Silicon anisotropic etching in Triton-mixed and isopropyl alcohol-mixed tetramethyl ammonium hydroxide solution

The anisotropic silicon (Si) etching characteristics of Si (100) in 25 wt.% tetramethyl ammonium hydroxide (TMAH) solutions containing Triton X-100 and isopropyl alcohol (IPA) were studied. The etch rate, convex corners and roughness of the etched surface were investigated. In this reported work two central goals, a mirror-like surface finish and a high reduction of undercutting, have been achieved. The best etched result was obtained in 25 wt.% TMAH + 0.25%v/v Triton + 16%v/v IPA, which has minimum convex corner undercutting and a smooth etched surface (R_a = 1 nm). This study is useful for engineering applications where the fabrication of microstructures for high-quality devices should simultaneously contain smooth surfaces on a large area and less convex corner undercutting.