Wake-up free Hf0.5Zr0.5O2 thin film with enhanced ferroelectricity and reliability synthesized by atomic layer crystallization induced by substrate biasing

Abstract

Attentions on HfO2-based ferroelectric thin films have been rapidly raised due to the promising non-volatile memory applications in advanced artificial intelligence. In this study, the novel “atomic layer substrate bias induced crystallization (ALCISB)” technique is proposed to prepare wake-up free and back-end-of-line compatible Hf0.5Zr0.5O2 (HZO) thin films. The adatom migration boosted by the energy transfer from the plasma in the ALCISB process contributes to the film densification and the crystallinity enhancement of the HZO layer. The ferroelectric remnant polarization (2Pr) and the dielectric constant are increased from 3 to 48 μC/cm2 and 21.4 to 27.7, respectively, which are attributed to the crystallization into orthorhombic phase by the ALCISB technique. Furthermore, the ALCISB treatment suppresses the amount of oxygen vacancies, leading to the extension of the endurance up to 109 cycles and the wake-up free operation of the HZO thin film. The retention characteristic is almost free of degradation after extrapolating to 10 years of thermal treatment. The exceptional ferroelectric properties of the HZO thin films synthesized by ALCISB are highly favorable to non-volatile ferroelectric memory devices in the near future.