JP2002327277A - Film forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film forming apparatus which enhances a film forming speed without damaging a magnetic film on a magnetic tape or the like, and effectively removes positive charge formed on a coated workpiece with a protective film without damaging the product. SOLUTION: The film forming apparatus 10 comprises a reaction chamber 16 in a vacuum chamber 20, which introduces reactant gas therein and forms a protective film on the magnetic film provided on the tape-shaped support 12 through a plasma reaction, and further an electron emission device 21 for emitting electron current toward the magnetic film on the support 12 held so as to face the reaction chamber 16. Thereby, the apparatus stabilizes generation of plasma in the reaction chamber 16, because it can supply electron current emitted from the electron emission device 21 to the reaction chamber 16 through the magnetic film of the support 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film forming apparatus using a plasma CVD method or the like, and more particularly, to a protective film formed on a metal thin film formed on a film to be formed such as a magnetic tape, a magnetic disk and a magnetic head. The present invention relates to a film forming apparatus suitable as an apparatus for forming a film.

[0002]

2. Description of the Related Art In recent years, in the field of magnetic tapes as recording media, a ferromagnetic material such as cobalt (Co) has been formed on a film-like base by a vapor deposition method or a sputtering method in response to a demand for high recording density. So-called evaporation tapes are being replaced by coating tapes in which oxide magnetic powder is mixed into an organic binder and applied. The vapor deposition tape is a tape in which a vapor such as Co is directly adhered to a film-like base in a vacuum chamber to form a film as a magnetic film. The coating type tape does not require an essential binder. For this reason, the vapor deposition tape can form a thin magnetic film with a high degree of filling, and can achieve improvement in high-frequency characteristics, high recording density, tape thinning, and the like.

[0003] Evaporated tapes are expected to provide higher recording density, higher reliability and lower cost as tapes for data backup of digital video and computers. Along with this, magnetic heads used in digital video and computers are being replaced by magnetoresistive heads (hereinafter, MR heads) capable of further reducing the track pitch from conventional inductive heads. Inductive type heads require high output for signal extraction in the electromagnetic conversion characteristics of the magnetic film, but MR heads do not require so high output. About 1/3 of about 60 nm is sufficient.

[0004] With the demand for higher recording density, an abnormal discharge on the vapor deposition tape side and an abnormal portion due to the attachment of foreign matter cause a relatively large error, so that the occurrence of the abnormal discharge and the abnormal portion can be more reliably prevented. Such a film forming apparatus and a film forming method are eagerly desired. In addition, the protective film is required to be thinner in order to reduce the spacing loss between the MR head and the recording layer, and at the same time, is durable by increasing the hardness and lowering the friction coefficient. There is also a demand for improving the performance, and realization of a uniform thickness without defects is desired.

By the way, diamond-like carbon (hereinafter, also referred to as DLC) is widely used for a protective film of a vapor deposition tape. DLC is mainly used for sputtering or plasma C
The film is formed by the VD method. In the sputtering method, carbon atoms of a carbon target are struck out by argon ions ionized in a vacuum.
That is, the ratio of target atoms ejected by one ion is extremely low, and the productivity is inferior to that of the plasma CVD method.

[0006] The plasma CVD method is a chemical process in which the energy of plasma generated using an electric field or a magnetic field is used to cause a chemical reaction such as decomposition and synthesis of a reaction gas (raw material gas) to form a film. , DLC with excellent characteristics
A membrane can be obtained. As one mode of a plasma CVD apparatus, there is a DC method. In the DC method, in a vacuum chamber, a plasma discharge is generated between the magnetic film and an anode discharge electrode provided in a reaction chamber, using a magnetic film formed in advance on a film-forming body as a cathode in a vacuum chamber, A protective film is deposited on the magnetic film.
This method is structurally simple and is suitable for industrial mass production. However, as described above, since the MR head tape does not require high output, the magnetic film is thin, and the electric resistance is higher than in the past. In the discharge, the discharge current is reduced, and as a result, the film forming speed when forming the protective film on the vapor deposition tape tends to decrease.

