The construction of orientation-dependent crystal growth and etch rate functions II: Application to wet chemical etching of silicon in potassium hydroxide

In Part I we introduced a construction method for analytical orientation de pendent growth and etch rate functions. In this article, this network const ruction principle is applied to wet chemical etching of silicon in concentr ated aqueous potassium hydroxide. Detailed measurements of the etch rate as a function of crystal surface orientation are used to fit the phenomenolog ical parameters in the network etch rate function. In this function, for ea ch crystal facet, two surface processes are accounted for, etching through misorientation step flow and etching through nucleation of pits. The fittin g procedure identifies additional mesoscopic, surface processes which influ ence the orientation dependence of the etch rate. These processes correspon d to instabilities of the surface. In the {111} region step bunching occurs which evolves into microfaceting for larger inclination angles. Moreover, for certain experimental circumstances, the fast etching {110} region break s up into a staircase structure of terraces. Additional network elements ar e defined to account for these instabilities. The step-bunching instability is treated using an ad hoc approach. With these amendments the experimenta l etch rate functions can be fitted to an accuracy of about 5% by a network function with nine parameters. This shows that it is possible to reproduce the essential features of an experimental growth or etch rate function usi ng an analytical function with a limited number of physically meaningful pa rameters. (C) 2000 American Institute of Physics. [S0021-8979(00)01712-6].