bluuebunny/crossref_metadata_2025 huggingface dataset:
The Application of Silicon Rich Nitride Films for Use as Deep-Ultraviolet Lithography Phase-Shifting Masks
Authors: Jiang Zhong-Tao , Yamaguchi Tomuo , Ohshimo Kentaro , Aoyama Mitsuru , Asinovsky Leo
Published: October 2002

Silicon rich nitride (SiRN) film prepared by plasma enhanced chemical vapor deposition (PECVD) for use as the phase-shifting mask for Deep-ultraviolet (UV) lithography has been developed. Optical properties and compositional characterizations of the SiRN films using Auger electron spectroscopy (AES) and spectroscopic ellipsometry (SE) combined with an empirical dielectric function (EDF), as well as phase-shifting mask simulation show that the SiRN is feasible for use in the application of single layer halftone phase-shifting mask (SLHTPSM) in the Deep-UV range. Optical constants of n ≈ 2.5 and k < 0.6 at 193 nm were realized by approaching the N/Si composition to the stoichiometric ratio of Si3N4. The deposition conditions for the films having the transmittance of 5 - 10% with a 180° phase shift at 193 nm (ArF) have been determined. Short wavelength extrapolation by EDF best-fit parameters based on a proper film-stack model provides a potential method to characterize the optical properties of amorphous SiRN down to about 190 nm, which is outside the range of most commercial SE's.
Study on Preparation Conditions of High-Quality ZrN Thin Films Using a Low-Temperature Process
Authors: Hideto Yanagisawa Hideto Yanagisawa , Katsutaka Sasaki Katsutaka Sasaki , Yoshio Abe Yoshio Abe , Midori Kawamura Midori Kawamura , Satoko Shinkai Satoko Shinkai
Published: October 2002

We have investigated the preparation conditions of stoichiometric ZrN films with low resistivity and high crystallinity at relatively low temperatures using an ultrahigh vacuum sputtering system.
The film quality was evaluated by means of X-ray diffraction, X-ray photoelectron spectroscopy and Auger electron spectroscopy analyses.
The resistivities were measured by a four-probe method.
We found that stoichiometric ZrN films with nearly single (100) orientation and resistivity of 17 µΩcm grew on (100) Si under the optimum conditions of N2 flow ratio of 3%, low sputtering power of 15 W and substrate temperature of 500°C.
It is therefore concluded that high-quality ZrN films can be obtained at a relatively low substrate temperature, if appropriate sputtering conditions are satisfied using an ultrahigh vacuum sputtering system.
Raman Scattering Studies of CuInS2 Films Grown by RF Ion Plating
Authors: Kondo Ken-ichi , Nakamura Susumu , Sato Katsuaki
Published: October 2002

CuInS2 films were grown by rf ion plating and their crystallinity was characterized by Raman
spectroscopy. Six Raman peaks were observed, most of which were assigned to the phonon
modes of CuInS2, except for a peak at 307 cm-1 that was clearly observed in the films with a poor
crystalline quality. The peak at 307 cm-1 was assigned to the totally symmetric mode by
polarized Raman measurement. This peak was related to some kind of a localized mode with
a smaller mean atomic weight of cations.
Hollow Density Profile on Electron Cyclotron Resonance Heating JFT-2M Plasma
Authors: Yamauchi Toshihiko , Hoshino Katsumichi , Kawashima Hisato , Ogawa Toshihide , Kawakami Tomohide , Shiina Tomio , Ishige Youichi
Published: October 2002

The first hollow electron density profile in the central region on the JAERI Fusion Torus-2M (JFT-2M) is measured during electron cyclotron resonance heating (ECRH) with a TV Thomson scattering system (TVTS). The peripheral region is not hollow but is accumulated due to pump-out from the central region. The hollowness increases with time but is saturated at ∼40 ms and maintains a constant hollow ratio. The hollowness is strongly related to the steep temperature gradient of the heated zone.
Concentric Spread Plasma Source
Authors: Watanabe Seiichi , Sumiya Masahiro , Kawasaki Sunao
Published: October 2002

A new microwave plasma source termed “concentric spread plasma (CSP)” is presented.
By mounting an inner conductor of the coaxial waveguide perpendicular to and directly on a quartz
plate, the CSP source can generate a disk-shaped plasma (electron density >3.8×1017 m-3) with
high stability below the quartz plate that faces the wafers, regardless of the process conditions.
One of the notable features of the CSP source is the concentric expansion of the plasma with
increasing microwave power. The CSP is generated by the following mechanism (process): (1) the
plasma itself becomes a part of the waveguide for microwave, (2) the microwaves are transmitted
concentrically in the quartz plate from its center toward its outer circumference, and (3) the CSP is
generated by Joule heating caused by the surface current of the microwave flowing in the plasma.
In short, the plasma is self-guided.
Electrostatic Phenomena in π-conjugated Langmuir-Blodgett Films on Metal Electrodes
Authors: Eiji Itoh Eiji Itoh , Haruo Kokubo Haruo Kokubo , Mitsumasa Iwamoto Mitsumasa Iwamoto , Marko Burghard Marko Burghard , Siegmar Roth Siegmar Roth , Michael Hanack Michael Hanack
Published: October 2002

The surface potentials of three kinds of π-conjugated Langmuir-Blodgget (LB) films (octasubstituted palladiumphthalocyanine (PcPd), perylene-tetra-carboxyldiimide derivative (PTCDI-SPent and PTCDI-OEt)) deposited on Au electrodes were measured using a Kelvin-probe method in a dark vacuum vessel at various temperatures. It was suggested that excess electronic charges were transferred from the electrodes into these LB films until thermodynamic equilibrium was established at the metalo-interface and resulted in the formation of an electrostatic layer on the order of several nano meters. The interfacial electrostatic potential formed at the interface between PcPd and PTCDI-SPent layers was also measured at various temperatures. It was found that electrons were transferred from PcPd to PTCDI-SPent layers at the interface.
Theoretical Calculations of Sensitivity of Deprotection Reactions for Acrylic Polymers for 193 nm Lithography II: Protection Groups Containing an Adamantyl Unit
Authors: Matsuzawa Nobuyuki N. , Takechi Satoshi , Ohfuji Takeshi , Kuhara Koichi , Mori Shigeyasu , Endo Masayuki , Kamon Kazuya , Morisawa Taku , Yamaguchi Atsuko , Sasago Masaru
Published: October 2002

