bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of Cr Silicide Formation on Si(100) Due to Solid-Phase Reaction Using Soft X-Ray Emission Spectroscopy
Authors: Heck Claire , Kusaka Masahiko , Hirai Masaaki , Nakamura Motohiro Iwami
Published: October 2002

Cr silicide formation on Si(100) substrate is studied by means of an alternative
analysis technique: soft X-ray emission spectroscopy (SXES). Intermixing between chromium
and silicon is observed at annealing temperatures ≥400° C. A nondestructive
depth profile analysis shows that CrSi2 grows homogeneously on Si(100) for specimens heat-treated at 450°C.
Novel Structure for Measuring the Density-of-State Distribution of High-Resistivity Semiconductor Films by Isothermal Capacitance Transient Spectroscopy
Authors: Chen Yeong E , Wang Fang Shing , Jun Wei Tsai Jun Wei Tsai , Huang Chung Cheng Huang Chung Cheng
Published: October 2002

A novel structure, metal/high-resistivity semiconductor (HRS)/n-type c-Si substrate
with the space charge region (SCR) entirely covering the HRS film and penetrating into
the c-Si substrate, has been proposed for determining the density-of-state distribution g(E)
of the HRS films via the isothermal capacitance transient spectroscopy (ICTS) method.
The structure has been tested and applied to the measurement of g(E) of the undoped
hydrogenated amorphous silicon (a-Si:H) film. For undoped a-Si:H film with optical gap
E
o=1.72 eV, a peak in g(E) is observed at 0.66 eV below the conduction
band mobility edge E
c, with the attempt-to-escape frequency of v

n
=1.61× 1013 s-1.
These midgap states are surmised to be correlated with the doubly occupied dangling bond D-.
Tunnel Gap Imaging Study of Highly Oriented Pyrolytic Graphite Using Scanning Tunneling Microscope
Authors: Kimura Masahiro , Okumura Akihiko , Kazuo Miyamura Kazuo Miyamura , Yohichi Gohshi Yohichi Gohshi
Published: October 2002

An STM system capable of measuring the tunnel gap separation (s) dependence of
tunnel current (I), i.e., the I-s characteristics, was constructed. The I-s
characteristics were successfully measured by sweeping the set current, instead of
modulating the tip position. It was found that the tunnel current could be detected
over a separation range of 1 nm. Furthermore, a new imaging technique, tunnel gap imaging,
which maps out the lateral distribution of the I-s characteristics, is proposed and realised.
Measurement of Sidewall Roughness of InP Etched by Reactive Ion Beam Etching
Authors: Matsutani Akihiro , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: October 2002

We have quantitatively measured the sidewall roughness of InP etched by reactive
ion beam etching (RIBE) for the first time. An electron probe surface roughness analyzer
was employed. The minimum value of average sidewall roughness appeared to be 1 nm and the
peak-to-peak roughness appeared to be 6 nm. The etching conditions were an ion extraction
voltage of 400 V and a Cl2 gas pressure of 1.2× 10-3 Torr.
It is found that the etched sidewall roughness is decreased by lower-ion-extraction-voltage
etching in a constant gas pressure, as well as by higher-gas-pressure etching with a constant ion extraction voltage.
Trends for Future Silicon Technology
Authors: Tadahiro Ohmi Tadahiro Ohmi
Published: October 2002

In addition to three-terminal devices such as metal oxide semiconductor (MOS)
transistors and bipolar transistors, the introduction of four-terminal devices such
as neuron MOS transistor is essentially required for the realization of intelligent
ULSI systems which is most crucial for electronics in the 21st century. Four-terminal
devices will allow us to make ULSI hardware more flexible, real-time programmable,
and thus more intelligent based on binary multi-valued analog-merged hardware computation
algorithm. For such systems to work, we must establish high-accuracy device fabrication
processes based on the concept of ultraclean technology. The simultaneous fulfillment
of three principles, viz. ultraclean wafer surface, ultraclean processing environment,
and perfect process-parameter control, is the key to high-performance processes for
fabricating advanced subhalf-micron and subquarter-micron ULSI devices. Advanced
process technologies have been realized for the first time by ultraclean processing,
making it possible to establish total low-temperature processing, such as gate oxidation
at 450°C, implanted region anneal at 450°C, BPSG film reflow at
450°C and single-crystal silicon epitaxy with simultaneous doping at
300°C by introducing very well regulated ion bombardment during processing
which is most essential for obtaining high-performance subhalf-micron and subquarter-micron ULSI.
The Exposure-Defocus Forest
Authors: Burn J. Lin Burn J. Lin
Published: October 2002

The exposure-defocus (E-D) forest, a large cluster of E-D trees, is a valuable
lithography characterization tool. With the E-D forest, processing parameters are compressed
into relevant ones that are significant for manufacturing. It forms a universal quantitative
base for comparison of lithographic performance, hence an essential vehicle to analyze
and optimize the imaging performance of lithographic systems. This paper shows the
physical meaning of the E-D space and the construction of E-D tree and E-D forest
from aerial, developed, or etched images either from simulation or from experimental
linewidth measurement results. The performance criteria based on E-D trees and optimization
in depth of focus, exposure latitude, and E-D window area, are explained. The significance
of dealing with an entire E-D forest, instead of single trees, is shown. The difference
between linewidth-based and edge-based E-D trees is given. Examples of E-D forest
application include: Determining the mutual dependence of depth of focus and exposure latitude;
Optimizing the imaging lens numerical aperture and the degree of partial coherence;
Determining the resist operation window; Characterizing and reducing optical proximity effects;
Evaluating phase shifting masks; Optimizing off-axis illumination; and Comparing the
performance of optical and X-ray lithography.
Application of Alternating-Type Phase Shift Mask to Polysilicon Level for Random Logic Circuits
Authors: Galan Gérald , Lalanne Frédéric , Patrick Schiavone Patrick Schiavone , Jean-Marc Temerson Jean-Marc Temerson
Published: October 2002

