bluuebunny/crossref_metadata_2025 huggingface dataset:
Slip Length in Silicon Wafers Caused by Indentation during Heat Treatment
Authors: Akatsuka Masanori , Sueoka Koji , Katahama Hisashi , Morimoto Nobuyuki , Adachi Naoshi
Published: October 2002

The relationship between the length of slip dislocation and applied stress in silicon
wafers was investigated. Czochralski (CZ) silicon wafers [boron-doped, interstitial
oxygen concentration [Oi]=(13.8–14.0)×1017/cm3], indented by a Vickers hardness tester,
were thermally stressed by insertion into and withdrawal from a horizontal furnace. The
length of slip dislocations generated during the heat treatment was measured by X-ray
topography (XRT). To estimate the applied thermal stress during the heat treatment,
temperature distribution in the wafer was measured with a thermocouple. From the
results of XRT observations, slip dislocations were found to be generated at peripheral
and central regions during the insertion and the withdrawal, respectively. The length of
slip dislocations was calculated using the experimentally estimated thermal stress. It
was found that the length of slip dislocation could be explained well by the model, with
consideration of the applied stress and the dislocation velocity.
Effects of Ni Silicidation on the Shallow p+n Junctions Formed by BF2
+ Implantation into Thin Polycrystalline-Si Films on Si Substrates
Authors: Juang Miin-Horng , Han Sui-Chan , Hu Man-Chun
Published: October 2002

Effects of Ni silicidation on the samples that form shallow p+n junctions
by BF2
+ implantation into thin polycrystalline-Si films on Si substrates have been
studied. The pre-formed junctions of the pre-annealed samples are slightly improved
as a post Ni silicidation is applied to them, since silicidation can enhance the dopant
diffusion. A silicided junction with a leakage of about 1 nA/cm2 at -5 V is obtained
by the sample pre-annealed at 800°C and post NiSi-silicided at 600°C. On the other
hand, as the samples are treated by depositing thin Ni films just after the implantation
and then annealing, the resulting junctions are much better than the above pre-formed
ones, without deepening the junction. During annealing, the simultaneous presence of
both the driving forces arising from the Si interstitial and the Ni silicidation would
significantly enhance the dopant drive-in efficiency. As a result, an NiSi-silicided
shallow junction with a leakage of about 0.8 nA/cm2 and an ideality factor of about
1.00 can be obtained even at 700°C.
Anisotropy in Magnetic Hysteresis of BSr2Can-1CunO2n+3 (n=3, 4, 5) Superconductors
Authors: Yu Shan , Kawashima Tetsuya , Uchida Yoshishige , Takayama-Muromachi Eiji
Published: October 2002

We investigated the anisotropy of magnetization hysteresis ΔM at various
temperatures for magnetically grain aligned samples of BSr2Ca
n-1Cu
n
O2n+3 [B-12(n-1)n,
n=3, 4, 5] superconductors. In the low-temperature region, ΔM
||
with magnetic field
parallel to the c-axis is larger than ΔM
⊥ with magnetic field perpendicular to the c-axis.
When temperature is increased, crossover between ΔM
||
and ΔM
⊥ occurs at a certain
magnetic field, i.e., ΔM
||
<ΔM
⊥ for an applied field higher than the critical value. This
crossover was observed for all members of the series and seems to be caused by different
vortex structures corresponding to magnetic fields parallel and perpendicular to the c-axis.
In-plane critical current density and irreversibility field corresponding to it were calculated
from ΔM
||
. Their temperature variations suggest B-1223<B-1245<B-1234 as the order of
anisotropy of electronic structures.
Well-Above Bandgap Transient Photoreflectance Characterization of Low-Temperature-Grown GaAs
Authors: Yu Jian-Shen , Horng Sheng-fu , Chi Cheng-Chung
Published: October 2002

Degenerate pump-probe photoreflectance (PR) was measured on as-grown and in situ annealed low-temperature-grown GaAs at photon energies well-above bandgap (1.54–1.71 eV) to investigate the effects of annealing and excitation energies on the initial carrier relaxation. The change in reflectivity was found to depend strongly on the photon energy, especially for the annealed sample. This dependence is attributed to the combined effect of absorption bleaching and enhanced absorption related to excess arsenic. A three-component decomposition procedure was used to analyze all the measured PR traces. With this procedure, we found that the initial carrier relaxation time was nearly a constant 160 fs for the as-grown sample, indicating that trapping would dominate the relaxation for excitation energies as high as 1.71 eV. For the annealed sample, the relaxation time increased slowly with the laser wavelength. After comparing it to the carrier trapping time obtained from photoconductive response, we conclude that the relaxation is dominated by trapping for excitation energies up to 1.58 eV and by both trapping and cooling for excitation energies larger than 1.62 eV.
Crystal Growth and Magnetic Properties of SmFe 2
Authors: Samata Hiroaki , Fujiwara Nobuto , Nagata Yujiro , Uchida Takayuki , Lan Ming Der
Published: October 2002

SmFe2 crystals were grown by the self-flux method using Sm as a flux, and the
crystallographic and magnetic properties of the crystal were studied for the first time.
SmFe2 crystallizes in a cubic MgCu2-type structure (space group of Fd3m) with lattice
constants of a=0.7425 nm. Saturation magnetization M
S at 5 K and 300 K and the
Curie temperature of SmFe2 are 64.4 emu/g, 59.8 emu/g, and 669 K, respectively. The
easy-direction of the magnetization is parallel to the [110] direction of the cubic crystal at
300 K, but it changes to the [111] direction at about 195 K.
Temperature Dependence of Piezoelectric, Dielectric, and Elastic Properties of Lead Lanthanum Zirconate Titanate Ceramics
Authors: andAdrijan Levstik Vid Bobnar
Published: October 2002

