Manufacturing method for single-crystal silicon substrates

Abstract

This technology improves the productivity of substrate manufacturing when using laser beams to produce substrates from workpieces such as ingots. [Solution] A first processing step is performed to form modified areas in multiple first regions, and then a second processing step is performed to form modified areas and cracks in multiple second regions. Here, the cracks formed in the second processing step tend to extend toward the modified areas formed in the first processing step. This makes it possible to arbitrarily set the direction in which the cracks tend to extend in the second processing step. In this case, it becomes easier to make the delamination layer formed inside the workpiece thinner. And if the delamination layer is thinner, the amount of material from the workpiece that is discarded when cutting out the substrate from the workpiece and planarizing the substrate is reduced. As a result, it becomes possible to improve the productivity of substrates when manufacturing substrates from a workpiece using a laser beam.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a single crystal silicon substrate 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 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 columnar single crystal silicon (hereinafter also simply referred to as an "ingot") using, for example, a wire saw (see, for example, Patent Document 1).

[0003] However, the cutting loss 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 during the cutting out of the substrate from the ingot and the flattening of 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 an 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 a substrate using a wire saw from an ingot.

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 Initiative] [Problems that the invention aims to solve]

[0007] Single-crystal silicon is most easily cleaved at a specific crystal plane within crystal plane {111}. For example, in an ingot where crystal plane (100), which is a specific crystal plane within crystal plane {100}, is exposed on both the front and back surfaces, the crystal orientation... <110> When a laser beam is irradiated along a specific crystal orientation

[0011] contained within the ingot to form a modified area inside the ingot, many cracks are generated that extend along the crystal planes parallel to the crystal orientation

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

number

[0008] Here, the angle that crystal plane (100) makes with a specific crystal plane included in crystal plane {111} is approximately 54.7°. Therefore, as described above, when a laser beam is irradiated onto the ingot, many cracks are generated in the thickness direction of the ingot, with a larger component in the thickness direction than in the direction parallel to the surface and back surface of the ingot.

[0009] In this case, the delamination layer formed inside the ingot becomes thicker, and the amount of ingot and substrate material discarded during the cutting of the substrate from the ingot and the planarization of the substrate increases. In view of this, the object of the present invention is to provide a method for manufacturing a single-crystal silicon substrate that can improve the productivity of substrates when manufacturing substrates from a workpiece such as an ingot using a laser beam. [Means for solving the problem]

[0010] 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 in which a delamination layer including a modified portion and cracks extending from the modified portion is formed inside the workpiece; and a separation step in which, after performing the delamination layer formation step, the substrate is separated from the workpiece starting from the delamination layer, wherein each of the delamination layer formation steps is parallel to the specific crystal plane and the crystal orientation <100> The process comprises: a first processing step for forming the modified portion in a plurality of first regions that extend along a first direction in which the angle with respect to a specific crystal orientation contained in the silicon is 5° or less, are parallel to the specific crystal plane, and are spaced apart from each other in a second direction perpendicular to the first direction; and a second processing step for forming the modified portion and the crack in a plurality of second regions, each of which extends along the first direction and is spaced apart from each other in a second direction, wherein one of the plurality of second regions is located between adjacent pairs of first regions, and one of the plurality of first regions is located between adjacent pairs of second regions, and the first processing step involves focusing a laser beam of a wavelength that penetrates the single crystal silicon at a focal point among the plurality of first regions. A method for manufacturing a single-crystal silicon substrate is provided, which is performed by alternately repeating a first laser beam irradiation step of moving the focusing point and the workpiece relatively along the first direction while the focusing point is located inside one of the plurality of second regions and at a first depth from the surface of the workpiece, and a first indexing feed step of moving the position where the focusing point is formed and the workpiece relatively along the second direction, wherein the second processing step is performed by alternately repeating a second laser beam irradiation step of moving the focusing point and the workpiece relatively along the first direction while the focusing point is located inside one 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 indexing feed step of moving the position where the focusing point is formed and the workpiece relatively along the second direction.

