JP2840700B2 - Film forming apparatus and film forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for forming a film at atmospheric pressure. This makes it possible to provide a low-cost film forming apparatus that does not require an exhaust device such as a vacuum pump. High hardness coatings such as hard carbon, silicon nitride, and silicon oxide can be formed as coatings. These coatings can be used for hardening, modifying surfaces, and preventing reflection of metals, plastics, glass, and organic photoreceptors. It can be applied, and its application range is wide. The present invention provides a method and an apparatus for mass-producing these coatings at low cost.

[0002]

2. Description of the Related Art At present, new functional material films such as hard carbon, silicon nitride, and silicon oxide are formed by plasma CVD (chemical vapor synthesis).
It is often created using a method, and most of these methods use a reduced pressure state. The main advantage of using a reduced pressure state is that, in the case of plasma in which the influence of impurities such as oxygen contained in the air is removed, stable discharge is easily obtained in a wide area, and the mean free path is long. For example, it is easy to improve the step coverage. However, in order to obtain a reduced pressure state, an expensive evacuation device and a vacuum container having sufficient strength to withstand the vacuum state are required.

Generally, in the field of semiconductors, which are extremely reluctant to mix impurities, it is necessary to achieve high performance. In addition, it is easy to pass on expensive equipment depreciation to the price of high value-added products. Low pressure plasma CVD
Was created by law. On the other hand, when a thin film is formed for the purpose of hardening the surface, modifying the surface of an organic photoreceptor or the like of a coating film of a vehicle body, a metal, a plastic, a glass, an organic photoreceptor, etc., a very high purity is required. Instead, the problem is that the cost is high due to the use of expensive equipment. That is, it is necessary to optimize performance and cost.

[0004] On the other hand, some plasma treatments that do not require a vacuum evacuation device are known, and those applied to etching are disclosed in Japanese Patent Application No. 2-286883. This means that an AC electric field is applied to a space filled with a gas containing helium as a main component in a flowing state at a pressure substantially equal to the atmospheric pressure, and the gas and a halogen-based etching gas added to the gas are applied. The exciton is generated by ionization, and is used for etching. Further, there is known a method in which discharge of a gas containing helium as a main component is applied to thin film deposition. (No. 37
Proceedings of the 2nd JSAP Lecture Meeting on Applied Physics 2nd Volume 28p
-ZH-10) However, in this research, since the reaction space needs to be replaced with a gas containing helium as a main component, the reaction space must be once evacuated to a vacuum.

As described above, the conventional reduced pressure film forming method is expensive for the purpose of processing only for hardening the surface of plastic, glass, organic photoreceptor, or the like, or for forming a film, and a more inexpensive method is required. I was Then, as an inexpensive film forming method, a film forming method using discharge at atmospheric pressure has been considered.
Use of this method has the following advantages. Since there is no need for evacuation, an expensive evacuation device is not required.
Conventionally, the time required for evacuation can be saved,
Takt time can be reduced. Since the collision time is short and the reaction speed is high because the film is formed at a high pressure, the film formation time can be shortened. These are all elements that can reduce the cost of the film forming apparatus and shorten the tact time, and thus greatly contribute to reducing the film forming cost.

[0006]

However, film formation at atmospheric pressure has the following three problems.

[0007] The first problem is contamination of atmospheric components. This is a problem that ions and radicals generated in the discharge space are combined with impurities in the atmosphere, particularly oxygen, before being transported to the surface of the substrate, thereby affecting the coating. In addition, the surface on which the film is being formed is active, and impurities such as oxygen attached to the surface cause deterioration of the performance of the film.

[0008] The second problem is that the discharge space is limited to a narrow area. In general, when a film is formed on a substrate, there is a demand to uniformly form a film over a wide area. For this purpose, plasma must be generated in a wide range, but discharge at atmospheric pressure has a short mean free path of particles of 1 μm or less.
The recombination (volume recombination) due to collisions between electrons and ions in the space increases, and depending on the case, the discharge region is usually several meters.
m or more.

A third problem is that the reaction speed is too high. That is, since the probability of collision of ions, radicals, and the like is high, they react in space before growing as a film on the surface of the substrate, and are deposited as powder on the substrate.

[0010]

In order to solve these problems, the present invention covers an arc discharge space so as to wrap it with a purge gas, and applies a bias between the arc discharge space and a substrate so as to generate spatter. Furthermore, the distance between the discharge part and the substrate is made constant to make the probability of the source particles activated by the plasma reach the substrate uniform and to make the effect of sputtering by the bias uniform. It is. Further, by applying a magnetic field to the discharge part, the plasma space region is controlled to improve the uniformity of the coating.

