Investigation of Ni/Co bilayer salicidation process for sub-40 nm gate technology

The nickel/cobalt bilayer salicidation technology which enables an agglomeration-free silicidation even on narrow-line poly gate was investigated and described in detail. Si/Ni/Co and Si/Co/Ni bilayer stack were evaluated and the effect of thickness ratio between Ni and Co on phase transformation and on thermal stability was examined and the optimum thickness ratio was extracted electrically. For the first time, the Ni/Co bilayer salicidation process was adopted in sub-40 nm poly gate and consequently, the good gate poly resistance and leakage characteristics were obtained. Therefore, Ni/Co bilayer can be regarded as a suitable solution for salicide process in sub-40 nm high performance devices.