bluuebunny/crossref_metadata_2025 huggingface dataset:
Scatterings of Shallow Threshold Voltage on Si-Implanted WN Self-Alignment Gate GaAs Metal-Semiconductor Field-Effect Transistors on Different Composition 2-Inch Substrates by Growing in Three Kinds of Furnaces
Authors: Saito Yasuyuki , Fukuda Katsuyoshi , Nozaki Chiharu , Yasuami Sigeru , Nishio Johji , Yashiro Satao , Washizuka Shoichi , Watanabe Masayuki , Hirose Mayumi , Kitaura Yoshiaki , Uchitomi Naotaka
Published: February 2005

Two-inch undoped GaAs crystal boules were grown from different composition melts in a pyrolytic boron nitride crucible in three kinds of furnaces in order to survey composition effect through a consecutive thermal cooling cycle after crystallization on Vth scattering of Si-implanted metal-semiconductor field-effect transistors (MESFETs). On the substrates (dislocation density: 2×103-105 cm-2 order) obtained from the crystal boules, a tungsten nitride self-alignment gate MESFET array of shallow Vth (3×1012 cm-2, 50 keV) was fabricated, and Vth scatterings were observed on them. The Vth scattering for the most As-rich melt-grown crystal boule in the furnace with the smallest ratio of bottom heating was the smallest as compared with those for the slightly Ga-rich or As-rich melt-grown crystal boules in the furnaces with the greatest ratio of bottom heating. There was an anticorrelation between the Vth scattering amplitude and carbon content in the substrate crystals.
Defects in Metalorganic Chemical Vapor Deposition Epitaxy-Grown ZnSe Films on GaAs Investigated by Monoenergetic Positrons
Authors: Wei Long , Cho Yang-Koo , Dosho Chisei , Tanigawa Shoichiro , Yodo Tokuo , Yamashita Ken
Published: February 2005

Defects in metalorganic chemical vapor deposition epitaxy (MOVPE)-grown ZnSe heteroepilayers on GaAs were investigated by monoenergetic positrons. The present work revealed clear differences between an as-grown specimen and a heat-treated one under different atmospheres. The as-grown specimen prepared at high temperature (350°C) showed a proliferation of a large number of defects near the surface and at the GaAs interface due to lattice mismatching and nonstoichiometry. Heat treatment at 70°C in N2 ambient introduced vacancies in high concentrations which contribute to the deep emission of photoluminescence. It is concluded that adequate heat treatment under zinc vapor is essential to reduce the concentration of native defects in MOVPE-grown ZnSe film on GaAs.
Defect Thermodynamics of Nd2-xCexCuO4-δ
Authors: Yasushi Idemoto Yasushi Idemoto , Kazuo Fueki Kazuo Fueki
Published: February 2005

The oxygen deficit δ of Nd2-x
Ce
x
CuO4-δ with x=0, 0.05 and 0.15 was determined as a function of oxygen partial pressure (Po2) at various temperatures. When the δ-log Po2 curve at a specified temperature was chosen and the curves for other temperatures were shifted along the abscissa, all the measured data were found to form a single smooth curve, which is called a master curve. A theoretical equation providing δ as functions of Po2 and cerium concentration was derived. The calculated curve was found to be in good agreement with the master curve.
Doping Effects of Metallic Elements on the Superconductivity in the Bi-(Pb)-Sr-Ca-Cu-O System
Authors: Jyodoi Kouki , Yasuyama Sigeyuki , Akihisa Sonoda Akihisa Sonoda , Akira Ohyoshi Akira Ohyoshi
Published: February 2005

Metals (Zn, Cd, Al, In and Bi) control the rate of solid-state reaction. Al, In and Bi metals produce a decrease in the resistivity at room temperature, increase in the superconducting volume fraction and high temperature shifts of T
c,zero. Zero resistivity was attained at 110 K by Bi doping. Zn and Cd metals cause the disappearance of the high-T
c phase and increase the low-T
c phase.
Micromagnetic Calculation of Applied Field Effect on Switching Mechanism of a Hexagonal Platelet Particle
Authors: Uesaka Yasutaro , Nakatani Yoshinobu , Hayashi Nobuo
Published: February 2005

The effect of the applied field on the switching mechanism of a hexagonal platelet particle was investigated by computer simulation. The fields were applied perpendicular to the platelet plane which is the easy axis direction of the platelet. As the applied field increases, the switching mechanism changes from the normal vortex mode (in which the magnetic moments in a hexagonal plane rotate about the center of the plane, and the moments in the top and bottom planes rotate in the same direction) to the crater mode (in which the moments do not form a vortex, and the moments at the center of the hexagon switch faster than the moments at the corners), then to the quasi-coherent rotation mode and finally to the twisted vortex mode (in which the moments in the top and bottom planes rotate in opposite directions).
1.5 µm Semiconductor Wavelength Tunable Optical Filter Using a λ/4-Shifted Passive Waveguide Grating Resonator
Authors: Takahiro Numai Takahiro Numai
Published: February 2005

A 1.5 µm semiconductor wavelength tunable optical filter using a λ/4-shifted passive waveguide grating resonator has been developed. Both wavelength channel number and transmissivity are analyzed with respect to grating coupling coefficient, filter length, and waveguide loss. The influence of facet reflectivity and phase-shift value on transmissivity and wavelength channel number are also investigated. A wavelength shift as wide as 42 Å is able to be obtained by carrier injection with the fabricated filter.
Structural Relaxation of a La55Al25Ni20 Amorphous Alloy Measured by an Internal Friction Method
Authors: Okumura Hiroshi , Chen Ho Sou , Akihisa Inoue Akihisa Inoue , Tsuyoshi Masumoto Tsuyoshi Masumoto
Published: February 2005

