bluuebunny/crossref_metadata_2025 huggingface dataset:
Monochromatic Projection Optical System for ArF Excimer Laser Lithography
Authors: Jun-ichi Yano Jun-ichi Yano , Akifumi Tada Akifumi Tada , Shinji Ito Shinji Ito , Hitoshi Sekita Hitoshi Sekita , Hiroyoshi Tanabe Hiroyoshi Tanabe , Yukio Ogura Yukio Ogura
Published: October 2002

We have developed an ArF excimer laser exposure system that combines a monochromatic quartz projection lens system and a spectrally-narrowed ArF excimer laser. The bandwidth of the laser was narrowed to 0.7 pm by using three prisms and an etalon. We delineated 0.2 µm lines-and-spaces using a chemically amplified resist and 0.16 µm lines-and-spaces using a top surface imaging resist.
The Electronic States of Nickel ions in Diamond Calculated by a Discrete-Variational Xα Method
Authors: Ohashi Naoki , Fukunaga Osamu , Isoya Junichi , Tanaka Junzo
Published: October 2002

The electronic states of nickel in diamond were calculated by a discrete-variational Xα (D
V-Xα) method. Model clusters used for substitutional and interstitial Ni sites were [ NiC28H36]- ( Ni\sits

- center) and [NiC30H40]+ ( Ni
i

+ center), respectively. Superhyperfine constants for electron paramagnetic resonance (EPR) spectra were estimated from results of D
V-Xα calculation and were compared with measured values. A triply degenerate state with total spin S=3/2 appears in the Ni
s

--center and a half-filled doubly degenerate state with total spin S=1/2 appears in the Ni
i

+-center. The total spin and electron occupancy of these clusters agree with the assignments of the EPR spectra. The electron population analysis result indicated that the Ni+ ion at the tetrahedral interstitial site formed more ionic bonding than the Ni- ion at the substitutional site. Superhyperfine interactions between Ni and the nearest-neighbor carbons were calculated as a function of Ni–C bond length, suggesting that a lattice relaxation occurred for the Ni–C bond to be elongated in the Ni
s

- center.
High Dielectric Constant Negative-Positive-Zero Dielectric Materials Based on (100-x)(La0.1Bi0.9)Ti2O7-xSrTiO3
Authors: Nakano Atsuyuki , David P. Cann David P. Cann , Thomas R. Shrout Thomas R. Shrout
Published: October 2002

Dielectric materials based on the solid solution system (100-x)( La0.1Bi0.9) Ti2O7–xSrTiO3 have been studied in order to obtain high performance capacitor materials. Compositions with temperature coefficient of capacitance as low as τ c<20 ppm and dielectric constant as high as 250 make them suitable for negative-positive-zero (NPO) capacitor designated applications. Using X-ray diffraction, a three-phase mixture of the two end members, SrTiO3, ( La0.1Bi0.9) Ti2O7, and a Bismuth-layer structure phase with only a limited amount of solid solution was observed. The low-temperature coefficient of capacitance was believed to be the result of the balancing of the positive and negative temperature coefficients characteristic of the three constituent phases.
Structural Changes in Ba(Sr 1/3Ta 2/3)O 3-Type Perovskite Compounds upon Tilting of Oxygen Octahedra
Authors: Toru Nagai Toru Nagai , Masaaki Sugiyama Masaaki Sugiyama , Mutsuo Sando Mutsuo Sando , Koichi Niihara Koichi Niihara
Published: October 2002

Since the early study by Galasso and Pyle, the structure of complex perovskite compounds with 1:2 ordering of B-site ions, ordered perovskite compounds, has been thought to be Ba(Sr1/3Ta2/3)O3-type hexagonal. Recently, a structural phase transformation has been found in A-site substituted ordered perovskite compounds, (Ba,Sr)(B'1/3B"2/3)O3. The structural change due to the phase transformation has been connected with the tilting of oxygen octahedra in the perovskite cell. However, the structure of the transformed phase has not been clarified because there has not been any model to treat the crystal structure of ordered perovskite compounds having tilted oxygen octahedra. In this paper, Glazer's model for structural changes in cubic perovskite due to the tilting of oxygen octahedra has been expanded to the 1:2 ordered perovskite. Based on the model, electron diffraction and X-ray diffraction of (Ba1-x
Sr
x
)(Mg1/3Ta2/3)O3 are discussed. A monoclinic unit cell in space group C
2h

6 with an angle γ > 90 °, which is derived from antiphase tilting of oxygen octahedra, successfully explains the experimental results.
Calculation of the hcp Ni 75Mo 25 Metastable Crystalline Phase by Discrete Variational Xα Method
Authors: X. Y. Huang X. Y. Huang , J. S. Pan J. S. Pan , Y. D. Fan Y. D. Fan
Published: October 2002

The self-consistent discrete variational method with the local Xα exchange approximation has been used to obtain the electronic structure of 19-atom cluster which represents the hcp Ni75Mo25 metastable phase induced by ion mixing in Ni-Mo multilayers. The total energy of this phase is calculated as a function of lattice constant with a fixed c/a=1.62 which is obtained experimentally. The predicted lattice constants, i.e., a=4.93 a.u. and c=7.99 a.u., are in good agreement with the experimental results, i.e., a=4.99 a.u. and c=8.08 a.u. Besides, the bonding charge density and the density of states (DOS) are used to clarify the characteristics of the bonding of this metastable crystalline phase.
Reflection and Transmission of the Longitudinal Wave at an Achiral-Chiral Boundary
Authors: Shiuh-Kuang Yang Shiuh-Kuang Yang , Shao-Yi Hsia Shao-Yi Hsia
Published: October 2002

