Method for manufacturing single crystal silicon substrate

Abstract

To provide a method for manufacturing a single crystal silicon substrate with high productivity as compared with manufacturing a single crystal silicon substrate from a workpiece using a wire saw.SOLUTION: After forming a peeling layer inside a workpiece made of single crystal silicon using a laser beam having a wavelength that can pass through single crystal silicon, a substrate is separated from the workpiece with this release layer as a starting point. Thereby, the productivity of the single crystal silicon substrate can be improved as compared with the case of manufacturing the substrate from the workpiece using a wire saw.SELECTED DRAWING: Figure 3

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). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-262826 Summary of the Invention [Problem to be solved by the invention]

[0004] When cutting a substrate from an ingot using a wire saw, the cutting width is relatively large, about 300 μm. Furthermore, the surface of the substrate cut in this way has minute irregularities and is curved overall (the substrate warps). Therefore, the surface of the substrate needs to be flattened by lapping, etching, and / or polishing.

[0005] 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.

[0006] In view of this, an object of the present invention is to provide a method for manufacturing a single crystal silicon substrate with high productivity. [Means for solving the problem]

[0007] 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 peeling layer in a plurality of second regions each extending along the first direction and spaced apart from one another in the second direction, the second processing step being parallel to the first direction and perpendicular to a specific crystal orientation included in the first direction, the angle being 5° or less with respect to the specific crystal orientation included in the first direction, the second processing step being perpendicular to the first direction, the second processing step being perpendicular to the first direction, the second processing step being perpendicular to the first direction, the first processing step being parallel to the specific crystal orientation included in the first direction, the second processing step being perpendicular to the first direction, the second processing step being perpendicular to the first direction, the second processing step being perpendicular to the first direction, the the second processing step is performed by alternately repeating a first laser beam application step in which, with the focal point of a long laser beam positioned in one of the plurality of first regions, the focal point and the workpiece are moved relatively along the first direction, and a first indexing / feeding step in which the position where the focal point is to be formed and the workpiece are moved relatively along the second direction, with the focal point being positioned in one of the plurality of second regions; and a second laser beam application step in which, with the focal point positioned in one of the plurality of second regions, the focal point and the workpiece are moved relatively along the first direction, with the second indexing / feeding step in which the position where the focal point is to be formed and the workpiece are moved relatively along the second direction.

[0008] Preferably, the peeling layer formation step includes a third processing step for forming the peeling layer in sequence from the region located at one end in the second direction among the plurality of first regions and the plurality of second regions to the region located at the other end before performing the first processing step, and the third processing step is performed by alternately repeating a third laser beam irradiation step in which the focal point is positioned in either the plurality of first regions or the plurality of second regions and the focal point and the workpiece are moved relatively along the first direction, and a third indexing feed step in which the position where the focal point is formed and the workpiece are moved relatively along the second direction. [Effects of the Invention]

