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Closed-Chamber Chemical Vapor Deposition: New Cyclic Method for Preparation of Microcrystalline Silicon Films
Authors: Stefan Grebner Svetoslav Koynov , Münder Herbert
Published: October 2002

A new cyclic chemical vapor deposition (CVD) process for low-temperature preparation of microcrystalline silicon and its alloys is proposed. The cycle includes an a-Si:H layer deposition step and a hydrogen-radical treatment step. The H-treatment step is carried out under closed-chamber CVD (CC-CVD). It provides conservation of Si mass at an equilibrium between H-etching and redeposition. Thus, films of high crystallinity can be achieved. The advantages are a high deposition rate, high reactive gas utilization and precise control of the film structure. In situ monitoring of the plasma emission spectrum has been used to investigate the CC-CVD process features. The films are characterized by Raman spectroscopy, scanning electron microscopy, temperature-dependent dark conductivity, and infrared transmission spectroscopy.
Preparation and Properties of Cd1-xMnxS Thin Films
Authors: Ikeda Mitsusuke , Wada Hiroko , Takahiro Wada Takahiro Wada , Takashi Hirao Takashi Hirao
Published: October 2002

Cd1-
x

Mn

x

S thin films have been prepared on glass substrates by coevaporation of CdS and Mn. Single-phase solid solutions with wurtzite structure were produced for a wider range of x up to 0.94 than the previously known soluble range of 0≤x ≤0.5. Lattice constants a and c decrease linearly with increasing x. Band-gap energy E
g varies linearly with x in the range of x>0.1, and the value of E
g extrapolated to x=1, corresponding to γ-MnS (wurtzite-type), is 3.30 eV at room temperature. The films thus formed are stable for annealing at or below 450° C.
TiWN Schottky Contacts to n-Ga0.51In0.49P
Authors: Lin Kun-Chuan , Chang Edward Y. , Wang Sheng-Ping , Yeong-Lin Lai Yeong-Lin Lai , Chun-Yen Chang Chun-Yen Chang
Published: October 2002

The study of the applicability of TiW nitrides ( TiWN

x

) as the Schottky contact metals to the n-type Ga0.51In0.49P has been made. The Ga0.51In0.49P epitaxial layer is successfully grown on the GaAs substrate by low-pressure metalorganic chemical vapor deposition (LP-MOCVD) to form a lattice-matched heterostructure. The RF-magnetron sputtering system is utilized for nitride deposition. Thermal stability of the nitride films is studied with the aid of a rapid thermal annealing system. The material properties are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Auger electron spectroscopy (AES). With sufficient nitrogen content, the Schottky contacts showed excellent electrical and physical characteristics even after a high-temperature annealing. The barrier heights, ranging from 0.81 to 1.05 eV, depend on the content of nitrogen and the rapid thermal annealing (RTA) annealing condition. The XRD and AES results indicate no interaction occurring at the TiWN

x

/GaInP interface of both as-deposited and annealed samples. The outstanding characteristics of the Schottky contact are attributed to the high band-gap nature of the GaInP and the incorporation of nitrogen into the TiW films.
Laser Plasma Soft X-Ray Contact Microscopy of Polymer Composites
Authors: Azuma Hirozumi , Akihiro Takeichi Akihiro Takeichi , Shoji Noda Shoji Noda
Published: October 2002

Microstructures of polymer composites are observed with a good contrast and with a submicron spatial resolution by contact soft X-ray microscopy with a laser plasma as a soft X-ray source. An iron target was irradiated by a YAG laser ( 2ω=532 nm, 0.4 J) at laser power density of 2.5×1012 W/cm2 and the emitted soft X-rays were filtered with a thin aluminum foil. For a 0.1-µ m-thick poly acrylonitrile-butadiene-styrene specimen, poly-butadiene or copolymer of butadiene spheres of about 500 nm diameter, which are selectively stained with osmium, is observed with soft X-rays in the wavelength region between 17 and 20 nm. For a 4-µ m-thick polyvinyl chloride film specimen formed by polymer powder compaction, peripheral areas of holes, grain boundaries, and areas probably degraded by HCl reduction are observed with soft X-rays in the wavelength region mainly around 2 nm.
Concentration Quenching of Infrared Stimulated Luminescence in CaS:Eu,Sm
Authors: Yasuaki Tamura Yasuaki Tamura
Published: October 2002

Concentration quenching of infrared stimulated luminescence (ISL) in CaS:Eu,Sm phosphors with various dopant concentrations is discussed. The discussion is based on experimental results on the dopant concentration dependence of ISL intensity and that of the intensity of the emission from a symmetric-site Sm (s-Sm) and from a defect-related asymmetric-site Sm (a-Sm). The excitation and emission spectra of s-Sm and a-Sm are revealed by site-selective photoluminescence measurements. The relationship between the concentration dependence of ISL intensity and that of both the s-Sm and a-Sm emission intensities is clarified. The s-Sm is shown to be the active center for ISL. Concentration quenching of ISL intensity is caused by a decrease in the s-Sm concentration resulting from excess doping of Sm and Eu.
Synthesis of Aliphatic Polyurea Films by Vapor Deposition Polymerization and Their Piezoelectric Properties
Authors: Hattori Takeshi , Iijima Masayuki , Takahashi Yoshikazu , Fukada Eiichi , Suzuki Yoshiichi , Kakimoto Masa-aki , Imai Yoshio
Published: October 2002

Aliphatic polyurea 9 films were prepared by vapor deposition polymerization of the monomers 1,9-diisocyanatononane and 1,9-diaminononane on a glass substrate cooled to various temperatures below 0° C. When the temperature of the substrate was low, the residence time of deposited monomers was sufficiently long to allow addition polymerization. The piezoelectric constant of poled films depended on the poling electric field and the poling temperature. Three relaxation processes were observed at -150° C (γ), -50° C (β) and 100–140° C (α) in the measurement of the temperature dependence of the elastic and dielectric constants. The thermal molecular motins at these three relaxations influenced the crystallization, poling process and thermal stability of piezoelectric activity.
Two-Dimensional Growth and Decomposition of Initial Thermal SiO2 Layer on Si(100)
Authors: Horie Tetsuhiro , Takakuwa Yuji , Nobuo Miyamoto Nobuo Miyamoto
Published: October 2002

