bluuebunny/crossref_metadata_2025 huggingface dataset:
Phase Transition Study of C70 Crystal at around 340 K by Single-Crystal X-Ray Diffraction
Authors: Mitsuki Tohru , Ono Yoko , Horiuchi Hiroyuki , Li Jing , Kino Nobuhiro , Kishio Kohji , Kitazawa Kohichi
Published: October 2002

Structural changes of C70 crystals were investigated in the temperature range between 295 K and 575 K
by a single-crystal X-ray diffraction using a precession camera. The crystal structure is based on a deformed
h
c
p with axial ratio c/a=1.85 at room temperature showing a remarkable stacking fault along the c axis.
Contraction of the c axis and a slight expansion of the a axis take place at the temperature around 340 K, and
as a result, the structure becomes close to an ideal h
c
p structure with c/a=1.65. Hysteresis of a wide temperature
range is also observed with the change of lattice constants. During phase transition, twinning by
(-1 0 2) often occurs by the combination of 90° rotation and shuffling of C70 ellipsoid molecules. The mechanism of the twin formation is also discussed.
Thermal Properties of Various Ta Precursors Used in Chemical Vapor Deposition of Tantalum Pentoxide
Authors: Koyama Hiroyuki , Tanimoto Satoshi , Kuroiwa Koichi , Tarui Yasuo
Published: October 2002

The volatilities of various Ta precursors which produce Ta2O5 in chemical vapor deposition (CVD)
are investigated by thermogravimetric analysis (TG) and differential thermal analysis (DTA). The Ta precursors
studied are Ta(OC2H5)5, Ta(OCH3)5, TaCl5 and Ta[N(CH3)2]5. The TG
and DTA measurements are carried out under both atmospheric pressure (760 Torr) and low pressure (0.6 Torr), and
the results are compared. These measurements are also performed after heat treatment for 6 h at 150° C
to compare the heat resistance of the precursors. It is shown that the evaporation starting temperature at 0.6 Torr
is significantly lower than that at 760 Torr for all Ta precursors studied, which suggests that the pressure in the
source bottle is an important deposition parameter. Ta(OC2H5)5 shows 100% volatility and superior
heat resistance. It is concluded that Ta(OC2H5)5 can serve as a good Ta precursor for CVD because of
its outstanding volatility and heat resistance.
Effect of Surface Roughness on Takeoff-Angle-Dependent X-Ray Fluorescence of Ultrathin Films at Glancing Incidence
Authors: Tsuji Kouichi , Sasaki Atsushi , Kichinosuke Hirokawa Kichinosuke Hirokawa
Published: October 2002

We had previously shown that takeoff-angle-dependent X-ray fluorescence (TAD-XRF) at glancing incidence is a useful method for the characterization of thin films. Here we report the effect of surface roughness of the substrate on TAD-XRF of an ultrathin film at a glancing incidence. An optically flat glass, scratched glasses and planoconvex lenses were used as substrates. A large-range contour such as warp and a roughness of microscopic scale affect the TAD-XRF profile. Therefore, to characterize the ultrathin film by the TAD-XRF method, the material whose roughness is being investigated should be used as the substrate in TAD-XRF measurement.
Effect of Nucleation Density on the Morphology of Diamond Thin Films
Authors: Park Young Soo , Sung Hoon Kim Sung Hoon Kim , Jo-Won Lee Jo-Won Lee
Published: October 2002

The morphology of diamond films deposited in the substrate temperature range of 550° C to
750° C by microwave plasma enhanced chemical vapor deposition (MPECVD) has been investigated as a
function of the nucleation density. Nucleation density can be controlled in the range of 1.5×107 to
1.0×1010 nuclei/cm2 by varying the ultrasonic pretreatment time and the particle size of diamond
powders. At high nucleation density, the thin films consist of well-faceted grains for all deposition times. Low
nucleation density leads to cauliflower-like morphology for the initial deposition time, which develops into the
well-faceted {100} grain with increasing deposition time. These results indicate that higher nucleation density
reduces the time required to develop well-faceted diamond grains. Therefore, we can conclude that the final surface
morphology of the diamond films is identical regardless of the nucleation density, after long growth time.
Line Shape of Saturated Absorption Spectra of Cs D2 Line
Authors: Oh Cha Hwan , Shin-ichi Ohshima Shin-ichi Ohshima
Published: October 2002

The line shape of the saturated absorption spectra of the 133Cs D2 line was examined. In
particular, the resonance signal for the transition from 6S1/2, F=4 to 6P3/2, F
′=5 was
carefully examined and found to be very sensitive to the saturating beam intensity and magnetic field, which was
due to the population redistribution of the ground hyperfiue level. When the polarizations of the saturating and
probing beams were linear and their directions were parallel, even the chage of sign was observed. The magnitude and
linewidth of the signal were controlled by adjusting the saturating beam intensity and the magnetic field as well as
the laser polarization.
Structural Studies on New Co Polyamine Complexes by X-Ray Absorption Fine Structure Spectroscopy
Authors: Akai Toshio , Okuda Masami , Horiuchi Kaoru , Matsuura Jun-ichi , Koike Yasuo , Yimagawa Masaru , Fujikawa Takashi
Published: October 2002

X-ray absorption fine structure (XAFS) studies are performed for a new Co(II) polyamine complex, N,N′-bis(3-aminopropyl)-1,3-propanediamine Co(II) complex (Co-APPD), and related complexes. The observed Co K-edge XANES spectra show that Co-APPD complex reacted with oxygen (Co-APPD( O2)) has a trivalent cobalt atom and has the octahedral structure around Co, whereas the difference in the structure between solid Co-APPD and Co-APPD dimethylsulfoxide (DMSO) solution is small. We also find the distortion from octahedral to tetrahedral structure with the increase of 2-furancarboxylic acid (FRA) concentration in DMSO solution. With the aid of short-range-order multiple scattering calculation, we study the Co K-edge X-ray absorption near edge structure (XANES) spectra of Co-APPD and Co-APPD ( O2) in more detail. From this theoretical study, we obtain information about oxygen bonding angle: the bond angle Co–O–O is about 120°.
Thin Film Transistors Made from Hydrogenated Microcrystalline Silicon
Authors: Hsu Kuo-Chiang , Chen Bor-Yir , Hsu Huey-Tzy , Wang Kun-Chih , Yew Tri-Rung , Huey-Liang Hwang Huey-Liang Hwang
Published: October 2002