[0009] In the present invention, a laser beam having a wavelength that passes through single crystal silicon is used to form a peeling layer inside a workpiece made of single crystal silicon, and then the substrate is separated from the workpiece using this peeling layer as a starting point. This improves the productivity of single crystal silicon substrates compared to when substrates are produced from workpieces using a wire saw. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view schematically showing an example of an ingot. [Figure 2] FIG. 2 is a top view schematically showing an example of an ingot. [Figure 3] FIG. 3 is a flow chart schematically illustrating an example of a method for manufacturing a single crystal silicon substrate. [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. [Figure 6] FIG. 6 is a diagram schematically illustrating an example of a laser processing device. [Figure 7] FIG. 7 is a top view schematically showing a holding table for holding an ingot. [Figure 8] FIG. 8 is a flowchart schematically illustrating an example of the first processing step. [Figure 9] Figure 9(A) is a top view schematically showing an example of the first laser beam irradiation step, and Figure 9(B) is a partially cross-sectional side view schematically showing an example of the first laser beam irradiation step. [Figure 10] FIG. 10 is a cross-sectional view schematically showing a peeling layer formed inside the ingot in the first laser beam irradiation step. [Figure 11] FIG. 11 is a cross-sectional view schematically showing a peeled layer formed inside the ingot by performing the first laser beam irradiation step again. [Figure 12] FIG. 12 is a flowchart schematically illustrating an example of the second processing step. [Figure 13] FIG. 13 is a cross-sectional view schematically showing a peeling layer formed inside the ingot by performing the second laser beam irradiation step. [Figure 14] 14(A) and 14(B) are each a partial cross-sectional side view that schematically shows an example of the separation step. [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] FIG. 16 is a flow chart schematically showing another example of the release layer forming step. [Figure 17] FIG. 17 is a flowchart schematically illustrating an example of the third processing step. [Figure 18] FIG. 18 is a cross-sectional view schematically showing a peeling layer formed inside the ingot by repeatedly performing the third laser beam irradiation step. [Figure 19] 19(A) and 19(B) are each a partial cross-sectional side view schematically showing another example of the separation step. [Figure 20]20(A), 20(B), and 20(C) are cross-sectional photographs showing the peeling layer formed in the ingot of Example 1. FIG. [Figure 21] 21(A), 21(B), and 21(C) are cross-sectional photographs showing the peeling layer formed in the ingot of Example 2. FIG. [Figure 22] Figure 22(A) is a graph showing the distribution of components in the thickness direction of the ingot for 20 cracks formed in the ingot of Example 1, and Figure 22(B) is a graph showing the distribution of components in the thickness direction of the ingot for 20 cracks formed in the ingot of Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a perspective view schematically showing an example of an ingot, and Fig. 2 is a top view schematically showing an example of an ingot. Fig. 1 also shows the crystal planes of single crystal silicon exposed on a plane included in the ingot. Fig. 2 also shows the crystal orientation of the single crystal silicon constituting the ingot.

[0012] 1 and 2 is made of cylindrical single-crystal silicon in which a specific crystal plane included in the crystal plane {100} (here, for convenience, it is referred to as the crystal plane (100)) is exposed on each of the front surface 11a and the back surface 11b. That is, this ingot 11 is made of cylindrical single-crystal silicon in which the perpendicular lines (crystal axes) to each of the front surface 11a and the back surface 11b are aligned along the crystal orientation

[0100] .

[0013] 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.

[0014] 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] .

[0015] 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.

[0016] 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).

[0017] In this separation layer forming step (S1), separation layers are formed in order in multiple regions included in the ingot 11. Fig. 4 is a top view schematically showing multiple regions included in the ingot 11. Fig. 5 is a flow chart schematically showing an example of the separation layer forming step (S1).

[0018] In this peeling layer forming step (S1), first, a peeling layer is 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).

[0019] Then, after the first processing step (S11) is completed, a peeling layer is formed in a plurality of second regions 11e, each extending along the crystal orientation

[0010] and positioned between a pair of adjacent first regions 11d (second processing step: S12).

[0020] In the separation layer forming step (S1), a laser processing device is used to form a separation layer inside the ingot 11. Figure 6 is a diagram schematically showing an example of a laser processing device used when forming a separation layer inside the ingot 11.

[0021] 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.

[0022] 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.

[0023] 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 negative pressure is generated in the space near the holding surface of the holding table 4. This allows, for example, the holding table 4 to hold an ingot 11 placed on the holding surface.

[0024] A laser beam irradiation unit 6 is provided above the holding table 4. This laser beam irradiation unit 6 has a laser oscillator 8. This laser oscillator 8 has, for example, Nd:YAG or the like as a laser medium, and irradiates a pulsed laser beam LB having a wavelength (for example, 1064 nm) that is transmitted through the material (single crystal silicon) that constitutes the ingot 11.

[0025] The output of this laser beam LB is adjusted by an attenuator 10, and then supplied to a branching unit 12. This branching unit 12 is configured to include a spatial light modulator including a liquid crystal phase control element generally called LCoS (Liquid Crystal on Silicon) and / or a diffractive optical element (DOE), etc.

