Statistical diagnosis for intermittent scan chain hold-time fault

Intermittent scan chain hold-time fault is discussed in this paper and a method to diagnose the faulty site in a scan chain is proposed a s well. Unlike the previous scan chain diagnosis methods that targeted p ermanent faults only, the proposed method targets both permanent faults and intermittent faults. Three ideas are presented in this paper. First an enhanced upper bound on the location o f candidate faulty scan cells is obtained. Second a n ew method to determine a lower bound is proposed. Finally a statistical diagnosis algorithm is proposed to calculate the probabilities of t he bounded set of candidate faulty scan cells. The proposed algorithm is shown to be efficient and effective for large industrial designs with multiple faulty scan chains.