JP2013235991A - Power feeding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-contact power feeding device which applies DC voltage to a pair of electrodes for attraction and uses a resonance circuit, and which is capable of easily detecting presence or absence of an absorbed object to be electrostatically attracted to a movable body.SOLUTION: A power feeding device comprises: a capacitor 1 mechanically separated between a pair of electrodes to be oppositely arranged; a feed circuit unit 2 connected to one of the electrodes; a power receiving circuit unit 3 connected between the other of the electrodes and an electrode for attraction; and control means 23 and 34. The feed circuit unit includes a free-running oscillator which oscillates at a resonance frequency of a resonance circuit including a capacitor and a modulator, and supplies a carrier wave modulated to a prescribed amplitude. The power receiving circuit unit includes a resistor provided in parallel to an electrode for attraction, a rectification circuit which rectifies a carrier wave, and a polarity switching circuit which applies reverse voltage between electrodes for attraction. The control means discriminate presence or absence of an absorbed object in a movable body from change of impedance when reverse voltage is applied between a pair of electrodes for attraction.

Description

  The present invention relates to a non-contact type power feeding device using a resonance circuit that applies a DC voltage to a pair of suction electrodes provided on a movable body in order to electrostatically attract an object to be attracted to the movable body.

  As this type of power supply apparatus, for example, Patent Document 1 discloses an apparatus applied to power supply to a drive device of a transfer robot used for transfer of a silicon wafer (hereinafter referred to as “wafer”). This device includes a power feeding circuit unit, a power receiving circuit unit, and a capacitor composed of a pair of mechanically separated electrodes so that a high frequency voltage is fed from the high frequency oscillator of the power feeding circuit unit to the electrode plate. ing.

  By the way, when a wafer is transferred by the transfer robot, a so-called electrostatic chuck may be provided on the robot hand so that the wafer is not detached or displaced from the robot hand of the transfer robot during transfer. Such a robot hand is known from Patent Document 2, for example. In this device, the robot hand includes a base end portion connected to the robot arm of the transfer robot and a finger portion having a rectangular shape in plan view extending forward from the base end portion, and a pair of positive and negative electrodes are embedded therein. (So-called bipolar type). Then, for example, the adsorption surface of the thin plate-like object to be conveyed of the robot hand is covered with a dielectric (insulating layer), and the wafer is adsorbed and held by electrostatic force generated by applying a DC voltage between the electrodes by a chuck power source. I have to. In order to apply a DC voltage to a pair of positive and negative electrodes provided on the robot hand, it is conceivable to use the non-contact type power feeding device.

  Here, when the wafer is transported to a predetermined position while the wafer is electrostatically attracted to the robot hand, it is necessary to confirm whether the wafer is reliably electrostatically attracted to the robot hand. For this reason, conventionally, for example, an optical sensor is arranged in the wafer transfer path to detect the presence of a wafer during transfer, or a robot hand is provided with a magnetic support pin and a magnetic sensor to detect the presence of a wafer. It is generally known (see, for example, Patent Document 3). However, detecting the presence / absence of a wafer with such a separate sensor complicates the configuration and control, resulting in high costs.

JP-A-9-300200 JP-A-6-63885 JP 2005-268556 A

  In view of the above points, it is an object of the present invention to provide a power feeding device that can easily detect the presence or absence of an object to be adsorbed when the object is electrostatically adsorbed to a movable body. is there.

  In order to solve the above problem, the non-contact type of the present invention using a resonance circuit that applies a DC voltage to a pair of adsorption electrodes provided on the movable body in order to electrostatically attract an object to be attracted to the movable body The power feeding device is mechanically separated between a pair of electrodes arranged opposite to each other, and one electrode is fixedly arranged, and the other electrode moves relative to each other while keeping the distance between the electrodes constant. A capacitor disposed on the electrode, a power supply circuit unit connected to one of the electrodes, a power receiving circuit unit connected between the other electrode and the adsorption electrode, and a power supply circuit unit and a power receiving circuit unit. The power supply circuit unit includes a self-excited oscillator that oscillates at a resonance frequency of a resonance circuit including a capacitor, and a modulator that applies amplitude modulation, and is modulated to a predetermined amplitude. The power receiving circuit unit includes a resistor provided in parallel with a pair of suction electrodes, a rectifier circuit for rectifying the carrier wave supplied to both ends of the resistor through a capacitor, and a pair of suction electrodes. A polarity switching circuit for applying a reverse voltage between the electrodes, and the control means determines whether or not there is an object to be adsorbed on the movable body from a change in impedance when a reverse voltage is applied between the pair of adsorption electrodes. It is comprised by this.