The film forming method of the present invention is intended to reduce the cost by performing the process at atmospheric pressure, and is characterized by having no exhaust device. In the present invention, an arc discharge is particularly used among the discharges under the atmospheric pressure. Since arc discharge has a high temperature in the plasma of several thousand K, there is an advantage that even a gas which is usually difficult to decompose can be easily decomposed. Therefore, there is no deterioration in film quality due to undecomposition, and the film formation speed is extremely high. The coatings formed by the present invention are diamond,
Earmon Like Carbon (DLC), BN _X , B
_{C X, BP X, SiN X} , SiC X, SiO X, AlO
_X (eg, Al ₂ O ₃ ), TaN _x , TaC _x , Ta
_{O X, TiN X, TiC X} , TiO X, ZrN X, Zr
C _X, ZrO _X (e.g. ZrO _2), HfC _X, HfN
_{X, VC X, NbC X,} 1 type of single selected from WC _X
One or two or more layers are stacked
You.

The gas introduced into the discharge space is composed of a raw material gas for forming a film and a buffer gas composed of an inert gas such as helium or argon. The buffer gas has a role of reducing the probability of collision between source gases activated by the plasma and suppressing the reaction of the source gas in the space, thereby reducing the generation of powder. In addition, since the inert gas generally has a high ionization voltage, the temperature of the plasma becomes higher. Especially when helium is used, its ionization voltage is the highest,
The decomposition efficiency in the plasma is best. The source gas concentration with respect to the buffer gas is 50% or less, preferably 20%.
The following is good.

The raw material gas is selected depending on the type of the film to be formed. In the case of forming a hard carbon film, a hydrocarbon-based gas such as methane, ethylene, acetylene, benzene, methylbenzene, etc .; In principle, any material may be used as long as it contains carbon such as halogenated carbon such as fluorobenzene, chlorobenzene and the like, halogenated hydrocarbon-based gas, alcohols such as ethanol and methanol, and has a certain vapor pressure at room temperature and 1 atm. However, since unreacted components of the raw material gas are released into the atmosphere, harmless substances such as methylbenzene, chlorobenzene and ethanol are preferable to toxic substances such as acetylene and benzene. In addition, since the reaction rate tends to increase as the number of carbon atoms in one molecule increases, ethylene is more preferable than methane, acetylene is more preferable than ethylene, and aromatic molecules such as benzene are more preferable. Further, the advantage of the film formation rate becomes greater when the source gas contains a halogen-based element. This is because halogen-based elements such as fluorine act catalytically,
This is because hydrogen of the hydrocarbon molecule is extracted in the form of HF, so that the hydrocarbon molecule is easily activated. Halogen elements include carbon tetrafluoride, carbon tetrachloride, fluorobenzene,
Even if supplied as a carbon compound molecule such as chlorobenzene,
Also, nitrogen trifluoride, sulfur hexafluoride, tungsten hexafluoride,
It may be supplied in a state of fluorine gas or the like. When a gas containing a group IIIV element such as nitrogen, boron, phosphorus or the like is added to the raw material gas, the hard carbon film becomes slightly conductive, and a film useful for countermeasures against static electricity can be obtained. For example, when nitrogen trifluoride is added to a hydrocarbon gas such as ethylene or methylbenzene, a semi-insulating hard carbon film (that is, a countermeasure against static electricity) having a high film forming rate can be obtained.
When hydrogen is mixed in the raw material gas, hydrogen is terminated to unbonded bonds in the hard carbon film, and unreacted s
The p and sp2 bonds easily become sp3 bonds due to the action of hydrogen, so that the hard carbon film is harder and has higher transparency.

When the film to be formed is silicon nitride, silane-based gas such as silane and disilane and nitrogen gas are used as raw material gases.
A nitrogen source such as ammonia gas can be used. In the case of silicon oxide, a silane-based gas, oxygen, N ₂ O, or the like can be used. Also, Al, Ta, Ti, Zr, Hf,
An organic metal gas having a methyl group, an ethyl group, or the like can be used as a source gas of a metal such as V, Nb, W, or the like.
They O ₂ as an oxidizing source of _metal, N 2 _O, etc., as the nitride source N _2, ammonia, methane as hydrocarbon source, a hydrocarbon such as ethylene, CO _2, etc. can be used. Diborane can be used as a boron source, and phosphine can be used as a phosphorus source. Alternatively, a halide such as tungsten fluoride can be used as a tungsten source. The use of a halogen-based substance is advantageous because the reaction rate is increased.

