JP6770780B2 - Thin film and thin film forming method - Google Patents

Description

The present disclosure relates to a thin film formed on the surface of a substrate and a method for forming the thin film. More specifically, a thin film such as a carbon thin film or a metal oxide thin film having an inclined structure having a high adhesion to a base material, and the thin film under atmospheric pressure or pressure near atmospheric pressure (hereinafter, also referred to as atmospheric pressure). There is.) The present invention relates to a method of forming a thin film on the surface of a base material by using the discharge plasma generated in).

By forming a thin film on the surface of a base material such as a polymer or metal material, the base material as a bulk has high functionality (for example, high hardness, scratch resistance or high gas barrier property) at low cost, resource saving and easily. Etc.) have been widely put into practical use. In recent years, a technique for coating an inorganic thin film made of a metal oxide such as silicon oxide or aluminum oxide on a plastic base material or the surface of a metal base material has been developed, and a technology for imparting functions such as surface protection, gas barrier property or cosmetic property. Is widespread (see, for example, Patent Document 1).

Further, a technique for coating an amorphous carbon-based thin film (DLC: diamond-like carbon) instead of a metal oxide is also disclosed (see, for example, Patent Document 2).

These inorganic thin films are conventionally plasma-deposited by activating chemical species by a physical vapor deposition method such as sputtering under vacuum, ion plating or vacuum vapor deposition, or plasma excited by high frequency or microwave. A method of forming a film by a (Chemical Vapor Deposition) method is common. In both cases, film formation in the low pressure region of high vacuum to medium vacuum is indispensable. In film formation in the low pressure region, the active species that are the raw materials of the film rarely collide with other molecules or active species in the gas phase, so the formed inorganic thin film may be a uniform amorphous film. It is a feature. However, on the other hand, since the formed thin film is uniform in the thickness direction, for example, a thin film having functions such as high hardness, wear resistance or high gas barrier property has characteristics with the base material at the interface with the base material. The difference was too large and peeling may occur, and there was a problem with adhesion.

For this reason, various laminated films have been proposed in which the thin film is formed into a laminated structure to maintain high adhesion on the surface of the thin film (see, for example, Patent Documents 3 and 4).

Further, on the manufacturing side, the film forming apparatus used for film formation in a low pressure region has a problem that equipment costs such as a chamber and a vacuum pump for maintaining a vacuum are required, and its operating cost and handling are not easy. In order to solve the problems caused by these vacuum processes, an atmospheric pressure plasma CVD method for forming an inorganic thin film under atmospheric pressure has also been proposed (see, for example, Patent Documents 5 and 6). Patent Document 5 and Patent Document 6 disclose a method for producing a diamond-like carbon thin film by dielectric barrier discharge under atmospheric pressure using a high-voltage pulse power source. In general, a glow discharge is used in the atmospheric pressure plasma CVD method using a dielectric barrier discharge (see, for example, Non-Patent Document 1).

Japanese Unexamined Patent Publication No. 11-348171 Japanese Unexamined Patent Publication No. 9-272567 Japanese Unexamined Patent Publication No. 2008-94447 JP-A-2010-242225 Japanese Unexamined Patent Publication No. 11-12735 JP-A-2010-208277

"Control and application of atmospheric pressure plasma", Masuhiro Ogoma (supervised), Kunihiko Fukushima (publisher), Science & Technology Co., Ltd., November 29, 2006, First Edition, 1st Edition, pp. 23-33 Kenichi Miura, Morimasa Nakamura, Surface Technology, 59, (2008) 203

However, as in Patent Document 3 or Patent Document 4, the method of improving the adhesion to the base material by the laminated structure of thin films requires the formation of a plurality of thin films having different compositions and structures, which complicates the apparatus in production and also makes the apparatus complicated. There was a problem that the cost required for manufacturing was also high.

As shown in Non-Patent Document 1, the method using the dielectric barrier discharge as in Patent Document 5 or Patent Document 6 maintains the atmospheric glow discharge and obtains a uniform plasma state at a low temperature, so that the electric field strength is obtained. Is low and the gas density is high, but high-density plasma cannot be generated. Therefore, there is a problem that the functions such as density, hardness, and gas barrier property of the formed thin film are lower than those of the vacuum method (plasma CVD method using vacuum). In addition, in film formation under atmospheric pressure or pressure near atmospheric pressure, active species often collide with other molecules or active species in the gas phase, so unlike the thin film obtained by the vacuum method, the particles are mutual. It has a non-uniform structure with grain boundaries formed by adhesion. Further, since the kinetic energy is reduced due to the mutual collision in the gas phase, the collision energy with the base material is also smaller than that of the vacuum method, and as a result, the adhesion to the base material is also lower. When the electric field strength is increased to obtain a high-density plasma under atmospheric pressure, ionization is rapidly derived. As a result, the electron avalanche grows linearly, and streamer discharge occurs. When a streamer discharge occurs, the plasma becomes non-uniform, and as the thermions are generated, the plasma shifts to an arc discharge to become a high-temperature plasma, so that the base material is damaged and it is difficult to form a thin film. For this reason, conventionally, in the atmospheric pressure plasma CVD method, it has been preferable to suppress the occurrence of streamer discharge.

The present disclosure solves the above-mentioned problems and has high functionality (hardness, abrasion resistance, etc.) equal to or higher than that of a thin film obtained by a plasma CVD method using a vacuum on the surface of the base material, and the base material. It is an object of the present invention to provide a thin film having high adhesion to and a method for forming the thin film.

As described above, conventionally, in the atmospheric pressure plasma CVD method using a dielectric barrier discharge, it has been preferable to suppress the occurrence of streamer discharge. However, the present inventors have found that in the atmospheric pressure plasma CVD method using a dielectric barrier discharge, a thin film having high functionality can be formed by utilizing the streamer discharge, and have completed the present invention. That is, the thin film according to the present invention is a thin film provided on the surface of a base material, and the grain boundary density of the thin film decreases continuously or intermittently from the inner surface of the thin film toward the outer surface of the thin film. It has an inclined structure, and the innermost region of the thin film in contact with the surface of the base material has a grain boundary structure in which the grain size of the crystal grains is 10 to 30 nm.

The thin film forming method according to the present invention includes a pair of counter electrodes composed of a first electrode connected to a power source to which a voltage is applied and a second grounded electrode, and a reaction gas and a discharge gas between the pair of counter electrodes. In a thin film forming method using a film forming apparatus including a gas supply path for supplying a mixed gas and the facing surface of the first electrode is covered with a solid dielectric material, the facing surface of the second electrode is placed on the facing surface. The mixed gas is introduced from the gas supply path between the pair of counter electrodes in the step of installing a base material having a surface resistance in the range of ^10-8 to 10 ³ ohms / sq and under a pressure of atmospheric pressure or near atmospheric pressure. It has a step of supplying and applying a voltage by the power source to generate a streamer discharge to form a thin film on the surface of the base material by plasma CVD, and the voltage applied by the power source has a high frequency or a rest period. a pulsed voltage having a frequency of the high frequency or the pulse voltage is in the range of 1-100 kHz, and converted field is in the range of 30～1000Td, are most proximate between the counter electrode The distance between the facing surfaces is 3 to 20 mm.

