Method for manufacturing single crystal silicon substrate

Abstract

To provide a method for manufacturing single crystal silicon substrates with high productivity.SOLUTION: After forming a delamination layer inside the workpiece (ingot, bare wafer or device wafer, etc.) made of monocrystalline silicon using a laser beam with a wavelength that penetrates monocrystalline silicon, the substrate is separated from the workpiece using this delamination layer as a starting point. This improves the productivity of single-crystal silicon substrates compared to the case where substrates are manufactured 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 is provided, in which a substrate is manufactured from a workpiece made of single crystal silicon manufactured so that a specific crystal plane included in the crystal plane {100} is exposed on each of the front and back surfaces, and a laser beam having a wavelength that is transmitted through the single crystal silicon is focused to form a focal point, which is positioned inside the workpiece, and a laser beam is focused to form a focal point that is parallel to the specific crystal plane and has a crystal orientation <100> a separation step of relatively moving the focal point and the workpiece along a first direction, the focal point making an angle of 5° or less with respect to a specific crystal orientation included in the crystal plane, thereby forming a separation layer in a linear region along the first direction inside the workpiece; an indexing step of relatively moving the workpiece and a position where the focal point is formed by focusing the laser beam along a second direction that is parallel to the specific crystal plane and perpendicular to the first direction; and a separation step of separating the substrate from the workpiece using the peeling layer as a starting point after repeatedly performing the separation layer formation step and the indexing step. The release layer includes, for example, a plurality of modified regions and cracks extending from each of the plurality of modified regions. [Effects of the Invention]

[0008] 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]

[0009] [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 diagram schematically illustrating an example of a laser processing device. [Figure 5] FIG. 5(A) is a top view schematically showing a holding table that holds an ingot, and FIG. 5(B) is a top view schematically showing an irradiation head positioned at a first irradiation start position. [Figure 6] Figure 6(A) is a partial cross-sectional side view showing a schematic cross-sectional area parallel to the X-axis direction and the Z-axis direction of an ingot irradiated with a laser beam from an irradiation head moving in the -X-axis direction from the first irradiation start position, and Figure 6(B) is a cross-sectional view showing a schematic cross-sectional area parallel to the Y-axis direction and the Z-axis direction of an ingot irradiated with a laser beam from an irradiation head moving in the -X-axis direction from the first irradiation start position. [Figure 7] Figure 7(A) is a partially cross-sectional side view schematically showing the irradiation head positioned at the first irradiation end position, and Figure 7(B) is a partially cross-sectional side view schematically showing the irradiation head being returned to the first irradiation start position. [Figure 8] Figure 8(A) is a partial cross-sectional side view schematically showing a cross-sectional area parallel to the X-axis and Z-axis directions of an ingot irradiated with a laser beam from an irradiation head moving in the +X-axis direction from a first irradiation start position, and Figure 8(B) is a partial cross-sectional side view schematically showing the irradiation head positioned at a second irradiation end position. [Figure 9] Figure 9(A) is a top view schematically showing the irradiation head positioned at the second irradiation start position, and Figure 9(B) is a partial cross-sectional side view schematically showing a cross-sectional area parallel to the X-axis direction and Z-axis direction of the ingot irradiated with a laser beam from the irradiation head moving in the -X-axis direction from the second irradiation start position. [Figure 10]Figure 10(A) is a cross-sectional view schematically showing a cross-sectional area parallel to the Y-axis and Z-axis directions of an ingot after it has been irradiated with a laser beam from an irradiation head moving in the -X-axis direction from the second irradiation start position, and Figure 10(B) is a partial cross-sectional side view schematically showing the irradiation head positioned at the fourth irradiation end position. [Figure 11] 11(A) and 11(B) are each a partial cross-sectional side view schematically showing an example of how a substrate is separated from an ingot. [Figure 12] FIG. 12 is a graph showing the width of the peeled layer formed inside a workpiece made of single crystal silicon when a laser beam is irradiated onto linear regions each along a different crystal orientation. [Figure 13] 13(A) and 13(B) are each a partial cross-sectional side view schematically showing another example of how a substrate is separated from an ingot. DETAILED DESCRIPTION OF THE INVENTION

[0010] 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.

[0011] 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] .

[0012] 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 plane slightly tilted from the crystal plane (100) may be exposed on each of the front surface 11a and the back surface 11b. Specifically, a plane that forms an angle of 1° or less with 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 the crystal orientation

[0100] .

