Diamond processing method

Abstract

To manufacture a substrate having a main surface of {001} plane from a single crystal diamond having the main surface of {001} plane.SOLUTION: A diamond substrate processing method comprises: arranging a laser beam condensing part 190 so as to face a main surface 10a of a {001} plane of a substrate 10; irradiating positions setting on first and second crystal planes 111 and 112 forming a wedge-shaped structure having a tip becoming thinner toward the main surface 10a in the inside of the substrate 10 with a laser beam B in crystal planes constituting a {111} plane to form first and second starting points 221 and 222 consisting of a processing mark 21; repeatedly irradiating the first and second starting points 221 and 222 with the laser beam B to form starting points in the formed processing marks 21; and irradiating a portion between the first and second starting points 221 and 222 with the laser beam so that cleavages caused from the first and second starting points 221 and 222 repeatedly irradiated with the laser beam B extend along the first and second crystal planes 111 and 112, respectively, and connect at the tip having the wedge-shaped structure to form a processing mark.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] Conventionally, silicon carbide (SiC) and gallium nitride (GaN) have been used instead of silicon (Si) as semiconductor materials suitable for power devices, but diamond semiconductors have a higher edge 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 practical use. In addition, nitrogen-vacancy centers (NV centers) in diamond are capable of highly sensitive magnetic detection at room temperature, so there are hopes for their application in magnetic sensors, and research into this is also being conducted (see Patent Document 1).

[0003] Single crystal diamond, which is expected to be applied to these semiconductors, is synthesized by the high pressure, high temperature (HPHT) method or homoepitaxial growth, but these synthesis methods are considered to be difficult to produce large-area bulk substrates of single crystal diamond for use in semiconductor processes. Therefore, the chemical vapor deposition (CVD) method, which grows single crystal diamond heteroepitaxially on single crystal magnesium oxide (MgO) as a base crystal, has been applied as it has 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 with a wire saw with diamond abrasives. Since the wire of the wire saw has a diameter of at least several tens of μm, when slicing a single crystal diamond ingot or block into diamond substrates, a certain width of the cut surface is lost as a grinding allowance.

[0005] Also, a diamond substrate manufacturing method has been disclosed in which a diamond substrate is manufactured from a diamond ingot using laser light (see Patent Document 2). In this method, a laser light is focused and irradiated to a predetermined depth from the main surface of the diamond ingot, and a modified layer with a modified crystal structure is formed by scanning it two-dimensionally, and the diamond substrate is peeled off at this modified layer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2015-59069 A [Patent Document 2] JP 2020-50563 A Summary of the Invention [Problem to be solved by the invention]

[0007] Diamond single crystals have the property that cleavage tends to proceed along the {111} plane, and when a laser beam is scanned two-dimensionally on a diamond ingot or block whose main surface is the {001} plane, 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 with the desired {001} plane as its main surface.

[0008] The present invention has been proposed in view of the above-mentioned circumstances, and has as its object to provide a diamond processing method capable of producing a diamond substrate whose main surface is a {001} plane from a single crystal diamond whose main surface is a {001} plane. [Means for solving the problem]

[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 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 make up 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 forming a starting point in the processing mark formed by irradiating the first starting point and the second starting point with the laser light in an overlapping manner; and 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.

[0010] The step of forming the processing mark may include forming a processing mark graphitized by pyrolyzing diamond and a modified layer including cleavage formed along the surrounding {111} plane. 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 processing mark by irradiating the laser light between the first and second starting points may include forming the processing mark by concentrating 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 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.

[0012] 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 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 tip of the wedge-shaped structure along the first crystal face or the second crystal face.

[0013] The step of irradiating laser light between the first starting point and the second starting point to form a processed mark may form a processed mark graphitized by pyrolyzing diamond and a modified layer including cleavage along the {111} plane surrounding the processed mark.

[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 a processing mark such that a cleavage is formed from the first starting point along the first crystal plane to the tip of the wedge-shaped structure, and a process of forming a processing mark such that a cleavage is formed from the second starting point along the second crystal plane to the tip of the wedge-shaped structure. Effect of the Invention

[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. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 is a perspective view showing a schematic configuration of a processing device. [Diagram 2] 2 is a plan view of a substrate to be processed by the processing apparatus; FIG. [Diagram 3] FIG. 2 is a schematic diagram showing the arrangement of {111} planes on a substrate. [Figure 4] 1A to 1C are cross-sectional views showing a processing method according to the present embodiment. [Diagram 5] 1A to 1C are diagrams illustrating the principle of a processing method according to an embodiment of the present invention. [Figure 6] 1A to 1C are diagrams illustrating a processing method according to an embodiment of the present invention. [Figure 7] 1A to 1C are diagrams illustrating a processing method according to an embodiment of the present invention. [Figure 8] 1A to 1C are diagrams illustrating a processing method according to an embodiment of the present invention. [Figure 9] 1 is a micrograph showing Experimental Example 1. [Figure 10] 1 is a micrograph showing Experimental Example 2. [Figure 11] 1 is a micrograph showing Experimental Example 3. [Figure 12]1 is a micrograph showing Experimental Example 4. [Figure 13] 1 is a micrograph showing Experimental Example 5. [Figure 14] 1 is a micrograph showing Experimental Example 5. [Figure 15] 13A to 13C are diagrams illustrating a processing method of a modified example. [Figure 16] 13A to 13C are diagrams illustrating a processing method of a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 given 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., differ from the actual ones. Therefore, the specific thickness and dimensions should be determined with reference to the following description. In addition, it goes without saying that the drawings include parts with different dimensional relationships and ratios.

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

[0019] 1 is a perspective view showing a 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 XY directions in a horizontal plane, and a fixture 130 that fixes 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-like substrate 10 having a rectangular periphery obtained by cutting a single crystal diamond ingot to a predetermined length as the object to be processed is fixed on the stage 110 with its main surface, the {001} plane with 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 so long as the main surface 10a is similarly a {001} plane, it may be, for example, a single crystal diamond ingot or a disk-shaped wafer, or a bulk crystal of single crystal diamond.

[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 laser light B emitted from the laser light source 160 toward the {001} plane of the main surface 10a of the single crystal diamond substrate 10 via the laser focusing unit 190.

[0022] 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 a main surface 10a, and the direction indicated by the arrow is <110> The substrate 10 may have, for example, a (100) plane as the main surface 10a, and the direction indicated by the arrow as the

[0110] 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 in order to indicate the crystal orientation of the substrate 10. Since there are restrictions on the characters that can be used in this specification, for the sake of convenience, the overscores added to the numbers in the Miller indices are 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 the cleavage planes of the substrate 10, which is a diamond single crystal. FIG. 3 is a plan view of the crystal structure of the substrate 10, whose main surface 10a is the (001) plane, as viewed from the main surface 10a. The orientation of

[0110] 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 that constitutes the substrate 10 are covalently bonded to adjacent carbon elements by the arms of sp3 hybrid orbitals that extend in the direction of 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 the diamond structure. In the diamond structure, the carbon atoms form covalent bonds with the four adjacent carbon atoms, and therefore single crystal diamond is known to be very hard. However, the carbon atoms <111> In the direction, it is covalently bonded to the adjacent carbon atom by only one arm of an sp3 hybrid orbital. <111> In the direction of the {111} plane perpendicular to the cleavage direction, it can be separated relatively easily by simply cutting the covalent bond of one of these arms, and therefore the {111} plane becomes the cleavage plane.

[0025] 4 is a diagram showing the principle of the processing method of the present embodiment. The processing method of the present embodiment is a process for forming a first crystal plane 11 among the {111} planes that intersect so as to form a wedge-shaped structure tapered toward the {001} plane of the main surface 10a inside the substrate 10. 1 and the second crystal face 11 2 The depth D from the main surface 10a and the starting point pitch BP are set, and the laser beam B is focused from the laser focusing unit 190 to form the first starting points 22 consisting of processing marks. 1 and the second starting point 22 2 Next, the first starting point 22 is formed. 1 and the second starting point 22 2 That is, the laser beams B are irradiated in a superimposed manner so as to be focused at the positions set by the depth D and the starting point pitch BP, thereby forming starting points at these positions, and the first crystal face 11 1 and the second crystal face 11 2 First starting point 22 on top 1 and the second starting point 22 2 A graphitized machining mark is formed from the first starting point 22 toward the tip of the wedge-shaped structure. 1 and the second starting point 22 2 The cleavage extending from each of the first crystal faces 11 1 and the second crystal face 11 2The depth D is formed along the {111} plane including the {111} plane. Since the depth D is set as the focal depth of the laser light B by the laser focusing unit 190, it is sometimes referred to as the focal depth D.

[0026] Next, the first starting point 22 1 and the second starting point 22 2 The second starting point 22 facing each other 2 and the first starting point 22 1 The laser beam B is scanned toward the first crystal face 11 at a line pitch LP so as to be focused while maintaining a depth D from the laser focusing portion 190. 1 and the second crystal face 11 2 First starting point 22 on top 1 and the second starting point 22 2 As a result, the laser beam B is absorbed by the graphitized processing marks. 1 and the second crystal face 11 2 While a processing mark 21 is formed in the wedge-shaped structure formed by the first starting point 22, no processing mark is formed at the focal depth D. Furthermore, at this time, the interval of the line pitch LP is 1 and the second starting point 22 2 This is reflected as an interval LP' between the processed marks 21. The direction in which the focal point of the laser beam B moves is shown as a line pitch direction 102 in the drawing.

[0027] More specifically, the first starting point 22 1 and the second starting point 22 2 The first crystal face 11 is located around the 1 and the second crystal face 11 2 The graphitized processing trace and the cleavage generated around it are formed along the {111} plane including the first starting point 22. 1 and the second starting point 22 2 When the laser beam 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 22, 1 and the second starting point 22 2The light is absorbed by the graphitized machining marks along the {111} plane extending from the first crystal face 11 and reflected by the cleavage, forming the graphitized machining marks 21. 1 and the second crystal face 11 2 The formation of the processing marks 21 on the first crystal face 11 1 and the second crystal face 11 2 Then, the laser beam B irradiated to a position further forward by the line pitch LP in the line pitch direction 102 also cleaves along the first crystal face 11. 1 and the second crystal face 11 2 The light is absorbed by the graphitized processing marks along the first crystal face 11 and reflected by the cleavage. 1 and the second crystal face 11 2 The next processing marks 21 are formed on the first crystal face 11. 1 and the second crystal face 11 2 This cleavage is called the first crystal plane 11. 1 and the second crystal face 11 2 1, the diamond substrate 10 is continuously formed along the first crystal face 11. 1 and the second crystal face 11 2 As described above, the line pitch LP is reflected as the distance LP' between the processing marks 21, and is optimized by appropriately setting the laser processing conditions as exemplified in the experimental examples described later.

[0028] The processing mark 21 is the first crystal face 11 1 and the second crystal face 11 2 The first crystal face 11 joins at the tip of the wedge-shaped structure, and the processing mark 21 formed at the tip of the wedge-shaped structure forms a vertex 23. 1 and the second crystal face 11 2 Since the processed trace 21 formed along the first crystal face 11 is also formed in a wedge-shaped structure, 1 and the second crystal face 11 2 The processing mark 21 formed along the first starting point 22 is also referred to as a processing mark 21 having a wedge-shaped structure. 1 and the second starting point 22 2 The first crystal face 11 is at a height H. 1and the second crystal face 11 2 The first starting point is 22 1 and the second starting point 22 2 A cleavage is formed along the processed mark 21 formed from the first crystal face 11 and joined at an apex 23, and a modified layer is formed in which the cleavage extends to an adjacent processed mark. 1 and the second crystal face 11 2 The cleavage formed along the line 22 is connected to each other, extends parallel to the main surface 10a, and is completed at the apex 23. The thickness of the modified layer is approximately from the first starting point 22 to the depth D. 1 and the second starting point 22 2 It corresponds to the height H from the first starting point 22 to the apex 23. 1 and the second starting point 22 2 The starting point pitch BP between the adjacent two points can be set based on the height H that corresponds to the desired thickness of the modified layer.

[0029] 5 to 8 are diagrams showing the processing method of the present embodiment. In FIG. 4, the first starting point 22 formed on the substrate 10 is 1 and the second starting point 22 2 5 to 8, a method of forming cleavage lines connected along the main surface 10a of the substrate 10 by applying the principle shown in FIG. 4 will be described. For convenience, the following description will be limited to the first crystal face 11 in FIG. 1 and the second crystal face 11 2 A pair of crystal faces 11 and a first origin 22 1 and the second starting point 22 2 The starting points formed by irradiating the first laser beam B with the second laser beam B will be referred to as a pair of starting points 22 .

[0030] Fig. 5 shows a processing mark 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. 5(a) is a plan view of the substrate 10, and Fig. 5(b) is a cross-sectional view of the substrate 10 taken along the cutting line VB-VB in Fig. 5(a).

[0031] Inside the substrate 10, on a plane formed by a pair of crystal planes 11 among the {111} planes that intersect to form a wedge-shaped structure tapered toward the {001} plane of the main surface 10a, processing marks 21 are formed at a starting point pitch BP in the starting point pitch direction 103 at a depth D. The starting point pitch direction is one direction of the line pitch direction 102 shown in FIG. 4. A pair of processing marks 21 adjacent to the starting point pitch direction 103 are on a pair of crystal planes that form a wedge-shaped structure and are separated by the starting point pitch BP. Such processing marks 21 are formed at a dot pitch DP in the dot pitch direction 101. The dot pitch direction 101 is one of the directions perpendicular to the starting point pitch direction 103 in a plane parallel to the main surface 10a. The processed marks 21 are formed by scanning the laser light B at a dot pitch DP in a dot pitch direction 101 to form a row of processed marks 21, and when the formation of the row of processed marks 21 is completed, the laser light B is moved in a starting point pitch direction 103 to repeat the scanning of an adjacent row of processed marks in the same manner. 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 the processing marks 21 formed by irradiating the substrate 10 with the laser light B for the second time. FIG. 6(a) is a plan view of the substrate 10, and FIG. 6(b) is a cross-sectional view of the substrate 10 taken along the cutting line VIB-VIB in FIG. 6(a). 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 for the second time to form the starting points 22, and then moving the light beam B in the starting point pitch direction 103 to irradiate an adjacent row of processing marks 21 for the second time in the same manner. The laser light B is focused and irradiated to a depth D of the substrate 10.

[0033] In FIG. 7, the first starting point 22 1 and the second starting point 22 21 shows the processed marks 21 formed from the starting points 22 formed by concentrating the laser light on the starting point 22 at the starting point pitch direction 103 toward the opposing starting points 22. The processed 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 processed marks 21 are formed by scanning the laser light B in the dot pitch direction 101 to form a row of processed marks 21, and then moving the light beam B in the starting point pitch direction 103 to irradiate the row of processed marks 21 in the same manner. The laser light B is focused and irradiated to the depth D of the substrate 10, similar to the starting point 22. As described above, the laser light B is focused and irradiated to the depth D of the substrate 10, but the processed marks 21 are formed at an interval LP' on a set of crystal faces 11 forming a wedge shape.

[0034] In FIG. 8, the first starting point 22 1 and the second starting point 22 2 1 shows the processed marks 21 formed from the origin 22 formed by concentrating the laser light again at the origin 22 toward the opposing origin 22 along the origin pitch direction 103 and joining at the apex 23. The processed marks 21 formed at the line pitch direction 102 with the line pitch LP from the origin 22 toward the opposing origin 22 form the processed marks 21 that become the apex 23 at the tip of the wedge-shaped structure formed by a pair of crystal faces 11. The processed marks 21 of the apex 23 are formed by scanning the laser light B in the dot pitch direction 101 to form the processed marks 21 of the apex 23 in a row, and then moving the light beam B in the origin pitch direction 103 to similarly form the processed marks 21 of the adjacent row of apexes. The laser light B is concentrated and irradiated to the depth D of the substrate 10, similar to the origin 22. As described above, the laser light B is focused and irradiated to the depth D of the substrate, and the processing mark 21 of the apex 23 is formed at the tip of the wedge shape formed by the pair of crystal faces 11. The processing mark 21 of the apex 23 is located at a height H from the starting point 22 of the depth D.

[0035] It is to be noted that the processing marks 21 are connected at this vertex 23, and more specifically, the modified layers including the cleavage are connected. 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, processing marks 21 are formed along the main surface 10a of the substrate 10. Cleavage extending between adjacent processing marks 21 in the starting point pitch direction 103 or the line pitch direction 102 connect to each other, and cleavage extending between adjacent processing marks 21 in the dot pitch direction 101 also connect to each other, forming a modified layer extending in parallel along 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) FIG. 9 is a micrograph showing the results of Experimental Example 1. FIG. 9(a) shows a micrograph of the substrate 10 processed according to Experimental Example 1, and FIG. 9(b) shows a micrograph of the substrate 10 of a comparative example in which no starting point is formed. In Experimental Example 1, the substrate 10 was processed under the processing conditions shown in Table 1 below according to the processing method of this embodiment. The starting point pitch BP is set to 80 μm and the height H is set to 9.42 μm. In the substrate 10 of Experimental Example 1 in FIG. 9(a), processing marks 21 are formed in the line pitch direction 102 at the dot pitch DP, and it was observed that the processing marks 21 were graphitized around the processing marks 21 and that cleavage also occurred around them. It was also observed that the cleavage was connected in the direction of the dot pitch DP. FIG. 9(a) shows a schematic diagram of the 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 point 22 as in FIG. 4, clarifying the correspondence between the micrograph and the wedge-shaped structure of the processing marks 21.

[0038] [Table 1]

[0039] In the comparative example of FIG. 9(b), 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 the processing mark 21. As described above, the origin 22 is formed by irradiating the processing mark 21 with the laser light B for the second time after the processing mark 21 is formed by irradiating the laser light B for the first time. Therefore, the processing mark 21 is formed instead of the origin 22 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. Referring to FIG. 9(b), the processing mark is formed in the line pitch direction 102 as in FIG. 9(a) of Experimental Example 1, but it was observed that the cleavage did not extend much around the processing mark 21 compared to Experimental Example 1.

[0040] (Experimental Example 2) FIG. 10 is a micrograph showing the results of Experimental Example 2. FIG. 10(a) shows a micrograph of the substrate 10 processed with a dot pitch DP of 10 μm, FIG. 10(b) shows a dot pitch DP of 12 μm, and FIG. 10(c) shows a micrograph of the substrate 10 processed with a dot pitch DP of 15 μm. As shown in Table 2 below, the processing conditions of Experimental Example 2 are different from those of Experimental Example 1 in the values ​​of the height H and the starting pitch BP, and the number of dot pitches DP is increased, but the other processing conditions are the same as those of Experimental Example 1. In all of FIG. 10(a) with a dot pitch DP of 10 μm, FIG. 10(b) with a dot pitch DP of 12 μm, and FIG. 10(c) with a dot pitch DP of 15 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, as in FIG. 9(a) of Experimental Example 1. It is also observed that the cleavage is connected in the direction of the dot pitch DP.

[0041] [Table 2]

[0042] (Experimental Example 3) FIG. 11 is a micrograph showing the results of Experimental Example 3. FIG. 11(a) shows a micrograph of the substrate 10 processed with a dot pitch DP of 10 μm, FIG. 11(b) shows a dot pitch DP of 12 μm, and FIG. 11(c) shows a micrograph of the substrate 10 processed with a dot pitch DP of 15 μm. As shown in Table 3 below, the processing conditions of Experimental Example 3 are different from those of Experimental Example 1 in that the values ​​of the height H and the starting point pitch BP and the interval of the dot pitch DP were changed, but the other processing conditions are the same as those of Experimental Example 1. In all of FIG. 11(a) with a dot pitch DP of 10 μm, FIG. 11(b) with a dot pitch DP of 12 μm, and FIG. 11(c) with a dot pitch DP of 15 μm, processing marks 21 were formed in the line pitch direction 102, as in FIG. 9(a) of Experimental Example 1, and graphitization of the processing marks 21 and cleavage extending around them were observed. 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] [Table 3]

[0045] (Experimental Example 4) FIG. 12 is a micrograph showing the results of Experimental Example 4. FIG. 12(a) shows a micrograph of the substrate 10 processed with a dot pitch DP of 15 μm, and FIG. 12(b) shows a micrograph of the substrate 10 processed with a dot pitch DP of 20 μm. Experimental Example 4 is an example in which the number of processed lines is increased from Experimental Examples 1 to 3. As shown in Table 4 below, the processing conditions of Experimental Example 4 are different from Experimental Example 1 in the values ​​of the height H, the starting point pitch LP, and the number of processed wedge-shaped structures, and in that the number of dot pitches DP is increased, but the other processing conditions are the same as those of Experimental Example 1. In FIG. 12(a) where the dot pitch DP is 15 μm, it was observed that processed marks 21 were formed in the line pitch direction 102, and cleavage extended around the processed marks 21. It was also observed that the cleavage was connected in the direction of the dot pitch DP. 12(b) where the dot pitch DP is 20 μm, processing marks 21 are formed in the line pitch direction 102, and it is observed that the processing marks 21 are graphitized and that cleavage extends around them, but the cleavage is not sufficiently connected in the dot pitch DP direction. Since 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] [Table 4]

[0047] (Experimental Example 5) 13 and 14 are micrographs showing the results of Experimental Example 5. FIG. 13(a) is a micrograph of the lower surface of the peeled substrate 10, and FIG. 13(b) is a micrograph of the upper surface. FIG. 14(a) and FIG. 14(b) are micrographs enlarged from the micrographs of FIG. 13(a) and FIG. 13(b), respectively. Experimental Example 5 is a case where, after forming connected cleavage along the main surface 10a of the substrate 10 by the processing method of the present embodiment, the substrate 10 is divided into upper and lower individual pieces by the connected cleavage. As shown in Table 5 below, the processing conditions of Experimental Example 4 are different from those of Experimental Example 1 in that the values ​​of the height H and the number of starting point pitches LP and the number of dot pitches DP are increased, but the other processing conditions are the same as those of Experimental Example 1. In Experimental Example 5, countless processed marks 21 of wedge-shaped structures were formed so as to cover the main surface 10a, so the number of processed wedge-shaped structures is not specified in Table 5.

[0048] 13(a) and 13(b), it is observed that connected cleavage is formed over substantially the entire main surface 10a of the substrate 10, and the substrate 10 is divided along the connected cleavage. 13(a) and 13(b) and 14(a) and 14(b) show that pyramids formed by {111} planes as shown in FIG. 3 are regularly formed on the peeled surfaces of both the lower and upper surfaces, and peeling has occurred along the connected cleavage formed along the {111} planes. In the connected cleavage, the pyramids formed by {111} planes are arranged to form {001} planes parallel to the main surface 10a.

[0049] As shown in this experimental example, in order to peel off the substrate 10, the processing marks formed on the {111} planes constituting the wedge-shaped structure need to 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 spacing LP' between the processing marks exceeds 3 μm, the processing marks will become dot-like and will not be connected. In order to make the spacing between the processing marks 3 μm or less, the laser light scanning spacing LP needs to be 1.7 μm or less.

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

[0051] [Table 5]

[0052] As described above, according to this embodiment, a diamond substrate having a {001} main surface can be manufactured by peeling off a single crystal diamond substrate 10 having a {001} main surface. In this embodiment, the cleavage generated from the processing marks is connected so as to extend 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 effectively used.

[0053] (Modification) FIG. 15 is a diagram showing a first step of the processing method of the modified example. FIG. 15(a) is a plan view of the substrate 10, FIG. 15(b) is a cross-sectional view of the substrate 10 cut along the cutting line XVB-XVB of FIG. 15(a), and FIG. 15(c) is a micrograph of the cross section of FIG. 5(b). In the processing method of the present embodiment shown in FIG. 5 to FIG. 8, the processing marks 21 are formed in sequence from a pair of opposing starting points 22 toward the vertices 23, whereas in the modified example, the processing is performed in a first step of forming the processing marks 21 from one of the opposing starting points 22 to the vertex 23 in the starting point pitch direction 103, and then in a second step of forming the processing marks 21 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 modified example, such as the formation of the starting points 22, are the same as those of the processing method of the embodiment. FIG. 15 shows the processing marks 21 formed in the first step among these steps.

