bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Density Land/Groove Recording for Digital Video File System
Authors: IwanagaH Toshiaki , Honma Hiromi , Kayanuma Kinji , Segawa Satoshi , Nakada Masafumi , Katayama Ryuichi , Hiroshi Inada Hiroshi Inada
Published: February 2005

High-density land/groove recording technology for magnetooptical (MO) disks, using a high-speed crosstalk canceller which eliminates crosstalk from adjacent tracks, has been developed. A 0.50 µm/bit linear density with a 0.8 µm track pitch has been confirmed with a bit error rate (BER) less than 10-5. A digital video file system using this technology has also been developed. As a result, the authors confirmed the validity for the high-density land/groove recording technology in realizing larger capacity for digital video file systems.
2 GB/130 mm Capacity Direct-Overwrite Magneto-Optical Disk
Authors: Miyamoto Harukazu , Ojima Masahiro , Toda Tsuyoshi , Niihara Toshio , Maeda Takeshi , Saito Jun , Matsumoto Hiroyuki , Hosokawa Tetsuo , Akasaka Hideki
Published: February 2005

Precise mark-edge recording on a high signal-to-noise ratio (S/N) exchange-coupled direct overwrite magneto-optical (MO) disk provides 2 GB capacity on a 130 mm disk with a sufficient edge jitter margin. Write compensation technology was proven to be effective for both non- and direct-overwrite MO disks.
Proposal of Optical Floppy Disk Head and Preliminary Spacing Experiment between Lensless Head and Disk
Authors: Goto Kenya , Toshihisa Sato Toshihisa Sato , Shiho Mita Shiho Mita
Published: February 2005

A new optical floppy disk system using a very simple optical head which consists of a laser diode chip, a photodiode chip and a heatsink is proposed, and fundamental experiments with laser diodes are performed. The system has no optical element like a lens or a prism, and also no focus actuator. Experimental results show that the spacing between the recording film and the light-emitting edge of a laser chip could be designed to be as great as 5-10 µm, which is greater than the expected value. This is avarable solution for improving the dust problem between the head and the disk. As the head is simple and low in weight, a low-cost disk drive with high access time may be possible.
Analytical Simulation of Electrooptical Performance of Amorphous Twisted Nematic Liquid Crystal Displays
Authors: Sugiyama Takashi , Toko Yasuo , Hashimoto Toru , Katoh Kazuhisa , Iimura Yasufumi , Kobayashi Shunsuke
Published: February 2005

A simulation of the electrooptical (EO) performance of an amorphous twisted nematic liquid crystal display (a-TN-LCD) has been performed. The a-TN-LCDs are prepared by filling chiral-molecule-doped NLCs into empty cells in the isotropic phase and cooling them to room temperature; the inner surfaces of the cells are topographically and optically homogeneous and no rubbing is performed. The a-TN-LCDs exhibit wide and uniform viewing angle characteristics and suitable EO performance for gray-scale operation, in comparison with those of conventional TN-LCDs. These characteristics of the a-TN-LCD are successfully reproduced and explained by computer simulation.
Characteristics of BaTiO3 Films Prepared by Pulsed Laser Deposition
Authors: Cheng Hsiu-Fung , Yeh Ming-Hua , Liu Kuo-Shung , Lin I-Nan
Published: February 2005

BaTiO3 thin films possessing ferroelectric characteristics have been successfully synthesized using the laser ablation technique. The films are polycrystalline when deposited with substrate temperature higher than 550°C at 1 mbar oxygen pressure. All of the films are highly textured and dominated by (111) grains. The zero-voltage dielectric constant and ferroelectricity derived from C-V measurement increase with substrate temperature. The best properties obtained are εr=485, P
r=0.32 µC/cm2, P
s=2.65 µC/cm2 and E
c=7.38 kV/cm. The charge storage density is highest and the leakage current density is lowest for 750°C-deposited films. They are Q
c=1.14 µC/cm2 and J
1=0.55 µA/cm2, respectively. The results indicate that the BaTiO3 films are promising for application as high-density memory dielectrics.
Contactless Measurement of Carrier Lifetime in Silicon Thick Wafers
Authors: Maekawa Takao , Yasuhiko Yamagishi Yasuhiko Yamagishi , Shozo Inoue Shozo Inoue
Published: February 2005

Contactless methods of measuring bulk carrier lifetime with a reliable accuracy have scarcely been reported thus far. A contactless method has been studied for Si wafers with thickness of up to 10 mm. This method makes use of the eddy current in the wafer induced by the magnetic fluxes (5 MHz) passing through a thick wafer. To confirm the reliability of this method, the decay of photoconductivity Δσ0 and injection level Δσ0/σ measured by this method are compared with those of the dc method. In the eddy current method, the bulk lifetime and diffusion coefficient are obtained as 1.88 ms and 12.4 cm2/s for an n-Si crystal, and 26 ms and 37.3 cm2/s for a p-Si crystal. The latter value, 26 ms, for bulk lifetime is almost in agreement with the value, 29 ms, obtained by the American Society for Testing and Materials (ASTM) dc method. The sensitivity of this method and the desired thickness of wafer for evaluating the bulk lifetime are discussed.
Resolution Limit for Optical Lithography Using Polarized Light Illumination
Authors: Asai Satoru , Isamu Hanyu Isamu Hanyu , Masahiko Takikawa Masahiko Takikawa
Published: February 2005

We studied the effects of polarized illumination using a phase-shifting mask and obtained periodic patterns near the resolution limit of i-line steppers. Our study focused on the basics of imaging in high-numerical-aperture (NA) optical stepper systems. We demonstrated the superior resolution of S-polarized illumination. We obtained 0.175-µm (=0.26λ/NA) lines and spaces using a phase-shifting mask at a wavelength of 0.365 µm and a numerical aperture of 0.54. We also study an “alternating aperture polarized mask” without a phase shifter.
Computer Aided Design Software for Designing Phase-Shifting Masks
Authors: Ooi Kazuko , Shigehiro Hara Shigehiro Hara , Kiyomi Koyama Kiyomi Koyama
Published: February 2005

