JP4483234B2 - Cleaning method for atmospheric pressure plasma processing apparatus and atmospheric pressure plasma processing apparatus - Google Patents

Description

  The present invention relates to a cleaning method for an atmospheric pressure plasma processing apparatus and an atmospheric pressure plasma processing apparatus.

  In thin film forming equipment such as sputtering, vacuum deposition, thermal CVD, vacuum CVD, and plasma CVD, high performance is achieved on the substrate in a vacuum system or high-temperature system using a gas that vaporizes a metal compound or organometallic compound. A thin film is formed. However, in these thin film forming apparatuses, the gas becomes powder or a film and adheres to the inner wall of the apparatus, thereby deteriorating the apparatus performance.

  Etching to form a thin film on the surface of a substrate with a low-cost and simple device configuration that does not require a vacuum device, using excited active species generated by plasma discharge under pressure near atmospheric pressure recently. Various techniques have been proposed, such as ashing, ashing, or reforming.

  However, when the discharge gas, which is the main component of the thin film forming gas or the surface treatment gas, and the thin film forming gas are mixed and introduced into the plasma space, in addition to performing the thin film formation or surface treatment on the substrate, the powder or film It has been found that it tends to adhere to the inner wall of the apparatus and cause contamination.

  In particular, when dirt adheres to the electrode, it leads to a decrease in discharge capability and occurrence of discharge unevenness, resulting in deterioration of the quality of the thin film.

Various cleaning methods have been proposed to remove these deposits. For example, cleaning is performed by passing a CIF ₃ gas reactive to dirt such as tungsten through the apparatus (see Patent Document 1). Similarly, a method of cleaning parallel plate electrodes by introducing a cleaning gas into a dry etching apparatus is described (see Patent Document 2). However, both are cleaning techniques performed in a state close to vacuum.

  As a method for plasma treatment under a pressure near atmospheric pressure, a method of directly exposing the substrate to be treated to plasma generated between the counter electrodes (see FIG. 1 (1)) and a method of generating between the counter electrodes. There is a method of indirectly exposing excited active species generated by plasma to a substrate to be treated (see FIG. 1 (2)). In FIG. 1, 1 is a first electrode, 2 is a second electrode, and 3 is a gas supply / gas exhaust mechanism.

Since the latter is not suitable for large area processing and speeding up, it is actually desirable to perform the processing by the former method. However, the degree of contamination generated on the electrodes is more serious in the former, and when the discharge space is dirty, the former is a problem that is difficult to clean.
JP-A-7-86169 JP 2000-195846 A

  The present invention has been made in view of the above problems, and an object of the present invention is a method for treating (cleaning) surface contamination of an atmospheric pressure plasma discharge treatment apparatus after thin film formation or treatment, particularly atmospheric pressure plasma discharge treatment. An object of the present invention is to provide a method of cleaning the counter electrode soiled by the apparatus.

  Roughly speaking, there are the following four methods for supplying / exhausting gas between the opposing electrodes (discharge space) at atmospheric pressure or a pressure in the vicinity thereof, and the range for surface treatment (cleaning) of dirt on the electrodes.

  1) A mixed gas mainly composed of a discharge gas and a surface treatment (cleaning) gas is introduced into the discharge space, and a high frequency voltage is applied to generate a discharge to bring the cleaning gas into a plasma state. Direct exposure of the electrode to a cleaning gas in condition.

  2) A mixed gas containing a discharge gas and a cleaning gas as main components is introduced into the discharge space, and a high frequency voltage is applied to generate a discharge to bring the cleaning gas into a plasma state. A method in which gas is blown out in a jet shape outside the discharge space (processing space), and the electrode is indirectly exposed to the clean gas in the plasma state in the processing space.

  3) A method in which a discharge gas and a cleaning gas are separately introduced into a discharge space, a discharge is generated by applying a high-frequency voltage to bring the cleaning gas into a plasma state, and the electrode is directly exposed to the cleaning gas in the plasma state in the discharge space. .

  4) A discharge gas is introduced into the discharge space, a discharge is generated by applying a high-frequency voltage to excite the discharge gas to form a plasma state, and the jet is blown into the processing space, and the cleaning gas is separately introduced into the processing space. Then, the electrode is indirectly exposed to a plasma cleaning gas generated by contacting the plasma discharge gas.

  In the present invention, in consideration of the method for supplying and exhausting gas between the opposing electrodes (discharge space) at atmospheric pressure or a pressure in the vicinity thereof, the range for cleaning dirt on the electrodes, etc. We have eagerly studied methods suitable for crystallization. Furthermore, by examining the requirements for obtaining better results, and by devising the gas supply or exhaust mechanism, damage to the electrodes is minimal even if the electrodes are directly exposed to plasma cleaning gas in the discharge space. Therefore, it is possible to remove and clean the dirt on the electrode attached when forming the thin film.

  The method for cleaning an atmospheric pressure plasma discharge treatment apparatus (especially electrodes) in the present invention is to change the thin film forming gas to a cleaning gas between the counter electrodes of the atmospheric pressure plasma discharge treatment apparatus used for thin film formation, Alternatively, only the cleaning gas is used without using the above discharge gas, the cleaning gas is introduced between the counter electrodes and excited, and the counter electrode is brought into contact with the excited cleaning gas (exposed to the excited cleaning gas). As a result, the part in the apparatus, particularly the counter electrode is cleaned.

  In this way, cleaning can be performed in almost the same manner as the thin film forming method, such as discharging between the counter electrodes under atmospheric pressure.

  That is, it has been found that the object of the present invention can be achieved by adopting any one of the following configurations.

[1] In a cleaning method for an atmospheric pressure plasma processing apparatus in which a gas is supplied and filled in a discharge space of an atmospheric pressure plasma processing apparatus to generate plasma by a high frequency electric field.
90-99.9 volume% of the composition of the gas is the discharge gas,
The discharge gas is at least one gas selected from He, Ne, Ar, Kr, Xe and N ₂ ,
Other surface treatment gas (cleaning _{gas), COF 2, F 3 NO} , CF 3 OF, C 2 F 6, F 2, SiF 4, BCl 3, C 4 F 8, C 3 F 4, CHF 3, CF ₄ , CF ₃ Cl, CF ₃ Br, CCl ₄ , NF ₃ and SF ₆ are used, and O ₂ , H ₂ , H ₂ O, CO ₂ and CO are added as additive gases,
The method for cleaning an atmospheric pressure plasma processing apparatus is characterized in that the flow of the discharge gas is opposite to the flow of the gas during the thin film forming electric discharge machining.

