Theoretical analysis of coma aberration measurement for aerial image sidelobe peaks

By analyzing aerial images, we characterize the lowest order coma aberration measurements for the projection optics of a microlithography exposure apparatus based on scalar diffraction theory. Our developed method for measuring the coma aberration exploits the intensity difference between the sidelobe peaks appearing near the boundaries of the bright field ("negative") single-line or plural-line patterns. Our method further demonstrates linearity between the intensity difference of the sidelobe peaks and the amount of residual lowest order coma aberration. We analyze the coma aberration sensitivity formula and determine the duty ratio of the line-and-space pattern that realizes the highest aberration sensitivity.