bluuebunny/crossref_metadata_2025 huggingface dataset:
Soft X-Ray Microscope with Zone Plates at UVSOR I: Performance
Authors: Watanabe Norio , Shimanuki Yoshio , Kihara Mieko Taniguchi
Published: February 2005

A soft X-ray microscope with zone plates was set up at UVSOR (synchrotron radiation facility at Institute for Molecular Science, Okazaki).
A 0.41 µm line-and-space pattern was clearly distinguished using an objective zone plate with the outermost zone width of 0.41 µm.
Modulation transfer functions were measured at wavelengths of 3.1 nm and 5.4 nm, and compared with theoretical calculations.
The experimental results corresponded fairly well with the theoretical ones, taking into account that a point spread function of a microchannel plate and fluorescent plate assembly used as a detector had a full width at half-maximum of 50 µm.
A theoretical calculation of an intensity–wavelength distribution of illumination at an object plane was performed and compared with experimental results.
Nonuniformity of illumination can be explained in terms of a distance between a specimen and a pinhole in front of it.
High-Resolution Proximity Exposure through a Phase Shifter Mask
Authors: Saburo Nonogaki Saburo Nonogaki , Akira Imai Akira Imai
Published: February 2005

A simple method to fabricate fine lines of photoresist has been developed. The method utilizes a mask containing an equal-width line-and-space pattern of the half-wavelength phase shifter. A film of photoresist formed on a substrate is placed in close proximity to the mask and exposed through the mask by flooding with a beam of light. The beam, diffracted by the mask, produces an interference pattern, which extends long enough to expose the film patternwise. The film is then developed to form a resist pattern. An array of 0.2-µm-spaced, 0.1-µm-wide lines of a positive photoresist has been obtained by this method using the i-line with a peak intensity at the wavelength of 0.365 µm. Calculation based on a rigorous solution of the two-dimensional diffraction problem indicates that a high-contrast 0.1 µm line-and-space exposure using the i-line is feasible if the light is polarized.
Electrode Temperature Effect in Narrow-Gap Reactive Ion Etching
Authors: Tsukada Tsutomu , Supika Mashiro Supika Mashiro , Kimiko Mashimo Kimiko Mashimo
Published: February 2005

The SiO2 etch characteristics were investigated using a narrow-gap reactive ion etching (RIE) apparatus. The etch rate was decreased and the selectivity to Si was increased when the upper electrode temperature was increased. However, the etch characteristics were independent of the absolute temperatures of the electrodes. This phenomenon can be explained in terms of the difference in the polymer deposition rate on walls that have different temperatures.
Kerr Effect for Three-Dimensional Electric Fields
Authors: Uto Sadahito , Ihori Haruo , Masaharu Fujii Masaharu Fujii , Kiyomitsu Arii Kiyomitsu Arii
Published: February 2005

An optical method using the Kerr effect is useful to measure electric fields in dielectric liquids without disturbing the field. A conventional relation of the Kerr effect cannot be applied to the measurement of a three-dimensional field, the direction of which is not always perpendicular to an incident light. We have derived the relation of the Kerr effect which can be applied to three-dimensional measurement and confirmed it experimentally.
High Purity Liquid Phase Epitaxial Growth of InP
Authors: Amano Toshimasa , Susumu Kondo Susumu Kondo , Haruo Nagai Haruo Nagai
Published: February 2005

This paper reports a study of indium solvent baking in wet hydrogen and solution recyclic usage techniques for high purity InP liquid phase epitaxial growth (LPE). Obtained purity, as indicated by RT mobility of 6460 cm2/Vs, is the highest ever reported. However at 77 K, the carrier concentration range was only 3-4?1014 cm-3 and electron mobility was ?112200 cm2/Vs during a series of recyclic growth. The limit to the purity obtainable by LPE appears to be mainly due to an enhanced contamination process native to materials containing phosphor, and perhaps partially due to difficulty in keeping the solution saturation stable during the recyclic growth series.
Characterization of Single Crystals of High-Tc Superconductor La2-xSrxCuO4
Authors: Aomine Nobutaka , Yamada Hiroshi , Soejima Yuji , Okazaki Atsushi , Tanaka Isao , Kojima Hironao
Published: February 2005

High-angle double-crystal X-ray diffractometry (HADOX) has been applied to examine the quality of La2-x
Sr
x
CuO4 crystals grown by the travelling-solvent floating-zone method. The two-dimensional intensity distribution in reciprocal space is measured for 0014 and 400 with CoK?1 radiation in a temperature range 60-260 K. The temperature dependence of the lattice constants is also measured. It is found that the crystal consists of grains or regions with different chemical compositions (?x?0.01), and that the corresponding crystallographic axes in different grains are parallel. A tetragonal-to-orthorhombic phase transition is reflected in changes in the crystal orientation, peak splittings and lattice constants as functions of temperature.
Piezoceramic HF Resonator with Zero Temperature Coefficient
Authors: Long Wu Long Wu , Yi-Yeh Lee Yi-Yeh Lee
Published: February 2005

The ternary piezoelectric material Pb0.97Sr0.03[Zr0.458Ti0.452(Mn1/3Nb2/3)0.09]O3 in the tetragonal phase near the morphotropic phase boundary (MPB) was prepared in this study. By properly varying the sintering and poling conditions, the zero temperature coefficient of the resonant frequency of the thickness vibration mode can be reached due to the slight shift of the MPB region. The computed Bechmann number based on the principle of trapped energy revealed that the high-frequency resonators with electrode width of at least less than 1 mm are suggested corresponding to the plate thickness of 0.205 mm to exhibit better resonance performance due to the suppression of unwanted mode coupling.
Improved Ferroelectric Properties of Niobium-Doped Pb[(Sc1/2Nb1/2)Ti]O3 Ceramic Material
Authors: Yohachi Yamashita Yohachi Yamashita
Published: February 2005

