Diamond substrate manufacturing method, diamond substrate

Abstract

A method for manufacturing a diamond substrate that can efficiently manufacture single-crystal diamond, and a diamond substrate manufactured by this manufacturing method are provided. [Solution] A method for manufacturing a diamond substrate includes a plasma generation step in which a plasma ball is generated in a container containing a substrate by introducing microwaves into the container; a center heating step in which the center of the substrate is heated by a heating device to raise the temperature of the center of the substrate above the temperature of the edge of the substrate; and a crystallization step, which is carried out in parallel with the center heating step, in which the substrate is heated by the plasma ball.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a diamond substrate and a diamond substrate. [Background technology]

[0002] Patent Document 1 discloses a method for manufacturing a diamond substrate using the so-called CVD (Chemical Vapor Deposition) method, in which microwaves are output from a microwave source into a container to generate a plasma ball near a substrate placed in the container. In the CVD method, diamond is grown by decomposing hydrogen and methane using a plasma ball and depositing them on the substrate. The diamond substrate includes a base material and crystalline diamond formed on the base material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 4-230019 Summary of the Invention [Problem to be solved by the invention]

[0004] When considering the production of single-crystal diamond, the above production method has the following problem: Macrosteps are formed starting from the periphery of the substrate, and as the macrosteps progress toward the center, they meet with each other, forming spot-like polycrystalline portions inside the single crystal.

[0005] An object of the present invention is to provide a method for manufacturing a diamond substrate that can efficiently produce single-crystal diamond, and a diamond substrate manufactured by this manufacturing method. [Means for solving the problem]

[0006] A method for manufacturing a diamond substrate according to a first aspect of the present invention includes a plasma generation step in which a plasma ball is generated in a container containing a substrate by introducing microwaves into the container; a center heating step in which the center of the substrate is heated by a heating device to increase the temperature of the center of the substrate above the temperature of the edge of the substrate; and a crystallization step that is carried out in parallel with the center heating step in which the substrate is heated by the plasma ball.

[0007] A method for manufacturing a diamond substrate according to a second aspect of the present invention is the method for manufacturing a diamond substrate according to the first aspect, in which the substrate is contained in a holder having an opening, and in the crystal generation process, the substrate is heated by the plasma ball while being spaced apart from the plasma ball.

[0008] A method for manufacturing a diamond substrate according to a third aspect of the present invention is a method for manufacturing a diamond substrate according to the first or second aspect, wherein in the central heating step, the heating device heats the substrate from the side of the surface of the substrate that faces the plasma ball.

[0009] A fourth aspect of the present invention relates to a method for manufacturing a diamond substrate according to the first or second aspect, and in the central heating step, the heating device heats the substrate from the side of the substrate opposite to the side facing the plasma ball.

[0010] A fifth aspect of the present invention relates to a method for manufacturing a diamond substrate according to any one of the first to fourth aspects, wherein the maximum diameter of the outer periphery of the substrate is larger than the maximum diameter of the plasma ball, and further includes an edge heating step of heating a portion of the substrate including its edge from the side of the surface of the substrate opposite the surface facing the plasma ball using a heating device separate from the heating device.

[0011] A diamond substrate according to a sixth aspect of the present invention includes a base material and a single crystal diamond formed on the base material, the single crystal diamond having a centrally convex shape. [Effects of the Invention]

[0012] According to the present invention, a method for manufacturing a diamond substrate and a diamond substrate manufactured by this manufacturing method enable efficient production of single crystal diamond. [Brief explanation of the drawings]

