Convex corner undercutting of {100} silicon in anisotropic KOH etching: The new step-flow model of 3-D structuring and first simulation results

In this paper, the mechanism of convex corner (CC) undercutting of Si_{100} in pure aqueous KOH solutions is revisited by proposing the step-flow model of 3-D structuring as a proper description of the observed phenomena. The basic idea is to conceive the Si_{100} anisotropic etching process, on the atomic scale, as a "peeling" process of terraced {111} planes at (110) oriented steps to understand also the arising shape in Si_{100} etching. On the basis of our new model, we are able to predict the microscopic three-dimensional (3-D) structure of the characteristic CC undercutting without any compensation etchmask structures. Furthermore, the theoretical description has been implemented in a new 3-D simulation tool. Its ability to calculate the shape of simple beam structures of different orientation is experimentally shown.