Perturbative analysis of partially coherent illumination for coma aberration measurements

The theory of coma aberration measurement for aerial image sidelobe peaks is extended from coherent illumination to partial illumination. We prove that the intensity difference between the two peaks is linear to the amount of coma aberration in the partially coherent case. Using weak diffraction approximation, we analytically reveal the coherence dependency of the aberration measurement sensitivity for a single line in a bright field. We confirm that our derived formulas are well matched with the numerical lithography simulation results. These results provide guidelines for the measurement condition; higher aberration sensitivity is available under the higher illumination pupil coherence.