Reactive ion etching of GaAs with high aspect ratios with Cl2–CH4–H2–Ar mixtures

A new process for RIE of GaAs employing Cl2–CH4–H2–Ar etching gases is presented. The effect of CH4 and H2 on etch rate, etch profile, and surface morphology is studied. The plasma excited species are monitored in situ by emission spectroscopy and etch depths measured by laser interferometry. Anisotropic profiles and residue-free surfaces are obtained with Cl2–CH4–H2–Ar and Cl2–CH4–H2–Ar gases. Depending on process parameters, selectivities up to 180 with respect to SiO2 are obtained allowing deep etching. X-ray photoelectron spectroscopy and Auger electron spectroscopy of different etched surfaces are compared with a chemically etched reference surface. This shows that a Cl2/H2/Ar etch leaves the surfaces, contamination free.