Substrate manufacturing method

Abstract

To provide a method for manufacturing a substrate, capable of suppressing decrease in productivity of substrates.SOLUTION: A release layer is finally formed in an area (a first inner area or a second inner area) close to the center of a workpiece among a plurality of areas along a machining feed direction of the workpiece. Here, the workpiece has a cylindrical shape, so that the second inner area is wider than other areas (for example, a second outer area) where the release layer is formed. Thus, when the release layer is finally formed in the second inner area, internal stress of the workpiece is dispersed over a wide range, as compared with the case where the release layer is finally formed in the second outer area. In this case, the extension of cracks with a large component in a thickness direction of the workpiece from a reformed portion included in the release layer can be suppressed. Thus, a decrease in productivity of substrates can be suppressed without increasing the amount of materials wasted during substrate planarization.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a substrate from a cylindrical workpiece having a circular first surface and a circular second surface located opposite the first surface. [Background technology]

[0002] Semiconductor device chips are generally manufactured using cylindrical substrates made of semiconductor materials such as silicon (Si) or silicon carbide (SiC), which are cut from cylindrical ingots of semiconductor material using, for example, a wire saw (see, for example, Patent Document 1).

[0003] However, when cutting a substrate from an ingot using a wire saw, the cutting width is relatively large, about 300 μm. Furthermore, the surface of the substrate cut in this way has minute irregularities and is curved overall (the wafer warps). Therefore, the surface of the substrate needs to be flattened by lapping, etching, and / or polishing.

[0004] In this case, the amount of material ultimately used for the substrate is about two-thirds of the total ingot material. In other words, about one-third of the total ingot material is discarded during cutting and flattening of the substrate. Therefore, productivity is low when manufacturing substrates using a wire saw in this way.

[0005] In view of this, it has been proposed to manufacture a substrate from an ingot by using a laser beam with a wavelength that is transparent to the material that constitutes the ingot (see, for example, Patent Document 2). In this method, first, the focal point of the laser beam is positioned inside the ingot, and the ingot and the focal point are repeatedly moved relative to each other along the processing feed direction.

[0006] As a result, a peeling layer including a modified portion formed around the focal point and cracks extending from the modified portion is formed in each of a plurality of regions along the processing feed direction of the ingot. Then, by applying an external force to the ingot, the substrate is separated from the ingot starting from the peeling layer.

[0007] In this case, the amount of material discarded can be reduced compared to when manufacturing substrates using a wire saw, and as a result, this substrate manufacturing method can improve substrate productivity. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 9-262826 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-111143 Summary of the Invention [Problem to be solved by the invention]

[0009] In the substrate manufacturing method described above, a delamination layer is formed in the indexing feed direction of the ingot (a direction perpendicular to the processing feed direction in a plan view) from one end to the other end. That is, in this substrate manufacturing method, once a delamination layer is formed in one of the multiple regions of the ingot, a delamination layer is then formed in another region adjacent to the previous region, which is located in the indexing feed direction as viewed from the region where the delamination layer was formed immediately before.

[0010] The modified portion included in the peeling layer is a portion where the crystal structure of the material constituting the ingot is disrupted. Therefore, when such a modified portion is formed inside the ingot, internal stress is generated in the ingot. Furthermore, such internal stress increases as the volume of the modified portion formed in the ingot increases.

[0011] Furthermore, the internal stress of the ingot promotes the propagation of cracks from the modified portion. Therefore, in the above-described method, when a separation layer is formed in the region on the other end side of the ingot in the indexing direction (the region where the separation layer is formed last among the multiple regions), a crack with a large component in the thickness direction of the ingot may propagate from the modified portion.

[0012] In this case, a substrate is produced in which the separated portion in the region on the other end side in the indexing feed direction of the ingot is coarser than the remaining portion. When planarizing the produced substrate, the entire substrate must be planarized until the separated portion in the region on the other end side of the ingot is flat. Therefore, in the above-described substrate manufacturing method, the amount of material wasted during substrate planarization increases, which may reduce substrate productivity.

[0013] In view of this, an object of the present invention is to provide a method for manufacturing a substrate that can suppress a decrease in productivity of the substrate. [Means for solving the problem]

[0015] The present invention oneAccording to an aspect, a method for manufacturing a substrate from a cylindrical workpiece having a circular first surface and a circular second surface located on the opposite side of the first surface includes: a peeling layer forming step of forming a peeling layer including a modified portion formed around the focal point and cracks extending from the modified portion in each of a plurality of regions of the workpiece along the processing feed direction by repeating relative movement between the workpiece and the focal point of a laser beam having a wavelength that transmits through a material constituting the workpiece, with the focal point positioned inside the workpiece, and a separation step of separating the substrate from the workpiece using the peeling layer as a starting point; and a separation step of separating the substrate from the workpiece using the peeling layer as a starting point, the plurality of regions including a first semi-cylindrical region having a boundary surface that passes through the center of the workpiece and is parallel to the processing feed direction. a first outer region, a first intermediate region included in one of the two semi-cylindrical regions and closer to the center of the workpiece than the first outer region, a first inner region included in one of the two semi-cylindrical regions and closer to the center of the workpiece than the first intermediate region, a second outer region included in the other of the two semi-cylindrical regions, a second intermediate region included in the other of the two semi-cylindrical regions and closer to the center of the workpiece than the second outer region, and a second inner region included in the other of the two semi-cylindrical regions and closer to the center of the workpiece than the second intermediate region, wherein in the peeling layer forming step, the peeling layer is formed in the order of the first outer region, the first intermediate region, the first inner region, the second outer region, the second intermediate region, and the second inner region. The material is, for example, single crystal silicon.

