CONTROLLABLE LAYER-BY-LAYER ETCHING OF III-V COMPOUND SEMICONDUCTORS WITH AN ELECTRON-CYCLOTRON-RESONANCE SOURCE

A highly controllable etching technique, in which the etching proceeds layer by layer, has been studied using a plasma generated by an electron cyclotron resonance (ECR) source. In this etching technique, the sample is exposed to reactive chlorine radicals and low energy Ar ions separately and repeatedly. For GaAs etching, the chlorine radicals were typically generated with 35 W microwave power and the Ar ions were produced using 50 W microwave power and 6 W rf power, with a self-induced dc bias of - 38 V. When there was complete coverage of the surface by reactive chlorine radicals, the etch rate was found to be independent of chlorine radical or Ar ion reaction time. Layer-by-layer etching with the etch rate in the range of 0.5 nm/cycle has been achieved on GaAs. No GaAs etching was observed at - 120-degrees-C and the etch rate increased significantly with temperature. The etch rate increased initially with microwave power used in the adsorption step, then decreased at microwave power > 60 W due to passivation effects. Faster etch rates were obtained on samples etched al higher rf power during the etch product desorption step and/or longer distance from the ECR source. Layer-by-layer etching of GaInAs, AlInAs, and InP has been demonstrated for the first time. For GaInAs and AlInAs, etching was observed at room temperature and rf power level similar to that used for etching of GaAs. For InP, etching was obtained only at higher temperature (150-degrees-C) and rf power (8 W) during the etch product desorption step. Etch-induced damage was minimal since electrical characteristics of Schottky diodes fabricated on the etched surface were similar to an unetched sample.