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3 October 2018 Ion beam processing for critical EUV photomask process steps: mask blank deposition and photomask absorber etch
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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.
Conference Presentation
© (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
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);

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