JP6543982B2 - Deposition apparatus and deposition method - Google Patents

Description

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

  In order to improve the corrosion resistance, the wear resistance, the slidability, the designability and the like 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: physical vapor deposition) method or a CVD (Chemical Vapor Deposition: 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 of various shapes. Among them, plasma CVD methods capable of processing at relatively low temperatures and capable of forming dense thin films of various compositions are widely used.

  Although there are various plasma generation methods, CVD using a general capacitively coupled plasma (CCP) is generally performed as follows. A flat anode electrode and a cathode electrode are disposed opposite to each other in a vacuum chamber, and source gas supplied from the anode electrode side is plasmified by (glow) discharge between the electrodes to mount various plasma particles on the cathode electrode. It is deposited (deposited) on the surface of the placed object to be treated.

  Such a general plasma CVD method is intended to form a film on the surface of a member or bulk material having a suitable size, and it is possible to use particulates such as particles and small parts (screws etc.) or an aggregate thereof (powder Etc.) was not suitable. Therefore, a plasma CVD method capable of uniformly forming a film even if the object to be treated is powder particles or the like is proposed in the following patent documents.

Japanese Patent Application Laid-Open No. 2003-13229 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 and 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, the object to be treated (powder or the like) is subjected to the CVD treatment while being stirred in the cathode electrode, so that uniform film formation is possible even on fine particles and the like.

  However, when forming a film on the surface etc. of innumerable fine particles, the total film forming surface area is much larger than the bulk material etc. of the same mass. For this reason, even if using the apparatus and method described in those patent documents, as long as CVD processing is performed using plasma generated on the same principle as in the prior art, it is bulk to be deposited on powder etc. As compared with the case of forming a film on a material or the like, processing for a much longer time is required, and efficient processing is difficult.

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

  As a result of extensive research and trial and error to solve this problem, the inventor of the present invention conceived of the idea of carrying out a CVD process using plasma generated by hollow cathode discharge, unlike the conventional plasma CVD method. I succeeded in realizing this idea. The development of this result has led to the completion of the invention described hereinafter.

<< Deposition apparatus >>
(1) film formation apparatus of the present invention, there is provided a film formation apparatus that performs film formation by plasma CVD method on the surface of the object, receiving portion and the accommodation of a bottomed hollow shape capable of accommodating the object to be treated A hollow electrode having an opening communicating with the inside and outside of the part, a changing means for changing the posture of the object in the storage part, and a feeding means for supplying electric power for generating plasma to the hollow electrode The hollow electrode is in a chamber forming an enclosed space and no counter electrode is disposed in the storage portion , and the power supply means comprises a pulse power source, and plasma is generated by hollow cathode discharge in the hollow electrode. It is characterized in that it can be generated.

(2) According to the film forming apparatus of the present invention, the plasma density in the hollow electrode can be increased by the hollow cathode discharge, and the film forming by plasma CVD is efficiently performed on the object to be processed in the hollow electrode storage portion. It can do. Therefore, when the film forming apparatus of the present invention is used, plasma CVD processing is also performed on an object (for example, particulate matter) having a large ratio of surface area (film formation area) to mass (appropriately referred to as "specific surface area"). The time (film forming time) can be shortened, and the production cost of the thin film-coated product can be reduced.

(3) Incidentally, the reason why the plasma density in the hollow electrode (hollow cathode) is larger than the plasma density between parallel plate electrodes etc. is considered as follows. When the hollow electrode is a cathode (cathode), secondary electrons emitted from the cathode surface on the inner side thereof are treated by a sheath (a charged particle layer of a single polarity formed in the vicinity of the electrode surface in contact with the plasma phase) It is accelerated in the direction of the inner opposite cathode surface (radially if the housing is cylindrical or spherical). At this time, the secondary electrons approach the opposing cathode surface when the mean free path is sufficiently long (longer than the diameter if the container is cylindrical or spherical).

  However, if the thickness of the sheath is smaller than or approximately equal to half of the distance between the facing cathode surfaces (the radius if the housing is cylindrical or spherical), the secondary electrons are 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-lived electrons are confined in the hollow electrode, and the number of times of ionization increases in the hollow electrode, so that a high plasma density can be obtained. It is believed that cathodic discharge occurs.

<< Deposition method >>
The present invention can be grasped not only as the above-mentioned film formation apparatus but also as the following film formation method. That is, the present invention provides, in a hollow electrode opposing electrode with in a chamber constituting a closed space is not arranged on the inner side, forming a film by plasma CVD method to be treated by generating plasma by hollow cathode discharge comprising a film forming process,該被treated are granules, film-forming step may be a film forming method according to claim Rukoto made with pulse current to said hollow electrode with stirring granulate . Although the film forming method of the present invention can of course be carried out using the above-described film forming apparatus, it is not limited (limited) in that case.

