Passivation strategies for minimizing inversion leakage in SiC MOS capacitors

Abstract

In this work, MOS capacitors were developed to study the effect of thin SiO₂ films at the TiO₂/SiC interface. This thin layer aims to reduce the leakage current observed in capacitors with TiO₂ and potentially serves as a passivation layer for the SiC substrate, thereby decreasing the charge density at the interface. SiO₂ films of thicknesses of 2 nm and 10 nm and a 50 nm-thick TiO₂ film were used. Structural characterization revealed that the SiO₂ films are silicon-rich, while the TiO₂ film is titanium-rich. Raman and FTIR analyses of the TiO₂ film deposited on SiC showed that the film exhibits an anatase crystalline structure. Electrical characterization confirmed that the 2 nm-thick SiO₂ film reduced the device leakage current by two orders of magnitude, although it was ineffective in passivating the SiC surface. On the other hand, passivation with N2+O2 plasma yielded a superior-quality interface, as evidenced by an almost null C-V hysteresis, indicating a significant reduction of trapped charges at the interface.