The slit CD uniformity is 3a 2.6 ～ 4.8nm. The effective factors of slit CD uniformity are considered by the uniformity of relative dose intensity, mask CD and aberration. To achieve of 10% CDU of design rule in DRAM device, it's very important that control of slit CD uniformity. To satisfy EUV PPT target proposed by Hynix, aberration could be improved above 100% compared to the current level.
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