Study of the sputter rate of thin aluminium layers deposited on polymer (PET) substrates

Aluminium thin layers thermally evaporated on polyethylene terephthalate (PET) films were sputter etched by 2 keV Xe ion bombardment. Significant sputter rate differences are observed for layers deposited under different metallization conditions and on different PET substrates. Differences in grain sizes are observed by transmission electron microscopy for the Al layers whereas no difference either in crystallographic orientations or in phase composition is observed on the electron diffraction patterns. The depth-composition profiles of impurities are obtained by SIMS: they show that higher mean sputter rates are achieved for Al layers and Al/PET interfaces containing less oxygen. These differences are shown to be related not only to the depth composition profiles of the impurities in the Al layers and to the Al/PET interface chemistry but also to the microstructure of the Al layers. A decrease of sputter yield is observed for samples exhibiting Al grain sizes greater than the Al layer thickness.Anglai