Abstract: A substrate processing system includes a processing chamber and a plasma source located external to the chamber. A conduit connects the plasma source to an interior region of the chamber to provide a reactive species to the chamber interior for cleaning interior surfaces of the chamber. A shower head, disposed between the plasma source and an interior region of the chamber, can serve as an electrode and also can serve as a gas distribution mechanism. The shower head includes a surface treatment, such as a non-anodized aluminum outer layer, an electro-polished surface of bare aluminum, or a fluorine-based protective outer layer. The surface-treated shower head improves the rate of removal of materials deposited on the interior surfaces of the chamber during cleaning, reduces contamination of substrates during processing, and provides more efficient use of the power source used for heating the substrate during processing.