JP7635767B2 - Wafer Manufacturing Method - Google Patents

Description

The present invention relates to a wafer manufacturing method.

As a method for manufacturing a SiC wafer with relatively little SiC loss, a method is known in which a laser beam with a wavelength that is transparent to SiC is focused inside a SiC single crystal ingot to form a modified layer and cracks extending from the modified layer, and then the ingot is cleaved. In this method, the focal point of the laser beam is positioned at a predetermined depth position in the SiC single crystal ingot, and the laser beam is scanned along the cleaved surface to form a modified layer along the cleaved surface. Meanwhile, in the growth process of a SiC single crystal, regions called facet regions and non-facet regions, which have different growth modes, are formed. The facet regions and non-facet regions have different transmittances. For this reason, when a laser beam with a wavelength that is transparent to SiC is irradiated to a predetermined depth from the surface of a SiC single crystal ingot to form a modified layer, the facet regions and non-facet regions reach different depths at which the energy density exceeds the threshold at which the modified layer is formed. In this regard, JP 2020-31134 A discloses that the laser beam absorbency differs between the facet region and the non-facet region, specifically, the laser beam absorbency in the non-facet region is lower than the laser beam absorbency in the facet region. The document also discloses that the intensity of the laser beam reaching the focal point is stronger in the non-facet region than in the facet region. The document also discloses that a uniform modified layer can be formed at a predetermined depth position of the SiC single crystal ingot by irradiating the facet region and the non-facet region with a laser beam that is transparent to SiC under conditions suitable for each of them.

JP 2020-47619 A

As described above, JP 2020-31134 A discloses that the intensity of the laser beam reaching the focal point is stronger in the non-facet area than in the facet area, and that the laser beam is irradiated under conditions suitable for each of the facet area and the non-facet area. However, the publication does not disclose anything about how to control the irradiation conditions. On the other hand, Patent Document 1 discloses a technology for increasing the energy of the laser beam and raising the position of the condenser when irradiating the facet area with a laser beam in the processing feed process. The "processing feed process" is a process in which the focal point of a laser beam having a wavelength that is transparent to SiC is positioned at a depth equivalent to the thickness of the wafer to be generated from the top surface of the SiC ingot, and the SiC ingot and the focal point are processed and fed relatively in the X-axis direction while irradiating the SiC ingot with a laser beam from the condenser of the laser processing device, so that the SiC is separated into Si and C and a strip-shaped peeling layer in which the crack extends along the c-plane is formed. However, even with this technology, there is a certain response delay when raising the collector, and it cannot keep up with high-speed laser beam scanning. Also, moving the collector up and down generates vibrations, which causes variation in the depth of the modified layer and increases material loss.

The present invention has been made in consideration of the circumstances exemplified above. That is, the present invention provides a wafer manufacturing method that can improve manufacturing efficiency compared to conventional methods, for example by forming a peeling layer satisfactorily over the entire area including the facet area and the non-facet area.

A method for producing wafers according to claim 1, comprising the steps of: obtaining wafers (1) from an ingot (2), the steps comprising:
forming a peeling layer by irradiating a surface (21) of the ingot at one end in the height direction with a laser beam having transparency to form a peeling layer (25) from the surface to a depth corresponding to the thickness of the wafer;
a wafer delamination step of delaminating a wafer precursor (26) between the surface and the delamination layer from the ingot at the delamination layer;
a wafer planarization step for planarizing a main surface (32) of the plate-shaped peeled body (30) obtained by the wafer peeling;
Including,
The peeling layer is formed by irradiating the surface with the laser beam so that the facet regions (RF) are irradiated more frequently than the non-facet regions (RN).

In this wafer manufacturing method, first, the laser beam having transparency is irradiated onto the surface of the ingot at one end in the height direction, thereby forming the peeling layer from the surface to a depth corresponding to the thickness of the wafer. Next, the wafer precursor, which is the portion between the surface of the ingot and the peeling layer, is peeled off from the ingot at the peeling layer. Next, the main surface of the plate-shaped peeled body obtained by peeling the wafer precursor from the ingot is flattened to obtain the wafer.

Here, as described above, the intensity of the laser beam reaching the focal point is stronger in the non-facet region than in the facet region. Therefore, when forming the peeling layer, the laser beam is irradiated onto the surface so that the facet region is irradiated more frequently than the non-facet region. Specifically, for example, the repetition frequency of the laser beam is made higher in the facet region than in the non-facet region, and the irradiation interval in the first direction is narrowed. Alternatively, for example, the irradiation interval in the facet region is made narrower than in the non-facet region. Alternatively, for example, the laser beam is irradiated onto the facet region separately from the irradiation of the entire region including the facet region and the non-facet region. According to this wafer manufacturing method, it is possible to form the peeling layer well in the entire region including the facet region and the non-facet region. Therefore, according to this wafer manufacturing method, it is possible to improve manufacturing efficiency more than before.

In addition, in each section of the application documents, each element may be given a reference symbol in parentheses. In this case, the reference symbol merely indicates an example of the correspondence between the element and the specific configuration described in the embodiment described below. Therefore, the present invention is not limited in any way by the description of the reference symbol.

1 is a side view showing a schematic configuration of a wafer, an ingot, and a peeled body in a wafer manufacturing method according to an embodiment of the present invention. 1A to 1C are process diagrams illustrating an outline of a wafer manufacturing method according to an embodiment of the present invention. 3 is a side view showing a schematic configuration of the ingot that has undergone the peeling layer forming step shown in FIG. 2. FIG. 3B is a plan view of the ingot shown in FIG. 3A. 3 is a side view showing an outline of the release layer forming step shown in FIG. 2 and a release layer forming apparatus used therein. FIG. FIG. 3 is a front view showing an overview of the release layer forming step shown in FIG. 2 and a release layer forming apparatus used therein. FIG. 5 is a diagram showing an outline of the release layer forming step shown in FIG. 4A and FIG. 4B. FIG. 5 is a diagram showing an outline of the release layer forming step shown in FIG. 4A and FIG. 4B. FIG. 5 is a plan view showing an outline of the release layer forming step shown in FIGS. 4A and 4B. FIG. 5 is an enlarged view of the laser beam shown in FIGS. 4A and 4B near the focal point. FIG. 4B is a side view showing an outline of the release layer forming step shown in FIG. 4A. FIG. 11 is a side view illustrating an outline of a release layer forming step in another example. FIG. 4B is a side view showing an outline of the release layer forming step shown in FIG. 4A. FIG. 4B is a side view showing an outline of the release layer forming step shown in FIG. 4A. 3 is a side view showing an outline of the wafer peeling step shown in FIG. 2 and a peeling apparatus used therein. FIG. FIG. 5B is a plan view showing a modified example of the arrangement of multiple laser beams shown in FIG. 5A. FIG. 5B is a plan view showing another modified example of the arrangement of the multiple laser beams shown in FIG. 5A. 10A to 10C are process diagrams illustrating an outline of a wafer manufacturing method according to a modified example. 15 is a plan view showing an example of a setting mode of a measurement position in the wafer optical measurement shown in FIG. 14. 15 is a plan view showing how the measurement position is scanned in the wafer optical measurement shown in FIG. 14. 17 is a graph showing the state of change in absorption coefficient calculated from transmittance measured by scanning the measurement positions shown in FIG. 16 depending on the measurement position. 15 is a side cross-sectional view showing the difference in the position where a modified layer is generated depending on the transmittance in the laser slicing, i.e., the peeling layer forming process shown in FIG. 14 . 15 is a side cross-sectional view showing the difference in the position where a modified layer is generated depending on the transmittance in the laser slicing, i.e., the peeling layer forming process shown in FIG. 14 . 15 is a side cross-sectional view showing the difference in the position where a modified layer is generated depending on the transmittance in the laser slicing, i.e., the peeling layer forming process shown in FIG. 14 . FIG. 15 is a side cross-sectional view for explaining an example of a method for setting the irradiation conditions of a laser beam in the laser slicing, i.e., peeling layer forming step, shown in FIG. 14. FIG. 11 is a plan view for explaining a method of deriving the amount of change in absorption coefficient shown in equation (2). 21 is a graph showing the change in absorption coefficient in the depth direction of the ingot at the in-plane center position shown in FIG. 20 . 21 is a graph showing the change in absorption coefficient in the depth direction of the ingot at the first end position shown in FIG. 20 . 21 is a graph showing the change in absorption coefficient in the depth direction of the ingot at the second end position shown in FIG. 20 . 1 is a graph for explaining an example of a method for deriving an absorption coefficient. 15 is a side view showing a first product and a second product generated for setting the irradiation conditions of the laser beam in the laser slicing, i.e., the peeling layer forming step, shown in FIG. 14. FIG. 15 is a graph showing the change in absorption coefficient when the measurement pitch is made finer in the wafer optical measurement shown in FIG. 14 .

(Embodiment)
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that, if various modified examples applicable to one embodiment are inserted in the middle of a series of explanations related to the embodiment, it may hinder understanding of the embodiment. For this reason, the modified examples are not inserted in the middle of a series of explanations related to the embodiment, but are explained together after the series of explanations.

(Wafer and ingot structure)
1, a wafer 1 manufactured by the wafer manufacturing method according to the present embodiment is obtained by slicing an ingot 2 that is substantially cylindrical in side view, and is formed in a substantially circular thin plate shape in plan view. That is, the wafer 1 and the ingot 2 have substantially cylindrical side or end faces surrounding a central axis L. The central axis L is a virtual straight line that is parallel to the substantially cylindrical side or end faces of the wafer 1 and the ingot 2 and passes through the axial center of the wafer 1 and the ingot 2. Note that, from the viewpoint of simplifying the illustration and explanation, the so-called orientation flat that is usually provided on the wafer 1 and the ingot 2 is not illustrated or explained in this specification.

