Temperature Dependent Reaction of Thin Ni-Silicide Transrotational Layers on [001]Si

The phase transition from pure Ni to Ni2Si and NiSi was studied by in situ Transmission Electron Microscopy analyses from room temperature to 260 C. The reaction starts at 180 C with the formation of small Ni2Si transrotational domains. Their density and size increase by increasing the annealing temperature to 260 C. After 50 min, a uniform transrotational NiSi layer is formed by a grain by grain transition process. A polycrystalline NiSi layer was instead obtained at 550 C. It was concluded that the final layer structure is the result of a competition: at low temperature (260 C) transrotational domains prevails since slow structural modifications allow the match between silicide and silicon during the Ni2Si - NiSi phase transition; at high temperature (550 C), the growth of randomly oriented silicide grains is favoured.