Improved 4H-SiC N-MOSFET interface passivation by combining N2O oxidation with Boron diffusion

A new oxide configuration for the development of high mobility 4H-SiC lateral MOSFETs is proposed in this work. The oxide is composed by a rapid thermal oxidation (RTO) in N₂O environment, a Boron diffusion into the SiO₂ and a PECVD TEOS deposited oxide, in order to improve the interface quality. The obtained MOSFETs show very high peak field effect mobilities ranging from 80 up to more than 170 cm²V^-1s^-1 in MOSFETs with higher channel length than the tested transistors. The physical (SIMS) and electrical analysis of the oxide and SiC surface reveals that the Boron has not diffused into the SiC. This is most probably due to the high concentration of Nitrogen at the interface generated during the N₂O oxidation.