Routes to the Formation of Air Gap Structures Using PECVD

Fabrication of air gap features have been achieved by three processes utilizing the diffusion of materials through a porous OSG layer. The first process involves the decomposition of a PECVD deposited organic material, either thermally or via UV anneal, to create a void with the decomposition by-products diffusing through the porous OSG layer. The second process uses the etch selectivity of XeF2 or BrF3 towards silicon versus OSG to diffuse through the porous OSG layer to etch the underlying silicon. Finally the water solubility of films such as GeO2 or B2O3, which can be easily deposited by PECVD, can be utilized for void formation via dissolution of the sacrificial inorganic layer through the porous OSG.