Laser beam machining device, method for chamfering workpiece and method for manufacturing wafer

Abstract

To reduce time and effort necessary for chamfering a workpiece and also to improve throughput for the chamfering.SOLUTION: A laser beam machining device is provided which can chamfer a workpiece by irradiating the workpiece with laser beam having wavelength absorbed to raw material of the workpiece in order to remove both of a one surface-side outer periphery and the other surface-side outer periphery of the workpiece, the laser beam machining device comprises: a holding table having a flat holding surface; an oscillator emitting laser beam; a collector which collects the laser beam emitted from the oscillator; a movement mechanism which relatively moves the holding table and a focal point to which the laser beam is collected; and a rotation mechanism which rotates the holding table by using a straight line parallel to the holding surface of the holding table as an axis of rotation.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 absorbed by the workpiece so as to remove both the outer periphery on one side and the outer periphery on the other 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] Device chips such as ICs (Integrated Circuits) are essential components in various electronic devices such as mobile phones and personal computers. Such 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 included in a cylindrical ingot, and then processing the outer periphery of the cut-out portion (i.e., the as-sliced ​​wafer) (see, for example, Patent Document 1). Specifically, this processing is performed by, for example, irradiating the as-sliced ​​wafer with a laser beam having a wavelength absorbed by the material of the as-sliced ​​wafer so as to remove both the outer periphery on one surface side and the outer periphery on the other surface side of the as-sliced ​​wafer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-212761 A Summary of the Invention [Problem to be solved by the invention]

[0005] A laser processing device capable of chamfering a workpiece such as an as-sliced ​​wafer generally includes a holding table having a flat holding surface, an oscillator that emits a laser beam, a collector that collects the laser beam emitted from the oscillator, and a moving mechanism that relatively moves the holding table and a focal point at which the laser beam is collected. The laser processing device processes the workpiece by irradiating the workpiece with a laser beam so as to relatively move the holding table and the focal point with the focal point positioned inside the workpiece held on the holding surface of the holding table.

[0006] For example, when chamfering a workpiece with this laser processing device, first, one side of the workpiece is held on the holding surface of the holding table so that the other side of the workpiece is exposed. Next, the laser beam is irradiated onto the workpiece while the focusing point where the laser beam is focused is positioned on the outer periphery of the other 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 other side 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 other side of the workpiece is held on the holding surface of the holding table so that the one side of the workpiece is exposed. Next, the laser beam is irradiated onto the workpiece while the focusing point where the laser beam is focused is positioned on the outer periphery of the one side of the workpiece, and the holding table and the focusing point are moved relatively. This removes the outer periphery of the one side of the workpiece. As a result, a chamfered workpiece is manufactured.

[0008] As described above, when a workpiece is chamfered, it is necessary to separate the workpiece from the holding surface of the holding table, turn it over, and then hold the workpiece again on the holding surface of the holding table. This is time-consuming and reduces the throughput when chamfering a workpiece in a laser processing device. In view of this, an object of the present invention is to reduce the time and effort required when chamfering a workpiece and to improve the throughput. [Means for solving the problem]

[0009] According to one aspect of the present invention, there is provided a laser processing apparatus capable of chamfering a workpiece by irradiating the workpiece with a laser beam of a wavelength that is absorbed by the material of the workpiece so as to remove both the outer periphery of one surface side and the outer periphery of the other surface side of the workpiece, the laser processing apparatus comprising: a holding table 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 table and a focusing point at which the laser beam is collected, and a rotation mechanism that rotates the holding table around a rotation axis that is a straight line parallel to the holding surface of the holding table.

[0010] According to another aspect of the present invention, there is provided a method for chamfering a workpiece, the method including: a holding step of holding a central portion of one side of the workpiece on a flat holding surface of a holding table so that both an outer periphery of one side and an outer periphery of the other side of the workpiece are exposed; and after the holding step, a laser beam having a wavelength absorbed by the material of the workpiece is irradiated onto the workpiece so that a focusing point at which the laser beam is focused is positioned on the outer periphery of the other side of the workpiece, and the holding table and the focusing point are moved relatively to each other, thereby chamfering the outer periphery of the other side of the workpiece. a first chamfering step of removing a portion of the outer periphery of one side of the workpiece, a second chamfering step of removing the outer periphery of the one side of the workpiece after the holding step by irradiating the workpiece with the laser beam so as to move the holding table and the focusing point relatively while positioning the focusing point on the outer periphery of the one side of the workpiece, and a rotation step of rotating the holding table around a straight line parallel to the holding surface of the holding table as a rotation axis so as to invert the workpiece between the first chamfering step and the second chamfering step.

