Methods of forming a metal silicide layer for semiconductor devices

Abstract

Methods of forming a metal silicide layer are provided that include exposing polysilicon through just dry etching (JDE) and recessesing an oxide layer through chemical dry etching (CDE). In particular, dry etching is primarily performed to an extent to expose the polysilicon. Then, CDE is secondarily performed to expose the polysilicon. The CDE process includes selecting an etchant source among combinations of NFand NH, HF and NH, and N, H, and NF, dissociating the etchant source, forming an etchant of NHF and NHF.HF through the dissociation, producing solid by-products of (NH)SiFthrough the reaction between the etchant and an oxide at a low temperature, and annealing the by-products at a high temperature such that the by-products are sublimated into gas-phase SiF, NH, and HF.