Depolarization Field Induced Instability of Polarization States in HfO2 Based Ferroelectric FET

Doped HfO2 based ferroelectric FET (FeFET) exhibits a greatly improved retention performance compared with its perovskite counterpart due to its large coercive field, which prevents domain flip during retention. In this work, however, through extensive temperature dependent experimental characterization and modeling, we are demonstrating that: 1) with FeFET geometry scaling, the polarization states are no longer stable, but exhibit multi-step degradation and cause reduced sense margin in distinguishable adjacent levels or even eventual memory window collapse; 2) the instability is caused by the temperature activated accumulation of switching probability under depolarization field stress, which could cause domain switching within the retention time at operating temperatures.