Diamond crystal growth apparatus and diamond crystal growth method

Abstract

The present invention provides a diamond crystal growth apparatus that can increase the surface area on which diamond crystals grow on a substrate while appropriately reducing the content of non-diamond components in the diamond thin film on which crystals grow on the substrate. [Solution] The diamond crystal growth apparatus includes a vacuum chamber through which microwaves are transmitted by a microwave source and into which raw material gas and etching gas flow from a gas supply source, The diamond crystal growth apparatus includes a moving mechanism for moving a substrate within a vacuum chamber relative to a plasma ball generated by microwaves within the vacuum chamber. The diamond crystal growth apparatus grows diamond in a first region on the substrate surface directly beneath the plasma ball, and the moving mechanism changes the diamond crystal growth region on the substrate surface, including the substrate surface directly beneath the plasma ball, from the first region to a second region. After selectively etching away the non-diamond components formed in the second region, diamond is grown in the second region.

Description

Technical Field

[0001] This disclosure relates to a diamond crystal growth apparatus and a diamond crystal growth method.

Background Art

[0002] As a diamond crystal growth method, the plasma CVD method is generally known. By this plasma CVD method, for example, a mixed plasma of hydrogen and methane is generated by microwaves, and diamond can be grown on a substrate by utilizing the dissociation and synthesis of gas-phase molecules by electrons, ions, and radical species in this plasma.

[0003] In such a diamond crystal growth method, it is often necessary to reduce the content of non-diamond components such as graphite present in the diamond thin film on the substrate, and various methods have been proposed conventionally.

[0004] For example, Patent Document 1 proposes a method of forming diamond on a substrate by alternately bringing a gas obtained by exciting a raw material gas and a gas obtained by exciting an etching gas into contact with the substrate surface.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] This disclosure, as an example, aims to provide a diamond crystal growth apparatus and a diamond crystal growth method that can appropriately reduce the content of non-diamond components in a diamond thin film grown on a substrate while expanding the substrate area on which diamond grows more than before.

Means for Solving the Problems

[0007] To solve the above problems, a diamond crystal growth apparatus according to one aspect of the present disclosure comprises a vacuum chamber into which microwaves are transmitted from a microwave source and raw material gas and etching gas flow in from a gas supply source, and a moving mechanism for moving a substrate in the vacuum chamber with respect to plasma balls generated in the vacuum chamber by the microwaves, wherein diamond is grown in a first region on the substrate surface directly below the plasma balls, the diamond crystal growth region in the plane including the substrate surface directly below the plasma balls is changed from the first region to a second region on the substrate surface by the moving mechanism, non-diamond components formed in the second region are selectively etched away, and then diamond is grown in the second region.

[0008] Furthermore, a diamond crystal growth method according to one aspect of the present disclosure comprises: a first crystal growth step in which methane gas and hydrogen gas are supplied into a vacuum chamber from a gas supply source to grow diamond crystals in a first region on the surface of a substrate directly beneath a plasma ball generated by microwaves transmitted into the vacuum chamber from a microwave source; a substrate moving step in which, after the supply of methane gas into the vacuum chamber is stopped, the substrate is moved by a moving mechanism so that the diamond crystal growth region on the plane including the substrate surface directly beneath the plasma ball changes from the first region to a second region on the substrate surface; a cleaning step in which non-diamond components are selectively etched and removed in the second region; and a second crystal growth step in which methane gas is resupplied into the vacuum chamber to grow diamond crystals in the second region. [Effects of the Invention]

[0009] One embodiment of the present disclosure provides a diamond crystal growth apparatus and a diamond crystal growth method that can appropriately reduce the content of non-diamond components in the diamond thin film on which crystals are grown on the substrate, while increasing the substrate area on which diamond crystals are grown compared to conventional methods. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 shows an example of a diamond crystal growth apparatus according to the first embodiment. [Figure 2] Figure 2 shows an example of a diamond crystal growth apparatus according to the first embodiment. [Figure 3] Figure 3 is a flowchart showing an example of the operation of the diamond crystal growth apparatus (diamond crystal growth method) according to the first embodiment. [Figure 4A] Figure 4A is a diagram illustrating an example of the operation (diamond crystal growth method) of the diamond crystal growth apparatus of the first embodiment. [Figure 4B] Figure 4B is a diagram illustrating an example of the operation (diamond crystal growth method) of the diamond crystal growth apparatus of the first embodiment. [Figure 4C] Figure 4C is a diagram illustrating an example of the operation (diamond crystal growth method) of the diamond crystal growth apparatus of the first embodiment. [Figure 4D] Figure 4D is a diagram illustrating an example of the operation (diamond crystal growth method) of the diamond crystal growth apparatus of the first embodiment. [Figure 5] Figure 5 shows an example of a diamond crystal growth apparatus according to the second embodiment. [Modes for carrying out the invention]

