A substantially oxygen-free and nitrogen-free plasma ashing process for removing photoresist in the presence of a low k material from a semiconductor substrate includes forming reactive species by exposing a plasma gas composition to an energy source to form plasma. The plasma gas composition is substantially free from oxygen-bearing and nitrogen-bearing gases. The plasma selectively removes the photoresist from the underlying substrate containing low k material by exposing the photoresist to substantially oxygen and nitrogen free reactive species. The process can be used with carbon containing low k dielectric materials.