A new novel pretreatment technology for integration of organic low-dielectric material in copper interconnects for ultralarge scale integration applications is developed. Using NH3 plasma treatment, two extremely important advantages were achieved in spin-on organic polymer (SOP), including the reduction of copper diffusion and the improvement of ashing resistance. A copper/SOP/Si capacitor structure is used to study the electrical characteristics of SOP film after ashing treatment or postanneal. Higher barrier capability and better ashing resistance can be achieved by the SOP layer after NH3 plasma treatment. After annealing at 500°C for 60 min, secondary ion mass spectroscopy depths profile shows that the Cu atoms do not penetrate into the SOP when they are pre-treated by NH3 plasma. Furthermore after the ashing step, the carbon atoms in the SOP film almost remain the same when they are pretreated by NH3 plasma. On the other hand, the concentration of carbon in as-cured SOP is no longer seen. The reason of improving ashing resistance and better barrier capability was due to the organic polymer film rearranging to form a carbon-containing silicon nitride film.