bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Image Shortening for Rectangular Array Patterns in X-Ray Lithography
Authors: Mitsui Soichiro , Tanaka Yuusuke , Taguchi Takao , Hisatsugu Yoshio Gomei andTokushige
Published: October 2002

The image shortening of rectangular array patterns replicated by proximity X-ray lithography was investigated.
The shorter pattern width was 100 to 200 nm, and shortening on the longer side was
studied. Either a negative or positive tone of the mask was used. The experimental results were compared with the absorbed dose distribution calculated using ToolSet developed at the Center for X-ray Lithography (CXrL). The geometrical features of mask patterns, such as absorber side-wall angle, corner rounding, and pattern resize were taken into account. It
was found that image shortening is greater with negative tone masks, while
negative tone masks provide higher resolution than positive tone masks. It was also found that the slope of the absorber side wall plays an important role in image shortening. The results suggest that the use of negative tone masks, careful tailoring of the absorber side wall, and proper pattern resizing will provide required dimensions for rectangular array patterns.
Photoresist Exposure Parameter Extraction from Refractive Index Change during Exposure
Authors: Sohn Young-Soo , Sung Moon-Gyu , Lee Young-Mi , Lee Eun-Mi , Oh Jin-Kyung , Byun Sung-Hwan , Jeong Yeon-Un , Oh Hye-Keun , An Ilsin , Lee Kun-Sang , Park In-Ho , Cho Joon-Yeon , Lee Sang-Ho
Published: October 2002

The refractive indices of photoresist are usually measured by
an ellipsometer or spectrophotometer, but the values are limited to pre-exposure. It is known that
the real and imaginary indices are changed during the exposure.
But there is little report on these variations since it
is difficult to measure this refractive index change at deep ultraviolet. The Dill
A
B
C parameters show a significant variation with the resist and substrate thickness
as well as the experimental conditions.
A method is suggested to extract the parameters from the refractive index changes.
We can get the refractive index change and extract the Dill A
B
C exposure parameters from that.
The multiple thin film interference calculation is used to fit the measured transmittance data.
The results of our experiments and calculations for several resists including
193 nm chemically amplified resists are compared with other methods.
The results are agreed well with the full multilayer thin film simulation.
Synthesis and Characterization of Alicyclic Polymers with Hydrophilic Groups for 193 nm Single-Layer Resist
Authors: Jung Min-Ho , Jung Jae-Chang , Lee Geunsu , Baik Ki-Ho
Published: October 2002

A novel substituted alicyclic polymer for a 193 nm resist has been developed. The goal was to
enhance the adhesion to Si substrates while ensuring compatibility with a tetramethylammonium
hydroxide (TMAH) developer for our polyolefin resist. We designed alicyclic polymers
including hydrophilic groups to improve the adhesion property. The hydrophilicity of the
hydroxy group affords good adhesion of the formulated resist patterns to Si substrates. We have
synthesized an ArF polymer resin, poly(2-hydroxyethyl 5-norbornene-2-carboxylate/t-butyl
5-norbornene-2-carboxylate/5-norbornene-2,3-dicarboxylic acid/maleic anhydride), in which all
of the main chains are composed of alicyclic units. 2-Hydroxyethyl 5-norbornene-2-carboxylate
and 5-norbornene-2,3-dicarboxylic acid were found to be very suitable adhesion and
sensitivity promoters, respectively. A 0.12 µm L/S (lines/spaces) pattern was obtained at
14 mJ/cm2 doses, using an ArF stepper on the developer and 2.38 wt% TMAH aqueous solution.
The Effect of Ar+ Ion Bombardment on SiO2 Aerogel Film
Authors: Kim Hong-Ryul , Park Hyung-Ho
Published: October 2002

Ar+ ion bombardment on SiO2 aerogel films was introduced to
investigate the physical collision effect of oxygen plasma treatment on the
films. The changes of internal surface adsorbing species and microstructure
in the films were analyzed through the treatments. Through chemically inert
Ar+ ion bombarding treatment, internal surface organic groups were
partially removed. A slight increase in surface particle size was observed,
which results from the condensation of SiO2 particles due to the
elimination of internal surface adsorbing organics. According to the
increase in the accelerating voltage of Ar+ ion, the reduction of film
thickness became larger than that observed with oxygen plasma treatment. The
film thickness is maintained uniform with varying the treatment time and
this confirms that there is no measurable etching happened within our
treatment conditions. From these it is confirmed that a collapse of
3-dimensional network structure of SiO2 aerogel film was happened
though Ar+ ion bombarding treatment.
Hydrogen Effects on Heteroepitaxial Growth of Ge Films on Si(111) Surfaces by Solid Phase Epitaxy
Authors: Masahisa Okada Masahisa Okada , Akiyoshi Muto Akiyoshi Muto , Isao Suzumura Isao Suzumura , Hiroya Ikeda Hiroya Ikeda , Shigeaki Zaima Shigeaki Zaima , Yukio Yasuda Yukio Yasuda
Published: October 2002

The influences of hydrogen atoms on Ge heteroepitaxial growth on
Si(111) surfaces using solid phase epitaxy (SPE) have been investigated
by scanning tunneling microscopy (STM).
In the SPE growth of Ge films on H-terminated Si(111) surfaces, the formation of
3-dimensional (3D) Ge islands
are suppressed.
With the desorption of H atoms, the 3D islands appear on the Ge surface,
which are considered to be formed by the agglomeration of Ge atoms.
The density of the islands is decreased and the size of the islands is increased
by the existence of Si-H bonding at the Ge/Si interface.
These phenomena are considered to be caused by the release of the stress in the Ge
film and the weakening of the interaction between the Ge film and the Si
substrate by Si–H bonding.
In addition, the activation energy of the migration of Ge atoms during
the agglomeration is determined to be 0.3 eV.
New Method for Estimation of Grain Boundaries Contribution to Resistance of Highly Doped Polysilicon
Authors: Spoutai Serguei , Chun Hui-Gon , Ahn Kang-Ho
Published: October 2002

