The present invention relates to semiconductor processing equipment and, more particularly, to a flat voice coil motor.
Flat voice coil motors made in accordance with the Ampere force law are suited to use in servo control applications requiring high speeds, high accelerations, linear force or torque response, because of their structural simplicity, convenient maintenance, high reliability, high energy conversion efficiency, fixed strokes, direct drivability, smooth force-stroke outputs, linear controllability, low electrical and mechanical time constants, high thrust/mass ratios, absence of slot effects, no need for direction adjustments, theoretically unlimited degrees of position sensitivity, and absence of cogging and delayed response. These features also make the flat voice coil motors suitable for use in precision positioning components for photolithography tools which require high speed, high-precision positioning
In recent years, with the increasing integration degree of semiconductor devices, wafer positioning stages with multiple degrees of freedom used in photolithography tools for semiconductor processing are required to achieve a positioning precision on the order of sub-microns. In order to reduce vibration and increase positioning accuracy of these wafer stages, voice coil motors are generally used for their actuation. In addition, the voice coil motors may also be used as actuating mechanisms for focusing of objectives in photolithography tools in order to improve photolithography accuracy.
However, due to absence of mover gravity compensation of conventional flat voice coil motors, unnecessary gravity-caused errors may occur during operation of the motors. On the other hand, use of external means for gravity compensation may in high likelihood adversely lead to motor overheating.
It is an objective of the present invention to provide a flat voice coil motor with mover gravity compensation.
This objective is attained by a flat voice coil motor according to the present invention, which includes a coil unit and two primary magnetic pole units exerting an Ampere force on the coil unit, wherein the coil unit includes a small, weak magnet, and the Ampere force exerted by the two primary magnetic pole units on the small, weak magnet is a vertically upward resultant force.
Each of the two primary magnetic pole units at least may include a pair of primary magnets equidistant from the coil unit, and the two primary magnetic pole units may be symmetric relative to the coil unit.
In the two primary magnetic pole units, every two primary magnets that are symmetric to each other may have the same magnetization direction, and the pair of primary magnets in each of the two primary magnetic pole units may have opposite magnetization directions.
The two primary magnetic pole units may be disposed left and right to the coil unit to create a horizontal primary magnetic field; the coil unit may include two energized conductor portions cutting the primary magnetic field; and the two energized conductor portions may be arranged vertically with respect to each other.
The two primary magnetic pole units may exert a vertically upward Ampere force on the coil unit, wherein the small, weak magnet may have a magnetization direction same as magnetization directions of two primary magnets that are disposed above the small, weak magnet in the two primary magnetic pole units.
The two primary magnets that are disposed above the small, weak magnet may exert a vertically upward resultant magnetic attraction force on the small, weak magnet, and the two primary magnets that are disposed under the small, weak magnet may exert a vertically upward resultant magnetic repulsion force on the small, weak magnet.
The two primary magnetic pole units may be disposed above and under the coil unit to create a vertical primary magnetic field; the coil unit may include two energized conductor portions cutting the vertical primary magnetic field; and the two energized conductor portions may be arranged horizontally with respect to each other.
The small, weak magnet may have a magnetization direction same as a direction of the Ampere force exerted on the coil unit.
The two primary magnets in the two primary magnetic pole units that are disposed above the small, weak magnet in the two primary magnetic pole units may exert a vertically upward resultant magnetic attraction force on the small, weak magnet, and the two primary magnets that are disposed under the small, weak magnet may exert a vertically upward resultant magnetic repulsion force on the small, weak magnet.
The flat voice coil motor may further include spacer magnets and back irons, each of the spacer magnets is disposed between two primary magnets of a corresponding pair of primary magnets, and each of the spacer magnets together with the corresponding pair of primary magnets are fixed on a corresponding one of the back irons.
The flat voice coil motor may further include spacer magnets, wherein each of the spacer magnets is disposed between the two primary magnets of a corresponding pair of primary magnets, a left one of the spacer magnets having a magnetization direction opposite to a direction of the Ampere force exerted on the coil unit and a right one of the spacer magnets having a magnetization direction same as the direction of the Ampere force exerted on the coil unit.
The flat voice coil motor may further include spacer magnets, wherein each of the spacer magnets is disposed between the two primary magnets of a corresponding pair of primary magnets, a lower one of the spacer magnets having a magnetization direction same as a direction of the Ampere force exerted on the coil unit and an upper one of the spacer magnets having a magnetization direction opposite to the direction of the Ampere force exerted on the coil unit.
The small, weak magnet may have a dimension extending along a direction in which the small, weak magnet faces the energized conductor portions cutting the primary magnetic field that is greater than a dimension of the small, weak magnet extending along a direction in which the small, weak magnet faces the primary magnets.
The coil unit may further include a bobbin and a coil wound on the bobbin; the small weak magnet is disposed in the bobbin, and the bobbin is oriented in a direction around which the coil is wound.
The coil unit may further include back irons, each pair of primary magnets is fixed on a corresponding one of the back irons; the coil is wound on the bobbin around an axis that is parallel to the primary magnetic field created by the two primary magnetic pole units and perpendicular to the back irons.
