bluuebunny/crossref_metadata_2025 huggingface dataset:
Grown-in Microdefects in a Slowly Grown Czochralski Silicon Crystal Observed by Synchrotron Radiation Topography
Authors: Iida Satoshi , Aoki Yoshirou , Sugita Yoshimitsu , Abe Takao , Kawata Hiroshi
Published: October 2002

Grown-in microdefects of a slowly grown Czochralski (CZ) silicon crystal were studied by short wavelength synchrotron radiation topography and successfully visualized. It was shown that the microdefects had spherical strain fields, by comparing the defect images in the two topographs taken with the Bragg reflections perpendicular and parallel to the growth direction. The radial distributions of the microdefect size and density were measured from the defect images in the topographs. The misfit volume of the microdefects was approximately 1 ×10-12cm3at the central axis region of the crystal ingot, and decreased monotonically toward the peripheral region of the crystal. The density of the microdefects was approximately 300/cm3at the center of the crystal, increased toward the periphery and then decreased rapidly to almost zero in the very peripheral region approximately 7 mm from the surface of the crystal ingot. These radial distributions are discussed in connection with the self-interstitial atoms of silicon crystals.
Complex Flow and Gas-Phase Reactions in a Horizontal Reactor for GaN Metalorganic Vapor Phase Epitaxy
Authors: Harafuji Kenji , Hasegawa Yoshiaki , Ishibashi Akihiko , Tsujimura Ayumu , Kidoguchi Isao , Ban Yuzaburoh , Ohnaka Kiyoshi
Published: October 2002

Three-dimensional fluid simulations are performed in a horizontal reactor for GaN epitaxy. Attention is paid to the effect of gas flow velocity at the inlet and gas pressure. It is found that the gas flow rate rather than the velocity or the pressure is a key parameter which controls the spatial distribution of streamlines, temperature and gas-phase species. As the gas flow rate increases, the size of return-flow or flow-separation appearing near the gas entrance of the expansion region with a tapering angle increases. This causes velocity peaking near the reactor symmetry plane and complicated transport of gas-phase species along the streamlines of the return-flow. If an optimum gas flow rate which gives minimum return-flow and uniform macroscopic spatial distribution for flow pattern and gas-phase species can be determined, then it is desirable to change the gas flow velocity and the gas pressure on the condition that the gas flow rate is maintained.
Slurry Chemical Corrosion and Galvanic Corrosion during Copper Chemical Mechanical Polishing
Authors: Kondo Seiichi , Sakuma Noriyuki , Homma Yoshio , Ohashi Naofumi
Published: October 2002

Copper (Cu) corrosion during chemical mechanical polishing (CMP) was controlled in order to improve the Cu damascene interconnect process. Slurry chemical corrosion was found to be enhanced when the slurry was diluted by deionized (DI) water during rinsing just after CMP. Since the corrosion inhibitor, benzotriazole (BTA), reduces the Cu removal rate, adding it to the rinse solution prevents chemical corrosion more effectively than adding it to the slurry. On the other hand, galvanic corrosion occurs at the interface between Cu and the barrier metal, and it can be prevented by selecting appropriate barrier metals. Because the difference between the electrochemical potentials of Cu and the barrier metal is small in the slurry, refractory metals such as Ta, TaN, and TiN were found to be appropriate barrier metals. On the other hand, W, WN, and Ti have large potential differences, so galvanic corrosion was clearly observed when Cu/W damascene interconnects were fabricated.
Frequency Properties of Nonlinear Transverse Electric Surface Waves
Authors: Zhou Jiongmao , Wang Qi , Wu Zhong , Li Chunfang
Published: October 2002

The frequency properties of the nonlinear transverse electric (TE) waves on the interface between a dielectric and a nonlinear antiferromagnet are studied. The analyzed expressions of the field components of TE waves are derived in a large power case. We find that the peak magnetic field moves into the nonlinear antiferromagnet from the interface when the power of TE waves increases. Using the explicit dispersion equation obtained in this article we analyze in detail the frequency regions of the TE surface waves. The results show the nonlinear TE surface waves have frequency passband and stopband, which can be switched into each other by varying the power. It is also revealed that, under certain conditions, the nonlinear TE waves on the interface are backward surface waves with the group and phase velocities opposite in direction.
GaAs Photonic Crystals on SiO2 Fabricated by Very-High-Frequency Anode-Coupled Reactive Ion Etching and Wafer Bonding
Authors: Saitoh Tadashi , Sogawa Tetsuomi , Notomi Masaya , Tamamura Toshiaki , Kodama Satoshi , Furuta Tomofumi , Ando Hiroaki
Published: October 2002

High-aspect-ratio, two-dimensional (2D) air-column GaAs photonic crystals (PhCs) on SiO2 layers with a lattice constant ranging from 240 nm to 1.0 µm have been fabricated using a novel method combining wafer bonding and low-temperature very-high-frequency (VHF) reactive ion etching (RIE). The obtained PhCs exhibit near-field patterns of sixfold symmetry or fourfold symmetry due to lateral interference, depending on the lattice structure. We have obtained photoluminescence (PL) spectra of PhCs which reveal the low damage feature of the combined process of low-temperature RIE and wafer bonding. Reflectance spectra exhibit fine structures which originate from the resonance coupling of the external light to the zone-folded bands of the photonic structure. This vertical confinement structure, obtained by forming GaAs PhCs on SiO2, is useful for taking advantage of 2D photonic crystals since it prevents photon dissipation from the lattice plane. The fabrication method combining low-temperature RIE with wafer bonding is a promising process for developing 2D photonic crystals on SiO2 layers.
Output Characteristics of P-doped Raman Fiber Laser at 1484 nm with 2.11 W Maximum Output Power Pumped by CW 1064 nm Yb-doped Double-Clad Fiber Laser
Authors: Kim Nam Seong , Prabhu Mahendra , Li Cheng , Song Jie , Ueda Ken-ichi
Published: October 2002

