Statistical SRAM Read Access Yield Improvement Using Negative Capacitance Circuits

SRAM has become the dominant block in modern ICs and constitutes more than 50% of the die area. The increase of process variations with continued CMOS technology scaling is considered one of the major challenges for SRAM designers. This process variations increase causes the SRAM cells to functionally fail and reduces the chip functional yield considering the static noise margin stability failures (i.e., cell flips when accessed), write failures (i.e., cell is not written within the write window), and read access failures (i.e., incorrect read operation). In this paper, novel negative capacitance circuits are developed, for the first time, to statistically improve the SRAM read access yield under process variations by reducing the bitlines parasitic capacitance. Post layout simulation results, referring to an industrial hardware-calibrated TSMC 65-nm CMOS technology, show that the adoption of the negative capacitance circuit to a 512 SRAM cells column is capable of improving the read access yield from 61.9% to 100%.