Test set customization for improved fault diagnosis without sacrificing coverage

Diagnosis is extremely important to ramp up the yield during the integrated circuit manufacturing process. It reduces the time to market and product cost. The back bone of any diagnosis algorithm is the test set in use. In this paper, a novel method has been proposed to increase the diagnosability of a given test set. The proposed method, which takes as input a test set generated for high fault coverage, is capable of increasing the diagnostic power of the test set without affecting its fault coverage. It is able to achieve this with either no or small increase in number of patterns. The crux of the method lies in introducing test patterns having `X´ bits into the test set without changing its coverage, and using a `X´ bit filling algorithm to maximize its diagnostic power.