Anisotropic etching properties of silicon in KOH and TMAH solutions

We investigated anisotropic etching properties of single-crystal silicon as a function of crystallographic orientations in order to fabricate a variety of 3D microstructures on silicon substrates. We measured etching rates for a number of crystallographic orientations using hemispherical specimens. From the dimensional change of the specimen surface, we evaluated the etching rates for a number of crystallographic orientations. We carried out a series of experiments in KOH and TMAH solutions changing their concentration and temperature and compared anisotropic etching properties between KOH and TMAH solutions. The orientation dependencies of their etching rates differed, especially for near (111) orientations. This means that these two etchants have different etching mechanisms. Effects of etchant circulation on the etching rates were not negligible in TMAH in contrast to KOH