Influence of substrate surface morphology on defect generation during silicon carbide single crystal growth
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Influence of substrate surface morphology on defect generation during silicon carbide single crystal growth Myung Yoon Um, Jae Kyeong Jeong, Bum Seok Kim, Hoon Joo Na, In Bok Song, and Hyeong Joon Kim School of Material Science and Engineering, Seoul National Univ., Seoul, 151-742, Korea ABSTRACT 6H-SiC single crystals were grown on various substrates, treated mechanically and chemically in different conditions, by physical vapor transport. To investigate the defect evolution according to the different substrate treatment prior to the growth, the grown crystals were examined by optical micrograph, scanning electron microscopy, atomic force microscopy and molten KOH etching technique. The smoother substrate surface was, the lower defect density the grown SiC had. The highest quality SiC crystal was grown on substrate etched by
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hydrogen after polished by 0.25 diamond paste, having an edge/screw dislocation density of 2 2 7.3 10 / cm without micropipes. Defects, such as dislocations and micropipes, of the grown crystals are found to be strongly correlated with the substrate morphology.
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INTRODUCTION Silicon carbide has been expected as a new promising material for high power, high temperature, high frequency devices [1-5]. And thus the growth of large diameter wafer with low defect density has been actively tried by several research groups. Even though the structural defects, such as micropipe, edge/screw dislocation, low angle grain boundary, and stacking faults, have decreased continuously, there are still high defect concentrations in SiC wafer. Especially, micropipes and dislocations have a virtually harmful effect on SiC electronic device performance. However, it is still not clear what their formation mechanism is. Some researchers have reported that the seed surface quality is a major influence on the initiation of defect generation, while others have suggested that defects are caused by second phases, such as silicon droplet and carbon [6,7]. This study sheds more light on this issue, especially in connection with the influence of substrate surface morphology on defect generation during SiC single crystal growth.
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EXPERIMENTAL DETAILS A schematic diagram of the silicon carbide single crystal growing is the conventional system, as shown in figure 1. Physical vapor transport growth was performed using a quartz tube reactor with a water-cooled jacket. The seed crystal was fixed to the graphite lid. Abrasive commercial SiC powder for a source material was charged in the graphite crucible. And then the graphite crucible was heated to 2200 oC. Table 1 shows the detailed process parameters used in this experiment. The crucible was heated by RF induction heating with a frequency of 20kHz. The top of the crucible was kept at the temperature of 2200 o
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