Vibration-preventive apparatus and exposure apparatus

• US 5,812,420 A
• Filed: 09/03/1996
• Issued: 09/22/1998
• Est. Priority Date: 09/05/1995
• Status: Expired due to Fees

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Takahashi, Masato
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): MILLER, ROSE MARY
• Application Number:
  US08/707,216
• Time in Patent Office: 749 Days
• Field of Search: 248/548, 248/550, 248/562, 248/563, 248/565, 248/566, 248/557, 248/636, 248/638, 356/400, 356/401, 355/53, 355/54, 355/30, 355/43, 378/34, 378/35, 364/508, 73/662, 73/663, 73/664, 73/665
• US Class Current: 700/280
• 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: F16F 15/03 using magnetic or electromagnetic means F16F9/53, F16F15/005 take precedence
• CPC Class Codes: G03F 7/70725 control
• CPC Class Codes: G03F 7/70833 Mounting of optical systems, e.g. mounting of illumination system, projection system or stage systems on base-plate or ground
• 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 7/709 Vibration, e.g. vibration detection, compensation, suppression or isolation

Abstract

A position of movement of a stage is measured by an interferometer when the stage placed on a vibration-preventive pedestal of an exposure apparatus is moved. An output of the interferometer is multiplied by K so as to correct an amount of inclination of the vibration-preventive pedestal caused by movement of a position of a center of gravity during the movement of the stage, and an obtained value is feedforward-inputted into a vibration control system of a control unit. The vibration control system controls actuators on the basis of outputs of a displacement sensor and a vibration sensor and the feedforward-inputted value so that vibration of the vibration-preventive pedestal is suppressed. A vibration-compensating system multiplies, by g, displacements θ_x, θ_y in a direction of inclination with respect to a horizontal plane obtained on the basis of outputs of three vertical displacement sensors. Obtained results are subtracted from outputs of horizontal acceleration sensors. Thus gravitational acceleration components can be removed from the outputs of the horizontal sensors. The suppressing effect on disturbance vibration can be improved without being affected by the movement of the position of the center of gravity of the main apparatus body associated with the movement of the stage.

Claims

1. A vibration-preventive apparatus comprising:

a vibration-preventive pedestal held horizontally through at least three vibration-preventive pads;

at least one stage movable on the vibration-preventive pedestal;

at least three actuators for moving the vibration-preventive pedestal in a vertical direction;

at least one displacement sensor for detecting displacement of the vibration-preventive pedestal;

at least one vibration sensor for detecting vibration of the vibration-preventive pedestal;

a vibration control system for controlling the respective actuators on the basis of outputs of the displacement sensor and the vibration sensor so that the vibration of the vibration-preventive pedestal is suppressed;

a position-measuring unit for measuring a position of the at least one stage; and

a vibration-compensating system for forecasting an amount of inclination of the vibration-preventive pedestal caused by movement of a position of a center of gravity during movement of the stage on the basis of an output of the position-measuring unit, and inputting a command value to correct the amount of inclination into the vibration control system in a feedforward manner.

2. The vibration-preventive apparatus according to claim 1, further comprising a scan counter for feedforward-inputting, into the vibration control system, command values for reaction forces having directions opposite to those of accelerations immediately after start and immediately before stop of the movement of the stage.

3. The vibration-preventive apparatus according to claim 1, wherein the vibration control system comprises:

a first coordinate-converting unit for converting the output of the displacement sensor into displacements in directions of degrees of freedom of the center of gravity of the vibration-preventive pedestal;

a first velocity converting unit for determining velocity command values obtained on the basis of differences between outputs from the first coordinate-converting unit and target values of the position of the center of gravity of the vibration-preventive pedestal;

a second coordinate-converting unit for converting the output of the vibration sensor into accelerations for each of the degrees of freedom of the center of gravity of the vibration-preventive pedestal;

a second velocity converting unit for determining velocities of the center of gravity of the vibration-preventive pedestal from the accelerations of the second coordinate-converting unit;

subtracters for determining velocity deviations for each of the degrees of freedom of the center of gravity of the vibration-preventive pedestal from the velocities and the velocity command values; and

velocity controllers for generating, from outputs of the subtracters, velocity control amounts of the center of gravity of the vibration-preventive pedestal for each of the degrees of freedom; and

wherein the vibration-compensating system feedforward-inputs command values to correct the amount of inclination obtained from the output of the position-measuring unit.