According to the present invention, the coil unit is provided with a small, weak magnet disposed therein, which creates magnetic repulsion or attraction forces with the primary magnetic pole units, thereby always ensuring a vertically upward force on the coil unit to provide gravity compensation. In addition, this arrangement is achieved simply by replacing an internal portion of the coil unit with the small, weak magnet, which neither has influence on the Ampere force acting on the coil in the coil unit nor adversely leads to motor overheating caused by a structural addition. In this way, a flat voice coil motor with mover gravity compensation is entailed.
In these figures, 101a, 101b, 102a and 102b represent primary magnets, 103a and 103b indicate spacer magnets, 104 represents coil, 105 represents bobbin, 106 represents back irons, and 107 represents weak magnet.
Reference is made below to four Embodiments, in conjunction with
Referring to
In this Embodiment, as the coil unit includes the weak magnet 107, the magnetic repulsion or attraction forces between the weak magnet 107 and the primary magnetic pole units always ensure a vertically upward force on the coil unit to provide gravity compensation. In addition, this arrangement is simply achieved by replacing an internal portion of the coil unit with the small, weak magnet 107, which neither has influence on the Ampere force acting on the coil 104 in the coil unit nor adversely leads to motor overheating caused by a structural addition. In this way, a flat voice coil motor with mover gravity compensation is entailed.
Referring to
In the two primary magnetic pole units, those two primary magnets that are symmetric to each other have the same magnetization direction, i.e., according to this Embodiment, the primary magnets 101a and 101b have the same magnetization direction and the primary magnets 102a and 102b have the same magnetization direction. On the other hand, the two primary magnets in each primary magnetic pole unit have opposite magnetization directions, i.e., according to this Embodiment, the primary magnets 101a and 102a have opposite magnetization directions and the primary magnets 101b and 102b have opposite magnetization directions.
In this Embodiment, with reference to
In this Embodiment, with reference to
In this Embodiment, referring to
Therefore, in this Embodiment, the two primary magnetic pole units exert a vertically upward Ampere force on the coil unit, and the small, weak magnet 107 has the same magnetization direction as the two primary magnets disposed above it. Referring to
Referring to
Referring to
A dimension of the small, weak magnet 107 extending along the direction of the Ampere force exerted on the coil unit is greater than a dimension of the small, weak magnet 107 extending along a direction in which the small, weak magnet 107 faces the two spacer magnets 103. In particular, according to this Embodiment, with emphasized reference to
Referring to
It is to be understood by those skilled in the art that, substituting the magnetization directions of all the magnets 101, 102, 103 and 107 in
Referring to
In this Embodiment, the flat voice coil motor further includes spacer magnets 103 each disposed between the magnets of one of the pairs of primary magnets 101 and 102, with a lower spacer magnet 103b having the same magnetization direction as the direction of the Ampere force exerted on the coil unit and an upper spacer magnet 103a having a magnetization direction opposite to the direction of the Ampere force exerted on the coil unit.
This Embodiment is similar to Embodiment 1 in the rest part of the flat voice coil motor. Specifically, the flat voice coil motor according to this Embodiment also includes back irons 106 and magnets 103, and the coil unit according to this Embodiment is structurally identical to that of Embodiment 1, as schematically illustrated in
It is to be understood by those skilled in the art that, substituting the magnetization directions of all the magnets 101, 102, 103 and 107 in
Referring to
Referring to
The present invention provides an improved solution for the overheating issue of voice coil motors of a fine-motion vector motor responsible for outputting vertical forces. The fine-motion vector motor consists of six voice coil motors, including three for horizontal outputs and three for vertical outputs, and is designed to bear a load of 20 kilograms. After allocation of the load to the three voice coil motors for vertical outputs, each of these motors needs to output a force as great as 66 N in order to levitate the load even without acceleration. In this state, each motor will generate heat at 50 W (even more when required to accelerate the load), thus creating a great challenge to the water-cooling system.
Voice coil motors are single-phase short-stroke motors with only one degree of freedom. When outputting a vertical force (
To sum up, according to the present invention, the coil unit is provided with a small, weak magnet disposed therein, which creates magnetic repulsion and attraction forces with the primary magnetic pole units, thereby always ensuring a vertically upward force on the coil unit to provide gravity compensation. In addition, this arrangement is achieved simply by replacing an internal portion of the coil unit with the small, weak magnet, which neither has influence on the Ampere force acting on the coil in the coil unit nor adversely leads to motor overheating caused by a structural addition. In this way, a flat voice coil motor with mover gravity compensation is entailed. In practical applications, the small, weak magnet itself is susceptible to damage, and the force needed to provide gravity compensation is relatively minor. So, in order to prevent the small, weak magnet from cracking, the small, weak magnet is desired to be miniaturized and embedded in the bobbin.
Number | Date | Country | Kind |
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201310612815.0 | Nov 2013 | CN | national |
Filing Document | Filing Date | Country | Kind |
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PCT/CN2014/090589 | 11/7/2014 | WO | 00 |