Microlithographic projection exposure apparatus

1. A projection exposure apparatus, comprising:

a birefringent retardation arrangement comprising a retardation element, the retardation element comprising:

a first subelement comprising an optically positively uniaxial crystal material which has a first optical crystal axis; and

a second subelement comprising an optically negatively uniaxial crystal material which has a second optical crystal axis and which is arranged along an element axis of the retardation element before or after the first subelement,

wherein:

the first crystal axis and the second crystal axis are disposed in a plane perpendicular to an optical axis of the projection exposure apparatus;

the first crystal axis and the second crystal axis are either arranged at an angle of 0° ±5° relative to each other or at an angle of 90° ±5° relative to each other; and

the projection exposure apparatus is a microlithographic projection exposure apparatus.

2. A projection exposure apparatus as set forth in claim 1 , wherein the first subelement and the second subelement are substantially in the form of plane-plates.

3. A projection exposure apparatus as set forth in claim 1 , wherein the first subelement and/or the second subelement is of a thickness profile which varies transversely with respect to the optical axis of the projection exposure apparatus.

4. A projection exposure apparatus as set forth in claim 1 , wherein the retardation element is of a rotationally symmetrical configuration relative to the element axis.

5. A projection exposure apparatus as set forth in claim 1 , wherein the retardation element axis is parallel to the optical axis of the projection exposure apparatus.

6. A projection exposure apparatus as set forth in claim 1 , wherein the first subelement and/or the second subelement is/are arranged on a carrier element of optically isotropic material.

7. A projection exposure apparatus as set forth in claim 1 , wherein for light passing through in parallel relationship with the projection optical axis of the projection exposure apparatus, of a predetermined working wavelength, the retardation arrangement produces a retardation of R=R 0 +K*λ, wherein K is at least 3.

8. A projection exposure apparatus as set forth in claim 1 , wherein with a mutually parallel arrangement of the first and second crystal axis one of the two subelements whose crystal material has a greater mean refractive index than that of the other subelement causes a greater retardation for light passing through the retardation element along the element axis than the other subelement.

9. A projection exposure apparatus as set forth in claim 1 , wherein the arrangement further comprises a second retardation element arranged relative to the first retardation element so that the optical crystal axes of the subelements of optically positively uniaxial material are respectively oriented in mutually perpendicular relationship and the optical crystal axes of the subelements of optically negatively uniaxial material are respectively oriented in mutually perpendicular relationship.

10. A projection exposure apparatus as set forth in claim 9 , wherein the arrangement further comprises at least one third retardation element arranged relative to the first and second retardation elements so that in a subelement of optically positively uniaxial material of the third retardation element the optical crystal axis is oriented at an angle different from an integral multiple of 90° relative to the respective optical crystal axes of the subelements of optically positively uniaxial material in the first and second retardation elements.

11. A projection exposure apparatus as set forth in claim 9 , wherein the retardation elements are arranged in immediately following relationship along the optical axis of the projection exposure apparatus.

12. A projection exposure apparatus as set forth in claim 11 , wherein the respective mutually following retardation elements are arranged in direct contact with each other.

13. A projection exposure apparatus as set forth in claim 1 , wherein the optically positively uniaxial crystal material is selected from the group consisting of crystalline quartz (SiO 2 ) and magnesium fluoride (MgF 2 ).

14. A projection exposure apparatus as set forth in claim 1 , wherein the optically negatively uniaxial crystal material is selected from the group consisting of sapphire (Al 2 O 3 ) and lanthanum fluoride (LaF 3 ).

15. An arrangement, comprising:

a retardation element, the retardation element comprising:

a first subelement comprising an optically positively uniaxial crystal material which has a first optical crystal axis; and

a second subelement comprising an optically negatively uniaxial crystal material which has a second optical crystal axis and which is arranged along an element axis of the retardation element before or after the first subelement;

wherein:

the first crystal axis and the second crystal axis are respectively disposed in a plane perpendicular to an optical axis of the arrangement;

The first crystal axis and the second crystal axis are either arranged at an angle of 0° ±5° relative to each other or at an angle of 90° ±5° relative to each other;

the first subelement and/or the second subelement have a thickness profile varying transversely with respect to the optical system axis; and

the arrangement is a birefringent retardation arrangement.

16. An arrangement, comprising:

a retardation element, the retardation element comprising:

a first subelement comprising an optically positively uniaxial crystal material which has a first optical crystal axis; and

a second subelement comprising an optically negatively uniaxial crystal material which has a second optical crystal axis and which is arranged along an element axis of the retardation element before or after the first subelement;

wherein:

the first crystal axis and the second crystal axis are respectively disposed in a plane perpendicular to an optical axis of the arrangement;

the first crystal axis and the second crystal axis are either arranged at an angle of 0° ±5° relative to each other or at an angle of 90° ±5° relative to each other;

the optically negatively uniaxial crystal material is selected from the group consisting of sapphire (Al 2 O 3 ) and lanthanum fluoride (LaF 3 ); and

the arrangement is a birefringent retardation arrangement.

17. An arrangement, comprising:

a retardation element, the retardation element comprising:

a first subelement comprising an optically positively uniaxial crystal material which has a first optical crystal axis; and

a second subelement comprising an optically negatively uniaxial crystal material which has a second optical crystal axis and which is arranged along an element axis of the retardation element before or after the first subelement;

wherein:

the first crystal axis and the second crystal axis are respectively disposed in a plane perpendicular to an optical axis of the arrangement;

the first crystal axis and the second crystal axis are either arranged at an angle of 0° ±5° relative to each other or at an angle of 90° ±5° relative to each other;

wherein the optically positively uniaxial crystal material comprises magnesium fluoride (MgF 2 ); and

the arrangement is a birefringent retardation arrangement.

18. An apparatus, comprising:

an illumination device; and

a projection objective,

wherein the illumination device and/or the projection objective comprises a retardation arrangement as set forth in claim 15 , and the apparatus is a microlithographic projection exposure apparatus.

19. A process, comprising:

using the projection exposure apparatus as set forth in claim 18 to provide a microstructured component.

20. The process of claim 19 , wherein the process comprises:

providing a substrate to which a layer of a light-sensitive material is at least partially applied;

providing a mask having structures to be reproduced; and

projecting at least as part of the mask on to a region of the layer using the projection exposure apparatus.