bluuebunny/crossref_metadata_2025 huggingface dataset:
Polymer Optimization of Pigmented Photoresists for Color Filter Production
Authors: Kudo Takanori , Nanjo Yuki , Nozaki Yuko , Yamaguchi Hidemasa , Kang Wen-Bing , Pawlowski Georg
Published: October 2002

The lithographic performance of pigmented photoresists for color filter production is affected by the structure of the employed polymer. Four polymers with acrylate backbones and pendant reactive acrylate/methacrylate groups were prepared, and the effects of their molecular weights and acid values on the pixel pattern quality, development time, sensitivity and development mode were elucidated. ECHIPTM, a statistical experimental design program was used for optimization studies revealing that the red resist performs best, when polymers with relatively low acid values (<40 mg KOH/g polymer) and high molecular weights >50,000 are used. The green and the blue resists yielded optimal patterns at molecular weights in the range of 20,000–30,000 with acid values of about 50–60 mg KOH/g polymer. The sensitivity of resists containing polymers with pendant acryloyl groups is in general higher than that of the corresponding methacryloyl derivatives. Polymers having butyl acrylate-methacrylic acid backbone units showed the highest sensitivity among the polymers investigated. When developed with an optimized tetramethyl ammonium hydroxide (TMAH) based developer, resists using polymers with methyl methacrylate units showed peeling type development, while butyl acrylate copolymers effected homogeneous dissolution yielding higher resolution.
Power Durability of Al–W Alloy Electrodes Used in RF-Band Surface Acoustic Wave Filters
Authors: Noritoshi Kimura Noritoshi Kimura , Masahiro Nakano Masahiro Nakano , Katsuo Sato Katsuo Sato
Published: October 2002

For the RF-band surface acoustic wave (SAW) filters, the power durability of Al–W alloy electrodes was studied. It was shown that the power durability of Al–0.5 at.% W alloy electrodes is superior to that of the Al–0.5 at.% Ti alloy electrodes which have been known as power-durable electrodes. The amount of hillocks decreases as the W content in the Al–W alloy increases, on the other hand, the lifetime of the electrodes is maximized at a W content of 0.5 at.%. These phenomena suggest that the whiskers, instead of hillocks, grown on the sides of the electrodes, cause the electrical short between the hot and the ground electrodes and suppress the lifetime increase.
High Performance 0.2 µm Dual Gate Complementary MOS Technologies by Suppression of Transient-Enhanced-Diffusion using Rapid Thermal Annealing
Authors: Nishida Yukio , Sayama Hirokazu , Shimizu Satoshi , Kuroi Takashi , Furukawa Akihiko , Teramoto Akinobu , Uchida Tetsuya , Inoue Yasuo , Nishimura Tadashi
Published: October 2002

Rapid thermal annealing (RTA) before the low temperature process is introduced in the 0.2 µm dual gate complementary metal oxide semiconductor (CMOS) process and its effect has been systematically investigated. Channel profiles of boron and phosphorus remain steep by the additional RTA process before gate oxidation, as seen by using secondary ion mass spectrometry and a simulation with the point defect based diffusion model. The most effective temperature to suppress transient-enhanced-diffusion (TED) is 900–1000°C, which can be remarkably suppressed by a 30 s treatment in the case of 900°C RTA. A steep channel profile decreases the threshold voltage and increases the transconductance. Shallow source/drain extension profiles of BF2 and phosphorus can be fabricated by an additional RTA process before sidewall spacer film deposition, which can improve the threshold voltage lowering. Consequently, a high current drivability of a 0.2 µm CMOS has been achieved by the suppression of TED using two additional RTA processes.
Gate-Overlapped Lightly Doped Drain Poly-Si Thin Film Transistors by Employing Low-Temperature Doping Techniques
Authors: Choi Kwon-Young , Park Kee-Chan , Han Min-Koo
Published: October 2002

We have fabricated a gate-overlapped lightly doped drain (GO-LDD) polycrystalline silicon thin film transistor (poly-Si TFT) applicable for large area AMLCD by employing the large area- and low-temperature-doping techniques, such as ion shower doping and in-situ doping. Experimental results show that the leakage current of the proposed TFTs is reduced by more than the magnitude of two orders, compared with that of conventional non-offset TFT, while the ON current is scarcely decreased. The degradation phenomena after gate bias stress in GO-LDD TFTs with in-situ doping has not been found because the electron trapping into the overlayer may be suppressed effectively by the high quality TEOS interlayer.
Characteristics of Metal/Ferroelectric/Insulator/Semiconductor Field Effect Transistors Using a Pt/SrBi2Ta2O9/Y2O3/Si Structure
Authors: Nyung Lee Ho , Tae Kim Myoung-Ho Lim , S. Kalkur T. , Ho Choh Sung
Published: October 2002

For the fabrication of metal/ferroelectric/insulator/semiconductor field effect transistors (MEFISFETs), SrBi2Ta2O9 (SBT) film was formed onto Y2O3 layer using the metal organic deposition (MOD) method. Memory windows of MEFISFET were in the range of 0.96–1.38 V when the gate voltage varied from 5 to 7 V. Current-voltage characteristic and transconductance curve of the MEFISFET show the effective gate modulation and the stable memory effect induced by the ferroelectric properties.
Positron Annihilation in [Fe(ptz)6](BF4)2 and [Zn(ptz)6](BF4)2 Single Crystals Studied with One-Dimensional Angular Correlation of Annihilation Radiation
Authors: Saito Haruo , Nagai Yasuyoshi , Hyodo Toshio , Süvegh Károly , Vértes Attila
Published: October 2002

