Wafer manufacturing method and ingot processing method

Abstract

To suppress the consumption of a grinding wheel in grinding a wafer having a peeling layer and an ingot having the peeling layer when manufacturing the wafer from the ingot.SOLUTION: A method of manufacturing a wafer 10 includes a peeling layer forming step S10 of forming a peeling layer 110, a peeling step S11 of peeling the wafer 10, and a polishing step S12 of polishing and planarizing a peeling surface 120 of the wafer 10 to remove the peeling layer 110. The processing step S12 includes a first processing step S13 of relatively moving the holding table 204 holding the wafer 10 and the processing unit 210 in a first processing feed direction parallel to the holding surface 204a to grind the wafer 10, and a second processing step S14 of holding the wafer 10 on the holding table 204 and relatively moving the holding table 204 and the processing unit 210 in a second processing feed direction perpendicular to the holding surface 204a to grind the wafer 10 after the first processing step LA. S13.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] A method for cutting substrates such as wafers from a workpiece made of an ingot using a laser beam has been proposed (for example, Patent Document 1). In this method, a laser beam having a wavelength that can pass through the ingot is irradiated from a focal point positioned inside the ingot, forming a modified layer inside the ingot that serves as a starting point for delamination. The ingot is then delaminated from this modified layer to cut out wafers. The delamination layers remaining on the delamination surfaces of the ingot and wafer are then removed by grinding, and the delamination surfaces are flattened. [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] In grinding, a cut wafer is held on the holding surface of a holding table, and a grinding unit equipped with a grinding wheel containing a grinding stone is moved in a processing feed direction perpendicular to the holding surface. The lower surface of the grinding stone contacts the upper surface of the wafer, grinding the wafer surface. This grinding method is called infeed grinding. Infeed grinding is effective in achieving a predetermined finished thickness and reducing the surface roughness of the processed wafer. However, the surface of a wafer cut from an ingot is uneven due to cracks caused by the formation of a modified layer. These large unevennesses result in significant wear of the grinding stone during infeed grinding. This same problem also occurs when planarizing the peeled surface of an ingot.

[0005] The present invention provides a wafer manufacturing method and an ingot processing method that, when manufacturing wafers from ingots, can appropriately grind wafers having a peeling layer and ingots having a peeling layer while suppressing wear of the grinding wheel. [Means for solving the problem]

[0006] One aspect of the present invention is A wafer manufacturing method for manufacturing wafers from an ingot, comprising: a separation layer forming step of irradiating a surface of the ingot with a laser beam having a wavelength that can pass through the ingot, positioning a focal point of the laser beam at a position deeper than the surface of the ingot to form a modified region, and relatively moving the ingot and the focal point to form a separation layer including the modified region inside the ingot; a peeling step of peeling the wafer starting from the peeling layer after the peeling layer forming step; a grinding step of grinding the delaminated surface of the wafer after the delamination step to flatten it and remove the delamination layer, The grinding step includes: a first grinding step in which a first holding table that holds the wafer on a first holding surface and a first grinding unit that has a first grinding wheel including a grinding stone are moved relatively in a first processing feed direction parallel to the first holding surface to perform grinding; and a second grinding step in which, after the first grinding step, the wafer is held on a second holding surface of a second holding table, and the second holding table and a second grinding unit having a second grinding wheel including a grinding stone are moved relatively in a second processing feed direction perpendicular to the second holding surface to perform grinding.

[0007] Another aspect of the present invention is A method for processing an ingot when producing wafers from the ingot, comprising: a separation layer forming step of irradiating a surface of the ingot with a laser beam having a wavelength that can pass through the ingot, positioning a focal point of the laser beam at a position deeper than the surface of the ingot to form a modified region, and relatively moving the ingot and the focal point to form a separation layer including the modified region inside the ingot; a peeling step of peeling the wafer starting from the peeling layer after the peeling layer forming step; a grinding step of grinding the separated surface of the ingot to flatten it and remove the separated layer after the separation step, The grinding step includes: a first grinding step in which a first holding table that holds the ingot on a first holding surface and a first grinding unit that has a first grinding wheel including a grinding stone are moved relatively in a first processing feed direction parallel to the first holding surface to perform grinding; and a second grinding step in which, after the first grinding step, the ingot is held on a second holding surface of a second holding table, and the second holding table and a second grinding unit having a second grinding wheel including a grinding stone are moved relatively in a second processing feed direction perpendicular to the second holding surface to perform grinding. [Effects of the Invention]

[0008] According to the present invention, when manufacturing wafers from ingots, it is possible to appropriately grind wafers having a peeling layer and ingots having a peeling layer while reducing wear on the grinding wheel. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a flowchart showing an example of a method for manufacturing a wafer 10 and a method for processing an ingot 20. [Figure 2] FIG. 2 is a perspective view showing an example of the laser processing device 1. As shown in FIG. [Figure 3] FIG. 3 is a diagram illustrating an example of the laser beam irradiation mechanism 7. As shown in FIG. [Figure 4] FIG. 4 is a diagram for explaining an example of the ingot 20. As shown in FIG. [Figure 5] FIG. 5 is a diagram illustrating an example of the release layer forming step S10. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5, illustrating an example of the release layer 110 formed in the release layer forming step S10. [Figure 7] FIG. 7 is a diagram illustrating an example of the peeling step S11. [Figure 8] FIG. 8 is a perspective view showing an example of the separation surface 120 of the wafer 10 formed in the separation step S11. [Figure 9] FIG. 9 is a diagram illustrating the unevenness of the release layer 110. As shown in FIG. [Figure 10] FIG. 10 is a perspective view showing an example of a grinding device 200. As shown in FIG. [Figure 11] FIG. 11 is a diagram for explaining an example of the first grinding step S13 in the grinding step S12. [Figure 12] FIG. 12 is a diagram for explaining an example of the second grinding step S14 in the grinding step S12. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a wafer manufacturing method and an ingot processing method according to one embodiment of the present invention will be described with reference to the drawings.

[0011] 1 is a flowchart showing an example of a wafer manufacturing method. The manufacturing method of the wafer 10 according to the embodiment includes, as processing steps, a separation layer forming step S10 in which a separation layer 110 is formed inside the ingot 20, a separation step S11 in which the wafer 10 is separated from the ingot 20 starting from the separation layer 110, and a grinding step S12 in which a separation surface 120 of the wafer 10 is ground. The grinding step S12 includes a first grinding step S13 and a second grinding step S14 in which the separation surface 120 of the wafer 10 is ground after the first grinding step S13.

[0012] Note that the processing for grinding the delaminated surface of the ingot 20 is performed after the delamination step S11. However, in the embodiment, the processing for grinding the delaminated surface of the ingot 20 may be the same as the processing for grinding the delaminated surface 120 of the wafer 10. That is, when grinding the delaminated surface of the ingot 20, the first grinding step S13 and the second grinding step S14 may be performed. In this way, the manufacturing method of the wafer 10 and the processing method of the ingot 20 share the same processing. Therefore, in the example described below, the manufacturing method of the wafer 10 will be described first as a representative example, and the processing method of the ingot 20 will be described later in a simplified manner.

[0013] In addition, in the method for manufacturing the wafer 10 and the method for processing the ingot 20, the processing in each step is performed using a laser processing device 1 and a grinding device 200. Specifically, the peeling layer forming step S10 and the peeling step S11 are performed by the laser processing device 1, and the first grinding step S13 and the second grinding step S14 in the grinding step S12 are performed by the grinding device 200. Therefore, the laser processing device 1 and the grinding device 200 will be described below along with an explanation of each step.

