JP2016176127A - Film deposition apparatus, and deposition method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film deposition apparatus capable of filming even a processing object such as powder efficiently by a plasma CVD method.SOLUTION: A film deposition apparatus (M) of the present invention comprises a hollow electrode (21) arranged in a chamber constituting a closed space. The hollow electrode has a hollow housing part of a bottomed hollow shape capable of accommodating a processed product, and an aperture communicating the inside and the outside of the housing part. Since no counter electrode is arranged in the housing part, a hollow cathode discharge occurs at the hollow electrode, when a negative voltage is applied to the hollow electrode, so that a plasma of a high density is established. According the film deposition apparatus of the invention, therefore, the firm formation by a plasma CVD method can be efficiently performed. In the case where the processed product is granular, on the other hand, the hollow electrode is rotated so that the plasma CVD processing may be performed while performing the agitation. In this case, a DC pulse power source or the like may be used as the plasma power source.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a film forming apparatus and a film forming method capable of efficiently forming a film on an object to be processed by a plasma CVD method.

  In order to improve the corrosion resistance, wear resistance, slidability, designability, etc. of the member, the surface of the member is often covered with a thin film such as a DLC film or a TiN film. For such thin film formation (film formation), a PVD (Physical Vapor Deposition) method or a CVD (Chemical Vapor Deposition) method is used. However, a CVD method capable of efficiently forming a thin film with a uniform thickness is widely used for members having various shapes. Among them, the plasma CVD method, which can be processed at a relatively low temperature and can form a dense thin film having various compositions, is often used.

  Although there are various plasma generation methods, CVD using general CCP (Capacitively Coupled Plasma) is usually performed as follows. A plate-like anode electrode and cathode electrode are placed facing each other in a vacuum chamber, and the source gas supplied from the anode electrode side is turned into plasma by (glow) discharge between the electrodes, and various plasma particles are mounted on the cathode electrode. It is deposited (evaporated) on the surface of the workpiece to be placed.

  Such a general plasma CVD method is intended to form a film on the surface of an appropriately sized member, a bulk material, etc., and is a granular material such as particles or small items (screws) or an aggregate thereof (powder). Etc.). Therefore, the following patent document proposes a plasma CVD method capable of forming a film evenly even if the object to be processed is powder particles or the like.

JP 2003-13229 A JP 2014-157760 A

  In both Patent Document 1 and Patent Document 2, plasma is generated between a cylindrical cathode electrode (vacuum chamber) containing powder or the like and an anode electrode (counter electrode) disposed opposite to the center of the vacuum chamber. The CVD process is performed while rotating the cathode electrode. In this case, since the object to be processed (powder or the like) is CVD-treated while being stirred in the cathode electrode, a uniform film can be formed even on fine particles.

  However, when a film is formed on the surface of countless fine particles, the total surface area of the film is much larger than a bulk material having the same mass. For this reason, even if the apparatus and method described in these patent documents are used, as long as the CVD process is performed using the plasma generated based on the same principle as in the past, a bulk film can be formed on a powder or the like. Compared with the case where a film is formed on a material or the like, a much longer processing time is required, and an efficient processing is difficult.

  The present invention has been made in view of such circumstances, and even when the object to be processed is granular and the film formation area by CVD is substantially increased, uniform film formation is efficiently performed. It is an object of the present invention to provide a film forming apparatus and a film forming method that can be used.

  The present inventor has intensively studied to solve this problem, and as a result of repeated trial and error, the conventional plasma CVD method is different from the conventional plasma CVD method, and the idea is that CVD processing is performed using plasma generated by hollow cathode discharge, We succeeded in embodying this idea. By developing this result, the present invention described below has been completed.

<Film deposition system>
(1) A film forming apparatus according to the present invention is a film forming apparatus that forms a film by a plasma CVD method on the surface of an object to be processed in a chamber that forms a sealed space, and has a bottom that can accommodate the object to be processed. A hollow electrode having a hollow housing portion and an opening communicating with the inside and the outside of the housing portion is provided, and a counter electrode is not disposed in the housing portion, and plasma can be generated by hollow cathode discharge. .

