Fundamental Selective Etching Characteristics of HF + H 2 O 2 + H 2 O Mixtures for GaAs

Abstract

Selective etching characteristics of mixtures have been investigated for (111)A, (111)B, (001), and (110) surfaces. Mixtures with excess have shown excellent selective etching characteristics controlled by the and contents for extensive practical applications. The lowest etching rate in directions other than [111]A has been achieved with the present mixture system. Etching profiles strongly reflecting crystallographic anisotropy have been produced for low and high concentrations, while those for high and low concentrations have shown similar isotropic features irrespective of the substrate orientation. A continuous and extensive control of the intersection angle between the side wall and the substrate surface has been achieved successfully on all substrates. The etching profile and its dependence on the mixture composition for the four substrates have been discussed in detail in connection with the degree of anisotropy of the etching rate and the contrast that the (111)A plane sharply intersects with other planes while the (111)B plane has a round intersection corner. The etching characteristics of the mixture have been discussed based on the special chemical properties of and and compared with those of other mixture systems.