Wafer manufacturing method

Abstract

To provide a wafer manufacturing method with higher manufacturing efficiency than before.SOLUTION: A surface on one end side in a height direction of an ingot is irradiated with a laser beam (B) having transmissivity to form a peeling layer at a depth corresponding to the thickness of a wafer. In formation of a peeling layer, laser scanning of irradiating the surface with the laser beam while moving an irradiation position (PR) of the laser beam in a first direction (Ds) is performed multiple times while changing the position with respect to a second direction (Df). In single laser scanning, the surface is irradiated with a plurality of laser beams (B1, B2, B3) different in irradiation positions in the first direction and second direction.SELECTED DRAWING: Figure 5A

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a wafer.

Background Art

[0002] Patent Document 1 provides a method for generating a wafer that can efficiently generate a wafer from an ingot. Specifically, the method for generating a wafer described in Patent Document 1 includes a separation starting point formation step and a wafer peeling step. In the separation starting point formation step, the focal point of a laser beam having a wavelength that is transmissive to the hexagonal single crystal ingot is positioned at a depth corresponding to the thickness of the wafer to be generated from the surface, and the focal point and the ingot are relatively moved to irradiate the surface with the laser beam. Thereby, a modified layer parallel to the surface and cracks extending from this modified layer are formed to form a separation starting point. The wafer peeling step peels a plate-shaped object corresponding to the thickness of the wafer from the ingot starting from the separation starting point to generate a hexagonal single crystal wafer. In the separation starting point formation step, two or more focal points of the laser beam are positioned at predetermined intervals in the direction in which an off-angle is formed, and two or more linear modified layers are formed simultaneously.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the method for producing a wafer described in Patent Document 1, a modified layer is simultaneously formed by each of a plurality of laser beams having different irradiation positions in the direction in which an off-angle is formed. At this time, in each of the plurality of modified layers formed simultaneously and having different positions in the direction in which the off-angle is formed, variations in depth may occur. When variations in the depth of the modified layer occur, steps are generated on the peeling surface, the processing cost of grinding and polishing increases, or peeling failure occurs, resulting in a decrease in manufacturing efficiency. The present invention has been made in view of the circumstances exemplified above. That is, the present invention provides, for example, a wafer manufacturing method with higher manufacturing efficiency than in the past.

Means for Solving the Problems

[0005] The wafer manufacturing method according to claim 1 is a method for obtaining a wafer (1) from an ingot (2), and includes the following steps, processes, or treatments: Forming a peeling layer (25) at a depth corresponding to the thickness of the wafer from the surface by irradiating a laser beam having permeability with respect to one end surface (21) in the height direction of the ingot, peeling layer formation, and Peeling the wafer precursor (26), which is a portion between the surface and the peeling layer, from the ingot at the peeling layer, wafer peeling, and Flattening the main surface (32) of the plate-like peeled body (30) obtained by the wafer peeling, wafer flattening, and including The peeling layer formation is Measure the transmittance of the obtained separated body or the wafer at a plurality of positions in a first direction (Ds) along the surface and in a second direction (Df) perpendicular to the first direction and along the surface, Based on the measurement results of the transmittance, obtain the absorption coefficient of the laser beam, Based on the change tendency of the absorption coefficient in the depth direction of the ingot for each different position in the in-plane along the surface, determine the irradiation energy of the laser beam at each of the irradiation positions (PR) of the plurality of laser beams on the surface, Move the irradiation position in the first direction Performing laser scanning in which the laser beam is irradiated on the surface while being moved, and performing the laser scanning a plurality of times while changing the position, and forming a plurality of scanning lines (Ls), which are irradiation marks of the linear laser beam along the first direction, along the second direction to form the peeling layer, In the second direction and By irradiating the surface with a plurality of the laser beams in which the irradiation positions in the first direction and the second direction are different in one laser scanning, a plurality of the scanning lines are formed. The wafer manufacturing method according to claim 2 is a method for obtaining a wafer (1) from an ingot (2), and includes the following steps, processes, or treatments: By irradiating a laser beam having permeability to one end surface (21) in the height direction of the ingot, a separation layer (25) is formed at a depth corresponding to the thickness of the wafer from the surface, which is separation layer formation, The wafer precursor (26), which is the portion between the surface and the separation layer, is separated from the ingot at the separation layer, which is wafer separation, The main surface (32) of the plate-shaped separated body (30) obtained by the wafer separation is flattened, which is wafer flattening, Including, The separation layer formation is, While moving the irradiation position (PR) of the laser beam on the surface in a first direction (Ds) along the surface, the laser beam is irradiated on the surface, and laser scanning is performed a plurality of times while changing the position in a second direction (Df) perpendicular to the first direction and along the surface. By forming a plurality of scanning lines (Ls), which are linear irradiation marks of the laser beam along the first direction, along the second direction, the separation layer is formed, In one laser scanning, a plurality of the scanning lines are formed by irradiating the surface with a plurality of laser beams having different irradiation positions in the first direction and the second direction, The plurality of laser beams include a first beam, a second beam, and a third beam arranged at different positions from each other in the second direction, The first beam, the second beam, and the third beam are arranged in a V shape on the surface.