Computer aided design software has been developed in order to improve the efficiency of completing the design of Levenson-type phase-shifting masks. The software assists designers with the functions of automatic shifter arrangement and verification. In addition, to cope with contradictory spots where Levenson-type alternating phase shifting is impossible, the functions of extracting the shapes causing contradiction and of phase assignment with priority are also offered. The principle of shifter arrangement is that when the distance between clear mask areas is less than a certain threshold, a shifter is positioned into one of the clear areas. According to the principle, the number of pairs whose mutual phases have to be opposite decreases, and thus the degree of freedom to arrange shifters increases. The software was developed on a workstation, and its performance was evaluated using several layouts of 64Mbit dynamic random access memory. The average processing time for layouts with 300–400 shapes was about 1 min.
Sub-0.1 µm Resist Patterning in Soft X-Ray (13 nm) Projection Lithography
Authors: Oizumi Hiroaki , Maejima Yukihiko , Watanabe Takeo , Taguchi Takao , Yamashita Yoshio , Atoda Nobufumi , Murakami Katsuhiko , Ohtani Masayuki , Nagata Hiroshi
Published: February 2005

Poly (methylmethacrylate) (PMMA) resist performance for soft X-ray projection lithography (SXPL) at an exposure wavelength of 13 nm was investigated with an special emphasis on development condition dependence. The resist contrast value γ for 13 nm SXPL showed strong dependence on the developer, in contrast with proximity X-ray lithography (XRL) at the peak-wavelength of 0.7 nm. With an optimized developer, a resolution as high as 0.05 µm was achieved. A wide focus range of 1.5 µm with a 0.1 µm line-and-space pattern was also confirmed.
Improvement in Radiation Stability of SiN X-Ray Mask Membranes
Authors: Arakawa Tomiyuki , Okuyama Hiroshi , Yamashita Yoshio , Ohta Tuneaki , Kumar Rakesh , Noda Shuichi , Hoga Hiroshi
Published: February 2005

The synchrotron radiation (SR) stability of silicon nitride (SiN) X-ray mask membranes was successfully improved by low-pressure chemical vapor deposition at a growth temperature of 1000°C. The transmission of the SiN membrane formed at 1000°C exceeded 90% at about 633 nm even after SR absorption with a dose of about 100 MJ/cm3, although those of membranes formed at 800 and 900°C decreased to below 85% after the same SR absorption. In addition, SR-induced pattern displacements for the SiN membrane formed at 1000°C were suppressed to σ
x
=11 nm and σ
y
=10 nm with a dose of 20 MJ/cm3. The N/Si atomic ratio increased, and the H and O concentrations in the SiN decreased with the increase of the growth temperature. The increase ratio of the spin density before and after the SR absorption decreased with the increase of the growth temperature.
Simulation of AZ-PN100 Resist Pattern Fluctuation in X-Ray Lithography, Including Synchrotron Beam Polarization
Authors: Scheckler Edward W. , Ogawa Taro , Tanaka Toshihiko , Oizumi Hiroaki , Takeda Eiji
Published: February 2005

A new simulation model for nanometer-scale pattern fluctuation in X-ray lithography is presented and applied to a study of AZ-PN100 negative chemical amplification resist. The exposure simulation considers polarized photons from a synchrotron radiation (SR) source. Monte Carlo simulation of Auger and photoelectron generation is followed by electron scattering simulation to determine the deposited energy distribution at the nanometer scale, including beam polarization effects. An acid-catalyst random walk model simulates the post-exposure bake (PEB) step. Fourier transform infrared (FTIR) spectroscopy and developed resist thickness measurements are used to fit PEB and rate models for AZ-PN100. A polymer removal model for development simulation predicts the macroscopic resist shape and pattern roughness. The simulated 3σ linewidth variation is in excess of 24 nm. Simulation also shows a detrimental effect if the beam polarization is perpendicular to the line. Simulation assuming a theoretical ideal exposure yields a 50 nm minimum line for standard process conditions.
Analysis of Sub-0.15 µm Pattern Replicationin Synchrotron Radiation Lithography
Authors: Kikuchi Yukiko , Kondo Kenzo , Hiroshi Nomura Hiroshi Nomura , Yoshio Gomei Yoshio Gomei
Published: February 2005

An absorber profile is essential when replicating deep quarter-micron patterns because of the X-ray phase-shifting effect in the absorber. We have compared experimental results of 0.15 µm line-and-space (L/S) pattern with calculation based on Fresnel diffraction using the measured absorber profile and resist property. The experimental mask had a beveled absorber edge profile, and the 0.15 µm L/S exposure latitude values obtained with this mask are ±6% for a 30 µm gap, ±8% for 20 µm, and ±12% for 10 µm. The calculation showed good coincidence with respect to the dependence of the latitude on the gap, but the calculated pattern size is about 0.05 µm less than the experimental one. Simulation on the 0.1 µm L/S printability was further carried out for a 20 µm gap. Although the applied exposure dose was rather small, the pattern was resolved by the beveled-edge mask with a mask contrast of about 6.
Process Latitude for Sub-200-Nanometer Synchrotron Orbital Radiation X-Ray Lithography
Authors: Oertel Heinrich K. , Jürgen Chlebek Jürgen Chlebek , Manfred Weiß Manfred Weiß
Published: February 2005

