Interdiffusion coefficients and conductivity in gold/nickel bilayer thin films on silicon(111) wafers

Interdiffusion in the gold/nickel bilayer thin films deposited on silicon(111) wafers in the temperature range 200-500 °C has been studied using x-ray photoelectron spectroscopy (XPS), sheet resistance measurements (SRM) and x-ray diffraction. Two independent methods have been used to determine the diffusion coefficients: the accumulation concentration of nickel on the gold surface using XPS; and the variation of sheet resistance as a function of annealing time and temperature. The diffusion coefficients deduced from XPS and SRM are (4.0 X 10 -11 cm 2 s -1 ) exp(-0.79 eV/kT) and (4.8 X 10 -11 cm 2 s -1 ) exp(-0.83 eV/kT), respectively. It is shown that diffusion of nickel through the gold layer causes a considerable loss in conductivity of the bilayer thin films.