Projection exposure apparatus

A projection exposure apparatus for projecting a predetermined pattern formed on a mask onto a photosensitive substrate, comprising;

• a projection optical system for forming an image of the pattern on said substrate under exposure light having a first wavelength;
• an illumination system for illuminating a mark on said photosensitive substrate with light having a second wavelength different from the first wavelength through said projection optical system so as to attain alignment;
• and said mark,
• said illumination system comprising;
• a light source for emitting the light having the second wavelength;
• a first field stop for defining an illumination region on said photosensitive substrate said first field stop having at least two linear edges which extend in a direction substantially perpendicular to a sagittal direction in a visual field of said projection optical system and which are juxtaposed at a predetermined interval in the sagittal direction;
• and
• a second field stop, for defining an illumination region on said photosensitive substrate, said second field stop having at least two linear edges which extend in a direction substantially perpendicular to a meridional direction in a visual field of said projection optical system and which are juxtaposed to be separated at a predetermined interval in the meridional direction:
• and
• said first and second field stops being juxtaposed to be separated in an optical axis direction of said illumination system by a distance according to an astigmatism of said projection optical system caused by the light having the second wavelength, and said edges of said first and second field stops being focused on said photosensitive substrate through said projection optical system.