HfO-ZrO Ferroelectric Capacitors with Superlattice Structure: Improving Fatigue Stability, Fatigue Recovery, and Switching Speed.

HfO-ZrO ferroelectric films have recently gained considerable attention from integrated circuit researchers due to their excellent ferroelectric properties over a wide doping range and low deposition temperature. In this work, different HfO-ZrO superlattice (SL) FE films with varying periodicity of HfO (5 cycles)-ZrO (5 cycles) (SL), HfO (10 cycles)-ZrO (10 cycles) (SL), and HfO (15 cycles)-ZrO (15 cycles) (SL) were studied systematically. The HfZrO (HZO) alloy was used as a comparison device. The SL film demonstrated improved ferroelectric properties compared to the HZO film, with the 2 times remnant polarization (2) values increasing from 41.4 to 48.6 μC/cm at an applied voltage of 3 V/10 kHz. Furthermore, the first-order reversal curve diagrams of different SL and HZO capacitors at different states (initial, wake-up, fatigue, and recovery) were measured. The SL capacitors were found to effectively suppress the diffusion of defects during - cycling, resulting in improved fatigue stability characteristics and fatigue recovery capability compared to the HZO capacitor. Moreover, an improved switching speed of the SL films compared to the HZO capacitor was concluded based on the inhomogeneous field mechanism (IFM) model. These results indicate that the SL structure has a high potential in future high-speed ferroelectric memory applications with excellent stability and recovery capability.