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P: Fachverband Plasmaphysik

P 2: Plasmatechnologie

P 2.7: Talk

Monday, March 30, 2009, 15:40–15:55, HS Biochemie (groß)

Enhanced process simulation for Plasma Assisted Chemical Etching — •Johannes Meister and Thomas Arnold — Leibniz-Institut für Oberflächenmodifizierung e.V., Permoserstrasse 15, 04303 Leipzig, Germany

Surface figuring using CNC chemically reactive plasma jets containing fluorine species is a promising technology for the manufacture of optical elements, especially made of fused silica. However, the etching rate during plasma jet treatment strongly depends on the surface temperature which is influenced by the jet heat flux. A conventional process simulation does not consider these resulting nonlinear effects. In order to improve the process stability an enhanced etching simulation, based on a heat transfer model, is introduced. The determination is divided into two parts: At first a three-dimensional FEM heat transfer model of the work piece is established. The boundary conditions and the jet heat flux are reconstructed on the base of IR thermography during a locally fixed etching. The second step implies the calculation of the temperature dependent removal rates by use of different groove etchings. The measured and simulated topology of an etching process agree well. For figuring of a desired surface topology the conventional method of computing the CNC jet motion is applied. An improved contour accuracy is achieved by modifying the target topology according to the result of the enhanced simulation routine.