[0017] The present invention AnotherAccording to the aspect of the present invention, there is provided a method for manufacturing a substrate from a cylindrical workpiece having a circular first surface and a circular second surface located on the opposite side of the first surface, the method comprising: a peeling layer forming step of forming a peeling layer including a modified portion formed around the focal point and cracks extending from the modified portion in each of a plurality of regions of the workpiece along the processing feed direction, the modified portion being formed around the focal point and a crack extending from the modified portion, in a state where the focal point of a laser beam having a wavelength that is transmitted through a material constituting the workpiece is positioned inside the workpiece, and the peeling layer forming step is performed by repeating relative movement between the workpiece and the focal point along a processing feed direction parallel to the first surface; and a separation step of separating the substrate from the workpiece using the peeling layer as a starting point, the plurality of regions being a first region including a second region that passes through the center of the workpiece and is included in one of two semi-cylindrical regions having a boundary surface that is parallel to the processing feed direction. a first outer region, a first intermediate region included in one of the two semi-cylindrical regions and closer to the center of the workpiece than the first outer region, a first inner region included in one of the two semi-cylindrical regions and closer to the center of the workpiece than the first intermediate region, a second outer region included in the other of the two semi-cylindrical regions, a second intermediate region included in the other of the two semi-cylindrical regions and closer to the center of the workpiece than the second outer region, and a second inner region included in the other of the two semi-cylindrical regions and closer to the center of the workpiece than the second intermediate region, wherein the exfoliation layer is formed in the order of the first outer region, the first intermediate region, the second outer region, the second intermediate region, the first inner region, and the second inner region. The material is, for example, single crystal silicon. [Effects of the Invention]

[0018] In the present invention, a release layer is finally formed in a region (first inner region or second inner region) close to the center of the workpiece among multiple regions along the processing feed direction of the workpiece. Here, since the workpiece has a cylindrical shape, the second inner region is wider than the other regions (e.g., the second outer region) where the release layer is to be formed.

[0019] Therefore, when the release layer is formed last in the second inner region, the internal stress of the workpiece is dispersed over a wider area than when the release layer is formed last in the second outer region. In this case, it is possible to suppress the propagation of cracks with a large component in the thickness direction of the workpiece from the modified portion contained in the release layer. As a result, in the present invention, it is possible to suppress a decrease in substrate productivity without increasing the amount of material discarded during substrate planarization. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a perspective view schematically showing an example of an ingot. [Figure 2] FIG. 2 is a top view schematically showing an example of an ingot. [Figure 3] FIG. 3 is a flowchart schematically illustrating an example of a method for manufacturing a substrate. [Figure 4] FIG. 4 is a diagram schematically illustrating an example of a laser processing device. [Figure 5] FIG. 5 is a top view schematically showing a holding table for holding an ingot. [Figure 6] FIG. 6 is a top view schematically showing an example of the trajectory of the irradiation head moving in the peeling layer forming step. [Figure 7] FIG. 7 is a cross-sectional view schematically showing how an ingot is irradiated with a laser beam. [Figure 8] 8(A) and 8(B) are each a partial cross-sectional side view that schematically shows an example of the separation step. [Figure 9] 9(A) and 9(B) are top views each schematically showing another example of the trajectory of the irradiation head moving in the peeling layer forming step. [Figure 10] 10(A) and 10(B) are each a partial cross-sectional side view schematically showing another example of the separation step. DETAILED DESCRIPTION OF THE INVENTION

[0021] Embodiments of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a perspective view schematically showing an example of a cylindrical ingot made of single crystal silicon, and Fig. 2 is a top view schematically showing this example of the ingot. Fig. 1 also shows the crystal planes of the single crystal silicon exposed on the planes included in this ingot. Fig. 2 also shows the crystal orientation of the single crystal silicon constituting this ingot.

[0022] 1 and 2, a specific crystal plane included in the crystal plane {100} (here, for convenience, referred to as the crystal plane (100)) is exposed on each of the circular front surface (first surface) 11a and the circular back surface (second surface) 11b. That is, in this ingot 11, the perpendicular lines (crystal axes) of the front surface 11a and the back surface 11b are aligned along the crystal orientation

[0100] .

[0023] Although the ingot 11 is manufactured so that the crystal plane (100) is exposed on each of the front surface 11a and the back surface 11b, due to processing errors during manufacturing, a plane slightly tilted from the crystal plane (100) may be exposed on each of the front surface 11a and the back surface 11b. Specifically, a plane that forms an angle of 1° or less with the crystal plane (100) may be exposed on each of the front surface 11a and the back surface 11b of the ingot 11. In other words, the crystal axis of the ingot 11 may be along a direction that forms an angle of 1° or less with the crystal orientation

[0100] .

