Alignment method and apparatus, lithographic apparatus, device manufacturing method, and alignment tool

摘要

In one embodiment, front to back side alignment optics are used to project a mark on the back side of a substrate. The front to back side alignment optics are arranged such that the image projected into the image window of the front to back side alignment optics is a translational replica of the mark on the back side of the substrate. One potential advantage of such an arrangement is that any slight inaccuracies in the location of the optical axis do not result in inaccuracies in the image of the substrate mark. The translational replica image can be used for alignment of the substrate.