Reduction of Electromigration-Induced Failure in Aluminum Metallization Through Anodization

Anodization of aluminum metallization was studied as a means of improving resistance to electromigration-induced failure. Strips of evaporated aluminum 1 ¿m thick, 0.6 mil wide and of various lengths were formed on oxidized silicon wafers. Following anodization to a thickness of about 0.2 ¿m, samples were lifetested at ¿ 150°C with current densities in the 106 A/cm2 range. Lifetimes were improved by factors of 7-14 over those of nonanodized aluminum for test at 220°C with a current density of 8 × 105 A/cm2. Improvement was more pronounced at lower temperatures and for shorter strips. These effects are discussed in terms of mechanisms such as limited vacancy supply, reduced electrotransport rate or reduced density of void-nucleating sites.