The effects of doping niobium and scandium in Pb[(Sc1/2Nb1/2)0.575Ti0.425]O3 piezoelectric polycrystalline ceramics were investigated. Complete single-phase perovskite with high density was obtained with all samples fired at 1275?C. Niobium doping decreased the grain size, enhanced the maximum dielectric constant value and increased the electrical resistivity by two orders of magnitude compared with nondoped samples. Large electromechanical coupling factors of k
p=69%, k
t=52% and k
33=76%, which are almost equivalent to value for the best PZT-based piezoelectric ceramics, were obtained in niobium-doped specimens. The material has the largest electromechanical coupling factor of all relaxor-lead titanate binary ceramics systems so far reported.
Dynamic Response of Surface-Stabilized Ferroelectric Liquid Crystals with Chevron Layer Structure
Authors: Akahane Tadashi , Kazumasa Itoh Kazumasa Itoh , Norio Nihei Norio Nihei
Published: February 2005

The dynamic response of surface-stabilized ferroelectric liquid crystals with chevron layer structure to a triangular wave voltage is studied based on the continuum theory. From systematic numerical calculations, the shape of polarization reversal current is found to be crucially affected by the surface-anchoring condition, and the frequency and the amplitude of applied voltages. The theoretical results are confirmed through comparison with the experimental results.
Effects of Growth Rate on Properties of Pb(Zr, Ti)O3 Thin Films Grown by Chemical Vapor Deposition
Authors: Katayama Takuma , Masaru Shimizu Masaru Shimizu , Tadashi Shiosaki Tadashi Shiosaki
Published: February 2005

The effects of the growth rate on the dielectric and ferroelectric properties are studied using tetragonal Pb(Zr, Ti)O3 thin films grown by chemical vapor deposition. The growth rates of the films were controlled by changing the carrier flow rates and tank pressures for metallorganic sources. In particular, when the source tank pressures were changed, the growth rates were successfully controlled. The electrical properties of the films were dependent on the growth rate. With reduced growth rate, Pb(Zr, Ti)O3 films with higher dielectric constants and lower remanent polarizations were obtained. In order to clarify the cause of this effect, changes in the orientation and microstructures of the films were also investigated.
Solvent Effects on Gel Characteristics of Conducting Polymer
Authors: Morita Shigenori , Shakuda Shuzo , Sugimoto Ryu-ichi , Katsumi Yoshino Katsumi Yoshino
Published: February 2005

The response time of volume change of poly(3-alkylthiophene) gel film is dependent on both film size and solvent used; that is, it becomes longer with increasing film size and shorter in a solvent of larger Taft parameter ?*, respectively. In chloroform-ethanol mixture, the response time becomes longer with increasing ethanol concentration. Poly(3-alkylthiophene) gel expanded in chloroform shrinks upon introduction of alcohol above the critical concentration and also with decreasing temperature below a critical temperature. The critical temperature increases with increasing concentration of alcohol. In terms of concentration dependence of volume change, the critical concentration of alcohol depends on the kind of alcohol used. That is, alcohol (C
n
H2n+1OH) with larger carbon number n exhibits larger critical concentration. These results are discussed in terms of the interactions between alkyl chains and solvent molecules and also between main chains and solvent molecules.
Charging Effect of Ion Implantation on Glass
Authors: Oyoshi Keiji , Takashi Tagami Takashi Tagami , Shuhei Tanaka Shuhei Tanaka
Published: February 2005

Methods to suppress charge build-up during ion implantation in glass and the charging effect of ion implantation on glass have been investigated. The methods to suppress charge build-up, such as use of an electron flood gun or metal film coating, and electron generation from ion-irradiated metal, are effective and sufficient in the present experiment. Positive charge accumulates on the glass surface without these charge neutralization methods. A decrease in the projected range of implanted ions and in actual ion dose, and inhomogeneous planar distribution due to the charging have become evident. Strong visible light emission and broadening of the light-emitted area due to the charging are also observed during the ion implantation.
Magnetic Properties and Read/Write Characteristics of Exchange-Coupled Double-Layered Magnetooptical Media Using GdFeCo/TbFeTi Film
Authors: Murakami Yoshitake , Hasegawa Toshiyuki , Morita Noboru , Eizo Fukami Eizo Fukami , Masaki Itoh Masaki Itoh
Published: February 2005

We have developed a 200 mm magnetooptical disc using an exchange-coupled GdFeCo/TbFeTi layer and a heat-sink reflective layer of AlTi. Magnetic properties were measured and reported. It was confirmed that this disc had high writing sensitivity suitable for a speed of more than 3600 rpm, high carrier-to-noise ratio, high reflectance and interchangeability under the condition of a high data density of 0.46 µm/bit.
Measurement of Domain Wall Mobility in Magneto-Optic Media
Authors: Du Mann , Mark D. Schultz Mark D. Schultz , Mark H. Kryder Mark H. Kryder
Published: February 2005

Domain wall mobility in magneto-optic (MO) media is important in determining the thermomagnetic recording and erase process. However, measurement of domain wall mobility has been difficult due to the large coercivity of MO media near room temperature and the weak MO signal at high temperature. With an improved high speed polar Kerr MO camera system, the dynamics of domain wall motion can now be imaged and measured at temperatures nearTcurie. The domain wall mobility in GdTbFe samples was measured with the bubble collapse method. The experimental results show that the domain wall motion velocity is a linear function of applied bias field and the domain wall mobility is about 0.3 cm/sOe. Samples with different preparation methods are compared and the experiment shows that whereas the dynamic coercivity varies with the preparation method, the mobility is an intrinsic property and dependent primarily upon sample composition.
Premastered Optical Disk by Superresolution
Authors: Yasuda Kouichi , Ono Masumi , Aratani Katsuhisa , Atsushi Fukumoto Atsushi Fukumoto , Masahiko Kaneko Masahiko Kaneko
Published: February 2005

