Analysis of step-based silicon surfaces at facet boundaries during wet anisotropic etching

A step-based model describing the anisotropic etching of silicon by the advancement of steps on flat {111} planes is supported by under-etch experiments on {100} and {110} silicon wafers. However, such a model does not explain etch rate variations of surfaces having the same families of Miller Indices exposed to the same etchant. This work analyzes crystal features at intersections between facets composed of two different types of steps, one called “rows of kinks,” and the other called “periodic bond chains,” intersecting at an angle of 120°. This important configuration, called K-P-120°, is analyzed with a view to whether step movement would propagate across a boundary between facets. An under-etched surface, composed of three facets and a cavity bottom, having alternating K-P-K-P combinations, (where all of the facet boundary step interactions are K-P-120°), is analyzed. Facet roughness patterns, comparative etch rates, and analysis of boundary atom positions support the conclusion that that across-face...