Minimizing mapping-induced OPD errors when testing aspheric mirrors

Russell M. Hudyma; Gary E. Sommargren

doi:10.1117/12.309561

5 June 1998 Minimizing mapping-induced OPD errors when testing aspheric mirrors

Russell M. Hudyma, Gary E. Sommargren

Proceedings Volume 3331, Emerging Lithographic Technologies II; (1998) https://doi.org/10.1117/12.309561
Event: 23rd Annual International Symposium on Microlithography, 1998, Santa Clara, CA, United States

Abstract

Extreme UV (EUV) projection system are designed with mild spheres so that the mirrors can be tested at the center of curvature without null optics. The elimination of the null optics improves the fundamental accuracy of the test. However, this test configuration is not stigmatic, and the rays from the test wavefront and reference wavefront will not trace the same optical path through the viewing system. Effectively, the test and reference wavefront are sheared in the exit pupil of the viewing system. This shear leads to an OPD contribution from the viewing system that we label the mapping error. For visible light metrology, this induced OPD error can be a significant fraction of the EUV wavelength.

Citation Download Citation

Russell M. Hudyma and Gary E. Sommargren "Minimizing mapping-induced OPD errors when testing aspheric mirrors", Proc. SPIE 3331, Emerging Lithographic Technologies II, (5 June 1998); https://doi.org/10.1117/12.309561

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