Manufacturing method for single-crystal silicon substrates

Abstract

To provide a method for manufacturing a single-crystal silicon substrate which can enhance throughput.SOLUTION: A method for manufacturing a single-crystal silicon substrate includes forming a release layer including a plurality of modified portions that are positioned at a predetermined depth from the surface of a workpiece and cracks extending from the plurality of modified portions, by alternately repeating irradiation of at least two regions included in a plurality of regions, each of which extends along a predetermined direction, with a laser beam, and a change of the region to be irradiated with the laser beam. Specifically, at least two regions are simultaneously irradiated with the laser beam, so as to form the release layer on the workpiece. Thereby, throughput can be enhanced as compared with a case in which each a plurality of regions is sequentially irradiated with the laser beam.SELECTED DRAWING: Figure 9

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a single-crystal silicon substrate by manufacturing a substrate from a workpiece made of single-crystal silicon manufactured so that specific crystal planes included in the crystal plane {100} are exposed on each of the front and back surfaces.

Background Art

[0002] Chips of semiconductor devices are generally manufactured using a disk-shaped single-crystal silicon substrate (hereinafter, also simply referred to as a "substrate"). This substrate is cut out from an ingot made of single-crystal silicon in a columnar shape (hereinafter, also simply referred to as an "ingot") using, for example, a wire saw (see, for example, Patent Document 1).

[0003] However, the cutting cost when cutting out a substrate from an ingot using a wire saw is around 300 μm, which is relatively large. In addition, fine irregularities are formed on the surface of the substrate cut out in this way, and this substrate is curved as a whole (the substrate warps). Therefore, in this substrate, it is necessary to perform lapping, etching, and / or polishing on the surface to flatten the surface.

[0004] In this case, the amount of the single-crystal silicon material finally used as a substrate is about 2 / 3 of the amount of the material of the entire ingot. That is, about 1 / 3 of the amount of the material of the entire ingot is discarded when cutting out the substrate from the ingot and flattening the substrate. Therefore, when manufacturing a substrate using a wire saw in this way, the productivity is low.

[0005] In view of this point, a method has been proposed in which after forming a separation layer including a modified portion and cracks extending from the modified portion inside the ingot using a laser beam having a wavelength that penetrates single-crystal silicon, the substrate is separated from the ingot starting from this separation layer (see, for example, Patent Document 2). Thereby, the productivity of the substrate can be improved as compared with the case of manufacturing the substrate from an ingot using a wire saw.

Prior Art Documents

[0006] [Patent Document 1] Japanese Patent Application Publication No. 9-262826 [Patent Document 2] Japanese Patent Publication No. 2022-25566 [Overview of the project] [Problems that the invention aims to solve]

[0007] In the method described above, a delamination layer is formed by alternately repeating the irradiation of one of a plurality of regions, each extending in a predetermined direction, with the region to which the laser beam is irradiated, and by changing the region to which the laser beam is irradiated. This layer includes a plurality of modified portions located at a predetermined depth from the surface of the ingot and cracks extending from each of the plurality of modified portions.

[0008] In this case, the time required to manufacture the substrate from the ingot will increase, which may lead to a decrease in throughput. In view of this, an object of the present invention is to provide a method for manufacturing a single-crystal silicon substrate that can improve throughput. [Means for solving the problem]

[0009] According to the present invention, a method for manufacturing a single-crystal silicon substrate is provided for manufacturing a substrate from a workpiece made of single-crystal silicon manufactured such that a specific crystal plane included in the crystal plane {100} is exposed on the front and back surfaces, respectively, comprising: a delamination layer formation step of forming a delamination layer in each of a plurality of regions included in the workpiece, the delamination layer including a plurality of modified portions and cracks extending from each of the plurality of modified portions; and a separation step of separating the substrate from the workpiece using the delamination layer as a starting point after performing the delamination layer formation step, wherein each of the plurality of regions extends along a first direction, the first direction is parallel to the specific crystal plane, and the crystal orientation <100> A method for manufacturing a single-crystal silicon substrate is provided, wherein the direction is such that the angle it makes with a specific crystal orientation contained therein is 5° or less, the plurality of regions are provided at predetermined central intervals in the second direction, the second direction is parallel to the specific crystal plane and perpendicular to the first direction, the predetermined central interval is 100 μm or more and 1 mm or less, and the delamination layer formation step is performed by alternately repeating the following steps: a laser beam irradiation step in which a laser beam of a wavelength that penetrates the single-crystal silicon is focused at each of the plurality of focal points formed so as to be aligned along the second direction, the workpiece and the plurality of focal points are moved relative to the first direction while the workpiece and the plurality of focal points are positioned at a predetermined depth from the surface of the workpiece and inside each of at least two of the plurality of regions; and an indexing feed step in which the position in which the plurality of focal points are formed is changed from inside each of the at least two regions to inside each of at least two other regions among the plurality of regions.

[0010] Preferably, the distance between adjacent pairs of focal points among the plurality of focal points formed within each of the at least two regions is smaller than the predetermined center distance. Preferably, in the laser beam irradiation step, the crack is formed such that the crack formed in one of the two adjacent regions is connected to the crack formed in the other of the two adjacent regions. [Effects of the Invention]

[0011] In this invention, a delamination layer is formed by alternately repeating the irradiation of a laser beam to at least two regions included in a plurality of regions, each extending along a predetermined direction, and changing the at least two regions irradiated with the laser beam, thereby forming a plurality of modified portions located at a predetermined depth from the surface of the workpiece and cracks extending from each of the plurality of modified portions.

