JP2005089865A - Film deposition method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for depositing a DLC (Diamond Like Carbon) film by a CVD method on a surface of a recording medium in order to protect the recording medium such as an optical disk and a magnetic tape. <P>SOLUTION: In a film deposition device having a first electrode and a second electrode facing the first electrode, plasma is generated between the first and second electrodes by applying the electromagnetic energy with a plurality of frequencies combined to the first electrode, raw gas is activated by the plasma to deposit a film on a base body in the film deposition method. A dense film of high hardness and adhesion with less pin holes can be deposited thereby. In addition, film deposition can be performed with high-density plasma, and high-speed film deposition can be realized. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a manufacturing apparatus and a forming method for forming a magnetic recording medium having a high durability and a high recording density on a polymer substrate material. In particular, the present invention relates to a protective film forming apparatus and a forming method which require functions of wear resistance and lubricity. Its industrial application fields are diverse such as video equipment and information equipment.

In recent years, the density of magnetic recording media has been increasing. As an example of a conventional magnetic recording medium, a coating type in which γ-Fe ₂ O ₃ powder, CrO powder, pure iron powder and the like used for audio and video tape materials are coated on a polymer substrate material together with an abrasive and a binder. Things are known. Further, a magnetic recording medium having a high performance uses a metal magnetic material deposited thereon.

  In addition, a technique is known in which a film containing carbon as a main component (also called a carbon film, DLC or hard carbon film) is formed on the surface of these magnetic recording media to provide surface protection, wear resistance or lubricity. ing. The coating containing carbon as a main component is usually formed by a CVD method typified by a plasma CVD method.

  In a typical plasma CVD method, a substrate is placed on the high-frequency voltage supply side (cathode), and a high hardness film is produced using a self-bias formed in the vicinity of the cathode. In general, a carbon film having high hardness cannot be formed on the ground electrode (anode) side.

  When a film mainly composed of carbon is formed using a parallel plate type plasma CVD method, the organic resin substrate serving as the base of the magnetic storage medium must be placed on the cathode electrode side. Since a magnetic recording medium for high-density recording is generally obtained by vapor-depositing a metal magnetic material, it is not preferable to contact such a base with the cathode electrode, which causes the base to become part of the electrode and leaks a high-frequency electric field. Discharge occurs in the region. Such discharge has a high possibility of damaging the organic resin film as a substrate, and has a problem in terms of production stability and reliability.

  Further, if a hard carbon film as a protective film is formed simultaneously with the roll-to-roll type magnetic layer manufacturing process, the film forming speed of the carbon film is slow, which is impossible.

  Conventionally, a technique for forming a diamond-like carbon film is known. This diamond-like carbon film is a carbon film having a diamond structure, and is also called a diamond-like carbon (DLC) film. Hereinafter, such a carbon coating is referred to as a hard carbon coating.

  Such a hard carbon film is coated on the surface of a resin or a polymer film and can be used as a wear-resistant layer or a protective film. As a method for forming such a hard carbon film, a film forming apparatus as shown in FIG. 11 is known. In the film forming apparatus shown in FIG. 11, a pair of electrodes 112 and 114 are provided in a vacuum vessel 111, and one electrode 112 is connected to a high-frequency (generally 13.56 MHz) power source 115, and one electrode 114 is grounded. The substrate or substrate on which the film is formed is indicated by 113 and is disposed on the electrode 112 side to which high-frequency power is supplied. Although not shown, a reactive gas supply system, an exhaust system, and a matching device for power feeding are provided.

In the plasma CVD apparatus shown in FIG. 11, electrons are charged on the electrode side to which a high-frequency power source is connected, that is, on the electrode side opposite to the ground electrode, and further on the substrate side. A carbon film having a diamond structure can be formed by collision of H ⁺ ions and H radicals that contribute to quality improvement.

  Such a hard carbon film can be used as a protective film for a magnetic recording medium such as a magnetic tape or a magneto-optical disk. These magnetic recording media use a magnetic material and need to be protected in order to prevent foreign matters from being mixed or damaged.

As such a technique, there is a technique described in Patent Document 1. This publication describes that, in addition to high-frequency discharge, a carbon film having 10 ² to 10 ⁵ pinholes / mm ^{2 is} formed on the surface of a magnetic recording medium by applying a DC bias. .
Japanese Patent Publication No.3-23973

  However, according to the experiments by the present inventors, it has been found that the hard carbon film in which pinholes are present is inferior in long-term reliability as a protective film due to moisture or the like entering the pinholes. . Further, it has been found that the hardness and adhesion of the hard carbon coating and the elimination of pinholes are not always compatible.

  The main object of the present invention is to provide an apparatus capable of stably and reliably producing a hard carbon film on the surface of a magnetic recording medium having a conductive metal magnetic layer.

  That is, it is possible to provide an apparatus capable of forming a carbon film having sufficient wear resistance and lubricity in contact with the anode as the ground electrode.

  Another object of the present invention is to provide an apparatus capable of high-speed film formation to the extent that a hard carbon film as a protective film can be formed simultaneously with a magnetic layer manufacturing process.

  Furthermore, the objective of this invention is providing the apparatus which can suppress generation | occurrence | production of the flake resulting from the dirt of an electrode which is a new problem by achieving high-speed film-forming.

  Another object of the present invention is to form a hard carbon film having a high density, high hardness, and low pinholes as a protective film for a magnetic recording medium.

  In the present invention, a first electrode to which electromagnetic energy is applied and a grounded second electrode are arranged to face each other, and plasma is generated between the first and second electrodes by applying a high-frequency electric field. In the film forming apparatus for activating the source gas introduced into the plasma to form a film, the distance between the first electrode and the second electrode is 6 mm or less, and the pressure between the electrodes is 15 Torr. The film forming apparatus is characterized by being between 100 and 100 Torr.

  As the electromagnetic energy, a frequency of several tens of KHz to several GHz can be used. Generally, a high frequency of 13.56 MHz is used. Further, a combination of a plurality of frequencies may be used as electromagnetic energy. For example, you may employ | adopt the method of combining a very low frequency of 1-200 Hz, a low frequency of 1 KHz-1 MHz, and also combining a high frequency of 10-100 MHz into electromagnetic energy. That is, you may employ | adopt the method of combining multiple characteristics which each frequency has.

  Further, according to the present invention, if the distance between the first electrode and the second electrode is 6 mm or less and the pressure is between 15 Torr and 100 Torr, even if the substrate is in contact with the second electrode as the ground electrode, it has high hardness. The main point is that a simple carbon film can be formed, which is based on the experimental knowledge of the inventors.

  Prior to the above findings, the present inventor generally observed the physical properties of plasma in a pressure region (5 Torr to 760 Torr) much higher than the pressure region (10 mTorr to 1 Torr) selected by plasma CVD. The reason for paying attention to such a pressure range higher than that generally considered is that it is intended to improve the deposition rate of normal plasma CVD by an order of magnitude.

Considering the film formation process in plasma CVD (generation of radicals, transport to the substrate surface, reaction on the surface)
(1) Improvement of the density of radicals serving as a precursor for film formation (2) It can be understood that the film formation speed can be improved if two points of improvement in the efficiency of transport of radicals to the substrate surface can be improved. In the case of plasma CVD, radicals are generated in the entire plasma space, and it can be inferred that the generation has a greater influence on the deposition rate than the transport of radicals. It can be expected that the radical density can be increased by increasing the reaction pressure. In other words, film formation in a high pressure region can be expected to be high-speed film formation.

In the film formation process,
(3) Reaction on the film surface (suppression of surface desorption)
However, in the case of a low temperature process such as plasma CVD, the surface reaction rate is not limited, and the reaction process on the film surface does not contribute to the film formation rate. However, when a hard carbon film is formed, the action of ions on the surface greatly affects the film quality. That is, in a hard carbon film, ion bombardment is positively applied during film formation, leaving strong bonds in the film and forming films while cutting weak bonds. Therefore, generally, a substrate is placed on the cathode side, and film formation is performed using self-bias.

