  We perform 3D lithography simulations by using a finite-element solver. To
proof applicability to real 3D problems we investigate DUV light propagation
through a structure of size 9 microns times 4 microns times 65 nm. On this
relatively large computational domain we perform rigorous computations (No
Hopkins) taking into account a grid of 11 times 21 source points with two
polarization directions each. We obtain well converged results with an accuracy
of the diffraction orders of about one percent. The results compare well to
experimental aerial imaging results. We further investigate the convergence of
3D solutions towards quasi-exact results obtained with different methods.
