Wafer manufacturing method, laser processing apparatus, and wafer manufacturing apparatus

Abstract

To provide a wafer manufacturing method capable of reducing warpage of a wafer when manufacturing the wafer from an ingot, and to provide a laser processing apparatus and a wafer manufacturing apparatus.SOLUTION: The wafer manufacturing method for manufacturing the wafer 20 from the single-crystal SiC ingot 11 includes the separation layer forming step S11 of forming the separation layer 15 including the plural modified regions inside the single-crystal SiC ingot 11 by forming the modified regions by irradiating the single-crystal SiC ingot 11 with the laser beam from the 11a portion of the front side of the single-crystal SiC ingot 11 and positioning the focal point of the laser beam at a position deeper than the 11a portion of the front side of the single-crystal SiC ingot 11 and relatively processing-feeding the single-crystal SiC ingot 11 and the focal point. In the separation layer forming step S11, the depth of the focal point for forming the modified region is changed to form a separation surface 17 between the single-crystal SiC ingot 11 and the wafer 20 into a three dimensional shape instead of a horizontal surface.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a wafer manufacturing method for manufacturing wafers from an ingot, a laser processing device, and a wafer manufacturing device. [Background technology]

[0002] As a method for manufacturing wafers of semiconductors or the like, a method has been proposed in which a laser beam having a wavelength that passes through single crystal material is irradiated from the surface side of an ingot to form a separation layer inside the ingot that includes a modified region and cracks extending from the modified region, and then the wafer is separated from the ingot using this separation layer as a starting point (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-111143 Summary of the Invention [Problem to be solved by the invention]

[0004] This method is a so-called single-wafer method in which wafers are produced one by one from an ingot. The separated wafers have a mirror surface on one side and a separated surface with a modified region on the other side. Therefore, in addition to the warpage of the original material, warpage due to the expansion of the modified region also occurs.

[0005] The separated wafers are then ground at their separated surfaces to remove the modified regions, but warped wafers can be difficult to transport.

[0006] The present invention provides a wafer manufacturing method, a laser processing apparatus, and a wafer manufacturing apparatus that are capable of reducing warpage of wafers when manufacturing wafers from an ingot. [Means for solving the problem]

[0007] The present invention provides A wafer manufacturing method for manufacturing wafers from an ingot, comprising: a holding step of holding the ingot; a separation layer forming step of forming a modified region by irradiating a laser beam having a wavelength that can transmit through the ingot from the surface of the ingot and positioning the focal point of the laser beam at a position deeper than the surface of the ingot, and processing and feeding the ingot and the focal point relatively to form a separation layer including a plurality of the modified regions inside the ingot; a separation step of separating a workpiece including the surface of the ingot as the wafer from the ingot starting from the separation layer; a grinding step of grinding the separation surface of the wafer to remove the modified region, In the separation layer forming step, The depth of the light condensing point that forms the modified region is changed so that the separation surface is not a horizontal surface but a three-dimensional shape.

[0008] The present invention also provides A laser processing device, a holding table for holding an ingot; a laser beam irradiation unit that irradiates a surface of the ingot held on the holding table with a laser beam having a wavelength that can pass through the ingot, positioning the focal point of the laser beam at a position deeper than the surface of the ingot to form a modified region, and processing and feeding the ingot and the focal point relatively to form a separation layer including a plurality of the modified regions inside the ingot; a moving unit capable of changing the relative position between the ingot held on the holding table and a condenser lens of the laser beam irradiation unit; a control unit for controlling the laser processing device, The control unit The moving unit is controlled to vary the depth of the focal spot that forms the modified region within the ingot.

[0009] The present invention also provides A wafer manufacturing apparatus for manufacturing wafers from an ingot, The above laser processing device, a separation device that separates a workpiece including the surface of the ingot as the wafer from the ingot, starting from the separation layer; a first grinding device that grinds the separation surface of the wafer to make the separation surface of the wafer a horizontal plane; and a second grinding device that grinds the separated surface of the ingot to make the separated surface of the ingot a horizontal surface. [Effects of the Invention]

