JP2019212648A - Film forming apparatus and film forming method - Google Patents

Abstract

To provide a technology capable of achieving both high electron density, low ion energy, and high uniformity.SOLUTION: A film forming apparatus according to the present disclosure includes a processing vessel capable of being evacuated, a lower electrode, an upper electrode, a gas supply unit, and a voltage application unit. A substrate to be processed is placed on the lower electrode. The upper electrode is disposed to face the lower electrode in the processing vessel. The gas supply unit supplies a film forming material gas, which is converted into plasma in a processing space between the upper electrode and the lower electrode, into the processing space. The voltage application unit applies an AC voltage whose reference potential alternately changes up and down with time to the upper electrode.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a film forming apparatus and a film forming method.

  In manufacturing a semiconductor integrated circuit, a film is formed on a substrate such as a semiconductor wafer by a film forming apparatus. In a film forming apparatus, a substrate is placed in a chamber (processing container) that has a predetermined degree of vacuum, and a film forming raw material gas is supplied into the chamber to generate plasma, thereby forming a film on the substrate. Is called. As film formation techniques, for example, plasma CVD (Chemical Vapor Deposition), plasma ALD (Atomic Layer Deposition), and the like are known.

JP 2009-239012 A

  Under high pressure conditions of several hundred mTorr to several Torr such as plasma CVD or plasma ALD, it is necessary to generate plasma capable of increasing the electron density. On the other hand, in the oxide film forming process, a low frequency of several MHz or less is necessary for increasing the electron density, whereas a high frequency of several tens of MHz or more is necessary for reducing the ion energy. . On the other hand, in the nitride film forming process, a high frequency of several hundred MHz or more is necessary for increasing the electron density, while a low frequency of several tens of MHz or less is necessary for high uniformity.

  Therefore, it has been difficult to achieve high electron density, low ion energy, and high uniformity in the conventional film forming apparatus. Therefore, there has been a demand for a film forming apparatus capable of achieving both high electron density, low ion energy, and high uniformity for any film forming process.

  The present disclosure provides a technique capable of achieving both high electron density, low ion energy, and high uniformity.

  The film formation apparatus of one embodiment of the present disclosure includes a processing container that can be evacuated, a lower electrode, an upper electrode, a gas supply unit, and a voltage application unit. A substrate to be processed is placed on the lower electrode. The upper electrode is disposed to face the lower electrode in the processing container. The gas supply unit supplies a film forming material gas to be converted into plasma in the processing space between the upper electrode and the lower electrode to the processing space. The voltage application unit applies an AC voltage whose reference potential alternately changes up and down with time to the upper electrode.

  According to the technique of the present disclosure, it is possible to achieve both high electron density, low ion energy, and high uniformity.

FIG. 1 is a diagram illustrating a configuration example of a film forming apparatus according to the embodiment. FIG. 2 is a diagram illustrating an example of the high-frequency voltage according to the embodiment. FIG. 3 is a diagram illustrating an example of a DC pulse voltage according to the embodiment. FIG. 4 is a diagram illustrating an example of the superimposed voltage according to the embodiment. FIG. 5 is a diagram illustrating an example of an experimental result in a comparative example. FIG. 6 is a diagram illustrating an example of an experimental result in a comparative example. FIG. 7 is a diagram illustrating an example of the experimental result 1 according to the embodiment. FIG. 8 is a diagram illustrating an example of the experimental result 2 according to the embodiment. FIG. 9 is a diagram illustrating an example of the experimental result 2 according to the embodiment. FIG. 10 is a diagram illustrating an example of the experimental result 3 according to the embodiment.

  Hereinafter, embodiments of the technology of the present disclosure will be described with reference to the drawings.

<Configuration of film forming apparatus>
FIG. 1 is a diagram illustrating a configuration example of a film forming apparatus according to the embodiment.

  In FIG. 1, a film forming apparatus 1 has a chamber 10 which is a metal processing vessel made of, for example, aluminum or stainless steel. The chamber 10 is grounded for safety.

  A disc-shaped susceptor 12 on which a semiconductor wafer W as a substrate to be processed is placed is horizontally disposed in the chamber 10. The susceptor 12 also functions as a lower electrode. A gate valve 28 for opening and closing the loading / unloading port for the semiconductor wafer W is attached to the side wall of the chamber 10. The susceptor 12 is made of, for example, AlN ceramic, and is supported by an insulating cylindrical support portion 14 that extends vertically upward from the bottom of the chamber 10.

