bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of Yttrium-Dihydride Film for Use in Cold Cathode Lamps
Authors: Nakamura Osamu , Kanbara Minoru , Suzuki Shigemi , Mori Yuichi
Published: October 2002

In this paper, we examine the research and discovery of a highly efficient electrode material which we called yttrium-dihydride. This material is effective in a cold cathode lamp which is illuminant. The composition of crystal yttrium-dihydride (YH
x
) film was compared from the optical reflectivity. A cold cathode lamp with a tube of 63 mm length and an outside diameter of 2.6 mm was fabricated for the experiment, and the glow-discharge voltage was measured to evaluate the performance of the electrode using the YH
x
film. The lamp current was set at 5 mA for the measurement. The lamp voltage in the nickel electrode for the reference lamp was 220 V. The lamp voltage in the YH
x
electrode was 169 V. The yttrium-dihydride is revealed to be a more highly emission efficient material. In addition, the lamp voltage remained constant for more than 7,500 h, thus demonstrating that this material is extremely stable.
Characterization of Neutron Elastic Recoil Detection Analysis with Low-Energy Neutron Beams
Authors: Mizota Takeshi , Nakao Setsuo , Niwa Hiroaki , Saitoh Kazuo
Published: October 2002

The applicability of a low-energy neutron beam for neutron elastic recoil detection (NERD) has been studied. With this objective, we have constructed a compact gas counter consisting of a gridded ionization chamber and a solid-state detector (SSD) to detect and distinguish the low-energy species elastically recoiled by the neutron beam. By using the 241Am-α source, the optimum parameter set of this gas counter, i.e., the ratio of electric field to gas pressure, has been determined. In the NERD experiment using this gas counter with the optimum parameters, the energy distributions of hydrogen emitted from the polyethylene and Mylar sample targets by the neutron beam coming from the reaction 7Li(p, n)7Be were measured and compared with theoretical calculations. It has been shown that the NERD using the low-energy neutron beam can be a useful, noncontaminating technique for analyzing light species from materials.
Improved Fabrication Method for Nb/Al/AlOx/Al/Nb Superconducting Tunnel Junctions as X-Ray Detectors
Authors: Hiromi Sato Hiromi Sato , Yoshiyuki Takizawa Yoshiyuki Takizawa , Wataru Ootani Wataru Ootani , Tokihiro Ikeda Tokihiro Ikeda , Takayuki Oku Takayuki Oku , Chiko Otani Chiko Otani , Hiroshi Watanabe Hiroshi Watanabe , Kazuhiko Kawai Kazuhiko Kawai , Hiromasa Miyasaka Hiromasa Miyasaka , Hiroshi Kato Hiroshi Kato , Hirohiko M. Shimizu Hirohiko M. Shimizu , Hiroshi Nakagawa Hiroshi Nakagawa , Hiroshi Akoh Hiroshi Akoh , Masahiro Aoyagi Masahiro Aoyagi , Tohru Taino Tohru Taino
Published: October 2002

Niobium-based superconducting tunnel junctions (STJs) with aluminum trapping layers as X-ray detectors were fabricated. We applied a fabrication technique for reducing the leakage current and improving the energy resolution for X-rays at around 6 keV. The edges of two Al layers sandwiching a tunneling barrier were oxidized by plasma discharge. The performance of these new STJs was compared with other types of STJs to which thermal oxidization in an O2 atmosphere had been applied. The oxidization process in O2 plasma significantly improved the energy resolution for X-rays, which reached values (FWHM) of 41 eV, 58 eV, 65 eV, and 129 eV for STJs with the size of 20×20 µm2, 100×100 µm2, 200×200 µm2, and 500×500 µm2, respectively.
Ultraviolet Photoelectron Spectroscopy and Surface Potential of π-conjugated Langmuir-Blodgett Films on Gold Metal Electrode
Authors: Itoh Eiji , Iwamoto Mitsumasa , Burghard Marko , Roth Sigmar
Published: October 2002

The interfacial electronic structure of π-conjugated Langmuir-Blodgett (LB) films [octasubstituted palladiumphthalocyanine (PcPd) and preylene-tetra-carboxyldiimide derivative (PTCDI-Spent)] deposited on Au electrodes was examined by ultraviolet (UV) photoelectron spectroscopy (UPS), and the results were compared with these obtained by the surface potential measurement in a dark vacuum vessel. As the number of deposited layers increases, the energy shift was observed in the UPS spectra, which were found to correspond well with the surface potential change. This result indicates that excess electronic charges are transferred from LB-films to the Au electrodes until a thermodynamic equilibrium is established at the metal-film interface, resulting in the formation of an electrostatic double layer within the range of 1 to 2 nanometers in thickness. The contribution of layers sandwiched between the metal and the PcPd molecular film to the UPS spectra was also examined.
In situ Observation of the Crystallization Process of Ferroelectric Thin Films by Raman Microspectroscopy
Authors: Nomura Kenji , Takeda Yasutoshi , Maeda Masunobu , Shibata Noriyoshi
Published: October 2002

Crystallization processes of ferroelectric strontium bismuth tantalate (SrBi2Ta2O9; SBT) films with a Bi-layered structure and lead zirconate titanate [Pb(Zr0.5Ti0.5)O3; PZT] films with a perovskite structure have been investigated by Raman microspectroscopy. Amorphous films were prepared by rf-magnetron sputtering at room temperature using nearly stoichiometric ceramic targets. In situ Raman observations were performed at intervals with increasing sample temperatures. Under a heating rate of 20°C/min, the SBT films began to crystallize at 710°C, and completed crystallization at 850°C. It was found that SBT film crystallization advanced rapidly in the temperature region from 750 to 800°C. Raman mapping measurements of the SBT films at room temperature after annealing at 700 and 800°C clearly indicated the nucleation and growth processes of the crystal grains, respectively. The Raman peaks of the PZT films, which were observed in situ in spite of the cubic symmetry at the annealing temperatures, showed perovskite structure formation at temperatures as low as 500°C.
Langmuir Probe Measurement of Cesium Plasma in Thermionic Energy Converter
Authors: Zheng Wei , Kando Masashi
Published: October 2002

