Improved theoretical reflectivities of extreme ultraviolet mirrors

Mandeep Singh; Joseph J. M. Braat

doi:10.1117/12.390078

21 July 2000 Improved theoretical reflectivities of extreme ultraviolet mirrors

Mandeep Singh, Joseph J. M. Braat

Proceedings Volume 3997, Emerging Lithographic Technologies IV; (2000) https://doi.org/10.1117/12.390078
Event: Microlithography 2000, 2000, Santa Clara, CA, United States

Abstract

We show that the theoretical reflectivities of multilayered Mo/Be and Mo/Si extreme ultraviolet (EUV) mirrors tuned for the 11 - 14 nm spectral region can be enhanced significantly by incorporating additional materials within the stack. The reflectivity performance of these quarter-wave multilayers can be enhanced further by global optimization procedures by which the layer thicknesses are varied for optimum performance. By incorporating additional materials of differing complex refractive indices -- e.g. Rh, Ru and Sr -- in various regions of the stack we calculate peak reflectivity enhancements of up to approximately 5% for a single reflector compared to standard unoptimized stacks. For an EUV optical system with nine near-normal-incidence mirrors, the theoretical optical throughput may be increased by up to 100%. We also show that protective capping layers such as Rh and Ru, in addition to protecting the mirrors from environmental attack, may serve to improve the reflectivity characteristics.

Citation Download Citation

Mandeep Singh and Joseph J. M. Braat "Improved theoretical reflectivities of extreme ultraviolet mirrors", Proc. SPIE 3997, Emerging Lithographic Technologies IV, (21 July 2000); https://doi.org/10.1117/12.390078

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