A fluorine-doped amorphous silicon-oxycarbide (SiCOF) dielectric barrier deposited by chemical vapor deposition system is used to replace nitrogen doped silicon carbide (SiCN) and silicon oxycarbide (SiCO) in the 45 nm Cu-interconnect structure due to its low leakage current and dielectric constant. In this article, the low leakage current and dielectric constant of SiCOF mechanism are reported for the first time. The low leakage current of the SiCOF films is due to less trapped sites of electron transportation via Pool-Frenkel model than SiCO. The dangling and weak bonds such as Si-H and -CHx are eliminated by fluorine to form Si-F, and less charge will be trapped in the SiCOF film. A dielectric polarization model is proposed to explain the low dielectric constant of SiCOF. The elimination of molecule dipole is attributed to the incorporated fluorine atoms, which destroy the Si-O-Si tetrahedral network structures. A carrier injection model combined with the polarization is proposed to explain the flatband voltage (V-fb) shift of the C-V curves. The polarization is further verified by using thermal oxide under carbide films to reject the carrier injection from the silicon. At a high electrical field of 2 MV/cm, undoped SiCO has an obvious C-V hysteresis loop, but SiCOF does not. Both at low I MV/cm and high 2 MV/cm electric fields SiCOF had a lower C-V hysteresis loop and flatband voltage shift than undoped SiCO. The root causes of this phenomena are the unsaturated bonds in the film and the interface trap sites of SiCO(SiCOF)/silicon elimination. SiCOF is therefore a good candidate as a dielectric barrier for processes with a back end line requirement under 45 nm. (c) 2006 American Vacuum Society.