The growth and decomposition kinetics of initial thermal oxide layers on Si(100) were investigated by in situ ultraviolet photoelectron spectroscopy (UPS). From a time evolution of the correlation between the amount of oxide and the clean area observed, it was found that the initial thermal oxidation as well as the decomposition proceed two-dimensionally with the formation of oxide islands until the clean surface is fully covered with oxides, after which the oxides grow deeply toward the substrate with a very slow oxidation rate. The oxide island thickness was evaluated from the X-ray photoelectron spectra of Si-2p to be 7.1 Å. The two-dimensional oxidation, in which the oxide growth predominantly occurs at the periphery of oxide islands, means that adsorbed oxygen atoms migrate on the clean surface to be captured at the periphery of the oxide islands, resulting in the two-dimensional enlargement of islands, and be desorbed as SiO during the initial thermal oxidation.
Characteristics of Fluorocarbon Radicals and CHF3Molecule in CHF3Electron Cyclotron Resonance Downstream Plasma
Authors: Takahashi Kunimasa , Masaru Hori Masaru Hori , Toshio Goto Toshio Goto
Published: October 2002

The CF, CF2and CF3radical densities and CHF3molecule density were measured in a CHF3electron cyclotron resonance (ECR) downstream plasma using infrared diode laser absorption spectroscopy (IRLAS). The intensities of emission lines F*, Ar*and Hα were also measured in a CHF3/3 % Ar ECR downstream plasma using optical emission spectroscopy (OES). These measurements were carried out as a function of the microwave power and the pressure with modulation of the power with an on-period of 15 ms and an off-period of 85 ms. On the basis of the results of IRLAS and OES measurements, the behaviors of the radicals in the ECR plasma have been investigated in detail.
Growth and Stability of H2-Phthalocyanine Thin Films on MoS2 Surfaces Studied by Means of Low-Energy Electron Transmission Spectroscopy
Authors: Momose Masahiro , Kamiya Koji , Sugita Kazuyuki , Ueno Nobuo
Published: October 2002

The growth of H2-phthalocyanine ( H2Pc) thin films on MoS2 single-crystal surfaces was studied by low-energy electron transmission (LEET) spectroscopy. We observed LEET features typical of ultrathin films prepared by direct molecular-beam deposition of H2Pc molecules as well as by thinning thicker films by heat treatment. The dependence of the work function of the film on the film thickness showed the minimum value at the film thickness at which LEET features characteristic of ultrathin film were observed. The results indicate that the ultrathin film consists of a monolayer of H2Pc molecules, and the growth of the H2Pc monolayer is realizable on the MoS2 surface. Furthermore, it was found that films about 100 Å thick show poor molecular order due to aging at room temperature, while multilayer films of thickness below ∼50 Å are stable. The latter results indicate the difficulty in preparing well-ordered H2Pc multilayers of sufficient thickness on the MoS2 surface at room temperature.
Dynamical Formation Process of Pure Edge Misfit Dislocations at GaAs/Si Interfaces in Post-Annealing
Authors: Asai Koyu , Hisashi Katahama Hisashi Katahama , Yasunari Shiba Yasunari Shiba
Published: October 2002

We investigate the dynamical formation process of pure edge misfit dislocations (90° type) in GaAs/Si(100) (3° off toward [011]). The cross sections at the interfaces of GaAs/Si annealed at various temperatures (300–600° C) are observed by high-resolution transmission electron microscopy. The pure edge dislocation is formed by the reaction of two mixed dislocations (60° type) at the interface, and is not introduced directly from the epilayer surface. To explain the experimental results, we present a new formation process of pure edge dislocations: (1) glide from the epilayer surface, (2) climb along the interface and (3) reaction. In this process, the climb motion along the interface is most important. In addition, the difference in the ratio of pure edge dislocations to the total dislocations was observed between stepped and flat directions of the Si substrate. This asymmetry may be caused by the difference in climb velocities along the interface. The Si surface steps probably enhance this climb motion.
Amorphous Silicon Double-Injection Device with Gate-Controllable N-Type Negative Resistance
Authors: Chen Kuin-Hui , Fang Yean-Kuen , Liu Ching-Ru , Hwang Jun-Dar , Kuo Yue-Kae Lin
Published: October 2002

An amorphous silicon double-injection pin diode with an injection gate was fabricated and analyzed. The device possesses a gate-controllable N-type negative-resistance current/voltage ( I/V) curve, which can be employed for switching or logic control and can be combined with other amorphous devices to develop optical electronic IC's on a glass substrate for low-cost applications. A model to illustrate the operating mechanism is included. Also, the design considerations to fit various applications were studied.
Second Harmonic Generation of a Copper Vapor Laser Using an Anamorphic Optical System
Authors: Omatsu Takashige , Kuroda Kazuo , Takase Tomohiro , Akira Hasegawa Akira Hasegawa , Iwao Ogura Iwao Ogura
Published: October 2002

We analyzed theoretically the conversion efficiency of a second harmonic generation (SHG) in a copper vapor laser (CVL) at 510.6 nm using the β- BaB2O4 crystal and the anamorphic optics. It was found that a higher conversion efficiency compared with that of a conventional spherical focus can be achieved using several anamorphic systems with different anamorphicities.
Spectral Properties of Nd3+-Doped RO·Na2O·Al2O3·P2O5 (R=Mg, Ca, Ba) Glass System
Authors: Byun Jong-Oh , Kim Byong-Ho , Hong Kug-Sun , Jung Hyung-Jin , Lee Sang-Won , Ryoo Kun-Sang , Izyneev A. A. , Kravchenko V. B.
Published: October 2002

