METHOD FOR PRODUCE DIAMOND THIN FILM AND DEVICE FOR PRODUCE DIAMOND THIN FILM

Abstract

The process for producing a diamond thin film comprises synthesizing a diamond thin film on a base material by a plasma-CVD process, wherein a starting gas containing C, H, and O is introduced into a vacuum vessel in which the base material is arranged, radio frequency current is applied to an antenna located inside or outside the vacuum vessel, which has a conductor element and a capacitive element electrically connected in series to generate an inductively coupled plasma inside the vacuum vessel, and the generated inductively coupled plasma is used for the plasma-CVD process. When the diamond thin film is synthesized, the plasma has the following properties: the electron temperature is 1.0 eV or higher and 2.0 eV or lower; the electron density is 1.0 × 10⁻⁶ 11 cm -3 or more and 1.0 × 10 12 cm -3or less; and the ion saturation current is 1.0 × 10 -4 A or more and 1.0 × 10 -2 A or less.

Description

Technical field

[0001] The present invention relates to a method for producing diamond thin film and a device for producing diamond thin film synthesized using a plasma-CVD process. Description of the state of the art

[0002] Previously known methods for producing diamond thin film synthesized using a CVD process include methods for producing diamond thin film using a wire CVD device, a microwave resonator plasma CVD device, a microwave surface wave plasma CVD device (e.g., patent specification 1), or a high-frequency inductively coupled (RF-ICP) plasma CVD device using a spiral electrode (e.g., patent specification 2).

[0003] In the manufacturing process using a wire CVD device, a metal wire with a high melting point is installed over the base material on which the diamond thin film is formed, and the diamond thin film is produced by decomposing the initial gas with thermo electrons that are released according to the heating of this metal wire.

[0004] In manufacturing processes using a plasma CVD device that utilizes microwaves or a plasma CVD device that utilizes radio frequency, plasma containing the starting gas is further generated by applying a radio frequency current, and the diamond thin film is synthesized with the activated gas.

[0005] In these processes, it is known that mainly active atomic hydrogen is generated in the plasma, and through its action non-diamond components with sp1 or sp2 bonding are removed, allowing mainly diamond components with sp3 bonding to grow. State of the art Documents Bibliography Patent specification 1: Japanese patent application, published publication no. 2013-40408. Patent specification 2: Japanese patent application, published publication no. 2003-55087. Brief description of the invention: Technical problem

[0006] However, when synthesizing diamond using the aforementioned plasma-CVD device, diamond can only be synthesized in a small area due to limitations in the device's configuration. For example, if the wire is lengthened to synthesize diamond in a larger area, there is a risk that the wire will not be able to support its own weight and will break during plasma generation. Furthermore, microwaves such as 2.45 GHz or 915 MHz are used, but the plasma size could not be increased due to problems with the resonant wavelength.

[0007] Furthermore, when synthesizing diamond thin films, graphite or diamond-like carbon (DLC) is also synthesized simultaneously with diamond, which degrades the film quality of the diamond thin film. As a result of intensive investigations, the current inventor discovered for the first time that the degradation of the diamond thin film quality can be suppressed if the electron temperature, electron density, and ion saturation current, which define the plasma characteristics during diamond thin film synthesis, remain within predetermined ranges.

[0008] The present invention was made to solve the above-mentioned problems, and its main objective is to synthesize diamond thin film over a larger area and to suppress deterioration of the film quality of diamond thin film. Solution to the problem

[0009] That is, the method for producing a diamond thin film according to the present invention is a method for producing a diamond thin film comprising: supplying a starting gas containing C, H, and O to a vacuum vessel in which a base material is arranged; generating an inductively coupled plasma in the vacuum vessel by passing a radio frequency current through an antenna arranged inside or outside the vacuum vessel, the antenna comprising a conductor element and a capacitive element electrically connected in series; and synthesizing a diamond thin film on the base material by a plasma-CVD process using the generated inductively coupled plasma. The plasma properties during the synthesis of the diamond thin film include: an electron temperature of 1.0 eV or more and 2.0 eV or less, and an electron density of 1.0 × 10⁻⁶ 11 cm -3 or more and 1.0×10 12cm -3 or less and an ion saturation current of 1.0×10 -4 A or more and 1.0×10 -2 A or less.

[0010] In such a configuration, since an antenna with conductor elements and capacitive elements electrically connected in series is used, compared to a configuration using a conventional plasma CVD device, a uniform plasma is generated in the longitudinal direction of the antenna, and a diamond thin film with a larger area can be synthesized.

[0011] Furthermore, if the plasma properties are within the numerical ranges mentioned above, deterioration of the film quality of the diamond thin film can be prevented, since the diamond thin film is synthesized in a state in which the amount of electrons and the electron temperature are appropriate.

