bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical Head with Annular Phase-Shifting Apodizer
Authors: Ando Hideo , Tsuneshi Yokota Tsuneshi Yokota , Koki Tanoue Koki Tanoue
Published: February 2005

An optical head with an annular phase-shifting apodizer was experimentally developed, and was found to have a high readout resolution and low readout signal error rate, permitting higher recording densities for the optical disk system. This apodizing head was confirmed experimentally and theoretically to have large tolerance for head defocusing and ample allowance for disk thickness variation, compared to conventional optical heads.
Optical Recording at 2.4 Gbit/in2 Using a Frequency Doubled Diode Laser
Authors: J. E. Hurst Jr. and W. J. Kozlovsky J. E. Hurst Jr. and W. J. Kozlovsky
Published: February 2005

Optical recording at 2.4 Gbit/in2 has been demonstrated at both 488 nm (argon-ion laser) and at 429 nm (doubled diode laser) using TbFeCo and CoPt multilayers on flat glass media with a soft sampled servo tracking system. The data was written using pulse width modulation (PWM), 2/3 (1, 7) run length limited (RLL) encoding, and detection accomplished using a dual clock channel. Edge shifts of 3.5% of the timing window and jitters of 7% of the timing window were observed. At a data rate of 2 MBytes/s and with data written on adjacent tracks, a bit error rate of 10-5 with noise margins of 10 dB and 8.5 dB were measured at 488 nm and 429 nm, respectively.
A High-Density Phase-Change Optical Disk System Possessing Read/Write Compatibility with 90 mm Magneto-Optical Disks
Authors: Ichinose Makoto , Ishida Takashi , Takagi Yuji , Ito Motoshi , Ohara Shunji , Satoh Isao , Okazaki Yukinori , Imanaka Ryoichi
Published: February 2005

High-density recording characteristics of phase-change optical disks were studied using 2-7 pulse-position-modulation (ppm) in-groove recording. Carrier-to-noise-ratio (CNR) was over 50 dB at a mark length of 0.60 µm and the crosstalk at the track pitch of 1.10 µm was less than -30 dB. In addition, a 256 MB 90 mm overwritable PC optical disk system having read/write compatibility with the ISO 128 MB MO disk has been developed based on the acquired results. The drive is based on the 90 mm MO drive at a wavelength of 780 nm and NA of 0.53. The user capacity of 256 MB was achieved using a mark length of 0.63 µm, track pitch of 1.25 µm, 2-7 ppm in-groove recording, and MCAV with 10 zones. The number of sectors per track was varied from 31 to 49.
Prerecorded Signal Characteristics of High-Density Optical Disks
Authors: Kubo Masae , Harada Shigenobu , Takeshima Hideharu , Kobayashi Toshihiro , Takeshi Ohmori Takeshi Ohmori , Yoshimitsu Kobayashi Yoshimitsu Kobayashi
Published: February 2005

For the high-density optical disk, the performance of prerecorded and servo signals is important. We studied the prerecorded and servo signals on 130 mm rewritable and partially read-only disks of 655 MB per side, as a function of pit and groove shape. Based on this study, the most suitable pit and groove shape for obtaining good performance in the prerecorded and servo signals was found.
Precise Mark Shape Control in Mark Length Recording on Magnetooptical Disk
Authors: Ide Hiroshi , Toda Takeshi , Kirino Fumiyoshi , Maeda Takeshi , Kugiya Fumio , Mita Seiichi , Shigematsu Kazuo
Published: February 2005

To realize higher storage density on a magnetooptical disk, we proposed the write control method, which controls shapes of recorded mark in marks length recording. In this paper, the analysis of this write control method is reported. Based on the model of the recording process, we discuss the necessary condition of the recording pulse waveform for the control of the recorded mark shape on magnetooptical recording media which have large heat conductivity. The write control method is examined under the condition of 880 Mb/in2 recording density. The precise control of the recording mark shape is confirmed through the experiment. From the result of the computer simulation, it is proven that this method satisfies the necessary condition, which clarified the effect of this method theoretically.
Erase Process and Tolerance Study of Pulse Erasure in a High-Density Magneto-Optical Disk Drive
Authors: Kwor Wai W. Wang
Published: February 2005

The pulse erasure process in a TbFeCo magneto-optical medium is investigated. The effects of erase power, linear velocity, and erase/write delay on the pulse erasure residue are reported.
A New Tracking Method for Helical Scanning Optical Tape Recorder
Authors: Narahara Tatsuya , Kamatani Yoshiteru , Nakao Takashi , Satoshi Kumai Satoshi Kumai , Tadashi Ozue Tadashi Ozue
Published: February 2005

Using a new tracking method, high track density recording on an optical tape has been achieved with a helical-scanning optical tape recorder (HS-OTR). In this recorder, the tape is wrapped around a drum, which has a high numerical-aperture objective lens of 0.50, without contact with the rotating part by means of air pressure. In the optical design, moving parts, both focus and tracking actuators, light source and reproducing optics are placed outside the rotary drum. With this system, a high carrier-to-noise-ratio of 51 dB for 1 µm mark length has been achieved. Using the tracking method, which includes a starting point servo loop, written marks have been reproduced track by track with a 2 µm pitch.
Video-on-Demand System Using Optical Mass Storage System
Authors: Mori Tatsuo , Nishimura Kazutoshi , Ishibashi Hirotaka Nakano
Published: February 2005