[2] The high-frequency electric field is a superposition of the first high-frequency electric field and the second high-frequency electric field,
It said first of said second high-frequency electric field than the frequency omega ₁ of the high-frequency electric field frequency omega ₂ is high,
The strength V ₁ of the _first high-frequency electric field is greater than the strength V ₂ of the second high-frequency electric field,
The method for cleaning an atmospheric pressure plasma processing apparatus according to [1], wherein an output density of the second high-frequency electric field is 1 W / cm ² or more.

  [3] The method for cleaning an atmospheric pressure plasma processing apparatus according to [1] or [2], wherein the discharge space includes a first electrode and a second electrode facing each other.

[4] The method for cleaning an atmospheric pressure plasma processing apparatus according to [2] or [3] , wherein the first high-frequency electric field and the second high-frequency electric field are sine waves .

[5] The atmospheric pressure plasma according to [3] or [4] , wherein the first high-frequency electric field is applied to the first electrode, and the second high-frequency electric field is applied to the second electrode. Cleaning method for processing apparatus.

[ 6 ]
[1] to [5] The method for cleaning an atmospheric pressure plasma processing apparatus according to any one of [1] to [5], and having a supply or exhaust mechanism for supplying and exhausting the discharge gas so as to flow into and out of the discharge space. atmospheric pressure plasma processing apparatus said.

[ 7 ]
[1] to [5] The atmospheric pressure plasma processing apparatus cleaning method according to any one of [1] to [5] is used, and at the time of cleaning, the discharge gas flows into the discharge space from the opposite direction to that during the thin film formation process. and atmospheric pressure plasma processing apparatus you and performing discharge.

  According to the present invention, it is possible to provide a method for treating (cleaning) the surface contamination of the atmospheric pressure plasma discharge treatment apparatus after thin film formation or treatment, and in particular, a method for cleaning the contamination of the counter electrode of the atmospheric pressure plasma discharge treatment apparatus. .

  In the cleaning method of the present invention, after the thin film is formed or after the surface treatment, dirt in the atmospheric pressure plasma discharge treatment apparatus, particularly dirt adhering to the electrode is removed by the same operation as the thin film formation or surface treatment, that is, atmospheric pressure plasma discharge. It is characterized in that it can be performed using a cleaning gas by sewing between thin film formation or surface treatment.

  The atmospheric pressure plasma discharge treatment method and apparatus used in the present invention may be any plasma discharge treatment method and apparatus under atmospheric pressure or a pressure in the vicinity thereof.

  The atmospheric pressure plasma discharge processing apparatus according to the present invention includes at least a counter electrode capable of applying a high-frequency voltage between two electrodes, a voltage applying unit, and a gas supply unit, and an electrode temperature adjusting unit as necessary. Is. Functionally speaking, a gas (a gas mainly composed of a discharge gas and a surface treatment gas) is introduced between the counter electrodes (sometimes called a discharge space), and a high-frequency voltage from a high-frequency power source is applied between the counter electrodes. By applying and discharging, the gas is brought into a plasma state, and the surface of the electrode is cleaned (cleaned) by the plasma state gas (more precisely, the surface treatment gas in the plasma state).

The discharge gas is at least one gas selected from He, Ne, Ar, Kr, Xe and N ₂ , and the surface treatment (cleaning) gas is COF ₂ , F ₃ NO, CF ₃ OF, C _2. At least one selected from F ₆ , F ₂ , SiF ₄ , BCl ₃ , C ₄ F ₈ , C ₃ F ₄ , CHF ₃ , CF ₄ , CF ₃ Cl, CF ₃ Br, CCl ₄ , NF ₃ and SF ₆ It is desirable to be a seed gas.

  The atmospheric pressure plasma discharge treatment apparatus according to the present invention is preferably capable of controlling gas supply / exhaust or gas flow velocity and direction.

  The time required for surface treatment (cleaning) varies depending on the type of gas used for cleaning, the formation time, etc. If the composition of the dirt to be cleaned is known, the gas concentration, the high frequency output to be applied, and the flow rate and direction relating to the gas flow are adjusted. The optimum conditions can be selected.

  If such surface treatment (cleaning) is insufficient, the removal of dirt on the apparatus, particularly the electrodes, becomes incomplete, and the above-described generation of particles and discharge unevenness are caused. Further, if the surface treatment (cleaning) is too excessive, the smoothness of the electrode discharge surface is deteriorated, so that it is necessary to perform sufficient cleaning. However, these problems can be easily solved by the present invention.

  The present invention is described in detail below.

  In the present invention, the plasma discharge treatment is performed under atmospheric pressure or a pressure in the vicinity thereof, and the atmospheric pressure or the pressure in the vicinity thereof is about 20 to 110 kPa, and in order to obtain the good effects described in the present invention. Is preferably 93 to 104 kPa.

Discharge condition in the present invention, in the discharge space, wherein the first superimposing a high frequency electric field and a second high-frequency electric field, the frequency omega ₂ of the first of the more frequency omega ₁ of the high frequency electric field second high frequency electric field is The first high-frequency electric field strength V ₁ is higher than the second high-frequency electric field strength V ₂ , and the output density of the second high-frequency electric field is 1 W / cm ² or more. preferable.

  High frequency refers to one having a frequency of at least 0.5 kHz.

High frequency electric field to be superimposed, if are both sine wave becomes a first high-frequency electric field of a frequency omega ₁ and the frequency omega higher than ₁ second high-frequency electric field of a frequency omega ₂ and the superposed component, its waveform frequency A sine wave having a higher frequency ω ₂ is superimposed on the sine wave of ω ₁ , resulting in a sawtooth waveform.

  By applying a high-frequency electric field as described above to the discharge space, it is presumed that a discharge that can be cleaned is generated and high-density plasma necessary for forming a high-quality thin film can be generated.

  What is important here is that a voltage for forming such a high-frequency electric field is applied to the opposing electrodes, that is, applied to the same discharge space. As described in Japanese Patent Application Laid-Open No. 11-16696, the cleaning of the present invention cannot be achieved by a method in which two application electrodes are juxtaposed and different high frequency electric fields are applied to the different discharge spaces.

  Although the superposition of continuous waves such as sine waves has been described above, the present invention is not limited to this, and both pulse waves may be used, one of them may be a continuous wave and the other may be a pulse wave. Further, it may have a third electric field.

