Solutions and emulsions containing water, hydrocarbon surfactant and CO 2 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 2min for 0.13μm features. The vias and trenches were cleaned with a hydrocarbon surfactant, polyoxyethylene 2,6,8-triethyl-4-nonyl ether (5b-C 12 E 8 ), in water solution to provide detergency, followed by emulsification with the addition of pure CO 2 . 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–CO 2 , and water–CO 2 interfaces. The residues, water and surfactant were displaced from the cleaning vessel with CO 2 assisted by gravity to reduce the rinse time from well over 10min to approximately 1min. The low interfacial tension produced by surfactant and supercritical CO 2 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 50nm.