bluuebunny/crossref_metadata_2025 huggingface dataset:
Ion Backscattering and Sputtering of Plasma-Irradiated Carbon and Tungsten Surfaces in an Oblique Magnetic Field
Authors: Kawata Jun , Ohya Kaoru
Published: October 2002

A Monte Carlo simulation model which combines ion backscattering and sputtering of solids with transport of emitted particles in the scrape-off layer plasma is developed for the study of the plasma-wall interaction in magnetic confinement fusion devices. The emphasis is put on the precise understanding of ionization and redeposition processes of backscattered and sputtered particles. In the model, Maxwellian ion-solid interaction, ionization of backscattered and sputtered neutral particles in the plasma, and gyromotion of the ionized particles in an oblique magnetic field are included. The heavier masses (lower charge states and lower energies) the particles have, the more they are redeposited. Due to impact of carbon ions on carbon and tungsten, therefore, less backscattered carbon is redeposited, whereas most of the sputtered tungsten atoms are redeposited. The redeposition causes substantially lower effective sputtering yields and a decrease in low-energy component of the sputtered atoms.
Estimated Errors in Determination of Electron Temperature for Symmetric Triple Probes Deposited with Contaminants
Authors: Okano Daisuke , Matsumae Hiromi , Akazaki Masanori
Published: October 2002

For a planar or cylindrical triple probe which is contaminated with metal or gas, errors in the determination of electron temperature are numerically studied. As factors of error, we focus on i) relative contact voltage due to contaminants between two probes of the triple probe and ii) ion current parameter represented by a constant of proportionality between the square of ion current and probe bias. It is found that errors due to relative contact voltage and ion current parameter can be minimized by selecting the DC bias of the triple probe for the two probe types.
Depth and State Analyses of Deuterium and Helium in D2-Annealed He+-Implanted Yttrium Iron Garnet
Authors: Furuya Keiichi , Matsushita Kenichi , Aratani Michi , Yanokura Minoru , Imura Ryo , Uematsu Kenichi
Published: October 2002

Simultaneous depth analysis of deuterium and helium in the surface layer of deuterium-annealed He+-implanted yttrium iron garnet (YIG) was achieved by means of elastic recoil depth analysis (ERDA) and the results were compared with those of state analysis of deuterium and helium extracted by thermal desorption mass spectrometry (TDS). As a result, it was shown that both deuterium and helium moved to the strained lattice sites due to implantation via thermal annealing of the samples. By annealing the critically helium-saturated sample, helium atoms remained at the stable sites in the lattice, while deuterium occupied the less stable sites. Stabilization of helium sites at annealing temperature of around 350° C was observed for unsaturated and critically saturated samples. In the case of an oversaturated sample, three kinds of sites for helium were found, and it was observed that helium formed bubbles and that deuterium concentrated at sites corresponding to those of helium via annealing.
Thin-Film Formation by Spin Coating: Characteristics of a Positive Photoresist
Authors: Yada Toshio , Maejima Taro , Aoki Masaru , Mitsumasa Umesaki Mitsumasa Umesaki
Published: October 2002

Thin-film formation of a positive photoresist was investigated experimentally in terms of weight loss and temperature shift of the photoresist solution on a glass wafer during the spinning process. The former is analyzed by gravimetry and the latter by thermometry. The results show that weight loss of the photoresist solution is dominated mainly by outflow and is influenced only slightly by the evaporation of the solvent during the spinning process. Furthermore, film uniformity has been improved by a large quantity of radial flow, during which the solution behaved as a Newtonian fluid, at the middle stages of the spinning process. Film uniformity is degraded by non-Newtonian flow and the temperature difference in the glass wafer at the later stages of the spinning process. Consequently, a most suitable spinning time (minimum thickness deviation) exists for each spin velocity.
Concise Short-Channel Effect Model for Inversion-type Ultrathin Silicon-on-Insulator p-Channel Metal-Oxide-Silicon Field-Effect Transistors Based on Partitioning of Thin-Film
Authors: Shiao-Shien Chen Shiao-Shien Chen , James B. Kuo James B. Kuo
Published: October 2002

This paper reports a concise short-channel effect model for inversion-type ultrathin silicon-on-insulator (SOI) metal-oxide-silicon field-effect transistors (MOSFETs). As verified by the 2D simulation data, the concise short-channel effect model based on partitioning of the thin-film region provides a good prediction. According to the analytical model, the short-channel effect is strongly influenced by its thin-film thickness.
Study on Droop Characteristics of Laser Diodes as Light Sources of Laser Beam Printer
Authors: Nagai Yutaka , Mihashi Yutaka , Kakimoto Shoichi , Ikeda Kenzi , Susaki Wataru
Published: October 2002

To obtain a small droop, which is the ratio of transient reduction of output power after the laser diode (LD) is turned on, the influence of quantum efficiency and transient thermal flow of laser diodes is investigated both theoretically and experimentally. The analysis shows that as the thermal resistance between active region and heatsink is decreased and the reflectivity of front facet is increased, the droop decreases. The results are applied to self-aligned structures with bent active layer laser diodes (SBA LD's). By employing a junction-down configuration for assembly of the SBA laser chips and silicon carbide (SiC) as a submount material, and by coating the front facet so as to have reflectivity of 50% with taking into reduction of catastrophic optical damage (COD) level, the droop is decreased to 7.0%. In contrast, in the conventional SBA LD's which have a junction-up configuration with silicon (Si) as the submount material and have only a passivation coating on the front facet, value of the droop is 17.5%. Our results serve as a guide to the design of the light source of laser beam printers (LBP's).
Influence of Temperature and Humidity Change on Optical Waveguide Circuits Composed of Deuterated and Fluorinated Methacrylate Polymers
Authors: Hida Yasuhiro , Saburo Imamura Saburo Imamura
Published: October 2002