[0011] Among the various methods for forming diamond thin films, microwave plasma CVD is one method that does not use electrodes in a vacuum chamber. It has the advantage of eliminating impurity contamination from electrodes and enabling stable, long-term diamond crystal growth with good reproducibility. However, due to the characteristics of microwaves, the substrate area on which diamond crystals can be grown is limited to approximately 2 to 4 inches in diameter. For example, in Japan, microwaves of approximately 2.45 GHz in the ISM band are generally used for microwave plasma CVD. In this case, the film deposition area on the substrate is generally limited to about 2 inches in diameter. In other countries, the 900 MHz band is designated as the ISM band, and as the microwave frequency decreases, the plasma region expands, meaning the area that can be film-deposited by microwave plasma CVD expands. Therefore, 915 MHz microwaves are often used for microwave plasma CVD. However, even in this case, the film deposition area on the substrate is generally limited to about 4 inches in diameter.

[0012] Therefore, by moving a substrate with a larger area than 4 inches in diameter (for example, an 8-inch diameter substrate) relative to the plasma ball in a vacuum chamber generated by microwaves, the diamond crystal growth region in the plane including the substrate surface directly beneath the plasma ball can be changed, thereby expanding the substrate area on which diamond crystal growth is possible.

[0013] However, there are the following problems with methods for moving a large-area substrate relative to such a plasma ball.

[0014] For example, when diamond crystal growth is carried out using microwaves to dissociate a raw material gas, the surface temperature of the substrate needs to be maintained at a predetermined temperature of approximately 800°C-1000°C. This substrate surface temperature is generally ensured by controlling the distance between the high-temperature plasma and the substrate.

[0015] Furthermore, for example, in microwave plasma, the reach of atomic hydrogen and CH radicals generated by the dissociation of source gases including methane and hydrogen gas depends on the vacuum pressure in the vacuum chamber, but is generally about 10 mm.

[0016] Therefore, in a region where the surface temperature of the substrate does not reach the above-mentioned predetermined temperature or a region where atomic hydrogen and CH radicals do not reach, non-diamond components such as graphite may be deposited. Then, when moving a large-area substrate with respect to the plasma ball in the vacuum chamber generated by microwaves, diamond will crystallize and grow on non-diamond components such as graphite. As a result, the quality of the diamond thin film deteriorates. That is, in the above-mentioned measures, it is difficult to increase the area of the substrate surface where diamond crystal growth is possible from the perspective of ensuring the quality of the diamond thin film.

[0017] Therefore, as a result of intensive studies to solve the above conventional problems, the present inventor has found that by appropriately combining substrate movement and cleaning of non-diamond components, it is possible to expand the area of the substrate surface where diamond crystal growth is possible for the practical application of large-area diamond thin films used in power semiconductors and the like, and has conceived the following aspects of the present disclosure.

[0018] Note that the invention disclosed in Patent Document 1 aims to improve the quality of diamond in a specific region on the substrate and does not intend to increase the area of the substrate surface where diamond crystal growth is possible.

[0019] That is, the diamond crystal growth apparatus according to the first aspect of the present disclosure includes a vacuum chamber through which microwaves are transmitted from a microwave generation source and into which a raw material gas and an etching gas flow from a gas supply source, and a moving mechanism for moving a substrate in the vacuum chamber with respect to the plasma ball generated in the vacuum chamber by microwaves. Diamond is caused to crystallize and grow in a first region on the surface of the substrate directly below the plasma ball, and the diamond crystal growth region (hereinafter, the diamond crystal growth region) in a plane including the surface of the substrate directly below the plasma ball is changed from the first region to the second region on the surface of the substrate by the moving mechanism. After selectively etching and removing the non-diamond components formed in the second region, diamond is caused to crystallize and grow in the second region.

[0020] With the above configuration, the diamond crystal growth apparatus of this embodiment can appropriately reduce the content of non-diamond components in the diamond thin film on which crystals are grown on the substrate, while increasing the substrate area on which diamond crystals are grown compared to conventional methods.

[0021] Specifically, the diamond crystal growth apparatus of this embodiment changes the diamond crystal growth region on the substrate surface from a first region to a second region by a moving mechanism, so that diamond crystals can grow in both the first and second regions. Therefore, compared to a case where the substrate is not moved by the moving mechanism, the substrate area on which diamond crystals can be grown can be expanded.

