At this moment, extreme ultraviolet (EUV) systems equipped with a 0.33 numerical aperture (NA) have proven themselves and are successfully applied in high-volume manufacturing. The next step is 0.55 NA and is ready to enter mass production. This so-called high NA scanner, targeting an ultimate resolution of 8 nm half-pitch, will bring multiple benefits to the semiconductor market such as reduction of process complexity, yield improvement, higher resolution enabling printability of smaller features at increased density, and cost of technology reduction. It will extend Moore’s law for at least another decade. A lens design, capable of providing the required NA, has been identified; this so-called anamorphic lens will provide 8 nm resolution in all orientations. Paired with new, faster stages, and more accurate sensors providing the tight focus and overlay control, it enables future nodes. The first 0.55 NA scanner is located in the so-called high NA Lab in Veldhoven where it is interfaced with a track and operated in cooperation with Imec, Leuven. It also allows for early customer access. We will provide the backgrounds of the architecture of the high NA tool. Next to this, an update will be given on the status of the imaging and overlay performance of this exposure tool.
An increased interest to stitching for High NA EUVL is observed; this is driven by expected higher demand of larger size chips for various applications. In the past a recommendation was published [1] to have 1-5 um band where no critical structures of a High NA layer would be allowed. In [2], we have introduced new insights on at-resolution stitching. In this publication, we present new experimental results obtained on NXE:3400B scanner. In the past we showed NXE feasibility results of vertical lines and contact holes stitching at relaxed resolution (40-48 nm pitch) in a single wafer location. In this study we evaluate stitching behavior through slit at more aggressive resolutions (P36 and P24 lines / spaces). We provide an overview of interactions in the stitching area such as aerial image interactions, absorber reflection, absorber to black border transition, black border vicinity impact and show corresponding experimental and simulations results. We formulate initial requirements for black border edge placement control and show performance of new masks. For stitching with low-n masks, we discuss using sub-resolution gratings to suppress the elevated mask reflectivity. We show rigorous simulations of stitched images, its sensitivity to overlay errors and propose mitigation mechanisms for OPC. Finally, an overview of stitching enablers will be described: from improved reticle black border position accuracy and absorber reflectivity control to mask resolution and OPC requirements.
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