The present invention generally provides a method for forming multilevel interconnect structures, including multilevel interconnect structures that include an air gap. One embodiment provides a method for forming conductive lines in a semiconductor structure comprising forming trenches in a first dielectric layer, wherein air gaps are to be formed in the first dielectric layer, depositing a conformal dielectric barrier film in the trenches, wherein the conformal dielectric barrier film comprises a low k dielectric material configured to serve as a barrier against a wet etching chemistry used in forming the air gaps in the first dielectric layer, depositing a metallic diffusion barrier film over the conformal low k dielectric layer, and depositing a conductive material to fill the trenches.