Comprehensive Study of VFB Shift in High-k CMOS - Dipole Formation, Fermi-level Pinning and Oxygen Vacancy Effect

We have quantitatively investigated effective work function (Phi_m,eff) shift, and experimentally demonstrated that high-k/SiO₂ dipole and Si-based gate/high-k contribution are critically important for understanding anomalous V_FB shift. Furthermore, we have also found that annealing of metal/high-k gate stack in the reduction ambient induces another dipole formation at the high-k/Si02 interface. Finally, by using the AI₂O₃ and Y₂O₃ layer as a bottom high-k, the symmetric V_TH CMOS is successfully achieved with a single metal gate electrode.