Re-Investigation of SiC/SiO<sub>2</sub> Interface Passivation by Nitrogen Annealing

Abstract

Effect of nitrogen annealing on SiC/SiO2 interface properties was comparatively investigated for SiC MOS capacitors. Interface properties were characterized by normalized parallel conductance and interface state density value, and dielectric strength was evaluated by the electric-field-to-breakdown (Ebd). The results exhibited that both fast and slow states were present at the nitrogen-annealed samples’ parallel conductance characteristics. Thus, we could conclude that nitrogen annealing led to incomplete nitridation of SiC/SiO2 interface. Based on the results, nitridation mechanism was simply analyzed. It seemed that the nitridation process started from near conduction band, extending till to mid-band-gap. Besides, when the samples underwent higher temperature nitrogen annealing, more slow states were converted into fast ones, indicating that higher annealing temperature could lead to more effective nitridation. It was suggested that nitrogen annealing resulted in incomplete nitridation of SiC/SiO2 interface regardless of oxide thickness and that this process was limited to the annealing temperature. The higher the annealing temperature was, the more effective the nitridation effects were.