Embodiments of the present invention provide apparatus and methods for performing UV treatment and chemical treatment and/or deposition in the same chamber. One embodiment of the present invention provides a processing chamber including a UV transparent gas distribution showerhead disposed above a substrate support located in an inner volume of the processing chamber, a UV transparent window disposed above the UV transparent gas distribution showerhead, and a UV unit disposed outside the inner volume. The UV unit is configured to direct UV lights towards the substrate support through the UV transparent window and the UV transparent gas distribution showerhead.