Electromigration-induced short-circuit failure in aluminum underlaid with chemically vapor deposited tungsten

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Abstract
Electromigration was studied in Al conductors underlaid with chemically vapor deposited W, and the results compared to the more conventional Al/TiW metallization. In Al/TiW conductors electromigration results in Al whisker growth, causing metal short rather than open-circuit failure. Contrary to expectations, the Al/W metallization was found to be more susceptible to the formation of whiskers during current stress, with Al/W lifetimes reduced by about one-half compared with Al/TiW. The temperature and current density failure dependencies were not significantly affected by the composition of the underlayer. The mechanical stress in the underlayer was not found to significantly affect the stress distribution in the overlying Al film.