2D Strain FET (2D-SFET)-Based SRAMs—Part II: Back Voltage-Enabled Designs

In Part I of this article, we had discussed the device characteristics of 2D Strain FET (2D-SFET) and 6T-SRAM with 2D-SFET used as a drop-in replacement for 2D-FET. Here (in Part II), we propose 2D-SFET-based 6T-SRAM designs targeted toward improving cell robustness (which is otherwise low in 2D-SFET SRAMs analyzed in Part I). Our 2D-SFET-based 6T-SRAM designs, namely Schmitt Trigger (ST) SRAM, Schmitt Trigger with Data-Driven Access Feedback (ST-DAF) SRAM and Schmitt Trigger with Dual Word-line (ST-DWL) SRAM leverage back voltage (VB)-driven dynamic bandgap change in 2D-SFET to mitigate the design conflicts. We show that in all designs ST action is achieved by dynamically tuning the strength of pull-up 2D-SFETs enabled by VB. This along with other optimizations result in up to 33% higher read stability in the proposed designs over 2D-FET-based standard 6T SRAM, while mitigating the design conflicts present in standard 6T SRAMs. Our analysis also highlights the benefits and trade-offs for write and hold operations for each of our designs. All the proposed 2D-SFET VB-enabled SRAMs achieve the enhanced functionalities at iso-area compared to 2D-SFET drop-in SRAM in Part I.