Effects of Etch-Induced Damage and Contamination on the Physical and Electrical Properties of Cobalt Silicides

Damage and residue remaining on the silicon wafer after oxide overetching using C4F8/H2 plasmas and the effects of various post treatments after the overetching on the formation of contact silicides were investigated. The Co silicides formed on the variously etched surfaces were unstable, therefore, the sheet resistances were high and dependent on the etching conditions. However, stable Co silicides could be formed on the etched silicon surfaces regardless of etch conditions after O2 plasma cleaning followed by thermal annealing at 600°C and the sheet resistance and the thickness of the silicides were close to those of the silicides formed on a clean control silicon surface. The formation of stable Co silicides was more dependent on the characteristics of the residue than on the damage remaining on the silicon surface. The effects of the remanent residue and damage on the formation of stable silicides following Ti silicidation were similar to those following Co silicidation.