  An annular exhaust path 18 is formed between the conductive cylindrical support portion (inner wall portion) 16 extending vertically upward from the bottom of the chamber 10 along the outer periphery of the cylindrical support portion 14 and the side wall of the chamber 10. Yes. An exhaust port 22 is provided at the bottom of the exhaust path 18.

  An exhaust device 26 is connected to the exhaust port 22 via an exhaust pipe 24. The exhaust device 26 has a vacuum pump such as a turbo molecular pump, for example, and depressurizes the processing space in the chamber 10 to a desired degree of vacuum. The inside of the chamber 10 is preferably maintained at a constant pressure in the range of, for example, 200 mTorr to 1700 mTorr.

  An impedance adjusting circuit 100 having a coil 101 and a variable capacitor 102 is electrically connected via a connecting rod 36 between the susceptor 12 used as the lower electrode and the ground.

  A semiconductor wafer W to be processed is placed on the susceptor 12, and a ring 38 is provided so as to surround the semiconductor wafer W. The ring 38 is made of a conductive material (for example, Ni, Al, etc.) and is detachably attached to the upper surface of the susceptor 12.

  On the upper surface of the susceptor 12, an electrostatic chuck 40 for attracting the wafer is provided. The electrostatic chuck 40 is formed by sandwiching a sheet-like or mesh-like conductor between film-like or plate-like dielectrics. A DC power source 42 disposed outside the chamber 10 is electrically connected to the conductor in the electrostatic chuck 40 via an on / off switch 44 and a power supply line 46. The semiconductor wafer W is attracted and held on the electrostatic chuck 40 by the Coulomb force generated in the electrostatic chuck 40 by the DC voltage applied from the DC power source 42.

  An annular coolant chamber 48 extending in the circumferential direction is provided inside the susceptor 12. A refrigerant (for example, cooling water) having a predetermined temperature is circulated and supplied to the refrigerant chamber 48 via pipes 50 and 52 from a chiller unit (not shown). The temperature of the semiconductor wafer W on the electrostatic chuck 40 is controlled by the temperature of the coolant. Further, in order to further increase the accuracy of the wafer temperature, a heat transfer gas (for example, He gas) from a heat transfer gas supply unit (not shown) is passed through the gas supply pipe 51 and the gas passage 56 in the susceptor 12. It is supplied between the electrostatic chuck 40 and the semiconductor wafer W.

  A disk-shaped inner upper electrode 60 and a ring-shaped outer upper electrode 62 are concentrically provided on the ceiling of the chamber 10 so as to face (that is, face each other) in parallel with the susceptor 12. As a preferred size in the radial direction, the inner upper electrode 60 has the same diameter (diameter) as the semiconductor wafer W, and the outer upper electrode 62 has the same diameter (inner diameter / outer diameter) as the ring 38. Yes. However, the inner upper electrode 60 and the outer upper electrode 62 are electrically insulated from each other (more accurately, DC). A ring-shaped insulator 63 made of ceramic, for example, is inserted between the electrodes 60 and 62.

  The inner upper electrode 60 includes an electrode plate 64 facing the susceptor 12 directly in front, and an electrode support 66 that detachably supports the electrode plate 64 from behind (upper) thereof. As the material of the electrode plate 64, a conductive material such as Ni or Al is preferable. The electrode support 66 is made of alumite-treated aluminum, for example. The outer upper electrode 62 also has an electrode plate 68 facing the susceptor 12 and an electrode support 70 that detachably supports the electrode plate 68 from behind (upper) thereof. The electrode plate 68 and the electrode support 70 are preferably made of the same material as the electrode plate 64 and the electrode support 66, respectively. Hereinafter, the inner upper electrode 60 and the outer upper electrode 62 may be collectively referred to as “upper electrodes 60, 62”. As described above, in the film forming apparatus 1, the disk-shaped susceptor 12 (that is, the lower electrode) and the disk-shaped upper electrodes 60 and 62 face each other in parallel.

  In the present embodiment, the case where the upper electrodes 60 and 62 are constituted by two members of the inner upper electrode 60 and the outer upper electrode 62 is taken as an example. However, the upper electrode may be composed of one member.

