The role of silanol groups on the reaction of SiO ₂ and anhydrous hydrogen fluoride gas

It is essential to etch SiO2 for producing silica glass components, semiconductor devices, and so on. Although wet-etching with hydrogen fluoride (HF) solutions usually employed this purpose, it faces a drawback that microstructures stick during the drying of solution. To overcome problem, we have developed dry-etching technique gaseous HF at high temperatures. In present study, an interesting phenomenon was found silicon thermal oxides were much less etched than vitreous by HF. Such difference had not been in wet- or humid gas etching. Because their bulk chemical formulae are same (SiO2), suggested surface species affected reaction rate. fact, preprocessing water vapor plasma remarkably increased etching rate on layer, vacuum heating almost completely suppressed plasma-treated oxides. These results indicate silanol groups enhance between Based results, model chain proposed, where act as center.