Embodiments of the present invention will be described below with reference to the accompanying drawings.
In the first embodiment, a Lorentz's force actuator 23 is used to support a reference object 21 by a constant force. The position of a surface plate 2 is feedback-controlled with respect to the reference object 21 supported by the constant force. An anti-vibration apparatus excellent in low-frequency component removal performance is thus provided. In the first embodiment, a target object is the surface plate 2.
An anti-vibration table will be explained first. The anti-vibration table is formed by causing passive dampers 10a to 10c including, for example, gas springs to support the surface plate 2 from a floor 1.
Z actuators 11z1 to 11z3, X actuator 11x1, and Y actuators 11y1 and 11y2 are interposed between the surface plate 2 and the floor 1. The Z actuators 11z1 to 11z3 each generate a driving force in the Z-axis direction. The X actuator 11x1 generates a driving force in the X-axis direction. The Y actuators 11y1 and 11y2 each generate a driving force in the Y-axis direction. The actuator 11 uses a linear motor here. The above-described six actuators 11 can drive the surface plate 2 in the six axis-directions.
The reference object 21 is supported by a constant force output from the Lorentz's force actuator 23. The Lorentz's force actuator can use, for example, a linear motor or voice coil motor.
As shown in
The coreless coil 25 connects to a power supply device 26. The power supply device 26 incorporates a current minor loop for supplying a constant current to the coreless coil 25. Adjusting the gain of the current minor loop makes it possible to adjust a counter electromotive force generated by the Lorentz's force actuator 23. A larger counter electromotive force produces a greater effect of damping vibration acting on the reference object 21. However, an excessively large counter electromotive force makes the reference object 21 susceptible to the velocity of the floor 1 if it occurs.
To improve the disturbance characteristic of the reference object, it suffices to insert an integrator in the current minor loop.
As shown in
Non-contact measuring devices 12x1 and 12x2 can measure a relative displacement between the surface plate 2 and the reference object 21 in the X-axis direction and their relative angle around the Z-axis. A non-contact measuring device 12y1 can measure a relative displacement between the surface plate 2 and the reference object 21 in the Y-axis direction. Non-contact measuring devices 12z1, 12z2, and 12z3 can measure a relative displacement between the surface plate 2 and the reference object 21 in the Z-axis direction and their relative angles around the X- and Y-axes. The above-described six non-contact measuring devices 12 can measure the relative position between the reference object 21 and the surface plate 2 in the six axis-directions.
A compensator 14 converts measurement information 13 obtained by the non-contact measuring device 12 into a command value to be input to the actuator 11. The compensator 14 includes, for example, a decoupled matrix, PID compensator, and output distribution matrix.
As described above, it is possible to feedback-control the position of the surface plate 2 with respect to the reference object 21. Since the reference object 21 completely floats in the air and hence becomes free from the influence of any displacement due to floor vibration, the surface plate 2 the position of which is feedback-controlled with respect to the reference object 21 also becomes free from the influence of any displacement due to vibration of the floor 1. The velocity of the surface plate 2 may be feedback-controlled with respect to the reference object 21.
The anti-vibration apparatus according to the present invention removes vibration components up to a frequency as low as 2 Hz or less. In addition, since a support spring for supporting the reference object is used unlike the prior art, the anti-vibration does not resonate at its natural frequency.
