Influence of bias voltage on the Ar/CH2F2/O2 plasma etching of Si3N4 films

Abstract

The etching mechanism of silicon nitride (Si3N4) film depending on peak-to-peak bias voltage (V pp) in Ar/CH2F2/O2 gas-mixture plasmas for high-aspect-ratio etching process was investigated. It was observed that the Si3N4-film etch rate initially decreased with increase in the V pp up to 3630 V, but then increased beyond this threshold. This unusual etching behavior can be attributed to the formation of a modified layer on the surface of the Si3N4 film. The characteristics of the modified layer, such as thickness and atomic composition, were found to be strongly influenced by the ion energy and gas chemistry of the process conditions.