Influence of ion beam parameters onto two-dimensional optical thin film thickness distributions deposited by ion beam sputtering

Abstract

In the present study, the influence of different ion beam parameters onto the two-dimensional thickness distribution of optical coatings in an industrial scale coating process is investigated. Ta2O5 and TiO2 films were deposited by reactive ion beam sputtering under variation of ion species, ion beam current, ion energy and beamlet pattern of the applied ion optic. Also the distance between ion optic and target was varied. The corresponding thickness distributions over a planar area of 0.9 × 1.0 m2 were determined by the collection method and characterized with respect to maximum deposition rate, distribution width and deposition volume rate as a measure of productivity. To interpolate the discrete mapping data accurately, an empirical model function was determined. Concerning the ion beam current it has been verified that the maximum deposition rate and the deposition volume rate scale identically and directly proportional to the ion beam current. The normalized distribution itself is almost independent of the varied beam parameters. Furthermore, it has been found that the ion energies of 1.5 and 2.0 keV have no significant impact on the material distribution. In contrast, it was observed that the ion species and the distance between the ion optic and the target affect the productivity significantly.