JP2010261059A - Film-forming method and film-forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film-forming apparatus which employs an arc as a plasma source, and can form a thin film of high quality at a high film-forming rate, while reducing the number of macroparticles which deposit on the surface to be film-formed, and to provide a film-forming method. <P>SOLUTION: The plasma which has been generated in a plasma-generating section 10 enters a plasma-separating section 20. The traveling direction is curved there by a magnetic field generated by a coil 23 for generating the oblique magnetic field. Then, the plasma enters a film-forming chamber 50 through a plasma-transporting section 40. On the other hand, the macroparticles which have been generated by arc discharge are not affected so much by the magnetic field, and accordingly move straight through the plasma-separating section 20 and are captured by a particle-trapping section 30. The plasma-transporting section 40 is divided into two electric-field filter portions 40a and 40b which are electrically insulated from each other, along a flow passage of the plasma. The voltage of -20 V, for instance, is applied to the electric-field filter portion 40a in a plasma-separating section 20 side and the voltage of -5 V, for instance, is applied to the electric-field filter portion 40b in a film-forming chamber 50 side. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a film forming method and a film forming apparatus suitable for forming a protective film for protecting the surface of a magnetic recording medium used in a magnetic recording apparatus and the tip of a magnetic head.

  In recent years, magnetic recording devices (hard disk drives) have come to be used not only for computers but also for video recording devices such as hard disk video recorders, portable music playback devices, and the like. Accordingly, there is a demand for further downsizing and increasing capacity of the magnetic recording apparatus.

  In a magnetic recording apparatus, data is recorded by magnetizing a recording layer of a disk-shaped magnetic recording medium (magnetic disk) rotating at high speed with a magnetic head. A protective film is provided on the recording layer in order to protect the recording layer from physical and chemical damage. Usually, a diamond-like carbon film (hereinafter referred to as “DLC film”) formed by a CVD (Chemical Vapor Deposition) method is used as a protective film of a magnetic recording medium.

  In recent years, further improvement in the recording density of magnetic recording media has been desired. For this purpose, it is essential to reduce the distance (magnetic spacing) between the recording layer of the magnetic recording medium and the magnetic head, and further reduction in the thickness of the protective film is required.

At present, the thickness of the DLC film formed as a protective film on the surface of the magnetic recording medium is about 4 nm, and is formed by the CVD method as described above. However, in the CVD method, when an attempt is made to form a DLC film having a thickness of 4 nm or less, the variation in the film thickness becomes large and the reliability of the protective film decreases. Therefore, in recent years, it has been proposed to form a DLC film on the surface of a magnetic recording medium using an FCA (Filtered Cathodic Arc) method using an arc as a plasma source. In the DLC film formed by the FCA method, since the ratio of the sp ³ bonding component to the sp ² bonding component is high, the hardness is higher than that of the DLC film formed by the CVD method. In addition, the FCA method has better DLC film coverage than the CVD method, and even if the thickness of the DLC film is 3.5 nm or less, the reliability as a protective film is not impaired. Hereinafter, an apparatus for forming a film by the FCA method is referred to as an FCA film forming apparatus.

  By the way, in the FCA method, since an arc is used as a plasma source, it is difficult to suppress the generation of macro particles (fine particles having a diameter of 0.01 to several hundred μm). For this reason, macro particles adhere to the surface of the magnetic recording medium when the protective film is formed. When the magnetic recording medium to which the macro particles are attached in this way is used in the magnetic recording apparatus, the magnetic head may come into contact with the macro particles during data recording or reproduction, and the magnetic head may be damaged.

  Therefore, it is also conceivable to remove the macro particles by polishing or the like after forming the protective film (DLC film). However, if macro particles adhering to the protective film are removed by polishing, the macro particles detached from the protective film during polishing will rub against the protective film and become wrinkled, or a dent will appear on the traces of the macro particles being detached. The reliability as a film is significantly reduced.

  In order to solve the above problems, for example, an FCA film forming apparatus that separates plasma and macroparticles by bending the plasma traveling direction using an oblique magnetic field (magnetic field filter) generated by an oblique magnetic field generating coil has been proposed. .

JP 2002-25794 A JP 2005-72175 A

  However, although the above-described FCA film forming apparatus using the magnetic field filter can reduce the number of macro particles adhering to the film forming surface, the film forming rate is reduced. For this reason, it takes time to form the protective film, which causes an increase in product cost.