The output dependence on output reflectivity and fiber length is reported for a phosphosilicate Raman fiber laser (RFL) at the second Stokes wavelength of 1484 nm using a pump of CW 8.4 W/1064 nm Yb-doped double-clad fiber laser (DCFL) and cascaded cavities for the first and second Stokes wavelength. The output reflectivities for the second Stokes light were 15 and 50% and the lengths of the P-doped Raman fiber (PDF) were 300, 700, and 1000 m. The maximum output of 2.11 W/1484 nm was obtained using 15% output reflectivity and 700 m PDF length and the corresponding slope efficiency from the pump was 33.2%. The laser performance for the six configurations was investigated by observing the maximum output power, slope efficiency, threshold pump power, and full-width at half maximum at the second Stokes wavelength.
Mechanism of Photocarrier Generation and Transport in Poly(3-Alkylthiophene) Films
Authors: S. Pandey Shyam , Shuichi Nagamatsu Shuichi Nagamatsu , Wataru Takashima Wataru Takashima , Keiichi Kaneto Keiichi Kaneto
Published: October 2002

Carrier mobilities in poly(3-alkylthiophene) (PAT) films (alkyl = 6, 12 and 18), synthesized by chemical oxidation of 3-alkylthiophenes with FeCl3, have been studied using the time of flight (TOF) method. The response of photocurrents indicates the hole as the carrier sign and the highly dispersive transport particularly in the films substituted with long alkyl chains. Using regioregular poly(3-dodecylthiophene) (PAT12) and indium tin oxide (ITO) in the ITO/PAT12/Al sandwich cell, the depletion layer width at the Al/PAT12 interface was estimated to be 60 nm. It has been proposed that photocarriers are effectively generated at the interface and the high internal field helps in the separation of photocarriers. The drift mobilities in PAT12 and PAT18 are 8 ×10-6 cm2/V.s and 3 ×10-6 cm2/V.s, respectively, at the bias field, E = 1.0 MV/cm. They depend on the field as exp
(βE
1/2/kT), indicating the Poole-Frenkel mechanism for the carrier transport. On the other hand, the mobility of PAT6 is 1.1 ×10-4 cm2/V.s at E = 0.1 MV/cm, shows very weak positive field dependence. The mechanisms of photocarrier generation and transport are discussed taking the polymer structure into consideration and are compared with the results of regioregular PAT films.
Resonance Modulations of Surface Plasmons in Arbitrary Modified Otto and Sarid Structures
Authors: Liao Chih-Hsiung , Shyu Jiann-Shing
Published: October 2002

In this paper, from the Fresnel formulas and pole expansion, we derived approximation formulas of the reflectivity and resonant split in arbitrary modified Otto and Sarid structures. In accordance with the simulation results, we conclude that the modulation sensitivity of the reflectivity versus the gap thickness is larger for a modified Otto structure with a high dielectric constant prism and gold film (or silver film). In addition, the modulation sensitivity of the reflectivity versus the electro-optic dielectric constant for a modified Sarid structure with a high dielectric constant prism and silver film is much larger than that with other prisms and metal films.
Characteristics of (Ba, Sr)TiO3 Capacitors with Textured Ru Bottom Electrode
Authors: Aoyama Tomonori , Yamazaki Soichi , Imai Keitaro
Published: October 2002

Ru films were fabricated by dc magnetron sputtering in an Ar/O2 mixture ambient in order to examine the Ru films as electrodes of Ba0.5Sr0.5TiO3 (BST) thin-film capacitors. The 100-nm-thick Ru film deposited on Si at 450°C at an O2/(Ar+O2) flow ratio of 40% at 0.5 kW was textured along c-axis. The full-width at half maximum (FWHM) of 3.14° was obtained for the Ru (002) diffraction peak in an X-ray diffraction (XRD) pattern. BST films deposited on the Ru bottom electrode were also textured along (110). The relative dielectric constant of BST films increased with a decrease in the FWHM of BST (110). The relationship between electrical properties of Ru/BST/Ru capacitors and the orientation of the Ru bottom electrode and BST films was also investigated.
Structures and Ferroelectric Natures of Epitaxially Grown Vinylidene Fluoride Oligomer Thin Films
Authors: Kei Noda Kei Noda , Kenji Ishida Kenji Ishida , Atsushi Kubono Atsushi Kubono , Toshihisa Horiuchi Toshihisa Horiuchi , Hirofumi Yamada Hirofumi Yamada , Kazumi Matsushige Kazumi Matsushige
Published: October 2002

Structural and electrical properties of newly synthesized vinylidene fluoride (VDF) oligomer thin film have been investigated. The FTIR spectrum showed that the epitaxially grown film on KBr(001) substrate consists of form I (β phase) crystals and their c axes (molecular axes) and b axes (polar axes) are arranged parallel to the KBr substrate. To make electrical measurements possible, this film was transferred onto a gold bottom electrode without causing any changes in the crystalline structures. By using a modified atomic force microscope, we succeeded in the formation of local polarized domains as well as the clear observation of piezoresponse hysteresis curves in this sample. The coercive field and piezoelectric coefficient (d
33) for the 37-nm-thick film were about 200 MV/m and -3 pm/V, respectively. It was suggested that the b axis in the as-grown film rotated from the parallel to the perpendicular direction to the film surface during the poling process. This study reveals the ferroelectric characteristics in the VDF oligomer thin films for the first time.
Mobility-Lifetime Products in N-Carbazolyl-Substituted Polysilanes
Authors: Mimura Shinya , Naito Hiroyoshi , Dohmaru Takaaki , Aramata Mikio
Published: October 2002

