Field-position dependent apodization in dark-field digital holographic microscopy for semiconductor metrology

Publication date
DOI http://dx.doi.org/10.1364/oe.476157
Reference T. van Gardingen-Cromwijk, M. Adhikary, C. Messinis, S. Konijnenberg, W.M.J. Coene, S. Witte, J.F. de Boer and A.J. den Boef, Field-position dependent apodization in dark-field digital holographic microscopy for semiconductor metrology, Opt. Express 31, (1), 411-425 (2023)
Groups Computational Imaging, EUV Generation & Imaging

Measuring overlay between two layers of semiconductor devices is a crucial step during electronic chip fabrication. We present dark-field digital holographic microscopy that addresses various overlay metrology challenges that are encountered in the semiconductor industry. We present measurement results that show that the point-spread function of our microscope depends on the position in the field-of-view. We will show that this novel observation can be explained by a combination of the finite bandwidth of the light source and a wavelength-dependent focal length of the imaging lens. Moreover, we will also present additional experimental data that supports our theoretical understanding. Finally, we will propose solutions that reduce this effect to acceptable levels.