bluuebunny/crossref_metadata_2025 huggingface dataset:
Heterodyne Spectroscopy Using Broadband Short-Pulse Laser for Long-Path Absorption Measurement of Atmospheric Trace Species
Authors: Nobuo Sugimoto Nobuo Sugimoto , Atsushi Minato Atsushi Minato
Published: October 2002

A concept of heterodyne spectroscopy for absorption measurements which employs a broadband short-pulse laser is presented. The absorption line structure of the sample in the spectral width of a short-pulse laser is measured with broadband heterodyne detection. The absorption spectrum can be measured, in principle, with a single laser shot, and the method is potentially useful for laser long-path absorption measurements of atmospheric trace species. Application to an airborne laser long-path absorption system for measuring CH4 is discussed.
The Effect of Additions on Admittance-Frequency Response of ZnO Varistors
Authors: Chi-Yen Shen Chi-Yen Shen
Published: October 2002

In this study, several different metal ions, i.e., Mn2+, Mn4+, Co2+, Co3+, Sb2+ and Sb3+, were added in ZnO varistors to investigate their effect on admittance-frequency response. When manganese and cobalt with high valencies are added, the depression angle and relaxation time become minimal, whereas if manganese and cobalt with low valencies are added, they become maximal. On the other hand, the relaxation time is independent of the valency of antimony ions. However, the depression angle increases with increasing valency of antimony ions.
Electrochemical Properties of Poly(3-alkylthiophene) Gel and Its Characteristics as an Electrode Active Material in Secondary Battery
Authors: Shakuda Shuzo , Kawai Tsuyoshi , Shigenori Morita Shigenori Morita , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Electrochemical characteristics of an electrochemically prepared poly(3-alkylthiophene) gel and its battery characteristics have been studied. The gel film exhibited an oxidation wave in electrochemical measurements whereas the as-prepared film showed an additional peak at lower potential. Oxidation and reduction peak potentials showed marked decrease with increasing concentrations of chloroform in the electrolyte solution. These results have been explained in terms of structural disorders in the side and the main chains. Upon increasing the polymerization potential, the expansion ratio and the diffusion coefficient of dopant ion, D
app, of the gel film increased. The gel film exhibited better characteristics as an electrode active material in comparison with the as-prepared film. These results of electrochemical properties of the gel film have been attributed to the effects of free volume in the gel having a three-dimensional network structure.
Enhancement of Photochromism in Tungstic Acid Gels with Some Organic Additives: Effects of End Groups
Authors: Keiichi Kuboyama Keiichi Kuboyama , Kazuhiro Hara Kazuhiro Hara , Kazumi Matsushige Kazumi Matsushige
Published: October 2002

A systematic investigation was performed on photochromism of tungstic acid gels with some organic additives (alcohol, aldehyde, carboxylic acid and ketone). It was found that all of the tungstic acid gels containing alcohols showed remarkable enhancement of photochromism. The enhancement of photochromism in tungstic acid gels is discussed in terms of the photoactivity activated by alcohols.
Electron Impact Cross Section Data for Carbon Tetrafluoride
Authors: Russell A. Bonham Russell A. Bonham
Published: October 2002

Recent electron impact cross section data on CF4are critically reviewed and a cross-section data set suitable for plasma modeling purposes is suggested.
Effect of Dilution Gases on the SiH3Radical Density in an RF SiH4Plasma
Authors: Hideshi Nomura Hideshi Nomura , Akihiro Kono Akihiro Kono , Toshio Goto Toshio Goto
Published: October 2002

Infrared diode laser absorption spectroscopy was used to measure the density of silyl ( SiH3) radicals in low-pressure (4.0 Pa) 13.56-MHz rf plasmas utilizing H2/, He/, Ar/, and Xe/SiH4gas mixtures. The SiH3production frequency per SiH4molecule was also derived from the SiH3density and its decay rate in the afterglow. The observed SiH3density decreased with increasing dilution ratio in all the gas mixtures, but the SiH3production frequency per SiH4molecule increased significantly for Xe dilution and remained nearly constant for H2, He, and Ar dilution. Based on these results, the relative importance of different SiH3production channels is discussed.
Investigation of Particulate Growth Processes in RF Silane Plasmas Using Light Absorption and Scanning Electron Microscopic Methods
Authors: Kawasaki Hiroharu , Fukuzawa Tsuyoshi , Tsuruoka Hideto , Yoshioka Takashi , Masaharu Shiratani Masaharu Shiratani , Yukio Watanabe Yukio Watanabe
Published: October 2002

Particulate growth processes in Ar+SiH4RF plasmas are studied using ultraviolet light-absorption and scanning electron microscopic (SEM) methods. Measurements of particulate size and density using the SEM method show that they grow through three phases: nucleation, rapid growth and growth saturation. Such features of temporal evolutions of their size and density are very similar to those for He+SiH4RF plasmas previously obtained by SEM and in situ laser light scattering methods. It is also found that particulates in two different size ranges coexist after the initiation of the rapid growth phase, and their coagulation plays an important role in this phase. Close similarities among spatial profiles of Si emission intensity, Si density, and amount of particulates are revealed in wide discharge-parameter ranges of 1–100% SiH4, 11–20 Pa, and 40–100 W. These results suggest that many short-lifetime neutral radicals such as SiHn(n=0–2) contribute to nucleation and subsequent initial growth of a particulate, since other short-lifetime radicals are also expected to have similar spatial profiles.
Dynamics of Silicon Particles in DC Silane Plasmas Transported by a Modulated Magnetic Field
Authors: Kawasaki Hiroshi Fujiyama , Sung-Chae Yang Sung-Chae Yang , Yoshinobu Matsuda Yoshinobu Matsuda
Published: October 2002