[0012] In other words, in the present invention, the laser beam is irradiated to at least two regions simultaneously to form a peel layer on the workpiece. This makes it possible to improve throughput in the present invention compared to the case where the laser beam is irradiated sequentially to each of the multiple regions. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a schematic perspective view showing an example of an ingot used in the manufacture of a circuit board. [Figure 2] Figure 2 is a schematic top view of the ingot shown in Figure 1. [Figure 3] Figure 3 is a schematic flowchart illustrating an example of a method for manufacturing a single-crystal silicon substrate from an ingot, which is the workpiece. [Figure 4] Figure 4 is a schematic top view showing multiple regions contained within the ingot. [Figure 5] Figure 5 is a schematic diagram showing an example of a laser processing apparatus used to form a delamination layer in each of the multiple regions contained in an ingot. [Figure 6] Figure 6 is a schematic top view showing how the ingot is held by the holding table of the laser processing machine. [Figure 7] Figure 7 is a flowchart schematically showing an example of the delamination layer formation step shown in Figure 3. [Figure 8]FIG. 8(A) is a top view schematically showing an example of the laser beam irradiation step, and FIG. 8(B) is a partial cross-sectional side view schematically showing an example of the laser beam irradiation step. [Figure 9] FIG. 9 is a cross-sectional view schematically showing a separation layer formed inside the ingot in the laser beam irradiation step. [Figure 10] Each of FIGS. 10(A) and 10(B) is a partial cross-sectional side view schematically showing an example of the separation step shown in FIG. 3. [Figure 11] FIG. 11 is a diagram schematically showing another example of a laser processing apparatus used when forming a separation layer in each of a plurality of regions included in the ingot. [Figure 12] FIG. 12 is a graph showing the width of a separation layer formed inside a workpiece made of single crystal silicon when a laser beam is irradiated onto regions along different crystal orientations. [Figure 13] Each of FIGS. 13(A) and 13(B) is a partial cross-sectional side view schematically showing an example of another separation step shown in FIG. 3. MODE FOR CARRYING OUT THE INVENTION

[0014] 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 an ingot used for manufacturing a substrate, and FIG. 2 is a top view schematically showing the ingot shown in FIG. 1.

[0015] In FIG. 1, the crystal plane of the single crystal silicon exposed on the plane included in this ingot is also shown. Further, in FIG. 2, the crystal orientation of the single crystal silicon constituting this ingot is also shown.

[0016] In the ingot 11 shown in Figures 1 and 2, a specific crystal plane included in the crystal plane {100} (referred to here as crystal plane (100) for convenience) is exposed on both the front surface 11a and the back surface 11b. That is, in this ingot 11, the perpendiculars (crystal axes) of both the front surface 11a and the back surface 11b are aligned with the crystal orientation

[0100] .

[0017] In addition, although the ingot 11 is manufactured so that the crystal planes (100) are exposed on both the front surface 11a and the back surface 11b, due to processing errors during manufacturing, a plane that is slightly tilted from the crystal planes (100) may be exposed on both the front surface 11a and the back surface 11b.

[0018] Specifically, the front surface 11a and back surface 11b of the ingot 11 may each have surfaces exposed that make an angle of 1° or less with respect to the crystal plane (100). In other words, the crystal axis of the ingot 11 may be aligned in a direction that makes an angle of 1° or less with respect to the crystal orientation

[0100] .

[0019] Furthermore, an orientation flat 13 is formed on the side surface 11c of the ingot 11, and the crystal orientation is as seen from this orientation flat 13. <110> The center C of the ingot 11 is located in a specific crystal orientation (for convenience, this will be referred to as crystal orientation

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

[0020] Figure 3 is a schematic flowchart illustrating an example of a method for manufacturing a single-crystal silicon substrate from an ingot 11, which is the workpiece. In this method, first, a delamination layer is formed in each of the multiple regions contained in the ingot 11, which includes multiple modified areas and cracks extending from each of the multiple modified areas (delamination layer formation step: S1).

[0021] Figure 4 is a schematic top view showing multiple regions in which a delamination layer is formed in the delamination layer formation step (S1). As shown in Figure 4, each of the multiple regions 11d (for example, n regions 11d_1, 11d_2, 11d_3, 11d_4 to 11d_n-1, 11d_n, where n is an even number of 20 or more) extends along the crystal orientation

[0010] .

[0022] Furthermore, the central spacing I1 in the crystal orientation

[0001] of multiple regions 11d is between 100 μm and 1 mm. This central spacing I1 is the distance between a straight line L1 that passes through the center of one of a pair of adjacent regions (for example, region 11d_2) and is aligned with the crystal orientation

[0010] , and a straight line L2 that passes through the center of the other region (for example, region 11d_3) and is aligned with the crystal orientation

[0010] .

[0023] Furthermore, in the delamination layer formation step (S1), a laser processing device is used to form a delamination layer in each of the multiple regions 11d contained in the ingot 11, which includes multiple modified parts and cracks extending from each of the multiple modified parts. Figure 5 is a schematic diagram showing an example of this laser processing device.

[0024] In Figure 5, the X-axis direction (first direction) and the Y-axis direction (second direction) are mutually orthogonal directions on the horizontal plane, and the Z-axis direction is perpendicular to both the X-axis and Y-axis directions (vertical direction). Also, in Figure 5, some components of the laser processing apparatus are shown as functional blocks.

[0025] The laser processing apparatus 2 shown in Figure 5 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 and Y-axis directions. The holding table 4 also has a disc-shaped porous plate (not shown) whose upper surface is exposed on this holding surface.

[0026] Furthermore, this porous plate is in communication with a suction source (not shown), such as an ejector, via a channel formed inside the holding table 4. When this suction source operates, a suction force acts on the space near the holding surface of the holding table 4. As a result, for example, an ingot 11 placed on the holding surface can be held by the holding table 4.

[0027] Furthermore, 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 as the laser medium.

[0028] The laser oscillator 8 then irradiates the ingot 11 with a pulsed laser beam LB (e.g., with a frequency of 60 kHz) of a wavelength (e.g., 1064 nm or 1342 nm) that penetrates the material (single-crystal silicon) that makes up the ingot 11.