The dependence of spectral properties of the Nd3+-doped (45- x)RO· xNa2O·2.5Al2O3·52.5P2O5 (R=Mg, Ca, Ba, 0≤x ≤31, mol%) glasses on RO and on its substitution with Na2O was investigated. Absorption, fluorescence spectra and lifetimes were measured. Both the stimulated emission cross section and the spontaneous emission probability for the 4F3/2→4I11/2 transition of Nd3+ in glass were calculated. The results indicate that the effect of RO depends on its ionic field strength and that the substitution of RO with Na2O loosens the glass structure so as to lower the degree of disorder of the phosphate chain structure. A stimulated emission cross section as large as 4.2×10-20 cm2 and half-lifetime concentration as high as 8×1020 ions/cm3 were obtained.
Effects of Magnetic Field Gradient on Crystallographic Properties in Tin-Doped Indium Oxide Films Deposited by Electron Cyclotron Resonance Plasma Sputtering
Authors: Kubota Eishi , Shigesato Yuzo , Igarashi Masaru , Haranou Takeshi , Suzuki Kohichi
Published: October 2002

Tin-doped indium oxide (ITO) films were deposited by sputtering of sintered oxide targets, employing an electron cyclotron resonance (ECR) microwave plasma system. The effects of Ar ion bombardment on crystallographic and electrical properties of the films were investigated with control of the ion energy by submagnetic field application. It was found that ion bombardment with energies lower than ∼ 40 eV enhances crystallization whereas bombardment with higher energies suppresses crystallization. The surface roughness of the film was below 50 Å. The smooth surface formation could be attributed to the microstructural modification arising from ion bombardment.
Capillary Wave Propagation on Water Covered with Polyamic Acid Monolayer Films
Authors: Kaoru Tamada Kaoru Tamada , Kenjiro Miyano Kenjiro Miyano
Published: October 2002

Externally generated capillary wave propagation has been studied on water covered with poly(amic acid) alkylammonium salts. In addition, fluorescence microscope observation was performed with a poly(amic acid) containing a fluorophore dye. The octadecylammonium salt of this polymer exhibits condensed liquid/gas coexistence films when the pressure is very low (pressure Π≃0), where the liquid phase is highly viscoelastic. Such domain structures were not found in the hexadecylammonium salts of other polymers. However, all films used here can be compressed homogeneously and isotropically at higher pressures, independent of the chain length of alkyl amines. These observations suggest that the mechanical character in the highly condensed state is determined mainly by the flexibility of polymer chains, while the degree of condensation in the dilute state is more influenced by the alkyl amines.
Measurement of Density Distribution of Metastable He Atom in a Plane-Parallel Hollow Cathode He Plasma
Authors: Takiyama Ken , Sakai Hisashi , Motokuni Yamasaki Motokuni Yamasaki , Toshiatsu Oda Toshiatsu Oda
Published: October 2002

The density distribution of the singlet metastable He atom in a plane-parallel hollow cathode plasma was measured by the laser-induced fluorescence (LIF) method along with the absorption method, where the alignment of the atom excited by the linearly polarized laser light, the self-absorption of the fluorescence light by the 21S atom in the plasma and the effect of the atomic collisions as well as the electronic ones were considered. The alignment is demonstrated to play important roles in the determination of distribution of the metastable He atom density in a glow plasma with the electron density of (2.0±0.5)×1011cm-3, temperature of 1.3 eV and gas pressure of 0.7 Torr. Applicability of a simplified model used for the analysis of the present experiment was also discussed.
Characteristic Change Due to Polarization Fatigue of Sol-Gel Ferroelectric Pb(Zr0.4Ti0.6)O3Thin-Film Capacitors
Authors: Mihara Takashi , Paz de Araujo Hitoshi Watanabe
Published: October 2002

We studied the fatigue characteristics of sol-gel ferroelectric Pb(Zr0.4Ti0.6)O3(PZT) thin-film capacitors measuring hysteresis loops, time-zero current voltage characteristics and the dielectric constant after polarization switching. All evaluations were carried out on samples with certain switching cycles at the slow fatigue stage, logarithmic fatigue stage and saturated stage. Oxygen-deficient regions at the interfaces at both the top and bottom electrodes were formed after fatigue, as found by observing Auger electron spectroscopy (AES) depth profiles. Time-zero current-voltage (I-V) characteristics show that ohmic leakage current increased as the switching cycles increased during fatigue. This indicates that oxygen vacancies as donors arising during fatigue may compensate the lead vacancies as acceptors. The electric field dependence of Pr+-Pr-and that of the dielectric constant show that the motion of domains, which can move in the electric field near a coercive field, is suppressed after fatigue. We conclude that the oxygen vacancies suppress the domain motion and cause remanent polarization degradation. Since the biased-dielectric constant beyond 150 kV/cm showed no significant change after fatigue, it seems that no low-dielectric-constant regions adjacent to the electrode were generated during fatigue.
Pyroelectric Properties of La-Modified PbTiO3 Thin Films Prepared by Screen Printing
Authors: Tomoaki Futakuchi Tomoaki Futakuchi , Kastumi Tanino Kastumi Tanino
Published: October 2002

Pb1.05-
x

La

x

Ti1-
x
/4O3 (x=0–0.2) thin films were obtained by the screen printing method on Au bottom electrodes using Si(100) substrates at the annealing temperature of 600° C. The screen-printable pastes were synthesized from Pb–Ti–La complex alkoxide and abietic acid. The remanent polarization and coercive field of this thin film decreased with increasing La content. The maximum pyroelectric coefficient of 1.07×10-8 C/(cm2·K) was obtained at x=0.1 after poling. The diffusion of (Pb, La)TiO3 to the Au electrode and that to Pt electrodes was on the same level, therefore Au electrodes can be prepared by screen printing for practical use of these films at a low cost.
Crystallographic and Ferroelectric Properties Subjected to Two-Dimensional Stress in c-Axis-Oriented PbTiO3 Thin Films
Authors: Takashi Yamamoto Takashi Yamamoto , Hiroyuki Matsuoka Hiroyuki Matsuoka
Published: October 2002