4. The vibration-preventive apparatus according to claim 1, further comprising at least one actuator for moving the vibration-preventive pedestal in X and Y directions perpendicular to the vertical direction respectively.

5. In an exposure apparatus that forms a pattern onto a photosensitive substrate by projecting illuminating light through a projection optical system, a vibration control apparatus comprising:

a vibration-preventive pedestal held horizontally through at least three vibration-preventive pads;

a substrate stage, movable on the vibration-preventive pedestal, for holding the photosensitive substrate;

at least three actuators for moving the vibration-preventive pedestal in a vertical direction;

at least one displacement sensor for detecting displacement of the vibration-preventive pedestal;

at least one vibration sensor for detecting vibration of the vibration-preventive pedestal;

a vibration control system for controlling the respective actuators on the basis of outputs of the displacement sensor and the vibration sensor so that the vibration of the vibration-preventive pedestal is suppressed;

a position-measuring unit for measuring a position of the substrate stage; and

a vibration-compensating system for forecasting an amount of inclination of the vibration-preventive pedestal caused by movement of a position of a center of gravity during movement of the substrate stage on the basis of an output of the position-measuring unit, and inputting a command value to correct the amount of inclination into the vibration control system in a feedforward manner.

6. The exposure apparatus according to claim 5, further comprising a scan counter for feedforward-inputting, into the vibration control system, command values for reaction forces having directions opposite to those of accelerations immediately after start and immediately before stop of the movement of the substrate stage.

7. The exposure apparatus according to claim 5, further comprising a mask stage movable in synchronization with the substrate stage, and a position-measuring unit for measuring a position of the mask stage, wherein the vibration-compensating system forecasts an amount of inclination of the vibration-preventive pedestal caused by movement of a position of a center of gravity during movement of the substrate stage and the mask stage on the basis of outputs of the position-measuring units for the respective stages, and inputs a command value to correct the amount of inclination into the vibration control system in a feedforward manner.

8. The exposure apparatus according to claim 7, further comprising a scan counter for feedforward-inputting, into the vibration control system, command values for reaction forces having directions opposite to those of accelerations immediately after start and immediately before stop of the movement of the substrate stage and the mask stage.

9. The exposure apparatus according to claim 5, wherein the vibration control system comprises:

a first coordinate-converting unit for converting the output of the displacement sensor into displacements in directions of degrees of freedom of the center of gravity of the vibration-preventive pedestal;

a first velocity converting unit for determining velocity command values obtained on the basis of differences between outputs from the first coordinate-converting unit and target values of the position of the center of gravity of the vibration-preventive pedestal;

a second coordinate-converting unit for converting the output of the vibration sensor into accelerations for each of the degrees of freedom of the center of gravity of the vibration-preventive pedestal;

a second velocity converting unit for determining velocities of the center of gravity of the vibration-preventive pedestal from the accelerations of the second coordinate-converting unit;

subtracters for determining velocity deviations for each of the degrees of freedom of the center of gravity of the vibration-preventive pedestal from the velocities and the velocity command values; and

velocity controllers for generating, from outputs of the subtracters, velocity control amounts of the center of gravity of the vibration-preventive pedestal for each of the degrees of freedom; and

wherein the vibration-compensating system feedforward-inputs command values to correct the amount of inclination obtained from the output of the position-measuring unit.

10. A vibration-preventive apparatus comprising:

a vibration-preventive pedestal held horizontally through at least three vibration-preventive pads;

at least three actuators for driving the vibration-preventive pedestal in a vertical direction at different positions;

at least three vertical displacement sensors for detecting vertical displacement of the vibration-preventive pedestal at different points;

a vibration sensor for detecting at least an acceleration of the vibration-preventive pedestal in a horizontal plane;

a vibration control system for controlling the respective actuators on the basis of outputs of the displacement sensors and the vibration sensor so that vibration of the vibration-preventive pedestal is suppressed; and

a vibration-compensating system for removing a gravitational acceleration component contained in a detected value obtained by the vibration sensor on the basis of displacement in a direction of inclination with respect to the horizontal plane obtained on the basis of the outputs of the three vertical displacement sensors.

