On computing the sizes of detected delay faults

Defects in integrated circuits can cause delay faults of various sizes. Testing for delay faults has the goal of detecting a large fraction of these faults for a wide range of fault sizes. Hence, an evaluation scheme for a delay fault test must not only compute whether or not a delay fault was detected, but also calculate the sizes of detected delay faults. Delay faults have the counterintuitive property that a test for a fault of one size need not be a test for a similar fault of a larger size. This makes it difficult to answer questions about the sizes of delay faults detected by a set of tests. A model for delay faults that answers such questions correctly, but with calculations simple enough to be done for large circuits, is presented