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.