Microcrystalline silicon films were deposited by diluted-hydrogen method and hydrogen-atom-treatment method at 250° C in a plasma enhanced chemical vapor deposition system and they were characterized by nuclear magnetic resonance, Raman spectroscopy, and optical bandgap measurements. One-mask a-Si:H thin film transistors (TFT's) were fabricated with those microcrystalline materials as the channel layer. The highest electron mobilities of the TFT's fabricated by diluted-hydrogen method and hydrogen-atom-treatment method were 1.23 and 1.04 cm2/V·s, respectively without any thermal treatment steps.
New Compact Small-Angle Neutron Scattering Spectrometer
Authors: Masaaki Sugiyama Masaaki Sugiyama , Yutaka Maeda Yutaka Maeda
Published: October 2002

A small-angle neutron scattering spectrometer has been installed at the exit of the guide tube glancing at the
cold neutron source of Kyoto University Reactor. In this spectrometer, double-reflection Ni?Ti mirrors are used as
a monochromator instead of a mechanical velocity selector. The scattered neutrons are detected by a 2-dimensional
position-sensitive detector which has been developed by the authors. The geometry of the spectrometer is designed
in consideration of the compromise between the resolution for scattering vectors and the intensity of scattered
neutrons. The average flux of 5.5 ? neutrons with the resolution of 15% is 3.9 ?104 n?cm-2?s-1 at the sample
position. The Q-range covered is from 0.004 ?-1 to 0.28 ?-1. In the preliminary experiments the performance
of the spectrometer is checked with a biomolecule, ferritin. The results indicate that the spectrometer has an
adequate performance for structure analysis of macromolecular systems.
Nondestructive Internal Observation in Electron-Acoustic Microscopy Using Metal-Oxide-Semiconductor LSI Chip
Authors: Takenoshita Mutsuo Kobayashi
Published: October 2002

A metal-oxide-semiconductor (MOS)-LSI was observed by electron-acoustic microscopy (EAM) under various operating
conditions of acceleration voltage (HV). The results are as follows. (1) When HV=20 kV, arrays of contact holes which
were covered with both an Al (thickness: 0.5 µm) and an SiO2 ( 0.6 µm) layer could be
observed. (2) However they could not be observed when HV=15 kV. (3) The observable depth of EAM is controllable
using HV as a parameter. (4) The adjustment of the irradiation power of the electron beam should make it possible to
achieve nondestructive internal observation of MOS-LSI specimens.
Electron Scattering from Si Surface and Interface by Cross-Sectional Transmission Electron Microscopy
Authors: Miyatake Hiroshi , Yoneda Masahiro , Harada Keiichi Murayama
Published: October 2002

Streak-shaped scattering, referred to as crystal truncation rod (CTR) scattering in X-ray diffraction, is observed in electron diffraction patterns obtained from the Si surface and the interface boundary by the cross-sectional observation technique. CTR scattering can be seen due to the truncation of a crystal at the side wall of a trench as well as at the surface. It becomes possible to evaluate the morphological quality of the surface and the interface on an atomic scale from CTR scattering in electron diffraction, of which the intensity is sensitive to the roughness.
Comparison of Hydride Vapor Phase Epitaxy of GaN Layers on Cubic GaN/(100)GaAs and Hexagonal GaN/(111)GaAs Substrates
Authors: Tsuchiya Harutoshi , Hasegawa Fumio , Okumura Hajime , Yoshida Sadafumi
Published: October 2002

GaN layers were homoepitaxially grown by hydride vapor phase epitaxy (HVPE) on
cubic GaN/(100)GaAs and hexagonal GaN/(111)GaAs substrates, and the growth conditions
and crystalline qualities were compared between both cases. HVPE GaN layers were epitaxially
grown on hexagonal GaN/(111)GaAs substrates when the substrate temperature was below 700°C,
whereas on cubic GaN/(100)GaAs substrates, they were epitaxially grown only at substrate
temperatures above 800°C. Two-step growth was necessary for higher-quality
hexagonal GaN epilayers to be grown at 900°C. The growth rate of HVPE GaN
epilayers on hexagonal GaN/(111)GaAs substrates was about 2.5 times higher than that
on cubic GaN/(100)GaAs substrates at the same HVPE growth conditions. Cathodoluminescence
spectra were measured for HVPE epilayers grown on both substrates.
Electrical Properties of Hg1-xCdxTe Grown by Low-Temperature Metalorganic Vapor Phase Epitaxy
Authors: Ferid Touati , Yasuda Kazuhito , Hatano Hiroki , Maejima Takayuki , Masaya Minamide Masaya Minamide , Kazuhiro Kawamoto Kazuhiro Kawamoto
Published: October 2002

Electrical properties of Hg1-
x

Cd

x

Te layers grown by low-temperature
metalorganic vapor phase epitaxy at 275°C have been studied. Substrates
used were (100) GaAs. The precursors used were dimethylcadmium (DMCd), elemental mercury,
and ditertiarybutyltelluride. Cadmium composition x of the layers was controlled from 0 to 1
by DMCd flow. Van der Pauw measurements were carried out in the temperature range from
25 to 300 K. For HgTe layers, typical 80 K electron concentration and Hall mobility of
4.4× 1016 cm-3 and 8.0× 104 cm2/V·s were obtained.
For CdTe, 300 K hole concentration and hole Hall mobility of 1.2× 1015 cm-3 and
6.5× 101 cm2/V·s were obtained. In the intermediate Cd composition
region of x=0.44, 80 K electron concentration of 8.0× 1015 cm-3 and Hall mobility as high as
7.4× 103 cm2/V·s were also obtained. The experimental mobilities
were explained by polar-optical phonon and alloy scattering.
Mobility Enhancement in Highly Strained δ-Doped InP/InGaAs/InP Heterostructure with InGaP Cap Layer Grown by Low-Pressure Metalorganic Chemical Vapor Deposition
Authors: Hsu Rong-Tay , Lin Wei , Wei-Chou Hsu Wei-Chou Hsu , Jan-Shing Su Jan-Shing Su
Published: October 2002

