Patent ID: 6839132

Claim:
An aberration measuring method of a projection optical system, comprising: preparing an exposure apparatus comprising a light source, an illuminating optical system which divides a light from the light source into a plurality of point sources to form a secondary light source and which guides an illuminating light from the secondary light source into a finite region of a photomask, and a projection optical system which transfers a reduced projected image of a transmitted light generated through a pattern disposed in the photomask onto a wafer; collectively irradiating the finite region of the photomask in which a diffraction grating is formed with the illuminating light; projecting a 0th-order diffracted light and 1st-order diffracted light passed through the photomask onto a first measurement plane conjugated with the secondary light source by using the projection optical system; measuring a relation of projected positions in the first measurement plane between the 0th-order diffracted light and 1st-order diffracted light of the light emitted from one arbitrary point source in the secondary light source; projecting the 0th-order diffracted light and 1st-order diffracted light onto a second measurement plane which is conjugated with the secondary light source and in which the position of the light of an optical axis direction is different by using the projection optical system; measuring the relation of the projected positions of the second measurement plane between the 0th-order diffracted light and 1st-order diffracted light of the light emitted from the point source; and obtaining lay aberration concerning the light emitted from the point source on the basis of the obtained two relations of projected positions.