(2) According to the film forming apparatus of the present invention, the plasma density in the hollow electrode can be increased by hollow cathode discharge, and film formation by plasma CVD can be efficiently performed on the object to be processed in the housing portion of the hollow electrode. Yes. For this reason, if the film forming apparatus of the present invention is used, the plasma CVD process is performed even on an object to be processed (for example, a granular material) having a large ratio of surface area (film forming area) to mass (referred to as “specific surface area” as appropriate). The time (deposition time) can be shortened, and as a result, the production cost of a product coated with a thin film can be reduced.

(3) Incidentally, the reason why the plasma density in the hollow electrode (hollow cathode) becomes larger than the plasma density between the parallel plate electrodes is considered as follows. When the hollow electrode is a cathode (cathode), secondary electrons emitted from the cathode surface inside the hollow electrode are caused by the sheath (single polarity charged particle layer formed near the electrode surface in contact with the plasma phase). It is accelerated in the direction of the inner facing cathode surface (in the radial direction if the accommodating portion is cylindrical or spherical). At this time, if the mean free path is sufficiently long (longer than the diameter if the accommodating portion is cylindrical or spherical), the secondary electrons approach the opposing cathode surface.

  However, if the sheath thickness is smaller than or approximately equal to ½ of the distance between the opposing cathode surfaces (the radius if the accommodating portion is cylindrical or spherical), the secondary electrons are on the opposing cathode surface. It loses kinetic energy in the sheath on the front side, is reflected, and is accelerated toward the original cathode surface. As a result of repeated occurrence of such a phenomenon in the hollow electrode, high-energy and long-life electrons are confined in the hollow electrode, and the number of ionization increases in the hollow electrode, resulting in a hollow plasma with high plasma density. It is thought that cathode discharge occurs.

<Film formation method>
The present invention can be grasped not only as the film forming apparatus described above but also as the following film forming method. That is, the present invention may be a film forming method characterized by including a film forming process in which plasma is generated by hollow cathode discharge in a chamber constituting a sealed space and a film is formed on a workpiece by a plasma CVD method. The film forming method of the present invention can of course be carried out using the film forming apparatus described above, but is not limited (limited) in that case.

  In addition, the film forming method of the present invention can target various objects to be processed. However, when the object to be processed is a granular material, the film forming process according to the present invention involves an agitation step of stirring the granular material. Is preferable. Thereby, uniform film formation can be efficiently performed even on granular materials. The stirring step may be intermittently performed, but it is preferable that the stirring step be continuously performed during the film formation because a more uniform film formation is possible.

<Others>
(1) The film forming apparatus of the present invention is greatly different from the conventional plasma CVD apparatus in that the counter electrode (anode electrode) is not included in the hollow electrode. However, the counter electrode is not essential for the film forming apparatus of the present invention. This is because various plasma sources () can be used as long as hollow cathode discharge occurs in the hollow electrode. For example, besides CCP, ECP (Electron Cyclotron Resonance Plasma), HWP (Helicon Wave Plasma), ICP (Inductively Coupled Plasma), SWP (Surface Wave Plasma): Microwave excitation surface wave plasma) can be used, and the presence or absence of the counter electrode depends on the type of plasma source.

(2) Unless otherwise specified, “x to y” in this specification includes a lower limit value x and an upper limit value y. A range such as “a to b” can be newly established with any numerical value included in various numerical values or numerical ranges described in the present specification as a new lower limit value or upper limit value.