As a specific method for applying the high-frequency electric field of the present invention to the same discharge space, a first high-frequency electric field having a frequency ω ₁ and an electric field strength V ₁ is applied to the first electrode constituting the counter electrode. An atmospheric pressure plasma discharge treatment apparatus is used in which a first power source is connected, and a second power source is connected to the second electrode to apply a second high-frequency electric field having a frequency ω ₂ and an electric field strength V ₂ .

  Further, it is preferable to connect the first filter to the first electrode, the first power source or any of them, and connect the second filter to the second electrode, the second power source or any of them, The first filter facilitates the passage of the first high-frequency electric field current from the first power source to the first electrode, grounds the second high-frequency electric field current, and the second filter from the second power source to the first power source. It makes it difficult to pass the current of high frequency electric field. On the other hand, the second filter makes it easy to pass the current of the second high-frequency electric field from the second power source to the second electrode, grounds the current of the first high-frequency electric field, and the second power from the first power source. A power supply having a function of making it difficult to pass the current of the first high-frequency electric field to the power supply is used. Here, being difficult to pass means that it preferably passes only 20% or less of the current, more preferably 10% or less. On the contrary, being easy to pass means preferably passing 80% or more of the current, more preferably 90% or more.

  Furthermore, it is preferable that the first power source of the atmospheric pressure plasma discharge processing apparatus of the present invention has a capability of applying a higher frequency electric field strength than the second power source.

  Here, the high frequency electric field strength (applied electric field strength) and the discharge starting electric field strength referred to in the present invention are those measured by the following method.

Measuring method of high-frequency electric field strengths V ₁ and V ₂ (unit: kV / mm):
A high-frequency voltage probe (P6015A) is installed in each electrode section, and the output signal of the high-frequency voltage probe is connected to an oscilloscope (Tektronix, TDS3012B), and the electric field strength is measured.

  The positional relationship between the high-frequency voltage probe used for the measurement and the oscilloscope is shown in FIG.

  By taking the discharge conditions specified in the present invention, even a discharge gas having a high discharge start electric field strength such as nitrogen gas can start discharge, maintain a high density and stable plasma state, and perform high performance cleaning. It can be done.

  Here, the frequency of the first power source is preferably 200 kHz or less. The electric field waveform may be a continuous wave or a pulse wave. The lower limit is preferably about 1 kHz.

  On the other hand, the frequency of the second power source is preferably 800 kHz or more. The higher the frequency of the second power source, the higher the plasma density, and a dense and high-quality thin film can be obtained. The upper limit is preferably about 200 MHz.

  The application of a high frequency electric field from such two power sources is necessary to start the discharge of a discharge gas having a high discharge start electric field strength by the first high frequency electric field, and the high frequency of the second high frequency electric field. It is also desirable in the present invention to perform good cleaning by increasing the plasma density due to the high power density.

  Also, by increasing the output density of the first high-frequency electric field, the output density of the second high-frequency electric field can be improved while maintaining the uniformity of discharge. Thereby, a further uniform high-density plasma can be generated, and the cleaning property can be further improved.

  As described above, the atmospheric pressure plasma discharge treatment apparatus to which the present invention is applied discharges between the counter electrodes, puts the gas introduced between the counter electrodes into a plasma state, and is placed between the counter electrodes or between the electrodes. The thin film is formed on the base material by exposing the base material to be transported to the gas in the plasma state.

  FIG. 1 (1) is a schematic view showing an example of an atmospheric pressure plasma discharge treatment apparatus of a type in which a substrate to be treated is directly exposed to plasma useful for the present invention.

  In FIG. 1 (2), the atmospheric pressure plasma discharge treatment apparatus discharges between the counter electrodes similar to the above, excites the gas introduced between the counter electrodes or puts it in a plasma state, and excites it in a jet form outside the counter electrode. Alternatively, there is an apparatus of a type in which a thin film is formed on a base material by blowing gas in a plasma state and exposing a base material (which may be stationary or transferred) in the vicinity of the counter electrode .

  1 (1) and 1 (2) show a gas supply / gas exhaust mechanism 3 for a discharge gas and a surface treatment gas (cleaning gas) necessary in the present invention. These control the speed and direction of gas flow.

  FIG. 2 is a schematic view showing an example of an actual atmospheric pressure plasma discharge treatment apparatus.

  The jet type atmospheric pressure plasma discharge processing apparatus shown in FIG. 2 is not shown in FIG. 2 in addition to the plasma discharge processing apparatus and the electric field applying means having two power sources (shown in FIG. 3 described later). Is an apparatus having gas supply means and electrode temperature adjustment means.

The plasma discharge processing apparatus 10 has a counter electrode composed of a first electrode 11 and a second electrode 12, and the frequency ω ₁ from the first power supply 21 is output from the first electrode 11 between the counter electrodes. A first high frequency electric field having electric field strength V ₁ and current I ₁ is applied, and a second high frequency electric field having frequency ω ₂ , electric field strength V ₂ and current I ₂ from second power source 22 is applied from second electrode 12. Is applied. The first power supply 21 can apply a higher frequency electric field strength (V ₁ > V ₂ ) than the second power supply 22, and the first frequency ω ₁ of the first power supply 21 is higher than the second frequency ω ₂ of the second power supply 22. A low frequency can be applied.

  A first filter 23 is installed between the first electrode 11 and the first power source 21 to facilitate passage of current from the first power source 21 to the first electrode 11, and current from the second power source 22. Is designed so that the current from the second power source 22 to the first power source 21 is less likely to pass through.

  In addition, a second filter 24 is installed between the second electrode 12 and the second power source 22 to facilitate passage of current from the second power source 22 to the second electrode, and from the first power source 21. It is designed to ground the current and make it difficult to pass the current from the first power source 21 to the second power source.

  A gas G is introduced into the space (discharge space) 13 between the first electrode 11 and the second electrode 12 from a gas supply means as shown in FIG. 3 to be described later, and the first electrode 11 and the second electrode A high frequency electric field is applied from 12 to generate a discharge. As a result, while the gas G is in the plasma state, the gas G is blown out in the form of a jet to the lower side (the lower side of the paper), the base material F is placed there, and the processing space formed by the lower surface of the counter electrode and the base material is in the plasma state. In this method, a thin film is formed on the base material F by filling with gas G °.

