JP2865369B2 - Magnetic suction gas floating type pad - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing mechanism used for a stage device, and more particularly to a pad used for movably supporting an object on a base surface.

The pad of the present invention is not particularly limited in its use, but is particularly suitable for movably supporting an object on a base having a vertical guide surface. Hereinafter, a vertical stage device will be mainly described as an example.

[Prior Art] A stage of a step moving exposure apparatus for manufacturing a semiconductor device conventionally has a horizontal stage surface, light is radiated vertically from a light source to a wafer, and the stage can be horizontally step-driven. .

Usually, a base such as an optical bench or a gantry mounted thereon has a horizontal surface and has sufficiently high rigidity. The movable stage is supported on the base by gravity, and moves in a horizontal plane using the horizontal plane of the base as a guide.

In recent years, an exposure apparatus for manufacturing a semiconductor device using an orbital radiation (SOR) light source has been considered. In this device, the electron orbit is usually formed in the horizontal plane,
Light is emitted horizontally. To perform exposure by directly receiving light traveling horizontally, the stage for moving the semiconductor wafer is a vertical movable stage that moves in the vertical direction, unlike the conventional horizontal movement stage. The vertically movable stage device requires a support element for supporting gravity and a guide element extending in the vertical direction. The support element and the guide element may be integrated.

FIG. 5 shows the appearance of a conventional four-sided vertical movable stage device. In this method, a rigid guide structure 42 is mounted on a base body 41 having a vertical plane.
Are used as guide posts, and a slider 43 carried so as to surround the periphery thereof is movable in the vertical direction of the arrow (Z direction). Air is supplied between the slider 43 and the guide structure 42 from an air bearing device (not shown) to apply a floating force to the slider 43 from four sides. The movement of the slider 43 is performed by an electromagnetic driving device. Usually, two or more sets of such a guide structure 42 and a slider 43 are arranged in parallel, and a stage is fixed across the
It is a movable stage in the direction. The object is placed on the movable stage, and the slider 43 is moved up and down to drive the object in the Z direction.

Instead of directly supporting the stage on the Z-direction movable slider, for example, two guide structures oriented in the X-direction perpendicular to the Z-direction are supported on the Z-direction movable slider. -Z A two-dimensional vertical plane movable stage device is configured.

[Means for Solving the Problems] FIG. 6 is a side view of the slider 43 of FIG. 5 in which the stage 44 is fixed. 2 on stage 44
As indicated by the dashed line, a part of the driving device or the air bearing device or the X-direction movable stage is further supported.
Therefore, the movable part is considerably heavy as a whole. This weight is supported by the guide structure 42 via the slider 43. It is difficult to make the center of gravity at which the weight of the movable portion acts and the point of application of the driving force (or supporting force) in the Z direction coincide with each other due to structural restrictions. That is, the driving force acts near the interface between the slider 43 and the guide structure 42, but the center of gravity is shifted to the stage 44 side. Due to the difference between the position of the center of gravity and the point of application of the driving force, a moment about the X axis is generated. In FIG. 5, since the center of gravity is shifted to the right, a downward moment is generated. As a result, as shown by the dotted line in FIG. 5, the movable portion tilts, and the guide structure 42 is deformed. In addition, the position where the moment is generated moves in the Z-axis direction as the stage moves. By the way, the guide structure
42 is supported up and down, and its rigidity changes with the vertical position. As a result, movement errors such as rolling around the Z axis and pitching around the X axis occur with respect to the stage 44, and this causes deterioration in positioning accuracy.

An object of the present invention is to provide a movable support pad used for realizing a stage device or the like with high positioning accuracy.

[Problem to be Solved by the Invention] The pad of the present invention uses a magnetic attraction force and a floating force by gas blowing.

The magnetic suction gas floating type pad of the present invention is a pad for movably holding an object on a magnetic base, a permanent magnet for generating a magnetic attractive force on the pad with respect to the magnetic base, It has a gas blowing mechanism for floating a pad on a magnetic base, and electromagnet means capable of generating a magnetic force in a direction to cancel the magnetic force of the permanent magnet when the pad is separated.

[Operation] Since the magnetic base is not limited by its diameter or the like, it can be configured to have sufficiently high rigidity. The pad receives a floating force against the base by the gas bearing action of the gas blowing mechanism. The permanent magnet generates an attractive force between the base and the pad by a magnetic attractive force. The pad is supported at a predetermined height above the base by a floating force and a magnetic attraction force caused by the gas bearing action.