[0013] 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.

[0014] 3 is a flow chart showing a schematic example of a method for manufacturing a single crystal silicon substrate, in which a substrate is manufactured from a workpiece, ingot 11. Briefly, in this method, a peeling layer is formed throughout the interior of ingot 11 using a laser processing device, and then the substrate is separated from ingot 11 using this peeling layer as a starting point.

[0015] Figure 4 is a diagram schematically illustrating an example of a laser processing device used to form a peeling layer inside an ingot 11. The +X-axis direction and the -X-axis direction shown in Figure 4 are parallel to each other, and in this specification, both are collectively referred to as the X-axis direction. The +Y-axis direction and the -Y-axis direction shown in Figure 4 are parallel to each other, and in this specification, both are collectively referred to as the Y-axis direction.

[0016] The X-axis and Y-axis directions are perpendicular to each other on a horizontal plane. The +Z-axis and -Z-axis directions shown in Fig. 4 are parallel to each other, and in this specification, both are collectively referred to as the Z-axis direction. The Z-axis direction is perpendicular to both the X-axis and Y-axis directions (vertical direction). In Fig. 4, some of the components of the laser processing device are shown in functional blocks.

[0017] The laser processing apparatus 2 shown in Fig. 4 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.

[0018] 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 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.

[0019] 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 single crystal silicon.

[0020] The output of this laser beam LB is adjusted by an attenuator 10, and then supplied to a spatial light modulator 12. The laser beam LB is then branched in the spatial light modulator 12. For example, the spatial light modulator 12 branches the laser beam LB so that the laser beam LB irradiated from an irradiation head 16 (described later) forms multiple (e.g., five) focusing points arranged at equal intervals along the Y-axis direction.

[0021] Furthermore, the laser beam LB branched by the spatial light modulator 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, and the like. The laser beam LB condensed by this condenser lens is irradiated onto the holding surface side of the holding table 4.

[0022] 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. In the laser processing apparatus 2, by operating this movement mechanism, the position (coordinates) of the focal point of the laser beam LB irradiated from the irradiation head 16 in the X-axis, Y-axis, and Z-axis directions is adjusted.

[0023] When forming a peeling layer over the entire interior area of ​​the ingot 11 in the laser processing device 2, first, the ingot 11 is held on the holding table 4 with the surface 11a facing upward. Fig. 5(A) is a top view schematically showing the holding table 4 holding the ingot 11.

[0024] This ingot 11 is held on the holding table 4 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. For example, the ingot 11 is held on the holding table 4 in a state where the crystal orientation

[0010] is in the same direction as the +X-axis direction, and the crystal orientation

[0001] is in the same direction as the +Y-axis direction.

[0025] Next, in order to form a peeling layer in a linear region along the X-axis direction on one end side (-Y-axis direction side) in the Y-axis direction inside the ingot 11, the irradiation head 16 is moved to a position (first irradiation start position) where irradiation of the ingot 11 with the laser beam LB starts. This first irradiation start position is a position where a focal point is formed inside the side surface 11c of the ingot 11 when the laser beam LB is irradiated from the irradiation head 16 (a position closer to the center C than the side surface 11c).

[0026] 5(B) is a top view schematically showing the irradiation head 16 positioned at the first irradiation start position. The center of the irradiation head 16 positioned at this first irradiation start position is, for example, located slightly inside the side surface 11c of the ingot 11. Furthermore, the center C of the ingot 11 is located in the +Y-axis direction (crystal orientation

[0001] ) when viewed from the center of the irradiation head 16 positioned at the first irradiation start position.

[0027] Next, a peeling layer is formed in a linear region along the +X-axis direction (crystal orientation

[0010] ) inside the ingot 11 (peeling layer forming step: S1). In this peeling layer forming step (S1), first, with the focal point positioned inside the ingot 11, the irradiation head 16 is moved along the X-axis direction (towards the -X-axis direction) to irradiate the ingot 11 with the laser beam LB.