Further, in order to reduce the collision probability of the film-forming precursor during the reaction and thereby suppress the generation of powder, hydrogen gas can be mixed with the source gas as a buffer gas in addition to the rare gas.

These source gases are adjusted to a pressure slightly higher than 1 atm by a pressure regulator, mixed with a similarly regulated buffer gas, and then introduced into the reaction space. The reaction space is a space sandwiched between a first electrode for applying a voltage at the center and a ground electrode arranged concentrically outside the first electrode. When an electric field is applied between the first electrode and the ground electrode, a glow discharge occurs first, and when the electric power is further increased, a transition to an arc discharge occurs. In arc discharge, the voltage between electrodes is smaller than in glow discharge.
This is because the electron emission mechanism at the electrode is secondary electron emission in glow discharge, while it is thermionic emission in arc discharge, so the potential difference of the electrode with respect to the positive column of the discharge becomes smaller in arc discharge. The current value can be made 100 times or more larger in arc discharge than in glow discharge. That is, the electric power is supplied to the positive column, which mainly generates the film material gas radicals, in the arc discharge, which can be performed more efficiently.

In the case of arc discharge, since the electron emission mechanism is thermionic emission, it is preferable that the thermoelectron emission coefficients of both electrodes are large. Since the electron emission coefficient increases as the temperature increases,
High temperature stability in tungsten, a refractory metal such as tantalum, metal boride such as LaB _6, an oxide conductor and the like are useful. It is also effective to coat the surface of the refractory metal, metal boride, oxide conductor or the like with a substance having a large electron emission coefficient, that is, a substance having a small work function, such as MgO or CaO.

The electric field applied to the arc discharge may be either DC or AC. In this case, the arc discharge is a continuous discharge, but when a pulse or a rectangular wave-modulated high frequency is applied, the arc discharge becomes a pulse discharge whose discharge form changes with time.
If the duty is 50% or less, the influence of plasma and afterglow at the beginning of the arc discharge becomes large, and properties different from those at the time of continuous arc discharge are generated. At the beginning of the arc discharge, the plasma impedance is high, so
The voltage applied in the space increases. That is, the energy obtained per electron in the plasma is large, and the electron temperature is high. At this time, the source gas existing in the plasma space is efficiently excited. Next, the plasma becomes an afterglow from when the applied power is stopped. At this time, there is no external electric field applied to the space, but only an internal electric field existing in the space. This internal electric field also quickly disappears due to recombination of ions and electrons in the afterglow. In continuous arc discharge, film growth occurs selectively due to electric field concentration at minute projections on the surface of the substrate, causing pinholes and voids. Electric field concentration does not occur, so that a high-quality film without pinholes or voids is formed. That is, when a pulse or a rectangular wave-modulated high frequency is used, a film-forming precursor such as a cluster efficiently activated uniformly adheres to the substrate surface, so that a high-quality film with a high film-forming speed can be obtained. Further, in the pulse discharge, only the initial stage of avalanche collapse before the electrode is heated can be selectively used, so that the effect of protecting the electrode is also produced. Note that the pulse cycle is suitably several milliseconds, which is equal to the time at which the afterglow disappears.

The arc discharge space of the present invention has the simplest shape and can be concentric cylindrical. The gap between the ground electrode arranged concentrically on the outside and the first electrode at the center may be 5 mm or less, preferably 1 mm or less. Concentric cylinders are like point light sources,
If not moved, a coating is formed on the surface of the substrate in a dot-like manner. Therefore, in order to uniformly form a film on a substrate having a large area, it is necessary to move the substrate or the film forming apparatus. When the base is flat, a two-axis driving device (XY table) may be combined. Add one more axis (X
-YZ table), a film can be formed on an arbitrary curved surface if controlled by a computer or the like.

As a purge gas to be used, a non-oxidizing gas is used. For example, nitrogen, argon, helium, krypton and the like are typical. The role of these gases is to shield the arc discharge region and atmospheric components, and to block the atmospheric components, especially oxygen, and the reaction space, and to prevent these atmospheric components from being mixed into the film formed by the arc discharge. It is. As a method of introducing the purge gas, for example, in the case of the above-described concentric film forming apparatus so as to surround the arc discharge region, a discharge nozzle or outlet is provided outside the outer electrode so as to surround the outer electrode, and the arc discharge region is formed. A purge gas is introduced so as to surround it. At this time, the amount of the purge gas is considerably larger than the arc discharge atmosphere gas, and the purge gas itself is not discharged,
It is better to introduce at a higher pressure.