[0024] An orientation flat 13 is formed on the side surface 11c of the ingot 11, and the crystal orientation as viewed from this orientation flat 13 is <110> The center C of the ingot 11 is located in a specific crystal orientation (here, for convenience, it is assumed to be the crystal orientation

[0011] ) included in the above. In other words, in this orientation flat 13, the crystal plane (011) of the single crystal silicon is exposed.

[0025] 3 is a flow chart showing a schematic example of a method for manufacturing a substrate from a workpiece, that is, an ingot 11. In short, in this method, a peeling layer is formed inside the ingot 11 using a laser processing device, and then the substrate is separated from the ingot 11 using this peeling layer as a starting point.

[0026] Fig. 4 is a diagram schematically illustrating an example of a laser processing device used when forming a peeling layer inside an ingot 11. Note that the X-axis direction and Y-axis direction shown in Fig. 4 are directions perpendicular to each other on a horizontal plane, and the Z-axis direction is a direction (vertical direction) perpendicular to each of the X-axis direction and the Y-axis direction. Also, in Fig. 4, some of the components of the laser processing device are shown in functional blocks.

[0027] The laser processing apparatus 2 shown in Fig. 4 has a cylindrical holding table 4. This holding table 4 has a circular upper surface (holding surface) that is wider than the front surface 11a and back surface 11b of the ingot 11, and holds the ingot 11 on this holding surface. Also, a cylindrical porous plate (not shown) is exposed on this holding surface.

[0028] Furthermore, this porous plate is connected to a suction source (not shown) such as a vacuum pump via a flow path or the like provided inside the holding table 4. When this suction source is activated, a negative pressure is generated in the space near the holding surface of the holding table 4. This allows, for example, the holding table 4 to hold an ingot 11 placed on the holding surface.

[0029] A laser beam irradiation unit 6 is provided above the holding table 4. This laser beam irradiation unit 6 has a laser oscillator 8. This laser oscillator 8 has, for example, Nd:YAG or the like as a laser medium, and irradiates a pulsed laser beam LB having a wavelength (for example, 1064 nm) that is transmitted through the material (single crystal silicon) that constitutes the ingot 11.

[0030] The output of this laser beam LB is adjusted by an attenuator 10, and then supplied to a spatial light modulator 12. The laser beam LB is then branched in the spatial light modulator 12. For example, the spatial light modulator 12 branches the laser beam LB so that the laser beam LB irradiated from an irradiation head 16 (described later) forms multiple (e.g., five) focusing points arranged at equal intervals along the Y-axis direction.

[0031] Furthermore, the laser beam LB branched by the spatial light modulator 12 is reflected by a mirror 14 and guided to an irradiation head 16. This irradiation head 16 contains a condenser lens (not shown) that condenses the laser beam LB, and the like. The laser beam LB condensed by this condenser lens is irradiated onto the holding surface side of the holding table 4.

[0032] Furthermore, the irradiation head 16 of the laser beam irradiation unit 6 is connected to a movement mechanism (not shown). This movement mechanism includes, for example, a ball screw or the like, and moves the irradiation head 16 along the X-axis, Y-axis, and / or Z-axis directions. In the laser processing apparatus 2, by operating this movement mechanism, the position (coordinates) of the focal point of the laser beam LB irradiated from the irradiation head 16 in the X-axis, Y-axis, and Z-axis directions is adjusted.

[0033] 3, a laser processing device 2 is used to form a peeling layer in each of a plurality of regions along the processing feed direction of the ingot 11 (peeling layer forming step: S1). In this laser processing device 2, for example, the X-axis direction and the direction opposite to the X-axis direction are set as the processing feed direction. When performing the peeling layer forming step (S1), first, the ingot 11 is held on the holding table 4 with the surface 11a facing upward.

[0034] 5 is a top view schematically showing the holding table 4 holding the ingot 11. The ingot 11 is held on the holding table 4 in a state where the direction from the orientation flat 13 toward the center C of the ingot 11 (the crystal orientation

[0011] ) forms an angle of 45° with the X-axis direction and the Y-axis direction. For example, the ingot 11 is held on the holding table 4 in a state where the crystal orientation

[0010] is parallel to the X-axis direction and the crystal orientation

[0001] is parallel to the Y-axis direction.

[0035] Next, the irradiation head 16 is moved so that the region on one end side of the ingot 11 in the Y-axis direction is positioned in the X-axis direction when viewed from the irradiation head 16. Next, the irradiation head 16 is raised and lowered so that the focal point of the laser beam LB is positioned at a height corresponding to the interior of the ingot 11.

[0036] The laser beam LB is branched to form, for example, five focal points arranged at equal intervals along the Y-axis direction. Next, with the focal points positioned inside the ingot 11, the irradiation head 16 is moved to irradiate the laser beam LB toward the ingot 11.

[0037] 6 is a top view schematically showing an example of the trajectory of the irradiation head 16 moving in the peeling layer forming step (S1). That is, in the peeling layer forming step (S1), for example, the irradiation head 16 is moved along the dotted line shown in FIG. 6 to irradiate the ingot 11 with the laser beam LB.