[0012] In particular, if the electron temperature exceeds the upper limit, electron collisions with the base material increase, causing the base material's temperature to rise excessively, and there is a possibility that graphite will be synthesized. Conversely, if the electron temperature falls below the lower limit, insufficient dissociation of the starting gas occurs, and the synthesized thin film becomes a DLC film with many sp or sp² bonds. Therefore, the electron temperature must remain within the aforementioned numerical range. Similarly, the electron density must also remain within the aforementioned numerical range for the same reason as the electron temperature, in order to prevent the synthesis of graphite or the synthesis of a DLC film.

[0013] In the synthesis of the diamond thin film, ionic carbon species (C) are present in the plasma.2+ , CH3 + , CH +etc.) are present. Consequently, two phenomena occur simultaneously: (1) Secondary nuclei are generated on the diamond through the collision of ionic carbon species with the growth surface, and (2) the growth of the diamond thin film is inhibited by the ionic carbon species. To synthesize the diamond thin film while simultaneously suppressing these two phenomena, it is necessary to keep the ion saturation current within the aforementioned numerical range. More precisely, this means that if the ion saturation current exceeds the upper limit, the frequency of collisions between ionic carbon species and the base material increases, and the inhibition of diamond thin film growth by the ionic carbon species becomes greater. As a result, the growth rate of the diamond thin film decreases, or the quality of the diamond thin film deteriorates.If, however, the ion saturation current falls below the lower limit, the ionic carbon species required for the growth of the diamond thin film are not present in sufficient quantities on the surface of the base material, and the growth rate of the diamond thin film decreases. Therefore, the ion saturation current must be within the numerical range mentioned above.

[0014] A specific aspect of the antenna can be described as having a linear shape and a length of 30 cm or more in the longitudinal direction.

[0015] With such a configuration, compared to a configuration using a conventional plasma CVD device, a diamond thin film with a larger area in the longitudinal direction can be synthesized uniformly.

[0016] Another specific aspect of the diamond thin film manufacturing process is that the distance between the antenna and the base material is 100 mm or less.

[0017] In such a configuration, uniform plasma is generated within the vacuum chamber in the longitudinal direction of the antenna, and diamond thin film can be synthesized uniformly with respect to the longitudinal direction of the antenna.

[0018] In the process for producing the diamond thin film, a preload is applied to the base material, wherein a negative preload of -100 V or less is applied to the base material and a positive preload of 100 V or less is applied to the base material.

[0019] In such a configuration, applying a bias voltage to the base material allows control of the energy when positive ions in the plasma collide with the base material, and thus controls the crystallinity of the film formed on the surface of the base material. Specifically, applying a negative bias voltage of -100 V or less to the base material promotes the formation of diamond growth nuclei, while applying a positive bias voltage of 100 V or less promotes the growth of the diamond thin film.

[0020] The starting gas preferably also contains a noble gas, such as Ar, He, or Ne. With such a configuration, those components in the gas that are difficult to decompose, such as carbon dioxide, can be more easily decomposed.

[0021] To produce a diamond thin film using radio frequency instead of microwaves, the radio frequency of the radio frequency current can have a frequency of 400 kHz or more and 100 MHz or less.

[0022] A device for producing a diamond thin film, for synthesizing a diamond thin film on a base material by a plasma-CVD process using an inductively coupled plasma, comprises: a vacuum vessel in which the base material is arranged and to which a starting gas containing C, H, and O is supplied; an antenna, arranged inside or outside the vacuum vessel, comprising a conductor element and a capacitive element electrically connected in series; and a radio frequency power source for applying radio frequency to the antenna to generate inductively coupled plasma in the vacuum vessel. The plasma properties in the vacuum vessel during the synthesis of the diamond thin film include: an electron temperature of 1.0 eV or more and 2.0 eV or less, and an electron density of 1.0 × 10⁻⁶ 11 cm -3 or more and 1.0×10 12 cm -3or less and an ion saturation current of 1.0×10 -4 A or more and 1.0×10 -2 A or less.

[0023] With such a configuration, the same effects can be obtained as with the above-mentioned method for producing the diamond thin film. Effects of the invention

[0024] According to the present invention, configured in this way, a diamond thin film can be synthesized over a larger area, and deterioration of the film quality of the diamond thin film can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS [ Fig. Figure 1] is a diagram schematically showing a configuration of a film forming device according to an embodiment of the present invention. [ Fig. Figure 2] is a diagram showing a gas composition range of the starting gas supplied by the film forming device and the method for producing the diamond thin film of the same embodiment. DESCRIPTION OF THE EXECUTION FORMS

[0025] A film-forming device and a method for producing a diamond thin film according to an embodiment of the present invention are described below with reference to the drawings. It should be noted that each of the drawings shown below may be schematic, with appropriate omissions or exaggerations for clarity. The same reference numerals are assigned to the same components, and their descriptions are omitted accordingly. <Gerätekonfiguration>

[0026] The film formation device 100 of this embodiment is a plasma-CVD device that forms a diamond thin film F on a base material W by a plasma-CVD process using an inductively coupled plasma P.

