF4 concentration in the gas feed, and the polymer deposition rate depends on CF4% and other process conditions such as source power, bias power, and pressure. Surface temperature also affects the polymer deposition rate. Adding O2 into the plasma can clean the organic polymer, but the O2 amount has to be well controlled in order to prevent the formation of silicon oxide. Based on a series of tests to evaluate polymer deposition and oxide cleaning with O2 addition, an optimized process regime in terms of O2-to-CF4 ratio has been identified to simultaneously suppress the polymer and oxide deposition so that the etch process becomes self-cleaning.
Field activated lateral-type polysilicon emitter with extremely high emission current and very low turn-on voltage
Authors: Lee Jae-Hoon , Lee Myoung-Bok , Hahm Sung-Ho , Choi Hyun-Chul , Lee Jong-Hyun , Lee Jung-Hee , Kim Jin-Sup , Choi Kyu-Man , Choi Chang-Auck
Published: July 2002

A lateral-type poly-Si field emission device was fabricated by utilizing the local oxidation of silicon (LOCOS) process and a simple and efficient activation technique of the tip end was proposed to achieve a high emission current. The fabricated single field emitter exhibits excellent electrical characteristics such as a very low turn-on voltage of 2 V and an extremely high current of ∼500 μA at anode to cathode voltage of 30 V. These superior field emission characteristics are believed to be due to both an increased enhancement factor (β) by appropriate activation and originally sharpened tip by the LOCOS process.
Monolayer formation of 6-deoxy-6-thiol-β-cyclodextrin on a Au(111) surface studied by scanning tunneling microscopy
Authors: Yasuda Satoshi , Futaba Don Norimi , Takeuchi Osamu , Suzuki Iwao , Yase Kiyoshi , Sumaoka Jun , Komiyama Makoto , Shigekawa Hidemi
Published: July 2002

Mono(6-deoxy-6-thiol) β-cyclodextrins (β-CyD–SH) were grown on a Au(111) surface in ethanol solution, and monolayer formation process of which was studied by scanning tunneling microscopy for the first time. At the initial stage, β-CyD–SH molecules were adsorbed on the Au(111) surface not only randomly, but also partially in a linear ordering. In the following stage, islands were formed and resulted in a uniform monolayer. The observed mechanism is completely different from the model predicted on the basis of the macroscopic result, the Langmuir model. An attractive interaction exists between β-CyD–SHs, contrary to the prediction by the model. The observed growth processes are quite similar to what was previously observed for lipoamide–β-cyclodextrin (LP–β-CyD). However, in the case of β-CyD–SH, the islands did not grow in size as compared to the case of LP–β-CyD, and the number of the islands increased to form a uniform monolayer. This characteristic indicates that the interaction strength ratio of CyD–Au to CyD–CyD is larger for β-CyD–SH than that for LP–β-CyD.
Field-emission properties of vertically aligned carbon-nanotube array dependent on gas exposures and growth conditions
Authors: Lim S. C. , Jeong H. J. , Park Y. S. , Bae D. S. , Choi Y. C. , Shin Y. M. , Kim W. S. , An K. H. , Lee Y. H.
Published: July 2002

We grew vertically aligned carbon nanotubes (CNTs) using microwave plasma-enhanced (MPE) and thermal chemical-vapor deposition (CVD) and characterized their field emission properties. We observe that the flickering and instability in the field emission are due to the metal particles present on the field-emission array (FEA) surface, particularly from the MPECVD-grown samples. The existence of metal particles is an obstacle to obtaining reliable emission properties. The emission properties of the CNT–FEA are studied as a function of gas-exposure time with hydrogen, nitrogen, and oxygen gases. Gas exposures affected turn-on voltage, hysteresis, and the slope of Fowler–Nordheim plots. We observe that the saturation of emission currents is attributed to gas adsorbates present on the surface of the FEA. Oxygen exposures induce more severe degradation on the field-emission properties than nitrogen, whereas emission properties are improved by hydrogen gas exposures that clean the surface of emitters. In addition, hydrogenation of carbon nanotubes has technical importance for activation of the CNT–FEA.
Novel resistive layer structure using via holes of an insulating interdielectric as a current path
Authors: Ha J. K. , Chung B. H. , Han S. Y. , Choi J. O. , Kim H. G.
Published: July 2002