Highly strained δ- and uniformly doped InP/InGaAs/InP high-electron-mobility
transistor (HEMT) structures with InGaP cap layers were fabricated. Photoluminescence (PL),
secondary ion mass spectrometry (SIMS) and Hall measurement were used to analyse
these two structures. The δ-doped HEMT structure revealed higher mobilities
than the uniformly doped HEMT's, especially at low temperature, due to the reduction of
impurity scattering. The carrier concentrations and mobilities at 77 K were
2.7× 1012 cm-2 and 57861 cm2/v·s for the uniformly doped structure, and were
1.8× 1012 cm-2 and 99300 cm2/v·s for the δ-doped structure.
Phosphorus Doping Using Electron Cyclotron Resonance Plasma for Large-Area Polycrystalline Silicon Thin Film Transistors
Authors: Kakinuma Hiroaki , Mikio Mohri Mikio Mohri , Taiji Tsuruoka Taiji Tsuruoka
Published: October 2002

We have investigated phosphorus doping using an electron cyclotron resonance (ECR) plasma, for application to the poly-Si driving circuits of liquid crystal displays or image sensors. The PH3/He was ionized and accelerated to poly-Si and c-Si substrates with a self bias of -220 V. The P concentration, as detected by secondary ion mass spectroscopy (SIMS), is ∼5×1021 cm-3 at the surface, which decayed to ∼1017 cm-3 within 50–100 nm depth. The surface is found to be etched during doping. The etching is restored by adding a small amount of SiH4 and the sheet resistance R
s decreases. The optimized as-irradiated R
s is ∼1×105 Ω/\Box and 1.7×102 Ω/\Box for poly-Si and (110) c-Si, respectively. The dependence of R
s on the substrates and the anomalous diffusion constants derived from SIMS are also discussed.
Ferromagnetic Resonance in Metal Audio Tapes
Authors: Osamu Kohmoto Osamu Kohmoto
Published: October 2002

Ferromagnetic resonance measurements at 34 GHz were carried out to study the
magnetic anisotropy field of the acicular Fe particles in commercially available particulate
metal tapes for audio recording. The value of the average anisotropy field (H
a)
due to the acicular shape of the oriented particles has been determined to be 7.57 kOe,
assuming the saturation magnetization (4πM) of 17.2 kG, 80% of bulk Fe. Using
the obtained H
a value, the axial ratio of the acicular particles is deduced as 4.8.
The linewidth of 5 kOe along the tape length direction is four times as large as that of
video Co-γ-Fe2O3 tapes, which is due to a large distribution of the Fe particle axis and/or pores in the particles.
Analytical Description of Partially Coherent Optical Systems for Optimization of Numerical Aperture and Degree of Coherence
Authors: Hisashi Watanabe Hisashi Watanabe
Published: October 2002

The original Rayleigh equations for resolution, R and depth of focus, DOF,
are becoming less useful as new steppers incorporate the variable coherence factor, σ,
and numerical aperture, NA. We describe here simple extensions of the Rayleigh
equations to partially coherent illumination, which allow us to optimize values of NA and
σ according to the wavelength, λ, and the required image contrast,
C, when projecting the image of a grating object. Experimental values agree well with those derived from the equations.
Refractive Index Profiles of KTiOPO4 Ion-Exchanged Waveguides and Effect of Barium Ion
Authors: Noriko Yamada Noriko Yamada , Yukihiro Yamamoto Yukihiro Yamamoto
Published: October 2002

Planar waveguides in KTiOPO4 (KTP) have been fabricated by using molten
salts of RbNO3, CsNO3, 80/20 RbNO3/Ba(NO3)2 (molar ratio)
and 78/19/3 CsNO3/Ba(NO3)2/KNO3. The increase in the refractive index
of the waveguide per mole caused by the replaced Cs+ is one order of magnitude
greater than that caused by Rb+. The Ba2+ ion can contribute to
both the increase in the refractive index and the promotion of Rb diffusion. A Rb/Ba-exchanged
waveguide exhibited an increase in the refractive index three times as large as that
in a Rb-exchanged one with the same surface Rb+ concentration. When Ba2+
coexists with Rb+ in the molten salts, the diffusion constants of Rb+
in KTP at 350°C were 2.0 µ m2/min for the TM mode and 2.5 µ m2/min for the TE mode.
Luminescent Characteristics of Plasma-Oxidized Porous Silicon
Authors: Arakaki Osamu , Hatta Akimitsu , Toshimichi Ito Toshimichi Ito , Akio Hiraki Akio Hiraki
Published: October 2002

Porous silicon (PS) partially oxidized using electron-cyclotron-resonance plasma has been investigated. Blueshifting of photoluminescence (PL) peaks with progressive oxidation was observed at the initial stage whereas a sufficiently oxidized PS specimen had a room-temperature PL peak fixed at ∼685 nm. Electroluminescence (EL) from the specimens was stabilized by an additional H-plasma treatment after oxidation. This fact is well correlated with a significant reduction, after the H treatment, in intensity of cathodoluminescence (CL) peaks originating from defects in a SiO2matrix of oxidized PS. These results are discussed in relation to the origins of PL, EL and CL.
Electrical and Luminescent Properties of Color-Changeable Organic Electroluminescent Diode Using Squarylium Dyes
Authors: Mori Tatsuo , Miyachi Kiyokazu , Tomoaki Kichimi Tomoaki Kichimi , Teruyoshi Mizutani Teruyoshi Mizutani
Published: October 2002

