Method for manufacturing single crystal silicon substrate

Abstract

[Project] Improve the productivity of the substrate when manufacturing a substrate from a workpiece such as an ingot using a laser beam. [Solution] A first processing step is performed to form a modified portion in a plurality of first regions, and then a second processing step is performed to form a modified portion and a crack in a plurality of second regions. Here, the crack formed in the second processing step is likely to extend toward the modified portion formed in the first processing step. By doing so, the direction in which the crack is likely to extend in the second processing step can be arbitrarily set. In this case, it becomes easier to thin the release layer formed inside the workpiece. Furthermore, if the release layer is thinned, the amount of workpiece material that is discarded during the cutting of the substrate from the workpiece and the planarization of the substrate is reduced. As a result, it becomes possible to improve the productivity of the substrate when manufacturing a substrate from a workpiece using a laser beam.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing a single-crystal silicon substrate, wherein the substrate is manufactured from a workpiece made of single-crystal silicon such that a specific crystal plane included in the crystal plane {100} is exposed on the surface and the back surface, respectively. Background Technology

[0002] A chip of a semiconductor device is generally manufactured using a disc-shaped single-crystal silicon substrate (hereinafter also simply referred to as a "substrate"). This substrate is cut from a cylindrical single-crystal silicon ingot (hereinafter also simply referred to as an "ingot") 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 margin is relatively large, around 300 μm. In addition, fine irregularities are formed on the surface of the substrate cut in this way, and the substrate is curved overall (bending occurs in the substrate). Therefore, in this substrate, it is necessary to flatten the surface by performing lapping, etching, and / or polishing on the surface.

[0004] In this case, the amount of single-crystal silicon material ultimately used as a substrate is about two-thirds of the total material amount of the ingot. That is, about one-third of the total material amount of the ingot is discarded during the cutting of the substrate from the ingot and the planarization of the substrate. Therefore, when manufacturing substrates using a wire saw in this way, productivity is low.

[0005] Taking this into account, a method has been proposed to form a peeling layer containing a modified portion and a crack extending from the modified portion inside the ingot using a laser beam of a wavelength that passes through single-crystal silicon, and then to separate the substrate from the ingot starting from this peeling layer (see, for example, Patent Document 2). By doing so, the productivity of the substrate can be improved compared to the case where the substrate is manufactured from the ingot using a wire saw. Prior art literature

[0006] Japanese Published Patent Application No. Hei 9-262826 Japanese Published Patent Application No. 2022-25566 The problem to be solved

[0007] Single-crystal silicon is most prone to cleavage in specific crystal planes included in crystal planes {111}. For example, if a laser beam is irradiated along a specific crystal orientation

[0011] included in crystal orientation <110> to form a modified part inside an ingot in which a specific crystal plane (100) included in crystal planes {100} is exposed on both the front and back sides, then many cracks are generated along crystal planes parallel to the crystal orientation

[0011] among the specific crystal planes included in crystal planes {111} (specifically, the crystal plane shown in (1) below).

[0008]

[0009] Here, the angle formed by the crystal plane (100) with respect to a specific crystal plane included in the crystal plane {111} is approximately 54.7°. Therefore, when a laser beam is irradiated onto the ingot as described above, cracks are generated in greater quantities along the thickness direction than along the direction parallel to the surface and back surface of the ingot.

[0010] In this case, the peeling layer formed inside the ingot becomes thicker, and the amount of ingot and substrate material that is discarded during the cutting of the substrate from the ingot and the planarization of the substrate increases. Taking this into account, the objective of the present invention is to provide a method for manufacturing a single-crystal silicon substrate that can improve the productivity of the substrate when manufacturing a substrate from a workpiece such as an ingot using a laser beam. means of solving the problem

[0011] According to the present invention, a method for manufacturing a single-crystal silicon substrate comprises manufacturing a substrate from a workpiece made of single-crystal silicon such that a specific crystal plane included in a crystal plane {100} is exposed on the front surface and the back surface, respectively, comprising: a peeling layer forming step for forming a peeling layer including a modified portion and a crack extending from the modified portion inside the workpiece; and a separation step for separating the substrate from the workpiece starting from the peeling layer after performing the peeling layer forming step, wherein the peeling layer forming step comprises: a first processing step for forming the modified portion in a plurality of first regions spaced apart from each other in a second direction that is parallel to the specific crystal plane and orthogonal to the first direction, and extending along a first direction in which each is parallel to the specific crystal plane and the angle formed with respect to a specific crystal orientation included in crystal orientation <100> is 5° or less; and after performing the first processing step, each extending along the first direction Together, the method has a second processing step for forming the modified portion and the crack in a plurality of second regions spaced apart from each other in the second direction, wherein any of the plurality of second regions is located between an adjacent pair of first regions among the plurality of first regions, and any of the plurality of first regions is located between an adjacent pair of second regions among the plurality of second regions, and the first processing step is performed by alternately repeating a first laser beam irradiation step in which a focusing point, where a laser beam of a wavelength passing through the single crystal silicon is focused, is located at a first depth from the surface of the workpiece and inside any of the plurality of first regions, and the focusing point and the workpiece are moved relatively along the first direction, and a first output transfer step in which the position where the focusing point is formed and the workpiece are moved relatively along the second direction, and the second processing step isA method for manufacturing a single-crystal silicon substrate is provided, wherein the focusing point is positioned at a second depth different from the first depth from the surface of the workpiece and within any of the plurality of second regions, and the focusing point and the workpiece are moved relatively along the first direction, and the second output transfer step is performed by alternately repeating the second laser beam irradiation step and the second output transfer step, wherein the power of the laser beam focused at the focusing point during the second laser beam irradiation step is greater than the power of the laser beam focused at the focusing point during the first laser beam irradiation step.

[0012] Also, preferably, the second depth is deeper than the first depth.

