A surface science investigation of silicon carbide: Oxidation, crystal growth and surface structural analysis

Abstract

For the semiconductor SiC to fulfill its potential as an electronic material, methods must be developed to produce insulating surface oxide layers in a reproducible fashion. Auger electron spectroscopy (AES), low energy electron diffraction (LEED) and x-ray photoelectron spectroscopy (XPS) were used to investigate the oxidation of single crystal α-SiC over a wide temperature and O2 pressure range. The α-SiC surface becomes graphitic at high temperatures and low O2 pressures due to Si and SiO sublimation from the surface. Amorphous SiO2 surface layers from on α-SiC at elevated O2 pressures and temperatures. Both the graphitization and oxidation of α-SiC appears to be enhanced by surface roughness. Chemical vapor deposition (CVD) is currently the preferred method of producing single crystal SiC, although the method is slow and prone to contamination. We have attempted to produce SiC films at lower temperatures and higher deposition rates using plasma enhanced CVD with CH3SiH3. Scanning AES, XPS and scanning electron microscopy (SEM) were utilized to study the composition and morphology of the deposited SixCyHz films as a function of substrate temperature, plasma power and ion flux bombardment of the film during deposition. High energy ion bombardment during deposition was found to increase film density and substrate adhesion while simultaneously reducing hydrogen and oxygen incorporation in the film. Under all deposition conditions the SixCyHz films were found to be amorphous, with the ion bombarded films showing promise as hard protective coatings. Studies with LEED and AES have shown that β-SiC (100) exhibits multiple surface reconstructions, depending on the surface composition. These surface reconstructions possess substantially different surface reactivities at elevated temperatures, which can complicate the fabrication of metal on SiC junctions.