Plasma Potential Sensor

Abstract

To provide a plasma potential sensor capable of increasing the detection accuracy of plasma potential.SOLUTION: A plasma potential sensor 10 is configured to be installed on the inner wall of a chamber 103 of plasma processing equipment 100 for detecting the potential of plasma generated in the chamber 103. The plasma potential sensor includes: a first main surface 11 attached to the inner wall of the chamber 103; a second main surface 12 facing the plasma when in use; a plate-shaped conductive detection electrode 13; an electronic circuit 18 placed in the first main surface 11 side rather than the detection electrode 13 and that processes electrical signal detected by detection electrode 13, which has an input terminal 18a where electrical signals are input and an output terminal 18b that outputs processing results; a connection part 23 that electrically connects the detection electrode 13 and the input terminal 18a; a signal leader line 14 electrically connected to the output terminal 18b; and a protective layer 15 that has insulation properties and covers the detection electrode 13, the electronic circuit 18, and the signal leader line 14.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a plasma potential sensor. [Background technology]

[0002] In various processes for manufacturing electronic components and circuit boards, plasma processing equipment is used to generate plasma in a processing chamber to etch or clean the surface of the workpiece. To determine whether plasma discharge is occurring normally in the processing chamber, a probe electrode for measuring the plasma potential is installed on the sidewall of the processing chamber. The probe electrode detects the charge or potential induced in response to changes in the plasma discharge.

[0003] For example, Patent Document 1 proposes a window-type probe having a conductive support member with an opening in at least a portion of the surface facing the plasma, and a dielectric member placed in the opening of the conductive support member, with a probe electrode provided on one surface of the dielectric member.

[0004] The charge or potential of the probe electrode is usually converted into a digital value by an analog-to-digital converter (ADC), and the time-series data of the digital value is mathematically processed to determine whether or not an abnormal discharge has occurred. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3773189 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, the detection signal of the probe electrode (or plasma potential sensor) in Patent Document 1 is sent via external wiring to an electronic circuit that processes the detection signal. In particular, if this external wiring is long, the detection signal may be buried in external noise, etc., and the plasma potential may not be detected accurately. In such a situation, one of the objects of the present disclosure is to improve the detection accuracy of the plasma potential. [Means for solving the problem]

[0007] One aspect of the present disclosure relates to a plasma potential sensor that is mountable to an inner wall of a chamber included in a plasma processing apparatus and detects the potential of plasma generated in the chamber, the plasma potential sensor comprising: a first main surface mounted to the inner wall of the chamber; a second main surface located opposite the first main surface and facing the plasma during use; a conductive plate-shaped detection electrode; an electronic circuit disposed closer to the first main surface than the detection electrode and processing an electrical signal detected by the detection electrode, the electronic circuit having an input terminal for inputting the electrical signal and an output terminal for outputting a processing result; a connector electrically connecting the detection electrode to the input terminal; a signal lead wire electrically connected to the output terminal; and an insulating protective layer that covers the detection electrode, the electronic circuit, and the signal lead wire. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to improve the detection accuracy of the plasma potential. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a conceptual diagram showing a cross-sectional view of a schematic structure of an example of a plasma processing apparatus in which a plasma potential sensor according to the present disclosure is used; [Figure 2] 1A and 1B are diagrams showing a plasma potential sensor according to a first embodiment, in which (a) is a plan view and (b) is a cross-sectional view taken along line II-II. [Figure 3]3A and 3B are diagrams showing a plasma potential sensor according to a second embodiment, in which (a) is a plan view and (b) is a cross-sectional view taken along line III-III. [Figure 4] 4A and 4B are diagrams showing a plasma potential sensor according to a third embodiment, in which (a) is a plan view and (b) is a cross-sectional view taken along line IV-IV. [Figure 5] 10A and 10B are diagrams showing a plasma potential sensor according to a fourth embodiment, in which (a) is a plan view and (b) is a cross-sectional view taken along line VV. [Figure 6] FIG. 10 is a circuit diagram showing a part of an electronic circuit included in a plasma potential sensor according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of a plasma potential sensor according to the present disclosure will be described below using examples. However, the present disclosure is not limited to the examples described below. While specific numerical values ​​and materials are used in the following description, other numerical values ​​and materials may be used as long as the effects of the present disclosure are obtained.

