Doped selective metal caps to improve copper electromigration with ruthenium liner

An interconnect structure for a semiconductor device, comprising:

• a substrate comprising a metal region, a dielectric region surrounding the metal region, and an intermediate region disposed between the metal region and the dielectric region, the intermediate region comprising:
• a barrier layer adjacent to the dielectric region;
• a liner layer formed on the barrier layer, the liner layer comprising Ru, Pt, Pd, Os, or Ni material, wherein the Ru, Pt, Pd, Os, or Ni material of the liner layer is not present in the barrier layer;
• and
• a seed layer formed on the liner layer;
• and
• a cobalt-containing alloy cap layer formed on the metal region and the intermediate region, wherein the cobalt-containing alloy cap layer extends onto the liner layer.

A method for forming a structure in a substrate, comprising:

• forming a barrier layer on exposed surfaces of a feature in a dielectric layer;
• forming an Ru liner layer on the barrier layer, wherein Ru is not present in the barrier layer;
• forming a copper containing seed layer on the liner layer;
• forming a metal fill on the seed layer by a metal fill process and overburdening the feature using an electroplating process;
• performing a planarization process to expose a top surface of the dielectric layer;
• and
• selectively forming a cobalt-aluminum alloy cap layer on the barrier layer, the liner layer, the seed layer, and the metal fill by exposing the substrate to a cobalt-containing precursor and an aluminum-containing precursor, wherein the cobalt-aluminum alloy cap layer extends onto the liner layer, wherein the substrate is exposed to the aluminum-containing precursor and the cobalt-containing precursor in an alternating manner or at the same time until a desired thickness of the cobalt-aluminum alloy cap layer is reached,