Of all phase shift mask techniques, the alternating type is both the best for
improving resolution and the most difficult to use. The problems in its use include
complicated design modifications, unwanted phase-transition printing and very challenging
mask fabrication. This paper is the first report of a solution using an automatic
shifter arrangement and a three-step phase-transition technique on etched-quartz
alternating-type phase shift mask (PSM). The lithographic results as well as the
electrical results presented demonstrate the feasibility of the technique for application
to complex circuits and show the capabilities of this kind of mask in printing smaller dimension lines.
Implementing Attenuated Phase Shift Masks for Contacts in Production
Authors: Yuan Chi-Min , Pol Victor , Garofalo Joseph , Pierrat Christophe
Published: October 2002

It has been shown that the attenuated phase shift mask (PSM) is best suited for
imaging dark-field patterns ( e.g., contacts, vias, and metal lines) when positive
photoresists are used. This paper presents our experience and technical data in implementing
the attenuated PSM on a contact level in production. Specifically, implementation issues
such as mask transmission, mask bias, printing linearity, overlay results, opaque border,
mask defects and process latitudes are addressed.
Effect of Electron Beam Orbit Distortion on Optical Performance of the Synchrotron Radiation Lithography Beamline
Authors: Shimano Hiroki , Asano Kazuo , Yoshihiko Ozaki Yoshihiko Ozaki , Yasuji Matsui Yasuji Matsui
Published: October 2002

We have investigated the effect of the synchrotron radiation (SR) source drifts,
namely, the source position and emission angle, caused by electron beam closed orbit
distortion (COD) on optical performance of the beamline such as the exposure field size,
the illumination intensity and the uniformity. We theoretically derived that SR source
drifts should be controlled within ± 0.4 mm and ± 0.2 mrad for the
position and emission angle drifts, respectively, to obtain uniformity better than 15%
for our beamline. We also propose a new technique to directly measure the SR source
drifts using the focusing property of the mirror and the SR beam monitor installed
in the beamline, which can be applied to predict the changes of optical performance
of the beamline, and to monitor the electron beam drifts for correcting COD.
Resist Performance in 5 nm Soft X-Ray Projection Lithography
Authors: Oizumi Hiroaki , Ohtani Masayuki , Yamashita Yoshio , Murakami Katsuhiko , Nagata Hiroshi , Nobufumi Atoda Nobufumi Atoda
Published: October 2002

Imaging experiments in 5 nm soft X-ray projection lithography (SXPL) were performed
using 32:1 reduction Schwarzschild optics with NiCr/C multilayer, which was illuminated
with synchrotron radiation (SR) from the SORTEC ring. Sensitivities of 0.7 µ m-thick
polymethylmethacrylate (PMMA), ZEP and AZ-PN100 are 285, 34, and 15 mJ/cm2,
respectively. Resist contrasts (γ-values) of 0.7 µ m-thick PMMA,
ZEP and AZ-PN100 are 2.5, 1.6 and 3.1, respectively. A 0.15 µ m line-and-space
pattern can be replicated by 5 nm exposure. Resist performance in 5 nm SXPL was
investigated with a special emphasis on the effect of resist film thickness. Resist
contrasts of PMMA did not change markedly with increasing resist thickness. By 5 nm
exposure, a 0.3 µ m line-and-space pattern was clearly delineated in 0.9 µ m-thick PMMA.
This result confirms that a single resist scheme is applicable in 5 nm SXPL.
Character Projection EB Data Conversion System Combined with Throughput Analyzer
Authors: Hara Shigehiro , Shunko Magoshi Shunko Magoshi , Kiyomi Koyama Kiyomi Koyama
Published: October 2002

An electron beam (EB) data conversion system for a character projection (CP)
writing method has been constructed. The system has been developed based on an EB data
conversion system for a variable-shaped beam (VSB), and a formatting module for CP
writing was added. In addition, several functions have been developed to analyze CP
writing patterns, and combined with the system. The functions aim to select the CP
writing patterns that best reduce writing time and to achieve the highest throughput.
The new system was applied to a real LSI pattern to test the conversion function and
to estimate the conversion speed. A model pattern of a 1 Gbit dynamic random access
memory was successfully converted to EB data format. The conversion processing time was less than 14 min for each layer.
Improved Proximity Effect Correction Technique Suitable for Cell Projection Electron Beam Direct Writing System
Authors: Tamura Takao , Ken Nakajima Ken Nakajima , Hiroshi Nozue Hiroshi Nozue
Published: October 2002

Electron beam (EB) direct writing is expected to play an important role in the
field of lithography for manufacturing future advanced ULSIs. Cell projection techniques
are of particular interest, which may make the EB direct writing system practical for
use in ULSI memories with many repeated patterns. However, the proximity effect of
such systems disturbs the formation of fine 0.2 µ m level patterns throughout
the patterning area. In order to solve this problem, we have developed an improved
proximity effect correction technique suitable for use in a cell projection EB direct
writing system. This technique makes use of smaller cell projection shot (CPS) size in
the edge region than in the center region in the EB direct writing area with dose
compensation between CPSs, based on the self-consistent method. Utilizing this technique,
we can obtain fine 0.2 µ m patterns with 0.02 µ m critical dimension
(CD) control patterns, which are required to manufacture 1Gbit dynamic random access memories (DRAMs).
Repetitive One-Tenth Micron Pattern Fabrication Using An EB Block Exposure System
Authors: Yamada Akio , Sakamoto Kiichi , Yamazaki Satoru , Kobayashi Katsuhiko , Sagoh Satoru , Ohno Manabu , Hitoshi Watanabe Hitoshi Watanabe , Hiroshi Yasuda Hiroshi Yasuda
Published: October 2002

