Plasma polishing apparatus and plasma polishing method

Abstract

This invention provides a plasma polishing method that can polish and smooth high-hardness carbon substrates. [Solution] One aspect of the present invention is a plasma polishing method in which a carbon substrate 51 is placed on the carbon sheet 22 of a first electrode 21 on which a carbon sheet 22 is arranged on the surface, the carbon substrate 51 is placed in an atmosphere of oxygen gas or H2O gas, a second electrode 23 which is placed opposite the first electrode 21 is connected to earth, plasma generation power is applied to the first electrode 21 to generate plasma on the surface of the carbon substrate 51, and the plasma is used for polishing.

Description

[Technical Field]

[0001] The present invention relates to a plasma polishing apparatus and a plasma polishing method. [Background technology]

[0002] In recent years, diamond has attracted attention as a next-generation semiconductor material. Compared to silicon, diamond has a wider bandgap, superior dielectric strength, and high thermal conductivity, which is why it has garnered particular attention in recent years. Recently, for example, it has become possible to manufacture diamond substrates by heteroepitaxial growth of diamond using CVD (chemical vapor deposition), and diamond, along with GaN and SiC, is attracting attention for practical application.

[0003] When manufacturing diamond substrates, it is necessary to smooth the surface of the diamond substrate. A technology related to this is described in Patent Document 1.

[0004] However, because diamond is extremely hard and chemically inert, it is difficult to sufficiently smooth a diamond substrate using conventional chemical mechanical polishing.

[0005] Furthermore, polishing and smoothing high-hardness carbon substrates, not just diamond substrates, is extremely difficult. Therefore, there is a need for methods to polish and smooth high-hardness carbon substrates. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 7411143 [Overview of the project] [Problems that the invention aims to solve]

[0007] Various aspects of the present invention aim to provide a plasma polishing apparatus and a plasma polishing method capable of polishing and smoothing a high-hardness carbon substrate. [Means for solving the problem]

[0008] Various aspects of the present invention will be described below. [1] A carbon substrate or carbon thin film is placed on the carbon-based film or carbon-based tray of a first electrode on which a carbon-based film or carbon-based tray is arranged on the surface. A plasma polishing method characterized by applying plasma generation power to the first electrode in an atmosphere of oxygen gas or H2O gas to generate plasma on the surface of the carbon substrate or carbon thin film, and polishing using the plasma. In the plasma polishing method described above, the plasma generation power may be applied to the first electrode after connecting the second electrode, which is positioned opposite the first electrode, to ground. Alternatively, the plasma polishing method described above may be performed in a chamber connected to ground.

[0009] [2] In the above [1], A plasma polishing method characterized in that the aforementioned atmosphere is an atmosphere in which an inert gas is added to the oxygen gas or H2O gas.

[0010] [3] In the above [1] or [2], The carbon-based film or carbon-based tray is C a H b N c It consists of the following materials: A plasma polishing method characterized in that a, b, and c satisfy the following equations 1 to 3. (Formula 1) 0.25≦a≦1 (Formula 2)0≦b≦0.6 (Formula 3)0≦c≦0.6

[0011] [4] In any one of the above items [1] to [3], The plasma polishing method is characterized in that the carbon-based tray has a carbon-based film formed on the surface of the tray body.

[0012] [5] A plasma polishing method, wherein the surface roughness Ra of the polished surface of a carbon substrate or a carbon thin film polished by the plasma polishing method according to any one of [1] to [4] above is 1 nm or less.

[0013] [6] A plasma polishing method, wherein the surface roughness Ra of the polished surface of a carbon substrate or a carbon thin film polished by the plasma polishing method according to any one of [1] to [4] above is 1 nm or less and has a hardness of 5 GPa or more.

[0014] [7] In the plasma polishing method according to any one of [1] to [4] above, the surface roughness Ra of the polished surface of a carbon substrate or a carbon thin film is 1 nm or less, the carbon substrate is a diamond gemstone or a diamond substrate, and the carbon thin film is a diamond thin film, characterized by the plasma polishing method.

[0015] [8] A chamber, a first electrode disposed in the chamber, a carbon-based film or a carbon-based tray disposed on the surface of the first electrode, a second electrode disposed in the chamber and opposed to the first electrode, a plasma generation power source electrically connected to the first electrode, a ground electrically connected to the second electrode, an exhaust mechanism for evacuating the chamber, a gas introduction mechanism for introducing O2 gas or H2O gas into the chamber, and having, the first electrode is one on which a carbon substrate or a carbon thin film to be polished on the surface is placed on the carbon-based film or the carbon-based tray, characterized by the plasma polishing apparatus.

