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Proceedings Paper

Interfacial quality of high-reflectivity Mo-Si multilayers for EUV mask blanks
Author(s): Narasimhan Srinivasan; Katrina Rook; Paul Turner; Tania Henry; Kenji Yamamoto; Devlin Donnelly; Thu Van Nguyen; Vincent Ip; Meng H. Lee; Sandeep Kohli; Frank Cerio; Adrian J. Devahasayam
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Paper Abstract

As Extreme Ultra Violet lithography (EUVL) is becoming adopted into manufacturing, there is an ongoing need to identify and improve the EUV mask multilayer properties that impact reflectivity. Key properties include the roughness and inter-diffusion depth at the Mo-Si interfaces. During mask usage, on exposure to EUV, the interfaces are impacted during thermal cycling, so interfacial stability is key. We report on the use of X-ray reflectivity (XRR) to probe the interfacial depth and roughness of Mo/Si multilayers deposited via secondary ion beam deposition (IBD). We confirm top-surface roughness by AFM. We measure minimal impact of the underlying substrate on top-surface roughness of Mo-Si multilayer stacks. Mo and Si single-layer roughness are shown to be primarily dependent on deposition angle; with minimal roughness at intermediate angles and significant deterioration beyond a deposition angle of about 60 degrees. We use this angular dependence to systematically vary the interfacial roughness and monitor the impact on the XRR measurement. We demonstrate that XRR, with attention to the Fourier Transform, may also be used to quantify the inter-diffusion depth at the Mo-Si interfaces. We measure inter-diffusion depths of 0.5 - 1.8nm. A simulated model is developed, incorporating both interfacial depth and roughness, and the experimental data are compared with this model. The model could be applied to quantify the impact on the interfaces of: beam energy and flux; incidence angles; gas species and pressure; interfacial treatments; thermal treatment; or mask usage.

Paper Details

Date Published: 26 September 2019
PDF: 6 pages
Proc. SPIE 11147, International Conference on Extreme Ultraviolet Lithography 2019, 111470N (26 September 2019); doi: 10.1117/12.2536935
Show Author Affiliations
Narasimhan Srinivasan, Veeco Instruments Inc. (United States)
Katrina Rook, Veeco Instruments Inc. (United States)
Paul Turner, Veeco Instruments Inc. (United States)
Tania Henry, Veeco Instruments Inc. (United States)
Kenji Yamamoto, Veeco Instruments Inc. (United States)
Devlin Donnelly, Veeco Instruments Inc. (United States)
Stony Brook Univ. (United States)
Thu Van Nguyen, Aerotek (United States)
Vincent Ip, Veeco Instruments Inc. (United States)
Meng H. Lee, Veeco Instruments Inc. (United States)
Sandeep Kohli, Veeco Instruments Inc. (United States)
Frank Cerio, Veeco Instruments Inc. (United States)
Adrian J. Devahasayam, Veeco Instruments Inc. (United States)

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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