Silicon Anisotropic Etching in Ternary Solution Composed of TΜΑΗ+Triton+NH₂ΟΗ

Present work reports the anisotropic etching characteristics of silicon in various concentrations of tetramethylammonium hydroxide (TMAH) without and with addition of 10% hydroxylamine (NH₂OH) and Triton X-100 ranging from ppb to ppm. The etch rate, undercutting at convex corners, and etched surface morphology are investigated in pure TMAH, TMAH+NH₂OH, and different compositions of TMAH+NH₂OH+Triton (i.e. ternary solution). High etch rate and undercutting are achieved in NH₂OH-added 15 wt% TMAH, while 25 wt% TMAH + 10% NH₂OH + 1 ppm Triton provided significantly less corner undercutting with reasonably good etch rate of Si{100}. This work is very useful for engineering applications for the fabrication of microstructures using silicon wet bulk micromachining for MEMS-based devices.