Power supply device for electrostatic chucks

Abstract

The present invention provides a power supply device for an electrostatic chuck that can apply an AC voltage through the capacitance of the electrostatic chuck without using a high-insulation-voltage transformer. [Solution] The electrostatic chuck power supply device PS for supplying power to the electrostatic chuck Ec that adsorbs and holds the substrate W to be processed comprises a DC power supply circuit 4 that applies a DC voltage to electrodes 3a and 3b provided on the electrostatic chuck Ec, and an AC superposition circuit 5 that applies an AC voltage that passes through the capacitance of the electrostatic chuck Ec. High-voltage amplifiers 43 and 44 with predetermined frequency characteristics are interposed in the DC power supply circuit 4. The AC superposition circuit 5 has an AC power supply unit 51 and a control unit 52 that controls the voltage applied to electrodes 3a and 3b. The control voltage from the control unit 52 is superimposed with an AC voltage and input to the high-voltage amplifiers 43 and 44, and this control voltage with the AC voltage superimposed is amplified by the high-voltage amplifiers 43 and 44 and applied to electrodes 3a and 3b.

Description

Technical Field

[0001] The present invention relates to a power supply device for an electrostatic chuck that supplies power to an electrostatic chuck that adsorbs and holds a substrate to be processed in a vacuum chamber.

Background Art

[0002] In semiconductor manufacturing processes, in order to obtain a desired device structure, various processes such as film formation processing by sputtering method and plasma CVD method, heat treatment, ion implantation processing, and etching processing are performed on substrates to be processed such as silicon wafers and glass substrates. A processing apparatus for performing these processes is provided with an electrostatic chuck for positioning and holding the substrate to be processed in a vacuum chamber in a vacuum atmosphere. The electrostatic chuck has, for example, a metal base and a ceramic plate (chuck plate) made of, for example, PBN (Pyrolytic Boron Nitride) mounted on its surface, and a pair of electrodes are embedded in this chuck plate (so-called bipolar type). Then, a power supply device is used to apply a DC voltage (chuck voltage) between the pair of electrodes, and the substrate to be processed is adsorbed and held on the surface of the chuck plate by the electrostatic force generated by applying the DC voltage between both electrodes (see, for example, Patent Document 1).

[0003] The power supply device of the above conventional example further includes an AC superposition circuit that superimposes an AC voltage that passes through the capacitance of the electrostatic chuck on the DC voltage, in addition to a DC power supply circuit that applies a DC voltage between a pair of electrodes. Then, by measuring the AC voltage (or AC current) superimposed on the DC voltage with a voltmeter (ammeter), the state of the substrate to be processed, such as the occurrence of poor adsorption between the substrate to be processed and the chuck plate, can be grasped. Here, when the circuit configuration of the power supply device of the above conventional example is specifically shown in FIG. 3, the DC power supply circuit Cd includes DC power supply units P DC 1, P DC 2.

[0004] The AC superposition circuit Cs is an AC power supply unit P that outputs an AC voltageAC And the primary side is the AC power supply unit P AC It is connected to the DC power supply unit P on the secondary side. DC Connected to the output from 1, AC power supply unit P AC The AC voltage output from is boosted and used to power the DC power supply unit P DC The device includes an AC superposition transformer T that is superimposed on the DC voltage output from 1. In such a power supply device, a high voltage is also applied to the AC superposition transformer, requiring a very high dielectric strength, which results in the transformer itself being large. Therefore, the power supply device itself becomes large, and there is a problem that this leads to increased manufacturing costs. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2011 / 125292 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The present invention has been made in view of the above points, and its objective is to provide a power supply device for an electrostatic chuck that can ensure the function of understanding the state of a substrate being processed by applying an AC voltage through the capacitance of the electrostatic chuck without using a high-insulation-voltage transformer. [Means for solving the problem]

[0007] To solve the above problems, the present invention provides a power supply device for an electrostatic chuck that adsorbs and holds a substrate to be processed in a vacuum chamber, comprising a DC power supply circuit that applies a DC voltage to electrodes provided on the electrostatic chuck, and an AC superposition circuit that applies an AC voltage through the capacitance of the electrostatic chuck, wherein a high-voltage amplifier with a predetermined frequency characteristic is interposed in the DC power supply circuit, and the AC superposition circuit comprises an AC power supply unit and a control unit that controls the voltage applied to the electrodes, wherein the control voltage from the control unit is superimposed with an AC voltage and input to the high-voltage amplifier, and this control voltage with the AC voltage superimposed is amplified by the high-voltage amplifier and applied to the electrodes.

