Effects of Ti and TiN Capping Layers on Cobalt-silicided MOS Device Characteristics in Embedded DRAM and Logic

Cobalt silicide has been employed to Embedded DRAM (Dynamic Random Access Memory) and Logic (EDL) as contact material to improve its speed. We have investigated the influences of Ti and TiN capping layers on cobalt-silicided Complementary Metal-Oxide-Semiconductor (CMOS) device characteristics. TiN capping layer is shown to be superior to Ti capping layer with respect to high thermal stability and the current driving capability of pMOSFETs. Secondary Ion Mass Spectrometry (SIMS) showed that the Ti capping layer could not prevent the out-diffusion of boron dopants. The resulting operating current of MOS devices with Ti capping layer was degraded by more than 10%, compared with those with TiN.