Self-aligned alloy capping layers for copper interconnect structures

Abstract

Embodiments of the invention include a capping layer of alloy material formed over a copper-containing layer, the alloy configured to prevent diffusion of copper through the capping layer. In another embodiment the alloy capping layer is self-aligned to the underlying conducting layer. Specific embodiments include capping layers formed of alloys of copper with materials including but not limited to calcium, strontium, barium, and other alkaline earth metals, as well as materials from other groups, for example, cadmium or selenium. The invention also includes methods for forming an alloy capping layer on a copper-containing conducting structure. One such method includes providing a substrate having formed thereon electrically conducting layer comprised of a copper-containing material and forming an alloy capping layer on the electrically conducting layer. In another method embodiment, forming the alloy capping layer includes forming a self-aligned capping layer over the conducting layer. In another method embodiment for forming a capping layer on a copper-containing conducting structure, a substrate having formed thereon electrically conducting layer comprised of a copper-containing material is provided. A layer of reactive material is then formed on the surface of the substrate. This is followed by reacting a portion of the layer of reactive material with the copper-containing material of the conducting layer to form an alloy material on the conducting layer. Unalloyed reactive material is removed from the substrate by heating the substrate to a temperature where the unalloyed reactive material desorbs from the surface of the substrate but where the alloy material remains in place on the substrate surface thereby forming a self-aligned capping layer. In another embodiment, the process is repeated iteratively until a capping layer having the desired thickness is formed.

Dependencies are inferred from the claim text.