[0026] The branching unit 12 branches the laser beam LB so that the laser beam LB irradiated from the irradiation head 16 (described later) onto the holding surface side of the holding table 4 forms a plurality of focusing points aligned along the Y-axis direction.

[0027] 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. The laser beam LB condensed by this condenser lens is irradiated onto the holding surface side of the holding table 4.

[0028] Furthermore, the irradiation head 16 of the laser beam irradiation unit 6 is connected to a movement mechanism (not shown). This movement mechanism includes, for example, a ball screw or the like, and moves the irradiation head 16 along the X-axis, Y-axis, and / or Z-axis directions.

[0029] 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 of the laser beam LB irradiated from the irradiation head 16 onto the holding surface side of the holding table 4 can be adjusted.

[0030] 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 holding table 4 holding the ingot 11.

[0031] 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.

[0032] 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.

[0033] 8 is a flow chart showing an example of the first processing step (S11). In this first processing step (S11), first, with the focal point of the laser beam LB positioned in one of the plurality of first regions 11d, the focal point and the ingot 11 are moved relatively along the X-axis direction (crystal orientation

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

[0034] Fig. 9(A) is a top view schematically showing an example of the first laser beam irradiation step (S111), Fig. 9(B) is a partial cross-sectional side view schematically showing an example of the first laser beam irradiation step (S111), and Fig. 10 is a cross-sectional view schematically showing a peeling layer formed inside the ingot 11 in the first laser beam irradiation step (S111).

[0035] 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.

[0036] 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 heights corresponding to the interior of the ingot 11 .

[0037] Next, while irradiating the laser beam LB from the irradiation head 16 toward the holding table 4, the irradiation head 16 is moved so that it passes 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)).

[0038] As a result, the multiple focusing points and the ingot 11 move relatively along the X-axis direction (crystal orientation

[0010] ) with the multiple focusing points positioned inside the ingot 11. Note that the laser beam LB is branched and focused so as to form multiple (e.g., five) focusing points arranged at equal intervals in the Y-axis direction (crystal orientation

[0001] ) (see FIG. 10).

[0039] Then, 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.

[0040] This internal stress is alleviated by the propagation of cracks 15b from the modified portions 15a, resulting in the formation of a peeled layer 15 inside the ingot 11, the peeled layer 15 including a plurality of modified portions 15a and cracks 15b propagating from each of the plurality of modified portions 15a.

[0041] Generally, single crystal silicon is most easily cleaved along a specific crystal plane included in the crystal plane {111}, and second most easily cleaved along a specific crystal plane included in the crystal plane {110}.

[0042] Therefore, for example, the crystal orientation of the single crystal silicon that constitutes the ingot <110> When a modified portion is formed along a specific crystal orientation (for example, crystal orientation

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

[0043] On the other hand, the crystal orientation of single crystal silicon <100> When multiple modified areas are formed in a region along a specific crystal orientation included in the above, so that they are lined up in a direction perpendicular to the direction in which this region extends in a planar view, many cracks are generated from each of the multiple modified areas, extending along crystal planes of {N10} (N is an integer with an absolute value of 10 or less, excluding 0) that are parallel to the direction in which the region extends.

[0044] For example, as described above, when multiple modified portions 15a are formed in a region along the crystal orientation

[0010] so as to be arranged at equal intervals in the crystal orientation

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

[0010] .

[0045] Specifically, when a plurality of modified regions 15a are formed in this way, cracks tend to propagate in the following crystal planes.

number

number

[0046] The angle that the crystal plane (100) exposed on the front surface 11a and back surface 11b of the ingot 11 makes with the crystal plane {N10} parallel to the crystal orientation

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

[0047] Therefore, when the laser beam LB is irradiated onto the ingot 11 along the crystal orientation

[0010] (the former case), the peeling layer 15 is more likely to be wide and thin than when the laser beam LB is irradiated onto the ingot 11 along the crystal orientation

[0011] (the latter case). That is, the ratio (W1 / T1) of the width (W1) to the thickness (T1) of the peeling layer 15 shown in Fig. 10 is larger in the former case than in the latter case.

[0048] 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).

[0049] 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.

