A method for forming an air gap structure on a substrate is described. The method comprises forming a sacrificial layer on a substrate, wherein the sacrificial layer comprises a decomposable material that thermally decomposes at a thermal decomposition temperature above approximately 350 degrees C. Thereafter, a cap layer is formed on the sacrificial layer at a substrate temperature less than the thermal decomposition temperature of the sacrificial layer. The sacrificial layer is decomposed by performing a first exposure of the substrate to ultraviolet (UV) radiation and heating the substrate to a first temperature less than the thermal decomposition temperature of the sacrificial layer, and the decomposed sacrificial layer is removed through the cap layer. The cap layer is cured to cross-link the cap layer by performing a second exposure of the substrate to UV radiation and heating the substrate to a second temperature greater than the first temperature.