Energetic Sn+ irradiation effects on ruthenium mirror specular reflectivity at 13.5-nm |
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Authors: | J P Allain M Nieto-Perez M R Hendricks P Zink C Metzmacher K Bergmann |
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Institution: | (1) Department of Applied Physics, Helsinki University of Technology (TKK), P.O. Box 3500, Espoo, 02015 TKK, Finland;(2) TKK Micronova, Helsinki University of Technology (TKK), P.O. Box 3500, Espoo, 02015 TKK, Finland |
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Abstract: | Sn+ irradiations of Ru single-layer mirrors (SLM) simulate conditions of fast-Sn ion exposure in high-intensity 13.5 nm lithography
lamps. Ultra-shallow implantation of Sn is measured down to 1–1.5 nm depth for energies between 1–1.3 keV at near-normal incident
angles on Ru mirror surfaces. The Sn surface concentration reaches an equilibrium of 55–58% Sn/Ru for near-normal incidence
and 36–38% for grazing incidence at approximately 63 degrees with respect to the mirror surface normal. The relative reflectivity
at 13.5 nm at 15-degree incidence was measured in-situ during Sn+ irradiation. For near-normal Sn+ exposures the reflectivity is measured to decrease between 4–7% for a total Sn fluence of 1016 cm−2. Theoretical Fresnel reflectivity modeling shows for the same fluence assuming all Sn atoms form a layer on the Ru mirror
surface, that the reflectivity loss should be between 15–18% for this dose. Ex-situ absolute 13.5 nm reflectivity data corroborate
these results, indicating that implanted energetic Sn atoms mixed with Ru reflect 13.5-nm light differently than theoretically
predicted by Fresnel reflectivity models. |
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