[0011] The plasma potential sensor according to the present disclosure is configured to be attachable to the inner wall of a chamber included in a plasma processing apparatus and detects the potential of plasma generated in the chamber. The plasma processing apparatus may be, for example, a plasma etching apparatus, a plasma cleaning apparatus, a plasma dicer, a plasma ashing apparatus, or a plasma CVD apparatus. The plasma potential sensor according to the present disclosure includes a first main surface, a second main surface, a detection electrode, an electronic circuit, a connection portion, a signal lead wire, and a protective layer.

[0012] The first main surface is a main surface that is attached to the inner wall of the chamber. The first main surface may be attached to the inner wall of the chamber by, for example, pasting, bonding, or embedding. The first main surface may be exposed to the outside of the plasma potential sensor. The first main surface may be flat or uneven.

[0013] The second major surface is a major surface located opposite the first major surface. The second major surface faces the plasma in the chamber when the plasma potential sensor is in use. The second major surface may be exposed to the outside of the plasma potential sensor. The second major surface may or may not be flat. The second major surface may or may not be parallel to the first major surface.

[0014] The detection electrode is a conductive plate-like electrode. The shape of the detection electrode may be, for example, but is not limited to, a rectangular plate. The detection electrode may be made of the same material as the material constituting the inner wall of the chamber (e.g., aluminum, stainless steel, etc.), or may be made of another conductive material (e.g., copper, aluminum, etc.). When the plasma potential sensor is in use, a charge corresponding to the potential of the plasma generated in the chamber can be induced in the detection electrode.

[0015] The electronic circuit is provided closer to the first principal surface than the detection electrodes. The electronic circuit processes the electrical signal detected by the detection electrodes. The electronic circuit has an input terminal to which the electrical signal is input and an output terminal to which the processed result is output. The electronic circuit is mounted on, for example, a substrate, which may be a rectangular plate. The size of the electronic circuit as viewed from the first principal surface side or the second principal surface side may be equal to or smaller than the size of the detection electrodes. The electrical signal input to the input terminal may be an analog signal. The electronic circuit may amplify the input analog signal or convert it into a digital signal. The output terminal may output the amplified analog signal or digital signal as the processed result.

[0016] The connection portion electrically connects the detection electrode and the input terminal, and may be made of a conductive material (for example, a metal).

[0017] The signal lead-out wire is connected to an output terminal of the electronic circuit and may be made of a conductive material (e.g., metal).

[0018] The protective layer has insulating properties. The protective layer may be made of, for example, glass or insulating resin. The protective layer covers the detection electrodes, the electronic circuit, and the signal lead wires. A portion of the outer surface of the protective layer may constitute a first main surface of the plasma potential sensor. Another portion of the outer surface of the protective layer may constitute a second main surface of the plasma potential sensor.

[0019] The plasma potential sensor having the above configuration can be attached to any available space on the inner wall (or side wall) of the chamber of a plasma processing apparatus to detect the potential of the plasma generated in the chamber. Therefore, the measurement position of the plasma potential can be set according to the user's needs without changing the configuration of the plasma processing apparatus.

[0020] The plasma potential sensor also includes an electronic circuit that processes the electrical signal detected by the detection electrode and a connector that electrically connects the detection electrode to an input terminal of the electronic circuit. This makes the plasma potential sensor less susceptible to external noise than conventional configurations that connect the plasma potential sensor (e.g., the probe electrode of Patent Document 1) to the electronic circuit via external wiring. This is because the plasma potential sensor has a compact configuration in which the connector corresponding to the conventional external wiring is built into the plasma potential sensor, making it less susceptible to external noise than the external wiring. The output terminal of the electronic circuit then outputs a processed electrical signal that is virtually unaffected by external noise. This processed result accurately reflects the plasma potential in the chamber. Therefore, the plasma potential sensor of the present disclosure can improve the accuracy of plasma potential detection.

