Novel failure mechanism and anomalous acceleration factor on a beam-lead IC

The authors identify a previously unreported corrosion mechanism as a primary cause of field failure in a particular beam-lead sealed junction IC (integrated circuit). This mechanism has been reproduced under laboratory bias-humidity-temperature (BHT) test conditions. They determine an acceleration factor for the corrosion mechanism by comparing the failure distribution obtained in BHT tests with that from a field tracking study. The primary failure mechanism in the field tracking study is corrosion near the interface of the beam leads and the silicon substrate. The corrosion mechanism results in an artifact situated on the beam lead and juxtaposed with the silicon substrate. The results of Auger spectroscopy indicate that the constituents of such artifacts are silicon and usually oxygen and gold or platinum. These artifacts are frequently accompanied by voids in the adjacent silicon substrate. A significant number of failures also exhibit blow beams. It is suggested that in some cases the corrosion may progress to a point at which the artifact provides a conductive path between the substrate and the beam and allows excessive current flow through the beam, resulting in an overstress condition.<
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