A Family of Compact Non-Volatile Flip-Flops With Ferroelectric FET

Abstract

In this paper, we propose two ferroelectric FET (FEFET)-based non-volatile flip-flops (NVFFs). The proposed NVFFs can handle both controlled and automatic per-cycle backup to address sudden power failure. FE layer can be either positively polarized or negatively polarized. Depending on these polarization states, the FE layer can save either “1” or “0.” To depolarize (i.e., negatively polarize) the ferroelectric layer of an n-type FEFET, a negative gate-to-source voltage is needed, which introduces a challenge. We exploit data-dependent source voltage control to achieve both polarization and depolarization. The proposed NVFFs (NVFF-1 and NVFF-2) can store data every cycle, which is necessary for energy-harvesting applications and devices with an unreliable power source. We also present a modified version of NVFF-2 (NVFF-2a) that can backup data in a controlled fashion and facilitate low-voltage normal mode operation. The proposed circuits introduce only three-to-four additional transistors in the design, which offer a lower area-overhead than contemporary standard FEFET-based NVFFs. Moreover, the FEFET-based NVFFs offer low energy (in the order of fJ) and delay (in the order of tens of ps) behavior, which is advantageous in energy-harvesting non-volatile processors.