New Crucible Design for SiC Single Crystal Growth by Sublimation
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New Crucible Design for SiC Single Crystal Growth by Sublimation
Shin-ichi Nishizawa1, Hirotaka Yamaguchi1, Tomohisa Kato1, M.Nasir Khan1, Kazuo Arai1, Naoki Oyanagi2, Yasuo Kitou2 and Wook Bahng2 Ultra-Low-Loss Power Device Technology Research Body 1 Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba, Ibaraki, 305-8568 Japan 2 Association for Future Electron Devices, c/o Electrotechnical Laboratory ABSTRACT SiC bulk single crystal growth by sublimation was investigated. A new crucible design, double-walled crucible, was proposed, and its effect was confirmed numerically and experimentally. On the point of heat transfer in a growth cavity, double-walled crucible is better than conventional crucible. With a double-walled crucible, temperature of seed and source surfaces could be kept constant with better uniformity than that with a conventional crucible. It was deduced that a crystal growth rate could be kept constant with flat surface. Furthermore, in case of a double walled crucible, crystal enlarged rapidly with less inclusion. As the results, a double-walled crucible is useful to grow high quality SiC single crystal by sublimation. INTRODUCTION SiC single crystal is usually grown by sublimation which is called modified Lely method[1]. This process is invisible because it is carried out in a closed carbon crucible. Recently this black box process is visualized by X-ray[2,3,4], and numerically[5,6,7]. From these works, it was made clear that this process is time-dependent, and growth conditions such as growing surface temperature, source condition, diffusion length were changed by time. In order to grow a high quality SiC single crystal, growth condition must be controlled precisely. However it is difficult to control it because of invisible process. In this study, a double-walled crucible was proposed to keep growth conditions constant, and to grow high quality crystal. The effect of it was examined numerically and experimentally, and discussed in comparison to the conventional crucible. NUMERICAL SIMULATION AND EXPERIMENTS
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The configuration of numerical modeling was based on the RF induction heating furnace that we used in our experiments. For the crucible geometry, a conventional crucible and a double-walled crucible shown in figure 1 were considered. Double-walled crucible is composed of conventional crucible with inner-cone tube. Source powder was set between crucible and inner-cone tube. Electromagnetic and thermal fields were analyzed by finite element method with Flux-Expert[8]. Since convective heat transfer could be neglected in our experimental conditions, the equation for momentum transfer was not considered. In a growth cavity, radiation and conduction heat transfer was considered.[5] For the experiments, the system in this study is same as that for the in-situ observation of SiC bulk single crystal growth by X-ray topography[2,3,9]. Crystal growth rate was evaluated by X-ray observation technique, and grown crystal quality was analyzed by optical microscope. VHHG
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