Dynamics of HfZrO2 Ferroelectric Structures: Experiments and Models

We have carried out a detailed experimental study of the switching dynamics of HfZrO ₂ Metal-Ferroelectric-Metal (MFM) and Metal-Ferroelectric-Insulator-Metal (MFIM) structures. In order to extract the intrinsic dynamic response, our experimental methodology has paid close attention to minimizing and calibrating all circuit and sample parasitics. In MFM structures, we have found no evidence of negative capacitance (NC) effect. A new dynamic model based on the multi-domain Preisach model describes well all observed behavior including major and minor charge-voltage loops. Our study also reveals the crucial role that parasitics play in the observed device dynamics and can explain claims of NC effects in MFM structures in the literature. In our MFIM structures, we observe clear NC behavior. We not only confirm the transient quasi-static S-like ferroelectric (FE) charge-field behavior described in the literature, but for the first time, we report a dynamic response that displays a hysteretic behavior in the NC region. A model based on the Landau-Khalatnikov (L-K) equation that incorporates FE dynamics via a phenomenological frictional resistance adequately describes the observed results when that resistance is made dependent on the direction of the voltage drive vs. time. Mitigation of this hysteretic NC behavior will be crucial for the harnessing of NC in practical MOSFETs.