Film formation device and film formation process

Abstract

The film-forming device comprises: a vacuum chamber in which a substrate is arranged; an antenna that generates inductively coupled plasma within the vacuum chamber and contains a conductor element and a capacitor element electrically connected in series; a high-frequency power supply that provides high-frequency current to the antenna; and a gas supply mechanism that introduces raw material gas containing C, H, and O into the vacuum chamber. A carbon-based thin film is formed on the substrate within the vacuum chamber by a plasma-CVD process using the inductively coupled plasma generated in the vacuum chamber by applying the high-frequency current to the antenna.

Description

Technical area

[0001] The present invention relates to a film forming apparatus and a film forming method that form a carbon-based thin film by a plasma CVD method. State of the art

[0002] Conventionally, film-forming devices that synthesize a carbon-based thin film, such as diamond, using a CVD method are known, such as a filament CVD device, a microwave resonator-type plasma CVD device, a microwave surface acoustic wave plasma CVD device, a radio-frequency inductive coupling plasma CVD device (RF-ICP) using coil-shaped electrodes, etc. (e.g., Patent Document 1). In addition, a straight-line ICP plasma CVD device with an antenna is also known in the RF plasma type.

[0003] The filament CVD apparatus is configured to include a high-melting-point metal wire arranged over a substrate that forms diamond, and to decompose a raw material gas with thermoelectrons emitted when the metal wire is heated to synthesize diamond. Furthermore, in a plasma CVD apparatus that uses microwaves or a plasma CVD apparatus that uses radio frequencies, a plasma containing a raw material gas is generated by an applied high-frequency current, and diamond is synthesized by an activated gas. It is known that in these CVD apparatuses, active atomic hydrogen is mainly generated in the plasma, and by its action, non-diamond components of sp1 bonds or sp2 bonds are removed, and diamond components of sp3 bonds can be mainly grown. BibliographyPatent document

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2003-55087 SUMMARY OF THE INVENTION Problem to be solved by the invention

[0005] When synthesizing diamond using the plasma CVD devices described above, diamond can only be synthesized in a small area due to the limited device configurations. Even if the filament is elongated, for example, it cannot support its own weight and will break upon heating. Even when using microwaves of 2.45 GHz, 915 MHz, etc., the plasma size cannot be increased due to the resonance wavelength.

[0006] Furthermore, inductive high-frequency coupling with coil-shaped electrodes results in plasma inhomogeneity due to the size of the coil. Although the ratio of the elements C (carbon), H (hydrogen), and O (oxygen) in the raw material gas is important, conventional CVD processes have the problem that diamond can only be synthesized using a raw material gas with a very narrow composition range. As shown in a Bachmann CHO diagram ( Fig. As shown in Figure 9, which shows the elemental ratios between C, H, and O, diamond can only be synthesized in ranges of 0.8 ≤ H / (H + C) and O / (O + H) ≤ 0.1. Furthermore, it was difficult to generate a high-density plasma for rectilinear antennas, and diamond could not be synthesized.

[0007] The present invention has been made to solve the above-mentioned problems, and a main object thereof is to make it possible to form a carbon-based thin film with a raw material gas having a wide composition range and to form a film in a large area in a film forming apparatus that forms a carbon-based thin film such as diamond according to a CVD method. Means to solve the problem

[0008] That is, a film forming apparatus according to the present invention includes a vacuum vessel, an antenna, a high-frequency power supply, and a gas supply mechanism. A substrate is disposed in the vacuum vessel. The antenna generates an inductively coupled plasma in the vacuum vessel and includes a conductor element and a capacitor element electrically connected in series. The high-frequency power supply supplies high-frequency power to the antenna. The gas supply mechanism supplies a raw material gas containing C, H, and O to the vacuum vessel. A carbon-based thin film is formed on the substrate in the vacuum vessel by a plasma CVD method using the inductively coupled plasma generated in the vacuum vessel by passing the high-frequency current through the antenna.

[0009] With such a configuration, by using an inductively coupled plasma generated by a high-frequency induced electric field, it becomes possible to decompose CO2 or the like, which is a molecule with a high binding energy contained in the raw material gas, over a wide range, and the generation of oxygen-containing radicals can be promoted. Since the inductively coupled plasma is generated by a so-called LC antenna with a conductor element serving as an inductor and a capacitor element serving as a capacitor, activation can be carried out for a long time even when the raw material gas has a gas composition with a high oxygen content.Alternatively, the inductively coupled plasma can also be generated by a linear antenna in which a plurality of linear conductor elements serving as inductors and an intermediate capacitor element serving as a capacitor are connected in series. Here, the capacitor element serving as a capacitor refers to a capacitor element, which is different from a matching box. In this way, a carbon-based thin film such as diamond can be formed using a raw material gas having a wide composition range, which cannot be realized by a method using a conventional CVD apparatus, and a carbon-based thin film with a large area can be formed compared with a conventional plasma CVD apparatus.

[0010] In a composition range of the raw material gas supplied from the gas supply mechanism, the ratio of the concentration of O atoms to the total concentration of O and H atoms is preferably 10 atomic% or more and 60 atomic% or less.

[0011] In the above-described film forming apparatus of the present invention, a carbon-based thin film can be formed even in such a composition range of the raw material gas.