  In view of the above, an object is to provide a film forming method and a film forming apparatus capable of forming a high-quality thin film at a high film forming rate while using an arc as a plasma source and reducing the number of macro particles adhering to the film forming surface. And

  According to one aspect, a plasma generation unit that generates plasma by arc discharge, a plasma separation unit connected to the plasma generation unit, a particle trap unit connected to the plasma separation unit, and a film on which a substrate is placed Film formation using a film forming apparatus having a chamber and a plurality of electric field filter portions arranged along a plasma flow path, and having a plasma transport portion connecting between the plasma separation portion and the film formation chamber A method of generating a plasma in the plasma generator, and flowing the plasma generated in the plasma generator into the plasma separator, and applying a magnetic field to the plasma flow path in the plasma separator The direction of plasma travel is bent to separate the macro particles toward the particle trap and the plasma toward the deposition chamber. In the plasma transport unit, a negative voltage is applied to the electric field filter unit closest to the plasma separation unit among the plurality of electric field filter units, and a voltage lower than a voltage applied to the other electric field filter units is applied. There is provided a film forming method comprising the steps of transporting the plasma to the film forming chamber and forming a film by depositing ions contained in the plasma on the substrate in the film forming chamber. .

  According to the above aspect, the plasma is transported to the film forming chamber through the plasma transport section including the plurality of electric field filter sections arranged along the plasma flow path. A negative voltage that is lower than the voltage applied to the other electric field filter units is applied to the electric field filter unit closest to the plasma separation unit. As a result, the positively charged macro particles entering the plasma transport portion are attracted to the electric field filter portion, and the macro particles are removed from the plasma.

  In addition, since the electric field filter unit closest to the plasma separation unit is applied with a negative voltage that is lower than the voltage applied to the other electric field filter units, ions in the plasma are accelerated as described later. The This improves the rate at which ions are deposited on the substrate, that is, the film formation rate.

FIG. 1 is a schematic diagram showing a film forming apparatus according to an embodiment. FIG. 2 is a schematic diagram showing the transporting part of the film forming apparatus. FIG. 3 is a schematic view of a plasma transport portion in the film forming method of Example 2. FIG. 4 is a diagram showing the relationship between the potential difference between the first and second electric field filter sections and the film formation rate. FIG. 5 is a schematic view of a plasma transport portion in the film forming methods of Comparative Examples 2 to 4. FIG. 6 is a diagram collectively showing the film formation rate and the number of macro particles in Examples 1 and 2 and Comparative Examples 1 to 4.

  Hereinafter, embodiments will be described with reference to the accompanying drawings.

(Deposition system)
FIG. 1 is a schematic diagram illustrating a film forming apparatus (FCA film forming apparatus) according to an embodiment. As shown in FIG. 1, the film forming apparatus according to this embodiment includes a plasma generation unit 10, a plasma separation unit 20, a particle trap unit 30, a plasma transport unit 40, and a film formation chamber 50. ing. The plasma generation unit 10, the plasma separation unit 20, and the particle trap unit 30 are all formed in a cylindrical shape, and the plasma generation unit 10, the plasma separation unit 20, and the particle trap unit 30 are arranged and connected on a straight line in this order. .

  The plasma transport unit 40 is also formed in a cylindrical shape, and one end side thereof is connected to the plasma separation unit 20 substantially perpendicularly, and the other end side is connected to the film forming chamber 50. In the film formation chamber 50, a stage (not shown) on which a substrate (base body) 51 to be formed is placed is provided.

  Hereinafter, each part of the film forming apparatus will be described in more detail. An insulating plate 11 is disposed at the lower end of the casing of the plasma generating unit 10, and a target (cathode) 12 is disposed on the insulating plate 11. Further, a cathode coil 14 is provided on the outer side of the lower end of the casing of the plasma generator 10, and an anode 13 is provided on the inner wall surface of the casing. At the time of film formation, a predetermined voltage is applied between the target (cathode) 12 and the anode 13 from a power source (not shown) to generate arc discharge, and plasma is generated above the surface of the target 12. In addition, a predetermined current is supplied from the power source to the cathode coil 14, and a magnetic field that stabilizes arc discharge is generated from the cathode coil 14.

