Salicide process for a mos semiconductor device using nitrogen implant

Abstract

A salicide process for manufacturing a lightly doped drain (LDD) MOS transistor having unshorted titanium silicide gate electrode and source/drain contacts. The salicide method comprises forming a titanium (Ti) layer on the surface of the substrate, the sidewall spacers and the gate electrode. Nitrogen is implanted at a large angle into the Ti layer, especially over the sidewall spacers, thus converting all the titanium layer over the spacers to titanium nitride. Next, the titanium layer is thermally annealed forming titanium silicide on the top surface of the gate electrode and in the highly doped source/drain regions. The titanium nitride layer and any of the remaining titanium layer is etched away thereby leaving unshorted titanium silicide on the top surface of the gate electrode and in the highly doped source/drain regions. The TiN layer over the sidewall spacers prevents a titanium silicide bridge from forming between/he gate electrode and the source/drain regions during the thermal anneal process. This prevent electrical shorting between titanium silicide on the top surface of the gate electrode and the highly doped source/drain regions.