Measurement of As diffusivity in Ni2Si thin films

The lattice and grain boundary diffusion coefficients of As in 260 nm-thick Ni2Si films were measured. The Ni2Si layers were prepared via the reaction between a Si layer deposited by low pressure chemical vapor deposition and a Ni layer deposited by magnetron sputtering on a Si substrate covered with a SiO2 film. As was implanted in the silicide. Its concentration profiles were measured using secondary ion mass spectroscopy before and after annealing (550–700 °C). 2D finite element diffusion simulations taking into account lattice diffusion and grain boundary (GB) diffusion were performed based on the microstructure of the samples. They were found to fit accurately the measured profiles and allowed to measure the diffusion coefficients for each temperature. Lattice diffusion is characterized by a pre-exponential factor D0v ∼ 1.5 × 10−1 cm2 s−1 and an activation energy Qv ∼ 2.72 eV. In the case of GB diffusion P0 = sδD0gb = 9.0 × 10−3 cm3 s−1 and the activation energy was found to be higher than for lattice diffusion with Qgb ∼ 3.07 eV. Existing data concerning diffusion in silicides and other materials is used to discuss these results. The diffusion of As in Ni2Si could be reduced due to impurity segregation in GBs.