[0028] Note that this laser beam LB is branched so as to form, for example, five focusing points arranged at equal intervals along the Y-axis direction. Fig. 6(A) is a partial cross-sectional side view schematically showing a cross-sectional area parallel to the X-axis and Z-axis directions of the ingot 11 irradiated with the laser beam LB from the irradiation head 16 moving in the -X-axis direction from the first irradiation start position, and Fig. 6(B) is a cross-sectional view schematically showing a cross-sectional area parallel to the Y-axis and Z-axis directions of the ingot 11 irradiated with the laser beam LB from the irradiation head 16 moving in the -X-axis direction from the first irradiation start position.

[0029] By irradiating the laser beam LB, modified regions 15a in which the crystal structure of the single crystal silicon is disrupted are formed around each of the multiple focal points inside the ingot 11. That is, multiple modified regions 15a are formed aligned along the Y-axis direction.

[0030] At this time, cracks 15b propagate from each of the modified regions 15a along a predetermined crystal plane, resulting in the formation of a peeled layer 15 inside the ingot 11, the peeled layer 15 including the modified regions 15a and the cracks 15b propagating from each of the modified regions 15a.

[0031] 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}. <110> When a modified region 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 region, extending along a specific crystal plane included in the crystal plane {111}.

[0032] On the other hand, the crystal orientation of single crystal silicon <100> When multiple modified regions are formed in a linear region along a specific crystal orientation included in the above, so that they are aligned in a direction perpendicular to the direction in which this linear region extends in a planar view, many cracks will occur from each of the multiple modified regions, extending along crystal planes among the crystal planes {N10} (N is an integer with an absolute value of 10 or less, excluding 0) that are parallel to the direction in which the linear region extends.

[0033] For example, as described above, when multiple modified regions 15a are formed in a linear region along the crystal orientation

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

[0001] (+Y-axis direction), an increasing number of cracks extend from each of the multiple modified regions 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] .

[0034] Specifically, when a plurality of modified regions 15a are formed in this way, cracks tend to propagate in the following crystal planes.

number

number

[0035] 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°.

[0036] 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 (W / T) of the width (W) to the thickness (T) of the peeling layer 15 shown in Fig. 6(B) is larger in the former case than in the latter case.

[0037] Furthermore, the ingot 11 is irradiated with the laser beam LB while the irradiation head 16 is moved along the X-axis direction (in the -X-axis direction) until the irradiation head 16 reaches a position (first irradiation end position) where irradiation of the laser beam LB from the irradiation head 16 toward the ingot 11 is ended. This first irradiation end position is a position where a focal point is formed outside the side surface 11c of the ingot 11 when the laser beam LB is irradiated from the irradiation head 16.

[0038] 7(A) is a partial cross-sectional side view schematically showing the irradiation head 16 positioned at the first irradiation end position. In plan view, the center of the irradiation head 16 positioned at this first irradiation end position is located slightly outside the side surface 11c of the ingot 11. In addition, the first irradiation start position is located in the +X-axis direction as viewed from the first irradiation end position.

[0039] Here, the power of the laser beam LB at the focal point may be unstable when the laser beam LB is irradiated onto a region near the side surface 11c of the ingot 11. In this case, due to the difference between the refractive index of the ingot 11 and the refractive index of the atmosphere, the position of the focal point of the laser beam LB that has passed through the surface 11a of the ingot 11 is shifted from the position of the focal point of the laser beam LB that has passed through the side surface 11c of the ingot 11.

[0040] That is, the laser beam LB emitted from the irradiation head 16 is not focused at a single point. As a result, the modified region 15a may not be sufficiently formed in the region near the side surface 11c of the ingot 11. Furthermore, if the modified region 15a is not formed, the crack 15b extending from the modified region 15a is also not formed. As a result, there is a risk that the peeling layer 15 will not be formed in the region near the side surface 11c of the ingot 11.

[0041] On the other hand, if crack 15b is formed inside the region near side surface 11c of ingot 11, crack 15b tends to extend toward side surface 11c to release the stress that occurs in ingot 11 as a result of the formation of crack 15b. Therefore, it is preferable to irradiate this region with laser beam LB when crack 15b has formed inside this region.

[0042] That is, it is preferable that the ingot 11 is irradiated with the laser beam LB while moving the focal point of the laser beam LB from the inside to the outside of the ingot 11. In this case, it becomes easier to form the peeling layer 15 in the region near the side surface 11c of the ingot 11 compared to when the ingot 11 is irradiated with the laser beam LB while moving the focal point of the laser beam LB from the outside to the inside of the ingot 11.

