In this paper we perform a fundamental study on the impact of mask absorber in ArF immersions
lithography: the mask 3D effects. From simulations and analysis of diffraction coefficients we could
identify a range of relevant features and imaging and placement phenomena. For these features,
experimental results were obtained to pinpoint the mask 3D effects. We will demonstrate how to
model and understand the mask 3D effects and give solutions to counteract the mask 3D effects.