JP5388740B2 - Linear motor and stage device - Google Patents

Description

  The present invention relates to a linear motor and a stage device used in a feed mechanism such as an optical die processing machine and a shape measuring device, an XY stage such as a semiconductor exposure device, or a precision positioning device.

  In an optical die processing machine, a shape measuring apparatus, or an exposure apparatus for manufacturing a semiconductor, it is required to position a workpiece or a measured object with high accuracy and speed. Therefore, development of an XY stage and the like using a linear motor excellent in positioning accuracy and responsiveness as a drive unit and an aerostatic bearing as a guide is progressing.

  FIG. 6A shows an XY stage apparatus according to a conventional example, and the XY moving body 103 is configured to be able to move on the base surface 101 in the XY directions via an aerostatic bearing 104. The Y linear motor 105 generates a driving force for moving the X guide 106 in the Y direction. Thereby, the XY moving body 103 connected through the box-type static air bearing 107 also moves in the Y direction. In the X direction, the XY moving body 103 is directly driven in the X direction by the propulsive force of the X linear motor 108.

  In order to improve the surface roughness of the processing surface in die processing or the like, it is necessary to suppress the apparatus vibration generated by the contact processing. For this reason, it is necessary to improve the servo gain of the linear motor that controls the stage device and improve the disturbance suppression characteristics.

  However, as the servo gain is improved, the propulsive force of the linear motor excites the rigid body mode. In particular, the pitching mode is difficult to control even in the rigid body mode, and the gain crossover frequency in the servo characteristics of the linear motor is lower than the pitching frequency, and the servo gain cannot be increased any more. For this reason, disturbance suppression characteristics cannot be improved.

  Therefore, as shown in FIG. 6B, a stage with a damping mechanism has been proposed in which a vibration damping mechanism for removing the apparatus vibration of the stage is attached (see Patent Document 1). This is because an insulator moving plate 211 is attached to a stage upper plate 210 that is driven by a linear motor having a mover composed of a coil 201 and a yoke 202 and a stator composed of a magnet 203 and a yoke 204. A damping mechanism inserted in 212; An anode 213 and a cathode 214 are attached to the side walls on both inner sides of the container 212, and an electrorheological fluid 215 is placed therein. The moving plate 211 moves with a slight gap of 0.5 mm or less from each of the anode 213 and the cathode 214. With this configuration, it is possible to generate a damping force between the container 212 and the moving plate 211 and remove the stage vibration.

JP 2001-311789 A

  However, in the prior art, since a damping mechanism is separately added to the stage apparatus, the apparatus becomes larger and the weight increases. As a result, the rigid body mode frequency of the stage device is lowered and the servo gain must be lowered, and the disturbance suppression characteristic by the servo is lowered.

  Further, since the center of gravity of the stage does not exist on the extension line of the damping force vector by the damping mechanism and the propulsive force vector of the linear motor, the stage rigid body mode such as pitching is excited when the stage is driven. As a result, the servo gain is further reduced, and the disturbance suppression characteristic is deteriorated.

  It is an object of the present invention to provide a linear motor and a stage apparatus having a damping mechanism that can eliminate the increase in size of the apparatus and avoid a decrease in disturbance suppression characteristics.

  In order to achieve the above object, a stage apparatus of the present invention includes a base, a stator that is fixed to the base and includes a coil, and a magnet that is movable on the base and faces the coil. A mover, current supply means for supplying a current to the coil and generating a propulsive force to the mover, and at the end of the mover on the base side, the base or the stator and the mover, A first damping mechanism for holding a viscous fluid in a gap formed between the movable element and an end portion of the movable element opposite to the base side, and formed between the movable element and the stator. And a second damping mechanism for holding the viscous fluid in the gap, and the first and second damping mechanisms respectively generate damping forces at both ends of the mover.

  Since the damping mechanism is configured by sandwiching the viscous fluid between the mover and the stator constituting the linear motor and between the mover and the base, the increase in size of the apparatus can be eliminated.