  In addition, although the film forming method of the present invention can be applied to various objects to be treated, when the object to be treated is a particulate matter, the film forming step according to the present invention involves a stirring step of agitating the particulate matter. Is preferable. Thereby, uniform film formation can be efficiently performed also on particulate matter. Note that this stirring step may be performed intermittently, but if performed continuously during film formation, more uniform film formation becomes possible, which is preferable.

<< Others >>
(1) The film forming apparatus of the present invention is largely 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 to 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, in addition to CCP, ECP (Electron Cyclotron resonance Plasma: electron cyclotron resonance plasma), HWP (Helicon Wave Plasma: helicon wave excitation plasma), ICP (Inductively Coupled Plasma: inductively coupled plasma), SWP (Surface Wave Plasma: A 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 the present specification includes the lower limit x and the upper limit y. Ranges such as “a to b” may be newly established as new lower limit values or upper limit values for arbitrary numerical values included in various numerical values or numerical ranges described in the present specification.

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

  One 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 the present specification can be appropriately applied not only to the film forming apparatus of the present invention but also to the film forming method. It can be a methodical component or a physical component. A component related to the method can also be a component related to an object if it is understood as a product-by-process claim. Whether or not which embodiment is the best depends on the target, required performance, and the like.

«Hollow electrode»
The hollow electrode according to the present invention comprises a housing portion and an opening. The housing portion is a bottomed hollow shape capable of housing an object to be treated, and may have any shape as long as it is a shape capable of hollow cathode discharge. The housing portion can take various forms such as, for example, 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 the opening portion. In addition, the inner wall surface of the housing portion is a smooth curved surface with few corners, and it is preferable that the corners have a rounded shape when there is a connecting portion between the side and the bottom. As a result, concentration of discharge to a part is suppressed, and a stable hollow cathode discharge can be easily obtained.

  The opening can be used not only to put the object to be processed into and out of the container but also for exhausting the air in the container and supplying air to the container. The opening may have any form, arrangement, size and the like as long as the object to be treated is stably held in the storage unit. For example, the opening is a hole or the like that opens upward (horizontal position to vertically upward) with reference to the arrangement of the hollow electrode during processing.

<< Deposition apparatus >>
(1) The film forming apparatus of the present invention includes a gas supply means for supplying various gases (raw material gas, carrier gas, etc.) into the chamber in addition to the chamber and the hollow electrode to perform plasma CVD. A power supply circuit for supplying power necessary for the cathode discharge) or a supply source of such power, etc. is appropriately provided. Although atmospheric pressure plasma may be used, generally, plasma (vacuum plasma) generated in a reduced pressure atmosphere is often used, so it is preferable to have an exhaust unit for exhausting (depressurizing) the inside of the chamber.

  As a power supply (plasma power supply) at the time of film formation, a direct current power supply, a high frequency power supply, a pulse power supply, or the like can be used. However, objects having a large specific surface area (or light weight) such as powder particles may float due to charging during processing, making stable plasma generation and film formation difficult. In such a case, stable film formation becomes possible when film formation is performed by applying high frequency current or pulse current (particularly, DC pulse current). Therefore, it is preferable that the feeding means for supplying the power for generating plasma in the chamber be a high frequency power circuit or a pulse power circuit. The pressure may be adjusted appropriately depending on the object to be treated, the raw material gas, the internal pressure of the chamber, etc. For example, when applying a DC pulse to a hollow electrode containing particulates (especially powder), applied voltage: 300 to 3000 V, 400 to 600 V, The frequency: 5 kHz to 350 kHz, preferably 50 kHz to 150 kHz, and the rest time: 0.4 to 5 μs, and further preferably 0.5 to 2 μs.

(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 unit that changes the posture of the object to be processed in the storage unit. There are various variation means, and an appropriate means may be selected according to the object to be treated. For example, in the case where the object to be treated is a granular material such as powder, as the fluctuation means, a vibrating means for applying vibration or oscillation to the object to be treated or a stirring means for moving or rolling the object to be treated is used. be able to.

  However, when an object to be treated (powder or the like) having a large specific surface area is vibrated during the treatment, it may be easily floated, which may make stable film formation difficult. In such a case, when the object to be treated is slowly rolled along the inner wall surface of the housing portion using a rotating means for rotating the hollow electrode as the changing means, the posture is slowly changed and processed. Stable film formation is possible for various objects to be processed. The term "rotation" as used herein includes not only the case where the hollow electrode rotates but also the case where it revolves, and also the case where both rotation and revolution are performed. Although it may be appropriately adjusted depending on the object to be treated etc., for example, in the case of rotating a hollow electrode containing particles (in particular, powder), the number of rotations may be about 0.1 to 10 rpm and further about 0.5 to 5 rpm.