In the thin film forming method according to the present invention, the discharge gas is preferably at least one of helium, argon, and nitrogen, or a mixture thereof.

In the thin film forming method according to the present invention, the discharge gas is composed of helium or helium and argon, and the composition of the discharge gas contains helium in the range of 40 to 100% as a volume ratio in a standard state. , Argon is preferably contained in the range of 60 to 0%.

According to the present disclosure, it has high functionality (hardness, wear resistance, etc.) equal to or higher than that of a thin film obtained by a plasma CVD method using a vacuum on the surface of a base material, and has adhesion to the base material. It is possible to provide a high thin film and a method for forming the thin film.

It is a thin film cross section according to this embodiment, and is a scanning electron microscope image of the thin film cross section formed by the atmospheric pressure method (streamer discharge). It is a scanning electron microscope image of the cross section of a thin film formed by the vacuum method. It is a scanning electron microscope image of the cross section of a thin film formed by the atmospheric pressure method (glow discharge). It is the schematic which shows an example of the film forming apparatus used in the thin film forming method which concerns on this embodiment. It is a schematic diagram for demonstrating a glow discharge. It is a schematic diagram for demonstrating streamer discharge. It is a figure for demonstrating the mechanism for forming a thin film which concerns on this embodiment. It is a photograph which shows the discharge form at each distance between the counter electrodes, and the distance between the counter electrodes is 1 mm in (a), 2 mm in (b), 3 mm in (c), and 4 mm in (d). It is a graph which shows the relationship between the distance between counter electrodes and the film formation rate. It is a Raman spectrum of the specimens 1 to 4. The relationship between the distance between the counter electrodes and N / (N + S) is shown. It is an IR spectrum of the specimens 1 to 4. The relationship between the distance between the counter electrodes and the pushing depth is shown. The relationship between the film thickness and N / (N + S) is shown. It is a Raman spectrum of specimens 5-8. The relationship between the distance between the counter electrodes and N / (N + S) is shown. It is a Raman spectrum of specimens 9-12. The relationship between the film formation time and N / (N + S) is shown. The relationship between the distance between the counter electrodes and the indentation hardness is shown.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiments shown below. Examples of these embodiments are merely examples, and the present invention can be implemented in a form in which various modifications and improvements have been made based on the knowledge of those skilled in the art. In this specification and drawings, the components having the same reference numerals shall indicate the same components.

FIG. 1 is a scanning electron microscope image of a cross section of a thin film according to the present embodiment. As shown in FIG. 1, the thin film according to the present embodiment is a thin film provided on the surface of a base material, and the thin film has a continuous or intermittent grain boundary density from the inner surface of the thin film toward the outer surface of the thin film. The innermost region of the thin film in contact with the surface of the base material has a grain boundary structure in which the grain size of the crystal grains is 10 to 30 nm.

The type of the thin film is not particularly limited, and is, for example, a carbon-based thin film, a metal oxide thin film, or a silicon-based thin film. The thickness of the thin film is preferably 100 to 800 nm, more preferably 200 to 600 nm.

In the present specification, the innermost region is the deepest portion of the thin film as viewed from the outer surface, and includes the inner surface of the thin film (the surface on the side in contact with the base material of the thin film). The innermost region preferably includes a region up to 30 nm in the direction from the inner surface of the thin film to the outer surface of the thin film (the surface opposite to the side in contact with the base material of the thin film) in the thickness direction of the thin film. The outermost region is the shallowest portion of the thin film as seen from the outer surface, and includes the outer surface of the thin film. The outermost region preferably includes a region up to 30 nm in the direction from the outer surface of the thin film toward the substrate in the thickness direction of the thin film. Further, in the image of the scanning electron microscope (SEM) or the transmission electron microscope (TEM) in which the cross section of the thin film is observed at a magnification of 40,000 times, the case where the grain boundary is observed is judged as the grain boundary structure, and the grain boundary is observed. If it is not, it is judged to be an amorphous structure.

The thin film shown in FIG. 1 can be formed by, for example, the film forming apparatus shown in FIG. Of the counter electrodes 2 and 12 made of copper, for example, which are arranged parallel to each other, the solid dielectric 3 is arranged on the facing surface side of the counter electrode 2. As the solid dielectric 3, for example, a plastic such as polytetrafluoroethylene, polyethylene terephthalate or polyethylene, glass, or a metal oxide such as alumina can be used. The base material 4 is arranged between the solid dielectric 3 and the other counter electrode 12.

Between the counter electrodes 2 and 12, the mixed gas 6 containing the reaction gas component is supplied to the gap between the counter electrodes 2 and 12 at a predetermined flow rate through the gas supply path 5. The mixed gas 6 is turned into plasma by the high frequency voltage applied between the counter electrodes 2 and 12, and becomes the plasmaized mixed gas 7. A part of the reaction gas component contained in the plasma mixture gas 7 is deposited on the surface of the base material 4 to form a thin film (not shown). The mixed gas 6 that has passed between the counter electrodes 2 and 12 and has consumed a part of the reaction gas component is discharged to the outside of the system through the exhaust passage 8.

The thin film of FIG. 1 is a thin film formed by an atmospheric pressure plasma CVD method (hereinafter, also referred to as “atmospheric pressure method (streamer discharge)”) using streamer discharge. The thin film shown in FIG. 1 was formed as follows. That is, the distance d between the counter electrodes 2 and 12 is 4 mm, and a silicon base material (surface resistance 260 ohm / sq, thickness 0.38 mm) is arranged as the base material 4 on the facing surface of the electrodes 12, and the pressure is 100 kPa. Below, a mixed gas containing 400 mL / min of methane (CH ₄ ) as a reaction gas and 4 L / min of helium (He) and 1 L / min of argon (Ar) as a discharge gas is supplied from the gas supply path, and the frequency is increased. A pulsed voltage was applied under power supply conditions of 30 kHz, a pulse width of 5 μs, and a voltage of 7 kV to generate an electric discharge to form a thin film having a thickness of 500 nm on the surface of the base material 4. The film formation time was 250 s. In the film forming apparatus 1, the counter electrodes 2 and 12 are made of copper.

As shown in FIG. 1, the structure of the thin film formed by the atmospheric pressure method (streamer discharge) had a grain boundary structure in which grain boundaries were clearly formed in the innermost region in contact with the surface of the base material. The grain size of the crystal grains in the innermost region was in the range of 10 to 30 nm. Here, the grain size of the crystal grains is the vertical diameter of the outer edge of the integrated grain boundary structure when the grain boundary structure can be confirmed by shading at a magnification of 40,000 times by cross-sectional observation by SEM or TEM. It is calculated as the average value of the lateral diameter. The thin film showed a structure in which the grain boundaries became indistinct as it approached the outermost region of the thin film and approached a uniform amorphous structure.

The thin film according to the present embodiment has an inclined structure in which the grain boundary density decreases continuously or intermittently from the inner surface of the thin film toward the outer surface of the thin film. The grain boundary density (dimensionless number) is per unit area of the grain boundary structure confirmed by shading and the continuous amorphous portion between the grain boundary structures at a magnification of 40,000 times of cross-sectional observation in SEM or TEM. Area ratio of.