[0011] Furthermore, preferably, the second depth is deeper than the first depth.

[0012] Preferably, the angle between the first plane passing through the center of a second region located between the adjacent pair of first regions and the center of one of the adjacent pair of first regions and the front and back surfaces of the workpiece is 45° or less, and the angle between the second plane passing through the first line and the center of the other of the adjacent pair of first regions and the front and back surfaces of the workpiece is 45° or less. [Effects of the Invention]

[0013] In the present invention, a first processing step is performed to form modified portions in a plurality of first regions, and then a second processing step is performed to form modified portions and cracks in a plurality of second regions.

[0014] In the first processing step, when a modified area is formed, the volume of the workpiece expands, creating internal stress in the workpiece. Furthermore, cracks formed in the second processing step tend to propagate towards the areas where internal stress is present.

[0015] Therefore, cracks formed in the second processing step tend to extend towards the modified portion formed in the first processing step. This makes it possible to arbitrarily set the direction in which cracks tend to extend in the second processing step in the present invention.

[0016] In this case, it becomes easier to make the release layer formed inside the workpiece thinner. And if the release layer is thinner, the amount of material from the workpiece that is discarded during cutting and planarization of the substrate is reduced. As a result, in this invention, it is possible to improve the productivity of substrates when manufacturing substrates from a workpiece using a laser beam.

Brief Description of the Drawings

[0017] [Figure 1] FIG. 1 is a perspective view schematically showing an example of an ingot used in the production of a substrate. [Figure 2] FIG. 2 is a top view schematically showing the ingot shown in FIG. 1. [Figure 3] FIG. 3 is a flowchart schematically showing an example of a method for manufacturing a single crystal silicon substrate by manufacturing a substrate from an ingot to be processed. [Figure 4] FIG. 4 is a top view schematically showing a plurality of regions included in the ingot. [Figure 5] FIG. 5 is a flowchart schematically showing an example of the peeling layer formation step shown in FIG. 3. [Figure 6] FIG. 6 is a view schematically showing an example of a laser processing apparatus used when forming a peeling layer inside the ingot. [Figure 7] FIG. 7 is a top view schematically showing a state in which the ingot is held on the holding table of the laser processing apparatus. [Figure 8] FIG. 8 is a flowchart schematically showing an example of the first processing step shown in FIG. 5. [Figure 9] FIG. 9(A) is a top view schematically showing the state 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 state of the first laser beam irradiation step shown in FIG. 8. [Figure 10] FIG. 10 is a cross-sectional view schematically showing a peeling layer including a modified portion formed inside the ingot and cracks extending from the modified portion in the first laser beam irradiation step shown in FIG. 8. [Figure 11] FIG. 11 is a cross-sectional view schematically showing a peeling layer formed inside the ingot by performing the first laser beam irradiation step shown in FIG. 8 twice. [Figure 12] FIG. 12 is a flowchart schematically showing an example of the second processing step shown in FIG. 5. [Figure 13] Figure 13 is a schematic cross-sectional view showing the delamination layer formed inside the ingot by performing the second laser beam irradiation step shown in Figure 12. [Figure 14] Figures 14(A) and 14(B) are schematic cross-sectional side views illustrating an example of the separation step shown in Figure 3. [Figure 15] Figure 15 is a graph showing the width of the delamination layer formed inside a workpiece made of single-crystal silicon when a laser beam is irradiated onto regions aligned with different crystal orientations. [Figure 16] Figures 16(A) and 16(B) are schematic partial cross-sectional side views illustrating another example of the separation step shown in Figure 3. [Modes for carrying out the invention]

[0018] Embodiments of the present invention will be described with reference to the attached drawings. Figure 1 is a schematic perspective view showing an example of an ingot used in the manufacture of a substrate, and Figure 2 is a schematic top view showing the ingot shown in Figure 1.