By using a Mie scattering method, dynamics of silicon particles in DC and AC silane plasmas in the presence of a modulated magnetic field, B, perpendicular to the discharge electric field, E, were observed. In AC plasmas, Mie scattering signals were not observed. In DC plasmas, silicon particles were transported in the opposite direction of the E ×B drift, and particle density was decreased with increasing applied magnetic flux density. The experimental results support the assumption that spatially inhomogeneous discharge current by E ×B drift causes the balance among electrostatic force, ion drag force and force of gravity exerted on the particles to be lost and generates the particle transport.
Production of High-Density Plasmas in Electron-Beam-Excited Plasma Device
Authors: Ito Akihiro , Miyano Ryuichi , Kitada Ryouji , Shinya Izumi Shinya Izumi , Shunjiro Ikezawa Shunjiro Ikezawa
Published: October 2002

We tried to enlarge the diameter of high-density beam plasmas in an electron-beam-excited plasma (EBEP) device. In order to enlarge the beam plasma, we made a cusp configuration at the end of the ion source region in the EBEP device. Also, a surface confined ring with permanent magnets called “surmac” was mounted on the cusp center to make the plasma profiles flat. It was found that high electron density (7×1011 cm-3) and uniformity (ΔN
e/N
e<4% over 6 cmφ) could be obtained at low pressure (7×10-4 Torr).
Modeling of Particle Growth in RF Silane-Helium Plasma
Authors: Sato Nobuyasu , Shiratani Masaharu , Watanabe Yukio
Published: October 2002

A model for an early stage of particle growth is developed in order to investigate the process of particle growth around the electrode sheath boundary observed experimentally in an rf silane-helium plasma. In this model, it is assumed that formation of higher silane radicals produced by reaction chains of short-lifetime radicals and fast accretion of the higher silane radicals may lead to particle growth. Negatively charged particles are not taken into account in this model. The spatial distribution of the short-lifetime radicals such as SiH2 generated in the rf silane-helium plasma is obtained using a fluid model. Using the density of SiH2 as an initial condition, the spatiotemporal evolutions of the particles having up to 100 SiH

n

s are calculated. This indicates that short-lifetime higher silane radicals are responsible for particle growth in the rf silane-helium plasma.
Influence of Ar Metastable on the Discharge Structure in Ar and N2Mixture in RF Discharges at 13.56 MHz
Authors: Lj Petrović Fumiyoshi Tochikubo , Nobuhiko Nakano and Toshiaki Makabe Nobuhiko Nakano and Toshiaki Makabe
Published: October 2002

The influence of Ar metastable atoms on the discharge structure in rf glow discharges is investigated in Ar and N2mixed gas experimentally and theoretically. The purpose of adding a small amount of N2is to control the metastable density. Time- and space-resolved optical emission spectroscopy is applied to investigate the behavior of high-energy electrons. The density profile of Ar metastables in Ar and N2mixture is estimated from the optical emission intensity of the second positive band of N2, which results from the energy transfer from Ar metastables to N2molecules. The decreases of current and optical emission intensity, as well as the Ar metastable density with increase of N2ratio, are observed. It is concluded that ionization through metastables is one of the important processes in increasing the plasma density, especially at higher pressures.
Simulation of Ion Trajectories near Submicron-Patterned Surface Including Effects of Local Charging and Ion Drift Velocity toward Wafer
Authors: Ootera Hiroki , Oomori Tatsuo , Mutumi Tuda Mutumi Tuda , Keisuke Namba Keisuke Namba
Published: October 2002

Ion trajectories near a submicron-patterned surface were investigated using numerical simulations including the effects of local charging on the patterned surface and ion drift velocity toward the wafer. The simulation results were also discussed relative to the etched profile characteristics in electron cyclotron resonance (ECR) plasmas with a divergent magnetic field. Since the pattern size was much smaller than the Debye length, charge neutrality was not satisfied on the submicron-patterned surface. The simulated ion trajectories were largely deflected at the inside of the outermost lines of line-and-space patterns. Moreover, the ion trajectory deflection was reduced with increasing ion drift velocity. These simulation results showed a similar tendency as the etching characteristics.
CF3, CF2and CF Radical Measurements in RF CHF3Etching Plasma Using Infrared Diode Laser Absorption Spectroscopy
Authors: Koji Maruyama Koji Maruyama , Katsunori Ohkouchi Katsunori Ohkouchi , Yasunori Ohtsu Yasunori Ohtsu , Toshio Goto Toshio Goto
Published: October 2002

We have measured the characteristics of CF3, CF2and CF radical densities in RF CHF3etching plasma under the same condition using infrared diode laser absorption spectroscopy, for the first time. The CFxradical density measurements have been performed as a function of input RF power, CHF3gas pressure and distance from the RF electrode. On the basis of these systematic measurements, the generation and loss processes of CFxradicals in RF CHF3plasma were discussed.
Experimental Study of Very-High-Frequency Plasmas in H2by Spatiotemporally Resolved Optical Emission Spectroscopy
Authors: Shigeru Kakuta Shigeru Kakuta , Takeshi Kitajima Takeshi Kitajima , Yutaka Okabe and Toshiaki Makabe Yutaka Okabe and Toshiaki Makabe
Published: October 2002

A very-high-frequency (VHF) plasma at 100 MHz is experimentally investigated in parallel-plate configuration in H2using spatiotemporal optical emission spectroscopy and current-voltage-power waveforms. The observed optical emission intensity and net excitation rate profiles have strong temporal and spatial variations. The VHF plasma is still capacitive, and is maintained by reflected electrons in the oscillating sheath next to the instantaneous cathode. The characteristics of VHF plasmas, that the excitation rate increases in proportion to the square of driving frequency, and that the minimum sustaining voltage and pressure decrease with increasing frequency, are experimentally confirmed at pressures, ranging from 0.01 to 2 Torr and at the frequency of 100 MHz .
Influence of Heavy Particle Collision on Optical Emission in Cathode Fall of DC Argon/Silane Glow Discharge
Authors: Yoshinobu Matsuda Yoshinobu Matsuda , Kazumi Ano Kazumi Ano , Hiroharu Kawasaki Hiroharu Kawasaki , Hiroshi Fujiyama Hiroshi Fujiyama
Published: October 2002

