Aliasing error for a mask ROM built-in self-test

To develop better ROM BIST techniques we first experimentally surveyed cell faults, word-line faults, bit-line faults, delay faults and other types of faults occurring in 1,000 faulty mask ROM chips. We found that most of the stuck-at faults were within a single mat. We then theoretically analyzed the aliasing probability for a mask ROM containing a fault or faults within a single mat. To experimentally evaluate BIST aliasing errors we implemented six MISRs on a custom board and observed actual aliasing errors. The experimentally measured aliasing probabilities agreed with the probabilities derived theoretically. No aliasing error occurred for the 16-stage, 8-input MISR.