Enabling static random-access memory cell scaling with monolithic 3D integration of 2D field-effect transistors.

Abstract

Static Random-Access Memory (SRAM) cells are fundamental in computer architecture, serving crucial roles in cache memory, buffers, and registers due to their high-speed performance and low power consumption. However, scaling SRAM cells to advanced technology nodes poses significant challenges. Three-dimensional (3D) integration offers a promising solution for reinstating SRAM scaling by vertically stacking devices, thereby reducing the physical footprint. In this study, we demonstrate approximately 40% reduction in cell area and improved interconnect length for 3D SRAM cells constructed from field-effect transistors (FETs) based on monolayer MoS₂, compared to the planar design. Using the layout for the 450 nm technology node, our 2-tier 3D SRAM design achieves better integration density than the planar 350 nm node. Furthermore, we project up to 70% reduction in cell area for 3-tier 3D SRAM cells, closely matching the cell area of the planar 250 nm node. We have successfully realized 1 kilobit of planar SRAM and 2-tier 3D SRAM cell arrays occupying areas of 0.0358 mm² and 0.0251 mm², respectively, each comprising 6144 MoS₂ FETs. Finally, we project the footprint advantage for 3D SRAM cells at scaled technology nodes. Our demonstration highlights the potential of 3D integration of 2D FETs in advancing SRAM technology.