Patent ID: 7511799

Claim:
A lithographic projection apparatus comprising: an illumination system configured to illuminate a mask pattern with radiation from an intensity distribution in a pupil, said pupil having four quadrants defined by two axes that intersect one another in a center of the pupil, said intensity distribution having a first pole located in one of said quadrants, a second pole located in one of said quadrants opposite to the quadrant in which said first pole is located, a third pole located in one of the quadrants that contains neither of said first or second poles, and a fourth pole located in the quadrant located opposite to the quadrant in which said third pole is located, each of said first, second, third, and fourth poles having an enhanced intensity with respect to an intensity surrounding said poles, and a projection system configured to project an image of the mask pattern, formed by diffracted beams produced from the pattern by radiation from the intensity distribution, onto a photoresist layer coated on a substrate, wherein the projection system comprises an aperture device arranged to transmit zeroth order diffracted beams associated with the first and second poles, and to block zeroth order diffracted beams associated with the third and fourth poles.