[0010] According to the present invention, warping of the wafer can be suppressed by changing the focal point of the laser beam to form a three-dimensional separation surface. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a flow diagram of one embodiment of a method for manufacturing a wafer 20 . [Figure 2] FIG. 2 is a perspective view showing the laser processing device 1. As shown in FIG. [Figure 3] FIG. 3 is a diagram illustrating the laser beam irradiation mechanism 8 of the laser processing device 1. As shown in FIG. [Figure 4] FIG. 4 is a diagram showing a state in which a laser beam is irradiated from the surface 11a of the ingot 11 by a condenser 84 in the separation layer forming step S11. [Figure 5] FIG. 5 is a diagram showing a state in which separation surface 17 is processed to have a triangular shape when viewed from the X-axis direction in separation layer forming step S11. [Figure 6] FIG. 6 is a diagram illustrating a modified laser beam irradiation mechanism 8. In FIG. [Figure 7]FIG. 7 is a diagram showing the state before the wafers 20 are separated from the ingot 11 in the separation step S12. [Figure 8] FIG. 8 is a diagram showing the state after the wafer 20 has been separated from the ingot 11 in the separation step S12. [Figure 9] FIG. 9 is a diagram illustrating grinding of the front surface 20a (separation surface 17) of the wafer 20 in the first grinding step S13. [Figure 10] FIG. 10 is a diagram illustrating grinding of the separated surface 17 of the ingot 11 in the second grinding step S14. [Figure 11] FIG. 11 is a block diagram of the wafer manufacturing apparatus 100. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0013] FIG. 1 is a flow diagram of one embodiment of a method for manufacturing a wafer 20 . The method for manufacturing the wafer 20 of this embodiment includes a holding step S10 for holding the ingot 11, a separation layer forming step S11 for forming a separation layer 15 inside the ingot 11, a separation step S12 for separating the workpiece including the surface 11a of the ingot 11 as a wafer 20 from the ingot 11 starting from the separation layer 15, a first grinding step S13 for grinding the separated surface of the wafer 20, and a second grinding step S14 for grinding the separated surface of the ingot 11. The second grinding step S14 is a pretreatment for manufacturing the next wafer 20.

[0014] First, an example of a laser processing apparatus 1 that performs the holding step S10 and the separation layer forming step S11 will be described. Fig. 2 is a perspective view showing the laser processing apparatus 1. In the following description, the X-axis direction is one direction in a horizontal plane. The Y-axis direction is a direction perpendicular to the X-axis direction in a horizontal plane. The Z-axis direction is a direction perpendicular to the X-axis direction and the Y-axis direction.

[0015] The laser processing apparatus 1 of this embodiment comprises a base 2, a first slide block 4 mounted on the base 2 so as to be movable in the Y-axis direction, a second slide block 6 mounted above the first slide block 4 so as to be movable in the X-axis direction, a holding table 10 provided on the second slide block 6, a column 12 erected on the base 2, a laser beam irradiation mechanism 8 attached to the column 12, and a control unit 14 for controlling the laser processing apparatus 1.

[0016] The first slide block 4 is configured to be movable in the indexing direction, that is, the Y-axis direction, along a pair of guide rails 48 by an indexing mechanism 46 configured of a ball screw 42 and a pulse motor 44 .

[0017] A second slide block 6 is mounted above the first slide block 4 so as to be movable in the X-axis direction. That is, the second slide block 6 is configured so as to be movable in the processing feed direction, i.e., in the X-axis direction, along a pair of guide rails 68 by a processing feed mechanism 66 composed of a ball screw 62 and a pulse motor 64.

[0018] A holding table 10 is mounted on the first slide block 4. The holding table 10 is movable in the X-axis and Y-axis directions by a processing feed mechanism 66 and an indexing feed mechanism 46, and is rotatable by a motor housed in the second slide block 6.

[0019] A column 12 is erected on the base 2, and a laser beam irradiation mechanism 8 is attached to this column 12.

[0020] Figure 3 is a diagram illustrating the laser beam irradiation mechanism 8 of the laser processing apparatus 1. As shown in Figures 2 and 3, the laser beam irradiation mechanism 8 is composed of a laser beam generating unit 82 housed in a casing 13, and a condenser (laser head) 84 attached to the tip of the casing 13. An imaging unit 86 having a microscope and a camera is attached to the tip of the casing 13 adjacent to the condenser 84.

[0021] The laser beam generating unit 82 includes a laser oscillator 80 that oscillates a YAG laser or a YVO4 laser, and an output adjustment unit 81. Although not specifically shown, the laser oscillator 80 has a Brewster window, and the laser beam emitted from the laser oscillator 80 is a linearly polarized laser beam.

[0022] The pulsed laser beam, adjusted to a predetermined power by the output adjustment unit 81 of the laser beam generating unit 82, is reflected by the mirror 87 of the collector 84 and then irradiated by the collector lens 88, with the focal point positioned inside the ingot 11, which is the workpiece fixed on the holding table 10.

