PVT法生长SiC过程生长界面形状对热应力的影响

Effect of the Growth Interface Shape on the Thermoelastic Stresses in SiC Crystal Prepared by PVT Technique

PVT法生长SiC过程中晶体内部的热应力是其位错产生的主要原因,而生长界面的形状对晶体热应力及缺陷的产生都有一定影响。本文对不同生长界面晶体的温场及应力场进行了数值分析,结果显示相对于凸出及平整界面的晶体,微凹界面晶体的轴向温差最小,同时产生缺陷的切应力τrz及引起开裂的径向正应力σrr值都为最小。

The main reason for the formation of dislocations in SiC is owing to the thermoelastic stresses,which are induced by the nonhomogeneous temperature distribution during the crystal growth process in PVT technique.However,the profile of growth interface is believed to influence the generation of thermoelastic stresses,and hence to cause structural defects.Therefore,the effect of the growth interface shape on the thermoelastic stresses was investigated.Here,the temperature and stress fields in the crystal were mainly simulated using different growth interfaces.The results show that the axial temperature gradient of a little concave growth interface is lower than that of the convex and planar interfaces.As for the concave interface,the value of the corresponding shear stress（τrz） and normal stress（σrr）,which induces the structural defects and crack in the crystal respectively,is the minimum.