A copper alloy layer is blanket deposited over a low k dielectric layer and in via openings within the low k dielectric layer. The blanket deposited layer is then anisotropically etch to form horizontal interconnects. The interconnects are annealed to form a metal oxide barrier lining. A second low k dielectric layer is then depositing over the horizontal interconnects. Air gaps can be formed between adjacent interconnects to lower parasitic capacitance therebetween.