Spatially resolved optical emission profiles were investigated in dc silane-argon discharge plasmas under the highE/Ncondition, whereEis electric field strength andNis gas density. The optical line emission intensities of Ar, H, and SiH in both the cathode fall and negative glow regions were well explained by a simple collisional excitation model, in which heavy particle collisions in the cathode fall and electron collisions in the negative glow are taken into account, respectively. As a result, it was confirmed that radical production by heavy particle collision is indispensable in such chemical vapor deposition (CVD) plasmas for operation under the highE/Ncondition.
Potential Profiles in an Electron-Beam-Excited Plasma
Authors: Manabu Hamagaki Manabu Hamagaki , Tamio Hara Tamio Hara
Published: October 2002

Potential profiles are measured in an electron-beam-excited plasma (EBEP) system with the high-current low-energy electron beam. It is found that there is a potential step around the anode. The space potential at the center of the plasma is more negative than that at the edge plasma by the space charge of beam electrons. It is shown that the potential dip of the radial profile changes into a hill by increasing the beam energy. The radial profile becomes flat with increase of gas pressure.
Effect of Heating SiH4 on the Plasma Chemical Vapor Deposition of Hydrogenated Amorphous Silicon
Authors: Hishikawa Yoshihiro , Sasaki Manabu , Sadaji Tsuge Sadaji Tsuge , Shinya Tsuda Shinya Tsuda
Published: October 2002

The application of vibrational/rotational energy to material gas ( SiH4) and radicals by heating the material gas has been investigated in order to improve the properties of hydrogenated amorphous silicon (a-Si:H) for solar cells. It has been found that the optical gap (E
opt) of a-Si:H films deposited from heated SiH4 (temperature of the gas heater: 280–380° C) is narrower by about 20–30 meV than those of conventional films where SiH4 is not heated, using the same substrate temperature (T
s) and deposition rate (R
d). This result suggests that the heated SiH4 molecules or related radicals promote reactions at or near the film-growing surface. In other words, applying vibrational, rotational, or translational energy to SiH4 gas has the same effect as raising T
s in plasma chemical vapor deposition (plasma-CVD) of a-Si:H. It is demonstrated that gas heating can improve the conversion efficiency of a-Si solar cells by reducing the damage to underlying layers during i-layer deposition.
Growth of Cubic Boron Nitride Films by Low-Pressure Inductively Coupled Plasma Enhanced Chemical Vapor Deposition
Authors: Takanori Ichiki Takanori Ichiki , Toyonobu Yoshida Toyonobu Yoshida
Published: October 2002

Cubic boron nitride ( c-BN) films were deposited on silicon (100) wafer substrates from the B2H6+N2+He+Ar system at pressures ranging from 5×10-4–2×10-3 Torr by low-pressure inductively coupled plasma enhanced chemical vapor deposition (ICP-CVD). The substrate bias was controlled by varying auxiliary rf power to the substrate. The effects of the process parameters such as substrate bias and working pressure on the c-BN growth have mainly been investigated. The results are discussed in relation to the plasma diagnostics by electric probe and optical emission spectroscopy.
Structure of Microcrystalline Silicon Carbide Films Prepared by Hydrogen-Radical-Enhanced Chemical Vapor Deposition in Magnetic Field
Authors: Yasui Kanji , Masayoshi Muramoto Masayoshi Muramoto , Tadashi Akahane Tadashi Akahane
Published: October 2002

Microcrystalline silicon carbide films were grown by hydrogen-radical-enhanced chemical vapor deposition in magnetic field. Tetramethylsilane was used as source material. Hydrogen radicals were generated by microwave plasma in magnetic field. Microcrystalline films grew on the Si substrate by supplying hydrogen radicals at temperatures higher than 250° C. The structure and the crystallinity of SiC films were investigated by cross-section transmission electron microscopy, electron probe microanalysis and X-ray photoelectron spectroscopy.
Reduction of Plasma Damage in Reactive Ion Etching by Means of Suppressing Self-Bias
Authors: Ohte Takeo , Aoyama Hidetake , Goto Makoto , Sugawara Minoru
Published: October 2002

We discuss a technique for suppressing the sheath voltage of the powered electrode (the self-bias) without introducing a substantial disturbance to the main plasma and reduce plasma damage in the etching of amorphous silicon (a-Si) films. It has been shown experimentally that the sheath voltage can be reduced in a wide voltage range by reducing the floating potential. The plasma density was almost constant at the disk on which the wafer was placed. The damage introduced to a-Si films by ion bombardment was reduced by 41% of that obtained at the sheath voltage of -73 V by suppressing the sheath voltage from -73 V to -36 V. Also, it was ascertained experimentally that a threshold sheath voltage for the ion damage may exist.
Laser-Induced Fluorescence Observation of In-Atoms Produced by DC Reactive Sputtering of Indium-Tin-Oxide Target
Authors: Yoshinobu Matsuda Yoshinobu Matsuda , Takuya Kido Takuya Kido , Kazumi Ano Kazumi Ano , Kazuhiro Shirakata Kazuhiro Shirakata , Hiroshi Fujiyama Hiroshi Fujiyama
Published: October 2002

Spatial density profiles of sputtered In-atoms in a dc glow discharge with an indium-tin-oxide (ITO) cathode were measured by laser-induced fluorescence (LIF) spectroscopy. The absolute density of In-atoms was obtained by calibrating the LIF signal with the Rayleigh scattering signal for Ar. The spatial density profile of In-atoms had a peak at a certain distance from the cathode, and this peak density was about 1011 cm-3 for pure Ar dc discharge at 0.2 Torr and 0.6 Wcm-2. The behavior of spatial profiles of the absolute In-density was investigated as a function of dc discharge power, total pressure ( Ar+O2), and O2 partial pressure. Addition of a small amount of O2 caused a drastic change in both the absolute In-density and its spatial distribution. From these observations, the reactive sputtering mechanism in a dc glow discharge is discussed.
Improvement of the Interface between Selectively Deposited Aluminum and Silicon by Annealing
Authors: Kouichi Tani Kouichi Tani , Satoshi Nishikawa Satoshi Nishikawa
Published: October 2002

