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Proceedings Paper

Actinic inband EUV reflectometry AIMER compared to ALS blank qualification and applied to structured masks
Author(s): A. Biermanns-Föth; C. Phiesel; T. Missalla; J. Arps; C. Piel; R. Lebert
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Paper Abstract

Spectral reflectometry is an established technique for actinic qualification of EUV mask and blanks. For production in the EUV scanner, however, the homogeneity of the effective inband property – e.g. reflectance - is more relevant than the spectral reflectance curves. The effective reflectance is usually extrapolated indirectly from the knowledge of Rmax, CWL50 and FWHM, in which the efficiency is mainly proportional to Rmax if the spectral reflectance distribution and its central wavelength are similar to those of the scanner. This fact is accounted for in our AIMERTM metrology solution. In a single measurement AIMER registers the signal from an area of about 20×20 mm2 with a typical 13.5×13.5 μm2 pixel resolution. This technique is very robust and fast by irradiating the sample with a beam, which is spectrally filtered (e.g. from the Xenon EUV emission of a discharge source) to 2 % spectral bandwidth around the CWL of the scanner. With such an “inband EUV beam”, the efficiency of the sample is recorded with respect to its quality factors throughput and homogeneity “as seen by the scanner”. With multiple exposures stitched together AIMER maps the effective reflectance while being sensitive to the convoluted influence of the single parameter just as effective in scanner use. Mapping of the effective reflectance of a full EUV mask surface is accomplished in less than one hour. In this paper, we compare conventional ALS spectral reflectometry with AIMER results and show first tests of AIMER on structured EUV masks.

Paper Details

Date Published: 26 March 2019
PDF: 9 pages
Proc. SPIE 10957, Extreme Ultraviolet (EUV) Lithography X, 109571G (26 March 2019); doi: 10.1117/12.2515336
Show Author Affiliations
A. Biermanns-Föth, RI Research Instruments GmbH (Germany)
C. Phiesel, RI Research Instruments GmbH (Germany)
T. Missalla, RI Research Instruments GmbH (Germany)
J. Arps, RI Research Instruments GmbH (Germany)
C. Piel, RI Research Instruments GmbH (Germany)
R. Lebert, RI Research Instruments GmbH (Germany)


Published in SPIE Proceedings Vol. 10957:
Extreme Ultraviolet (EUV) Lithography X
Kenneth A. Goldberg, Editor(s)

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