Defect level as a function of fault coverage and yield

An extension of the well known formula relating yield, fault coverage and defect level has been derived by removing the hypothesis of equally likely faults and exploiting the concept of critical area to evaluate the probabilities of individual faults, under the hypothesis of Poisson´s yield model. A generalized weighted fault coverage figure has been introduced with reference to realistic faults and implications on the test strategy to adopt for a given product have been put into evidence