In order to determine the optimum conditions for thermionic energy converter (TEC) operation, a Langmuir probe has been applied to investigate a cesium plasma in a TEC operating in an unignited mode, which has a large electrode gap, and is operating at a relatively low emitter temperature. In the analysis of the probe characteristics, the work functions of and the electron emission from the emitter, collector and probe have been taken into account. It is confirmed by the present experiment that the floating and emitter sheath potentials estimated using parameters such as the electrode and probe work functions, thermionic emission current density and ion current density, produced by surface ionization together with measured electron and ion saturation currents, are in good agreement with those analyzed from the measured probe characteristics. Moreover, it is verified that the space-charge neutrality near the emitter affects the plasma density in the space between two electrodes more significantly than the thermionic electron current from the emitter. This leads to the conclusion that the relaxation of the negative space potential by the effective auxiliary discharge is important for the improvement of TEC output characteristics.
Nondestructive Internal Observation of Metal-Oxide-Semiconductor LSI Designed by 0.8 µm Rule
Authors: Takenoshita Hiroshi
Published: October 2002

A metal-oxide-semiconductor (MOS)-LSI chip was designed by the 0.8 µm rule, and a passivated film on the chip was etched off while keeping the chip mounted on a ceramic package. The acoustic signal generated by irradiation of a chopped electron beam was picked up by a piezoelectric detector (PZT element) attached to the back of the package. The results of observation by electron-acoustic microscopy (EAM) are as follows: (a) the observable depth (t
x) was proportional to the electron range (R
e); (b) t
x shifted to a shallower side (about 50% of R
e) compared to the case of bipolar transistors; (c) contact holes (0.8 µm2) were distinctly observed at HV=19 kV; and (d) the resolution of our EAM was estimated to be about 0.4 µm at a chopping frequency of the electron beam of 1 MHz and an acceleration voltage of 18–19 kV.
Composition Distribution of Compound Oxide Films Deposited by Magnetron Sputtering
Authors: Konishi Yoshinori , Harada Keiko , Yonezawa Yoshiyuki , Kawamura Yukinori
Published: October 2002

In this study, the mechanism of composition deviation of compound oxide films deposited by magnetron sputtering is examined. Composition distributions of SrTiO3 films and SrRuO3 films were analyzed on a substrate plane. On the area directly facing the erosion area of the target, not only were the ratios of Ti in SrTiO3 films and Ru in SrRuO3 films in excess of other areas, but also the amount of deposited Ti and Ru atoms was increased. The composition profiles were explained through simulations using angular distribution functions of sputtered atoms. Assuming the angular distribution of Ti in SrTiO3 films as a summation of a homogenous fraction and a highly preferential forward direction fraction, the unique Ti composition profile is represented. This result can be interpreted as a small amount of negative metal (or metal oxide) ions that emerged from the erosion area of the target and enriched the area directly facing the erosion area. Such negative ions are one of the main origins of composition deviation.
Preparation and Properties of SrBi2Ta2O9 Ceramics II
Authors: Shoji Kazuo , Shibata Kazuo , Nakayama Tohru , Sakata Koichiro
Published: October 2002

The purpose of this study is to investigate the preparation and properties of two types of SrBi2Ta2O9 ceramics, SrBi2Ta2O9 ceramics with excess Bi2O3, and two-phase ceramics formed with SrBi2Ta2O9 and BiTaO4. The samples were prepared by a conventional ceramic technique at 900 to 1300°C for 2 h. The optimum firing temperature for ceramics with excess Bi2O3 was about 1000°C when Bi2O3 was added in the amount of 0.75 wt%. The Curie temperature T
c of the two types of samples varied between 302°C and 440°C. The substitution in SrBi2Ta2O9 was estimated from the change of T
c. The values of the dielectric constant and remanent polarization for the two-phase ceramics, SrBi2Ta2O9/BiTaO4, were greater than those of SrBi2Ta2O9 ceramics.
Initial Stage of Oxidation of Si(001)-2×1 Surface Studied by X-Ray Photoelectron Spectroscopy
Authors: Harada Yoshinao , Niwa Masaaki , Nagatomi Takaharu , Shimizu Ryuichi
Published: October 2002

The surface composition of a Si(001)-2 ×1 reconstructed surface after various
O2 exposures and the oxidation process in an atomic scale based on the experiments
using X-ray photoelectron spectroscopy have been investigated. We have
demonstrated that the initial oxidation process is explained by our modified random
bonding layer-by-layer mechanism. The suboxide contents (Si1+:Si2+:Si3+) change
from 1:0:0, to 2:1:0 to 3:2:1 with increasing O2 exposure. The total suboxide
saturates to SiO5/6 which is an intermediate state of the layer-by-layer oxidation,
and to a metastable state prior to the nucleation of the two-dimensional SiO2 islands.
The ratio of the bridging oxygen atoms to the on-top oxygen atoms is approximately
4:1. The portion of oxygen at the on-top site decreases with increasing O2 exposure.
The oxygen atoms preferentially insert into the back bond of the dimer
down-atom.
Crystallization Process of TiNi Thin Films Sputtered at Elevated Temperatures on Pt/Si Oxide/Si and Si Oxide/Si Substrates
Authors: Kim Ick-Jun , Nanjo Hiroshi , Iijima Takashi , Abe Toshihiko
Published: October 2002

