Diamond processing method

Abstract

In this diamond substrate processing method, a laser condensing part 190 is disposed so as to face a main surface 10a in the [001] plane of a substrate 10, and a first starting point 221 and a second starting point 222 each comprising a processing mark 21 are formed by emitting laser beams B to positions, set respectively in a first crystal plane 111 and a second crystal plane 112 forming a wedge-shaped structure in which the tip becomes thinner toward the main surface 10a, inside the substrate 10 within the crystal plane constituting the [111] plane. Starting points are formed at the processing marks 21 formed by irradiating the first starting point 221 and the second starting point 222 with the laser beams B in an overlapping manner. A processing mark is formed by emitting laser beams to between the first starting point 221 and the second starting point 222 such that the cleavages generated from the first starting point 221 and the second starting point 222 irradiated with the laser beams B in an overlapping manner extend along the first crystal plane 111 and the second crystal plane 112 and are connected at the tip of the wedge-shaped structure.

Description

Diamond processing methods

[0001] The present invention relates to a diamond processing method, and more particularly to a diamond processing method for processing a single crystal diamond using a laser beam.

[0002] Conventionally, silicon carbide (SiC) and gallium nitride (GaN) have replaced silicon (Si) as semiconductor materials suitable for power devices, but diamond semiconductors have a higher breakdown field and power control index than these semiconductor materials, and also have the highest thermal conductivity, so they are attracting attention as a next-generation material, and research and development is progressing toward their practical use. Furthermore, nitrogen-vacancy centers (NV centers) in diamond are capable of highly sensitive magnetic detection at room temperature, so there is hope for their application in magnetic sensors, and research in this area is also being conducted (see Patent Document 1).

[0003] Single crystal diamonds, which are expected to be applied to these semiconductors, are synthesized by high-pressure, high-temperature (HPHT) or homoepicapital growth, but these synthesis methods are considered difficult to produce large-area bulk substrates of single crystal diamond for use in semiconductor processes. Therefore, chemical vapor deposition (CVD) methods, which grow single crystal diamond heteroepicapically using single crystal magnesium oxide (MgO) as a base crystal, have been adopted as they have an advantage in producing large-area substrates.

[0004] Diamond substrates are manufactured by slicing a single-crystal diamond ingot or a block cut from the ingot to a certain length to a certain thickness using a wire saw with diamond abrasive grains. Because the wire of the wire saw has a diameter of at least several tens of micrometers, when slicing a single-crystal diamond ingot or block into diamond substrates, a certain width of the slice along the cut surface is lost as a grinding allowance.

[0005] Also disclosed is a method for producing a diamond substrate from a diamond ingot using laser light (see Patent Document 2). In this method, a laser beam is focused and irradiated to a predetermined depth from the main surface of the diamond ingot, and scanned two-dimensionally to form a modified layer with a modified crystal structure, and the diamond substrate is then peeled off from this modified layer.

[0006] JP 2015-59069 A JP 2020-50563 A

[0007] Diamond single crystals have the property that cleavage tends to proceed along the {111} plane, and when a diamond ingot or block whose main surface is the {001} plane is scanned two-dimensionally with laser light, a modified layer develops on the {111} plane, which is the cleavage plane, and cleavage tends to occur along the {111} plane rather than the {001} plane, making it difficult to create a diamond substrate whose main surface is the desired {001} plane.

[0008] The present invention has been proposed in view of the above-mentioned circumstances, and aims to provide a diamond processing method that can produce a diamond substrate whose main surface is a {001} plane from a single crystal diamond whose main surface is a {001} plane.

[0009] In order to solve the above-mentioned problems, the substrate processing method of the present invention includes the steps of: arranging a laser focusing unit that focuses laser light so as to face the main surface of the {001} plane of a single crystal diamond substrate; focusing the laser light with the laser focusing unit, and irradiating the laser at set positions on a first crystal face and a second crystal face that form a wedge-shaped structure inside the substrate, the tip of which becomes thinner toward the main surface, among the crystal faces that make up the {111} plane, to form a first starting point and a second starting point consisting of a processing mark; focusing the laser light with the laser focusing unit, and irradiating the first starting point and the second starting point with the laser light so that cleavage extends from the starting point along the first crystal face and the second crystal face, respectively, and connects at the tip of the wedge-shaped structure, to form a processing mark.

[0010] The step of forming the processed mark may include forming a processed mark graphitized by pyrolyzing diamond and a modified layer including cleavage formed along the {111} plane around the processed mark. The first and second starting points may be set at the same depth from the main surface of the substrate. The step of forming the processed mark by irradiating laser light between the first and second starting points may include forming the processed mark by focusing the laser light at the same depth as the first and second starting points.

[0011] The process of irradiating laser light between the first starting point and the second starting point to form processing marks may form processing marks from the first starting point and the second starting point toward the opposing second starting point and the first starting point along the first crystal face and the second crystal face until they meet at the tip of the wedge-shaped structure.

[0012] The process of forming a processing mark by irradiating laser light between the first starting point and the second starting point may include a process of forming a processing mark from one of the first starting point and the second starting point toward the other along the first crystal face or the second crystal face to the tip of the wedge-shaped structure, and a process of forming a processing mark from the other of the first starting point and the second starting point toward the other along the first crystal face or the second crystal face to the tip of the wedge-shaped structure.

[0013] The step of irradiating a laser beam between the first starting point and the second starting point to form a processed mark may involve thermally decomposing the diamond to form graphitized processed marks and a modified layer surrounding the processed marks that includes cleavage along the {111} plane.

[0014] The process of irradiating laser light between the first starting point and the second starting point to form a processing mark may include a process of forming the processing mark so that a cleavage is formed from the first starting point along the first crystal face to the tip of the wedge-shaped structure, and a process of forming the processing mark so that a cleavage is formed from the second starting point along the second crystal face to the tip of the wedge-shaped structure.

[0015] According to the present invention, a diamond substrate whose main surface is a {001} plane can be produced from a single crystal diamond whose main surface is a {001} plane.

[0016] 1 is a perspective view showing a schematic configuration of a processing apparatus; FIG. 2 is a plan view of a substrate processed by the processing apparatus; FIG. 3 is a schematic view showing the arrangement of {111} planes on a substrate; FIG. 4 is a cross-sectional view showing a processing method of the present embodiment; FIG. 5 is a view showing the principle of the processing method of the present embodiment; FIG. 6 is a view showing the principle of the processing method of the present embodiment; FIG. 7 is a view showing the processing method of the present embodiment; FIG. 8 is a view showing the processing method of the present embodiment; FIG. 9 is a view showing the processing method of the present embodiment; FIG. 10 is a view showing the processing method of the present embodiment; FIG. 11 is a view showing the processing method of the present embodiment; FIG. 12 is a view showing the processing method of the present embodiment; FIG. 13 is a view showing the processing method of the present embodiment; FIG. 14 is a view showing the processing method of the present embodiment; FIG. 15 is a view showing the processing method of the present embodiment; FIG. 16 is a micrograph showing Experimental Example 1; FIG. 17 is a micrograph showing Experimental Example 2; FIG. 18 is a micrograph showing Experimental Example 2; FIG. 19 is a micrograph showing Experimental Example 3; FIG. 19 is a micrograph showing Experimental Example 3; FIG. 19 is a micrograph showing Experimental Example 4; FIG. 19 is a micrograph showing Experimental Example 5; FIG. 19 is a micrograph showing Experimental Example 5; FIG. 19 is a micrograph showing Experimental Example 5; FIG. 19 is a micrograph showing Experimental Example 5; FIG. 19 is a view showing a processing method of a modified example; FIG. 19 is a view showing a processing method of a modified example. 10A and 10B are diagrams illustrating a processing method according to a modified example, a processing method according to a modified example, and a processing method according to a modified example.

[0017] Next, an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are designated by 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 thickness ratio of each layer, etc., may differ from the actual ones. Therefore, specific thicknesses and dimensions should be determined with reference to the following description. Furthermore, it goes without saying that the drawings may include parts with different dimensional relationships and ratios.

[0018] Furthermore, the embodiments shown below are merely examples of devices and methods for embodying the technical ideas of this invention, and the materials, shapes, structures, arrangements, etc. of the components of the embodiments of this invention are not limited to those described below. Various modifications can be made to the embodiments of this invention within the scope of the claims.

[0019] Figure 1 is a perspective view showing the schematic configuration of a processing apparatus 100 used in the diamond processing method of this embodiment. The processing apparatus 100 has a stage 110 on which a single crystal diamond substrate 10 is placed, a stage support 120 that supports the stage 110 so that it can move in the X and Y directions in a horizontal plane, and a fixture 130 that secures the single crystal diamond substrate 10. The fixture 130 can be an adhesive layer, a mechanical chuck, an electrostatic chuck, a vacuum chuck, or the like.

[0020] A plate-shaped substrate 10 having a rectangular periphery, obtained by cutting a single crystal diamond ingot to a predetermined length, is fixed on the stage 110 as the object to be processed, with the {001} plane, which is the main surface and has an off-angle of 0°, as the upper main surface 10a. The shape of the object to be processed is not limited to this, and it may be, for example, a single crystal diamond ingot or a disk-shaped wafer, or a bulk crystal of single crystal diamond, as long as the main surface 10a is similarly the {001} plane.

[0021] The processing apparatus 100 also has a laser light source 160 that generates pulsed laser light, and a laser focusing unit 190 that includes an objective lens 170 and an aberration adjustment unit 180, and irradiates the laser light B emitted from the laser light source 160 via the laser focusing unit 190 onto the {001} plane of the main surface 10a of the single-crystal diamond substrate 10.

[0022] FIG. 2 is a plan view showing a substrate 10 to be processed by the processing apparatus 100. The substrate 10 has a rectangular {001} plane as its main surface 10a, and the direction indicated by the arrow is the <110> direction. The substrate 10 may have, for example, a (100) plane as its main surface 10a, and the direction indicated by the arrow is the

[110] direction. In this case, an orientation flat may be provided by cutting out a corner of the rectangular substrate 10 in the [0-10] direction to indicate the crystal orientation of the substrate 10. Note that, due to limitations on the characters that can be used in this specification, for convenience, the overscores attached to the numbers in the Miller indices will be replaced with a negative sign "-" before the numbers.

[0023] FIG. 3 is a schematic diagram showing the arrangement of the {111} planes in the substrate 10. The {111} planes are cleavage planes of the substrate 10, which is a single-crystal diamond. FIG. 3 is a plan view of the crystal structure of the substrate 10, with the (001) plane as the main surface 10a, as viewed from the main surface 10a. The

[110] orientation is also shown in the figure. The {111} planes constitute the (111), (-111), (-1-11), and (1-11) slopes of a square pyramid that protrudes from the (100) plane with the (001) plane as its base.

[0024] The carbon atoms in the diamond single crystal constituting the substrate 10 are covalently bonded to adjacent carbon elements through the arms of sp3 hybrid orbitals extending toward the four vertices of a regular tetrahedron centered on the carbon atom. The carbon atoms covalently bonded to the four adjacent carbon atoms form a body-centered cubic lattice called a diamond structure. In the diamond structure, carbon atoms form covalent bonds with the four adjacent carbon atoms, so single-crystal diamond is known to be very hard. However, in the <111> direction, a carbon atom is covalently bonded to one adjacent carbon atom only through one arm of the sp3 hybrid orbital. Therefore, in the {111} plane direction perpendicular to the <111> direction, it can be relatively easily separated by simply cutting the covalent bond of this one arm, and therefore the {111} plane becomes the cleavage plane.

[0025] 4 is a diagram illustrating the principle of the processing method of this embodiment. In the processing method of this embodiment, laser light B is focused from laser focusing unit 190 on first crystal face 111 and second crystal face 112 of {111} planes that intersect within substrate 10 to form a wedge-shaped structure tapering toward the {001} plane of main surface 10a, with a depth D and a starting point pitch BP set from main surface 10a, to form first starting points 221 and second starting points 222, respectively, consisting of processing marks. Next, laser light B is irradiated in a superimposed manner so as to be focused at the first starting points 221 and second starting points 222, i.e., at the positions set by the depth D and starting point pitch BP, to form starting points at these positions, and graphitized processing marks are formed on first crystal face 111 and second crystal face 112 from first starting points 221 and second starting points 222 toward the tips of the wedge-shaped structures. As a result, cleavages extending from the first starting point 221 and the second starting point 222 to the periphery are formed along the {111} plane including the first crystal face 111 and the second crystal face 112. Note that the depth D is set as the focal depth of the laser light B by the laser focusing unit 190, and is therefore also referred to as the focal depth D.

[0026] Next, laser light B is scanned from the first starting point 221 and the second starting point 222 toward the opposing second starting point 222 and the first starting point 221, respectively, at a line pitch LP, focusing at a depth D from the laser focusing portion 190. At this time, the laser light B is set to be irradiated so as to overlap the graphitized processing marks formed on the first crystal face 111 and the second crystal face 112 from the first starting point 221 and the second starting point 222. As a result, the laser light B is absorbed by the graphitized processing marks. Processing marks 21 are formed in the wedge-shaped structures formed by the first crystal face 111 and the second crystal face 112, while no processing marks are formed at the focal depth D. Furthermore, the spacing of the line pitch LP is reflected as a spacing LP' between the first starting point 221 and the second starting point 222 and the processing marks 21. The direction in which the focusing point of the laser light B moves is indicated as a line pitch direction 102 in the figure.

[0027] More specifically, graphitized processing marks and cleavage occurring around the graphitized processing marks are formed along the {111} plane including the first crystal face 111 and the second crystal face 112 around the first starting point 221 and the second starting point 222. When laser light B is focused at a position at a depth D that is the line pitch LP in the line pitch direction 102 from the first starting point 221 and the second starting point 222, the laser light B is absorbed by the graphitized processing marks along the {111} plane extending from the first starting point 221 and the second starting point 222 and is reflected by the cleavage, forming graphitized processing marks 21. Then, due to the formation of the processing marks 21 on the first crystal face 111 and the second crystal face 112, cleavage progresses along the first crystal face 111 and the second crystal face 112. Furthermore, the laser light B irradiated at a position further advanced by the line pitch LP in the line pitch direction 102 is also absorbed by the graphitized processing marks along the first crystal face 111 and the second crystal face 112, and is also reflected by the cleavage, forming the next processing marks 21 on the first crystal face 111 and the second crystal face 112, respectively, and the cleavage along the first crystal face 111 and the second crystal face 112 also progresses. If this cleavage is continuously formed along the first crystal face 111 and the second crystal face 112, it becomes possible to make the diamond substrate 10 in a state where it is peeled off at the first crystal face 111 and the second crystal face 112. As described above, the interval of the line pitch LP is reflected as the interval LP' between the processing marks 21, and is optimized by appropriately setting the laser processing conditions as exemplified in the experimental example described later.

[0028] The processing marks 21 meet at the tip of a wedge-shaped structure where the first crystal face 111 and the second crystal face 112 intersect, and the processing marks 21 formed at the tip of the wedge-shaped structure form an apex 23. Because the processing marks 21 formed along the first crystal face 111 and the second crystal face 112 are also formed in a wedge-shaped structure, hereinafter the processing marks 21 formed along the first crystal face 111 and the second crystal face 112 may also be referred to as wedge-shaped processing marks 21. The apex 23 is at a height H from the first starting point 221 and the second starting point 222. Cleavage is formed in the first crystal face 111 and the second crystal face 112 along the processing marks 21 formed from the first starting point 221 and the second starting point 222 and meeting at the apex 23, and a modified layer is formed in which the cleavage extends to adjacent processing marks. In the modified layer, the cleavages formed along the first crystal face 111 and the second crystal face 112 connect to each other, extend parallel to the main surface 10a, and complete at the apex 23. The thickness of the modified layer corresponds to a height H from the first and second starting points 221 and 222 at a depth D to the apex 23. The starting point pitch BP between the first and second starting points 221 and 222 can be set based on the height H, which corresponds to the desired thickness of the modified layer.

[0029] 5 to 8 are diagrams illustrating the processing method of this embodiment. While Fig. 4 illustrates the principle of the processing method of this embodiment, which links cleavages between two points, the first starting point 221 and the second starting point 222, formed on the substrate 10, Figs. 5 to 8 illustrate a method of forming linked cleavages along the main surface 10a of the substrate 10 by applying the principle illustrated in Fig. 4. For convenience, hereinafter, the first crystal face 111 and the second crystal face 112 in Fig. 4 will be referred to as a pair of crystal faces 11, and the starting points formed by irradiating the first starting point 221 and the second starting point 222 with the laser beam B for the second time will be referred to as a pair of starting points 22.

[0030] 5 shows processing marks 21 formed by irradiating the substrate 10 with laser light B for the first time at the position of the starting point 22 in order to form the starting point 22 on the substrate 10. Fig. 5A is a plan view of the substrate 10, and Fig. 5B is a cross-sectional view of the substrate 10 taken along the cutting line VB-VB in Fig. 5A.

[0031] Within the substrate 10, processing marks 21 are formed at a depth D in an origin pitch direction 103 at an origin pitch BP on a plane formed by a pair of crystal planes 11 among {111} planes that intersect to form a wedge-shaped structure tapering toward the {001} plane of the main surface 10a. The origin pitch direction is one direction of the line pitch direction 102 shown in FIG. 4. A pair of processing marks 21 adjacent to each other in the origin pitch direction 103 is on a pair of crystal planes that form the wedge-shaped structure and is separated by the origin pitch BP. These processing marks 21 are formed at a dot pitch DP in a dot pitch direction 101. The dot pitch direction 101 is one of the directions perpendicular to the origin pitch direction 103 within a plane parallel to the main surface 10a. The processed marks 21 are formed by scanning the laser light B in the dot pitch direction 101 at a dot pitch DP to form a row of processed marks 21, and after completing the formation of this row of processed marks 21, moving the laser light B in the starting point pitch direction 103 and repeating the same process to scan an adjacent row of processed marks 21. The laser light B is focused and irradiated to a depth D of the substrate 10.

[0032] 6 shows starting points 22 formed by irradiating processing marks 21 formed by irradiating the substrate 10 with laser light B a second time. FIG. 6A is a plan view of the substrate 10, and FIG. 6B is a cross-sectional view of the substrate 10 taken along the cutting line VIB-VIB in FIG. 6A. The starting points 22 are formed by scanning the laser light B in the dot pitch direction 101 to irradiate a row of processing marks 21 a second time, and then moving the light beam B in the starting point pitch direction 103 to irradiate an adjacent row of processing marks 21 a second time in the same manner. The laser light B is focused and irradiated to a depth D in the substrate 10.

[0033] FIG. 7 shows processing marks 21 formed from starting points 22 formed by focusing laser light again on the first starting points 221 and the second starting points 222 toward opposing starting points 22 along the starting point pitch direction 103. FIG. 7A is a plan view of the substrate 10, and FIG. 7B is a cross-sectional view of the substrate 10 taken along the cutting line VIIB-VIIB in FIG. 7A . The processing marks 21 are formed at a line pitch LP in the line pitch direction 102 from the starting points 22 toward the opposing starting points 22. The processing marks 21 are formed by scanning laser light B in the dot pitch direction 101 to form a row of processing marks 21, and then moving the light beam B in the starting point pitch direction 103 and irradiating the row of processing marks 21 in the same manner. The laser light B is focused and irradiated to a depth D of the substrate 10, similar to the starting points 22. As described above, the laser light B is focused and irradiated to the depth D of the substrate 10, and the processed marks 21 are formed at an interval LP' on a pair of crystal faces 11 forming a wedge shape.

[0034] 8 shows processing marks 21 formed from starting points 22 formed by focusing laser light again on the first starting points 221 and the second starting points 222 along the starting point pitch direction 103 toward opposing starting points 22, and joining at vertices 23. FIG. 8A is a plan view of the substrate 10, and FIG. 8B is a cross-sectional view of the substrate 10 taken along the cutting line VIIIB-VIIIB in FIG. 8A. The processing marks 21 formed at a line pitch LP in the line pitch direction 102 from the starting points 22 toward the opposing starting points 22 form processing marks 21 that become vertices 23 at the tips of wedge-shaped structures formed by a pair of crystal planes 11. The processing marks 21 at the vertices 23 are formed by scanning the laser light B in the dot pitch direction 101 to form a row of processing marks 21 at the vertices 23, and then moving the light beam B in the starting point pitch direction 103 to similarly form adjacent rows of processing marks 21 at the vertices. The laser beam B is focused and irradiated to the depth D of the substrate 10, similar to the starting point 22. As described above, the laser beam B is focused and irradiated to the depth D of the substrate, but the processing mark 21 at the vertex 23 is formed at the tip of the wedge shape formed by the pair of crystal faces 11. The processing mark 21 at the vertex 23 is located at a height H from the starting point 22 at the depth D.

[0035] It should be noted that the processing marks 21 are connected at this vertex 23, and more specifically, the modified layers including the cleavage are connected, and it is preferable that the progression of the modified layer is completed at this vertex 21, and that the cleavage and modified layer do not extend significantly from the vertex 21 toward the main surface.

[0036] 5 to 8 form processing marks 21 along the main surface 10a of the substrate 10. Cleavage lines extending between adjacent processing marks 21 in the starting point pitch direction 103 or the line pitch direction 102 are connected to each other, and cleavage lines extending between adjacent processing marks 21 in the dot pitch direction 101 are also connected to each other, thereby forming a modified layer extending parallel to the main surface 10a. The thickness of the modified layer corresponds roughly to the height H from the starting point 22 to the apex 23.

[0037] (Experimental Example 1) Figure 9 shows micrographs illustrating the results of Experimental Example 1. Figure 9A shows a micrograph of a substrate 10 processed according to Experimental Example 1, and Figure 9B shows a micrograph of a comparative substrate 10 without any starting points. In Experimental Example 1, the substrate 10 was processed according to the processing method of the present embodiment under the processing conditions shown in Table 1 below. The starting point pitch BP was set to 80 μm and the height H was set to 9.42 μm. In the substrate 10 of Experimental Example 1 shown in Figure 9A, processing marks 21 were formed in the line pitch direction 102 at the dot pitch DP. Graphitization was observed around the processing marks 21, and cleavage was also observed around the processing marks 21. It was also observed that the cleavages were connected in the direction of the dot pitch DP. Figure 9A also shows a schematic diagram of processing marks 21 formed in the line pitch direction 102 along a pair of crystal planes 11 that form a wedge-shaped structure from the starting points 22, as shown in Figure 4, clarifying the correspondence between the micrograph and the wedge-shaped structure of the processing marks 21.

[0038]

[0039] In the comparative example of Figure 9B, the substrate 10 was processed under the same processing conditions as in Experimental Example 1, except that the origin 22 was not formed and was replaced with a processing mark 21. As described above, the origin 22 is formed by forming the processing mark 21 by irradiating the laser light B a first time and then irradiating the processing mark 21 a second time. Therefore, by irradiating the laser light B only once at the position where the origin 22 was formed by irradiating the laser light B twice in Experimental Example 1, the processing mark 21 was formed instead of the origin 22. Referring to Figure 9B, a processing mark is formed in the line pitch direction 102 as in Figure 9A of Experimental Example 1, but it was observed that the cleavage did not extend as much around the processing mark 21 as in Experimental Example 1.

[0040] (Experimental Example 2) Figure 10 shows micrographs illustrating the results of Experimental Example 2. Figure 10A shows micrographs of substrate 10 processed at a dot pitch DP of 10 μm, Figure 10B shows micrographs of substrate 10 processed at a dot pitch DP of 12 μm, and Figure 10C shows micrographs of substrate 10 processed at a dot pitch DP of 15 μm. As shown in Table 2 below, the processing conditions of Experimental Example 2 differ from those of Experimental Example 1 in the values ​​of height H and starting point pitch BP, and in the fact that the number of dot pitches DP was increased, but the other processing conditions were the same as those of Experimental Example 1. In Figure 10A where the dot pitch DP was 10 μm, Figure 10B where the dot pitch DP was 12 μm, and Figure 10C where the dot pitch DP was 15 μm, processing marks 21 were formed in the line pitch direction 102, and graphitization of the processing marks 21 and cleavage extending around them were observed, as in Figure 9A of Experimental Example 1. It was also observed that the cleavage was connected in the direction of the dot pitch DP.

[0041]

[0042] (Experimental Example 3) Figure 11 shows micrographs illustrating the results of Experimental Example 3. Figure 11A shows micrographs of substrate 10 processed at a dot pitch DP of 10 μm, Figure 11B shows micrographs of substrate 10 processed at a dot pitch DP of 12 μm, and Figure 11C shows micrographs of substrate 10 processed at a dot pitch DP of 15 μm. As shown in Table 3 below, the processing conditions of Experimental Example 3 differ from those of Experimental Example 1 in that the values ​​of height H and starting point pitch BP and the spacing of the dot pitch DP were changed, but the other processing conditions were the same as those of Experimental Example 1. In Figure 11A where the dot pitch DP was 10 μm, Figure 11B where the dot pitch DP was 12 μm, and Figure 11C where the dot pitch DP was 15 μm, processing marks 21 were formed in the line pitch direction 102, and graphitization of the processing marks 21 and cleavage extending around them were observed, as in Figure 9A of Experimental Example 1. It was also observed that the cleavage was connected in the direction of the dot pitch DP.

[0043] In this experimental example, the height H is set to 3.14 μm, which has the advantage that the thickness of the modified layer formed inside the diamond substrate 10 is small.

[0044]

[0045] (Experimental Example 4) Figure 12 is a micrograph showing the results of Experimental Example 4. Figure 12A shows a micrograph of a substrate 10 processed with a dot pitch DP of 15 μm, and Figure 12B shows a micrograph of a substrate 10 processed with a dot pitch DP of 20 μm. Experimental Example 4 is an example in which the number of processed lines was increased compared to Experimental Examples 1 to 3. As shown in Table 4 below, the processing conditions for Experimental Example 4 differ from Experimental Example 1 in the values ​​of height H, starting point pitch LP, and number of processed wedge-shaped structures, as well as the increased number of dot pitches DP, but the other processing conditions were the same as those for Experimental Example 1. In Figure 12A, where the dot pitch DP was 15 μm, processing marks 21 were formed in the line pitch direction 102, and cleavage was observed extending around the processing marks 21. It was also observed that the cleavage was connected in the direction of the dot pitch DP. 12B where the dot pitch DP is 20 μm, processing marks 21 are formed in the line pitch direction 102, and graphitization of the processing marks 21 and cleavage extending around them are observed, but it is also observed that the cleavage is not sufficiently connected in the dot pitch DP direction. Because it was observed that the cleavage is sufficiently connected when the dot pitch DP is 20 μm, a dot pitch DP of 15 μm is considered to be the upper limit in the dot pitch DP direction.

[0046]

[0047] (Experimental Example 5) FIGS. 13 and 14 are micrographs showing the results of Experimental Example 5. FIG. 13A is a micrograph of the underside of the peeled substrate 10, and FIG. 13B is a micrograph of the top side. FIGS. 14A and 14B are micrographs enlarged from the micrographs of FIGS. 13A and 13B, respectively. In Experimental Example 5, connected cleavages were formed along the main surface 10a of the substrate 10 using the processing method of this embodiment, and then the substrate 10 was divided into upper and lower individual pieces using the connected cleavages. As shown in Table 5 below, the processing conditions for Experimental Example 4 differ from those for Experimental Example 1 in that the height H, the number of starting point pitches LP, and the number of dot pitches DP were increased, but the other processing conditions were the same as those for Experimental Example 1. In Experimental Example 5, countless wedge-shaped processed marks 21 were formed to cover the main surface 10a, so the number of processed wedge-shaped structures is not specified in Table 5.

[0048] 13A and 13B, it can be seen that connected cleavages are formed across substantially the entire main surface 10a of the substrate 10, and that the substrate 10 is separated along the connected cleavages. 13A and 13B and 14A and 14B, it can be seen that square pyramids formed by {111} planes as shown in FIG. 3 are regularly formed on both the lower and upper peeled surfaces, and that peeling has occurred along the connected cleavages formed along the {111} planes. In the connected cleavages, the square pyramids formed by {111} planes are arranged to form a {001} plane parallel to the main surface 10a.

[0049] As illustrated in this experimental example, in order to peel off the substrate 10, the processing marks formed on the {111} planes that make up the wedge-shaped structure must be graphitized and connected to allow cleavage to progress, and for this purpose, the spacing LP' between the processing marks is preferably 3 μm or less. If the processing mark spacing LP' exceeds 3 μm, the processing marks will become dot-like and will not be connected. In order to keep the spacing between the processing marks 3 μm or less, the laser light scanning spacing LP must be 1.7 μm or less.

[0050] In this experimental example, the line pitch LP is 1.1 μm, and the processing mark interval LP' is 1.917 ≒ 2 μm.

[0051]

[0052] As described above, according to this embodiment, a diamond substrate whose main surface is a {001} plane can be manufactured by peeling off a single crystal diamond substrate 10 whose main surface is a {001} plane. In this embodiment, the cleavage generated from the processing marks is connected so that it extends along the {111} plane, so the width of the modified layer including the processing marks and cleavage is relatively small and remains around the processing marks. Since the portion of the modified layer that becomes the cut margin when dividing the substrate 10 is relatively small, the single crystal diamond substrate 10 can be used effectively.

[0053] (Modification) FIG. 15 is a diagram showing the first step of a processing method of a modification. FIG. 15A is a plan view of the substrate 10, FIG. 15B is a cross-sectional view of the substrate 10 cut along the cutting line XVB-XVB in FIG. 15A, and FIG. 15C is a micrograph of the cross-section of FIG. 15B. In the processing method of the present embodiment shown in FIGS. 5 to 8, processing marks 21 are formed sequentially from a pair of opposing starting points 22 toward the vertices 23, respectively. In contrast, the modification differs in that the processing is performed in a first step in which processing marks 21 are formed from one of the opposing starting points 22 to the vertex 23 in the starting point pitch direction 103, and then a second step in which processing marks 21 are formed from the other starting point 22 to the vertex 23 in the direction opposite to the starting point pitch direction 103. Other configurations of the modification, such as the formation of the starting points 22, are similar to those of the processing method of the embodiment. FIG. 15 shows the processing marks 21 formed in the first step of these steps.

[0054] As shown in FIGS. 15A and 15B , processing marks 21 are formed at a line pitch LP along one of a pair of crystal planes 11 forming a wedge-shaped structure inside the substrate 10, from a starting point 22 in a starting point pitch direction 103 to a vertex 23. The processing marks 21 are formed by scanning a laser beam B in a dot pitch direction 101 to form a line of processing marks 21. After this line of processing marks 21 is formed, a second irradiation of the laser beam B is performed to form starting points. The laser beam B is then moved in the starting point pitch direction 103, and similarly scanned across an adjacent line of processing marks. The laser beam B is focused and irradiated to a depth D of the substrate 10. In the line pitch direction 103, the processing width L1 for forming the processing marks 21 in the first step and the movement width L2 for moving without forming the processing marks 21 are both set to 40 μm.

[0055] 15C shows a processing mark 21 formed from the starting point 22 along one of the pair of crystal faces 11 in the starting point pitch direction 103 to reach the apex 23. The starting point 22 is formed at a depth D in the substrate 10, and the apex 23 is formed from the depth D to a height H. It can be observed that the processing mark 21 is formed along one of the pair of crystal faces 11 from the starting point 22 to the apex 23 at a height H.

[0056] Fig. 16 is a diagram showing the second step of the processing method of the modified example. Fig. 16A is a plan view of the substrate 10, and Fig. 16B is a cross-sectional view of the substrate 10 taken along the cutting line XVIB-XVIB in Fig. 16A. Fig. 15 shows processing marks 21 formed in the first step of these steps.

[0057] As shown in Figures 16A and 16B, processing marks 21 are formed at a line pitch LP along the other of a pair of crystal faces 11 forming a wedge-shaped structure inside the substrate 10, from a starting point 22 in a direction opposite to the starting point pitch direction 103 to a vertex 23. The processing marks 21 are formed by scanning laser light B in the dot pitch direction 101 to form a line of processing marks 21, and then irradiating the laser light B a second time to form starting points. Next, the laser light B is moved in the direction opposite to the starting point pitch direction 103, and similarly scanning an adjacent line of processing marks 21 repeatedly. The laser light B is focused and irradiated to a depth D of the substrate 10. In the line pitch direction 102, the processing width L2 for forming the processing marks 21 in the second step and the movement width L1 for moving without forming the processing marks 21 are both set to 40 µm.

