GaAs and AlGaAs anisotropic fine pattern etching using a new reactive ion beam etching system

Abstract

High aspect-ratio anisotropic etching for GaAs has been obtained with Cl2 plasma in a new reactive ion beam etching (RIBE) system equipped with an ultrahigh vacuum chamber. A vertical wall with 0.5 μm thickness and 7 μm height was obtained at a 500 V ion extraction voltage and etching gas pressure of 8×10−4 Torr. A normalized etching rate was 2 ( μm/min)/(mA/cm2) which corresponds to a sputtering yield of 23 atoms/ion. Such a high aspect-ratio etching was mainly owing to use of a high-temperature (250 °C) baked photoresist mask with a sharp cut profile. GaAs and AlGaAs equirate etching, which is often difficult in the conventional reactive ion etching (RIE), has also been obtained using this system. It was found that decrease of the AlGaAs etching rate in the RIE is attributed to Al2O3 formation due to residual H2O during etching.