Patent ID: 8345221

Claim:
A method for measuring a spherical aberration amount of a projection optical system that projects an image of a pattern formed on an original plate onto a substrate, the method comprising: obtaining a first focal position in a direction of an optical axis of the projection optical system under a first measurement condition by illuminating a mark on the side of an object plane using the first measurement condition so as to project an image of the mark on the side of the object plane onto a mark on the side of an image plane using the projection optical system, and by detecting light passing through the mark on the side of the image plane at a plurality of positions in the direction of the optical axis; obtaining a second focal position in the direction of the optical axis of the projection optical system under a second measurement condition by illuminating the mark on the side of the object plane using the second measurement condition so as to project an image of the mark on the side of the object plane onto the mark on the side of the image plane using the projection optical system, and by detecting light passing through the mark on the side of the image plane at a plurality of positions in the direction of the optical axis; and calculating the spherical aberration amount of the projection optical system based on a difference between the first focal position and the second focal position, wherein the first measurement condition is a condition under which the focal position in the direction of the optical axis with respect to the spherical aberration amount does not change, and wherein the second measurement condition is a condition under which the focal position in the direction of the optical axis with respect to the spherical aberration amount changes.