  Even if the increase in radical density is realized by increasing the pressure at the time of film formation, it is meaningless if the plasma, which is a premise of radical generation, greatly changes its physical properties by increasing the pressure. Therefore, as described above, the present inventor observed plasma in a high pressure region (5 Torr to 760 Torr).

  First, it is a requirement for generating plasma in a high pressure region (5 Torr to 760 Torr). Conventionally, the low-pressure glow discharge is generated in the pressure region of 10 mTorr to 1 Torr because the discharge is most easily generated in the pressure region (that is, the discharge is stable). The number of times a particle existing between parallel plate electrodes having a certain electrode interval d (d = several tens of millimeters in the case of a normal low-pressure glow) collides with electrons (the electrons are accelerated by the electric field between the electrodes, and from one electrode to another Is assumed to be flying in the direction of one electrode) is proportional to the pressure of the atmosphere (inversely proportional to the mean free path). That is, if the pressure is low and the number of collisions is small, the electrons have sufficient energy, and if they collide, ionization of the particles occurs. However, because of the low pressure, the particles themselves are few and cannot be plasma. On the other hand, when the pressure is high, the number of collisions of electrons increases, and electrons cannot have sufficient energy before the next collision, and particles cannot be ionized even if they collide. This is known as Paschen's law. The discharge start voltage V is a function of the product of the pressure p and the electrode interval d (pd product), and the minimum discharge start voltage Vmin exists at a certain pd product value. It is to do.

  That is, in order to generate plasma in a high pressure region, it is necessary to give electrons an electric field sufficient to ionize particles during a short free path. This can be dealt with by reducing the electrode interval d and increasing the voltage applied between the electrodes.

  However, the effect of increasing the voltage applied between the electrodes is limited. That is, in the case of glow discharge, the electric field distribution in the plasma is not uniform, and the electric field is the largest on the sheath portion formed in the vicinity of the electrode. Next, the positive column portion following the sheath portion is applied. The length of the sheath part is about the Debye length peculiar to plasma, and an electric field is not so much applied to the positive column that occupies most of the space. Therefore, even if a large voltage is applied between the electrodes, a substantial increase in the electric field at the positive column that occupies most of the space cannot be expected. However, since the increase in the interelectrode voltage is applied to the sheath portion, ionization in the region is promoted. When the electric field applied to the sheath exceeds the limit, accelerated electrons collide with the electrode surface, and thermionic emission from the electrode is generated by heating the electrode. In the case of glow discharge, the electron emission mechanism from the electrode is field emission and secondary electron emission. However, when thermionic emission occurs, the electric field consumed for electron emission from the electrode is almost eliminated, and the electric field corresponding to the electron emission is the sheath part. It will take to. When this happens, the electrons in the sheath portion are further accelerated to heat the electrode, causing thermal runaway as long as the electrode potential is maintained. Such a state is a negative resistance, and when an electric current flows through the entire path, it shifts to arc discharge.

Therefore, it is effective to reduce the electrode interval for plasma generation in a high pressure region. However, there is also a lower limit value for the electrode spacing. In order for the plasma to exist, the electrode interval needs to be at least several times the Debye distance. The Debye distance λ is expressed by the following equation.
λ = (ε ₀ · κ · Te / q ² · Ne) ^1/2
Where ε ₀ is the dielectric constant of the vacuum
κ is Boltzmann constant
q is the elementary charge
Te is the electron temperature
Ne is the charge density.

Since the plasma of the present invention has an electron density of 10 ¹⁵ / m ³ and an electron temperature of about 2 eV, the Debye distance is about 0.3 mm. Therefore, the electrode spacing is desirably 1 mm or more.

  As described above, discharge at a pressure from 1 Torr to 760 Torr is possible, but the physical properties of the plasma vary greatly.

  In the pressure region of about 100 Torr to 760 Torr, the discharge tends to become unstable in the normal electrode structure as shown in the above-described mechanism of transition to arc discharge. Therefore, the method for generating atmospheric pressure discharge, which is another invention of the present inventor, can be used.

  A heat-resistant dielectric is inserted on the electrode surface so that the entire system does not exhibit a negative resistance even if the discharge exhibits a negative resistance. Since the dielectric has a positive resistance, the entire system has a positive resistance. In this case, since the dielectric enters the series in terms of an equivalent circuit, the electric field applied between the electrodes needs to be an alternating current.

  Further, in this region, the pressure is high, the probability of collision and recombination of ions and electrons in the space is increased, and the plasma is easily extinguished. Therefore, it is necessary to promote the diffusion of ions and electrons (particularly, the diffusion of ions) to widen the plasma. Therefore, the addition of a rare gas having a metastable state, particularly helium or argon, is effective. The rare gas is preferably 80% or more of the total gas.

  It is also effective to diffuse particles constituting the plasma by applying a magnetic field. The distribution of the magnetic field is preferably such that the magnetic flux is diverged in the direction of the outside from the center of the electrode. In this way, electrons drift along the diverging magnetic flux, and cations are attracted so as to cancel the electric field created by the electrons. As a result, the plasma diffuses.

  As described above, in the pressure region of about 100 Torr to 760 Torr, addition of the dielectric and rare gas on the electrode surface is necessary, but in the pressure region of about 100 Torr or less, the dielectric and rare gas are not necessarily required. However, the presence of a dielectric and a rare gas in a pressure region of about 100 Torr or less is effective because it has the effect of stabilizing the discharge. However, this causes an increase in cost and a decrease in film formation rate.

  The present inventor has observed the physical properties of plasma at 5 Torr to 760 Torr using the above-described means.

  The gas used in the experiment was argon, and the electrode used was a dielectric inserted to stabilize the plasma. As the dielectric, 0.5 mm thick sintered alumina was used. The frequency of the high frequency is 13.56 MHz.

  As typical physical properties of plasma, electron temperature (Te), electron density (Ne), and minimum voltage (sustaining voltage) required to maintain the plasma were measured. The electron temperature (Te) and the electron density (Ne) were measured using the Langmuir probe method (single probe method), and the lowest voltage (sustaining voltage) required for maintaining the plasma was measured as the terminal voltage of the power source. The results are shown in FIGS.

FIG. 9 shows the electron temperature (Te) and the electron density (Ne) simultaneously. The electron density (Ne) cannot be calculated because the electron saturation current region that can be observed when the probe voltage is applied in the positive voltage direction, and there is a pressure region (60 Torr or more) that cannot be observed. Not shown. The electron density (Ne) at 40 Torr or lower gradually increases from 1 × 10 ¹⁴ / m ³ to 1.7 × 10 ¹⁴ / m ³ with increasing pressure, and rapidly increases to 8 × 10 ¹⁴ in the region from 40 Torr to 60 Torr. It has risen to / m ³ . This indicates that arc discharge is locally generated at about 40 Torr as a boundary, indicating that the plasma in the region (from 40 Torr to 60 Torr) is becoming unstable. However, when this is used, a very high density plasma can be obtained.

  FIG. 7 shows simultaneously the electron temperature (Te) and the minimum voltage required to maintain the plasma (Sustaining Voltage). The minimum voltage required to maintain the plasma (Sustaining Voltage) is not limited to its physical meaning, but indicates the ease of handling of the plasma as an apparatus, and is preferably as low as possible. From this point of view, it shows a minimum between 10 Torr and 100 Torr, and is preferably used in this region.

  On the other hand, the graph of the electron temperature (Te) has a U-shaped shape with a minimum of 60 Torr. In the medium pressure region from 15 Torr to 100 Torr, the electron temperature (Te) is lower than the lower pressure region and the higher pressure region, and is 3 eV or less.

