High-index silicon planes have been etched with KOH of concentrations ranging from 2 mol/l to 12 mol/l (10-46 wt.%) at temperatures between 50-degrees-C and 95-degrees-C, using two kinds of samples. We have etched mechanically prepared {n11} and {nn1} (n = 2, 3, 4) crystal planes which we obtained by bevelling silicon samples at accurately adjusted angles. Furthermore, we etched samples that were cut out of industrially fabricated <211> wafers. The results for the two kinds of <211> samples are found to agree for crystal planes that keep their orientation during etching. Non-reproducible etch rates are obtained, however, for those high-index etch fronts that disintegrate into facets of dissimilar crystal orientations.