Mobility-lifetime products, µτ, of N-carbazolyl-substituted silane co- and homopolymers have been studied by means of photo-induced discharge measurements. With increasing concentration of N-carbazolyl groups, the µτ product is abruptly decreased at a certain concentration of N-carbazolyl groups. The result is consistent with our earlier finding that the hole transit was unobservable above the concentration in the time-of-flight measurements. The origin of the decrease in the µτ product is discussed.
Improvement of Optical Properties and Beam Steering Functions in a Liquid Crystal Microlens with an Extra Controlling Electrode by a Planar Structure
Authors: Nose Toshiaki , Yamada Yoshiteru , Sato Susumu
Published: October 2002

A new type of liquid-crystal microlens with an extra controlling electrode has been proposed for precise control of the refractive index distribution properties. The extra electrode is fabricated on a substrate outside of the conventional driving electrode in the planar structure. Fundamental optical properties, that is, the refractive index distribution and focusing properties, are investigated by using a cylinder lens which has a striped electrode structure. Variable focusing and beam steering functions are enhanced by using the additional electrode with an appropriate driving method. The improvement of the lens property is very effective particularly in the deformed electrode structure which deviates from the optimum conditions, and this finding facilitates designing of an optical system using the liquid crystal (LC) microlens for application in various fields. The beam steering range can also be extended without extreme degradation of the lens quality with some assistance from the external electrode. The extra electrode structure is also introduced in the LC microlens, and the same advantages as with the cylindrical lens can be obtained.
Millimeter-Wave Transmission Properties of Nematic Liquid-Crystal Cells with a Grating-Patterned Electrode Structure
Authors: Tanaka Masaki , Nose Toshiaki , Sato Susumu
Published: October 2002

Nematic liquid-crystal (LC) cells with a grating-patterned electrode structure such as that used in the visible wavelength region are fabricated and investigated experimentally in the millimeter-wave region. The millimeter-wave transmission properties of the LC cells are measured at 50 GHz with respect to the applied voltage, molecular orientations and polarization directions of the wave. The transmittances of the LC cells for the polarization direction parallel and perpendicular to the grating vector are about 70–80% and 7–8%, respectively. Changes in the transmission induced by the reorientation of LC molecules by applying a voltage to the LC cell are observed. It is confirmed that the transmission change in the LC cell is mainly dependent on the anisotropy of the permittivity of LC materials. The LC cell with relatively large thickness may be applicable in this wavelength region.
Thermal Stability and Oxidation Resistance of W, TiW, W(N) and TiW(N) Thin Films Deposited on Si
Authors: Chang Chich Shang , Wu Tai Bor , Huang Chun Kai , Shih Wong Cheng , Chao Lan Lin
Published: October 2002

The thermal stability and oxidation resistance of ∼100-nm-thick W, TiW, W(N) and TiW(N) thin films deposited on Si substrate by rf magnetron sputtering were investigated by X-ray diffraction, resistivity measurement, X-ray photoelectron spectroscopy, Auger electron spectroscopy and scanning electron microscopy. All films showed good thermal stability against rapid thermal annealing in nitrogen (RTN) at 800°C for 1 min, except the W(N) film which decomposed to W and N2 at 800°C. The films also exhibited differences in oxidation resistance against rapid thermal annealing in oxygen (RTO). Both W and W(N) films were significantly oxidized at temperatures above 450 and 500°C, respectively, while TiW and TiW(N) films showed much better oxidation resistance up to temperatures of 750 and 650°C, respectively. In general, nitridized films, i.e., W(N) and TiW(N), exhibit better resistance against oxidation than metallic films. However, TiW films exhibit better oxidation resistance than nitridized films at RTO temperatures ≧600°C due to a change in surface oxide formation from a uniform oxide to a Ti-rich oxide. Once the films were completely oxidized, they were peeled off.
In-situ Annealing of Thin SrO Films Grown on Si(001)-2×1 by Molecular Beam Epitaxy
Authors: Tambo Toyokazu , Shimizu Atsushi , Matsuda Akiyoshi , Tatsuyama Chiei
Published: October 2002

Thin strontium oxide films were grown at 350°C in an oxygen atmosphere of 5 ×10-8 Torr by Sr-deposition using molecular beam epitaxy (MBE). The evolution of 300-Å-thick SrO films on a Si(001)-2 ×1 substrate is studied by reflection high-energy electron diffraction (RHEED) as a function of annealing temperature in an oxygen atmosphere of around 1 ×10-6 Torr. The RHEED patterns of the SrO crystalline films show streaks with spots up to an annealing temperature of 625°C, and then Debye-Scherrer rings appear with broad spots at 650°C. Above this temperature, the patterns consist only of the rings. From the results, we find that the growth temperature for any epitaxial film on Si with a MBE-grown SrO buffer layer is restricted to be under 625°C.
Galvanomagnetic Effect of Submicron Exchange-Coupled Co/Ni Wire
Authors: Kimura Takashi , Wakaya Fujio , Yanagisawa Junichi , Yuba Yoshihiko , Gamo Kenji
Published: October 2002