In FIG. 1, in the thickness direction of the thin film, in the region up to 30 nm in the direction from the inner surface of the thin film to the outer surface of the thin film (the surface opposite to the side in contact with the base material of the thin film) (innermost region). It had a grain boundary structure in which the grain size of the crystal grains was 10 to 30 nm. Further, in the thickness direction of the thin film, the region up to 30 nm in the direction from the outer surface of the thin film toward the substrate (outermost region) had an amorphous structure. In the region between the innermost region and the outermost region, a portion having a grain boundary structure and a portion having an amorphous structure were mixed. When the region between the innermost region and the outermost region was bisected in the thickness direction, more portions having grain boundary structures were observed in the regions on the innermost region side than those having an amorphous structure. However, in the region on the outermost region side, more portions having an amorphous structure were found than portions having a grain boundary structure. In addition, the grain boundary density tended to decrease from the inner surface of the thin film toward the outer surface of the thin film.

In FIG. 1, the outermost region of the thin film has an amorphous structure, but in the present embodiment, the outermost region of the thin film may have a grain boundary structure. In the present embodiment, when the outermost region has a grain boundary structure, the particle size of the crystal grains in the outermost region is preferably larger than the particle size of the crystal grains in the innermost region. A thin film having a grain boundary structure in the outermost region can be obtained, for example, by stopping at a predetermined film thickness in the formation of the thin film. The predetermined film thickness varies depending on the film forming conditions such as the type of the base material, the type of the mixed gas, the gas flow rate, and the power supply conditions of the film forming apparatus, but is 100 to 250 nm under the thin film forming conditions of FIG. 1, for example.

Next, the cross-sectional structures of the thin film according to the present embodiment and the conventional thin film are compared.

FIG. 2 is a scanning electron microscope image of a cross section of a thin film formed by a vacuum plasma CVD method (hereinafter, also referred to as a “vacuum method”). The thin film shown in FIG. 2 was formed as follows. That is, using a high-frequency plasma CVD apparatus by the parallel plate method, using acetylene (C ₂ H ₂ ) as a reaction gas under a pressure of 0.1 Torr (13.3 Pa), under the conditions of high-frequency power of 200 W and frequency of 13.56 MHz. A film was formed. The film thickness of the thin film was 500 nm, and the film formation time was 100 s.

FIG. 3 is a scanning electron microscope image of a cross section of a thin film formed by an atmospheric pressure plasma CVD method (hereinafter, also referred to as “atmospheric pressure method (glow discharge)”) using glow discharge. The thin film shown in FIG. 3 was formed as follows. That is, in the preparation of the thin film of FIG. 1, a mixed gas containing 20 mL / min of acetylene (C ₂ H ₂ ) as a reaction gas and 1 L / min of nitrogen (N ₂ ) as a discharge gas was used with the distance between the counter electrodes set to 1 mm. It was produced in the same manner as the thin film of FIG. 1 except that the power supply conditions were changed to a frequency of 10 kHz, a pulse width of 5 μs, and a voltage of 18 kV. The film thickness of the thin film was 800 nm, and the film formation time was 50 s.

1 to 3 are images observed at a magnification of 40,000 times.

As shown in FIG. 2, the structure of the thin film formed by the vacuum method had a uniform amorphous shape over the entire thickness direction of the thin film, and did not show a structure forming grain boundaries. Further, as shown in FIG. 3, the structure of the thin film formed by the atmospheric pressure method (glow discharge) has a clear grain boundary structure in which the grain size of the crystal grains is 50 to 100 nm over the entire thickness direction of the thin film. Was shown.

The hardness of the thin film was 12 GPa by the atmospheric pressure method (streamer discharge), 3 GPa by the atmospheric pressure method (glow discharge), and 12 GPa by the vacuum method. Hardness was measured by performing a nanoindentation test using a Berkovich indenter in accordance with ISO 14577-2002 using a nanoindenter system (“NanoIndenter G200” manufactured by Agilent Technologies) and measuring the indentation depth. The indentation hardness was calculated. The peeling resistance of the thin film is determined by the cross-cut peeling test (JIS K 5600-5-6: 1999 "General paint test method-Part 5: Mechanical properties of coating film-Section 6: Adhesion (cross-cut method)". ), The atmospheric pressure method (streamer discharge), the vacuum method, and the atmospheric pressure method (glow discharge) were used in order from the best. From this result, it can be seen that at the interface between the base material and the thin film, the grain boundary structure having a particle size of about 10 to 30 nm has higher adhesion than the uniform amorphous structure without grain boundaries. Further, it can be seen that when the particle size is 50 nm or more, the kinetic energy is lost in the gas phase, so that the adhesion to the substrate is lowered as compared with the case where the particle size is 10 to 30 nm. On the other hand, it was confirmed that the outermost region of the thin film had an amorphous structure as in the thin films of FIGS. 1 and 2, and thus exhibited high hardness characteristics. From the above, the thin film formed by the atmospheric pressure method (streamer discharge) has a tilted structure, so that it has high hardness characteristics and high adhesion characteristics equal to or higher than the thin film obtained by the vacuum method. Admitted.

Comparing the atmospheric pressure method (streamer discharge) and the atmospheric pressure method (glow discharge) with respect to the surface roughness of the thin film, the atmospheric pressure method (streamer discharge) has a surface roughness more than the atmospheric pressure method (glow discharge). Was small. The surface roughness is measured using a scanning probe microscope ("SPM-9700", manufactured by Shimadzu Corporation) in accordance with JIS R 1683: 2007 "Method for measuring surface roughness of fine ceramic thin films with an atomic force microscope". did.

When the wear resistance is evaluated by a Taber type wear tester in accordance with JIS K 7204: 1999 "Plastic-wear test method using wear wheels", the thin film obtained by the atmospheric pressure method (streamer discharge) is the most wear resistant. The sex was high. This was followed by the vacuum method and the atmospheric pressure method (glow discharge).

The thin film according to the present embodiment preferably has an inclined structure in which the hydrogen concentration increases as it approaches the outer surface of the thin film. By having an inclined property in which the hydrogen concentration in the outermost region is increased as compared with the innermost region, the slidability and cushioning property are increased, and as a result, the abrasion resistance of the thin film is improved.

The hydrogen concentration in the thin film can be measured, for example, by analyzing the thin film in the depth direction by secondary ion mass spectrometry (SIMS). Further, the hydrogen concentration in the thin film may be estimated from the Raman analysis result. Raman spectroscopy is an analytical method that spectroscopically measures scattered light (Raman scattered light) of light irradiated to a substance, and can analyze the composition and structure of the substance. The Raman spectrum of a typical DLC film is composed of a G band near 1500 cm ^-1 and a D band near 1300 cm ^-1 . The degree of graphite clustering or the sp ³ / sp ² bond component ratio can be indirectly obtained from these intensity ratios, but it is known that the background (fluorescent component) intensity increases as the hydrogen concentration increases. Therefore, when the Raman scattered light intensity at the peak position of the G band is S and the fluorescence component intensity is N, log (N / S) or N / (N + S) is defined as a parameter that can be a hydrogen concentration qualitative analysis value. (See, for example, Non-Patent Document 2.).