We fabricated a 57 cm long waveguide circuit and an arrayed-waveguide-grating (AWG) demulti/multiplexer using deuterated and fluorinated methacrylate polymers, and examined the influence of environmental change on their transmission characteristics. A 57 cm waveguide with a loss of 0.1 dB/cm at 1.3 µ m exhibited a slight loss increase of 0.03 dB/cm when the humidity was raised from 13 to 98%RH and a negligible loss change when the temperature was increased to 70° C. On the other hand temperature and humidity changes respectively caused wavelength shifts of 0.9 and 5 nm in the transmission peaks of an AWG with an adjacent channel spacing of 0.65 nm. Furthermore we confirmed that the influence of the humidity resulted from water sorption in the waveguide polymers.
Enhancement of Photoelectric Conversion Efficiency in Copper Phthalocyanine Solar Cell: White Light Excitation of Surface Plasmon Polaritons
Authors: Kume Tetsuji , Hayashi Shinji , Ohkuma Hiroshi , Yamamoto Keiichi
Published: October 2002

Excitation of surface plasmon polaritons (SPP) in copper phthalocyanine (CuPc) solar cells was achieved by means of a wavelength-scan attenuated total reflection (λ-scan ATR) method. The action spectra of the solar cell (wavelength dependence of the photocurrent) were measured simultaneously with the λ-scan ATR spectra for various incident angles. The action spectra were found to exhibit a pronounced peak around 550 nm due to the excitation of SPP.
The existence of an optimum incident angle which yields a maximum enhancement of the photoelectric conversion was also found. The enhancement of the conversion efficiency under white light illumination was demonstrated by using a Xe lamp.
Energy Distribution and Yield Measurement of Secondary Electrons to Evaluate the Equilibrium Charging Voltage of an Isolated Electrode during Negative-Ion Implantation
Authors: Toyota Yoshitaka , Tsuji Hiroshi , Yasuhito Gotoh Yasuhito Gotoh , Junzo Ishikawa Junzo Ishikawa
Published: October 2002

The negative-ion implantation method has the advantage that the charging voltage of an isolated electrode, or electrically insulated conductive material, stays as low as at most +10 V during implantation without any charge neutralization. The significant parameters, the energy distribution and the yield of secondary electrons in negative-ion implantation, have been measured in the energy range below 40 keV. The results show that the energy distribution, which is independent of ion energy in shape, has a low energy peak together with a long tail extending toward the high-energy region, and that the yield increases with ion energy. Furthermore, the equilibrium charging-voltage equation of an isolated electrode during negative-ion implantation is presented. The charging voltages estimated according to the equation are found to be in good agreement with those measured directly with a high-input-impedance voltmeter. It is also demonstrated that the charging voltage is proportional to the yield and to ion velocity in the linear region of the kinetic electron emission.
Scanning Positron-Annihilation Microscope
Authors: Chihiro Yamanaka Chihiro Yamanaka , Kouji Hosokawa Kouji Hosokawa , Motoji Ikeya Motoji Ikeya , Shigehiro Nishijima Shigehiro Nishijima , Toichi Okada Toichi Okada
Published: October 2002

A simple positron annihilation imaging device was developed using conventional positron annihilation apparatus and a sample scanning stage. A positron source of 22NaCl was scanned on a sample, and a two-dimensional map of positron lifetime spectra was constructed by a personal computer. Shocked aluminum and natural banded iron formations were imaged as examples.
Simple Method of Correcting Optical Proximity Effect for 0.35 µm Logic LSI Circuits
Authors: Kawamura Eiichi , Haruki Tamae , Manabe Yasuo , Isamu Hanyu Isamu Hanyu
Published: October 2002

We propose a practical optical proximity correction (OPC) system, whose characteristics are simple and effective, for logic LSI circuits and outline all the steps for OPC.
We also report the improvement of gate length deviations in a logic device with OPC.
Application of Mark Detection Using the Vibration Method to an Electron Beam Exposure System
Authors: Takamoto Kiichi , Nobuo Shimazu Nobuo Shimazu
Published: October 2002

The possibility of applying a mark detection method using the vibration method to an electron beam exposure system is investigated. The function V(t) with a period T can be used as the function vibrating the beam when V(t) has the properties: V(t)=-V(-t), V(t)=V(-T/2-t) for t≤0, and V(t)=V(T/2-t) for t≥0. Functions included are triangle, ladder, and discontinuous functions. This leads to the possibility of applying the mark detection technique to an excimer laser lithography system. Fluctuation in the center of gravity of the beam power density distribution is the most serious source of error in determining mark location. The experimental result shows that the vibration method is an effective mark detection technique.
Standing Wave Effect of Various Illumination Methods in 0.25 µm KrF Excimer Laser Lithography
Authors: Uchiyama Takayuki , Shioiri Satomi , Hashimoto Takeo , Kunihiko Kasama Kunihiko Kasama
Published: October 2002

Illumination dependence of the standing wave effect was investigated by experiment and simulation in variously sized line and space (L&S) patterns. A chemically amplified positive resist and a KrF excimer laser stepper with 0.5 N
A (numerical aperture) were used under various defocus conditions. The amplitude of the swing curve increased with increasing defocus value and showed complicated illumination dependence. At a focused position, higher σ (partial coherence) and oblique illuminations induced a larger amplitude of the swing curve; however, in the defocused region of ±0.6 µ m, necessary for actual device fabrication, the amplitudes of these illuminations were smaller than that of low σ illumination. Moreover, it was found that the amplitude variation was closely related to the log-slope value of exposure light intensity distribution at the nominal pattern edge.
Analysis of Nonplanar Topography Effects of Phase Shift Masks on Imaging Characteristics
Authors: Terasawa Tsuneo , Hasegawa Norio , Imai Akira , Okazaki Shinji
Published: October 2002

