bluuebunny/crossref_metadata_2025 huggingface dataset:
Collection Efficiency of the Nuclepore Membrane Filter for Aerosol Sampling and Its Application to 218Po Measurement
Authors: Fukami Kenji , Shizuma Kiyoshi , Kazuo Iwatani Kazuo Iwatani , Hiromi Hasai Hiromi Hasai
Published: February 2005

An α spectrometry combined with a filter sampling method has been applied for the measurement of radioactive aerosols. The Nuclepore membrane filter was used for the aerosol sampling, and its collection efficiency was experimentally determined. Examples of measured 218Po concentrations in three rooms were given.
Laser Spectroscopic Detection of Radicals in the Photolysis of Disilane with an ArF Laser
Authors: Okada Tatsuo , Nishimi Akihiro , Noboru Shibamaru Noboru Shibamaru , Mitsuo Maeda Mitsuo Maeda
Published: February 2005

Disilane (Si2H6) was photodissociated with an ArF excimer laser and the radicals produced were probed by resonantly enhanced multiphoton ionization spectroscopy (REMPI) and laser-induced fluorescence spectroscopy (LIF). Silicon and hydrogen atoms, and SiH and Si2 molecules were detected. It was found that temporal changes of the densities of Si and Si2 were controlled by diffusion in the present experiment. Absolute density calibration of the measured REMPI signals is also presented.
Improved High-Temperature X-Ray Lang Camera
Authors: Mizuno Kaoru , Ono Kotaro , Kino Kazuyoshi Ito
Published: February 2005

A high-temperature X-ray Lang camera which has very slow translational speed without multiscanning is designed to observe slowly changing phenomena using a conventional X-ray source. A single-scanned topograph of a nearly perfect aluminum crystal taken by this camera indicates an annihilation profile of interstitial-type dislocation loops grown as vacancy sources due to a temperature rise.
Transient Characteristics of Luminescence from CdS-Doped Glass
Authors: Tadaki Miyoshi Tadaki Miyoshi
Published: February 2005

Time-resolved luminescence spectra were measured at 300 K and 77 K in CdS-doped glass under N2 laser excitation. Transient characteristics of luminescence were affected by trapping and detrapping of electrons with trapping states. The experimental results were in agreement with calculated results based on a four-level system.
Determination of Characteristics of Yb+ Ion Cloud Trapped in a RF Trap with He Buffer Gas
Authors: Jun Yoda Jun Yoda , Kazuhiko Sugiyama Kazuhiko Sugiyama
Published: February 2005

Characteristics of the Yb+ ion cloud trapped in a rf trap in the presence of He buffer gas were determined by fluorescence detection as well as the rf resonance method. Combining the results obtained by the two methods, we determined the spatial ion density distribution and found that the trapped ions were thermalized by collisions with the He buffer gas. It was confirmed by both methods that the harmonic motion of the trapped ions was excited by the trapping field leaked to the rf resonance detection circuit (subharmonic oscillation), and moreover, by the fluorescence detection method, that the probing rf field used for the rf resonance method was indispensable as “the initial push” for exciting the amplitude.
Spectroscopic-Ellipsometry Analysis of Si Films Prepared by RF Sputtering
Authors: Takayuki Miyazaki Takayuki Miyazaki , Sadao Adachi Sadao Adachi
Published: February 2005

Optical properties of Si films sputter-deposited on HF-treated (100)Si substrates have been investigated using spectroscopic ellipsometry in the 2.5-5.5-eV photon-energy range. Homoepitaxial Si films are grown at a high substrate temperature (∼410°C), while films deposited at lower temperatures show that they have polycrystalline (∼380°C) or amorphous structures (∼310°C). A linear regression analysis and a Bruggeman effective-medium approximation reveal that the homoepitaxial film has a few void networks in the film and a rough-surface overlayer of a few tens of Å. Polycrystalline and amorphous films are also found to contain a large number of void networks deep in the film mediums.
Stable, Metastable and Charged Dangling Bonds in Transient Light-Induced ESR of Undoped a-Si:H
Authors: Saleh Zaki M. , Tarui Hisaki , Nakamura Noboru , Nishikuni Masato , Tsuda Shinya , Shoichi Nakano Shoichi Nakano , Yukinori Kuwano Yukinori Kuwano
Published: February 2005

Transient light-induced electron spin resonance (LESR) at 120 K, has been used to investigate potential differences between intrinsic (stable) and light-induced (metastable) defects in a-Si:H through changes in the line shape. Previously, we have reported that when the line shape is decomposed into broad and narrow components, the narrow component decreases dramatically, relative to the broad component, with increasing light-soaking time. The present results indicate, however, that similar changes are not observed when the defect density is increased by changing deposition conditions or by high-temperature annealing. A dangling-bond-conversion process involving charged dangling bonds is proposed to explain these changes. We suggest that stable and metastable defects play different roles in transient LESR and may occupy different energy positions in the gap of a-Si:H.
Differences in Tunneling Time between 77 K and Room Temperature for Tunneling Biquantum Wells
Authors: Tackeuchi Atsushi , Sugiyama Yoshihiro , Tsuguo Inata Tsuguo Inata , Shunichi Muto Shunichi Muto
Published: February 2005

We measured the recovery time from excitonic absorption bleaching in tunneling biquantum wells at 77 K and room temperature. The absorption recovery time corresponds to the tunneling time of electrons from narrow to wide wells. We have found that tunneling at 77 K is about 2.5 times slower than at room temperature.
Suppression of Superconductivity in Y1-xPrxBa2Cu4O8 Prepared by Nitrite Pyrolysis Method
Authors: Meen Teen-Hang , Chen Ying-Chung , Lin Ming-Wei , Yang Hung-Duen , Tai Ming-Fong
Published: February 2005

