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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 17, Iss. 19 — Sep. 14, 2009
  • pp: 16969–16979

Detection and characterization of carbon contamination on EUV multilayer mirrors

Juequan Chen, Eric Louis, Chris J. Lee, Herbert Wormeester, Reinhard Kunze, Hagen Schmidt, Dieter Schneider, Roel Moors, Willem van Schaik, Monika Lubomska, and Fred Bijkerk  »View Author Affiliations


Optics Express, Vol. 17, Issue 19, pp. 16969-16979 (2009)
http://dx.doi.org/10.1364/OE.17.016969


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Abstract

In this paper, we detect and characterize the carbon contamination layers that are formed during the illumination of extreme ultraviolet (EUV) multilayer mirrors. The EUV induced carbon layers were characterized ex situ using spectroscopic ellipsometry (SE) and laser generated surface acoustic waves (LG-SAW). We show that both LG-SAW and SE are very sensitive for measuring carbon layers, even in the presence of the highly heterogeneous structure of the multilayer. SE has better overall sensitivity, with a detection limit of 0.2 nm, while LG-SAW has an estimated detection limit of 2 nm. In addition, SE reveals that the optical properties of the EUV induced carbon contamination layer are consistent with the presence of a hydrogenated, polymeric like carbon. On the other hand, LG-SAW reveals that the EUV induced carbon contamination layer has a low Young’s modulus (<100 GPa), which means that the layer is mechanically soft. We compare the limits of detection and quantification of the two techniques and discuss their prospective for monitoring carbon contamination build up on EUV optics.

© 2009 OSA

OCIS Codes
(120.1880) Instrumentation, measurement, and metrology : Detection
(120.2130) Instrumentation, measurement, and metrology : Ellipsometry and polarimetry
(120.4530) Instrumentation, measurement, and metrology : Optical constants
(310.6860) Thin films : Thin films, optical properties
(340.7480) X-ray optics : X-rays, soft x-rays, extreme ultraviolet (EUV)

ToC Category:
Instrumentation, Measurement, and Metrology

History
Original Manuscript: May 6, 2009
Revised Manuscript: September 7, 2009
Manuscript Accepted: September 7, 2009
Published: September 9, 2009

Citation
Juequan Chen, Eric Louis, Chris J. Lee, Herbert Wormeester, Reinhard Kunze, Hagen Schmidt, Dieter Schneider, Roel Moors, Willem van Schaik, Monika Lubomska, and Fred Bijkerk, "Detection and characterization of carbon contamination on EUV multilayer mirrors," Opt. Express 17, 16969-16979 (2009)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-17-19-16969


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