[0021] The detection electrode may cover at least a portion of the electronic circuit when viewed from the second principal surface. Here, the detection electrode preferably covers 80% or more of the electronic circuit when viewed from the second principal surface, and more preferably covers the entire electronic circuit. With this configuration, the detection electrode can suppress the influence of plasma on the electronic circuit. Therefore, unintended operation of the electronic circuit is prevented, and the detection accuracy of the plasma potential can be further improved.

[0022] The plasma potential sensor may further include an auxiliary electrode provided inside the protective layer on the second principal surface side of the signal lead-out line, electrically insulated from the signal lead-out line, and covering at least a portion of the signal lead-out line as viewed from the second principal surface side. Here, the auxiliary electrode preferably covers 80% or more of the signal lead-out line as viewed from the second principal surface side, and more preferably covers the entire signal lead-out line. By providing such an auxiliary electrode, mutual interference between the plasma and the signal lead-out line can be suppressed. Specifically, the auxiliary electrode suppresses the influence of the plasma on the signal lead-out line from affecting the processing result signal, and the influence of the signal lead-out line on the plasma from affecting the state of the plasma. A predetermined voltage may be applied to the auxiliary electrode. The predetermined voltage may be, for example, the same as the voltage applied to the sidewall of the chamber, or may be a ground voltage.

[0023] The auxiliary electrode may extend between the detection electrode and the electronic circuit. The auxiliary electrode may extend between the detection electrode and the electronic circuit when viewed in a direction parallel to the first principal surface. This configuration reduces the influence of stray capacitance formed between the detection electrode and the electronic circuit. That is, the electrical signal detected by the detection electrode is prevented from affecting the operation of the electronic circuit via the stray capacitance, and the charge generated by the operation of the electronic circuit is prevented from affecting the detection signal of the detection electrode via the stray capacitance. This further improves the accuracy of plasma potential detection.

[0024] The plasma potential sensor may further include a guard electrode disposed between the detection electrode and the electronic circuit, electrically insulated from the detection electrode, and covering at least a portion of the detection electrode as viewed from the first principal surface. The guard electrode preferably covers 80% or more of the detection electrode as viewed from the first principal surface, and more preferably covers the entire detection electrode. The guard electrode may be disposed between the detection electrode and the electronic circuit as viewed in a direction parallel to the first principal surface. Providing such a guard electrode reduces the influence of stray capacitance formed between the detection electrode and the electronic circuit, thereby further improving the detection accuracy of the plasma potential sensor.

[0025] The guard electrode may be virtually short-circuited to the detection electrode. With this configuration, the potential of the detection electrode and the potential of the guard electrode are equalized, thereby suppressing the movement of charge between the stray capacitance and the detection electrode. This allows almost all of the charge induced in the detection electrode to be sent to the input terminal of the electronic circuit via the connection, further improving the detection accuracy of the plasma potential sensor.

[0026] The term "virtually short-circuiting the guard electrode with the detection electrode" means that the potential of the guard electrode is controlled to be the same as that of the detection electrode in response to potential fluctuations of the detection electrode. However, unlike a normal short circuit, current does not necessarily flow from the detection electrode to the guard electrode or vice versa, and the current flowing in the detection electrode can be controlled independently of the current flowing in the guard electrode.

[0027] The guard electrode may be virtually shorted to the detection electrode via an operational amplifier. The operational amplifier may include a current mirror circuit configured by combining multiple transistors. The operational amplifier may be configured as a commercially available IC chip as a general operational amplifier circuit.