[0014] First, the configuration of a laser processing apparatus 1 that performs the release layer forming step S10 and the release step S11 will be described. Fig. 2 is a perspective view showing an example of 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] [Laser processing equipment] The laser processing apparatus 1 mainly comprises a base 2, a first slide block 3 mounted on the base 2 so as to be movable in the X-axis direction, a second slide block 4 mounted above the first slide block 3 and movable in the Y-axis direction, a holding table 5 provided on the second slide block 4, a frame 6 erected on the base 2, a laser beam irradiation mechanism 7 attached to the frame 6, a peeling unit 8 which peels off a wafer 10 from an ingot 20, and a control unit 9 which controls the laser processing apparatus 1.

[0016] The first slide block 3 is configured to be movable in the processing feed direction, that is, in the X-axis direction, along a pair of guide rails 33 by a processing feed mechanism 32 configured with a ball screw 30 and a pulse motor 31.

[0017] A second slide block 4 is mounted above the first slide block 3 so as to be movable in the Y-axis direction. That is, the second slide block 4 is configured to be movable in the indexing feed direction, i.e., in the Y-axis direction, along a pair of guide rails 43 by an indexing feed mechanism 42 composed of a ball screw 40 and a pulse motor 41.

[0018] A holding table 5 is mounted on the second slide block 4. The holding table 5 is movable in the X-axis direction and the Y-axis direction by a processing feed mechanism 32 and an indexing feed mechanism 42, and is configured to be rotatable about an axis parallel to the Z-axis direction by a rotation unit (not shown) supported by the second slide block 4.

[0019] A frame 6 is erected on the base 2, and a laser beam irradiation mechanism 7 is attached to the frame 6.

[0020] FIG. 3 is a diagram illustrating the laser beam irradiation mechanism 7 of the laser processing apparatus 1. As shown in FIG. 3, the laser beam irradiation mechanism 7 is composed of a laser beam generating unit 71 and a condenser 72 attached to the tip of the frame 6. An imaging unit 73 having a microscope and a camera is attached to the tip of the frame 6 adjacent to the condenser 72. The imaging element of the imaging unit 73 includes, for example, a CCD (Charge-Coupled Device) imaging element or a CMOS (Complementary Metal Oxide Semiconductor) imaging element. The imaging unit 73 acquires an image for aligning the ingot 20 with the laser beam irradiation mechanism 7, and outputs the image data to the control unit 9.

[0021] The laser beam generating unit 71 includes a laser oscillator 71a that oscillates, for example, a YAG laser or a YVO4 laser, and an output adjustment unit 71b. Although not shown, the laser oscillator 71a has a Brewster window, and the laser beam emitted from the laser oscillator 71a is a linearly polarized laser beam.

[0022] The pulsed laser beam, adjusted to a predetermined power by the output adjustment unit 71b of the laser beam generating unit 71, is reflected by the mirror 74 of the collector 72 and then irradiated by the collecting lens 75, with the focal point positioned inside the ingot 20, which is the workpiece held on the holding table 5.

[0023] Here, an ingot 20 in an embodiment will be described. FIG. 4 is a diagram for explaining the ingot 20 in an embodiment, where (a) of FIG. 4 shows a plan view of the ingot 20 and (b) of FIG. 4 shows a side view of the ingot 20. The ingot 20 is, for example, a cylindrical ingot made of single crystal SiC (silicon carbide) and is typically manufactured by a sublimation recrystallization method. The ingot 20 has a circular front surface 20a and a circular back surface 20b located opposite the front surface 20a and substantially parallel to the front surface 20a. The front surface 20a of the ingot 20 is polished to a mirror finish because it is the surface to be irradiated with a laser beam.

[0024] During the process of growing a crystal to produce an ingot 20, the c-axis of the single-crystal SiC constituting the ingot 20 is tilted at an angle "α" with respect to a perpendicular line 21 to the front surface 20a and back surface 20b. This angle "α" is called the off-angle. In other words, the c-plane perpendicular to the c-axis also forms an angle "α" with respect to the front surface 20a and back surface 20b. "α" is typically 4°, but can be freely set within a range of, for example, 1° to 6°. In FIG. 4, the direction in which the off-angle α with respect to the perpendicular line 21 is formed is indicated by an arrow and the letter "A."

[0025] A first orientation flat 23 and a second orientation flat 24 are provided on the peripheral surface 22 of the ingot 20. The first orientation flat 23 and the second orientation flat 24 are both intended to indicate the crystal orientation of the single crystal SiC that constitutes the ingot 20, and are rectangular when viewed radially and in the direction opposite to each other.

[0026] The first orientation flat 23 is parallel to the direction A in which the off angle α is formed, and the second orientation flat 24 is perpendicular to the direction A in which the off angle α is formed. As shown in FIG. 4(a), when viewed from above, the length L2 of the second orientation flat 24 is shorter than the length L1 of the first orientation flat 23 (L2 <L1)。

[0027] The laser processing apparatus 1 in the embodiment is used when manufacturing a wafer 10 from such an ingot 20. In the embodiment, the ingot 20 made of single crystal SiC is used as the workpiece, as an example, but the workpiece may be an ingot made of other materials such as gallium nitride (GaN), lithium tantalate (LT), diamond, silicon (Si), etc. Furthermore, the ingot 20 is not limited to a single crystal ingot, and may also be a polycrystalline ingot.

[0028] 2, the peeling unit 8 is provided on the base 2 and near the end of the guide rail 33 along which the above-mentioned first slide block 3 moves. The peeling unit 8 includes a casing 81, an arm 82 partially housed within the casing 81 and supported so as to be movable up and down in the Z-axis direction, a pulse motor 83 provided at the tip of the arm 82, and a suction unit 84 rotatably supported by the pulse motor 83 below the pulse motor 83 and having a plurality of suction holes on its underside. The suction unit 84 incorporates an ultrasonic vibration imparting mechanism that imparts ultrasonic vibrations to the underside of the suction unit 84.

[0029] The control unit 9 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 ingot 20, which is the workpiece. The control unit 9 is a computer including a control unit 90 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 9. The control unit 90 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 90 performs various calculations based on predetermined programs stored in the memory unit. Based on the calculation results, the control unit 90 outputs various control signals to each of the above-mentioned components via the input / output interface, thereby controlling the laser processing apparatus 1.

[0030] The control unit 90 executes various programs stored in the storage unit 91. As an example, the control unit 90 executes the release layer forming step S10 and the release step S11 in FIG.

[0031] [Release layer formation step] In the peeling layer forming step S10, the control unit 90 irradiates the surface 20a of the ingot 20 held on the holding table 5 with a laser beam having a wavelength that transmits through the ingot 20, and positions the focal point of the laser beam at a position deeper than the surface 20a of the ingot 20 to form a modified region 100. Then, the control unit 90 processes and feeds the ingot 20 and the focal point relatively in the X-axis direction, thereby forming a peeling layer 110 including a plurality of modified regions 100 inside the ingot 20.

[0032] FIG. 5 is a diagram showing a state in which the laser beam is irradiated from the surface 20a of the ingot 20 by the condenser 72 in the laser beam irradiation mechanism 7 in the peeling layer forming step S10.

[0033] Specifically, in the peeling layer formation step S10, the control unit 90 first images the ingot 20 held on the holding table 5 using the imaging unit 73, and based on the image of the ingot 20, adjusts the orientation of the ingot 20 to a predetermined orientation and adjusts the positional relationship between the ingot 20 and the collector 72.

[0034] When adjusting the orientation of the ingot 20 to a predetermined orientation, for example, as shown in Fig. 5, the second orientation flat 24 is aligned with the X-axis direction. As a result, the direction perpendicular to the direction A in which the off-angle "α" is formed is aligned with the X-axis direction, and the direction A in which the off-angle "α" is formed is aligned with the Y-axis direction.

[0035] Next, the control unit 90 irradiates the ingot 20 with a laser beam having a wavelength that allows transmission, from the surface 20a thereof, and positions the focal point of the laser beam at a position deeper than the surface 20a. Specifically, the control unit 90 positions the focal point of the laser beam at a depth corresponding to the thickness of the target wafer.