In this embodiment, the ingot 2 is a single crystal SiC ingot having a c-axis Lc and a (0001) plane Pc that are perpendicular to each other, and has an off-angle θ that exceeds 0 degrees. The c-axis Lc is a crystal axis indicated by a direction index as [0001]. The (0001) plane Pc is a crystal plane that is perpendicular to the c-axis Lc and is called a "C-plane" in the strict sense of crystallography. The off-angle θ is the angle between the central axis L of the wafer 1 or ingot 2 and the c-axis Lc, and is, for example, about 1 to 4 degrees. That is, the c-axis Lc in the wafer 1 and ingot 2 is provided with the central axis L tilted in the off-angle direction Dθ by an off-angle θ that exceeds 0 degrees. The off-angle direction Dθ is the direction of movement of a point on the central axis L located on the laser irradiation surface (i.e., the upper surface or top surface in the figure) of the wafer 1 or ingot 2 when the central axis L is rotated toward the c-axis Lc around the intersection of the central axis L and the c-axis Lc.

For the sake of simplicity, the right-handed XYZ coordinate system is set as shown in FIG. 1. In this right-handed XYZ coordinate system, the off-angle direction Dθ and the positive X-axis direction are assumed to be the same direction. The X-axis and Y-axis are assumed to be parallel to the main surfaces of the wafer 1 and the ingot 2. The "main surface" is a surface that is perpendicular to the thickness direction of a plate-like object, and may also be called the "top surface", "bottom surface", or "plate surface". Alternatively, the "main surface" is a surface that is perpendicular to the height direction of a columnar object such as the ingot 2, and may also be called the "top surface" or "bottom surface". Furthermore, the thickness direction of the wafer 1 and the height direction of the ingot 2 are assumed to be parallel to the Z-axis. Any direction perpendicular to the Z-axis may be referred to as the "in-plane direction" below.

The wafer 1 has a pair of main surfaces, the wafer C surface 11 and the wafer Si surface 12. In this embodiment, the wafer 1 is formed so that the wafer C surface 11, which is the top surface, is inclined at an off angle θ with respect to the (0001) surface Pc. Similarly, the ingot 2 has a pair of main surfaces, the ingot C surface 21 and the ingot Si surface 22. The ingot 2 is formed so that the ingot C surface 21, which is the top surface, is inclined at an off angle θ with respect to the (0001) surface Pc. Hereinafter, one end of the ingot 2 in the off angle direction Dθ, i.e., the upstream end, will be referred to as the first end 23, and the other end, i.e., the downstream end, will be referred to as the second end 24. In FIG. 1, the direction in which the wafer C surface 11 and the ingot C surface 21 face is shown as the positive direction of the Z axis.

The ingot 2 also has a facet region RF. The facet region RF may also be referred to as a "facet portion." The portion of the ingot 2 other than the facet region RF will hereinafter be referred to as a non-facet region RN. Similarly, the non-facet region RN may also be referred to as a "non-facet portion."

(Overview of wafer manufacturing method)
The wafer manufacturing method according to this embodiment is a method for obtaining a wafer 1 from an ingot 2, and includes the following steps.

(1) Peeling layer formation process: A laser beam having a predetermined degree of transparency to the ingot 2 is irradiated onto the ingot C surface 21, which is the main surface at one end side of the ingot 2 in the height direction, to form a peeling layer 25 from the ingot C surface 21 to a depth corresponding to the thickness of the wafer 1.
Here, the "predetermined degree of transparency" refers to a degree of transparency that allows a focal point of the laser beam to be formed at a depth corresponding to the thickness of the wafer 1 inside the ingot 2. Also, the "depth corresponding to the thickness of the wafer 1" is a dimension obtained by adding a thickness corresponding to a predetermined processing allowance in a wafer flattening process or the like described below to the thickness of the wafer 1, which is the finished product (i.e., the target thickness value), and may also be referred to as the "depth corresponding to the thickness of the wafer 1."

(2) Wafer peeling process: The wafer precursor 26 , which is the portion between the ingot C-face 21 , which is the laser irradiated surface, and the peeling layer 25 , is peeled off from the ingot 2 at the peeling layer 25 .
Here, as in the expression "wafer peeling process" above, the plate-like object obtained by peeling the wafer precursor 26 from the ingot 2 may be commonly referred to as a "wafer." However, in order to distinguish it from the final wafer 1 after production having an epi-ready mirror-finished main surface, such a plate-like object will be referred to as a "peeled body 30" below.
The peeling body 30 has a pair of main surfaces, a non-peeled surface 31 and a peeled surface 32. The non-peeled surface 31 is a surface on the side that did not constitute the peeling layer 25 before the wafer peeling process, and corresponds to the ingot C-face 21 before the peeling layer forming process and the wafer peeling process. The peeled surface 32 constituted the peeling layer 25 before the wafer peeling process, and is a surface newly generated by the wafer peeling process. The peeled surface 32 has rough unevenness (i.e., to the extent that grinding or polishing is required) caused by the peeling layer 25 and peeling by the wafer peeling process.

(3) Wafer planarization process: At least the peeled surface 32 of the non-peeled surface 31 and the peeled surface 32, which are the main surfaces of the peeler 30, is planarized to obtain the final wafer 1 after manufacture. In the wafer planarization process, in addition to general grinding stone polishing and CMP, ECMG and ECMP can be used. Note that CMP is an abbreviation for Chemical Mechanical Polishing. ECMG is an abbreviation for Electro-Chemical Mechanical Grinding. ECMP is an abbreviation for Electro-Chemical Mechanical Polishing. The wafer planarization process can be performed by using these multiple types of planarization processes alone or in appropriate combination.

(4) Ingot planarization process: After the wafer precursor 26 is peeled off, the top surface of the newly generated ingot 2 is planarized, i.e., mirror-finished, so that it can be used again in the peeling layer formation process. In the ingot planarization process, in addition to general grinding stone polishing and CMP, ECMG and ECMP can also be used. The ingot planarization process can also be performed by using these multiple types of planarization processes alone or in appropriate combination.

2 is a process diagram showing a typical example of the wafer manufacturing method according to the present embodiment. As shown in FIG. 2, a peeled body 30 peeled from an ingot 2 through a peeling layer forming process and a wafer peeling process is finished into an epi-ready wafer 1 through the following processes.
Rough grinding of the peeled surface 32 that is to become the Si surface 12 of the wafer; ECMG grinding of the peeled surface 32 that has been subjected to rough grinding; ECMP polishing and cleaning of the peeled surface 32 that has been subjected to ECMG grinding.

In addition, the ingot 2 remaining after the peeled body 30 is peeled off from the ingot 2 through the peeling layer forming step and the wafer peeling step can be subjected to the peeling layer forming step again through the following steps.
Rough grinding of the ingot C-face 21 newly generated by the wafer peeling process, and finish grinding and cleaning of the ingot C-face 21 that has been roughly ground

The details of each step are explained below using other figures in addition to Figures 1 and 2.

(Release layer forming process)
3A and 3B show a schematic configuration of the ingot 2 in a state in which a separation layer 25 and a wafer precursor 26 are formed by the separation layer forming process. FIGs. 4A and 4B show an overview of the separation layer forming process and a schematic configuration of a separation layer forming apparatus 40 used in the process. Note that the right-handed XYZ coordinates shown in FIGs. 3A to 4B are displayed so as to match the right-handed XYZ coordinates shown in FIG.

Referring to Figures 3A and 3B, the peeling layer 25 is formed by forming multiple scan lines Ls, which are linear laser beam irradiation marks along the X-axis, in the Y-axis direction. The scan lines Ls are linearly formed laser beam irradiation marks RM on the ingot 2. In this embodiment, the scan lines Ls are provided along the off-angle direction Dθ. The multiple scan lines Ls are arranged in the line feed direction Df. The line feed direction Df is an in-plane direction perpendicular to the off-angle direction Dθ. In other words, the line feed direction Df is a direction perpendicular to the off-angle direction Dθ and perpendicular to the height direction of the ingot 2.

4A and 4B, the peeling layer forming device 40 includes a chuck table 41 and a focusing device 42. The chuck table 41 is configured to hold the ingot 2 on the side of the ingot Si surface 22, which is its bottom surface. Specifically, for example, the chuck table 41 includes an adsorption mechanism that adsorbs the ingot Si surface 22 by air pressure or the like. As will be described later, the method of fixing the ingot 2 to the chuck table 41 is not limited to this embodiment. The focusing device 42 is disposed opposite the chuck table 41 in the beam axis direction, which is the irradiation direction of the laser beam B, so that the laser beam B oscillated by a pulse laser oscillator (not shown) is irradiated onto the ingot 2, which is the workpiece fixed to the chuck table 41. That is, the focusing device 42 is provided so as to irradiate the ingot 2 with the laser beam B from the ingot C surface 21, which is the top surface of the ingot 2. Specifically, the focusing device 42 is configured to form a focal point BP of the laser beam B inside the ingot 2 at a depth from the ingot C surface 21 corresponding to the thickness of the wafer 1. The focusing device 42 can also be called a "focuser" and is equipped with an optical element (e.g., a lens) for forming the focal point BP of the laser beam B at a predetermined position. The peeling layer forming device 40 is configured to be able to move the focal point BP of the laser beam B relatively to the ingot 2 at least in the in-plane direction, i.e., the XY direction in the figure. Here, the "in-plane direction" is the direction parallel to the ingot C surface 21, which is the upper surface of the ingot 2.