[0008] According to the present invention, a DC voltage amplified by a high-voltage amplifier can be applied to the electrodes of an electrostatic chuck without using a high-insulation voltage-resistant transformer (AC superposition transformer), and an AC voltage can be applied by superimposing it on the DC voltage and passing through the capacitance of the electrostatic chuck, without impairing functions such as understanding the state of the substrate being processed. Furthermore, since it can be constructed with a general analog circuit that does not require a high-insulation voltage-resistant transformer, it not only suppresses increases in manufacturing costs but also allows for miniaturization of the power supply device.

[0009] Furthermore, in this invention, it is preferable that the frequency of the AC voltage is F (Hz), and that the frequency characteristics of the high-voltage amplifier remain constant in a frequency band of 2F (Hz) or less. This has been confirmed to ensure that the amplified AC voltage (i.e., the AC voltage superimposed on the amplified DC voltage) has an output waveform equivalent to that of the conventional example described above, thereby guaranteeing the function of understanding the state of the substrate being processed. [Brief explanation of the drawing]

[0010] [Figure 1] A schematic diagram showing the circuit configuration of a power supply device for an electrostatic chuck according to an embodiment of the present invention. [Figure 2] (a) A diagram showing the frequency characteristics of a high-voltage amplifier, (b) A diagram showing the output waveform of an AC voltage superimposed on a DC voltage. [Figure 3] A schematic diagram showing the circuit configuration of a conventional power supply device for electrostatic chucks. [Modes for carrying out the invention]

[0011] The following describes an embodiment of the electrostatic chuck power supply device of the present invention for supplying power to an electrostatic chuck that adsorbs wafer W on its surface, with reference to the drawings. In the following, directions such as "up" and "down" will be described based on the orientation of the electrostatic chuck shown in Figure 1.

[0012] Referring to Figure 1, Ec is an electrostatic chuck powered by the power supply device of this embodiment. The electrostatic chuck Ec is placed inside the vacuum chamber of an processing device (not shown) that performs various processes such as film deposition by sputtering, and is designed to position and hold the wafer W within the vacuum chamber. The electrostatic chuck Ec consists of a metal base 1 and a dielectric chuck plate 2 provided on the upper surface of the base 1. The base 1 is made of an aluminum cylinder with a contour corresponding to the wafer W. On the other hand, the chuck plate 2 is made of PBN, ALN, or silicon rubber, and a pair of electrodes 3a and 3b are provided inside it via an insulating layer (not shown). The power supply device PS of this embodiment is used to apply a DC voltage (chuck voltage) between the two electrodes 3a and 3b.

[0013] The power supply device PS comprises a DC power supply circuit 4 that applies a DC voltage between the two electrodes 3a and 3b, and an AC superposition circuit 5 that applies an AC voltage through the capacitance of the chuck plate 2. The DC power supply circuit 4 is provided with DC power supply units 41 and 42 that output a predetermined positive or negative DC voltage (e.g., ±2kV), respectively, and high-voltage amplifiers 43 and 44. The positive and negative outputs 41a and 42a of the DC power supply units 41 and 42 are connected to the positive and negative power supplies of the respective high-voltage amplifiers 43 and 44. Resistors R1 and R2 are interposed between the outputs 41a and 42a, respectively, and voltmeters (not shown) are connected in parallel with each of the resistors R1 and R2. Furthermore, a phase inversion amplifier 45 is interposed between the AC superposition circuit 5 and the high-voltage amplifier 44, so that the phase of the voltage output from the AC superposition circuit 5 is inverted before being input to the high-voltage amplifier 44. Since known high-voltage amplifiers 43, 44 and phase inversion amplifier 45 can be used, a detailed explanation will be omitted. However, it is preferable that the frequency characteristics of the high-voltage amplifiers 43, 44 are constant in a frequency band of 2F (Hz) or less, where F (Hz) is the frequency of the AC voltage output from the AC power supply unit 51 described later.