[0008] Or In such a wafer manufacturing method, the variation in the depth of the scanning lines constituting the peeling layer can be suppressed as much as possible. As a result, the height of steps and unevenness on the peeling surface generated by peeling in the peeling layer is favorably suppressed, the processing cost of grinding and polishing on the peeling surface is reduced, or the occurrence of peeling defects is favorably suppressed. In addition, the cycle time for forming the peeling layer can be shortened. Therefore, according to such a wafer manufacturing method, it is possible to improve the manufacturing efficiency as compared with the prior art.

[0009] Note that in each column of the application documents, there may be cases where each element is given a reference sign with parentheses. In this case, the reference sign is merely an example showing the correspondence relationship between the same element and the specific configuration described in the embodiments described later. Therefore, the present invention is not limited by the description of the reference sign at all.

Brief Description of the Drawings

[0010]

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Mode for Carrying Out the Invention

[0011] (Embodiment) Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that, regarding various modification examples applicable to one embodiment, if they are inserted in the middle of a series of explanations regarding the embodiment, there is a risk of hindering the understanding of the embodiment. For this reason, the modification examples will not be inserted in the middle of the series of explanations regarding the embodiment, but will be collectively explained later.

[0012] (Structure of Wafer and Ingot) Referring to FIG. 1, the wafer 1 manufactured by the wafer manufacturing method according to the present embodiment is obtained by slicing an ingot 2 having a substantially cylindrical shape in a side view, and is formed in a substantially circular thin plate shape in a plan view. That is, the wafer 1 and the ingot 2 have a substantially cylindrical side surface or end surface surrounding the central axis L. The central axis L is a virtual straight line parallel to the substantially cylindrical side surface or end surface of the wafer 1 or the ingot 2 and passing through the axis center of the wafer 1 or the ingot 2. Note that, from the viewpoint of simplification of illustration and explanation, the so-called orientation flat usually provided on the wafer 1 or the ingot 2 is omitted from illustration and explanation in this specification.

[0013] In the present embodiment, the ingot 2 is a single-crystalline SiC ingot having a c-axis Lc and a (0001) plane Pc that are orthogonal to each other, and has an off-angle θ greater than 0 degrees. The c-axis Lc is a crystal axis represented as

[0001] by the direction index. The (0001) plane Pc is a crystal plane that is orthogonal to the c-axis Lc and is called the "C plane" in a strictly crystallographic sense. The off-angle θ is an angle formed by the central axis L of the wafer 1 or the 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 the ingot 2 is provided in a state where the central axis L is tilted by an off-angle θ greater than 0 degrees in the off-angle direction Dθ. The off-angle direction Dθ is the moving direction of a point on the central axis L located on the laser irradiation surface (i.e., the upper surface or the top surface in the figure) of the wafer 1 or the ingot 2 when the central axis L is rotated toward the c-axis Lc with the intersection of the central axis L and the c-axis Lc as the center, mapped onto the laser irradiation surface.

[0014] For simplicity of explanation, a right-handed XYZ coordinate system is set as shown in FIG. 1. In such a right-handed XYZ coordinate system, it is assumed that the off-angle direction Dθ and the positive X-axis direction are the same direction. Also, the X-axis and the 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 orthogonal to the plate thickness direction in a plate-shaped object, and can also be referred to as the "upper surface", "bottom surface", or "plate surface". Alternatively, the "main surface" is a surface orthogonal to the height direction in a columnar object such as the ingot 2, and can also be referred to as the "top surface" or "bottom surface". Further, it is assumed that the thickness direction of the wafer 1 and the height direction of the ingot 2 are parallel to the Z-axis. Any direction orthogonal to the Z-axis may be hereinafter referred to as the "in-plane direction".

