Chemical etching of InP (1 0 0) wafer based on a volcanic mineral water

We have successfully demonstrated that a solution of spa water [Tamagawa Spa water (TaSW):H2O2 = 1:1] etches InP (1 0 0) wafer. The TaSW is a colorless acidic liquid of pH ∼1.1. It contains a considerable amount of positive ions, such as H+, Al3+, and Ca2+. The Cl−, HSO42−, and SO42− ions are the main anions. The TaSW-etchant system provides shiny flat surfaces on the etched bottoms. The spa-etchant system has reproducible etching rates and does not erode photoresist masks. The etching kinetics is reaction-rate limited. The spa-etchant system is also found to etch GaAs (1 0 0) wafer, but the etched surface is considerably roughened.