[0043] Next, the irradiation head 16 is moved along the X-axis direction (+X-axis direction) and returned to the first irradiation start position. FIG. 7(B) is a partial cross-sectional side view schematically showing the irradiation head 16 being returned to the first irradiation start position. At this time, the irradiation head 16 may be returned to the first irradiation start position while irradiating the ingot 11 with the above-mentioned laser beam LB. In this case, the density of each of the modified regions 15a and cracks 15b contained in the already formed peeling layer 15 can be increased.

[0044] Next, the above-mentioned laser beam LB is irradiated onto the ingot 11 while moving the irradiation head 16 along the X-axis direction (in the +X-axis direction). Fig. 8(A) is a partial cross-sectional side view schematically showing a cross-sectional area parallel to the X-axis and Z-axis directions of the ingot 11 onto which the laser beam LB is irradiated from the irradiation head 16 moving in the +X-axis direction from the first irradiation start position. By irradiating the laser beam LB, a new peeling layer 15 is formed so that the peeling layer 15 formed inside the ingot 11 extends in the +X-axis direction.

[0045] The region of the ingot 11 irradiated with the laser beam LB while the irradiation head 16 is moved in the +X-axis direction may overlap a part of the region of the ingot 11 on which the peeling layer 15 has already been formed. Specifically, the irradiation head 16 may be returned to a position slightly shifted in the -X-axis direction from the first irradiation start position, and then the above-mentioned laser beam LB may be irradiated onto the ingot 11 while the irradiation head 16 is moved in the +X-axis direction from the shifted position.

[0046] Furthermore, the ingot 11 is irradiated with the laser beam LB while the irradiation head 16 is moved along the X-axis direction (in the +X-axis direction) until the irradiation head 16 reaches a position (second irradiation end position) where irradiation of the laser beam LB from the irradiation head 16 toward the ingot 11 is ended. This second irradiation end position is a position where a focal point is formed outside the side surface 11c of the ingot 11 when the laser beam LB is irradiated from the irradiation head 16.

[0047] 8(B) is a partial cross-sectional side view schematically showing the irradiation head 16 positioned at the second irradiation end position. The center of the irradiation head 16 positioned at this second irradiation end position is located slightly outside the side surface 11c of the ingot 11 in a plan view, and is located in the +X-axis direction as viewed from the first irradiation end position. As a result, a peeling layer 15 is formed in a linear region along the +X-axis direction (crystal orientation

[0010] ) inside the ingot 11.

[0048] Next, along the +Y-axis direction (crystal orientation

[0001] ), the position where the laser beam LB is focused to form a focal point is moved relative to the ingot 11 (indexing step: S2). In this indexing step (S2), the irradiation head 16 is moved to a position (second irradiation start position) where irradiation of the laser beam LB onto the ingot 11 starts in order to form the peeling layer 15 in a linear region parallel to the linear region where the peeling layer 15 has already been formed.

[0049] 9(A) is a top view schematically showing the irradiation head 16 positioned at the second irradiation start position. In the indexing step (S2), for example, the irradiation head 16 is moved along the X-axis direction (in the -X-axis direction) until it returns to the first irradiation start position, and then the irradiation head 16 is moved along the Y-axis direction (in the +Y-axis direction) until it reaches the second irradiation start position.

[0050] When the irradiation head 16 is returned to the first irradiation start position, the above-mentioned laser beam LB may be irradiated onto the ingot 11. In this case, the density of each of the modified regions 15a and the cracks 15b included in the peeling layer 15 that has already been formed can be increased.

[0051] Furthermore, the movement distance (index) of the irradiation head 16 along the Y-axis direction is set to be, for example, equal to or greater than the width (W) of the peeling layer 15. Specifically, if the width (W) of the peeling layer 15 is a predetermined length included in the range of 250 μm to 280 μm, the index is set to about 530 μm.

[0052] Next, the above-described peeling layer forming step (S1) is performed again. Specifically, first, the above-described laser beam LB is irradiated onto the ingot 11 while the irradiation head 16 is moved along the X-axis direction (in the -X-axis direction) with the focal point positioned inside the ingot 11.

[0053] 9(B) is a partial cross-sectional side view showing a cross-sectional area parallel to the X-axis and Z-axis directions of the ingot 11 irradiated with the laser beam LB from the irradiation head 16 moving in the −X-axis direction from the second irradiation start position, and FIG. 10(A) is a cross-sectional view showing a cross-sectional area parallel to the Y-axis and Z-axis directions of the ingot 11 after being irradiated with the laser beam LB from the irradiation head 16 moving in the −X-axis direction from the second irradiation start position. In this case, a peeling layer 15 (peeling layer 15-2) is formed inside the ingot 11, which 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.

[0054] Furthermore, the ingot 11 is irradiated with the laser beam LB while the irradiation head 16 is moved along the X-axis direction (in the -X-axis direction) until the irradiation head 16 reaches a position (third irradiation end position) where irradiation of the laser beam LB from the irradiation head 16 toward the ingot 11 is ended. This third irradiation end position is a position where a focal point is formed slightly outside the side surface 11c of the ingot 11 when the laser beam LB is irradiated from the irradiation head 16.

[0055] Next, the irradiation head 16 is moved along the X-axis direction (+X-axis direction) and returned to the second irradiation start position. At this time, the irradiation head 16 may be returned to the second irradiation start position while irradiating the ingot 11 with the above-mentioned laser beam LB. In this case, the density of each of the modified regions 15a and cracks 15b contained in the already formed peeling layer 15 (peeling layer 15-2) can be increased.

[0056] Next, while moving the irradiation head 16 along the X-axis direction (+X-axis direction), the ingot 11 is irradiated with the above-mentioned laser beam LB. By this irradiation with the laser beam LB, a new peeling layer 15 (peeling layer 15-2) is formed so that the peeling layer 15 (peeling layer 15-2) formed inside the ingot 11 extends in the +X-axis direction.

[0057] The region of the ingot 11 irradiated with the laser beam LB while the irradiation head 16 is moved in the +X-axis direction may overlap a part of the region of the ingot 11 on which the peeling layer 15 (peeling layer 15-2) has already been formed. Specifically, after the irradiation head 16 is returned to a position slightly shifted in the -X-axis direction from the second irradiation start position, the above-mentioned laser beam LB may be irradiated onto the ingot 11 while the irradiation head 16 is moved in the +X-axis direction from the shifted position.

[0058] Furthermore, the ingot 11 is irradiated with the laser beam LB while the irradiation head 16 is moved along the X-axis direction (in the +X-axis direction) until the irradiation head 16 reaches a position (fourth irradiation end position) where irradiation of the laser beam LB from the irradiation head 16 toward the ingot 11 is ended. This fourth irradiation end position is a position where a focal point is formed outside the side surface 11c of the ingot 11 when the laser beam LB is irradiated from the irradiation head 16.

[0059] 10(B) is a partial cross-sectional side view schematically showing the irradiation head 16 positioned at the fourth irradiation end position. The center of the irradiation head 16 positioned at this fourth irradiation end position is located slightly outside the side surface 11c of the ingot 11 in a plan view, and is located in the +X-axis direction as viewed from the third irradiation end position.

[0060] As a result of the above, a separation layer 15 (separation layer 15-2) is formed in a linear region along the X-axis direction (crystal orientation

[0010] ) inside ingot 11. This separation layer 15-2 is closer to the center C of ingot 11 than the separation layer 15-1 formed initially, and its length along the X-axis direction is longer than the length along the X-axis direction of separation layer 15-1.

[0061] Furthermore, the indexing step (S2) and the peeling layer forming step (S1) are repeatedly performed until a peeling layer 15 is formed in a linear region along the X-axis direction in the region on the other end side in the Y-axis direction inside the ingot 11. Then, when the peeling layer 15 is formed (over the entire region) from the region on one end side (-Y-axis direction side) to the region on the other end side (+Y-axis direction side) in the Y-axis direction inside the ingot 11 (step (S3): YES), the substrate is separated from the ingot 11 starting from the peeling layer 15 (separation step: S4).

[0062] 11(A) and 11(B) are partial cross-sectional side views each showing a schematic example of how a substrate is separated from an ingot 11. This separation step (S4) is performed, for example, in a separation apparatus 18 shown in FIGS. 11(A) and 11(B). This separation apparatus 18 has a holding table 20 that holds the ingot 11 on which a peeling layer 15 has been formed.

[0063] 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.

[0064] A separation unit 22 is provided above the holding table 20. The separation unit 22 has a cylindrical support member 24. To the top of the support member 24, for example, a ball screw type lifting mechanism (not shown) and a rotary drive source (not shown) such as a motor are connected. The separation unit 22 is raised and lowered by operating the lifting mechanism. The support member 24 is rotated 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 by operating the rotary drive source.