The generation of powder, which is a problem of the atmospheric pressure arc discharge, is that the film precursor (cluster) grows in space before being transported to the substrate surface, and becomes too large. To prevent this, reduce the reaction speed in space,
It is necessary to take measures such as positively transporting ions, radicals, film precursors, and the like to the film surface, and increasing the reaction rate on the substrate surface. These countermeasures include utilization of the magnetic field effect and application of a bias to the substrate.

In order to reliably transport the active species in the plasma of the arc discharge atmosphere gas generated by the atmospheric pressure arc discharge to the substrate for film formation, the present invention applies a bias electric field to the substrate and applies a bias electric field to the arc discharge plasma. Is applied. There are various methods for applying a magnetic field to the plasma. For example, installing a generally known permanent magnet on the back surface of the film forming substrate at a position opposed to the arc discharge device, or applying a magnetic field by providing a solenoid coil near the arc discharge region of the arc discharge device, and There are combinations. In any case, these magnetic field generating means are provided so that the direction of the applied magnetic field is such that the active species in the plasma of the arc discharge atmosphere gas generated by the normal pressure arc discharge is transported to the film-forming substrate without fail. . The application of a magnetic field to the plasma mainly functions as an action of causing radical species having spin, electrons and ionized active species to reach the film forming surface of the substrate. Thereby, the density of the active species near the surface of the base is increased. The stronger the magnetic field, the better, more than 200 Gauss,
Preferably, it is 500 gauss or more.

The effect of the magnetic field can be used not only for transporting radicals but also for controlling the spatial shape of plasma. This utilizes the fact that electrons are extracted from the discharge space along the magnetic flux by cyclotron motion and ions are also extracted simultaneously to satisfy the electrical neutral condition of the plasma, so that the plasma is deformed along the magnetic flux. That is, if a converging magnetic field is formed, the plasma converges, and if a diverging magnetic field is formed, the plasma can be expanded. In addition, if a magnetic field that bends in a certain direction is formed, the plasma can be bent. This makes it possible to form a coating on portions where plasma does not easily enter, such as corners of a rectangular parallelepiped, corners of concave portions and corners of convex portions.

On the other hand, as a method of applying a bias electric field to the base, a bias may be applied between the base and the arc discharge electrode by a DC or high frequency power supply. Due to this bias electric field, ion active species in the plasma are attracted to the substrate side, and the density of high-energy ions near the substrate is increased. The source gas receives energy from these ions, and the density of radical species is increased near the substrate.

Further, the ions collide with the substrate due to the bias electric field. Due to this collision, energy is transferred from the ions to the substrate, the temperature of a portion very close to the surface of the substrate is increased, the adhesion of the coating to the substrate is improved, and the reaction of film formation on the substrate surface is promoted. That is, the same effect as the heating of the substrate can be realized by the ions moved to the substrate by the bias electric field. When the distance between the base and the discharge electrode changes, the effect of the electric field applied to the base significantly changes. Further, since the density of radicals generated in the discharge space decreases as the distance from the discharge space increases, the radical density on the surface of the substrate is strongly affected by the distance between the substrate and the discharge electrode, and the film formation speed and the like change. Therefore, the distance between the base and the discharge electrode needs to be kept constant at all times, and thus a distance measuring device and a distance control mechanism are required.

The frequency of the bias electric field needs to be lower than the ion plasma frequency determined by the ion density in the plasma. If the frequency is lower than the ion plasma frequency, the ions vibrate due to the bias electric field, and their kinetic energy can be transmitted to the substrate. Generally 1M
Hz or less is appropriate.

The radicals generated in the space by these measures are surely transported to the substrate surface, and the reaction on the substrate surface is promoted, so that a dense film with little powder (ie, without pinholes) is high. The film is formed at a film forming speed.

