Method for manufacturing substrate

Abstract

To provide a method of manufacturing a substrate capable of appropriately and smoothly separating the substrate from a workpiece.SOLUTION: According to an aspect of the present invention, there is provided a substrate manufacturing method for manufacturing a substrate from a workpiece having a first surface, a second surface located on a side opposite to the first surface, and a side surface connected to an outer edge of the first surface and an outer edge of the second surface. The method includes a separation layer forming step of forming a separation layer including a modified portion and a crack extending from the modified portion inside the workpiece, an external force applying step of applying an external force to the workpiece from a side surface side, and a separating step of separating the substrate from the workpiece with the separation layer as a starting point.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a substrate from a workpiece. [Background technology]

[0002] The device chip manufacturing process uses a wafer in which devices are formed in multiple regions defined by multiple streets (planned division lines) arranged in a grid pattern. Device chips equipped with devices are manufactured by dividing the wafer along the streets into individual pieces. Device chips are incorporated into various electronic devices such as mobile phones and personal computers.

[0003] Wafers are typically produced by slicing cylindrical ingots with a wire saw. However, the wires in a wire saw can have a diameter equal to or greater than the thickness of the wafer, making it difficult to precisely process the ingot. Therefore, when slicing an ingot with a wire saw, a certain amount of kerf must be secured, and a significant portion of the ingot is removed before it can be used as wafers. This limits the number of wafers that can be produced from a single ingot and increases costs.

[0004] Therefore, a method has been proposed in which a laser beam is irradiated onto an ingot to form a separation layer composed of modified portions and cracks inside the ingot (see, for example, Patent Document 1). The region of the ingot where the separation layer is formed is more brittle than other regions, so when an external force is applied to the ingot on which the separation layer is formed, the ingot breaks starting from the separation layer, and a wafer is separated from the ingot. By using such a method, the amount of ingot removed in the process of separating the wafer from the ingot is reduced, improving wafer productivity. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-111143 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, after a separation layer is formed on a workpiece such as an ingot by irradiating it with a laser beam, an external force can be applied to the workpiece to separate a substrate such as a wafer from the workpiece. However, depending on the material of the workpiece and the conditions of the laser beam irradiation, the laser beam irradiation may not result in the intended formation of a modified portion or cracks inside the workpiece, resulting in incomplete formation of the separation layer.

[0007] If an external force is applied to the workpiece when the separation layer is incompletely formed, the separation layer will not function adequately as a separation starting point, making it difficult to separate the substrate from the workpiece. In this case, if a strong external force is applied to the substrate in an attempt to forcibly separate the substrate from the workpiece, the separation of the substrate may proceed in an unintended direction, potentially causing cracks or chips in the substrate. Furthermore, even if it were possible to properly separate the substrate, it would be necessary to adjust the strength of the external force so that a stronger external force than usual is applied to the workpiece, which would hinder smooth separation of the substrate.

[0008] The present invention has been made in view of the above problems, and has as its object to provide a method for manufacturing a substrate that is capable of properly and smoothly separating the substrate from a workpiece. [Means for solving the problem]

[0009] According to one aspect of the present invention, there is provided a method for manufacturing a substrate from a workpiece having a first surface, a second surface located opposite the first surface, and a side surface connected to the outer edge of the first surface and the outer edge of the second surface, the method comprising: a separation layer formation step in which a laser beam having a wavelength that passes through the workpiece is irradiated from the first surface side or the second surface side while the focal point of the laser beam is positioned inside the workpiece, thereby forming a separation layer inside the workpiece that includes a modified portion and a crack extending from the modified portion; an external force application step in which, after the separation layer formation step, an external force is applied to the workpiece from the side surface side; and a separation step in which, after the external force application step, the substrate is separated from the workpiece starting from the separation layer.

[0010] Preferably, the method for manufacturing a substrate further comprises, after the separating step, a grinding step of grinding the substrate separated from the workpiece.

[0011] Preferably, in the external force applying step, a laser beam is irradiated onto the workpiece from the side surface. Also, preferably, in the external force applying step, a tool is brought into contact with the side surface of the workpiece.

[0012] Preferably, in the external force applying step, the side surface of the workpiece in a region corresponding to the substrate is processed to have a predetermined shape, thereby applying an external force to the workpiece from the side surface. Also preferably, in the external force applying step, the side surface of the workpiece in a region corresponding to the substrate is processed to have a predetermined shape, thereby applying an external force to the workpiece from the side surface, and in the external force applying step, the position on the workpiece where the processing is to be performed is determined based on the planned amount of grinding of the substrate in the grinding step. [Effects of the Invention]

[0013] In a substrate manufacturing method according to one aspect of the present invention, after a separation layer is formed on a workpiece, an external force is applied to the side surface of the workpiece, which improves the function of the separation layer and promotes separation of the substrate, thereby enabling the substrate to be properly and smoothly separated from the workpiece. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1(A) is a perspective view showing a workpiece, and FIG. 1(B) is a side view showing the workpiece. [Figure 2] 1 is a flowchart showing a method for manufacturing a substrate. [Figure 3] FIG. 10 is a perspective view showing the workpiece in a separation layer forming step. [Figure 4] FIG. 4(A) is a plan view showing a workpiece on which a modified portion is formed, and FIG. 4(B) is a front view showing a workpiece on which a separation layer is formed. [Figure 5] FIG. 5(A) is a perspective view showing a workpiece to which an external force is applied by irradiation with a laser beam, and FIG. 5(B) is a front view showing the workpiece to which an external force is applied by irradiation with a laser beam. [Figure 6] FIG. 6(A) is a perspective view showing a workpiece to which an external force is applied by contact with a tool, and FIG. 6(B) is a front view showing the workpiece to which an external force is applied by contact with a tool. [Figure 7] FIG. 7(A) is a front view showing a separation device that holds a workpiece, and FIG. 7(B) is a front view showing a separation device that separates a substrate from the workpiece. [Figure 8] FIG. 10 is a perspective view showing the substrate in a grinding step. [Figure 9] FIG. 9(A) is a front view showing a workpiece to be machined by a laser beam, and FIG. 9(B) is a front view showing a workpiece to be machined by a tool. [Figure 10] FIG. 2 is a front view showing a portion of a separation region of a workpiece. DETAILED DESCRIPTION OF THE INVENTION

[0015] (Embodiment 1) An embodiment of the present invention will be described below with reference to the accompanying drawings. First, an example of the structure of a workpiece that can be used in a substrate manufacturing method according to this embodiment will be described. Fig. 1(A) is a perspective view showing workpiece 11, and Fig. 1(B) is a side view showing workpiece 11.

[0016] The workpiece 11 is a base material used to form a substrate, and is typically a cylindrical ingot. A substrate of a predetermined thickness can be obtained by separating a portion of the workpiece 11 from the main body of the workpiece 11. For example, the workpiece 11 is a single crystal ingot made of a semiconductor material such as silicon, silicon carbide, gallium nitride, or gallium oxide. In this case, a semiconductor wafer can be obtained by separating the substrate from the workpiece 11.

[0017] In the following, as an example, a case where the workpiece 11 is an ingot made of β-gallium oxide will be described. Figures 1(A) and 1(B) show the appearance of the workpiece 11 and the crystal planes and crystal orientations of the β-gallium oxide that constitutes the workpiece 11.

[0018] The workpiece 11 has a first surface (front surface) 11a, a second surface (back surface) 11b located opposite the first surface 11a, and a side surface (outer peripheral surface) 11c connected to the outer edges of the first surface 11a and the second surface 11b. The first surface 11a and the second surface 11b are disposed approximately parallel to each other, and the side surface 11c is disposed approximately perpendicular to the first surface 11a and the second surface 11b.