Premastered optical disk by superresolution (PSR) for practical use has been achieved for the first time. The PSR disk has a phase-change material Ge2Sb2Te5 with stoichiometric composition. Superresolution results from a high contrast ratio of reflectance in the light spot between highly reflective crystal region and lowly reflective melted region. A high C/N ratio of 56 dB is obtained at a pit length of 0.4 µm using PSR. The C/N ratio is still as high as 50 dB for a pit length of 0.3 µm. The PSR disk with double linear densities of current CD is successfully read out with a clear eye pattern and a low error rate using current optics.
Recording Characteristics and Reliability of Novel Writable Compact Disc Using a Au-Sn Alloy Single Layer
Authors: Tamura Reiji , Keiko Hiratsuka Keiko Hiratsuka , Norio Ohta Norio Ohta
Published: February 2005

We have developed a novel writable compact disc (CD) using a Au70Sn30 alloy recording film. This has the advantages of a single-layered, simple structure suitable for conventional CD processes, high reflectivity, low toxicity and high reliability. Recording marks are formed by filling up the grooves resulting from thermal deformation and deconstruction of polycarbonate resin. Modulation amplitudes of 0.37 (3 T) and 0.87 (11 T) are obtained by this new recording method. The addition of Ti to the recording film improves its reliability by preventing Sn oxidization.
Completely Erasable Phase Change Optical Disc II: Application of Ag-In-Sb-Te Mixed-Phase System for Rewritable Compact Disc Compatible with CD-Velocity and Double CD-Velocity
Authors: Iwasaki Hiroko , Harigaya Makoto , Nonoyama Osamu , Kageyama Yoshiyuki , Takahashi Masaetsu , Yamada Katsuyuki , Hiroshi Deguchi Hiroshi Deguchi , Yukio Ide Yukio Ide
Published: February 2005

Aiming to obtain a rewritable compact disc (CD-rewritable) with high performance at both CD-velocity (CD1X) and double CD-velocity (CD2X), the phase change optical disc with the Ag-In-Sb-Te system has been developed. In the one-pass overwriting mode with eight-to-fourteen modulation, high carrier-to-noise ratio, wide power margin and high erase ratio have been obtained at both velocities. As for stability, we acquired a satisfactory result in the read-out test of 106 cycles with read power of 1.5 mW. We conclude that the phase change optical disc with the Ag-In-Sb-Te system is suitable for use at both CD1X and CD2X. Furthermore, the phase change process of the Ag-In-Sb-Te system has also been investigated. The chemical structure of the Ag-In-Sb-Te system in its ordered state was found to be (Ag-Sb-Te)
x
(In1-y
Sb
y
)1-x
.
Thin Optical Head with Flip-Chip Bonded Module for Compact Disc Read Only Memory Drives
Authors: Nagano Tsuyoshi , Ueda Eiichi , Onayama Shuichi , Katayama Ryuichi , Hamada Hiroshi , Ono Yuzo
Published: February 2005

A thin optical head for compact disc read only memory drives, whose thickness is 6.9 mm including the objective lens working distance, has been developed. It features a flip-chip bonded module, in which a laser diode chip, a micromirror and a preamplifier chip are integrated on a photodiode chip. The module size is 6 mm(W)×6 mm(D)×1.64 mm(H), and its weight is 0.25 g. Readout operation was successfully carried out for a compact disc, and a 19 ns jitter signal was obtained.
Newly Packaged 50-µm-Spaced 8-Element Laser Diode Array with a Thermoelectric Cooler
Authors: Murata Setsuko , Nakada Hiroshi , Abe Tetsuo , Hidenao Tanaka Hidenao Tanaka , Akinori Watabe Akinori Watabe
Published: February 2005

We report that the junction temperature of individually addressable high-power laser diode elements in an array can be reduced by adjusting cavity length and by mounting the array in a copper package that has a thermoelectric cooler and cooling fins. We fabricated a 50-µm-spaced 8-element array and verified its low thermal interaction. We also experimentally evaluated the cooling characteristics of the new package: when all array elements operate simultaneously and continuously at 50 mW, the measured temperature reduction achieved with this package corresponds to an 8-fold increase in array lifetime.
High Density Optical Disk System Using Variable Five Modulation and Second Harmonic Generation Green Laser
Authors: Naoya Eguchi Naoya Eguchi , Yoshiyuki Akiyama Yoshiyuki Akiyama
Published: February 2005

We have realized the readout of optical disks with 6 times higher areal density than that of conventional compact discs (CDs). This system uses a new variable-length block code variable five modulation (VFM) and an optical pick-up with a miniature integrated diode-pumped second harmonic generation (SHG) green laser (mi-green laser) and a 0.6 NA objective lens.
Land and Groove Recording for High Track Density on Phase-Change Optical Disks
Authors: Miyagawa Naoyasu , Gotoh Yasuhiro , Ohno Eiji , Nishiuchi Kenichi , Akahira Nobuo
Published: February 2005

We have proposed a high-track-density optical recording method, which records signals on both the land area and groove area. From a computer simulation based on the scalar diffraction theory, we found that crosstalk between recording tracks depends on the groove depth, and is most reduced at the groove depth of 80 nm∼90 nm for a laser wavelength of 780 nm, a numerical aperture of 0.55 and a track pitch of 0.8 µm. Applying this method to a phase-change optical disk, we experimentally confirmed that crosstalk depends on the groove depth and obtained a crosstalk level of less than -32 dB for a groove depth of 64 nm to 78 nm and 0.9 µm length marks. In order to prove that this recording method can be used for rewritable media, we also measured change of carrier-to-noise ratio (CNR) when signals were repeatedly recorded on an adjacent track. The reduction of CNR after 1000 repetitions of writing was less than 2 dB for a linear velocity of 5 m/s.
High-Speed Access Mechanism for 90 mm 1-Inch-High Optical Disk Drive
Authors: Takizawa Teruyuki , Shinoda Masayuki , Wakabayashi Kanji , Takamine Kouichi , Ikawa Yoshihiro , Yoshikazu Gotoh Yoshikazu Gotoh , Isao Satoh Isao Satoh
Published: February 2005

