Test Set Compression Through Alternation Between Deterministic and Pseudorandom Test Patterns

This paper presents a new reseeding technique that reduces the storage required for the seeds as well as the test application time by alternating between ATPG and reseeding to optimize the seed selection. The technique avoids loading a new seed into the PRPG whenever the PRPG can be placed in a state that generates test patterns without explicitly loading a seed. The ATPG process is tuned to target only undetected faults as the PRPG goes through its natural sequence which is maximally used to generate useful test patterns. The test application procedure is slightly modified to enable higher flexibility and more reduction in tester storage and test time. The results of applying the technique show up to 90% reduction in tester storage and 80% reduction in test time compared to classic reseeding. They also show 70% improvement in defect coverage when the technique is emulated on test chips with real defects.