Therefore, in order to increase the film formation speed, a method of expanding the effective area of the film formation by expanding the reaction chamber or increasing the number of the reaction chambers has been attempted. In addition, techniques for promoting activation of the reaction gas by increasing the discharge voltage, increasing the pressure in the reaction chamber, or increasing the proportion of argon gas mixed into the reaction gas have been attempted. In either case, it is necessary to increase the current flowing through the magnetic film on the surface of the evaporation tape, that is, the discharge current (plasma discharge current) between the magnetic film and the discharge electrode in the reaction chamber.

[0008]

However, if the discharge current is forcibly increased to increase the deposition rate by increasing the discharge voltage as described above, an arc discharge is caused from a stable glow discharge. This results in damage to the magnetic film of the evaporation tape. Further, as a method of releasing the increased discharge current, there is a method of removing a positive charge from the vapor deposition tape by using a metal roller contacting the vapor deposition tape via a resistor. However, in this method, a pinpoint spark may be generated on the contact surface between the magnetic film and the metal roller. In this case, the vapor deposition tape is damaged and a product defect is caused. Therefore, such as reducing the electrical resistance by contacting a plurality of conductive rollers to the magnetic film,
Despite efforts to reduce defects, it was not possible to effectively prevent product defects. In addition, there is a problem that the electric resistance slightly changes depending on the state of the magnetic film of the evaporation tape, the local location of the magnetic film, the lot of the evaporation tape, and the like. May vary.

Furthermore, since a positive charge is applied to the vapor deposition tape on which the protective film is formed by the plasma CVD method, there is a problem that the vapor deposition tape cannot be satisfactorily wound around a roller due to the influence of the positive charge.

The present invention has been made in view of the above problems, and has as its object to increase the film forming speed without damaging a magnetic film formed on a magnetic tape or the like, that is, a metal thin film of a film-forming body. Another object of the present invention is to provide a film forming apparatus capable of effectively removing a positive charge charged on a film-formed body after forming a protective film without causing a product defect.

[0011]

In order to achieve the above object, a film forming apparatus according to the present invention introduces a reactive gas, and forms a protective film by a plasma reaction on a metal thin film provided on an object to be formed. In a film forming apparatus having a reaction chamber for forming a film in a vacuum chamber, an electron emission device for emitting an electron flow toward a metal thin film of a film-forming target held so as to face the reaction chamber is provided. Features.

In the film forming apparatus of the present invention, the electron flow emitted from the electron emitting device can be supplied to the reaction chamber via the metal thin film of the object to be formed, so that the generation of plasma in the reaction chamber is stable. I do. At the same time, even if the electrical resistance of the metal thin film is greatly increased due to the thinning, a part or all of the discharge current can flow between the reaction chamber and the metal thin film by supplying electrons from the electron emission device. For this reason, there is no need for a method of releasing a discharge current through a metal roller that comes into contact with a film-forming object as in the related art. And the film forming speed can be improved. Therefore, it is possible to solve the problem of damaging the metal thin film of the film-forming object generated by the conventional plasma CVD apparatus.

Further, by supplying electrons from the electron-emitting device, it is possible to offset the positive charges charged on the metal thin film during film formation. In the present invention, a film-forming object on which a protective film can be formed includes a magnetic tape including a vapor deposition tape, a recording medium such as a magnetic disk, or a thin metal thin film on a sliding contact surface with the recording medium. A magnetic head such as an MR head having a magnetic film can be used.

In a preferred film forming apparatus of the present invention, a supply roller for supplying a tape-like support having a metal thin film on one surface as a film-forming object, and a metal film of the tape-like support supplied by the supply roller A rotatable main roller that contacts and supports the tape-shaped support on the back surface while facing the reaction chamber,
A winding roller for winding the tape-like support sent from the main roller, and the electron emission device emits an electron stream to the tape-like support in one of a state before and after the formation of the protective film. It is arranged to be. This allows
Electrons can be efficiently supplied to the reaction chamber, and plasma generation in the reaction chamber is stabilized.

Further, in the preferred film forming apparatus of the present invention, the electron-emitting device includes an electron-emitting device on the tape-like support in the other state in addition to one of the states before and after the formation of the protective film. It is arranged to emit a flow. This allows
Electron supply to the reaction chamber becomes more efficient, and plasma generation in the reaction chamber becomes more stable.