The galvanomagnetic effect of an exchange-coupled Co/Ni wire on a submicron scale was investigated by comparing it with the galvanomagnetic effects of single-layered Ni and Co wires. The observed longitudinal magnetoresistance of the Co/Ni wire resembled that of the single-layered Co wire. In the Co/Ni wire, abrupt Hall resistance changes due to the planar Hall effect were observed and were as large as that of the single-layered Co wire. The Hall resistance slopes of the Co/Ni wire due to the extraordinary Hall effect of the Ni layer were also observed, and were smaller than that of the single-layered Ni wire because of the exchange interaction from the Co layer. It was found that, in a low magnetic field, the magnetization processes of both the Ni and Co layers in the Co/Ni wire were almost the same, and were in agreement with that of the single-layered Co wire which is as thick as the Co layer in the Co/Ni wire.
Second-Harmonic Generation from Thermally Poled Mixed Alkali Silicate Glasses Containing Various Alkaline-Earth Oxides
Authors: Nasu Hiroyuki , Suzuki Yoshiyuki , Ohta Hiroya , Yamamoto Yoshitugu , Ito Yusuke , Hashimoto Tadanori , Kamiya Kanichi , Narasaki Aiko , Tanaka Katsuhisa , Hirao Kazuyuki
Published: October 2002

Second-harmonic generation (SHG) was observed from thermally poled alkaline earth containing mixed alkali silicate glasses. Since no SHG could be observed in alkaline-earth oxide-free glasses, it was considered that alkaline-earth oxide played a significant role in the generation. The intensity of SHG increased with the time and applied voltage of poling. However, no oscillation fringe pattern was observed even in the glasses poled most intensively in the present work, at 3 kV for 6 h, which indicates that the poled layer is limited near the surface area and thinner than the coherent length. On the basis of IR reflection spectroscopy and electron probe microanalysis (EPMA) data, the SHG was related to the positive ion depletion immediately beneath the glass surface on the anode side. From the finding that the migration of cations or ion depletion on the anode side was larger in the glass containing larger alkaline-earth ions, it was considered that the large migration reduced the space charge gradient and resulted in a lower SHG intensity.
Femtosecond Self-Mode-Locked La1-xMgNdxAl11O19 Laser Pumped by a Laser Diode
Authors: Xie Hongru Yang , Gu Jianhui
Published: October 2002

A laser-diode-pumped self-mode-locked La1-x
MgNd
x
Al11O19 laser has been demonstrated. Transform-limited pulses of 631 fs duration have been generated from the laser, which corresponds to a spectral width of 2.03 nm. The time-bandwidth product and average output power were 0.34 and 11 mW, respectively. Characteristic parameters of the LNA laser, such as the stability, the strength of the self-mode-locking, and the change of beam spot size with intracavity normalized power have been calculated and optimized. The theoretical simulation results are in good agreement with the experiments.
Multiport Lattice Filter Model for Long-Period Fiber Gratings
Authors: Bae Jinho , Chun Joohwan , Lee Sang Bae
Published: October 2002

We propose a new modeling technique for long-period fiber gratings. The proposed model which has a multiport lattice filter configuration is useful in analyzing (or synthesizing) piecewise-uniform long-period fiber gratings when the spectrum band of interest is wide or when each uniform section is in a different coupled mode. The validity of the proposed model is confirmed by comparing the calculated spectrum curves with the measured ones.
Preparation of Ferroelectric Glycine Phosphite Single Crystals
Authors: Jannatul Nayeem Jannatul Nayeem , Toshio Kikuta Toshio Kikuta , Toshinari Yamazaki Toshinari Yamazaki , Noriyuki Nakatani Noriyuki Nakatani
Published: October 2002

An experimental procedure to prepare single crystals of ferroelectric glycine phosphite (GPI) is presented. Since the solubility of GPI in water increases with temperature, the single crystals are grown from fine seed crystals in a saturated aqueous solution by the gradually-decreasing-temperature method. Full faced, transparent, colorless crystals weighing about 10 g are obtained within 20–30 days. Crystallographic axes and the Miller indices for all faces of the obtained crystals are determined using the lattice parameters as a clue.
Ion-Implantation Treatment (Ba, Sr)TiO3 Thin Films
Authors: Horng Ray-Hua , Wuu Dong-Sing , Kung Chung-Yuan , Lin Chin-Ching , Leu Ching-Chich , Haung Tiao-Yuan , Sze Simon Min
Published: October 2002

The effects of ion-implantation on the properties of spin-on sol-gel (Ba, Sr),TiO3 (BST) thin films were studied by implanting with Ar+, N+ and F+ doses. The F+ implanted BST samples present better electrical and dielectric properties than the Ar+ or N+ implanted BST do. The pronounced thickness shrinkage was observed in BST films after the F+ implantation (before annealing treatment) and a respective increase in the refractive index was measured. After the implanted samples are annealed, the changes of thickness and refractive index depend on the concentration of the implanted dose. If the F+ implanted dose is low (∼5×1014 cm-2), the BST preserves the densification properties. Its refractive index increases to 2.23 and it also presents a high dielectric constant of about 520. If the F+ implanted dose is high (≥∼1×1015 cm-2), excess F+ ions form Sr or Ba bondings with F+. This will degrade the material, electric and dielectric properties. The corresponding dielectric constant is about 440. An infrared transmission study of the samples suggests that the ion-implanted sample with lower doses have fewer –OH contaminants than the non-implanted or implanted samples with high doses. Based on the results presented, it was concluded that suitable ion-implantation densifies the spin-on sol–gel BST films and reduces the –OH contaminants in the films.
Effect of Waveform Slew-rate on Bistable Cholesteric Displays
Authors: Yip W. C. , Kwok H. S.
Published: October 2002