  According to the present invention, a carrier wave having a predetermined frequency is output from the self-excited oscillator of the power supply circuit unit, subjected to amplitude modulation by the modulator, and the modulated carrier wave is supplied to both ends of the resistor through the capacitor. Then, the carrier wave is rectified by a rectifier circuit, and a high voltage necessary for electrostatic adsorption of the object to be adsorbed is applied to a pair of adsorption electrodes for electrostatically adsorbing the object to be adsorbed to the movable body. Alternatively, the voltage may be boosted by a voltage doubler rectification method or the like. When detecting whether or not the object to be adsorbed is reliably adsorbed to the movable body, if the polarity of the voltage applied to the pair of adsorption electrodes is reversed by the polarity switching circuit, the voltage difference between the pair of adsorption electrodes The charging current corresponding to is flowing in the power receiving circuit unit. Since the time during which this charging current flows depends on the circuit resistance and the capacitance of the pair of adsorption electrodes, the charging current is regarded as a change in impedance connected in parallel to the resistance. Since it forms part of an element that determines the oscillation frequency of the excitation oscillator, the presence or absence of an object to be adsorbed can be detected in the power supply circuit unit by detecting a change in the oscillation frequency. As described above, according to the present invention, the presence or absence of the object to be adsorbed can be easily detected by providing the polarity switching circuit and simply switching the polarity after the object to be adsorbed is electrostatically adsorbed to the movable body. As a result, a sensor for detecting the object to be adsorbed can be dispensed with, which is advantageous.

  In the present invention, the movable body is a transfer robot including a rotating shaft and a robot arm connected to the rotating shaft and having a robot hand with an electrostatic chuck. What is necessary is just to comprise the cylindrical electrode provided concentrically with a rotating shaft while the extra electrode is extrapolated to a rotating shaft.

The model perspective view which shows the conveyance robot provided with the electric power feeder of this invention. 2A and 2B illustrate a structure of a power feeding device. The figure which shows the equivalent circuit of a feed circuit. The graph of the experimental result which confirms the effect of this invention.

  Hereinafter, referring to the drawings, the movable body is a transfer robot arranged in the vacuum processing chamber, and a DC voltage is applied to a pair of suction electrodes for an electrostatic chuck assembled in the robot hand of the transfer robot, and the suction target is The embodiment of the power supply apparatus of the present invention will be described by taking as an example the case of adsorbing an actual wafer W.

  Referring to FIG. 1, TR represents a so-called frog-leg type transfer robot, and the transfer robot TR is arranged concentrically, and two rotation axes R11 and R12 that are respectively rotated by a drive source (not shown), Each of the rotary shafts R11 and R12 is connected to a robot arm R3 having a robot hand R2 at the tip. The rotating shafts R11 and R12, the robot hand R2 and the robot arm R3 are each made of metal, and the chucking electrodes P1 and P2 of the electrostatic chuck constituting the electrostatic chuck are respectively embedded in the robot hand R2. A power feeding device PS is used to feed power to both chuck electrodes P1 and P2.