One-dimensional angular correlation of positron annihilation radiation spectra (1D-ACAR) from single crystals of [Fe(ptz)6](BF4)2 and [Zn(ptz)6](BF4)2 along the c-axis are measured in the temperature range between 23 K and 295 K. A remarkable temperature dependence of the ACAR spectra for [Fe(ptz)6](BF4)2 around the spin-crossover temperature (130 K) is observed and interpreted as being due to spin-conversion of positronium atoms. This observation suggests that the positronium atoms are localized in the vicinity of the central Fe(II) ion of [Fe(ptz)6](BF4)2. In contrast, ACAR spectra for [Zn(ptz)6](BF4)2, which shows no spin-crossover, are almost independent of temperature. No evidence for the formation of delocalized free positronium atoms is found in either sample.
The Effect of Isopropyl Alcohol Adsorption on the Electrical Characteristics of Thin Oxide
Authors: Motai Kumi , Itoga Toshihiko , Irie Takashi
Published: October 2002

The effect of isopropyl alcohol (IPA) adsorption on the electrical characteristics of thin oxide has been investigated. Metal-oxide-semiconductor (MOS) capacitors were fabricated on Si substrates after IPA was intentionally adsorbed on the substrate surfaces. The leakage current was raised in the low electric field region for the 5-nm-thick thin oxide due to increased IPA adsorption, but the leakage current was not affected in the 8- and 10-nm-thick oxides. Using X-ray photoelectron spectroscopy, we found that the heat treatment creates C-Si bonds in the oxide due to organic adsorbates including IPA. These bonds appear likely to cause weak points or prevent uniform oxidation. A pre-annealing treatment was found to be effective in suppressing the formation of the C-Si bonds.
STM and Cluster Calculation Study of Segregated B on Si(001) Surface
Authors: Komeda Tadahiro , Nishioka Yasushiro
Published: October 2002

The atomic configuration of B atoms on the Si(001)-2×1 surface which are segregated on the top surface is investigated with scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) whose data are further analyzed by comparison with a cluster model calculation with a local density approximation method. Unoccupied state STM images show characteristic paired protrusions which are located on both sides of the Si dimer rows in a symmetrical manner. They can be observed only at a higher sample bias (>1.4 V) and are enhanced at ∼2.0 V, which is further confirmed quantitatively by STS measurements. The cluster calculation shows that a model where a B atom is bridging two neighboring Si dimers in the same dimer row can reproduce the STM and STS observations.
Boron Diffusion in Nitrided-Oxide Gate Dielectrics Leading to High Suppression of Boron Penetration in P-MOSFETs
Authors: Aoyama Takayuki , Ohkubo Satoshi , Tashiro Hiroko , Tada Yoko , Suzuki Kunihiro , Horiuchi Kei
Published: October 2002

Nitrided-oxide gate dielectrics have been proposed to suppress boron penetration in deep submicron metal-oxide-semiconductor field effect transistors (MOSFETs). However, few quantitative reports have been released on how nitrided oxides enlarge the permissible thermal budget. We evaluated the diffusivities of a nitrided oxide formed by annealing SiO2 in NO gas and demonstrated that this film enables us to use BF2
+ for scaled devices. We also proposed a model depicting boron penetration through the nitrided-oxide layer.
Effect of Low-Dose Ion Implantation on the Stress of Low-Pressure Chemical Vapor Deposited Silicon Nitride Films
Authors: Yamamoto Ichiro , Kasai Naoki , Nishimoto Shozo
Published: October 2002

We investigated the effect of reducing stress in low-pressure chemical vapor deposited (LPCVD)-Si3N4 films by a low-dose ion implantation of P, Ar and As. The tensile stress of the Si3N4 films was eliminated by implanting these ions in the middle of the films in doses as low as 3×1013 to 1.2×1014 cm-2. After annealing, although the stress of the implanted nitride films recovers partially, its value still does not reach that of the unimplanted films. The influence of implantation on the local oxidation of silicon (LOCOS) profile and the device characteristics is negligible.
New Analytical Model for Subthreshold Current in Short-Channel Fully-Depleted SOI MOSFETs
Authors: Sergey Pidin Sergey Pidin , Mitsumasa Koyanagi Mitsumasa Koyanagi
Published: October 2002

A new two-dimensional model for subthreshold current in fully-depleted silicon-on-insulator metal-oxide-semiconductor field effect transistor (SOI MOSFET) is developed. The model is based on analytical approximation of two-dimensional Poissons's equation solution, drift-diffusion current equation and accounts for the drain-induced barrier lowering and channel-length modulation in weak inversion. The model provides a convenient tool for the design of submicron SOI MOSFETs.
Suppressing Plasma Induced Degradation of Gate Oxide Using Silicon-on-Insulator Structures
Authors: Kiyoshi Arita Kiyoshi Arita , Masashi Akamatsu Masashi Akamatsu , Tanemasa Asano Tanemasa Asano
Published: October 2002

Plasma-process induced degradation of gate oxide of metal/oxide/silicon (MOS) devices on silicon-on-insulator (SOI) structures and bulk wafers was investigated. In order to evaluate the degradation of the gate oxide, the charge-to-breakdown Q
bd of the MOS capacitors was measured under a constant current condition. It was found that the degradation of the gate oxide could be drastically suppressed using SOI. A thicker buried oxide layer showed greater suppression of the gate oxide degradation. A smaller device island size showed lower gate oxide degradation, although the dependence was rather weak. An electrical model is discussed, to account for the effect of SOI, in which the capacitance of the buried oxide played a key role in suppressing the degradation.
Surface Segregation Behaviors of B, Ga, and Sb during Si Molecular Beam Epitaxy: Calculation Using a First-Principles Method
Authors: Ushio Jiro , Nakagawa Kiyokazu , Miyao Masanobu , Maruizumi Takuya
Published: October 2002

