Hybrid Pass/Fail and Full Fail Data for Reduced Fail Data Volume

Fail data is collected by a tester from faulty units to allow defect diagnosis to be carried out. The fail data describes the full output response of the unit. The volume of fail data that faulty units produce during volume diagnosis can exceed the tester memory capacity. Existing solutions stop the fail data collection for a faulty unit after sufficient fail data has been collected or modify the test set to produce less fail data. This article considers the format for storing fail data on the tester. This article suggests a hybrid approach, where full output responses are stored for some tests, and only pass/fail information is stored for the remaining tests. This article describes procedures based on diagnostic fault simulation to determine a subset of tests for which full output responses are needed and for adding new tests such that fewer tests in the extended test set would require full output responses. The experimental results for benchmark circuits demonstrate the reductions in fail data volume that can be achieved by a hybrid approach.