The authors propose a new method for estimation of the
contribution of the grain boundaries (GB) to the total resistance of
highly doped polysilicon resistors. The method is based on the
technique known as “current trimming". The resistance of the polysilicon resistor and its temperature coefficient is measured before and
after application of current pulses: on the basis of obtained changes
in those parameters the share of the resistance attributed to the
grain boundaries as well as the temperature coefficient of grain boundaries' resistance are deduced. The experiments
were carried out on the resistors patterned in the 625°C
LPCVD polysilicon doped by ion implantation of Boron and annealed at
1050°C for 30 min in a dry oxygen atmosphere. The properties
were estimated in the doping range from 4×1025 to
1.2×1026 m-3. The method can be extended to other polycrystalline materials.
Thin Film Growth and Surface Modification by keV Ion Beam
Authors: Choi Sung-Chang , Park Yong-Wook , Choi Won-Kook , Kim Ki-Hwan , Cho Jun-Sik , Han Sung , Cho Jung , Jung Sun , Han Young-Gun , Yoo Byong-Kook , Jung Hyung-Jin , Koh Seok-Keun
Published: October 2002

High-quality ZnO film and highly wettable polymethylmethacrylate (PMMA) are
obtained by using a keV ion beam. ZnO films are grown on glass substrates by ion
beam sputter deposition, changing the oxygen/argon gas ratio, ion beam energy, and
substrate temperature. Physical properties of ZnO films were investigated by X-ray
diffraction, Rutherford backscattering spectroscopy, and the Van der Pauw method. All
the films show a strong preferred orientation along the c-axis. The electrical resistivity
is varied from 10-3 to 106 Ωcm and its dependence on the deposition parameters is
discussed. The PMMA surface was modified by the ion-assisted reaction technique. Ion
dose, ion energy, and oxygen gas flow rate are varied from 5×1015 to 1×1017 ions/cm2,
from 0.6 to1.2 kV, and from 0 to 8 ml/min, respectively. A highly wettable PMMA
surface can be obtained by irradiating oxygen ions in an oxygen gas environment. X-ray
photoelectron spectroscopic analysis shows that hydrophilic groups are formed on the
surface of PMMA.
Electrical Properties of Electron-Beam Exposed Silicon Dioxides and Their Application to Nano-devices
Authors: Ho Choi Bum , Koo Jung Suk , Il Kim Suk , Woo Hwang Sung , Ho Park Jung , Kyu Kim Yong Kim , Ki Min Suk
Published: October 2002

Electrical properties of the electron-beam induced carbon contamination layers have been reported.
Contacts to the contamination layers are achieved by a simple deposition of aluminum and the
current-voltage characteristics are successfully measured. A double junction structure, with the
size smaller than 10 nm, has been fabricated by a one-step electron beam irradiation and it
exhibits Coulomb staircases at room temperature.
Analysis of High-Acceleration-Voltage Scanning Electron Microscope Images
Authors: Moniwa Akemi , Terasawa Tsuneo
Published: October 2002

Scanning electron microscope (SEM) images of holes or trenches obtained at high
acceleration voltages, such as 200 kV, are analyzed by computer simulation.
Secondary
electrons generated by forward-scattered primary electrons (SE1s), and
those by
backward-scattered primary electrons (SE2s) are calculated separately,
although a
detector catches both SE1 and SE2 without distinction. The straightforward
penetration of the primary electrons accelerated at 200 kV gives large edge
effects and
slight lateral scattering in the sample. Therefore, the image contrast of the SE1 intensity, which provides information on surface topography, becomes high. Moreover,
as the SE2 intensity is almost a uniform background, it becomes easy to
extract the SE1
intensity from the detected secondary electrons. For observations of the
inside structure
of a sample, although the SE2 contrast is low at 200 kV, a small degree of
lateral
scattering in the sample results in a sharp image.
Micro Electro Mechanical Systems: From Research to Applications
Authors: Lang Walter , Sandmaier Hermann
Published: October 2002

Micro electro mechanical systems (MEMS) are in the transition phase from research
to industry. This paper intends to describe this process from the point of view of a
European R&D institution. The MEMS market, its development and its most
important products are discussed. In the second part, the R&D activities at HSG-IMIT in Germany are described. The last chapter deals with the cooperation between
the R&D institution and industry, in particular with local German small-and medium-sized enterprises.
Fabrication of a New Field Emitter Array with a Built-in Thin-Film Transistor on Glass
Authors: Gamo Hidenori , Kanemaru Seigo , Itoh Junji
Published: October 2002

We have designed and fabricated a new amorphous-silicon (a-Si) field
emitter array (FEA) monolithically integrated with a thin-film transistor (TFT)
on glass. In this FEA, a TFT was made of a-Si film deposited on a glass
substrate with a chromium insertion electrode. A-Si emitter tips were formed
on the drain of the TFT. The gate was separated into two parts: one was
biased to about 140 V and used as an extraction gate for field electron emission,
and the other was used as a conventional TFT gate to control the drain current,
that is, the emission current. From the experimental results obtained using a
1000-tip FEA, the emission characteristics were found to be well controlled and
stabilized by the TFT. The emission current of approximately 0.05 µA and
with fluctuations of less than 1% was achieved at the extraction and the TFT
gate voltages of 140 V and 30 V, respectively.
Fabrication of Self-Assembled GaAs/AlGaAs Quantum Dots by Low-Temperature Droplet Epitaxy
Authors: Joo Lee Chae-Deok Lee , Gyung Park Kyu-Seok Lee , Kyu Noh Sam , andNobuyuki Koguchi andNobuyuki Koguchi
Published: October 2002

