3 April 2008 Performance and lifetime of EUV source collectors measured with a full size EUV collector reflectometer
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The lifetime and the efficiency of EUV source collector optics will have direct impact on the cost effectiveness of the EUV lithography semiconductor production. Therefore the collector optics was identified as a critical issue in EUVL. To continually improve and optimize the source collector optics precise measurements of the optics characteristics are required as well as life time studies. Adequate measuring equipment must be designed to perform these measurements on-site, at-wavelength and under realistic conditions. Moreover, the measurement accuracy must be sufficient to allow the detection of small changes in reflectivity and homogeneity of the EUV source collector optics. This makes it possible to predict the lifetime of an EUV source collector operated with a high power EUV source after a fraction of the specified pulse number, e.g. after a couple of hours. A reflectometer for the investigation of full EUV source collectors was developed, designed and set up. As an EUV source a commercial microfocus EUV tube was used. This source is particularly suitable for application in metrology, as it is very stable in its output parameters (namely power, spectrum, spot size, spot position), and it does not emit debris. The radiation cone emitted by the EUV source is tailored with a Schwarzschild objective to the spectral and geometrical requirements of the Wolter-shell EUV source collector optics At the time of this contribution the measurement system presented here is in operation since 18 months, and a large number of collector measurements was performed. It is used for the quality control of factory-new EUV source collectors as well as for repeated measurements within the context of lifetime tests. With this device the efficiency of debris filters, which prevent the EUV source collector optics from contamination, could be determined and improved. The concept of the device and the implementation together with measurement results are described.
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Ulf Hinze, Ulf Hinze, Boris N. Chichkov, Boris N. Chichkov, Torsten Feigl, Torsten Feigl, Uwe D. Zeitner, Uwe D. Zeitner, Christoph Damm, Christoph Damm, Denis Bolshukhin, Denis Bolshukhin, Jürgen Kleinschmidt, Jürgen Kleinschmidt, Guido Schriever, Guido Schriever, Max-Christian Schürmann, Max-Christian Schürmann, "Performance and lifetime of EUV source collectors measured with a full size EUV collector reflectometer", Proc. SPIE 6921, Emerging Lithographic Technologies XII, 69213A (3 April 2008); doi: 10.1117/12.772486; https://doi.org/10.1117/12.772486

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