The interaction between Al deposited selectively by chemical vapor deposition (CVD) and Si has been investigated. The structure of Al depended on the size of contact holes. Single-crystalline Al was formed in 0.7 µm contact holes, but polycrystalline Al in 1.2 µm and 2.0 µm holes. In the case of single-crystalline Al, Si at the bottom of contact holes was eroded uniformly by Al after deposition and after annealing at 400° C. In the case of polycrystalline Al, Si was eroded non uniformly and Al spikes were formed. However, after annealing at 400° C, Al spikes disappeared and the surface of eroded Si became extremely flat. Junction leakage current of the 2.0 µm n+ contact was found to increase after Al deposition. However, after annealing at 400° C, increase of junction leakage current was not found to 10 V. This change may be due to the improvement of the interface. These results indicate that selective Al-CVD can be used as a contact-hole-filling method.
Filling of Sub-µm Through-holes by Self-sputter Deposition
Authors: Asamaki Tatsuo , Miura Tsutomu , Takagi Akira , Hirata Ryuji Mori
Published: October 2002

Filling of sub-µ m holes with a high aspect ratio by self-sputter deposition of copper is investigated. Good bottom coverages of 100% by means of thinner thin-film deposition and 50% by thicker thin-film deposition are attained. It is found that the bottom coverage decreases sharply when the ratio of the distance between the target and the substrate, D
st, to the diameter of the erosion center ring is less than 1, and although the bottom coverage by the self-sputter deposition at lower pressures saturates at longer D
st, that by the conventional sputter deposition at higher pressures decreases with D
st. The bottom coverage also decreases with increases of the pressure, the thin film thickness deposited, and the radial distance of the substrate position from the target center toward the erosion center.
Examinations of Superconducting Transition Width, Oxygen Deficiency and Crystallographic Quality in YBa2Cu3O7-δ
Authors: Akihiko Nishida Akihiko Nishida , Nobuhiro Fuketa Nobuhiro Fuketa , Kouki Furuya Kouki Furuya , Kazumi Horai Kazumi Horai
Published: October 2002

A series of high-T
c YBa2Cu3O7-δ ceramics has been investigated through electrical resistivity measurements, least squares analyses and Rietveld refinements of X-ray powder diffractions; with emphasis on crystallographic and superconducting homogeneities. We have applied a simple method for estimating oxygen contents in the specimen through determination of unit cell parameters by X-ray diffraction peaks. Structural and stoichiometric examinations have also been performed through the Rietveld refinement. By the good agreement of our X-ray Rietveld analyses with the neutron diffraction results, we have confirmed the reliability of our X-ray studies. Nonlinear correlation between full widths at half-maximum of several diffraction peaks and superconducting transition widths has been observed, and the importance of local structural variation has been discussed.
Homogeneity of Single Crystal of High-Tc Superconductor La2-xSrxCuO4
Authors: Fujii Yoshiharu , Lu Zhili , Soejima Yuji , Okazaki Atsushi , Tanaka Isao , Kojima Hironao
Published: October 2002

High-angle double-crystal X-ray diffractometry (HADOX) has been applied to examine the quality of La2-
x

Sr

x

CuO4 single crystals grown by the travelling-solvent floating-zone method. The two-dimensional intensity distribution in reciprocal space is measured at room temperature for 0014 with CoKα1 radiation. Measurements are made over a range of 7 mm along the axis of growth at intervals of 1 mm. It is found that the crystal contains small part of different orientation with slightly different chemical composition Δx<0.002. In a limited region, the crystal is well orientated and the composition is homogeneous.
Effects of Substrates on Formation of Metastable Bi2Sr2+(n-1)CunOy Thin Films
Authors: Sato Rie , Takeno Shiro , Tadao Miura Tadao Miura
Published: October 2002

Metastable Bi2Sr2+(
n
-1)Cu

n

O

y

thin films isostructual with the Bi2Sr2Ca

n
-1Cu

n

O

y

system were prepared on SrTiO3 (100) substrates by metalorganic chemical vapor deposition (MOCVD). It has been deduced by comparing the crystal structure of films prepared on SrTiO3, MgO and on LaAlO3 that the formation of metastable n=2, 3 phases is highly dependent on the lattice constant of the substrates. The superconducting properties of the films were examined in relation to their structures. Among the films, the Bi2Sr3Cu2O

y

(n=2) phase with a c-axis length of 3.12 nm formed on SrTiO3 exhibited the highest onset superconducting transition temperature of about 90 K.
Carrier Transport in p-Type GaInAsP/InP Distributed Bragg Reflectors
Authors: Miyamoto Tomoyuki , Mori Kenichi , Maekawa Hiroaki , Inaba Yuichi , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: October 2002

The current-voltage characteristic of a p-type GaInAsP/InP distributed Bragg reflector (DBR) is theoretically and experimentally investigated. It is pointed out that the light hole tunneling current is dominant in the reverse bias condition. Highly selective p-doping in InP is effective to reduce the excess bias in the DBR. Experimentally, an excess bias of 0.5 V is observed for a five-pair GaInAsP (λ g=1.45 µ m)/ InP DBR grown by chemical beam epitaxy.
Self-Phase Modulation Spectra for Superposed Pair of Pulses in Optical Fiber: Suggestion for Phase Shift Keying Modulation
Authors: Taek-Hyun Lee Taek-Hyun Lee , Jong-Jean Kim Jong-Jean Kim
Published: October 2002

