Compact 3-D-SRAM Memory With Concurrent Row and Column Data Access Capability Using Sequential Monolithic 3-D Integration

Srivatsa Rangachar Srinivasa, Xueqing Li, Meng-Fan Chang, John Sampson, Sumeet Kumar Gupta, Vijaykrishnan Narayanan

Abstract: This paper proposes the use of monolithic 3-D integration technology in designing a novel two-layer 3-D-static random access memory (3-D-SRAM) cell in standard 6T-SRAM footprint. The proposed 3-D-SRAM cell is capable of data access from both the layers. The cell is designed to retrieve row-wise and column-wise data concurrently from the memory array. This memory design can cater to applications and workloads requiring multidimensional data access for enhancing system performance. The novel 3-D layout technique ensures the same footprint as a 6T-SRAM cell despite enhancing the functionality. The design ensures no degradation in the cell stability and performance. Voltage reduction in layer-2 provides 5.4× power savings during column-wise data access. We analyze the implications of employing the proposed SRAM to achieve efficient data access for integral image algorithm. We obtain 2.15× savings in access time and 7.81% access energy savings while accessing data from a 32-kB memory array to compute integral image for a region of 32 rows and 16 columns.