[0011] According to yet another aspect of the present invention, there is provided a method for manufacturing a wafer that is chamfered from an ingot, the method including: a separation layer forming step of irradiating the 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 and move the ingot and the first focal point relatively to each other, thereby forming a separation layer inside the ingot; a peeling step of peeling off a wafer from the ingot, the other side of which becomes rougher than the one side due to the cleavage by applying an external force to the ingot so as to cleave the ingot at the separation layer after the separation layer forming step; and a holding step of holding a central portion of one side of the wafer on a flat holding surface of a holding table so as to expose both an outer periphery of one side and an outer periphery of the other side of the wafer after the peeling step. a first chamfering step of removing the outer periphery of the other side of the wafer after the holding step, by irradiating the wafer with the second laser beam so as to move the holding table and the second focusing point relatively while a second focusing point, where the second laser beam having a wavelength absorbed by the wafer, is positioned on the outer periphery of the other side of the wafer; a second chamfering step of removing the outer periphery of the one side of the wafer after the holding step, by irradiating the wafer with the second laser beam so as to move the holding table and the second focusing point relatively while the second focusing point is positioned on the outer periphery of the one side of the wafer; and a rotation step of rotating the holding table around a straight line parallel to the holding surface of the holding table as a rotation axis to invert the wafer between the first chamfering step and the second chamfering step. Effect of the Invention

[0012] The laser processing device of the present invention is provided with a rotation mechanism that rotates the holding table around a straight line parallel to the holding surface of the holding table as a rotation axis. Therefore, in this laser processing device, when chamfering the workpiece, it is possible to turn over the workpiece without separating it from the holding surface of the holding table. As a result, in this laser processing device, it is possible to reduce the effort required for chamfering the workpiece and improve throughput. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view that diagrammatically illustrates an example of a workpiece. [Diagram 2] FIG. 2 is a perspective view illustrating an example of a laser processing apparatus. [Diagram 3] FIG. 3 is a partial enlarged view that illustrates a schematic diagram of some of the components of the laser processing apparatus illustrated in FIG. [Figure 4] FIG. 4 is a diagram illustrating a schematic configuration of an optical system included in the laser processing apparatus shown in FIG. [Diagram 5] FIG. 5 is a flow chart that illustrates an example of a method for chamfering the workpiece shown in FIG. 1 in the laser processing apparatus shown in FIG. [Figure 6] FIG. 6(A) is a side view showing the workpiece after the holding step, FIG. 6(B) is a side view showing the first chamfering step, and FIG. 6(C) is a partially enlarged side view showing the workpiece after the first chamfering step. [Figure 7] Figure 7(A) is a side view showing the workpiece after the rotation step, Figure 7(B) is a side view showing the second chamfering step, and Figure 7(C) is a partially enlarged side view showing the workpiece after the second chamfering step. [Figure 8] FIG. 8 is a partial cross-sectional side view that illustrates an example of how the laser beam is irradiated onto the workpiece in a state where the holding surface of the holding table is inclined in the first chamfering step. [Figure 9]FIG. 9 is a partial cross-sectional side view that illustrates a schematic diagram of another example of how the laser beam is irradiated onto the workpiece in a state where the holding surface of the holding table is inclined in the first chamfering step. [Figure 10] FIG. 10 is a flow chart that illustrates a schematic example of a wafer manufacturing method for manufacturing a chamfered wafer from an ingot. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] An embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a perspective view showing an example of a workpiece. The workpiece 11 shown in Fig. 1 is, for example, a disk-shaped wafer in which both one surface (front surface) 11a and the other surface (back surface) 11b opposite to the one surface 11a are mirror surfaces, and both the outer periphery of the one surface 11a and the outer periphery of the other surface 11b are angular. In addition, two flat portions, i.e., 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.

[0015] Fig. 2 is a perspective view showing a schematic example of a laser processing device capable of chamfering the workpiece 11 by irradiating the workpiece 11 with a laser beam having a wavelength absorbed by the workpiece 11 so as to remove both the outer periphery on one surface 11a side and the outer periphery on the other surface 11b side of the workpiece 11. Note that the X-axis direction and the Y-axis direction 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 each of the X-axis direction and the Y-axis direction.

