Modeling and Investigating Total Ionizing Dose Impact on FeFET

Abstract

This article presents a novel, simulation-based study of the long-term impact of X-ray irradiation on the ferroelectric field effect transistor (FeFET). The analysis is conducted through accurate multiphysics technology CAD (TCAD) simulations and radiation impact on the two FeFET memory states—high-voltage threshold (HVT) and low-voltage threshold (LVT)—is studied. For both the states, we investigate the deterioration of device characteristics, such as threshold voltage shift ( $\Delta V_{\text {th}}$ ) and memory window (MW) degradation, resulting from total ionizing dose (TID) exposure between 10 krad/s and 3 Mrad/s. At a dose rate of 10 krad/s, the FeFET is adequately radiation hardened for both HVT and LVT due to negligible change in MW from the baseline, unradiated case. At a dose rate of 3 Mad/s, an MW degradation of 40% is observed, and the greatest contributor is identified as the HVT state, which shows a 0.5-V increase in $\Delta V_{\text {th}}$ , compared with 0.08 V $\Delta V_{\text {th}}$ for LVT at the same dose rate. The difference in radiation responses for HVT and LVT at the same TID is investigated and attributed to the impact of the depolarization electric field ( $E_{\text {dep}}$ ) on the transport of electrons and holes. Consequently, holes form oxide traps that occupy deeper energy levels for HVT compared with LVT, which underlies the $V_{\text {th}}$ shift and MW degradation. The resultant $I_{d}$ – $V_{g}$ characteristics are in good agreement with the experimental data. Our analysis highlights that the HVT state is sensitive to TID relative to LVT.