It is a schematic diagram which shows one Example of the film-forming apparatus. It is a half sectional view showing a container used as a hollow electrode. It is a top view which shows the hemisphere which comprises the container. It is the figure which showed typically the discharge (plasma production | generation) which arises in a hollow electrode. This is a picture of the situation. It is the figure which showed typically the discharge (plasma production | generation) which arises in an open electrode. This is a picture of the situation. It is an emission analysis result when carrying out plasma CVD processing using a hollow electrode and an open electrode, respectively.

  One or two or more components arbitrarily selected from the present specification may be added to the above-described components of the present invention. The contents described in this specification can be appropriately applied not only to the film forming apparatus of the present invention but also to the film forming method. Even a method component can be a physical component. A component related to a method can be a component related to an object if understood as a product-by-process claim. Which embodiment is the best depends on the target, required performance, and the like.

<< Hollow electrode >>
The hollow electrode according to the present invention includes an accommodating portion and an opening. The accommodating portion may be of any specific shape as long as it has a bottomed hollow shape capable of accommodating an object to be processed and is capable of hollow cathode discharge. The accommodating portion can take various forms such as a bottomed cylindrical shape, an open spherical shape, and an open shell shape. In any case, the housing portion may have a shape in which the inner wall surfaces (electrode surfaces) face each other except for the opening portion. Further, the inner wall surface of the housing portion is formed in a smooth curved surface with few corners, and when there is a connection portion between the side surface and the bottom surface, the corner portion is preferably rounded. As a result, it is possible to prevent the discharge from being concentrated on a part, and it is easy to obtain a stable hollow cathode discharge.

  The opening can be used not only for putting the object to be processed into and out of the container, but also for exhausting the container and supplying air to the container. As long as the to-be-processed object in process is stably hold | maintained in an accommodating part, an opening part does not ask | require the form, arrangement | positioning, magnitude | size, etc. For example, the opening is a hole or the like opened on the upper side (horizontal position to vertically above) with respect to the arrangement of the hollow electrode being processed.

<Film deposition system>
(1) In order to perform plasma CVD, the film forming apparatus according to the present invention includes an air supply means for supplying various gases (source gas, carrier gas, etc.) into the chamber, plasma generation (hollow), in addition to the chamber and the hollow electrode. A power supply circuit for supplying electric power necessary for cathode discharge) or a supply source of such electric power is appropriately provided. In some cases, atmospheric pressure plasma is used, but generally, plasma (vacuum plasma) generated in a reduced pressure atmosphere is often used, and therefore it is preferable that there is an exhaust means for exhausting (reducing pressure) the chamber.

  A DC power source, a high frequency power source, a pulse power source, or the like can be used as a power source (plasma power source) during film formation. However, an object to be processed having a large specific surface area (or light weight) such as powder particles may float due to charging during the process, and stable plasma generation and film formation may be difficult. In such a case, when film formation is performed by high-frequency energization or pulse energization (particularly DC pulse energization), stable film formation becomes possible. Therefore, it is preferable that the power supply means for supplying electric power for generating plasma in the chamber comprises a high frequency power supply circuit or a pulse power supply circuit. The pressure can be adjusted as appropriate depending on the object to be processed, the raw material gas, the internal pressure of the chamber, etc. For example, when a DC pulse is applied to a hollow electrode containing a granular material (particularly powder), applied voltage: 300 to 3000 V, further 400 to 600 V, Frequency: 5 kHz to 350 kHz, further 50 kHz to 150 kHz, pause time: 0.4 to 5 μs, further 0.5 to 2 μs may be used.

(2) In order to perform uniform film formation on the object to be processed, it is preferable that the film forming apparatus of the present invention includes a changing means for changing the posture of the object to be processed in the accommodating portion. Various fluctuating means may be considered, and an appropriate means may be selected according to the object to be processed. For example, when the object to be processed is a granular material such as a powder, the fluctuation means uses an oscillating means for imparting vibration or swinging to the object to be processed or an agitating means for moving or rolling the object to be processed. be able to.

