Diamond substrate manufacturing method

Abstract

To provide a diamond substrate manufacturing method capable of quickly manufacturing a substrate from a workpiece made of diamond.SOLUTION: After or at the same time of forming an exfoliation layer inside a workpiece, by radiating a vaporizing laser beam with a wavelength penetrating through diamond and absorbed in an allotrope of carbon other than diamond, the exfoliation layer is heated to generate carbon dioxide from carbon contained in a modification part and oxygen contained in atmosphere. Also, the vaporizing laser beam is radiated to a first area included in the workpiece, and then radiated to a second area nearer a center of the workpiece than the first area. In this case, the modification part is decreased together with generation of carbon dioxide to form a cavity, and gas existing in the cavity and a crack is locally heated and expanded. Thereby, the crack is quickly extended on the exfoliation layer and the workpiece is cleaved. As a result, a substrate is quickly manufactured from the workpiece.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for producing a diamond substrate from a workpiece made of diamond and including a first surface, a second surface opposite to the first surface, and a side surface located between the first surface and the second surface. [Background technology]

[0002] Diamond has a large band gap, dielectric breakdown field strength, and thermal conductivity, and is therefore expected to be a material for substrates used to form semiconductor devices. Such substrates are generally produced by peeling off a portion of a predetermined thickness on the surface side of a workpiece such as a diamond ingot.

[0003] Peeling of the substrate from the workpiece is performed, for example, in the following order (see, for example, Patent Document 1): First, the laser beam, which has a wavelength that transmits diamond, is focused at a focal point positioned at a predetermined depth from the surface of the workpiece that corresponds to the thickness of the substrate, and the focal point and the workpiece are moved relative to each other while the laser beam is irradiated onto the workpiece.

[0004] As a result, a peeling layer is formed inside the workpiece, which includes a modified portion made of a carbon allotrope other than diamond (e.g., amorphous carbon such as graphite or carbon black) and cracks extending from the modified portion. Then, ultrasonic vibration is applied to the workpiece through water so as to further extend the cracks contained in the peeling layer. As a result, the workpiece is cleaved at the peeling layer to produce a substrate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-50563 A Summary of the Invention [Problem to be solved by the invention]

[0006] When ultrasonic vibration is applied to a workpiece having a peeling layer formed therein through water, the cracks in the peeling layer gradually grow. In this case, it is necessary to dry both the workpiece and the substrate produced from the workpiece before performing a new process. Therefore, in this case, it tends to take a long time to produce a substrate from the workpiece that can be used for a new process.

[0007] In view of this, an object of the present invention is to provide a method for manufacturing a diamond substrate that is capable of quickly manufacturing a substrate from a workpiece made of diamond. [Means for solving the problem]

[0008] According to the present invention, there is provided a method for producing a diamond substrate from a workpiece made of diamond and including a first face, a second face opposite to the first face, and a side face located between the first face and the second face, wherein a modification laser beam having a wavelength that transmits the diamond is irradiated onto the workpiece so as to move the first focus point and the workpiece relatively in a state where the first focus point of the modification laser beam is positioned at a predetermined depth corresponding to the thickness of the substrate from the first face, thereby forming a modified portion made of a carbon allotrope other than diamond and a crack extending from the modified portion, and forming a peeling layer exposed on the side face of the workpiece into the interior of the workpiece. The present invention provides a method for manufacturing a diamond substrate, comprising: a peeling layer formation step in which a peeling layer is formed on the workpiece; and a heating step, performed after or in parallel with the peeling layer formation step, of irradiating the workpiece with a vaporization laser beam so as to move a second focal point of the vaporization laser beam, which transmits through the diamond and has a wavelength that is absorbed by the carbon allotrope, relative to the workpiece, thereby heating the peeling layer so that carbon dioxide is produced from the carbon contained in the modified portion and the oxygen contained in the atmosphere, wherein in the heating step, the vaporization laser beam is irradiated onto a first region contained in the workpiece and then onto a second region that is closer to the center of the workpiece than the first region.

[0009] Preferably, the heating step includes a first vaporization laser beam irradiation step of irradiating the first region with the vaporization laser beam, a determination step of determining whether or not the first region has been peeled off after the first vaporization laser beam irradiation step is performed, and a second vaporization laser beam irradiation step of irradiating the second region with the vaporization laser beam when it is determined in the determination step that the first region has been peeled off. Also, preferably, the vaporization laser beam uses carbon dioxide gas as a laser medium. Effect of the Invention

[0010] In the present invention, after or in parallel with the formation of a peeling layer inside the workpiece, the peeling layer is heated by irradiating it with a vaporization laser beam having a wavelength that penetrates diamond and is absorbed by carbon allotropes other than diamond, so that carbon dioxide is produced from the carbon contained in the modified portion and the oxygen contained in the atmosphere.