[0054] As shown in FIG. 15(a) and FIG. 15(b), a processing mark 21 is formed at a line pitch LP from a starting point 22 to a vertex 23 in a starting point pitch direction 103 along one of a pair of crystal faces 11 forming a wedge-shaped structure inside the substrate 10. The processing mark 21 is formed by scanning the laser light B in the dot pitch direction 101 to form a line of processing marks 21, and after the line of processing marks 21 is formed, a second irradiation of the laser light B is performed to form a starting point. Next, the laser light B is moved in the starting point pitch direction 103 to repeatedly scan an adjacent line of processing in the same manner. The laser light 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 mark 21 in the first step and the movement width L2 for moving without forming the processing mark 21 are the same, 40 μm.

[0055] The micrograph in Figure 15(c) 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 from the starting point 22 to the apex 23 at height H along one of the pair of crystal faces 11.

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

[0057] As shown in Figs. 16(a) and 16(b), a processing mark 21 is formed at a line pitch LP from a starting point 22 to a vertex 23 in a direction opposite to the starting point pitch direction 103 along the other of a pair of crystal faces 11 forming a wedge-shaped structure inside the substrate 10. The processing mark 21 is formed by scanning the 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 a starting point. Next, the laser light B is moved in a direction opposite to the starting point pitch direction 103 to repeatedly scan an adjacent line of processing in the same manner. 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 mark 21 in the second step and the movement width L1 for moving without forming the processing mark 21 are the same, 40 µm.

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

[0059] According to the modified example, in the first step, the processed mark 21 is formed along one crystal face 11 forming the wedge-shaped structure, and in the second step, the processed mark is formed along the other crystal face 11 forming the wedge-shaped structure. Since the processed mark 21 is continuously formed on one side and the other side of the crystal face 11, the moving distance of the laser focusing unit 190 that focuses and irradiates the laser light B that forms the processed mark 21 is shortened. Therefore, according to the modified example, the time required to form the wedge-shaped structure of the processed mark 21 is shortened, and the processing of the substrate 10 can be accelerated. [Explanation of symbols]

[0060] 10 Substrate 10a Main surface 11 Crystal Faces 21 Machining marks 22 Starting point 23 Vertex 101 Dot pitch direction 102 Line pitch direction 103 Starting point pitch direction 190 Laser focusing unit

Claims

1. a step of positioning a laser focusing unit for focusing a laser beam so as to face a main surface of a {001} plane of a single crystal diamond substrate; a step of focusing a laser beam by the laser focusing unit, and irradiating the laser beam to positions set on a first crystal face and a second crystal face that form a wedge-shaped structure tapering toward the main surface inside the substrate, among crystal faces that constitute a {111} plane, to form a first starting point and a second starting point consisting of processing marks; a step of focusing a laser beam by the laser focusing unit, and irradiating the first starting point and the second starting point with the laser beam in an overlapping manner to form a starting point in the formed processing mark; a step of concentrating a laser beam by the laser focusing unit and irradiating a laser beam 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 a tip of the wedge-shaped structure, thereby forming a processing mark; A substrate processing method comprising:

2. 2. The method for processing a substrate according to claim 1, wherein the step of forming the processing trace comprises forming a processing trace graphitized by pyrolyzing diamond and a modified layer including cleavage formed along a {111} plane surrounding the processing trace.

3. The 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. The substrate processing method according to 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 the processing mark.

5. 5. The substrate processing method according to 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 a tip of the wedge-shaped structure.

6. The step of irradiating a laser beam between the first starting point and the second starting point to form a processing mark includes: 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 a tip of the wedge-shaped structure; forming a processing mark from the other of the first starting point and the second starting point toward the other of the first starting point along the first crystal face or the second crystal face to a tip of the wedge-shaped structure; The method for processing a substrate according to claim 4 , further comprising:

7. 2. The substrate processing method according to 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 a {111} plane around the processed mark.

8. The step of irradiating a laser beam between the first starting point and the second starting point to form a processing mark includes: forming a processing mark such that a cleavage is formed from the first starting point along the first crystal plane to a tip of the wedge-shaped structure; forming a processing trace so that a cleavage is formed from the second starting point along the second crystal plane to a tip of the wedge-shaped structure; The method for processing a substrate according to claim 1 , comprising:

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