Gallium arsenide etching using ion beams from hydrogen/methane mixtures

Abstract

In order to characterize the process of etching of GaAs with a mixture on methane-hydrogen, a low energy ion beam study, using a Kaufman source, has been developed. For an accelerating voltage of 500 V and with a pressure of 0.06 Pa at the etching chamber, the resulting bombarding current densities are below 1 mA/cm 2. The effect of the etch time and two experimentally controlled variables, arc current and solenoid current, on the etch rate and etch yield has been analyzed using a response surface experimental design methodology. We have found a non-linear dependence of the etch depth with the time and the aim of this study has been the understanding of this behavior. For a fraction of CH 4 in H 2 over 20%, approximately, a black polymeric film is deposited on the GaAs. Below this concentration, an etch rate in the nm/min range is measured. The identification of trimethylgallium ions with mass spectrometry during GaAs RIBE suggests an etch mechanism related to the production of organo-metallic compounds between the beam species and the GaAs, enhanced by the ion energy.