[0012] Further, the gas supply mechanism in the film forming apparatus may supply an Ar gas together with the raw material gas into the vacuum vessel, and the ratio of the flow rate of the Ar gas to the total flow rate of all the gases supplied into the vacuum vessel is preferably set to 50% or more and 90% or less.

[0013] By supplying Ar gas along with the raw material gas, Ar, which is easily ionized, can serve as a catalyst to promote the decomposition of the raw material gas. Accordingly, the composition range of the raw material gas in which the carbon-based thin film can be formed can be adjusted to a wider range. This effect is notable when the Ar gas flow ratio is set to 50% or more and 90% or less.

[0014] Further, in the film forming apparatus, in an emission spectrum of the inductively coupled plasma, the ratio of the luminous intensity of the C2 radicals to the luminous intensity of the Hα radicals is preferably 30% or more and 300% or less.

[0015] If the ratio of the light intensity of the C2 radicals to the light intensity of the Hα radicals is less than 30%, there is a possibility that the etching will exceed the film formation and nucleation will not occur. However, if the ratio of the light intensity of the C2 radicals to the light intensity of the Hα radicals is over 300%, there is a possibility that the non-diamond components will increase and graphite or a DLC film will form.

[0016] The pressure in the vacuum container during film formation is preferably 7 Pa or more and 100 Pa or less.

[0017] If the pressure in the vacuum chamber during film formation is less than 7 Pa, there is a possibility that the ionic impact on the synthesized film will increase and a graphite film will be formed. Conversely, if the pressure in the vacuum chamber during film formation is more than 100 Pa, there is a possibility that the plasma will concentrate around the antenna and a carbon-based thin film cannot be formed.

[0018] As a specific example of the film forming device, the carbon-based thin film is a diamond film.

[0019] A film-forming method according to the present invention further includes the following steps. A raw material gas containing C, H, and O is introduced into a vacuum vessel in which a substrate is disposed. An inductively coupled plasma is generated in the vacuum vessel by passing a high-frequency current through an antenna disposed inside or outside the vacuum vessel and including a conductor element and a capacitor element electrically connected in series. A carbon-based thin film is formed on the substrate by a plasma CVD method using the generated inductively coupled plasma.

[0020] With the film forming method as described above, the same action and effect as with the film forming apparatus of the present invention described above can be achieved. Effect of the invention

[0021] According to the present invention configured as described above, in the film forming apparatus that forms a carbon-based thin film such as diamond according to the CVD method, the carbon-based thin film can be formed with a raw material gas having a wide composition range, and the film can be formed in a large area. BRIEF DESCRIPTION OF THE DRAWINGS [ Fig. 1] is a view schematically showing a configuration of a film forming apparatus according to an embodiment of the present invention. [ Fig. 2] is a diagram showing a gas composition range of a raw material gas supplied into the film forming apparatus and a first film forming method of the embodiment. [ Fig. 3] is a diagram showing the relationship between the ratio of supplied Ar gas and the luminous intensity ratio of C2 radicals and Hα radicals in a generated plasma. [ Fig. 4] is a diagram showing the gas composition range of a raw material gas supplied in a second film forming process. [ Fig. 5] is a view showing a gas composition and pressure during film formation of each sample synthesized in Example 1. [ Fig. 6] is a graph showing the Raman scattering spectra of each sample synthesized in Example 1. [ Fig. [Figure 7] is a view showing a gas composition and pressure during film formation of each sample synthesized in Example 2. [ Fig. [Figure 8] is a graph showing the Raman scattering spectra of each sample synthesized in Example 2. [ Fig. [Figure 9] is a diagram showing a composition range of a raw material gas that can be used to synthesize diamond in a conventional CVD process. DESCRIPTION OF THE EMBODIMENTS

[0022] Hereinafter, a film forming apparatus and a film forming method according to an embodiment of the invention will be described with reference to the drawings. <1. the device configuration>

[0023] A film forming apparatus 100 of the present embodiment is a plasma CVD apparatus that performs the formation of a carbon-based thin film on a substrate W according to a plasma CVD method using an inductively coupled plasma P.

[0024] The substrate W of the present embodiment is a plate-shaped substrate made of a material suitable for forming a carbon-based thin film. The substrate W may be made of, for example, but is not limited to, glass, plastic, silicon, metal such as iron, titanium, copper, and cemented carbide, another alloy material such as tool steel, or a material such as SiC, GaN, AlN, BN, and diamond.

[0025] The substrate W has a rectangular shape, a circular shape, or a similar shape in plan view. The length of the substrate W may be, for example, 20 cm or more or 50 cm or more, but is not limited thereto. Furthermore, the substrate W may be, for example, a substrate in which a plurality of small chip-shaped substrates of about 1 mm, 5 mm, or 10 mm with the same length or area are arranged. The substrate W is not limited to a plate shape, but may also have a columnar, perforated, or porous shape. Furthermore, it may have a complicated shape such as a tool, e.g., a drill or an end mill.

[0026] In addition, the substrate W may be subjected to a surface treatment, such as a so-called scratch treatment or seed treatment. For example, if the substrate W is silicon, a scratch treatment or seed treatment may be performed to immerse it in alcohol together with fine diamond particles and create roughness on the surface through ultrasonic treatment. If the substrate W is made of cemented carbide, the above-described seed treatment may be performed after immersion in an acidic solution, such as an aqueous nitric acid solution, to remove Co in the substrate, or after treating the surface of WC (tungsten carbide) particles with an alkaline solution, such as diluted NaOH.

