A projection aligner of the present invention, in which ultraviolet light
emitted from a lamp housing is split by a fly-eye lens into a large
number of point light sources which are independent of one another.
Further, in this projection aligner, the light is shaped by an aperture,
so that a secondary light source plane is formed. Moreover, after an
exposure area is established by a blind, a photomask is illuminated.
Thereafter, an image of a light source is formed on a pupillary surface
of a projection optical system from light diffracted by the photomask.
Furthermore, a wave front aberration is compensated by an aberration
eliminating filter placed on the pupillary surface of the optical system
of the projection aligner. Then, the image of a circuit pattern is formed
on a wafer. Thereby, the influence of the aberration of the optical
system is eliminated. Consequently, the high-accuracy transferring of the
pattern can be achieved.