The fracture stress of 8-inch silicon carbide during the PVT growth

Abstract

The primary challenge for preparing SiC crystals during the PVT process is the fractures, especially with the increase in diameter (≥8 inches). In this study, the elastic–plastic behaviors of the azimuthal component (σ_ϕϕ) of primary stress causing SiC crystal fractures have been investigated to research the fracture mechanism. It is concluded that the plastic deformations caused by prismatic plane slips contribute positively to σ_ϕϕ. Besides, the magnitude of the plastic component of σ_ϕϕ is determined by the magnitude of resolved shear stresses (RSS) on each prismatic slip system over the same period, according to the Alexander–Haasen (AH) model. Further, the evolution of the magnitude of RSS (|RSS|) during the cooling process has been simulated, and the effects of the experimental conditions on the elastic–plastic behaviors of σ_ϕϕ have been investigated qualitatively. Control experiments of SiC crystal growth have been carried out simultaneously, and our conclusions have been verified by the experimental results. Lastly, the maximum |RSS| can be a criterion for the fracture of SiC crystal, giving a critical value near 30 MPa under our experimental conditions. The analysis of the relation between the growth conditions and fractures guides the growth of perfect 8-inch SiC crystals.