25 June 1999 Film-stress-induced deformation of EUV reflective optics
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Results of numerical studies on the deformation of multilayer coated optics for EUV lithography are presented and compared. The primary materials-dependent characteristics of EUV multilayer mirrors are reflectance, stress, and stability. Understanding and controlling these mirror characteristics is critical for the efficient operation of an EUVL system. Optimized for reflectance, the multilayer coatings typically have film stress values large enough to deform the optic. We use finite element models to predict the distortion caused by the film stress. Input parameters to the models include the size, shape, and material properties of the optical substrate as well as the magnitude and spatial variations of the film stress. The distortion results are coupled with optical analysis software to predict wavefront aberrations for the candidate optical design. Finally, lithographic analysis software is used to predict the aerial image and linewidth variation. Model predictions have guided the design of the optical substrates so that lithographic errors induced by film- stress-deformation are expected to be within the acceptable error budget.
© (1999) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Paul A. Spence, Paul A. Spence, Michael P. Kanouff, Michael P. Kanouff, Avijit K. Ray-Chaudhuri, Avijit K. Ray-Chaudhuri, } "Film-stress-induced deformation of EUV reflective optics", Proc. SPIE 3676, Emerging Lithographic Technologies III, (25 June 1999); doi: 10.1117/12.351166; https://doi.org/10.1117/12.351166

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