Back end of line (BEOL) structures and methods generally includes forming at least two adjacent conductors separated by a space formed in a first dielectric material, wherein a liner layer is intermediate the first dielectric material and each of the at least two adjacent conductors. A second dielectric material in the space between the at least two adjacent conductors and in contact with the first dielectric material at a bottom surface thereof, wherein the first dielectric material is different from the second dielectric material, and wherein the first dielectric material has a nitrogen enriched surface at an interface between the first dielectric material and the second dielectric material. The nitrogen enriched surface can be formed by plasma nitridation, thermal nitridation, or laser annealing in the presence of nitrogen gas, ammonia, or a combination thereof.