LOW-TEMPERATURE ELECTRON-CYCLOTRON-RESONANCE PLASMA-ETCHING OF GAAS, ALGAAS, AND GASB IN CL2/AR

Sidewall etching of GaAs, AlGaAs, and GaSb in electron cyclotron resonance Cl2/Ar discharges is found to be completely suppressed by cooling the semiconductor sample to -30-degrees-C during the process. Vertical etch rates of > 1500 angstrom min-1 at 1 mTorr and - 50 V dc bias are obtained for all three materials under conditions where the lateral etch rates are negligible. Ex situ chemical analysis of the sidewall shows substantially increased Cl-containing residue on low temperature etched samples, which can be removed by a 5 min H-2 plasma clean-up step. The exploitation of temperature to control undercutting enables use of simpler gas chemistries because there is no need to form a sidewall polymer.