Embodiments of the invention generally provide methods for cleaning a UV processing chamber. In one embodiment, the method includes flowing an oxygen-containing gas through a plurality of passages formed in a UV transparent gas distribution showerhead and into a processing region located between the UV transparent gas distribution showerhead and a substrate support disposed within the thermal processing chamber, exposing the oxygen-containing gas to UV radiation under a pressure scheme comprising a low pressure stage and a high pressure stage to generate reactive oxygen radicals, and removing unwanted residues or deposition build-up from exposed surfaces of chamber components presented in the thermal processing chamber using the reactive oxygen radicals.