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Proceedings Paper

Saddle points in the merit function landscape of lithographic objectives
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Paper Abstract

The multidimensional merit function space of complex optical systems contains a large number of local minima that are connected via links that contain saddle points. In this work, we illustrate a method to construct such saddle points with examples of deep UV objectives and extreme UV mirror systems for lithography. The central idea of our method is that, at certain positions in a system with N surfaces that is a local minimum, a thin meniscus lens or two mirror surfaces can be introduced to construct a system with N+2 surfaces that is a saddle point. When the optimization goes down on the two sides of the saddle point, two minima are obtained. We show that often one of these two minima can be reached from several other saddle points constructed in the same way. The practical advantage of saddle-point construction is that we can produce new designs from the existing ones in a simple, efficient and systematic manner.

Paper Details

Date Published: 14 October 2005
PDF: 8 pages
Proc. SPIE 5962, Optical Design and Engineering II, 59620T (14 October 2005); doi: 10.1117/12.624864
Show Author Affiliations
Oana Marinescu, Delft Univ. of Technology (Netherlands)
Florian Bociort, Delft Univ. of Technology (Netherlands)

Published in SPIE Proceedings Vol. 5962:
Optical Design and Engineering II
Laurent Mazuray; Rolf Wartmann, Editor(s)

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