bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical Response and Heat Characteristics in Y1Ba2Cu3O7-δ Microbridges with Different Surface Morphologies
Authors: Chen Hone-Zern , Chen Y. C. , Wu Z. S. , Jia S. C. , Lin C. H. , Chou Hsiung
Published: October 2002

Y1Ba2Cu3O7-δ (YBCO) films with different surface morphologies have been used to study the dependence of the bolometric effect on the precipitates on the films. Films were patterned into microbridge bolometers with 25 µ m width and 650 µ m length. Although these microbridges had different T
co (R=0), they had similar transition widths of about 1.8–2 K and similar ( dR/ dT) max values of about 71–78 Ω/ K. The precipitate coverages were varied from 0% to 100%. The photoresponses decreased exponentially from 2300 to 431 V/W with increasing precipitate coverage. We propose that the precipitate can be regarded as a low thermal conductive layer. This layer absorbed the incident light and preserved the thermal energy in it before passing it to the YBCO background layer. The modulated A
C thermal signal ΔT is, therefore, suppressed by this layer such that a small signal is detected in the YBCO film. The noise equivalent power, however, increased with precipitation coverage; this implies an enhanced scattering of the superconducting carrier to the precipitates. The best values of noise equivalent power (NEP) and the detectivity (D
*) in the present study were about NEP ≦5×10-12 W·Hz-0.5 and D
* ≧109 cm·Hz0.5·W-1.
Electron-Beam Electroreflectance Spectroscopy of Semiconductors
Authors: Takashi Kita Takashi Kita , Taneo Nishino Taneo Nishino
Published: October 2002

An electron-beam electroreflectance (EBER) spectroscopy system combined with a scanning electron microscope has been newly developed. We can obtain the electron-beam electroreflectance spectrum from a local area monitored by the scanning electron microscope. Utilizing this contactless system, electron-beam electroreflectance spectra of GaAs and Si wafers, CuAlSe2 and CuGaSe2 chalcopyrite crystals grown on GaAs(001), and ZnSe thin films on GaAs(001) were measured in the range of 1.0–6.0 eV. The modulation mechanism of EBER was clarified by a systematic investigation of the modulated signal as a function of beam-current density, electron energy, and modulation frequency. We suggest that the electron-beam electroreflectance system is suitable for studying and characterizing electronic structures of semiconductors: bulk, surface/interface, heterostructures, and microstructures.
Melting CuO in BaTiO3-based System
Authors: Cheng-Fu Yang Cheng-Fu Yang
Published: October 2002

A liquid phase formed from the melt of CuO has been demonstrated to appear at temperatures lower than 900° C in the BaTi1.01O3.02 system. Differential thermal analysis (DTA) and thermogravimetric (TGA) for BaTi1.01O3.02 with 1 wt% CuO added reveal an endothermic peak, starting at about 900° C and accompanied by a weight loss of about 0.12 wt%. The more CuO is added into BaTi1.01O3.02, the lower the temperature ranges of endothermic peaks and the more the weight loss will be. BaTi1.01O3.02 with CuO added can be densified at a temperature lower than 1100° C. The DTA and TGA curves for pure BaTiO3 with only CuO or with CuO and TiO2 each exhibit a shallow endothermic peak. These endothermic peaks begin at about 990° C and finish at about 1030° C, accompanied by an insignificant weight loss. CuO can also improve the densification of both pure BaTiO3 and pure BaTiO3 with TiO2 added at a temperature lower than 1250° C.
X-Ray Reflectometry and Infrared Analysis of Native Oxides on Si (100) Formed by Chemical Treatment
Authors: Sugita Yoshihiro , Satoru Watanabe Satoru Watanabe , Naoki Awaji Naoki Awaji
Published: October 2002

We investigated native-oxide formation on Si(100) in some cleaning solutions. The macroscopic density and thickness of the native oxides were determined by glancing incidence X-ray reflectometry (GIXR). The chemical structures were revealed by Fourier transform infrared (FT-IR) analysis and compared with the macroscopic parameters. Low density and chemical imperfections were found in oxides formed in some chemical solutions ( HCl/H2O2, NH4OH/H2O2 and HNO3 solutions). The films with the most chemically homogeneous and densest oxide were prepared using H2SO4/H2O2 solution and ozonized water. The variations of the chemical structures were correlatively well explained in term of macroscopic parameters. We discuss the possible physical structures of native oxides based on the results of our experiments, as well as previous observations.
In Situ Laser Beam Alignment for Thomson Scattering System
Authors: Kazumichi Narihara Kazumichi Narihara , Kenji Yamauchi Kenji Yamauchi
Published: October 2002

An in situ laser beam alignment method was developed for a tokamak plasma Thomson scattering system. The laser beam position was swept rapidly while observing the scattered light signals from 28-channel polychromators, using which the tilt angle and position of the laser beam were optimized.
Overlay Accuracy Measurement Technique Using the Latent Image on a Chemically Amplified Resist
Authors: Yamashita Kazuhiro , Muro Masahiro , Kobayashi Satoshi , Akiko Katsuyama Akiko Katsuyama , Masayuki Endo Masayuki Endo
Published: October 2002

An overlay accuracy measurement technique has been devised using the latent image on a chemically amplified resist developed in-house. A latent image with step height of over 0.1 µ m was formed after KrF excimer laser irradiation. It has been confirmed that it is possible to measure overlay accuracy using this latent image with measurement accuracy within 10 nm. This technique is very useful for overlay accuracy measurement of an exposure system using a double exposure method with a chemically amplified resist. It has been verified that heterodyne holographic wafer alignment (HHWA) has the capability to detect a latent image with shallow step height. Overlay accuracy within 60 nm was obtained using overlay error correction with this developed overlay accuracy measurement technique.
Suppression of <100> Dark-Line Defect Growth in AlGaAs/InGaAs Single Quantum Well Lasers Grown on Si Substrates
Authors: Hasegawa Yoshiaki , Egawa Takashi , Jimbo Takashi , Masayoshi Umeno Masayoshi Umeno
Published: October 2002