  In order to supply the film forming source gas to the processing space PS set between the upper electrodes 60 and 62 and the susceptor 12, the inner upper electrode 60 is also used as a shower head. More specifically, a gas diffusion chamber 72 is provided inside the electrode support 66, and a number of gas discharge holes 74 penetrating from the gas diffusion chamber 72 toward the susceptor 12 are formed in the electrode support 66 and the electrode plate 64. A gas supply pipe 78 extending from the source gas supply unit 76 is connected to the gas introduction port 72 a provided in the upper part of the gas diffusion chamber 72. Note that a shower head may be provided not only on the inner upper electrode 60 but also on the outer upper electrode 62.

  A voltage application unit 5 that outputs an applied voltage is disposed outside the chamber 10. The voltage application unit 5 is connected to the upper electrodes 60 and 62 via the power supply line 88. The voltage application unit 5 includes a high frequency power source 30, a matching unit 34, a variable DC power source 80, a pulse generator 84, a filter 86, a superimposing unit 91, and an on / off switch 92.

  The high-frequency power supply 30 generates a high-frequency AC voltage (hereinafter sometimes referred to as “high-frequency voltage”) that contributes to plasma generation, and the generated high-frequency voltage is passed through the matching unit 34 and the on / off switch 92. To the superimposer 91. When the on / off switch 92 is turned on, the high frequency voltage is supplied to the superimposing unit 91, while when the on / off switching switch 92 is off, the high frequency voltage is supplied to the superimposing unit 91. Not supplied. The frequency of the high frequency voltage generated by the high frequency power supply 30 is preferably, for example, 13 MHz or more.

  FIG. 2 is a diagram illustrating an example of the high-frequency voltage according to the embodiment. As illustrated in FIG. 2, the high frequency power supply 30 generates a high frequency voltage V <b> 1 of −250 V to 250 V with 0 V as a reference potential RP, for example. The matching unit 34 matches the impedance on the high frequency power supply 30 side and the impedance on the load (mainly electrodes, plasma, chamber) side.

  The output terminal of the variable DC power supply 80 is connected to the pulse generator 84, and the variable DC power supply 80 outputs a negative DC voltage (that is, a negative DC voltage) to the pulse generator 84. The pulse generator 84 uses a negative DC voltage input from the variable DC power supply 80 to generate a rectangular wave DC pulse voltage (that is, a DC pulse voltage), and superimposes the generated DC pulse voltage via a filter 86. To the container 91. The frequency of the DC pulse voltage generated by the pulse generator 84 is preferably, for example, 10 kHz to 1 MHz. The duty ratio of the DC pulse voltage generated by the pulse generator 84 is preferably 10% to 90%.

  FIG. 3 is a diagram illustrating an example of a DC pulse voltage according to the embodiment. As shown in FIG. 3, the pulse generator 84 generates a DC pulse voltage V <b> 2 having a rectangular wave of −500 V to 0 V, for example. The filter 86 outputs the direct-current pulse voltage output from the pulse generator 84 to the superimposer 91 through, while passing the high-frequency voltage output from the high-frequency power supply 30 to the ground line and to the pulse generator 84 side. Is configured to not.

  The superimposing unit 91 superimposes the high-frequency voltage output from the high-frequency power supply 30 and the direct-current pulse voltage output from the pulse generator 84, thereby superimposing the high-frequency voltage and the direct-current pulse voltage (hereinafter “ (Sometimes referred to as "superimposed voltage"). The generated superimposed voltage is applied to the upper electrodes 60 and 62 via the power supply line 88. The superimposer 91 is an example of a voltage superimposing unit.

  FIG. 4 is a diagram illustrating an example of the superimposed voltage according to the embodiment. When the high-frequency voltage V1 shown in FIG. 2 and the DC pulse voltage V2 shown in FIG. 3 are superimposed, a superimposed voltage V3 shown in FIG. 4 is generated. By superimposing the direct-current pulse voltage on the high-frequency voltage, as shown in FIG. 4, in the superimposed voltage V3, the high-frequency voltage V1 (FIG. 2) is matched to the waveform of the rectangular DC pulse voltage V2 (FIG. 3). The reference potential RP changes alternately up and down over time. That is, when the on / off switch 92 is turned on, the voltage application unit 5 outputs a high-frequency voltage that changes in a pulse shape (that is, a rectangular wave shape).

  When the on / off changeover switch 92 is on, the high frequency voltage output from the matching unit 34 is supplied to the superimposer 91, and thus the superimposing voltage is output from the superimposer 91. On the other hand, when the on / off switch 92 is off, the high-frequency voltage output from the matching unit 34 is not supplied to the superimposer 91, so the DC pulse voltage output from the filter 86 is used as it is. Is output from.

