Residual stress analysis of 4H-SiC crystals obtained by a top-seeded solution growth method

Abstract

The top-seeded solution growth (TSSG) method is an alternative technique for growing SiC which can reduce the defect levels in the crystal. With TSSG, the SiC crystal is grown on a SiC seed crystal attached to a seed shaft. The seed shaft is typically graphite; the mismatch in the thermal expansion coefficients between the materials induces residual stresses in the grown crystal. Furthermore, liquid droplets remaining on the grown SiC surface after crystal growth may contribute to residual surface stresses. Hence, in this study, we analyzed the residual stress of SiC crystals grown via the TSSG method, which has not yet been extensively studied. The surface stress was quantitatively evaluated using high-resolution X-ray diffraction (HRXRD) and Raman spectroscopy before and after the TSSG process. The dislocation distribution and crystalline quality were also characterized using synchrotron white beam X-ray topography (SWBXRT) and HRXRD. Many micropipes (MPs) were generated during the post-growth in the liquid droplets. The formation of these MPs was assumed to reduce the residual stresses on the crystal surface.