The piezoelectric resonance and the ferroelectric hysteresis loop
in 8/65/35 lead lanthanum zirconate titanate (PLZT) ceramics were measured
simultaneously at temperatures ranging from 20 to 140°C. The complex
elastic compliance and the complex piezoelectric and dielectric constants
were extracted from the piezoelectric resonance data, while the
temperature-dependent remanent polarization and coercive field were obtained
from the ferroelectric hysteresis loops. From the temperature behavior of the
above quantities, it is possible to conclude that below 50°C, a
strong dc electric field induces a long-range ferroelectric order, while in
the temperature range of 90–140°C, the piezoelectric resonance peak
and the slim ferroelectric hysteresis loop are both a consequence of
short-range polar clusters. In particular, the smeared continuous transition
through which the long-range ferroelectric state is established reflects
itself in the changes of the electrical and electromechanical quality factor.
Effects of Ambient Gas on Dielectric Constant of Sputtered SrTiO3 Epitaxial Thin Films
Authors: Komatsu Shuichi , Abe Kazuhide , Fukushima Noburu
Published: October 2002

Epitaxial strontium titanate (SrTiO3) thin films were
fabricated on Pt/MgO substrates by rf magnetron sputtering in O2 (100 sccm) and Ar/O2 (40/10 sccm) ambients. Films prepared in an O2
ambient exhibit an anomalous dielectric constant (ε
r=450), larger
than that of the bulk single crystal. An investigation was carried out on
the relationship between stoichiometry, deposition rate, and peening
effects and this anomalous dielectric constant. We conclude that the
anomalous dielectric constant is attributable to the lattice elongation
along the c-axis caused due to the peening effect of O species.
High-Density Plasma Produced by a Holey-Plate Surface-Wave Structure Cavity
Authors: Yoshida Yoshikazu , Sakurai Takeki
Published: October 2002

An argon microwave discharge, created and sustained by a surface wave, using a
partial-coaxial cavity resonator has been studied. A 2.45 GHz microwave is propagated
through a 77D-coaxial waveguide and enters at the circumference of a dielectric disk,
which is set at the terminal of the cavity. One flat surface of the disk is in contact
with an inner conductor. The other surface is covered with a holey plate. An evanescent
electric field is produced from the holey plate to a 40-mm-diameter plasma production
chamber. Thus, high-density plasma is generated by the interaction of the evanescent field
with particles. The plasma density is 7.5×1011 cm-3 with an electron temperature of 3 eV,
at an argon gas pressure of 13 Pa and microwave power of 160 W.
Electronic State Distributions of He(ns, np, nd) Rydberg States Produced from Three-Body Collisional Radiative Recombination of He+ in a Helium Flowing Afterglow
Authors: Masaharu Tsuji Masaharu Tsuji , Masafumi Nakamura Masafumi Nakamura , Erika Oda Erika Oda , Masahiro Hisano Masahiro Hisano , Yukio Nishimura Yukio Nishimura
Published: October 2002

Singlet and triplet ns, np, and nd Rydberg states of He* in the 22.72–24.53 eV range have been produced in a helium flowing afterglow. The highest excited levels in each Rydberg state increased from n=6 to 16 with an increase in the degeneracy of the upper state. The dependence of the emission intensity of He* on the He pressure and the electron density indicated that these He* states were formed by the He+/2e- three-body collisional radiative recombination reaction. The electronic state distributions, which were independent of He pressure in the range of 1.0–2.7 Torr, increased with decreasing excitation energy of He*. They were expressed by double Boltzmann distributions with effective electronic temperatures of 0.46 eV in the 22.7–24.4 eV range and 0.089 eV in the 24.4–24.5 eV range. The observed distributions were discussed in terms of the Saha equilibrium between He* and free electrons for high-energy states and the non-Saha equilibrium for low-energy states due to the collisional excitation to a neighboring state and low reionization rates. The total steady-state distributions of ns 1S, np 1P, nd 1D, ns 3S, np 3P, and nd 3D states were 0.048, 0.053, 0.18, 0.24, 0.13, and 0.35, respectively.
Effects of Doping of Fullerene Derivative in a Self-Assembled Multilayer of Conducting Polymers
Authors: Kawai Tsuyoshi , Yamaue Takahiro , Onoda Mitsuyoshi , Yoshino Katsumi
Published: October 2002

Thermally labile Diels-Alder adduct of C60 and 8-(9-anthryl)-7-oxaoctanoic acid (AOOA), C60AOOA2, has been introduced into a self-assembled multilayer of positively and negatively charged conducting polymers. C60AOOA2 of high
concentration in a polymer deposition solution suppresses the multilayer formation and its low concentration solution yields the C60AOOA2-doped multilayered structure. Thermal treatment of the doped multilayer results in marked enhancement
of photoconduction with C60AOOA2 doping. Thermal decomposition of C60AOOA2 into C60 and the difference in the electronic accepting natures of C60 and C60AOOA2 are discussed to be the origins of the enhanced doping effect in the photoconduction of the conducting polymer multilayer film.
A Fast Method of Simulating Resist Pattern Contours Based on Mean Inhibitor Concentration
Authors: Kubota Hiroyuki , Moniwa Akemi , Terasawa Tsuneo
Published: October 2002