We report the suppression of <100> dark-line defect growth in AlGaAs/In

x

Ga1-
x

As quantum well lasers on Si substrates grown by metalorganic chemical vapor deposition. An AlGaAs/In0.02Ga0.98As laser on Si with an In0.08Ga0.92As intermediate layer (InGaAs IL) has a stress-relieved active layer, while an AlGaAs/In0.07Ga0.93As laser on Si with an InGaAs IL has a compressive-stress induced active layer. The AlGaAs/In0.07Ga0.93As laser had a higher threshold current density than the AlGaAs/In0.02Ga0.98As laser due to the increased bending of the threading dislocations in the active layer. The lifetimes of these lasers at 300 K were markedly increased, due to the reduction in the dark spot density resulting from the introduction of the InGaAs IL and the reduction in the <100> dark-line defect growth velocity resulting from the dislocation pinning in the InGaAs active layer.
Comment on “Optical Characterization of Si 1 - xCx/Si (0≤ x ≤0.014) Semiconductor Alloys"
Authors: Zollner Stefan , Junge Kelly E. , Lange Rüdiger , Affolder Anthony A.
Published: October 2002

A comment on Lee et al.: Jpn. J. Appl. Phys. 34 (1995) L1340.
Simulation of Collector Current Distribution in Heterojunction Bipolar Transistors Using Newly Proposed Empirical Expression
Authors: Shimura Teruyuki , Sakai Masayuki , Kato Manabu , Izumi Sigekazu , Hattori Ryo , Takuji Sonoda Takuji Sonoda , Saburou Takamiya Saburou Takamiya
Published: October 2002

This paper proposes a new empirical expression of the collector current in multifinger HBTs (Heterojunction Bipolar Transistors) as a function of the junction temperature, which is essential for optimizing the device layout and the ballasting resistor. The novel calculation yields more precise agreement with measured data than the conventional one. This scheme should be useful for elucidating the actual collector current distribution over each finger in multifinger HBTs.
A Rigorous Series Solution for Diamond Heat Spreaders with Temperature-Dependent Thermal Conductivity Used in Microwave Power Devices
Authors: Hui Ping , Tso Chih Ping , Hong Siang Tan Hong Siang Tan
Published: October 2002

In this paper we derive a rigorous series solution of the nonlinear heat transfer equation using the modified Kirchhoff transformation for a cylindrical diamond heat spreader with temperature-dependent thermal conductivity, situated on the top of a copper heat sink. We point out what we believe to be errors in two analytical approaches applied to the same problem which were published recently [Proc. R. Soc. Lond. A 441 (1993) 181; Proc. R. Soc. Lond. A 445 (1995) 375; and IEEE Trans. Microwave Theor. & Technol. 42 (1994) 573]. The basic difference between our work and these previous studies lies in the boundary condition (b.c.) of the transformed heat potential over the spreader-sink interface–we use nonlinear b.c. whereas the boundary conditions in the previous studies have been assumed to be linear. Calculations of change in the thermal resistance with the geometrical dimensions of the spreader, the input power, and the ambient temperature show up the profound influence which the assumed b.c. have on the problem. Our study has also revealed errors in numerical results presented in another paper [IEEE Semi-Therm Proc. (4th Annu. Semiconductor Thermal and Temperature Measurement Symp.), p. 113].
A Streak Mode Soft X-ray Imaging System
Authors: Takeshi Yanagidaira Takeshi Yanagidaira , Morihiko Sato Morihiko Sato , Katsumi Hirano Katsumi Hirano
Published: October 2002

A streak mode soft X-ray imaging system was newly developed. The system is composed of a combination of a six-channel scintillator-photomultiplier array and a pinhole camera. In this system, the pinhole camera was used to obtain the spatial distribution of the impulsive soft X-ray source quantitatively. Analog signals from the photomultiplier array were provided to obtain the time variation of the source intensity. Software was developed to perform a streak mode display consisting of a 25×20 mesh (3.2 ns/div and 1 mm/div). This system has been successfully employed to observe the time evolution of X-ray emission in plasma focus discharges with puffed Ar. The lifetime and the intensity of the soft X-ray emitting spots around 4 Å were found typically to be ∼5 ns and ∼1016 photons/(mrad2·mm·s), respectively.
Capture Cross Section of Electric-Stress-Induced Interface States in (100) Si Metal/Oxide/Semiconductor Capacitors
Authors: Masao Inoue Masao Inoue , Akihiro Shimada Akihiro Shimada , Junji Shirafuji Junji Shirafuji
Published: October 2002

The capture cross section of interface states induced by Fowler-Nordheim tunneling electron injection in (100) n- and p-Si metal/oxide/semiconductor (MOS) capacitors has been measured as a function of interface-state density by means of the ac conductance method. In n-Si MOS capacitors two interface states are generated in the upper half of the Si gap, while in p-Si MOS capacitors only one interface state is observed in the lower half of the gap. The capture cross section for electrons (upper half of the gap) and for holes (lower half of the gap) tends to decrease when the interface-state densities exceed about 1.5×1011cm-2eV-1. This behavior is explained by taking the occurrence of additional tunneling to defect states in the oxide into account. Moreover, the difference in the slopes of the descending characteristics of electron and hole capture cross sections is used to estimate the effective-mass ratio of an electron and a hole in the SiO2gap.
Time Responses of Photovoltage and Photocurrent Observed in Ag-Rich Ag–As(Ge)–S Glass
Authors: Takeshi Kawaguchi Takeshi Kawaguchi , Shigeo Maruno Shigeo Maruno
Published: October 2002