The effective chiral (isotropic, noncentrosymmetric) composite can be fabricated by embedding the helical arrangement of microstructures in a host medium. In such a composite, six independent wavenumbers can be found from the dispersion equations. Two of the wavenumbers represent the nondispersive longitudinal waves while the remaining four represent the dispersive circularly polarized shear waves. According to the dispersion equations derived in our previous research that two cut-off frequencies divide the frequency spectrum of the transverse wavenumbers into three different groups, and hence the four transverse modes can only be distinguished in a specified frequency range. In this paper, we study the longitudinal plane wave propagation at an isotropic-effective chiral boundary. Numerical results show that an additional horizontal shear wave (SH wave), due to the mode conversion in the chiral composite, is enhanced between the first and second cut-off frequencies. The embedded handed microstructures may hence be properly chosen that the resulting composite is effectively chiral in a specified frequency range.
Electrical Properties of BaTiO3 Thin Film Grown by the Hydrothermal-Electrochemical Method
Authors: Kajiyoshi Koji , Yoshimura Yukio Sakabe
Published: October 2002

Crystalline BaTiO3 thin films were prepared directly on Ti substrates in aqueous solutions of Ba(OH)2 at 150 °C by a hydrothermal-electrochemical method and their electrical properties for capacitors were measured. The leakage current-voltage characteristics exhibited rectifications, the degree of which depended on the top electrodes used. Resistivities as high as 1012 Ω· cm were obtained in the voltage range up to 2 V for the 0.40-µ m-thick BaTiO3 thin film and its breakdown voltage was higher than 12 V. The grown films were paraelectric with dielectric constants of 340–350 and dielectric losses of 7–10% at 1 kHz, 0.1 V rms, and 25 °C. The capacitance variation with dc bias voltage from -2.5 to +2.5 V was 9% of the zero-bias value, and that with temperature from -60° to 130 °C was 24% of the room-temperature value.
New Synthesis Method of TiC Film by Applying High Pressure and Electric Field
Authors: Suzuki Katsuhiko , Nihei Tomomichi , Ikeda Senri , Matsumoto Makoto Matsuura
Published: October 2002

A new synthesis method for TiC films is developed by applying high pressure (1.45 or 10.9 kbar) and electric field (37 or 99 MV/m) to a double layer consisting of a polyethylene film and a Ti film on a steel substrate at room temperature. Not only TiC+ ions but also (TiC2)2
+, TiC2H+ and (TiC2)2H+ ions are detected, using secondary ion mass spectroscopy, on the surfaces of the synthesized samples. An X-ray diffraction peak of TiC(111) is clearly visible in the sample heat treated at 600°C for 2 days after synthesising under the conditions of 10.9 kbar and 37 MV/m with a negative electrode on the Ti-film side. The Knoop hardness of this sample shows a higher value than those synthesized using other conditions.
The Effects of Pretreatment, CH4 Gas Ratio and Bias Potential on the Microstructure of Microwave Plasma Enhanced Chemical Vapor Deposited Diamond Thin Films
Authors: Park Jong-Wan , Lee You-Kee , Lee Sei-Hyun , Cho Kwang-Joon , Lee Jae-Suk , Lee Seoghyeong , Hyeongtag Jeon Hyeongtag Jeon , Ji-Hwan Choi Ji-Hwan Choi
Published: October 2002

Diamond thin films were deposited on p-type Si(100) wafers by microwave plasma enhanced chemical vapor deposition (MPECVD) using mixtures of H2, CH4 and O2 gases. Deposition was carried out at a substrate temperature of 900°C and a pressure of 40 Torr. In order to examine the effect of pretreatment on the film formation, SiC and diamond powders were used as pretreatment powders. Also, the methane gas ratio in the gas mixture was varied to observe its effect on the crystal structure of diamond films. Furthermore, the substrate bias effect on the diamond film formation was examined. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy were utilized to characterize the microstructures of diamond thin films. The highest nucleus density was obtained by pretreatment with diamond powders of 40mbox-60 µm in size and a negative bias potential to the substrates. The deposited diamond films were found to contain many defects. The density of the defects increased with CH4 concentration in the gas mixtures. It is believed that the gas mixture with a high CH4 ratio must have promoted the formation of a graphite phase, probably due to the insufficient amount of atomic hydrogen acting as a selective etchant for graphite. Diamond films with good quality and a nucleus density of 108/cm2 could be deposited by utilizing the combined effects of a negative bias potential and a magnetic field.
Time-of-Flight Mass Spectrometry of Positive Ions in Helicon-Wave Excited High-Density CF 4 and C 4F 8 Plasmas
Authors: Koichi Sasaki Koichi Sasaki , Kenichiro Ura Kenichiro Ura , Kazunari Suzuki Kazunari Suzuki , Kiyoshi Kadota Kiyoshi Kadota
Published: October 2002

The composition of positive ions was investigated using a time-of-flight mass spectrometer in high-density CF4 and C4F8 helicon plasmas. For low (n
e <1 ×1012 cm-3) electron densities, the dominant positive ions were CF3
+ and CF+ in the CF4 and C4F8 plasmas, respectively, while for high (n
e >8 ×1012 cm-3) electron densities, the dominant positive ions were C+ and F+ in both the CF4 and C4F8 plasmas. However, the C+/F+ ion current ratio was higher in the C4F8 plasma than the CF4 plasma. The reaction kinetics of positive ions is discussed based on the electron density dependence of the mass spectral intensities.
Behavior of Gallium Secondary Ion Intensity in Gallium Focused Ion Beam Secondary Ion Mass Spectrometry
Authors: Tetsuo Sakamoto Tetsuo Sakamoto , Masanori Owari Masanori Owari , Yoshimasa Nihei Yoshimasa Nihei
Published: October 2002

We studied the behavior of Ga+ secondary ion intensity in relation to oxygen matrix effect in gallium focused ion beam secondary ion mass spectrometry (Ga FIB SIMS). In two types of experiments, namely, ambient oxygen gas introduction and removal of native oxide film, the Ga+ intensity was found to behave in relation to the oxygen matrix effect in the same way as the matrix ion intensity. From the results, we proposed a way to cancel the oxygen matrix effect by using implanted Ga as an internal standard. Furthermore, the accumulation manner of Ga in a sample was examined by changing the Ga+ dose rate and the incident angle of the FIB in order to clarify the experimental conditions under which the use of Ga+ standard is applicable.
Comprehensive Spectral Analysis of Time Series Data of Recurrent Epidemics
Authors: Sumi Ayako , Ohtomo Norio , Tanaka Yukio , Akio Koyama Akio Koyama , Kazuo Saito Kazuo Saito
Published: October 2002

