Effects of high- Kappa gate dielectric materials on metal and silicon gate workfunctions

The dependence of metal and polysilicon gate workfunctions on the underlying gate dielectric in advanced MOS gate stacks is explored. We observe that the metal workfunctions on high- Kappa dielectrics differ appreciably from their values on SiO sub(2) or in a vacuum. We also show the first application of the interface dipole theory on the metal-dielectric interface and obtained excellent agreement with experimental data. Important parameters such as the slope parameters for SiO sub(2), Si sub(3)N sub(4), ZrO sub(2), and HfO sub(2) are extracted. In addition, we also explain the weaker dependence of n+ and p+ polysilicon gate workfunctions on the gate dielectric. Challenges for gate workfunction engineering are highlighted. This work provides additional guidelines on the choice of gate materials for future CMOS technology incorporating high- Kappa gate dielectrics.