Controlled beam dry etching of InP by using Br-2-N-2 gas

Indium phosphide dry etching is carried out using a reactive beam extracted from a Br-2-N-2 gas discharge plasma. Keeping the N-2 gas pressure constant at 0.23 mTorr, the Br-2 gas pressure was varied from 0 to 0.1 mTorr and the sample temperature was varied from 40 to 200 degrees 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 Br-2 gas pressure. Smooth vertical side walls and a temperature independent etching rate can be obtained at a Br-2 gas pressure of 0.04 mTorr or less and a temperature above 100 degrees C, where the etching is induced by the ambient Br-2 gas species and N-2 beam. Undercut etching with a temperature dependent etching rate is seen at a Br-2 gas pressure of 0.07 mTorr or higher, where the etching beam contains both N-2 and Br-2 gas species. Neutralized Br species generated by the discharge of the Br-2 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 Dr species.