[0029] The laser beam LB is supplied to the branching unit 12 after its output (power) is adjusted in the attenuator 10. The branching unit 12 includes, for example, a spatial light modulator and / or a diffractive optical element (DOE) that includes a liquid crystal phase control element called LCoS (Liquid Crystal on Silicon).

[0030] The branching unit 12 then branches the laser beam LB, which is irradiated from the irradiation head 16 (described later) to the holding surface side of the holding table 4, so as to form multiple (for example, 4 to 40) focusing points aligned along the Y axis.

[0031] Furthermore, the branching unit 12 branches the laser beam LB such that the distance I2 between the pair of focal points located towards the center of the multiple focal points is relatively large, and the distance I3 between the other adjacent pairs of focal points is relatively small.

[0032] In other words, the branching unit 12 separates a set of multiple (eight in Figure 5) focusing points S1, which is formed at intervals I3, and a set of multiple (eight in Figure 5) focusing points S2, which is also formed at intervals I3, by an interval I2 that is larger than the interval I3.

[0033] The central spacing I4 of these sets S1 and S2 is adjusted to match, for example, the central spacing I1 of the multiple regions 11d contained in the ingot 11 shown in Figure 4. That is, this central spacing I4 is, for example, between 100 μm and 1 mm. Also, the above spacing I3 is, for example, between 1 μm and 20 μm.

[0034] The laser beam LB, branched in the branching unit 12, is reflected by the mirror 14 and guided to the irradiation head 16. The irradiation head 16 houses a focusing lens (not shown) for focusing the laser beam LB. The laser beam LB, focused by this focusing lens, is emitted from the central region of the lower surface of the irradiation head 16, and is projected onto the holding surface side of the holding table 4, or more precisely, directly downwards.

[0035] Furthermore, 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 and a motor. When this moving mechanism operates, the emission area of ​​the laser beam LB moves along the X-axis, Y-axis, and / or Z-axis.

[0036] Furthermore, in the laser processing apparatus 2, by operating this moving mechanism, the positions (coordinates) in the X-axis, Y-axis, and Z-axis directions of multiple focal points where the laser beam LB irradiated from the irradiation head 16 to the holding surface side of the holding table 4 is focused can be adjusted.

[0037] When the ingot 11 is loaded into the laser processing apparatus 2, the ingot 11 is held by the holding table 4 with its surface 11a facing upwards. Figure 6 is a schematic top view showing how the ingot 11 is held by the holding table 4 of the laser processing apparatus 2.

[0038] Specifically, first, the ingot 11 is placed on the holding table 20 such that the angle between the direction from the orientation flat 13 toward the center C of the ingot 11 (crystal orientation

[0011] ) and the X-axis and Y-axis directions is 45°. For example, the ingot 11 is placed on the holding table 4 such that the crystal orientation

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

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

[0039] Next, a suction source communicating with the porous plate exposed on the holding surface of the holding table 4 is activated. This causes the ingot 11 to be held by the holding table 4. Once the ingot 11 is held by the holding table 4, the delamination layer formation step (S1) is performed.

[0040] Figure 7 is a schematic flowchart illustrating an example of the delamination layer formation step (S1). In this delamination layer formation step (S1), first, with multiple focal points positioned at a predetermined depth from the surface 11a of the ingot 11 and within each of the two regions, the ingot 11 and the multiple focal points are moved relative to each other along the X-axis direction (crystal orientation

[0010] ) (laser beam irradiation step: S11).

[0041] Figure 8(A) is a schematic top view showing an example of the laser beam irradiation step (S11), and Figure 8(B) is a schematic partial cross-sectional side view showing an example of the laser beam irradiation step (S11). Figure 9 is a schematic cross-sectional view showing the delamination layer formed inside the ingot 11 during the laser beam irradiation step (S11).

[0042] In this laser beam irradiation step (S11), for example, a delamination layer is first formed in two regions 11d_1 and 11d_2 located at one end of the multiple regions 11d in the Y-axis direction (crystal orientation

[0001] ).

[0043] Specifically, first, in a plan view, the irradiation head 16 of the laser beam irradiation unit 6 is positioned such that two regions 11d_1 and 11d_2 are positioned in the X-axis direction from the perspective of the irradiation head 16. Next, when irradiating the ingot 11 with the laser beam LB, the irradiation head 16 is raised and lowered so that the collection of multiple focal points S1 and S2 shown in Figure 5 are positioned at a predetermined depth from the surface 11a of the ingot 11.

[0044] Next, while irradiating the laser beam LB from the irradiation head 16 toward the holding table 4, the irradiation head 16 is moved so that, in a plan view, it passes from one end to the other in the X-axis direction of the ingot 11 (see Figures 8(A) and 8(B)).

[0045] As a result, the set of multiple focal points S1 is positioned inside region 11d_1, and the set of multiple focal points S2 is positioned inside region 11d_2, and the multiple focal points and the ingot 11 move relative to each other along the X-axis direction.

[0046] Then, within each of the two regions 11d_1 and 11d_2, a modified region 15a is formed in which the crystal structure of the single-crystal silicon is disordered, centered around each of several focal points located at a predetermined depth D from the surface 11a of the ingot 11 (see Figure 9). Furthermore, when the modified region 15a is formed inside the ingot 11, the volume of the ingot 11 expands, and internal stress is generated in the ingot 11.

[0047] This internal stress is relieved by the extension of cracks 15b from the modified portion 15a. As a result, a delamination layer 15, including multiple modified portions 15a and cracks 15b propagating from each of the multiple modified portions 15a, is formed inside each of the two regions 11d_1 and 11d_2.

[0048] Then, if the irradiation of the laser beam LB to all of the multiple regions 11d has not been completed (step (S12): NO), the positions where the multiple focal points are formed are changed to at least two other regions 11d (indexing feed step: S13).

[0049] In this indexing feed step (S13), for example, the irradiation head 16 is moved along the Y-axis until it is positioned in the X-axis direction with respect to two adjacent regions 11d_3 and 11d_4 where the peeling layer 15 has not yet been formed, with respect to the two regions 11d_1 and 11d_2 where the peeling layer 15 has already been formed.

[0050] Next, the laser beam irradiation step (S11) described above is performed again. When the laser beam irradiation step (S11) is performed in this manner, a peeling layer 15 similar to the peeling layer 15 shown in Figure 9 is formed inside each of the two regions 11d_3 and 11d_4.

[0051] Furthermore, the indexing feed step (S13) and the laser beam irradiation step (S11) are repeatedly performed alternately until a delamination layer 15 is formed inside all of the multiple regions 11d contained in the ingot 11, that is, until a delamination layer 15 is formed inside each of the two regions 11d_n and 11d_n-1.

[0052] Then, once the delamination layer 15 is formed inside all of the multiple regions 11d (step (S12): YES), the delamination layer formation step (S1) shown in Figure 3 is completed. After performing the delamination layer formation step (S1), the substrate is separated from the ingot 11 starting from the delamination layer 15 (separation step: S2).

[0053] Figures 10(A) and 10(B) are schematic partial cross-sectional side views illustrating an example of the separation step (S2) shown in Figure 3. This separation step (S2) is carried out, for example, in the separation apparatus 18 shown in Figures 10(A) and 10(B).

[0054] The separation device 18 has a holding table 20 that holds the ingot 11 on which the peeled layer 15 is formed. The holding table 20 has a circular top surface (holding surface), on which a porous plate (not shown) is exposed.

[0055] Furthermore, this porous plate is in communication with a suction source (not shown), such as an ejector, via a flow path or the like provided 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. As a result, for example, an ingot 11 placed on the holding surface can be held by the holding table 20.

[0056] Furthermore, a separation unit 22 is provided above the holding table 20. This separation unit 22 has a cylindrical support member 24. A rotational drive 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.

[0057] By operating this lifting mechanism, the support member 24 moves up and down. Also, by operating this rotational drive source, the support member 24 rotates around a straight line passing through its center and perpendicular to the holding surface of the holding table 20 as its axis of rotation.

[0058] Furthermore, the lower end of the support member 24 is fixed to the center of the upper part of the disc-shaped base 26. On the lower side of the outer peripheral region of the base 26, a plurality of movable members 28 are provided at roughly equal intervals along the circumferential direction of the base 26. These movable members 28 have plate-shaped upright portions 28a that extend downward from the lower surface of the base 26.

[0059] The upper end of this upright 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, a plate-shaped wedge portion 28b is provided on the inner surface of the lower end of this upright portion 28a, extending toward the center of the base 26 and becoming thinner as it approaches the tip.

[0060] When the ingot 11 is loaded into the separation device 18, the ingot 11 is held by the holding table 20 with its surface 11a facing upwards. 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 aligns with the center of the holding surface of the holding table 20.

[0061] Next, a suction source communicating with the porous plate exposed on the holding surface is activated. This causes the ingot 11 to be held by the holding table 20. Once the ingot 11 is held by the holding table 20, the separation step (S2) is performed.

[0062] Specifically, first, the actuator is operated to position each of the multiple movable members 28 radially outward from the base 26. 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.

[0063] Next, the actuator is operated so that the wedge portion 28b is driven into the side surface 11c of the ingot 11 (see Figure 10(A)). Next, the rotation drive source is operated so that the wedge portion 28b, which has been driven into the side surface 11c of the ingot 11, rotates. Next, the lifting mechanism is operated to raise the wedge portion 28b (see Figure 10(B)).

[0064] As described above, after driving the wedge portion 28b into the side surface 11c of the ingot 11 and rotating it, raising the wedge portion 28b further extends the cracks 15b contained in the delamination layer 15. As a result, the front surface 11a and the back surface 11b of the ingot 11 are separated. In other words, the substrate 17 is manufactured from the ingot 11, starting from the delamination layer 15.

[0065] Furthermore, if the front surface 11a and 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, it is not necessary to rotate the wedge portion 28b. Alternatively, the actuator and the rotation drive source may be operated simultaneously to drive the rotating wedge portion 28b into the side surface 11c of the ingot 11.

[0066] In the method shown in Figure 3, a delamination layer 15 is formed by alternately repeating the irradiation of two regions with a laser beam LB to two regions included in a plurality of regions 11d, each extending along a predetermined direction (crystal orientation

[0010] ), and changing the two regions irradiated with the laser beam LB, thereby forming a delamination layer 15 that includes a plurality of modified portions 15a located at a predetermined depth D from the surface 11a of the ingot 11 and cracks 15b extending from each of the plurality of modified portions 15a.

[0067] In other words, in this method, the laser beam LB for forming the exfoliation layer 15 on the ingot 11 is irradiated to two regions simultaneously. This makes it possible to improve throughput in this method compared to the case where the laser beam LB is irradiated to each of the multiple regions 11d sequentially.

[0068] Furthermore, in this method, a laser beam LB is irradiated along the crystal orientation

[0010] onto an ingot 11 made of single-crystal silicon, which is manufactured so that the crystal plane (100) is exposed on the surface 11a and the back surface 11b, respectively. In this case, the exfoliation layer 15 formed inside each of the multiple regions 11d contained in the ingot 11 can be made thinner. This point will be explained below.

