A method is provided for depositing a dielectric film on a substrate. According to one embodiment, the method includes providing the substrate in a process chamber, exposing the substrate to a gaseous precursor to form an adsorbed layer on the substrate, exposing the adsorbed layer to an oxygen-containing gas, a nitrogen-containing gas, or an oxygen- and nitrogen-containing gas, or a combination thereof, to form the dielectric film on the substrate, generating a hydrogen halide gas in the process chamber by a decomposition reaction of a hydrogen halide precursor gas, and exposing the dielectric film to the hydrogen halide gas to remove contaminants from the dielectric film.