The reference object 21 floats in the air upon receiving a constant force that balances its gravitational force from the Lorentz's force actuator 23. For this reason, a variation in atmospheric pressure acts to move the reference object 21. Furthermore, when the magnetic field acts on the Lorentz's force actuator 23, a force generated by it does not balance the gravitational force of the reference object 21 any longer. This results in the movement of the reference object 21. To prevent these problems, as shown in
As the Lorentz's force actuator 23 generates a force that balances the gravitational force of the reference object 21 and it floats in the air, it is displaced in a direction opposite to that of rotation of the earth upon receiving a Coriolis force. The reference object 21 is likely to move upon receiving a force due to some kind of external factor, in addition to the Coriolis force. It is therefore necessary to correct the position of the reference object 21 periodically or occasionally. As shown in
As shown in
As in the first embodiment, a non-contact measuring device 12 measures the position of the reference object 21 to be able to measure a displacement of the surface plate 2 relative to the reference object 21. Feedback-controlling the position of the surface plate 2 based on the measured relative displacement allows it to be free from the influence of any displacement due to vibration of the floor. The velocity of the surface plate 2 may be feedback-controlled with respect to the reference object 21. Also according to the second embodiment, it is possible to provide an anti-vibration apparatus excellent in low-frequency component removal performance, which is free from any natural frequency in principle.
In the third embodiment, a reference object 21 is supported using six Lorentz's force actuators. Lorentz's force actuators 23x1 and 23x2 generate forces to drive the reference object 21 in the X-axis direction and around the Z-axis. A Lorentz's force actuator 23y1 generates a force to drive the reference object 21 in the Y-axis direction. Lorentz's force actuators 23z1, 23z2, and 23z3 generate forces to drive the reference object 21 in the Z-axis direction.
The Lorentz's force actuator has a property of generating forces in directions other than an intended driving direction. In view of this, as shown in
A non-contact measuring device 12 measures the reference object 21 to be able to calculate a displacement of a surface plate 2 relative to the reference object 21. Feedback-controlling the position of the surface plate 2 based on the measured relative displacement allows it to be free from the influence of any displacement due to vibration of the floor. The velocity of the surface plate 2 may be feedback-controlled with respect to the reference object 21.
It is therefore possible to provide an anti-vibration apparatus excellent in low-frequency component removal performance, which is free from any natural frequency in principle. Although the six-Lorentz's force actuators are used in the third embodiment, the number of Lorentz's force actuators is not limited to six.
In the fourth embodiment, the Lorentz's force actuators 23x1, 23x2, and 23y1 according to the third embodiment are omitted. Instead, guides 30x1, 30x2, 30y1, and 30y2 are provided to constrain the movement of a reference object 21a in the X- and Y-axis directions and around the Z-axis.
Lorentz's force actuators 23z1, 23z2, and 23z3 support the reference object 21a by constant position independent forces regarding the Z-axis direction and around the X- and Y-axes. This makes it possible to use the reference object 21a as the measurement reference of a position feedback control system for a surface plate 2.
However, the use of the guides 30x1, 30x2, 30y1, and 30y2 makes the reference object 21a exhibit springness in the X- and Y-axis directions and around the Z-axis. For this reason, it is impossible to use the reference object 21a as the measurement reference of the position feedback control system for the surface plate 2 in the X- and Y-axis directions and around the Z-axis. In view of this, as shown in
As shown in
It is therefore possible to use the reference object 21a as a measurement reference in the Z-axis direction and around the X- and Y-axes. Using the reference object 21b as a measurement reference in the X- and Y-axis directions and around the Z-axis makes it possible to provide measurement references free from any position dependent forces in the six axis-directions.
Measuring the reference object 21a using non-contact measuring devices 12z1, 12z2, and 12z3 makes it possible to measure a displacement of the surface plate 2 relative to the reference object 21a in the Z-axis direction and their relative angles around the X- and Y-axes. The reference object 21b is measured using non-contact measuring devices 12x1, 12x2, and 12y1 as well. This makes it possible to measure a displacement of the surface plate 2 relative to the reference object 21b in the X- and Y-axis directions and their relative angle around the Z-axis.
Feedback-controlling the position of the surface plate 2 based on the measured relative displacement and relative angle allows it to be free from the influence of any displacement due to vibration of the floor. The velocity of the surface plate 2 may be feedback-controlled with respect to the reference object 21.
As described above, it is possible to provide an anti-vibration apparatus excellent in low-frequency component removal performance, which is free from any natural frequency in principle.
