Generation of interface states in α-SiC/SiO2 by electron injection

Generation of electrically active defects at the interfaces between hexagonal SiC polytypes and thermally grown oxide was studied under conditions of electron injection, which simulates the SiC/oxide interface damage induced by plasma processing or hot-carrier injection in SiC device structures. The injection-induced degradation of 4H, 6H–SiC(0001)/SiO2 interfaces is found to be enhanced significantly when compared with the structurally isomorphic (111)Si/SiO2 interface, particularly in terms of the generation of interface acceptor-type defects. Moreover, a much higher density of these defects is generated in the oxidized 4H–SiC as compared to 6H–SiC. Most of these interface states are resistant against passivation with hydrogen up to 500°C, which suggests these to be related to some stable bonding configuration created at the SiC/SiO2 interface during electron injection. The observed enhancement of the SiC/oxide interface degradation with increasing amount of carbon at the semiconductor surface points to a relationship between the degradation process and formation of some carbon-related defect states. The sensitivity of the degradation to the SiC polytype suggests that the crystal surface imperfections may also be part of the defect generation (activation) process.