bluuebunny/crossref_metadata_2025 huggingface dataset:
Defeating Compensation in Wide Gap Semiconductors by Growing in H that is Removed by Low Temperature De-Ionizing Radiation
Authors: Vechten James A. Van , Zook J. David , Horning Robert D. , Goldenberg Barbara
Published: February 2005

We propose a general method to obtain high conductivity of either type in wide gap semiconductors where compensation normally limits conductivity of one or both types. We suggest that the successes of Amano et al. and of Nakamura et al. in obtaining more than 1018 cm-3 holes in GaN are particular examples of the general process that we propose.
Emission of Radiation Induced by Bombardment of Slow Electrons from a Clean (100) Surface of Tungsten
Authors: Tanaka Masatoshi , Wakasugi Hirohiko , Matsuzaki Taku , Koyu Ota Koyu Ota , Seiji Usami Seiji Usami
Published: February 2005

The mechanism of emission of radiation from a clean W (100) surface bombarded by electrons of about 1 keV has been studied. The radiation spectra in the range from 610 to 240 nm and their dependences on light polarization, observation angle, and incident electron energy have been systematically measured at room temperature. The experimental results are compared qualitatively with the calculation performed in the framework of classical electrodynamics. It is concluded that both transition radiation (or reflection radiation) and bremsstrahlung contribute to the observed radiation, and dominant mechanisms can be distinguished under selected conditions.
Surface Potential of Heat-Treated PI Langmuir-Blodgett Films Deposited on Metal Electrodes
Authors: Iwamoto Mitsumasa , Yoshihiro Yoneda Yoshihiro Yoneda , Atsushi Fukuda Atsushi Fukuda
Published: February 2005

The surface potential of polyimide (PI) Langmuir-Blodgett (LB) films deposited on base-Au or -Cr electrodes was measured in a box shielded from light while nitrogen gas flowed through the box. Potential differences across PI LB films before and after heat treatment (at 100°C) were measured as a function of the number of deposited layers. The surface potential observed after the heat treatment was independent of the time elapsed. It was found that the surface potentials obtained after heat treatment depend on the base-electrode materials and the number of deposited layers, possibly due to the displacement of electrons from base-Au and -Cr electrodes into as-deposited PI multilayers. Finally, we concluded that photogenerated carriers in PI LB films were conveyed along the electric field established by the electrons displaced into as-deposited PI LB films from base-Au or Cr electrodes.
Scanning Probe Microscopic Investigation of Epitaxially Grown C60 Film on MoS2
Authors: Manivannan Ayyakkannu , Hoshi Hajime , Nagahara Larry A. , Mori Yoshihisa , Maruyama Yusei , Kikuchi Koichi , Achiba Yohji , Akira Fujishima Akira Fujishima
Published: February 2005

C60 thin films have been fabricated on MoS2 surface by the molecular-beam epitaxy (MBE) and their monolayer coverages on this substrate have been investigated by scanning tunneling microscopy (STM) and atomic force microscopy (AFM). STM study indicates that the C60 molecules pack either in a square lattice with lattice parameter of 11±1 Å or a hexagonal close packed structure with lattice parameter of 10±1 Å. The AFM images show column like structures similar to the square lattice pattern of STM images. Both STM and AFM techniques have been used to make a comparative study of C60 film grown on MoS2. The substrate lattice has also been imaged together with C60 molecular contours by STM in order to determine the epitaxial nature of the film.
High-Sensitivity Infrared Characterization of Ultrathin SiO2 Film by Grazing Internal Reflection Method
Authors: Matsui Yuichi , Miyagawa Yasuo , Izumitani Junko , Masanori Okuyama Masanori Okuyama , Yoshihiro Hamakawa Yoshihiro Hamakawa
Published: February 2005

A new kind of high-sensitivity infrared spectroscopy for characterizing SiO2 ultrathin film of 2-10 nm thickness of metal-SiO2-Si structure has been developed by the grazing internal reflection (GIR) method. At a large incident angle of 80 degrees onto the metal-SiO2-Si interface having SiO2 film of 2 nm thickness, a very large absorption of about 90% has been obtained at around 1240 cm-1 corresponding to the Si-O-Si bond. The measured data including the incident-angle dependence agree well with the calculated values analyzed by Fresnel's formula. Moreover, slight absorptions of Si-H and Si-OH have easily been measured as a strong signal change of about 1-7%.
Influence of DC Electric Field on Optical Detection by Short-Gap Electrode Glow Discharge in DC Magnetic Field
Authors: Ueda Hiroyuki , Miyawaki Sawami , Iida Yukio , Morita Masanobu
Published: February 2005

In optical detection of a short-gap electrode glow discharge tube (PIG type), the influence of DC electric field on the optical detection sensitivity is discussed. The sensitivity decreases with increasing DC degree of ionization. This tendency is marked in the range from normal glow to abnormal glow.
Characteristics of Ag-Se/Ge-Se as a Recording Medium for X-Ray Holograms
Authors: Somemura Yoh , Akira Yoshikawa Akira Yoshikawa , Yasushi Utsugi Yasushi Utsugi
Published: February 2005

The characteristics of Ag-Se/Ge-Se are evaluated as a recording medium for soft X-ray holograms. An Ag-Se/Ge-Se film is feasible for real-time observation with high-resolution X-ray images because soft X-rays induce reflectance changes on this film without any additional processes after exposure. The variations in reflectance dependence on Ag-photodoping dispersion depth into chalcogenide film are analyzed by using multi-layer reflection. The trend of variations in reflectance changes greatly for a total thickness difference of only ±10 nm. The dispersion depth is dependent on the X-ray exposure dose. The refractive index of Ag-Se (Ag-photodoped Ge-Se) is estimated to be 2.95±0.05 at wavelengths ranging from 600 to 900 nm. The value of the diffraction efficiency is computed and also confirmed to be dependent on the exposure dose.
Analysis for Superposed-Laser Electron Acceleration: Scaling Law, Beam Quality and Diffraction Effect of Laser
Authors: Tetsuya Maruyama Tetsuya Maruyama , Shigeo Kawata Shigeo Kawata
Published: February 2005