[0058] 15 and the second step shown in FIG. 16 are performed after the step of forming the starting points 22, thereby forming processing marks 21 along the main surface 10a of the substrate 10. The cleavages extending between adjacent processing marks 21 in the starting point pitch direction 103 are connected to each other, and the cleavages extending between adjacent processing marks 21 in the dot pitch direction 101 are also connected to each other, thereby forming a modified layer that extends parallel to the main surface 10a. The thickness of the modified layer corresponds roughly to the height H from the starting points 22 to the vertices 23.

[0059] According to the modified example, in the first step, processing marks 21 are formed along one crystal face 11 that forms the wedge-shaped structure, and in the second step, processing marks are formed along the other crystal face 11 that forms the wedge-shaped structure. Because processing marks 21 are formed continuously on one and the other crystal face 11, the travel distance of the laser focusing unit 190 that focuses and irradiates the laser light B that forms processing marks 21 is shortened. Therefore, according to the modified example, the time required to form the wedge-shaped structure of processing marks 21 is shortened, and the processing of substrate 10 can be sped up.

[0060] Although the embodiments and experimental examples have been described above, these embodiments and experimental examples are merely examples for embodying the technical ideas of the present invention, and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention.

[0061] This application claims priority based on Japanese Patent Application No. 2023-140527, filed on August 30, 2023, the entire contents of which are incorporated herein by reference.

[0062] 10 Substrate 10a Main surface 11 Crystal plane 21 Processing mark 22 Starting point 23 Vertex 101 Dot pitch direction 102 Line pitch direction 103 Starting point pitch direction 190 Laser focusing part

Claims

1. A substrate processing method comprising the steps of: arranging a laser focusing unit that focuses laser light so as to face a main surface of a {001} plane of a single crystal diamond substrate; focusing the laser light with the laser focusing unit, and irradiating the laser light to positions set on a first crystal face and a second crystal face that form a wedge-shaped structure inside the substrate and whose tip becomes thinner toward the main surface within the crystal faces that constitute the {111} plane, thereby forming a first starting point and a second starting point consisting of a processing mark; focusing the laser light with the laser focusing unit, and irradiating the first starting point and the second starting point with overlapping laser light to form a starting point in the formed processing mark; focusing the laser light with the laser focusing unit, and irradiating the laser light between the first starting point and the second starting point so that cleavage extends from the starting point along the first crystal face and the second crystal face, respectively, and connects at the tip of the wedge-shaped structure, thereby forming a processing mark.

2. A substrate processing method as set forth in claim 1, wherein the step of forming the processing trace comprises pyrolyzing diamond to form graphitized processing traces and forming a modified layer including cleavage formed along the surrounding {111} plane.

3. A substrate processing method according to claim 1, wherein the first starting point and the second starting point are set at the same depth from the main surface of the substrate.

4. A substrate processing method as described in claim 3, wherein the step of irradiating laser light between the first starting point and the second starting point to form a processing mark comprises concentrating laser light to the same depth as the first starting point and the second starting point to form a processing mark.

5. A substrate processing method as described in claim 4, wherein the step of irradiating laser light between the first starting point and the second starting point to form processing marks forms processing marks along the first crystal face and the second crystal face from the first starting point and the second starting point toward the opposing second starting point and the first starting point, respectively, until they meet at the tip of the wedge-shaped structure.

6. A substrate processing method as described in claim 4, wherein the step of irradiating laser light between the first starting point and the second starting point to form a processing mark includes the steps of: forming a processing mark from one of the first starting point and the second starting point toward the other along the first crystal face or the second crystal face to the tip of the wedge-shaped structure; and forming a processing mark from the other of the first starting point and the second starting point toward the tip of the wedge-shaped structure along the first crystal face or the second crystal face.

7. A substrate processing method as set forth in claim 1, wherein the step of irradiating a laser beam between the first starting point and the second starting point to form a processed mark comprises forming a processed mark in which diamond is thermally decomposed and graphitized, and a modified layer including cleavage along the {111} plane surrounding the processed mark.

8. A substrate processing method as described in claim 1, wherein the step of irradiating laser light between the first starting point and the second starting point to form a processing mark includes the steps of: forming a processing mark such that a cleavage is formed from the first starting point along the first crystal face to the tip of the wedge-shaped structure; and forming a processing mark such that a cleavage is formed from the second starting point along the second crystal face to the tip of the wedge-shaped structure.

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