  In addition, a ring-shaped ground part 96 made of a conductive member such as Ni or Al is attached to an appropriate portion facing the processing space PS in the chamber 10 (for example, the outside in the radial direction of the outer upper electrode 62). ing. The ground part 96 is attached to a ring-shaped insulator 98 made of, for example, ceramic, is connected to the ceiling wall of the chamber 10, and is grounded through the chamber 10. When a superimposed voltage is applied from the voltage application unit 5 to the upper electrodes 60 and 62 during the plasma processing, an electron current flows between the upper electrodes 60 and 62 and the ground part 96 via the plasma.

  Each component (for example, exhaust device 26, high frequency power supply 30, on / off switch 44, 92, source gas supply unit 76, chiller unit (not shown), heat transfer gas supply unit (not shown) in film forming apparatus 1 1) and the like, and the entire operation (sequence) of the film forming apparatus 1 are controlled by a control unit (not shown) including, for example, a microcomputer.

<Film forming process in film forming apparatus>
In order to perform film formation in the film forming apparatus 1, first, the gate valve 28 is opened, and the semiconductor wafer W to be processed is loaded into the chamber 10 and placed on the electrostatic chuck 40. Next, the on / off switch 44 is turned on, and the semiconductor wafer W is attracted and held on the electrostatic chuck 40 by electrostatic attraction force. Then, a film forming source gas is introduced into the chamber 10 from the source gas supply unit 76 at a predetermined flow rate, and the pressure in the chamber 10 is adjusted to a set value by the exhaust device 26. As the film forming source gas, for example, a negative gas such as Ar / O 2 gas or N 2 gas is used. Further, the high frequency power supply 30 and the variable DC power supply 80 are turned on, and the superimposed voltage is applied to the upper electrodes 60 and 62. Further, a heat transfer gas is supplied between the electrostatic chuck 40 and the semiconductor wafer W. The film-forming source gas discharged from the upper electrode 60 is turned into plasma by discharge between the upper electrodes 60 and 62 and the susceptor 12 used as the lower electrode, and the surface of the semiconductor wafer W is generated by radicals and ions generated from the plasma. A film is formed on the surface.

<Experimental result of comparative example (deposition source gas: Ar / O2)>
5 and 6 are diagrams illustrating an example of experimental results in the comparative example. In FIG. 5, as an experimental result in the comparative example, instead of applying a superimposed voltage to the upper electrodes 60 and 62, only an AC voltage having a frequency of 450 kHz, 2 MHz, 13 MHz, or 40 MHz is applied to the upper electrodes 60 and 62. The relationship between the pressure and the electron density is shown. In FIG. 6, as an experimental result in the comparative example, an alternating current having a frequency of 450 kHz is applied to the upper electrodes 60 and 62 in a state where the pressure in the chamber 10 is set to 500 mTorr instead of applying a superimposed voltage to the upper electrodes 60 and 62. The relationship between ion energy and ion energy distribution (IED: Ion Energy Distribution) when only a voltage is applied is shown.

  In the case where only a low frequency AC voltage having a frequency of 450 kHz is applied to the upper electrodes 60 and 62, as shown in FIG. 5, since the electron density is high even in the negative gas plasma containing O2, the pressure in the chamber 10 is particularly high. In the vicinity of 0.7 Torr, a sufficient electron density for film formation can be obtained. On the other hand, as shown in FIG. 6, when the power of the AC voltage is 1000 W, the ion energy increases and the damage to the generated film increases. Moreover, even if the pressure is increased with the AC voltage power set to 1000 W, a significant decrease in ion energy cannot be expected. On the other hand, as shown in FIG. 6, the ion voltage can be reduced by reducing the power of the AC voltage to 300 W and 150 W, but the electron density is lowered by the reduction of the power. The film rate decreases.

  In addition, as shown in FIG. 5, when the frequency of the AC voltage is increased to 2 MHz, 13 MHz, 40 MHz in order to decrease the ion energy, the electron temperature decreases, so that the electrons adhere to the radicals and negative ions are generated. As a result, the electron density is reduced. Further, as shown in FIG. 5, when the pressure is increased in order to decrease the ion energy, the electron temperature is decreased, so that negative ions are generated and the electron density is decreased as in the case of the higher frequency.

