Carbon inclusions in the growth of an 8 inch 4H-SiC crystal

Abstract

During the physical vapor transport (PVT) growth of a 4H silicon carbide (4H-SiC) crystal, carbon inclusions may be incorporated, which can substantially degrade the performance of devices based on 4H-SiC. In this work, carbon inclusions in the growth of an 8 inch 4H-SiC crystal are investigated. The distribution and size of carbon inclusions within the crystal are systematically characterized. Numerical simulations are performed to analyze the influences of drag, thermophoretic, and gravitational forces on the transport behavior of graphite particles, which serve as the precursor for carbon inclusions. It is found that the critical gas velocity required at the powder surface suppresses carbon inclusions of a given size. The critical size at which graphite particles detach from the powder surface under specific conditions is also determined. The calculated critical carbon inclusion size agrees well with experimental measurements. Studies have shown that increasing the pressure and reducing the axial temperature difference can effectively reduce the size of carbon inclusions. This study provides valuable insights into controlling and reducing the size of carbon inclusions in SiC crystals during growth.