[0013] Also, preferably, the angle formed by a first straight line along the first direction passing through the center of a second region located between one of the adjacent pair of first regions and a first plane passing through the center of one of the adjacent pair of first regions with respect to the surface and the back surface of the workpiece is 45° or less, and the angle formed by a second plane passing through the first straight line and the center of the other of the adjacent pair of first regions with respect to the surface and the back surface of the workpiece is 45° or less. Effects of the invention

[0014] In the present invention, a first processing step is performed to form a modified portion in a plurality of first regions, and then a second processing step is performed to form a modified portion and a crack in a plurality of second regions.

[0015] Here, when a modified part is formed in the first processing step, the volume of the workpiece expands, and internal stress is generated in the workpiece. In addition, the crack formed in the second processing step is prone to extending toward the point where internal stress is generated.

[0016] Therefore, the crack formed in the second processing step is likely to extend toward the modified part formed in the first processing step. Thus, in the present invention, the direction in which the crack is likely to extend in the second processing step can be arbitrarily set.

[0017] In this case, it becomes easier to thin the release layer formed inside the workpiece. And, when the release layer is thinned, the amount of workpiece material that is discarded during cutting the substrate from the workpiece and planarizing the substrate is reduced. As a result, in the present invention, it is possible to improve the productivity of the substrate when manufacturing a substrate from a workpiece using a laser beam. Brief explanation of the drawing

[0018] FIG. 1 is a perspective view schematically showing an example of an ingot used in the manufacture of a substrate. FIG. 2 is a top view schematically showing the ingot shown in FIG. 1. FIG. 3 is a flowchart schematically illustrating an example of a method for manufacturing a single-crystal silicon substrate, in which a substrate is manufactured from an ingot that is the workpiece. FIG. 4 is a top view schematically showing a plurality of regions included in an ingot. Figure 5 is a flowchart schematically illustrating an example of the peeling layer formation step shown in Figure 3. FIG. 6 is a schematic diagram showing an example of a laser processing device used to form a peeling layer inside an ingot. FIG. 7 is a top view schematically showing an ingot being held in a holding table of a laser processing device. FIG. 8 is a flowchart schematically illustrating an example of the first processing step shown in FIG. 5. FIG. 9(A) is a top view schematically showing the appearance of the first laser beam irradiation step shown in FIG. 8, and FIG. 9(B) is a partial cross-sectional side view schematically showing the appearance of the first laser beam irradiation step shown in FIG. 8. FIG. 10 is a cross-sectional view schematically showing a peeling layer including a modified portion formed inside an ingot and a crack extending from the modified portion in the first laser beam irradiation step shown in FIG. 8. FIG. 11 is a cross-sectional view schematically showing a peeling layer formed inside an ingot by performing the first laser beam irradiation step shown in FIG. 8 twice. FIG. 12 is a flowchart schematically illustrating an example of the second processing step shown in FIG. 5. FIG. 13 is a cross-sectional view schematically showing a peeling layer formed inside an ingot by performing the second laser beam irradiation step shown in FIG. 12. Figures 14(A) and 14(B) are each schematic cross-sectional side views illustrating an example of the separation step shown in Figure 3. Figure 15 is a graph showing the width of the peeling layer formed inside a workpiece made of single-crystal silicon when a laser beam is irradiated onto a region following a different crystal orientation. Figures 16(A) and 16(B) are each schematic cross-sectional side views illustrating different examples of the separation steps shown in Figure 3. Specific details for implementing the invention

[0019] An embodiment of the present invention will be described with reference to the attached drawings. FIG. 1 is a perspective view schematically showing an example of an ingot used in the manufacture of a substrate, and FIG. 2 is a top view schematically showing the ingot shown in FIG. 1.

[0020] In addition, in FIG. 1, the crystal plane of single-crystal silicon exposed in the plane contained in this ingot is also shown. Also, in FIG. 2, the crystal orientation of the single-crystal silicon constituting this ingot is also shown.

[0021] In the ingot (11) shown in FIGS. 1 and 2, a specific crystal plane (here, for convenience, referred to as crystal plane (100)) included in the crystal plane {100} is exposed on the surface (11a) and the back side (11b), respectively. That is, in this ingot (11), the perpendicular (crystal axis) of the surface (11a) and the back side (11b), respectively, follows the crystal orientation

[0100] .

[0022] In addition, in the ingot (11), the crystal plane (100) is manufactured to be exposed on the surface (11a) and the back side (11b), respectively, but due to processing errors during manufacturing, a slightly inclined plane from the crystal plane (100) may be exposed on the surface (11a) and the back side (11b), respectively.

[0023] Specifically, on each of the surface (11a) and back surface (11b) of the ingot (11), a plane may be exposed that forms an angle of 1° or less with respect to the crystal plane (100). That is, the crystal axis of the ingot (11) may follow a direction that forms an angle of 1° or less with respect to the crystal orientation

[0100] .

[0024] Also, an orientation flat (13) is formed on the side (11c) of the ingot (11), and the center C of the ingot (11) is located in a specific crystal orientation that is included in the crystal orientation <110> when viewed from the orientation flat (13) (here, for convenience, it is referred to as crystal orientation

[0011] ). That is, in this orientation flat (13), the crystal plane (011) of single-crystal silicon is exposed.

[0025] FIG. 3 is a flowchart schematically illustrating an example of a method for manufacturing a single-crystal silicon substrate, wherein the substrate is manufactured from an ingot (11) that is to be processed. In this method, first, a peeling layer is formed inside the ingot (11) and includes a modified portion and a crack extending from the modified portion (peeling layer formation step: S1).

[0026] In this peeling layer formation step (S1), peeling layers are formed sequentially on a plurality of regions included in the ingot (11). FIG. 4 is a top view schematically showing a plurality of regions included in the ingot (11). FIG. 5 is a flowchart schematically showing an example of the peeling layer formation step (S1) shown in FIG. 3.

[0027] In this peeling layer forming step (S1), first, a modified portion is formed in a plurality of first regions (11d) that are spaced apart from each other in crystal orientation

[0001] , each extending along crystal orientation

[0010] (first processing step: S11).

