Threshold-Voltage Reduction of FinFETs by Ta/Mo Interdiffusion Dual Metal-Gate Technology for Low-Operating-Power Application

In this paper, Ta/Mo interdiffusion dual metal-gate technology, which has an advantage in realizing dual gate work functions without etching of metals from the gate dielectrics, has been introduced for a FinFET. Gate-first fabrication of the FinFET was successfully implemented by optimizing the deposition and patterning of the Mo and Ta/Mo metal gates on the ultra- thin fin channels. The Ta/Mo-gated n-MOS and Mo-gated p-MOS FinFET exhibit symmetrical values of Vth (0.31/-0.36 V), which are desirable for FinFET CMOS circuit operation with enhanced current drivability, because the threshold voltage (Vth) is reduced due to Ta diffusion in the Ta/Mo gate. It was experimentally found that the Ta/Mo interdiffusion process causes no degradation in integrity of the gate dielectric or the carrier mobility. It was also confirmed that the Ta/Mo interdiffusion process is appropriate for a scaled gate length down to 100 nm.