[0027] The base material W of this embodiment is plate-shaped and consists of a material suitable for forming the diamond thin film F. The base material W can be made of materials such as glass, plastic, silicon, metals such as iron, titanium, copper and cemented carbide, other alloy materials such as tool steel and materials such as SiC, GaN, AlN, BN and diamond, but is not limited to these.

[0028] The base material W has a rectangular or circular shape in plan view. Its length can be, for example, 20 cm or more, or 50 cm or more, but is not limited to these dimensions. The base material W can also consist of several small, chip-shaped base materials, for example, approximately 1 mm, 5 mm, or 10 mm in size, arranged with similar lengths or areas. The base material W is not limited to a sheet shape and can be columnar, perforated, or porous. Furthermore, the base material W can also have a complex shape, such as tools like drills and end mills.

[0029] The base material W can also undergo surface treatments such as damage treatment or seeding. If the base material W is silicon, for example, damage treatment or seeding can be performed by immersing it in alcohol along with fine diamond particles and creating surface irregularities through ultrasonic treatment. Furthermore, if the base material W is made of cemented carbide, for example, cobalt in the base material can be removed by immersion in an acidic solution, such as aqueous nitric acid, or the surfaces of the WC (tungsten carbide) particles can be treated with an alkaline solution, such as dilute NaOH, and then the seeding treatment described above can be performed.

[0030] As in Fig. As shown in Figure 1, the film-forming device 100 comprises a vacuum vessel 2, which is vacuum-evacuated and immersed in gas G, a gas supply mechanism 7 that supplies gas G into the vacuum vessel 2, a linear antenna 3 located inside the vacuum vessel 2, and a high-frequency current source 4 that applies high frequency to the antenna 3 to generate inductively coupled plasma P in the vacuum vessel 2. In this film-forming device 100, by applying high frequency from the high-frequency current source 4 to the antenna 3, a high-frequency current IR flows through the antenna 3, an induced electric field is generated inside the vacuum vessel 2, and inductively coupled plasma P is produced.

[0031] The vacuum vessel 2 is a metal container, made, for example, of SUS or aluminum, and its interior is vacuum-evacuated by a vacuum extraction device 6. In this example, the vacuum vessel 2 is electrically grounded. It should be noted that the vacuum extraction device 6 includes a pressure regulator 61, for example, a valve, which regulates the pressure inside the vacuum vessel 2. The pressure regulator 61 is controlled to regulate the pressure inside the vacuum vessel 2 during plasma generation and is configured to regulate the pressure, for example, to 7 Pa or more and 100 Pa or less.

[0032] Gas G, for example the output gas, is introduced into the vacuum vessel 2 via, for example, a flow regulator (not shown) and several gas inlet openings 21, which are arranged in one direction along the antenna 3.

[0033] Furthermore, a base material holder 8 is provided within the vacuum vessel 2, which holds the base material W, and a heater 81 is provided within this base material holder 8, which heats the base material W. It should be noted that the base material holder 8 must not be electrically connected to the vacuum vessel 2. The film forming device 100 of this embodiment can have a function for adjusting the 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 source 9 to the base material holder 8. The applied bias voltage is, for example, a negative DC voltage, but is not limited to this.With such a bias, for example, the energy when positive ions in the plasma P collide with the base material W can be controlled in order to control the crystallinity of the film formed on the surface of the base material W.

[0034] The gas supply mechanism 7 supplies gas G, for example, output gas, into the vacuum vessel 2 via the gas inlet opening 21. The gas supply mechanism 7 is configured to supply gas G downwards from the gas inlet opening 21, which is provided on the upper wall of the vacuum vessel 2. This gas supply mechanism 7 is configured to supply output gas containing at least C (carbon), H (hydrogen), and O (oxygen), and is specifically configured to supply H₂ gas, CH₄ gas, and CO₂ gas as output gas. It should be noted that the gas supply mechanism 7 can be configured to supply any other gas as output gas in addition to or instead of H₂ gas, CH₄ gas, and CO₂ gas, as long as it is configured to supply output gas containing C, H, and O into the vacuum vessel 2.

