Effect of structure and processing on electromigration-induced failure in anodized aluminum

Abstract

The effect of barrier and porous anodizations, either singly or sequentially, on the electromigration resistance of aluminum films was characterized. Samples were tested for current densities in the 4×105−2×106-A/cm2 range and temperatures between 150 and 280°C with the median failure time being used as a basis for comparison of lifetimes. An initial barrier anodization was found to be necessary in order to consistently enhance lifetime. The addition of a porous layer as well led to the best result—an increase in lifetime by a factor of 23 at 227°C. All lifetime increases were attributable to increased activation energy for the electromigration-failure process. An increase of 0.14 eV was obtained for the double anodic structure. Results for structures having a barrier layer adjacent to aluminum were considered in terms of surface sealing of the aluminum and/or response to mechanical constraints of the overlayer. Direct porous anodization resulted in preferential oxidation at grain boundaries, thereby widening these regions, in pitting at grain boundaries, and in general cratering characteristic of this type of anodization. It was concluded that the widening phenomenon was most instrumental in reducing activation energy and lifetime.

A Critical Review on the Electromigration Effect, the Electroplastic Effect, and Perspectives on the Effects of Electric Current Upon Alloy Phase Stability

“…EM occurrence was found to be delayed when fullycovered layers were present, e.g. anodization [73], and passivated layers [50]. These "rigid walls" may suppress the lattice deformation induced by an electric current.…”

Ionic transport and barrier effect of anodic oxide layer in a solid-state Al2O3 capacitor under high electric field

“…In a water-starved environment, aluminum cations Al 3+ could be migrated toward and arrived at the Al pad. In fact, similar phenomenon which is called as 'electromigration-induced failure' has been reported in microelectronics industry [26,32,33]. Arthur J.…”

“…Arthur J. Learn [32] has studied the electromigration-induced failure in anodized aluminum, where the structure of the sample is similar to the one that used in this work.…”

The electromigration effect revisited: non-uniform local tensile stress-driven diffusion

“…In contrast, the pre-existing compressive stress in materials helps hinder the total tensile strain from the yield point. (2) Adding rigid cap-layers on metal strips delayed the occurrence of EM 26 , 28 , 29 , while if the cap-layers were not fully covered 26 or not well contacted 30 , the decelerating of EM-induced failure became invalid. This phenomenon can also be comprehended based on the proposed mechanism.…”