TiCo bilayers in salicide technology: electrical evaluation

A detailed investigation of the applicability of TiCo bilayers for the salicide technology is presented. In the first place the silicide formation on poly-Si gate lines using TiCo bilayers has been studied. It is demonstrated that lateral silicide growth over the spacers can be avoided by making use of a two-step silicidation. In addition, the thermal stability of CoSi2 obtained on small poly-Si lines by two-step silicidation of a TiCo bilayer has been investigated and compared to the thermal stability of CoSi2 obtained by standard silicidation of a 20 nm Co film. The performance of TiCo silicidation with respect to bridging has been studied making use of a special yield monitor chip with dedicated bridging cells. Similar as for standard Co silicidation, close to 100% yield numbers are obtained for two-step TiCo silicidation. Finally, the contact resistance between the silicide and the p+ and n+ diffusion areas has been evaluated making use of four terminal cross-bridge Kelvin resistor structures. Contact resistivity values were calculated to be in the range of 5−6 × 10−7 Ω · cm2 for CoSi2p+ contacts and in the range of 1–2 × 10−7 Ω · cm2 for CoSi2n+ contacts.