[0022] It is known that non-diamond components such as graphite can be etched away using etching gases such as hydrogen gas, and experimental results have been reported showing that the etching rate of non-diamond components is about 40 to 50 times faster than the etching rate of diamond.

[0023] In this embodiment, when the diamond crystal growth apparatus changes the diamond crystal growth region from a first region to a second region on the substrate surface by the moving mechanism, the non-diamond components formed in the second region can be selectively removed with etching gas. Therefore, compared to cases where such etching is not performed, the deterioration of the quality of the diamond thin film due to the inclusion of non-diamond components in the diamond thin film can be suppressed in the second region.

[0024] A diamond crystal growth apparatus according to a second aspect of the present disclosure, in which the moving mechanism comprises a rotating device that intermittently rotates the disc-shaped substrate at predetermined angle intervals, and the axis of rotation of the substrate may be offset from the center of the plasma ball.

[0025] With this configuration, the diamond crystal growth apparatus of this embodiment rotates the disc-shaped substrate by a rotating device while the rotation axis of the substrate is offset from the center of the plasma ball. As a result, the trajectory of the center of the diamond crystal growth region moves along the periphery of the substrate, allowing for efficient diamond crystal growth across the entire surface of the substrate.

[0026] In the diamond crystal growth apparatus of the third aspect of this disclosure, the diamond crystal growth apparatus of the second aspect may include the rotation axis of the substrate and a portion of the outer circumference of the trajectory when the substrate is rotated around the rotation axis as part of the diamond crystal growth region.

[0027] If the rotation axis of the substrate is not included in the diamond crystal growth region, a dead space may occur in the center of the substrate surface where diamond crystal growth does not occur. Also, if the outer circumference of the trajectory when the substrate is rotated 360° around the rotation axis is not included in the diamond crystal growth region, a dead space may occur in the peripheral area of ​​the substrate surface where diamond crystal growth does not occur.

[0028] Therefore, by configuring the diamond crystal growth apparatus of this embodiment so that the rotation axis of the substrate is included in the diamond crystal growth region, the possibility of a dead space occurring in the central part of the substrate surface where diamond crystal growth does not occur can be reduced.

[0029] Furthermore, the diamond crystal growth apparatus of this embodiment is configured such that a portion of the outer circumference of the trajectory when the substrate is rotated 360° around the pivot axis is included in the diamond crystal growth region, thereby reducing the possibility of dead space occurring in the peripheral area of ​​the substrate surface where diamond crystal growth does not occur.

[0030] In a fourth aspect of the present disclosure, the diamond crystal growth apparatus, in the diamond crystal growth apparatus of the second aspect, may vary in accordance with the rotation of the substrate by the rotating device, in accordance with the rotation of the substrate.

[0031] With this configuration, the diamond crystal growth apparatus of this embodiment can reduce the possibility of dead spaces occurring in the central and peripheral parts of the substrate surface where diamond crystal growth does not occur, compared to when the separation distance is constant, by changing the separation distance.

[0032] Specifically, even if the distance between the rotation axis of the substrate before rotation and the center of the diamond crystal growth region is greater than or equal to half the radius of the substrate, if the relative trajectory of the center of the diamond crystal growth region on the substrate traces a spiral shape such that the distance between them decreases as the substrate rotates, it becomes less likely that a dead space will occur in the center of the substrate surface where diamond crystal growth does not occur.

[0033] Furthermore, even if a portion of the outer circumference of the substrate before rotation is not included in the diamond crystal growth region, if the relative trajectory of the center of the diamond crystal growth region on the substrate traces a spiral shape such that the separation distance increases as the substrate rotates, it becomes less likely that dead space will occur around the surface of the substrate where diamond crystal growth does not occur.

[0034] A diamond crystal growth apparatus according to the fifth aspect of this disclosure is a diamond crystal growth apparatus according to any one of the first to fourth aspects, wherein the raw material gas includes methane gas and hydrogen gas, and the etching gas may also include hydrogen gas.

[0035] A diamond crystal growth method according to a sixth aspect of the present disclosure comprises: a first crystal growth step in which methane gas and hydrogen gas are supplied into a vacuum chamber from a gas supply source to grow diamond crystals in a first region on a substrate directly beneath a plasma ball generated by microwaves transmitted into the vacuum chamber from a microwave source; a substrate moving step in which, after the supply of methane gas into the vacuum chamber is stopped, the substrate is moved by a moving mechanism so that the diamond crystal growth region changes from a first region to a second region on the substrate surface; a cleaning step in which non-diamond components are selectively etched and removed in the second region; and a second crystal growth step in which methane gas is resupplied into the vacuum chamber to grow diamond crystals in the second region.

