Modulating Oxygen Vacancy Concentration for High-Performance Undoped HfO₂ Ferroelectric Capacitors

Ferroelectric HfO₂ thin film has attracted considerable attention due to its ability to induce ferroelectricity without doping. However, its performance is still far inferior to that of doped HfO₂-based ferroelectric films, which limits its further development. In this study, the ferroelectric performance of TiN/HfO2/TiN devices was significantly enhanced by modulating the oxygen vacancy concentration in undoped HfO₂ films. TEM and EELS analysis demonstrate that the increase in oxygen vacancy concentration within the undoped HfO₂ film promotes the crystallization of the ferroelectric o-phase, accompanied by an increase in dielectric constant, leading to a substantial enhancement in device performance. Ultimately, the TiN/HfO₂/TiN ferroelectric capacitor achieved a high remanent polarization (2Pr ~ 40 μC/cm²). Under an electric field of 2.5 MV/cm, the device sustained over 4 × 10⁹ switching cycles before hard breakdown.