Even if the substantial center of gravity of the pad member and the support point deviate from each other and a rotational moment is generated, the base can be manufactured to have sufficiently high rigidity, unlike the columnar guide structure,
Substantially no deformation of the base can occur.

When the balance between the suction force and the levitation force is lost, a force for always returning to the equilibrium position acts, and high-precision positioning can be performed.

When the pad is separated from the base, the pad can be safely and easily separated from the base by weakening the attraction force by generating a magnetic force in a direction opposite to that of the permanent magnet by the electromagnet means. It is safe to reduce the suction force when mounting the pad on the base.

By using three or more such pads in combination with a magnetic base and assembling a stage thereon, a vertically movable stage device with high positioning accuracy can be realized.

FIG. 1 shows a magnetic suction air floating type pad according to an embodiment of the present invention.

The pad 10 is mainly composed of a yoke 2 formed of a magnetic material such as iron. A spherical hinge 1 is connected to a back surface of the yoke 2. The spherical hinge 1 has a shape in which a part of a columnar member such as iron is gradually reduced in diameter toward the center of the hinge. Because the diameter is reduced, the spherical hinge 1
Has a high rigidity in the axial direction, but is elastically deformable in a direction perpendicular to the axis. On the side of the yoke 2 facing the magnetic base 8, a concave portion is formed in the center,
An electromagnet 3, a permanent magnet 4, a pad member 5, and a non-magnetic spacer 7 are housed therein. The pad member 5 is formed of a magnetic material such as iron, and its surface is designed to protrude from the surface of the yoke 2. The permanent magnet 4 has magnetic poles on the upper and lower surfaces in the figure. The permanent magnet 4, the yoke 2, and the pad member 5 form a magnetic circuit that opens downward. Non-magnetic spacer 7
Has a thickness sufficient to prevent the magnetic circuit from closing within the pad 10. When the pad 10 is disposed on the magnetic base 8, the pad 10 and the magnetic base 8 close a magnetic circuit through a thin layer of air. That is, the pad 10 and the magnetic base 8 attract each other by the magnetic attraction of the permanent magnet 4.

A gas flow passage for air or the like is formed through the yoke 2, the permanent magnet 4, and the pad member 5. Hereinafter, a case where air is used will be described as an example. An air outlet 9 is formed in the center of the pad member 5 to blow air toward the magnetic base 8. There are various air blowing mechanisms, examples of which are shown in FIGS. 2 (A) and 2 (B).

2 (A) and 2 (B) show the structure of the surface drawing type air pad surface. FIG. 2A is a bottom view, and FIG. 2B is a partial cross-sectional view. The bottom surface of the pad member 5 has an air outlet 9 at the center, and a plurality of grooves 15 are formed radially continuously from the air outlet 9.

FIG. 2B shows a cross-sectional shape of the groove 15. In the case shown, a groove having a rectangular cross section is formed. That is, when air is supplied to the pad, the air is supplied to the air outlet 9 and all the grooves 15.
From the surface of the pad member 5 toward the entire surface. The pad 10 floats on the magnetic base 4 by the blowing pressure of the air.

FIG. 3 shows the relationship between the attractive force F1 by the permanent magnet 4 and the floating force F2 by air blowing. Force F1 by permanent magnet
Is a suction force for sucking the pad 10 toward the magnetic substance base 8, and decreases as the distance between the magnetic substance and the pad increases. The force F2 generated by air blowing is a repulsive force acting in a direction to separate the pad 10 from the magnetic base 8.
When the distance from the magnetic base 8 to the pad 10 increases, the resistance to the flow of air sharply decreases, so that the repulsive force F2 due to air blowing rapidly decreases as the distance increases. The attractive force of the permanent magnet and the repulsive force of the air supply from the air supply source are opposite to each other, and stop the pad 10 at a balanced height.

By the way, when the stage is formed by using the pad as described above, it is necessary to separate the pad 10 from the magnetic base 8 for maintenance of the stage or replacement of a workpiece such as a semiconductor wafer arranged on the stage. There is time. In particular, there may be a case where a step of separating the stage from the base is required every time the workpiece is replaced due to space constraints of the entire apparatus.

