The study of diffusion and nucleation for COSi2 formation by oxide-mediated cobalt silicidation

Abstract

The role of cobalt in oxide-mediated silicidation is studied in terms of diffusion and nucleation by varying annealing conditions, oxide thickness and implantation in Si substrate. Electroscopic imaging in transmission electron microscopy shows that SiOx act as a one-way diffusion barrier reducing the Co effective concentration at the cobalt silicide growth interface leading to CoSi2 as the first formation phase during silicidation. X-ray photoelectron spectroscopy analysis shows that unreacted Co coexists with CoSi2 at the interface between the SiOx layer and Si substrate, implying that Co diffusion rate is faster than CoSi, nucleation rate. An Si-implanted substrate can increase the CoSi2 nucleation rate and reduce the Co accumulation. (c) 2005 Elsevier B.V. All rights reserved.