Evaluation of Imprint and Multi-Level Dynamics in Ferroelectric Capacitors

Fluorite-structured ferroelectrics are one of the most promising material systems for emerging memory technologies. However, when integrated into electronic devices, these materials exhibit strong imprint effects that can lead to a failure during writing or retention operations. To improve the performance and reliability of these devices, it is cardinal to understand the physical mechanisms underlying the imprint during operation. In this work, the comparison of First-Order Reversal Curves measurements with a new gradual switching experimental approach named "Unipolar Reversal Curves" is used to analyze both the fluid imprint and the time-dependent imprint effects within a 10 nm-thick Hf0.5Zr0.5O2 capacitor. Interestingly, the application of delay times (ranging from 100 mu s up to 10 s) between the partial switching pulses of a Unipolar Reversal Curve sequence enables analysis of the connection between the two aforementioned imprint types. Based on these results, the study finally reports a unified physical interpretation of imprint in the context of a charge injection model, which explains both types of imprint and sheds light on the dynamics of multi-level polarization switching in ferroelectrics. Multi-level ferroelectric switching depends strongly on pulse timings. A hysteresis shift along the voltage axis ("imprint") occurs when a ferroelectric device is left in a particular state. Here, different pulse sequences are adopted to investigate and explain the contrasting effects of fluid (short time scales) and time-dependent imprint (long time scales) on multi-level switching in Hf0.5Zr0.5O2 capacitors. image