A new electron acceleration mechanism of the superposed laser acceleration which was proposed in a paper [Jpn. J. Appl. Phys. 30 (1991) L1887] is reexamined by numerical analyses and analytical work in order to obtain a scaling law for this mechanism, and to check beam quality and the diffraction effect of laser. In this mechanism, electrons are accelerated by means of two superposed laser beams in which a longitudinal electric field is produced. The numerical analyses show that the acceleration gradient can be 1∼10 GeV/m or more depending on the laser parameter employed, when this mechanism is employed appropriately in an acceleration system. In this paper the following important results are obtained: 1) The scaling law is derived in the analytical work and it is numerically reproduced. 2) An electron beam should be collimated well in order to be accelerated well. 3) The diffraction effect of laser beams has a great influence on the electron acceleration. Under the influence of the diffraction, electrons may not be accelerated at all. Drift tubes which lead electrons to only the acceleration region may be required for effective acceleration.
Preparation of TiO2-SnO2 Solid Solution Film by Ion Beam Sputtering
Authors: Okamura Takeshi , Yoji Seki Yoji Seki , Nobukazu Sagawa Nobukazu Sagawa
Published: February 2005

Thin film of rutile-type TiO2-SnO2 solid solution was successfully prepared by reactive ion beam sputtering without postannealing. The crystallinity of the film was highly dependent on the temperature of the substrate. The (101)-oriented film with rutile structure was obtained at substrate temperatures higher than 300°C.
Low Angle Light Scattering Measurement Using Fourier Transform Lens
Authors: Kenji Kubota Kenji Kubota , Nobuhiro Kuwahara Nobuhiro Kuwahara
Published: February 2005

A simple and high-speed low-angle light scattering measurement system using a Fourier transform lens and photodiode array is described. This system is useful in tracing the time evolution of fluctuation with a low wave number in homogeneous materials. Great improvement in the signal-to-noise ratio of the scattered light intensity is obtained by integrating over the wide scattering volume. This system is used for the analysis of the dynamic process of spinodal decomposition.
Effective Combination of Stimulating Coils for Magnetic Heart Stimulation
Authors: Hosono Akihiko , Andoh Tomio , Goto Tsuneaki , Kawakami Tadashi , Okumura Fukuichiro , Takayama Kenichi , Takenaka Toshifumi , Ueno Shoogo , Masuhiro Yamaguchi Masuhiro Yamaguchi , Isao Yamamoto Isao Yamamoto
Published: February 2005

A combination of stimulating coils was proposed to improve the effect of a magnetic stimulus applied to cardiac muscle. Two flat cylindrical coils were arranged side by side with appropriate angles θ between their surfaces. Both the field calculation and the stimulation experiment of a dog heart indicated that the arrangements with θ=90°∼120° are effective in stimulating the entire volume of the heart. The discrepancies in stimulation effects between different arrangements of the coils were interpreted in terms of the total eddy currents passing through the heart.
New Efficient Treatment of Impact Ionization in Submicron Metal-Oxide-Semiconductor Field-Effect Transistors
Authors: Fukuda Koichi , Peifer Hermann-Josef , Meinerzhagen Bernd , Thoma Rainer , Engl Walter L.
Published: February 2005

Shockley's lucky electron model has been widely used for modeling impact ionization. Various nonlocal generalizations of this model have been proposed in order to model impact ionization more accurately for strongly inhomogeneous material and field conditions which exist, e.g., in n-channel metal-oxide-semiconductor field-effect transistors (MOSFETs). Recently it has been shown that the spatial distribution of impact ionization events resulting from the nonlocal variant is in close agreement with corresponding results derived from an advanced Monte Carlo model. However, the former lucky electron model fails to closely reflect the underlying microscopic processes and is based on the restrictive assumption that the electron trajectories are electrostatic field lines. In order to incorporate more microscopic features, an improved lucky electron modeling approach including ballistic and diffusive transport effects is proposed, which yields comparably favorable results if compared to Monte Carlo data.
Numerically Simulated and Experimentally Obtained X-Ray Section Topographs of a Spherical Strain Field in a Floating Zone Silicon Crystal
Authors: Okitsu Kouhei , Iida Satoshi , Sugita Yoshimitsu , Takeno Hiroshi , Kawata Yasuyoshi Yagou
Published: February 2005

An undoped floating zone (FZ) silicon crystal has been investigated by synchrotron X-radiation section topography with high-order reflections up to 14 14 0. Numerically simulated topographs based on the Takagi-Taupin equations were in good agreement with experimental distorted patterns when a spherical strain field was assumed in the crystal. The volume change of the lattice caused by the strain center was estimated to correspond to a sphere with a radius of 10 µm.
Reduction of Stress in GaAs with In-Doped GaAs Intermediate Layer Grown on Si Substrate by Metalorganic Chemical Vapor Deposition
Authors: Yamaichi Eiji , Onozawa Sachiko , Ueda Takashi , Chouho Yamagishi Chouho Yamagishi , Masahiro Akiyama Masahiro Akiyama
Published: February 2005

This paper is the first report on the In doping effect to control the stress in the GaAs layer on a Si substrate. The wafer bending of InGaAs on Si decreases as the In concentration increases. The wafer bending linearly changes with the growth temperature, in contrast to undoped GaAs on Si in which the wafer bending is not changed with the growth temperature. By inserting the In-doped layer as an intermediate layer between GaAs and the Si substrate, the stress and dislocation in the upper undoped GaAs layer are reduced. These results show the possibility of controlling the stress and the dislocation in the GaAs layer on Si.
Estimation of Electron Temperatures from I-V Characteristics of a Plasma Electrode of a Negative Ion Source
Authors: Wada Motoi , Sasao Hiroshi Tsuda
Published: February 2005

