The reliability of SiOF films for intermetal dielectrics in multilevel interconnections of ULSIs is investigated. SiOF films were deposited by ECRCVD using H-free source gases, i.e., SiF4 and O2. The effect of post plasma treatment on the moisture absorption and dielectric properties of SiOF films were carried out in terms of air exposure time. The reliability test of Cu / TiN / SiOF / Si specimen was carried out in terms of temperatures by RTA in N2 ambient. After O2 plasma treatment, no appreciable peak directly related to moisture absorption was detected. The C-V characteristics of the O2 plasma treated SiOF film showed that the film remained to hold the sound dielectric properties even after boiling treatment. The Cu / TiN / SiOF / Si system was found to be reliable up to 600 °C.