Use of hydrogenated chlorofluorocarbon mixtures for reactive ion etching of In-based III–V semiconductors

Abstract

The reactive ion etching (RIE) of InP, InAs, InSb, InGaAs, and AlInAs 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 Å min−1 (AlInAs) to 390 Å 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 ∼2000 Å 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 Å) 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.