The potential energies of B, Ga, and Sb dopant atoms in the three top layers of Si(100) surfaces were evaluated by accurate density functional calculations of the model clusters. The different behaviors of B and Ga in the surface segregation can be understood by considering the bond energies between the dopant and Si atoms as the driving force for segregation. The energy of the B–Si bond is greater than that of the Si–Si bond, and the incorporated state is more stable than the adsorbed state, which increases the segregation resistance to the Si surface. The incorporated state of the B atom is most stable in the second Si surface layer. The Sb atom has a higher potential barrier between the surface and the subsurface site than Ga, which causes less segregation of Sb to the Si surface under the same experimental conditions.
Fabrication Technology of Ferroelectric Memories
Authors: Takashi Nakamura Takashi Nakamura , Yoshikazu Fujimori Yoshikazu Fujimori , Naoki Izumi Naoki Izumi , Akira Kamisawa Akira Kamisawa
Published: October 2002

Two types of ferroelectric memories have been proposed. One is a 1 transistor and 1 capacitor (1T1C) type and another is an FET (field effect transistor) type. The fabrication technique for fabrication ferroelectric capacitors on polycrystalline Si (poly-Si) was very effective for high density 1T1C ferroelectric memory and metal-ferroelectric-metal-insulator-semiconductor (MFMIS) FET with stable properties. MFMIS FET is one type of FET ferroelectric memory which we proposed. To obtain good ferroelectric capacitors on poly-Si, we used Ir based materials as electrodes of the capacitors. By using Ir based electrodes, the characteristics of Pb(Zi,Ti)O3 (PZT) capacitors on poly-Si were equivalent to those on SiO2. Moreover, the PZT capacitors with Ir based electrodes showed dramatic improvement in fatigue and imprint properties.
Vertical-Cavity Surface-Emitting Laser and Its Applications for Optical Interconnection and Switch
Authors: Kosaka Hideo
Published: October 2002

A two-dimensional (2D) optical-parallel interconnection module was developed using vertical-cavity surface-emitting lasers (VCSELs) which have a low threshold, high temperature tolerance and uniform and effective fiber coupling characteristics. The 8×2–arrayed VCSEL was self-aligned to a developed plastic-molded receptacle-type package using flip-chip solder bonding technique and a developed ball-guide die bonding technique. The module exhibited high data throughput of 1 Gb/s at temperatures up to 70°C, high optical coupling efficiency of 85.8±2.93% and high mechanical durability of less than 0.26 dB for 100 times of manual push/pull matings with a developed multifiber push-on (MPO)–type 2D fiber connector. As an application of the high-density, high-throughput an optical parallel interconnections, optical full crossbar switch with a simple architecture and fabricated plastic-molded optical crossbar connectors was demonstrated.
Optical and Transport Properties of Single Quantum Well Infrared Photodetectors
Authors: Shimada Yozo , Hirakawa Kazuhiko
Published: October 2002

We have studied the optical and transport properties of AlGaAs/GaAs single quantum well infrared photodetectors (SQWIPs). The SQWIP shows a narrowband photocurrent at around 9.2 µm, due to intersubband transition in the steady state characteristics, measured using a Fourier transform infrared spectrometer. The bias voltage dependence of the magnitude and the spectral shape of the observed steady state photocurrent indicates that the photocurrent is strongly affected by the tunneling escape process. Furthermore, a transient photoresponse of the SQWIP has been studied using free electron laser (FEL) pulses. A comparison of the steady state photocurrent and the transient photoresponse shows that the charging current induced by the band bending effect contributes to an increased photo sensitivity.
The Effect of Different Group V Precursors on the Evolution of Quantum Dots Monitored by Optical In Situ Measurements
Authors: Elisabeth Steimetz Elisabeth Steimetz , Wolfgang Richter Wolfgang Richter , Frank Schienle Frank Schienle , Daniel Fischer Daniel Fischer , Michael Klein Michael Klein , Jörg-Thomas Zettler Jörg-Thomas Zettler
Published: October 2002

The influence of different As-precursors [TMAs (trimethylarsine), TBAs (tertiarybutylarsine) and AsH3 (arsine)] on the formation of InAs-quantum-dots and their evolution was studied by applying reflectance anisotropy spectroscopy (RAS) and spectroscopic ellipsometry (SE). Hydrogen radicals at the surface are found to enhance the ripening and coalescence processes. The use of TBAs instead of AsH3 can partly reduce coalescence. Monitoring the GaAs overgrowth on InAs-quantum dots, the level of GaAs-covering was determined by RAS-measurements. Temperature dependent In-segregation effects were observed in situ.
Self-Organizing Semiconductor Epitaxial Films by Turing Instability
Authors: Temmyo Jiro , Tamamura Toshiaki
Published: October 2002

We describe for the first time diagrams of the surface topography domain in a strained InGaAs/AlGaAs system grown on GaAs (311)B/A surfaces during metalorganic-vapor-phase-epitaxial growth. The surface rearrangement process resulting in the stationary pattern formation of the various quasi-periodic nanostructures seems to belong to the class of a Turing-type self-organization phenomenon in non-linear dynamic systems. Experimental results might indicate the existence of a novel fourth growth mode due to Turing-type self-organization in addition to the three well-known epitaxial growth modes.
Effects of As2 Flux and Atomic Hydrogen Irradiation for Growth of InGaAs Quantum Wires by Molecular Beam Epitaxy
Authors: Sugaya Takeyoshi , Tanuma Yasuhiko , Nakagawa Tadashi , Sekiguchi Takashi , Yonei Kenji , Sugiyama Yoshinobu
Published: October 2002

InGaAs/InAlAs quantum wire structures on V-grooved InP substrates have been fabricated with As2 flux and atomic hydrogen irradiation using molecular beam epitaxy. Under As2 flux, the V-grooves are preserved during the InAlAs barrier layer growth due to a small migration of the In atoms, but the V-shape is not preserved and hence the quantum wires cannot be fabricated under an As4 flux. The InGaAs quantum wires grown with atomic hydrogen have a narrow photoluminescence peak and a uniform cathode-luminescence image. These phenomena maybe caused by the absence of (311)A sidewall quantum wells due to re-evaporation of the group-III atoms by the atomic hydrogen irradiation.
Photoluminescence Study of InAs Quantum Dots and Quantum Dashes Grown on GaAs(211)B
Authors: Guo Shiping , Ohno Hideo , Shen Aidong , Ohno Yuzo , Matsukura Fumihiro
Published: October 2002

