Laser processing apparatus, chamfering method for workpiece, and wafer manufacturing method

Abstract

To reduce the labor required for chamfering a workpiece and improve throughput.SOLUTION: A laser processing apparatus capable of laser-processing a workpiece by irradiating the workpiece with a laser beam, comprises: a holding unit that has a flat holding surface; an oscillator that emits the laser beam; a condenser that focuses the laser beam emitted from the oscillator; a moving mechanism that relatively moves the holding unit and a focal point at which the laser beam is focused; and a rotation mechanism that rotates the holding unit about a straight line intersecting the holding surface of the holding unit as a rotation center. Relative positions and orientation of the condenser and the holding unit can be adjusted such that the condenser faces a side surface connecting a first surface and a second surface of the workpiece held by the holding unit, and the laser beam emitted from the oscillator and focused by the condenser can be irradiated to the workpiece held by the holding unit from the side surface.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a laser processing device capable of chamfering a workpiece by irradiating the workpiece with a laser beam having a wavelength that is absorbed by the workpiece so as to remove both the outer periphery on the first surface side and the outer periphery on the second surface side of the workpiece, a processing method for chamfering the workpiece, and a wafer manufacturing method for producing chamfered wafers from an ingot. [Background technology]

[0002] Chips for devices such as integrated circuits (ICs) are essential components in various electronic devices such as mobile phones and personal computers. These chips are generally made of single crystals such as silicon (Si), silicon carbide (SiC), gallium nitride (GaN), lithium tantalate (LiTaO3:LT), or lithium niobate (LiNbO3:LN), and are manufactured using chamfered wafers.

[0003] This wafer is manufactured, for example, by cutting out a portion having a predetermined thickness on the front surface side of a cylindrical ingot, and then processing the outer periphery of the cut-out portion (i.e., the as-sliced ​​wafer) to form a chamfered portion (see, for example, Patent Document 1). Specifically, this chamfering is performed by, for example, irradiating the as-sliced ​​wafer with a laser beam having a wavelength that is absorbed by the material of the as-sliced ​​wafer so as to remove both the outer periphery on the first surface side and the outer periphery on the second surface side of the as-sliced ​​wafer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-212761 Summary of the Invention [Problem to be solved by the invention]

[0005] A laser processing apparatus capable of chamfering a workpiece such as an as-sliced ​​wafer generally includes a holding table having a flat holding surface, an oscillator, a condenser that condenses a laser beam emitted from the oscillator, and a movement mechanism that moves the focal point where the laser beam is focused relative to the holding table. The laser processing apparatus processes the workpiece by irradiating the workpiece with a laser beam while positioning the focal point inside the workpiece held on the holding surface of the holding table and moving the holding table relative to the focal point.

[0006] More specifically, when chamfering a workpiece, first, the first surface of the workpiece is held on the holding surface of the holding table so that the second surface of the workpiece is exposed. Next, the laser beam is irradiated onto the workpiece while the focusing point is positioned on the outer periphery of the second surface of the workpiece and the holding table and the focusing point are moved relative to each other. This removes the outer periphery of the second surface of the workpiece.

[0007] Next, the workpiece is separated from the holding surface of the holding table and inverted, and then held again on the holding surface of the holding table. That is, the second surface side of the workpiece is held on the holding surface of the holding table so that the first surface side of the workpiece is exposed. Thereafter, the laser beam is irradiated onto the workpiece while the focusing point is positioned on the outer periphery of the first surface side of the workpiece and the holding table and the focusing point are moved relative to each other. This removes the outer periphery of the first surface side of the workpiece.

[0008] However, the process of turning the workpiece over to perform laser processing from each side requires not only the time required for the turning operation itself, but also the time required for the process of precisely re-detecting the position of the workpiece on the holding surface after turning the workpiece over and determining the processing position. As a result, chamfering using this method has a problem of low throughput.

[0009] In view of this, an object of the present invention is to provide a processing apparatus that can perform chamfering of a workpiece with high throughput. [Means for solving the problem]

[0010] According to one aspect of the present invention, there is provided a laser processing apparatus capable of laser processing a workpiece by irradiating the workpiece with a laser beam of a wavelength that is absorbed by the material of the workpiece, the laser processing apparatus comprising: a holding unit having a flat holding surface; an oscillator that emits the laser beam; a collector that collects the laser beam emitted from the oscillator; a movement mechanism that moves the holding unit and the collecting point at which the laser beam is collected relatively; and a rotation mechanism that rotates the holding unit around a straight line that intersects with the holding surface of the holding unit as the center of rotation, the relative position and orientation of the collector and the holding unit being adjustable so that the collector faces the side surface connecting the first and second surfaces of the workpiece held by the holding unit, and the laser processing apparatus is characterized in that the laser beam emitted from the oscillator and collected by the collector can be irradiated onto the workpiece held by the holding unit from the side surface.

[0011] Preferably, the direction of travel of the laser beam can be adjusted so that the laser beam is incident on the side surface of the workpiece and travels toward the first surface or the second surface.

[0012] More preferably, the apparatus further comprises a position detection unit that detects the positional relationship between the condenser and the side surface of the workpiece held by the holding unit.

[0013] According to another aspect of the present invention, there is provided a method for chamfering a workpiece, the method comprising: a holding step of holding a central portion of a first surface side of the workpiece on a flat holding surface of a holding unit so that an outer periphery of the workpiece is exposed; a first chamfering step of removing the outer periphery of the first surface side of the workpiece after the holding step by irradiating the workpiece with a laser beam of a wavelength absorbed by the material of the workpiece so that the laser beam is incident on the side of the workpiece and exits to the first surface side while rotating the holding unit around a straight line intersecting the holding surface as a rotation axis; and a second chamfering step of removing the outer periphery of the second surface side of the workpiece after the holding step by rotating the holding unit around the rotation axis while irradiating the workpiece with the laser beam so that the laser beam is incident on the side of the workpiece and exits to the second surface side.

[0014] Preferably, the workpiece is not turned over between the first chamfering step and the second chamfering step.

