Computational study demonstrates overlay distortion prediction using optical aberrations and non-telecentricity in DRAM devices, highlighting improved precision for EUV lithography systems.
Extreme ultraviolet (EUV) lithography systems have become one of the representative system nodes in the semiconductor industry. As EUV systems have been widely implemented to shrink integrated circuits, the importance of overlay control is increasing as much as patterning control. In terms of overlay control in lithography systems, a projection optics module is a key factor in determining the distortion of the overlay. In this paper, we present characteristics of EUV projection optics affecting overlay and propose a methodology predicting distortion of the overlay by calculating pattern shift using aberrations of EUV projection optics as an input. Also, the non-telecentricity of EUV systems is taken into account while calculating pattern shift as understanding the optical feature of EUV is required to explain the results of calculated distortion. Experimental results of dynamic random-access memory (DRAM) devices are presented to understand different behaviors between the projection optics structure of DUV and EUV scanners.
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Hwang et al. (2024) studied this question.
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