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Vote-taking lithography is a method for mitigating mask defects, which has been applied in the 1980s to enhance yield. Vote-taking sums up N different mask images with identical content, each at 1/N dose, to mitigate the defects on each individual mask. The fundamental assumption is that the mask defects do not correlate in position from mask to mask, and so each individual defect will be blended with good images from the other N - 1 masks. Vote-taking has recently been reconsidered for extreme ultraviolet (EUV) lithography, where it might provide a temporary solution for situations in which the defectivity conditions are not yet meeting expectations. This paper provides a thorough experimental assessment of the implementation of vote-taking and discusses its pro's and con's. Based on N = 4 vote-taking, we demonstrate the capability to mitigate different types of mask defects. We found additional benefits of blending different mask images, distinct from mask defect reduction. Experimental results will be shown that demonstrate improved critical dimension uniformity (CDU), both local CDU and intrafield CDU, reduced overlay errors, and smaller stochastic defect levels. Finally, we perform dedicated throughput calculations based on the qualification performance of ASML's NXE:3400B scanner. This work must be seen in the light of an open-minded search for options to optimally enable and implement EUV lithography. Although defect-free masks and EUV pellicles are without argument essential for most of the applications, we investigate whether some applications could benefit from vote-taking. [ABSTRACT FROM AUTHOR]

Directed self-assembly (DSA) of block copolymers (BCP) is considered a promising patterning approach for the 7-nm node and beyond. Specifically, a graphoepitaxy process using a cylindrical phase BCP may offer an efficient solution for patterning randomly distributed contact holes with subresolution pitches, such as found in via and cut mask levels. In any graphoepitaxy process, the pattern density impacts the template fill (local BCP thickness inside the template) and may cause defects due to over- or underfilling of the template. In order to tackle this issue thoroughly, the parameters that determine template fill and the influence of template fill on the resulting pattern should be investigated. Using three process flow variations (with different template surface energy), template fill is experimentally characterized as a function of pattern density and film thickness. The impact of these parameters on template fill is highly dependent on the process flow, and thus prepattern surface energy. Template fill has a considerable effect on the pattern transfer of the DSA contact holes into the underlying layer. Higher fill levels give rise to smaller contact holes and worse critical dimension uniformity. These results are important for DSA-aware design and show that fill is a crucial parameter in graphoepitaxy DSA. [ABSTRACT FROM AUTHOR]