[0019] The β-gallium oxide constituting the workpiece 11 has a monoclinic crystal structure. Specifically, the angle between the crystal orientation

[0100] (a-axis) and the crystal orientation

[0010] (b-axis) is 90°, the angle between the crystal orientation

[0010] (b-axis) and the crystal orientation

[0001] (c-axis) is 90°, and the angle between the crystal orientation

[0100] (a-axis) and the crystal orientation

[0001] (c-axis) is 103.7°.

[0020] The workpiece 11 is manufactured so that the crystal plane {001} is exposed on the first surface 11a and the second surface 11b. However, due to processing errors during the manufacture of the workpiece 11, a surface slightly tilted from the crystal plane {001} (for example, a surface forming an angle of 1° or less with the crystal plane {001}) may be exposed on the first surface 11a and the second surface 11b. For convenience, it is assumed below that the surface exposed on the first surface 11a is the crystal plane (001).

[0021] Orientation flats 13A and 13B indicating the crystal orientation of workpiece 11 (β-gallium oxide) are provided on the outer periphery of workpiece 11. Orientation flats 13A and 13B are cutouts formed by cutting off part of the outer periphery of workpiece 11 along the thickness direction (height direction) of workpiece 11, and are provided at predetermined positions with respect to a predetermined crystal orientation of workpiece 11.

[0022] For example, orientation flat 13A is oriented in the direction of the crystal orientation

[0100] when viewed from the center of workpiece 11, and orientation flat 13B is oriented in the direction of the crystal orientation

[0010] when viewed from the center of workpiece 11. The crystal plane (010) is exposed on orientation flat 13B. Furthermore, orientation flat 13B is positioned perpendicular to the crystal plane (100), and the angle between the crystal plane (100) and the first surface 11a and the second surface 11b is 103.7°.

[0023] When the workpiece 11 is an ingot made of β-gallium oxide, the orientation flats 13A and 13B are provided, for example, as described above. However, the presence or absence, number, and position of orientation flats can be determined appropriately depending on the material, application, etc. of the workpiece 11. For example, the workpiece 11 may have only one of the orientation flats 13A and 13B, or may not have either of the orientation flats 13A and 13B. Furthermore, the workpiece 11 may have a notch indicating the crystal orientation of the workpiece 11 instead of the orientation flats 13A and 13B.

[0024] 2 is a flowchart showing a method for manufacturing a substrate. In this embodiment, a substrate is manufactured by processing the workpiece 11 described above. Specifically, in the method for manufacturing a substrate according to this embodiment, a separation layer that functions as a separation starting point for the substrate is formed inside the workpiece 11 (separation layer forming step S1), and then an external force is applied to the workpiece 11 to improve the function of the separation layer (external force application step S2). Then, the substrate is separated from the workpiece 11 using the separation layer as a starting point (separation step S3), and the substrate is ground as necessary (grinding step S4). Each step will be described in detail below.

[0025] 3 is a perspective view showing the workpiece 11 in the separation layer forming step S1. For example, in the separation layer forming step S1, a separation layer is formed inside the workpiece 11 by performing laser processing on the workpiece 11 using a laser processing device 2. In FIG. 3, the X-axis direction (processing feed direction, first horizontal direction, left-right direction) and the Y-axis direction (indexing feed direction, second horizontal direction, front-rear direction) are perpendicular to each other. Furthermore, the Z-axis direction (up-down direction, height direction, vertical direction) is perpendicular to the X-axis direction and the Y-axis direction.

[0026] The laser processing device 2 includes a chuck table (holding table) 4 that holds the workpiece 11. The upper surface of the chuck table 4 is a flat surface that is roughly parallel to the horizontal plane (XY plane), and forms a circular holding surface 4a that holds the workpiece 11. The holding surface 4a is connected to a suction source (not shown) such as an ejector via a flow path (not shown), a valve (not shown), and the like that are formed inside the chuck table 4.

[0027] The chuck table 4 is connected to a moving unit (not shown) that moves the chuck table 4 and a rotary drive source (not shown) that rotates the chuck table 4. The moving unit is configured with, for example, a ball screw type moving mechanism, and moves the chuck table 4 along the X-axis direction and the Y-axis direction. The rotary drive source is configured with a motor or the like, and rotates the chuck table 4 around a rotation axis that is roughly parallel to the Z-axis direction.

[0028] The laser processing device 2 also includes a laser irradiation unit 6 that irradiates a laser beam 12 onto the workpiece 11. The laser irradiation unit 6 includes a laser oscillator (not shown), such as a YAG laser, YVO4 laser, or YLF laser, that emits a pulsed laser beam 12, a housing 8 that is provided above the chuck table 4, and a laser processing head 10. The housing 8 is formed in a hollow cylindrical shape and is disposed along the Y-axis direction. The laser processing head 10 that irradiates the laser beam 12 toward the chuck table 4 is attached to the tip of the housing 8.

[0029] The housing 8 and the laser processing head 10 house an attenuator that adjusts the output of the laser beam 12 emitted from the laser oscillator, an optical system that guides the laser beam 12 emitted from the laser oscillator to the workpiece 11 held by the chuck table 4, and other components. The optical system includes optical elements such as lenses, mirrors, polarizing beam splitters (PBS), diffractive optical elements (DOE), and liquid crystal on silicon spatial light modulators (LCOS-SLMs), and controls the traveling direction, shape, focusing position, and other aspects of the laser beam 12.

[0030] The laser processing head 10 houses a condenser (not shown), which is a component of the optical system. The condenser has a focusing lens such as an fθ lens, and focuses the laser beam 12 to irradiate the workpiece 11. The laser processing head 10 irradiates the workpiece 11 with the laser beam 12, thereby performing laser processing on the workpiece 11.

[0031] An imaging unit 14 that captures an image of a subject is also attached to the laser irradiation unit 6. For example, the imaging unit 14 is fixed to the housing 8 and installed adjacent to the laser processing head 10. The imaging unit 14 includes an image sensor such as a CCD (Charged-Coupled Devices) sensor or a CMOS (Complementary Metal-Oxide-Semiconductor) sensor, and captures an image of the workpiece 11 held by the chuck table 4. There are no limitations on the type of imaging unit 14, and a visible light camera or an infrared camera, for example, may be used.

[0032] The imaging unit 14 captures an image of the workpiece 11. Based on the image captured by the imaging unit 14, the alignment of the workpiece 11 with the laser processing head 10 and the state of the workpiece 11 are performed.

[0033] The housing 8 may be connected to a moving unit (not shown) that moves the housing 8. For example, the moving unit is configured with a ball screw type moving mechanism, and moves (raises and lowers) the housing 8 along the Z-axis direction together with the laser processing head 10 and the imaging unit 14. This makes it possible to adjust the height position of the focal point of the laser beam 12, focus the imaging unit 14, etc.

[0034] In the separation layer forming step S1, first, the workpiece 11 is held by the chuck table 4. For example, the workpiece 11 is placed on the chuck table 4 so that the first surface 11a is exposed upward and the second surface 11b faces the holding surface 4a. In this state, when the suction force (negative pressure) of the suction source is applied to the holding surface 4a, the workpiece 11 is sucked and held by the chuck table 4.

[0035] Next, the laser irradiation unit 6 is activated, and the laser processing head 10 irradiates the workpiece 11 with a laser beam 12. This performs laser processing on the workpiece 11. The irradiation conditions of the laser beam 12 are set so that a separation layer that functions as a separation starting point is formed inside the workpiece 11.