[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 (S4) is performed, for example, in the following order: Specifically, first, the ingot 11 is placed on the holding table 20 so that the center of the back surface 11b of the ingot 11 on which the peeling layer 15 is formed 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. 11(A)). Next, the rotation drive source is operated to rotate the wedge portion 28b driven into the side surface 11c of the ingot 11.

[0070] Next, the lifting mechanism is operated to lift the wedge portion 28b (see FIG. 11(B)). After the wedge portion 28b is driven into the side surface 11c of the ingot 11 and rotated as described above, the wedge portion 28b is lifted, whereby the crack 15b contained in the separation layer 15 is further extended. As a result, 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 separation layer 15.

[0071] 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.

[0072] In the method for manufacturing substrate 17 described above, a laser beam LB having a wavelength that transmits single crystal silicon is used to form a peeling layer 15 inside ingot 11, and then substrate 17 is separated from ingot 11 starting from this peeling layer 15. This reduces the amount of material wasted when manufacturing substrate 17 from ingot 11, and improves the productivity of substrate 17, compared to when substrate 17 is manufactured from ingot 11 using a wire saw.

[0073] Furthermore, in the above-described method, multiple modified regions 15a are formed in a linear 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 multiple 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] .

[0074] As a result, in the above-described method, the peeling layer 15 can be made 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.

[0075] Furthermore, in the above-described method, the focal point of the laser beam LB is moved from the inside to the outside of the ingot 11, thereby forming the peeling layer 15 inside the ingot 11. As a result, in the above-described method, the peeling layer 15 can be sufficiently formed even in the region near the side surface 11c of the ingot 11. As a result, the substrate 17 can be easily separated from the ingot 11 in the separation step.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] Furthermore, in the peeling layer forming step (S1) of the present invention, the linear region inside the ingot 11 that is irradiated with the laser beam LB is not limited to a linear region along the crystal orientation

[0010] . For example, in the present invention, the laser beam LB may be irradiated to a linear region along the crystal orientation

[0001] .

[0081] 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

[0082] Furthermore, in the present invention, the laser beam LB may be irradiated onto a linear 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.

[0083] 12 is a graph showing the width (width (W) shown in FIG. 6(B)) of the peeled layer formed inside a workpiece made of single-crystal silicon when a laser beam LB is irradiated onto linear regions each along a different crystal orientation. The horizontal axis of this graph indicates the angle between the direction in which a linear region (reference region) perpendicular to the crystal orientation

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

[0084] That is, when the horizontal axis of this graph is 45°, the linear region along the crystal orientation

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

[0010] is the measurement target. Furthermore, the vertical axis of this graph represents the value obtained by dividing the width of the peeled layer formed in the measurement region by irradiating the laser beam LB onto the measurement region by the width of the peeled layer formed in the reference region by irradiating the laser beam LB onto the reference region.

[0085] 12, 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 along the crystal orientation

[0001] or the crystal orientation

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

[0086] Therefore, in the peeling layer formation step (S1) of the present invention, the laser beam LB may be irradiated onto a linear region along a direction tilted by 5° or less from the crystal orientation

[0001] or the crystal orientation

[0010] in a planar view.

[0087] 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 linear region along a direction (first direction) that forms an angle of 5° or less with respect to a specific crystal orientation (here, crystal orientation

[0001] or crystal orientation

[0010] ) included in the above.

[0088] Furthermore, when the peeling layer formation step (S1) is performed in this manner, the indexing and feeding step (S2) is performed by moving the ingot 11 relatively to the position where a focal point is formed by focusing the laser beam LB along a direction (second direction) that is parallel to a specific crystal plane (here, crystal plane (100)) included in the crystal plane {100} that is exposed on each of the front surface 11a and back surface 11b of the ingot 11 and is perpendicular to the first direction.

[0089] Furthermore, in the present invention, after the separation layer 15 is formed (over the entire area) from the region on one end side (-Y-axis direction side) to the region on the other end side (+Y-axis direction side) in the Y-axis direction inside the ingot 11 (step S3: YES), the separation layer forming step (S1) and the indexing step (S2) may be repeated again. That is, the laser beam LB may be irradiated again from the region on one end side to the region on the other end side in the Y-axis direction inside the ingot 11 where the separation layer 15 has already been formed, so as to form the separation layer 15.