  Although not shown, the substrate is unwound from the original winding (unwinder) and conveyed, or the substrate conveyed from the previous step is passed between the counter electrodes to form a thin film. During the thin film formation, the medium heats or cools the electrode through the pipe from the electrode temperature adjusting means as shown in FIG. Depending on the temperature of the base material during the plasma discharge treatment, the properties, composition, etc. of the thin film obtained may change, and it is desirable to appropriately control this. As the temperature control medium, an insulating material such as distilled water or oil is preferably used. During the plasma discharge treatment, it is desirable to uniformly adjust the temperature inside the electrode so that the temperature unevenness of the base material in the width direction or the longitudinal direction does not occur as much as possible.

  FIG. 2 shows a measuring instrument used for measuring the above-described high-frequency electric field strength (applied electric field strength) and discharge starting electric field strength. Reference numerals 25 and 26 are high-frequency voltage probes, and reference numerals 27 and 28 are oscilloscopes.

  In the description of FIG. 2 above, the gas G is in a plasma state and blown out in the form of a jet to the lower side (lower side of the paper) of the counter electrode, and a base material is placed there, and the processing space created by the lower surface of the counter electrode and the base material. Is filled with plasma gas G °, and a thin film is formed on the substrate. However, this method has already been described as having various problems.

  FIG. 3 is a schematic view showing an example of an atmospheric pressure plasma discharge treatment apparatus that treats a substrate between counter electrodes useful for the present invention.

  The atmospheric pressure plasma discharge treatment apparatus of the present invention is an apparatus having at least a plasma discharge treatment apparatus 30, an electric field application means 40 having two power supplies, a gas supply means 50, and an electrode temperature adjustment means 60.

  FIG. 3 shows a thin film formed by subjecting the base material F to plasma discharge treatment between the opposed electrodes (discharge space) 32 between the roll rotating electrode (first electrode) 35 and the square tube type fixed electrode group (second electrode) 36. To do.

In the discharge space (between the counter electrodes) 32 between the roll rotating electrode (first electrode) 35 and the square tube type fixed electrode group (second electrode) 36, the roll rotating electrode (first electrode) 35 has a first power source. The first high-frequency electric field having frequency ω ₁ , electric field strength V ₁ and current I ₁ from 41, and the frequency ω ₂ and electric field strength V ₂ from the second power source 42 to the square tube fixed electrode group (second electrode) 36. A second high-frequency electric field of current I ₂ is applied.

  A first filter 43 is installed between the roll rotation electrode (first electrode) 35 and the first power supply 41, and the first filter 43 easily passes a current from the first power supply 41 to the first electrode. The current from the second power supply 42 is grounded so that the current from the second power supply 42 to the first power supply is difficult to pass. Further, a second filter 44 is provided between the square tube type fixed electrode group (second electrode) 36 and the second power source 42, and the second filter 44 is connected from the second power source 42 to the second electrode. It is designed so that the current from the first power supply 41 is grounded and the current from the first power supply 41 to the second power supply is difficult to pass.

In the present invention, the roll rotation electrode 35 may be the second electrode, and the rectangular tube-shaped fixed electrode group 36 may be the first electrode. In any case, the first power source is connected to the first electrode, and the second power source is connected to the second electrode. The first power supply preferably applies a higher frequency electric field strength (V ₁ > V ₂ ) than the second power supply. Further, the frequency has the ability to satisfy ω ₁ <ω ₂ .

The current is preferably I ₁ <I ₂ . Current I ₁ of the first high-frequency electric field is preferably ^{0.3mA / cm 2 ~20mA / cm 2} , more preferably at ^{1.0mA / cm 2 ~20mA / cm 2} . The current I ₂ of the second high-frequency electric field is preferably ^{10mA / cm 2 ~100mA / cm 2} , more preferably ^{20mA / cm 2 ~100mA / cm 2} .

  The gas G generated by the gas generator 51 of the gas supply means 50 is introduced into the plasma discharge processing vessel 31 from the air supply port 52 while controlling the flow rate.

  The substrate F is unwound from the original winding (not shown) or conveyed from the previous process, or is conveyed from the previous process, and air or the like accompanying the substrate is blocked by the nip roll 65 via the guide roll 64. Then, while being wound while being in contact with the roll rotating electrode 35, it is transferred between the square tube fixed electrode group 36 and the roll rotating electrode (first electrode) 35 and the square tube fixed electrode group (second electrode) 36. An electric field is applied from both of them to generate discharge plasma between the counter electrodes (discharge space) 32. The base material F forms a thin film with a gas in a plasma state while being wound while being in contact with the roll rotating electrode 35. The base material F passes through the nip roll 66 and the guide roll 67 and is wound up by a winder (not shown) or transferred to the next process.

  Discharged treated exhaust gas G ′ is discharged from the exhaust port 53.

  In order to heat or cool the roll rotating electrode (first electrode) 35 and the rectangular tube type fixed electrode group (second electrode) 36 during the formation of the thin film, a medium whose temperature is adjusted by the electrode temperature adjusting means 60 is used as a liquid feed pump. P is sent to both electrodes through the pipe 61, and the temperature is adjusted from the inside of the electrode. Reference numerals 68 and 69 denote partition plates that partition the plasma discharge processing vessel 31 from the outside.

  In addition, since a plurality of atmospheric pressure plasma discharge treatment apparatuses are connected in series and the gas in the same plasma state can be discharged at the same time, it can be processed many times and processed at high speed. Further, if each device produces gas in different plasma states, it is possible to form laminated thin films having different layers.

  FIG. 4 is a perspective view showing an example of the structure of the conductive metallic base material of the roll rotating electrode shown in FIG. 3 and the dielectric material coated thereon.

  In FIG. 4, a roll electrode 35a is formed by covering a conductive metallic base material 35A and a dielectric 35B thereon. In order to control the electrode surface temperature during the plasma discharge treatment, a temperature adjusting medium (water, silicon oil or the like) can be circulated.

  FIG. 5 is a perspective view showing an example of the structure of a conductive metallic base material of a rectangular tube electrode and a dielectric material coated thereon.

  In FIG. 5, a rectangular tube type electrode 36a has a coating of a dielectric 36B similar to FIG. 3 on a conductive metallic base material 36A, and the structure of the electrode is a metallic pipe. , It becomes a jacket so that the temperature can be adjusted during discharge.

  In addition, the number of the rectangular tube-shaped fixed electrodes is set in plural along the circumference larger than the circumference of the roll electrode, and the discharge area of the electrodes is a full square tube type facing the roll rotating electrode 35. It is represented by the sum of the area of the fixed electrode surface.

  The rectangular tube electrode 36a shown in FIG. 3 may be a cylindrical electrode, but the rectangular tube electrode has an effect of expanding the discharge range (discharge area) as compared with the cylindrical electrode, and thus is preferably used in the present invention. .

