High quality surface micromachining of LiNbO3 by ion implantation-assisted etching

A surface micromachining technique of LiNbO 3 substrates, based on an improved implantation-assisted wet etching process, will be presented and discussed. 2.3 μm high relief structures with optical quality surfaces were fabricated on LiNbO 3 by 5 MeV Cu ion implantation through an SU-8 10 μm thick photoresist masking layer patterned by a standard photolithographic process. The LiNbO 3 regions amorphized by implantation were etched in a 49% HF aqueous solution at a rate of 100 nm/s exploiting the high differential etching rate between damaged and undamaged LiNbO 3 (100 nm/s against 1 nm/s). The process can be repeated to obtain higher aspect ratios. In this work the results of both single and double step processes will be presented. The sidewalls morphology of the microstructures will be also discussed. Both the surface quality and features of the manufactured structures make this technology highly promising for integrated optics and acousto/opto-fluidics.