Reactive ion etching of GaAs with CCl2F2:O2: Etch rates, surface chemistry, and residual damage

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Abstract
The reactive ion etching of GaAs with a CCl2F2:O2 discharge was investigated as a function of gas flow rate (10–60 sccm), total pressure (2–50 mTorr), power density (0.25–1.31 W cm−2), gas composition (0%–70% O2), and etch time (1–64 min). The etch rate decreases with increasing gas flow rate, increases with increasing power density, and goes through a maximum at a gas composition of 75:25 CCl2F2:O2 under our conditions. After etching at low‐power densities (0.56 W cm−2) and for high CCl2F2 ratios (19:1 to O2), carbon and chlorine could be detected in the GaAs to a depth of less than 15 Å by x‐ray photoelectron spectroscopy. Under these conditions there was a Ga deficiency to a depth of ∼100 Å, which we ascribe to surface roughening and the preferential vaporization of As2O3 over Ga2O3. At high‐power densities (1.31 W cm−2) a polymeric layer several hundred angstroms thick containing CCl and CF bonds was observed on the GaAs surface. Etching under O2‐rich conditions did not lead to any additional creation of surface oxides. Both ion channeling and electron microscopy detected a thin disordered layer on the GaAs after etching. Small (−2 (380‐V self‐bias) plasma power density to ∼2200 Å for 1.31 W cm−2 (680‐V self‐bias). The disorder was stable against a 500 °C annealing treatment.