Lattice and grain-boundary diffusion of As in Ni2Si

The diffusion coefficient of As in 260 nm thick polycrystalline Ni2Si layers has been measured both in grains and in grain boundaries (GBs). As was implanted in Ni2Si layers prepared via the reaction between a Si layer and a Ni layer deposited by magnetron sputtering on a (100) Si substrate covered with a SiO2 film. The As concentration profiles in the samples were measured using secondary ion mass spectroscopy before and after annealing (400-700 degrees C). The diffusion coefficients in the grains and the GBs have been determined using two-dimensional finite element simulations based on the Fisher model geometry. For short time annealing (1 h and temperatures lower than 600 degrees C, lattice diffusion has not been observed. However, GB diffusion was evidenced for temperatures as low as 400 degrees C. For higher thermal budgets, As diffuses simultaneously in the volume of the grains and in the GBs. Lattice diffusion is characterized by a pre-exponential factor D-0v similar to 1.5 X 10(-1) cm(2) s(-1) and an activation energy Q(v) similar to 2.72 +/- 0.10 eV. In the case of GB diffusion, the triple product of the As segregation coefficient (s), the GB width (delta), and the diffusion coefficient (D-GB) is found to be s delta D-GB = 9.0 X 10(-3) exp(-3.07 +/- 0.15 eV/kT) cm(3) s(-1). Various types of simulations were used in order to support the discussion of the results. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3035836]