Selective etching of Al2O3 on GaAs using excimer lasers

Selective etching of Al2O3 thin films on GaAs immersed in a H3PO4 aqueous solution by irradiation with excimer lasers is demonstrated. The dark etching of Al2O3 films (0.4 nm/min) is negligibly small compared with that of the laser-induced etching. It is found that the process cannot etch the GaAs substrates. Therefore, the etching stops at the Al2O3/GaAs interface, and the Al2O3 films are selectivity etched only in laser irradiation regions. The etching characteristics of different wavelengths of ArF and KrF excimer lasers are also discussed.