  4 and 5, a roll electrode 35a and a rectangular tube electrode 36a are formed by spraying ceramics as dielectrics 35B and 36B on conductive metallic base materials 35A and 36A, respectively, and then sealing the inorganic compound sealing material. Used and sealed. The ceramic dielectric may be covered by about 1 mm with a single wall. As the ceramic material used for thermal spraying, alumina, silicon nitride, or the like is preferably used. Among these, alumina is particularly preferable because it is easily processed. The dielectric layer may be a lining-processed dielectric provided with an inorganic material by lining.

  Examples of the conductive metal base materials 35A and 36A include titanium metal or titanium alloy, metal such as silver, platinum, stainless steel, aluminum, and iron, a composite material of iron and ceramics, or a composite material of aluminum and ceramics. Although titanium metal or a titanium alloy is particularly preferable for the reasons described later.

  When the dielectric is provided on one of the electrodes, the distance between the opposing first electrode and second electrode is the shortest distance between the surface of the dielectric and the surface of the conductive metal base material of the other electrode. Say that. When a dielectric is provided on both electrodes, it means the shortest distance between the dielectric surfaces. The distance between the electrodes is determined in consideration of the thickness of the dielectric provided on the conductive metallic base material, the magnitude of the applied electric field strength, the purpose of using the plasma, etc. From the viewpoint of performing 0.15 mm, 0.1 to 20 mm is preferable, and 0.5 to 2 mm is particularly preferable.

  Details of the conductive metallic base material and dielectric useful in the present invention will be described later.

  The plasma discharge treatment vessel 31 is preferably a treatment vessel made of Pyrex (R) glass or the like, but can be made of metal as long as it can be insulated from the electrodes. For example, polyimide resin or the like may be attached to the inner surface of an aluminum or stainless steel frame, and the metal frame may be thermally sprayed to obtain insulation. It is preferable to cover both side surfaces of the parallel electrodes (up to the vicinity of the base material surface) with an object made of the above-described material.

As the first power source (high frequency power source) installed in the atmospheric pressure plasma discharge processing apparatus of the present invention,
Applied power symbol Manufacturer Frequency Product name A1 Shinko Electric 3kHz SPG3-4500
A2 Shinko Electric 5kHz SPG5-4500
A3 Kasuga Electric 15kHz AGI-023
A4 Shinko Electric 50kHz SPG50-4500
A5 HEIDEN Research Laboratories 100kHz * PHF-6k
A6 Pearl Industry 200kHz CF-2000-200k A7 Pearl Industry 400kHz CF-2000-400k
And the like, and any of them can be used.

As the second power source (high frequency power source),
Applied power supply symbol Manufacturer Frequency Product name B1 Pearl Industry 800kHz CF-2000-800k
B2 Pearl Industry 2MHz CF-2000-2M
B3 Pearl Industry 13.56MHz CF-5000-13M
B4 Pearl Industry 27MHz CF-2000-27M
B5 Pearl Industry 150MHz CF-2000-150M
And the like, and any of them can be preferably used.

  Of the above power supplies, * indicates a HEIDEN Laboratory impulse high-frequency power supply (100 kHz in continuous mode). Other than that, it is a high-frequency power source that can apply only a continuous sine wave.

  In the present invention, it is preferable to employ an electrode capable of maintaining a uniform and stable discharge state by applying such an electric field in an atmospheric pressure plasma discharge treatment apparatus.

In the present invention, the electric power applied between the electrodes facing each other supplies power (power density) of 1 W / cm ² or more to the second electrode (second high-frequency electric field) to excite the discharge gas to generate plasma. The energy is applied to the thin film forming gas to form a thin film. The upper limit value of the power supplied to the second electrode is preferably 50 W / cm ² , more preferably 20 W / cm ² . The lower limit is preferably 1.2 W / cm ² . The discharge area (cm ² ) refers to an area in a range where discharge occurs in the electrode.

Further, by supplying power (output density) of 1 W / cm ² or more to the first electrode (first high frequency electric field), the output density is improved while maintaining the uniformity of the second high frequency electric field. I can do it. Thereby, a further uniform high-density plasma can be generated, and a further improvement in film forming speed and an improvement in film quality can be achieved. Preferably it is 5 W / cm ² or more. The upper limit value of the power supplied to the first electrode is preferably 50 W / cm ² .

  Here, the waveform of the high-frequency electric field is not particularly limited. There are a continuous sine wave continuous oscillation mode called a continuous mode, an intermittent oscillation mode called ON / OFF intermittently called a pulse mode, and either of them may be adopted, but at least the second electrode side (second The high-frequency electric field is preferably a continuous sine wave because a denser and better quality film can be obtained.

  An electrode used in such a method for forming a thin film by atmospheric pressure plasma must be able to withstand severe conditions in terms of structure and performance. Such an electrode is preferably a metal base material coated with a dielectric.

In the dielectric-coated electrode used in the present invention, it is preferable that the characteristics match between various metallic base materials and dielectrics. One of the characteristics is linear thermal expansion between the metallic base material and the dielectric. The combination is such that the difference in coefficient is 10 × 10 ⁻⁶ / ° C. or less. It is preferably 8 × 10 ⁻⁶ / ° C. or less, more preferably 5 × 10 ⁻⁶ / ° C. or less, and further preferably 2 × 10 ⁻⁶ / ° C. or less. The linear thermal expansion coefficient is a well-known physical property value of a material.

As a combination of a conductive metallic base material and a dielectric whose difference in linear thermal expansion coefficient is within this range,
1: Metal base material is pure titanium or titanium alloy, dielectric is ceramic spray coating 2: Metal base material is pure titanium or titanium alloy, dielectric is glass lining 3: Metal base material is stainless steel, Dielectric is ceramic spray coating 4: Metal base material is stainless steel, Dielectric is glass lining 5: Metal base material is a composite material of ceramics and iron, Dielectric is ceramic spray coating 6: Metal base material Ceramic and iron composite material, dielectric is glass lining 7: Metal base material is ceramic and aluminum composite material, dielectric is ceramic sprayed coating 8: Metal base material is ceramic and aluminum composite material, dielectric The body has glass lining. From the viewpoint of the difference in linear thermal expansion coefficient, the above 1 or 2 and 5 to 8 are preferable, and 1 is particularly preferable.

  In the present invention, titanium or a titanium alloy is particularly useful as the metallic base material from the above characteristics. By using titanium or a titanium alloy as the metal base material, the dielectric is used as described above, so that there is no deterioration of the electrode in use, especially cracking, peeling, or falling off, and it can be used for a long time under harsh conditions. Can withstand.