[0011] In this case, the modified area is reduced in volume with the generation of carbon dioxide, forming cavities, and the gas present in the cavities and cracks is locally heated and expands, causing the cracks in the peeling layer to rapidly propagate and the workpiece to cleave. As a result, a substrate is rapidly produced from the workpiece. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view that illustrates an example of an ingot used in the manufacture of a diamond substrate. [Diagram 2] FIG. 2 is a top view diagrammatically illustrating an ingot. [Diagram 3] FIG. 3 is a flow chart that illustrates an example of a diamond substrate manufacturing method for manufacturing a substrate from an ingot. [Figure 4] FIG. 4 is a perspective view that illustrates the release layer forming step. [Diagram 5] FIG. 5 is a partially enlarged side view showing a schematic diagram of the ingot after the peeling layer forming step. [Figure 6] FIG. 6 is a perspective view that illustrates the heating step. [Figure 7] FIG. 7 is a side view that illustrates an example of how the release layer forming step and the heating step are performed in parallel. [Figure 8] FIG. 8 is a side view that illustrates another example of how the release layer forming step and the heating step are performed in parallel. [Figure 9] FIG. 9 is a side view diagrammatically illustrating yet another example of how the release layer forming step and the heating step are performed in parallel. [Figure 10]FIG. 10 is a flow chart that illustrates an example of a heating step that is performed while checking the state of the ingot. [Figure 11] FIG. 11 is a flow chart that illustrates a schematic diagram of another example of a method for producing a diamond substrate from an ingot. [Figure 12] Each of FIG. 12(A) and FIG. 12(B) is a side view that typically illustrates the state of the peeling step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The embodiment of the present invention will be described with reference to the attached drawings. Fig. 1 is a perspective view showing an example of an ingot used for manufacturing a diamond substrate, and Fig. 2 is a top view showing the ingot shown in Fig. 1. In Fig. 1, the crystal plane of diamond exposed on the plane included in this ingot is also shown. In Fig. 2, the crystal orientation of the diamond constituting this ingot is also shown.

[0014] 1 and 2, a specific crystal plane included in the crystal plane {100} (here, for convenience, it is assumed to be the crystal plane (001)) is exposed on each of the front surface (first surface) 11a and the back surface (second surface) 11b. That is, in this ingot 11, the perpendicular lines (crystal axes) of the front surface 11a and the back surface 11b are aligned along the crystal orientation

[0001] .

[0015] Although the ingot 11 is manufactured so that the crystal plane (001) is exposed on each of the front surface 11a and the back surface 11b, a surface slightly inclined from the crystal plane (001) may be exposed on each of the front surface 11a and the back surface 11b due to processing errors during manufacturing, etc. Specifically, a surface having an angle of 1° or less with respect to the crystal plane (001) may be exposed on each of the front surface 11a and the back surface 11b of the ingot 11. In other words, the crystal axis of the ingot 11 may be aligned along a direction having an angle of 1° or less with respect to the crystal orientation

[0001] .

[0016] In addition, an orientation flat 13 is formed on a side surface 11c of the ingot 11. The orientation flat 13 is aligned along the crystal orientation <110> The orientation flat 13 is located in a specific crystal orientation (here, for convenience, it is assumed to be the crystal orientation

[0110] ) included in the above. In other words, in the orientation flat 13, the crystal face (110) of the diamond is exposed.

[0017] 3 is a flow chart showing a schematic example of a method for manufacturing a diamond substrate from a workpiece ingot 11. In this method, first, a peeling layer is formed inside ingot 11, the peeling layer including a modified portion made of a carbon allotrope other than diamond and cracks extending from the modified portion and exposed at a side surface 11c of ingot 11 (peeling layer forming step S1).

[0018] Fig. 4 is a perspective view showing the release layer forming step S1. Note that the X-axis direction and the Y-axis direction shown in Fig. 4 are directions perpendicular to each other on a horizontal plane, and the Z-axis direction is a direction (vertical direction) perpendicular to the X-axis direction and the Y-axis direction.

[0019] This peeling layer forming step S1 is performed in a laser processing device 2. The laser processing device 2 includes a chuck table 4 having a circular holding surface that is approximately parallel to a horizontal plane and capable of holding an ingot 11 on this holding surface.

