Method for manufacturing a diamond thin film and apparatus for manufacturing a diamond thin film

Abstract

This method for producing a diamond thin film involves synthesizing a diamond thin film on a base material through a plasma CVD method, wherein a raw material gas containing C, H, and O is supplied to a vacuum vessel in which the base material is disposed, high-frequency current is applied to an antenna that is disposed inside or outside the vacuum vessel and that has a conductor element and a capacitive element which are electrically connected to each other in series to generate inductively coupled plasma inside the vacuum vessel, and the generated inductively coupled plasma is used for the plasma CVD method. When the diamond thin film is being synthesized, the plasma has the following characteristics: the electron temperature is 1.0 eV or more and 2.0 eV or less; the electron density is 1.0 × 1011cm-3 or more and 1.0 × 1012cm-3 or 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 manufacturing a diamond thin film synthesized using a plasma CVD method and a diamond thin film manufacturing apparatus.

Background Art

[0002] Conventionally, as a method for manufacturing a diamond thin film synthesized using a CVD method, there are known methods for manufacturing a diamond thin film using a filament CVD apparatus, a microwave resonator type plasma CVD apparatus, a microwave surface wave plasma CVD apparatus (for example, Patent Document 1), or a radio frequency inductively coupled (RF-ICP) type plasma CVD apparatus using a coil-shaped electrode (for example, Patent Document 2).

[0003] In the manufacturing method using a filament CVD apparatus, a high melting point metal wire is installed above a substrate on which a diamond thin film is formed, and the raw material gas is decomposed by thermoelectrons emitted when this metal wire is heated to manufacture a diamond thin film.

[0004] Also, in the manufacturing method using a plasma CVD apparatus using microwaves or a plasma CVD apparatus using high frequencies, a plasma containing a raw material gas is generated by an applied high-frequency current, and a diamond thin film is synthesized with the activated gas.

[0005] In these manufacturing methods, it is known that mainly active atomic hydrogen is generated in the plasma, and by its action, non-diamond components with sp1 bonds or sp2 bonds are removed, and the diamond component with sp3 bonds can mainly grow.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

[0007] Incidentally, when synthesizing diamond using the plasma CVD apparatus described above, diamond could only be synthesized in a small area due to limitations in the apparatus configuration. For example, if the filament were made longer to synthesize diamond over a large area, there was a risk that the filament would break under its own weight during plasma generation. Also, although microwaves such as 2.45 GHz or 915 MHz are used, the plasma size could not be increased due to the problem of resonance wavelength.

[0008] Furthermore, during the synthesis of diamond thin films, graphite or diamond-like carbon (DLC) was synthesized simultaneously with the diamond, resulting in a deterioration of the film quality of the diamond thin film. After extensive research, the inventors of this application have discovered for the first time that the deterioration of the film quality of the diamond thin film can be suppressed when the electron temperature, electron density, and ion saturation current, which are the plasma characteristics when synthesizing diamond thin films, are within a predetermined range.

[0009] This invention was made to solve the above-mentioned problems, and its main objectives are to synthesize diamond thin films over a wider area and to suppress the deterioration of the film quality of the diamond thin films. [Means for solving the problem]

[0010] In other words, the method for manufacturing a diamond thin film according to the present invention involves supplying a raw material gas containing C, H, and O into a vacuum vessel on which a substrate is placed, generating an inductively coupled plasma in the vacuum vessel by passing a high-frequency current through an antenna placed inside or outside the vacuum vessel, which has conductive elements and capacitive elements electrically connected in series with each other, and synthesizing a diamond thin film on the substrate by a plasma CVD method using the generated inductively coupled plasma, wherein the plasma characteristics when synthesizing the diamond thin film are such that the electron temperature is 1.0 eV or more and 2.0 eV or less, and the electron density is 1.0 × 10⁻¹⁶ 11 cm -3 The above 1.0 × 10 12 cm -3 The following applies, and the ion saturation current is 1.0 × 10⁻⁶. -4 A or higher 1.0 x 10 -2 It is characterized by being A or less.