A La55Al25Ni20 amorphous alloy exhibits a relaxation peak at temperatures well below the glass transition temperature by dynamic mechanical measurements. When the frequency is 62.8 rad/s, the peak appears at about 400 K and the decrease in frequency results in the shift of the peak temperature to the lower side. From the frequency scan measurements, a master curve for the storage modulus E'(log ω) is constructed. Also, the relaxation spectrum H(ln ω) in which the half width is as broad as about two decades is obtained. The activation energy for the relaxation approximated from the shift factors is about 100 kJ/mol which is nearly the same as that for diffusion of Al and Ni in Al. It is therefore presumed that the low temperature relaxation is caused by the local atomic rearrangements of Al-Al and Al-Ni pairs.
Single-Crystal Growth of Cu2Sb in Evaporated Sb Fims with Cu Specimen Grids
Authors: Kojima Satoshi , Yoshiaki Tanaka Yoshiaki Tanaka , Ryozi Suganuma Ryozi Suganuma
Published: February 2005

Cu2Sb single crystals in (011) orientation grow from the hole edge of Cu specimen grids for electron microscopy into (111) Sb films about 40 nm thick when heated at about 300°C for about one hour. The arrangement of Sb in the (011) plane of Cu2Sb is similar to that of Sb in the (111) plane of pure Sb films. The Cu2Sb crystal growth is in close relation to the atomic arrangement in Sb films.
Intermittent Automodulation Observed in Fe-3%Si Reeds
Authors: Yoshimura Masamichi , Akiyama Tomoko , Shigekawa Hidemi , Tsuno Takao , Nakamura Yoshio , Shin-ichi Hyodo Shin-ichi Hyodo
Published: February 2005

Automodulation was observed to occur in Fe-3%Si polycrystalline reed specimens intermittently and rather irregularly. This forms a striking contrast to the continuous automodulation usually observed in such materials as Zn or Mg. This unfamiliar automodulation, which seems to have three different modes, was explained in terms of phase transformation and stochastic processes.
Characterization of FexSiO (0<x<3) Granular Films by Electron Spin Resonance
Authors: Matsubara Kakuei , Kawamura Koh'ichi , Nagao Keigo , Miki Yasuo Kadonaga
Published: February 2005

Films of Fe
x
SiO (0<x<3) prepared by coevaporation of iron and silicon monoxide were characterized by electron spin resonance (ESR), X-ray diffractometry (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electrical conductivity measurements. A ferromagnetic resonance (FMR) signal attributable to ferromagnetic iron grains was detected in as-deposited Fe
x
SiO (x>0.5) films. The room-temperature electrical conductivity increases with the Fe/Si ratio steeply at x<0.5 but gently at x>0.5. The formation of a metallic iron phase in as-deposited Fe
x
SiO (x>2) films and in annealed films was confirmed by XRD and TEM investigations. The critical Fe/Si ratio of 0.5 observed in ESR and conductivity measurements is associated with the granular structure growth. The granular iron growth in the as-deposited films is discussed.
AlN Sputtered Film Properties Prepared at Low Gas Pressures by Facing Target System
Authors: Tominaga Kikuo , Hiroshi Imai Hiroshi Imai , Masaki Shirai Masaki Shirai
Published: February 2005

Several properties of sputtered AlN films prepared in N2 gas by planar magnetron sputtering with facing targets were investigated. Highly c-axis-oriented films with columnar structure were obtained at the pressure range of 10-3 Torr of N2 gas. Film degradations such as the decrease of the degree of c-axis orientation, film coloring, and film peeling were also observed at lower gas pressures below 1×10-3 Torr. From the results of optical transmittance and film composition estimation by energy-dispersion X-ray spectroscopy, these film degradation were related to the excess of N atoms in the film growth process.
Characteristics of the Switching in a Superconducting Y-Ba-Cu-O Thin Film by Laser Irradiation
Authors: Kato Keizo , Takahashi Kuniharu , Minami Kazuo , Hayashi Noriki , Okuda Shigeru , Takano Satoshi , Ohtsuka Mieko , Awano Mitsuru
Published: February 2005

Radiation-induced switching of a Y-Ba-Cu-O thin film sample is studied using a 1.06 µm pulsed Q-switched Nd:YAG laser with a duration of 10 ns. The results of the switching from the super- to normal conducting states in our sample caused by laser irradiation are attributed to a bolometric effect, i.e., heating of the sample by radiation. The response time of the switching is less than 30 ns and it almost agrees with the relaxation time of the thermal conduction in the film. Using a simple model assuming uniform distribution of energy through the film thickness, the specific heat of the film is also estimated and a clear jump in the specific heat at the critical temperature is shown.
In Situ Imaging of Electrochemical Deposition of Ag on Au(111)
Authors: Endo Katsumi , Sugawara Yasuhiro , Mishima Syuzo , Okada Takao , Morita Seizo
Published: February 2005

Under potentiostatic control, we imaged the electrochemical deposition of Ag onto an Au(111) surface with scanning tunneling microscopy (STM). As a result, at the initial stage of Ag deposition, we observed homogeneous growth of small Ag islands 50∼80 Å in diameter and 4.5∼7.0 Å in height (2∼3 atomic height).
Elastic Scattering Cross Sections of Low-Energy Electron in Solids
Authors: Ohya Kaoru , Kawata Jun , Ichiro Mori Ichiro Mori
Published: February 2005

The elastic scattering cross sections of 100 eV-10 keV electrons in solids (Z=3-48) are calculated using the partial wave expansion technique and the `muffin-tin' bound-atom potential. The results show considerably less forward scattering in comparison with the free-atom scattering at all energies and elements. In addition, the substantial variation of the cross sections with atomic number, which is related to the nearest-neighbor distance, is calculated.
An Energy Compression System for High-Efficiency Injection in a Compact Storage Ring
Authors: Takada Hiroshi , Tsutsui Yasumitsu , Tomimasu Yoshihiro Hirata
Published: February 2005

