Optical element unit

• US 20060238892A1
• Filed: 03/08/2006
• Published: 10/26/2006
• Est. Priority Date: 03/09/2005
• Status: Active Grant

• Current Assignee: CARL Zeiss SMT GmbH (Carl-Zeiss-Stiftung)
• Original Assignee: Carl Zeiss AG (Carl-Zeiss-Stiftung)
• Inventors: Lippert, Johannes
• Granted Patent: US 7,944,628 B2
• Time in Patent Office: Days
• US Class Current: 359/692
• CPC Class Codes: G02B 7/021 for more than one lens
• CPC Class Codes: G02B 7/023 permitting adjustment
• CPC Class Codes: G02B 7/182 for mirrors
• CPC Class Codes: G03F 7/7015 Details of optical elements
• CPC Class Codes: G03G 15/0409 Details of projection optics for projection printing apparatus G03B27/522

Abstract

An optical element unit is provided comprising an optical element group for projecting light along an optical axis of the optical element group and a housing having an inner housing part partly defining a first space and a light passageway between the inner housing part and a second space. The inner housing part receives the optical element group. The optical element group comprises an ultimate optical element located in the region of the light passageway. A load-relieving device is provided adjacent to the ultimate optical element, the load relieving device partly defining the first space and the second space and at least partly relieving the ultimate optical element from loads resulting from pressure differences between the first space.

Claims

1. An optical element unit comprising:

an optical element group for projecting light along an optical axis of said optical element group and

a housing having an inner housing part partly defining a first space and a light passageway between said inner housing part and a second space;

said inner housing part receiving said optical element group;

said optical element group comprising an ultimate optical element located in the region of said light passageway and being part of an ultimate optical element arrangement; and

a load relieving device being provided adjacent to said ultimate optical element arrangement, said load relieving device partly defining said first space and said second space and at least partly relieving said ultimate optical element arrangement from loads resulting from pressure differences between said first space and said second space.

2. The optical element unit according to claim 1, wherein

said ultimate optical element mainly extends in a first plane and has a first projection onto said first plane, said first projection having a first area;

said load relieving device comprises a cover section extending between said housing and said ultimate optical element and having an inner circumference,

said inner circumference being located adjacent to said ultimate optical element and forming an aperture,

said aperture having a second projection onto said first plane, said second projection having a second area being smaller than said first area.

3. The optical element unit according to claim 2, wherein

said ultimate optical element has a first optical element surface located adjacent to said cover section,

said first optical element surface having a first surface region optically used when using said optical element group for projecting light along said optical axis,

said first surface region having a third projection onto said first plane, said third projection being one of substantially identical to said second projection and located within said second projection.

4. The optical element unit according to claim 3, wherein said third projection has a third area corresponding to at least 80% of said second area.

5. The optical element unit according to claim 2, wherein said cover section comprises a thin wall segment extending between said housing and said ultimate optical element and in a circumferential direction of said ultimate optical element.

6. The optical element unit according to claim 1, wherein said load relieving device is not directly contacting said ultimate optical element.

7. The optical element unit according to claim 1, wherein said load relieving device is of sufficient rigidity to prevent direct contact with said ultimate optical element under any pressure difference between said first space and said second space that is to be expected at least during normal use of said optical element unit.

8. The optical element unit according to claim 1, wherein said load relieving device is contacting said ultimate optical element via a sealing device.

9. The optical element unit according to claim 1, wherein

said optical element group comprises a penultimate optical element located adjacent to said ultimate optical element,

said load relieving device is associated to a first optical element surface of said ultimate optical element,

said first optical element surface is one of facing towards said penultimate optical element and facing away from said penultimate optical element.

10. The optical element unit according to claim 1, wherein

said ultimate optical element arrangement comprises at least one ultimate optical element holder holding said ultimate optical element within said housing;

said ultimate optical element holder having a first side facing towards said load relieving device and a second side facing away from said load relieving device,

a third space is defined on said first side of said ultimate optical element holder between said ultimate optical element holder and said load relieving device,

at least one of said housing, said ultimate optical element holder and said ultimate optical element provides at least a first venting passageway towards said third space from said second side of said ultimate optical element holder.

11. The optical element unit according to claim 1, wherein

said optical element group comprises a further optical element;

said load relieving device is a sealing device separating said first space from said second space;

said sealing device is located between said further optical element and said ultimate optical element such that said ultimate optical element is located within said second space;

said sealing device has at least a first translucent section;

12. The optical element unit according to claim 11, wherein said sealing device provides a pressure tight separation between said first space and said second space.

13. The optical element unit according to claim 11, wherein said first translucent section is optically insensitive to movements caused by variations of a pressure difference between said first space and said second space.

14. The optical element unit according to claim 11, wherein said first translucent section comprises a plane parallel plate.

15. The optical element unit according to claim 11, wherein said first translucent section is supported resiliently to minimize deformations of said first translucent section caused by a pressure difference between said first space and said second space.

34. An optical exposure apparatus for transferring an image of a pattern formed on a mask onto a substrate comprising:

a light path;

a mask location located within said light path and receiving said mask;

a substrate location located at an end of said light path and receiving said substrate;

an optical element unit according to claim 1, said optical element unit being located within said light path between said mask location and said and said substrate location.

