Patent ID: 6947192

Claim:
A photolithography tool comprising: a light source outputting light for illuminating a reticle; condenser optics positioned to receive light from said light source, said condenser optics positioned to direct an optical beam formed from said light through said reticle; and projection optics configured to form an image of said reticle onto a substrate, said projection optics having an exit pupil, said projection optics including: a first cubic crystalline optical element aligned along an optical axis, said first cubic crystalline optical element having intrinsic birefringence that contributes to retardance in said exit pupil, said intrinsic birefringence of said first optical element having increased magnitude at a first set of lobes at a first set of locations arranged in an azimuthal direction about said optical axis; a second cubic crystalline optical element aligned along said optical axis, said second cubic crystalline optical element having intrinsic birefringence that contributes to retardance in said exit pupil, said intrinsic birefringence of said second optical element having increased magnitude at a second set of lobes at a second set of locations arranged in an azimuthal direction about said optical axis; a third cubic crystalline optical element aligned along said optical axis, said third cubic crystalline optical element having intrinsic birefringence that contributes to retardance in said exit pupil, said intrinsic birefringence of said third optical element having increased magnitude at a third set of lobes at a third set of locations arranged in an azimuthal direction about said optical axis, wherein said first, second, and third cubic crystalline optical elements have a common lattice direction aligned parallel to said optical axis and said first, second, and third cubic crystalline optical elements have their respective crystal lattices selectively azimuthally rotated with respect to each other to reduce retardance over a substantial portion of said exit pupil, said first set of lobes being selectively azimuthally rotated with respect to said second set of lobes and said second set of lobes being selectively azimuthally rotated with respect to said third set of lobes such that said first set of lobes, said second set of lobes, and said third set of lobes are oriented differently with respect to each other.