Process for incorporating silicon oxynitride darc layer into formation

Abstract

A process flow for forming a silicided polysilicon feature avoids removal of the SiON dielectric anti-reflective coating (DARC) used to pattern the polysilicon. Instead, following polysilicon formation and etching aided by the DARC, the DARC is modified to enrich its silicon content. This modification may take the form of densification by annealing in conjunction with formation of a seal oxide, densification by annealing in an inert ambient prior to exposure to oxidizing conditions, or direct ion implantation of semiconductor material into the DARC. As a result of this modification, the DARC becomes sufficiently enriched in semiconductor material to permit formation of silicide. Thermal densification of DARC during formation of a seal oxide is sufficient to permit formation of silicide upon exposure to a silicide-forming metal. In this embodiment however, implantation of semiconductor material prior to silicide formation is generally necessary to permit silicidation of a thin oxide layer created between DARC and polysilicon as a by-product of the prior thermal seal oxidation step.