  Since the target molecule evaporates and supplies the film forming material into the plasma, the target 12 needs to be formed of a material containing the film forming material. In the present embodiment, since a DLC film is formed on the substrate 51, carbon graphite is used as the target 12. The plasma generating unit 10 includes a trigger electrode for applying a voltage that triggers arc discharge, but the illustration thereof is omitted in FIG. The plasma generator 10 is provided with a gas supply port (not shown) for supplying a reactive gas or an inert gas into the plasma generator 10 as necessary.

  As shown in FIG. 1, the plasma separation unit 20 has a smaller diameter than the plasma generation unit 10. Further, an insulating member 21 is provided at a boundary portion between the plasma generation unit 10 and the plasma separation unit 20. The insulating member 21 electrically separates the plasma generator 10 and the plasma separator 20.

  Guide coils 22a and 22b for generating a magnetic field for moving the plasma generated by the plasma generation unit 10 in a predetermined direction while converging the plasma generated by the plasma generation unit 10 to the center of the case are provided on the outer periphery of the case of the plasma separation unit 20. Yes. In addition, an oblique magnetic field generating coil 23 that generates a magnetic field (hereinafter referred to as “an oblique magnetic field”) that bends the traveling direction of the plasma by approximately 90 ° is provided at a branch portion between the particle trap unit 30 and the plasma transport unit 40. .

  Macro particles generated by the plasma generation unit 10 go straight into the particle trap unit 30 without being affected by the oblique magnetic field of the plasma separation unit 20. At the upper end of the particle trap section 30, a particle capturing member 31 composed of a plurality of inclined plates that capture macro particles is disposed.

  The plasma transport unit 40 includes a first electric field filter unit 40a on the plasma separation unit 20 side and a second electric field filter unit 40b on the film forming chamber 50 side. Between the plasma separation unit 20 and the first electric field filter 40a, between the first electric field filter 40a and the second electric field filter 40b, and between the second electric field filter 40b and the film forming chamber 50, respectively, by insulating members 43. Electrically separated. Further, on the inner wall surfaces of the first electric field filter 40a and the second electric field filter 40b, a particle capturing member 42 made of a plurality of inclined plates for capturing macro particles that have entered the plasma transport unit 40 is provided.

  A guide coil 41 that generates a magnetic field that moves the plasma separated by the plasma separation unit 20 toward the film forming chamber 50 while converging the plasma separated by the plasma separation unit 20 to the center of the casing is provided on the outer periphery of the plasma transport unit 40. In FIG. 1, the guide coil 41 is provided around the second electric field filter portion 40b. However, the guide coil 41 may be provided on the first electric field filter 40a side. Moreover, the guide coil 41 may be provided in both the 1st electric field filter part 40a and the 2nd electric field filter part 40b.

  As shown in FIG. 2, a negative first voltage is applied to the first electric field filter unit 40a from the power source 44a, and a second electric potential higher than the first voltage from the power source 44b is applied to the second electric field filter unit 44b. Is applied. The first voltage needs to be negative, but the second voltage may be negative or positive. However, the potential difference between the first voltage and the second voltage is preferably 10 V or more. The second voltage is preferably + 5V or less. Here, the first voltage is set to −20V, and the second voltage is set to −5V.

  As described above, the film formation chamber 50 is provided with a stage (not shown) on which the substrate 51 is placed. The substrate 51 is arranged with its surface (film formation surface) facing in the direction in which plasma flows. Note that the stage may be provided with a mechanism for tilting the substrate 51 with respect to the plasma inflow direction and a mechanism for rotating the substrate 51. Further, a vacuum apparatus (not shown) is connected to the film forming chamber 50, and the internal space of the film forming apparatus can be maintained at a predetermined pressure by this vacuum apparatus. As the substrate 51, a magnetic recording medium substrate on which a recording layer (magnetic layer) is previously formed, a magnetic head substrate on which a recording element and a reproducing element (MR element, etc.) are formed, or the like can be used.

(Film formation method)
Hereinafter, a method of forming a DLC film using the film forming apparatus according to this embodiment having the above-described structure will be described.

When a DLC film is formed on the substrate 51, a carbon graphite target is used as the cathode. And a vacuum apparatus is operated and the pressure in the film-forming apparatus is maintained at 10 < ^-5 > Pa-10 < ^-3 > Pa. Further, for example, plasma is generated under the conditions of an arc current of 60 A, an arc voltage of 30 V, and a cathode coil current of 10 A.

