Fast dry etching of doped GaN films in Cl-2-based inductively coupled highdensity plasmas

A parametric study of dry etching of undoped, n- and p-type GaN films was c arried out in Cl-2 based inductively coupled plasmas (ICPs). The etch rates of the GaN films were strong functions of Cl-2 concentration, pressure, IC P source power; and rf chuck power. The maximum etch rates were: 7900 Angst rom/min of n-GaN, 6000 Angstrom/min of p-GaN, and 6200 Angstrom/min of undo ped GaN. The etch rates of the GaN films increased up to 50 % Cl-2 and rema ined relatively constant at higher concentrations, resulting in fairly anis otropic and smooth etch profiles at 50 % Cl-2. The surface roughness was re latively independent of the ICP source power and of the rf chuck power up t o 150 W, resulting in quite smooth morphology (rms roughness 0.4 similar to 1.3 nm). Stoichiometry at the etched surfaces of undoped and p-type GaN fi lms was maintained, while n-GaN showed some depletion of nitrogen from the surface.