[0050] Next, the first laser beam irradiation step (S111) described above is performed again. When the first laser beam irradiation step (S111) is performed again in this manner, a peeling layer 15 (peeling layer 15-2) that is parallel to the already formed peeling layer 15 (peeling layer 15-1) and separated from the peeling layer 15-1 in the Y-axis direction (crystal orientation

[0001] ) is formed inside the ingot 11, as shown in FIG.

[0051] 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.

[0052] 12 is a flow chart showing an example of the second processing step (S12). In this second processing step (S12), first, with the focal point of the laser beam LB positioned in one of the plurality of second regions 11e, the focal point and the ingot 11 are moved relatively along the X-axis direction (crystal orientation

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

[0053] The second laser beam irradiation step (S121) is performed in the same manner as the first laser beam irradiation step (S111), and therefore the details thereof will not be described here. When the second laser beam irradiation step (S121) is performed, a peeling layer 15 (peeling layer 15-3) is formed inside the ingot 11, parallel to and positioned between the already formed peeling layers 15 (peeling layers 15-1 and 15-2), as shown in FIG.

[0054] Here, the cracks 15b (former cracks) extending from the modified portions 15a included in the release layer 15-3 tend to extend so as to connect with the cracks 15b (latter cracks) included in the existing release layers 15-1 and 15-2.

[0055] Therefore, in the former crack, compared to the latter crack, the component along the Y-axis direction (crystal orientation

[0001] ) is more likely to be larger than the component along the Z-axis direction (crystal orientation

[0100] ).

[0056] In this case, the release layer 15-3 is wider and thinner than the release layers 15-1 and 15-2. That is, the ratio (W2 / T2) of the width (W2) to the thickness (T2) of the release layer 15-3 shown in Fig. 13 is greater than the ratio (W1 / T1) of the width (W1) to the thickness (T1) of the release layer 15 (release layers 15-1 and 15-2) shown in Fig. 10.

[0057] 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).

[0058] 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.

[0059] 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.

[0060] Then, when the separation layer 15 is formed in all of the plurality of second regions 11e (step (S122): YES), the substrate is separated from the ingot 11 starting from the separation layer 15 (separation step: S4).

[0061] 14(A) and 14(B) are partial cross-sectional side views each showing a schematic diagram of an example of the separation step (S2). This separation step (S2) is performed, for example, in a separation apparatus 18 shown in FIGS. 14(A) and 14(B). This separation apparatus 18 has a holding table 20 that holds the ingot 11 on which the peeled layer 15 is formed.

[0062] The holding table 20 has a circular upper surface (holding surface), and a porous plate (not shown) is exposed on this holding surface. Furthermore, this porous plate is in communication with a suction source (not shown), such as a vacuum pump, via a flow path or the like provided inside the holding table 20. When this suction source is activated, negative pressure is generated in the space near the holding surface of the holding table 20.

[0063] 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.

[0064] 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.

[0065] 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 periphery 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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)).

[0070] 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)).

[0071] As described above, by driving wedge portion 28b into side surface 11c of ingot 11 and rotating it, and then raising wedge portion 28b, crack 15b contained in peeling layer 15 is further extended. As a result, ingot 11 is separated into front surface 11a and back surface 11b. That is, substrate 17 is produced from ingot 11, starting from peeling layer 15.

[0072] 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.

[0073] In the above-described method for manufacturing a single crystal silicon substrate, a laser beam LB having a wavelength that passes through single crystal silicon is used to form a peeling layer 15 inside the ingot 11, and then the substrate 17 is separated from the ingot 11 using this peeling layer 15 as a starting point.

[0074] This reduces the amount of material wasted when manufacturing substrate 17 from ingot 11, compared to manufacturing substrate 17 from ingot 11 using a wire saw, and improves the productivity of substrate 17.

[0075] Furthermore, in this method, a plurality of modified regions 15a are formed in a region along the crystal orientation

[0010] (X-axis direction) so as to be aligned along the crystal orientation

[0001] (Y-axis direction). In this case, many cracks extend from each of the modified regions 15a along the crystal planes {N10} (N is a natural number equal to or less than 10) that are parallel to the crystal orientation

[0010] .

