Electrostatic adsorption method and plasma processing device

Abstract

The present invention provides an electrostatic adsorption method and plasma processing apparatus that can easily suppress a decrease in the adsorption force of a ring member. Voltages of different polarities are applied to an electrode for each plasma processing unit. The electrode is disposed within a mounting table that supports a substrate to be processed by the plasma and a ring member surrounding the substrate, at least in a region corresponding to the ring member.

Description

Technical Field

[0001] The present disclosure relates to an electrostatic adsorption method and a plasma processing device. Background Art

[0002] Patent Document 1 discloses a plasma processing apparatus in which an electrode is provided inside a mounting table on which a focus ring is mounted so as to face the focus ring, and voltages of different polarities are periodically applied to the electrode during plasma processing.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-206935 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] The present disclosure provides a technology for simply suppressing a decrease in the adsorption force of a ring member.

[0008] Solutions for solving problems

[0009] In one embodiment of the electrostatic adsorption method disclosed herein, a voltage of different polarity is applied to an electrode provided in at least an area corresponding to a ring member inside a mounting table for mounting a substrate and a ring member, wherein the substrate is the object of plasma processing and the ring member surrounds the substrate.

[0010] Effects of the Invention

[0011] According to the present disclosure, it is possible to easily suppress a decrease in adsorption force. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a cross-sectional view schematically showing the structure of the plasma processing apparatus according to the first embodiment.

[0013] Figure 2 This is a diagram showing an example of an arrangement of electrode plates according to the first embodiment.

[0014] Figure 3 FIG. 1 is a diagram schematically showing charge migration in the conventional art.

[0015] Figure 4 This is a diagram schematically showing an example of a change pattern of the applied voltage according to the first embodiment.

[0016] Figure 5This is a diagram schematically showing an example of a change pattern of the applied voltage according to the first embodiment.

[0017] Figure 6 It is a diagram explaining the plasma processing and the voltage application pattern of the WLDC.

[0018] Figure 7 It is a diagram illustrating a voltage application pattern in plasma processing.

[0019] Figure 8 This is a diagram showing an example of the results of an experiment for measuring the leakage amount of heat transfer gas in an application pattern of a comparative example.

[0020] Figure 9 This is a graph showing the average leakage amount of heat transfer gas per wafer in the application mode of the comparative example.

[0021] Figure 10 This is a diagram showing an example of the results of an experiment measuring the leakage amount of heat transfer gas in the application mode according to the embodiment.

[0022] Figure 11 Graph showing the average leakage amount of heat transfer gas per wafer in the application pattern of the embodiment.

[0023] Figure 12 This is a diagram schematically showing an example of a change pattern of the applied voltage according to the first embodiment.

[0024] Figure 13A This is a diagram schematically showing an example of a change pattern of the applied voltage according to the first embodiment.

[0025] Figure 13B This is a diagram schematically showing an example of a change pattern of the applied voltage according to the first embodiment.

[0026] Figure 14 This is a diagram showing an example of an arrangement of electrode plates according to the first embodiment.

[0027] Figure 15 It is a cross-sectional view schematically showing the structure of a plasma processing apparatus according to a second embodiment.

[0028] Figure 16 This is a diagram schematically showing an example of the data structure of charge transfer information according to the second embodiment.

[0029] Description of Reference Numerals

[0030] 1: Plasma processing device; 10: Processing container; 11: Base; 21a: First high-frequency power supply; 21b: Second high-frequency power supply; 25: Electrostatic suction cup; 25a: Center; 25b: Peripheral; 26: Electrode plate; 27: DC power supply; 28: DC power supply; 29: Electrode plate; 30: Edge ring; 50: Control unit; 51: Process controller; 52: User interface; 53: Storage unit; 53a: Charge transfer information; W: Wafer. DETAILED DESCRIPTION

[0031] Below, embodiments of the electrostatic adsorption method and plasma processing apparatus disclosed in this application are described in detail with reference to the accompanying drawings. Furthermore, the disclosed electrostatic adsorption method and plasma processing apparatus are not limited to these embodiments. The various embodiments can be appropriately combined within the scope of the treatment contents that do not conflict.

[0032] Furthermore, plasma processing apparatuses apply voltage to electrodes within the stage to electrostatically attract edge rings, such as focus rings. However, charge migration from the edge ring to the electrostatic chuck can sometimes occur, reducing the edge ring's attraction. Therefore, in Patent Document 1, voltages of different polarities are periodically applied to the electrodes during plasma processing. However, when voltages of different polarities are periodically applied during plasma processing, the timing and frequency of polarity switching must be optimized. Plasma processing involves a wide variety of processes, and optimizing each requires considerable effort. Therefore, a simple method for suppressing the reduction in edge ring attraction is required.

[0033] (First embodiment)

[0034] Next, the plasma processing apparatus 1 according to the embodiment will be described. Figure 1 1 is a cross-sectional view schematically illustrating the structure of a plasma processing apparatus 1 according to the first embodiment. In the first embodiment, the plasma processing apparatus 1 is described as an example of an RIE (Reactive Ion Etching) type plasma processing apparatus. However, the plasma processing apparatus 1 may be a plasma etching apparatus utilizing surface plasma, a plasma CVD apparatus, or the like.

[0035] exist Figure 1In the present invention, the plasma processing apparatus 1 has a cylindrical processing container 10 that is safely grounded and made of metal, such as aluminum or stainless steel. The plasma processing apparatus 1 is provided with a disc-shaped susceptor (lower electrode) 11 in the processing container 10 for mounting a semiconductor wafer (hereinafter referred to as a "wafer") W, which is a substrate to be processed by the plasma. The susceptor 11 is made of aluminum, for example, and is supported by a cylindrical support portion 13 via an insulating cylindrical retaining member 12. The cylindrical support portion 13 extends vertically upward from the bottom of the processing container 10. The susceptor 11 is an example of a mounting table disclosed herein.

[0036] An exhaust passage 14 is formed between the side wall of the processing container 10 and the cylindrical support portion 13. An annular baffle 15 is provided at the entrance or midway of the exhaust passage 14. The processing container 10 is provided with an exhaust port 16 at the bottom of the exhaust passage 14. The exhaust port 16 is connected to the exhaust device 18 via an exhaust pipe 17. The exhaust device 18 has a vacuum pump for reducing the pressure of the processing space in the processing container 10 to a specified vacuum level. In addition, the exhaust pipe 17 has an automatic pressure control valve (hereinafter referred to as "APC") (not shown) which is an adjustable butterfly valve. The APC automatically controls the pressure in the processing container 10. In addition, a gate valve 20 for opening and closing the loading and unloading port 19 of the wafer W is installed on the side wall of the processing container 10.

