The formation and phase analysis of Ni-Si diffusion layers formed by gas siliconizing of nickel

摘要

Nickel plate was siliconized with a gas mixture ofSiCl4 and H2 in the temperature range from 1173K to 1323K.Effect of siliconizing variables on the growth behavior andmicrostructures of Ni-Si diffusion layers was studied. The nickelsilicide layers consisted of r-Ni5Si2, δ-Ni2Si and θ-Ni2Siphase at siliconizing temperature. During furnace cooling fromsiliconizing temperature to room temperature, the θ-Ni2Si phasewas decomposed to large δ-Ni2Si, small δ-Ni2Si, ε-Ni3Si2and NiSi phase depending on the silicon concentration. After anincubation period necessary for nucleation of each phase, thegrowth rate of nickel silicide layers obeyed a parabolic law andwas controlled by solid diffusion of nickel which was the primarydiffuser in Ni-Si compounds leading to the void formation at thesilicides-nickel interface. There was a tendency for the thickness oflower silicide layer to be a constant at the beginning of thenucleation and growth of the adjacent higher silicide layer. Thegrowth behavior and microstructures of nickel silicide diffusionlayers was dependent on the difference between the silicon fluxsupplied by gas siliconizing and the nickel flux supplied by soliddiffusion from substrate which were controlled by siliconizing variables.