[0023] The material of the ingot 11 is not particularly limited, and may be, for example, a SiC single crystal ingot or a GaN single crystal ingot. The ingot 11 is not limited to a single crystal ingot, but may be a polycrystalline ingot. The ingot 11 has a front surface 11a and a back surface 11b opposite to the front surface 11a. The front surface 11a of the ingot 11 is polished to a mirror finish as it is the surface to be irradiated with the laser beam. The thickness of the ingot 11 is, for example, 0.35 mm to 100 mm.

[0024] Furthermore, the condenser 84 is provided with a vertical movement unit 89, which is configured to be able to move the position of the condenser lens 88 in the Z-axis direction. Therefore, by moving the position of the condenser lens 88 upward with the vertical movement unit 89, the focal point inside the ingot 11 can be moved toward the front surface 11a, and by moving the position of the condenser lens 88 downward, the focal point inside the ingot 11 can be moved toward the back surface 11b.

[0025] The control unit 14 controls each of the above-mentioned components of the laser processing apparatus 1, causing the laser processing apparatus 1 to perform various processes on the workpiece. The control unit 14 is a computer including a control unit that performs various calculations, a memory unit having a storage medium, and an input / output interface (not shown) that controls the input and output of data to and from the control unit 14. The control unit includes a microprocessor such as a CPU (Central Processing Unit). The memory unit has memories such as an HDD (Hard Disk Drive), ROM (Read Only Memory), or RAM (Random Access Memory). The control unit performs various calculations based on predetermined programs stored in the memory unit. The control unit outputs various control signals to each of the above-mentioned components via the input / output interface according to the calculation results, thereby controlling the laser processing apparatus 1.

[0026] The control unit 14 , which will be described in detail later, controls the vertical movement unit 89 to change the focal point of the laser beam emitted from the laser oscillator 80 inside the ingot 11 .

[0027] In the laser processing apparatus 1 configured as above, the ingot 11 is held by the holding table 10 on the second slide block 6 in the holding step S10.

[0028] In the separation layer formation step S11, a laser beam having a wavelength that transmits through the ingot 11 is irradiated onto the surface 11a of the ingot 11, and the focal point of the laser beam is positioned deeper than the surface 11a of the ingot 11 to form a modified region, and the ingot 11 and the focal point are processed and fed relatively in the X-axis direction to form a separation layer 15 including multiple modified regions inside the ingot 11.

[0029] 4 is a diagram showing a state in which a laser beam is irradiated from the surface 11a of the ingot 11 by a condenser 84 in the separation layer formation step S11. In the separation layer formation step S11, the focal point of a laser beam having a wavelength (e.g., a wavelength of 1064 nm) that is transparent to the ingot 11 fixed on the holding table 10 is positioned at a position deeper than the surface 11a. Then, the ingot 11 is processed and fed so that the focal point moves from one end of the ingot 11 to the other end along the X-axis direction, forming a modified region along the X-axis. Subsequently, the ingot 11 is indexed and fed a predetermined distance along the Y-axis, and then processed and fed so that the focal point moves from the other end of the ingot 11 to one end along the X-axis direction, repeating the process of forming a modified region along the X-axis. As a result, a modified region and cracks extending from the modified region are formed inside the ingot 11, and a separation layer 15 is formed.

[0030] Here, in the separation layer forming step S11, the depth of the focal point of the laser beam that forms the modified region is changed so that the separation surface 17 between the wafer 20 and the ingot 11, which is formed starting from the separation layer 15, has a three-dimensional shape rather than a horizontal plane. The depth of the focal point of the laser beam is achieved by changing the position of the condenser lens 88 in the Z-axis direction using the vertical movement unit 89.

[0031] FIG. 5 is a diagram showing the state in which, in the separation layer formation step S11, the separation surface 17 is processed to have a triangular shape when viewed from the X-axis direction. In the separation layer formation step S11, first, the ingot 11 is processed and fed so that the focal point moves from one end of the ingot 11 to the other end along the X-axis direction (perpendicular to the paper surface) without changing the height position of the focal point in the Z-axis direction, thereby forming a modified region along the X-axis direction. Next, the condenser 84 is moved upward along the Z-axis by a predetermined amount while indexing and feeding by a predetermined amount along the Y-axis direction (to the right of the paper surface). Then, the condenser 84 is processed and fed so that the focal point moves from the other end of the ingot 11 to one end along the X-axis direction without changing the height position of the focal point in the Z-axis direction, thereby forming a modified region along the X-axis direction. This series of processes is repeated up to the center in the Y-axis direction. Furthermore, from the center in the Y-axis direction, the same process is performed, but the condenser 84 is moved downward along the Z-axis by a predetermined amount while indexing and feeding by a predetermined amount along the Y-axis direction. As a result, inside the ingot 11, the separation layer 15 is processed to have a triangular shape when viewed from the X-axis direction.

