Method for manufacturing single crystal silicon substrate

Abstract

To improve productivity of a substrate when manufacturing the substrate from a workpiece such as an ingot utilizing laser beams.SOLUTION: After implementing a first processing step for forming modified parts in a plurality of first regions, a second processing step is implemented for forming modified parts and cracks in a plurality of second regions. The crack formed in the second processing step easily extends toward the modified part formed in the first processing step. Thus, a direction in which the crack easily extends can be arbitrarily set in the second processing step. In such a case, a release layer formed inside of a workpiece can be easily thinned. If the release layer becomes thin, a material amount of the workpiece disposed in segmenting the substrate from the workpiece and flattening the substrate is reduced. As a result, it is possible to improve productivity of the substrate in manufacturing the substrate from the workpiece utilizing laser beams.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a single crystal silicon substrate, which manufactures 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 both the front and back surfaces. [Background technology]

[0002] Semiconductor device chips are generally manufactured using a disk-shaped single crystal silicon substrate (hereinafter simply referred to as "substrate"), which is cut from a cylindrical single crystal silicon ingot (hereinafter simply referred to as "ingot") using, for example, a wire saw (see, for example, Patent Document 1).

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

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

[0005] In view of this, a method has been proposed in which a laser beam having a wavelength that passes through single crystal silicon is used to form a peeling layer inside an ingot that includes a modified portion and cracks extending from the modified portion, and then the substrate is separated from the ingot using this peeling layer as a starting point (see, for example, Patent Document 2). This method can improve substrate productivity compared to manufacturing substrates from ingots using a wire saw. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 9-262826 [Patent Document 2] Japanese Patent Publication No. 2022-25566 Summary of the Invention [Problem to be solved by the invention]

[0007] Single crystal silicon is most easily cleaved along a specific crystal plane included in the crystal plane {111}. For example, when an ingot is cleaved in which the crystal plane (100), which is a specific crystal plane included in the crystal plane {100}, is exposed on both the front and back surfaces, <110> When a modified area is formed inside an ingot by irradiating a laser beam along the crystal orientation

[0011] , which is a specific crystal orientation included in the crystal plane {111}, many cracks are generated that extend along the specific crystal planes included in the crystal plane {111} that are parallel to the crystal orientation

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

number

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

[0009] In this case, a peeled layer formed inside the ingot becomes thick, and a large amount of ingot and substrate material is discarded when cutting the substrate from the ingot and flattening the substrate. 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 productivity 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 includes a step of forming a peeling layer in the workpiece, the peeling layer including a modified portion and a crack extending from the modified portion, and a step of separating the substrate from the workpiece starting from the peeling layer, the step including forming a peeling layer in the workpiece, the peeling layer being parallel to the specific crystal plane and aligned along the crystal orientation {100}. <100> and a second processing step, after the first processing step, for forming the modified portions and the cracks in a plurality of second regions each extending along the first direction and spaced apart from one another in the second direction, the second region extending along the first direction and spaced apart from one another in the second direction, wherein any one of the plurality of second regions is positioned between a pair of adjacent first regions among the plurality of first regions, and any one of the plurality of first regions is positioned between a pair of adjacent second regions among the plurality of second regions, and the first processing step is performed by focusing a laser beam having a wavelength that is transmitted through the single crystal silicon. the second machining step is carried out by alternately repeating a first laser beam application step of relatively moving the focal point and the workpiece along the first direction, with the focal point being positioned inside any of the plurality of first regions and at a first depth from the surface of the workpiece, and a first indexing / feeding step of relatively moving the position where the focal point is to be formed and the workpiece along the second direction, with the focal point being positioned inside any of the plurality of second regions and at a second depth different from the first depth from the surface of the workpiece; and the second machining step is carried out by alternately repeating a second laser beam application step of relatively moving the focal point and the workpiece along the first direction, with the focal point being positioned inside any of the plurality of second regions and at a second depth from the surface of the workpiece that is different from the first depth, and a second indexing / feeding step of relatively moving the position where the focal point is to be formed and the workpiece along the second direction,The power of the laser beam focused at the focusing point during the second laser beam irradiation step is greater than the power of the laser beam focused at the focusing point during the first laser beam irradiation step.