Digital video-on-demand systems based on high-speed digital networks and video compression techniques have been proposed recently. One serious problem for these systems is achieving mass storage with quick access. In this paper we propose a video storage hierarchy of magnetic disks and an optical mass storage system (MSS). To solve the problems that occur when optical mass storage systems are used in video-on-demand services, we have proposed techniques such as quick-start and linking of playback, multiple readout, and visual search in a storage hierarchy with magnetic disks. A trial system has verified the feasibility of these new techniques. The average response time for “quick-start and linking” is less than one second. Another technical problem is the implementation of visual search functions such as fast forward and fast reverse together with multiple access. Average switchover time between visual search functions is also less than one second. In this trial system, which uses the JPEG encoding algorithm, we proposed and verified a new method for synchronizing fixed bit-rate audio and variable bit-rate video.
Write/Erase Cyclability of TbFeCo for Mark-Edge Recording
Authors: Yoshihiro Masafumi , Shimazaki Katsusuke , Ohta Norio , Toda Tsuyoshi , Awano Hiroyuki , Ojima Masahiro
Published: February 2005

Write/erase cyclability for mark-edge recording is studied using rare-earth element[RE]-rich TbFeCo media. Mark-edge jitter for the (1-7) random pattern is small enough even after millions of cycles of data writing and erasing.
Optical Pickup for Compact Disc Player Using Computer-Generated Hologram and Reflection-Type Grating
Authors: Chul Woo Lee Chul Woo Lee , Chong Sam Chung Chong Sam Chung
Published: February 2005

A functional prototype of an optical pickup using a Computer-generated hologram (CGH) has been developed for compact disc player (CDP). A 780 nm-wavelength laser diode, a finite conjugated objective lens, and a reflection-type grating are used in the pickup. The fringe pattern of the CGH functions as cylindrical and negative power lenses, and produces astigmatism for focusing signal to the objective lens. Also, the effect of chromatic aberration of the CGH on the pickup is estimated.
Performance Characteristics of Frequency-Doubled Nd:YAG Laser Used in Digital Video Disk Recorder
Authors: Choi B. S. , Chee J. K. , Hwang Y. M. , Jang H. Y. , Y. D. Kwon Y. D. Kwon , S. H. Lee S. H. Lee
Published: February 2005

A compact and green laser is developed using a diode-pumped, frequency-doubled Nd:YAG laser. Single-mode operation is achieved with the combination of a Brewster plate and a type-II phase-matched KTiOPO4 (KTP) crystal. With the feedback control of green laser output, A stable operation longer than 10 hours with a relative intensity noise of -130 dB/Hz was obtained. This green laser source was successfully used in a digital video disk recording.
Profile Tail Effects on Low Temperature Operation of Silicon Bipolar Transistors
Authors: Alain Chantre Alain Chantre , Alain Nouailhat Alain Nouailhat
Published: February 2005

We present a detailed investigation, in the temperature range between 340 K and 80 K, of the static properties of advanced single-polysilicon bipolar transistors covering a wide range of base doping concentrations. Special attention is paid to the temperature dependence of the intrinsic current gain β. We find that the rate of degradation of β with temperature below about 150 K is nearly independent of the peak or average base doping concentration. Our data do not match the conventional theory of the temperature dependence of β using available band-gap narrowing models for p-type silicon. We show that these, as well as other recently published related results, can be understood considering the importance of profile tail regions in controlling the operation of bipolar transistors at low temperature.
Transient Response of Junction Temperature in Power Heterojunction Bipolar Transistors
Authors: William Liu William Liu
Published: February 2005

We present a theoretical analysis for calculating the transient device junction temperature as a function of position and time upon a stepwise increase of power dissipation. The derivation applies in particular to multifinger heterojunction bipolar transistors designed for microwave power application. It is determined that for a typical substrate thickness of 100 µm, the rise time of the junction temperature is roughly 3×10-7 s.
Micro-Temperature Measurements on Semiconductor Laser Mirrors by Reflectance Modulation: A Newly Developed Technique for Laser Characterization
Authors: Peter-Wolfgang Epperlein Peter-Wolfgang Epperlein
Published: February 2005

Thermoreflectance measurements performed for the first time on laser diode mirrors have supplied a vast amount of novel information. Heating efficiency has been found to depend sensitively on the mirror treatment, the mirror structure design, the geometry of a deposited heat spreader, the type of coupling of the laser to a heat sink, the number of active quantum wells, the type of cladding layer and the strength of lattice disorder at the mirror surfaces. Degradation processes have been observed in real time by continuously monitoring the mirror temperature. Dark line defects formed during laser operation exhibit a temperature gradually increasing with time. The mirrors suffer catastrophic optical damage within seconds after having reached a critical temperature. Temperature maps show a striking localized hot spot within the optical near-field pattern.
Estimation of Grown Layer Thickness by Cathodoluminescence Measurement
Authors: Kato Takamasa , Yoko Nakazawa Yoko Nakazawa , Takashi Matsumoto Takashi Matsumoto
Published: February 2005

We propose a new method for measuring the thickness of an epitaxially grown layer with a direct band gap. The beam voltage which gives the maximum cathodoluminescence intensity is related to the layer thickness under a constant beam power. The layer thickness in the range between 0.1 to 1 µm can be estimated without prior knowledge of material parameters such as diffusion length and absorption coefficient.
Linear and Nonlinear Optical Properties of 2-Methoxy-5-Nitrophenol Single Crystals
Authors: Nagasawa Yuko , Katoh Takayuki , Hidetaka Ninomiya Hidetaka Ninomiya , Yoshio Takeuchi Yoshio Takeuchi
Published: February 2005