[0032] If the reformed region extending in the X-axis direction is called a reformed line 16, then, as shown in Figure 4, multiple reformed lines 16 extending linearly in the X-axis direction between one end and the other end of the ingot 11 are formed in the Y-axis direction inside the ingot 11. As shown in Figure 5, the same reformed line 16 has the same depth from the surface 11a, but one reformed line 16 and another reformed line 16 have different depths from the surface 11a. Therefore, the separation layer 15 formed inside the ingot 11 is not flat but has a three-dimensional shape.

[0033] If the separation layer 15 were processed to have a horizontal surface, the wafer 20 separated from the ingot 11 in the separation step S12 would warp due to the expansion of the modified region in addition to the warp of the original material of the wafer 20. In contrast, by forming the separation layer 15 into a three-dimensional shape, warping of the wafer 20 can be suppressed. In particular, as in the example shown in Figure 5, by irradiating the laser beam so that the focal point is farther away from the surface 11a the closer it is to the outer periphery of the ingot 11 in the Y-axis direction, the thickness of the outer periphery of the wafer 20 in the Y-axis direction increases, and warping in the outer periphery of the wafer 20, which is prone to warping, can be suppressed.

[0034] The laser beam irradiation mechanism 8 of the laser processing apparatus 1 is not limited to the configuration shown in FIG. 3 , and may have the configuration shown in FIG. 6 . FIG. 6 is a diagram illustrating a modified laser beam irradiation mechanism 8. In the modified laser beam irradiation mechanism 8 shown in FIG. 6 , a laser beam generating unit 82 has a branching unit 83 in addition to a laser oscillator 80 and an output adjustment unit 81. The branching unit 83 branches the laser beam, whose output has been adjusted by the output adjustment unit 81, into multiple beams (five beams in this embodiment) at predetermined intervals in a predetermined direction in the XY plane. For example, by branching the laser beam into multiple beams in the Y-axis direction in the XY plane, multiple modification lines 16 can be formed in a single processing feed.

[0035] In this case, the depth from the surface 11a varies for each of the multiple reforming lines 16, so that inside the ingot 11, the separation layer 15 has a triangular shape with stepped slopes when viewed from the X-axis direction.

[0036] The three-dimensional shape of the separation layer 15 is not limited to this, and the depth from the surface 11a may continuously change along the same modified line 16, and the depth from the surface 11a may be different between one modified line 16 and another modified line 16. In particular, by irradiating the laser beam so that the focal point is farther away from the surface 11a the closer it is to the outer circumferential region of the ingot 11 in the X-axis direction and the Y-axis direction, a conical shape is formed in which the thickness increases in the X-axis direction and the Y-axis direction in the outer circumferential region of the wafer 20, thereby suppressing warpage in the outer circumferential region of the wafer 20, which is prone to warpage. In this case, the modified region is formed along the X-axis direction by processing the ingot 11 so that the focal point moves from one end of the ingot 11 to the other end or from the other end to one end along the X-axis direction while continuously changing the height position of the focal point in the Z-axis direction, which is different from the example shown in FIG. 5.

[0037] In the separation step S12, a thin plate including the surface 11a of the ingot 11 is peeled off from the separation layer 15 as a wafer 20. In other words, a part of the ingot 11 is separated from the ingot 11 as the wafer 20. FIG. 7 is a diagram showing the state before the wafer 20 is separated from the ingot 11 in the separation step S12, and FIG. 8 is a diagram showing the state after the wafer 20 is separated from the ingot 11 in the separation step S12.

[0038] 7, the separation apparatus 9 performing the separation step S12 includes a separation unit 92 that applies ultrasonic vibrations to the front surface 11a of the ingot 11, a holding table 94 that holds the back surface 11b of the ingot 11, and a nozzle 96 that supplies water between the lower surface 92a of the separation unit 92 and the front surface 11a of the ingot 11. In the separation step S12, a small gap (e.g., 0.6 mm) is provided between the lower surface 92a of the separation unit 92 and the front surface 11a of the ingot 11, and ultrasonic vibrations are applied by the separation unit 92 while water is supplied into the gap from the nozzle 96, thereby separating the wafer 20 from the ingot 11 starting from the separation layer 15. Then, as shown in FIG. 8, the wafer 20 is separated from the ingot 11 by suctioning it with a robot arm 98 and moving it upward. The separation method is not limited to this, and the wafer 20 may be separated from the ingot 11 starting from the separation layer 15 by applying physical impact by rotating or pressing the separation unit 92 holding the surface 11a of the ingot 11 against the holding table 94.

