Study on Al2O3 Film in Anhydrous HF Vapor

Abstract

HF vapor etching using thin Al2O3film as etch stop material was studied. It was found that behavior of Al2O3film in HF vapor can not be predicted from the blanket film studies only but it is important to use samples that resemble closely real process conditions instead. Resistivity of Al2O3against HF vapor depends on whether a SiO2was etched on top of it or not. Other affecting factors are the thickness of the Al2O3film, HF vapor process, stress of the oxide on top of it as well as topography under it. Even very thin 3 nm Al2O3film resist HF vapor if no SiO2film is etched on top of it and etch process is slow enough.