AES and XPS studies of surface films deposited during the plasma etching of silicon dioxide layers

Surface films deposited during the selective plasma etching of SiO2 on Si by CHF3 have been studied using Auger electron spectroscopy (AES)2 and x-ray photoelectron spectroscopy (XPS). The films have been subdivided into two types: ‘persistent’ and ‘non-persistent’. Non-persistent films could be etched in an oxygen plasma and consisted of a fluorocarbon polymer. The main components of persistent films (unreactive in an oxygen plasma) were oxygen and fluorine compounds of silicon with impregnated metal atoms sputtered from electrodes in the plasma etcher. The thickness of persistent films was found to depend on the electrode spacing and electrode material. This effect has been explained in terms of the ion sputtering inherent within the parallel plate plasma etching system.