[0037] The susceptor 11 is connected to a first high-frequency power supply 21a via a first matching unit 22a. Furthermore, the susceptor 11 is connected to a second high-frequency power supply 21b via a second matching unit 22b. The first high-frequency power supply 21a is used to generate plasma and supplies high-frequency power of a predetermined frequency (e.g., 100 MHz) to the susceptor 11 during plasma processing. The second high-frequency power supply 21b is used to attract ions (for generating a bias voltage) and supplies high-frequency power of a predetermined frequency (e.g., 13 MHz) lower than that of the first high-frequency power supply 21a to the susceptor 11 during plasma processing. A showerhead 24, which serves as an upper electrode and will be described later, is provided at the top of the processing container 10 and is at a ground potential. Thus, high-frequency voltages of two frequencies are applied between the susceptor 11 and the showerhead 24 from the first high-frequency power supply 21a and the second high-frequency power supply 21b.

[0038] An electrostatic chuck 25 for adsorbing the wafer W by electrostatic adsorption is provided on the upper surface of the base 11. The electrostatic chuck 25 has a disk-shaped center portion 25a for mounting the wafer W and an annular outer peripheral portion 25b formed so as to surround the center portion 25a. The center portion 25a protrudes upward in the figure relative to the outer peripheral portion 25b. An annular edge ring 30 such as a focus ring is arranged on the upper surface of the outer peripheral portion 25b so as to surround the center portion 25a in an annular shape. The edge ring 30 is an example of a ring member disclosed herein. The edge ring 30 is consumed by the plasma treatment. In addition, the center portion 25a is formed by sandwiching an electrode plate 26 including a conductive film between a pair of dielectric films. The outer peripheral portion 25b is formed by sandwiching an electrode plate 29 including a conductive film between a pair of dielectric films. In this embodiment, two annular electrode plates 29 are arranged side by side. The electrode plate 26 is electrically connected to a DC power supply 27. The two electrode plates 29 are electrically connected to a DC power supply 28 separately. The DC power supply 27 and the DC power supply 28 are configured to be able to change the level and polarity of the DC voltage supplied. The DC power supply 27 applies a DC voltage to the electrode plate 26 under the control of the control unit 50 described later. The DC power supply 28 applies a DC voltage to each of the two electrode plates 29 under the control of the control unit 50 described later. The electrostatic chuck 25 generates an electrostatic force such as a Coulomb force by the voltage applied from the DC power supply 27 to the electrode plate 26, and the wafer W is adsorbed and held on the electrostatic chuck 25 by the electrostatic force. In addition, the electrostatic chuck 25 generates an electrostatic force such as a Coulomb force by the voltage applied from the DC power supply 28 to the electrode plate 29, and the edge ring 30 is adsorbed and held on the electrostatic chuck 25 by the electrostatic force. The details of the arrangement of the electrode plate 29 will be described later.

[0039] Furthermore, an annular refrigerant chamber 31, for example, extending in the circumferential direction, is provided inside the susceptor 11. A refrigerant, such as cooling water, at a predetermined temperature is circulated from a cooling device 32 via pipes 33 and 34 into the refrigerant chamber 31. The temperature of the refrigerant is used to control the processing temperature of the wafer W on the electrostatic chuck 25.

[0040] In addition, the electrostatic chuck 25 is connected to the heat transfer gas supply unit 35 via a gas supply line 36. The gas supply line 36 branches into a wafer-side line 36a that reaches the center portion 25a of the electrostatic chuck 25 and an edge ring-side line 36b that reaches the outer peripheral portion 25b of the electrostatic chuck 25. The heat transfer gas supply unit 35 uses the wafer-side line 36a to supply heat transfer gas to the space between the center portion 25a of the electrostatic chuck 25 and the wafer W. In addition, the heat transfer gas supply unit 35 uses the edge ring-side line 36b to supply heat transfer gas to the space between the outer peripheral portion 25b of the electrostatic chuck 25 and the edge ring 30. As the heat transfer gas, a gas with thermal conductivity, such as He gas, is preferably used. The heat transfer gas is equivalent to an example of a heat medium, and the heat transfer gas supply unit 35 is equivalent to an example of a supply unit that supplies the heat medium.

[0041] The top showerhead 24 has an electrode plate 37 on its lower surface, which has numerous vent holes 37a, and an electrode support 38 that detachably supports the electrode plate 37. Electrode support 38 also has a buffer chamber 39 within it and a gas inlet 38a on its upper surface that communicates with the buffer chamber 39. Gas inlet 38a is connected to a gas supply line 41, which is connected to a process gas supply unit 40. A magnet 42 is also arranged around the processing container 10, extending in an annular or concentric manner.

[0042] Each component of the plasma processing apparatus 1 is connected to a control unit 50. For example, the exhaust device 18, the first high-frequency power supply 21a, the second high-frequency power supply 21b, the DC power supplies 27 and 28, the cooling device 32, the heat transfer gas supply 35, and the processing gas supply 40 are connected to the control unit 50. The control unit 50 is, for example, a computer, and controls each component of the plasma processing apparatus 1.

[0043] The control unit 50 includes a user interface 52 , a storage unit 53 , and a process controller 51 that includes a CPU and controls various components of the plasma processing apparatus 1 .

[0044] The user interface 52 is composed of a keyboard for a process manager to input commands for managing the plasma processing apparatus 1 , a display for visually displaying the operating status of the plasma processing apparatus 1 , and the like.

[0045] The storage unit 53 stores control programs (software) for implementing various processes performed by the plasma processing apparatus 1 under the control of the process controller 51, as well as recipes storing processing condition data. Furthermore, as needed, a desired recipe can be retrieved from the storage unit 53 by instructions from the user interface 52 and executed by the process controller 51, thereby performing a desired process in the plasma processing apparatus 1 under the control of the process controller 51.

[0046] The process controller 51 reads and executes the control program and recipe stored in the storage unit 53, thereby controlling the various components of the plasma processing apparatus 1 to perform desired processing within the plasma processing apparatus 1. For example, the process controller 51 controls the various components of the plasma processing apparatus 1 to perform plasma processing on the wafer W. Furthermore, the process controller 51 performs an electrostatic attraction process for electrostatically adsorbing the edge ring 30. Details of the electrostatic attraction process performed by the control unit 50 will be described later.

