Cross-sectional shape evaluation of a particle by scatterometry

Reconstructing an image from the scattering pattern of particles with several wavelengths is difficult. This is because precise calculation in such cases is difficult, and because there is no proper procedure to evaluate shapes from the scattering pattern. We use rigorous coupled-wave analysis (RCWA), which we previously developed and applied to an isolated scatterer, and rotate the particle to reconstruct the image. We find that it is possible to discriminate between rectangles, triangles, and squares. The precision of length can be less than 0.2 of the wavelength, provided that the refractive index of the scatterer is known.