The reaction energy of deprotection reactions, glass transition
temperature, and the dielectric constant were calculated for
photoresists having a 2-alkyl-2-adamantyl group. It was found
that the lower sensitivity of the polymer with a 2-methyl-2-adamantyl group (compared with the sensitivities of the polymers
with a 2-ethyl-2-adamantyl group and a 2-butyl-2-adamantyl
group) can be attributed to the smaller exothermic (or greater
endothermic) reaction energy of its deprotection reaction. It was
also found that the sensitivity difference between the polymers
with the 2-ethyl-2-adamantyl and 2-butyl-2-adamantyl groups can
be attributed to the difference in the calculated dielectric constant,
where a higher dielectric constant leads to a higher sensitivity.
Comparison of Copper and Stainless Steel Used for Low Voltage Electrode in Wire-to-Plane Electrode Configuration for NO x Treatment
Authors: Gasparik Robert , Yamabe Chobei , Ihara Satoshi , Satoh Saburoh
Published: October 2002

Copper and stainless steel have been investigated as low voltage electrodes in
wire-to-plane electrode configuration under conditions of DC positive streamer corona
discharge. Copper has been chosen due to its well-known catalytic activity while, on the
other hand, stainless steel was selected as an opposite extreme to copper–due to its high
passivity. The initial gas contained 400 ppm NO/N2, 10% O2, and water vapors or 40%
aqueous solution citric acid. Removal rates of NO
x
have been calculated as a function of
the applied voltage. Results have shown that the highest removal rate, 56% for NO, have
been obtained while employing Cu plate and citric acid. We suppose that Cu participates
in the process of treatment, while stainless remains inactive. Therefore, while using a
stainless steel plate, removal rates have reached lower values than while employing a
copper plate.
Evaluation of Cu and Pb Particles with Different Sizes as Regenerator Materials in the Gifford-McMahon-Cycle Refrigerator
Authors: Biwa Tetsushi , Ikuta Hiroshi , Mizutani Uichiro
Published: October 2002

The time-averaged enthalpy flow <\dotH> into the second-stage
expansion space was evaluated by analyzing the measured pressure
in the second-stage expansion space and temperature in the tube
connecting the regenerator and the expansion space. Pb and Cu
particles with diameters ranging from 0.2 to 1.0 mm were chosen
as the second-stage regenerator materials. <\dotH> was calculated
as a function of operating temperature for all these regenerator
materials. It was found that the magnitude of <\dotH> always
increases with decreasing operating temperature, and that <\dotH>
strongly depends on both the specific heat and the diameter of
the particles. We clearly show how <\dotH> depends on these two
parameters by analyzing the temperature profile in the second-stage regenerator. Heat loss <\dotQ
loss> was also evaluated by taking
the energy balance in the second-stage expansion space into
account.
X-Ray Fluorescence Analysis by Multiple-Glancing X-Ray Beam Excitation
Authors: Tsuji Kouichi , Sato Tasaku , Wagatsuma Kazuaki
Published: October 2002

Total-reflection X-ray fluorescence analysis is usually carried out
using a single X-ray beam to irradiate a sample surface at a glancing angle from one direction.
We have attempted to conduct X-ray fluorescence analysis using multiple glancing
X-ray beams emitted from a glow discharge X-ray tube. Fe characteristic X-rays were
used as the primary X-rays to irradiate a thin Cr film (sample) on a flat acrylic
carrier at multiple glancing angles. We have concluded that multiple X-ray beam excitation is an
effective method for enhancement of X-ray fluorescence intensity.
Thermo-Flow Structure and Epitaxial Uniformity in Large-Scale Metalorganic Chemical Vapor Deposition Reactors with Rotating Susceptor and Inlet Flow Control
Authors: Soong Chyi-Yeou , Chyuan Chung-Hsing , Tzong Ruey-Yau
Published: October 2002

The transport phenomena in large-scale metalorganic chemical vapor deposition (MOCVD)
reactors with a rotating susceptor are investigated by numerical simulation of thin-film epitaxial
growth of gallium arsenide. We are mainly concerned with the thermo-flow structure, its influence on
epitaxial growth rate, and the means of improving epilayer flatness. The effects of susceptor rotation
and thermo-flow conditions on gas flow, temperature and concentration fields are studied. The
present results show the flow structure and transport characteristics in various flow regimes. A
parameter map and the associated correlations of boundary curves of the flow-mode transition are
proposed. It is demonstrated that the epilayer flatness can be tuned either by properly controlling the
vortex strength in a rotation-dominated flow regime and/or by employing an inlet flow control
technique proposed in the present work.
Identification and Quantification of Transition Metal Impurities in Czochralski Silicon Wafers using Microwave Photoconductive Decay Lifetime Measurements
Authors: Kurita Kazunari , Shingyouji Takayuki
Published: October 2002

The identification of metallic impurities in p-type silicon has been studied using a microwave photoconductive decay lifetime measurement method at various high injection levels. The light illumination time and carrier injection level dependences of the recombination lifetime show unique characteristics for recombination centers attributed to Fe- and Cr-related levels. The clear identification of iron and chromium is achieved by analyzing the carrier injection level dependence curve and the light illumination time measured before and after the light illumination treatment.
Scanning Tunneling Microscopy Study of Faceting on Vicinal Si(113)
Authors: Koichi Sudoh Koichi Sudoh , Tatsuo Yoshinobu Tatsuo Yoshinobu , Hiroshi Iwasaki Hiroshi Iwasaki
Published: October 2002

