For the logic generations of the 15 nm node and beyond, the printing of pitches at 64nm and below are needed. For EUV lithography to replace ArF-based multi-exposure techniques, it is required to print these patterns in a single exposure process. The k1 factor is roughly 0.6 for 64nm pitch at an NA of 0.25, and k1 0.52 for 56nm pitch. These k1 numbers are of the same order at which model based OPC was introduced in KrF and ArF lithography a decade or so earlier.

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