[0036] Next, the control unit 90 irradiates the ingot 20 with a laser beam having a wavelength that is transparent to the ingot 20 from the condenser 72 while moving the focal point and the ingot 20 relatively in the X-axis direction, i.e., in a direction perpendicular to the direction A in which the off-angle α is formed. That is, the control unit 90 feeds the ingot 20 so that the focal point moves from one end of the ingot 20 to the other end along the X-axis direction. As a result, as shown in FIGS. 5 and 6, for example, a linear modified region 100 is formed in the ingot 20 along the X-axis direction to a depth corresponding to the thickness of the wafer 10. In other words, the modified region 100 is continuously formed in the direction perpendicular to the direction A in which the off-angle α is formed. Note that since the modified region 100 is formed inside the ingot 20, the modified region 100 does not usually appear on the surface 20a of the ingot 20. However, for convenience of explanation, the modified region 100 is indicated by a dashed line in the example of FIG. 5. Then, cracks 105 extending along the c-plane are generated on both sides of the modified region 100. As a result, a peeling layer 110 including the modified region 100 and the cracks 105 is formed continuously along the X-axis direction.

[0037] Next, the control unit 90 indexes the wafer 10 a predetermined distance in the Y-axis direction. This predetermined distance is, for example, a length that does not exceed the width of the crack 105 extending along the c-plane, and is such that adjacent cracks 105 in the Y-axis direction overlap in the Z-axis direction. Indexing the wafer 10 in the Y-axis direction forms a new delamination layer 110 adjacent to the previously formed delamination layer 110. The control unit 90 repeatedly performs this series of processes, namely, processing feed in the X-axis direction and indexing feed in the Y-axis direction, over the entire surface 20a of the ingot 20. In this manner, multiple delamination layers 110, including the modified regions 100 and cracks 105, can be sequentially formed along the X-axis direction from the surface 20a of the ingot 20 to a predetermined depth of the wafer 10. The delamination layers 110 are portions where mechanical strength is reduced due to the modified regions 100 and cracks 105, and serve as interfaces for delaminating the wafer 10 from the ingot 20. That is, the wafer 10 is separated from the ingot 20 starting from the separation layer 110 .

[0038] [Peeling step] In the delamination step S11, the control unit 90 delaminates a thin plate including the surface 20a of the ingot 20 starting from the delamination layer 110 as the wafer 10. In other words, a part of the ingot 20 is separated from the ingot 20 as the wafer 10. FIG. 7 is a diagram for explaining the process of delaminating the wafer 10 from the ingot 20 in the delamination step S11.

[0039] The control unit 90 controls the first slide block 3 and the second slide block 4 to position the holding table 5 below the suction unit 84 of the separation unit 8. Next, the arm 82 of the separation unit 8 is lowered to bring the lower surface of the suction unit 84 into close contact with and adsorb the ingot 20. FIG. 7 shows an example in which the ingot 20 is in close contact with and adsorbed to the lower surface of the suction unit 84. In this state, the ultrasonic vibration applying mechanism (not shown) is activated to apply ultrasonic vibration to the lower surface of the suction unit 84, and the pulse motor 83 is driven to rotate the suction unit 84 in the direction of the arrow (i.e., the circumferential direction), thereby applying a torsional force to the ingot 20. When the torsional force is applied to the ingot 20, the ingot 20 is fractured starting from the peeled layer 110 including the modified region 100 and the crack 105, and the upper side of the ingot 20 is peeled off. Then, as the upper side of the ingot 20 is peeled off, one wafer 10 is peeled off to produce one wafer 10. Note that the method of peeling off the wafer 10 is not limited to this, and the peeling unit 8 may be configured to apply a physical impact by rotating or pressing the peeling unit 8, thereby peeling off the wafer 10 from the ingot 20 starting from the peeling layer 110.

[0040] The surface of the wafer 10 delaminated in the delamination step S11, i.e., the delamination surface 120 of the wafer 10, exposes a plurality of delamination layers 110, including the modified regions 100 formed inside the ingot 20 and cracks 105 extending from the modified regions 100. FIG. 8 shows an example of the delaminated wafer 10, and FIG. 9 shows an example of the wafer 10 having the delaminated surface 120 of FIG. 8, viewed in cross section from the direction in which the modified regions 100 were formed, i.e., the X-axis direction. As shown in FIGS. 8 and 9, each of the plurality of delamination layers 110 has unevenness and undulations due to the cracks 105. Specifically, when viewed in cross section from the direction in which the linear modified regions 100 were formed, the delamination layer 110 has an inclined surface 130 having an inclination angle β of less than 90° in one direction (the +Y-axis direction in FIG. 9) perpendicular to the direction in which the modified regions 100 were formed. The inclined surfaces 130 are continuous in the Y-axis direction, and the continuous inclined surfaces 130 are connected to adjacent cracks 105 in the Y-axis direction to form edge surfaces 140. In the example shown in FIG. 9 , the edge surfaces 140 form a substantially right angle. However, depending on the length and shape of the cracks 105 extending from the modified region 100, the edge surfaces 140 may not form a right angle. In such cases, the edge surfaces 140 also have an inclination angle on one side in the Y-axis direction. In this case, the inclination angle β of the inclined surfaces 130 and the inclination angle of the edge surfaces 140 are assumed to be larger in absolute value than the inclination angle of the edge surfaces 140. In other words, the inclination angle of the inclined surfaces 130 is smaller relative to the edge surfaces 140.

[0041] As described above, the peeled surface 120 of the wafer 10 has a plurality of uneven layers 110. In order to form devices on this peeled surface 120, it is necessary to flatten the peeled surface 120. Known processes for flattening the peeled surface 120 of the wafer 10 include, for example, in-feed grinding and creep feed grinding.

[0042] Here, we will explain infeed grinding and creep feed grinding. In infeed grinding, the positional relationship between the holding table and the grinding unit is adjusted so that the center of the workpiece held on the holding surface of the holding table overlaps the trajectory of the grinding wheel. Then, while the holding table and grinding wheel are rotated, the grinding wheel is lowered in the processing feed direction parallel to the rotation axis of the spindle, i.e., vertically. This brings the bottom surface of the grinding wheel into contact with the top surface of the workpiece, grinding it.

[0043] In creep feed grinding, the grinding wheel is positioned outside the workpiece, and the positional relationship between the holding table and the grinding unit is adjusted so that the bottom surface of the grinding wheel is positioned below the top surface of the workpiece. The grinding wheel is then rotated and moved in a processing feed direction parallel to the holding surface of the holding table, i.e., horizontally. This brings mainly the side surface of the grinding wheel into contact with the top surface of the workpiece, grinding the workpiece.

[0044] As described above, the grinding process for planarizing the wafer 10 includes in-feed grinding and creep feed grinding. Generally, the wafer 10 is processed by in-feed grinding, which is effective in achieving a predetermined finished thickness and reducing surface roughness. However, as described above, when the irregularities caused by the modified region 100 or cracks 105 are large, in-feed grinding may result in significant wear of the grinding wheel. Therefore, in the embodiment, when grinding the peeling layer 110 of the wafer 10, grinding is performed to achieve a predetermined target finished thickness with a predetermined surface roughness while suppressing wear of the grinding wheel.

[0045] Specifically, in this embodiment, the grinding step S12 includes a first grinding step S13 and a second grinding step S14. Here, the first grinding step S13 is creep feed grinding, and the second grinding step S14 is in-feed grinding.

