First principles calculation of the effects of solute atom on electromigration resistance of Al interconnects

Electromigration (EM) resistance of Al could be improved through the addition of a small amount of alloying elements, such as copper and magnesium. In this paper, an Al31X (X = Sc-Zn and Mg) supercell model was constructed to calculate the effects of a solute element on the properties of face central cubic Al, including the heat of formation, diffusion energy and electronic structure, etc, by employing the density functional theory. It is found that the diffusion energy of Al near Ti, V, Cr, Cu, Zn and Mg solutes could be enhanced. Likewise, the value of the density of states of the system at the Fermi level (N(EF)), as well as that of the Al atoms at the specific sites, could also be reduced slightly by the addition of Sc, Ni, Cu, Zn and Mg. These two results indicate that the nearest neighbour Al atoms could be stabilized by Cu, Zn and Mg. Thus they would be beneficial in prolonging the EM lifetime of Al interconnects. Our calculations are in good agreement with the previous calculations and the experimental phenomenon to some extent.