Diamond substrate manufacturing method
The described method addresses the challenge of creating diamond substrates with a {100} plane by using laser scanning to form cleavage on the {111} plane, enhancing manufacturing efficiency and reducing material loss.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- SAITAMA UNIVERSITY
- Filing Date
- 2022-07-29
- Publication Date
- 2026-05-22
AI Technical Summary
The challenge in manufacturing diamond substrates is the difficulty in creating a single-crystal diamond substrate with a {100} plane as the main surface due to the tendency for cleavage to occur along the {111} plane when using laser scanning, leading to material loss and reduced yield.
A method involving laser beam irradiation and scanning techniques to form processing marks along the {100} plane, followed by forming cleavage on the {111} plane, allowing the diamond substrate to be peeled off with minimal loss, utilizing pulsed lasers and precise scanning patterns to create a modified crystal structure.
This method enables the production of single-crystal diamond substrates with a {100} plane as the main surface with reduced material waste, improving yield and efficiency in substrate manufacturing.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention relates to a method for manufacturing a diamond substrate, and more particularly to a method for manufacturing a diamond substrate by processing single-crystal diamond using a laser beam to produce a diamond substrate.
Background Art
[0002] Conventionally, as semiconductor materials suitable for power devices, silicon carbide (SiC) and gallium nitride (GaN) have been provided as alternatives to silicon (Si). However, diamond semiconductors have attracted attention as next-generation materials because they have the highest breakdown electric field, high power control index, and thermal conductivity compared to these semiconductor materials, and research and development are underway towards practical application. In addition, since the nitrogen-vacancy center (NV center) in diamond enables highly sensitive magnetic detection at room temperature, its application to magnetic sensors is expected and research is also being conducted (see Patent Document 1).
[0003] Single-crystal diamond expected to be applied to these semiconductors is synthesized by the high-pressure high-temperature method (HPHT method) or homoepitaxial growth. However, with these synthesis methods, it is difficult to increase the area of the bulk substrate of single-crystal diamond for use in semiconductor processes. Therefore, the vapor-phase synthesis method (CVD method) for heteroepitaxially growing single-crystal diamond using single-crystal magnesium oxide (MgO) as a substrate crystal has been applied because of its superiority in increasing the area.
[0004] Diamond substrates are manufactured by slicing an ingot of single-crystal diamond or a block obtained by further cutting the ingot to a certain length into a certain thickness using a wire saw with diamond as abrasive grains. Since the wire of the wire saw has a diameter of at least several tens of μm, for example, when slicing an ingot or block of single-crystal diamond into a diamond substrate, a portion with a certain width along the cutting surface is lost as cutting waste.
[0005] Furthermore, a method for manufacturing diamond substrates from diamond ingots using laser light has been disclosed (see Patent Document 2). In this method, laser light is focused and irradiated from the main surface of the diamond ingot to a predetermined depth, and a modified layer with a modified crystal structure is formed by scanning in a two-dimensional manner, and the diamond substrate is peeled off using this modified layer. [Prior art documents] [Patent Documents]
[0006] [Patent Document 1] Japanese Patent Publication No. 2015-59069 [Patent Document 2] Japanese Patent Publication No. 2020-50563 [Overview of the project] [Problems that the invention aims to solve]
[0007] Diamond single crystals have a property that cleavage tends to proceed along the {111} plane. When a laser beam is scanned in two dimensions over a diamond ingot or block with the {100} plane as its main surface, a modified layer develops along the {111} plane, which is the cleavage plane. As a result, cleavage is more likely to occur along the {111} plane than the {100} plane, making it difficult to create a diamond substrate with the desired {100} plane as its main surface.
[0008] This invention is proposed in view of the above circumstances and aims to provide a method for manufacturing a single-crystal diamond substrate, in which the main surface is a {100} plane, from a single-crystal diamond in which the main surface is a {100} plane. [Means for solving the problem]
[0009] To solve the above-mentioned problems, the method for manufacturing a diamond substrate according to this application includes the steps of: positioning a laser focusing unit for focusing laser light so as to face the main surface of a block of single-crystal diamond whose main surface is a (100) plane; and irradiating the main surface of the block with laser light from the laser focusing unit to focus the laser light into the interior of the block while moving the laser focusing unit and the block. <110> The first step is to move the block relatively in a two-dimensional direction to form a scanning line consisting of processing marks along the (100) plane of a single-crystal diamond from the main surface of the block to a predetermined depth, and the second step is to move the focal point of the laser beam by a predetermined amount along the {111} plane by moving the laser focusing unit and the block relatively in a three-dimensional direction, and these first and second steps are repeated to produce cleavage of the {111} plane.