[0014] The AC superposition circuit 5 includes an AC power supply unit 51 that outputs an AC voltage (e.g., 0 to 30V) at a predetermined frequency (e.g., 0 to 30kHz), and a control unit 52 that controls the voltage applied between the two electrodes 3a and 3b. The control voltage (e.g., +10V) output from the control unit 52 is superimposed with the AC voltage output from the AC power supply unit 51 and output from the AC superposition circuit 5. Furthermore, since the AC superposition circuit 5 can be constructed using a general analog circuit consisting of known capacitors, resistors, preamplifiers, etc., interposed at the outputs 51a and 52a of the AC power supply unit 51 and the control unit 52, a further detailed explanation is omitted.

[0015] The control voltage, which is a superimposed AC voltage output from the AC superposition circuit 5, is then input to the high-voltage amplifiers 43 and 44. The control voltage input to the high-voltage amplifiers 43 and 44 is amplified to a voltage set according to the potential difference between the DC power supply units 41 and 42 (for example, ±2kV), and the amplified DC voltage is applied between the two electrodes 3a and 3b. The operation of the DC power supply units 41 and 42, the AC power supply unit 51, and the control unit 52 is centrally controlled by a control unit (not shown).

[0016] According to the above embodiment, a DC voltage amplified by high-voltage amplifiers 43 and 44 can be applied between the two electrodes 3a and 3b without using a high-insulation voltage transformer (AC superposition transformer), and an AC voltage passing through the capacitance of the chuck plate 2 can be applied superimposed on the DC voltage. At this time, by measuring the AC voltage with each voltmeter (not shown) connected in parallel with each resistor R1 and R2, the state of the wafer W can be determined in the same way as in the conventional example described above. Furthermore, since it can be constructed with a general analog circuit that does not require a high-insulation voltage transformer, it is possible to suppress increases in manufacturing costs and to miniaturize the power supply device PS.

[0017] Furthermore, if the frequency of the AC voltage is F (Hz), and high-voltage amplifiers 43 and 44 are used whose frequency characteristics are constant in the frequency band of 2F (Hz) or less, as shown in Figure 2(a), it was confirmed that the amplified AC voltage (i.e., the AC voltage superimposed on the amplified DC voltage) has an output waveform equivalent to that of the conventional example shown in Figure 2(b), thus ensuring the function of understanding the state of the wafer W.

[0018] Although the embodiments of the present invention have been described above, the present invention is not limited to the above, and can be appropriately modified without departing from the technical idea of the present invention. In the above embodiment, the so-called bipolar electrostatic chuck Ec is applied as an example, but it is not limited to this, and the present invention can also be applied to a unipolar type. Further, in the above embodiment, as the high-voltage amplifiers 43 and 44, the frequency of the AC voltage is set to F (Hz), and the one that is constant in the frequency band of 2F (Hz) or less is described as an example, but the frequency characteristics of the high-voltage amplifiers 43 and 44 are not limited to this.

Explanation of Reference Numerals

[0019] Ec... Electrostatic chuck, PS... Power supply device for electrostatic chuck, W... Wafer (substrate to be processed), 3a, 3b... Electrodes, 4... DC power supply circuit, 43, 44... High-voltage amplifiers, 5... AC superposition circuit, 51... AC power supply unit, 52... Control unit.

Claims

1. A power supply device for an electrostatic chuck that supplies power to an electrostatic chuck that holds a substrate to be processed by adsorption in a vacuum chamber, The electrostatic chuck comprises a DC power supply circuit that applies a DC voltage to electrodes provided on the electrostatic chuck, and an AC superposition circuit that applies an AC voltage through the capacitance of the electrostatic chuck. A high-voltage amplifier with a predetermined frequency characteristic is interposed in the DC power supply circuit. The AC superposition circuit is a power supply device for an electrostatic chuck, characterized in that it has an AC power supply unit and a control unit that controls the voltage applied to the electrodes, and an AC voltage is superimposed on the control voltage from the control unit and input to a high-voltage amplifier, and this control voltage with the AC voltage superimposed is amplified by the high-voltage amplifier and applied to the electrodes.

2. The power supply device for an electrostatic chuck according to claim 1, characterized in that the frequency of the AC voltage is F (Hz), and the frequency characteristics of the high-voltage amplifier are constant in a frequency band of 2F (Hz) or less.

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