Three-dimensional Simulation of Light-scattering over Nonplanar Substrates in Photolithography

A key step in photolithography simulation is a rigorous three-dimensional modeling of the exposure/bleaching of the resist's photoactive compound (PAC). Thereby electromagnetic (EM) scattering of light caused by the nonlinear resist as well as by a nonplanar topography has to be considered. We present a novel three-dimensional approach, based on a numerical solution of the Maxwell equations. Furthermore, we give a physically rigorous description of scattering effects as necessary for sub-micrometer-photolithography. A similar method in two dimensions was first proposed in the simulation of diffraction gratings [l] and adapted for photolithography in [2).