Further, in the preferred film forming apparatus of the present invention, a supply roller for supplying a tape-like support having a metal thin film on one surface as a film-forming object, and a tape-like support supplied by the supply roller are provided. A rotatable main roller that contacts and supports the tape-shaped support on the back surface while the metal film faces the reaction chamber, and a take-up roller that winds up the tape-shaped support sent from the main roller. Are arranged at radial positions around the main roller, and the electron emission device emits an electron flow to the tape-like support in a state before and after the formation of the protective film by the respective reaction chambers. Are located in According to this configuration, it is possible to further increase the film forming speed by increasing the discharge current, thereby contributing to further improvement in productivity.

It is desirable from the viewpoint of hardness that the protective film of the object to be formed is made of diamond-like carbon.
“Diamond-like carbon” referred to in the present specification means carbon having a diamond structure in at least a part thereof and having a peak derived from the diamond structure observed by Raman spectroscopy.

Further, the electron emission device has an electron supply source, a plasma electron gun for emitting an electron flow by plasma generated by introducing an inert gas, and a radiation path of the electron flow from the plasma electron gun. It is desirable to provide an electron supply chamber which is configured to surround the electron beam emission path and to be kept at the ground potential to confine the plasma discharge generated by the plasma electron gun. According to this configuration, the electron supply chamber regulates the radiation path of the electron flow from the plasma electron gun, and confines the plasma discharge generated by the plasma electron gun, so that the emission of the electron current from the plasma electron gun is improved.

The electron supply source is configured to heat a filament made of an alloy or a tungsten made of an alloy which has a low work function and easily emits electrons, and emits the emitted thermoelectrons by applying a bias voltage. be able to. In this case, it is possible to prevent a problem that the inert gas introduced into the electron supply chamber causes the filament to react with the reaction gas and corrode. When the gap between the electron outlet of the electron supply chamber and the object to be film-formed is 2 mm or less, interference of discharge between the electron supply chamber and the reaction chamber and abnormal discharge outside the electron supply chamber can be effectively prevented.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the accompanying drawings based on embodiments. Embodiment 1 In this embodiment, a film forming apparatus according to the present invention is a plasma CV.
FIG. 1 is a schematic view showing a film forming apparatus 10 according to an embodiment applied to a film forming apparatus using a method D. FIG.

As shown in FIG. 1, a film-forming apparatus 10 is supplied with a non-magnetic tape-shaped support (hereinafter referred to as a support).
12, a device for forming a protective film on the magnetic film by a plasma CVD method, having an exhaust device 14 at the upper part, a reaction chamber 16 at the lower part inside, and facing the reaction chamber 16 at the center of the inner part. There is provided a vacuum chamber 20 having a tape feeding section 18 for feeding the support 12 so as to make the support 12 move. Vacuum chamber 20
The electron-emitting device 21 which is a feature of the present invention is disposed on the side wall of. The inside of the vacuum chamber 20 is maintained at a pressure required for film formation by the operation of the exhaust device 14.

The tape feeding section 18 includes a cooling roller 22 and
The cooling roller 2 arranged in a horizontal direction above the cooling roller 22
A supply roller (unwinding roller) 24, an insulating guide roller 26, 28, and a winding roller 29 having a diameter smaller than 2 are provided. The insulating guide rollers 26 and 28 hold the support 12 from both sides to provide an appropriate tension to the support 12 and realize smooth running of the support 12. The supply roller 24, the cooling roller 22, the insulating guide rollers 26 and 28, and the winding roller 29 are each formed in a cylindrical shape having an axial length substantially equal to the width of the support 12. The supply roller 24 rotates the support 12 on which a magnetic film such as Co is formed by a vacuum deposition method, a sputtering method, or the like in a previous process via the insulating guide roller 26, while rotating in the direction of arrow A, to the cooling roller 22. Supply.

The cooling roller 22 is rotatably supported so as to rotate at a constant speed in the direction of arrow B. The cooling roller 22 holds the support 12 while the magnetic film of the support 12 supplied by the supply roller 22 faces the reaction chamber 16. Contact support on the back side. The surface of the cooling roller 22 is cooled by a liquid refrigerant circulating therein, and cools the contact-supported support 12.
Protect from deformation and damage caused by heat during film formation. The support 12 having passed through the cooling roller 22 is further taken up by a take-up roller 29 rotating in the direction of arrow C via an insulating guide roller 28.

