Evidence for an incubation time in electromigration phenomena

A large number of identical structures as well as many different structures were analyzed. The question of which distribution provides the best fit for electromigration failure is discussed. The possible choices of a distribution are extended, and it is shown that the inclusion of a third parameter, an incubation time, leads to the most successful fit. The use of an incubation time is explored for both the log-normal and Weibull distributions. A significant incubation time was found in all cases along with characteristic times that varied from lot to lot. In all of the structures examined there was not a compelling argument for selecting either distribution. The incubation time was found to be significant in every case and, unlike the median time to failure, does not vary among evaporations.<
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