[0076] This allows the separation layer 15 to be wider and thinner than when the laser beam LB is irradiated along the crystal orientation

[0011] on the ingot 11. As a result, the amount of material wasted when manufacturing the substrate 17 from the ingot 11 can be further reduced, and the productivity of the substrate 17 can be further improved.

[0077] In this method, after forming peeling layers 15 (peeling layers 15-1 and 15-2) in a plurality of first regions 11d included in the ingot 11, peeling layers 15 (peeling layers 15-3) are formed in a plurality of second regions 11e. Here, cracks 15b having a larger component along the Y-axis direction (crystal orientation

[0001] ) are more likely to form in peeling layer 15-3 than cracks 15b included in peeling layers 15-1 and 15-2.

[0078] That is, in this case, the ratio (W2 / T2) of the width (W2) to the thickness (T2) of separation layer 15-3 is greater than the ratio (W1 / T1) of the width (W1) to the thickness (T1) of separation layers 15-1 and 15-2. As a result, the amount of material discarded when manufacturing substrate 17 from ingot 11 can be further reduced, and the productivity of substrate 17 can be further improved.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] That is, in the present invention, it is sufficient that the holding table 4 that holds the ingot 11 and the irradiation head 16 of the laser beam irradiation unit 6 that irradiates the laser beam LB can move relatively along each of the X-axis, Y-axis, and Z-axis directions, and there are no limitations on the structure for this purpose.

[0083] 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 the plurality of first regions 11d and the plurality of second regions 11e shown in Fig. 4. For example, in the present invention, each of the plurality of first regions may be positioned between a pair of adjacent second regions.

[0084] 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] .

[0085] When the ingot 11 is irradiated with the laser beam LB in this manner, cracks tend to propagate in the following crystal planes.

number

number

[0086] 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.

[0087] 15 is a graph showing the width (width (W1) shown in FIG. 10) 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.

[0088] 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.

[0089] 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.

[0090] 15, the width of the peeling 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 peeling 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 these crystal orientations.

[0091] 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.

[0092] 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.

[0093] In the separation layer forming step (S1) of the present invention, the laser beam LB may be irradiated multiple times onto each of the multiple first regions 11d and the multiple second regions 11e included in the ingot 11. Fig. 16 is a flow chart schematically showing an example of such a separation layer forming step (S1).

[0094] In the peeling layer formation step (S1) shown in Figure 16, before the first processing step (S11), a peeling layer 15 is formed in order from the region (first region 11d or second region 11e) located at one end in the Y-axis direction (crystal orientation

[0001] ) among the multiple first regions 11d and multiple second regions 11e to the region (first region 11d or second region 11e) located at the other end (third processing step: S13).

[0095] 17 is a flow chart showing an example of the third processing step (S13). In this third processing step (S13), first, with the focal point of the laser beam LB positioned in either one of the first regions 11d or the second regions 11e, the focal point and the ingot 11 are moved relatively along the X-axis direction (crystal orientation

[0010] ) (third laser beam irradiation step: S131).

[0096] The third laser beam irradiation step (S131) ​​is performed in the same manner as the first laser beam irradiation step (S111) and the second laser beam irradiation step (S121) described above, and therefore details thereof will be omitted.

[0097] Then, in a situation where irradiation of the laser beam LB to all of the plurality of first regions 11d and the plurality of second regions 11e has not been completed (step (S132): NO), the position where the focal point is formed and the ingot 11 are moved relatively along the Y-axis direction (crystal orientation

[0001] ) (third indexing and feeding step: S133).

[0098] The third indexing feed step (S133) is performed in the same manner as the first indexing feed step (S113) and the second indexing feed step (S123) described above, and therefore details thereof will be omitted.

[0099] Next, the third laser beam irradiation step (S131) ​​described above is performed again. Furthermore, the third indexing step (S133) and the third laser beam irradiation step (S131) ​​are alternately repeated until the peeling layer 15 is formed in all of the first regions 11d and the second regions 11e included in the ingot 11.