[0036] Specifically, the irradiation conditions of the laser beam 12 are set so that the area inside the workpiece 11 irradiated with the laser beam 12 is modified (altered) to form a modified portion (altered portion) 15. More specifically, the wavelength of the laser beam 12 is set so that at least a portion of the laser beam 12 passes through the workpiece 11. Other irradiation conditions of the laser beam 12 are also set appropriately so that the modified portion 15 is appropriately formed in the workpiece 11. For example, when the workpiece 11 is an ingot made of β-gallium oxide, the irradiation conditions of the laser beam 12 can be set as follows. Wavelength: 1064nm Average power: 1.5W Repetition frequency: 50kHz Processing feed rate: 450mm / s

[0037] When irradiating the workpiece 11 with the laser beam 12, first, the imaging unit 14 images the workpiece 11 to obtain an image of the first surface 11a of the workpiece 11. Then, the orientation of the workpiece 11 is identified based on the image, and the chuck table 4 is rotated to adjust the orientation of the workpiece 11. For example, the rotation angle of the chuck table 4 is adjusted so that the orientation flat 13B provided on the workpiece 11 is parallel to the X-axis direction. In this case, the crystal orientation

[0100] of the β-gallium oxide constituting the workpiece 11 is aligned parallel to the X-axis direction, and the crystal orientation

[0010] is aligned parallel to the Y-axis direction.

[0038] Next, the positional relationship between the workpiece 11 and the laser processing head 10 is adjusted. Specifically, the position of the chuck table 4 in the X-axis direction is adjusted so that the laser processing head 10 is positioned outside the workpiece 11 in the X-axis direction. In addition, the position of the chuck table 4 in the Y-axis direction is adjusted so that the end of the workpiece 11 near the orientation flat 13B and the laser processing head 10 are positioned in the Y-axis direction.

[0039] Furthermore, the height position of the focal point of the laser beam 12 is adjusted to coincide with the height position inside (between the first surface 11a and the second surface 11b) of the workpiece 11. The difference in height between the first surface 11a of the workpiece 11 and the focal point of the laser beam 12 at this time corresponds to the depth of the modified portion 15 formed inside the workpiece 11.

[0040] Then, while emitting a laser beam 12 from the laser processing head 10, the chuck table 4 is moved along the X-axis direction at a predetermined processing feed rate, and the workpiece 11 and the laser processing head 10 are moved relatively along the X-axis direction (processing feed). As a result, with the focal point of the laser beam 12 positioned inside the workpiece 11, the laser beam 12 having a wavelength that transmits through the workpiece 11 is irradiated from the first surface 11a side of the workpiece 11, and scanned from one end to the other end in the X-axis direction of the workpiece 11. Specifically, the laser beam 12 is scanned along a direction parallel to the crystal orientation

[0100] of β-gallium oxide.

[0041] When the workpiece 11 is irradiated with the laser beam 12 as described above, the area inside the workpiece 11 irradiated with the laser beam 12 expands, causing a disturbance (distortion) in the crystal structure, thereby modifying the workpiece 11. As a result, a linear modified region 15 is formed inside the workpiece 11 along the X-axis direction.

[0042] Thereafter, the chuck table 4 is moved along the Y-axis direction by a predetermined index amount (for example, about 0.2 mm), and the workpiece 11 and the laser processing head 10 are moved relatively along the Y-axis direction (indexing feed). Then, processing feed is performed while irradiating the laser beam 12 from the laser processing head 10 in the same procedure as above. By repeating this operation, multiple roughly parallel modified regions 15 are formed at predetermined intervals at a predetermined depth position inside the workpiece 11.

[0043] The workpiece 11 may be irradiated with the laser beam 12 only on the outgoing path of the processing feed, or on both the outgoing and return paths of the processing feed. Instead of moving the chuck table 4, the laser processing head 10 may be moved to scan the laser beam 12. Furthermore, instead of moving the chuck table 4 or the laser processing head 10, a scanning optical system for scanning the laser beam 12 may be mounted on the laser irradiation unit 6. For example, the scanning optical system may include optical elements such as a galvanometer scanner, an acousto-optical device (AOD), and a polygon mirror.

[0044] Fig. 4(A) is a plan view showing the workpiece 11 on which the modified portion 15 is formed. For ease of explanation, the modified portion 15 formed at a predetermined depth position inside the workpiece 11 is shown by a solid line in Fig. 4(A).

[0045] When the laser beam 12 is scanned with the focal point 12a of the laser beam 12 positioned at a predetermined depth inside the workpiece 11, the workpiece 11 is modified at and near the focal point 12a, forming linear modified regions 15. Furthermore, internal stress acts in the modified regions 15, causing multiple fine cracks 17 to form, and the cracks 17 extend from the modified regions 15 in a direction intersecting the thickness direction of the workpiece 11. Then, by forming multiple modified regions 15 at predetermined intervals, the modified regions 15 and cracks 17 are formed throughout the entire area of ​​the workpiece 11.

[0046] FIG. 4(B) is a front view showing the workpiece 11 on which a separation layer (modified layer) 19 has been formed. When the modified portions 15 and cracks 17 are formed as described above, the separation layer 19 is formed at a predetermined depth position inside the workpiece 11. The separation layer 19 corresponds to the region inside the workpiece 11 where the modified portions 15 or cracks 17 have been formed. The depth at which the separation layer 19 of the workpiece 11 is formed (the distance between the first surface of the workpiece 11 and the separation layer 19) corresponds to the thickness of the substrate to be separated from the workpiece 11 in the separation step S3 (see FIGS. 7(A) and 7(B)) described below.

[0047] In the above, an example has been described in which the laser beam 12 is irradiated from the first surface side of the workpiece 11 and scanned along the crystal orientation

[0100] of β-gallium oxide. However, there are no limitations on the method of irradiating the laser beam 12 as long as it is possible to form the separation layer 19 at a predetermined depth position inside the workpiece 11.

[0048] For example, the laser beam 12 may be irradiated onto the second surface 11b of the workpiece 11. In this case, the first surface 11a of the workpiece 11 is held by the chuck table 4, and the laser processing head 10 irradiates the laser beam 12 onto the second surface 11b of the workpiece 11.

[0049] Furthermore, the scanning direction (processing feed direction) of the laser beam 12 may be non-parallel to the crystal orientation

[0100] of β-gallium oxide. However, the smaller the angle between the scanning direction of the laser beam 12 and the crystal orientation

[0100] of β-gallium oxide, the more likely the crack 17 will propagate along the crystal plane (001) and the less likely it will propagate along the crystal plane (100). Therefore, to efficiently form the separation layer 19 over the entire area of ​​the workpiece 11 while avoiding the separation layer 19 from being formed unnecessarily thick, it is preferable that the angle between the scanning direction of the laser beam 12 and the crystal orientation

[0100] of β-gallium oxide is small. For example, the angle between the scanning direction of the laser beam 12 (the lengthwise direction of the modified region 15) and the crystal orientation

[0100] of β-gallium oxide is preferably set to 35° or less, more preferably 10° or less, and even more preferably 5° or less.

[0050] The region of workpiece 11 where separation layer 19 is formed has lower mechanical strength and is more fragile than other regions of workpiece 11. Therefore, separation layer 19 functions as a separation starting point (a trigger for separation) when separating the substrate from workpiece 11. Specifically, when an external force is applied to workpiece 11 in a separation step S3 (see FIGS. 7(A) and 7(B)) described below, the first surface 11a side of workpiece 11 breaks starting from separation layer 19, and a substrate of a predetermined thickness is separated from workpiece 11.

[0051] However, depending on the material of the workpiece 11 and the irradiation conditions of the laser beam 12, the irradiation of the laser beam 12 may not result in the intended formation of the modified region 15 or crack 17 inside the workpiece 11, resulting in incomplete formation of the separation layer 19. In this case, if a strong external force is applied to the workpiece 11 in an attempt to forcibly separate the workpiece 11 from the substrate, the separation of the substrate may proceed in an unintended direction, resulting in cracks or chips in the substrate. Furthermore, even if it were possible to properly separate the substrate, it would be necessary to adjust the strength of the external force so that a stronger external force than usual is applied to the workpiece 11, which would hinder smooth separation of the substrate.