Photovoltage and photocurrent for Ag–As(Ge)–S glass with Ag content of 30–45 at.% sandwiched between Au films have been investigated under various conditions. The unique time responses have been explained in terms of migration of Ag+ ions by counterflow to the motion of photoexcited holes, and subsequent formation of a Ag+ ion-depleted layer in the vicinity of the illuminated electrode.
Elementary Cellular Automaton Actions in a RF-Superconducting Quantum Interference Device Network
Authors: Saitoh Kazuo , Willy Hioe Willy Hioe , Toshikazu Nishino Toshikazu Nishino
Published: October 2002

The cellular automaton (CA) is promising as a distinctive information processing unit which can be used to solve optimization problems or to process images in a very small circuit with very high speed. In this paper, we clarified a novel application of the rf-superconducting quantum interference device (SQUID) for obtaining CA actions, based on numerical simulations. It has been shown that the features of the rf-SQUID, such as non-linear characteristics, latching effect and multiple inputs, are very efficient for implementation of CA. By virtue of these features, basic operations in CA actions such as setting up local transition rules and synchronous update of cell states can be obtained straightforwardly. Furthermore, we discuss the relationship between CA actions in the rf-SQUID network and information processing.
Critical Current Densities and Irreversibility Lines of Twinning Plane-Free La–Ca–Ba–Cu–O Superconductors with YBa2Cu3Oy-Type Structure
Authors: Fujii Hiroki , Hiroaki Kumakura Hiroaki Kumakura , Kazumasa Togano Kazumasa Togano
Published: October 2002

Ca-doped tetragonal La3Ca

x

Ba4-
x

Cu7O

y

superconductors were prepared. The critical temperature (T
c) and irreversibility field (B
irr) of La3Ca

x

Ba4-
x

Cu7O

y

strongly depended on the amount of Ca and the sample with the composition close to La1.29Ca0.43Ba1.29Cu3O

y

(referred to as La3Ca1Ba3Cu7O

y

; La-3137) showed the highest T
c, 78 K. The slope of B
irr-T lines increased with increasing Ca content for x≤1, and then, decreased for x>1, although the c-axis monotonically decreased with increasing Ca content. This behavior can be explained by the change of the carrier (hole) concentration with Ca content. The J
c-B (critical current density-field) curves of La-3137 were similar to those of YBa2Cu3O

y

(Y-123) because of the similarity in anisotropy. However, the temperature dependence of J
c of La-3137 was larger than that of Y-123, and the slope of B
irr-T lines was smaller than that of Y-123 due to the absence of twinning planes.
Investigation of the Crystal Shape Controllability of YBa2Cu3O7-x Single Crystals in the Pulling Method
Authors: Namikawa Yasuo , Masahiro Egami Masahiro Egami , Yuh Shiohara Yuh Shiohara
Published: October 2002

The influence of the geometrical difference on the crystal growth rate of YBa2Cu3O7-
x

(Y123) single crystals in the modified pulling method was investigated. The growth rate of {001} faces appeared on the bottom of the crystals grown along <001> direction (R

c
v

c
) was about 1.6–2.0 times higher than that of {100} faces appeared on the bottom of the crystals grown along <100> direction (R

a
v

a
). R

a
v

a
is more sensitive to the change of supersaturation than R

a
h

a
(the crystal growth rate of {100} faces appeared on the side of the crystals grown along <100> direction) for the low crystal pulling rate and for the low supersaturation regime, although these faces are crystallographically the same. These difference is attributed to the increase of the temperature at the crystal bottom face during the crystal growth. It is supposed from the experimental results that Y123 single crystals having long and nearly straight body parts with expanding about 25° can be obtained in the <001> direction growth of the modified pulling method.
Calculation of Demagnetizing Field Distribution Based on Fast Fourier Transform of Convolution
Authors: Nobuo Hayashi Nobuo Hayashi , Koji Saito Koji Saito , Yoshinobu Nakatani Yoshinobu Nakatani
Published: October 2002

It is confirmed that the calculation of the demagnetizing field in micromagnetic simulations can be accelerated significantly by using the discrete convolution theorem and the fast Fourier transform (FFT). When the magnetization distribution is periodic, application of the theorem to the demagnetizing field calculation is straightforward. Unlike the previously reported FFT method which is based on the continuous Fourier transform of the demagnetizing field, the method can also be used in the case of non-periodic magnetization structures. It is also confirmed that the result obtained using the new FFT method coincides with that of the conventional direct method, as expected. The principle of calculation and the results of one- and two-dimensional calculations which show the validity and effectiveness of the developed method are presented.
Exchange Coupling between Antiferromagnetic Mn–Ir and Ferromagnetic Ni–Fe Layers
Authors: Hoshino Katsumi , Nakatani Ryoichi , Hoshiya Hiroyuki , Sugita Yutaka , Tsunashima Shigeru
Published: October 2002

Exchange couplings between antiferromagnetic Mn–Ir and ferromagnetic Ni–Fe layers have been investigated while varying the Mn–Ir composition. These exchange couplings appeared at room temperature at Ir compositions between 20 and 46 at.%. The maximum exchange coupling field of 3.2 kA/m was obtained for Mn–20 at.%Ir(59 nm)/Ni–Fe(20 nm)/Zr(10 nm). Dependence of the exchange coupling fields on each layer thickness was also investigated. The Mn–Ir/Ni–Fe bilayers maintained high exchange coupling fields at Mn–Ir layer thicknesses above 10 nm.
Electron Transport in Vapor-Deposited Naphtlalene Dicarboximide Glasses
Authors: Borsenberger P. M. , Gruenbaum W. T. , E. H. Magin E. H. Magin , L. J. Rossi L. J. Rossi
Published: October 2002

