New UltraThin SRAM Layout

Technology scaling has made it nearly impossible to maintain SRAM bitcell stability for dense cells. In technologies below 32nm, the SRAM bitcell size has begun to rise above the area predicted by the scaling trend followed over recent technology generations. We propose a new layout for the 6T SRAM that substantially increases the lithographic friendliness of the cell.

Our new ultra thin SRAM cell uses all straight lines in all layers, and it eliminates the lithographically challenging notch in the diffusion between the passgate and pulldown in the conventional design while maintaining the ability to separately size those devices. The cross coupling is easily accomplished due to the placement of the diffusions. The topology is also well suited for finFETs and other non planar technologies.

Mann, R., and B. Calhoun, "New category of ultra-thin notchless 6T SRAM cell layout topologies for sub-22nm", ISQED , 2011.