Anisotropic reactive ion etching technique of GaAs and AlGaAs materials for integrated optical device fabrication

Abstract

This paper reports a reactive ion etching (RIE) technique using a Cl2–Ar gas mixture for anisotropic microprocessing of GaAs and AlGaAs materials and its fundamental characteristics aimed to applications to monolithic integration of optical devices. This technique allows one to realize very fine as well as deep processing perpendicular to the wafer surface with smooth side walls, independent of the crystallographic orientation of these semiconductor materials. The etching rate was found to be controllable over a wide range by suitably adjusting the gas composition and the total gas pressure in this gas mixture. We experimentally obtained the optimum condition for smooth and perpendicular etching for both the materials at the total gas pressure of 2 Pa (1.5×10−2 Torr) with the gas flow ratio of Cl2 : Ar=1 : 5. Under this condition the etching rate ratio of GaAs to SiO2 was demonstrated more than 70. The surface damage introduced by this RIE was confirmed to be comparable at least to the case of the wet chemical etching through the measurement of photoluminescence intensities from GaAs samples.