Electron mobilities have been measured in vapor-deposited layers of N-(1,2-dimethylpropyl)benzo[k,l]thioxanthene-3,4-dicarboximide-7,7-dioxide (BTDD) and N,N′-bis(1,2-dimethylpropyl)-1,4,5,8-naphthalenetetracarboxylic diimide (NTDI). BTDD is a highly polar acceptor molecule that incorporates both an imide and a sulfone electronegative functionality. NTDI is a weakly polar acceptor molecule that contains two imide functionalities. The results are described by a formalism based on disorder, due to Bässler and coworkers. The formalism is based on the assumption that transport occurs by hopping through a manifold of localized states that are distributed in energy. The key parameter of the formalism is σ, the energy width of the hopping site manifold. The width is described by a model based on dipolar disorder. The model is premised on the argument that the width is comprised of a dipolar component σ d and a van der Waals component σ vdW. Describing the dipolar component by an expression due to Young yields σ d=0.133 eV for BTDD and 0.009 eV for NTDI. The van der Waals component for both molecules is 0.092 eV. The difference in the dipolar component is the principal reason for the large difference in mobility of these molecules.
Valence Band Structure of Si–As–Te Chalcogenide Glasses Prepared in the Gravity Environment of the Earth and in a Microgravity Environment in Space
Authors: Wahid Shams-Kolahi Wahid Shams-Kolahi , Michihiro Kobayashi Michihiro Kobayashi , Hiromasa Hanzawa Hiromasa Hanzawa , Tomohiro Kubota Tomohiro Kubota , Hikaru Kobayashi Hikaru Kobayashi , Hiroaki Okamoto Hiroaki Okamoto , Shoichi Endo Shoichi Endo , Yuki Kobayashi Yuki Kobayashi , Yoshihiro Hamakawa Yoshihiro Hamakawa
Published: October 2002

Photoemission spectra have been measured for two kinds of Si9As14Te21 chalcogenide glasses, prepared in the gravity environment of the earth and in a microgravity environment in space, respectively. The valence band structures of both of the glasses are in general similar, but exhibit a distinct difference close to the Fermi level. The top of the valence band states splits into a non-bonding level and a bonding level. The bonding/non-bonding splitting is smaller for space-made material than for its terrestrial-made counterpart. The X-ray Photoelectron Spectra indicate that the top of the valence band has a non-bonding lone-pair characteristic in the case of terrestrial-made material and a covalent bonding characteristic in the case of space-made material.
Substrate Temperature Dependence of ZnO Films Prepared by Ultrasonic Spray Pyrolysis
Authors: Ma Tae Young , Kim Sang Hyun , Moon Hyun Yul , Park Gi Cheol , Kim Young Jin , Kim Ki Wan
Published: October 2002

Strongly c-axis oriented zinc oxide (ZnO) films were deposited on silicon wafers coated with SiO2 or 7059 corning glass substrates from a solution containing zinc acetate. The films were deposited in a hot wall reactor by the pyrolysis of an aerosol produced by an ultrasonic generator. The crystallinity, surface morphology and composition of the films were studied using X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and Rutherford back-scattering spectrometry (RBS), respectively. The influences of the concentration of zinc acetate in the solution and the substrate temperature on the crystallinity of the films were studied. The films grown at a substrate temperature of 350–450° C from a 0.03 M/ l solution exhibited strong (002) orientation with a very smooth surface. The resistivity of the films was around 10 Ω· cm. Oxidation resulted in a 10,000-fold increase in the resistivity.
SrRuO3 Thin Films Grown under Reduced Oxygen Pressure
Authors: Hiratani Masahiko , Okazaki Choichiro , Kazushige Imagawa Kazushige Imagawa , Kazumasa Takagi Kazumasa Takagi
Published: October 2002

SrRuO3 thin films are grown under reduced oxygen pressures between 10-6 Torr and 100 mTorr by pulsed laser deposition. The thin films grown at temperatures above 640° C and at a pressure of 10-6 Torr are characterized in terms of the lattice shrinkage due to oxygen deficiency. The resistivity increases and the temperature dependence changes to semiconductive from metallic as the oxygen pressure during growth is decreased. The Hall coefficient of the film grown at 740° C and at a pressure of 10-6 Torr is thirty times higher at low temperatures than at room temperature. The transport properties of the film are thought to result from the high carrier concentration but the low mobility due to the oxygen deficiency.
Water Absorption Properties of Fluorine-Doped SiO2 Films Using Plasma-Enhanced Chemical Vapor Deposition
Authors: Miyajima Hideshi , Katsumata Ryota , Nakasaki Yasushi , Hayasaka Yukio Nishiyama
Published: October 2002

The water absorption properties of a PE-CVD (plasma-enhanced chemical vapor deposition) fluorine-doped SiO2 film with a low dielectric constant were studied. It was concluded that highly stable F-doped SiO2 film was obtained at F contents from 2.0% to 4.2% (3.2≤k≤3.6) using high-density plasma CVD. However, at F contents higher than 4.2% (k<3.2), the amount of water absorption was markedly increased due to the presence of Si–F bonds, such as Si(–F)2 bonds, which are highly reactive with water. On the other hand, water absorption was observed at every F content for conventional plasma CVD films. Through gas phase component analysis and investigation of the incident ion energy distribution using a quadrupole mass spectrometer, it was confirmed that a high efficiency of gas dissociation and high-energy ion bombardment are the keys to obtaining high-quality films with a high resistance to water absorption.
Recrystallization of Arsenic Implanted Layer in Silicon by Vacuum-Ultraviolet-Light Irradiation
Authors: Saito Yoji , Imai Hideo , Sugita Yoshihiro , Ito Takashi
Published: October 2002