[0016] [9] In the above [8], The plasma polishing apparatus is characterized in that the gas introduction mechanism is a mechanism for introducing the O2 gas or H2O gas and an inert gas into the chamber.

[0017]

[10] In the above [8] or [9], A plasma polishing apparatus characterized in that the carbon substrate or carbon thin film has a hardness of 5 GPa or more.

[0018]

[11] In any one of the above items [8] to

[10] , The plasma polishing apparatus is characterized in that the plasma generating power supply is one of the following: a high-frequency power supply with a frequency of 10 kHz or more and 24 GHz or less; a power supply that superimposes the high-frequency power supply and a DC power supply; a power supply that applies the high-frequency power supply in a pulsed manner; and a power supply that superimposes the power supply that applies the high-frequency power supply in a pulsed manner and a DC power supply.

[0019]

[12] In any one of the above items [8] to

[11] , A plasma polishing apparatus characterized in that the carbon substrate or carbon thin film is a single-crystal diamond substrate or a single-crystal diamond film. [Effects of the Invention]

[0020] According to various aspects of the present invention, a plasma polishing apparatus and a plasma polishing method capable of polishing and smoothing a high-hardness carbon substrate can be provided. [Brief explanation of the drawing]

[0021] [Figure 1] This is a schematic cross-sectional view showing a plasma polishing apparatus according to one aspect of the present invention. [Figure 2] This figure illustrates the results of the example and shows AFM images of the artificial diamond substrate before polishing and after plasma polishing. [Figure 3] This figure illustrates the results of the example and shows AFM images of the artificial diamond substrate before polishing and after plasma polishing. [Modes for carrying out the invention]

[0022] Embodiments of the present invention will be described in detail below with reference to the drawings. However, it will be readily apparent to those skilled in the art that the present invention is not limited to the following description, and that its form and details can be modified in various ways without departing from the spirit and scope of the present invention. Accordingly, the present invention shall not be interpreted as being limited to the descriptions of the embodiments shown below.

[0023] (First embodiment) Figure 1 is a schematic cross-sectional view showing a plasma polishing apparatus according to one aspect of the present invention.

[0024] As shown in Figure 1, the plasma polishing apparatus has a vacuum chamber 11, which is electrically connected to earth. The vacuum chamber 11 has a lower surface portion 11, a cylindrical side portion 11b which is hermetically sealed and connected to the lower surface portion 11 by an O-ring 12, and an upper surface portion 11c which is hermetically sealed and connected to the upper part of the side portion 11b by an O-ring 13.

[0025] A plasma electrode 21, serving as the first electrode, is placed inside the vacuum chamber 11. A carbon sheet 22 is placed on the surface of this plasma electrode 21. The plasma power supply (first electrode) 21 consists of a single-crystal diamond substrate 51, whose surface is polished, placed on the carbon sheet 22. The single-crystal diamond substrate 51 is preferably a single crystal. Alternatively, the single-crystal diamond substrate 51 may be made of synthetic diamond.

[0026] In this embodiment, a carbon sheet 22 is placed on the surface of the plasma electrode 21, but it is also possible to place a carbon-based film or a carbon-based tray on the surface of the plasma electrode 21. Here, placing a carbon-based film on the surface of the plasma electrode 21 may involve forming a carbon-based film on the surface or on both the surface and sides of the plasma electrode 21, or it may involve placing a sheet-like carbon-based film (carbon sheet) on the surface of the plasma electrode 21. Here, the carbon-based film or carbon-based tray is made of a material of C a H b N c and it is preferable that a, b, and c satisfy the following formulas 1 to 3. (Formula 1) 0.25 ≤ a ≤ 1 (Formula 2) 0 ≤ b ≤ 0.6 (Formula 3) 0 ≤ c ≤ 0.6

[0027] Also, the carbon-based tray may be one in which the above carbon-based film is formed on the surface of the tray body. The tray body may be made of a material other than the above C a H b N c material, for example, it may be made of SUS (Steel Use Stainless). Also, the first electrode itself may be made of a carbon-based material. However, if it is consumed by repeating plasma polishing, the first electrode itself must be replaced.