Relationships among Curie point, spontaneous polarization, lattice parameters with consideration of spontaneous strain and piezoelectric charge coefficient were calculated as functions of two-dimensional stress in c-axis-oriented PbTiO3 thin films using a modified Devonshire form of the elastic Gibbs free energy. A compressive stress of approximately 500 MPa was predicted by a finite-element method analysis of the PbTiO3/Pt/Ti/SiO2/Si structure. A 90° C shift in the Curie point was estimated from the compressive stress, and shifts of other properties were accompanied with a shift of phase transition.
Dielectric and Piezoelectric Properties of Solid-Solution Ceramics BaPb[(Li1/4Nb3/4)Ti]O3
Authors: Masaru Yokosuka Masaru Yokosuka , Masakazu Marutake Masakazu Marutake
Published: October 2002

Investigations have been conducted on the ferroelectric ceramics of solid-solution BaPb[(Li1/4Nb3/4)Ti]O3, which can be alternately represented as a binary system of Ba(Li1/4Nb3/4)O3–PbTiO3. First, sinterability was examined with appropriate control of the firing temperature for various compositions. As a result, highly dense ceramics were obtained. Next, for these ceramic specimens, various measurements such as of lattice constants, dielectric constants, remanent polarization and electromechanical coupling coefficients were carried out as a function of composition as well as of temperature. Finally, dielectric and piezoelectric characteristics were evaluated.
Dielectric Properties of Pb(Fe1/2Nb1/2)O3-Based Ceramics
Authors: Noboru Ichinose Noboru Ichinose , Nobuyuki Kato Nobuyuki Kato
Published: October 2002

A broad peak above the Curie temperature of lead iron niobate Pb(Fe1/2Nb1/2)O3may be related to interfaces at the grain boundary. The origin of the anomalous second peak is not clear. The Sr-substituted lead iron niobate Pb1-xSrx(Fe1/2Nb1/2)O3ceramics were prepared for the purpose of investigating this anomaly. The dielectric anomaly and pyroelectric current in this system at around 200° C may be explained by the space-charge polarization in the interfaces of the grain boundary due to ionic valence changes from Fe3+to Fe2+in the B-site of the perovskite structure.
Microwave Dielectric Characteristics of Ilmenite-Type Titanates with High Q Values
Authors: Sohn Jeong-Ho , Inaguma Yoshiyuki , Yoon Sang-Ok , Itoh Mitsuru , Nakamura Tetsuro , Yoon Seok-Jin , Kim Hyun-Jai
Published: October 2002

The microwave dielectric characteristics of ilmenite titanates, M
2+TiO3 (where M
2+=Ni, Mg and Mn) and ( Mg0.95
M
0.05
2+)TiO3 (where M
2+= Ni, Mg, Co and Mn) series, have been investigated as a function of ionic radius of M
2+ and (Mg0.95
M
0.05
2+)2+ ions, respectively. The ilmenite titanates have high Q value and low dielectric constant due to the isolation of TiO6 octahedra by the M O6 octahedron layer and cation vacancy layer in comparison with the perovskite titanates. The existence of localized 3d electrons in Ni2+(3 d
8) and Mn2+(3 d
5) is concerned with the microwave dielectric properties of the M
2+ TiO3 series. The dielectric constant ε
r at 10 GHz of the (Mg0.95
M
0.05
2+)TiO3 series shows the minimum value around the average ionic radius of 0.721 Å, while the Q value shows a maximum, probably due to a local lattice distortion. The (Mg0.95Co0.05)TiO3 compound shows a maximum Q value of 23,000 at 10 GHz, dielectric constant of 16.8, and τ f of -54 ppm/K.
Diffraction Characteristics of Ferroelectric Liquid Crystal Grating
Authors: Seiji Fukushima Seiji Fukushima , Takashi Kurokawa Takashi Kurokawa
Published: October 2002

A ferroelectric liquid crystal grating is investigated. Diffraction behavior is
analyzed on the basis of a model where the birefringent grating generated in the
ferroelectric liquid crystal layer acts as an absorption/phase hybrid grating. Light
diffraction is observed by using an optically addressed spatial light modulator that
contains a photoconductive film and a ferroelectric liquid crystal. We find some
disagreement between the simulation and experimental results. The errors are found
to be caused by the incomplete bistability of the ferroelectric liquid crystal.
Cross-Linked Poled Polymer: Poling and Thermal Stability
Authors: Aramaki Shinji , Yuko Okamoto Yuko Okamoto , Tetsuo Murayama Tetsuo Murayama
Published: October 2002

Cross-linked poled polymers were studied with a methacrylate polymer containing
chromophores and epoxide groups as side chains. The cross-linking and poling processes
were monitored by electrooptic (EO) measurement. Contribution of molecular motions of
the chromophores was observed with low-frequency AC electric field. This contribution
decreased as the cross-linking reaction proceeded, and was found to be a good monitor
of poling with cross-linking. The resultant cross-linked poled polymers showed significant
improvement of thermal stability. The stability was studied by changing the concentrations
of cross-linking agents, curing temperatures, and type of cross-linking agent.
Dielectric Relaxation in Polyurea Thin Films Prepared by Vapor Deposition Polymerization
Authors: Wang Xian-Shan , Takahashi Yoshikazu , Masayuki Iijima Masayuki Iijima , Eiichi Fukada Eiichi Fukada
Published: October 2002