[0019] Figure 1 also shows the crystal planes of the single-crystal silicon exposed in the plane contained within this ingot. Furthermore, Figure 2 shows the crystal orientation of the single-crystal silicon constituting this ingot.

[0020] 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] .

[0021] 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.

[0022] 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] .

[0023] 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.

[0024] 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 inside the ingot 11, which includes a modified portion and cracks extending from the modified portion (delamination layer formation step: S1).

[0025] In this delamination layer formation step (S1), delamination layers are formed sequentially on multiple regions contained in the ingot 11. Figure 4 is a schematic top view showing multiple regions contained in the ingot 11. Figure 5 is a schematic flowchart showing an example of the delamination layer formation step (S1) shown in Figure 3.

[0026] In this delamination layer formation step (S1), first, modified portions are formed in a plurality of first regions 11d, each extending along the crystal orientation

[0010] and separated from each other in the crystal orientation

[0001] (first processing step: S11).

[0027] Then, after the completion of the first processing step (S11), modified portions and cracks are formed in a plurality of second regions 11e, each extending along a crystal orientation

[0010] and positioned between a pair of adjacent first regions 11d, and each having a width along a crystal orientation

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

[0028] Furthermore, in the delamination layer formation step (S1), a delamination layer containing modified parts and cracks is formed inside the ingot 11 using a laser processing device. Figure 6 is a schematic diagram showing an example of a laser processing device used when forming a delamination layer inside the ingot 11.

[0029] In Figure 6, 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 6, some of the components of the laser processing apparatus are shown as functional blocks.

[0030] The laser processing apparatus 2 shown in Figure 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 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.

[0031] 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 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.

[0032] 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.

[0033] 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.

[0034] 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).

[0035] 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 16) focusing points aligned along the Y axis.

[0036] 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.

[0037] 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. When this moving mechanism operates, the emission area of ​​the laser beam LB moves along the X-axis, Y-axis, and / or Z-axis.

[0038] Furthermore, in the laser processing apparatus 2, by operating this moving mechanism, the position (coordinates) of the focal point where the laser beam LB, which is irradiated from the irradiation head 16 to the holding surface side of the holding table 4, is focused can be adjusted in the X-axis, Y-axis, and Z-axis directions.

[0039] When performing the delamination layer formation step (S1) in the laser processing apparatus 2, the holding table 4 first holds the ingot 11 with its surface 11a facing upwards. Figure 7 is a schematic top view showing how the holding table 4 of the laser processing apparatus 2 holds the ingot 11.

[0040] The ingot 11 is held on the holding table 4 in such a state 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°.

[0041] In other words, 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. Once the ingot 11 is held on the holding table 4 in this manner, the first processing step (S11) is performed.

[0042] Figure 8 is a schematic flowchart illustrating an example of the first processing step (S11) shown in Figure 5. In this first processing step (S11), first, with the focal point where the laser beam LB is focused positioned inside one of the plurality of first regions 11d and at a first depth from the surface 11a of the ingot 11, the focal point and the ingot 11 are moved relative to each other along the X-axis direction (crystal orientation

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

[0043] Figure 9(A) is a schematic top view showing the first laser beam irradiation step (S111) shown in Figure 8, and Figure 9(B) is a schematic partial cross-sectional side view showing the first laser beam irradiation step (S111) shown in Figure 8. Figure 10 is a schematic cross-sectional view showing the delamination layer, which includes the modified portion formed inside the ingot 11 and the cracks extending from the modified portion, during the first laser beam irradiation step (S111) shown in Figure 8.

[0044] In this first laser beam irradiation step (S111), for example, a delamination layer is first formed in a first region 11d located at one end of a plurality of first regions 11d in the Y-axis direction (crystal orientation

[0001] ). Specifically, first, the irradiation head 16 of the laser beam irradiation unit 6 is positioned in the X-axis direction when viewed from the irradiation head 16 in a plan view.

