Photoelectron spectroscopy has been performed on SiC surfaces to investigate the valence band characteristics during SiO2 formation. Various stages of the oxide development were investigated. The √3×√3R30° surface is used as the initial surface for the oxidation experiments. The substrates were exposed to a succession of a 30 s oxygen exposure, two 30 s oxygen plasmas, and finally, a plasma-enhanced chemical vapor deposition SiO2 deposition. Ultraviolet photoemission spectroscopy was employed to measure the valence band discontinuity for the oxide on n-type 6H and n-type 4H SiC substrates for each step in the oxidation process. X-ray photoemission spectroscopy was used to confirm the valence band offset. The valence band discontinuity was determined to be 2.0 eV. Furthermore, the location of the valence band maximum of the SiC to the conduction band minimum of the SiO2 is determined to be a constant (∼7.0 eV) between 6H and 4H SiC. Band bending effects are directly measured from ultraviolet photoemission spectroscopy (UPS) and x-ray photoemission spectroscopy. From the UPS measurements of the band bending effects, the interface state density is determined to be ∼5×1012 cm−2.

The development of high power devices based on silicon carbide requires a more complete understanding of the oxide formation process and interface characteristics. By using an integrated UHV system, samples were cleaned and oxides deposited in situ. The approach of the oxide formation process was to form the initial insulator, a few angstroms thick, and then deposit an oxide. Various deposition techniques are used in the oxide growth process; both thermal and plasma enhanced chemical vapor deposition were employed with two different precursors (oxygen and nitrous oxide), and the results were compared with thermal oxidation. The morphology of each of the deposited oxides was compared to the bare substrate and the thermal oxide wafers. This study focuses on the morphology of the different deposition processes using AFM. Examination of the morphology of the initial insulator growth process and the oxide deposition process gives insight into the physical characteristics of the silicon dioxide deposited on silicon carbide. The RMS values of the initial insulator formation and the control wafers are 0.93 and 0.95 nm respectively. Meanwhile, the RMS values for PECVD (200–400°C) and thermal CVD (400–600°C for oxygen-silane and 800–1000°C for nitrous oxide-silane) range from 1.43 to 1.93 nm.