[0011] With this configuration, since an antenna having conductive elements and capacitive elements electrically connected in series is used, a uniform plasma is generated in the longitudinal direction of the antenna compared to a configuration using a conventional plasma CVD apparatus, and a diamond thin film can be synthesized over a wider area. Furthermore, if the plasma characteristics are within the above numerical range, the diamond thin film is synthesized with appropriate electron quantity and electron temperature, thus preventing deterioration of the film quality of the diamond thin film. Specifically, if the electron temperature exceeds the upper limit, electron collisions with the substrate increase, causing the substrate temperature to rise too high and potentially leading to graphite synthesis. On the other hand, if the electron temperature falls below the lower limit, the raw material gas does not dissociate sufficiently, and the resulting thin film becomes a DLC film with many sp or sp2 bonds. Therefore, the electron temperature must be within the above numerical range. Similarly, for the same reasons as the electron temperature, the electron density must also be within the above numerical range to prevent graphite synthesis or DLC film synthesis. Here, in the synthesis of diamond thin films, ionic carbon species (C) are introduced into the plasma. 2+ CH3 +, CH + exist, etc. As a result, two events occur simultaneously: (1) secondary nuclei are generated on diamond when ionic carbon species collide with the growth surface, and (2) the growth of the diamond thin film is inhibited by the ionic carbon species. In order to synthesize a diamond thin film while suppressing these two events, it is necessary to control the ion saturation current within the above numerical range. Specifically, when the ion saturation current exceeds the upper limit value, the frequency of collision of ionic carbon species with the substrate 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 film quality of the diamond thin film deteriorates. On the other hand, when the ion saturation current is less than the lower limit value, the ionic carbon species necessary for the growth of the diamond thin film do not sufficiently exist on the surface of the substrate, and the growth rate of the diamond thin film decreases. Therefore, the ion saturation current needs to be within the above numerical range.

[0012] Specific examples of the antenna include those that are linear and have a length of 30 cm or more in the longitudinal direction. With such a configuration, compared with a configuration using a conventional plasma CVD apparatus, a diamond thin film with a larger area can be synthesized uniformly in the longitudinal direction.

[0013] Specific examples of the method for manufacturing the diamond thin film include those in which the distance between the antenna and the substrate is 100 mm or less. With such a configuration, a uniform plasma can be generated in the longitudinal direction of the antenna within the vacuum chamber, and the diamond thin film can be synthesized uniformly with respect to the longitudinal direction of the antenna.

[0014] The method for manufacturing the diamond thin film applies a bias voltage to the substrate, and it is preferable to apply a negative bias voltage of -100 V or less and a positive bias voltage of 100 V or less to the substrate. With this configuration, by applying a bias voltage to the substrate, the energy of positive ions in the plasma when they strike the substrate can be controlled, thereby controlling the crystallinity of the film formed on the substrate's surface. Specifically, applying a negative bias voltage of -100V or less to the substrate promotes the formation of diamond growth nuclei, while applying a positive bias voltage of 100V or less promotes the growth of the diamond thin film.

[0015] The aforementioned raw material gas preferably further contains a noble gas which is Ar, He, or Ne. With this configuration, components of the gas that are difficult to decompose, such as carbon dioxide, can be made easier to break down.

[0016] In order to manufacture a diamond thin film using high frequency rather than microwave, the high frequency of the high-frequency current should be between 400 kHz and 100 MHz.

[0017] A diamond thin film manufacturing apparatus for synthesizing a diamond thin film on a substrate by plasma CVD using inductively coupled plasma comprises a vacuum chamber on which the substrate is placed and to which a raw material gas containing C, H, and O is supplied; an antenna disposed inside or outside the vacuum chamber and having a conductive element and a capacitive element electrically connected in series with each other; and a high-frequency power supply that applies high frequency to the antenna to generate an inductively coupled plasma inside the vacuum chamber. In the plasma characteristics inside the vacuum chamber when synthesizing the diamond thin film, the electron temperature is 1.0 eV or more and 2.0 eV or less, and the electron density is 1.0 × 10⁻¹⁶ 11 cm -3 The above 1.0 × 10 12 cm -3 The following applies, and the ion saturation current is 1.0 × 10⁻⁶. -4 A or higher 1.0 x 10 -2 Examples include those that are A or less. With this configuration, the same effects and advantages as those for the diamond thin film manufacturing method described above can be obtained. [Effects of the Invention]

[0018] According to the present invention configured in this way, it is possible to synthesize a diamond thin film over a wider area and to suppress deterioration of the film quality of the diamond thin film. [Brief explanation of the drawing]

[0019] [Figure 1] A schematic diagram showing the configuration of a film deposition apparatus according to one embodiment of the present invention. [Figure 2] This figure shows the gas composition range of the raw material gas supplied in the film deposition apparatus and diamond thin film manufacturing method of the same embodiment. [Modes for carrying out the invention]

[0020] The following describes a film deposition apparatus and a method for manufacturing a diamond thin film according to one embodiment of the present invention, with reference to the drawings. Note that, for the sake of clarity, some figures in the following diagrams may be simplified or exaggerated for illustrative purposes. The same reference numerals are used for identical components, and their descriptions are omitted as appropriate.

