Shoichi Onda
Denso
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by Shoichi Onda.
Materials Science Forum | 2008
Takeshi Endo; Eiichi Okuno; Toshio Sakakibara; Shoichi Onda
We studied the annealing process to improve the field-effect channel mobility (μFE) on the 4H-SiC (11-20) face. We found that wet annealing, in which a wet atmosphere was maintained during the cooling-down period to 600°C after wet oxidation, was effective. The interface states (Dit) near the conduction band edge decreased and the μFE increased up to 244 cm2/Vs. Furthermore, the origin of this high channel mobility was investigated using secondary ion mass spectroscopy (SIMS) measurement and thermal desorption spectroscopy (TDS) analysis. It was indicated that the hydrogen density at the MOS interface was increased by the wet annealing and the hydrogen was desorbed mainly at temperatures between 800 °C and 900 °C. These hydrogen desorption temperatures also corresponded to the temperatures of the μFE reduction by argon annealing after the wet annealing. These results indicated that this high channel mobility was achieved by hydrogen passivation during the wet annealing at temperatures between 800 °C and 900 °C.
Philosophical Magazine Letters | 2013
Shoichi Onda; Hiroki Watanabe; Yasuo Kito; Hiroyuki Kondo; Hideyuki Uehigashi; Norikazu Hosokawa; Yoshiyuki Hisada; Kenji Shiraishi; Hiroyasu Saka
Threading dislocations (TD’s) in a 4H-SiC MOSFET were characterized using transmission electron microscopy with special emphasis of their effects on leakage in a p–n junction. Two types of TD’s were identified; a threading near-screw dislocation (TnSD) with , and a threading mixed dislocation (TMD) with , the last of which has been found for the first time in this study. The TnSD show only negligibly small leakage, while TMD shows a large leakage. Origins of the difference in the degree of the leakage have been discussed.
Materials Science Forum | 2008
Takeo Yamamoto; Jun Kojima; Takeshi Endo; Eiichi Okuno; Toshio Sakakibara; Shoichi Onda
4H-SiC SBDs have been developed by many researchers and commercialized for power application devices in recent years. At present time, the issues of an SiC-SBD are lower on-state current and a relatively larger-leakage current at the reverse bias than Si-PN diodes. A JBS (Junction Barrier Schottky) diode was proposed as a structure to realize a lower leakage current. We simulated the electrical characteristics of JBS diodes, where the Schottky electrode was made of molybdenum in order to optimize its performance. We fabricated JBS diodes based on the simulation with a diameter of 3.9mm (11.9 mm2). The JBS diode has a lower threshold voltage of 0.45 V, a large forward current of 40 A at Vf = 2.5V and a high breakdown voltage of 1660 V. Furthermore, the leakage current at 1200 V was remarkably low (Ir = 20 nA).
Materials Science Forum | 2012
Yasushi Urakami; Itaru Gunjishima; Satoshi Yamaguchi; Hiroyuki Kondo; Fusao Hirose; Ayumu Adachi; Shoichi Onda
A reduction in threading screw dislocation (TSD) density in 4H-SiC (silicon carbide) crystal is required for SiC power devices. In this study, TSD’s transformation by the RAF (repeated a-face) growth method [1] is observed by transmission X-ray topography (g=0004) of the cross-section of the crystal. Increasing the number of repetitions of a-face growth and offsetting c-face growth to an angle of several degrees reduce TSDs. TSD density is reduced to 1.3 TSD/cm2. The RAF growth method is very effective towards growing high quality SiC crystals.
Materials Science Forum | 2011
Fujiwara Hirokazu; Masaki Konishi; Toyokazu Ohnishi; Tutomu Nakamura; Kimimori Hamada; Takashi Katsuno; Yukihiko Watanabe; Takeshi Endo; Takeo Yamamoto; Kazuhiro Tsuruta; Shoichi Onda
The impacts of threading dislocations, surface defects, donor concentration, and schottky Schottky barrier height on the reverse IV characteristic of silicon carbide (SiC) junction barrier schottky Schottky (JBS) diodes were investigated. The 100 A JBS diodes were fabricated on 4H-SiC 3-inch N-type wafers with two types of threading dislocation density. The typical densities are were 0.2×104 and 3.8×104 cm-2, respectively. The improvement of vIt was found that variations in the leakage current and the high yield of large area JBS diodes werecould be were obtained improved by using a wafer with a low threading dislocation density. In the range of low leakage current, the investigation shows showed a correlation between leakage current and threading dislocation density.
