Fabrication of an AIN ridge structure using inductively coupled Cl2/BCl3 plasma and a TMAH solution

We fabricated an AIN ridge structure using a chlorine-based inductive-coupled plasma reactive-ion etching (ICP-RIE) and a tetramethylammonium hydroxide (TMAH) solution. The ICP etching of single-crystal AIN was systematically investigated by varying ICP power, chamber pressure, and Cl-2/BCl3/Ar mixture gas composition. The selectivity and anisotropy for all samples with a Ni mask were more than 20 and similar to 1, respectively. Etching of AIN in a Cl-2/BCl3 mixture gas yields a higher etch rate compared with a Cl-2/Ar mixture gas. The etch rate of AIN increases with increasing ICP power, reaching 286 nm min(-1) for 400 W. The TMAH solution has an anisotropic characteristic for an AIN etch. A ridge structure with smooth {1 (1) over bar 00} sidewalls was achieved by dipping AIN in the TMAH solution after ICP-RIE. (C) 2019 The Japan Society of Applied Physics