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5 June 1998 Multilayer reflective coatings for extreme-ultraviolet lithography
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Multilayer mirror coatings which reflect extreme UV (EUV) radiation are a key enabling technology for EUV lithography. So/Si multilayers with reflectances of 67.5 percent at 13.4 nm are now routinely achieved and reflectances of 70.2 percent at 11.4 nm were obtained with Mo/Be multilayers. High reflectance is achieved with careful control of substrate quality, layer thicknesses, multilayer materials, interface quality, and surface termination. Reflectance and film stress were found to be stable relative to the requirements for application to EUV lithography. The run-to- run reproducibility of the reflectance peak position was characterized to be better than 0.2 percent, providing the required wavelength matching among the seven multilayer- coated mirrors used in the present lithography system design. Uniformity of coating was improved to better than 0.5 percent across 150 mm diameter substrates. These improvements in EUV multilayer mirror technology will enable us to meet the stringent specifications for coating the large optical substrates for our next-generation EUV lithography system.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Claude Montcalm, Sasa Bajt, Paul B. Mirkarimi, Eberhard Adolf Spiller, Frank J. Weber, and James A. Folta "Multilayer reflective coatings for extreme-ultraviolet lithography", Proc. SPIE 3331, Emerging Lithographic Technologies II, (5 June 1998);

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