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Proceedings Paper

Shearing interferometer to characterize EUV optics with a laser plasma source
Author(s): Matthieu Visser; Raluca C. Constantinescu; Petra Hegeman; Jeroen Jonkers; Martijn K. Dekker; Eric Louis; Dirk Hambach
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Paper Abstract

In order to assess the imaging quality of EUV optics, extensive metrology needs to be performed. Mirror substrates are commonly investigated with AFM, while optical probes and visible light interferometry are used to probe respectively high-, mid- and low spatial frequencies. Coatings on flat substrates are usually investigated using Cu-K(alpha) , i.e. X- ray reflectometry at grazing incidence. EUV-reflectometry can be performed on curved optics as well. Assembled EUV imaging systems have been evaluated by both visible-light and EUV interferometry. Most EUV interferometry has been performed with a point-diffraction interferometer, requiring the laser- like spatial coherence of a synchrotron. Early demonstrations indicated that the compact laser plasma source proposed for EUV lithographic tools could also be used. We have continued in this direction, and have demonstrated by means of computer simulation and experiments with visible light that an absolute accuracy of better than 10 milliwaves, i.e. 0.13 nm when using EUV, can be achieved by a shearing interferometer. This contribution describes the realization and first results of such an interferometer, employing a laser plasma as a EUV light source. The same scheme could however be used for all EUV sources proposed for EUV lithography.

Paper Details

Date Published: 21 July 2000
PDF: 7 pages
Proc. SPIE 3997, Emerging Lithographic Technologies IV, (21 July 2000); doi: 10.1117/12.390112
Show Author Affiliations
Matthieu Visser, Philips Research Labs. (Netherlands)
Raluca C. Constantinescu, Philips Research Labs. (Netherlands)
Petra Hegeman, Philips Research Labs. (Netherlands)
Jeroen Jonkers, Philips Research Labs. (Germany)
Martijn K. Dekker, Philips Research Labs. (Netherlands)
Eric Louis, FOM-Institute for Plasma Physics Rijnhuizen (Netherlands)
Dirk Hambach, Georg-August-Univ. Goettingen (Germany)

Published in SPIE Proceedings Vol. 3997:
Emerging Lithographic Technologies IV
Elizabeth A. Dobisz, Editor(s)

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