Insights into oxygen vacancy dynamics in HfO2–ZrO2 superlattice ferroelectric films: Implications for device reliability

Compared with solid solution (SS) Hf0.5Zr0.5O2, HfO2–ZrO2 superlattice (SL) ferroelectric films exhibit enhanced endurance and reduced leakage. However, so far, the underlying physical mechanism is still missing. In this work, first-principle calculations reveal that the superior reliability arises from the precise control in the spatial profile of oxygen vacancy with the stacked structure in SL in which oxygen vacancies (Vo) exhibit different formation energies and different energy profiles in Zr- and Hf-layers. However, Vo have the tendency to migrate and its suppression become critical to maintain the superiority of SL. A low annealing temperature is, therefore, suggested and validated with our fabricated SL- and SS-ferroelectric films with different annealing temperatures. This understanding can pave ways for the optimization in SL ferroelectric films.