Image intensity profile and resist profile calculations using the X-ray modeling and simulation (XMAS) program are presented for storagering X-ray lithography proximity printing. The calculations indicate that there exists a sufficiently wide process window for the replication of 100-nm-wide absorber features, using an optimized set of parameters. The effect of nonvertical absorber sidewalls on the process window is investigated.
Resolution Enhancement of Hole Patterns in Sychrotron Radiation Lithography
Authors: Somemura Yoh , Deduchi Kimiyoshi , Kazunori Miyoshi Kazunori Miyoshi , Tadahito Matsuda Tadahito Matsuda
Published: February 2005

This paper analyzes the influence of Fresnel diffraction on the patterning characteristics of isolated hole patterns in synchrotron radiation lithography by comparing Fresnel diffraction simulation extended to 2-dimensional patterns and pattern replication experiments with mask contrast as a parameter. It is possible to replicate hole patterns down to 0.1 µm at a large proximity gap of 30 µm by keeping the mask contrast at 2.5-7. However, the exposure latitude for fine patterns below 0.1 µm diminishes abruptly. It also becomes clear that the phase-shifting mask which we previously proposed offers the possibility of replicating ultra-fine hole patterns (<0.1 µm) with a large exposure latitude at the 30-µm proximity gap. Moreover, by using an X-ray mask with a circular absorber pattern instead of the conventional square pattern, it should be possible to solve the problem of pattern deformation and improve the exposure latitude.
Linear-Fresnel-Zone-Plate-Based Two-State Alignment Method for Sub-0.25 µm X-Ray Lithography System
Authors: Chen Gong , John P. Wallace John P. Wallace , Franco Cerrina Franco Cerrina
Published: February 2005

In this paper, we present a linear-fresnel-zone-plate-based two-state alignment method developed at the Center for X-ray Lithography. The alignment system uses a linear Fresnel zone plate (LFZP) as a mask alignment mark and an array of dots as a wafer alignment mark. The alignment error signal extraction is based on a two-state modulation of the incident light. The optical system is arranged outside of the exposure X-ray path and alignment can be performed during X-ray exposures. In the experiment, we obtained an alignment signal depth of focus larger than 4 µm and the gap change between the mask and wafer did not affect the alignment position. The X-ray double-exposure experiment on the system demonstrated an alignment accuracy better than 0.035 µm (3σ) on both Al and silicon nitride marks.
Electron Beam Block Exposure System for 256 M Dynamic Random Access Memory Lithography
Authors: Sakamoto Kiichi , Fueki Shunsuke , Yamazaki Satoru , Abe Tomohiko , Kobayashi Katsuhiko , Nishino Hisayasu , Satoh Takamasa , Takemoto Akio , Ookura Akio , Ohno Manabu , Sagoh Satoru , Oae Yoshihisa , Yamada Akio , Junichi Kai Junichi Kai , Hiroshi Yasuda Hiroshi Yasuda
Published: February 2005

The NOWEL-3 block exposure system that we developed contains a data transaction system, high-speed exposure control hardware and a column which has a block mask and mask deflectors. The block patterns are taken from LSI design data. Three kinds of format data, exposure data, mask information data, and mask fabrication data, are generated in the transaction system. The mask deflectors select one of forty-eight blocks on the mask. They are calibrated before the exposure. We exposed a 256 M-bit dynamic random access memory (DRAM) contact hole layer using this system. NOWEL-3 has good resolution and dimensional accuracy. It can expose patterns less than 0.1 µm wide. The block exposure system reduces the total number of shots required to 21.46×106, about 1/8 of that required in a conventional system. Each chip is exposed for 10.5 s. The throughput is about 10 wafers per hour (6”).
Fast Electron Beam Lithography System with 1024 Beams Individually Controlled by Blanking Aperture Array
Authors: Yasuda Hiroshi , Arai Soichiro , Kai Jun-ichi , Ooae Yoshihisa , Abe Tomohiko , Takahashi Yasushi , Hueki Syunsuke , Maruyama Sigeru , Satoru Sago Satoru Sago , Keiichi Betsui Keiichi Betsui
Published: February 2005

A new electron beam lithography system with a two-dimensional blanking aperture array (BAA) is proposed. The BAA produces 1024 individually controlled beams. The demagnification ratio of BAA on the wafer is 0.3%. An actual BAA device was fabricated and a preliminary experiment was carried out with a block exposure system and Si stencil mask. Very high resolution of 0.08µm holes was confirmed. The system parameters are designed by setting the system throughput at more than twenty 8-inch wafers per hour. Below a 0.2 µm minimum feature size, BAA exposure is suitable for random patterning of wiring layers in dynamic random access memories (DRAMs), application specified integrated circuit (ASICs) and microcode processing units (MPUs), and will be a useful lithographic tool.
The Requirements for Future Electron-Beam Reticle Fabrication Systems from an Error Analysis Viewpoint
Authors: Matsuzaka Takashi , Ohta Hiroya , Saitou Norio , Kawasaki Katsuhiro , Kohno Toshihiko , Hoga Morihisa
Published: February 2005

To pave the way for giga-scale reticle fabrication, error analysis in the development of an electron-beam reticle fabrication system for 0.3 µm production and 0.2 µm development of devices is re-examined. To improve the stitching accuracy, it is necessary to constrain some kinds of mechanical vibration. For higher pattern width accuracy, higher accelerating voltage and thorough proximity correction are needed. To realize ultimate positioning accuracy, it is important to control fluctuation in reticle temperature precisely. The analysis results strongly suggest that it is necessary to constrain environmental disturbances. Control technology that minimizes the influence of disturbances and a design strategy established from this guideline will be needed in the not so distant future. This paper discusses requirements of a giga-scale electron-beam reticle fabrication system from an error-analysis viewpoint.
Stitching Error Analysis in an Electron Beam Lithography System: Column Vibration Effect
Authors: Ohta Hiroya , Matsuzaka Takashi , Saitou Norio , Kawasaki Katsuhiro , Kohno Toshihiko , Hoga Morihisa
Published: February 2005