In the preparation of the thin film of FIG. 1, the thin film was formed by the same method as the preparation of the thin film of FIG. 1 except that the film thickness was set to 1000 nm. At this time, Raman analysis was performed every 200 nm film thickness to determine N / (N + S). The relationship between the film thickness and N / (N + S) is shown in FIG.

As shown in FIG. 14, N / (N + S) was 0.5 at 200 nm and 0.75 at 800 nm. Up to 800 nm, N / (N + S) increased toward the outer surface of the thin film, and above 800 nm, N / (N + S) was substantially constant. From this, it was confirmed that the thin film of the specimen 5 had an inclined structure in which the hydrogen concentration increased as it approached the outer surface of the thin film.

The thin film formed by the atmospheric pressure method (glow discharge) shown in FIG. 2 had an N / (N + S) of about 0.9 to 1, and no gradient in hydrogen concentration was observed. It was confirmed that the atmospheric pressure method (streamer discharge) has a lower hydrogen concentration on the outer surface of the thin film than the atmospheric method (glow discharge). Further, the thin film formed by the vacuum method shown in FIG. 3 had an N / (N + S) of about 0.6 to 0.7, and no gradient in hydrogen concentration was observed. From this, it was confirmed that the hydrogen concentration on the outer surface of the thin film of the atmospheric pressure method (streamer discharge) is about the same as that of the vacuum method. This result is consistent with the result of the wear resistance evaluation.

Furthermore, when the raw material gas is diluted with helium as a mixed gas of trimethylsilane and oxygen to form a SiOx thin film on a silicon substrate, the abrasion resistance of the SiOx thin film obtained by the atmospheric pressure method (streamer discharge) is the highest. it was high. The reason for this is that the closer the thin film is to the surface, the more unclear the grain boundaries and the closer to a uniform amorphous structure, and at the same time, the hydrogen concentration in the outermost region increases compared to the innermost region, and the density accompanies it. It is believed that the reduced tilting properties increased slidability and cushioning, resulting in increased wear resistance.

Next, the thin film forming method according to the present embodiment will be described with reference to FIG. The present invention is not limited to the film forming apparatus shown in FIG. In the thin film forming method according to the present embodiment, between a pair of counter electrodes 2 and 12 composed of a first electrode 2 connected to a power source to which a voltage is applied and a second electrode 12 grounded, and a pair of counter electrodes 2 and 12. In a thin film forming method using a film forming apparatus 1 provided with a gas supply path 5 for supplying a mixed gas containing a reaction gas and a discharge gas, and the facing surface of the first electrode 2 is covered with a solid dielectric material 3. , A step of installing the base material 4 having a surface resistance in the range of ^10-8 to 10 ³ ohms / sq on the facing surface of the second electrode 12, and a pair of facing electrodes under atmospheric pressure or pressure near the atmospheric pressure. It has a step of supplying a mixed gas 6 from a gas supply path 5 between 2 and 12 and applying a voltage by a power source to generate a streamer discharge to form a thin film on the surface of the base material 4 by plasma CVD.

The reaction gas is appropriately selected depending on the type of thin film, and the present invention is not limited thereto. When forming a carbon-based thin film, the reaction gas is, for example, a compound containing carbon, hydrogen and / or oxygen, and is preferably any one of methane, ethane or propane, or a mixture thereof. When forming a metal oxide thin film, the reaction gas is, for example, an organometallic compound and oxygen. The organometallic compound is, for example, trimethylaluminum or titanium tetraisopolopoxide. When forming a silicon-based thin film, the reaction gas is, for example, an organic silicon compound and oxygen. The organic silicon compound is, for example, trimethylsilane (TrMS), tetraethoxysilane (TEOS), tetramethoxysilane (TMS) or hexamethyldisiloxane (HMDSO). In the formation of various thin films, one type of reaction gas may be used alone, or two or more types may be mixed and used.

The discharge gas preferably uses at least one of helium, argon or nitrogen, or a mixture thereof, and particularly preferably contains helium in an amount of 40% or more, more preferably 60% or more by volume in the standard state. Further, the discharge gas is composed of helium or helium and argon, and the composition of the discharge gas contains helium in the range of 40 to 100% and argon in the range of 60 to 0% as the volume ratio in the standard state. It is preferable to include in.

As shown in FIG. 4, one of the counter electrodes (upper electrode in FIG. 4) 2 is preferably applied with a high frequency voltage or a pulse voltage, and the other electrode (lower electrode in FIG. 4) 12 is grounded. ing. A mixed gas 6 containing a reaction gas that is a raw material for a thin film and a discharge gas that is ionized to generate a discharge plasma is supplied between the facing electrodes. The facing surface of the counter electrode 2 to which the voltage is applied is covered with a solid dielectric 3 such as alumina. When the discharge is started, the discharge voltage is lowered due to the charge accumulation on the surface of the solid dielectric 3. Therefore, in the solid dielectric 3, when the electrode 2 covered with the solid dielectric 3 is on the cathode side, streamer discharge is suppressed from being continuously generated on the surface of the solid dielectric 3, and the discharge is arced. It acts as a dielectric barrier that prevents the transition to discharge. In FIG. 4, of the counter electrodes 2 and 12, only the facing surface of the electrode 2 to which the voltage is applied is covered with the solid dielectric 3, but in the present embodiment, the facing surface of the electrode 2 is covered. In addition, the facing surface of the grounded electrode 12 may also be covered with a solid dielectric (not shown).

In the conventional thin film forming method using atmospheric pressure plasma, for example, as shown in Non-Patent Document 1, the distance between the counter electrodes 2 and 12 is set to the distance at which the glow discharge is sustained, and the dielectric barrier discharge (DBD) is performed. In a glow discharge state, the reaction gas was activated and plasma CVD treatment was performed to form a thin film. However, in glow dielectric barrier discharge (GDBD) using atmospheric pressure plasma, although the electron density and ion density in the plasma are higher than those in the glow discharge by the vacuum method, the density of gas molecules is high, so in the gas phase. The rate of particle formation or loss of reactivity is high, the rate of film formation on the substrate surface is low relative to the ion density, and the density of the formed thin film tends to be low.

In the thin film forming method according to the present embodiment, a streamer discharge is generated between the counter electrodes 2 and 12 instead of a glow discharge to form a thin film on the surface of the base material. 5 and 6 are schematic views for explaining a discharge mode, FIG. 5 shows a glow discharge 11B, and FIG. 6 shows a streamer discharge 11A. Conventionally, when a streamer discharge occurs, the plasma becomes non-uniform and unstable, making it difficult to form a uniform thin film, and the concentrated discharge causes the temperature to rise, causing thermal damage to plastic substrates that require low-temperature plasma treatment. There was a problem that it would end up. The present inventors cover the facing surface of the counter electrode 2 to which the voltage is applied with the solid dielectric 3 and have a condition that the distance between the counter electrodes 2 and 12 is narrow (for example, the distance between the counter electrodes 2 and 12 is 1 mm and the frequency is 20 kHz. At positive and negative pulse voltages with a peak width of 7 kV, discharge gas He, and device internal pressure (1 atm), a glow-like discharge (glow discharge) 11B is generated in which the creepage discharge on the dielectric surface reaches the ground electrode as shown in FIG. However, when the electrode spacing is widened, as shown in FIG. 6, a near-uniform discharge such as a glow discharge is maintained in the vicinity (within 0.5 mm) of the facing surface of the electrode 2 to which the voltage is applied, and this uniform discharge is maintained. It has been found that the streamer discharge 11A is generated from a close discharge-like region toward the surface of a base material having a surface resistance value in a specific range installed on the facing surface of the grounded electrode 12. About 2 to 10 streamer discharges are generated per 1 cm ² , and this is a discharge form also called filamentous discharge.