[0045] Next, the irradiation head 16 is raised and lowered so that the multiple focal points formed by focusing each branched laser beam LB are positioned at a height corresponding to a first depth from the surface 11a of the ingot 11.

[0046] Next, while irradiating the holding table 4 with the laser beam LB from the irradiation head 16, the irradiation head 16 is moved so that, in a plan view, it passes from one end to the other of the ingot 11 in the X-axis direction (crystal orientation

[0010] ) (see Figures 9(A) and 9(B)).

[0047] As the irradiation head 16 moves while irradiating with the laser beam LB in this manner, the multiple focal points are positioned at a first depth from the surface 11a of the ingot 11, and the multiple focal points and the ingot 11 move relative to each other along the X-axis direction (crystal orientation

[0010] ).

[0048] The laser beam LB is branched and focused to form multiple (for example, 5) focal points that are equally spaced in the Y-axis direction (crystal orientation

[0001] ) (see Figure 10). At this time, the distance between adjacent pairs of focal points is set to, for example, 5 μm to 20 μm, typically 10 μm.

[0049] Furthermore, the power of the laser beam LB focused at each of the multiple focusing points, that is, the power obtained by dividing the power of the laser beam LB adjusted in the attenuator 10 by the number of branches (for example, 5), is relatively small, for example, set to be between 0.1W and 0.3W, and typically 0.2W.

[0050] As a result, modified regions 15a are formed inside the ingot 11, with the crystal structure of the single-crystal silicon being disordered, centered around each of the multiple focal points. Furthermore, when modified regions 15a are formed inside the ingot 11, the volume of the ingot 11 expands, causing internal stress to be generated within the ingot 11.

[0051] Then, within the ingot 11, cracks 15b extend from the modified portion 15a to relieve this internal stress. As a result, a delamination layer 15 is formed inside the ingot 11, which includes multiple modified portions 15a and cracks 15b that propagate from each of the multiple modified portions 15a.

[0052] In the first laser beam irradiation step (S111), a laser beam LB with such low power that a modified portion 15a is formed inside the ingot 11 but cracks 15b do not extend from the modified portion 15a may be irradiated. In other words, the delamination layer 15 formed in the first laser beam irradiation step (S111) does not necessarily contain cracks 15b.

[0053] Then, if the irradiation of all of the multiple first regions 11d with the laser beam LB has not been completed (step (S112): NO), the position where the focal point is formed and the ingot 11 are moved relative to each other along the Y axis (crystal orientation

[0001] ) (first indexing feed step: S113).

[0054] In this first indexing feed 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] ) with respect to the first region 11d adjacent to the first region 11d where the delamination layer 15 has already been formed, but where the delamination layer 15 has not been formed.

[0055] 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 way, as shown in Figure 11, a new detached layer 15 (detached layer 15-2) is formed inside the ingot 11, which is parallel to the already formed detached layer 15 (detached layer 15-1) and separated from the detached layer 15-1 in the Y-axis direction (crystal orientation

[0001] ).

[0056] Furthermore, the first indexing feed step (S113) and the first laser beam irradiation step (S111) are repeatedly performed alternately until a peeling layer 15 is formed on all of the multiple first regions 11d contained in the ingot 11. Once a peeling layer 15 is formed on all of the multiple first regions 11d (step (S112): YES), the second processing step (S12) is performed.

[0057] Figure 12 is a schematic flowchart illustrating an example of the second processing step (S12) shown in Figure 5. In this second processing step (S12), first, the focal point where the laser beam LB is focused is positioned inside one of the multiple second regions 11e and at a second depth from the surface 11a of the ingot 11, and the focal point and the ingot 11 are moved relative to each other along the X-axis direction (crystal orientation

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

[0058] The second depth is different from the first depth, and is, 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. Furthermore, this difference is set to be shorter than the interval between which the multiple first regions 11d and the multiple second regions 11e are provided.