Polyurea thin films with the thickness of 500 nm were prepared by the vapor
deposition of 4,4′-diamino diphenylmethane (MDA) and 4,4′-diphenylmethane
diisocyanate (MDI) on a polyimide film substrate. The dielectric constants observed at
10 Hz for poled MDA-rich and MDI-rich films were about 10 and 3.5, respectively,
and almost independent of temperature up to 200°C. The dielectric constant at
10 Hz for a poled balanced film was 4 at room temperature and increased with increasing
temperature. A large dielectric relaxation was observed for the poled balanced film
at the temperature range from 152 to 192°C and the frequency range from 10-2 to
102 Hz. The estimated relaxation strength was about 700. It was presumed that
polar domains consisting of about 20 monomers were formed by the poling process,
in which urea bonds were aligned in parallel and linked by hydrogen bonds.
Hall Coefficient Measurement of Pyrolytic Polyimide Film Prepared Using Langmuir-Blodgett Method
Authors: Takenaga Mitsuru , Abdulla Aniwar , Kasai Akinari , Akatsuka Takahisa , Tanaka Hideaki
Published: October 2002

Hall effect measurements of pyrolytic Langmuir-Blodgett films based on a biphenyl-type
polyimide have been done using a double frequency method. The Hall coefficient had a
negative sign over the measuring temperature range; an electron density of 1021 cm-3
and a Hall mobility of around 0.5 cm2(Vs)-1 could be estimated on the
assumption of a one-carrier conduction. The Hall mobility is characterized by a single activated process with 5.4 meV.
Effect of Isothermal Annealing on Crystallization Mechanism of Amorphous Ni65Cr16P19 Metallic Alloys
Authors: Kouji Maeda Kouji Maeda , Tetsuo Ikari Tetsuo Ikari , Yoshito Akashi Yoshito Akashi , Koji Futagami Koji Futagami
Published: October 2002

Crystallization behavior of amorphous
Ni65Cr16P19 metallic
alloy during the isothermal annealing process from 617 K to 648 K
was studied using differential scanning thermal analysis and X-ray
diffraction analysis. Two crystallization peaks are observed.
The activation energies E
A for the crystallization
are determined
to be 403 kJ/mol and 306 kJ/mol for the first and the second peak,
respectively. Ni crystals precipitate in the first peak by a
two-dimensional crystallization mechanism with a constant nucleation
rate, and stable Ni3P crystallizes in the second peak. With the
use of the Avrami index, the activation energy for nucleation of
the Ni crystal is determined to be 470 kJ/mol.
Sputtering Behavior of Boron Using Electron Cyclotron Resonance Plasma
Authors: Yoshifumi Ito Yoshifumi Ito , Shunichi Kuriki Shunichi Kuriki , Masahiro Saidoh Masahiro Saidoh , Masahiro Nishikawa Masahiro Nishikawa
Published: October 2002

Boron sputtering by plasma ions is investigated using electron cyclotron resonance (ECR) discharge of neon gas. The temperature of boron on an electrode during the discharge becomes high enough that the resistance of boron is sufficiently small in comparison with that of the plasma sheath in the application of negative voltage V. Ion current flowing from the plasma and the line emission from the sputtered boron are measured as a function ofVunder conditions of microwave input power 200–500 W and the neon gas pressure 1–10 mTorr. The sputtering yield at ion energyE=3 keV is about one order of magnitude larger than that atE=0.5 keV. Boron thin films are prepared by the sputtering method in the case ofV=-2 kV. The deposition rate normalized by the ion current is about 100 Å/s/A measured at a distance of about 2 cm from the boron surface.
Dielectric Breakdown and Molecular Orientation of Poly( 4,4′-Oxydiphenylene Pyromellitimide)
Authors: Iida Kazuo , Shuhei Nakamura Shuhei Nakamura , Goro Sawa Goro Sawa
Published: October 2002

The electrical breakdown of polyimide (PI) thin films was investigated in the thickness range 0.8–2 µ m and in the temperature range -100–200° C, by taking advantage of self-healing. Two kinds of PI films were formed by vapor deposition polymerization (VDP) and coating of polyamic acid precursor in solution, VDP and S films, respectively. Breakdown characteristics of the films in the micron thickness range can be divided into two temperature regions. In the high-temperature region, the thermal process is operative and in the low-temperature region, the avalanche process seems to be predominant probable as compared with the thermal process. The breakdown characteristics were compared between VDP and S films. The results were explained with reference to the infrared reflection absorption spectroscopy of PI which indicates the crystallization and the molecular orientation of VDP film.
Electrooptical Properties of Poly(vinyl alcohol)/Liquid Crystal Composite Films with Added Photocured Polymers
Authors: Hiroshi Ono Hiroshi Ono , Nobuhiro Kawatsuki Nobuhiro Kawatsuki
Published: October 2002

Electrooptical properties were studied on a new type of polymer/liquid crystal (LC) composite film composed
of a poly(vinyl alcohol) (PVA), LC, and a photocured polymer. The composite films were prepared by casting the PVA/LC
emulsion with a mixture of benzylmethacrylate (BzMA) with perfluorooctylethylacrylate (FA-108) followed by
photocuring, resulting in a low driving voltage of 19 V
r
m
s
, a rapid turn-on time of 0.2 ms, and a rapid
turn-off time of 11 ms. The results cannot be entirely explained by the change in droplet shape and size. It was
suggested that photocurable monomers polymerized at the interface which caused change in the boundary condition
between PVA and the LC.
Acoustic Imaging of Plate Thickness and Sound Velocity during Tensile Testing at Low Temperature
Authors: Sato Harumichi , Kolosov Oleg V. , Nagata Yoshihiko , Koda Toshio , Yamanaka Kazushi
Published: October 2002

In many procedures important in engineering and science, such as plastic working, tensile, bending, creep and
fatigue tests, both the geometrical shape and material properties of objects change simultaneously. Therefore,
simultaneous measurement of these quantities has been sought. In this paper we present a novel method for simultaneous
imaging of the thickness of and sound velocity in a plate. After evaluating the accuracy of this method in a
low-temperature acoustic microscope, it was applied to a stainless steel plate that underwent the stress-induced
martensitic transformation, and thickness and sound velocity images around a notch in the plate were obtained. Since
the thickness and velocity images differ slightly, the possibility of independent but simultaneous imaging of plate
thickness and sound velocity was confirmed.
Sénarmont's Compensator for Entire Visible Light Region
Authors: Yunoki Akiko , Ichirou Shima Ichirou Shima , Ryuichi Shintani Ryuichi Shintani
Published: October 2002