[0036] Based on the above, the diamond crystal growth method of this embodiment can appropriately reduce the content of non-diamond components in the diamond thin film on which crystals grow on the substrate, while expanding the substrate area on which diamond crystals grow compared to conventional methods. The details of the effects and benefits of the diamond crystal growth method of this embodiment are the same as those of the diamond crystal growth apparatus of the first embodiment, so a detailed explanation is omitted.

[0037] The following describes specific examples of each of the above embodiments of this disclosure with reference to the attached drawings. The specific examples described below are all examples of each of the above embodiments of this disclosure. Therefore, the shapes, numerical values, components, arrangement positions of components, and connection configurations shown below do not limit the scope of the claims unless they are described in the claims.

[0038] Furthermore, among the components described below, those not described in the independent claim representing the highest-level concept of this disclosure will be described as optional components. Also, in the drawings, components with the same reference numeral may not be described. The drawings are schematic representations of each component for ease of understanding, and the shape and dimensional ratios may not be accurately represented.

[0039] Furthermore, in the operation of the apparatus, the order of the processes may be changed as needed, or known processes may be added.

[0040] (First Embodiment) [Device configuration] Figures 1 and 2 show an example of a diamond crystal growth apparatus according to the first embodiment. Note that in Figure 1, "up and down" is taken as shown in the figure. Figure 2 is a plan view of the inside of the vacuum chamber 10 of the diamond crystal growth apparatus 100 of Figure 1, viewed from the top and bottom.

[0041] As shown in Figure 1, the diamond crystal growth apparatus 100 of this embodiment comprises a vacuum chamber 10, a substrate 12, and a table 11.

[0042] The vacuum chamber 10 is a metal container through which microwaves are transmitted from a microwave source and into which raw material gas and etching gas flow from a gas supply source. The vacuum chamber 10 may, for example, have an upper lid and a lower lid and be made of a stainless steel cylinder, but is not limited thereto. The appropriate parts of the vacuum chamber 10 are connected to the gas supply source and the vacuum exhaust system. As a result, the inside of the vacuum chamber 10 is maintained at a desired vacuum pressure (for example, about 2 Pa) when appropriate vacuum processing is performed on the substrate 12.

[0043] The microwave source includes, for example, a microwave power supply and a waveguide connected to a vacuum chamber 10. The microwave frequency can be approximately 2.45 GHz, approximately 915 MHz, etc., but is not limited to these. The waveguide is a metal pipe used for transmitting the microwaves.

[0044] The gas supply source, as an example, includes a methane gas tank, a hydrogen gas tank, gas piping, and a switching valve.

[0045] Here, a mixed gas of methane and hydrogen gas corresponds to an example of the “raw material gas” in this disclosure. Hydrogen gas also corresponds to an example of the “etching gas” in this disclosure. However, these are illustrative examples, and the “raw material gas” and “etching gas” are not limited to these examples.

[0046] When appropriate vacuum processing is performed on the substrate 12, which is made of single-crystal diamond, the valve operation of a switching valve installed at an appropriate location in the gas supply pipe supplies the above mixed gas, which is an example of a "raw material gas," to the vacuum chamber 10 as a reaction gas, and stops the supply of methane gas contained in the raw material gas, so that only hydrogen gas, which is an example of an "etching gas," is supplied to the vacuum chamber 10 as a reaction gas. The switching valve may be an on / off valve such as a solenoid valve installed in a pair of branch pipes that branch off from the main piping connected to the vacuum chamber 10, each of which extends to a methane gas tank and a hydrogen gas tank, respectively.

[0047] Table 11 is a component that holds the substrate 12. Cooling water flows inside table 11. As a result, when appropriate vacuum treatment is performed on the substrate 12, the surface temperature of the substrate is maintained at a predetermined temperature (for example, about 800°C-1000°C).

[0048] In this manner, the diamond crystal growth apparatus 100 of this embodiment generates plasma balls 30 in the vacuum chamber 10 when the reaction gas is dissociated by microwaves transmitted into the vacuum chamber 10. Then, diamond can be grown on a substrate 12 made of single-crystal diamond, but since vacuum film deposition in such a diamond crystal growth apparatus 100 is well known, a detailed explanation will be omitted. At this time, the substrate surface temperature is maintained at the predetermined temperature by the temperature balance between heating of the substrate by the radiant heat of the high-temperature plasma balls 30 and cooling of the substrate by the cooling water flowing through the table 11.