[0020] The chuck table 4 is connected to a suction mechanism (not shown). This suction mechanism has, for example, an ejector. When the suction mechanism operates, a suction force acts on the space near the holding surface of the chuck table 4. Therefore, when the suction mechanism operates with the ingot 11 placed on the holding surface, the ingot 11 is held on the holding surface of the chuck table 4.

[0021] The chuck table 4 is also connected to a rotation mechanism (not shown). This rotation mechanism includes, for example, a pulley and a motor. When the rotation mechanism operates, the chuck table 4 rotates about a rotation axis that passes through the center of the holding surface and is a straight line along the Z-axis direction. For example, the rotation mechanism rotates the chuck table 4 so that the orientation flat 13 of the ingot 11 held on the holding surface of the chuck table 4 is parallel to the Y-axis direction.

[0022] The chuck table 4 is connected to a moving mechanism (not shown). The moving mechanism includes, for example, a ball screw and a motor. When the moving mechanism operates, the chuck table 4 moves along the X-axis direction, the Y-axis direction, and / or the Z-axis direction.

[0023] A head 8 of the laser beam irradiation unit 6 is provided above the chuck table 4. This head 8 is provided at the tip of a cylindrical housing 10 extending along the Y-axis direction. The head 8 houses an optical system such as a condenser lens and a mirror, and the housing 10 houses an optical system such as a mirror and / or a lens.

[0024] The laser beam irradiation unit 6 also has a modification laser oscillator (not shown) containing, for example, Nd:YAG or the like as a laser medium. This modification laser oscillator generates a pulsed laser beam (modification laser beam) LB1 having a wavelength (for example, 1030 nm or 1064 nm) that transmits through diamond. The modification laser beam LB1 is then emitted directly downward from the head 8 via the housing 10 and an optical system housed in the head 8 after its output (power) is adjusted by an attenuator (not shown).

[0025] Furthermore, an imaging unit 12 capable of capturing an image of the area directly below is provided on the side of the housing 10. The imaging unit 12 has, for example, a light source such as an LED (Light Emitting Diode), an objective lens, and an imaging element such as a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor.

[0026] When performing the peeling layer forming step S1 in the laser processing apparatus 2, first, the ingot 11 is placed on the holding surface of the chuck table 4 with the surface 11a facing up. Next, the suction mechanism is operated so that the ingot 11 is held on the holding surface of the chuck table 4. Next, the imaging unit 12 is operated so as to form an image of the surface 11a of the ingot 11.

[0027] Next, referring to this image, for example, the rotation mechanism rotates the chuck table 4 so that the orientation flat 13 is parallel to the Y-axis direction. In other words, the rotation mechanism rotates the chuck table 4 so that the crystal orientation

[0110] of the diamond is parallel to the X-axis direction.

[0028] Next, the movement mechanism moves the chuck table 4 along the X-axis direction and / or the Y-axis direction so that a region of the ingot 11 near one end in the Y-axis direction is positioned in the X-axis direction when viewed in a plan view from the head 8. Next, the movement mechanism moves the chuck table 4 along the Z-axis direction so that a focal point (first focal point) at which the modifying laser beam LB1 emitted from the head 8 is focused is positioned at a predetermined depth from the surface 11a of the ingot 11 that corresponds to the thickness of a substrate to be manufactured from the ingot 11.

[0029] Next, while emitting the modifying laser beam LB1 from the head 8, the moving mechanism moves the chuck table 4 along the X-axis direction so that the focal point at which the modifying laser beam LB1 is focused passes from one end to the other end in the X-axis direction of the ingot 11. In other words, the modifying laser beam LB1 is irradiated onto the ingot 11 with the scanning direction of the modifying laser beam LB1 being parallel to the crystal orientation

[0110] of diamond.

[0030] Next, the moving mechanism moves the chuck table 4 along the Y-axis direction so that the head 8 is positioned in the X-axis direction when viewed from a region of the ingot 11 that is slightly inside the region that has already been irradiated with the modifying laser beam LB1 in a plan view. Next, the ingot 11 is irradiated with the modifying laser beam LB1 as described above, with the direction opposite to the X-axis direction being the scanning direction of the modifying laser beam LB1.

[0031] Furthermore, the above-mentioned operation is repeated until irradiation of the region of the ingot 11 near the other end in the Y-axis direction with the modifying laser beam LB1 is completed. That is, the relative movement of the ingot 11 along the Y-axis direction and the position where the focal point of the modifying laser beam LB1 is formed (specifically, the movement of the chuck table 4) and the irradiation of the ingot 11 with the modifying laser beam LB1 in the X-axis direction or the opposite direction are alternately repeated.

