File:EUVL in-plane resolution degradation.PNG

English: The 1st diffracted order is reflected by the mask multilayer in the process of forming the image. However, in-plane diffraction, where the incident and diffracted light lie in a common plane, suffers from more severe degradation of the reflectivity than out-of-plane diffraction, where the incident and diffracted light do not share the same plane. The lower reflectivity of the first order means this fundamental component of the pattern information is more readily absorbed by the multilayer and substrate.

The assumption here is an illumination angle of 6 degrees. For a numerical aperture of 0.32, the first order will be cutoff for 21 nm half-pitch (red line). At this point, higher illumination angles would be required.

As a result, the resolution is not expected to be superior to what is currently achievable with 193 nm immersion double patterning lithography (18 nm half-pitch).

• M. Sugawara et al., J. Vac. Sci. Tech. B 21, 2701 (2003).
• F. T. Chen, Proc. SPIE 5037, pp. 347-357 (2003).
• R. Petit (ed.), Electromagnetic Theory of Gratings (Springer-Verlag, 1980).