Reactive ion etching of GaAs in CCl2F2

Abstract

The reactive ion etching of (100) GaAs in CCl₂F₂ and mixed CCl₂F₂+Ar discharges has been investigated. Anisotropic etching with removal rates R of 0.8 mm/min have been obtained in pure CCl₂F₂ discharges operated at 5.3 Pa (40 mTorr) and −3 kV, whereas the physical sputtering rate in pure Ar discharges under these conditions was only 0.04 mm/min. A combination of optical emission and absorption spectroscopies have been used to show that in CCl₂F₂ and even in dilute 10% CCl₂F₂+90% Ar discharges operated under the same conditions, physical sputtering is not a primary etching mechanism for GaAs, although is is important for minimizing residual carbon accumulation. Rather, etching is believed to occur by the formation and desorption of Ga and As halides with the rate limiting step being the removal of GaF₃. The kinetics of this process are aided by ion‐bombardment‐enhanced diffusion and stimulated desorption.