  The above results are only representative results and do not represent all. For example, if the gas is changed to helium, neon, etc., a hydrocarbon gas is added, or the gas flow rate is changed, the results are different. For example, the pressure at which the electron temperature (Te) is minimized varies in the range of 60 Torr to 100 Torr, and the pressure at which the electron density (Ne) increases rapidly varies in the range of 40 Torr to 80 Torr, which is necessary to maintain the plasma. The pressure at which the minimum voltage (Sustaining Voltage) is minimized varies from 20 Torr to 100 Torr. However, qualitatively almost the same result is obtained.

  From the above, in the medium pressure region (range of 15 Torr to 100 Torr), the minimum voltage (Sustaining Voltage) required to maintain the plasma is low, which reduces the usability of the device, the weight of the power source, and the cost reduction. From the point of view, an increase in electron density (Ne) is preferable in terms of an effect of increasing radical density.

  Further, in the intermediate pressure region (range of 15 Torr to 100 Torr), the electron temperature is low, which is disadvantageous for the generation of radicals, but the plasma potential rises with respect to the anode which is the ground potential, so the anode Ion bombardment occurs. This is very convenient for producing a hard carbon film installed on the anode side. The reason will be described below.

  Electrons and ions in the plasma move more easily under the same electric field strength than the difference in mass. Therefore, the probability that electrons will reach the container is higher. If the container is an insulator, the container will be negatively charged. If the container is a conductor, assuming that the container in contact with the plasma has the same potential as the plasma, a current flows in the direction of the plasma through the container. When the current flows, the charge neutral condition is violated, so that the plasma potential moves in the positive direction with respect to the container so as to cancel the current flow. That is, regardless of whether the container is a conductor or an insulator, the plasma is positively charged with respect to the container due to the difference in mobility of electrons and ions.

  This indicates that an ion sheath is also present on the ground electrode side. Of course, an ion sheath is also present on the cathode (feeding electrode side). However, the naturally occurring ion sheath is ignored because it is sufficiently smaller than the sheath generated by self-bias.

  The electric field generated by the ion sheath can be estimated by assuming that the ion sheath is equivalent to a capacitor having an electric double layer.

Assuming that the electron velocity is Boltzmann distributed, the electron density in the ion sheath decreases exponentially, and the space charge in the ion sheath becomes an exponential curve. The boundary between the ion sheath and the plasma is relative to the bulk potential of the plasma.
Vt = −κ · Te / 2q
It is reasonable to define the position as a potential of a certain level.

  This is because electrons in the plasma bulk move with energy of about κ · Te / 2.

  As the electron temperature (Te) increases, the electrons enter the ion sheath, so that the thickness d of the ion sheath decreases and the capacitance C of the electric double layer increases. Conversely, when the electron temperature (Te) decreases, the capacitance C of the electric double layer decreases.

Since the amount of charge accumulated in the ion sheath is proportional to the electron density (Ne), that is, the ion density (Ni), the voltage V applied to both ends of the electric double layer is
V = Q / C
= (Ne) ^2/3 · d / ε ₀ · S
Where d is the thickness of the ion sheath
S is the electrode area. That is, the smaller the electron temperature (Te), the stronger the electric field in the ion sheath and the greater the bombardment of ions to the anode.

  Conventionally, a hard carbon film could not be formed on the anode side. However, in the apparatus of the present invention, the pressure was set to an intermediate pressure (from 15 Torr to 100 Torr), and as a result, the electron temperature was lowered, so that ion bombardment was also applied to the anode. As a result, a hard carbon film can be formed on the anode side.

  The present invention also includes a second electrode having a cylindrical shape that is grounded so as to face the first electrode, and a film that is a base on which a film is to be formed is formed on a part of the second electrode. When the cylindrical second electrode is wound, the film has a mechanism that passes between the first and second electrodes, and a high-frequency electric field is applied to the first electrode. In the film forming apparatus for forming a film by activating the space between the first and second electrodes into plasma and activating the raw material gas introduced into the plasma, the peripheral end of the first electrode is Covered with an insulator, a substantially closed space is constituted by the first electrode and the second electrode and the insulator, and gas is passed through the pores provided in the first electrode in the closed space. Supplied, and the plasma is confined in the closed space, making it difficult to leak outside. And a gap between the first electrode and the second electrode is 6 mm or less, and a pressure in the closed space is between 15 Torr and 100 Torr. Device.

  In addition to medium pressure, this confines the plasma in a closed space, preventing discharge in unfavorable areas, and generating a higher density plasma, increasing bombardment to the anode Is realized.

  The unfavorable region is specifically the peripheral portion of the electrode. In general, the electric field at the center of the electrode has a constant or uniform rate of change. However, the electric field strength increases at the periphery of the electrode, particularly at the end of the power supply electrode, and the discharge concentrates in the region. That is, the impedance is reduced by increasing the plasma density in the region, and a large amount of current flows in the region. As a result, most of the electric power is consumed at the peripheral portion, and the plasma density at the center of the electrode is lowered. This leads to an increase in electron density and a decrease in ion bombardment at the center of the electrode.

  Therefore, the above-mentioned problem is solved by covering the peripheral end portion of the feeding electrode (first electrode) with an insulator and confining the plasma in the central portion.

  Further, according to the present invention, there is provided a second electrode having a cylindrical shape which is grounded so as to face the first electrode, and a film which is a substrate on which a film is to be formed is formed on a part of the second electrode. When the cylindrical second electrode is wound, the film has a mechanism for passing between the first and second electrodes, and a high-frequency electric field is applied to the first electrode. In the film forming apparatus, the space between the first and second electrodes is converted into plasma, and the raw material gas introduced into the plasma is activated to form a film, wherein the first electrode is the second electrode. The electrode is configured so that the electric field strength formed on the electrode is the strongest on the surface of the first electrode and the weakest on the surface of the second electrode, and the first electrode and the second electrode The shortest interval is 6 mm or less, and Pressure between the first electrode and the second electrode is a film-forming apparatus characterized in that between 100Torr from 15 Torr.

  In addition to the intermediate pressure, the electric field intensity around the first electrode, that is, the cathode is increased, and the plasma density is increased in this region. As the shape of the first electrode, that is, the cathode electrode, a knife-like or needle-like one is effective in addition to the one using the end of the flat plate.

  That is, a high-density plasma is realized by actively utilizing a region where the electric field strength is not uniform.

  In the present invention, a first electrode to which a high-frequency electric field is applied and a grounded second electrode are arranged to face each other, and plasma is generated between the first and second electrodes by applying the high-frequency electric field. A film forming apparatus for forming a film by activating a raw material gas generated and introduced into the plasma, wherein a plasma generated between the first and second electrodes is formed on a grounded cylindrical metal surface The cylindrical metal is arranged so as to be sprayed, a film which is a base on which a film is to be formed is wound around a part of the cylindrical metal, and the cylindrical metal is rotated, whereby the film is In the film forming apparatus having a mechanism that passes through the sprayed plasma region, the distance between the first electrode and the second electrode is 6 mm or less, and the first electrode and the second electrode The pressure in between is 15T A film forming apparatus, characterized in that is between rr of 100 Torr.

  This is a plasma generator with a parallel plate or concentric cylindrical electrode structure, which can form high-density plasma by setting it to a medium pressure in the same way. . Due to the medium pressure, gas diffusion is slower than low pressure, and radical transport may be rate-limiting. This is solved by spraying.

  Further, according to the present invention, the gas supplied into the plasma space may be a gas selected from the group consisting of hydrocarbons, halogenated carbons and halogenated hydrocarbons and a mixed gas of hydrogen, or a mixed gas and a rare gas. It is a mixed gas, It is a film forming apparatus as described in each claim characterized by the above-mentioned.

  Although the medium pressure allows the film to be formed at a high speed, the adhesion of the film to the cathode becomes a problem. This is solved by adding a carbon halide.

  In the present invention, an ion bombardment is allowed to act on the anode side to form a hard carbon film also on the anode side. However, since a larger self-bias is applied on the cathode side than on the anode side, It becomes stronger than the anode side. In the present invention, utilizing this phenomenon, a halogen-based gas having an etching action is added to the raw material gas, and etching is performed on the cathode side instead of film formation.