An energy compression system was installed in the beam transport system of the NIJI-II compact storage ring in order to improve the momentum spread of the linac and increase injection efficiency. The system consisted of three separate magnets and a short accelerating section. The measured spectrum width was improved to a satisfactory level with this system.
Application of Singular-Value Decomposition for Structural Modal Analysis
Authors: Ku Ming-Fong Pan
Published: February 2005

This paper presents the methods of singular-value decomposition and pseudoinverse to refine the original polyreference time domain (PRTD) modal parameter identification algorithm. The automatic determination of the number of physical modes over the desired frequency range is strongly addressed. Meanwhile, distinguishing between the physical and computational modes is achieved through the modified modal assurance criterion. To evaluate the effectiveness of this method, two test cases were constructed. Verification results show that the current method yields a very good improvement of the PRTD method.
Wet Chemical Etching Behavior of Ga(Al)As and In(Ga)P(As) Layers
Authors: Franz Gerhard , Charlotte Hoyler Charlotte Hoyler , Dagmar Sacher Dagmar Sacher
Published: February 2005

The chemical etching behavior of Ga(Al)As and In(Ga)P(As) containing sandwich layers grown by metalorganic vapor phase epitaxy has been investigated using various etching solutions. The chemical background is described by a potential-pH diagram. Activation energies obtained were between 0.28 and 0.46 eV. The inclination angle of the etched walls is mainly 55°. In both the systems, a transition from a reaction-rate limited process to a diffusion-rate-limited one is observed. In InP, a reactive intermediate with an inclination angle of 45° could be trapped.
Time Evolution of Excitonic Absorption Bleaching of Resonant Tunneling Bi-Quantum-Well Structures
Authors: Tackeuchi Atsushi , Muto Shunichi , Tsuguo Inata Tsuguo Inata , Toshio Fujii Toshio Fujii
Published: February 2005

We report the time evolution of excitonic absorption bleaching in resonant tunneling bi-quantum-well (TBQ) structures, in which the ground electron level in a narrow well has the same energy as the second electron level in a wide well. In resonant TBQ structure, we observed a reduction in the absorption recovery time and an increase in the tail-to-peak ratio of the absorption change. By comparing the absorption change of resonant TBQ with the e2-hh2 excitonic absorption change of conventional multiple quantum wells (MQW), we show that the increase in the tail-to-peak ratio of a resonant TBQ can be attributed to the thermally remaining holes in the first excited subband of heavy holes.
Boron Ion Doping Effects on Superconductivity of YBa2Cu3-xBxO7-y Ceramics
Authors: Katsura Hiroshi , Suemune Takasu Hashimoto
Published: February 2005

Impurity effects of small ionic size, light atomic weight boron ions on the superconductivity of YBa2Cu3O7-y
are investigated. The doped boron content x is from 0.00 to 0.52 in YBa2Cu3-x
B
x
O7-y
as a nominal composition, and the ceramic samples fired in air or annealed in high-pressure oxygen gases are examined with X-ray diffraction, dc electrical resistivity, and ac magnetic susceptibility. The crystal lattice is found to shrink due to the boron doping and to deform from orthorhombic to tetragonal form for values of x of more than about 0.2. Superconductivity is found to be modified by the partial B3+ replacement for Cu(1) ions so as to lower the critical temperature T
c and to broaden the transition width. Change from metallic behavior to semiconductive behavior is accompanied by the boron incorporation of x above 0.30 in the normal electrical conduction states. Steep transition is revealed on the high-pressure oxygen gas annealed samples.
Effects of Low-Temperature Neutron Irradiation on Tc of LnBa2Cu3O7-y (Ln=Y, La) and La2CuO4
Authors: Ichiro Mukouda Ichiro Mukouda , Yoshiharu Shimomura Yoshiharu Shimomura
Published: February 2005

The results of in-pile resistance measurements of three different oxides, LnBa2Cu3O7-y
(Ln=Y, La) and La2CuO4, which were irradiated with fission neutrons at low-temperature at the Kyoto University Research Reactor facility are reported. After the neutron irradiation at 20 K to the fluence in the range of 1016 n/cm2, LaBa2Cu3O7-y
and La2CuO4 of non superconducting specimens did not show any radiation-induced superconductivity, and the resistance increased in the temperature range above 20 K. In YBa2Cu3O7-y
, the transition temperature did not change appreciably with the low-temperature neutron irradiation. The remarkable improvement of transition temperature T
c of these superconductors after the neutron irradiation, which was reported previously by Atobe and Yoshida, could not be detected.
Amorphous Fluoropolymer Films for Superconductive Microwave Components Using High-Tc Superconducting Films
Authors: Nagai Yasuhiro , Suzuki Naobumi , Sato Makoto , Konaka Tsuneo
Published: February 2005

This paper describes the influence of amorphous fluoropolymer (AF) film on the properties of high-T
c superconductive microwave components, when it is used for surface protection and as a spacer. It is found that AF film can protect EuBaCuO and TlBaCaCuO superconducting film from dampness, thus maintaining the properties of a microstrip resonator for at least 1000 h. The AF protection has almost no effect on properties such as temperature dependence and unloaded-Q values in high-Q microwave components. Additionally, the use of AF film as a spacer in a strip-line structure reduces the influence of spacing on the effective dielectric constant and characteristic impedance.
New Type Galvanomagnetic Effect in Magnetic Thin Films
Authors: Keiichi Kakuno Keiichi Kakuno
Published: February 2005

