An etch back air gap (EBAG) process is provided. The EBAG process includes forming an initial structure that includes a dielectric layer disposed on a substrate and a liner disposed to line a trench defined in the dielectric layer. The process further includes impregnating a metallic interconnect material with dopant materials, filling a remainder of the trench with the impregnated metallic interconnect materials to form an intermediate structure and drive-out annealing of the intermediate structure. The drive-out annealing of the intermediate structure serves to drive the dopant materials out of the impregnated metallic interconnect materials and thereby forms a chemical- and plasma-attack immune material.