[0047] During plasma processing, a horizontal magnetic field oriented in one direction is generated within the processing container 10 by the magnet 42, and a vertical RF electric field is generated by a high-frequency voltage applied between the susceptor 11 and the showerhead 24. This generates magnetron discharge through the processing gas within the processing container 10, generating a high-density plasma from the processing gas near the surface of the susceptor 11.

[0048] In plasma processing apparatus 1, when performing a dry etching process, gate valve 20 is first opened, and wafer W, the target wafer, is loaded into processing container 10 and placed on electrostatic chuck 25. In plasma processing apparatus 1, processing gas (e.g., a mixed gas consisting of C₄F₈ gas, O₂ gas, and Ar gas at predetermined flow rates and ratios) is introduced into processing container 10 via processing gas supply unit 40. The pressure within processing container 10 is maintained at a predetermined value via exhaust system 18 and the like. In plasma processing apparatus 1, high-frequency power is supplied to susceptor 11 via first and second high-frequency power supplies 21a and 21b, respectively. In plasma processing apparatus 1, a DC voltage is applied to electrode plate 26 of electrostatic chuck 25 via DC power supply 27, thereby holding wafer W on electrostatic chuck 25. In plasma processing apparatus 1, a DC voltage is applied to electrode plate 29 of electrostatic chuck 25 via DC power supply 28, thereby holding edge ring 30 on electrostatic chuck 25. The processing gas ejected from the shower head 24 is converted into plasma as described above, and the surface of the wafer W is etched by radicals and ions generated by the plasma.

[0049] Then, Figure 1 The arrangement of the electrode plate 29 shown is described below. Figure 2 FIG. 1 is a diagram showing an example of the arrangement of the electrode plates according to the first embodiment. Figure 2 As shown, two electrode plates 29 are provided in an area corresponding to the edge ring 30 within the outer peripheral portion 25b of the electrostatic chuck 25. Hereinafter, the inner electrode plate 29 of the two electrode plates 29 will be referred to as the inner peripheral electrode plate 29-1, and the outer electrode plate 29 will be referred to as the outer peripheral electrode plate 29-2.

[0050] The inner electrode plate 29-1 is annularly arranged on the inner circumference of the edge ring 30. The outer electrode plate 29-2 is annularly arranged on the outer circumference of the edge ring 30. The inner electrode plate 29-1 and the outer electrode plate 29-2 are electrically connected to the DC power supply 28. In this embodiment, a case where power is supplied from a single DC power supply 28 to the inner electrode plate 29-1 and the outer electrode plate 29-2 is described. However, two DC power supplies 28 may be provided corresponding to the inner electrode plate 29-1 and the outer electrode plate 29-2 to supply power separately.

[0051] The plasma processing apparatus 1 applies voltage to the inner electrode plate 29 - 1 and the outer electrode plate 29 - 2 to electrostatically attract the edge ring 30 . However, charge transfer, or migration, may occur in the edge ring 30 , reducing the attraction force of the edge ring 30 .

[0052] The dielectric film of electrostatic chuck 25 is made of ceramic. Examples of ceramics include alumina plates, alumina spraying, yttrium oxide plates, and yttrium oxide spraying. Such ceramics tend to decrease in electrical resistance as the temperature increases. Therefore, in high-temperature, high-bias environments, charge transfer from edge ring 30 to the dielectric film constituting electrostatic chuck 25 may occur, causing the attraction force of electrostatic chuck 25 to decrease.

[0053] Figure 3 FIG is a diagram schematically showing charge transfer in the prior art. Figure 3 The structure of the outer peripheral portion 25b of the electrostatic chuck 25 is briefly shown in FIG. The electrostatic chuck 25 includes an inner peripheral electrode plate 29-1 and an outer peripheral electrode plate 29-2. For example, as in the prior art, a fixed positive voltage is applied to the inner peripheral electrode plate 29-1 and the outer peripheral electrode plate 29-2 to adsorb the edge ring 30. In this case, for example, Figure 3 As shown, the negative charge of the edge ring 30 migrates to the dielectric film on the inner electrode plate 29 - 1 and the outer electrode plate 29 - 2 , and the attraction force holding the edge ring 30 to the electrostatic chuck 25 decreases.

[0054] In the plasma processing apparatus 1 , when the attraction force holding the edge ring 30 to the electrostatic chuck 25 decreases, leakage of the heat transfer gas supplied between the edge ring 30 and the electrostatic chuck 25 increases.

[0055] In plasma processing apparatus 1, increased leakage of heat transfer gas reduces the efficiency of heat dissipation from edge ring 30. Heat from the plasma processing causes edge ring 30 to reach a high temperature, which in turn causes fluctuations in the processing characteristics of the plasma processing. Furthermore, increased leakage of heat transfer gas in plasma processing apparatus 1 reduces the degree of vacuum, causing changes in plasma characteristics and thus causing fluctuations in the processing characteristics of the plasma processing.

[0056] Therefore, as in Patent Document 1, for example, it is conceivable to periodically apply voltages of different polarities to the inner electrode plate 29 - 1 and the outer electrode plate 29 - 2 during plasma processing.

[0057] However, plasma is also affected by the voltage applied to the inner and outer electrode plates 29-1, 29-2. Therefore, if you want to switch the voltages applied to the inner and outer electrode plates 29-1, 29-2 during plasma processing to reduce the amount of charge transferred, you need to optimize the timing and frequency of polarity switching. Plasma processing has a variety of processes. The amount of charge transferred by plasma processing varies depending on the process. Therefore, optimizing each plasma processing process requires a significant amount of effort.

[0058] Therefore, in the plasma processing apparatus 1 involved in this embodiment, voltages of different polarities are applied to the inner circumference side electrode plate 29-1 and the outer circumference side electrode plate 29-2 for each processing unit of the plasma processing. The control unit 50 controls the DC power supply 28 for each processing unit of the plasma processing so as to periodically apply voltages of different polarities. Preferably, the voltages of different polarities are voltages of the same degree except for the different polarities. The voltages of different polarities are, for example, voltages with the same absolute value but different polarities, such as +3000V and -3000V. For example, in the case where post-processing is performed on each wafer W after the wafer W is subjected to plasma processing, the control unit 50 controls the DC power supply 28 for the units of plasma processing and post-processing so as to apply voltages with the same absolute value but different polarities to the inner circumference side electrode plate 29-1 and the outer circumference side electrode plate 29-2. In addition, for example, when the wafer W is replaced to continuously perform plasma processing on each wafer W, the control unit 50 controls the DC power supply 28 every specified number of wafers W to apply voltages with the same absolute value but different polarities to the inner electrode plate 29-1 and the outer electrode plate 29-2.