An application study of the composite quarter-wave plate was carried out for the Sénarmont's compensator
method. The composite quarter-wave plate transforms linearly polarized light to a polarized state in a manner similar
to that of the quarter-wave plate, thus it could also be used for Sénarmont's compensator. Using this method,
retardation of a phase plate can be measured for the entire visible light region.
Anisotropic Dielectric Constants of Bi2Sr2(Ca1-xYx)Cu2O8+y (x=0.0, 0.6) Single Crystals in 0.5–5.0 eV Region
Authors: Yabuki Hideshi , Kataura Hiromichi , Takahashi Seigo , Ishii Hiroyoshi , Takaaki Hanyu Takaaki Hanyu , Shigeo Yamaguchi Shigeo Yamaguchi
Published: October 2002

We have measured the reflectance spectra of the (001) surface of single crystals of Bi2Sr2(Ca1-x
Y
x
)Cu2O8+y

(x=0.0, 0.6) with polarized light from 0.5 to 5.0 eV. We have successfully obtained the anisotropic dielectric
constants for a-, b- and c-axis directions separately with an original analysis using Fresnel's formula in which
the anisotropy of the crystal is considered. We report the method of analysis and the results. We discuss the
anisotropy of the dielectric constants and attempt to determine the origin of some absorption peaks. We compare
the spectra for two types of samples with different carrier concentrations.
Rotational, Vibrational and Translational Temperatures for Regular and Sequence Band Transitions in Waveguide CO2 Laser
Authors: Shimizu Fumiko O. , Osano Ryuji , Hirata Tadashi , Minoh Kenji Kawai
Published: October 2002

From small signal gain measurement for the regular and sequence band transitions
in the waveguide laser medium, the rotational temperature and the vibrational temperature
of the ν3 mode are determined and compared with those in the ordinary laser medium.
The rotational temperature is well defined and is apparently higher than the translational
temperature. The vibrational temperature shows saturation behavior as a function of
discharge current density and this is caused by electron deexcitation at higher vibrational levels.
Effect of Self-Induced Raman Scattering on Soliton Propagation-Comparison between Raman Response Function Method and Linear-Gain Approximation
Authors: Toru Mizunami Toru Mizunami , Keiji Takagi Keiji Takagi
Published: October 2002

Pulse delay due to self-induced Raman scattering is calculated for soliton widths
less than 100 fs. Two different methods to modify the nonlinear Schrödinger equation
are directly compared. The calculated delay time using the Raman response function is
smaller than that of linear-gain approximation, especially for short pulses. The ratio
of the result of the Raman response function method to that of linear-gain approximation
is 0.9 for 100-fs pulses and 0.2 for 20-fs pulses.
Photoconductivity of Ultrathin Zinc Oxide Films
Authors: Takahashi Yasutaka , Kanamori Masaaki , Kondoh Akiko , Hideki Minoura Hideki Minoura , Yutaka Ohya Yutaka Ohya
Published: October 2002

Electrical and photoelectrical properties of nondoped and doped zinc oxide films coated on glass plates by the
dip-coating method are investigated at room temperature in various ambient atmospheres. The dark conductivity
of the nondoped films exponentially decreased with decreasing film thickness while the conductivity under illumination of 350 nm light was almost constant at 100 S·cm-1 irrespective of the film thickness. Consequently thinner
films showed larger photoresponse than thicker films. This thickness dependence is explained by the variation of
ZnO particle size with the film thickness (fine particle model) and the additional effect of the Schottky barrier
generated between the film and gold electrodes.
Microstructure and Electrical Properties of Tantalum Oxide Thin Film Prepared by Electron Cyclotron Resonance Plasma-Enhanced Chemical Vapor Deposition
Authors: Kim Il , Ahn Sung-Duck , Cho Bok-Won , Ahn Sung-Tae , Lee Jeong Yong , John S. Chun John S. Chun , Won-Jong Lee Won-Jong Lee
Published: October 2002

High-quality tantalum oxide thin film was prepared by electron cyclotron resonance
plasma-enhanced chemical vapor deposition (ECR PECVD) for high-density memory devices.
The tantalum oxide film deposited at 205°C showed excellent electrical properties:
E
bd= 4.4 MV/cm, ε (Ta2O5)=25 and J< 1×10-9 A/cm2
at 2.5 V. The deposited film was annealed at various temperatures in an oxygen ambient.
The microstructure and the composition of the annealed tantalum oxide film were examined
and they were related to the electrical properties of the film. The growth of the
interfacial silicon oxide layer was observed by using a high-resolution transmission
electron microscope (TEM) and its effects on the electrical properties of the dielectric
film were also studied. The electrical properties of the film could not be improved
by annealing in an oxygen ambient at high temperatures due to the crystallization of
the tantalum oxide film and the growth of the interfacial silicon oxide layer.
Parameter Dependence of Stable State of Densely Contact-Electrified Electrons on Thin Silicon Oxide
Authors: Fukano Yoshinobu , Uchihashi Takayuki , Okusako Takahiro , Chayahara Ayumi , Sugawara Yasuhiro , Yamanishi Yoshiki , Oasa Takahiko , Seizo Morita Seizo Morita
Published: October 2002