A 90 mm, 1-inch-high optical disk drive with a 17-mm-high mechanism and a 27 ms seek time was developed using a separated optical system with an improved galvanomirror. This optical layout reduced the weight of the movable optical part to 7 g. The maximum acceleration of 127 m/s2 was driven by 8 W. The major component parts of the galvanomirror, such as the mirror holder and base, were made of anisotropic liquid-crystalline polymer. The use of this material, which has high rigidity and low thermal expansion, resulted in optical spot drifting due to mirror rotation of less than 3 µm from room temperature to 65°C.
Repetitive Track Seeking Algorithm for Optical Disk Drives
Authors: Minoru Akiyama Minoru Akiyama , Jun Ishikawa Jun Ishikawa
Published: February 2005

In order to achieve stable and rapid track seeking, a repetitive track seeking algorithm, which realizes highly accurate velocity control through velocity error integration, has been developed. Simulations and experiments show that the algorithm is effective in optical head velocity control. The algorithm reduces velocity error, compared with the conventional approach, so that the transient response at the seek end is greatly improved. The total seek time is reduced by adopting a reference velocity trajectory with larger deceleration rate, using this algorithm.
Feasibility Study on High Data Transfer Rate of 300 Mbit/s with 8-Beam Laser Diode Array
Authors: Arai Ryoichi , Mizukami Makoto , Tanabe Takaya , Katoh Kikuji , Yoshizawa Takashi , Yamazaki Hiroki , Murata Setsuko , Yasuaki Tanaka Yasuaki Tanaka , Isamu Sato Isamu Sato
Published: February 2005

This study aims at achieving a high speed optical disk drive for multimedia storage used in network systems. The feasibility of our target has been confirmed by the following results and techniques. High speed parallel data transfer at 336 Mbit/s in 2/7 run length limited (RLL) code or 300 Mbit/s in 1/7 RLL code has been achieved experimentally with eight beams. Focus offset has been reduced by a multibeam laser diode fabricated in junction down structure and a wide-angle lens system. Tracking error is reduced by nearly 6 dB compared with that of a conventional method. This was achieved by suppressing the mechanical interaction between the lens actuator and the beam rotation prism. The crosstalk canceler reduces both intercircuit crosstalk and optical crosstalk with pseudo crosstalk generated by a circuit. It reduces the worst-case intercircuit crosstalk by more than 14 dB.
High-Precision Head Positioning Using Multiple Offset Beams
Authors: Mizukami Makoto , Takashi Yoshizawa Takashi Yoshizawa , Isamu Sato Isamu Sato
Published: February 2005

This paper describes a new tracking technique with a multiple beam mechanism that will lead to low profile optical disk storage units with faster access speeds. In this technique, data tracking involves selection among multiple beams with minute offsets. It can accommodate four-beam laser diodes while assuring twice the tracking accuracy and ten times the tracking bandwidth of conventional approaches. Its servo performance depends on the total distance between the two outermost beams in the beam series on the medium.
Analysis on Read-Out Signal in Magnetooptical Disc Drive System
Authors: Lee Chul Woo , Kyung-Hwa Rim Kyung-Hwa Rim , Young Woong Kim Young Woong Kim
Published: February 2005

Waveforms of read-out signals are calculated for a magnetooptical disc drive system by using diffraction theories on slits. Also, using a Yttrium aluminum garnet; second-harmonic generation (YAG;SHG) laser (λ=532 nm) as a light source, the read-out signals are measured from a magnetooptical disc drive system. Jitter is investigated with the theoretical and experimental results. Good agreement is found between the results.
High Recording Density Optical Disc Mastering
Authors: Iida Tetsuya , Higuchi Takanobu , Sasaki Hironao , Kunizo Ogoshi Kunizo Ogoshi , Shin'ichi Yokozeki Shin'ichi Yokozeki
Published: February 2005

Aiming at obtaining a high CNR (carrier-to-noise ratio) and four times higher recording density than that of the conventional Laser Disc, we have developed a mastering process for a Laser Beam Recorder utilizing an ultraviolet laser. A photoresist claiming high resolution and high CNR has been screened out from the photoresists available on the market. By the improvement of the photoactive component in the photoresist, a CNR of 61.5 dB was obtained in the case of the 4-times higher density.
A New Tape Product for Optical Data Storage
Authors: Larsen Ted L. , Floyd E. Woodard Floyd E. Woodard , Steve J. Pace Steve J. Pace
Published: February 2005

A new tape product has been developed for optical data storage. Laser data recording is based on hole or pit formation in a low melting metal alloy system. The media structure, sputter deposition process, and media characteristics, including write sensitivity, error rates, wear resistance and archival storage, are discussed.
Four Types and Origins of Transient Si Wafer Deformation with Furnace Insertion and Withdrawal
Authors: Kai Manabu Itsumi
Published: February 2005

Several types of transient deformations (200-1000 µm) of silicon wafers, observed when the wafers are inserted into or withdrawn from a hot horizontal furnace, are shown to be due to small asymmetries (2-10 µm) in the actual wafer shapes. Saddle-type deformation during the insertion process is categorized in two types along axes which are at right angles. The type of deformation depends on a small difference (asymmetry) between the extent of deformation in two crystallographically equivalent (100) directions with the same Young's modulus. During withdrawal, two kinds of bowl-type deformations (concave and convex) are observed. This is also due to small inherent deformations (asymmetry) in the original wafers.
Characterization of Carbon-Doped GaAs Grown by Molecular Beam Epitaxy Using Neopentane as Carbon Source
Authors: Shirahama Masanori , Nagao Keisuke , Tokumitsu Eisuke , Takahashi Makoto Konagai
Published: February 2005