A novel resistive layer structure was proposed for a Mo-tip field emitter array, where the electrons travel along a resistive path running from a cathode electrode to a tip through nearest neighboring via holes of an insulating interdielectric film. To study the field emission characteristics of the new structure, Mo-tip arrays with a gate hole size of 1.2 μm were fabricated using a PH3 doped amorphous Si (a-Si:H) film as the resistive layer and a silicon oxide (SiOx) interdielectric film with 1.2-μm-diam via holes. Before the measurements of current–voltage characteristics, the arrays were annealed in an Ar environment, which is used for the vacuum packaging of a display panel. The arrays showed a strong dependence of an emission current on the resistive layer thickness, i.e., an average current density of 10 nA/tip at a gate voltage of 108, 93, and 82 V for a-Si:H film with a thickness of 0.36, 0.6, and 1.2 μm, respectively. The new structure exhibited a smaller voltage drop than that of a conventional mesh structure, with the gate voltage of the former being decreased by 35 V at a current density of 10 nA/tip. It was also found that the new structure was robust enough to sustain above 70 nA/tip, which is more than enough to be used for a wide variety of field emission display applications. The dependence of the resistivity of the a-Si:H on a sealing process was also discussed.
Near-surface generation of negative ions in low-pressure discharges
Authors: Stoffels E. , Stoffels W. W. , Kroutilina V. M. , Wagner H.-E. , Meichsner J.
Published: July 2002

Formation processes of negative ions in low-pressure plasmas are not yet fully understood: as a rule experiments reveal higher negative ion density than predicted by the models. In this work we report near-surface generation of negative ions. This hitherto neglected formation mechanism appears to be important in low-pressure discharges and can have large impacts on the bulk plasma chemistry. We monitor energy-resolved positive and negative ion fluxes arriving at the electrodes in an oxygen parallel-plate radio-frequency (rf, 13.56 MHz) and dc glow plasmas by means of a quadrupole mass spectrometer. Negative ions formed in the plasma volume are observed by extracting them through an orifice in the anode of a dc glow discharge. Unexpectedly, we record large negative ion signals at the cathode of a dc discharge and at the grounded electrode of an rf discharge. These ions are formed in the plasma sheath, in collision processes involving high-energy species. We propose an efficient mechanism of negative ion generation due to ion pair formation in the sheath.
Cross-sectional transmission electron microscopy investigation of the dead layer of ZnS:Ag,Al phosphors in field emission displays
Authors: Kajiwara K.
Published: July 2002

The dead surface layer of blue-emitting ZnS:Ag,Al phosphor with Al metallized thin film in high-voltage field emission displays (FEDs) has been investigated by means of cross-sectional transmission electron microscopy. From these observations, it was found that electron irradiation at 6 keV excitation causes the decomposition of ZnS and the subsequent evolution of sulfur in the topmost surface layer ∼30 nm, and also causes the formation of lattice defects within the electron penetration depth of ∼300 nm in a life-end stage. When this evidence was taken into account, it was estimated that the decomposition rate of ZnS and the formation rate of lattice defects depend mainly on the degree of crystallinity and the atomic-scale surface roughness of ZnS phosphor particles. Necessary characteristics of ZnS:Ag,Al phosphors for longer luminescence lifetime in FEDs were suggested in this work.
Patterning-induced image placement distortions on electron beam projection lithography membrane masks
Authors: Lercel Michael , Magg Christopher , Lawliss Mark , Williams Carey , Caldwell Neal , Ackel Robin , Kindt Louis , Racette Kenneth , Reu Phillip , Engelstad Roxann , Mackay R. Scott
Published: July 2002

