Etching of SiO2 Films by Si in Ultra-High Vacuum

Publisher Website
Google Scholar
Abstract
SiO2 etching resulting from reaction with impinging Si or substrate Si was clearly observed in an ultra-high vacuum by using step measurement, Auger electron spectroscopy and/or ellipsometry. In etching by impinging Si, the etching rate decreases with the substrate temperature, and increases with the Si impinging rate. These results are explained by a model proposed here that involves Si adsorption on SiO2, and a subsequent chemical reaction. It was found that SiO2 films thinner than 2.5 nm are etched by the same reaction with substrate Si, whereas those thicker than 2.5 nm are not etched at all, since reaction products cannot diffuse through the SiO2 film to the vacuum. These phenomena can be used in Si molecular beam epitaxy.