[0028]

[Embodiment 1] In this embodiment, a point-like device and a method for forming a film using the device will be described. FIG. 1 shows a sectional view of the apparatus and a system diagram of a gas system and an electric system at the same time. The central conductor (1) and the purge gas nozzle (3) are arranged coaxially, and the central conductor (1) is supported by an insulating support (4). The purge gas nozzle (3) also serves as an outer ground electrode. The central conductor (1) is made of tantalum, the purge gas nozzle (3) is made of stainless steel, and both the central conductor (1) and the purge gas nozzle (3) are made of MgO and C
an insulating support coated with a mixed material of aO (4)
Is composed of alumina. Purge gas nozzle (3)
Has a double coaxial cylinder structure, in which a purge gas is introduced at about 1 atm between the double structures, and the purge gas is ejected from the outlet (6). The outlet (6) is directed outward so as to blow in the outer peripheral direction. An arc discharge occurs between the center conductor (1) and the purge gas nozzle (3) to generate radicals. The generated radicals are carried by the gas flow in the direction of the substrate (71). In the present invention, the solenoids (61) and the permanent magnets (62) are further disposed on the outer periphery of the apparatus and on the back side of the substrate holder (70), respectively. Along the direction of the substrate (71). The outer diameter of the central conductor (1) is 1 mm, and the inner diameter of the purge gas nozzle (3) is 1.7 mm. The length of the arc discharge space is 2
0 mm. The substrate (71) is made of polycarbonate, and is made of a paramagnetic stainless steel substrate holder (7).
0). The substrate (71) is not actively heated. The distance from the arc discharge space edge to the substrate surface is 1
mm.

The gas introduced into the arc discharge space is pressure-regulated by a pressure regulator (21) from a raw material gas cylinder (11), and is supplied to a flow controller (4) via a stop valve (31).
The raw material gas whose flow rate is controlled by 1) and the pressure of the helium gas cylinder (12) are similarly regulated by a pressure regulator (22), and the flow rate controller (4) is controlled via a stop valve (32).
Helium gas whose flow rate is controlled by 2) is mixed,
It is introduced into the arc discharge space. Raw material gas cylinder (1
1) is filled with 10% methane gas balanced with hydrogen gas. The mixing ratio of helium and the source gas was 99: 1 (source gas 1%). The total flow rate of helium and the source gas is 100 sccm.

The power supplied to the center conductor (1) is supplied to a high-frequency power supply (51) via a blocking capacitor (53).
Supplied by The power supply frequency was 50 kHz, and the effective input power was 100 W. Further, the bias voltage, which is a feature of the present invention, is supplied from the bias power supply (52) to the high-frequency blocking coil 1.
(55), the voltage was applied via the high frequency blocking coil 2 (56). The bypass capacitor (54) is a high-frequency blocking coil 1
It has a role of releasing high-frequency power passing through (55) and protecting the bias power supply (52). In this embodiment, the applied bias was DC, and the voltage was -100 V with respect to the substrate holder.

The pressure of the purge gas is regulated by a pressure regulator (23) from a cylinder (13), and the flow rate of the purge gas is controlled by a flow controller (43) via a stop valve (33) to be supplied to a purge gas nozzle. In this embodiment, nitrogen was used as the purge gas. The flow rate is 1000 sccm.

A hard carbon film was formed on a polycarbonate substrate by the above-described apparatus and method. The film formation rate was 1.0 μm / min immediately below the opening of the arc discharge region.
Although it was a very high value, almost no powder was generated, and the film was a good quality film with few pinholes. The hardness measured by the microindentation hardness tester was about 3000 kgf / mm ² , and the transmittance in the visible region in the spectral transmittance measurement was 90%.
The above was almost transparent. Also, FT-I
According to R, Raman spectroscopy, and the like, the ratio of sp3 bond to sp2 bond was 1.6: 1, indicating that the structure had a structure close to that of diamond.

Although the film forming apparatus was not moved in this embodiment, it is needless to say that a film can be uniformly formed on a large-area substrate by scanning at a constant speed on a plane.

[Comparative Example 1]

In this comparative example, a case in which there is no magnetic field in the first embodiment will be described. The conditions for film formation and the like are the same as in Example 1 except that there is no magnetic field. The film formed by this method had almost no change in the hardness measurement value and transmittance as compared with Comparative Example 1, but the film formation rate was slightly reduced, and much powder was generated.

"Comparative Example 2"

In this comparative example, a case without bias in the first embodiment will be described. The conditions for film formation and the like are the same as those of the first embodiment except that there is no bias. The film formed by this method had a lower hardness and a higher transmittance than Comparative Example 1. Further, generation of powder was observed as much as in “Comparative Example 1”. No change in the film forming rate was observed.