[0059] Furthermore, when multiple electrode plates 29 are provided, the control unit 50 applies voltages of different polarities to adjacent electrode plates 29. For example, the control unit 50 controls the DC power supply 28 in each processing unit so that voltages of the same absolute value but different polarities are applied to the inner electrode plate 29-1 and the outer electrode plate 29-2.

[0060] Here, a specific example of a variation pattern for changing the voltage applied to the electrode plate 29 will be described. First, a variation pattern for changing the voltage applied to the electrode plate 29 for each plasma process and post-process will be described.

[0061] Figure 4 : is a diagram schematically showing an example of a change pattern of the applied voltage involved in the first embodiment. Figure 4Figure 2 shows the changing patterns of the applied voltages to the inner and outer electrode plates 29-1 and 29-2 when two consecutive wafers W are subjected to plasma treatment and post-treatment, respectively. The post-treatment is waferless dry cleaning, such as cleaning deposits generated by the plasma treatment without placing wafers W. Waferless dry cleaning is also referred to as WLDC below. Post-treatment is not limited to waferless dry cleaning and can be any treatment performed after plasma treatment.

[0062] The control unit 50 controls the DC power supply 28 for each plasma processing unit and post-processing unit (e.g., WLDC) to apply voltages of different polarities to the inner electrode plate 29-1 and the outer electrode plate 29-2. Furthermore, the control unit 50 controls the DC power supply 28 for each processing unit to apply voltages of different polarities to the inner electrode plate 29-1 and the outer electrode plate 29-2.

[0063] For example, in Figure 4 In this case, during the plasma processing of the first wafer W, a predetermined voltage with a positive polarity is applied to the inner electrode plate 29-1, and a predetermined voltage with a negative polarity is applied to the outer electrode plate 29-2. As a result, on the inner side of the edge ring 30, negative charges are generated in the edge ring 30 due to the positive voltage applied to the inner electrode plate 29-1, and the edge ring 30 is attracted. A portion of the generated negative charges migrates (Migration) to the dielectric film of the electrostatic chuck 25. On the outer side of the edge ring 30, positive charges are generated in the edge ring 30 due to the negative voltage applied to the outer electrode plate 29-2, and the edge ring 30 is attracted. A portion of the generated positive charges migrates to the dielectric film of the electrostatic chuck 25.

[0064] In the first WLDC, the polarity of the voltages applied to the inner electrode plate 29-1 and outer electrode plate 29-2 is switched, with a predetermined negative voltage applied to the inner electrode plate 29-1 and a predetermined positive voltage applied to the outer electrode plate 29-2. This generates positive charges on the inner side of the edge ring 30 due to the negative voltage applied to the inner electrode plate 29-1. Furthermore, on the outer side of the edge ring 30, negative charges are generated on the outer side of the edge ring 30 due to the positive voltage applied to the outer electrode plate 29-2. On the inner side of the edge ring 30, the negative voltage applied to the inner electrode plate 29-1 and the presence of negative charges that migrated to the dielectric film of the electrostatic chuck 25 during the first plasma processing enhance the suction force of the edge ring 30. On the outside of edge ring 30, the positive voltage applied to outer electrode plate 29-2 and the presence of positive charges in the dielectric film that migrated to electrostatic chuck 25 during the first plasma process also enhance the suction force of edge ring 30. On the inside of edge ring 30, negative charges in the dielectric film that migrated to electrostatic chuck 25 gradually migrate to edge ring 30. On the outside of edge ring 30, positive charges in the dielectric film that migrated to electrostatic chuck 25 gradually migrate to edge ring 30. The process of charges that migrated to the dielectric film of electrostatic chuck 25 and then returned to edge ring 30 is hereinafter referred to as remigration.

[0065] During plasma processing of the second wafer W, similar to the first WLDC, a predetermined negative voltage is applied to the inner electrode plate 29-1, and a predetermined positive voltage is applied to the outer electrode plate 29-2. This generates positive charges on the inner side of edge ring 30 due to the negative voltage applied to the inner electrode plate 29-1. Furthermore, on the outer side of edge ring 30, a negative charge is generated due to the positive voltage applied to the outer electrode plate 29-2. On the inner side of edge ring 30, the negative voltage applied to the inner electrode plate 29-1 and the presence of negative charges that migrated to the dielectric film of electrostatic chuck 25 during the first plasma processing enhance the attraction force of edge ring 30. Similarly, on the outer side of edge ring 30, the positive voltage applied to the outer electrode plate 29-2 and the presence of positive charges that migrated to the dielectric film of electrostatic chuck 25 during the first plasma processing enhance the attraction force of edge ring 30. On the inner side of edge ring 30 , negative charges that migrated to the dielectric film of electrostatic chuck 25 migrate back to edge ring 30 . On the outer side of edge ring 30 , positive charges that migrated to the dielectric film of electrostatic chuck 25 migrate back to edge ring 30 .

[0066] In the second WLDC, the polarity of the voltages applied to the inner electrode plate 29-1 and outer electrode plate 29-2 is switched: a predetermined positive voltage is applied to the inner electrode plate 29-1, and a predetermined negative voltage is applied to the outer electrode plate 29-2. As a result, the positive voltage applied to the inner electrode plate 29-1 generates a negative charge on the inner side of the edge ring 30, attracting the edge ring 30. On the outer side of the edge ring 30, the negative voltage applied to the outer electrode plate 29-2 generates a positive charge on the edge ring 30, attracting the edge ring 30.

[0067] Here, the amount of charge transferred by plasma processing varies depending on the plasma processing process. Furthermore, generally speaking, in plasma processing and WLDC of wafer W, the amount of charge transferred increases because the plasma processing of wafer W is performed in a high-temperature, high-bias environment and the processing time is also long. For example, when the amount of charge transferred by plasma processing of wafer W is MA and the amount of charge returned by WLDC is RA, the difference in charge amount ΔA is expressed as the following equation (1).