[0027] As in Fig. Specifically, as shown in Figure 1, the film forming apparatus 100 includes a vacuum vessel 2 that is vacuum-evacuated and into which a gas G is introduced, a gas supply mechanism 7 that supplies the gas G into the vacuum vessel 2, an antenna 3 in a rectilinear shape arranged in the vacuum vessel 2, and a high-frequency power supply 4 that applies a high frequency to the antenna 3 to generate an inductively coupled plasma P in the vacuum vessel 2. In the film forming apparatus 100, a high-frequency current IR flows through the antenna 3 by applying a high frequency from the high-frequency power supply 4 to the antenna 3, and an induced electric field is generated in the vacuum vessel 2 to generate the inductively coupled plasma P.

[0028] The vacuum vessel 2 is a metal vessel, such as SUS or aluminum, and the interior of the vacuum vessel 2 is vacuumed by a vacuum evacuation device 6. In this example, the vacuum vessel 2 is electrically grounded. The vacuum evacuation device 6 includes a pressure regulator 61, such as a valve, that regulates the pressure in the vacuum vessel 2. The pressure regulator 61 can be controlled to regulate the pressure in the vacuum vessel 2 during plasma generation, for example, to a pressure of 7 Pa or more and 100 Pa or less.

[0029] The gas G, e.g., a raw material gas, is introduced into the vacuum vessel 2, e.g., via a flow regulator (not shown) and a plurality of gas inlets 21 arranged toward the antenna 3.

[0030] Further, a substrate holder 8 that holds the substrate W is provided in the vacuum vessel 2, and a heater 81 that heats the substrate W is provided in the substrate holder 8. The substrate holder 8 may not be electrically connected to the vacuum vessel 2. The film forming apparatus 100 of this embodiment may have the function of regulating a potential with respect to the generated inductively coupled plasma in a range of, for example, +100 V to -100 V by applying a bias voltage from a bias power supply 9 to the substrate holder 8. The applied bias voltage is, for example, a negative DC voltage, but not limited thereto. With such a bias voltage, for example, the energy can be controlled when positive ions in the plasma P are injected into the substrate W to control the crystallinity or the like of the film formed on the surface of the substrate W.

[0031] The gas supply mechanism 7 supplies the gas G, such as the raw material gas, into the vacuum vessel via the gas inlets 21. The gas supply mechanism 7 is configured to supply the gas G downward from the gas inlets 21 provided on an upper wall of the vacuum vessel 2. The gas supply mechanism 7 is configured to be capable of supplying a raw material gas containing at least C (carbon), H (hydrogen), and O (oxygen), and specifically, it is configured to be capable of supplying an H2 gas, a CH4 gas, and a CO2 gas as the raw material gas. The gas supply mechanism 7 may also be configured to supply any other gas as raw material gas in addition to or instead of the H2 gas, the CH4 gas, and the CO2 gas, as long as the gas supply mechanism 7 is configured to be capable of supplying a raw material gas containing C, H, and O into the vacuum vessel 2.

[0032] The gas supply mechanism 7 is configured to supply the H2 gas, the CH4 gas, and the CO2 gas at arbitrary flow rates. The gas supply mechanism 7 of the present embodiment is configured to regulate the flow rate of each gas and supply the gas so that a ratio (O / (O + H)) of a concentration of O atoms to a total concentration of O atoms and H atoms contained in the raw material gas containing the H2 gas, the CH4 gas, and the CO2 gas is, for example, 10 at% or more and 60 at% or less.

[0033] Furthermore, the gas supply mechanism 7 is configured to supply a catalyst gas at any flow rate along with the raw material gas into the vacuum vessel 2. The catalyst gas acts as a catalyst during plasma generation and promotes the decomposition of the raw material gas. Specifically, the gas supply mechanism 7 is configured to supply the catalyst gas at a ratio of 50% or more to 90% or less to the total flow rate of all the gases supplied into the vacuum vessel 2 (here, the total flow rate of the raw material gas and the catalyst gas), for example, and preferably 75% or more to 90% or less. Examples of the catalyst gas include, in particular, noble gases such as Ar gas, He gas, and Ne gas.

[0034] The antenna 3 is arranged above the substrate W in the vacuum vessel 2 along the surface of the substrate W. In the present embodiment, a plurality of antennas 3 are arranged in a straight line parallel to the substrate W (e.g., substantially parallel to the surface of the substrate W). In this way, the plasma P can be generated with good uniformity over a larger area, enabling the treatment of a larger substrate W.

[0035] The number of antennas 3 is not limited to a plurality and may be only one. In the case where a plurality of antennas 3 are provided, the number of antennas 3 is preferably an even number (e.g., two, four, six, etc.). Further, in the case where the plurality of antennas 3 are provided, in order to avoid radio wave interference, the distance between the antennas 3 is preferably 5 cm or more, more preferably 10 cm or more, and even more preferably 15 cm or more. On the other hand, the distance between the antennas 3 is preferably 25 cm or less to form a uniform carbon-based thin film.In the case where a plurality of antennas 3 are included, the plurality of antennas 3 are preferably arranged parallel to each other and in the same plane, and arranged so that a plane surrounded by the antennas 3 at both ends has a square or rectangular shape (preferably, one side is 40 cm or more). More preferably, one side is 50 cm or more, even more preferably, one side is 70 cm or more, and even more preferably, one side is 100 cm or more.