[0100] When the third indexing step (S133) and the third laser beam irradiation step (S131) ​​are alternately and repeatedly performed, for example, as shown in Figure 18, multiple peeling layers 15-4 spaced apart from each other in the Y-axis direction (crystal orientation

[0001] ) can be formed inside the ingot 11.

[0101] Then, if a peeling layer 15 is formed in all of the plurality of first regions 11d and the plurality of second regions 11e (step (S132): YES), the above-mentioned first processing step (S11) and second processing step (S12) are carried out in sequence.

[0102] In this way, when the laser beam LB is again irradiated onto the plurality of first regions 11d and the plurality of second regions 11e on which the peeling layer 15-4 has already been formed, the density of the modified portions 15a and the cracks 15b contained in the already formed peeling layer 15-4 increases.

[0103] This facilitates the separation of substrate 17 from ingot 11 in the separation step (S2). Furthermore, in this case, cracks 15b contained in separation layer 15-4 extend further, widening separation layer 15-4.

[0104] Therefore, in this case, the relative movement distance (index) between the ingot 11 and the irradiation head 16 of the laser beam irradiation unit 6 can be increased in each of the first indexing feed step (S113), the second indexing feed step (S123), and the third indexing feed step (S133).

[0105] 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 crack 15b extends 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).

[0106] 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.

[0107] 19(A) and 19(B) are partial cross-sectional side views each showing an example of the separation step (S2) performed in this manner. The separation apparatus 30 shown in FIG. 19(A) and FIG. 19(B) has a holding table 32 for holding the ingot 11 on which the peeling layer 15 is formed.

[0108] The holding table 32 has a circular upper surface (holding surface), and a porous plate (not shown) is exposed on this holding surface. Furthermore, this porous plate is in communication with a suction source (not shown), such as a vacuum pump, via a flow path or the like provided inside the holding table 32. Therefore, when this suction source operates, negative pressure is generated in the space near the holding surface of the holding table 32.

[0109] 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.

[0110] 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 is connected to a suction source (not shown), such as a vacuum pump, via a flow path or the like provided inside the suction plate 38. Therefore, when the suction source is operated, a negative pressure is generated in the space near the lower surface of the suction plate 38.

[0111] 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.

[0112] 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.

[0113] 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. 19(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. 19(B)).

[0114] 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.

[0115] Furthermore, in the separation step (S2) of the present invention, prior to separation of the front surface 11a side and the back surface 11b side of the ingot 11, ultrasonic waves may be applied to the front surface 11a side of the ingot 11. In this case, the cracks 15b contained in the peeling layer 15 are further extended, making it easier to separate the front surface 11a side and the back surface 11b side of the ingot 11.

[0116] 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.

[0117] Specifically, when the ingot 11 is separated at the separation layer 15 to produce the substrate 17, the newly exposed surface of the ingot 11 has irregularities that reflect the distribution of the modified portions 15a and cracks 15b contained in the separation layer 15. Therefore, when a new substrate is produced from this ingot 11, it is preferable to flatten the surface of the ingot 11 prior to the separation layer formation step (S1).

[0118] 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.

[0119] 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.

[0120] The bare wafer has a thickness, for example, two to five times that of the substrate to be manufactured. The bare wafer is manufactured by being separated from the ingot 11 by the same method as the above-mentioned method. In this case, it can also be said that the substrate is manufactured by repeating the above-mentioned method twice.

[0121] 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. In addition, the structures and methods according to the above-described embodiments can be appropriately modified and implemented without departing from the scope of the present invention. [Example]

[0122] Ingots of Examples 1 and 2 made of single crystal silicon were prepared. Then, a separation layer was formed inside the ingot of Example 1 by the same procedure as the separation layer formation step (S1) shown in Fig. 16. That is, a laser beam was irradiated twice onto each of the multiple first regions and multiple second regions included in the ingot of Example 1.

[0123] The power of the laser beam used in each of the first laser beam irradiation step (S111), second laser beam irradiation step (S121), and third laser beam irradiation step (S131) ​​was 2.0 W to 5.0 W, and the number of branches was 8.

