TIS & pupil transmittance distribution in measurement optics

The progress of semiconductor requires imaging optics with the highest accuracy of an exposure system. Miniaturization of LSZ needs the projection lenses with high accuracy. And it also needs the alignment optics with high accuracy. The alignment system with the alignment optics must measure a pattern position within one-third of the fine pattern width. Therefore the required performance of the optics is very high. In this paper, an imaging type alignment system is discussed. The alignment system has illumination optics, imaging optics, image pickup devices, and an image processing system.