[0038] Specifically, first, while irradiating the laser beam LB from the irradiation head 16, the irradiation head 16 is moved in the X-axis direction (processing feed direction) so as to pass from one end to the other end in the X-axis direction of the ingot 11 in a plan view. In other words, while irradiating the laser beam LB from the irradiation head 16, the irradiation head 16 is moved linearly until the center of the irradiation head 16 moves from position P0 to position P1 shown in FIG.

[0039] 7 is a cross-sectional view schematically showing how the ingot 11 is irradiated with the laser beam LB. This irradiation of the laser beam LB forms modified portions 15a inside the ingot 11, each centered on a plurality of focal points, in which the crystalline structure of the material (single crystal silicon) constituting the ingot 11 is disrupted. The volume of the ingot 11 expands as the modified portions 15a are formed.

[0040] Furthermore, the formation of the modified regions 15a generates internal stress in the ingot 11. Then, cracks 15b extend from the modified regions 15a in the ingot 11, thereby relieving the internal stress. As a result, a peeling layer 15 including a plurality of modified regions 15a formed around each of the plurality of light-focusing points and cracks 15b extending from each of the plurality of modified regions 15a is formed in a region (first outer region) on one end side in the Y-axis direction of the ingot 11.

[0041] Next, the irradiation head 16 is moved in the Y-axis direction so that the movement distance of the irradiation head 16 is longer than the width along the Y-axis of the peeling layer 15. In other words, the irradiation head 16 is moved linearly until the center of the irradiation head 16 reaches a position P2 from position P1 shown in FIG.

[0042] Next, while irradiating the laser beam LB from the irradiation head 16, the irradiation head 16 is moved in the opposite direction to the X-axis direction (processing feed direction) so as to pass from one end to the other end in the X-axis direction of the ingot 11 in a plan view. In other words, while irradiating the laser beam LB from the irradiation head 16, the irradiation head 16 is moved linearly until the center of the irradiation head 16 moves from position P2 to position P3 shown in FIG.

[0043] As a result, a peeling layer 15 is formed in a region (first intermediate region) closer to the center C of the ingot 11 than the first outer region. Next, the irradiation head 16 is moved in the Y-axis direction so that the movement distance of the irradiation head 16 is longer than the width of the peeling layer 15 along the Y-axis direction. In other words, the irradiation head 16 is moved linearly until the center of the irradiation head 16 moves from position P3 to position P4 shown in FIG. 6.

[0044] Next, a peeling layer 15 is formed in the entire region (first inner region) existing between the first intermediate region and the center C of the ingot 11. Specifically, while appropriately irradiating the laser beam LB from the irradiation head 16, linear movement of the irradiation head 16 and switching of the traveling direction of the irradiation head 16 are repeated until the center of the irradiation head 16 moves from position P4 to position P5 shown in FIG.

[0045] As a result, a peeling layer 15 is formed over substantially the entirety of one of two semi-cylindrical regions that pass through the center C of the ingot 11 and have a boundary surface that is parallel to the X-axis direction (processing feed direction). Next, the irradiation head 16 is moved in the Y-axis direction so that the region on the other end side of the ingot 11 in the Y-axis direction is positioned in the opposite direction to the X-axis direction when viewed from the irradiation head 16. That is, the irradiation head 16 is moved linearly until the center of the irradiation head 16 reaches a position P6 from position P5 shown in FIG.

[0046] Next, while irradiating the laser beam LB from the irradiation head 16, the irradiation head 16 is moved in the opposite direction to the X-axis direction (the processing feed direction) so as to pass from one end to the other end in the X-axis direction of the ingot 11 in a plan view. In other words, while irradiating the laser beam LB from the irradiation head 16, the irradiation head 16 is moved linearly until the center of the irradiation head 16 moves from position P6 to position P7 shown in FIG.

[0047] As a result, as described above, peeling layer 15 is formed in the region (second outer region) on the other end side in the Y-axis direction of ingot 11. Next, irradiation head 16 is moved in the opposite direction along the Y-axis direction so that the movement distance of irradiation head 16 is longer than the width along the Y-axis direction of peeling layer 15. In other words, irradiation head 16 is moved linearly until the center of irradiation head 16 reaches position P8 from position P7 shown in FIG.

[0048] Next, while irradiating the laser beam LB from the irradiation head 16, the irradiation head 16 is moved in the X-axis direction (processing feed direction) so as to pass from one end to the other end in the X-axis direction of the ingot 11 in a plan view. In other words, while irradiating the laser beam LB from the irradiation head 16, the irradiation head 16 is moved linearly until the center of the irradiation head 16 moves from position P8 to position P9 shown in FIG.

[0049] As a result, a peeling layer 15 is formed in a region (second intermediate region) closer to the center C of the ingot 11 than the second outer region. Next, the irradiation head 16 is moved in the opposite direction to the Y-axis direction so that the movement distance of the irradiation head 16 is longer than the width of the peeling layer 15 along the Y-axis direction. In other words, the irradiation head 16 is moved linearly until the center of the irradiation head 16 reaches a position P10 from position P9 shown in FIG. 6 .

[0050] Next, a peeling layer 15 is formed in the entire region (second inner region) existing between the second intermediate region and the center C of the ingot 11. Specifically, while appropriately irradiating a laser beam LB from the irradiation head 16, linear movement of the irradiation head 16 and switching of the traveling direction of the irradiation head 16 are repeated until the center of the irradiation head 16 moves from position P10 to position P11 shown in FIG.