Since the typical peak-to-peak voltage needed to drive the bistable cholesteric display is two to three times higher than that for super twist nematic (STN) displays, the transient current can be excessively large and detrimental to most semiconductor drivers. To reduce the maximum switching current, the voltage transition time should be restricted in addition to reducing the peak voltage. In this paper, we studied the effect of slew-rate on the maximum output current, average output power and the dynamic optical responses. Based on circuit theory, we obtained a good agreement between experimental and calculated results. The optimal settings can be incorporated into our driving scheme so that low voltage and current requirements can be met for very large-scale integration (VLSI) implementation.
Effects of Alignment Layer on Pretilt Angle and Electrical Characteristics for The Photo-Aligned Twisted Nematic Cell on Polyimide Surfaces
Authors: Seo Dae-Shik , Park Tae-Gyu , Lee Seung-Hee
Published: October 2002

The alignment layer effects on the pretilt angle generation and electrical characteristics of photoaligned twisted nematic (TN)-liquid crystal displays (LCDs) for a polyimide (PI) surface with side chains were studied. The generated pretilt angle of nematic liquid crystal (NLC) on the rubbed PI surface with one layer was almost the same as that on the PI surface with two layers. However, the generated pretilt angle of NLC on the photoinduced PI surface with two layers was larger than that on the PI surface with one layer generated by oblique UV exposure on the PI surface. The different mechanisms of pretilt generation in NLC in the rubbing- and photoalignment methods were examined. The pretilt angle of the NLC on the photoinduced PI surface is attributed to surface roughness and side chains due to photodissociation of the polymer with UV exposure on the PI surface. We observed the same characteristics of voltage–transmittance (V–T) and response time for one and two layers on the PI surface. We also observed the same voltage holding ratio (VHR) characteristics for one and two layers on the photoaligned TN-LCD. Finally, we suggest that the VHR of photoaligned TN-LCDs was higher than that of the rubbing-aligned TN-LCDs.
Thermoelectric Properties of Bi2.3-xPbxSr2.6Co2Oy Single Crystals
Authors: Itoh Takayuki , Terasaki Ichiro
Published: October 2002

A set of single crystals of the layered cobaltite Bi2.3-x
PbxSr2.6Co2Oy (0 ≤x≤0.44) were prepared by a flux technique. The resistivity ρ and the thermopower S along the in-plane direction were measured, and the thermoelectric properties were compared with those of other oxides. The Pb substitution causes a decrease in ρ and an increase in S below 100 K, which improves the power factor S
2/ρ by 3–4 times. The transport parameters exhibit an anomaly near 25–50 K, such as a plateau in S and an upturn in ρ, which we ascribe to the reduction of the density of states owing to a pseudogap.
Novel Barrier Dielectric Liner Prepared by Liquid-Phase Deposition and NH3-Plasma Annealing
Authors: Yeh Ching-Fa , Lee Yueh-Chuan , Chen Chi-Ming , Wu Kwo-Hau
Published: October 2002

A novel barrier dielectric liner prepared by liquid-phase deposition and post-deposition NH3-plasma annealing is proposed as a capping layer to be used on damascene trenches of low-permittivity dielectric. The liner technology meets the essential requirements such as (1) thin and conformal deposition, (2) a low leakage current level, and (3) effective blocking of Cu penetration. With this barrier dielectric liner, Cu damascene interconnection is expected to have a low leakage current and high resistance to Cu penetration into the low-permittivity dielectrics even if the barrier metal fails locally.
Priority of the Mn Deposition Rate in Reactive Evaporation Conditions
Authors: Isai Masaaki , Ichikawa Hiroshi , Shimada Takeyoshi , Morimoto Keiichiro , Fujiyasu Hiroshi , Ito Yasumitsu
Published: October 2002

Manganese (Mn) oxide films used in lithium secondary batteries were prepared using the reactive evaporation method. One of the problems of using this method is that the manganese evaporant in the crucible suffers oxidation in an oxygen atmosphere. This deteriorates the Mn deposition rate with increasing the deposition run. A separator was introduced in the bottom of the Mn crucible. It could successfully isolate Mn evaporant from incoming oxygen atoms. The film properties depend on the oxygen flow rate, Mn deposition rate, and substrate temperature. These three parameters correlate closely with each other. The importance of Mn deposition rate compared to the rest of the parameters was recognized. The Mn deposition rate is governed by two parameters. One is the source temperature, and the other is the aperture size of the separator. The Mn3O4 films with a hausmannite structure can be prepared under the conditions of Mn deposition rate of 3–10 Å/s, separator aperture size of 6 mmφ, source temperature of 960°C, wall temperature of 900°C and oxygen flow rate of 5 sccm.
Applications of a Chemically Adsorbed Monomolecular Layer Having a Fluorocarbon Chain as an Anti-Contamination Film
Authors: Ogawa Kazufumi , Ohtake Tadashi , Nomura Takaiki , Soga Mamoru , Mino Norihisa
Published: October 2002

Monomolecular layers having a fluorocarbon chain were developed and made suitable for practical use as anti-contamination films for glasses, such as front door window glass plates of automobiles and window glass plates of electric ovens or microwave ovens, and also for stainless steel applications, such as covers of electric rice cookers, by using a chemical adsorption technique for the first time in the world. The layer was anchored to the substrate surface through covalent bonds. Thus the layer did not peel off and was durable against rubbing and scratching. As the film thickness was from about 1 to 2 nm, the layer was also optically transparent and the luster and color tone of the substrates was maintained. The lowest surface tension obtained was 8.2 mN/m, which is about a half that of Teflon. Although thermo-durability was a little low in comparison with that of Teflon, the production cost was lower. Thus this anti-contamination film should be very useful in the field of anti-contamination surface treatment.
Impedance of Barrier-Type Oxide Layer on Aluminum
Authors: Oh Han-Jun , Kim Jung-Gu , Jeong Yong-Soo , Chi Choong-Soo
Published: October 2002