A comprehensive spectral analysis of data from the surveillance of infectious diseases in Japan on the weekly incidences of measles, chickenpox, mumps and rubella was carried out using a computing program known as “MemCalc.” Each power spectral density (PSD) indicated exponential decay until it leveled off at a limit determined by the accuracy of the present data. Many spectral lines observed in the PSD could be fully assigned using linear combinations of a few fundamental periods. The optimum least squares fitting curve calculated using these fundamental periods essentially reproduced the underlying variation of disease data and an extension of the curve could be used to predict the incidence of the diseases. The effect of mass vaccinations on measles was quantitatively estimated by analyzing the monthly data from Statistics on Communicable Disease. The periodic modes for seasonal oscillations were also estimated. Some discussions including the chaotic dynamics of data on the outbreak of diseases are presented. The method of analysis was confirmed to be a highly effective in elucidating temporal variations of disease data of short data length.
A Novel Shallow Trench Isolation Technique
Authors: Cheng Juing-Yi , Chao Tan Fu Lei
Published: October 2002

Shallow-trench isolation processes which involve refilling using deposition of oxide and polysilicon were investigated. Our results show that the oxide-filled shallow-trench isolation technology based on chemical-mechanical polishing (CMP) is difficult to control and results in poor uniformity. Use of this technology also involves in the dishing effect in wide field regions. However, shallow-trench isolation technology using a masking nitride layer, polysilicon refill, the CMP process with high etch selectivity, and local oxidation of polysilicon is easily implemented and absolutely field oxide encroachment (bird's beak) free. Although the CMP process results in the dishing effect in wide field regions, the local oxidation of polysilicon can reduce the amount of dishing. The polysilicon-filled shallow-trench isolation process can also achieve excellent uniformity across 6-inch diameter silicon wafers due to the high etching selectivity of polysilicon to chemical-vapor-deposited (CVD) oxide and SiN. Moreover, the n+/p junction leakage current of polysilicon-filled shallow trenches is comparable to that of oxide-filled shallow trenches. This simple and easily controllable process is a very promising candidate for shallow trench isolation.
Charge Storage Effects in Pseudomorphic High Electron Mobility Transistors
Authors: Schuermeyer Fritz , Cerny Charles , Bozada Chris , Fang Z-Q. , Look D. C.
Published: October 2002

We present for the first time results on charging effects in fully fabricated pseudomorphic high electron mobility transistors (PHEMTs), using in-situ photoemission and conduction (PEC) studies. The experiments were performed on GaAs based FETs with strained InGaAs channels. These studies evaluate hole storage in the channel area which modifies the threshold voltage of the field effect transistors (FETs). Deep level transient spectroscopy (DLTS) measurements were performed and the results compared to the data obtain from the photo studies. Understanding of hole storage is of significance in modeling the devices since holes are attracted towards the channel when the device is pinched off.
Effects of Cleavage on Local Cross-Sectional Stress Distribution in Trench Isolation Structure
Authors: Yagishita Atsushi , Saito Tomohiro , Satoshi Matsuda Satoshi Matsuda , Yukihiro Ushiku Yukihiro Ushiku
Published: October 2002

We have taken polarized micro-Raman spectra around the cleaved (011) cross section of a trench embedded in the (100) surface of a silicon substrate and found that the cleavage greatly affects the local cross-sectional stress distribution. That is, the stress distribution obtained from Raman measurements on the cleaved surface differs from the original stress distribution before cleavage. We found that a three-dimensional stress simulation based on the elastic model using specific boundary conditions is useful in explaining these cleavage effects and estimating the local cross-sectional stress distribution before cleavage. We describe the change in distribution and direction of each of stress component caused by the cleavage effects in a trench isolation structure. Further, we show that the three normal stress components are important for analyzing the stress distribution obtained from Raman spectra measured on the cleaved cross section of the trench.
Time Resolved Analysis of C2Emission from Laser Induced Graphite Plasma in Helium Atmosphere
Authors: Harilal S. S. , Issac Riju C. , Bindhu C. V. , V. P. N. Nampoori V. P. N. Nampoori , C. P. G. Vallabhan C. P. G. Vallabhan
Published: October 2002

We report time resolved study of C2emission from laser produced carbon plasma in presence of ambient helium gas. The 1.06 µm radiation from a Nd:YAG laser was focused onto a graphite target where it produced a transient plasma. We observed double peak structure in the time profile of C2species. The twin peaks were observed only after a threshold laser fluence. It is proposed that the faster velocity component in the temporal profiles originates mainly due to recombination processes. The laser fluence and ambient gas dependence of the double peak intensity distribution is also reported.
Indium Doped nMOSFETs and Buried Channel pMOSFETs with n+ Polysilicon Gate
Authors: Lee Yeong-Taek , Song Ki-Whan , Byung-Gook Park Byung-Gook Park , Jong Duk Lee Jong Duk Lee
Published: October 2002

We have investigated the properties of indium for channel doping engineering. We have fabricated 0.1 µ m super-steep-retrograde (SSR) channel nMOSFETs and buried channel pMOSFETs with an indium counter doping layer. It is found that: (1) Indium is a promising channel dopant when it is implanted into a sub-surface with relatively high energy and its steep profile is maintained throughout the entire process of SSR nMOSFETs. (2) However, it is not practical as a dopant for near-surface p-type conduction layers such as buried channels or p- LDDs in pMOSFETs due to its incomplete ionization and high diffusivity in oxide.
Impact of Tunnel Film Oxynitridation on Band-to-Band Tunneling Current and Electron Injection in Flash Memory
Authors: Arakawa Tomiyuki , Matsumoto Ryoichi , Takahisa Hayashi Takahisa Hayashi
Published: October 2002

