Topographically-selective atomic layer etching of SiO2 using radical fluorination of the surface followed by Ar ion bombardment

Abstract

The chemical nature of surface fluorination followed by ion bombardment has been explored to achieve a topographically selective atomic layer etching of silicon dioxide at RT. In this work, a two-step low-pressure sulfur hexafluoride (SF6) remote plasma modification (without any ion bombardment) followed by argon (Ar) ion bombardment is presented. In situ investigations of the surface bonding confirmed the modification during the half-reaction steps and spectroscopic ellipsometry data reveal the thickness change while suggesting an incubation period prior to obtaining a uniform etch per cycle of 0.14 nm with a synergistic 30 s fluorination of the surface followed by a 60 s Ar bombardment. The etch profile of the trenched structured sample displays the isotropic etch for the two-step process, as well as the feasibility of a topo-selective top-and-bottom etch by bias application in the Ar bombardment step.