X-ray diffraction patterns show that samples contain the nearly single 124 phase for x<0.7. Lattice parameters a and b increase with Pr concentration. Thermal stability is reduced with increasing Pr concentration. Zero resistance temperature T
co decreases monotonically fiom 80 K at x=0 to 12 K at x=0.65. Room-temperature resistivity changes linearly to x=0.7 and increases abruptly at x=0.75. Thus the critical concentration x
cr is estimated to be 0.7. Effective magnetic moments of Y1-x
Pr
x
Ba2Cu4O8 are 3.63, 3.35 and 3.23µB for x=0.2, 0.4 and 0.6, respectively. In addition, the similarities and differences between Y1-x
Pr
x
Ba2Cu4O8 and Y1-x
Pr
x
Ba2Cu3O7-y
are discussed.
Hall Coefficient and Oxygen Deficiency in BaPb0.7Bi0.3O3 Single-Crystal Thin Films
Authors: Minoru Suzuki Minoru Suzuki
Published: February 2005

The Hall coefficient and resistivity of single-crystal thin films of BaPb0.7Bi0.3O3-δ are measured for various numbers of oxygen vacancies incorporated by successive oxygen reduction treatments. It is found that increasing the number of oxygen vacancies in this system causes a significant increase in resistivity and an abrupt depression of T
c. The Hall coefficient decreases with increasing number of oxygen vacancies, reflecting a significant decrease in the carrier density. These changes are also accompanied by a noticeable decrease in the Hall mobility. It is also found that the depression of T
c is proportional to the decrease in the Hall carrier density, showing a linear relationship between T
c and the carrier density. The effects of oxygen vacancies on the transport properties in conducting oxides are discussed in relation to the high-T
c cuprates.
Synthesis and Magnetic Properties of Ultrafine Iron Particles Prepared by Pyrolysis of Carbonyl Iron
Authors: Sawada Yoshiaki , Kageyama Yoshiteru , Iwata Masashi , Tasaki Akira
Published: February 2005

Magnetic characteristics of fine iron particles prepared by a new chemical process, were studied. In this semi-industrial process, iron pentacarbonyl, Fe(CO)5 was used as a starting material, and it was thermally decomposed under a magnetic field. Diameter of obtained particles was between 150 and 250 Å, and the particles were aligned along the magnetic field like a necklace. The highest coercive force appeared when particle diameter was about 200 Å. To stabilize the particles, surfaces of particles were slightly oxidized before they were exposed to the open air. The saturation magnetization of treated particles was about 70% of the bulk value. Some test tapes were made by using these fine iron particles.
A Model for Emissions from ZnS:Ce3+ and SrS:Ce3+ Thin-Film Electroluminescent Devices
Authors: Sang Ho Sohn Sang Ho Sohn , Yoshihiro Hamakawa Yoshihiro Hamakawa
Published: February 2005

ZnS:CeF3 thin-film electroluminescent devices are prepared in the vacuum and the oxygen atmosphere by means of an electron-beam evaporation method. The Auger depth profiles for the ZnS films prepared in the oxygen atmosphere show that oxygen substitutes for sulfur. The luminescent decay time for 475 nm and 530 nm emissions of Ce3+ ions reveals an increase, particularly in the 530 nm emission when the films are prepared in the oxygen atmosphere. The experimental results suggest that a nonradiative energy transfer via a certain defect occurs in ZnS:Ce3+ films. A simple model for emissions from ZnS:Ce3+ films is proposed, based on the Auger type-nonradiative energy transfer via sulfur vacancies. The electroluminescent characteristics seen in SrS:Ce3+ films are also discussed on the basis of the same mechanism.
Effect of Cr2O3 Additives on Microstructure and Electrical Properties of Nd-Modified PbTiO3 Ceramics
Authors: Wu Long , Lee Yi-Yeh , Chich-Kow Liang Chich-Kow Liang , Tien-Shou Wu Tien-Shou Wu
Published: February 2005

Chromium addition has been investigated extensively in lead zirconate titanate (PZT)-type ceramics but seldom mentioned in lead titanate (PT)-type ceramics. In this study, the effect of Cr2O3 additives (0-0.6 wt%) on the microstructure and electrical properties of Pb0.88Nd0.08(Ti0.98Mn0.02)O3 (PNT) ceramics is discussed. The chromium ions enter into the lattice structure of PNT ceramics within the doping range, and from the measurements of the temperature dependence of electrical conductivity, it is believed that the chromium ion substitutes for the Ti site with a lower valence state. Results indicate that the chromium ion functions as a grain growth promoter to accelerate densification in the microstructure and acts as a hardener which favors the higher mechanical quality factor, lower dielectric loss and lower electrical resistivity in electrical properties.
Densification and Dielectric Properties of Cordierite-Lead Borosilicate Glasses
Authors: Fu Lih-Shan Chen
Published: February 2005

To improve the sinterability of P2O5-added cordierite glass, lead borosilicate glass was adopted as a sintering aid. Various sintering temperatures and times were used to observe the effects of heat treatments on the sintering behavior of the cordierite-lead borosilicate glass. The flux effect of lead borosilicate glass aids the coalescence of cordierite glass particles, which promotes the densification. Phase transformation from cordierite glass to the high-temperature α-cordierite form is the major reaction during the sintering of cordierite-lead borosilicate glass. The dielectric constant of the sintered composites is determined by both the existing crystalline structure and the completeness of densification. The relationship between the volume fraction of lead borosilicate glass and the dielectric constant can be approximated by a linear equation.
Lattice-Dynamical Aspects in Photoexcited Chalcogenide Glasses
Authors: Mizushima Yasushi Utsugi
Published: February 2005

