A novel low resistance gate fill for extreme gate length scaling at 20nm and beyond for gate-last high-k/metal gate CMOS technology

Replacement metal gate (RMG) process requires gate fill with low resistance materials on top of work function tuning metals. Conventional titanium (Ti)-aluminum (Al) based RMG metal fill scheme for low resistance gate formation becomes challenging with further gate length scaling for 20nm node and beyond. In this work, we have demonstrated competitive low resistance gate formation at smaller than 25nm L gate using a novel cobalt (Co)-aluminum based metal fill scheme for extreme gate length scaling. Challenges in CMP for the implementation as well as assessment on resistance and device characteristics of this new low resistance fill scheme are also discussed.