An Efficient SRAM Yield Analysis and Optimization Method With Adaptive Online Surrogate Modeling

SRAM cells usually require extremely low failure rate or equivalently extremely high production yield, making it impractical to perform yield analysis using Monte Carlo (MC) method as huge amount of samples are needed. FastMC methods, e. g., importance sampling methods, are still too expensive as the anticipated failure rate is very low. In this paper, a new SRAM yield analysis method is proposed to tackle this issue. The key idea is to improve traditional importance sampling method with an efficient online surrogate model. Experimental results show that the proposed yield analysis method achieves 5x-22x speedup over existing state-of-the-art techniques without sacrificing estimation accuracy. Sigma distribution and schmoo plot can be quickly generated by the proposed method, which is very useful for realistic applications. Based on the proposed yield analysis method, an efficient yield optimization method has been developed to further automate the SRAM cell design procedure where process variations can be fully considered. Experimental results show that a fully automatic yield optimization for SRAM cells can be done within only a few hours.