Characterization of ultraviolet excited Br*-radical etching of InGaAs/InAlAs material system

Abstract

Dry selective photochemical etching of InGaAs/InAlAs material system, in HBr gas excited by a 172 nm excimer lamp, has been characterized. The etching is thought to be due to the formation of reactive Br*-radicals which are photocreated in the gas phase and then diffused into the solid semiconductor to create volatile products. The etching is temperature sensitive with best etching results at 50–110° C. Atomic force microscope and scanning electron microscope pictures reveal that the surface morphology at this temperature range is smooth and fine. Auger electron spectroscopy and x-ray photoelectron spectroscopy measurements show that at low temperatures the etch products are primarily salts of bromide and are in the liquid phase and thus remain at the surface and a desorption process stops further etching. At slightly elevated temperature range, the creation of oxides and deposition of bromine compounds reduces the etch rate and causes the surface quality to deteriorate. Etching at higher pressure range increases the etch rate of InGaAs but results in surface quality deterioration.