Effects of etch-induced damage and contamination on the physical and electrical properties of cobalt sulcides

Damage and residue remaining on the silicon wafer after oxide ovcrctching using C₄F₈/H₂ plasmas and the effects of various post treatments after the overctching on the formation of contact suicides were investigated. The Co suicides formed on the variously etched surfaces were unstable, therefore, the sheet resistances were high and dependent on the etching conditions. However, stable Co suicides 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 suicides were close to those of the suicides formed on a clean control silicon surface. The formation of stable Co suicides 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 silicidcs following Ti silicidation were similar to those following Co silicidation.