11. The vibration-preventive apparatus according to claim 10, wherein the vibration sensor comprises an acceleration sensor for an X direction and an acceleration sensor for a Y direction, and wherein the vibration control system comprises:

a first coordinate-converting unit for converting the output of the displacement sensor into displacements in directions of degrees of freedom of the center of gravity of the vibration-preventive pedestal;

a first velocity converting unit for determining velocity command values obtained on the basis of differences between outputs from the first coordinate-converting unit and target values of the position of the center of gravity of the vibration-preventive pedestal;

a second coordinate-converting unit for converting the output of the vibration sensor into accelerations for each of the degrees of freedom of the center of gravity of the vibration-preventive pedestal;

a second velocity converting unit for determining velocities of the center of gravity of the vibration-preventive pedestal from the accelerations of the second coordinate-converting unit;

subtracters for determining velocity deviations for each of the degrees of freedom of the center of gravity of the vibration-preventive pedestal from velocities of the center of gravity obtained from the second velocity converting unit;

velocity controllers for generating, from outputs of the subtracters, velocity control amounts of the center of gravity of the vibration-preventive pedestal for each of the degrees of freedom; and

wherein the vibration-compensating system comprises respective amplifiers for multiplying, by a gravitational acceleration, an output of an inclination component θ

_x about an X axis and an output of an inclination component θ

_y about a Y axis outputted from the first coordinate-converting unit, and subtracters for determining the differences between outputs from the respective amplifiers and outputs of the acceleration sensors for the X and Y directions so that outputs of the subtracters are outputted to the second coordinate-converting unit.

12. The vibration-preventive apparatus according to claim 10, further comprising at least one stage movable on the vibration-preventive pedestal.

13. The vibration-preventive apparatus according to claim 10, further comprising at least one actuator for moving the vibration-preventive pedestal in X and Y directions perpendicular to the vertical direction respectively.

14. The vibration-preventive apparatus according to claim 10, further comprising a vibration sensor for detecting an acceleration of the vibration-preventive pedestal in the vertical direction.

15. In an exposure apparatus that forms a pattern onto a photosensitive substrate by projecting illuminating light through a projection optical system, a vibration control apparatus comprising:

a vibration-preventive pedestal held horizontally through at least three vibration-preventive pads;

at least one stage, movable on the vibration-preventive pedestal, for holding the photosensitive substrate;

at least three actuators for driving the vibration-preventive pedestal in a vertical direction at different positions;

at least three vertical displacement sensors for detecting vertical displacement of the vibration-preventive pedestal at different points;

a vibration sensor for detecting at least an acceleration of the vibration-preventive pedestal in a horizontal plane;

a vibration control system for controlling the respective actuators on the basis of outputs of the displacement sensors and the vibration sensor so that vibration of the vibration-preventive pedestal is suppressed; and

a vibration-compensating system for removing a gravitational acceleration component contained in a detected value obtained by the vibration sensor on the basis of displacement in a direction of inclination with respect to the horizontal plane obtained on the basis of the outputs of the three vertical displacement sensors.

16. The exposure apparatus according to claim 15, further comprising a position-measuring unit for measuring a position of the at least one stage, wherein the vibration-compensating system further forecasts an amount of inclination of the vibration-preventive pedestal caused by movement of a position of a center of gravity during movement of the at least one stage on the basis of an output of the stage position-measuring unit, and inputs a command value to correct the amount of inclination into the vibration control system in a feedforward manner.

17. The exposure apparatus according to claim 16, provided as a scanning type exposure apparatus, further comprising a mask stage movable in synchronization with the at least one stage as a substrate stage, and a position-measuring unit for the mask stage.

18. The exposure apparatus according to claim 17, further comprising a scan counter for feedforward-inputting, into the vibration control system, command values for reaction forces having directions opposite to those of accelerations immediately after start and immediately before stop of the movement of the substrate stage and the mask stage.

