Plasma etching of III–V compound semiconductor materials and their oxides

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Abstract
Sixteen reagents were investigated for their ability to etch either GaAs, GaAs–oxide, or both. Except for CCl2F2, fluorine containing reagents such as HF, C2F6, CF3Cl, and CHF3 did not etch. In addition, no etching occurred with the six compounds C2Cl4, CBr2Cl2, CHCl3, PH3, H2 or H2O. Both GaAs and its oxide were etched by CCl4, CCl2F2, PCl3, and HCl; while Cl2 and COCl2 etched only GaAs. Chlorine etched GaAs five times faster than HCl did. Addition of 40% H2 to HCl reduced the etch-rate ratio of GaAs to oxide by 1/8, from 400:1 to 50:1. A 42% H2/58% CCl2F2 plasma etched GaAs only 12 times faster than it etched oxide; this is 1/33 the ratio found for neat HCl and 1/200 the rate of etching GaAs with Cl2. A Cl2 plasma readily etched both GaP and GaSb but not the corresponding oxides. An HCl plasma etched GaP and GaSb and their oxides but did not etch InP or its oxide. The chemistry of these systems is discussed and a model for selective etching of GaAs–oxide over GaAs is proposed.

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