  Also, by matching the resultant force of the damping force of the two damping mechanisms and the point of action of the propulsive force of the linear motor to match the center of gravity of the stage, it is possible to improve disturbance suppression characteristics such as pitching.

The stage apparatus by Example 1 is shown, (a) is the top view, (b) is sectional drawing seen from the AA line of (a). It is sectional drawing which looked at the apparatus shown to Fig.1 (a) from the direction of arrow B. FIG. 6 is a graph showing a vibration reduction effect according to Example 1. It is a graph which shows the servo gain improvement effect. The stage apparatus by Example 2 is shown, (a) is sectional drawing which shows the inside of a linear motor, (b) is a side view. It is a figure explaining a prior art.

  1 and 2 relate to a stage apparatus according to the first embodiment. As shown in FIG. 1A, in the stage apparatus according to the present embodiment, a guide 2 is fixed to a base 1, and the stage 3 can move along the guide 2 on the base via an air bearing 4. Two linear motors 5 are attached to drive the stage 3. As shown in cross section in FIG. 1B, each linear motor 5 has a mover having a magnet 7 fixed to a yoke 6 and a coil 9 held by a coil fixing member 8 fixed to the base 1. And a stator. The Lorentz force is generated in the moving direction of the stage 3 by driving the current supplied to the coil 9 from the current supply means with the magnetic flux of the magnet 7 facing the coil 9 to drive the stage 3.

  Each linear motor 5 is provided with a damping mechanism at each of the upper and lower ends of the mover. The first is formed between the lower surface of the upper yoke 10 constituting the end of the mover opposite to the base side and the holding member 11 attached on the coil fixing member 8 constituting the stator. This is a damping mechanism (second damping mechanism) in which a viscous fluid is held in a gap of several tens of μm. As shown in FIG. 2, the holding member 11 is disposed in the region 8 a where the magnetic flux does not substantially pass among the coil fixing members 8.

  The second is a gap of several tens of μm between the damping plate 12 attached to the lower surface of the yoke 6 that constitutes the base side end of the mover of the linear motor 5 and the holding member 13 that is integral with the base 1. Is a damping mechanism (first damping mechanism) that holds viscous fluid. As the viscous fluid, silicon oil having a kinematic viscosity of about 1000 CS is used. By doing so, even if the stage 3 receives a processing force due to contact processing, the vibration can be absorbed by the two damping mechanisms.

  The holding member 11 is integrated with the coil fixing member 8, the holding member 13 is integrated with the base 1, and the damping plate 12 is integrated with the yoke 6, so that further space saving and weight reduction are possible. Therefore, the weight increase due to the addition of the damping mechanism is substantially eliminated.

  The effect of the above damping mechanism will be described with reference to FIG. This is a measurement of stage vibration. As shown in FIG. 3A, when there is no damping mechanism, the stage vibration is 4.5 nm PP, but as shown in FIG. In addition, the stage vibration is reduced to 2.3 nm PP.

  As shown in FIG. 1 (a), the center of gravity G of the stage 3 is at the center, and as shown in FIG. 1 (b), the linear force is generated so that the propulsive force Ra by Lorentz force is generated at the same height as the stage center of gravity G. A motor 5 is attached. Therefore, the point of action of the resultant force R of the propulsive force Ra by the two linear motors 5 and the stage center of gravity G can be matched.

Each linear motor 5 is provided with two damping mechanisms. If the damping force generated by the upper damping mechanism is Da, the damping force generated by the lower damping mechanism is Db, and the height from the center of gravity G of each stage is L1 and L2, the damping forces Da, Db and L1 , L2 satisfies the following relational expression.
L1 × Da = L2 × Db

  Thereby, as shown in FIG. 2, the height of the resultant force of the damping force Da and the damping force Db can be matched with the height of the stage gravity center G. Also, the point of action of the resultant force D of the four damping forces generated by the four damping mechanisms in the two linear motors 5, the stage center of gravity G, and the point of action of the resultant force R of the propulsive force Ra of each linear motor 5 coincide. Can be made. As a result, excitation of a rigid body mode such as pitching that hinders the servo gain improvement can be prevented, the servo gain can be improved, and the disturbance suppression characteristics of the stage 3 can be improved.