[0069] Single-crystal silicon is most easily cleaved at a specific crystal plane within the crystal plane {111}. For example, in an ingot 11 where the crystal plane (100), which is a specific crystal plane within the crystal plane {100}, is exposed on both the front and back surfaces, the crystal orientation <110> When a laser beam LB is irradiated along a specific crystal orientation

[0011] contained within the ingot 11 to form a modified portion 15a, many cracks 15b are generated that extend along a specific crystal plane within the crystal plane {111} that is parallel to the crystal orientation

[0011] (specifically, the crystal plane shown in (1) below).

number

[0070] Here, the angle that crystal plane (100) makes with a specific crystal plane included in crystal plane {111} is approximately 54.7°. Therefore, when the laser beam LB is irradiated onto the ingot 11 in this manner, many cracks 15b are generated in which the component along the thickness direction is larger than the component along the direction parallel to the surface 11a and back surface 11b of the ingot 11.

[0071] On the other hand, crystal orientation

[0010] is crystal orientation <110> This is a direction with a large angle (for example, 45°) with respect to a specific crystal orientation (for example, crystal orientation

[0011] ) contained within the crystal plane. Therefore, in the method shown in Figure 3, cracks are less likely to occur that extend from the modified portion 15a formed inside the ingot 11 by irradiation with the laser beam LB, along a specific crystal plane (for example, the crystal plane shown in (1) above) contained within the crystal plane {111}.

[0072] Furthermore, in the method shown in Figure 3, many cracks are generated from the modified portion 15a formed inside the ingot 11 by irradiation with the laser beam LB, extending along specific crystal planes within the crystal plane {110} that are parallel to the crystal orientation

[0010] (specifically, the crystal planes shown in (2) below).

number

[0073] Furthermore, the angle between a specific crystal plane included in crystal plane {111} and crystal plane (100) is approximately 54.7°, while the angle between a specific crystal plane included in crystal plane {110} that is parallel to the crystal orientation

[0010] (for example, crystal plane (101)) and crystal plane (100) is 45°.

[0074] Therefore, this method can suppress the occurrence of cracks 15b in which the component along the thickness direction is larger than the component along the direction parallel to the surface 11a and back surface 11b of the ingot 11. In this case, the thickening of the delamination layer 15 formed inside the ingot 11 is suppressed.

[0075] Furthermore, suppressing the thickening of the delamination layer 15 reduces the amount of ingot 11 and substrate 17 material discarded during the cutting of the substrate 17 from the ingot 11 and the planarization of the substrate 17. Therefore, in the method shown in Figure 3, it is possible to further improve the productivity of the substrate 17 when manufacturing the substrate 17 from the ingot 11 using the laser beam LB.

[0076] 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 Figures 1 and 2, etc.

[0077] Specifically, in the present invention, the substrate may be manufactured from an ingot having notches formed on its side surface. Alternatively, in the present invention, the substrate may be manufactured from an ingot in which neither orientation flats nor notches are formed on its side surface.

[0078] Furthermore, the structure of the laser processing apparatus used in the peel layer formation step (S1) of the present invention is not limited to the structure of the laser processing apparatus 2 described above. For example, the peel layer formation step (S1) may be carried out using a laser processing apparatus equipped with a moving mechanism that moves the holding table 4 along the X-axis, Y-axis, and / or Z-axis directions, respectively.

[0079] Alternatively, the delamination layer formation step (S1) of the present invention may be carried out using a laser processing apparatus in which a scanning optical system capable of changing the direction of the laser beam LB irradiated from the irradiation head 16 is provided in the laser beam irradiation unit 6. This scanning optical system includes, for example, a galvanometer scanner, an acousto-optic element (AOD), and / or a polygon mirror.

[0080] In other words, in the peel layer formation step (S1) of the present invention, it is sufficient that the ingot 11 held by the holding table 4 and the multiple focal points where the laser beam LB irradiated from the irradiation head 16 is focused can move relative to each other along the X-axis, Y-axis, and Z-axis directions, and there are no limitations on the structure for this purpose.

[0081] Furthermore, the peeling layer formation step (S1) of the present invention may be carried out using a laser processing apparatus equipped with a beam splitter in the laser beam irradiation unit. This beam splitter is provided, for example, between a laser oscillator having a structure similar to the laser oscillator 8 shown in Figure 5 and a branching unit including a spatial light modulator including an LCoS and / or a DOE.

[0082] In this laser beam irradiation unit, first, the laser beam emitted from the laser oscillator is split into two in a beam splitter. Then, each of the two split laser beams is further split in a branching unit so that a pair of adjacent focal points among multiple focal points are positioned at approximately equal intervals, and is guided to an irradiation head having a structure similar to the irradiation head 16 shown in Figure 5.

[0083] This allows the laser beam to be split such that the distance between the two centrally located focal points is relatively large, while the distance between the other adjacent focal points is relatively small. In other words, the irradiation head of this laser beam irradiation unit can emit a laser beam similar to the laser beam LB shown in Figure 5.

[0084] Furthermore, the peel layer formation step (S1) of the present invention may be carried out using a laser processing apparatus equipped with two laser oscillators in the laser beam irradiation unit. Figure 11 is a schematic diagram showing an example of such a laser processing apparatus.

[0085] Note that the X-axis, Y-axis, and Z-axis directions shown in Figure 11 correspond to the X-axis, Y-axis, and Z-axis directions shown in Figure 5, respectively. Also, in Figure 11, some components of the laser processing apparatus are shown as functional blocks.

[0086] The laser processing apparatus 30 shown in Figure 11 has a holding table 32 having a structure similar to the holding table 4 shown in Figure 5, for example. A laser beam irradiation unit 34 is also provided above the holding table 32.

[0087] This laser beam irradiation unit 34 has two laser oscillators 36a and 36b. Each laser oscillator 36a and 36b has a structure similar to, for example, the laser oscillator 8 shown in Figure 5.

