Observation of interfacial atomic steps during silicon oxidation

SILICON oxidation is perhaps the most common process in the fabrication of electronic devices. The silicon/silicon dioxide inter-face has excellent electrical properties which are employed in field-effect devices and surface passivation, and are arguably responsible for the dominance of silicon technology in the micro-electronics industry. As device dimensions shrink, the need for high-quality oxides grown at increasingly lower thicknesses and temperatures has demanded ever more perfect, extremely flat Si/SiO2 interfaces. Here we use transmission electron microscopy to image exposed and buried monatomic interfacial steps at the Si/SiO2 interface during oxidation. The results show that extremely flat boundaries can be formed at low temperatures and that atomic steps do not play a dominant role in the oxidation process itself. A simple bulk-terminated Si/amorphous SiO2 inter-face is consistent with our data.