Re-crystallization of implanted layers and electrical activation of implanted As atoms by vacuum-ultraviolet (VUV) light irradiation in silicon substrates below 470° C were investigated by means of sheet resistance measurements and reflection high-energy electron diffraction (RHEED). The reduction in the process temperature by irradiation of VUV light onto the implanted layer at 1 Wcm-2 is estimated to be about 50°.
Analysis of Wavelet Transform in Electric Charge Distribution in Dielectric Liquids Using Pressure Wave Method
Authors: Hirai Naoshi , Takao Noriaki , Sakae Nishimoto Sakae Nishimoto , Kiyomitsu Arii Kiyomitsu Arii
Published: October 2002

In our laboratory, a polymer piezoelectric vibrator and an acoustic emission sensor have been used for generation of pressure waves in dielectric liquids. A large amount of noise is contained in experimental data of charge distribution obtained using the pressure wave method. For removal of this noise, the wavelet transform was used in the data analysis. The noise removal from and time-frequency analysis of experimental data were performed simultaneously. The removal of noise from data using the wavelet transform could make more clear waveform than waveform of measured data. Therefore, it was clear that the wavelet analysis can be applied to measurement of charge distribution in dielectric liquids using the pressure wave method.
Evaluation of Tribological Properties of a Longitudinal Magnetic Recording Medium using Lateral Modulation Friction Force Microscope
Authors: Kumagai Akiyasu , Harada Kiyoko , Ozawa Kenji , Osamu Ishiwata Osamu Ishiwata
Published: October 2002

The lateral modulation friction force microscopy (LM-FFM) technique was used to investigate the tribological characteristics of a longitudinal magnetic recording medium (hard disk). The load dependence of the frictional force between the hard disk and the Si tip should be influenced by the dynamic elasticity of the tip. Very slight wear of the hard disk due to scanning of the tip was observed and the wear depth increased linearly with increasing load. The frictional force in areas which were significantly deformed increased due to scanning of the tip. The frictional force decreased in the first stage of repeated scanning and then increased with the number of scans under a load of 1.5 or 3.5 µ N. For a load of 130 nN, the frictional force between the tip and the sample increased with the number of scans.
Reaction Mechanism of Selective Plating between TiW and Au:An Innovative Metallization Scheme for High-Speed Electronics
Authors: Tai-Chin Lo Tai-Chin Lo , Miu-Ying Chan Miu-Ying Chan
Published: October 2002

In our previous letter, we presented a novel fabrication process which allows us to form submicron gold interconnections with high aspect ratio. The process was made possible by selective electroplating which is an important key technique to build a submicron interconnection, particularly by a simple fabrication process. We found in our recent experiments that the “sheet resistance” difference, as mentioned in our previous letter, is not what makes the electroplating process selective. Through voltammetry measurements, it was found that much higher deposition potential is required for the oxidized TiW electrode than that for the Au electrode. We concluded that the difference in the “deposition potential” between metal and semiconducting electrodes is what makes the electro-plating pocess selective.
Image Simulation of Extreme Ultraviolet Lithography Optics: Effect of Multilayer Coatings
Authors: Hiromasa Yamanashi Hiromasa Yamanashi , Masaaki Ito Masaaki Ito
Published: October 2002

Multilayer deposition technology is indispensable to the production of extreme ultraviolet (EUV) optics. However, the criteria of the multilayer d-spacing control techniques that are needed from the viewpoint of ULSI lithography has not yet been made clear. We have numerically evaluated EUV lithography optics in terms of the imaging performance and pattern placement accuracy. The tolerance of d-spacing distribution error for a two-mirror imaging optics was derived from a simulation method that takes multilayer reflectance and phase shift into consideration. Also, an image-contrast enhancement technique based on the d-spacing distribution is proposed for a three-mirror imaging optics.
Gas Species Dependent Charge Build-Up in Reactive Ion Etching
Authors: Kiyoshi Arita Kiyoshi Arita , Tanemasa Asano Tanemasa Asano
Published: October 2002

The effects of gas species on the charge build-up in reactive ion etching (RIE) have been investigated. The charge build-up was evaluated using metal/nitride/oxide/silicon (MNOS) capacitors and metal/oxide/silicon (MOS) capacitors. It was found that etching with electronegative gases such as O2 and CF4 results in considerable charge build-up. The spatial distribution of plasma parameters was diagnosed using a Langmuir probe. It was found that the spatial distribution of plasma parameters is non-uniform in plasmas of negative gases,while it is uniform in H2, He, Ar, and Xe gas plasmas. The results suggest that we must take the effect of the gas species into consideration for the nonuniformity in a plasma, which causes the significant charge build-up. Models that can be used to explain the effect of gas species are discussed. It was also found that the charge build-up can be drastically reduced by adding H2 gas to negative gases.
Carbon Contamination in Synchrotron-Radiation-Stimulated Al Deposition Using a Low Temperature Condensed Layer of Dimethyl Aluminum Hydride
Authors: Imaizumi Yoshiaki , Tsusaka Yoshiyuki , Tsuneo Urisu Tsuneo Urisu , Toshio Ibuki Toshio Ibuki
Published: October 2002

The carbon contamination in photochemically deposited Al films fabricated using non-monochromatized synchrotron radiation (SR) and Mg K
α line (1253.6 eV) irradiation were compared by X-ray photoelectron spectroscopy (XPS) analysis. The excitation energy dependence of the carbon contamination, especially the effects of core electron excitations, in the photo-CVD of Al using a low-temperature condensed layer of dimethyl aluminum hydride was determined using XPS spectra and gas-phase photo absorption cross section spectra. A significant decrease of the carbon contaminations was observed in the films fabricated using SR irradiation, which can excite Al 2s and Al 2p core electrons as well as the valence electrons, while no change was observed in the films fabricated using Mg K
α line irradiation. This is explained by the fact that core electron excitation breaks the Al–C bonds site-specifically.
Fabrication of an Integrated Silicon-Based Lens for Low-Energy Miniaturized Electron Columns
Authors: Rooij Michel Despont
Published: October 2002