[0032] As a result, the ingot 11 is irradiated with the modifying laser beam LB1 so that the focal point of the modifying laser beam LB1 draws a plurality of linear loci (specifically, a plurality of linear loci each parallel to the crystal orientation

[0110] of the diamond) T1 inside the ingot 11. As a result, the peeling layer forming step S1 is completed.

[0033] In the above-mentioned peeling layer formation step S1, a direction parallel to the diamond crystal orientation

[0110] (the X-axis direction or the opposite direction) is set as the scanning direction of the modifying laser beam LB1, but a direction non-parallel to this may also be set as the scanning direction of the modifying laser beam LB1.

[0034] In addition, in the peeling layer forming step S1, the ingot 11 may be irradiated with the modifying laser beam LB1 only along one direction (for example, the X-axis direction). That is, in the peeling layer forming step S1, the ingot 11 may be repeatedly irradiated with the modifying laser beam LB1 in the one direction as the scanning direction, without setting the opposite direction to the one direction (for example, the opposite direction to the X-axis direction) as the scanning direction.

[0035] Furthermore, in the peeling layer forming step S1, the ingot 11 may be irradiated with the modifying laser beam LB1 in a non-linear manner. For example, in the peeling layer forming step S1, the ingot 11 may be irradiated with the modifying laser beam LB1 so that the locus of the modifying laser beam LB1 on the ingot 11 is zigzag, radial, spiral, or concentric.

[0036] 5 is a partially enlarged side view showing the ingot 11 after the peeling layer forming step S1. When the ingot 11 is irradiated with the modifying laser beam LB1, a modified portion 15 made of a carbon allotrope other than diamond is formed around the focal point of the modifying laser beam LB1. Examples of carbon allotropes include amorphous carbon such as graphite or carbon black.

[0037] Furthermore, when the modified portion 15 is formed inside the ingot 11, the volume of the ingot 11 expands, causing internal stress in the ingot 11. This internal stress is then alleviated by the extension of the cracks 17 from the modified portion 15. As a result, a peeling layer 19 is formed inside the ingot 11, which includes the modified portion 15 and the cracks 17 extending from the modified portion 15, and is exposed at the side surface 11c of the ingot 11.

[0038] After the peeling layer forming step S1, the peeling layer 19 is heated so that carbon dioxide is generated from the carbon contained in the modified section 15 and the oxygen contained in the atmosphere (heating step S2). Fig. 6 is a perspective view showing the heating step S2. Note that the U-axis direction and the V-axis direction shown in Fig. 6 are directions perpendicular to each other on a horizontal plane, and the W-axis direction is a direction (vertical direction) perpendicular to the U-axis direction and the V-axis direction.

[0039] This heating step S2 is performed in a laser processing device 42. The laser processing device 42 includes a chuck table 44 having a structure similar to that of the chuck table 4 shown in Fig. 4, and this chuck table 44 is connected to a suction mechanism (not shown), a rotation mechanism (not shown), and a movement mechanism (not shown) in the same manner as the chuck table 4.

[0040] Therefore, in the laser processing apparatus 42, while the ingot 11 is held on the holding surface of the chuck table 44, the chuck table 44 can be rotated about a straight line passing through the center of the holding surface and along the W-axis direction as the rotation axis, and / or the chuck table 44 can be moved along the U-axis direction, V-axis direction, and / or W-axis direction.

[0041] A head 48 of a laser beam irradiation unit 46 having a structure similar to that of the head 8 of the laser beam irradiation unit 6 shown in Fig. 4 is provided above the chuck table 44. The head 48 is provided at the tip of a housing 50 having a structure similar to that of the housing 10 shown in Fig. 4.

[0042] The laser beam irradiation unit 46 also has a vaporization laser oscillator (not shown) that contains, for example, carbon dioxide gas as a laser medium. This vaporization laser oscillator generates a pulsed laser beam that transmits through diamond and oscillates an output in a pulsed manner with a wavelength (for example, 9.2 μm to 10.8 μm) that is absorbed by carbon allotropes other than diamond, or a CW (continuous wave) laser beam (vaporization laser beam) LB2 that oscillates an output continuously. Then, the vaporization laser beam LB2 is emitted directly downward from the head 48 through the housing 50 and an optical system contained in the head 48 after its output (power) is adjusted by an attenuator (not shown).

[0043] Furthermore, an imaging unit 52 having a structure similar to that of imaging unit 12 shown in Fig. 4 is provided on the side of housing 50. This imaging unit 52 forms an image by imaging, for example, the area of ​​ingot 11 irradiated with vaporization laser beam LB2. This image is then used, for example, to determine whether this area has been cleaved.