[0068] ΔA=MA-RA>0···(1)

[0069] Therefore, for example, when simply switching the polarity of the voltage applied to the inner electrode plate 29 - 1 and the outer electrode plate 29 - 2 during plasma processing and WLDC, the difference in charge amount ΔA accumulates as the number of wafers W processed increases. As a result, the suction force of the edge ring 30 decreases, increasing the leakage of the heat transfer gas supplied between the edge ring 30 and the electrostatic chuck 25.

[0070] Therefore, in this embodiment, the voltage applied to the electrode plate 29 is changed in units of plasma processing and WLDC. Figure 4 In the embodiment, the voltage applied to the electrode plate 29 is switched at a timing after the plasma treatment is performed and before the WLDC is performed. Figure 4As shown, in the plasma treatment of the first sheet and the plasma treatment of the second sheet, and in the WLDC of the first sheet and the WLDC of the second sheet, the polarities of the voltages applied to the inner electrode plate 29-1 and the outer electrode plate 29-2 are opposite. That is, the polarities of the voltages applied to the inner electrode plate 29-1 and the outer electrode plate 29-2 of the first sheet and the second sheet as a group of two are opposite. With respect to the plasma treatment and WLDC of the first sheet and the second sheet, the processes are the same except for the polarity of the voltages applied to the inner electrode plate 29-1 and the outer electrode plate 29-2, so it can be considered that the amount of charge transferred is the same. In the first sheet and the second sheet, the polarities of the voltages are opposite, so the difference ΔA in the amount of charge transferred is opposite. Therefore, as shown in the following formula (2), the charge transfer can be eliminated in a group of two sheets.

[0071] ΔA(first sheet)-ΔA(second sheet)=0···(2)

[0072] Thus, even when the number of wafers W processed increases, the attraction force holding edge ring 30 to electrostatic chuck 25 can be maintained. This prevents leakage of heat transfer gas supplied between edge ring 30 and electrostatic chuck 25 .

[0073] Next, a description will be given of a change pattern in which the voltage applied to the electrode plate 29 is changed for each predetermined number of wafers W when the wafers W are replaced and plasma processing is continuously performed on each wafer W. Figure 5 : is a diagram schematically showing an example of a change pattern of the applied voltage involved in the first embodiment. Figure 5 2 shows a variation pattern of the voltage applied to the inner electrode plate 29-1 and the outer electrode plate 29-2 when plasma processing is continuously performed on four wafers W. The control unit 50 controls the DC power supply 28 to apply predetermined voltages of different polarities to the inner electrode plate 29-1 and the outer electrode plate 29-2 each time a wafer W is processed. Figure 5 In the example shown in FIG1 , positive and negative predetermined voltages are alternately applied to the inner electrode plate 29-1 and the outer electrode plate 29-2 each time a wafer W is processed. In this case, the amount of charge transferred can be eliminated in groups of two wafers. For example, if the amount of charge transferred due to plasma processing of wafer W is MA, the charge amounts MA are opposite in the first and second wafers. Therefore, as shown in the following equation (3), the charge transfer can be eliminated in groups of two wafers.

[0074] MA(first)-MA(second)=0···(3)

[0075] Thus, even when the number of wafers W processed increases, the attraction force holding edge ring 30 to electrostatic chuck 25 can be maintained. This prevents leakage of heat transfer gas supplied between edge ring 30 and electrostatic chuck 25 .

[0076] Next, the results of an experiment to measure the leakage of heat transfer gas are described. In the experiment, wafers W were replaced and plasma treatment and post-treatment were performed on each wafer W. Post-treatment was set as wafer-free dry cleaning (WLDC). As an example of this embodiment, the following was performed: Figure 6 The voltage application mode shown in the "Implementation Mode" is shown in FIG. Figure 6 1 is a diagram illustrating the plasma processing and the voltage application mode of WLDC. Figure 6 Schematically shows the application mode of the voltage applied to the inner electrode plate 29-1 and the outer electrode plate 29-2 in the plasma processing and WLDC. Figure 4 Similarly, the polarity of the voltage applied is switched between plasma processing and WLDC in units of plasma processing and WLDC. Figure 4 Similarly, switching is performed so that voltages of different polarities are applied to the inner electrode plate 29-1 and the outer electrode plate 29-2. The "+, - / -, +" of plasma processing and the "-, + / +, -" of WLDC represent various voltage application modes in groups of two. The left side of the " / " represents the voltage application mode of the first sheet, and the right side of the " / " represents the voltage application mode of the second sheet. In addition, in the voltage application modes of the first and second sheets, the left side of the "," represents the voltage application mode of the inner electrode plate 29-1, and the right side of the "," represents the voltage application mode of the outer electrode plate 29-2. For example, "+, - / -, +" means: a positive voltage is applied to the inner electrode plate 29-1 of the first sheet, and a negative voltage is applied to the outer electrode plate 29-2 of the first sheet. In addition, "+, - / -, +" means: a negative voltage is applied to the inner electrode plate 29-1 of the second sheet, and a positive voltage is applied to the outer electrode plate 29-2 of the second sheet.

[0077] The plasma treatment used in the experiment includes four steps, namely, processes P1 to P4. Figure 7 1 and 2 are diagrams illustrating a voltage application pattern for plasma processing. In the plasma processing processes P1 to P4, the voltages applied to the inner electrode plate 29 - 1 and the outer electrode plate 29 - 2 are kept constant and maintained at the same state.

[0078] For example, "Bipolar" indicates the voltage application pattern in the processes P1 to P4 of the plasma treatment of the first wafer W in a pair. The left side of "," indicates the voltage application pattern of the inner electrode plate 29-1, and the right side of "," indicates the voltage application pattern of the outer electrode plate 29-2. Figure 4 Similarly, during the plasma processing of the first pair of wafers W, a positive voltage is applied to the inner electrode plate 29-1, and a negative voltage is applied to the outer electrode plate 29-2. "Anti Bipolar" indicates the voltage application pattern in processes P1 to P4 for the plasma processing of the second pair of wafers W. During the plasma processing of the second pair of wafers W, a negative voltage is applied to the inner electrode plate 29-1, and a positive voltage is applied to the outer electrode plate 29-2.

[0079] The voltage application pattern of the embodiment is to repeat the following operation: applying the same voltage as in the previous WLDC during plasma processing to the inner electrode plate 29 - 1 and the outer electrode plate 29 - 2 , and switching the polarity of the applied voltage in the WLDC.