The reaction chamber 16 is for introducing a reaction gas (raw material gas) through a gas inlet 28 and forming a protective film on the magnetic film formed on the support 12 by a plasma reaction. An electrode 25 is provided inside. The reaction chamber 16 can be formed of an insulating material such as quartz, Pyrex glass (trademark), plastic, or the like, or a metal material whose surface is insulated.

The discharge electrode 25 is connected to a DC power supply 27 disposed outside the vacuum chamber 20 so as to be able to be switched on / off. When the DC power supply 27 is turned on, the discharge electrode 25 is connected to the magnetic film on the support 12. Is applied with a voltage of + 500V to + 2000V. Further, the shape of the discharge electrode 25 is desirably, for example, a mesh shape in order to make the permeation of the reaction gas good, to make the electric field uniform, and to obtain more flexibility. Copper can be used as a material for the discharge electrode 25, but any conductive metal may be used, and examples thereof include stainless steel, brass (brass), and gold (Au). Also,
In the present embodiment, methane, ethane,
Butane, ethylene, butylene, benzene and the like can be used. By appropriately selecting these reaction gases according to the film quality required for the protective film, a hard DLC film or the like is formed on the magnetic film of the support 12. A film can be formed.

The electron emission device 21 includes a plasma electron gun,
An electron supply chamber 30 is provided. The plasma electron gun has an electron supply source 32, and emits an electron flow by plasma generated by introducing an inert gas such as argon from a gas inlet 34. The electron supply chamber 30 regulates the radiation path of the electron flow by surrounding the radiation path of the electron flow from the plasma electron gun,
Further, it is configured to be held at the ground potential and confine the plasma discharge generated by the plasma electron gun.

An auxiliary exhaust device 36 provided outside the vacuum chamber 20 communicates with the electron supply chamber 30. The auxiliary exhaust device 36 exhausts the inside of the electron supply chamber 30 so that the reaction gas flowing out of the reaction chamber 16 does not contaminate the electron supply source 32 or interfere with the discharge in the reaction chamber 16.

The film forming apparatus 10 of this embodiment operates as follows. That is, when forming the protective film, the tape feeding unit 18 moves the support 12 from the supply roller 24 to the insulating guide roller 26, the cooling roll 22, and the insulating guide roll 2.
8 and is fed at a constant speed toward the take-up roller 29. At this time, the magnetic film of the support 12 held at a position facing the reaction chamber 16 by the cooling roller 22 and the reaction chamber 1
A voltage is applied from a DC power supply 27 to the discharge electrode 25 in the reactor 6, and plasma is generated in the reaction chamber 16.

As a result, the reaction gas introduced into the reaction chamber 16 is activated by the energy of the plasma, and the activated gas molecules return to the ground state on the support 12, and the molecules are connected in a chain. At this time, some of the hydrogen atoms become H ₂ gas molecules and are exhausted from the exhaust device 14, and the amorphous DLC film is deposited and deposited as a protective film on the magnetic film of the support 12. The reaction gas that has flowed out of the reaction chamber 16 but has not been used for film formation is exhausted from the exhaust device 14 to the outside of the vacuum chamber 20.

In order to continuously and stably perform the plasma discharge in the reaction chamber 16, the electron flow must be stably supplied to the discharge electrode 25 from the cathode, that is, the magnetic film of the support 12. In the present film forming apparatus 10, an electron emitting device 21 as a supply source of the electron flow to the magnetic film is arranged so as to emit the electron flow to the support 12 after the formation of the protective film. That is, in the electron supply chamber 30, the electrons generated in the electron supply source 32 collide with gas molecules such as argon to generate electron-excited plasma, and the electrons generated in the plasma are extracted at a high voltage and cooled. The light is emitted to the magnetic film of the support 12 that travels while being supported by the rollers 22.

The electron flow emitted from the electron supply chamber 30 of the electron emission device 21 flows through the magnetic film of the support 12, is attracted by an electric field near the reaction chamber 16, and jumps into the space.
6 collides with gas molecules generated by the plasma reaction, ionizes the reaction gas, and continuously generates plasma. The current at this time has a flow opposite to that of the electrons. As a result, the ground current flowing through the support 12 is stabilized, so that the discharge voltage is reduced, the glow discharge is stabilized, and the arc discharge is reduced. As a result, improvement in product yield can be expected. Further, since an inert gas is introduced into the electron supply chamber 30 for generating plasma, the electron supply source 3
2 uses a tungsten filament, the tungsten filament is not used for film formation and the reaction chamber 16 is not used.
It does not react with the reaction gas flowing out of the reactor, and the service life is not shortened due to corrosion or the like.

