A kinetic study of structured surface relief patterning of GaP (\bar 1\bar 1\bar 1)

Orientation dependent etching of photolithographically patterned GaP was investigated using solutions of HCl:CH₃COOH:H₂O₂. The pattern was prepared using standard ultraviolet lithography and was a two-dimensional grid with an 18 μm repeat, consisting of 15 μm squares separated by 3 μm spaces. The mask sides were aligned along the and directions. Under appropriate etching conditions, high quality arrays of pyramids were prepared. These pyramids were defined by , and facets. It was shown that the etching process depended on the degree of solution aging after initial mixing. For a freshly prepared solution, the etching rate showed an inverse dependence on time. For short etching times (below 5 min), an intermediate etching profile was followed, while for long times (greater than 5 min) etching was kinetically controlled. We demonstrated that controlled etching at extremely low rates (0.1–0.5 μm/min) is feasible with this new approach.