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3.2 Unidirectional Etching/Deposition

Linear structuring elements are also successfully applied for unidirectional etching and deposition. Unidirectional etching is a borderline case of reactive ion etching where particles have such a high directionality that they arrive only from one single direction. No lateral etching is assumed. The incidence direction is checked for visibility and if the actual position is not shadowed a linear structuring element with the beam direction is applied. Fig. 8 shows unidirectional etching through a resist mask with a beam tilted by 25$^\circ$. Unidirectional etching is also applied for patterning the metal layers in Fig. 12 through the resist mask generated from the layout.

Figure 8: Unidirectional etching of silicon through a resist mask.
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W. Pyka, R. Martins, and S. Selberherr: Optimized Algorithms for Three-Dimensional Cellular Topography Simulation