At this time in order to generate a streamer discharge, a surface resistance of at least the substrate was found to be required to be 10 ³ ohm / sq or less. Substrate 4, when the surface resistance is made of a polymer material of greater than 10 ³ ohms / sq, the surface resistance of the substrate 4, either to impart conductivity compound on the surface of the substrate 4, or the substrate 4 It is preferable to mix and adjust the conductive compound. The conductive compound is, for example, a metal such as carbon black, silver or copper, or a metal compound such as tin oxide or indium oxide. For example, when carbon black is kneaded into a plastic sheet (thickness 0.1 mm) such as a polyethylene terephthalate (PET) sheet or a polypropylene sheet, and the surface resistance is adjusted to a range of 1 to 1000 ohms / sq depending on the amount of carbon black added. Alternatively, a streamer discharge occurred in the case of a boron-doped silicon wafer (thickness 0.4 mm, surface resistance 50 to 260 ohms / sq). Of course, the metal sheet (steel plate, aluminum, titanium, etc., which has a surface resistance of about ^10-8 ohms / sq at a thickness of 0.3 mm), which is a conductor, also generated a streamer discharge without any problem. In the present specification, the surface resistivity is a value measured in accordance with JIS C 2139: 2008 "Solid Electrical Insulation Material-Measuring Method of Volume resistivity and Surface resistivity".

A polymer material having high surface resistance and high transparency may be used as the base material, and the polymer material may be coated with a film of a transparent conductive compound. As the film of the transparent conductive compound, for example, indium oxide / tin (ITO) film or PEDOT / PSS (poly (3,4-ethylenedioxythiophene) / poly (4-styrene sulphonic acid)) particles are used as the binder resin. Examples include dispersed membranes.

A commercially available product may be used as the base material. For example, Leopound PET M3000 (thickness 0.15 mm, surface resistance 49.8 ohms / sq) manufactured by Lion Co., Ltd. is commercially available as a master batch pellet in which about 10% of carbon black is kneaded into PET. By dispersing the master batch pellets in PET pellets at a constant ratio, a PET sheet having a predetermined surface resistance can be obtained.

The voltage applied by the power supply may be a high frequency or a pulsed voltage having a rest period, but since the facing surface of the electrode 2 to be applied is covered with the solid dielectric material 3, in order to sustain the discharge, the voltage is described above. The high frequency and pulsed voltages preferably have an AC waveform. Further, the voltage between the positive peak and the negative peak is preferably in the range of 2 to 10 times the discharge start voltage determined by the distance between the counter electrodes 2 and 12, the discharge gas type and the pressure. The condition of the distance between the counter electrodes 2 and 12 at which the streamer discharge starts to occur is expressed by the equation (1) (see, for example, Non-Patent Document 1). Equation (1) is called the Make condition.
(Equation 1) αd = 20 ... (1)
In the equation (1), d is the distance (mm) between the counter electrodes, and α is the ionization coefficient.

As a result of the research by the inventors, under atmospheric pressure or pressure conditions near the atmospheric pressure, a streamer discharge suitable for forming a high-quality thin film is generated by applying a voltage in the range of 2 to 10 times the discharge start voltage. I found that I could do it. In the present specification, the "pressure condition near the atmospheric pressure" includes the pressure near the atmospheric pressure, and specifically, the absolute pressure means a pressure in the range of 80 to 120 kPa, for example. When the distance d between the counter electrodes is increased or the applied voltage is made less than twice the discharge start voltage, the converted electric field Td (electric field / particle density) between the electrodes decreases, which is a function of Td (1). Since the ionization coefficient α in the equation drops sharply in inverse proportion to the increase in the distance d between the electrodes, the condition in equation (1) is no longer satisfied and the streamer discharge stops. According to the research by the inventors, in order to form a thin film having a plasma density that does not damage the substrate and a temperature of 200 ° C. or lower, the distance between the counter electrodes should be in the range of 3 mm or more and 20 mm or less. Is preferable. If it is less than 3 mm, the growth of streamer discharge is suppressed because the influence of creeping discharge on the dielectric surface and the discharge distance are short, and the electron density and ion density cannot be increased. If it is larger than 20 mm, it is necessary to increase the applied voltage in order to maintain the converted electric field between the electrodes, the plasma density in the generated streamer becomes high, and the high temperature causes damage to the base material and thermal deterioration. There is a fear. The distance between the counter electrodes is more preferably 4 mm or more and 15 mm or less. Within this range, streamer discharge can be generated more reliably, and damage to the substrate can be further suppressed. In the present specification, as shown in FIG. 4, the distance between the facing electrodes is the distance between the facing surfaces of the facing electrodes 2 and 12, and is the distance d at the portion where the facing surfaces are closest to each other. ..

In order to eliminate damage to the substrate and maintain a stable streamer discharge, it is preferable that the frequency of the AC high frequency and the pulsed voltage is in the range of 1 to 100 kHz and the converted electric field is in the range of 30 to 1000 Td. .. When the counter electrodes 2 and 12 are arranged so as to face the parallel plate shape, the case where at least one counter electrode has a prismatic shape is included. In FIG. 4, as an example, one electrode 2 has a prismatic shape, and the other electrode 12 has a flat plate shape. In this case, the prismatic shape of the electrode 2 has a depth that matches the width of the other electrode 12 in the depth direction (the normal direction of the paper surface shown in FIG. 4), and in FIG. 4, the electrode 2 or the electrode 12 is shown. By moving any one of the above in the lateral direction (the left-right direction of the paper surface shown in FIG. 4), a large area can be continuously formed.

Next, the mechanism by which the streamer discharge under the conditions of the present invention forms a highly functional thin film equivalent to the vacuum method even under atmospheric pressure will be described with reference to FIG. 7. As shown in the left figure of FIG. 7, when the film formation is started, the tip of the streamer discharge 11A reaches the surface of the base material 4 having a low surface resistance, and the ions derived from the reaction gas collide with the surface of the base material 4. It diffuses on the surface of the base material 4 and combines with each other to form the thin film 10. At this time, in the streamer, the power density is about 10 times that of the glow discharge, the ion density and the electron density are both maintained at a high density of about 1000 times, and the recombination in the streamer is small, so that the vacuum method is used. It collides with the base material with the same level of collision energy as in the case of the plasma CVD method. As a result, a thin film 10 having an insulating inorganic bond is formed at a high density similar to that obtained by the vacuum method. Further, since the thin film 10 having high insulating property is synthesized on the surface of the base material on which the streamer discharge 11A has landed, the surface resistivity of the thin film forming portion becomes high. As a result, the streamer discharge 11A moves to the undeposited portion having a lower surface resistivity or the portion where the thickness of the insulating thin film 10 is thinner, as shown in the right figure of FIG. By repeating the above process, a thin film 10 having a uniform thickness is formed. As the insulating thin film is formed on the surface of the base material 4, the surface resistance increases and the electric field density in the streamer discharge gradually decreases. As a result, the power density in the plasma is also reduced, and the thickness of the thin film 10 formed accordingly is increased in uniformity and the density is also reduced. Then, the thin film 10 has an inclined structure in which the grain boundaries become unclear toward the outer surface thereof.