[0028] And, after the completion of the first processing step (S11), a modified area and crack are formed in a plurality of second regions (11e) located between adjacent pairs of first regions (11d), each extending along the crystal orientation

[0010] and also having a width along each crystal orientation

[0001] greater than that of each of the plurality of first regions (11d) (second processing step: S12).

[0029] Also, in the peeling layer formation step (S1), a peeling layer including a modified portion and a crack is formed inside the ingot (11) using a laser processing device. FIG. 6 is a schematic diagram showing an example of a laser processing device used when forming a peeling layer inside the ingot (11).

[0030] In addition, the X-axis direction (first direction) and the Y-axis direction (second direction) shown in FIG. 6 are directions that are orthogonal to each other on a horizontal plane, and the Z-axis direction is a direction that is orthogonal to each of the X-axis direction and the Y-axis direction (vertical direction). Also, in FIG. 6, some of the components of the laser processing device are shown as functional blocks.

[0031] The laser processing device (2) shown in FIG. 6 has a disc-shaped holding table (4). This holding table (4) has, for example, a circular upper surface (holding surface) parallel to the X-axis direction and the Y-axis direction. In addition, the holding table (4) has a disc-shaped porous plate (not shown) in which the upper surface is exposed on this holding surface.

[0032] In addition, this porous plate is connected to a suction source (not shown), such as an ejector, through a channel formed inside the holding table (4). And when this suction source operates, a suction force acts in the space near the holding surface of the holding table (4). Thus, for example, an ingot (11) placed on the holding surface can be held by the holding table (4).

[0033] Additionally, a laser beam irradiation unit (6) is formed 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 as a laser medium.

[0034] Then, the laser oscillator (8) irradiates a laser beam (LB) of pulsed form (e.g., frequency 60 kHz) of wavelength (e.g., 1064 nm or 1342 nm) that penetrates the material (single-crystal silicon) constituting the ingot (11).

[0035] This laser beam (LB) is supplied to a branching unit (12) after its output (power) is adjusted in an attenuator (10). This branching unit (12) has a spatial light modulator and / or a diffraction optical element (DOE), such as a liquid crystal phase control element called LCoS (Liquid Crystal on Silicon), for example.

[0036] And, the branching unit (12) branches the laser beam (LB) so that the laser beam (LB) irradiated from the irradiation head (16) described later onto the holding surface of the holding table (4) forms a plurality of (e.g., 4 or more, 16 or fewer) focusing points arranged along the Y-axis direction.

[0037] The laser beam (LB) branched from the branching unit (12) is reflected by the mirror (14) and guided to the irradiation head (16). The irradiation head (16) is equipped with a focusing lens (not shown) for focusing the laser beam (LB). Then, the laser beam (LB) focused by the focusing lens is directed to the holding surface side of the holding table (4), specifically directly below, with the central area of ​​the lower surface of the irradiation head (16) as the emission area.

[0038] Additionally, the irradiation head (16) of the laser beam irradiation unit (6) and the optical system (e.g., mirror (14)) for guiding the laser beam (LB) to the irradiation head (16) are connected to a moving mechanism (not shown). This moving mechanism includes, for example, a ball screw, etc. And, when this moving mechanism operates, the emission area of ​​the laser beam (LB) moves along the X-axis direction, the Y-axis direction and / or the Z-axis direction.

[0039] In addition, in the laser processing device (2), by operating this moving mechanism, the position (coordinates) in the X-axis direction, Y-axis direction, and Z-axis direction of the point of concentration where the laser beam (LB) irradiated from the irradiation head (16) to the holding surface side of the holding table (4) is concentrated can be adjusted.

[0040] When performing the peeling layer formation step (S1) in the laser processing device (2), first, the holding table (4) holds the ingot (11) with its surface (11a) facing upward. FIG. 7 is a top view schematically showing the holding table (4) of the laser processing device (2) holding the ingot (11).

[0041] This ingot (11) is held on a holding table (4) in such a state that the angle formed by the direction (crystallization orientation

[0011] ) from the orientation flat (13) toward the center C of the ingot (11) with respect to the X-axis direction and the Y-axis direction, respectively, is 45°.

[0042] That is, the ingot (11) is held on the holding table (4) in a state where, for example, the crystal orientation

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

[0001] is parallel to the Y-axis direction. When the ingot (11) is held on the holding table (4) in this manner, the first processing step (S11) is performed.

[0043] FIG. 8 is a flowchart schematically illustrating an example of the first processing step (S11) shown in FIG. 5. In this first processing step (S11), first, the focusing point where the laser beam (LB) is focused is positioned at a first depth from the surface (11a) of the ingot (11) and inside one of the plurality of first regions (11d), and the focusing point and the ingot (11) are moved relatively along the X-axis direction (crystal orientation

[0010] ) (first laser beam irradiation step: S111).

[0044] FIG. 9(A) is a top view schematically showing the appearance of the first laser beam irradiation step (S111) shown in FIG. 8, and FIG. 9(B) is a partial cross-sectional side view schematically showing the appearance of the first laser beam irradiation step (S111) shown in FIG. 8. Also, FIG. 10 is a cross-sectional view schematically showing a peeling layer including a modified part formed inside the ingot (11) and a crack extending from the modified part in the first laser beam irradiation step (S111) shown in FIG. 8.

[0045] In this first laser beam irradiation step (S111), for example, a peeling layer is first formed in a first region (11d) located at one end in the Y-axis direction (crystal orientation

[0001] ) among a plurality of first regions (11d). Specifically, first, the irradiation head (16) is positioned so that when viewed from a plane, the first region (11d) is located in the X-axis direction when viewed from the irradiation head (16) of the laser beam irradiation unit (6).

[0046] Next, the irradiation head (16) is raised so that a plurality of concentrated points formed by concentrating each branched laser beam (LB) are positioned at a height corresponding to a first depth from the surface (11a) of the ingot (11).

