DRY ETCHING OF III-V SEMICONDUCTORS IN CH3I, C2H5I, AND C3H7I DISCHARGES

The characteristics of plasma etching of InP, InAs, InSb, GaAs, AlGaAs, GaSb, AlInAs, InGaAs, and AlInP in microwave (2.45 GHz) discharges of methyl-, ethyl-, and propyl-iodide have been examined with respect to etch rates, surface morphology, damage introduction, and etch anisotropy. The etch rates for all of these semiconductors are somewhat faster than for conventional CH4-based discharges under the same conditions of direct-current bias, pressure, and microwave power, but are not as fast as with HI discharges. Polymer deposition on the mask and within the chamber occurs as with CH4-based mixtures, but is minimized at low pressure (less-than-or-equal-to 10 mTorr) and with H-2 dilution. The etched surface morphologies are smooth over a wide range of plasma parameters and show roughness only under conditions of significant polymer deposition. Chemical analysis by Auger electron spectroscopy and x-ray photoelectron spectroscopy also shows that the near surface of the etched samples retains its stoichiometry under most conditions. While the etch rates are slower than for HI-based discharges, the halocarbon iodides are significantly less corrosive and much more stable.