Influence of dry etching on the properties of SiO₂ and HfO₂ single layers

A comparative study was performed to investigate how etching methods and parameters affect the properties of SiO₂ and HfO₂ coatings. SiO₂ and HfO₂ single layers were prepared by electron-beam evaporation (EBE), ion-beam assisted deposition (IAD), and ion-beam sputtering (IBS). Then, ion-beam etching (IBE), reactive ion etching (RIE), and inductively coupled plasma etching (ICPE) were used to study the influence of ion bombardment energy and chemical reaction on the etching rates and properties of the prepared SiO₂ and HfO₂ single layers. For SiO₂ coatings, chemical reaction plays a dominant role in determining the etching rates, so ICPE that has the strongest CHF₃ plasma shows the highest etching rate. Moreover, all three etching methods have barely any influence on the properties of SiO₂ coatings. For HfO₂ coatings, the etching rates are more dependent on the ion bombardment energy, although the chemical reaction using CHF₃ plasma also helps to increase the etching rates to some extent. To our surprise, the ion bombardment with energy as high as 900 V does not change the amorphous microstructure or crystalline states of prepared HfO₂ coatings. However, the high-energy ion bombardment in IBE significantly increases the absorption of the HfO₂ coatings prepared by all deposition techniques and decreases their laser damage resistance to different extents.