  Thus, it is difficult to achieve both high electron density and low ion energy by applying only an alternating voltage to the upper electrodes 60 and 62.

<Experimental result 1 of embodiment (deposition source gas: Ar / O2)>
FIG. 7 is a diagram illustrating an example of the experimental result 1 according to the embodiment. In FIG. 7, as an experimental result 1 according to the embodiment, a frequency of 500 kHz is applied to the upper electrodes 60 and 62 in a state where the pressure in the chamber 10 is set to 500 mTorr instead of applying a superimposed voltage to the upper electrodes 60 and 62. 3 shows the relationship between ion energy and ion energy distribution when only the DC pulse voltage is applied. That is, the experimental result 1 is an experimental result when the on / off switch 92 shown in FIG. 1 is turned off.

  When only a low-frequency DC pulse voltage with a frequency of 500 kHz is applied to the upper electrodes 60 and 62, as shown in FIG. 7, the ion energy is higher than that in FIG. 6 regardless of the power of the DC pulse voltage. And very low. Further, as shown in FIG. 7, by increasing the power of the DC pulse voltage, it is possible to increase only the electron density while keeping the ion energy low.

  Thus, by applying only the DC pulse voltage to the upper electrodes 60 and 62, it is possible to achieve both high electron density for a high film formation rate and low ion energy for low damage. become.

<Experimental result 2 of embodiment (deposition source gas: Ar / O2)>
8 and 9 are diagrams illustrating an example of the experimental result 2 according to the embodiment. FIG. 8 shows the relationship between the ion energy and the ion energy distribution when the superimposed voltage is applied to the upper electrodes 60 and 62 in the state where the pressure in the chamber 10 is 500 mTorr, as the experimental result 2 according to the embodiment. . In FIG. 8, the frequency of the DC pulse voltage is 500 kHz, the power of the DC pulse voltage is 300 W, the frequency of the AC voltage is 40.68 MHz, and the power of the AC voltage is 200 W or 500 W. FIG. 9 shows the relationship between the pressure and the electron density when the superimposed voltage is applied to the upper electrodes 60 and 62 as the experimental result 2 according to the embodiment. In FIG. 9, the frequency of the DC pulse voltage is 500 kHz, and the power of the DC pulse voltage is 300 W. In FIG. 9, the plots of 450 kHz, 2 MHz, 13 MHz, and 40 MHz are the same as those in FIG. 5, and the plot of 40 MHz + DC is obtained when a superimposed voltage is applied.

  According to the above experimental result 1, as shown in FIG. 7, even if the power of the DC pulse voltage is changed, the ion energy hardly changes.

  On the other hand, in the experimental result 2, as shown in FIG. 8, by changing the power of the alternating voltage that is the source of the superimposed voltage, the ion energy is changed while maintaining the electron density equivalent to the case of FIG. Can be made.

  As described above, when the superimposed voltage is applied to the upper electrodes 60 and 62, compared with the case where only the DC pulse voltage is applied to the upper electrodes 60 and 62, the control of the electron density based on the DC pulse voltage and the AC voltage are performed. The ion energy control based on can be performed independently. In other words, by applying a superimposed voltage to the upper electrodes 60 and 62 to achieve both high electron density and low ion energy, the electron density control and the ion energy control are performed independently. Can do.

  Further, as shown in FIG. 9, even when a superimposed voltage is applied to the upper electrodes 60 and 62, sufficient electrons for film formation are formed in the same manner as in FIG. 5, particularly when the pressure in the chamber 10 is around 0.7 Torr. Density is obtained.

<Experimental result 3 of embodiment (deposition source gas: N2)>
FIG. 10 is a diagram illustrating an example of the experimental result 3 according to the embodiment. FIG. 10 shows the relationship between the wavelength and the emission intensity when the superimposed voltage is applied to the upper electrodes 60 and 62 in the state where the pressure in the chamber 10 is 500 mTorr, as the experimental result 3 according to the embodiment.

  When only an alternating voltage is applied to the upper electrodes 60 and 62 to generate N2 plasma, the nitriding power is weak and it is difficult to form a nitride film with good film quality. In general, the higher the frequency of the alternating voltage, the better the quality of the nitride film. Therefore, the film formed by μ-wave plasma is the highest quality film. The μ-wave plasma has a very high electron temperature immediately below the upper electrodes 60 and 62 and becomes a diffusion plasma toward the susceptor 12 (that is, the lower electrode).

