In view of extended applications of ion sources towards improved high precision multilayer structures, the etching behavior for different optical coating materials and deposition techniques as well as the performance of an etching process in a multilayer structure were investigated. Etching stabilities of the oxide materials Ta2O5, TiO2, HfO2, Al2O3, and SiO2 as well as the fluoride materials MgF2 and LaF3 were considered in dependence of material type, deposition technique, and etching process. For etching of the single layers a radio frequency pumped ion source operated with Argon or Oxygen plasma is employed. The ions are extracted from the plasma by means of a three grid extraction system with adjustable energy in the range between a few and several hundred eV. The etching behavior of the various single layer systems was associated to the etch rates and evaluated under consideration of the sputter power, to enable a selection of more and less stable materials. As an example for the influence of etched interfaces in a multilayer, a high reflective system at 532nm with modification between high and low index materials will be discussed. A significant absorption decrease due to the plasma treatment could be determined without affecting the damage threshold and total scattering of the model system.