The fabrication of nanometer-scale GaAs dots on AlGaAs layer by molecular beam epitaxy was
demonstrated. Unlike the stress-driven transition of the three-dimensional growth mode in the
lattice-mismatched system, the limited migration of Ga droplets on the AlGaAs
layer grown at low substrate temperature was exploited to give rise to the formation of
three-dimensional GaAs islands. The resulting GaAs dots show crater-like features
having {111} facets. In micro-photoluminescence measurements of the
buried structures, the emission spectra were clearly observed, and the
sharp lines of the spectra might be considered as the exciton
emissions from individual dots with various sizes.
Fabrication of InP Submicron Pillars for Two-Dimensional Photonic Crystals by Reactive Ion Etching
Authors: Hatate Hitoshi , Hashimoto Masayuki , Shirakawa Hirofumi , Fujiwara Yasufumi , Takeda Yoshikazu , Nakano Hirohiko , Tatsuta Toshiaki , Tsuji Osamu
Published: October 2002

We have fabricated periodic arrays of InP pillars for two-dimensional (2D) photonic crystals by reactive ion etching (RIE) with SiCl4/Ar inductively coupled plasma (ICP) and Cl2 electron cyclotron resonance (ECR) plasma chemistry. Prior to the fabrication of the arrays, photonic band structures for electromagnetic waves are calculated theoretically, and photonic band gaps are predicted to appear in the optical wavelength region. Periodic arrays of InP micron pillars with fairly smooth etched surfaces are fabricated by ICP-RIE with SiCl4/Ar. The reflective properties of the arrays have been characterized in the optical wavelength region by Fourier-transformed infrared reflection absorption spectrometry (FTIR-RAS). FTIR-RAS spectra of the arrays exhibit characteristic features such as a blue shift with decreasing period of pillars. In ECR-RIE, we systematically investigate InP etch characteristics as functions of various etching parameters, and successfully fabricate periodic arrays of vertical submicron pillars with smooth surfaces.
A High-Performance Polycrystalline Silicon Thin-Film Transistor Using Metal-Induced Crystallization with Ni Solution
Authors: Yoon Soo Young , Kim Sung Ki , Oh Jae Young , Choi YoungJin , Shon Woo Sung , Kim Chae Ok , Jang andJin
Published: October 2002

A new fabrication process
for polycrystalline silicon (poly-Si) thin-film transistors (TFTs)
on glass substrate is reported.
Amorphous silicon (a-Si) was crystallized
by metal-induced crystallization (MIC)
using a Ni solution for low-temperature crystallization.
The a-Si film spin-coated
with a 5000 ppm Ni solution
was fully crystallized at 500°C.
The poly-Si TFT made of the poly-Si
exhibited a field-effect mobility of 105 cm2/Vs
and a threshold voltage of -4 V.
The high performance of the poly-Si TFT
appears to be due to the absence of intragrain microdefects in the poly-Si,
which is confirmed
from the plane-view TEM image.
Absorption of InGaN Single Quantum Wells Determined by Photothermal Deflection Spectroscopy
Authors: Ambacher O. , Brunner D. , Dimitrov R. , Stutzmann M. , Sohmer A. , Scholz F.
Published: October 2002

Photothermal deflection spectroscopy (PDS) is used to study the absorption of GaN/InGaN/GaN double heterostructures in the energy range from 0.6 to 3.8 eV. The heterostructures containing 1–77-nm-thick InGaN single quantum wells were deposited by chemical vapour deposition from organometallic precursors. They are measured to investigate the absorption coefficient, bandgap, indium concentration and fluctuation of the quantum wells. A bandgap increase of hexagonal In
x
Ga1-x
N (x≈0.14) of 60 meV is observed with decreasing well thicknesses from 15 to 1 nm. The distribution of In-concentration of the In
x
Ga1-x
N layers was estimated from the slope of the absorption coefficient versus photon energy for energies below the bandgap and found to be Gaussian with a full width of half maximum of Δx=0.03.
Spin Dependent Luminescence of GaAs Thin Layers under Tensile Strain and Compressive Strain Induced by Interface Stress
Authors: Zhen Wendong , Horinaka Hiromichi , Wada Kenji , Nakanishi Tsutomu , Okumi Shoji , Saka Takashi , Kato Toshihiro
Published: October 2002

Luminescence polarization was measured on two types of samples of p-GaAs thin layers grown on p-In1-x
Ga
x
P thick layers: one had uniaxial tensile strain and another had uniaxial compressive strain caused by the lattice mismatch. The GaAs layer under compressive strain exhibited luminescence polarization opposite to that exhibited under tensile strain at the shifted band edge. The residual internal strains were estimated from wavelengths of the peak and the dip of the photoluminescence polarization spectra.
Studies on the Structural Transformation of Pt Clusters with Adsorbed Hydrogen on α-Al2O3(0001) Using Multiple Scattering Approach to Pt L3-edge Polarized X-Ray Absorption Near Edge Structure Spectra for the Pt Cluster
Authors: Ohtani Kunihiro
Published: October 2002

The X-ray absorption near edge structure (XANES) or the Extended X-ray absorption fine structure (EXAFS) study with polarization dependence is useful for determining the structures of the metal clusters. We have calculated Pt L3-edge XANES spectra for various structures of Pt clusters with adsorbed hydrogen, such as the one-layer-thick raft, and the hemispherical and spherical structures on α-Al2O3(0001), using the full multiple scattering approach. Comparison of the calculated results with the experimental results have yielded important information. With an increase in the spherically symmetric character of Pt clusters, the influence of Pt-support interaction on the XANES spectra decreases, that is, the hydrogen-Pt interaction plays a dominant role in such cases. We expect that Pt clusters with the one-layer-thick raft, or hemispherical structures are on the top site of surface oxygen atoms.
Pt/RuO2 Hybrid Bottom Electrodes and Their Effects on the Electrical Properties of (Ba, Sr)TiO3 Thin Films
Authors: Ahn Joon-Hyung , Choi Gwang-Pyo , Lee Won-Jae , Kim Ho-Gi
Published: October 2002