19. The exposure apparatus according to claim 15, wherein the vibration sensor comprises an acceleration sensor for an X direction and an acceleration sensor for a Y direction wherein the vibration control system comprises:

a first coordinate-converting unit for converting the output of the displacement sensor into displacements in directions of degrees of freedom of the center of gravity of the vibration-preventive pedestal;

a first velocity converting unit for determining velocity command values obtained on the basis of differences between outputs from the first coordinate-converting unit and target values of the position of the center of gravity of the vibration-preventive pedestal;

a second coordinate-converting unit for converting the output of the vibration sensor into accelerations for each of the degrees of freedom of the center of gravity of the vibration-preventive pedestal;

a second velocity converting unit for determining velocities of the center of gravity of the vibration-preventive pedestal from the accelerations of the second coordinate-converting unit;

subtracters for determining velocity deviations for each of the degrees of freedom of the center of gravity of the vibration-preventive pedestal from velocities of the center of gravity obtained from the second velocity converting unit;

velocity controllers for generating, from outputs of the subtracters, velocity control amounts of the center of gravity of the vibration-preventive pedestal for each of the degrees of freedom; and

wherein the vibration-compensating system comprises respective amplifiers for multiplying, by a gravitational acceleration, an output of an inclination component θ

_x about an X axis and an output of an inclination component θ

_y about a Y axis outputted from the first coordinate-converting unit, and subtracters for determining the differences between outputs from the respective amplifiers and outputs of the acceleration sensors for the X and Y directions so that outputs of the subtracters are outputted to the second coordinate-converting unit.

20. The exposure apparatus according to claim 15, further comprising at least one actuator for moving the vibration-preventive pedestal in X and Y directions perpendicular to the vertical direction respectively.

21. The exposure apparatus according to claim 15, further comprising a vibration sensor for detecting an acceleration of the vibration-preventive pedestal in the vertical direction.

22. A method of compensating for vibrations in an apparatus having a pedestal, at least one movable stage movable on the pedestal, at least three actuators for vertically moving the pedestal, at least one displacement sensor for detecting displacement of the pedestal and at least one vibration sensor for detecting vibration of the pedestal, the method comprising:

measuring a position of the at least one stage;

forecasting an amount of inclination of the pedestal based on the position of the at least one stage; and

controlling the actuators on the basis of outputs from the displacement sensor, the vibration sensor and the forecast amount of inclination to suppress vibration of the pedestal and to correct the amount of inclination in a feedforward manner.

23. The method of claim 22, wherein controlling the actuators comprises:

converting the output of the displacement sensor into displacements in the directions of degrees of freedom of a center of gravity of the pedestal;

determining velocity command values on the basis of differences between the displacements and target values of the position of the center of gravity of the pedestal;

converting the output of the vibration sensor into accelerations for each of the degrees of freedom of the center of gravity of the pedestal;

determining velocities of the center of gravity of the pedestal from the accelerations;

determining deviations of the center of gravity of the pedestal for each of the degrees of freedom from the velocity command values and the velocities of the center of gravity of the pedestal; and

generating velocity control amounts of the center of gravity for each of the degrees of freedom.

24. A method of compensating for vibrations in an apparatus having a pedestal, at least three actuators for vertically moving the pedestal, at least three vertical displacement sensors for detecting vertical displacement of the pedestal at different points, and at least one vibration sensor for detecting at least an acceleration of the pedestal in a horizontal plane, the method comprising:

removing a gravitational acceleration component contained in a detected value obtained by the vibration sensor based on a direction of inclination of the pedestal with respect to the horizontal plane obtained from the output of the vertical displacement sensors; and

controlling the actuators on the basis of outputs from the displacement sensor and the vibration sensor, with the gravitational acceleration component removed, to suppress vibration of the pedestal.

25. The method of claim 24, wherein removing the gravitational acceleration component comprises:

converting the output of the vibration sensor into accelerations for each of the degrees of freedom of a center of gravity of the pedestal;

multiplying an inclination component about an X axis and an inclination component about a Y axis by a gravitational acceleration; and

determining differences between the multiplied inclinations and the accelerations.