Stage device, control system, and method for stabilizing wafer stage and wafer table

• US 6,504,162 B1
• Filed: 09/15/2000
• Issued: 01/07/2003
• Est. Priority Date: 09/15/2000
• Status: Expired due to Fees

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Binnard, Michael, Ueta, Toshio
• Primary Examiner(s): ANDERSON, BRUCE C
• Application Number:
  US09/662,843
• Time in Patent Office: 844 Days
• Field of Search: 250/492.2, 250/442.11
• US Class Current: 250/492.2
• CPC Class Codes: G03F 7/70725 control

Abstract

A wafer stage device and control system are provided to stabilize a wafer stage and a wafer table in a wafer manufacturing process. The wafer table supports the semiconductor wafer, while the wafer stage is accelerated in response to a wafer manufacturing control system to position the wafer table. The wafer stage device includes a set of flexures connecting the wafer table to the wafer stage. The flexures are positioned in a plane which is substantially in alignment with an upper surface of the wafer. The flexure'"'"'s configuration causes a rotational error, such as pitching or rolling, of the wafer table as the wafer stage moves. The wafer stage device further includes a plurality of actuators to control the rotational error by exerting a stabilizing torque to the wafer table. The control system determines the stabilizing torque necessary to correct the pitching or rolling error of the wafer table.

Claims

1. A wafer stage control system, comprising:

a first feedforward control system to determine a stabilizing force to be exerted onto a wafer table to counteract a rotational motion of the wafer table caused by an acceleration of a wafer stage; and

a second feedforward control system to determine a correction force to be exerted on the wafer stage to correct a leveling shift caused by a rotation of the wafer table.

2. The wafer stage control system of claim 1, further comprising:

a wafer stage control loop to determine a wafer stage position error and to generate a wafer stage force to be exerted on the wafer stage to correct the wafer stage position error.

3. The wafer stage control system of claim 2, wherein the wafer stage control loop comprises:

a wafer stage position sensor to measure an actual position of the wafer stage;

a summing junction to compare the actual position and a position reference of the wafer stage to generate a wafer stage position error signal; and

a controller to determine the wafer stage force based on the wafer stage position error signal.

4. The wafer stage control system of claim 2, wherein the wafer stage control loop further comprises:

a wafer stage acceleration reference to determine the wafer stage position reference.

5. The wafer stage control system of claim 1, further comprising:

a wafer table control loop to determine a wafer table position error and to generate a wafer table force to be exerted onto the wafer table to correct a wafer table position error.

6. The wafer stage control system of claim 5, wherein the wafer table control loop comprises:

a wafer table position sensor to measure an actual position of the wafer table;

a summing junction to compare the actual position and a position reference of the wafer table to generate a wafer table position error signal; and

a controller to determine the wafer table force based on the wafer table position error signal.

36. A lithography system comprising:

an illumination system that irradiates radiant energy;

a wafer stage device that carries an object disposed on a path of said radiant energy, and

the wafer stage control system according to claim 1, said wafer stage control system being connected to the wafer stage device.

37. A device on which an image has been formed by the lithography system of claim 36.

7. A method for operating a wafer stage and wafer table control system, comprising the steps of:

determining a stabilizing force to be exerted on a wafer table to counteract a rotational motion of the wafer table caused by an acceleration of a wafer stage; and

determining a force to be exerted on the wafer stage to counteract a leveling shift of the wafer table due to a rotation of the wafer table.

8. The method of claim 7, further comprising the steps of:

determining a wafer stage position error based on an actual position and a reference position of the wafer stage; and

generating a wafer stage force to be exerted on the wafer stage to correct the wafer stage position error.

9. The method of claim 7, further comprising the steps of:

determining a wafer table position error based on an actual position and a reference position of the wafer table; and

generating a wafer table force to be exerted on the wafer table to correct the wafer table position error.

10. A method for operating a wafer stage and wafer table control system, comprising the steps of:

creating a wafer stage loop to correct a wafer stage position error, a wafer stage acceleration reference signal being an input to the wafer stage loop;

creating a wafer table loop to correct a wafer table position error;

inputting the wafer stage acceleration reference signal to the wafer table loop to determine a stabilizing force to be exerted onto the wafer table to counteract a rotational motion of the wafer table caused by an acceleration of the wafer stage; and

determining a force to be exerted on the wafer stage to correct a leveling shift of the wafer table due to a rotation of the wafer table.

11. The method of claim 10, wherein the step of creating a wafer stage loop further comprises:

comparing a wafer stage actual position with a wafer stage position reference to generate a wafer stage position error signal; and

calculating a wafer stage force signal corresponding to the wafer stage position error signal to correct the wafer stage position error.

12. The method of claim 10, wherein the step of creating a wafer table loop further comprises:

comparing a wafer table actual position with a wafer table position reference to generate a wafer table position error signal; and

calculating a wafer table force signal corresponding to the wafer table position error signal to correct the wafer stage position error.

13. A method for stabilizing a wafer table in a wafer manufacturing apparatus, the wafer table supporting a wafer, the wafer stage being subject to acceleration in response to a wafer manufacturing control system to position the wafer table, the method comprising the steps of:

generating a wafer stage force to be exerted onto a wafer stage to correct a position error of the wafer stage;

generating a wafer table force to be exerted onto a wafer table to correct a position error of the wafer table;

generating a stabilizing force to be exerted onto the wafer table to counteract a rotational motion of the wafer table caused by acceleration of the wafer stage; and

generating a correction force to be exerted onto the wafer stage to compensate leveling shift of the wafer table.

