Formation kinetics and structure of Pd 2Si films on Si

Abstract

Backscattering and X-ray techniques have been used to study properties of palladium silicide (Pd 2Si) formed by evaporating thin Pd layers on Si followed by heat treatment. The rate of formation of Pd 2Si in the temperature range of 200–275°C has been measured by 2-MeV 4He + ion backscattering. The Pd 2Si layer is found to grow at a rate proportional to the square root of time for thicknesses ranging from approximately 200–4000 Å. The rate of growth is found to be independent of Si substrate orientation or doping type and the rate constant is found to fit a single activation energy of E a = 1·5±0·1 eV over the temperature range measured. X-ray diffraction indicates the structure to be Pd 2Si with the basal plane roughly parallel to the substrate surface for films formed on 〈111〉, 〈110〉, 〈100〉 and evaporated (amorphous) silicon substrates. The degree of preferred orientation is markedly stronger on [111] Si. Ion channeling measurements confirm that in this case the c-direction of the Pd 2Si is parallel with the [111] direction in the underlying Si.