The organic electoluminescent diode (LED) with squarylium (Sq) dye-doped Alq3
changes color upon application of voltage (current). The luminescent color from the
organic LED changes from red (electroluminescence (EL) of Sq dye) at low voltage to
light green (EL of Alq3) at high voltage. We studied the EL efficiency and EL spectrum
of organic Sq-doped Alq3 LED with various doping positions in the emission layer.
Consequentially, it was clarified that Sq doping near TPD considerably reduced the
EL efficiency. The EL mechanism of the organic LED was concluded to be associated with
the energy transfer from the excited Alq3 to the guest dye and hole trapping of the guest dye in Alq3.
High-Frequency Shear Viscoelastic Study of Cyanobiphenyl Series in the Smectic A and Nematic Mesophases
Authors: Tozaki Ken-ichi , Itou Mitsunobu Kimura
Published: October 2002

The temperature dependence of the shear viscosity η′ and the shear
elasticity G
′ for homeotropically aligned liquid crystals, cyanobiphenyl series,
7CB, 8CB, 9CB, and 10CB at 10, 30, and 50 MHz was determined by use of the piezoelectric
composite resonator method. In the vicinity of the phase transition points, the temperature
dependences of η′ and G
′ show characteristic behaviors corresponding
to the phase transition types; in particular, it is found that the dependence of G
′
shows an inflection point at the nematic-smectic A transition temperature. Arrhenius
plots of η′ are linear with an activation energy of 2.3× 104 Jmol-1
on the isotropic, nematic, and smectic A phases except in the neighborhood of the phase
transition points. The results of frequency dependence suggest the existence of the fiequency dispersion.
Point and Swirl Defects in Silicon
Authors: Onishi Takahisa Okino
Published: October 2002

In the previous paper [Jpn. J. Appl. Phys. 32 (1993) L856], vacancy and
silicon self-interstitial thermal equilibrium concentrations, i.e., C
V
0= 2.1×1017 cm-3 and C
I
0= 3.4×1016 cm-3,
were determined at 1100°C from an analysis of experimental data of P and Sb
diffusions in silicon during thermal oxidation. From the relationship between these
values and the Boltzmann factor, C
V
0 and C
I
0 are obtained as
functions of the absolute temperature, T. Vacancy and self-interstitial diffusivities,
D
V and D
I, are also given as functions of T by using the equation of
D
V
C
V
0 or D
I
C
I
0 derived from Au diffusion experiments
in silicon. Furthermore, the silicon self-diffusion mechanism is discussed and a successful
model on the swirl defect formation mechanism is also proposed, using the obtained
C
V
0, C
I
0, D
V and D
I. Consequently, C
I
0<C
V
0 and D
V<D
I
relations hold for arbitrary T. That is, the dominant thermal equilibrium defects
in silicon are vacancies. It was also found that self-diffusion is mainly governed by
the interstitialcy or vacancy mechanism for T>1158 K or T≤1158 K.
Etch Pit Observation of GaP Grown on Si Substrate by Metalorganic Chemical Vapor Deposition
Authors: Nishikawa Hironobu , Soga Tetsuo , Jimbo Takashi , Umeno Masayoshi
Published: October 2002

This paper describes the observation of the etch pits for GaP grown on Si substrate
which correspond to dislocations. The etching solution is composed of HF and HNO3
at room temperature. The etch pits revealed by this solution correspond to those revealed
by H3PO4 at 180°C.
Angular Distributions of Sputtered Particles Ejected from Pure Cu, Pt and Cu–Pt Alloy under 3 keV Ar+ Ion Bombardment
Authors: Nagatomi Takaharu , Kyung-youl Min Kyung-youl Min , Ryuichi Shimizu Ryuichi Shimizu
Published: October 2002

The `over-cosine' distribution peculiar to the angular distribution of Pt atoms
sputtered from pure Pt and Cu-Pt (19 at.%) alloy targets has been studied experimentally
and theoretically. The angular distributions were measured for pure Cu, Pt and Cu-Pt
alloy under 3 keV Ar+ ion bombardment at different incident angles in ultrahigh vacuum.
Significant `over-cosine' distributions of sputtered Pt atoms have been observed for
both the pure Pt and Cu-Pt alloy, as reported by Andersen et al.. As a theoretical approach,
Monte Carlo simulation has been performed by taking into account the altered layer formed
on the alloy surface, which was obtained experimentally in the previous study. The
comparison between the experiment and the simulation has revealed that the peculiarity
of the angular distribution of sputtered Pt atoms still cannot be understood by the
present simulation, whilst the simulation describes the angular distributions of other
metals with considerable success.
Hole Trapping and Detrapping Characteristics Investigated by Substrate Hot-Hole Injection into Oxide of Metal-Oxide-Semiconductor Structure
Authors: Khosru Quazi Deen Mohd , Yasuda Naoki , Kenji Taniguchi Kenji Taniguchi , Chihiro Hamaguchi Chihiro Hamaguchi
Published: October 2002

Substrate hole injection experiments have been carried out to investigate hot-hole-induced damage of SiO2 and the nature of trapping characteristics of hole traps present in the oxide of metal-oxide-semiconductor (MOS) structure using thin oxide p-channel MOS transistors. In contrast to the effect of hot electrons, oxide damage is somewhat less severe since no new traps were generated during hot-hole injection. Trapping phenomena are observed to be independent of the energy of injecting holes and oxide thickness, which implies identical distribution of traps in the oxide. Intrinsic hole traps are found to have retrapping capability. Detrapping of trapped holes is strongly dependent on oxide field polarity and magnitude, which is consistent with the concept of tunneling discharge, and detrapping is found to be dominant through the Si/SiO2 interface.
Statistical Behaviour of Internal Partial Discharges at DC Voltage
Authors: Udo Fromm Udo Fromm , Frederik H. Kreuger Frederik H. Kreuger
Published: October 2002

In this paper the succession of partial discharges at DC voltage is discussed. For the measurements presented here, the Townsend-like discharge mechanism was found to be dominant. Using a simpleRCcircuit, the discharge behaviour can be described. Several discharge parameters, such as the average time lag or the voltage drop of a discharge, can be evaluated. The discharge magnitude can also be predicted.
Diffusion and Quenching of Metastable Xe Atoms in Mixtures of Xe and Rare Gases
Authors: Tachibana Kunihide , Takahashi Kazuo , Matsuzaki Hideomi , Sakai Tetsuo
Published: October 2002

The diffusion coefficient of metastable Xe*(6s[3/2]2

o
) atoms
has been measured in mixtures of Xe with rare gases. Experimental values ranging from
5.5× 1017 cm-1s-1 in pure Xe to 6.1× 1018 cm-1s-1
in pure He are compared with those obtained from the gas kinetic theory using Lennard-Jones
potential parameters. Quenching rate coefficients of Xe* for two-body and
three-body collisions with rare-gas atoms have also been determined.
Degradation Phenomenon under Low Drain Voltage Stress in p-channel Metal-Oxide-Semiconductor Field-Effect-Transistors
Authors: Morii Tomoyuki , Murai Ryoko , Yukiharu Uraoka Yukiharu Uraoka , Kazuhiko Tsuji Kazuhiko Tsuji
Published: October 2002

A new hot-carrier degradation of p-channel metal-oxide-semiconductor field-effect-transistors (pMOSFETs) under low drain voltage stress has been investigated. It is found that the degradation occurs under high gate voltage stress (HG stress) after avalanche hot-carrier injection (AHC injection) for pMOSFETs with thin gate oxide ( ∼10 nm). When AHC stress and HG stress are repeatedly imposed on pMOSFETs, the degradation of threshold voltage is enhanced. Moreover, this degradation under HG stress occurs even in areas where channel current does not flow. This enhanced degradation is strongly dependent on the cycle frequency and gate-to-drain voltage of HG stress. We have proposed a simple model based on the experimental results.
Effect of Phase Error on Lithographic Characteristics Using Attenuated Phase-Shifting Mask
Authors: Miyazaki Junji , Nakae Akihiro , Kusunose Haruhiko , Yoshioka Nobuyuki , Wataru Wakamiya Wataru Wakamiya , Keiichi Murayama Keiichi Murayama
Published: October 2002

An attenuated phase-shifting mask is one of the most useful technologies for
sub-half-micron lithography. However, it is necessary to control new parameters such
as phase or transmittance when a phase-shifting mask is applied to practical use.
We investigated the effect of phase error on lithographic characteristics for a hole
pattern using an attenuated phase shifting mask. It is found that a phase error causes
a decrease of depth of focus (DOF) and shift of best focus position. It is indicated
that this effect depends on several optical parameters such as hole size and wavelength.
In the case of the 0.4 µ m hole pattern with i-line stepper, the phase tolerance
must be less than 2.7° to control loss of DOF within 0.1 µ m. It is
also found that the edge slope effect of the shifter is rather small and the side wall
angle of 70° is acceptable.
Evaluation of Phase-Shifting Masks for Dense Contact Holes Using the Exposure-Defocus and Mask Fabrication Latitude Methodology
Authors: Sugawara Minoru , Kawahira Hiroichi , Tsudaka Keisuke , Akihiro Ogura Akihiro Ogura , Satoru Nozawa Satoru Nozawa
Published: October 2002

Alternating phase-shifting mask (Alt PSM) and subresolution-assisted alternating
phase-shifting mask (SAA PSM) are applied for a 0.3 µ m dense contact hole
(C/H) layout and evaluated by using the EDM methodology
(Exposure-Defocus and Mask fabrication latitude methodology)
in which mask line width latitude is considered as well as conventional exposure-defocus
parameters. The Alt and SAA PSMs are considered to release the constraint of pattern
layout for rim and outrigger PSMs, and are studied to overcome critical problems of
the optical proximity effect for attenuated PSM and binary masks. The EDM process
window evaluation shows that the Alt PSM is markedly effective for a two-dimensionally
arrayed C/H layout and the SAA PSM is suitable for a layout of several C/Hs. In this paper,
the Alt and SAA PSMs are considered in detail, after characteristics of a binary mask
and attenuated PSM are reviewed by using the EDM process windows.
Simulation and Process Design of Gray-Tone Lithography for the Fabrication of Arbitrarily Shaped Surfaces
Authors: Henke Wolfgang , Hoppe Wolfgang , Quenzer Hans-Jochen , Peter Staudt-Fischbach Peter Staudt-Fischbach , Bernhard Wagner Bernhard Wagner
Published: October 2002

This paper reports on a study of a methodology for fabrication of arbitrarily shaped silicon structures using technologies common to standard IC manufacturing processes. Particular emphasis is placed on the design and use of halftone transmission masks for the lithography step required in the fabrication process of mechanical, optical or electronics components. The design and experimental investigation of gray-tone masks were supported by lithography simulation. Results are presented for both simulated gray-tone patterns and experimental trials.
Performance of Single Sideband Optical Lithography Using a Pupil Filter in Replicating Isolated Patterns
Authors: Toshiyuki Horiuchi Toshiyuki Horiuchi , Katsuhiro Harada Katsuhiro Harada
Published: October 2002

This paper describes how oblique illumination optical lithography using a transmittance-adjusted
pupil filter is efficient for isolated patterns as well as periodical patterns. This
method is successful for the following reasons. When a pupil filter has a small transmittance
in the area where 0th-order diffraction light image of secondary light source is made,
the 0th-order diffraction light is selectively attenuated. From this attenuation, the
ratio of the light components with a middle and high spatial frequency becomes larger
than it would without a pupil filter. As a result, because the light intensity curves
for isolated line patterns and space patterns are sharpened, high resolution and large
focus latitude are obtained. Lines-and-spaces patterns and both types of isolated
patterns with a critical size near the resolution limit are replicated into the designed
width simultaneously with the same exposure dose.
Substrate Nitridation Effects on GaN Grown on GaAs Substrates by Molecular Beam Epitaxy Using RF-Radical Nitrogen Source
Authors: Kikuchi Akihiko , Hiroyuki Hoshi Hiroyuki Hoshi , Katsumi Kishino Katsumi Kishino
Published: October 2002