[0021] <Device configuration> The film deposition apparatus 100 of this embodiment is a plasma CVD apparatus that forms a diamond thin film F on a substrate W using an inductively coupled plasma P.

[0022] The substrate W in this embodiment is a plate-shaped material made of a material suitable for forming a diamond thin film F. The substrate W may be, but is not limited to, glass, plastic, silicon, iron, titanium, copper, metals such as cemented carbide, other alloy materials such as tool steel, or materials such as SiC, GaN, AlN, BN, and diamond.

[0023] The base material W has a rectangular or circular shape when viewed from above. The length of the base material W may be, for example, 20 cm or more or 50 cm or more, but is not limited to these lengths. The base material W may also be made up of multiple small chip-shaped base materials of similar length or area, such as 1 mm, 5 mm, or 10 mm in size. Furthermore, the base material W is not limited to a plate shape; it may be columnar, perforated, or porous. It may also have a complex shape, such as that of tools like drills or end mills.

[0024] Furthermore, the substrate W may be subjected to surface treatments such as scratching or seeding. For example, if the substrate W is silicon, it may be subjected to scratching or seeding by immersing it in alcohol together with diamond nanoparticles and forming irregularities on the surface by ultrasonic treatment. Alternatively, if the substrate W is cemented carbide, it may be immersed in an acidic solution such as an aqueous nitric acid solution to remove Co from the substrate, or the surface of the WC (tungsten carbide) particles may be treated with an alkaline solution such as diluted NaOH before performing the seeding treatment described above.

[0025] Specifically, as shown in Figure 1, the film deposition apparatus 100 comprises a vacuum chamber 2 that is evacuated and into which gas G is introduced, a gas supply mechanism 7 that supplies gas G to the vacuum chamber 2, a linear antenna 3 positioned inside the vacuum chamber 2, and a high-frequency power supply 4 that applies high frequency to the antenna 3 to generate an inductively coupled plasma P inside the vacuum chamber 2. In this film deposition apparatus 100, by applying high frequency from the high-frequency power supply 4 to the antenna 3, a high-frequency current IR flows through the antenna 3, an induced electric field is generated inside the vacuum chamber 2, and an inductively coupled plasma P is generated.

[0026] The vacuum vessel 2 is a metal container, such as SUS or aluminum, and its interior is evacuated by a vacuum evacuation device 6. In this example, the vacuum vessel 2 is electrically grounded. The vacuum evacuation device 6 is equipped with a pressure regulator 61, such as a valve, to adjust the pressure inside the vacuum vessel 2. This pressure regulator 61 is controlled to adjust the pressure inside the vacuum vessel 2 during plasma generation, and is configured to adjust the pressure to, for example, between 7 Pa and 100 Pa.

[0027] A gas G, such as a raw material gas, is introduced into the vacuum container 2 via multiple gas inlets 21, for example, arranged in the direction of a flow regulator (not shown) and an antenna 3.

[0028] Furthermore, a substrate holder 8 for holding the substrate W is provided inside the vacuum vessel 2, and a heater 81 for heating the substrate W is provided inside the substrate holder 8. The substrate holder 8 does not necessarily have to be electrically connected to the vacuum vessel 2. The film deposition apparatus 100 of this embodiment may have a function to adjust the potential of the generated inductively coupled plasma in the range of, for example, +100V to -100V 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 is not limited to this. By using such a bias voltage, it is possible to control, for example, the energy when positive ions in the plasma P are incident on the substrate W, thereby controlling the degree of crystallinity of the film formed on the surface of the substrate W.

[0029] The gas supply mechanism 7 supplies gas G, such as raw material gas, into the vacuum container 2 through the gas inlet 21. The gas supply mechanism 7 is configured to supply gas G downward from the gas inlet 21 provided on the upper wall of the vacuum container 2. This gas supply mechanism 7 is configured to supply raw material gas containing at least C (carbon), H (hydrogen), and O (oxygen), and specifically, it is configured to supply H2 gas, CH4 gas, and CO2 gas as raw material gas. The gas supply mechanism 7 may be configured to supply any other gas as a raw material gas in addition to, or instead of, H2 gas, CH4 gas, and CO2 gas, as long as it is configured to supply raw material gas containing C, H, and O into the vacuum container 2.