[0059] Specifically, this difference is set to be shorter than the distance in a plan view between a straight line along the X-axis that is located at the center of the second region 11e in the Y-axis direction and a straight line along the X-axis that is located at the center of the first region 11d adjacent to the second region 11e in the Y-axis direction.

[0060] In other words, the first and second depths 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. Furthermore, this angle is preferably 40° or less, more preferably 35° or less, and most preferably 30° or less.

[0061] Furthermore, in the laser processing apparatus 2, by changing the position of the irradiation head 16 in the Z-axis direction, the focal point where the laser beam LB is focused can be positioned at a second depth from the surface 11a of the ingot 11.

[0062] Furthermore, in the second laser beam irradiation step (S121), similar to the first laser beam irradiation step (S111) described above, the irradiation head 16 is moved along the X-axis direction (crystal orientation

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

[0001] ) while irradiating the holding table 4 with the laser beam LB from the irradiation head 16.

[0063] As the irradiation head 16 moves while irradiating with the laser beam LB in this manner, the multiple focal points are positioned at a second depth from the surface 11a of the ingot 11, and the multiple focal points and the ingot 11 move relative to each other along the X-axis direction (crystal orientation

[0010] ).

[0064] Furthermore, during the second laser beam irradiation step (S121), the power of the laser beam LB focused at each of the multiple focal points is adjusted to be greater than the power of the laser beam LB focused at each of the multiple focal points during the first laser beam irradiation step (S111).

[0065] For example, in the second laser beam irradiation step (S121), the power of the laser beam LB focused at each of the multiple focusing points is set to, for example, greater than 0.3W and less than or equal to 0.6W.

[0066] As a result, within the ingot 11, as shown in Figure 13, modified sections 15c are formed around each of the multiple focal points, where the crystal structure of the single-crystal silicon is disordered. In the second laser beam irradiation step (S121), the power of the laser beam LB focused at each of the multiple focal points is greater than in the first laser beam irradiation step (S111), so the size of the modified section 15c is also larger than that of the modified section 15a.

[0067] Furthermore, since the volume expansion of the ingot 11 due to the formation of the modified portion 15c is greater than the volume expansion due to the formation of the modified portion 15a, the second laser beam irradiation step (S121) generates greater internal stress in the ingot 11 than in the first laser beam irradiation step (S111).

[0068] Furthermore, within the ingot 11, cracks 15d, which are larger than cracks 15b, extend from the modified portion 15c to relieve this internal stress. In addition, cracks 15d that occur within the ingot 11 tend to extend towards areas where internal stress is occurring within the ingot 11.

[0069] Therefore, cracks 15d extending from the modified portion 15c tend to extend toward the modified portion 15a and / or cracks 15b contained in the already formed delamination layer 15 (delamination layer 15-1, 15-2). As a result, a delamination layer 15 (delamination layer 15-3) containing multiple modified portions 15c and cracks 15d progressing from each of the multiple modified portions 15c is formed inside the ingot 11.

[0070] Then, if the irradiation of all of the multiple second regions 11e with the laser beam LB has not been completed (step (S122): NO), the position where the focal point is formed and the ingot 11 are moved relative to each other along the Y axis (crystal orientation

[0001] ) (second indexing feed step: S123).

[0071] In this second indexing feed 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] ) with respect to the second region 11e adjacent to the second region 11e where the peeling layer 15 has already been formed, but where the peeling layer 15 has not been formed.

[0072] Next, the second laser beam irradiation step (S121) described above is performed again. Furthermore, the second indexing and feeding step (S123) and the second laser beam irradiation step (S121) are repeatedly performed alternately until a peeling layer 15 is formed in all of the multiple second regions 11e contained in the ingot 11.

[0073] Then, once the delamination layer 15 is formed in all of the multiple second regions 11e (step (S122): YES), the delamination layer 15 is formed throughout the entire interior of the ingot 11, and the delamination layer formation step (S1) shown in Figure 3 is completed.