100-nm-thick TiNi films were deposited at elevated temperatures on a Si
oxide(300 nm)/Si and Pt(10 nm)/Si oxide(300 nm)/Si substrates. TiNi films
with a (100)-oriented plane were crystallized on the Si oxide surface heated above
823 K, while films with a (110)-oriented plane were crystallized on the Pt surface
heated above 623 K. These crystallization behaviors were investigated in terms of
the surface morphology using X-ray diffraction analysis, and by considering the adatom
surface mobility and interfacial adsorption.
Morphology Change of Octahedral Oxide Precipitates in Czochralski Silicon Wafers Stretched by Tension
Authors: Ojima Kozo , Sakai Kazufumi , Yamagami Takehisa
Published: October 2002

Alterations in the morphology of thermally induced oxide precipitates have been studied by transmission electron microscopy in a Czochralski silicon wafer deformed by tension at 850°C and 950°C. Precipitates with complex shapes are frequently observed in specimens deformed at 950°C. Some octahedral oxide precipitates are observed to expand at the vertices of the square shape in the plan view in a specimen heat-treated at 1050°C for 8 h after deformation at 950°C. Precipitates grow on residual dislocations around octahedral oxide precipitates. These observations suggest that a large number of vacancies form in the vicinity of octahedral oxide precipitates through interaction with bypassing dislocations.
Turnaround Phenomenon of Threshold Voltage Shifts in Amorphous Silicon Thin Film Transistors under Negative Bias Stress
Authors: Huang Chun-Yao , Tsai Jun-Wei , Teng Teh-Hung , Yang Cheng-Jer , Cheng Huang-Chung
Published: October 2002

The turnaround phenomenon of threshold voltage shifts is investigated in thin film transistors (TFTs) with different defect densities of hydrogenated amorphous silicon (a-Si:H) films and compositions of SiN
x
. It was found that TFTs with high-defect-density a-Si:H films and N-rich SiN
x
gate exhibit the turnaround phenomenon while TFTs with other conditions of a-Si:H and SiN
x
films do not. Results reveal that the turnaround phenomenon is greatly influenced by charge traps in SiN
x
and state creation in the a-Si:H layer. When state creation is dominant at low bias stress, the turnaround phenomenon occurs. In contrast, if charge trapping is dominant at low bias stress, the turnaround phenomenon does not occur.
Solid-State Dye Laser with Photo-Induced Distributed Feedback
Authors: Fukuda Makoto , Mito Keiichi
Published: October 2002

This paper describes the action of a solid-state dye laser utilizing a photo-induced distributed feedback (DFB) resonator. We solidified rhodamine B into a dried xerogel monolith using the sol–gel method, and used it as an active laser medium. The pump source was third-harmonic generation (THG) produced by a pulsed Nd:YAG laser. We divided the pump beam in two and irradiated the two beams on the active medium. The interference fringes simultaneously form both a spatial periodic modulation of optical gain and a refractive index in the active medium. This periodical structure functions as a DFB resonator. Without an external resonator, we achieved a laser oscillation with a narrowed spectrum. The full width at half maximum (FWHM) of the laser wavelength was approximately 1 nm. We tuned the center wavelength of the laser from 600 nm to 635 nm. In addition, we achieved a second-order DFB laser oscillation with second-harmonic generation (SHG) of a Nd:YAG laser.
Growth Kinetics of Cu–Sn Intermetallic Compounds at Interface of 80Sn–20Pb Electrodeposits and Cu Based Leadframe Alloy, and Its Influence on the Fracture Resistance to 90°-Bending
Authors: Suh Min-Suk , Kwon Hyuk-Sang
Published: October 2002

Electrodeposits of 80Sn–20Pb were formed on a Cu-based leadframe alloy from organic sulfonate solutions under different plating conditions, and were then aged at 100 to 180°C to examine the effects of the microstructure of electrodeposits on the growth kinetics of the Cu–Sn intermetallic layer formed at the electrodeposit/substrate interface, and the resultant influence on the fracture resistance of the electrodeposits under bending. The Cu–Sn intermetallic compound layers [ε (Cu3Sn) + η (Cu6Sn5)] increase linearly in thickness with the square root of aging time. However, the growth rate of the intermetallic compounds layer exhibits significant differences depending on the deposition condition; it is fastest in an extremely fine elecrodeposit formed using pulse current in a bath without any grain refiner, but is slowest in that formed using dc current in a bath with grain refiner, in spite of an equivalent grain size in both electrodeposits. This is due primarily to the inhibiting effects of the grain refiner remaining at grain boundaries of the electrodeposit on the diffusion of Sn across the intermetallic compounds/electrodeposit interface. The occurrence frequency and the degree of opening of surface cracks, formed when the aged samples are subjected to the 90°-bending test, are found to be associated with the growth rate of the intermetallic compound layer and the ductility of the electrodeposit. For samples aged under the same conditions, the sample electrodeposited from the solution containing grain refiner shows the highest resistance to surface cracking during the 90°-bending test due to the lower growth rate of its intermetallic layer and the higher ductility of the electrodeposit compared with those of other samples.
An Intense Pulsed Atomic Hydrogen Beam Source
Authors: Kubo Atsushi , Kitajima Masahiro , Yata Masanori , Fukutani Hirohito
Published: October 2002

A pulsed atomic hydrogen beam source has been developed especially for studies of surface reactions. Atomic hydrogen is generated using a microwave discharge in a quartz tube and is collimated to a beam by differentially pumped stages. A hydrogen dissociation fraction of ∼70% and a beam flux of 4×1014 atoms·cm-2·s-1 with a spot size 7 mm in diameter are obtained. The beam is chopped with a mechanical disk chopper, and a pulse duration of 50 µs for a repetition rate of 100 pulses/s is obtained. The velocity distribution of the atomic hydrogen beam is fitted with a shifted Maxwell-Boltzmann distribution that gives a most probable velocity of 2410 m/s and a beam temperature of 70 K.
Selective Epitaxial Growth by Ultrahigh-Vacuum Chemical Vapor Deposition with Alternating Gas Supply of Si2H6 and Cl2
Authors: Maruno Shigemitsu , Nakahata Takumi , Furukawa Taisuke , Tokuda Yasunori , Satoh Shinichi , Yamamoto Kazuma , Inagaki Toru , Kiyama Hiromi
Published: October 2002