[0030] The gas supply mechanism 7 is configured to supply H2 gas, CH4 gas, and CO2 gas at any desired flow rate. In this embodiment, the gas supply mechanism 7 is configured to adjust the flow rate of each gas and supply it so that the ratio of the concentration of O atoms to the total concentration of O atoms and H atoms (O / (O+H)) in the raw material gas, which is composed of H2 gas, CH4 gas, and CO2 gas, is, for example, 5 at% or more and 45 at% or less.

[0031] The gas supply mechanism 7 is configured to supply catalyst gas into the vacuum vessel 2 at an arbitrary flow rate, along with the raw material gas. This catalyst gas functions as a catalyst during plasma generation, promoting the decomposition of the raw material gas. Specifically, the gas supply mechanism 7 is configured to supply catalyst gas such that its ratio to the total flow rate of all gases supplied into the vacuum vessel 2 (in this case, the total flow rate of raw material gas and catalyst gas) is, for example, 50% to 95%, preferably 70% to 90%. Examples of this catalyst gas include noble gases such as Ar gas, He gas, and Ne gas.

[0032] Antenna 3 is positioned above the substrate W within the vacuum chamber 2, along the surface of the substrate W. In this embodiment, multiple linear antennas 3 are arranged in parallel along the substrate W (for example, substantially parallel to the surface of the substrate W). This allows for the generation of a more uniform plasma P over a wider area, and therefore enables the processing of larger substrates W.

[0033] Note that the number of antennas 3 is not limited to multiple antennas; it may be just one. If multiple antennas 3 are provided, it is preferable that the number be even (for example, 2, 4, 6, etc.). Also, when multiple antennas 3 are provided, in order to avoid radio wave interference, the spacing between each antenna 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, in order to deposit a uniform diamond thin film F, the spacing between antennas 3 is preferably 25 cm or less.

[0034] As shown in Figure 1, the ends of the antenna 3 penetrate a pair of opposing side walls 2a and 2b of the vacuum container 2. Insulating members 11 are provided at the portions of the antenna 3 that penetrate to the outside of the vacuum container 2. The ends of the antenna 3 pass through each of these insulating members 11, and these penetrations are vacuum-sealed by, for example, a packing 12. Through these insulating members 11, the antenna 3 is supported in a state of electrical insulation from the opposing side walls 2a and 2b of the vacuum container 2. The space between each insulating member 11 and the vacuum container 2 is also vacuum-sealed by, for example, a packing 13. The material of the insulating members 11 is, for example, ceramics such as alumina, quartz, or engineering plastics such as polyphenylene sulfide (PPS) or polyetheretherketone (PEEK).

[0035] Furthermore, antenna 3 is a so-called LC antenna, comprising an inductor (L) and a capacitor (C). Specifically, antenna 3 comprises at least two tubular metal conductor elements 31 (hereinafter referred to as metal pipes 31), a tubular insulating element 32 (hereinafter referred to as insulating pipe 32) provided between adjacent metal pipes 31 to insulate them, and a capacitor 33, which is a capacitive element, provided between adjacent metal pipes 31 and electrically connected in series with them. The conductor elements 31 function as the L section, and the capacitor 33 function as the C section.

[0036] In this embodiment, there are three metal pipes 31, and two insulating pipes 32 and two capacitors 33. The antenna 3 may also have four or more metal pipes 31; in this case, the number of insulating pipes 32 and capacitors 33 will each be one less than the number of metal pipes 31.

[0037] The material of the metal pipe 31 may be, for example, copper, aluminum, alloys thereof, stainless steel, etc., but is not limited to these. Alternatively, the antenna 3 may be made hollow and cooled by circulating a coolant such as cooling water through it.

[0038] The insulating pipe 32 in this embodiment is formed from a single component, but is not limited to this. The material of the insulating pipe 32 may be, for example, alumina, fluororesin, polyethylene (PE), engineering plastics (e.g., polyphenylene sulfide (PPS), polyetheretherketone (PEEK), etc.).

[0039] Furthermore, in the antenna 3, the portion located inside the vacuum vessel 2 is covered by a straight-tube insulating cover (antenna protection tube) 10. Both ends of this insulating cover 10 are supported by insulating members 11. It is not necessary to seal the gap between both ends of the insulating cover 10 and the insulating members 11. This is because even if gas G enters the space inside the insulating cover 10, the space is small and the distance electrons travel is short, so plasma P is not usually generated in the space. The material of the insulating cover 10 can be, for example, quartz, alumina, fluororesin, silicon nitride, silicon carbide, or silicon.

