Ion beam etching of high resolution structures in Ta2O5 for grating-assisted directional coupler applications

An investigation on thin Ta₂O₅ films patterning using argon ion beam etching (IBE) is presented. The etch rates are characterised by varying the angle of incidence of the beam onto the substrate. Ta₂O₅ gratings with a period of 2.2 μm (1.1 μm linewidth) and 0.25 μm thickness are fabricated using an angle of incidence of 0°. The resulting Ta₂O₅ grating cross sectional profiles are analysed using AFM and SEM imaging. A fabrication method is thus demonstrated which could be used to implement wavelength selective gratings in applications such as grating-assisted directional couplers (GADCs).