Electrical generator or motor structure – Dynamoelectric – Linear
Reexamination Certificate
1998-11-16
2001-03-27
LaBalle, Clayton (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Linear
C414S935000
Reexamination Certificate
active
06208045
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to electric motors and more particularly to two-dimensional electric motors.
BACKGROUND ART
Electric motors are used in a variety of electrical equipment. For example, linear electric motors produce electrical power propelling an armature in one dimension. Wafer stages utilize linear electric motors to position a wafer during photolithography and other semiconductor processing.
A typical one-dimensional linear electric motor has a magnet track with pairs of opposing magnets facing each other. (Copending U.S. Ser. No. 09/059,056, entitled “Linear Motor Having Polygonal-Shaped Coil Unit” filed on Apr. 10, 1998, by Hazelton et al. discusses one-dimensional linear electric motors and is incorporated herein by reference in its entirety.) Within spaces between the pairs of opposing magnets, an armature moves. The armature has windings of a conductor which are connected to an electrical current. When the electrical current is turned on, the electric current interacts with the magnetic fields of the magnet pairs to exert force on the armature, causing the armature to move. When the armature is attached to a wafer stage, the wafer stage experiences the same force as and moves in concert with the armature.
In a multiphase motor, the armature has various windings grouped into phases. The electric currents are selected applied to the phase groups to create a more efficient motor. As the armature moves within the magnet track as current is applied to a first group of coils, the first group moves out of its optimal position between the pairs of magnets. Then, it becomes more efficient to apply current to a second group of windings. More phase groups are theoretically more efficient since a more even application of force and utilization of power input is maintained. However, each additional phase group complicates a timing of the applied current to the various phase groups. Presently, three-phase motors and armatures have gained favor in balancing these considerations.
Linear two-dimensional motors are also used in manufacturing. (U.S. Pat. No. 4,654,571, entitled “Single Plane Orthogonally Moveable Drive System,” issued to Hinds on Mar. 31, 1987 (“Hinds”) and U.S. Pat. No. 4,535,278, entitled “Two-Dimensional Precise Positioning Device for Use in a Semiconductor Manufacturing Apparatus,” issued to Asakawa on Aug. 13, 1985 discuss two-dimensional linear electric motors and are incorporated herein by reference in their entireties.) The motors are two-dimensional in that they have two-dimensional arrays of magnets and armatures instead of magnet tracks and one-dimensional armatures. However, the magnet arrays and two-dimensional armatures may move with respect to each other in more than two dimensions depending upon the design. Conventional two-dimensional linear motors typically have an array of magnets and an armature having one or more coils on one side of the array of magnets.
U.S. Pat. No. 5,623,853, entitled “Precision Motion Stage with Single Guide Beam and Follower Stage,” issued to Novak et al. on Apr. 29, 1997 and U.S. Pat. No. 5,528,118, entitled “Guideless Stage With Isolated Reaction Stage,” issued to Lee on Jun. 18, 1996 discuss examples of semiconductor fabrication equipment and are incorporated herein by reference in their entireties.
When attached to part of a two-dimensional linear motor, a platform can be moved in two or more dimensions by the motor. For example, a wafer stage in semiconductor processing equipment may be attached to an armature or magnet array of a two-dimensional motor and the two-dimensional motor would control positioning of the wafer stage.
When used to position a platform, conventional two-dimensional electric motors do not smoothly and accurately position the platform. Presently, coils in the two-dimensional electric motors move with respect to the magnets. As exemplified in U.S. Pat. No. 4,654,571, entitled “Single Plane Orthogonally Moveable Drive System” issued to Hinds on Mar. 31, 1987, referenced above and incorporated herein by reference in its entirety, cables and hoses are attached to the coil assembly. The cables are for electrical current and the hoses may be used to carry coil cooling fluid or air supply. Unfortunately, the hoses and cables impede free motion of the coil assembly. If the hoses could be eliminated, the stability of motion of the motor and positioning of the platform would be improved.
Also, conventional technology relies upon cumbersome stacked arrangements to achieve six degrees of freedom movement of the platform. The six degrees of freedom include three translational and three rotational degrees of freedom. (Richard P. Feynman, Robert B. Leighton, and Matthew Sands,
The Feynman Lectures on Physics,
Addison-Wesley, 1962, discusses translational and rotational motion and degrees of freedom and is incorporated herein by reference in its entirety.) Unfortunately, many designs obtain six degrees of freedom by essentially stacking multiple two dimensional and/or one dimensional motors which move only in two dimensions within a plane. (U.S. Pat. No. 5,623,853, entitled “Precision Motion Stage with Single Guide Beam and Follower Stage” issued to Novak et al. on Apr. 29, 1997, discusses examples of such stacked arrangements and is incorporated herein by reference in its entirety.) For example, a platform may be propelled back and forth in one dimension under the control of linear electric motors. The linear electric motors are part of a holder which holds the platform. In turn, a second holder holds that entire holder and platform arrangement via joint connections and propels it back and forth in a second dimension by another set of linear electric motors. Additional degrees of motion may be provided by voice coil motors which are attached to these holders.
These types of stacked arrangements have a few drawbacks. Each additional holder enabling more degrees of freedom also adds mass requiring additional power for the electric motors to move the platform. Also, the complicated joint connections degrade accuracy of positioning of the platform and build-in resonant frequencies.
The platforms need a better electric motor to position them. The improved electric motor would eliminate the air hoses and position the platform in multiple degrees of freedom without the cumbersome stacked arrangements.
SUMMARY OF THE INVENTION
The invention features a moving magnet array or a moving coil array electric motor. The electric motor includes a magnet array and a coil array. The magnet array has a magnet array width and also a first period in a first direction and a second period in a second direction. The coil array has a coil array width which is larger than the magnet array width. The coil array interacts with the magnet array to provide motion of the magnet array relative to the coil array in the first direction and the second direction, and a third direction away from the coil array. Although the present invention is described in terms of a moving magnet array electric motor, the electric motor may be modified to be a moving coil array electric motor wherein the coil array moves relative to the magnet array.
The invention also features a process of achieving motion of a coil array with respect to a magnet array in six degrees of freedom. In some embodiments, the process includes positioning a coil of a periodic coil array in proximity to and overlapping a magnet of a periodic magnet array. The process also includes controlling a separation between a portion of the coil array and a portion of the magnet array. The controlling is achieved by the interaction of current in the coil and a magnetic field associated with the magnet.
In some embodiments, the method includes providing an electrical current distribution to a coil to control movement of the coils with respect to a magnetic field array. The motion is controlled in a first direction and a vertical direction between a portion of the coils and a portion the magnet array. The electrical current distribution has two wavelike components havin
Binnard Michael B.
Gery Jean-Marc
Hazelton Andrew J.
Jones Judson H.
LaBalle Clayton
Morrison & Foerster / LLP
Nikon Corporation
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