  By applying the DC pulse voltage to the upper electrodes 60 and 62, the electron temperature immediately below the upper electrodes 60 and 62 can be made very high as in the case of the μ-wave plasma, so that the same plasma as the μ-wave plasma is generated. be able to. Dissociation of N2 requires high-energy electrons. By applying only the DC pulse voltage or the superimposed voltage to the upper electrodes 60 and 62, N2 can be dissociated with high efficiency as shown in FIG. It becomes possible. In FIG. 10, it can be seen that the dissociation of N 2 proceeds due to the application of the DC pulse voltage, and the emission intensity of N radicals increases while the emission intensity of N 2 decreases.

  Furthermore, since the wavelength becomes shorter as the frequency becomes higher, the uniformity of the plasma distribution deteriorates due to the wavelength effect. On the other hand, in the conventional technique, it was difficult to achieve both high dissociation of N2 and plasma uniformity, so it is necessary to increase the distance between the upper electrode and the lower electrode or to devise the shape of the upper electrode. was there. On the other hand, when the plate-like upper electrode and the disk-like lower electrode face each other in parallel, the plasma uniformity is improved by the application of the DC pulse voltage. For this reason, by applying only the DC pulse voltage or applying the superimposed voltage, it is possible to achieve both a high dissociation degree of N2 and plasma uniformity, and to reduce the distance between the upper electrode and the lower electrode. Therefore, the technology of the present disclosure can be applied to a process such as PEALD (Plasma Enhanced Atomic Layer Deposition) in which the gas replacement time has a large influence on the process throughput.

  As described above, in the embodiment, the film forming apparatus 1 includes the chamber 10 that can be evacuated, the susceptor 12 that is used as the lower electrode, the upper electrodes 60 and 62, the source gas supply unit 76, and the voltage application unit 5. Have A substrate to be processed is placed on the susceptor 12. The upper electrodes 60 and 62 are disposed in the chamber 10 so as to face the susceptor 12. The raw material gas supply unit 76 supplies a film forming raw material gas that is turned into plasma in the processing space PS between the upper electrodes 60 and 62 and the susceptor 12 to the processing space PS. The voltage application unit 5 applies to the upper electrodes 60 and 62 a superimposed voltage that is a voltage obtained by superimposing an alternating voltage and a direct-current pulse voltage in which the reference potential alternately changes up and down with time.

  By doing so, it is possible to achieve both high electron density, low ion energy, and high uniformity during film formation. Furthermore, the control of the electron density and the control of the ion energy can be performed independently while achieving both high electron density and low ion energy.

  In the embodiment, the film forming apparatus 1 includes the impedance adjustment circuit 100 connected between the susceptor 12 and the ground.

  By doing so, the impedance between the upper electrodes 60 and 62 and the susceptor 12 can be reduced, so that the alternating voltage component of the superimposed voltage easily reaches the susceptor 12.

  In addition, it should be thought that embodiment of this indication is an illustration and restrictive at no points. Indeed, the above embodiments may be implemented in various forms. The above-described embodiments may be omitted, replaced, and changed in various forms without departing from the scope and spirit of the claims.

DESCRIPTION OF SYMBOLS 1 Film-forming apparatus 5 Voltage application part 10 Chamber 12 Susceptor 60 Inner upper electrode 62 Outer upper electrode 76 Raw material gas supply part

Claims (3)

A processing container capable of being evacuated;
A lower electrode on which a substrate to be processed is placed in the processing container;
An upper electrode disposed opposite to the lower electrode in the processing vessel;
A gas supply unit that supplies a film forming material gas to be converted into plasma in a processing space between the upper electrode and the lower electrode into the processing space;
A voltage application unit for applying an alternating voltage, which is alternately changed up and down as time passes, to the upper electrode;
A film forming apparatus comprising: An impedance adjustment circuit connected between the lower electrode and ground;
The film forming apparatus according to claim 1, further comprising: A processing container capable of being evacuated;
A lower electrode on which a substrate to be processed is placed in the processing container;
An upper electrode disposed opposite to the lower electrode in the processing vessel;
A film forming method in a film forming apparatus comprising:
Supplying a film forming source gas to be converted into plasma in the processing space between the upper electrode and the lower electrode to the processing space;
Applying an alternating voltage, in which the reference potential alternately changes up and down with time, to the upper electrode;
A film forming method comprising:

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