[0036] As in Fig. 1, the two end portions of the antenna 3 each penetrate a pair of opposite side walls 2a and 2b of the vacuum vessel 2. Insulating members 11 are provided at portions allowing the two end portions of the antenna 3 to penetrate the outside of the vacuum vessel 2. The two end portions of the antenna 3 penetrate the insulating members 11, and the penetrated portions are sealed in a vacuum-tight manner, for example, by a gasket 12. The antenna 3 is maintained via the insulating members 11 in a state where it is electrically insulated from the opposite side walls 2a and 2b of the vacuum vessel 2. A gap between each insulating member 11 and the vacuum vessel 2 is also sealed in a vacuum-tight manner, for example, by a gasket 13.The material of the insulating element 11 is, for example, a ceramic such as aluminum oxide, quartz or an engineering plastic such as polyphenylene sulfide (PPS) and polyetheretherketone (PEEK).

[0037] Furthermore, the antenna 3 is a so-called LC antenna having an L part serving as an inductor and a C part serving as a capacitor. Specifically, the antenna 3 includes at least two conductor elements 31 (hereinafter referred to as "metal tubes 31") made of metal having a tubular shape, an insulating element 32 (hereinafter referred to as "insulating tube 32") in a tubular shape provided between the adjacent metal tubes 31 to insulate the metal tubes 31, and a capacitor 33, which is a capacitor element provided between the adjacent metal tubes 31 and electrically connected in series with them. The conductor element 31 functions as the L part, and the capacitor 33 functions as the C part.

[0038] In the present embodiment, the number of metal tubes 31 is three, and the number of insulating tubes 32 and capacitors 33 is two each. The antenna 3 may also have a configuration with four or more metal tubes 31, and in this case, the number of insulating tubes 32 and capacitors 33 is one less than the number of metal tubes 31.

[0039] The material of the metal tube 31 is, for example, copper, aluminum, an alloy thereof, stainless steel, etc., but is not limited thereto. The antenna 3 may be hollowed out, and a coolant such as cooling water may be introduced therein to cool the antenna 3.

[0040] The insulating tube 32 of the present embodiment is formed from a single member, but is not limited thereto. A material of the insulating tube 32 includes, for example, alumina, fluororesin, polyethylene (PE), engineering plastics (e.g., polyphenylene sulfide (PPS) and polyetheretherketone (PEEK)), etc.

[0041] Furthermore, a portion of the antenna 3 located within the vacuum vessel 2 is covered by an insulating cover (antenna protection tube) 10 in the shape of a straight tube. Both ends of the insulating cover 10 are supported by insulating members 11. Sealing between the two ends of the insulating cover 10 and the insulating members 11 is not possible. This is because even if the gas G enters the space within the insulating cover 10, the plasma P is generally not generated in the space because the space is small and the electron movement distance is short. Materials of the insulating cover 10 include quartz, alumina, fluororesin, silicon nitride, silicon carbide, silicon, etc.

[0042] By providing the insulating cover 10, since charged particles in the plasma P are injected into the metal tube 31 constituting the antenna 3, it is possible to suppress an increase in the plasma potential caused by the injection of charged particles (mainly electrons) into the metal tube 31, and it is possible to suppress the sputtering of the metal tube 31 by charged particles (mainly ions), thus preventing the occurrence of metal impurities in the plasma P and the substrate W.

[0043] For example, the length of the antenna 3 is preferably 20 cm or more, preferably 50 cm or more, and more preferably 100 cm or more. On the other hand, from the viewpoint of ensuring the strength of the insulating tube 32, the length of the antenna 3 is preferably 1000 cm or less, and more preferably 500 cm or less.

[0044] As in Fig. As shown in Figure 1, the antenna 3 includes a feed end portion 3a to which high-frequency power is supplied in the antenna direction (longitudinal direction X), and a grounded end portion 3b that is grounded. Specifically, at both end portions of each antenna 3 in the longitudinal direction X, a portion extending outward from one side wall 2a or 2b serves as the feed end portion 3a, and a portion extending outward from the other side wall 2a or 2b serves as the grounded end portion 3b.

[0045] Here, a high frequency is applied from the high-frequency power supply 4 to the power supply end 3a of each antenna 3 via a matching device 41. The frequency of the high frequency is 400 kHz or more and 100 MHz or less, and is generally, for example, 13.56 MHz, but is not limited thereto. The frequency can be, for example, 27.12 MHz, 40.68 MHz, 60 MHz, etc. <2. Film formation process>

[0046] Next, a method for forming a carbon-based thin film using the above-described film-forming apparatus 100 will be described. A first film-forming method and a second film-forming method in which the composition ratios of the supplied raw material gas differ from each other will be described below. According to the above-described film-forming apparatus 100, a carbon-based thin film such as diamond can be formed by either of the film-forming methods. [First film formation process]

