Dry and wet etching of single-crystal AlN

The dry etching of high crystal quality c-plane AlN grown by metal organic chemical vapor deposition was examined as a function of source and chuck power in inductively coupled plasmas of Cl₂/Ar or Cl₂/Ar/CHF₃. Maximum etch rates of ∼1500 Å min⁻¹ were obtained at high powers, with selectivity over SiO₂ up to 3. The as-etched surfaces in Cl₂/Ar/CHF₃ have F-related residues, which can be removed in NH₄OH solutions. The Al-polar basal plane was found to etch slowly in either KOH or H₃PO₄ liquid formulations with extensive formation of hexagonal etch pits related to dislocations. The activation energies for KOH- or H₃PO₄-based wet etching rates within these pits were 124 and 183 kJ/mol, respectively, which are indicative of reaction-limited etching.