[0039] Modified regions formed inside the ingot 11 and cracks propagating from the modified regions are exposed on the separation surface 17 of the wafer 20 separated in the separation step S12. The irregularities on the separation surface 17 caused by the modified regions and cracks are, for example, 1 μm to 5 μm. In contrast, the height difference of the three-dimensional shape of the separation layer 15 is, for example, 10 μm to 20 μm.

[0040] Following the separation step S12, in the first grinding step S13, the modified regions formed on the separation surface 17 of the wafer 20, cracks propagating from the modified regions, and a three-dimensional shape are formed on a horizontal surface (flat surface) by grinding. Here, if the separation surface 17 of the wafer 20 is a horizontal surface at the beginning of grinding, the grinding wheel may become clogged and the grinding efficiency may deteriorate. However, by forming the separation surface 17 into a three-dimensional shape, the grinding wheel may become clogged and the grinding efficiency may be improved.

[0041] FIG. 9 is a diagram illustrating grinding of the front surface 20a (separation surface 17) of the wafer 20 in the first grinding step S13. The first grinding device 71 performing the first grinding step S13 includes, for example, a holding table 72 that holds the back surface 20b of the wafer 20, which is the front surface 11a of the ingot 11 before separation, and a grinding unit 73 that is arranged opposite the holding table 72 and is configured to be vertically movable and rotatable. The first grinding device 71 grinds the separation surface 17, which is the front surface 20a of the wafer 20 held on the holding table 72, with a grinding wheel 74 of the grinding unit 73. In the first grinding step S13, the grinding wheel 74 of the grinding unit 73 is rotated and pressed against the separation surface 17 of the wafer 20, thereby grinding away modified regions, cracks, and three-dimensional shapes formed on the separation surface 17 of the wafer 20 and turning the separation surface 17 into a horizontal plane. This forms a thin wafer 20 with a uniform thickness.

[0042] In the second grinding step S14, the modified regions formed on the separation surface 17 of the ingot 11, cracks propagating from the modified regions, and a three-dimensional shape are formed on a horizontal surface (flat surface) by grinding. The second grinding step S14 may be performed in parallel with the first grinding step S13, or may be performed before or after the first grinding step S13.

[0043] FIG. 10 is a diagram illustrating grinding of the separation surface 17 of the ingot 11 in the second grinding step S14. The second grinding device 75 performing the second grinding step S14 includes, for example, a holding table 76 that holds the back surface 11b of the ingot 11 before separation, and a grinding unit 77 that is arranged opposite the holding table 76 and is configured to be vertically movable and rotatable. The second grinding device 75 grinds the separation surface 17 of the ingot 11 held on the holding table 76 with a grinding wheel 78 of the grinding unit 77. In the second grinding step S14, the grinding wheel 78 of the grinding unit 77 is rotated and pressed against the separation surface 17 of the ingot 11, thereby grinding away the modified regions, cracks, and three-dimensional shapes formed on the separation surface 17 of the ingot 11 to make the separation surface 17 a horizontal surface. This results in the separation surface 17 of the ingot 11 becoming a new horizontal surface 11a, which is then used to manufacture the next wafer 20.

[0044] FIG. 11 shows an example of a wafer manufacturing apparatus 100 capable of implementing the method for manufacturing the wafer 20 of this embodiment. The wafer manufacturing apparatus 100 includes a laser processing apparatus 1, a separating apparatus 9, a first grinding apparatus 71, a second grinding apparatus 75, a first transfer apparatus 101 that transfers an ingot 11 processed by the laser processing apparatus 1 to the separating apparatus 9, and a second transfer apparatus 102 that transfers wafers 20 separated by the separating apparatus 9 to the first grinding apparatus 71 and transfers the ingot 11 from which the wafers 20 have been separated by the separating apparatus 9 to the second grinding apparatus 75. The configurations of the first transfer apparatus 101 and the second transfer apparatus 102 are not particularly limited as long as they are mechanisms that can appropriately transfer objects to be transferred, and may be transfers by conveyors or by robot arms.

[0045] Furthermore, in the method for manufacturing the wafer 20 of this embodiment, each device does not need to be integrated into the wafer manufacturing apparatus 100, and each device may perform processing separately.

