Faraday cage angled-etching of nanostructures in bulk dielectrics

For many emerging optoelectronic materials, heteroepitaxial growth techniques do not offer the same high material quality afforded by bulk, single-crystal growth. However, the need for optical, electrical, or mechanical isolation at the nanoscale level often necessitates the use of a dissimilar substrate, upon which the active device layer stands. Faraday cage angled-etching (FCAE) obviates the need for these planar, thin-film technologies by enabling in situ device release and isolation through an angled-etching process. By placing a Faraday cage around the sample during inductively coupled plasma reactive ion etching, the etching plasma develops an equipotential at the cage surface, directing ions normal to its face. In this article, the effects that Faraday cage angle, mesh size, and sample placement have on etch angle, uniformity, and mask selectivity are investigated within a silicon etching platform. Simulation results qualitatively confirm experiments and help to clarify the physical mechanisms at work. These results will help guide FCAE process design across a wide range of material platforms.