The thin film according to the present embodiment has a high adhesion to the base material due to the inclined structure in which the crystal structure changes in the thickness direction of the thin film, and has the same or higher functionality as the thin film formed by the vacuum method. Can be demonstrated.

Further, in the thin film forming method according to the present embodiment, a thin film having high functionality (high hardness, scratch resistance, etc.) equivalent to that of the vacuum method is formed on the base material under atmospheric pressure by using streamer discharge. It is possible. Further, the temperature at the time of forming the thin film can be low (from room temperature to about 100 ° C.), and it can be applied to a plastic base material. Further, since atmospheric pressure CVD is used, the equipment cost and the operating cost are lower than those of the conventional vacuum process. Furthermore, since the film formation speed is faster than that of the vacuum process, it can be expected that the manufacturing cost will be significantly reduced. In particular, it has been found that even if it is an insulating plastic base material, a highly functional thin film can be formed by blending or applying carbon black or an antistatic agent to reduce the surface resistance to a certain level, and silicon. Alternatively, they have found that it is possible to apply a low-cost and simple high-performance thin film to conductive industrial materials such as alloys.

Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to such Examples.

Using the film forming apparatus 1 shown in FIG. 4, the film was formed by changing the distance between the counter electrodes 2 and 12.

(Preparation of specimen 1)
The distance d between the counter electrodes 2 and 12 is 1 mm, and a silicon base material (surface resistance 263 ohm / sq, thickness 0.38 mm) is placed on the facing surface of the electrodes 12 as the base material 4, and the pressure is 100 kPa. A mixed gas containing 200 mL / min of methane (CH ₄ ) as a reaction gas and 4 L / min of helium (He) and 1 L / min of argon (Ar) as a discharge gas is supplied from the gas supply path, and the frequency is 30 kHz. A pulsed voltage was applied under power supply conditions of a pulse width of 5 μs and a voltage of 10 kV to generate an electric discharge to form a thin film having a thickness of 500 nm on the surface of the base material 4. The film thickness was measured using a stylus type surface shape measuring device (Dektake 3030, Veco Instruments Inc., manufactured by USA).

(Preparation of specimens 2-4)
A thin film is formed on the substrate in the same manner as the specimen 1 except that the distance d between the counter electrodes 2 and 12 is changed to 2 mm (specimen 2), 3 mm (specimen 3), and 4 mm (specimen 4). did.

(Experimental Example 1) Discharge form The discharge form at the time of preparation of the specimens 1 to 4 was observed. The discharge form of the specimens 1 to 4 is shown in FIG. As shown in FIG. 8, the specimen 1 (distance between counter electrodes 1 mm) was glow discharged. In the specimen 2 (distance between counter electrodes 2 mm), glow discharge and streamer discharge were mixed. Specimens 3 and 4 (distance between counter electrodes 3, 4 mm) were streamered as a whole. From the above, it was confirmed that streamer discharge was generated by setting the distance between the counter electrodes to 3 mm or more. In FIG. 8, an image in which the discharge form is processed in gray tones is shown, but the discharge form is more accurately represented by a color image before being processed in gray tones.

(Experimental Example 2) Film formation rate The relationship between the distance between the counter electrodes and the film formation rate was confirmed. Five specimens 1 to 4 were prepared. In producing each specimen, the time required to form a thin film having a film thickness of 500 nm (deposition time) was measured. For each of the specimens 1 to 4, the average film formation time for 5 times of preparation was obtained, and the film thickness (unit: nm) was divided by the average value of the film formation time (unit: s) to form the film formation rate (unit: s). nm / s) was determined. The relationship between the distance between the counter electrodes and the film formation rate is shown in FIG.

As shown in FIG. 9, the film formation rate sharply increased by setting the distance between the counter electrodes to 3 mm or more. It is considered that this is because the streamer discharge has a higher ion density inside the streamer than the glow discharge, so that the decomposition of the reaction gas is further promoted.

(Experimental Example 3) Raman analysis Thin films of specimens 1 to 4 were analyzed by Raman spectroscopy. The Raman spectra of specimens 1 to 4 are shown in FIG. The Raman analysis was performed using a Raman spectroscopic measuring device (in Via Streamline Plus, manufactured by RENISHAW) with reference to JIS K 0137: 2010 “General rules for Raman spectroscopic analysis”.

As shown in FIG. 10, by setting the distance between the counter electrodes to 3 mm or more, the fluorescence due to the polymer structure was reduced. It is considered that this is because the streamer discharge has a higher ion density inside the streamer than the glow discharge, so that the reaction between the ions is further promoted.

In Raman analysis, N / (N + S) was determined, and the high and low hydrogen concentration in the thin film was estimated. The relationship between the distance between the counter electrodes and N / (N + S) is shown in FIG.

As shown in FIG. 11, by setting the distance between the counter electrodes to 3 mm or more, N / (N + S) sharply decreased. From this, it can be inferred that the thin film formed by the streamer discharge has a lower hydrogen concentration in the thin film than the thin film formed by the glow discharge. It is considered that this is because the streamer discharge has a higher ion density inside the streamer than the glow discharge, so that the ion reaction is more activated and hydrogen is extracted.

(Experimental Example 4) IR analysis For specimens 1 to 4, thin films were analyzed by FTIR (Fourier Transform infrared spectroscopy) method, and the relationship between the distance between counter electrodes and the sp ^3- CHx peak was confirmed. The FTIR spectra of the specimens 1 to 4 are shown in FIG. The FTIR analysis was performed using an infrared spectroscope (ALPHA-T, Bruker Corp., manufactured by USA).

As shown in FIG. 12, by setting the distance between the counter electrodes to 3 mm or more, the peak intensity in the vicinity of 2800 to 3000 cm ^-1 due to CH was significantly reduced. In particular, since the peak of sp ^3- CH ₃ is weakened, it is considered that the terminal due to CH ₃ decreases as H decreases.

(Experimental Example 5) Surface Roughness For the specimens 1 to 4, the surface roughness of the thin film was measured by using a scanning probe microscope ("SPM-9700", manufactured by Shimadzu Corporation), JIS R 1683: 2007 "Atomic Force". The measurement was performed in accordance with "Method for measuring surface roughness of fine ceramic thin film using a microscope". The surface roughness was 0.41 nm for the specimen 1, 0.29 nm for the specimen 2, 0.19 nm for the specimen 3, and 0.25 nm for the specimen 4.