Nonplanar topography effects of phase shift masks (PSMs) on imaging characteristics are analyzed by using vector theory. Intensity distributions along the cross-sectional plane of the mask and image plane are calculated. The polarization effects of transverse electric (TE) and transverse magnetic (TM) waves are examined and the difference between the diffraction efficiency of TE waves and that of TM waves is evaluated. Imaging characteristics obtained using several types of alternate PSMs are examined, taking nonplanar topography effects into account. The lack of intensity balance between adjacent aperture images and asymmetry in the intensity with respect to the best focal plane are predicted by accurately calculating optical diffraction at the PSM.
Also, 360° phase shifting by fabricating a subtractive structure in a chromeless area is examined and is found to produce a dip in the image intensity; such a dip would not be predicted by conventional scalar theory.
New Systematic Evaluation Method for Attenuated Phase-Shifting Mask Specifications
Authors: Kagami Ichiro , Sugawara Minoru , Kawahira Hiroichi , Tsudaka Keisuke , Ishikawa Kiichi , Nozawa Satoru , Shimizu Hideo , Ogawa Tohru
Published: October 2002

A new simulation-based approach for specifying an attenuated phase-shifting mask (att-PSM) is proposed with systematically evaluating entire process parameters related to illumination sources, resist development in a wafer and process latitude. Exposure-defocus and mask fabrication latitude (EDM) methodology is adopted for considering the process latitude of exposure, defocus and mask line width. Transmittance and mask bias are targetted in the specifications, because these parameters are essential in the selection of the optimum att-PSM characteristics. The suppression of optical proximity effects by modified beam illumination (MBI) is also verified by the new evaluation method. The technique of combined att-PSMs and MBI can be applied to various types of dense hole patterns with the appropriate transmittance and mask bias.
Particle Simulation of Relativistic Charged Beams Using Integral Kernel Method
Authors: Hideya Nakanishi Hideya Nakanishi , Jumei Matsui Jumei Matsui , Tetsuya Uchimoto Tetsuya Uchimoto , Nobuaki Isei Nobuaki Isei , Masayuki Watanabe Masayuki Watanabe , Zensho Yoshida Zensho Yoshida , Yuichi Ogawa Yuichi Ogawa , Nobuyuki Inoue Nobuyuki Inoue
Published: October 2002

A three-dimensional particle simulation scheme has been developed and applied to the study of relativistic charged particle beams. To simulate the nonlinear behaviors of beam electrons with self-induced space-charge effects, it simultaneously solves the canonical equations of motion and the integrated Maxwell equations of radiated waves for each particle. Verifications of this algorithm show that calculations for the retarded structure of radiated waves dominate the total throughput, and the near-field approximation to the calculations of space-charge potentials improves its numerical efficiency. The code has been applied to a simulation of the Raman regime free-electron laser (FEL) to demonstrate that this scheme simulates the parametric amplification of FEL properly and is suitable for relativistic treatments of such wave-particle resonances.
0.2 µm Hole Pattern Generation by Critical Dimension Biassing Using Resin Overcoat
Authors: Yamauchi Takahiro , Matsui Takayuki , Kanamori Jun , Miyakawa Yasuhiro , Kouhei Shimoyama Kouhei Shimoyama
Published: October 2002

A method of generating very small hole patterns by introduction of transfer bias into a resist pattern after original resist pattern generation has been developed and evaluated. Introduction of transfer bias was carried out using a resin overcoating and strippig process and a novolak resist pattern was used as the original hole pattern. The overcoating resin used was polymethylmethacrylate (PMMA) and transfer bias was introduced by intermixing of novolak resin and PMMA during the PMMA baking step. From scanning electron microscope (SEM) observation, it appeared that 0.20 µ m hole pattern generation was possible by i-line lithography. The amount of undersize was controllable by PMMA bake temperature, and 0.06-0.15 µ m undersize could be achieved by using a bake temperature range of 60-120° C. From results of etching SiO2 substrate using overcoat treated hole pattern, it appeared that the mixinglayer functioned as an etching mask for oxide film.
Reduction of Electron Beam Drift Caused by Deflecting Electrode by Downflow Cleaning Process
Authors: Ogasawara Munehiro , Ohtoshi Kenji , Kazuyoshi Sugihara Kazuyoshi Sugihara
Published: October 2002

We studied the electron beam drift caused by charging up of deflector electrode surfaces oxidized by a dry cleaning process used to remove the contamination layer. The process adopted was a downflow ashing process with a mixture of CF4 and oxygen as a source gas. It was found that even a gold surface is oxidized and suffers from charging up after the cleaning process. It was also found that such a gold oxide layer can be removed by a postprocessing with nitrogen radicals, and that the charging up is reduced. However, when the surface is nickel, the nitrogen postprocess does not remove the oxide layer, leaving large beam drift.
Proximity Effect Correction in Projection Electron Beam Lithography (Scattering with Angular Limitation Projection Electron-Beam Lithography)
Authors: Liddle J. Alexander , Watson G. Patrick , Berger Steven D. , Miller Peter D.
Published: October 2002