Selective epitaxial growth of Si using a Si3N4 mask has been carried out by ultrahigh-vacuum chemical vapor deposition with an alternating supply of disilane (Si2H6) and chlorine (Cl2) gases. In the present gas supply method, selectivity of Si to Si3N4 is attained mainly by etching of poly-Si deposited on Si3N4 with Cl2, while grown film structures depend on the substrate temperature and the total supply of Si2H6 and Cl2 gases. The passivation effect of chlorine on growing film surfaces dominates at a low growth temperature (600°C). On the other hand, the passivation effect weakens with increasing temperature and thus the epitaxial film thickness is determined by both the growth rate with Si2H6 and the etching rate with Cl2 on Si.
Two-Dimensional Effects on Measurement of Thermal Diffusivity by AC Calorimetric Method: III. Advantage of Double-Heating Method
Authors: Takahashi Fumiaki , Hamada Yukihiro , Hatta Ichiro
Published: October 2002

In our previous paper [F. Takahashi, Y. Hamada and I. Hatta: Jpn. J. Appl. Phys. 38 (1999) 5278], the conditions required for precise thermal diffusivity measurement along the surface of a plate-like sample using an ac calorimetric method was proposed. It was concluded that an ac calorimetric method could be applied to a relatively thick sample. In the present paper, to perform the measurement in a much thick sample, we propose a new measuring system in which ac heat flux is applied to both surfaces of the sample, and analyze the two-dimensional temperature wave propagation. Consequently, the conditions for measuring thermal diffusivity to an accuracy of ±1% are proposed.
Cr:YSO Saturable Absorber for the Three-Level Cr:BeAl2O4 Laser at 680.4 nm
Authors: Yen-Kuang Kuo Yen-Kuang Kuo , Horng-Min Chen Horng-Min Chen
Published: October 2002

In addition to being an efficient saturable absorber Q switch for the tunable Cr:BeAl2O4 laser for its entire tuning range from 700 to 818 nm, the Cr:YSO is shown to be an effective saturable absorber Q switch for the 3-level Cr:BeAl2O4 laser at 680.4 nm. The passive Q-switching performance of this 3-level laser is similar to that of the passively Q-switched ruby laser.
Optimization of Dipole Off-Axis Illumination by 1st-Order Efficiency Method for Sub-120 nm Node with KrF Lithography
Authors: Kim Seo-Min , Kim Sang-Jin , Bang Chang-Jin , Ham Young-Mog , Baik Ki-Ho
Published: October 2002

To extend the limitation of KrF lithography into the 110 nm design rule region, dipole off-axis illumination (OAI) is suggested. We have investigated the availability of the 1st-order efficiency as a method of optimization and confirmed it in the conventional OAI. By the 1st-order-efficiency method, we have designed two dipole apertures that are capable of resolving horizontal and vertical dense patterns, and have evaluated the basic performance of the modified dipole apertures. To verify the applicability of the modified dipole apertures to memory devices, we tested a variety of patterns and obtained fine patterns with the help of optical proximity correction (OPC). In this study, we found that the optimized dipole OAI can serve as an extension method of KrF lithography for 110 nm devices.
A Novel Procedure for Evaluating Design Scalability Based on Device Performance Linked to Photolithography
Authors: Karklin Linard , Balasinski Artur , Axelrad Valery
Published: October 2002

We propose a novel procedure for evaluating design scalability based on printed (silicon) pattern simulation and experimental data followed by the extraction of metal oxide semiconductor field effect transistor (MOSFET) geometry and the distribution of device electrical parameters. We demonstrate the procedure on a six-transistor dual word line static random access memory (SRAM) cell, to optimize photolithography process for a technology shrink from 0.16 to 0.13 µm.
Sub-10 nm Linewidth and Overlay Performance Achieved with a Fine-Tuned EBPG-5000 TFE Electron Beam Lithography System
Authors: Bernd E. Maile Bernd E. Maile , Wolfgang Henschel Wolfgang Henschel , Heinrich Kurz Heinrich Kurz , Bert Rienks Bert Rienks , Roelof Polman Roelof Polman , Piet Kaars Piet Kaars
Published: October 2002

A Leica EBPG-5000 TFE electron beam lithography system has been evaluated and optimized. Sources of beam positional noise have been eliminated, resulting in an effectively useable spot size of less than 6 nm. Hydrogen silsesquioxane (HSQ) negative resist shows excellent resolution in combination with the fine-tuned instrument. Linewidths smaller than 8 nm have been reproducibly achieved at 100 kV under relaxed processing conditions, making HSQ an excellent test vehicle for system benchmarking in the nanometer regime. Using ultra-small vernier patterns exposed in HSQ resist, the intrinsic overlay accuracy of the system has been determined. A |mean| + 2 σ value better than 4 nm has been obtained.
Dominance of Cl2
+ or Cl+ Ions in Time-Modulated Inductively Coupled Cl2 Plasma Investigated with Laser-Induced Fluorescence Technique and Probe Measurements
Authors: Shinya Kumagai Shinya Kumagai , Minoru Sasaki Minoru Sasaki , Mitsumasa Koyanagi Mitsumasa Koyanagi , Kazuhiro Hane Kazuhiro Hane
Published: October 2002

Relative densities of chlorine molecular ions Cl2
+ and metastable chlorine atomic ions Cl+* were measured by a laser-induced fluorescence technique in cw and time-modulated inductively coupled chlorine plasma. In the discharge-off period of the time-modulated plasma, a considerable amount of Cl2
+ persisted. Under the modulation frequency of 100 kHz, the decrease of the Cl2
+ density in the discharge-off period was less than 30% and the decay time constant of Cl2
+ density was longer than that of Cl+*. In order to investigate the dominance between Cl2
+ and chlorine atomic ions Cl+, the relative densities of Cl2
+ and Cl+* were calibrated
as absolute densities along with the Langmuir probe measurements. The dominant ions in the cw plasma were Cl+, however, the Cl2
+ density became comparable to the Cl+ density in the time-modulated plasma.
Initial Stage of Hydrogen Etching of Si Surfaces Investigated by Infrared Reflection Absorption Spectroscopy
Authors: Noda Hideyuki , Urisu Tsuneo , Kobayashi Yoshihiro , Ogino Toshio
Published: October 2002

