Measurement method of Zernike coma aberration coefficient

摘要

The present invention provides a method for measuring lens aberration of light on a wafer. The method includes printing a pattern on the wafer by projecting the pattern through a lens in a plurality of pitches and directions; measuring a plurality of critical dimension (CD) differences between two locations on the printed pattern for each of the plurality of pitches and directions; and determining at least one Zernike coma aberration coefficient based on the measured plurality of CD differences. The method in accordance with the present invention measures the CD difference between two locations on the printed pattern on a wafer. This CD difference is then used to calculate the Zernike coma aberration coefficients. No projected reference pattern is required to measure the CD difference, and thus an absolute coma aberration can be calculated. Also, the coma aberration coefficients are based on the light projected onto the wafer, allowing chip manufacturers to more precisely select a stepper with an appropriate lens aberration. This in turn allows better quality control in the clarity of patterns printed on wafers.