[0047] Next, while irradiating a laser beam (LB) from the irradiation head (16) toward the holding table (4), the irradiation head (16) is moved to pass from one end to the other end in the X-axis direction (crystal orientation

[0010] ) of the ingot (11) when viewed in a plane (see FIG. 9(A) and FIG. 9(B).

[0048] As the laser beam (LB) is irradiated and the irradiation head (16) moves, the multiple irradiation points and the ingot (11) move relative to each other along the X-axis direction (crystal orientation

[0010] ) while the multiple irradiation points are positioned at a first depth from the surface (11a) of the ingot (11).

[0049] In addition, the laser beam (LB) is branched and focused to form a plurality (e.g., 5) of focused points arranged at equal intervals in the Y-axis direction (crystal orientation

[0001] ) (see FIG. 10). At this time, the spacing between adjacent pairs of focused points is set to be, for example, 5 μm or more and 20 μm or less, typically 10 μm.

[0050] Also, the power of the laser beam (LB) concentrated at each of the multiple concentration points, that is, the power of the laser beam (LB) adjusted in the attenuator (10), is divided by a number of divisions (e.g., 5) to obtain a relatively small power, for example, 0.1 W or more and 0.3 W or less, typically 0.2 W.

[0051] Thus, within the ingot (11), a modified portion (15a) is formed with a disordered crystal structure of single-crystal silicon centered around each of the multiple concentration points. Also, when the modified portion (15a) is formed within the ingot (11), the volume of the ingot (11) expands, and internal stress is generated in the ingot (11).

[0052] And, inside the ingot (11), a crack (15b) extends from the modified portion (15a) to relieve this internal stress. As a result, a peeling layer (15) is formed inside the ingot (11) comprising a plurality of modified portions (15a) and a crack (15b) advancing from each of the plurality of modified portions (15a).

[0053] Additionally, in the first laser beam irradiation step (S111), although a modified portion (15a) is formed inside the ingot (11), a laser beam (LB) with low power such that cracks (15b) do not extend from the modified portion (15a) may be irradiated. That is, the peeling layer (15) formed in the first laser beam irradiation step (S111) does not need to contain cracks (15b).

[0054] And, in a situation where the laser beam (LB) irradiation of all of the multiple first regions (11d) is not completed (step (S112): NO), the location where the condensation point is formed and the ingot (11) are moved relative to each other along the Y-axis direction (crystal orientation

[0001] ) (first output transfer step: S113).

[0055] In this first output transfer step (S113), for example, the irradiation head (16) is moved along the Y-axis direction (crystal orientation

[0001] ) until the irradiation head (16) is positioned in the X-axis direction (crystal orientation

[0010] ) when viewed from the first area (11d) where the peeling layer (15) has already been formed and the first area (11d) where the peeling layer (15) has not been formed.

[0056] Next, the first laser beam irradiation step (S111) described above is performed again. When the first laser beam irradiation step (S111) is performed twice in this manner, as shown in FIG. 11, a peeling layer (15) (peeling layer (15-2)) that is parallel to the already formed peeling layer (15-1) and is also spaced apart from the peeling layer (15-1) in the Y-axis direction (crystal orientation

[0001] ) is formed inside the ingot (11).

[0057] Additionally, the first output transfer step (S113) and the first laser beam irradiation step (S111) are alternately repeated until a peeling layer (15) is formed on all of the plurality of first regions (11d) included in the ingot (11). Then, when a peeling layer (15) is formed on all of the plurality of first regions (11d) (step (S112): YES), a second processing step (S12) is performed.

[0058] FIG. 12 is a flowchart schematically illustrating an example of the second processing step (S12) shown in FIG. 5. In this second processing step (S12), first, the focusing point where the laser beam (LB) is focused is positioned at a second depth from the surface (11a) of the ingot (11) and inside any of the plurality of second regions (11e), and the focusing point and the ingot (11) are moved relatively along the X-axis direction (crystal orientation

[0010] ) (second laser beam irradiation step: S121).

[0059] In addition, the second depth is a depth different from the first depth described above, for example, deeper than the first depth. For example, the difference between the first depth and the second depth is greater than 0 μm and less than or equal to 120 μm. Also, this difference is set to be shorter than the interval between the plurality of first regions (11d) and the plurality of second regions (11e) formed.

[0060] Specifically, this difference is set so that the distance between the straight line along the X-axis direction located at the center in the Y-axis direction of the second region (11e) and the straight line along the X-axis direction located at the center in the Y-axis direction of the first region (11d) adjacent to the second region (11e) is shorter when viewed in a plane.

[0061] That is, the first depth and the second depth are set such that the angle formed by the plane passing through both straight lines with respect to the surface (11a) and back surface (11b) of the ingot (11) is 45° or less. Additionally, this angle is preferably 40° or less, more preferably 35° or less, and most preferably 30° or less.

[0062] Also, in the laser processing device (2), by changing the position of the irradiation head (16) in the Z-axis direction, the point where the laser beam (LB) is concentrated can be positioned at a second depth from the surface (11a) of the ingot (11).

[0063] Also, in the second laser beam irradiation step (S121), the laser beam (LB) is irradiated from the irradiation head (16) toward the holding table (4) in the same way as in the first laser beam irradiation step (S111) described above, while moving the irradiation head (16) along the X-axis direction (crystal orientation

[0010] ) and the Y-axis direction (crystal orientation

[0001] ).

[0064] As the laser beam (LB) is irradiated and the irradiation head (16) moves, the multiple irradiation points and the ingot (11) move relative to each other along the X-axis direction (crystal orientation

[0010] ) while the multiple irradiation points are positioned at a second depth from the surface (11a) of the ingot (11).

[0065] In addition, the power of the laser beam (LB) focused at each of the multiple focusing points during the second laser beam irradiation step (S121) is adjusted to be greater than the power of the laser beam (LB) focused at each of the multiple focusing points during the first laser beam irradiation step (S111).

[0066] For example, in the second laser beam irradiation step (S121), the power of the laser beam (LB) focused at each of the plurality of focusing points is set to, for example, greater than 0.3 W and less than or equal to 0.6 W.