The peeling layer forming device 40 forms a scan line Ls along the scanning direction Ds by "laser scanning" in which the laser beam B is scanned on the ingot C surface 21 in the scanning direction Ds (i.e., the first direction). That is, "laser scanning" is to irradiate the ingot C surface 21 with the laser beam B while moving the irradiation position PR of the laser beam B on the ingot C surface 21, which is the laser irradiation surface, in the scanning direction Ds. In this embodiment, the scanning direction Ds is a direction along the off-angle direction Dθ, specifically, the same direction as the off-angle direction Dθ or the opposite direction. The peeling layer forming device 40 performs laser scanning multiple times while changing the position in the line feed direction Df (i.e., the second direction), and forms multiple scan lines Ls along the line feed direction Df to form the peeling layer 25. The line feed direction Df and the scanning direction Ds are both in-plane directions (i.e., directions along the ingot C surface 21) and are perpendicular to each other.

In this embodiment, the peeling layer forming device 40 moves the chuck table 41 on which the ingot 2 is placed relative to the focusing device 42 in the scanning direction Ds to scan the laser beam B on the ingot C surface 21, thereby forming the scanning line Ls along the scanning direction Ds. After performing one laser scan, the peeling layer forming device 40 moves the chuck table 41 relative to the focusing device 42 by a predetermined amount along the line feed direction Df. Then, the peeling layer forming device 40 again moves the chuck table 41 relative to the focusing device 42 in the scanning direction Ds (i.e., the same or opposite direction as in the previous laser scan) to scan the laser beam B, thereby forming the scanning line Ls. In this way, the peeling layer forming device 40 scans the laser beam B over almost the entire width in the line feed direction Df to form a plurality of scanning lines Ls along the line feed direction Df. In this way, the peeling layer 25 is formed by the plurality of scanning lines Ls provided along the line feed direction Df. Further, the wafer precursor 26 to be the wafer 1 in the future is formed on the ingot C-face 21 side of the peeling layer 25. As described above, in this embodiment, the focusing device 42 is fixed in the in-plane direction, while the chuck table 41 supporting the ingot 2 is provided so as to move at least in the in-plane direction by a scanning device such as an electric stage device (not shown). On the other hand, as described later, the present invention is not limited to such an embodiment. That is, for example, there may be an embodiment in which the chuck table 41 supporting the ingot 2 is fixed in the in-plane direction, while the focusing device 42 is provided so as to be movable in the in-plane direction by a scanning device (not shown). However, in any of these embodiments, the laser beam B and its irradiation position PR appear to move in the in-plane direction on the main surface of the ingot 2, or the laser beam B and its focusing point BP appear to move in the in-plane direction within the ingot 2. Therefore, for the sake of simplicity, the following description may be given assuming that the laser beam B and its irradiation position PR move in an in-plane direction on the main surface of the ingot 2, or that the laser beam B and its focal point BP move in an in-plane direction within the ingot 2. However, as described below, the present invention is not limited to such an embodiment.

In this embodiment, as shown in Figures 4A and 4B, multiple laser beams B with different irradiation positions PR in the scanning direction Ds and the line feed direction Df are irradiated onto the ingot C surface 21 in a single laser scan. Specifically, as shown in Figures 5A and 5B, multiple laser beams B (i.e., first beam B1, etc.) whose irradiation positions PR on the ingot C surface 21 are arranged at an angle to both the scanning direction Ds and the line feed direction Df in a plan view move along the scanning direction Ds. As a result, multiple scan lines Ls are formed in a single laser scan. Therefore, the cycle time in the peeling layer formation process can be effectively shortened.

In addition, in Figures 4A, 4B, and 5A, an example of three laser beams B is illustrated as the multiple laser beams B. However, this is for the convenience of simplifying the illustration, and there is no particular limit to the number of laser beams B. However, for the sake of simplicity, the following description will be continued assuming that the multiple laser beams B include at least a first beam B1, a second beam B2, and a third beam B3. Of the first beam B1, the second beam B2, and the third beam B3, the first beam B1 is the most advanced, that is, the beam closest to the scanning direction Ds. On the other hand, the third beam B3 is the most trailing. The second beam B2 is positioned between the first beam B1 and the third beam B3 in the scanning direction Ds and the line feed direction Df.

As shown in FIG. 5A, the first beam B1 advances in the scanning direction Ds ahead of the second beam B2. As shown in FIG. 5B, the irradiation of the first beam B1 generates an irradiation-affected area RA at a predetermined depth from the ingot C surface 21, which is the laser-irradiated surface. The irradiation-affected area RA includes an irradiation mark RM consisting of a modified area formed by the separation of SiC into Si and C by the irradiation of the laser beam B, and a crack C extending from the irradiation mark RM to its periphery along the (0001) plane Pc. For this reason, the irradiation position PR of the second beam B2 may overlap at least the crack C in the irradiation-affected area RA formed by the preceding first beam B1 in the in-plane direction. If the irradiation mark RM or the crack C included in the irradiation-affected area RA by the preceding first beam B1 exists at the irradiation position PR of the following second beam B2, the absorption rate of the second beam B2 is increased by the irradiation-affected area RA. For this reason, the irradiation marks RM by the following second beam B2 tend to occur at approximately the same depth as the depth of the irradiation affected area RA by the preceding first beam B1. The same applies to the relationship between the second beam B2 and the third beam B3. Therefore, three adjacent irradiation marks RM or irradiation affected areas RA in the line feed direction Df formed at once by the first beam B1 to the third beam B3 in one laser scan tend to occur at approximately the same depth. In other words, multiple scanning lines Ls that constitute the peeling layer 25 and are adjacent in the line feed direction Df tend to occur at approximately the same depth.

In this manner, in this embodiment, the variation in the depth of the irradiation marks RM, i.e., the scanning lines Ls, that constitute the peeling layer 25 can be suppressed as much as possible. This effectively suppresses the size of the steps and unevenness on the peeling surface 32 that occurs due to peeling in the peeling layer 25, reduces the amount of grinding and polishing required on the peeling surface 32, and effectively suppresses the occurrence of peeling defects. In addition, the cycle time for forming the peeling layer 25 can be shortened. Therefore, according to this embodiment, it is possible to improve manufacturing efficiency compared to the conventional method.

Figure 6 shows the trajectory of the relative movement of the central position of the focusing device 42 in the in-plane direction with respect to the ingot 2. The "central position of the focusing device 42 in the in-plane direction" is typically, for example, the central position in the arrangement of multiple laser beams B. As shown in Figures 4A and 6, in this embodiment, the ingot 2 is oriented so that the facet region RF is positioned on the "low off-angle side" and the laser beam B is irradiated from the C-face side to perform the peeling layer formation process. The "low off-angle side" refers to the side with a low inclination of the C-face, i.e., the (0001) plane Pc, when the ingot 2 is oriented so that the ingot C-face 21, which is one main surface, is the upper surface. In contrast, the "high off-angle side" refers to the side with a high inclination of the C-face, i.e., the (0001) plane Pc, when the ingot 2 is oriented so that the ingot C-face 21 is the upper surface.

As described later, by applying a unidirectional load to peel the wafer precursor 26 from the ingot 2 at one end of the "high off-angle side" of the ingot 2, extremely good wafer peeling is achieved. Here, an assumed example is considered in which the ingot 2 is oriented so that the facet region RF is located at the "high off-angle side", the laser beam B is irradiated from the Si-face side, and then a unidirectional load is applied at one end of the ingot 2 at the "high off-angle side". In this regard, the end of the ingot 2 close to the facet region RF is difficult to crack in the first place. Therefore, in this assumed example, the peeling start position is the end close to the facet region RF where cracks are difficult to occur, so that the success rate of the wafer peeling process may be low. In contrast, in this embodiment, the ingot 2 is oriented so that the facet region RF is located at the "low off-angle side", the laser beam B is irradiated from the C-face side, and then a unidirectional load is applied at one end of the ingot 2 at the "high off-angle side". In this case, the peeling start position is a part far from the facet region RF, where cracks are relatively likely to occur. Therefore, according to this embodiment, the success rate of the wafer peeling process is improved.

It is known that the intensity of the laser beam B reaching the focal point BP is stronger in the non-facet region RN than in the facet region RF. Therefore, in this embodiment, in the peeling layer formation process, the laser beam B is irradiated onto the main surface of the ingot 2 so that the energy application density due to the irradiation of the laser beam B is higher in the facet region RF than in the non-facet region RN. The "energy application density" referred to here is the energy application density in a plane along the main surface of the ingot 2. The following means may be used alone or in combination. Specifically, for example, the output of the laser beam B is made higher in the facet region RF than in the non-facet region RN. Alternatively, for example, the laser beam B is irradiated onto the main surface of the ingot 2 so that the frequency of irradiation of the laser beam B is higher in the facet region RF than in the non-facet region RN. More specifically, for example, the repetition frequency of the laser beam B is made higher in the facet region RF than in the non-facet region RN, or the scanning speed is made lower with the repetition frequency constant, thereby narrowing the irradiation interval in the scanning direction Ds. When making the output higher in the facet region RF than in the non-facet region RN, the output in the facet region RF is preferably 1.5 times the output in the non-facet region RN. When making the irradiation interval in the scanning direction Ds or the line feed direction Df in the facet region RF narrower than in the non-facet region RN, the irradiation interval in the facet region RF is preferably 2/5 of the irradiation interval in the non-facet region RN. Alternatively, for example, the facet region RF is irradiated with the laser beam B separately from the irradiation of the entire region including the facet region RF and the non-facet region RN. Note that when irradiating the facet region RF with the laser beam B, the laser beam B may also be irradiated to the region in the non-facet region RN adjacent to the facet region RF.