Neopentane, C(CH3)4, has been successfully used as a new carbon source in the molecular beam epitaxial (MBE) growth of carbon-doped GaAs. The hole concentration, which agrees with the carbon concentration, increases with increasing cracking temperature in the temperature range above 700°C. The highest hole concentration obtained using neopentane is 1.6×1020 cm-3. Optical and electrical properties of a MBE-grown C-doped GaAs layer with neopentane are comparable to those of a metalorganic molecular beam epitaxy (MOMBE) grown C-doped GaAs layer using TMG and solid arsenic and MBE-grown Be-doped GaAs. The maximum hole concentration of 1.6×1020 cm-3 increases to 2.5×1020 cm-3 after annealing at 400^°C for 1 h in N2 ambient. This is due to removal of hydrogen which passivates carbon acceptors in the as-grown GaAs.
Thermal Resistance and Electronic Characteristics for High Electron Mobility Transistors Grown on Si and GaAs Substrates by Metal-Organic Chemical Vapor Deposition
Authors: Aigo Takashi , Yashiro Hirokatsu , Goto Mitsuhiko , Jono Aiji , Akiyoshi Tachikawa Akiyoshi Tachikawa , Akihiro Moritani Akihiro Moritani
Published: February 2005

We report dc and microwave characteristics of 0.8 µm gate length GaAs/AlGaAs high electron mobility transistors (HEMTs) grown on Si substrates by metal-organic chemical vapor deposition (MOCVD) and demonstrate direct evaluation of thermal resistance for these HEMTs on Si for the first time. A maximum transconductance of 330 mS/mm is obtained, which is almost the same as that for HEMT/GaAs fabricated simultaneously. From microwave S-parameter measurements, a current gain cutoff frequency (f
T) of 9.8 GHz is obtained for the HEMTs on Si, which is about 20% lower than that for HEMT/GaAs, because of the larger parasitic capacitances for HEMT/Si mainly caused by the device-process-related factors. Thermal resistance evaluation of these HEMTs utilizing the gate Schottky junction has revealed that thermal resistance for HEMT/Si is twice as small as that for HEMT/GaAs, namely 36±5 deg/W and 57±5 deg/W, respectively. From these results, it is shown that GaAs on Si is applicable to high-speed devices and very effective in improving the performances of CaAs ICs which are fairly influenced by the power dissipation.
The Power Increase and Absolute Frequency-Stabilization of an Optically-Pumped Far Infrared Laser
Authors: Toshihiro Hori Toshihiro Hori , Norihisa Hiromoto Norihisa Hiromoto
Published: February 2005

Far infrared (FIR) power more than or close to 100 mW has been obtained for FIR lines of CH3OH, HCOOH and CH3I gases from an FIR laser optically pumped by a 100-W CO2 laser, by adopting concave dichroic output couplers and adding a buffer gas. Frequency characteristics of the laser were examined absolutely by harmonic-mixing the FIR with a millimeter wave from a PLL'ed Gunn oscillator on a Schottky barrier diode mixer. Short-term linewidths were less than 10 kHz (FWHM) and the frequency drift in free running was in the order of several hundreds of kHz during 100 min. Absolute frequency stabilization was actively achieved for the FIR system by personal-computer (PC) aided feedback control, and a frequency stability of ±20 kHz was obtained in the experiment.
Determination of Organic Crystal Orientation in Glass Capillaries by Microscopic Raman Spectroscopy
Authors: Todori Kenji , Mori Yasushi , Murayama Hitoshi , Muta Ken-ichi
Published: February 2005

Crystallographic axis orientation of 2-cyano-3-(3,4-methylene dioxy phenyl)-2-propenoic acid ethyl ester (CMPE) in a glass capillary with a 10-µm-diameter core was successfully clarified by polarizing microscopic Raman scattering spectroscopy. Polymorphic crystals of CMPE could also be distinguished in the glass capillaries by use of this method.
Optimization of Threshold Current Density for Compressive-Strained InGaAs/GaAs Quantum Well Lasers
Authors: Park Seounghwan , Jeong Weonguk , Kim Hwamin , Kim In , Choe Byungdoo
Published: February 2005

The threshold current density (J
th) of compressive-strained InGaAs/GaAs quantum well (QW) lasers is investigated theoretically as a function of the well thicknes L
z and the well number. L
z is varied from 50 to 100 A. The optical gain is calculated with the band-mixing effects taken into account. The optimum QW thickness is determined to be about 70 A. The optimum well numbers are shown to be a function of cavity lengh.
Electric and Pyroelectric Behaviors of PbTiO3 Thin Films Formed by an Excimer Laser Ablation Technique
Authors: Tabata Hitoshi , Murata Osamu , Kawai Tomoji , Kawai Shichio , Okuyama Masanori
Published: February 2005

Ferroelectric PbTiO3 thin films have been formed on base electrodes of platinum by an ArF excimer laser ablation technique. X-ray diffraction patterns of the films show c-axis orientation with a rocking angle of 0.8°-0.5° under the cooling rate conditions of less than -75°C/min. These films exhibit ferroelectric hysteresis loops. The PbTiO3 film, formed at 550°C in O2 pressure of 100 mTorr, has a dielectric constant, coercive field and remnant polarization of 130, 280 kV/cm and 80 µC/cm2, respectively. These values are too large but they are rather similar to the values of theoretical data. Voltage responsivities of these films are 1000-1500 V/W at the frequency of 10 Hz even without poling treatment.
Structural Analysis of Molten Bismuth Germanate Compounds
Authors: Takeda Susumu , Sugiyama Kazumasa , Waseda Yoshio
Published: February 2005

