Insights into Oxygen Vacancy Effects on Ferroelectric Behavior of Hafnium Oxide: A Review

Ferroelectricity in hafnium oxide thin films has become a scalable and silicon‐compatible solution for nonvolatile memory and logic applications. The orthorhombic ferroelectric phase, while metastable, becomes accessible through oxygen vacancies, which play a complex role in enabling and degrading device performance. Controlled vacancy incorporation can stabilize polarization and enhance endurance, while uncontrolled migration under an electric field leads to wake‐up effects, fatigue, imprint, and leakage. This review examines how oxygen vacancies influence ferroelectric phase formation, switching behavior, and reliability in hafnium oxide systems. First‐principles simulations reveal that vacancy charge states modulate phase energetics and dipole formation. Experimental methods—including X‐ray photoelectron spectroscopy, electron paramagnetic resonance, and electron energy loss spectroscopy—offer insight into vacancy distributions at the atomic scale. Vacancy behavior is linked to remnant polarization stability and switching degradation at the device level. Process strategies such as dopant engineering, thermal annealing, and interface design are shown to be critical for vacancy control. A deeper understanding of vacancy dynamics, combined with in situ characterization and predictive modeling, is essential for advancing hafnium oxide‐based ferroelectric memories and neuromorphic architectures.