[0049] As shown in Figure 1, the diamond crystal growth apparatus 100 of this embodiment includes a moving mechanism 20.

[0050] The moving mechanism 20 is a device that moves the substrate 12 inside the vacuum chamber 10 relative to the plasma balls 30 generated inside the vacuum chamber 10 by microwaves.

[0051] The moving mechanism 20 can have any configuration as long as it can move the substrate 12 in the vacuum chamber 10 relative to the plasma ball 30.

[0052] As described above, the diamond crystal growth apparatus 100 of this embodiment grows diamond crystals in a first region 30A (see Figure 4A) on the substrate 12 directly beneath the plasma ball, and the diamond crystal growth region (hereinafter referred to as the diamond crystal growth region) on the plane including the substrate surface directly beneath the plasma ball is changed from the first region 30A to a second region on the substrate surface by the moving mechanism 20, and after selective etching and removal of non-diamond components formed in the second region, diamond crystals are grown in the second region.

[0053] In the examples shown in Figures 1 and 2, the moving mechanism 20 includes a rotating device 20A that intermittently rotates the disc-shaped base material 12 at predetermined angles, and the axis of rotation of the base material 12 is offset from the center of the plasma ball 30. The "predetermined angle" is set to an appropriate angle depending on the size of the base material 12. The "predetermined angle" may be, for example, an angle selected from the range of 10° or more and 15° or less.

[0054] In this embodiment of the diamond crystal growth apparatus 100, the central axis 200 extending vertically from the center of the substrate 12 corresponds to the rotation axis of the substrate 12 by the rotation device 20A, and is offset by a predetermined amount with respect to the radial direction of the substrate 12, with respect to a straight line 201 extending downward from the center of the plasma ball 30. The straight line 201 passes through the center of the diamond crystal growth region.

[0055] The amount of deviation between the central axis 200 (rotation axis) and the straight line 201 is preferably set such that a portion of the boundary 50A that demarcates the diamond crystal growth region protrudes outward from the substrate surface, as shown in Figure 2, and the central axis 200 (rotation axis) is located inside the boundary 50A. If the entire boundary were located within the substrate surface region, diamond crystal growth would be difficult on the substrate surface outside the boundary in the direction of the deviation between the central axis 200 (rotation axis) and the straight line 201, and as a result, it may become difficult to grow diamond crystals over the entire surface of the substrate 12. However, the diamond crystal growth apparatus 100 of this embodiment can reduce this possibility by having a portion of the boundary 50A protrude outward from the substrate surface.

[0056] [Operation] Figure 3 is a flowchart illustrating an example of the operation (diamond crystal growth method) of the diamond crystal growth apparatus of the first embodiment. Figures 4A, 4B, 4C, and 4D are diagrams illustrating an example of the operation (diamond crystal growth method) of the diamond crystal growth apparatus of the first embodiment.

[0057] The following description will focus on the case where a mixed gas of methane and hydrogen is supplied to the vacuum chamber 10 as a raw material gas, and hydrogen gas is also supplied to the vacuum chamber 10 as an etching gas.

[0058] Furthermore, the following operations may also be performed, for example, by the control unit's arithmetic circuit (not shown) reading the control program from the control unit's memory circuit. However, it is not necessarily required that the control unit perform the following operations. The operator may perform some of these operations. The following examples will explain the case in which the control unit performs the following operations.

[0059] In the first crystal growth step of step S1, methane gas and hydrogen gas are supplied into the vacuum chamber 10 from a gas supply source, causing diamond crystals to grow in the first region 30A on the substrate 12 directly beneath the plasma ball generated by microwaves transmitted from the microwave source. At this time, the pressure inside the vacuum chamber 10 is maintained at approximately 2 Pa, and the surface temperature of the substrate 12 is maintained at, for example, approximately 800°C-1000°C. The duration of the first crystal growth step may be several tens of hours when the diamond crystal growth rate is approximately 5 μm / H, but is not limited to this.

[0060] Here, in the microwave plasma, the reach of atomic hydrogen and CH radicals generated by the dissociation of methane and hydrogen gases depends on the vacuum pressure in the vacuum chamber 10, but is generally about 10 mm. For this reason, in the outer region of the first region 30A where the surface temperature of the substrate 12 does not reach the predetermined temperature, and in the outer region of the first region 30A where atomic hydrogen and CH radicals cannot reach, non-diamond components 300 such as graphite may precipitate, as shown in Figure 4A.