[0052] Therefore, in this embodiment, before separating the substrate from the workpiece 11 on which the separation layer 19 is formed, an external force is applied to the workpiece 11 to further extend the cracks 17 contained in the separation layer 19 (external force application step S2). As a result, even if the separation layer 19 formed in the separation layer formation step S1 is incomplete, the function of the separation layer 19 as a separation starting point can be improved afterwards in the external force application step S2.

[0053] 5(A) is a perspective view showing the workpiece 11 to which an external force is applied by irradiation with the laser beam 28, and FIG. 5(B) is a front view showing the workpiece 11 to which an external force is applied by irradiation with the laser beam 28. For example, in the external force applying step S2, an external force applying device 20 is used that applies an external force to the workpiece 11 by irradiating it with the laser beam 28.

[0054] The external force application device 20 includes a chuck table (holding table) 22 that holds the workpiece 11. The upper surface of the chuck table 22 is a flat surface that is roughly parallel to the horizontal plane, and forms a circular holding surface 22a that holds the workpiece 11. The holding surface 22a is connected to a suction source (not shown) such as an ejector via a flow path (not shown), a valve (not shown), and the like that are formed inside the chuck table 22.

[0055] The chuck table 22 is connected to a moving unit (not shown) that moves the chuck table 22 and a rotary drive source (not shown) that rotates the chuck table 22. The moving unit is configured by, for example, a ball screw type moving mechanism, and moves the chuck table 22 in the horizontal direction. The rotary drive source is configured by a motor or the like, and rotates the chuck table 22 around a rotation axis that is approximately parallel to the vertical direction.

[0056] The external force imparting device 20 also includes a laser irradiation unit 24 that irradiates a laser beam onto the workpiece 11. The laser irradiation unit 24 can be configured in the same manner as the laser irradiation unit 6 (see FIG. 3) of the laser processing device 2. However, the laser irradiation unit 24 includes a laser processing head 26 that irradiates a laser beam 28, located on the side of the chuck table 22. The laser processing head 26 is also connected to a movement mechanism (not shown) that moves (raises and lowers) the laser processing head 26 in the vertical direction.

[0057] In the external force application step S2, first, the workpiece 11 is held by the chuck table 22. For example, the workpiece 11 is placed on the chuck table 22 so that the first surface 11a is exposed upward and the second surface 11b faces the holding surface 22a. In this state, when a suction force (negative pressure) from a suction source is applied to the holding surface 22a, the workpiece 11 is sucked and held by the chuck table 22. However, the chuck table 22 may hold the first surface 11a of the workpiece 11.

[0058] Next, the positional relationship between the chuck table 22 and the laser processing head 26 is adjusted. Specifically, the horizontal position of the chuck table 22 and the height position of the laser processing head 26 are adjusted so that the laser processing head 26 is positioned to the side of the workpiece 11. In addition, the focal point of the laser beam 28 irradiated from the laser processing head 26 is positioned on or near the side surface 11c of the workpiece 11. For example, the focal point of the laser beam 28 is positioned at a depth position on the side surface 11c of the workpiece 11 where the separation layer 19 is formed (the end of the separation layer 19).

[0059] Then, while rotating the chuck table 22, a laser beam 28 is irradiated from the laser processing head 26 toward the workpiece 11. As a result, the laser beam 28 is irradiated onto the side surface 11c of the workpiece 11, and is circularly scanned along the side surface 11c.

[0060] The irradiation conditions of the laser beam 28 are set so that an external force is applied to the region of the workpiece 11 irradiated with the laser beam 28 (the irradiated region). For example, the irradiation conditions of the laser beam 28 are set so that ablation processing is performed on the irradiated region of the workpiece 11. Specifically, the wavelength of the laser beam 28 is set so that at least a portion of the laser beam 28 is absorbed by the workpiece 11. In addition, other irradiation conditions of the laser beam 28 are also set appropriately so that ablation processing is performed on the workpiece 11. For example, when the workpiece 11 is an ingot made of β-gallium oxide, the irradiation conditions of the laser beam 28 can be set as follows. Wavelength: 355nm Average power: 13.5W Repetition frequency: 100kHz

[0061] The rotation speed of the chuck table 22 is set according to the size (diameter) of the workpiece 11 so that the desired ablation processing is performed on the workpiece 11. Then, the chuck table 22 is rotated once while the laser processing head 26 irradiates the laser beam 28 toward the side surface 11c of the workpiece 11. This causes the laser beam 28 to scan in a circular pattern along the side surface 11c of the workpiece 11. However, the number of rotations of the chuck table 22 may be two or more.

[0062] As described above, the laser beam 28 is irradiated onto or near the end of the separation layer 19, which is a part of the side surface 11c of the workpiece 11. This causes laser processing to be performed on the side surface 11c of the workpiece 11, and the external force (impact) applied to the workpiece 11 at this time is transmitted to the separation layer 19. As a result, the cracks 17 (see FIG. 4(A)) formed in the separation layer 19 further extend. In addition, new cracks 17 may extend from the modified portions 15 (see FIG. 4(A)). This promotes modification of the separation layer 19 and improves the function of the separation layer 19 as a separation starting point.

[0063] Furthermore, an annular groove (laser-processed groove) may be formed on the side surface 11c of the workpiece 11 by ablation processing using irradiation with the laser beam 28. In this case, the laser-processed groove also functions as a separation starting point together with the separation layer 19, further facilitating separation of the substrate from the workpiece 11.

[0064] Although the above describes an example in which the laser beam 28 is scanned by rotating the chuck table 22 while the position of the laser processing head 26 is fixed, the method of scanning the laser beam 28 is not limited to rotating the chuck table 22. For example, when applying an external force to the areas of the workpiece 11 where the orientation flats 13A and 13B are provided, the chuck table 22 and the laser processing head 26 may be moved relatively in a direction parallel to the orientation flats 13A and 13B instead of rotating the chuck table 22. This allows the laser beam 28 to linearly scan the areas of the workpiece 11 where the orientation flats 13A and 13B are provided.

[0065] Furthermore, as long as the extension of the crack 17 is promoted in the separation layer 19, the laser beam 28 does not necessarily have to be irradiated along the entire circumference of the side surface 11c of the workpiece 11. For example, the laser beam 28 may be irradiated intermittently along the side surface 11c of the workpiece 11, or may be irradiated onto an arc-shaped region corresponding to a part of the side surface 11c of the workpiece 11.

[0066] Furthermore, in the external force applying step S2, the external force may be applied to the workpiece 11 by a method other than irradiation with the laser beam 28. For example, the external force may be applied to the workpiece 11 by bringing a tool into contact with the side surface 11c of the workpiece 11.

[0067] 6(A) is a perspective view showing workpiece 11 to which an external force is applied by contact with tool 40, and Fig. 6(B) is a front view showing workpiece 11 to which an external force is applied by contact with tool 40. In external force applying step S2, an external force applying device 30 can also be used, which applies an external force to workpiece 11 by bringing tool 40 into contact with workpiece 11.

[0068] The external force application device 30 includes a chuck table (holding table) 32 that holds the workpiece 11. The upper surface of the chuck table 32 is a flat surface that is roughly parallel to the horizontal plane, and forms a circular holding surface 32a that holds the workpiece 11. The holding surface 32a is connected to a suction source (not shown) such as an ejector via a flow path (not shown), a valve (not shown), and the like that are formed inside the chuck table 32.

[0069] The chuck table 32 is connected to a moving unit (not shown) that moves the chuck table 32 and a rotary drive source (not shown) that rotates the chuck table 32. The moving unit is configured by, for example, a ball screw type moving mechanism, and moves the chuck table 32 in the horizontal direction. The rotary drive source is configured by a motor or the like, and rotates the chuck table 32 around a rotation axis that is approximately parallel to the vertical direction.

