Papers by Author: Shin Ichi Nishizawa

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Authors: Naoki Oyanagi, Shin Ichi Nishizawa, Kazuo Arai
Authors: Akimasa Kinoshita, Junji Senzaki, Makoto Katou, Shinsuke Harada, Mitsuo Okamoto, Shin Ichi Nishizawa, Kenji Fukuda, Fukuyoshi Morigasa, Tomoyoshi Endou, Takuo Isii, Teruyuki Yashima
Abstract: We perform rapid thermal annealing (RTA) on areas as large as 2-inch φ (diameter) at high temperature using the hybrid super RTA (HS-RTA) equipment. The HS-RTA equipment consists of an infrared annealing unit and a RF induction annealing unit in order to uniformly anneal over 2-inch φ susceptor. As a result of annealing by the HS-RTA equipment, the temperature is elevated from RT to peak temperature (~1800°C) for less than 1 min, remain stable at annealing temperature for 30s and falls from peak temperature to 1000°C within less than 20s. The temperature distributions on a 2-inch φ susceptor are ±10°C, ±33°C and ±55°C at 1565°C, 1671°C and 1752°C, respectively. Phosphorus (P) ion implanted silicon carbide (SiC) samples are used to evaluate the performance of the HS-RTA equipment. The five implanted samples placed on the 2-inch φ susceptor are annealed for 30s at 1565°C, 1671°C and 1752°C. The mean sheet resistances of the 5 samples annealed at 1565°C, 1671°C and 1752°C are 92.6Ω/􀀀, 82.6Ω/􀀀 and 75.5Ω/􀀀, respectively. The sheet resistance uniformities are 9.9%, 7.9% and 9.3%. The average roughness (Ra) is calculated from 10 μm square Atomic Force Microscopy (AFM) image. Ra values of the samples annealed at 1565°C, 1671°C and 1752°C are 2.399 nm, 2.408 nm and 3.282 nm, respectively.
Authors: T. Henkel, Yasuhito Tanaka, Naoto Kobayashi, Shin Ichi Nishizawa, Shunichi Hishita
Authors: Frédéric Mercier, Shin Ichi Nishizawa
Abstract: We investigated with ab initio calculations the 3C-, 6H-, 4H- and 2H-SiC polytypes. We discuss the geometry and the energetics of bulk and surface relaxed structures ((0001) Si face and the (000-1) C face surfaces). The polytype stability is discussed regarding the bulk and surface effects.
Authors: Tsubasa Matsumoto, Shin Ichi Nishizawa, Satoshi Yamasaki
Abstract: Calculations of lattice constant of 4H-SiC and diamond have been carried out. Lattice constant of 4H-SiC trends to decrease when nitrogen concentration increases. On the other hand, lattice constant of 4H-SiC trends to increase when aluminum concentration increases. Lattice constant of boron and phosphorus doped diamond trends to increase when impurity concentration increases. The effect of phosphorus on diamond lattice constant is about six times larger than that of boron.
Authors: Kenji Fukuda, Shinsuke Harada, Junji Senzaki, Mitsuo Okamoto, Yasunori Tanaka, Akimasa Kinoshita, Ryouji Kosugi, Kazu Kojima, Makoto Kato, Atsushi Shimozato, Kenji Suzuki, Yusuke Hayashi, Kazuto Takao, Tomohisa Kato, Shin Ichi Nishizawa, Tsutomu Yatsuo, Hajime Okumura, Hiromichi Ohashi, Kazuo Arai
Abstract: The C(000-1) face of 4H-SiC has a lot of advantages for the power device fabrication such as the highest oxidation ratio and a smooth surface. However, the DMOS type power MOSFETs on the C(000-1) face have not been realized because of the difficulty of epitaxial growth and of high quality MOS interface formation. We have systematically investigated the device fabrication techniques for power MOSFETs on the C(000-1) face, and succeeded with the IEMOS which have blocking voltage of 660V and an on-resistance of 1.8mΩcm2 and excellent dynamic characteristics.
Authors: Fusao Hirose, Yasuo Kitou, Naoki Oyanagi, Tomohisa Kato, Shin Ichi Nishizawa, Kazuo Arai
Authors: Yoshimitsu Yamada, Shin Ichi Nishizawa, Shinichi Nakashima, Kazuo Arai
Authors: Tomohisa Kato, Naoki Oyanagi, Hirotaka Yamaguchi, Shin Ichi Nishizawa, Kazuo Arai
Authors: Tomohisa Kato, Tomonori Miura, Keisuke Wada, Eiji Hozomi, Hiroyoshi Taniguchi, Shin Ichi Nishizawa, Kazuo Arai
Abstract: In this study, we report defect analysis in 4H-SiC crystals of high nitrogen doping grown by sublimation method, and we discuss key points for defect restraint. The growth was performed in two kinds of growth directions; c-axis and a-axis. In the c-axis grown crystal with carrier density greater than 1×10-19cm-3, defect propagation was confirmed in the vertical direction for a growth direction affected by the doping by x-ray topography. This phenomenon was not observed in the a-axis grown crystals. In sublimation growth, the quantity of impurities tends to increase as growth rate decreases. Therefore, in the c-axis growth of doped 4H-SiC bulk crystals, we have to be careful so that dopant does not increase too much without intention in grown layers with lower growth rate, for example at the beginning and end of the growth.
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