  Carbon halides, such as carbon tetrafluoride, are known as etching gases. In carbon tetrafluoride, only an etching action can be seen, but in carbon 6 fluoride 2 or carbon 8 fluoride 3 or the like, it is etched or formed into a film by the strength of self-bias. That is, etching is performed when the self-bias is strong and ion bombardment is strong, and the film is formed when the self-bias is weak and ion bombardment is weak.

  In the present invention, the bombardment is stronger on the cathode side where film formation is not preferable, which is very convenient.

  Thereby, the film | membrane production | generation of a cathode side can be suppressed and generation | occurrence | production of flakes can be suppressed. Furthermore, since the maintenance period of the apparatus can be extended, the throughput can be improved and the cost can be greatly reduced.

  Further, in the case of a VLSI process or the like, it is a cause of contamination, so it can be avoided. However, in the case of forming a carbon film as in the present invention, there is no need to worry about contamination.

  According to another aspect of the present invention, there is provided the film forming apparatus, wherein the film as the substrate is a conductive film.

  In the case of a conductive film that can be placed only on the anode side, not on the cathode side, the present invention is most effective.

  Furthermore, the gist of the present invention is to form a hard carbon film while ultrasonically vibrating the substrate. In particular, a magnetic recording medium is used as a substrate, and a hard carbon film is formed as a protective film of the magnetic recording medium.

  In addition, in a plasma CVD apparatus having a parallel plate configuration in which a high-frequency power source is connected to an electrode on which a substrate on which a hard carbon film is formed is disposed and the other electrode is a ground electrode, while applying ultrasonic vibration to the substrate, A carbon film is formed.

  Furthermore, the present invention is characterized in that a belt-like film substrate (for example, a tape-like film) is used as the substrate, and the substrate is caused to run while applying ultrasonic vibration to form a hard carbon film on the surface thereof.

  In addition, a film-like substrate is used as the substrate, and the substrate is vibrated in the direction between the electrodes, thereby realizing a state in which a bias is applied in a pulse mode or a high-frequency mode.

Furthermore, the present invention is characterized in that the number of pinholes per 1 mm ^{2 of the} hard carbon coating is 30 or less. The film thickness of the hard carbon film may be 5 nm to 200 nm, preferably 10 nm to 50 nm.

  Inclusion of 20 atomic% or less of at least one element selected from Si, B, N, P, and F in the hard carbon film used as the protective film improves the adhesion of the film, It is effective to give conductivity. For example, by including Si and P in the hard carbon film, the conductivity can be increased and a protective film that is less likely to be charged with static electricity can be obtained.

  When the substrate vibrates ultrasonically, cluster-like carbon having small grains or carbon molecules can be deposited on the surface of the substrate, and the carbon film to be formed can be made dense and uniform. This is because large carbon molecules are repelled from the vibrating substrate because the substrate is ultrasonically vibrated, and molecules having a specific size or less are easily deposited on the surface of the substrate.

  Further, when an elongated film-like material such as a magnetic tape is used as the substrate, it is possible to prevent the substrate from being entangled by applying ultrasonic vibration to the substrate.

  Further, particles adhering to the substrate surface (powder raw material that does not become a film) can be removed by ultrasonic vibration.

  In addition, by applying ultrasonic vibration in the direction between the electrodes arranged in parallel, a state in which an AC bias voltage is applied between the electrodes can be realized. This action is particularly effective when a film-like substrate such as a magnetic tape that is flexible and has a large amplitude is used.

  The configuration for applying ultrasonic vibration to the substrate can be used in all the inventions disclosed in this specification.

  According to the present invention, it is possible to provide an apparatus capable of stably and reliably producing a hard carbon film on the surface of a magnetic recording medium having a conductive metal magnetic layer.

  Further, conventionally, a sufficiently hard carbon film could not be formed on the ground electrode side, but according to the present invention, it has sufficient wear resistance and lubricity even in a state where it is in contact with the anode as the ground electrode. An apparatus capable of forming a carbon film can be provided.

  Furthermore, the present invention can provide an apparatus capable of high-speed film formation that can form a hard carbon film as a protective film simultaneously with the magnetic layer manufacturing process.

  In addition, according to the present invention, it is possible to provide an apparatus capable of suppressing the generation of flakes caused by electrode contamination, which is a new problem caused by achieving high-speed film formation.

  Thereby, the film | membrane production | generation of a cathode side can be suppressed and generation | occurrence | production of flakes can be suppressed. Furthermore, since the maintenance period of the apparatus can be extended, the throughput can be improved and the cost can be greatly reduced.

  In addition, the magnetic recording medium produced by the production apparatus of the present invention can be improved in the interface characteristics and adhesion between the magnetic layer and the film mainly composed of carbon, and can be of high quality. Further, the lower oxide produced on the surface of the magnetic layer cannot be essentially removed simply by avoiding exposure to the atmosphere, but the plasma activation treatment according to the present invention is effective.

  Also, the surface properties of carbon-based coatings, that is, wear resistance, high smoothness, hardness, etc., are remarkably improved, making it possible to produce industrially valuable magnetic recording media, which has been a problem in the past. It is possible to avoid the rule points on continuous formation.

By forming the hard carbon film while applying ultrasonic vibration to the substrate, a dense and good film quality can be obtained. In particular, it is possible to obtain a very dense carbon film having 30 or less pinholes / mm ^2, which is extremely useful as a protective film.

  An embodiment of the present invention will be described with reference to the drawings.

  In FIG. 4, the polymer substrate material 3 sent from the supply roll 2 in the vacuum container 1 travels in the direction of the arrow along the cylindrical can 7 via the free roller guide 4.

  In this example, a polyimide film (generally used as a substrate for a magnetic tape) having a width of 4 cm and a thickness of 6 μm was used as the polymer substrate material 3.

  The metal atoms evaporated from the evaporation source 6 are deposited on the polymer substrate material 3 to form a magnetic layer having a thickness of 0.15 to 0.18 μm.

In this embodiment, a Co-Cr-Ni alloy is used as the evaporation material, a Pierce type electron gun capable of scanning in a wide range is used, an acceleration voltage is applied to 35 KV, and electron beam evaporation is performed at an operating pressure of 5 × 10 ⁻⁴ Torr. Formed by the method. The passing speed of the polymer substrate material 3 was set to 135 m / min. The shielding plate 5 is provided to limit the deposition area.

  A potential difference is applied between the cylindrical can 7 and the formed magnetic layer by the DC power supply 15 via the free roller guide 4. Here, a voltage of 80 V was applied so that the polymer substrate material 3 and the cylindrical can 7 were in close electrostatic contact.

  The polymer substrate material 3 on which the magnetic layer is formed is guided to the vacuum vessel 9 through the intermediate roll 8 and subjected to plasma activation processing.

  Here, the plasma activation process will be described.

Hydrogen gas is introduced from the source gas supply system 18 between the electrodes in which the ground electrode 10 and the high-frequency power supply electrode 11 are arranged in parallel at an interval of 3 cm, and the operating pressure is 10 ⁻¹ to 10 ⁻ while being exhausted by the exhaust system 19. Controlled to ² Torr, a high frequency of 13.56 MHz is applied from the high frequency power supply system 12 at a power density of 0.5 W / cm ² to form hydrogen plasma. The polymer substrate material 3 passes through the formed plasma region 16 at a speed synchronized with the magnetic layer forming step.

  By performing this step, the surface of the magnetic layer is exposed to active hydrogen radicals or hydrogen ions. As a result, the surface of the magnetic layer is activated at the same time as being appropriately cleaned. A similar effect can be achieved even when argon gas or a mixed gas of argon and hydrogen is used.

  The size of the gap through which the polymer substrate material 3 opened on the wall separating the vacuum chamber 9 and the buffer chamber 20 should pass depends on the Debye distance of the plasma 16 generated in the vacuum vessel 2 or the pressure in the plasma region 16. It should be smaller than the mean free path. As a result, plasma does not leak into the buffer chamber 20.