  In the case where the hollow electrode is rotated, it is preferable that the storage portion have a stirring portion which protrudes from at least a part (for example, the inner bottom side) of the inner wall surface in contact with the object to be treated. With such a hollow electrode, more uniform film formation can be efficiently performed even if the object to be processed is particulate.

<< object to be processed >>
The film forming apparatus or the film forming method of the present invention targets various objects to be treated, but is suitable for forming particles such as powder (including abrasive powder), screws, nuts, washers, etc. . The material of the object to be treated may be any of metal, ceramics, resin and the like. Further, even in the case of an object to be processed in a complicated form, uniform film formation is possible according to the film forming apparatus of the present invention. In addition, since the size of the particulate matter is different depending on the object to be treated, it is difficult to specify uniquely, but for example, the average mass per one particle or one item is 2.1 × 10 ⁻⁶ mg to 0.5 g and further 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 hollow electrodes was manufactured, and the powder was subjected to plasma CVD processing. Also in the film forming apparatus in which the hollow electrode was replaced with the open electrode, the powder was similarly subjected to the plasma CVD process. The state during each treatment was observed to evaluate the influence of the difference of the electrodes. Hereinafter, the present invention will be described in more detail by way of such specific examples.

<< Deposition apparatus >>
(1) The outline | summary of the film-forming apparatus M which is one Example of this invention was shown typically 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 the plasma CVD process is performed.

  The processing mechanism unit 2 includes a container 21 (hollow electrode) for containing the object to be processed w (powder) and a pair of bevel gears (shafts) rotatably supporting the container 21 around an axis extending obliquely upward. A support 22 having an obtuse angle (for example, 135 °) and an input shaft 23 having one end connected to one bevel gear in the support 22 and extending vertically downward and penetrating the vacuum chamber 1 And the rotation speed control type motor 24 for driving the input shaft 23, and the insulation for supporting the input shaft 23 with respect to the vacuum chamber 1 while securing insulation and airtightness between the vacuum chamber 1 and the input shaft 23. It has a bearing 25 with a vacuum seal, and an insulating coupling 26 which insulates and connects the input shaft 23 and the rotation shaft of the motor 24. 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 case 21 corresponds to the rotation means (variation means) in the present invention.

  The power supply unit 3 (power supply means) is provided with a power supply from a commercial power supply (not shown), and includes a plasma power supply circuit 30 capable of applying 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 is connected to the input shaft 23. Thus, 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 (gas supply means) includes a gas supply shower 41 disposed in the vacuum chamber 1 for supplying gas into the vacuum chamber 1, a gas storage body 42 serving as the gas source, and a gas storage body 42. And a flow controller (mass flow controller) 43 for controlling the amount of gas supplied to the gas supply shower 41. The gas storage body 42 is composed of gas cylinders storing various source gases or carrier gases, or a gas generator for generating 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 unit) is an exhaust passage 51 communicating the inside and the outside of the vacuum chamber 1, and a control valve (butterfly adjusting the amount of vacuum (vacuum degree in the vacuum chamber 1) by switching communication and interruption of the exhaust passage 51. And a vacuum pump 53 for evacuating the inside of the vacuum chamber 1 through the exhaust path 51 and the adjusting valve 52.

(2) As shown in FIG. 2A, which is a half sectional view, the container 21 to be a hollow electrode has a hemispherical body 211 having a flat disk-like bottom surface 211a and a hemispherical side surface 211b, and a circular opening It consists of a hemispherical cylinder 212 having an opening 212a and a hemispherical side surface 212b. Then, the hemispherical body 211 and the hemispherical cylindrical body 212 abut each other on the flange surface projecting from the outer peripheral side, and are connected by the fixing tool 213 formed of a bolt and a nut. The hemispherical body 211 and the hemispherical cylinder 212 are also made of a conductive material (stainless steel / JIS SUS304).

  As shown in FIG. 2B, which is a plan view, the hemispherical body 211 has a protrusion row 214 (stirring portion) protruding in the center (central) direction from the inner wall surface 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 object w to be treated introduced into the container 21 is agitated by the row of protrusions 214 along the inner wall surface of the hemisphere 211.