[0046] When the irregularities due to the modified regions 100 or cracks 105 are large, the wear of the grinding wheel may be significant. This is particularly true in infeed grinding. In infeed grinding, the grinding wheel is rotated and lowered vertically to grind the wafer 10 located below the grinding wheel. Therefore, the irregular surface that comes into contact with the grinding wheel is not uniquely determined. Therefore, the grinding wheel is likely to come into contact with the edge surface 140 during the rotation of the grinding wheel, which can easily cause wear of the grinding wheel. In contrast, creep feed grinding grinds the wafer 10 by rotating the grinding wheel and moving it along the processing feed direction parallel to the holding surface of the holding table. Therefore, the surface that comes into contact with the grinding wheel can be uniquely determined. Therefore, grinding can be performed while avoiding the edge surface 140, thereby reducing wear of the grinding wheel. Furthermore, as described above, the inclined surfaces 130 are inclined at an inclination angle β of less than 90° in the +Y-axis direction in Figure 9, and the edge surfaces 140 are formed by connecting adjacent inclined surfaces 130. Therefore, by performing grinding from the -Y-axis direction side to the +Y-axis direction side in Figure 9, it is possible to grind while avoiding the grinding wheel coming into contact with the edge surfaces 140.

[0047] Therefore, in this embodiment, the first grinding step S13 uses creep feed grinding to roughly finish the wafer 10 by grinding away most of the irregularities from the -Y axis direction in Figure 9, and the second grinding step after the first grinding step S13 uses infeed grinding to bring the wafer 10 to a predetermined finished thickness and reduce the surface roughness. That is, in this embodiment, grinding is performed from a direction that takes into account the irregularities of the release layer 110.

[0048] Here, the configuration of the grinding device 200 that performs the first grinding step S13 and the second grinding step S14 will be described.

[0049] [Grinding equipment] FIG. 10 is a diagram showing an example of such a grinding apparatus 200. A rectangular opening 201a extending in the longitudinal direction is formed on the upper surface of a base 201 of the grinding apparatus 200. This opening 201a is covered by a movable plate 202 that is movable together with a holding table 204 and a bellows-shaped waterproof cover 203. A known ball-screw type moving mechanism (not shown) that feeds the holding table 204 in the Y-axis direction is provided below the waterproof cover 203. The feeding in the Y-axis direction is performed by the creep feed grinding method described above. The holding table 204 is connected to a rotation unit (not shown) and can be rotated by the rotation drive of the rotation unit. A holding surface 204a made of a porous material is formed on the upper surface of the holding table 204 to suction-hold the wafer 10, which is the workpiece.

[0050] A column 205 on the base 201 is provided with an elevator mechanism 220 that moves the grinding unit 210, which grinds the wafer 10, toward and away from the holding table 204 in the Z-axis direction for processing feed. The processing feed in the Z-axis direction is performed by the in-feed grinding described above. The elevator mechanism 220 has a pair of guide rails 221 arranged along the Z-axis direction. A flat elevator plate 222 is attached to the pair of guide rails 221 so as to be slidable along the guide rails 221.

[0051] A nut (not shown) is provided on the back side of the lifting plate 222, and the nut is connected to a ball screw 223 that is arranged along the Z-axis direction between a pair of guide rails 221. A pulse motor 224 that rotates the ball screw 223 is connected to an end of the ball screw 223. When the ball screw 223 is rotated by the pulse motor 224, the lifting plate 222 moves along the guide rails 221 in the Z-axis direction.

[0052] A housing 240 that protrudes from the front surface of the lift plate 222 is fixed to the lift plate 222. The housing 240 supports the grinding unit 210. The grinding unit 210 is housed in the housing 240 and includes a cylindrical spindle 211 that is disposed approximately perpendicular to the holding surface 204a of the holding table 204, and a rotational drive source (not shown) such as a motor that rotates the spindle 211 in a direction approximately parallel to the Z-axis direction. A disk-shaped wheel mount 212 is fixed to the lower end of the spindle 211, and a grinding wheel 213 is fixed to the lower end of the wheel mount 212.

[0053] The grinding wheel 213 has an annular wheel base 214 made of a metal material such as stainless steel or aluminum, and a plurality of grinding stones 215 arranged in a ring shape on the underside of the wheel base 214. The grinding stones 215 include a binder made of, for example, ceramic, resin, or a metal material, and numerous abrasive grains such as diamond dispersed and fixed in the binder.

[0054] The grinding apparatus 200 also includes a control unit 250 that controls the grinding apparatus 200. The control unit 250 is connected to each component of the grinding apparatus 200 and generates control signals that control the operation of each component. The control unit 250 is a computer that includes, for example, a control unit 250a that performs various calculations, a storage unit having a storage medium, and an input / output interface (not shown) that controls input and output of data to and from the inside and outside of the control unit 250. The control unit 250a performs various calculations based on predetermined programs stored in the storage unit. The control unit 250a outputs various control signals to each of the above-mentioned components via the input / output interface in accordance with the calculation results, thereby controlling the grinding apparatus 200.

[0055] The control unit 250a executes various programs stored in the storage unit. As an example, the control unit 250a executes the processing of the grinding step S12, which includes the first grinding step S13 and the second grinding step S14 in FIG. 1. Before proceeding from the peeling step S11 to the first grinding step S13, the wafer 10 is transported from the laser processing device 1 to the grinding device 200 by, for example, a transport device (not shown). The transport device may be a known transport device such as a conveyor or a robot arm.

[0056] [First grinding step] In the first grinding step S13, the control unit 250a performs creep feed grinding as described above. That is, in the first grinding step S13, the grinding wheel 213 is rotated while the wafer 10 and the grinding unit 210 are moved relatively along the processing feed direction of the Y axis, so that the wafer 10 is ground from one end side to the other end side by the grinding stone 215.

[0057] Figure 11 is a diagram for explaining the grinding process by the grinding device 200 in the first grinding step S13, where (a) of Figure 11 shows the state of the wafer 10 before grinding in the first grinding step S13, and (b) of Figure 11 shows the state of the wafer 10 after grinding in the first grinding step S13.

[0058] Specifically, as shown in FIG. 11(a), the control unit 250a first adjusts the positional relationship between the holding table 204 and the grinding unit 210 so that the grinding wheel 215 is positioned outside the workpiece and the lower surface of the grinding wheel 215 is positioned lower than the upper surface of the workpiece. Then, the spindle 211 is rotated to rotate the grinding wheel 213 around the rotation axis of the spindle 211. As a result, each of the grinding wheels 215 revolves along a circular orbit centered on the rotation axis of the spindle 211. Then, with the grinding wheel 213 rotating but the holding table 204 not rotating, the moving mechanism moves the holding table 204 along the processing feed direction, which is the Y-axis direction. As a result, the holding table 204 and the grinding wheel 213 move relatively along a direction parallel to the holding surface 204a of the holding table 204 and perpendicular to the rotation axis of the spindle 211, and approach each other.

[0059] From this state, in the creep feed grinding of the embodiment, grinding is performed in a direction that takes into account the unevenness of the peeling layer 110. That is, processing is performed so as to grind the unevenness formed on the wafer 10 in the Y-axis direction, which is perpendicular to the direction in which the modified region 100 was formed (i.e., the X-axis direction).

[0060] 11(a), grinding is performed by relatively feeding the holding table 204 and the grinding unit 210 in the Y-axis direction so that grinding is performed from an ascending direction up the uneven inclined surface 130. That is, grinding is performed so that the inclined surface 130 ascends from the -Y-axis direction toward the +Y-axis direction described above with reference to FIG. 9. In other words, grinding is performed by feeding the holding table 204 and the grinding unit 210 in the processing direction so that grinding is performed from the opposite direction to the surface on which the edge surface 140 is formed, so as to avoid the edge surface 140.

[0061] Furthermore, as described above, depending on the length, size, etc. of the cracks 105 that make up the peeling layer 110, the edge surface 140 may also be inclined to one side in the Y-axis direction. In such a case, assuming that the inclination angle of the edge surface 140 is larger than the inclination angle β of the inclined surface 130, it can also be said that the creep feed grinding in this first grinding step S13 is performed by relatively feeding the holding table 204 and the grinding unit 210 so that grinding is performed from the side of the inclined surface 130, which has the smaller inclination angle.