Structural analysis of molten Bi4Ge3O12(2Bi2O33GeO2), Bi2GeO5(Bi2O3GeO2) and Bi12GeO20(6Bi2O3GeO2) has been carried out using the high-temperature energy dispersive X-ray diffraction (EDXD) method. The local ordering unit structure of GeO4 tetrahedra is recognized in the bismuth germanate (BGO) melts of the three compositions. On the other hand, distorted octahedral unit structure of BiO6 is suggested in the Bi2GeO5 melt. Specific heats of these three BGO compounds have also been estimated from the differential scanning calorimetry (DSC) measurements, but no particular temperature dependence is detected after melting.
Effect of Nonuniform Implosion on High-Gain Intertial Confinement Fusion Targets
Authors: Hideaki Takabe Hideaki Takabe , Tadaaki Ishii Tadaaki Ishii
Published: February 2005

High-gain target design and gain sensitivity to nonuniform implosion dynamics have been studied numerically. First of all, sensitivity of the pellet gain to the tailored pulse shape has been studied using the laser implosin code ILESTA-1D, and the gain scaling law has been obtained through an optimization of target and laser parameters. Then, the two-dimensional code, ILESTA-2D, was used to study the sensitivity of the pellet gain to the nonuniformity in target implosion. It is found that the fire-polishing effect by alpha-particle heating drastically smooths the spark structure. The implosion mode optimized with the ILESTA-1D code is relatively sensitive to nonuniformity and, therefore, higher implosion velocity modes are recommended from stability.
Computational Studies on the Shape and Control of Plasmas in Magnetron Sputtering Systems
Authors: Shunji Ido Shunji Ido , Koji Nakamura Koji Nakamura
Published: February 2005

The three-dimensional motions of electrons are traced in magnetron sputtering systems. Electrons are emitted from a cathode and show drift motion. Collisions between electrons and neutral gas atoms of Ar are examined using the Monte Carlo method. The distribution of ionization points is used to show the shape of plasmas. The results of the simulations are as follows. The profiles of plasma distribution correspond to the shape of the magnetic field. The shape of erosion profile caused by sputtering agrees well with the plasma profile. The increase of ionization points is obtained by increasing the neutral gas pressure.
Effect of Rare Gas Dilution on CH3 Radical Density in RF-Discharge CH4 Plasma
Authors: Naito Susumu , Ikeda Masanobu , Ito Nobuei , Hattori Tadashi , Goto Toshio
Published: February 2005

The behavior of the CH3 radical density in a parallel-plate RF CH4 plasma diluted with rare gases (He, Ne, Ar, Kr, and Xe) was investigated systematically using infrared diode laser absorption spectroscopy. The CH3 radical density increased in CH4/Xe and CH4/Kr plasmas with increasing rare gas dilution. The Xe* atom densities in the lowest metastable state 3
P
2 and the resonant state 3
P
1 were measured in CH4/Xe plasma through absorption spectroscopy using a Xe hollow cathode lamp in order to clarify the role of Xe* (3
P
2 and 3
P
1) atoms. It was shown that the increase in the CH3 radical density in CH4/Xe plasma was mainly caused by the collision of Xe* atoms with CH4 molecules.
Effects of Space Charges in Gridded Energy Analyzer
Authors: Honzawa Tadao , Sekizawa Toshimitsu , Yasunori Miyauchi Yasunori Miyauchi , Takeshi Nagasawa Takeshi Nagasawa
Published: February 2005

When a gridded energy analyzer is used for energy analysis of plasma particles, it is experimentally found that the characteristics of the analyzer can be heavily affected by the space charge of particles accumulating behind its entrance grid. In this experiment, using a large model analyzer, the current profiles of accumulating ions in the analyzer and the effects of the space charges on ion energy distributions are directly measured in detail. Finally, problems related to the ion accumulation and the space charge effects in a gridded energy analyzer are generally discussed on the basis of the above experimental results.
High-Resolution Analysis on Patterned Resist by Auger Electron Spectroscopy
Authors: Manabe Yuji , Takahashi Reiko , Yanagihara Toru Shiibashi
Published: February 2005

The distribution of silicon in the 0.5 µm resist pattern formed using a silylation reagent was analyzed by the Auger electron spectroscopy (AES) method. Since the resist was an insulator, a special technique was required during AES analyses. Spatial resolution was estimated by a line-scan method on the resist pattern. Both qualitative and quantitative analyses were carried out. The spatial distribution of silicon atoms derived from the silylation reagent was measured, and the surface of the resist pattern was found to be covered with a thin SiO2 layer of 3 nm thickness. From the depth profile of silicon content, it was found that the distribution of silicon was strongly influenced by the intensity of photon exposure, and that the diffusion mechanism of the silylation reagent is non-Fickian type, the so-called “Case II” diffusion.
Understanding Lithography Technology Issues through Simulation
Authors: Andrew W. Neureuther Andrew W. Neureuther
Published: February 2005

Simulation has become a very effective means of understanding tradeoffs which arise in implementing innovation in optical projection printing. A number of examples associated with current concerns in image formation under investigation at Berkeley using the SPLAT, SAMPLE and TEMPEST simulators are described. The examples include diffusion effects in chemically amplified resists, imaging in thin films with high numerical aperture lenses, image quality in an exploratory extreme ultra violent (X-ray) system developed by Wood et al. [J. Vac. Sci. Technol. B 7 (1989) 1613] of AT & T, printability of out-of-focus phase-shift defects, edge effects in phase-shift masks, and scattering from underlying topography.
Resolution Improvement Using Auxiliary Pattern Groups in Oblique Illumination Lithography
Authors: Tamechika Emi , Toshiyuki Horiuchi Toshiyuki Horiuchi , Katsuhiro Harada Katsuhiro Harada
Published: February 2005

