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

The new step-flow model of 3-D structuring and first simulation results
: Schröder, H.; Obermeier, E.; Horn, A.; Wachutka, G.K.M.


Journal of Microelectromechanical Systems 10 (2001), Nr.1, S.88-97
ISSN: 1057-7157
ISSN: 1941-0158
Fraunhofer IZM ()

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.