We investigated the time evolution of a stable state which appeared in the dissipation
of contact-electrified electrons. Here, four analytical quantities in the stable state,
i.e., initial (electrostatic) force F
0, critical force F
c, critical time
t
c at stable-unstable phase transition and time constant τ1 of the
stable state, were investigated with respect to parameters of measurement (measurement
voltage V
s and tip-sample distance Z) and contact electrification (contact voltage
V
c and contact time t
0). As a result, we found that measurement parameters
do not affect time evolution of the stable state, whereas contact electrification
parameters strongly affect it. Furthermore, we obtained the approximated expression
of the electrostatic force as a function of parameters on measurement and contact
electrification, and time after contact electrification.
Modified Mask for Annular Pupil Filtering
Authors: Hisashi Watanabe Hisashi Watanabe
Published: October 2002

A novel method to improve the resolution limit of optical lithography is proposed.
The method combines an annular filter in a pupil plane of the projection lens and an
appropriately modified mask. The annular pupil filter has two major advantages.
The annular pupil filter makes it possible to fabricate (1) high-resolution contact
hole with large depth-of-focus (DOF) and (2) high-resolution gratings with large DOF.
However, it has disadvantages in the light intensity reduction and in the limitation
of formable patterns. In order to solve these problems, modification of the mask pattern
layouts is investigated. The light intensity of a contact hole can be increased by
the addition of dummy patterns around the main pattern. With the modified mask combined
with an annular filter, 25% smaller contact holes and fine periodic structures can be
formed. The modified mask layouts for dynamic random access memory (DRAM) cell are
designed to demonstrate the possibility of application to LSI manufacturing.
Proposal of a Next-Generation Super Resolution Technique
Authors: Kamon Kazuya , Miyamoto Teruo , Myoi Yasuhito , Wakamiya Wataru , Tanaka Hitoshi Nagata
Published: October 2002

A super resolution technique has been developed in order to support next-generation devices. We found that the
super resolution technique was effective for smaller patterns but not for larger ones, leading to the restriction of
its applicability. In order to obtain wider applicability, we propose a new optical system which has been improved
and is applicable to all kinds of mask patterns. According to the proposed optical system, the mask pattern
produces a specific source shape preferable for the mask pattern itself. Then the mask pattern is illuminated by
this self-optimized illumination source. Thus optimal improvements can be obtained under the same illumination
conditions, even if conventional patterns and phase-shift patterns of spatial frequency modulation types and
diffracted amplitude modulation types are on the same photomask. Consequently, the super resolution technique
will be brought into full use by this optical system.
Sub-0.15 µm Pattern Replication Using a Low-Contrast X-Ray Mask
Authors: Kikuchi Yukiko , Nomura Hiroshi , Iwao Higashikawa Iwao Higashikawa , Yoshio Gomei Yoshio Gomei
Published: October 2002

Mask contrast optimization is essential for replicating sub-0.15-µ m patterns
with relatively large mask-to-wafer gaps, e.g., larger than 20 µ m,
which is strongly desired for industrial production. We have confirmed that decreasing
the mask contrast to around 4 is very effective for increasing the exposure latitude
for the grating patterns with pitch around 0.24 µ m, without deteriorating the
exposure quality of larger patterns. The obtained exposure latitude for 0.12 µ m
lines and spaces at the gap of 20 µ m was ±8.7% for ±10% replicated
line-width change. How the mask pattern bias affects the replicated pattern was checked
using the 0.24-µ m-pitch grating patterns. It was revealed that
the dependence of the absorber width bias on the replicated pattern width is weaker
than the linear correlation, as is suggested from the calculation of the Fresnel diffraction
feature. It seems that when applying the larger mask-to-wafer gap to resolve a given
pitch of grating patterns, the replicated pattern width becomes less sensitive to the line/space ratio on the mask.
Application of Proximity Effect Correction Using Pattern-Area Density to Patterning on a Heavy-Metal Substrate and the Cell-Projection Exposure
Authors: Fujino Takeshi , Maeda Hiroshi , Moriizumi Koichi , Takaaki Kato Takaaki Kato , Natsuro Tsubouchi Natsuro Tsubouchi
Published: October 2002

Proximity effect correction for electron beam (EB) direct writing is studied in this paper.
An iterative calculation of exposure-dose modulation by equalizing the deposited energy
of all figures requires an extremely long calculation time, especially in the case of
high EB acceleration voltage. Therefore it is not practical for the correction of LSI.
The correction method using pattern-area density, however, could realize the high-speed
proximity effect correction. In this paper, this method is first investigated from the
standpoint of the correction accuracy. Next, the applicability of this method to two
critical cases is examined. One is the patterning on a heavy-metal substrate, on which
backscattering yield of electrons is high. The other is the application to the cell-projection
exposure, in which it is impossible to modulate exposure dose inside the cell. Lastly,
the calculation time of the proximity effect correction is evaluated for 64 Mbit dynamic
random access memories (MbDRAMs).
Proximity Effect Correction for X-Ray Mask Fabrication
Authors: Kuriyama Youichi , Moriya Shigeru , Shingo Uchiyama Shingo Uchiyama , Nobuo Shimazu Nobuo Shimazu
Published: October 2002

Our conventional proximity effect correction program has been improved to fabricate
X-ray masks in a subtractive process. The improved program calculates a correction dose
for each exposure pattern, using an offset energy map. Two partitioning steps related
to delineation and mesh boundary are introduced to improve the correction accuracy.
The mesh size for calculating the offset energy map is determined to be 0.2 µ m at
30 kV to maintain the error in the dose calculation within 4%. Using this program,
0.2-µ m-level LSI patterns can be fabricated even at comparatively
low acceleration voltage of 30 kV.
Lateral Growth of Poly-Si Film by Excimer Laser and Its Thin Film Transistor Application
Authors: Choi Do-Hyun , Sadayuki Eiichi , Osamu Sugiura Osamu Sugiura , Masakiyo Matsumura Masakiyo Matsumura
Published: October 2002

