Sequential Tests for Integrated Circuit Failures

& Conclusion| We propose a sequential probability ratio test based on a two parameter Weibull distribution for IC failure analysis. The shape parameter of the Weibull distribution characterizes the decreasing, constant and the increasing failure rate regions in the bath tub model for ICs. The algorithm detects the operating region of the IC based on the observed failure times. Unlike the xed-length tests, the proposed algorithm due to its sequential nature uses the minimum average number of devices for the test for xed error tolerances in the detection procedure. We nd that the proposed test is on an average 96% more ee-cient than the xed-length test. Our algorithm is shown to be highly robust to the variations in the model parameters unlike other existing sequential tests. Since the accuracy of the tests and the test length are connicting requirements, we also propose a truncated SPRT which allows a better control of this tradeoo. It has both the sequential nature of examining measurements and the xed-length property of guaranteeing that the tolerances be met approximately with a speciied number of available measurements.