Process-variability aware delay fault testing of delta VT and weak-open defects

Circuits are tested for both functionality and performance. As opposed to circuits with large delay faults, circuits with small delay faults are difficult to diagnose and as such are potential test escapes. This paper presents a strategy to diagnose these types of defective circuits. Our approach takes into account the effect of inter and intra die process variability in the detection method. Unlike conventional delay fault testing, our approach propagates a delay fault in such a way that the mean of the statistical delay distribution of the faulty circuit is further increased with respect to the mean of a fault-free circuit. This is a two-step strategy that is derived from a simple fault model. The paper further presents simulation results supporting the delay fault testing.