The electron temperature of a lithium plasma near the plasma electrode of a volume-production-type negative lithium ion source was estimated from the current-voltage characteristics of the plasma electrode. The estimated electron temperature was close to that measured using a Langmuir probe when the plasma electrode was biased to be more negative than the plasma potential.
A Method of Obtaining Ion Current Parameter Characterized by Plasma Ion-Sheath Growth with a Contaminated Asymmetric Cylindrical Double Probe
Authors: Daisuke Okano Daisuke Okano
Published: February 2005

An equation giving an ion current parameter characterized by the effective surface area of a clean or contaminated probe is proposed on the basis of a qualitative consideration of voltage-current characteristics of both a single and an asymmetric double probe. In order to determine the ion current parameter from the equation, only the data obtained by an asymmetric double probe with a clean or contaminated surface are necessary.
Preparation and Characterization of YBaCuO Superconducting Films by Low-Temperature Chemical Vapor Deposition Using β-Diketonate Complex and N2O
Authors: Zama Hideaki , Miyake Takayuki , Hattori Takeo , Shunri Oda Shunri Oda
Published: February 2005

Low-temperature growth of YBa2Cu3O
x
superconducting films by chemical vapor deposition (CVD) has been investigated using dipivaloylmetanato (DPM) chelates of Y, Ba and Cu as starting materials and N2O as an oxidizing agent. YBa2Cu3O
x
structure has been prepared at a substrate temperature (T
sub) of 530°C. Superconducting films with superconductive critical temperature (T
c_onset) of 87 K and zero-resistivity critical temperature (T
c_zero) of 15 K have been obtained at T
sub=610°C and T
c_onset=89 K, T
c_zero=83 K at T
sub=650°C. The relationship between surface morphology, chemical composition and superconductivity is discussed.
Magnetic Properties of Chemical Vapour Deposited Cobalt Dope Gamma Iron Oxide Thin Films
Authors: Dhara Sandip , Kotnala Ravinder Kumar , Alok Chandra Rastogi Alok Chandra Rastogi , Bijoy Kishore Das Bijoy Kishore Das
Published: February 2005

Magnetic properties of chemical vapour deposited (CVD) Fe3O4 and γ-Fe2O3 obtained by co-pyrolysis of ferric and cobaltus acetyl acetonate complexes are described. Saturation magnetization, remanent magnetization and coercivity value of 3.7 kG, 2.2 kG and 820 Oe respectively have been obtained for Co-γ Fe2O3 films. Chemically vapour deposited Co-Fe3O4 films are laterally inhomogeneous with only a fraction of Co2+ ions at octahedral sites (B sites) of spinnel ferrite and excess Co2+ ions distributed in the interstitial matrix. Oxidation conversion to γ-Fe2O3 phase at temperatures above 350°C lead to Co2+ ion diffusion to B sites with activation energy of 0.27 eV. Consequent increase in magneto-crystalline anisotropy results in considerable enhancement in coercivity.
Molecular Orientation in Vacuum-Deposited Poly(thiophene) Film Studied by Second-Harmonic Generation
Authors: Kurata Tetsuyuki , Fuchigami Hiroyuki , Koezuka Hiroshi , Yamamoto Takakazu , Fukuda Takashi
Published: February 2005

The molecular orientation of the vacuum-deposited polythiophene (PT) film has been studied by second-harmonic generation (SHG). The polythiophene main chain is preferably oriented to be perpendicular to the substrate normal. The chain tilt angle from the surface normal decreased with increasing substrate temperature during the vacuum deposition. These results are consistent with the reported electron diffraction results. It has been considered that the SHG originates from the modification of the electronic states of PT due to the interaction between PT and the glass substrate.
Nonresonant-Type Third-order Nonlinearity of (PbO, Nb2O5)-TiO2-TeO2 Glass Measured by Third-Harmonic Generation
Authors: Nasu Hiroyuki , Uchigaki Tomoyoshi , Kamiya Kanichi , Kanbara Hirohisa , Kubodera Ken'ichi
Published: February 2005

Nonresonant-type third-order nonlinearity of high refractive index PbO-TiO2-TeO2 and Nb2O5-TiO2-TeO2 glass has been evaluated by means of third-harmonic generation. The PbO-containing glass show higher χ(3) than Nb2O5-containing glass, and the largest χ(3) of 3.7×10-12 esu is obtained for 10 mol%PbO-10 mol%TiO2-80 mol%TeO2 and 25 mol%PbO-10 mol%TiO2-65 mol%TeO2 glass.
Molecular Process of Evaporation in Gas Atmosphere without Convection
Authors: Dohi Minoru , Sawai Shinya , Kato Manabu , Nobuhiko Wada Nobuhiko Wada
Published: February 2005

A proposed modified diffusion equation for the molecular process of evaporation of materials in the gas atmosphere without convection was solved, and the existence of a zone of maximum vapor density higher than the saturation near the evaporation source was found. Actual density distributions of Zn vapor in He gas atmosphere at various pressures were calculated to be sensitively dependent on the gas pressure and the shape of the evaporation source.
Hermetic Coatings on Fluoride Glass Fibers Using Cylindrical Magnetron Reactive Sputtering
Authors: Yu Zengqi , Collins George , Harbison Barry , Aggawal Ishwar , Reicher David , McNeil John
Published: February 2005

