A New Etching Solution System, H 3 PO 4 ‐ H 2 O 2 ‐ H 2 O , for GaAs and Its Kinetics

A new solution system consisting of , , and was found useful for etching wafers. This solution system can be divided into four regions a–d, according to etching characteristics. The boundaries between the regions are given by a mole ratio of to of about 2.3 and a mole fraction of of about 0.9 at room temperature. Rate‐limiting processes are: a, adsorption of ( , ); b, diffusion of ( , ); c, dissolution of oxidized products ( , ); and d, adsorption of ( , ). Solutions in region a have a reproducible etching rate of 0.01–0.1 μm/min, which is useful for MESFET processing. Crystallographic etching is also available with solutions in region c.