The linear and nonlinear optical properties of 2-methoxy-5-nitrophenol (MNP) have been investigated. MNP crystals belong to the monoclinic system with space group P21. The optical axis Y was identical to the crystal axis b, and the dipole axis was found to be nearly parallel to these. The cut-off wavelength was 522 nm. The second-order nonlinear optical coefficient d
22 at 1064 nm was 46±7 pm/V.
Structure Analysis of Nylon6-Clay Hybrid by Spectral Reflectance of Laser-Plasma Soft X-Rays
Authors: Azuma Hirozumi , Akihiro Takeichi Akihiro Takeichi , Shoji Noda Shoji Noda
Published: February 2005

Structure analysis of nylon6-clay hybrid (NCH) was carried out by means of spectral reflectance of soft X-rays
between 8 and 17 nm wavelength from laser-produced plasma. Spectral reflectance composed of specular reflectance and Bragg reflectance was measured by a flat field XUV spectrometer equipped with a toroidal mirror. The
observed Bragg reflectance was very weak, but it suggested that NCH had a periodicity of about 13 nm. The calculated spectral reflectance, using a sea-and-island model (sea was nylon6 matrix and island was a multilayer whose unit consisted of a silicate layer (0.66 nm thick) and a nylon-6 layer (about 12 nm thick)) agreed with the observed spectral reflectance. The structural feature of NCH thus deduced was consistent with the TEM observation. The present results indicated the spectral reflectance of soft X-rays from laser-produced plasma to be a useful method for the structure analysis of a nanometer-scale composite which has rather poor periodicity.
Visualization of the CH Molecule by Exciting C2Σ+(v=1) State in Turbulent Flames by Planar Laser-Induced Fluorescence
Authors: Tsujishita Masahide , Masamichi Ipponmatsu Masamichi Ipponmatsu , Akira Hirano Akira Hirano
Published: February 2005

A novel visualization technique for the CH molecule has been demonstrated. The technique described in this paper is the CH visualization by exciting the C2Σ+ state which predissociates and gives the opportunity of semi-quantitative CH visualization at a significantly high pressure. The visualization methods have been developed by taking practical application into account, and the detection wavelength is made different from that of excitation in order to avoid the stray light problem. In addition, CH can be visualized by a single-shot laser, and this technique has been proven to be applicable for the analysis of nonstationary chemical reactions such as turbulent flames. Furthermore, the visualization results show good spatial resolution, sufficient signal level, and greatly improved image quality.
Low-Energy Electronic States Related to Contact Electrification of Pendant-Group Polymers: Photoemission and Contact Potential Difference Measurement
Authors: Yanagida Kazuhiko , Okimasa Okada Okimasa Okada , Kozo Oka Kozo Oka
Published: February 2005

Low-energy electronic states, 3-6 eV below the vacuum level, relevant to contact electrification of pendant-group polymers were investigated by means of photoemission and contact potential difference (CPD) measurements under atmospheric conditions. As a result, it was shown that the thresholds of photoemission of the polymers are related to their highest occupied molecular orbital (HOMO) levels derived from modified neglect of diatomic overlap (MNDO) molecular orbital calculation, and that the thresholds exist near the energy corresponding to their work function inferred from CPD measurement. Furthermore, it was found that the contact electrification of the polymers is related to their threshold of photoemission. These results are interpreted in terms of a molecular ion model proposed by Duke et al. [Phys. Rev. B 18 (1978) 5717].
Spectral Analysis of Light Emitted by Streamers and Gas Chromatography in Liquid Dielectrics
Authors: Abderrahmane BerouaL Abderrahmane BerouaL
Published: February 2005

Spectral analysis of the light emitted by streamers during their propagation in liquid dielectrics reveals the presence of the Hα line and C2 Swan bands as well as a continuum which corresponds to dissociation and fragmentation of liquid molecules and recombination of molecular fragments. Spectra of the emitted light vary according to polarity and streamer velocities. The more energetic the streamer, that is, the faster it is, the higher the characteristic lines emerging from the continuum. The above results confirm those obtained by gas chromatography conducted in a blend of mono- and dibenzyltoluene (M/DBT) and phenylxylylethane (PXE). Indeed, the latter shows the presence of decomposition products such as H2, CH4, C2H2, C2H4 and C2H6. However, hydrogen and acetylene are predominant. These gases may result from vaporization for slow bushlike streamers, whereas for fast filamentary ones the dominant mechanisms may be dissociation and ionization in the liquid phase.
Growth of GaInSb on Gd3Ga5O12 Substrate by Metalorganic Chemical Vapor Deposition
Authors: Totoki Machiko , Mizumoto Tetsuya , Toshio Fujisawa Toshio Fujisawa , Yoshiyuki Naito Yoshiyuki Naito
Published: February 2005

Metal-organic chemical vapor deposition of GaInSb on a Gd3Ga5O12 (GGG) substrate is reported. (111)-Oriented GaInSb thin layers are grown on both (111) and (100)GGG substrates. The lattice constant of the grown layer is dependent on the growth temperature and the flow rate as a function of the mixed ratio of the gas-phase group III components, but is independent of V/III ratio and total carrier gas flow rate. The surface morphology has been improved by lowering growth temperature, reducing total flow rate through bubbling cylinders and increasing gas-phase group III components. We obtained a smooth surface of GaInSb at a growth temperature of 450°C with a reduced total flow rate and a V/III ratio of between 0.5 and 0.7.
Characterization of GaAs-(001) Surface Photo-Oxide Formed by Visible-Light Irradiation
Authors: Tone Kiyoshi , Yuichi Ide Yuichi Ide , Masamichi Yamada Masamichi Yamada
Published: February 2005