[0067] Thus, within the ingot (11), as shown in FIG. 13, a modified portion (15c) is formed with a disordered crystal structure of single-crystal silicon centered around each of the plurality of focusing points. In addition, in the second laser beam irradiation step (S121), the power of the laser beam (LB) focused at each of the plurality of focusing points is greater than in the first laser beam irradiation step (S111), so the size of the modified portion (15c) is also larger than that of the modified portion (15a).

[0068] Also, since the volume expansion of the ingot (11) accompanying the formation of the modified part (15c) is greater than the volume expansion accompanying the formation of the modified part (15a), in the second laser beam irradiation step (S121), internal stress greater than that in the first laser beam irradiation step (S111) is generated in the ingot (11).

[0069] And, inside the ingot (11), a crack (15d) larger than the crack (15b) extends from the modified part (15c) to relieve this internal stress. Also, the crack (15d) that occurs inside the ingot (11) is likely to extend toward the point where internal stress is generated in the ingot (11).

[0070] For this reason, the crack (15d) extending from the modified portion (15c) is likely to extend toward the modified portion (15a) and / or crack (15b) included in the already formed peeling layer (15) (peeling layer (15-1, 15-2). As a result, a peeling layer (15) (peeling layer (15-3)) containing a plurality of modified portions (15c) and a crack (15d) extending from each of the plurality of modified portions (15c) is formed inside the ingot (11).

[0071] And, in a situation where the laser beam (LB) irradiation of all of the multiple second regions (11e) is not completed (step (S122): NO), the location where the condensation point is formed and the ingot (11) are moved relative to each other along the Y-axis direction (crystal orientation

[0001] ) (second output transfer step: S123).

[0072] In this second output transfer step (S123), for example, the irradiation head (16) is moved along the Y-axis direction (crystal orientation

[0001] ) until the irradiation head (16) is positioned in the X-axis direction (crystal orientation

[0010] ) when viewed from the second region (11e) adjacent to the second region (11e) where the peeling layer (15) has already been formed, and where the peeling layer (15) has not been formed.

[0073] Next, the second laser beam irradiation step (S121) described above is performed again. Additionally, the second output transfer step (S123) and the second laser beam irradiation step (S121) are alternately repeated until a peeling layer (15) is formed on all of the plurality of second regions (11e) included in the ingot (11).

[0074] And, when a peeling layer (15) is formed on all of the multiple second regions (11e) (step (S122): YES), a peeling layer (15) is formed on the entire interior of the ingot (11), and the peeling layer formation step (S1) shown in FIG. 3 is completed.

[0075] Here, in this peeling layer formation step (S1), since the first depth and the second depth are set as described above, the thickness of the peeling layer (15) formed inside the ingot (11) can be reduced. This point will be explained below.

[0076] First, the method of forming a peeling layer (15) over the entire interior of the ingot (11) is not limited to the method described above. For example, the peeling layer (15) can be formed over the entire interior of the ingot (11) by performing only the second processing step (S12) without performing the first processing step (S11) described above. However, in this case, there is a risk that the component of the crack (15d) extending during the second processing step (S12) along the thickness direction of the ingot (11) will increase.

[0077] Meanwhile, the first processing step (S11) is performed prior to the second processing step (S12), and in addition, when the first depth and the second depth are set as described above, the component perpendicular to the thickness direction of the crack (15d) tends to be larger than the component along the thickness direction of the ingot (11). As a result, when the first depth and the second depth are set as described above, the thickness of the peeling layer (15) formed inside the ingot (11) becomes relatively thin.

[0078] Then, when the peeling layer formation step (S1) shown in FIG. 3 is completed, the substrate is separated from the ingot (11) starting from the peeling layer (15) (separation step: S2). FIG. 14(A) and FIG. 14(B) are each schematic cross-sectional side views showing an example of the separation step (S2) shown in FIG. 3. This separation step (S2) is carried out, for example, in the separation device (18) shown in FIG. 14(A) and FIG. 14(B).

[0079] This separation device (18) has a holding table (20) that holds an ingot (11) on which a peeling layer (15) is formed. This holding table (20) has a circular upper surface (holding surface), and a porous plate (not shown) is exposed on this holding surface.

[0080] In addition, this porous plate is connected to a suction source (not shown), such as a vacuum pump, through a channel formed inside the holding table (20). When this suction source operates, a suction force acts on the space near the holding surface of the holding table (20). Thus, for example, an ingot (11) placed on the holding surface can be held by the holding table (20).

[0081] Additionally, a separation unit (22) is formed above the maintenance table (20). This separation unit (22) has a circumferential support member (24). A rotational driving source, such as a ball screw type lifting mechanism (not shown) and a motor, is connected to the upper part of this support member (24).

[0082] And, by operating this lifting mechanism, the separation unit (22) is raised. Also, by operating this rotational drive source, the support member (24) rotates with a straight line passing through the center of the support member (24) and perpendicular to the holding surface of the holding table (20) as the axis of rotation.

[0083] Additionally, the lower end of the support member (24) is fixed to the center of the upper part of the disc-shaped base (26). And, on the lower side of the outer circumference area of ​​the base (26), a plurality of movable members (28) are formed at generally equal intervals along the circumferential direction of the base (26). These movable members (28) have a plate-shaped upright part (28a) that extends downward from the lower surface of the base (26).

[0084] The upper part of this upright section (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 diameter direction of the base (26). Also, on the inner surface of the lower part of this upright section (28a), a plate-shaped wedge section (28b) is formed that extends toward the center of the base (26) and becomes thinner as it approaches the tip.

[0085] In the separation device (18), for example, the separation step (S2) is performed in the following order. Specifically, 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 aligns with the center of the holding surface of the holding table (20).

[0086] Next, a suction source communicating with a porous plate exposed on the holding surface is actuated so that the ingot (11) is held by the holding table (20). Next, an actuator is actuated so that each of the plurality of movable members (28) is positioned on the outer side in the radial direction of the support (26).

