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/SiO
₂
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 AI
₂
O
₃
and Y
₂
O
₃
layer as a bottom high-k, the symmetric V
_TH
CMOS is successfully achieved with a single metal gate electrode.