A new scalar planewave model for high NA lithography simulations

A high NA photolithography simulator has been developed based on the angular spectrum analysis of planewaves. Spatial partial coherence is modelled using Van Cittert-Zernike theorem, which allows the extended source in a stepper to be divided into a number of point sources. Fast Fourier transform is applied to the coherent imaging by the point sources, leading to an efficient computation of the intensities in the image space. Special attention is devoted to source discretization to avoid the intensity fluctuations and improve the speed performance. The simulator can be used to calculate the aerial images of full circuit cells in a time scale proportional to NlogN. For resist profile calculations, a new approximation method has been developed for modelling photoresist bleaching during a high NA stepper exposure. The simulator has been applied to simulation-based global proximity correction and design rule generation for IC manufacturing