Thermal oxidation and electrical properties of silicon carbide metal-oxide-semiconductor structures

Fabrication processes of metal-oxide-semiconductor (MOS) capacitors on n-type, Si-face 6H-SiC, and its electrical properties, have been reported in this article. The effects of thermal oxidation conditions at temperatures between 1150 and 1250 °C on the electrical properties of MOS capacitors were studied. After oxidation, the wafers were annealed under argon ambient to improve the capacitance-voltage (C-V) characteristics. The C-V characteristics of the Al-SiO2-SiC metal-oxide-semiconductor capacitors were measured at high frequency in the dark and under illumination. Under dark conditions, inversion did not occur, probably owing to the absence of minority carriers due to the large band gap of 6H-SiC. The C-V measurements made under illumination for both wet and dry thermally grown oxides show accumulation, depletion, and inversion regions. The ac conductance method was used to determine the interface trap densities and emission time constants of fast states. From the analysis of the data a total of fixed charges and the slow interface traps, Not+NitSlow of 1.5–3.3×1012 cm−2, fast interface trap densities, NitFast of 0.5–1.7×1011 cm−2 eV−1, and an emission time constant of 0.3–1.4 μs were obtained for wet oxidation. For dry oxidation, Not+NitSlow of 3.5–11.2×1011 cm−2, NitFast of 0.7–1.25×1010 cm−2 eV−1, and emission time constants of 0.6–2 μs were obtained.