A new type novel galvanomagnetic effect is found experimentally which corresponds to neither Hall nor the usual magnetoresistance effect. The dependence of this effect on the angle θ between the current and the magnetic induction is also found to be the form of sin 2θ, in contrast with that of the magnetoresistance effect cos 2θ and that of Hall effect sin θ. An outstanding feature of the present novel galvanomagnetic effect is that the rate of the voltage variation depending on the magnetic induction is extremely large as compared with that of the usual magnetoresistance effect. It is theoretically confirmed that this effect is well understood on the basis of the two carrier types model.
Phase Transitions in an Antiferroelectric Liquid Crystal TFMHPOBC
Authors: Fujikawa Tetsuya , Orihara Hiroshi , Ishibashi Yoshihiro , Yamada Yuichiro , Yamamoto Norio , Mori Kahoru , Nakamura Koji , Suzuki Yoshiichi , Hagiwara Takashi , Kawamura Ichiro
Published: February 2005

We studied phase transitions in an antiferroelectric liquid crystal TFMHPOBC (C8H17O-&benzf;-&benzf;-COO-&benzf;-*CH(CF3)C6H13) by means of dielectric measurements and microscopic observations. Both a Goldstone mode and a soft mode were observed in the SmC* phase, but only a soft mode in the SmCA
* phase. From the temperature dependence of the relaxational frequency, it was clarified that the ferroelectric mode tends to be soft even in the antiferroelectric phase transition. The unwinding process of the helical structure in the SmCA
* phase was observed with a reflecting microscope. It was also found that all the transitions, i.e., SmA-SmCA
*, SmA-SmC* and SmC*-SmCA
*, are of the first order. We present the E(electric field)-T(temperature) phase diagram of the optically pure TFMHPOBC and the mixture of R- and S-enantiomers.
Structure and Morphology of Solid C60/C70 and C60 Grown from Benzene Solution
Authors: Saito Yahachi , Suzuki Noritomo , Shinohara Hisanori , Ando Yoshinori
Published: February 2005

Crystallites of C60/C70 mixture and pure C60 have been produced from benzene solution by evaporating the benzene solvent. The new forms of solid carbon have been examined by electron microscopy with particular attention to the structure of crystallites with platelet shape. Electron diffraction patterns and high-resolution images reveal that they have an hcp structure (a=10.1±0.1 Å, c=16.5±0.2 Å) with stacking faults of molecular layers perpendicular to the c-axis.
Composition Dependence of Some Electrical Properties of Fe1-yMySix (M=Cr, Co) Thin Films
Authors: Ido Masashi Komabayashi
Published: February 2005

The composition dependence of the Seebeck coefficient, electrical resistivity and activation energy associated with acceptor or donor levels of Fe1-y
M
y
Si
x
(M=Cr, Co) thin films obtained by rf sputtering were examined. The activation energy associated with defect levels in undoped films were strongly dependent on the composition (x). For Cr-doped or Co-doped films, the activation energy was smaller than that of a undoped film and insensible to x when the impurity density was sufficiently high. It follows that the variation of the defect levels did not influence the activation energy when the impurity levels were shallower than the defect levels. Accordingly, the Seebeck coefficient and electrical resistivity for Cr-doped and Co-doped films are insensible to the composition (x), although they were influenced by the defect density when the electrical polarity of defects and impurities was different.
Mobility Profiles in Self-Aligned WNX-Undoped AlGaAs/n-GaAs/Undoped AlGaAs Doped-Channel Hetero-MISFETs
Authors: Steiner Klaus , Mikami Hitoshi , Kazuya Nishihori Kazuya Nishihori , Naotaka Uchitomi Naotaka Uchitomi
Published: February 2005

Drift mobility profiles in self-aligned WNX-undoped AlGaAs/n-GaAs/undoped AlGaAs doped-channel hetero MISFETs (DMT) with different gate lengths are evaluated (L
G=1, 2, 4, 9 µm). The mobility profiles peak between 1400 and 1600 cm2/Vs in the accumulation mode of operation. The drift mobility maximum is shifted to higher gate voltages with decreasing the gate length.
Optimization of the Photopyroelectric Hydrogen Gas Sensor: Geometry and Temperature Measurements
Authors: Christofides Constantinos , Andreas Mandelis Andreas Mandelis , John Enright John Enright
Published: February 2005

A new study towards the optimization of a new photopyroelectric hydrogen detector is performed. It has been found that the thickness of the palladium layer evaporated on the active polyvinylidene fluoride (PVDF) film plays an important role in the sensitivity of the device, but it does not influence the time response. In an effort to better understand the thermodynamics of the device during the solid-gas exchange interaction, the influence of ambient temperature has been studied. Further experiments have demonstrated device sensitivity to hydrogen even at cryogenic temperatures.
Focusing Efficiency and Resolution of a Nickel Phase Zone Plate for Soft X-rays
Authors: Fujisaki Hisao , Nakagiri Nobuyuki , Kihara Hiroshi , Watanabe Norio , Taniguchi Mieko
Published: February 2005

A nickel phase zone plate and a gold Fresnel zone plate were experimentally examined in terms of focusing efficiency and spatial resolution in the soft X-ray region. The focusing efficiencies were obtained at wavelengths of 1.8, 2.34, and 5 nm with various monochromaticities. A computer simulation of the focusing efficiency was also performed. A discrepancy was found between these experimental and simulated results at 2.34 nm, indicating that the thickness of the phase zone plate was 75% of the designed thickness or that the optical constants of the actual phase zone plate were 75% of the nickel's optical constants listed in the literature and used for the computer simulation. Spatial resolution obtained at 1.8 nm varied slightly with varying monochromaticity of the incident X-rays; the better monochromaticity gave the better resolution.
Characteristics of Etch Rate Uniformity in Aluminum Reactive Ion Etching
Authors: Tsutomu Tsukada Tsutomu Tsukada
Published: February 2005