The peeling layer formation process according to this embodiment makes it possible to form the peeling layer 25 well in the entire region including the facet region RF and the non-facet region RN. In particular, the formation of the peeling layer 25 in the facet region RF can be performed in the same manner as in the non-facet region RN without adjusting the distance in the Z-axis direction between the focusing device 42 on the irradiation side of the laser beam B and the chuck table 41 supporting the ingot 2. Therefore, according to this embodiment, it is possible to improve manufacturing efficiency compared to the conventional method.

Referring to Figures 4A and 6, in the peeling layer formation process, there is an outward scan Sc1 in which the irradiation position PR when irradiating the laser beam B moves on the main surface of the ingot 2 in the same direction as the off-angle direction Dθ, and a return scan Sc2 in which the irradiation position PR when irradiating the laser beam B moves on the main surface of the ingot 2 in the opposite direction to the off-angle direction Dθ. That is, in the outward scan Sc1, the scanning direction Ds is the same direction as the off-angle direction Dθ. In contrast, in the return scan Sc2, the scanning direction Ds is the opposite direction to the off-angle direction Dθ. The outward scan Sc1 and the return scan Sc2 are performed alternately.

Between the end of one forward scan Sc1 and the start of the next forward scan Sc1, the relative position of the focusing device 42 to the ingot 2 moves a predetermined amount in the line feed direction Df. However, between the end of one forward scan Sc1 and the start of the return scan Sc2 performed immediately thereafter, the relative position of the focusing device 42 in the line feed direction Df may or may not move. The same applies to the period between the end of one return scan Sc2 and the start of the subsequent forward scan Sc1. The amount of relative movement in the line feed direction Df at each stage can be set appropriately depending on the irradiation conditions of the laser beam B, etc.

In the forward scan Sc1, the laser beam B is irradiated over the entire width of the ingot 2 in the scanning direction Ds. That is, in the forward scan Sc1, the laser beam B is irradiated onto the main surface of the ingot 2 while moving the irradiation position PR on the main surface of the ingot 2 in the scanning direction Ds, which is the same direction as the off-angle direction Dθ. This forms a scan line Ls between both ends of the ingot 2 in the scanning direction Ds. In contrast, in the return scan Sc2, the laser beam B may be irradiated over the entire width of the ingot 2 in the scanning direction Ds, or may not be irradiated over the entire width of the ingot 2 in the scanning direction Ds. Alternatively, in the return scan Sc2, the laser beam B may be irradiated over a portion of the ingot 2 in the scanning direction Ds rather than the entire width of the ingot 2.

Specifically, for example, in the return scan Sc2, the laser beam B may be irradiated only to the facet region RF and its periphery. This allows the peeling layer 25 to be formed well over the entire region including the facet region RF and the non-facet region RN. Alternatively, for example, in the return scan Sc2, the laser beam B may be irradiated only to the end of the ingot 2 in the scanning direction Ds. In this case, in the return scan Sc2, the irradiation position PR moves in the scanning direction Ds, which is the opposite direction to the off-angle direction Dθ, on the main surface of the ingot 2, and a scan line Ls is formed at the end of the ingot 2 in the scanning direction Ds. This promotes the start of peeling in the wafer peeling process and improves the success rate of the wafer peeling process. In addition, in the return scan Sc2, the laser beam B may be irradiated only to the facet region RF and its periphery, and the end of the ingot 2 in the scanning direction Ds.

As shown in FIG. 7, in this embodiment, the laser beam B has an intensity distribution in which the intensity is higher at the outer peripheral portion than at the center in the beam diameter direction, which is the direction extending radially from the axial center. Specifically, the laser beam B has a ring-shaped, i.e. hollow, beam shape in front of the focusing point BP, while it is focused in a point shape at the focusing point BP. At the focusing point BP, the laser beam B has a focusing diameter dc, which is the minimum beam diameter. The intersection range RX shown in FIG. 7 is a predetermined range centered on the focusing point BP in the beam axis direction, where the peripheral portions of the laser beam B with high intensity overlap each other.

In this way, the peeling layer forming device 40 irradiates the ingot 2 with the annular laser beam B. Such annular laser beam B and devices that generate such laser beam B and irradiate the workpiece with such laser beam B were already publicly known or well-known at the time of filing of this application (see, for example, JP 2006-130691 A, JP 2014-147946 A, etc.). For this reason, detailed descriptions of the device and method for generating such laser beam B will be omitted in this specification.

Figure 8A shows how an irradiation affected area RA including an irradiation mark RM is formed by an annular laser beam B according to this embodiment. Figure 8B shows how an irradiation affected area RA including an irradiation mark RM is formed by a non-annular, i.e., solid, laser beam B as another example different from this embodiment.

8B, when a solid laser beam B is used, the irradiation mark RM, which is a modified region formed by the separation of SiC into Si and C by the irradiation of the laser beam B, may occur at a depth different from the focal point BP. Therefore, the depth of the irradiation affected region RA consisting of the irradiation mark RM and the crack C that develops from the irradiation mark RM may also be different from the focal point BP. Specifically, for example, at a position shallower than the focal point BP, the applied density of energy by the irradiation of the laser beam B may increase to a level that can generate the irradiation mark RM. Then, the irradiation mark RM may occur at a position shallower than the focal point BP. The depth at which the irradiation mark RM occurs may vary due to variations in the irradiation energy of the laser beam B, variations in the refractive index of the ingot 2, variations in the optical system in the focusing device 42, etc. The region where the irradiation mark RM may occur is shown in the figure as a modifiable range RC. The irradiation mark RM corresponds to the "modified layer" in Patent Document 1.

In contrast, as shown in FIG. 8A, when an annular laser beam B is used, the energy application density due to the irradiation of the laser beam B increases to a level at which the irradiation mark RM can be generated, limited to a depth near the focal point BP. That is, for example, as in the case of using a solid laser beam B, it is difficult for the energy application density due to the irradiation of the laser beam B to increase to a level at a position shallower than the focal point BP to a level at which the irradiation mark RM can be generated. Therefore, the irradiation mark RM is generated stably at a depth near the focal point BP. That is, unlike the case of using a solid laser beam B, the modifiable range RC is limited to a narrow depth range centered on the depth of the focal point BP. Therefore, the variation in the depth at which the irradiation mark RM is generated can be effectively suppressed. In other words, it is possible to form the peeling layer 25 as thin as possible, and the processing cost in grinding and polishing after peeling can be effectively reduced. Therefore, according to this embodiment, it is possible to improve manufacturing efficiency compared to the conventional art.

By the way, in the method described in Patent Document 1, the laser scanning direction is perpendicular to the "direction in which the off-angle θ is formed (i.e., the off-angle direction Dθ in FIG. 1, FIG. 3A, etc.)". For this reason, cleavage is unstable and material loss increases. In contrast, in this embodiment, as shown in FIG. 4A, the scanning direction Ds, which is the moving direction of the focal point BP of the laser beam B inside the ingot 2, is parallel to the off-angle direction Dθ. That is, in the peeling layer formation process, the irradiation position PR is moved in the scanning direction Ds along the off-angle direction Dθ by laser scanning. In other words, the peeling layer formation device 40 moves the focusing device 42 relative to the ingot 2 in the scanning direction Ds parallel to the off-angle direction Dθ to scan the laser beam B, thereby forming the scanning line Ls along the off-angle direction Dθ. Then, as shown in FIG. 9 and FIG. 10, the irradiation mark RM and the crack C are formed along the (0001) plane Pc. This makes it possible to stabilize the cleavage in the peeling layer 25 during the wafer peeling process, effectively reducing material loss. In addition, the processing cost during the wafer flattening process is effectively reduced, thereby making it possible to shorten the process time as much as possible. Therefore, according to this embodiment, it is possible to provide a wafer manufacturing method with higher manufacturing efficiency than conventional methods.

Figure 9 shows an example in which the scanning direction Ds is the same direction as the off-angle direction Dθ. Figure 10 shows an example in which the scanning direction Ds is opposite to the off-angle direction Dθ. That is, in the example shown in Figure 9, when the orientation of the ingot 2 is set so that the ingot C-face 21 is the upper surface as shown in Figure 4A, the irradiation position PR is moved by laser scanning from the higher side to the lower side of the (0001) plane Pc. In contrast, in the example shown in Figure 10, when the orientation of the ingot 2 is set so that the ingot C-face 21 is the upper surface, the irradiation position PR is moved by laser scanning from the lower side to the higher side of the (0001) plane Pc.

For example, assume a situation where there is no irradiation affected area RA, i.e., no irradiation marks RM or cracks C, around the irradiation position PR in the in-plane direction. In such a situation, irradiation with the laser beam B tends to cause the irradiation marks RM to occur at a depth near the focal point BP. However, in reality, the laser beam B moves in the scanning direction Ds while generating irradiation marks RM and cracks C one after another. For this reason, the above situation mainly occurs when the irradiation mark RM corresponding to the start point of the scanning line Ls, which is formed first in one laser scan, is formed. Therefore, in most situations during laser scanning, a situation occurs where the irradiation affected area RA exists around the irradiation position PR in the in-plane direction.

That is, as shown in Figures 9 and 10, the current irradiation position PR usually has an irradiation-affected area RA formed previously (e.g., immediately before). Then, the absorption rate of the laser beam B is increased in the irradiation-affected area RA. In addition, the irradiation-affected area RA is formed along the (0001) plane Pc. Therefore, the irradiation mark RM tends to progress along the (0001) plane Pc by laser scanning.

