Ion beam processing for critical EUV photomask process steps: mask blank deposition and photomask absorber etch

Katrina Rook; Meng H. Lee; Narasimhan Srinivasan; Vincent Ip; Sandeep Kohli; Mathew S. Levoso; Frank Cerio; Adrian J. Devasahayam

doi:10.1117/12.2501832

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3 October 2018 Ion beam processing for critical EUV photomask process steps: mask blank deposition and photomask absorber etch

Katrina Rook, Meng H. Lee, Narasimhan Srinivasan, Vincent Ip, Sandeep Kohli, Mathew S. Levoso, Frank Cerio, Adrian J. Devasahayam

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Proceedings Volume 10809, International Conference on Extreme Ultraviolet Lithography 2018; 108090F (2018) https://doi.org/10.1117/12.2501832
Event: SPIE Photomask Technology + Extreme Ultraviolet Lithography, 2018, Monterey, California, United States

Abstract

Development progress and roadmap, for high-reflective Mo/Si multilayers for EUV mask-blanks, are reviewed. We outline the state-of-the-art in low-defect-density secondary ion beam deposition (IBD), and ongoing hardware development for performance improvement and high-volume manufacturing. We further discuss extension of ion beam technology to later steps in the EUV mask manufacturing: deposition of highly-uniform 2.5 – 3nm Ru capping layers; and patterning of novel Ni absorber structures. IBD-deposited Ru films are demonstrated with uniformity of 0.7% 3σ over a 188mm diameter area. By x-ray reflection with Cu Kα radiation, we measure a film density of 12.4 g/cm³, and a roughness of less than 1.0nm. Deposition rates of ~ 1 – 7 nm/min are demonstrated, implying a capping layer deposition time of 20 seconds – 3 minutes. . For advanced absorber patterning, we discuss Argon ion beam etch (IBE) of Ni films. Ni and Ru IBE etch rates of ~ 8 – 80 nm/min are demonstrated, implying absorber etch times of ~ 30 seconds – 5 minutes. IBE Ni:Ru etch selectivity is 1:1 to 1.3:1, so Ru is not a ‘stopping layer’, etch depth must be controlled by time, and Ni uniformity is a requirement. IBE Ni:Photoresist etch selectivity is 0.8:1 to 1.6:1. We simulate the IBE absorber pattern definition for mask features of half-pitch 96nm (24nm at wafer level). Ion beam incidence angle can be optimized to maintain critical dimension within 6% of the pre-etch value.

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Katrina Rook, Meng H. Lee, Narasimhan Srinivasan, Vincent Ip, Sandeep Kohli, Mathew S. Levoso, Frank Cerio, and Adrian J. Devasahayam "Ion beam processing for critical EUV photomask process steps: mask blank deposition and photomask absorber etch", Proc. SPIE 10809, International Conference on Extreme Ultraviolet Lithography 2018, 108090F (3 October 2018); https://doi.org/10.1117/12.2501832

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