Experimental evidence for the flatband voltage shift of high- k metal-oxide-semiconductor devices due to the dipole formation at the high- k ∕ Si O 2 interface

We have examined an origin of the flatband voltage ( V FB ) shift in metal-oxide-semiconductor capacitors by employing bilayer high- k gate dielectrics consisting of Hf O 2 and Al 2 O 3 on the interfacial Si O 2 layer. We found that the high- k ∕ Si O 2 interface affects the V FB shift through an electrical dipole layer formation at its interface, regardless of the gate electrode materials. Furthermore, we demonstrated that the V FB shift in the metal/high- k gate stack is determined only by the dipole at high- k ∕ Si O 2 interface, while for the Si-based gate it is determined by both gate/high- k and high- k ∕ Si O 2 interfaces.