The column vibration effects on field stitching accuracy in an electron beam lithography system are investigated. Field stitching error analysis shows that beam placement error caused by column vibration is about 0.04 µm. This corresponds to 80% of the required accuracy for 0.3-µm ULSIs. In this study, the relation between column vibration and field stitching accuracy is clarified using modal analyses by measurement of column acceleration and by computer simulation. Based on these analyses, a new anti-vibration system was designed. As a result, stitching error due to column vibration is reduced to less than 0.01 µm, and field stitching accuracy of 0.05 µm (|Mean|+3σ) is achieved. In the next-generation, quantitative understanding of disturbance effects such as vibration will be the most critical issue in designing more accurate electron beam lithography systems.
Effects of Impurities on Processes of Acid Generation in Chemically Amplified Resists for Electron Beam and X-Ray Lithography
Authors: Kozawa Takahiro , Uesaka Mitsuru , Yoshida Yoichi , Tagawa Seiichi
Published: February 2005

It has been reported that some types of impurities severely degrade resist performance of chemically amplified resists. The effects of impurities on the processes of acid generation in the chemically amplified electron beam (EB) and X-ray resists have been studied by means of nanosecond pulse radiolysis. Amines, water, oxygen, alcohols, silanol and casting solvents were used as impurities. The effects of the impurities in the model solutions of chemically amplified resists (onium salt solutions in m-cresol) were measured using pyrene as an indicator of protonation and charge transfer reaction. The rate constants for the reactions of several kinds of impurities with proton adducts of m-cresol were obtained.
A New Analytical Technique for Evaluating Standing Wave Effect of Chemically Amplified Positive Resist
Authors: Matsuoka Koji , Yamashita Kazuhiro , Masaru Sasago Masaru Sasago , Noboru Nomura Noboru Nomura
Published: February 2005

A new analyticai system for evaluating the standing wave effect in chemically amplified positive resist has been developed. In this paper, we describe a new system for calculating the linewidth variation due to the standing wave effect and compare simulation and experimental results. The linewidth for different resist thicknesses is calculated by changing the exposure energy at constant resist thickness. The exposure energy is determined using two series of the experimental dissolution rate data. The development effect for the different resist thicknesses is simulated by modifying the dissolution rate in the direction of resist depth. To verify this system, a two-component chemicaily amplified positive resist was used. The exposure was performed with a KrF excimer laser stepper. The results show that the newly designed system is able to rapidly evaluate the standing wave effect of resist. The system is an effective tool for optimizing resist materials and lithographic process conditions.
Platinum Etching and Plasma Characteristics in RF Magnetron and Electron Cyclotron Resonance Plasmas
Authors: Nishikawa Kazuyasu , Kusumi Yoshihiro , Oomori Tatsuo , Minoru Hanazaki Minoru Hanazaki , Keisuke Namba Keisuke Namba
Published: February 2005

The properties of platinum etching were investigated using both rf magnetron and electron cyclotron resonance plasmas, together with measurement of the plasma parameters. Experiments were performed over a wide pressure range from 0.4 to 50 mTorr in Cl2 plasmas. In rf magnetron plasmas, the etch rate of Pt was constant at the substrate temperature from 20 to 160°C. The etch rate and the plasma electron density increased with decreasing gas pressure from 50 to 5 mTorr. In ECR plasmas for rf power of 300 W, the etch rate of Pt was almost constant (∼100 nm/min) with decreasing gas pressure from 5 to 0.4 mTorr, while the plasma electron density was gradually increased with decreasing gas pressure. These experimental results were discussed with respect to the relationship between the etch yield and ratio of neutral Cl flux and ion flux incident on the substrate. Submicron patterning (0.5 µm lines & spaces) of platinum masked with photoresist was demonstrated using Cl2 plasmas in ECR discharges. High accuracy was obtained with no undercutting.
Etch Rate Acceleration of SiO2 during Wet Treatment after Gate Etching
Authors: Tatsumi Tetsuya , Seiichi Fukuda Seiichi Fukuda , Shingo Kadomura Shingo Kadomura
Published: February 2005

The etch rate of SiO2 during HF wet treatment was accelerated after gate etching. This was caused by a formation of a damaged layer on the SiO2 surface induced by the exposure to plasma. X-ray photoelectron spectroscopy (XPS), thermal desorption spectroscopy (TDS) and atomic force microscopy (AFM) analysis established that the damaged layer includes three types of “damage”: disordering, bromine contamination and surface roughening. It was found that vacuum ultraviolet rays (VUV) contributed to the disordering of the SiO2 network. The damaged layer has a weaker binding energy and greater roughening that enable more extensive contact with the HF etchant, making it more susceptible to etching.
Performance of the Plasma-Deposited Tungsten Nitride Diffusion Barrier for Al and Au Metallization
Authors: Kim Yong Tae , Chang Woo Lee Chang Woo Lee , Suk-Ki Min Suk-Ki Min
Published: February 2005

The thermal stability of plasma-enhanced chemical-vapor-deposited tungsten nitride (PECVD-W-N) thin film has been investigated as a diffusion barrier between Al or Au and Si during subsequent annealing at 550-850°C. The atomic concentrations of N in as-deposited W100-x
N
x
films are varied from 0 to 75 at.% corresponding to NH3/WF6 ratio, and their resistivities are varied from 10-460 µΩ·cm. Rutherford backscattering spectrometry, Auger electron depth profiles, X-ray diffraction and transmission electron microscopy show that 900 Å PECVD-W67N33 film interposed between Al or Au and Si is less permeable than sputtered TiN and PECVD-W film due to interstitial N atoms and Si/W67N33/Au maintaining the integrity of interface while the furnace post annealing is carried out at 850°C for 30 min.
Electrical Properties of Silicon Nitride Films Prepared by Photo-Assisted Chemical Vapor Deposition under Controlled Decomposition of Ammonia
Authors: Yoshimoto Masahiro , Ohtsuki Tetsuya , Takubo Kenji , Michio Komoda Michio Komoda , Hiroyuki Matsunami Hiroyuki Matsunami
Published: February 2005

