Method for distortion correction in a microlithographic projection exposure apparatus
View Patent ↗For the correction of anamorphism in the case of a projection lens of an EUV projection exposure apparatus for wafers it is proposed to tilt the reticle bearing the pattern to be projected and preferably also the wafer by a small angle about an axis that is perpendicular to the axis A of the lens and perpendicular to the scan direction and that in each instance passes through the middle of the light field generated on the reticle or on the wafer. For the correction of a substantially antisymmetric quadratic distortion the reticle and/or the substrate is instead rotated about an axis of rotation that is disposed at least approximately parallel to an optical axis of the projection lens.
1. A microlithographic projection exposure apparatus, comprising:
a reticle stage for moving a reticle along a scan direction;
a wafer stage for moving a wafer;
a projection lens being non-telecentric on an object side and having
an optical axis,
a usable field region that does not contain the optical axis, and
a substantially antisymmetric quadratic distortion in the field region; and,
a manipulator which is configured to rotate the reticle, the wafer or both about an axis of rotation that is disposed at least approximately parallel to the optical axis.
2. The apparatus of claim 1 , wherein the axis of rotation extends through the field region.
3. The apparatus of claim 2 , wherein the axis of rotation lies in a plane of symmetry of the projection lens in which the optical axis also extends.
4. The apparatus of claim 1 , comprising a further manipulator which is configured to change the spatial position of at least one optical element contained in the projection lens.
5. The apparatus of claim 4 , wherein the further manipulator is configured to displace the at least one optical element parallel to the optical axis.
6. The apparatus of claim 4 , wherein the further manipulator is configured to displace the at least one optical element translationally in a plane perpendicular to the optical axis.
7. The apparatus of claim 4 , wherein the further manipulator is configured to displace the at least one optical element along the scan direction.
8. The apparatus of claim 4 , wherein the further manipulator is configured to displace the at least one optical element perpendicular to the scan direction.
9. The apparatus of claim 4 , wherein the further manipulator is configured to tilt the at least one optical element about a tilt axis that is disposed at least approximately perpendicular to the optical axis of the projection lens and to the scan direction.
10. The apparatus of claim 4 , wherein the further manipulator is configured to tilt the at least one optical element about a tilt axis that is disposed at least approximately perpendicular to the optical axis of the projection lens and parallel to the scan direction.
11. The apparatus of claim 1 , further comprising a device which is configured to change the linear magnification of the projection lens.
12. The apparatus of claim 1 , wherein the projection lens comprises only reflective optical elements.
13. The apparatus of claim 12 , wherein the projection lens further comprises at least four mirrors.
14. The apparatus of claim 1 , wherein the ratio of the correction of the distortion to the angle of rotation generated by the manipulator is greater than 1.5 nm/μrad.