Impact of measured pupil illumination fill distribution on lithography simulation and OPC models

Increasing miniaturization and decreasing k1 factors impose continuously growing demands on optical lithography. These requirements are reflected in the need for increasingly accurate lithography simulations, which are prerequisite for successful optical proximity correction (OPC) of the mask layout. Therefore, the physical conditions of the lithography tools and their impact on the resulting printed image have to be carefully considered. The illumination distribution in scanners and steppers is commonly simplified by a top-hat (rectangular cross-section) function. The illuminator is therefore assumed to consist of either completely dark or homogeneously bright areas. In this paper, we investigate the effect of using the measured source, which can deviate significantly from a simple top-hat function, on simulation results and OPC treatment. We compare simulations with measurement and show that there are cases where significant improvements occur by using the real source distribution.