Optical element for the beam guidance of imaging light in projection lithography
An optical element is configured to guide imaging light in projection lithography. The optical element has a main body and at least one optical surface carried by the main body. At least one compensation weight element, which is attached to the main body, serves for a weight compensation of a figure deformation of the optical surface caused by gravity. This results in an optical element with a small figure deformation at the use location.
1. An optical element, comprising:
a main body;
an optical surface supported by the main body;
a compensation weight element supported by the main body, the compensation weight element comprising a compensation weight; and
a lever connecting the compensation weight to the main body in a connection region so that a direction of a gravitational force of the compensation weight, proceeding from a center of mass thereof, extends a distance from the connection region,
wherein:
the lever has an adjustable length, and/or the lever has an adjustable direction; and
the compensation weight element is configured to compensate a figure deformation of the optical surface caused by gravity.
2. The optical element of claim 1 , wherein the optical element comprises a mirror, and the compensation weight element is supported by a side of the main body that faces away from the optical surface.
3. The optical element of claim 2 , wherein the compensation weight element is supported by an edge of the main body.
4. The optical element of claim 1 , wherein the optical element comprises a mirror, and the compensation weight element is supported by an edge of the main body.
5. The optical element of claim 1 , wherein the compensation weight element is supported by the main body in a region of a center-of-mass axis of the optical element.
6. The optical element of claim 1 , further comprising a plurality of bearing sites configured so that the optical element is bearable in a bearing receptacle via the plurality of bearing sites, wherein the compensation weight element is between two bearing sites that are adjacent each other in a circumferential direction of the optical element.
7. The optical element of claim 6 , further comprising a plurality of compensation weight elements, wherein respectively one compensation weight element is arranged between all bearing sites that are adjacent to one another in the circumferential direction.
8. The optical element of claim 1 , wherein the compensation weight element is supported by the main body in an interlocking manner.
9. The optical element of claim 1 , wherein the compensation weight element is supported by the main body in an integrally bonded manner.
10. The optical element of claim 1 , wherein the lever has an adjustable length.
11. The optical element of claim 1 , further comprising an additional element connecting the compensation weight element to the main body.
12. The optical element of claim 1 , further comprising a plurality of compensation weight elements, wherein each compensation weight element is configured compensate a figure deformation of the optical surface caused by gravity.
13. The optical element of claim 12 , wherein:
the optical element comprises a mirror; and
at least one of the following holds:
at least one of the plurality of compensation weight elements is supported by a side of the main body that faces away from the optical surface; and
at least one of the plurality of compensation weight elements is supported by an edge of the main body.
14. The optical element of claim 12 , wherein at least one of the compensation weight elements is supported by the main body in a region of a center-of-mass axis of the optical element.
15. An imaging optical unit, comprising:
an optical element according to claim 1 ,
wherein the imaging optical unit is configured to image an object field into an image field.
16. An optical system, comprising:
an illumination optical unit configured to illuminate an object field; and
an imaging optical unit configured to image an object field into an image field,
wherein the imaging optical unit comprises an optical element according to claim 1 .
17. A projection exposure apparatus, comprising:
a light source configured to produce illumination light;
an illumination optical unit configured to illuminate an object field with the illumination light; and
an imaging optical unit configured to image an object field into an image field,
wherein the imaging optical unit comprises an optical element according to claim 1 .
18. A method of using a projection exposure apparatus comprising an illumination optical unit and an imaging optical unit, the method comprising:
using the illumination optical unit configured to illuminate an object in an object field; and
using the imaging optical unit configured to image an object field into an image field,
wherein the imaging optical unit comprises an optical element according to claim 1 .
19. The optical element of claim 1 , wherein the lever has an adjustable direction.
20. A method, comprising:
producing a blank of an optical element taking account of a negative deformation allowance so that the optical element has a desired figure only under a gravitational force of at least one compensation weight;
transporting the blank to a use location of an apparatus for projection lithography; and
attaching the at least one compensation weight element to a main body of the optical element taking account of a gravitational acceleration at the use location for weight compensation of a figure deformation of an optical surface of the optical element caused by gravity,
wherein attaching the at least one compensation weight element to the main body of the optical element comprises:
a) attaching at least one raw compensation weight element to the main body of the optical element, the at least one raw compensation weight element being designed to overcompensate an expected effect of gravity on the figure deformation of the optical surface of the optical element and
b) after a), removing part of the at least one raw compensation weight element to reduce its weight to achieve a desired figure deformation of the optical surface of the optical element.
21. The method of claim 20 , wherein the method results in the optical surface of the optical element having a deformation from a theoretical best fit which is less than 350 pm.
22. The method of claim 20 , wherein the method results in the optical surface of the optical element having a deformation from a theoretical best fit which is approximately 13 pm.