The effect of germanium on the Co-SiGe thin-film reaction

Germanium was found to have a strong influence on the path and products of the Co-SiGe reaction, and on the interfacial stability and crystallographic orientation of the suicide film. The segregation of Ge that occurs during the reaction of blanket Co films with SiGe results in thickness effects not present in the reaction of Co with Si. The thickness effect was modelled in terms of the energy cost of Ge segregation, and good agreement with experimental results was obtained. In situ EXAFS experiments on sub-monolayer Co films annealed on SiGe substrates indicate a strong preference for the formation of Co-Si bonds at the silicide-SiGe interface. The implications of these results for the stability of the interface and the epitaxial orientation of co-deposited cobalt disilicide (CoSi₂) films will be discussed.