Enhanced nanoform metrology by imaging Mueller matrix ellipsometry combined with plasmonic support structures (Conference Presentation)

Abstract

With the persistent progress in nanotechnology the importance to accurately characterize nanoscale structures steadily increases. Optical measurement techniques have proven to be well suited for this purpose. We investigate different approaches to gain more information about nanoscale features by combining polarimetric setups with specially designed nanostructures. Our experimental setup combines a dual-rotating compensator Mueller matrix ellipsometer with an optical microscope. One arm of the ellipsometer is rigid and consists of a light source, polarization state generator, and optics to focus the light onto a sample. Samples under investigation are mounted on top of a combination of rotation and translation stages to precisely adjust them into the microscope’s focus. The other arm forms the microscope part with a long working distance objective, a polarization state analyser and a CCD camera. A large aperture rotation stage allows to rotate this arm around the sample stage. Thus, measurements in reflection and transmission under different angles of incidence can be performed. The setup measures Mueller matrices for each pixel in the obtained image. Therefore, it allows to examine the polarizing properties of the sample spatially and helps to gain further topological information. This information can be additionally enhanced by supporting nanostructures placed close to the sample to extract information from the near field. Therefore, we designed plasmonic lenses for different measurement configurations. The investigations are complemented by numerical finite element simulations. These are performed to validate the design of the nanostructures and to compare them with measured values. Up to now, we characterized the experimental setup and designed and validated the supporting nanostructures and reference structures. Future steps include extending the setup with a monochromator to ensure flexible illumination, measurement of the reference structures, and the combination of setup and plasmonic lenses to further enhance the sensitivity to subwavelength sized features.