Light scattering off semi-infinite structures

Light scattering computations are often used for optical metrology. The goal is to determine parameters such as layer thicknesses, line widths, sidewall-angles or other geometrical or material quantities. In standard simulations it is assumed that the structures resides on a layered substrate and are either periodically repeated along the substrate surface or are encapsulated within the computational domain (isolated). Structures with an infinite line can be reduced to a 2D simulation where the line cross-section appears as an isolated scatterer. In this contribution we generalize the geometry reconstruction algorithms to situations where a structure is neither periodically arranged nor isolated. Prominent examples are a truncated line which ends within the computational domain or a step profile forming an infinite edge. A detailed mathematical treatment of the far-field’s Fourier transform is needed as it is neither discrete (as for periodic setup) nor smooth within the propagating k-range (as for isolated structures). We acknowledge funding by the German Federal Ministry of Education and Research (BMBF, project number 01IS20080A, SiM4diM).