Homoepitaxial 4H-SiC films grown by microwave plasma chemical vapor deposition
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Homoepitaxial 4H-SiC films grown by microwave plasma chemical vapor deposition Mitsuo Okamoto1,2, Ryoji Kosugi1,2, Shinichi Nakashima1,2,3, Kenji Fukuda1,2 and Kazuo Arai1,2 1 National Institute of Advanced Industrial Science and Technology, Power Electronics Research Center, Tsukuba Central 2, Umezono 1-1-1, Tsukuba, Ibaraki 305-8568, JAPAN 2 Ultra-Low-Loss Power Device Technology Research Body, Ibaraki, JAPAN 3 R&D Association for Future Electron Devices, Advanced Power Device laboratory, Tokyo, JAPAN ABSTRACT Homoepitaxial 4H-SiC film growth has been carried out at temperatures as low as 1000ºC on 4H-SiC of Si-face and C-face by microwave plasma chemical vapor deposition method. The extent of step-bunching of those films grown on C-face was low in comparison with that on Si-face, although large and irregular shaped step-bunching was occurred in both films grown on Si-face and C-face. For the first step to application for the electrical devices, the electrical properties of the µPCVD grown films was characterized by fabricating simple pn-junction structure. The obtained SiC films indicated n-type conductivity and the amount of background donor impurities of the films grown on C-face substrates were lower by one order than that on Si-face. INTRODUCTION Silicon carbide (SiC) is of great interest for high-power and high-frequency applications due to its superior properties [1]. Homoepitaxial SiC layers are required to realize these applications. In general, homoepitaxial SiC films are grown by a chemical vapor deposition (CVD) method at temperatures as high as around 1500°C [2]. Such a high growth temperature restricts SiC device processing to some extent. If SiC growth below 1000°C could be realized, various techniques could be utilized for SiC processing. For example, because oxide layer will not be degraded at such a low growth temperature, epitaxial growth on SiCOI substrate, in which SiC thin layer bonded on Si wafer by oxide [3], and selective epitaxial growth by use of oxide mask could be realized. It is known that the CVD growth temperature is decreased by use of plasma enhancement [4]. The microwave plasma chemical vapor deposition (µPCVD) technique has succeeded in growth of high-quality homoepitaxial diamond films at relatively low temperatures [5]. This technique has also been applied to heteroepitaxial β-SiC growth on Si substrates [6-8], but, to our knowledge, there are no papers reporting about homoepitaxial growth of α-SiC using µPCVD. We have achieved homoepitaxial α-SiC film growth below 1000°C by µPCVD for the purpose of providing more flexibility in the SiC device processing [9]. In this report, the dependence on substrate polarity was investigated. Since the surface free energy depends on the polarity, crystal growth may be different. Recently it is reported that the MOSFETs fabricated on C-face 4H-SiC has superior properties [10]. We investigated the surface morphology of 4H-SiC film grown on Si-face and C-face, and furthermore the electrical properties of the µPCVD grown films were char
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