[0016] The laser processing apparatus 2 shown in Fig. 2 has a base 4 that supports each of the components. A horizontal movement mechanism 6 is disposed on the upper surface of the base 4. The horizontal movement mechanism 6 is fixed to the upper surface of the base 4 and has a pair of Y-axis guide rails 8 that extend along the Y-axis direction. A Y-axis movement plate 10 is connected to the upper surface side of the pair of Y-axis guide rails 8 in a manner that allows it to slide along the pair of Y-axis guide rails 8.

[0017] A screw shaft 12 extending along the Y-axis direction is disposed between the pair of Y-axis guide rails 8. A motor 14 for rotating the screw shaft 12 is connected to the front end (one end) of this screw shaft 12. A nut (not shown) that houses a large number of balls that roll on the surface of the rotating screw shaft 12 is provided on the surface of the screw shaft 12 on which a spiral groove is formed, thereby forming a ball screw.

[0018] That is, when the screw shaft 12 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 lower surface side of the Y-axis moving plate 10. Therefore, when the screw shaft 12 is rotated by the motor 14, the Y-axis moving plate 10 moves along the Y-axis direction together with the nut. Furthermore, a pair of X-axis guide rails 16 extending along the X-axis direction are fixed to the upper surface of the Y-axis moving plate 10.

[0019] An X-axis moving member 18 is connected to the upper surfaces of the pair of X-axis guide rails 16 in a manner that allows it to slide along the pair of X-axis guide rails 16. The X-axis moving member 18 has a U-shape. Specifically, the X-axis moving member 18 has a flat bottom portion 18a whose lower surface is connected to the pair of X-axis guide rails 16, and a pair of side portions 18b, 18c standing upright from both ends of the bottom portion 18a in the Y-axis direction.

[0020] A screw shaft 20 extending along the X-axis direction is disposed between the pair of X-axis guide rails 16. A motor 22 for rotating the screw shaft 20 is connected to one end of the screw shaft 20. A nut (not shown) that houses a large number of balls that roll on the surface of the rotating screw shaft 20 is provided on the surface of the screw shaft 20 on which a spiral groove is formed, thereby forming a ball screw.

[0021] That is, when the screw shaft 20 rotates, many balls circulate inside the nut, and the nut moves along the X-axis direction. Furthermore, this nut is fixed to the underside of the bottom part 18a of the X-axis moving member 18. Therefore, when the screw shaft 20 is rotated by the motor 22, the X-axis moving member 18 moves along the X-axis direction together with the nut.

[0022] The X-axis moving member 18 is connected to a holding table 24 having a flat holding surface, and to a rotation mechanism 26 that rotates the holding table 24 about a rotation axis that is a straight line parallel to the holding surface of the holding table 24, specifically, a straight line parallel to the Y-axis direction. Figure 3 is a partial enlarged view showing the X-axis moving member 18, the holding table 24, and the rotation mechanism 26.

[0023] The holding table 24 has a disk-shaped frame 24a made of ceramics or the like. The frame 24a has a disk-shaped bottom wall and a cylindrical side wall standing on the outer periphery of the bottom wall. The outer diameter of the side wall of the frame 24a is smaller than the width of the workpiece 11. A disk-shaped porous plate 24b made of, for example, porous ceramics is fixed to a recess defined by the bottom wall and the side wall of the frame 24a.

[0024] The porous plate 24b has a diameter approximately equal to the inner diameter of the side wall of the frame 24a. Furthermore, the porous plate 24b communicates with a suction mechanism (not shown) including, for example, an ejector, via a through hole or the like formed in the bottom wall of the frame 24a. Furthermore, the surface of the side wall of the frame 24a and the surface of the porous plate 24b are parallel to the Y-axis direction and function as the holding surface of the holding table 24 when holding the workpiece 11.

[0025] Specifically, when the workpiece 11 is carried into the laser processing device 2, the workpiece 11 is placed on the holding surface of the holding table 24. When the suction mechanism communicating with the porous plate 24b is operated in this state, a suction force acts on the workpiece 11. As a result, the workpiece 11 is held on the holding surface of the holding table 24.

[0026] The bottom wall of the frame 24a of the holding table 24 is attached to the tip of the base 28 via a bearing (not shown) or the like. A circumferential movement mechanism (not shown) including, for example, a pulley and a motor is provided inside the base 28. When this circumferential movement mechanism is operated, the holding table 24 rotates along the circumferential direction. Specifically, when this circumferential movement mechanism is operated, the holding table 24 rotates around a rotation axis that is a straight line that passes through the center of the holding surface and extends along a direction perpendicular to the holding surface.

