Experimental investigation of dipole formation and modulation at Hf0.5Zr0.5O₂/SiO₂ interface

HfO 2 -doped ferroelectric field-effect transistors have been extensively studied since the discovery of ferroelectricity in HfO 2 . A metal/ferroelectric/insulator/semiconductor structure is widely used in FeFETs. The dipole at the doped-HfO 2 /SiO 2 interface is not well understood, though it plays an important role in the flat voltage shift and band alignment which strongly affects charge trapping. This study investigates the band alignment and dipole distribution at the Hf 0.5 Zr 0.5 O 2 /SiO 2 interface using X-ray photoelectron spectroscopy. The band bending of the Hf 0.5 Zr 0.5 O 2 /SiO 2 /Si structure is found to vary with Hf 0.5 Zr 0.5 O 2 layer thickness. The valence band offset (VBO) at the Hf 0.5 Zr 0.5 O 2 /SiO 2 interface decreases with increasing Hf 0.5 Zr 0.5 O 2 thickness. It is confirmed that the dipole contributes to the dependence of band bending and VBO on Hf 0.5 Zr 0.5 O 2 thickness. Dipole formation is caused by the charge neutral level mismatch between Hf 0.5 Zr 0.5 O 2 and the SiO 2 /Si stack, which induces electron transfer and band bending. O 2 post deposition annealing (PDA) can modulate the dipole distribution and generate a larger dipole at the Hf 0.5 Zr 0.5 O 2 /SiO 2 interface than that of the sample not subjected PDA.