The initial substrate nitridation effects on the crystal structure of GaN epitaxial layers grown on GaAs substrates by gas source molecular beam epitaxy using RF-radical N2 as a nitrogen source were investigated. The crystal structure of GaN grown on (100) GaAs substrates was critically influenced by substrate nitridation time, that is, zincblende GaN was grown on the substrate without nitridation, and wurtzite GaN was grown on the nitrided substrate (longer than 120 s). The substrate misorientation effects on surface morphology and X-ray full width at half-maximum of zincblende GaN layers were also studied. A featureless smooth surface was obtained for a layer grown under the high V/III beam flux ratio condition.
Overlay Repeatability in Mix-and-Match Exposure Using the SR Stepper: SS-1
Authors: Shibayama Akinori , Fukuda Makoto , Suzuki Masanori , Tsuyuzaki Haruo , Tadahito Matsuda Tadahito Matsuda , Sunao Ishihara Sunao Ishihara
Published: October 2002

Proximity X-ray lithography using synchrotron orbital radiation (SR) is potentially
able to replicate patterns with a width of less than 0.2 µ m. We developed a
die-by-die alignment basis SR stepper, which is equipped with air-lubricated lead screws
for the XY stage and an optical heterodyne alignment system. An overlay repeatability of
23 nm (3σ) is obtained with only X and Y alignment when evaluated by the double
exposure method. In practice, the mix-and-match scheme between the SR and optical exposures
is important for reducing the cost of lithography. In the mix-and-match exposure between
the SR and optical steppers, an overlay repeatability of 45 nm (3σ) is achieved
with the X, Y, and θ alignment mode of the SR stepper. Analysis of the error
factors in this overlay exposure experiment showed that the optically printed patterns
have chip shape distortions causing overlay error of about 35 nm (3σ).
Evaluation of a Solid State Detector for X-Ray Lithography Dosimetry
Authors: Wells Gregory M. , Anderson Paul D. , Leonard Quinn J. , Cerrina Franco , Waldo Whit G. , Yamazaki Kuniaki
Published: October 2002

Dosimetry of the X-ray radiation delivered to the mask-wafer plane of a stepper
is essential for the development of a controlled X-ray lithography process. A wafer
plane detector using a silicon photo-diode has been designed and evaluated for X-ray
lithography applications. This detector was designed to provide real time measurements
of beam fluence, delivered dose and beam uniformity. The detector has been evaluated
on two CXrL beamlines, one with a scanning mirror and the other a beamline used in
conjunction with a Karl Suss XRS 200 stepper that scans mask and wafer (and wafer plane monitor)
vertically through the beam for exposures.
Cell Projection Lithography with Scattering Contrast
Authors: Sohda Yasunari , Someda Yasuhiro , Satoh Hidetoshi , Nakayama Yoshinori , Itoh Norio Saitou
Published: October 2002

A scattering-type cell projection method is proposed and its characteristics
are estimated by simulation and experiment. In this method, a mask consisting of thin
scatterers and apertures is used to shape an electron beam. Thus, this method has
advantages over the conventional cell projection method. First, a high aspect ratio
is not necessary to fabricate the mask. Thus, the mask pattern is easily fabricated
and its experimental dimensional accuracy is better than 0.2 µ m. Second,
the simulated heat deposition on the mask drastically decreases. In addition, simulation
and experiment show good contrast of over 105 related to using a limiting aperture to
intercept scattered electrons. As a result, this method is considered to be a key
technology in future electron beam lithography systems.
Metal-Free Acid Generators for Chemically Amplified Monodispersal Polyhydroxystyrene-Based Positive Resist and Post-Exposure Delay Problem
Authors: Tanaka Akinobu , Kawai Yoshio , Nakamura Jiro , Hiroshi Ban Hiroshi Ban , Tadahito Matsuda Tadahito Matsuda
Published: October 2002

Our studies of metal-free acid generators (AG) for chemically amplified monodispersal
PHS-based positive resist (MDPR) show that bis(t-butylphenyl)iodonium triflate (BBITf)
is the most promising for practical use. It inhibits dissolution strongly before exposure
and weakly after post-exposure baking. A 0.25-µ m l&s pattern can be
fabricated by KrF excimer laser lithography using MDPR with a BBITf acid generator.
MDPR is highly susceptible to contamination from the air, as are other chemically
amplified resists. Adding an organic base to MDPR is very effective in improving stability
against airborne contamination, but at the expense of sensitivity.
The Effect of an Organic Base in Chemically Amplified Resist on Patterning Characteristics Using KrF Lithography
Authors: Kawai Yoshio , Otaka Akihiro , Akinobu Tanaka Akinobu Tanaka , Tadahito Matsuda Tadahito Matsuda
Published: October 2002

A new resist system composed of an SEPR chemically amplified (CA) positive resist
and an N-methyl pyrrolidone (NMP) organic base has been developed for KrF excimer laser
lithography. Using 0.30-µ m l&s patterns formed with KrF stepper, we
studied the effect of contamination from substrate films of plasma chemical vapor
deposition silicon dioxide (P-CVD SiO2), low pressure CVD silicon nitride
(LP-CVD Si3N4) and reactive sputtered titanium nitride (TiN), and of airborne
contamination under the condition of an 8-ppb of ammonia. The results clarify the new
resist system reduces the effect of substrate film as well as airborne contamination.
The new resist system enables us to form fine patterns on any substrate and attains
more than one hour post-exposure delay without overcoat and undercoat films.
Thermal Desorption Spectroscopy and X-Ray Photoelectron Spectroscopy Study of CFx Layer Deposited on Si and SiO2
Authors: Miyakawa Yasuhiro , Fujita Ken , Hirashita Norio , Ikegami Naokatsu , Hashimoto Jun , Takayuki Matsui Takayuki Matsui , Jun Kanamori Jun Kanamori
Published: October 2002