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

[0012] Also, preferably, the angle formed by a first plane passing through a first straight line along the first direction passing through the center of a second region positioned between the pair of adjacent first regions and a second straight line along the first direction passing through the center of one of the pair of adjacent first regions, with respect to the front and back surfaces of the workpiece is 45° or less, and the angle formed by a second plane passing through the first straight line and a third straight line along the first direction passing through the center of the other of the pair of adjacent first regions, with respect to 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 carried out to form modified areas in a plurality of first regions, and then a second processing step is carried out to form modified areas and cracks in a plurality of second regions.

[0014] When the modified portion is formed in the first processing step, the volume of the workpiece expands, causing internal stress in the workpiece, and cracks formed in the second processing step tend to propagate toward the location where the internal stress is occurring.

[0015] Therefore, the cracks formed in the second processing step tend to propagate toward the modified portion formed in the first processing step, which allows the direction in which the cracks tend to propagate in the second processing step to be set arbitrarily.

[0016] In this case, it is easy to thin the release layer formed inside the workpiece. Furthermore, a thinner release layer reduces the amount of workpiece material discarded during cutting and planarizing of the substrate from the workpiece. As a result, the present invention makes it possible to improve productivity of substrates when manufacturing substrates from workpieces using a laser beam. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a perspective view schematically showing an example of an ingot used in manufacturing a substrate. [Figure 2] FIG. 2 is a top view schematically showing the ingot shown in FIG. [Figure 3] FIG. 3 is a flow chart schematically showing an example of a method for manufacturing a single crystal silicon substrate, in which a substrate is manufactured from an ingot that serves as a workpiece. [Figure 4] FIG. 4 is a top view schematically showing a plurality of regions included in an ingot. [Figure 5] FIG. 5 is a flow chart schematically illustrating an example of the release layer forming step shown in FIG. [Figure 6] FIG. 6 is a diagram schematically illustrating an example of a laser processing device used when forming a peeling layer inside an ingot. [Figure 7] FIG. 7 is a top view schematically showing how an ingot is held on a holding table of the laser processing device. [Figure 8] FIG. 8 is a flowchart schematically illustrating an example of the first processing step shown in FIG. [Figure 9] 9(A) is a top view schematically showing the first laser beam irradiation step shown in FIG. 8, and FIG. 9(B) is a partially cross-sectional side view schematically showing 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 in the first laser beam irradiation step shown in FIG. 8 and a crack extending from the modified portion. [Figure 11] FIG. 11 is a cross-sectional view schematically showing a separation layer formed inside an ingot by performing the first laser beam irradiation step shown in FIG. 8 twice. [Figure 12] FIG. 12 is a flowchart schematically illustrating an example of the second processing step shown in FIG. [Figure 13] FIG. 13 is a cross-sectional view schematically showing a separation layer formed inside the ingot by performing the second laser beam irradiation step shown in FIG. [Figure 14] 14(A) and 14(B) are each a partial cross-sectional side view that schematically illustrates an example of the separation step shown in FIG. [Figure 15] FIG. 15 is a graph showing the width of the exfoliation layer formed within a workpiece made of single crystal silicon when a laser beam is applied to regions along different crystal orientations. [Figure 16] 16(A) and 16(B) are each a partial cross-sectional side view schematically showing another example of the separation step shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0018] An embodiment of the present invention will be described with reference to the accompanying drawings, in which Fig. 1 is a perspective view schematically showing an example of an ingot used in manufacturing a substrate, and Fig. 2 is a top view schematically showing the ingot shown in Fig. 1.

[0019] 1 also shows the crystal planes of the single crystal silicon exposed on the planes included in the ingot, and FIG. 2 also shows the crystal orientation of the single crystal silicon that constitutes the ingot.

[0020] 1 and 2, a specific crystal plane included in the crystal plane {100} (here, for convenience, referred to as the crystal plane (100)) is exposed on each of the front surface 11a and the back surface 11b. That is, in this ingot 11, the perpendicular lines (crystal axes) of the front surface 11a and the back surface 11b are aligned along the crystal orientation

[0100] .

[0021] Although the ingot 11 is manufactured so that the crystal plane (100) is exposed on each of the front surface 11a and the back surface 11b, due to processing errors during manufacturing, a surface slightly tilted from the crystal plane (100) may be exposed on each of the front surface 11a and the back surface 11b.

[0022] Specifically, a surface that forms an angle of 1° or less with respect to the crystal plane (100) may be exposed on each of the front surface 11a and the back surface 11b of the ingot 11. In other words, the crystal axis of the ingot 11 may be along a direction that forms an angle of 1° or less with respect to the crystal orientation

[0100] .