The hollow cathode cylindrical magnetron is demonstrated to be capable of depositing uniform coatings on heavy metal fluoride fibers while maintaining the fiber temperature below 150°C. Pure metal coatings were deposited at typically 3000 Å/min, while oxynitride coatings were deposited at roughly 300 Å/min. We also demonstrated the hermeticity of AlN coatings for periods of several hundred hours even when immersed in water.
Absorption Coefficient and Sensitivity of Positive and Negative Resists in the Vacuum Ultraviolet Region
Authors: Kudo Kazuhiro , Miyazaki Kenzo , Sakai Hirofumi , Iwabuchi Takashi , Mutoh Katsuhiko , Miyata Takeo , Tomiki Tetsuhiko
Published: February 2005

Absorption coefficients for the resist materials (polymethyl methacrylate (PMMA) and partially chloromethylated polystyrene (CMS-DU)) were obtained in the vacuum ultraviolet (VUV) region. Negative and positive resist characteristics were investigated using a coherent VUV radiation source (λ=110-150 nm) generated by two-photon resonant four-wave mixing in Cd vapor. A very low exposure energy of approximately 1 mJ/cm2 was realized by employing a very thin resist film and using VUV light from the high-absorption region of the resist materials.
In-Situ X-Ray Observation of Molecular Structure in Organic Thin Films during Evaporation Process by Total Reflection In-Plane X-Ray Diffractometer
Authors: Hayashi Kouichi , Ishida Kenji , Toshihisa Horiuchi Toshihisa Horiuchi , Kazumi Matsushige Kazumi Matsushige
Published: February 2005

The in-plane X-ray diffractometer equipped with a vacuum evaporation apparatus was newly developed utilizing the total reflection phenomenon. The measuring system was applied to conduct an in-situ observation of the crystal growth and structural changes in the n-C33H68 molecules during an evaporation process. The results revealed that a certain amount of molecules in the as-evaporated films orient their (010) planes parallel to the surface of the SiO2 substrate. Moreover, the integrated intensity of the 110 reflection showed variation in the thickness dependence, suggesting that the molecular orientation altered as the interaction between the substrate and the adsored molecules became weaker.
Medium-Energy Ion Scattering Analysis with 50 keV He+ by the Time-of-Flight Technique
Authors: Konomi Ichiro , Akira Kawano Akira Kawano , Tatsumi Hioki Tatsumi Hioki
Published: February 2005

A newly developed time-of-flight spectrometer for medium-energy ion scattering is presented. The system mainly consists of a 60 kV duoplasmatron ion source, a beam chopper and an annular microchannel plate. Time and depth resolutions are found to be 7.8 ns and 2.9 nm, respectively. The probing depth is limited by the multiple scattering effect and is estimated experimentally to be up to ∼20 nm for Au.
Model for Measurement of Tissue Oxygenated Blood Volume by the Dynamic Light Scattering Method
Authors: Kashima Susumu , Nishihara Minoru , Takehiko Kondo Takehiko Kondo , Toshihiko Ohsawa Toshihiko Ohsawa
Published: February 2005

A method for the theoretical estimation of the volume of oxygenated erythrocytes in small vessels in tissue, using the dynamic light scattering method for different wavelengths, has been obtained. The volume of erythrocytes in tissue can be obtained from the integrated intensity of the power spectrum of scattered light that can be expressed as a function of the optical properties of an erythrocyte. The number ratio of oxygenated erythrocytes in tissue can be obtained from a function of two integrated intensity of the power spectra for two wavelengths, an isosbestic and a nonisosbestic wavelength for oxygenated and deoxygenated erythrocytes. The theory was compared with an experimental tissue blood flow model system. The results show the possibility of measuring oxygenated blood volume and oxygenated blood flow in tissue simultaneously.
Analytical Method for Image Characteristics of Annular Illumination with a Spatial Filter in Optical Projection Lithography
Authors: Takeuchi Yoshinobu , Matsuo Seitaro , Emi Tamechika Emi Tamechika , Katsuhiro Harada Katsuhiro Harada
Published: February 2005

Annular illumination with a spatial filter, or SSBL (single-sideband optical lithography), has performance equivalent to phase shifting in optical column technology. This paper presents an analytical method for examining image deformation characteristics in optical projection systems including SSBL. We express image intensity as the sum of a symmetric and an antisymmetric component. Image deformation can be clearly observed by using the antisymmetric component. From the point of view of proximate interaction, we show that the real part of mutual intensity is useful in interpreting image deformations. Optical image deformations are unavoidable in the range of 0.2-0.3 µm at the KrF-line wavelength. We present a simplified correction method for mask data which reduces computational time.
A New Pupil Filter for Annular Illumination in Optical Lithography
Authors: Hiroshi Fukuda Hiroshi Fukuda , Ryoko Yamanaka Ryoko Yamanaka
Published: February 2005

Several super-resolution photolithography techniques are investigated. In annular illumination, both the resolution and depth of focus (DOF) are enhanced most effectively when 0.6<σ<0.7, whether or not contrast enhancement techniques, such as pupil filters or edge-enhancing phase-shift masks (PSMs), are used. Various contrast enhancement techniques are investigated from the viewpoint of spatial frequency characteristics, since flat characteristics are required for good mask-to-image fidelity. We propose a new high-spatial-frequency enhancing filter for annular illumination system which meets this requirement. We also optimize edge-enhancing PSMs for use with annular illumination. It is shown that both methods can improve the resolution/DOF characteristics while maintaining good mask-to-image fidelity. A practical resolution analysis shows that 0.2 (0.3) µm patterns can be delineated with a DOF of ±0.6 (±0.75) µm, if a KrF (i-line) stepper with an NA0.5 lens and high-contrast resist materials are used, with few restrictions on the pattern layout.
Design Optimization of Synchrotron Radiation Lithography Beamline for a Compact Storage Ring
Authors: Shimano Hiroki , Takashi Hifumi Takashi Hifumi , Yoshihiko Ozaki Yoshihiko Ozaki
Published: February 2005