Thin platinum layer of 100 Å thickness was used for the modification of the interface state between (Ba, Sr)TiO3 (BST) thin films and RuO2 bottom electrodes. Pt/RuO2 hybrid bottom electrodes were fabricated with various platinum deposition temperatures by a conventional dc magnetron sputtering method. Although the surface morphology and X-ray diffraction (XRD) patterns of BST thin films were not changed, the electrical properties of BST films deposited on Pt/RuO2 hybrid electrodes were improved compared to the films on RuO2 electrodes. Dielectric constant (ε
r) and leakage current density of the 1000 Å thick BST thin films on Pt/RuO2 hybrid electrodes prepared at the platinum deposition temperature of 400°C were 498 and 8.6×10-8 A/cm2 at 1.5 V, respectively.
Electron Spin Relaxation Dynamics in InGaAs/InP Multiple-Quantum Wells
Authors: Tackeuchi Atsushi , Wada Osamu
Published: October 2002

The electron spin relaxation of InGaAs/InP multiple-quantum wells is investigated at room temperature using time-resolved polarization-dependent absorption measurements. The spin relaxation time is dependent on the quantum confined energy, E
1e, according to τs∝E
1e
-1. The dependence differs from that of the D'yakonov-Perel' interaction, which governs the spin relaxation of GaAs quantum wells at room temperature, and suggests the possibility of the existence of an additional spin relaxation mechanism.
Production of Large-Diameter Microwave Plasma with a High-Permittivity Material Window
Authors: Furukawa Masakazu , Saito Naoki , Kawamura Katsufumi , Koromogawa Takashi , Shindo Haruo
Published: October 2002

As a large-diameter plasma generation method for ultralarge-scale integrated (ULSI)
circuit processes, microwave plasma production was studied by employing a high-permittivity material window. The plasma parameters were examined in conjunction with
the permittivity of the dielectric window material. The results revealed that the alumina
window with higher permittivity provided higher electron density in both Ar and O2
plasmas. Since this dependence was only seen in the regime above the cut-off density of
2.45 GHz microwave, it was concluded that the plasma production was due to the
surface-wave mode. The method was emphasized to be promising in producing a large-diameter plasma for ULSI processes.
Formation of Carbon-Related Defects During the Carbon-Enhanced Annihilation of Thermal Donors in Silicon
Authors: Yoichi Kamiura Yoichi Kamiura , Takashi Maeda Takashi Maeda , Yoshifumi Yamashita Yoshifumi Yamashita , Minoru Nakamura Minoru Nakamura
Published: October 2002

We observed that a defect related to carbon and phosphorus was formed during the carbon-enhanced annihilation of thermal donors at 470°C in silicon. We determined, using deep-level transient spectroscopy (DLTS), that the defect has a deep level at E

c
-0.36 eV and its density has positive correlation with carbon and phosphorus densities. The formation rate of the defect is proportional to the phosphorus density. We also observed the 767 meV photoluminescence line (P-line) that had been identified as the complex with a core of interstitial carbon, vacancy and oxygen dimer. We tentatively ascribe the E

c
-0.36 eV defect to the pair of interstitial carbon and substitutional phosphorus.
Residual Strain Dependence of Stimulated Emission in GaN Layers Grown on (0001) Sapphire Substrates
Authors: Funato Kenji , Nakamura Fumihiko , Hashimoto Shigeki , Ikeda Masao
Published: October 2002

We have grown 1.5 µm-thick GaN layers on (0001) sapphire substrates by metalorganic chemical vapor deposition with various flow rates of trimethylgallium. The lattice constants a and c in the layer were estimated by X-ray diffraction.
The threshold power density for stimulated emission was measured by photopumping the layers. It was found that the grown layers were elastically deformed and that the residual strain can be sustained by decreasing the flow rate of trimethylgallium.
It was also found that the threshold power density of stimulated emission decreases as the lattice constant a decreases. This tendency indicates that the strain relaxation mechanism is associated with enhancement of nonradiative recombination.
Effects of Degree of Dissociation on Aluminum Etching in High-Density Cl2 Plasmas
Authors: Samukawa Seiji , Donnelly Vincent. M.
Published: October 2002

At the same input power (1000 W), inductive coupled plasma (ICP) and ultrahigh-frequency
(UHF) plasma sources produced electron densities of 1 ×1011 cm-3 at 3.5 mTorr, yet the
UHF plasma was much less dissociated (30%) than the ICP plasma (70%). This can be attributed
to differences in the electron energy distribution functions in the UHF and ICP plasmas, especially
at low pressure. Under these conditions, Al etching profiles were investigated to understand the
influences of the degree of dissociation on the etching reactions. UHF plasmas could completely
accomplish anisotropic etching with just Cl2 as the feed gas, whereas the ICP produced isotropic
etching profiles under the same conditions. This implies that the degree of dissociation strongly
influences etching of the Al sidewall, as well as the anisotropic etching rate in a high density Cl2 plasma.
Optical Pulse Generation from a Frequency Modulated Er-Doped Fiber Laser by Frequency Filtering
Authors: Sarwar Abedin Noriaki Onodera , Masaharu Hyodo Masaharu Hyodo
Published: October 2002

An optical pulse train with a repetition rate in the gigahertz range has been successfully generated by an FM fiber ring laser that uses an optical circulator and a fiber grating for frequency filtering. The FM laser generates optical output with maximum chirping rate of more than 1.3×1021 Hz/s under intracavity phase modulation at 3.3 GHz. By shifting the frequency filtering window of fiber grating, the pulse repetition rate can be doubled, and optical pulses with a repetition rate of 6.6 GHz rate are obtained.
The Effect of Acceleration Voltages on the Preparation of CuInSe2 Thin Films by Ionized Cluster Beam Technique
Authors: Sano Hiroyuki , Ishibashi Takayuki , Sato Katsuaki
Published: October 2002