[0074] In this delamination layer formation step (S1), since the first and second depths are set as described above, the thickness of the delamination layer 15 formed inside the ingot 11 can be reduced. This point will be explained below.

[0075] First, the method for forming the delamination layer 15 throughout the entire interior of the ingot 11 is not limited to the method described above. For example, the delamination layer 15 can also be formed throughout 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 cracks 15d that extend during the second processing step (S12) along the thickness direction of the ingot 11 will become larger.

[0076] On the other hand, if the first processing step (S11) is performed prior to the second processing step (S12), and the first and second depths are set as described above, the component of the crack 15d perpendicular to the thickness direction of the ingot 11 tends to be larger than the component along the thickness direction of the ingot 11. As a result, when the first and second depths are set as described above, the thickness of the delamination layer 15 formed inside the ingot 11 becomes relatively thin.

[0077] Then, once the delamination layer formation step (S1) shown in Figure 3 is completed, the substrate is separated from the ingot 11 starting from the delamination layer 15 (separation step: S2). Figures 14(A) and 14(B) are schematic partial cross-sectional side views showing 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 14(A) and 14(B).

[0078] 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.

[0079] Furthermore, this porous plate is in communication with a suction source (not shown), such as a vacuum pump, via a flow path or the like provided inside the holding table 20. When this suction source 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.

[0080] 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.

[0081] By operating this lifting mechanism, the separation unit 22 moves up and down. Also, by operating this rotational drive source, the support member 24 rotates with a rotation axis that passes through the center of the support member 24 and is aligned perpendicular to the holding surface of the holding table 20.

[0082] 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.

[0083] 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.

[0084] In the separation device 18, for example, the separation step (S2) is carried out 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 peeled layer 15 is formed coincides with the center of the holding surface of the holding table 20.

[0085] Next, a suction source communicating with a porous plate exposed on the holding surface is activated so that the ingot 11 is held by the holding table 20. Then, actuators are activated to position each of the multiple movable members 28 radially outward from the base 26.

[0086] Next, the lifting mechanism is operated to position the tips of the wedge portions 28b of each of the multiple movable members 28 at a height corresponding to the peeling layer 15 formed inside the ingot 11. Then, the actuator is operated so that the wedge portions 28b are driven into the side surface 11c of the ingot 11 (see Figure 14(A)).

[0087] Next, the rotation drive source is operated so that the wedge portion 28b driven into the side surface 11c of the ingot 11 rotates. Then, the lifting mechanism is operated to raise the wedge portion 28b (see Figure 14(B)).

[0088] 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 and 15d 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.

[0089] 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.

[0090] In the method for manufacturing a single-crystal silicon substrate described above, a first processing step (S11) is performed to form modified portions 15a in a plurality of first regions 11d, and then a second processing step (S12) is performed to form modified portions 15c and cracks 15d in a plurality of second regions 11e.

[0091] In the first processing step (S11), when the modified portion 15a is formed, the volume of the ingot 11 expands, causing internal stress to be generated in the ingot 11. Furthermore, the crack 15d formed in the second processing step (S12) tends to extend towards the area where internal stress is generated.

[0092] Therefore, the cracks formed in the second processing step (S12) tend to extend towards the modified portion 15a formed in the first processing step (S11). This makes it possible to arbitrarily set the direction in which the cracks 15d tend to extend in the second processing step (S12).

[0093] In this case, it becomes easier to make the delamination layer 15 formed inside the ingot 11 thinner. And if the delamination layer 15 is thinner, the amount of ingot material discarded during the cutting of the substrate 17 from the ingot 11 and the planarization of the substrate 17 is reduced. As a result, this method makes it possible to improve the productivity of manufacturing the substrate 17 from the ingot 11 using a laser beam LB.

[0094] 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 front surface 11a and the back surface 11b, respectively.

