The ongoing evolution from SiO2 to insulator materials with lower dielectric constant, k, through the introduction of pores, brings new challenges in terms of processing and reliability. Porosity enhances penetration of undesired chemical species. A method of sealing microporous low-k dielectric chemical vapor deposited silicon oxycarbide films using UV-ozone induced oxidation has been investigated. The film thickness, refractive index, porosity, pore size, and sealing as a function of exposure time have been characterized by ellipsometry. The films are sealed without modification of the underlying porosity, an essential first step in integrating porous materials. (C) 2003 The Electrochemical Society.