Beam calibration techniques of an EB block exposure system (NOWEL 3) are developed
to determine deflection and correction data to deflect beams through each mask pattern.
After the calibration, the current densities in a deflection area differ less than 1.6%
from the mean value. The exposure positioning errors are below 0.03 µ m in magnitude.
The calibration results are used to expose a repetitive pattern of DRAM storage capacitors.
The block mask has doughnut-type structures held by 2 µ m-wide bridges.
Rectangular 0.45×0.85 µ m2 resist patterns with clear edges are resolved
at 0.11 µ m intervals. Repetitive patterns in a logic LSIC are also exposed
with the block exposure. We extract mask patterns from the cache memory and shift
register regions. The number of exposure spots is decreased to about 1/5 of that used
in conventional rectangular shaped beam methods. The stitching errors between the mask
patterns are measured from the exposure results, which are less than 0.04 µ m.
Selective, Maskless Growth of InSb on Selenium-Treated GaAs by Molecular Beam Epitaxy
Authors: Watanabe Yoshio , Scimeca Tom , Fumihiko Maeda Fumihiko Maeda , Masaharu Oshima Masaharu Oshima
Published: October 2002

InSb nanoscale crystal islands were grown on a Se-terminated GaAs substrate by molecular beam epitaxy (MBE). In situ synchrotron radiation photoelectron spectroscopy studies for InSb island formation on this surface show that Sb atoms do not chemisorb directly onto the Se-terminated GaAs surface. The In overlayer is grown in a nearly laminar mode on the Se-terminated GaAs, and then Sb atoms diffuse across this surface until they bond to In or desorb. Consequently, InSb islands are formed. This islanding phenomenon is associated with the energy difference between the surface free energy of InSb and that of the Se-terminated surface, and with the strain energy due to the high lattice-mismatch stress. Furthermore, it is found that the InSb islands grown at 200° C have an average size of 30 nm and a density of the order of 1010 cm-2.
Resist Development Mechanism Study: Its Effect on the Submicron Microlithography Process Window
Authors: Dai Chang-Ming , Hwang-Kuen Lin Hwang-Kuen Lin , Daniel Hao-Tien Lee Daniel Hao-Tien Lee
Published: October 2002

The resist development mechanism of both spray puddle and stream puddle methods
was addressed in this paper. Two mechanisms were proposed: the pressure effect in which
the spray pressure contributes to the development rate of line/space structure layers,
but has little influence on the developing mechanism of the contact hole; and the
geometry effect in which the developer solution is more freely diffused in the line/space
structure than in the contact hole. These mechanisms have been verified in this study.
Strain-Generated Internal Fields in Pseudomorphic (In, Ga)As/GaAs Quantum Well Structures on {11l} GaAs Substrates
Authors: Decai Sun Decai Sun , Elias Towe Elias Towe
Published: October 2002

A study of the piezoelectric effect in pseudomorphic (In, Ga)As/GaAs multiple quantum well structures grown on GaAs substrates oriented in the general [11 l ] direction is reported. Theoretical calculations of the transverse polarization fields and longitudinal electric fields are presented. The calculated electric fields for the [111]- and [112]-oriented structures are compared to experimental estimates reported by other workers. Additional results to support the validity of the method are provided for structures on (110) surfaces intentionally misoriented by 6° toward the (111)B surface. The pseudomorphic (In, Ga)As/GaAs multiple quantum well structures grown on the vicinal (110) GaAs substrates were characterized by photoluminescence. It is shown that the luminescent peak intensity from these structures exhibits a spectral blue-shift with increasing excitation density. This shift is interpreted to be a manifestation of the screening of the internal, strain-induced field by photogenerated carriers.
Highly Transparent Chemically Amplified ArF Excimer Laser Resists by Absorption Band Shift for 193 nm Wavelength
Authors: Naito Takuya , Asakawa Koji , Shida Naomi , Tohru Ushirogouchi Tohru Ushirogouchi , Makoto Nakase Makoto Nakase
Published: October 2002

Naphthalene-containing chemically amplified resists for ArF excimer laser exposure
are proposed, based on the concept of the absorption band shift by conjugation extension.
Newly developed ArF excimer resists show a high transparency at 193 nm wavelength, a
high sensitivity and a high contrast. The sensitivity of the resist is 150 mJ/cm2,
which is 20 times greater than that of poly(methylmethacrylate) (PMMA). Furthermore, a 0.16 µ m
pattern could be successfully fabricated by an ArF excimer laser stepper with 0.55 numerical
aperture (N
A) projection lens.
Integration of Plasma-Assisted and Rapid Thermal Processing for Low-Thermal Budget Preparation of Ultra-Thin Dielectrics for Stacked-Gate Device Structures
Authors: Lucovsky Gerald , Ma Yi , Hattangady Sunil V. , Lee David R. , Lu Zhong , Misra Veena , Wortman Jimmie J. , Jing Ze , Whitten Jerry L.
Published: October 2002

This paper discusses a new approach to the formation of ultra-thin gate dielectrics
for Si-ULSI applications in which separately controlled plasma-assisted and/or rapid
thermal processing steps are combined to fix the chemical bonding and minimize the
defect structure at the Si–SiO2 interface, and within the dielectric layers.
One example of this approach combines (i) low-temperature (300° C) plasma-assisted
processing to control the initial bonding chemistries at (a) the Si–SiO2
interface, and (b) in homogeneous oxide, or composite dielectrics with nitride or oxynitride layers,
with (ii) higher temperature (900° C), but low-thermal budget, rapid thermal
annealing to promote physical and/or chemical relaxations that minimize both interfacial
and bulk dielectric defects, thereby improving device performance.
Formation of SiN Films by Plazma-Enhanced Chemical Vapor Deposition Using [(CH3)2N]3SiN3
Authors: Hideyuki Kitoh Hideyuki Kitoh , Masakazu Muroyama Masakazu Muroyama
Published: October 2002