The impact of the use of oxynitride tunnel film on write, erase and read operations of flash memories was investigated. We found that during electron ejection from a floating gate into a drain, band-to-band tunneling currents of flash memory cells with tunnel films having a high degree of nitridation are two orders of magnitude smaller than that of flash memory cells with oxide tunnel films. Consequently, higher-nitridation tunnel films improve the endurance characteristics of flash memory. However, during electron injection from a channel into the floating gate, Fowler-Nordheim tunneling gate currents of flash memory cells with higher-nitridation tunnel films are two orders of magnitude smaller than that of flash memory cells with oxide tunnel films. Moreover, the threshold voltage of flash memory cells with oxynitride tunnel films is 0.24–0.48 V smaller than that of flash memory cells with oxide tunnel films in read operations. These results can be explained by the modification of the electric field under oxynitride tunnel films due to the formation of donor layers, which is induced by nitridation of tunnel oxide films.
High-Quality CVD/Thermal Stacked Gate Oxide Films with Hydrogen-Free CVD SiO2 Formed in a SiCl4–N2O System
Authors: Ogata Tamotsu , Kobayashi Kiyoteru , Watanabe Hajime , Kurokawa Hiroshi , Yasuji Matsui Yasuji Matsui , Makoto Hirayama Makoto Hirayama
Published: October 2002

We have developed and evaluated chemical vapor deposition (CVD) SiO2 films formed in a hydrogen-free system in which tetrachlorosilane ( SiCl4; TCS) and nitrous oxide ( N2O) are used as low pressure CVD source gases. It has been found that the hot-carrier degradation, the constant current time-dependent dielectric breakdown (TDDB) and the charge-trapping characteristics are superior to those of conventional CVD SiO2 films formed from dichlorosilane ( SiH2Cl2; DCS) and N2O. We have concluded that TCS–SiO2 is appropriate for CVD stacked gate oxide films due to its low electron trap density and high reliability.
Mechanism for Desorption of SiF4 from an SiO2 Film Surface in HF Solutions
Authors: Oku Tomoki , Kazuhiko Sato Kazuhiko Sato , Mutsuyuki Otsubo Mutsuyuki Otsubo
Published: October 2002

An extended Hückel calculation was employed to calculate the change in the electron density on the Si–O back bonds and the total electronic energy during the reaction at the SiO2 film surface. We demonstrate that the desorption of SiF4 occurs as follows: (1) bifluoride ( HF2
-) ions dissociate into HF monomers and F- ions near the surface, (2) F- ions attack the - SiF3 surfaces and hydrogen ions attack the oxygen atoms of the back bond, (3) the O–Si–F bond angle decreases and the Si–O bond strength is weakened, (4) the hydrogen atoms passivate the oxygen atoms after tetrahedral SiF4 molecules are generated and the Si–O back bonds are broken. The evaluated activation energy of the desorption of SiF4 is 0.8 eV.
Low Temperature (≤550°C) Fabrication of CMOS TFT's on Rapid-Thermal CVD Polycrystalline Silicon-Germanium Films
Authors: Lee Seo-Kyu , Choe Seong-Min , Ahn Chang-Geun , Chung Wook-Jin , Kwon Young-Kyu , Bong-Koo Kang Bong-Koo Kang , Ohyun Kim Ohyun Kim
Published: October 2002

N-channel and p-channel metal-oxide-semiconductor (MOS) thin-film transistors (TFT's) have been fabricated on rapid thermal chemical vapor deposition (RTCVD) polycrystalline silicon-germanium (poly- Si0.88Ge0.12) films by a low temperature (≤550° C) process. These devices employ in-situ n+ doped poly- Si0.65Ge0.35 films as gate electrodes to reduce the process time and temperature, dual-offset spacers to reduce the electric field in the drain junction region, and silicon capping layers to protect the poly-Si1-x
Ge
x
films against oxygen. The I
d-V
g characteristics in n-channel TFT's, as well as in p-channel TFT's, exhibit good behavior after remote-PECVD hydrogenation. Further improvements on electrical properties in n-channel TFT's are limited by trap-inducing G
e behaviors in poly-Si1-x
Ge
x
films.
Formation and Properties of Proton-exchanged Z-cut MgO:LiNbO3 Crystal Waveguides
Authors: Zhuo Zhuang , Chong Tow C. , Chow Y. T.
Published: October 2002

Proton-exchanged waveguides of Z-cut LiNbO3 (LN) doped with different contents of MgO are fabricated in benzoic acid. The effective refractive indexes of the guided modes are measured by prism-coupling method at different wavelengths of 480 nm, 514.5 nm, 532 nm, 632.8 nm and 1064 nm respectively, and the dispersion of the refractive index increments of the waveguides is given. The refractive index profiles are obtained by IWKB method and the diffusion coefficients are calculated. The results show that the waveguides have the step-like profiles and the diffusion characteristics are influenced by the doping MgO contents in the LiNbO3 crystal. The diffusion mechanisms are discussed finally.
Diffusion and Segregation of Carbon in SiO2 Films
Authors: Mizushima Ichiro , Kamiya Eiji , Arai Norihisa , Sonoda Masahisa , Yoshiki Masahiko , Takagi Shin-ichi , Wakamiya Mikio , Kambayashi Shigeru , Mikata Yuichi , Kashiwagi Sei-ichi Mori
Published: October 2002

