Comparison of different microscope imaging models for different structure geometries on the basis of rigorous diffraction calculation

High resolution optical microscopy is still an important instrument for dimensional characterisation of micro- und nanostructures. For precise measurements of dimensional quantities a high quality modelling of the optical imaging on the basis of rigorous diffraction calculation is essential, which account both for polarisation effects and the 2D or 3D geometry of the structures. At PTB we use two different rigorous grating diffraction models for modelling of the intensity distribution in the image plane, the rigorous coupled wave analysis (RCWA) method and the finite elements (FEM) method. We investigated both the diffraction efficiencies and the resulting microscopic (far field) images for three different edge geometries: binary, sinusoidal and trapezoidal gratings. We will present results of this investigations for TE, TM and unpolarised illumination of the gratings. Deviations between both methods will be discussed.