Cleaning of patterned porous low-k dielectrics with water, carbon dioxide and ambidextrous surfactants

Solutions and emulsions containing water, hydrocarbon surfactant and CO2 were utilized to remove post-etch residues from vias and trenches in low dielectric constant (k) patterned porous methylsilsesquioxane (pMSQ) interlayer dielectrics. The time for cleaning and rinsing was reduced to 2 min for 0.13 μm features. The vias and trenches were cleaned with a hydrocarbon surfactant, polyoxyethylene 2,6,8-triethyl-4-nonyl ether (5b-C12E8), in water solution to provide detergency, followed by emulsification with the addition of pure CO2. The post-etch and post-ash residues were removed from the vias and trenches both as a suspension and in a dissolved state in microemulsions and/or macroemulsions of water and carbon dioxide. The surfactant is ambidextrous in that it is interfacially active in fundamentally different types of interfaces: the solid–water, solid–CO2, and water–CO2 interfaces. The residues, water and surfactant were displaced from the cleaning vessel with CO2 assisted by gravity to reduce the rinse time from well over 10 min to approximately 1 min. The low interfacial tension produced by surfactant and supercritical CO2 is beneficial in reducing the Laplace pressure to facilitate both penetration and removal of the cleaning solution. This benefit will become increasingly more important as the feature size decreases below 50 nm.