[0080] In addition, as a comparative example, Figure 6 The voltage application mode shown in the "Comparative Example" of the comparative example. The application mode of the comparative example is to simply switch the polarity of the voltage applied to the inner electrode plate 29-1 and the outer electrode plate 29-2 for plasma processing and WLDC. In plasma processing, a positive voltage is applied to the inner electrode plate 29-1, and a negative voltage is applied to the outer electrode plate 29-2. In WLDC, a negative voltage is applied to the inner electrode plate 29-1, and a positive voltage is applied to the outer electrode plate 29-2. In plasma processing, only Figure 7 The voltage of the "Bipolar" mode is shown as applied.

[0081] Figure 8 This is a diagram showing an example of the results of an experiment for measuring the leakage amount of heat transfer gas in an application pattern of a comparative example. Figure 8 Indicates that it is in use Figure 6 The heat transfer gas (He gas) leakage rate of the first and fifteenth wafers W in the process P1 to P4 is shown when fifteen wafers W are processed using the application pattern of the comparative example. Figure 8 As shown, in the application pattern of the comparative example, the leakage amount of the heat transfer gas in the processes P1 to P4 of the fifteenth sheet increases compared to the first sheet. Figure 9 Graph showing the average leakage amount of heat transfer gas per wafer W in the application mode of the comparative example. Figure 9 Indicates that it is in use Figure 6The comparative example application pattern shown shows the average leakage of the heat transfer gas (He gas) during processes P1 to P4, from the first to the fifteenth wafer W. It can be seen that the average leakage increases from the first to the fifteenth wafer in processes P1 to P4, with the leakage increasing as the number of wafers processed increases. This increase in leakage is believed to be due to the cumulative difference ΔA in charge amount as the number of wafers processed increases, as described above.

[0082] Figure 10 This is a diagram showing an example of the results of an experiment measuring the leakage amount of heat transfer gas in the application mode according to the embodiment. Figure 10 Indicates the use of the above Figure 6 and Figure 7 The amount of heat transfer gas (He gas) leaked from the first and fifteenth wafers W when fifteen wafers W were processed using the application pattern of the embodiment shown. Figure 10 As shown, in the application pattern of the embodiment, the leakage amount of the heat transfer gas in the first and fifteenth processes P1 to P4 is in a state of being equally low. Figure 11 Graph showing the average leakage amount of heat transfer gas per wafer W in the application mode according to the embodiment. Figure 11 Indicates use Figure 6 The average leakage rate of the heat transfer gas (He gas) in processes P1 to P4 for the first through fifteenth wafers W, when the application pattern of the embodiment shown is applied, is shown. It can be seen that the average leakage rate does not increase from the first through fifteenth wafers in processes P1 to P4, but remains substantially constant.

[0083] As described above, the application pattern of the embodiment can suppress leakage of the heat transfer gas even when the number of wafers W to be processed increases.

[0084] In addition, the change pattern of the applied voltage is not limited to this. Figure 4 As shown in the example, when voltages of different polarities are applied to the inner electrode plate 29-1 and the outer electrode plate 29-2 in units of plasma processing and post-processing, the polarity of the voltage can be switched between post-processing and the next plasma processing. Figure 12 : is a diagram schematically showing an example of a change pattern of the applied voltage involved in the first embodiment. Figure 12 In the example shown in Figure 2, the polarity of the voltage applied to the inner and outer electrode plates 29-1 and 29-2 is switched between the WLDC process in the first sheet and the plasma process in the second sheet. In this case, the polarity of the voltage applied to the inner and outer electrode plates 29-1 and 29-2 in the first and second sheets, which form a pair, is opposite. Therefore, charge migration can be eliminated in pairs.

[0085] In addition, Figure 4 In the example, the polarity of the voltage applied to the inner electrode plate 29-1 and the outer electrode plate 29-2 is reversed for the first and second sheets in a pair, but the present invention is not limited to this. Alternatively, 2n sheets (n is a natural number greater than or equal to 1) may be formed into a pair, and the polarity of the voltage applied to the inner electrode plate 29-1 and the outer electrode plate 29-2 may be reversed for the first to nth sheets and the n+1th to 2nth sheets.

[0086] In addition, Figure 5 In the example of FIG, the polarity of the voltage applied to the electrode plate 29 is switched every time one wafer W is processed, but the present invention is not limited thereto. The polarity of the voltage applied to the electrode plate 29 may be switched every time several wafers W are processed.

[0087] In addition, one electrode plate 29 may be formed on the outer peripheral portion 25 b , or three or more electrode plates may be formed thereon.

[0088] Figure 13A This is a diagram schematically showing an example of a change pattern of the applied voltage according to the first embodiment. Figure 13A The example shown in FIG. 1 shows an example of a change pattern of the applied voltage when an electrode plate 29 is formed on the outer peripheral portion 25b. For example, the control unit 50 can control the DC power supply 28 in each processing unit of the plasma processing to apply voltages of different polarities to the electrode plate 29. For example, when plasma processing is performed on each wafer W and then post-processing is performed on the wafer W, the control unit 50 controls the DC power supply 28 in each unit of the plasma processing and post-processing to apply voltages of the same absolute value but different polarities to the electrode plate 29. In addition, for example, when the wafer W is replaced to continuously perform plasma processing on each wafer W, the control unit 50 controls the DC power supply 28 in each unit of the predetermined number of wafers W to apply voltages of the same absolute value but different polarities to the inner peripheral electrode plate 29-1 and the outer peripheral electrode plate 29-2.

[0089] Figure 13B This is a diagram schematically showing an example of a change pattern of the applied voltage according to the first embodiment. Figure 13BThe example of FIG shows an example of a change pattern of the applied voltage when three electrode plates 29 (one each of 29-1, 29-2, and 29-3) are formed on the outer peripheral portion 25b. For example, the control unit 50 can control the DC power supply 28 according to the processing unit of the plasma treatment to apply voltages of different polarities to the electrode plates 29-1, 29-2, and 29-3. For example, when plasma treatment is performed on each wafer W and then post-processing is performed on the wafer W, the control unit 50 controls the DC power supply 28 according to the units of plasma treatment and post-processing to apply voltages of the same absolute value but different polarities to the electrode plates 29-1, 29-2, and 29-3. In addition, for example, when the wafer W is replaced to continuously perform plasma treatment on each wafer W, the control unit 50 controls the DC power supply 28 according to a specified number of wafers W to apply voltages of the same absolute value but different polarities to the electrode plates 29-1, 29-2, and 29-3. Furthermore, when multiple electrode plates 29 are provided, the control unit 50 applies voltages of different polarities to adjacent electrode plates 29. For example, the control unit 50 controls the DC power supply 28 to apply a positive voltage to the electrode plates 29-1 and 29-3 and a negative voltage to the electrode plate 29-2. Alternatively, the control unit 50 controls the DC power supply 28 to apply a negative voltage to the electrode plates 29-1 and 29-3 and a positive voltage to the electrode plate 29-2.