  However, an object to be processed (powder or the like) having a large specific surface area is likely to float when it is vibrated during processing, and stable film formation may be difficult. In such a case, using the rotating means that rotates the hollow electrode as the changing means, while slowly rolling the object to be processed along the inner wall surface of the container, etc. Stable film formation can be performed on various objects to be processed. The “rotation” referred to here includes not only the case where the hollow electrode rotates, but also the case where it revolves, and further includes the case where both rotation and revolution are performed. Although it can adjust suitably with a to-be-processed object etc., for example, when rotating the hollow electrode containing a granular material (especially powder), rotation speed: 0.1-10 rpm Furthermore, about 0.5-5 rpm may be sufficient.

  When the hollow electrode rotates, it is preferable that the housing portion has a stirring portion protruding from at least a part (for example, the inner bottom surface side) of the inner wall surface in contact with the object to be processed. When such a hollow electrode is used, even if the object to be processed is a granular material, more uniform film formation can be performed efficiently.

<Processed object>
The film forming apparatus or film forming method of the present invention targets various objects to be processed, and is suitable for film formation of granular materials such as powder (including abrasive powder), screws, nuts, washers, and the like. . The material of the object to be processed may be any of metal, ceramics, resin and the like. Further, even a complex object to be processed can be uniformly formed by the film forming apparatus of the present invention. Although the size of the granules is difficult to identify categorically different for each object to be processed, for example, the average mass per particle or article is 2.1 × 10 ^-6 mg~0.5g more When it is ^{4.0 × 10 -6 mg~6.0 × 10 -6} g, suitable for a plasma CVD process according to the present invention.

  A film forming apparatus provided with a hollow electrode was manufactured, and plasma CVD treatment was performed on the powder. Moreover, plasma CVD treatment was similarly performed on the powder in a film forming apparatus in which the hollow electrode was replaced with an open electrode. The state during each treatment was observed, and the influence due to the difference in electrodes was evaluated. Hereinafter, the present invention will be described in more detail with reference to such specific examples.

<Film deposition system>
(1) An outline of a film forming apparatus M which is an embodiment of the present invention is schematically shown in FIG. The film forming apparatus M includes a vacuum chamber 1, a processing mechanism unit 2, a power supply unit 3, a gas supply unit 4, and an exhaust unit 5.

  The vacuum chamber 1 is made of a conductive material (stainless steel / JIS SUS304), and the whole serves as an anode (anode electrode) when performing plasma CVD processing.

  The processing mechanism unit 2 includes a container 21 (hollow electrode) that accommodates a workpiece w (powder) and a set of bevel gears (shafts) that rotatably support the container 21 around an axis extending obliquely upward. A support body 22 having an obtuse angle (for example, 135 °), and an input shaft 23 having one end connected to one bevel gear in the support body 22 and extending vertically downward through the vacuum chamber 1. Insulation for supporting the input shaft 23 with respect to the vacuum chamber 1 while ensuring insulation and airtightness between the vacuum chamber 1 and the input shaft 23, and a rotational speed control type motor 24 that drives the input shaft 23. A bearing 25 with a vacuum seal and an insulating coupling 26 that insulates and connects the input shaft 23 and the rotating shaft of the motor 24 are provided. The container 21 and the support 22 are disposed in the vacuum chamber 1, and the motor 24 is disposed outside the vacuum chamber 1. The processing mechanism unit 2 excluding the container 21 corresponds to the rotating means (fluctuating means) in the present invention.

  The power supply unit 3 (power supply means) includes a plasma power supply circuit 30 that is supplied with power from a commercial power supply (not shown) and can apply a DC pulse voltage necessary for plasma generation between the vacuum chamber 1 and the input shaft 23. The anode 31 of the plasma power supply circuit 30 is connected to the vacuum chamber 1 and grounded (earthed), and the cathode 32 thereof is connected to the input shaft 23. Thereby, the vacuum chamber 1 becomes an anode electrode, and the container 21 through the input shaft 23 becomes a cathode electrode to which a negative voltage is applied.