[0095] Here, crystal orientation

[0010] is crystal orientation <110> This is a direction in which the angle with respect to a specific crystal orientation (for example, crystal orientation

[0011] ) is large (for example, 45°). Therefore, in this method, cracks are less likely to occur that extend from the modified parts 15a and 15c formed inside the ingot 11 by irradiation with the laser beam LB, along a specific crystal plane (for example, the crystal plane shown in (2) below) included in the crystal plane {111}.

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[0096] Furthermore, in this method, many cracks are generated from the modified parts 15a and 15c 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 (3) below).

number

[0097] 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°.

[0098] Therefore, this method can suppress the occurrence of cracks in which the component along the thickness direction of the ingot 11 is larger than the component along the direction parallel to the surface 11a and back surface 11b.

[0099] In this case, the thickness of the delamination layer 15 formed inside the ingot 11 is suppressed, and the amount of material from the ingot 11 and substrate 17 that is discarded during the cutting of the substrate 17 from the ingot 11 and the planarization of the substrate 17 is reduced. As a result, this method makes it possible to further improve the productivity of the substrate 17 when manufacturing the substrate 17 from the ingot 11 using a laser beam LB.

[0100] 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.

[0101] 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.

[0102] Furthermore, the structure of the laser processing apparatus used in the present invention is not limited to the structure of the laser processing apparatus 2 described above. For example, the present invention may be carried out using a laser processing apparatus provided with a moving mechanism that moves the holding table 4 along the X-axis, Y-axis, and / or Z-axis directions, respectively.

[0103] Alternatively, the present invention may be implemented using a laser processing apparatus in which a scanning optical system capable of changing the direction of the laser beam LB emitted 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.

[0104] In other words, in the present invention, it is sufficient that the ingot 11 held by the holding table 4 and the focal point of the laser beam LB irradiated from the irradiation head 16 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.

[0105] Furthermore, the plurality of first regions and plurality of second 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 a region along the crystal orientation

[0001] .

[0106] 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 (4) below.

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[0107] 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 15.

[0108] Figure 15 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.

[0109] 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.

[0110] 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.

[0111] As shown in Figure 15, 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.

[0112] Therefore, in the peel layer formation step (S1) of the present invention, the laser beam LB may be irradiated to a region in a plan view that is tilted by 5° or less from the crystal orientation

[0001] or the crystal orientation

[0010] .

[0113] 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 a region 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.

[0114] 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).

[0115] Furthermore, in the present invention, in the second laser beam irradiation step (S121), the focal point where the laser beam LB is focused may be positioned at a second depth that is shallower than the first depth, and the focal point and the ingot 11 may be moved relative to each other.

[0116] 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 14(A) and 14(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.

[0117] Figures 16(A) and 16(B) are schematic cross-sectional side views illustrating the separation step (S2) performed in this manner. The separation apparatus 30 shown in Figures 16(A) and 16(B) has a holding table 32 for holding the ingot 11 on which the peeled layer 15 is formed.

[0118] The holding table 32 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 a vacuum pump, via a flow path or the like provided inside the holding table 32.

[0119] Therefore, when this suction source operates, an attractive force acts on the space near the holding surface of the holding table 32. This allows, for example, the holding table 32 to hold the ingot 11 placed on the holding surface.

[0120] Furthermore, a separation unit 34 is provided above the holding table 32. This separation unit 34 has a cylindrical support member 36. A ball screw type lifting mechanism (not shown), for example, is connected to the upper part of this support member 36, and the separation unit 34 moves up and down by operating this lifting mechanism.

[0121] Furthermore, the lower end of the support member 36 is fixed to the center of the upper part of the disc-shaped suction plate 38. Multiple suction ports are formed on the lower surface of the suction plate 38, and each of these ports is connected to a suction source (not shown), such as a vacuum pump, via a flow path or the like provided inside the suction plate 38.