[0028] The electronic circuit may have a power supply terminal for supplying power to the electronic circuit. The plasma potential sensor may further include a power supply line electrically connected to the power supply terminal and covered with a protective layer. With this configuration, power is supplied to the electronic circuit via the power supply line and the power supply terminal. Power may be supplied to the power supply line from an external power supply device.

[0029] As described above, according to the present disclosure, the plasma potential sensor has built-in electronic circuits and connection parts, thereby improving the detection accuracy of the plasma potential.

[0030] An example of a plasma potential sensor according to the present disclosure will be described in detail below with reference to the drawings. The components described above can be applied to the components of the example plasma potential sensor described below. The components of the example plasma potential sensor described below can be modified based on the above description. Furthermore, the matters described below may be applied to the above embodiment. Of the components of the example plasma potential sensor described below, components that are not essential to the plasma potential sensor according to the present disclosure may be omitted. Note that the diagrams shown below are schematic and do not accurately reflect the shapes and numbers of actual components.

[0031] First Embodiment A first embodiment of the present disclosure will be described. A plasma potential sensor 10 of this embodiment is used in a plasma processing apparatus 100 that generates plasma, which is the target of plasma potential detection. Below, the plasma processing apparatus 100 will be described first, followed by the plasma potential sensor 10.

[0032] (Plasma processing equipment) The plasma processing apparatus includes a processing chamber, an electrode unit provided in the processing chamber and on which an object to be processed is placed, and a high-frequency power supply unit that applies high-frequency power to the electrode unit. Plasma is generated within the processing chamber when a plasma generating gas is supplied to the processing chamber and high-frequency power is applied to the electrode unit. The generated plasma can be used, for example, to etch or clean the surface of the object to be processed placed on the electrode unit. A detection circuit for detecting the plasma potential is connected to the plasma processing apparatus. The output of the detection circuit is connected to a signal analysis unit. The signal analysis unit detects the plasma potential based on the output of the detection circuit and determines whether the generated plasma is normal based on the detected plasma potential.

[0033] FIG. 1 is a conceptual cross-sectional view of the general structure of a plasma processing apparatus 100 in which plasma, the target of plasma potential detection, is generated. A processing chamber 103a is formed by sealing a chamber (vacuum chamber) 103, which is composed of a horizontal base 101 and a lid 102. The lid 102 is arranged so that it can be raised and lowered by a lifting mechanism (not shown). When the lid 102 descends and abuts against the upper surface of the base 101, the chamber 103 is sealed. A sealing member 104 is interposed between the lid 102 and the base 101, ensuring that the processing chamber 103a is sealed. In the processing chamber 103a, a processing target 109 is subjected to plasma processing. An opening 101a is provided in the base 101, and an electrode 105 is fitted in the opening 101a via an insulating member 106. The upper surface of the electrode 105 is covered with an insulating layer 107. On the upper surface of the insulating layer 107, a guide member 108 for positioning the processing object 109 is arranged.

[0034] A through-hole 101b is formed around the periphery of the opening 101a of the base 101. A conduit 111 is inserted into the through-hole 101b, and a vent valve 112, a gas supply valve 113, a vacuum valve 114, and a vacuum gauge 115 are connected to the conduit 111. A gas supply unit 116 and a vacuum pump 117 are connected to the gas supply valve 113 and the vacuum valve 114, respectively. By opening the vacuum valve 114 and operating the vacuum pump 117, gas is discharged from the processing chamber 103a, creating a reduced pressure. The degree of vacuum in the processing chamber 103a is measured by the vacuum gauge 115. Meanwhile, when the gas supply valve 113 is opened, plasma generating gas is supplied from the gas supply unit 116 into the processing chamber 103a. The gas supply unit 116 has a built-in flow rate adjustment mechanism that adjusts the flow rate of the plasma generating gas supplied into the processing chamber 103a. When the vent valve 112 is opened, the atmosphere is supplied into the processing chamber 103a.