A new process for the microfabrication of a fully integrated electrostatic lens in silicon, in particular the design of a low-energy miniaturized electron column, is described. It is suitable for batch processing and reduces considerably the difficulties associated with lens assembly. The electrode–spacer–electrode stack comprises an epitaxial p–n–p doped layer structure in silicon, which serves as electrodes and spacers, respectively. Because this technique allows the dimensions of the lens to be reduced, and owing to a new technique to align the electrode bores, the aberration of the lens is expected to be lower than that of lenses fabricated with previously reported techniques.
Microwave Dielectric Properties of LaZn0.5Ti0.5O3 Ceramics Prepared by Sol–Gel Process
Authors: Sergei Kucheiko Sergei Kucheiko , Hyun-Jai Kim Hyun-Jai Kim , Dong-Hun Yeo Dong-Hun Yeo , Hyung-Jin Jung Hyung-Jin Jung
Published: October 2002

Some dielectric properties of LaZn0.5Ti0.5O3 (LZT) ceramics prepared by means of the sol–gel method have been investigated. The calcination of powders derived from amorphous gel at 600° C results in the formation of a pure orthorhombic phase of LZT. The high sintering ability of the prepared powders enables the fabrication of dielectric ceramics at low sintering temperatures (1350–1400° C). At higher temperatures, the sintering process is followed by a decomposition reaction with the formation of La2TiO5 and ZnO vapor. A dielectric material having ε
r≃30 and Q·f
0≃60000 GHz is obtained at 1350° C.
Dielectric and Electrooptical Responses of Antiferroelectric Liquid Crystals in the Smectic-A Phase
Authors: Sako Teiyu , Kimura Yasuyuki , Hayakawa Reinosuke , Okabe Nobuhiro , Suzuki Yoshiichi
Published: October 2002

The Smectic-A (SmA) phases of the antiferroelectric liquid crystals (R)-MHPOBC, (R)-MHPOCBC and slightly racemized MHPOBC (R:S=17:3) have been studied by means of simultaneous measurements of the electric displacement and the tilt angle induced by the electric field. The SmA–SmCα
* phase transition was observed in (R)-MHPOBC and (R)-MHPOCBC, while a phase transition similar to the SmA–SmC* one was observed in slightly racemized MHPOBC. In both cases, the Landau-type phenomenological theory explains well the critical behavior in the SmA phase, and the coefficients related to the theory can be determined.
Crystal Orientation and Surface Roughness of Bi Films Prepared in Ionized Cluster Beam Apparatus
Authors: Nakada Masafumi , Norikazu Ohshima Norikazu Ohshima , Mitsuya Okada Mitsuya Okada
Published: October 2002

We have studied the effects of deposition conditions and underlayers on the crystal orientation and surface roughness of Bi films deposited by the ionized cluster beam method as a means of reducing the noise of MnBi magneto-optical disks. Substrate temperature and applied voltage strongly affect the crystal orientation and the surface roughness of Bi films. The c-axis orientation and surface flatness drastically deteriorate at substrate temperatures above 100° C, and the degree of orientation/flatness decreases as the applied voltage is increased. Surface roughness of Bi films is inversely proportional to the degree of c-axis crystal orientation, indicating that the surface roughness is determined by the growth rate of Bi crystal planes. The c-axis orientation and the surface flatness can be improved by using low-wettability underlayers, since crystal reorientation of the Bi films easily occurs on such underlayers. We find that sputter etching of SiN underlayers can improve the surface flatness of Bi films at 20 nm thickness.
Optimization of the Deposition Process Parameters for Preparation of In2O3 Films by Reactive Evaporation of Indium Metal
Authors: Qiamin Wang Qiamin Wang
Published: October 2002

Optimal deposition process parameters for preparing In2O3 films by reactive evaporation of indium metal are determined by means of experiments. With the optimum conditions determined in this work one can easily prepare In2O3 films of low resistivity of about 3×10-4 Ω· cm and high visible transmission of over 90%, and the deposition rate of 219 Å/min of the films can be obtained. The formation mechanism of the abnormalities of the films caused by departure from the optimal deposition parameters is discussed.
Anomalous Heat Evolution of Deuteron-Implanted Al upon Electron Bombardment
Authors: Kamada Kohji , Kinoshita Hiroshi , Takahashi Heishitiro
Published: October 2002

Anomalous heat evolution was observed for the first time in deuteron-implanted Al foils upon 175 keV electron bombardment. Local regions with linear dimension of more than 100 nm showed simultaneous transformation from single-crystalline to polycrystalline structure within roughly one minute during the electron bombardment, indicating a temperature rise to above the melting point of Al from room temperature. The amount of energy evolved was estimated to be typically 160 MeV for each transformed region. The transformation was never observed in proton-implanted Al foils. Microstructures in the subsurface layer of the implanted Al, investigated by elastic recoil detection (ERD) method and transmission electron microscopy (TEM), were presented for numerical discussions of the experimental results. Possible causes of the surface melting, such as the heating effect of the electron beam, size effect of the melting point, difference in the implanted depth profiles between hydrogen and deuterium, and possible chemical reactions due to the electron bombardment in D2collections, were investigated. We consider that some kind of nuclear reaction occurring in the D2collections is the only explanation for the observed melting. The reaction was estimated to continue only for a short time, presumably less than 10-10s, and the energy gain, which is defined as the ratio between the amount of energy evolved and the energy loss of the impinging electros through the Al specimen, amounts to more than 1×105.
Synchrotron-Radiation-Induced Deposition of Etch-Protecting Film on Si in CF4Plasma
Authors: Chunlin Shao Chunlin Shao , Shinzo Morita Shinzo Morita , Tetsuo Soga Tetsuo Soga , Ryoichi Inanami Ryoichi Inanami , Shuzo Hattori Shuzo Hattori
Published: October 2002

