Electrical generator or motor structure – Dynamoelectric – Linear
Reexamination Certificate
2001-02-21
2003-03-25
Tamai, Karl (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Linear
C074S721000, C318S625000
Reexamination Certificate
active
06538348
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a stage device which is used in an aligner used in a lithography process in manufacture of a semiconductor element or the like, a machine tool used for machining of works and a precision mechanical equipment such as a measuring device or the like for measuring a shape of an object to be measured and moves an object to be positioned such as a work or the like to a target position.
As a device for moving an object to be positioned to a target position, for example, an aligner for use in a lithography process, in which a mask pattern is transferred onto a substrate such as a wafer or the like, in manufacture of a semiconductor element, liquid crystal display element, thin film magnetic head or the like needs to precisely position the wafer, which is an object to be positioned, to a predetermined exposure position. Therefore, the aligner is provided with a wafer stage on which a wafer is mounted and a stage device having a travel mechanism for supplying the wafer stage with thrusts in two directions (X and Y directions) perpendicular to each other.
Thus, the thrusts generated in the travel mechanism must be supplied to the object to be positioned in a highly precise manner without generating a backlash in precision mechanical equipment where an object to be positioned needs to be precisely aligned to a target position. Occurrence of vibration or the like needs to be prevented when the object to be positioned travels.
Therefore, in general, a linear motor, which linearly moves a movable element in no contact with a stator, is used in a conventional travel mechanism constituting a stage device for precision mechanical equipment.
In a constitution disclosed in Japanese Patent Laid-Open Publication No. Hei 11-243132, for example, in a device where thrusts generated by a linear motor are acted on both ends of a stage supported on a base via a static air pressure bearing to move a stage, an inertial body traveling in parallel to the stage is provided on the base. When the stage travels, this inertial body is moved so that a force for canceling a reaction force acting on the base via the linear motor is acted on the base, thereby preventing displacement of the centroid position of the base including the stage and the inertial body. Thus, vibration of the stage is prevented.
In a constitution disclosed in Japanese Patent Laid-Open Publication No. Hei 11-168064, a surface plate is supported on a base via a vibration isolating table or the like. An X-stage provided with a Y-guide bar and a Y-guide bar carrier is provided movably along an X-guide bar on the surface plate. This X-stage is driven in the X direction via an X-axis linear motor and the stators of the X-axis linear motor are supported so that the stators can travel in the X direction on the surface plate via a direct acting guide. Thus, a damping force for canceling a reaction force when the X-stage is driven is given to the stators by an X-damping member attached to a damping frame fixed on the base.
A bottom surface and an outer surface of a first Y-guide bar carrier are provided with air exhaust nozzles each constituting a bearing. Furthermore, a pre-load mechanism such as a magnet, vacuum pocket or the like is installed in the vicinity of these air exhaust nozzles. The first Y-guide bar carrier can travel in the X direction maintaining a certain gap with a surface of the surface plate and a side surface of an X-guide bar while being confined in the Z direction and Y direction. Similarly, an air exhaust nozzle constituting an air bearing and a pre-load mechanism such as a magnet, vacuum pocket or the like are also installed in a bottom surface of a second Y-guide bar carrier. Thus, the Y-guide bar carrier can also travel in the X direction maintaining a certain gap with the top surface of the surface plate while being confined.
With this constitution, when the movable section travels, occurrence of a moment, deforming force and the like is prevented and thereby vibration can be prevented.
In a constitution disclosed in Japanese Patent Laid-Open Publication No. Hei 8-63231, a movable stage device uses a rectifying linear motor. The linear motor moves a guideless stage in one linear motion direction and allows the stage to perform a fine yaw rotation in a plane. A carrier/jogging element holding a single voice coil motor is controlled so as to generally follow the stage traveling in the linear motion direction. A voice coil motor is given an electromagnetic force in a plane so that the stage is allowed to perform a fine motion in a direction perpendicular to the linear motion direction to achieve an appropriate alignment. Furthermore, one element (coil or magnet) of the rectifying linear motor is provided on a driving frame which can travel freely on the plane. The driving frame is driven by a reaction force so that the centroid position of the device is maintained. In this constitution, when one linear motor is used, two voice coil motors are used to correct the yaw rotation.
In a conventional stage device, however, when an object to be positioned is moved in one of two directions perpendicular to each other and then moved in the other remaining direction, the object to be positioned may not be positioned in the driving center of a drive mechanism (central position between the linear motors when the drive mechanism is constituted by a pair of linear motors in parallel in the other remaining direction). Also, the centroid position of the object to be positioned in a direction perpendicular to two respective traveling directions may not be positioned in the driving center of the drive mechanism depending on the shape of the object to be positioned. When the object to be positioned travels in this state, the object to be positioned is deflected in a yawing or pitching direction and thereby the object to be positioned cannot be moved precisely to a target position.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a stage device which can prevent deflection of an object to be positioned and a stage in a yawing or pitching direction due to displacement of the centroid position thereof when the object to be positioned travels and move the object to be positioned precisely to a target position and to provide a stage device which can prevent vibration of a support due to movement of the stage and move the object to be positioned precisely to a target position.
The present invention is provided with the following constitutions to achieve the above object.
(1) A stage device which moves a stage on a support by thrusts generated by a pair of thrust generating means in parallel to a stage traveling direction is characterized in that there is provided a control section for moving a stage in a state that moments acted on the stage around the centroid are balanced by the thrusts supplied from each of the pair of thrust generating means.
In this constitution, when the stage travels, the moments about the centroid of the stage are balanced. Therefore, the stage traveling direction is not deflected in a yawing direction and thereby the object to be positioned can be precisely moved to a target position.
(2) The stage device is characterized in that the control section relatively changes the thrust generated by each of the pair of thrust generating means depending on the centroid position of the stage in a direction perpendicular to its traveling direction.
In this constitution, the respective thrusts of the pair of thrust generating means are determined so that the moments about the centroid of the stage are balanced depending on the centroid position of the stage in a direction perpendicular to its traveling direction when the stage travels. Therefore, irrespective of the centroid position of the stage in a direction perpendicular to its traveling direction, the moments acted on the stage about its centroid are balanced by the respective thrusts from the pair of thrust generating means and thereby the stage traveling direction is not deflected to a
Ishii Hiroshi
Sawai Hiroyuki
Birch & Stewart Kolasch & Birch, LLP
Jones Judson H.
Sharp Kabushiki Kaisha
Tamai Karl
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