Polycrystalline CuInSe2 thin films were prepared on Mo-coated soda-lime glass
substrates by the ionized cluster beam (ICB) technique, in which Cu, In and Se vapors
were ionized and accelerated. The dependence of the film properties on acceleration
voltage were studied. The substrate temperature was maintained below 350°C. The films
were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM),
an electron-probe microanalyzer (EPMA) and the Rutherford backscattering
spectrometry (RBS). It was found that polycrystalline films with improved grain size and
uniformity were obtained when the acceleration voltage exceeded 4 kV, and the
acceleration voltage played an important role in the formation of the ternary compound
during the crystal growth.
Cubic Boron Nitride Film Synthesis by Reactive Sputtering of Pure Boron Target in Electron Cyclotron Resonance Plasmas
Authors: Masayuki Wakatsuchi Masayuki Wakatsuchi , Yoshiro Takaba Yoshiro Takaba , Yoshio Ueda Yoshio Ueda , Masahiro Nishikawa Masahiro Nishikawa
Published: October 2002

Cubic boron nitride (c-BN) thin films are synthesized by reactive
sputtering.
Pure boron is used as the sputtering target, which is dc-biassed in an
Ar/N2 electron cyclotron resonance plasma.
Substrates are rf-biased with a frequency of 13.56 MHz.
BN films with a dominant cubic phase are obtained in the case of a high
ion-to-boron flux ratio of 12 at the substrate self-bias higher
than -175 V; the transferred momentum per atom is about 1260 (eV
amu)1/2, which is larger than the value predicted using the
momentum transfer model for c-BN synthesis by a factor of 4.
An intermediate layer between the c-BN layer and the substrate
improves the adhesion of the c-BN layer and prevent a exfoliation.
This intermediate layer is deposited under an Ar/N2 gas mixing
ratio of 9 without rf bias.
New Radical-Control Method for SiO2 Etching with Non-Perfluorocompound Gas Chemistries
Authors: Samukawa Seiji , Tsuda Ken-ichiro
Published: October 2002

To control radical generation in the etching of silicon dioxide, we propose a new radical control method using the iodofluorocarbon chemistries in ultra-high-frequency (UHF) plasma we developed.
In the UHF plasma, the mean electron energy is about 2 eV and there are a small number of high-energy electrons. The plasma can only dissociate C-I bonds (2.0 eV) in the iodofluorocarbon plasma (CF3I,
C2F5I) and it mainly generates CF3 and CF2 radicals. The ratio of each radical density can then be precisely controlled by changing the ratio of the mixture of CF3I and C2F5I.
As a result, etching selectivity and microloading effects are drastically improved. The iodofluorocarbon species are also alternatives to perfluorocarbon chemistries (PFCs) from an environmental standpoint.
Photoluminescence Visible at 77 K from Indirect-Gap AlxGa1-xAs Grown by Organometallic Vapor Phase Epitaxy
Authors: Kakinuma Hiroaki
Published: October 2002

We have observed two intense photoluminescence bands in the energy range of 1.84 to 1.98 eV
for indirect-gap p-type Al
x
Ga1-x
As. They are extraordinarily intense (visible at 77 K) for
indirect recombination. Their full-widths at half maximum are relatively broad (30–60 meV).
Their peak energies and relative intensities depend on the type of sample used (x, undoped,
intentionally C-doped or annealed). Their intensities increase superlinearly with increasing
excitation intensity, which is indicative of exciton recombination. These bands are absent for
slightly Si-doped n-type materials. The origin of these strong emissions is also discussed.
Susceptor-Based Rapid Thermal Processing System and Its Silicide Application
Authors: Yoo Woo Sik , Atanos Ashur J. , Daviet Jean-Francois
Published: October 2002

The design concept and hardware configuration of a constant heat source, susceptor-based
dual wafer rapid thermal processing (RTP) system are described. The temperature
measurement/control techniques and thermal characteristics of the RTP system are
described. Typical process results in CoSi and TiSi formation using the RTP system are
reported. Change in sheet resistance uniformity before and after RTP steps and wafer-to-wafer
temperature repeatability were kept below 0.5% and 1°C, respectively, in both
processes. Due to the dual wafer process capability and steady state temperature control, a
very high throughput at a minimal power consumption was realized. Many thermal
processes used in furnaces can easily be converted to RTP processes without decreasing
cost performance and/or deteriorating process results by using the RTP system.
Time-Dependent Leakage Current of BaSrTiO3 Film under High Temperature Bias Stress
Authors: Yamabe Kikuo , Inomoto Minoru , Imai Keitaro
Published: October 2002

Time-dependent leakage currents are investigated under high voltage
stress to BaSrTiO3 thin film at high temperatures. Under the
application of negative gate stress, the leakage current increases once and
decreases after reaching the maximum point. Under the application of
positive gate stress, the leakage current steeply increases after a given time.
Based on current-voltage characteristics observed following the
application of positive and negative stresses and current-time
characteristics at low voltage, the degradation mechanism is discussed.
Thermal Stability of Low-Temperature GaN and AlN Buffer Layers During Metalorganic Vapor Phase Epitaxy Monitored by In Situ Shallow-Angle Reflectance Using Ultraviolet Light
Authors: Kobayashi Yasuyuki , Akasaka Tetsuya , Kobayashi Naoki
Published: October 2002

