Electrical properties of oxidized polycrystalline silicon as a gate insulator for n-type 4H-SiC MOS devices

MOS capacitors were produced on n-type 4H-SiC using oxidized polycrystalline silicon (polyoxide). The polyoxide samples grown by dry oxidation without an anneal had a high interface state density (Dit) of 1.8 × 1012 cm−2 eV−1 and the polyoxide samples grown by wet oxidation had a lower Dit of 1.2 × 1012 cm−2 eV−1 (both at 0.5 eV below the conduction band). After 1 h Ar annealing, the Dit of wet polyoxide was reduced significantly to 2.6 × 1011 cm−2 eV−1 (at 0.5 eV below the conduction band). Dry polyoxide exhibits higher breakdown electric fields than wet polyoxide. The interface quality and breakdown characteristics of polyoxide are comparable to published results of low-temperature CVD deposited oxides.