[0047] First, a substrate W is placed on the substrate holder 8 in the vacuum vessel 2 of the film forming apparatus 100, and the vacuum vessel 2 is vacuumized by the vacuum evacuation device 6. Preferably, the substrate W is heated by the heater 81, and the temperature of the substrate W is set to 100°C or more and 1200°C or less. The temperature range of the substrate W can be changed depending on the particle size or crystallinity of the diamond to be synthesized. In the first film forming method, for example, in the synthesis of a carbon-based thin film in which diamond microcrystals are present in a DLC film, the temperature of the substrate W is preferably set to 100°C or more and 400°C or less.In the case of synthesizing a carbon-based thin film containing diamond with a particle size of 200 nm or less, the temperature of the substrate W is preferably set to 200 °C or more and less than 500 °C. In the case of synthesizing a carbon-based thin film containing diamond with a particle size of 200 nm or more and 1000 nm or less, the temperature of the substrate W is preferably set to 200 °C or more and less than 500 °C. In the case of synthesizing a carbon-based thin film containing diamond with a particle size of 1000 nm or more, the temperature of the substrate W is preferably set to 700 °C or more and 1200 °C or less. [Supply of the raw material gas]

[0048] Next, an H2 gas, a CH4 gas, and a CO2 gas serving as raw material gas are supplied into the vacuum container 2 at predetermined flow rates through the gas supply mechanism 7. In the film forming method of the present embodiment, each flow rate of the H2 gas, the CH4 gas, and the CO2 gas is regulated so that the atomic number ratios of the O atoms, C atoms, and H atoms in the raw material gas fall within the range of the oblique lines shown in a ternary composition diagram (CHO diagram) of Fig. 2. The atomic number ratios of the individual atoms are described below. [Atomic number ratio between oxygen and hydrogen]

[0049] Each flow rate of the H2 gas, the CH4 gas, and the CO2 gas is controlled and supplied so that the ratio (O / (O + H)) of a concentration of O atoms to a total concentration of O atoms and H atoms contained in the supplied raw material gas is preferably 10 atomic % or more and 60 atomic % or less, and more preferably 30 atomic % or more and 50 atomic % or less. [Atomic number ratio between oxygen and carbon]

[0050] Each flow rate of the H2 gas, the CH4 gas, and the CO2 gas is controlled and supplied so that the ratio (C / (O + C)) of a concentration of C atoms to a total concentration of O atoms and C atoms contained in the supplied raw material gas is preferably 30 atomic % or more and 45 atomic % or less, and more preferably 35 atomic % or more and 45 atomic % or less. [Atomic number ratio between carbon and hydrogen]

[0051] Further, each flow rate of the H2 gas, the CH4 gas, and the CO2 gas is controlled and supplied so that the ratio (H / (C + H)) of a concentration of H atoms to a total concentration of C atoms and H atoms contained in the supplied raw material gas is preferably 40 at% or more and 90 at% or less, and more preferably 50 at% or more and 80 at% or less. [Supply of catalyst gas]

[0052] In addition, a catalyst gas, such as Ar gas, is supplied into the vacuum vessel 2 together with the raw material gas via the gas supply mechanism 7. The flow rate of the supplied catalyst gas is adjusted so that the ratio to the total flow rate of all the gases supplied to the vacuum vessel 2 is preferably 50% or more and 90% or less, and more preferably 75% or more and 90% or less. By adjusting the flow rate of the supplied catalyst gas within such a range, energy can be transferred from, for example, Ar, which is easily ionized, to CH4 during film formation, and a large number of C2 radicals can be generated, which easily generate diamond. Accordingly, as shown in Fig. 3, in an emission spectrum of the generated inductively coupled plasma, a ratio of a light intensity of C2 radicals to a light intensity of Hα radicals may be set to 30% or more and 300% or less, and preferably 90% or more and 250% or less. [Pressure in the vacuum container]

[0053] Then, a pressure in the vacuum vessel 2 is controlled by the pressure regulator 61 to 7 Pa or more and 100 Pa or less, preferably 10 Pa or more and 50 Pa or less, while the raw material gas and the catalyst gas are introduced through the gas supply mechanism 7. [Generation of plasma and film formation of carbon-based thin films]

[0054] Then, the antenna 3 is supplied with high-frequency power from the high-frequency power supply 4, with the flow rates of the raw material gas and the catalyst gas, as well as the pressure in the vacuum vessel 2, controlled as described above. Accordingly, an induced electric field is generated in the vacuum vessel 2 to generate an inductively coupled plasma P and form a carbon-based thin film on the substrate W. The frequency of the high-frequency power is 400 kHz or more and 100 MHz or less, preferably, for example, 13.56 MHz. Furthermore, the power density of the supplied high-frequency power is preferably 0.1 W / cm 2 or more, preferably 0.5 W / cm 2 or more and more preferably 1 W / cm 2 or more. Furthermore, the power density is preferably 1000 W / cm 2 or less, more preferably 100 W / cm 2 or less and more preferably 50 W / cm 2 or less. [Second film formation process]

[0055] Next, a second film-forming method will be described in which the gas composition ratio of the supplied raw material gas differs from that of the first film-forming method. First, a substrate W is placed on the substrate holder 8 in the vacuum vessel 2 of the film-forming apparatus 100, and the vacuum vessel 2 is vacuum-evacuated by the vacuum evacuation device 6. Preferably, the substrate W is heated by the heater 81, and the temperature of the substrate W is set to 100°C or more and 1200°C or less. The temperature range of the substrate W can be changed depending on the particle size or crystallinity of the diamond to be synthesized.In the second film formation method, in the case of synthesizing a carbon-based thin film containing diamond with a particle size of 50 nm or less, a hydrogen-rich raw material gas is preferably supplied, and the temperature of the substrate W is set to 500°C or more and 1200°C or less. In the case of synthesizing a carbon-based thin film containing diamond with a particle size of 10 nm or less, the supplied raw material gas is preferably oxygen-rich, and the temperature of the substrate W is set to 800°C or less. [Supply of raw material gas]

