Impact of Oxygen Vacancy on Ferroelectric Characteristics and Its Implication for Wake-Up and Fatigue of HfO2-Based Thin Films

In this article, a phase-field polarization switching model for ferroelectric HfO ₂ -based thin films considering oxygen vacancies ( ${V}_{o}$ ) has been developed based on the 2-D time-dependent Ginzburg–Landau (TDGL) equation coupling with Poisson’s equation. The impacts of nonuniform ${V}_{o}$ distributions induced by the monolayer grains in ultra-scaled Hf _0.5 Zr _0.5 O ₂ (HZO) films and ${V}_{o}$ concentrations on ferroelectric characteristics are investigated in detail by the developed model which is verified and calibrated by measurement results of HZO. Furthermore, possible mechanisms of wake-up and fatigue are revealed by the simulation with the proposed model. It is clarified that the redistribution of nonuniform ${V}_{o}$ in the in-plane direction leads to the transition from a pinched polarization-voltage curve to a conventional one at the early stage of wake-up, while the generation of ${V}_{o}$ within a ferroelectric film results in ferroelectricity enhancement and reduction in wake-up and fatigue processes, respectively.