Lattice-dynamical aspects are coherently applied to the reversible photostructural change (PSC) effect and associated phenomena in chalcogenide glasses. Far-infrared, X-ray photoelectron and optical absorption measurements reveal that photo-induced distortions and quenching in lattice configurations are characterized by increased randomness, which can be reversed by thermal annealing for full recovery. A statistical analysis reveals clearly that PSCs such as photodarkening and photoexpansion are essentially equivalent to a thermally frozen-in effect. The PSCs can be directly traced to the strong electron-lattice coupling and localized bond strain of chalcogenide glasses. A lattice-dynamic energy diagram highlights the importance of the quadratic-term of atomic distortion (δq)2 in relating PSC to the glass transition phenomenon. The photochemical and photodoping effects are then described, on the same basis, in terms of the lattice fluctuation and high fictive temperature.
Alignment Layers for Ferro and Antiferroelectric Liquid Crystal Cells
Authors: Negi Yuvraj Singh , Yamamoto Norio , Suzuki Yoshiichi , Kawamura Ichiro , Yamada Yuichiro , Kakimoto Masa-aki , Imai Yoshio
Published: February 2005

Aromatic fluorine and nonfluorine containing polyimides, polyamide-imides and polyamides were developed and utilized as alignment layers in ferroelectric (FLC) and antiferroelectric liquid crystal (AFLC) cells. The FLC and AFLC blend (AFLCB-1) of liquid crystals used in the experiment were CS-1011 and [S(-)4-(1-methylheptyloxycarbonyl) phenyl-4-octyloxybiphenyl-4-carboxylate (MHPOBC), R(+)4-(1-trifluoromethylheptyloxy carbonyl)phenyl-4-octyloxybiphenyl-4-carboxylate (TFMHPOBC), and other homologues, [AFLCB-1], respectively. The alignment layer deposited over an ITO-coated glass electrode plate with 2 µm cell gap showed good or random alignment of liquid crystal in FLC and AFLC cells. The AFLC cells exhibited contrast ratio values greater than 10:1 depending on the molecular structure of the alignment layer. The alignment quality of FLC and AFLC cells was also compared by using different molecular structure of polymer alignment layers.
Growth of Pb1-x-yCdxSryS Films and SLs by Hot Wall Epitaxy for 3 µm Lasers, and Their Electrical Properties
Authors: Mohammadnejad Shahram , Matsushita Keiichi , Izutsu Takashi , Akihiro Ishida Akihiro Ishida , Hiroshi Fujiyasu Hiroshi Fujiyasu
Published: February 2005

PbCdS, PbSrS and PbCdSrS films were prepared on BaF2(111) and KCl(100) using the hot wall epitaxy (HWE) technique and their growths were studied. For Pb1-xCdxS films, it was observed that CdS incorporation in (111) surface is greater than the CdS incorporation in (100) surface, while in Pb1-ySryS films SrS was incorporated equally in either surface. Pb1-xCdxS/PbS and Pb1-ySryS/PbS superlattices (SLs) were also prepared and their structures were studied by the high-angle X-ray diffraction measurement. It was observed that a considerable amount of Cd is diffused into the PbS layers during the growth. On the other hand, the amount of Sr diffusion was small. PbCdS, PbSrS and PbCdSrS p-type and n-type films were obtained by doping with Tl and Bi. Both PbSrS and PbCdSrS showed high carrier concentration and mobility, while the carrier concentration and mobility of PbCdS were relatively low.
Effect of RF Bias on Low-Temperature Synthesis of Aluminium Nitride Film by Hollow Cathode Discharge-Type Ion Plating
Authors: Kishi Matsuo , Mizuaki Suzuki Mizuaki Suzuki , Kenichi Ogawa Kenichi Ogawa
Published: February 2005

The effects of RF bias potential on the synthesis of aluminium nitride (AlN) film on a glass substrate using the hollow cathode discharge (HCD) ion plating technique, and on some properties of the film were investigated. The deposits were characterized by X-ray diffraction and scanning electron microscopy. The AlN films prepared with application of RF bias potential were superior in flatness to those prepared without applying of RF bias potential, but excess RF bias voltage to the substrate caused the film to come off not just from the substrate, but also with peeling of the glass substrate surface. The Vickers microhardness of film consisting of AlN single phase was estimated to be about 2300 kg/mm2. The film density was increased by applying RF bias voltage, its value being close to the theoretical value.
X-Ray Photoelectron Spectroscopic Analysis of the Oxide of GaAs
Authors: Toshifumi Ishikawa Toshifumi Ishikawa , Hideaki Ikoma Hideaki Ikoma
Published: February 2005

Oxides of GaAs grown using various oxidation processes were analyzed with X-ray photoelectron spectroscopy (XPS). Oxides investigated were the native (naturally grown or exposed to air), the chemical (grown in boiling deionized water) and the thermal (at 350°C and 500°C in dry oxygen) ones. With the use of a spectral deconvolution technique, all types of suboxides of both As and Ga including elemental arsenic were observed in addition to well-known As2O3 and Ga2O3. Elemental arsenic is considered to be one of the oxidized forms of GaAs. As2O5 was observed in the thermal oxides. In the chemical oxide and the native oxide grown in short exposure to air, elemental arsenic is the main component of oxide, while As2O3 is the dominant species in more highly oxidized films such as the thermal oxide. XPS data suggest that oxidation of As bonded in GaAs proceeds as GaAs→elemental As (As0)→As2O (As1+)→AsO (As2+)→As2O3 (As3+)→As2O5 (As5+). Oxidation of Ga bonded in GaAs advances as GaAs→Ga2O (Ga1+)→GaO (Ga2+)→Ga2O3 (Ga3+). Angle-resolved XPS measurements and semiquantitative analyses of these data were performed and an effective thickness of each oxide was also derived with simplified assumptions. The native and the chemical oxides were nearly stoichiometric. However, the thermal oxide was substantially Ga-rich due to desorption and evaporation of As2O3 from the surface during oxidation.
In Situ Interface Control of Pseudomorphic InAs/InP Quantum Well Structure Growth by Surface Photo-Absorption
Authors: Yasuyuki Kobayashi Yasuyuki Kobayashi , Naoki Kobayashi Naoki Kobayashi
Published: February 2005