[0070] The external force imparting device 30 also includes an external force imparting unit 34 that applies an external force to the workpiece 11 by bringing a tool 40 into contact with the workpiece 11. For example, the external force imparting unit 34 includes a hollow, cylindrical housing 36 and a cylindrical spindle 38 housed in the housing 36. The spindle 38 is disposed along the vertical direction, and the tip end (lower end) of the spindle 38 protrudes downward from the housing 36. A rotational drive source (not shown), such as a motor, is connected to the base end (upper end) of the spindle 38 to rotate the spindle around a rotation axis that is approximately parallel to the vertical direction.

[0071] A tool 40 that comes into contact with the workpiece 11 and applies an external force is attached to the tip of the spindle 38. For example, the tool 40 is an annular cutting blade that is fixed to the tip of the spindle 38 by a fixing nut (not shown) or the like. When the spindle 38 is rotated by a rotary drive source, the cutting blade rotates around a rotation axis that is approximately parallel to the vertical direction.

[0072] The tool 40 may be, for example, a hub-type cutting blade (hub blade). The hub blade has an annular hub base made of a metal such as an aluminum alloy and an annular cutting edge formed along the outer periphery of the hub base. The cutting edge of the hub blade is formed by an electroformed grinding stone containing abrasive grains made of diamond, cubic boron nitride (cBN), or the like, and a binder such as a nickel-plated layer that secures the abrasive grains. However, a washer-type cutting blade (washer blade) may also be used as the tool 40. A washer blade is formed only by an annular cutting edge that contains abrasive grains and a binder made of a metal, ceramic, resin, or the like that secures the abrasive grains.

[0073] In the external force application step S2, first, the workpiece 11 is held by the chuck table 32. For example, the workpiece 11 is placed on the chuck table 32 so that the first surface 11a is exposed upward and the second surface 11b faces the holding surface 32a. In this state, when a suction force (negative pressure) from a suction source is applied to the holding surface 32a, the workpiece 11 is sucked and held by the chuck table 32. However, the chuck table 32 may hold the first surface 11a of the workpiece 11.

[0074] Next, the positional relationship between the chuck table 32 and the external force imparting unit 34 is adjusted by moving the chuck table 32 and / or the external force imparting unit 34. Specifically, the horizontal position and height position of the chuck table 32 and / or the external force imparting unit 34 are adjusted so that the tool 40 is disposed to the side of the workpiece 11. At this time, the external force imparting unit 34 is disposed so that the height position of the separation layer 19 formed on the workpiece 11 and the height position of the tool 40 coincide with each other.

[0075] Then, while rotating the chuck table 32 and the tool 40, the chuck table 32 and / or the external force applying unit 34 are moved in a direction in which the workpiece 11 and the tool 40 approach each other. As a result, the tool 40 comes into contact with the side surface 11c of the workpiece 11 along the circumferential direction of the workpiece 11. As a result, an external force is applied to the side surface 11c of the workpiece 11.

[0076] The external force (impact) applied to the workpiece 11 by the tool 40 is transmitted to the separation layer 19. This causes the crack 17 (see FIG. 4(A)) formed in the separation layer 19 to further extend. In addition, a new crack 17 may extend from the modified portion 15 (see FIG. 4(A)).

[0077] Furthermore, an annular groove (cut groove) may be formed on the side surface 11c of the workpiece 11 by positioning the tip (outer peripheral edge) of the tool 40 closer to the center of the workpiece 11 than the side surface 11c of the workpiece 11. In this case, the cut groove also functions as a separation starting point together with the separation layer 19, further facilitating separation of the substrate from the workpiece 11.

[0078] The method of bringing the tool 40 into contact with the workpiece 11 along the side surface 11c is not limited to rotating the chuck table 32. For example, when applying an external force to the area of ​​the workpiece 11 where the orientation flats 13A and 13B are provided, instead of rotating the chuck table 32, the chuck table 32 and the external force applying unit 34 may be moved relatively in a direction parallel to the orientation flats 13A and 13B. This allows the tool 40 to come into linear contact with the area of ​​the workpiece 11 where the orientation flats 13A and 13B are provided.

[0079] Furthermore, as long as the extension of the crack 17 is promoted in the separation layer 19, the tool 40 does not necessarily have to come into contact with the entire circumference of the side surface 11c of the workpiece 11. For example, the tool 40 may come into contact intermittently along the side surface 11c of the workpiece 11, or may come into contact with an arc-shaped region corresponding to a part of the side surface 11c of the workpiece 11.

[0080] As described above, in the external force application step S2, an external force is applied to the workpiece 11 from the side surface 11c under conditions that allow the cracks 17 contained in the separation layer 19 to extend. This promotes modification of the separation layer 19, improving the function of the separation layer 19 and making it easier to properly separate the substrate from the workpiece 11 in the separation step S3 described below.

[0081] Note that there are no limitations on the specific conditions for applying an external force to the workpiece 11, as long as it is possible to extend the cracks 17 contained in the separation layer 19. For example, in the above example, an external force is applied to a portion of the side surface 11c of the workpiece 11 where the separation layer 19 is formed (an end portion of the separation layer 19) (see FIGS. 5(B) and 6(B)). However, as long as the external force is transmitted to the separation layer 19, the position of the separation layer 19 and the position to which the external force is applied do not necessarily have to coincide. For example, the external force (e.g., irradiation of a laser beam 28 or contact with a tool 40) may be applied to a position on the side surface 11c of the workpiece 11 that is slightly shifted above or below the separation layer 19.

[0082] Next, the substrate is separated from the workpiece 11 starting from the separation layer 19 (separation step S3). The workpiece 11 in separation step S3 is shown in Figures 7(A) and 7(B). For example, in separation step S3, a substrate (plate-like object) 21 is separated from the workpiece 11 using a separation device 50.

[0083] The separating device 50 includes a chuck table (holding table) 52 that holds the workpiece 11. The upper surface of the chuck table 52 is a flat surface that is roughly parallel to the horizontal plane, and forms a circular holding surface 52a that holds the workpiece 11. The holding surface 52a is connected to a suction source (not shown) such as an ejector via a flow path (not shown), a valve (not shown), and the like that are formed inside the chuck table 52.

[0084] The separating device 50 also includes a separating unit 54 provided above the chuck table 52. The separating unit 54 includes a holding unit 56 that holds the surface (first surface 11a) of the workpiece 11 opposite to the surface (second surface 11b) held by the chuck table 52. The lower surface of the holding unit 56 is a flat surface that is approximately parallel to the horizontal plane, and forms a circular holding surface 56a that holds the workpiece 11.

[0085] For example, the holding unit 56 is configured by a disk-shaped holding member and has a plurality of suction ports (not shown) that suck the workpiece 11. One end of the suction port opens at the holding surface 56a, and the other end of the suction port is connected to a suction source (not shown) such as an ejector via a flow path (not shown) formed inside the holding unit 56. The number and arrangement of the suction ports are appropriately set so that the plurality of suction ports are blocked by the workpiece 11 when the workpiece 11 comes into contact with the holding surface 56a.

[0086] A columnar support member 58 that supports the holding unit 56 is connected to the upper end side of the holding unit 56. The lower end of the support member 58 is fixed to the center of the holding unit 56. In addition, a moving unit (not shown) that moves the support member 58 is connected to the upper end side of the support member 58. For example, the moving unit is configured with a ball screw type moving mechanism, and moves (raises and lowers) the support member 58 together with the holding unit 56 in the vertical direction.

[0087] 7(A) is a front view showing the separating device 50 holding the workpiece 11. In the separating step S3, first, the workpiece 11 is held by the chuck table 52 and the holding unit 56.

[0088] Specifically, the workpiece 11 is placed on the chuck table 52 with a space wider than the thickness of the workpiece 11 secured between the holding surface 52a of the chuck table 52 and the holding surface 56a of the holding unit 56. At this time, the workpiece 11 is placed so that the first surface 11a is exposed upward and the second surface 11b faces the holding surface 52a. Then, the suction force (negative pressure) of the suction source is applied to the holding surface 52a, whereby the workpiece 11 is suction-held by the chuck table 52.