[0027] The rotation mechanism 26 has a support member 30 having a U-shape. Specifically, the support member 30 has a flat bottom portion 30a whose length along the Y-axis direction is smaller than the distance between a pair of side portions 18b, 18c of the X-axis moving member 18, and a pair of side portions 30b, 30c standing upright from both ends of the bottom portion 30a in the Y-axis direction. The base end portion of the base 28 is fixed to the front surface side of the bottom portion 30a. The width of the bottom portion 30a (specifically, the length in a direction parallel to the holding surface of the holding table 24 and perpendicular to the Y-axis direction) is smaller than the outer diameter of the frame body 24a of the holding table 24.

[0028] Furthermore, one end of a cylindrical shaft 32a is fixed to the outer surface of the side portion 30b, and one end of a cylindrical shaft 32b is fixed to the outer surface of the side portion 30c. These shafts 32a, 32b are arranged side by side along the Y-axis direction. A through hole is formed in each of the pair of side portions 18b, 18c of the X-axis moving member 18 along the Y-axis direction, and the shafts 32a, 32b pass through each through hole via a bearing (not shown).

[0029] That is, each of the shafts 32a, 32b is supported by the X-axis moving member 18 in a rotatable manner. In addition, a motor 34 is fixed to the side portion 18b of the X-axis moving member 18 via, for example, a connecting member (not shown), and the other end of the shaft 32a is connected to this motor 34. Therefore, when the shaft 32a is rotated by the motor 34, the holding table 24 rotates together with the shaft 32b, the support member 30, and the base 28 around a rotation axis that is a straight line parallel to the holding surface of the holding table 24, specifically, a straight line parallel to the Y-axis direction.

[0030] 2, a support structure 36 having side surfaces generally parallel to both the Y-axis and Z-axis directions is provided on the Y-axis side as viewed from the horizontal movement mechanism 6. A vertical movement mechanism 38 is disposed on the side surface of the support structure 36. The vertical movement mechanism 38 is fixed to the side surface of the support structure 36 and has a pair of Z-axis guide rails 40 extending along the Z-axis direction.

[0031] A Z-axis moving plate 42 is connected to the front surface side of the pair of Z-axis guide rails 40 in a manner that allows it to slide along the pair of Z-axis guide rails 40. A screw shaft (not shown) extending along the Z-axis direction is disposed between the pair of Z-axis guide rails 40. A motor 44 for rotating the screw shaft is connected to the upper end (one end) of this screw shaft.

[0032] In addition, a nut (not shown) that accommodates a large number of balls that roll on the surface of the rotating screw shaft is provided on the surface of the screw shaft on which the helical groove is formed, forming a ball screw. That is, when the screw shaft rotates, a large number of 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 42. Therefore, when the screw shaft arranged between the pair of Z-axis guide rails 40 is rotated by the motor 44, the Z-axis moving plate 42 moves along the Z-axis direction together with the nut.

[0033] A support 46 is fixed to the front surface side of the Z-axis moving plate 42. This support 46 supports some of the components of an optical system 48 included in the laser processing apparatus 2. Fig. 4 is a diagram showing a schematic configuration of the optical system 48. In Fig. 4, some of the components of the optical system 48 are shown as blocks.

[0034] The optical system 48 has an oscillator 50 fixed to the base 4. The oscillator 50 has, for example, Nd:YAG or the like as a laser medium, and emits a laser beam of a wavelength (for example, 355 nm) that is absorbed by the material of the workpiece 11. The laser beam emitted from the oscillator 50 is supplied to a dichroic mirror 52.

[0035] The dichroic mirror 52 is designed to transmit the laser beam emitted from the oscillator 50 and to reflect light (imaging light) of a wavelength used for imaging by the camera 54 so that the optical path of the imaging light is coaxial with the optical path of the laser beam. The camera 54 includes a light source such as an LED (Light Emitting Diode) and an imaging element such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor.

[0036] The laser beam transmitted through the dichroic mirror 52 and the imaging light reflected thereby are supplied to a condenser 56. The condenser 56 includes, for example, a condenser lens that condenses the laser beam and the imaging light. The laser beam and the imaging light that have passed through the condenser lens are emitted directly downward from the bottom surface of the condenser 56. As shown in FIG. 2, the condenser 56 is provided at the tip of a cylindrical housing 58. The base end of the housing 58 is fixed to the support 46.

[0037] Fig. 5 is a flow chart showing a schematic example of a method for chamfering the workpiece 11 in the laser processing device 2. In this method, first, the center of one surface 11a of the workpiece 11 is held on the holding surface of the holding table 24 (holding step S1). Fig. 6(A) is a side view showing the workpiece 11 after the holding step S1.

