A supercritical fluid such as CO.sub.2 cleans an opening formed in a Si-containing dielectric material and removes polymeric and organic residue produced by the etching process used to form the opening. The opening may be a contact, via or other opening and may include a cross-sectional area of less than 0.2 or 0.1 micron square. Atomic layer chemical vapor deposition (ALCVD) is used to form a thin barrier layer within the opening after the supercritical cleaning. A conductive material is formed over the barrier layer to provide a contact structure with improved contact resistance in VLSI devices.