Low resistance metal silicides are widely used in advanced CMOS device as contact and interconnect materials. As device feature size shrinks, Ni silicides are widely used to replace Co silicides due to lower resistivity and ability to silicide narrower feature size (<4nm). During silicide formation, crystallization of the Ni silicide phase is controlled by Ni diffusion upon annealing since Ni is the diffusing species. First, Ni forms Ni 2 Si during annealing at 300ºC, then NiSi is formed at 250ºC and all of the deposited Ni is consumed. NiSi is the desired phase for CMOS device application because it has the lowest sheet resistance among Ni-based silicides. Finally, NiSi 2 is formed at higher temperatures of around 800ºC [1].