Interface-Modulated Antiferroelectric-to-Ferroelectric-Like Transition in Ultrathin Hf0.5Zr0.5O2 Films

Abstract

The development of ultrathin (≤5 nm) hafnia-based ferroelectric (FE) films is essential for achieving low operating voltages, facilitating their integration into advanced process nodes for low-power and non-volatile memory applications. However, challenges in ultrathin FE films arise from the depolarization field and interface-related issues, leading to an antiferroelectric-like (AFE-like) polarization switching behavior and more significant wake-up effects, causing operational inconvenience and reliability concerns. Here, interface-modulated ferroelectricity is reported in 4 nm Hf_0.5Zr_0.5O₂ (HZO) thin films, demonstrating excellent properties with low operating voltage, enhanced switching speed, and high reliability. Electrical and structural characterizations reveal that adjusting interface asymmetry may introduce a substantial built-in field (E_bi) and an AFE-like switching behavior can exhibit a robust FE-like characteristic. This AFE-to-FE-like transition is driven by switching kinetics rather than commonly proposed phase transitions. Furthermore, a comprehensive model is developed to elucidate the intricate physics of the modulation mechanism by asymmetric interfaces, emphasizing the critical roles of depolarizing effects and E_bi on ferroelectricity. This work underscores the importance of interfaces in engineering ferroelectricity for advanced electronic applications.