A simulation study on two-dimensional patterns with different post-OPC mask variations
Due to the existence of diffraction, for the same printing target pattern, there may exist different mask patterns. With the introduction of source-mask optimization (SMO) method, such variation can be extensively explored and an optimum pattern can be found up to a given set of criteria. However, without the SMO, when the illumination condition is set, it is entirely up to the quality of the optical proximity correction (OPC) to set up a suitable final mask to achieve acceptable overlapping process windows. In this paper, we attempt to understand the underlying physical or optical mechanism with several representative patterns. Such mechanism includes how the coherent length under a given illumination condition contributes to the difference in process window for mask variations even that such mask variation may result in the same best focus and best dose printing profiles. We will also explore the implications to the design rule restrictions.