Method and apparatus for operating a vibration isolation system having electronic and pneumatic control systems

• US 6,758,313 B2
• Filed: 10/30/2002
• Issued: 07/06/2004
• Est. Priority Date: 09/15/2000
• Status: Expired due to Fees

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Binnard, Michael
• Primary Examiner(s): Graham, Matthew C.
• Application Number:
  US10/283,155
• Publication Number:
  US 20030057619A1
• Time in Patent Office: 615 Days
• Field of Search: 188/378, 188/379, 188/380, 268/64.11, 268/146.14, 268/146.15, 268/64.28, 268/136, 248/550, 248/638, 248/562, 248/563, 248/636, 736/64
• US Class Current: 188/378
• CPC Class Codes: F16F 15/0275 Control of stiffness
• CPC Class Codes: G03F 7/709 Vibration, e.g. vibration detection, compensation, suppression or isolation

Abstract

A method and apparatus for implementing an active vibration isolation system (AVIS) is provided. The AVIS includes a pneumatic control system and an electronic control system. The pneumatic control system supports a mass sensitive to vibration and isolates the mass from high frequency external disturbances. The electronic control system isolates the mass from low frequency external disturbances. The pneumatic control system includes a compliance chamber filled with a fluid to pneumatically support the mass, pressure sensor to measure the pressure level in the compliance chamber, and pneumatic actuator to control the pressure level to minimize the effects of pressure variation in the compliance chamber. The electronic control system includes at least one motion sensor to measure the actual position of the mass as the mass moves due to vibration, at least one feedback system to generate a corresponding signal, an electronic controller to generate signal(s) representing the calculated electronic force needed to compensate for the vibration, and an electronic actuator to generate the electric force to isolate the mass from the external disturbances. The pneumatic and electronic control systems work together to provide high frequency response and eliminate heat dissipation from the electronic control system.

Claims

1. A method for operating a vibration isolation system having a pneumatic control system and an electronic control system, comprising the steps of:

generating a pneumatic force in the pneumatic control system to support a mass, the pneumatic force produced by a pressure level in a compliance chamber, the pressure level being controlled in response to a pressure error signal;

delivering the pressure error signal to the electronic control system; and

monitoring a motion error signal of the mass in the electronic control system, the motion error signal being used to generate an electronic force to isolate the mass from vibration, the electronic force being determined based on a combination of the pressure error signal and the motion error signal.

2. The method of claim 1, wherein the step of generating a pneumatic force in the pneumatic control system, further comprises:

measuring the pressure level of the compliance chamber to generate a pressure signal;

generating the pressure error signal based on the pressure signal and a reference pressure signal; and

controlling the pressure level in the compliance chamber in response to the pressure error signal.

3. The method of claim 2, wherein the step of measuring the pressure level, further comprises:

determining the pressure signal based on a measured pressure level.

4. The method claim 2, wherein the step of generating the pressure error signal, further comprises:

determining the reference pressure signal.

5. The method of claim 2, wherein the step of generating the pressure error signal, further comprises:

comparing the pressure signal with the reference pressure signal.

6. The method of claim 2, wherein the step of controlling the pressure level, further comprises:

maintaining a constant pressure level in the compliance chamber.

7. The method of claim 1, wherein the step of monitoring a motion error signal in the electronic control system, further comprises:

measuring a motion of the mass to generate a motion signal; and

generating the motion error signal based on the motion signal and a reference motion signal.

8. The method of claim 7, wherein the step of measuring a motion of the mass, further comprises:

measuring a position of the mass.

9. The method of claim 8, wherein the step of generating the motion error signal, further comprises:

determining a position signal based on the measured position; and

comparing the position signal with a reference position signal to generate the motion error signal.

10. The method of claim 7, further comprising:

determining the reference motion signal.

11. The method of claim 10, further comprising:

determining a motion force error signal based on the motion error signal.

12. The method of claim 11, further comprising:

generating a disturbance canceling force signal to counteract the motion force error signal, and resulting in an electronic error signal; and

combining the electronic error signal and the pressure error signal to generate the electronic force.

