The reaction of Co and Si1−xGex for MOSFET with poly-Si1−xGex gate

The effects of Ge on the interfacial reaction between Co and poly-Si1−xGex materials were studied. Poly-Si1−xGex layers prepared at 580°C by ultra-high vacuum chemical molecular epitaxy (UHVCME) system were subjected to Co silicidation at various rapid thermal annealing (RTA) temperatures ranging from 500 to 900°C. From X-ray diffractometry (XRD), Co(Si1−yGey) cubic structure was formed with RTA temperature ranging from 500 to 800°C for x=0.09, while CoSi2 was formed at 900°C. However, for x=0.21, Co(Si1−yGey) persisted even after 900°C RTA annealing, and CoSi2 was not found. These results indicate that Ge atoms retard the formation of CoSi2. As a result, the RTA temperature needed to obtain low sheet resistance has to be increased with increasing Ge content. Finally, p-channel metal-oxide-semiconductor (MOS) transistors with poly-Si1−xGex-gate have been successfully integrated with Co salicidation process.