[0087] Next, a lifting mechanism is operated so that the tip of each wedge portion (28b) of a plurality of movable members (28) is positioned at a height corresponding to the peeling layer (15) formed inside the ingot (11). Next, an actuator is operated so that the wedge portion (28b) is embedded in the side (11c) of the ingot (11) (see FIG. 14(A)).

[0088] Next, a rotary drive source is operated to rotate the wedge portion (28b) embedded in the side (11c) of the ingot (11). Next, a lifting mechanism is operated to raise the wedge portion (28b) (see FIG. 14(B)).

[0089] As described above, after rotating the wedge portion (28b) while embedding it into the side (11c) of the ingot (11), the wedge portion (28b) is raised, thereby further extending the cracks (15b, 15d) contained in the peeling layer (15). As a result, the surface (11a) side and the back side (11b) side of the ingot (11) are separated. That is, a substrate (17) is manufactured from the ingot (11) starting from the peeling layer (15).

[0090] Additionally, if the surface (11a) side and the back (11b) side of the ingot (11) are separated at the point where the wedge portion (28b) is driven into the side (11c) of the ingot (11), the wedge portion (28b) does not need to be rotated. Also, the actuator and the rotational driving source may be operated simultaneously to drive the rotating wedge portion (28b) into the side (11c) of the ingot (11).

[0091] In the method for manufacturing a single-crystal silicon substrate described above, a first processing step (S11) is performed to form a modified portion (15a) in a plurality of first regions (11d), and then a second processing step (S12) is performed to form a modified portion (15c) and a crack (15d) in a plurality of second regions (11e).

[0092] Here, when the modified portion (15a) is formed in the first processing step (S11), the volume of the ingot (11) expands, and internal stress is generated in the ingot (11). Also, the crack (15d) formed in the second processing step (S12) is likely to extend toward the point where internal stress is generated.

[0093] Therefore, the crack formed in the second processing step (S12) is likely to extend toward the modified part (15a) formed in the first processing step (S11). Thus, in this method, the direction in which the crack (15d) is likely to extend in the second processing step (S12) can be arbitrarily set.

[0094] In this case, it becomes easier to thin the peeling layer (15) formed inside the ingot (11). And, when the peeling layer (15) is thinned, the amount of material from the ingot that is discarded during cutting the substrate (17) from the ingot (11) and flattening the substrate (17) is reduced. As a result, in this method, it is possible to improve the productivity of the substrate (17) when manufacturing the substrate (17) from the ingot (11) using a laser beam (LB).

[0095] In addition, in this method, a laser beam (LB) is irradiated along the crystal orientation

[0010] on an ingot (11) made of single-crystal silicon, such that the crystal plane (100) is exposed to the surface (11a) and the back surface (11b), respectively.

[0096] Here, the crystal orientation

[0010] is a direction in which the angle formed with a specific crystal orientation (e.g., crystal orientation

[0011] ) included in the crystal orientation <110> is large (e.g., 45°). Therefore, in this method, cracks extending along a specific crystal plane (e.g., the crystal plane shown in (2) below) included in the crystal plane {111} are not easily generated from the modified portion (15a, 15c) formed inside the ingot (11) by irradiation of the laser beam (LB).

[0097]

[0098] Also, in this method, many cracks are generated along a crystal plane (specifically, the crystal plane shown in (3) below) that is parallel to the crystal orientation

[0010] among specific crystal planes included in the crystal plane {110} from the modified portion (15a, 15c) formed inside the ingot (11) by irradiation of a laser beam (LB).

[0099]

[0100] And, compared to the angle formed by a specific crystal plane included in the crystal plane {111} with respect to the crystal plane (100) being about 54.7°, the angle formed by a specific crystal plane included in the crystal plane {110} with respect to the crystal plane (100) that is parallel to the crystal orientation

[0010] (e.g., crystal plane (101)) is 45°.

[0101] For this reason, in this method, the occurrence of large cracks can be suppressed in the thickness direction component than in the direction parallel to the surface (11a) and back surface (11b) of the ingot (11).

[0102] In this case, the thickness of the peeling layer (15) formed inside the ingot (11) is suppressed, and the amount of material of the ingot (11) and substrate (17) that is discarded during cutting the substrate (17) from the ingot (11) and flattening the substrate (17) is reduced. As a result, in this method, it is possible to further improve the productivity of the substrate (17) when manufacturing the substrate (17) from the ingot (11) using a laser beam (LB).

[0103] In addition, the method for manufacturing a single-crystal silicon substrate described above is one aspect of the present invention, and the present invention is not limited to the method described above. For example, the ingot used to manufacture the substrate in the present invention is not limited to the ingot (11) shown in FIG. 1 and FIG. 2, etc.

[0104] Specifically, in the present invention, a substrate may be manufactured from an ingot in which a notch is formed on the side. Alternatively, in the present invention, a substrate may be manufactured from an ingot in which neither an orientation flat nor a notch is formed on the side.

[0105] In addition, the structure of the laser processing device used in the present invention is not limited to the structure of the laser processing device (2) described above. For example, the present invention may be implemented using a laser processing device having a moving mechanism formed to move the holding table (4) along the X-axis direction, the Y-axis direction, and / or the Z-axis direction, respectively.

[0106] Alternatively, the present invention may be implemented using a laser processing device in which a scanning optical system capable of changing the direction of a laser beam (LB) irradiated from an irradiation head (16) is formed in a laser beam irradiation unit (6). In addition, this scanning optical system includes, for example, a galvano scanner, an acousto-optical element (AOD), and / or a polygon mirror.

[0107] That is, in the present invention, the point of concentration of the laser beam (LB) irradiated from the ingot (11) held by the holding table (4) and the irradiation head (16) can move relatively along the X-axis direction, Y-axis direction and Z-axis direction, respectively, and there are no limitations on the structure for this.

[0108] In addition, in the peeling layer forming step (S1) of the present invention, the plurality of first regions and the plurality of second regions included in the ingot (11) where the laser beam (LB) is irradiated are not limited to regions following the crystal orientation

[0010] . For example, in the present invention, the laser beam (LB) may be irradiated to regions following the crystal orientation

[0001] .

