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Proceedings Paper

Alternative reticles for low-k1 EUV imaging
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Paper Abstract

Alternative reticles have the potential to improve EPE for low-k1 EUV lithography on multiple aspects, by reducing mask 3D effects and improving optical contrast. We study the application of high-k masks and attenuated phase-shift masks at diffraction level and show that mitigation of mask 3D effects, such as contrast fading, is crucial for both good performance of both alternative-reticle types. We present optimum embodiments for both mask types. We find that the optimum attenuated phase-shift mask (PSM) results in a phase shift of 1.2 π. The extra 0.2 π phase shift required for the EUV mask compared to its DUV counterpart is needed to compensate the strong mask 3D effects; the 1.2 π phase shift is crucial for good performance at small pitch and was found for all 3 materials studied in this work: Ru, Pd, and Mo. We show that our Rubased attenuated PSM embodiment results in a strong gain in normalized image log slope (NILS). <30% NILS gain can be achieved compared to a Ta-based reference mask. To demonstrate the generic applicability of the mask, we show NILS gain using the same attenuated PSM embodiment for different use cases for 0.33 and 0.55-NA EUV lithography, including regular contacts, DRAM patterns, and contacts through pitch. We show that the optimum mask-type choice is application dependent and present our recommendations in a mask-decision tree. We discuss the implications of using new reticle absorbers for scanner integration.

Paper Details

Date Published: 26 September 2019
PDF: 11 pages
Proc. SPIE 11147, International Conference on Extreme Ultraviolet Lithography 2019, 111470D (26 September 2019); doi: 10.1117/12.2536415
Show Author Affiliations
M.-Claire van Lare, ASML Netherlands B.V. (Netherlands)
Frank J. Timmermans, ASML Netherlands B.V. (Netherlands)
Jo Finders, ASML Netherlands B.V. (Netherlands)

Published in SPIE Proceedings Vol. 11147:
International Conference on Extreme Ultraviolet Lithography 2019
Toshiro Itani; Paolo A. Gargini; Patrick P. Naulleau; Kurt G. Ronse, Editor(s)

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