Optical element damping systems

• US 20070153348A1
• Filed: 12/07/2006
• Published: 07/05/2007
• Est. Priority Date: 12/30/2005
• Status: Active Grant

• Current Assignee: ASML Holding NV
• Original Assignee: ASML Holding NV
• Inventors: Roux, Stephen, Kreuzer, Justin, Kochersperger, Peter
• Granted Patent: US 7,751,130 B2
• Time in Patent Office: Days
• US Class Current: 359/198.100
• CPC Class Codes: G02B 7/00 Mountings, adjusting means, or light-tight connections, for optical elements
• CPC Class Codes: G03F 7/70825 Mounting of individual elements, e.g. mounts, holders or supports workpiece or mask holders G03F7/707
• CPC Class Codes: G03F 7/709 Vibration, e.g. vibration detection, compensation, suppression or isolation

Abstract

The present invention is directed to optical element damping systems. In particular, an eddy current damper is disclosed. The eddy current damper includes a rod, a series of conducting plates coupled to the rod, and layers of magnets. The alternating layers have alternating magnetic fields. When an optical element moves, the optical element will exert a force on the rod. The rod causes the conducting plates to move relative to the alternating layers of magnets to generate eddy currents within each of the conducting plates, such that the eddy currents damp the motion of an optical element. In an alternative embodiment, an eddy current damper motion amplifier is used to provide additional mechanical advantage that significantly increases the damping provided by the eddy current damper. Eddy current dampers are provided within conventional scanning lithography devices and optical maskless lithography devices to improve performance by stabilizing optical element motion.

Claims

1. An optical element assembly, comprising:

an optical element mount that secures an optical element; and

one or more eddy current dampers coupled to the optical element mount that reduce movement of an optical element held within the optical element mount, wherein a motion of the optical element generates eddy currents within the one or more eddy current dampers that limits the motion of the optical element.

2. The optical element assembly of claim 1, further comprising an optical element that is secured by the optical element mount.

3. The optical element assembly of claim 2, wherein the optical element comprises a refractive, reflective, or catadioptric optical component for directing, shaping, or controlling a beam of radiation.

4. The optical element assembly of claim 2, wherein the optical element comprises a lens or mirror.

5. The optical element assembly of claim 1, wherein the eddy current damper includes:

a rod that pushes against an optical element when an optical element moves in a direction generating a force parallel to the axis of the rod;

a series of conducting plates coupled to the rod; and

layers of magnets with magnetic fields that alternate from layer to layer, wherein the conducting plates move relative to the layers of magnets when an optical element exerts a force on the rod to generate eddy currents within the conducting plates, wherein the eddy currents dampen the motion of an optical element.

6. The optical element assembly of claim 5, wherein said eddy current damper further comprises a front end plate that affixes the rod to the series of conducting plates.

7. The optical element assembly of claim 5, wherein said eddy current damper further comprises an eddy current damper housing that houses the rod, the series of conducting plates, and the layers of magnets.

8. The optical element assembly of claim 7, wherein the eddy current damper housing includes a front damper flexure, wherein the front damper flexure is affixed to the front end plate and top portion of the eddy current damper housing.

9. The optical element assembly of claim 8, wherein the front damper flexure comprises a flexible material that enables the rod to move laterally, such that the series of conducting plates move relative to the layers of magnets when a force is exerted on the rod.

10. The optical element assembly of claim 5, wherein the conducting plates comprise copper.

11. The optical element assembly of claim 5, wherein the magnets comprise permanent magnets and/or electromagnets.

12. The optical element assembly of claim 2, wherein said eddy current damper includes:

a rod that is coupled to the optical element;

a damper motion amplifier that attaches to the optical mount, wherein when the optical element moves in the axial direction of the rod, the rod exerts a force on the damper motion amplifier;

a series of conducting plates coupled to the damper motion amplifier, wherein the damper motion amplifier stimulates movement of the series of conducting plates upon the rod exerting a force on the damper motion amplifier; and

layers of magnets with magnetic fields that alternate from layer to layer, wherein the conducting plates move relative to the layers of magnets when an optical element exerts a force on the rod to generate eddy currents within the conducting plates, wherein the eddy currents dampen the motion of an optical element.

13. The optical element assembly of claim 12, wherein said eddy current damper further comprises an eddy current housing that houses the series of conducting plates and the layers of magnets.

14. The optical element assembly of claim 12, wherein said conducting plates comprise copper.

15. The optical element assembly of claim 12, wherein the magnets comprise permanent magnets and/or electromagnets.

16. An eddy current damper, comprising:

a rod that pushes against an optical element when an optical element moves in a direction generating a force parallel to the axis of the rod;

a series of conducting plates coupled to the rod; and

layers of magnets with magnetic fields that alternate from layer to layer, wherein the conducting plates move relative to the layers of magnets when an optical element exerts a force on the rod to generate eddy currents within the conducting plates, wherein the eddy currents dampen the motion of an optical element.

17. The eddy current damper of claim 16, further comprising a front end plate that affixes the rod to the series of conducting plates.

18. The eddy current damper of claim 16, further comprising an eddy current damper housing that houses the rod, the series of conducting plates, and the layers of magnets.

19. The eddy current damper of claim 16, wherein the eddy current damper housing includes a front damper flexure, wherein the front damper flexure is affixed to the front end plate and top portion of the eddy current damper housing.

20. The eddy current damper of claim 19, wherein the front damper flexure comprises a flexible material that enables the rod to move laterally, such that the series of conducting plates move relative to the layers of magnets when a force parallel to the axis of the rod is exerted on the rod.

21. The eddy current damper of claim 16, wherein the conducting plates comprise copper.

22. The eddy current damper of claim 16, wherein the magnets comprise permanent magnets and/or electromagnets.

23. An eddy current damper, comprising:

a rod that is coupled to an optical element;

a damper motion amplifier that attaches to an optical mount, wherein when the optical element moves in the axial direction of the rod, the rod exerts a force on the damper motion amplifier;

a series of conducting plates coupled to the damper motion amplifier, wherein the damper motion amplifier stimulates movement of the series of conducting plates upon the rod exerting a force on the damper motion amplifier; and

layers of magnets with magnetic fields that alternate from layer to layer, wherein the conducting plates move relative to the layers of magnets when an optical element exerts a force on the rod to generate eddy currents within the conducting plates, wherein the eddy currents dampen the motion of an optical element.

24. The optical element assembly of claim 23, wherein said conducting plates comprise copper.

25. The optical element assembly of claim 23, wherein the magnets comprise permanent magnets and/or electromagnets.

26. A lithography system comprising one or more eddy current dampers.

27. The lithography system of claim 26, wherein the lithography system is an optical maskless lithography system or a conventional lithographic scanner system.