The effects of visible-light irradiation (70-280 mW/cm2) on oxidation of a GaAs (001) surface under an oxygen atmosphere (3.6×101 and 8.6×104 Pa) were investigated by temperature programmed desorption and X-ray photoelectron spectroscopy (XPS). XPS showed that irradiation at an intensity of 140 mW/cm2 increased the amount of surface oxygen by about 15% over dark oxidation of the corresponding oxygen exposure. Under 540°C isothermal conditions, the oxide desorption rate was initially low, but reached its maximum level with a time delay, showing the existence of expanding voids in the oxide layer during desorption. Light irradiation, as well as higher oxygen exposure, decreased the initial desorption rate, and increased the time delay by up to 6.4 min. This is interpreted as indicating that irradiation reduces the density of the weak parts in the oxide layer through an increase in the oxide thickness.
Effect of Heating Probe on Reactively Sputtered TiO2 Film Growth
Authors: Shibata Akira , Okimura Kunio , Matubara Yukio Yamamoto
Published: February 2005

In this paper we propose a simple method to ionize sputtered neutral Ti and added oxygen gas, by inserting a heating probe into the plasma space. The effect of bias voltage applied to the heating probe on the crystalline structure and optical properties was investigated for the TiO2 films deposited by reactive sputtering using this method. In the films deposited with the heating probe applying positive bias voltage to the substrate, the rutile phase was grown on the Si(111) substrate at a low temperature, and this film showed better optical properties than the films prepared without bias voltage. These changes in crystalline and optical properties were attributed to the ionization and acceleration of Ti and oxygen particles.
Roughness Assessment of Polysilicon Using Power Spectral Density
Authors: Vatel Olivier , Dumas Philippe , Chollet Frederic , Salvan Franck , Elie André Elie André
Published: February 2005

Atomic force microscopy (AFM) has been used to investigate the surface morphology of polysilicon deposits grown under two different temperature conditions. We also present results obtained with scanning tunneling microscopy (STM) and transmission electron microscopy (TEM). Surface morphology data have been quantitatively analysed and compared using standard roughness criteria such as the root mean square of the surface roughness. Moreover, spatial frequency analysis of roughness power spectrum is used to determine characteristic dimensions in the surface plane.
New Type of Doppler Free Spectroscopy by Heterodyne Detection of Backward-Scattered Light from Velocity-Selected Atoms
Authors: Mitsui Takahisa , Hidetoshi Numata Hidetoshi Numata , Katsumi Sakurai Katsumi Sakurai
Published: February 2005

We demonstrated a new type of Doppler free spectroscopy by using optical heterodyne detection of the backward-scattered light from Rb atoms velocity-selected by a single-mode diode laser. The principle is based on the Doppler-shifted backward light scattering due to the number density inhomogeneity of velocity-selected atoms.
Ultrafine-Particle Beam Deposition II: Mechanism of Film Formation
Authors: Kizaki Yoshimi , Hiroshi Osada Hiroshi Osada , Hiroshi Aoki Hiroshi Aoki
Published: February 2005

A new handling technique of ultrafine particles, called “ultrafine-particle beam deposition,” was applied to the preparation of various films, such as of Ag, Au, Cu, Fe, Ni, Pt, Ta and W. The mechanism of deposition and coalescence of ultrafine particles is thought to be described by the diffusion process. The high surface activity of ultrafine particles was preserved in this handling technique, and the obtained films had low electric resistances close to those of corresponding bulk metals.
GaAs Surface Cleaning/Etching Using Plasma-Dissociated Cl Radical
Authors: Kohmoto Shigeru , Ide Yuichi , Yoshimasa Sugimoto Yoshimasa Sugimoto , Kiyoshi Asakawa Kiyoshi Asakawa
Published: February 2005

Cl radical etching (RE) of GaAs, a previously evaluated dry etching method with very low damage which is suitable for nanometer-scale fabrication, damage removal and surface cleaning, is investigated in comparison with Cl2 etching. At room temperature, etching conditions with a higher chiorine pressure of about 10-3 Torr provide no significant etching rate, whereas etching conditions at a lower chlorine pressure of (4±1)×10-5 Torr provide a moderately slow etching rate (40 Å/min) and precise control of etching depth, both of which are useful for shallow etching of nanometer-scale structures. Effective cleaning of GaAs native oxide and carbon contaminants by the Cl radicals is clearly demonstrated, but this cleaning does not occur when using Cl2 molecules. When the GaAs surface is not covered with such contaminants, both the Cl-RE and the Cl2 etching progress. The roughness of the Cl-radical-etched surface is as low as 50 Å after etching to a depth of 2640 Å. After heat treatment of the Cl-radical-etched sample at 400°C, an atomically ordered and stoichiometric GaAs surface is obtained.
A Comprehensive Study of Thin Rapid Thermal Oxide Films
Authors: Messaoud Abdellatif Yahia , Scheid Emmanuel , Sarrabayrouse Gérard , Claverie Alain , Martinez Augustin
Published: February 2005

