Method to selectively etch silicon nitride to silicon oxide using surface alkylation

Abstract

Embodiments of processes and methods that provide selective etching of silicon nitride are disclosed herein. More specifically, new processes, methods and etch chemistries are provided to selectively etch silicon nitride layers formed on a substrate, while protecting silicon oxide layers formed on the same substrate. In the method embodiments, a substrate having a silicon nitride (SiN) layer and a silicon oxide layer formed on the same substrate is exposed to an alkylating agent, which reacts with the amine groups on the exposed SiN surfaces to form an alkylated surface layer on the SiN layer. The substrate is exposed to a fluorinating agent to remove the alkylated surface layer and selectively etch the SiN layer without significantly etching the silicon oxide layer. The disclosed methods can be used to selectively etch silicon nitride over silicon oxide using a wet or dry process.