InAs self-organized quantum dots (QDs) and quantum dashes (QDHs) were grown by molecular beam epitaxy on GaAs (211)B substrates. QDs with bimodal size distribution were formed at lower growth temperatures, whereas QDHs were observed at higher growth temperatures. Photoluminescence (PL) intensity and peak position of QDs and QDHs showed similar temperature dependence, whereas the excitation density dependence of the PL peak intensity and the PL peak energy of the two nanostructures was different. The blue shift in QDH peak energy with the increase of the excitation density is suggested to be due to the existence of the piezoelectric field in InAs QDHs.
Polarization Characteristics of Crescent-Shaped Tensile-Strained GaAsP/AlGaAs Quantum Wire-Like Lasers
Authors: Mitsuteru Ishikawa Mitsuteru Ishikawa , Wugen Pan Wugen Pan , Yasuhisa Kaneko Yasuhisa Kaneko , Hiroyuki Yaguchi Hiroyuki Yaguchi , Kentaro Onabe Kentaro Onabe , Ryoichi Ito Ryoichi Ito , Yasuhiro Shiraki Yasuhiro Shiraki
Published: October 2002

Crescent-shaped tensile-strained GaAsP/AlGaAs quantum wire-like lasers are fabricated on V-grooved GaAs(100) substrates by metalorganic vapor phase epitaxy. Light-output versus current characteristics, polarized lasing spectra and near-field patterns show lasing from the quantum wires in the TM mode. The threshold current density per wire is as low as 500 A/cm2 and the lasing wavelength is 780 nm.
Improvement in the Electrical Properties of GaAs/InAs/GaAs Structures through the Use of (111)A Substrates
Authors: Yamaguchi Hiroshi , Hirayama Yoshiro
Published: October 2002

We compare the electrical properties of InAs thin films embedded in GaAs layers grown by solid source molecular beam epitaxy on (111)A and (001) substrates. A major improvement in Hall mobility through the use of (111)A substrates is confirmed. The carrier concentration is found to saturate at a value of 3×1012 cm-2 after 50 nm as a function of the InAs thickness. Self-consistent calculation assuming interface Fermi level pinning produces results which are in good agreement with the experimental results, and the pinning position is estimated to be about 0.15 eV above the bottom of the conduction band. The origin of Fermi level pinning seems to be the misfit dislocations confined at the InAs/GaAs interfaces based on structural characterization by transmission electron microscopy
Liquid Phase Epitaxial Growth of (3GaAs) x{(3ZnSe) y(Ga2Se3)1- y}1- x Alloy
Authors: Kaji Masanori , Katsuno Hironobu , Kimura Masakazu , Tanaka Akira , Sukegawa Tokuzo
Published: October 2002

Quasi-ternary alloys of (3GaAs)
x
{(3ZnSe)
y
(Ga2Se3)1-y
}1-x
were grown on a ZnSe(100) substrate from Ga solvent to which a certain amount of GaAs was added and saturated with ZnSe at 900°C, using a slide boat in a sealed quartz ampoule. Applying Se vapor pressure to the growth solution increased the Ga2Se3 content in the grown alloy layer, while the addition of Zn to the Ga solvent decreased it. The GaAs component in the grown alloy increased along the growth direction. Its content and variation range could be determined by the amount of source GaAs.
Influence of Γ-X Resonance on Photocurrent-Voltage Characteristics in GaAs/InAlAs Strained Superlattices
Authors: Kuroyanagi Kazuyoshi , Ohtani Naoki , Egami Norifumi , Tominaga Koji , Nakayama Masaaki
Published: October 2002

We have investigated the influence of Γ-X resonance on the photocurrent-voltage characteristics in GaAs/InAlAs type-I strained superlattices. To explain the experimental results, we have calculated the energies of the Γ and X electron states, which are confined in the GaAs and InAlAs layers, respectively, using an effective-mass approximation taking into account the strain effect. We conclude that the Γ1-X1
x
y
resonance causes peaky profiles in the photocurrent-voltage characteristics.
Observation of Resonances by Individual Energy Levels in InGaAs/AlAs Triple-Barrier Resonant Tunneling Diodes
Authors: Jo Jungyol , Choi Yearn-Ik , Kim Dong Myong , Alt Kevin , Wang Kang L.
Published: October 2002

Current-voltage characteristics in InGaAs/AlAs triple-barrier resonant tunneling diodes were investigated. Our data show that a current peak is observed when any of the quantum well energy levels is resonant with the emitter level, without level alignment between neighboring wells. When one of the well widths was increased, some peak voltages shifted, while others remained unchanged. This indicates that the peak positions are associated to a specific well. When the temperature was lowered, some peaks became stronger, while others became weaker. Our analysis shows that the weaker peaks are caused by the resonances between the emitter and the far side well. At low temperatures, current injection to the far side well is more difficult, and the current peak becomes weaker. These results indicate the conculsion that neighboring energy levels are not aligned in these structures.
The Concentration Dependence of the Hole Mobility of a Hydrazone Doped Polymer
Authors: Borsenberger P. M. , Magin E. H. , J. A. Sinicropi J. A. Sinicropi , L.-B. Lin L.-B. Lin
Published: October 2002