Silicon nitride (SiN
x
) films have been deposited at lower substrate temperatures (≤500°C) by direct (without Hg-sensitization) photo-chemical vapor deposition (photo-CVD) with a low-pressure Hg lamp using SiH4 and NH3. The resistivity was as high as 5×1016 Ωcm. The minimum value of interface-trap density in Al/SiN
x
/Si metal-nitride-semiconductor (MNS) diodes was estimated to be 9×1010 cm-2 eV-1 by a quasi-static capacitance-voltage measurement. In contrast to conventional plasma CVD of SiN
x
, the formation of intermediate species is controlled by the decomposition of NH3 which is decomposed to a lesser extent in a plasma process, based on analyses of film structures and transient mass spectroscopy. This effect causes the properties of SiN
x
to not change in a wide range of NH3/SiH4 gas composition.
Comparative Study of Al2O3 Optical Crystalline Thin Films Grown by Vapor Combinations of Al(CH3)3/N2O and Al(CH3)3/H2O2
Authors: Kumagai Hiroshi , Toyoda Koichi , Matsumoto Masahiko , Obara Minoru
Published: February 2005

We compared the use of nitrous oxide (N2O) and hydrogen peroxide (H2O2) as the oxidant in digital chemical vapor deposition to obtain high-quality optical crystalline thin films of Al2O3. Optical constants and thicknesses of these films were investigated in terms of growth temperature, by using variable-angle spectroscopic ellipsometry.
Vacuum-Ultra-Violet and Ozone Induced Oxidation of Silicon and Silicon-Germanium
Authors: Boyd Ian W. , Valentin Craciun Valentin Craciun , Asghar Kazor Asghar Kazor
Published: February 2005

UV radiation has been used to induce low temperature oxidation of crystalline silicon (c-Si) surfaces and silicon-germanium (Si-Ge) strained layers on Si. For c-Si at 550°C, growth rate enhancements of up to 50 times the dry thermal oxidation rate are achieved, equivalent to what is normally only obtainable thermally at 900°C. When irradiated under identical conditions by the UV light, SiGe layers were found to oxidise two times faster than c-Si. Prolonged oxidation of SiGe produced a dielectric structure consisting of a pure SiO2 film on top of a SiO2 layer containing several percent of trapped Ge, with the remaining SiGe layer snow-ploughed at the Si interface but retaining its epitaxial structure. Simple modelling qualitatively explains the observed features of the silicon oxidation and has led to further studies of ozone oxidation of c-Si.
Electron Beam Irradiation Effects on Cl2/GaAs
Authors: Heiji Watanabe Heiji Watanabe , Shinji Matsui Shinji Matsui
Published: February 2005

A chlorine-gas-etched (100) GaAs surface is studied using in-situ X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). The Ga 2p3/2 core level shifts to a higher binding energy, which indicates the preferential formation of Ga-Cl bonds. An As-rich surface is also observed for the gas-etched GaAs. Removal of the chlorine-adsorbed GaAs surface, due to the electron-stimulated desorption (ESD) effect, occurs and is evaluated by measuring both the change of the chlorine signal in AES spectra and the chemical shift in XPS spectra. These observations suggest the existence of two types of ESD processes, each with a different cross section to electron beam irradiation. The results are explained in relation to a theoretically predicted chlorine gas etching model.
Study of Shallow p+n Junction Formation Using SiGe/Si System
Authors: Junichi Sakano Junichi Sakano , Seijiro Furukawa Seijiro Furukawa
Published: February 2005

The fabrication of p+n shallow junctions using strained grown SiGe/Si heterostructure was studied. Because of the lower chemical potential of B in SiGe, the effective diffusion constant of B reduces in the SiGe/Si interface region when B diffuses from the SiGe layer to the Si layer. We have proposed a new method for shallow junction formation using this phenomenon and have shown that the profile of implanted B in SiGe/Si system is kept shallow by thermal treatment compared to that in Si.
Broad-Pulsed Ga Ion-Beam-Assisted Etching of Si with Cl2
Authors: Satoshi Haraichi Satoshi Haraichi , Masanori Komuro Masanori Komuro
Published: February 2005

The characteristics of ion-beam-assisted etching (IBAE) of Si with Cl2 have been investigated using a broad-pulsed Ga ion beam, with several parameters such as Cl2 gas flux, ion beam dwell time, sample temperature, and beam diameter. A simple adsorption model where the density of the adsorbed Cl2 molecules mainly rules the etching yield, can explain the trend of the process in a short dwell-time region of less than 1 ms, and etching parameters are determined. However in a longer dwell-time region of more than 10 ms, the experiment showed several times higher etching yield than the prediction using the simple model with a 2.2-µm-diam beam. The etching model with consideration of Cl2 surface diffusion can explain this difference in etching yield and shows good agreement with the experiment throughout the entire region of dwell time. A diffusion coefficient of 8.0×10-6 cm2/s at room temperature was obtained by fitting theoretical curves in the experiment.
Lateral Grain Growth of Poly-Si Films with a Specific Orientation by an Excimer Laser Annealing Method
Authors: Kuriyama Hiroyuki , Nohda Tomoyuki , Ishida Satoshi , Kuwahara Takashi , Noguchi Shigeru , Kiyama Seiichi , Tsuda Shinya , Nakano Shoichi
Published: February 2005