  Referring also to FIGS. 2 and 3, the power feeding device PS has a constant inter-electrode distance from one electrode 1 a integrally provided on the rotation axis R <b> 12, mechanically separated between a pair of opposed electrodes. A capacitor (so-called air gap type) 1 composed of the other electrode 1b made of a metallic cylindrical member extrapolated to the rotation axis R12 so as to move relative to the cylindrical shaft, and a cylindrical member. A power feeding circuit unit 2 connected to the other electrode 1b via the wiring W1, and a power receiving circuit unit 3 connected via the wiring W2 between the one electrode 1a and the suction electrodes P1 and P2. . One electrode 1a can be configured, for example, by sticking a film-like conductive sheet to the rotation axis R12 at a predetermined position on the outer surface. Further, when a metal cylindrical member constituting the capacitor 1 is extrapolated to the rotation axis R12, it may be supported by an insulating pin (not shown) erected on the bottom surface of the vacuum processing chamber. It moves relative to each other while keeping the distance between 1a and 1b constant. In this case, the surface area of both electrodes 1a, 1b and the distance between both electrodes 1a, 1b are appropriately selected according to the application so that the voltage applied to capacitor 1 is equal to or higher than the discharge voltage limited by Paschen's law, Further, the opposing areas of both electrodes 1a and 1b need not be the same.

  The power supply circuit unit 2 is housed in, for example, a driver of the transport robot TR, and controls the self-excited oscillator 21 that oscillates at the resonance frequency of the resonance circuit including the capacitor 1, the modulator 22 that applies amplitude modulation, and the overall operation thereof. And a known first control unit 23 having a microcomputer, a memory, and the like. In this case, for example, an oscillator having a known structure can be used as the self-excited oscillator 21 and the modulator 22, and the drive frequency thereof is 100 kHz to several tens of MHz, and includes a drive frequency in a high frequency band.

  On the other hand, the power receiving circuit unit 3 is housed in a metal housing 3a attached to the lower surface of the robot arm R3, and a resistor 31 provided in parallel with the suction electrodes P1 and P2 and both ends of the resistor 31 through the capacitor 1. A rectifying circuit 32 for rectifying the carrier wave supplied to the first electrode, a polarity switching circuit 33 for applying a reverse voltage between the adsorption electrodes P1 and P2, and a known second circuit equipped with a microcomputer and a memory for controlling the operation thereof. And a control unit 34. In this case, both the first and second control units 23 and 34 can perform wireless communication, for example. In the present embodiment, one of the suction electrodes P2 is grounded to the robot hand R2, and the resistor 31 is grounded to the housing 3a. The rectifier circuit 32 and the polarity switching circuit 33 can use known ones using diodes, switching transistors, and the like, and thus detailed description thereof is omitted here. Hereinafter, description will be given of application of a DC voltage to the suction electrodes P1 and P2 and determination of the presence or absence of the wafer W when the wafer W is electrostatically attracted by the surface of the robot hand R2.

  First, when the wafer W is placed on the upper surface of the robot hand R2, a carrier wave having a predetermined frequency is output from the self-excited oscillator 21 of the power supply circuit unit 2 by the first control unit 23, and amplitude modulation is performed by the modulator 22. Then, the modulated carrier wave is supplied to both ends of the resistor 31 through the capacitor 1. Then, this carrier wave is rectified by the rectifier circuit 32, and a (positive) high voltage necessary for electrostatic chucking of the wafer W is applied to the chucking electrode P1. The voltage may be boosted by a rectification method or the like. Thereby, the wafer W is electrostatically attracted to the surface of the robot hand R2.

  Next, when the wafer W is electrostatically adsorbed on the surface of the robot hand R2, for example, after the wafer W is transported to a predetermined position, it is detected whether the wafer W is still electrostatically adsorbed on the surface of the robot hand R2. First, the polarity switching circuit 33 is controlled by the second control unit 34 to invert the polarity of the voltage applied to the adsorption electrode P1. When the polarity of the voltage applied to the adsorption electrode P1 is reversed, a charging current corresponding to the voltage difference between the adsorption electrode P1 and the ground flows in the power receiving circuit unit 3. In this case, since the time during which this charging current flows depends on the circuit resistance and the capacitance of the pair of adsorption electrodes P1 and P2, the charging current is regarded as a change in impedance connected in parallel to the resistor 31. Is a part of an element that determines the oscillation frequency of the self-excited oscillator 21 of the power supply circuit unit 2. Therefore, the first control unit 23 of the power supply circuit unit 2 detects a change in the oscillation frequency, and this oscillation If the frequency is compared with a normal oscillation frequency to which a (positive) high voltage necessary for electrostatic attraction of the wafer W is applied, the presence or absence of the wafer W is detected from the comparison result.