The impedance characteristics of barrier-type oxide layers on aluminum was studied using impedance spectroscopy. Since anodic films on Al have a variable stoichiometry with a gradual reduction of oxygen deficiency towards the oxide-electrolyte interface, the interpretation of impedance spectra for oxide layers is complex and the impedance of surface layers differs from those of ideal capacitors. This frequency response of the layer with conductance gradients cannot be described by a single resistance–capacitance (RC) element. The oxide layers of Al are properly described by the Young model of dielectric constant with a vertical decay of conductivity.
X-Ray Analysis of the Structure of Premelted Layers at Ice Interfaces
Authors: Maruyama Minoru , Satoi Tomoki , Taniguchi Shinji , Kawamura Maiko , Kodera Shiro , Kishimoto Yuko , Furukawa Yoshinori
Published: October 2002

X-ray diffraction patterns of a premelted layer of ice and liquid water were obtained by a glancing-incidence method. Diffuse intensity patterns due to the premelted layer exhibited variation with temperature. Fourier transformation of the intensity curves gave pair-correlation functions, where the first, second and third peaks were observed in the premelted layer and liquid water. This suggests that there is a short range order in their molecular distribution. The average intermolecular distances between the nearest neighbors were 1–2% smaller in the premelted layer than in liquid water.
Structural Study of Ultrathin Hydrogenated Amorphous Carbon Films Using Spectroscopic Ellipsometry and Ultraviolet Raman Spectroscopy
Authors: Azuma Kazufumi , Inaba Hiroshi , Tasaka Kenji , Shirai Hajime
Published: October 2002

Ultrathin hydrogenated amorphous carbon (a-C:H) films in the initial stage of growth were prepared by the electron cyclotron resonance (ECR) plasma enhanced chemical vapor deposition (PECVD) method, varying the thickness within the range of 20 nm. Structural changes of the films were estimated by spectroscopic ellipsometry (SE) and ultraviolet (UV) Raman analysis. The SE results show that the refractive index increases and the extinction coefficient decreases superlinearly with the increase of the thickness up to 5 nm. The deposition rate decreases and the sp3 fraction increases simultaneously. The increment of the sp3 fraction decreases toward the region which is more than 10 nm in thickness. Direct observation of sp3 C–C by UV Raman analysis completely coincides with the SE analysis, i.e., the sp3 peak intensity becomes stronger and the peak position shifts to the lower wavenumber region with an increase of thickness. These facts imply that an sp2 fraction-rich growth zone exists on the surface and that the sp2 rich contribution decreases with an increase of thickness.
Crystallization in Pb(Zr, Ti)O3/Pt Thin Films on Mg2TiO4 Buffer Layer
Authors: Lee Choon-Ho , Yeom Jung-Hoon
Published: October 2002

Pb(Zr, Ti)O3 (PZT)/Pt structures were fabricated on an Si substrate with a Mg2TiO4 buffer layer and their crystallographic and morphological properties were studied. PZT and Mg2TiO4 thin films were deposited by the ultrasonic spraying metal-organic chemical vapor deposition (MOCVD) at atmospheric pressure. Pt thin films were deposited by RF magnetron sputtering. The crystallographic properties of Pt films were affected by the structure of the Mg2TiO4 films on which they grow. (111)-oriented platinum films were deposited on (111) Mg2TiO4 independently of deposition conditions. However, the Pt films deposited on (100)-oriented Mg2TiO4 films show a mixed orientation of (111) and (100), and the degree of (100) orientation was a function of the deposition temperature and crystallinity of Mg2TiO4 films. The surface morphology of Pt films differs depending on their crystallographic properties. (111)-oriented Pt films have excellently flat and dense surface morphology. (111)- or (100)-oriented PZT thin films were deposited on (111)- or (100)-oriented Pt layers, respectively. The surface morphology of (111)-oriented PZT thin films was more dense and flat than that of (100)-oriented PZT films.
Thomson Scattering Measurement of Electron Density and Temperature of a Microwave Plasma Produced in a Hydrogen Gas at a Moderate Pressure
Authors: Narishige Soushi , Suzuki Seiji , Bowden Mark D. , Uchino Kiichiro , Muraoka Katsunori , Sakoda Tadanori , Park Won Zoo
Published: October 2002

Laser Thomson scattering was applied successfully for the first time to a microwave discharge plasma suitable for deposition of diamond thin film. The plasma was produced in pure hydrogen gas, but the conditions were otherwise identical to those used for diamond deposition. The local electron density and temperature at the plasma center were (3.0±0.2)×1017 m-3 and (1.7±0.2) eV. Although the degree of ionization of the plasma was very low (<10-6), Thomson scattering signals could be detected clearly by using a double-monochromator which has a stray light rejection of 10-6 at the differential wavelength of Δλ=1 nm from the laser wavelength. Various checks were made to exclude the possibility of the probing laser from affecting the measured values, confirming the reliability of the measurement.
Compensation of Beam-Beam Interaction in a 50 GeV ×50 GeV Muon-Collider Ring
Authors: Kim Eun-San , Yoon Moohyun
Published: October 2002

The effect of a beam-beam interaction on the motion of a circulating beam in a 50 GeV ×50 GeV muon-collider ring is investigated by weak-strong beam modeling. In the present design of the muon-collider storage ring, the frequency-slippage factor η1 is approximately -5×10-7 so that the synchrotron motion is nearly frozen. This may lead to an increase in the energy spread due to the beam-beam interaction. Through the weak-strong beam modeling, we have investigated the parametric dependencies of the energy spread induced by the beam-beam interaction. We show in this paper that the energy spread due to the beam-beam interaction is large and can be compensated for by employing one rf cavity in the ring with a modest rf voltage.
Trapping of Atmospheric HO2 in Solid CO2 on Icy Satellites: Simulation Using Electron Spin Resonance and Thermoluminescence Analyses
Authors: Kimihiro Norizawa Kimihiro Norizawa , Makoto Hirai Makoto Hirai , Kazunori Kanosue Kazunori Kanosue , Motoji Ikeya Motoji Ikeya
Published: October 2002