The kinetics of silicon oxidation by rapid thermal processing has been studied in the 1060-1240°C temperature range. Particular attention has been paid to homogenization and optimization of heating as well as to the initial conditions, that is, for example, sample preparation and initial thickness measurements. A great effort has also been made to achieve accurate measurements of temperature and oxide thicknesses using ellipsometry and the associated computations associated to it. The values of the experimental oxide film thickness have been compared to simulated ones, using Han and Helms' model [J. Electrochem. Soc. 134 (1987) 1297]. A good fit was found and it was concluded that rapid thermal oxidation (RTO) kinetics does not show any particular characteristics in the 2-20 nm range for the lightly doped silicon (ρ>2×10-2 Ω·cm). Electrical measurements on RTO capacitors have been performed. Typically, electrical field breakdown of 15 MV/cm and a charge injected at breakdown (Q
bd) equal to 40 C cm-2 (J=1 A cm-2, A=1.6×10-4 cm2) were obtained for oxide thicknesses between 8 and 10 nm. These characteristics compare favorably with the best electrical properties reported in the literature using RTO. Hence, by enhancing temperature uniformity control and achieving process reproducibility, the RTO technique can become a promising candidate for submicron metal oxide semiconductor (MOS) technologies.
Freeze-Drying Process to Avoid Resist Pattern Collapse
Authors: Tanaka Toshihiko , Morigami Mitsuaki , Oizumi Hiroaki , Taro Ogawa Taro Ogawa
Published: February 2005

Freeze-drying, which is a surface-tension-free process, was applied in resist processing to avoid resist pattern collapse and the mechanism was investigated. The freeze-drying, in which tert-butylalcohol was used, prevents resist patterns from collapsing. The driving force of collapse is surface tension of the rinsing liquid.
Level Crossings of Phase of Sine Wave Plus Gaussian Noise
Authors: Youssef Neji , Munakata Tsutomu , Tadashi Mimaki Tadashi Mimaki
Published: February 2005

Theoretical results concerning the level crossings of the phase -π≤θ(t)≤π of the process consisting of a sine wave disturbed by additive Gaussian noise are presented, along with the experimental results supporting the theory. The average number of crossings of the phase angle θ(t), as well as the conditional probability densities for R(t), the envelope of the considered process, and for θ′(t), the time derivative of θ(t), are derived for an arbitrary crossing level θ. These derivations are a generalization of the existing theory to the case of a nonsymmetric (about the sine wave frequency) noise spectrum and an arbitrary crossing level -π≤θ≤π. To verify the derivations, experimental measurement of the considered quantities is performed for the case of a Gaussian noise having the 7th-order Butterworth spectrum. The experimental results are compared with the corresponding theoretical ones, and are found to be in good agreement.
Patterning of Self-Assembled Films Using Lithographic Exposure Tools
Authors: Walter J. Dressick Walter J. Dressick , Jeffrey M. Calvert Jeffrey M. Calvert
Published: February 2005

This paper presents an approach for fabricating surfaces with precise positional control of chemical functionalities at submicron resolutions using direct patterning of organosilane self-assembled monolayer films (SAFs) with lithographic exposure tools. Although the process is of general applicability, microelectronics applications are emphasized here. The suitability of monolayer SAFs for high resolution patterning is discussed and deep UV photochemical mechanisms for several classes of SAFs are presented. Selective electroless metallization of patterned SAFs provides sufficient plasma etch resistance and compatibility with current microelectronics processing technologies to allow fabrication of functioning Si MOSFET test structures. Unique features of the process, including an ability to utilize a variety of substrates and control metal film adhesion by judicious choice of the SAF, are discussed.
The Effect of Gaps in Markle-Dyson Optics for Sub-Quarter-Micron Lithography
Authors: Owen Geraint , Grenville Andrew , Bünau Rudolf von , Jeong Hwan , Markle David A. , Pease R. Fabian
Published: February 2005

The feasibility of Markle-Dyson optics has previously been demonstrated experimentally, using a prototype system in which the wafer is in contact with the mask. However, for semiconductor manufacturing, a gapped system is required. The introduction of a gap creates spherical aberration, which must be compensated. Two possible techniques for doing this are described. The first is to choose suitable materials for the Dyson lens and the mask, and this can work well unless the gap is much greater than 25 µm, in which case the residual aberration is unacceptably large. For this reason, the second compensation technique, the use of an aspheric mirror is preferred, since it affords complete correction. A gapped prototype system using an aspheric mirror is under experimental investigation. In this, the gap is controlled by a capacitance gauge, and the gauge is calibrated using an interferometric technique.
Evaluation of Pupil-Filtering in High-Numerical Aperture I-Line Lens
Authors: Fukuda Hiroshi , Kobayashi Yasushi , Hama Katsunobu , Tawa Tsutomu , Shinji Okazaki Shinji Okazaki
Published: February 2005

The pupil-filtering lens system for optical lithography experimentally evaluated in this study is based on an i-line stepper lens with a numerical aperture (NA) of 0.5, and its pupil function can be set arbitrarily to change the image characteristics. With the previously proposed super-FLEX filter, the depth of focus was three times that of the system without the filter, and the resolution for window patterns was 20% higher. Image characteristics of the filter, such as the edge-enhancing effect and the proximity effect, are discussed and were experimentally evaluated. The optical and mechanical tolerances required for this system are shown to be within ranges that are attainable in practical stepper systems.
Optimization of Pupil Filters for Increased Depth of Focus
Authors: Bünau Rudolf M. von , Owen Geraint , R. Fabian Pease R. Fabian Pease
Published: February 2005

The use of pupil filtering in optical lithography raises the question of an appropriate optimization method for such filters. We have suggested a pattern-independent procedure based on optimal energy concentration. Here, we discuss several different methods of implementing pupil filters in lithographic projection systems. We have assembled a simple telecentric test system and fabricated three filters optimized according to the suggested procedure. The results are shown to be in close agreement with predictions. We also present extensions of our calculations to large numerical apertures and non-unity magnification.
Algorithm for Phase-Shift Mask Design with Priority on Shifter Placement
Authors: Moniwa Akemi , Terasawa Tsuneo , Norio Hasegawa Norio Hasegawa , Shinji Okazaki Shinji Okazaki
Published: February 2005

