A method is provided for forming a capping layer comprising Cu, N, and also Si and / or Ge onto a copper conductive structure, said method comprising the sequential steps of: forming, at a temperature range between 200° C. up to 400° C., at least one capping layer onto said copper conductive structure by exposing said structure to a GeH4 and / or a SiH4 comprising ambient, performing a NH3 plasma treatment thereby forming an at least partly nitrided capping layer, forming a dielectric barrier layer onto said at least partly nitrided capping layer, wherein prior to said step of forming said at least one capping layer a pre-annealing step of said copper conductive structure is performed at a temperature range between 250° C. up to 450° C.