Faceting on Si(113) surfaces misoriented towards a low-symmetry direction which is rotated by 57° from [332] to [110] has been studied using scanning tunneling microscopy. The faceting temperature of this surface is shown to be around 720°C, which is appreciably lower than those of the surfaces miscut towards the high-symmetry [332] direction. During faceting, the average terrace width varies as a power law versus annealing time with an exponent of ∼1/6 for temperatures of 600 and 650°C in agreement with previous results for surfaces miscut towards the [332] direction.
Temperature Dependence of the Initial Ageing of Dielectric Constant in a Lead Magnesium Niobate Based Ceramic
Authors: Wang Yu , Chan Yan Cheong , Gui Zhi Lun , Li Long Tu
Published: October 2002

The initial dielectric ageing behaviors of a doped Pb[Mg1/3Nb2/3]O3-based ceramic were investigated over a wide temperature range. The dielectric constant and logarithmic ageing time were regressed in terms of a linear relationship and the temperature dependence of ageing rate at different frequencies was obtained. The strongest ageing at a particular measurement frequency is confirmed to take place at the temperature of maximum dielectric constant of the deaged ceramic at that frequency. When the ageing temperature differs from this temperature, the ageing rate decreases. The curve of ageing rate against temperature, which is found to be symmetrical in shape, is fitted by a Gaussian equation. Microstructural factors responsible for the phenomenon are analysed.
Magnetic Properties of Ultrathin Co/Si(111) Films
Authors: Tsay Jyh-Shen , Yang Cheng-Shiuh , Yao Yeong-Der , Liou Yung , Lee Shang-Fan
Published: October 2002

The orientation of magnetization and the thickness of the
ferromagnetic inactive layer at the interface of Co film and Si substrate
in an ultrathin Co/Si(111) film have been studied. At the Si substrate
temperature of 120 K, Co films (≤10 monolayers) with in-plane easy axis
of magnetization have been successfully prepared. At the Si substrate
temperature of 300 K, ultrathin Co films (3.5–10 monolayers) with
canted out-of-plane easy axis of magnetization were observed. The
ferromagnetic inactive layers were formed at the interface due to the
intermixing of Co and Si; and were 2.8 monolayers thick for Co films
deposited at 300 K. However, their thicknesses were reduced to 1.4
monolayers when deposited at 120 K.
Analysis of InGaN High-Brightness Light-Emitting Diodes
Authors: Lee Song Jae
Published: October 2002

InGaN high-brightness light-emitting diodes (LEDs) have been analyzed. The analysis, based on non-absorbing ohmic electrode model, shows that InGaN LEDs have an extremely wide escape cone solid angle which is about 2.8 times that in conventional high-brightness LEDs. As a result, the external quantum efficiency in InGaN LEDs is as high as 9% despite the presumably very low internal quantum efficiency.
Quasi-CW Room Temperature Operation of 1.52 µm InGaAsP/AlGaAs Vertical Cavity Lasers Obtained by Localised Fusion
Authors: Syrbu A. V. , Iakovlev V. P. , Berseth C.-A. , Dehaese O. , Rudra A. , Kapon E. , Stark C. , Boucart J. , Gaborit F. , Jacquet J. , Sagnes I. , Harmand J. C. , Raj R.
Published: October 2002

1.52 µm double fused InGaAsP/AlGaAs vertical cavity surface emitting lasers with in-situ
built-in lateral current confinement were fabricated using localised wafer fusion process.
These devices operate at room temperature in quasi-CW regime at 10% duty cycle.
Operation characteristics of these lasers are limited by the high resistivity of p-InP/p-GaAs
fused junctions which is a result of using carbon-doped p-AlGaAs/GaAs
distributed Bragg-mirrors.
Phase Retrieval Microscope for Quantitative Imaging of a Weak Phase Object
Authors: Yohei Kamura Yohei Kamura , Shinichi Komatsu Shinichi Komatsu
Published: October 2002

Optical phase retrieval using the iterative Fourier transform algorithm has long been believed inadequate for the quantitative imaging of weak phase objects, but in this letter it is shown to be greatly improved by introducing the preprocess of Fourier intensity data as well as by adopting a cooled charge coupled device (C-CCD) camera to record the data. The preprocess consists of the addition of multiple data, the sensitivity correction of the C-CCD camera, and the modification of the Fourier intensity data with a Wiener optimal filter. The phase distribution of a very weak phase object ( maximum path difference of λ/32 ) is experimentally retrieved fairly well.
Acoustic and Ferro- and Antiferroelectric Properties near Phase Transition Temperatures of Modified PbZrxTi1-xO3-based Ceramics
Authors: Ochiai Tsutomu , Yokosuka Masaru , Mitsuhashi Hideto , Koyama Shoji , Sasaki Yukihiko
Published: October 2002

Acoustic and ferroelectric properties were obtained using an
ultrasonic pulse-echo-overlap method, a self-resonator method and
a composite-bar resonator method for ferroelectric ceramics
0.08(SrLa0.5Nb0.5O3)–0.92(PbZr0.53Ti0.47O3),
Pb0.902La0.098–(Zr0.55Ti0.45)0.976O3, Pb1-x
La
x
(Zr
y
Ti1-y
)1-x/4O3 and
x(BaCa1/3Nb2/3O3)–(1-x)(PbZr0.975Ti0.025O3). Ferro- and
antiferroelectric properties were also obtained for the last one.
Ultrasonic attenuations in some of these ceramics are discussed,
related to grain and domain symmetries observed through a
transparent electron microscope.
Computer Simulation of Core Structure and Stress Field of Edge Dislocations in C60 Crystals Using Girifalco Potential
Authors: Shigeru Tamaki Shigeru Tamaki , Naoki Ide Naoki Ide , Isamu Okada Isamu Okada , Kenichi Kojima Kenichi Kojima
Published: October 2002