  Next, the vacuum vessel 13 that is a formation region of a film containing carbon as a main component will be described. On the polymer substrate material 3 on which the magnetic layer guided through the free roller guide 4 is deposited, a coating containing high-quality carbon as a main component in the process of passing through a region where a plurality of beam-type plasma generators are disposed. Is formed.

  Here, a plasma generator for generating beam-type plasma will be described with reference to FIG. The plasma generator shown in FIG. 1 uses a gas mainly composed of a rare gas such as helium or argon, at a medium pressure exceeding 1 Torr and less than 200 Torr, preferably 5 to 150 Torr, more preferably 50 to 100 Torr. Can be generated. As the rare gas, at least one gas selected from helium, argon, xenon, neon, and krypton can be used. Of course, these rare gases may be mixed and used.

  However, if the cost is not taken into account, helium is preferable because of its good discharge stability. Considering the cost, although the discharge stability is difficult, argon is advantageous in that it is cheaper. When argon is used, an insulator having a relative dielectric constant of 9 or more, such as alumina, is preferable.

  In the present embodiment, since the plasma region generated by one plasma generator shown in FIG. 1 is slightly over 20 mmφ, as shown in FIG. 5, four plasma generators 52 are arranged alternately and have a width of 20 mm. In this configuration, a film mainly composed of carbon can be uniformly formed on the surface of the polymer substrate material 3.

  The outline of the plasma generator shown in FIG. 1 will be described below.

  The plasma generator shown in FIG. 1 generates a plasma by generating a discharge between coaxially configured electrodes, and injects this plasma in the form of a beam outside the apparatus. The discharge is performed by using a gas mainly composed of a rare gas. A film mainly composed of carbon is formed by adding a hydrocarbon gas as a raw material gas such as methane or alcohol to a rare gas. Further, as will be described later, the electrode structure can be devised and film formation can be performed by separately supplying a source gas.

  In the apparatus shown in FIG. 1, the discharge is performed by a coaxial cylindrical electrode composed of a central conductor 31, a cylindrical insulator 33, and an outer conductor 29. Specifically, discharge is performed in the gap between the center conductor 31 and the cylindrical insulator 33. In this embodiment, since no gas is supplied to the gap between the cylindrical insulator 33 and the outer conductor 29, no discharge is performed in this portion.

  In this embodiment, the central conductor 31 is made of stainless steel, the cylindrical insulator 33 is made of quartz glass, and the outer conductor 29 is made of stainless steel. As the cylindrical insulator, it is desirable to use a material having a dielectric constant as large as possible. It is also useful to provide unevenness and protrusions on the surface of the central conductor 31 so that discharge is easy.

  The center conductor 31 is connected to the MHV coaxial plug 21, and an AC electric field is applied from the AC power source 12 (see FIG. 4) via a coaxial cable connected to the MHV coaxial plug 21. In the meantime, electromagnetic energy is supplied. A gas mainly composed of a rare gas (for example, helium) supplied between the center conductor 31 and the cylindrical insulator 33 is supplied from the gas inlet 10, and the insulators 22 and 27 made of Teflon (registered trademark) are supplied. Flows through. Insulators 22 and 27 made of Teflon (registered trademark) also have a role of preventing discharge in unnecessary places. The casings 23 and 28 are fixed by fastening jigs 25 and 26. The casings 23 and 28 and the fastening jigs 25 and 26 are made of stainless steel and are kept at the ground potential together with the outer conductor 29.

  The ratio of the rare gas in the gas mainly composed of the rare gas is desirably 80% or more of the rare gas. This is because, at a pressure of several Torr or higher, the rare gas is mainly converted into plasma, and the raw material gas is activated by the energy of the plasma-generated rare gas, and the raw material gas (for example, methane) is hardly activated directly. is there. Further, the unnecessary gas is exhausted from the exhaust system 19 (see FIG. 4).

  The introduced main gas is sealed with an O-ring 24 so as not to leak from the gaps between the components. The gap between the cylindrical insulator 33 and the outer conductor 29 is filled with a conductive metal foil. Therefore, no gas flows in the gap between the cylindrical insulator 33 and the outer conductor 29. Of course, gas may flow through this gap.

  In this embodiment, the distance between the surface to be formed (polymer substrate material 3) and the center conductor 31 is 2 mm. The diameter of the central conductor 31 is 5 mm, the outer diameter of the cylindrical insulator 33 is 22 mm, and the thickness is 1 mm. The length of the electrode is 30 mm. When a 90% helium gas is used as a rare gas, a plasma having a diameter of 20 mm or more is generated. That is, plasma treatment can be performed on a region having a diameter of 20 mm or more.

  A cross section taken along line A-A 'in FIG. 1 is shown in FIG. FIG. 2 shows the center conductor 31, the outer conductor 29, and the cylindrical insulator 33. A mixed gas of rare gas and source gas (a gas mainly composed of rare gas) passes through the gap 32 and is converted into plasma in the gap 32. Then, beam-shaped plasma is sprayed to the outside of the apparatus, and film formation is performed with the activated source gas.

  In the configuration shown in FIG. 4, since the width of the polymer substrate material 3 is 20 mm, four plasma generators (shown as 52 in FIG. 5) shown in FIG. 1 are alternately arranged as shown in FIG. In this configuration, uniform film formation is performed. The four plasma generators 52 are arranged in a portion indicated by 41 in FIG. 4, and a high frequency of 13.56 MHz is individually supplied from the power supply 12 by 500 W. The plasma is generated in a region indicated by 51, and film formation is performed in that region. In this embodiment, a film containing carbon as a main component can be formed by using helium as a rare gas and methane as a source gas.

The film forming conditions are shown below.
Input power 500W (per unit)
Pressure 100 Torr
Gas Helium: methane = 100 sccm: 10 sccm (per unit)

  The generated plasma is a low-temperature glow discharge, and its temperature is 100 ° C. or lower. Therefore, even if the gas is a polymer substrate material, there is no problem and good film formation can be performed.

  Note that a bias voltage of direct current or alternating current (high frequency) may be applied to the surface to be formed by using a bias power source 42 indicated by 42 in FIG. Further, a magnetic field may be applied to the surface to be formed so that beam-shaped plasma is effectively injected onto the surface to be formed.

  The arrangement method of the plasma generator as shown in FIG. 5 can be freely set according to the required film forming speed and the size of the surface to be formed. For example, if another set of configurations as shown in FIG. 5 is provided, the deposition rate can be doubled.

  The film containing carbon as a main component is formed at a passing speed linked to the above-described two steps, and a film having carbon as a main component with a film thickness of about 20 nm is formed. The polymer substrate material 3 on which film formation has been completed is collected on the take-up roll 14 via the free roller guide 4.

  In carrying out the present invention, the treatment before the formation of the magnetic layer can be carried out using a known technique such as irradiation with ions and electrons, or heating, as necessary. As the substrate, for example, a polyimide film is used in this embodiment, but a metal resin, plastic, or the like may be used in a roll shape or a plate shape.

  The magnetic recording medium produced in this example was cut into a tape shape with a width of 8 mm, and the reproduction output and durability were evaluated using a commercially available 8 mm video deck. With the above, a stable reproduction output with excellent drop stability and excellent running stability and still durability was obtained.

  In addition to the normal playback operation, it has been confirmed that it has excellent durability in continuous and intermittent tests of special playback operations.

  The present embodiment is an example in which the reaction product does not adhere to the coaxial discharge electrode portion in the configuration shown in the first embodiment. The present embodiment is different from the configuration shown in Embodiment 1 in that the center conductor (center electrode 31) is hollow and the raw material gas is allowed to flow through the hollow portion 30 as shown in FIG. FIG. 3 is a schematic view of a cross section taken along line A-A ′ of FIG. 1.