[0028] Also, in the present embodiment, the carbon sheet 22 is disposed on the surface of the plasma power supply 21, but the carbon sheet 22 may also be disposed on the side surface of the plasma power supply 21, or the carbon sheet 22 may have a sheet shape that covers the surface of the plasma electrode 21 (the first electrode).

[0029] Also, in the present embodiment, the single crystal diamond substrate 51 is used as the one for polishing the surface, but it is not limited to this, and other carbon substrates or carbon thin films can also be polished. The carbon substrate or carbon thin film preferably has a hardness of 5 GPa or more or 10 GPa or more. Also, the carbon substrate may be a diamond gemstone or a diamond substrate, and the carbon thin film may be a diamond thin film. The diamond mentioned here is preferably a single crystal. Also, the plasma polishing apparatus according to the present embodiment smoothes the surface of a high-hardness carbon substrate or carbon thin film.

[0030] The plasma electrode 21 is supported by a lower surface portion 11a, and the plasma electrode 21 and the lower surface portion 11a are insulated from each other by an insulator 31. A plasma generation power supply 41 is electrically connected to the plasma electrode (first electrode) 21. The plasma electrode 21 also has a structure that allows for internal water cooling (not shown).

[0031] The plasma generation power supply 41 may be one of the following: a high-frequency power supply (RF power supply) with a frequency of 10 kHz to 24 GHz, a DC power supply, a power supply that superimposes a high-frequency power supply and a DC power supply (RF superimposed DC power supply), a power supply that applies a high-frequency power supply in a pulsed manner, or a power supply that superimposes a power supply that applies a high-frequency power supply in a pulsed manner and a DC power supply. By applying a high-frequency power supply in a pulsed manner, it becomes possible to control the polishing rate and suppress abnormal discharges.

[0032] A gas shower electrode 23 is positioned inside the vacuum chamber 11 as a second electrode, facing the plasma electrode 21. The gas shower electrode 23 is supported by an upper surface portion 11c, and the gas shower electrode 23 and the upper surface portion 11c are insulated from each other by an insulator 32. The gas shower electrode (second electrode) 23 is electrically connected to earth.

[0033] The gas shower electrode 23 is connected to a gas introduction mechanism 42 that introduces an inert gas (e.g., Ar gas) and O2 gas into the vacuum chamber 11. Specifically, the gas shower electrode 23 is configured to supply Ar gas and O2 gas in a shower-like manner toward the surface of the plasma electrode 21. Alternatively, N2 gas or a mixture of halogen gas and N2 gas may be used instead of halogen gas. In this embodiment, O2 gas is used, but it is also possible to use H2O gas, NO2, or a mixture thereof instead of O2 gas. Furthermore, in this embodiment, Ar gas and O2 gas are supplied in a shower-like manner, but it is also possible to supply only O2 gas or only H2O gas in a shower-like manner without supplying Ar gas. If Ar gas is not supplied, the polishing rate will be slower, and therefore the polishing time will be longer.

[0034] Furthermore, the plasma polishing apparatus has an exhaust mechanism for evacuating the vacuum chamber 11. Specifically, the exhaust mechanism includes an exhaust path 11d provided on the side surface 11b of the vacuum chamber 11, one end of an exhaust path 11e connected to the exhaust path 11d, one side of a vacuum valve 43 connected to the other end of the exhaust path 11e, one end of an exhaust path 11f connected to the other side of the vacuum valve 43, and a vacuum pump 44 connected to the other end of the exhaust path 11f.

[0035] Next, a method for polishing a single-crystal diamond substrate 51 using the plasma polishing apparatus described above will be explained.

[0036] A single-crystal diamond substrate 51 is placed on the carbon sheet 22 of the plasma electrode 21. Next, the vacuum valve 43 is opened, and the vacuum chamber 11 is evacuated by the vacuum pump 44. As a result, the gas in the vacuum chamber 11 is exhausted through the exhaust paths 11d, 11e, vacuum valve 43, and exhaust path 11f. Simultaneously, the gas introduction mechanism 42 introduces Ar gas and oxygen gas (O2 gas) into the gas shower electrode 23 at a predetermined flow rate, spraying each gas in a shower-like manner towards the surface of the plasma electrode 21. The pressure is then adjusted to a predetermined level by balancing the introduction of Ar gas and oxygen gas into the vacuum chamber 11 and the exhaust of gas from the vacuum chamber 11 by the vacuum pump 44.