[0035] The electrode 105 is electrically connected to a high-frequency power supply 119 via a matching box 118. Meanwhile, the lid 102 is grounded to a grounding unit 110. When plasma generating gas is supplied into the processing chamber 103a and the high-frequency power supply 119 is operated, a high-frequency voltage is applied between the electrode 105 and the lid 102. This generates plasma in the processing chamber 103a. The matching box 118 matches the impedance between the high-frequency power supply 119 and a plasma discharge circuit (not shown) that generates plasma. The vent valve 112, gas supply valve 113, vacuum valve 114, vacuum gauge 115, gas supply unit 116, vacuum pump 117, and high-frequency power supply 119 are controlled by an apparatus control unit 124 in a control unit 120. That is, the apparatus control unit 124 has a normal operational control function for executing plasma processing operations. A display unit 130, an input unit 140, and a plasma potential sensor 10 are connected to the control unit 120. The display unit 130 displays the results of abnormality determination by the signal analysis unit 121, which will be described later. The input unit 140 receives input of a process recipe and the like.

[0036] A plasma potential sensor 10 is attached, in this example by adhesive, to the inner wall (side wall) of the chamber 103. The configuration of the plasma potential sensor 10 will be described in detail later.

[0037] When a plasma discharge occurs in the processing chamber 103a, a potential and charge corresponding to the state of the plasma are induced in the detection electrode 13 (described below) of the plasma potential sensor 10. The charge induced in the detection electrode 13 is sent as an analog signal to the electronic circuit 18 (described below) of the plasma potential sensor 10, where it is converted to a digital signal or amplified. The digital signal or the amplified analog signal is sent to the signal analysis unit 121 of the control unit 120. Based on the sent signal, the signal analysis unit 121 determines whether the plasma state is normal. If the plasma state is determined to be abnormal and in an abnormal discharge state, a retry process, cumulative plasma processing, maintenance determination, etc. may be performed. Note that it is not necessary to perform all of the retry process, cumulative plasma processing, and maintenance determination; one or more of these processes may be performed.

[0038] The device control unit 124 may also include a processing history storage unit, a retry processing unit, a cumulative plasma processing unit, and a maintenance determination function unit (not shown). In other words, in addition to the normal operation control functions described above, the device control unit 124 may determine the state of plasma discharge in the processing chamber 103a based on the abnormal discharge detection results by the signal analysis unit 121 and reset the plasma processing. The determination of the plasma discharge state and the resetting of the plasma processing may be performed by the retry processing unit, the cumulative plasma processing unit, and the maintenance determination unit. The processing history storage unit stores, as processing history data for the plasma processing apparatus 100, temporal changes in the signal from the electronic circuit 18 that are temporarily recorded in memory and intermediate data required by the signal analysis unit 121 to determine the detection of abnormal discharge. This allows detailed processing history data to be obtained for the processing object 109 processed by the plasma processing apparatus 100, ensuring traceability for quality control and production management.

[0039] (Plasma potential sensor) Plasma potential sensor 10 is a device for detecting the potential of plasma generated in chamber 103 of plasma processing apparatus 100. Plasma potential sensor 10 may be flexible enough to deform along the shape of the inner wall of chamber 103. As shown in FIG. 2 , plasma potential sensor 10 includes first main surface 11, second main surface 12, detection electrode 13, electronic circuit 18, first connection portion 23, signal lead wire 14, first and second power supply wires 21 and 22, and protective layer 15.

[0040] The first main surface 11 is a main surface that is attached to the inner wall of the chamber 103. In this embodiment, the first main surface 11 is attached to the inner wall of the chamber 103 by bonding, but this is not limiting. The first main surface 11 is exposed to the outside of the plasma potential sensor 10. The first main surface 11 is flat.

[0041] The second main surface 12 is a main surface located opposite to the first main surface 11. The second main surface 12 faces the plasma in the chamber 103 when the plasma potential sensor 10 is in use. The second main surface 12 is exposed to the outside of the plasma potential sensor 10. The second main surface 12 is flat. The second main surface 12 is parallel to the first main surface 11.