  The plasma generated by the plasma generation unit 10 enters the plasma separation unit 20, and moves to the branching unit by the magnetic field generated by the guide coils 22a and 22b. Then, the traveling direction is suddenly bent by the oblique magnetic field generated by the oblique magnetic field generating coil 23 and enters the plasma transport unit 40. An arrow A in FIG. 1 indicates the moving direction of the plasma whose traveling direction is bent toward the film forming chamber 50 by the oblique magnetic field generated by the oblique magnetic field generating coil 23.

  On the other hand, since the macro particles generated by the arc discharge in the plasma generation unit 10 have no charge or only a very small charge with respect to the weight, the magnetic particles generated by the guide coils 22a and 22b and the oblique magnetic field generation coil 23 are reduced. Go straight with almost no influence. Then, the particles are captured by the particle capturing member 31 in the particle trap unit 30. An arrow B in FIG. 1 indicates the moving direction of the macro particle.

  Some of the macro particles having electric charges enter the plasma transport unit 40 with the traveling direction being bent by the oblique magnetic field generated by the oblique magnetic field generating coil 23. In addition, some of the macro particles reflected by the wall surfaces of the plasma generation unit 10 and the plasma separation unit 20 also enter the plasma transport unit 40.

  The plasma that has entered the plasma transport unit 40 is transported to the film forming chamber 50 by the guide coil 41. In the plasma transport unit 40, positively charged macro particles are attracted and captured by the particle capturing member 42 by the first electric field filter unit 40 a and the second electric field filter unit 40 b to which a negative voltage is applied. In addition, macro particles that move in the direction of the film forming chamber 50 while reflecting the wall surface of the housing are also captured by the particle capturing member 42.

  In this way, most of the macro particles that have entered the plasma transport section 40 are captured by the particle capturing member 42 provided on the inner surface of the plasma transport section 40.

  On the other hand, the plasma that has entered the plasma transport unit 40 is accelerated by the voltage applied to the first electric field filter 40a and the second electric field filter 40b, and is guided by the magnetic field generated by the guide coil 41 to enter the film forming chamber 50. Moving. Then, carbon contained in the plasma is deposited on the surface of the substrate 51 to form a DLC film.

  In this way, a high quality DLC film containing almost no macro particles can be formed on the surface of the substrate 51. When a DLC film is formed as a protective film for a magnetic recording medium or a magnetic head, it is preferable that the thickness of the DLC film is 3.5 nm or less in order to reduce the magnetic spacing.

(Experiment)
Below, the result of having investigated the relationship between the voltage applied to the 1st electric field filter part 40a and the 2nd electric field filter part 40b, and the film-forming rate of a DLC film is demonstrated.

  First, a plurality of substrates made of an aluminum alloy having a diameter of 2.5 inches (about 65 mm) was prepared. On these substrates, a base film made of a Cr alloy with a thickness of 20 nm and a CoCrPtTa alloy with a thickness of 3 nm (Co: 67%, Cr: 20%, Pt: 10%, Ta: 3%) and a multilayer film including a CoCrPtB alloy film (Co: 60%, Cr: 25%, Pt: 14%, B: 6%) having a thickness of 10 nm.

  Next, using carbon graphite as a target, a DLC film having a thickness of about 3.0 nm was formed on the substrate (on the Co metal film). At this time, a voltage of −20V is applied to the first electric field filter unit 40a of the plasma transport unit 40, and voltages applied to the second electric field filter unit 40b are −20V, −15V, −12V, −10V, −5V. , 0V (ground potential) and + 5V. The arc current is 60A, the arc voltage is 30V, and the cathode coil current is 10A.

  FIG. 4 is a diagram showing the relationship between the voltage applied to the first electric field filter unit 40a and the voltage applied to the second electric field filter unit 40b on the horizontal axis and the film formation rate on the vertical axis. It is. FIG. 4 shows that the film formation rate can be increased to 0.19 nm / sec or more by setting the potential difference between the first electric field filter section 40a and the second electric field filter section 40b to 10 V or more. In addition, it can be seen from FIG. 4 that the film formation rate hardly changes even when the potential difference between the first electric field filter unit 40a and the second electric field filter unit 40b is 20 V or more.