[0062] Furthermore, the grinding direction in this first grinding step S13 can also be defined in relation to the scanning direction of the laser beam in the above-mentioned peeling layer forming step S10. Specifically, in the peeling layer forming step S10, the ingot 20 and the focal point of the laser beam are moved relatively in a processing feed direction parallel to the holding surface of the holding table 5, i.e., in the X-axis direction. In contrast, in the first grinding step S13, the holding table 204 and the grinding unit 210 are moved relatively in a direction intersecting the processing feed direction parallel to the holding surface of the holding table 5, where the ingot 20 and the focal point of the laser beam are moved. In this embodiment, the "intersecting direction" refers to the Y-axis direction, which is perpendicular to the X-axis direction.

[0063] When the holding table 204 reaches one end of the wafer 10 due to this relative movement between the holding table 204 and the grinding unit 210, the peeled surface 120 on one end of the wafer 10 is ground away by the grinding wheel 215. Furthermore, when the holding table 204 is moved and processing feed is advanced in the Y-axis direction, grinding by the grinding wheel 215 proceeds sequentially from one end of the wafer 10 to the other end, thereby grinding away the peeled surface 120 (see FIG. 11(b)). As a result, the wafer 10 is ground from one end to the other end by the grinding wheel 215, and the entire wafer 10 is thinned.

[0064] Then, grinding in the first grinding step S13, i.e., creep feed grinding, is repeated multiple times until the thickness of the wafer 10 reaches, for example, a predetermined thickness or a predetermined surface roughness for in-feed grinding. During this process, creep feed grinding returns to the initial position and repeats grinding from the same direction. If grinding were performed, for example, from the other end of the wafer 10 to one end without returning to the initial position, the grinding wheel 215 would come into contact with the edge surface 140, accelerating wear of the grinding wheel 215. The number of creep feed grinding operations is appropriately set depending on, for example, the grinding amount. For example, the number of creep feed grinding operations may be determined taking into account the grinding amount per operation in creep feed grinding and the wear of the grinding wheel 215 during the creep feed grinding process, with a target grinding amount set to be greater than the height of the unevenness of the release layer 110 (for example, the above-mentioned 20 μm to 30 μm).

[0065] During grinding of the wafer 10, a grinding fluid such as pure water is supplied from a grinding fluid supply unit (not shown) to the wafer 10 and the grinding wheel 215. This cools the wafer 10 and the grinding wheel 215 and washes away grinding debris generated by the grinding process.

[0066] Furthermore, in creep feed grinding, as described above, the grinding process is performed multiple times to remove most of the irregularities, which means that the grinding wheel 215 is likely to wear out. Therefore, the grinding wheel 215 may be coated in advance to suppress wear. For example, a coating may be applied to the side of the grinding wheel 215, which is likely to wear out during creep feed grinding. Furthermore, since the contact area between the grinding wheel 215 and the wafer 10 may change during the process of grinding the wafer 10 from one end to the other end, the relative movement speed between the wafer 10 and the grinding wheel 213, i.e., the processing feed speed, may be changed depending on the contact area between the wafer 10 and the grinding wheel 215. This is because, for example, it is possible to suppress wear of the grinding wheel 215 during creep feed grinding compared to when the processing feed is performed at the same speed.

[0067] [Second grinding step] In the second grinding step S14, the control unit 250a performs the in-feed grinding described above. This in-feed grinding is performed after the creep feed grinding in the first grinding step S13. That is, in the second grinding step S14, the grinding wheel 213 is rotated while the wafer 10 and the grinding unit 210 are moved relatively along the processing feed direction of the Z axis perpendicular to the holding surface 204a, thereby grinding the wafer 10 with the grinding stone 215 and performing finish processing on the wafer 10.

[0068] Figure 12 is a diagram for explaining the grinding process by the grinding device 200 in the second grinding step S14, where (a) of Figure 12 shows the state of the wafer 10 before grinding in the second grinding step S14, and (b) of Figure 12 shows the state of the wafer 10 after grinding in the second grinding step S14.

[0069] 12(a), the control unit 250a first adjusts the positional relationship between the holding table 204 and the grinding unit 210 so that the center of the wafer 10 held by the holding surface 204a of the holding table 204 overlaps the trajectory of the grinding wheel. Then, while rotating the holding table 204 and the grinding wheel 213, the control unit 250a lowers the grinding wheel 213 in the processing feed direction parallel to the rotation axis of the spindle 211, i.e., along the Z-axis direction. This brings the lower surface of the grinding wheel 215 and the upper surface of the wafer 10 closer to each other.

[0070] The control unit 250a starts grinding of the wafer 10 by lowering the grinding unit 210 and bringing the lower surface of the grinding wheel 215 into contact with the wafer 10 held by suction on the holding table 204. As the grinding of the wafer 10 progresses, the thickness of the wafer 10 gradually becomes thinner, as shown in (b) of FIG.

[0071] A height gauge (not shown), which is a contact-type thickness measuring device, is provided on the surface of the wafer 10 during infeed grinding. This allows the thickness of the wafer 10 to be measured while grinding is being performed, and infeed grinding is terminated when the wafer 10 reaches a predetermined target thickness. The measuring device for measuring the thickness of the wafer 10 may also be a non-contact thickness measuring device. In this manner, in this embodiment, grinding is performed in the first grinding step S13 and the second grinding step, removing the peeling layer 110 including the unevenness, and finishing the wafer 10 to a target thickness and a predetermined surface roughness. This produces a wafer 10 on which devices can be formed.

[0072] The grinding unit 210 used in the second grinding step S14 is preferably the same as the grinding unit 210 used in the first grinding step S13. While it is possible to change the grinding wheel and holding table between the first grinding step S13 and the second grinding step S14, for example, by using the same grinding wheel 213 in both the first grinding step S13 and the second grinding step S14, the creep feed grinding in the first grinding step S13 primarily wears or wears the side surface of the grinding wheel 215, i.e., the outer edge. Due to this wear, the side surface of the grinding wheel 215, which has been formed in a rectangular parallelepiped shape, becomes tapered. Then, by performing infeed grinding in the second grinding step S14, the lower surface of the grinding wheel 215 is actively worn or worn. As a result, the tapered portion is ground from the lower surface, and the grinding wheel 215 returns to its original shape, i.e., a rectangular parallelepiped. In other words, the grinding wheel 215 can be repaired.

[0073] Furthermore, in this embodiment, since the grinding unit 210 is shared between the first grinding step S13 and the second grinding step S14, the grinding unit 210 is an example of a "first grinding unit" and a "second grinding unit," the grinding wheel 213 is an example of a "first grinding wheel" and a "second grinding wheel," the holding table 204 is an example of a "first holding table" and a "second holding table," and the holding surface 204a is an example of a "first holding surface" and a "second holding surface," respectively.

[0074] In the embodiment, the processing feed direction in the first grinding step S13 is an example of a "first processing feed direction," the processing feed direction in the second grinding step S14 is an example of a "second processing feed direction," and the processing feed direction in the peeling layer formation step S10 is an example of a "third processing feed direction."

[0075] [Ingot processing method] After the wafer 10 is separated from the ingot 20 through the series of processes shown in the flowchart of FIG. 1 , the surface of the separated ingot 20, i.e., the separated surface of the ingot 20, is then ground. That is, by separating the wafer 10 from the ingot 20 in the separation step S11, the surface of the ingot 20 also becomes uneven. Therefore, the control unit 250a uses the grinding device 200 to grind the ingot 20 using a method similar to the method used to grind the separated surface 120 of the wafer 10 described above. That is, creep feed grinding is performed on the surface of the ingot 20 in the first grinding step S13, followed by infeed grinding in the second grinding step S14. The grinding processes in the first grinding step S13 and the second grinding step S14 are as described above, and therefore will not be described in detail here. Thereafter, the process of FIG. 1 is repeated to produce multiple wafers 10.

