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.