Several schemes have been proposed for proximity effect correction (PEC) in e-beam lithography systems: biasing, dose control and GHOST.
Typically, the correction is applied to the pattern data, a process that is computationally demanding and expensive in terms of data handling. A process which is independent of the pattern information, and could be implemented in the tool hardware, would be an attractive alternative. In this paper we present such a solution to the proximity effect correction problem, for use in SCALPEL (SCattering with Angular Limitation in Projection Electron Beam Lithography).
Electron Beam Calibration Method for Character Projection Exposure System EX-8D
Authors: Hitoshi Sunaoshi Hitoshi Sunaoshi , Kiyoshi Hattori Kiyoshi Hattori , Jun Takamatsu Jun Takamatsu , Atsushi Ando Atsushi Ando , Hirotsugu Wada Hirotsugu Wada , Shunko Magoshi Shunko Magoshi , Toshio Yamaguchi Toshio Yamaguchi , Shinji Sato Shinji Sato , Shinsuke Nishimura Shinsuke Nishimura , Hiroaki Housai Hiroaki Housai , Susumu Hashimoto Susumu Hashimoto , Ryouichi Yoshikawa Ryouichi Yoshikawa , Tadahiro Takigawa Tadahiro Takigawa
Published: October 2002

A character beam calibration method has been developed for the electron beam exposure system EX-8D. The method concerns the character selection deflector, beam current density uniformity, beam size, direction, and position on the target. For the current density, the uniformity of less than 1.4 has been obtained in a 2-mm-square field. The beam size and the direction has been calibrated with an error of less than 1 nm in a 1-µm-square character beam. The overall error of the resist pattern size exposed by the character beam was estimated to be 7.2 nm. For the beam position on the target, the calibration accuracy of 0.023 µm has been obtained by a pattern matching method. After applying the calibration, 0.15 µm line-and-space patterns were exposed with good resolution by using the character beam. Also, a test pattern has been written with 0.02 µm stitching accuracy between variable shaped and character beams.
Electroplated Reflection Masks for Soft X-Ray Projection Lithography
Authors: Murakami Katsuhiko , Shimizu Sumito , Ohtani Masayuki , Nagata Hiroshi , Oizumi Hiroaki , Yamashita Yoshio , Atoda Nobufumi
Published: October 2002

A new process for fabricating reflection masks for soft X-ray projection lithography (SXPL) using an electroplating method was developed. Resist patterns were formed on molybdenum/silicon (Mo/Si) multilayers with the Mo layer on top, and nickel (Ni) absorber patterns were then electroplated on the multilayers using the top Mo layer as the electrode in nickel sulfamate solution. Subsequently, the resist patterns were removed. Using the reflection masks fabricated by the above process, SXPL was performed using 1/32 reduction Schwarzschild optics tuned to the wavelength of 13 nm and the synchrotron radiation source at SORTEC.
Line-and-space patterns down to 0.1 µ m were printed in polymethylmethacrylate (PMMA) resist.
Method for Drawing Locus of a Sliding Ski as Observed from Direction Perpendicular to Snow Surface
Authors: Sahashi Toshio , Ichino Shoji
Published: October 2002

The aim of the current study is to develop a drawing method for quantitative evaluation of the movement of a sliding ski as a function of time. In order to accomplish this, several serial photographs of a ski sliding downhill were taken. On the basis of these photographs, the locus of the sliding ski was drawn as observed from the direction perpendicular to the snow surface.
Determination of Deformability of Erythrocytes by Change in Scattering Cross Section
Authors: Kashima Susumu , Sohda Akihiko , Yagyu Yoshiyuki , Toshihiko Ohsawa Toshihiko Ohsawa
Published: October 2002

A simple method to measure the deformability of erythrocytes was proposed. The scattering cross section depends on the shape and the size of a particle. In addition, the deformation of erythrocytes under shear stress can be established from the change in the scattering cross section. An integrating sphere spectrophotometer and a special flow cell were used to measure the optical properties of blood samples. The blood samples were made to flow into the flow cell at various velocities controlled by a pump. Normal, shrunken and swollen erythrocytes were compared by this method. The characteristic of the change in the scattering cross section under shear stress was different for each sample. Moreover, the shape of the erythrocytes was estimated by a computational method.
High-Rate Deposition of High-Quality Silicon Nitride Film at Room Temperature by Quasi-Remote Plasma Chemical Vapor Deposition
Authors: Suzuki Nobumasa , Hayashi Sen'ichi , Masu Kazuya , Tsubouchi Kazuo
Published: October 2002

High-rate deposition of high-quality SiN films at room temperature has been achieved by quasi-remote plasma chemical vapor deposition method using a cylindrical multislot waveguide. The quasi-remote plasma is defined as the plasma whose density near the substrate is less than 1/10 of that in the densest region. Since the number of incident ions is reduced, the temperature rise of the substrate is suppressed even when the high-density plasma is used. Nitrogen excited by the high-density plasma reacts with monosilane to generate a silicon nitride precursor. The precursor is further excited by many electrons to emit hydrogen atoms. The excited precursor is adsorbed on the substrate surface and the silicon nitride film with low hydrogen content is deposited even at room temperature.
Nonlinear Ionization Instability of Plasma in Inert Gas Cycle Direct Power Generation
Authors: Kan Yasui Kan Yasui , Vladimir M. Zubtsov Vladimir M. Zubtsov , Kunio Yoshikawa Kunio Yoshikawa , Shigeharu Kabashima Shigeharu Kabashima
Published: October 2002

Ionization instability of nonequilibrium magnetohydrodynamic (MHD) plasma in a disk-type inert gas cycle direct (ICD) power generator has been examined by numerical simulation based on the two-temperature model. The plasma is metastable and becomes unstable when the amplitude of disturbances exceeds a critical value. Transition to an unstable state also depends on the direction of the disturbance wave, and the result shows good agreement with theory. Appearances of inhomogeneous structures when the plasma is unstable are revealed by two-dimensional numerical calculation.
Desorption of Ga and As Atoms from GaAs Surface Induced by Slow Multiply Charged Ar Ions
Authors: Itabashi Naoshi , Mochiji Kozo , Shimizu Hiroshi , Ohtani Shunsuke , Kato Yoshihiro , Tanuma Hajime , Kobayashi Nobuo
Published: October 2002