The characteristics of aluminum etch rate uniformity across a wafer were studied using a parallel-plate reactive ion etching apparatus. The etch rate uniformity was found to be affected by the process gases, the cover materials of the cathode, the rotation of the cathode and the gas inlet positions. Results indicated that it was difficult to improve the uniformity under the condition of the etchant being distributed uniformly over the cathode. In order to obtain good uniformity, the etchant must be confined on the wafer surface. Procedures to improve the etch rate uniformity are discussed.
Representative Figure Method for Proximity Effect Correction [II]
Authors: Abe Takayuki , Yamasaki Satoshi , Yamaguchi Toshio , Ryoichi Yoshikawa Ryoichi Yoshikawa , Tadahiro Takigawa Tadahiro Takigawa
Published: February 2005

The representative figure method, which was proposed to greatly reduce the proximity effect correction time, is studied in detail in this paper. The method is shown to have a high correction accuracy (the error is 0.25% for a 50 kV acceleration voltage and a 2 µm small area) and a high speed correction time (which includes the time for preparing representative rectangles; 1/10 compared with the conventional method). The basic idea of the present method is found to be applicable to data compaction. The compaction ratio by this method is (1/2)-(1/100) of that by the conventional method. The representative figure method has a wide range of applications and has many advantages.
Induction Linear Accelerators with High-Tc Bulk Superconductor Lenses
Authors: Matsuzawa Hidenori , Wada Haruhisa , Satoshi Mori Satoshi Mori , Tadashi Yamamoto Tadashi Yamamoto
Published: February 2005

Solenoidal coils in a one-stage induction accelerator were replaced by a high-T
c bulk superconductor lens (Supertron). The accelerator postaccelerated injected electron beams to ∼400 keV, ∼0.35 kA, and ∼10 ns of duration time.
Improvement of Phase-Shifter Edge Line Mask Method
Authors: Hideyuki Jinbo Hideyuki Jinbo , Yoshio Yamashita Yoshio Yamashita
Published: February 2005

Two kinds of improved phase-shifter edge line (PEL) masks have been developed for critical dimension control. One new mask consists of a chrome line and partially overlapped shifter film. In this mask, exposed pattern sizes are controlled by adjusting the chrome linewidth. It has been found that a set of repeated fine-chrome lines (“blind”) acts as a uniform light attenuator. The other new mask (“blind PEL mask”) has been devised by combining the “blind” and shifter pattern. These new masks make it possible to delineate different-sized fine patterns (≥0.2 µm) at the same exposure dose. With the “blind PEL-mask”, unnecessary shifter edge patterns can be eliminated by only one-time exposure.
Simulation Study on Phase-Shifting Masks for Isolated Patterns
Authors: Inoue Soichi , Tanaka Yoko , Sato Takashi , Shuichi Tamamushi Shuichi Tamamushi , Makoto Nakase Makoto Nakase
Published: February 2005

Optimization for various phase-shifting masks to fabricate 0.25-µm isolated resist patterns was carried out, and their performances were compared among themselves by simulation. They were evaluated under the assumptions that isolated patterns were located on the same layer with 0.25-µm lines and spaces with the Levenson-type phase-shifters and that the exposure dose was adjusted to the dense patterns. It was found that isolated patterns need to be designed with regard to unavoidable errors in the feature size. None of the isolated line masks studied is effective in improving resolution, except in the case where the Levenson-type phase shifter (shifter edge) can be located. All isolated space masks with optimized dimensions, in contrast, are effective in improving depth of focus for the 0.25-µm isolated pattern.
Detection and Printability of Shifter Defects in Phase-Shifting Masks
Authors: Watanabe Hisashi , Yoshihiro Todokoro Yoshihiro Todokoro , Morio Inoue Morio Inoue
Published: February 2005

Because of the high printability of shifter defects in phase-shifting masks, it is worthwhile to characterize the inspection and printing of the shifter defects. The detectability and printability of shifter defects as a function of size and location have been investigated by experiments and simulation. A test mask with various programmed shifter defects was inspected by means of a die-to-die inspection system and printed in positive resist with an i-line stepper. Corner defects are difficult to detect and have low printability. A defect located in small features has high printability. We have also investigated the detectability and printability of the phase angle defects which have phase angles other than 180°. Defects with 120° to 180° phase angles have high printability. Defects with phase angles below 90° are not printed.
Sub-0.5 µm Lithography Using an Excimer Laser at 248 nm
Authors: Kung E. H. , Cheng M. , Nalamasu O. , Timko A. G. , C. B. Case C. B. Case , V. Pol V. Pol
Published: February 2005

The advent of deep ultra-violet (DUV) lithography using an excimer laser stepper at 248 nm has extended the capability of photolithography in achieving sub-0.5 µm resolution required for the fabrication of 64MB DRAM and 16MB SRAM. This paper reports on the progress of our DUV R&D efforts in working toward this goal. To qualify the stepper, electrical wafer probing was found effective in providing a large volume of data with high sensitivity, accuracy, and precision in the measurements. Advanced resist materials based on the chemical amplification principle demonstrated good sub-0.5 µm resolution, excellent sensitivity, and good etch selectivity required for DUV lithography. However, resist processes for both the positive and negative tone materials still require further optimization incorporating the use of anti-reflective coatings (ARC). Spin-on organic ARC has proven feasible in eliminating both thin-film interference effects and reflective notching. DUV lithography promises to be a strong contender for the next generation of ULSI fabrication, where the limiting factor may lie in the high cost of advanced resist and ARC materials.
Axial Image Superposing (Super-FLEX) Effect Using the Mask Modulation Method for Optical Lithography
Authors: Hiroshi Fukuda Hiroshi Fukuda
Published: February 2005

