A method and apparatus for generating air gaps in a dielectric material of an interconnect structure. One embodiment provides a method for forming a semiconductor structure comprising depositing a first dielectric layer on a substrate, forming trenches in the first dielectric layer, filling the trenches with a conductive material, planarizing the conductive material to expose the first dielectric layer, depositing a dielectric barrier film on the conductive material and exposed first dielectric layer, depositing a hard mask layer over the dielectric barrier film, forming a pattern in the dielectric barrier film and the hard mask layer to expose selected regions of the substrate, oxidizing at least a portion of the first dielectric layer in the selected region of the substrate, removing oxidized portion of the first dielectric layer to form reversed trenches around the conductive material, and forming air gaps in the reversed trenches while depositing a second dielectric material in the reversed trenches.