The initial stage of etching reactions (breaking the Si–Si back bonds) of Si(100) and Si(111) surfaces exposed to hydrogen at room temperature was investigated by buried metal layer-infrared reflection absorption spectroscopy. The peaks of SiH2 scissors and SiH3 deformation modes (<1000 cm-1) were successfully observed as clear indicators of the initial stage of hydrogen etching reactions. On the Si(100) surface, the hydrogen exposure dependence of these peaks indicated that the etching reaction starts in the relatively low-exposure region of ≥300 L (1 L=1×10-6 Torr s). We found that the adjacent dihydride is a precursor to breaking the Si back bonds. On the Si(111) surface, it was found that the adatom's two back bonds are easily broken, and that adatom trihydride is generated at a low H-exposure of 70–500 L. Adding to this dominant reaction, the etching of the rest-atom layer was observed at H-exposures higher than 10000 L.
Inspection of Critical Dimension and Transmission Uniformity of Contact Patterns by Deep UV Imaging and Regression Algorithm
Authors: Kyoji Yamashita Kyoji Yamashita , Shinji Yamaguchi Shinji Yamaguchi
Published: October 2002

We have developed an inspection method for critical dimension (CD) and transmission uniformity using deep UV imaging (257 nm) and regression algorithm. Evaluation of this inspection system was performed using specimens with programmed CD errors or ionized beam radiation. The magnitude of transmission sensitivity at 257 nm is 93% of that at the stepper's exposure wavelength (248 nm). The minimum sensitivity is 10.0% in transmission for 600 nm contact patterns and 5.8% for 800 nm contact patterns with a range of 6–25% pattern density. This method will improve current inspection capabilities, thereby meeting the requirements of 180 nm node.
Formation of Individual Holes in Amorphous SiO2 by Swift Heavy-Ion Bombardment Followed by Wet and Dry Etching
Authors: Awazu Koichi , Ishii Satoshi , Shima Kunihiro
Published: October 2002

Individual holes in amorphous SiO2 were formed from latent tracks which were introduced by bombardment with swift iodine ions. Hole contours strongly depend on the etching method used. Conic holes with the highest aspect ratio were obtained by etching with 48% hydrofluoric acid. The aspect ratio of the holes increased with the acidity of the hydrofluoric acid. Selective etching of the latent tracks was not observed with reactive ion etching, yet 48% hydrofluoric acid etching followed by reactive ion etching formed columnar holes. The etching mechanism is briefly discussed.
10-nm-Size Fabrication of Semiconductor Substrates and Metal Thin Lines by Conventional Photolithography
Authors: Shingi Hashioka Shingi Hashioka , Hideki Matsumura Hideki Matsumura
Published: October 2002

A novel technique for nano-fabrication is proposed, in which only conventional photolithography is used for patterning in conjunction with the anodic oxidation method. A contact pattern-mask with nanometer-size slits (nanometer slit mask) is actually fabricated by this technique. 10-nm-size trenches are formed in semiconductor substrates by using such a nanometer slit mask. Lateral metal/insulator/metal (MIM) structure with a 10-nm-size middle insulator is also fabricated using a similar mask, and the Fowler-Nordheim (F-N) tunneling currents can be observed in this lateral MIM structure. It is confirmed that the present proposed technique can be applied to the fabrication of future nanometer-size devices.
Direct Nanolithography of Organic Polysilane Films Using Carbon Nanotube Tips
Authors: Ai Okazaki Ai Okazaki , Takayoshi Kishida Takayoshi Kishida , Seiji Akita Seiji Akita , Hidehiro Nishijima Hidehiro Nishijima , Yoshikazu Nakayama Yoshikazu Nakayama
Published: October 2002

Nanolithography of polysilane films is performed by means of a tapping-mode-scanning probe microscope (SPM) equipped with a carbon nanotube tip. The tapping mode enables us to perform finer lithography than that by the contact mode. Electrons injected from the tip directly groove the polysilane film. A constant current operation is more stable in the tapping-mode lithography than a constant bias voltage operation. The mechanism of direct lithography is discussed on the basis of the model that the excess electrons in the Si backbone break Si-Si bonds.
Preparation of Diamond Mold Using Electron Beam Lithography for Application to Nanoimprint Lithography
Authors: Jun Taniguchi Jun Taniguchi , Yuji Tokano Yuji Tokano , Iwao Miyamoto Iwao Miyamoto , Masanori Komuro Masanori Komuro , Hiroshi Hiroshima Hiroshi Hiroshima , Kazuhiko Kobayashi Kazuhiko Kobayashi , Takeshi Miyazaki Takeshi Miyazaki , Hideyuki Ohyi Hideyuki Ohyi
Published: October 2002

Diamond molds were fabricated by two types of fabrication processes, both of which use a conductive intermediate layer between the diamond surface and polymethylmethacrylate (PMMA) resist to prevent surface charge-up. Using a PtPd intermediate layer, electron beam lithography and ion beam etching, a denting line pattern of 600 nm width and 70 nm depth was fabricated. Using a carbon intermediate layer, electron beam lithography, PtPd lift-off and oxygen ion beam etching, a convex line pattern of 600 nm width and 110 nm height was fabricated. These diamond molds were pressed into PMMA on a silicon substrate that was heated to a temperature of 150°C and kept at a pressure of 23.5 MPa until the temperature dropped below 90°C, and then the diamond mold was released from the PMMA. The convex line pattern of 600 nm width and 150 nm height was imprinted using a denting diamond mold. The denting pattern of 1100 nm width and 180 nm height was imprinted using a convex diamond mold. PMMA patterns were transferred well over the imprinted area by the diamond molds.
Novel Nano-Faceting Structures Grown on Patterned Vicinal (110) GaAs Substrates by Metal-Organic Vapor Phase Epitaxy (MOVPE)
Authors: Harada Toshifumi , Oda Yasuhiro , Motohisa Junichi , Fukui Takashi
Published: October 2002

