Fieldstitching with Kirchhoff-boundaries as a model based description for line edge roughness (LER) in scatterometry

Optical scatterometry has established itself as one of the mainly applied methods for CD metrology besides CD-SEM during the recent years. However, grating imperfections such as line edge roughness have been largely neglected in scatterometry models so far. Since imperfections of the perfect periodicity would yield large unit cells in a fully rigorous computation of the scatterograms an approximative method has to be used instead. To that end we propose a fieldstitching method which introduces virtual lateral Kirchhoff-boundaries.