Dramatic lateral grain growth of nondoped poly-Si films (maximum grain size: ∼4.5 µm, film thickness: 500 Å) with strong crystallographic (111) orientation on glass substrates has been achieved using an excimer laser annealing method, namely at low temperature below 400°C and in a processing time shorter than a second, for the first time. The surface morphology of these poly-Si films was very smooth and the crystallinity was excellent with minimal internal defects. These poly-Si films have monomodally distributed grain sizes, with an average grain size of around 1.5 µm. As a result of experimental study, we speculate that the basic driving force behind this lateral grain growth was surface free energy anisotropy, as the same mechanism was observed in high-temperature furnace annealing of doped poly-Si thin films.
Plasma-Induced Damage Behavior in GaAs by Photoreflectance Spectroscopy
Authors: Hideo Nakanishi Hideo Nakanishi , Kazumi Wada Kazumi Wada
Published: February 2005

Photoreflectance spectroscopy (PR) is applied to in situ, noninvasive determination of plasma-induced damage in GaAs for the first time. PR can evaluate damage such as nonradiative recombination centers and compensation centers in a near-surface layer. A new source of damage is revealed: short-term introduction followed by reduction of nonradiative recombination centers. This phenomenon cannot be detected by photoluminescence spectroscopy, a conventional noninvasive method. Comparing PR to the C-V method, we show that PR can be used as a highly sensitive probe for damage confined within the near-surface layer. This discovery will be helpful in developing methods that can be used for real-time, noninvasive detection of process-induced damage occurring during device processing.
Research on Information Processing by Neural Networks Cultured on Substrates
Authors: Chris D. W. Wilkinson Chris D. W. Wilkinson
Published: February 2005

The technology of microfabrication can be applied to the formation of structures of use in biology applications. The behaviour of biological cells on surfaces containing steps and grooves is described. The guidance of ihe processes of nerve cels can be used to form networks of predetermined topography. Progress in the formation and observation of nerve cells in vitro on such structures is reviewed.
Focused-Ion-Beam Surface Modification for Selective Growth of InP Wires and GaAs
Authors: Lezec Henri J. , Ahopelto Jouni , Usui Akira , Yukinori Ochiai Yukinori Ochiai
Published: February 2005

A novel method for selective, maskless deposition of InP on GaAs has been developed. This method combines focused-ion-beam (FIB) implantation of a GaAs substrate followed by hydride vapor phase epitaxy (VPE) of InP. The dependence of the selective growth mechanism on ion mass and dose is explored, and its cause is sought by examining the implanted surface with an atomic-force microscope (AFM). Since InP forms a single crystal with few defects, this new selective-epitaxy technique shows great promise for applications in quantum device fabrication.
Charge Collection Control Using Retrograde Well Tested by Proton Microprobe Irradiation
Authors: Sayama Hirokazu , Kimura Hiroshi , Ohno Yoshikazu , Satoh Shinichi , Sonoda Kenichirou , Kotani Norihiko , Mikio Takai Mikio Takai
Published: February 2005

Soft error reduction by high-energy ion-implanted layers has been investigated by novel evaluation techniques using high-energy proton microprobes. A retrograde well formed by 160 and 700 keV boron ion implantation could completely suppress soft errors induced by the proton microprobes at 400 keV. The proton-induced current revealed the charge collection efficiency for the retrograde well structure. The collected charge for the retrograde well in the soft-error mapping was proved to be lower than the critical charge of the measured DRAMs (dynamic random-access memories). Complementary use of soft-etror mapping and ion-induced-current measurement could clarify well structures immune against soft errors.
Molecular Beam Epitaxy and Migration-Enhanced Epitaxial Growth of InP Using Polycrystalline InP as Phosphorus Source
Authors: Yang Bing Xiong , Hasegawa Hideki
Published: February 2005

InP was grown by means of molecular beam epitaxy (MBE) and migration-enhanced epitaxy (MEE) using polycrystalline InP as the phosphorus source. Pregrowth thermal cleaning of the InP substrate was performed under either P2-beam or As4-beam irradiation. It is shown that polycrystalline InP is a highly controllable and useful source of a P2 beam for MBE and MEE growth of high-quality InP in the standard MBE system. The As4 cleaning was found to be more controllable and reproducible than the P2 cleaning. Although the As4 cleaning produced an ultrathin InAs interface layer, no inclusion of As was detected and no influence was found on the crystalline and electrical properties of the epilayer. Unintentionally doped layers showed n-type conduction with carrier concentration in the range of 5×1016-1×1018 cm-3, showing a remarkable dependence on the growth temperature.
Identification of a New Defect in Silicon Nitride Films
Authors: Yan Hui , Kumeda Minoru , Ishii Nobuhiko , Tatsuo Shimizu Tatsuo Shimizu
Published: February 2005

When silicon nitride films are prepared at a high deposition rate, a complicated ESR spectrum appears, which cannot be attributed to Si dangling bonds or N dangling bonds. It is found by the substitution of 14N with 15N that the hyperfine interaction with nitrogen nuclei is the origin of the complicated ESR spectrum. With comparison of the observed ESR spectra with the results of a computer simulation and a first-principles calculation, the new defect is designated as a pure p-type unpaired spin strongly localized on two inequivalent nitrogen atoms bonded to each other. Furthermore, we have also observed the change in the ESR spectra originating from the N-pair defect, the N dangling bond and the Si dangling bond in the 14N and 15N samples with ultraviolet soaking after high-temperature annealing.
High-Vacuum Planar Magnetron Sputtering
Authors: Asamaki Tatsuo , Miura Tsutomu , Hotate Kohichi , Yonaiyama Shingo , Nakamura Gen , Ishibashi Keiji , Hosokawa Naokichi
Published: February 2005