The exchange reaction of group V atoms was monitored in situ by surface photo-absorption on a submonolayer scale during metalorganic vapor phase epitaxial growth of pseudomorphic InAs/InP heterostructure on (001) InP substrates. About a 0.4-monolayer As/P exchange reaction was observed after arsine was supplied at 0.2 µmol/s onto the In surface of InP at a substrate temperature (T
s) of 400°C. At a T
s of 350°C, this As/P exchange reaction was suppressed to less than 0.1 monolayer. In contrast, the P/As exchange reaction was less than 0.1 monolayer below 400°C. The benefits of in situ control were shown by growing pseudomorphic InAs/InP single and multiple quantum wells with 1-12 InAs well layers at T
s=350°C and characterizing them by cross sectional transmission electron microscopy, photoluminescence, and double crystal X-ray diffraction. Metallurgically abrupt and atomically flat heterostructures without dislocations were grown up to 10 monolayer (ML) of InAs well, which corresponds to the critical layer thickness.
Epitaxial Growth of Vanadium Films Evaporated on NaCl Substrates
Authors: Yamada Yukio , Kasukabe Yoshitaka , Nagata Shinji , Yamaguchi Sadae
Published: February 2005

The epitaxial growth of vanadium (V) films evaporated on an NaCl cleavage surface has been studied by electron microscopy. It has been found that body-centered tetragonal (bct) VH
x
(x\lesssim0.1; a=0.301 nm, c=0.312 nm) and NaCl-type VO
y
(y\fallingdotseq1.0; a
′=0.408 nm) are formed on the substrate held at 270°C in the early growth stage of the film. With increasing film thickness, body-centered cubic (bcc) V is formed. When the substrate temperature is raised up to 400°C, bcc V films (a=0.302 nm) grow from the early growth stage. On the other hand, bct VH
x
(x\fallingdotseq0.5; a=0.297 nm, c=0.338 nm) grows mainly when the substrate temperature is lowered to -170°C. The existence of oxygen and hydrogen atoms in the film was confirmed by nuclear reaction analysis and elastic recoil detection analysis respectively. The present paper has verified also that hydrogen and oxygen atoms which dissolve in V films, escape from the NaCl substrate.
Photolithography System Using a Combination of Modified Illumination and Phase Shift Mask
Authors: Kamon Kazuya , Miyamoto Teruo , Myoi Yasuhito , Nagata Hitoshi , Tanaka Norihiko Kotani
Published: February 2005

Various methods have been developed to overcome the limitations in photolithography. Modified illumination and phase shift mask technologies have been developed in order to improve the depth of focus and resolution limit. We have combined these two methods and applied them to the step and repeat exposure system. Experiments using the modified illumination were carried out and subhalf-micron patterns were produced. The process latitude of 64M dynamic random access memory (DRAM) is doubled by this combination process.
Dependence of Defects in Optical Lithography
Authors: Ham Y. M. , Hur I. B. , Kim Y. S. , Ahn D. J. , Cha Zion , Choi S. S. , H. J. Kim H. J. Kim , Y. J. Jeon Y. J. Jeon
Published: February 2005

In the optical lithography process, the effect of defects on the patterns is related to the process ability and the device design rule. It is, however, very difficult to predict the defect generation and influences. By simulation and experiments, we examined the designed patterns with a typical defect according to the process ability and condition in order to predict and analyze the printability, the effect of defects, and the device performance. In the experiments, the electrical and the scanning electron microscopy (SEM) monitoring method were used for the analysis of the defect patterns on the oxide, poly, nitride, and metal layers with process and design parameters. We propose that the results confirm the defect size to be controlled in the real process.
Phase Defect Repair Method for Alternating Phase Shift Masks Conjugate Twin-Shifter Method
Authors: Ohtsuka Hiroshi , Kuwahara Kazuyuki , Toshio Onodera Toshio Onodera , Takashi Taguchi Takashi Taguchi
Published: February 2005

Phase shift masks (PSMs) enable current optical exposure systems to provide significantly higher resolution in effective depth of focus (DOF). Localized phase errors, or other transparent defects in the mask phase shifter elements, can cause loss of DOF and degradation of image contrast. Transparent defects of this type have prevented PSMs from becoming practical for large-scale production of integrated circuits containing deep submicrometer features. This paper describes a new technique that is useful for repairing Alternating PSMs containing transparent defects in the phase shifter elements.
0.05 µm (3σ) Overlay Accuracy Through-the-lens Alignment in an Excimer Laser Lithography System
Authors: Higashiki Tatsuhiko , Tojo Toru , Takahashi Yoshihiko , Tabata Mitsuo , Nishizaka Takeshi , Kuwabara Osamu , Uchida Norio , Yoshino Hisakazu , Saito Susumu
Published: February 2005

This paper presents a through-the-lens (TTL) alignment, called separated mark TTL alignment (SMART), applied to a KrF excimer laser lithography system. This SMART optical system does not require any complicated compensation mechanisms for longitudinal chromatic aberration. Several advanced methods for SMART optics to obtain higher overlay accuracy, such as optical heterodyne interferometry, real-time alignment system, and alignment signal processor, have been developed and adopted. The performance of such an improved SMART in an excimer laser lithography system was experimentally evaluated using dynamic random access memory (DRAM)-processed wafers. An overlay accuracy of 0.05 µm (3σ) has been achieved.
Fabrication of 0.2 µm Fine Patterns Using Optical Projection Lithography with an Oil Immersion Lens
Authors: Kawata Hiroaki , Matsumura Ippei , Hitoshi Yoshida Hitoshi Yoshida , Kenji Murata Kenji Murata
Published: February 2005

