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.