Fundamentals of SiC-Based Device Processing

Since the commercial availability of SiC substrates in 1990, SiC processing technology has advanced rapidly. There have been demonstrations of monolithic digital and analogue integrated circuits, complementary metal-oxide-semiconductor (CMOS) analog integrated circuits, nonvolatile random-access memories, self-aligned polysilicon-gate metal-oxide-semiconductor field-effect transistors (MOSFETs), and buried-channel polysilicon-gate charge-coupled devices (CCDs). In this article, we review processing technologies for SiC.OxidationA beneficial feature of SiC processing technology is that SiC can be thermally oxidized to form SiO2. When a thermal oxide of thickness x is grown, 0.5x of the SiC surface is consumed, and the excess carbon leaves the sample as CO. Shown in Figure 1 are the oxide thicknesses as a function of time for the Si-face and the C-face of 6H-SiC, and for Si. The oxidation rates are considerably lower for SiC than for Si. The oxidation rate of the C-face of 6H-SiC is considerably greater than that of the Si-face. Hornetz et al. have shown that the reason for the slower oxidation rate of the Si-face is due to a 1-nm Si4C4−xO2 (x < 2) layer that forms between the SiC and the SiO2 during oxidation of the Si-face. When oxidizing the Si-face, the Si atoms oxidize first, which inhibits the oxidation of the underlying C atoms that are 0.063 nm below the Si atoms. When oxidizing the C-face, the C atoms readily oxidize first to form CO, with no formation of the Si4C4−xO2 layer for temperatures above 1000°C.