Prospects and Limits of the Rayleigh Fourier Approach for Diffraction Modelling in Scatterometry and Lithography

In this paper, we are suggesting an approach which is based on the so-called Rayleigh hypothesis. The basic idea of this method is to extend the expansion of the electromagnetic field components into Rayleigh modes inside the grating grooves as opposed to the RCWA where the expansion within the slices is done in so-called Bragg modes. Therefore, the Rayleigh-Fourier method does not need a diagonalization for the decoupling of the modes. It requires only the formation of an interface transition matrix, the elements of which can be computed analytically. As a consequence, it is very fast both for 2D as well as for 3D.