Experimental evidence for the flatband voltage shift of high-k metal-oxide-semiconductor devices due to the dipole formation at the high-k∕SiO2 interface

Abstract

We have examined an origin of the flatband voltage (VFB) shift in metal-oxide-semiconductor capacitors by employing bilayer high-k gate dielectrics consisting of HfO2 and Al2O3 on the interfacial SiO2 layer. We found that the high-k∕SiO2 interface affects the VFB shift through an electrical dipole layer formation at its interface, regardless of the gate electrode materials. Furthermore, we demonstrated that the VFB shift in the metal/high-k gate stack is determined only by the dipole at high-k∕SiO2 interface, while for the Si-based gate it is determined by both gate/high-k and high-k∕SiO2 interfaces.