The thermal stability of low-temperature (LT) GaN and AlN buffer layers during the
annealing process in metalorganic vapor phase epitaxy (MOVPE) was monitored in situ by
shallow-angle reflectance using p-polarized ultra-violet light (325 nm). A LT-GaN or LT-AlN
buffer layer was grown on c-plane sapphire substrates at 600 and 700°C, respectively, by low
pressure (76 Torr) MOVPE. These LT-buffer layers were annealed in H2 or N2 carrier gases
and their thermal stability was examined. During annealing at 1020°C under NH3 supply with
H2 carrier gas, the reflectivity dipped, indicating the desorption of the LT-GaN. In contrast,
the reflectivity remained constant during annealing in N2 carrier gas, indicating the LT-GaN
layer was stable in N2. The LT-AlN buffer layer was stable even in H2 carrier gas. These
results indicate that N2 carrier gas stabilizes the LT-GaN buffer layer during annealing over
1000°C.
Crystal Growth and Optical Property of GaN on Silica Glass by Electron-Cyclotron-Resonance Plasma-Excited Molecular Beam Epitaxy (ECR-MBE)
Authors: Murata Naoya , Tochishita Hikari , Shimizu Yuui , Araki Tsutomu , Nanishi Yasushi
Published: October 2002

GaN films were grown on a silica glass substrate by electron-cyclotron-resonance
plasma-excited molecular beam epitaxy (ECR-MBE). It was found that GaN films grown on silica
glass exhibited stronger photoluminescence (PL) intensity than that exhibited by GaN films
grown on sapphire substrates and the PL peak position was the near-band-edge emission of
hexagonal GaN. In addition, the full-width at half maximum of the PL spectrum for GaN
grown on silica glass was smaller than that of GaN grown on sapphire. GaN films grown on
silica glass were c-oriented polycrystalline films consisting of columnar domains. It is
believed that c-axis orientation and columnar growth are strongly related to the optical
properties.
Simple Criterion for Wurtzite-Zinc-Blende Polytypism in Semiconductors
Authors: Ito Tomonori
Published: October 2002

The relative stability between wurtzite and zinc-blende structures in
semiconductors is systematically investigated using a simple formula for calculating
the energy difference between them. Using the well-known values of ionicity and
lattice parameter for semiconductors, the energy formula gives good estimates of
the energy difference for group IV, III–V and II–VI semiconductors. The
calculated energy differences for 16 semiconductors agree well with those obtained
by ab initio calculations in the literature. A simple criterion for wurtzite-zinc-blende polytypes in semiconductors is extracted in terms of ionicity from the
formula. The criterion implies that the wurtzite structure is stabler than the zinc
blende structure when the ionicity is greater than 0.319 for group IV, 0.455 for III–V and 0.652 for II–VI semiconductors.
Field-Cooled Flux Distributions as Tool to Analyze Pinning Properties
Authors: R. Koblischka Michael , Murakami Arabinda Das
Published: October 2002

Flux distributions obtained after field-cooling of melt-processed superconductors are analyzed
using magneto-optic imaging.
We propose such flux patterns as an ideal means to study the interactions between the flux line
lattice and the microstructure of the sample as a fully-penetrated state can be reached even in
bulk samples. Furthermore, in remnant states obtained after field-cooling, the presence of weak
channels in the sample is scanned if the applied field was large enough.
Thermal Stability of Co-Sputtered Ru–Ti Alloy Electrodes for Dynamic Random Access Memory Applications
Authors: Horng Ray-Hua , Wuu Dong-Sing , Wu Luh-Huei , Lee Ming-Kwei , Chan Shih-Hsiung , Leu Ching-Chich , Huang Tiao-Yuan , Sze Simon Min
Published: October 2002

Ru–Ti alloy films were studied for use as a bottom electrode of
ferroelectric/paraelectric thin film capacitors. These thin films with different Ru/Ti
compositions were first prepared by co-sputtering. The Ru/Ti ratio in the alloy was found
to strongly affect the resistivity, structure formation and thermal stability. The resistivity of
the as-deposited films decreases and closes to that of pure Ru metal films as the amount of
Ru atoms increasing. From X-ray diffraction measurement, it was found that the RuTi
phase has formed for the as-deposited sample. There also exist Ru and Ti phases for Ru-enriched and Ti-enriched samples, respectively. As-deposited alloy films were also
annealed by rapid thermal processing (RTP, 600–750°C, 1 min) in oxygen ambient to
simulate the processing of ferroelectric/paraelectric thin film capacitors. It was found that
the composition of the thin film has a large effect on the thermal stability. The resistivity of
alloy thin films is thermally stable as the Ru composition varies from 0.68 to 0.81. It may
be due to the RuTiO2 formation at the surface and play an important role in preventing
further oxidation of the Ru-enriched layer. This oxide also presents conductive behavior.
On the other hand, the interface between Ru-enriched alloys and Si substrate was still
sharp for the RTP-treated sample at 600°C for 1 min. The alloy film with high Ru
composition shows excellent thermal stability and barriers against interdiffusion of Si and
oxygen. These results suggest that the Ru-enriched alloy films are suitable for the bottom
electrode application in ferroelectric/paraelectric thin film capacitors.
A Simple and Novel Way to Synthesize Aligned Nanotube Bundles at Low Temperature
Authors: Mukhopadhyay Kingsuk , Koshio Akira , Tanaka Nobuo , Shinohara Hisanori
Published: October 2002

Large scale quantities of quasi-aligned carbon nanotube bundles have been synthesized by
catalytic decomposition of acetylene over well dispersed metal particles (cobalt and
vanadium) embedded in commercially available zeolite at 700°C. Scanning electron
microscopy analysis revealed the homogenous nature of the sample while transmission
electron microscopy studies revealed the perfect graphitization as well as the inner and
outer diameters of the tubes.
Study on Initial Growth of Particles in Low-Pressure and Low-Power GeH4 RF Discharges Using the High-Sensitivity Photon-Counting Laser-Light-Scattering Method
Authors: Kawasaki Hiroharu , Sakamoto Kazutaka , Maeda Shinichi , Fukuzawa Tsuyoshi , Shiratani Masaharu , Watanabe Yukio
Published: October 2002