[0015] Wafer 1 has a pair of main surfaces, namely, wafer C surface 11 and wafer Si surface 12. In this embodiment, wafer 1 is formed such that wafer C surface 11, which is the upper surface, is inclined at an off-angle θ with respect to (0001) plane Pc. Similarly, ingot 2 has a pair of main surfaces, namely, ingot C surface 21 and ingot Si surface 22. Ingot 2 is formed such that ingot C surface 21, which is the top surface, is inclined at an off-angle θ with respect to (0001) plane Pc. Hereinafter, one end, i.e., the upstream end, in the off-angle direction Dθ of ingot 2 is referred to as first end 23, and the other end, i.e., the downstream end, is referred to as second end 24. In FIG. 1, the direction in which wafer C surface 11 and ingot C surface 21 face is shown as the positive Z-axis direction.

[0016] Further, ingot 2 has a facet region RF. The facet region RF may also be referred to as a "facet portion". The portion of ingot 2 other than the facet region RF is hereinafter referred to as a non-facet region RN. Similarly, the non-facet region RN may also be referred to as a "non-facet portion".

[0017] (Outline of Wafer Manufacturing Method) The wafer manufacturing method according to this embodiment is a method for obtaining wafer 1 from ingot 2 and includes the following steps.

[0018] (1) Release Layer Formation Step: By irradiating ingot C surface 21, which is one end side main surface in the height direction of ingot 2, with a laser beam having a predetermined degree of permeability with respect to ingot 2, a release layer 25 is formed at a depth corresponding to the thickness of wafer 1 from ingot C surface 21. Here, the "predetermined degree of permeability" means a degree of permeability that enables the formation of a laser beam focus point at a depth corresponding to the thickness of wafer 1 inside ingot 2. Further, the "depth corresponding to the thickness of wafer 1" is a dimension obtained by adding a thickness corresponding to a predetermined processing allowance in a wafer planarization step or the like to the thickness of wafer 1 as a finished product (i.e., the target value of the thickness), and may also be referred to as the "depth corresponding to the thickness of wafer 1".

[0019] (2) Wafer separation process: The wafer precursor 26, which is the part between the ingot C surface 21, which is the laser irradiation surface, and the separation layer 25, is separated from the ingot 2 at the separation layer 25. Here, as in the above expression of "wafer separation process", the plate-like object obtained by separating the wafer precursor 26 from the ingot 2 may be referred to as a "wafer" in the common social concept. However, in order to distinguish it from the final wafer 1 after manufacturing, which has a mirror-finished main surface for epitaxy, such a plate-like object is hereinafter referred to as a "separated body 30". The separated body 30 has a non-separation surface 31 and a separation surface 32, which are a pair of main surfaces. The non-separation surface 31 is the surface on the side that did not form the separation layer 25 before the wafer separation process, and corresponds to the ingot C surface 21 before the separation layer formation process and the wafer separation process. The separation surface 32 constituted the separation layer 25 before the wafer separation process and is a newly generated surface by the wafer separation process. The separation surface 32 has rough (that is, the degree that requires grinding or polishing) unevenness due to the separation layer 25 and the separation by the wafer separation process.

[0020] (3) Wafer planarization process: The final wafer 1 after manufacturing is obtained by planarizing at least the separation surface 32 among the non-separation surface 31 and the separation surface 32, which are the main surfaces of the separated body 30. In the wafer planarization process, in addition to general grinding wheel polishing and CMP, ECMG and ECMP can be used. Note that CMP is the abbreviation of Chemical Mechanical Polishing. ECMG is the abbreviation of Electro-Chemical Mechanical Grinding. ECMP is the abbreviation of Electro-Chemical Mechanical Polishing. The wafer planarization process can be performed by using a single type or an appropriate combination of these multiple types of planarization processes.

[0021] (4) Ingot flattening process: After peeling off the wafer precursor 26, the newly formed upper surface of the ingot 2 is flattened or polished to a mirror finish so that it can be reused in the peeling layer formation process. In the ingot flattening process, in addition to general grinding wheel polishing and CMP, ECMG or ECMP can also be used. The ingot flattening process can also be carried out by using these multiple types of flattening processes alone or in appropriate combinations.

