Analysis of surface-plasmon-polaritons-assisted interference imaging by using silver film with rough surface

In the surface plasmon polaritons (SPPs) interference lithography, the scattering effect caused by the rough surface of silver film deteriorates the quality of lithography patterns. Research shows that under this condition the light field in the photoresist is not the results of SPPs interference but comes from the SPPs assisted imaging in which the scattered light propagates from the upper surface of the silver film to the photoresist. The near-field optical transfer function (NOTF) is used to study this process and a method of evaluating the imaging quality is presented. The validity of NOTF is verified by both SPPs assisted interference imaging experiments and simulations by the FDTD. It is also shown that the NOTF method is not only a convenient approach to describe the nano-scale information transmission in the near-field but also a good method to optimize experimental parameters.