STRUCTURAL MACRO-DEFECTS IN 6H-SIC WAFERS

SiC is considered to be a good candidate for high-power device material. For this application, however, large (> 1 cm2), defect-free areas must be available in SiC wafers. In the present work, commercially available Lely and modified Lely grown single crystal 6H-SiC wafers have been analyzed as to their large-area structural quality. Scanning electron microscopy (SEM) and high resolution X-ray diffractometry (HRXRD) have been utilized. The latter technique was used to conduct reciprocal space mapping about on- and off-axis reciprocal lattice points (RLPs). SEM analysis showed the existence of macro-defects such as pin-holes, pits and inclusions in the modified Lely material, while HRXRD-RLP analyses showed the effects of a mosaic structure. These data indicated the presence of a domain structure, with varying domain densities. These results are discussed in the context of the SiC growth process. The possibility of a relationship between these macro-defects and the growth spiral mechanism is presented.