Control of powder recrystallization and crystallization interface shape for 8-inch SiC crystal growth by PVT method

The 8-inch silicon carbide (SiC) crystal grown by physical vapor transport (PVT) method is becoming the mainstream in the semiconductor market. Induction heating is widely used in the SiC crystal growth and theoretically it can create a temperature distribution that is beneficial for the formation of a convex crystallization interface, whereas experimental observations often reveal a concave interface. In this study, the problems of powder recrystallization and its influence on crystallization interface shape for 8-inch SiC crystal growth by PVT method are studied by experiments and numerical simulations. It's found that the low temperature at the top central region of the SiC powder leads to recrystallization of the sublimated powder and formation of a blockage, which results in a concave crystallization interface shape. Two techniques including temperature control and powder height control are proposed to influence the recrystallization and the interface shape. Results show that the powder recrystallization can be completely avoided by reducing the powder height, whereas the interface shape presents significant deformation at the crystal periphery. Therefore, the effect of powder recrystallization is not always negative, and it can be used to obtain a slight convex interface shape for high-quality SiC crystal growth.