bluuebunny/crossref_metadata_2025 huggingface dataset:
Atomic Force Microscopy of Solution Grown Polyethylene Single Crystals
Authors: Nakagawa Yoshitsugu , Hayashi Hitomi , Takahagi Takayuki , Soeda Fusami , Ishitani Akira , Toda Akihiko , Miyaji Hideki
Published: October 2002

Atomic force microscopy (AFM) was applied to the precise thickness measurements of thin lamellae about 10 nm thick of polyethylene single crystals which were grown from dilute solutions and precipitated on cleaved mica. The obtained values agree well with the thickness determined by small angle X-ray scattering. Moreover, AFM observation allowed determination of the thickness difference of several angstroms in the different growth sectors of small crystals about several µ m wide. From the measurements, it was concluded that the free energy of the fold surface in the 110 growth sector was 30% larger than the values in the 100 sector. The larger surface free energy in the 110 sector means higher fold energy in the growth sector.
Electrical Characteristics and Surface Chemistry of P2S5-Passivated GaAs
Authors: Minoru Sakata Minoru Sakata , Hideaki Ikoma Hideaki Ikoma
Published: October 2002

Sulfur passivations of the GaAs surface using P2S5/(NH4)2S

x

and P2S5/NH4OH solutions were investigated by electrical measurements of the Schottky diodes and by X-ray photoelectron spectroscopy (XPS). The GaAs samples lightly washed in deionized water after both P2S5 passivations showed the lowest degree of degradations in the ideality factor n and the Schottky barrier height φ B due to exposure to air ambient. XPS data indicated that oxidation of As was drastically suppressed by P2S5 passivation with and without washing in deionized water, while oxidation of Ga was not efficiently suppressed by these passivations without washing. This is probably due to the preferential formation of As–S bonds over Ga–S bonds. However, oxidation of Ga was found to be greatly suppressed in the water-washed samples after the P2S5 passivations. A fair amount of As–S bonds ( As

x

S

y

, probably AsS and As2S3) was observed in the P2S5-passivated samples without washing, which increased as these samples were exposed to air. This indicates that As atoms diffuse through the rather thick sulfur film and react with S to create As–S bonds during exposure to air. The increase in the amount of unstable As–S bonds is considered to be a cause of the deteriorations in the electrical haracteristics. The amount of As–S bonds was observed to drastically decrease after lightly washing the P2S5-passivated samples in deionized water, whereas the amount of stable Ga–S bonds did not substantially decrease. This is a possible reason for the more stable passivation effect with washing. From the experimental results obtained in this study, it was concluded that the Ga–S bonds are useful and a large amount of the As–S bonds is probably detrimental to stable passivation, though a certain amount of the As–S bonds is necessary to effectively suppress oxidation of As. It is very important to control the amount of sulfur on the GaAs surface to obtain stable passivation.
Scaling Analysis of SiO2/Si Interface Roughness by Atomic Force Microscopy
Authors: Yoshinobu Tatsuo , Atsushi Iwamoto Atsushi Iwamoto , Hiroshi Iwasaki Hiroshi Iwasaki
Published: October 2002

The scaling behavior of SiO2/Si interface roughness was investigated by atomic force microscopy. The rms value of the roughness increased as a power of the scale up to 100 nm with the scaling exponent of 0.3–0.5, and saturated at about 0.3 nm above the 100 nm scale. The scaling behavior of the observed roughness was well approximated by an exponential autocorrelation function with the correlation length of about 15 nm, but not by a Gaussian one. Such scaling behavior should be taken into account in theoretical calculation of surface roughness scattering, and also in metrology of roughness parameters.
Influence of Substrate Misorientation on Current Gain in AlGaAs/GaAs Heterojunction Bipolar Transistors Grown by Metal Organic Chemical Vapor Deposition
Authors: Ito Hiroshi , Watanabe Noriyuki , Nittono Takumi , Tomofumi Furuta Tomofumi Furuta , Tadao Ishibashi Tadao Ishibashi
Published: October 2002

The influence of substrate misorientation on the current gain characteristics of AlGaAs/GaAs heterojunction bipolar transistors (HBTs) is systematically investigated. The current gain is found to increase by a factor of up to three when the substrate is tilted from (100). The behavior of the minority electron lifetime determined separately in thick C-doped GaAs layers grown on the same set of misoriented substrates correlates very well with that of the current gain. This is consistent with the result of base current ideality factors, which are close to unity for all devices. These improvements in the current gain and the minority electron lifetime are commonly observed in layers grown on misoriented substrates regardless of the substrate misorientation direction. These results can be interpreted in terms of the incorporation of nonradiative recombination centers such as native defects, where the substrate misorientation can effectively suppress the formation of these centers.
New Evaluation Method of Resist Coating Using Heterodyne Holographic Wafer Alignment
Authors: Kazuhiro Yamashita Kazuhiro Yamashita , Noboru Nomura Noboru Nomura
Published: October 2002

A new method to evaluate nonuniform resist coating using heterodyne holographic wafer alignment was proposed. In this method, the resist coating nonuniformity is measured as the displacement of the alignment position after resist coating on deep-UV-hardened resist alignment gratings. It has been confirmed that nonuniformity of resist coating was mainly caused by the nonuniform evaporation speed of the resist solvent, and the uniformity of resist coating was obtained by optimizing the solvent and the viscosity of the resist. The resultant overlay accuracy was improved to 59 nm/3σ for the optimized resist coating. The overlay error budget for processed wafers was analyzed and the overlay accuracy was confirmed to be better than 80 nm/3σ using this method and wafer scaling correction.
Gamma-Ray-Induced Loss of Er3+-Doped Silica-Core Optical Fiber
Authors: Koyama Takeshi , Dohguchi Nobuyuki , Ohki Yoshimichi , Nishikawa Hiroyuki , Kusama Yasuo , Seguchi Tadao
Published: October 2002