[0089] Next, the holding unit 56 is lowered vertically by a moving unit (not shown) so that the holding surface 56a comes into contact with the first surface 11a of the workpiece 11. In this state, when the suction force (negative pressure) of the suction source is applied to the holding surface 56a, the workpiece 11 is sucked and held by the holding unit 56. As a result, the second surface 11b side of the workpiece 11 is fixed to the holding surface 52a, and the first surface 11a side is fixed to the holding surface 56a.

[0090] FIG. 7B is a front view showing a separation device 50 that separates the substrate 21 from the workpiece 11. After the workpiece 11 is fixed to the chuck table 52 and the holding unit 56, the holding unit 56 is raised vertically by a moving unit (not shown) while the position of the chuck table 52 is fixed. As a result, the holding surfaces 52a and 56a are separated from each other, and an external force is applied to the workpiece 11 that separates the first surface 11a and the second surface 11b of the workpiece 11. As a result, the workpiece 11 is broken starting from the separation layer 19, and the substrate 21 corresponding to the first surface 11a of the workpiece 11 is separated from the rest of the workpiece 11. In this manner, the substrate 21 is produced from the workpiece 11.

[0091] Substrate 21 has a first surface (front surface) 21a corresponding to first surface 11a of workpiece 11, and a second surface (back surface) 21b located on the opposite side of first surface 21a. Second surface 21b of substrate 21 corresponds to a separation surface (fracture surface) formed by separation of substrate 21. Furthermore, the depth to which separation layer 19 of workpiece 11 is formed before separation of substrate 21 (the distance between the first surface of workpiece 11 and separation layer 19) corresponds to the thickness of substrate 21 separated from workpiece 11.

[0092] As described above, in this embodiment, an external force is applied to workpiece 11 in external force application step S2 (see FIGS. 5(A) to 6(B)) to improve the function of separation layer 19 as a separation starting point, and then separation step S3 is performed. This makes it easier for workpiece 11 to break starting from separation layer 19 in separation step S3, and allows substrate 21 to be properly and smoothly separated from workpiece 11.

[0093] Incidentally, unevenness remains as fracture marks on the substrate 21 separated from the workpiece 11. Therefore, after the separation step S3, a grinding step S4 is performed as needed to grind the substrate 21 separated from the workpiece 11.

[0094] 8 is a perspective view showing the substrate 21 in the grinding step S4. For example, in the grinding step S4, the second surface 21b side of the substrate 21 is ground by a grinding device 60, thereby removing or reducing unevenness remaining on the second surface 21b side of the substrate 21.

[0095] The grinding device 60 includes a chuck table (holding table) 62 that holds the substrate 21. The upper surface of the chuck table 62 forms a circular holding surface 62a that holds the substrate 21. The holding surface 62a is connected to a suction source (not shown) such as an ejector via a flow path (not shown), a valve (not shown), and the like formed inside the chuck table 62.

[0096] The chuck table 62 is connected to a moving unit (not shown) that moves the chuck table 62 and a rotary drive source (not shown) that rotates the chuck table 62. The moving unit is configured with, for example, a ball screw type moving mechanism or a turntable, and moves the chuck table 62 in the horizontal direction. The rotary drive source is configured with a motor or the like, and rotates the chuck table 62 around a rotation axis that is approximately parallel to the vertical direction.

[0097] The grinding device 60 also includes a grinding unit 64 that grinds the substrate 21. The grinding unit 64 is provided above the chuck table 62 and includes a cylindrical spindle 66 arranged along the Z-axis direction. A disk-shaped wheel mount 68 made of metal such as SUS (stainless steel) is fixed to the tip end (lower end) of the spindle 66. A rotational drive source (not shown) such as a motor is connected to the base end (upper end) of the spindle 66.

[0098] An annular grinding wheel 70 for grinding the substrate 21 is attached to the underside of the wheel mount 68. For example, the grinding wheel 70 is detachably fixed to the wheel mount 68 by a fastener such as a bolt.

[0099] The grinding wheel 70 includes an annular wheel base 72. The wheel base 72 is made of a metal such as aluminum or stainless steel, and is formed to have approximately the same diameter as the wheel mount 68. The upper surface of the wheel base 72 is fixed to the lower surface of the wheel mount 68. A plurality of grinding stones 74 are fixed to the lower surface of the wheel base 72. For example, the grinding stones 74 are formed in a rectangular parallelepiped shape, and are arranged in a ring shape at approximately equal intervals along the outer periphery of the wheel base 72. The lower surfaces of the grinding stones 74 form a grinding surface that grinds the substrate 21.

[0100] The grinding wheel 74 is formed by fixing abrasive grains made of diamond, cBN (cubic boron nitride), or the like with a bonding material (bond material) such as a metal bond, a resin bond, or a vitrified bond. However, there are no restrictions on the material, shape, structure, size, etc. of the grinding wheel 74. The number of grinding wheels 74 can also be set arbitrarily.

[0101] When the rotation drive source connected to the spindle 66 is operated, the spindle 66, wheel mount 68, and grinding wheel 70 rotate around a rotation axis that is generally parallel to the vertical direction. As a result, the multiple grinding wheels 74 each revolve along a circular revolution path centered on the rotation axis. The outer diameter of the revolution path of the grinding wheels 74 is set to be equal to or greater than the radius of the substrate 21.

[0102] The substrate 21 is placed on the chuck table 62 so that the surface to be ground (separation surface, second surface 21b) is exposed upward and the surface opposite to the surface to be ground (first surface 21a) faces the holding surface 62a. In this state, the suction force (negative pressure) of the suction source is applied to the holding surface 62a, whereby the substrate 21 is sucked and held by the chuck table 62.

[0103] When grinding the substrate 21, a protective sheet (not shown) for protecting the substrate 21 may be attached to the first surface 21a of the substrate 21. For example, the protective sheet may be a tape having an adhesive layer formed on a base material, or a thermocompression sheet that does not have an adhesive layer and can be thermocompressed to the substrate 21. In this case, the substrate 21 is held by the chuck table 62 via the protective sheet.

[0104] Next, the chuck table 62 is positioned below the grinding unit 64. At this time, the positional relationship between the chuck table 62 and the grinding unit 64 is adjusted so that the rotation axis of the chuck table 62 (the center of the substrate 21) and the rotation path of the grinding wheels 74 overlap in the vertical direction. Then, the grinding unit 64 is lowered in the vertical direction while rotating the chuck table 62 and the grinding wheels 70 at a predetermined speed. As a result, the multiple grinding wheels 74 approach the substrate 21 while rotating and come into contact with the second surface 21b of the substrate 21.

[0105] When the plurality of grinding wheels 74 come into contact with the second surface 21b side of the substrate 21, the second surface 21b side of the substrate 21 is scraped off and ground. This removes or reduces unevenness remaining on the second surface 21b side of the substrate 21. Then, after the substrate 21 has been ground and thinned to a predetermined thickness, the grinding unit 64 rises and grinding stops.

[0106] By performing the grinding step S4, the second surface 21b side of the substrate 21 is flattened. After the grinding step S4, the substrate 21 may be polished (polishing step). For example, in the polishing step, the second surface 21b side of the substrate 21 is polished with a disc-shaped polishing pad. This further flattens the second surface 21b side of the substrate 21 and makes it mirror-finished.

[0107] By sequentially carrying out the separation layer forming step S1 to the grinding step S4, the substrate 21 is manufactured from the workpiece 11. For example, if the workpiece 11 is an ingot made of β-gallium oxide, a gallium oxide wafer is obtained as the substrate 21. However, the material of the workpiece 11 is appropriately selected depending on the substrate 21 to be manufactured. For example, by using a single crystal ingot made of a semiconductor material such as silicon, silicon carbide, or gallium nitride as the workpiece 11, it is possible to manufacture a silicon wafer, a silicon carbide wafer, a gallium nitride wafer, or the like.

