In this paper we introduce an inverse lithography technology (ILT) solution that provides masks with perfect symmetry and minimal complexity. In this solution we divide the ILT problem into three steps and strictly maintain symmetry in each of these steps. First, we optimize an ideal grayscale mask. Second, we seed this ideal mask with polygons. Finally, we grow these seeds in a separate optimization flow. The final mask perfectly maintains the symmetry properties of the illumination source. To the best of our knowledge, this is the first ILT solution that can be used on the original design hierarchy on a full chip scale.
Bayram Yenikaya, Bayram Yenikaya,
"Full chip hierarchical inverse lithography: a solution with perfect symmetry", Proc. SPIE 10147, Optical Microlithography XXX, 101470L (24 March 2017); doi: 10.1117/12.2257608; https://doi.org/10.1117/12.2257608