Erbium-doped silica optical fibers were irradiated by γ-rays, and their loss-increasing characteristics were analyzed. The loss is mainly induced by Er2+ created by the reduction of Er3+. It does not show a simple dependence on the Er3+ concentration. The loss increase is described by the sum of several saturating exponential terms and one linear term, which can be derived from the yield equation of E
′γ centers or other species induced from precursors by hole trapping. It is considered that hole trapping supplies electrons to induce the reduction, and plays an important role in the loss increase.
Electron Tunneling through Ultrathin Gate Oxide Formed on Hydrogen-Terminated Si(100) Surfaces
Authors: Hiroshima Masahito , Yasaka Tatsuhiro , Seiichi Miyazaki Seiichi Miyazaki , Masataka Hirose Masataka Hirose
Published: October 2002

Current transport through ultrathin gate oxides grown on chemically cleaned Si(100) surfaces has been systematically investigated. It is shown that current through oxides thinner than 4.2 nm is controlled by direct tunneling (DT), while Fowler-Nordheim tunneling (FNT) predominates in transport through SiO2 thicker than 5.1 nm. In the oxide thickness range between 4.2 and 5.1 nm, DT limits the current at low electric fields and FNT at high fields. The observed tunneling current is quantitatively explained by a theory based on the Wentzel-Kramers- Brillouin method (WKB approximation). Also, the influence of the Si surface microroughness on the tunneling current is discussed.
Fabrication of a ZnSe-Based Vertical Fabry-Perot Cavity Using SiO2/TiO2 Multilayer Reflectors and Resonant Emission Characteristics
Authors: Honda Tohru , Yanashima Katsunori , Yoshino Junji , Kukimoto Hiroshi , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: October 2002

We have fabricated a SiO2/TiO2 dielectric multilayer mirror applicable for ZnSe-based surface emitting lasers operating at green to blue spectral regions. The fabricated SiO2/TiO2 dielectric mirrors have exhibited a reasonably high reflectivity, greater than 96% at 493 nm. A photo-pumped ZnCdSe/ZnSe/ZnSSe single quantum well (SQW) with dielectric mirrors has shown the cavity mode emission in the surface normal direction at 10 K.
Dielectric and Structural Characteristics of Ba- and Sr-based Complex Perovskites as a Function of Tolerance Factor
Authors: Reaney Ian M. , Enrico L. Colla Enrico L. Colla , Nava Setter Nava Setter
Published: October 2002

The temperature coefficient of the dielectric permittivity (τε) of nonferroelectric complex perovskites is of importance in the application of these cermaics to microwave filters and resonators. Recent work has directly related changes in the τεof complex perovskites to the onset of structural phase transitions which involve tilting of the octahedra. It can be argued that the onset of octahedral tilting is controlled by the tolerance factor (t). Thus, a relationship between τεandtis postulated. This relationship is discussed and transmission electron microscopy is used to demonstrate examples of the structural modifications which cause the anomalies in τεat given values oft.
The Mechanism of Thermo-Induced Electrostatic Image Formation in Poled Ferroelectric Polymer Films
Authors: Kikuchi Masahiro , Yoshimura Toshiya , Katsuyoshi Hoshino Katsuyoshi Hoshino , Hiroshi Kokado Hiroshi Kokado
Published: October 2002

Ferroelectric polymer films have been shown to be useful for heat-mode electrostatic image recording. In connection with this novel imaging process, changes of state at heating were investigated on a copolymer of vinylidene fluoride and tetrafluoroethylene. First, an attempt to estimate the degree of polarization from the analysis of corona charging curves of films partially depolarized with heat pulses is described. For films exposed to a flash light ( 50 mJ/cm2, 10 ms), dipoles were estimated to be disordered by about 20%. This magnitude seems to be insufficient for explaining the observed electrostatic contrast. Another heating effect likely responsible for image formation was found. When poled films were subjected to heat pulse, they were charged up to 40 to 60 V with a polarity opposite that employed for poling. This can be attributed to a combined effect of pyroelectricity and leakage of surface charges.
Crystallization Behavior of A Bulk Amorphous Mg62Cu26Y12Alloy
Authors: Wu Shyue-Sheng , Chin Tsung-Shune , Su Kuo-Chang
Published: October 2002

The crystallization temperature, the associated activation energy and the crystallized structure of a bulk amorphous Mg62Cu26Y12alloy with a diameter of 2.5 mm were studied. It possesses a one-step crystallization behavior. The crystallization reaction was found to be represented by: AM(MG62Cu26Y12)→Mg2Cu+MgY+CuY+Mg, (Tx=188°C,Eac=134 kJ/mol) where AM represents the amorphous state,Txthe crystallization temperature at an infinitesimal heating rate, andEacthe associated activation energy. The amount of crystalline phases were found to be Mg2Cu:MgY:CuY=76:17:7. The Mg phase is identifiable only by high resolution electron microscopy, not by X-ray diffraction. The crystallization leads to a sharp rise in electrical resistivity which is reversed to those of iron-based amorphous alloys.
Quasi-Static and Dynamic Density Fluctuations in the Glassy State IV. Dynamic Thermal Density Fluctuation and Isothermal Compressibility of Glass
Authors: Tomoyoshi Yamashita Tomoyoshi Yamashita
Published: October 2002

