Impact of nitridation on the active near-interface traps in gate oxides on 4H-SiC

Abstract

In this paper we have implemented a recently proposed direct-measurement technique to characterize near-interface oxide traps (NITs) in SiC MOS capacitors with gate oxides obtained by four different processes. This measurement technique enables characterization of NITs with energy levels above the bottom of the conduction band, which are active in the accumulation mode of MOS capacitors on N-type SiC and in the strong inversion of N-channel MOSFETs. The measurements revealed that annealing in nitric oxide of thermally grown oxides in dry oxygen removes NITs that are further away from the SiC surface, but it leaves a defect with energy levels located between 0.13 eV and 0.23 eV above the bottom of conduction band. The oxides grown in pure nitric oxide exhibit NITs with energy levels above 0.2 eV. The measurements also show that low-temperature oxide deposition and subsequent annealing in nitric oxide resulted in the lowest density of NITs.