Macroscopic etch anisotropies and microscopic reaction mechanisms: a micromachined structure for the rapid assay of etchant anisotropy

A new technique for the rapid quantification of orientation-dependent etch rates, which uses micromachined test patterns and optical microscopy, has b een developed. The etching of silicon in KOH etchants with and without isop ropanol was studied. Etch rates measured with this technique are in good ag reement with conventionally measured rates. In most cases, the etch rate an isotropies are well described by a simple model that is based on step-flow etching. Kinetic Monte Carlo simulations of etching were used to test the s imple model and to generate approximate morphologies of the etched surfaces . Vicinal Si(110) surfaces display unusual, orientation-dependent etch rate s in some etchants; the functional form of the etch rate anisotropy suggest s that a morphological transition occurs on these highly reactive faces. In moderately concentrated KOH solutions where isopropanol is readily soluble , the measured etch rate anisotropies suggest that isopropanol stabilizes s tep-flow etching. (C) 2000 Elsevier Science B.V. All rights reserved.