Improved Polarization‐Retention‐Endurance in Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub> Films by ZrO<sub>2</sub> Capping via Electrostatic Effects
Tingfeng Song, Panagiotis Koutsogiannis, César Magén, J. A. Pardo, F. Sánchez, Ignasi Fina
Abstract
Abstract Ferroelectric hafnia is one of the most promising materials for next generation of non‐volatile memory devices. Several strategies have demonstrated to be of interest to improve its functional properties. Interface engineering, realized by the introduction of additional layer in the capacitor structure, is demonstrated as a promising strategy. However, interface layers can have multiple implications, such as changes in the chemistry of the interfaces and an increase of depolarization field, whose effects are difficult to discriminate. The role of HfO 2 and ZrO 2 capping is explored on polarization, retention, endurance, and leakage properties of Hf 0.5 Zr 0.5 O 2 epitaxial films. In HfO 2 capped films, lower polarization is observed, and endurance and retention are also comparably worse than in ZrO 2 capped films. Complementary under illumination ferroelectric characterization and capacitance measurements indicate a reduction of defects and interface capacitance contribution in ZrO 2 capped films. For both cappings, the interfaces with the Hf 0.5 Zr 0.5 O 2 layer are shown to be compositionally sharp and the phase of Hf 0.5 Zr 0.5 O 2 (HZO) grains is replicated on the capping layer, indicating that electrostatic effects prevail and that the use of interface layers with high permittivity, here ZrO 2 , is crucial to favor good functional properties.