Development of a Lithography Simulation Tool Set in Various Optical Conditions for Source Mask Optimization

Resolution Enhancement Techniques (RETs) in optical lithography have become essential for achieving the continuous shrinkage of technology nodes. The primary techniques in RETs include source mask optimization. Generally, lithography simulation, which estimates the image formed on wafers, is utilized in RETs. To optimize the light source and mask, optical conditions such as the light-source shape, numerical aperture, and exposure wavelength need to be adjusted in the lithography simulation. However, there is a shortage of open lithography simulation tools that cover various optical conditions. In academia, the study of source optimization in optical lithography is challenging. In this paper, we present the development of a lithography simulation tool set for source mask optimization. In our lithography simulation tool set, users can set optical conditions such as the light-source shape, mask shape, numerical aperture, and exposure wavelength. One function in our lithography simulation tool set calculates light intensity using the Transmission Cross Coefficient (TCC) model, while another function calculates it using the Sum of Coherent System (SOCS) for the specified optical conditions. In experiments, we verified the accuracy of our lithography simulation tool set and evaluated its execution time.