[0015] According to yet another aspect of the present invention, there is provided a wafer manufacturing method for manufacturing a chamfered wafer from an ingot, the method including: a separation layer forming step of irradiating an ingot with a first laser beam having a wavelength that transmits through a material of the ingot so as to position a first focal point inside the ingot, the first laser beam being focused on the ingot, and relatively moving the ingot and the first focal point, thereby forming a separation layer inside the ingot; a separation step of peeling a wafer from the ingot after the separation layer forming step by applying an external force to the ingot so as to cleave the ingot at the separation layer; and a separation step of peeling the wafer after the peeling step so as to expose both a first surface side outer periphery and a second surface side outer periphery of the wafer. A method for manufacturing a wafer is provided, comprising: a holding step of holding a central portion of a first surface side of a wafer on a flat holding surface of a holding unit; a first chamfering step of removing an outer periphery of the first surface side of the wafer after the holding step by rotating the holding unit around a straight line intersecting the holding surface as a rotation axis while irradiating the wafer with a second laser beam having a wavelength that is absorbed by the material of the wafer, so that the second laser beam is incident on the side of the wafer and exits on the first surface side; and a second chamfering step of removing an outer periphery of the second surface side of the wafer after the holding step by rotating the holding unit around the rotation axis while irradiating the wafer with the second laser beam, so that the second laser beam is incident on the side of the wafer and exits on the second surface side.

[0016] 7. The method for producing a wafer according to claim 6, wherein the wafer is preferably not turned over between the first chamfering step and the second chamfering step. [Effects of the Invention]

[0017] In a laser processing apparatus, a method for chamfering a workpiece, and a method for manufacturing a wafer according to one aspect of the present invention, a laser beam is irradiated onto the workpiece (wafer) from the side of the workpiece. In this case, the laser beam can be irradiated onto both the first-surface outer periphery and the second-surface outer periphery of the workpiece, so there is no need to turn the workpiece over when chamfering it. As a result, the effort required for chamfering the workpiece can be reduced and throughput can be improved. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a perspective view schematically illustrating an example of a workpiece. [Figure 2] FIG. 1 is a perspective view schematically illustrating an example of a laser processing device. [Figure 3] FIG. 2 is a block diagram schematically illustrating an example of the configuration of an optical system provided in the laser processing apparatus. [Figure 4] 10 is a side view schematically showing a state in which a laser beam is irradiated from the side onto a workpiece held by a holding unit. FIG. [Figure 5] Figure 5(A) is a cross-sectional view showing a schematic diagram of a laser beam being irradiated onto the outer periphery of the first surface side of the workpiece, and Figure 5(B) is a cross-sectional view showing a schematic diagram of a laser beam being irradiated onto the outer periphery of the second surface side of the workpiece. [Figure 6] FIG. 2 is an enlarged side view schematically showing the outer periphery of the chamfered workpiece. [Figure 7] FIG. 7(A) is a flowchart illustrating the flow of each step of a laser processing method for a workpiece, and FIG. 7(B) is a flowchart illustrating the flow of each step of a wafer manufacturing method. [Figure 8] Figure 8(A) is a cross-sectional view that schematically shows how a separation layer is formed on an ingot in the separation layer formation step, and Figure 8(B) is a cross-sectional view that schematically shows how a wafer is separated from the ingot in the separation step. [Figure 9] FIG. 10 is a perspective view schematically showing another example of a laser processing device. [Figure 10]FIG. 10 is a perspective view schematically showing another example of a laser processing device. DETAILED DESCRIPTION OF THE INVENTION

[0019] An embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a perspective view schematically showing an example of a workpiece. The workpiece 11 shown in Fig. 1 is a disk-shaped wafer having a first surface (front surface) 11a and a second surface (back surface) 11b opposite to the first surface 11a, which are mirror-finished, and both the outer periphery on the first surface 11a side and the outer periphery on the second surface 11b side are angular.

[0020] Two flat portions, namely, a primary orientation flat 13a and a secondary orientation flat 13b, are formed on the side surface 11c of the workpiece 11 to indicate the crystal orientation of the material of the workpiece 11. Note that the primary orientation flat 13a and the secondary orientation flat 13b are omitted in figures other than Fig. 1.

[0021] 2 is a perspective view schematically showing an example of a laser processing device 2 that can laser process the workpiece 11 by irradiating the workpiece 11 from the side surface 11c with a laser beam having a wavelength that is absorbed by the workpiece 11. The laser processing device 2 shown in FIG. 2 can chamfer the workpiece 11 by irradiating the laser beam onto the outer periphery on the first surface 11a side and the outer periphery on the second surface 11b side of the workpiece 11.

[0022] The X-axis and Y-axis directions shown in FIG. 2 are directions perpendicular to each other on a horizontal plane, and the Z-axis direction is a direction (vertical direction) perpendicular to both the X-axis and Y-axis directions.

[0023] 2 has a base 4 that supports each of the components. On the base 4, a support section (wall section) 6 that mainly supports a holding unit 10 that holds a workpiece 11, and a support section (wall section) 8 that mainly supports a laser beam irradiation unit 12 that mainly irradiates a laser beam toward the workpiece 11 are provided.

[0024] A Y-axis movement mechanism 14 that moves the holding unit 10 along the Y-axis direction, and a Z-axis movement mechanism 16 that moves the holding unit 10 along the Z-axis direction are provided on the front surface 6a of the support part 6. The support part 6 also has a loading / unloading port 18 that serves as a movement path for the workpiece 11 that moves between the front and rear sides of the support part 6. The workpiece 11 is loaded from the rear side of the support part 6 through the loading / unloading port 18 to the front side, processed, and then loaded from the front side of the support part 6 to the rear side through the loading / unloading port 18.

[0025] The Y-axis movement mechanism 14 has a pair of Y-axis guide rails 20 that are fixed to the front surface 6a of the support part 6 and extend along the Y-axis direction. A Y-axis movement plate 22 is connected to the front side of the pair of Y-axis guide rails 20 in a manner that allows it to slide along the pair of Y-axis guide rails 20.

[0026] A screw shaft 24 extending along the Y-axis direction is disposed between the pair of Y-axis guide rails 20. A motor 26 for rotating the screw shaft 24 is connected to the front end (one end) of this screw shaft 24. A nut (not shown) that houses a large number of balls that roll on the surface of the rotating screw shaft 24 is provided on the surface of the screw shaft 24 on which a spiral groove is formed, thereby forming a ball screw.

[0027] That is, when screw shaft 24 rotates, a large number of balls circulate inside the nut, causing the nut to move along the Y-axis direction. Furthermore, this nut is fixed to the back side of Y-axis moving plate 22. Therefore, when screw shaft 24 is rotated by motor 26, Y-axis moving plate 22 moves along the Y-axis direction together with the nut.

[0028] The Z-axis moving mechanism 16 is fixed to the front surface of the Y-axis moving plate 22. The Z-axis moving mechanism 16 is fixed to the front surface of the Y-axis moving plate 22 and has a pair of Z-axis guide rails 28 extending along the Z-axis direction. A Z-axis moving plate 30 is connected to the front side of the pair of Z-axis guide rails 28 in a manner that allows it to slide along the pair of Z-axis guide rails 28.

