Vibration isolation system, vibration isolation method, lithographic apparatus and device manufacturing method

• US 20050224687A1
• Filed: 04/12/2004
• Published: 10/13/2005
• Est. Priority Date: 04/12/2004
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: Van Der Toorn, Jan-Gerard Cornelis, Heertjes, Marcel Francois
• Granted Patent: US 7,817,243 B2
• Time in Patent Office: Days
• US Class Current: 248/638
• CPC Class Codes: F16F 15/02 Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems F16F15/005 takes precedence ; layered products B32B; suppression of vibration in ships B63; relieving load on bearings, using magnetic means F16C39/06
• CPC Class Codes: G03F 7/709 Vibration, e.g. vibration detection, compensation, suppression or isolation

Abstract

A vibration isolation system isolates a body from its surroundings with respect to vibrations. The vibration isolation system includes active isolator devices that isolate and damp the body in unstable directions. However, such active isolators may exert damping forces not only in the unstable direction, but simultaneously in other stable directions due to mechanical coupling of the stable and unstable directions. As a result the damping and isolation in the other stable directions may be deteriorated due to the active isolation and damping. Employing modal decoupling, i.e. decomposing any vibration into independent directions, and isolating and damping in the independent directions, enables compensation of any vibration in an unstable direction without influencing the isolation and damping performance in any other, possibly stable, direction.

Claims

1. A vibration isolation system for at least partially damping and isolating vibrations of a body, the system comprising:

a plurality of active isolator devices mechanically coupled to the body; and

a control system configured to control the active isolator devices, wherein the control system is configured to;

decouple vibrations in modal directions;

determine a modal compensation signal for each modal direction;

recouple each modal compensation signal into an active isolator control signal for each active isolator device; and

stabilize at least one unstable natural mode of the body.

2. The vibration isolation system according to claim 1, wherein the at least one unstable natural mode stabilized by the control system is directed substantially vertically.

3. The vibration isolation system according to claim 1, wherein the body is positioned on a base frame by air mounts.

4. The vibration isolation system according to claim 1, wherein a passive isolator device and an active isolator device engage the body at the same location on the body.

5. The vibration isolation system according to claim 1, wherein the system comprises a plurality of sensors to detect vibrations of the body.

6. A lithographic apparatus, comprising:

an illumination system configured to provide a beam of radiation;

a support configured to support a patterning device, the patterning device configured to impart the beam with a pattern in its cross-section;

a substrate table configured to hold a substrate; and

a projection system configured to project the patterned beam onto a target portion of the substrate, wherein the projection system is supported by and positioned relative to a metrology frame, vibrations of the metrology frame being at least partially isolated and damped by a plurality of active isolator devices which are controllable by a control system, the control system being configured to;

decouple vibrations in modal directions;

determine a modal compensation signal for each modal direction;

recouple each modal compensation signal in an active isolator control signal for each active isolator device; and

stabilize at least one unstable natural mode of the metrology frame.

7. An apparatus according to claim 6, wherein the at least one unstable natural mode stabilized by the control system is directed substantially vertically.

8. An apparatus according to claim 6, wherein the projection system is positioned on the metrology frame by air mounts.

9. An apparatus according to claim 6, wherein a passive isolator device and an active isolator device engage the projection system at the same location on the projection system.

10. An apparatus according to claim 6, further comprising a plurality of sensors to detect vibrations of the projection system.

11. A vibration isolation method for at least partially isolating and damping vibrations of a body, the method comprising:

detecting vibrations in the body;

decoupling the detected vibrations in modal directions;

determining a modal compensation signal for each modal direction;

recoupling the modal compensation signal to an active isolator control signal for each of a number of active isolator devices which are mechanically coupled to the body; and

feeding the active isolator control signals to the respective active isolator devices, wherein at least one unstable natural mode of the body is stabilized.

12. A method according to claim 11, wherein the at least one unstable natural mode that is stabilized is directed substantially vertically.

13. A method according to claim 11, wherein the body is positioned on a base frame by air mounts.

14. A method according to claim 11, wherein a passive isolator device and an active isolator device engage the body at the same location on the body.

15. A method according to claim 11, wherein the vibrations of the body are detected by a plurality of sensors.

16. A device manufacturing method comprising the steps of:

providing a substrate;

projecting a patterned beam of radiation onto a target portion of the substrate, wherein disturbing vibrations in a system performing the projecting of the patterned beam of radiation are prevented by;

detecting vibrations in the projecting system;

decoupling the detected vibrations in modal directions of the projecting system;

determining a modal compensation signal in each modal direction;

recoupling the modal compensation signal into an active isolator control signal for each of a number of active isolator devices which are mechanically coupled to the projecting system; and

feeding the active isolator control signals to the respective active isolator devices, wherein at least one unstable natural mode of the projecting system is stabilized.

17. An apparatus according to claim 16, wherein the at least one unstable natural mode stabilized by the control system is directed substantially vertically.

18. An apparatus according to claim 16, wherein the projection system is positioned on the metrology frame by air mounts.

19. An apparatus according to claim 16, wherein a passive isolator device and an active isolator device engage the projection system at the same location on the projection system.

20. A method according to claim 16, wherein the vibrations of the projection system are detected by a plurality of sensors.