[0090] Alternatively, a plurality of electrode plates 29 may be arranged in the outer peripheral portion 25 b so as to be aligned in the annular circumferential direction.

[0091] Figure 14 : is a diagram showing an example of the arrangement of the electrode plates according to the first embodiment. Figure 14 In FIG. 1 , the upper portion shows a schematic diagram of the outer peripheral portion 25b of the electrostatic chuck 25 as viewed from above, and the lower portion shows a schematic diagram of the outer peripheral portion 25b of the electrostatic chuck 25 as viewed from the side. Figure 14 In the example of FIG, three electrode plates 29 (29-1, 29-2, 29-3) are arranged circumferentially on the outer peripheral portion 25b. In this case, the control unit 50 also controls the DC power supply 28 according to the processing unit of the plasma processing to apply voltages of different polarities to the electrode plates 29-1, 29-2, and 29-3.

[0092] In addition, the plasma processing apparatus 1 according to this embodiment has been described as a case where the control unit 50 controls the DC power supply 28 to periodically switch the voltage applied to the electrode plate 29 to different polarities, but the present invention is not limited thereto. The plasma processing apparatus 1 may also be configured such that the DC power supply 28 autonomously and periodically switches the voltage applied to the electrode plate 29 to different polarities.

[0093] As described above, the plasma processing apparatus 1 according to the first embodiment includes a mounting table (base 11), an electrode (electrode plate 29), and a voltage applying unit (DC power supply 28). The mounting table is used to mount a substrate (wafer W) to be subjected to plasma treatment and a ring member (edge ​​ring 30) surrounding the substrate. The electrode is provided in an area corresponding to at least the ring member inside the mounting table. The voltage applying unit applies voltages of different polarities to the electrode for each treatment unit of the plasma treatment. Thus, the plasma processing apparatus 1 can easily suppress a decrease in the adsorption force of the ring member (edge ​​ring 30) even when performing plasma treatment of various processes. As a result, the plasma processing apparatus 1 can ensure the airtightness of the space sandwiched between the electrostatic chuck 25 and the edge ring 30, and can suppress an increase in the amount of leakage of the heat transfer gas supplied to the space sandwiched between the edge ring 30 and the electrostatic chuck 25 during plasma treatment.

[0094] Furthermore, in the first embodiment, when plasma treatment is continuously performed on each substrate by replacing the substrate, the plasma treatment unit is set to a predetermined number of substrates. Furthermore, when post-processing is performed on each substrate after plasma treatment, the plasma treatment unit is set to a combination of plasma treatment and post-processing. This allows the plasma processing apparatus 1 to eliminate charge migration, thereby suppressing a decrease in the attraction force of the edge ring 30.

[0095] In the first embodiment, a plurality of electrodes (electrode plates 29 - 1 , 29 - 2 , and 29 - 3 ) are provided in the radial direction of the ring member. This allows the plasma processing apparatus 1 to control the voltage applied to each electrode plate 29 , thereby controlling the suction force for each electrode plate 29 .

[0096] In the first embodiment, voltages of different polarities are applied to adjacent electrodes (electrode plates 29 - 1 , 29 - 2 , and 29 - 3 ), thereby enabling the plasma processing apparatus 1 to enhance the suction force of each electrode plate 29 .

[0097] (Second embodiment)

[0098] Next, a second embodiment will be described. Figure 15 2 is a cross-sectional view showing a schematic structure of a plasma processing apparatus 1 according to a second embodiment. Figure 1 The plasma processing apparatus 1 according to the first embodiment shown has partially the same structure, and therefore the same reference numerals are given to the same parts and their description is omitted, and the description will focus on the different parts.

[0099] In the plasma processing apparatus 1 according to the second embodiment, charge transfer information 53a is stored in the storage unit 53. The charge transfer information 53a stores the amount of charge transferred between the electrostatic chuck 25 and the edge ring 30 for each type of plasma processing.

[0100] Figure 16 This figure schematically illustrates an example of the data structure of charge transfer information 53a according to the second embodiment. Charge transfer information 53a stores the amount of transferred charge for each type of plasma treatment. The amount of transferred charge for each type of plasma treatment is determined and set through experiments and simulations. For example, charge transfer information 53a stores the amount of transferred charge for plasma treatment a as 3, the amount of transferred charge for plasma treatment b as 1, and the amount of transferred charge for plasma treatment c as 12.

[0101] Before substrate processing begins, the control unit 50 determines the polarity application pattern of the voltage applied to the electrode plate 29 for each processing unit of the plasma processing being performed, based on charge transfer information 53a corresponding to the type of plasma processing being performed, so that the amount of charge transferred between the electrostatic chuck 25 and the edge ring 30 does not exceed a certain threshold. The threshold value is, for example, the amount of charge transferred when the edge ring 30 decouples from the electrostatic chuck 25 due to charge transfer from the edge ring 30 to the electrostatic chuck 25, causing the attraction of the edge ring 30 to decrease. The charge threshold value can be stored in the storage unit 53 or externally set via the user interface 52. For example, the charge threshold value is stored as 10 in the storage unit 53. Before plasma processing a begins, the control unit 50 determines the polarity application pattern of the voltage to be applied to the electrode plate 29 based on the charge transfer information 53a for plasma processing a and the threshold value. Specifically, if the amount of charge transferred during plasma process a is 3 and the threshold is 10, the amount of charge transferred when processing four substrates using plasma process a is 3×4=12, exceeding the threshold. Therefore, the maximum number of substrates that can be applied with the same polarity is three. Therefore, the control unit 50 determines to switch polarity every three substrates. However, the control unit 50 may also determine to switch polarity every three substrates or every two substrates. As another example, before the start of plasma process a and the post-processing process b, the polarity of the voltage to be applied to the electrode plate 29 is determined based on the charge transfer information 53a for plasma process a and plasma process b and the threshold. Specifically, if the amount of charge transferred during plasma process a and plasma process b is 3 and 1, respectively, and the threshold is 10, the amount of charge transferred when processing one substrate is 3+1=4. Therefore, the amount of charge transferred when processing three substrates is 4×3=12, exceeding the threshold. Therefore, the maximum number of substrates that can be applied with the same polarity is two. Therefore, the control unit 50 decides to perform control to switch polarity every two sheets. However, the control unit 50 may also decide to perform control to switch polarity every two sheets. As an example of a plasma process a and a plasma process b as a post-process, the amount of transferred charge is calculated by assuming that the plasma processes a and b have the same polarity (if the inner electrode plate 29-1 in plasma process a is + and the outer electrode plate 29-2 is -, then the inner electrode plate 29-1 in plasma process b is + and the outer electrode plate 29-2 is -). However, the calculation may also be performed by switching the polarity of the plasma processes a and b (if the inner electrode plate 29-1 in plasma process a is + and the outer electrode plate 29-2 is -, then the inner electrode plate 29-1 in plasma process b is - and the outer electrode plate 29-2 is +).That is, the amount of charge transferred during the processing of one substrate is 3+(-1)=2. Therefore, the amount of charge transferred when processing six substrates is 2×6=12, which exceeds the threshold value. Therefore, the maximum number of substrates that can be applied with the same polarity is 5. Therefore, the control unit 50 can decide to perform control to switch the polarity every five substrates. In this case, it can also decide to perform control to switch the polarity every four substrates. In addition, before the processing in plasma processing c begins, the amount of charge transferred and the threshold value of plasma processing c are stored as 12 and 10, respectively. When the control unit 50 starts processing directly based on this information, the edge ring may be separated from the electrostatic chuck during the processing of the first substrate, so a notification prohibiting the start of processing can be output.

