USE OF HYDROGENATED CHLOROFLUOROCARBON MIXTURES FOR REACTIVE ION ETCHING OF IN-BASED III-V-SEMICONDUCTORS

The reactive ion etching (RIE) of InP, InAs, InSb, InGaAs, and AIInAs in CHCl2F-or CHClF2-based discharges was investigated as a function of plasma power density, pressure, and gas composition. For 0.56 W cm-2, 4 mTorr discharges the etch rates are in the range 125-angstrom-min-1 (AlInAs) to 390-angstrom-min-1 (InAs). These are comparable to the etch rates obtained with C2H6/H2 RIE under similar conditions. All of these materials exhibit smooth surface morphologies over a wide range of RIE parameters. Carrier compensation is observed to depths of approximately-2000-angstrom in n-type InP for high power density (1.3 W cm2) etching, but lower powers yield surfaces that display reasonable Schottky diode behavior for evaporated Au contacts. Thin (20-30-angstrom) residue layers containing 3-9 at. % Cl and 1-3 at. % F (24 at. % for AlInAs) are present after the dry etching, although this contamination can be removed by solvent cleaning. The formation of a high concentration of AlF3 on AlInAs provides a natural etch stop for removal of InGaAs layers in AlInAs/InGaAs heterojunction bipolar transistor structures.