(Experimental Example 6) Hardness The hardness of the thin films was evaluated for the specimens 1 to 4. The relationship between the distance between the counter electrodes and the pushing depth is shown in FIG. Further, FIG. 19 shows the relationship between the distance between the counter electrodes and the indentation hardness. Hardness was measured by performing a nanoindentation test using a Berkovich indenter in accordance with ISO 14577-2002 using a nanoindenter system (“NanoIndenter G200” manufactured by Agilent Technologies) and measuring the indentation depth. The indentation hardness was calculated.

As shown in FIG. 13, as the distance between the counter electrodes was increased, the indent depth tended to decrease. Further, as shown in FIG. 19, the indentation hardness (Hardness) calculated by using the indentation depth value tends to increase as the distance between the counter electrodes increases. In particular, when the distance between the counter electrodes was 3 mm or more, the indentation hardness was substantially constant. It is considered that this is because the streamer discharge has a higher ion density inside the streamer than the glow discharge, so that the ion reaction is more activated and hydrogen is extracted, resulting in a lower hydrogen concentration in the thin film. ..

(Preparation of specimen 5)
Using the film forming apparatus 1 shown in FIG. 4, the distance d between the counter electrodes 2 and 12 is set to 1 mm, and the electrode 12 uses SUS304 (surface resistance 7 × 10 ^-3 ohm / sq, thickness 0.1 mm) as the base material 4. A mixed gas containing 200 mL / min of methane (CH ₄ ) as a reaction gas and 4 L / min of helium (He) and 1 L / min of argon (Ar) as a discharge gas under a pressure of 100 kPa. Was supplied from the gas supply path, and a pulsed voltage was applied under power supply conditions of a frequency of 20 kHz, a pulse width of 5 μs, and a voltage of 7 kV to generate an electric discharge to form a thin film having a thickness of 280 nm on the surface of the base material 4. .. The film formation time was 120 s. The discharge form of the specimen 5 was glow discharge.

(Preparation of specimens 6 to 8)
A thin film is formed on the substrate in the same manner as the specimen 5 except that the distance d between the counter electrodes 2 and 12 is changed to 3 mm (specimen 6), 4 mm (specimen 7), and 5 mm (specimen 8). did. The discharge form of the specimens 6 to 8 was streamer discharge.

Specimens 5 are comparative examples, and specimens 6 to 8 are products of the present invention.

(Experimental Example 7)
Raman analysis was performed on the specimens 5 to 8 in the same manner as in Experimental Example 3. FIG. 15 is a Raman spectrum of specimens 5 to 8. FIG. 16 shows the relationship between the distance between the counter electrodes and N / (N + S). As shown in FIG. 15, G-band could not be confirmed when the distance between the electrodes was 1 mm, but G-band could be confirmed when the distance between the electrodes was 3 mm or more. As shown in FIG. 16, by setting the distance between the electrodes to 3 mm or more, N / (N + S) sharply decreased. In this way, it was confirmed that by generating the streamer discharge, a good film formation can be performed even if a metal base material is used.

(Preparation of specimen 9)
Using the film forming apparatus 1 shown in FIG. 4, the distance d between the counter electrodes 2 and 12 is 5 mm, and the base material 4 is a base material 4 coated with a 1 μm-thick SnO ₂ on a 1.8 mm-thick SiO _2. A surface resistance of 10 ³ ohms / sq) is placed on the facing surface of the electrode 12 with the SnO ₂ coating surface facing upward, and under a pressure of 100 kPa, methane (CH ₄ ) 200 mL / min as a reaction gas and 200 mL / min as a discharge gas. A mixed gas containing 4 L / min of helium (He) and 1 L / min of argon (Ar) is supplied from the gas supply path, and a pulsed voltage is applied under power supply conditions of a frequency of 30 kHz, a pulse width of 5 μs, and a voltage of 11 kV. , A thin film having a thickness of 60 nm was formed on the surface of the base material 4 by generating an electric discharge. The film formation time was 25 s.

(Sample 10)
It was produced in the same manner as the sample 9 except that the film formation time was changed to 50 s and the film thickness was 120 nm.

(Sample 11)
It was produced in the same manner as the sample 9 except that the film formation time was changed to 100 s and the film thickness was 240 nm.

(Sample 12)
A voltage was applied in the same manner as in the preparation of the specimen 9 except that the base material was changed to a thickness SiO ₂ substrate (surface resistance 10 ¹² ohms / sq, thickness 1.8 mm), but streamer discharge did not occur. No thin film was formed.

Specimens 9 to 11 are products of the present invention, and specimen 12 is a comparative example.

(Experimental Example 8)
Raman analysis was performed on the specimens 9 to 12 in the same manner as in Experimental Example 3. FIG. 17 is a Raman spectrum of specimens 9 to 12. FIG. 18 shows the relationship between the film formation time and N / (N + S). As shown in FIG. 17, the specimen 12 could not form a film because it used an insulating SiO ₂ substrate, but the specimens 9 to 11 were coated with the conductive SnO ₂ on the insulating SiO ₂ substrate. A thin film having a G-band could be formed. From this, it was confirmed that by adjusting the surface resistance within a predetermined range, a film can be formed regardless of the material of the base material. As shown in FIG. 18, the specimens 9 to 11 had an N / (N + S) of about 0.7 to 0.8. Compared with the N / (N + S) of the specimens 1 to 4 using the Si substrate shown in FIG. 11 (about 0.5 to 0.6), the specimens 9 to 11 were slightly higher.

(Preparation of specimen 13)
Using the film forming apparatus 1 shown in FIG. 4, the distance d between the counter electrodes 2 and 12 is set to 2 mm, and a silicon base material (surface resistance 263 ohm / sq, thickness 0.38 mm) is used as the base material 4 to face the electrodes 12. Arranged on a surface, under a pressure of 100 kPa, TrMS (trimethylsilane) 0.5 mL / min and oxygen (O ₂ ) 0.5 L / min as reaction gas, and nitrogen (N ₂ ) 20 L / min as discharge gas. A mixed gas containing the above is supplied from the gas supply path, and a pulsed voltage is applied under power supply conditions of a frequency of 30 kHz, a pulse width of 5 μs, and a voltage of 18 kV to generate an electric discharge to form a SiOx thin film on the surface of the base material 4. did. The discharge form was streamer discharge.

The specimen 13 is the product of the present invention. It was confirmed that the thin film forming method according to the present invention can form a good film regardless of the type of reaction gas.

(Preparation of specimen 14)
Using the film forming apparatus 1 shown in FIG. 4, the distance d between the counter electrodes 2 and 12 is set to 3 mm, and a silicon base material (surface resistance 263 ohm / sq, thickness 0.38 mm) is used as the base material 4 to face the electrodes 12. Arranged on a surface, under a pressure of 100 kPa, methane (CH ₄ ) 400 mL / min as a reaction gas and helium (He) 5 L / min as a discharge gas are supplied from the gas supply path, and the frequency is 30 kHz and the pulse width is A pulsed voltage was applied under power supply conditions of 5 μs and a voltage of 7 kV to generate an electric discharge to form a thin film having a thickness of 240 nm on the surface of the base material 4. The film formation time was 100 s.