[0042] The detection electrode 13 is a conductive rectangular plate-shaped electrode. The detection electrode 13 covers the electronic circuit 18 when viewed from the second main surface 12 side. When the plasma potential sensor 10 is in use, a charge corresponding to the potential of the plasma generated in the chamber 103 can be induced in the detection electrode 13. A signal of the induced charge is sent to the electronic circuit 18 via the first connection part 23.

[0043] The electronic circuit 18 is provided closer to the first main surface 11 than the detection electrodes 13. The electronic circuit 18 processes the electrical signals detected by the detection electrodes 13. The electronic circuit 18 has an input terminal 18a to which the electrical signals are input, an output terminal 18b that outputs the processing results, and a power supply terminal 18c that supplies power to the electronic circuit 18. The electronic circuit 18 is mounted on a rectangular plate-shaped substrate 19. The substrate 19 is smaller than the detection electrodes 13 when viewed in a direction perpendicular to the surface of the detection electrodes 13. The electrical signals input to the input terminal 18a are analog signals, and the electronic circuit 18 converts the analog signals into digital signals. The output terminal 18b outputs the digital signals as the processing results.

[0044] The first connection portion 23 electrically connects the detection electrode 13 and the input terminal 18a. The first connection portion 23 extends in a direction perpendicular to the surface of the detection electrode 13, but is not limited to this. The first connection portion 23 is made of a conductive metal. The first connection portion 23 is an example of a connection portion.

[0045] The signal lead-out wire 14 is connected to the output terminal 18b of the electronic circuit 18. The signal lead-out wire 14 is made of a conductive metal. The signal lead-out wire 14 may have a terminal portion (not shown) connected to wiring (not shown) that connects the signal lead-out wire 14 and the control unit 120. The terminal portion may be exposed to the outside of the plasma potential sensor 10.

[0046] The first and second power supply lines 21 and 22 are each connected to a power supply terminal 18c of the electronic circuit 18. Power is supplied to the first and second power supply lines 21 and 22 from an external power supply device (not shown). A power supply voltage is applied to one of the first and second power supply lines 21 and 22. A ground voltage is applied to the other of the first and second power supply lines 21 and 22. However, as long as a voltage sufficient for operating the electronic circuit 18 is applied between the first and second power supply lines 21 and 22, the voltages applied to the power supply lines 21 and 22 can be set arbitrarily. The first and second power supply lines 21 and 22 are each an example of a power supply line.

[0047] The protective layer 15 has insulating properties. In this embodiment, the protective layer 15 is made of glass, but is not limited to this. The protective layer 15 covers the detection electrode 13, the electronic circuit 18, the first connection portion 23, the signal lead wire 14, and the first and second power supply wires 21 and 22. As shown in FIG. 2( a ), the protective layer 15 has a shape that follows the outline of the detection electrode 13, the signal lead wire 14, and the first and second power supply wires 21 and 22 when viewed from a direction perpendicular to the surface of the detection electrode 13.

[0048] Second Embodiment A second embodiment of the present disclosure will be described. The plasma potential sensor 10 of this embodiment differs from the first embodiment in that it includes an auxiliary electrode 16. The following mainly describes the differences from the first embodiment.

[0049] As shown in FIG. 3 , the plasma potential sensor 10 includes an auxiliary electrode 16 provided on the second main surface 12 side of the signal lead-out wire 14. The auxiliary electrode 16 is provided inside the protective layer 15 on the second main surface 12 side of the signal lead-out wire 14 and covers the signal lead-out wire 14 when viewed from the second main surface 12 side while being insulated from the signal lead-out wire 14. The auxiliary electrode 16 also serves as the first power supply wire 21 and is electrically connected to, for example, the lid portion 102, to which a ground voltage is applied. The auxiliary electrode 16 also covers the second power supply wire 22 when viewed from the second main surface 12 side. The auxiliary electrode 16 does not have to cover the detection electrode 13 when viewed from the second main surface 12 side.