A fast and simple method of simulating developed resist pattern contours
obtained with optical lithography has been developed. This simulation
method consists of calculating the aerial image intensity, the inhibitor
concentration in the resist film, and the mean inhibitor concentration
obtained by averaging the inhibitor concentration along the axis normal to
the resist layer. The contours of a resist pattern formed with optical
lithography are determined from contours related to the threshold value of
the mean inhibitor concentration. Although the calculation of post-exposure
baking (PEB) diffusion and development is eliminated, the influences of the
resist thickness and a multiple-layer substrate structure on the resist
pattern width and contours due to interference in the resist film are taken
into account. The validity of this method was tested by comparing the
calculation results with experimental data. The computing time was
between one-sixth and one-twelfth of that needed for a conventional
three-dimensional simulation which includes calculation of the aerial image
intensity, inhibitor concentration in the resist layer, PEB diffusion, and
development. Moreover, the new method requires much less memory than
the conventional three-dimensional simulation since only a two-dimensional
array representing the resist plane is necessary. When the new method was
applied to model patterns, we found that the pattern dimensions and
contours varied as the thickness of the resist film and the thin layer between
the resist film and substrate changed, which demonstrates the effectiveness
of this method.
The Influence of X-Ray Irradiation on Structural Relaxation and Crystallization of Amorphous Silicon Films
Authors: Muto Shunsuke , Kobayashi Yumiko , Yu Kin Man , Walukiewicz Wladyslaw , Echer Charles J. , McCormick Scott , Abelson John R.
Published: October 2002

The effect of intense X-ray irradiation on the short range structure and the thermal crystallization process in sputter deposited amorphous silicon films has been examined by extended energy-loss fine structure spectroscopy and transmission electron microscopy. The coordination number and the mean square disorder of the first neighbor shell in the amorphous state were increased following X-ray irradiation. The crystallization by post-annealing was delayed, the crystallized particles were dispersed homogeneously throughout the film, and the size of the individual particles was larger than in samples without X-ray irradiation. The above facts suggest that the number of unsaturated bonds is reduced by the X-ray irradiation, which can suppress the atomic diffusion and rearrangement, necessary for the crystallization.
Current Noise in Semiconductor Quantum Dots
Authors: Zhong Wang Zhong Wang , Masaomi Iwanaga Masaomi Iwanaga , Tanroku Miyoshi Tanroku Miyoshi
Published: October 2002

We have studied the shot-noise characteristics of semiconductor quantum dots using Keldysh's perturbation theory based on nonequilibrium Green's function techniques, where the electron-electron interaction is well described in terms of self-energy. We have found that the shot noise at peaks of Coulomb oscillations decreases sharply to almost zero when the two barriers are equal and increases to almost the full Poisson noise for the dot with highly unequal barriers. We have also found that the Coulomb interaction between electrons in the current-carrying state and the bound state hardly affect the noise characteristics in Coulomb oscillations. As for the Coulomb staircase, we have found that the shot noise is suppressed over each current step and the noise power ratio to the full Poisson noise changes periodically with the current. However, the noise power ratio has a minimum value of about 0.4 and is 0.5 on average for a dot with equal barriers, and for unequal barriers it is always larger than that for equal barriers on an average.
A Solar Cell Based on sp2 Carbonaceous Film/n-Type Silicon Heterojunction
Authors: Yu Hong-an , Kaneko Tomohiko , Otani Sugio , Sasaki Yoshitomo , Suhng Yiirern , Yoshimura Susumu
Published: October 2002

A solar cell with carbonaceous thin film/n-type silicon (C/n-Si) was fabricated utilizing a process in which an sp2 arranged carbonaceous thin film was deposited on an n-type silicon substrate by chemical vapor deposition of 2,5-dimethyl-p-benzoquinone at 500°C. The C/n-Si solar cell has a hetero-type junction with a junction barrier of 0.54 eV and a depletion layer of 1.1 µm in thickness at zero bias. Under simulated light of 15 mW·cm-2, the C/n-Si cell gives an energy conversion efficiency of 6.45% and an intrinsic energy conversion efficiency of about 13%.
Step Coverage of Molybdenum Silicide Sputtering Films Investigated by Monte Carlo Method
Authors: Yoshizawa Toshio , Yamazaki Toshinari , Yamabuchi Tatsuo , Nakatani Noriyuki , Yuhara Junji , Morita Kenji
Published: October 2002

The step coverage of molybdenum silicide films deposited using a MoSi2.5
target was observed by Auger analysis and scanning electron microscopy.
The composition of the films deposited on substrates placed parallel or
perpendicular to the target was also measured by the Rutherford
backscattering spectroscopy (RBS) method. It was found that the films
deposited on the sidewall of the steps or the substrates placed
perpendicular facing the outside of the sputtering chamber were very rich
in Si compared with the target with Si/Mo ratio of 2.5. The compositions of
those films could take values as large as 5. A considerable part of this
excess Si was ascribed to the turning around of Si atoms due to scattering
by Ar gas. In order to understand the experimental results, simulation of
film deposition was carried out, where the scattering effect by Ar gas was
considered using the Monte Carlo method.
Phase Transition in Ferroelectric SrBi2Ta2O9 Thin Films with Change of Heat-treatment Temperature
Authors: Osaka Tetsuya , Sakakibara Akira , Seki Tomonori , Ono Sachiko , Koiwa Ichiro , Hashimoto Akira
Published: October 2002

Changes in the composition and the crystal structure of micro-grains have been studied using transmission electron microscopy (TEM) and energy dispersive X-ray microanalysis in order to clarify the phase formation of ferroelectric SrBi2Ta2O9 (SBT) with heat-treatment at 650–750°C. Micrograins crystallized at 650°C begin to change to bismuth-layer-structure-family (BLSF) grains at temperatures exceeding 700°C, and form pure-BLSF phase grains at 800°C. Hence, a micrograins phase exists in thin films at 650–750°C and we determined that the bismuth composition in these grains decreases. Using selected diffraction and high-resolution TEM, we found that a pyrochlore phase was formed in the bismuth-poor micrograins that were heat treated at 750°C. The formation of pyrochlore made pure-phase BLSF difficult to obtain.
Optical and Photorefractive Properties of Strongly Reduced BaTiO3
Authors: Huang Chi-Yi , Yueh Ruey-Ren , Chang Jenq-Yang , Chu Chen-Fu
Published: October 2002

