Random work function variation induced threshold voltage fluctuation in 16-nm bulk FinFET devices with high-k-metal-gate material

Random work-function (WK) induced threshold voltage fluctuation (σV_th) in 16-nm TiN metal-gate fin-type field effect transistors (FinFETs) is explored and modeled by using an experimentally validated Monte Carlo simulation approach. The influences of metal-grain size and device geometry aspect ratio on the random WK-induced σV_th are studied analytically. The results of this study allow us to identify suitable materials for metal gate and to clarify reduction of the σV_th owing to WKF. Among four different gate materials, the titanium nitride possesses the smallest σV_th due to small size of metal grains.