  The metallic base material of the electrode useful in the present invention is a titanium alloy or titanium metal containing 70% by mass or more of titanium. In the present invention, if the titanium content in the titanium alloy or titanium metal is 70% by mass or more, it can be used without any problem, but preferably contains 80% by mass or more of titanium. As the titanium alloy or titanium metal useful in the present invention, those generally used as industrial pure titanium, corrosion resistant titanium, high strength titanium and the like can be used. Examples of pure titanium for industrial use include TIA, TIB, TIC, TID, etc., all of which contain very little iron atom, carbon atom, nitrogen atom, oxygen atom, hydrogen atom, etc. As content, it has 99 mass% or more. As the corrosion-resistant titanium alloy, T15PB can be preferably used, and it contains lead in addition to the above-mentioned atoms, and the titanium content is 98% by mass or more. Further, as the titanium alloy, T64, T325, T525, TA3, etc. containing aluminum and vanadium or tin in addition to the above atoms except lead can be preferably used. As a quantity, it contains 85 mass% or more. These titanium alloys or titanium metals have a thermal expansion coefficient that is about 1/2 smaller than that of stainless steel, such as AISI 316, and are combined with a dielectric described later applied on the titanium alloy or titanium metal as a metallic base material. It can withstand the use at high temperature for a long time.

  On the other hand, as a required characteristic of the dielectric, specifically, an inorganic compound having a relative dielectric constant of 6 to 45 is preferable, and examples of such a dielectric include ceramics such as alumina and silicon nitride, Alternatively, there are glass lining materials such as silicate glass and borate glass. In this, what sprayed the ceramics mentioned later and the thing provided by glass lining are preferable. In particular, a dielectric provided by spraying alumina is preferable.

  Alternatively, as one of the specifications that can withstand high power as described above, the porosity of the dielectric is 10% by volume or less, preferably 8% by volume or less, preferably more than 0% by volume and 5% by volume or less. It is. The porosity of the dielectric can be measured by a BET adsorption method or a mercury porosimeter. In the examples described later, the porosity is measured using a dielectric fragment covered with a metallic base material by a mercury porosimeter manufactured by Shimadzu Corporation. High durability is achieved because the dielectric has a low porosity. Examples of the dielectric having such a void and a low void ratio include a high-density, high-adhesion ceramic spray coating by an atmospheric plasma spraying method described later. In order to further reduce the porosity, it is preferable to perform sealing treatment.

  The above-mentioned atmospheric plasma spraying method is a technique in which fine powder such as ceramics, wire, or the like is put into a plasma heat source and sprayed onto a metallic base material to be coated as fine particles in a molten or semi-molten state to form a film. A plasma heat source is a high-temperature plasma gas in which a molecular gas is heated to a high temperature, dissociated into atoms, and further given energy to release electrons. The plasma gas injection speed is high, and since the sprayed material collides with the metallic base material at a higher speed than conventional arc spraying or flame spraying, high adhesion strength and high density coating can be obtained. Specifically, reference can be made to a thermal spraying method for forming a heat shielding film on a high-temperature exposed member described in JP-A No. 2000-301655. By this method, the porosity of the dielectric (ceramic sprayed film) to be coated can be obtained.

  Another preferable specification that can withstand high power is that the dielectric thickness is 0.5 to 2 mm. The film thickness variation is desirably 5% or less, preferably 3% or less, and more preferably 1% or less.

In order to further reduce the porosity of the dielectric, it is preferable to further perform a sealing treatment with an inorganic compound on the sprayed film such as ceramics as described above. As the inorganic compound, a metal oxide is preferable, and among these, a compound containing silicon oxide (SiO _x ) as a main component is particularly preferable.

  The inorganic compound for sealing treatment is preferably formed by curing by a sol-gel reaction. In the case where the inorganic compound for sealing treatment contains a metal oxide as a main component, a metal alkoxide or the like is applied as a sealing liquid on the ceramic sprayed film and cured by a sol-gel reaction. When the inorganic compound is mainly composed of silica, it is preferable to use alkoxysilane as the sealing liquid.

  Here, it is preferable to use energy treatment for promoting the sol-gel reaction. Examples of the energy treatment include thermal curing (preferably 200 ° C. or less) and ultraviolet irradiation. Furthermore, as a method of sealing treatment, when the sealing liquid is diluted and coating and curing are sequentially repeated several times, mineralization is further improved and a dense electrode without deterioration can be obtained.

In the case of performing a sealing treatment that cures by a sol-gel reaction after coating a ceramic sprayed film using the metal alkoxide or the like of the dielectric-coated electrode according to the present invention as a sealing liquid, the content of the metal oxide after curing is 60 It is preferably at least mol%. When alkoxysilane is used as the metal alkoxide of the sealing liquid, the content of SiO _x (x is 2 or less) after curing is preferably 60 mol% or more. The cured SiO _x content is measured by analyzing a tomographic layer of the dielectric layer by XPS (X-ray photoelectron spectroscopy).

  In the electrode according to the thin film forming method of the present invention, the maximum height (Rmax) of the surface roughness defined by JIS B 0601 on the side in contact with at least the substrate of the electrode is adjusted to be 10 μm or less. Although it is preferable from the viewpoint of obtaining the effects described in the present invention, the maximum value of the surface roughness is more preferably 8 μm or less, and particularly preferably adjusted to 7 μm or less. In this way, the dielectric surface of the dielectric-coated electrode can be polished and the dielectric thickness and the gap between the electrodes can be kept constant, the discharge state can be stabilized, the heat shrinkage difference and Distortion and cracking due to residual stress can be eliminated, and durability can be greatly improved with high accuracy. The polishing finish of the dielectric surface is preferably performed at least on the dielectric in contact with the substrate. Furthermore, the centerline average surface roughness (Ra) defined by JIS B 0601 is preferably 0.5 μm or less, more preferably 0.1 μm or less.

  In the dielectric-coated electrode used in the present invention, another preferred specification that can withstand high power is that the heat-resistant temperature is 100 ° C. or higher. More preferably, it is 120 degreeC or more, Most preferably, it is 150 degreeC or more. The upper limit is 500 ° C. The heat-resistant temperature refers to the highest temperature that can withstand normal discharge without causing dielectric breakdown at the voltage used in the atmospheric pressure plasma treatment. Such heat-resistant temperature can be applied within the range of the difference between the linear thermal expansion coefficient of the metallic base material and the dielectric material by applying the dielectric material provided by the above-mentioned ceramic spraying or layered glass lining with different bubble mixing amounts. This can be achieved by appropriately combining means for appropriately selecting the materials.

