5 June 1998 Materials for reflective multilayer coatings for EUV wavelengths
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Abstract
By operating at wavelength near 10-20 nm, EUV lithography can allow for imaging below 100 nm with limited diffractive losses. The reflective optics involved in such systems require multilayer coatings with stringent demands on throughput, uniformity, and stability. The performance of such multilayers is dependent on the optical properties leading to multilayer stacks requiring up to 40 layer pairs. An exhaustive study of potential material combinations has been performed. Detailed results from the investigation of candidate EUV reflective multilayers is presented. Beryllium and silicon are unique in the 10 to 20 nm wavelength range as materials with high index values and suitably low absorption. The best performing coatings within this range are therefore combinations of these two materials with low absorbing low index films, including many refractory metals. For each multilayer coating type investigated, the wavelength of maximum reflectivity has been optimized, and stress, thickness variation, scattering, and interfacial layer formation effects have been characterized.
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Bruce W. Smith, Bruce W. Smith, Parthasarathy Venkataraman, Parthasarathy Venkataraman, Santosh K. Kurinec, Santosh K. Kurinec, R. Scott Mackay, R. Scott Mackay, } "Materials for reflective multilayer coatings for EUV wavelengths", Proc. SPIE 3331, Emerging Lithographic Technologies II, (5 June 1998); doi: 10.1117/12.309614; https://doi.org/10.1117/12.309614
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