Chemical dry etching of GaAs(100) by HC1: products, rate, and a kinetic model

The chemical dry etching of GaAs by HC1 has been studied using molecular beam scattering techniques. Unlike Cl₂ which etches GaAs at room temperature, HCl does not etch GaAs at a measurable rate below 670 K. For an incident HCl flux of 3.6 monolayers/s and surface temperatures of 670-870 K, the major volatile reaction products are GaCl and As₂. Above 850 K, GaAs evaporation also produces Ga atoms. Quantitative analysis of the product mass spectra and angular distributions shows that the product evolution rates are consistent with stoichiometric etching. Studies of the etching kinetics by modulated molecular beam scattering (MMBS) indicate that the rate of arsenic evolution limits GaAs etching to temperatures above 670 K. A simple reaction model which utilizes kinetic parameters derived from independent studies in the literature quantitatively reproduces the etching products, rate, and kinetics under both steady state and modulation conditions with only one adjustable parameter.