In the example shown in FIG. 9, the irradiation mark RM is formed at a gradually deeper position as it progresses in the scanning direction Ds along the (0001) plane Pc by laser scanning, and gradually moves away from the focal point BP. Then, at approximately the same depth as the irradiation mark RM formed immediately before, the applied energy density of the laser beam B irradiated this time may not be increased to a level that can generate a new irradiation mark RM. In this case, the irradiation mark RM cannot progress any further along the (0001) plane Pc. Then, as shown in FIG. 9, the newly formed irradiation mark RM is formed at a depth near the focal point BP of the laser beam B irradiated this time. In other words, a step occurs between the irradiation mark RM formed immediately before and the irradiation mark RM formed this time.

On the other hand, in the example shown in FIG. 10, the irradiation mark RM is formed at a gradually shallower position as it progresses in the scanning direction Ds along the (0001) plane Pc by laser scanning, and gradually moves away from the focal point BP. Then, at approximately the same depth as the irradiation mark RM formed immediately before, if the applied density of energy by the laser beam B irradiated this time cannot be increased to a level that can generate a new irradiation mark RM, the irradiation mark RM cannot progress any further along the (0001) plane Pc. Then, as shown in FIG. 10, the newly formed irradiation mark RM is formed at a depth near the focal point BP of the laser beam B irradiated this time. However, in the example shown in FIG. 10, unlike the example shown in FIG. 9, the direction of progression of the irradiation mark RM is closer to the light source side of the laser beam B, that is, the laser irradiation surface side of the ingot 2. Therefore, in the example shown in FIG. 10, the irradiation mark RM is more likely to progress longer than in the example shown in FIG. 9. Therefore, in the example shown in FIG. 10, the step between the previously formed irradiation mark RM and the currently formed irradiation mark RM is larger than in the example shown in FIG. 9.

In this way, by moving the irradiation position PR in the laser scan from the high side to the low side on the C surface with the scanning direction Ds being the same as the off-angle direction Dθ, the step between the irradiation mark RM formed immediately before and the irradiation mark RM formed this time can be reduced. This makes it possible to form the peeling layer 25 as thin as possible, thereby effectively reducing the processing cost in grinding and polishing after peeling. Therefore, according to this aspect, it is possible to further improve manufacturing efficiency compared to the conventional case.

(Wafer peeling process)
11 shows an outline of a wafer peeling process and a peeling apparatus 50 used in the process. Note that the right-handed XYZ coordinate system shown in FIG. 11 is displayed so as to match the right-handed XYZ coordinate system shown in FIG.

The peeling device 50 is configured to peel the wafer precursor 26 from the ingot 2 at the peeling layer 25 by applying a load in one direction at the first end 23, which is one end of the ingot 2 in the in-plane direction parallel to the ingot C-face 21, i.e., the off-angle direction Dθ. The first end 23 is the end on the "higher off-angle side", that is, the higher end of the C-face, i.e., the (0001) plane Pc, when the attitude of the ingot 2 is set so that the ingot C-face 21 is the upper surface. In this embodiment, the peeling device 50 is configured to apply a static and/or dynamic load in the Z-axis direction in the figure to the ingot 2 at the first end 23 in such a manner as to separate the ingot C-face 21 from the ingot Si-face 22. Specifically, in this embodiment, the peeling device 50 includes a support table 51, a peeling pad 52, and a driving member 53.

The support table 51 is provided to support the ingot 2 from below. Specifically, the support table 51 has a number of suction holes (not shown) that open on its upper surface, the support suction surface 51a, and is configured to suction the ingot Si surface 22 to the support suction surface 51a by air pressure. The support table 51 has a first table end 51b and a second table end 51c, which are both ends in the off-angle direction Dθ. The second table end 51c, which is the end on one side (i.e., the left side in the figure) in the off-angle direction Dθ, has a table base end surface 51d. The table base end surface 51d is formed in an inclined surface that rises toward the off-angle direction Dθ. That is, the support table 51 is formed in a trapezoid shape in which the lower base is longer than the upper base when viewed from the side, as shown in FIG. 11.

The stripping pad 52 is provided above the support table 51 so as to be able to approach and move away from the support table 51 along the Z axis in the figure. That is, the stripping device 50 is configured so that the support table 51 and the stripping pad 52 can move relatively in the height direction of the ingot 2. The stripping pad 52 has a number of suction holes (not shown) that open on its bottom surface, the pad suction surface 52a, and is configured to adsorb the ingot C surface 21 to the pad suction surface 52a by air pressure. The stripping pad 52 has a first pad end 52b and a second pad end 52c, which are both ends in the off-angle direction Dθ. The second pad end 52c, which is the end on one side (i.e., the left side in the figure) in the off-angle direction Dθ, has a pad end surface 52d. The pad end surface 52d is formed in an inclined surface shape that descends toward the off-angle direction Dθ. That is, the stripping pad 52 is formed in a trapezoid shape in which the lower base is shorter than the upper base when viewed from the side, as shown in FIG. The pad end surface 52d is provided at a position corresponding to (i.e. directly above) the table base end surface 51d. The state in which the ingot C-face 21 is fixed to the peeling pad 52 by suction and the ingot Si-face 22 is fixed to the support table 51 by suction, and the ingot 2 is sandwiched between the support table 51 and the peeling pad 52, is hereinafter referred to as the "clamped state."

The driving member 53 is arranged to apply an external force to at least one of the support table 51 and the stripping pad 52 in a clamped state to move the support table 51 and the stripping pad 52 relative to each other along the height direction of the ingot 2. Specifically, the driving member 53 has a first driving end surface 53a and a second driving end surface 53b. The first driving end surface 53a is formed in an inclined surface shape that descends toward the off-angle direction Dθ. More specifically, the first driving end surface 53a is arranged parallel to the pad end surface 52d. The second driving end surface 53b is formed in an inclined surface shape that ascends toward the off-angle direction Dθ. More specifically, the second driving end surface 53b is arranged parallel to the table base end surface 51d. In addition, the driving member 53 is arranged so that, in a clamped state, the first driving end surface 53a abuts against the pad end surface 52d and the second driving end surface 53b abuts against the table base end surface 51d. That is, as shown in Fig. 11, the driving member 53 is formed in a shape obtained by rotating a trapezoid, in which the lower base is longer than the upper base, 90 degrees clockwise in a side view. The driving member 53 is configured to be driven by a driving means (not shown) upward along the height direction of the ingot 2 and/or in an off-angle direction Dθ, which is a direction approaching the ingot 2. That is, the driving member 53 is configured to apply a moment to the ingot 2 with the second pad end 52c as the force point FP and the first end 23 as the fulcrum PP and the action point WP by being driven upward and/or in the off-angle direction Dθ.

The wafer peeling process for peeling the wafer precursor 26 from the ingot 2 includes a table fixing process, a clamping process, and a peeling force application process. The table fixing process is a process of fixing the ingot 2 to the support table 51 by adsorbing the ingot Si surface 22 to the support adsorption surface 51a. The clamping process is a process of forming a clamped state by adsorbing the ingot C surface 21 to the pad adsorption surface 52a and fixing the ingot 2 to the peeling pad 52. The peeling force application process is a process of applying a static or dynamic load with the second pad end 52c, which is the end of the peeling pad 52 on one side in the off-angle direction Dθ, as the force point FP so that a moment with the first end 23 as the fulcrum PP acts on the ingot 2 in the clamped state. Specifically, the peeling force application process is a process of pressing the second pad end 52c upward along the height direction of the ingot 2 by driving the driving member 53 upward and/or in the off-angle direction Dθ in the clamped state. This allows the wafer precursor 26, which is part of the ingot 2, to be peeled off from the ingot 2 using the peeling layer 25 as the interface.

Thus, in this embodiment, the wafer peeling process is performed by applying a load in one direction to the first end 23, which is one end of the ingot 2 in an in-plane direction parallel to the top surface of the ingot 2 (i.e., the ingot C-face 21 in the example of FIG. 11). Then, a moment acts on the ingot 2 with the first end 23 as the fulcrum PP and the point of application WP.

In this regard, in the wafer peeling process described in Japanese Patent No. 6678522, the application point WP and the fulcrum PP were set inside the ingot 2, that is, inside the outer edge of the peeling layer 25 in the in-plane direction. In this comparative example, a much larger load than in this embodiment was required to generate good peeling with the peeling layer 25 as the interface. In addition, since the load was applied to a wide area of the peeling layer 25, the position of the peeling crack was not determined, and partial unpeeled parts and damage to the removed wafer 1 sometimes occurred. Furthermore, there was a problem that the peeled cross section became rough, and the processing cost for grinding and polishing became large. Therefore, in the comparative example, there was room for improvement in terms of reducing the load, yield, etc.

In contrast, in the wafer peeling process according to the present embodiment, in order to peel the wafer precursor 26 from the ingot 2 at the peeling layer 25, a load is applied in one direction at one end of the ingot 2 in the off-angle direction Dθ. That is, the load is concentrated at one end of the peeling layer 25 in the off-angle direction Dθ. Then, a moment with the one end as the fulcrum PP and the point of application WP acts on the ingot 2. As a result, peeling proceeds from a crack formed at the end of the one end side of the ingot 2 in the off-angle direction Dθ, so that the fracture can proceed stably over the entire surface of the peeling layer 25 while reducing the applied load. In addition, by stably setting the fracture occurrence location, it is possible to reduce the surface roughness of the peeled surface 32 in the peeled body 30 and the ingot C-face 21 generated after peeling. In particular, by setting the first end 23, which is the starting point of fracture occurrence, at one end of the "higher off-angle side" in the off-angle direction Dθ, fracture occurs smoothly and cleavage becomes more stable. This effectively reduces the rate of defects in the wafer peeling process and the processing cost required for grinding and polishing the ingot 2 and the peeled body 30 after the wafer peeling process. Therefore, this embodiment makes it possible to provide a wafer manufacturing method with higher manufacturing efficiency than conventional methods.

