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 degrees C. The reaction starts at 180 degrees C with the formation of small Ni2Si transrotational domains. Their. density and size increase by increasing the annealing temperature to 260 degrees 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 degrees C. It was concluded that the final layer structure is the result of a competition: at low temperature (260 degrees C) transrotational domains prevails since slow structural modifications allow the match between silicide and silicon during the Ni,Si - NiSi phase transition; at high temperature (550 degrees), the growth of randomly oriented silicide grains is favoured.