An attempt was made to predict electromigration resistance on the basis of the basic properties of the atoms involved in forming dilute alloys; such as a Cu matrix with various chemically different solute elements. The relevant property was generated by the formation of solute atom-vacancy pairs, and the electronic charging state. A semi empirical rule was formulated which considered the valence state of the matrix and solute atoms, and which permitted the prediction of the level of void formation or suppression during electromigration stressing. It was found that the formation of voids was suppressed if the valence electron number of the matrix atom and that of the alloying impurity atom added to give an odd number. A literature search indicated that there were only very few cases where agreement between the prediction and the experimental result failed. The rule was justified on the grounds of microscopic considerations within the framework of the inhomogeneous electron gas model.

A Selection Rule of Solutes for Void-Resistant Crystalline Metallic Alloys Exposed to Electromigration. A.Zehe: Crystal Research and Technology, 2002, 37[8], 817-26. See also: Materials Letters, 2003, 57[24-25], 3729-34