For dielectric coatings, be it for any type of filter or AR coatings, a structured photoresist and lift-off technology are used: at a low temperature, the coating is deposited onto the substrate which is already coated with the patterned photoresist, and the coating is removed by lift-off together with the photoresist. Recent advances allow us to apply this technology for very large filter thicknesses of > 10 µm. Chrome-based layers are typically removed by wet etching: After coating, the chrome layer is covered with a photoresist, the photoresist is patterned and the chrome layer is removed chemically at the opened surfaces. This process produces very well-defined edges with a jaggedness of <1 µm. Instead of wet etching, reactive ion etching can be used to produce – much finer – structures in dielectric materials. For larger structures, a more cost-effective masked coating can be used as well.
For quality control, an automated optical inspection system is used, which automatically checks for defects and confirms that the specified pattern dimensions were produced.
Materion Balzers Optics offers patterning solutions for all high quality optical coatings described above. Depending on the product and its applications, various patterning techniques are available to meet a broad range of customer requirements for feature sizes and shapes:
