Diamond substrate manufacturing method

Abstract

A novel diamond substrate having a {100} main surface is manufactured from a single crystal diamond having a {100} main surface. The present invention is provided with: a step for pre-processing a first starting point (42a) and a second starting point (42b), which are respectively set on a first crystal surface (11a) and a second crystal surface (11b), in which a wedge-shaped structure (12) having a tip that tapers toward a main surface (10a) is formed inside a single crystal diamond block (10), within crystal surfaces constituting a {111} surface; and a step for forming a first scanning line (41a) and a second scanning line (41b) based on a machining mark from a first starting point (42a) and a second starting point (42b) on the first crystal face (11a) and the second crystal face (11b) toward the main surface (10a), respectively, by condensing the laser light (B) by a laser light condensing unit (190), the first scanning line (41a) and the second scanning line (41b) being connected at the tip of the wedge-shaped structure (12) to constitute a scanning line unit (41).

Description

Technical Field

[0001] This invention relates to a method for manufacturing diamond substrates, and more specifically, to a method for manufacturing diamond substrates using laser processing of single-crystal diamond. Background Technology

[0002] Previously, silicon carbide (SiC) and gallium nitride (GaN) have been offered as semiconductor materials suitable for power devices to replace silicon (Si). However, compared with these semiconductor materials, diamond semiconductors have higher edge breakdown electric field and power control index, as well as the highest thermal conductivity. Therefore, it has attracted attention as a next-generation material and is being researched and developed for practical application. In addition, the nitrogen-hole centers (NV centers) in diamond can perform high-sensitivity magnetic detection at room temperature, so it is expected to be used in magnetic sensors, and this research has also been carried out (see Patent Document 1).

[0003] Single-crystal diamonds intended for use in these semiconductors are expected to be synthesized via high-temperature, high-pressure (HPHT) methods and homoepitaxial growth. However, these methods make it difficult to achieve large-area production of bulk substrates for single-crystal diamonds used in semiconductor processes. Therefore, vapor-phase (CVD) synthesis, which uses single-crystal magnesium oxide (MgO) as the substrate crystal for heteroepitaxial growth of single-crystal diamonds, has been adopted due to its advantages in large-area production.

[0004] Diamond substrates are manufactured by using a wire saw with diamond abrasive grains to cut diamond single crystal ingots or further cut ingots into blocks of a certain length and thickness. Since the metal wire of the wire saw has a diameter of, for example, at least tens of μm, a portion along a certain width of the cut surface is lost as a cutting allowance during the grinding process when slicing diamond single crystal ingots or blocks into diamond substrates.

[0005] In addition, a method for manufacturing a diamond substrate using a laser to produce a diamond substrate from a diamond ingot is disclosed (see Patent Document 2). In this method, a laser is focused and irradiated from the main surface of the diamond ingot to a predetermined depth, and scanned in a two-dimensional manner to form a modified layer with a modified crystal structure. The diamond substrate is then peeled off using this modified layer.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2015-59069

[0009] Patent Document 2: Japanese Patent Application Publication No. 2020-50563 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] Diamond single crystals have the property of easily cleaving along the {111} plane. If a diamond ingot or block with the {100} plane as the main surface is scanned with a two-dimensional laser, the modified layer will advance along the {111} plane, which is the cleavage plane. Cleavage is more likely to occur on the {111} plane than on the {100} plane. Therefore, it is difficult to manufacture the desired diamond substrate with the {100} plane as the main surface.

[0012] The present invention is proposed in view of the above-mentioned actual situation, and its purpose is to provide a method for manufacturing a single crystal diamond substrate with a main surface {100} facet from single crystal diamond with a main surface {100} facet.

[0013] Methods for solving problems

[0014] To address the aforementioned issues, the diamond substrate manufacturing method of this application includes: a step of arranging a laser focusing section for focusing laser light in a manner facing the main surface {100} of a single-crystal diamond block; a step of focusing laser light using the laser focusing section and pre-processing a first starting point and a second starting point respectively set on a first crystal plane and a second crystal plane forming a wedge-shaped structure with a front end thinning towards the main surface within the crystal plane constituting the {111} plane; and a step of focusing laser light using the laser focusing section and forming a first scan line and a second scan line based on processing marks from the first starting point and the second starting point towards the main surface in the first crystal plane and the second crystal plane respectively, wherein the first scan line and the second scan line are connected at the front end of the wedge-shaped structure to form a scan line unit.

[0015] The process of forming the first scan line and the aforementioned second scan line may include the process of forming a modified layer, which includes the processing marks of thermally decomposing diamond into graphitized material and the cleavage of the {111} surface around them.

[0016] Pre-processing can be a process that forms processing marks at a first starting point and a second starting point. Pre-processing can also be a process that forms a first pre-scan line and a second pre-scan line based on the processing marks at a first crystal plane and a second crystal plane, respectively, from the first starting point and the second starting point to the front end of the wedge structure.

[0017] The first and second starting points can be formed at the same depth from the main surface. The scan line unit can also be formed by an isosceles triangle with the line segment connecting the first and second starting points as the base and the first and second scan lines as the hypotenuses.

[0018] It may further include: focusing the laser beam through a laser focusing section; performing additional preliminary processing on other first crystal planes and other second crystal planes that are parallel to the first crystal plane and the second crystal plane respectively and form other wedge-shaped structures with their front ends thinning towards the main surface inside the single crystal diamond block; and performing additional preliminary processing on other first starting points in other first crystal planes that replace the second starting points and other second starting points set on other second crystal planes; and focusing the laser beam through a laser focusing section; forming other first scan lines and other second scan lines based on processing marks from other first starting points and other second starting points towards the main surface in other first crystal planes and other second crystal planes respectively; and connecting the front ends of other wedge-shaped structures to form other scan line units.

[0019] The process of forming other first scan lines and other second scan lines may include the process of forming a modified layer comprising the processing marks of diamond thermally decomposed and graphitized and the cleavage of the {111} surface around them.

[0020] Other preliminary processing can also be processing that forms processing marks at other first starting points and other second starting points. Other preliminary processing can also be processing that forms other first preliminary scan lines and other second preliminary scan lines based on processing marks at other first crystal planes and other second crystal planes, respectively, from other first starting points and other second starting points to the front end of other wedge structures.

[0021] It may further include a process of replacing other scan line units with scan line units. It may further include the following processes: by repeatedly performing the process of replacing other scan line units with scan line units, the process of replacing the second starting point with other first starting points and forming other second starting points, and the process of forming other first scan lines and other second scan lines from other first starting points and other second starting points to constitute other scan line units, thereby splicing scan line units to form a scan line.

[0022] It can further include a process of forming multiple scan lines in a parallel manner inside the single-crystal diamond block. The first and second scan lines constituting the scan line unit can be formed on a common crystal plane with the first and second scan lines constituting adjacent scan line units.

[0023] Alternatively, the cleavage of the {111} plane formed around the graphitized processing marks of the modified layer formed on each scan line also progresses between adjacent scan lines, forming a modified layer extending along the {100} plane parallel to the main surface. It may further include a process of dividing the single-crystal diamond block within the modified layer along the cleavage of the {111} plane that progresses between the processing marks.

[0024] Invention Effects

[0025] According to the present invention, a {100} substrate can be fabricated with minimal processing loss from a bulk crystal of single-crystal diamond with {100} as the main surface and a single-crystal diamond ingot or block obtained by the HTHP method, thereby improving the yield when manufacturing diamond substrates. Attached Figure Description

[0026] Figure 1 It is a three-dimensional view showing the general structure of the processing device.

[0027] Figure 2A This is a schematic diagram illustrating the {111} plane of a single-crystal diamond (100) plane.

[0028] Figure 2B This is a schematic diagram illustrating the {111} plane of a single-crystal diamond (100) plane.

[0029] Figure 3A This is a schematic diagram illustrating the crystal orientation along the {111} plane of a single-crystal diamond toward the main surface.

[0030] Figure 3B This is a schematic diagram illustrating the crystal orientation along the {111} plane of a single-crystal diamond toward the main surface.

[0031] Figure 4 This is a cross-sectional view illustrating the scan line unit.

[0032] Figure 5A It is a cross-sectional view illustrating the formation of scan line units.

[0033] Figure 5B It is a cross-sectional view illustrating the formation of scan line units.

[0034] Figure 5C It is a cross-sectional view illustrating the formation of scan line units.

[0035] Figure 5D It is a cross-sectional view illustrating the formation of scan line units.

[0036] Figure 6A It is a cross-sectional view illustrating the formation of the scan lines.

[0037] Figure 6B It is a cross-sectional view illustrating the formation of the scan lines.

[0038] Figure 6C It is a cross-sectional view illustrating the formation of the scan lines.

[0039] Figure 6D It is a cross-sectional view illustrating the formation of the scan lines.

[0040] Figure 7 This is a three-dimensional diagram showing the formation of the modified layer.

[0041] Figure 8 This is a cross-sectional view showing the modified layer.

[0042] Figure 9A This is a diagram showing the scan lines formed by the laser scanning method according to the implementation method.

[0043] Figure 9B This is a diagram showing the scan lines formed by the laser scanning method according to the implementation method.

[0044] Figure 9C This is a diagram showing the scan lines formed by the laser scanning method according to the implementation method.

[0045] Figure 10A This is a three-dimensional diagram illustrating a modified laser scanning method.

[0046] Figure 10B This is a three-dimensional diagram illustrating a modified laser scanning method.

[0047] Figure 11 It is a photograph showing the scan lines formed by a modified laser scanning method.

[0048] Figure 12A It is a photograph of a block processed using a modified laser scanning method.

[0049] Figure 12B It is a photograph of a block processed using a modified laser scanning method.

[0050] Figure 13A It is a photograph showing the surface segmented from a block processed by a modified laser scanning method through peeling.

[0051] Figure 13B It is a photograph showing the surface segmented from a block processed by a modified laser scanning method through peeling.

[0052] Figure 14A This is a schematic diagram illustrating the laser scanning method used in the experimental example.

[0053] Figure 14B This is a schematic diagram illustrating the laser scanning method used in the experimental example.

[0054] Figure 14C This is a schematic diagram illustrating the laser scanning method used in the experimental example.

[0055] Figure 14D This is a schematic diagram illustrating the laser scanning method used in the experimental example.

[0056] Figure 15 This is a photograph showing the machining marks formed according to the scanning method shown in Figure 14.

[0057] Figure 16This is a photograph showing the machining marks formed according to the scanning method shown in Figure 14.

[0058] Figure 17A This is a photograph showing the machining marks formed according to the scanning method shown in Figure 14.

[0059] Figure 17B This is a photograph showing the machining marks formed according to the scanning method shown in Figure 14.

[0060] Figure 17C This is a photograph showing the machining marks formed according to the scanning method shown in Figure 14.

[0061] Figure 18 This is a schematic diagram illustrating the laser scanning method of the comparative example.

[0062] Figure 19A This is a diagram showing the scan lines formed using the laser scanning method of the comparative example.

[0063] Figure 19B This is a diagram showing the scan lines formed using the laser scanning method of the comparative example. Detailed Implementation

[0064] Next, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description of the drawings, the same or similar parts will be labeled with the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between thickness and planar dimensions, the ratio of thickness of each layer, etc., differs from reality. Therefore, specific thicknesses and dimensions should be determined by referring to the following description. Furthermore, the drawings also include parts where the dimensional relationships and ratios differ from each other.

[0065] Furthermore, the embodiments shown below illustrate apparatus and methods for embodying the technical concept of the present invention. The embodiments of the present invention do not limit the materials, shapes, structures, and arrangements of the constituent components to the following content. Various modifications can be made to the embodiments of the present invention as described in the claims.

[0066] Figure 1 This is a perspective view showing the schematic structure of the processing apparatus 100. The processing apparatus 100 includes a worktable 110 for holding a block 10 of single-crystal diamond, a worktable support 120 for supporting the worktable 110 in a manner that allows it to move in the XY direction within a horizontal plane, and a fixing member 130 for fixing the block 10 of single-crystal diamond. The fixing member 130 may be an adhesive layer, a mechanical chuck, an electrostatic chuck, a vacuum chuck, etc.

[0067] On the worktable 110, a plate-shaped block 10, cut from a single-crystal diamond ingot to a predetermined length and having a rectangular outer perimeter, is fixed with the (100) surface, whose offset angle is 0°, as the main surface 10a. In this embodiment, the (100) surface is described as an example of the {100} surface, but it can be applied similarly to other surfaces included in the {100} surface. Furthermore, the shape of the object being processed is not limited to this; similarly, as long as the main surface 10a is set as the (100) surface, it can be, for example, a single-crystal diamond ingot or a disk-shaped wafer, or a block-shaped single-crystal diamond crystal.

[0068] In addition, the processing apparatus 100 has a laser source 160 that generates pulsed laser and a laser focusing section 190 that includes an objective lens 170 and an aberration adjustment section 180, so that the laser B emitted from the laser source 160 is directed through the laser focusing section 190 toward the (100) surface of the main surface 10a of the block 10 of single crystal diamond.

[0069] Figure 2 is a schematic diagram illustrating the configuration of the {111} plane when observing the crystal structure of a block 10 of single-crystal diamond with the (100) plane as the main surface from the main surface 10a of the upper surface. Figure 2A This is a top view of block 10 of single-crystal diamond. Figure 2B It is Figure 2A A cross-sectional view of block 10 of single-crystal diamond, cut along cutting line IIB-IIB. The orientations of

[110] and [01-1] are also shown in the figure. Figure 2A As shown, there are four {111} faces on the square pyramid with face (100) as its base: (111), (1-11), (1-1-1), and (11-1). Furthermore, as... Figure 2B As shown, the {111} plane has an angle of 55° relative to the (100) plane. It should be noted that there are limitations on the text that can be used in this specification; therefore, for convenience, the upper line above the number in the Miller index display is replaced with a minus sign "-" before the number. The same applies below.

[0070] Here, in a diamond crystal, carbon atoms are covalently bonded to adjacent carbon atoms at the arms of sp3 hybrid orbitals extending along the four vertices of a tetrahedron centered on the carbon atom. These covalently bonded carbon atoms form a body-centered cubic lattice known as the diamond structure. In the diamond structure, carbon atoms form covalent bonds with adjacent tetragonal carbon atoms, hence single-crystal diamond is known to be very hard. However, carbon atoms in… <111> In this direction, it covalently bonds with an adjacent carbon atom only through one arm of its sp3 hybrid orbital. Therefore, in relation to... <111> In the direction of the orthogonal {111} plane, it is relatively easy to cut off the covalent bond of only one arm, and the {111} plane becomes the cleavage plane.

[0071] Figure 3 is a schematic diagram illustrating the crystal orientation of a single-crystal diamond {111} plane toward the main surface along the (100) plane. Figure 3A This is a top view of block 10 of single-crystal diamond. Figure 3B It is Figure 3A A cross-sectional view of block 10 of single-crystal diamond cut with cutting line IIIB-IIIB. Figure 3A This indicates the crystal orientation along the four faces (111), (1-11), (1-1-1), and (11-1) toward the base of the pyramid, i.e., toward the main surface 10a of the single-crystal diamond block 10 with a deviation angle of 0°. The diagrams illustrate the [2-1-1] direction along the (111) face, the [21-1] direction along the (1-11) face, the

[211] direction along the (1-1-1) face, and the [2-11] direction along the (11-1) face. That is, as shown... Figure 3B As shown, the crystal orientation of the surface of block 10, which faces the single-crystal diamond along the {111} plane, is... <211> When organized and represented, it is shown in Table 1.

[0072] [Table 1]

[0073]

[0074] Figure 4This is a cross-sectional view illustrating the scan line unit. According to the laser B scanning method of this embodiment, the scan line formed by the laser B irradiating the single-crystal diamond block 10 from the laser focusing section 190 is composed of scan line units 41. For scan line unit 41, inside the block 10 of single crystal diamond, for the (1-11) plane of the first crystal plane 11a and the (11-1) plane of the second crystal plane 11b of the wedge structure 12 formed at a first depth D1 from the main surface 10a, the (100) plane of the wedge structure 12 with the front end thinning towards the main surface 10a and the front end extending in the

[011] direction, a first scan line 41a is formed in the first crystal plane 11a from a first starting point 42a based on the processing mark formed at a second depth D2 from the main surface 10a toward the main surface 10a in the [21-1] direction, and a second scan line 41b is formed in the second crystal plane 11b from a second starting point 42b based on the processing mark formed at a second depth D2 from the main surface 10a toward the main surface 10a in the [2-11] direction, and the first scan line 41a and the second scan line 41b are connected at the front end of the wedge structure 12.

[0075] The first starting point 42a and the second starting point 42b are formed prior to the formation of the first scan line 41a and the second scan line 41b, respectively. The first scan line 41a and the second scan line 41b are formed by focusing the laser B onto the pre-formed first starting point 42a and the second starting point 42b while scanning the laser B through a dot pitch DP. The first starting point 42a and the second starting point 42b are processing marks formed at the focusing point by focusing the laser B. These processing marks may not be graphitized, but are preferably graphitized, because even if the output power of the laser B is reduced during the scan line formation process, the focusing effect will be improved. In this embodiment, a phase transition of the crystal occurs at the starting point described as the first starting point 42a and the second starting point 42b. During the formation of the scan line described as the first scan line 41a and the second scan line 41b, by focusing the laser B onto the starting point, a graphitized processing mark is easily formed.

[0076] The first scan line 41a and the second scan line 41b form a modified layer containing graphitized processing marks formed at intervals of dot pitch DP and cleavage along the {111} plane, which serves as a cleavage plane, generated around the processing marks due to volume changes based on graphite. It should be noted that the processing marks of the first starting point 42a and the second starting point 42b are formed prior to the first scan line 41a and the second scan line 41b, and are therefore sometimes referred to as being formed by prior processing. Prior processing is a process performed to induce a crystal phase transition in the focusing section. Volume changes are generated through phase transitions, but the purpose of prior processing is to control the energy imparted to the crystal to induce a localized phase transition so that cleavage along unintended crystal orientations does not extend due to the volume change.

[0077] In the scan line unit 41, the first scan line 41a extends in the [21-1] direction, and the second scan line 41b extends in the [2-11] direction. The first scan line 41a and the second scan line 41b connected at the front end of the wedge structure 12 are in the same plane and form the hypotenuse of an isosceles triangle. When the distance P between the first starting point 42a and the second starting point 42b is set as the length of the base, the distance from the second depth D2 to the first depth D1 is set as the height H, and the base angle is set as θ, the isosceles triangle satisfies the following relationship (1). As mentioned above, the base angle θ is 55°.

[0078] [Number 1]

[0079]

[0080] According to the relation (1), the distance P of the starting point is obtained from the height H from the second depth D2 to the first depth D1 and the bottom angle θ. In other words, the second starting point 42b only needs to be formed such that it advances by the distance P of the starting point obtained from the height H and the bottom angle θ in the [01-1] direction of the bottom edge with the first starting point 42a as the reference. Furthermore, in the relation (1), by reducing the height H, the distance between depths D1 and D2 can be reduced, that is, by reducing the processing area, processing loss can be reduced.

[0081] It should be noted that, generally speaking, for the scan line unit 41, inside the block 10 of single-crystal diamond with the {100} plane as the main surface 10a, for the first crystal plane 11a and the second crystal plane 11b of the wedge-shaped structure 12 formed in the crystal plane constituting the {111} plane, a first scan line 41a is formed in the first crystal plane 11a from the processing mark of the first starting point 42a formed at the second depth D2 of the main surface 10a toward the main surface 10a, and a second scan line 41b is formed in the second crystal plane 11b from the processing mark of the second starting point 42b formed at the second depth D2 of the main surface 10a toward the main surface 10a. The first scan line 41a and the second scan line 41b are connected at the front end of the wedge-shaped structure 12. In this case, the first scan line 41a and the second scan line 41b connected at the front end of the wedge structure 12 are also in the same plane, forming the hypotenuse of an isosceles triangle. If the interval between the first starting point 42a and the second starting point 42b, i.e. the distance P between the starting points, is set as the length of the base, and the distance from the second depth D2 to the first depth D1 is set as the height H, and the base angle of the isosceles triangle is set as θ, then the relationship shown in equation (1) is satisfied.

[0082] Figure 5 is a cross-sectional view illustrating the formation of scan line unit 41. For example... Figure 5AAs shown, inside the block 10 of single-crystal diamond, the (1-11) facet of the first crystal facet 11a and the (11-1) facet of the second crystal facet 11b form a wedge-shaped structure 12 that thins towards the (100) facet of the main surface 10a and extends along the

[011] direction. In the first crystal facet 11a, laser B is focused from the laser focusing section 190 to form a first starting point 42a based on the processing mark at a second depth D2 from the main surface 10a.

[0083] like Figure 5B As shown, after the formation of the first starting point 42a, laser B is focused from the laser focusing part 190 in the second crystal plane 11b, forming a second starting point 42b based on the processing mark at a second depth D2 from the main surface 10a. As described above, the first starting point 42a and the second starting point 42b correspond to the vertices of the base of an isosceles triangle with the first scan line 41a and the second scan line 41b as the hypotenuses. Therefore, the second starting point 42b is based on the first starting point 42a and is located at a distance P that advances the starting point in the [01-1] direction orthogonal to the direction extending from the front end of the wedge structure 12. If the distance from the second depth D2 to the first depth D1 is defined as the height H, and the base angle of the isosceles triangle is defined as θ, then the distance P of the starting points is obtained from the relationship shown in equation (1).

[0084] like Figure 5C As shown, after the formation of the second starting point 42b, laser B is irradiated from the laser focusing section 190 in the (1-11) plane of the first crystal plane 11a, forming a first scan line 41a from the first starting point 42a to the front end of the wedge structure 12. By focusing laser B and irradiating the first starting point 42a, a modified layer is formed in the scanning direction of the first scan line 41a. This modified layer includes graphitized processing marks and cleavage along the (1-11) plane around the processing marks.

[0085] Furthermore, such as Figure 5D As shown, in the (11-1) plane of the second crystal plane 11b, laser B is irradiated from the laser focusing part 190, forming a second scan line 41b from the second starting point 42b to the front end of the wedge structure 12. Similarly, a graphitized region and surrounding cleavage are also formed in the second scan line 41b. The first scan line 41a and the second scan line 41b are connected at the front end of the wedge structure 12 to form a scan line unit 41 formed by the connection of the first scan line 41a and the second scan line 41b.

[0086] Here, the connection state refers to the state in which the modified layers constituting the first scan line 41a and the second scan line 41b are connected at the first depth D1. Specifically, in the modified layers of the first scan line 41a and the second scan line 41b, there are any states where the focal points of laser B overlap, the focal points do not overlap but the graphite regions are connected, or the focal points and graphite regions are not connected but the surrounding cleavage is connected. In any of these states, it is necessary to prevent the first scan line 41a and the second scan line 41b from extending from the front end of the wedge structure 12 towards the main surface. This is achieved through optimization of laser processing conditions and high-precision processing position control.

[0087] Typically, when the main surface 10a of the single-crystal diamond block 10 is a {100} plane, laser B is focused by laser focusing section 190. Within the crystal plane constituting the {111} plane, a first crystal plane 11a and a second crystal plane 11b, which are thinner towards the main surface 10a, are formed inside the single-crystal diamond block 10. A first starting point 42a and a second starting point 42b based on machining marks are formed on the first crystal plane 11a and the second crystal plane 11b, respectively. Furthermore, laser B is focused by laser focusing section 190, and a first scan line 41a and a second scan line 41b based on machining marks are formed from the first starting point 42a and the second starting point 42b towards the main surface 10a on the first crystal plane 11a and the second crystal plane 11b, respectively. The first scan line 41a and the second scan line 41b are connected at the front end of the wedge-shaped structure 12 to form a scan line unit 41.

[0088] Figure 6 is a cross-sectional view illustrating the formation of the scan line. In Figure 6, as... Figure 5D As shown, scan lines are formed by splicing other scan line units 41' onto scan line units 41 formed on block 10 of single-crystal diamond.

[0089] like Figure 6A As shown, inside the block 10 of single-crystal diamond, the (1-11) facets of other first crystal faces 11a' and the (11-1) facets of other second crystal faces 11b' are parallel to the (1-11) facets of the first crystal facet 11a and the (11-1) facets of the second crystal facet 11b, respectively, and form other wedge-shaped structures 12' that are thinner at the (100) facet facing the main surface 10a and extend in the

[011] direction. The second starting point 42b is replaced with other first starting points 42a'. Other first crystal faces 11a' are selected by means of other first starting points 42a'.

[0090] like Figure 6BAs shown, after the replacement of the other first starting point 42a', in the other second crystal plane 11b', laser B is focused from the laser focusing part 190 to form another second starting point 42b' based on the processing mark at a second depth d2 from the main surface 10a. The other first starting point 42a' and the other second starting point 42b' correspond to the vertices of the base of the isosceles triangle with the other first scan line 41a' and the other second scan line 41b' as the hypotenuse, as described later. Therefore, the other second starting point 42b' is located at a distance of the starting point spacing P in the [01-1] direction orthogonal to the direction of the front end extension of the other wedge structure 12', with the other first starting point 42a' as the reference. As described above, if the distance from the second depth D2 to the first depth D1 is set as the height H, and the base angle of the isosceles triangle is set as θ, then the starting point spacing P is obtained from the relationship (1).