We have developed a novel beamline for SR (synchrotron radiation) lithography using a compact storage ring. The beamline consists of two ellipsoidal focusing mirrors, collecting 34.9 mrad of the horizontal angle of the fan-shaped SR, which delivers X-rays of high intensity onto the wafer. Moreover, an X-ray stepper of Karl Süss, XRS-200, will be attached to the end of the beamline; it offers the exposure field of 25×25 mm2 in the atmospheric environment. An optical design was realized using a sophisticated method which combines a ray-tracing method with a nonlinear optimization method, the Davidon-Fletcher-Powel (DFP) method. This optimized optical design yielded excellent transmission of photon flux throughout the beamline. We will also discuss the spectral and the spatial uniformity of the illumination, and the quality of the printed image.
Microfabrication of X-Ray Absorber W Utilizing Al2O3 as an Etching Mask
Authors: Sugihara Shinji , Masamitsu Itoh Masamitsu Itoh , Yoshio Gomei Yoshio Gomei
Published: February 2005

Microfabrication of W X-ray absorber for X-ray masks was studied. The absorber patterns were fabricated by etching processes using double layer resists which consist of a top resist and second Al2O3 layers. The thickness of the top layer was 0.3 µm to relieve the effect of both forward and backward scattering in electron beam writing. The etching gases for W patterning were SF6 and CHF3. The selectivity between W and Al2O3 was more than 20 by properly adjusting the gas mixture ratio, pressure and etching power. The required thickness of the second Al2O3 layer was only 0.05 µm which could easily be etched using BCl3 gas. Nearly vertical 0.2 µm lines and spaces were fabricated for 0.5 µm thick W absorber.
Main-Field Stitching Accuracy Analysis in Electron Beam Writing Systems
Authors: Anze Hirohito , Tamamushi Shuichi , Nishimura Eiji , Yoji Ogawa Yoji Ogawa , Tadahiro Takigawa Tadahiro Takigawa
Published: February 2005

A new evaluation method for main-field positioning error for electron beam (E-Beam) writing systems has been developed. Main-field distortion caused by system-based main-field positioning error such as contamination charging, deflector calibration error, substrate height error and so on is the main factor impairing accuracy in E-Beam writing systems. Main-field distortion after elimination of deflection distortion is classified into four modes. The origin of main-field positioning error can be estimated by investigating the behavior of these four modes of main-field distortion. This method has been applied to the variable shaped beam (VSB), vector scanning, and continuously moving stage E-Beam system. Contamination charging problems in the final lens surface in opposition to substrate and problems in the deflector calibration method have been found. Main-field positioning error of the E-Beam system decreased from 0.1 µm to 0.04 µm after solving the above problems. The evaluation method for main-field positioning error has been proved to be very effective in accuracy improvement of E-Beam systems.
Error Analysis in Electron Beam Lithography System -Thermal Effects on Positioning Accuracy-
Authors: Ohta Hiroya , Matsuzaka Takashi , Saitou Norio , Kawasaki Katsuhiro , Nakamura Kazumitsu , Kohno Toshihiko , Hoga Morihisa
Published: February 2005

Thermal effects on positioning accuracy in an electron beam lithography system have been evaluated. In order to make 5X reticles for 0.3-µm ULSIs, positioning accuracy as small as 0.06 µm is required. Thermal effects are significant problems in achieving highly accurate reticle judging from positioning error analysis. In this study, internal thermal effects were investigated; these were (1) heating by electron beam illumination and (2) stage friction with step-and-repeat movement. As a result, the positioning error due to electron beam illumination is negligibly small compared with 0.06 µm and the stage temperature fluctuation must be controlled within 0.07°C to maintain a positioning error within 0.06 µm. Furthermore, internal thermal effects of the system could be fatal in next-generation electron beam lithography systems without improvement of materials and systems.
Thermal Characteristics of Si Mask for EB Cell Projection Lithography
Authors: NakayamA Yoshinori , Satoh Hidetoshi , Saitou Norio , Hirasawa Shigeki , Yanagid Takehiko , Todokoro Hideo
Published: February 2005

We evaluated the thermal characteristics of a single crystal Si mask for electron beam (EB) cell projection lithography by computer simulation. Due to the low thermal conductivity, the thermal characteristics of the Si mask are more critical than that of a conventional heavy metal mask. If the Si mask is assembled by the conventional method which thermal dispersion is due to only radiation, the temperature at the beam position rises drastically with the irradiation power of the EB. Moreover, the displacement caused by thermal expansion can not be ignored for a quarter-micron lithography. The Si mask assembly using thermally conductive adhesion and a new Si mask structure with ribs gives good thermal characteristics satisfying the necessary conditions for a high-throughput and highly accurate EB lithography.
Advances in Chemical Amplification Resist Systems
Authors: Hiroshi Ito Hiroshi Ito
Published: February 2005

The chemical amplification concept proposed in 1982 to boost resist sensitivities is now well accepted by the lithography community, which stems not only from high sensitivities that chemical amplification resist systems can offer but also from additional benefits of high contrasts and unexpectedly high resolution capabilities. The design flexibility and versatility that the use of acid as a catalytic species offers are another attractive feature of chemical amplification, giving rise to a birth of an entire family of advanced resist systems. Manufacture and prototype fabrication of DRAM's by deep UV lithography have been accomplished with use of chemical amplification resists. However, some process problems uniquely associated with chemical amplification resists have surfaced recently, which include their latent image instability due to their sensitivity toward minute amounts of air-borne contaminants.
This paper reviews recent advances made in our laboratory in the field of chemical amplification resist systems and discusses 1) influence of residual casting solvent on absorption of NMP by polymer films, 2) effects of polymer end groups on resist sensitivity, and 3) new imaging mechanisms based on acid-catalyzed dehydration.
Surface-Imaged Silicon Polymers for 193-nm Excimer Laser Lithography
Authors: Kunz Roderick R. , Horn Mark W. , Wallraff Greg M. , Bianconi Patricia A. , Miller Robert D. , Goodman Russell W. , Smith David A. , Eshelman Jon R. , Ginsberg Eric J.
Published: February 2005