According to the film forming apparatus 10, a protective film can be formed on a thin magnetic film provided on an MR head, in addition to the tape-like support 12. In that case, 50-200
It is possible to obtain an extremely thin protective film such as nm. Thereby, the spacing loss between the magnetic film, which is the recording layer of the vapor deposition tape, and the MR head can be reduced.

The film forming apparatus 10 solves the problem that the electric resistance is slightly changed depending on the film forming place or lot depending on the surface condition of the magnetic film on the support 12 side. The problem of variation in thickness and quality can be solved. Furthermore, an error in an abnormal portion due to abnormal discharge or foreign matter adhesion is small, and an excellent recording medium can be realized. Further, in the present film forming apparatus 10, the support 12
Although a DLC protective film was formed on the magnetic film and a vapor deposition tape was manufactured, the discharge in the reaction chamber 16 was smaller than when a vapor deposition tape was formed using a conventional film forming apparatus without the electron emission device 21. The effective voltage applied to the electrode 25 and the magnetic film was reduced by 10%, and the frequency of abnormal discharge was reduced by 50% or more. Also,
The film formation rate was improved by 20% as compared with the case of forming a film using a conventional film forming apparatus.

Embodiment 2 FIG. 2 is a schematic view showing a film forming apparatus 13 of this embodiment. Among the configurations of the film forming apparatus 13 of the present embodiment, the configuration different from the film forming apparatus 10 of the first embodiment is that the electron emission device is
That is, in addition to the position where the electron flow is emitted to the support 12 in a state after the formation of the protective film, it is also arranged at a position where the electron flow can be emitted to the support 12 in a state before the formation of the protective film. That is, in the film forming apparatus 13 of the present embodiment, the electron emitting device 21
An electron supply chamber 30 is formed so as to surround the outer periphery of the reaction chamber 16, and an electron current can be simultaneously emitted to the support 12 before and after the formation of the protective film by the reaction chamber 16. .

In the film forming apparatus 13, the electron supply source 32
The electron supply chamber 30 surrounding the outer periphery of the reaction chamber 16 is provided at positions before and after formation of the protective film on the support 12. One auxiliary exhaust device 36 communicates with the electron supply chamber 30, and both electron supply sources 3
The gas inlets 34 communicate with each other. Similarly to the first embodiment, the electron supply chamber 30 of the present embodiment is also maintained at the ground potential, and the electron flow from the plasma electron gun including the electron supply source 32 into which the reaction gas is introduced from the gas inlet 34. And restricts the radiation path of the electron flow to confine the plasma discharge generated by the plasma electron gun. With this configuration, electrons can be more efficiently supplied to the reaction chamber 16 than in the film forming apparatus 10 of the first embodiment, and the discharge current is increased to further increase the film forming speed, contributing to an improvement in productivity. can do.

Third Embodiment FIG. 3 is a schematic view showing a film forming apparatus 15 in which the film forming speed of the film forming apparatus 13 of the second embodiment is further increased. Main film forming apparatus 1
5, three reaction chambers 16A, 1
6B and 16C are arranged at radial positions around the cooling roll 22, respectively, and the electron supply chambers 30A, 30B,
0C and 30D are the reaction chambers 16A, 16B and 1 respectively.
The electron flow is arranged to be emitted to the support 12 before and after the formation of the protective film by 6C.

Each of the electron supply chambers 30A to 30D is provided with an electron supply source 32 and a gas inlet 34 for introducing an inert gas from the electron supply source 32. Each of the electron supply chambers 30A to 30D is similar to the first embodiment.
It is maintained at the ground potential and surrounds the radiation path of the electron flow from the plasma electron gun including the electron supply source 32, restricts the radiation path of the electron flow, and confines the plasma discharge generated by the plasma electron gun. The insulating guide rollers are arranged with a smaller interval than the insulating guide rollers 26 and 28 of the second embodiment, and are configured as upper rollers 26A and 28A and lower rollers 26B and 28B, respectively. In such a film forming apparatus 15 according to the second embodiment, three reaction chambers 16 </ b> A to 16 </ b> C around the cooling roller 22 exist.
The discharge current is further increased as compared with the film forming apparatus 13 and the film forming speed is further improved.