[0091] like Figure 6C As shown, after the formation of other second starting points 42b', laser B is irradiated from the laser focusing part 190 in the (1-11) plane of other first crystal plane 11a', forming other first scan lines 41a' from the other first starting points 42a' to the front end of other wedge-shaped structures 12'. Furthermore, laser B is irradiated from the laser focusing part 190 in the (11-1) plane of other second crystal plane 11b', forming other second scan lines 41b' from the other second starting points 42b' to the front end of other wedge-shaped structure edges 12'. The other first scan lines 41a' and the other second scan lines 41b' connect at the front end of other wedge-shaped structures 12' to form other scan line units 41' formed by connecting the other first scan lines 41a' and the second scan lines 41b'.

[0092] like Figure 6D As shown, other scan line units 41' are replaced with scan line units 41. Other first starting points 42a', other second starting points 42b', other first scan lines 41a', and other second scan lines 41b' constituting other scan line units 41' are also replaced with first starting point 42a, second starting point 42b, first scan line 41a, and other second scan lines 41b, respectively. Similarly, other first crystal planes 11a', other second crystal planes 11b', and other wedge structures 12' are also replaced with first crystal plane 11a, second crystal plane 11b, and wedge structure 12, respectively.

[0093] And, with Figure 6A Similarly, in the process shown, Figure 6DIn the block 10 of single-crystal diamond, the (1-11) facets of other first crystal faces 11a' and the (11-1) facets of other second crystal faces 11b' are parallel to the (1-11) facets of the first crystal faces 11a and the (11-1) facets of the other second crystal faces 11b, forming other wedge-shaped structures 12' that are thinner at the (100) facets facing the main surface 10a and extend at the front end in the

[011] direction. In the other first crystal faces 11a', the second starting point 42b is replaced with another first starting point 42a'. The other first crystal faces 11a' are selected in such a way as by means of other first starting points 42a'. Then, in the other second crystal faces 11b', laser B is focused from the laser focusing section 190 to form another second starting point 42b' based on the processing mark at a second depth d2 from the main surface 10a. The other second starting point 42b' is located at a distance P from the aforementioned starting point, which is advanced in a [01-1] direction orthogonal to the other wedge-shaped structures 12', based on the other first starting point 42a'. Hereinafter, the above operation is repeated to form other scan line units 41'. Thus, scan lines are formed by splicing other scan line units 41' onto the scan line units 41.

[0094] Typically, when the main surface 10a of the single-crystal diamond block 10 is a {100} plane, for other first crystal planes 11a' and other second crystal planes 11b' that are parallel to the first crystal plane 11a and the second crystal plane 11b respectively and form other wedge-shaped structures 12' that thin towards the main surface 10a, the second starting point 42b is replaced with another first starting point 42a' among the other first crystal planes 11a'. The other first crystal planes 11a' are selected in such a way as by means of the other first starting point 42a'. The laser B is focused by the laser focusing section 190 to form other second starting points 42b' based on the processing marks on the other second crystal planes 11b'. Then, the laser B is focused by the laser focusing section 190 to form other first scan lines 41a' and other second scan lines 41b' based on the processing marks on the other first crystal planes 11a' and other second crystal planes 11b' respectively from the other first starting points 42a' and other second starting points 42b' towards the main surface 10a. Other first scan lines 41a' and other second scan lines 41b' are connected at other edges 12' to form other scan line units 41'. The other scan line units 41' thus formed are replaced with scan line units 41 to form other scan line units 41', thereby splicing scan line units 41 to form scan lines.

[0095] Figure 7 This is a perspective view showing the formation of a modified layer on a block 10 of single-crystal diamond. By forming the modified layer in parallel to the scan lines 40, a modified layer is formed covering the entire surface 10a of the main surface of the block 10 of single-crystal diamond. Figure 7As shown, scan line units 41 are spliced ​​from one end of the single-crystal diamond block 10 toward the other end to form a scan line 40. When the scan line 40 reaches the other end of the block 10, the interval of the line spacing LP is separated from the scan line 40, for example, the position of the irradiating laser B is moved in the

[011] direction extending from the front end of the wedge structure 12, and this time the scan line units 41 are spliced ​​from the other end of the block 10 toward one end to form the scan line 40. By repeating this operation, the scan line 40 is formed from the main surface 10a of the block 10 to the entire surface of the main surface 10a at a predetermined depth.

[0096] Here, in the opposing scan line units 41 of adjacent scan lines 40, each first scan line 41a and second scan line 41b can also be formed on a common crystal plane. For example, the first crystal plane 11a and second crystal plane 11b of the scan line unit 41 constituting a certain scan line 40, which forms the first scan line 41a and the second scan line 41b, can also be common to the other second crystal plane 11b' and other first crystal plane 11a' of the other scan line units 41' opposite to the first scan line 41' in adjacent other scan lines 40'. Here, it is considered that in an adjacent pair of scan lines 40, the traveling directions of the scan line units 41 are opposite. If the crystal planes in adjacent and opposing scan line units 41 are common, then between the modified layers constituting adjacent scan lines 40, cleavage is formed in a manner that progresses across the scan line 40 along the common crystal plane. Cleavage progresses between the modified layers constituting adjacent scan lines 40, thereby forming a modified layer containing cleavage across the entire surface of the main surface 10a of the block.

[0097] Typically, when the main surface 10a of the single-crystal diamond block 10 is a {100} plane, scan line units 41 are spliced ​​from one end of the block 10 toward the other to form a scan line 40. When the scan line 40 reaches the other end of the block 10, the spacing LP is separated from the scan line 40, and the position of the irradiating laser B is moved in a predetermined direction extending towards the front end of the wedge structure 12. This time, scan line units 41 are spliced ​​from the other end of the block 10 toward one end to form a scan line 40. By repeating this operation, a scan line 40 is formed from the main surface 10a of the block 10 to the entire surface of the main surface 10a at a predetermined depth. The cleavage between the modified layers constituting such a scan line 40 progresses, forming a modified layer covering the entire surface of the main surface.

[0098] Figure 8This is a cross-sectional view showing the modified layer formed on block 10 of single-crystal diamond. In block 10, the modified layer, including the machining marks and the cleavage of the {111} facets around them, forms scan lines 40. The cleavage also extends between the modified layers forming adjacent scan lines 40 and connects the modified layers 48. The modified layer 48 extends parallel to the (100) facet of the main surface 10a. Therefore, by peeling and dividing block 10 at the modified layer 48, a substrate thinned to the thickness from the main surface 10a to the modified layer 48 can be fabricated.

