Cl-2/Ar and CH4/H-2/Ar dry etching of III-V nitrides

Electron-cyclotron-resonance (ECR) and reactive ion etching (RIE) rates for GaN, AIN, InN, and InGaN were measured using the same reactor and plasma parameters in Cl-2/Ar or CH4/H-2/Ar plasmas. The etch rates of all four materials were found to be significantly faster for ECR relative to RIE conditions in both chemistries, indicating that a high ion density is an important factor in the etch. The ion density under ECR conditions is similar to-3x10(11) cm(-3) as measured by microwave cm interferometry, compared to similar to 2x10(9) cm(-3) for RTE conditions, and optical emission intensities are at least an order of magnitude higher in the ECR discharges. It appears that the nitride etch rates are largely determined by the initial bond breaking that must precede etch product formation, since the etch products are as volatile as those of conventional III-V materials such as GaAs, but the etch rates are typically a factor of about 5 lower for the nitrides. Cl-2/Ar plasmas were found to etch GaN, InN, and InGaN faster than CH4/H-2/Ar under ECR conditions, while AlN was etched slightly faster in CH4/H2Ar plasmas. The surface morphology of InN was found to be the most sensitive to changes in plasma parameters and was a strong function of both rf power and etch chemistry for ECR etching. (C) 1996 American Institute of Physics.