As shown in
Non-contact measuring devices 50x1 and 50x2 can measure a displacement of the reference object 21a in the X-axis direction and its rotation angle around the Z-axis, while a non-contact measuring device 50y1 can measure a displacement of the reference object 21a in the Y-axis direction. Actuators 51x1 and 51x2 can drive the reference object 21a in the X-axis direction and around the Z-axis, while an actuator 51y1 can drive the reference object 21a in the Y-axis direction. The actuators 51x1, 51x2, and 51y1 are driven based on the pieces of measurement information obtained by the non-contact measuring devices 50x1, 50x2, and 50y1. This makes it possible to feedback-control the position of the reference object 21a in the X- and Y-axis directions and around the Z-axis.
Lorentz's force actuators 23z1, 23z2, and 23z3 support the reference object 21a by constant position independent forces regarding the Z-axis direction and around the X- and Y-axes. This makes it possible to use the reference object 21a as the measurement reference of the position feedback control system for a surface plate 2.
However, the non-contact measuring device 50 and actuator 51 feedback-control the position of the reference object 21a. For this reason, it is impossible to use the reference object 21a as the measurement reference of the position feedback control system for the surface plate 2 in the X- and Y-axis directions and around the Z-axis.
As in the fourth embodiment, it suffices to use a reference object 21b as the second reference object. That is, the reference object 21a is used as a measurement reference in the Z-axis direction and around the X- and Y-axes, while the reference object 21b is used as a measurement reference in the X- and Y-axis directions and around the Z-axis. This makes it possible to provide measurement references free from any position dependent forces in the six axis-directions.
Measuring the reference object 21a using non-contact measuring devices 12z1, 12z2, and 12z3 makes it possible to measure a displacement of the surface plate 2 relative to the reference object 21a in the Z-axis direction and their relative angles around the X- and Y-axes. The reference object 21b is measured using non-contact measuring devices 12x1, 12x2, and 12y1 as well. This makes it possible to measure a displacement of the surface plate 2 relative to the reference object 21b in the X- and Y-axis directions and their relative angle around the Z-axis.
Feedback-controlling the position of the surface plate 2 based on the measured relative displacement and relative angle allows it to be free from the influence of any displacement due to vibration of the floor. The velocity of the surface plate 2 may be feedback-controlled with respect to the reference object 21.
As described above, also according to the fifth embodiment, it is possible to provide an anti-vibration apparatus excellent in low-frequency component removal performance, which is free from any natural frequency in principle.
In the sixth embodiment shown in
An actuator 20 for supporting the reference object by the gas pressure comprises a pressure sensor 61 for measuring the gas pressure, a controller 62 for adjusting the degree of opening of a servo valve 63 based on the measurement information obtained by the pressure sensor 61, and a pressure source 64 for supplying a gas. Adjusting the degree of opening of the servo valve 63 based on the measurement information obtained by the pressure sensor 61 makes it possible to supply, to the reference object 21, a gas at a constant pressure that balances its gravitational force.
In addition, measuring the position of the reference object 21 using a non-contact measuring device 12 makes it possible to calculate a displacement of a surface plate 2 relative to the reference object 21 supported by a constant force and their relative angle. Feedback-controlling the position of the surface plate 2 with respect to the reference object 21 based on the measured relative displacement and relative angle allows it to be free from the influence of any displacement due to vibration of the floor. The velocity of the surface plate 2 may be feedback-controlled with respect to the reference object 21.
Also according to the sixth embodiment, it is possible to provide an anti-vibration apparatus excellent in low-frequency component removal performance, which is free from any natural frequency in principle.
In the seventh embodiment, a Lorentz's force actuator 23 includes a velocity feedback control system for suppressing a change in the velocity of a reference object 21 if it occurs. The velocity feedback control system for the reference object 21 will be explained.