Phase and amplitude modulation in a mask can achieve amplitude superposition for multiple images along the light axis and phase control between them. This improves the depth of focus while keeping high resolution under high coherence illumination in optical lithography. This method explains the mechanism of the depth-of-focus enhancement effect in “peripherally added” or “edge-enhancing” phase-shifting masks and provides the most effective phase-shifter arrangement. Because a high coherency is required in this method, however, the proximity effect becomes a serious problem in practical LSI patterns.
The Effects of HCl Added to Chemical Vapor Deposition Source Gases for Producing a SiC X-Ray Mask Membrane
Authors: Murooka Ken-ichi , Itoh Masamitsu , Haruki Komano Haruki Komano , Yoshio Gomei Yoshio Gomei
Published: February 2005

The effects of adding HCl to the chemical vapor deposition source gases on the stress, optical transparency, and surface roughness of a SiC X-ray mask membrane were examined. It was found that the stress dependence on the source gas carbon-to-silicon ratio was changed by adding HCl, and that a SiC membrane with low stress and high optical transparency is obtainable by adjusting these parameters. The surface roughness was about 15 nm from peak to valley under a good condition. The X-ray diffraction results of the SiC membranes showed that the peak sharpness, which indicates the crystal qualities such as densities of various intrinsic defects and the size of each crystal grain, is related to the optical transparency, and that the crystal orientation parameter is related to the surface roughness.
Effect of EB Acceleration Voltage and Beam Sharpness on Process Latitude of 0.2 µm Lines
Authors: Akemi Moniwa Akemi Moniwa , Shinji Okazaki Shinji Okazaki
Published: February 2005

The 0.2µm line delineation capability of electron beam direct-writing is estimated by computer simulation. The effects of acceleration voltage and beam sharpness are evaluated by looking at process latitudes. The process latitudes refer to dose and development time latitudes, where proper resist profiles are obtained. The process latitudes are compared for acceleration voltages of 30 and 50 keV; and beam blurs of 0.0, 0.05, and 0.1 µm. For patterning on a bare Si substrate, an acceleration voltage higher than 30 keV with beam blur less than 0.1 µm can fabrlcate 0.2 µm lines. However, a 50 keV acceleration voltage is required for patterning on a W layer, because 30 kev, even with 0.0 µm beam blur, has only a small dose latitude.
Effect of Low-Molecular-Weight Novolak Resin on Microgrooves
Authors: Nakano Ritsuko , Hirose Minoru , Santoh Nobuaki , Shigematsu Kenji Nakagawa
Published: February 2005

Microgrooves, by our definition, mean the deformed bottom profile-a protrusion and an undercut-of photoresist patterns, a problem encountered in high-resolution photoresist involving a postexposure bake (PEB). Microgrooves degrade process stability. In studying the relationship between microgrooves and photoresist materials, we found that microgrooves can be suppressed by reducing the content of low-molecular-weight novolak resin, and they are caused by excess dissolution inhibition and imbalanced solubility.
Development and Applications of a Compact Electron Cyclotron Resonance Source
Authors: O'keeffe Patrick , Komuro Shuji , Den Shoji , Morikawa Takitaro , Yoshinobu Aoyagi Yoshinobu Aoyagi
Published: February 2005

A new compact ECR plasma source has been developed. The characteristics of this source and it's applications are discussed. Irradiation by oxygen radicals O* for the oxidation during deposition process was found to produce high quality superconducting thin films with increased characteristic temperatures. Hydrogen radical H* beam cleaning of GaAs substrate surfaces was achieved at temperatures as low as 100°C.
Charge Build-Up in Magnetron-Enhanced Reactive Ion Etching
Authors: Hoga Hiroshi , Orita Toshiyuki , Hayashi Takashi Yokoyama
Published: February 2005

Charge build-up in magnetron-enhanced reactive ion etching (MERIE) was evaluated with metal nitride oxide semiconductor (MNOS) capacitors. In static magnetic field, negative flat band voltage (V
fb) shifts of more than -1.5 V were observed in the area under high-density plasma, and more than 2-V V
fb shifts were observed at the edge of the wafer near the N and S poles. This distributed V
fb shift was considered to result from nonuniform plasma potential caused by secondary electron E×B drift motion. In rotated magnetic field, V
fb shifts were reduced. No significant V
fb shifts were observed when the magnet was rotated at 120 rpm. The V
fb shift reduction in rotated magnetic field was supposed to result from charge neutralization by alternate charge build-up.
In-Line Monitoring of Some Planarization Processes
Authors: Tissier A. , Teissier J. F. , P. Cerruti P. Cerruti , J. M. Eymery J. M. Eymery
Published: February 2005

The processes used for the surface planarization of the interlevel dielectrics which is one of the major problems of the multilevel interconnection CMOS technology, are becoming increasingly sophisticated. As a consequence, the reproducibility of the total process requires an accurate control of these technics in order to increase die yields. The DOPED method, developed for a non-contact on-line monitoring of flow annealing of BPSG films has been applied to the “cold” planarization techniques implemented in the CNET 0.7 µm technology. Results are obtained for TEOS deposition and etchback techniques and SOG total etchback.
Selective Etching of Al2O3 on GaAs using Excimer Lasers
Authors: Sugioka Koji , Fan Jia-Fa , Kita Kazuhiro , Tanaka Shunichi , Koichi Toyoda Koichi Toyoda
Published: February 2005

Selective etching of Al2O3 thin films on GaAs immersed in a H3PO4 aqueous solution by irradiation with excimer lasers is demonstrated. The dark etching of Al2O3 films (0.4 nm/min) is negligibly small compared with that of the laser-induced etching. It is found that the process cannot etch the GaAs substrates. Therefore, the etching stops at the Al2O3/GaAs interface, and the Al2O3 films are selectively etched only in laser irradiation regions. The etching characteristics of different wavelengths of ArF and KrF excimer lasers are also discussed.
Synchrotron-Radiation-Induced Modification of Silicon Dioxide Film at Room Temperature
Authors: Sugita Yoshihiro , Nara Yasuo , Noriaki Nakayama Noriaki Nakayama , Takashi Ito Takashi Ito
Published: February 2005