[0088] The laser beam LB1 emitted from the laser oscillator 36a is then supplied to the branching unit 40a after its output (power) is adjusted by the attenuator 38a. The branching unit 40a branches the laser beam LB1 so that the laser beam LB1 emitted from the irradiation head 44a (described later) to the holding surface side of the holding table 32 forms multiple (for example, 2 to 20) focusing points aligned along the Y axis.

[0089] Furthermore, the branching unit 40a branches the laser beam LB1 so that two adjacent pairs of focal points (eight in Figure 11) are positioned at approximately equal intervals. For example, the branching unit 40a branches the laser beam LB1 so that multiple focal points are positioned at intervals of 1 μm to 20 μm.

[0090] The laser beam LB1, which is branched in the branching unit 40a, is reflected by the mirror 42a and guided to an irradiation head 44a having a structure similar to the irradiation head 16 shown in Figure 5. This irradiation head 44a and the optical system for guiding the laser beam LB to the irradiation head 44a (e.g., the mirror 42a) are connected to a first moving mechanism (not shown).

[0091] This first moving mechanism includes, for example, a ball screw and a motor. When this first moving mechanism operates, the emission area of ​​the laser beam LB1 moves along the X-axis, Y-axis, and / or Z-axis.

[0092] In other words, in the laser processing apparatus 30, by operating this first moving mechanism, the positions (coordinates) in the X-axis, Y-axis, and Z-axis directions of multiple focal points where the laser beam LB1 irradiated from the irradiation head 44a to the holding surface side of the holding table 32 is focused can be adjusted.

[0093] Similarly, the laser beam LB2 emitted from the laser oscillator 36b is supplied to the branching unit 40b after its output (power) is adjusted in the attenuator 38b. This branching unit 40b branches the laser beam LB2 so that the laser beam LB2 emitted from the irradiation head 44b (described later) to the holding surface side of the holding table 32 forms multiple (for example, 2 to 20) focal points aligned along the Y-axis.

[0094] Furthermore, the branching unit 40b branches the laser beam LB2 so that two adjacent pairs of focal points (eight in Figure 11) are positioned at approximately equal intervals. For example, the branching unit 40b branches the laser beam LB2 so that multiple focal points are positioned at intervals of 1 μm to 20 μm.

[0095] The laser beam LB2, branched in the branching unit 40b, is reflected by the mirror 42b and guided to an irradiation head 44b having a structure similar to the irradiation head 16 shown in Figure 5. This irradiation head 44b and the optical system (e.g., the mirror 42b) for guiding the laser beam LB to the irradiation head 44b are connected to a second moving mechanism (not shown).

[0096] This second moving mechanism includes, for example, a ball screw and a motor. When this second moving mechanism operates, the emission area of ​​the laser beam LB2 moves along the X-axis, Y-axis, and / or Z-axis.

[0097] In other words, in the laser processing apparatus 30, by operating this second moving mechanism, the positions (coordinates) in the X-axis, Y-axis, and Z-axis directions of multiple focal points where the laser beam LB2 irradiated from the irradiation head 44b to the holding surface side of the holding table 32 is focused can be adjusted.

[0098] Therefore, in the laser processing apparatus 30, for example, the spacing in the Y-axis direction between the set of multiple focal points S3, where the laser beam LB1 is focused, and the set of multiple focal points S4, where the laser beam LB2 is focused, can be arbitrarily changed.

[0099] Furthermore, when the delamination layer formation step (S1) is performed using the laser processing apparatus 30, any two regions from among the multiple regions 11d contained in the ingot 11 can be selected to form the delamination layer 15. For example, in this case, the delamination layer 15 may be formed sequentially from the outer regions 11d contained in the ingot 11 toward the inner regions.

[0100] In other words, in this case, in the first laser beam irradiation step (S11) performed, a peeling layer 15 may be formed inside each of region 11d_1 and region 11d_n, and in the kth laser beam irradiation step (S11) performed (where k is a natural number between 2 and n / 2), a peeling layer may be formed inside each of region 11d_k and region 11d_n+1-k.

[0101] Furthermore, the peel layer formation step (S1) of the present invention may be carried out using a laser processing apparatus capable of forming three or more clusters of multiple focal points where the laser beam is focused.

[0102] Such a laser processing apparatus includes, for example, a laser beam irradiation unit having a branching unit for forming three or more sets of multiple focal points. Specifically, this branching unit forms at least three sets of multiple focal points that are formed at predetermined intervals, and branches the laser beam so that at least two adjacent sets of the three sets are separated by an interval greater than the predetermined interval.

[0103] Alternatively, such a laser processing apparatus may include a laser beam irradiation unit having at least three laser oscillators having a structure similar to that of the laser oscillator 8 shown in Figure 5. Each laser oscillator, for example, has a structure similar to that of the laser oscillator 8 shown in Figure 5.

[0104] Furthermore, the laser beams emitted from each laser oscillator are guided, for example, to an irradiation head having a structure similar to the irradiation head 16 shown in 5, via a branching unit having a structure similar to the branching units 40a and 40b shown in Figure 11.

[0105] In other words, such a laser processing apparatus is equipped with at least three branching units and at least three irradiation heads, and the laser beam emitted from each of the at least three laser oscillators is guided to one of the at least three irradiation heads via one of the at least three branching units.

[0106] Furthermore, at least three irradiation heads and the optical systems for guiding the laser beams to these irradiation heads are connected, for example, to independent moving mechanisms. When these moving mechanisms operate, the emission area of ​​the laser beams emitted from at least three irradiation heads moves along the X-axis, Y-axis, and / or Z-axis.

[0107] In other words, in such a laser processing apparatus, by operating these moving mechanisms, the positions (coordinates) in the X-axis, Y-axis, and Z-axis directions of multiple focal points where the laser beam irradiated from the irradiation head to the holding surface side of the holding table is focused can be adjusted.

