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EUV lithography has been ramped to successful volume manufacturing through a combination of improvements in process technology, layout design and device interactions, and also optimization of the overall product integration to reduce undesirable interactions. Because EUV has additional sources of systematic and stochastic variation that did not exist in DUV lithography, it is now even more important to have accurate predictive capability to test and understand the design and lithography process interactions. EUV-specific physical behavior such as shadowing, flare, mask topography (i.e., Mask3D) effects, mask stack reflectivity, mask absorber behavior and other effects are key differences in how EUV forms an image on the mask and subsequently on the wafer. The reflective mask substrate and EUV-specific mask absorber stack are therefore highly important technologies to optimize as the industry pushes both low NA (0.33NA) and high NA (0.55NA) technologies to cover the patterning requirements of upcoming 3nm and below technology nodes. Recently there have been substantial industry interest in optimizing EUV mask stacks to further enhance imaging behavior and achieve better pattern resolution, increase process window, lower stochastic defectivity and optimize flare. Several different options have been proposed for these new EUV mask stacks for lower K1 EUV patterning. All of these new options require excellent simulation accuracy in OPC, SrAF placement, OPC verification and ILT mask synthesis steps in order to realize the benefits of the new mask stacks. In this paper we will focus on analyzing and improving the accurate prediction of a range of new EUV mask stack options for full-chip OPC/ILT compatible compact models. We will show for advanced mask designs the accuracy requirements and capability of leading-edge compact models. The accuracy requirements and capability will be referenced to fully rigorous electromagnetic solver (e.g., Mask3D) results to ensure industry needs are met. We will also explore the mask stack options to highlight the imaging benefits for different material thickness, refractive index (n) and extinction coefficient (k) on important mask pattern feature and layer types.
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