Investigation on the dipole distribution at ferroelectric/dielectric interface

Ferroelectric field-effect transistors (FeFETs) have attracted considerable attention for their potential in non-volatile memory applications. Doped-HfO2 film is a promising FE material for the application in FeFETs due to its compatibility with complementary metal-oxide-semiconductor (CMOS). A significant challenge for these devices is the reliability undermining due to charge trapping which shifts the flat band voltage (VFB) and degrades the electrical performance. This study investigates dipole formation at the Hf0.5Zr0.5O2/dielectric oxide interface and its impact on band alignment. The band offset affected by dipole at the Hf0.5Zr0.5O2/dielectric oxide (SiO2, Y2O3, SiON, and Al2O3) interface is studied using X-ray photoelectron spectroscopy (XPS). The charge neutrality level theory is applied to explain the charge transfer behavior and dipole formation at these interfaces. Our results show that negative dipoles are formed at the Hf0.5Zr0.5O2/SiO2 and Hf0.5Zr0.5O2/Y2O3 interfaces, while positive dipoles arise at the Hf0.5Zr0.5O2/SiON and Hf0.5Zr0.5O2/Al2O3 interfaces. The conduction and valence band offset between Hf0.5Zr0.5O2/Si changes with different dipole distribution. This work will be helpful for understanding the mechanisms of dipole formation and for engineering the reliability optimization of FeFET devices.