[0029] A screw shaft 32 extending along the Z-axis direction is disposed between the pair of Z-axis guide rails 28. A motor 34 for rotating the screw shaft 32 is connected to one end of the screw shaft 32. A nut (not shown) that houses a large number of balls that roll on the surface of the rotating screw shaft 32 is provided on the surface of the screw shaft 32 on which a spiral groove is formed, thereby forming a ball screw.

[0030] That is, when the screw shaft 32 rotates, many balls circulate inside the nut, causing the nut to move along the Z-axis direction. Furthermore, this nut is fixed to the back side of the Z-axis moving plate 30. Therefore, when the screw shaft 32 is rotated by the motor 34, the Z-axis moving plate 30 moves along the Z-axis direction together with the nut.

[0031] A support plate 38 is fixed to the front surface of the Z-axis moving plate 30. The support plate 38 supports the holding unit 10 and a rotation unit 36 ​​that rotates the holding unit 10. The rotation unit 36 ​​is placed on the support plate 38, and a portion of the holding unit 10 protrudes below the support plate 38.

[0032] The holding unit 10 includes a suction portion 40 that protrudes below the support plate 38, and a shaft portion 42 that is connected to the suction portion 40 and protrudes above the support plate 38. The lower surface of the suction portion 40 forms a holding surface 40a. The holding unit 10 includes a suction path (not shown) that leads to the holding surface 40a, and a suction source (not shown), such as an ejector, that is connected to the suction path. The outer diameter of the holding surface 40a is smaller than the width of the workpiece 11. The holding unit 10 adsorbs the workpiece 11 that comes into contact with the holding surface 40a.

[0033] The rotation unit 36 ​​includes a housing 44, a motor 46 protruding above the housing 44, and a rotation shaft 48 having an upper end rotatably housed in the housing 44 and a lower end protruding below the housing 44. The housing 44 is fixed to the support plate 38. The upper end of the rotation shaft 48 is connected to the motor 46, and when the motor 46 is driven, the rotation shaft 48 rotates around the Z-axis direction.

[0034] A belt 50 is wound between a rotation shaft 48 of the rotation unit 36 ​​and the shaft 42 of the holding unit 10, and when the rotation shaft 48 is rotated by the motor 46, the belt 50 rotates the rotation shaft 48. In other words, the holding unit 10 rotates around the Z-axis direction. In other words, the rotation unit 36 ​​functions as a rotation mechanism that rotates the holding unit 10 around a straight line intersecting with the holding surface 40a (adsorption surface) of the holding unit 10 as the rotation center.

[0035] An X-axis movement mechanism 52 that moves the laser beam irradiation unit 12 along the X-axis direction is provided on the front surface 8a of the support part 8. A through-hole 55 that connects the front side and the rear side of the support part 8 is formed in the support part 8. A part of the configuration of the laser beam irradiation unit 12 can be moved along the X-axis direction by the X-axis movement mechanism 52 while passing through this through-hole 55.

[0036] The X-axis movement mechanism 52 is fixed to the front surface 8a of the support part 8 and has a pair of X-axis guide rails 54 extending along the X-axis direction. An X-axis movement plate 56 is connected to the front side of the pair of X-axis guide rails 54 in a manner that allows it to slide along the pair of X-axis guide rails 54.

[0037] Additionally, a screw shaft 58 extending along the X-axis direction is disposed adjacent to the pair of X-axis guide rails 54. A motor 60 for rotating the screw shaft 58 is connected to one end of the screw shaft 58. A nut (not shown) that accommodates a large number of balls that roll on the surface of the rotating screw shaft 58 is provided on the surface of the screw shaft 58, on which a spiral groove is formed, to form a ball screw. This nut is fixed to the back side of the X-axis moving plate 56. Therefore, when the screw shaft 58 is rotated by the motor 60, the X-axis moving plate 56 moves along the X-axis direction together with the nut.

[0038] In addition to the laser beam irradiation unit 12, a position detection unit 62 is fixed to the X-axis moving plate 56. The position detection unit 62 is mainly used when performing alignment work for the laser beam irradiation unit 12, and detects the position of the workpiece 11 held by the holding unit 10.

[0039] The position detection unit 62 includes a light receiving element such as a CMOS (Complementary Metal Oxide Semiconductor) sensor or a CCD (Charge Coupled Device) sensor, and detects the position of the workpiece 11 by detecting light reflected from the workpiece 11.

[0040] Next, we will explain the configuration of the laser beam irradiation unit 12. Fig. 3 is a diagram schematically showing an example of the simplest configuration of the laser beam irradiation unit 12. In Fig. 3, some of the components of the laser beam irradiation unit 12 are shown as blocks.

[0041] The laser beam irradiation unit 12 has an oscillator 64. The oscillator 64 is fixed to, for example, the base 4. The oscillator 64 has Nd:YAG or the like as a laser medium, and emits a laser beam having a wavelength (for example, 355 nm) that is absorbed by the material of the workpiece 11. The laser beam emitted from the oscillator 64 is reflected by mirrors 66a and 66b and supplied to a condenser 68.

[0042] The condenser 68 includes a condenser lens that condenses the laser beam. The laser beam that passes through the condenser lens is emitted from the condenser 68 toward the workpiece 11 held by the holding unit 10. As shown in FIG. 2, the condenser 68 is provided at the tip end of a cylindrical housing 70. The base end of the housing 70 is fixed to the X-axis moving plate 56.

[0043] 4 is a side view that schematically shows how a laser beam 68b is irradiated from the side onto the workpiece 11 held by the holding unit 10. The condenser 68 has a function of focusing the laser beam 68b at a focusing point 68a.

[0044] When the X-axis moving plate 56 moves, the condenser 68 moves together with the housing 70, and the position of the focal point 68a relative to the holding unit 10 moves. Furthermore, moving the holding unit 10 also moves the position of the focal point 68a relative to the holding unit 10. In other words, the X-axis moving mechanism 52, the Y-axis moving mechanism 14, and the Z-axis moving mechanism 16 function as moving mechanisms that relatively move the holding unit 10 and the focal point 68a where the laser beam is focused.

[0045] The multiple mirrors 66a, 66b included in the laser beam irradiation unit 12 are disposed and oriented so that they can supply a laser beam 68b to a condenser 68 that moves along the X-axis direction. In addition, the positions or orientations of some of the mirrors 66a, 66b may be changeable so as to correspond to the movement of the condenser 68.