[0076] As described above, in the embodiment, the grinding step for grinding and planarizing the release surface 120 of the wafer 10 and removing the release layer 110 includes a first grinding step S13 by creepfeed grinding and a second grinding step S14 by infeed grinding performed after the first grinding step. As described above, creepfeed grinding involves moving the grinding unit 210 in a direction parallel to the holding surface of the wafer 10, so grinding can be performed while the grinding wheel 215 is in contact with a predetermined surface of the release layer 110 that avoids the uneven edge surface 140. On the other hand, infeed grinding involves rotating and lowering the grinding unit 210 in the vertical direction, so there is a relatively high possibility that the grinding wheel 215 will come into contact with the uneven edge surface 140 of the release layer 110 while the grinding wheel 213 is rotating. In other words, infeed grinding is more likely to wear the grinding wheel during the grinding process. Therefore, in this embodiment, most of the irregularities are ground by creep feed grinding, a rough finish is performed, and then a finish is performed by infeed grinding. This makes it possible to grind the wafer 10 to the target wafer thickness with a predetermined surface roughness while suppressing wear of the grinding wheel 215 compared to, for example, performing grinding only by infeed grinding. In other words, it becomes possible to grind the wafer 10 appropriately while suppressing wear of the grinding wheel 215.

[0077] In this way, in the initial stage of the grinding process when the unevenness is large, creep feed grinding is performed as the first grinding step S13. If in-feed grinding were performed in this initial stage when the unevenness is large, it may be difficult to balance the amount of engagement of the grinding wheel 215 with the wafer 10 and the amount of wear of the grinding wheel 215. That is, in in-feed grinding, because grinding is performed vertically to the wafer 10, for example, if a relatively hard grinding wheel 215 is selected to suppress the amount of wear of the grinding wheel 215, the amount of engagement of the grinding wheel 215 with the wafer 10 may be poor, and if a relatively soft grinding wheel 215 is selected to improve the amount of engagement of the grinding wheel 215 with the wafer 10, the amount of wear of the grinding wheel 215 may be increased. On the other hand, when creep feed grinding is performed in the early stages when the unevenness is large, as in the above-described embodiment, the grinding wheel 215 is positioned below the top surface of the wafer 10 and is processed and fed horizontally relative to the holding table 204, so that the wafer 10 can be ground in a manner that slices it. Therefore, compared to in-feed grinding, it is easier to balance the engagement of the grinding wheel 215 with the wafer 10 and the amount of wear of the grinding wheel 215, and as a result, grinding is possible while suppressing the amount of wear of the grinding wheel 215.

[0078] In this embodiment, the creep feed grinding in the first grinding step S13 and the in-feed grinding in the second grinding step S14 are performed using the same grinding wheel 213. The grinding wheel 215 on the grinding wheel 213 has a rectangular parallelepiped shape as described above. Therefore, by performing creep feed grinding in the first grinding step S13, the side surfaces of the grinding wheel 215, i.e., the outer peripheral edge, are actively worn away, and the side surfaces of the grinding wheel 215, which have been formed into a rectangular parallelepiped shape, become tapered. Then, by performing in-feed grinding in the second grinding step S14, the lower surface of the grinding wheel 215 is actively worn away. As a result, the tapered portion is ground from the lower surface, and the grinding wheel 215 returns to its original shape, i.e., a rectangular parallelepiped shape. As a result, the grinding wheel 215 can be repaired during the process of grinding the wafer 10.

[0079] In addition, in this embodiment, the second orientation flat 24, which indicates the crystal orientation, is aligned with the X-axis direction, thereby aligning the direction perpendicular to the direction in which the off-angle α is formed with the X-axis direction. Then, a linear modified region 100 is formed with the X-axis direction as the processing feed direction. When the modified region 100 is formed in this manner, cracks 105, such as irregularities, extend along the c-plane from both sides of the modified region 100. A delamination layer 110 is then formed, including the cracks 105 and the modified region 100. When the wafer 10 is delaminated from the ingot 20 starting from the delamination layer 110, the delamination layer 110 is exposed on the delamination surface 120 of the wafer 10. In the exposed delamination layer 110, irregularities caused by the cracks 105 are formed in a direction perpendicular to the direction in which the modified region 100 was formed. In this embodiment, when grinding the peeled surface 120, the above-mentioned creep feed grinding is performed, in which the holding table 204 and the grinding unit 210 are moved relatively by processing feed so as to be perpendicular to the direction in which the modified region 100 was formed, in other words, in the same direction as the direction in which the irregularities were formed. This allows the holding table 204 and the grinding unit 210 to be moved relatively in the direction in which the irregularities caused by the cracks 105 extend, making it possible to remove the peeled layer while easily grinding the peeled surface 120 on which the irregularities were formed, compared to, for example, grinding from other directions.

[0080] Furthermore, the release layer 110 includes an inclined surface 130 that is inclined at an angle of less than 90° relative to the direction of creep feed grinding in the direction in which the linear modified region 100 was formed, i.e., in a cross-sectional view from the X-axis direction. Grinding by creep feed grinding is then performed in the ascending direction along the inclined surface 130. This increases the likelihood that the grinding wheel 215 will not come into contact with the edge surface 140 formed by the connection of the inclined surfaces 130 that are continuous in the processing feed direction, thereby suppressing wear on the grinding wheel 215.

[0081] The above-described inclined surface 130 may also be formed on the edge surface 140. In other words, if the edge surface 140 is not a right angle, the edge surface 140 will also have an inclination angle on one side in the Y-axis direction. In this case, it is assumed that the inclination angle of the edge surface 140 is greater in absolute value than the inclination angle β of the inclined surface 130 in the processing feed direction. In such a case, in this embodiment, grinding is performed from the side of the inclined surface 130 with the smaller inclination angle. This prevents the grinding wheel 215 from coming into contact with the edge surface 140, thereby suppressing wear of the grinding wheel 215.

[0082] It can also be said that the processing feed direction (Y-axis direction) of creep feed grinding is a direction perpendicular to the processing feed direction (X-axis direction) of the peeling layer formation step S10. In the peeling layer formation step S10, processing feed is performed in the direction in which the modified region 100 is formed, and therefore the direction perpendicular to that direction is the direction in which the cracks 105 including the unevenness extend, as described above. Therefore, by setting the direction perpendicular to the processing feed direction of the peeling layer formation step S10 as the processing feed direction of creep feed grinding in this way, it becomes possible to grind the peeling layer 110 including the uneven cracks 105 more easily than when the processing feed direction of creep feed grinding is set to another direction.

[0083] In addition, in this embodiment, the in-feed grinding in the second grinding step S14 is performed after the creep feed grinding in the first grinding step S13 is performed multiple times in the same direction. That is, the wafer 10 is ground to a thickness close to the target thickness by creep feed grinding, and then the wafer is ground by in-feed grinding to the target wafer thickness. This reduces the number of times in-feed grinding, which wears the grinding wheel 215 relatively more, and thus the wear of the grinding wheel 215 can be further suppressed.

[0084] In addition, in the embodiment, creep feed grinding in the first grinding step S13 is a rough finishing process for the wafer 10, and in-feed grinding in the second grinding step S14 is a finishing process for grinding the wafer 10 to a target finishing thickness. As described above, creep feed grinding is more suitable for rough finishing because it can perform grinding while avoiding the edge surface 140, while in-feed grinding is more suitable for finishing because it is good at aligning the wafer 10 to a predetermined finishing thickness and reducing surface roughness. Therefore, by using each grinding method according to the grinding process, wear on the grinding wheel 215 can be further suppressed.

[0085] In the embodiment, a process similar to the process of grinding and flattening the delamination layer 110 of the wafer 10 is also performed on the ingot 20 obtained by delaminating the wafer 10. That is, since a delamination layer including a similar uneven shape is formed on the surface of the ingot 20 by delaminating the wafer 10 from the ingot 20, creep feed grinding in the first grinding step S13 and infeed grinding in the second grinding step S14 are performed in this order. This makes it possible to perform appropriate grinding while suppressing wear of the grinding wheel 215.

[0086] [Variations] Next, a modified example will be described. In the above-described embodiment, creep feed grinding is performed for rough finishing, and in-feed grinding is performed for the target finish, but as long as creep feed grinding is performed for rough finishing, creep feed grinding and in-feed grinding may also be performed for finish processing. In other words, as long as rough finishing is performed by creep feed grinding alone, and in-feed grinding is performed for the final finish processing, creep feed grinding may also be performed for finish processing.

[0087] Furthermore, the peripheral surface 22 of the ingot 20 does not necessarily need to have a first orientation flat or a second orientation flat formed thereon; for example, instead of the first orientation flat or the second orientation flat, another orientation flat or notch, etc., depending on the crystal orientation may be provided on the ingot.

[0088] In the above-described embodiment, after the wafer 10 is separated from the ingot 20, a process for grinding the separated surface 120 of the wafer 10 is performed, and then a process for grinding the separated surface of the ingot 20 is performed, but the order may be reversed. That is, after the wafer 10 is separated from the ingot 20 in the separation step S11, a process for grinding the separated surface of the ingot 20 may be performed, and then a process for grinding the separated surface 120 of the wafer 10 may be performed.

[0089] In the above-described embodiment, an ingot made of SiC is described as an example of the workpiece. However, as described above, the workpiece may be an ingot made of other materials, such as gallium nitride (GaN), lithium tantalate (LT), diamond, or silicon (Si). In this case, for example, in the case of SiC, unevenness due to cracks 105 is formed on the peeled surface 120 in a direction perpendicular to the modified region 100. However, in the case of an ingot made of another semiconductor material, unevenness is not necessarily formed in a direction perpendicular to the modified region 100. In such a case, it is possible to assume that unevenness will be formed at least in a direction intersecting the modified region 100. Therefore, in such a case, for example, creep feed grinding in the first grinding step S13 may be performed in at least a direction intersecting the laser beam scanning direction in the peeled layer forming step S10.

[0090] Furthermore, as described above, the direction in which creep feed grinding is performed is determined by the direction in which the peeling layer 110 is formed relative to the crystal orientation, so the direction in which creep feed grinding is performed may be determined based on that direction, or the direction in which the peeling layer 110 is formed may be obtained using the imaging unit 73 in the laser processing device 1, and the direction in which creep feed grinding is performed may be determined based on the obtained direction.

[0091] Furthermore, in the above-described embodiment, the grinding unit 210 that performs the first grinding step S13 and the second grinding step S14 are performed using the same grinding unit 210, but each process may be performed using a different grinding unit or grinding device.

[0092] Although the embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such embodiments. It is clear that a person skilled in the art can conceive of various modifications and 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.

[0093] For example, the above-described laser processing apparatus 1 may be separated into multiple devices. For example, in the above-described embodiment, the peeling unit 8 included in the laser processing apparatus 1 may be a device separate from the laser processing apparatus 1.

[0094] The wafer manufacturing method and ingot processing method described in the above embodiments can be realized by executing a prepared control program on a computer. The control program is recorded on a computer-readable storage medium and executed by being read from the storage medium. The control program may be provided in a form stored on a non-transitory storage medium such as a flash memory, or may be provided via a network such as the Internet. The computer that executes the control program may be included in a processing device, or may be included in an electronic device such as a smartphone, tablet, or personal computer that can communicate with the processing device, or may be included in a server device that can communicate with these processing devices and electronic devices.

[0095] 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.

[0096] (1) A wafer manufacturing method for manufacturing wafers (wafers 10) from an ingot (ingot 20), a separation layer forming step (separation layer forming step S10) in which a laser beam having a wavelength that can pass through the ingot is irradiated onto the surface (surface 20a) of the ingot, and a modified region (modified region 100) is formed by positioning the focal point of the laser beam at a position deeper than the surface of the ingot, and the ingot and the focal point are moved relatively to form a separation layer (separation layer 110) including the modified region inside the ingot; After the separation layer forming step, a separation step (separation step S11) of separating the wafer from the separation layer as a starting point; After the peeling step, a grinding step (grinding step S12) is performed to grind and flatten the peeled surface (peeled surface 120) of the peeled wafer and remove the peeled layer, The grinding step includes: a first grinding step (first grinding step S13) in which a first holding table (holding table 204) that holds the wafer on a first holding surface (holding surface 204a) and a first grinding unit (grinding unit 210) having a first grinding wheel (grinding wheel 213) including a grinding stone (grinding stone 215) are moved relatively in a first processing feed direction (Y-axis direction) parallel to the first holding surface to perform grinding; a second grinding step (second grinding step S14) in which, after the first grinding step, the wafer is held on a second holding surface (holding surface 204a) of a second holding table (holding table 204), and grinding is performed by relatively moving the second holding table and a second grinding unit (grinding unit 210) having a second grinding wheel (grinding wheel 213) including a grinding stone (grinding stone 215) in a second processing feed direction (Z-axis direction) perpendicular to the second holding surface, Wafer manufacturing method.

[0097] According to (1), it is possible to reduce the amount of wear on the grinding wheel while grinding the wafer to the target wafer thickness with a predetermined surface roughness, compared to, for example, performing grinding processing on the peeled surface of the wafer only through the first grinding step.

[0098] (2) A method for manufacturing a wafer according to (1), The first grinding wheel in the first grinding step and the second grinding wheel in the second grinding step are the same grinding wheel. Wafer manufacturing method.

[0099] According to (2), by using the same grinding wheel in the first grinding step and the second grinding step, the side of the grinding wheel, i.e., the outer edge, is actively worn away by grinding in the first grinding step, and the shape of the grinding wheel becomes tapered. Then, by grinding in the second grinding step, the bottom surface of the grinding wheel is actively worn away. As a result, the tapered portion is ground from the bottom surface, and the shape of the grinding wheel returns to its original shape. As a result, the grinding wheel can be repaired during the wafer grinding process.

[0100] (3) A method for manufacturing a wafer according to (1) or (2), In the peeling layer forming step, The peeling layer is formed to include the modified region that is linear with respect to a predetermined direction (X-axis direction) based on the crystal orientation, and a crack (crack 105) extending from the modified region, The first grinding step includes: Grinding is performed by relatively moving the first holding table and the first grinding unit in the first processing feed direction perpendicular to the predetermined direction. Wafer manufacturing method.

[0101] According to (3), by performing the first grinding step so as to be perpendicular to the predetermined direction based on the crystal orientation, it becomes possible to grind the peeled surface more easily than, for example, performing the first grinding step from another direction. In other words, by forming a modified region in the predetermined direction based on the crystal orientation, the direction in which the peeled layer including the unevenness is formed is also determined. Therefore, by performing grinding in the first grinding step in the direction based on that, i.e., the direction perpendicular to the predetermined direction, it becomes possible to grind the peeled surface easily.

[0102] (4) A method for manufacturing a wafer according to (3), The release layer includes an inclined surface (inclined surface 130) that is inclined at an angle of less than 90° in the first processing feed direction when viewed in cross section from the predetermined direction, The first grinding step includes: Grinding is performed by relatively moving the first holding table and the first grinding unit in the first processing feed direction so that grinding is performed in an ascending direction up the inclined surface. Wafer manufacturing method.

[0103] According to (4), by performing grinding in the first grinding step from the direction of ascending the inclined surface, it is more likely that the grinding wheel will not come into contact with the edge surface formed by connecting consecutive inclined surfaces in the processing feed direction, and as a result, wear on the grinding wheel can be suppressed.

[0104] (5) A method for manufacturing a wafer according to (3), The peeling layer includes a plurality of inclined surfaces (inclined surfaces 130, edge surfaces 140) that are inclined in the first processing feed direction when viewed in cross section from the predetermined direction, The first grinding step includes: grinding is performed by relatively moving the first holding table and the first grinding unit in the first processing feed direction so that grinding is performed from the side of the inclined surface having a smaller inclination angle among the plurality of inclined surfaces; Wafer manufacturing method.

