Efficient test-point selection for scan-based BIST

Abstract

We propose a test point selection algorithm for scan-based built-in self-test (BIST). Under a pseudorandom BIST scheme, the objectives are (1) achieving a high random pattern fault coverage, (2) reducing the computational complexity, and (3) minimizing the performance as well as the area overheads due to the insertion of test points. The proposed algorithm uses a hybrid approach to accurately estimate the profit of the global random testability of a test point candidate. The timing information is fully integrated into the algorithm to access the performance impact of a test point. In addition, a symbolic procedure is proposed to compute testability measures more efficiently for circuits with feedbacks so that the test point selection algorithm can be applied to partial-scan circuits. The experimental results show the proposed algorithm achieves higher fault coverages than previous approaches,with a significant reduction of computational complexity. By taking timing information into consideration, the performance degradation can he minimized with possibly more test points.