An ATE assisted DFD technique for Volume Diagnosis of scan chains

Volume Diagnosis is extremely important to ramp up the yield during the IC manufacturing process. Limited observability due to test response compaction negatively affects the diagnosis procedure. Hence, in a compaction environment, it is important to implement Design For Diagnosis (DFD) methodology to restore diagnostic resolution. In this paper, a novel DFD technique which makes the faulty chains to behave as good chains during loading, has been proposed. As a result, the errors introduced in the responses, must occur during unloading of the scan chains. Diagnosis can then be performed by directly comparing the actual and expected responses without any fault simulation - leading to significant reduction in time. Results on benchmark circuits show that the average number of suspected cells for single chain failure is 1.27 (ideal value being 1) and the time taken for diagnosis is in the order of milli-seconds.