[0051] As a result, the peeling layer 15 is formed over almost the entire other of the two semi-cylindrical regions. Specifically, the peeling layer 15 is formed in each of a plurality of regions that are aligned along the processing feed direction of the ingot 11 and that are at approximately the same depth from the surface 11a of the ingot 11.

[0052] 6, for convenience, the trajectory of the irradiation head 16 when five parallel peeling layers 15 are formed in the semi-cylindrical region included in the ingot 11 is shown, but the number of peeling layers 15 formed in this semi-cylindrical region is not limited to five. If the number of peeling layers 15 formed in the semi-cylindrical region is even, the movement of the irradiation head 16 along the X-axis direction when forming the peeling layer 15 in the other of the two cylindrical regions will be reversed.

[0053] This completes the separation layer forming step (S1). Next, the substrate is separated from the ingot 11 starting from the separation layer 15 (separation step: S2). Figures 9(A) and 9(B) are partial cross-sectional side views each showing a schematic view of an example of the separation step (S2).

[0054] This separation step (S2) is performed, for example, in a separation apparatus 18 shown in Figures 8(A) and 8(B). This separation apparatus 18 has a circular upper surface (holding surface) that is wider than the front surface 11a and back surface 11b of the ingot 11 on which the peeling layer 15 is formed, and has a cylindrical holding table 20 that holds the ingot 11 on this holding surface.

[0055] A cylindrical porous plate (not shown) is exposed on the holding surface of the holding table 20. Furthermore, this porous plate is in communication with a suction source (not shown) such as a vacuum pump via a flow path or the like provided inside the holding table 20. When this suction source is activated, a negative pressure is generated in the space near the holding surface of the holding table 20.

[0056] A separation unit 22 is provided above the holding table 20. The separation unit 22 has a cylindrical support member 24. A ball screw type lifting mechanism (not shown) and a rotary drive source such as a motor are connected to the upper part of the support member 24. The separation unit 22 moves up and down by operating the lifting mechanism. The support member 24 rotates around a rotation axis that passes through the center of the support member 24 and is perpendicular to the holding surface of the holding table 20 by operating the rotary drive source.

[0057] The lower end of the support member 24 is fixed to the center of the upper part of a cylindrical base 26. A plurality of movable members 28 are provided below the outer peripheral region of the base 26 at approximately equal intervals along the circumferential direction of the base 26. The movable members 28 have plate-shaped erected portions 28a extending downward from the lower surface of the base 26.

[0058] The upper end of this standing portion 28a is connected to an actuator such as an air cylinder built into the base 26, and by operating this actuator, the movable member 28 moves along the radial direction of the base 26. In addition, on the inner surface of the lower end of this standing portion 28a, a plate-shaped wedge portion 28b is provided which extends toward the center of the base 26 and becomes thinner as it approaches the tip.

[0059] In the separation device 18, the separation step (S2) is performed, for example, in the following order: First, the ingot 11 is placed on the holding table 20 so that the center of the back surface 11b of the ingot 11 on which the peeling layer 15 is formed is aligned with the center of the holding surface of the holding table 20.

[0060] Next, a suction source communicating with the porous plate exposed on the holding surface is operated so that the ingot 11 is held by the holding table 20. Next, the actuator is operated so that each of the plurality of movable members 28 is positioned radially outward of the base 26.

[0061] Next, the lifting mechanism is operated to position the tip of each wedge portion 28b of the multiple movable members 28 at a height corresponding to the peeling layer 15 formed inside the ingot 11. Next, the actuator is operated to drive the wedge portion 28b into the side surface 11c of the ingot 11 (see FIG. 9(A)). Next, the rotation drive source is operated to rotate the wedge portion 28b driven into the side surface 11c of the ingot 11.

[0062] Next, the lifting mechanism is operated to lift the wedge portion 28b (see FIG. 8(B)). After the wedge portion 28b is driven into the side surface 11c of the ingot 11 and rotated as described above, the wedge portion 28b is lifted, whereby the crack 15b contained in the separation layer 15 is further extended. As a result, the front surface 11a side and the back surface 11b side of the ingot 11 are separated. That is, the substrate 17 is produced from the ingot 11, starting from the separation layer 15.

[0063] It should be noted that the wedge portion 28b does not need to be rotated if the front surface 11a and the back surface 11b of the ingot 11 are separated when the wedge portion 28b is driven into the side surface 11c of the ingot 11. Alternatively, the actuator and the rotary drive source may be operated simultaneously to drive the rotating wedge portion 28b into the side surface 11c of the ingot 11.

[0064] In the above-described method for manufacturing a substrate, the peeling layer 15 is finally formed in a region (second inner region) close to the center of the ingot 11 among multiple regions along the processing feed direction of the ingot 11. Here, since the ingot 11 has a cylindrical shape, the second inner region is wider than the other regions (for example, the second outer region) where the peeling layer 15 is formed.