In this paper we present a new resolution improvement technique for nonperiodic patterns where oblique illumination effects are limited. Since the problems are caused by nonperiodicity, a technique called auxiliary pattern group (APG) is introduced to supplement the periodicity. The effects of the APG are shown by simulation, and parameter dependence is also discussed. Experimental results for oblique illumination with a t-π mask confirm that using APGs improves the resolution and focus latitude.
Shot Leveling and Focusing with Interferometry for Optical Lithography of Sub-Half-Micron LSI
Authors: Watanabe Masahiro , Oshida Yoshitada , Nakayama Yasuhiko , Funatsu Ryuichi , Inagaki Akira , Fujii Akira , Ninomiya Taku
Published: February 2005

This paper presents a shot-by-shot leveling applied to an i-line stepper system. This shot leveler utilizes laser interferometry with a laser beam that has S-polarization and a large incident angle to the exposure surface of the LSI wafer. Thereby leveling and focusing accuracy is preserved regardless of the wafer surface condition under the photoresist. This system acquires interference fringe data with charge-coupled device (CCD) line image detector, and extracts the fringe frequency and phase information with a fast-Fourier-transformation (FFT). These correspond to the tilt and height information of the photoresist surface. The performance was evaluated with 4M-DRAM process wafers. Tilt and height measurement linearity was proved to be ±2 µrad and ±0.3 µm respectively, and total leveling control accuracy was proved to be better than ±7 µrad.
Hole Pattern Fabrication using Halftone Phase-Shifting Masks in KrF Lithography
Authors: Otaka Akihiro , Yoshio Kawai Yoshio Kawai , Tadahito Matsuda Tadahito Matsuda
Published: February 2005

A new concept for enhancing the depth of focus of fine hole patterns is proposed. The concept is based on modulating the complex amplitude of the hole pattern image. It is shown that shifting the origin of the complex amplitude plane enhances the depth of focus. Simulations show that the resolution limit improves to 0.5 λ/NA with the depth of focus of ±1.0 λ/N
A
2. It is also shown that halftone phase-shifting masks can be used to shift the origin. The optimum intensity transmittance of the halftone region for maximizing depth of focus is 17.3% for a 0.6 λ/NA hole pattern. Using the optimized halftone phase-shifting mask, a quarter-micron hole pattern can be fabricated with the large depth of focus of 1.4 µm in KrF lithography. Proximity effects for holes arrayed in a row are also discussed.
Study on X-Ray Mask Distortion Applying Direct Bonding to Frame Mounting
Authors: Mitsui Soichiro , Itoh Masamitsu , Alberto Moel Alberto Moel , Yoshio Gomei Yoshio Gomei
Published: February 2005

The application of direct bonding to X-ray mask frame mounting is reported. The bonding strength was increased by reducing frame surface roughness and by annealing at 200°C after bonding. Using SiCN membrane masks, the substrate in-plane distortion (IPD) induced by back-etching was measured. The mean x and y IPDs on the annealed mask were 0.0096 and 0.0015 µm, respectively, which were attributed to the difference in the membrane stress in both directions. These values were about 40% smaller than the one for the unannealed mask. The membrane IPD induced by back-etching was also measured, using a SiC membrane mask. The maximum IPD in this case was 0.049 µm which is over the measurement resolution. We also found a umidirectional tendency in both x and y membrane IPDs. A possible source of this directional IPD is thought to be nonuniformity of the membrane stress in each direction.
Mask Distortion Analysis for the Fabrication of 1 GBit Dynamic Random Access Memories by X-Ray Lithography
Authors: Moel Alberto , Itoh Masamitsu , Soichiro Mitsui Soichiro Mitsui , Yoshio Gomei Yoshio Gomei
Published: February 2005

In order to fabricate 1 Gbit dynamic random access memories, or DRAMs, with 0.15 µm minimum features using X-ray lithography, the total overlay error must be no more than 0.05 µm. We assign 0.03 µm to the budget for mask distortion overlay error, which can be subdivided into fabrication-process-induced distortion (0.024 µm), fixturing-induced distortion (0.01 µm), and X-ray exposure-induced distortion (0.01 µm). We study, through theoretical models, these sources of distortion. In our mask-making process, a 75-mm-dia., 0.6-mm-thick Si wafer coated with 1-µm-thick SiC is direct-bonded to a 100-mm-dia., 4-mm-thick Si frame. Tungsten absorber is patterned on the SiC film, and then the wafer is back-etched to form the membrane window. The mask frame opening is used as the back-etching mask. We found that in order to meet the budget for the fabrication-process-induced distortion for a 46-mm-dia. SiC membrane (corresponding to the area of two 1 Gbit DRAM chips) and a target membrane stress of 1 × 109 dyn/cm2, the nonuniformity in the membrane stress or thickness must be under 2 % and the absorber stress no more than 5 × 107 dyn/cm2. High X-ray exposure power leads to a temperature rise of the mask. We found that as long as the X-ray exposures are performed in helium, the distortion in the printed image is within budget, even at high exposure intensities (340 mW/cm2 absorbed power). We also determine that a properly designed three-point mask-holding fixture is sufficient to meet the budget for fixturing induced distortion.
An Approach for Nanolithography Using Electron Holography
Authors: Ogai Keiko , Matsui Shinji , Yoshihide Kimura Yoshihide Kimura , Ryuichi Shimizu Ryuichi Shimizu
Published: February 2005

A technique of electron holography was applied to nanofabrication. Electron interference fringes whose spacing was 108 nm were successfully recorded on polymethylmethacrylate (PMMA) resist using a W<100> thermal field emission (TFE) gun and an electron biprism both set on a conventional transmission electron microscope (TEM). Furthermore, we have attempted the fabrication of a free-standing multi-biprism by electron beam lithography and dry etching, leading to a new fabrication method of a nanoscale grating with a short exposure.
Overlay Error Estimation of Wafer Rear Surface Alignment for 0.1-µm Lithography
Authors: Katagiri Souichi , Shigeo Moriyama Shigeo Moriyama , Tsuneo Terasawa Tsuneo Terasawa
Published: February 2005

