Simulation Study of a Metal / High-κ Gate Stack for Low-Power Applications

The performance of a near-midgap metal/high-k gate stack for low-power applications is compared to that of a polysilicon/oxynitride gate stack using mixed-mode simulations. Realistic gate insulator stacks having leakages which are a small fraction of the source-drain leakage are used. In the first part of the study, the gate lengths are chosen based on fixed DIBL, and the performance of metal gate stacks is found to significantly exceed that of polysilicon gate stacks for low-power applications, but with poorer rolloff due to lower halo doping. In the second part of the study, the metal gate stack is allowed to have a longer gate length in order to match the rolloff of the polysilicon gate stack. In this case the impact of the longer gate length on performance is found to be surprisingly weak. The metal gate stack is found to have a performance advantage even when the effect of mobility degradation due to the high-k stack is included. Finally, an ultralow power case is considered, where the lower halo doping of the metal gate stack leads to lower junction leakage