Diffusion of carbon in SiO2 films and its segregation at the Si/SiO2 interface were investigated using carbon-incorporated borophosphosilicateglass (BPSG) films and carbon-implanted SiO2 films. It was found that carbon atoms diffuse in SiO2 film at a temperature as low as 500° C. Carbon atoms segregated at the Si/SiO2 interface and induced positive charge. The positive charge density was proportional to the segregated carbon concentration. Field emission transmission electron microscopy (FE-TEM) and electron energy loss spectra (EELS) observations revealed that carbon atoms exist on the SiO2 side of the interface, and another carbon-rich phase is formed in S
i
O
2.
The Characteristics of SrS:Ce Thin Film Electroluminescent Devices
Authors: Kina Hideki , Tamura Yukihisa , Yamada Yoji , Maruta Yukihiro
Published: October 2002

SrS:Ce thin films were fabricated by electron beam evaporation under several conditions such as substrate temperature, deposition rate and sulphur pressure during evaporation. The relationship between the quality of phosphor layers and the luminance of EL (electroluminescent) devices investigated. The bigger dead layer of SrS:Ce phosphor layer produced the larger spike current when bipolar trapezoidal voltage pulses were loaded on the SrS:Ce TFEL (thin film electroluminescent) devices. The low crystallinity of the phosphor bulk layer reduced the spike current. The magnitude of spike current is limitted by a balance between the number of hot electrons injected into the phosphor layer from the phosphor-insulator interface and the number of hot electrons captured by defect levels in phosphor layer. The luminance of EL devices is determined by the effective number of hot electrons and the crystallinity of phosphor layer.
Chemical Vapor Deposition of Hydrogen-Free Silicon-Dioxide Films
Authors: Uchida Yasutaka , Matsumura Shu Takei
Published: October 2002

A new source gas mixture of Si(NCO)4 and N(CH3)3 has been investigated for low-temperature chemical vapor deposition of silicon dioxide. Hydrogen-free films have been successfully deposited at 200° C for the first time. Evaluated results are also presented for deposition characteristics and deposited film properties. The breakdown-field strength and low-field resistivity were as high as 5.9 MV/cm and 6×1016 Ωcm, respectively, for the as-deposited film.
Reconditioning-Free Polishing for Interlayer-Dielectric Planarization
Authors: Nakamura Ko , Sadahiro Kishii Sadahiro Kishii , Yoshihiro Arimoto Yoshihiro Arimoto
Published: October 2002

In chemical mechanical polishing (CMP) using a colloidal silica slurry with a pH of 10–11 for interlayer-dielectric (ILD) planarization, the removal rate of the oxide film drops off rapidly because the pad surface becomes flat during a CMP process. Thus we must recondition the polishing pad surface in order to obtain the rough polishing pad surface. In result, we can maintain a constant removal rate of the oxide film during the life time of the pad. We clarified that the alteration of the polishing pad surface was caused by the KOH solution in a conventional slurry. We also found that our newly developed MnO2 slurry could prevent the alteration of the polishing pad surface in reconditioning-free CMP.
Anomalous Junction Leakage Behavior of Ti Self Aligned Silicide Contacts on Ultra-Shallow Junctions
Authors: Sakata Atsuko , Tomita Mitsuhiro , Koike Mitsuo , Koyama Masato , Kunishima Iwao
Published: October 2002

An anomalous junction leakage is observed in Ti self aligned silicide (Ti-SALICIDE) contacts on ultra-shallow junctions less than 0.1 µ m. After annealing at around 460° C for 30 min, the leakage current increases considerably for n+/p junctions and decreases slightly for p+/n junctions. At a reverse bias of 1 V, the activation energies of the leakage current for n+/p junctions and p+/n junctions annealed at 460° C for 30 min are 0.16 eV and 0.97 eV, respectively. The very small activation energy for the n+/p junction can be explained by a tunneling current. The results of secondary-ion mass spectroscopy (SIMS), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX) analyses indicate that a considerable amount of Ti diffuses into n+-Si at around 460° C. However, only a small amount of Ti diffuses into p+-Si. This anomalous junction leakage can be explained in terms of tunneling assisted by traps due to the diffused Ti. These low temperature phenomena are thought to represent the process in the early stage of Ti silicidation.
Proposal of Pseudo Source and Drain MOSFETs for Evaluating 10-nm Gate MOSFETs
Authors: Hisao Kawaura Hisao Kawaura , Toshitsugu Sakamoto Toshitsugu Sakamoto , Toshio Baba Toshio Baba , Yukinori Ochiai Yukinori Ochiai , Jun'ichi Fujita Jun'ichi Fujita , Shinji Matsui Shinji Matsui , Jun'ichi Sone Jun'ichi Sone
Published: October 2002

We propose a Pseudo source and drain metal oxide semiconductor field effect transistors (Ps-MOSFET) for investigating the electrical characteristics and physical phenomena in 10-nm gate MOSFETs. The Ps-MOSFET consists of a lower gate and an upper gate which electrically induce pseudo source and drain regions at the silicon surface. In this structure, the pseudo source/drain regions act as doped source/drain regions in a MOSFET. Since the pseudo source/drain regions are extremely shallow, short-channel effects are expected to be suppressed in this structure. To minimize the channel length and the leakage current, we optimized the substrate doping concentration to be approximately 1018 cm-3 by using a two-dimensional numerical simulation. In this case, we obtained a channel length of approximately 16 nm for 10-nm gate Ps-MOSFETs. Under this optimal doping condition, numerical calculations showed satisfactory transistor operations for the 10-nm gate Ps-MOSFETs: ON/OFF current ratio ∼106 and subthreshold slope ∼100 mV/decade. We also showed by calculation that the direct source-drain tunneling current was not negligible in the sub-10-nm regime.
Transient Light Scattering of a Ferroelectric and an Antiferroelectric Liquid Crystal with Short Pitch
Authors: Heinz-Siegfried Kitzerow Heinz-Siegfried Kitzerow
Published: October 2002