[0038] In this holding step S1, the workpiece 11 is placed on the holding table 24 so that the center of the first surface 11a of the workpiece 11 is in contact with the holding surface of the holding table 24, i.e., so that both the outer periphery of the first surface 11a of the workpiece 11 and the outer periphery of the other surface 11b of the workpiece 11 are exposed. Then, in this state, the suction mechanism communicating with the porous plate 24b is operated. As a result, a suction force acts on the center of the first surface 11a of the workpiece 11, and the center of the first surface 11a of the workpiece 11 is held by the holding surface of the holding table 24.

[0039] Before placing the workpiece 11 on the holding table 24, the rotation mechanism 26 may be operated, if necessary, to rotate the holding table 24 about a straight line along the Y-axis direction as a rotation axis. For example, if the holding surface of the holding table 24 is inclined with respect to the X-axis direction, the rotation mechanism 26 may rotate the holding table 24 before placing the workpiece 11 on the holding table 24 so that the holding surface becomes parallel to the X-axis direction.

[0040] After the holding step S1, the outer periphery of the workpiece 11 on the other surface 11b side is removed by irradiating the workpiece 11 with a laser beam (first chamfering step S2). Fig. 6(B) is a side view showing the first chamfering step S2, and Fig. 6(C) is a partially enlarged side view showing the workpiece 11 after the first chamfering step S2.

[0041] In this first chamfering step S2, first, the workpiece 11 is imaged by the camera 54 so as to form an image (whole image) including the outer periphery of the other surface 11b of the workpiece 11. For example, imaging by the camera 54 including part of the outer periphery of the other surface 11b of the workpiece 11 in its angle of view and movement of the holding table 24 in the circumferential direction and / or horizontal direction to change the part of the outer periphery of the other surface 11b of the workpiece 11 included in the angle of view of the camera 54 are alternately repeated. Then, the whole image is formed by combining a plurality of images (partial images) formed by imaging by the camera 54 multiple times.

[0042] Next, the position of the outer periphery on the other surface 11b side 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, and then the portion existing between this outer periphery and a virtual line located a predetermined distance inward from the outer periphery is identified as the position of the outer periphery on the other surface 11b side. At this time, the linearly extending portion of the identified outer periphery is identified as the positions of the primary orientation flat 13a and the secondary orientation flat 13b.

[0043] Next, the holding table 24 is moved in the circumferential direction and / or horizontal direction so that the collector 56 is positioned directly above the specified position of the outer periphery of the other surface 11b of the workpiece 11. Next, the housing 58 is raised and lowered so that the focal point of the laser beam LB emitted from the collector 56 is positioned on the outer periphery of the other surface 11b of the workpiece 11. Next, while the laser beam LB is being emitted from the collector 56, the holding table 24 is moved in the circumferential direction and / or horizontal direction with the focal point of the laser beam LB positioned on the outer periphery of the other end side of the workpiece 11.

[0044] For example, when the focal point is located in a region inside the primary orientation flat 13a and the secondary orientation flat 13b of the outer periphery of the other surface 11b of the workpiece 11, the holding table 24 is moved in the horizontal direction. When the focal point is located in another region (specifically, a region extending in a curved manner) of the outer periphery of the other surface 11b of the workpiece 11, the holding table 24 is moved in the circumferential direction. However, when there is a correlation between the crystal orientation of the material of the workpiece 11 and the laser beam LB, the holding table 24 may be moved in the horizontal direction even when the focal point is located in the other region.

[0045] As a result, the outer periphery of the other surface 11b side of the workpiece 11 is removed by laser ablation, and a chamfered portion 15a is formed on the other surface 11b side of the workpiece 11. Although FIG. 6(C) shows the chamfered portion 15a having a surface shaped to correspond to the side surface of a truncated cone, the shape of the surface of the chamfered portion 15a is not limited thereto. For example, the chamfered portion 15a may have a surface shaped such that its vertical cross section is curved. Furthermore, in the first chamfering step S2, the workpiece 11 and the focal point at which the laser beam LB is focused may be moved relatively along the radial direction and / or thickness direction of the holding table 24 so that the surface of the chamfered portion 15a has a desired shape.

[0046] After the first chamfering step S2, the holding table 24 is rotated around a straight line parallel to the holding surface of the holding table 24 as a rotation axis so as to invert the workpiece 11 (rotation step S3). Fig. 7(A) is a side view showing the workpiece 11 after the rotation step S3. In this rotation step S3, the rotation mechanism 26 is operated so as to rotate the holding table 24 180° around a straight line along the Y-axis direction as a rotation axis.