[0010] In other words, a laser beam is focused from the main surface of a single-crystal diamond whose main surface is a {100} plane to a predetermined depth and irradiated onto it. The laser beam is scanned in a predetermined three-dimensional direction including the direction along the {111} plane to form scanning lines consisting of processing marks. These scanning lines are arranged in parallel to form a modified layer with a modified crystal structure, causing cleavage on the {111} plane. By connecting these cleavage planes of the {111} plane, the diamond substrate whose main surface is a {100} plane is peeled off. Note that the main surface is not limited to the (100) plane; the same method can be applied to any {100} plane.
[0011] The diamond substrate may be separated from the block by forming cleavage planes on opposing {111} planes and connecting these cleavage planes to form a continuous cleavage plane.
[0012] The first step may involve forming a scanning line consisting of processing marks along the (100) plane of the single-crystal diamond.
[0013] The first step may involve forming multiple scanning lines consisting of processing marks along the (100) plane of the single-crystal diamond.
[0014] The first and second steps may involve forming a modified layer to a predetermined depth across the entire surface of the main surface.
[0015] The method for manufacturing a diamond substrate according to this application includes the steps of: positioning a laser focusing unit for focusing laser light opposite the main surface of a block of single-crystal diamond whose main surface is a (100) plane; forming a scanning line which includes irradiating the main surface of the block with laser light from the laser focusing unit and moving the laser focusing unit and the block relatively in two dimensions, and moving the focal point of the laser light in the depth direction, forming a scanning line consisting of processing marks from a first depth in the
[0211] direction from the main surface, and when the scanning line reaches a second depth which is shallower than the first depth, forming a scanning line consisting of processing marks from the second depth to the first depth in the [-211] direction; and moving the focal point of the laser light by a predetermined amount in the [01-1] direction by moving the laser focusing unit and the block relatively in two dimensions, and the first and second steps may be repeated to produce cleavage of the {111} plane.
[0016] In other words, when a single crystal diamond whose main surface is a {100} plane is irradiated with laser light, the position of the laser beam is moved in a predetermined direction along the main surface, and the focal point of the laser beam is moved in a W shape in the depth direction from the main surface so that the focal point of the laser beam moves along the slope of the peaks and valleys formed by the {111} planes in a range of depths from the main surface, thereby forming scanning lines consisting of processing marks. These scanning lines are arranged in parallel to form a modified layer with a modified crystal structure, causing cleavage on the {111} planes, and by connecting these cleavage planes of the {111} planes, the diamond substrate whose main surface is a {100} plane is peeled off. Note that the main surface is not limited to the (100) plane, but can be similarly applied as long as it is a {100} plane.
[0017] The method for manufacturing a diamond substrate according to this application includes the steps of: positioning a laser focusing unit for focusing laser light so as to face the main surface of a block of single-crystal diamond whose main surface is a (100) plane; and moving the laser focusing unit and the block relatively in two dimensions so as to irradiate the main surface of the block with laser light from the laser focusing unit and focus the laser light into the interior of the block, and moving the focal point of the laser light in the depth direction, thereby forming a scanning line consisting of processing marks in the
[0211] direction from a first depth at a first position on the main surface of the block, and the scanning line The first step of forming a scanning line includes, when a second depth shallower than the first depth is reached at a second position on the main surface, forming a scanning line consisting of processing marks from a first depth at a third position symmetrical to the first position on the main surface in the [2-1-1] direction to a second depth at the second position; and the second step of moving the focal point of the laser beam by a predetermined amount in the [01-1] direction by moving the laser focusing unit and the block relative to each other in two dimensions, and the first and second steps may be repeated to produce cleavage of the {111} plane.
[0018] In other words, by moving the laser beam in a W-shape from the main surface to the depth direction of a single-crystal diamond whose main surface is a {100} plane, while moving the position from which the laser beam is irradiated toward the main surface in a predetermined direction along the main surface, the focal point of the laser beam is moved in a W-shape from the main surface to the depth direction, along the slope of the peaks and valleys formed by the {111} planes within a predetermined depth range from the main surface, thereby forming scanning lines consisting of processing marks. These scanning lines are arranged in parallel to form a modified layer with a modified crystal structure, causing cleavage on the {111} planes, and by connecting these cleavage planes of the {111} planes, the diamond substrate whose main surface is a {100} plane is peeled off. Note that the main surface is not limited to the (100) plane, but can be similarly applied as long as it is a {100} plane. [Effects of the Invention]
[0019] According to this invention, a bulk crystal of single crystal diamond having a {100} plane as a main surface, a single crystal diamond ingot or block obtained by the HTHP method can be processed with less loss to create a {100} substrate, and thus the yield in manufacturing a diamond substrate can be improved.
