Switching dynamics of ferroelectric HfO2-ZrO2 with various ZrO2 contents

Abstract

To explore the effect of the ZrO2 content on the switching speed of ferroelectric HfO2-ZrO2 (FE-HZO), we demonstrate 10 nm FE-HZO capacitors fabricated with 5:5, 6:4, and 7:3 HfO2 and ZrO2 atomic-layer-deposition-cycling ratios. The FE-HZO devices show high remanent polarization (Pr) of 26, 20, and 11 μC/cm2 for the 5:5, 6:4, and 7:3 samples, respectively. The FE-HZO capacitors with lower ZrO2 contents show increasing coercive fields, which intuitively seem to increase switching difficulty. However, the FE-HZO devices with 50 mol. %, 40 mol. %, and 30 mol. % ZrO2 contents show decreasing switching times for 80% polarization, namely, 1.2, 0.9, and 0.7 μs, respectively. Because of the polycrystalline nature of FE-HZO, the distribution of local fields in the film is analyzed based on the inhomogeneous field mechanism model. The results show that the FE-HZO devices with lower ZrO2 contents have higher active fields and less uniform distribution of local fields. However, time constants for the 5:5, 6:4, and 7:3 samples decrease dramatically, being 137, 98, and 14 ps, respectively. These results unveil the distribution of the local fields in FE-HZO with varying ZrO2 contents and are helpful for understanding and optimizing the switching dynamics of FE-HZO for non-volatile memory applications.