Kinetics of shift of individual interfaces in Ni/Si system during low temperature reactions

Abstract

Nanocrystalline Ni(20nm)/crystalline-Si and Ni(20nm)/amorphous-Si systems were heat treated at 453K and 473K for 0.25–2h. The formation of the reaction layer at the interface and the positions of the individual interfaces were followed by depth profiling using Secondary Neutral Mass Spectrometry and a profilometer. The kinetics of the shrinkage of the initial nanocrystalline Ni film and the Si layer, as well as the average growth kinetics of the product layer containing Ni2Si and NiSi phases, were determined in the very early stage of the solid state reaction. The kinetics of the Si and Ni shrinkage followed the parabolic growth law in both systems i.e. the change of the thicknesses were proportional to t1/2. In systems with a-Si, at longer annealing times, a layer with composition of about 40% Ni was developed suggesting the formation of the NiSi2. This was interpreted by the relatively high diffusivity of Ni in a-Si. Results on the effect of Pt on the enhanced homogeneity of the NiSi phase formed as well as on the growth kinetics are also presented.