[0061] Therefore, in the substrate movement process of step S2, after the supply of methane gas from the gas supply source to the vacuum chamber 10 is stopped, the substrate 12 is moved by the movement mechanism 20 so that the diamond crystal growth region changes from the first region 30A to the second region 30B on the substrate surface, as shown in Figure 4B. In other words, the boundary that demarcates the diamond crystal growth region changes from boundary 50A to boundary 50B as the substrate 12 is moved by the movement mechanism 20.

[0062] In this embodiment, the base material 12 is intermittently rotated by the rotating device 20A around the central axis 200 (rotation axis) at predetermined angles. In the example shown in Figure 4B, the base material 12 is rotated counterclockwise by a predetermined angle around the central axis 200 (rotation axis) relative to the state of the base material 12 in Figure 4A. The "determined angle" is set to an appropriate angle depending on the size of the base material 12. The "determined angle" may be, for example, an angle selected from the range of 10° or more and 15° or less. If the "determined angle" is too large, the overlapping area between boundary 50A and boundary 50B will become smaller, which may create a gap between them on the surface of the base material. In that case, it will be difficult for diamond to crystallize on the surface of the base material in such a gap, and as a result, it may become difficult to crystallize diamond over the entire surface of the base material 12. However, the diamond crystal growth apparatus 100 of this embodiment can reduce this possibility by setting the angle at which the base material 12 is intermittently rotated within the above range.

[0063] Next, in the cleaning process of step S3, the non-diamond component 300 is selectively etched away in the second region 30B, as shown in Figure 4C. That is, since hydrogen gas is supplied as the etching gas into the vacuum chamber 10, the non-diamond component 300, such as graphite, present within the boundary 50B can be etched away using hydrogen gas. Furthermore, since the etching rate of the non-diamond component 300 is sufficiently faster than the etching rate of diamond, even when the cleaning process of step S3 is performed, the etching of the diamond thin film on the substrate 12 present within the boundary 50B can be appropriately suppressed by limiting the time of this cleaning process to a short period. The time of the cleaning process may be, for example, several tens of minutes, but is not limited thereto. At this time, the pressure inside the vacuum chamber 10 is maintained at about 2 Pa, and the surface temperature of the substrate 12 is maintained at, for example, about 800°C-1000°C.

[0064] Next, in the second crystal growth step of step S4, methane gas is resupplied into the vacuum chamber 10 from the gas supply source, causing diamond crystal growth in the second region 30B, as shown in Figure 4D. In other words, in the region where the first region 30A and the second region 30B overlap, a diamond thin film is formed, comprising a lower layer formed by diamond crystal growth in the first crystal growth step of step S1 and an upper layer formed by diamond crystal growth in the second crystal growth step of step S4. At this time, similar to step S1, non-diamond components 300 such as graphite may precipitate in the outer region of the second region 30B, including on the first region 30A where diamond crystal growth occurred in step S1.

[0065] Subsequently, after the supply of methane gas from the gas supply source to the vacuum chamber 10 is stopped, the substrate 12 is rotated counterclockwise by a predetermined angle around the central axis 200 (rotation axis) by the rotating device 20A, thereby changing the diamond crystal growth region on the substrate surface from the second region 30B to the next region, and the same cleaning and crystal growth processes as described above are re-executed for the next region. In other words, in this case, the "second region 30B" corresponds to the "first region" of this disclosure, and the "next region" corresponds to the "second region" of this disclosure.

[0066] By repeating this operation, the diamond crystal growth apparatus 100 of this embodiment can form a diamond thin film of a desired thickness (for example, about 300 μm) on the substrate 12.

[0067] The above is merely an example and is not limited to this example. For instance, the thickness of the diamond thin film can be set to an appropriate value according to the specifications of the product manufactured by the diamond crystal growth apparatus 100.

[0068] As described above, the diamond crystal growth apparatus 100 and diamond crystal growth method of this embodiment can appropriately reduce the content of non-diamond components 300 in the diamond thin film crystallized on the substrate 12, while expanding the substrate area on which diamond crystals grow compared to conventional methods.

[0069] Specifically, the diamond crystal growth apparatus 100 and diamond crystal growth method of this embodiment change the diamond crystal growth region on the substrate surface from a first region 30A to a second region 30B using the moving mechanism 20, thereby enabling diamond crystal growth in both the first region 30A and the second region 30B. This expands the substrate area on which diamond crystal growth is possible compared to when the substrate is not moved by the moving mechanism 20.

