Formation of a SiOF reaction intermixing layer on SiO2 etching using C4F6/O2/Ar plasmas

High aspect-ratio etching of SiO2 by fluorocarbon (FC) plasmas (C4F6/O-2/Ar) requires an in-depth understanding of the reactions on the SiO2 surface. Reactive gaseous FC species deposited on the surface and the bombardment of this FC layer with highly energetic ions lead to intermixing of FC and SiO2 to form volatiles that subsequently desorb, and silicon oxyfluoride (SiOF) intermediates are believed to accumulate at the reactive interface. The authors report the successful observation of a SiOF layer with a depth of less than 1.5 nm by time-of-flight secondary ion mass spectrometry using C-60(2+). (C) 2016 American Vacuum Society.