  The voltage applied to the first electric field filter 40a needs to be negative from the viewpoint of removing positively charged macro particles. Although the reason why the film formation rate is improved by applying a potential difference of 10 V or more between the first electric field filter 40a and the second electric field filter 40b is not clear, it can be considered as follows.

  That is, the plasma that has entered the plasma transport path 40 contains electrons and carbon ions. When a voltage higher than that of the first electric field filter unit 40a is applied to the second electric field filter unit 40b, electrons in the plasma are accelerated by a potential difference between the first electric field filter unit 40a and the second electric field filter unit 40b. Following the movement of the electrons, the carbon ions are also accelerated, and the amount of carbon ions reaching the film forming chamber 50 per unit time increases. As a result, it is considered that the deposition rate of the DLC film is increased.

(Example)
Hereinafter, a result of actually forming a DLC film by the film forming method of the embodiment and examining the film forming rate and the number of macro particles will be described in comparison with a comparative example. In Examples 1 and 2 and Comparative Examples 1 to 4 below, conditions such as arc current, arc voltage, and pressure during film formation are the same as the conditions during the above-described experiment.

  As a substrate, a disk having a base layer (Cr) and a Co alloy layer formed on an aluminum alloy plate having a diameter of 2.5 inches (about 65 mm) was prepared. Then, as Example 1, the film forming apparatus shown in FIG. 1 is used, and as shown in FIG. 2, a negative voltage is applied to both the first electric field filter unit 40a and the second electric field filter unit 40b to form a DLC film. Formed. That is, the voltage applied to the first electric field filter 40a (voltage of the power supply 44a) is −20V, the voltage applied to the second electric field filter 40b (voltage of the power supply 44b) is −5V, and the DLC film is about 3 nm on the substrate. Formed to a thickness.

  Further, as Example 2, the film forming apparatus shown in FIG. 1 is used, and a negative voltage is applied to the first electric field filter unit 40a and a positive voltage is applied to the second electric field filter unit 40b as shown in FIG. Thus, a DLC film was formed. That is, the voltage applied to the first electric field filter 40a (voltage of the power supply 44a) is −20V, the voltage applied to the second electric field filter 40b (voltage of the power supply 44b) is + 5V, and the DLC film is about 3 nm thick on the substrate. Formed.

  On the other hand, as Comparative Example 1, the film forming apparatus shown in FIG. 1 is used, the voltage applied to the first electric field filter 40a is + 5V, the voltage applied to the second electric field filter 40b is + 20V, and the DLC film is approximately formed on the substrate. It was formed to a thickness of 3 nm.

  Further, as Comparative Example 2, a film forming apparatus having the same structure as the film forming apparatus shown in FIG. 1 is used except that the plasma transport part 50 is integrally formed as shown in FIG. A voltage of +15 V was applied to the (electric field filter part 40c) from the power supply 44c to form a DLC film on the substrate with a thickness of about 3 nm.

  Further, as Comparative Example 3, a film forming apparatus similar to that of Comparative Example 2 is used, a voltage of +40 V is applied from the power source 44c to the plasma transport unit 50 (electric field filter unit 40c), and a DLC film is formed on the substrate by about 3 nm. The thickness was formed.

  Furthermore, as Comparative Example 4, the same film forming apparatus as in Comparative Example 2 was used, and a voltage of −15 V was applied from the power source 44 c to the plasma transport unit 50 (electric field filter unit 40 c) to form a DLC film on the substrate. A thickness of about 3 nm was formed.

  With respect to the substrates of Examples 1 and 2 and Comparative Examples 1 to 4, the relationship between the film formation time and the average film thickness was examined, and the film formation rate was calculated. The average film thickness is measured by cross-sectional observation using a transmission electron microscope (TEM). Further, the number of macro particles when the thickness of the DLC film was 3.0 nm was measured using an optical surface analyzer (OSA). These results are summarized in FIG.

  From FIG. 6, it can be seen that the number of macro particles is 70 in Example 1, and the number of macro particles is 76 in Example 2, both of which have a small number of particles. In addition, it can be seen that the film formation rate of Example 1 is 0.2 nm / sec and the film formation rate of Example 2 is 0.22 nm / sec, and a high film formation rate is obtained. In the case of a 2.5 inch disk, the number of macro particles on the film formation surface should be 100 or less.