[0013] [Figure 1] Schematic diagram of a microwave plasma processing apparatus used in the method for manufacturing a diamond substrate. [Figure 2] 1 is a flowchart showing an example of a method for manufacturing a diamond substrate according to an embodiment. [Figure 3] 3 is a diagram showing an example of the shape of a single-crystal diamond of a diamond substrate manufactured by the method for manufacturing a diamond substrate of FIG. 2. [Figure 4] FIG. 10 is a schematic diagram of a microwave plasma processing apparatus used in the method for manufacturing a diamond substrate according to the first modified example. [Figure 5] FIG. 10 is a schematic diagram of a microwave plasma processing apparatus used in a method for manufacturing a diamond substrate according to a second modified example. [Figure 6] FIG. 10 is a schematic diagram of a microwave plasma processing apparatus used in a method for manufacturing a diamond substrate according to another modified example of the second modified example. [Figure 7] FIG. 10 is a schematic diagram of a microwave plasma processing apparatus used in a diamond substrate manufacturing method according to a third modified example. [Figure 8] FIG. 10 is a schematic diagram of a microwave plasma processing apparatus used in a method for manufacturing a diamond substrate that is another modified example of the third modified example. [Figure 9] 10 is a flowchart showing an example of a method for manufacturing a diamond substrate according to the third modified example or another modified example of the third modified example. DETAILED DESCRIPTION OF THE INVENTION

[0014] A method for manufacturing a diamond substrate according to one embodiment of the present invention will be described below with reference to the drawings.

[0015] <1-1. Overall configuration of microwave plasma processing equipment> FIG. 1 is a schematic diagram of a microwave plasma processing apparatus 10 used in a method for manufacturing a diamond substrate. The microwave plasma processing apparatus 10 manufactures a diamond substrate 120 (see FIG. 3) containing single-crystal diamond. The microwave plasma processing apparatus 10 is used to manufacture diamond substrates having a diameter of, for example, 2 inches or less by a CVD method. The microwave plasma processing apparatus 10 includes a microwave oscillation source 20, a resonator 30, a waveguide 40, a heating device 50, an output controller 60, a control device 70, and a radiation thermometer 90.

[0016] The microwave source 20 outputs microwaves to be supplied into the container 30A of the resonator 30. The microwave source 20 is, for example, a magnetron power supply. The center frequency of the microwaves is, for example, 2450 MHz (2.45 GHz), 915 MHz, or 10 GHz or higher.

[0017] The resonator 30 includes a container 30A, a substrate support 30B, a source gas supply path 30C, an exhaust path 30D, and windows 81, 82, and 83.

[0018] The vessel 30A is a vacuum vessel. The pressure inside the vessel 30A is, for example, in the range of 50 Torr to 200 Torr. The shape of the vessel 30A can be selected arbitrarily. In this embodiment, the vessel 30A is cylindrical. A waveguide 40 is attached to a portion of the peripheral wall 32 of the vessel 30A. A substrate support 30B is accommodated in the internal space 31 of the vessel 30A. A base material 100 for manufacturing the diamond substrate 120 is placed on the substrate support 30B. The substrate support 30B may have a function of cooling the diamond substrate 120 after manufacturing the diamond substrate 120. The shape of the substrate support 30B can be selected arbitrarily. In this embodiment, the substrate support 30B is disk-shaped.

[0019] The material constituting the substrate 100 can be selected arbitrarily as long as it allows a carbon source in the raw material gas described below to form a film on the substrate 100 and grow a diamond having a diamond crystal structure. The material constituting the substrate 100 is, for example, a single crystal diamond, a polycrystalline diamond, silicon, 3C silicon carbide, gallium nitride, gallium oxide, iridium, platinum, nickel, magnesium oxide, yttrium-stabilized zirconia, or a high-melting point metal such as molybdenum.

[0020] The source gas supply line 30C supplies the source gas for forming the diamond substrate 120 to the internal space 31 of the container 30A. The source gas supply line 30C is connected to the peripheral wall 32 of the container 30A. The source gas is, for example, a mixed gas containing carbon, hydrogen, nitrogen, oxygen, and methane.

[0021] The exhaust passage 30D is connected to, for example, the peripheral wall 32 of the container 30A so that the gas inside the container 30A can be exhausted. The end of the exhaust passage 30D opposite the container 30A is connected to a vacuum pump (not shown). When the vacuum pump is operated, the gas inside the container 30A is exhausted to the outside of the container 30A through the exhaust passage 30D.

