Ion Beam Sputtering for High- and Anti-Reflective Coatings

Ion beam sputtering is well-established in research and industry for optical coatings. Typical applications are coatings of precision optics, like filters, mirrors, and beam splitters. Optical multilayer stacks benefit from the high mobility of the sputtered particles on the substrate surface, and hence the good mechanical characteristics of the layers. The principle of ion beam sputtering is the ejection of target material by bombardment with high energy ions. The control of the ion energy allows material removal with Angstrom accuracy. In contrast to magnetron sputtering the low base pressure of 10^-4 mbar and temperatures below 100 °C result in low contamination and high quality coatings. This is further supported by the higher energy (mobility) of the incoming material on the substrate compared to magnetron sputtering or thermal evaporation. Thus, also the density of the deposited material is usually larger by enhanced self-organization processes. These film properties make ion beam sputtering the preferred deposition method for high quality optical coatings.

For coatings in the visible and near-infrared wavelength regions oxides are usually used due to their negligible absorption in this range. Furthermore, oxides are stable in air and usually hazard-free. Oxide thin films can be deposited in the scia Systems deposition systems either reactivly, by ion beam sputtering of an elemental target in oxygen atmosphere, or by direct sputtering of an oxide target.

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