[0023] An orientation flat 13 is formed on the side surface 11c of the ingot 11, and the crystal orientation as viewed from this orientation flat 13 is <110> The center C of the ingot 11 is located in a specific crystal orientation (here, for convenience, it is assumed to be the crystal orientation

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

[0024] 3 is a flow chart schematically illustrating an example of a method for manufacturing a single crystal silicon substrate, in which a substrate is manufactured from a workpiece, that is, an ingot 11. In this method, first, a peeling layer including a modified portion and cracks extending from the modified portion is formed inside the ingot 11 (peeling layer forming step: S1).

[0025] In this separation layer forming step (S1), separation layers are formed in order in multiple regions included in ingot 11. Fig. 4 is a top view schematically showing multiple regions included in ingot 11. Fig. 5 is a flow chart schematically showing an example of the separation layer forming step (S1) shown in Fig. 3.

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

[0010] and spaced apart from each other in the crystal orientation

[0001] (first processing step: S11).

[0027] Then, after the first processing step (S11) is completed, modified areas and cracks are formed in a plurality of second regions 11e, each of which extends along the crystal orientation

[0010] , is positioned between a pair of adjacent first regions 11d, and has a width along the crystal orientation

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

[0028] In the peeling layer forming step (S1), a laser processing device is used to form a peeling layer including a modified portion and cracks inside the ingot 11. Figure 6 is a diagram schematically showing an example of a laser processing device used when forming a peeling layer inside the ingot 11.

[0029] 6, the X-axis direction (first direction) and the Y-axis direction (second direction) are directions perpendicular to each other on a horizontal plane, and the Z-axis direction is a direction (vertical direction) perpendicular to both the X-axis direction and the Y-axis direction. Also, in FIG. 6, some of the components of the laser processing device are shown in functional blocks.

[0030] 6 has a disk-shaped holding table 4. This holding table 4 has, for example, a circular upper surface (holding surface) parallel to the X-axis direction and the Y-axis direction. The holding table 4 also has a disk-shaped porous plate (not shown) whose upper surface is exposed on this holding surface.

[0031] Furthermore, this porous plate is connected to 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 is activated, a suction force acts on the space near the holding surface of the holding table 4. This allows, for example, the holding table 4 to hold an ingot 11 placed on the holding surface.

[0032] A laser beam irradiation unit 6 is provided above the holding table 4. The laser beam irradiation unit 6 has a laser oscillator 8. The laser oscillator 8 has, for example, Nd:YAG or the like as a laser medium.

[0033] The laser oscillator 8 then irradiates the ingot 11 with a pulsed laser beam LB (for example, with a frequency of 60 kHz) having a wavelength (for example, 1064 nm or 1342 nm) that is transparent to the material (single crystal silicon) that constitutes the ingot 11.

[0034] The output (power) of this laser beam LB is adjusted by an attenuator 10, and then supplied to a branching unit 12. This branching unit 12 has, for example, a spatial light modulator including a liquid crystal phase control element called LCoS (Liquid Crystal on Silicon) and / or a diffractive optical element (DOE).

[0035] The branching unit 12 then branches the laser beam LB so that the laser beam LB irradiated from the irradiation head 16 described later onto the holding surface side of the holding table 4 forms multiple (for example, 4 to 16) focal points aligned along the Y-axis direction.

[0036] The laser beam LB branched by the branching unit 12 is reflected by a mirror 14 and guided to an irradiation head 16. This irradiation head 16 contains a condenser lens (not shown) that condenses the laser beam LB, etc. The laser beam LB condensed by the condenser lens is irradiated onto the holding surface side of the holding table 4, or more simply, directly below, with the central region of the lower surface of the irradiation head 16 as its emission region.

[0037] Furthermore, the irradiation head 16 of the laser beam irradiation unit 6 and an optical system (e.g., mirror 14) for guiding the laser beam LB to the irradiation head 16 are connected to a movement mechanism (not shown). This movement mechanism includes, for example, a ball screw. When this movement mechanism operates, the emission area of ​​the laser beam LB moves along the X-axis direction, the Y-axis direction, and / or the Z-axis direction.

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

[0039] When the peeling layer forming step (S1) is performed in the laser processing apparatus 2, first, the ingot 11 with the surface 11a facing upward is held by the holding table 4. Fig. 7 is a top view schematically showing the state in which the ingot 11 is held on the holding table 4 of the laser processing apparatus 2.

[0040] This ingot 11 is held on the holding table 4, for example, in a state where the direction from the orientation flat 13 toward the center C of the ingot 11 (crystal orientation

[0011] ) forms an angle of 45° with respect to each of the X-axis direction and the Y-axis direction.