[0046] The laser beam irradiation unit 12 further includes an angle adjustment unit 71 located on the propagation path of the laser beam 68b between the oscillator 64 and the condenser 68. The angle adjustment unit 71 has a function of adjusting the propagation direction of the laser beam 68b.

[0047] The angle adjustment unit 71 is configured by, for example, a galvanometer scanner, an acousto-optic device (AOD), or a polygon mirror, etc. However, the angle adjustment unit 71 is not limited to these. Depending on the configuration of the angle adjustment unit 71, an fθ lens may be provided in the condenser 68.

[0048] By controlling the movement mechanisms (X-axis movement mechanism 52, Y-axis movement mechanism 14, Z-axis movement mechanism 16) and the angle adjustment unit 71, it is possible to change the position of the focal point 68a relative to the workpiece 11 held by the holding unit 10 and the traveling direction of the laser beam 68b focused at the focal point 68a. The movement mechanisms and the angle adjustment unit 71 make it possible to adjust the relative positions and orientations of the condenser 68 and the holding unit 10 so that the condenser 68 faces the side surface 11c connecting the first surface 11a and the second surface 11b of the workpiece 11 held by the holding unit 10.

[0049] The laser beam irradiation unit 12 of the laser processing device 2 can irradiate the workpiece 11 held by the holding unit 10 from the side surface 11c with a laser beam 68b emitted from the oscillator 64 and collected by the collector 68. Furthermore, the traveling direction of the laser beam 68b can be adjusted so that the laser beam 68b enters the side surface 11c of the workpiece 11 and travels to the first surface 11a or the second surface 11b.

[0050] Here, the position detection unit 62 detects the positional relationship between the condenser 68 and the side surface 11c of the workpiece 11 held by the holding unit 10. Therefore, the position detection unit 62 is used when adjusting the position of the condenser 68a relative to the workpiece 11 and the traveling direction of the laser beam 68b.

[0051] Next, a procedure for chamfering the workpiece 11 using the laser processing device 2 configured as above will be described. That is, a method for chamfering the workpiece 11 will be described. Fig. 7(A) is a flowchart showing the flow of each step of the method for chamfering the workpiece.

[0052] In the method for chamfering a workpiece shown in Figure 7(A), first, a holding step S10 is performed in which the central portion of the workpiece 11 on the first surface 11a side is held on the flat holding surface 40a of the suction portion 40 of the holding unit 10 so that the outer periphery of the workpiece 11 (the portion including the side surface 11c) is exposed.

[0053] More specifically, in the holding step S10, the workpiece 11 is held by a transport unit provided in the laser processing device 2, and the workpiece 11 is transported by the transport unit through the carry-in / out port 18, and the workpiece 11 is brought into contact with the holding surface 40a of the suction portion 40 of the holding unit 10. At this time, the center of the first surface 11a side of the workpiece 11 is made to face the holding surface 40a so that the outer periphery of the workpiece 11 does not overlap with the holding surface 40a.

[0054] Next, the suction source connected to the suction part 40 is activated, and the suction part 40 of the holding unit 10 starts suction-holding the workpiece 11. As a result, a suction force acts on the central part of the first surface 11a side of the workpiece 11, and the workpiece 11 is suction-held on the holding surface 40a. At this time, both the outer periphery of the workpiece 11 on the first surface 11a side and the outer periphery on the second surface 11b side are exposed.

[0055] Thereafter, the workpiece 11 is released from the transport unit, and the transport unit is caused to exit the vicinity of the holding unit 10 through the transfer port 18. This completes the holding step S10. Figure 4 includes a side view that schematically shows the workpiece 11 held by the holding unit 10.

[0056] In order to process a predetermined position on the outer periphery of the workpiece 11 in the laser processing device 2, a step of identifying the position of each point on the side surface 11c of the workpiece 11 may be carried out after the workpiece 11 is held by the holding unit 10. In this step, the relative positions of the holding unit 10 and the position detection unit 62 are adjusted by the movement mechanisms (X-axis movement mechanism 52, Y-axis movement mechanism 14, Z-axis movement mechanism 16) so that the side surface 11c of the workpiece 11 faces the position detection unit 62.

[0057] Then, the workpiece 11 is imaged by the light receiving elements of the position detection unit 62 so as to form an image (entire image) including the outer periphery of the workpiece 11. For example, imaging of an area including part of the outer periphery of the workpiece 11 and rotation and movement of the suction part 40 are alternately repeated. Then, the entire image is formed by combining multiple images (partial images) formed by multiple imaging operations using the light receiving elements.

[0058] Next, the position of the outer periphery of the workpiece 11 is identified based on the formed image. For example, the outer periphery of the workpiece 11 is identified by binarizing the formed image using a processor or the like built into the laser processing device 2. At this time, the linearly extending portions of the identified outer periphery are identified as the positions of the primary orientation flat 13a and the secondary orientation flat 13b.

[0059] In the first chamfering step S20 and the second chamfering step S30 described below, the movement mechanism can be operated so that a predetermined position of the workpiece 11 can be machined by referring to the position of each point on the side surface 11c of the workpiece 11.

[0060] In the method for chamfering a workpiece shown in Fig. 7(A), a first chamfering step S20 is performed after the holding step S10. In the first chamfering step S20, the outer periphery of the first surface 11a side of the workpiece 11 is removed. Fig. 5(A) is a side view schematically showing the condenser 68 and the workpiece 11 when the first chamfering step S20 is performed. In the first chamfering step S20, first, before irradiating the workpiece 11 with the laser beam 68b, the traveling direction of the laser beam 68b and the position of the focal point 68a are adjusted.

[0061] More specifically, the focal point 68a is positioned near the outer periphery of the workpiece 11 and on the outside of the first surface 11a side. Then, when the laser beam 68b is irradiated onto the side surface 11c of the workpiece 11, the traveling direction of the laser beam 68b is adjusted so that the laser beam 68b passes through the workpiece 11 and exits onto the first surface 11a of the workpiece 11.

[0062] Thereafter, the laser beam irradiation unit 12 is operated to irradiate the workpiece 11 with a laser beam 68b having a wavelength that is absorbed by the material of the workpiece 11, so that the laser beam 68b is incident on the side surface 11c of the workpiece 11 and exits toward the first surface 11a. At this time, the holding unit 10 (the suction part 40) is rotated around a straight line intersecting the holding surface 40a as the rotation axis. As a result, the laser beam 68b is irradiated along the entire outer periphery of the workpiece 11 on the first surface 11a side, and the outer periphery of the workpiece 11 on the first surface 11a side is removed.