[0046] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0047] For example, in the above embodiment, the three-dimensional shape of the separation layer 15 for suppressing warpage of the wafer 20 is exemplified as a shape in which the thickness increases in the peripheral region of the wafer 20 in the Y-axis direction, and a conical shape in which the thickness increases in the peripheral region of the wafer 20 in the X-axis and Y-axis directions. However, the three-dimensional shape of the separation layer 15 is not limited to this, and may be a shape in which the thickness increases in the central region of the wafer 20 in the Y-axis direction, or an inverted conical shape in which the thickness increases in the central region of the wafer 20 in the X-axis and Y-axis directions.

[0048] When the three-dimensional shape of the separation layer 15 is to be increased in thickness in the central region of the wafer 20 in the Y-axis direction, in the separation layer formation step S11, first, the ingot 11 is processed and fed so that the focal point moves from one end of the ingot 11 to the other end along the X-axis direction without changing the height position of the focal point in the Z-axis direction, thereby forming a modified region along the X-axis direction. Next, while indexing and feeding the ingot 11 by a predetermined amount along the Y-axis direction, the condenser 84 is moved downward along the Z-axis by a predetermined amount. Then, without changing the height position of the focal point in the Z-axis direction, the condenser 84 is processed and fed so that the focal point moves from the other end of the ingot 11 to one end along the X-axis direction, thereby forming a modified region along the X-axis direction. This series of processes is repeated up to the center in the Y-axis direction. Furthermore, from the center in the Y-axis direction, the same process is performed, but the condenser 84 is moved upward along the Z-axis by a predetermined amount while indexing and feeding the ingot 11 by a predetermined amount along the Y-axis direction. As a result, the separation layer 15 inside the ingot 11 is processed to have a downwardly convex inverted triangular shape when viewed from the X-axis direction.

[0049] Furthermore, when the three-dimensional shape of the separation layer 15 is increased in thickness in the central region of the wafer 20 in the X-axis direction and the Y-axis direction, in the separation layer formation step S11, the height position of the focal point in the Z-axis direction is continuously changed while the ingot 11 is processed and fed so that the focal point moves from one end of the ingot 11 to the other end, or from the other end to the one end, along the X-axis direction, thereby forming a modified region, which differs from the case where the thickness is increased in the central region of the wafer 20 in the Y-axis direction.

[0050] This specification describes at least the following items. Note that the components in parentheses correspond to those in the above-described embodiment, but are not limited to these.

[0051] (1) A wafer manufacturing method for manufacturing wafers (wafers 20) from an ingot (ingot 11), a holding step (holding step S10) for holding the ingot; a separation layer forming step (separation layer forming step S11) in which a laser beam having a wavelength that can pass through the ingot is irradiated onto the surface (surface 11a) of the ingot, the focal point of the laser beam is positioned at a position deeper than the surface of the ingot to form a modified region, and the ingot and the focal point are processed and fed relatively to form a separation layer (separation layer 15) including a plurality of the modified regions inside the ingot; a separation step (separation step S12) of separating the workpiece including the surface of the ingot as the wafer from the ingot starting from the separation layer; a grinding step (first grinding step S13) of grinding the separation surface of the wafer to remove the modified region, In the separation layer forming step, The depth of the light-condensing point that forms the modified region is changed so that the separation surface has a three-dimensional shape rather than a horizontal surface. Wafer manufacturing method.

[0052] Wafers separated from an ingot are subject to warping due to the expansion of the modified region in addition to the warping of the original workpiece. Therefore, according to (1), wafer warping can be suppressed by changing the depth of the laser beam focal point to create a three-dimensional shape for the separation surface. Furthermore, in the grinding step, if the separation surface of the wafer is a horizontal surface, the grinding wheel may become clogged, resulting in a deterioration in grinding efficiency. However, by making the separation surface three-dimensional, clogging of the grinding wheel can be suppressed, thereby improving grinding efficiency.

[0053] (2) A method for manufacturing a wafer according to (1), In the separation layer forming step, A plurality of reforming lines (reformation lines 16) extending linearly in a first direction (X-axis direction) between one end side and the other end side of the ingot are formed inside the ingot in a second direction (Y-axis direction) perpendicular to the first direction, The laser beam is irradiated so that the depth from the surface is equal for the same reforming line, and the depth from the surface is different for one reforming line and another reforming line. Wafer manufacturing method.

[0054] According to (2), the depth from the surface is the same for the same modification line, which prevents the control from becoming complicated.

[0055] (3) A method for manufacturing a wafer according to (2), In the separation layer forming step, the laser beam is irradiated such that the focal point is farther from the surface as it approaches the outer circumferential region of the ingot in the second direction. Wafer manufacturing method.

