Controlled beam dry etching of InP by using Br₂-N₂ Gas

Abstract

Indium phosphide dry etching is carried out using a reactive beam extracted from a Br₂-N₂ gas discharge plasma. Keeping the N₂ gas pressure constant at 0.23 mTorr, the Br₂ gas pressure was varied from 0 to 0.1 mTorr and the sample temperature was varied from 40 to 200°C. The etched shapes and etching rates are investigated in terms of the etching beam composition. Two distinct types of etching mechanisms come into play depending on the Br₂ gas pressure. Smooth vertical side walls and a temperature independent etching rate can be obtained at a Br₂ gas pressure of 0.04 mTorr or less and a temperature above 100°C, where the etching is induced by the ambient Br₂ gas species and N₂ beam. Undercut etching with a temperature dependent etching rate is seen at a Br₂ gas pressure of 0.07 mTorr or higher, where the etching beam contains both N₂ and Br₂ gas species. Neutralized Br species generated by the discharge of the Br₂ gas are shown to form the undercut. A waveguide corner mirror with a loss of less than 1 dB is made by using an etching beam with no neutralized Br species.