Line edge roughness (LER) has been identified as a potential source of uncertainty in optical scatterometry measurements. Characterizing the effect of LER on optical scatterometry signals is required to assess measurement uncertainty. However, rigorous approaches to modeling the structures that are needed to simulate LER can be computationally expensive. In this work, we compare the effect of LER on angle resolved scatterometry signals computed using an effective medium approximation to those computed with realizations of rough interfaces. We find that for correlation lengths much less than the wavelength but greater than the rms roughness , that an anisotropic effective medium approximation provide a satisfactory approximation in the cases studied.
Citation: Journal of the Optical Society of America A-Optics Image Science and Vision
Pub Type: Journals
effective medium approximation, gratings, line edge roughness, reflectance, scatterometry