Hybrid FDTD-Fresnel modeling of microscope imaging

Application of the electromagnetic analysis by finite-difference time-domain (FDTD) method coupled with the scalar diffraction (SD) method for the electromagnetic (EM) modeling of optical microscope imaging is introduced. FDTD method is applied for the modeling of scattering from a 2D target - typically an IC structure with size of elements comparable to the wavelength of the considered wave. Here a full-wave propagation model must be considered. Afterwards, obtained results are coupled with a scalar diffraction method based on a Fresnel approximation to project a magnified image through the cylindrical lens onto the image plane. The lens structure may be even bigger than 1000 wavelengths and thus is out of range of application of the full-wave electromagnetic analysis. The considered hybrid method seems to be the best choice for an accurate simulation of the imaging results.