SRAM yield-per-area optimization under spatially-correlated process variation

Spatial correlation of process variation increases the probability that nearby transistors have similar variation values. However, the impact of spatial correlation on yield enhancement techniques, such as spare rows and columns for SRAM arrays, has not been well understood. In this paper we find that the clustering of failing cells caused by spatially-correlated process variation makes the SRAM array yield much less sensitive to the number of spare rows and columns. We then propose a coarse-to-fine search method to optimize yield-per-area (YPA) of SRAM systems under correlated process variation. We show that the proposed method can identify the optimal design efficiently.