[0070] Here, it is known that non-diamond components 300, such as graphite, can be etched away using etching gases such as hydrogen gas, and experimental results have been reported showing that the etching rate of non-diamond components 300 is about 40 to 50 times faster than the etching rate of diamond.

[0071] As a result, in the diamond crystal growth apparatus 100 and diamond crystal growth method of this embodiment, when the diamond crystal growth region is changed from the first region 30A to the second region 30B on the substrate surface by the moving mechanism 20, the non-diamond component 300 formed in the second region 30B can be selectively removed with etching gas. Therefore, compared to when such etching treatment is not performed, the deterioration of the quality of the diamond thin film due to the inclusion of non-diamond components in the diamond thin film can be suppressed in the second region 30B.

[0072] Furthermore, in this embodiment, the diamond crystal growth apparatus 100 and diamond crystal growth method rotate the substrate 12 by a rotating device 20A while the central axis 200 (rotation axis) of the disc-shaped substrate 12 is offset from the center of the plasma ball 30. As a result, the trajectory of the center of the diamond crystal growth region moves along the periphery of the substrate 12, allowing for efficient diamond crystal growth across the entire surface of the substrate. Details will be described in the second embodiment.

[0073] (Second Embodiment) Figure 5 shows an example of a diamond crystal growth apparatus according to the second embodiment.

[0074] The diamond crystal growth apparatus 100 and diamond crystal growth method of this embodiment are the same as the diamond crystal growth apparatus 100 and diamond crystal growth method of the first embodiment, except that the central axis 200 (rotation axis) of the substrate 12 and a part of the outer circumference of the trajectory when the substrate 12 is rotated around the rotation axis are included in the diamond crystal growth region.

[0075] If the distance L between the central axis 200 (rotation axis) of the substrate 12 and the center of the diamond crystal growth region is 1 / 2 or more of the radius of the substrate 12, then if the diameter of the diamond crystal growth region is approximately the radius of the substrate 12, even if the substrate 12 is rotated 360°, there is a possibility that a dead space will occur in the central part of the substrate surface where diamond crystal growth does not occur. Also, if the distance L is less than 1 / 2 of the radius of the substrate 12, then if the diameter of the diamond crystal growth region is approximately the radius of the substrate 12, even if the substrate 12 is rotated 360°, there is a possibility that a dead space will occur in the peripheral part of the substrate surface where diamond crystal growth does not occur.

[0076] Therefore, the diamond crystal growth apparatus 100 and diamond crystal growth method of this embodiment are configured such that the central axis 200 (rotation axis) of the substrate 12 is included in the diamond crystal growth region, thereby reducing the possibility of a dead space occurring in the central part of the substrate surface where diamond crystal growth does not occur.

[0077] Furthermore, the diamond crystal growth apparatus 100 and diamond crystal growth method of this embodiment are configured such that a portion of the outer circumference of the trajectory when the substrate 12 is rotated 360° around the pivot axis is included in the diamond crystal growth region, thereby reducing the possibility of dead space occurring in the peripheral area of ​​the substrate surface where diamond crystal growth does not occur.

[0078] The diamond crystal growth apparatus 100 and diamond crystal growth method of this embodiment may be the same as those of the first embodiment, except for the features described above.

[0079] (modified version) The diamond crystal growth apparatus 100 and diamond crystal growth method of this modified example are the same as the diamond crystal growth apparatus 100 and diamond crystal growth method of the first embodiment, except that the separation distance L changes in accordance with the rotation of the substrate 12 by the rotating device 20A.

[0080] As an example, the relative trajectory of the center 150 of the diamond crystal growth region on the substrate 12 may trace a spiral shape such that the separation distance L changes as the rotation of the substrate 12 progresses. The diamond crystal growth apparatus 100 may have a horizontal movement mechanism that allows the central axis 200 (rotation axis) of the substrate 12 to move in a direction perpendicular to the coaxial axis as a means of changing the separation distance L. The horizontal movement mechanism may be added to the movement mechanism 20.

[0081] As described above, the diamond crystal growth apparatus 100 and diamond crystal growth method of this modified example can reduce the possibility of dead spaces occurring in the central and peripheral parts of the substrate surface where diamond crystal growth does not occur, compared to the case where the separation distance L is constant, by changing the separation distance L.

[0082] Specifically, even if the central axis 200 (rotation axis) of the substrate 12 before rotation is not included in the diamond crystal growth region, if the relative trajectory of the center 150 of the diamond crystal growth region on the substrate 12 traces a spiral shape such that the separation distance L decreases as the rotation of the substrate 12 progresses, the rotation axis of the substrate 12 can be included in the diamond crystal growth region as the substrate 12 rotates, thus making it less likely for a dead space to occur in the center of the substrate surface where diamond crystal growth does not occur.