[0102] As described above, the plasma processing apparatus 1 according to the second embodiment determines the polarity of the voltage applied to each processing unit of the plasma process being performed before substrate processing begins, based on charge transfer information and a threshold value corresponding to the type of plasma process being performed, thereby varying the polarity of the voltage applied to the electrode. For example, based on the charge transfer information 53a, the plasma processing apparatus 1 varies the polarity of the voltage applied to the electrode for each processing unit of the plasma process being performed, thereby minimizing charge transfer. Consequently, the plasma processing apparatus 1 can suppress a decrease in the suction force of the edge ring 30 even when performing various plasma processes, and can also prevent problems such as the edge ring detaching from the electrostatic chuck during the first substrate processing.

[0103] While the embodiments described above are intended to be illustrative in all respects, they should be construed as non-restrictive. In practice, the embodiments described above can be implemented in a variety of ways. Furthermore, the embodiments described above may be omitted, replaced, or modified in various ways without departing from the scope of the claims and their intended meaning.

[0104] For example, in the embodiment, the plasma processing apparatus 1 is described as a plasma etching apparatus using a capacitively coupled plasma (CCP) as an example. However, the embodiment is not limited to the above-described embodiment, and various modifications are possible. For example, the plasma processing apparatus 1 described above is a CCP-type plasma processing apparatus 1, but any plasma processing apparatus 1 can be used. For example, the plasma processing apparatus 1 can be applied to any type of plasma, such as an inductively coupled plasma (ICP), a radial line slot antenna (RLS), an electron cyclotron resonance plasma (ECR), or a helicon wave plasma (HWP).

[0105] In addition, in the embodiments, the substrate is described as a semiconductor wafer as an example, but the present invention is not limited to this. The semiconductor wafer may be silicon or a compound semiconductor such as GaAs, SiC, or GaN. Furthermore, the substrate is not limited to a semiconductor wafer and may also be applied to glass substrates and ceramic substrates used in FPDs (flat panel displays) such as liquid crystal display devices.

Claims

1. An electrostatic adsorption method, in which: A voltage is applied to a first electrode and a second electrode provided at least in a region corresponding to the ring member inside a mounting table for mounting a substrate and a ring member, the ring member surrounding the substrate, during plasma treatment and post-treatment. In the electrostatic adsorption method, a combination of the plasma treatment and the post-treatment for the first substrate and a combination of the plasma treatment and the post-treatment for the second substrate are controlled as one treatment cycle. in, During a first plasma treatment performed on the first substrate, controlling the application of a first voltage to the first electrode and the application of a second voltage having a polarity opposite to that of the first voltage to the second electrode; After the first plasma treatment of the first substrate, during a first post-treatment of the first substrate, controlling the application of the second voltage to the first electrode and the application of the first voltage to the second electrode; After the first post-processing on the first substrate, during a second plasma processing on the second substrate, controlling to apply the second voltage to the first electrode and the first voltage to the second electrode, After the second plasma treatment on the second substrate, while a second post-treatment on the second substrate is performed, control is performed such that the first voltage is applied to the first electrode and the second voltage is applied to the second electrode.

2. The electrostatic adsorption method according to claim 1, characterized in that: Two or more electrodes are provided in the radial direction of the ring member.

3. The electrostatic adsorption method according to claim 2, characterized in that: Voltages of different polarities are applied to the adjacent electrodes.

4. The electrostatic adsorption method according to claim 1, characterized in that: The post-processing is dry cleaning performed in a state where the substrate is not placed on the mounting table.

5. The electrostatic adsorption method according to claim 4, characterized in that: The polarity of the voltage applied to the first electrode and the second electrode is switched between the plasma treatment and the dry cleaning.

6. A plasma processing apparatus comprising: a mounting table for mounting a substrate to be subjected to plasma treatment and a ring member surrounding the substrate; and a first electrode and a second electrode provided in a region at least corresponding to the ring member inside the mounting table; a voltage applying unit for applying a voltage to the first electrode and the second electrode during plasma processing and post-processing; a control unit configured to control the combination of the plasma treatment and the post-treatment for the first substrate and the combination of the plasma treatment and the post-treatment for the second substrate as one treatment cycle, During the first plasma treatment on the first substrate, the control unit controls the voltage applying unit to apply a first voltage to the first electrode and a second voltage having a polarity opposite to the first voltage to the second electrode. After the first plasma treatment on the first substrate, while a first post-treatment on the first substrate is performed, the control unit controls the voltage applying unit to apply the second voltage to the first electrode and the first voltage to the second electrode. After the first post-processing on the first substrate, during a second plasma processing on the second substrate, the control unit controls the voltage applying unit to apply the second voltage to the first electrode and the first voltage to the second electrode. After the second plasma treatment on the second substrate, while a second post-treatment on the second substrate is performed, the control unit controls the voltage application unit to apply the first voltage to the first electrode and the second voltage to the second electrode.

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