[0108] The substrate 21 can be used for manufacturing device chips, etc. For example, the substrate 21 is divided into a plurality of rectangular regions by a plurality of streets (planned division lines) arranged in a grid pattern so as to intersect with one another. Devices such as ICs (Integrated Circuits), LSIs (Large Scale Integration), LEDs (Light Emitting Diodes), and MEMS (Micro Electro Mechanical Systems) devices are formed in each of the plurality of regions divided by the streets 13.

[0109] Thereafter, a processing device is used to divide the substrate 21 along the streets and separate it into individual chips, thereby manufacturing a plurality of device chips each equipped with a device. To divide the substrate 21, a cutting device that cuts the workpiece with an annular cutting blade, a laser processing device that performs laser processing on the workpiece, or the like can be used.

[0110] On the other hand, the workpiece 11 (see FIG. 7(B)) after separation of the substrate 21 is reused to manufacture the next substrate 21. Specifically, the separated surface (fracture surface) of the workpiece 11 is subjected to grinding, polishing, etc., to flatten and polish the separated surface of the workpiece 11. Thereafter, the workpiece 11 is subjected to the separation layer forming step S1 to the grinding step S4, thereby manufacturing a new substrate 21.

[0111] As described above, in the method for manufacturing a substrate according to this embodiment, after the separation layer 19 is formed on the workpiece 11, an external force is applied to the side surface 11c of the workpiece 11. This improves the function of the separation layer 19 and promotes the separation of the substrate 21, making it possible to properly and smoothly separate the substrate 21 from the workpiece 11.

[0112] The structures, methods, etc. according to the above-described embodiments can be appropriately modified and implemented without departing from the scope of the object of the present invention. Furthermore, the structures, methods, etc. according to the present embodiments can be appropriately combined with other embodiments.

[0113] (Embodiment 2) In the first embodiment, the case where the external force applying step S2 is an independent step whose purpose is to apply an external force to the workpiece 11 has been described. However, in the external force applying step S2, processing to be performed on the workpiece 11 or the substrate 21 separated from the workpiece 11 may be performed, and as a result, an external force may be applied to the workpiece 11. Below, a description will be given of an embodiment in which processing is performed on the workpiece 11 in the external force applying step S2. Note that details of the steps that are not described in this embodiment are the same as those in the first embodiment.

[0114] The workpiece 11 or the substrate 21 may be subjected to processing to form the workpiece 11 or the substrate 21 into a predetermined shape. For example, after the substrate 21 is separated from the workpiece 11, the outer periphery of the substrate 21 is chamfered. The chamfering is a process for removing corners formed on the outer periphery of the substrate 21 (the connection between the first surface 21a and the side surface, and the connection between the second surface 21b and the side surface). Typically, the side surface (outer periphery) of the substrate 21 is shaped into a curved surface (arc shape) extending from the first surface 21a to the second surface 21b so as to be curved outward from the substrate 21.

[0115] Therefore, in the external force applying step S2, the side surface 11c of the region of the workpiece 11 corresponding to the substrate 21 may be processed to have a predetermined shape, thereby applying an external force from the side surface 11c to the workpiece 11. For example, a shaping process corresponding to the chamfering process that is originally performed on the substrate 21 separated from the workpiece 11 is performed on the workpiece 11 before the substrate 21 is separated.

[0116] Fig. 9(A) is a front view showing workpiece 11 to be machined by laser beam 28A. For example, in external force applying step S2, by irradiating workpiece 11 with laser beam 28A using external force applying device 20, it is possible to perform a process equivalent to chamfering on workpiece 11 and apply an external force to workpiece 11. The configuration, functions, operations, etc. of external force applying device 20 shown in Fig. 9(A) are the same as those described in embodiment 1, except for the matters described below (see Figs. 5(A) and 5(B)).

[0117] In the external force application step S2, while rotating the chuck table 22 holding the workpiece 11, a laser beam 28A is irradiated from the laser processing head 26 to process a separation region 11d of the workpiece 11 that corresponds to the substrate 21, and the separation region 11d is shaped into a predetermined shape. The separation region 11d is a region of the workpiece 11 that is located closer to the first surface 11a than the separation layer 19, and corresponds to the substrate 21 that will be separated from the workpiece 11 in a subsequent separation step S3 (see FIG. 7(B)).

[0118] The irradiation conditions of the laser beam 28A are set so that ablation processing is performed on the region of the workpiece 11 irradiated with the laser beam 28A. Specific examples of the irradiation conditions of the laser beam 28A are the same as the example of the irradiation conditions of the laser beam 28 in embodiment 1 (see FIGS. 5(A) and 5(B)). Then, while the laser beam 28A is irradiated from the laser processing head 26 onto the side surface 11c of the workpiece 11, the laser processing head 26 is raised and lowered in the vertical direction, and laser processing is performed on the separation region 11d of the workpiece 11.

[0119] Specifically, the outer peripheral surface of separation region 11d is shaped into a curved surface so as to bend outward from separation region 11d. As a result, separation region 11d is subjected to a process corresponding to chamfering. Note that while laser beam 28A is irradiating workpiece 11, the position of the focal point of laser beam 28A and the position of chuck table 22 may be adjusted as appropriate so that separation region 11d is processed into a desired shape.

[0120] When workpiece 11 is processed as described above, the chamfering process that is normally performed on substrate 21 (see FIG. 7(B)) separated from workpiece 11 is performed on separation region 11d of workpiece 11. In this case, by separating substrate 21 from workpiece 11 in the subsequent separation step S3, substrate 21 that has already been chamfered can be obtained.

[0121] Furthermore, when separation region 11d of workpiece 11 is processed, an external force is applied to side surface 11c of workpiece 11. The external force (impact) applied to workpiece 11 is then transmitted to separation layer 19, and cracks 17 (see FIG. 4(A)) contained in separation layer 19 extend. This promotes modification of separation layer 19, improving the function of separation layer 19 as a separation starting point.

[0122] Fig. 9(B) is a front view showing workpiece 11 to be machined by tool 40A. In external force applying step S2, external force applying device 30 may be used to process workpiece 11 with tool 40A, thereby performing a process equivalent to chamfering on workpiece 11 and applying an external force to workpiece 11. The configuration, functions, operations, etc. of external force applying device 30 shown in Fig. 9(B) are the same as those described in embodiment 1, except for the matters described below (see Figs. 6(A) and 6(B)).

[0123] In this embodiment, a chamfering tool 40A is attached to the tip of the spindle 38 of the external force imparting unit 34. For example, the tool 40A is an annular grindstone (blade) made of the same material as the tool 40 (see FIGS. 6A and 6B). However, the thickness of the tool 40A is set according to the type of processing to be performed on the separation region 11d of the workpiece 11. Furthermore, the shape of the tip (outer periphery) 40a of the tool 40A is adjusted to a shape corresponding to the processing to be performed on the separation region 11d. For example, when processing corresponding to chamfering is performed on the separation region 11d, the tip 40a of the tool 40A is formed into a curved surface that curves inward of the tool 40A.

[0124] In the external force imparting step S2, the chuck table 32 and / or the external force imparting unit 34 holding the workpiece 11 are moved to adjust the positional relationship between the chuck table 32 and the external force imparting unit 34 so that the tool 40A is positioned to the side of the workpiece 11. At this time, the external force imparting unit 34 is positioned so that the height positions of the separation region 11d of the workpiece 11 and the tool 40A coincide with each other.

