CHARACTERISTICS OF III-V DRY ETCHING IN HBR-BASED DISCHARGES

Electron cyclotron resonance (ECR) discharges of HBr/Ar, HBr/H-2, or HBr/CH4 were used for dry etching of Ga-based (GaAs, GaSb, and AlGaAs) and In-based (InP, InAs, InSb, InGaAs, and InAlAs) III-V semiconductors. The effects of variations in pressure (1-20 mTorr), gas composition, and additional RF-induced bias on the sample were examined. At least -100 V of dc bias is required to initiate etching under all conditions, with the etch rates found to be fastest with CH4 addition, followed by H-2 and then Ar. The etched surface morphologies are smooth with HBr/Ar and HBr/CH4 discharges, but tend to become increasingly rough as the microwave power into HBr/H-2 discharges is increased, particularly with the In-based materials. The surfaces are chemically very clean after dry etching, with no evidence of Br-containing contamination remaining on any of the materials. The HBr/Ar and HBr/CH4 discharges produce the smallest changes in the electrical properties of the semiconductors, while HBr/H-2 plasma exposure may cause dopant passivation and changes in barrier height under some conditions.