Fast modeling of 3D planar resist images for high-NA projection lithography

A 3D planar pseudo-vector approach to modeling resist exposure has been implemented for optical projection lithography. The approach allows for high numeric aperture effects revealed by others in the resist latent images; comparisons made show its fine agreement with rigorous vector modeling up to NA value of 0.7. Fast Fourier transform technique has been applied to reduce mask and resist (including postbake) modeling runtime; the effects of finite accuracy approximations of the mask areas and mask periodicity have been investigated and compensated. The overall performance of the exposure model has been optimized to be 10X faster than for a similar vertical propagation model. A modified `cell' algorithm has also been used to model resist development; this resulted in more accurate resist profiles for the same latent image accuracy, providing additional runtime savings to resist profile simulations.