Reactive diffusion in the Ni-Si system: Influence of Ni thickness on the phase formation sequence

Abstract

Ni films on c-Si (001) with thicknesses between 10 and 500 nm were studied during annealing using in situ x-ray diffraction, diffuse light scattering, resistance and stress measurement in combination with ex situ RBS. Ramp-type anneals were used to revisit the phase sequence of Ni-Si reactions in the non-equilibrium regime (3 °C/s), allowing for the identification of Ni 3Si2 both in the early and later stages of the reaction, in apparent contradiction with most of the previously published schemes. Ni 3Si2 is present in all samples, forms at the same temperature and at the same time regardless of the initial Ni thickness. Ni 31Si12 is only observed in samples with more than 100nm initial Ni thickness. Slight variations were observed in samples that received a higher thermal budget during deposition. Rapid shifts of the XRD peaks of Ni3Si2 suggest large variations of stress during its formation could be combined with a possible compositional.