Carbonous film was deposited on silicon wafer in CF4plasma when the silicon wafer was irradiated by synchrotron radiation (SR). The deposition rate was 183 Å/min at a SR intensity of 1.43 W/cm2, DC discharge voltage of 700 V, discharge current of 6 mA and CF4gas pressure of 0.13 Torr. The film was characterized by Auger electron spectroscopy. The deposition mechanism of the film was due to photoexcitation of the silicon surface by SR irradiation.
Tungsten Gate Technology for Quarter-Micron Application
Authors: Noda Hiromasa , Sakiyama Hideyuki , Goto Yasushi , Kure Tokuo , Kimura Shin'ichiro
Published: October 2002

The feasibility of pure tungsten as a gate electrode of quarter-micron MOSFETs (metal-oxide-semiconductor field effect transistors) was investigated experimentally. Issues investigated are 1) tungsten gate dry etching, 2) gate oxide dielectric for the tungsten gate, and 3) threshold voltage control of tungsten gate MOSFET. A 0.1-µm tungsten gate electrode on a 5-nm-thick gate oxide was fabricated successfully for the first time, using microwave plasma etching and chlorine as the reaction gas. It was confirmed that the dielectric characteristics of the gate oxide for the tungsten gate are acceptable when its thickness exceeds 6 nm. It was demonstrated that the threshold voltage of tungsten gate MOSFETs was successfully controlled by counter-doping without degradation of the short-channel characteristics.
Random Telegraph Noise in Advanced Self-Aligned Bipolar Transistors
Authors: Jian-Qiang Lü Jian-Qiang Lü , Frederick Koch Frederick Koch
Published: October 2002

In studies of the degradation effect in advanced self-aligned bipolar transistors, we observe random telegraph noise (RTN). This phenomenon closely resembles that in metal-oxide-semiconductor field-effect transistors (MOSFETs), but the temperature and voltage dependences are different. Based on tunneling transitions between a single border trap, Si–SiO2 interface states and the Si-band structure, a model is suggested to explain this RTN in advanced self-aligned bipolar transistors. The analysis of the complicated voltage and temperature dependences of the capture/emission time and the amplitude of the RTN affords a unique opportunity to study the nature of defects and the occupation kinetics of an individual trap in SiO2. This study of the RTN also directly provides information about the microscopic origin of hot carrier degradation and low-frequency noise.
Guided Modes in a Si-Quantum Wire and Their Control
Authors: Yasushi Okawa Yasushi Okawa , Hideaki Tsuchiya Hideaki Tsuchiya , Tanroku Miyoshi Tanroku Miyoshi
Published: October 2002

The eigenmodes of an electron wave propagating through a Si-quantum wire are analyzed self-consistently by a finite-element method. The anisotropic effective mass tensor corresponding to the three inequivalent alignments of conduction band valleys in Si and the continuity of the probability current densities at the Si– SiO2 interface are taken into account. As a result, the eigenenergies of the electron wave and the electron density distribution are found to be greatly affected by the electron-electron interaction. It is also demonstrated that the number of guided modes in the Si-quantum wire is controlled by the gate bias voltage.
Stress Effect on the Reliability of pMOS TFTs for 16 Mb SRAM: DC Stress at Room and Elevated Temperatures
Authors: Son Kwang Sik , Yoon Hee Koo , Lee Yoon Jong , Su Jin Ahn Su Jin Ahn , Dae Mann Kim Dae Mann Kim
Published: October 2002

We present a systematic experimental study of the electrical stress effects in p-channel metal-oxide-semiconductor thin film transistors (pMOS TFTs) used as active loads in high density static random access memory (SRAM) circuits. Specifically, the effects of dc stresses occurring during standby were investigated in devices both with and without offset and at room and elevated substrate temperatures. The stresses associated with the OFF regime biases give rise to a drastic reduction of leakage current and at the same time, a significant increase in the ON current. These effects are particularly pronounced in devices without offset and for stress biases applied at room temperature or below. Although at elevated substrate temperature the leakage current itself is enhanced by a few orders of magnitude, the stress-induced parameter shifts are shown to be smaller than those at lower temperatures. Additionally, the stress induced reliability aspects of pMOS TFTs used for 4 Mb and 16 Mb SRAM are compared and discussed.
Development of Sub-Quarter-µm MONOS (metal/oxide/nitride/oxide/semiconductor) Type Memory Transistor
Authors: Thomas Böhm Thomas Böhm , Akihiro Nakamura Akihiro Nakamura , Hiroshi Aozasa Hiroshi Aozasa , Machio Yamagishi Machio Yamagishi , Yasutoshi Komatsu Yasutoshi Komatsu
Published: October 2002

A MONOS (metal/oxide/nitride/oxide/semiconductor) type nonvolatile memory transistor with a gate length of 0.23 µm has been developed. This memory transistor offers high endurance, low programming voltage and a narrow distribution of programmed threshold voltages. By introducing a rapid thermal nitridation (RTN) step into the fabrication prosecc of the ONO (oxide/nitride/oxide) layer, an enhancement in erase speed of one order of magnitude is achieved. The RTN also improves the oxidation resistance of the nitride layer, so that scaling down the thickness of the ONO film in order to reduce the programming voltage is feasible.
A 4:1 MUX Circuit Using 1/4 Micron CMOS/SIMOX for High-Speed and Low-Power Applications
Authors: Sadayuki Yasuda Sadayuki Yasuda , Yusuke Ohtomo Yusuke Ohtomo , Masayuki Ino Masayuki Ino , Yuichi Kado Yuichi Kado , Hiroshi Inokawa Hiroshi Inokawa , Toshiaki Tsuchiya Toshiaki Tsuchiya
Published: October 2002