Materials Science Forum | 2006
Yasuo Kitou; Emi Makino; Kei Ikeda; Masao Nagakubo; Shoichi Onda
High temperature chemical vapor deposition (HTCVD) simulations of silicon carbide (SiC) were demonstrated with experimental results. A vertical cylindrical reactor was used in an RF inductive heating furnace and the temperature was more than 2200. SiH4 and C3H8 were used as source gases and H2 as carrier gas. A gas phase reaction model from the literature was used on the condition that the gas phase reaction is a quasi-equilibrium state. It was found that the major species were Si, Si2C, SiC2 and C2H2 in the gas phase reaction model as well as in the thermodynamic equilibrium calculation. Sublimation etching was considered in the surface reaction rates by modifying partial pressures of species with equilibrium vapor pressures. CFD-ACE+ and MALT2 software packages were used in the present calculation. The sticking coefficients were determined by fitting the calculated growth rates to the experimental ones. The simulated growth rate in a different reactor is in good agreement with the experimental value, using the same sticking coefficients. The present simulation could be useful to design a new reactor and to find optimum conditions.
Materials Science Forum | 2014
Hiroyuki Kondo; Hidetaka Takaba; Masanori Yamada; Yasushi Urakami; Takeshi Okamoto; Masakazu Kobayashi; Takashi Masuda; Itaru Gunjishima; K. Shigeto; Nobuyuki Ooya; Naohiro Sugiyama; Akihiro Matsuse; Takahiro Kozawa; Takayuki Sato; Fusao Hirose; Shoichi Yamauchi; Shoichi Onda
We have developed RAF (Repeated a-face) growth method which is high quality bulk crystal growth technology [1, 2]. A block crystal more than 150 mm square size was produced by the RAF growth method. Since c-face growth crystal was produced on the seed obtained from the block crystal, high quality 150mm 4H-SiC wafer was achieved. This paper reports the results of the quality evaluation.
Materials Science Forum | 2008
Eiichi Okuno; Takeshi Endo; Jun Kawai; Toshio Sakakibara; Shoichi Onda
We have investigated the techniques to improve the channel mobility of SiC MOSFETs and found that the hydrogen termination of dangling bonds at a MOS interface is very effective in improving the channel mobility, particularly that of the interface fabricated on a (11-20) face wafer. A high channel mobility of MOSFET on the (11-20) face was achieved to 244cm2/Vs by new process which can terminate dangling bonds by hydrogen. The vertical MOSFET, which is prepared using this process, has a low on-resistance of 5.7 mΩcm2 and a breakdown voltage of 1100 V. The channel resistance is estimated at 0.58 mΩcm2.
Journal of Crystal Growth | 2002
Masami Naitoh; Kazukuni Hara; Fusao Hirose; Shoichi Onda
Abstract 6H-SiC crystals have been grown on the Si-face and the C-face of 6H-SiC seed crystals by sublimation growth, respectively, and their deep photoluminescence (PL) have been investigated in detail. The deep PL spectrum of undoped 6H-SiC crystal grown on the C-face consisted of multiple broad emissions. On the other hand, undoped 6H-SiC crystal grown on the Si-face showed a single weak emission peak. In the case of the nitrogen-doped 6H-SiC crystals grown on the C-face, the emissions decreased with increasing nitrogen doping concentration and that of the nitrogen-doped 4H-SiC crystals grown on the C-face also showed the same behavior. As a C-vacancy is easy to form during the sublimation growth on the C-face, we think that nitrogen occupies the C-vacancy during the doping growth and leads to a decrease in the C-vacancy concentration as reflected by the PL analysis. We speculated that the difference in the doping concentration of nitrogen in the C-face and the Si-face-grown SiC crystal is related to the presence of the C-vacancy during crystal growth.
Materials Science Forum | 2014
Yuichiro Tokuda; Jun Kojima; Kazukuni Hara; Hidekazu Tsuchida; Shoichi Onda
Our latest results of SiC bulk growth by High-Temperature Gas Source Method are given in this paper. Based on Mullins-Sekerka instability, optimal growth conditions to preclude dendrite crystals, which are one of the pending issues for high-speed bulk growth, was studied. First, the simulation studies showed that high temperature gradient in a growing crystal is required for high-speed bulk growth without dendrite crystals. Second, high-speed bulk growth was demonstrated under high temperature gradient.