Interfacial quality of high-reflectivity Mo-Si multilayers for EUV mask blanks

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

doi:10.1117/12.2536935

26 September 2019 Interfacial quality of high-reflectivity Mo-Si multilayers for EUV mask blanks

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

Author Affiliations +

Proceedings Volume 11147, International Conference on Extreme Ultraviolet Lithography 2019; 111470N (2019) https://doi.org/10.1117/12.2536935
Event: SPIE Photomask Technology + EUV Lithography, 2019, Monterey, California, United States

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.

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Narasimhan Srinivasan, Katrina Rook, Paul Turner, Tania Henry, Kenji Yamamoto, Devlin Donnelly, Thu Van Nguyen, Vincent Ip, Meng H. Lee, Sandeep Kohli, Frank Cerio, and Adrian J. Devahasayam "Interfacial quality of high-reflectivity Mo-Si multilayers for EUV mask blanks", Proc. SPIE 11147, International Conference on Extreme Ultraviolet Lithography 2019, 111470N (26 September 2019); https://doi.org/10.1117/12.2536935

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