The Effects of N₂ and Ar as the Ambient Gas During Rapid Thermal Annealing of Tungsten Silicide

Abstract

Rapid thermal annealing of amorphous tungsten silicide thin films (W_0.62 Si_{0 38}) on Si at 1100°C in Ar and N₂ ambient gases was studied. All films annealed in N₂ exhibited good adhesion and remained smooth with no large grain growth. Films annealed in Ar showed grain nucleation and growth from the film perimeter until a critical stress was achieved, followed by stress-assisted grain growth. The resulting growth of large columnar grains caused the films to delaminate. Removal of the surface oxide/nitride layer from the silicide prior to annealing resulted in uniform nucleation and growth over the entire film during annealing in Ar, with no stress-assisted grain growth or film delamination. No difference, however, was observed during annealing in N₂. These results suggest that a surface film produced during annealing in N₂ slows the nucleation and growth and consequently enhances film adhesion.