Sidewalls of electroplated copper interconnects

A method of plating a structure comprising an opening etched in a nonmetallic material and a diffusion barrier deposited along a sidewall and along a bottom of the opening, the method comprising:

• depositing a seed layer along the sidewall and the bottom of the opening in direct contact with the diffusion barrier, wherein the seed layer comprises a crystalline structure suitable for plating copper;
• depositing an alloying layer along the sidewall of the opening and in direct contact with the seed layer and parallel to the sidewall of the opening, wherein the alloying layer comprises a crystalline structure that cannot serve as a seed for plating a conductive material;
• exposing the opening to an electroplating solution comprising the conductive material wherein the conductive material is not present in the alloying layer;
• applying an electrical potential to a cathode causing the conductive material to deposit from the electroplating solution onto the cathode exposed at the bottom of the opening and causing the opening to fill with the conductive material, wherein the cathode comprises an exposed portion of the seed layer and excludes the alloying layer;
• and
• forming a first intermetallic compound along an intersection between the alloying layer and the conductive material, the first intermetallic compound is formed as a precipitate within a solid solution of the alloying layer and the conductive material.