Improved Read Stability and Writability of Negative Capacitance FinFET SRAM Cell for Subthreshold Operation

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Abstract
In this work, we compare the read stability and writability between 6T negative capacitance FinFET (NC-FinFET) SRAM cell and the baseline 6T FinFET SRAM cell in the subthreshold and superthreshold operations. In the subthreshold operation (V DD = 0.4V), NC-FinFET SRAM cell shows better read, write, and hold static noise margins than FinFET SRAM cell. During read operation at V DD = 0.4V, pass-gate (PG) NC-FinFET becomes weaker due to the negative differential resistance (NDR) in the saturation region, which reduces the read disturb voltage of NC-FinFET SRAM cell. During write operation at V DD = 0.4V, PG NC-FinFET with internal voltage amplification becomes stronger in the linear region, and pull-up NC-FinFET with NDR effect becomes weaker in the saturation region, which improves the writability of NC-FinFET SRAM cell. In other words, negative capacitance effect resolves the conflict between read stability and writability for subthreshold operation. For the superthreshold operation (V DD = 1V), NC-FinFET SRAM cell still exhibits 1.73 times larger RSNM (= 183mV) than FinFET SRAM cell, and adequate WSNM (= 198mV). 6T NC-FinFET SRAM cell performs superior stability for both subthreshold and superthreshold operations.

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