A high-sensitivity photon-counting laser-light-scattering method is applied
to obtain information on initial growth of particles formed in low pressure and
low power GeH4 RF discharges. Particles of about 1 nm in size are detected
principally around the plasma/sheath boundary near the RF electrode at an early
time of 0.2 s after the discharge initiation and the corresponding particle density
of 2×1011 cm-3 is about two orders of magnitude higher than ion density. Spatial
profiles of particle amount are very similar to those of Ge emission intensity,
which indicates a radical production rate. These results suggest that short-lifetime
radicals such as GeH2, having a high production rate, are candidates for
key species contributing to the nucleation and initial growth of particles, even for
a low pressure (8–13 Pa) and a low power density (0.04 W/cm2). Furthermore,
surface reflection probabilities of particles 1–12 nm in size, measured after
RF-power-off, are found to be more than 80%.
Synthesis of Amino Acids from N2, H2O Vapor and CO2 Gas Mixture by Synchrotron Radiation Induced Photochemical Reactions at Atmospheric Pressure
Authors: Utsumi Yuichi , Takahashi Jun-ichi
Published: October 2002

Amino acid precursors are synthesized from an N2, CO2 and H2O vapor
mixture by synchrotron radiation induced photochemical reactions at
atmospheric pressure and at room temperature. It was found that the
alanine and aspartic acid in the precursors are enriched in the L-isomer by about 15% over the antipodal D-isomer.
Anomalous Difference between Reaction Energies Generated within D2O-Cell and H2O-Cell
Authors: Arata Yoshiaki , Zhang Yue-Chang
Published: October 2002

Both D2O-cell and H2O-cell are constructed with the same Double Structure Cathode
(DS-cathode), and connected in series as a “Double-cell” to examine the energy generation
under the same electrolytic current. D2O-cell generates tremendously excess energy during a
long period such as over several thousand hours, but any energy is never generated in H2O-cell
when the chemical energy is subtracted in both cells.
Furthermore, “Mixed-cell” blended with D2O and H2O electrolytes (D2O/H2O=2 in
weight) also generates an excess energy, but with the considerably different
characteristics from D2O-cell.
Improvement in Photoelectric Conversion of a Nanostructured TiO2 Electrode Cosensitized with Phthalocyanine and Porphyrin
Authors: Deng Huihua , Zhang Hong , Liang Bingjie , Lu Zuhong
Published: October 2002

The cosensitization of a nanostructured titanium dioxide (TiO2) electrode with tetrasulfonated gallium phthalocyanine (0.39) and tetrasulfonated zinc porphyrin (0.61) greatly enhances the photocurrent response in the GaTsPc Q band (640–760 nm), with sixtyfold improvement in the quantum efficiency at 700 nm, and markedly decreases the photocurrent response in the Soret band of ZnTsPP, with an eightfold drop of the quantum efficiency at 430 nm. The quantum efficiency of 32.2% at 700 nm is obtained for monochromatic illumination at 13.8 µW·cm-2, which presents one of the highest efficiencies reported for long wavelengths. This is attributed to the formation of the Pc/PP heteroaggregates on the cosensitized TiO2 electrode resulting from charge-transfer interaction.
Effect of Hydrogen Partial Pressure on the Reliability Characteristics of Ultrathin Gate Oxide
Authors: Jihwan Park Jihwan Park , Yun Jun Huh Yun Jun Huh , Hyunsang Hwang Hyunsang Hwang
Published: October 2002

In this letter, we have investigated the reliability characteristics
65Å-thick gate oxide
grown in various hydrogen partial pressure. Compared with a dry oxide, device reliability
characteristics such as charge-to-breakdown and stress-induced leakage current were
improved with increasing hydrogen partial pressure. The electron trapping rate
increases with increasing hydrogen partial pressure during the gate oxidation
process. However, initial hole trapping rate was reduced for oxide grown in
hydrogen and oxygen ambient. In addition, we found that the defect density
for large area capacitors was also improved with increasing hydrogen partial pressure. The
improvement can be explained by a reduction of strain in the Si–O bond due to the
incorporation of hydrogen during the oxidation process.
Improvement of the Electrical Properties of Cu-Poor CuInS2 Thin Films by Sodium Incorporation
Authors: Watanabe Takayuki , Nakazawa Hidenobu , Matsui Masahiro
Published: October 2002

We investigated the effects of intentional sodium incorporation
on the electrical conductivity of Cu-poor CuInS2 thin films. CuInS2
films were fabricated by sulfurization of In–S/Cu/Na2S/In precursors.
Sodium incorporation resulted in a remarkable increase in the lateral
conductivity and the cell efficiency of CuInS2-based solar cells.
Photoluminescence measurements revealed that the enhancements
were attributed to the annihilation of donor states, most likely In
interstitials, by sodium incorporation.
Periodically-Poled LiNbO3 Optical Parametric Oscillator with 55% Slope Efficiency Pumped by a Q-switched Nd:YAG Laser
Authors: Izumi Shunsuke , Sato Manabu , Suzuki Johji , Taniuchi Tetsuo , Ito Hiromasa
Published: October 2002

We have demonstrated an efficient quasi-phase matched optical parametric oscillation using
periodically poled LiNbO3 of a 40-mm interaction length and 500-µm thickness. The tuning
ranges of signal and idler waves were 1.56–1.74 µm and 2.75–3.34 µm, respectively, for the
temperature change of 60–230°C. We obtained a 55% slope efficiency for the signal
wave and the maximum signal power of 590 mW at a 1.66 W pump power using 1.064-µm Q-switched Nd:YAG laser with the repetition rate of 1 kHz. The linewidth of the signal was
0.24–0.35 nm without any controlling element.
New Photo-Aligned Multi-Domain Liquid Crystal Display Formed Utilizing a Liquid Crystal Polarizer
Authors: Nishikawa Michinori , Taheri Bahman , West John L. , Rennikov Yuri
Published: October 2002

