Formation of well-separated buried and surface nickel-silicide layers in a single ion implantation step

An unusual Ni distribution with two completely separated buried and surface silicide layers has been observed after Ni ion implantation in Si(111) kept at a temperature of 300?? C, with a dose of 1.1 ?? 1017/cm2 and at a fixed energy of 90 keV. RBS/channeling, AES and cross-sectional TEM have been used to study this phenomenon as a function of the substrate temperature and Co co-implantation. A model is presented, based on the diffusion of the transition metal, the defect annealing during the implantation, and the gettering power of the surface and the end of range defects.EI