In-Field Testing of Functionally-Possible Transition Faults With High Activation Frequencies

Motivated by the reliability requirements of chips in state-of-the-art technologies, this article develops an approach to periodic in-field testing that has the following features. The faults targeted are functionally-possible transition faults, implying that the faults can affect the correct functional operation of a chip. The fault sites in areas of the chip with higher switching activities during functional operation are considered important to target more often. This is because a higher switching activity can lead to faster aging, and therefore, a higher likelihood for defects. Under the approach described in this article, the computation of the functional switching activity, the identification of functionally-possible transition faults, and the generation of tests that are applicable in-field, are performed using the same set of functional test sequences. Experimental results for benchmark circuits demonstrate that small numbers of tests are sufficient for detecting functionally-possible transition faults in areas with high switching activities, making it possible to apply the tests frequently during the lifetime of the chip.