  On the other hand, in Comparative Example 1 in which a positive voltage was applied to both the first and second electric field filter sections, the film formation rate was as high as 0.2 nm / sec, but the number of macro particles was as large as 200. It was.

  In addition, Comparative Example 2 in which a voltage of +15 V is applied to the integrally formed plasma transport portion and Comparative Example 3 in which a voltage of +40 V is applied have a high film formation rate but a large number of particles. Further, in Comparative Example 4 in which a voltage of −15 V was applied to the integrally formed plasma transport part, although the number of particles was as small as 70, the film formation rate was extremely slow as 0.05 nm / sec.

  In the above-described embodiment, the case where the DLC film is formed on the substrate 51 has been described. However, the application of the film forming apparatus according to the present invention is not limited to the formation of the DLC film. Of course, the film forming apparatus can be used to form films made of various materials.

  In the above-described embodiment, the case where two electric field filter units (electric field filters 40a and 40b) are provided in the plasma transport unit 40 has been described. However, three or more electric field filter units are provided in the plasma transport unit 40. May be. In that case, the lowest voltage may be applied to the electric field filter section closest to the plasma generating section.

  DESCRIPTION OF SYMBOLS 10 ... Plasma generating part, 11 ... Insulating plate, 12 ... Target (cathode), 13 ... Anode, 14 ... Cathode coil, 20 ... Plasma separation part, 21 ... Insulating member, 22a, 22b, 41 ... Guide coil, 23 ... Diagonal Magnetic field generating coil, 30 ... Particle trap part, 31,42 ... Particle trapping member, 40 ... Plasma transport part, 40a-44c ... Electric field filter part, 43 ... Insulating member, 44a-44c ... Power source, 50 ... Deposition chamber, 51 …substrate.

Claims (6)

A plasma generator for generating plasma by arc discharge; a plasma separator connected to the plasma generator; a particle trap connected to the plasma separator; a film forming chamber on which a substrate is placed; and a plasma flow A film forming method using a film forming apparatus including a plurality of electric field filter units arranged along a path, and having a plasma transport unit connecting between the plasma separation unit and the film forming chamber,
Generating plasma in the plasma generator;
The plasma generated in the plasma generating unit is caused to flow into the plasma separating unit, and a magnetic field is applied to the plasma flow path in the plasma separating unit to bend the traveling direction of the plasma, and the macro particles toward the particle trap unit and the particles Separating the plasma into the deposition chamber;
In the plasma transport part, the plasma is applied while applying a negative voltage to the electric field filter part closest to the plasma separation part among the plurality of electric field filter parts and a voltage lower than the voltage applied to the other electric field filter parts. Transporting to the deposition chamber;
Forming a film by depositing ions contained in the plasma on the substrate in the film forming chamber.   2. The film forming method according to claim 1, wherein a voltage applied to an electric field filter unit closest to the plasma separation unit among the plurality of electric field filter units is −15 V or less.   Among the plurality of electric field filter units, the voltage applied to the electric field filter unit farthest from the plasma separation unit is 10 V or more than the voltage applied to the electric field filter unit closest to the plasma separation unit among the plurality of electric field filter units. The film forming method according to claim 1, wherein a high voltage is used.   4. The film forming method according to claim 1, wherein a diamond-like carbon film is formed on the substrate.   5. The film forming method according to claim 1, wherein a voltage applied to an electric field filter unit farthest from the plasma separation unit among the plurality of electric field filter units is set to +5 V or less. A plasma generator for generating plasma by generating an arc discharge between the target and the anode;
A plasma separation unit that separates plasma and macroparticles by bending a flow path of plasma that has entered from the plasma generation unit with a magnetic field;
A particle trap section for capturing the macro particles separated by the plasma separation section;
A film forming chamber in which a base is disposed, and ions contained in the plasma separated by the plasma separation unit are deposited on the base to form a film;
A plasma transport unit for transporting the plasma separated by the plasma separation unit to the film forming chamber;
A power source for applying a voltage to the plasma transport part,
The plasma transport unit includes a plurality of electric field filter units arranged along the plasma flow path, and the power source has a negative voltage applied to an electric field filter unit closest to the plasma generation unit among the plurality of electric field filter units. A film forming apparatus that applies a voltage lower than a voltage applied to another electric field filter unit.

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