"Comparative Example 3"

In this comparative example, the case where no purge gas is used in the first embodiment will be described. The conditions such as film formation are the same as those of the first embodiment except that no purge gas is used. In the film formed by this method, the film was slightly formed just below the opening of the arc discharge region, and the film formation speed was reduced to about one tenth. This is presumably because the coating near the outer periphery was etched by the incorporation of oxygen. No change was observed in hardness and transmittance.

[0040]

According to the present invention, a gas containing helium as a main component is subjected to arc discharge at atmospheric pressure, and a gas as a raw material (methane, hydrogen, etc. in the case of a hard carbon film) is mixed into the gas, and the arc discharge is simultaneously wrapped. By purging with nitrogen or the like, and applying a magnetic field and a bias voltage, the generation of the conventional powder was remarkable and the deposition rate was slow.
It has become possible to form a high-quality coating film having a high film forming rate.

Although not described in the examples, a film having good step coverage was formed even at the bottom and corners of the concave portion by applying a magnetic field particularly strongly to the surface where the concave portion exists.

[Brief description of the drawings]

FIG. 1 shows a sectional view of a coaxial cylindrical film forming apparatus and a system diagram of gas and electric systems.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Central conductor 3 Purge gas nozzle 4 Insulating support 61 Solenoid magnet 62 Permanent magnet 11 Raw material gas cylinder 12 Helium cylinder 13 Purge gas cylinder 51 High frequency power supply 52 Bias power supply 61 Solenoid magnet 62 Permanent magnet 71 Substrate

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-239189 (JP, A) JP-A-63-277767 (JP, A) JP-A-58-379 (JP, A) JP-A-2- 156089 (JP, A) JP-A-2-254170 (JP, A)

Claims (9)

(57) [Claims] An arc discharge space having an opening with respect to a substrate on which a film is to be formed, and a purge gas nozzle disposed so as to surround the arc discharge space, wherein the purge gas blown from the purge gas nozzle substantially emits the arc gas. What is claimed is: 1. A film forming apparatus for shielding a discharge space from an atmospheric atmosphere, comprising: means for applying an electric field and a magnetic field to plasma generated in said arc discharge space. 2. The arc discharge space according to claim 1, wherein the arc discharge space is sandwiched between a first electrode disposed at the center and a second electrode disposed concentrically outside the first electrode. And the distance between the first electrode and the second electrode is 5 mm
A film forming apparatus characterized by the following. 3. The film forming apparatus according to claim 1, further comprising a control mechanism for keeping a distance between the electrode for arc discharge and the substrate constant. 4. The method according to claim 1, wherein
A film forming apparatus, wherein the substrate has a convex surface or a concave surface. 5. The method according to claim 1, wherein:
The coating formed is diamond, diamond-like carbon (DLC), BN _x , BC _x , BP _x , Si
_{N X, SiC X, SiO X} , AlO X, TaN X, Ta
C _X , TaO _X , TiN _X , TiC _X , TiO _X , Zr
_{N X, ZrC X, ZrO X} , HfC X, HfN X, VC
A film forming apparatus having a structure in which one kind of single layer selected from _X , NbC _X , and WC _X or two or more kinds of layers are laminated. 6. A film forming method using a film forming apparatus having an arc discharge space having an opening with respect to a substrate on which a film is to be formed and a purge gas nozzle disposed so as to surround the arc discharge space, wherein the purge gas is provided. Introducing a purge gas from a nozzle, substantially shutting off the arc discharge space from the air atmosphere, mixing a raw material gas for a coating film and a helium gas, introducing the mixture into the arc discharge space, generating plasma in the arc discharge space, and Coating characterized by comprising a method of applying a magnetic field to plasma generated in the arc discharge space by applying an electric field that causes spatter between the arc discharge space and the base to form a coating on the base. Forming method. 7. The method of claim 6, wherein in order to generate a plasma in the arc discharge space, the film forming method characterized in that by applying an electric field to the arc discharge by power pulse or rectangle modulated high frequency. 8. The method according to claim 6, wherein the base is a convex surface or a concave surface. 9. The method according to claim 6, wherein
The coating formed is diamond, diamond-like carbon (DLC), BN _x , BC _x , BP _x , Si
_{N X, SiC X, SiO X} , AlO X, TaN X, Ta
C _X , TaO _X , TiN _X , TiC _X , TiO _X , Zr
_{N X, ZrC X, ZrO X} , HfC X, HfN X, VC
_A method for forming a coating film comprising a single layer selected from _X , NbC _X , and WC _X or a structure in which two or more layers are stacked.