[0044] In the laser processing apparatus 42, the vaporization laser beam LB2 can be irradiated onto the ingot 11 with the chuck table 44, head 48, housing 50 and imaging unit 52 positioned in an atmosphere containing oxygen (for example, in the air or in a chamber maintained in an oxygen atmosphere). In addition, the laser processing apparatus 42 may be provided with an oxygen supply unit including a nozzle or the like for supplying oxygen to the peeling layer 19 exposed at the side surface 11c of the ingot 11.

[0045] When the heating step S2 is performed in the laser processing device 42, first, the ingot 11 on which the peeling layer 19 is formed is placed on the holding surface of the chuck table 44 so that the surface 11a faces up. Next, the suction mechanism is operated so that the ingot 11 is held on the holding surface of the chuck table 44. Next, the imaging unit 52 is operated so as to form an image of the surface 11a of the ingot 11.

[0046] Next, with reference to this image, for example, in a plan view, the movement mechanism moves the chuck table 44 along the U-axis direction and / or the V-axis direction so that the center of the ingot 11 is located in the U-axis direction and slightly outside the side surface 11c of the ingot 11 as seen from the head 48. Next, the movement mechanism moves the chuck table 44 along the W-axis direction so that the focal point (second focal point) at which the vaporization laser beam LB2 emitted from the head 48 is focused is positioned inside the peeling layer 19.

[0047] Next, vaporization laser beam LB2 is emitted from head 48, and chuck table 44 is gradually moved along the U-axis direction while rotating multiple times until head 48 is positioned directly above the center of ingot 11. As a result, vaporization laser beam LB2 is irradiated onto ingot 11 so that the focal point at which vaporization laser beam LB2 is focused traces a spiral trajectory T2 inside ingot 11. As a result, heating step S2 is completed.

[0048] The heating step S2 is performed in an atmosphere containing oxygen (for example, in the air or in a chamber maintained in an oxygen atmosphere). The heating step S2 may be performed while supplying oxygen from an oxygen supply unit to the peeling layer 19 exposed on the side surface 11c of the ingot 11.

[0049] In this heating step S2, oxygen contained in the atmosphere reaches the modified portion 15 through the cracks 17 extending from the side surface 11c of the ingot 11 toward the inside, and the carbon contained in the modified portion 15 reacts with the oxygen to generate carbon dioxide. When carbon dioxide is generated in this manner, the modified portion 15 is reduced in size, forming a cavity.

[0050] Furthermore, when the ingot 11 is irradiated with the vaporization laser beam LB2, the gas present in the cavities and cracks 17 is locally heated and expands. This causes the cracks 17 to rapidly extend in the peeling layer 19, cleaving the ingot 11. As a result, it becomes possible to rapidly manufacture a substrate from the ingot 11.

[0051] The above is one aspect of the present invention, and the present invention is not limited to the above. For example, the laser processing device used in each of the peeling layer forming step S1 and the heating step S2 may be any device capable of relatively moving the ingot 11 and the focal point where the modifying laser beam LB1 or the vaporization laser beam LB2 is focused, and there is no limitation on the structure for this purpose.

[0052] Specifically, the peeling layer forming step S1 may be performed in a laser processing device provided with a moving mechanism for moving a housing having a head of a laser beam irradiation unit at its tip along each of the X-axis, Y-axis, and / or Z-axis directions. Similarly, the heating step S2 may be performed in a laser processing device provided with a moving mechanism for moving a housing having a head of a laser beam irradiation unit at its tip along each of the U-axis, V-axis, and / or W-axis directions.

[0053] Alternatively, each of the peeling layer forming step S1 and the heating step S2 may be performed in a laser processing apparatus in which a scanning optical system capable of changing the direction of the modification laser beam LB1 or the vaporization laser beam LB2 emitted from the head is provided in the laser beam irradiation unit. Note that this scanning optical system includes, for example, a galvanometer scanner, an acousto-optical device (AOD), and / or a polygon mirror.

[0054] Also, the peeling layer forming step S1 and the heating step S2 may be performed in parallel. Each of Fig. 7, Fig. 8 and Fig. 9 is a side view showing a state where the peeling layer forming step S1 and the heating step S2 are performed in parallel in a laser processing apparatus including both a modification laser oscillator and a vaporization laser oscillator. That is, each of Fig. 7, Fig. 8 and Fig. 9 shows a state where the modification laser beam LB1 and the vaporization laser beam LB2 are irradiated to the ingot 11 at the same time.