[0083] Furthermore, even if the diamond crystal growth region does not protrude from the surface of the substrate 12 before rotation, if the relative trajectory of the center 150 of the diamond crystal growth region on the substrate 12 traces a spiral shape such that the separation distance L increases as the rotation of the central axis 200 (rotation axis) of the substrate 12 progresses, the diamond crystal growth region can ultimately be made to protrude from the surface of the substrate 12, and dead space where diamond crystal growth does not occur in the peripheral area of ​​the substrate surface becomes less likely.

[0084] In other words, even if the diameter of the diamond crystal growth region is less than or equal to the substrate radius, diamond crystals can be grown across the entire surface of the substrate.

[0085] Furthermore, the diamond crystal growth apparatus 100 of this modified example is equipped with a horizontal movement mechanism, which allows for easier changes in the separation distance L compared to a case where such a horizontal movement mechanism is not provided. In other words, since controlling the generation position of the plasma balls 30 is difficult, in this modified example, the separation distance L can be easily changed mechanically using the horizontal movement mechanism.

[0086] The diamond crystal growth apparatus 100 and diamond crystal growth method of this modified example may be the same as those of the first or second embodiment, except for the features described above.

[0087] The first embodiment, the second embodiment, and the modifications of the second embodiment may be combined with each other, provided that they do not exclude one another. Many improvements and other embodiments of the disclosure will be apparent to those skilled in the art from the above description. Therefore, the above description should be interpreted as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the disclosure. The details of its structure and / or function can be substantially modified without departing from the spirit of the disclosure. [Industrial applicability]

[0088] One aspect of this disclosure can be used in a diamond crystal growth apparatus and a diamond crystal growth method that can increase the substrate area on which diamond crystals grow compared to conventional methods, while appropriately reducing the content of non-diamond components in a diamond thin film on which crystals grow on a substrate. [Explanation of Symbols]

[0089] 10: Vacuum chamber 11: Table 12: Base material 20: Movement mechanism 20A: Rotating device 30: Plasma Ball 30A: 1st area 30B:Second area 50A: Boundary 50B: Boundary 100: Diamond crystal growth apparatus 150: Center 200: Central axis (rotation axis) 300: Non-diamond component L: Separation distance

Claims

1. A vacuum chamber through which microwaves are transmitted by a microwave source, and into which raw material gas and etching gas flow from a gas supply source, A moving mechanism for moving a substrate in the vacuum chamber relative to the plasma balls in the vacuum chamber generated by the microwaves, Equipped with, Diamond is grown as a crystal in a first region on the substrate surface directly beneath the plasma ball. The diamond crystal growth region in the plane including the substrate surface directly beneath the plasma ball is changed from a first region to a second region on the substrate surface by the moving mechanism. A diamond crystal growth apparatus for selectively etching away non-diamond components formed in the second region and then growing diamond crystals in the second region.

2. The diamond crystal growth apparatus according to claim 1, wherein the moving mechanism includes a rotating device that intermittently rotates the disc-shaped substrate at predetermined angles, and the axis of rotation of the substrate is offset from the central part of the plasma ball.

3. The diamond crystal growth apparatus according to claim 2, wherein the pivot axis of the substrate and a portion of the outer circumference of the trajectory when the substrate is rotated around the pivot axis are included in the diamond crystal growth region.

4. The diamond crystal growth apparatus according to claim 2, wherein the distance between the pivot axis of the substrate and the center of the diamond crystal growth region changes in accordance with the rotation of the substrate by the pivoting device.

5. The diamond crystal growth apparatus according to any one of claims 1 to 4, wherein the raw material gas comprises methane gas and hydrogen gas, and the etching gas comprises hydrogen gas.

6. The process involves supplying methane gas and hydrogen gas from a gas supply source into a vacuum chamber, thereby growing diamond crystals in a first region on the substrate surface directly beneath a plasma ball generated by microwaves transmitted from a microwave source into the vacuum chamber, and After the supply of methane gas into the vacuum chamber is stopped, a substrate moving step is performed in which the substrate is moved by a moving mechanism so that the diamond crystal growth region on the plane including the substrate surface directly below the plasma ball changes from the first region to the second region on the substrate surface, In the second region, a cleaning process is performed to selectively etch away non-diamond components, The second crystal growth step involves resupplying methane gas into the vacuum chamber to grow diamond crystals in the second region, A diamond crystal growth method comprising the following features.

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