(Modification)
The present invention is not limited to the above embodiment. Therefore, the above embodiment can be modified as appropriate. Representative modified examples will be described below. In the following description of the modified examples, differences from the above embodiment will be mainly described. In addition, the same reference numerals are used for parts that are the same or equivalent to each other in the above embodiment and the modified examples. Therefore, in the following description of the modified examples, the description of the above embodiment can be appropriately used for components that have the same reference numerals as the above embodiment, unless there is a technical contradiction or special additional explanation.

The present invention is not limited to the specific configuration shown in the above embodiment. That is, for example, there is no particular limitation on the outer diameter or planar shape (for example, the presence or absence of a so-called orientation flat, etc.) of the wafer 1, i.e., the ingot 2. There is also no particular limitation on the magnitude of the off-angle θ. In addition, in the above embodiment, the wafer C-face 11 and the ingot C-face 21 do not coincide with the C-face in the strict crystallographic sense, i.e., the (0001) face Pc. However, even in such a case, the term "C-face" is accepted in the social sense, so the expression "C-face" is used. However, the present invention is not limited to such an embodiment. That is, the wafer C-face 11 and the ingot C-face 21 may coincide with the C-face in the strict crystallographic sense, i.e., the (0001) face Pc. In other words, the off-angle θ may be 0 degrees.

The irradiation conditions and scanning conditions of the laser beam B are not limited to the specific examples shown in the above embodiment. That is, for example, the arrangement of the multiple laser beams B irradiated in one laser scan can be appropriately changed from the specific embodiment shown in FIG. 5A. Specifically, for example, as shown in FIG. 12, the first beam B1, the second beam B2, and the third beam B3 arranged at different positions in the line feed direction Df (i.e., the second direction) may be arranged in a V-shape on the laser irradiation surface. More specifically, the first beam B1, the second beam B2, and the third beam B3 are arranged in this order along the line feed direction Df. And the second beam B2 is provided at a position protruding in the scanning direction Ds more than the first beam B1 and the third beam B3. In other words, as shown in FIG. 13, the multiple laser beams B can be arranged in a W-shape or a staggered shape. According to such an arrangement of the multiple laser beams B, it is possible to suppress interference between the cleavage and the modified layer by forming the next modified layer at an interval wider than the length of the cleavage generated by the previously processed modified layer. Also, for example, in the return scan Sc2, when the laser beam B is irradiated to the entire width of the ingot 2 in the scanning direction Ds as in the forward scan Sc1, the irradiation conditions for both scans may be different. Specifically, for example, the distance (i.e., irradiation distance) from the laser irradiation surface of the focusing device 42, i.e., the ingot C surface 21, may be changed between the forward scan Sc1 and the return scan Sc2.

Depending on the irradiation conditions and scanning conditions of the laser beam B, the peeled surface 32 may have a surface condition that allows it to be well ground or polished even if it is directly subjected to the ECMG process. For this reason, the rough grinding process of the peeled surface 32 shown in FIG. 2 may be omitted. The same applies to the rough grinding of the top surface of the ingot 2 after the wafer peeling process.

The peeling layer forming apparatus 40 shown in FIG. 4A and FIG. 4B is a simplified schematic diagram for simply explaining the outline of the peeling layer forming process according to the present invention. Therefore, the specific configuration of the peeling layer forming apparatus 40 that is actually realized in industry does not necessarily match the exemplary configuration shown in FIG. 4A and FIG. 4B. Specifically, for example, the chuck table 41 may be configured to hold the ingot 2 by a method other than a suction mechanism using air pressure. In addition, the chuck table 41 may be configured to be movable relative to the focusing device 42 at least in the in-plane direction, i.e., the XY direction in the figure. Alternatively, the peeling layer forming apparatus 40 may include a scanning device configured to be able to move the focusing point BP of the laser beam B relative to the ingot 2 in the XYZ directions in the figure. Alternatively, in the above embodiment, the peeling layer forming apparatus 40 is configured such that the chuck table 41 supporting the ingot 2 is movable at least in the in-plane direction, while the focusing device 42 is fixed in the in-plane direction. However, the present invention is not limited to such an embodiment. That is, for example, the peeling layer forming apparatus 40 may be configured such that the chuck table 41 supporting the ingot 2 is fixed in the in-plane direction, while the focusing device 42 is moved in the in-plane direction by a scanning device (not shown). In addition, in accordance with whether the facet region RF or the non-facet region RN is present, or regardless of this, adjusting the distance in the Z-axis direction between the focusing device 42 on the irradiation side of the laser beam B and the chuck table 41 supporting the ingot 2 is an optional item in the present invention. In addition, the specific configuration of the peeling layer forming apparatus 40 that is actually realized in industry may be appropriately changed from the exemplary configuration shown in FIG. 4A or FIG. 4B.

In the above embodiment, the peeling layer 25 is formed on the ingot C-face 21 side by "C-face side irradiation" in which the laser beam B is irradiated onto the ingot C-face 21. However, the present invention is not limited to this aspect. In other words, the present invention is also applicable to "Si-face side irradiation" in which the laser beam B is irradiated onto the ingot Si-face 22 to form the peeling layer 25 on the ingot Si-face 22 side.

The peeling device 50 shown in FIG. 11 is a simplified schematic diagram for easily explaining the outline of the wafer peeling process according to the present invention. Therefore, the specific configuration of the peeling device 50 that is actually realized in industry does not necessarily match the exemplary configuration shown in FIG. 11. Specifically, for example, the support table 51 may be configured to adsorb the ingot Si surface 22 to the support adsorption surface 51a using a method other than an air pressure adsorption mechanism (e.g., wax, adhesive, etc.).

The optical properties, i.e., the transmittance and the refractive index, of the obtained wafer 1 or peeled body 30 may be measured at multiple positions in the scanning direction Ds and the line feed direction Df, and the irradiation conditions of the next laser beam B may be controlled based on the measurement results. FIG. 14 shows an outline of such an embodiment. In the figure, "input/discharge" indicates the process of inputting and discharging the peeled body 30 or the ingot 2, which is the workpiece. "Laser slice" indicates the peeling layer formation process. "Peeling" indicates the wafer peeling process. "Rough grinding" indicates the process of roughly grinding the main surface of the ingot 2 or the peeled body 30. For rough grinding, for example, an abrasive with a grit size of about #800 can be used. "Finish grinding" indicates the process of finish grinding the surface. For finish grinding, for example, an abrasive with a grit size of about #30000 can be used. "Wafer optical measurement" refers to a process of measuring the optical characteristics (i.e., transmittance and refractive index) of the peeled body 30 that has undergone finish grinding at multiple positions in the scanning direction Ds and the line feed direction Df. "Ingot cleaning" refers to a process of cleaning the ingot 2 after finish grinding. The arrows on the left side of the blocks showing each process indicate the processing flow of the ingot 2, and the arrows on the right side indicate the processing flow of the wafer 1, or the peeled body 30 that can be commonly referred to as a "wafer."

Referring to FIG. 14, first, the ingot 2 is loaded into a wafer manufacturing apparatus including a peeling layer forming device 40. Next, the loaded ingot 2 is subjected to a peeling layer forming process by irradiating it with a laser beam B. Then, in a wafer peeling process, a peeling body 30 is peeled off from the ingot 2 that has undergone the peeling layer forming process. The top surface of the ingot 2 newly generated in the ingot 2 that has undergone the wafer peeling process is flattened by rough grinding and finish grinding. After that, the ingot 2 is cleaned and then subjected to the peeling layer forming process again. Note that the ingot 2 that has undergone the peeling layer forming process or the ingot cleaning process is discharged from the wafer manufacturing apparatus if its height falls below a predetermined value.

The peeled body 30 peeled off from the ingot 2 by the wafer peeling process is subjected to optical measurement, i.e., measurement of transmittance and refractive index, after rough grinding and finish grinding. The measurement results are used to determine the irradiation conditions (e.g., irradiation energy and/or irradiation distance) of the laser beam B in the next peeling layer formation process. That is, based on the measurement results of the transmittance and refractive index for each location in the in-plane direction of the wafer 1, the irradiation conditions for each location in the in-plane direction of the ingot C surface 21 in the next peeling layer formation process are controlled. This makes it possible to change the irradiation conditions finely in response to the variation in optical characteristics for each location in the in-plane direction, thereby reducing material loss. This is particularly effective when the ingot 2 has a facet region RF. Note that only one of the transmittance and refractive index may be measured. Alternatively, the transmittance and refractive index may be measured on the finally obtained epi-ready wafer 1. Depending on the rough grinding conditions (e.g., in the case of ECMG), finish grinding may not be necessary. That is, rough grinding and finish grinding can be integrated.

FIG. 15 shows an example of the setting of the optical measurement positions in the generator 100. The generator 100 is an object of optical measurement, and corresponds to the wafer 1 or the peeled body 30 whose surface has been flattened to a predetermined degree after being peeled off from the ingot 2. In this example, the optical measurement positions are set at a constant pitch (e.g., 3 mm) in each of the X-axis direction (i.e., the first direction) and the Y-axis direction (i.e., the second direction). The X-axis direction is parallel to the scanning direction Ds shown in FIG. 6 and the like. The Y-axis direction is parallel to the line feed direction Df shown in FIG. 6 and the like. Here, FIG. 17 shows the change in the absorption coefficient of the laser beam B with the change in the measurement position when optical measurement is performed at a plurality of measurement positions on the measurement line Lx as shown in FIG. 16. The measurement line Lx is a virtual straight line that passes through the center in the in-plane direction of the generator 100 and the facet region RF and is parallel to the X-axis. The absorption coefficient is obtained, that is, calculated, by the following formula (1). In the following formula (1), α represents the absorption coefficient, D represents the work thickness, i.e., the thickness of the product 100, and T represents the transmittance.