Brief Description of the Drawings
[0020] [Figure 1] It is a perspective view showing a schematic configuration of a processing apparatus. [Figure 2] It is a schematic diagram explaining the {111} plane of a single crystal diamond (100) plane. [Figure 3] It is a schematic diagram explaining the crystal orientation toward the main surface along the {111} plane of a single crystal diamond. [Figure 4] It is a schematic diagram explaining a first laser beam scanning method. [Figure 5] It is a schematic diagram further explaining the first laser beam scanning method. [Figure 6] It is a schematic diagram showing a state in which cleavage planes due to processing marks on the {111} plane are connected in a W shape. [Figure 7] It is a schematic diagram explaining a second laser beam scanning method. [Figure 8] It is a schematic diagram explaining a third laser beam scanning method. [Figure 9] It is a schematic diagram explaining a fourth laser beam scanning method. [Figure 10] It is a schematic diagram explaining the formation of grooves on the side surface of a single crystal diamond block. [Figure 11] It is a micrograph showing a test piece of a single crystal diamond block peeled and separated by cleavage of the {111} plane obtained by an experimental example. [Figure 12] It is a micrograph of the state of a modified layer on a single crystal diamond block by the first laser beam scanning method. [Figure 13] It is a micrograph of a single crystal diamond block peeled and separated by the first laser beam scanning method. [Figure 14]This is a micrograph illustrating a method for forming a modified layer on a block of single-crystal diamond using a second laser scanning method. [Figure 15] This is a micrograph of the cleavage plane of a single-crystal diamond block obtained by a second laser scanning method. [Figure 16] This is an infrared microscope image of a block of single-crystal diamond obtained using the fourth laser scanning method. [Figure 17] This figure illustrates the shape of the cleavage plane of a single-crystal diamond block obtained by the fourth laser scanning method. [Modes for carrying out the invention]
[0021] Next, embodiments of the present invention will be described with reference to the drawings. In the following drawings, identical or similar parts are denoted 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 ratio of the thickness of each layer, etc., may differ from reality. Therefore, specific thicknesses and dimensions should be determined by referring to the following explanation. Furthermore, it goes without saying that there are parts where the relationships and ratios of dimensions differ between drawings.
[0022] Furthermore, the embodiments described below illustrate devices and methods for realizing the technical idea of this invention, and the embodiments of this invention do not limit the materials, shapes, structures, arrangements, etc., of the components to those described below. Various modifications can be made to the embodiments of this invention within the scope of the claims.
[0023] Figure 1 is a perspective view showing the schematic configuration of the processing apparatus 100. The processing apparatus 100 includes a stage 110 on which a block of single-crystal diamond 10 is placed, a stage support section 120 that supports the stage 110 so that it can move in the XY direction in the horizontal plane, and a fixing device 130 for fixing the block of single-crystal diamond 10. The fixing device 130 can be an adhesive layer, a mechanical chuck, an electrostatic chuck, a vacuum chuck, or the like.
[0024] On the stage 110, a plate-shaped block 10 having a rectangular outer circumference, which is obtained by cutting a single-crystal diamond ingot to a predetermined length, is fixed as the workpiece, with the (100) plane, which is the main surface with an off-angle of 0°, serving as the main surface 10a on the top. The shape of the workpiece is not limited to this; similarly, any workpiece with the (100) plane as the main surface 10a may be, for example, a single-crystal diamond ingot, a disc-shaped wafer, or a bulk crystal of single-crystal diamond.
[0025] Furthermore, the processing apparatus 100 includes 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. The laser light B emitted from the laser light source 160 is irradiated through the laser focusing unit 190 toward the (100) plane of the main surface 10a of the single-crystal diamond block 10.
[0026] Figure 2 is a schematic diagram illustrating the arrangement of {111} planes in the crystal structure of block 10 of single-crystal diamond, with the (100) plane as the main surface, as viewed from the main surface 10a on the top. Figure 2(a) is a top view of block 10 of single-crystal diamond, and Figure 2(b) is a cross-sectional view of block 10 of single-crystal diamond from Figure 2(a) cut along the cutting line IIB-IIB. The orientations of
[0110] and [01-1] are also shown in the figures. As shown in Figure 2(a), there are four {111} planes, (111), (1-11), (1-1-1), and (11-1), in a square pyramid with the (100) plane as the base. Furthermore, as shown in Figure 2(b), these {111} planes have an angle of 55° with respect to the (100) plane. Due to limitations on the characters that can be used in this specification, for convenience, the overline placed above the numbers in Miller indices will be replaced with a negative sign "-" before the number. The same applies hereafter.
[0027] Here, in a diamond crystal, carbon atoms are sp² extending in the direction of the four vertices of a regular tetrahedron centered on a carbon atom. 3Carbon atoms are covalently bonded to adjacent carbon elements in the arms of their hybrid orbitals. Carbon atoms covalently bonded to their four adjacent carbon atoms form a body-centered cubic lattice known as the diamond structure. Because carbon atoms in the diamond structure form covalent bonds with their four adjacent carbon atoms, single-crystal diamond is known to be extremely hard. However, carbon atoms... <111> In the direction of the adjacent carbon atom and sp 3 It is covalently bonded by only one arm of the hybrid orbital. Therefore, <111> In the direction perpendicular to the direction of the (111) plane, this single arm can be separated relatively easily by simply cutting the covalent bond, and this (111) plane becomes the cleavage plane.