We describe periodic nano-faceting structures formed naturally on patterned vicinal (110) GaAs grown by metal-organic vapor phase epitaxy (MOVPE). Periodic trenches are formed along the [1–10] direction on initial surfaces with pattern periods of 2 µm, 1 µm, 800 nm, and 600 nm. Periodic nano-faceting structures consisting of (110) and (111)B surfaces are clearly formed on the GaAs grown surfaces, and the periods are almost exactly equal to the pattern periods. The growth modes are observed from cross-sectional scanning electron microscope (SEM) images of GaAs/AlGaAs multilayer growth. The growth rate of the (111)B sidewall facets is higher than that of the (110) terraces, which indicates that quantum wire (QWR) structures can be formed naturally at step edges. Quantum well (QW) structures of GaAs/In0.18Ga0.82As/GaAs are also grown on patterned vicinal substrates. A photoluminescence (PL) spectrum at 4 K shows two sharp emission peaks from QWs on the (111)B sidewall facets at a lower energy and on the (110) terraces at a higher energy. These results suggest that it is possible to fabricate QWR arrays with high uniformity on (111)B sidewall facets.
Control of Current Hysteresis Effects in a GaAs/n-AlGaAs Quantum Trap Field Effect Transistor with Embedded InAs Quantum Dots
Authors: Kim Hoon , Noda Takeshi , Kawazu Takuya , Sakaki Hiroyuki
Published: October 2002

The drain current I
d vs gate voltage V
g characteristics in GaAs/n-AlGaAs heterojunction field effect transistors (FETs) with embedded InAs quantum dots (QDs) are studied in detail. It is found that the presence or absence of the current hysteresis can be controlled by the initial gate voltage before the gate scan. It is also found that those with positive shift of current hysteresis is observed in FETs with 5-nm-high QDs, while the negative shift is observed in those with 3-nm-high QDs. This property can be explained by the fact that electrons trapped in QDs escape more easily from 5-nm-high QDs than in 3-nm-high QWs. We thus conclude that the current hysteresis or the threshold voltage (V
th) in quantum-trap FETs with embedded InAs QDs can be controlled by engineering charging states of QDs via the gate or the geometrical shape of QDs. A V
th shift-controllable floating dot memory device is suggested.
Atomic Force Microscope Probe Tips Using Heavily Boron-Doped Silicon Cantilevers Realized in a <110> Bulk Silicon Wafer
Authors: Cho Il-Joo , Park Eun-Chul , Hong Songcheol , Yoon Euisik
Published: October 2002

A new method of fabricating atomic force microscope (AFM) probe tip is presented. In this process, the probe tips were implemented using self-aligned heavily boron-doped silicon cantilevers in a <110> bulk silicon wafer. In this structure, a stress-free cantilever can be easily defined by selective etch stop by the heavily boron-doped region in an anisotropic silicon etchant. The proposed tips do not require expensive silicon on insulator (SOI) wafers and double-side alignment. The probe tip dimensions can be exactly defined regardless of wafer thickness by the self-aligned etch from the front side. In addition, the cantilever thickness can be easily controlled by adjusting the diffusion time, and fabricated at low cost by using bulk silicon wafers. The fabricated probe tips showed resonant frequencies of 71.420 kHz with a 1.8-µm-thick probe tip and 122.660 kHz with a 3.0-µm-thick probe tip. Using the two fabricated probe tips, we successfully demonstrate image scanning of a 1 µm grating reference sample in contact and noncontact modes, respectively.
Fabrication of Cantilever-Bump Type Si Probe Card
Authors: Park Jeong-Yong , Lee Dong-Seok , Kim Dong-Kwon , Lee Jong-Hyun
Published: October 2002

Probe card is most important part in the test system which selects the good or bad chip of integrated circuit (IC) chips. Silicon vertical probe card is able to test multiple semiconductor chips simultaneously. We presented cantilever-bump type vertical probe card. It was fabricated by dry etching using RIE(reactive ion etching) technique and porous silicon micromachining using silicon direct bonded (SDB) wafer. Cantilevers and bumps were fabricated by isotropic etching using RIE. 3-dimensional structures were formed by porous silicon micromachining technique using SDB wafer. Contact resistance of fabricated probe card was less than 2 Ω and its life time was more than 200,000 turns. The process used in this work is very simple and reproducible, which has good controllability in the tip dimension and spacing. It is expected that the fabricated probe card can reduce testing time, can promote productivity and enables burn-in test.
A Surface-Bulk-Micromachined Electromagnetic Gyroscope Operating at Atmospheric Pressure
Authors: Kim Seong-Hyok , Kim Yong-Kweon , Song Jin-Woo , Lee Jang-Gyu
Published: October 2002

In this paper, we report an electrostatically driven and electromagnetically sensed planar vibratory gyroscope based on a surface-bulk combined micromachining. The gyroscope has comb electrodes fabricated by (110) silicon anisotropic etching. These comb electrodes are 400 µm thick, 18 µm wide, 600 µm long and are separated by 7 µm so that the height-gap ratio is about 57. It also has electroplated gold springs which are 15 µm wide, 14 µm thick and 500 µm long on both sides of the inertial mass. The electromagnetic detecting system is fabricated by a conventional machining process and then attached to the fabricated comb actuators. The open-loop characteristics of the gyroscope are measured using a rate table at atmospheric pressure. The fabricated gyroscope has a driving resonant frequency of 1090 Hz, and a sensing resonant frequency of 1200 Hz. The sensitivity is 30 mV/deg/s, and the resolution is 0.15 deg/s at atmospheric pressure. Also, a dynamic range of ±500 deg/s with a nonlinearity of less than 0.8% full-scale output is expected.
Analysis of Heavy-Metal Ions Using Mercury Microelectrodes and a Solid-State Reference Electrode on a Si Wafer
Authors: Yun Kwang-Seok , Kim Hong-Jeong , Joo Segyeong , Kwak Juhyoun , Yoon Euisik
Published: October 2002

