Interlayer dielectrics with low dielectric constants are needed for current and future ULSI technology nodes. [1,2] However an understanding of the defects which limit reliability and cause increased leakage currents is not yet developed for these low-k films. As reported previously , we have observed several performance limiting defects with electron paramagnetic resonance (EPR) that correlate quite strongly to leakage current measurements. We have recently made significant progress in developing a fundamental understanding of how film composition and processing parameters affect specific defects and how these defects are related to leakage currents. In this new work we utilize EPR and leakage current measurements to investigate over fifty low-k dielectrics with potential use as ILDs and ESLs. Films investigated include various compositions of SiOC, SiO2, SiN, SiCN, and SiC deposited deposition on 300 mm (100) silicon wafers. They exhibit a wide range of dielectric constant, sample chemistry, and density.