[0050] The auxiliary electrode 16 is connected to a ground line (not shown) of the electronic circuit 18 by a second connection portion 24. The second connection portion 24 extends in a direction perpendicular to the surface of the electronic circuit 18 (substrate 19), but is not limited to this. The second connection portion 24 is made of a conductive metal. The second connection portion 24 is electrically insulated from the first connection portion 23. In other words, the auxiliary electrode 16 is electrically insulated from the detection electrode 13.

[0051] Third Embodiment A third embodiment of the present disclosure will be described. The plasma potential sensor 10 of this embodiment differs from the second embodiment in the configuration of the auxiliary electrode 16. The following mainly describes the differences from the second embodiment.

[0052] 4, the auxiliary electrode 16 of this embodiment extends between the detection electrode 13 and the electronic circuit 18. When viewed from the second main surface 12 side, the auxiliary electrode 16 may cover more than half (50% or more) of the electronic circuit 18, may cover more than 60%, or may cover more than 70%.

[0053] Fourth Embodiment A fourth embodiment of the present disclosure will be described. The plasma potential sensor 10 of this embodiment differs from the third embodiment in that it includes a guard electrode 17. The following mainly describes the differences from the third embodiment.

[0054] 5, plasma potential sensor 10 includes guard electrode 17 provided between detection electrode 13 and electronic circuit 18. Guard electrode 17 is electrically insulated from detection electrode 13 and covers the entire detection electrode 13 when viewed from first main surface 11. Guard electrode 17 also covers the entire electronic circuit 18 when viewed from second main surface 12.

[0055] The guard electrode 17 is connected to a first operational amplifier 18d (described later) included in the electronic circuit 18 by a third connection portion 25. The third connection portion 25 extends in a direction perpendicular to the surface of the electronic circuit 18 (substrate 19), but is not limited to this. The third connection portion 25 is made of a conductive metal. The third connection portion 25 is electrically insulated from the first connection portion 23. In other words, the guard electrode 17 is electrically insulated from the detection electrode 13. The guard electrode 17 has a through-hole (not shown) through which the first connection portion 23 is inserted without contact.

[0056] FIG. 6 is a circuit diagram showing a portion of the electronic circuit 18 of this embodiment. The electronic components and wiring shown in this circuit diagram are included in the electronic circuit 18 of the plasma potential sensor 10. As shown in FIG. 6, the electronic circuit 18 includes a first operational amplifier 18d and a second operational amplifier 18e. The guard electrode 17 is virtually short-circuited to the detection electrode 13 via the first operational amplifier 18d. The first operational amplifier 18d is an example of an operational amplifier.

[0057] The non-inverting input terminal of the first operational amplifier 18d is connected to the first connection part 23 (detection electrode 13) via wiring 18f within the electronic circuit 18. The output terminal of the first operational amplifier 18d is connected to the third connection part 25 (guard electrode 17) via wiring 18g within the electronic circuit 18. The output terminal of the first operational amplifier 18d is also connected to the inverting input terminal of the first operational amplifier 18d without a feedback resistor. As a result, the first operational amplifier 18d forms a non-inverting amplifier circuit with a gain of 1, and the detection electrode 13, which is electrically connected to the non-inverting input terminal of the first operational amplifier 18d, and the guard electrode 17, which is electrically connected to the inverting input terminal of the first operational amplifier 18d, are virtually short-circuited.

[0058] Due to the effect of the virtual short circuit of the operational amplifier, the potential of the inverting input terminal of the first operational amplifier 18d, which is electrically connected to the guard electrode 17, operates to be the same potential as the potential of the non-inverting input terminal of the first operational amplifier 18d, which is electrically connected to the detection electrode 13.

[0059] The inverting input terminal of the second operational amplifier 18e is connected to the first connection unit 23 (detection electrode 13) via a resistor R1. The non-inverting input terminal of the second operational amplifier 18e is grounded. The output terminal of the second operational amplifier 18e is connected to the inverting input terminal of the second operational amplifier 18e via a feedback resistor R2. This causes the second operational amplifier 18e to form an inverting amplifier circuit, and a voltage obtained by amplifying the potential of the detection electrode 13 is output to the output terminal of the second operational amplifier 18e. The output voltage is sent to a signal analysis unit 121 of the control unit 120.

