Extended Nijboer-Zernike (ENZ) based mask imaging : efficient coupling of electromagnetic field solvers and the ENZ imaging algorithm

Results are presented of mask imaging using the Extended Nijboer-Zernike (ENZ) theory of diffraction. We show that the efficiency of a mask imaging algorithm, derived from this theory, can be increased. By adjusting the basic Finite Difference Time Domain (FDTD) algorithm, we can calculate the near field of isolated mask structures efficiently, without resorting to periodic domains. In addition, the calculations for the points on the entrance sphere of the imaging system can be done separately with a Fourier transformed Stratton-Chu near-to-far-field transformation. By clever sampling in the radial direction of the entrance pupil, the computational effort is already reduced by at least a factor of 4