Strong reduction of BaTiO3 induced the appearance of an absorption peak around 600–610 nm and a high dark conductivity, both of which increase with increasing reduction
level. The carriers change from holes to electrons after reduction. Because of the
influence of the high dark conductivity, beam coupling gain becomes highly dependent
on incident light intensity, and response time changes little with intensity. For the
sample reduced at 10-15 atm oxygen partial pressure and a temperature of 900°C, the dark
conductivity is estimated to be 1.6×10-10 ( Ω·cm)-1, which increases by about four orders
of magnitude after reduction.
Electrochromic Coloration of Sputtered Nickel Oxide Films by Injection of Anions (Br- Ions)
Authors: Kitao Michihiko , Shiotsu Fuminori , Urabe Kazuo , Mehta Mary Anne , Fujinami Tatsuo
Published: October 2002

Electrochromic (EC) coloration of nickel oxide films has been achieved by the injection
of anions (Br- ions). This was effected by the use of a polymeric anion conductor. Nickel
oxide films were prepared by rf-sputtering in an Ar/O2/H2 atmosphere from a compressed-powder NiO target. In order to achieve reversible EC phenomena, as-deposited films required
an aging process (i.e. several cycles of injection and extraction of charge carriers). After aging,
charges (Br- ions) were observed to remain in the films. The residual charge in the films was
observed to increase with hydrogen content in the sputtering atmosphere, however, coloring
efficiency was observed to decrease. It was proposed that the residual charge (Br- ions) was
responsible for deactivation of the EC color centers.
Relaxation Time of Short Wavelength Intersubband Transition in InGaAs/AlAs Quantum Wells
Authors: Asano Takashi , Noda Susumu
Published: October 2002

Linear and nonlinear light absorption characteristics of
short-wavelength (near-infrared) intersubband transition in InGaAs/AlAs
quantum wells are investigated for estimation of the intersubband
relaxation time. Linear absorption measurements reveal that the
intersubband absorption width is dominated by the inhomogeneous
broadening caused by well-width fluctuations. Nonlinear absorption
measurement results are analyzed by focusing on the inhomogeneous
broadening and probe pulse width, which reveals that the intersubband
energy relaxation time is as short as 1–10 ps. The observed relaxation time
is of the same order as those of long wavelength (far-infrared) intersubband
transitions. This result is expected to be useful for the ultrafast application
of short-wavelength intersubband transition.
Highly Oriented Nb-Doped Lead Titanate Thin Films by Reactive Sputtering: Electrical Properties
Authors: Matsushige Ricardo Cury Ibrahim
Published: October 2002

Some electrical properties of niobium-doped highly (001)-oriented lead titanate thin films epitaxially grown on (100)Pt/(100)MgO substrates by reactive sputtering have been analyzed. The dielectric permittivity, which ranged from 160 to 200, had its minimum value corresponding to a niobium concentration of 1 mol%. Doped samples exhibited outstanding low dielectric losses, lower than 2.5%, compared to undoped ones. Current-voltage (I–V) leakage characteristics of doped samples were considerably better than those of the undoped samples. Such enhancement of resistivity is related to a decrease in the characteristic p-type semiconductive behavior of undoped PbTiO3 due to a reduction in lead vacancies which occurs in the presence of niobium. Doped samples exhibited electric displacement-electric field (D–E) hysteresis curves with high remanent polarization, around 30 µC/cm2, and high coercive field, around 150 kV/cm. In addition, voltage offsets in the hysteresis curves of doped samples could be lowered by applying a DC bias.
Nematic Director Reorientation Dynamics Studied by Time-Resolved Fourier-Transform Infrared Spectroscopy
Authors: Hirokazu Toriumi Hirokazu Toriumi , Tadashi Akahane Tadashi Akahane
Published: October 2002

It is shown that the transient absorption behavior of the C≡N stretching band of the nematic liquid crystal 5CB experimentally obtained by the time-resolved Fourier-transform infrared spectroscopy (FT-IR) can be completely reproduced by the simulation based on Frank's elastic continuum theory. In particular, it is clarified that the fast relaxation process found in experimental results appears only when the applied electric field is high enough and the surface anchoring strength is strong, and that this is due to the director relaxation in the vicinity of the substrate surfaces.
Laser Recording on a Solid Cholesteric Glass of a Medium-Molecular-Weight Compound
Authors: Tamaoki Nobuyuki , Terai Tomohiko , Matsuda Hiro
Published: October 2002

The possibility of laser-addressing a new full color recording material, that is, a solid
film of a medium-molecular weight cholesteric compound, was investigated. A red image
was clearly recorded on the blue background by laser-heating using CO2 laser followed
by natural cooling. By increasing the laser power, the fixed color is changed from red to
yellow and then to blue. A resolution of about 500 µm, that should depend on the profile
of the laser beam, was obtained after 1 s of recording time.
The Molecular Arrangements of Alkanethiol Self-Assembled Monolayers on Au(111) Studied by Scanning Tunneling Microscopy
Authors: Kei Kobayashi Kei Kobayashi , Hirofumi Yamada Hirofumi Yamada , Toshihisa Horiuchi Toshihisa Horiuchi , Kazumi Matsushige Kazumi Matsushige
Published: October 2002