In order to separate the pad from the base, it is conceivable to pull the pad with as much force as necessary, or to increase the pressure of the air blow to overcome the suction force. However, in the former method, each part of the stage is easily deformed, and the accuracy is likely to be deteriorated thereafter. The latter method seems to be possible in principle if a sufficient air pressure can be obtained.However, in general, the air piping is thin, and there is resistance due to restrictions such as self-generated throttles and orifice throttles. Have difficulty. In other words, the pad can be pulled away from the base to some extent by the repulsive force of air, but it is extremely difficult to obtain more force.

The pad 10 shown in FIG. 1 has the electromagnet 3 together with the permanent magnet 4. A current source 11 is connected to the electromagnet 3 via a controller 13. The current source 11 has a configuration capable of supplying a reversible DC current. When the pad 10 is separated, a current for generating a magnetic force in a direction opposite to that of the permanent magnet 4 is supplied to the electromagnet 3 from the current source 11.

FIG. 3 illustrates a state where a force F3 generated by the electromagnet is generated in a direction opposite to the force F1 generated by the permanent magnet. Electromagnetic repulsion F3
Is sufficiently strong, the attractive force F1 by the permanent magnet is canceled even at a distance where the repulsive force due to the air blowing is reduced, and the pad 10 can be easily separated from the magnetic base 8. This state is schematically shown in the upper right of FIG. That is, the electromagnet 3 is disposed in the opposite direction to the permanent magnet 4, and the magnetic forces of both are canceled.

The pad 10 shown in FIG. 1 further includes a position detector 6. The position detector 6 detects a distance between the magnetic base 8 and the pad 10. By supplying a detection signal from the position detector 6 to the controller 13, the current supplied to the electromagnet 3 can be controlled.

For example, the attraction force of the pad 10 may vary from pad to pad and from place to place due to variations in magnetic force due to variations in the manufacturing conditions of the permanent magnet 4 and distribution of magnetic properties in the magnetic base 8. When the suction force changes, the flying height of the pad 10 changes. This change is detected by the position detector 6, and a current corresponding to the distance between the pad 10 and the magnetic base 8 is supplied to the electromagnet 3 via the controller 13, thereby controlling the magnetic attraction of the pad 10 and It is possible to control so that the distance between 10 and the magnetic base 8 is kept constant.

When the flying height of each pad changes, the posture of the stage changes, and the rigidity of the air bearing portion of the pad may change, and the controllability and accuracy of the stage may deteriorate. Position detector 6
Such a problem can be corrected by exciting the electromagnet 3 by the signal from the controller and making the characteristics of the pads uniform. The magnetic force generated by the electromagnet 3 for performing such fine adjustment may be the same as the permanent magnet 4 or the opposite. When the magnetic force of the permanent magnet 4 alone may be insufficient, the magnetic force of the electromagnet 3 is
The direction should be the same as the direction of the magnetic force.

 FIG. 4 shows a vertical movable stage according to another embodiment.

A pad 10 similar to the pad shown in FIG. 1 is coupled to a magnetic base 8 having a vertical plane by magnetic attraction. The gravity acting on the pad 10 is offset by other appropriate means such as a linear motor. Air from a compressed air source 21 such as a high-pressure gas cylinder is supplied to a regulator 23 via a filter 22, and becomes a medium-pressure air at a constant pressure.
This medium-pressure air is set to a predetermined pressure via the electropneumatic regulator 24 and supplied to the air supply port of the pad 10. The pressure of the supplied air is detected by the pressure detector 25, and the pressure of the supplied air is controlled by controlling the electropneumatic regulator 24. When air is supplied, an air layer is formed between the pad 10 and the magnetic base 8, and the pad 10 floats from the magnetic base 8. The pad 10 stops at a position where the levitation force by the air blowing is balanced with the magnetic attraction force. The position detector 6 detects the distance that the pad 10 floats from the magnetic body 8 and supplies the signal to the sensor amplifier 34. The sensor amplifier 34 supplies the flying height of the pad 10 to the comparator 32 in the controller 31. In the controller 31, the comparator 32 compares the set position value with the detected position signal supplied from the sensor amplifier 34, and supplies a control signal to the amplifier 33 so that the actual distance becomes equal to the set distance. The amplifier 33 supplies a controlled current to the electromagnet 3 to adjust the flying height of the pad 10 by increasing or decreasing the magnetic attraction, thereby obtaining a desired flying height.