Self-phase modulation spectral patterns are studied through numerical calculations in the optical fiber for input signals formed by a superposition of a pair of pulses of half-width greater than ∼40 ps, when the group velocity dispersion effect on the self-phase modulation can be neglected. The self-phase-modulated output from the optical fiber is found to show distinctive spectral patterns of varying side lobes depending on the phase shifts between the input pulse pairs. A possible application of this observation as a new method of phase shift keying modulation is suggested.
Piezoelectric Properties of Niobium-Doped [Pb(Sc1/2Nb1/2)1-xTix]O3 Ceramics Material near the Morphotropic Phase Boundary
Authors: Yohachi Yamashita Yohachi Yamashita
Published: October 2002

The physical and electrical properties of Pb[(Sc1/2Nb1/2)1-
x

Ti

x

]O3 (x=0.40–0.45)+0.01 PbNb2 O6 piezoelectric polycrystalline ceramic materials near the morphotropic phase boundary (MPB) were investigated. The maximum dielectric constant (ε
33
T/ε
0=3200) and maximum piezoelectric constant (d
33=590×10-12 m/V) were found at x=0.435, where the coupling factors were k
p=67 %, k
31=41 %, and k
33=74 %. The maximum electromechanical coupling factors, (k
p=71 %, k
31=44 %, and k
33=77 %) were found at x=0.420, where ε
33
T/ε
0=2080 and d
33=480×10-12 m/V were obtained. The x=0.420 composition exhibited the largest electromechanical coupling factor of all binary piezoelectric ceramics systems so far reported, including the most widely used conventional ceramic, Pb(Zr1-
x

, Ti

x

)O3.
In Situ Rapid Thermal Nitridation of Collimated Titanium by Physical Vapor Deposition as a Blanket Tungsten Barrier
Authors: Yamazaki Osamu , Nakamura Kazuyo , Sakamoto Hiromi , Shigeo Ohnishi Shigeo Ohnishi , Keizo Sakiyama Keizo Sakiyama
Published: October 2002

A very thin bilayered titanium nitride/titanium barrier was obtained from in situ rapid thermal nitridation (RTN) for collimated Ti by physical vapor deposition for blanket tungsten plug. Ti with in situ RTN results in fine barrier properties compared with those by RTN with exposure to air after Ti deposition. Furthermore, this thinner film without the re-entrant profile at the contact shoulder was effective for complete contact filling at 0.25 µm diameter with the aspect ratio of 4. This is one of the barrier technologies applicable to quarter-micron devices.
Electrical Breakdown Properties in Liquid-Gas Composite N2
Authors: Kim Sanghyun , Ma Daeyoung , Ryu Hyunhee Kim
Published: October 2002

Electrical breakdown characteristics of composite insulators consisting of cryogenic gas and liquid in a non-uniform field have been investigated. The breakdown voltage increases slightly as the electrode distance of gas layer, d
′, increases. After the breakdown voltage decreases abruptly with increasing d
′, it again increases slightly with further increase of d
′. These results observed at both AC and DC voltages were interpreted as the Sumoto effect and corona wind.
Ion-Assisted Deposition of Lead Titanate Thin Films by Controlled-Magnetic Field Sputtering
Authors: Fujisawa Akira , Rai Toshiki , Minemura Isamu , Fukami Tatsuo
Published: October 2002

Ferroelectric thin films of lead titanate were deposited on glass and MgO(100) of 15 mm×15 mm in size by dc magnetron sputtering. The discharge characteristics were studied through the observation of the target erosion pattern and by the probe current technique at the substrate site with different magnetic field configurations. The radius of the target erosion pattern corresponded to the magnetic field component vertical to the target surface, which in turn affected the plasma density distribution over the substrate holder. Low-energy ion bombardment onto a growing film on the glass enhanced the surface reaction rate and growth kinetics, and hence the crystallinity and the orientation were also affected. In the case of the film on MgO(100), the c-axis lattice parameter was expanded by the induced defect structure.
Electrode Lifetimes in a Plasma Focus Soft X-Ray Source
Authors: Yasuo Kato Yasuo Kato
Published: October 2002

The lifetime of electrodes and the insulator in a plasma focus device is investigated for application to short-wavelength radiation sources. Evaporation and sputtering of electrodes are the root of almost all problems when a plasma X-ray source is applied to lithography. The erosion of electrodes is reduced by the combination of polarity inversion of the applied voltage to the electrodes, application of tungsten-inserted hollow electrode to the inner electrode, and improvements in the shape of the outer and inner electrodes. Weight of the debris is reduced from 38 µg/shot to 9 µ g/shot at 3.5 kJ energy discharge upon introducing these improvements. After 400,000 discharges, electrode lifetimes are estimated at more than 1 million discharges, and the ceramic insulator maintains a high discharge repetition rate. The X-ray intensity increases as the copper vapor is reduced in the pinched plasma.
Wavelength Dependence of Excimer Laser Irradiation Effects on Ethylene-Tetrafluoroethylene Copolymer
Authors: Hamada Yuji , Kawanishi Shunichi , Nishii Masanobu , Sugimoto Shun'ichi , Yamamoto Tadashi
Published: October 2002

Irradiation with an ArF laser at wavelength of 193 nm formed diene in a whole ethylene-tetrafluoroethylene copolymer (ETFE) film and irradiation with a KrF and a XeCl laser at 248 and 308 nm induced the carbonization of ETFE. ArF-laser radiation at 193 nm formed diene in the bulk of ETFE via the process of single-photon absorption, and in case of KrF and XeCl-laser irradiation multiphoton absorption brought about the carbonization of ETFE. The surface analysis by X-ray photoelectron spectroscopy showed that excimer laser-induced elimination of fluorine atoms depended on the laser wavelength.
In-Situ Observation of Photodoping Process by Infrared Attenuated Total Reflection Method
Authors: Lee Jaeman , Ogawa Tsutomu , Wakaki Moriaki , Uehara Fumiya , Arai Toshihiro
Published: October 2002

