Optical arrangement having improved temperature distribution within an optical element

• US 6,521,877 B1
• Filed: 11/22/2000
• Issued: 02/18/2003
• Est. Priority Date: 11/24/1999
• Status: Expired due to Term

• Current Assignee: CARL Zeiss SMT AG (Carl-Zeiss-Stiftung)
• Original Assignee: Carl-Zeiss-Stiftung
• Inventors: Holderer, Hubert, Hummel, Wolfgang, Becker, Jochen, Wagner, Christian, Xalter, Stefan, Von Bünau, Rudolf, Müller-Rissmann, Werner
• Primary Examiner(s): Allen, Stephone B.
• Assistant Examiner(s): HILL, BRADFORD K
• Application Number:
  US09/721,451
• Time in Patent Office: 818 Days
• Field of Search: 250/201.1, 250/216, 250/548, 359/290, 359/291, 359/820, 355/67, 355/30
• US Class Current: 250/201.1
• CPC Class Codes: G03F 7/70891 Temperature

Abstract

An optical arrangement, in particular a microlithographic projection printing installation, has in particular a slot-shaped image field or rotationally non-symmetrical illumination. A refractive optical element, e.g. a lens (2), is heated by the rotationally non-symmetrical radiated impingement (3) of a light source. At least one electric heating element is coupled to the optical element. Said heating element comprises a resistance heating coating carried by the optical element. In the region of the surface (3) of the optical element acted upon by the radiation of the light source the resistance heating coating is substantially optically transparent. It comprises a plurality of parallel, electrically mutually insulated coating strips (5 to 10). A heating current source (17 to 19) is additionally part of the heating element. By virtue of the combined heating of the optical element by the radiated impingement (3) and the resistance heating, a correction of imaging defects induced by illumination in the optical element is achieved by means of a symmetrical and/or homogeneous temperature and refractive index distribution.

Claims

1. An optical arrangement comprising a light source, which emits radiation, and a refractive optical element, which is heated by being acted upon in a rotationally non-symmetrical manner by the radiation, wherein at least one electric heating element is coupled to the optical element, wherein

the heating element comprises:

a resistance heating coating, which is carried by the optical element (4) and which is substantially optically transparent in the region of the surface (3) of the optical element (4) acted upon by the radiation of the light source and comprises a plurality of parallel, electrically and mutually insulated coating strips (5 to 10);

as well as a heating current source (17 to 19).

2. An optical arrangement as claimed in claim 1, wherein the coating strips (5 to 10) form a layer which substantially covers the optical element (4) at least in the region surrounding the surface (3) acted upon by the radiation of the light source, wherein only narrow gaps (11) remain between the individual coating strips (5 to 10).

3. An optical arrangement as claimed in claim 1, wherein the coating strips (5 to 10) carry an anti-reflecting coat (23) at the side remote from the optical element (4).

4. An optical arrangement as claimed in claim 3, wherein the anti-reflecting coat (23) is a continuous coat on the optical element (4).

5. An optical arrangement as claimed in claim 1, wherein the coating strips (5 to 10) are made of a material, which in the region of the wavelength of the radiation has substantially the same refractive index as the material of the optical element (4).

6. An optical arrangement as claimed in claim 1, wherein at least two coating strips (5 to 10) have electrical resistances per unit length which differ from one another.

7. An optical arrangement as claimed in claim 1, wherein the coating strips (7, 8) comprise a plurality of zones (14, 15, 16) of differing electrical resistance per unit length.

8. An optical arrangement as claimed in claim 7, wherein a continuous change of the electrical resistance per unit length is effected between the zones (14, 15, 16) along the coating strips (7, 8).

9. An optical arrangement as claimed in claim 1, wherein the coating strips (5 to 10) are disposed mirror-symmetrically relative to a meridional plane of symmetry (12), which lies parallel to the coating strips (5 to 10).

10. An optical arrangement as claimed in claim 9, wherein the coating strips (7, 8;

6, 9;

5, 10) associated mirror-symmetrically with one another as a result of the meridional plane of symmetry (12) have identical electrical resistances.

11. An optical arrangement as claimed in claim 1, wherein the heating current source comprises at least two electric supply devices (17 to 19) and wherein the coating strips (7, 8;

6, 9;

5, 10) associated mirror-symmetrically with one another as a result of the meridional plane of symmetry (12) are heated by the same electric supply device (17;

18;

19).

12. An optical arrangement as claimed in claim 1, wherein the heating current source (17 to 19) has a communication link to a heating current control circuit (20), which preselects the outputs to be delivered by the electric supply devices (17;

18;

19).

13. An optical arrangement as claimed in claim 12, wherein the heating current control circuit (20, 21) has a communication link to a sensor (22), which measures the imaging properties of the optical element (4) and/or optical arrangement, and the preselection of the outputs to be delivered by the electric supply devices (17, 18, 19) is effected in dependence upon the measurement result of the sensor (22).

14. An optical arrangement as claimed in claim 13, wherein the sensor (22) is a position-sensitive sensor, which is disposed in a focal plane of the optical element (4) and/or optical arrangement.

15. An optical arrangement as claimed in claim 14, wherein the position-sensitive sensor (22) is a CCD detector.

16. The invention according to claim 1, wherein the optical arrangement comprises a microlithographic projection printing installation.

17. The invention according to claim 1, wherein the image field is at least one of slot shaped or rotationally non-symmetrical illumination.