High-vacuum planar magnetron sputtering is performed in a wide pressure range of 10-1 Pa to 10-3 Pa. The measured sputter-deposition rates of Al are 0.2 µm/min at a pressure of 0.12 Pa (discharge current 0.2 A) to 8.3 Å/min at 0.0025 Pa (1 mA). The deposition rate is proportional to the discharge current, and increases rapidly with the discharge voltage and the magnetic flux density. It is found that the optimum distance between the substrate (anode) and target surface gives the maximum deposition rate.
Effects of [H2S]/[DMZn] Molar Ratio on ZnS Films Grown by Low-Pressure Metalorganic Chemical Vapor Deposition
Authors: Li Jiin Wen , Yan Kuin Su Yan Kuin Su , Meiso Yokoyama Meiso Yokoyama
Published: February 2005

Effects of [H2S]/[DMZn] molar ratio on the crystallinity and surface morphology of epitaxial ZnS films grown on glass substrate by low-pressure metalorganic chemical vapor deposition have been studied. The surface morphology has been evaluated and the results show it to be relatively flat and uniform. The crystallization has also been measured. We find that the samples deposited under the following conditions have better crystallinity: even after the deposition was completed, H2S flux was still introduced into the reactor until the substrate temperature fell to 200°C. From the experimental results, an optimum [H2S]/[DMZn] molar ratio can be concluded to exist somewhere near 20.
One-Dimensional Propagation of Fluctuation in Magnetohydrodynamic Channels
Authors: Okinaka Noriyuki , Oikawa Shun-ichi , Yatsu Shigeo , Yoshiaki Aoki Yoshiaki Aoki , Naoyuki Kayukawa Naoyuki Kayukawa
Published: February 2005

One-dimensional propagation characteristics of the plasma disturbance which originates from the temperature disturbance at the inlet of a linear-type magnetohydrodynamic (MHD) channel were analysed numerically. It was shown that the temperature fluctuation propagates with two different speeds. One is the mean flow convection speed and the other is the acoustic plus convection speed. Both waves appeared at the same time when a single-pulse temperature disturbance was induced adiabatically at the channel upstream. By contrast, the velocity wave excited inside the channel always propagates with the latter speed.
Depth Profiling of As in an AlAs/GaAs Multilayer by a New Laser-Induced Sputtered Neutral Mass Spectrometry System
Authors: Higashi Yasuhiro , Maruo Tetsuya , Tohru Tanaka Tohru Tanaka , Yoshikazu Homma Yoshikazu Homma
Published: February 2005

Depth profiling of As in an AlAs/GaAs multilayer has been measured with a pulse-counting photoion mass spectrometer (PPMS) that can perform depth profiling in two different modes: a secondary ion mass spectrometry (SIMS) mode and a laser-induced sputtered neutral mass spectrometry (SNMS) mode. In SIMS mode, the As secondary ion intensity in GaAs layers is about three orders of magnitude less than that in AlAs layers under O2
+ bombardment even though the As concentration is the same in both layers. In SNMS mode, the As photoion intensity in GaAs is only about twice that in AlAs. This difference can be attributed to sputtering yield differences between GaAs and AlAs. This result suggests that laser-induced SNMS by PPMS will give quantitative information and accurate depth profiling of layered samples by simply correcting sputtering yields.
Regenerative Switching Phenomenon of a GaAs Metal-n-δ(p+)-n-n+ Structure
Authors: Guo Der-Feng , Yeou Wen-Chen , Lour Wen-Shiung , Hsu Wei-Chou , Liu Wen-Chau
Published: February 2005

A new GaAs regenerative switching device with metal-n-δ(p+)-n-n+ structure has been fabricated and demonstrated. An InGaAs delta-doped quantum well was employed to provide the potential barrier for carriers transport and improve the confinement effect of holes. Due to the sequential avalanche multiplication near the reverse biased n-GaAs layer and the Schottky-semiconductor (M-S) junction, an interestingly double S-shaped negative-differential-resistance (NDR) phenomenon and three different operation points were obtained at low temperature. However, only single S-shaped NDR behavior was observed at room temperature due to the higher thermal energy and poor carrier confinement effect. Therefore, with an appropriate adjustments on device parameters, the proposed structure is suitable for switching device and multiple-value logic circuit applications.
Growth of Native Oxide and Accumulation of Organic Matter on Bare Si Wafer in Air
Authors: Okada Chizuko , Kobayashi Hiroyuki , Takahashi Isao , Jiro Ryuta Jiro Ryuta , Takayuki Shingyouji Takayuki Shingyouji
Published: February 2005

This letter reports the effect of organic matter on the growth of native oxide on a Si surface. Bare Si wafers and Si wafers with native oxide were stored under various conditions in a clean room and the thickness of native oxide was examined. In the case of the bare Si wafers, the native oxide hardly grew in a closed system but the native oxide grew to 6 Å in an open system when the storage time was 24 h. On the other hand, in the case of Si wafers with native oxide, this suggests that accumulation of organic matter occurs on Si wafers in the open system in the clean room. It was suggested that the accumulation of organic matter on Si wafers facilitates the growth of native oxide.
High-Quality GaAs/AlAs Buried Heterostructures Grown by Molecular Beam Epitaxy on Patterned Substrates
Authors: Saito Hideaki , Sugimoto Mitsunori , Ochiai Masami Anan
Published: February 2005

GaAs wires completely embedded in AlAs are successfully grown by molecular beam epitaxy at substrate temperatures higher than 725°C without interrupting growth. Crescent-shaped 1800-Å-wide GaAs wires are embedded in AlAs using this technique and electron beam lithography. We also investigate the dependence of photoluminescence on the GaAs wire width at room temperature. This investigation indicates that the emission efficiency of the narrowest GaAs wires (1800 Å wide) is at least as high as that of a quantum well grown on a planar substrate.
Arsenic Pressure Dependence of the Surface Diffusion in Molecular Beam Epitaxy on (111)B-(001) Mesa-Etched GaAs Substrates Studied by In Situ Scanning Microprobe Reflection High-Energy Electron Diffraction
Authors: Xu-Qiang Shen Xu-Qiang Shen , Tatau Nishinaga Tatau Nishinaga
Published: February 2005

