Electrical generator or motor structure – Dynamoelectric – Linear
Reexamination Certificate
2000-09-19
2002-01-15
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Linear
C310S091000
Reexamination Certificate
active
06339266
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a planar motor device, a stage unit, an exposure apparatus and its making method, and a device and its manufacturing method. More particularly, the present invention relates to a planar motor device that has a mover and a stator and operates to drive the mover in a noncontacting manner in two-dimensional directions by electromagnetic force, a stage unit including a movable body to which the mover of the planar motor device is integrally attached, and an exposure apparatus incorporating the stage unit, and a method of making the exposure apparatus, and a device to be manufactured by using the exposure apparatus, and a device manufacturing method using the exposure apparatus.
2. Description of the Related Art
Conventionally, in a lithographic process for manufacturing semiconductor devices and liquid crystal display devices, an exposure apparatus that transfers a pattern formed on a mask or a reticle (hereunder generically referred to as a “reticle”) through a projection optical system onto a substrate such as a wafer or a glass plate (hereunder generically referred to as a “substrate or wafer”), on which a resist is coated, has been used. This exposure apparatus is required to position the wafer at an exposure position with high precision. Thus, the wafer is held on a wafer holder by vacuum chucking, and the wafer holder is fixed onto a wafer table (that is, movable body) which structures a stage unit.
Recently, to position the wafer more quickly and with high precision without being affected by the mechanical accuracy of a guide surface, as well as to avoid mechanical friction and to prolong the life of the stage unit, a stage unit is being developed. This stage unit performs positional control of the wafer by supporting the movable body on which the wafer is placed above a supporting member by levitation and drives the movable body in a non-contacting manner. To accomplish such a stage unit, the key technology is the technique of levitating a mover above a stator of a planar motor device, and driving the mover in a predetermined direction (including a rotational direction) in an XY plane in order to move the mover. On driving such a planar motor device, a variable reluctance driving method and a Lorentz (electromagnetic) force method can be employed.
As a planar motor device used in the variable reluctance driving method, a motor as in a Sawyer motor, which has a structure of linear pulse motor s using the variable reluctance driving method respective to two axes being combined with each other, is the current mainstream. With the linear pulse motor using the variable reluctance driving method, it has a stator structured of; for instance, a plate-shaped magnetic substance having a gear tooth port ion (with an uneven shape) arranged along the longitudinal direction in equivalent intervals. It also has a mover that has a plurality of armature coils having an uneven portion different in phase with the gear tooth portion of the stator. The plurality of armature coils are arranged opposing the tooth portion of the stator, and are connected via a permanent magnet. And, the mover is driven by utilizing a force generated so as to minimize the magnetic reluctance between the stator and the mover at each point. That is, by adjusting and controlling the value and phase of pulse current supplied to each armature coil, the mover can be driven stepwise in a stepping operation.
Such a Sawyer type motor is configured of combining linear pulse motors that respectively correspond to 2 axes, on a moving plane. The driving portion which drive the mover movable in a plane in each axis direction, however, is separated from each other, thus making the mover heavy. To improve such inconvenience, an improved planar motor that can be moved on a plane by a single driving portion is being developed.
Also, with the planar motor device based on the Lorentz force method, the driving force is obtained by utilizing a Lorentz force F. This force is generated in the direction determined according to Fleming's left hand law in the presence of an electric current I and a magnetic flux density B, which are perpendicular to each other, and expressed by the following equation:
F=I×B×L (1)
In this equation, F designates a force generated on a current path; and L denotes the length of the current path. A conventionally proposed Lorentz force driving planar motor device is disclosed in, for example, the U.S. Pat. No. 5,196,745. With this planar motor device, magnets are respectively arranged so that the adjacent pairs of magnetic arrays alternately have the opposite polarity in the X-axis direction on a mover (or a stator). The magnets in the Y-axis direction are arranged in the Y-axis direction so that the adjacent pairs of magnetic arrays alternately have the opposite polarity, without the array intersecting that of the X-axis direction. Also, on a stator (or a mover), multi-phase coils for driving operations in the X-axis direction are arranged along the X-axis while multi-phase coils for the Y-axis direction are arranged along the Y-axis direction without the array intersecting with those of the X-axis direction. Thus, the thrust in the X-axis direction is generated by generating a Lorentz force, by sending an electric current to the multi-phase coil oppositely facing the magnets used for driving operations in the X-axis direction. And, the thrust in the Y-axis direction is also generated by generating a Lorentz force, by sending an electric current to the multi-phase coil oppositely facing the magnets used for driving operations in the Y-axis direction.
Among the conventional planar motor devices described above, the planar motor devices employing the variable reluctance method obtained high thrust between magnetic substances or between a magnetic substance and a permanent magnet by magnetic attraction or by repulsive force. It was, however, essentially difficult to reduce thrust variation, that is thrust cogging, when the current was not supplied to create a magnetized state. Furthermore, thrust generated by current excitation varies with the movable position. Therefore, to stabilize the thrust force that varies with the movable position, a higher level of a current pattern was required.
Also, the variable reluctance motor usually is configured of what is called an iron core coil, which is formed of winding an armature coil around a magnetic substance. Since it has a high armature coil inductance, the response time is slow; therefore a high voltage power supply is required to increase the response time, depriving the motor of its efficiency.
Furthermore, with the iron core coil, magnetic saturation of the iron core is caused due to the current flowing through it, so it is difficult to obtain the thrust linearity in a high current region making the design of the control system complex.
Meanwhile, with the conventional Lorentz force driving planar motor device, it excels in controllability, thrust linearity, and positioning ability. However, due to the limitation of the magnetic and coil array, the number of magnets and coils that are used for driving operations cannot be increased, therefore, it is difficult for this planar motor device to increase the thrust to be generated. Accordingly, it is difficult to move the mover, which carries an object of a certain weight such as a wafer holder or a substrate table, at a high speed.
Also, in order to use the planar motor device based on the variable reluctance driving method for precise positioning and to achieve high speed positioning, a large driving force is necessary. Naturally, a large current needs to be supplied to the armature coil. This, however, results in increasing the amount of heat generated in the armature coil. Such an increase in the amount of heat generated in the armature coil similarly occurs in the case of the planar motor device employing the Lorentz force method, in which the armature coil has to be supplied with a l
Nguyen Tran
Nikon Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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