Handbook of Silicon Based MEMS Materials and Technologies

24.8.4. Addition of Alcohols and Surfactants (I. Zubel and M.A. Gosálvez)

The etchants are often modified with different additives as this can improve the roughness of the etched wafer orientation and/or the facets developed during etching. This must be done carefully as the etching anisotropy also is typically modified. The additives are usually tensioactive compounds, such as alcohols, or typical surfactants. Generally, at high etchant concentrations these additives reduce the etch rate and improve the morphology of the planes containing SM sites ({h + 2 h + 2 h} and {h h 1} surfaces = exact and vicinal {110}), while they do not affect significantly the etch rate of planes with SD sites ({h + 2 h h} and {h 1 1} surfaces = exact and vicinal ...