A systematic approach to assigning aperture phases for the alternate-type phase-shift mask is proposed. Since the alternate-type phase-shift mask requires a 180° phase difference between adjacent apertures, there is the possibility that phase conflicts will arise, thus requiring pattern design modification. As a way to make pattern modification easier, this paper proposes a novel algorithm for successively assigning phases to apertures which are arranged in descending order of pattern design modification difficulty. Relative difficulty can be input by the pattern designer and/or calculated by the system from the pattern features. The system's successive shifter arrangement and phase conflict display is demonstrated on a test pattern.
Monolayer Halftone Phase-Shifting Mask for KrF Excimer Laser Lithography
Authors: Iwabuchi Yohko , Ushioda Jun , Tanabe Hiroyoshi , Yukio Ogura Yukio Ogura , Shunji Kishida Shunji Kishida
Published: February 2005

A new monolayer halftone phase-shifting mask has been developed. The phase-shifting film consists of the compounds SiO2 and Cr2O3. The transmittance of the film is controlled by changing the mixing ratio of the two materials. Our mask can be easily fabricated because the structure of the mask is very simple and the film is considerably thicker than the Cr layer of the original double-layer halftone phase-shifting mask. Experimental results using a KrF excimer laser stepper confirm the effect of increasing the depth of focus of hole patterns.
Optimization of Amorphous Carbon-Deposited Antireflective Layer for Advanced Lithography
Authors: Tani Yoshiyuki , Mito Hideaki , Okuda Yoshimitsu , Todokoro Yoshihiro , Tatsuta Toshiaki , Sawai Mikio , Tsuji Osamu
Published: February 2005

Critical dimension variation due to the multiple interference effect is the greatest problem for improving the actual resolution limit in optical lithography. To overcome this problem, amorphous carbon-deposited antireflective layer has been developed. This paper reports on the results of optimization for the antireflective layer film and application to advanced lithography. First, we optimized the deposition process of antireflective layer by measuring the reflectivity. Second, we applied the antireflective layer films in i-line (365 nm) and KrF excimer laser (248 nm) lithography. With the antireflective layer films, the reflectivity from the substrate reduces to less than 20%, which leads to a multiple interference effect of less than 1/7. With optimized antireflective layer films, resolution and depth-of-focus are almost same as those of the films without antireflective layer.
A Schottky-Emitter Electron Source for Wide Range Lithography Applications
Authors: Koek Bert H. , Chisholm Thomas , Davey Julian P. , Romijn Johannes , Run Arnold J. v.
Published: February 2005

A new 3-lens electron optical column using a Schottky emitter has been designed to perform very high-resolution lithography and also to produce reticles with good throughput. The theoretical performance has been computed from the source and lens characteristics and stochastic beam broadening. Measurements have shown excellent stability off the beam position and current. The measured current in a given spot-size is not as great as the theory predicts and further investigation is required. Examples are given of nanostructures formed by gold lift-off and of a DRAM reticle. The column is in use by research workers in the Technical University of Delft and examples of masks for Josephson junctions are shown.
0.25 µm Electron Beam Direct Writing Techniques for 256 Mbit Dynamic Random Access Memory Fabrication
Authors: Nakajima Ken , Kojima Yoshikatsu , Hirasawa Satomi , Mukai Hiroshi , Ishida Shinji , Hirota Takao , Kenji Kondoh Kenji Kondoh , Naoaki Aizaki Naoaki Aizaki
Published: February 2005

This paper describes improved 0.25 µm electron beam (EB) direct writing techniques for 256 Mbit dynamic random access memory (DRAM) fabrication. In particular, three techniques were each improved and optimized: (1) an EB writing system technique for improving overlay accuracy, (2) a resist process technique for fabricating reliable fine patterns, and (3) a pattern data preparation technique for correcting proximity effect and reducing data conversion time. The overlay accuracy for the EB direct writing layer to the mark detection layer was improved to under 0.075 µm(||
x̄||
+3σ), which is sufficient for the required alignment tolerance. The resist system was optimized for each EB direct writing layer considering a deposited energy distribution, which was calculated by the Monte Carlo method. To reduce data conversion time (central processing unit (CPU) time), a vector processing technique and a 1-dimensional caiculation method applied to proximity effect correction were developed, and a drastic reduction to about 30-60 min was achieved. Utilizing these iechniques, a 256 Mbit DRAM having a feature size of 0.25 µm was successfully fabricated.
A New Proximity Parameter Evaluation Method Utilizing Auxiliary Patterns for Dose Compensation
Authors: Uchiyama Shingo , Shigehisa Ohki Shigehisa Ohki , Tadahito Matsuda Tadahito Matsuda
Published: February 2005

A new proximity parameter evaluation method is proposed to separately evaluate the five proximity parameters of the triple Gaussian exposure intensity distribution function. This method is characterized by a separate evaluation of each term. This is based on equalizing the dose contribution of each term in different patterns. Using this method, the proximity parameters for an X-ray mask constructed with a high-atomic-number substrate are determined as Q
c=23.76 µC/cm2, α=0.261 µm, β=3.12 µm, γ=1.17 µm, η=0.101 and η′=0.447. The evaluated result shows that the third term is absolutely necessary for proximity effect correction on the X-ray mask.
Poly(siloxane)-Based Chemically Amplified Resist Convertible into Silicate Glass
Authors: Ito Toshio , Sakata Miwa , Endo Akihiro , Jinbo Hideyuki , Ashida Itsuji
Published: February 2005

