Defects in differently annealed oxides on 4H- and 6H-SiC

This contribution reports on the reduction of oxide defects on 6H- and 4H-SiC by POA (Post Oxidation Annealing). At POA temperatures of 1150 degrees C and times between 30 and 60 min drastically reduced densities of initial oxide charges, interface states and oxide traps can be achieved. Oxidation and annealing of 6H- and 4H-SiC reveals comparable results, indicating the same surface chemistry for both polytypes. Additional low temperature anneals in forming gas up to 600 degrees C slightly increase the oxide qualities. Fowler Nordheim charge injection experiments reveal an efficient negative charging at the SiO2-SiC interface, which is drastically reduced by POA. A charging in the bulk of the oxide is negligible.