Effect of gate oxidation method on electrical properties of metal-oxide-semiconductor field-effect transistors fabricated on 4H-SiC C(0001̄) face

The effect of gate oxidation method on the electrical properties of metal-oxide-semiconductor field-effect transistors (MOSFETs) fabricated on 4H-SiC C(0001̄) face has been investigated. In the case of SiC MOSFETs fabricated by dry gate oxidation, the peak value of field-effect mobility (μFE) is 16.3 cm2/V s. On the other hand, pyrogenic gate oxidation and pyrogenic gate oxidation followed by H2 postoxidation annealing (POA) considerably decreased the interface trap density (Dit) and the threshold voltage, and markedly improved the μFE. The depth profiles of hydrogen density were measured using secondary ion mass spectroscopy. These verified that pyrogenic gate oxidation increases hydrogen density at the SiO2/SiC interface compared to dry gate oxidation, and that the pyrogenic gate oxidation followed by H2 POA increases considerably it. It is thought that the Dit reduction might be caused by the passivation of interface states by –H or –OH. The peak value of μFE for SiC MOSFETs fabricated by pyrogenic gate oxidation followed by H2 POA is 111 cm2/V s, which is much higher than that of SiC MOSFETs fabricated on a Si(0001) face. Therefore, the 4H-SiC C(0001̄) face is suitable for the fabrication of SiC power MOSFETs.