[0090] In the present invention, after the separation layer forming step (S1) and before the indexing step (S2), the separation layer forming step (S1) may be performed again. That is, the laser beam LB may be irradiated again to the linear region inside the ingot 11 where the separation layer 15 has already been formed, so as to form the separation layer 15.

[0091] When the separation layer forming step (S1) is performed again on the region where the separation layer 15 has already been formed, the density of the modified regions 15a and the cracks 15b included in the already formed separation layer 15 increases, which makes it easier to separate the substrate 17 from the ingot 11 in the separation step (S4).

[0092] Furthermore, in this case, the cracks 15b contained in the peeling layer 15 extend further, widening the width (width (W) shown in FIG. 6(B)) of the peeling layer 15. Therefore, in this case, the movement distance (index) of the irradiation head 16 of the laser beam irradiation unit 6 in the indexing feed step (S2) can be increased.

[0093] 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 (S2). For example, if it is possible to extend the crack 15b to the area near the side surface 11c of the ingot 11 by performing the separation step (S4) using the separation device 18, it is not necessary to form the peeling layer 15 in part or all of the area near the side surface 11c of the ingot 11 in the peeling layer forming step (S2).

[0094] Furthermore, the separation step (S4) of the present invention may be performed using an apparatus other than the separation apparatus 18 shown in Figures 11(A) and 11(B). For example, in the separation step (S4) of the present invention, the substrate 17 may be separated from the ingot 11 by suctioning the surface 11a side of the ingot 11.

[0095] 13(A) and 13(B) are partial cross-sectional side views each showing a schematic example of how the substrate 17 is separated from the ingot 11. The separation device 30 shown in FIGS. 13(A) and 13(B) has a holding table 32 that holds the ingot 11 on which the peeling layer 15 is formed.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] In the separation device 30, the separation step (S4) 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.

[0100] 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.

[0101] 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. 13(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. 13(B)).

[0102] 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 crack 15b contained in the peeling layer 15 further extends, and the front surface 11a side and the back surface 11b side of the ingot 11 are separated. In other words, the substrate 17 is produced from the ingot 11, starting from the peeling layer 15.

[0103] Furthermore, in the separation step (S4) 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.

[0104] 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. Specifically, when the ingot 11 is separated at the separation layer 15 to manufacture the substrates 17, the newly exposed surface of the ingot 11 has irregularities that reflect the distribution of the modified regions 15a and cracks 15b contained in the separation layer 15.

[0105] Therefore, when a new substrate is manufactured from this ingot 11, it is preferable to flatten the surface of ingot 11 prior to the peeling layer forming step (S1). This makes it possible to suppress diffuse reflection of the laser beam LB irradiated onto ingot 11 at the surface of ingot 11 in the peeling layer forming step (S1). Similarly, in the present invention, the surface of substrate 17 separated from ingot 11 on the peeling layer 15 side may be flattened by grinding or polishing.

[0106] 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.

[0107] 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.

[0108] 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. [Explanation of symbols]

[0109] 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) 12: Spatial light modulator 13: Orientation Flat 14: Mirror 15: Peeling layer (15a: modified region, 15b: crack) 15-1, 15-2: 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 separation layer forming step in which, while a focal point formed by focusing a laser beam having a wavelength that is transmitted through the single crystal silicon is positioned inside the workpiece, the focal point and the workpiece are moved relatively along a first direction that is parallel to the specific crystal plane and forms an angle of 5° or less with respect to a specific crystal orientation included in the crystal orientation <100>, thereby forming a separation layer in a linear region along the first direction inside the workpiece; an indexing step of relatively moving the position where the focal point is formed by focusing the laser beam and the workpiece along a second direction that is parallel to the specific crystal plane and perpendicular to the first direction; a separation step of separating the substrate from the workpiece starting from the release layer after repeatedly performing the release layer forming step and the indexing step; A method for manufacturing a single crystal silicon substrate, characterized in that in the peeling layer formation step, the focal point and the workpiece are moved relatively so that the focal point moves from the inside to the outside of the workpiece.

2. A method for manufacturing a single crystal silicon substrate as described in claim 1, characterized in that the peeling layer includes a plurality of modified regions and cracks extending from each of the plurality of modified regions.

Images