A reaction on a semiconductor surface induced by the potential energy of slow multiply charged ions (MCIs) has been investigated. By using an Einzel-type ion decelerator, beams of slow MCIs ( Ar

q
+; q≤10) with an ion current of several tens of nanoamperes and with the kinetic energy (E
k) of 30×q eV were produced. Irradiating a GaAs surface with the slow Ar

q
+ induced the desorption of Ga and As atoms, and this desorption was almost independent of the E
k but strongly dependent on the q; that is, on the potential energy (E
p) of the Ar

q
+. The effect of E
p on atom desorption was analyzed quantitatively in terms of a model based on the Coulomb repulsion between holes generated on the surface through neutralization of the MCIs.
Rapid Formation of Arsenic-Doped Layer More Than 1.0 µm Deep in Si Using Two KrF Excimer Lasers
Authors: Jyumonji Masayuki , Sugioka Koji , Takai Hiroshi , Toyoda Koichi
Published: October 2002

Sequential irradiation by two KrF excimer lasers (λ=248 nm) has been used to activate arsenic atoms implanted into Si substrates. The 1st laser pulse having 34 ns pulse width followed by the 2nd laser pulse of 23 ns after a time delay was irradiated to the sample. Laser fluences of the 1st laser pulse and the 2nd laser pulse were set at 2.4 J/cm2 and 0.5 J/cm2, respectively. The substrate was heated to 700° C. From Rutherford backscattering spectroscopy (RBS) analysis, the depth of the doped layer is confirmed to be 1.0 µ m. Severely rippled surface was observed by atomic force microscope (AFM) for the sample irradiated without the 2nd laser pulse, but the surface morphology can be improved by the sequential irradiation of two pulses. For a time delay of 150 ns, the minimum values of χmin
(4.61%) and sheet resistance (41.43 Ω/\Box) were obtained.
Fabrication and Characterization of Diamond-Clad Silicon Field Emitter Arrays
Authors: Cheng Huang-Chung , Ku Tzu-Kun , Hsieh Biing-Bang , Chen Sheng-Hsiung , Leu Shye-Yuh , Wang Chih-Chong , Chen Chia-Fu , Hsieh Iing-Jar , Huang Jammy C. M.
Published: October 2002

Microsized silicon tip arrays with sharp curvature were formed based on the techniques including reactive ion etching and oxidation-sbarpening. A new fabrication technology of polycrystalline diamond-clad Si microtips using microwave plasma CVD (MPCVD) was subsequently developed to improve the capability and stability of the field emission from the pure Si tips. By means of SEM and transmission electron microscopy (TEM), the as-deposited films are found to be polycrystalline diamond with fine grain (∼800 Å) structure. With the anode voltage of 1100 V and anode-to-cathode distance of 30 µ m, the emission current of 240 µA in a 50×50 diamond-clad Si microtip array can be achieved, which is much higher than those for Cr-clad and pure Si microtip arrays. Based on curve fitting of a Fowler-Nordheim ( F-N ) plot, such great improvement is partially attributed to the lowering of the effective work function from 5.5 eV to 2.08 eV.
Coherence and Structural Design of Free-Standing Gratings for Atom-Wave Optics
Authors: Rooks Michael J. , Tiberio Richard C. , Chapman Michael , Hammond Troy , Smith Edward , Lenef Alan , Rubenstein Richard , Pritchard David , Adams Scott , Ferrera Juan , Carter James M. , Smith Henry I.
Published: October 2002

Improvements in electron-beam writing techniques have allowed us to compensate for electron-beam system drift, making feasible the exposure of 800×800 µ m gratings with period as small as 0.14 µ m. Placement errors due to drift, calibration errors, and nonplanar substrates are measured with verniers. Gratings patterned with interferometric photolithography provide an absolute reference for a measure of stage nonlinearity (runout.) Simulation of fracture formation in silicon nitride films has given us a tool for the prediction of structures that will fail during fabrication, and a way of evaluating stress relief patterns in arbitrary structures. We have used two sets of simple patterns to identify the critical stress intensity factors in thin, free-standing films of nonstoichiometric silicon nitride.
An Electron Beam Nanolithography System and its Application to Si Nanofabrication
Authors: Kurihara Kenji , Iwadate Kazumi , Namatsu Hideo , Nagase Masao , Takenaka Hisataka , Katsumi Murase Katsumi Murase
Published: October 2002

We present an electron beam nanolithography system which features sub-10-nm beam size over a large 480×480 µ m2 field and a high 70 kV acceleration voltage with a Zr/O/W thermal field emitter tip. A beam can be deflected at 100 MHz in 2-nm steps, which allows the use of highly sensitive resist. The system is equipped with a highly sensitive YAG detector for electrons backscattered from a registration mark as well as a C/W multilayer knife edge for beam size measurement and focusing. These techniques achieve a beam size of about 6 nm. A 10-nm-scale resist pattern was obtained using ZEP520 resist with this system. Furthermore, Si nanostructures have been obtained by using an image reversal process with ECR plasma oxidation. Photoluminescence was observed from the Si nanowires fabricated with this system.
Self-Developing Properties of an Inorganic Electron Beam Resist and Nanometer-Scale Patterning Using a Scanning Electron Beam
Authors: Watanabe Heiji , Fujita Jun-ichi , Ochiai Yukinori , Matsui Shinji , Masakazu Ichikawa Masakazu Ichikawa
Published: October 2002