[0063] Here, the conditions for irradiating the workpiece 11 with the laser beam 68b are set, for example, as follows: However, the irradiation conditions are not limited to these. Wavelength: 355nm Repetition frequency: 50kHz Average power: 2.0W

[0064] When rotating the holding unit 10, it is advisable to operate the movement mechanism so that the distance between the side surface 11c of the workpiece 11 and the condenser 68 is constant, by referring to the orientation of the workpiece 11 at each point and the position of the side surface 11c of the workpiece 11. As a result, corners are similarly removed by laser ablation at each point on the side surface 11c of the workpiece 11, and a chamfer having a uniform shape is formed around the entire outer periphery of the first surface 11a side of the workpiece 11.

[0065] 7(A), the second chamfering step S30 is performed after the holding step S10. For example, the second chamfering step S30 is performed after the first chamfering step S20. However, the second chamfering step S30 may be performed before the first chamfering step S20.

[0066] In the second chamfering step S30, the outer periphery on the second surface 11b side of the workpiece 11 is removed. Fig. 5(B) is a side view schematically showing the condenser 68 and the workpiece 11 when the second chamfering step S30 is performed. In the second chamfering step S30, similar to the first chamfering step S20, before the laser beam 68b is irradiated onto the workpiece 11, the traveling direction of the laser beam 68b and the position of the focal point 68a are adjusted.

[0067] More specifically, the focal point 68a is positioned near the outer periphery of the workpiece 11 and on the outer side of the second surface 11b. The traveling direction of the laser beam 68b is adjusted so that when the laser beam 68b is irradiated onto the side surface 11c of the workpiece 11, the laser beam 68b passes through the workpiece 11 and exits onto the second surface 11b of the workpiece 11.

[0068] Thereafter, the laser beam irradiation unit 12 is operated to irradiate the workpiece 11 with a laser beam 68b having a wavelength absorbed by the material of the workpiece 11, so that the laser beam 68b is incident on the side surface 11c of the workpiece 11 and exits on the second surface 11b side. At this time, the holding unit 10 (suction part 40) is rotated around a straight line intersecting the holding surface 40a as the rotation axis. This removes the entire outer periphery of the workpiece 11 on the second surface 11b side.

[0069] In the second chamfering step S30, the movement mechanism or the like is operated so that corners are similarly removed at each position on the side surface 11c of the workpiece 11, and a chamfer having a uniform shape is formed around the entire outer periphery of the second surface 11b side. As a result, a chamfer having the same shape as the outer periphery of the first surface 11a side is also formed on the outer periphery of the second surface 11b side by ablation.

[0070] 6 is an enlarged partial side view schematically showing a workpiece 11 having a chamfered portion formed on its outer periphery. When the first chamfering step S20 and the second chamfering step S30 are performed, a first cutout 15a is formed on the outer periphery of the workpiece 11 on the first surface 11a side, and a second cutout 15b is formed on the outer periphery of the workpiece 11 on the second surface 11b side, as shown in FIG. 6. In other words, a chamfered portion consisting of the first cutout 15a and the second cutout 15b is formed on the outer periphery of the workpiece 11.

[0071] 6 shows cutouts 15a and 15b having surfaces shaped to correspond to the side surfaces of a truncated cone, but the shape of cutouts 15a and 15b constituting the chamfered portion is not limited to this. For example, the chamfered portion may have a surface shaped such that its vertical cross section is curved. Furthermore, in the first chamfering step S20 and the second chamfering step S30, workpiece 11 and condenser 68a may be moved relatively along the thickness direction of workpiece 11 so that the surface of the chamfered portion has a desired shape.

[0072] After the first chamfering step S20 and the second chamfering step S30, the transport unit is brought into contact with the workpiece 11 sucked by the suction part 40, and the workpiece 11 is held by the transport unit, and the suction and holding of the workpiece 11 by the suction part 40 is released. Then, the transport unit is moved to carry the workpiece 11 out of the vicinity of the holding unit 10. This results in the workpiece 11 having been chamfered.

[0073] Here, in the laser processing apparatus 2 according to this embodiment, it is not necessary to turn the workpiece 11 over between the first chamfering step S20 and the second chamfering step S30. This is because the two chamfering steps can be performed consecutively by simply moving the light condensing point 68a between the outside of the first surface 11a side of the workpiece 11 and the outside of the second surface 11b side between the first chamfering step S20 and the second chamfering step S30.

[0074] Therefore, the laser processing device 2 can form a chamfer on the outer periphery of the workpiece 11 without taking the time required to turn the workpiece 11 over. Moreover, in this case, there is no need to precisely re-detect the position of the outer periphery of the workpiece 11 to be processed and determine the processing position after turning the workpiece 11 over. Therefore, this method increases the throughput of the chamfering process.

[0075] Here, in the laser processing apparatus 2 according to this embodiment, a wafer whose second surface is rougher than its first surface may be used as the workpiece. Such a wafer is manufactured, for example, by being separated from an ingot. The wafer immediately after being separated from the ingot is prone to damage because it does not have a chamfered portion formed on its outer periphery. Therefore, the laser processing apparatus 2 may be used for chamfering in the process of manufacturing wafers from ingots.

[0076] Next, a wafer manufacturing method will be described in which a wafer is chamfered from an ingot using the laser processing apparatus 2 in some steps. Fig. 7(B) is a flowchart showing the flow of each step of the wafer manufacturing method. In this wafer manufacturing method, after the wafer is separated from the ingot, the above-mentioned workpiece chamfering method is carried out using the laser processing apparatus 2 with the wafer as the workpiece 11.

[0077] In the wafer manufacturing method shown in Fig. 7(B), first, a separation layer forming step S40 is performed. Fig. 8(A) is a cross-sectional view schematically showing the ingot 17 during the separation layer forming step S40 during which the formation of the separation layer 19 is in progress. In the separation layer forming step S40, a laser processing device 124 is used that can irradiate the ingot 17 with a first laser beam 130 having a wavelength that is transmitted through the material of the ingot 17.

[0078] The laser processing device 124 used in the separation layer formation step S40 includes a holding table 132 that holds a workpiece such as an ingot 17, and a laser beam irradiation unit 126 that irradiates the workpiece held on the holding table 132 with a first laser beam 130.

[0079] The holding table 132 is, for example, a chuck table that can suck and hold a workpiece placed thereon. The laser beam irradiation unit 126 also includes an oscillator (not shown) that emits a first laser beam 130, and a condenser 128 that focuses the first laser beam 130 emitted from the oscillator on the workpiece held by the holding table 132. The laser beam irradiation unit 126 also includes an optical system that guides the first laser beam 130 from the oscillator to the condenser 128.