We developed a new photo-aligned multi-domain liquid crystal display formed
utilizing a liquid crystal polarizer (LCP). The LCP was fabricated using double
ultraviolet light (UV) exposure and special liquid crystal materials. Any desired multi-domain
liquid crystal configuration can be fabricated with a single UV exposure through the
LCP. The resulting multi-domain liquid crystal cell made using the LCP showed high
resolution with the identical pattern of the LCP and with a high dichroic ratio,
comparable to liquid crystal cells made by rubbing.
Seedless Crystallization of Levitated Ge and GaSb Spherical Melts under Microgravity
Authors: Jōsuke Nakata Jōsuke Nakata , Noriaki Kuratani Noriaki Kuratani , Hidemasa Tomozawa Hidemasa Tomozawa , Yuichi Nishimura Yuichi Nishimura , Naohiro Yokogawa Naohiro Yokogawa , Ikuo Inagawa Ikuo Inagawa
Published: October 2002

Seedless crystallization of Ge and GaSb melts was achieved under microgravity occurring in a drop-shaft capsule.
It was observed that melts levitated in Ar atmosphere, formed into a spherical shape and were solidified instantaneously when they collided with the container quartz wall.
X-ray diffraction pattern of these samples showed clear Laue spots signifying a single-crystal structure, while Ge or GaSb solidified in crucibles under normal gravity did not show Laue spots.
These results indicate that single crystal growth rapidly occurs without seed crystals from the spherical melt under microgravity.
This can be understood by assuming that an ordered structure like a single crystal is already formed in a levitated melt, and assists rapid crystallization when the melt touches the crucible wall and latent heat is deprived.
First-Principles Study on Piezoelectric Constants in Strained BN, AlN, and GaN
Authors: Suzuki Kazuhiro Shimada , Hajime Okumura Hajime Okumura
Published: October 2002

Piezoelectric constants at the states suffering
volume-conserving strains have been calculated by using
geometric quantum Berry phase approach for bulk BN, AlN, and GaN
with wurtzite structure. Two step calculations have been
carried out: for given strains the first-principles molecular
dynamics method has been applied to relax the electronic ground
state and the ionic position in the unit cell, after then the
piezoelectric constants have been calculated by applying the
other probing strains. Very large changes have been found in
piezoelectric constants at the states distorted
differently. This nonlinear piezoelectricity is shown to come
from the structural parameters in the distorted unit cell for
each strained state.
Diversity of Quantum Dynamical Tunneling Induced by Sublevel Transitions with a Train of Laser Pulses
Authors: Tsukada Noriaki , Nomura Yoshinori , Isu Toshiro
Published: October 2002

Dynamical control of quantum tunneling in a coupled quantum well is predicted to occur
when laser pulses drive sublevel transitions in one of the wells. The sublevel transition by
the laser pulse induces phase change of the wave packets involved in the transition, which
alters the successive evolutions of the wave packets, resulting in phase reversal of the
tunneling oscillations and the inhibition of tunneling. It is also shown that complete tunneling
oscillations can be realized, even between the nonresonant states, by means of a train of
short pulses which has an appropriate pulse interval and pulse area.
The Effect of D.C. Bias on the Synthesis of Crystalline Carbon Nitrides on Silicon by Microwave Plasma Enhanced Chemical Vapor Deposition (CVD)
Authors: Sung Shing L. , Tsai Tzeng G. , Huang Kuen P. , Huang Jin H. , Shih Han. C.
Published: October 2002

Crystalline carbon nitride compounds have been successfully deposited on a silicon wafer over an intermediate layer of Si3N4 formed by chemical conversion of the silicon using a microwave plasma enhanced chemical vapor deposition (MPECVD) process. Both nitrogen and methane were used as the primary precursors for the initial nitriding of silicon and the subsequent formation of crystalline carbon nitride. In the later step, a negative dc bias of -150 V was applied to the nitrided silicon substrate. The crystalline carbon nitride compounds were characterized by X-ray diffractormeter and X-ray photoelectron spectroscopy, and compared to α- and β-Si3N4. It should be noted that crystalline carbon nitride has never been observed to form simply by reaction of solid carbon with nitrogen plasma. Application of a negative dc bias to the substrate has proved to be a prerequisite for the formation of carbon nitride in this study.
Metallic Conductivity of Langmuir-Blodgett Films Based on Ditetradecyldimethylammonium-Au(dmit)2, where dmit is 1,3 dithiol-2-thione-4,5-dithiolate
Authors: Miura Yasuhiro F. , Okuma Yoshihito , Ohnishi Hideaki , Kawasaki Takumi , Sugi Michio
Published: October 2002

Conductive Langmuir-Blodgett films of ditetradecyldimethylammonium-Au(dmit)2 (dmit=1,3 dithiol-2-thione-4,5-dithiolate) have been fabricated
without the use of matrix molecules. The in-plane dc conductivity was as high as 40 S/cm after electrochemical oxidation at room temperature.
A metallic conductivity with a negative temperature derivative was observed in the temperature range of 250–300 K. At lower temperatures,
the temperature dependence of the conductivity was of Arrhenius' type with an activation energy of 2.5 meV.
Bisector Effect on the Twisted-Nematic Cells
Authors: Wu Shin-Tson , Wu Chiung-Sheng
Published: October 2002

Bisector effects of the twisted-nematic cells are analyzed using Jones matrix method. When
the incident polarization angle is at the bisector of the twist angle, the dark state voltage in the
crossed-polarizer configuration is greatly reduced. The 90° and 60° twisted cells are used as
examples for demonstrating the bisector effect of the transmissive and reflective displays,
respectively. Owing to the increased color dispersion, this bisector effect is more suitable for
projection systems than for direct-view displays.
Green Light Emission From GaInNAs/GaN Multiple Quantum Well
Authors: Shiro Sakai Shiro Sakai , Jie Wang Jie Wang
Published: October 2002

10 period of multiple quantum well structure of GaN/GaInN/GaInNAs/GaInN
was grown on GaN, and the photoluminescence in the green wavelength region
of 500–600 nm has been obtained at room temperature for the first time.