[0022] Figure 2 is a process diagram showing a typical example embodying the wafer manufacturing method according to this embodiment. As shown in Figure 2, the separated body 30 separated from the ingot 2 through the peeling layer formation process and the wafer peeling process is finished into the epitaxial wafer 1 through the following processes. · Rough grinding of the separation surface 32 to be the wafer Si surface 12 · ECMG grinding of the separation surface 32 after rough grinding · ECMP polishing of the separation surface 32 after ECMG grinding · Cleaning

[0023] Also, after the separated body 30 is separated from the ingot 2 through the peeling layer formation process and the wafer peeling process, the remaining ingot 2 can be reused in the peeling layer formation process through the following processes. · Rough grinding of the newly formed ingot C surface 21 by the wafer peeling process · Finish grinding of the ingot C surface 21 after rough grinding · Cleaning

[0024] Hereinafter, the details of each process will be described with reference to Figures 1 and 2 in addition to other figures.

[0025] (Peeling layer formation process) Figures 3A and 3B show a schematic configuration of the ingot 2 in a state where the release layer 25 and the wafer precursor 26 are formed by the release layer formation process. Figures 4A and 4B show an outline of the release layer formation process and a schematic configuration of a release layer forming apparatus 40 used in such a process. It should be noted that the right-handed XYZ coordinates shown in FIGS. 3A to 4B are displayed so as to be consistent with the right-handed XYZ coordinates shown in FIG. 1.

[0026] Referring to FIGS. 3A and 3B, the release layer 25 is formed by forming a plurality of scanning lines Ls, which are irradiation marks of a linear laser beam along the X axis, in the Y-axis direction. The scanning line Ls is formed by linearly forming an irradiation mark RM of the laser beam on the ingot 2. In the present embodiment, the scanning line Ls is provided along the off-angle direction Dθ. And the plurality of scanning lines Ls are arranged in the line feed direction Df. The line feed direction Df is a plane inner direction orthogonal to the off-angle direction Dθ. That is, the line feed direction Df is orthogonal to the off-angle direction Dθ and orthogonal to the height direction of the ingot 2.

[0027] Referring to FIGS. 4A and 4B, the peeling layer forming apparatus 40 includes a chuck table 41 and a condenser 42. The chuck table 41 is configured to hold the ingot 2 on the side of the ingot Si surface 22 which is the bottom surface thereof. Specifically, for example, the chuck table 41 includes an adsorption mechanism or the like that adsorbs the ingot Si surface 22 by air pressure or the like. Note that, as will be described later, the method of fixing the ingot 2 to the chuck table 41 is not limited to such a mode. The condenser 42 is disposed opposite the chuck table 41 in the beam axis direction which is the irradiation direction of the laser beam B so as to irradiate the ingot 2, which is a workpiece fixed to the chuck table 41, with the laser beam B oscillated by a pulse laser oscillator (not shown). That is, the condenser 42 is provided so as to irradiate the ingot 2 with the laser beam B from the side of the ingot C surface 21 which is the upper surface of the ingot 2. Specifically, the condenser 42 is configured to form a condensing point BP of the laser beam B at a depth corresponding to the thickness of the wafer 1 inside the ingot 2 from the ingot C surface 21. The condenser 42, which may also be referred to as a "condenser", includes an optical element (for example, a lens) for forming the condensing point BP of the laser beam B at a predetermined position. The peeling layer forming apparatus 40 is configured such that the condensing point BP of the laser beam B is relatively movable with respect to the ingot 2 at least in the in-plane direction, that is, the XY direction in the drawing. Here, the "in-plane direction" is a direction parallel to the ingot C surface 21 which is the upper surface of the ingot 2.

[0028] The peeling layer forming apparatus 40 forms scanning lines Ls along the scanning direction Ds (i.e., the first direction) by "laser scanning" in which the laser beam B is scanned on the surface 21 of the ingot C in the scanning direction Ds. 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 the present 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 thereof. Then, the peeling layer forming apparatus 40 performs laser scanning a plurality of times while changing the position in the line feed direction Df (i.e., the second direction), and forms a plurality of scanning lines Ls along the line feed direction Df, thereby forming the peeling layer 25. Both the line feed direction Df and the scanning direction Ds are in-plane directions (i.e., directions along the ingot C surface 21) and are perpendicular to each other.

