Reactive ultraviolet thermal processing of low dielectric constant materials

Various embodiments herein relate to methods and apparatus for preparing a low-k dielectric material on a semiconductor substrate. The dielectric material may include porogens distributed throughout a structural matrix. A reactive ultraviolet thermal processing operation is performed to promote removal of the porogens from the dielectric material. By flowing a weak oxidizer such as carbon dioxide into the reaction chamber during UV exposure, the rate at which the porogens are removed can be enhanced in a controllable manner.