Micro working electrodes and a solid-state reference electrode have been fabricated using semiconductor processes for electrochemical detection of heavy-metal ions in aqueous media. The working electrodes are mercury-coated platinum microelectrodes 5 µm, 10 µm and 25 µm in diameter. The smaller electrode shows the higher sensitivity and the detection limits of the 5-µm-diameter electrodes are about 0.2 ppb and 0.4 ppb for cadmium and lead ions, respectively. The reference electrode is a Ag/AgCl electrode coated by polyvinyl chloride (PVC)/Nafion layer containing Cl- ions. The potential variation of the fabricated solid-state reference electrodes is about 55 mV under a 0.1 M Cl- concentration.
Proposal of a Near-Field Optical Head Using a New Solid Immersion Mirror
Authors: Ueyanagi Kiichi , Tomono Takao
Published: October 2002

A new near-field optical head using a hemi-paraboloidal solid
immersion mirror (HP-SIM) is proposed. The possibility of
diffraction-limited focusing with the HP-SIM is ascertained with a
simulation.
The elimination of the mechanical servo from the head is demonstrated,
which makes it possible for the height and weight of the head to be less
than 1 mm and 1 g, respectively and comparable to the magnetic head
of HDDs. The succeeding generations of optical heads with slits or
apertures are also proposed for higher density recording. These heads
are especially suitable for optically assisted magnetic recording.
Optical Disc System for Digital Video Recording
Authors: Narahara Tatsuya , Kobayashi Shoei , Hattori Masayuki , Shimpuku Yoshihide , Kahlman Gijs J. van den Enden , Marten van Dijk Marten van Dijk , Roel van Woudenberg Roel van Woudenberg
Published: October 2002

We have developed a new error correction method (Picket: a
combination of a long distance code (LDC) and a burst
indicator subcode (BIS)), a new channel modulation scheme (17PP, or
(1, 7) RLL parity preserve (PP)-prohibit
repeated minimum transition runlength (RMTR) in full), and a new
address format (zoned constant angular velocity
(ZCAV) with headers and wobble, and practically constant linear
density) for a digital video recording system (DVR)
using a phase change disc with 9.2 GB capacity with the use of a red
(λ=650 nm) laser and an objective lens with a
numerical aperture (NA) of 0.85 in combination with a thin cover
layer. Despite its high density, this new format is
highly reliable and efficient. When extended for use with blue-violet
(λ≈405 nm) diode lasers, the format is well suited
to be the basis of a third-generation optical recording system with
over 22 GB capacity on a single layer of a 12-cm-diameter disc.
A Rewritable Optical Disk with a New Addressing Method for Increasing Recording Density and Random Accessibility
Authors: Suh Sang-Woon , Kim Dae-Young , Jong Il-Yong , Park Jong-Wook , Kim Jin-Yong
Published: October 2002

We developed a rewritable optical disk format with a new addressing method using phase-modulated
wobble signals in a land/groove recording structure. The disk format is able to increase the recording density compared with that of the digital versatile disk-random access memory (DVD-RAM) standard by reducing the redundancy due to header fields, and to improve random accessibility compared with that of the
digital versatile disk-rewritable (DVD+RW) standard on account of a frame addressing with 104 wobble
signals.
27.4 Gbyte Read-Only Dual-Layer Disc for Blue Lasers
Authors: Higuchi Takanobu , Koyanagi Hajime
Published: October 2002

We prototyped a next-generation digital-versatile-disc (DVD) dual-layer disc system
using a blue laser diode. Numerous technologies were investigated for our proposal,
such as new signal-processing techniques, a disc mastering process using
photobleachable dye and silver alloy as a semireflective material. The dual-layer disc
for the blue laser system has a 27.4 Gbyte capacity on a 12 cm disc. Where the
threshold level of the jitter value was provided at 15%, the radial tilt margin was within
±0.66 degrees on layer 0 and ±0.64 degrees on layer 1, while the tangential tilt margin
was within ±0.73 degrees on layer 0 and ±0.70 degrees on layer 1. These values are
sufficiently large for the playback system when compared with the DVD
system.
Electron Transport in AlGaN/GaN Heterostructures Grown by Plasma-Assisted Molecular Beam Epitaxy
Authors: Elsass Christopher R. , Smorchkova Iolia P. , Heying Ben , Haus Erik , Poblenz Christiane , Fini Paul , Maranowski Kevin , Petroff Pierre M. , DenBaars Steven P. , Mishra Umesh K. , Speck James S. , Saxler Adam , Elhamri Said , Mitchel William C.
Published: October 2002

High quality AlGaN/GaN heterostructures have been grown by rf plasma-assisted molecular beam epitaxy (MBE) on n-type GaN templates grown on sapphire by metalorganic chemical vapor deposition (MOCVD). By optimizing the AlGaN thickness and the Al content, record low temperature mobilities have been achieved. Temperature and magnetic field dependent Hall effect, and Shubnikov-de Haas oscillations, were used to probe the two-dimensional electron gas (2DEG) with consistent results. The unintentionally doped Al0.09Ga0.91N heterostructures exhibit a measured 77 K Hall mobility of 24,000 cm2/V·s (n
sh=2.5×1012), 12 K mobility of 52,000 cm2/V·s and ∼4 K mobility of 60,000 cm2/V·s (n
sh=2.25×1012), all records for this material system. The magnetic field dependent Hall effect revealed carriers from the bulk GaN freeze out and that a single carrier system is dominant below 80 K.
Selective Area Growth of Cubic GaN on 3C-SiC (001) by Metalorganic Molecular Beam Epitaxy
Authors: Jun Suda Jun Suda , Tatsuro Kurobe Tatsuro Kurobe , Shigeru Nakamura Shigeru Nakamura , Hiroyuki Matsunami Hiroyuki Matsunami
Published: October 2002