Structures of self-assembled monolayers (SAMs) of alkanethiol molecules were studied by scanning tunneling microscopy (STM) in ultrahigh vacuum (UHV). Molecularly resolved STM images of alkanethiol SAMs were obtained under a high-resistance tunneling condition. The observed images show that the monolayers consist of the (√3×√3)R30° lattice structure, c(4×2) superlattice and the stripe structures which have a unit cell of p×√3. We observed a new molecular arrangement in the c(4×2) superlattice. The details of the stripe structures are also described.
Radiative Recombination and Afterglow Characteristics of X-Ray Irradiated BaFCl:Eu2+ and KCl:Eu2+
Authors: Taku Kimura Taku Kimura , Katsuyuki Inabe Katsuyuki Inabe
Published: October 2002

Time and temperature dependence of afterglow intensity and of the F-band in the optical absorption spectra are studied for BaFCl:Eu2+ and KCl:Eu2+.
Afterglow reveals a single emission band with a peak around 420 nm and 400 nm in BaFCl:Eu2+ and KCl:Eu2+, respectively.
Decay curves of afterglow and the F-band intensity are analysed using a recombination probability depending on temperature and the distance between electron and hole centers.
The theoretical curve with three reasonable parameters, is found to be in good agreement with the experimental data of BaFCl:Eu2+ as well as of KCl:Eu2+.
Surviving probability of the centers in these crystals is also discussed on the basis of the proposed recombination model.
Using Auger Electron Spectroscopy for Chemical Analysis of Plasma Damage Induced by Reactive Ion Etching of SiO2
Authors: Matsui Miyako , Uchida Fumihiko , Katsuyama Kiyomi , Tokunaga Takafumi , Kojima Masayuki
Published: October 2002

Surface damage induced by reactive ion etching (RIE) at the bottom of the pattern was investigated in terms of chemical information by Auger electron spectroscopy (AES). The Si-L23VV line shape was changed during the removal of the damage by chemical dry etching after RIE. The relationship between the changing of the Si-L23VV line shape and the
chemically damaged layer, which contains SiO
x
and SiC, was investigated by X-ray photoelectron spectroscopy (XPS) and AES for nonpatterned wafers. The height of the peaks at 90 eV and 79 eV in the Si-L23VV spectra were correlated with the amounts of chemical damage in the layer measured by XPS. The thickness of the residual SiO
x
damage was estimated from the relationship between the Si-L23VV line shape and the thickness of the SiO
x
layer. This relationship was applied to the chemical analysis for patterned wafers. The line shape of the Si-L23VV spectrum from the bottom of the pattern was also changed as the chemical-dry-etching time increased.
Determination of the Purity of Gold Alloys Using Gamma-Ray Transmisson Techniques
Authors: Suzuki Takashi , Kitsutaka Raita , Muto Toshio , Morisaki Sigeyosi
Published: October 2002

Triple and dual energy γ-ray transmission (TEGAT and DEGAT)
techniques were examined to determine nondestructively the purity of gold
alloys. The experimental system was composed of a radioactive source 152Eu
(31 MBq) emitting many energies of γ-ray and a high-purity germanium
detector having a high-energy resolution. The TEGAT technique suggested that
the purity of gold alloys of 1–5 mm thickness can be determined with a
precision of more than 99% under an allowance range condition of two karats.
By the DEGAT technique, on the other hand, the purity of gold alloys of 3–5 mm thickness could be determined with 95–99% precision under the same
condition as above. For the DEGAT technique, it was assumed in this study that
the mass attenuation coefficient of silver was equal to that of copper. It was
found that the γ-ray transmission techniques can be effectively applied for the
measurements of the purities of thick gold alloys which are otherwise impossible
to determine by fluorescence X-ray analysis.
High-Frequency Response of Metal-Semiconductor-Metal Photodetectors Limited by Dynamic and Recombination Effects
Authors: Irina Khmyrova Irina Khmyrova , Victor Ryzhii Victor Ryzhii , Maxim Ryzhii Maxim Ryzhii , Magnus Willander Magnus Willander
Published: October 2002

A simplified quasi-two-dimensional analytical model of planar
interdigitated metal-semiconductor-metal (MSM) photodetectors is presented. The model takes into account the transit-time and velocity overshoot
effects of photogenerated electrons and holes and their recombination.
The response is derived as a function of the signal frequency and the
device structural parameters. It is shown that MSM photodetectors with
relatively large contact spacing can exhibit rather high-frequency
response in the terahertz range due to electron velocity overshoot. The
obtained MSM photodetector response is in good agreement with the results
of a Monte Carlo simulation. The response-frequency product reveals a high
maximum corresponding to a frequency of about a few terahertz. The MSM
photodetectors exploiting the velocity overshoot effect can be
advantageous in comparison to the MSM photodetectors with ultrashort
lifetime of the photogenerated electrons and holes.
Experimental Study of the Cavity Modes of Stressed High-Birefringent Fiber Fabry-Perot Cavities
Authors: Ho Min-Jou , Tseng Shiao-Min
Published: October 2002

We investigated the evolutions of the cavity modes and modal retardation
of high-birefringent fibers by constructing single-mode fiber
Fabry-Perot cavities. In such a fiber cavity, the changes of two
cavity modes were different at various misaligned forces and we were
able to distinguish the two principal fiber axes. Verification of our
approach was also experimentally carried out by using a conventional
elastooptic alignment method. Applications as fiber polarimetric sensors
are also presented.
Ultrathin (5 µm) Flexible Reflective Waveplate of Fluorinated Polyimide and Elimination of Polarization Sensitivity in Titanium-Diffused Lithium Niobate Waveguide Circuits
Authors: Sawada Takashi , Ando Shinji , Miyazawa Hiroshi , Takenaka Hisataka , Sasaki Shigekuni
Published: October 2002