[0080] Furthermore, the laser processing device 124 includes a moving unit (not shown) that moves the holding table 132 and the laser beam irradiation unit 126 (collector 128) relatively in a direction parallel to the upper surface of the holding table 132.

[0081] In the separation layer forming step S40, first, the ingot 17 is transferred onto the holding table 132, and the ingot 17 is suction-held by the holding table 132. Next, a first focal point 134 of a first laser beam 130 focused by the condenser 128 of the laser beam irradiation unit 126 is positioned at a predetermined depth inside the ingot 17. For example, the first focal point 134 is positioned at a depth of about 100 μm from the top surface 17 a of the ingot 17.

[0082] Then, the laser beam irradiation unit 126 is operated to irradiate the first laser beam 130 toward the upper surface 17a of the ingot 17 and focus the first laser beam 130 at the first focus point 134, while moving the ingot 17 and the first focus point 134 relative to each other. The relative movement of the ingot 17 and the first focus point 134 is performed by the moving unit described above.

[0083] Here, the conditions for irradiating the ingot 17 with the first laser beam 130 are set, for example, as follows: However, the irradiation conditions are not limited to these. Wavelength: 1064nm Repetition frequency: 60kHz Average power: 1.5W

[0084] When the ingot 17 is irradiated with the first laser beam 130, a separation layer 19 including a modified portion and cracks extending from the modified portion is formed near a first focal point 134 inside the ingot 17. Then, when the ingot 17 is irradiated with the first laser beam 130 while scanning the first focal point 134 over the entire area within a plane parallel to the upper surface 17a of the ingot 17, a separation layer 19 approximately parallel to the upper surface 17a of the ingot 17 is formed in the ingot 17.

[0085] In the wafer manufacturing method shown in Fig. 7(B), after the separation layer forming step S40, a separation step S50 is performed in which the wafer is separated from the ingot 17 by applying an external force to the ingot 17 so as to cleave the ingot 17 at the separation layer 19. Fig. 8(B) is a cross-sectional view schematically showing how the wafer 21 is separated from the ingot 17 in the separation step S50.

[0086] In this peeling step S50, the cracks contained in the separation layer 19 further extend, cleaving the ingot 17. As a result, due to this cleavage, the wafer 21 having a second surface 21b (i.e., the surface on the cleaved separation layer 19 side) rougher than the first surface 21a (i.e., the surface corresponding to the upper surface 17a of the ingot 17) is peeled off from the ingot 17. After the peeling step S50, for example, the method for chamfering the workpiece described in FIG. 7(A) is carried out in the laser processing apparatus 2 using the wafer 21 as the workpiece 11.

[0087] That is, after the peeling step S50, the holding step S10 described using Fig. 4 etc. is performed. In the holding step S10, the central portion of the first surface 21a side of the wafer 21 is held on the flat holding surface 40a of the holding unit 10 (suction part 40) so that both the outer periphery on the first surface 21a side and the outer periphery on the second surface 21b side of the wafer 21 are exposed.

[0088] 5(A) and the like is performed. In the first chamfering step S20, a second laser beam (laser beam 68b) having a wavelength absorbed by the material of the wafer 21 is incident on the side surface 21c of the wafer 21 and irradiated onto the wafer 21 so that the second laser beam is incident on the side surface 21c of the wafer 21 and exits on the first surface 21a side. Then, while the second laser beam is being irradiated onto the wafer 21, the holding unit 10 (suction part 40) is rotated around a straight line intersecting the holding surface 40a as a rotation axis, thereby removing the outer periphery of the wafer 21 on the first surface 21a side.

[0089] 5(B) and the like is performed. In the second chamfering step S30, a second laser beam (laser beam 68b) is irradiated onto the wafer 21 so that it is incident on the side surface 21c of the wafer 21 and exits on the second surface 21b side. Then, while the second laser beam is being irradiated onto the wafer 21, the holding unit 10 (suction part 40) is rotated around the rotation axis described above, thereby removing the outer periphery of the wafer 21 on the second surface 21b side.

[0090] As a result, a chamfered wafer 21 is manufactured. In the wafer manufacturing method shown in Fig. 7(B), it is not necessary to turn the wafer 21 over between the first chamfering step S20 and the second chamfering step S30. Therefore, the chamfered wafer 21 can be manufactured without reducing throughput. Note that the second chamfering step S30 may be performed before the first chamfering step S20.

[0091] In the above embodiment, a workpiece processing method (wafer manufacturing method) has been described in which the second chamfering step S30 is performed before or after the first chamfering step S20 in the laser processing apparatus 2. However, one aspect of the present invention is not limited to this. That is, the second chamfering step S30 may be performed simultaneously with the first chamfering step S20.

[0092] To simultaneously perform the first chamfering step S20 and the second chamfering step S30 by the laser processing apparatus 2, a laser beam irradiation unit 12 that focuses the laser beam 68b at two focusing points 68a is used. In this case, it is preferable that a branching DOE (Diffractive Beam Splitter) is incorporated into the optical system of the laser beam irradiation unit 12.

[0093] In the first chamfering step S20 and the second chamfering step S30, which are performed simultaneously, the focal points 68a are positioned respectively on the outside of the first surface 11a side and the outside of the second surface 11b side of the workpiece 11. In other words, the two focal points 68a are positioned so as to sandwich the workpiece 11. In this state, the laser beam 68b is irradiated onto the side surface 11c of the workpiece 11 so as to be focused toward each focal point 68a.

[0094] In this case, the outer periphery on the first surface 11a side of the workpiece 11 and the outer periphery on the second surface 11b side are simultaneously removed, forming a chamfered portion on the workpiece 11. Therefore, the throughput when chamfering the workpiece 11 can be further improved.

[0095] Furthermore, in the above embodiment, the case where the laser processing device 2 irradiates the laser beam 68b from the horizontal direction toward the side surface 11c of the workpiece 11 has been described, but one aspect of the present invention is not limited to this. That is, the laser processing device according to one aspect of the present invention may be capable of irradiating the laser beam from the vertical direction toward the side surface 11c of the workpiece 11. Next, a laser processing device according to a modified example will be described.

[0096] Fig. 9 is a perspective view that schematically shows a laser processing apparatus 72 according to a modified example. The laser processing apparatus 72 shown in Fig. 9 has many components in common with the laser processing apparatus 2 described in Fig. 2 and other figures. Therefore, components of the laser processing apparatus 72 described below that are common to the laser processing apparatus 2 may be given the same names as the corresponding components of the laser processing apparatus 2. Since the description of the laser processing apparatus 2 can be taken into consideration as appropriate for explaining such components, in the following description, explanations of some of the components will be omitted.

