HCl, H2 and Cl2 radical-beam ion-beam etching of AlxGa1-xAs substrates with varying Al mole fraction

The possible benefits of H* radicals on dry etching characteristics of AlGaAs were explored using HCl and separately mixed H2 and Cl2 radical-beam ion-beam etching. H* radicals strongly affect the Cl*-AlGaAs surface chemistry resulting in large changes in etch rate and surface morphology. Etch rates were measured in situ by reflectance interferometry using a quarter-wavelength structure with varying AlxGa1-xAs mole fraction. The presence of H* (from HCl or H2 added to Cl2) increases the Cl* etch rate threefold. An increase in surface roughness with H* (compared to Cl* alone) is correlated with increased Al content. 18 refs., 7 figs