[0037] Subsequently, the plasma generating power supply 41 applies power to the plasma electrode 21 using one of the following: an RF power supply with a frequency of 10 kHz to 24 GHz, a DC power supply, an RF superimposed DC power supply, a power supply that applies an RF power supply in a pulsed manner, or a power supply that applies an RF power supply in a pulsed manner and a DC power supply superimposed on it. This generates plasma 61 between the plasma electrode 21 and the gas shower electrode 23, and the surface of the single-crystal diamond substrate 51 is polished by sputtering with Ar gas ionized by this plasma 61, while the carbon ions generated during this polishing are removed from the surface of the single-crystal diamond substrate 51 as CO2 gas using ionized oxygen gas. In this way, the surface of the single-crystal diamond substrate 51 is polished.

[0038] According to this embodiment, the surface of the plasma electrode 21 is C a H b N c A carbon sheet 22 (a carbon-based film or carbon-based tray) made of the same material is placed, and a single-crystal diamond substrate 51 is placed on this carbon sheet 22. Because the carbon sheet 22 is positioned between the single-crystal diamond substrate 51, which serves as the carbon substrate, and the plasma electrode 21, the carbon ions scraped off the surfaces of the single-crystal diamond substrate 51 and the carbon sheet 21 by ionized Ar gas can be converted into CO2 gas by ionized oxygen, thereby allowing the scraped carbon ions to be gasified and removed from the surfaces of the single-crystal diamond substrate 51 and the carbon sheet 22. Therefore, when the surface of the single-crystal diamond substrate 51 is plasma polished, no other substances such as films are re-adhered to the surface of the single-crystal diamond substrate 51. As a result, the surface of the single-crystal diamond substrate 51 can be polished in a clean state, and the surface of the single-crystal diamond substrate 51 can be flattened and smoothed. The surface roughness Ra of the polished surface of the carbon substrate polished in this way can be, for example, 1 nm or less (preferably 0.45 nm or less, more preferably 0.35 nm or less). For example, the surface roughness Ra of a diamond gemstone, diamond substrate, or diamond thin film can be reduced to 1 nm or less.

[0039] Furthermore, the carbon sheet 22 is the above C a H b N c Because it is made of the same material, when the carbon sheet 22 is plasma polished, hydrogen ions and nitrogen ions are also converted into gas. Therefore, it is possible to prevent them from re-adhering to the single-crystal diamond substrate 51 by plasma polishing.

[0040] (Second embodiment) A plasma polishing method according to one aspect of the present invention will be described below. A carbon substrate or carbon thin film is placed on a carbon-based film or carbon-based tray (for example, the carbon sheet 22 shown in Figure 1) on the surface of a first electrode (for example, the plasma electrode 21 shown in Figure 1). Then, the carbon substrate or carbon thin film is placed in an atmosphere of inert gas (for example, Ar gas shown in Figure 1) and oxygen gas or H2O gas, and a second electrode (for example, the gas shower electrode 23 shown in Figure 1), which is positioned opposite the first electrode, is connected to ground. Plasma generation power is applied to the first electrode to generate plasma (for example, the plasma 61 shown in Figure 1) on the surface of the carbon substrate or carbon thin film. This allows the surface of the carbon substrate or carbon thin film to be polished using the plasma. In other words, the surface of the carbon substrate or carbon thin film is polished with the inert gas (Ar gas) ionized by the plasma generated between the first electrode (plasma electrode 21) and the second electrode (gas shower electrode 23), while the carbon ions generated by polishing are removed from the surface of the carbon substrate as CO2 gas by ionized oxygen.

[0041] The carbon substrate or carbon thin film described above should preferably have a hardness of 5 GPa or higher. This is because the plasma polishing method described above smooths the surface of a high-hardness carbon substrate.

[0042] In this embodiment, plasma is generated on a carbon substrate or carbon thin film in an atmosphere of inert gas and oxygen gas or H2O gas. However, it is also possible to generate plasma in an atmosphere of oxygen gas only or H2O gas only without supplying an inert gas. If an inert gas is not supplied, the polishing rate will be slower, and therefore the polishing time will be longer.

[0043] Furthermore, the carbon-based film or carbon-based tray may be made of the same material as in the first embodiment. Also, the carbon-based tray can be the same as in the first embodiment.