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

The container 21 (see FIG. 2A) was attached to the support 22 and the object to be treated w was placed in 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 a vacuum state (7 Pa). A source 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 rotating the container 21 by the processing mechanism unit 2 (rotation speed: 1 rpm) (stirring process), a DC pulse voltage of -600 V was applied from the power supply unit 3 (pulse energizing process). At this time, the pulse pause time (T) was 1.5 μsec, and the frequency was 50 kHz. The plasma CVD process is carried out for 30 minutes (film forming process), and SEM observation of the cross section of the powder particle is carried out that an amorphous carbon film of about 0.1 μm is formed on the surface of each powder particle (S manufactured by Hitachi High-Technologies Corporation S -4300).

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

  The hemispherical cylindrical body 212 of the container 21 was removed, and the same plasma CVD process was performed using the open electrode made only of the hemispherical body 211. The appearance of the periphery of the hemispherical body 211 during this processing is schematically shown in FIG. 4B, and a photograph of the upper surface side is shown in FIG. 4B.

(2) A plasma generated when using a hollow electrode (see FIG. 3B) and a plasma generated when using an open electrode (see FIG. 4B) are plasma process monitors (C10346 manufactured by Hamamatsu Photonics Co., Ltd.). The luminescence analysis was performed using -1). The result obtained by this is shown in FIG.

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

  As described above, it was found that a large plasma density can be obtained by using the hollow electrode, and the plasma CVD process can be efficiently performed. Moreover, even if it is an object to be treated consisting of fine particles such as powder, it is possible to perform uniform film formation on each particle by processing while stirring as in the film forming apparatus M. .

(2) The inner wall surface of the housing 21 is composed of spherical side surfaces and a flat surface, and the boundary between them is also connected by an arc curved surface. As described above, when the inner wall surface of the storage portion of the object to be processed is formed into a smooth curved surface, it is possible to prevent the discharge from becoming uneven due to the concentration of electric potential in the hollow electrode. Therefore, if a hollow electrode as in this embodiment is used, uniform and high-density plasma can be generated throughout the inside, and thus uniform film formation can be efficiently performed even on the entire surface of a fine object to be treated. It can do.

  In the case where the object to be treated is composed of particles having a large specific surface area, etc., the object to be treated may be suspended during the CVD process, or the suspended particles may be contained in the container if a simple DC power source is used as a plasma power source. An arc discharge may occur when the inner wall surface is recontacted, and the discharge and thus the plasma generation may become unstable. On the other hand, when a pulse power source is used as a plasma power source as in this embodiment, the discharge and hence the plasma generation is stabilized, and high-quality film formation is efficiently performed even if the object to be treated is powder or the like. obtain.

  As shown in FIG. 3A, when the plasma sheath is smaller than or approximately equal to a half of the maximum inner diameter (diameter) of the container 21 (hollow electrode), a stable hollow cathode discharge tends to occur, which is efficient and stable The plasma CVD process can be performed.

1 vacuum chamber 2 processing mechanism (rotation means)
21 capacity (hollow electrode)
214 protrusion row (stirring section)
3 Power supply unit (feeding means)
4 Gas supply unit (air supply means)
5 Exhaust part (exhaust means)

Claims (8)

A film forming apparatus for forming a film by plasma CVD on the surface of an object to be processed, comprising
A hollow electrode having an opening for communicating the inside and outside of the bottomed hollow housing portion capable of housing the object to be processed and said housing portion,
Variation means for varying the posture of the object in the storage section;
Power supply means for supplying electric power for generating plasma to the hollow electrode;
The hollow electrode is in a chamber forming a sealed space and no counter electrode is disposed in the housing .
The feeding means comprises a pulse power supply,
A film forming apparatus characterized in that plasma can be generated by hollow cathode discharge in the hollow electrode . The film forming apparatus according to claim 1 , wherein the changing unit is a rotating unit that rotates the hollow electrode. The film forming apparatus according to claim 2, wherein the rotating unit rotates the hollow electrode around an obliquely extending axis . It said rotating means, rotating speed: film formation apparatus according to claim 2 or 3 to rotate the hollow electrode in 0.1～10Rpm. The film forming apparatus according to any one of claims 1 to 4, wherein the hollow electrode has a stirring portion which protrudes from an inner wall surface of the storage portion to which the object to be processed can come in contact. The film forming apparatus according to any one of claims 1 to 5, wherein the object to be treated is a particulate matter. In enclosed spaces constituting the hollow electrode is the counter electrode is not disposed inside together in the chamber, comprising a film forming process carried out by generating plasma by hollow cathode discharge in the object to be treated film formation by plasma CVD method ,
The object to be treated is a particulate matter,
Film forming step, the film forming method according to claim Rukoto made with pulse current to said hollow electrode with stirring granulate. The film forming method according to claim 7, wherein the pulse energization is direct current pulse energization, applied voltage: 300 to 3000 V, frequency: 5 kHz to 350 kHz, and rest time: 0.4 to 5 μs.