Modeling of three-dimensional photoresist profiles exposed by localized fields of high-transmission nano-apertures.

Using a simple theoretical model, we calculate three-dimensional profiles of photoresist exposed by arbitrarily shaped localized fields of high-transmission metal nano-apertures. We apply the finite difference time domain (FDTD) method to obtain the localized field distributions, which are generated by excitation of localized surface plasmon polaritons underneath a C-shaped or a bow-tie-shaped aperture. Incorporating the results of FDTD simulations with the theoretical model, we visualize three-dimensional exposure profiles of the photoresist as a function of the exposure dose and the gap distance between the aperture and the photoresist. It is found that the three-dimensional exposure profiles provide useful information for choosing process parameters for nanopatterning by plasmonic lithography using the aperture.