This paper proposes using the wafer rear surface alignment (RSA) method in a lithography system in order to achieve 0.1-µm lithography. To evaluate alignment limitations, the error due to processed layers, which induces degradation of mark visibility, is measured with two conventional sensors. One is a heterodyne sensor that is stable for grained aluminum samples. The other is a broad-band sensor effective for reducing the multiple interference effect in resist films. With these sensors, the estimated limitation is 0.053 µm (M±3σ), obtained in both experiments and in simulations. The RSA method is effective in overcoming this limitation, because there are no disturbance marks due to resist film or grained aluminum film. The RSA is shown to improve the alignment limitation from 0.053 µm to 0.031 µm (M±3σ).
Mechanism of Resist Pattern Collapse during Development Process
Authors: Tanaka Toshihiko , Mitsuaki Morigami Mitsuaki Morigami , Nobufumi Atoda Nobufumi Atoda
Published: February 2005

In this study, the mechanism of resist pattern collapse during the resist development process is investigated. Resist pattern collapse occurs while the rinse liquid is being dried off. This conclusion was reached after observing the resist pattern before and after the rinse-liquid drying process. The resist pattern in the rinse liquid was observed using an atomic force microscope. The source of resist pattern collapse is the surface tension of the rinse liquid. The force increases with decreasing space width between resist patterns. To avoid the resist pattern collapse problem, the use of a low-surface-tension rinse liquid, a rinse liquid with contact angle ∼90° at the resist surface, or a rigid and highly adhesive resist material is effective.
RF Self-Bias Characteristics in Inductively Coupled Plasma
Authors: Fukasawa Takayuki , Nouda Tatuki , Nakamura Akihiro , Shindo Haruo , Yasuhiro Horiike Yasuhiro Horiike
Published: February 2005

The plasma characteristics and RF self-bias behavior in inductively coupled plasma were studied. In the absence of magnetic field, a newly developed 1-turn antenna provided more uniform radial distribution of electron density than the spiral antenna with the present relatively small diameter, and uniformity of ±5% with 4.5×1011cm-3was achieved for 12 cmφ at 600 W. The electron density increased linearly with increasing power and did not saturate even at 1 kW input power. Theneof 7×1011cm-3was obtained in Ar at 1 kW power. For such high-density and large-diameter uniform plasma, the RF self-bias voltage was difficult to generate, because the sheath capacitance is too large. An equivalent circuit analysis clarified that the self-bias voltage behaved asVpp4ne-2, whereVppis RF voltage.
The Anisotropic Plasma-Enhanced Chemical Vapor Deposition SiO2/Spin-on Glass Process for 0.35 µm Technology
Authors: Chen Lai-Juh , Shaw-Tzeng Hsia Shaw-Tzeng Hsia , Kuang-Chao Chen Kuang-Chao Chen
Published: February 2005

A new plasma enhanced chemical vapor deposition (PECVD) oxide is proposed to form an anisotropic SiO2 film with ultra low sidewall step coverage for the intermetal dielectric (IMD) process. This oxide is named anisotropic plasma oxide (APO). In the APO technology, the anisotropic deposition is achieved by reducing the O2/TEOS (tetraethylorthosilicate) feed ratio in current PECVD process. The APO sidewall step coverage can be lowered to 20% compared to 65% for the conventional PECVD oxide. Reflective index, measured by ellipsometry method, indicates that the APO film is Si-rich. High deposition rate and low film stress show the APO is suitable to the IC production. This technology is successfully applied to the 0.5 µm 16 M dynamic random access memory (DRAM) products and is expected to apply to 0.35 µm ULSI technology.
Characteristics of SiO2 as a High-Resolution Electron Beam Resist
Authors: Hiroshi Hiroshima Hiroshi Hiroshima , Masanori Komuro Masanori Komuro
Published: February 2005

Characteristics of thermally grown SiO2, which is a candidate for high-resolution electron beam resists, are studied. In order to improve the selectivity (the etch rate ratio of electron-irradiated area to unirradiated area) which defines the profile of developed patterns, the etching property of electron-irradiated SiO2 is investigated for various solutions. To eliminate the effect of contamination resulting from electron irradiation, oxygen plasma ashing is used after the irradiation. The saturated selectivity at a dose of about 2 C/cm2 is 1.6 to 3.3 for HF-based solution while it is almost unity for aqueous KOH. Although the etch rate of unirradiated SiO2 follows the linear combination of [HF] and [HF2
-], that of electron irradiated SiO2 does not follow such a relation. The saturated selectivity of a mixture of HF and NH4F takes a maximum at the composition of [HF] and [HF2
-] of nearly equal quantities. The profile of the etched groove is well calculated by using a string model. A 20 nm line is fabricated onto SiO2 of an initial thickness of 120 nm by this process.
Digital Etching Using KrF Excimer Laser: Approach to Atomic-Order-Controlled Etching by Photo Induced Reaction
Authors: Ishii Masashi , Meguro Takashi , Gamo Kenji , Sugano Takuo , Aoyagi Yoshinobu
Published: February 2005

Cl2-based digital etching of GaAs has been studied using a 248 nm KrF excimer laser, which allowed a self-limited etching reaction. A threshold fluence for etching of 13 mJ/cm2 was found, above which the etch rate abruptly increases and finally saturates at around 0.2 nm/cycle from 20 to 33 mJ/cm2. The self-limiting etching characteristics can be explained assuming the etching reaction to be limited by the amount of adsorbed Cl2. The etched depth is proportional to the number of digital etching cycles, and atomic-order-controlled etching is achieved.