The self-developing properties of an AlF3-doped LiF inorganic resist are studied. Electron-stimulated desorption (ESD) from the resist film is characterized by Auger electron spectroscopy and X-ray photoelectron spectroscopy. A conventional scanning electron microscope is employed for nanometer-scale direct writing and for in situ surface observation. Results show that a metal-rich layer which is formed by rapid and preferential fluorine desorption due to ESD suppresses subsequent fluorine desorption. This indicates that the surface diffusion of this residual metal plays an important role in the self-developing reaction. Nanometer-scale lithography onto the LiF(AlF3) film is achieved using a scanning electron beam.
The Multiple-Tunnel Junction and Its Application to Single-Electron Memory and Logic Circuits
Authors: Nakazato Kazuo , Ahmed Haroon
Published: October 2002

The multiple-tunnel junction (MTJ) produced by forming a side-gated constriction in δ-doped GaAs is demonstrated as a basic component of single electronics. A single-electron memory cell, in which one bit of information is represented by the excess or lack of a precise number of electrons, was fabricated and the operation was confirmed at liquid helium temperature. A new switching element, the variable-barrier MTJ, and a new circuit, the single-charge injection logic circuit, are proposed.
Initial Stage of Oxidation of Hydrogen-Terminated Si(100)-2×1 Surface
Authors: Aiba Takeshi , Yamauchi Ken , Shimizu Yuichi , Tate Naoto , Katayama Masatake , Takeo Hattori Takeo Hattori
Published: October 2002

The initial stage of SiO2/Si interface formation on an atomically flat hydrogen-terminated Si(100)-2×1 surface was studied by X-ray photoelectron spectroscopy. The following results were obtained: 1) the initial stage of interface formation does not depend on the initial surface morphology, 2) the interface layer becomes continuous at the oxide film thickness of 0.5 nm, and 3) at thicknesses greater than this the deviation from an atomically flat interface increases with the progress of oxidation, however, an abrupt compositional transition occurs.
Mo Contamination in p/p+Epitaxial Silicon Wafers
Authors: Aoki Masaki , Itakura Toru , Nobuo Sasaki Nobuo Sasaki
Published: October 2002

We detected the same deep level in the epitaxial layer of all as-grown p/p+epitaxial wafers from three vendors. The deep level is characterized by an energy of Ev+0.30 eV and a hole-capture cross section of 6.0×10-16cm2. This deep level is determined as being a Mo deep level. These Mo deep levels vary with vendor in concentration from 3.0×1011to 1.5×1012cm-3, and are found to reduce the minority-carrier recombination lifetime in the epitaxial layer. We examined the gettering effect of the p+substrate, which is heavily doped with boron, on Mo impurities. We found that Mo impurities are not gettered in the p+substrate, unlike 3d-transition metals such as Fe impurities.
Atomic Scale Morphology of Hydrogen-Terminated Si(100) Surfaces Studied by Fourier-Transform Infrared Attenuated Total Reflection Spectroscopy and Scanning Probe Microscopies
Authors: Bjorkman Claes H. , Fukuda Masatoshi , Yamazaki Tadayuki , Miyazaki Seiichi , Hirose Masataka
Published: October 2002

Using Fourier-transform infrared attenuated total reflection (FT-IR-ATR) spectroscopy and scanning probe microscopies, we have systematically studied hydrogen-terminated Si(100) surfaces. These surfaces were obtained by varying the solutions for removal of the chemical oxide grown during the SC1 cleaning step. We find that the smoothest surfaces are obtained using an acidic HF solution containing an oxidizing agent such as H2O2. Surfaces treated in an HF:H2O2=1:9 solution exhibited an FT-IR-ATR spectrum dominated by the asymmetric=SiH2 stretching mode, while scanning probe microscopy studies verified the formation of parallel steps on such surfaces. On the other hand, a basic solution such as NH4F resulted in locally rougher surfaces. For such surfaces, we observed a correlation between the degree of - SiH3 termination and the number of round structures on the Si(100) surface.
Oxygen and Fluorine Treatment Effect on Silicon Surface Characterized by Infrared Reflection Absorption Spectroscopy
Authors: Okuyama Masanori , Nishida Masahiro , Yoshihiro Hamakawa Yoshihiro Hamakawa
Published: October 2002

Chemical bonds on Si(111) such as Si-H, Si-O and Si-F have been precisely measured by infrared reflection absorption spectroscopy. A Si wafer 4 inches in diameter was treated in various atmospheres in the temperature range from room temperature to 400° C. The heat treatment at 400° C in vacuum removes H bonded with Si from edge sites of the terrace plane, and oxygen treatment at 400° C removes H bonded with Si from the terrace plane. Initial oxidation begins at about 200° C in vacuum before H desorption. F2 treatment at room temperature removes H from Si and forms Si-F bonds immediately. Reflection peaks due to absorption arising from Si-F bonds shift from 850 cm-1 to higher wave number with further treatment and three peaks appear corresponding to SiF
x
(x=2-4) . Fluorination near the Si surface might be induced as the absorption of SiF
x
increases with the treatment time.
Ferroelectric Properties of Crystalline-Oriented Lead-Zirconate-Titanates Formed by Sol-Gel Deposition Technique
Authors: Aoki Katsuhiro , Fukuda Yukio , Numata Ken , Akitoshi Nishimura Akitoshi Nishimura
Published: October 2002

