High Quality Uniform Thick Epitaxy of 4H-SiC for High Power Device Applications
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0911-B09-03
High Quality Uniform Thick Epitaxy of 4H-SiC for High Power Device Applications Jie Zhang, Janice Mazzola, Esteban Romano, Carl Hoff, Mike Mazzola, Janna Casady, and Jeff Casady SemiSouth Laboratories, Inc., Starkville, Mississippi, 39759 ABSTRACT Growth of thick SiC epilayers has been investigated in a horizontal hot-wall CVD reactor capable of growing 3x2-in wafers or single wafer with a diameter up to 100mm. Good uniformity of lower than 3% for thickness and lower than 20% for doping has been obtained on 2-in or 3-in epi wafers with thickness of 60 - 120 µm. Low intentional nitrogen doping of 5.8x1014 cm-3 was achieved on a 3-in epi wafer with a thickness of 120 µm. A higher growth rate of 10 µm/h was achieved while good uniformity was maintained. Surface morphology of the thick epilayers was carefully examined and smooth surface was observed for epilayers thicker than 100 µm. The defect density of the thick epilayers was also discussed and the high purity of the thick epi was verified by low temperature PL measurement. INTRODUCTION Silicon carbide (SiC) possesses unique semiconductor properties such as wide band-gap, high breakdown electric field and high electron saturation velocity, which make it particularly suitable for high power switching applications. In order to sustain a high blocking voltage, thick SiC epilayers with low doping are required as the active blocking layer. The rapid progress in SiC epitaxy has enabled sufficient technology maturity for producing standard SiC epilayers with thickness below 15µm, which has contributed to the commercialization of SiC devices with blocking voltage of 300V to 1200V. However, for the applications in the higher power sector with blocking voltages of several to tens of kilovolts, SiC epilayers with much higher thickness in the range of 50 µm to above 100 µm are required [1]. It is still a challenging task to maintain good layer uniformity, smooth surface morphology and low defect density in very thick SiC epilayers. Thick SiC epilayers grown at growth rates greater than 20 µm/h have earlier been reported using vertical hot-wall reactors [2, 3, 4]. However, much recent research on the SiC thick epitaxy has been conducted in horizontal hot-wall CVD reactors, mainly attributed to the fact that these reactors are most commonly available and have demonstrated the capability of producing high quality SiC epilayers [5]. Successful growth of thick SiC epilayers has been reported in the horizontal hot-wall reactors with most of them being research tools with limited wafer handling capacity [6, 7]. Most recently, encouraging results on the growth of thick epilayers have also been reported in large-scale, multi-wafer CVD systems [8, 9]. Hecht et al. reported growth of 75 µm thick epilayers in a commercial horizontal hot-wall system with gas foil rotation. Burk et al. also reported a maximum epi thickness of 80 µm in a warm-wall multiwafer planetary system. However, no details have been discussed on the thick epi-growth in these reactors. In this paper, we will
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