[0055] Specifically, Figure 7 shows the modification laser beam LB1 and the vaporization laser beam LB2 passing through the same focusing lens 16 provided above the chuck table 14 and being focused at the same position on the ingot 11 held on the holding surface of the chuck table 14.

[0056] In this case, the optical path of the modification laser beam LB1 is set, for example, by using a mirror 18 or the like so that it passes through a region near the center of the condenser lens 16. In addition, the optical path of the vaporization laser beam LB2 is set so that it passes through a region surrounding the center of the condenser lens 16 after being shaped, for example, by an axicon lens (not shown) or the like so that its beam profile becomes ring-shaped.

[0057] The condenser lens 16 is made of, for example, zinc selenide (ZnSe) or glass, etc. Alternatively, the condenser lens 16 may be configured such that the region through which the modification laser beam LB1 passes (region near the center) is made of glass, and the region through which the vaporization laser beam LB2 passes (region surrounding the center) is made of ZnSe.

[0058] Figure 8 shows the modification laser beam LB1 passing through a focusing lens 22 provided above the chuck table 20, and the vaporization laser beam LB2 passing through a focusing lens 24 provided below the chuck table 20, and being focused at the same position inside the ingot 11 held on the holding surface of the chuck table 20.

[0059] The condenser lens 22 is made of, for example, glass. The condenser lens 24 is made of, for example, ZnSe. The chuck table 20 is made of, for example, ZnSe, glass or diamond through which the vaporization laser beam LB2 having a wavelength of 9.2 μm to 10.8 μm passes. Alternatively, the chuck table 20 may be replaced with a holding mechanism capable of holding the ingot 11 from the side surface 11c so that the front surface 11a and the back surface 11b are exposed.

[0060] Figure 9 shows the modification laser beam LB1 passing through a focusing lens 28 provided above the chuck table 26, and the vaporization laser beam LB2 passing through a focusing lens 30 provided above the chuck table 26 and behind the focusing lens 28, and being focused at different positions inside the ingot 11 held on the holding surface of the chuck table 26.

[0061] In this case, the modification laser beam LB1 and the vaporization laser beam LB2 are irradiated onto the ingot 11 so that the focal point of the vaporization laser beam LB2 follows the focal point of the modification laser beam LB1. The condenser lens 28 is made of, for example, glass, etc. The condenser lens 30 is made of, for example, ZnSe, etc.

[0062] 7, 8, and 9, when the peeling layer forming step S1 and the heating step S2 are performed in parallel, the locus of the focal point (first focal point) where the modification laser beam LB1 is focused on the ingot 11 overlaps with the locus of the focal point (second focal point) where the vaporization laser beam LB2 is focused. In this case, the throughput when manufacturing substrates from the ingot 11 can be improved compared to the case where the heating step S2 is performed after the peeling layer forming step S1.

[0063] In the heating step S2, the ingot 11 is heated so that the carbon and oxygen contained in the modified portion 15 react with each other to generate carbon dioxide, and there is no limitation on the irradiation conditions of the vaporization laser beam LB2 for this purpose. For example, the heating step S2 may be performed in a state where the second focal point is positioned inside the peeling layer 19, i.e., in a just-focused state, or may be performed in a state where the second focal point is positioned outside the peeling layer 19, i.e., in a defocused state.

[0064] Alternatively, the heating step S2 may be performed in a state where the second focal point is positioned inside the peeling layer 19, but at a depth that is shifted from a predetermined depth from the surface 11a of the ingot 11 that corresponds to the thickness of a substrate to be manufactured from the ingot 11. That is, the heating step S2 may be performed in a state where the second focal point is positioned at a depth that is shifted from the depth at which the first focal point is positioned in the peeling layer forming step S1.

[0065] Furthermore, in the heating step S2, the trajectory of the second focusing point does not have to be spiral, so long as the vaporization laser beam LB2 is irradiated to a region (first region) included in the ingot 11 and then to a region (second region) closer to the center of the ingot 11 than the first region. That is, in the heating step S2, the vaporization laser beam LB2 may be irradiated to a region of the ingot 11 that is easy for oxygen to reach prior to a region that is difficult for oxygen to reach, so that the reaction between the oxygen included in the atmosphere and the carbon included in the modifying section 15 actively occurs.

[0066] For example, the vaporization laser beam LB2 may be irradiated onto the ingot 11 so that the second focal point moves linearly from each of a plurality of points included in the side surface 11c of the ingot 11 toward the center of the ingot 11. In this case, the vaporization laser beam LB2 is irradiated onto the ingot 11 multiple times such that the second focal point moves from the first region to the second region in each irradiation. In this case, the second focal point draws a radial trajectory inside the ingot 11.