The temperature dependence of isothermal compressibility {β(T) dilato} in the glassy state was measured by dilatometry at temperatures ranging from room temperature to around the glass transition temperature (T
g) for polymethyl methacrylate (PMMA) and polycarbonate (PC) glasses. The results were compared with those of β(T) light obtained from isotropic light scattering caused by dynamic thermal density fluctuation (V
v
iso
dyn), not V
v
iso (=V
v-( 4/3)Hv;Hv is anisotropic scattering), in order to test the validity of Einstein's fluctuation theory for the glassy state. Consequently, it was experimentally demonstrated for the first time that β(T) light is in very good agreement with β(T) dilato at all temperatures below T
g for PMMA and PC. These experimental findings indicate that the isothermal compressibility of glass in a nonequilibrium system is thermodynamically dominated by the dynamic thermal density fluctuation having relaxation times much shorter than the experimental observation time scale. Furthermore, the isothermal compressibility of glass, in general, increases drastically as the temperature increases in the glass transition region. However, it has been suggested that this drastic increase is the result of a dramatic increase of the dynamic thermal density fluctuation, with thawing of quasi-static thermal density fluctuation.
Hole Generation without Annealing in High Dose Boron Implanted Silicon: Heavy Doping by B12 Icosahedron as a Double Acceptor
Authors: Mizushima Ichiro , Murakoshi Atsushi , Watanabe Masaharu , Yoshiki Masahiko , Masaki Hotta Masaki Hotta , Masahiro Kashiwagi Masahiro Kashiwagi
Published: October 2002

A high hole concentration region of about 1×1021 cm-3 was generated without any post-annealing by the implantation of high doses of boron into silicon substrates. X-ray photoelectron spectroscopy (XPS) measurement and Fourier transform IR spectroscopy (FTIR) absorption spectra revealed that B12 icosahedra were created in as-implanted samples. A new model of the generation of holes is proposed in which B12 icosahedron acts as a double acceptor.
c-Axis-Oriented Pb(Zr, Ti)O3 Thin Films Prepared by Digital Metalorganic Chemical Vapor Deposition Method
Authors: Sotome Yoshihiro , Senzaki Junji , Morita Shin-ichi , Tanimoto Satoshi , Hirai Tadahiko , Ueno Tomo , Tarui Koichi Kuroiwa
Published: October 2002

Tetragonal perovskite Pb(Zr

x

Ti1-
x

)O3 (PZT) film with single c-axis orientation was successfully fabricated on a single-crystalline MgO(100) substrate at a surface temperature as low as 480°C using a “digital metalorganic chemical vapor deposition (digital MOCVD)” method. In this method, each metalorganic source was supplied alternately into the MOCVD reactor to prevent the formation of unexpected phases such as pyrochlore due to gas phase reaction at the low processing temperature. For layer-by-layer growth in the MOCVD method, the introduction sequence and amount of metalorganic sources supplied were adjusted to correspond to the crystal structure and density of the fabricated film. This is the first report on the fabrication of tetragonal perovskite PZT film with single c-axis orientation using the “digital MOCVD” method.
Stress and Resistivity of Ta–Mo and Ta–W Sputtered Thin Films
Authors: Oshio Shozo , Mamoru Takeda Mamoru Takeda , Tomizo Matsuoka Tomizo Matsuoka
Published: October 2002

Mo or W doping of sputtered Ta films resulted in the phase transition from tetragonal to cubic and significantly varied stress and resistivity. Prior to complete transition, films consisting of two phases exhibited stress relaxation, and tended to transition to the cubic phase with subsequent annealing. With the complete transition to the cubic phase, films showed an increase in stress. Resistivity was approximately 10–30 µ Ω·cm for cubic films, while that for tetragonal films was measured to be 120 µ Ω·cm. We determined pure Mo films to be suitable as electrodes due to their lower resistivity, lower stress and better thermal stability in Ta–Mo alloy systems. The proposed Ta–Mo and Ta–W films exhibited the very small stress required for utilization as X-ray absorbers for X-ray photolithographic masks caused by the relaxation due to coexistence of cubic and tetragonal phases.
Highly Sensitive Precise Double AC Hall Effect Apparatus for Wide Resistance Range
Authors: Kasai Akinari , Abdulla Aniwar , Watanabe Takeru , Mitsuru Takenaga Mitsuru Takenaga
Published: October 2002

A double AC apparatus having new functions is described. So far, in a highly sensitive double AC apparatus, the false signal generation due to nonlinearity at terminal junctions of the specimen and induced emf has been a decisive drawback. In the present apparatus, which eliminates the induced emfin situby using specially designed transformers, the false signal can be completely removed. This result enables us to measure, with high precision, the Hall emf down to a voltage level comparable to the thermal noise of the specimen. In addition, the current shunting effect by capacitances in the region of high specimen resistance is reduced by the proper arrangement of lead wire and by the bootstrapping technique. The upper limit of specimen resistance for which the Hall effect is measurable with the double AC method is extended up to 100 G Ω.
Pretilt Angles of Liquid Crystal on Organic-Solvent-Soluble Polyimide Alignment Films
Authors: Nishikawa Michinori , Sano Kimiyasu , Miyamoto Tsuyoshi , Yokoyama Yasuaki , Bessho Nobuo , Seo Dae-Shik , Iimura Yasufumi , Kobayashi Shunsuke
Published: October 2002

The increase of pretilt angle of liquid crystal in an active matrix (AM) liquid crystal display (LCD) is one of the most important issues to achieve high-contrast and defect-free AM LCDs. We have developed a new generation method of the pretilt angle by using newly synthesized organic-solvent-soluble polyimides containing two types of diamine. The maximum pretilt angle of 2.8° for a nematic liquid crystal is obtained using new polyimides.
Quarter-Micron Contact Hole Filling by Ionized Beam Deposition
Authors: Ito Hiroki , Kajita Naoyuki , Hanai Masahiro , Hashimoto Yoichi , Nobuo Tanaka Nobuo Tanaka
Published: October 2002

The ionized beam deposition (IBD) technique has been developed to fill quarter-micron contacts with TiN/Ti/TiSi2 barrier metal. IBD shows lower contact resistance and higher throughput than a collimated sputtering (CSP) technique. The bottom coverages of IBD and CSP are 50% and 10%, respectively, at a contact aspect ratio of 4. Non-equilibrium higher axial and lower radial velocity profiles of depositing particles can account for this bottom coverage difference.
Analysis of Spherical Carbon Particle Growth in Methane Plasma by Mie-Scattering Ellipsometry
Authors: Yasuaki Hayashi Yasuaki Hayashi , Kunihide Tachibana Kunihide Tachibana
Published: October 2002