Attenuated total reflection (ATR) spectra of a Ag/As2S3 double layer deposited on a Ge prism were observed. Three samples having the As2S3 layer thicknesses of 750 Å, 3000 Å and 12000 Å were studied. Characteristic spectra related to As2S3 thickness, light-irradiation time and wave number were obtained. The spectra were fitted by a simulation procedure using a multilayer model. The spectra were well fitted by introducing the interface layer of a Ag cluster having the thickness typically of 1 nm at the diffusion front of the photodoped region. Spectra and fitted results were discussed in relation to the photodoping mechanism.
Influence of Metalorganic Sources on the Composition Uniformity of Selectively Grown GaXIn1-XP
Authors: Chan Shih-Hsiung , Chun-Yen Chang Chun-Yen Chang , Simon Ming Sze Simon Ming Sze
Published: October 2002

In this work, selective epitaxial growth (SEG) of GaInP on a GaAs substrate patterned with silicon nitride is performed by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). The group III sources employed are the combinations of triethylgallium and ethyldimethylindium (TEG+EDMI), triethylgallium and trimethylindium (TEG+TMI), and trimethylgallium and trimethylindium (TMG+TMI). Completely selective epitaxy can be achieved at a growth temperature of 675° C and a growth pressure of 40 Torr when TEG+EDMI is used; while completely selective epitaxy can be achieved under the conditions of 650° C and 40 Torr when the other two sources are used. For the three sources, GaP and InP incorporation increase near the edges of the patterns due to the extra flux of Ga-containing and In-containing species from the region of masking film. Different combinations of group III sources lead to different extents of these incorporations due to the decomposition and diffusion characteristics of the precursors.
Improvement of the Stability of Hydrogenated Amorphous Silicon by Hydrogen Plasma Treatment*
Authors: Nevin W. Andrew , Hideo Yamagishi Hideo Yamagishi , Yoshihisa Tawada Yoshihisa Tawada
Published: October 2002

The effect of post-deposition treatment by a hydrogen plasma on the structural properties, electrical properties and in particular, the stability under sunlight illumination, of device-quality intrinsic hydrogenated amorphous silicon films is described. Comparison is made with samples annealed in hydrogen gas under similar conditions. Reduction of the light-induced degradation is observed after plasma treatment, by an amount depending on the treatment temperature, plasma rf power and treatment time.
Formation of Sources/Drains Using Self-Activation Technique on Polysilicon Thin Film Transistors
Authors: Yoshinouchi Atsushi , Oda Akihiro , Murata Yasuaki , Tatsuo Morita Tatsuo Morita , Shuhei Tsuchimoto Shuhei Tsuchimoto
Published: October 2002

Source/drain formation by ion doping using self-activation technique without thermal anneal on polysilicon thin film transistors (TFT's) have been investigated. Phosphorus ions and protons were simultaneously implanted into polysilicon films. At total ion doses over 8×1015 ions/cm2, resistivities of self-activated films have been found equal to those of the ones annealed after the implantation. This self-activation technique enabled us to fabricate self-aligned TFT's having low-resistance Al gates and, at the same time, to hydrogenate active layers. With the case of self-activation technique, field-effect mobilities as high as 58 and 49 cm2/(V·s) were achieved in n-channel and p-channel TFT's, respectively, fabricated on glass substrates.
Electron Spin Resonance-Computer Tomography with Field Gradient Wires inside the Cavity: Images of Alanine Dosimeters and Some Materials
Authors: Masahiro Yamamoto Masahiro Yamamoto , Motoji Ikeya Motoji Ikeya
Published: October 2002

A large magnetic field gradient with high linearity was obtained for electron spin resonance (ESR) imaging using sixteen straight wires inserted into a cylindrical microwave cavity of TE011mode. Pentacrinus, a carbonate fossil and commercial alanine dosimeters irradiated by 30 kGy have been imaged with the magnetic field gradient intensity of 1 T/m or 2 T/m to determine the resolution of the ESR-computer tomography (CT) imaging. The distribution of radicals in a γ- and an X-irradiated alanine dosimeter has been imaged to investigate the uniformity of an alanine pellet with polystyrene and the self-attenuation effect. A piece of burned wood has been imaged to visualize the oxidation reaction.
Calculation of Size Effect on Galvanomagnetic Electromotive Force Effect Using a Circuit-Array Model
Authors: Shibasaki Masanori , Takemura Yasushi , Tsutomu Yamada Tsutomu Yamada , Keiichi Kakuno Keiichi Kakuno
Published: October 2002

A method of calculation is proposed in order to investigate the size effect on the galvanomagnetic electromotive force effect in a magnetic thin film. The calculation is based on a model which divides a magnetic thin film into circuits. The circuits are designed with consideration given to the electromotive force which is generated by the galvanomagnetic effect, and a set of equations is solved with each circuit. It is found that the calculation describes the experimental data on size effect well, and that the method is applicable to other examples.
Spontaneous Trasition between Relaxor and Ferroelectric States in Lanthanum-Modified Lead Zirconate Titanate (6–7)/65/35
Authors: Krumins Andris , Tadashi Shiosaki Tadashi Shiosaki , Satoshi Koizumi Satoshi Koizumi
Published: October 2002

Dielectric and light scattering measurements are performed in lanthanum modified lead zirconate titanate (PLZT) (6–8)/65/35 hot-pressed ceramics in order to refine the phase diagram. A relaxor-ferroelectric phase transition takes place in PLZT (6–7)/65/35 at temperature lower than the temperature of the dispersive dielectric constant maximum. At this temperature the size of polar regions “a” essentially increases up to a>λ (=0.63 µ m). The appearence of ferroelectric long-range order in PLZT with decreased concentration of La ions is explained by larger coupling between ferroelectrically active BO6 octahedrons due to the smaller concentration of defects and higher dielectric constant.
Effect of Oxygen Radicals for Epitaxial Growth of Al2O3 on Si
Authors: Hayama Kiyoteru , Ishida Makoto , Nakamura Tetsuro
Published: October 2002

