Convex corner undercutting of (100) silicon in anisotropic KOH etching

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 stale, 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 teal. Its ability to calculate the shape of simple beam structures of different orientation is experimentally shown.