  The gas supply unit 4 (air supply means) includes a gas supply shower 41 that is disposed in the vacuum chamber 1 and supplies gas into the vacuum chamber 1, a gas storage body 42 that is a gas source thereof, and a gas storage body 42. And a flow rate regulator (mass flow controller) 43 that controls the amount of gas supplied to the gas supply shower 41. The gas storage body 42 includes a gas cylinder that stores various source gases or carrier gases, or a gas generator that generates a synthesis gas as a source. The gas supply shower 41 and the flow rate regulator 43 are disposed outside the vacuum chamber 1.

  The exhaust unit 5 (exhaust means) includes an exhaust passage 51 that communicates between the inside and outside of the vacuum chamber 1, and an adjustment valve (butterfly) that adjusts the exhaust amount (the degree of vacuum in the vacuum chamber 1) by switching between communication and blocking of the exhaust passage 51. Valve) 52 and a vacuum pump 53 for exhausting the inside of the vacuum chamber 1 through the exhaust path 51 and the regulating valve 52.

(2) As shown in FIG. 2A, which is a half sectional view of the container 21, which is a hollow electrode, a hemisphere 211 having a flat disk-shaped bottom surface 211a and a hemispherical side surface 211b, and a circular opening 212a (opening) and a hemispherical cylinder 212 having a hemispherical side surface 212b. The hemispherical body 211 and the hemispherical tubular body 212 are connected by a fixture 213 made up of a bolt and a nut, with the flange surfaces projecting from the respective outer peripheral sides abutting each other. The hemisphere 211 and the hemisphere cylinder 212 are also made of a conductive material (stainless steel / JIS SUS304).

  As shown in FIG. 2B, which is a plan view of the hemisphere 211, the hemisphere 211 has a protrusion row 214 (stirring portion) protruding from the inner wall surface toward the center (center) direction along the side surface 211. The protrusion rows 214 are arranged in eight rows at the same pitch in the circumferential direction. When the container 21 rotates around the axis p, the workpiece w put into the container 21 is agitated by the projection row 214 along the inner wall surface of the hemisphere 211.

<< Plasma CVD process / film formation method >>
Using the film forming apparatus M, a plasma CVD process was performed on 20 g (pure Fe powder / particle size: 74 to 106 μm) of the powder to be processed w under the following conditions.

The container 21 (see FIG. 2A) was attached to the support 22, and the workpiece w was put into the container 21 (see FIG. 2A) to seal the vacuum chamber 1. The inside of the vacuum chamber 1 was evacuated by the exhaust unit 5 to be in a vacuum state (7 Pa). A raw material gas (hydrocarbon gas: 70 sccm, nitrogen gas (N ₂ ): 120 sccm) was supplied from the gas supply unit 4 into the vacuum chamber 1. While the container 21 was rotated (rotation speed: 1 rpm) by the processing mechanism unit 2 (stirring step), a DC pulse voltage of −600 V was applied from the power source unit 3 (pulse energization step). At this time, the pulse pause time (T) was 1.5 μsec, and the frequency was 50 kHz. This plasma CVD treatment is performed for 30 minutes (film formation step), and an SEM observation of the cross section of the powder particle (S manufactured by Hitachi High-Technologies Corporation) confirms that an amorphous carbon film of about 0.1 μm is formed on the surface of each powder particle. -4300).

<< Plasma observation >>
(1) FIG. 3A schematically shows the surroundings of the container 21 (hollow electrode) during the plasma CVD process, and a photograph of the vicinity of the opening 212a of the container 21 is shown in FIG. 3B.

  A similar plasma CVD process was performed using an open electrode in which the hemispherical cylinder 212 of the container 21 was removed and only the hemisphere 211 was formed. A state around the hemisphere 211 during this processing is schematically shown in FIG. 4B, and a photograph of the upper surface side is shown in FIG. 4B.

