The role of texture in the electromigration behavior of pure aluminum lines

The effects of microstructure on electromigration behavior were evaluated in three nominally 1 mu m thick pure aluminum films, which were tested at temperatures from 423 to 523 K. The three Al films had essentially the same grain structure but different variants of an [111] texture. Texture had a very strong effect on the electromigration behavior in similar to 2 mu m wide polycrystalline lines, where both a reduced fraction of randomly oriented grains and a tighter [111] distribution increased the electromigration lifetime. The apparent activation energy for electromigration decreased as the texture strengthened. The near bamboo microstructure of 0.5 mu m narrow lines showed extensive orientation clustering with an unusually high proportion of low angle boundaries in the most strongly [111] textured film. The electromigration damage in both 2 and 0.5 mu m wide lines was correlated with the types of flux divergence sites in each film. The texture impacts the character of the grain boundaries and interfaces which control the mass transport during electromigration. A weaker texture has more juxtaposed ''fast'' and ''slow'' diffusivity grain boundaries and interfaces, which results in faster mass transport, more flux divergence sites, and a more rapid accumulation of damage. (C) 1996 American Institute of Physics.