[0056] Next, an H2 gas, a CH4 gas, and a CO2 gas serving as raw material gas are supplied into the vacuum container 2 at predetermined flow rates through the gas supply mechanism 7. In the film forming method of the present embodiment, each flow rate of the H2 gas, the CH4 gas, and the CO2 gas is regulated so that the atomic number ratios of the O atoms, C atoms, and H atoms in the raw material gas fall within the range of the oblique lines shown in a ternary composition diagram (CHO diagram) of Fig. 4. The atomic number ratios of the individual atoms are described below. [Atomic number ratio between oxygen and hydrogen]

[0057] Each flow rate of the H2 gas, the CH4 gas, and the CO2 gas is controlled and supplied so that the ratio (O / (O + H)) of a concentration of O atoms to a total concentration of O atoms and H atoms contained in the supplied raw material gas is preferably 5 at% or more and 45 at% or less, and more preferably 5 at% or more and 10 at% or less. [Atomic number ratio between oxygen and carbon]

[0058] Each flow rate of the H2 gas, the CH4 gas, and the CO2 gas is controlled and supplied so that the ratio (C / (O + C)) of a concentration of C atoms to a total concentration of O atoms and C atoms contained in the supplied raw material gas is preferably 45 at% or more and 70 at% or less. [Atomic number ratio between carbon and hydrogen]

[0059] Further, each flow rate of the H2 gas, the CH4 gas, and the CO2 gas is controlled and supplied so that the ratio (H / (C + H)) of a concentration of H atoms to a total concentration of C atoms and H atoms contained in the supplied raw material gas is preferably 60 at% or more and 95 at% or less, and more preferably 90 at% or more and 95 at% or less. [Supply of catalyst gas]

[0060] In addition, a catalyst gas such as Ar gas is supplied into the vacuum vessel 2 along with the raw material gas via the gas supply mechanism 7. The flow rate of the supplied catalyst gas is adjusted so that the ratio to the total flow rate of all the gases supplied to the vacuum vessel 2 is preferably 50% or more and 95% or less, and more preferably 70% or more and 90% or less. By adjusting the flow rate of the supplied catalyst gas within such a range, the ratio of the luminous intensity of the C2 radicals to the luminous intensity of the Hα radicals in an emission spectrum of the generated inductively coupled plasma can be adjusted to 30% or more and 300% or less, and more preferably to 90% or more and 250% or less. [Pressure in the vacuum container]

[0061] Then, a pressure in the vacuum vessel 2 is controlled by the pressure regulator 61 to 7 Pa or more and 100 Pa or less, preferably 10 Pa or more and 50 Pa or less, while the raw material gas and the catalyst gas are introduced through the gas supply mechanism 7. [Generation of plasma and film formation of carbon-based thin films]

[0062] Then, high-frequency power is supplied to the antenna 3 from the high-frequency power supply 4, with the flow rates of the raw material gas and the catalyst gas, as well as the pressure in the vacuum vessel 2, controlled as described above. Accordingly, an induced electric field is generated in the vacuum vessel 2 to generate an inductively coupled plasma P and form a carbon-based thin film on the substrate W. The frequency of the high-frequency power is 400 kHz or more and 100 MHz or less, preferably, for example, 13.56 MHz. Furthermore, the power density of the supplied high-frequency power is preferably 0.1 W / cm 2 or more, preferably 0.5 W / cm 2 or more and more preferably 1 W / cm 2 or more. Furthermore, the power density is preferably 1000 W / cm 2 or less, more preferably 100 W / cm 2 or less and more preferably 50 W / cm 2 or less. < 3. Effect of the present embodiment>

[0063] According to the film forming apparatus 100 and the film forming method of the present embodiment configured in this way, by using an inductively coupled plasma P generated by an induced electric field having a high frequency, it becomes possible to decompose CO2 or the like, which is a molecule with a high binding energy contained in the raw material gas, over a wide range, and the generation of oxygen-containing radicals can be promoted. Since the inductively coupled plasma is generated by the antenna 3, long-term activation can be performed even when the raw material gas has a gas composition with a high oxygen content. Accordingly, a carbon-based thin film such as carbon can be formed.Diamond can be formed with a raw material gas having a wide composition range which cannot be realized by a process using a conventional CVD apparatus, and a carbon-based thin film having a large area can be formed compared with a conventional plasma CVD apparatus.

[0064] Furthermore, the introduction of Ar gas as a catalyst gas can promote the generation of C2 radicals. By forming a film on the substrate W with the C2 radicals and the like and removing a non-diamond component with oxygen-containing radicals and hydrogen radicals, a carbon-based thin film such as diamond can be easily formed on the substrate W.

[0065] Furthermore, according to the film forming apparatus 100 and the film forming method of the present embodiment described above, in the case where Raman spectroscopic analysis is performed with 325 nm excitation, a diamond film can be formed in which a peak intensity of diamond is in the vicinity of 1333 cm -1 more than 20%, preferably 100% or more, and more preferably 1000% or more, of a peak intensity of a G-band near 1550 cm -1 amounts.