The equilibrium molecular configuration around a 1/2[101](111) edge dislocation
in fcc C60 crystals
was calculated using molecular dynamics with
the Girifalco potential.
The dislocation was found to dissociate into
two Shockley partials.
The core of the partial dislocation was wider than that of
the screw dislocation
and its width was 17.5 times the Burgers vector.
The compressive stress at the core reached 0.74 GPa at maximum.
The extent of redshift of photoluminescence spectra was estimated.
Thin CoSi2 Formation on SiO2 with Low-Energy Ion Irradiation
Authors: Atsushi Matsushita Atsushi Matsushita , Taizoh Sadoh Taizoh Sadoh , Toshio Tsurushima Toshio Tsurushima
Published: October 2002

Cobalt silicides were formed by heat treatment and ion irradiation for stacked 7 nm Co and 25 nm Si layers on 20 nm SiO2 films.
Irradiation was performed with 25 keV Ar+ ions to a dose of 5 ×1015 cm-2 at sample temperatures between room temperature and 700°C.
The phase, atomic concentration profiles, and sheet resistance of the silicide layers were investigated as a function of the processing temperature.
X-ray diffraction measurement showed that the phase of CoSi2 was formed by irradiation at temperatures above 300°C, and X-ray photoelectron spectroscopy measurement revealed uniform distributions of Co and Si atoms with the atomic ratio of Co:Si=1:2 for samples irradiated at temperatures above 200°C.
Sheet resistance measurement showed that almost complete di-silicidation occurred by irradiation at 700°C.
It is concluded that the energy deposited by ions contributes to the migration of the species for silicidation at a lower temperature, and Co/Si mixed layers with an atomic ratio of 1:2 are easily obtained by irradiation of the stacked thin films with low-energy ions.
Since the silicide regions formed in the deposited thin films were decomposed during the irradiation at temperatures below 700°C, thermal annealing at 700°C is necessary to obtain completely uniform CoSi2 layers after the irradiation.
Influence of pH on the Morphology of KBr Solution Growth
Authors: Fujisaki Naohiro , Aikawa Fumihiro , Tsukamoto Takeyo , Kaneko Tsutomu , Futama Hideo
Published: October 2002

The morphodrom of KBr crystal, growing in aqueous solution, has been obtained as a function of pH and supersaturation, by means of in situ observation with an optical microscope. The habit of the crystal changed from cubic to octahedral with increasing pH and supersaturation. The growth rate along [100] increased with increasing pH, while that along [111] decreased. The preferential adsorption of hydronium ions on the {100} face and OH- ions on the {111} face, resulting in the restriction of the growth rates was proposed for the interpretation of the influence of pH on the change of crystal habit. In situ observation of the macroscopic growth step patterns on the {100} face supported this presumption for the influence of pH on its growth.
Epitaxial Growth of (Sr, Ba)Nb2O6 Thin Films by Pulsed Laser Deposition
Authors: Tanaka Katsuhiko , Nakagawara Osamu , Nakano Mitsuru , Shimuta Tooru , Tabata Hitoshi , Kawai Tomoji
Published: October 2002

Thin films of (Sr, Ba)Nb2O6 (SBN) were prepared on SrTiO3 (100) substrates by a
pulsed laser deposition and their crystallographic properties were investigated.
Epitaxially grown films with the c-axis perpendicular to the substrate were obtained at
substrate temperatures higher than 650°C in an oxygen atmosphere (containing 8% O3)
of 3 mTorr. An X-ray phi scan analysis indicates that the films have antiphase domains
in the c-plane and the relationship is SBN<100>//SrTiO3<310>. The lattice mismatch
between the film and the substrate is less than 1%, which contributes to the desirable
crystalline quality of SBN films. A smooth surface of roughness Rms=0.8 nm was
obtained by controlling the morphology of the initial growth layer in a two-step
deposition.
Direct Mapping of Reciprocal Lattice Rods of Metal-Induced Facet on Si(001) Surface
Authors: Urano Toshio , Takeda Yasushi , Ohtani Takuya , Tamiya Kenichi , Hongo Shozo
Published: October 2002

On Si(001) surfaces annealed at 700°C after the deposition of 1.5 monolayer (ML) of Ba at room temperature, facet spots were observed in addition to the 2×1 pattern of the Si(001) clean surface. These patterns were recorded using a TV camera and stored in a personal computer as an image. Line profiles were obtained on the line along which the facet spot moved. From these profiles the peak position of facet spots was extracted and superposed on a reciprocal lattice space to construct reciprocal lattice rods. From the angle of these rods to those of the Si(001) substrate, the facet is indicated to be a metal-induced Si(113) face.
Magnetically Enhanced Dual Frequency Capacitively Coupled Plasma Source for Large-area Wafer Processing
Authors: Wickramanayaka Sunil , Nakagawa Yukito
Published: October 2002

A magnetron-type plasma source of parallel plate configuration has been developed for large-area wafer processing in the semiconductor industry. In this plasma source there are 80 equally separated magnets arranged with alternative polarities on a 40-cm-diameter top rf electrode. These magnets generate magnetic field cusps below the top rf electrode. Since electrons that lie in the magnetic field cusps are confined, a lower self-bias voltage of the top rf electrode results. With this magnet arrangement, the E×B drifts of charged particles are limited to smaller localized areas and canceled out in macro-scale. Therefore, the radial uniformity of the plasma does not differ much from that of a nonmagnetic parallel plate capacitively coupled plasma source. The plasma density of this magnetron-type plasma source monitored at 1.3 Pa is above 1011 cm-3 for rf powers over 1000 W. The plasma nonuniformity over φ300 mm area is <±5% at the pressures below 4 Pa. Further, this magnet arrangement yields a magnetic-field-free environment for wafer processing in the close vicinity of the top rf electrode–a feature that cannot be seen in most of the magnetron-type plasma sources.
Real-time Impedance Matching by Frequency Feedback Control in Ion Cyclotron Range of Frequency Heating Experiments in JT-60U and Future Tokamaks
Authors: Moriyama Shinichi , Kimura Haruyuki , Fujii Tsuneyuki , Yamamoto Takumi , Saigusa Mikio
Published: October 2002