Selective area growth (SAG) of cubic GaN (c-GaN) was performed by metalorganic molecular beam epitaxy (MOMBE).
The substrates used in this study were vapor phase epitaxy (VPE)-grown 3C-SiC on Si (001) 4°-off substrates.
As a mask, 70-nm-thick SiO2 was formed by thermal oxidation of 3C-SiC and patterned by photolithography or focused ion beam (FIB) etching. GaN was grown on these patterned 3C-SiC substrates without a low-temperature-grown (LT) buffer layer. At a high growth temperature (850°C), growth of GaN did not occur even on a 3C-SiC surface. At a low temperature (800°C), c-GaN was epitaxially grown on a 3C-SiC surface, while polycrystalline GaN (poly-GaN) was grown on the SiO2-masked region. Growth of poly-GaN on the mask was suppressed by optimizing the growth temperature and V/III supply ratio. The possibility of positioning control for c-GaN microcrystals is also presented.
Characterization of Silicon-on-Insulator Wafers by Photoluminescence Decay Lifetime Measurement
Authors: Shigeo Ibuka Shigeo Ibuka , Michio Tajima Michio Tajima
Published: October 2002

The lifetime of an electron-hole droplet (EHD) generated in a superficial Si layer of a silicon-on-insulator (SOI) wafer was investigated using time-resolved photoluminescence technique. Formation of the EHD in the superficial Si layer was realized employing pulsed ultraviolet laser light as an excitation source, because of its shallow penetration depth and confinement of photo-excited carriers in the layer. Dependence of the EHD lifetime on surface condition, fabrication technique and wafer vendor was successfully observed. We demonstrated that the EHD lifetime is sensitive to crystalline quality of the superficial Si layer, and propose that the present method has great potential for characterization of SOI wafers.
Free-Standing GaN Substrates by Hydride Vapor Phase Epitaxy
Authors: Park Sung S. , Park Il-W. , Choh Sung H.
Published: October 2002

Thick gallium nitride films 250–350 µm in thickness were grown on 2-inch-diameter (0001) sapphire wafers by hydride vapor phase epitaxy. The size of the free-standing GaN substrates without cracks separated from the sapphire substrates by laser processing was equal to that of the initial sapphire substrates. The origin of bowing and the broad photoluminescence (PL) spectra of GaN films was considered the difference in the residual strain between the front and bottom surfaces caused by threading dislocations.
Growth of (111)-Oriented Diamond Grains on Hexagonal GaN
Authors: Masato Oba Masato Oba , Takashi Sugino Takashi Sugino
Published: October 2002

Oriented growth of diamond on hexagonal GaN thin films has been performed using microwave plasma-assisted chemical vapor deposition (MPCVD). GaN layers grown on sapphire substrates are utilized as a substrate. The growth process consists of three steps: (i) carburization, (ii) bias-enhanced nucleation (BEN) and (iii) deposition. Diamond synthesized on the GaN layer is characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The SEM image shows oriented growth of diamond grains on the GaN substrate. A diffraction signal due to the (111) face of diamond is observed at 2θ=43.9°. A Raman signal peak at 1333 cm-1 confirms the growth of diamond. In addition, it is found by XRD and XPS measurements that carbon nitride is produced on the GaN substrate without growth of diamond grains.
Synthesis of Carbon Tubule Nanocoils in High Yield Using Iron-Coated Indium Tin Oxide as Catalyst
Authors: Mei Zhang Mei Zhang , Yoshikazu Nakayama Yoshikazu Nakayama , Lujun Pan Lujun Pan
Published: October 2002

We have synthesized carbon coils of nanometer-scale size by catalytic thermal chemical vapor deposition. The catalyst used is iron-coated indium tin oxide and the carbon source is acetylene. The yield of carbon coils is over 95% at a growth temperature of 700°C. The carbon coil usually consists of two or more carbon tubules and each of them grows with its own diameter and pitch. The external diameters of the coils are from several tens to several hundreds of nanometers. It is found that iron plays an important role in the growth of carbon nanotubes, while indium, tin, oxygen, and/or their alloys are necessary in the formation of the coils.
Characteristics of Interface-Modified Josephson Junctions Fabricated under Various Etching Conditions
Authors: Masahiro Horibe Masahiro Horibe , Yukitoshi Inagaki Yukitoshi Inagaki , Kazuhiro Yoshida Kazuhiro Yoshida , Gen-ichiro Matsuda Gen-ichiro Matsuda , Noriyoshi Hayashi Noriyoshi Hayashi , Akira Fujimaki Akira Fujimaki , Hisao Hayakawa Hisao Hayakawa
Published: October 2002

We have studied the influence of process parameters on electrical properties for interface-modified junctions (IMJs) based on YBa2Cu3Ox.
Tunnel barriers are produced by an electron cyclotron resonance (ECR) plasma etching process and subsequent vacuum annealing.
We have found that time and accelerating voltage (V
acc) in the etching sequence,
in which the ramp-edge geometry is defined, are very important parameters for the barrier formation.
Increasing the etching time and accelerating voltage lead to the reduction of critical current densities.
By setting these parameters at appropriate values, we can control the critical current of the IMJs.
We have also found that the IMJs with high junction resistance, which are fabricated at higher accelerating voltages above 700 V, have transport mechanisms via localized states for quasi particles.
The X-ray photo spectroscopy analysis suggests that accelerating voltages above 700 V enhance the thickness of the barrier, while those below 700 V affect both barrier resistivity and thickness.