Etching of gallium arsenide and indium phosphide in rf discharges through mixtures of trichlorofluoromethane and oxygen

Abstract

Optical emission, mass spectrometry, and Auger electron spectroscopy were used to study the kinetics of etching GaAs and InP in a 55-KHz discharge through mixtures of CCl3F and O2. Etching rates increase with increasing O2 concentration (peaking at about 60%), rf power, and residence time. However, at oxygen concentrations greater than 60%, oxide formation competes favorably with etching. Formation of nonvolatile group III fluorides does not appear to be an important process. Gallium arsenide etching shows a weak loading effect and forms an oxide more readily than does InP. Indium phosphide etching shows a stronger loading effect and seems more sensitive to ion bombardment than does GaAs. Above a 60% oxygen concentration, there is little evidence of carbon polymer deposition. This results from oxidation of halocarbon species in the discharge. Both InP and GaAs form thick oxides. The oxide for the latter appears to consist primarily of Ga2O3 while that for the former is most likely InPO4. At long residence times (∼1 sec) and high rf power densities (∼0.38 W/cm2), fast etching rates are obtained for both GaAs (∼12 μm/min) and InP (∼19 μm/min). These results are compared with similar studies of the etching of GaAs and InP in rf discharges through CCl4 and O2.