[0041] That is, the ingot 11 is held on the holding table 4 in a state where, for example, the crystal orientation

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

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

[0042] Fig. 8 is a flowchart schematically illustrating an example of the first processing step (S11) shown in Fig. 5. In this first processing step (S11), first, with the focal point at which 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 relatively along the X-axis direction (crystal orientation

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

[0043] Fig. 9(A) is a top view schematically showing the first laser beam irradiation step (S111) shown in Fig. 8, and Fig. 9(B) is a partial cross-sectional side view schematically showing the first laser beam irradiation step (S111) shown in Fig. 8. Also, Fig. 10 is a cross-sectional view schematically showing a peeling layer including a modified portion formed inside ingot 11 and a crack extending from the modified portion in the first laser beam irradiation step (S111) shown in Fig. 8.

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

[0001] ) among the plurality of first regions 11d. Specifically, first, the irradiation head 16 of the laser beam irradiation unit 6 is positioned so that the first region 11d 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 a plurality of focal points formed by converging the branched laser beams LB are positioned at a height corresponding to a first depth from the surface 11a of the ingot 11.

[0046] Next, while irradiating the laser beam LB from the irradiation head 16 toward the holding table 4, the irradiation head 16 is moved so as to pass from one end to the other end of the ingot 11 in the X-axis direction (crystal orientation

[0010] ) in a planar view (see Figures 9(A) and 9(B)).

[0047] When the irradiation head 16 moves while irradiating the laser beam LB in this manner, the multiple focal points and the ingot 11 move relatively along the X-axis direction (crystal orientation

[0010] ) with the multiple focal points positioned at a first depth from the surface 11a of the ingot 11.

[0048] The laser beam LB is branched and focused so as to form a plurality of (e.g., five) focusing points arranged at equal intervals in the Y-axis direction (crystal orientation

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

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

[0050] As a result, modified portions 15a in which the crystal structure of the single crystal silicon is disturbed are formed around each of the plurality of light-focusing points inside the ingot 11. Furthermore, when the modified portions 15a are formed inside the ingot 11, the volume of the ingot 11 expands, and internal stress is generated in the ingot 11.

[0051] Then, cracks 15b propagate from the modified portions 15a inside the ingot 11 so as to relieve this internal stress. As a result, a peeling layer 15 including a plurality of modified portions 15a and cracks 15b propagating from each of the plurality of modified portions 15a is formed inside the ingot 11.

[0052] In the first laser beam irradiation step (S111), the laser beam LB may be irradiated with a power small enough to form the modified region 15a inside the ingot 11 but not to cause the cracks 15b to extend from the modified region 15a. In other words, the peeling layer 15 formed in the first laser beam irradiation step (S111) may not include the cracks 15b.

[0053] Then, in a situation where irradiation of the laser beam LB to all of the multiple first regions 11d has not been completed (step (S112): NO), the position where the focal point is formed and the ingot 11 are moved relatively along the Y-axis direction (crystal orientation

[0001] ) (first indexing and feeding 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] ) when viewed from a first region 11d in which the peeling layer 15 has already been formed and in which the peeling layer 15 has not been formed, adjacent to the first region 11d in which the peeling layer 15 has already 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 manner, a separation layer 15 (separation layer 15-2) is formed inside the ingot 11, which is parallel to the previously formed separation layer 15 (separation layer 15-1) and separated from the separation layer 15-1 in the Y-axis direction (crystal orientation

[0001] ), as shown in FIG.

[0056] Furthermore, the first indexing step (S113) and the first laser beam irradiation step (S111) are alternately repeated until peeling layers 15 are formed in all of the plurality of first regions 11d included in the ingot 11. Then, if peeling layers 15 are formed in all of the plurality of first regions 11d (step (S112): YES), the second processing step (S12) is performed.

[0057] Fig. 12 is a flowchart schematically illustrating an example of the second processing step (S12) shown in Fig. 5. In this second processing step (S12), first, with the focal point at which the laser beam LB is focused positioned inside one of the plurality of second regions 11e and at a second depth from the surface 11a of the ingot 11, the focal point and the ingot 11 are moved relatively 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 equal to or less than 120 μm. This difference is set to be shorter than the interval between the first regions 11d and the second regions 11e.