The time evolution of polarization state of Mie-scattered light from carbon particles trapped in a methane plasma was measured by a newly developed ellipsometric method. By comparison of the experimental results with a model simulation, it is found that the particles grow by coating with hydrogenated amorphous carbon. It is also found that they have been isotropically and equally coated independent of their initial shape and diameter without homogeneous nucleation and that spherical and monodisperse particles have grown consequently.
Electron Cyclotron Resonance Devices with Permanent Magnets for Production of Large-Diameter Uniform Plasmas
Authors: Satoru Iizuka Satoru Iizuka , Noriyoshi Sato Noriyoshi Sato
Published: October 2002

A review is presented of experimental devices with permanent magnets for electron cyclotron resonance to produce large-diameter uniform plasmas. The devices are classified into 7 groups depending on device symmetry, magnet arrangement, plasma-drift direction and microwave coupling. Their characteristic points are clarified and the most optimal device construction and arrangement are discussed from a viewpoint of producing uniform plasmas necessary for large-scale plasma processing.
Modelling of Noble Gas-SiH4Gas Mixture Glow Discharge Positive Column Plasmas
Authors: Chang Jen-Shih , Kikuchi Mitsuru , Berezin Alexander A. , Hobson Robert M. , Teii Shosaku Matsumura
Published: October 2002

Numerical modelling of He-SiH4, Ne-SiH4and Ar-SiH4gas mixture glow discharge positive column plasmas is conducted for the gas pressure from 0.1 to 30 Torr, the percentage silane gas mixture in a noble gas from 0.01 to 10%, and the electron density from 109to 1013cm-3. The results show that the plasma parameters significantly depend on the combination of the choice of the noble gas and the silane mixture fraction.
A New Portrayal of Oxidation of Undoped Polycrystalline Silicon Films in a Short Duration
Authors: Wang Ping-Wei , Su Huan-Ping , Tsai Meng-Jin , Hong Gary , Feng Ming-Shiann , Huang-Chung Cheng Huang-Chung Cheng
Published: October 2002

Both polysilicon films low-pressure chemical-vapor-deposited (LPCVD) at 625° C and amorphous films deposited at 550° C with subsequent annealing at 600° C for 24 h to form polysilicon films were used to grow polyoxides at 850° C in wet or dry oxygen. Detailed high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) studies have been performed to determine the microstructures of the polyoxide/polysilicon interface and the crystallinity of the polysilicon films. It is found that the oxidation phenomena of these two films are very different. For the recrystallized amorphous silicon specimens, the polyoxide/polysilicon interface is very flat because of the poor crystallinity and low-angle grain boundaries between the grains. On the other hand, the polyoxide/polysilicon interface is rough for the as-deposited polysilicon samples due to the distinct grain characteristics and the high-angle grain boundaries between these grains.
Mass Spectrometry Detection of SiHm and CHm Radicals from SiH4–CH4–H2 RF Discharges under High Temperature Deposition Conditions of Silicon Carbide
Authors: Kae-Nune Patrick , Perrin Jérôme , Jean Guillon Jean Guillon , Jacques Jolly Jacques Jolly
Published: October 2002

The technique of threshold ionization mass spectrometry is applied to the measurement of SiH3, SiH2 and CH3, CH2 radical concentrations under plasma-enhanced chemical vapor deposition (PECVD) conditions from SiH4 and CH4 radio-frequency (RF) discharges between 250° C and 750° C. Relative surface reaction probabilities and gas phase reactivities of the radicals are analyzed. It appears that the surface reaction probability of CH3 on a growing hydrogenated amorphous carbon film is about 18 times smaller than the corresponding surface reaction probability of SiH3 on a growing hydrogenated amorphous silicon film. However, at high temperature above ≈500° C the surface reaction probability of CH3 is enhanced upon transition from a pure hydrogenated carbon film to a silicon-rich surface.
Measurement of Negative Ions Using Improved Probe for Detection of Photodetached Electrons
Authors: Masashi Matsuyama Masashi Matsuyama , Atsushi Hirosawa Atsushi Hirosawa , Shosaku Matsumura Shosaku Matsumura
Published: October 2002

Negative ion measurement applying an electrostatic probe to detect photodetached electrons in noisy plasma has been performed using a compensation circuit with an additional probe. The detected photodetachment current is dependent on the probe surface material. A carbon-coated probe yields the best results in reproducibility and sensitivity in our experiments. The time response of photodetached electron current caused by laser irradiation has also been monitored. The transient current is two to three orders of magnitude larger than the steadystate current at the instant the laser is turned on. Therefore, the absolute determination of steadystate photodetachment current using laser light chopping and the lock-in amplifier is unreliable.
Measurement of Absolute Densities of Si, SiH and SiH3in Electron Cyclotron Resonance SiH4/H2Plasma
Authors: Yamamoto Yasuo , Nomura Hideshi , Tanaka Takao , Hiramatsu Mineo , Masaru Hori Masaru Hori , Toshio Goto Toshio Goto
Published: October 2002

The absolute densities of Si, SiH and SiH3radicals in the electron cyclotron resonance (ECR) SiH4/H2plasma were measured as a function of microwave power and total pressure, using infrared diode laser absorption spectroscopy (IRLAS) and ultraviolet absorption spectroscopy (UVAS). Si, SiH and SiH3radical densities in the SiH4(50%)/H2ECR plasma were 3.6×109, approximately 1×109and 1.7×1010cm-3, respectively, at the microwave power of 400 W and the total pressure of 1.3 Pa. The comparison between these radical densities in the ECR SiH4/H2plasma and those in the RF SiH4/H2plasma is discussed.
Detection of H Atoms in RF-Discharge SiH4, CH4 and H2 Plasmas by Two-Photon Absorption Laser-Induced Fluorescence Spectroscopy
Authors: Kunihide Tachibana Kunihide Tachibana
Published: October 2002