[0099] Typically, when the main surface 10a of the single-crystal diamond block 10 is a {100} plane, the modified layer 48 is formed parallel to the {100} plane of the main surface 10a. Therefore, by peeling and dividing the block 10 at the modified layer 48, it is possible to fabricate a substrate thinned to the thickness from the {100} plane of the main surface 10a to the modified layer 48.

[0100] Figure 9 is a diagram showing the scan line 40 formed on the block 10 of single-crystal diamond by the scanning method of laser B according to the embodiment. Figure 9A This is a schematic diagram of the scan line 40 formed in the formed block 10. Figure 9B According to Figure 9A A photograph of scan line 40 formed in block 10.

[0101] The processing conditions are shown in Table 2. First starting point 42a and second starting point 42b are processed first at a second depth D2 (not shown) with a starting point spacing P and a line spacing LP. Next, laser B is scanned from the first starting point 42a and second starting point 42b along the (11-1) and (1-11) surfaces with a point spacing DP to a first depth D1 (not shown), forming a first scan line 41a and a second scan line 41b with a line spacing LP. The scan line units are formed with a starting point spacing P = 140 μm and a height H = 100 μm. Figure 9B In the photograph, regarding the scan line unit 41 constituting the scan line 40, regardless of the first scan line 41a and the second scan line 41b, a modified layer containing graphite-based processing marks and surrounding cleavage is formed along the scan line 40 with approximately the same thickness. It is observed that the cleavage extends between adjacent scan lines 40 and connects the modified layer between the scan lines 40.

[0102] [Table 2]

[0103]

[0104] (Variation example)

[0105] Next, the scanning method of laser B in the modified example will be described. Figure 10 is a perspective view showing the scanning method of laser B in the modified example. In the scanning method of the modified example, as a preliminary processing for the first starting point 42a and the second starting point 42b, [the following is omitted as it is not relevant to the preceding text]. Figure 4The formation of the machining marks shown creates first and second starting points 42a and 42b, respectively, leading to first and second advance scan lines 43a and 43b at the front end of the wedge-shaped structure 12. The first and second advance scan lines 43a and 43b are connected at the edge 12 as described above. In a modified example, the first and second starting points 42a and 42b only serve as the starting points of the first and second advance scan lines 43a and 43b.

[0106] Next, first scan lines 41a and 41b, which overlap with the first leading scan lines 43a and 43b to form up to the front end of the wedge-shaped structure 12, are connected at the front end of the wedge-shaped structure 12 to form scan line unit 41. Here, the dot pitch DP1 of the machining marks forming the first leading scan lines 43a and 43b is larger than the second dot pitch DP2 of the first scan lines 41a and 41b, which is preferable because the presence of the starting point facilitates graphitization.

[0107] Figure 10A This is a perspective view showing the first advance scan line 43a and the second advance scan line 43b formed on the entire surface of the block 10 of single-crystal diamond. Figure 10B This is a perspective view showing the first scan line 41a and the second scan line 41b formed covering the entire surface of the block 10 of single-crystal diamond. As described above, the first scan line 41a and the second scan line 41b are formed overlapping with the first preceding scan line 43a and the second preceding scan line 43b, and are connected at the front end of the wedge-shaped structure 12 to form a scan line unit 41. Figure 10A As shown, the first advance scan line 43a and the second advance scan line 43b can be formed in advance across the entire surface 10a of the main surface of the single-crystal diamond block 10, or they can be formed as scan line units 41 as described in the processes of Figures 5 and 6, and the scan line units 41 are spliced ​​together to form the scan line 40. Furthermore, for the formed scan line units, for example, the first starting point 42a can be continuously formed into a W-shaped cross-section with a dot pitch DP1. In this way, the first advance scan line 43a and the second advance scan line 43b are formed. The formation of the modified layer 48 based on the modified example is the same as in the above embodiment.

[0108] Figure 11 This is a photograph of scan lines 40 formed on a block 10 of single-crystal diamond using a modified laser B scanning method. Figure 11 The image shows the scan line spacing LP of scan line 40 set to 15 μm, with processing conditions as shown in Table 3. Figure 11In the scan line 40, graphite of approximately the same thickness is observed to form along the scan line 40, independent of the first scan line 41a and the second scan line 41b constituting the scan line unit 41. Furthermore, cleavage is observed to extend between the modified layers constituting adjacent scan lines 40, connecting the modified layers.

[0109] [Table 3]

[0110]

[0111] Figure 12 is a photograph of block 10 of single-crystal diamond processed by the scanning method of laser B in the modified example. Figure 12A The graph shows the scan line spacing LP of 40 as shown in Table 3, with the processing conditions set to 15 μm. Figure 12B This is a graph where the line spacing LP of scan line 40 is set to 20 μm under the processing conditions in Table 3. The graph shows a line spacing LP of 15 μm. Figure 12A In the study, it was observed that the entire surface of block 10 was blackened, and a modified layer was formed as cleavage progressed.

[0112] Figure 13 is a photograph showing the facets of block 10 of single-crystal diamond processed by the scanning method of laser B in the modified example, which are separated by peeling. Figure 13A It is to peel off the lower surface. Figure 13B It involves peeling off the upper surface. Then, it involves peeling off the lower surface. Figure 13A and peeling the upper surface Figure 13B In the study, graphite was observed to form along the exfoliation surface.

[0113] As described above, when a two-dimensional scanning laser is used on a diamond ingot or block, a modified layer progresses around the processing marks formed by graphite on the {111} plane, which serves as a cleavage plane, thus forming a modified layer through cleavage on the {111} plane. On the other hand, in order to form processing marks through graphitization, the laser pulse energy needs to be sufficiently increased to about 1W, but it is difficult to control the propagation of cleavage from the graphite region. Furthermore, if the pulse energy is insufficient, graphitization does not occur.

[0114] In this embodiment, a modified layer is formed by cleaving the {111} surface of the graphitization process marks created using a small laser pulse energy. Furthermore, the propagation of the cleavage within the modified layer can be controlled, thus utilizing the starting point of the previous processing. The details are illustrated by the following experimental examples. It should be noted that the processing conditions in this embodiment were obtained using the processing apparatus described in this embodiment; however, appropriate processing conditions can be set according to the specifications of the processing apparatus. In this case, the laser pulse energy must be adjusted appropriately.

[0115] (Experimental Example)

[0116] An experimental example of forming scan line 40 relative to the scanning method of laser B will be described. Figure 14 is a schematic diagram showing the scanning method of laser B in the experimental example.