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

[0060] That is, the first depth and the second depth are set so that the angle formed by a plane passing through both straight lines with the front surface 11a and the 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 device 2, the focal point at which the laser beam LB is focused can be positioned at a second depth from the surface 11a of the ingot 11 by changing the position of the irradiation head 16 in the Z-axis direction.

[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 laser beam LB from the irradiation head 16 toward the holding table 4.

[0063] When the irradiation head 16 moves while irradiating the laser beam LB in this manner, the multiple focal points and the ingot 11 move relatively along the X-axis direction (crystal orientation

[0010] ) with the multiple focal points positioned at a second depth from the surface 11a of the ingot 11.

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

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

[0066] 13, modified portions 15c in which the crystal structure of the single crystal silicon is disrupted are formed around each of the plurality of focal points inside the ingot 11. Note that in the second laser beam irradiation step (S121), the power of the laser beam LB focused at each of the plurality of focal points is greater than in the first laser beam irradiation step (S111), and therefore the size of the modified portions 15c is also greater than that of the modified portions 15a.

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

[0068] Then, cracks 15d larger than cracks 15b extend from modified portions 15c to relieve this internal stress inside ingot 11. Furthermore, cracks 15d that occur inside ingot 11 tend to extend toward the locations in ingot 11 where internal stress is occurring.

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

[0070] Then, in a situation where irradiation of the laser beam LB to all of the multiple second regions 11e has not been completed (step (S122): NO), the position where the focal point is formed and the ingot 11 are moved relatively along the Y-axis direction (crystal orientation

[0001] ) (second indexing and feeding step: S123).

[0071] In this second indexing step (S123), for example, the irradiation head 16 is moved along the Y-axis direction (crystal orientation

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

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

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

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

[0074] Here, in this separation layer forming step (S1), since the first depth and the second depth are set as described above, it is possible to reduce the thickness of the separation layer 15 formed inside the ingot 11. This point will be described below.

[0075] First, the method for forming the peeling layer 15 throughout the interior of the ingot 11 is not limited to the above-described method. For example, the peeling layer 15 can be formed throughout the interior of the ingot 11 by performing only the second processing step (S12) without performing the first processing step (S11) described above. However, in this case, there is a risk that the component of the crack 15d that propagates along the thickness direction of the ingot 11 during the second processing step (S12) will become large.

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

[0077] Then, once the separation layer forming step (S1) shown in Fig. 3 is completed, the substrate is separated from the ingot 11 starting from the separation layer 15 (separation step: S2). Fig. 14(A) and Fig. 14(B) are each a partial cross-sectional side view schematically showing an example of the separation step (S2) shown in Fig. 3. This separation step (S2) is performed, for example, in a separation apparatus 18 shown in Fig. 14(A) and Fig. 14(B).

[0078] The separation device 18 has a holding table 20 that holds the ingot 11 on which the peeling layer 15 is formed. The holding table 20 has a circular upper surface (holding surface), and a porous plate (not shown) is exposed on this holding surface.

[0079] Furthermore, this porous plate is connected to a suction source (not shown) such as a vacuum pump via a flow path or the like provided inside the holding table 20. When this suction source is activated, a suction force acts on the space near the holding surface of the holding table 20. This allows, for example, the ingot 11 placed on the holding surface to be held by the holding table 20.

[0080] A separation unit 22 is provided above the holding table 20. The separation unit 22 has a cylindrical support member 24. A ball screw type lifting mechanism (not shown) and a rotation drive source such as a motor are connected to the upper part of the support member 24.

[0081] Operating this lifting mechanism raises and lowers the separation unit 22. Operating this rotation drive source also rotates the support member 24 around a rotation axis that passes through the center of the support member 24 and is perpendicular to the holding surface of the holding table 20.

[0082] The lower end of the support member 24 is fixed to the center of the upper part of a disk-shaped base 26. A plurality of movable members 28 are provided below the outer peripheral region of the base 26 at approximately equal intervals along the circumferential direction of the base 26. Each movable member 28 has a plate-shaped erected portion 28a extending downward from the lower surface of the base 26.

[0083] The upper end of this standing portion 28a is connected to an actuator such as an air cylinder built into the base 26, and by operating this actuator, the movable member 28 moves along the radial direction of the base 26. In addition, on the inner surface of the lower end of this standing portion 28a, a plate-shaped wedge portion 28b is provided which extends toward the center of the base 26 and becomes thinner as it approaches the tip.

[0084] In the separation device 18, the separation step (S2) is performed, for example, in the following order: First, the ingot 11 is placed on the holding table 20 so that the center of the back surface 11b of the ingot 11 on which the peeling layer 15 is formed is aligned with the center of the holding surface of the holding table 20.

[0085] Next, a suction source communicating with the porous plate exposed on the holding surface is operated so that the ingot 11 is held by the holding table 20. Next, the actuator is operated so that each of the plurality of movable members 28 is positioned radially outward of the base 26.

[0086] Next, the lifting mechanism is operated to position the tip of each wedge portion 28b of the multiple movable members 28 at a height corresponding to the peeling layer 15 formed inside the ingot 11. Next, the actuator is operated to drive the wedge portion 28b into the side surface 11c of the ingot 11 (see FIG. 14(A)).

[0087] Next, the rotary drive source is operated to rotate the wedge portion 28b driven into the side surface 11c of the ingot 11. Next, the lifting mechanism is operated to lift the wedge portion 28b (see FIG. 14(B)).

[0088] As described above, by driving wedge portion 28b into side surface 11c of ingot 11 and rotating it, and then raising wedge portion 28b, cracks 15b and 15d contained in peeling layer 15 are further extended. As a result, the front surface 11a side and the back surface 11b side of ingot 11 are separated. That is, substrate 17 is produced from ingot 11, starting from peeling layer 15.

[0089] It should be noted that the wedge portion 28b does not need to be rotated if the front surface 11a and the back surface 11b of the ingot 11 are separated when the wedge portion 28b is driven into the side surface 11c of the ingot 11. Alternatively, the actuator and the rotary drive source may be operated simultaneously to drive the rotating wedge portion 28b into the side surface 11c of the ingot 11.

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

[0091] Here, when modified portion 15a is formed in first processing step (S11), the volume of ingot 11 expands, causing internal stress in ingot 11. Furthermore, cracks 15d formed in second processing step (S12) tend to propagate toward the location where internal stress is occurring.

[0092] Therefore, the cracks formed in the second processing step (S12) tend to propagate toward the modified portion 15a formed in the first processing step (S11). This allows the method to arbitrarily set the direction in which the cracks 15d tend to propagate in the second processing step (S12).

[0093] In this case, it becomes easy to thin the peeling layer 15 formed inside the ingot 11. Furthermore, if the peeling layer 15 is thin, the amount of ingot material that is discarded when cutting out the substrate 17 from the ingot 11 and flattening the substrate 17 is reduced. As a result, this method makes it possible to improve the productivity of the substrate 17 when manufacturing the substrate 17 from the ingot 11 using the 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 manufactured so that the crystal plane (100) is exposed on each of the front surface 11a and the back surface 11b.

[0095] Here, the crystal orientation

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

[0011] ) included in the {111} crystal plane. Therefore, in this method, cracks extending from the modified portions 15a, 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 {111} crystal plane are unlikely to occur.

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[0096] Furthermore, in this method, many cracks are generated from the modified areas 15a, 15c formed inside the ingot 11 by irradiation with the laser beam LB, extending along specific crystal planes included in the crystal plane {110} that are parallel to the crystal orientation

[0010] (specifically, the crystal planes shown in (3) below).

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[0097] The angle that a specific crystal plane included in the crystal plane {111} makes with respect to the crystal plane (100) is approximately 54.7°, while the angle that a specific crystal plane included in the crystal plane {110} that is parallel to the crystal orientation

[0010] (for example, the crystal plane (101)) makes with respect to the crystal plane (100) is 45°.

[0098] Therefore, in this method, it is possible to 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 front surface 11a and back surface 11b of the ingot 11.

[0099] In this case, the thickness of the peeled layer 15 formed inside the ingot 11 is suppressed, and the amount of material of the ingot 11 and the substrate 17 that is discarded when cutting the substrate 17 from the ingot 11 and flattening 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 the laser beam LB.

[0100] The above-described method for manufacturing a single crystal silicon substrate is one embodiment of the present invention, and the present invention is not limited to the above-described method. For example, the ingot used to manufacture a substrate in the present invention is not limited to the ingot 11 shown in Figures 1 and 2.

[0101] Specifically, in the present invention, the substrate may be manufactured from an ingot having a notch formed on the side surface, or from an ingot having neither an orientation flat nor a notch formed on the side surface.

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

[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. Note that this scanning optical system includes, for example, a galvanometer scanner, an acousto-optical device (AOD), and / or a polygon mirror.

[0104] That is, 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 relatively along the X-axis direction, the Y-axis direction, and the Z-axis direction, respectively, and there are no limitations on the structure for this purpose.

