A design- for-diagnosis technique for diagnosing both scan chain faults and combinational circuit faults

The amount of die area consumed by scan chains and scan control circuit can range from 15%~30%, and scan chain failures account for almost 50% of chip failures. As the conventional diagnosis process usually runs on the faulty free scan chain, scan chain faults may disable the diagnostic process, leaving large failure area to time-consuming failure analysis. In this paper, a design-for-diagnosis (DFD) technique is proposed to diagnose faulty scan chains precisely and efficiently, moreover, with the assistant of the proposed technique, the conventional logic diagnostic process can be carried on with faulty scan chains. The proposed approach is entirely compatible with conventional scan-based design. Previously proposed software-based diagnostic methods for conventional scan designs can still be applied to our design. Experiments on ISCAS´89 benchmark circuits are conducted to demonstrate the efficiency of the proposed DFD technique.