[0097] 9 has a base 74 that supports each of the components. On the base 74, a support part 76 that supports a holding unit 80 that mainly holds the workpiece 11, and a support part 78 that supports a laser beam irradiation unit 82 that mainly irradiates the workpiece 11 with a laser beam 120 are provided.

[0098] A Y-axis movement mechanism 84 that moves the holding unit 80 along the Y-axis direction, and a Z-axis movement mechanism 86 that moves the holding unit 80 along the Z-axis direction are provided on the front surface 76a of the support part 76. In addition, the support part 76 is formed with a carry-in / out port 88 that serves as a movement path for the workpiece 11 that moves between the front side and the rear side of the support part 76.

[0099] The Y-axis movement mechanism 84 has a pair of Y-axis guide rails 90 that are fixed to the front surface 76a of the support portion 76 and extend along the Y-axis direction. A Y-axis movement plate 92 is connected to the front side of the pair of Y-axis guide rails 90 in a manner that allows it to slide along the pair of Y-axis guide rails 90.

[0100] A screw shaft 94 extending along the Y-axis direction is disposed between the pair of Y-axis guide rails 90. A motor 96 for rotating the screw shaft 94 is coupled to the front end (one end) of this screw shaft 94. A nut (not shown) that accommodates a large number of balls that roll on the surface of the rotating screw shaft 94 is provided on the surface of the screw shaft 94, on which a spiral groove is formed, thereby constituting a ball screw. When the screw shaft 94 is rotated by the motor 96, the Y-axis moving plate 92 moves along the Y-axis direction together with the nut.

[0101] A Z-axis movement mechanism 86 is fixed to the front surface of the Y-axis movement plate 92. A pair of Z-axis guide rails 98 extending along the Z-axis direction are fixed to the Z-axis movement mechanism 86. A Z-axis movement plate 100 is connected to the front side of the pair of Z-axis guide rails 98 in a manner that allows it to slide along the pair of Z-axis guide rails 98.

[0102] A screw shaft 102 extending along the Z-axis direction is disposed between the pair of Z-axis guide rails 98. A motor 104 for rotating the screw shaft 102 is coupled to the front end (one end) of the screw shaft 102. A nut (not shown) that houses a large number of balls that roll on the surface of the rotating screw shaft 102 is provided on the surface of the screw shaft 102, on which a spiral groove is formed, thereby forming a ball screw. When the screw shaft 102 is rotated by the motor 104, the Z-axis moving plate 100 moves along the Z-axis direction together with the nut.

[0103] A holding unit 80 and a rotation unit 108 that rotates the holding unit 80 (suction portion 110) are fixed to the front surface of the Z-axis moving plate 100. The holding unit 80 and the rotation unit 108 are configured similarly to the holding unit 10 and the rotation unit 36 ​​shown in FIG. 2 and other figures. That is, the holding unit 80 has a suction portion 110, and the underside of the suction portion 110 serves as the holding surface. The suction portion 110 can suction and hold the workpiece 11 that comes into contact with the holding surface. The rotation unit 108 is a rotation mechanism that rotates the holding unit 80 around a straight line that intersects with the holding surface (suction surface) of the suction portion 110 of the holding unit 80 as the center of rotation.

[0104] 9 includes an orientation change unit 106, which changes the orientation of the holding unit 80, on the front surface of the Z-axis moving plate 100. The holding unit 80 is supported by the Z-axis moving plate 100 via the orientation change unit 106. The orientation change unit 106 rotates the holding unit 80 around a rotation axis that extends in a direction parallel to the holding surface of the suction part 110 (for example, in the X-axis direction).

[0105] The support part 78 has a through hole 122 formed therein, which connects the front side and the rear side of the support part 78. A part or all of the components of the laser beam irradiation unit 82 are provided on the front side of the support part 78, passing through this through hole 122.

[0106] A position detection unit 112 is fixed to the front surface 78a of the support part 78. The position detection unit 112 is mainly used when performing alignment work for the laser beam irradiation unit 82, and detects the position of the workpiece 11 held by the holding unit 80. The position detection unit 112 is equipped with a light receiving element, and detects the position of the workpiece 11 by detecting light reflected from the workpiece 11.

[0107] The laser beam irradiation unit 82 is configured in the same manner as the laser beam irradiation unit 12 of the laser processing apparatus 2 shown in Fig. 2 etc. The laser beam irradiation unit 82 includes an oscillator (not shown) that emits a laser beam 120, and a condenser 116 that focuses the laser beam 120 emitted from the oscillator at a focusing point 116a. The condenser 116 includes a focusing lens that focuses the laser beam 120, etc.

[0108] As shown in Figure 9, the condenser 116 is arranged above the workpiece 11 held by the holding unit 80, and the laser beam irradiation unit 82 irradiates the laser beam 120 toward the workpiece 11 from above.

[0109] Furthermore, the laser beam irradiation unit 82 includes an angle adjustment unit 118 on the traveling path of the laser beam 120 from the oscillator to the condenser 116. The angle adjustment unit 118 has a function of adjusting the traveling direction of the laser beam.

[0110] By controlling the movement mechanisms (Y-axis movement mechanism 84, Z-axis movement mechanism 86) and the angle adjustment unit 118, it is possible to change the position of the focal point of the collector 116 with respect to the workpiece 11 held by the holding unit 80 and the traveling direction of the laser beam 120 focused at the focal point. The movement mechanism and the angle adjustment unit 118 make it possible to adjust the relative position and orientation of the collector 116 and the holding unit 80 so that the collector 116 faces the side surface 11c connecting the first surface 11a and the second surface 11b of the workpiece 11 held by the holding unit 80.

[0111] When the workpiece 11 is sucked and held by the suction part 110 of the holding unit 80, the orientation change unit 106 is operated so that the holding surface of the suction part 110 is roughly parallel to the X-axis and Y-axis directions. In this state, when the center of the first surface 11a of the workpiece 11 is brought into contact with the holding surface of the suction part 110 and the workpiece 11 is sucked and held by the suction part 110, the outer periphery of the first surface 11a of the workpiece 11 is positioned directly below the condenser 116.

[0112] Furthermore, in the laser processing apparatus 72 according to the modified example, the orientation of the workpiece 11 can be changed by operating the orientation changing unit 106 while the holding unit 80 is holding the workpiece 11. For example, by operating the orientation changing unit 106 and rotating it by 90 degrees, the holding surface of the suction part 110 becomes parallel to the X-axis direction and the Z-axis direction, and the orientation of the workpiece 11 is changed. At this time, the side surface 11c of the workpiece 11 faces the condenser 116 of the laser beam irradiation unit 82. FIG. 10 is a perspective view schematically showing the laser processing apparatus 72 when the side surface 11c of the workpiece 11 faces the condenser 116.

