Effects of high-/spl kappa/ dielectrics on the workfunctions of metal and silicon gates

Abstract

We explore the dependence of metal and polysilicon gate work functions on the underlying gate dielectric in advanced MOS transistors. The interface dipole theory is employed to explain our experimental observation that metal work functions on high-/spl kappa/ dielectrics differ appreciably from their values on SiO/sub 2/ or in vacuum. This model shows excellent agreement with original data and reported results in the literature. In addition, we also explain the weaker dependence of n/sup +/ and p/sup +/ polysilicon gate work functions on the gate dielectric. Challenges for gate work function engineering are highlighted. This work provides additional guidelines on the choice of gate materials for future CMOS technology incorporating high-/spl kappa/ gate dielectrics.