In FIG. 17, the horizontal axis indicates the measurement position when the center of the generator 100 in the in-plane direction is the origin, i.e., "0". As shown in FIG. 17, the absorption coefficient is not constant in the in-plane direction, but changes with the change in the measurement position. Specifically, the region with a high absorption coefficient on the right end side in FIG. 17 corresponds to the facet region RF. Also, the non-facet region RN, which has a lower absorption coefficient than the facet region RF, has a distribution in the in-plane direction, i.e., the radial direction. The "radial direction" is the direction extending radially from the center in the in-plane direction of the generator 100. Specifically, in the example of FIG. 17, there is a region with a low absorption coefficient to the left of the center position, i.e., on the outside.

Figures 18A to 18C show how the position where the modified layer occurs changes with changes in transmittance, i.e., absorption coefficient. The position where the modified layer occurs is the position where the modified layer, i.e., the irradiation affected area RA, occurs due to the focusing of the laser beam B, and can be indicated by the dimension in the depth direction of the ingot 2 from the ingot C surface 21, which is the laser irradiation surface. Here, the depth direction of the ingot 2 is a direction parallel to the height direction of the ingot 2, and more specifically, is the direction opposite to the height direction of the ingot 2 (i.e., the negative direction of the Z axis in Figure 1, etc.). In the figures, the circle shown by the dashed line next to the irradiation affected area RA indicates the focusing state of the laser beam B at the modified layer occurrence position, i.e., the beam diameter.

First, referring to FIG. 18A, the laser beam B is focused while being attenuated according to the absorption coefficient as it advances in the ingot 2 in the depth direction. Then, when the energy density increases to a certain level due to focusing, it reaches the processing threshold and a modified layer, i.e., the irradiation affected area RA, is formed. Here, when the transmittance is low (i.e., the absorption coefficient is high), the amount of attenuation is large, so as shown in FIG. 18B, the energy density corresponding to the processing threshold is reached at a deep position where the focusing cross-sectional area is smaller, and modification occurs. On the other hand, when the transmittance is high (i.e., the absorption coefficient is low), the amount of attenuation is small, so as shown in FIG. 18C, even at a shallow position where the focusing cross-sectional area is larger, the energy density corresponding to the processing threshold is reached and modification occurs. In this way, if the position where the modified layer occurs varies due to differences in transmittance, i.e., the absorption coefficient, the surface of the product 100 after peeling becomes rough, and the processing cost of grinding and polishing, i.e., the material loss, increases.

Therefore, in this modified example, the transmittance is measured at multiple positions in the in-plane direction, and the irradiation conditions of the laser beam B at each of the multiple positions are controlled based on the measurement results. Specifically, in this modified example, the absorption coefficient is obtained, i.e., calculated, based on the transmittance measured for the generated body 100 generated in the past, including the previous time. Then, this modified example determines the irradiation energy of the laser beam B based on the change tendency of the absorption coefficient in the depth direction of the ingot 2 for each different position in the plane.

A specific example of controlling the next irradiation conditions of the laser beam B from the optical measurement results of the product 100 obtained last time will be described below. First, the transmittance of the product 100 obtained last time is measured using a transmittance meter. At this time, the thickness of the workpiece is also measured. The absorption coefficient is calculated based on the measured transmittance, the workpiece thickness, and the above formula (1). Then, the input energy, which is the irradiation energy of the laser beam B, is derived using the following formula (2). In the following formula (2) and FIG. 19, I ₀ indicates the input energy, I indicates the energy required at the processing point, i.e., the minimum applied energy required for modification, and z indicates the depth. k indicates the amount of change in the absorption coefficient in the depth direction, that is, the change tendency of the absorption coefficient in the depth direction of the ingot 2.

The method of deriving the amount of change in the absorption coefficient will be described below. As shown in FIG. 20, the center of the ingot 2 in the in-plane direction is the in-plane center position Ma. The end position of the ingot 2 located in the facet region RF, which is a position on the measurement line Lx parallel to the X-axis passing through the in-plane center position Ma, is the first end position Mb. The position on the measurement line Lx opposite to the first end position Mb is the second end position Mc. The second end position Mc is a position that is almost symmetrical to the first end position Mb with respect to the in-plane center position Ma. FIG. 21A shows the change in the absorption coefficient in the depth direction of the ingot 2 at the in-plane center position Ma. FIG. 21B shows the change in the absorption coefficient in the depth direction of the ingot 2 at the first end position Mb. FIG. 21C shows the change in the absorption coefficient in the depth direction of the ingot 2 at the second end position Mc. As shown in Figures 21A to 21C, the change in absorption coefficient in the depth direction of the ingot 2 has a certain tendency, and it is different for each in-plane position. Based on this tendency of change in absorption coefficient in the depth direction for each in-plane position, the amount of change in absorption coefficient is derived, and this value is added to or multiplied by the previously obtained absorption coefficient, and the value can be applied to the determination of the input energy for the next processing.

For example, as shown in Fig. 22, it is possible to acquire, i.e., calculate, the absorption coefficient estimated value α _n to be used in the current processing based on the amount of change between the previously acquired absorption coefficient α _{n-1 and} the absorption coefficient α n-2 acquired two times before. Specifically, for example, the difference between the previously acquired absorption coefficient α _n-1 and the absorption coefficient α _n-2 acquired two times before is taken as the amount of change in the absorption coefficient, and this is added to the previously acquired absorption coefficient α _n-1 to calculate the absorption coefficient estimated value α _n . Then, it is possible to determine the irradiation energy of the laser beam B based on this absorption coefficient estimated value α _n . Note that, when calculating the amount of change in the absorption coefficient, statistical processing using a so-called "smoothing filter" or the like may be performed.

Also, as shown in FIG. 23, a first product 101 and a second product 102 are generated. The first product 101 is a product 100 obtained from one end side in the height direction of the ingot 2, i.e., the ingot C-face 21 side. The second product 102 is a product 100 obtained from the other end side in the height direction of the ingot 2, i.e., the ingot Si-face 22 side. Next, a first absorption coefficient, which is the absorption coefficient in the first product 101, and a second absorption coefficient, which is the absorption coefficient in the second product 102, are obtained. Then, the higher value of the first absorption coefficient and the second absorption coefficient is set as the upper limit value of the absorption coefficient, and it is possible to determine the irradiation conditions of the laser beam B, i.e., the irradiation energy. In other words, a coefficient setting may be used that sets the absorption coefficient obtained from the product 100 with the higher absorption coefficient, i.e., the wafer, as the upper limit value and does not change any further.

The measurement pitch of the optical measurement may be measured at an equal pitch as shown in FIG. 15, but may be changed as appropriate. That is, for example, the pitch may be different in the X-axis direction and the Y-axis direction. Alternatively, the measurement pitch may be made finer in a region where the change in the absorption coefficient is larger than in other regions, such as the region surrounded by the dashed line rectangle in FIG. 24. Specifically, such a region is, for example, the boundary region between the non-facet region RN and the facet region RF. That is, the measurement pitch may be made finer in such a boundary region than in other regions. The region in which the measurement pitch is made finer may include the entire facet region RF. More specifically, for example, referring to FIG. 24, the measurement pitch may be made finer in a region to the right of the measurement position of 40 mm than in a region to the left of the measurement position of 40 mm. In other words, the measurement pitch may be made finer in a predetermined region formed by the non-facet region RN and the boundary region between the non-facet region RN and the facet region RF than in the region outside such a predetermined region.

The above-mentioned effects were confirmed by an experiment. The laser beam B used in the experiment was a pulsed laser with a wavelength of 1064 nm, a pulse width of 7 ns, and an oscillation frequency of 25 kHz. The laser beam B was a ring-shaped beam with an outer diameter of 4.85 mm and an inner diameter of 2.82 mm. The laser beam B was made to enter a lens with a numerical aperture of 0.65, and processing was performed with an irradiation pitch (i.e., irradiation interval in the scanning direction Ds) of 8 μm and a scanning interval (i.e., interval between scanning lines Ls in the line feed direction Df) of 120 μm. The ingot 2 to be processed had an outer diameter of 6 inches and an in-plane absorption coefficient difference of 2.49 mm ⁻¹ . The transmittance was measured at a pitch of 3 mm for the wafer 1 with a thickness of 0.385 mm that had been previously cut. The input energy was set to an output setting such that 20 μJ of energy was input at a depth of 0.4 mm in the center of the ingot 2. When processing was performed under constant power, the height difference of the modified layer generation position within the surface was 61 μm. However, by performing power correction according to the change in the absorption coefficient within the surface, the height difference of the modified layer generation position was improved to 18 μm. This showed that material loss could be reduced.

Needless to say, the elements constituting the above embodiments are not necessarily essential, except when expressly stated as essential or when it is considered to be clearly essential in principle. Furthermore, when the numbers, amounts, ranges, etc. of components are mentioned, the present invention is not limited to those specific values, except when expressly stated as essential or when it is clearly limited to specific values in principle. Similarly, when the shapes, directions, positional relationships, etc. of components are mentioned, the present invention is not limited to those shapes, directions, positional relationships, etc., except when expressly stated as essential or when it is clearly limited to specific shapes, directions, positional relationships, etc., in principle.

The modified examples are also not limited to the above examples. That is, for example, other than those exemplified above, multiple embodiments may be combined with each other as long as there is no technical contradiction. Similarly, multiple modified examples may be combined with each other as long as there is no technical contradiction.