A novel poly(siloxane)-based chemically amplified resist has been developed. The polymer is a glass precursor, and it can be converted to silicate glass through merely a lithographic procedure. The developed resist has a high sensitivity of 1.3 µC/cm2 and a high resolution of 0.1 µm lines and spaces. Simple and highly selective etching processes using the silicate glass mask obtained from this resist system have been proposed, which is substantiated in the bilevel resist process and tungsten-etching process.
Time-Modulated Electron Cyclotron Resonance Plasma Discharge for Controlling the Polymerization in SiO2 Etching
Authors: Seiji Samukawa Seiji Samukawa
Published: February 2005

This study examines 10-100 µs modulated electron cyclotron resonance (ECR) plasma discharge for controlling the generation of reactive species in plasmas. The electron temperature, density and reactive species are measured by means of a Langmuir probe and an actinometric optical emission spectroscopy in the pulsed plasma. Good correlation is found between the density ratio of CF2 radicals and F atoms in the CHF3 plasma, and the combination of the pulse duration and intervals. These characteristics are explained in terms of the dependence of the generation of reactive species in the ECR plasma on time (10-100 µs). This method provides for control of the polymerization and achievement of highly selective etching to Si during SiO2 etching.
Role of Fluorine in Reactive Ion Etching of Silicon Dioxide
Authors: Ikegami Naokatsu , Miyakawa Yasuhiro , Hashimoto Jun , Nobuo Ozawa Nobuo Ozawa , Jun Kanamori Jun Kanamori
Published: February 2005

Thermal desorption from 15 keV, fluorine positive ion (F+)-implanted SiO2 has been studied using thermal desorption and X-ray photoelectron spectroscopies. Primary fluorine-related outgassing species SiF3
+, gaseous O2, and a great amount of water evolution representing the SiO2 network modification were observed. From comparatively well-investigated desorption spectra from NF3/Ar reactive-ion-etching (RIE)-exposed and CF4/Ar RIE-exposed SiO2, similar outgassing species and the desorption temperatures were observed. The desorption states for SiF3
+ were not single as previously reported in the study of desorption states related to the thermal reaction with fluorocarbon polymer, but several desorption pathways existed. The observed similarity for SiF3
+ is considered to be related to the induced microstructural changes, which possibly determine the final desorption path in RIE.
New Phenomena of Charge Damage in Plasma Etching: Heavy Damage Only through Dense-Line Antenna
Authors: Koichi Hashimoto Koichi Hashimoto
Published: February 2005

The effect of antenna shape on charge damage has been examined using electron cyclotron resonance (ECR) plasma metal etching and test devices with an 8-nm-thick gate oxide. A dense-line antenna causes capacitor breakdown and the positive shift of the transistor's threshold voltage (V
t), while a sparse-line antenna does not. This positive V
t shift corresponds to a positive charge-up of the dense line, and is not dependent on overetching. Such damage is hardly observed when the antenna's top surface is exposed to the plasma, indicating that the plasma is uniform in terms of conventional charge damage. These new phenomena can be explained by a new mechanism consisting of electron shading with photoresist patterns. This shading leads to less neutralization of the ion charge impinging onto the transitory metal which remains between the antenna lines because of the microloading effect, and thus the excess positive charge causes the damage.
Formation of Dielectric Films for Gap-Filling by NH3-Added H2O-Tetraethoxysilane Plasma Chemical Vapor Deposition
Authors: Muroyama Masakazu , Atsushi Kawashima Atsushi Kawashima , Jun-ichi Sato Jun-ichi Sato
Published: February 2005

Multilevel metallization is becoming increasingly important for ultra large-scale integrated circuit (ULSI) fabrication. For this purpose, dielectric films with good filling capability are required. Plasma chemical vapor deposition (CVD) using H2O and tetraethoxysilane (TEOS) has been proposed for interlayer-metal dielectric gap-filling in advanced ULSI devices, because of its self-planarization characteristic. There remain problems, however, because film made using plasma CVD contains organic components which must be reduced to improve film quality. H2O plasma treatment after deposition has been proposed to reduce organic components, but much time is required for this procedure. To satisfy the gap-filling requirement and obtain good film quality in a reasonable amount of time, a new CVD method using NH3 as a catalyst is proposed in this paper. NH3 as a catalyst accelerates the elimination of ethoxy groups and reduces the organic components.
Scanning Tunneling Microscopy Observation of Ar-Ion-Bombarded Si(001) Surfaces and Regrowth Processes by Thermal Annealing
Authors: Uesugi Katsuhiro , Yoshimura Masamichi , Sato Tomoshige , Sueyoshi Takashi , Iwatsuki Masashi , Takafumi Yao Takafumi Yao
Published: February 2005

The surface morphology of Ar+-ion-bombarded Si(001) surfaces and its regrowth processes during thermal annealing are studied “in situ” using a scanning tunneling microscope (STM). The amorphous layer consists of grains 0.63∼1.6 nm in diameter. The grains gradually coalesce and forms clusters 2∼3.6 nm in diameter at the annealing temperature of 245°C. The (2×1) and (1×2) reconstructed regions surrounded by amorphous regions are partially observed on the surface after prolonged annealing, which suggests the onset of solid phase epitaxy (SPE). Real-time observation reveals that the smoothing of the surface occurs layer by layer. As the annealing temperature is raised to 445°C, the amorphous layer epitaxially crystallizes up to the topmost surface, and the (2×1) reconstructed surface with monatomic-height steps is observed.
Proposal of Trench-Oxide Metal-Oxide-Semiconductor Structure and Computer Simulation of Silicon Quantum-Wire Characteristics
Authors: Tetsuya Tsukui Tetsuya Tsukui , Shunri Oda Shunri Oda
Published: February 2005