Thermally grown SiO2 films were irradiated by synchrotron radiation at room temperature and changes in film properties were analyzed to clarify the irradiation effects and explain the mechanism of the photo-stimulated desorption (PSD) of SiO2. The irradiated SiO2 was chemically weakened throughout the film of 89-nm thickness by Si-O bond breaking following core electron excitation. The broken bonds were recombined by postannealing at 850°C. The irradiated surface was deoxidized by oxygen desorption and the remaining Si-rich layer was evaporated by postannealing over 700°C. Results indicate that irradiation effects are bond breaking and the desorption of oxygen and that thermal effects are the recombination of broken bonds and the evaporation of the deoxidized layer. It is supposed that the PSD of SiO2 at elevated temperature consists of photo-desorption of oxygen and thermal evaporation of SiO.
Diagnostics of Hydrogen Role in the Si Surface Reaction Processes Employing In-situ Fourier Transform Infrared-Attenuated Total Reflection
Authors: Kawamura Kohei , Ishizuka Shuichi , Hiroyuki Sakaue Hiroyuki Sakaue , Yasuhiro Horiike Yasuhiro Horiike
Published: February 2005

The oxidation process of H-terminated amorphous Si film on Ge and the reaction mechanism of the triethylsilane (TES)/H system which allows us to deposit an organic Si film conformably have been investigated employing in-situ FTIR(Fourier transform infra red)-ATR(attenuated total reflection). This measurement was demonstrated to be a sensitive and simple method to inspect the role of H(hydrogen) in their surface reactions. In the Si oxidation case, the H-terminated Si is readily oxidized by O(oxygen) atoms. The oxidation with O2 molecules proceeds gradually as the breaking of Si-H bonds and forming of H-Si-O bonds due to binding of O atoms with the back bond of Si for 700 min. After about 700 min, dissociated O atoms rapidly penetrate the Si film, and oxidize the bulk Si, leaving both Si-H and H-Si-O bonds still on the Si surface. Next, in the TES/H reaction system, gas phase FTIR spectra obtained by reactions of H atoms or H2 molecules with TES do not show appreciable change in a wide range of pressure. Nevertheless, in-situ FTIR-ATR reveals that TES reacts easily with H atoms on the surface, desorbing H2, methyl and ethyl groups.
Evaluation of Device Charging in Ion Implantation
Authors: Namura Takashi , Ishikawa Katsuya , Aoki Norishige , Fukuzaki Yoshiki , Yoshihiro Todokoro Yoshihiro Todokoro , Morio Inoue Morio Inoue
Published: February 2005

Device charging in the ion implantation is evaluated by using two different types of electrically erasable-programmable read-only memory (EEPROM) devices and two different types of metal-oxide-semiconductor (MOS) capacitors. The averaged charging voltage is measured by the turn-on voltage shift (ΔV
T) of a grounded source EEPROM, while the transient charging effect is detected by a floating source EEPROM. The yield of the MOS capacitor reaches its maximum when the grounded source EEPROM shows the minimum ΔV
T. The effects of the charge-collecting electrode area and substrate type of the MOS capacitor are also examined.
The Characteristics of Ion-Beam-Induced Spontaneous Etching of GaAs by Low-Energy Focused Ion Beam Irradiation
Authors: Kosugi Toshihiko , Yamashiro Tomoki , Aihara Ryuzo , Gamo Kenji , Namba Susumu
Published: February 2005

We have investigated the characteristics of ion-beam-induced spontaneous etching (IBISE) of GaAs in Cl2 ambient by using a Ga-focused ion beam (FIB) with an energy ranging from 3 to 15 keV. The etched depth of the irradiated region was more than 20 times greater than that of unirradiated region. When the sputtered depth by FIB irradiation amounted to around 8 Å at each ion energy, the etched depth in Cl2 ambient for 1 hour became saturated. The saturated etched depths were 450, 550, 750 and 800 Å at the ion energy of 3, 5, 10 and 15 keV, respectively. The residual damage of the etched surface was also investigated by photoluminescence (PL) measurement. The maximal PL intensity was obtained at around the threshold dose of IBISE and increased with decreasing ion energy. The full recovery of PL intensity was observed at the ion energy of 3 keV after annealing at 400°C.
50-nm Metal Line Fabrication by Focused Ion Beam and Oxide Resists
Authors: Koshida Nobuyoshi , Yoshida Kazuyoshi , Watanuki Shinichi , Komuro Masanori , Atoda Nobufumi
Published: February 2005

Ultrafine patterning of refractory metals has been studied by the use of focused ion beam (FIB) and oxide resists. Thin amorphous films of MoO3 and WO3 were deposited by electron beam evaporation onto Si wafers, and were exposed to a 50 keV Ga+ FIB. Developed resist patterns were directly reduced to Mo and W by heat treatment in H2 gas atmosphere. The linewidth before and after reduction was measured as a function of the line dose. It is demonstrated that from a bilayer resist MoO3/WO3, a 50 nm refractory metal line can be controllably fabricated without any other complicated processes. Some information about the electrical properties of the reduced patterns is also presented.
Interfacial Interaction between Nematic Liquid Crystal and Polymer in the Composite Film Consisting of Nematic Liquid Crystal and Connected Polymer Microspheres
Authors: Nomura Hideshi , Sachio Suzuki Sachio Suzuki , Yuji Atarashi Yuji Atarashi
Published: February 2005

