Variation-Tolerant Recall Operation for Nonvolatile SRAM Integrated with Ferroelectric Capacitor

We proposed a variation-tolerant recall scheme for nonvolatile 6T SRAM (NV-SRAM) integrated with two ferroelectric capacitors. Two recall schemes (Type-1 and Type-2) are analyzed considering the impact of threshold voltage mismatch in SRAM cells. The proposed recall scheme (Type-2) shows higher variation immunity as the coercive electric field (E
c
) reduces and remanent polarization (P
r
) increases. The Type-2 recall scheme with optimized ferroelectric parameters can tolerate 110 mV threshold voltage mismatch, which is 4.23 times larger than the Type-1 recall scheme. The proposed variation-tolerant NV-SRAM with ferroelectric capacitors is a promising solution for ultralow-power embedded memory applications.