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 u sing C4F8/H-2 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 he formed on the etched silicon surfaces regardless of etch conditions after O-2 plasma cleaning followed by therma l annealing at 600 degrees C and the sheet resistance and the thickness of the silicides were close to those of the silicides formed on a clean contro l silicon surface. The formation of stable Co silicides was more dependent on the characteristics of the residue than on the damage remaining on the s ilicon surface. The effects of the remanent residue and damage on the forma tion of stable silicides following Ti silicidation were similar to those fo llowing Co silicidation.