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.[521]

We demonstrate a simulation tool for orientationdependent wet chemical etching of silicon, which. is able to correctly reproduce the detailed shape and morphology of the etch front. In previous work we investigated the capabilities of our simulation approach by the analysis of etch mask compensation stmctures featuring mask edges which were aligned precisely along the principal crystal directions.Recently we extended our simulation approach to the analysis of arbitrarily shaped mask geometries and misaligned mask edges. Now our simulation approach provides a solid basis for the predictive simulation of progressively complex MEMS structures.

No abstract

We developed a simulation tool for the three-dimensional orientation-dependent wet etching of silicon, based on the "step flow model" proposed by Schröder [1]. Its extension and its implementation in our simulation tool have been described in detail in [3,4]. Employing numerical simulation we could demonstrate the applicability of the step flow model to complex three-dimensional structures. In this paper we demonstrate the simulation of the etch process of basic exemplary structures featuring buried etch stop layers and polysilicon layers, and the "virtual fabrication" of an industrial sensor structure manufactured by means of bulk micromachining.