Efficient computational techniques for aerial imaging simulation

We discuss computational techniques for calculating aerial image intensity distributions from large GDS II files recently implemented in Depict, a photolithography simulator for projection imaging, resist exposure, post-exposure bake and development. In particular, an algorithm for rapid and accurate evaluation of the mask Fourier transform over large domains containing non-uniformly positioned mask elements is implemented. By controlling aliasing errors within the context of a multiple level scheme, this algorithm renders feasible the simulation of aerial images across large portions of integrated circuits. The algorithm also allows overlapping phase mask elements obeying multiplicative transmission rules, and mask element merging. Accuracy for integration of the extended light source is also reported.