[0035] The gas supply mechanism 7 is configured to supply H2 gas, CH4 gas, and CO2 gas at desired flow rates. In this embodiment, the gas supply mechanism 7 is configured to adjust and supply the flow rate of each gas such that, in the initial gas, which is configured to contain H2 gas, CH4 gas, and CO2 gas, the ratio of the concentration of O atoms to the total concentration of O atoms and H atoms (O / (O+H)) is, for example, 5 at% or more and 45 at% or less.

[0036] The gas supply mechanism 7 is also configured to supply catalyst gas at an arbitrary flow rate together with the feed gas into the vacuum vessel 2. This catalyst gas acts as a catalyst during plasma generation and promotes the decomposition of the feed gas. In particular, the gas supply mechanism 7 is configured to supply catalyst gas such that the ratio of the catalyst gas to the total flow rate of all gases supplied to the vacuum vessel 2 (here, the total flow rate of feed gas and catalyst gas) is, for example, 50% or more and 95% or less, preferably 70% or more and 90% or less. Examples of this catalyst gas include, in particular, noble gases such as argon gas, helium gas, and neron gas.

[0037] The antenna 3 is positioned above the base material W in the vacuum vessel 2 such that it extends along the surface of the base material W. In this embodiment, several linear antennas 3 are arranged parallel to the base material W (e.g., substantially parallel to the surface of the base material W). In this way, plasma P can be generated with good uniformity over a larger area, thus enabling the processing of larger base materials W.

[0038] It should be noted that the number of antennas 3 is not limited to multiple antennas, but can also be just one antenna. If multiple antennas 3 are provided, the number is preferably an even number (2, 4, 6, etc.). Furthermore, if multiple antennas 3 are provided, the spacing between the individual antennas 3 is preferably 5 cm or more, particularly preferably 10 cm or more, and even more preferably 15 cm or more, to avoid radio wave interference. However, to form a uniform diamond thin film F, the spacing between the antennas 3 is preferably 25 cm or less.

[0039] As in Fig. As shown in Figure 1, the areas near the two ends of the antenna 3 each penetrate a pair of opposing side walls 2a and 2b of the vacuum vessel 2. Insulating elements 11 are provided at sections where both ends of the antenna 3 protrude outwards from the vacuum vessel 2. The two ends of the antenna 3 penetrate one of these insulating elements 11, and the penetrating portions are vacuum-sealed, for example, by a gasket 12. The antenna 3 is supported by these insulating elements 11 in an electrically insulated state from the opposing side walls 2a and 2b of the vacuum vessel 2. The space between each insulating element 11 and the vacuum vessel 2 is also vacuum-sealed, for example, by a gasket 13. Note that the material of the insulating element 11 is, for example, a ceramic such as aluminum oxide or quartz, or an engineering plastic such as polyphenylene sulfide (PPS) or polyetheretherketone (PEEK).

[0040] Furthermore, the antenna 3 is a so-called LC antenna, which includes an L-section serving as an inductor and a C-section serving as a capacitor. In particular, this antenna 3 includes at least two tubular metallic conductor elements 31 (hereinafter referred to as metal tubes 31), tubular insulating elements 32 (hereinafter referred to as insulating tubes 32) provided between adjacent metal tubes 31 to insulate these metal tubes 31, and capacitors 33, which are capacitive elements provided between adjacent metal tubes 31 and electrically connected in series with them. The conductor elements 31 function as L-sections and the capacitors 33 function as C-sections.

[0041] In this embodiment, the number of metal tubes 31 is three, and the number of insulating tubes 32 and capacitors 33 is two each. It should be noted that the antenna 3 can have a configuration with four or more metal tubes 31, and in this case, the number of insulating tubes 32 and capacitors 33 is each one less than the number of metal tubes 31.

[0042] The material of the metal tube 31 is, for example, copper, aluminum, alloys thereof, stainless steel, or the like, but is not limited to these. It should be noted that the antenna 3 may be hollow, allowing a coolant such as cooling water to flow through it to cool the antenna 3.

[0043] The insulating tube 32 of this embodiment is formed from a single element, but is not limited to this. It should be noted that the material of the insulating tube 32 is, for example, aluminum oxide, fluorocarbon resin, polyethylene (PE), engineering plastics (such as polyphenylene sulfide (PPS), polyetheretherketone (PEEK)) or the like.

[0044] Furthermore, in the antenna 3, the section located inside the vacuum chamber 2 is covered by a straight, tubular insulating cover (antenna protection tube) 10. The two ends of this insulating cover 10 are supported by the insulating elements 11. It should be noted that the two ends of the insulating cover 10 and the insulating elements 11 do not need to be sealed. Even if gas G enters the space inside the insulating cover 10, the space is small and the electron path is short, so plasma P does not normally form in this space. It should be noted that the material of the insulating cover 10 is, for example, quartz, aluminum oxide, fluorocarbon resin, silicon nitride, silicon carbide, silicon, or the like.

