Influence of partial coherent illumination on aerial image based aberration measurement of projection optics in lithographic tools

摘要

In this paper, the aberration measurement technique using aerial image sensor (AIS) is further derived, and the influence of partially coherent illumination on the performance of this technique is analyzed comprehensively in practice. The AIS based technique detects the intensity of the aerial image to obtain the wavefront aberration on each sampling point of the exit pupil using a set of 36 binary gratings with different pitches and orientations. The simulation work conducted by the lithographic simulator PROLITH has demonstrated that the aberration measurement errors grow with the partial coherent factor increasing. Two effects of the partially coherent illumination are proposed to interpret such influence that causes the measurement errors.