Ferroelectric properties of lead-zirconate-titanate (PZT) films formed by the sol-gel deposition technique have been discussed from the standpoint of ferroelectric random-access memory (FRAM) and dynamic random-access memory (DRAM) applications. PZT films with <111>-preferred orientation and random orientation were formed on Pt/Ti/SiO2/Si substrates by optimizing fabrication conditions. Remanent polarization of the <111>-preferred film was 23.5 µ C/cm2 which is somewhat higher than that of the randomly oriented one. An abrupt saturation of remanent polarization was observed only for the <111>-preferred film. The voltages which provide saturations of remanent polarization densities for the <111>-preferred films are almost constant between 3.5 V to 4 V independent of thickness. The dielectric constant of the randomly oriented film was 730 which is larger than that of the <111>-preferred one and gradually decreased depending on the applied electric field. The <111>-preferred PZT film is appropriate for FRAM application, and the randomly oriented one is preferred for DRAM application.
Suppression of Boron Penetration in PMOS by Using Oxide Gettering Effect in Poly-Si Gate
Authors: Lin Yung Hao , Lee Chung Len , Lei Tan Fu , Chao Tien Sheng
Published: October 2002

A new stacked poly-Si gate structure with a thin ( ∼20 Å) oxide inserted in-between for p-channel metal-oxide semiconductor feild effect transistor (pMOSFET) application is proposed and demonstrated. Due to the gettering fluorine effect of this thin oxide for BF2
+-implanted poly-Si gate, the amount of fluorine in the gate oxide, consequently, the boron penetration enhanced by fluorine are reduced. The thicker or the more apart from the gate oxide of this gettering fluorine oxide is, the more effectively it can suppress the boron penetration. Moreover, this new structure improves more the electrical characteristics than the conventional and the stacked layer poly silicon gate structures.
Low Temperature Chemical Vapor Deposition of High Quality SiO2Film Using Helicon Plasma Source
Authors: Nishimoto Yuko , Tokumasu Noboru , Kazuo Maeda Kazuo Maeda
Published: October 2002

Helicon plasma, a new compact high density plasma source, was investigated for chemical vapor deposition (CVD) of dielectric oxide. High quality films having low compressive stress of 1-2×109dyne/cm2, lower SiOH content with water-blocking capability and a wet HF etch rate comparable to that of thermal oxide were obtained. Sub-half-micron gaps with high aspect ratio were successfully filled by applying a substrate bias. A combination of biased helicon plasma CVD and atmospheric pressure (AP) tetraethyl orthosilicate [TEOS]-O3nondoped silicate glass (NSG) which has self-planarizing characteristics is proposed for planarization without chemical-mechanical polish (CMP).
The Impact of Nitrogen Implantation into Highly Doped Polysilicon Gates for Highly Reliable and High-Performance Sub-Quarter-Micron Dual-Gate Complementary Metal Oxide Semiconductor
Authors: Kuroi Takashi , Kobayashi Maiko , Shirahata Masayoshi , Okumura Yoshiki , Kusunoki Shigeru , Inuishi Masahide , Natsuro Tsubouchi Natsuro Tsubouchi
Published: October 2002

We studied the effects of nitrogen implantation into highly doped polysilicon gates in detail. It was found that highly arsenic-doped polysilicon gates caused degradation of gate oxide films and highly boron-doped polysilicon gates resulted in a shift of threshold voltage by boron penetration. Nitrogen implantation into polysilicon gates can effectively overcome these problems. The nitrogen implanted into the polysilicon gate is segregated into the gate oxide film during heat treatment after implantation. The nitrogen in the gate oxide film can act as a barrier layer for boron penetration and reduce the random failures of gate oxide films under highly doped polysilicon gates. Moreover, the hot carrier resistance can also be improved by nitrogen implantation. Highly reliable and high-performance dual-gate Complementary metal oxide semiconductor (CMOS) can be realized by the highly doped gate and the nitrogen implantation technique.
Modification Effect of a-Si 1-xNx:H Surface by Hydrogen Radicals
Authors: Yamaguchi Misako , Nagayoshi Hiroshi , Ikeda Makoto , Yamamoto Yuichi , Kamisako Koichi , Tarui Yasuo
Published: October 2002

The modification effect of a-Si1-
x

N

x

:H surface by hydrogen radicals is clarified by stacking ultrathin a-Si1-
x

N

x

:H layers intermittently on a substrate using the NH3 microwave afterglow method and by performing hydrogen radical treatment between each layer-deposition cycle. Hydrogen radicals etched surplus Si atoms from Si-rich film surfaces containing many Si-H bonds, and N atoms from film surfaces containing many N-H bonds. These results suggest that the H radicals selectively remove SiH4 from a-Si1-
x

N

x

:H surfaces containing many Si-H bonds and NH3 from a-Si1-
x

N

x

:H film surfaces containing many N-H bonds.
Reducing Reverse-Bias Current in 450°C-Annealed n+p Junction by Hydrogen Radical Sintering
Authors: Oka Mauricio Massazumi , Nakada Akira , Tomita Kazuo , Shibata Tadashi , Ohmi Tadahiro , Nitta Takahisa
Published: October 2002

Ultra-shallow n+p junctions featuring very low reverse-bias current densities ( 3.1×10-9 A·cm-2 at 5 V) have been successfully formed at a post-implantation annealing temperature as low as 450° C. Such a low reverse-bias current level has been achieved by eliminating residual point defects remaining after 450° C post-implantation annealing. A newly developed hydrogen radical sintering ( H* sintering) is presented as a promising method to eliminate these defects and thus improve the characteristics of junctions formed by low-temperature post-implantation annealing.
Abrupt and Arbitrary Profile Formation in Silicon Using a Low-Kinetic-Energy Ion Bombardment Process
Authors: Shindo Wataru , Hirayama Masaki , Tadahiro Ohmi Tadahiro Ohmi
Published: October 2002