Fine patterns are fabricated by using optical projection lithography with both an oil immersion lens of NA=1.25 and a conventional single-layer resist. Chlorobenzene soak is used in order to remove the immersion oil and to improve the side wall profile of the resist patterns. Some samples are lightly etched by O2 plasmas in order to remove a residual resist at the bottom of the resist patterns. Finally, it is found that a 0.18 µm fine resist pattern with a good edge definition can be fabricated. Al line and space pattern with a width of about 0.21 µm is also fabricated by lift-off technique.
Optically High Transparent SiN Mask Membrane with Low Stress Deposited by Low Pressure Chemical Vapor Deposition
Authors: Kumar Rakesh , Ohta Tuneaki , Yamashita Yoshio , Koga Hiroshi Hoga
Published: February 2005

Optically high transparent and low-stress silicon nitride film for X-ray mask membrane was successfully deposited by low pressure chemical vapor deposition (LPCVD). Deposition of silicon nitride films in a relatively higher temperature range of 900°C-1000°C was investigated as a function of deposition temperature and reactant gas flow (SiH2Cl2 and NH3). Silicon nitride films of low tensile stress in the order of 3-5×108 dyn/cm2 with low refractive index of 2.05 were obtained at 1000°C. Silicon nitride membrane deposited at 1000°C showed optical transparency ∼95% (λ=633 nm). Use of such optically high transparent silicon nitride film will be helpful in reducing the alignment signal detection error, which is required for highly efficient mask wafer alignment.
`NOWEL-2' Variable-Shaped Electron Beam Lithography System for 0.1 µm Patterns with Refocusing and Eddy Current Compensation
Authors: Yasutake Nobuyuki , Takahashi Yasushi , Oae Yoshihisa , Yamada Akio , Kai Jun-ichi , Hiroshi Yasuda Hiroshi Yasuda , Ken-ichi Kawashima Ken-ichi Kawashima
Published: February 2005

We have developed a variable-shaped electron beam (EB) lithography system which we call NOWEL-2. The system has the following features: (1) a short objective lens and a four-stage major deflection system; the landing angle at the corner of the 1.6 mm square major field is less than 2 mrad, and patterns from 0.1 to 3.0 µm are well resolved over the whole deflection field, (2) 20-bit digital-to-analog converter and high-precision current output amplifier, in which the least significant bit (LSB) corresponds to 0.0025 µm; linearity error is less than 1/4 LSB at 23±5°C, (3) refocusing and refocus-flyback; the edge sharpness of a 3 µm square beam was improved from 0.5 µm to 0.25 µm, (4) eddy current compensation; for a 100 µm electromagnetic jump, the waiting time is less than 50 µs, (5) continuously moving stage mode exposure; beam position accuracy is about 0.05 µm (3σ).
High-Speed Electron Beam Data Conversion System Combining Hierarchical Operation with Parallel Processing
Authors: Magoshi Shunko , Koyama Kiyomi , Ikenaga Osamu , Watanabe Susumu , Saito Tamaki , Sakamoto Shinji , Ooki Shin-ichiro
Published: February 2005

A new high-speed electron beam (EB) data conversion system has been developed for the variable-shaped beam EB reticle writing system EX-8. The target conversion rate from computer-aided design (CAD) data to EX-8 data is five reticles per hour for the class of 16-Mbit dynamic random access memory (DRAM) and beyond. To achieve this, both the hierarchical and parallel shape data operations and the parallel EB formatting have been adopted. Preprocesses for the hierarchical operations have been integrated, such as cell-overlap eliminations and the “doughnut process” which involves partially expanding shapes near cell boundaries. A 64-Mb DRAM design was successfully converted in the hierarchical method on an engineering workstation (EWS) with a single processor, and the number of processed shapes was reduced by four orders of magnitude and the average processing time was less than nine minutes. The processing time of the shape data operations for one layer of a 129 k gate array was reduced to 1/3 when four processes were performed in parallel on an EWS with four processors.
Acid-Catalyzed Reactions of Tetrahydropyranyl-Protected Polyvinylphenol in a Novolak-Resin-Based Positive Resist
Authors: Sakamizu Toshio , Shiraishi Hiroshi , Yamaguchi Hidenori , Takumi Ueno Takumi Ueno , Nobuaki Hayashi Nobuaki Hayashi
Published: February 2005

This paper deals with an acid-catalyzed reaction mechanism of a polymeric dissolution inhibitor of a novolak-resin-based positive chemical amplification resist system. This resist system consists of a novolak matrix resin, tri(methanesulfonyloxy)benzene as an acid generator, and tetrahydropyranyl-protected polyvinylphenol (THP-M) as a polymeric dissolution inhibitor. The acid-catalyzed deprotection products of THP-M in the resist film are detected and their subsequent acid-catalyzed reactivities are evaluated. It is found that tetrahydropyranyl group are exchanged between THP-M and the matrix to yield a strong dissolution inhibitor, causing negative tone behavior at the overexposure dose. High-resolution patterns (0.3-µm contact holes) are achieved with high sensitivity (2.4 µC/cm2 at 50 kV).
Influence of Acid Diffusion on the Lithographic Performance of Chemically Amplified Resists
Authors: Nakamura Jiro , Hiroshi Ban Hiroshi Ban , Akinobu Tanaka Akinobu Tanaka
Published: February 2005

The distribution of chemical amplification reactions incidental to catalytic acid diffusion is calculated to clarify its influence on the lithographic performance of chemically amplified resists. The distribution of the chemical amplification reaction is less extensive than that of catalytic acid. There exists an optimum diffusion length for maximizing sensitivity without sacrificing resolution. Acid diffusion coefficients in the chemically amplified resist EXP are 15 nm2/s at 55°C and 50 nm2/s at 65°C. A trade-off between sensitivity and resolution is observed in the EXP, which is attributed to acid diffusion. The relation between the variables is formulated by (Resolution)\propt(Sensitivity)-1/2 on the basis of a simple model, and guidelines are proposed for the material design of high-performance chemically amplified resists.
Radiation-Induced Acid Generation Reactions in Chemically Amplified Resists for Electron Beam and X-Ray Lithography
Authors: Kozawa Takahiro , Yoshida Yoichi , Tagawa Mitsuru Uesaka
Published: February 2005

