We investigated the properties of plasma polymer films deposited by plasma-enhanced chemical vapor deposition using a Mixture of decamethyl-cyclopentasiloxane (C10H30O5Si5) and cyclohexane (C6H12) as the precursors, which we refer to as plasma polymerized decamethyl-cyclopentasiloxane: cyclohexane (PPDMCPSO:CHex) films. The relative dielectric constants, k, of the plasma polymer films were correlated with the Fourier transform infrared absorption peaks of the C-Hx, Si-CH3, and Si-O related groups. As the amount of the CHx species in the as-deposited plasma polymer films increased, the k value and the leakage Current density of the thin films decreased. The subsequent annealing of the PPDMCPSO:CHex film at 400 degrees C for I It further reduced the k value to as low as k=2.05. This annealed PPDMCPSO:CHex thin film showed a leakage cut-rent density of the order of 4 X 10(-7) A/cm(2) at 1 MV/cm and a breakdown field of 6.5 MV/cm. Through the bias-temperature stress test, it was estimated that the PPDMCPSO:CHex film with a k value of 2.05 would retain its insulating properties for ten years at 167 degrees C under an electrical field of 1 MV/cm, when it is presented as a layer adjacent to Cu/TaN(10 nm). (c) 2006 American Vacuum Society.