A negative-tone surface-imaged resist process based upon the area-selective oxidation of silicon-backbone polymers, is described. A bromine-based plasma is the resist developer, where the oxidized polymer inhibits the bromine-initiated etching to yield a negative-tone image. Using either polysilanes or polysilynes, resist sensitivities in the range of 50 mJ/cm2 have been obtained and resolutions to 0.2 µm achieved. Photosensitizers can be added to further accelerate the photoxidation, resulting in sensitivities less than 20 mJ/cm2. The latent image formation is reciprocal with respect to fluence in the range 0.05 to 1.5 mJ/cm2 per pulse and with respect to repetition rate. The photooxidation contrast is one, whereas the bromine-based etch step can have a contrast as high as 5. In addition, the exposure, focus, and development latitudes have all been characterized and compared to other surface-imaged 193-nm resist systems. When high-ion-density plasma sources are used, throughput levels appropriate for single-wafer processing can be achieved.
Optimally Stable Electron Cyclotron Resonance Plasma Generation and Essential Points for Compact Plasma Source
Authors: Samukawa Seiji , Nakamura Tsuyoshi , Ishida Toshinori , Ishitani Akihiko
Published: February 2005

This study examines the strong dependence of electron cyclotron resonance (ECR) plasma generation on the microwave conditions and the magnetic field profiles in the ECR plasma. When an introduced microwave frequency oscillates and has a large ripple, the ECR plasma around the ECR region vibrates and regularly turns on and off. The microwave oscillation and the microwave ripple must be eliminated to prevent poor etching anisotropy. Moreover, the nonuniform plasma causes disturbed ion motions due to magnetohydrodynamic (MHD) plasma instability. It is found that uniform and high-density ECR plasma is generated by optimizing the waveguide, the location of the ECR region and the magnetic field profiles for precise ULSI patterning. Based on these results, we determine the essential features for realizing a compact ECR plasma source.
Suppression of Microloading Effect by Low-Temperature SiO2 Etching
Authors: Sato Masayuki , Takehara Daisuke , Uda Keichiro , Hara Keizo Sakiyama
Published: February 2005

The generation mechanism of the microloading effect in magnetron enhanced reactive ion etching (MERIE) and its suppression have been investigated. The suppression of damage to the substrate was achieved with fluorocarbon gases of high molecular weight in MERIE, however, strong microloading effect generation was observed. In this study, it was found that low-temperature etching is the most effective technique for reducing the microloading effect.
Chlorine-Based Smooth Reactive Ion Beam Etching of Indium-Containing III-V Compound Semiconductor
Authors: Yoshikawa Takashi , Kohmoto Sigeru , Anan Masami , Hamao Noboru , Baba Masakazu , Takado Norikazu , Sugimoto Yoshimasa , Sugimoto Mitsunori , Asakawa Kiyoshi
Published: February 2005

Very smooth and vertical etching of InP by Cl2 reactive ion beam etching has been achieved under high temperature (≈200°C), high ion energy (≈1 keV) and low Cl2 pressure (∼10-5 Torr). The roughness is estimated to be a few nm by scanning tunneling microscopy and no contamination except for Cl was observed by in situ Auger electron spectroscopy. Under these etching conditions, the etched depth is precisely controlled (σ=22 nm) by simply monitoring the electrode curtent of the ion accelerating grid. Other III-V compound semiconductors, such as GaAs, InGaAs, AlGaInP and InAlAs have also been etched smoothly and vertically. Multilayers of these materials, such as InP/InGaAsP, AlGaInP/GaInP, and InAlAs/InGaAs/InP have been etched without steps between the layers on the sidewalls.
Spatial Controllability of Periodic Ripple Structures Generated in Laser Etching of n-GaAs
Authors: Kumagai Hiroshi , Ezaki Mizunori , Obara Koichi Toyoda
Published: February 2005

Spatial controllability of periodic ripple structures was investigated in laser etching of n-GaAs. For single-beam etching and holographic etching with high ratios of average spacing of holographic grating to average spacing of ripple structures (Λh/Λh), ripple structures were observed. In particular, in p-polarization, spatial fluctuation was greater than that in s-polarization. This might occur because phase distortion cannot be eliminated by p-polarization beam irradiation. For holographic etching with small Λh/Λr ratios, ripple structures were changed into grating structures because these grating structures might be generated in phase with holographic gratings.
Role of an Electron Beam in the Modification of a GaAs Oxide Mask for in situ EB Lithography
Authors: Kawanishi Hidenori , Sugimoto Yoshimasa , Nobuyuki Tanaka Nobuyuki Tanaka , Tomonori Ishikawa Tomonori Ishikawa
Published: February 2005

The electron beam (EB)-induced modification of GaAs oxide for the in situ lithography process has been investigated. The oxide formed on an as-grown GaAs surface is irradiated with an electron beam at doses in the range of 1.5×1017 to 4×1019 electrons/cm2 at beam energies of 10-25 keV. Subsequent Cl2 gas exposure results in selective etching only in the irradiated area. EB-induced modification of the GaAs oxide is found to involve a partial removal of oxygen by in situ Auger measurements. The threshold dose for the etching depends on electron energy, whereas it is independent of the wafer temperature between 25 and 100°C during EB-irradiation. These results indicate that the modification is not a thermally activated process, but a direct interaction of the electron beam with the oxide.
Evaluation of Photoemitted Current from SiO2 Film on Silicon During Synchrotron Radiation Irradiation
Authors: Nara Yasuo , Moscheni Fabrice , Sugita Yoshihiro , Kei Horiuchi Kei Horiuchi , Takashi Ito Takashi Ito
Published: February 2005

