A method of processing a substrate including depositing a low dielectric constant film comprising silicon, carbon, and oxygen on the substrate and depositing an oxide rich cap on the low dielectric constant film is provided. The low dielectric constant film is deposited from a gas mixture comprising an organosilicon compound and an oxidizing gas in the presence of RF power in a chamber. The RF power and a flow of the organosilicon compound and the oxidizing gas are continued in the chamber after the deposition of the low dielectric constant film at flow rates sufficient to deposit an oxide rich cap on the low dielectric constant film.