  FIG. 4 is a graph showing servo characteristics (open loop characteristics) when a damping mechanism is added according to the above relational expression. It can be seen that the gain is higher in the case with the damping mechanism than in the case without the damping mechanism. As a numerical value, the gain crossover frequency (frequency at which the gain becomes 0 dB) is 100 Hz in the case where there is no attenuation mechanism, but increases to 150 Hz by appropriately adding the attenuation mechanism. As a result, the minimum dynamic rigidity is increased about twice.

  For example, since the vibration of the workpiece at the time of processing the optical element mold is halved, the conventional surface roughness PV of about 20 nm can be reduced to half that of 10 nm.

  According to the present embodiment, in an XY stage or precision positioning device such as an optical element mold processing device, a shape measuring device, a semiconductor exposure device, etc., it is possible to eliminate the increase in size of the device due to the attenuation mechanism and the decrease in disturbance suppression characteristics. .

  FIG. 5 relates to a stage apparatus according to the second embodiment. In the present embodiment, the second damping mechanism in which a viscous fluid is sandwiched between the upper surface of the coil fixing member 8 and the upper yoke 10 of the mover, the lower surface of the coil fixing member 8 and the bottom of the yoke 6 of the mover. The only difference from the first embodiment is the use of a first damping mechanism in which a viscous fluid is sandwiched in the gap between the wall inner surface. The holding members 11 and 13 of Example 1 are omitted. Viscous fluid is applied (held) to the upper and lower regions 8a of the stator coil fixing member 8 where the magnetic flux does not substantially pass. The damping mechanism is configured by maintaining the gap. By doing so, vibration can be absorbed by the two damping mechanisms even when the stage receives a processing force due to contact processing.

  Each linear motor 5 generates a propulsive force Ra when the magnetic flux generated by the magnet 7 attached to the yoke 6 intersects with the current flowing through the coil 9 fixed to the coil fixing member 8. Due to this propulsive force Ra, the mover comprising the yoke 6, the upper yoke 10 and the magnet 7 advances straight along the coil fixing member 8. At this time, damping forces Da and Db are generated in the upper and lower damping mechanisms. The relationship between the distances L1 and L2 of the points of action of the damping forces Da and Db and the damping forces Da and Db is the same as in the first embodiment.

  Compared to the first embodiment, it is possible to remove minute vibrations without increasing the weight, and since it is not necessary to attach the holding member 13 to the base 1, it is possible to further increase the degree of freedom in design with further space saving. .

  Widely applied to XY stages composed of a combination of linear motors and aerostatic bearings and tool spindles, etc., to improve processing measurement accuracy of optical element mold processing devices, shape measuring devices, semiconductor exposure devices, etc. be able to.

DESCRIPTION OF SYMBOLS 1 Base 2 Guide 3 Stage 4 Air bearing 5 Linear motor 6 Yoke 7 Magnet 8 Coil fixing member 9 Coil 10 Upper yoke 11, 13 Holding member 12 Damping plate

Claims (3)

Base and
A stator with a coil fixed to the base;
A mover comprising a magnet facing the coil, movable on the base;
Current supply means for supplying a current to the coil and generating a driving force for the mover;
A first damping mechanism that holds viscous fluid in a gap formed between the base or the stator and the mover at an end of the mover on the base side;
A second damping mechanism for holding a viscous fluid in a gap formed between the mover and the stator at an end of the mover opposite to the base side;
A linear motor characterized in that a damping force is generated at each end of the mover by the first and second damping mechanisms.   2. The linear motor according to claim 1, wherein an application point of the resultant force of the damping force by the first and second damping mechanisms coincides with an application point of the propulsion force. The linear motor according to claim 1 or 2,
And a stage that moves on the base by the linear motor.

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