As shown in
In addition, measuring the position of the reference object 21 using a non-contact measuring device 12 makes it possible to calculate a displacement of a surface plate 2 relative to the reference object 21 with a better stability of velocity and their relative angle. Feedback-controlling the position of the surface plate 2 with respect to the reference object 21 based on the measured relative displacement and relative angle allows it to be less susceptible to the influence of any velocity due to vibration of the floor. This makes it possible to provide an anti-vibration apparatus that is excellent in stability against velocity.
The eighth embodiment exemplifies a case wherein an anti-vibration apparatus according to the present invention is applied to a lens barrel supporting member of an exposure apparatus, as shown in
In the following description, the direction in which the projection optical system PO projects the exposure light onto the wafer W is the optical axis direction of the projection optical system PO. This optical axis direction is the Z-axis direction. An in-plane direction perpendicular to the Z-axis direction within the sheet surface of
The exposure apparatus 100 scans the reticle R and wafer W relative to the projection optical system PO linearly (in the Y-axis direction here) while projecting a partial device pattern drawn on the reticle R onto the wafer W via the projection optical system PO. With this operation, the entire device pattern of the reticle R is transferred onto a plurality of shot regions on the wafer W by the step & scan scheme.
A surface plate 2 supports the projection optical system PO. A floor 1 supports the surface plate 2 via passive dampers 10. Actuators 11 are interposed between the surface plate 2 and the floor 1. The actuator 11 uses a linear motor here.
The floor supports a reference object 21 via a Lorentz's force actuator 23. Supplying a constant current to the Lorentz's force actuator 23 allows it to output a constant force. The constant force output from the Lorentz's force actuator 23 is fully balanced gravitational force acting on the reference object 21. With this operation, the reference object 21 completely floats in the air and hence becomes free from the influence of any displacement due to floor vibration.
Measuring the reference object 21 using a non-contact measuring device 12 makes it possible to measure a displacement of the surface plate 2 relative to the reference object 21 supported by a constant force.
A compensator 14 converts measurement information 13 obtained by the non-contact measuring device 12 into a command value to be input to the actuator 11. The compensator 14 includes, for example, a decoupled matrix, PID compensator, and output distribution matrix.
As described above, it is possible to control to position the surface plate 2 with respect to the reference object 21 in the six axis-directions. Since the reference object 21 completely floats in the air and hence becomes free from the influence of any displacement due to vibration of the floor 1, the surface plate 2 the position of which is feedback-controlled with respect to the reference object 21 also becomes free from the influence of any displacement due to vibration of the floor 1.
As the reference object 21 receives a force that balances its gravitational force from the Lorentz's force actuator 23 and hence completely floats in the air, it is displaced in a direction opposite to that of rotation of the earth upon receiving a Coriolis force. The reference object 21 is likely to be displaced upon receiving a force due to some kind of external factor, in addition to the Coriolis force. It is therefore necessary to correct the position of the reference object 21 periodically or occasionally. The exposure apparatus 100 must correct the position of the reference object 21 by the step & scan scheme while the pattern on the reticle R is not transferred onto the wafer W.
An embodiment of a device manufacturing method using the above-described exposure apparatus will be explained next with reference to
In step S1 (circuit design), the circuit of a semiconductor device is designed. In step S2 (mask fabrication), a mask is fabricated based on the designed circuit pattern. In step S3 (wafer manufacture), a wafer (substrate) is manufactured using a material such as silicon. In step S4 (wafer process) called a pre-process, the above-described exposure apparatus forms an actual circuit on the wafer by lithography using the mask and wafer. In step S5 (assembly) called a post-process, a semiconductor chip is formed using the wafer manufactured in step S4. This step includes an assembly step (dicing and bonding) and packaging step (chip encapsulation). In step S6 (inspection), the semiconductor device manufactured in step S5 undergoes inspections such as an operation confirmation test and durability test. After these steps, the semiconductor device is completed and shipped in step S7.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2006-249957, filed Sep. 14, 2006, which is hereby incorporated by reference herein in its entirety.
Number | Date | Country | Kind |
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2006-249957 | Sep 2006 | JP | national |