Membrane masks are needed for charged particle lithography and can include both stencil masks and masks with thin continuous membranes. Producing accurate image placement on membrane masks requires careful control of mask shape, pattern writing, and stress control of the mask materials. Pattern density and pattern density gradients also affect image placement (IP) control. This article discusses IP distortions on electron projection lithography masks caused by patterning the imaging layers with low and high density patterns and patterns with large gradients in the density. The process-induced distortion has been found to be largest with the largest vector distortion at the boundary when high pattern density gradients are present. The anisotropic stiffness of the unit cell also affects the process-induced distortion. Qualitatively, the results between continuous membrane and stencil masks show similar characters. The results provide distortion information that could be used to determine the maximum allowable membrane stress (for stencil masks) and scatterer layer stress (for continuous membrane masks) to meet necessary mask production targets.
Simulating the effects of pattern density gradients on electron-beam projection lithography pattern transfer distortions
Authors: Reu P. L. , Engelstad R. L. , Lovell E. G. , Magg C. K. , Lercel M. J. , Mackay R. S.
Published: July 2002

The development of a low-distortion mask is critical to the success of the sub-0.1 μm lithography technologies. Electron-beam projection lithography (EPL) is one of the potential candidates for next-generation lithography. In order to minimize mask image placement (IP) errors, it is important to understand the factors that induce pattern distortions during mask fabrication and pattern transfer. The fabrication process flows for two EPL mask formats were numerically simulated and experimentally assessed for IP. This study included continuous membranes and stencil membranes for 1 mm ×1 mm and 1 mm ×12 mm window sizes on a 4 in. wafer. Both intramembrane (i.e., within a single window) and intermembrane (i.e., cross-mask) results are reported with excellent correlation between the finite element (FE) data and the experimental measurements. In this article details of the FE simulations are presented; an article by (M. Lercel et al., J. Vac. Sci. Technol. B, these proceedings) describes the corresponding experimental work.
Focusing x-ray masks for printing very narrow features
Authors: Feldman M. , Khan M. , Cerrina F.
Published: July 2002

X-ray masks may be fabricated with features that have parabolic rather than the usual rectangular or trapezoidal cross sections. Phase shift effects in such features cause them to act as tiny lenses that focus the x rays on to the wafer. The lenses may either be cylindrical, to form line images on the wafer, or spherical, to form points. Wider images, with very sharp outlines, may also be formed on the wafer by using wider mask features, which have parabolic cross sections only near their edges. Features down to at least 50 nm may be imaged, with wide latitudes in mask parameters, gap, and resist processing.
Substrate cooling efficiency during cryogenic inductively coupled plasma polymer etching for diffractive optics on membranes
Authors: Olynick Deirdre L. , Anderson Erik H. , Harteneck Bruce , Veklerov Eugene
Published: July 2002

We fabricate high-resolution diffractive optics on membranes using a bilayer resist system consisting of hydrogensilsesquioxane as a negative electron-beam imaging layer and hardbaked AZPN114 as the underlay. To minimize sidewall etching of the polymer, the AZPN114 layer was etched at −100 °C in a cryogenically cooled inductively coupled plasma etcher. Features fabricated on Si supported membrane wafers, where the areas of interest are separated from the platen by the wafer thickness, provide an additional challenge to the low-temperature dry etch process due to low cooling efficiency (and thus membrane heating). Using cooling theory and experimental verification we look at membrane cooling efficiency for different hardware and membrane size combinations. Diffusive cooling in membranes less than 140 μm wide dominates membrane cooling during the etch process. With these small membranes we have fabricated high efficiency x-ray zone plates with linewidths as small as 30 nm and 6:1 aspect ratios.
Progress toward a high-brightness photoemission source for multiple-electron beam lithography
Authors: Coyle S. T. , Fernandez A. , Janaway G. , Sagle A. , Mankos M.
Published: July 2002

A high-brightness photoemission source is being developed for use in a multiple-electron beam lithography system suitable for mask patterning. Cesium telluride (Cs2Te) photocathodes have achieved stable brightness of 2–3×106 A/cm2 Sr and current densities of 30–60 A/cm2. Magnesium photocathodes have achieved stable brightness of 1–3×106 A/cm2 Sr and current density of 40 A/cm2. Long term current stability of better than the required specification of 17%/5 min has been obtained at photoyields of ∼30 nA/mW.