[0113] Therefore, because the laser processing apparatus 72 according to the modified example has the direction changing unit 106, the laser beam 120 can be irradiated onto both the outer periphery on the first surface 11a side and the side surface 11c side of the workpiece 11. For example, when the laser beam 120 is irradiated onto the first surface 11a of the workpiece 11, characters, symbols, etc. can be printed on the first surface 11a. Furthermore, when the focal point 116a, etc. is adjusted so that the laser beam 120 enters the side surface 11c of the workpiece 11 and travels to the first surface 11a or the second surface 11b, the workpiece 11 can be chamfered with the laser beam 120.

[0114] Here, the position detection unit 112 detects the positional relationship between the condenser 116 and the workpiece 11 held by the holding unit 80. Therefore, the position detection unit 112 is used when adjusting the position of the condensing point 116a relative to the workpiece 11 and the traveling direction of the laser beam.

[0115] In the laser processing apparatus 72 according to this modification, the laser beam 120 can also be irradiated onto the workpiece 11 from the side surface 11c. Then, the outer periphery of the workpiece 11 on the first surface 11a side and the outer periphery on the second surface 11b side can be processed while changing the position of the focal point 116a. In this case, there is no need to turn over the workpiece 11, which results in a reduction in the effort required to chamfer the workpiece 11 and an improvement in throughput.

[0116] 9 and 10, the laser beam irradiation unit 82 causes the laser beam 120 to travel along the Z-axis direction from the condenser 116. Therefore, even if the door of the housing that covers the components of the laser processing apparatus 72 is opened due to some kind of malfunction while the laser beam 120 is being irradiated toward the workpiece 11, the laser beam 120 will not travel outside the housing. This makes the laser processing apparatus 72 relatively safe.

[0117] 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]

[0118] 11 Workpiece 11a,21a 1st page 11b,21b 2nd side 11c,21c side 13a Primary Orientation Flat 13b Secondary Orientation Flat 15a, 15b Notch 17 ingots 17a Top side 19 Separation layer 21 wafers 2,72 Laser processing equipment 4,74 Foundation 6,8,76,78 Support part 6a,8a,76a,78a Front 10,80 holding unit 12,82 Laser beam irradiation unit 14,16,52,84,86 Movement mechanism 18,88 Loading / unloading entrance 20, 28, 54, 90, 98 guide rails 22,30,56,92,100 Moving Plate 24, 32, 58, 94, 102 screw shaft 26,34,60,96,104 motor 36,108 rotating units 38 Support plate 40,110 Adsorption part 40a Holding surface 42 Shaft 44 Case 46 Motor 48 Rotational Axis 50 Belt 55,122 through holes 62,112 Position detection unit 64 Oscillators 66a,66b mirror 68,116 Concentrators 68a,116a Focus point 68b,120 Laser beam 70 Housing 71,118 Angle adjustment unit 106 Orientation change unit 124 Laser processing equipment 126 Laser beam irradiation unit 128 Concentrator 130 First laser beam 132 Holding table 134 1st focal point

Claims

1. A laser processing device that can laser process a workpiece by irradiating the workpiece with a laser beam having a wavelength that is absorbed by the material of the workpiece, a holding unit having a flat holding surface; an oscillator that emits the laser beam; a collector that collects the laser beam emitted from the oscillator; a moving mechanism that relatively moves the holding unit and a focal point at which the laser beam is focused; a rotation mechanism that rotates the holding unit about a straight line that intersects with the holding surface of the holding unit; Equipped with a relative position and orientation of the condenser and the holding unit can be adjusted so that the condenser faces a side surface connecting the first surface and the second surface of the workpiece held by the holding unit; The laser processing device is characterized in that the laser beam emitted from the oscillator and focused by the focusing device can be irradiated onto the workpiece held by the holding unit from the side.

2. 2. The laser processing apparatus according to claim 1, wherein the direction of travel of the laser beam can be adjusted so that the laser beam is incident on the side surface of the workpiece and travels toward the first surface or the second surface.

3. 3. The laser processing apparatus according to claim 1, further comprising a position detection unit that detects the positional relationship between the condenser and the side surface of the workpiece held by the holding unit.

4. A method for chamfering a workpiece, comprising: a holding step of holding a central portion of the workpiece on a first surface side on a flat holding surface of a holding unit so that an outer periphery of the workpiece is exposed; a first chamfering step in which, after the holding step, a laser beam having a wavelength absorbed by the material of the workpiece is incident on the side of the workpiece and irradiated onto the workpiece so that the laser beam exits on the first surface side, while rotating the holding unit about a straight line intersecting the holding surface as a rotation axis, thereby removing an outer periphery of the first surface side of the workpiece; a second chamfering step of removing an outer periphery of the second surface side of the workpiece by rotating the holding unit around the rotation axis while irradiating the workpiece with the laser beam so that the laser beam is incident on the side of the workpiece and exits on the second surface side after the holding step; A method for chamfering a workpiece, comprising:

5. 5. The method for chamfering a workpiece according to claim 4, wherein the workpiece is not turned over between the first chamfering step and the second chamfering step.

6. A wafer manufacturing method for manufacturing a chamfered wafer from an ingot, a separation layer forming step of forming a separation layer inside the ingot by irradiating the ingot with a first laser beam having a wavelength that transmits through the material of the ingot so as to move the ingot and the first focusing point relative to each other while positioning the first focusing point inside the ingot at the first focusing point; a separation step of separating a wafer from the ingot by applying an external force to the ingot so as to cleave the ingot at the separation layer after the separation layer formation step; a holding step of holding a central portion of the first surface side of the wafer on a flat holding surface of a holding unit so that both an outer periphery of the first surface side and an outer periphery of the second surface side of the wafer are exposed after the peeling step; a first chamfering step after the holding step, in which a second laser beam having a wavelength absorbed by the material of the wafer is incident on the side of the wafer and irradiated onto the wafer so that the second laser beam exits the first surface side, while rotating the holding unit about a straight line intersecting the holding surface as a rotation axis, thereby removing an outer periphery of the first surface side of the wafer; a second chamfering step of removing an outer periphery of the second surface side of the wafer by rotating the holding unit around the rotation axis while irradiating the wafer with the second laser beam so that the second laser beam is incident on the side of the wafer and exits on the second surface side after the holding step; A wafer manufacturing method comprising:

7. 7. The method for producing a wafer according to claim 6, wherein the wafer is not turned over between the first chamfering step and the second chamfering step.

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