[0044] According to this embodiment, a carbon-based film or carbon-based tray is placed on the surface of the first electrode, a high-hardness carbon substrate or carbon thin film is placed on the carbon-based film or carbon-based tray, the second electrode is connected to earth, and plasma generation power is applied to the first electrode to generate plasma between the first electrode and the second electrode. The surface of the carbon substrate or carbon thin film is sputtered with an inert gas ionized by this plasma. At this time, since the carbon-based film or carbon-based tray is located between the first electrode and the carbon substrate or carbon thin film, the carbon ions scraped off the surface of the carbon substrate or carbon thin film and the surface of the carbon-based film or carbon-based tray by the ionized inert gas can be converted into CO2 gas by ionized oxygen, thereby gasifying and removing the scraped carbon ions from the surface of the carbon substrate or carbon thin film and the surface of the carbon-based film or carbon-based tray. Therefore, when the surface of the carbon substrate or carbon thin film is plasma polished, other substances such as films do not re-adhere to the surface of the carbon substrate or carbon thin film. As a result, the surface of the carbon substrate or carbon thin film can be polished in a clean state, and the surface of the carbon substrate or carbon thin film can be planarized and smoothed. The surface roughness Ra of the polished surface of the carbon substrate or carbon thin film polished in this way can be set to, for example, 1 nm or less, and by adjusting the polishing conditions, it can also be set to, for example, 0.45 nm or less or 0.35 nm or less. For example, the surface roughness Ra of a diamond gemstone, diamond substrate, or diamond thin film can be set to 1 nm or less (preferably 0.45 nm or less, more preferably 0.35 nm or less).

[0045] In this embodiment, plasma is generated on the surface of the carbon substrate or carbon thin film by applying plasma generation power to the first electrode while the carbon substrate or carbon thin film is placed in an atmosphere of inert gas and oxygen gas or H2O gas, with the second electrode positioned opposite the first electrode connected to ground. However, it is also possible to generate plasma on the surface of the carbon substrate or carbon thin film by applying plasma generation power to the first electrode while the carbon substrate or carbon thin film is placed in an atmosphere of inert gas and oxygen gas or H2O gas. In this case, plasma can be generated between the first electrode and the chamber connected to ground.

[0046] I will explain in more detail. If a single-crystal diamond substrate 51 is placed directly on the plasma electrode 21 without placing a carbon sheet 22 on the surface of the plasma electrode 21, the carbon ions removed from the surface of the single-crystal diamond substrate 51 by plasma polishing using ionized Ar gas are converted into CO2 gas by ionized oxygen, and then gasified and removed from the surface of the single-crystal diamond substrate 51. Furthermore, if the plasma electrode is made of, for example, Al or stainless steel, the plasma electrode is sputtered, and an Al2O3 film or Fe2O3 film, which has bonded with oxygen ions, adheres to the surface of the single-crystal diamond substrate 51. This is the same even if only O2 gas or only H2O gas is supplied without supplying Ar gas, and an Al2O3 film or Fe2O3 film adheres to the surface of the single-crystal diamond substrate 51. As a result, the single-crystal diamond substrate becomes a defective product. In contrast, in the embodiment described above, since the carbon sheet 22 is placed on the surface of the plasma electrode 21, it is possible to suppress the plasma electrode 21 from being sputtered and the oxide film adhering to the surface of the single crystal diamond substrate 51. Also, as described above, the surface of the single crystal diamond substrate 51 is gas or CO2 +By covering the substrate, even if a small amount of contaminant remains in the vacuum chamber 11, it is possible to prevent that contaminant from adhering to the single-crystal diamond substrate 51. Therefore, a diamond single-crystal substrate with a clean surface and an Ra of 0.31 nm or less, as shown in Figure 2, was produced. Furthermore, the single-crystal diamond substrate shown in Figure 2, with a clean surface and an Ra of 0.31 nm or less, is expected to be used as a substrate (wafer) for next-generation semiconductors and next-generation electronic devices with extremely high thermal conductivity, i.e., extremely high heat dissipation. [Examples]

[0047] Using the plasma polishing apparatus shown in Figure 1, a diamond substrate was polished under the following plasma polishing conditions. • RF output of plasma generation power supply 41: 300W ·O2 flow rate: 20cc / min ·Ar flow rate: 2cc / min Oxygen pressure: 18 Pa • Polishing time: 20 minutes • Vacuum chamber 11: Stainless steel • Plasma electrode 21: Stainless steel • Gas shower electrode 23: Stainless steel • Substrate to be polished: Single-crystal artificial diamond substrate before treatment, as shown in Figures 2 and 3. The artificial single-crystal diamond substrate before processing is a substrate that has been mechanically polished from artificial single-crystal diamond.

