Compressed Skewed-Load Delay Test Generation Based on Evolution and Deterministic Initialization of Populations

The current design and manufacturing semiconductor technologies require to test the products against delay related defects. However, complex acpSOC require low-overhead testability methods to keep the test cost at an acceptable level. Skewed-load tests seem to be the appropriate way to test delay faults in these acpSOC because the test application requires only one storage element per scan cell. Compressed skewed-load test generator based on genetic algorithm is proposed for wrapper-based logic cores of acpSOC. Deterministic population initialization is used to ensure the highest achievable aclTDF coverage for the given wrapper and scan cell order. The developed method performs test data compression by generating test vectors containing already overlapped test vector pairs. The experimental results show high fault coverages, decreased test lengths and better scalability in comparison to recent methods

Layout-Aware Scan Chain Reorder for Launch-Off-Shift Transition Test Coverage

Launch-off-shift (LOS) is a popular delay test technique for scan-based designs. However, it is usually not possible to achieve good delay fault coverage in LOS test due to conflicts in test vectors. In this article, we propose a layout-based scan chain ordering method to improve fault coverage for LOS test with limited routing overhead. A fast and effective algorithm is used to eliminate conflicts in test vectors while at the same time restrict the extra scan chain routing. This approach provides many advantages. (1) The proposed method can improve delay fault coverage for LOS test. (2) With layout information taken into account, the routing penalty is limited, and thus the impact on circuit performance will not be significant. Experimental results show that the proposed LOS test method achieves about the same level of delay fault coverage as enhanced scan does, while the average scan chain wire length is about 2.2 times of the shortest scan chain