Thermal Stability of Cobalt Silicide on Polysilicon Implanted with Germanium

The thermal stability of CoSi2 layers on P-doped polycrystalline Si was investigated. It was observed that the additional Ge+ implant is performed prior to Co sputtering can suppress the CoSi2 agglomeration behavior. The samples with Ge+ implant at 50KeV implanted energy and more than or equal to the dose of 2E15 ions/cm2 show that the agglomeration of CoSi2 film is completely suppressed during high temperature RTA annealing. The grain size by the CoSi2 formation with the Ge+ implantation is much smaller than that without Ge+ implantation during post annealing. In addition, the cobalt atom in polysilicon layer with Ge+ implantation is shallower compared to without Ge+ implantation. The thermal stability of CoSi2 is significantly improved by adding the Ge+ implantation into polysilicon.