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Early Reliability Assessment Using Deep Censoring



Harry A. Schafft, Linda M. Head, Jason Gill, Timothy D. Sullivan


A method is described for making direct characterizations of the early part of the intrinsic electromigration fail-time distribution of interconnects. The method involves stressing a large number of test lines only long enough for a relatively few lines to fail, enough to characterize the percentile of interest. Groups of test lines are electrically monitored to detect failures without having to measure the many lines on test individually. Two types of deep censoring are described: deep censoring without removals (where more than one line failure in a group can be detected with confidence) and deep censoring with removals (where, when one failure occurs, the other lines in the group are removed from the test). Sample estimates of sigma and one or more early percentiles of the distribution are corrected for bias and their confidence limits calculated. Deep censoring offers important benefits over the present practice of placing tens of test lines on test to obtain sample estimates of t50 and sigma that are used to extrapolate to the early part of the fail-time distribution. The benefits are reduced testing times, better confidence of the sample estimates of early percentiles, and the ability to detect defect fail-time populations. A detailed procedure to implement the method is provided in the appendix.
Microelectronics Reliability


censored data, early percentile failure, electromigration, interconnects, reliability, stress tests


Schafft, H. , Head, L. , Gill, J. and Sullivan, T. (2003), Early Reliability Assessment Using Deep Censoring, Microelectronics Reliability (Accessed May 22, 2024)


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Created December 31, 2002, Updated October 12, 2021