[0056] According to (3), warpage of the wafer can be suppressed by making the focal point deeper closer to the outer peripheral region of the ingot, where warpage of the wafer is likely to occur.

[0057] (4) A method for manufacturing a wafer according to (2), In the separation layer forming step, the laser beam is irradiated such that the focal point is farther from the surface as it approaches the central region of the ingot in the second direction. Wafer manufacturing method.

[0058] According to (4), by making the center of the wafer thicker, warpage of the wafer in the peripheral region can be suppressed.

[0059] (5) A method for manufacturing a wafer according to (1), In the separation layer forming step, A plurality of reforming lines (reformation lines 16) extending linearly in a first direction (X-axis direction) between one end side and the other end side of the ingot are formed inside the ingot in a second direction (Y-axis direction) perpendicular to the first direction, The laser beam is irradiated so that the depth from the surface changes continuously in the same modification line, and the depth from the surface differs between one modification line and another modification line. Wafer manufacturing method.

[0060] According to (5), a three-dimensional shape can be formed more precisely on the separation surface.

[0061] (6) A method for manufacturing a wafer according to (5), In the separation layer forming step, the laser beam is irradiated such that the focal point is farther from the surface as it approaches the outer circumferential region of the ingot in the first direction and the second direction. Wafer manufacturing method.

[0062] According to (6), warpage of the wafer can be suppressed by making the focal point deeper closer to the outer peripheral region of the ingot, where warpage of the wafer is likely to occur.

[0063] (7) A method for manufacturing a wafer according to (5), In the separation layer forming step, the laser beam is irradiated such that the focal point is farther from the surface as it approaches a central region of the ingot in the first direction and the second direction. Wafer manufacturing method.

[0064] According to (7), by making the center of the wafer thicker, warpage of the wafer in the peripheral region can be suppressed.

[0065] (8) A method for producing a wafer according to any one of (1) to (7), In the grinding step, the separation surface of the wafer is ground to a horizontal surface. Wafer manufacturing method.

[0066] According to (8), wafers with a uniform thickness can be formed.

[0067] (9) A method for manufacturing a wafer according to (1), Further, another grinding step (second grinding step S14) is provided, in which the separation surface of the ingot is ground to remove the modified region. In the other grinding step, the separated surface of the ingot is ground to a horizontal surface. Wafer manufacturing method.

[0068] According to (9), the surface of the ingot to be irradiated with the laser beam to manufacture the next wafer can be made horizontal, and the separation surface of the next wafer can be made three-dimensional with high precision.

[0069] (10) A laser processing device (laser processing device 1), a holding table (holding table 10) for holding an ingot (ingot 11); a laser beam irradiation unit (laser beam irradiation mechanism 8) that irradiates a surface (surface 11a) of the ingot held on the holding table with a laser beam having a wavelength that transmits through the ingot, positions the focal point of the laser beam at a position deeper than the surface of the ingot to form a modified region, and processes and feeds the ingot and the focal point relatively to form a separation layer (separation layer 15) inside the ingot that includes a plurality of the modified regions; a moving unit (vertical moving unit 89) capable of changing the relative position between the ingot held on the holding table and a condenser lens (condenser lens 88) of the laser beam irradiation unit; a control unit (control unit 14) that controls the laser processing device; The control unit controlling the moving unit to vary the depth of the focal point that forms the modified region within the ingot; Laser processing equipment.

[0070] According to (10), warping of the wafer can be suppressed by changing the depth of the focal point of the laser beam to form a three-dimensional separation surface. In addition, by forming the separation surface into a three-dimensional shape, clogging of the grinding wheel can be suppressed, improving grinding efficiency.

[0071] (11) A wafer manufacturing apparatus (wafer manufacturing apparatus 100) that manufactures wafers from ingots, The laser processing device according to (10), a separation device (separation device 9) that separates the workpiece including the surface of the ingot as the wafer from the ingot, starting from the separation layer; a first grinding device (first grinding device 71) that grinds the separation surface (separation surface 17) of the wafer to make the separation surface of the wafer a horizontal plane; a second grinding device (second grinding device 75) that grinds the separation surface (separation surface 17) of the ingot to make the separation surface of the ingot a horizontal surface; Wafer manufacturing equipment.

