Dielectric strength of thermal oxides on 6H-SiC and 4H-SiC

Abstract

This work reports on the dielectric strength of oxide layers formed by thermal oxidation of silicon carbide (SiC). SiC epilayers grown homoepitaxially on the silicon face of 6H-SiC and 4H-SiC substrates were oxidized in dry or wet ambient at 1100°C. The dielectric strength was investigated using metal-oxide-semiconductor capacitors and was found to be tightly bound to 10 MV/cm for oxide thicknesses around 65 nm and independent of the SiC polytype and substrate doping. Considering the current-voltage characteristics in the prebreakdown region, dry oxides exhibit superior quality. Fowler-Nordheim tunneling was identified as the limiting current mechanism in the dry oxides. The corresponding barrier heights between the two SiC polytypes and thermal silicon dioxide were determined.