Method for determining a structure-independent contribution of a lithography mask to a fluctuation of the line width

摘要

Method for determining a structure-independent contribution of a lithography mask (5) to a linewidth fluctuation (LWR) comprising the following steps: 1.1. Providing an optical system (2) with imaging optics (8) for imaging lithographic masks (5) 1.2. Providing a lithography mask (5) with at least one measuring range which is free of structures to be imaged, 1.3. Illuminating the at least one measuring range with illumination radiation (1), 1.4. Picking up a focus stack of the at least one measurement region of the lithography mask (5), 1.5. spatially resolved evaluation of 2D intensity distributions (15) of the recorded focus stack, wherein the evaluation of the 2D intensity distributions (15) comprises the following steps: 1.6. Determining a spectrum of the 2D intensity distributions (15) by Fourier transforming the 2D intensity distributions (15zi), 1.7. Determining a defocus dependence of a plurality of spectral components S (v, v) of the spectrum1.8. Determining a Fourier transform of a function to describe the optical surface roughness of the lithography mask (5) from the determined defocus dependence of the spectral components S (v, v), 1.9. wherein evaluating the 2D intensity distributions (15) comprises determining a speckle contrast (ΔI).