Hydrogen atoms were detected quantitatively by a two-photon absorption laser-induced fluorescence technique in capacitively coupled and inductively coupled RF-discharge plasmas. In a parallel-plate RF-discharge reactor the density of H atoms measured in a SiH4 plasma diluted with Ar was higher than that diluted with H2. A comparison of the densities in SiH4, CH4 and H2 plasmas measured by changing dilution ratio with Ar also showed that H2 molecules were not easily decomposed and H atoms were mostly produced from decomposition of source SiH4 and CH4 molecules at low RF-power level. Spatial distribution of H atoms effused from an inductively coupled RF-discharge radical source was also measured. Its axial and radial profiles showed the expansion of H atoms towards the chamber wall by diffusion and gas flow. The absolute calibration of H atom density was carried out by a comparison with absorption of Lyα line at 121.6 nm.
Single Crystalline Si Metal/Oxide/Semiconductor Field-Effect Transistors Using High-Quality Gate SiO2 Deposited at 300°C by Remote Plasma Technique
Authors: Fuyuki Takashi , Tohru Oka Tohru Oka , Hiroyuki Matsunami Hiroyuki Matsunami
Published: October 2002

High-quality gate SiO2 for metal/oxide/semiconductor field-effect transistors (MOSFETs) could be deposited at as low as 300° C in remote plasma chemical vapor deposition (CVD) utilizing activated neutral oxygen species and SiH4. The interface between deposited SiO2 and Si was improved with the formation of thin SiO2 by low-temperature oxidation using activated neutral oxygen species just before film deposition. The resistivity and breakdown field were as high as 1016 Ω ·cm and 10 MV/cm, respectively, equivalent to those of thermal SiO2 grown at high temperatures. The achieved minimum interface state density was as low as 4×1010 cm-2 eV-1. Fabricated MOSFETs using single crystalline Si showed excellent performance, and an effective channel mobility of 135 cm2 V-1 s-1 for holes was obtained.
Formation of Diamond Films by Intermittent Discharge Plasma Chemical Vapor Deposition
Authors: Noda Mikio , Kusakabe Hiroshi , Taniguchi Kazuya , Maruno Shigeo
Published: October 2002

Formation of diamond film by DC plasma chemical vapor deposition (CVD), wherein the waveform of the power supply is half-wave-rectified (HWR), has been investigated. When HWR voltage is applied to the electrodes, the waveforms of the discharge voltage (V
d) and current (I
d) are intermittent and show a large peak at the beginning of the discharge. The films deposited by intermittent discharge (ID) are superior in crystalline quality compared with that by conventional continuous discharge (CD). The average value of electron temperature (T
e) in ID, measured by a Langmuir probe (LP) in the plasma of hydrogen gas, is higher than that of CD. The LP current shows a very high peak at the beginning of the ID process, and the value of T
e and density of electrons (N
e) at this peak are very large. These rises in T
e by ID are effective in enhancing the dissociation of the source gas by electron collision. It has been concluded from the present study that ID is an effectual method to obtain high-quality diamond film.
Carrier Passivation in Heavily Doped GaAs:Be by Hydrogen Plasma
Authors: Tetsuro Nozu Tetsuro Nozu , Masao Obara Masao Obara
Published: October 2002

The electrical property around the surface of a heavily Be-doped p+GaAs layer exposed to hydrogen plasma has been investigated. The resistance around the surface has been made over six orders of magnitude larger by a 150 W and 10 min plasma exposure. Sheet carrier measurement with step etching has shown that the depth of the passivated front proceeds by diffusion. The time dependence of carrier removal has been found to have three distinct regions including a plateau. These regions have been explained by a 50 nm thick highly resistive layer which is formed within the first 1 minute during the plasma treatment prior to passivation due to hydrogen diffusion.
Etching Characteristics by M= 0 Helicon Wave Plasma
Authors: Tsukada Tsutomu , Nogami Hiroshi , Yukito Nakagawa Yukito Nakagawa , Etsuo Wani Etsuo Wani
Published: October 2002

The each characteristics of SiO2and Al–Si–0.5%Cu were studied using theM=0 helicon wave plasma etching apparatus. A high concentration of F radicals was observed during SiO2etching using fluorocarbon gases. The etch rate of SiO2was strongly dependent on the concentration of F radicals in the plasma. A method of increasing the selectivity of SiO2to poly-Si was discussed. The Al–Si–0.5%Cu film deposited on the wafer of 200 mm diameter was anisotropically etched with high selectivity to photoresist using Cl2and BCl3gases. The etch rate uniformity across a wafer was also discussed.
Direct Measurement of Surface Charging during Plasma Etching
Authors: Shigemi Murakawa Shigemi Murakawa , James P. McVittie James P. McVittie
Published: October 2002

An on-wafer surface potential probe was developed for the direct real-time measurement of the local charging on a wafer surface during plasma etching. Pressure and rf power dependencies of the surface charging potential were measured in a nonuniform magnetron plasma by this probe. The variation in etching profiles was also observed by scanning electron microscopy (SEM). The measured surface charging potential was consistent with previously expected values from the profile distortion and device damage results. The local surface charging and the profile distortion increased as the pressure was reduced, while they were insensitive to the rf power change.
Using SEMATECH Electrical Test Structures in Assessing Plasma Induced Damage in Poly Etching
Authors: Y. David Chan Y. David Chan
Published: October 2002