13. The method of claim 12, wherein the step of generating a disturbance canceling force signal further comprises:

determining the disturbance canceling force signal.

14. The method of claim 7, wherein the step of monitoring a motion error signal, further comprises:

determining the electronic force based on the combination of the pressure error signal and the motion error signal.

15. The method of claim 7, wherein the step of measuring a motion of the mass, further comprises:

measuring a velocity of the mass.

16. The method of claim 15, wherein the step of generating the motion error signal, further comprises:

determining a velocity signal based on a measured velocity; and

comparing the velocity signal with a reference velocity signal to generate the motion error signal.

17. A vibration isolation system using the method as claimed in claim 1.

18. A lithography system comprising a vibration isolation system as claimed in claim 17.

19. An object on which an image has been formed by the lithography system of claim 18.

20. A vibration isolation system, comprising:

a pneumatic control system having a compliance chamber to generate a pneumatic force that supports a mass based on a pressure error signal;

an electronic control system having a motion sensor to generate a motion error signal of the mass;

a force generator connected with the pneumatic control system and the electronic control system, the force generator generating an electronic force based on results of a combination of the pressure error signal and the motion error signal to isolate the mass from vibration.

21. A method for operating a vibration isolation system having a pneumatic control system and an electronic control system, comprising the

generating a pressure error signal in the pneumatic control system based on a pressure signal of a compliance chamber and a reference pressure signal;

controlling the pressure level in the compliance chamber in response to the pressure error signal, the compliance chamber generating a pneumatic force in proportion to a controlled pressure level to pneumatically support a mass;

delivering the pressure error signal to the electronic control system;

comparing a motion signal of the mass in the electronic control system with a reference motion signal to generate a motion error signal;

combining the motion error signal and the pressure error signal; and

determining an electronic force to isolate the mass from vibration based on a combination of the motion and pressure error signals.

22. The method of claim 21, wherein the generating step in the pneumatic control system, further comprises:

measuring the pressure level in the compliance chamber; and

determining the pressure signal based on a measured pressure level.

23. A vibration isolation system using the method as claimed in claim 22.

24. The method of claim 21, wherein the generating step in the pneumatic control system, further comprises:

determining the reference pressure signal.

25. The method of claim 21, wherein the controlling step in the pneumatic control system, further comprises:

maintaining a constant pressure level in the compliance chamber.

26. The method of claim 21, wherein the comparing step in the electronic control system, further comprises:

measuring a position of the mass;

determining a position signal based on a measured position; and

comparing the position signal with a reference position signal to generate the motion error signal.

27. The method of claim 21, wherein the comparing step in the electronic control system, further comprises:

measuring a velocity of the mass;

determining a velocity signal based on a measured velocity of the mass; and

comparing the velocity signal with a reference velocity signal to generate the motion error signal.

28. The method of claim 21, wherein the comparing step in the electronic control system, further comprises:

determining a motion force error signal based on the motion error signal.

29. The method of claim 28, further comprising:

generating a disturbance canceling force signal to counteract known or estimated diturbances; and

combining the disturbance canceling force signal, the electronic error signal and the pressure error signal to generate the electric force.

31. A lithography system comprising the vibration isolation system of claim 22.

32. An object on which an image has been formed by the lithography system of claim 31.

30. A vibration isolation system having a pneumatic control system and an electronic control system, comprising:

a pressure sensor for generating a pressure error signal based on a pressure information of a compliance chamber and a reference pressure information;

a first controller connected to the pressure sensor, the first controller controlling a pressure level in the compliance chamber in response to the pressure error signal;

a pneumatic force generator connected to the first controller, the pneumatic force generator generating a pneumatic force determined based on a controlled pressure level to pneumatically support a mass;

a second controller connected to the first controller, the second controller comparing a motion information of the mass with a reference motion signal to generate a motion error signal, and generating an electronic force signal based on the motion error signal and the pressure error signal; and

an electronic force generator connected to the second controller, the electronic force generator generating an electronic force to isolate the mass from vibration based on the motion error signal and the pressure error signal.