[0047] After the rotation step S3, the outer periphery of the one surface 11a side of the workpiece 11 is removed by irradiating the workpiece 11 with a laser beam LB (second chamfering step S4). Fig. 7(B) is a side view showing the second chamfering step S4, and Fig. 7(C) is a partially enlarged side view showing the workpiece 11 after the second chamfering step S4.

[0048] In this second chamfering step S4, for example, each component of the laser processing device 2 is operated in the same procedure as in the first chamfering step S2. However, since the position of the outer periphery of the one surface 11a of the workpiece 11 can be identified based on the image formed in the first chamfering step S2, it is not necessary to newly capture an image by the camera 54 in the second chamfering step S4.

[0049] Then, when the second chamfering step S4 is performed, the outer periphery of the one surface 11a side of the workpiece 11 is removed by laser ablation to form a chamfered portion 15b on the one surface 11a side of the workpiece 11. Note that, although FIG. 7(C) shows the chamfered portion 15b having a shape corresponding to the side surface of a truncated cone, the shape of the chamfered portion 15b is not limited thereto. For example, the chamfered portion 15b may have a surface having a shape whose longitudinal section is curved. Furthermore, in the second chamfering step S4, the workpiece 11 and the focal point where the laser beam LB is focused may be moved relatively along the radial direction and / or thickness direction of the holding table 24 so that the surface of the chamfered portion 15b has a desired shape.

[0050] As described above, the laser processing apparatus 2 is provided with the rotation mechanism 26 that rotates the holding table 24 about a straight line parallel to the holding surface of the holding table 24, specifically, a straight line along the Y-axis direction, as the rotation axis. Therefore, in this laser processing apparatus 2, when chamfering the workpiece 11, it is possible to turn over the workpiece 11 without separating the workpiece 11 from the holding surface of the holding table 24. As a result, in this laser processing apparatus 2, it is possible to reduce the effort required when chamfering the workpiece 11 and improve throughput.

[0051] The above is one embodiment of the present invention, and the present invention is not limited to the above. For example, in the laser processing device of the present invention, a moving mechanism for relatively moving the workpiece 11 and the focal point where the laser beam LB is focused may be provided, and the structure of the moving mechanism is not limited.

[0052] Specifically, in the laser processing apparatus of the present invention, in addition to or instead of at least one of the horizontal movement mechanism 6, the circumferential movement mechanism provided inside the base 28, or the vertical movement mechanism 38, a vertical movement mechanism for moving the holding table 24 along the vertical direction and / or a horizontal movement mechanism for moving the housing 58 along the horizontal direction may be provided.

[0053] Alternatively, in the laser processing apparatus of the present invention, a scanning optical system capable of changing the direction of the laser beam LB emitted from the condenser 56 may be provided as a moving mechanism for relatively moving the workpiece 11 and the focal point where the laser beam LB is focused. This scanning optical system is provided, for example, between the dichroic mirror 52 included in the optical system 48 and the condenser 56. Note that this scanning optical system includes, for example, a galvanometer scanner, an acousto-optical device (AOD), and / or a polygon mirror. In this case, an fθ lens may be provided in the condenser 56.

[0054] Moreover, the laser processing apparatus of the present invention may not be provided with the dichroic mirror 52 and the camera 54. Moreover, in the laser processing apparatus of the present invention, instead of the dichroic mirror 52 and the camera 54, a camera whose optical path of the imaging light is not coaxial with the optical path of the laser beam may be provided.

[0055] In the method of chamfering a workpiece of the present invention, the outer periphery on one end side of the workpiece 11 may be removed first, and then the outer periphery on the other end side. In such a method of chamfering a workpiece, the above-mentioned steps are carried out in the order of, for example, the holding step S1, the rotating step S3, the second chamfering step S4, the rotating step S3, and the first chamfering step S2.

[0056] In the first chamfering step S2 and the second chamfering step S4 of the method for chamfering a workpiece of the present invention, the laser beam LB may be irradiated onto the workpiece 11 with the holding surface of the holding table 24 tilted with respect to the X-axis direction. Each of Figures 8 and 9 is a partial cross-sectional side view that shows a schematic view of the state in which the laser beam LB is irradiated onto the workpiece 11 in this manner.

[0057] Specifically, Figures 8 and 9 show the first chamfering step S2, which is performed with the holding table 24 tilted so that the optical axis of the laser beam LB is parallel (Figure 8) or perpendicular (Figure 9) to the surface of the chamfered portion 15a (see Figure 6(C)) formed on the other side 11b of the workpiece 11 (in other words, the inner surface of the removal area 11d to be removed by irradiation with the laser beam LB).

