Statistical diagnosis for intermittent scan chain hold-time fault

Abstract

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 as well. Unlike the previous scan chain diagnosis methods that targeted permanent 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 of candidate faulty scan cells is obtained. Second a new method to determine a lower bound is proposed. Finally a statistical diagnosis algorithm is proposed to calculate the probabilities of the 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. 1