[0045] By providing the insulating cover 10, the impact of charged particles in the plasma P on the metal tube 31, which forms the antenna 3, can be suppressed, so that an increase in the plasma potential due to the impact of charged particles (mainly electrons) on the metal tube 31 can be suppressed and metal contamination of the plasma P and the base material W due to sputtering of the metal tube 31 by charged particles (mainly ions) can be suppressed.

[0046] The longitudinal length of the antenna 3 is preferably 30 cm or more, particularly preferably 50 cm or more, and even more preferably 100 cm or more, to allow for the synthesis of the diamond thin film F over a larger area. On the other hand, to ensure the strength of the insulating tube 32, the length of the antenna 3 is preferably 1000 cm or less, and particularly preferably 500 cm or less.

[0047] Furthermore, the distance between the antenna 3 and the base material W is preferably 100 mm or less, and particularly preferably 40 mm or more and 60 mm or less, in order to generate uniform plasma P in the longitudinal direction of the antenna 3 within the vacuum vessel 2. If the distance between the antenna 3 and the base material W is too small, the electron density and the electron temperature increase, and graphitization of the thin film occurs, so that the distance between the antenna 3 and the base material W is preferably a predetermined distance.

[0048] As in Fig. As shown in Figure 1, the antenna 3 has a power supply terminal 3a, to which high frequency is supplied in the antenna direction (longitudinal direction X), and a grounded earthing terminal 3b. In particular, at both ends of each antenna 3 in longitudinal direction X, a section extending outwards from one side wall 2a or 2b becomes the power supply terminal 3a, and a section extending outwards from the other side wall 2a or 2b becomes the earthing terminal 3b.

[0049] Here, high frequency is applied from the high-frequency power source 4 via a matching unit 41 to the power supply connection 3a of each antenna 3. The frequency of the high frequency is 400 kHz or more and 100 MHz or less and is, for example, a common 13.56 MHz, but is not limited to this. It can be, for example, 27.12 MHz, 40.68 MHz, 60 MHz, or the like. <Verfahren zur Herstellung eines Diamantdünnfilms>

[0050] Next, a method for producing a diamond thin film F using the film forming device 100 described above is described.

[0051] First, the base material W is placed on the base material holder 8 in the vacuum chamber 2 of the film forming device 100, and the vacuum chamber 2 is evacuated by the vacuum extraction device 6. Then, the base material W is heated by the heater 81, and the temperature of the base material W is preferably set to 100 °C or more and 1200 °C or less. (Introduction of initial gas)

[0052] Next, H2 gas, CH4 gas, and CO2 gas are supplied as feed gases at predetermined flow rates through the gas supply mechanism 7 into the vacuum vessel 2. In the process for producing the diamond thin film F of this embodiment, the flow rates of H2 gas, CH4 gas, and CO2 gas are adjusted such that the atomic ratio of O atoms, C atoms, and H atoms in the feed gas falls within the hatched area shown in the composition ternary diagram (CHO diagram) of Fig. Figure 2 is shown. The atomic number ratio of each atom is described below. (ratio of oxygen and hydrogen atoms)

[0053] In the supplied starting gas, the flow rates of H2 gas, CH4 gas and CO2 gas are controlled and supplied such that the ratio of the concentration of O atoms to the total concentration of the contained O atoms and H atoms (O / (O+H)) is preferably 5 at% or more and 45 at% or less, particularly preferably 5 at% or more and 10 at% or less. (ratio of oxygen to carbon atoms)

[0054] In the supplied starting gas, the flow rates of H2 gas, CH4 gas and CO2 gas are controlled and supplied such that the ratio of the concentration of C atoms to the total concentration of the contained O atoms and C atoms (C / (O+C)) is preferably 45 at% or more and 70 at% or less. (ratio of carbon and hydrogen atoms)

[0055] Furthermore, the flow rates of H2 gas, CH4 gas and CO2 gas in the supplied starting gas are controlled and supplied in such a way that the ratio of the concentration of H atoms to the total concentration of the contained C atoms and H atoms (H / (C+H)) is preferably 60 at% or more and 95 at% or less, particularly preferably 90 at% or more and 95 at% or less. (Addition of catalyst gas)