[0122] Therefore, when this suction source operates, a suction force acts on the space near the lower surface of the suction plate 38. This allows, for example, an ingot 11 adjacent to the lower surface of the suction plate 38 to be pulled upward by suction.

[0123] In the separation device 30, for example, the separation step (S2) is carried out 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 peeled layer 15 is formed coincides with the center of the holding surface of the holding table 32.

[0124] Next, a suction source communicating with a porous plate exposed on the holding surface is activated so that the ingot 11 is held by the holding table 32. Then, the lifting mechanism is activated 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.

[0125] Next, a suction source communicating with multiple suction ports is activated so that the surface 11a side of the ingot 11 is sucked through the multiple suction ports formed in the suction plate 38 (see Figure 16(A)). Then, the lifting mechanism is activated to raise the separation unit 34 so that the suction plate 38 is separated from the holding table 32 (see Figure 16(B)).

[0126] At this time, an upward force acts on the surface 11a side of the ingot 11, which is being sucked in through multiple suction ports formed in the suction plate 38. As a result, the cracks 15b contained in the release layer 15 extend further, separating the surface 11a side and the back surface 11b side of the ingot 11. In other words, the substrate 17 is manufactured from the ingot 11, starting from the release layer 15.

[0127] 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 and 15d 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.

[0128] 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.

[0129] 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 parts 15a, 15c and cracks 15b, 15d 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).

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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]

[0135] 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: First domain, 11e: Second domain) 12: Branch Unit 13: Orientation Flat 14: Miller 15: Detachment layer (15a: Modified area, 15b: Crack) (15c: Modified area, 15d: Crack) 15-1: Exfoliation layer 15-2: Delamination layer 15-3: Exfoliation layer 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: Separation device 32: Holding Table 34: Separation Unit 36: Support member 38: 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 peeling layer forming step in which a peeling layer is formed inside the workpiece, which includes a modified portion and cracks extending from the modified portion, The separation step includes, after performing the delamination layer formation step, separating the substrate from the workpiece using the delamination layer as a starting point, The peel layer formation step is, A first processing step for forming the modified portion in a plurality of first regions, each of which is parallel to the specific crystal plane and extends along a first direction in which the angle it makes with a specific crystal orientation included in the crystal orientation <100> is 5° or less, and which is parallel to the specific crystal plane and is spaced apart from each other in a second direction perpendicular to the first direction, The process includes, after performing the first processing step, a second processing step for forming the modified portion and the crack in a plurality of second regions, each extending along the first direction and separated from each other in the second direction, Between a pair of adjacent first regions, one of the multiple second regions is located. Between any two adjacent pairs of the multiple second regions, one of the multiple first regions is located. The first processing step is, A first laser beam irradiation step involves moving the focal point and the workpiece relative to each other along the first direction, with the focal point, where a laser beam of a wavelength that penetrates the single crystal silicon is focused, positioned inside one of the plurality of first regions and at a first depth from the surface of the workpiece. A first indexing feed step that moves the position where the focusing point is formed and the workpiece relative to each other along the second direction, This is done by alternating between the following: The second processing step is, A second laser beam irradiation step in which the focusing point and the workpiece are moved relative to each other along the first direction, with the focusing point positioned inside one of the plurality of second regions and at a second depth different from the first depth from the surface of the workpiece; A second indexing feed step that moves the position where the focusing point is formed and the workpiece relative to each other along the second direction, 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 second depth is deeper than the first depth.

3. The angle between the first plane passing through the center of a second region located between the pair of adjacent first regions and the center of one of the pair of adjacent first regions and the front and back surfaces of the workpiece is 45° or less. A method for manufacturing a single-crystal silicon substrate according to claim 1 or 2, wherein the angle between a second plane passing through the first straight line and a third straight line along the first direction passing through the center of the other of the pair of adjacent first regions, and the front and back surfaces of the workpiece, is 45° or less.

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