[0048] Figures 2 and 3 illustrate the results of the example and show AFM (Atomic Force Microscopy) images of the artificial diamond substrate before polishing and after plasma polishing.

[0049] As shown in Figures 2 and 3, a diamond substrate with a surface roughness Ra of 2.21 nm and a surface roughness Rq of 4.33 was plasma polished under the above polishing conditions to achieve a surface roughness Ra of 0.31 nm and a surface roughness Rq of 0.41 nm. [Explanation of Symbols]

[0050] 11… Vacuum Chamber 11a...Lower surface of the vacuum chamber 11b...Side section of the vacuum chamber 11c... Top surface of the vacuum chamber 11d, 11e, 11f... Exhaust path 12, 13…O-rings 21…Plasma electrode (first electrode) 22…Carbon sheet (carbon-based film or carbon-based tray) 23…Gas shower electrode (second electrode) 31, 32... Insulator 40... Exhaust mechanism 41…Plasma generation power supply 42...Gas introduction mechanism 43…Vacuum valve 44… Vacuum pump 51…Single-crystal diamond substrate (carbon substrate or carbon thin film) 61…Plasma

Claims

1. A carbon substrate or carbon thin film is placed on the carbon-based film or carbon-based tray of a first electrode on which a carbon-based film or carbon-based tray is arranged on the surface. The carbon substrate or carbon thin film is treated with oxygen gas or H ２ A plasma polishing method characterized by applying plasma generation power to the first electrode in an O gas atmosphere to generate plasma on the surface of the carbon substrate or carbon thin film, and polishing using the plasma.

2. In claim 1, In the aforementioned atmosphere, the oxygen gas or H ２ A plasma polishing method characterized by being performed in an atmosphere in which an inert gas is added to O gas.

3. In claim 1 or 2, The carbon-based film or carbon-based tray is C ａ H ｂ N ｃ It consists of the following materials: A plasma polishing method characterized in that a, b, and c satisfy the following equations 1 to 3. (Formula 1) 0.25≦a≦1 (Formula 2) 0≦b≦0.6 (Formula 3) 0≦c≦0.6

4. In claim 1 or 2, The plasma polishing method is characterized in that the carbon-based tray has a carbon-based film formed on the surface of the tray body.

5. A plasma polishing method characterized in that the surface roughness Ra of the polished surface of a carbon substrate or carbon thin film polished by the plasma polishing method according to claim 1 or 2 is 1 nm or less.

6. A plasma polishing method characterized in that the polished surface of a carbon substrate or carbon thin film polished by the plasma polishing method described in claim 1 or 2 has a surface roughness Ra of 1 nm or less and a hardness of 5 GPa or more.

7. The surface roughness Ra of the polished surface of the carbon substrate or carbon thin film polished by the plasma polishing method described in claim 1 or 2 is 1 nm or less. The carbon substrate is a diamond gemstone or a diamond substrate, A plasma polishing method characterized in that the carbon thin film is a diamond thin film.

8. Chamber and A first electrode disposed within the chamber, A carbon-based film or carbon-based tray placed on the surface of the aforementioned first electrode, A second electrode is placed inside the chamber and is positioned opposite the first electrode, A plasma generating power supply electrically connected to the first electrode, The ground is electrically connected to the second electrode, An exhaust mechanism for evacuating the chamber, O ２ Gas or H ２ A gas introduction mechanism for introducing O gas, It has, The plasma polishing apparatus is characterized in that the first electrode has a carbon substrate or carbon thin film on which the surface to be polished is placed on the carbon-based film or carbon-based tray.

9. In claim 8, The gas introduction mechanism introduces the O ２ gas or H ２ O gas and an inert gas into the chamber, and the plasma polishing apparatus is characterized by this.

10. In claim 8 or 9, A plasma polishing apparatus characterized in that the carbon substrate or carbon thin film has a hardness of 5 GPa or more.

11. In claim 8 or 9, The plasma polishing apparatus is characterized in that the plasma generating power supply is one of the following: a high-frequency power supply with a frequency of 10 kHz or more and 24 GHz or less; a power supply that superimposes the high-frequency power supply and a DC power supply; a power supply that applies the high-frequency power supply in a pulsed manner; and a power supply that superimposes the power supply that applies the high-frequency power supply in a pulsed manner and a DC power supply.

12. In claim 8 or 9, A plasma polishing apparatus characterized in that the carbon substrate or carbon thin film is a single-crystal diamond substrate or a single-crystal diamond film.

Images