[0066] The film forming apparatus 100 of the present invention is not limited to the above-described embodiment.

[0067] For example, in the film forming apparatus 100 of the above embodiment, the antenna 3 that generates the inductively coupled plasma is arranged inside the vacuum container 2, but the present invention is not limited thereto. A film forming apparatus 100 of another embodiment may have a structure in which the antenna 3 is arranged outside the vacuum container 2.

[0068] The present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the spirit and scope of the present invention. Thus, those skilled in the art will understand that the above-described exemplary embodiments are specific examples of the following embodiments.

[0069] (Embodiment 1) A film forming apparatus comprising: a vacuum vessel in which a substrate is disposed; an antenna that generates an inductively coupled plasma in the vacuum vessel and includes a conductor element and a capacitor element electrically connected in series with each other; a high-frequency power supply that supplies a high-frequency current to the antenna; and a gas supply mechanism that supplies a raw material gas containing C, H, and O into the vacuum vessel, wherein a carbon-based thin film is formed on the substrate in the vacuum vessel according to a plasma CVD method using the inductively coupled plasma generated in the vacuum vessel by passing the high-frequency current through the antenna.

[0070] (Embodiment 2) The film forming apparatus according to Embodiment 1, wherein in a composition of the raw material gas supplied from the gas supply device, the ratio of a concentration of O atoms to a total concentration of O atoms and H atoms is 10 at% or more and 60 at% or less.

[0071] (Embodiment 3) The film forming apparatus according to Embodiment 1 or 2, wherein the gas supply mechanism supplies a catalyst gas together with the raw material gas into the vacuum vessel, and a ratio of the flow rate of the catalyst gas to a total flow rate of all the gases supplied into the vacuum vessel is set to 50% or more and 90% or less.

[0072] (Embodiment 4) The film forming apparatus according to Embodiment 3, wherein the catalyst gas is an Ar gas.

[0073] (Embodiment 5) The film forming apparatus according to any one of Embodiments 1 to 4, wherein in an emission spectrum of the inductively coupled plasma, the ratio of the luminous intensity of the C2 radicals to the luminous intensity of the Hα radicals is 30% or more and 300% or less.

[0074] (Embodiment 6) The film forming apparatus according to any one of Embodiments 1 to 5, wherein the pressure in the vacuum container during film formation is 7 Pa or more and 100 Pa or less.

[0075] (Embodiment 7) The film forming apparatus according to any one of Embodiments 1 to 6, wherein the antenna has a rectilinear shape and a length of 20 cm or more.

[0076] (Embodiment 8) The film forming apparatus according to any one of Embodiments 1 to 5, wherein the carbon-based thin film is a diamond film.

[0077] (Embodiment 9) The film forming apparatus according to any one of Embodiments 1 to 8, wherein in a Raman spectroscopic analysis with 325 nm excitation, a peak intensity of diamond of the diamond film is in the vicinity of 1333 cm -1 more than 20% of a peak intensity of a G-band near 1550 cm -1 amounts.

[0078] (Embodiment 10) A film forming method comprising: supplying a raw material gas containing C, H, and O into a vacuum vessel in which a substrate is disposed; generating an inductively coupled plasma in the vacuum vessel by passing a high-frequency current through an antenna disposed inside or outside the vacuum vessel and including a conductor element and a capacitor element electrically connected in series with each other; and forming a carbon-based thin film on the substrate according to a plasma CVD method using the generated inductively coupled plasma.

[0079] (Embodiment 11) The film forming method according to Embodiment 10, wherein the carbon-based thin film is a diamond film, and in a Raman spectroscopic analysis with 325 nm excitation, a peak intensity of diamond of the diamond film is in the vicinity of 1333 cm -1more than 20% of a peak intensity of a G-band near 1550 cm -1 amounts. <4. Examples>

[0080] The present invention will be described in more detail below with reference to examples. The present invention is not limited by the following examples and can be implemented with modifications within the scope that can be adapted to the gist described below, and all of these are included in the technical scope of the present invention. (Example 1)

[0081] In Example 1, according to a plasma CVD method using the above-described film forming apparatus, 100 films were formed from a plurality of samples (No. 1 to No. 10) on substrates by changing the composition of the raw material gas, the pressure of the vacuum vessel 2, and the flow rate ratio of the Ar gas. Furthermore, Sample No. 11 was formed on a substrate using a film forming apparatus having an antenna in a simple rectilinear shape that is not an LC antenna (i.e., without a capacitor part). The flow rate of the raw material gas, the composition of the raw material gas, the flow rate ratio of the Ar gas, and the pressure in the vacuum vessel 2 during film formation of each sample are shown in Fig. 5. Other conditions for film formation are as follows. - Frequency of the delivered radio frequency power: 13.56 MHz - Power density of the delivered high-frequency power: 1.4 W / cm2 - Substrate temperature: 500°C

