Method of forming a solute-enriched layer in a substrate surface and article formed thereby

Abstract

A method of enriching the surface of a substrate with a solute material that was originally dissolved in the substrate material, to yield a uniform dispersion of the solute material at the substrate surface. The method generally entails the use of a solvent material that is more reactive than the solute material to a chosen reactive agent. The surface of the substrate is reacted with the reactive agent to preferentially form a reaction compound of the solvent material at the surface of the substrate. As the compound layer develops, the solute material segregates or diffuses out of the compound layer and into the underlying substrate, such that the region of the substrate nearest the compound layer becomes enriched with the solute material. At least a portion of the compound layer is then removed without removing the underlying enriched region of the substrate. For microcircuit applications, the method can be used to enrich the surface of an aluminum line with elemental copper to improve the electromigration resistance of the line.