[0124] The index in the first indexing feed step (S113) and the second indexing feed step (S123) at this time was 1140 μm, and the index in the third indexing feed step (S133) at this time was 570 μm.

[0125] 20(A), 20(B), and 20(C) are cross-sectional photographs showing the separation layer formed in the ingot of Example 1. When a separation layer is formed inside the ingot using the same procedure as the separation layer formation step (S1) shown in Fig. 16, it was found that cracks contained in the separation layer extend linearly to connect adjacent modified portions.

[0126] 16 was repeated twice to form a peeling layer inside the ingot of Example 2. That is, similar to the ingot of Example 1, the laser beam was irradiated twice onto each of the plurality of first regions and the plurality of second regions included in the ingot of Example 2.

[0127] The power of the laser beam used in the third laser beam irradiation step (S13) was 2.0 W to 5.0 W, and the number of branches was 8. The index in the third indexing feed step (S133) was 560 μm.

[0128] 21(A), 21(B), and 21(C) are cross-sectional photographs showing the delamination layer formed in the ingot of Example 2. When the third processing step (S131) ​​shown in Fig. 16 is repeated twice to form the delamination layer inside the ingot, it was found that the cracks contained in the delamination layer extend in an arch shape to connect adjacent modified portions.

[0129] Figure 22(A) is a graph showing the distribution of components (vertical length in Figure 20(A) etc.) of 20 cracks formed in the ingot of Example 1 in the thickness direction of the ingot, and Figure 22(B) is a graph showing the distribution of components (vertical length in Figure 21(A) etc.) of 20 cracks formed in the ingot of Example 2 in the thickness direction of the ingot.

[0130] Table 1 below shows the average (Avg) and maximum (Max) values ​​of the components of the 20 cracks formed in the ingot of Example 1 and the average (Avg) and maximum (Max) values ​​of the components of the 20 cracks formed in the ingot of Example 2. [Table 1]

[0131] It was found that the cracks contained in the peeling layer formed in the ingot of Example 1 had a smaller component in the thickness direction of the ingot compared to the cracks contained in the peeling layer formed in the ingot of Example 2.

[0132] Therefore, when a peeling layer is formed on an ingot using the same procedure as the peeling layer formation step (S1) shown in Figure 16, it was found that the amount of material wasted when manufacturing a substrate from this ingot can be reduced and substrate productivity can be improved compared to when a peeling layer is formed inside the ingot of Example 2 by repeating the third processing step (S13) shown in Figure 16 twice. [Explanation of symbols]

[0133] 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) 15-1, 15-2, 15-3, 15-4: 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 peeling layer in a plurality of first regions, each extending along a first direction parallel to the specific crystal plane and forming an angle of 5° or less with respect to a specific crystal orientation included in the crystal orientation <100>, and spaced apart from each other in a second direction parallel to the specific crystal plane and perpendicular to the first direction; a second processing step, after performing the first processing step, for forming the release layer in a plurality of second regions each extending along the first direction and spaced apart from one another in the second direction; 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 of a laser beam having a wavelength that is transmitted through the single crystal silicon and the workpiece along the first direction while the focal point is positioned in any one of the plurality of first regions; 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 the focal point is positioned in any of the plurality of second regions; a second indexing step of relatively moving the position where the focal point is formed and the workpiece along the second direction; The method for manufacturing a single crystal silicon substrate is carried out by alternately repeating the steps of:

2. the release layer forming step includes a third processing step for forming the release layer in order from a region located at one end in the second direction to a region located at the other end of the plurality of first regions and the plurality of second regions before carrying out the first processing step; The third processing step comprises: a third laser beam irradiation step of relatively moving the focal point and the workpiece along the first direction while the focal point is positioned in either one of the plurality of first regions or the plurality of second regions; a third indexing step of relatively moving the position where the focal point is formed and the workpiece along the second direction; 2. The method for producing a single crystal silicon substrate according to claim 1, wherein the method is carried out by alternately repeating the steps of:

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