[0105] According to (5), if the edge surface is not a right angle, the edge surface will also have an inclination angle to one side of the processing feed direction. However, by grinding from the inclined surface side with the smaller inclination angle, it is possible to avoid the grinding wheel coming into contact with the edge surface, and as a result, wear on the grinding wheel can be suppressed.

[0106] (6) A method for producing a wafer according to (1) or (2), In the peeling layer forming step, the ingot and the focal point are moved relatively in a third processing feed direction (X-axis direction) parallel to the first holding surface, The first processing feed direction in the first grinding step is a direction intersecting the third processing feed direction. Wafer manufacturing method.

[0107] According to (6), by performing the first grinding step in a direction intersecting the processing feed direction in the peeling layer formation step, it becomes possible to grind the peeling layer surface more easily than, for example, when the processing feed direction in the first grinding step is another direction.

[0108] (7) A method for manufacturing a wafer according to (1) or (2), The second grinding step includes: This is performed after the first grinding step is performed multiple times in the same direction. Wafer manufacturing method.

[0109] According to (7), for example, it is possible to reduce the number of times grinding is performed in the second grinding step, which involves a relatively high degree of wear of the grinding wheel, and therefore it is possible to further suppress wear of the grinding wheel.

[0110] (8) A method for producing a wafer according to (1) or (2), the first grinding step is a rough finishing process of the wafer; The second grinding step is a finishing process for grinding the wafer to a target finished thickness. Wafer manufacturing method.

[0111] According to (8), by using each grinding treatment according to the grinding process, wear of the grinding wheel can be further suppressed.

[0112] (9) A method for processing an ingot (ingot 20) when manufacturing a wafer (wafer 10), comprising: a separation layer forming step (separation layer forming step S10) in which a laser beam having a wavelength that can pass through the ingot is irradiated onto the surface (surface 20a) of the ingot, and a modified region (modified region 100) is formed by positioning the focal point of the laser beam at a position deeper than the surface of the ingot, and the ingot and the focal point are moved relatively to form a separation layer (separation layer 110) including the modified region inside the ingot; After the separation layer forming step, a separation step (separation step S11) of separating the wafer from the separation layer as a starting point; After the peeling step, a grinding step (grinding step S12) is performed to grind and flatten the peeled surface of the ingot and remove the peeled layer, The grinding step includes: a first grinding step (first grinding step S13) in which a first holding table (holding table 204) that holds the ingot on a first holding surface (holding surface 204a) and a first grinding unit (grinding unit 210) having a first grinding wheel (grinding wheel 213) including a grinding wheel (grinding wheel 215) are moved relatively in a first processing feed direction (Y-axis direction) parallel to the first holding surface to perform grinding; a second grinding step (second grinding step S14) in which, after the first grinding step, the ingot is held on a second holding surface (holding surface 204a) of a second holding table (holding table 204), and the second holding table and a second grinding unit (grinding unit 210) having a second grinding wheel (grinding wheel 213) including a grinding wheel (grinding wheel 215) are moved relatively in a second processing feed direction (Z-axis direction) perpendicular to the second holding surface to perform grinding, How to process ingots.

[0113] According to (9), the wear amount of the grinding wheel can be reduced compared to when the peeled surface of the ingot is ground only in the first grinding step. [Explanation of symbols]

[0114] 10 wafers 20 ingots 20a surface 100 Modified Area 105 Crack 110 Peeling layer 120 Peeling surface 130 Slope 204 Holding Table 204a Holding surface 210 Grinding Unit 213 Grinding Wheel 215 Grinding Wheel S10 Peeling layer formation step S11 Peeling step S12 Grinding Step S13 First grinding step S14 Second grinding step

Claims

1. A wafer manufacturing method for manufacturing wafers from an ingot, comprising: a separation layer forming step of irradiating a surface of the ingot with a laser beam having a wavelength that can pass through the ingot, positioning a focal point of the laser beam at a position deeper than the surface of the ingot to form a modified region, and relatively moving the ingot and the focal point to form a separation layer including the modified region inside the ingot; a peeling step of peeling the wafer starting from the peeling layer after the peeling layer forming step; a grinding step of grinding the delaminated surface of the wafer after the delamination step to flatten it and remove the delamination layer, The grinding step includes: a first grinding step in which a first holding table that holds the wafer on a first holding surface and a first grinding unit that has a first grinding wheel including a grinding stone are moved relatively in a first processing feed direction parallel to the first holding surface to perform grinding; a second grinding step in which, after the first grinding step, the wafer is held on a second holding surface of a second holding table, and the second holding table and a second grinding unit having a second grinding wheel including a grinding stone are moved relatively in a second processing feed direction perpendicular to the second holding surface to perform grinding. Wafer manufacturing method.

2. 2. The method for manufacturing a wafer according to claim 1, the first grinding wheel in the first grinding step and the second grinding wheel in the second grinding step are the same grinding wheel; Wafer manufacturing method.

3. 3. The method for manufacturing a wafer according to claim 1 or 2, In the peeling layer forming step, the peeling layer is formed, the peeling layer including the modified region linear with respect to a predetermined direction based on the crystal orientation and cracks extending from the modified region; The first grinding step includes: Grinding is performed by relatively moving the first holding table and the first grinding unit in the first processing feed direction perpendicular to the predetermined direction. Wafer manufacturing method.

4. 4. The method for manufacturing a wafer according to claim 3, the release layer includes an inclined surface that is inclined at an angle of less than 90° toward the first processing feed direction when viewed in cross section from the predetermined direction, The first grinding step includes: grinding is performed by relatively moving the first holding table and the first grinding unit in the first processing feed direction so that grinding is performed in an ascending direction on the inclined surface; Wafer manufacturing method.

5. 4. The method for manufacturing a wafer according to claim 3, the peeling layer includes a plurality of inclined surfaces that are inclined in the first processing feed direction when viewed in cross section from the predetermined direction, The first grinding step includes: grinding is performed by relatively moving the first holding table and the first grinding unit in the first processing feed direction so that grinding is performed from the side of the inclined surface having a smaller inclination angle among the plurality of inclined surfaces; Wafer manufacturing method.

6. 3. The method for manufacturing a wafer according to claim 1 or 2, In the peeling layer forming step, the ingot and the focal point are moved relatively in a third processing feed direction parallel to the first holding surface, The first processing feed direction in the first grinding step is a direction intersecting the third processing feed direction. Wafer manufacturing method.

7. 3. The method for manufacturing a wafer according to claim 1 or 2, The second grinding step includes: The first grinding step is performed multiple times in the same direction. Wafer manufacturing method.

8. 3. The method for manufacturing a wafer according to claim 1 or 2, the first grinding step is a rough finishing process of the wafer; The second grinding step is a finishing process for grinding the wafer to a target finished thickness. Wafer manufacturing method.

9. A method for processing an ingot when producing wafers from the ingot, comprising: a separation layer forming step of irradiating a surface of the ingot with a laser beam having a wavelength that can pass through the ingot, positioning a focal point of the laser beam at a position deeper than the surface of the ingot to form a modified region, and relatively moving the ingot and the focal point to form a separation layer including the modified region inside the ingot; a peeling step of peeling the wafer starting from the peeling layer after the peeling layer forming step; a grinding step of grinding the separated surface of the ingot to flatten it and remove the separated layer after the separation step, The grinding step includes: a first grinding step in which a first holding table that holds the ingot on a first holding surface and a first grinding unit having a first grinding wheel including a grinding stone are moved relatively in a first processing feed direction parallel to the first holding surface to perform grinding; a second grinding step in which, after the first grinding step, the ingot is held on a second holding surface of a second holding table, and the second holding table and a second grinding unit having a second grinding wheel including a grinding stone are moved relatively in a second processing feed direction perpendicular to the second holding surface to perform grinding. How to process ingots.

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