[0022] The waveguide 40 is, for example, a circular waveguide or a rectangular waveguide, and connects the microwave source 20 and the container 30A so that microwaves are introduced into the container 30A.

[0023] Holes 32A, 32B, and 32C are formed in the peripheral wall 32 of the container 30A. Hole 32A is formed in a position of the peripheral wall 32 of the container 30A facing the waveguide 40. A window 81 that transmits microwaves is attached to hole 32A. The window 81 is made of, for example, quartz glass or alumina.

[0024] The hole 32B is attached to the peripheral wall 32 of the container 30A at a position facing the head 52 of the heating device 50, which will be described later. A window 82 that transmits the laser output from the head 52 is attached to the hole 32B. The window 82 is made of, for example, quartz glass or alumina.

[0025] The hole 32C is attached to the peripheral wall 32 of the container 30A at a position facing the radiation thermometer 90. A window 83 that transmits infrared rays emitted from the substrate 100 is attached to the hole 32C. The window 83 is made of, for example, quartz glass or alumina.

[0026] Microwaves output from microwave source 20 are introduced into container 30A, creating a region of locally high electric field strength within container 30A. In the region of locally high electric field strength, molecules of the source gas dissociate into electrons and chemically active species, generating a plasma ball 150. The chemically active species include ions and radicals. The diameter of the generated plasma ball 150 is, for example, 50 mm. The chemically active species contained in plasma ball 150 react with the surface of substrate 100 to form a single-crystal diamond, which grows to produce a diamond substrate 120. The manufactured diamond substrate 120 includes substrate 100 and single-crystal diamond 110 formed on substrate 100.

[0027] The heating device 50 is positioned so as to heat the center of the substrate 100. The specific configuration of the heating device 50 can be selected arbitrarily as long as it is capable of heating the center of the substrate 100. In this embodiment, the heating device 50 is a laser device including a main body 51 and a head 52. The head 52 is communicatively connected to the main body 51. The laser output from the head 52 travels toward the center of the substrate 100. The heating device 50 heats the surface of the substrate 100 facing the plasma ball 150. During the production of the diamond substrate 120, the temperature of the center of the substrate 100 reaches, for example, approximately 1000°C. The laser output may be constant or may be feedback-controlled based on the temperature of the center of the substrate 100 measured by the radiation thermometer 90.

[0028] The output controller 60 controls the output of the laser output from the head 52 to a value set by the control device 70. The output controller 60 is connected to the main body 51 so as to be able to communicate with it.

[0029] The control device 70 sets the output power of the laser output from the head 52. The control device 70 is communicatively connected to the output controller 60. The control device 70 is, for example, a personal computer. The control device 70 may also be a tablet terminal or a smartphone.

[0030] The radiation thermometer 90 measures the temperature at the center of the substrate 100. The radiation thermometer 90 may be communicably connected to the control device 70.

[0031] <1-2. Diamond substrate manufacturing method> An example of a method for manufacturing a diamond substrate using the microwave plasma processing apparatus 10 will be described with reference to Fig. 2. The method for manufacturing a diamond substrate includes a plasma generation step, a central heating step, and a crystallization step.

[0032] In the plasma generation process of step S11, microwaves output from microwave oscillation source 20 are introduced into container 30A, thereby generating plasma ball 150 within container 30A.

[0033] The central heating step of step S12 is performed in parallel with the plasma generating step. In the central heating step, a laser is output from the head 52 of the heating device 50 toward the center of the substrate 100.

[0034] The crystal growth step in step S13 is carried out in parallel with the plasma generation step and the central heating step. In the crystal growth step, a diamond substrate 120 is produced in which a single crystal diamond 110 is grown on a base material 100.

[0035] <1-3. Shape of diamond substrate> Figure 3 is a diagram showing an example of the shape of a single crystal diamond 110 in a diamond substrate 120 manufactured by the diamond substrate manufacturing method of this embodiment. The horizontal axis of Figure 3 is the diameter of the single crystal diamond 110. The vertical axis of Figure 3 is the height of the single crystal diamond 110.

