Mirror assembly with heat transfer mechanism

• US 10,371,920 B2
• Filed: 03/07/2013
• Issued: 08/06/2019
• Est. Priority Date: 03/22/2012
• Status: Active Grant

• Current Assignee: Nikon Research Corporation Of America (Nikon Corporation)
• Original Assignee: Nikon Research Corporation Of America (Nikon Corporation)
• Inventors: Margeson, Christopher, Bow, Travis
• Primary Examiner(s): Dzierzynski, Evan P
• Assistant Examiner(s): Oestreich, Mitchell T
• Application Number:
  US14/387,130
• Publication Number:
  US 20150042970A1
• Time in Patent Office: 2,343 Days
• Field of Search: 359872
• CPC Class Codes: G02B 7/028 with means for compensating for changes in temperature or for controlling the temperature; thermal stabilisation
• CPC Class Codes: G02B 7/181 with means for compensating for changes in temperature or for controlling the temperature; thermal stabilisation
• CPC Class Codes: G02B 7/1815 with cooling or heating systems cooling arrangements for laser mirrors H01S3/0401
• CPC Class Codes: G02B 7/182 for mirrors
• CPC Class Codes: G03F 7/70075 Homogenization of illumination intensity in the mask plane by using an integrator, e.g. fly's eye lens, facet mirror or glass rod, by using a diffusing optical element or by beam deflection
• CPC Class Codes: G03F 7/70116 Off-axis setting using a programmable means, e.g. liquid crystal display [LCD], digital micromirror device [DMD] or pupil facets
• CPC Class Codes: G03F 7/70316 Details of optical elements, e.g. of Bragg reflectors, extreme ultraviolet [EUV] multilayer or bilayer mirrors or diffractive optical elements
• CPC Class Codes: G03F 7/70891 Temperature

Abstract

A mirror assembly (32) for directing a beam (28) includes a base (450), and an optical element (454) that includes (i) a mirror (460), (ii) a stage (462) that retains the mirror (460), (iii) a mover assembly (464) that moves the stage (462) and the mirror (460) relative to the base (450), and (v) a thermally conductive medium (466) that is positioned between the stage (462) and the base (450) to transfer heat between the stage (462) and the base (450). The thermally conductive medium (466) has a thermal conductivity that is greater than the thermal conductivity of air. The thermally conductive medium (466) can include an ionic fluid or a liquid metal.

Claims

1. An optical element assembly for directing a beam, the optical element assembly comprising:

a base including a plurality of recesses; and

a plurality of elements, each of the plurality of elements including (i) an optical element, (ii) a stage that retains the optical element, the stage including a transfer region that is sized and shaped to fit within one of the plurality of recesses with a gap therebetween, and a connector region that is connected to and extends between the optical element and the transfer region such that the transfer region is rigidly connected to the optical element, (iii) a mover assembly that is coupled to the optical element, the mover assembly moving the optical element and the stage about a first axis and about a second axis that is orthogonal to the first axis relative to the base while maintaining the transfer region spaced apart the gap from the base, the mover assembly being secured in direct contact with the connector region between the optical element and the transfer region, and (iv) a thermally conductive medium positioned within the gap between the transfer region and the base to transfer heat from the transfer region to the base so that heat transferred with the thermally conductive medium does not cause thermal distortion of the mover assembly;

wherein the optical elements are arranged in a patterned array such that the optical elements are adjacent to one another and are positioned in approximately the same plane.

2. The optical element assembly of claim 1 wherein the patterned array of optical elements is substantially circle-shaped.

3. The optical element assembly of claim 1 wherein each optical element includes at least one of (i) a mirror;

(ii) a reflective surface;

or (iii) a lens.

4. The optical element assembly of claim 1 wherein for at least one of the plurality of elements the mover assembly includes (i) a first axis movement assembly that moves the optical element about the first axis, the first axis movement assembly including a first flexure so that movement of the optical element about the first axis with the first axis movement assembly is decoupled from the movement of the optical element about the second axis;

and (ii) a second axis movement assembly that moves the optical element about the second axis, the second axis movement assembly including a second flexure so that movement of the optical element about the second axis with the second axis movement assembly is decoupled from the movement of the optical element about the first axis.