A frequency feedback control (FFC) system was designed and fabricated for, and
utilized in, an ion cyclotron range of frequency (ICRF) heating system in JT-60U. The
FFC was confirmed to be quite effective in maintaining the impedance matching between
the antenna and the transmission line of the ICRF heating system, to couple high RF
power continuously to a plasma with variable parameters in nuclear fusion experiments.
Calculations of the Rotational Lines and Their Strength for the Swan Band of C2 Molecules: A Study on the Degenerate Four Wave Mixing Spectrum
Authors: Won Hahn Jae-seok Ryu
Published: October 2002

Molecular constants of (0,0) and (1,0) bands of C2 are obtained for
the Hamiltonian formalism proposed by Zare et al. [J. Mol. Spectrosc. 46 (1973) 37].
Both a conversion method from
molecular constants of Brown's Hamiltonian formalism and a
nonlinear least-square-fit method are applied. The calculated
rotational lines match the results of experiment within
the range of 0.06–0.001 cm-1.
Using these molecular constants, the spectrum of degenerate four wave mixing
for (0,0) and (1,0) bands of C2 is
calculated at 3000 K for a line-shape function
of a Lorentzian cubed profile.
Surface Pretreatment of Bulk GaN for Homoepitaxial Growth by Metalorganic Chemical Vapor Deposition
Authors: Sato Hisao , Sugahara Tomoya , Hao Maosheng , Naoi Yoshiki , Kurai Satoshi , Yamashita Kenji , Nishino Katsushi , Sakai Shiro
Published: October 2002

Homoepitaxial growth of GaN on bulk GaN prepared by the sublimation method was performed by metalorganic chemical vapor deposition (MOCVD). Two kinds of bulk substrates were used for homoepitaxial growth: (i) a polished bulk GaN C-face, selectively grown on MOCVD-GaN on a sapphire (0001) substrate which was partly covered by SiO2 (“quasi-bulk” GaN) and (ii) a bulk GaN spontaneously nucleated on the source powder used in the sublimation method (“free-standing” bulk GaN). A smooth surface and strong CL band-edge emission from the homoepitaxial layer were obtained when proper surface pretreatment of the substrate, such as H3PO4 etching, RIE and photoassisted wet chemical etching (PAW), was adapted before loading into the MOCVD reactor. The CL intensity of the band-edge emission was stronger and the CL image more uniform for homoepitaxial GaN compared to that of heteroepitaxial GaN on sapphire. The dislocation density of the homoepitaxial layer was also decreased after proper surface treatment of the substrate.
Bi-Surface Photoconductivity Decay Analysis for Polysilicon Back Sealed Wafers with Thermal Process Induced Contamination
Authors: Daio Hiroshi , Uematsu Yugo , Ogita Yoichiro
Published: October 2002

Bi-surface photoconductivity decay (BSPCD) method has been developed to
investigate minority-carrier recombination lifetime property in silicon wafers
with variously finished surfaces. The lifetime analysis for thermally oxidized
n-type Czochralski (CZ) silicon wafers with and without a polysilicon back
seal (PBS) was carried out with the BSPCD method using 500 MHz-UHF wave
reflection. The surface recombination velocity of the PBS surface has been
first obtained to be ∼4000 cm/s. Moreover, the BSPCD study has revealed the
existence of the thermal process induced contamination contributing to the
bulk lifetime degradation and the PBS gettering performance for the
contamination.
Improving the Characteristics of Ultra-Thin-Film Fully-Depleted Metal-Oxide-Semiconductor Field Effect Transistors on SIMOX (Separation by IMplanted OXygen) by Selective Tungsten Deposition on Source and Drain Region
Authors: Sato Yasuhiro , Kosugi Toshihiko , Tsuchiya Toshiaki , Ishii Hiromu
Published: October 2002

Selective tungsten (W) chemical-vapor-deposition (CVD) with
hydrogenation and hydrogen-termination (HHT) is applied to ultra-thin-film
fully-depleted (FD) metal-oxide-semiconductor field effect transistors
(MOSFETs) on SIMOX (Separation by IMplanted OXygen) for reducing the sheet
resistance of source and drain regions. 0.25-µm-gate MOSFETs on SIMOX
(MOSFETs/SIMOX) with a top Si layer with a thickness of 50 nm are
fabricated using selective W-CVD, and their characteristics, including hot-carrier effects and latch-onset voltage, are systematically investigated.
It is found that selective W-CVD with HHT can reduce the source/drain (S/D)
sheet resistance in 50-nm-thick ultra-thin-film SIMOX to 10 Ω/sq. or less.
This ensures that W deposition increases the drain saturation current. It
is also found that W deposition largely suppresses the parasitic bipolar
effects. Consequently, the anomalous subthreshold slope diminishes, hot
carrier reliability improves, and the latch-onset voltage rises to over 2.5 V. Moreover, it is clarified that the parasitic bipolar effects are
largely suppressed when the W layer is within 0.3 µm from the source/body
junction. This is because W effectively extracts the holes generated by
impact ionization, and thus suppresses the accumulation of holes which
would otherwise induce an increase in the body potential.
Phase Diagram for Metalorganic Vapor Phase Epitaxy of Strained and Unstrained InGaAsP/InP
Authors: Kuphal Eckart , Pöcker Armin
Published: October 2002

