Porous ultra low-k (ULK) dielectrics are used to reduce resistance-capacitance delay for advanced complementary metal oxide semiconductor interconnects. Since the porosity leads to an increased sensitivity of the material to plasma processes (etching and post-etching plasmas), dedicated characterization techniques are needed to assess the ULK properties during its integration. This study shows that ellipsometric porosimetry, employed with an appropriate multi-solvent protocol, can be effectively used to characterize different plasma-treated porous SiOCH (p-SiOCH) films in terms of porosity, pore sealing and hydrophobicity. It was found that after exposure to fluorocarbon, NH(3), H(2), CH(4) or O(2) based plasmas the p-SiOCH surface is modified leading to moisture uptake. According to the plasma, the solvent adsorption is also modified due to a densification of the surface. In that case solvent adsorption measurements were performed in a kinetic mode to quantify the plasma-sealing effect. (c) 2010 Elsevier B.V. All rights reserved.