The radiation-induced reactions of onium salts in some kinds of solutions and model compound solutions of chemically amplified electron beam (EB) and X-ray resists have been studied by means of picosecond and nanosecond pulse radiolysis. The following reaction mechanisms of the chemically amplified EB and X-ray resists have been elucidated. The radiation-induced reaction mechanisms are complicated due to the presence of several proton donors. The onium salts directly produce small amounts of Brønsted acids by EB and X-ray exposure and most of the Brønsted acids are formed from proton adducts of the base polymer. The onium salts are strong electron scavengers and promote the generation of the proton adducts in the chemically amplified resists.
Bisazidobiphenyls/Novolak Resin Negative Resist Systems for i-Line Phase-Shifting Lithography
Authors: Hattori Keiko T. , Hattori Takashi , Uchino Shouichi , Ueno Takumi , Hayashi Nobuaki , Shirai Seiichiro , Moriuchi Noboru , Morita Masayuki
Published: February 2005

Bisazidobiphenyls have been evaluated as photosensitive compounds of negative resists for i-line phase-shifting lithography. The optical parameters of the bisazidobiphenyl resists such as Dill's A, B, and C parameters, molar absorption coefficients, and quantum yields are measured to select an appropriate bisazidobiphenyl for an i-line negative resist. The quantum yields of bisazidobiphenyls strongly depend on the substituents on the aromatic rings and vary between 0.25 and 0.83. The resist sensitivities are proportional to the product of ε and φ, which means the nitrenes produced from each bisazidobiphenyl have the same reactivity with novolak resin. 2,7-Diazidofluorene (azide 6), which has the largest ε·φ, gives the highest sensitivity. However, the resist using a mixture of azide 6 and 4,4'-diazido-3,3'-dimethoxybiphenyl (azide 1) is subjected to lithographic evaluation because azide 6 has low solubility in the casting solvents. The new resist resolves 0.275-µm line-and-space patterns in 1-µm-thick film when it is exposed with an i-line stepper in conjunction with a phase-shifting mask. The required dose of the new resist for imaging is 240 mJ/cm2.
Improvement of Dry Etching Resistance of Cyclized Polybutadiene Negative Resist by Vacuum Baking
Authors: Cornu Toshio Shimizu
Published: February 2005

The dry etching resistance of cyclized polybutadiene negative resist, baked both in air and in vacuum, was investigated. After postbaking in air at above 160°C, the resist etching rate sharply rises. It was clarified by differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FT-IR, RAS method) and X-ray photoelectron spectroscopy (XPS) that the resist oxidation decreases dry etching resistance. On the other hand, the highest resistance was obtained by baking the resist in vacuum at 200°C. The postbaking technique was confirmed as a method for increasing-dry etching resistance.
Characteristics of a Monodisperse PHS-Based Positive Resist (MDPR) in KrF Excimer Laser Lithography
Authors: Kawai Yoshio , Akinobu Tanaka Akinobu Tanaka , Tadahito Matsuda Tadahito Matsuda
Published: February 2005

A new chemically amplified monodisperse PHS-based positive resist (MDPR) has been developed for KrF excimer laser lithography. MDPR is an alkali-developable single-layer resist, composed of partially tBOC-protected PHS, a dissolution inhibitor and a photoacid generator. We used nearly monodisperse PHS synthesized by living polymerization and obtained fine patterning. The MDPR has a high contrast value γ of 4, which results in excellent resolution: the MDPR can easily generate l & s patterns down to 0.25 µm in width at 90 mJ/cm2. A higher sensitivity of 45 mJ/cm2 and a contrast value γ of 12 were achieved with a blended MDPR.
Surface Imaging Resists for 193 nm Lithography
Authors: Hartney Donald W. Johnson
Published: February 2005

193 nm radiation causes direct photocrosslinking of polymer films which is sufficient to generate silylation selectivity under appropriate conditions. A variety of phenolic based polymers and blends with photoactive compounds were studied for their suitability as resists in a 193 nm, positive-tone, silylation process. Meta-cresol novolac resists and polyvinylphenol resists show the best sensitivity for this process. The threshold dose required to restrict diffusion of the silylating agent depends strongly on the composition of the resist. Sensitivities range from 12 mJ/cm2 to over 100 mJ/cm2 for various novolac and polyvinylphenol materials. Wide variations in sensitivity have been found between different synthetic methods for the same resin, different molecular weight characteristics, and different functional modifications.
Si Etching Employing Steady-State Magnetron Plasma with Magnet at Anode Centered in a Cylindrical Reactor
Authors: Koto Makoto , Narai Akira , Sakaue Hiroyuki , Shindo Haruo , Yasuhiro Horiike Yasuhiro Horiike
Published: February 2005

Magnetron plasma without localization of electrons has been studied by coupling electric fields on a cylindrical cathode with magnetic fields from a steady-state magnet in a centered anode. Since the area of the cathode is wider than that of the anode, the present plasma is likely to be generated by fields by self-bias voltage and plasma potential. Various distributions of Si etch rate, electron density, current of double probe and fluorine (7037 Å) emission intensity were measured by setting a quartz plate on a part of the metal cathode or covering half of the cathode circumference with a polyimide film. These results revealed that plasma density changed considerably in the vicinity of the boundary of different cathode materials and ranged in forward side of electron drift direction. Accordingly, selection of cathode materials with similar emissivity of secondary electrons to a wafer is important in the steady-state magnetron etching.
New Etching System with a Large Diameter Using Electron Beam Excited Plasma
Authors: Ryoji Makoto , Hara Tamio , Ohnishi Katsu , Hamagaki Manabu , Dake Yosinori , Tohkai Masakuni , Yoshinobu Aoyagi Yoshinobu Aoyagi
Published: February 2005

