A realistic fault model and test algorithms for static random access memories

摘要

Testing static random access memories (SRAMs) for all possible failures is not feasible and one must restrict the class of faults to be considered. This restricted class is called a fault model. A fault model for SRAMs based on physical spot defects, which are modeled as local disturbances in the layout of the SRAM, is presented. Two linear test algorithms that cover 100% of the faults under the fault model are proposed. A general solution is given for testing word-oriented SRAMs. The practical validity of the fault model and the two test algorithms are verified by a large number of actual wafer tests and device failure analyses.