An organic source gas, tris-dimethyl-amino-silyl-azide (TDSA, [(CH3)2N]3SiN3),
was newly synthesized and utilized for the deposition of a passivation film of sub-half-micrometer
devices. Deposition temperature dependence of the film formed by plasma-enhanced chemical
vapor deposition (PECVD) using TDSA was investigated and step coverage of the TDSA film
was examined. As a result, it was clarified that hydrocarbon content in the film decreased
with increasing deposition temperature. The bottom step coverage of the films formed using
TDSA was greatly improved compared to that of the conventional silicon nitride film.
Efficient Er Luminescence Centers Formed in GaAs by Metalorganic Chemical Vapor Deposition with Oxygen Codoping
Authors: Kenichiro Takahei Kenichiro Takahei , Akihito Taguchi Akihito Taguchi
Published: October 2002

Er-doped GaAs is grown by low-pressure metalorganic chemical vapor deposition with and without oxygen codoping. Optically efficient Er-oxygen complex centers are formed when a small amount of oxygen is present in the growth atmosphere. In situ monitoring of the surface morphology by light scattering from the growing surface with and without oxygen codoping suggests that migration of Er atoms on the surface is pinned by the formation of an Er-oxygen complex. We speculate that this effect suppresses the formation of Er-rich clusters and allows the formation of a high concentration of uniformly dispersed Er-oxygen complex centers that have a high luminescence efficiency.
Sub-1/4-µm Periodic Patterns with Nd:YAG Laser and Image Transfer to Silicon Surface by Reactive Ion Etching
Authors: Hiraoka Hiroyuki , Mariana Sendova Mariana Sendova , Cheng-Hao Lee Cheng-Hao Lee
Published: October 2002

Quarter-micron linear and dot patterns were made on polyimide surface spin-coated
onto silicon substrates with the Q-switched 4th-harmonic UV-pulses of Nd:YAG laser at 266 nm.
Shallow polymer images were then transferred to silicon substrates by successive reactive
ion etchings of SF6, O2 and SF6–C2ClF5 after
filling in valleys of ripples with poly(dimethylsiloxane). We were successful in fabricating
≈ 100 nm silicon structures with vertical wall profiles. Because this process
does not use any masks or scanning beam system, nanostructures can be formed on wide
surface areas of polymers, silicon, GaAs, and other surfaces. The dimensions can be
varied by varying the laser wavelength and geometrical arrangement.
Investigation of In Situ Process for GaAs/AlGaAs Buried Quantum Wires
Authors: Wakaya Fujio , Umeda Kazuhiro , Yanagisawa Junichi , Yuba Yoshihiko , Takaoka Sadao , Murase Kazuo , Gamo Kenji
Published: October 2002

To reveal the possibility of fabricating buried electron waveguides in GaAs/AlGaAs heterostructures, lateral
confinement potentials formed by in situ low-energy Si focused ion beam implantation are numerically evaluated
and the effect of growth interruption on two-dimensional electron gas (2DEG) formation is investigated. The
confinement potentials and energy eigenvalues are calculated self-consistently as a function of undoped AlGaAs
spacer layer thickness. It is confirmed that carrier depletion induced by growth interruption can be compensated
by excess doping. An unusual dependence of the 2DEG density on the growth interruption position is observed.
It may be caused by the interface states near the Fermi level at the growth-interrupted layer.
Effects of Substrate Misorientation on Improvement of Electrical Properties in Zn-Doped InAlP Alloys
Authors: Suzuki Mariko , Kazuhiko Itaya Kazuhiko Itaya , Masaki Okajima Masaki Okajima
Published: October 2002

High-concentration, low-resistivity p-type Zn-doped InAlP alloy layers were achieved using metalorganic chemical vapor deposition (MOCVD) and off-axis substrates. The highest net acceptor concentration (N
A-N
D=1.3×1018 cm-3), obtained using an off-axis substrate, is one order of magnitude higher than the previously reported maximum value. Substrate misorientation was found to improve the Zn electrical activity in addition to the enhancement of Zn incorporation efficiency. Electrical resistivities as low as 0.68 Ω ·cm were obtained. High device performance was obtained for 630 nm band laser diodes (LDs) and green light emitting diodes (LEDs) fabricated with the highly Zn-doped InAlP as the p-type cladding layers.
Ultra-Low Resistance Base Ohmic Contact with Pt/Ti/Pt/Au for High-fmax AlGaAs/GaAs Heterojunction Bipolar Transistors
Authors: Sugiyama Tohru , Kuriyama Yasuhiko , Asaka Masayuki , Iizuka Norio , Torakichi Kobayashi Torakichi Kobayashi , Masao Obara Masao Obara
Published: October 2002

Ohmic contacts to 500-Å-thick p-Al0.1Ga0.9As layer formed with a Pt/Ti/Pt/Au metal system were investigated. An extremely low contact resistivity of 4.2×10-7 Ω ·cm2 was obtained. The contact resistance increased with the increment of the Pt thickness, because the thicker the intermetallic layer becomes the thinner the AlGaAs layer beneath it, which leads to a higher contact resistance. The optimum Pt thickness was around 50 Å. Moreover, this metal scheme was thermally stable at 350° C. A high f
max of 160 GHz was obtained for AlGaAs/GaAs HBTs using Pt/Ti/Pt/Au base electrodes. A multiplexer (MUX) lC implemented with these high-f
max HBTs operated properly up to 40 Gbps, the highest speed ever reported. This value was restricted by the measuring instrument capability.
600-nm-Range GaInP/AlInP Strained Quantum Well Lasers Grown by Gas Source Molecular Beam Epitaxy
Authors: Nomura Ichirou , Kishino Katsumi , Akihiko Kikuchi Akihiko Kikuchi , Yawara Kaneko Yawara Kaneko
Published: October 2002