[0060] In the second operational amplifier 18e, a capacitor C1 (not shown) may be connected between the output terminal and the inverting input terminal instead of the feedback resistor R2. In this case, the second operational amplifier 18e forms an integrating circuit, amplifies the amount of charge induced in the detection electrode 13, and outputs a voltage corresponding to the amplified amount of charge to the output terminal. [Industrial Applicability]

[0061] The present disclosure can be used in a plasma potential sensor. [Explanation of symbols]

[0062] 10: Plasma potential sensor 11: First main surface 12: Second main surface 13: Detection electrode 14: Signal lead wire 15:Protective layer 16: Auxiliary electrode 17: Guard electrode 18:Electronic circuit 18a: Input terminal 18b: Output terminal 18c: Power terminal 18d: 1st operational amplifier (op-amp) 18e: Second operational amplifier 18f, 18g: Wiring 19: Circuit board 21: 1st power line (power line) 22: 2nd power line (power line) 23: First connection part (connection part) 24: Second connection part 25: Third connection part 100: Plasma processing device 101: Base section 101a: Opening 101b: Through hole 102: Lid part 103: Chamber 103a: Processing room 104: Sealing material 105: Electrode part 106: Insulating material 107: Insulating layer 108: Guide member 109: Processing object 110: Grounding part 111: Pipeline 112: Vent valve 113: Gas supply valve 114: Vacuum valve 115: Vacuum gauge 116: Gas supply unit 117: Vacuum pump 118: Matching box 119: High frequency power supply section 120: Control unit 121: Signal analysis section 124: Device control unit 130: Display section 140: Input section

Claims

1. A plasma potential sensor configured to be attachable to an inner wall of a chamber included in a plasma processing apparatus, the plasma potential sensor detecting a potential of plasma generated in the chamber, a first major surface attached to an inner wall of the chamber; a second major surface opposite the first major surface and facing the plasma in use; a conductive plate-shaped detection electrode; an electronic circuit that is provided closer to the first main surface than the detection electrodes and processes the electrical signals detected by the detection electrodes, the electronic circuit having an input terminal to which the electrical signals are input and an output terminal to which a processing result is output; a connection portion that electrically connects the detection electrode and the input terminal; a signal lead wire electrically connected to the output terminal; a protective layer having insulating properties and covering the detection electrodes, the electronic circuit, and the signal lead wires; A plasma potential sensor comprising:

2. The plasma potential sensor according to claim 1 , wherein the detection electrode covers at least a portion of the electronic circuit when viewed from the second main surface side.

3. 3. The plasma potential sensor according to claim 1, further comprising an auxiliary electrode provided inside the protective layer on the second main surface side of the signal lead wire, the auxiliary electrode being electrically insulated from the signal lead wire and covering at least a portion of the signal lead wire when viewed from the second main surface side.

4. The plasma potential sensor of claim 3 , wherein the auxiliary electrode extends between the sensing electrode and the electronic circuitry.

5. 5. The plasma potential sensor according to claim 1, further comprising a guard electrode provided between the detection electrode and the electronic circuit, the guard electrode being electrically insulated from the detection electrode and covering at least a portion of the detection electrode when viewed from the first main surface side.

6. 6. The plasma potential sensor according to claim 5, wherein the guard electrode is virtually short-circuited to the detection electrode.

7. 7. The plasma potential sensor according to claim 6, wherein the guard electrode is virtually short-circuited to the detection electrode via an operational amplifier.

8. the electronic circuit has a power supply terminal for supplying power to the electronic circuit; 8. The plasma potential sensor according to claim 1, further comprising a power supply line electrically connected to the power supply terminal and covered with the protective layer.

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