Epitaxial Al2O3 films were grown on Si substrates by metal-organic molecular beam epitaxy (MOMBE) using oxygen radicals excited with remote rf plasma and trimethylaluminum (TMA) as source gases. The epitaxial temperature of Al2O3 on Si decreased from 800° C to 700° C using this method. The growth rate of the Al2O3 films increased 1.4–1.6 times at excitation rf power of 400 W, compared with that without rf plasma excitation. The Auger electron spectroscopy (AES) measurement showed that the carbon contamination in the Al2O3 film was removed by the oxygen radicals during the growth. The flatness of the grown Al2O3 surface was improved using oxygen radicals.
Annealing Behavior of Defects Induced by Self-Implantation in Si
Authors: Kim Kwang Il , Kuwano Hiroshi , Kwon Young Kyu , Hahn Soo Kap
Published: October 2002

The morphology of amorphous/crystalline interfaces, regrowth of the amorphous layer and the annealing behavior of secondary defects during rapid thermal annealing for continuous and buried amorphous layers created by double and single self-implantations in Si wafers were investigated by cross-sectional transmission electron microscopy and Rutherford backscattering spectroscopy. In the case of single Si+-ion-implanted Si samples, there are numerous detached microcrystallites throughout the buried amorphous layer, and their density decreases substantially even with rapid thermal annealing at the temperature as low as 500° C. The most striking difference in the secondary defects after complete recovery between the buried and continuous amorphous layers is that zipper-shaped defects only form in the samples with a buried amorphous layer. Extended defects from the zipper dislocations at the middie of the regrown region in the buried amorphous layer act as sinks for point defects.
Suppression of Cone Formation on Carbon Target during Sputtering
Authors: Hoshi Yoichi , Suzuki Atsushi , Judy Jack H.
Published: October 2002

The mechanism of cone formation on a carbon target in sputtering was investigated. Marked whisker growth was observed on the target surfaces of both graphite and glasslike carbon during sputtering when the target was not cooled sufficiently. This whisker growth causes significant cone formation on the target surface, which makes it difficult to perform sputter deposition at a gas pressure below 1 mTorr. On the other hand, cone formation was completely suppressed on the glasslike carbon target when target cooling was improved, which made it possible to perform sputtering at a gas pressure as low as 1×10-4 Torr. This indicates that the use of the glasslike carbon target and cooling of the target during sputtering are effective for suppressing cone formation on the target.
Total Pressure Effects on the Properties of Silicon Nitride Films Fabricated by Photoenhanced Chemical Vapor Deposition
Authors: Shigeichi Yamamoto Shigeichi Yamamoto , Masatoshi Migitaka Masatoshi Migitaka
Published: October 2002

Silicon nitride ( SiN

x

) films were deposited on (100)Si substrates using silane and ammonia gases by the direct-photolysis photoenhanced chemical vapor deposition method at 280° C. The depositions were performed with emphasis on the total pressures, which ranged from 0.51 Torr to 4.04 Torr. As the total pressure increased, the film resistivity decreased from 3.7×1015 Ω· cm to 4.8×109 Ω· cm. The effective trapped carrier density at the SiN

x

/(100)Si interface reached a minimum value (2.1×1010 cm-2) at 1.52 Torr. The film included silicon bonded with silicon (Si–Si) components as well as nitrified silicon (Si–N) components. The Si–Si components increased and the Si–N components decreased in number as the total pressure increased. Based on these results and gas analysis findings, two important reactions to characterize the film properties were discussed.
Fabrication and Structure of Nucleic Acid Base Thin Films
Authors: Kim Joo-Tae , Kanai Masaki , Tomoji Kawai Tomoji Kawai , Shichio Kawai Shichio Kawai
Published: October 2002

Thin films of nucleic acid bases have been grown on cleaved KBr (100) by evaporation deposition. The structures of the thin films are investigated by infrared spectrometry and X-ray diffraction. The orientation of these molecules on the substrate has also been determined by the measurement of FT-IR (fourier transform infrared reflection) absorbance. It is revealed that adenine and thymine molecules are evaporated on the substrate to form thin films without decomposition.
Calculated Three Dimensional Spatial Distribution of CH3Radical Density in the RF Discharge CH4Plasma with Parallel-Plate Electrodes
Authors: Susumu Naito Susumu Naito , Nobuei Ito Nobuei Ito , Tadashi Hattori Tadashi Hattori , Toshio Goto Toshio Goto
Published: October 2002

The three-dimensional spatial distribution of the CH3radical density has been calculated in the model of an RF discharge CH4plasma-enhanced chemical vapor deposition (P-CVD) chamber with parallel-plate electrodes in both cases with and without the White-type multiple reflection arrangement for absorption spectroscopy. The result showed that the CH3radical density decreased sharply and was negligible outside the plasma region irrespective of the geometry of the White-type multiple reflection of the glass tube. The deposition of carbon thin film was also measured. The result showed a tendency similar to that of the calculated distribution of the CH3radical. Therefore, it is concluded that the absorption path length of the laser beam can be defined as the length of the beam which passes through the plasma region in the case of CH3radical density measurement using infrared laser absorption spectroscopy.
A Fitting Formula for Screening Constants of Partially Ionized Atoms in Plasma
Authors: Shigeo Kawata Shigeo Kawata , Shigeru Kato Shigeru Kato , Syuji Kiyokawa Syuji Kiyokawa
Published: October 2002

