IMPROVEMENT OF THE ADHESION TO POLYIMIDE SUBSTRATES OF COPPER-FILMS PREPARED BY AN ION-BEAM AND VAPOR-DEPOSITION (IVD) METHOD

Copper films were prepared by evaporation of copper metal and simultan eous bombardment by nitrogen ions with ion energy in the range 0.2 keV to 2.0 keV. The adhesion of copper films was improved by increasing t he ion energy of the nitrogen ions. The copper film prepared with 2.0 keV nitrogen ions had the strongest adhesion. The structure of the int erlayer between the copper film and the polyimide substrate was evalua ted by transmission electron microscopy. The copper atoms were diffuse d into the polyimide substrate by nitrogen ion bombardment. The chemic al states of the polyimide film surface and the chemical binding state s at the interlayer were analyzed by X-ray photoelectron spectrometry. Nitrogen ion bombardment caused carbonization of the polyimide surfac e, and the irradiated nitrogen ions combined with the carbon atoms of the polyimide film. At the interlayer, X-ray photoelectron spectrometr y showed that copper compounds were formed by nitrogen ion bombardment . It was considered that the increase in adhesion due to nitrogen ion bombardment could be attributed to a combination of the anchor effect caused by the diffusion of copper atoms into the substrate and the for mation of copper compounds at the interlayer.