Implanted oxygen in NiSi formation

Abstract

The effects of implanted oxygen on Nisi formation are studied using MeV 4He+ backscattering spectrometry and the 16O(d, α) 14N nuclear reaction. Ni2Si films on Si 〈100〉substrates are implanted with 2 to 3 × 1016 O/cm2 halfway through the film. Upon annealing, Nisi grows with square root of time in both implanted and unimplanted samples. This disagrees with the linear rate reported by Coe et al. The growth is slightly slower for the unimplanted samples. The slowing is uncorrelated with the amount of oxygen suggesting that a structural change due to ion implantation is the cause. During Nisi formation, oxygen is incorporated into the Nisi film without interfacial accumulation, but the oxygen distribution is seen to move toward the surface. This motion is explained in terms of a simple model based on the chemical affinity of oxygen to Si and Ni and the fact that Ni is the moving species in Nisi growth. The shift in the oxygen peak position during Nisi formation enables the implanted oxygen to act as a diffusion marker, thus confirming Ni as the diffusing species in Nisi formation. The use of implanted oxygen as a diffusion marker in thin film studies is explored briefly.