Nitrogen and Hydrogen Induced Trap Passivation at the SiO_2/ 4H-SiC interface

摘要

Post-oxidation anneals that introduce nitrogen at the SiO_2/4H-SiC interface have been most effective in reducing the large interface trap density near the 4H-SiC conduction band-edge for (0001) Si face 4H-SiC. Herein, we report the effect of nitridation on interfaces created on the (1120) a-face and the (0001) C-face of 4H-SiC. Significant reductions in trap density (from > 10~(13) cm~(-2) eV~(-1) to ～ 10~(12) cm~(-2) eV~(-1) at E_C-E ～0.1 eV) were observed for these different interfaces, indicating the presence of substantial nitrogen susceptible defects for all crystal faces. Annealing nitridated interfaces in hydrogen results in a further reduction of trap density (from ～10~(12) cm~(-2) eV~(-1) to ～5 x 10~(11) cm~(-2) eV~(-1) at E_C-E ～0.1 eV). Using sequential anneals in NO and H_2, maximum field effect mobilities of ～55 cm~(-2) V~(-1)s~(-1) and ～100 cm~(-2) V~(-1)s~(-1) have been obtained for lateral MOSFETs fabricated on the (0001) and (1120) faces, respectively. These electronic measurements have been correlated to the interface chemical composition.