Surface kinetics and morphology of ArF laser-assisted etching of (113)A GaAs in a Cl2 environment

ArF laser-assisted etching of (113)A-oriented GaAs in a Cl2Ar environment has been investigated for the first time and a reaction mechanism deduced from the dependence of the GaAs etch rate on laser fluence, temperature, and gas-phase composition has been proposed. The etching process is shown to result from a combination of photochemically and thermally activated reaction steps. The etch reaction kinetics have been found to be first order in Cl2 in the (1–6) × 10−3 Torr pressure range. For temperatures below 200°C, the etch reaction is kinetically controlled by the formation of GaCl2 via the reaction between chemisorbed GaCl and Cl radicals from the gas phase, with an activation energy of 7.9 kcal/mol. The etch rate becomes independent of temperature above 200°C, indicating a predominantly diffusion-controlled process. Finally, a kinetic polar diagram of etch rate versus crystallographic orientation obtained from Cl2 etching experiments of (001) GaAs masked with stripes along the [110] and [110] directions has been used to predict the etch profiles of (113)A-oriented GaAs masked along the [110] direction.