Photolithography simulations are widely used to predict, to analyze and to design imaging
processes in scanners used for IC manufacture. The success of these efforts is strongly dependent
on their ability to accurately capture the key drivers responsible for the image formation. Much
effort has been devoted to understanding the impacts of illuminator and projection lens models on
the accuracy of the lithography simulations [1-3]. However, of equal significance is the role of
the mask models and their interactions with the illuminator models.