A 3-D Numerical Study of Pinhole Diffraction to Predict the Accuracy of EUV Point Diffraction Interferometry

A three-dimensional (3-D) electromagnetic field simulation is used to model the propagation of extreme ultraviolet (EUV), 13 nm wavelength, light through sub-1500 Å diameter pinholes in a highly absorptive medium. Deviations of the diffracted wavefront phase from an ideal sphere are studied within 0.1 numerical aperture, to predict the accuracy of EUV point diffraction interferometers used in at-wavelength testing of nearly diffraction-limited EUV optical systems. Aberration magnitudes are studied for various 3-D pinhole models, including cylindrical and conical pinhole bores.