  Next, the gas supplied to the discharge space will be described.

  The supplied gas contains at least a discharge gas and a thin film forming gas. The discharge gas and the thin film forming gas may be mixed and supplied, or may be supplied separately.

  The discharge gas is a gas capable of causing glow discharge capable of forming a thin film. Examples of the discharge gas include nitrogen, rare gas, air, hydrogen gas, oxygen, and the like. These may be used alone as a discharge gas or may be mixed. In the present invention, nitrogen is preferred as the discharge gas. It is preferable that 50-100 volume% of discharge gas is nitrogen gas. At this time, as the discharge gas other than nitrogen, it is preferable to contain a rare gas of less than 50% by volume. Moreover, it is preferable to contain 90-99.9 volume% of quantity of discharge gas with respect to the total gas quantity supplied to discharge space.

  A thin film forming gas is a raw material that is excited and activated to form a thin film by being chemically deposited on a substrate.

  Next, the gas supplied to the discharge space for forming the thin film used in the present invention will be described. The discharge gas and the thin film forming gas are basically used, but an additive gas may be further added. It is preferable to contain 90-99.9 volume% of discharge gas in the total gas amount supplied to discharge space.

  Examples of the thin film forming gas used in the present invention include organometallic compounds, halogen metal compounds, and metal hydrogen compounds.

  The organometallic compounds useful in the present invention are preferably those represented by the following general formula (I).

Formula (I)
R ¹ _x MR ² _y R ³ _z
In the formula, M is a metal, R ¹ is an alkyl group, R ² is an alkoxy group, R ³ is a β-diketone complex group, a β-ketocarboxylic acid ester complex group, a β-ketocarboxylic acid complex group, and a ketooxy group (ketooxy complex group). X + y + z = m, x = 0 to m, or x = 0 to m−1, and y = 0 to m, z = 0. ~ M, each of which is 0 or a positive integer. Examples of the alkyl group for R ¹ include a methyl group, an ethyl group, a propyl group, and a butyl group. Examples of the alkoxy group for R ² include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, and a 3,3,3-trifluoropropoxy group. Moreover, the hydrogen atom of the alkyl group may be substituted with a fluorine atom. Examples of the group selected from the β-diketone complex group, β-ketocarboxylic acid ester complex group, β-ketocarboxylic acid complex group and ketooxy group (ketooxy complex group) of R ³ include, for example, 2,4 -Pentanedione (also called acetylacetone or acetoacetone), 1,1,1,5,5,5-hexamethyl-2,4-pentanedione, 2,2,6,6-tetramethyl-3,5-heptanedione 1,1,1-trifluoro-2,4-pentanedione, etc., and β-ketocarboxylic acid ester complex groups include, for example, acetoacetic acid methyl ester, acetoacetic acid ethyl ester, acetoacetic acid propyl ester, trimethyl Examples thereof include ethyl acetoacetate and methyl trifluoroacetoacetate. As β-ketocarboxylic acid, Eg to acetoacetate, can be mentioned trimethyl acetoacetate, and as Ketookishi, for example, acetoxy group (or an acetoxy group), a propionyloxy group, Buchirirokishi group, acryloyloxy group, methacryloyloxy group and the like. The number of carbon atoms of these groups is preferably 18 or less, including the above-mentioned organometallic compounds. Further, as illustrated, it may be linear or branched, or a hydrogen atom substituted with a fluorine atom.

In the present invention, an organometallic compound having a low risk of explosion is preferred from the viewpoint of handling, and an organometallic compound having at least one oxygen in the molecule is preferred. As such, an organometallic compound containing at least one alkoxy group of R ² , a β-diketone complex group, a β-ketocarboxylic acid ester complex group, a β-ketocarboxylic acid complex group and a ketooxy group (ketooxy group) of R ³ A metal compound having at least one group selected from (complex group) is preferred.

  A specific organometallic compound will be described later.

  In the present invention, the gas supplied to the discharge space may be mixed with an additive gas that accelerates the reaction for forming a thin film, in addition to the discharge gas and the thin film forming gas. Examples of the additive gas include oxygen, ozone, hydrogen peroxide, carbon dioxide, carbon monoxide, hydrogen, ammonia and the like, but oxygen, carbon monoxide and hydrogen are preferable, and components selected from these are mixed. It is preferable to do so. The content is preferably 0.01 to 5% by volume based on the total amount of gas, whereby the reaction is promoted and a dense and high-quality thin film can be formed.

  The thickness of the formed oxide or composite compound thin film is preferably in the range of 0.1 to 1000 nm.

  In the present invention, Li, Be, B, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, as the metal of the organometallic compound, metal halide, and metal hydride used in the thin film forming gas. Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Rb, Sr, Y, Zr, Nb, Mo, Cd, In, Ir, Sn, Sb, Cs, Ba, La, Hf, Ta, Examples include W, Tl, Pb, Bi, Ce, Pr, Nd, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

  In the thin film forming method of the present invention, various high-functional thin films can be obtained by using a metal compound such as an organic metal compound, a halogen metal compound, or a metal hydrogen compound together with a discharge gas. Although the example of the thin film of this invention is shown below, this invention is not limited to this.

Electrode film: Au, Al, Ag, Ti, Ti, Pt, Mo, Mo-Si
Dielectric protective film: SiO ₂ , SiO, Si ₃ N ₄ , Al ₂ O ₃ , Al ₂ O ₃ , Y ₂ O ₃
Transparent conductive film: In ₂ O ₃ , SnO ₂
Electrochromic film: WO ₃ , IrO ₂ , MoO ₃ , V ₂ O ₅
Fluorescent film: ZnS, ZnS + ZnSe, ZnS + CdS
Magnetic recording film: Fe—Ni, Fe—Si—Al, γ-Fe ₂ O ₃ , Co, Fe ₃ O ₄ , Cr, SiO ₂ , AlO ₃
Super conductive film: Nb, Nb-Ge, NbN
Solar cell film: a-Si, Si
Reflective film: Ag, Al, Au, Cu
Selective absorption membrane: ZrC-Zr
Selective permeable membrane: In ₂ O ₃ , SnO ₂
Antireflection film: SiO ₂ , TiO ₂ , SnO ₂
Shadow mask: Cr
Abrasion resistant film: Cr, Ta, Pt, TiC, TiN
Corrosion resistant film: Al, Zn, Cd, Ta, Ti, Cr
Heat-resistant film: W, Ta, Ti
Lubricating film: MoS ₂
Decorative film: Cr, Al, Ag, Au, TiC, Cu
The nitridation degree of the nitride, the oxidation degree of the oxide, the sulfide degree of the sulfide, and the carbonization degree of the carbide are merely examples, and the composition ratio with the metal may be changed as appropriate. In addition to the metal compound, the thin film may contain impurities such as a carbon compound, a nitrogen compound, and a hydrogen compound.

