An atomic force microscopy study of thin CoSi2 films formed by solid state reaction

With the continued scaling down of device features surface roughness of silicides used as contacts is a growing concern. In this work we present an atomic force microscopy (AFM) study of thin CoSi₂ films formed by solid state reaction. Four structures, Co/Si, TiN/Co/Si, Ti/Co/Si and Co/Ti/Si, were used to form the silicide. A study of the thermal stability of these films was made. The topography and surface roughness of CoSi₂ related to thermal agglomeration were investigated in detail post-annealing at 950°C with time duration varying from 60 to 300 s was applied to the CoSi₂ formed from Co/Si reaction. The surface roughness increases with the anneal time. With a TiN capping layer or Ti interfacial layer in deposited structures the surface roughness significantly decreases compared to that from Co/Si reaction, especially in the case of high temperature annealing processes. The sheet resistance of all CoSi₂ was measured by the four point probe technique and correlated to the roughness