[0040] By providing the insulating cover 10, it is possible to suppress the incidence of charged particles in the plasma P onto the metal pipe 31 that constitutes the antenna 3. This suppresses the rise in plasma potential caused by the incidence of charged particles (mainly electrons) onto the metal pipe 31, and also suppresses metal contamination of the plasma P and substrate W caused by sputtering of the metal pipe 31 by charged particles (mainly ions).

[0041] From the viewpoint of synthesizing the diamond thin film F over a wider area, the length of the antenna 3 in the longitudinal direction is preferably 30 cm or more, more preferably 50 cm or more, and even more preferably 100 cm or more. On the other hand, from the viewpoint of ensuring the strength of the insulating pipe 32, the length of the antenna 3 is preferably 1000 cm or less, and more preferably 500 cm or less.

[0042] Furthermore, the distance between the antenna 3 and the substrate W is preferably 100 mm or less, and more preferably 40 mm to 60 mm, in order to generate a uniform plasma P in the longitudinal direction of the antenna 3 within the vacuum chamber 2. Here, if the distance between the antenna 3 and the substrate W is too close, the electron density and electron temperature will rise, causing graphitization of the thin film, so it is preferable that the distance between the antenna 3 and the substrate W be a predetermined distance.

[0043] As shown in Figure 1, the antenna 3 has a feed end 3a to which high frequency power is supplied in the antenna direction (longitudinal direction X) and a grounded end 3b that is grounded. Specifically, at both ends of the longitudinal direction X of each antenna 3, the portion extending outward from one side wall 2a or 2b becomes the feed end 3a, and the portion extending outward from the other side wall 2a or 2b becomes the grounded end 3b.

[0044] Here, a high frequency is applied to the feed end 3a of each antenna 3 from a high-frequency power supply 4 via a matching circuit 41. The frequency of the high frequency is between 400 kHz and 100 MHz, for example, a common 13.56 MHz, but is not limited to this. For example, it may be 27.12 MHz, 40.68 MHz, 60 MHz, etc.

[0045] <Method for manufacturing diamond thin films> Next, a method for manufacturing a diamond thin film F using the film deposition apparatus 100 described above will be explained.

[0046] First, the substrate W is placed in the substrate holder 8 inside the vacuum chamber 2 of the film deposition apparatus 100, and the vacuum chamber 2 is evacuated using the vacuum exhaust device 6. Then, the substrate W is heated by the heater 81, and it is preferable to raise the temperature of the substrate W to between 100°C and 1200°C.

[0047] (Supply of raw material gas) Next, the gas supply mechanism 7 supplies H2 gas, CH4 gas, and CO2 gas as raw material gases into the vacuum container 2 at predetermined flow rates. In the manufacturing method of the diamond thin film F of this embodiment, the flow rates of H2 gas, CH4 gas, and CO2 gas are adjusted so that the atomic ratios of O atoms, C atoms, and H atoms in the raw material gas fall within the shaded area shown in the composition ternary diagram (CHO diagram) of Figure 2. The atomic ratios of each atom are described below.

[0048] (Atomic ratio of oxygen and hydrogen) The flow rates of H2 gas, CH4 gas, and CO2 gas are controlled and supplied so that the ratio of the concentration of O atoms to the total concentration of O atoms and H atoms in the supplied raw material gas (O / (O+H)) is preferably 5 at% to 45 at%, and more preferably 5 at% to 10 at%.

[0049] (Atomic ratio of oxygen to carbon) The flow rates of H2 gas, CH4 gas, and CO2 gas are controlled and supplied so that the ratio of the concentration of carbon atoms to the total concentration of oxygen and carbon atoms in the supplied raw material gas (C / (O+C)) is preferably 45 at% or more and 70 at% or less.

[0050] (Atomic ratio of carbon to hydrogen) Furthermore, the flow rates of H2 gas, CH4 gas, and CO2 gas are controlled and supplied so that the ratio of the concentration of H atoms to the total concentration of C atoms and H atoms in the supplied raw material gas (H / (C+H)) is preferably 60 at% to 95 at%, more preferably 90 at% to 95 at%.

[0051] (Supply of catalytic gas) Furthermore, the gas supply mechanism 7 supplies catalyst gases such as Ar gas into the vacuum vessel 2 along with the raw material gas. The flow rate of the supplied catalyst gas is preferably set to be 50% to 95%, more preferably 70% to 90%, relative to the total flow rate of all gases supplied to the vacuum vessel 2. By setting the flow rate of the supplied catalyst gas within this range, it is possible to generate a large amount of C2 radicals during film formation, which readily ionize, for example, Ar, to CH4 and readily form diamond. As a result, in the emission spectrum of the generated inductively coupled plasma, the ratio of the emission intensity of C2 radicals to the emission intensity of Hα radicals can be set to 30% to 300%, more preferably 90% to 250%.

