Improving the thermodynamic stability and EUV reflectance in Mo/Si multilayer mirrors by rubidium incorporation  (Conference Presentation)

Amirmehdi Saedi; Cristina Sfiligoj; Joost W. M. Frenken; Jan Verhoeven

doi:10.1117/12.2321181

18 September 2018 Improving the thermodynamic stability and EUV reflectance in Mo/Si multilayer mirrors by rubidium incorporation (Conference Presentation)

Amirmehdi Saedi, Cristina Sfiligoj, Joost W. M. Frenken, Jan Verhoeven

Author Affiliations +

Proceedings Volume 10760, Advances in X-Ray/EUV Optics and Components XIII; 1076007 (2018) https://doi.org/10.1117/12.2321181
Event: SPIE Optical Engineering + Applications, 2018, San Diego, California, United States

Abstract

State of the art optics for Extreme Ultra-Violet Lithography (EUVL) is based on Mo/Si multilayer mirrors (MLMs) integrated with diffusion barriers and capping layers to increase the optics lifetime and experimental reflectance (the current record being 71.3%[1]). In this work, we focus on interface thermodynamics control as a method to optimize the MLM performance. We develop a general framework to select potential elements that could be used as additives in the Si spacing layer to suppress intermixing, while ensuring high EUV reflectivity. We identify rubidium (Rb) as the material giving the highest MLM reflectance and we provide a rigorous estimation of the EUV optical properties of its silicide compounds, RbnSim. We show an increase in optical contrast between RbnSim and Mo via a negative shift of the Si L-edge, and a negligible effect on the absorption coefficient, that remains low. Our calculations indicate that intermixing with Mo can be reduced by 82% and a maximum reflectance of 73.9% can be achieved. Provided that the optics for EUVL must function in a hydrogen environment, we calculate the reflectance also for MLMs with RbH and RbSiH3 as spacing layers. For Mo/RbH MLMs we estimate a full suppression of intermixing and a 74.8% maximum reflectance, while for Mo/RbSiH3 MLMs, if integrated with RbH diffusion barriers, a superior value of 77.4% can be achieved. By implementing the proposed MLM solutions we predict that the optics lifetime can be enhanced and that the total EUVL throughput can be increased up to a factor 2. [1] E. Louis , A.E. Yakshin, T. Tsarfati, F. Bijkerk, "Nanometer interface and materials control for multilayer EUV-optical applications", Progress in Surface Science 86 (2011) 255-294.

Conference Presentation

Citation Download Citation

Amirmehdi Saedi, Cristina Sfiligoj, Joost W. M. Frenken, and Jan Verhoeven "Improving the thermodynamic stability and EUV reflectance in Mo/Si multilayer mirrors by rubidium incorporation (Conference Presentation)", Proc. SPIE 10760, Advances in X-Ray/EUV Optics and Components XIII, 1076007 (18 September 2018); https://doi.org/10.1117/12.2321181

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KEYWORDS

Reflectivity

Extreme ultraviolet

Rubidium

Mirrors

Thermodynamics

Extreme ultraviolet lithography

Diffusion

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