Interfacial Dipole at High-k Dielectric/SiO2 Interface: X-ray Photoelectron Spectroscopy Characteristics

Abstract

Band bending at both the SiO2 side and the high-k side of the high-k/SiO2 interface has been investigated using X-ray photoelectron spectroscopy (XPS). This band bending is not understandable on the basis of silicate formation or the fixed charges in high-k/SiO2/Si stacks if we do not consider dipole formation at the high-k/SiO2 interface, which in turn confirms the dipole formation at the HfO2/SiO2 interface and at the Y2O3/SiO2 interface. By investigating band bending behavior, the opposite dipole directions have been evaluated between these two interfaces, and the relative difference in dipole magnitude has been demonstrated between the HfO2/SiO2 interface and the Y2O3/SiO2 interface. Although the band bending of SiO2 is underestimated and that of high-k is overestimated, the estimation of relative dipole magnitude is not affected. The relative difference in dipole magnitude is estimated to be ∼0.6 eV between the HfO2/SiO2 interface and the Y2O3/SiO2 interface, which is consistent with relative flatband voltage shifts of ∼0.5 V.