This paper presents a simple fitting formula for the numerical screening constants which were obtained for each of 33 materials recently by the authors [Jpn. J. Appl. Phys. 32 (1993) 5681]. Using the screening constants, the atomic energy levels are obtained for the finite-temperature materials based on the screened-hydrogen model. The formula is convenient for users of the screening constants and reproduces well the Hartree-Fock-Slater (HFS) energy levels: the deviations from the HFS levels are 5.99% for n=1 and 55.3% for n=2 by averaging results for the 33 materials. Here n is the principal quantum number.
Anomalous Behaviour of Silicon Single-Crystals Observed by X-Ray Diffraction
Authors: Kohno Atsushi , Aomine Nobutaka , Yuji Soejima Yuji Soejima , Atsushi Okazaki Atsushi Okazaki
Published: October 2002

Silicon crystals have been examined at low temperatures by high-angle double-crystal X-ray diffractometry (HADOX). By a new experimental procedure named 2θ-resolved HADOX, the change in the lattice spacing and that in the crystal orientation are independently determined. Diffraction for a region without or with stresses has been examined on specimen crystals in a special form. It is found that the silicon crystal shows normal behaviour on both cooling and heating when it is stress free. With stresses, anomalies are found around 210 K on cooling.
Synthesis of Novel Sr Sources for Metalorganic Chemical Vapor Deposition of SrTiO3
Authors: Kimura Takafumi , Yamauchi Hideaki , Machida Hideaki , Kokubun Hiroshi , Masao Yamada Masao Yamada
Published: October 2002

Novel Sr source materials for metalorganic chemical vapor deposition (MOCVD) of SrTiO3 have been developed. They were synthesized by adding amine, triethylenetetramine (trien) or tetraethylenepentamine (tetraen), to bis-dipivaloylmethanato strontium ( Sr(DPM)2, or strontium-bis-2,2,6,6-tetramethyl-3,5-heptanedionate). The new sources, Sr(DPM)2-trien2 and Sr(DPM)2-tetraen2, have a low melting point (43–75° C), and are liquid in phase when they are vaporized at 120–130° C. SrTiO3 thin films were prepared on Pt/Ta/ SiO2/Si substrates by MOCVD using the new Sr sources. The dielectric constant of films prepared with Sr(DPM)2-trien2 was 215 for 125 nm thick SrTiO3 films, and leakage current densities were below 10-6 A/cm2 at 1.5 V for 80 nm thick SrTiO3 films. The new Sr sources did not change in quality after 20-time heat cycles between room temperature and 130° C in Ar atmosphere at 40 Torr.
Preparation of BaTiO3 Thin Films by Metalorganic Chemical Vapor Deposition Using Ultrasonic Spraying
Authors: Kim In-Tae , Lee Choon-Ho , Soon Ja Park Soon Ja Park
Published: October 2002

Ferroelectric BaTiO3 thin films were fabricated by metalorganic chemical vapor deposition (MOCVD) at atmospheric pressure. The ultrasonic spraying technique has been used to carry the source materials. The common solutions of barium-diethylhexanoate and diisopropoxy-titanium-bis-acetylacetonate in n-butanol were used as the starting materials. Since the concentration of sources can be controlled in the common solution, this method is more simple and precise than other CVD processes. The films had (110) preferred orientation with increasing temperature. The dielectric constant (ε) and the loss factor (tan
δ) of thin film deposited at 550° C were about 250 and 0.1, respectively. The leakage current density was 10-5 A/cm2 at 0.1 MV/cm.
Step Coverage and Electrical Properties of (Ba, Sr)TiO3 Films Prepared by Liquid Source Chemical Vapor Deposition Using TiO(DPM)2
Authors: Kawahara Takaaki , Yamamuka Mikio , Makita Tetsuro , Naka Jiro , Yuuki Akimasa , Noboru Mikami Noboru Mikami , Kouichi Ono Kouichi Ono
Published: October 2002

Thin films of (Ba, Sr)TiO3 (BST) with high dielectric constant were prepared on Pt/ SiO2/Si substrates of 6-inch-diameter by liquid source chemical vapor deposition using Ba(DPM)2, Sr(DPM)2 and TiO(DPM)2 (DPM=dipivaloylmethanato; C11H19O2) dissolved in tetrahydrofuran (THF). The reproducibility of ±3 % for the film composition was achieved by optimizing the deposition procedures. It was found that the coverage of 72%, obtained at the substrate temperature T
s=753 K, was better than those obtained using other Ti sources such as Ti(O-i-Pr)4 (TTIP) and Ti(O-i-Pr)2(DPM)2. The electrical properties of the 480-Å-thick BST film, deposited at T
s=753 K using TiO(DPM)2, were as follows: dielectric constant ε=230, equivalent SiO2 thickness t
eq=7.8 Å, leakage current density J
L=6.7×10-6 A/cm2 at 1.65 V and dielectric loss tan
δ=0.013.
Electrical Properties for Capacitors of Dynamic Random Access Memory on (Pb, La)(Zr, Ti)O3 Thin Films by Metalorganic Chemical Vapor Deposition
Authors: Nakasima Hiroshi , Hazumi Sigeki , Kamiya Tadashi , Kouji Tominaga Kouji Tominaga , Masaru Okada Masaru Okada
Published: October 2002

Lanthanum-modified lead zirconate titanate (PLZT) thin films (0.2–0.35 µ m) have been prepared on Pt/ SiO2/Si substrates at 650° C by the metalorganic chemical vapor deposition (MOCVD) method. The electrical properties of the films were examined as a function of lanthanum content in the range of 0–22 at.%. The remanent polarization and coercive field decreased as the La content increased in the range of 0–14 at.%, whereas they were maintained at constant values of 1 µ C/cm2 and 20 kV/cm, respectively, even in the paraelectric region where La content exceeds 15 at.% in ceramics. The effective dielectric constant of 1200 was obtained at La=10 at.%, and the effective charge densities were about 30 fF/µm2 when La=8–22 at.%. It has been suggested that the breakdown of the films does not occur up to about 1× 1015 cycles at an access voltage of 3 V by the unipolar acceleration test.