[0109] In addition, when a laser beam (LB) is irradiated onto the ingot (11) in this manner, cracks are more likely to spread on the crystal plane shown in (4) below.

[0110]

[0111] In addition, in the present invention, a laser beam (LB) may be irradiated onto a region that follows a direction slightly inclined from the crystal orientation

[0010] or crystal orientation

[0001] when viewed in a plane. This point will be explained with reference to FIG. 15.

[0112] FIG. 15 is a graph showing the width of the peeling layer formed inside a workpiece made of single-crystal silicon when a laser beam (LB) is irradiated onto a region following a different crystal orientation. In addition, the horizontal axis of this graph represents the angle formed between the direction in which the region orthogonal to the crystal orientation

[0011] (reference region) extends and the direction in which the region to be measured (measurement region) extends when viewed from a plane.

[0113] That is, when the value of the horizontal axis of this graph becomes 45°, the region along the crystal orientation

[0001] becomes the subject of measurement. Likewise, when the value of the horizontal axis of this graph becomes 135°, the region along the crystal orientation

[0010] becomes the subject of measurement.

[0114] Also, the vertical axis of this graph represents the value obtained by dividing the width of the peeling layer formed in the measurement area by irradiating the measurement area with a laser beam (LB) by the width of the peeling layer formed in the reference area by irradiating the reference area with a laser beam (LB).

[0115] As shown in FIG. 15, the width of the peeling layer widens when the angle formed by the direction in which the reference area extends and the direction in which the measurement area extends is 40° or more and 50° or 130° or more and 140° or less. That is, the width of the peeling layer widens when a laser beam (LB) is irradiated not only on the crystal orientation

[0001] or crystal orientation

[0010] , but also on the area along the direction in which the angle formed with these crystal orientations is 5° or less.

[0116] For this reason, in the peeling layer forming step (S1) of the present invention, a laser beam (LB) may be irradiated on an area along a direction inclined at 5° or less from the crystal orientation

[0001] or crystal orientation

[0010] when viewed from a plane.

[0117] That is, in the peeling layer forming step (S1) of the present invention, a laser beam (LB) may be irradiated in a region along a direction (first direction) that is parallel to the crystal plane (here, crystal plane (100)) exposed to each of the surface (11a) and back surface (11b) of the ingot (11) among the specific crystal planes included in the crystal plane {100}, and also has an angle of 5° or less with respect to a specific crystal orientation (here, crystal orientation

[0001] or crystal orientation

[0010] ) included in the crystal orientation <100>.

[0118] In addition, in the present invention, forming a peeling layer (15) over the entire interior of the ingot (11) in the peeling layer forming step (S1) is not an indispensable feature. For example, if a crack (15b, 15d) extends to an area near the side (11c) of the ingot (11) in the separation step (S2), the peeling layer (15) does not need to be formed in part or all of the area near the side (11c) of the ingot (11) in the peeling layer forming step (S1).

[0119] In addition, in the present invention, in the second laser beam irradiation step (S121), the point at which the laser beam (LB) is concentrated may be positioned at a second depth shallower than the first depth, and the point at which the laser beam (LB) is concentrated may be moved relative to the ingot (11).

[0120] Additionally, the separation step (S2) of the present invention may be performed using a device other than the separation device (18) shown in FIG. 14(A) and FIG. 14(B). For example, in the separation step (S2) of the present invention, the substrate (17) may be separated from the ingot (11) by sucking the surface (11a) side of the ingot (11).

[0121] FIGS. 16(A) and FIGS. 16(B) are each schematic cross-sectional side views illustrating the appearance of the separation step (S2) carried out in this manner. The separation device (30) shown in FIGS. 16(A) and FIGS. 16(B) has a holding table (32) that holds an ingot (11) on which a peeling layer (15) is formed.

[0122] This holding table (32) has a circular upper surface (holding surface), and a porous plate (not shown) is exposed on this holding surface. In addition, this porous plate is connected to a suction source (not shown), such as a vacuum pump, through a flow path formed inside the holding table (32).

[0123] Therefore, when this suction source operates, a suction force acts on the space near the holding surface of the holding table (32). Thus, for example, an ingot (11) placed on the holding surface can be held by the holding table (32).

[0124] Additionally, a separation unit (34) is formed above the maintenance table (32). This separation unit (34) has a cylindrical support member (36). For example, a ball screw type lifting mechanism (not shown) is connected to the upper part of this support member (36), and the separation unit (34) is raised by operating this lifting mechanism.

[0125] Also, the lower end of the support member (36) is fixed to the center of the upper part of the disc-shaped suction plate (38). And, a plurality of suction holes are formed on the lower surface of the suction plate (38), and each of the plurality of suction holes is connected to a suction source (not shown), such as a vacuum pump, through a flow path formed inside the suction plate (38).

[0126] Therefore, when this suction source operates, a suction force acts on the space near the lower surface of the suction plate (38). As a result, for example, an ingot (11) approaching the lower surface of the suction plate (38) can be sucked upward.

[0127] In the separation device (30), for example, the separation step (S2) is performed 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 aligns with the center of the holding surface of the holding table (32).

[0128] Next, a suction source communicating with a porous plate exposed on the holding surface is operated so that the ingot (11) is held by the holding table (32). Next, a lifting mechanism is operated to lower the separation unit (34) so ​​that the lower surface of the suction plate (38) comes into contact with the surface (11a) of the ingot (11).

[0129] Next, a suction source communicating with a plurality of suction holes is operated so that the surface (11a) side of the ingot (11) is sucked through a plurality of suction holes formed in the suction plate (38) (see FIG. 16(A)). Next, a lifting mechanism is operated to raise the separation unit (34) so ​​that the suction plate (38) is separated from the holding table (32) (see FIG. 16(B)).