  When such a configuration is adopted, a rare gas (for example, helium) is caused to flow through the gap 32 and a raw material gas (for example, methane) is caused to flow through the hollow portion 30. Since no discharge occurs in the hollow portion 30, the raw material gas is not activated at all here and is discharged to the outside of the apparatus. On the other hand, the rare gas flowing through the gap 32 is turned into plasma by high-frequency discharge performed between the center conductor 31 and the outer conductor 29. Then, the raw material gas that has not been activated when leaving the apparatus is encapsulated coaxially by the rare gas that has been made plasma, and is activated or plasmaized by the plasma energy of the rare gas.

  Since the source gas is activated outside the apparatus, it is possible to fundamentally eliminate the possibility that reaction products adhere to the apparatus and flakes are generated. In addition, since the source gas is encased in the rare gas converted into plasma outside the apparatus, the collection efficiency can be made extremely high.

  The present embodiment is an example in which the plasma generator disposed in the portion indicated by 41 in FIG. 4 is a sheet-shaped (plate-shaped) plasma generator. The structure of this sheet-shaped plasma generator is shown in FIG.

  The apparatus shown in FIG. 6 has parallel plate type electrodes, and the plasma generated by the parallel plate electrodes is drawn out to the outside of the apparatus as plate-shaped plasma, and this sheet-shaped plasma is used.

  In FIG. 6, the parallel plate electrode portion includes an electrode plate 61, an insulator plate 63, and an outer casing 62. The insulator plate 63 is provided in close contact with the outer casing 62. In this embodiment, the electrode plate 61 is made of stainless steel, the insulator plate 63 is made of quartz glass, and the outer casing 62 is made of stainless steel. The electrode plate 61 is insulated from others by three Teflon (registered trademark) shields 620, 621, and 622, and is connected to the MHV coaxial plug 611. An AC electric field is applied to the electrode plate 61 from an AC power source (13.56 MHz) 64 (corresponding to 42 in FIG. 4) via a coaxial cable (not shown) connected to the MHV coaxial plug 611. The rare gas supplied between the electrode plate 61 and the insulator plate 63 is supplied from a gas inlet 612 and supplied through a gas groove carved in a Teflon (registered trademark) insulator 613. The insulator 613 made of Teflon (registered trademark) also has a role of preventing discharge in an unnecessary place. The outer casing 62 and the electrode plate holder 616 are screwed at the top plate 617. The electrode plate holder 616 and the top plate 617 are made of stainless steel and are kept at the ground potential together with the outer casing 62. The width of the opposing insulator plate, that is, the discharge portion width (the length in the depth direction of the electrode in FIG. 6) is 25 mm, and the insulator thickness is 1.0 mm. The electrode interval is 5 mm, and the electrode length (length in the vertical direction in FIG. 6) is 30 mm. Accordingly, a sheet type plasma of approximately 5 mm × 25 mm is generated.

  When 100 sccm of helium was supplied to the above apparatus and 500 W of high frequency power with a frequency of 13.56 MHz was applied at a pressure of 100 Torr, a stable discharge was obtained over the entire width of the discharge section, and a sheet-like (plate-like) plasma was produced. It was possible to release it to the outside. Further, even if this state was maintained for 10 minutes or more, no trouble on the apparatus such as overheating occurred.

  When the temperature of the plasma formed by the discharge was measured by blowing the plasma onto a thermocouple, a temperature of about room temperature to about 70 ° C. was shown. This confirms that low-temperature glow discharge is being performed.

  When used in the configuration shown in FIG. 4, a source gas such as methane or ethylene may be flowed as an additive gas. In order to increase the deposition rate or increase the deposition area, a plurality of apparatuses may be arranged as shown in FIG.

  This embodiment is an example in which the portion indicated by 41 in FIG. 4 is configured as shown in FIG. In FIG. 8, reference numeral 81 denotes a film-like substrate. An example of such a film-like substrate is a magnetic storage medium tape. Reference numeral 82 denotes a cathode electrode, which is connected to a high-frequency power source 87 via a matching box 86. Reference numeral 85 denotes a cylindrical electrode constituting an anode electrode, which is grounded. High frequency discharge is performed in the plasma reaction space 89 between the anode electrode 85 and the cathode electrode 82. Further, the anode electrode 82 is rotated so that the film-like substrate 81 moves smoothly. 83 is an insulator. Reference numeral 84 denotes a gas introduction tube, and the raw material gas, the dilution gas, and the additive gas are guided to the plasma discharge space 89 through the gas introduction tube 84. These gases are guided from the gas introduction pipe 84 to the pores 88 provided in the anode electrode 82 and are ejected into the plasma reaction space.

  The width of the cathode electrode 82 (the width effective for discharge) is 20 mm, and the length is 30 cm. The cylindrical anode electrode 85 has a diameter of 20 mm and a length of 30 cm. The distance between the cathode electrode 82 and the anode electrode 85 is 5 mm. The interval between the pair of electrodes is preferably 10 mm or less.

  An example in which a 10-inch wide organic resin film on which a metal magnetic material is deposited is used as the film-like substrate 81 and a hard carbon film is formed on the surface thereof to a thickness of 30 nm will be described. Here, the film-like substrate is moved at 12 m / min (20 cm / sec). In this case, the film-like substrate moves in the discharge space 89 having a width of 20 mm in 0.1 seconds. Therefore, in order to form a film with a thickness of 30 nm, a film formation speed of 300 nm / sec is required.

Hereinafter, conditions for obtaining a deposition rate of 300 nm / sec will be described using the configuration shown in FIG.
Reaction pressure 60 Torr
Input power 300W (5W / cm ² ) (13.56MHz)
Source gas C ₂ H ₄ : H ₂ : Ar = 1: 1: 2 (total 1000 sccm)
Additive gas C ₂ F ₆ (10% added to C ₂ H ₄ )

  By setting it as the said film-forming conditions, the film-forming speed | rate of 300 nm / sec can be obtained. A hard carbon film can be formed on the surface of the film-like substrate 81 to a thickness of 30 nm.

The reason why C ₂ F ₆ is used as the additive gas is as follows. In general, when a film is formed at a high film formation rate as described above, a large amount of reaction products adhere to the cathode electrode. This reaction product becomes flakes and becomes an obstacle to film formation. Therefore, a device that prevents the reaction product from adhering to the cathode electrode is required.

  On the other hand, when the configuration shown in FIG. 8 is adopted, the cathode electrode 82 is biased to a negative potential by the action of the self-bias, and positive ions generated by the plasma discharge are attracted to the cathode electrode 82 side. As a result, the cathode electrode 82 side is sputtered.

Therefore, when C ₂ F ₆ is used as the additive gas as in this embodiment, the cathode electrode 82 side is sputtered and etched. Accordingly, the reaction product adhering to the cathode electrode 82 is etched simultaneously with the adhering. Thus, the hard carbon film can be formed without the reaction product adhering to the cathode electrode.

Here, C ₂ F ₆ is used because C ₂ F ₆ has an etching action by F and a film-forming action of a hard carbon film by C. Here, CF ₄ can also be used as an additive gas. However, since CF ₄ has no film forming action on the hard carbon film, it is preferable to use C ₂ F ₆ that contributes to the film formation of the hard carbon film.

  As described above, film formation is performed on the substrate on the anode electrode 85 side without causing reaction products to adhere to the cathode electrode 82 while etching the cathode electrode 82 with a halogen-based gas. A film can be formed on the surface of the substrate 81.

  FIG. 10 shows a plasma CVD apparatus that forms a hard carbon film on the surface of the base 113. The apparatus shown in FIG. 10 is characterized in that film formation is performed while ultrasonically vibrating the substrate 113. Hereinafter, the plasma CVD apparatus shown in FIG. 10 will be described. The base 113 is a magnetic recording medium such as a magneto-optical disk.