GaInP strained single quantum well (SSQW) lasers in the 630–710 nm range grown by gas source molecular beam epitaxy (GSMBE) using a novel shutter control method were systematically investigated. A good controllability in strain amount as well as good in-plane compositional homogeneity over 4-cm-long distance of the laser wafers were confirmed. For +1.1% compressive SSQW lasers (708 nm in wavelength), a very low threshold current density (J
th) of 175 A/cm2 was obtained. These facts suggest that the novel shutter control method is very effective for fabricating GaInP SSQW lasers. Furthermore, the post-annealing effect on lasing characteristics of GaInP SSQW lasers was investigated. The increased p carrier density of Be-doped AlInP layers was obtained with the remarkable reduction in J
th value of 633 nm tensile SSQW lasers from 850 A/cm2 to 555 A/cm2.
Comparison of Electrical and Optical Properties of n-i-i and p-i-n ZnSSe Heterostructure Diodes
Authors: Fujii Yoshihisa , Ikuo Suemune Ikuo Suemune , Masahiro Fujimoto Masahiro Fujimoto
Published: October 2002

Contribution of p-type doping to ZnSSe heterostructure diodes was studied by comparing electrical and optical properties of n-i-i and p-i-n diodes grown by metalorganic vapor phase epitaxy. Although the current flow was observed in the n-i-i heterostructure diode, the redshift of an electroluminescence peak was observed for a higher bias voltage. This was interpreted to be the Stark shift due to the electric field induced in the quantum well structure in the n-i-i diode. The current flow in p-i-n diodes showed much lower voltage operations than that in n-i-i diodes. It was also much better than that of the blue-green laser diodes grown by molecular beam epitaxy.
Quantum Well Local-to-Global State Transitions under an Electric Field
Authors: Chen Weiquan , Thorvald G. Andersson Thorvald G. Andersson , Shumin Wang Shumin Wang
Published: October 2002

Electric-field-induced optical effects have been studied in two-step and inverse parabolic quantum wells grown by molecular beam epitaxy. The inverse parabolic well was grown by digital and analog compositional grading techniques. Both types of wells had much larger Stark shifts than the conventional square well. This is an effect of the special shape of the well allowing local-to-global state transitions. Observed deviations from calculated results for the analog inverse parabolic well are attributed to fluctuation in quantum well parameters.
Si Epitaxy below 400°C from Fluorinated Precursors SiFnHm (n+m≤ 3) under In Situ Observation with Ellipsometry
Authors: Akasaka Tetsuya , Yuhzo Araki Yuhzo Araki , Isamu Shimizu Isamu Shimizu
Published: October 2002

A systematic study of Si epitaxy below 400°C was performed under in situ observation with ellipsometry. From the fluorinated precursors SiF

n

H

m

(m+n≤3), epitaxial films were fabricated on (100)-oriented Si substrates in the temperature range from 260 to 400°C. According to in situ ellipsometric observation, a highly ordered crystalline layer over 500 nm thick was grown on a partially fluctuating initial layer 8 nm thick. On the other hand, epitaxial growth was limited to within 50 nm thick on both (110)- and (111)-oriented substrates. Polycrystalline Si with columnar texture was finally grown with increasing thickness on these substrates. In situ ellipsometry is very useful for monitoring crystalline growth in chemical vapor deposition (CVD) techniques.
Temperature Dependence of Quantized States in Strained-Layer In0.21Ga0.79As/GaAs Single Quantum Well
Authors: Chi Wuh-Sheng , Huang Ying-Sheng , Qiang Hao , Pollak Fred H. , Pettit David G. , Woodall Jerry M.
Published: October 2002

The piezoreflectance (PzR) and photoreflectance (PR) measurements of a strained-layer (001) In0.21Ga0.79As/GaAs single quantum well as a function of temperature in the range of 20 to 300 K have been carried out. A careful analysis of the PzR and PR spectra has led to the identification of various excitonic transitions, mnH(L), between the mth conduction band state to the nth heavy (light)-hole band state. The parameters that describe the temperature dependence of E
mnH(L) are evaluated. The detailed study of the temperature variation of excitonic transition energies indicates that the main influence of temperature on quantized transitions is through the temperature dependence of the band gap of the constituent material in the well. The temperature dependence of the linewidth of the 11H exciton is evaluated and compared with that of the bulk material.
Thermal Stress and Dislocation Density in Undercut GaAs on Si
Authors: Wada Naoki , Shiro Sakai Shiro Sakai , Masuo Fukui Masuo Fukui
Published: October 2002

Thermal stress and dislocation density in undercut GaAs on Si(UCGAS) in which the GaAs/Si interface was partially eliminated by post-growth processing were investigated. Thermal stress of less than 2×108 dyn/cm2 was obtained in the area that is large enough for practical applications. The dislocation density was also reduced to less than 5×105 cm-2 by growing strained-layer superlattice (SLS) and GaAs layers on the UCGAS. The dislocation reduction was due to the fact that the UCGAS was free from the stress-induced dislocations during cooling after the growth. As a result, photoluminescence peak wavelength and peak intensity measured in the UCGAS have become almost the same as those in homoepitaxial GaAs.
Comparison of Dry Development Techniques using O2 and SO2/O2 Low-Pressure Plasmas
Authors: Pons Michel , Joubert Olivier , Martinet Christine , Pelletier Jacques , Jean-Pierre Panabière Jean-Pierre Panabière , André Weill André Weill
Published: October 2002

