We have investigated the mechanisms of As redistribution during Ni2Si formation on polycrystalline Si/SiO2 and amorphous Si/SiO2 stacks on (100) Si by secondary ion mass spectroscopy measurements. We found a significant impact of the Si crystallinity and pre-silicidation thermal treatments on the dopant redistribution. There is a significantly higher dose of As accumulated in the vicinity of SiO2 after full Ni2Si silicidation on poly-Si (similar to 51%) than on amorphous-Si (similar to 13%). We demonstrate that the As redistribution during Ni2Si formation on amorphous silicon is dominated by snowplow of As in front of the growing silicide. In contrast, when Ni2Si is formed on recrystallized poly-silicon there are three segregation mechanisms: (1) thermal diffusion during high temperature recrystallization annealing (similar to 17%), (2) snowplow during silicidation (similar to 13%), not dependent on the substrate crystallinity and (3) diffusion along poly-Si grain boundaries during silicidation (similar to 22%). (C) 2005 American Institute of Physics.