Actinic inband EUV reflectometry AIMER compared to ALS blank qualification and applied to structured masks

A. Biermanns-Föth; C. Phiesel; T. Missalla; J. Arps; C. Piel; R. Lebert

doi:10.1117/12.2515336

26 March 2019 Actinic inband EUV reflectometry AIMER compared to ALS blank qualification and applied to structured masks

A. Biermanns-Föth, C. Phiesel, T. Missalla, J. Arps, C. Piel, R. Lebert

Author Affiliations +

Proceedings Volume 10957, Extreme Ultraviolet (EUV) Lithography X; 109571G (2019) https://doi.org/10.1117/12.2515336
Event: SPIE Advanced Lithography, 2019, San Jose, California, United States

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 R_max, CWL₅₀ and FWHM, in which the efficiency is mainly proportional to R_max if the spectral reflectance distribution and its central wavelength are similar to those of the scanner. This fact is accounted for in our AIMER^TM 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.

Citation Download Citation

A. Biermanns-Föth, C. Phiesel, T. Missalla, J. Arps, C. Piel, and R. Lebert "Actinic inband EUV reflectometry AIMER compared to ALS blank qualification and applied to structured masks", Proc. SPIE 10957, Extreme Ultraviolet (EUV) Lithography X, 109571G (26 March 2019); https://doi.org/10.1117/12.2515336

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KEYWORDS

Reflectivity

Extreme ultraviolet

Photomasks

Extreme ultraviolet lithography

Scanners

Reflectometry

Charge-coupled devices

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