Thin Si film on a SiO2membrane has been recrystallized by single-shot excimer laser. Since there is no substrate acting as a heat sink to the latent heat in the molten Si film, the heat flow can be reduced immensely and also controlled well to form a temperature gradient along the membrane, resulting in the lateral growth of large grains, more than 70 µ m in length and a few µ m in width. Two thin film transistors (TFTs) with the channels parallel and perpendicular to the grain boundary, were fabricated using the laterally grown poly-Si film. The parallel TFT showed the maximum field-effect mobilities of more than 600 cm2/Vs for electrons and about 300 cm2/Vs for holes.
Observation of Etching Reaction for Si/XeF2 System Using Second-Harmonic Generation
Authors: Haraichi Satoshi , Sasaki Fumio , Kobayashi Shunsuke , Masanori Komuro Masanori Komuro , Toshiro Tani Toshiro Tani
Published: October 2002

Observation of surface change with etching reaction for the Si(111)/XeF2 system
has been demonstrated using second-harmonic generation (SHG). Both of the p-polarized and
the s-polarized SHG outputs decay quickly with the spontaneous etching because of the
formation of a SiF

x

reaction layer. Fluorine atoms probably attack not
only dangling bonds but also back bonds in the time duration observed here. Surface
symmetry which is observed by rotating the polarization of the linearly polarized,
normally incident beam initially seemed to be 2×2. The symmetry is broken by 1–2-langmuir
exposure to XeF2 and recovered by ohmic heating to 800° C.
Atomic Sites of S on (NH4)2Sx-Treated GaAs(100) Surface
Authors: Yokoi Naoki , Taketani Masayuki , Hiroya Andoh Hiroya Andoh , Mikio Takai Mikio Takai
Published: October 2002

Locations of S atoms on (NH4)2S

x

-treated GaAs(100) surfaces annealed at
200°C and 400°C have been studied on atomic scale by X-ray
photoemission spectroscopy (XPS), scanning tunneling microscopy (STM) and medium-energy
ion scattering (MEIS) using blocking. XPS spectra showed that the growth of native oxide
layers on GaAs surfaces was suppressed after (NH4)2S

x

treatment
and that most S atoms were bonded to only As or Ga atoms depending on the annealing temperature.
STM observations revealed that S atoms on a GaAs(100) surface were reconstructed in a
periodic structure of 1×1 in the case of annealing at 200°C,
while 2×1 reconstruction was observed after annealing at 400°C.
The distance between the S adsorbed layer and the uppermost layer of GaAs(100) could
be estimated from the angle-resolved MEIS blocking spectra.
Mask Defect Inspection Method by Database Comparison with 0.25–0.35 µ m Sensitivity
Authors: Tojo Toru , Tabata Mitsuo , Yamashita Kyoji , Tsuchiya Hideo , Watanabe Toshiyuki , Itoh Chikara , Ono Akira , Inoue Hiromu , Okuda Kentaro , Yoshino Hisakazu
Published: October 2002

Photomasks used in the fabrication of ultra-LSI (ULSI) circuits must be inspected
for defects. For 256 Mbit dynamic random access read write memory (DRAM), it is necessary
to inspect defects as small as 0.15 µ m. Moreover, inspection of defects of
phase-shift masks is becoming an important task of an inspection system. This paper
describes an automated mask inspection system (MC-100) based on die-to-database comparison,
and a defect inspection method with 0.15 µ m sensitivity for edge and pindot defects.
System configuration and the defect inspection method are discussed in detail, including
the difficulties of defect detection in an attenuated phase-shift mask.
Fabrication of Superconducting Quantum Interference Device with Thin-Film Quantum Point Contacts
Authors: Abe Hiroya , Katuyoshi Hamasaki Katuyoshi Hamasaki , Takashi Ishiguro Takashi Ishiguro
Published: October 2002

We have fabricated dc-superconducting quantum interference devices (SQUIDs) with
all-thin-film point contacts (Nb–Nb nanoconstriction-NbN). The size of the nanoconstriction
may be smaller than the superconducting coherence length of bulk Nb. The quasiparticle
characteristic of the all-thin-film point contact can be explained using the Blonder,
Tinkham and Klapwijk (BTK) quasiparticle current which is applicable to the superconducting
quantum point contact. The flux noise of SQUID with 10 pH operated in a flux locked loop is
8 µΦ0/ Hz1/2 at 1 Hz, and 4 µΦ0/ Hz1/2 at frequencies
above 10 Hz is limited by the preamplifier.
Contributions of Silicon-Hydride Radicals to Hydrogenated Amorphous Silicon Film Formation in Windowless Photochemical Vapor Deposition System
Authors: Sawado Yoshinori , Akiyama Takeshi , Ueno Tomo , Kamisako Koichi , Koichi Kuroiwa Koichi Kuroiwa , Yasuo Tarui Yasuo Tarui
Published: October 2002

Hydrogenated amorphous silicon (a-Si:H) films are prepared using a windowless photochemical vapor deposition system. Vacuum ultraviolet light of 121.6 nm from hydrogen-helium mixture plasma is thought to decompose silane molecules into mainly SiH and SiH2 radicals. Contributions of these radicals to film growth result in growth rate dependence upon substrate temperature (T
s). The apparent sticking probability of both radicals is determined to be 0.84 at T
s=100° C and 0.68 at T
s=250° C, from the variation of step coverage as a function of T
s. Adjusting the substrate position close to the light source brings about an increase of incident SiH and SiH2 radicals through primary photolysis by 121.6 nm light, as well as decrease of gas-phase reactions, which allows us to control the Si–H2 bond density in the film. The effect of the Si–H2 bond in the film is also shown.
Raman Scattering Spectroscopy of 3C-SiC(111) Heteroepitaxial Films
Authors: Yamanaka Mitsugu , Ikoma Keiko , Ohtsuka Miyuki , Ishizawa Tomomi , Shichi Yushi
Published: October 2002

Raman scattering spectra of 3C-SiC films, grown heteroepitaxially on Si(111) substrates by chemical vapor deposition (CVD), were measured to obtain information on the relaxation mechanism of the internal stress of the 3C-SiC films. The internal stress is found to be relaxed by the formation of the voids at the interface between 3C-SiC film and Si substrate during the CVD process.