In the vertical movable stage, three or more pads 10 as shown in FIG. 4 are fixed to the stage so as to be movable on the stage magnetic base 8 surface. By adjusting the magnetic force of the electromagnet 3, it is possible to adjust the dispersion of the performance for each pad and handle the pad as a pad having a constant performance.

When the stage device is separated from the magnetic base 8 as described above, the electromagnet 3 generates a magnetic force in a direction opposite to that of the permanent magnet 4, thereby weakening the magnetic attraction force and moving the stage without adversely affecting the other. It can be separated from the magnetic base 8.

Also, the stage once separated is replaced with the magnetic base 8 again.
Even when the magnetic head is mounted on an upper surface, if the magnetic attraction increases as the distance decreases, the pad 10 collides with the magnetic base 8, which may cause deformation of the stage device or decrease in accuracy. In such a case as well, a current is supplied to the electromagnet 3 in a direction to decrease the magnetic force of the permanent magnet 4, and the operation is performed with the magnetic attraction force weakened, so that the stage device is safely disposed on the magnetic base 8. be able to.

In the case of a magnetic intake air levitation stage, it is conceivable that the stage may vibrate in the levitation direction. In such a case, if the vibration is detected by the position detector and a magnetic force is generated by the electromagnet in a direction to eliminate the vibration, the vibration can be rapidly attenuated.

Although the case where one permanent magnet and one electromagnet are provided on the pad has been described, a plurality of permanent magnets,
A structure having a plurality of electromagnets may be used. Further, by providing a plurality of position detectors, it is possible to control the surface of the pad 10 to be kept parallel to the magnetic base 8. Although the case where air is used as the working fluid has been described, other gases such as nitrogen may be used. Although the configuration in which the electromagnet is disposed behind the permanent magnet has been described, any arrangement may be used as long as the magnetic force generated by the electromagnet and the magnetic force generated by the permanent magnet interfere with each other. Although the attractive force of the electromagnet is controllable, heat is generated by the current that excites the electromagnet. It is preferred that

Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[Effects of the Invention] As described above, according to the present invention, there is provided a pad with little friction due to a levitation force caused by gas blowing and an attraction force caused by a permanent magnet. By generating a magnetic force that cancels out the magnetic force of the magnet, the pads can be separated without difficulty. The same applies to pad mounting. Therefore, the operation can be performed safely and reliably even when the pad is attached to or detached from the magnetic base.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a magnetic suction air floating type pad according to an embodiment of the present invention. FIGS. 2 (A) and 2 (B) are a bottom view and a partial sectional view showing a surface drawing type air pad surface. FIG. 4 is a graph for explaining the concept of operation of the magnetic suction air floating type pad of FIG. 1, FIG. 4 is a schematic block diagram showing a vertical movable stage device according to another embodiment of the present invention, FIG. 5 and FIG. The figures are a perspective view and a side view showing a conventional vertical movable bearing. In the drawing, 1 ... spherical hinge 2 ... yoke 3 ... electromagnet 4 ... permanent magnet 5 ... pad member 6 ... position detector 7 ... nonmagnetic spacer 8 ... magnetic base 9 ... air blowing Port 10 Pad 11 Current source 13 Controller 15 Groove 21 Compressed air source 22 Filter 23 Regulator 24 Electropneumatic regulator 25 Pressure detector 31 Controller 32 … Comparator 33 …… Amplifier 34 …… Sensor amplifier

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-216120 (JP, A) JP-A-62-35112 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F16C 32/00-32/06

Claims (2)

(57) [Claims] 1. A pad for movably holding an object on a magnetic base, a permanent magnet for generating a magnetic attraction to the pad with respect to the magnetic base, and a permanent magnet on the magnetic base. A magnetic suction / gas floating type pad comprising: a gas blowing mechanism for floating a pad; and electromagnet means capable of generating a magnetic force in a direction to cancel the magnetic force of the permanent magnet when the pad is separated. 2. The apparatus according to claim 1, further comprising a position detector for detecting a distance from said magnetic base, wherein said electromagnet means can control a magnetic force in accordance with a signal from said position detector. Magnetic suction / gas floating type pad.