The use of capacitive antenna structures to assess process-induced charging damage is well documented. A description of a subset of the SEMATECH process-induced damage effect revealer (SPIDER) module set is given in this report. SPIDER utilizes various sizes and shapes of antenna structures tied to transistors. In this investigation, the evaluation of plasma etch damage, primarily from the gate polysilicon etch, is reported using 0.5 µ m n-channel metal-oxide-semiconductor (NMOS) antenna transistor. Damage appears to occur at the gate oxide bulk and interface. A portion of this damage is not measured after post-metallization annealing unless activated by electrical stress or some subsequent processing. The damage does not correlate with transistor antenna area present during the poly-Si etch. However, a correlation is observed for transistor parameters measured after activation by Fowler-Nordheim stress. This latency may be attributed to hydrogen passivation. A damage model is presented here.
Substrate Position Dependence of Characteristics of Te–C:H Film Prepared by DC Magnetron Sputtering in Methane Atmosphere
Authors: Ohkawa Hideki , Ozawa Norio , Ichihara Katsutaro , Yasuda Nobuaki
Published: October 2002

A valence band and a Raman spectrum of Te–C:H film deposited in 50% methane atmosphere with argon as a dilution gas have been confirmed to vary according to the substrate arrangement on the anode in dc magnetron sputtering processes. The effect of bombardment by neutralized recoil argon was discussed for the sputtering processes of the Te–C:H film. Optical emission spectroscopy of the sputtering processes on tellurium was carried out for three gas atmospheres: argon, 50% methane, and pure methane. The optical emissions from atomic and ionic tellurium were recognized even in pure methane atmosphere. A chemical reaction and chemical sputtering have been considered to be involved in the sputtering process between the tellurium target and hydrocarbon species in the plasma.
Shallow Donor Clusters in InP
Authors: Murakami Kouichi , Takasumi Ohyanagi Takasumi Ohyanagi , Kohzoh Masuda Kohzoh Masuda
Published: October 2002

Electronic states of a shallow donor in InP are investigated as functions of donor concentration (ND–NA) from 4.0×1015to 5.5×1016/cm3by electron spin resonance (ESR) at low temperatures. The Overhauser shift, nuclear spin-lattice relaxation timeT1N, andg-value are found to strongly depend onND–NA; i.e.,T1Nhas a maximum at around 7×1015/cm3, while theg-value increases with increasing donor concentration, ranging from 1.2024 to 1.2143. Sweeping the magnetic field at appropriate speeds yields significantly inhomogeneous broadening of the ESR line, indicating that the ESR comes from bound donor electrons at least belowND–NAof 1.5×1016/cm3. A model of donor clusters is proposed to interpret the obtained results. The donor-concentration dependence of theg-values indicates that the donor states are significantly changed with the average donor-cluster size.
Fabry-Pèrot Resonance in Aharonov-Bohm Conductance Oscillation at Finite Temperatures
Authors: Kuniichi Ohta Kuniichi Ohta , Daisuke Takai Daisuke Takai
Published: October 2002

The line shape of Fabry-Pérot resonance in Aharonov-Bohm conductance oscillation in a mesoscopic ring is calculated as a function of magnetic phase shift at finite temperatures. The case of the maximum coupling between the ring and leads is considered. It is shown that the 2π periodic series of resonance peaks with height e
2/h and width zero at temperature T=0 is broadened as a result of energy dispersion. The peak height is almost kept invariant below 10 K. This is because Fermi energy is far larger than thermal breadth at the step of the Fermi function in this temperature range. Implications of these results are discussed in relation to application to small-area-single-flux-quantum devices.
Disk-Shaped Stacked Capacitor Cell for 256 Mb Dynamic Random-Access Memory
Authors: Morihara Toshinori , Ohno Yoshikazu , Eimori Takahisa , Katayama Toshiharu , Satoh Shinichi , Tadashi Nishimura Tadashi Nishimura , Hirokazu Miyoshi Hirokazu Miyoshi
Published: October 2002

A new cell structure using the disk-shaped stacked capacitor is proposed for 256 Mb dynamic random-access memory (DRAM). This capacitor structure is formed on the sidewall of a cylindrical storage node by means of a self-alignment method. The lithographic process of the disk-shaped storage node is the same as that of the cylindrical one. The distance between adjacent storage node patterns of 0.1 µ m can be realized beyond the limits set by lithographic resolution. It is estimated that the capacitance of 25 fF/cell can be obtained in the 0.4 µ m storage node height in a 0.72 µ m2 cell area. The disk-shaped stacked capacitor, to which ON dielectric film (t
eq=4 or 5 nm) is applied, is investigated with regard to electrical characteristics.
Electrical Properties of Gallium Manganese Antimonide: a New Diluted Magnetic Semiconductor
Authors: Tanusree Adhikari Tanusree Adhikari , Sukumar Basu Sukumar Basu
Published: October 2002

Ga1-
x

Mn

x

Sb, a ternary diluted magnetic semiconductor (DMS) alloy was newly synthesised with different Mn concentrations (x=0.0048, 0.01, 0.05 and 0.14) using Bridgman growth technique. The stoichiometry and the composition were verified by the electron probe microanalysis and X-ray diffraction analysis. At room temperature electrical parameters like resistivity, Hall co-efficient, carrier concentration and mobility were determined. The variations of resistivity and Hall co-efficient with temperature were studied and it was found that the alloy was degenerate in nature.
BaCuO2 Single-Crystal Growth on Ceramic Substrate under Reducing Atmosphere
Authors: Kubota Hiroshi , Miyagawa Ryuji , Fujiyoshi Takanori , Onuki Kuniyuki Miyahara
Published: October 2002

A BaCuO2 single-crystal growth has been achieved on a porous BaCuO2 ceramic substrate, where only the surface was melted and recrystallized under H2+Ar reducing atmosphere by pulse heating.
Injection Locking of a Modified-Unstable-Resonator XeCl Laser by Using a Line-Narrowed Hemiconfocal Oscillator
Authors: Chu Hong , Kim Dong Hwan , Jhon Young Min , Choi Sang Sam , Obidin Alexei Z. , Park Dae Yoon
Published: October 2002

