POLYMER METALLIZATION - LOW-ENERGY ION-BEAM SURFACE MODIFICATION TO IMPROVE ADHESION

The interface formation between copper and poly(ethylene terephthalate ) (PET) and poly(methyl methacrylate) (PMMA) films is studied in situ by Ion Scattering Spectrometry (ISS). Very low metal fluxes(similar to 10(13) atoms/cm(2) s) and hence low deposition rates are obtained by using a Knudsen's effusion cell. This allows to reach very low metal c overages down to the sub-monolayer regime. The results indicate that w ithout surface activation, Cu atoms interact only very weakly with bot h polymer surfaces. Indeed, the oxygen/carbon ISS intensify ratio rema ins nearly unaffected by the metal deposition, showing no preferential shadowing effect. Moreover, the ISS polymer signals are still detecte d after exposure to Cu atom fluences corresponding to several monolaye rs coverage. Cu diffusion below the polymer surface is evidenced by th e presence of an inelastic multiple collision contribution in the ISS spectra. It is observed that 2 keV He-3(+) ion beam irradiation prior to metallization induces a drastic modification in the interface forma tion. Ion beam irradiation prevents the metal diffusion into the polym er bulk and leads to an increase of the metal concentration at the sur face. In order to explain these results, the surface modifications pro duced by the ion beam on pristine polymers are studied by ISS and ToF- SIMS. Dehydrogenation and preferential loss of O containing fragments are found. These modifications are associated with the production of r adicals leading to the creation of new adsorption sites for the Cu ato ms. II is proposed that the reaction between radicals of different mac rochains induces a surface crosslinking, that can prevent the diffusio n for the deposited metal atoms into the polymer bulk.