The electrooptic properties due to the transient light scattering mode (TSM) are studied for non-aligned ferroelectric and antiferro-electric liquid crystals with short pitch. The transient light scattering appears in thick samples without polarizers if the sign of an applied dc field is reversed. As a consequence, an ac field of suitable frequency can be used to switch the sample from a transparent to a scattering state. Due to the short pitch, a colored scattering can be observed under oblique angles. The latter effect provides high contrast ratios.
Effect of SiO2 Film Deposition on the Ferroelectric Properties of a Pt/Pb(Zr, Ti)O3/Pt Capacitor
Authors: Park Sejun Oh , Kim Byung Hee , Lee Sang Min , Yoo Cha Young , Moon Jong , Lee Sang In , Young Bum Koh Young Bum Koh , Moon Yong Lee Moon Yong Lee
Published: October 2002

The degradation of the ferroelectric properties of a Pt/Pb(Zr, Ti)O3/Pt capacitor due to the back-end process of the ferroelectric random access memory (FRAM) device fabrication process is studied with particular reference to the interlayer dielectric (ILD) and its passivation. The SiO2 film for the ILD layer was deposited by two methods: electron cyclotron resonance chemical vapor deposition (ECR CVD) using SiH4/ N2O gas and atmospheric pressure thermal CVD using tetra ethyl ortho-silicate (TEOS) and O3 ( O3-TEOS CVD). The ECR CVD-SiO2 deposition at temperatures higher than 300° C severely damaged the ferroelectric properties of the Pt/Pb(Zr, Ti)O3/Pt capacitor. However, when the SiO2 film was deposited at temperatures lower than 250° C by ECR CVD, the nonvolatile remnant polarization of a capacitor with an area of 100×100 µ m2 was found to be about 10 µ C/cm2, which makes this a valuable ILD process for FRAM fabrication. The ferroelectric property degradation of the Pt/Pb(Zr, Ti)O3/Pt capacitor by the O3-TEOS SiO2 was less severe than that of the ECR CVD-SiO2. The ferroelectricity of the capacitors damaged by the SiO2 film deposition was recovered by post-annealing.
Reliability of Ultra-Thin Gate Oxide Below 3 nm in the Direct Tunneling Regime
Authors: Depas Michel , Degraeve Robin , Nigam Tanya , Guido Groeseneken Guido Groeseneken , Marc Heyns Marc Heyns
Published: October 2002

Cluster tool furnace technology was used to control the growth of extremely uniform ultra-thin 1.5 nm to 3 nm SiO2 layers on Si. The transition from Fowler-Nordheim tunneling to direct tunneling electron injection for sub-3-nm oxide poly-Si gate metal-oxide-silicon capacitor structures is described and the influence on the oxide reliability is discussed. It is shown that oxide breakdown can still occur at low voltages in the direct tunneling regime under the condition of electron injection from the poly-Si gate. Soft breakdown of these ultra-thin oxide layers, accompanied by the occurrence of complex fluctuations in the direct tunneling current, is demonstrated. Using this as the definition of sub-3-nm oxide breakdown, it is shown for the first time that the time to dielectric breakdown of the sub-3-nm gate oxide in the direct tunneling regime is determined by the electrical field strength in the oxide similarly to the case of the sub-3-nm dielectric breakdown in Fowler-Nordheim tunnel stressing.
Structural and Electrical Properties for Fluorine-Doped Silicon Oxide Films Prepared by Biased Helicon-Plasma Chemical Vapor Deposition
Authors: Tamura Takahiro , Sakai Junro , Satoh Makoto , Yoichi Inoue Yoichi Inoue , Hikaru Yoshitaka Hikaru Yoshitaka
Published: October 2002

Fluorine-doped silicon oxide (SiOF) films, prepared using biased helicon-plasma chemical vapor deposition, are investigated to clarify the relationship between their bond structures and electrical properties. For this purpose, C-V characteristics, I-V characteristics, FT-IR and Raman spectra were measured. In this investigation, two kinds of SiOF films prepared with SiF4 flow ratios of 0.5 and 1.0 were compared. The SiOF film prepared with a SiF4 flow ratio of 0.5 has a low leakage current and its relative dielectric constant is 3.6, whereas the film prepared with a SiF4 flow ratio of 1.0 has a high leakage current and its relative dielectric constant is 3.2. FT-IR and Raman spectra studies clarify the following: (1) The SiOF film with a low leakage current contains Si–F bonds, as well as 3-fold or 4-fold rings. (2) The SiOF film with a high leakage current contains F–Si–F bonds or near-neighbor Si–F bonds in addition to Si–F bonds, but it does not contain 3-fold or 4-fold rings.
Suppression of Parasitic MOSFETs at LOCOS Edge Region in Partially Depleted SOI MOSFETs
Authors: Yasuoka Akihiko , Iwamatsu Toshiaki , Ipposhi Takashi , Miyamoto Shoichi , Yamaguchi Yasuo , Yasuo Inoue Yasuo Inoue , Hirokazu Miyoshi Hirokazu Miyoshi
Published: October 2002

The fixed oxide charge at a SOI/buried oxide interface and the fixed oxide charge in the LOCOS (LOCal Oxidation of Silicon) edge region are analyzed by measuring I
d-V
g and I
d-V
back characteristics of partially depleted SOI NMOSFETs with and without hydrogenation. It is considered that threshold voltage lowering of the parasitic MOSFET is caused by both the fixed oxide charges. It is also shown that hydrogenation is effective in suppressing a hump in the subthreshold region of LOCOS-isolated SOI MOSFETs. The density of the fixed oxide charge in the LOCOS edge region is reduced by hydrogenation, but the fixed oxide charge at the SOI/buried oxide interface is not. It is found that the change of the fixed oxide charge density caused by hydrogenation shows almost the same behavior in SIMOX (Separation by IMplanted OXygen) substrates of different manufacturers, but the threshold voltage of the parasitic MOSFET depends on the SIMOX substrate due to the difference in the fixed oxide charge density at the SOI/buried oxide interface.
A New Low-Resistance Antifuse with Planar Metal/Dielectric/Poly-Si/Dielectric/Metal Structure
Authors: Baek Jong Tae , Chung Sung Hoon , Kang Sang Won , Ahn Byung Tae , Hyung Joun Yoo Hyung Joun Yoo
Published: October 2002