Thermal reactions between a fluorocarbon ( CF

x

) layer formed with C4F8
magnetomicrowave plasma and Si and SiO2 are studied by thermal desorption spectroscopy
(TDS). Atomic compositions and core spectra of the CF

x

layer are measured by
temperature-programmed X-ray photoelectron spectroscopy (TP-XPS) with concomitant
desorption gas species analysis by quadrupole mass spectrometer. The TDS study reveals
that the primary reaction products are SiF4 in Si and SiF4 and CO
in SiO2, and F generated from the CF

x

layer is a primary reactive
species contributing to the formation of the reaction products not only in Si but also in
SiO2. The TP-XPS study reveals that the drastic decrease of F/C ratio agrees
with the desorption of SiF4 and CO.
Molecular Orientation and Photochemical Reaction of Organoaluminum Compounds Investigated by Buried Metal Layer Infrared Reflection Absorption Spectroscopy
Authors: Urisu Tsuneo , Zhang Yanping , Nagasono Mitsuru , Yoshigoe Akitaka , Imaizumi Yoshiaki , Ohshima Hisayoshi , Hattori Tadashi , Sato Shinri
Published: October 2002

The structure and synchrotron radiation (SR) irradiation effects of the low-temperature
condensed layer of several organoaluminum compounds on the SiO2 surface were
investigated by infrared reflection absorption spectroscopy using a buried metal layer
substrate (BML-IRAS). Trimethylaluminum is a dimer at temperatures lower than 180 K,
and a photoproduct having the methyl group is produced by SR irradiation. The condensed
layer of dimethylethylamine alane (DMEAA) as-deposited at temperatures less than 140 K
consists of randomly oriented dimer molecules, and changes to a more ordered orientation of
monomer molecules at temperatures higher than 140 K. Concerning the SR irradiations,
the results are different for the two different molecular orientations. Upon SR irradiations
of the ordered orientation layer, a new broad vibration band, possibly assigned to the
aggregation of inhomogeneous AlH stretching vibrations, appears. On the other hand,
in the case of the random orientations of the dimer molecules, such a new broad band does not appear,
and only an intensity decrease is observed for all bands.
Fabrication and Characterization of Cross-Edge-Structured Vertical Field Emitter Arrays
Authors: Ishizaki Mamoru , Gamo Hidenori , Seigo Kanemaru Seigo Kanemaru , Junji Itoh Junji Itoh
Published: October 2002

New field emitter arrays (FEAs), called cross-edge-structured vertical FEAs, were fabricated and characterized. Chromium (Cr) emitters and molybdenum/Cr emitters were tested. The anode-current fraction was 50%, being improved in comparison with that of disk-edge FEAs. Threshold voltage of the anode current was a low voltage of 25 V. From the light emission pattern, divergent angle was estimated to be 9°.
Fabrication of Cone-Shaped Metal-Insulator-Semiconductor Electron Tunneling Cathode
Authors: Inoue Kazunori , Gotoh Yasuhito , Hiroshi Tsuji Hiroshi Tsuji , Junzo Ishikawa Junzo Ishikawa
Published: October 2002

A new cone-shaped metal-insulator-semiconductor (MIS) cathode with an outside electrode is proposed for
vacuum microelectronics devices. This cathode has larger emission current and higher transfer ratio (the ratio of
electron emission current to the diode current) than those of the conventional MIS cathodes. In the present paper,
the general concept of this new cathode is presented. To ensure the effectiveness of the electrode configuration,
the cathode performance was investigated with a cone-shaped MIS cathode. The fundamental characteristics of
this cathode were measured. The emission into vacuum was confirmed and the transfer ratio of about 10-3 at
maximum was obtained.
Carrier Transport Properties of Conductive p-Si Wires by Focused Ion Beam Implantation
Authors: Iwano Hirotaka , Zaima Shigeaki , Kimura Tomonori , Kohji Matsuo Kohji Matsuo , Yukio Yasuda Yukio Yasuda
Published: October 2002

The carrier transport phenomena of p-Si wires on n-Si(100) substrates fabricated by selective ion implantation using focused Ga+ion beams have been examined. We have successfully controlled the electrical conduction in p-Si wires by changing doses and annealing temperatures, and found that three kinds of electrical conduction mechanisms, namely metallic conduction, one-dimensional variable-range-hopping (1D-VRH) conduction and nearest-neighbor-hopping (NNH) conduction, can be observed below 70 K. The 1D-VRH conduction is observed in samples with doses of 3.5 to 5.6× 109cm-1at annealing temperatures of 600 to 690°C and the NNH conduction in samples under the conditions of lower doses or higher temperatures. In these systems, negative magnetoresistance is observed in the NNH conduction and positive magnetoresistance in the VRH conduction. The density of localized states per unit energy in a localization length at the Fermi level, ρFα-1, is estimated to be 200–300 eV-1in the VRH conduction.
Fabrication of High Breakdown Pseudomorphic Modulation Doped Field Effect Transistors Using Double Dry Etched Gate Recess Technology in Combination with E-Beam T-Gate Lithography
Authors: Hülsmann Axel , Bronner Wolfgang , Köhler Klaus , Jürgen Braunstein Jürgen Braunstein , Paul J. Tasker Paul J. Tasker
Published: October 2002

We have developed a technology to fabricate pseudomorphic 0.3 µ m
gatelength modulation doped field-effect transistors (MODFETs) having a breakdown
voltage up to 20 Volts. This technology uses molecular beam epitaxy (MBE) to grow
the InGaAs/AlGaAs/GaAs heterostructure with two pulse doping layers on 3 inch semiisolating
GaAs wafers. A mix and match lithography was applied using an i-line stepper and an
electron beam direct write process to define the mushroom shaped gates (T-gates).
The breakdown enhancement is achieved by a self aligned selective double dry etched
gate recess using AlGaAs etch stop layers. We investigated the heterostructure doping
and the influence of the gate recess process to the device performance.
Nanostructure Fabrication Based on Spontaneous Formation Mechanisms
Authors: Miyao Masanobu , Nakagawa Kiyokazu , Ichikawa Masakazu , Nakazato Kenji Hiruma
Published: October 2002

