Etching of Silicon - Electrochemistry of Silicon and Its Oxide - page 316

A highly defective surface, such as a saw-damaged surface, may not exhibit
anisotropic etching rates as shown in Fig. 7.37 for as-cut (100) and (111) wafers. 490 The
difference in the etch rates between the two orientations becomes clear after the
damaged material is removed.
7.6.2. Mechanisms
Many models have been proposed for the silicon anisotropic etching in alkaline
solutions. They can be classified into two large groups: those that attribute the rela-
tively slower etch rate of (111) planes to the presence of a passive oxide film on the
surface, and those that consider the etch rate difference among different orientations
being governed by the reaction kinetics.