[0056] Furthermore, the gas supply mechanism 7 introduces catalyst gas, such as Ar gas, into the vacuum vessel 2 along with the initial gas. The flow rate of the supplied catalyst gas is set such that its ratio to the total flow rate of all gases supplied to the vacuum vessel 2 is preferably 50% or more and 95% or less, and particularly preferably 70% or more and 90% or less. By setting the flow rate of the supplied catalyst gas within such a range, energy can be transferred, for example, from readily ionizable Ar to CH4 during film formation, and many C2 radicals, which readily generate diamond, can be produced.This allows the ratio of the luminescence intensity of C2 radicals to the luminescence intensity of Hα radicals in the emission spectrum of the generated inductively coupled plasma to be set to 30% or more and 300% or less, particularly preferably to 90% or more and 250% or less. (Pressure in the vacuum container)

[0057] Then, while the initial gas and the catalyst gas are introduced through the gas supply mechanism 7, the pressure inside the vacuum vessel 2 is adjusted by the pressure regulator 61 to 7 Pa or more and 100 Pa or less, particularly preferably 10 Pa or more and 50 Pa or less. (Generation of plasma and film formation of diamond thin film)

[0058] Then, when the flow rates of the feed gas and the catalyst gas are set as described above and the pressure inside the vacuum vessel 2 is adjusted, radio frequency power is supplied from the radio frequency power source 4 to the antenna 3. This induces an electric field inside the vacuum vessel 2 to generate inductively coupled plasma P, and a diamond thin film F is formed on the base material W. The frequency of the radio frequency power is 13.56 MHz. The power density of the supplied radio frequency power is preferably 0.1 W / cm². 2 or more, especially preferably 0.5 W / cm² 2 or more and preferably 1 W / cm² 2 or more. The power density is preferably 1000 W / cm². 2 or less, especially preferably 100 W / cm² 2 or less and preferably 50 W / cm² 2 or less.

[0059] To suppress the synthesis of graphite or DLC film during the synthesis of the diamond thin film F, it is necessary to define the plasma properties within the following numerical ranges. If the plasma properties are within these ranges, the crystallinity of diamond in the diamond thin film F will be high, and the deterioration of the film quality of the diamond thin film F will be suppressed. It should be noted that the plasma properties mentioned here include the electron temperature Te, the electron density ne, and the ion saturation current Ii. s are. • Electron temperature Te: 1.0 eV ≦ Te ≦ 2.0 eV • Electron density ne: 1×10 11 cm -3 ≦ ne ≦ 1×10 12 cm -3 • Ion saturation current I is : 1 × 10 -4 A ≦ I is ≦ 1×10 -2 A <beispiele>

[0060] The present invention is described in more detail below with reference to examples. The present invention is not limited to the following examples and can be implemented with modifications within a range that may meet the purposes described above and below, all of which are included within the technical scope of the present invention.

[0061] In the examples below, samples on substrates were formed using plasma-CVD processes with the aforementioned film-forming device 100. The pressure in the vacuum vessel 2, the input power, the distance between the base material and the antenna, the frequency of the supplied radio frequency power, and the plasma properties during sample preparation are as follows. <Beispiel 1> • Pressure in vacuum container 2: 15 Pa • Input power: 3.0 kW • Distance between the base material W and the antenna 3: 50 mm • Frequency of the supplied high-frequency power: 13.56 MHz • Electron temperature Te: 1.5 eV • Electron density ne: 7.5×10 11 cm -3 • Ion saturation current I ist : 6×10 -4 A <Beispiel 2> • Pressure in vacuum container 2: 15 Pa • Input power: 3.0 kW • Distance between base material W and antenna 3: 30 mm • Frequency of the supplied high-frequency power: 13.56 MHz • Electron temperature Te: 1.98 eV • Electron density ne: 7.28×10 11 cm -3 • Ion saturation current I is : 1.03×10 -3 A <Beispiel 3> • Pressure in vacuum container 2: 15 Pa • Input power: 4.0 kW • Distance between base material W and antenna 3: 30 mm • Frequency of the supplied high-frequency power: 13.56 MHz • Electron temperature Te: 1.01 eV • Electron density ne: 9.8×10 11 cm -3 • Ion saturation current I is : 2.3×10 -3 A <Vergleichsbeispiel 1> • Pressure in vacuum container 2: 15 Pa • Input power: 2.0 kW • Distance between base material W and antenna 3: 50 mm • Frequency of the supplied high-frequency power: 13.56 MHz • Electron temperature Te: 1.99 eV • Electron density ne: 1.08×10 11 cm -3 • Ion saturation current I is : 9.89×10 -5 A <Vergleichsbeispiel 2> • Pressure in vacuum container 2: 30 Pa • Input power: 2.0 kW • Distance between base material W and antenna 3: 10 mm • Frequency of the supplied high-frequency power: 13.56 MHz • Electron temperature Te: 1.6 eV • Electron density ne: 2.66×10 12 cm -3 • Ion saturation current I is : 3.70×10 -3 A

[0062] Here, the electron temperature Te, the electron density ne, and the ion saturation current I were determined. is measured with a Langmuir probe, a known device for plasma measurement.

