Using fault model relaxation to diagnose real scan chain defects

Software-based scan chain fault diagnosis is typically composed of two steps. First, scan chain flush patterns are used to identify faulty chains and fault models. This is followed by chain diagnosis using scan patterns in the second step. In this paper, we target chain diagnosis on one special category of chain faults: intermittent scan chain faults. It is showed that these faults may not be modeled correctly in the first step. Hence, a novel diagnosis methodology based on scan chain fault model relaxation is proposed.