Dual workfunction Ni-Silicide/HfSiON gate stacks by phase-controlled full-silicidation (PC-FUSI) technique for 45nm-node LSTP and LOP devices

We present a new threshold-voltage (Vth) control technique for fully-silicided (FUSI) metal/high-k gate stacks which are suitable for 45nm-node LOP and LSTP CMOS. The key is the phase control of FUSI Ni-silicide by changing Ni film thickness prior to silicidation anneal. As a result, Ni₃Si and NiSi₂ are formed whose effective workfunctions (WFs) on HfSiON are found to be 4.8eV and 4.4eV, respectively, being largely displaced from Si-midgap by ±0.2eV. Meanwhile, the dopant segregation method, known to be successful in Vth-control of NiSi on SiO₂, did not work on HfSiON. With Ni₃Si-PMOS and NiSi₂-NMOS transistors, a wide range of Vth-tuning is achieved coping with both LSTP and LOP requirements. At the same time, leakage suppression merit is better than the 45nm-node targets at electrical thickness (Tinv) around 2.0 nm. Also, our phase-controlled fully silicided (PC-FUSI) devices show excellent mobility characteristics.