The composition parameters x and y of In1-x
Ga
x
As
y
P1-y
/InP grown by low-pressure metalorganic vapor phase epitaxy (MOVPE) have been extracted from photoluminescence and X-ray diffraction by an iterative analysis using an improved gap energy function E
g(x, y) with strain correction. These x and y values were confirmed by electron probe microanalysis. Phase diagrams (vapor-solid relations) between the input partial pressures of the precursors and x and y have been established, which are linear for both the group-III and group-V elements. These simple functions are very useful for practical applications. The temperature and pressure dependences of the ratios of the distribution coefficients k
In/k
Ga and k
P/k
As were measured for two different Ga precursors (TMGa and TEGa). The growth rate of InGaAsP was calculated as a function of composition, and good agreement with the measurements was found. An analysis of strongly strained (≤1.3%) InGaAsP layers shows that the above established function E
g(x, y) and the vapor-solid relations are valid not only for nearly unstrained, but also for strongly strained compositions. The vapor pressure of TMIn was measured.
Investigation of Hydrogenated Amorphous Silicon Germanium Fabricated under High Hydrogen Dilution and Low Deposition Temperature Conditions for Stable Solar Cells
Authors: Shima Masaki , Isomura Masao , Maruyama Eiji , Okamoto Shingo , Haku Hisao , Wakisaka Kenichiro , Kiyama Seiichi , Tsuda Shinya
Published: October 2002

The effects of hydrogen dilution of up to 54:1 (=H2:SiH4) on hydrogenated amorphous silicon germanium (a-SiGe:H) were investigated while keeping the optical gap (E
opt) constant. It was found that deterioration of the film properties of a-SiGe:H due to a decrease in substrate temperature (T
s) can be compensated by the high hydrogen dilution method. As T
s decreases from 230°C to 180°C, the high photoconductivity [∼1×10-5 (Ω·cm)-1] and low silicon dihydride content (∼1 at.%) of a-SiGe:H can be maintained with a high hydrogen dilution ratio of 54:1, although these properties deteriorate with the conventional low hydrogen dilution ratio of 2.5:1. Probably, hydrogen radicals supply the energy required for the surface reaction during a-SiGe:H deposition which is lost when T
s is decreased. This tendency is useful for solar cell fabrication, especially for superstrate-type a-Si/a-SiGe tandem solar cells, because the decrease in the deposition temperature of a-SiGe:H for the bottom photovoltaic layer can reduce damage to the underlying layers caused by a high deposition temperature. As a result of applying this technique to the fabrication process of an a-Si/a-SiGe stacked solar cell submodule (area: 1200 cm2), the world's highest stabilized efficiency of 9.5% (light-soaked and measured at JQA) was achieved.
Characterization of Wave Propagation on Traveling-Wave Field Effect Transistors
Authors: Koichi Narahara Koichi Narahara , Taiichi Otsuji Taiichi Otsuji
Published: October 2002

The wave propagation characteristics along the electrodes of traveling-wave
field effect transistors (TW-FETs) are described. Due to the fine gate
structure of present high-speed FETs, the performance is greatly
influenced by the electromagnetic coupling between the gate line and
the drain line. No previous study has introduced a design method that can resolve this issue. The main purpose of this article is to clarify the characteristics of TW-FETs, and then, propose new design methods that cope with the coupling. The conditions under which TW-FETs yield ultrafast operation even with coupling are derived and then the results and implications of experimental investigations that measured the impulse response of a TW-FET using electro-optic sampling techniques are discussed.
Scalability of Gate/N- Overlapped Lightly Doped Drain in Deep-Submicrometer Regime
Authors: Shimizu Masahiro , Mitsui Katsuyoshi , Inuishi Masahide , Arima Hideaki , Hamaguchi Chihiro
Published: October 2002

In this paper an experimental study of the scalability of a gate/N- overlapped lightly doped drain (OL-LDD) structure in the deep-submicrometer regime is presented. Devices were optimized for processes with a design rule down to 0.15 µm. The allowable power
supply voltage is obtained by investigating the time-dependent dielectric breakdown reliability, the minimum operating voltage, the gate-induced-drain-leakage current, the drain-induced-barrier-lowering effect and the DC hot carrier reliability. It was found that the maximum allowable supply voltage is mainly limited by the DC hot carrier reliability even in the deep-submicrometer range. A higher current-driving ability in the OL-LDD structure is achieved in comparison to that in a single drain (SD) structure when V
Dmax is applied as a supply voltage. The OL-LDD structure has a smaller C
GD in the inversion region as well as in the accumulated region, as compared with the SD structure, especially with smaller L
G. Consequently, the performance of complementary metal-oxide-semiconductor (CMOS) devices with the OL-LDD structure is superior to that with the SD structure in the deep-submicrometer regime. It is also confirmed that the OL-LDD structure has a scaling merit even for 0.15 µm CMOS devices.
Process Optimization of Plasma-Enhanced Chemical Vapor Deposited Passivation Thin Films for Improving Nonvolatile Memory IC Performance
Authors: Lin Chi-Fa , Tseng Wei-Tsu , Feng Ming-Shiann
Published: October 2002

Characteristics of plasma-enhanced chemical vapor deposited (PECVD) SiO2/SiN
x

passivation layers are modified to improve and optimize electrical performances such as
program/erase cycle and hot carrier reliability of floating-gate nonvolatile memory devices.
SiH4/N2O gas mixtures are utilized as precursors for oxide CVD process. Higher SiH4/N2O
flow rate ratios render the resulting oxide films more silicon-rich, as manifested by their
higher refractive index (RI) and wet etch rates. These modifications in film characteristics
also correspond to increased program/erase cycles and lower % hot-carrier linear drain
current (I
dlin) degradation. An increase in RI from 1.520 to 1.675 translates to a rise in
program/erase cycles from 17.3 K to 32 K and a fall in I
dlin from 8.2% to 4.9%. Further
improvement in device performance is fulfilled by modifying the stoichiometry of the
overlying nitride passivation layer. Water diffusion from oxide and hydrogen release from
nitride are both responsible for hot carrier drain current degradation and loss in
program/erase cycles. The utilization of a high-RI oxide in conjunction with a low hydrogen
content nitride would give rise to the optimal device reliability.
Chemical-Vapor Deposition of OH-free and Low-k Organic-Silica Films
Authors: Yasutaka Uchida Yasutaka Uchida , Kohshi Taguchi Kohshi Taguchi , Tomonori Nagai Tomonori Nagai , Satoshi Sugahara Satoshi Sugahara , Masakiyo Matsumura Masakiyo Matsumura
Published: October 2002

