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7.1.1 Surface Extraction

The first step in the simulation sequence is the preparation of the appropriate input for the meshing tool. The initial geometry is built up with a solid modeling tool based on the same cellular material representation as used for the deposition simulator (cf. Chapter 3). Therefore the surface of the initial geometry as well as of the geometries resulting after each time-step has to be extracted in a triangular format, suitable as input for the meshing tool.

Figure 7.2: Surface extraction from the cellular material representation (dashed lines) to a triangle description (shaded triangles in solid lines) using a marching cube algorithm and surface coarsening.
\begin{figure}\begin{center}
\ifthenelse{\boolean{nopics}}{\fbox{\texttt{eps-cvd...
...ncludegraphics[width=0.6\textwidth]{eps-cvd/mcube.eps}}
\end{center}\end{figure}

The conversion is accomplished with a marching cube algorithm [38] which guarantees that all triangle points are in the center of the cell faces. This is necessary for a non-ambiguous correlation between triangle points and surface cells. The only exception are points touching the horizontal bounding box. In this case the points are located at the edges of the cubes still permitting the non-ambiguous correlation. After the initial triangulation coplanar triangles are merged using a very small point to plane distance criterion according to [66]. In this way a higher efficiency of the following meshing and FEM steps is achieved without loosing any topography information. An example of such a surface extraction can be seen in Fig. 7.2.

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W. Pyka: Feature Scale Modeling for Etching and Deposition Processes in Semiconductor Manufacturing