An injection-locked XeCl excimer laser with a modified positive-branch confocal unstable resonator was developed and the output characteristics were investigated. We utilized the hemiconfocal scheme in the line-narrowed oscillator in order to obtain a seed beam with high energy as well as narrow linewidth. In this case we obtained 0.05 cm-1linewidth with 10 µ J output energy. The maximum output energy of the injection-locked oscillator was 110 mJ, which is 15% greater than that with free-running oscillation. We also presented a new method which can simply measure the power gain of the amplifier, by which the small signal gain coefficient of the amplifier was measured to be 10%/cm.
Thermal Stability of Interconnect of TiN/Cu/TiN Multilayered Structure
Authors: Igarashi Yasushi , Yamanobe Tomomi , Yamaji Tetsuo , Satoshi Nishikawa Satoshi Nishikawa , Toshio Ito Toshio Ito
Published: October 2002

The etching process for a Cu interconnect with self-aligned deposition of a thick sidewall film has been developed. This sidewall film acts as a barrier layer to prevent Cu from corrosion and oxidation during the subsequent process, such as formation of a passivation film. Using this etching process, the Cu interconnect of a TiN/Cu/TiN multilayered structure in a submicron feature is formed. Resistivity for the Cu interconnects is about 2 µ Ω ·cm, and it does not change on annealing up to 700° C. Diffusion of impurities into Cu is not observed up to 800° C annealing. Therefore, the structure of the Cu interconnect, that is, Cu covered with TiN and the thick sidewall film, is suitable for the ULSI process.
Calculation of Alloy Disorder Influence on Hole Ionization Behavior in Ga1-xAlxSb Compounds
Authors: Rmou Abdelaziz , Luquet Henri , Gouskov Léone , Michèle Perotin Michèle Perotin , Paul Coudray Paul Coudray
Published: October 2002

The calculation of the ionization probability and of the ionization coefficients of the holes of the spin split-off valence band in Ga1-
x

Al

x

Sb has been made for various compositions 0<x<0.08. This range allows us to obtain the situations in which the ratio of spin orbit splitting Δ to the energy gap E
g decreases from 1.05 to 0.89. It is shown that if the alloy disorder is neglected, the hole ionization coefficient k
p exhibits a continuous variation with Δ/E
g (or x); if not, k
p is strongly increased and shows a maximum for x=0.02 in the composition range in which Δ≥E
g (Δ/E
g=1.006). The comparison with experimental results is presented and allows an estimation of the mean free path of the holes; the strong influence of this parameter on the k
p values is discussed.
Video Rate Operation in High-Speed Smectic Liquid Crystal Light Modulator
Authors: Okada Hiroyuki , Kurabayashi Hiroyuki , Kidoh Yasuaki , Miyashita Hiroyoshi Onnagawa
Published: October 2002

Frequency characteristics in a smectic liquid crystal light modulator (SLCLM) for high-frequency (several MHz) and low driving voltage (±5 V) operation are investigated. The system configuration, necessary condition for optical communication, static characteristics and maximum operation frequency are discussed. Experimentally, static voltage versus output power characteristics without hysteresis and good high-frequency characteristics for operation at 1.3 MHz have been obtained. The experiment of optical transmission of full-color National Television System Committee (NTSC) video signal was successful for the first time.
Solid-State Amorphization in Palladium/Titanium Multilayer Films during Sputter Deposition and Postdeposition Annealing
Authors: Tadayyon Seyed-Mohammad , Fujimoto Yasutaka , Tanaka Kazuhide , Doi Masaaki , Matsui Masaaki
Published: October 2002

Microstructures in Pd/Ti multilayer films have been investigated using X-ray diffraction, Auger electron spectroscopy and cross-sectional transmission electron microscopy. Multilayer films consisting of crystallites with preferred orientations in Pd and Ti layers after deposition exhibit crystalline-to-amorphous phase transition during thermal annealing at 573–623 K. This solid-state amorphization reaction is discussed in terms of a metastable phase diagram calculated for this system.
Conformal Chemical Vapor Deposition TiN(111) Film Formation as an Underlayer of Al for Highly Reliable Interconnects
Authors: Kaizuka Takeshi , Shinriki Hiroshi , Nobuyuki Takeyasu Nobuyuki Takeyasu , Tomohiro Ohta Tomohiro Ohta
Published: October 2002

Chemical vapor deposition (CVD) TiN film having the (111) preferred orientation and conformal step coverage was developed for the first time. The key processes are predeposition of the Ti(002) layer before the CVD TiN film deposition and optimization of the flow rate of reactants: TiCl4, NH3 and H2. Growth of (111) crystal plane seems to be induced due to the lattice matching of crystal plane of the Ti film. On the other hand, conformal step coverage is obtained by using a lower flow rate of NH3, resulting in the surface-limited chemical reaction. It was also demonstrated that both sputtering and CVD Al, deposited on the CVD TiN having stronger (111) orientation, showed stronger (111) orientation which is advantageous for obtaining high electromigration (EM) resistance. Furthermore, simultaneous contact hole filling and interconnects formation using CVD Al/CVD TiN stacked film are successfully demonstrated.
Electric Resistance Changes of Metal Films Irradiated by a Weakly Ionized Plasma
Authors: Murakami Hiroyuki , Katsumata Teruo , Konno Masaki
Published: October 2002

