Reliability Assesement of Ferroelectric nvCAP for Small-signal Capacitive Read-out

Unlike the conventional way to use drain current as the read-out mechanism, ferroelectric field effect transistor (FeFET) can be read-out in a capacitive manner, namely nonvolatile capacitor (nvCAP) mode. This small-signal nvCAP mode is different from large-signal P-V read-out in the ferroelectric random-access memory (FeRAM) configuration. The reliability aspects such as endurance, retention, and multi-level cell (MLC) are evaluated for the first time in this study. The tunable capacitance CGS-CGD of FeFET devices in 28nm foundry platform was programmed to ON and OFF states. Impact of defect generation and charge-trapping during the ferroelectric switching on the endurance and retention behavior of nvCAP is investigated. We find that the device sustains up to 107 programerase cycles until the Con/Coff ratio becomes similar to 1, and a C-V sweep performed on the fatigued device help 'recover' the device performance. By repeatedly performing recovery-endurance operation, we demonstrate a recovered endurance of 108 cycles.