Effects of Unipolar and Bipolar Pulses on Leakage and Breakdown in HZO-Based FeFETs: A Path to Improved Endurance

Hf0.5Zr0.5O2 (HZO)-based ferroelectric field effect transistors (FeFETs) show great promise for nonvolatile memory (NVM) applications, but their endurance faces major challenges, with breakdown being a key limiting factor. In this study, we investigated the leakage behavior and breakdown mechanisms of FeFETs under varying unipolar positive, unipolar negative, and bipolar pulse amplitudes using carrier separation method. We identified distinct breakdown mechanisms for each pulse type: 1) unipolar positive pulses drive defects to form a breakdown path (BD path) rather than the generation of new defects, in addition, the breakdown characteristics are different depending on the location of the BD path; 2) a unipolar negative pulse suppresses defects movement but generates new defects, and near the SiO2 interfacial layer (IL) traps positive charges, increasing the electric field at the HZO layer, which leads to the formation of the initial BD path in the HZO layer of the channel region; and 3) bipolar pulses accelerate defects generation, leading to the creation of multiple BD paths and breakdown. Based on these findings, we developed a recovery scheme using unipolar negative pulses, achieving over 100 successful recoveries. Controlling defects movement and generation is crucial for enhancing FeFETs endurance.