We propose “trench-oxide metal-oxide-semiconductor (MOS)” structures as a novel formation method of silicon-based low-dimensional quantum structures, which are considered to be basic elements of future ultrahigh-speed and ultralarge-scale integrated devices. In this method, the applied gate voltage forms the potential well confined in an additional direction defined by ultrafine “trenches” on the oxide layer of the MOS structure. We characterize “trench-oxide MOS” quantum wire structures by two-dimensional numerical calculation of the shape of the potential well, the subband energy levels and the electron density, and investigate the possibility of the experimental observation of quantized density of states peculiar to quantum wires, by measuring capacitance-gate voltage (C-V) characteristics of “trench-oxide MOS capacitors.” We also have successfully fabricated “trench-oxide MOS” quantum wires with the width of 16 nm using electron beam (EB) lithography and electron cyclotron resonance reactive ion etching (ECR-RIE).
Fabrication of Metallic Structures in the 10 nm Region Using an Inorganic Electron Beam Resist
Authors: Wolfram Langheinrich Wolfram Langheinrich , Heinz Beneking Heinz Beneking
Published: February 2005

In order to make the sub-10 nm region accessible to lithography, an ultrahigh-resolution electron beam resist has been developed. This inorganic and self-developing resist is based on AlF3-doped LiF films. The resolution limit is ≈3 nm lines & spaces. This result is in excellent agreement with a rule which gives a correlation between resolution and threshold energy of a resist. The sensitivity is sufficient for the fabrication of complex mesoscopic devices. The problems concerning pattern transfer are discussed. As a first result, metallic structures with lateral dimensions down to 10 nm have been obtained using a lift-off technique.
Reactive Ion Etched II-VI Quantum Dots: Dependence of Etched Profile on Pattern Geometry
Authors: Tsutsui Kazuo , Hu Evelyn L. , Wilkinson Chris D. W.
Published: February 2005

The profiles of etched quantum dots are affected by both the geometrical pattern in which the dots are arranged and by the etching conditions. The dots were made by reactive ion etching (RIE) of ZnTe in a mixture of CH4and H2. In an uniform array of dots, the degree of undercut of the profile increases with the dot spacing, and is proportional to the etched area. When one dot is surrounded by a clearing with no dots, the degree of undercut of the profile is proportional to the radius of the clearing. The addition of a small amount of O2was found to be effective in controlling the undercut. Using these techniques, it is now possible to create high density arrays of vertical quantum dots in II-VI materials.
Transport Properties of Coupled Electron Waveguides Buried in Heterostructure
Authors: Wakaya Fujio , Yuba Yoshihiko , Takaoka Sadao , Murase Kazuo , Gamo Kenji
Published: February 2005

A new structure for coupled electron waveguides is proposed. The structure can be fabricated using the focused ion beam combined to the molecular beam epitaxy system. Transport properties of the device, such as transfer length and transfer coefficient, are calculated numerically. It is shown that an electron can be transferred completely from one waveguide to another if the structural and material parameters are chosen carefully.
The Transmission Properties of Quantum Dots at High Magnetic Fields
Authors: Ishibashi Koji , Bird Jonathan P. , Stopa Michael , Takuo Sugano Takuo Sugano , Yoshinobu Aoyagi Yoshinobu Aoyagi
Published: February 2005

We have fabricated quantum dot structures in GaAs/AlGaAs heterostructures using metallic surface gates defined by electron beam lithography and lift-off. Electrical transport measurements were performed on the dots at low temperatures (10 mK-1.5 K) and in magnetic fields of up to 8 T. Here we discuss the experimental characteristics of the devices, which include the observation of time dependent resistance changes at fixed gate voltage as well as a hysteresis in the resistance as the gate voltage is swept in different directions. These results demonstrate the influence of the dynamical nature of individual defects, charged states, or impurities, on the device behaviour. The corresponding magnetoresistance was found to show resonant peaks on the quantum Hall plateaus. Once the magnetoresistance exceeded the quantum resistance (h/e
2), however, periodic oscillations were observed in the magnetoresistance. We discuss these observations with respect to the scattering between different edge states, as well as Coulomb blockade effects, in high magnetic fields.
Transport Properties of Buried AlGaAs/GaAs Quantum Wires
Authors: Nakata Shunji , Ikuta Kenji , Masafumi Yamamoto Masafumi Yamamoto , Takashi Mizutani Takashi Mizutani
Published: February 2005

Buried wires with lateral interfaces consisting of AlGaAs/GaAs heterointerfaces are fabricated using wet etching and regrowth by MOCVD. The critical width of the buried wires was decreased to 0.1 µm, which was less than third of that of as-etched wires. The energy separation of one-dimensional subbands obtained from the Landau plots of Shubnikov-de Haas oscillations for the buried wires was increased to 2.8 meV, which was about two and half times larger than that of the as-etched wire. These results show that the buried quantum wire structure improves electrical transport properties.
High-Performance Pattern Placement Metrology on Dynamic Random Access Memory Layers of 0.25 µm Technology
Authors: Trube Jutta , Huber Hans-Ludwig , Bläsing-Bangert Carola , Rinn Klaus , Röth Klaus-Dieter
Published: February 2005

Pattern placement metrology is a key function in the evaluation of new manufacturing technology and processes. For future dynamic random access memory (DRAM) generations, ground rules of less than 0.25 µm must be achieved. This paper presents the results of an investigation of the Leitz LMS 2020 laser metrology system from Leica for pattern placement metrology for different layers of DRAM and X-ray mask fabrication processes. The results demonstrate clearly that the new Leitz LMS 2020 tool is well suited for pattern placement control of typical CMOS process wafers and X-ray masks with 30 nm accuracy.