5. The optical element assembly of claim 1 wherein for each of the plurality of elements the mover assembly includes (i) a first axis movement assembly that moves the optical element about the first axis, the first axis movement assembly including a first flexure so that movement of the optical element about the first axis with the first axis movement assembly is decoupled from the movement of the optical element about the second axis;

and (ii) a second axis movement assembly that moves the optical element about the second axis, the second axis movement assembly including a second flexure so that movement of the optical element about the second axis with the second axis movement assembly is decoupled from the movement of the optical element about the first axis.

6. The optical element assembly of claim 5 wherein the mover assembly moves the optical element to move approximately about a movement point that is near a center of a reflective surface of the optical element.

8. The optical element assembly of claim 1 wherein for at least one of the plurality of elements the mover assembly includes (i) a first axis movement assembly that moves the optical element about the first axis, the first axis movement assembly including a first mover and a first flexure that flexibly couples the first mover to the optical element so that movement by the first mover causes movement of the optical element about the first axis without movement of the optical element about the second axis;

and (ii) a second axis movement assembly that moves the optical element about the second axis, the second axis movement assembly including a second mover and a second flexure that flexibly couples the second mover to the optical element so that movement by the second mover causes movement of the optical element about the second axis without movement of the optical element about the first axis.

9. The optical element assembly of claim 1 wherein for each of the plurality of elements the mover assembly includes (i) a first axis movement assembly that moves the optical element about the first axis, the first axis movement assembly including a first mover and a first flexure that flexibly couples the first mover to the optical element so that movement by the first mover causes movement of the optical element about the first axis without movement of the optical element about the second axis;

and (ii) a second axis movement assembly that moves the optical element about the second axis, the second axis movement assembly including a second mover and a second flexure that flexibly couples the second mover to the optical element so that movement by the second mover causes movement of the optical element about the second axis without movement of the optical element about the first axis.

10. The optical element assembly of claim 1 wherein the base includes at least one fluid passageway for directing a circulation fluid through the base.

11. The optical element assembly of claim 1 further comprising a fluid system that circulates the thermally conductive medium for each of the plurality of elements within the gap between the transfer region and the base, and wherein the thermally conductive medium has a thermal conductivity that is greater than the thermal conductivity of air.

12. The optical element assembly of claim 1 wherein for each of the plurality of elements the thermally conductive medium is selected from the group that includes an ionic fluid and a liquid metal.

13. The optical element assembly of claim 1 wherein for at least one of the plurality of elements the transfer region includes a surface that is shaped somewhat similar to a truncated sphere;

and wherein each of the plurality of recesses defines an indentation that is shaped somewhat similar to a truncated sphere.

14. The optical element assembly of claim 1 wherein for each of the plurality of elements the transfer region includes a surface that is shaped somewhat similar to a truncated sphere;

and wherein each of the plurality of recesses defines an indentation that is shaped somewhat similar to a truncated sphere.

15. An exposure apparatus for transferring an image to a wafer, the exposure apparatus comprising:

a wafer stage that retains and positions the wafer;

an illumination source that generates a beam; and

the optical element assembly of claim 1 that directs the beam.

7. An optical element assembly for directing a beam, the optical element assembly comprising:

a base including a plurality of recesses; and

a plurality of elements, each of the plurality of elements including (i) an optical element, (ii) a stage that retains the optical element, the stage including a transfer region that is sized and shaped to fit within one of the plurality of recesses with a gap therebetween, and a connector region that is connected to and extends between the optical element and the transfer region such that the transfer region is rigidly connected to the optical element, (iii) a mover assembly that is coupled to the optical element, the mover assembly moving the optical element and the stage about a first axis and about a second axis that is orthogonal to the first axis relative to the base while maintaining the transfer region spaced apart the gap from the base, the mover assembly being secured to the connector region between the optical element and the transfer region, the mover assembly moving the optical element to move approximately about a movement point that is near a center of a reflective surface of the optical element, and (iv) a thermally conductive medium positioned within the gap between the transfer region and the base to transfer heat from the transfer region to the base so that heat transferred with the thermally conductive medium does not cause thermal distortion of the mover assembly;

wherein the optical elements are arranged in a patterned array such that the optical elements are adjacent to one another and are positioned in approximately the same plane;

wherein for each of the plurality of elements the mover assembly includes (i) a first axis movement assembly that moves the optical element about the first axis, the first axis movement assembly including a first flexure so that movement of the optical element about the first axis with the first axis movement assembly is decoupled from the movement of the optical element about the second axis; and

(ii) a second axis movement assembly that moves the optical element about the second axis, the second axis movement assembly including a second flexure so that movement of the optical element about the second axis with the second axis movement assembly is decoupled from the movement of the optical element about the first axis; and

wherein the mover assembly includes a linkage that is coupled to the optical element, and a mover that pivots the linkage about a pivot axis;

wherein the movement point is in a movement plane defined by the first axis and the second axis, and wherein the pivot axis is not in the movement plane.