[0058] 8, when the first chamfering step S2 is performed, the chamfered portion 15a can be formed by removing the second region 11f located inside the first region 11e of the removal region 11d without removing the first region 11e near the outer periphery. That is, in this case, the volume of the material of the workpiece 11 that needs to be removed by laser ablation can be reduced. Therefore, in this case, the throughput when chamfering the workpiece 11 can be further improved.

[0059] Furthermore, in this case, it becomes easy to form chamfered portion 15a having a surface shape corresponding to the side surface of a truncated cone, regardless of the surface shape of the outer periphery on the other surface 11b side of workpiece 11. Specifically, when the surface of the outer periphery on the other surface 11b side of workpiece 11 has an uneven shape, in order to form chamfered portion 15a, it is necessary to locally remove the convex portions included in the outer periphery on the other surface 11b side, rather than uniformly removing the entire outer periphery on the other surface 11b side.

[0060] However, it is often difficult to generate laser ablation with high accuracy so as to locally remove the convex portion included in the outer periphery on the other surface 11b side of the workpiece 11. In contrast, when the first chamfering step S2 is performed as shown in Fig. 8, the chamfered portion 15a can be formed by generating laser ablation so as to remove the second region 11f without removing the first region 11e whose surface has an uneven shape. Therefore, in this case, it becomes easy to form the chamfered portion 15a without depending on the surface shape of the outer periphery on the other surface 11b side of the workpiece 11.

[0061] 9, when the first chamfering step S2 is performed, the chamfered portion 15a having a surface shape corresponding to the side surface of a truncated cone can be formed by irradiating the workpiece 11 with the laser beam LB while maintaining the focal point of the laser beam LB positioned on the outer circumferential edge on the other surface 11b side of the workpiece 11. That is, in this case, it is not necessary to relatively move the workpiece 11 and the focal point of the laser beam LB along the radial direction and / or thickness direction of the holding table 24 in order to form the chamfered portion 15a. Therefore, in this case, the machining accuracy when forming the chamfered portion 15a on the workpiece 11 can be improved.

[0062] In the present invention, the workpiece may be a wafer having one side rougher than the other side. Such a wafer is manufactured, for example, by separating an ingot so that a part of the front side is peeled off using a laser beam (first laser beam) having a wavelength that transmits the ingot material. Fig. 10 is a flow chart that shows an example of a wafer manufacturing method for manufacturing a chamfered wafer from an ingot, specifically, a wafer having one side rougher than the other side is peeled off from the ingot and then chamfered.

[0063] In this method, first, a separation layer is formed inside the ingot (separation layer forming step S5). In this separation layer forming step S5, the first laser beam is irradiated onto the ingot so that the ingot and the focal point (first focal point) are moved relatively while the focal point of the first laser beam is positioned inside the ingot. As a result, a separation layer including a modified portion and cracks extending from the modified portion is formed inside the ingot.

[0064] After the separation layer forming step S5, an external force is applied to the ingot so as to cleave the ingot at the separation layer, thereby peeling the wafer from the ingot (peeling step S6). In this peeling step S6, the cracks contained in the separation layer further extend and the ingot cleaves. As a result, due to this cleavage, a wafer is peeled from the ingot, the other side (i.e., the surface on the cleaved separation layer side) being rougher than one side (i.e., the surface corresponding to the surface of the ingot).

[0065] After the peeling step S6, for example, the method for chamfering the workpiece shown in Fig. 5 is performed in the laser processing device 2 with the wafer as the workpiece. That is, the following steps are performed in order: a holding step S1' in which the center of one side of the wafer is held on the holding surface of the holding table 24, a first chamfering step S2' in which the outer periphery of the other side of the wafer is removed by irradiating the wafer with a laser beam, a rotation step S3' in which the holding table 24 is rotated about a straight line parallel to the holding surface of the holding table 24, specifically, a straight line parallel to the Y-axis direction, as the rotation axis so as to turn the wafer over, and a second chamfering step S4' in which the outer periphery of the one side of the wafer is removed by irradiating the wafer with a laser beam.

[0066] As a result, a chamfered wafer is manufactured. In the wafer manufacturing method shown in Fig. 10, a wafer having a rougher other side than the one side, i.e., a wafer having an uneven other side, is peeled off from an ingot, but the chamfered wafer can be manufactured without decreasing the throughput. That is, in this method, it is possible to remove both the outer periphery of one side and the outer periphery of the other side of the wafer to chamfer the wafer without performing grinding and / or polishing for holding the other side of the wafer on the holding surface of the holding table 24.