Whether atmospheric HO2 is trapped in the icy surface of solid CO2 on outer planets and their satellites has been studied in a laboratory using electron spin resonance (ESR) and thermoluminescence (TL) analyses. Gaseous CO2 (10 Torr) containing about 1% of H2O was discharged at radio frequency (1 MHz) and frozen at 77 K immediately. Free radicals trapped in solid CO2 were identified as HO2 from the ESR spectrum. This spectrum was found to be different from that of γ-irradiated solid CO2 with an impurity of H2O. The annealing parameters of HO2 were correlated with the TL parameters of a peak at 185 K. The results indicate that atmospheric HO2 can be trapped in solid CO2 during condensation. The lifetime of HO2 was calculated to be about 1025 years at Triton's temperature of 35 K using the activation energy of 0.27 eV and the frequency factor of 5 ×105 s-1.
Asymmetric Properties of the Aerial Image in Extreme Ultraviolet Lithography
Authors: Otaki Katsura
Published: October 2002

The extreme ultra violet lithography (EUVL) mask is reflective and has a very thick structure. When such a mask is illuminated obliquely, the diffracted waves occur asymmetrically. We have investigated the influence of asymmetric diffraction on the image properties by numerical simulation. We have shown that the shadowing caused by oblique illumination reduces the image intensity and deteriorates the telecentricity. It has been concluded that the desirable illumination angle is less than 6 deg and the desirable absorber thickness is less than 100 nm. We have shown that the diffraction pattern has a nonuniform intensity and have pointed out that the nonuniformity of the diffraction pattern must be considered in order to discuss telecentricity.
Dose and Shape Modification Proximity Effect Correction for Forward-Scattering Range Scale Features in Electron Beam Lithography
Authors: Eunsung Seo Eunsung Seo , Ohyun Kim Ohyun Kim
Published: October 2002

For forward-scattering range scale features (α-scale features), the exposure contrast has too small a value to delineate the α-scale features using conventional dose modification proximity effect correction (PEC) in electron beam lithography. To delineate the α-scale features, the exposure contrast should be increased by shape modification. Therefore, we propose a dose-and-shape-modification PEC for α-scale features. The proposed PEC consists of two steps. The first step is the conventional dose modification PEC for the backscattering effect. The second step is the shape modification and dose compensation for the forward-scattering effect. A significant advantage of the proposed PEC is its low cost in terms of computation time, because shape modification and dose compensation for forward scattering are noniterative computations which do not consider the backscattering effect. Considering the exposure contrast, a separation distance larger than 2α between patterns is sufficient to delineate the α-scale features in the case of an equal lines-and-spaces (L&S) array. Experimental results are consistent with the simulation results, within a margin of error of approximately 5%. Using the proposed PEC, a 1.32α L&S array was delineated.
Intra-Level Mix-and-Match Lithography Process for Fabricating Sub-100-nm Complementary Metal-Oxide-Semiconductor Devices using the JBX-9300FS Point-Electron-Beam System
Authors: Mitsuru Narihiro Mitsuru Narihiro , Hitoshi Wakabayashi Hitoshi Wakabayashi , Makoto Ueki Makoto Ueki , Kohichi Arai Kohichi Arai , Takashi Ogura Takashi Ogura , Yukinori Ochiai Yukinori Ochiai , Tohru Mogami Tohru Mogami
Published: October 2002

To increase the throughput of electron beam lithography used to fabricate sub-100-nm patterns, we developed an electron beam and deep UV intra-level mix-and-match lithography process, that uses the JBX-9300FS point-electron-beam system and a conventional KrF stepper. Pattern data preparation was improved for sub-100-nm patterns. To reduce the effect of line width variation caused by post-exposure delay on complementary metal-oxide-semiconductor (CMOS) devices, we first exposed KrF patterns and then added another post-exposure bake before the electron beam (EB) exposure. We have used this technique to expose the gate layer of sub-100-nm CMOS devices. When we set the threshold size between EB and KrF patterns at 0.16 µm, the throughput of electron beam lithography was about threefold that of the full exposure by the electron beam lithography process. Sub-50-nm CMOS devices with high drive current were successfully fabricated.
Fine Pattern Fabrication below 100 nm with 70 kV Cell Projection Electron Beam Lithography
Authors: Yamamoto Jiro , Murai Fumio , Someda Yasuhiro , Uchino Sho-ichi
Published: October 2002

Cell projection electron beam lithography has been developed to achieve high throughput, and this system is now available commercially. However, the cell projection method uses a beam current that is much higher than that of the variable shaped beam method, and the Coulomb interaction caused by electrical repulsion (the coulomb effect) is thus much stronger. It is important to control the Coulomb effect in fine pattern fabrication because it causes beam blur that degrades resolution. This paper describes the effects of the acceleration voltage on the resolution of fine patterns below 100 nm as determined through experiments and simulations. Using an electron beam (EB) lithography system with 70 kV acceleration, we made 120 nm pitch lines and spaces (L&S) patterns by the cell projection method. Throughput was improved by using an acceleration voltage higher than the usual 50 kV acceleration. Because the Coulomb effect under 70 kV acceleration is weaker, we could use a higher beam current density or a larger cell projection size. The 70 kV acceleration is particularly useful for fine patterns and enables throughput twice that possible with 50 kV acceleration for 70 nm L&S pattern delineation.
An Improved Electron Scattering Simulation at the Mask in a Projection Lithography System
Authors: Kotera Masatoshi , Ishida Yoshihisa , Naruse Kentarou , Shimizu Isao , Tomo Youichi , Yoshida Akira , Kojima Yoshinori , Yamabe Masaki
Published: October 2002

