Rigorous three-dimensional photoresist exposure and development simulation over nonplanar topography

A rigorous three-dimensional (3-D) simulation method for photoresist exposure and development is presented in which light scattering due to a nonplanar topography is calculated using the Maxwell equations. The method relies on a Fourier expansion of the electromagnetic field and extends the two-dimensional (2-D) differential method to the third dimension. The model accounts for partial coherent illumination and considers the nonlinear bleaching reaction of the photoresist. For the development process, the cellular-based topography simulator has been extended. A detailed description of the theory behind the simulation method is presented, the computational efficiency is discussed, and simulation results are given.