Cl₂-based dry etching of GaN and InGaN using inductively coupled plasma the effects of gas additives

The effects of added H₂, Ar, and CH₄ gases on the etch characteristics of GaN and InGaN were studied using an inductively coupled Cl₂-based plasma. Each added gas had a unique effect on the etch rate, anisotropy, surface roughness, and sidewall morphology. The most anisotropic etch profile was obtained using Cl₂, but the etched surface showed the roughest morphology and was covered with etch residues, the origins of which were the micromasking of the sputtered dielectric. When H₂ gas was added to the Cl₂ plasma, the etch residues were removed and the surface roughness was decreased, even though the etch rate was slightly decreased. The etch rate of GaN by Cl₂/H₂/Ar plasmas was saturated above an Ar flow rate of 16 sccm and the surface roughness of the etched GaN was lower, compared with Cl₂/H₂ plasmas at low source power. Finally, it was found that the In compound was etched as a result of reaction with CH₄.