Thin films composed of nematic liquid crystals in polymer matrices show a reversible optical response from an opaque state to a clear state under the action of an appropriate electric field which aligns the nematic director. Activating voltages of the films are strongly affected by the interfacial interaction between the liquid crystal and polymer. An investigation was performed on films consisting of nematic liquid crystal, micrometer-size polymer microspheres and polymer binders. The microspheres are covered with a thin layer of binders and connected by it. The voids between the microspheres are filled by the liquid crystal. These films were produced using various binders formed from two ingredients. The relationship between the composition of binders and electrooptical properties of films was studied.
Microfabricated Submicron Al-Filament Biprism as Applied to Electron Holography
Authors: Ogai Keiko , Kimura Yoshihide , Shimizu Ryuichi , Ishibashi Kouji , Aoyagi Yoshinobu , Namba Susumu
Published: February 2005

A novel type of electron blprism was made using a microprocess technique. This electron biprism is composed of several filaments lined in parallel on a silicon nitride membrane. Using this type of multi-biprism, we observed an electric field by electron interferometry and confirmed the potentiality of extending this technique to a local electric field.
Submicron 3-Dimensional Structure Observation by Cyclotron SEM(Scanning Electron Microscope)
Authors: Nomura Noboru , Taichi Koizumi Taichi Koizumi , Kenji Harafuji Kenji Harafuji
Published: February 2005

Experimental and numerical approaches have been taken to the study of the brightness of scanning electron microscope(SEM) images for bottom surfaces of deep holes and trenches by Cyclotron SEM. Secondary electrons emitted from the bottom are efficiently collected as an image signal by a couple of the following combinational effects. One is an electrostatic converging lens due to accumulated negative charges on the side wall of holes and trenches. The other is a strong magnetic field above the specimen surface generated by an immersion-type objective lens. The former plays the role of reducing the number of electrons which collide with the side wall. The latter binds diverged secondary electrons leaving from the specimen surface and introduces electrons into a detector.
Theoretical Evaluation of a Topographic Contrast of Scanning Electron Microscope Images
Authors: Kotera Masatoshi , Fujiwara Takafumi , Nobuhiro Kanai Nobuhiro Kanai , Hiroshi Suga Hiroshi Suga
Published: February 2005

Topographic contrasts found in a image of the scanning electron microscope are quantitatively discussed. We quantify various contributions separately to the total signal intensity of the image, using a simulation which takes into account electron trajectories in and out of the specimen surface. This analysis indicates that the pattern edge shows higher contrast at lower beam energy if the beam diameter is zero, but on the contrary, the same edge shows higher contrast at higher beam energy if the beam diameter is fairly large. It is also found that the signal from the side wall at the pattern edge gives the major contribution for determining the characteristic shape of the edge contrast for both intensity profiles of secondary and backscattered electron signals.
A Novel Probe Size Measurement Method for a Fine Electron Beam
Authors: Yoshinori Nakayama Yoshinori Nakayama , Shinji Okazaki Shinji Okazaki
Published: February 2005

A novel electron beam (EB) spot size measurement method is proposed. In this method, EB spot size is obtained from the relationship between the width of the trenches in the reference sample and the intensity profile of backscattered electrons. Selective chemical etching of a GaAlAs/GaAs superlattice produces an ideal structure for the reference sample. Such superlattice is fabricated by metalorganic chemical vapor deposition and trench widths are verified by transmission electron microscopy. Using 0.6 µm deep and 8.5-65 nm wide trenches, nanometer-level EB spot sizes can be accurately measured.
Field-Induction-Drain Thin-Film Transistors for Liquid-Crystal Display Applications
Authors: Tanaka Keiji , Suyama Shiro , Kinya Kato Kinya Kato
Published: February 2005

A field-induction-drain (FID) poly-Si thin-film transistor (TFT), in which an electrically induced layer is used as a drain, is proposed. This TFT achieves a low OFF current and a high ON/OFF current ratio by simply incorporating an additional gate electrode. Moreover, the structure can be modified to make it suitable for complementary MOS (CMOS) applications. In this unified-structure FID (UFID) TFT, n-channel operation and p-channel operation are interchangeable. This paper presents this electrically induced layer which works well as a TFT drain and has beneficial influence on TFT characteristics.
Printing Color Filter for Active Matrix Liquid-Crystal Display Color Filter
Authors: Katsuhiko Mizuno Katsuhiko Mizuno , Satoshi Okazaki Satoshi Okazaki
Published: February 2005

Printing methods are attractive as possible methods for producing low-cost color filters. In this paper, waterless offset, gravure offset, and the ink cure method which is an improved gravure offset were studied. By optimizing the ink properties and the blanket conditions in the gravure offset, fine lines with a width of 15 µm and 100-µm-wide lines without any pinholes could be reproduced. Additionally, 20-µm very fine lines could be achieved by using the ink cure method. By forming both black matrix (BM) and color layers using a printing process, there is great potential for considerable cost savings in the production of active matrix liquid-crystal display color filters (LCD-CFs).
Low-Temperature Microwave Plasma Etching of Crystalline Silicon
Authors: Tsujimoto Kazunori , Sadayuki Okudaira Sadayuki Okudaira , Shinichi Tachi Shinichi Tachi
Published: February 2005

Low-temperature microwave plasma etching of crystalline silicons is described. Vertical and lateral etch rates of Si and the selectivities of Si to photoresist are measured as a function of water temperature within a range of -150 to +30° for SF6, and (3) the selectivities become high at low temperatures (e.g., >40 at -90°C and 2.3 Pa). This etching enables highly anisotropic Si etching at a high etch rate and high selectivity with fluoride gases. Less-polymerizing-type gases can provide high etch rates. An etching model of the ion-bombarded surfaces in discussed. The model implies that separate control of the side wall reaction and the horizontal surface reaction is archived by the low-temperature etching.