[0108] Therefore, in such a laser processing apparatus, for example, the spacing between two adjacent pairs of points among at least three sets of multiple focal points where the laser beam is focused can be arbitrarily changed.

[0109] Furthermore, when performing the peel layer formation step (S1) using such a laser processing apparatus, the peel layer 15 may be formed simultaneously in at least three of the multiple regions 11d.

[0110] Furthermore, the multiple regions included in the ingot 11 irradiated with the laser beam LB in the delamination layer formation step (S1) of the present invention are not limited to regions along the crystal orientation

[0010] . For example, in the present invention, the laser beam LB may be irradiated to multiple regions, each along the crystal orientation

[0001] .

[0111] Furthermore, when the ingot 11 is irradiated with the laser beam LB in this manner, cracks tend to propagate in the crystal planes shown in (3) below.

number

[0112] Furthermore, in the present invention, the laser beam LB may be irradiated in a region along a direction slightly tilted from the crystal orientation

[0010] or the crystal orientation

[0001] in a plan view. This point will be explained with reference to Figure 12.

[0113] Figure 12 is a graph showing the width of the delamination layer formed inside a workpiece made of single-crystal silicon when a laser beam LB is irradiated onto regions aligned with different crystal orientations. The horizontal axis of this graph represents the angle between the direction in which the region perpendicular to the crystal orientation

[0011] (reference region) extends and the direction in which the region to be measured (measurement region) extends, in a plan view.

[0114] In other words, when the value on the horizontal axis of this graph is 45°, the region along crystal orientation

[0001] is the target of measurement. Similarly, when the value on the horizontal axis of this graph is 135°, the region along crystal orientation

[0010] is the target of measurement.

[0115] Furthermore, the vertical axis of this graph shows the value obtained by dividing the width of the delamination layer formed in the measurement area by irradiating the measurement area with the laser beam LB by the width of the delamination layer formed in the reference area by irradiating the reference area with the laser beam LB.

[0116] As shown in Figure 12, the width of the delamination layer widens when the angle between the direction in which the reference region extends and the direction in which the measurement region extends is 40° or more and 50° or 130° or more and 140°. In other words, the width of the delamination layer widens when the laser beam LB is irradiated not only along the crystal orientation

[0001] or crystal orientation

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

[0117] Therefore, in the peel layer formation step (S1) of the present invention, the laser beam LB may be irradiated to multiple regions that, in a plan view, extend along directions tilted by 5° or less from the crystal orientation

[0001] or the crystal orientation

[0010] .

[0118] In other words, in the peeling layer formation step (S1) of the present invention, the crystal planes included in the crystal plane {100} are parallel to the crystal planes (here, crystal plane (100)) that are exposed on the front surface 11a and back surface 11b of the ingot 11, and the crystal orientation <100> The laser beam LB may be irradiated onto multiple regions each extending along a direction (first direction) where the angle it makes with a specific crystal orientation (here, crystal orientation

[0001] or crystal orientation

[0010] ) is 5° or less.

[0119] Furthermore, in the present invention, forming the delamination layer 15 over the entire interior of the ingot 11 in the delamination layer formation step (S1) is not an essential feature. For example, if cracks 15b and 15d extend to the region near the side surface 11c of the ingot 11 in the separation step (S2), then the delamination layer 15 does not need to be formed over part or all of the region near the side surface 11c of the ingot 11 in the delamination layer formation step (S1).

[0120] Furthermore, the separation step (S2) of the present invention may be carried out using an apparatus other than the separation apparatus 18 shown in Figures 10(A) and 10(B). For example, in the separation step (S2) of the present invention, the substrate 17 may be separated from the ingot 11 by suction on the surface 11a side of the ingot 11.

[0121] Figures 13(A) and 13(B) are schematic cross-sectional side views illustrating the separation step (S2) performed in this manner. The separation apparatus 46 shown in Figures 13(A) and 13(B) has a holding table 48 for holding the ingot 11 on which the peeled layer 15 is formed.

[0122] The holding table 48 has a circular top surface (holding surface), on which a porous plate (not shown) is exposed. Furthermore, this porous plate is in communication with a suction source (not shown), such as an ejector, via a flow path or the like provided inside the holding table 48.

[0123] Therefore, when this suction source operates, an attractive force acts on the space near the holding surface of the holding table 48. This allows, for example, the holding table 48 to hold the ingot 11 placed on the holding surface.

[0124] Furthermore, a separation unit 50 is provided above the holding table 48. This separation unit 50 has a cylindrical support member 52. A ball screw type lifting mechanism (not shown), for example, is connected to the upper part of this support member 52, and the support member 52 moves up and down by operating this lifting mechanism.

[0125] Furthermore, the lower end of the support member 52 is fixed to the center of the upper part of the disc-shaped suction plate 54. Multiple suction ports are formed on the lower surface of the suction plate 54, and each of the multiple suction ports is connected to a suction source (not shown), such as an ejector, via a flow path or the like provided inside the suction plate 54.

[0126] Therefore, when this suction source operates, a suction force acts on the space near the lower surface of the suction plate 54. This allows, for example, an ingot 11 adjacent to the lower surface of the suction plate 54 to be pulled upward by suction.

[0127] When the ingot 11 is loaded into the separation device 46, the ingot 11 is held by the holding table 48 with its surface 11a facing upwards. Specifically, first, the ingot 11 is placed on the holding table 48 so that the center of the back surface 11b of the ingot 11 aligns with the center of the holding surface of the holding table 48.

[0128] Next, a suction source communicating with the porous plate exposed on the holding surface is activated. This causes the ingot 11 to be held by the holding table 48. Once the ingot 11 is held by the holding table 48, the separation step (S2) is performed.