We designed a new 4:1 multiplexer (MUX) circuit and fabricated it by 0.25-µm CMOS device process technology using Separation by IMplanted OXygen (SIMOX) wafer. This MUX circuit has a small number of fan-outs so that the SIMOX device, with smaller junction capacitance than a BULK device, effectively contributes to high-speed and low-power operation. We confirmed that the fabricated SIMOX MUX can operate at 2.7 GHz (@V
DD = 2.0 V), which is 25% faster than the BULK MUX, and the power consumption is 19% less at the same speed and V
DD. In addition, we confirmed that these improvements are mainly due to the reduced junction capacitance of SIMOX devices by estimating the gate speed in the critical path and the load capacitance in the SIMOX MUX circuit.
Effects of Semiconductor Thickness on Poly-Crystalline Silicon Thin Film Transistors
Authors: Miyasaka Mitsutoshi , Komatsu Tadakazu , Itoh Wataru , Yamaguchi Akemi , Hiroyuki Ohshima Hiroyuki Ohshima
Published: October 2002

The effects of semiconductor thickness on poly-crystalline silicon (poly-Si) thin film transistors (TFTs) are studied. The small value of the threshold voltage (V
th) appearing in thin film can improve the electrical properties of the corresponding TFTs. However, thin poly-Si film generally consists of small grains and contains many defects. When the film is extremely thin, it contains voids and it is in a separate island-like state. As a result, the extremely thin film possesses very many traps, which prevent the V
th value from further decreasing. The way that thickness affects film quality differs according to how that film was prepared. Therefore, different TFT fabrication methods make the optimum semiconductor thickness different.
Electric Field Enhanced Emission from Two Alpha-Particle Irradiation Induced Traps in n-GaAs
Authors: Meyer Walter E. , F. Danie Auret F. Danie Auret , Stewart A. Goodman Stewart A. Goodman
Published: October 2002

The electric field dependence of the emission rates of two alpha-particle irradiation-induced electron traps in epitaxially grown n-GaAs, Eα3 and Eα4, was studied using deep level transient spectroscopy (DLTS). We found the emission enhancement from Eα4 to be much more pronounced than that from Eα3, emphasising the difference in their structure. Neither of the two defects shows an emission enhancement characteristic of the Poole-Frenkel effect, commonly assumed to account for field dependent emission enhancement. The phonon-assisted tunnelling model accurately describes the field dependent emission enhancement of both the Eα3 and the Eα4 defects.
Growth of High-Quality AlN and AlN/GaN/AlN Heterostructure on Sapphire Substrate
Authors: Yasuo Ohba Yasuo Ohba , Ako Hatano Ako Hatano
Published: October 2002

Metalorganic chemical vapor deposition (MOCVD) growth of AlN on sapphire substrates was investigated, with the aim of device quality AlN/GaN/AlN double heterostructures. Growth temperature as high as 1300° C was required to obtain AlN epitaxial layers with sharp X-ray diffraction peaks. By growing AlN at the high growth temperature, residual stress at the heterointerface was effectively reduced. The AlN epitaxial layers with smooth surfaces were grown using a low V/III ratio together with the high growth temperature. AlN/GaN/AlN double heterostructures with appropriate layer thicknesses for DH lasers and flat heterointerfaces were grown on sapphire substrates.
Room-Temperature Operation of DC Axially Discharged Fast Axial-Flow CO Laser
Authors: Yutaka Kodama Yutaka Kodama , Heihachi Sato Heihachi Sato
Published: October 2002

A compact CO laser with a DC axially discharged fast-axial flow has been operated at room temperature (270 – 300 K), achieving ∼ 165 W per unit discharge length in CW mode under xenon (Xe) gas addition. A maximum power of 385 W per unit gain length (1 m) has been similarly achieved with Xe gas at 235 – 275 K. Dependence of output power on gas-flow velocity v , discharge current I
dis, and gas composition is examined experimentally and theoretically explained, and dependence of oscillation lines on v is also investigated. Moreover, the effect of gas-flow velocity on gas temperature is also examined.
Formation of Hydrogen Molecules in n-Type Silicon
Authors: Fukata Naoki , Sasaki Shin-ichi , Murakami Kouichi , Ishioka Kunie , Kitajima Masahiro , Fujimura Shuzo , Kikuchi Jun
Published: October 2002

We have investigated hydrogen molecules ( H2) formed in heavily doped n-type silicon by remote hydrogen atom treatment. We measure the Raman lines of H2 as a function of the substrate temperature during hydrogen atom treatment. A broad vibrational Raman line of H2 can be clearly observed at around 4158 cm-1 for substrate temperatures between 250 and 500° C, indicating that hydrogen exists in molecular form in crystalline silicon. The vibrational Raman line of H2 has a maximum intensity for a substrate temperature of 400° C. An isotope shift is also detected at around 2990 cm-1 in silicon treated with deuterium atoms at 400° C.
Array of the Self-Organized InGaAs Quantum Dots on GaAs (311)B Substrates by Atomic Hydrogen-Assisted Molecular Beam Epitaxy
Authors: Chun Yong Jin , Shigeru Nakajima Shigeru Nakajima , Mitsuo Kawabe Mitsuo Kawabe
Published: October 2002

We have investigated the ordering of the coherently strained InGaAs quantum dots (QDs) on GaAs (311)B substrates with molecular beam epitaxy (MBE). The uniform array of the In0.3Ga0.7As QDs is obtained with atomic hydrogen (H) irradiation with the density of 4.1×1010/ cm2 and dot size of 40 nm. The ordering of the QDs is still observed without atomic H, but the uniformity of the ordering of the QDs is deteriorated and the dot size increases. The ordered structure of the QDs shows the strong dependence of In content and the array of the QDs is almost disordered as the In content increases to In0.6Ga0.4As.