Accuracy and performance of 3D mask models in optical projection lithography

Abstract

Different mask models have been compared: rigorous electromagnetic field (EMF) modeling, rigorous EMF modeling with decomposition techniques and the thin mask approach (Kirchhoff approach) to simulate optical diffraction from different mask patterns in projection systems for lithography. In addition, each rigorous model was tested for two different formulations for partially coherent imaging: The Hopkins assumption and rigorous simulation of mask diffraction orders for multiple illumination angles. The aim of this work is to closely approximate results of the rigorous EMF method by the thin mask model enhanced with pupil filtering techniques. The validity of this approach for different feature sizes, shapes and illumination conditions is investigated

Robust source and mask optimization compensating for mask topography effects in computational lithography

“…Continuous development of advanced computational lithography techniques are required to reduce the deterioration of image fidelity and increase the process window (PW) in ultra lowk 1 optical lithography [1]. One of the limitations to PW is the noticeable difference in best focus among various feature sizes [2,3]. This best focus shift effect, together with several other significant physical effects, is investigated in rigorous 3D mask simulations [4].…”

Joint optimization of source, mask, and pupil in optical lithography

“…1 Rigorous 3D mask experiments have confirmed that mask topography is a leading cause due to the fact that the thickness of the mask absorber produces phase errors among different diffraction orders. 2,3 Unfortunately, the rigorous electromagnetic field (EMF) modeling used to describe light diffraction from the mask generally involves intensive computation, 4 which limits the wide adoption of rigorous 3D mask modeling for practical large layout simulations in advanced resolution enhancement techniques (RETs) such as source and mask optimization (SMO). 5,6 Additionally, although SMO is a powerful and effective technique which provides more flexibility regarding both the mask design and illumination configuration adjustment, [7][8][9][10] it is inadequate to control the phase in the lens pupil.…”