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

Results of room temperature capacitance-voltage measurements are reported f or SiO2/4H-SiC (n and p type) metal-oxide-semiconductor capacitors annealed in ammonia following oxide layer growth using standard wet oxidation techn iques. For n-SiC capacitors, both the interface state density near the cond uction band edge and the effective oxide charge are substantially reduced b y the ammonia anneals. For 2 h anneals, the oxide charge appears to have a minimum value for an anneal temperature of approximately 1100 degreesC. How ever, for p-SiC, anneals in ammonia produce no improvement in the interface state density near the valence band edge, and the effective oxide charge i s not reduced compared to samples that were not annealed. Results are compa red to those reported previously for anneals in nitric oxide. Ion beam anal yses of the oxide layers show substantially more nitrogen incorporation wit h the ammonia anneals, although for n-SiC, the decrease in D-it is comparab le for both nitric oxide and ammonia anneals. Results reported here for amm onia and those reported previously for nitric oxide are the first to demons trate that significant passivation of the interface state density near the conduction band edge in SiC can be achieved with high temperature anneals u sing either gas. This demonstration has important implications for SiC meta l-oxide-semiconductor field effect transistor technology development. (C) 2 000 American Institute of Physics. [S0003-6951(00)00948-7].