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Proceedings Paper

Thin absorber EUV photomask based on mixed Ni and TaN material
Author(s): Derrick Hay; Patrick Bagge; Ian Khaw; Lei Sun; Obert Wood; Yulu Chen; Ryoung-han Kim; Zhengqing John Qi; Zhimin Shi
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Paper Abstract

Lithographic patterning at the 7 and 5 nm nodes will likely require EUV (λ=13.5 nm) lithography for many of the critical levels. All optical elements in an EUV scanner are reflective which requires the EUV photomask to be illuminated at an angle to its normal. Current scanners have an incidence of 6 degree, but future designs will be <6 degrees for high-NA systems. Non-telecentricity has been shown to cause H-V bias due to shadowing, pattern shift through focus, and image contrast lost due to apodization by the reflective mask coating. A thinner EUV absorber can dramatically reduce these issues. Ni offers better EUV absorption than Ta-based materials, which hold promise as a thinner absorber candidate. Unfortunately, the challenge of etching Ni has prevented its adoption into manufacturing. We propose a new absorber material that infuses Ni nanoparticles into the TaN host medium, allowing for the use of established Ta etching chemistry. A thinner is absorber is created due to the enhanced absorption properties of the Ni-Ta nano-composite material. Finite integral method and effective medium theory-based transfer matrix method have been independently developed to analyze the performance of the nano-composite absorption layer. We show that inserting 15% volume fraction Ni nanoparticles into 40-nm of TaN absorber material can reduce the reflection below 2% over the EUV range. Numerical simulations confirm that the reduced reflectivity is due to the increased absorption of Ni, while scattering only contributes to approximately 0.2% of the reduction in reflectivity.

Paper Details

Date Published: 10 May 2016
PDF: 6 pages
Proc. SPIE 9984, Photomask Japan 2016: XXIII Symposium on Photomask and Next-Generation Lithography Mask Technology, 99840G (10 May 2016); doi: 10.1117/12.2240093
Show Author Affiliations
Derrick Hay, Univ. of South Florida (United States)
Patrick Bagge, Univ. of South Florida (United States)
Ian Khaw, Univ. of South Florida (United States)
Lei Sun, GLOBALFOUNDRIES Inc. (United States)
Obert Wood, GLOBALFOUNDRIES Inc. (United States)
Yulu Chen, GLOBALFOUNDRIES Inc. (United States)
Ryoung-han Kim, GLOBALFOUNDRIES Inc. (United States)
Zhengqing John Qi, GLOBALFOUNDRIES Inc. (United States)
Zhimin Shi, Univ. of South Florida (United States)


Published in SPIE Proceedings Vol. 9984:
Photomask Japan 2016: XXIII Symposium on Photomask and Next-Generation Lithography Mask Technology
Nobuyuki Yoshioka, Editor(s)

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