Electromigration early-failure distribution

Abstract

This work investigates the functional form of the electromigration early-failure distribution in thin Al-1% Si metal films. In a very-large-scale experiment with 28 320 packaged samples, an early-failure group was identified and found to correspond to a log-normal distribution, but with a larger dispersion than that which was typical of the primary, or wear-out, distribution. The total distribution for the failures is approximately bimodal, with the more disperse background distribution dominating at early times. Scanning electron micrographs were obtained to characterize the typical failure mode, which had the same appearance for both groups. Evidence for a test-condition stress-level effect on the form of the accelerated lifetime distribution is also presented.