Reactive Ion Etching of Y2O3 films applying F-, Cl- and Cl/Br-based Inductively Coupled Plasmas

Reactive ion etching of yttrium oxide thin films was investigated using CF4/O2, BCl3, HBr and Cl2 inductively coupled plasmas. For all gas combinations, with the exception of Cl2, the etch rate was found to be similar, indicating a primarily physical etch process, enhanced in Cl2 by an additional chemical-etching component. The highest observed etch rate was 53 nm/min in Cl2, suitable for controlled etching of optical ridge waveguide structures several hundred nm in height. Overall, the surface quality of the etched Y2O3 films was the highest after etching in CF4/O2 plasmas, indicating a trade-off in etch rate and film quality between the various process gases. Preliminary selectivity measurements show that Ni is a suitable material for etch-masking of high resolution structures in Y2O3