A parametric study of the pattern transfer step in a trilevel resist system using oxygen-based plasmas has been performed using a distributed electron cyclotron resonance reactor with independent rf biasing. In pure oxygen plasmas, critical dimension loss is always present. The mechanisms most likely to be responsible for these defects during the pattern transfer process are presented and discussed. A novel plasma etching process based on sidewall passivation by sulfur is proposed using SO2/O2 mixtures. Perfect anisotropy with negligiable critical dimension loss is obtained at room temperature.
Enhanced Tc and Strong Flux Pinning in Melt-Processed NdBa2Cu3Oy Superconductors
Authors: Yoo Sang-Im , Murakami Masato , Sakai Naomichi , Takamitsu Higuchi Takamitsu Higuchi , Shoji Tanaka Shoji Tanaka
Published: October 2002

The effects of various oxygen partial pressures (P
O2) during melt processing on the superconducting properties of fabricated NdBa2Cu3O

y

(Nd123) superconductors have been systematically investigated. Unlike in air or O2, samples melt-processed in reduced oxygen atmospheres exhibited unprecedentedly high T
c's of 95–96 K with a sharp superconducting transition. Especially, for a sample melt-processed in 0.1% O2 in Ar, the magnetization hysteresis ( M-H ) loop was kept open up to 7 T at 77 K and for the field parallel to the c-axis of the sample (H//c), implying that very effective flux pinning can be achieved in high magnetic fields.
Power Optimization of 2 µ m Tm,Ho:YAG Laser in Monolithic Crystal
Authors: Nakajima Hayato , Yokozawa Takeshi , Yamamoto Takanobu , Djeu Hiroshi Hara
Published: October 2002

This letter reports power optimization of a 2 µm Tm,Ho:YAG microchip laser when pumped by a Ti:sapphire laser at room temperature. A slope efficiency of 70% and a minimum threshold power of 12 mW with a half-symmetric stable resonator geometry was observed when pumping beam diameter coincided with the beam waist of the resonator. Lasing performance with the half-symmetric stable resonator was better than with a near-planar one, which is also reported.
Effect of Optical Breakdown on Second Harmonic Generation from Si(111)7×7 with Nd:YAG Laser
Authors: Nakamura Ken , Shingo Ichimura Shingo Ichimura , Hazime Shimizu Hazime Shimizu
Published: October 2002

Effect of optical breakdown on second harmonic generation (SHG) from Si(111)7×7 was investigated. After the irradiation of a laser beam with a threshold energy for the optical breakdown, the intensity of second harmonics (SH) polarized along the [011̄] axis measured as a function of pump-polarization showed deviation from 90° periodicity which is expected from the surface C
3v
symmetry, although low energy electron diffraction (LEED) still exhibited the 7×7 structure. The irradiation of a more intense laser beam led to structural disorder, resulting in complete disappearance of SH periodicity, and no pattern of LEED was exhibited.
Approximate Solution of Converging Shock Growth in Condensed Media
Authors: Kunihito Nagayama Kunihito Nagayama
Published: October 2002

The exact solution of the approximate differential equation for converging shock propagation has been found for the Grüneisen solids. The effects of the various material properties on the shock convergence phenomena can be discussed by using this explicit and closed-form solution to the problem. The solution of the cylindrical shock convergence problem in aluminum shows that the degree of compression has been suppressed by decreasing the Grüneisen parameter and the nonlinearity parameter. This result indicates the effects of the entropy increase on the phenomena.
Formation of ZnGa2Se4Epitaxial Layer during Molecular Beam Epitaxial Growth of Ga2Se3on ZnSe
Authors: Okamoto Tamotsu , Miyashita Toshihiko , Yamada Akira , Takahashi Makoto Konagai
Published: October 2002

Epitaxial ZnGa2Se4films were successfully grown on (100)GaAs substrates for the first time. When Ga2Se3/ZnSe heterostructures were prepared on (100)GaAs by molecular beam epitaxy (MBE), a ZnGa2Se4epitaxial layer was obtained at temperatures above 540° C. The electron diffraction and Raman spectra revealed that thec-axis-oriented ZnGa2Se4epitaxial film with a defect chalcopyrite structure was formed during the MBE growth of Ga2Se3on ZnSe. Furthermore, a broad emission peak centered around 670 nm was observed in epitaxial ZnGa2Se4film in low-temperature photoluminescence measurements.
Large Magnetic Interface Anisotropy in Molecular Beam Epitaxy Grown Pt/Co and Pt/Co/Ag Superlattices
Authors: Toshiki Kingetsu Toshiki Kingetsu
Published: October 2002

The magnetic anisotropy of (111)Pt/Co and Pt/Co/Ag superlattices (SLs) grown on 7×7 -(111)Si by molecular beam epitaxy was studied. The interface anisotropyKsof Pt/Co SLs is found to be 1.29 mJ/m2, which is much larger than the value reported previously. The effective anisotropy energyKef fof Pt/Co/Ag SLs is similar to the average ofKef fvalues of Pt/Co and Ag/Co SLs with the same Co layer thickness. This suggests that the origins of perpendicular anisotropy in the Pt/Co system are different from those in the Au/Co system investigated earlier, in which the difference between theKef fvalues of Au/Co and Au/Co/Ag SLs is small.
Temperature and Incident Beam-Current Dependence of Dominant Free-Exciton Recombination Radiation from High-Purity Chemical Vapor Deposition (CVD) Diamonds
Authors: Yamaguchi Akira , Yamashita Satoshi , Takahiro Tsutsumi Takahiro Tsutsumi , Hiroshi Kawarada Hiroshi Kawarada
Published: October 2002

Dominant free-exciton (FE) recombination radiation has been obtained from high-purity Chemical vapor deposition (CVD) diamond synthesized on Cu substrates by means of microwave plasma CVD using CH4+O2diluted with H2. The intensity of FE emission is almost constant between 80 K and 170 K, and is reduced by two orders of magnitude at room temperature. The emission increases in proportion to the incident beam current from 1×10-9A to 2×10-6A. The spectrum shapes between 200 nm and 600 nm do not depend on the beam current. In addition, the isotopic effect on the FE emission peak shift has been observed in the spectrum from13C-enriched (96.6%) CVD diamond for the first time.
Detection of Open Contact Using Optical-Beam-Induced Current Techniques
Authors: Hirotaka Komoda Hirotaka Komoda , Katsusuke Shimizu Katsusuke Shimizu
Published: October 2002