An ultrathin, flexible reflective half-waveplate, consisting of a 5-µm-thick polyimide quarter-waveplate sputtered with a thin gold film, was fabricated, and its property of eliminating polarization sensitivity in titanium-diffused lithium niobate waveguide circuits was investigated. Transverse electric/transverse magnetic mode-conversion ratios of 15–20 dB at 1.55 µm were obtained, and a polarization-insensitive intensity modulator with a low half-wave voltage of 4.5 V was successfully fabricated using a titanium-diffused lithium niobate waveguide. The excess loss of the polyimide reflective waveplate (1 dB) was much smaller than that using a conventional quartz waveplate (6 dB).
Chemical Bondings around Intercalated Li Atoms in LiTiX2 (X=S, Se, and Te)
Authors: Kim Yang-Soo , Koyama Yukinori , Tanaka Isao , Adachi Hirohiko
Published: October 2002

A systematic study of the electronic structure and chemical bonding of the Li-intercalated titanium dichalcogenides, LiTiX2 (X=S, Se, and Te), is performed by a first-principles molecular-orbital method using a model cluster composed of 75 atoms. The discrete-variational (DV)-Xα method was employed and Mulliken's population analyses were thoroughly conducted. The net charge of Li is found to be approximately 0.1 independently of X-species. Net charges of Ti and X are not significantly affected by the Li intercalation. Strong covalent bonding is formed between Li and X with a bond-overlap population (BOP) of 0.173–0.176. The BOP of Ti–X bonding decreases by about 10% due to the presence of Li. These results should be important for determining battery properties when the dichalcogenide are used for positive electrodes.
Dielectric Relaxation Study of a Liquid Crystal with a Sm C* to N* Transition Sequence
Authors: Masaki Maeda Masaki Maeda , Hisanori Kihara Hisanori Kihara , Akiko Makino Akiko Makino , Ikuo Suzuki Ikuo Suzuki
Published: October 2002

A dielectric relaxation study of a liquid crystal (CS-2005) with a phase sequence of Sm C*–N*–Iso was performed to investigate the molecular dynamics associated with the phase transitions. An extra relaxational mode in a low frequency (below 100 Hz) region was found in N* and Iso phases. The mechanism of phase transition of the liquid crystal (CS-2005) with a phase transition sequence of Sm C*–N*–Iso and the origin of the low frequency relaxational mode were investigated.
Remote Plasma-Assisted Metal Organic Chemical Vapor Deposition of Tantalum Nitride Thin Films with Different Radicals
Authors: Cho Kwang-Nam , Han Chang-Hee , Noh Kyung-Bong , Oh Jae-Eung , Park Su-HyounPaek , Lee Sang-In , Lee Moon Yong , Lee Jong Gil
Published: October 2002

Thin films of tantalum nitride have been deposited from remote plasma-assisted metal organic chemical vapor deposition (RP-MOCVD) using the reaction of pentakis-dimethyl-amino-tantalum (PDMATa) with different activated radicals. Microstructures of deposited films measured by X-ray diffraction (XRD) and transmission electron microscopy (TEM) depend on the deposition temperature and the type of radicals. At temperatures below 300°C, amorphous films are obtained which are independent of the reacting species. On the other hand, at higher deposition temperatures, (111)-preferred cubic TaN films are obtained when they react with ammonia plasma, while the reaction with hydrogen plasma produces amorphous films. All amorphous films obtained are recrystallized at an annealing temperature of 1000°C in an oxygen-containing (10%) ambient, showing (111) TaN, bcc Ta, and signals of orthorhombic Ta2O5. From detailed studies of film composition and chemical bonding in the obtained films, the impurity incorporation, especially carbon, is responsible for the dependence of film microstructures on different deposition conditions.
Cu(In1-xGax)S2 Thin Films Prepared by Sulfurization of Precursors Consisting of Metallic and Gallium Sulfide Layers
Authors: Ohashi Tsuyoshi , Wakamori Masaki , Hashimoto Yoshio , Ito Kentaro
Published: October 2002

Cu(In1-x
Gax)S2 alloy thin films were prepared by annealing Cu/In/GaS precursors under a H2S atmosphere. The adhesion of the film to a Mo-coated soda-lime glass substrate was improved by introducing a GaS deposit as the first precursor layer. Optical transmission measurements revealed that the band gap of the thinner alloy film shifts from 1.42 to 2.41 eV with increasing composition ratio x. This sulfurization process, however, does not give rise to a single-phase thick Cu(In1-x
Gax)S2 alloy film when x is larger than 0.2. Therefore, the composition of Ga in the film should be restricted to a smaller amount. A solar cell of over 10% efficiency has been obtained using the thin film prepared from the precursor with composition ratios of Cu/(In+Ga) = 1.2 and Ga/(In+Ga) = 0.05.
Al–Cu Texture Enhancement by Underlayer Texture
Authors: Sasaki Tsutomu , Dohnomae Hitoshi
Published: October 2002

Al–Cu layered films and interconnections (Al/underlayers) were fabricated and investigated
to observe the effects of underlayer texture on Al texture development and of Al texture on
electromigration resistance. Al(111) texture was enhanced by controlling Ti and TiN
underlayer textures. Values of full width at half maximum for Al(111) rocking curves ranged
from 0.64° to 4.7° for Al–Cu films grown on Ti, TiN/Ti, and Ti/TiN/Ti underlayers. Al(111)
texture and TiN(111) texture were improved when these films were consecutively deposited on Ti underlayers with (10·0) preferred orientation. Factors for Al texture development will be discussed in order to develop a model which explains texture development in terms of nucleation and growth of Al films and Al grain growth. It was confirmed that
Al interconnections with strong (111) textures had long electromigration lifetimes.
Effect of Sn Doping on the Crystal Growth of Indium Oxide Films
Authors: Taga Naoaki , Maekawa Mikako , Kamei Masayuki , Yasui Itaru , Shigesato Yuzo
Published: October 2002

