Effect of obstructions on the design of reflective ring-field projection systems

Matthieu Bal; Florian Bociort; Joseph J. M. Braat

doi:10.1117/12.450960

20 December 2001 Effect of obstructions on the design of reflective ring-field projection systems

Matthieu Bal, Florian Bociort, Joseph J. M. Braat

Proceedings Volume 4506, Soft X-Ray and EUV Imaging Systems II; (2001) https://doi.org/10.1117/12.450960
Event: International Symposium on Optical Science and Technology, 2001, San Diego, CA, United States

Abstract

The absence of obstructions is an essential requirement for reflective ring-field projection systems to be used in EUV lithography. However, due to the large number of variables and constraints involved, choosing unobstructed starting configurations for subsequent optimization is a nontrivial issue in EUV system design. For this purpose we have developed a systematic method based on paraxial obstruction analysis. Despite the fact that in the parameter space of all possible system configurations unobstructed domains are very small, we can identify the unobstructed regions very effectively. The paraxial results are validated through comparison with ray tracing. We can convert even most of the paraxial solutions that lead to ray failure into ray-traceable starting points for optimization. We also introduce a new classification method based on the relative arrangement of the mirrors in a EUV system - a feature which in typical situations is unaffected by optimization. We present some new possible design forms for EUV imaging systems belonging to different classes and show the remarkable flexibility of the obscuration borders.

Citation Download Citation

Matthieu Bal, Florian Bociort, and Joseph J. M. Braat "Effect of obstructions on the design of reflective ring-field projection systems", Proc. SPIE 4506, Soft X-Ray and EUV Imaging Systems II, (20 December 2001); https://doi.org/10.1117/12.450960

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