  The plasma CVD apparatus shown in FIG. 10 has a pair of electrodes 112 and 114 in a vacuum vessel 111 for activating (plasmaizing) a reactive gas. The electrode 114 is grounded, and the electrode 112 is connected to the high frequency power supply 115. Here, as the high-frequency power source 115, one that generates a high frequency of 13.56 MHz is used. Although not shown in the figure, a gas introduction system, an exhaust system, and a matching device are arranged. If necessary, a heating means such as a heater or an infrared lamp is provided.

  A piezoelectric element 121 sandwiched between a pair of electrodes 122 and 123 is provided on the electrode 112, and a base body 113 is disposed thereon. A high frequency is applied to the piezoelectric element 121 from the power supply 125, and the piezoelectric element 121 vibrates at a predetermined frequency. Although this frequency is arbitrary, for example, frequencies from 1 KHz to 100 MHz can be used.

  In addition, the electrode 123 and the electrode 112 need to be insulated. Further, the base 113 is mechanically fixed to the electrode 122 by a brazing material, an adhesive, and further a protrusion or a key-type locking member (member for fixing the base) as necessary.

  As the piezoelectric element 121, crystal, Rocheul salt, lithium niobate, barium titanate, lead zirconate titanate (PZP), other organic piezoelectric materials, piezoelectric ceramics, or the like can be used.

  FIG. 12 shows an enlarged schematic view of the piezoelectric element 121. FIG. 12 shows a piezoelectric element 121, a pair of electrodes 122 and 123 for applying a voltage to the piezoelectric element, a base 113 on which a hard carbon film is formed, and a voltage to the piezoelectric element. The high-frequency power supply 125 of FIG. The base 113 vibrates as the piezoelectric element 121 vibrates ultrasonically.

  The piezoelectric element 121 can select a vibration direction and a frequency depending on the cut direction. As the vibration direction, the thickness direction and the surface direction of the piezoelectric element 121 can be selected, and the vibration mode can also be a sliding vibration or a flexural vibration. The vibration output can be controlled by monitoring the voltage applied to the piezoelectric element 121.

  In the plasma CVD apparatus shown in FIG. 10, it is preferable that the distance between the pair of electrodes 112 and 114 be as narrow as possible. This is a fact found experimentally. Specifically, when the distance is 10 mm or less, a high film formation speed and a good film quality can be obtained. However, when the configuration as shown in FIG. 10 is adopted, the distance between the electrodes is limited by the thickness of the piezoelectric element 121 and the thickness of the base 113, and therefore the value is preferably 20 mm or less.

The conditions for forming a hard carbon film on the substrate 113 are shown below. Here, an organic resin plate is used as the substrate 113 instead of the magneto-optical disk.
Source gas Ethylene gas + Hydrogen gas Operating pressure 80Pa
High frequency power 1.5kW
Substrate temperature Unheated

The hard carbon coating film formed on the substrate 113 under the above conditions had a film thickness of 20 nm, little peeling, and a dense film quality. In addition, the number of pinholes in the hard carbon coating averaged 10 / mm ² or less.

The present embodiment relates to a configuration for applying ultrasonic vibration to the base 113 by means different from the fifth embodiment. FIG. 13 shows an outline of the plasma CVD apparatus of this example. A feature of FIG. 13 is a configuration in which the electrode 112 is vibrated by the ultrasonic transducer 141. With such a configuration, the base 113 can be ultrasonically vibrated. Further, by adopting the configuration as shown in FIG. 13, the distance between the pair of electrodes 112 and 114 can be made 10 mm or less, and high-speed film formation can be realized.

  In this embodiment, a hard carbon film is coated on a tape-like material such as a magnetic tape. FIG. 14 shows an outline of a plasma CVD apparatus used in this embodiment. The plasma CVD apparatus shown in FIG. 14 includes a roll-shaped electrode 155 in a vacuum vessel, an electrode 156 that forms a pair with the roll-shaped electrode 155, guide rollers 153 and 154 that also serve as an ultrasonic vibrator, Drum 151 or 152 and a drum 152 or 151 for winding are provided. Although not shown, a gas introduction system such as a reactive gas, a doping gas, and a dilution gas, and a gas exhaust system are provided.

  Here, a polyimide film strip substrate (magnetic tape substrate material) is used as the tape substrate. As shown in FIG. 14, the belt-shaped film base 157 is wound and moved from one drum 151 or 152 to the other drum 152 or 151. The drum-shaped electrode 155 is connected to a high frequency power supply 115 of 13.56 MHz, and discharge is performed between the electrode 156 which is a ground electrode. At this time, the drum-shaped electrode 155 also rotates as the base 157 moves. At this time, a hard carbon film is formed on the surface of the film-like substrate 157.

  That is, as each drum and roller rotate, the film-like substrate moves from one drum to the other drum, and at that time, a hard carbon film is formed on the surface of the film-like substrate.

An example of actual film forming conditions is shown below.
Substrate: 180 mm wide polyimide film Input power: 1.5 kW
Deposition pressure: 100 Pa
Board spacing: 10mm
Deposition gas: C ₂ H ₆ 200 sccm
H ₂ 50sccm

  The moving speed of the substrate was 50 m / min. The film thickness of the hard carbon film formed is 20 nm.

When the film quality of the formed hard carbon film was measured by Raman spectrum, it showed the characteristics as a diamond-like carbon film and was confirmed to be a good quality hard carbon film. Further, the number of pinholes was 30 / mm ² or less, and the chemical resistance and the blocking action against moisture were good.

  In the configuration shown in FIG. 14, the film-like substrate 157 is subjected to ultrasonic vibrations from the guide rollers 153 and 154, but in this case, the film-like substrate 157 is subjected to film-like vibration as surface vibration from the pair of guide rollers 153 and 154. Ultrasonic vibration can be applied to the base 157.

  In particular, by applying ultrasonic vibrations by the guide rollers 153 and 154 to the base body 157, the tape-like base film 157 is formed in a place other than the reaction space (the space between the electrodes 155 and 156 where discharge is performed). Tangle can be prevented. Furthermore, particles adhering to the surface of the base 157 can be removed, and productivity can be improved.

  Further, the substrate 157 after film formation is wound around the drum 151 or 152.

  The method of applying ultrasonic waves to the film-like substrate 157 is not based on the guide rollers 153 and 154, but may be a method in which an ultrasonic vibrator is separately brought into contact with the film-like substrate 157 to apply ultrasonic vibrations. Alternatively, the drum-shaped electrode 155 that is in contact with the film-shaped substrate 157 may be ultrasonically vibrated.

  In this embodiment, the drum-shaped electrode 155 is vibrated in the apparatus shown in FIG. In order to ultrasonically vibrate the drum-shaped electrode 155, an ultrasonic transducer may be disposed in close contact with the electrode 155.

  As shown by the arrows in FIG. 14, the vibration state of the electrodes 155 includes a method of applying vibration in a direction between electrodes, that is, a direction perpendicular to the base 157 (up and down in the drawing) There is a method of applying vibration in a vertical direction, that is, a direction parallel to the base 157 (left and right in the drawing).

  In FIG. 14, when the electrode 155 is ultrasonically vibrated up and down, a state in which an AC bias is just applied can be realized. As is well known, when the configuration as shown in FIG. 14 is adopted, the electrode 155 side connected to the high frequency power source is negatively charged with respect to the grounded electrode 156 side, and just a negative bias (referred to as self-bias). Is applied. In this state, when the electrode 155 vibrates up and down, for the ions accelerated in the direction of the electrode 155, the base 157 is accelerated and approaches at a certain period (determined by the frequency of ultrasonic vibration applied to the electrode 155). The state of going away is realized. That is, a state where an AC bias is applied to the electrode 155 is realized.

  The above action can be obtained even when ultrasonic vibration is applied to the guide rollers 153 and 154, but the effect is more remarkable when ultrasonic vibration is applied to the electrode 155. Further, when ultrasonic vibration is applied to a flexible substrate (for example, a substrate such as a magnetic tape) in the state shown in FIG. 5, the effect can be obtained remarkably.

