SURFACE-MORPHOLOGY OF SILICON-CARBIDE EPITAXIAL-FILMS

Silicon carbide (SiC) semiconductor technology has been advancing rapi dly, but there are numerous crystal growth problems that need to be so lved before SiC can reach its full,potential. Among these problems is a need for an improvement in the surface morphology of epitaxial films that are grown to produce device structures. Because of advantageous electrical properties, SiC development is shifting from the 6H to the 4H polytype. In this study of both 6H and 4H-SiC epilayers, atomic for ce microscopy and other techniques were used to characterize SiC epila yer surface morphology. Observed features included isolated growth pit s a few micrometers in size in both polytypes and triangles (in 4H onl y) approximately 50 mu m in size for epilayers 3 mu m in thickness. Al so observed in some epilayers were large steps with heights greater th an 20 nm. We found that there are significant differences between the morphology of 6H and 4H epilayers grown under identical conditions. We were able to improve surface morphology by avoiding conditions that l ead to excess silicon during the initial startup of the growth process . However, the observed morphological defect density in both 6H and 4H epilayers was still the order of 10(4) cm(-2) and varied widely from run to run. As expected, we found that morphological defects in the Si C substrates play a role in the formation of some epilayer surface fea tures.