Optical-beam-induced current (OBIC) techniques have been reported as very useful failure analysis tools for detecting leakage sites and latch-up sensitivity. In this study, this OBIC technique was successfully applied to detect an open contact site. Focused ion beam (FIB) cross-sectioning and observation of the open contact revealed the cause of open failure. This OBIC technique was proven to be very rapid and convenient, because no special sample preparation is necessary.
Microscopically Smooth Surface of Pulse Laser Deposited YBa2Cu3O7 Film Shown by Grazing Incidence X-Ray Reflectivity
Authors: Harumi Asami Harumi Asami , Yukio Watanabe Yukio Watanabe
Published: October 2002

Surface and film/substrate interface roughness of YBa2Cu3O7 films deposited on MgO(100) and SrTiO3(100) by rapid sequential pulse laser deposition has been determined from X-ray reflectivity data. The film on MgO had the average roughness of 26.2 Å at the film/substrate interface and roughness of one unit cell order at the surface. On the other hand, the film on SrTiO3 had approximately the average roughness of 40 Å at both the surface and film/substrate interface. Obviously, the surface of the film on MgO is smoother than that on STO. The rough surface of the film on SrTiO3 is considered to be partly due to the growth of the film along the steps of the substrate, while the film on MgO grows without the influence of the steps on the substrate.
Optical Absorption Spectra of A6C60: Reduction of Effective Coulomb Interactions
Authors: Kikuo Harigaya Kikuo Harigaya
Published: October 2002

We theoretically investigate optical absorption spectra of C60
6-, and discuss their relations with the optical properties of alkali metal-doped fullerides A
6 C60. We use a tight binding model with long-range Coulomb interactions and bond disorder. Frenkel exciton effects are taken into account by the Hartree-Fock approximation and the CI method. We find that the Coulomb interaction parameters relevant to the optical spectra of A
6 C60 are almost half of those of the neutral C60. This finding is closely related with the experimental result that dielectric constants of fullerides maximally doped with alkali metals become about twice as large as those of the neutral systems.
Unique Electric Field Dependence of Apparent Tilt Angle in Ferroelectric Liquid Crystal Mixtures Consisting of Fluorine-Substituted Compounds
Authors: Sakaigawa Akira , Sachiko Yokoi Sachiko Yokoi , Hiroyuki Nohira Hiroyuki Nohira
Published: October 2002

New ferroelectric liquid crystal mixtures having perfluoroalkyl groups were prepared. Apparent tilt angles of these mixtures largely depended on the electric field. The tilt angle increased linearly under electric field in the range from 0 to 12 V, and decreased under higher electric field over 12 V. The mechanism of this θ-V property has been proposed and a new light-modulator has been designed using the linear dependence of the tilt angles on the electric field.
Hydrogen Permeability of Palladium Needles and Possibility of New Field Ion Source
Authors: Teraoka Tsutomu , Hideaki Nakane Hideaki Nakane , Hiroshi Adachi Hiroshi Adachi
Published: October 2002

We believe that palladium has the potential to provide a new method of supplying hydrogen molecules to the apex of the needle electrode of a field ionization proton beam source, because it has the highest hydrogen permeability among all metals. Hydrogen permeability of a fine palladium needle was measured in a preliminary experiment, and was found to be 2.0×10-5Torr·l/sat 600° C for a hydrogen pressure of 1.5 atm. This value is of the same level as that for bulk palladium, and is expected to be sufficient for the proposed ion source. In the ionization experiments, a small ion curtent was detected.
Light-Induced-ESR Study of Undoped and N-Doped Hydrogenated Amorphous Silicon
Authors: Zhou Jiang-Huai , Okagawa Takatoshi , Minoru Kumeda Minoru Kumeda , Tatsuo Shimizu Tatsuo Shimizu
Published: October 2002

We have measured the light-induced electron spin resonance (LESR) in undoped and N-doped hydrogenated amorphous silicon over a wide range of excitation intensities. By decomposing the LESR signal into a broad component, the neutral-dangling-bond component and a narrow component, we find that the density of neutral dangling bonds (D
0) increases under illumination at 77 K in undoped samples in the annealed state and in N-doped samples in both the annealed and light-soaked states. No saturation of the D
0 density is seen even at excitation intensities of about 700 mW/cm2. However, a decrease in the D
0 density occurs in undoped samples in the light-soaked state at excitation intensities below about 10 mW/cm2. We show that the change of the D
0 density under illumination at 77 K can be accounted for qualitatively with a model in which conversion takes place between dangling bonds in various charge states.
Resonant Tunneling Spectroscopy of Sidewall-Confined States and Impurity-Bound States Using AlGaAs-GaAs Triple-Barrier Diodes
Authors: Kazumasa Nomoto Kazumasa Nomoto , Toshi-kazu Suzuki Toshi-kazu Suzuki , Kenichi Taira Kenichi Taira , Ichiro Hase Ichiro Hase
Published: October 2002

We have studied resonant tunneling (RT) through AlGaAs-GaAs triple-barrier diodes with diameters between 0.4 µm and 18 µm. We have observed two sets of fine structures just above and below the RT threshold voltage V
th in the current-voltage curve of a submicron diode at T=4 K. The magnetic field dependence of the structure set above V
th is well fitted by calculation assuming a diode sidewall-depletion confinement. The other set below V
th is sample dependent and tends to disappear as the diode becomes smaller, which suggests that their origin is RT through impurity-bound states.
Tilted Uniaxial Magnetic Anisotropy in Sputtered TbFeCo Films
Authors: Shiomi Shigeru , Kato Junji , Saito Seiji , Tadashi Kobayashi Tadashi Kobayashi , Morio Masuda Morio Masuda
Published: October 2002

