Crosshairs SRAM — An adaptive memory for mitigating parametric failures

We propose Crosshairs SRAM to adaptively fix parametric failures and increase yield. It mitigates process variation by tuning VDD and GND of each bitcell inverter independently from its cross-coupled counterpart. It targets failing cells at the intersection of individually-tuned orthogonal VDD and GND rails. We implement 70 32kb test arrays in 45nm CMOS with little modification to a commercial 6T design and no increase in bitcell area. Crosshairs improves performance by 13% and fixes an average of 70% of parametric failures for reasonable initial failure rates lower than 0.1%.