A simulation model is presented, which can be used to express the electron energy loss spectrum and the small angular scattering of electrons at the mask in the electron beam projection lithography optical system. The simulation model of electron trajectories in the mask material is described. It is shown that the calculated electron energy loss spectrum and the angular scattering distribution agree well with the experimental results. Using this simulation, we obtain the data of the energy, the position, the scattering angle and the scattering azimuthal angle for each transmitted electron through the mask. As the application of the data, the following two results are obtained: (1) The longitudinal Coulomb interaction effect among scattered electrons generated at the mask and the image forming electrons are calculated and the defocusing characteristics in a typical cell-projection optical system are obtained. (2) The electron displacement characteristics at the wafer plane are obtained considering the scattering at the mask in the scattering with angular limitation projection electron lithography (SCALPEL) proof of concept system by neglecting the Coulomb interaction effect among electrons.
Optical Disk Readout Analysis Using an Extended Point Spread Function
Authors: Saito Kimihiro , Uemura Kamon , Kato Yoshiaki , Hineno Satoshi , Matsumoto Yoshiyuki , Nishi Noriaki , Toyota Kiyoshi
Published: October 2002

We present a method to calculate the readout signals from
optical disks and their applications. Our method is based on a
convolution operation of marks recorded on a disk and an extended
point spread function (EPSF). Our method can be applied to the case
where the marks are recorded in a groove and the photodetector has
an arbitrary shape. Four analyses examples are reported: analysis of
the tracking error detection method termed the differential phase
detection (DPD), focus shift dependency of readout signal jitter
when the marks are recorded in a groove, EPSF for land and groove
readout, and a compatible readout method for digital versatile disks
and compact disks.
Dose Uniformity of a Compact Beamline in Routine Operation with a Storage Ring “AURORA-2S”
Authors: Hirose Sayumi , Amano Daizo , Miyatake Tsutomu , Li Xuan , Hori Toshitada
Published: October 2002

We have investigated the effects of the beam profile and beam drifts of synchrotron radiation (SR) on dose uniformity of a beamline for X-ray lithography (XRL). The dose uniformity varies only by ±1% even when the beam has changed in vertical width from 0.18 mm to 0.65 mm, while it varies within ±1.5% when the SR beam is moved ±1 mm in the horizontal and ±0.1 mm in the vertical. Moreover, the exposure intensity changes within ±2% under the various beam conditions. In routine operation, variation of the beam condition does not degrade the dose uniformity in our beamline.
Evaluation of Effective Image Blurring Factors in the Synchrotron Proximity X-Ray Lithography
Authors: Yongduck Seo Yongduck Seo , Ohyun Kim Ohyun Kim
Published: October 2002

The total effective blur, σTE, in synchrotron proximity X-ray lithography (PXRL) was evaluated to obtain a simple effective dose image. σTE characterizes the total amount of blur attributable to the source angular distribution, the exposure system, the resist material and the process. In general, the final image on the resist becomes more blurry than the aerial image due to the absorption of photons by resists and the following additional resist process such as post exposure bake (PEB). σTE
2 can be understood by the square sum of many kinds of blur sources, and can be decomposed into a gap-dependent factor, s
eff, and a gap-independent factor, σconst. These characteristics of σTE can be evaluated using the rate of the CD changes within a gap range. We demonstrated the procedure for evaluating σTE, s
eff and σconst, for a specific resist material and process, along with the exposure system such as a synchrotron source and a stepper.
Etching Characteristics of Fine Ta Patterns with Electron Cyclotron Resonance Chlorine Plasma
Authors: Woo Sang-Gyun , Kim Sang Hoon , Ju Sup-Youl , Son Joo-Hiuk , Ahn Jinho
Published: October 2002

In this research, the etching characteristics of a Ta thin film with chlorine plasma was studied using an electron cyclotron resonance plasma etching system. The native Ta oxide on the surface was removed by a sputtering mechanism, and then ion-assisted Ta etching, desorption of Ta chloride assisted by ion bombardment, proceeded. The atomic chlorine, which is believed to be the most active species responsible for etching, could be used as an indicator of the Ta etching process. By double step etching, an accelerated formation of Ta chloride by a chemical-reaction-dominant process in the second step, following the sputtering-dominant process step, successfully protected side walls, resulting in the suppression of the microloading effect.
Enhanced Fatigue Property through the Control of Interfacial Layer in Pt/PZT/Pt Structure
Authors: Sik Kim Jun-Kyu Yang , Hyung-Ho Park Hyung-Ho Park
Published: October 2002

Ferroelectric Pb(Zr
x
Ti1-x
)O3 PZT thin film capacitors with Pt(111)/SiO2/Si substrate were fabricated by sol-gel method. Ultrathin PZT layer containing various contents of excess Pb was adopted as an interfacial layer to investigate the role of excess Pb on the formation of interfacial region between PZT film and Pt bottom electrode. An improvement of electrical properties was observed according to the content of excess Pb in interfacial PZT layer due to the inhibition of inter-diffusion at film-substrate interface as well as defect formation. The formation of Ti-rich PZT at the initial stage of anneal due to excess Pb was responsible for the excellent ferroelectric characteristic. This implied that the role of excess Pb in film-substrate interface was of significance to the long-term reliability.