As described above, the first embodiment according to the present invention
According to the film forming apparatuses 10, 13, and 15, the protective film is formed on a magnetic film of a recording medium such as a magnetic tape or a magnetic disk, or the protective film is formed on a thin magnetic film of a magnetic head. In addition, it works well as a film forming device that achieves high productivity, high yield, etc., and achieves higher recording density, higher reliability,
Cost reduction and the like can be realized.

[0039]

As described above, according to the present invention,
Since the electron emission device that emits an electron stream toward the metal thin film of the film-forming object is provided, the film-forming speed can be increased without damaging the metal thin film of the film-forming object, and product defects are caused. Thus, the positive charges on the object after the formation of the protective film can be effectively removed.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a film forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a film forming apparatus according to a second embodiment of the present invention.

FIG. 3 is a schematic view illustrating a film forming apparatus according to a third embodiment of the present invention.

[Explanation of symbols]

10, 13, 15 ... film forming device, 12 ... tape-shaped support, 14 ... exhaust device, 16, 16A, 16B, 16C
... Reaction chamber, 18 tape feeding section, 20 vacuum chamber, 21 electron emission device, 22 cooling roller, 2
4 supply roller, 25 discharge electrode, 26, 28
Insulating guide rollers, 26A, 28A ... upper rollers, 2
6B, 28B: Lower roller, 27: DC power supply, 2
8, 34 gas inlet, 29 winding roller, 3
0, 30A, 30B, 30C, 30D ... Electron supply room,
32: an electron supply source, 36: an auxiliary exhaust device.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Hidetoshi Nishiyama 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation F-term (reference) 4K030 BA28 CA07 CA12 DA02 DA08 GA14 LA20 5D006 AA01 DA03 EA03 5D112 AA07 AA22 AA24 BC05 FA10 FB21

Claims (8)

[Claims] 1. A film forming apparatus in which a reaction gas is introduced and a reaction chamber for forming a protective film by a plasma reaction on a metal thin film provided on a film formation object is provided in a vacuum chamber, and the reaction apparatus faces the reaction chamber. A film-forming apparatus which emits an electron stream toward the metal thin film of the film-forming target held as described above. 2. A supply roller for supplying a tape-like support having a metal thin film on one surface as a film-forming object, and a metal film of the tape-like support supplied by the supply roller facing a reaction chamber. A rotatable main roller that contacts and supports the tape-shaped support on the back surface; and a take-up roller that winds up the tape-shaped support sent from the main roller. 2. The film forming apparatus according to claim 1, wherein the film forming apparatus is arranged so as to emit an electron current to the tape-shaped support in one of the states after the formation. 3. The electron emission device is arranged so as to emit an electron current to the tape-like support in the other state in addition to one of the states before and after the formation of the protective film. The film forming apparatus according to claim 2, wherein: 4. A supply roller for supplying a tape-like support having a metal thin film on one surface as a film-forming object, and a metal film of the tape-like support supplied by the supply roller facing the reaction chamber. A rotatable main roller that contacts and supports the tape-shaped support on the back surface, and a take-up roller that winds up the tape-shaped support sent from the main roller, wherein a plurality of reaction chambers are arranged around the main roller. The electron emission device is arranged so as to emit an electron flow to the tape-shaped support in a state before and after the formation of the protective film by each reaction chamber. The film forming apparatus according to claim 1. 5. An electron emission device comprising: a plasma electron gun having an electron supply source for emitting an electron flow by plasma generated by introducing an inert gas; and a radiation path of the electron flow from the plasma electron gun. And an electron supply chamber configured to restrict a radiation path of the electron flow by being surrounded and to be held at a ground potential to confine a plasma discharge generated by the plasma electron gun. The film forming apparatus according to any one of items 1 to 4. 6. The film forming apparatus according to claim 5, wherein a gap between the electron outlet of the electron supply chamber and the object to be formed is 2 mm or less. 7. An electron supply source is configured to heat a filament made of an alloy or a tungsten made of an alloy which has a low work function and easily emits electrons, and emits the emitted thermoelectrons by applying a bias voltage. The film forming apparatus according to claim 5, wherein: 8. The film forming apparatus according to claim 1, wherein the protective film of the object to be formed is made of diamond-like carbon.