Pseudo-random pattern testing of bridging faults

While previous research has focused on deterministic testing of bridging faults, this paper studies pseudo-random testing of bridging faults and describes a means for achieving high fault coverage in a built-in self-test (BIST) environment. Bridging faults are generally more random pattern testable than stuck-at faults, but examples are shown to illustrate that some bridging faults can be much less random pattern testable than stuck-at faults. A fast method for identifying these random-pattern-resistant bridging faults is described. State-of-the-art test point insertion techniques, which are based on the stuck-at fault model, are inadequate. Data is presented which indicates that even after inserting test points that result in 100% single stuck-at fault coverage, many bridging faults are still not detected. A test point insertion procedure that targets both single stuck-at faults and non-feedback bridging faults is presented. It is shown that by considering bath types of faults when selecting the location for test points, higher fault coverage can be obtained with little or no increase in overhead. Thus, the test point insertion procedure described here is a low-cost way to improve the quality of built-in self-test.