(2) Plasma generated when using a hollow electrode (see FIG. 3B) and plasma generated when using an open electrode (see FIG. 4B) are plasma process monitors (C10346 made by Hamamatsu Photonics). -1) was used for luminescence analysis. The results thus obtained are shown in FIG.

<Evaluation>
(1) As can be seen from a comparison between FIG. 3B and FIG. 4B, it can be seen that stronger light emission plasma is generated when the hollow electrode is used than when the open electrode is used. This is also clear from the respective emission intensities of CH (wavelength: 391.1 nm) shown in FIG. 5, and the emission intensity when using the hollow electrode is about 3 times that when using the open electrode. It was.

  Thus, it was found that by using the hollow electrode, a large plasma density can be obtained and the plasma CVD process can be performed efficiently. Further, even if the object to be processed is made of fine particles such as powder, the film can be uniformly formed on each particle by processing with stirring as in the film forming apparatus M. .

(2) The inner wall surface of the container 21 is composed of a spherical side surface and a flat surface, and the boundary between them is also connected by an arc curved surface. As described above, since the inner wall surface of the accommodating portion for the object to be processed is formed of a smooth curved surface, the discharge is prevented from being non-uniform due to potential concentration in the hollow electrode. Therefore, when a hollow electrode as in this embodiment is used, uniform and high-density plasma can be generated throughout the interior, and as a result, uniform film formation can be efficiently performed on the entire surface of a fine workpiece. Yes.

  In addition, when the object to be processed is composed of particles having a large specific surface area, if a simple DC power source is used as the plasma power source, the object to be processed floats during the CVD process, and furthermore, the suspended particles are stored in the container. When the inner wall surface is contacted again, an arc discharge may occur, and the discharge and thus the plasma generation may become unstable. In contrast, when a pulse power source is used as the plasma power source as in this embodiment, the discharge and thus the plasma generation is stabilized, and even if the object to be processed is a powder or the like, high-quality film formation is efficiently performed. obtain.

  As shown in FIG. 3A, when the plasma sheath is smaller than or substantially equal to ½ of the maximum inner diameter (diameter) of the container 21 (hollow electrode), a stable hollow cathode discharge is likely to occur, which is efficient and stable. It is possible to perform plasma CVD processing.

1 Vacuum chamber 2 Processing mechanism (rotating means)
21 Container (hollow electrode)
214 Projection row (stirring section)
3 Power supply (power supply means)
4 Gas supply section (air supply means)
5 Exhaust section (exhaust means)

Claims (8)

A film forming apparatus for forming a film by a plasma CVD method on a surface of an object to be processed in a chamber constituting a sealed space,
A hollow electrode having a bottomed hollow accommodating portion capable of accommodating the object to be processed and an opening communicating the inside and outside of the accommodating portion,
2. A film forming apparatus, wherein a counter electrode is not disposed in the housing portion and plasma can be generated by hollow cathode discharge.   Furthermore, the film-forming apparatus of Claim 1 provided with the fluctuation | variation means to fluctuate the attitude | position of the said to-be-processed object in the said accommodating part.   The film forming apparatus according to claim 2, wherein the changing unit is a rotating unit that rotates the hollow electrode.   The film forming apparatus according to claim 3, wherein the hollow electrode has a stirring portion protruding from an inner wall surface of the housing portion with which the object to be processed can come into contact. Furthermore, a power supply means for supplying electric power for generating plasma in the chamber is provided,
The film forming apparatus according to claim 1, wherein the power supply unit includes a high frequency power supply circuit or a pulse power supply circuit.   A film forming method comprising: forming a plasma by a hollow cathode discharge in a chamber constituting a sealed space and forming a film on an object to be processed by a plasma CVD method. The object to be processed is a granular material,
The film forming method according to claim 6, wherein the film forming step includes a stirring step of stirring the granular material.   The film forming method according to claim 7, wherein the film forming step is a step performed by high-frequency energization or pulse energization.