Tb

x

(Fe50Co50)1-
x

films were deposited on glass slides using a DC sputtering apparatus. Torque measurements revealed that both perpendicular and in-plane uniaxial anisotropy components are induced in resputtered films with FeCo-dominant composition. The easy axis of the in-plane anisotropy component is aligned with the magnetic field applied during deposition. Torque curve analysis revealed that tilting of the easy axis from the film normal in alternate directions can reproduce the measured torque curves very well. In GdCo, DyCo and ErCo films, however, no appreciable in-plane uniaxial anisotropy was induced.
Relaxation Processes in the Antiferroelectric Phase as Studied by Dielectric Spectroscopy
Authors: Hiller Steffen , Pikin Sergei A. , Haase Wolfgang , Goodby John W. , Nishiyama Isa
Published: October 2002

The dielectric behavior of the antiferroelectric liquid crystal (R)-1-methyl- heptyl-4-( 4′′-n-dodecyloxybiphenyl- 4′ carbonoyloxy)-3-fluorobenzoate was investigated by dielectric spectroscopy. In the antiferroelectric SmC
A

* phase three dielectric active processes were detected. At least one of them, the process at high frequencies, can also be observed in the ferrielectric phase. In addition to this absorption at high frequency, two other processes with weak intensities around 1 kHz and 50 kHz were detected. These processes are described as functions of temperature, bias voltage and oscillating voltage.
Reduction of Droplet Formation by Reducing Target Etching Rate in Pulsed Laser Ablation
Authors: Yonezawa Yasuto , Segawa Kazuhito , Katayama Syuji , Minamikawa Toshiharu , Morimoto Akiharu , Shimizu Tatsuo
Published: October 2002

Droplet formation in the film and maximum etching depth of the target in the process of pulsed-laser-ablation (PLA) deposition were investigated by scanning tunneling microscopy and stylus profilometry, respectively. The ratio of the droplet volume to the film volume (V
d/V
f) was found to be proportional to d
3
e (d
e being the maximum etching depth of the target) for a variety of ablated materials and wavelengths of the laser. This fact suggests that a laser with a low fluence, a short wavelength and a short pulse width, and a high-density target are preferred for the preparation of film with fewer droplets.
Fine-Patterning of ZrO2 Thin Films by the Photolysis of Chemically Modified Gel Films
Authors: Shinmou Katsuhide , Tohge Noboru , Tsutomu Minami Tsutomu Minami
Published: October 2002

The effects of UV irradiation on the properties of gel films prepared from Zr- n-butoxides modified with acetylacetone (AcAc) have been studied. The irradiation with UV light corresponding to the π-π* transition in the chelate ring of AcAc was found to dissociate the chelate bonds in the gel films and simultaneously decrease the solubility of these gel films in acidic solutions. This finding was applied to the patterning of ZrO2 thin films; a gel film was irradiated through a mask, leached in an acidic solution, and heat-treated. Through the process above, finely patterned ZrO2 films were fabricated on various substrates.
Reduction Imaging at 4.5 nm with Schwarzschild Optics
Authors: Nagata Hiroshi , Ohtani Masayuki , Murakami Katsuhiko , Oizumi Hiroaki , Yamashita Yoshio , Atoda Nobufumi
Published: October 2002

Soft X-ray reduction imaging with NiCr/C-multilayer-coated Schwarzschild optics was examined at 4.5 nm. The patterns on transmission masks were imaged with a synchrotron radiation light source. Line-and-space (L & S) patterns down to 0.15 µm were fabricated in 0.3-µm-thick resist, and 0.3 µm L & S patterns were fabricated in 0.9-µm-thick resist.
Glass Transition Temperature of Copolymers Used as Printer Toner
Authors: Makabe Akira , Araki Shin , Masatoshi Kimura Masatoshi Kimura , Yoshiyuki Aida Yoshiyuki Aida
Published: October 2002

The thermal characteristics of copolymers commonly used as toner in the electrophotographic process are critical- and in particular their glass transition temperature. We used emulsion polymerization to synthesize two kinds of copolymer toner with various molecular weights, styrene-n-butyl methacrylate and n-bythyl acrylate, and evaluated their glass transition temperatures using differential scanning calorimetry. The glass transition temperature of copolymers was determined not by their average molecular weight, but by their mole fractions.
Linewidth Broadening in Wavelength Tunable Laser Diode due to Absorption and Parasitic Currents
Authors: Andreas Dieckmann Andreas Dieckmann
Published: October 2002

The linewidth broadening mechanism of wavelength tunable laser diodes in the case of no carrier injection into the tuning region is explained by absorption of photons and by parasitic currents through the tuning region. The spectral linewidth due to spontaneous emission events in the lasing medium is significantly smaller which is proved experimentally for the tunable twin-guide laser diode. The results presented here agree with the theoretical predictions.
Precipitation of Silver Particles in Glasses by Ion Irradiation
Authors: Kitazawa Nobuaki , Yano Tetsuji , Shuichi Shibata Shuichi Shibata , Masayuki Yamane Masayuki Yamane
Published: October 2002

Quantum-sized silver particles have been precipitated from glass in the ternary system Ag2O–Al2O3–P2O5 by ion irradiation at 10–20 keV energy. The optical absorption band in the vicinity of 420 nm wavelength due to plasma resonance increased in intensity with increasing irradiation dose up to 1016 ions/cm2, but decreased with higher dose irradiation. The attainable absorption intensity caused by ion irradiation was influenced by parameters such as ion energy, ion species and Ag2O content in the glass. N+
2 and Ar+ ions with 20 keV energy gave the absorption coefficient of 20000 cm-1 for glass containing 20 mol% Ag2O. The driving force of particle formation is attributed to the preferential sputtering of oxygen over other constituents during ion irradiation.