Finite-difference time domain method for data analysis of spectroscopic ellipsometry

Variable Angle Spectroscopic Ellipsometry (VASE) data analysis using the finite-difference time-domain method (FDTD method) could provide a general method to indirectly resolve the optical properties and structural information of structurally complex samples, including periodic and non-periodic nanostructured thin films. Specifically, our results demonstrate extraction of structural information from 1D periodic structures. In this contribution, we show the accuracy limit of this approach by calculat- ing the SE response of both metallic and dielectric ideal thin films. We then demonstrate a practical multi-parameter broadband optimization of the SE response from 1D periodic structure. This method requires a variable angle variable wavelength approach in acquiring SE measurements as to overcome wide band frequency response limits in the FDTD method model. We address the challenge of this approach by comparing different strategies in the selection of angle of incidence (AoI) and wavelength for both SE measurement and FDTD method modeling. This FDTD–SE approach inherits the distinctive advantages of the FDTD method: (i) calculation of spectral broadband results from a single simulation; (ii) sources of error are well understood (iii) potential to simu- late arbitrary general subwavelength to nano-sized structures (iv) natural capacity as a time-domain technique to study complex optical phenomena such as plasmonic and non-linear effects; and (v) ability to visualize field dynamics.