A new sourcegas has been presented for quasi hydrogen-free chemical-vapor
deposition of organic-silica films.
The content of the methyl groups incorporated in
the film was as much as 25% of that of Si,
and the as-deposited film contained
only a few silanol and cyanate groups.
Thus it had good insulating characteristics
with a dielectric constant, k, as low as 3.5 even under
as-deposited conditions.
These characterisitcs were further improved by vacuum annealing. And,
the value of k became became 3.0 with a low-field
resistivity of more than 1015 Ωcm, after
500°C annealing.
Fe or Ni–Fe Alloy Coated Barium Ferrite Particles
Authors: Tung I-Chung , Yang Jyh-Shinn , Chin andTsung-Shune
Published: October 2002

Barium ferrite (BaFt) particles with Fe coating or Ni–Fe alloy
coating were prepared. To prepare the Fe coating, the BaFt particles (with
irregular shapes), about 900 nm in size, were directly reduced in a stream of hydrogen (at 1 atm). For the Ni–Fe alloy coating, the BaFt hexagonal
platelets, 200–500 nm in size, were dipped into a solution with a [Ni2+]/[Fe3+] molar ratio of 1/10, hydroxided by dripping 2 N NaOH solution onto the
BaFt particles, and finally reduced in a stream of hydrogen (at 1 atm). The results showed that the coercivity of BaFt particles could be reduced
significantly, while their saturation magnetizations were maintained at high
levels. With the Fe coating, the saturation magnetization of the BaFt
particles remained at about 63 emu/g, being comparable with that of pure
BaFt particles, 70 emu/g. With the Ni–Fe alloy coating, the saturation
magnetization of the BaFt particles was even higher than that of the pure
BaFt particles. Analytical calculations using micromagnetics were
successful in explaining the effect of the Ni–Fe coating on the coercivity of
coated BaFt particles. It was found that both surface reduction of BaFt and
Ni–Fe alloy coating contribute to coercivity decrement and magnetization
increment.
Facet-Coating Effects on the 1.3-µm Strained Multiple-Quantum-Well AlGaInAs/InP Laser Diodes
Authors: Lin Chia-Chien , Liu Kuo-Shung , Wu Meng-Chyi , Ko Sun-Chien , Wang Wei-Han
Published: October 2002

In this paper, we report the fabrication and characteristics of 1.3-µm strained multiple-quantum-well ridge-waveguide AlGaInAs/InP laser diodes
and the influence of reflective films on threshold current, slope efficiency, characteristic temperature and long-term reliability. A higher characteristic temperature and improved linearity of CW light-current characteristics can be obtained by increasing the facet reflectivity. With a high reflectivity coating of
70% on the front facet and 90% on the rear facet, the laser diodes exhibit a
high characteristic temperature of 92 K, an output power of 15 mW at 120°C, and only 0.7 dB slope efficiency drop at the output power of 30 mW and 20°C. Long-term aging was applied to test the facet-coating reliability using the
constant power mode of 10 mW at 85°C. The laser diodes have exhibited
stable operation up to 6000 h and no significant degradation has been
observed.
Polarization Anisotropy of Optical Gain in Two-Dimensional Photonic Crystals with Active Lattice Points
Authors: Nojima Shunji
Published: October 2002

Polarization anisotropic properties of optical gain are theoretically
investigated for the first time for photonic crystals with active lattice
points, in which all lattice points are made of the same gain material
embedded in other dissipative medium. The study of light scattering by
an isolated gain cylinder rod indicates that the reaction producing optical
gain for the light whose electric field is parallel to the rod axis always
occurs more strongly than that for the one perpendicular to it. This
anisotropy stems from the geometrical asymmetry of the rod. This
polarization anisotropy is taken over by the above photonic crystal, i.e.,
the periodic array of gain rods. In photonic crystals, however, the
anisotropy becomes more sensitive to the variation of the rod radius than
in an isolated rod. Morever, the polarization anisotropy is found to be
more pronounced for smaller rod radii or longer periods, indicating that
it is approximately determined soley by the filling rate of the rod. These
results can be regarded as a consequence of periodic arraying of multiple
gain rods.
Electrooptical Properties of Aligned Dye-doped Polymer Dispersed Liquid Crystal Films
Authors: Wu Jin-Jei , Wang Chih-Ming , Chen Wang-YangLi
Published: October 2002

We investigate how plane-parallel and twisted alignment treatments influence
the electrooptical properties of dye-doped polymer dispersed liquid
crystal (PDLC)
films. These films are transparent in the electric field-on state and opaque in the
field-off state. The relationship between field-off state transmittance of such dye-doped PDLC films and polarization of the incident light is discussed. Experimental
data confirm that, even for unpolarized incident light, the contrast ratio of these
aligned films surpasses that of a nonaligned dye-doped PDLC film.
Degradation of Photoluminescence and Electron Paramagnetic Defects in Naturally Oxidized or Oxygen-Implanted Porous Silicon with Electron Spin Resonance Imaging
Authors: Hiroshi Furuta Hiroshi Furuta , Chihiro Yamanaka Chihiro Yamanaka , Motoji Ikeya Motoji Ikeya
Published: October 2002

A spatial distribution of P
b centers in a disk of porous silicon measured using a microwave scanning electron spin resonance (ESR) microscope was compared with the image of photoluminescence (PL) observed using a charge-coupled device (CCD) camera. The intensity of PL had a negative correlation with ESR intensity of P
b centers having g
⊥=2.0092 and g
∥=2.0021 in the high-density area, while it was positively correlated with the low-density area. The generation process of P
b centers may accompany the production of radiative PL-related centers. The PL efficiency is decreased due to P
b centers acting as recombination centers leading to PL quenching. Oxygen ion implantation also decreased the PL intensity and produced dangling bonds having g=2.0056 and defects tentatively assigned as oxygen hole centers having g
1=2.0036, g
2=2.0064 and g
3=2.061 in porous silicon.
Electronic Structures of PbTiO3: I. Covalent Interaction between Ti and O Ions
Authors: Kaoru Miura Kaoru Miura , Masahiro Tanaka Masahiro Tanaka
Published: October 2002