16. An optical element unit comprising:

an optical element group for projecting light along an optical axis of said optical element group;

a housing; and

a cover device;

said housing having an inner housing part partly defining a first space and a light passageway between said first space and a second space, said inner housing part receiving said optical element group;

said optical element group comprising an ultimate optical element located in the region of said light passageway and having an optically used first surface;

said cover device being mounted to said housing and extending between said housing and said first surface of said ultimate optical element;

said cover device leaving a first surface part of said first surface of said ultimate optical element uncovered while covering a second surface part of said first surface of said ultimate optical element.

17. The optical element unit according to claim 16, wherein said inner circumference of said cover device is located adjacent to said ultimate optical element and forms an aperture.

18. The optical element unit according to claim 16, wherein said cover device has an inner circumference and an outer circumference and is mounted to said housing at said outer circumference.

19. The optical element unit according to claim 16, wherein

said first optical element surface has a first surface region optically used when using said optical element group for projecting light along said optical axis;

said first surface part of said first surface of said ultimate optical element left uncovered by said cover device including said first surface region optically used.

20. The optical element unit according to claim 19, wherein said first surface part of said first surface of said ultimate optical element left uncovered by said cover device is substantially identical to said first surface region optically used.

21. The optical element unit according to claim 16, wherein said cover device comprises a thin wall segment extending between said housing and said ultimate optical element and in a circumferential direction of said ultimate optical element.

22. The optical element unit according to claim 16, wherein said cover device is not directly contacting said ultimate optical element.

23. The optical element unit according to claim 16, wherein said cover device is contacting said ultimate optical element via a sealing device.

24. The optical element unit according to claim 16, wherein

said optical element group comprises a penultimate optical element located adjacent to said ultimate optical element,

said first optical element surface is one of facing towards said penultimate optical element and facing away from said penultimate optical element.

25. The optical element unit according to claim 16, wherein

said ultimate optical element arrangement comprises at least one ultimate optical element holder holding said ultimate optical element within said housing;

said ultimate optical element holder having a first side facing towards said cover device and a second side facing away from said cover device,

a third space is defined on said first side of said ultimate optical element holder between said ultimate optical element holder and said cover device,

at least one of said housing, said ultimate optical element holder and said ultimate optical element provides at least a first venting passageway towards said third space from said second side of said ultimate optical element holder.

26. The optical element unit according to claim 16, wherein said cover device comprises at least one heat exchanging element, said heat exchanging element being connectable to a heat exchanging device for providing at least one of heating and cooling said cover device.

27. An optical element unit comprising:

an optical element group for projecting light along an optical axis of said optical element group;

a housing; and

a sealing device;

said housing having an inner housing part partly defining a first space and a light passageway between said first space and a second space, said inner housing part receiving said optical element group;

said optical element group comprising an ultimate optical element located in the region of said light passageway and a further optical element;

said sealing device separating said first space from said second space;

said sealing device being located between said further optical element and said ultimate optical element such that said ultimate optical element is located within said second space;

said sealing device having at least a first translucent section;

28. The optical element unit according to claim 27, wherein said sealing device provides a pressure tight separation between said first space and said second space.

29. The optical element unit according to claim 27, wherein said first translucent section is optically insensitive to movements caused by variations of a pressure difference between said first space and said second space.

30. The optical element unit according to claim 27, wherein said first translucent section comprises a plane parallel plate.

31. The optical element unit according to claim 27, wherein said first translucent section is supported resiliently to minimize deformations of said first translucent section caused by a pressure difference between said first space and said second space.

32. The optical element unit according to claim 27, wherein said first translucent section is a third optical element of said optical element group.

33. The optical element unit according to claim 27, wherein

at least one ultimate optical element holder is provided holding said ultimate optical element within said housing, said ultimate optical element holder having first side facing towards said cover device and a second side facing away from said sealing device,

a third space is defined on said first side of said ultimate optical element holder between said ultimate optical element holder and said sealing device,

at least one of said housing, said ultimate optical element holder and said ultimate optical element provides at least a first venting passageway towards said third space from said second side of said ultimate optical element holder.

35. A method of holding an optical element, comprising:

providing a housing having an inner housing part partly defining a first space and a light passageway between said inner housing part and a second space, a first pressure prevailing in said first space and a second pressure prevailing in said second space;

providing and holding an optical element in the region of said light passageway, said optical element mainly extending in a first plane, a first part of said optical element partly defining said first space and a second part of said optical element partly defining said second space;

separating said first space and said second space such that a projection of said first part of said optical element onto said first plane is smaller than a projection of said second part of said optical element onto said first plane.

36. The method according to claim 35, wherein said separating said first space and said second space comprises providing a cover device extending between said housing and said optical element.

37. The method according to claim 36, wherein said providing said cover device comprises connecting at least one of said housing and said optical element in a pressure tight manner to said cover device.

38. The method according to claim 36, wherein said providing said cover device comprises providing sealing gap between said cover device and said optical element.

39. A method of holding an optical element, comprising:

providing a housing having an inner housing part partly defining a first space and a light passageway between said inner housing part and a second space, a first pressure prevailing in said first space and a second pressure prevailing in said second space;

providing and holding an optical element in the region of said light passageway;

separating said first space and said second space in a pressure tight but at least partly translucent manner such that said optical element is entirely located within said second space.

40. The method according to claim 39, wherein said separating said first space and said second space comprises providing and holding a sealing device within said housing, said sealing device having at least a first translucent section.