  In this example, a surface protective film of a magneto-optical disk as a magnetic recording medium is formed using the apparatus shown in FIG. 10 or FIG. A magneto-optical disk or an optical disk memory is widely known as a recording medium, as represented by a CD (compact disk). These discs are made of organic resin or industrial plastic material, and have characteristics such as high productivity and good handling.

  However, a protective film for protecting the surface layer is necessary. This protective film needs to transmit light in the visible light region (generally, a semiconductor laser beam having a wavelength of 700 to 800 nm is used), and high hardness and adhesion are required.

  As a protective film satisfying such requirements, it is conceivable to use a hard carbon film formed by the apparatus shown in FIGS. As a film forming method, an optical disk may be used as the substrate 113. Since the hard carbon film can be formed without heating, it is optimal as a surface protective film of an optical disk using a material that is weak against heat.

  In the above embodiment, an example in which a frequency of 13.56 MHz is used as a high frequency for causing discharge has been shown, but this is not limited to this frequency. Further, pulse discharge may be used. Further, in addition to the high frequency discharge, a DC or AC bias may be applied.

  Moreover, as source gas for a hard carbon film, hydrocarbon gas, such as methane, alcohol, etc. can be utilized. Further, hydrogen, other additive gas, or doping gas can be introduced during film formation.

  An outline of this embodiment is shown in FIG. The apparatus shown in FIG. 8 is an apparatus for forming a film on the surface of a tape or film-like substrate. In this embodiment, a structure in which a carbon film is formed as a surface protective film on the surface of the magnetic tape will be described.

  In the configuration shown in FIG. 8, reference numeral 81 denotes a film-like substrate. Here, a magnetic material is formed on the surface of a resin material such as polyimide by a vapor deposition method or the like.

  Reference numeral 82 denotes a cathode electrode, which is connected to a high-frequency power source 87 via a matching box 86. Reference numeral 85 denotes a can roll constituting an anode electrode, which rotates during film formation in order to transfer the substrate 81. The electrode 85 is configured to vibrate ultrasonically by a piezoelectric element. That is, during the film formation, the substrate 81 is ultrasonically vibrated by the cylindrical electrode 85 and thus vibrates ultrasonically.

  In film formation, high frequency discharge is performed in the plasma reaction space 89 between the anode electrode 85 and the cathode electrode 82. 83 is an insulator and 84 is a gas introduction pipe. A dilution gas such as methane and hydrogen, which are raw material gases, is introduced into the plasma reaction space 89 from the gas introduction pipe. The gas is ejected from the pores 88 provided in the anode electrode 82 into the reaction space 89.

  The width of the cathode electrode is 20 mm, for example. The length is, for example, 30 cm. The diameter of the cylindrical anode electrode 801 is set to 20 mm, for example. The length is, for example, 30 cm. In such a case, the substrate 81 having a width within 30 cm can be used.

An example of film forming conditions when the electrodes having the dimensions described above are used is shown below.
Reaction pressure 60 Torr
Input power 300W (13.56MHz)
Source gas C ₂ H ₄ : H ₂ : Ar = 1: 1: 2 (total 1000 sccm)
Additive gas C ₂ F ₆ (10% added to C ₂ H ₄ )
Ultrasonic frequency 30KHz (Ultrasonic vibration applied to electrode 801)

  By applying ultrasonic vibration to the substrate 81 through the electrode 85, the reaction product flakes do not adhere to the surface on which the substrate 81 is formed, and a dense carbon film without pinholes can be formed. it can.

1 shows a schematic cross section of a plasma generator. The cross section cut by A-A ′ in FIG. 1 is shown. The cross section cut by A-A ′ in FIG. 1 is shown. The outline | summary of the film-forming apparatus of an Example is shown. The arrangement state of the plasma generator is shown. 1 shows a schematic cross-sectional view of a plasma generator. The relationship between the pressure and the electron temperature (Te), and the minimum voltage required to maintain the plasma and the sustaining voltage (Sustaining Voltage) is shown. 1 shows a schematic cross section of a plasma generator. The relationship between pressure and electron temperature (Te), and pressure and electron density (Ne) is shown. The structure of an Example is shown. The structure of a prior art example is shown. The structure of an Example is shown. The structure of an Example is shown. The structure of an Example is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Vacuum container 2 ... Supply roll 3 ... Polymer substrate material 4 ... Free roller guide 5 ... Shielding plate 6 ... Evaporation source 7 ... Cylindrical can 8 ... Intermediate roll 9 ... Vacuum container (2)
10..Ground electrode 11..High frequency power supply electrode 12 .... High frequency power supply system 13 .... Vacuum container 14 .... Winding roll 15 .... DC power source 16 .... Plasma region 17 .... Sheet beam type plasma region 18 .... Raw material Gas supply system 19. Exhaust system 20. Buffer chamber 21. MHV plug 22. Teflon (registered trademark) insulator 23. Housing 25. Jig 26. Jig 27. Teflon ( (Registered Trademark) Insulator 28 .. Housing 29 .. Outer conductor 30 .. Gas inlet 31 .. Central conductor 33 .. Cylindrical insulator 42 .. Bias power source 52 .. Plasma generator 61 .. Electrode plate 62 ·· Outer housing 63 · · Insulator plate 81 · · Film-like substrate 82 · · Cathode electrode 83 · · Insulator 84 · · Gas introduction tube 85 · · Anode electrode 86 · · Matching box 87・ High-frequency power supply 88 ・ ・ Pore 89 ・ ・ Plasma discharge space 111 ・ ・ ・ ・ Vacuum vessel 112 ・ ・ ・ ・ Electrode 113 ・ ・ ・ ・ Substrate 114 ・ ・ ・ ・ Electrode 115 ・ ・ ・ ・ High-frequency power supply 121・ Piezoelectric element 122... Electrode 123... Electrode 125... High frequency power supply 141. / Feeding drum 153... Guide roller 154... Guide roller 155... Drum electrode 156... Ground electrode 157 ... Film-like substrate 611 MHV plug 612 Gas introduction Mouth 613-Teflon (registered trademark) insulator 616-Holder 617-Top plate 620-Teflon (registered trademark) shield 621-Teflon (registered trademark) seal De 622 Teflon (registered trademark) shield

Claims (8)

A first electrode;
A second electrode facing the first electrode;
In a film forming apparatus having
Applying electromagnetic energy combining a plurality of frequencies to the first electrode to generate plasma between the first electrode and the second electrode, and activating a source gas by the plasma, A film forming method for forming a film on a substrate. A first electrode;
A second electrode facing the first electrode;
In a film forming apparatus having
A plasma is generated between the first electrode and the second electrode by applying electromagnetic energy combining at least a low frequency and a high frequency to the first electrode, and a source gas is activated by the plasma. A film forming method for forming a film on the substrate. A first electrode;
A second electrode facing the first electrode;
In a film forming apparatus having
Applying electromagnetic energy combining at least a low frequency of 1 KHz to 1 MHz and a high frequency of 10 to 100 MHz to the first electrode to generate plasma between the first electrode and the second electrode, and A method for forming a film, wherein a raw material gas is activated by plasma to form a film on the substrate. A first electrode;
A second electrode facing the first electrode;
In a film forming apparatus having
Applying a frequency of several tens of KHz to several GHz to the first electrode to generate plasma between the first electrode and the second electrode, and activating a source gas by the plasma, A film forming method for forming a film on a substrate. A first electrode;
A second electrode facing the first electrode;
In a film forming apparatus having
A frequency of several tens of KHz to several GHz is applied to the first electrode to generate a sheet-like plasma between the first electrode and the second electrode, and a source gas is activated by the plasma. A film forming method for forming a film on the substrate. In any one of Claims 1 thru | or 5,
A method for forming a film, wherein a distance between the first electrode and the second electrode is 6 mm or less. In any one of Claims 1 thru | or 6,
A film forming method, wherein a rare gas is added to the source gas. In claim 7,
The method of forming a film, wherein the rare gas is helium or argon.

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