Experiments on anisotropic etching of Si in TMAH

Recently, TMAH has been widely studied due to its MOS compatibility, nontoxic, and good anisotropic etching characteristics. In this work, TMAH etching of Si was carried out at different temperatures (70°C, 80°C and 90°C) and concentrations (5, 15 and 25 wt%). From a patterned Si wafer, inverted pyramids with smooth surface and sharp pyramid vertices were obtained. Uniform random pyramids were obtained from a bare Si wafer, and optimum reflectanceas low as 0.2% was obtained by near normal incident reflectivity measurement.