Dry etching of III-V semiconductors in IBr/Ar electron cyclotron resonance plasmas

IBr/Ar plasmas were found to be promising candidates for roam temperature dry etch processing of the III-V semiconductors GaAs, AlGaAs, GaSb, InP, InGaAs, and InSb. Results showed fast etch rates (similar to 3,000 Angstrom/min) at high microwave power (1000W) and good surface morphology (typical root mean square roughness similar to 2 nm), while retaining the near-surface stoichiometry. There was little variation of surface smoothness over a wide range of plasma compositions for Ga-containing materials. By contrast, there was a plasma composition window of about 25-50% of IBr in IBr/Ar plasmas for maintaining good morphology of In-containing semiconductors like InP. Etch rates of the semiconductors generally increased with microwave power (400-1000 W) and rf power (50-250 W), whereas there was little dependence of the rates on the increasing percentage of IBr in the IBr/Ar plasma composition above 30% IBr for In-based, and 50% IBr for Ga-based materials. Those results show the etch rates over 30% of IBr in IBr/Ar are desorption-limited. Photoresist masks do not hold up well to the IBr under ECR conditions, resulting in poor profile control, whereas SiNx offers much better etch resistance.