(Preparation of specimen 15)
The discharge gas was prepared in the same manner as in the preparation of the specimen 14 except that the discharge gas was changed to a mixed gas containing 4 L / min of helium (He) and 1 L / min of argon (Ar).

(Preparation of specimen 16)
The discharge gas was prepared in the same manner as in the preparation of the specimen 14 except that the discharge gas was changed to a mixed gas containing 3 L / min of helium (He) and 2 L / min of argon (Ar).

(Preparation of specimen 17)
The discharge gas was prepared in the same manner as in the preparation of the specimen 14 except that the discharge gas was changed to a mixed gas containing 2 L / min of helium (He) and 3 L / min of argon (Ar).

(Preparation of specimen 18)
The discharge gas was prepared in the same manner as in the preparation of the specimen 14 except that the discharge gas was changed to a mixed gas containing 1 L / min of helium (He) and 4 L / min of argon (Ar).

(Preparation of specimen 19)
The discharge gas was prepared in the same manner as that of the specimen 14 except that the discharge gas was changed to argon (Ar) 5 L / min.

(Experimental Example 10)
The indentation hardness of the thin films formed on the specimens 14 to 19 was measured, and the surface condition was observed. The results are shown in Table 1. From the results in Table 1, the composition of the discharge gas preferably contains helium in the range of 40 to 100%, argon in the range of 60 to 0%, and helium in the range of 60 to 100% as the volume ratio in the standard state. It was confirmed that it was contained in the range, and it was more preferable to include argon in the range of 40 to 0%.

Some or all of the above embodiments may also be described, but not limited to:

(Appendix 1)
In the thin film provided on the surface of the base material,
The thin film has an inclined structure in which the grain boundary density decreases continuously or intermittently from the inner surface of the thin film toward the outer surface of the thin film.
The innermost region of the thin film in contact with the surface of the base material has a grain boundary structure in which the grain size of the crystal grains is 10 to 30 nm.

(Appendix 2)
A pair of counter electrodes consisting of a first electrode connected to a power source to which a voltage is applied and a second electrode grounded, and a gas supply path for supplying a mixed gas containing a reaction gas and a discharge gas between the pair of counter electrodes. With,
In the thin film forming method using a film forming apparatus in which the facing surface of the first electrode is covered with a solid dielectric material,
A step of installing a base material having a surface resistance in the range of ^10-8 to 10 ³ ohms / sq on the facing surface of the second electrode, and
Under atmospheric pressure or pressure near atmospheric pressure, the mixed gas is supplied from the gas supply path between the pair of counter electrodes, and a voltage is applied by the power source to generate a streamer discharge, and the substrate is subjected to plasma CVD. A method for forming a thin film, which comprises a step of forming a thin film on the surface of the above.

(Appendix 3)
The thin film forming method according to Appendix 2, wherein the facing surface of the second electrode is covered with a solid dielectric material.

(Appendix 4)
The thin film forming method according to Appendix 2 or 3, wherein the voltage applied by the power source is a high frequency or a pulsed voltage having a rest period.

(Appendix 5)
The high frequency or pulsed voltage has an AC waveform, and the voltage between the positive peak and the negative peak is the discharge start voltage determined by the distance between the counter electrodes, the discharge gas type, and the pressure. The thin film forming method according to Appendix 4, wherein the range is 2 to 10 times that of the above.

(Appendix 6)
The thin film forming method according to Appendix 4 or 5, wherein the frequency of the high frequency or pulsed voltage of the alternating current is in the range of 1 to 100 kHz, and the converted electric field is in the range of 30 to 1000 Td.

(Appendix 7)
The thin film forming method according to any one of Supplementary note 2 to 6, wherein the distance between the facing surfaces closest to each other is 3 to 20 mm.

(Appendix 8)
The counter electrode is arranged so as to face a flat plate shape, or according to any one of Supplementary note 2 to 7, wherein at least one electrode has a cylindrical shape, a prismatic shape, a cylindrical shape, or a spherical shape. Thin film forming method.

(Appendix 9)
The reaction gas is a compound containing carbon, hydrogen and / or oxygen when forming a carbon-based thin film, and an organometallic compound and oxygen when forming a metal oxide thin film. 8. The thin film forming method according to any one of 8.

(Appendix 10)
The thin film forming method according to Appendix 9, wherein when the carbon-based thin film is formed, any one of methane, ethane and propane or a mixture thereof is used as a reaction gas.

(Appendix 11)
The thin film forming method according to any one of Supplementary note 2 to 10, wherein the discharge gas uses at least one of helium, argon, and nitrogen, or a mixture thereof.

(Appendix 12)
The discharge gas is composed of helium or helium and argon, and the composition of the discharge gas contains helium in the range of 40 to 100% and argon in the range of 60 to 0% as the volume ratio in the standard state. The thin film forming method according to Appendix 11, which comprises the above.

(Appendix 13)
Substrate, when the surface resistance is made of a polymer material of greater than 10 ³ ohms / sq, conductive surface resistance of the substrate, or to impart conductivity compound on the surface of the substrate, or in the substrate The thin film forming method according to Appendix 2 to 12, wherein the sex compounds are mixed and adjusted.

1 Film deposition equipment 2 Electrodes (1st electrode)
3 Solid dielectric 4 Base material 5 Gas supply path 6 Mixed gas 7 Plasmaized mixed gas 8 Exhaust path 10 Thin film 11A Streamer discharge 11B Glow discharge 12 Electrode (second electrode)

Claims (4)

In the thin film provided on the surface of the base material,
The thin film has an inclined structure in which the grain boundary density decreases continuously or intermittently from the inner surface of the thin film toward the outer surface of the thin film.
The innermost region of the thin film in contact with the surface of the base material has a grain boundary structure in which the grain size of the crystal grains is 10 to 30 nm. A pair of counter electrodes consisting of a first electrode connected to a power source to which a voltage is applied and a second electrode grounded, and a gas supply path for supplying a mixed gas containing a reaction gas and a discharge gas between the pair of counter electrodes. With,
In the thin film forming method using a film forming apparatus in which the facing surface of the first electrode is covered with a solid dielectric material,
A step of installing a base material having a surface resistance in the range of ^10-8 to 10 ³ ohms / sq on the facing surface of the second electrode, and
Under atmospheric pressure or pressure near atmospheric pressure, the mixed gas is supplied from the gas supply path between the pair of counter electrodes, and a voltage is applied by the power source to generate a streamer discharge, and the substrate is subjected to plasma CVD. Has a process of forming a thin film on the surface of
The voltage applied by the power supply is a high frequency or a pulsed voltage having a rest period.
Frequency of the high frequency or the pulse voltage is in the range of 1-100 kHz, and converted field is in the range of 30～1000Td,
A method for forming a thin film, characterized in that the distance between the facing surfaces closest to each other is 3 to 20 mm. The thin film forming method according to claim 2, wherein the discharge gas is at least one of helium, argon, and nitrogen, or a mixture thereof. The discharge gas consists of helium or helium and argon.
The thin film forming method according to claim 2, wherein the composition of the discharge gas contains helium in the range of 40 to 100% and argon in the range of 60 to 0% as the volume ratio in the standard state.