Cell-aware diagnosis: Defective inmates exposed in their cells

Volume diagnosis of scan fails is au effective method of identifying dominant defect mechanisms for yield improvement. However, traditional diagnosis is at the library cell level and identifies only interconnect defects and defective cells. In practice, many defects affect only the internal logic of cells, such as polysilicon contacts, but cannot be pinpointed, resulting in not identifying some potential yield limiters. This paper describes a solution to the problem by showing how diagnosis can be extended to internal cell defects. This is enabled by characterizing a cell library similar to what is needed for cell-aware ATPG, but including more information for diagnosis such as layout data. A flow is described to produce the characterization, which includes requirements for the cell views. Diagnosis results include layout marker files for cell internal suspects which can be viewed in a GDS newer and used to obtain X/Y coordinates to guide physical failure analysis. Successful implementation is demonstrated for a 160nm automotive product.