Self-aligned contacts for semiconductor device

摘要

A plasma, formed from a mixture of C4F8 and CH2F2, is used to etch a self-aligned contact, the self-aligned contact being an opening in the oxide layer, the opening being aligned with an opening in an underlying nitride layer and extending to a substrate underlying the nitride. The mixture of C4F8 and CH2F2 provides a high ratio of oxide etch rate to nitride etch rate so that the etching is completed without substantially damaging the nitride layer. For thicker oxide layers a preliminary etch step using C2F6 and C2HF5 may be performed prior to using the mixture of C4F8 and CH2F2.