[0117] exist Figure 14A In the experimental example, similarly to the modified example, in the block 10 of single-crystal diamond, a first advance scan line 43a is formed along the (1-11) plane of the first crystal plane 11a in the [21-1] direction with a dot pitch of 4 μm, and a second advance scan line 43b is formed along the (11-1) plane of the second crystal plane 11b in the [2-11] direction with a dot pitch of 4 μm. After the first advance scan line 43a and the second advance scan line 43b are formed, a first scan line 41a and a second scan line 41b are formed with a dot pitch of 2 μm, overlapping with portions of the first advance scan line 43a and the second advance scan line 43b respectively. It should be noted that in the experimental example, since the formation of the scan line 40 is the focus, it is not required to connect the first advance scan line 43a and the second advance scan line 43b at the front end of the wedge structure 12 as in the embodiment and the modified example.

[0118] exist Figure 14B In the single-crystal diamond block 10, a first scan line 41a is formed along the (1-11) plane of the first crystal plane 11a in the [21-1] direction with a dot pitch of 2 μm without forming a starting point, and a second scan line 41b is formed along the (11-1) plane of the second crystal plane 11b in the [2-11] direction with a dot pitch of 4 μm.

[0119] exist Figure 14C In the recess extending along the [0-1-1] direction formed by the (1-11) plane and the (11-1) plane of the first crystal plane 11a, a reference line 44 is formed with a dot pitch of 2 μm by irradiation with laser B. On the reference line 44, graphitized processing marks are formed by prior processing as a continuous starting point. After the reference line 44 is formed, a first scan line 41a is formed along the (1-11) plane of the first crystal plane 11a in the [21-1] direction with a dot pitch of 4 μm, starting from the reference line 44. Similarly, a first scan line 41a is formed along the (11-1) plane of the second crystal plane 11b in the [2-11] direction with a dot pitch of 4 μm, starting from the reference line 44.

[0120] exist Figure 14DIn the recess extending along the [0-1-1] direction formed by the (1-11) plane of the first crystal plane 11a and the (11-1) plane of the second crystal plane 11b, a reference line 45 is formed with a dot pitch of 4 μm by irradiation with laser B. On the reference line 45, the graphitized processing marks are formed intermittently as the starting point of the prior processing. After the reference line 45 is formed, a first scan line 41a is formed along the (1-11) plane of the first crystal plane 11a in the [21-1] direction with a dot pitch of 4 μm, and a first scan line 41a is formed along the (11-1) plane of the second crystal plane 11b in the [2-11] direction with a dot pitch of 4 μm.

[0121] Figure 15 This is a photograph showing the machining marks on the first scan line 41a of Figure 14. Figure 15 In this context, pa, pb, pc, and pd represent alternating formation according to Figure 14A , Figure 14B , Figure 14C and Figure 14D The machining marks formed by the scanning method of laser B during the formation of the first scan line 41a and the second scan line 41b. Figure 15 In the first scan line 41a and the second scan line 41b, graphitization of the processing marks and the resulting cleavage were observed in the second scan line 41b. In the third scan line 41b, no starting point was formed, therefore the processing marks were not graphitized in the recesses, but graphitization was observed as each scan line elongated. This is believed to be because the formed processing marks began to function as starting points. In the fourth scan line 44, due to graphitization, it effectively functioned as a starting point, and the graphitization of the first scan line 41a and the second scan line 41b and the resulting cleavage progression were observed. In the fifth scan line 41b, with a dot pitch of 4 μm, graphitization of the processing marks and the progression of cleavage were observed when the processing marks overlapped with the focal points of the first scan line 41a and the second scan line 41b.

[0122] Figure 16 This is a photograph showing the machining mark formed when the first scan line 41a is formed according to the laser B scanning method shown in Figure 14. Figure 16 In the first scan line (PA), graphitization and cleavage along the first crystal plane 11a were observed. In the second scan line (PB), no starting point was formed, so graphitization and cleavage along the first scan line were barely observed. In the third scan line (PC), graphitization and cleavage along the first crystal plane 11a were observed. In the fourth scan line (PD), the graphitization and cleavage along the first scan line 41a were observed to be uneven and insufficient. Based on the results of this experimental example, it is confirmed that the starting point of the preceding processing is effective in generating graphitization of processing marks and cleavage extending from the scan line during the processing of the scan line.

[0123] Figure 17 is a photograph comparing the effects of pre-processed methods based on the starting point of the processing mark, using the laser B scanning method shown in Figure 14. Figure 17A In, such as Figure 14D As shown, a first scan line 41 is formed from a reference line 45 with a dot pitch of 4 μm and starting points based on machining marks. Graphitization and cleavage are observed in the first scan line 41a of pd1 formed from the starting point, but sufficient graphitization or cleavage is not observed in the first scan line 41a of pd2 formed between the starting points. Figure 17B In, with Figure 17A Similarly, as Figure 14D As shown, a first scan line 41a and a second scan line 41b are formed from a reference line 45 with a dot pitch of 4 μm, based on the starting point of the machining mark. Figure 17A Similarly, graphitization and cleavage were observed in the first scan line 41a and the second scan line 41b of pd1 formed from the starting point, but sufficient graphitization or cleavage was not observed in the first scan line 41a and the second scan line 41b of pd2 formed from between the starting points. Figure 17C In, such as Figure 14B As shown, a first scan line 41a and a second scan line 41b are formed from a baseline where no machining marks have been formed. Sufficient graphitization or cleavage was not observed in the first scan line 41a and the second scan line 41b. Based on these... Figures 17A-17C The experimental results show that if the scan line is formed from the starting point based on the processing mark, sufficient graphitization and cleavage can be obtained, but if the scan line is not formed from the starting point based on the processing mark, sufficient graphitization or cleavage cannot be obtained.

[0124] (Comparative example)

[0125] As a comparative example, a scanning method for laser B that does not perform preprocessing on the first starting point 42a and the second starting point 42b will be described. Figure 18 This is a schematic diagram illustrating the scanning method of laser B in the comparative example. In the comparative example, neither the first starting point 42a and the second starting point 42b based on the machining mark are formed, nor are the first advance scan line 43a and the second advance scan line 43b originating from the first starting point 42a and the second starting point 42b. The comparative example is the same as the scanning method of laser B in the embodiment, except that advance machining is not performed.