[0052] (Pressure inside a vacuum vessel) Then, the gas supply mechanism 7 introduces the raw material gas and catalyst gas, while the pressure regulator 61 adjusts the pressure inside the vacuum container 2 to be between 7 Pa and 100 Pa, more preferably between 10 Pa and 50 Pa.

[0053] (Plasma generation and diamond thin film deposition) Then, with the flow rates of the raw material gas and catalyst gas adjusted as described above, and the pressure inside the vacuum chamber 2 adjusted, high-frequency power is supplied from the high-frequency power supply 4 to the antenna 3. This generates an induced electric field inside the vacuum chamber 2, producing an inductively coupled plasma P, and forming a diamond thin film F on the substrate W. The frequency of the high-frequency power is 13.56 MHz. The power density of the supplied high-frequency power is 0.1 W / cm². 2 The above is preferable, and 0.5 W / cm² 2 The above is more preferable: 1 W / cm 2 The above is even more preferable. Furthermore, the power density is 1000 W / cm². 2 The following is preferable: 100 W / cm² 2 The following is more preferable: 50W / cm² 2 The following are even more preferable.

[0054] Here, in order to suppress the synthesis of graphite or DLC when synthesizing the diamond thin film F, the plasma characteristics must be within the following numerical range. When the plasma characteristics are within the following numerical range, the crystallinity of the diamond in the diamond thin film F increases, and the deterioration of the film quality of the diamond thin film F is suppressed. The plasma characteristics referred to here are the electron temperature Te, electron density ne, and ion saturation current I. is That is the case. ·Electron temperature Te: 1.0eV≦Te≦2.0eV ·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

[0055] <Examples> 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 it is possible to implement it with modifications within the scope that is consistent with the spirit described below, and all such modifications are included within the technical scope of the present invention.

[0056] In the examples, samples were deposited on substrates using the plasma CVD method with the aforementioned film deposition apparatus 100 in the following three examples and two comparative examples. The pressure inside the vacuum chamber 2, the input power, the distance between the substrate and the antenna, the frequency of the supplied high-frequency power, and the plasma characteristics during sample production are as follows.

[0057] <Example 1> • Pressure inside vacuum container 2: 15 Pa ·Input power: 3.0kW • Distance between substrate W and antenna 3: 50mm • Frequency of the high-frequency power supplied: 13.56MHz ·Electron temperature Te:1.5eV ·Electron density ne:7.5×10 11 cm-3 Ion saturation current I is :6×10 -4 A

[0058] <Example 2> • Pressure inside vacuum container 2: 15 Pa ·Input power: 3.0kW • Distance between substrate W and antenna 3: 30mm • Frequency of the high-frequency power supplied: 13.56MHz ·Electron temperature Te:1.98eV ·Electron density ne:7.28×10 11 cm -3 Ion saturation current I is :1.03×10 -3 A

[0059] <Example 3> • Pressure inside vacuum container 2: 15 Pa ·Input power: 4.0kW • Distance between substrate W and antenna 3: 30mm • Frequency of the high-frequency power supplied: 13.56MHz ·Electron temperature Te:1.01eV ·Electron density ne:9.8×10 11 cm -3 Ion saturation current I is :2.3×10 -3 A

[0060] <Comparative Example 1> • Pressure inside vacuum container 2: 15 Pa ·Input power: 2.0kW • Distance between substrate W and antenna 3: 50mm • Frequency of the high-frequency power supplied: 13.56MHz ·Electron temperature Te:1.99eV ·Electron density ne:1.08×10 11 cm -3 Ion saturation current I is :9.89×10 -5 A

[0061] <Comparative Example 2> • Pressure inside vacuum container 2: 30 Pa ·Input power: 2.0kW • Distance between substrate W and antenna 3: 10mm • Frequency of the high-frequency power supplied: 13.56MHz ·Electron temperature Te:1.6eV ·Electron density ne:2.66×10 12 cm -3 Ion saturation current I is :3.70×10 -3 A

[0062] Here, electron temperature Te, electron density ne, and ion saturation current I are given. is This was measured using a Langmuir Probe, a well-known plasma measuring instrument.

