As the feature sizes decrease, understanding manufacturing variations becomes essential to effectively design robust circuits. Manufacturing variations occur when process parameters deviate from their ideal or expected values, resulting in variations in device characteristics. Variations in the device characteristics cause the circuit to deviate from its expected behavior resulting in circuit instability, performance degradation, and yield loss. Both from an economic and performance standpoint, the yield and performance of Static Random Access Memories (SRAMs) are of great importance to the modern System-on-Chip designs. SRAM bitcells typically employ well-matched, minimum-sized transistors which make them highly sensitive to process variations. To overcome these challenges, researchers have proposed different topologies for SRAMs with 8T and 10T SRAM designs. These designs improve the cell stability but suffer from bitline-leakage noise, placing constraints on the number of cells shared by each bitline. These designs also have substantial area overhead when compared to the traditional 6T design.

In this work, the published SRAM designs are characterized using commercial CMOS 65 nm models and are compared based on critical SRAM parameters like read stability, write stability, bitline leakage and the impact of process variations. Furthermore, a single-ended 9T SRAM design is proposed that enhances data stability and simultaneously addresses the bitline leakage problem. The proposed design also satisfies the yield criterion to achieve 90% yield for a 1Mb SRAM array in the presence of process variations.