[0036] The growth of the single crystal diamond 110 depends on the temperature of the substrate 100. More specifically, the growth of the single crystal diamond 110 proceeds from the part of the substrate 100 where the temperature is high. In the method for manufacturing a diamond substrate of this embodiment, the center of the substrate 100 is heated by the heating device 50. In this embodiment, since the single crystal diamond 110 grows from the center of the substrate 100, the shape of the single crystal diamond 110 is a shape with a convex center.

[0037] 2. Effects of diamond substrate manufacturing methods In conventional diamond substrate manufacturing methods, macrosteps are formed starting from the outer periphery of the substrate, and as the macrosteps progress toward the center, they meet with each other, forming spot-like polycrystalline portions inside the single crystal. Note that the single crystal diamond of the diamond substrate manufactured by conventional diamond substrate manufacturing methods has a concave shape in the center.

[0038] In this embodiment, the method for manufacturing a diamond substrate includes a central heating step, so that single-crystal diamond 110 grows from the center of the substrate 100. Because the macrosteps progress from the center to the edge of the substrate 100, the macrosteps are prevented from meeting each other. Because spot-like polycrystalline portions are unlikely to form inside the single crystal, single-crystal diamond can be manufactured efficiently.

[0039] <3. Modifications> The above embodiments are examples of the diamond substrate manufacturing method and diamond substrate according to the present invention that can be used, and are not intended to limit the forms. The diamond substrate manufacturing method and diamond substrate according to the present invention can be used in forms different from those exemplified in the embodiments. One example is a form in which part of the configuration of the embodiment is replaced, changed, or omitted, or a form in which a new configuration is added to the embodiment. Below are some examples of modified forms of each embodiment. Note that the following modified forms can be combined with each other as long as there is no technical contradiction.

[0040] <3-1. First modified example> 4 is a schematic diagram of a microwave plasma processing apparatus 200 used in the method for manufacturing a diamond substrate of the first modified example. The microwave plasma processing apparatus 200 may have a holder 210 that houses the substrate 100. The holder 210 is made of, for example, a metal material. The holder 210 has an opening 210X on the surface facing the plasma ball 150.

[0041] If the electric field concentrates at the edge of the substrate 100, polycrystalline grains grow and the grain size increases. This may result in a reduction in the size of the single crystal portion. In the first modification, the microwave plasma processing apparatus 200 has a holder 210, so that in the crystal growth process, the substrate 100 is heated by the plasma ball 150 while separated from the plasma ball 150. In the crystal growth process, the substrate 100 and the plasma ball 150 do not come into direct contact with each other, which prevents the electric field from concentrating at the edge of the substrate 100. This allows the single crystal diamond 110 to be produced more efficiently.

[0042] <3-2. Second modified example> FIG. 5 is a schematic diagram of a microwave plasma processing apparatus 300 used in the second modified method for manufacturing a diamond substrate. The microwave plasma processing apparatus 300 has a heating device 350. The heating device 350 is a laser device including a main body 351 and a head 352. The heating device 350 heats the surface of the substrate 100 opposite the surface facing the plasma ball. In the second modified example, an opening 30AX is formed in the bottom wall of the peripheral wall 32 of the container 30A. A window 84 is preferably disposed in the opening 30AX. An opening 40X is formed in the substrate support table 30B. The laser output from the head 352 passes through the window 84 of the opening 30AX and the opening 40X and proceeds to the substrate 100.

[0043] 6 is a schematic diagram of a microwave plasma processing apparatus 300X used in a method for manufacturing a diamond substrate, which is yet another modification of the second modification. The heating apparatus 350 may have a heat source 352X that is smaller than the maximum diameter of the substrate 100. The heat source 352X is a resistance heater. In the example shown in FIG. 6, the window 84 may not be disposed in the opening 30AX.

