Deformable mirror with high-bandwidth servo for rigid body control

• US 20040017623A1
• Filed: 05/29/2003
• Published: 01/29/2004
• Est. Priority Date: 07/23/2002
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Watson, Douglas C.
• Granted Patent: US 6,842,277 B2
• Time in Patent Office: Days
• US Class Current: 359/849
• CPC Class Codes: G02B 26/0825 the reflecting element being a flexible sheet or membrane, e.g. for varying the focus flexible mirrors for cosmetic use A45D42/24
• CPC Class Codes: G02B 7/182 for mirrors
• CPC Class Codes: G03F 7/70266 Adaptive optics, e.g. deformable optical elements for wavefront control, e.g. for aberration adjustment or correction

Abstract

A deformable mirror arrangement has a plurality of constraint mechanisms contacting a deformable mirror at specified contact positions. At least three of these constraint mechanisms are rigid body servo control mechanisms such as high-bandwidth servo control mechanisms, each including a force actuator contacting the mirror at a corresponding one of the contact positions, a position sensor assisting to measure position of the mirror and a servo control unit for controlling the force actuator.

Claims

1. A deformable mirror arrangement comprising:

a deformable mirror; and

a plurality of constraint mechanisms contacting said mirror at specified contact positions, at least three of said constraint mechanisms being rigid body servo control mechanisms each including a force actuator contacting said mirror at a corresponding one of said contact positions, a position sensor assisting to measure position of said mirror and a servo control unit for controlling said force actuator.

2. The deformable mirror arrangement of claim 1 wherein said rigid body servo control mechanisms are high-bandwidth servo control mechanisms.

3. The deformable mirror arrangement of claim 1 wherein said three rigid body servo mechanisms control degrees of freedom of said mirror along a Z-axis, around an X-axis and a Y-axis, said Z-axis being perpendicular to said mirror, said X-axis and said Y-axis being perpendicular to each other and to said Z-axis.

4. The deformable mirror arrangement of claim 3 wherein degrees of freedom of said mirror along said X-axis, along said Y-axis and around said Z-axis are each controlled by a passive mechanical mount.

5. The deformable mirror arrangement of claim 3 wherein degrees of freedom of said mirror along said X-axis, along said Y-axis and around said Z-axis are each controlled by a flexure.

6. The deformable mirror arrangement of claim 1 further comprising a plurality of force actuators without servo control for adjusting deformation of said deformable mirror.

7. The deformable mirror arrangement of claim 3 wherein the three rigid body servo control mechanisms apply parallel constraints on said deformable mirror along said Z-axis.

8. The deformable mirror arrangement of claim 3 wherein each of the three rigid body servo control mechanisms and another corresponding one of said constraint mechanisms apply mutually perpendicular forces at a same position.

9. A method of controlling degrees of freedom of a deformable mirror, said method comprising the steps of:

providing a plurality of constraint mechanisms contacting said mirror at specified contact positions, at least three of said constraint mechanisms being rigid body servo control mechanisms each including a force actuator contacting said mirror at a corresponding one of said contact positions, a position sensor assisting to measure position of said mirror and a servo control unit for controlling said force actuator; and

operating said constraint mechanisms to control degrees of freedom of said deformable mirror.

10. The method of claim 9 wherein said rigid body servo control mechanisms are high-bandwidth servo control mechanisms.

11. The method of claim 9 wherein said three rigid body servo mechanisms control degrees of freedom of said mirror along a Z-axis, around an X-axis and a Y-axis, said Z-axis being perpendicular to said mirror, said X-axis and said Y-axis being perpendicular to each other and to said Z-axis.

12. The method of claim 11 wherein degrees of freedom of said mirror along said X-axis, along said Y-axis and around said Z-axis are each controlled by a passive mechanical mount.

13. The method of claim 11 wherein degrees of freedom of said mirror along said X-axis, along said Y-axis and around said Z-axis are each controlled by a flexure.

14. The method of claim 9 further comprising the step of controllingly deforming said mirror by means of a plurality of kinematic mounts without servo control.

15. A lithography system for projecting a pattern on a wafer by a projection beam by preliminarily determining a surface profile of the wafer on a stage and subsequently introducing the stage with the wafer into the projection beam, said lithographic system comprising:

an illumination source;

an optical system including a deformable mirror assembly;

a reticle stage arranged to retain a reticle;

a working stage arranged to retain a workpiece; and

an enclosure that surrounds at least a portion of the working stage, the enclosure having a sealing surface;

wherein said deformable mirror assembly includes a deformable mirror and a plurality of constraint mechanisms contacting said mirror at different contact positions, at least three of said constraint mechanisms being rigid body servo control mechanisms each including a force actuator contacting said mirror at a corresponding one of said contact positions, a position sensor for detecting the corresponding contact position and a servo control unit for controlling said force actuator.

16. An object manufactured with the lithography system of claim 15.

17. A wafer on which an image has been formed by the lithography system of claim 15.

18. A method for making an object using a lithography process, wherein the lithography process utilizes a lithography system as recited in claim 15.

19. A method for patterning a wafer using a lithography process, wherein the lithography process utilizes a lithography system as recited in claim 15.