[0126] Figure 19 is a diagram showing the scan line 40 formed on the block 10 of single-crystal diamond by the scanning method of laser B in the comparative example. Figure 19A This is a schematic diagram of scan line 40 formed in block 10. Figure 19B According to Figure 19A An image of scan line 40 formed on block 10. Scan line 40 is composed of first scan line 41a and second scan line 41b.

[0127] The processing conditions are shown in Table 4. Figure 19A In the image, laser B scans along the direction of the arrow, and the first scan line 41a, indicated by the thin arrow, is formed before the second scan line 41b, indicated by the thick arrow. For example, in L1, the second scan line 41b with the (11-1) plane is formed after the first scan line 41a with the (1-11) plane. Scan line 40 is formed from the aforementioned second depth D2 to a depth of H = 15 μm. In the photograph 19B, graphite and cleavage extending outwards are observed in the scan line unit 41 constituting scan line 40 in the subsequently processed second scan line 41b. On the other hand, in the first scan line 41a, which is processed earlier, the progress of graphitization and cleavage is insufficient. This is because a processing mark exists at the starting point of the second scan line 41b at the second depth D2, whereas no processing mark exists at the starting point in the first scan line 41a, which is processed earlier.

[0128] [Table 4]

[0129]

[0130] The embodiments and experimental examples have been described above, but these embodiments and experimental examples are merely illustrative of the technical concept of the present invention, and the scope of the invention is not intended to be limited thereto. These embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention.

[0131] This application claims priority based on Japanese Patent Application No. 2023-121832, filed on July 26, 2023, the entire contents of which are incorporated herein by reference.

[0132] Explanation of reference numerals in the attached figures

[0133] 10: Block, 10a: Main surface, 40: Scan line, 41: Scan line unit, 41a: First scan line, 41b: Second scan line, 42a: First starting point, 42b: Second starting point, 43a: First advance scan line, 43b: Second advance scan line, 44, 45: Reference lines, 100: Processing device, 190: Laser focusing section.

Claims

1. A method for manufacturing a diamond substrate, comprising: A process of arranging a laser focusing part to focus the laser in a manner that faces the main surface {100} of the single-crystal diamond block; The laser is focused by the laser focusing part, and a process is performed in the crystal plane that constitutes the {111} plane, for the first starting point and the second starting point respectively set on the first crystal plane and the second crystal plane that form a wedge-shaped structure with the front end thinning towards the main surface inside the single crystal diamond block. as well as The laser is focused by the laser focusing part, and a first scan line and a second scan line based on the processing mark are formed on the first crystal plane and the second crystal plane respectively from the first starting point and the second starting point toward the main surface. The first scan line and the second scan line are connected at the front end of the wedge-shaped structure to form a scan line unit.

2. The method for manufacturing a diamond substrate according to claim 1, wherein, The process of forming the first scan line and the second scan line includes the process of forming a modified layer, the modified layer comprising the processing marks of diamond thermally decomposed and graphitized and the cleavage of the {111} surface around them.

3. The method for manufacturing a diamond substrate according to claim 1 or 2, wherein, The preliminary processing refers to the processing that forms processing marks at the first starting point and the second starting point.

4. The method for manufacturing a diamond substrate according to claim 1 or 2, wherein, The preliminary processing involves forming a first preliminary scan line and a second preliminary scan line based on the processing mark in the first crystal plane and the second crystal plane, respectively, from the first starting point and the second starting point to the front end of the wedge structure.

5. The method for manufacturing a diamond substrate according to claim 1 or 2, wherein, The first starting point and the second starting point are formed at the same depth from the main surface.

6. The method for manufacturing a diamond substrate according to claim 5, wherein, The scan line unit is formed by an isosceles triangle with the line segment connecting the first starting point and the second starting point as the base and the first scan line and the second scan line as the hypotenuse.

7. The method for manufacturing a diamond substrate according to claim 1, further comprising: The laser is focused by the laser focusing part. For other first crystal planes and other second crystal planes that are parallel to the first crystal plane and the second crystal plane respectively and form other wedge-shaped structures with their front ends thinning towards the main surface inside the single crystal diamond block, other first starting points in the other first crystal planes that replace the second starting point and other second starting points set on the other second crystal planes are subjected to other preliminary processing steps. as well as The process involves focusing the laser beam through the laser focusing section, forming other first scan lines and other second scan lines based on machining marks from the other first starting point and the other second starting point toward the main surface on the other first crystal plane and the other second crystal plane, respectively, and connecting the other first scan lines and the other second scan lines at the front end of the other wedge structure to form other scan line units.

8. The method for manufacturing a diamond substrate according to claim 7, wherein, The process of forming the other first scan lines and the other second scan lines includes the process of forming a modified layer, the modified layer comprising the processing marks of diamond thermally decomposed and graphitized and the cleavage of the {111} surface around them.

9. The method for manufacturing a diamond substrate according to claim 7 or 8, wherein, The other preliminary processing refers to the processing that forms processing marks at the other first starting point and the other second starting point.

10. The method for manufacturing a diamond substrate according to claim 7 or 8, wherein, The other preliminary processing refers to the processing of forming other first preliminary scan lines and other second preliminary scan lines based on processing marks on the other first crystal plane and the other second crystal plane, respectively, from the other first starting point and the other second starting point to the front end of the other wedge structure.

11. The method for manufacturing a diamond substrate according to claim 7 or 8 further includes the step of replacing the other scan line units with the scan line unit.

12. The method for manufacturing a diamond substrate according to claim 7 or 8 further comprises the following steps: By repeatedly performing the steps of replacing the other scan line units with the scan line units, replacing the second starting point with other first starting points to form other second starting points, and forming other first scan lines and other second scan lines from the other first starting points and the other second starting points to constitute the other scan line units, the scan line units are spliced ​​together to form a scan line.

13. The method for manufacturing a diamond substrate according to claim 12 further includes a step of forming a plurality of the scan lines in a parallel manner inside the single-crystal diamond block.

14. The method for manufacturing a diamond substrate according to claim 13, wherein, The first scan line and the second scan line of the scan line unit constituting the scan line are formed on a common crystal plane with the first scan line and the second scan line constituting the adjacent scan line unit.

15. The method for manufacturing a diamond substrate according to claim 14, wherein, The graphitized processing marks formed on the modified layer at each scan line and the cleavage of the surrounding {111} plane also progress between adjacent scan lines, forming a modified layer extending along the {100} plane parallel to the main surface.

16. The method for manufacturing a diamond substrate according to claim 15, further comprising a step of dividing the single-crystal diamond block in the modified layer along a cleavage plane of {111} that progresses between the processing marks.

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