Process flow to reduce spacer undercut phenomena

Abstract

A process for forming a composite insulator spacer on the sides of a MOSFET gate structure, wherein the underlying component of the composite insulator spacer is comprised of a thin silicon oxide layer obtained via chemical vapor deposition procedures using tetraethylorthosilicate (TEOS), as a source, has been developed. To densify the underlying thin silicon oxide layer an anneal procedure usually performed after implantation of ions used for a lightly doped source/drain region, is delayed and performed after deposition of the thin silicon oxide layer. The anneal procedure is then used for both activation of the lightly doped source/drain ions, and densification of the thin silicon oxide layer. The etch rate of the densified silicon oxide layer, in dilute hydrofluoric acid procedures is now reduced allowing the underlying silicon oxide component, of the composite insulator spacer, to survive subsequent wet clean procedures employing dilute hydrofluoric acid.