14. The method of claim 13, wherein the step of generating a wafer stage force further comprises:

comparing an wafer stage actual position with a wafer stage position reference to determine a wafer stage position error; and

calculating the wafer stage force based on the wafer stage position error.

15. The method of claim 14, wherein the step of generating a wafer stage force further comprises:

determining the wafer stage position reference based on a wafer stage acceleration reference.

16. The method of claim 15 wherein the step of generating a stabilizing force further comprises:

determining the stabilizing force based on the wafer stage acceleration reference.

17. The method of claim 13, wherein the step of generating a wafer table force further comprises:

comparing a wafer table actual position with a wafer table position reference to determine a wafer table position error; and

calculating the wafer table force based on the wafer table position error.

18. The method of claim 13, wherein the step of generating a correction force further comprises:

connecting the wafer table and the wafer stage to determine the correction force.

19. A method for making a wafer stage device to manufacture semiconductor wafers, comprising the steps of:

aligning at least one flexure in a plane with a wafer, the wafer being supported by a wafer table and positioned by a wafer stage;

restraining shifting motion of the wafer table in the plane aligned with the wafer, while allowing the wafer table to move in a direction normal to the plane; and

generating a stabilizing force to stabilize the wafer table when the wafer stage is accelerated.

20. The method of claim 19, further comprising the step of:

providing a first feedforward control system to determine the stabilizing force.

21. The method of claim 19, further comprising the step of:

generating a correction force to stabilize the wafer stage from a leveling shift of the wafer table.

22. The method of claim 21, further comprising the step of:

providing a second feedforward control system to determine the correction force.

23. A wafer stage device for manufacturing semiconductor wafers, comprising:

a wafer stage to position a wafer, the wafer stage being subject to acceleration in response to a wafer manufacturing control system;

a wafer table to support the wafer, the wafer table having a predetermined center of gravity;

a set of flexures connecting the wafer table and the wafer stage, the set of flexures being substantially aligned in a plane with the wafer;

at least one actuator to stabilize the wafer table when the wafer stage is being accelerated; and

a first feedforward controller to control a stabilizing output of the at least one actuator.

24. The wafer stage device of claim 23, further comprising:

a second feedforward controller connected between the wafer stage and the wafer table to correct the wafer stage position to cancel a leveling shift of the wafer table due to a rotation of the wafer table.

25. The wafer stage device of claim 23, wherein the set of flexures restrains shifting motion of the wafer table in the plane aligned with the wafer, and allows the wafer table to move in a direction normal to the plane.

26. The wafer stage device of claim 23, wherein each of the at least one actuator exerts a stabilizing force onto the wafer table to control a rotational motion of the wafer table with respect to the wafer stage.

27. The wafer stage device of claim 26, wherein the at least one actuator comprises at least a set of two actuators, each set being separated by a predetermined distance.

28. The wafer stage device of claim 26, wherein the at least one actuator is one of a voice-coil motor type actuator and an EI core actuator.

29. The wafer stage device of claim 23, wherein each of the at least one actuator exerts a stabilizing torque onto the wafer table to control a rotational motion of the wafer table with respect to the wafer stage.

38. A lithography system comprising:

an illumination system that irradiates radiant energy; and

a wafer stage device according to claim 23, said wafer stage device carries the wafer disposed on a path of said radiant energy.

39. A device on which an image has been formed by the lithography system of claim 38.

30. A wafer stage control system for stabilizing a wafer table in a wafer manufacturing process, the wafer table supporting a wafer, a wafer stage being subject to acceleration in response to a wafer manufacturing control system to position the wafer table, comprising:

at least one flexure substantially aligned in a plane with the wafer and connecting the wafer table to the wafer stage;

at least one actuator mounted on the wafer stage to generate an output to stabilize the wafer table when the wafer stage is being accelerated; and

a first feedforward control system to control the output of the at least one actuator by determining a stabilizing force to be exerted on the wafer table to counteract a rotational motion of the wafer table caused by an acceleration of the wafer stage.

31. The wafer stage control system of claim 30, further comprising:

a second feedforward control system connected between the wafer stage and the wafer table to correct the wafer stage position to cancel a leveling shift of the wafer table due to a rotation of wafer table.

32. The wafer stage control system of claim 30, wherein the at least one flexure restrains shifting motion of the wafer table in the plane aligned with the wafer and allows the wafer table to move in a direction normal to the plane.

33. The wafer stage control system of claim 30, wherein the at least one actuator comprises at least a set of two actuators, each set being separated by a predetermined distance, and each set outputting a stabilizing force to be exerted onto the wafer table to control a rotational motion of the wafer table with respect to the wafer stage.

34. The wafer stage control system of claim 33, wherein the at least one actuator is one of a voice-coil motor type actuator and an EI core actuator.

35. The wafer stage control system of claim 30, wherein each of the at least one actuator outputs a stabilizing torque to be exerted onto the wafer table to control a rotational motion of the wafer table with respect to the wafer stage.

40. A lithography system comprising:

an illumination system that irradiates radiant energy;

a wafer stage device that carries an object disposed on a path of said radiant energy, and

the wafer stage control system according to claim 30, said wafer stage control system being connected to the wafer stage device.

41. A device on which an image has been formed by the lithography system of claim 40.