The scope of this study was to compare the plasma damage produced on porous dielectrics by different chemistries under identical plasma conditions and evaluate different techniques for characterization of the damage. We have investigated the effects of He + H-2, N-2 + H-2, and NH3 plasmas on the properties of three porous SiCOH dielectrics. All plasma treatments have been performed in the same plasma tool under identical conditions. The plasma treatment caused modifications to the bonding structure of the films, loss of film thickness, and increase in refractive index and dielectric constant that varied with plasma and among the films. Fourier transform infrared spectroscopy indicated the type of structural modification caused by a certain plasma treatment but could not be used to predict the damage to the dielectric constant. No correlation was observed between the shrinkage of the film and the corresponding increase of its dielectric constant. The increases of the dielectric constant correlated only to the increases of refractive index after the plasma treatments. The largest damages to the dielectric constants were caused by plasma treatments at room temperature. The most damaging to the porous SiCOH films was the He + H-2 plasma, while the overall lowest damage was produced by the NH3 plasma at 180 S C. (c) 2006 The Electrochemical Society.