Hole mobilities of 4-diethylaminobenzaldehyde diphenylhydrazone (HDZ-F) doped poly(styrene) have been measured over a wide concentration range. The results have been described by a formalism based on disorder. The formalism is premised on the argument that charge transport occurs by hopping through a manifold of localized states that are distributed in energy and distance. The key parameter of the formalism is σ, the energy with of the hopping site manifold. For HDZ-F doped PS, σ is concentration-dependent. The maximum value is 0.121 eV and occurs at approximately 15% HDZ-F. The width decreases sharply for concentrations above and below. The concentration dependence is described by a model of dipolr disorder. The model is based on the assumption that the total widths are comprised of a dipolar component and a van der Waals component. The interpretation of the experimental results leads to the conclusion that the concentration dependence of the total width is largely determined by the van der Waals component.
Analysis of Side-Wall Structure of Grown-in Twin-Type Octahedral Defects in Czochralski Silicon
Authors: Ueki Takemi , Itsumi Manabu , Takeda Tadao
Published: October 2002

We analyzed the side-wall structure of grown-in octahedral defects in Czochralski silicon standard wafers for large-scale integrated circuits. There are two types of twin octahedral defects: an overlapping type and an adjacent type. In the twin octahedral defects of the overlapping type, a hole is formed in the connection part. The side-wall layer in the hole part is formed continually and is the same thickness as the side-wall layers of both octahedrons. In the twin octahedral defects of the adjacent type, a partition layer is formed in the connection part. Our electron energy-loss spectroscopy analyses identified that the side-wall layer includes SiO2.
Ohmic Contact to P-Type GaN
Authors: Youn Doo-Hyeb , Hao Maosheng , Sato Hisao , Sugahara Tomoya , Naoi Yoshiki , Sakai Shiro
Published: October 2002

Investigations of the new metal scheme for ohmic contact to p-GaN have been carried out. The specific contact resistance was measured to be ρc=3.6×10-3 Ω cm2 which is the lowest value ever reported for moderately doped p-GaN (4.4×1017/cm3). All metals were deposited on metalorganic chemical vapour deposition (MOCVD) grown p-GaN. The interaction mechanism between Ni and p-GaN has been investigated. Zn diffusion has been observed during annealing in Au–Zn/Ni on p-GaN. The interfacial reaction mechanism during annealing has been studied by secondary ion mass spectroscopy (SIMS) measurement. From this measurement, it is observed that Ni dissociates at the p-GaN surface and this dissociation promotes the Zn diffusion upon heat treatment. The electrical properties were studied using current–voltage (I–V) measurements at room temperature. The microstructure between the Ni and p-GaN interface was investigated using high-resolution transmission electron microscopy (TEM) before and after the heat treatment.
The Design and Fabrication of 0.35 µm Single-Polysilicon Self-Aligned Bipolar Transistors
Authors: Chantre Alain , Gravier Thierry , Niel Stéphan , Kirtsch Jean , Granier André , Grouillet André , Guillermet Marc , Maury Delphine , Pantel Roland , Regolini Jorge Luis , Vincent Gilbert
Published: October 2002

Two innovative process technologies are introduced to overcome problems related to the downscaling of single-polysilicon self-aligned bipolar transistors. First, the use of a selective silicon deposition step before Ti salicidation of the structure is shown to improve TiSi2 formation on narrow As-doped polysilicon emitters. At the same time, the elevation of the extrinsic base regions around the emitter causes a significant reduction of peripheral electron recombination effects. Second, the implantation of the intrinsic base at a large tilt angle (LATIB) is demonstrated to suppress emitter-to-collector punchthrough along the isolation edges. The first 0.35 µm single-polysilicon self-aligned bipolar transistors fabricated using a 200 mm complementary metal oxide semiconductor (CMOS) derived bipolar process integrating these novel process technologies are described.
Analysis of Drain Field and Hot Carrier Stability of Poly-Si Thin Film Transistors
Authors: Ayres J. Richard , Brotherton Stan D. , McCulloch David J. , Trainor Michael J.
Published: October 2002

Hot carrier instabilities in poly-Si thin film transistors (TFTs) are caused by high electric fields at the drain. These high fields are determined mainly by the abruptness of the lateral n+ doping profile in the drain and the two-dimensional (2D) coupling of the x and y components of the electric field between the gate and drain. The density of trapping states in the poly-Si film, however, has a much less significant impact on the field. Further, it is shown that improving the properties of the poly-Si film tends to have an adverse affect on hot carrier stability. Consequently, it is concluded that drain field relief is essential for hot carrier stability of n-channel poly-Si TFTs. It is shown that gate overlapped lightly doped drain (GOLDD) architectures can be used to relieve the drain field without introducing series resistance. Stable TFTs have been fabricated with GOLDD, consistent with circuit operation up to drain biases of 20 V. GOLDD is also effective in reducing the field enhanced leakage current in the off-state.
Deep-Level Transient Spectroscopy Study of Hydrogen-Related Traps Formed by Wet Chemical Etching in Electron-Irradiated n-Type Silicon
Authors: Tokuda Yutaka
Published: October 2002

Hydrogen has been introduced into 10 MeV electron-irradiated n-type silicon by wet chemical etching. The introduction of hydrogen causes the reduction of the concentration of the A center and divacancy, while it induces the formation of the NH1 electron trap (E
c-0.31 eV). The NH1 trap is found to correspond to one of the hydrogen-related traps in hydrogen-implanted n-type silicon, which has not been observed in electron-irradiated hydrogenated n-type silicon. The NH1 trap is tentatively ascribed to the vacancy-oxygen pair which is partly saturated with hydrogen.
The Effect of Crystallization Fraction on In-Situ AC-Initial-Permeability of an Fe–Si–B Amorphous Alloy during Isothermal Annealing
Authors: Leu Ming-Sheng , Tung I-Chung , Chin Tsung-Shune
Published: October 2002

