An analytical technique for measuring the permeation rate of chlorine-tagged organic solvents through thin polymer films on low-k porous dielectrics was developed. All samples consisted of a silicon substrate with 450 nm thick porous silicon oxicarbide overlayer. The porous layers of some samples were sealed by a 17 nm thick chemical vapor deposited polymer (parylene X) film. Samples were exposed to liquid 3-chloro-1-propanol at room temperature and pressure. The chlorine atom on the propanol molecule was used as a marker, enabling Rutherford backscattering spectrometry analysis to determine the total amount of chemical penetration into the porous layer as a function of the exposure time. Solvent penetration into the sealed porous material increased linearly for exposure times of less than 30 min. Exposures over 30 min saturated the sealed samples with 10.5 mu g of solvent/cm(2). The permeation rate of 3-chloro-1-propanol through the 17 nm parylene X layer was approximately 6.5x10(-3) mu g/cm(2) s.