Heteroepitaxial growth of tin-doped indium oxide (ITO) and non-doped indium oxide
(IO) thin films was carried out on single-crystal yttria-stabilized zirconia substrates by
molecular beam epitaxy. The surface morphology of these epitaxial films was
characterized by scanning electron microscopy. The doped ITO and non doped IO
epitaxial films showed drastic changes in surface morphology, which suggested that Sn
acted not only as a dopant but also as a growth modifier for IO films. The surface
morphology analysis of IO and ITO films revealed a growth rate enhancement by Sn
doping along the <111> direction.
Decay of Metastable Argon Atoms in the Afterglow Plasma
Authors: Yuasa Kunio , Matayoshi Shinsaku , Sakurai Takeki
Published: October 2002

Time-dependent studies of the particle density in 1s5 state of Ar plasma are performed
using single-frequency laser absorption probing. The applied voltage on the 400 Pa striated
plasma (current: 0.01–20 mA DC) is cut off, and from the decay curve studies of the density,
the following rates are obtained: the rate of collision between 1s5–1s5 metastable atoms
α (cm3 s-1)=(2.0±0.5)×10-8, the rate of collision between 1s5 metastable atoms and electrons
F
e (cm3 s-1)=3.8×10-7 and the electron loss rate in the afterglow γe (s-1)=250+1.0×10-7×n
e,
where n
e (cm-3) is the electron density. We also present the time-dependent n
e behavior in one
striation peak using values obtained here.
The Conversion of Rigid-Body Rotational Dynamics to Particle Dynamics
Authors: Wang Wen-Tsung , Chang Chia-Ou , Chou Chan-Shin
Published: October 2002

In this paper we present a new method that converts rigid-body rotational motion to particle translational motion in a high-dimensional space. The inertial terms in the equations of rigid-body rotational motion are nonlinear in nature, while those in the equations of particle motion are linear. Therefore, the problem of maneuvering the rotation of a rigid body can be handled more easily by the theory of equivalent particle dynamics than by the theory of rigid-body rotational dynamics. An example of a rigid body tracking the desired time-varying orientation by supplying it with an appropriate control torque is given.
Optical Proximity Correction Methodology to Counteract Mask Error Effects in Sub-0.25 µm Lithography Generations
Authors: Kim Keeho , Lilygren John , Madhavan Sriram
Published: October 2002

A new methodology for optical proximity correction design is required for sub-0.25 µm
device generation, to predict and counteract mask error effects. We applied a new concept
of virtual mask technology to design an optical proximity correction (OPC), which involves adding a small dummy mask
pattern on a simulation mask layout, to realize mask error effect. The aerial image
simulation results for the new methodology suggested a totally different type of OPC.
Experimental results were more accurately predicted by the new methodology than the old
methodology. For 0.25 µm features hammerhead OPC shows much improved results of
intra-field CD uniformity of 20 nm, of 3 sigma, and wide usable process window of 14%
exposure latitude and 0.8 µm depth of focus, compared with serif OPC that was selected
by the old methodology. This new methodology with virtual mask technology will be
applied to sub-0.25 µm generations.
Pattern Displacement Error under Off Axis Illumination
Authors: Seong Nakgeuon , Kang Hoyoung , Kye Jongwook , Cho Hanku , Moon Jootae
Published: October 2002

Pattern displacement errors under off axis illumination (OAI) are investigated using multiple
OAI settings and patterns which simulate a dynamic random access memory (DRAM) device situation. Pattern displacement
errors of various systems were observed and aberration effects were simulated. The difficulty in
correlating between pattern displacement errors and line width asymmetries is observed from
measurement and analyzed with simulation. In order to avoid this problem, use of a larger pole
size and grouping of machines which have similar pattern displacement errors are suggested.
Printing Sub-100 Nanometer Features Near-field Photolithography
Authors: Shuji Tanaka Shuji Tanaka , Masayuki Nakao Masayuki Nakao , Yotaro Hatamura Yotaro Hatamura , Masanori Komuro Masanori Komuro , Hiroshi Hiroshima Hiroshi Hiroshima , andMasahiro Hatakeyama andMasahiro Hatakeyama
Published: October 2002

In this paper, a near-field photolithographic method which can
realize ultra high resolution beyond the diffraction limit of light is
described. Evanescent light generated on a transparent mold with a
micro-relief illuminated on the condition of total internal reflection
is used to expose a photoresist in contact with the mold. The plastic
replica mold is flexible to eliminate the difficulty of close contact
with the photoresist, and the replica mold damaged by the contact with
the photoresist is disposable to maintain a high yield rate. We printed
sub-100 nm features on a commercially available photoresist using
442-nm-wavelength light.
A New Approach of E-beam Proximity Effect Correction for High-Resolution Applications
Authors: Simecek Michal , Rosenbusch Anja , Ohta Tsuneaki , Jinbo Hideyuki
Published: October 2002

