Profile control by reactive sputter etching

Abstract

Reactive sputter etching in fluorocarbon gases (i.e. CF4, CHF3) not only results in a large increase of the etch rates, but it can also be used for a high fidelity pattern transfer from patterns delineated in positive photoresist into underlaying substrates (i.e. Si, SiO2, Si3N4). Square wave gratings with micron and submicron periodicities and etch depths of up to 3 μm have been etched. A relatively large etch selectivity of SiO2 over Si has been observed (etch rate ratio=15:1). Reactive sputter etching is primarily a chemical process due to highly reactive species produced on the substrate surface by an ion–molecule reaction between ions from the plasma and neutral gas molecules impinging onto the substrate surface.