[0125] Next, while rotating the chuck table 32 and the tool 40A, the chuck table 32 and / or the external force application unit 34 are moved to bring the separation region 11d of the workpiece 11 closer to the tip 40a of the tool 40A. This brings the tip 40a of the tool 40A into contact with the side surface 11c of the separation region 11d along the circumferential direction of the separation region 11d. As a result, the separation region 11d is machined so that the shape of the side surface 11c of the separation region 11d approaches the shape of the tip 40a of the tool 40A. In this way, the chamfering that would normally be performed on the substrate 21 (see FIG. 7(B)) separated from the workpiece 11 is performed on the separation region 11d of the workpiece 11.

[0126] Furthermore, when separation region 11d of workpiece 11 is machined by tool 40A, an external force is applied to side surface 11c of workpiece 11. The external force (impact) applied to workpiece 11 is then transmitted to separation layer 19, and cracks 17 (see FIG. 4(A)) contained in separation layer 19 extend. This promotes modification of separation layer 19, improving the function of separation layer 19 as a separation starting point.

[0127] As described above, in the external force applying step S2, it is also possible to perform a process that combines processing of the workpiece 11 and applying an external force to the workpiece 11. This makes it possible to omit an independent process for applying an external force to the workpiece 11, thereby improving the processing efficiency of the workpiece 11. Note that, although an example in which processing equivalent to chamfering is performed on the separation region 11d of the workpiece 11 has been described above, the type of processing performed on the workpiece 11 is not limited as long as it is possible to apply an external force to the workpiece 11.

[0128] After the external force application step S2, the aforementioned separation step S3 is carried out, and the separation region 11d is separated from the workpiece 11 as the substrate 21 (see FIG. 7(B)). Then, after the separation step S3, a grinding step S4 (see FIG. 8) is carried out as needed.

[0129] It should be noted that even if the desired processing is performed on the separation region 11d of the workpiece 11 in the external force applying step S2, if the substrate 21 corresponding to the separation region 11d is ground and thinned in the grinding step S4, the processing performed on the separation region 11d may not be reflected in the finally obtained substrate 21. Therefore, in the external force applying step S2, the position where the processing is performed on the workpiece 11 may be determined based on the planned amount of grinding of the substrate 21 in the grinding step S4.

[0130] 10 is a front view showing a part of separation region 11d of workpiece 11. As described above, separation region 11d is a region of workpiece 11 that is located closer to first surface 11a than separation layer 19, and corresponds to substrate 21 that is separated from workpiece 11.

[0131] In the external force application step S2, first, a planned grinding amount of the substrate 21 in the grinding step S4 is set and recorded. The planned grinding amount corresponds to the planned grinding amount of the substrate 21 in the grinding step S4 (see FIG. 8) (the difference in thickness of the substrate 21 before and after grinding). The planned grinding amount is set appropriately depending on the thickness and surface condition required for the substrate 21 to be finally manufactured. For example, the planned grinding amount is set so that unevenness remaining on the second surface 21b side of the substrate 21 (see FIG. 7(B)) is removed and the substrate 21 is thinned to a desired thickness.

[0132] Of the separation region 11d of the workpiece 11, a portion having a thickness equal to the planned grinding amount from the separation layer 19 corresponds to the planned grinding region A to be ground in the grinding step S4. The portion of the separation region 11d of the workpiece 11 other than the planned grinding region A is set as the processed region B to be processed in the external force applying step S2.

[0133] In the external force application step S2, processing (see FIGS. 9(A) and 9(B)) is performed on the processing area B to form a predetermined shape on the side surface 11c of the workpiece 11. That is, the position where the processing of the workpiece 11 is performed is determined based on the planned grinding amount. For example, as shown in FIG. 10, shaping equivalent to chamfering is performed on the outer periphery of the processing area B, and shaping is not performed on the planned grinding area A.

[0134] When the position where the workpiece 11 is processed is set as described above, the region to be ground A remains in the substrate 21 (separation region 11d) separated from the workpiece 11 in the subsequent separation step S3. Then, in the grinding step S4, the region to be ground A is removed by grinding, while the region to be processed B is not ground. This allows the processing (chamfering, etc.) performed on the separation region 11d of the workpiece 11 in the external force application step S2 to be reflected in the substrate 21 after grinding.

[0135] In the above, an example has been described in which the region to be ground A of the separation region 11d of the workpiece 11 is not processed, and only the region to be processed B is processed. However, when the desired processing is performed on the region to be processed B, the region to be ground A may be processed incidentally at the same time. Even in this case, the region to be ground A is removed by the grinding processing in the grinding step S4, and therefore the processing performed on the region to be ground A does not affect the shape of the substrate 21 that is finally obtained.

[0136] As described above, in the method for manufacturing a substrate according to this embodiment, the side surface 11c of the region (separation region 11d) of the workpiece 11 corresponding to the substrate 21 is processed to have a predetermined shape, and an external force is applied to the workpiece 11 from the side surface 11c. This allows the processing of the workpiece 11 to be performed in combination with the process of applying an external force to the workpiece 11, improving the processing efficiency of the workpiece 11.

[0137] The structures, methods, etc. according to the above-described embodiments can be appropriately modified and implemented without departing from the scope of the object of the present invention. Furthermore, the structures, methods, etc. according to the present embodiments can be appropriately combined with other embodiments. [Explanation of symbols]

[0138] 11 Workpiece 11a 1st side (front) 11b 2nd side (back side) 11c Side (outer surface) 11d Separation area 13A, 13B Orientation Flat 15 Modified section (deformed section) 17 Crack 19 Separation layer (modification layer) 21 Substrate (plate-like object) 21a 1st side (front) 21b 2nd side (back side) 2. Laser processing equipment 4 Chuck table (holding table) 4a Holding surface 6 Laser irradiation unit 8. Housing 10 Laser processing head 12 Laser Beam 12a Focus point 14 Imaging unit 20 External force application device 22 Chuck table (holding table) 22a Holding surface 24 Laser irradiation unit 26 Laser processing head 28,28A Laser beam 30 External force application device 32 Chuck table (holding table) 32a Holding surface 34 External force application unit 36 Housing 38 Spindle 40,40A tools 40a Tip (outer periphery) 50 Separation device 52 Chuck table (holding table) 52a Holding surface 54 Separation Unit 56 Holding Unit 56a Holding surface 58 Support member 60 Grinding equipment 62 Chuck table (holding table) 62a Holding surface 64 Grinding Unit 66 Spindle 68 Wheel Mount 70 Grinding Wheel 72 Wheel base 74 Grinding Wheel

Claims

1. A method for manufacturing a substrate from a workpiece having a first surface, a second surface located opposite to the first surface, and a side surface connected to an outer edge of the first surface and an outer edge of the second surface, comprising: a separation layer forming step of forming a separation layer including a modified portion and a crack extending from the modified portion inside the workpiece by irradiating the workpiece with a laser beam having a wavelength that transmits the workpiece from the first surface side or the second surface side while positioning the focal point of the laser beam inside the workpiece; an external force applying step of applying an external force to the workpiece from the side surface thereof after the separation layer forming step is performed; a separation step of separating the substrate from the workpiece starting from the separation layer after the external force application step is performed.

2. The method for manufacturing a substrate according to claim 1 , further comprising a grinding step of grinding the substrate separated from the workpiece after the separating step is performed.

3. 3. The method for manufacturing a substrate according to claim 1, wherein the external force applying step irradiates the workpiece with a laser beam from the side surface thereof.

4. The method for manufacturing a substrate according to claim 1 or 2, wherein the external force applying step brings a tool into contact with the side surface of the workpiece.

5. 3. The method for manufacturing a substrate according to claim 1, wherein in the external force application step, an external force is applied to the workpiece from the side by processing the side of the region of the workpiece corresponding to the substrate into a predetermined shape.

6. In the external force applying step, an external force is applied to the workpiece from the side surface by processing the side surface of the workpiece in a region corresponding to the substrate into a predetermined shape; 3. The method for manufacturing a substrate according to claim 2, wherein in the external force applying step, the position on the workpiece where the processing is to be performed is determined based on the amount of the substrate to be ground in the grinding step.

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