EUV lithography for resolution below 9 nm requires the numerical aperture of the projection optics to be significantly larger than 0.45. A configuration of 4x magnification, full field size and 6’’ reticle is not feasible anymore. The increased chief ray angle and higher NA at reticle lead to non-acceptable shadowing effects, which can only be controlled by increasing the magnification, hence reducing the system productivity. We demonstrate that the best compromise in imaging, productivity and field split is a so-called anamorphic magnification and a half field of 26 x 16.5 mm². We discuss the optical solutions for anamorphic high-NA lithography.
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Bernhard Kneer ; Sascha Migura ; Winfried Kaiser ; Jens Timo Neumann and Jan van Schoot
EUV lithography optics for sub-9nm resolution
", Proc. SPIE 9422, Extreme Ultraviolet (EUV) Lithography VI, 94221G (March 16, 2015); doi:10.1117/12.2175488; http://dx.doi.org/10.1117/12.2175488