A new etching system using electron-beam-excited plasma (EBEP) has been developed. This EBEP system is able to steadily produce a high-density plasma with a large diameter by introducing a high-current low electron beam into the etching chamber. The nonuniformity of plasma density and floating potential in an 8-inch wafer are improved up to ±2.5% and ±2 V, respectively. Anisotropic etching of n+-poly-Si in a pure Cl2 plasma is achieved with a high etch rate of 360 nm/min. The etching selectivity is 40 for poly-Si/photoresist and 150 for poly-Si/SiO2. These experimental results show that the EBEP etching system is suitable for manufacturing advanced ULSI.
Novel Surface Reaction Model in Dry-Etching Process Simulator
Authors: Misaka Akio , Harafuji Kenji , Masafumi Kubota Masafumi Kubota , Noboru Nomura Noboru Nomura
Published: February 2005

A new surface reaction model has been presented to simulate topological evolutions by taking into account the existence of adsorbed radicals on the substrate surface. The model treats the etching rate as a function of the coverage ratio by adsorbed radicals on the surface. Based on the model, a two-dimensional topography simulator has been developed. The simulator is applied to silicon-dioxide trench etchings made by hydrofluorocarbon gases. First, micro-loading effects in an important ion-assisted etching process are studied. It is confirmed that the micro-loading effect is due to the shortage of supplied active radicals inside the trench structure. Secondly, the competitive process between etching and deposition is examined. The side-wall protection phenomena resulting from the process are well simulated.
Low-Temperature Etching of 0.2 µm Al Patterns Using a SiO2 Mask
Authors: Aoki Hidemitsu , Hashimoto Toshiki , Eiji Ikawa Eiji Ikawa , Takamaro Kikkawa Takamaro Kikkawa
Published: February 2005

The effects of etching temperature and gases on the microloading and critical dimension (CD) shifts are investigated for Al etching using a SiO2 mask. Al etching with a SiO2 mask using Cl2 gas at low temperature achieved etching resistance against the mask, selective Al etching of underlying SiO2, suppression of microloading, CD shift, and after-corrosion. Al etching of 0.2 µm was successfully achieved by using the SiO2 mask and Cl2 gas chemistry at low temperature.
Radiation Induced Structural Changes in Amorphous SiO2: I. Point Defects
Authors: R. A. B. Devine R. A. B. Devine
Published: February 2005

Potential sources of damaging radiation present in technological processing steps (lithography, ion implantation, plasma assisted processing) are reviewed and the magnitude of the radiation present is estimated. Radiation induced “intrinsic” point defects in a-SiO2 are discussed with particular reference to their charge states. The kinetics of defect creation are studied for both the cases of ionizing and displacive radiation. The annealing kinetics of neutral and charged defects indicate that diffusion of molecular species (H2, H2O, O2) is involved and that temperatures ∼350°C are adequate to “passivate” them. Defect reactivation studies demonstrate clearly that point defects are not irreversibly removed from the a-SiO2 network unless temperatures ∼850°C are attained. At such temperatures, structural reorganisation occurs resulting in bond reorganisation and absorption of the defect.
Hall Effect Studies on Ar and Xe Sputtered Pt/Co Multilayer Films
Authors: Malmhäll Roger , Nakamura Junko , Awano Hiroyuki , Toshio Niihara Toshio Niihara , Masahiro Ojima Masahiro Ojima
Published: February 2005

The extra-ordinary Hall effect has been studied in Ar sputtered Pt(x Å)/Co(5 Å) and Xe sputtered Pt(x Å)/Co(3 Å) multilayers with coercivity ≤8 kA/m and ≥72 kA/m at RT, respectively. The Hall resistivity ρH was found to be larger and have a different Pt layer thickness dependence for the Ar sputtering case as x was varied from 5 Å to 20 Å, although the ohmic resistivity ρR and the saturation magnetization exhibit similar behavior. The estimated values for ρH, ρR, Hall conductivity γHS and extra-ordinary Hall coefficient R
1 for a hypothetical “multilayer” Co film (x=0) are all larger than those for “pure” sputtered Co films. Moreover, it was not possible to explain the observed variation of ρH with the Pt layer thickness with the short-circuiting effect from the non-magnetic Pt layers as predicted by a simple two-layer model. We suggest that the smaller ρH for the Xe sputtered Pt/Co films compared to Ar sputtered films can be attributed to reduced scattering suggesting a beneficial influence of the interface sharpness on the anisotropy of Pt/Co multilayers.
Mechanism of Layer-by-Layer Homoepitaxial Growth of SrTiO3(100) as Investigated by Molecular Dynamics and Computer Graphics
Authors: Miyamoto Akira , Takeichi Kentaro , Hattori Takahiro , Inui Momoji Kubo
Published: February 2005

The molecular dynamics method and computer graphics were found to be effective for simulating the deposition processes of the Ti4+, TiO2+, TiO2, and Sr4Ti4O12 species on SrTiO3(100). Although the collision of these species with the SrTiO3 surface greatly disturbed the surface atoms, the migration of the deposited species to the surface vacancies led to the formation of a smooth SrTiO3(100) surface.
Conductance Fluctuations in GaAs/AlGaAs Narrow Wires in Quasi-Ballistic Regime
Authors: ISHibashi Koji , Bird Jonathan P. , Sugano Takuo , Aoyagi Yoshinobu , Ochiai Yuichi , Onishi Taizo , Kawabe Mitsuo
Published: February 2005

Conductance Fluctuations due to the quantum interference of electrons have been studied in GaAs/AlGaAs narrow wires in the quasi-ballistic transport regime. Narrow channels of length 2 µm and 6 µm were confined by metallic split gates formed by electron beam lithography and a lift off technique. In the shorter wire, the amplitude of the fluctuations first increased as a function of increasing width, and finally approached to the constant value of e2/h. On the other hand, it was almost independent on channel width in the longer wire, as expected for the universal conductance mechanism in the diffusive transport regime. We suspect that the non universal width dependence in the shorter wire might result from averaging among the individual transmission channels, caused by the small number of scattering events.
Single-Beam Overwrite with a New Erase Mode of In3SbTe2 Phase-Change Optical Disks
Authors: Maeda Yoshihito , Ikuta Isao , Hisashi Andoh Hisashi Andoh , Yoshio Sato Yoshio Sato
Published: February 2005