[0065] Therefore, when separation layer 15 is formed last in the second inner region, the internal stress of ingot 11 is dispersed over a wider range than when separation layer 15 is formed last in the second outer region. In this case, it is possible to suppress the propagation of cracks 15b, which have a large component in the thickness direction of the workpiece, from modified portion 15a contained in separation layer 15. As a result, in the above-described substrate manufacturing method, it is possible to suppress a decrease in productivity of substrate 17 without increasing the amount of material discarded when substrate 17 is planarized.

[0066] Furthermore, in the above-described method for manufacturing a substrate, the peeling layer 15 is formed by relatively moving the ingot 11 and a plurality of focusing points aligned along the Y-axis direction (crystal orientation

[0001] ) along the X-axis direction (crystal orientation

[0010] ). In this case, the amount of material discarded when manufacturing the substrate 17 from the ingot 11 can be further reduced, and the productivity of the substrate 17 can be further improved.

[0067] This point will be explained in detail below. First, single crystal silicon generally cleaves most easily along a specific crystal plane included in the crystal plane {111}, and second most easily along a specific crystal plane included in the crystal plane {110}. Therefore, for example, when the crystal orientation of the single crystal silicon constituting the ingot 11 is <110> When a modified portion is formed along a specific crystal orientation (for example, crystal orientation

[0011] ) included in the crystal plane {111}, many cracks are generated from this modified portion, extending along a specific crystal plane included in the crystal plane {111}.

[0068] On the other hand, the crystal orientation of single crystal silicon <100> When multiple modified areas are formed in a region along a specific crystal orientation included in the above, so that they are lined up in a direction perpendicular to the direction in which this region extends in a planar view, many cracks will occur from each of these multiple modified areas, extending along crystal planes {N10} (N is an integer with an absolute value of 10 or less, excluding 0) that are parallel to the direction in which the region extends.

[0069] For example, as in the substrate manufacturing method described above, when multiple modified portions 15a are formed in a region along the crystal orientation

[0010] so as to be aligned along the crystal orientation

[0001] , an increasing number of cracks will extend from each of the multiple modified portions 15a along the crystal planes {N10} (N is a natural number less than or equal to 10) that are parallel to the crystal orientation

[0010] .

[0070] Specifically, when a plurality of modified regions 15a are formed in this way, cracks tend to propagate in the following crystal planes.

number

number

[0071] The angle that the crystal plane (100) exposed on the front surface 11a and back surface 11b of the ingot 11 makes with the crystal plane {N10} parallel to the crystal orientation

[0010] is 45° or less. On the other hand, the angle that the crystal plane (100) makes with a specific crystal plane included in the crystal plane {111} is about 54.7°.

[0072] Therefore, in the above-described substrate manufacturing method, the peeling layer 15 is likely to be wider and thinner than when a plurality of modified portions are formed in a region along the crystal orientation

[0011] of the single crystal silicon so as to be aligned in a direction perpendicular to the direction in which this region extends in a plan view. As a result, in the above-described substrate manufacturing method, the amount of material wasted when manufacturing the substrate 17 from the ingot 11 can be further reduced, and the productivity of the substrate 17 can be further improved.

[0073] The above-described method for manufacturing a substrate is one embodiment of the present invention, and the present invention is not limited to the above-described method. For example, the ingot used to manufacture a substrate in the present invention is not limited to the ingot 11 shown in Figures 1 and 2. Specifically, in the present invention, a substrate may be manufactured from an ingot made of single-crystal silicon in which crystal planes not included in the crystal plane {100} are exposed on the front and back surfaces.

[0074] In the present invention, the substrate may be manufactured from a cylindrical ingot having a notch formed on the side surface. Alternatively, in the present invention, the substrate may be manufactured from a cylindrical ingot having neither an orientation flat nor a notch formed on the side surface. In the present invention, the substrate may be manufactured from a cylindrical ingot made of a semiconductor material other than silicon, such as silicon carbide.

[0075] Furthermore, the structure of the laser processing device used in the present invention is not limited to the structure of the above-described laser processing device 2. For example, the present invention may be implemented using a laser processing device provided with a movement mechanism that moves the holding table 4 along each of the X-axis, Y-axis, and / or Z-axis directions.

[0076] That is, in the present invention, it is sufficient that the holding table 4 that holds the ingot 11 and the irradiation head 16 of the laser beam irradiation unit 6 that irradiates the laser beam LB can move relatively along each of the X-axis, Y-axis, and Z-axis directions, and there are no limitations on the structure for this purpose.

[0077] Furthermore, in the peeling layer forming step (S1) of the present invention, the order of forming the peeling layer 15 in a plurality of regions along the processing feed direction of the ingot 11 is not limited to the above-mentioned order (the order of the first outer region, the first intermediate region, the first inner region, the second outer region, the second intermediate region, and the second inner region). That is, in the present invention, the trajectory of the irradiation head 16 when irradiating the ingot 11 with the laser beam LB is not limited to the trajectory shown by the dotted line in FIG.

[0078] 9(A) and 9(B) are top views each showing a schematic example of the trajectory of the moving irradiation head 16 in the peeling layer forming step (S1). Specifically, when the laser beam LB is irradiated onto the ingot 11 while the irradiation head 16 is moving as shown in FIG. 9(A), one peeling layer 15 is formed alternately in the two semi-cylindrical regions.

[0079] In this case, the peeling layer is formed in the order of the first outer region, the second outer region, the first middle region, the second middle region, the first inner region, and the second inner region among the five regions (along the processing feed direction) included in each semi-cylindrical region.

[0080] 9(B), when the laser beam LB is irradiated onto the ingot 11 while the irradiation head 16 is moving, two peeling layers 15 are formed alternately in the two semi-cylindrical regions. In the peeling layer forming step (S1) of the present invention, three or more peeling layers 15 may be formed alternately in the two semi-cylindrical regions.

[0081] In these cases, the peeling layer is formed in the order of the outermost region among the five regions (five regions) included in each semi-cylindrical region along the processing feed direction. In other words, the peeling layer 15 is formed in the order of the first outer region, the first middle region, the second outer region, the second middle region, the first inner region, and the second inner region.

[0082] Furthermore, in the release layer forming step (S1) of the present invention, the release layer 15 may be formed last in the first inner region, not in the second inner region. For example, in the release layer forming step (S1) of the present invention, the release layer 15 may be formed in the order of the first outer region, the first intermediate region, the second outer region, the second intermediate region, the second inner region, and the first inner region.

[0083] 9(A) and 9(B), in order to clarify the trajectory of the irradiation head 16, the trajectory of the irradiation head 16 is drawn so as not to overlap or intersect even in the region outside the ingot 11, but the trajectory may intersect and / or overlap. That is, in the peeling layer forming step (S1) of the present invention, for example, in order to minimize the moving distance of the irradiation head 16, the irradiation head 16 may be moved so that the trajectories intersect and / or overlap in the region outside the ingot 11.

[0084] In the present invention, the separation layer forming step (S1) may be performed again after the separation layer forming step (S1). In this case, the density of the modified portions 15a and the cracks 15b included in the already formed separation layer 15 increases. This makes it easier to separate the substrate 17 from the ingot 11 in the separation step (S2).

[0085] Furthermore, the separation step (S2) of the present invention may be performed using an apparatus other than the separation apparatus 18 shown in Figures 8(A) and 8(B). Figures 10(A) and 10(B) are partial cross-sectional side views schematically showing an example of the separation step (S2) performed using an apparatus other than the separation apparatus 18.

[0086] The separation device 30 shown in Figures 10(A) and 10(B) has a circular upper surface (holding surface) that is wider than the front surface 11a and back surface 11b of the ingot 11 on which the peeling layer 15 is formed, and has a cylindrical holding table 32 that holds the ingot 11 on this holding surface.

[0087] A cylindrical porous plate (not shown) is exposed on the holding surface of the holding table 32. Furthermore, this porous plate is in communication with a suction source (not shown) such as a vacuum pump via a flow path or the like provided inside the holding table 32. Therefore, when the suction source operates, a negative pressure is generated in the space near the holding surface of the holding table 32.

[0088] A separation unit 34 is provided above the holding table 32. The separation unit 34 has a cylindrical support member 36. A ball screw type lifting mechanism (not shown), for example, is connected to the top of the support member 36, and the separation unit 34 moves up and down by operating this lifting mechanism.

[0089] The lower end of the support member 36 is fixed to the center of the upper part of a cylindrical suction plate 38. A plurality of suction ports are formed in the lower surface of the suction plate 38, and each of the plurality of suction ports is connected to a suction source (not shown), such as a vacuum pump, via a flow path or the like provided inside the suction plate 38. Therefore, when the suction source is operated, a negative pressure is generated in the space near the lower surface of the suction plate 38.

[0090] In the separation device 30, the separation step (S2) is performed, for example, in the following order: Specifically, first, the ingot 11 is placed on the holding table 32 so that the center of the back surface 11b of the ingot 11 on which the peeling layer 15 is formed is aligned with the center of the holding surface of the holding table 32.

[0091] Next, a suction source communicating with the porous plate exposed on the holding surface is operated so that the ingot 11 is held by the holding table 32. Next, the lifting mechanism is operated to lower the separation unit 34 so that the lower surface of the suction plate 38 contacts the surface 11a of the ingot 11.

[0092] Next, a suction source communicating with the plurality of suction ports is operated so that the front surface 11a side of the ingot 11 is sucked through the plurality of suction ports formed in the suction plate 38 (see FIG. 10(A)). Next, the lifting mechanism is operated to lift the separation unit 34 so that the suction plate 38 is separated from the holding table 32 (see FIG. 10(B)).

[0093] At this time, an upward force acts on the front surface 11a side of the ingot 11, which is being sucked through the multiple suction ports formed in the suction plate 38. As a result, the crack 15b contained in the peeling layer 15 further extends, and the front surface 11a side and the back surface 11b side of the ingot 11 are separated. In other words, the substrate 17 is produced from the ingot 11, starting from the peeling layer 15.

[0094] Furthermore, in the separation step (S2) of the present invention, prior to separation of the front surface 11a side and the back surface 11b side of the ingot 11, ultrasonic waves may be applied to the front surface 11a side of the ingot 11. In this case, the cracks 15b contained in the peeling layer 15 are further extended, making it easier to separate the front surface 11a side and the back surface 11b side of the ingot 11.