The arsenic pressure dependence of surface diffusion of Ga adatoms in molecular beam epitaxy (MBE) on (111)B-(001) mesa-etched substrates was investigated by means of in situ scanning microprobe reflection high-energy electron diffraction (µ-RHEED). It was observed for the first time that the direction of Ga adatom migration from or to the (111)B sidewall is changed depending on the arsenic pressure. Furthermore, the diffusion length of Ga adatoms on the (001) surface along the [1̄10] direction was found to vary with arsenic pressures exponentially; however, it was independent of the direction of lateral migration. The diffusion length of Ga adatoms on the (001) surface along the [1̄10] direction varied from about 0.25 µm to 1.2 µm at 600°C within our arsenic pressure range. This suggests that the lifetime of Ga adatoms before incorporation into the crystal on each surface depends strongly on arsenic pressure.
Optical Micromanipulation of a Lasing Polymer Particle in Water
Authors: Sasaki Keiji , Misawa Hiroaki , Kitamura Noboru , Ryo Fujisawa Ryo Fujisawa , Hiroshi Masuhara Hiroshi Masuhara
Published: February 2005

Optical manipulation of a lasing microparticle in water was demonstrated. A rhodamine B-doped poly(methyl methacrylate) particle was simultaneously manipulated and pumped by 1064 nm CW and 532 nm pulsed Nd3+:YAG laser beams, respectively. Optical interactions between lasing and closely positioned nonlasing particles were studied by a multibeam laser micromanipulation technique.
High-Pressure Synthesis of HgBa2Ca2Cu3O9-x Superconductor with Tc>130 K
Authors: Hirabayashi Masayuki , Tokiwa Kazuyasu , Ihara Madoka Tokumoto
Published: February 2005

A high-temperature superconductor of HgBa2Ca2Cu3O9-x
with T
c>130 K was prepared by the high-pressure technique. The lattice constants of a=3.852 Å and c=15.822 Å were determined by X-ray powder diffraction measurement, which were somewhat smaller than previously reported values. The T
c value of the annealed sample was 130.3 K.
Normal Atmospheric Preparation of YBa2Cu4O8 Superconductor from Nitrate Solution by Freeze-Drying Method
Authors: Takahashi Katsumasa , Ito Toshimichi , Hiroaki Yoshikawa Hiroaki Yoshikawa , Akio Hiraki Akio Hiraki
Published: February 2005

A homogeneous superconducting material of YBa2Cu4O8 has been successfully prepared under normal O2 pressures from nitrate solution by means of a freeze-drying method without any catalyst. Thermal decomposition of freeze-dried powders and subsequent sintering under 1-atm oxygen ambient resulted in the YBa2Cu4O8 superconductor. Among the experimental parameters, temperatures during the decomposition and sintering have been studied in detail. X-ray diffraction analysis and dc-susceptibility measurements revealed the optimum conditions of the present preparation method.
Force-Displacement Characteristics of Fluxoid Lattice and Pinning Potential in Y-Ba-Cu-O Bulk Superconductor
Authors: Ni Baorong , Kitagawa Hajime , Wakuda Tsuyoshi , Shigemitsu Takashi , Funaki Kazuo , Yamafuji Kaoru , Matsushita Teruo
Published: February 2005

Measurements of the pinning force density and the displacement of fluxoids in ac magnetic field were carried out for a melt -processed Y-Ba-Cu-O bulk superconductor using the Campbell method. The Labusch parameter, αL, and the interaction distance, d
i, were estimated from the obtained force-displacement profile. It was found that αL depended greatly on temperature and magnetic field, especially in the field parallel to the c-axcis, and d
i decreased gradually with increasing temperature. These variationss were deduced to be caused by flux creep. The depth of pinning potential, U
0, for the trapped flux bundle was estimated using the values of αL and d
i. This was compared with the apparent pinning potential which is commonly observed from magnetic relaxation measurements.
Properties of Metal-Semiconductor Field-Effect Transistors Fabricated on Carbon-Doped Semi-Insulating GaAs Crystal Grown by Liquid Encapsulated Czochralski Method
Authors: Otoki Yoohei , Watanabe Masatoshi , Kuma Shoji , Takahashi Susumu , Onishi Masaya , Kashiwa Mikio
Published: February 2005

Metal-semiconductor field-effect transistors (MESFETs) whose active layers were made by ion-implantation were fabricated on a new type of semi-insulating liquid-encapsulated Czochralski (LEC)-grown crystal doped with carbon. The short-channel effect was suppressed and transconductance (gm), drain conductance and breakdown voltage were improved by carbon doping. These improvements were deduced as being due to a reduction in leakage under the channel. No change in the frequency dependence of the gm was recognized. Thus, the doped carbon did not generate any observable traps by which the properties of MESFET were degraded.
Implicit Difference Scheme to Calculate Electric Fields
Authors: Seishiro Hashiguchi Seishiro Hashiguchi
Published: February 2005

A difference scheme was proposed to calculate glow discharges with a time step Δt that is not limited by the inequality Δt<ε0/e||
µe
N||
, where ε0 is the permittivity in free space, e is the unit charge, µe is the electron mobility and N is the electron density. Calculations were made with a beam model for helium dc glow discharges. The model predicted high-density cold electrons in the negative glow. Calculations were made with a Δt which was 50 times larger than the one limited by the above inequality for the proposed scheme; the value of Δt could be determined from a physical point of view.