The effect of CF4/O-2-based plasma treatment on two types of porous low dielectric constant (low-k) materials was investigated. For the microporous film, the surface appears to be sealed, most likely by the formation of a silicon oxide-like layer within 5 s of treatment. For both microporous and mesoporous materials, fluorine incorporation at the surface was low (similar to3 to 6 atom %) after 15 s exposure to the plasma. Processing using CF4/O-2-based plasma appears not to induce significant change to the porous low-k materials as evidenced by similar atomic compositions measured using Auger spectroscopy. These results point to a mechanism that involves a competition between surface modification/oxidation and material removal under the action of fluorine-containing species in the plasma. (C) 2004 The Electrochemical Society.