The crystallization fraction (X
f) was quantitatively determined by the decrement in the crystallization enthalpy of an annealed Fe78Si13B9 alloy as compared with that of the as-cast one. The X
f was used to interpret the variation in ac-initial permeability (µi) of the Fe78Si13B9 alloy in-situ measured during isothermal annealing at 646 and 666 K, respectively. There are two µi maxima as soaking time elapses for both annealings. The first µi maximum is attributed mainly to the stress-relaxation effect and some crystallization effect with a measured X
f of 2–3.5%. The second µi maximum, appearing at about 210 and 36 ks for the annealings at 646 and 666 K, respectively, is invariantly much higher than that of the first one. The two corresponding crystallization fractions (X
f) are the same, about 9 % for both annealings. The second maximum is thus associated with crystallization effect. The Curie temperature of the amorphous matrix, being 668.5 K for the as-cast sample, increases sharply with annealing time. This makes difference in the shape of the first maximum, leveling off for the 646 K annealing and sharpening for the other. Transmission electron microscopy (TEM) micrographs and X-ray diffractometry (XRD) studies of the crystallized α-Fe and Fe(Si) phases in the alloy annealed at 646 K for more than 180 ks were depicted.
Fabrication and Characterization of Diffraction Gratings Using Photosensitive Al2O3 Gel Films
Authors: Zhao Gaoyang , Tohge Noboru , Nishii Junji
Published: October 2002

A new process for the fabrication of diffraction gratings has been proposed using photosensitive Al2O3 gel films in combination with a phase mask. Photosensitive Al2O3 gel films were derived from Al(O-sec-Bu)3 chemically modified with benzoylacetone. These gel films exhibited an optical absorption band in the UV-range, which is associated with the π–π* transition of chelate rings of the β-diketonate ligand. The irradiation of these gel films with XeF and KrF excimer lasers decreased their solubility in acetone containing 1.2 vol%HNO3, simultaneously with the dissociation of the remaining chelate rings. The above findings were applied to the fabrication of Al2O3 film diffraction gratings on Si and silica substrates; the gel films were irradiated with the excimer lasers through a phase mask, leached, and then heat-treated. The diffraction efficiency of the fabricated gratings was evaluated in reflection (Si sub.) and transmission (silica sub.) modes with respect to the preparation conditions.
Holographic Video System with a Pulse Laser
Authors: Oh Hyun-Seo , Jeon Hyung-Wook , Shestak Sergey A. , Kim Sung-Kyu , Son Jung-Young , Lee Hyuk-Soo , Choi Yong-Jin , Kang Chang-Eon
Published: October 2002

A holographic video system operated by a pulse laser is described. The use of a pulse laser as the light source allows the polygon mirror (or scanners) in the system to be eliminated. At the same time, a single long aperture acousto-optic modulator (AOM) is replaced by 6 small aperture AOMs linearly aligned and a still polygon mirror set is used. The effective aperture length of the 6-AOM-combination is 6 times that of an individual AOM. Since in this system the computer-generated-hologram (CGH) data is divided into 6 equal parts and loaded into the corresponding AOMs independently and synchronously, the loading time of CGH data to an AOM is reduced. This system can display 36,864 (in the horizontal direction)×128 (in the vertical direction) holographic fringe data points in binary format and operate at a rate of 60 frames per second using a personal computer.
Optical Properties of Photostimulable Near IR Centers in BaFCl Single Crystals Produced by Two-Photon Excitation
Authors: Toshio Kurobori Toshio Kurobori , Takashi Matsuki Takashi Matsuki , Karnati Somaiah Karnati Somaiah , Taku Kimura Taku Kimura , Shoichi Nakamura Shoichi Nakamura , Katsuyuki Inabe Katsuyuki Inabe
Published: October 2002

The stable and photostimulable F-aggregate centers, besides the already established isolated centers, located in the near IR region in BaFCl single crystals are reported. These F-aggregate centers are producible by two-photon excitation and the production rate can be enhanced by monovalent doping like incorporating K+in BaFCl. The F-aggregate centers in BaFCl have been characterised by their growth behaviour, room temperature stability, optical bleaching, emission and the temperature dependence of the PSL lifetimes. It is a first time demonstration as applied to BaFCl single crystals to produce F-aggregate centers more efficiently by using the fourth harmonic of a Q-switched Nd:YAG laser as compared to X-irradiation.
Observation of Solitonlike Excitations in All- trans-β-Carotene Single Crystals
Authors: Hideki Hashimoto Hideki Hashimoto , Yoshiko Sawahara Yoshiko Sawahara , Yoshihiro Okada Yoshihiro Okada , Kingo Hattori Kingo Hattori , Tomokuni Inoue Tomokuni Inoue , Ryoka Matsushima Ryoka Matsushima
Published: October 2002

The crystal structure of all-trans-β-carotene was determined at 293 K. The space group determined in this investigation was consistent with that determined at 130 K by Senge et al. [Z. Naturforsch. C 47 (1992) 474]. Anisotropic displacements of lattice constants and molecular structures were observed upon raising the temperature from 130 K to 293 K. Photoinduced and time-resolved absorption spectroscopies were applied to all-trans-β-carotene single crystals. By exciting visible absorption bands of the crystals, we observed, for the first time, the photoinduced bleaching of infrared absorption bands. The bleaching typically showed a single-exponential recovery with a lifetime of ∼10 ms, which shows that some kind of metastable state is produced by exciting the visible absorption bands of the crystals. Depending on the crystals, however, we observed stretched-exponential and power-law recoveries. By inference based on the results for trans-polyacetylene, the cause of the latter two recoveries was attributed to the recombination of solitonlike excitations. Semi-empirical and ab initio molecular orbital calculations indicated the presence of solitonlike excitations in finite polyenes.
Large Hall Effect and Microstructure in Granular Fe–XCr–10Co Alloy Thin Films
Authors: Chang Hui-Chen , Chang Yen-Hwei
Published: October 2002

