Time‐Dependent Imprint in Hf0.5Zr0.5O2 Ferroelectric Thin Films

Abstract

AbstractThe discovery of the HfO2‐based ferroelectric films has opened new opportunities for using this silicon‐compatible ferroelectric material to realize low‐power logic circuits and high‐density non‐volatile memories. The functional performances of ferroelectrics are intimately related to their dynamic response to external stimuli, such as electric fields at finite temperatures. In the case of HfO2‐based films, the time‐dependent imprint and wake‐up effect, which distinguish them from conventional ferroelectrics, play important roles in understanding the remaining reliability issues, such as insufficient endurance. In this study, the time‐dependent imprint process is carefully investigated using Hf0.5Zr0.5O2 (HZO) films with different ferroelectric properties and defect density. The amount of redistributed charge, which causes imprint during polarization retention, is affected by the remanent polarization of the ferroelectric layer, suggesting that the depolarization field corresponding to the remanent polarization generates and works as a driving force of charge redistribution. The time‐dependent measurement of the imprint distinguishes the origins of charge redistribution processes, which have different time constants. In addition, the correlation between the amount of redistributed charge and the dielectric relaxation of the HZO films is discussed. Correlations are identified between the redistributed charge and the dielectric relaxation, indicating that the mobile charge contributes to the time‐dependent imprint.