The recent progress of nanostructure fabrication technology based on spontaneous
formation mechanisms is reviewed. Low-dimensional structures, i.e., 2-D crystal planes,
1-D crystal wires and 0-D quantum dots, have been successfully fabricated with atomic-scale
accuracy. Electrical and optical properties prove that carrier confinement is realized
in such mesoscopic structures. The new possibilities that are expected to open up for
quantum functional devices are also discussed.
Annealing Behavior of Irradiation-Induced Damage in an AlGaAs/GaAs Heterostructure by Low-Energy Electron Beam
Authors: Wada Toshimi , Kanayama Toshihiko , Ichimura Shingo , Yoshinobu Sugiyama Yoshinobu Sugiyama , Masanori Komuro Masanori Komuro
Published: October 2002

Evaluating the low-temperature mobility of the two-dimensional electron gas in AlGaAs/GaAs heterostructures, we have studied the nature of the damage induced in the heterostructure by low-energy electron-beam irradiation up to 7.5 keV at room temperature and at 90 K. The isochronal annealing revealed that at around 450 K the degraded mobility recovered quickly in the 90-K-irradiated sample and gradually in the sample irradiated at room temperature. However, the quality of both samples did not recover completely upon annealing at 675 K. The electron-beam irradiation was speculated to cause the formation of As-related defects.
A Study on Bilateral Latch-Up Self-Triggering in Complementary Metal-Oxide-Semiconductor Protection Circuits
Authors: Huang Heng-Sheng , Chang Chun-Yen , Chen Kun-Luh , Liu Ingdar , Hsu Chen-Chung , Lin Jyh-Kuang
Published: October 2002

The results of serial studies on the behavior of bilateral latch-up in complementary metal-oxide-semiconductor field effect transistor (CMOS) protection circuits are presented. Bilateral latch-up self-triggering resulting from serial resistance or serial inductance on V
dd or V
ss is discussed. Optimizing the layout and design of output buffers to improve product performance and reliability is also recommended. The studies on the behavior of bilateral latch-up in CMOS protection circuits are increasingly important since low-power applications are the future trend.
A New GaAs Field Effect Transistor (FET) with DIpole Barrier (DIB)
Authors: Cho Hyun-Ryong , Jeon Kye-Ik , Song-Cheol Hong Song-Cheol Hong , Young-Se Kwon Young-Se Kwon
Published: October 2002

A new GaAs field effect transistor (FET) with dipole-barrier (DIBFET) employing a delta-n (δ
n
) layer and a delta-p (δ
p
) layer is proposed and fabricated. Electrons are confined in the upper undoped-GaAs layer (the channel layer) rather than around the δ
n
layer by the influence of the transverse electric field resulting from the dipole-barrier formation. This leads to the high electron concentration of 1.5×1018 cm-3 with the electron drift mobility of 3600 cm2/V·s in the undoped GaAs channel at room temperature. The fabricated GaAs DIBFET with 0.8 µm gate length shows the maximum value of extrinsic transconductance of 366 mS/mm. The drain current density is larger than 800 mA/mm. The current gain cutoff frequency f
T of 16.7 GHz and the maximum oscillation frequency f
max of 67 GHz are obtained. One-dimensional calculation of device characteristics is performed for the purpose of evaluating the device performance.
Fabrication and Characterisation of Direct Schottky Contacts to Two-Dimensional Electron Gas in GaAs/AlGaAs Quantum Wells
Authors: Hartnagel Giorgio Schweeger
Published: October 2002

Pt Schottky contacts to the edge of a two-dimensional electron gas in a GaAs/AlGaAs system have been manufactured using a newly developed in-situ etching and electroplating technology. The electroplating takes place selectively on the edge of the quantum well. It is shown that the in-situ etching prior to deposition leads to more uniform electroplating due to the removal of native oxides. I-V and C-V measurements have been made in order to compare the diodes with conventional Schottky diodes. It can be shown that the capacitance shows functionally the relationship predicted by theory, which demonstrates that we have manufactured a contact to a 2-dimensional electron gas. I-V measurements at low temperatures reveal parallel ohmic conductance. It is shown qualitatively that tunneling through the extremely thin barrier plays an important role in the current conduction, which explains the high ideality factor and the low apparent barrier height compared to bulk Schottky diodes.
Threshold Logic Function on Both Positive and Negative Weighted Sums in Multiple-Input Monostable-Bistable Transition Logic Elements
Authors: Akeyoshi Tomoyuki , Koichi Maezawa Koichi Maezawa , Takashi Mizutani Takashi Mizutani
Published: October 2002

This paper describes the functional operation of a monostable-bistable transition logic element (MOBILE) with multiple-input logic gates. The MOBILE uses two resonant-tunneling transistors (RTTs) connected in series and driven by oscillating bias voltage to produce a mono-to-bistable transition of the circuit. It is experimentally shown that a fabricated 3-input MOBILE can perform threshold logic functions on the weighted sum of input signals. It can also easily handle both positive and negative weights when input signals are applied to both RTTs.
Operation Characteristics of a Side-Light-Injection Multiple-Quantum-Well Bistable Laser for All-Optical Switching
Authors: Uenohara Hiroyuki , Kawamura Yuichi , Iwamura Hidetoshi , Nonaka Kouji , Hiroyuki Tsuda Hiroyuki Tsuda , Takashi Kurokawa Takashi Kurokawa
Published: October 2002

An InGaAs/InAlAs side-light-injection multiple-quantum-well bistable laser for all-optical switching has been developed. It consists of one main bistable laser and two waveguides perpendicular to the main laser. Saturable absorption and gain quenching are used for set and reset operations. The voltages applied to the gain quenching and saturable absorption regions, which are located at the intersections of the main laser and the waveguide regions, are +1.00 and +0.29 V, respectively. As the input light intensity ( 1.55 µm range) increases, the turn-on and turn-off times decrease. The turn-on time is 200 ps when the input light peak intensity is 1 mW and the turn-off time is 2 ns when the input light peak intensity is 200 mW. The experimental results are supported by numerical simulation. Higher differential gain material is expected to enable faster switching speed.