A large Hall effect was observed in Fe–XCr–10Co (wt%) granular alloy films at room temperature. After aging, phase separation into α1 (ferromagnetic) and α2 (paramagnetic) phases was observed and verified using a high-resolution transmission electron microscope (HRTEM). The alloy composition and heat treatment conditions, which influence a film's microstructure, obviously affect the Hall effect. The Hall resistivity is positive for both as-deposited and annealed films. After aging the Fe–10Cr–10Co films at 200°C for 60 min, we observed the maximum Hall resistivity (ρH) of 12.6 µ Ω·cm (measured at 300 K and 14 kOe). The Hall resistivity varies almost linearly with the applied field.
Low-Temperature Deposition of SrTiO3 Thin Films by Electron-Cyclotron-Resonance Sputtering for Monolithic Microwave Integrated Circuits Operating in the mm-Wave Band
Authors: Kenji Ikuta Kenji Ikuta , Mitsuo Tsukada Mitsuo Tsukada , Hiroshi Nishimura Hiroshi Nishimura
Published: October 2002

Electron-cyclotron-resonance (ECR) plasma assisted deposition of strontium titanate (STO) thin films is discussed. Films having a high dielectric constant (ε
r) can be deposited at a temperature as low as 100°C by controlling the ECR plasma energy and ion current density. There exists a pressure that gives the maximum refractive index. The dependence of the refractive index and dielectric constant on the deposition temperature can be minimized at that pressure, where the ECR plasma energy and ion current density strongly assist the STO deposition. The pressure is approximately 0.05 Pa in an ECR sputter apparatus with a plasma energy of 10 eV and an ion current density of 5 mA/cm2. 100-nm-thick STO thin films, having ε
r of 70, a Qf product greater than 1000 in the mm-wave band up to 50 GHz, and dc leakage current less than 10-8 A/cm2 at 0.5 MV/cm, are realized by deposition at 0.05 Pa and 100°C. Deposition at other pressures results in a lower dielectric constant due to poor ECR plasma assistance. The properties of the STO thin films presented here are essential to process on-chip capacitors for monolithic microwave integrated circuits (MMICs).
A Two-Dimensional Stokes Parameter Method for Determination of Cell Thickness and Twist Angle Distributions in Twisted Nematic Liquid Crystal Devices
Authors: Zhan He Zhan He , Ying Zhou Ying Zhou , Susumu Sato Susumu Sato
Published: October 2002

In order to determine 2-dimensional (2D) cell thickness and twist angle distributions in twisted nematic (TN) liquid crystal (LC) devices, we propose a 2D Stokes parameter method (2DSPM). A 2DSPM system is set up using a polarizing microscope, in which some preliminary experiments are conducted to demonstrate the validity of this 2DSPM. Experimental results of 2D distributions of cell thickness and twist angle in TN LC sample cells are given for the first time. The measurement accuracy of the 2DSPM system is analyzed.
Drawing Effect on Thermal Properties of High-Strength Polyethylene Fibers
Authors: Fujishiro Hiroyuki , Ikebe Manabu , Kashima Toshihiro , Yamanaka Atsuhiko
Published: October 2002

The thermal conductivity κ and thermal diffusivity α of high-strength polyethylene fibers, DyneemaTM, with various draw ratios were measured from 10 K to 260 K. κ and α increased with increasing draw ratio and α was nearly proportional to the square root of the tensile modulus E of the fiber. The estimated phonon mean free path l (40–60 Å) was almost temperature independent. Boundarylike scattering due to characteristic microstructures with comparable size to l may effectively limit the thermal conduction in these fibers.
The Mechanism at Work in 40 MHz Discharge SiH4/NH3/N2 Plasma Chemical Vapor Deposition of SiNx Films at Very High Rates
Authors: Takechi Kazushige , Takagi Tomoko , Kaneko Setsuo
Published: October 2002

This paper reports a study on the mechanism involved in depositing SiN
x
films at very high rates by using 40 MHz discharge SiH4/NH3/N2 plasma enhanced chemical vapor deposition (PECVD). The quality of the films is comparable to that of films deposited at low rates at a conventional 13.56 MHz frequency. From film deposition experiments, plasma diagnostic studies, and analytical calculation for both frequencies, we have found that the mechanism of depositing SiN
x
films at very high rates with a 40 MHz discharge can be explained by the higher dissociation efficiency of both NH3 gas and SiH4 gas than at a conventional 13.56 MHz. We also report the performance of a thin film transistor (TFT), applicable to LCD switching devices, that was fabricated with SiN
x
film deposited at the high rate of 350 nm/min with a 40 MHz frequency.
Structural and Optical Properties of LiNbO3 Films Grown by Pulsed Laser Deposition with a Shadow Mask
Authors: W. Noh Dong-Wook Kim
Published: October 2002

High-quality LiNbO3 thin films were grown by pulsed laser deposition (PLD) with a shadow mask. Epitaxial and twin-free films were obtained using a single crystal target without a post-annealing process. The film had a very smooth surface without the particulate problem, which is common in films grown by conventional PLD. The root-mean-square surface roughness was only 3.6 nm, and optical propagation loss was as low as 3 dB/cm.
Hydrogen-Induced Restructuring and Crater Formation at Si(111) Surfaces: A Scanning Tunneling Microscopy Study
Authors: Masamichi Naitoh Masamichi Naitoh , Hiroshi Shimaya Hiroshi Shimaya , Akihiko Watanabe Akihiko Watanabe , Satoshi Nishigaki Satoshi Nishigaki
Published: October 2002

We report results of a scanning tunneling microscopy (STM) investigation of hydrogen-affected restructuring process at Si(111) surfaces. The hydrogen adsorption on the 7×7 surface produced clusters on the restlayer involving both Si adatoms from the initial dimer-adatom-stacking fault (DAS) structure and hydrogen atoms. Moreover, the restlayer was changed from the 7×7 to a 1×1-like structure by transferring dimer-walls. During the annealing process, the surface recovered the 7×7 structure via the formation of craters of bilayer depth. This is explained to be due to the local lack of Si atoms induced by migration-coalescence of the clusters at high temperatures.
Patterning Characteristics of Hole Patterns in Synchrotron Radiation Lithography
Authors: Nakanishi Kazuya , Deguchi Kimiyoshi , Matsuda Tadahito
Published: October 2002