A new antifuse with metal/dielectric/poly-Si/dielectric/metal structure has been developed for use in FPGAs as a voltage programmable link. This structure has two thermally grown dielectrics with an 8.5 nm thickness and a boron-doped poly-Si pad. Low programmed on-state resistance of ∼20 Ω was achieved by the formation of Al–Si metal alloy link in the doped poly-Si pad. The metal link was formed by the diffusion of Al from the positive electrode into poly-Si. The dielectric property of this antifuse might be reliable because of no hillocks on the bottom electrode and no interaction between the thermally grown SiO2 and the bottom electrode.
Observation of Coulomb Blockade Type Conductance Oscillations up to 50 K in Gated InGaAs Ridge Quantum Wires Grown by Molecular Beam Epitaxy on InP Substrates
Authors: Hiroshi Okada Hiroshi Okada , Hajime Fujikura Hajime Fujikura , Tamotsu Hashizume Tamotsu Hashizume , Hideki Hasegawa Hideki Hasegawa
Published: October 2002

InP-based quantum wire (QWR) transistors were successfully fabricated for the first time directly on InAlAs/InGaAs ridge QWRs grown by selective molecular beam epitaxy (MBE) on patterned (001) InP substrates. Each wire showed strong photoluminescence, cathodoluminescence and Shubnikov-de Haas (SdH) oscillations. The behavior of the SdH oscillations confirmed the presence of gate-controlled one-dimensional transport. Near pinch-off, QWR transistors showed Coulomb blockade type conductance oscillations up to 50 K. The effective value of the Coulomb gap was estimated to be 28 mV. Possible mechanisms for quantum dot formation are discussed.
In-Situ STM Observation of GaAs Surfaces after Nitridation
Authors: Makimoto Toshiki , Kasu Makoto , Jean L. Benchimol Jean L. Benchimol , Naoki Kobayashi Naoki Kobayashi
Published: October 2002

Scanning tunneling microscopy was used to study surface morphologies for various GaAs surfaces after nitridation using atomic nitrogen. For the (100) surface, 3-nm-wide stripes were observed along the [011] azimuth. Smooth surfaces densely covered with small GaN grains were observed for the (311)A and (111)A surfaces, while large GaN grains with some voids were observed for the (111)B surface. These results suggest that the (n11)A surfaces are promising for the growth of GaN on GaAs. Among the (100), (111)B, and (111)A GaAs surfaces, the (111)A surface after nitridation showed the largest selectivity of GaAs growth in metalorganic molecular beam epitaxy using trimethylgallium and tertiarybutylarsine. The surface roughness of GaAs after nitridation was also found to have a major effect on the selectivity of GaAs growth.
Fabrication of p+-Gate InAs-Channel HEMT Based on InP
Authors: Koizumi Ryoji , Toshiya Saitoh Toshiya Saitoh , Kanji Yoh Kanji Yoh
Published: October 2002

We have successfully fabricated a p+- n junction gate InGaAs/InAlAs high electron mobility transistor (HEMT) with a thin InAs layer inserted in the InGaAs channel. An intrinsic transconductance of over 400 mS/mm and maximum drain current of 250 mA/mm were obtained in a 1 µ m gate length device with relatively thick gate-to-channel barrier of 375 Å. We have also applied the present fabrication method to 0.25 µ m gate length device using electron beam lithography and wet chemical etching, verifying the decent dc operation with reduced gate leakage current. T-shaped gate electrode was shown to be successfully fabricated for the basic investigation of HEMT for high frequency operation.
A WSi Base Electrode and a Heavily-Doped Thin Base Layer for High-Speed and Low-Power InGaP/GaAs HBTs
Authors: Oka Tohru , Ouchi Kiyoshi , Kazuhiro Mochizuki Kazuhiro Mochizuki , Tohru Nakamura Tohru Nakamura
Published: October 2002

The characteristics of a WSi base electrode and a heavily-doped thin base layer in InGaP/GaAs heterojunction bipolar transistors (HBTs) are demonstrated. An HBT with a new structure using a WSi base electrode and a heavily-doped thin base layer is proposed to achieve high-speed and low-power operation. WSi is shown to be useful in fabricating a base electrode for HBTs with a narrow base-contact width and a buried SiO2 structure, and a contact resistance of under 2×10-7 Ω· cm2 was obtained with a hole concentration of over 2×1020 cm-3 by annealing for 30 minutes at 400° C. HBTs with a 30-nm-thick base doped to under 2×1020 cm-3 achieved current gain of more than 10.
Kelvin Probe Force Microscopy for Potential Distribution Measurement of Cleaved Surface of GaAs Devices
Authors: Arakawa Masashi , Shigeru Kishimoto Shigeru Kishimoto , Takashi Mizutani Takashi Mizutani
Published: October 2002

Kelvin probe force microscopy (KFM) was successfully applied to the measurement of two-dimensional potential distribution of the cleaved surface of GaAs devices under bias voltage. It was shown that the voltage resolution is less than 10 mV. The measured potential profile of the ungated HEMTs shows a potential knee, which probably originates from the charge trapped at the interface between the epitaxial layer and the substrate. It also shows a potential ridge which corresponds to the channel. Current crowding phenomena are also confirmed to occur at the edge of the drain electrode.
CBE Grown (GaIn)(AsP) Laser Diodes for Monolithic Integration
Authors: Kratzer Heinrich , Nutsch Andreas , Torabi Bahram , Tränkle Günther , Weimann Günter
Published: October 2002