[0028] Figure 3 is a schematic diagram illustrating the crystal orientation toward the main surface along the {111} plane of a single-crystal diamond with the (100) plane as the main surface. Figure 3(a) is a top view of block 10 of single-crystal diamond, and Figure 3(b) is a cross-sectional view of block 10 of single-crystal diamond in Figure 3(a) cut along the cutting line IIIB-IIIB. Figure 3(a) shows the crystal orientation toward the base of a square pyramid, i.e., toward the main surface 10a side of block 10 of single-crystal diamond with an off-angle of 0°, along the four (111), (1-11), (1-1-1), and (11-1) planes, and illustrates the [2-1-1] direction along the (111) plane, the [21-1] direction along the (1-11) plane, the
[0211] direction along the (1-1-1) plane, and the [2-11] direction along the (11-1) plane, respectively. That is, as shown in Figure 3(b), the crystal orientation toward the surface of block 10 of single-crystal diamond along the {111} plane is <211> This is the result. When organized and presented, it looks like Table 1.
[0029] [Table 1]
[0030] [First laser light scanning method] Figures 4 and 5 illustrate the scanning direction of the laser beam B in the first laser beam B scanning method. Figure 4 shows the scanning of the laser beam along one cleavage plane of the single-crystal diamond block 10, and Figure 5 shows the scanning of the laser beam along multiple cleavage planes of the single-crystal diamond block 10. The single-crystal diamond block 10, whose main surface 10a is a (100) plane with an off-angle of 0°, is placed on the stage 110 of the processing apparatus 100 in Figure 1, and is moved three-dimensionally along the {111} plane relative to the laser focusing unit 190 so that the laser beam B irradiated from the laser focusing unit 190 is directed toward a predetermined position on the main surface 10a of the single-crystal diamond block 10. The scanning line 41 of laser beam B first <110> Scanned in the direction with a dot pitch dp, then along the {111} plane with a line pitch d interval. <211> Move the focus of laser beam B in that direction. <110> A new scanning line 41 is formed in the direction. By repeatedly forming such scanning lines 41, a modified layer 20 is continuously formed along the {111} plane inside the block 10 of single-crystal diamond, thereby causing cleavage of the {111} plane.
[0031] According to the scanning method of laser light B described above, specifically, within the single-crystal diamond block 10, the laser light B is focused from the main surface 10a to a predetermined depth, forming a processed mark in graphite and cracks that spread along the {111} plane around this processed mark. The processed mark in graphite is formed when the laser light B of the pulsed laser emitted from the laser light source 160 is reflected by cracks formed along the {111} plane of the cleavage surface, causing the diamond to be thermally decomposed. Here, the pulsed laser is preferably a so-called picosecond pulsed laser or femtosecond pulsed laser, and refers to a laser with a pulse width, i.e., pulse duration of 100 ps or less.
[0032] The first laser beam scanning method shown in Figures 4 and 5 will be described in more detail in relation to Figure 3. When the scanning line 41 is formed by scanning the laser beam B in the
[0011] direction and the [0-1-1] direction, if the scanning line 41 is formed in the [21-1] direction, the scanning line 41 is formed along the (1-11) plane, and if the scanning line is formed in the [2-11] direction, the scanning line 41 is formed along the (11-1) plane. As a result, cleavage occurs on the (1-11) plane and the (11-1) plane due to processing marks caused by irradiation with the laser beam B. Although not shown in Figure 3, it is clear that the scanning line 41 is continuously formed on the {111} plane which is adjacent to the (1-11) plane and the (11-1) plane. On the other hand, by scanning the laser beam B along the crystal orientations of the respective crystal planes in the (1-1-1) and (111) planes, scanning lines 41 along the (1-1-1) and (111) planes can be similarly formed, causing cleavage in the (1-1-1) and (111) planes.
[0033] Figure 6 is a schematic diagram showing a state in which the cleavage planes formed by the processing marks of the {111} plane are connected in a W shape. With respect to the cleavage formed on the {111} plane as described above, in the square pyramidal structure showing the {111} plane in Figure 2, the combination of opposing planes, namely the (1-11) plane and the (11-1) plane, and the (1-1-1) plane and the (111) plane, allows for the formation of a cleavage plane 51 along the {111} plane, where the cross-sectional structure is formed by a series of cleavage planes schematically represented in a W shape, where the cleavage of the opposing planes is connected. In this case, it is preferable that the scanning line 41 along each {111} plane has a peak-and-trough structure with a predetermined period p, and that the scanning of the scanning line 41 is adjusted so that the peaks and troughs coincide. This mountain-valley structure is continuously formed in the plane direction of the single-crystal diamond block 10, making it possible to separate and exfoliate the single-crystal diamond block 10 using the cleavage of the {111} plane, thereby creating a new diamond with the (100) plane as its main surface.
[0034] In the formation of the scanning line 41, the dot pitch dp and line pitch d are appropriately set to adjust the progression of cleavage of the {111} plane from the processing marks formed by scanning with the laser beam B. When using the laser beam B from the pulsed laser, the dot pitch dp is preferably in the range of 1 μm to 10 μm and the line pitch d is preferably in the range of 1 μm to 20 μm, and more preferably selected from the range of 1 μm to 5 μm for the dot pitch dp and 5 μm to 15 μm for the line pitch.
[0035] If the line pitch dp and line pitch d are smaller than this range, cleavage from the machining marks will progress too far, while if they exceed this range, the cleavage between machining marks will not connect. The number of scans of the scanning line 41 is set considering the machining area D. By making this machining area D as small as possible, machining loss can be reduced.
[0036] [Second laser scanning method] Figure 7 is a perspective view of a single-crystal diamond block 10 illustrating the scanning direction of the laser beam B in the second laser beam B scanning method. The single-crystal diamond block 10, whose main surface 10a is a (100) plane with an off-angle of 0°, is placed on the stage 110 of the processing apparatus 100 in Figure 1. The block 10 is moved three-dimensionally along the {111} plane relative to the laser focusing unit 190 so that the laser beam B irradiated from the laser focusing unit 190 is directed toward a predetermined position on the main surface 10a of the single-crystal diamond block 10.
[0037] The scanning line 41 of laser beam B first <110> The image is scanned in the direction with a dot pitch dp, then forming multiple scanning lines 41 along the (100) plane at intervals of line pitch d0. Subsequently, along the {111} plane... <211> Move the focus of laser beam B in that direction. <110> Multiple new scanning lines 41 are similarly formed in the direction at intervals of line pitch d. By repeating the formation of such scanning lines 41, a modified layer 20 is continuously formed along the {111} plane inside the block 10 of single-crystal diamond, thereby causing cleavage of the {111} plane.
[0038] [Third laser scanning method] Figure 8 is a perspective view of a single-crystal diamond block 10 illustrating the scanning direction of laser beam B in the third laser beam B scanning method. The single-crystal diamond block 10, whose main surface 10a is a (100) plane with an off-angle of 0°, is placed on the stage 110 of the processing apparatus 100 in Figure 1. The block 10 is moved relatively in two dimensions so that the distance between the laser focusing unit 190 and the main surface 10a of the single-crystal diamond block 10 is kept constant, and the laser beam B emitted from the laser focusing unit 190 is directed toward the main surface 10a of the single-crystal diamond block 10. The focal point of the laser beam B emitted from the laser focusing unit 190 is moved in the depth direction according to the position of the main surface 10a of the single-crystal diamond block 10 irradiated by the laser beam B, so that it is focused along the {111} plane.
[0039] The scanning line 41 of the laser beam B is scanned from the main surface 10a from a first depth along the (1-11) plane in the [21-1] direction with a dot pitch dp. When the focal point of the laser beam B reaches a second depth which is shallower than the first depth, the laser beam is similarly scanned along the (11-1) plane, this time in the [-21-1] direction. When the focal point of the laser beam reaches the first depth, the laser beam is scanned again along the (1-11) plane in the [21-1] direction. By repeating this scanning, a scanning line 41 is formed along the main surface 10a in the [01-1] direction. Next, the focal point of the laser beam B is moved in the
[0011] direction at intervals of line pitch d to form a new scanning line 41 in the [01-1] direction. By repeatedly forming such scanning lines 41, a modified layer 20 can be continuously formed along the {111} plane inside the block 10 of single-crystal diamond, thereby creating {111} plane cleavage.
[0040] According to the scanning method of laser beam B described above, specifically, within the single-crystal diamond block 10, the laser beam B is focused from the main surface 10a to a predetermined depth, forming a processed mark in graphite and cracks that spread along the {111} plane around this processed mark. The processed mark in graphite is formed when the laser beam B of the pulsed laser emitted from the laser light source 160 is reflected by cracks formed along the {111} plane of the cleavage surface, causing the diamond to be thermally decomposed.
[0041] The third laser beam scanning method shown in Figure 8 will be described in more detail in relation to Figure 3. When the laser beam B is scanned in the [01-1] direction to form a scanning line 41, if the scanning line 41 is formed in the [21-1] direction, the scanning line 41 is formed along the (1-11) plane, and if the scanning line is formed in the [-21-1] direction, the scanning line 41 is formed along the (11-1) plane. As a result, cleavage occurs on the (1-11) plane and the (11-1) plane due to processing marks caused by irradiation with the laser beam B. Although not shown in Figure 3, it is clear that the scanning line 41 is continuously formed on the {111} plane which is adjacent to the (1-11) plane and the (11-1) plane. On the other hand, by scanning the laser beam B along the crystal orientations of the respective crystal planes in the (111) and (1-1-1) planes, scanning lines 41 along the (111) and (1-1-1) planes can be similarly formed, causing cleavage in the (111) and (1-1-1) planes.
[0042] [Fourth laser scanning method] Figure 9 is a perspective view of a single-crystal diamond block 10 illustrating the scanning direction of laser beam B in the fourth laser beam B scanning method. The single-crystal diamond block 10, whose main surface 10a is a (100) plane with an off-angle of 0°, is placed on the stage 110 of the processing apparatus 100 in Figure 1. The block 10 is moved relatively in two dimensions so that the distance between the laser focusing unit 190 and the main surface 10a of the single-crystal diamond block 10 is kept constant, and the laser beam B emitted from the laser focusing unit 190 is directed toward the main surface 10a of the single-crystal diamond block 10. The focal point of the laser beam B emitted from the laser focusing unit 190 is moved in the depth direction according to the position of the main surface 10a of the single-crystal diamond block 10 irradiated by the laser beam B, so that the laser beam B emitted from the laser focusing unit 190 is focused along the {111} plane.
[0043] The scanning line 41 of the laser beam B is scanned from the main surface 10a from a first depth along the (1-11) plane in the [21-1] direction with a dot pitch dp until the focal point of the laser beam B reaches a second depth which is shallower than the first depth, forming the first section 41a of the scanning line 41. Subsequently, the scanning line 41 is similarly scanned from the second depth along the (11-1) plane, this time in the [-21-1] direction, until the focal point of the laser beam B reaches the first depth, forming the second section 41b of the scanning line 41. In both the first section 41a and the second section 41b, the scanning line 41 ascends along the peak-valley structure formed on the {111} plane. By alternately repeating the formation of the first section 41a and the second section 41b, a scanning line 41 is formed along the main surface 10a in the [01-1] direction. Next, the focal point of the laser beam B is moved in the
[0011] direction at intervals of line pitch d to form a new scanning line 41 in the [01-1] direction. By repeating the formation of such scanning lines 41, a modified layer 20 is continuously formed along the {111} plane inside the block 10 of single-crystal diamond, thereby causing cleavage of the {111} plane.
[0044] According to the scanning method of laser beam B described above, specifically, within the single-crystal diamond block 10, the laser beam B is focused from the main surface 10a to a predetermined depth, forming a processed mark in graphite and cracks that spread along the {111} plane around this processed mark. The processed mark in graphite is formed when the laser beam B of the pulsed laser emitted from the laser light source 160 is reflected by cracks formed along the {111} plane of the cleavage surface, causing the diamond to be thermally decomposed.
[0045] The fourth laser beam scanning method shown in Figure 9 will be described in more detail in relation to Figure 3. When the laser beam B is scanned in the [01-1] direction to form a scanning line 41, if the scanning line 41 is formed in the [21-1] direction, a first section 41a of the scanning line 41 is formed along the (1-11) plane, and if the scanning line is formed in the [-21-1] direction, a second section 41b of the scanning line 41 is formed along the (11-1) plane. As a result, cleavage occurs on the (1-11) plane and the (11-1) plane due to processing marks caused by irradiation with the laser beam B. Although not shown in Figure 3, it is clear that the scanning line 41 is continuously formed on the {111} plane which is adjacent to the (1-11) plane and the (11-1) plane. On the other hand, by scanning the laser beam B along the crystal orientations of the respective crystal planes in the (111) and (1-1-1) planes, scanning lines 41 along the (111) and (1-1-1) planes can be similarly formed, causing cleavage in the (111) and (1-1-1) planes.
[0046] Figure 10 illustrates the formation of grooves on the side surface of a single-crystal diamond block 10. By applying the first to fourth laser scanning methods described above, laser light B is irradiated onto the single-crystal diamond block 10 to form a modified layer 20 over the entire surface of the main surface 10a within the block 10. Subsequently, grooves can be formed by irradiating the modified layer 20 that has reached the side surface of the block 10 with laser light B. To enable laser light to be irradiated onto the side surface B of the block 10, after the step of forming the modified layer 20 on the block 10, the orientation of the block 10 may be changed on the stage 110 of the processing apparatus 100 shown in Figure 1 so that the side surface of the block 10 faces the laser focusing unit 190 before irradiating with laser light B. By forming grooves along the modified layer 20 that reaches the side surface over the entire circumference of the side surface of the block 10, spontaneous delamination of the modified layer 20 may occur, and even if spontaneous delamination does not occur, delamination of the modified layer 20 can be induced by pressing a knife edge against the groove.
[0047] [Example of experiment] Figure 11 shows the results of an experimental example illustrating the processing principle of this embodiment. Figure 11(a) is a micrograph taken from above, and Figure 11(b) is a micrograph observed in the direction of arrow A in Figure 11(a). The experimental example was conducted using the processing conditions shown in Table 2 and the following procedure.
[0048] [Table 2]
[0049] The focus of laser beam B was aligned with the bottom surface of the 700 μm thick single-crystal diamond block 10, and laser beam B was scanned in the
[0011] direction. Next, the focus of laser beam B was moved in the [2-11] direction along the (1-11) plane at a line pitch of approximately 6 μm, and laser beam B was scanned again in the
[0011] direction. At this time, the movement of the focus of laser beam B in the [2-11] direction was at an angle of 55° with respect to the (100) plane. This scanning was performed up to the surface of the single-crystal diamond block 10. Next, the focus of laser beam B was aligned with the bottom surface of the single-crystal diamond block 10 again, and the (11-1) plane opposite to the (1-11) plane was processed. Laser beam B was scanned in the
[0011] direction to form a processing line, and then the focus of laser beam B was moved in the [2-11] direction along (11-1). Similarly to the above, cleavage was created on the (11-1) plane by scanning the laser beam in the
[0011] direction. As a result, it can be seen that peeling is possible at the cleavage plane, as shown in Figure 11. Note that this is not limited to the scanning direction of the laser beam B in this experimental example, <110> Direction and <211> Similar results can be obtained by appropriately combining the scanning of laser beam B in different directions.
[0050] [Examples] [Examples]
[0051] Example 1 of the first laser beam B scanning method in this embodiment will be described. The processing conditions are shown in Table 3.
[0052] [Table 3]
[0053] As shown in Figure 12, a block of single-crystal diamond 10 was scanned with laser beam B under the processing conditions shown in Table 3. The block of single-crystal diamond 10 was a rectangular parallelepiped with dimensions of 0.5 × 0.5 mm and a thickness of 500 μm. Figure 12(a) is a micrograph of the cross-section of the cleavage plane along the {111} direction of the block of single-crystal diamond 10, and Figure 12(b) is a schematic diagram illustrating the cross-section in Figure 12(a). The arrows in Figure 12(a) indicate the scanning direction of laser beam B.
[0054] Figure 13 is a micrograph showing that the cleavage planes of opposing {111} faces within a single-crystal diamond block 10 after laser processing have a peak-valley structure. Figure 13(a) is a micrograph of the single-crystal diamond block 10 observed from above, and Figure 13(b) is a schematic diagram illustrating Figure 13. As shown in the cleavage plane 51 of Figure 13(b), the cleavage plane in Figure 13(a) has a peak-valley structure.
[0055] Figure 14 shows micrographs of the samples separated and detached at the cleavage plane. [Examples]
[0056] Example 2, which uses the second laser beam B scanning method in this embodiment, will now be described.
[0057] The processing conditions are shown in Table 4.
[0058] [Table 4]
[0059] As shown in Figure 14, laser beam B was scanned using a single-crystal diamond block 10 under the processing conditions shown in Table 4. The single-crystal diamond block 10 was a rectangular parallelepiped with dimensions of 0.5 × 0.5 mm and a thickness of 500 μm.
[0060] In Example 2, five laser beam B scanning lines were formed on the (100) plane with a line pitch d0 = 1 μm. The focal point of the laser beam B was moved 10 μm along the (11-1) plane from the last scanning line, and five more scanning lines were formed on the (100) plane at intervals of d0 = 1 μm. This movement and scanning was repeated to form processing areas corresponding to 20 stages. Next, processing areas consisting of laser beam B scanning lines were similarly formed on the opposing (11-1) plane.
[0061] Figure 15 can be seen as a micrograph showing that the cleavage planes of opposing {111} faces within a single-crystal diamond block 10 after laser processing have a mountain-valley structure. [Examples]
[0062] Example 3, which uses the fourth laser beam B scanning method in this embodiment, will now be described.
[0063] The processing conditions are shown in Table 5.
[0064] [Table 5]
[0065] Figure 16 is an infrared microscope image of a single-crystal diamond block 10 after laser processing. This microscope image shows the single-crystal diamond block 10 observed from the laser light irradiation side. The single-crystal diamond block 10 is a rectangular parallelepiped with dimensions of 0.5 × 0.5 mm and a thickness of 500 μm. Figure 16(a) is an infrared microscope image of the entire single-crystal diamond block 10. Laser light B is scanned over the entire surface of the single-crystal diamond block 10, and the first section 41a and the second section 41b of the scanning line 41 shown in Figure 9 are connected, and it can be observed that the cross-sectional profile has a peak-and-valley structure. The position of the peak-and-valley structure of the cleavage plane 51 profile is shown at the bottom of the microscope image. Figure 16(b) is an infrared microscope image of the area within the frame of Figure 16(a). Similar to Figure 16(a), the peak-and-valley structure of the cleavage plane 51 profile is shown at the bottom of the microscope image. It is observed that the peaks 51c in the cleavage plane 51 are formed by a cleavage plane 51a that becomes higher as the scanning line 41 moves in the direction of [01-1] corresponding to the first section 41a of the scanning line 41, and a cleavage plane 51b that becomes higher as the scanning line 41 moves in the direction of [0-11] corresponding to the second section 41b of the scanning line 41.
[0066] Figure 17 illustrates the separation of a single-crystal diamond block 10 at its cleavage plane. Here, the single-crystal diamond block 10 was separated by irradiating it with laser light B around its entire circumference along a modified layer 20 that reached the side surface of the block 10, as shown in Figure 10, to form grooves, and then pressing a knife edge against the modified layer 20 along the grooves to exfoliate it at the cleavage plane 51. Figure 17(a) is a micrograph showing the cleavage plane of the single-crystal diamond block 10. Figure 17(b) is a cross-sectional view showing the cleavage plane 51 with a peak-and-valley structure, formed by irradiating the single-crystal diamond block 10 with laser light B. Figure 17(c) is a graph showing the position of the cleavage plane formed on the single-crystal diamond block 10, measured using a confocal laser microscope. The x-direction of the graph is the scanning direction of the laser light B [01-1], and the z-direction is the normal direction
[0100] of the main surface 10a of the single-crystal diamond block 10. In the graph, it can be observed that the profile of the cleavage plane 51 has a peak-and-valley structure corresponding to Figure 17(b). [Explanation of Symbols]
[0067] 10 blocks 10a main surface 51 Cleavage plane 100 Processing equipment 190 Laser focusing section
Claims
1. A step of arranging a laser focusing unit that focuses laser light so as to face the main surface of a block of single-crystal diamond whose main surface is a (100) plane, A first step involves irradiating the main surface of the block with laser light from the laser focusing unit to focus the laser light into the interior of the block, while moving the laser focusing unit and the block relative to each other in a two-dimensional manner in the <110> direction, thereby forming a scanning line consisting of a processing mark along the (100) plane of the single-crystal diamond to a predetermined depth from the main surface of the block. A second step involves moving the laser beam's focal point by a predetermined amount along the {111} plane by relatively moving the laser focusing unit and the block in three dimensions, The first and second steps are repeated to produce cleavage of the {111} plane, A method for manufacturing a diamond substrate, comprising forming cleavage planes on opposing {111} planes and separating the diamond substrate from the block by connecting these cleavage planes to form a continuous cleavage plane.
2. The method for manufacturing a diamond substrate according to claim 1, wherein the first step is to form a scanning line consisting of processing marks along the (100) plane of the single crystal diamond.
3. The method for manufacturing a diamond substrate according to claim 1, wherein the first step is to form a plurality of scanning lines consisting of processing marks along the (100) plane of the single crystal diamond.
4. The method for manufacturing a diamond substrate according to any one of claims 1 to 3, wherein the first and second steps involve forming a modified layer to a predetermined depth over the entire surface of the main surface.
5. A step of arranging a laser focusing unit that focuses laser light so as to face the main surface of a block of single-crystal diamond whose main surface is a (100) plane, A first step of forming a scanning line, which includes irradiating the main surface of the block with laser light from the laser focusing unit and focusing the laser light into the interior of the block by moving the laser focusing unit and the block relative to each other in a two-dimensional manner, and moving the focal point of the laser light in the depth direction, forming a scanning line consisting of processing marks in the [211] direction from a first depth from the main surface, and when the scanning line reaches a second depth shallower than the first depth, forming a scanning line consisting of processing marks in the [-211] direction from the second depth to the first depth, A second step involves moving the laser beam's focal point by a predetermined amount in the [01-1] direction by relatively moving the laser focusing unit and the block in a two-dimensional manner, The first and second steps are repeated to produce cleavage of the {111} plane, A method for manufacturing a diamond substrate, comprising forming cleavage planes on opposing {111} planes and separating the diamond substrate from the block by connecting these cleavage planes to form a continuous cleavage plane.
6. A step of arranging a laser focusing unit that focuses laser light so as to face the main surface of a block of single-crystal diamond whose main surface is a (100) plane, A first step of forming a scanning line, which includes irradiating the main surface of the block with laser light from the laser focusing unit and focusing the laser light into the interior of the block by moving the laser focusing unit and the block relative to each other in a two-dimensional manner, and moving the focal point of the laser light in the depth direction, forming a scanning line consisting of processing marks in the block from a first depth at a first position on the main surface in the [211] direction, and when the scanning line reaches a second depth at a second position on the main surface which is shallower than the first depth, forming a scanning line consisting of processing marks in the main surface from a first depth at a third position symmetrical to the first position with respect to the second position in the [2-1-1] direction to the second depth at the second position, A second step involves moving the laser beam's focal point by a predetermined amount in the [01-1] direction by relatively moving the laser focusing unit and the block in a two-dimensional manner, The first and second steps are repeated to produce cleavage of the {111} plane, A method for manufacturing a diamond substrate, comprising forming cleavage planes on opposing {111} planes and separating the diamond substrate from the block by connecting these cleavage planes to form a continuous cleavage plane.