Statistical simulation of metal-gate work-function fluctuation in high-κ/metal-gate devices

In this work, we statistically examine the emerging high-κ/ metal gate work-function fluctuation (WKF) induced threshold voltage (V_th) fluctuations in 16-nm-gate MOSFET devices. Our Monte-Carlo model extensively evaluates the impact of WKF for different technology node, metal grain size, and gate material. This model provides us to identify suitable materials and fabrication processes that can significantly reduce the impact of V_th fluctuation owing to WKF. First, four kinds of gate material are examined and TiN possesses the smallest V_th fluctuation. For fabrication process, a fast deposition of metal at lower temperature prevents the metal grain not to grow to large size result in a smaller variation. In addition, an idea of modeling multilayer metal gate WKF is also presented and discussed, in which the first layer plays the most important role, compared with other layers, for the fluctuation suppression.