[0063] In Example 1, the crystallinity of the synthesized sample was evaluated by laser Raman spectroscopy (325 nm excitation). The result was 1330 cm⁻¹. -1 The optical phonon peak of diamond observed near the wavelength of 1550 cm⁻¹ is -1 Compared to the G-band optical phonon peaks observed near this wavelength, the intensity was 2.5 times greater, confirming that it is possible to synthesize diamond thin films with high diamond crystallinity.

[0064] In Example 2, the crystallinity of the synthesized sample was evaluated by laser Raman spectroscopy (325 nm excitation). The result was 1330 cm⁻¹. -1 The optical phonon peak of diamond observed near the wavelength of 1550 cm was detected. -1 Since no G-band optical phonon peaks observed near the wavelength were detected, we were able to confirm that diamond thin films could be synthesized.

[0065] In Example 3, the crystallinity of the synthesized sample was evaluated by laser Raman spectroscopy (325 nm excitation). The result was 1330 cm⁻¹. -1The optical phonon peak of diamond observed near the wavelength of 1550 cm was detected. -1 Since no G-band optical phonon peaks observed near the wavelength were detected, we were able to confirm that diamond thin films could be synthesized.

[0066] In Comparative Example 1, the type of synthesized sample was evaluated by Raman spectroscopy (325 nm excitation). As a result, the peak for diamond (1330 cm⁻¹) was observed. -1 ~1335cm -1 ) was not detected, D band (1340cm) -1 ~1380cm -1 ) and G band (1510cm -1 ~1560cm -1 Since ) was detected, we were able to confirm that the synthesized sample was a DLC film, not a diamond thin film.

[0067] In Comparative Example 2, the type of synthesized sample was evaluated by Raman spectroscopy (325 nm excitation). As a result, the peak for diamond (1330 cm⁻¹) was observed. -1 ~1335cm -1 ) was not detected, and the graphite-derived G-band (1580cm) was not detected. -1 ~1620cm -1 Since ) was detected, we were able to confirm that the synthesized sample was graphite, not a diamond thin film.

[0068] From the above, the plasma characteristics when synthesizing a diamond thin film are such that the electron temperature is between 1.0 eV and 2.0 eV, and the electron density is 1.0 × 10⁻¹⁶. 11 cm -3 The above 1.0 × 10 12 cm -3 The following applies, and the ion saturation current is 1.0 × 10⁻⁶. -4 A or higher 1.0 x 10 -2 We confirmed that a diamond thin film with high diamond crystallinity can be synthesized when the value is A or less.

[0069] <Effects of this embodiment> According to this embodiment, since an antenna 3 having a conductive element 31 and a capacitive element electrically connected in series is used, a uniform plasma P is generated in the longitudinal direction of the antenna 3 compared to a configuration using a conventional plasma CVD apparatus, and a diamond thin film F with a larger area can be synthesized.

[0070] Furthermore, if the plasma characteristics are within the above numerical range, the diamond thin film F is synthesized with appropriate electron temperature Te and electron density ne, thereby preventing deterioration of the film quality of the diamond thin film F. Specifically, if the electron temperature Te exceeds the upper limit, electron collisions with the substrate W increase, causing the temperature of the substrate W to rise too high, potentially leading to graphite synthesis. On the other hand, if the electron temperature Te falls below the lower limit, sufficient dissociation of the raw material gas does not occur, and the synthesized thin film becomes a DLC film with many sp or sp2 bonds. Therefore, the electron temperature Te must be within the above numerical range. Similarly, for the same reasons as the electron temperature Te, the electron density ne must also be within the above numerical range to prevent graphite synthesis or DLC film synthesis. Here, in the synthesis of the diamond thin film F, ionic carbon species (C) are introduced into the plasma P. 2+ CH3 + CH + (etc.) exist. As a result, two events occur simultaneously: (1) secondary nuclei are generated on the diamond when ionic carbon species collide with the growth surface, and (2) the growth of the diamond thin film F is inhibited by the ionic carbon species. To synthesize a diamond thin film F while suppressing these two phenomena, the ion saturation current I is It is necessary to control this within the above numerical range. Specifically, the ion saturation current I is When the ion saturation current I exceeds the upper limit, the frequency of collisions between ionic carbon species and the substrate W increases, and the inhibition of diamond thin film F growth by ionic carbon species increases. As a result, the growth rate of diamond thin film F decreases, or the quality of the diamond thin film F deteriorates. On the other hand, the ion saturation current I isWhen the ion saturation current I falls below the lower limit, the ionic carbon species necessary for the growth of the diamond thin film F are not sufficiently present on the surface of the substrate W, and the growth rate of the diamond thin film F decreases. is The values ​​must be within the above range.

