Subthreshold 8T SRAM Sizing Utilizing Short-Channel V_t Roll-off and Inverse Narrow-Width Effect

Abstract

8T SRAM have been considered for robust subthreshold SRAM design. Their subthreshold operation was successfully demonstrated through real silicon measurements. However, Monte-Carlo simulation results show that this SRAM still may not deliver sufficient reliability in subthreshold operation. In this work, we overcome this problem by properly sizing SRAM transistors. We utilize short-channel V_t roll-off and inverse narrow-width effect for the sizing. Since minimum geometry transistors are employed in the SRAM bit-cell, these effects can have profound impact on SRAM stability. Hence, the proposed approach provides an efficient way to increase the yield of the 8T subthreshold SRAMs.