  In the present invention, particularly preferred metals of the metal compound are Si (silicon), Ti (titanium), Sn (tin), Zn (zinc), In (indium), and Al (aluminum) among these metals. Of the metal compounds that bind to, the organometallic compounds represented by the general formula (I) are preferred.

  The present invention will be described with reference to examples, but it is needless to say that the embodiments of the present invention are not limited thereto.

Examples 1-3
The state after cleaning of the electrode surface was evaluated by changing the electrode to be cleaned.

(Sample preparation and cleaning conditions)
Tables 1 to 3 below were carried out using TiO ₂ , SiO ₂ film, and tape-attached electrodes.

  Example 1 is a result of using an atmospheric pressure plasma discharge treatment apparatus having the configuration shown in FIG. 6, and Table 1 shows the cleaning conditions and evaluation results. In FIG. 6, 6 is a ceramic plate that covers the electrodes.

  Example 2 is a result of using an atmospheric pressure plasma discharge treatment apparatus having the configuration shown in FIG. 7, and Table 2 shows the experimental conditions and evaluation results.

  The pressure-sensitive adhesive tape used in the present invention is a polyimide tape No. 1 manufactured by Nitto Denko Corporation. 360 UL, which was affixed to the electrode surface and the degree of removal was observed.

  Example 3 is a result of using an atmospheric pressure plasma discharge treatment apparatus having the configuration shown in FIG. 8, and Table 3 shows the cleaning conditions and evaluation results.

  In each table, the discharge gap (discharge gap) refers to the distance between the electrodes, the gas flow refers to the direction during film formation (film formation) and cleaning, and the same is referred to as forward flow and the reverse is referred to as reverse flow. .

In addition, although the electrode used for each cleaning has been used for more than one year, the cleaned film is formed immediately before cleaning.
(Evaluation)
The state after the cleaning treatment of the electrode surface was visually observed according to the following criteria.

◎ Almost completely removed ○ Slightly removed but has residual area, that is, non-cleaning area × Removal is clearly insufficient XX Same as before cleaning process (Result)

  It should be noted that the state of the sample before the cleaning process is at an evaluation “XX” level.

  It should be noted that the state of the sample before the cleaning process is at an evaluation “XX” level.

  It should be noted that the state of the sample before the cleaning process is at an evaluation “XX” level.

  Both show good cleaning properties, but with regard to the gas flow, the direction of film formation (film formation) and cleaning are reversed (represented as reverse flow in the table), thereby removing dirt on the electrodes attached during thin film formation.・ It can be seen that washing is performed more completely.

It is the schematic which showed the atmospheric pressure plasma discharge processing apparatus example. It is the schematic which showed an example of the jet-type atmospheric pressure plasma discharge processing apparatus. It is the schematic which shows an example of the atmospheric pressure plasma discharge processing apparatus of the system which processes a base material between counter electrodes useful for this invention. It is a perspective view which shows an example of the roll rotating electrode which has an electroconductive metal base material and the dielectric material coat | covered on it. It is a perspective view which shows an example of the structure of the electroconductive metal preform | base_material of a rectangular tube type electrode, and the dielectric material coat | covered on it. It is the schematic of the atmospheric pressure plasma discharge processing apparatus used for the Example. It is the schematic of the atmospheric pressure plasma discharge processing apparatus used for the Example. It is the schematic of the atmospheric pressure plasma discharge processing apparatus used for the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 11 1st electrode 2, 12 2nd electrode 3 Gas supply / gas exhaust mechanism 10 Plasma discharge processing apparatus 20 Electric field application means 21 1st power supply 22 2nd power supply

Claims (7)

In the method for cleaning an atmospheric pressure plasma processing apparatus in which a gas is supplied and filled in the discharge space of the atmospheric pressure plasma processing apparatus, and plasma is generated by a high frequency electric field,
90-99.9 volume% of the composition of the gas is the discharge gas,
The discharge gas is at least one gas selected from He, Ne, Ar, Kr, Xe and N ₂ ,
Other surface treatment gas (cleaning _{gas), COF 2, F 3 NO} , CF 3 OF, C 2 F 6, F 2, SiF 4, BCl 3, C 4 F 8, C 3 F 4, CHF 3, CF ₄ , CF ₃ Cl, CF ₃ Br, CCl ₄ , NF ₃ and SF ₆ are used, and O ₂ , H ₂ , H ₂ O, CO ₂ and CO are added as additive gases,
The method for cleaning an atmospheric pressure plasma processing apparatus is characterized in that the flow of the discharge gas is opposite to the flow of the gas during the thin film forming electric discharge machining. The high-frequency electric field is a superposition of a first high-frequency electric field and a second high-frequency electric field;
The frequency ω _{2 of the second} high frequency electric field is higher than the frequency ω _{1 of the first} high frequency electric field,
The first high-frequency electric field strength V ₁ is greater than the _second high-frequency electric field strength V ₂ ,
The method for cleaning an atmospheric pressure plasma processing apparatus according to claim 1, wherein the output density of the second high-frequency electric field is 1 W / cm ² or more. The method for cleaning an atmospheric pressure plasma processing apparatus according to claim 1, wherein the discharge space includes a first electrode and a second electrode that face each other. 4. The cleaning method for an atmospheric pressure plasma processing apparatus according to claim 2, wherein the first high-frequency electric field and the second high-frequency electric field are sine waves. 5. The method for cleaning an atmospheric pressure plasma processing apparatus according to claim 3, wherein the first high-frequency electric field is applied to the first electrode, and the second high-frequency electric field is applied to the second electrode. . The method for cleaning an atmospheric pressure plasma processing apparatus according to any one of claims 1 to 5, wherein the discharge gas is supplied or exhausted to flow into and out of a discharge space. An atmospheric pressure plasma processing apparatus. 6. The method for cleaning an atmospheric pressure plasma processing apparatus according to claim 1, wherein the discharge gas flows into and out of the discharge space from a direction opposite to that during thin film formation during cleaning. An atmospheric pressure plasma processing apparatus.

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