[0071] Furthermore, according to this embodiment, since the antenna 3 has a length of 30 cm or more in the longitudinal direction and is linear, a diamond thin film F with a wider area can be uniformly synthesized in the longitudinal direction compared to a configuration using a conventional plasma CVD apparatus.

[0072] <Other Embodiments> However, the film deposition apparatus 100 of the present invention is not limited to the embodiments described above.

[0073] In addition to this embodiment, the method for manufacturing the diamond thin film F involves applying a bias voltage to the substrate W, and may include applying a negative bias voltage of -100V or less to the substrate W, or applying a positive bias voltage of 100V or less to the substrate W.

[0074] This allows for the control of the energy of positive ions in the plasma P when they are incident on the substrate W by applying a bias voltage to the substrate W, thereby controlling the crystallinity of the film formed on the surface of the substrate W. Specifically, by first applying a negative bias voltage of -100V or less to the substrate, the formation of diamond growth nuclei is promoted, and after the formation of the diamond nuclei, the growth of the diamond thin film F can be promoted by applying a positive bias voltage of 100V or less.

[0075] In the film deposition apparatus 100 of the above embodiment, the antenna 3 that generates the inductively coupled plasma was located inside the vacuum vessel 2, but this is not limited to that. In other embodiments of the film deposition apparatus 100, the antenna 3 may be located outside the vacuum vessel 2.

[0076] It goes without saying that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from its spirit. For example, the above-described exemplary embodiments will be understood by those skilled in the art to be specific examples of the following embodiments. [Industrial applicability]

[0077] According to the present invention, it is possible to synthesize a diamond thin film over a wider area while suppressing deterioration of the film quality of the diamond thin film. [Explanation of Symbols]

[0078] 100...Film deposition equipment 2...Vacuum container 3... Antenna 7. Gas supply mechanism F ···Diamond thin film W...Base material P...Plasma

Claims

1. A raw material gas containing C, H, and O is supplied into a vacuum container in which the substrate is placed. An antenna placed inside or outside the vacuum vessel, having a conductive element and a capacitive element electrically connected in series with each other, generates an inductively coupled plasma inside the vacuum vessel by passing a high-frequency current through the antenna. A method for producing a diamond thin film, comprising synthesizing a diamond thin film on a substrate using a plasma CVD method with generated inductively coupled plasma, In the plasma characteristics when synthesizing the aforementioned diamond thin film, Electron temperature is between 1.0 eV and 2.0 eV. Electron density is 1.0 × 10⁻⁶ １１ cm －３ The above 1.0 x 10 １２ cm －３ The following, and, The ion saturation current is 1.0 × 10⁻⁶ －４ A or higher 1.0 x 10 －２ A method for manufacturing a diamond thin film that is A or less.

2. The method for manufacturing a diamond thin film according to claim 1, wherein the antenna is linear and has a length of 30 cm or more in the longitudinal direction.

3. The method for manufacturing a diamond thin film according to claim 1, wherein the distance between the antenna and the substrate is 100 mm or less.

4. The method for manufacturing the diamond thin film involves applying a bias voltage to the substrate. A negative bias voltage of -100V or less is applied to the substrate. A method for manufacturing a diamond thin film according to claim 1, wherein a positive bias voltage of 100V or less is applied to the substrate.

5. The method for producing a diamond thin film according to claim 1, wherein the raw material gas further contains a noble gas which is Ar, He, or Ne.

6. The method for manufacturing a diamond thin film according to any one of claims 1 to 5, wherein the high frequency of the high-frequency current is a frequency of 400 kHz or more and 100 MHz or less.

7. A diamond thin film manufacturing apparatus that synthesizes a diamond thin film on a substrate using a plasma CVD method with inductively coupled plasma, A vacuum vessel in which the substrate is placed and a raw material gas containing C, H, and O is supplied, An antenna having a conductive element and a capacitive element arranged inside or outside the vacuum container and electrically connected in series with each other, The vacuum vessel is equipped with a high-frequency power supply that applies a high frequency to the antenna for generating an inductively coupled plasma within the vacuum vessel, In the plasma characteristics inside the vacuum vessel when synthesizing the diamond thin film, Electron temperature is between 1.0 eV and 2.0 eV. The electron density is 1.0×10 １１ cm －３ or more and 1.0×10 １２ cm －３ or less, and The ion saturation current is 1.0 × 10⁻⁶ －４ A or higher 1.0 x 10 －２ A diamond thin film manufacturing apparatus that is A or lower.

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