[0067] Alternatively, the vaporization laser beam LB2 may be irradiated onto the ingot 11 by moving the second focal point in the first region, for example, so as to draw a circular locus, and then moving the second focal point in the second region, for example, so as to draw a circular locus. In this case, the vaporization laser beam LB2 is irradiated onto the ingot 11 multiple times such that the diameter of the circular locus drawn by the second focal point gradually decreases. In this case, the second focal point draws a concentric locus inside the ingot 11.

[0068] In addition, in the heating step S2, the vaporization laser beam LB2 may be irradiated onto the ingot 11 while checking the state of cleavage in the peeling layer 19 of the ingot 11. Fig. 10 is a flow chart showing an example of the heating step S2 performed in this manner. Note that the heating step S2 is performed, for example, in the laser processing apparatus 42 shown in Fig. 6.

[0069] Specifically, in this heating step S2, first, the first region is irradiated with the vaporization laser beam LB2 (first vaporization laser beam irradiation step S21). In this first vaporization laser beam irradiation step S21, the vaporization laser beam LB2 is irradiated to the first region so that the second focal point draws, for example, a circular, spiral, or concentric locus in the first region.

[0070] After performing the first vaporization laser beam irradiation step S21, it is determined whether or not the first region has cleaved (determination step S22). In this determination step S22, for example, the imaging unit 52 is used to capture an image of the first region to form an image. Then, an operator refers to this image to determine whether or not the first region has cleaved. Alternatively, in this determination step S22, whether or not the first region has cleaved may be determined by an operator visually inspecting the ingot 11.

[0071] As a result, if it is determined that the first region has not been cleaved (S22: NO), the first vaporization laser beam irradiation step S21 is performed again. On the other hand, if it is determined that the first region has been cleaved (S22: YES), the vaporization laser beam LB2 is irradiated to the second region (second vaporization laser beam irradiation step S23). In this second vaporization laser beam irradiation step S23, the vaporization laser beam LB2 is irradiated to the second region so that the second focal point draws, for example, a circular, spiral, or concentric locus in the second region.

[0072] In addition, in the heating step S2, a part of the ingot 11 may be cleaved at the peeling layer 19, but the remainder may remain without being cleaved. Fig. 11 is a flow chart that shows a schematic example of a method for manufacturing a diamond substrate including the heating step S2 thus performed.

[0073] In this method, after performing the separation layer forming step S1 and the heating step S2, the substrate is separated from the ingot 11 starting from the separation layer 19 (separation step S3). Each of Figs. 12(A) and 12(B) is a side view showing the separation step S3. This separation step S3 is performed in a separation apparatus 32. The separation apparatus 32 includes a chuck table 34 having a structure similar to that of the chuck table 4 shown in Fig. 4.

[0074] The chuck table 34 is connected to a table-side suction mechanism (not shown). This table-side suction mechanism has, for example, a vacuum pump. When this table-side suction mechanism operates, a suction force acts on the space near the holding surface of the chuck table 34. Therefore, when the table-side suction mechanism operates with the ingot 11 placed on the holding surface, the ingot 11 is held on the holding surface of the chuck table 34.

[0075] A peeling unit 36 ​​is provided above the chuck table 34. The peeling unit 36 ​​has a suction plate 38 having a plurality of suction ports formed on the lower surface thereof. The plurality of suction ports communicate with a peeling unit side suction mechanism such as a vacuum pump via suction paths formed inside the suction plate 38. When the peeling unit side suction mechanism operates, a suction force acts on the space near the lower surface of the suction plate 38.

[0076] A vertical movement mechanism 40 is connected to the upper surface of the suction plate 38. The vertical movement mechanism 40 has, for example, a ball screw and a motor. When the vertical movement mechanism 40 operates, the suction plate 38 moves in the vertical direction.

[0077] When performing the peeling step S3 in the peeling device 32, first, with the chuck table 34 and the suction plate 38 sufficiently spaced apart, the ingot 11 having the peeled layer 19 formed therein is placed on the holding surface of the chuck table 34 with the surface 11a facing up. Next, the table-side suction mechanism is operated so that the ingot 11 is held on the holding surface of the chuck table 34.

[0078] Next, the vertical movement mechanism 40 lowers the suction plate 38 so that the lower surface of the suction plate 38 contacts the front surface 11a of the ingot 11 (see FIG. 12(A)). Next, the peeling unit side suction mechanism is operated so that the front surface 11a side of the ingot 11 is sucked upward. Next, the vertical movement mechanism 40 raises the suction plate 38 so as to separate the suction plate 38 from the chuck table 34 (see FIG. 12(B)).