It has been reported that materials eroded due to chemical reactions between material surfaces and high-velocity ( ∼8 km/s) oxygen atoms in flight tests of the space shuttle, and material erosion was confirmed by bombarding samples with beams of atomic oxygen on Earth. In this paper, crystallization on the Ag film surface was confirmed by observation with an atomic force microscope and component analysis with a scanning Auger spectrometer, after irradiation of a plasma which has components similar to those around the shuttle in low Earth orbit. The crystal formation mechanism accompanying an increase of electric resistance of the Ag film after plasma irradiation was explained by using a model of the ionically bonded crystal.
Measurements of Electrostatic Double-Layer Forces Due to Charged Functional Groups on Langmuir-Blodgett Films with an Atomic Force Microscope
Authors: Ishino Takashi , Hieda Hiroyuki , Kuniyoshi Tanaka Kuniyoshi Tanaka , Nobuhiro Gemma Nobuhiro Gemma
Published: October 2002

Using an atomic force microscope, we measured the forces between a Si3N4 tip and monolayers with different polar functional groups ( –NH2, –COOH, –CONH2, and –OH) prepared by the Langmuir-Blodgett method while varying the pH value of aqueous solutions. The obtained force vs distance curves were related to the surface charges of the tip and the dissociation of the functional groups from the pH dependency, and the charged state of functional groups could thus be discerned. In addition, the electrostatic origin of the force has been confirmed assuming constant potentials on both surfaces.
Secondary Electron Emission and Backscattering from a Metal Surface under Low-Energy Positron and Electron Bombardment
Authors: Kaoru Ohya Kaoru Ohya
Published: October 2002

A Monte Carlo simulation is performed to study the secondary electron emission and backscattering from Al bombarded by positrons and electrons. In the simulation, the elastic scattering cross section is calculated by taking into account the polarization of Al atoms by the projectiles and the indistinguishability of electrons, whereas excitation of conduction electrons is described using Lindhard's dielectric scattering formalism. The calculated secondary electron yield and backscattering coefficient for positrons are smaller than those for electrons.
Preparation of Iron Ultrafine Particles by the Dielectric Breakdown of Fe(CO)5 Using a Transversely Excited Atmospheric CO2 Laser and Their Characteristics
Authors: Majima Tetsuro , Miyahara Tesshu , Haneda Koichi , Ishii Tadahiro , Michio Takami Michio Takami
Published: October 2002

Iron ultrafine particles containing the γ-phase in a relatively high yield of approx. 50% were prepared by the dielectric breakdown of Fe(CO)5 upon irradiation with a tightly focused laser beam of a transversely excited atmospheric (TEA) CO2 laser. CO is also obtained as a volatile product. The iron particles are fine and isotropic in shape. The particle size is in the range of 9–16 nm with a mean particle size of 13 nm. In X-ray diffractometry, the iron ultrafine particles are found to be a mixture of fcc γ-iron which is normally stable only in the range of 1183–1662 K, bcc α-iron, and iron oxides with a weight ratio of γ-iron:α-iron:iron oxides=42:46:12. The γ-phase thus obtained is paramagnetic at least at 1.8–295 K, and transforms into ferromagnetic bcc α-iron above 473 K, with almost complete conversion into α-iron at 653–693 K Formation of γ-iron ultrafine particles by the dielectric breakdown of Fe(CO)5 is discussed and compared with that by the SF6-sensitized photodecomposition of Fe(CO)5.
Development of Time-Resolved High-Temperature X-Ray Powder Diffraction Apparatus and In Situ Observation of Phase Transition in YBa2Cu3O7-x
Authors: Oyama Yasunao , Hasegawa Masashi , Humihiko Takei Humihiko Takei
Published: October 2002

A time-resolved high-temperature X-ray powder diffraction apparatus has been developed using a position-sensitive proportional counter. X-ray diffraction in the range of Δ2θ≤40° can be simultaneously detected in less than 1 min. Orthorhombic-tetragonal phase transition in YBa2Cu3O7-
x

can be observed in situ moment by moment and investigated on an atomic scale using the developed diffraction apparatus.
Plasma Generation and Beam Extraction on Reentrant-Cavity-Type Electron Cyclotron Resonance Ion Source
Authors: Toshiaki Yasui Toshiaki Yasui , Hirokazu Tahara Hirokazu Tahara , Takao Yoshikawa Takao Yoshikawa
Published: October 2002

An electron cyclotron resonance (ECR) ion source 8 cm in diameter using a reentrant coaxial cavity and a ring cusp magnetic field was developed to improve plasma uniformity and operational reliability. The reentrant coaxial cavity is utilized to achieve electrical breakdown easily, to tune in variable electromagnetic fields and to introduce microwaves into plasma from an annular window of a discharge chamber sidewall. Microwaves are resonantly absorbed by the ECR magnetic field. Above 10 sccm flow rate for Ar, uniform and overdense plasmas were obtained in an area 4 cm in diameter from the center axis. The maximum plasma density of 1.26×1011 cm-3 was achieved on the center axis at 20 sccm. However, plasma densities for N2 and O2 were lower than the cutoff density. The maximum ion beam current density of 1.26 mA/cm2 was obtained at a forward power of 304 W for Ar.
Angular Distribution Measurement of Cesium Atomic Beam from Long Tube Collimators
Authors: Takeshi Ikegami Takeshi Ikegami
Published: October 2002

Angular distribution of a cesium atomic beam effusing from long tube collimators with circular cross section was measured. Two types of collimators, a stainless steel tube ( 0.7 mmφ×20 mm) and a glass capillary array ( 50 µmφ×2 mm) were examined. The glass capillary array was superior in terms of collimation and Cs consumption, and this was attributed to its small dimension.
Local Oxidation of 6H-SiC
Authors: Katsunori Ueno Katsunori Ueno , Yasukazu Seki Yasukazu Seki
Published: October 2002

SiC is a promising material for high-temperature and the high-power devices. We propose local oxidation for the isolation of the p-n junction. The oxidation rate of silicon nitride is found to be low enough compared to the C face of 6H-SiC, even at 1200° C. The comparison between the process simulation and the experiment is made, with the results showing that the bird's beak of 6H-SiC is longer than that of silicon due to the smaller oxidation rate of 6H-SiC.