  According to the embodiment described above, the polarity switching circuit 33 is provided in the power receiving circuit unit 3, and after the wafer W is electrostatically attracted to the robot hand R2, the presence / absence of the wafer W can be detected simply by switching the polarity. Can do. As a result, when the wafer W is electrostatically attracted to the robot hand R2 of the transfer robot TR and the wafer W is transferred, a sensor or the like for detecting the wafer W is not required in the transfer path, which is advantageous.

  Next, in order to confirm the effect of the present invention, the change in the emission frequency when the resistance value (kΩ) is changed in the equivalent circuit of the power feeding device PS is measured, and the result is shown in FIG. According to this, it can be seen that if the resistance value changes within the range of the resistance value up to 30 kΩ, the oscillation frequency can be greatly changed, and the wafer W can be detected.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to said thing. In the above-described embodiment, an example in which the movable body is a transfer robot has been described as an example, but the present invention is not limited to this. For example, a stage that is rotatably provided in a vacuum chamber and can electrostatically attract a wafer on its surface is used as a movable body, and power is supplied to an adsorption electrode built in the stage, and the presence or absence of a wafer on the stage is detected. However, the present invention can be applied.

  In the above embodiment, the first and second control units 23 and 34 are provided as control means. However, the control unit on the power receiving circuit unit side is omitted, and the power feeding circuit unit is modulated with a modulated signal. And the power receiving circuit unit may communicate with each other. Furthermore, in the above-described embodiment, the capacitor is constituted by the metal members arranged concentrically. However, the present invention is not limited to this, and the metal member may be moved relatively while maintaining the distance between the electrodes constant. Any other form can be used.

PS ... power feeding device, 1 ... capacitor, 1a, 1b ... electrode, 2 ... feed circuit unit, 21 ... self-excited oscillator, 22 ... modulator, 3 ... power receiving circuit unit, 31 ... resistor, 32 ... rectifier circuit, 33 ... polarity Switching circuit, 23, 34 ... first and second control units (control means), TR ... transfer robot (movable body), R2 ... robot hand, P1, P2 ... adsorption electrode, W ... wafer (adsorbed object) .

Claims (2)

A non-contact type power supply device using a resonance circuit that applies a DC voltage to a pair of adsorption electrodes provided on the movable body in order to electrostatically attract an object to be attracted to the movable body,
A capacitor that is mechanically separated between a pair of opposed electrodes, one electrode is fixedly arranged, and the other electrode is arranged on the movable body so as to move relative to each other while maintaining the distance between these electrodes constant. A power supply circuit unit connected to one of the electrodes, a power receiving circuit unit connected between the other electrode and the adsorption electrode, and a control for controlling the operation of the power supply circuit unit and the power receiving circuit unit Means and
The power supply circuit unit has a self-excited oscillator that oscillates at a resonance frequency of a resonance circuit including a capacitor, and a modulator that applies amplitude modulation, and supplies a carrier wave modulated to a predetermined amplitude.
The power receiving circuit unit includes a resistor provided in parallel to the pair of suction electrodes, a rectifier circuit for rectifying a carrier wave supplied to both ends of the resistor through a capacitor, and a polarity for applying a reverse voltage between the pair of suction electrodes. A switching circuit, and the control means is configured to determine the presence or absence of an object to be adsorbed on the movable body from a change in impedance when a reverse voltage is applied between the pair of adsorption electrodes. Power feeding device to do. The movable body is a transfer robot including a rotating shaft and a robot arm connected to the rotating shaft and having a robot hand with an electrostatic chuck, and extrapolates one electrode of the capacitor to the rotating shaft. 2. The power feeding apparatus according to claim 1, wherein the other electrode is formed of a cylindrical member provided concentrically with the rotating shaft.

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