[0129] Specifically, first, the lifting mechanism is operated to lower the support member 52 and the suction plate 54 so that the lower surface of the suction plate 54 comes into contact with the surface 11a of the ingot 11. Next, a suction source communicating with the multiple suction ports is operated so that the surface 11a side of the ingot 11 is sucked through the multiple suction ports formed in the suction plate 54 (see Figure 13(A)).

[0130] Next, the lifting mechanism is operated to raise the support member 52 and the suction plate 54 so that the suction plate 54 is separated from the holding table 48 (see Figure 13(B)). At this time, an upward force is applied to the surface 11a side of the ingot 11, which is being sucked in through the multiple suction ports formed in the suction plate 54.

[0131] As a result, the cracks 15b contained in the delamination layer 15 extend further, separating the front surface 11a and the back surface 11b of the ingot 11. In other words, the substrate 17 is manufactured from the ingot 11, starting from the delamination layer 15.

[0132] Furthermore, 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 surface 11b side of the ingot 11. In this case, the cracks 15b contained in the delamination layer 15 will extend further, making it easier to separate the surface 11a side and the back surface 11b side of the ingot 11.

[0133] Furthermore, in the present invention, prior to the release layer formation step (S1), the surface 11a of the ingot 11 may be planarized by grinding or polishing (planarization step). For example, this planarization may be performed when manufacturing multiple substrates from the ingot 11.

[0134] Specifically, when the ingot 11 separates in the release layer 15 to produce the substrate 17, the surface of the newly exposed ingot 11 will have irregularities that reflect the distribution of the modified portion 15a and cracks 15b contained in the release layer 15. Therefore, when producing a new substrate from this ingot 11, it is preferable to flatten the surface of the ingot 11 prior to the release layer formation step (S1).

[0135] This makes it possible to suppress diffuse reflection of the laser beam LB irradiated onto the ingot 11 in the delamination layer formation step (S1) on the surface of the ingot 11. Similarly, in the present invention, the surface of the substrate 17 separated from the ingot 11 on the side of the delamination layer 15 may be flattened by grinding or polishing.

[0136] Furthermore, in the present invention, a substrate may be manufactured using a bare wafer made of single-crystal silicon, which is manufactured such that a specific crystal plane included in the crystal plane {100} is exposed on both the front and back surfaces, respectively, as the workpiece.

[0137] Furthermore, this bare wafer has a thickness of, for example, two to five times that of the substrate to be manufactured. This bare wafer is manufactured, for example, by separating it from the ingot 11 using a method similar to that described above. In this case, the substrate can also be described as being manufactured by repeating the above method twice.

[0138] Furthermore, in the present invention, a substrate may be manufactured using a device wafer, which is produced by forming a semiconductor device on one surface of the bare wafer, as the workpiece. In this case, it is preferable that the laser beam LB is irradiated onto the device wafer from the side on which the semiconductor device is not formed, in order to prevent adverse effects on the semiconductor device.

[0139] Furthermore, the structures and methods of the embodiments described above can be modified as appropriate without departing from the scope of the present invention. [Explanation of symbols]

[0140] 2: Laser processing equipment 4: Holding Table 6: Laser beam irradiation unit 8: Laser Oscillator 10: Attenuator 11: Ingot (11a: Front, 11b: Back, 11c: Side) (11d: multiple regions, 11d_1~11d_n: regions) 12: Branch Unit 13: Orientation Flat 14: Mirror 15: Detachment layer (15a: Modified area, 15b: Crack) 16: Irradiation head 17: Circuit board 18: Separation device 20: Holding Table 22: Separation Unit 24: Support member 26: Base 28: Movable member (28a: Upright part, 28b: Wedge part) 30: Laser processing equipment 32: Holding Table 34: Laser beam irradiation unit 36a, 36b: Laser oscillator 38a, 38b: Attenuator 40a, 40b: Branching unit 42a,42b: Mirror 44a, 44b: Irradiation head 46: Separation device 48: Holding Table 50: Separation Unit 52: Support member 54: Suction plate

Claims

1. A method for manufacturing a single-crystal silicon substrate, comprising manufacturing a substrate from a workpiece made of single-crystal silicon manufactured such that specific crystal planes included in the crystal plane {100} are exposed on the front and back surfaces, respectively, A peel layer forming step, in which a peel layer is formed in each of a plurality of regions contained in the workpiece, the peel layer includes a plurality of modified portions and cracks extending from each of the plurality of modified portions, The separation step includes, after performing the peel layer formation step, separating the substrate from the workpiece using the peel layer as a starting point, Each of these multiple regions extends along the first direction, The first direction is parallel to the specific crystal plane and has an angle of 5° or less with respect to a specific crystal orientation included in crystal orientation <100>. These multiple regions are provided at predetermined central intervals in the second direction, The second direction is parallel to the specific crystal plane and perpendicular to the first direction. The predetermined center spacing is 100 μm or more and 1 mm or less. The peel layer formation step is, A laser beam irradiation step in which a laser beam of a wavelength that penetrates the single crystal silicon is focused at each of the multiple focal points, which are formed to be aligned along the second direction, and the workpiece and the multiple focal points are moved relative to each other along the first direction, with the focal points positioned at a predetermined depth from the surface of the workpiece and inside at least two of the multiple regions. An indexing feed step that changes the position where the plurality of focal points are formed from inside each of the at least two regions to inside each of at least two other regions that are different from the at least two regions, A method for manufacturing a single-crystal silicon substrate, which is carried out by repeatedly performing the following steps alternately.

2. The method for manufacturing a single-crystal silicon substrate according to claim 1, wherein the distance between adjacent pairs of focal points among the plurality of focal points formed within each of the at least two regions is smaller than the predetermined center distance.

3. The method for manufacturing a single-crystal silicon substrate according to claim 1 or 2, wherein in the laser beam irradiation step, the crack is formed such that the crack formed in one of the two adjacent regions of the at least two regions is connected to the crack formed in the other region.

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