RIE of GaSb with an ECR Source Using Methane/Hydrogen Chemistry in an Argon Plasma

Reactive ion etching (RIE) of GaSb samples was investigated under electron cyclotron resonance (ECR) conditions using CH4∕H2∕Ar gas mixtures. Different etching parameters [e.g., microwave and radio-frequency (rf) power levels, gas ratios, chamber pressure, etc.] were systematically varied to observe their effects on the etch characteristics. For microwave powers up to ∼200W the etch rate was found to increase with increasing microwave power. Above 200W the etch rate appears to saturate for lower rf power levels (100W) but at higher rf power (275W) the etch rate continues to increase linearly with microwave power over the range investigated. Gas ratios of CH4∕H2∕Ar of 4:16:7.6 and 8:12:25 were used with the latter ratio yielding higher etch rates. The etch rate decreased with increasing chamber pressure over the range of 2–20mTorr . Etching of the SiO2 mask was observed and the corresponding GaSb etch rates were adjusted to account for this mask erosion. Excellent feature geometries were observed with vertical sidewalls and a smooth surface morphology.