Polarization effects in plasmonic masks

In the implementation of most resolution enhancement techniques for optical lithography, full 3D simulation of effects such as topography imbalance in phase masks can be successfully modeled. However, these simulators do not appear to capture the full range of effects that impact the transmission of light through conducting (or partially conducting) films. In particular, certain resonant sub-wavelength geometric shapes, such as the C-aperture in a metallic conducting film, have been shown to have transmission values that are factors of 10^3-10^5 higher than simple geometric projections would predict. Using a new finite difference time domain solver that explicitly includes internal currents and analyzes the Poynting vector behavior of the EM fields, we can better understand the complex behavior of these resonant apertures. The currents are highly dependent on the polarization of the incoming EM excitation, as is the extraordinary transmission. We have also applied this in a limited fashion to geometries such as those expected to appear on photomasks in the 45nm node, when not extraordinary transmission but extraordinary opacity is predicted. These effects are also highly polarization dependent.