Selective in-filling growth by chemical beam epitaxy (CBE) is ideally suited for the monolithic integration of InP-based laser diodes and photonic devices. The growth was carried out on exactly oriented (100) n-InP substrates as well as on 2° off toward next [110] oriented substrates. The preparation of the substrates and the growth parameters, e.g. growth rate, strongly influences the shape and optical properties of embedded (GaIn)(AsP) laser diodes shown by scanning electron microscopy (SEM) and spatially resolved cathodoluminescence (CL) measurements. By reducing the growth rate from 1.3 µm/h to 0.4 µm/h at a high V/III
B
E
P
ratio of 18 during the growth of the InP buffer flat layers are grown within narrow grooves. Separate confinement heterostructure (SCH) multi quantum well (MQW) laser diodes (λ=1.55 µm) with cleaved mirrors selectively in-filled in 3 µm wide grooves show a device performance comparable to conventional `state of the art' quaternary laser diodes; e.g. lasers with 6 QW show threshold currents of 16 mA and light output of several mW in CW operation. By butt joining we integrated quaternary ridge waveguide (RW) laser diodes and waveguides.
Stark Ladder Photoluminescence of X States in GaAs/AlAs Type-I Superlattices
Authors: Naoki Ohtani Naoki Ohtani , Makoto Hosoda Makoto Hosoda , Hidenori Mimura Hidenori Mimura , Koji Tominaga Koji Tominaga , Toshihide Watanabe Toshihide Watanabe
Published: October 2002

We report on an observation of Stark ladder photoluminescence (PL) of X states in GaAs/AlAs type-I superlattices. The PL line exhibits a linear blue shift corresponding to one half the period of the superlattice with increasing bias voltage. The PL intensity then becomes maximum when X1-Γ2 mixing occurs. Carrier sweep-out from the X states is drastically improved by the X1-Γ2 mixing. These results demonstrate that optical properties even in type-I superlattices are seriously affected by the mixing of X states with a higher Γ subband under an electric field.
Heat-Treatment Study of Deep-Level Defects in Semi-Insulating Liquid-Encapsulated Czochralski Gallium Arsenide Substrates
Authors: Yoshida Hiroaki , Kiyama Makoto , Takebe Toshihiko , Keiichiro Fujita Keiichiro Fujita , Shin-ichi Akai Shin-ichi Akai
Published: October 2002

Deep-level defects in semi-insulating (S.I.) liquid-encapsulated Czochralski (LEC) GaAs substrates were studied using the thermally stimulated current (TSC) technique. From the heat-treatment temperature dependence of the TSC signal intensity and electrical properties, the thermal behavior of the detected defects with respect to the heat treatment and their correlation to the electrical properties of the substrate were clarified for the first time. The change in the resistivity was closely related to the changes in the TSC signal intensity of T3 (trap depth: 0.31 eV), T6 (0.58 eV) and T x (0.29 eV). The net concentration of these defects changed by 4×1014 cm-3 after heat treatment at 800°C, leading to a threefold increase of the resistivity. Precise thermal control of substrates is very important for consistently obtaining high-quality GaAs substrates.
Microwave Dielectric Properties of Certain Simple Alkaline Earth Perovskite Compounds as a Function of Tolerance Factor
Authors: Sivasubramanian V. , Viswanathan V. R. K. Murthy
Published: October 2002

Microwave dielectric properties of some simple alkaline earth perovskite compounds were studied with respect to the variation in the tolerance factor. It was found in the present study that the variation in dielectric constant (ε), Q·f
o product and the temperature coefficient of polarizability with tolerance factor is quite opposite to what is observed in some complex perovskite materials. It was also observed that the temperature coefficient of dielectric constant follows the same trend as in some complex perovskite materials with respect to the tolerance factor.
Time Constant for High-Field Domain Formation in Multiple Quantum Well Sequential Resonant Tunneling Diodes
Authors: Yozo Shimada Yozo Shimada , Kazuhiko Hirakawa Kazuhiko Hirakawa
Published: October 2002

We have investigated the frequency dependence of the tunneling current-voltage (I-V) characteristics of GaAs/ Al0.3Ga0.7As multiple quantum well (MQW) sequential resonant tunneling diodes. Although clear periodic negative differential resistances (NDRs) are observed in the dc measurement, such NDRs are found to disappear at high frequencies, indicating a finite time constant necessary for the formation of stable high-field domains. The observed time constant has been well explained by the product of the capacitance of a single tunneling barrier and the intrinsic tunneling resistance in the low-field domain.
Effect of ZnO Additive on Microstructure and Microwave Dielectric Properties of CaTi1-x(Fe0.5Nb0.5)xO3 Ceramics
Authors: Kucheiko Sergey , Kim Hyun-Jai , Seok-Jin Yoon Seok-Jin Yoon , Hyung-Jin Jung Hyung-Jin Jung
Published: October 2002

The microwave dielectric properties of the CaTi1-
x

(Fe0.5Nb0.5)

x

O3 (0.4≤x≤0.7) solid solutions and the influence of 1 wt% ZnO as a sintering additive are investigated. With the increase of x, dielectric constant (ε

r
) and product of quality factor and frequency (Q·f) decrease. The temperature coefficient of resonant frequency (τ
f
) value of nearly 0 ppm/°C can be realized for x=0.54. The properties of this material are: ε

r
=59.9, Q·f=3870 GHz. ZnO forms a liquid phase on the grain boundaries and improves the sinterability and grain growth. The correlation between average grain size and Q-factor is observed for ZnO-doped ceramics.
Breakdown Mechanism of Oxide Grown on Czochralski Silicon Wafers
Authors: Satoshi Oka Satoshi Oka , Masatake Katayama Masatake Katayama
Published: October 2002

The breakdown mechanism of oxide grown on Czochralski (Cz) silicon wafers was studied using a combination of copper decoration and transmission electron microscopy (TEM) observation. Recently, crystal defects with octahedral voids were found on the surface and in bulk silicon of as-grown Cz wafers. This result led researchers to infer that oxide breakdown occurs due to oxide thinning at the corner of the octahedral structure or heavy metal gettering at the void. Our study, however, does not support those models. We propose a new model that the crystal defect in the silicon wafer is filled with an “imperfect silicon”, not a void, and that the oxide breakdown occurs due to the formation of degraded oxide which is made of the imperfect silicon, during oxidation.