[0063] In Example 1, the crystallinity of the synthesized sample was evaluated using laser Raman spectroscopy (325 nm excitation). One result was the optical phonon peak of diamond, which was found in the region near the wavelength of 1330 cm⁻¹. -1 A 2.5 times higher intensity than the optical phonon peak of the G-band was observed, which is in the region near the wavelength of 1550 cm. -1 It was observed, and confirmed, that a thin diamond film with high diamond crystallinity could be synthesized.

[0064] In Example 2, the crystallinity of the synthesized sample was evaluated using laser Raman spectroscopy (325 nm excitation). One result was the optical phonon peak of diamond, which is found in the region near the wavelength of 1330 cm⁻¹. -1 was observed, proven, and the optical phonon peak of the G-band, which is in the region near the wavelength of 1550 cm -1 It was observed but not proven, thus confirming that a thin diamond film could be synthesized.

[0065] In Example 3, the crystallinity of the synthesized sample was evaluated using laser Raman spectroscopy (325 nm excitation). One result was the optical phonon peak of diamond, which is found in the region near the wavelength of 1330 cm⁻¹. -1 was observed, proven, and the optical phonon peak of the G-band, which is in the region near the wavelength of 1550 cm -1 It was observed but not proven, thus confirming that a thin diamond film could be synthesized.

[0066] In comparative example 1, the type of synthesized sample was evaluated using Raman spectroscopy (325 nm excitation). One result was the diamond peak (1330 cm⁻¹). -1 ~ 1335 cm -1 ) not proven, and the D-band (1340 cm -1 ~ 1380 cm -1 ) and the G-band (1510 cm -1 ~ 1560 cm -1 ) were detected, thus confirming that the synthesized sample was a DLC film and not a diamond thin film.

[0067] In comparative example 2, the type of synthesized sample was evaluated by Raman spectroscopy (325 nm excitation). One result was the diamond peak (1330 cm⁻¹). -1 ~ 1335 cm -1 ) not detected, and the graphite-derived G-band (1580 cm) -1 ~ 1620 cm -1 ) was detected, thus confirming that the synthesized sample was graphite and not a thin diamond film.

[0068] From the above, it has been confirmed that, in the synthesis of a diamond thin film, a diamond thin film with high diamond crystallinity can be synthesized under plasma properties when an electron temperature of 1.0 eV or more and 2.0 eV or less, and an electron density of 1.0×10 11 cm -3 or more and 1.0×10 12 cm -3 or less and an ion saturation current of 1.0×10 -4 A or more and 1.0×10 -2 A or less, can be synthesized. <Effekte dieser Ausführungsform>

[0069] According to this embodiment, since the antenna 3 is used with the conductor element 31 and the capacitive element, which are electrically connected in series, compared to a configuration that uses a conventional plasma CVD device, a uniform plasma P is generated in the longitudinal direction of the antenna 3, and a diamond thin film F with a larger area can be synthesized.

[0070] Furthermore, if the plasma properties are within the aforementioned numerical range, a deterioration of the film quality of the diamond thin film F can be prevented, since the diamond thin film F is synthesized in a state in which the electron temperature Te and the electron density ne are appropriate.

[0071] In particular, if the electron temperature Te exceeds the upper limit, electron collisions with the base material W increase, causing the base material's temperature to rise excessively and potentially leading to graphite synthesis. Conversely, if the electron temperature Te falls below the lower limit, insufficient dissociation of the starting gas occurs, and the synthesized thin film becomes a DLC film with many sp or sp² bonds. Therefore, the electron temperature Te must remain within the aforementioned numerical range. Similarly, the electron density ne must also remain within the aforementioned numerical range for the same reason as the electron temperature Te, in order to prevent graphite synthesis or the synthesis of a DLC film.

[0072] In the synthesis of the diamond thin film F, ionic carbon species (C) are present in the plasma P. 2+ , CH3 + , CH + etc.) are present. Consequently, two phenomena occur simultaneously: (1) Secondary nuclei are generated on the diamond through the collision of ionic carbon species with the growth surface, and (2) the growth of the diamond thin film F is inhibited by the ionic carbon species. To synthesize the diamond thin film F while simultaneously suppressing these two phenomena, it is necessary to increase the ion saturation current I. is to keep within the aforementioned numerical range. More precisely, this means that at an ion saturation current I is , which assumes a value above the upper limit, the frequency of collisions of ionic carbon species with the base material W increases, and the growth inhibition of the diamond thin film F by the ionic carbon species becomes greater. As a result, the growth rate of the diamond thin film F decreases, or the film quality of the diamond thin film F deteriorates. If, on the other hand, the ion saturation current I is If the ion saturation current falls below the lower limit, the ionic carbon species required for the growth of the diamond thin film F are not present in sufficient quantities on the surface of the base material W, and the growth rate of the diamond thin film F decreases. Therefore, the ion saturation current I must be increased. is lie within the aforementioned numerical range.