We calculated the electronic structures of ferroelectric PbTiO3 using the discrete variational Xα cluster method.
From our investigation of the π bond between the titanium ion and the oxygen ion,
we found that
the role of lead ions is to bring about a spatial change in the oxygen 2p orbital by covalent interaction between oxygen 2p and lead 6s orbitals.
This change favours titanium ion displacement.
Moreover, from the investigation of the σ bond, we found that
the role of the Madelung potential is to cause
the spatial changes in the titanium orbitals; the long-range Coulomb interaction causes a stronger σ bond.
We conclude that the origins of ferroelectricity in PbTiO3 are (i) the spatial change in the oxygen 2p orbital due to covalent interaction between oxygen 2p and lead 6s orbitals and (ii) the spatial changes in the titanium orbitals due to the Madelung potential.
Effects of the Interfacial Layers on the Time-Dependent Leakage Current Characteristics of (Ba,Sr)TiO 3 Thin Films
Authors: Ahn Joon-Hyung , Lee Won-Jae , Kim Ho-Gi
Published: October 2002

Current-voltage characteristics and time-dependent leakage
current behavior of (Ba,Sr)TiO3 (BST) thin films deposited by rf
magnetron sputtering have been studied in order to identify the
effects of interfacial layers between bottom electrodes and BST thin
films on the leakage properties of BST capacitors. Two different
methods were used to modify the interfacial layers. One is the 2-step
deposition of BST thin films and the other is the preparation of BST
films on various bottom electrodes of RuO2, Pt and Pt/RuO2
hybrid layers. From a comparison of time-dependent electrical
properties of the BSTcapacitors prepared by the 2-step deposition
method with the various bottom electrodes, it was concluded that the
oxygen vacancies in the interfacial layer between BST films and the
bottom electrodes are responsible for the observed time-dependent leakage properties.
Phase Behavior of Nematic-Nonnematic Binary Systems: III. The Effect of Hydrogen Bonding Interaction
Authors: Asaba Kazunori , Igarashi Atsuko , Kobinata Shunsuke
Published: October 2002

For the binary mixtures of nematic 4-pentyl-4′-cyanobiphenyl (5CB) with
some kinds of nonnematic solutes, which showed `unusual' increase in nematic-isotropic
phase transition temperature compared with that of pure 5CB, we have
measured the temperature dependence of the IR dichroic ratio for several bands of 5CB
and of the solutes. The dichroic ratios and their temperature dependence distinctly
showed the presence of rather firmly hydrogen-bonded complexes in these binary
systems. We found some interesting results, e.g., the dichroic ratios for the –OH
stretching mode of phenol, which is hydrogen bonded to the –CN group of 5CB, and for
p-ethyl benzoic acid were larger than the dichroic ratio of the –CN band. The
temperature dependence of the second-order parameters derived from IR dichroic ratios
was analyzed based on a Maier-Saupe-type mean field theory.
Synthesis of Carbon Nanotubes by Arc Discharge in CF4 Gas Atmosphere
Authors: Yokomichi Haruo , Matoba Masaaki , Sakima Hiroyuki , Ichihara Masaki , Sakai Fumiko
Published: October 2002

Carbon nanotubes were synthesized by arc discharge in a CF4 gas atmosphere
involving fluorine atoms, which are able to terminate carbon bonding, while no fullerenes
were synthesized in a CF4 gas atmosphere. The morphology of these nanotubes was
investigated by scanning electron microscopy (SEM) and transmission electron
microscopy (TEM). Based on these results, the synthesized conditions in CF4 gas were
compared with those in other gases, i.e., in CH4, H2, He and Ar gases. In addition,
electron spin resonance (ESR) measurements were performed in order to obtain
information about the electronic properties of these nanotubes.
Epitaxial Growth of Ferroelectric YMnO3 Thin Films on Si (111) Substrates by Molecular Beam Epitaxy
Authors: Shogo Imada Shogo Imada , Shigeto Shouriki Shigeto Shouriki , Eisuke Tokumitsu Eisuke Tokumitsu , Hiroshi Ishiwara Hiroshi Ishiwara
Published: October 2002

Ferroelectric YMnO3 thin films are grown on Si (111) substrates using Y2O3 buffer layers by molecular beam epitaxy (MBE). In situ reflection high-energy electron diffraction (RHEED) analyses show that both Y2O3 and YMnO3 films are epitaxially grown on Si substrates. X-ray rocking curve measurements also show that the best full-width at half maximum (FWHM) values for Y2O3 and YMnO3 films are 0.4° and 1.5°, respectively. Concerning the electrical properties, capacitance–voltage (C–V) characteristics of Al/YMnO3/Y2O3/Si structures indicate the ferroelectric properties of YMnO3 films with a memory window of 0.3 V.
Atomic-Configuration-Dependent Energy at Epitaxial Silicide-Silicon Interfaces
Authors: Kikuchi Akira
Published: October 2002

Equilibrium energy and the misfit-dislocation density of transition-metal silicide (tmSi)–Si systems are calculated as a function of the lattice mismatch (Δa) between tmSi and Si. For same thick tmSi films, the total energy of a type-B tmSi–Si system is found to be always lower than that of a type-A tmSi–Si system, especially when the tmSi films are thick. This is in good agreement with the experimental results indicating that the type-B film is a thermodynamically more favorable atomic structure at the NiSi2– and CoSi2–Si interfaces. The misfit-dislocation density increases with increasing Δa, whereas the equilibrium energy of type-B tmSi–Si is represented by a curve with a maximum near Δa=2%.