Defect Engineering of Hafnia-Based Ferroelectric Materials for High-Endurance Memory Applications

Zirconium-doped hafnium oxide (HfZrO) is one of the promising ferroelectric materials for next-generation memory applications. To realize high-performance HfZrO for next-generation memory applications, the formation of defects in HfZrO, including oxygen vacancies and interstitials, needs to be optimized, as it can affect the polarization and endurance characteristics of HfZrO. In this study, we investigated the effects of ozone exposure time during the atomic layer deposition (ALD) process on the polarization and endurance characteristics of 16-nm-thick HfZrO. HfZrO films showed different polarization and endurance characteristics depending on the ozone exposure time. HfZrO deposited using the ozone exposure time of 1 s showed small polarization and large defect concentration. The increase of the ozone exposure time to 2.5 s could reduce the defect concentration and improve the polarization characteristics of HfZrO. When the ozone exposure time further increased to 4 s, a reduction of polarization was observed in HfZrO due to the formation of oxygen interstitials and non-ferroelectric monoclinic phases. HfZrO, with an ozone exposure time of 2.5 s, exhibited the most stable endurance characteristics because of the low initial defect concentration in HfZrO, which was confirmed by the leakage current analysis. This study shows that the ozone exposure time of ALD needs to be controlled to optimize the formation of defects in HfZrO films for the improvement of polarization and endurance characteristics.