[0073] Since, according to this embodiment, the antenna 3 further has a length of 30 cm or more in the longitudinal direction and forms a linear shape, a diamond thin film F with a larger area in the longitudinal direction can be synthesized uniformly compared to a configuration using a conventional plasma CVD device. <Andere Ausführungsformen>

[0074] It should be noted that the film forming device 100 of the present invention is not limited to the embodiment mentioned above.

[0075] In addition to this embodiment, in the method for producing the diamond thin film F, a preload is applied to the base material W and can apply a negative preload of -100 V or less to the base material W and a positive preload of 100 V or less to the base material W.

[0076] This allows the energy to be controlled when positive ions in the plasma P collide with the base material W by applying a bias voltage to the base material W, and the crystallinity of the film formed on the surface of the base material W can be controlled. In particular, applying a negative bias voltage of -100 V or less to the base material initially promotes the formation of diamond growth nuclei, and after the formation of diamond nuclei, applying a positive bias voltage of 100 V or less promotes the growth of the diamond thin film F.

[0077] In the film-forming device 100 of the aforementioned embodiment, the antenna 3, which generates inductively coupled plasma, is arranged inside the vacuum chamber 2, but the present invention is not limited thereto. The film-forming device 100 of other embodiments may have a structure in which the antenna 3 is arranged outside the vacuum chamber 2.

[0078] It goes without saying that the present invention is not limited to the embodiments mentioned above and that various modifications are possible within the scope that does not deviate from the spirit of the invention. For example, it will be clear to those skilled in the art that the several exemplary embodiments described above are specific examples of the following aspects. Industrial applicability

[0079] According to the present invention, it is possible to synthesize diamond thin film over a larger area and to suppress a deterioration of the film quality of the diamond thin film. List of reference symbols 100 film education devices 2 vacuum containers 3 antennas 7 Gas supply mechanism F Diamond thin film W Basic material P Plasma QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] JP 2013-40408

[0005] JP 2003-55087

[0005] < / beispiele>

Claims

[1] Method for producing a diamond thin film, the method for producing the diamond thin film comprising: Feeding a starting gas containing C, H and O into a vacuum container in which a base material is arranged; Generating an inductively coupled plasma in the vacuum vessel by passing high-frequency current through an antenna arranged inside or outside the vacuum vessel, the antenna comprising a conductor element and a capacitive element electrically connected in series; and Synthesizing a diamond thin film on the base material by a plasma-CVD process using a generated inductively coupled plasma, plasma properties in the synthesis of the diamond thin film include: an electron temperature of 1.0 eV or more and 2.0 eV or less, an electron density of 1.0×10 11 cm -3or more and 1.0×10 12 cm -3 or less, and an ion saturation current of 1.0×10 -4 A or more and 1.0×10 -2 A or less. [2] Method for producing the diamond thin film according to claim 1, wherein the antenna has a linear shape and a length of 30 cm or more in a longitudinal direction. [3] Method for producing the diamond thin film according to claim 1, wherein the distance between the antenna and the base material is 100 mm or less. [4] Method for producing the diamond thin film according to claim 1, wherein in the method for producing the diamond thin film a prestress is applied to the base material, a negative bias voltage of -100 V or less is applied to the base material, and a positive bias voltage of 100 V or less is applied to the base material. [5] Method for producing the diamond thin film according to claim 1, wherein the starting gas further contains a noble gas which is Ar, He or Ne. [6] Method for producing the diamond thin film according to any one of claims 1 to 5, wherein a high frequency of the high frequency current has a frequency of 400 kHz or more and 100 MHz or less. [7] Device for producing a diamond thin film, comprising: a vacuum container in which the base material is arranged and to which a starting gas containing C, H and O is supplied; an antenna arranged inside or outside the vacuum vessel, comprising a conductor element and a capacitive element electrically connected in series; and a high-frequency current source for applying high frequency to the antenna to generate inductively coupled plasma in the vacuum vessel, where plasma properties in the vacuum vessel include the following during the synthesis of the diamond thin film: an electron temperature of 1.0 eV or more and 2.0 eV or less, an electron density of 1.0×10 11 cm -3 or more and 1.0×10 12 cm -3 or less, and an ion saturation current of 1.0×10 -4 A or more and 1.0×10 -2 A or less.

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