Atomic layer etching of SiO2 by alternating an O2 plasma with fluorocarbon film deposition

Abstract

This work demonstrated a process for the atomic-scale etching of SiO2 films, consisting of alternating nanometer-thick fluorocarbon film deposition with O2 plasma irradiation in a capacitively coupled plasma reactor. Ar plasma etching after fluorocarbon film deposition tends to suffer from nanometer- or subnanometer-thick carbon films deposited on the SiO2 surface and chamber walls. These carbon films cause various problems, such as reductions in the etching rate per cycle and degradation of the SiO2 quality. In contrast, in our two-step process, O2 plasma removes carbon atoms in such fluorocarbon films. This process therefore allows the atomic scale etching of SiO2 films without any residue or surface contamination. Additionally, since the etching rate per cycle plateaus as both the etching time and deposition time are extended, it is unnecessary to uniformly deposit a fluorocarbon film over the wafer.