Photoelectron current by an irradiation of broadband synchrotron radiation (SR) is evaluated experimentally and theoretically for silicon dioxide (SiO2) film on silicon. The SiO2 film is known to be evaporated during SR irradiation at elevated temperatures. It is found that the photoemitted current from SiO2 film on Si shows a characteristic change during SR-excited SiO2 evaporation. At the final stage of SiO2 evaporation, where the residual thickness decreases to less than 5 nm, the photoemitted current starts to decrease. By theoretical calculation, the decrease in photoemitted current at the end of SiO2 evaporation is attributed mainly to the decrease in the absorption of photons by O 2p electrons. It is shown that the photoelectron current is surface sensitive and the measurement of the current is a convenient approach for in-situ monitoring of the photoexcited surface reactions such as the end-point detection of SR-excited SiO2 etching.
Focused Ion Beam Assisted Etching of Quartz in XeF2 without Transmittance Reduction for Phase Shifting Mask Repair
Authors: Nakamura Hiroko , Haruki Komano Haruki Komano , Munehiro Ogasawara Munehiro Ogasawara
Published: February 2005

Focused ion beam (FIB) assisted etching of quartz by a Ga FIB and XeF2 gas was studied for the purpose of avoiding the transmittance reduction by a Ga FIB. Transmittance was above 99% with the existence of XeF2 to the extent that the etching yield was more than 1.7 times larger than that of sputtering. It was also found that postetching above 15 nm by a Ga FIB and XeF2 gas after the Ga ion implantation recovered the transmittance. These techniques will be applied to repairing phase shifting masks without transmittance reduction.
Novel Technique for Phase-Shifting-Mask Repair Using Focused-Ion-Beam Etch-Back Process
Authors: Hosono Kunihiro , Nagamura Yoshikazu , Kusunose Haruhiko , Yoshioka Nobuyuki , Yaichiro Watakabe Yaichiro Watakabe , Yoichi Akasaka Yoichi Akasaka
Published: February 2005

For the repair of phase-shifter (PS) defects with good topology and without optical deterioration, a new repair technique has been developed by using focused-ion-beam (FIB) etch-back and laser-explosion processes. This technique mainly consists of three steps: (1) leveling of defects by FIB-assisted chemical vapor deposition (CVD) or filling with spin-coated SOG film, (2) etch-back or/and exposure by Ga-FIB scanning with the detection of total secondary ions which inform the end point of etch-back, and (3) elimination of Ga-implanted shifter (or quartz) layer by a Nd:YAG laser shot. The excess shifter (bump defect) was rubbed out by adjusting the milling rate of the FIB-CVD film and its confined defects. For the missing shifter (divot defect), the filling SOG was screened off within the defect by use of Ga-FIB milling (exposure) and development. The Ga-implanted layer was eliminated by the laser explosion and so the repaired area was recovered in transmittance from less than 50% up to 98%.
Reliability Test on One-Side-Recordable Magnetooptical Disks by Block Error Rate Measurement
Authors: Kawasaki Satoshi , Kenichi Ishizuka Kenichi Ishizuka , Shinichi Katsuda Shinichi Katsuda
Published: February 2005

One-sided magnetooptical (MO) disks of compact-disc size have been evaluated with respect to their reliability by block error rate (BLER) measurement. We have carried out high-temperature and high-humidity tests on our disks. No marked changes in mechanical properties or carrier-to-noise ratio (CNR) after accelerated tests were observed. However, C1 and C2 error count increases were observed. The C2 error count increase indicated increase on large media defect numbers. An Arrhenius plot on the maximum BLER values at elevated temperatures revealed an activation energy of approximately 0.9 eV. Estimated lifetimes of our disks at 31°C are more than 10 years, which means one-sided MO disks have lifetimes as long as two-sided disks, such as the 130-mm MO disk.
Direct Patterning of Spin-on Glass by Focused Ion Beam Irradiation
Authors: Koh Young-Bum , Goto Toshikazu , Yanagisawa Junichi , Gamo Kenji
Published: February 2005

Maskless patterning of spin-on glass (SOG) by focused ion beam (FIB) irradiation was investigated. Silanol-type SOG and 100 keV Ga FIB were employed as SOG material and ion beam, respectively. Heat treatment up to 850°C was also performed for comparison with ion beam irradiation effect. The spectra of Fourier transform infrared (FTIR) transmission and X-ray photoelectron spectroscopy (XPS) for SOG material showed that the crosslinking reaction was induced in SOG by ion beam irradiation, which is almost the same behavior as that induced by the heat treatment. As a result, SOG can be used as a negative-type ion beam resist and patterned masklessly by FIB irradiation. The threshold dose for the exposure of SOG film using FIB was about 1.5 µC/cm2 and almost 2-3 orders of magnitude less than that for an electron beam (EB). A 0.15-µm line-and-space (L/S) pattern was delineated by 100 keV Ga FIB irradiation.
Electrical Properties of Nanometer-Width Refractory Metal Lines Fabricated by Focused Ion Beam and Oxide Resists
Authors: Koshida Nobuyoshi , Watanuki Shinichi , Yoshida Kazuyoshi , Endo Kinju , Komuro Masanori , Atoda Nobufumi
Published: February 2005