[0072] According to (11), wafers of uniform thickness can be manufactured using one wafer manufacturing device, and the surface of the ingot can be made horizontal for manufacturing the next wafer. [Explanation of symbols]

[0073] 1. Laser processing equipment 8 Laser beam irradiation mechanism (laser beam irradiation unit) 9 Separation device 10 Holding table 11 Ingot 11a surface 14 Control Unit 15 Separation layer 16 Reforming Line 17 Separation plane 20 wafers 71 First grinding device 75 Second grinding device 88 Condenser Lens 89 Up / down moving unit (moving unit) 100 Wafer manufacturing equipment S10 Hold step S11 Separation layer formation step S12 Separation step S13 First grinding step (grinding step) S14 Second grinding step (another grinding step)

Claims

1. A wafer manufacturing method for manufacturing wafers from an ingot, comprising: a holding step of holding the ingot; a separation layer forming step of forming a modified region by irradiating a laser beam having a wavelength that can transmit through the ingot from the surface of the ingot and positioning the focal point of the laser beam at a position deeper than the surface of the ingot, and processing and feeding the ingot and the focal point relatively to form a separation layer including a plurality of the modified regions inside the ingot; a separation step of separating a workpiece including the surface of the ingot as the wafer from the ingot starting from the separation layer; a grinding step of grinding the separation surface of the wafer to remove the modified region, In the separation layer forming step, The depth of the light-condensing point that forms the modified region is changed so that the separation surface has a three-dimensional shape rather than a horizontal surface. Wafer manufacturing method.

2. 2. The method for manufacturing a wafer according to claim 1, In the separation layer forming step, forming a plurality of reforming lines in the ingot, the reforming lines extending linearly in a first direction between one end side and the other end side of the ingot, in a second direction perpendicular to the first direction; The laser beam is irradiated so that the depth from the surface is equal for the same reforming line, and the depth from the surface is different for one reforming line and another reforming line. Wafer manufacturing method.

3. 3. The method for manufacturing a wafer according to claim 2, In the separation layer forming step, the laser beam is irradiated such that the focal point is farther from the surface as it approaches the outer circumferential region of the ingot in the second direction. Wafer manufacturing method.

4. 3. The method for manufacturing a wafer according to claim 2, In the separation layer forming step, the laser beam is irradiated such that the focal point is farther from the surface as it approaches the central region of the ingot in the second direction. Wafer manufacturing method.

5. 2. The method for manufacturing a wafer according to claim 1, In the separation layer forming step, forming a plurality of reforming lines in the ingot, the reforming lines extending linearly in a first direction between one end side and the other end side of the ingot, in a second direction perpendicular to the first direction; The laser beam is irradiated so that the depth from the surface changes continuously in the same modification line, and the depth from the surface differs between one modification line and another modification line. Wafer manufacturing method.

6. 6. The method for manufacturing a wafer according to claim 5, In the separation layer forming step, the laser beam is irradiated such that the focal point is farther from the surface as it approaches the outer circumferential region of the ingot in the first direction and the second direction. Wafer manufacturing method.

7. 6. The method for manufacturing a wafer according to claim 5, In the separation layer forming step, the laser beam is irradiated such that the focal point is farther from the surface as it approaches a central region of the ingot in the first direction and the second direction. Wafer manufacturing method.

8. The method for manufacturing a wafer according to any one of claims 1 to 7, In the grinding step, the separation surface of the wafer is ground to a horizontal surface. Wafer manufacturing method.

9. 2. The method for manufacturing a wafer according to claim 1, Further comprising another grinding step of grinding the separation surface of the ingot to remove the modified region; In the other grinding step, the separated surface of the ingot is ground to a horizontal surface. Wafer manufacturing method.

10. A laser processing device, a holding table for holding an ingot; a laser beam irradiation unit that irradiates a surface of the ingot held on the holding table with a laser beam having a wavelength that can pass through the ingot, positioning the focal point of the laser beam at a position deeper than the surface of the ingot to form a modified region, and processing and feeding the ingot and the focal point relatively to form a separation layer including a plurality of the modified regions inside the ingot; a moving unit capable of changing the relative position between the ingot held on the holding table and a condenser lens of the laser beam irradiation unit; a control unit for controlling the laser processing device, The control unit controlling the moving unit to vary the depth of the focal point that forms the modified region within the ingot; Laser processing equipment.

11. A wafer manufacturing apparatus for manufacturing wafers from an ingot, The laser processing device according to claim 10; a separation device that separates a workpiece including the surface of the ingot as the wafer from the ingot, starting from the separation layer; a first grinding device that grinds the separation surface of the wafer to make the separation surface of the wafer a horizontal plane; a second grinding device that grinds the separated surface of the ingot to make the separated surface of the ingot a horizontal surface; Wafer manufacturing equipment.

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