[0105] Furthermore, the plurality of first regions and the plurality of second regions included in the ingot 11 that are irradiated with the laser beam LB in the peeling layer forming 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 onto a region along the crystal orientation

[0001] .

[0106] 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 onto a region along a direction slightly tilted from the crystal orientation

[0010] or the crystal orientation

[0001] in plan view. This point will be described with reference to FIG.

[0108] 15 is a graph showing the width of the peeled layer formed inside a workpiece made of single-crystal silicon when a laser beam LB is irradiated onto regions along different crystal orientations. The horizontal axis of this graph shows the angle between the direction in which a region perpendicular to the crystal orientation

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

[0109] That is, when the horizontal axis of this graph is 45°, the area along the crystal orientation

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

[0010] is the measurement target.

[0110] Furthermore, the vertical axis of this graph shows the value obtained by dividing the width of the peeling layer formed in the measurement area by irradiating the measurement area with the laser beam LB by the width of the peeling layer formed in the reference area by irradiating the reference area with the laser beam LB.

[0111] 15, the width of the peeled layer increases when the angle between the direction in which the reference region extends and the direction in which the measurement region extends is 40° to 50° or 130° to 140°. That is, the width of the peeled layer increases when the laser beam LB is irradiated not only to the crystal orientation

[0001] or the crystal orientation

[0010] , but also to a region along a direction that forms an angle of 5° or less with respect to these crystal orientations.

[0112] Therefore, in the peeling layer forming step (S1) of the present invention, the laser beam LB may be irradiated to an area along a direction tilted by 5° or less from the crystal orientation

[0001] or the crystal orientation

[0010] in a planar view.

[0113] That is, in the peeling layer forming step (S1) of the present invention, a specific crystal plane included in the crystal plane {100} is parallel to the crystal plane (here, the crystal plane (100)) exposed on each of the front surface 11a and the 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) that has an angle of 5° or less with respect to a specific crystal orientation (here, crystal orientation

[0001] or crystal orientation

[0010] ) included in the crystal orientation.

[0114] Furthermore, in the present invention, it is not an essential feature to form the peeling layer 15 throughout the entire interior area of ​​the ingot 11 in the peeling layer forming step (S1). For example, if the cracks 15b and 15d extend to the area near the side surface 11c of the ingot 11 in the separation step (S2), the peeling layer 15 may not be formed in part or all of the area near the side surface 11c of the ingot 11 in the peeling layer forming step (S1).

[0115] In addition, in the present invention, in the second laser beam irradiation step (S121), the focal point at which the laser beam LB is focused may be positioned at a second depth 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 performed 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 suctioning the surface 11a side of the ingot 11.

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

[0118] The holding table 32 has a circular upper surface (holding surface), and a porous plate (not shown) is exposed on this holding surface. Furthermore, the 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 the suction source is activated, a suction force acts on the space near the holding surface of the holding table 32. This allows the holding table 32 to hold, for example, the ingot 11 placed on the holding surface.

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

[0121] The lower end of the support member 36 is fixed to the center of the upper part of a disk-shaped suction plate 38. A plurality of suction ports are formed in the lower surface of the suction plate 38, and each of the plurality of suction ports communicates with 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 the suction source is operated, a suction force acts on the space near the lower surface of the suction plate 38. This allows, for example, the ingot 11 close to the lower surface of the suction plate 38 to be sucked upward.

[0123] In the separation device 30, the separation step (S2) is performed, for example, in the following order: Specifically, first, the ingot 11 is placed on the holding table 32 so that the center of the back surface 11b of the ingot 11 on which the peeling layer 15 is formed is aligned with the center of the holding surface of the holding table 32.

[0124] Next, a suction source communicating with the porous plate exposed on the holding surface is operated so that the ingot 11 is held by the holding table 32. Next, the lifting mechanism is operated to lower the separation unit 34 so that the lower surface of the suction plate 38 contacts the surface 11a of the ingot 11.

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

[0126] At this time, an upward force acts on the front surface 11a side of the ingot 11, which is being sucked through the multiple suction ports formed in the suction plate 38. As a result, the cracks 15b contained in the peeling layer 15 extend further, and the front surface 11a side and the back surface 11b side of the ingot 11 are separated. That is, the substrate 17 is produced from the ingot 11, starting from the peeling layer 15.