The e-beam proximity effect is well known as one of the limiting factors
in e-beam lithography. As features get smaller the need for e-beam proximity
effect correction (EPC) increases. There exist different approaches to cover
these effects by varying dose or shape of the pattern layout during the exposure
step. Both of these basic approaches have drawbacks limiting their application.
For example, the EPC correction by shape variation underlies constraints such
as neighbouring features, the exposure grid of the e-beam tool and writing time.
EPC by dose variation fails in cases the feature size is very close to the process
dependent forward scattering parameter alpha. To guarantee CD uniformity in
these cases a negative dose assignment would be necessary, which is practically
impossible. The paper presents a new correction scheme based on dose assignment
and geometry variation at the same time. After a short introduction the theoretical
description of the method is given. Dose and geometry modifications are calculated
using a Fast Fourier Algorithm. Due to the ability of changing the geometry
depending on feature size and feature neighbourhood even very small features
can be printed correctly. This flexibility is the main advantage compared to
already existing methods. Pattern fidelity and linearity can be improved drastically.
Resolution limits can be pushed further down. The application of the automatic
correction to high resolution features with a feature size of 100 nm are demonstrated.
The CD linearity is investigated and demonstrated using a real device patterns.
Highly Anisotropic Etching of Tungsten-Nitride for an X-Ray Mask Absorber with an Inductively Coupled Plasma System
Authors: Hong Goo Lee Hong Goo Lee , Seung Yoon Lee Seung Yoon Lee , Ho Sung Moon Ho Sung Moon , Sang Hoon Kim Sang Hoon Kim , Joo-Hiuk Sohn Joo-Hiuk Sohn , Jinho Ahn Jinho Ahn
Published: October 2002

Inductively coupled plasma (ICP) etching of a WN
x
film using an auxiliary rf plasma source is applied for preparing X-ray mask absorber patterning. WN
x
is effectively etched with SF6 gas plasma and the addition of Ar and N2 results in higher dissociation of the SF6 gas and sidewall passivation effect, respectively. Pattern distortion observed for high-aspect-ratio patterns is minimized by multistep etching and an O2 plasma treatment process. As a result, 0.18 µm WN
x
line and space patterns with vertical sidewall profiles are successfully fabricated.
Dissolution Characteristics and Surface Morphology of Chemically Amplified Resists in X-Ray Lithography
Authors: Nakamura Jiro , Kawai Yoshio , Deguchi Kimiyoshi , Matsuda Tadahito , Oda Masatoshi
Published: October 2002

The surface morphology of chemically amplified resists was
evaluated when a half-tone X-ray mask with high transmittance (low-contrast) was used. The morphology of the top surface of chemically amplified resists is strongly related to the differential of the dissolution rate as a function of the exposure dose, but it is not directly affected by the γ value. A smaller change results in a smoother surface for both positive and negative resists. Increasing the concentration of dissolution inhibitors with t-butoxy groups is an effective way of reducing the change in dissolution
rate and making the top surface of a positive resist smooth while
maintaining the resolution.
Reduction of Image Shortening in Two-Dimensional Pattern Replication Using X-Ray Lithography
Authors: Nakanishi Kazuya , Deguchi Kimiyoshi , Matsuda Tadahito , Oda Masatoshi
Published: October 2002

Image shortening cannot be ignored in sub-100-nm pattern replication using X-ray lithography. It is important to know whether or not optical proximity correction is
necessary for the reduction of image shortening. The authors investigated the image
shortening of a rectangular pattern, and its reduction by adding a serif or mask bias. By
adding a serif, image shortening was reduced dramatically, but critical dimension control
of the resist pattern ends was degraded. On the other hand, image shortening for an ideal
rectangular pattern was expected to be lower than 50% of the designed spacing, and can
easily be canceled out with just a mask bias. This means that the use of a serif is not
necessary, and a mask bias is more effective in reducing image shortening in X-ray
lithography.
Design of Beamline Optics for Large-Field Exposure
Authors: Hasegawa Masaki , Gomei Yoshio , Hisatsugu Tokushige
Published: October 2002

New mirror designs for an X-ray lithography (XRL) beamline have been devised
for the large-field, high-power irradiation of wafers. In contrast to analytically described
mirrors, such as toroids, ellipsoids, etc., the new shapes were numerically determined.
The design method employed was developed by Xiao, et al. A beamline employing such
an optimized mirror design should provide a high X-ray power density of 58 mW/cm2 over
a 50-mm-square exposure area, and 88 mW/cm2 over a 40-mm-square exposure area, with
a uniformity of better than ±2%. The slope error margin was also estimated using
numerical simulations, and it was found that the exposure characteristics do not degrade
when the slope error is less than 25 arcsecs over the whole surface of the mirror.
Dynamic Response of Acoustic Delay Line for Beam Lines of Synchrotron Radiation Lithography System
Authors: Toyota Eijiro
Published: October 2002

Protecting against the sudden rupture of a beryllium window foil
has been a concern in synchrotron radiation lithography. This paper
presents a design study of a new acoustic delay line (ADL) for beam
line protection. The ADL consists of a stationary outer tube and a
movable inner tube. Between the outer tube and the inner tube, a
series of partitions consisting of stationary and floating plates
functions as a buffer against invading gas. The inner tube connects
the floating plates and the beryllium window and maintains an
internal narrow light path by moving synchronously with the scanning
mirror.

BLVAC, a computer program, has been developed to assist in the design and to simulate the dynamic response. The calculation results provide us with satisfactory design parameters to ensure that the closing time of the shut-off valve is within 30 milliseconds.
Development Process for Chemically Amplified Resist by KrF Imaging
Authors: Matsunaga Kentaro , Kawamura Daisuke , Mimotogi Shoji , Azuma Tsukasa , Onishi Yasunobu
Published: October 2002

The development process for chemically amplified resist by KrF imaging was
investigated. The effects of developer concentration, development time and
surfactant on process latitude were examined. In order to extend the process latitude,
the development condition with faster dissolution rate at the center of the exposed
area and slower dissolution rate at the edge of the exposed area was found to be
promising. It was also found that the addition of a surfactant to the developer
extended the process latitude. The developer with the surfactant tends to suppress
the slimmed resist linewidth in the overexposed area and to enhance resist
dissolution in the underexposed area.