Formation of Ridges on Gd₃Ga₅O₁₂ by Ion-Beam Etching and Subsequent Phosphoric Acid Treatment Utilizing Tri-Layered Etching Mask

This paper investigates the shapes of straight ridges about 4 µm high, that are formed on [1 1 1], [1 0 0] and [1 1 0] oriented Gd 3 Ga 5 O 12 (GGG) single crystal substrates by utilizing a Ta/organic layer/Si 3 N 4 tri-layered etching mask. Following argon ion-beam etching, the substrates are soaked in phosphoric acid solution. After soaking, the ridges on a [1 1 1] substrate have perpendicular side walls because the Si 3 N 4 film effectively protects the top surface of the ridge from acid. The stable dissolution form of a [0 0 1] direction ridge on a [1 0 0] substrate tends to have a {1 1 0} face which is inclined at 45° from the perpendicular. The side walls of a [0 0 1] direction ridge on a [1 1 0] substrate tends to be perpendicular after dissolution.