Fast dry etching of doped GaN films in Cl₂-based inductively coupled high density plasmas

A parametric study of dry etching of undoped, n-and p-type GaN films was carried out in Cl₂ based inductively coupled plasmas (ICPs). The etch rates of the GaN films were strong functions of Cl₂ concentration, pressure, ICP source power, and rf chuck power. The maximum etch rates were: 7900 Å/min of n-GaN, 6000 Å/min of p-GaN, and 6200 Å/mm of undoped GaN. The etch rates of the GaN films increased up to 50 % Cl₂ and remained relatively constant at higher concentrations, resulting in fairly anisotropic and smooth etch profiles at 50% Cl₂. The surface roughness was relatively independent of the ICP source power and of the rf chuck power up to 150 W, resulting in quite smooth morphology (rms roughness 0.4∼1.3 nm). Stoichiometry at the etched surfaces of undoped and p-type GaN films was maintained, while n-GaN showed some depletion of nitrogen from the surface.