Single-beam overwrite performance of 5.25 inch diam. In3SbTe2 phase-change optical disks was examined at a constant angular velocity (CAV) of 1800rpm (υ=5-11 m/s). We obtained overwrite with a new erase mode and achieved a large erasability of more than 35 dB and a carrier-to-noise ratio (C/N) of more than 50 dB. This good erasability was found to be supported by a new erase mode called the “winking erase mode”. From TEM observation of the overwritten structure, the erasing mechanism was discussed and the physical model due to the growth of crystalline grains was proposed.
Design of a 200 kV Focused Ion Beam Surface Analysis System
Authors: Mimura Ryoh , Sawaragi Hiroshi , Takai Ryuso Aihara
Published: February 2005

A nanometer nondestructive three-dimensional Rutherford back scattering (RBS) and medium energy ion scattering (MEIS) analysis system with a compact 200 kV focused ion beam (FIB) column has been designed. A high-vacuum sample chamber with a six-axis goniometer and an electrostatic toroidal analyzer for channeling and RBS analysis are connected to the acceleration column. A minimum beam spot size of less than 50 nm with a current of 50 pA is estimated by calculation for a 400 keV Be++ ion beam. As compared with MeV proton or helium ion microprobes, this compact system can produce about 10 times finer microprobes, 900-1600 times larger scattering cross section and higher depth resolution.
New Method for Soft-Error Mapping in Dynamic Random Access Memory Using Nuclear Microprobe
Authors: Sayama Hirokazu , Hara Shigenori , Kimura Hiroshi , Ohno Yoshikazu , Satoh Shinichi , Mikio Takai Mikio Takai
Published: February 2005

Locally sensitive positions against soft error in a dynamic random access memory (DRAM) have, for the first time, been investigated using a proton microprobe. Both soft-error (bit-state) mapping and secondary electron mapping images of the investigated area could locally identify sensitive positions against soft error. Two kinds of error modes in a DRAM (i.e., cell mode and bit-line mode) could be directly monitored.
High C/N Recording in Sb2Se3/Bi Write-Once Disk
Authors: Tokushuku Nobuhiro , Moritani Kouichi , Yanagihara Hitoshi , Katsuo Konishi Katsuo Konishi , Yoshihiko Noro Yoshihiko Noro
Published: February 2005

The read-out signal in an alloying disk, which has a large phase difference of the reflection coefficient between nonrecorded and recorded states, was analyzed by taking into account the effects of grooves. It was found that the read-out signal can be enhanced by interference between light reflected from a groove and recording media. A 60-dB CN (carrier-to-noise) ratio was obtained by applying this idea to the Sb2Se3/Bi alloying disk. NTSC (National Television System Committee) direct FM signal recording was confirmed by using this disk. It can be read by a modified Laser Disc player system.
Low-Temperature Activation of Impurities Implanted by Ion Doping Technique for Poly-Si Thin-Film Transistors
Authors: Matsuo Minoru , Takashi Nakazawa Takashi Nakazawa , Hiroyuki Ohshima Hiroyuki Ohshima
Published: February 2005

Low-temperature activation of impurities doped by high-energy non-mass-separated ion doping (I/D) technique has been investigated for fabricating self-aligned poly-Si thin-film transistors (S/A poly-Si TFTs) at low temperature on large-area glass substrates. Phosphorus atoms implanted by I/D are, surprisingly, activated through 300°C furnace annealing, and a sufficiently low value of sheet resistance is obtained for very thin film (≃25 nm) by combining with solid phase crystallization (SPC), which enhances crystallinity of poly-Si films. We have also confirmed excellent electrical properties of S/A poly-Si TFTs by using these techniques.
Afterimage Improvement for Thin-Film Diode (TFD) Liquid-Crystal Display Utilizing Tantalum Anodic Oxidation in Ammonium Borate Solution
Authors: Hirai Takanori , Miyake Kazushi , Nakamura Takashi , Shinichi Kamagami Shinichi Kamagami , Hiroshi Morita Hiroshi Morita
Published: February 2005

A thin-film diode liquid-crystal display (TFD-LCD) with anodic-oxidation in an ammonium borate solution was previously found to appear to reduce afterimages. From the experimental results using a TFD element with an oxide film anodized in an ammonium borate solution, the symmetry of the current-voltage characteristic has been found to be superior to that of a conventional TFD fabricated by anodic-oxidation in citric acid and phosphoric acid solutions. The authors have paid attention to the oxide layer state. Using the results of several measurements and analyses, this paper indicates the reason why a TFD-LCD with anodic-oxidation in an ammonium borate solution shows good display performance with a reduced afterimage.
Self-Sharpening Effect of Phase Change Erasable Media
Authors: Yoshida Tomio , Akahira Nobuo , Ohara Shunji , Kenichi Nishiuchi Kenichi Nishiuchi , Takashi Ishida Takashi Ishida
Published: February 2005

The characteristics of single-beam one-pass overwrite of SbTeGe phase change erasable (PCE) optical disks have been studied from a drive design point of view. In the recording process, an amorphous mark surrounded by a crystal ring (erase state) is recorded.The amorphous mark always has a clear edge even if erasability is relatively low in the low erase power area. We call this phenomenon the self-sharpening effect (SSE) which gives several advantages to the performance and design of the drive. SSE realizes wide power tolerance in a practical drive, which results in excellent interchangeability in terms of write/erase laser power. SSE also achieves a good off-track performance of less than +/- 0.1 µm of the optical beam and enables pulse edge recording even if overwrite erasability is relatively low.