The patterning characteristics of synchrotron radiation lithography for hole patterns using a low-contrast mask (contrast: 3.5) are investigated. A resolution of 110 nm provides a large exposure dose latitude of more than 10% when the proximity gap is less than 15 µm, and the replicated minimum hole size is 70 nm with a 10-µm gap. Resist pattern sizes from 110 to 360 nm are kept within ±10% with proximity gaps of less than 20 µm. However, the exposure dose margin to guarantee mask linearity decreases to several percent because of the different optimum exposure dose for each pattern. Pattern size correction using mask bias to improve the mask linearity and exposure dose margin is proposed.
State Analysis of Fluorides with Rare Earth Elements in Electron Probe X-Ray Microanalysis
Authors: Takahashi Hideyuki , Minato Ichiro , Kondo Yuji
Published: October 2002

The peak shapes of F-Kα for fluorides with rare earth elements are examined using electron probe X-ray microanalyser (EPMA). It is demonstrated that the F-Kα spectra in fluorine compounds from 57La to 71Lu indicate characteristic peak shapes and the intensity ratios of the satellite Kα3,4 to the main Kα increase with the number of valence electrons.
Phase-Change Optical Disk Having a Nitride Interface Layer
Authors: Yamada Noboru , Otoba Mayumi , Kawahara Katsumi , Miyagawa Naoyasu , Ohta Hiroyuki , Akahira Nobuo , Matsunaga Toshiyuki
Published: October 2002

A thin nitride layer formed at the interface of a Ge–Sb–Te recording layer and a ZnS–SiO2
protective layer successfully suppresses the phenomenon that reflectivity or signal
amplitude becomes markedly small due to repeated overwrites. Based on secondary ion mass
spectrometry (SIMS) observations, the 5-nm-thick interface layer was found to restrain sulfur
atoms in the ZnS–SiO2 layer from diffusing into the Ge–Sb–Te layer and from changing the
optical characteristics of the layer. Among several nitride materials, germanium nitride (Ge–N)
sputtered film is found to have the most suitable properties as an interface layer: high barrier
effect and good adhesiveness with Ge–Sb–Te and ZnS–SiO2 layers. The optical disk having the
Ge–N interface layer achieves more than 5×105 cycles of overwrites with almost no changes in
signal amplitude, reflectivity and jitter based on DVD-RAM specifications. The disk shows no
degradation such as cracking, peeling, and corrosion after exposure to accelerated
environmental conditions of 90°C and 80% RH for 200 h.
Determination of the Piezoelectric Coefficient of Monolayers on Water Surface by Maxwell-Displacement-Current Measurement
Authors: Sato Yoko , Wu Chen-Xu , Majima Yutaka , Iwamoto Mitsumasa
Published: October 2002

Using the Maxwell-displacement-current (MDC) measurement, the piezoelectric property of monolayers is examined. The equation representing the piezoelectric coefficient is derived in connection with the MDC. The piezoelectric coefficient of 4-cyano-4'-alkyl-biphenyle (5CB) monolayers was determined on the basis of the derived equation.
Evaluation of a 120 mm Sized Magneto optical Disk System of Over 6 GB Capacity
Authors: Tanaka Yasuhito , Sumi Satoshi , Matsubayashi Nobuhide , Sato Hideaki , Murakami Yoshiteru , Awano Hiroyuki , Matsuura Michio , Fujita Goro , Watanabe Tetsu
Published: October 2002

We have studied the feasibility of the 120-mm-sized magneto optical disk system which
achieves 6-GB user capacity using an optical pickup with a 640-nm wavelength laser and a
0.6-numerical aperture of the objective lens. We have used three technologies: a laser-pulsed
magnetic-field modulation recording, a center-aperture-detection type of magnetically-induced
super resolution disk with a 0.6-mm-thick single substrate and partial response equalization
with maximum likelihood detection. We have evaluated the system-margins of write power,
radial tilt, tracking and focusing offset and have confirmed the feasibility of the linear bit
density of 0.235 µm/bit in 0.6-µm track pitches.
Reflective Supertwisted Nematic Liquid Crystal Displays
Authors: Chen Jun , Yu Fei-Hong , Ho-Chi Huang Ho-Chi Huang , Hoi S. Kwok Hoi S. Kwok
Published: October 2002

Supertwisted nematic (STN) liquid crystal displays are widely used commercially. However, there is still room for improvement. In this paper, we discuss reflective STN displays in which the rear polarizer has been removed and no retardation film is used for dispersion compensation. This new design can potentially yield higher brightness than conventional STN displays. They can also have better chromaticity. Numerical calculations and experimental data on such reflective STN liquid crystal displays with twist angles of 190–240° are presented in this paper. These new displays have reasonably steep reflectance-voltage characteristics and can be multiplex-driven like ordinary transflective STN displays. An additional advantage of this new display is the absence of a viewing parallax if the reflector is placed inside the liquid crystal cell.
Lens Design for Optical Head Compatible with Compact Disk and Digital Versatile Disk
Authors: Tanaka Yasuhiro , Yamagata Michihiro , Komma Yoshiaki , Mizuno Sadao , Nagashima Kenji
Published: October 2002

This paper describes three approaches to lens design for reading different thickness
disks with one optical system. In the case of an optical head using two different objectives
with one actuator, the skew adjustments for both lenses are difficult. First we design
objective lenses that are coma free against skew adjustment. The method that uses one
objective lens with a liquid crystal shutter still results in a spherical aberration of 50 mλ for a
1.2 mm disk. Second, we design the inner area of the lens for a disk thickness of 0.9 mm, and
then the spherical aberration becomes half. The third order spherical aberration of the entire
aperture is made to be zero. Grating is integrated onto the surface of a dual focus lens, it
causes stray light. We propose a grating profile that reduces stray light to one-fifth.