Processing of photonic crystals in InP membranes by focused ion beam milling and plasma etching

We present a fabrication approach for photonic crystals and similar nanophotonic structures in InP using focused ion beam milling and plasma etching. The high quality of ion milling lithography in a dielectric hardmask is combined with reactive ion etching to obtain simultaneously fast processing speeds as well as smooth and vertical sidewalls. Different hardmask materials have been investigated yielding very good results for SiO2 and SixNy. Parameters for the optimization of lithography and plasma etching are given. Finally, results of a released InP membrane with a photonic crystal structure featuring elliptical base elements are presented.

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