Generation of very fast states by nitridation of the SiO2/SiC interface

Fast states at SiO2/SiC interfaces annealed in NO at 1150–1350 °C have been investigated. The response frequency of the interface states was measured by the conductance method with a maximum frequency of 100 MHz. The interface state density was evaluated based on the difference between quasi-static and theoretical capacitances (C−ψS method). Very fast states, which are not observed in as-oxidized samples, were generated by NO annealing, while states existing at an as-oxidized interface decreased by approximately 90%. The response frequency of the very fast states was higher than 1 MHz and increased when the energy level approaches the conduction band edge. For example, the response frequency (time) was 100 MHz (5 ns) at EC−ET = 0.4 eV and room temperature. The SiO2/SiC interface annealed in NO at 1250 °C showed the lowest interface state density, and NO annealing at a temperature higher than 1250 °C is not effective because of the increase in the very fast states.