Etching of Silicon - Electrochemistry of Silicon and Its Oxide - page 335

Fig. 7.55. 1002 At a microscopic scale, roughness is associated with lattice steps, vacan-
cies, and so only which are determined by the lattice structure of the surface. At a
macroscopic level, crystallographic character may be revealed in the topographic fea-
tures, for example, hillocks formed on the (100) surface. It has been found that the
etched surface in 25% KOH has well-defined terraces and step features, whereas it has
a nodule type of appearance in 50% KOH solution. 245 Table 7.5 provides a summary
of the characteristics of the surface etched features in KOH with respect to the crystal
orientation of the surfaces.
In particular, the macroroughness of the etched silicon surface in alkaline solu-
tions is a function of surface orientation. 206,672,673,1002 Sato et al. 1002 found that the