Effects of anneals in ammonia on the interface trap density near the band edges in 4H–silicon carbide metal-oxide-semiconductor capacitors

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Results of room temperature capacitance–voltage measurements are reported for SiO₂/4H–SiC (n and p type) metal-oxide-semiconductor capacitors annealed in ammonia following oxide layer growth using standard wet oxidation techniques. For n-SiC capacitors, both the interface state density near the conduction band edge and the effective oxide charge are substantially reduced by the ammonia anneals. For 2 h anneals, the oxide charge appears to have a minimum value for an anneal temperature of approximately 1100 °C. However, for p-SiC, anneals in ammonia produce no improvement in the interface state density near the valence band edge, and the effective oxide charge is not reduced compared to samples that were not annealed. Results are compared to those reported previously for anneals in nitric oxide. Ion beam analyses of the oxide layers show substantially more nitrogen incorporation with the ammonia anneals, although for n-SiC, the decrease in D_it is comparable for both nitric oxide and ammonia anneals. Results reported here for ammonia and those reported previously for nitric oxide are the first to demonstrate that significant passivation of the interface state density near the conduction band edge in SiC can be achieved with high temperature anneals using either gas. This demonstration has important implications for SiC metal-oxide-semiconductor field effect transistor technology development. ©2000 American Institute of Physics.