[0044] <3-3.Third modified example> FIG. 7 is a schematic diagram of a microwave plasma processing apparatus 400 used in the third modified diamond substrate manufacturing method. The microwave plasma processing apparatus 400 includes a heating apparatus 450 in addition to the heating apparatus 50. The heating apparatus 450 is a laser apparatus including a main body 451 and a head 452. The heating apparatus 450 heats the edge of the substrate 100 from the side of the substrate 100 opposite the side facing the plasma ball. The head 452 outputs a laser beam in, for example, a ring shape. In the third modified example, as in the second modified example, an opening 30AX is formed in the bottom wall of the peripheral wall 32 of the container 30A. A window 84 is preferably provided in the opening 30AX. An opening 40X is formed in the substrate support table 30B. The laser beam output from the head 352 passes through the window 84 of the opening 30AX and the opening 40X to advance to the substrate 100.

[0045] 8 is a schematic diagram of a microwave plasma processing apparatus 400X used in a method for manufacturing a diamond substrate, which is yet another modification of the third modification. The heating apparatus 450 may have a ring-shaped heat source 452X that is smaller than the maximum diameter of the substrate 100. The heat source 452X is a resistance heater. In the example shown in FIG. 8, the window 84 may not be disposed in the opening 30AX.

[0046] If the maximum diameter of the outer periphery of substrate 100 is larger than the maximum diameter of plasma ball 150, the portion including the edge of substrate 100 may not be sufficiently heated by plasma ball 150, and the temperature of the portion including the edge of substrate 100 may become significantly lower than the temperature at the center of substrate 100, resulting in a risk of uneven temperature across the surface of substrate 100. In the third modified example and the method for manufacturing a diamond substrate which is yet another modified example of the third modified example, heating device 450 is provided, thereby preventing the temperature of the portion including the edge of substrate 100 from becoming significantly lower than the temperature at the center of substrate 100.

[0047] 9 is a flowchart showing an example of a method for manufacturing a diamond substrate according to the third modification or another modification of the third modification. The method for manufacturing a diamond substrate may include an edge heating step in addition to the plasma generating step, the center heating step, and the crystal growing step of the embodiment.

[0048] The edge heating step of step S21 is performed in parallel with the plasma generation step, the central heating step, and the crystal growth step. In the edge heating step, the heating device 450 heats a portion of the surface of the substrate 100, including the edge, from the side opposite to the surface facing the plasma ball 150. [Explanation of symbols]

[0049] 30A: Container 50: Heating device 100: Base material 110: Single crystal diamond 120: Diamond substrate 150: Plasma Ball 210: Holder 210X:Aperture 450: Heating device

Claims

1. a plasma generating step of generating a plasma ball in a container by introducing microwaves into the container containing the substrate; a center heating step of heating the center of the substrate with a heating device to increase the temperature of the center of the substrate to be higher than the temperature of the edge of the substrate; a crystallization step, which is carried out in parallel with the central heating step, in which the substrate is heated by the plasma ball. A method for manufacturing a diamond substrate.

2. The substrate is accommodated in a holder having an opening; In the crystallization step, the substrate is heated by the plasma ball while being spaced apart from the plasma ball. The method for manufacturing a diamond substrate according to claim 1 .

3. In the central heating step, the heating device heats the substrate from a surface of the substrate facing the plasma ball. The method for manufacturing a diamond substrate according to claim 1 or 2.

4. In the central heating step, the heating device heats the substrate from a surface of the substrate opposite to a surface facing the plasma ball. The method for manufacturing a diamond substrate according to claim 1 or 2.

5. the maximum diameter of the outer periphery of the substrate is larger than the maximum diameter of the plasma ball; The method further includes an edge heating step of heating a portion of the substrate including the edge from the surface of the substrate opposite to the surface facing the plasma ball using a heating device separate from the heating device. The method for manufacturing a diamond substrate according to claim 1 or 2.

6. A diamond substrate, A substrate; a single crystal diamond formed on the substrate; The single crystal diamond has a convex shape at the center. Diamond substrate.

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