Nanometer-width refractory metal lines are generated on Si substrates with high resolution by focused ion beam (FIB) exposure to MoO3 and WO3 inorganic resists, development and subsequent reduction in dry H2 gas. On the basis of some experiments for optimizing the process parameters, the electrical properties of fabricated fine Mo and W lines are evaluated in terms of the sheet resistance and its temperature dependence. A 40-nm-wide line did not show any signs of electromigration after the electrical measurements at current densities of 105 A/cm2 for several tens of minutes.
Improving the Uniformity of Poly-Si Films Using a New Excimer Laser Annealing Method for Giant-Microelectronics
Authors: Kuriyama Hiroyuki , Kuwahara Takashi , Ishida Satoshi , Nohda Tomoyuki , Sano Keiichi , Iwata Hiroshi , Noguchi Shigeru , Kiyama Seiichi , Tsuda Shinya , Nakano Shoichi , Osumi Masato , Kuwano Yukinori
Published: February 2005

Film uniformity is the main problem when applying laser-recrystallised poly-Si films to thin film transistors (TFTs) in giant micro electronics. However, this has been dramatically improved by a new excimer laser annealing method in which the solidification process of molten Si is controlled by low-temperature (≦400°C) substrate heating during excimer laser annealing. Poly-Si TFT fabricated around the laser irradiation overlap region exhibited a high field effect mobility uniformity of within ±8%.
Effect of Ion Doping Conditions on Electrical Conductivity of Amorphous Silicon Films and Its Application to Thin Film Transistors
Authors: Kakkad Ramesh , Takuya Shimano Takuya Shimano , Nobuki Ibaraki Nobuki Ibaraki
Published: February 2005

In this paper, we present a systematic study of the effect of phophorus ion doping conditions on electrical properties of amorphous silicon (a-Si) films. A large variation in electrical conductivity for various ion doped amorphous silicon films was found to be related to simultaneous implantation of hydrogen during the P ion doping process. The electrical conductivities of amorphous silicon films were qualitatively related to incorporation of hydrogen during the ion doping process, by measuring optical gaps of ion-doped amorphous silicon films and by simulating the ion doping process. By minimizing hydrogen incorporation during ion doping, a-Si films with conductivity greater than 10-2 S/cm were obtained, which is at least one order of magnitude higher than the best results in literature for ion doping of plasma-enhanced chemical vapor deposited (PECVD) amorphous silicon films. Reasonably good thin film transistor (TFT) characteristics were obtained for ion doping energy of 10 keV (mobility=0.68 cm2 V-1 s-1, threshold voltage=3.8 V), which deteriorated upon increase of the ion doping energy.
Discussion on the Mechanism of Reversible Phase Change Optical Recording
Authors: Okuda Masahiro , Matsushita Hiroyoshi Naito
Published: February 2005

In stoichiometric GeTe-Sb2Te3 films, reversible phase change optical recording materials, Sb addition is used widely in order to improve the crystallization speed, the data retention time and the stability of cyclic operation, but its mechanism is not clear. V-VI compounds (GeTe, SnTe) are well known as compounds in which the ferroelectric structural phase transition occurs. The dielectric constant ε0 changes largely due to a change in the short-range order of weakly bound nearest neighbors in the crystal to more strongly bound nearest neighbors in the amorphous phase. Therefore, it is necessary to discuss the effect of Sb addition in the stoichiometric GeTe-Sb2Te3 composition upon the thermal stabilities, the dynamic properties of crystallization and the dielectric constant change Δε0 based on the amorphous-to-crystalline phase transition.
Fabrication of Glass Stamper for Injection Molding
Authors: Kondo Tetsuya , Kei Murata Kei Murata , Takayuki Onizawa Takayuki Onizawa
Published: February 2005

We have studied the fabrication process of a glass stamper for injection molding. Quartz was the optimum material because of its excellent heat-cycle resistance. Applying a photoresist for image reversal allowed the formation of a protrudent signal pit with 0.25-µm width. Reactive ion etching (RIE) using CHF3 gas enabled the quartz surface to be etched with small roughness. In the injection molding process, pits were precisely replicated from the glass stamper.
High-Power, 790 nm, Eight-Beam AlGaAs Laser Array with a Monitoring Photodiode
Authors: Minakuchi Kimihide , Bessho Yasuyuki , Inoue Yasuaki , Komeda Koji , Tabuchi Norio , Tominaga Koji , Tajiri Atsushi , Keiichi Yodoshi Keiichi Yodoshi , Takao Yamaguchi Takao Yamaguchi
Published: February 2005

A high-power, 790 nm, eight-beam individually addressable AlGaAs laser array on 50 µm centers with a monitoring photodiode has been developed for high-speed data transfer in optical memory systems. The maximum output power of each element is over 80 mW. When eight elements are simultaneously operated at 20 mW in APC (Automatic Power Control) mode using the one-beam monitoring control, the total light output variation is less than 7% at a heatsink temperature between 10 and 50°C.
Second-Harmonic Generation Green Laser for Higher-Density Optical Disks
Authors: Michio Oka Michio Oka , Shigeo Kubota Shigeo Kubota
Published: February 2005

A laser-diode-pumped intracavity frequency-doubled Nd:YAG laser (SHG green laser) is an excellent light source for reading out higher-density optical disks because of its shot-noise-limited output and diffraction-limited beam quality. Scaling of the green laser using a bundle of fibers was successfully demonstrated to obtain more than 1 W of output power. By using the high-power green laser, generation of continuous-wave fourth-harmonic ultra-violet light for future ultrahigh-density optical memory was also demonstrated.
Superresolution of Optical Disks Using a Small Aperture
Authors: Atsushi Fukumoto Atsushi Fukumoto , Shigeo Kubota Shigeo Kubota
Published: February 2005

We realized magnetically induced super resolution (MSR) using magneto-optical (MO) disks with a thermally formed aperture. The aperture size and position affect the spatial frequency response of the readout signal. Using the principle of superresolution in laser scanning microscopy, we analyze the optical transfer function (OTF) for various apertures. Applying the analysis to MSR readout, OTF of MSR is calculated using scalar diffraction theory. The calculated results agree well with experimental values.