[0079] This applies an external force to ingot 11 that separates front surface 11a and back surface 11b of ingot 11, further expanding crack 17 contained in peeling layer 19. As a result, ingot 11 is cleaved at peeling layer 19 to produce substrate 21. This completes peeling step S3, i.e., the method for producing a diamond substrate shown in FIG.

[0080] In addition, the peeling device 32 may be used to separate the substrate 21 from the ingot 11 by sucking the substrate 21, which has already been peeled off from the ingot 11 and is placed on the ingot 11, upward.

[0081] The peeling step S3 may be performed by any method. For example, in the peeling step S3, an external force may be applied to the ingot 11 such that a wedge is driven into the peeling layer 19 from the side surface 11c of the ingot 11 to separate the front surface 11a side and the back surface 11b side of the ingot 11 from each other.

[0082] Furthermore, the workpiece used in the manufacture of the diamond substrate may be an ingot manufactured so that a crystal face other than the (001) crystal face of diamond (for example, the (110) crystal face) is exposed on the surface.

[0083] Furthermore, the workpiece used to manufacture the diamond substrate may be, for example, a bare wafer having a thickness that is two to five times that of the substrate 21 to be manufactured. The bare wafer is manufactured, for example, by peeling it from the ingot 11 by the same method as the above-mentioned method. In this case, it can also be expressed that the substrate 21 is manufactured by repeating the above-mentioned method twice.

[0084] The workpiece used to manufacture the diamond substrate may be a device wafer manufactured by forming a semiconductor device on one side of the bare wafer. In this case, the modification laser beam and the vaporization laser beam are preferably irradiated onto the device wafer from the side on which the semiconductor device is not formed, in order to prevent adverse effects on the semiconductor device.

[0085] In addition, the structures and methods according to the above-described embodiments can be modified as appropriate without departing from the scope of the present invention. [Explanation of symbols]

[0086] 2: Laser processing equipment 4: Chuck table 6: Laser beam irradiation unit 8: Head 10: Housing 11: Ingot (11a: front surface, 11b: back surface, 11c: side surface) 12: Imaging unit 13: Orientation Flat 14: Chuck table 15: Modification section 16: Condenser lens 17: Crack 18: Mirror 19: Release layer 20: Chuck table 21: Substrate 22: Condenser lens 24: Condenser lens 26: Chuck table 28: Condenser lens 30: Condenser lens 32: Peeling device 34: Chuck table 36: Peeling unit 38: Suction plate 40: Vertical movement mechanism 42: Laser processing equipment 44: Chuck table 46: Laser beam irradiation unit 48: Head 50: Housing 52: Imaging unit

Claims

1. A method for producing a diamond substrate from a workpiece made of diamond and including a first surface, a second surface opposite to the first surface, and a side surface located between the first surface and the second surface, comprising: a peeling layer forming step of forming a peeling layer inside the workpiece, the peeling layer including a modified portion made of a carbon allotrope other than the diamond and cracks extending from the modified portion, and exposed at the side surface of the workpiece, by irradiating the workpiece with the modification laser beam while positioning a first focal point of the modification laser beam having a wavelength that transmits the diamond at a predetermined depth from the first surface corresponding to the thickness of the substrate and moving the first focal point and the workpiece relatively; a heating step, performed after or in parallel with the peeling layer formation step, of irradiating the workpiece with a vaporization laser beam so as to move a second focal point of the vaporization laser beam, the second focal point being transmitted through the diamond and having a wavelength that is absorbed by the carbon allotrope, relative to the workpiece, thereby heating the peeling layer so that carbon dioxide is generated from the carbon contained in the modified portion and oxygen contained in the atmosphere; A method for manufacturing a diamond substrate, wherein in the heating step, the vaporization laser beam is irradiated onto a first region included in the workpiece and then onto a second region that is closer to the center of the workpiece than the first region.

2. The heating step comprises: a first vaporization laser beam irradiation step of irradiating the first region with the vaporization laser beam; a determining step of determining whether or not the first region has been cleaved after the first vaporization laser beam irradiation step is performed; a second vaporization laser beam irradiation step of irradiating the second region with the vaporization laser beam when it is determined in the determination step that the first region has been cleaved; The method for producing a diamond substrate according to claim 1 , comprising:

3. 3. The method for producing a diamond substrate according to claim 1, wherein the vaporization laser beam uses carbon dioxide gas as a laser medium.

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