Compensating Temperature Effects in Magnetic Actuators

• US 20100284119A1
• Filed: 05/11/2009
• Published: 11/11/2010
• Est. Priority Date: 05/11/2009
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Coakley, Scott, Binnard, Michael B.
• Granted Patent: US 8,705,222 B2
• Time in Patent Office: Days
• US Class Current: 361/140
• CPC Class Codes: G03F 7/70525 Controlling normal operating mode, e.g. matching different apparatus, remote control or prediction of failure
• CPC Class Codes: G03F 7/70758 Drive means, e.g. actuators, motors for long- or short-stroke modules or fine or coarse driving
• CPC Class Codes: G03F 7/7085 Detection arrangement, e.g. detectors of apparatus alignment possibly mounted on wafers, exposure dose, photo-cleaning flux, stray light, thermal load
• CPC Class Codes: G03F 7/70858 Environment aspects, e.g. pressure of beam-path gas, temperature pollution aspects G03F7/70916
• CPC Class Codes: H01F 2007/1866 with regulation loop
• CPC Class Codes: H01F 7/1844 Monitoring or fail-safe circuits for relays H01H47/002

Abstract

Methods and apparatus for adjusting the amount of current provided to a magnetic actuator to compensate for a temperature change associated with the magnetic actuator are disclosed. According to one aspect of the present invention, an apparatus includes an actuator, which has at least one magnet and an associated force constant. The apparatus also includes a temperature sensing arrangement and a control arrangement, the temperature sensing arrangement being arranged to determine or measure a temperature of the magnet. The control arrangement adjusts the current provided to the actuator based on the temperature of the magnet. The current is adjusted to maintain a correct or desired force in light of temperature-induced variations to a force constant.

Claims

1. An apparatus comprising:

an actuator, the actuator having at least a magnet;

a temperature sensing arrangement, the temperature sensing arrangement being arranged to determine a temperature of the magnet; and

a control arrangement, the control arrangement being arranged to adjust a current provided to the actuator based on the temperature of the magnet, wherein the current is adjusted to maintain a force generated by the actuator when the temperature of the magnet varies.

2. The apparatus of claim 1 wherein the temperature sensing arrangement is configured to measure the temperature of the magnet in real-time and to provide the temperature of the magnet to the control arrangement.

3. The apparatus of claim 1 wherein the temperature sensing arrangement is an infra-red (IR) sensor.

4. The apparatus of claim 3 wherein the IR sensor is an IR camera positioned at a distance from the magnet.

5. The apparatus of claim 1 wherein the temperature sensing arrangement is a temperature sensor, the temperature sensor being arranged to contact the magnet.

6. The apparatus of claim 5 wherein the temperature sensor is one selected from the group including a thermistor, a thermocouple, an electronic thermometer, and a resistance temperature detector (RTD).

7. The apparatus of claim 1 further including:

a stage, wherein the actuator is arranged to cause the stage to move.

8. A stage apparatus comprising the apparatus of claim 1

9. An exposure apparatus comprising the stage apparatus of claim 8.

10. A stage apparatus comprising:

a stage;

a magnetic actuator, the magnetic actuator including at least a magnet and having an actuator force constant, the magnetic actuator being coupled to the stage and configured to cause the stage to move;

a temperature sensing arrangement, the temperature sensing arrangement being configured to measure a temperature associated with the magnet; and

a control arrangement, the control arrangement being arranged to provide an amount of current to the magnetic actuator, wherein the control arrangement is further arranged to obtain the temperature measured by the temperature sensing arrangement and to adjust the amount of current provided to the magnetic actuator based on the temperature measured by the temperature sensing arrangement to maintain an actuator force at a desired value in light of temperature-induced changes in the force constant.

11. The stage apparatus of claim 10 wherein the temperature sensing arrangement is configured to track movement of the magnet.

12. The stage apparatus of claim 10 wherein the temperature sensing arrangement is an infra-red (IR) sensor.

13. The stage apparatus of claim 12 wherein the IR sensor is an IR camera.

14. The stage apparatus of claim 10 wherein the temperature sensing arrangement is directly coupled to the magnet, the temperature sensing arrangement being one selected from the group including a thermistor, a thermocouple, an electronic thermometer, and a resistance temperature detector (RTD).

15. The stage apparatus of claim 10 wherein the stage is one selected from the group including a wafer stage and a reticle stage.

16. An exposure apparatus comprising the stage apparatus of claim 10.

17. A method for operating a stage apparatus, the stage apparatus including an actuator having a magnet, the method comprising:

determining a temperature of the magnet;

determining an amount of current to provide to the actuator based on the temperature of the magnet, wherein the amount of current is arranged to enable the actuator to sustain an actuator force at a desired value when a value of an actuator force constant changes with a temperature; and

providing the amount of current to the actuator.

18. The method of claim 17 wherein the stage apparatus includes a temperature sensing arrangement, and wherein determining the temperature of the magnet include measuring the temperature of the magnet using the temperature sensing arrangement.

19. The method of claim 18 wherein the temperature sensing arrangement is a thermal camera.

20. The method of claim 18 wherein the temperature sensing arrangement includes a temperature sensor that is in direct contact with the magnet.

21. The method of claim 18 wherein the magnet is a permanent magnet.