[0130] At this time, an upward force is applied to the surface (11a) side of the ingot (11) that is sucked in through a plurality of suction holes formed in the suction plate (38). As a result, the cracks (15b, 15d) contained in the peeling layer (15) are further extended, and the surface (11a) side and the back side (11b) side of the ingot (11) are separated. That is, a substrate (17) is manufactured from the ingot (11) starting from the peeling layer (15).

[0131] Additionally, in the separation step (S2) of the present invention, ultrasonic waves may be applied to the surface (11a) side of the ingot (11) prior to the separation of the surface (11a) side and the back side (11b) side of the ingot (11). In this case, the cracks (15b, 15d) included in the peeling layer (15) are further extended, so the separation of the surface (11a) side and the back side (11b) side of the ingot (11) becomes easier.

[0132] In addition, in the present invention, prior to the peeling 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).

[0133] Specifically, when the ingot (11) is separated from the peeling layer (15) to manufacture the substrate (17), irregularities are formed on the surface of the newly exposed ingot (11) that reflect the distribution of modified parts (15a, 15c) and cracks (15b, 15d) included in the peeling layer (15). Therefore, when manufacturing a new substrate from this ingot (11), it is preferable to flatten the surface of the ingot (11) prior to the peeling layer formation step (S1).

[0134] Thus, diffuse reflection of the laser beam (LB) irradiated onto the ingot (11) during the peeling layer formation step (S1) can be suppressed on the surface of the ingot (11). Likewise, in the present invention, the surface of the peeling layer (15) of the substrate (17) separated from the ingot (11) may be flattened by grinding or polishing.

[0135] In addition, in the present invention, a substrate may be manufactured using a bare wafer made of single-crystal silicon manufactured such that a specific crystal plane included in the crystal plane {100} is exposed on the surface and the back surface, respectively.

[0136] In addition, this bare wafer has a thickness of, for example, 2 to 5 times that of the substrate being manufactured. Also, this bare wafer is manufactured by separating it from the ingot (11) by, for example, the same method as described above. In this case, it may be said that the substrate is manufactured by repeating the method described above twice.

[0137] In addition, in the present invention, a substrate may be manufactured using a device wafer produced by forming a semiconductor device on one surface of the bare wafer as the workpiece. In this case, in order to prevent adverse effects on the semiconductor device, it is preferable that the laser beam (LB) be irradiated onto the device wafer from the side of the device wafer where the semiconductor device is not formed.

[0138] Furthermore, the structures and methods related to the embodiments described above may be appropriately modified and implemented as long as they do not deviate from the scope of the purpose of the present invention. Explanation of the symbols

[0139] 2 : Laser processing device 4: Maintenance Table 6: Laser beam irradiation unit 8 : Laser oscillator 10 : Damper 11 : Ingot (11a : Surface, 11b : Back, 11c : Side) (11d : 1st zone, 11e : 2nd zone) 12: Branch Unit 13: Orientation Flat 14 : Mirror 15: Delamination layer (15a: Modified part, 15b: Crack) (15c: modified zone, 15d: crack) 15-1 : Release layer 15-2 : Release layer 15-3 : Release layer 16: Investigation Head 17 : Substrate 18: Separator 20 : Maintenance Table 22 : Separation unit 24: Support member 26 : Expectation 28 : Movable member (28a : Upright part, 28b : Wedge part) 30: Separator 32 : Maintenance Table 34: Separation unit 36: Support member 38 : Suction plate

Claims

Claim 1 A method for manufacturing a single-crystal silicon substrate, comprising manufacturing a substrate from a workpiece made of single-crystal silicon such that a specific crystal plane included in a crystal plane {100} is exposed on the front and back surfaces, respectively, wherein the method comprises a peeling layer forming step for forming a peeling layer including a modified portion and a crack extending from the modified portion within the workpiece, and a separation step for separating the substrate from the workpiece starting from the peeling layer after performing the peeling layer forming step, wherein the peeling layer forming step comprises a first processing step for forming the modified portion in a plurality of first regions spaced apart from each other in a second direction that is parallel to the specific crystal plane and orthogonal to the first direction, while each extending along the first direction such that the angle formed with a specific crystal orientation included in the crystal orientation <100> is 5° or less, and after performing the first processing step, the The method comprises a second processing step for forming a modified portion and a crack in a plurality of second regions spaced apart from each other in two directions, wherein any of the plurality of second regions is located between an adjacent pair of first regions among the plurality of first regions, and any of the plurality of first regions is located between an adjacent pair of second regions among the plurality of second regions, and the first processing step is performed by alternately repeating a first laser beam irradiation step in which a focusing point, where a laser beam of a wavelength passing through the single crystal silicon is focused, is located at a first depth from the surface of the workpiece and inside any of the plurality of first regions, and the focusing point and the workpiece are moved relatively along the first direction, and a first output transfer step in which the position where the focusing point is formed and the workpiece are moved relatively along the second direction, and the second processing step isA method for manufacturing a single-crystal silicon substrate, wherein the focusing point is positioned within any of the plurality of second regions and at a second depth different from the first depth from the surface of the workpiece, and a second laser beam irradiation step in which the focusing point and the workpiece are moved relatively along the first direction, and a second output transfer step in which the position where the focusing point is formed and the workpiece are moved relatively along the second direction are alternately repeated, wherein the power of the laser beam focused at the focusing point during the second laser beam irradiation step is greater than the power of the laser beam focused at the focusing point during the first laser beam irradiation step. Claim 2 A method for manufacturing a single-crystal silicon substrate according to claim 1, wherein the second depth is deeper than the first depth. Claim 3 A method for manufacturing a single-crystal silicon substrate according to claim 1 or 2, wherein the angle formed by a first straight line along a first direction passing through the center of a second region located between an adjacent pair of first regions and a first plane passing through a second straight line along a first direction passing through the center of one of the adjacent pair of first regions with respect to the surface and the back surface of the workpiece is 45° or less, and the angle formed by a second plane passing through the first straight line and a third straight line along a first direction passing through the center of the other of the adjacent pair of first regions with respect to the surface and the back surface of the workpiece is 45° or less.

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