We have discovered that the carrier concentration in an epitaxial silicon film formed by the low-energy ion bombardment process is easily controlled by changing the ion bombardment energy during the film growth. While maintaining the perfect crystallinity of an epitaxial silicon layer grown at a temperature as low as 350° C, an arbitrary-shaped carrier concentration profile has been created in the film. Formation of box-shaped profiles as well as staircase-shaped profiles having very abrupt transitions is demonstrated. Formation of such arbitrary-shaped carrier profiles in an epitaxial layer is quite essential in the design of ultrasmall-dimension devices. The stability of carrier profiles against heat treatments also has been investigated.
Contactless Measurement of Surface Temperature and Surface Potential of Si by Photoreflectance Spectroscopy
Authors: Fujimoto Akira , Katsumi Hideo , Okuyama Masanori , Yoshihiro Hamakawa Yoshihiro Hamakawa
Published: October 2002

Surface temperature and surface potential of Si wafers have been measured by photoreflectance (PR) spectroscopy. The surface temperature was obtained in the range from 25° C to 134° C within the error of ±0.6° C from transition energy which was calculated from the PR spectrum by the 3-point method based on 3rd derivative theory. spatial distribution of surface temperature was also measured successfully in a Si wafer heated partially. Surface potential was estimated by comparison of experimental PR spectral intensity with theoretical values, taking into account photoinduced change of the surface field. The results show that the surface potential of Si wafers varies with temperature in the atmosphere.
Formation and Characterization of Epitaxial TiO2 and BaTiO3/TiO2 Films on Si Substrate
Authors: Lee Myung Bok , Kawasaki Masashi , Yoshimoto Mamoru , Moon Bum Ki , Ishiwara Hiroshi , Hideomi Koinuma Hideomi Koinuma
Published: October 2002

Rutile-phase TiO2 films were epitaxially grown on Si(100) substrates by oxidizing epitaxial TiN films grown by KrF pulsed excimer laser deposition. The TiO2 film was (110)-oriented and composed of two domains perpendicular to each other in the plane. The electrical resistivity at 2.5 V and the dielectric constant at 1 MHz of the film were 1.1×1010 Ω· cm and 49, respectively. This film could be used as a buffer layer for the growth of epitaxial BaTiO3 film on Si. The BaTiO3 (260 nm)/TiO2 (230 nm) double-layered film showed a high dielectric constant (ε
r=91) and a very low leakage current of 5×10-8 A/cm2 at 10 V.
Switching Characteristics of a Thin Film SOI Power MOSFET
Authors: Matsumoto Satoshi , Kim Il-Jung , Sakai Tatsuo , Fukumitsu Takao , Toshiaki Yachi Toshiaki Yachi
Published: October 2002

This paper describes switching characteristics of a thin-film silicon-on-insulator (SOI) power metal-oxide-semiconductor field-effect transistors (MOSFETs) based on the results of numerically simulating thin-film SOI power MOSFETs in the 50-V class. The dependence of the rise time and fall time on the doping concentration of the substrate, on the doping type of the substrate, and on the thickness of the buried oxide layer are studied. In addition, the optimum device structure of the thin-film SOI power MOSFET for high-frequency switching application is also described.
Two-Dimensional Analytical Modeling of the Source/Drain Engineering Influence on Short-Channel Effects in SOI MOSFET's
Authors: Joachim Hans-Oliver , Yamaguchi Yasuo , Inoue Yasuo , Natsuro Tsubouchi Natsuro Tsubouchi
Published: October 2002

The scaling of the metal-oxide-semiconductor field-effect transistor (MOSFET) into the deep-submicron regime increases the influence of source/drain engineering, e.g., the use of a lightly doped source and drain (LDD) structure, on the transistor subthreshold characteristics due to the two-dimensional potential distribution. Device parameters like the subthreshold slope ( S-factor) and the threshold voltage may become dependent on the LDD conditions. This paper presents a theoretical analysis of how source/drain conditions affect the short-channel behavior of fully depleted silicon-on-insulator (SOI) MOSFET's. Accurate two-dimensional analytical modeling which takes into account the non-linear potential variation inside the buried oxide helps elucidate the mechanisms involved. The results, supported by numerical device simulation, indicate that for a correct description in addition to the different built-in potential of the source and drain junctions, an increasing effective channel length with LDD doping reduction must be taken into account.
Numerical Prediction for 2 GHz RF Amplifier of SOI Power MOSFET
Authors: Ichiro Omura Ichiro Omura , Akio Nakagawa Akio Nakagawa
Published: October 2002

RF performance of a metal-oxide-semiconductor field effect transistor (MOSFET) on silicon-on-insulator (SOI) with 0.5 µm gate length and 2 µm buried oxide thickness has been numerically predicted using a 2-D device simulator to check its applicability to digital cellular telephones. The device has been found to have excellent performance for a 2 GHz high-power amplifier at a power supply of 2.8 V. The calculated cutoff frequency and maximum frequency of oscillation for the intrinsic MOSFET are 23 GHz and 65 GHz, respectively. The SOI MOSFET is a promising candidate for replacing GaAs MESFETs in 2 GHz RF applications.
Single Electron Digital Phase Modulator
Authors: Hwang Sung Woo , Sakamoto Toshitsugu , Kazuo Nakamura Kazuo Nakamura
Published: October 2002

It is well known that the AC voltage gain of a symmetric single electron transistor amplifier has a 180° phase shift whenever the equilibrium charge in the Coulomb island changes by e/2. Using this interesting phase shift property, we propose a single electron digital phase modulation scheme. We show that there is a trade-off between the intrinsic operating speed and the voltage gain of the modulator. We show that even though the two tunnel junctions of the modulator are not matched, there is no distortion in the output signal.