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 nearto-
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.
In this paper we introduce a new mask imaging algorithm that is based on the source point integration method
(or Abbe method). The method presented here distinguishes itself from existing methods by exploiting the
through-focus imaging feature of the Extended Nijboer-Zernike (ENZ) theory of diffraction. An introduction
to ENZ-theory and its application in general imaging is provided after which we describe the mask imaging
scheme that can be derived from it. The remainder of the paper is devoted to illustrating the advantages of the
new method over existing methods (Hopkins-based). To this extent several simulation results are included that
illustrate advantages arising from: the accurate incorporation of isolated structures, the rigorous treatment of the
object (mask topography) and the fully vectorial through-focus image formation of the ENZ-based algorithm.
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