[0127] Furthermore, in the separation step (S2) of the present invention, prior to separation of the front surface 11a side and the back surface 11b side of the ingot 11, ultrasonic waves may be applied to the front surface 11a side of the ingot 11. In this case, the cracks 15b and 15d contained in the peeling layer 15 are further extended, making it easier to separate the front surface 11a side and the back surface 11b side of the ingot 11.

[0128] Furthermore, in the present invention, prior to the separation layer forming step (S1), the surface 11a of the ingot 11 may be flattened by grinding or polishing (flattening step). For example, this flattening may be performed when manufacturing a plurality of substrates from the ingot 11.

[0129] Specifically, when ingot 11 is separated at peeling layer 15 to produce substrate 17, the newly exposed surface of ingot 11 has irregularities that reflect the distribution of modified portions 15a, 15c and cracks 15b, 15d contained in peeling layer 15. Therefore, when a new substrate is produced from this ingot 11, it is preferable to flatten the surface of ingot 11 prior to the peeling 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 peeling layer forming 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 peeling layer 15 side may be flattened by grinding or polishing.

[0131] In the present invention, a substrate may be manufactured using, as a workpiece, a bare wafer made of single crystal silicon manufactured so that specific crystal planes included in the crystal plane {100} are exposed on both the front and back surfaces.

[0132] The bare wafer has a thickness that is, for example, two to five times that of the substrate to be manufactured. The bare wafer is manufactured by being separated from the ingot 11 by the same method as described above. In this case, the substrate can also be expressed as being manufactured by repeating the above method twice.

[0133] In the present invention, a substrate may be manufactured using a device wafer, which is manufactured by forming semiconductor devices on one surface of the bare wafer, as a workpiece. In this case, the laser beam LB is preferably irradiated onto the device wafer from the side on which the semiconductor devices are not formed, in order to prevent adverse effects on the semiconductor devices.

[0134] In addition, the structures and methods according to the above-described embodiments 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 surface, 11b: back surface, 11c: side surface) (11d: First Realm, 11e: Second Realm) 12: Branch unit 13: Orientation Flat 14: Mirror 15: Peeling layer (15a: modified part, 15b: crack) (15c: Modified part, 15d: Crack) 15-1: Peeling layer 15-2: Peeling layer 15-3: Peeling layer 16: Irradiation head 17: Circuit board 18: Separation device 20: Holding table 22: Separation unit 24: Support member 26: Foundation 28: Movable member (28a: Standing portion, 28b: Wedge portion) 30: Separation device 32: Holding table 34: Separation unit 36: Support member 38: Suction plate

Claims

1. A method for manufacturing a single crystal silicon substrate, comprising the steps of: 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 the front and back surfaces, the method comprising: a peeling layer forming step of forming a peeling layer including a modified portion and a crack extending from the modified portion inside the workpiece; a separation step of separating the substrate from the workpiece starting from the release layer after the release layer formation step is performed, The release layer forming step includes: a first processing step for forming the modified portions in a plurality of first regions, each of which is parallel to the specific crystal plane and extends along a first direction that forms an angle of 5° or less with respect to a specific crystal orientation included in the crystal orientation <100>, and which is spaced apart from each other in a second direction that is parallel to the specific crystal plane and perpendicular to the first direction; a second processing step for forming the modified portions and the cracks in a plurality of second regions each extending along the first direction and spaced apart from one another in the second direction after the first processing step is performed; any one of the plurality of second regions is positioned between a pair of adjacent first regions among the plurality of first regions; any one of the plurality of first regions is positioned between a pair of adjacent second regions among the plurality of second regions; The first processing step comprises: a first laser beam irradiation step of relatively moving the focal point and the workpiece along the first direction, with the focal point at which the laser beam having a wavelength that is transmitted through the single crystal silicon is focused, positioned inside any one of the plurality of first regions and at a first depth from the surface of the workpiece; a first indexing step of relatively moving the position where the focal point is formed and the workpiece along the second direction; This is carried out by alternating The second processing step comprises: a second laser beam irradiation step of relatively moving the focal point and the workpiece along the first direction while positioning the focal point inside any of the plurality of second regions and at a second depth from the surface of the workpiece that is different from the first depth; a second indexing step of relatively moving the position where the focal point is formed and the workpiece along the second direction; This is carried out by alternating a power of the laser beam focused at the focusing point during the second laser beam irradiation step is greater than a power of the laser beam focused at the focusing point during the first laser beam irradiation step.

2. The method for producing a single crystal silicon substrate according to claim 1 , wherein the second depth is greater than the first depth.

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

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