16. A method for directing a beam, the method comprising the steps of:

providing a base including a plurality of recesses;

positioning a plurality of optical elements in a path of the beam, the plurality of optical elements being arranged in a patterned array such that the plurality of optical elements are adjacent to one another and are positioned in approximately the same plane;

retaining each of the plurality of optical elements with a corresponding stage, the stage including a transfer region that is positioned within one of the plurality of recesses with a gap therebetween, and a connector region that is connected to and extends between the optical element and the transfer region such that the transfer region is rigidly connected to the optical element;

moving each of the plurality of optical elements with a corresponding mover assembly about a first axis and about a second axis that is orthogonal to the first axis relative to the base while maintaining the gap between the base and the corresponding transfer region, wherein, the corresponding mover assembly is coupled in direct contact with the corresponding connector region between the optical element and the transfer region;

transferring heat away from each of the plurality of optical elements with the corresponding transfer region; and

transferring heat away from the transfer region for each stage with a thermally conductive medium positioned within the gap between the transfer region and the base so that heat transferred with the thermally conductive medium does not cause thermal distortion of the mover assembly.

17. The method of claim 16 wherein the step of moving each of the plurality of optical elements includes the steps of (i) moving each optical element about the first axis with a first axis movement assembly, the first axis movement assembly including a first flexure so that movement of the optical element about the first axis is decoupled from the movement of the optical element about the second axis;

and (ii) moving each optical element about the second axis with a second axis movement assembly, the second axis movement assembly including a second flexure so that movement of the optical element about the second axis is decoupled from the movement of the optical element about the first axis.

18. The method of claim 16 wherein the step of moving each of the plurality of optical elements includes the steps of (i) moving each optical element about the first axis with a first axis movement assembly, the first axis movement assembly including a first mover and a first flexure that flexibly couples the first mover to the optical element so that movement by the first mover causes movement of the optical element about the first axis without movement of the optical element about the second axis;

and (ii) moving each optical element about the second axis with a second axis movement assembly, the second axis movement assembly including a second mover and a second flexure that flexibly couples the second mover to the optical element so that movement by the second mover causes movement of the optical element about the second axis without movement of the optical element about the first axis.

19. The method of claim 16 further comprising the step of circulating the thermally conductive medium for each of the plurality of optical elements within the gap between the transfer region and the base with a fluid system, and wherein the thermally conductive medium has a thermal conductivity that is greater than the thermal conductivity of air.

20. The method of claim 16 wherein the step of retaining each of the plurality of optical elements includes the transfer region of each stage including a surface that is shaped somewhat similar to a truncated sphere;

and wherein the step of providing a base includes each of the plurality of recesses defining an indentation that is shaped somewhat similar to a truncated sphere.

21. An optical element assembly for directing a beam, the optical element assembly comprising:

a base including a plurality of recesses; and

a plurality of elements, each of the plurality of elements including (i) an optical element including a reflective surface, (ii) a stage that retains the optical element, the stage including a transfer region that is sized and shaped to fit within one of the plurality of recesses with a gap therebetween, and a connector region that is connected to and extends between the optical element and the transfer region such that the transfer region is rigidly connected to the optical element, (iii) a mover assembly including a linkage that is coupled to the optical element, and a mover that pivots the linkage about a pivot axis, the mover assembly moving the optical element and the stage about a first axis and about a second axis that is orthogonal to the first axis relative to the base while maintaining the gap, and (iv) a thermally conductive medium positioned within the gap between the transfer region and the base to transfer heat from the transfer region to the base so that heat transferred with the thermally conductive medium does not cause thermal distortion of the mover assembly;

wherein the optical elements are arranged in a patterned array such that the optical elements are adjacent to one another and are positioned in approximately the same plane; and

wherein the mover assembly moves the optical element about a movement point on the reflective surface that is in a movement plane defined by the first axis and the second axis, and wherein the pivot axis is not in the movement plane.