[0082] The crystallinity of the formed film of each sample was then evaluated using laser Raman spectroscopy (excitation at 325 nm). The Raman scattering spectra obtained for each sample are shown in Fig. 6. As shown in Fig. 6, an optical phonon peak of diamond was observed near the wavelength of 1333 cm -1observed, and it was confirmed that a diamond film can be formed in samples No. 1 to No. 4 in which the LC antenna was used, and in the raw material gas, the ratio of the concentration of O atoms to the total concentration of O atoms and H atoms was 10 atomic% or more and 60 atomic% or less, the flow rate ratio of the Ar gas in all gases was 50% or more and 90% or less, and the pressure in the vacuum vessel 2 was set to 7 Pa or more and 100 Pa or less. (Example 2)

[0083] In Example 2, according to a plasma CVD method using the above-described film-forming apparatus, 100 films were formed from a plurality of samples (No. 12 to No. 15) on substrates by changing the composition of the raw material gas, the pressure of the vacuum vessel 2, and the flow rate ratio of the Ar gas. The flow rate of the raw material gas, the composition of the raw material gas, the flow rate ratio of the Ar gas, and the pressure in the vacuum vessel 2 during film formation of each sample are shown in Fig. 7. Other conditions for film formation are as follows. - Frequency of the delivered radio frequency power: 13.56 MHz - Power density of the delivered high-frequency power: 1.4 W / cm 2 - Substrate temperature: 500°C

[0084] The crystallinity of the formed film of each sample was then evaluated using laser Raman spectroscopy (excitation at 325 nm). The Raman scattering spectra obtained for each sample are shown in Fig. 8. As shown in Fig. 8, an optical phonon peak of diamond was observed near the wavelength of 1333 cm -1observed, and it was confirmed that a diamond film can be formed in samples No. 12 to No. 15 in which the LC antenna was used. 15 in which the LC antenna was used, a diamond film can be formed, and in the raw material gas, the ratio of the concentration of O atoms to the total concentration of O atoms and H atoms was 5 at% or more and 45 at% or less, the ratio of the concentration of C atoms to the total concentration of O atoms and C atoms was 45 at% or more and 70 at% or less, the ratio of the concentration of H atoms to the total concentration of C atoms and H atoms was 60 at% or more and 95 at% or less, the flow ratio of the Ar gas in all gases was 50% or more and 95% or less, and the pressure in the vacuum vessel 2 was set to 7 Pa or more and 100 Pa or less (specifically, 15 Pa). Industrial applicability

[0085] According to the present invention, in the film forming apparatus that forms a carbon-based thin film such as diamond by the CVD method, it is possible to form a carbon-based thin film with a raw material gas having a wide composition range, and film formation in a wide range becomes possible. List of reference symbols 100 Plasma CVD device 2 vacuum containers 3 Antenna 7 Gas supply mechanism W substrate P Plasma QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2003

[0004] JP 55087

[0004]

Claims

[1] A film forming apparatus comprising: a vacuum container in which a substrate is arranged; an antenna generating an inductively coupled plasma in the vacuum vessel and comprising a conductor element and a capacitor element electrically connected in series; a radio frequency power supply that supplies a radio frequency current to the antenna; and a gas supply mechanism that supplies a raw material gas containing C, H and O into the vacuum vessel, wherein a carbon-based thin film is formed on the substrate in the vacuum vessel by a plasma CVD method using the inductively coupled plasma generated in the vacuum vessel by passing the high-frequency current through the antenna. [2] The film forming apparatus according to claim 1, wherein, in a composition of the raw material gas supplied by the gas supply mechanism, a ratio of a concentration of O atoms to a total concentration of O atoms and H atoms is 10 at% or more and 60 at% or less. [3] The film forming apparatus according to claim 1, wherein the gas supply mechanism supplies a catalyst gas together with the raw material gas into the vacuum vessel, and a ratio of a flow rate of the catalyst gas to a total flow rate of all the gases supplied into the vacuum vessel is set to 50% or more and 90% or less. [4] The film forming apparatus according to claim 3, wherein the catalyst gas is an Ar gas. [5] The film forming apparatus according to claim 1, wherein in an emission spectrum of the inductively coupled plasma, the ratio of the luminous intensity of the C2 radicals to the luminous intensity of the Hα radicals is 30% or more and 300% or less. [6] The film forming apparatus according to claim 1, wherein the pressure in the vacuum container during film formation is 7 Pa or more and 100 Pa or less. [7] The film forming apparatus according to claim 1, wherein the antenna has a rectilinear shape and has a length of 20 cm or more. [8] The film forming apparatus according to claim 1, wherein the carbon-based thin film is a diamond film. [9] The film forming apparatus according to claim 1, wherein in a Raman spectroscopic analysis with 325 nm excitation, a peak intensity of diamond of the diamond film is in the vicinity of 1333 cm -1 more than 20% of a peak intensity of a G-band near 1550 cm -1 amounts. [10] A film forming process comprising: Supplying a raw material gas containing C, H and O into a vacuum vessel in which a substrate is arranged; Generating an inductively coupled plasma in the vacuum vessel by passing a high-frequency current through an antenna arranged inside or outside the vacuum vessel and comprising a conductor element and a capacitor element electrically connected in series; and Forming a carbon-based thin film on the substrate by a plasma CVD process using the generated inductively coupled plasma. [11] The film forming method according to claim 10, wherein the carbon-based thin film is a diamond film, and in a Raman spectroscopic analysis with 325 nm excitation, a peak intensity of diamond of the diamond film is in the vicinity of 1333 cm -1more than 20% of a peak intensity of a G-band near 1550 cm -1 amounts.

Images