Test Data Compression of 100x for Scan-Based BIST

The authors have developed a scheme for scan-based BIST that can compress test stimuli and responses by more than 100 times. The scheme is based on a scan-BIST architecture, and combines four techniques: the invert-and-shift operation, run-length compression, scan address partitioning, and LFSR pre-shifting. The scheme achieved a 100times compression rate in environments where Xs do not occur without reducing the fault coverage of the original ATPG vectors. Furthermore, the masking logic was enhanced to reduce data for X-masking so that test data is still compressed to 1/100 in a practical environment where Xs occur. The scheme was applied to five real VLSI chips, and the technique compressed the test data by 100times for scan-based BIST