Accelerated direct flux calculations using an adaptively refined icosahedron

We present a method to accelerate the direct flux calculations in three-dimensional process simulations, highly relevant for plasma etching simulations. Especially for high aspect ratio structures, the direct flux calculations are the computational bottleneck when performing simulations with high spatial resolutions. Our method reduces the number of rays which have to be traced during the visibility calculation. A subdivided icosahedron is used to define the search directions on each level of refinement. The method is applicable if the apertures can be detected on the first level. We show that the accuracy of the integration is not reduced, when using a first level of refinement appropriate to the aspect ratio of the structure. The time for the visibility calculation is cut by 50% for meshes with more than 200k triangles when using only one level of refinement.