Etching of GaAs in a magnetron reactor was investigated using two different etch gases, namely SiCl4 and freon-12 (CF2Cl2). SiCl4 etching yielded vertical sidewalls, whereas the etched profiles in the case of freon exhibited a negative undercut. Surface characterization was undertaken using Auger electron spectroscopy, x-ray photoelectron spectroscopy, and secondary ion mass spectroscopy to determine the composition and chemical bonding in the near-surface region of the etched samples. The etched surface in the case of SiCl4 was found to be free of any chlorine residue and predominantly GaAs. However, there were residues of Si on the sidewalls. GaF3 formation was observed in GaAs samples etched in freon-12; in addition a CxFy fluorocarbon layer was present at high pressures which may not have been effectively removed due to reduced ion bombardment.
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Meyyappan et al. (1992) studied this question.