[0095] Furthermore, in the present invention, prior to the separation layer forming step (S1), the surface 11a of the ingot 11 may be flattened by grinding or polishing (flattening step). For example, this flattening may be performed when manufacturing a plurality of substrates from the ingot 11. Specifically, when the ingot 11 is separated at the separation layer 15 to manufacture the substrates 17, irregularities are formed on the newly exposed surface of the ingot 11 that reflect the distribution of the modified portions 15a and cracks 15b contained in the separation layer 15.

[0096] Therefore, when a new substrate is manufactured from this ingot 11, it is preferable to flatten the surface of ingot 11 prior to the peeling layer forming step (S1). This makes it possible to suppress diffuse reflection of the laser beam LB irradiated onto ingot 11 at the surface of ingot 11 in the peeling layer forming step (S1). Similarly, in the present invention, the surface of substrate 17 separated from ingot 11 on the peeling layer 15 side may be flattened by grinding or polishing.

[0097] In the present invention, a substrate may be manufactured using a cylindrical bare wafer made of a semiconductor material such as silicon or silicon carbide as the workpiece. The bare wafer has a thickness, for example, two to five times that of the substrate to be manufactured. The bare wafer is manufactured by separating it from an ingot made of a semiconductor material such as silicon or silicon carbide by a method similar to the method described above. In this case, the substrate can also be expressed as being manufactured by repeating the above method twice.

[0098] In addition, in the present invention, a cylindrical device wafer may be manufactured by forming semiconductor devices on one surface of the bare wafer, and the substrate may be manufactured using the device wafer as a workpiece. In addition, the structures and methods according to the above-described embodiments may be appropriately modified and implemented without departing from the scope of the object of the present invention. [Explanation of symbols]

[0099] 2: Laser processing equipment 4: Holding table 6: Laser beam irradiation unit 8: Laser oscillator 10: Attenuator 11: Ingot (11a: front surface, 11b: back surface, 11c: side surface) 12: Branch unit 13: Orientation Flat 14: Mirror 15: Peeling layer (15a: modified part, 15b: crack) 16: Irradiation head 17: Circuit board 18: Separation device 20: Holding table 22: Separation unit 24: Support member 26: Foundation 28: Movable member (28a: Standing portion, 28b: Wedge portion) 30: Separation device 32: Holding table 34: Separation unit 36: Support member 38: Suction plate

Claims

1. A method for manufacturing a substrate from a cylindrical workpiece having a circular first surface and a circular second surface located on the opposite side of the first surface, comprising: a peeling layer forming step in which a focal point of a laser beam having a wavelength that passes through the material constituting the workpiece is positioned inside the workpiece, and the workpiece and the focal point are repeatedly moved relative to each other along a processing feed direction parallel to the first surface, thereby forming a peeling layer including a modified portion formed around the focal point and a crack extending from the modified portion in each of a plurality of regions along the processing feed direction of the workpiece; a separation step of separating the substrate from the workpiece starting from the release layer, The plurality of regions are: a first outer region included in one of two semi-cylindrical regions having a boundary surface that passes through the center of the workpiece and is parallel to the machining feed direction; a first intermediate region included in one of the two semi-cylindrical regions and closer to the center of the workpiece than the first outer region; a first inner region included in one of the two semi-cylindrical regions and closer to the center of the workpiece than the first intermediate region; a second outer region included in the other of the two semi-cylindrical regions; a second intermediate region included in the other of the two semi-cylindrical regions and closer to the center of the workpiece than the second outer region; a second inner region included in the other of the two semi-cylindrical regions and closer to the center of the workpiece than the second intermediate region; A method for manufacturing a substrate, characterized in that in the peeling layer formation step, the peeling layer is formed in the order of the first outer region, the first intermediate region, the first inner region, the second outer region, the second intermediate region and the second inner region.

2. A method for manufacturing a substrate from a cylindrical workpiece having a circular first surface and a circular second surface located on the opposite side of the first surface, comprising: a peeling layer forming step in which a focal point of a laser beam having a wavelength that passes through the material constituting the workpiece is positioned inside the workpiece, and the workpiece and the focal point are repeatedly moved relative to each other along a processing feed direction parallel to the first surface, thereby forming a peeling layer including a modified portion formed around the focal point and a crack extending from the modified portion in each of a plurality of regions along the processing feed direction of the workpiece; a separation step of separating the substrate from the workpiece starting from the release layer, The plurality of regions are: a first outer region included in one of two semi-cylindrical regions having a boundary surface that passes through the center of the workpiece and is parallel to the machining feed direction; a first intermediate region included in one of the two semi-cylindrical regions and closer to the center of the workpiece than the first outer region; a first inner region included in one of the two semi-cylindrical regions and closer to the center of the workpiece than the first intermediate region; a second outer region included in the other of the two semi-cylindrical regions; a second intermediate region included in the other of the two semi-cylindrical regions and closer to the center of the workpiece than the second outer region; a second inner region included in the other of the two semi-cylindrical regions and closer to the center of the workpiece than the second intermediate region; A method for manufacturing a substrate, characterized in that in the release layer formation step, the release layer is formed in the order of the first outer region, the first intermediate region, the second outer region, the second intermediate region, the first inner region and the second inner region.

3. 3. The method for manufacturing a substrate according to claim 1, wherein the material is single crystal silicon.

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