Importance

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Abstract

A method includes: generating a designed mask overlay mark associated with an actual mask overlay mark to be formed in a mask; forming the actual mask overlay mark in the mask based on the designed mask overlay mark, the actual mask overlay mark including a plurality of overlay patterns; forming a device feature pattern adjacent to the actual mask overlay mark; forming an alignment of the mask by a mask metrology apparatus including a light source having a wavelength and a numerical aperture, wherein a pitch between adjacent two of the plurality of overlay patterns does not exceed the wavelength divided by twice the numerical aperture; and forming a pattern in a layer of a wafer by transferring the device feature pattern while the mask is under the alignment.

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First Claim