[0067] In the wafer manufacturing method shown in FIG. 10, a wafer having an uneven surface on the outer periphery of the other side is peeled off from an ingot, so when forming a chamfered portion having a surface shape corresponding to the side of a truncated cone in the first chamfering step S2', it is preferable that the first chamfering step S2' is performed as described with reference to FIG. 8.

[0068] 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]

[0069] 2: Laser processing equipment 4: Base 6: Horizontal movement mechanism 8: Y-axis guide rail 10: Y-axis moving plate 11: Workpiece (11a: One side (front side), 11b: Other side (back side), 11c: Side) (11d: area to be removed, 11e: first area, 11f: second area) 12: Screw shaft 13a: Primary orientation flat 13b: Secondary orientation flat 14: Motor 15a: Chamfered part 15b: Chamfered part 16: X-axis guide rail 18: X-axis moving member (18a: bottom, 18b, 18c: sides) 20: Screw shaft 22: Motor 24: Holding table (24a: frame, 24b: porous plate) 26: Rotation mechanism 28: Bass 30: Support member (30a: bottom, 30b, 30c: sides) 32a: shaft 32b: Shaft 34: Motor 36:Support structure 38: Vertical movement mechanism 40: Z-axis guide rail 42: Z-axis moving plate 44: Motor 46 :Support 48:Optical system 50: Oscillator 52:Dichroic mirror 54: Camera 56: Concentrator 58: Housing

Claims

1. A laser processing device capable of chamfering a workpiece by irradiating the workpiece with a laser beam having a wavelength that is absorbed by a material of the workpiece so as to remove both an outer periphery on one side and an outer periphery on another side of the workpiece, the device comprising: a holding table having a flat holding surface; an oscillator for emitting the laser beam; a collector for collecting the laser beam emitted from the oscillator; a moving mechanism for relatively moving the holding table and a focusing point at which the laser beam is focused; a rotation mechanism that rotates the holding table about a straight line parallel to the holding surface of the holding table as a rotation axis; A laser processing apparatus comprising:

2. A method for chamfering a workpiece, comprising the steps of: a holding step of holding a central portion of one side of the workpiece on a flat holding surface of a holding table so that both an outer periphery of one side of the workpiece and an outer periphery of the other side of the workpiece are exposed; a first chamfering step of removing the outer periphery of the other surface side of the workpiece by irradiating the workpiece with a laser beam having a wavelength absorbed by the material of the workpiece while positioning a focusing point at the outer periphery of the other surface side of the workpiece and moving the holding table and the focusing point relatively; a second chamfering step of removing the outer periphery of the one surface side of the workpiece by irradiating the workpiece with the laser beam while moving the holding table and the focusing point relatively in a state where the focusing point is positioned on the outer periphery of the one surface side of the workpiece after the holding step; a rotating step between the first chamfering step and the second chamfering step, of rotating the holding table about a straight line parallel to the holding surface of the holding table as a rotation axis so as to invert the workpiece; A method for chamfering a workpiece comprising:

3. A wafer manufacturing method for manufacturing a chamfered wafer from an ingot, comprising: 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 while positioning a first focusing point inside the ingot and relatively moving the ingot and the first focusing point; a peeling step of peeling off a wafer from the ingot, the wafer having one side rougher than the other side due to the cleavage by applying an external force to the ingot so as to cleave the ingot at the separation layer after the separation layer forming step; a holding step of holding a central portion of one surface of the wafer on a flat holding surface of a holding table so that both an outer peripheral portion of one surface of the wafer and an outer peripheral portion of the other surface of the wafer are exposed after the peeling step; a first chamfering step of removing the outer periphery of the other surface side of the wafer by irradiating the wafer with the second laser beam while positioning a second focusing point, at which the second laser beam having a wavelength absorbed by the wafer, on the outer periphery of the other surface side of the wafer and relatively moving the holding table and the second focusing point; a second chamfering step of removing the outer periphery of the one surface side of the wafer by irradiating the wafer with the second laser beam while relatively moving the holding table and the second focal point with the second focal point positioned at the outer periphery of the one surface side of the wafer after the holding step; a rotating step between the first chamfering step and the second chamfering step of rotating the holding table about a straight line parallel to the holding surface of the holding table as a rotation axis so as to invert the wafer; A method for manufacturing a wafer comprising the steps of:

Images