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unilogo University of Stuttgart
Institute of Engineering and Computational Mechanics

Model-based Identification and Suppression of Static and Dynamic Aberrations in High Performance Optics

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Project Description


  schematic EMBS model
of a lithography objective

High Performance Optics are high resoluting optical systems consisting of precise lenses and mirrors which are mounted with a high accuracy. The accuracy is in the range of few nanometers. A good example are lithographic projection lenses for manufactoring semiconductor devices. These objectives require such high accuracies to ensure sharp images at highest resolutions. However, they have a high susceptibility to failures, i.e. small vibrations of the lenses or mirrors can be sufficient to produce defective images. Sources for these small vibrations can be minimal excitations at the objective frame like noise of coolers.

Similar problems are well-known in photography, e.g. when an image is blurred because the camera was moved while pushing the reslease. For a compensation of those movements, many cameras provide optical image stabilizers. For this, sensors measure the camera movement and the optical elements get moved by actuators to fix the image at the image sensor. However, for High Performance Optics, the problem is more complex since movements can hardly be measured and it is difficult to determine causes.

The goal of this project is the development of a simulation environment to detect and avoid weaknesses in the mechanical design as well as in the optical design. It is important to make a clear description of the functional chain starting with dynamical excitation and ending with the produced result. With this, informations can be obtained for inverse calculations to determine causes for certain image aberrations.




  simulation of gravity effects on the lenses in a lithography objective



Workflow for dynamical-optical simulations


  schematic optomechanic-model of a EUV-lithography-objektivs, which consists ot of mirrors



  experiment in the ITM laboratory for investigating the optimization of the
dynamical behavior of an objective

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