Controllable Coercive Field of Ferroelectric HfO₂ Films via UV-Ozone Surface Modification

The endurance limitation related to high coercive fields ( ${E}_{\text{c}}$ ) has been one of the substantial challenges to future memory applications of ferroelectric HfO ₂ films. In this work, we demonstrate a simple, efficient, and accurate method to regulate the ${E}_{\text{c}}$ value of Hf _0.5 Zr _0.5 O ₂ (HZO) films via interface modification through ultraviolet-ozone (UV-O ₃ ) irradiation on the surface of bottom electrode. Growth behaviors and ferroelectricity of HZO films were systematically investigated by varying UV-O ₃ irradiation time. HZO samples show a well-controlled ${E}_{\text{c}}$ upon a suitable UV-O ₃ irradiation time. Compared with the $w/o$ sample, the ${E}_{\text{c}}$ value of 30-min irradiated sample drops by ~29.5%, and a comparatively high $2{P}_{r}$ of 28.6 $\mu \text{C}$ /cm ² remains. The tuning of ${E}_{\text{c}}$ is clarified to be due to the ratio change of orthogonal and tetragonal phases in HZO films, which can be well controlled by the change of surface energy of the bottom electrode via varying the UV-O ₃ irradiation time.