(Disclosure Perspective)
As is apparent from the above description of the embodiments and modifications, at least the following aspects are disclosed in this specification.
[Point 1]
A wafer manufacturing method for obtaining a wafer (1) from an ingot (2) comprises the steps of:
forming a peeling layer by irradiating a surface (21) of the ingot at one end in the height direction with a laser beam having transparency to form a peeling layer (25) from the surface to a depth corresponding to the thickness of the wafer;
a wafer delamination step of delaminating a wafer precursor (26) between the surface and the delamination layer from the ingot at the delamination layer;
a wafer planarization step for planarizing a main surface (32) of the plate-shaped peeled body (30) obtained by the wafer peeling;
Including,
The peeling layer is formed by irradiating the surface with the laser beam so that the facet region (RF) is irradiated more frequently than the non-facet region (RN).
Wafer manufacturing method.
[Point 2]
In Viewpoint 1,
The ingot is a single crystal SiC ingot having a c-axis (Lc) and a C-plane (Pc) perpendicular to each other,
The c-axis is provided in a state where a central axis (L) perpendicular to the surface is tilted in an off-angle direction (Dθ) by an off-angle (θ) exceeding 0 degrees,
The separation layer is formed in such a manner that, when the ingot is oriented so that the front surface faces up, the facet region is located on the lower side of the C-plane.
[Point 3]
In view point 2,
The wafer is peeled off by applying a load in one direction to one end (23) of the ingot in the off-angle direction.
[Point 4]
In view point 3,
The one end of the ingot in the off-angle direction is the higher end of the C-plane when the ingot is oriented so that the front surface faces up.
[Point 5]
In aspects 1 to 4,
The peeling layer is formed by performing laser scanning, in which the laser beam is irradiated onto the surface while moving an irradiation position (PR) of the laser beam on the surface along a first direction (Ds) along the surface, multiple times while changing the position in a second direction (Df) perpendicular to the first direction on the surface and along the surface, to form multiple scan lines (Ls), which are linear irradiation marks of the laser beam along the first direction, along the second direction, to form the peeling layer;
When the irradiation position is moved in the first direction, the scanning line is formed between both ends of the surface in the first direction;
When the irradiation position is moved in a direction opposite to the first direction, the irradiation mark is formed at an end of the surface in the first direction.
[Point 6]
In aspects 1 to 4,
The peeling layer is formed by performing laser scanning, in which the laser beam is irradiated onto the surface while moving an irradiation position (PR) of the laser beam on the surface along a first direction (Ds) along the surface, multiple times while changing the position in a second direction (Df) perpendicular to the first direction on the surface and along the surface, to form multiple scan lines (Ls), which are linear irradiation marks of the laser beam along the first direction, along the second direction, to form the peeling layer;
The distance from the surface of a focusing device (42) that irradiates the laser beam onto the surface is changed when the irradiation position is moved in the first direction and when the irradiation position is moved in the opposite direction to the first direction.
[Point 7]
In aspects 1 to 6,
The transmittance of the peeled body or the obtained wafer is measured at a plurality of positions in a first direction (Ds) along the surface and a second direction (Df) perpendicular to the first direction and along the surface;
Based on the measurement results of the transmittance, irradiation conditions of the laser beam at each of a plurality of positions in the first direction and the second direction are controlled.
[Point 8]
In aspect 7,
obtaining an absorption coefficient of the laser beam based on the transmittance;
The irradiation energy of the laser beam is determined based on the change tendency of the absorption coefficient in the depth direction of the ingot for each different position in a plane along the surface.
[Point 9]
In view 8,
acquiring an amount of change in the absorption coefficient in the depth direction based on a change trend of the absorption coefficient in the depth direction of the ingot;
The irradiation energy of the laser beam is determined based on a value obtained by adding or multiplying the previously acquired absorption coefficient by the amount of change in the absorption coefficient.
[Point 10]
In view of points 8 and 9,
The irradiation energy of the laser beam is determined based on an absorption coefficient estimate value obtained based on an amount of change between the absorption coefficient obtained previously and the absorption coefficient obtained two times previously.
[Point 11]
In points 8 to 10,
A first product (101) which is the peeled body or the wafer obtained from the ingot is produced at one end side in the height direction, and a second product (102) which is the peeled body or the wafer obtained from the ingot is produced at the other end side in the height direction;
obtaining a first absorption coefficient, which is the absorption coefficient in the first generation body, and a second absorption coefficient, which is the absorption coefficient in the second generation body;
The higher value of the first absorption coefficient and the second absorption coefficient is set as the upper limit value of the absorption coefficient, and the irradiation energy of the laser beam is determined.
[Point 12]
In aspects 7 to 11,
In a second region where the change in the absorption coefficient is larger than in the first region, the measurement pitch of the transmittance is made finer than that in the first region.
[Point 13]
In view 12,
The second region is a boundary region between the non-faceted region (RN) and the faceted region (RF).

1 Wafer 2 Ingot 21 Ingot C-face (front surface)
25 Release layer 26 Wafer precursor 30 Release body 32 Release surface (main surface)
L Central axis Lc c axis Pc (0001) plane

Claims (13)

A wafer manufacturing method for obtaining a wafer (1) from an ingot (2), comprising the steps of:
forming a peeling layer by irradiating a surface (21) of the ingot at one end in the height direction with a laser beam having transparency to form a peeling layer (25) from the surface to a depth corresponding to the thickness of the wafer;
a wafer delamination step of delaminating a wafer precursor (26) between the surface and the delamination layer from the ingot at the delamination layer;
a wafer planarization step for planarizing a main surface (32) of the plate-shaped peeled body (30) obtained by the wafer peeling;
Including,
The peeling layer is formed by irradiating the surface with the laser beam so that the facet region (RF) is irradiated more frequently than the non-facet region (RN).
Wafer manufacturing method. The ingot is a single crystal SiC ingot having a c-axis (Lc) and a C-plane (Pc) perpendicular to each other,
The c-axis is provided in a state where a central axis (L) perpendicular to the surface is tilted in an off-angle direction (Dθ) by an off-angle (θ) exceeding 0 degrees,
The separation layer is formed in such a manner that, when the orientation of the ingot is set so that the front surface faces up, the facet region is located on the lower side of the C-plane.
2. The wafer manufacturing method according to claim 1. The wafer is peeled off by applying a load in one direction at one end (23) of the ingot in the off-angle direction.
The wafer manufacturing method according to claim 2 . The one end of the ingot in the off-angle direction is a higher end of the C-plane when the ingot is oriented so that the front surface is the upper surface.
The wafer manufacturing method according to claim 3 . The peeling layer is formed by performing laser scanning, in which the laser beam is irradiated onto the surface while moving an irradiation position (PR) of the laser beam on the surface along a first direction (Ds) along the surface, multiple times while changing the position in a second direction (Df) perpendicular to the first direction on the surface and along the surface, to form multiple scan lines (Ls), which are linear irradiation marks of the laser beam along the first direction, along the second direction, to form the peeling layer;
When the irradiation position is moved in the first direction, the scanning line is formed between both ends of the surface in the first direction;
When the irradiation position is moved in a direction opposite to the first direction, the irradiation mark is formed at an end portion of the surface in the first direction.
2. The method of claim 1. The peeling layer is formed by performing laser scanning, in which the laser beam is irradiated onto the surface while moving an irradiation position (PR) of the laser beam on the surface along a first direction (Ds) along the surface, multiple times while changing the position in a second direction (Df) perpendicular to the first direction on the surface and along the surface, to form multiple scan lines (Ls), which are linear irradiation marks of the laser beam along the first direction, along the second direction, to form the peeling layer;
a distance from the surface of a focusing device (42) that irradiates the surface with the laser beam is changed between a case where the irradiation position is moved in the first direction and a case where the irradiation position is moved in a direction opposite to the first direction;
2. The method of claim 1. The transmittance of the peeled body or the obtained wafer is measured at a plurality of positions in a first direction (Ds) along the surface and a second direction (Df) perpendicular to the first direction and along the surface;
controlling irradiation conditions of the laser beam at each of the plurality of positions based on the measurement results of the transmittance;
2. The method of claim 1. obtaining an absorption coefficient of the laser beam based on the transmittance;
determining irradiation energy of the laser beam based on a change trend of the absorption coefficient in a depth direction of the ingot for each different position in a plane along the surface;
The wafer manufacturing method according to claim 7. acquiring an amount of change in the absorption coefficient in the depth direction based on a change trend of the absorption coefficient in the depth direction of the ingot;
determining the irradiation energy of the laser beam based on a value obtained by adding or multiplying the previously acquired absorption coefficient to the amount of change in the absorption coefficient;
The wafer manufacturing method according to claim 8. determining the irradiation energy of the laser beam based on an absorption coefficient estimate value obtained based on an amount of change between the absorption coefficient previously obtained and the absorption coefficient obtained before last;
The wafer manufacturing method according to claim 8. A first product (101) which is the peeled body or the wafer obtained from the ingot is produced at one end side in the height direction, and a second product (102) which is the peeled body or the wafer obtained from the ingot is produced at the other end side in the height direction;
obtaining a first absorption coefficient, which is the absorption coefficient in the first generation body, and a second absorption coefficient, which is the absorption coefficient in the second generation body;
determining the irradiation energy of the laser beam by setting the higher value of the first absorption coefficient and the second absorption coefficient as an upper limit value of the absorption coefficient;
The wafer manufacturing method according to claim 8. In a second region where the change in the absorption coefficient is larger than in the first region, the measurement pitch of the transmittance is set finer than that of the first region.
The wafer manufacturing method according to claim 8. The second region is a boundary region between the non-facet region (RN) and the facet region (RF),
The wafer manufacturing method according to claim 12.

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