[0029] In this embodiment, the peeling layer forming apparatus 40 forms scanning lines Ls along the scanning direction Ds by relatively moving the chuck table 41 on which the ingot 2 is placed relative to the condensing device 42 in the scanning direction Ds to scan the laser beam B on the C surface 21 of the ingot. Further, after performing one laser scan, the peeling layer forming apparatus 40 relatively moves the chuck table 41 by a predetermined amount along the line feed direction Df with respect to the condensing device 42. Then, the peeling layer forming apparatus 40 forms the scanning line Ls again by relatively moving the chuck table 41 relative to the condensing device 42 in the scanning direction Ds (i.e., the same or opposite direction as that during the previous laser scan) to scan the laser beam B. In this way, the peeling layer forming apparatus 40 forms a plurality of scanning lines Ls along the line feed direction Df by scanning the laser beam B over substantially the entire width in the line feed direction Df. In this way, the peeling layer 25 is formed by a plurality of scanning lines Ls provided along the line feed direction Df. Further, a wafer precursor 26 that should become the wafer 1 in the future is formed on the side of the C surface 21 of the ingot closer to the peeling layer 25. As described above, in this embodiment, while the condensing device 42 is fixedly provided in the in-plane direction, the chuck table 41 that supports 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 will be described later, the present invention is not limited to such an aspect. That is, for example, there may be an embodiment in which the chuck table 41 that supports the ingot 2 is fixedly provided in the in-plane direction, while the condensing device 42 is movably provided in the in-plane direction by a scanning device (not shown). However, in any of these aspects, apparently, the laser beam B and its irradiation position PR move in the in-plane direction on the main surface of the ingot 2, or the laser beam B and its condensing point BP move in the in-plane direction inside the ingot 2. Therefore, for the sake of simplicity of explanation, hereinafter, there may be an explanation such that the laser beam B and its irradiation position PR move in the in-plane direction on the main surface of the ingot 2, or the laser beam B and its condensing point BP move in the in-plane direction inside the ingot 2.However, as will be described later, the present invention is not limited to such an aspect.

[0030] In this embodiment, as shown in FIGS. 4A and 4B, a plurality of 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 one laser scan. Specifically, as shown in FIGS. 5A and 5B, a plurality of laser beams B (i.e., the first beam B1, etc.) whose irradiation positions PR on the ingot C surface 21 are arranged inclined with respect to both the scanning direction Ds and the line feed direction Df in plan view move along the scanning direction Ds. Thereby, a plurality of scanning lines Ls are formed in one laser scan. Therefore, the cycle time in the peeling layer forming process can be favorably shortened.

[0031] In FIGS. 4A, 4B, and 5A, as an example of the plurality of laser beams B, a case where there are three laser beams B is illustrated. However, this is due to the convenience of simplification of the illustration, and there is no particular limitation on the number of laser beams B. However, for the sake of simplifying the explanation, hereinafter, as the plurality of laser beams B, the explanation will continue assuming that at least the first beam B1, the second beam B2, and the third beam B3 are included. Among the first beam B1, the second beam B2, and the third beam B3, the first beam B1 is the most leading, that is, the one located on the most scanning direction Ds side. On the other hand, the third beam B3 is the most trailing. And the second beam B2 is located between the first beam B1 and the third beam B3 with respect to the scanning direction Ds and the line feed direction Df.

[0032] As shown in FIG. 5A, the first beam B1 travels in the scanning direction Ds ahead of the second beam B2. Due to the irradiation of the first beam B1, as shown in FIG. 5B, an irradiation affected region RA is generated to a predetermined depth from the ingot C surface 21, which is the laser irradiation surface. The irradiation affected region RA includes an irradiation mark RM formed by separating SiC into Si and C by the irradiation of the laser beam B, and a crack C extending from such an irradiation mark RM along the (0001) plane Pc to its periphery. Therefore, the irradiation position PR of the second beam B2 may at least overlap with the crack C in the irradiation affected region RA formed by the preceding first beam B1 in the in-plane direction. When the irradiation mark RM and the crack C included in the irradiation affected region RA by the preceding first beam B1 exist at the irradiation position PR of the subsequent second beam B2, the absorption rate of the second beam B2 is increased by such an irradiation affected region RA. For this reason, an irradiation mark RM by the subsequent second beam B2 is likely to be generated at a depth substantially the same as the depth of the irradiation affected region 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 irradiation marks RM or irradiation affected regions RA adjacent to each other in the line feed direction Df, which are formed at once by the first beam B1 to the third beam B3 in one laser scan, are likely to be generated at substantially the same depth. That is, a plurality of scanning lines Ls constituting the peeling layer 25 adjacent to each other in the line feed direction Df are likely to be generated at substantially the same depth.

[0033] Thus, in the present embodiment, the variation in the depth of the irradiation marks RM, that is, the scanning lines Ls, constituting the peeling layer 25 can be suppressed as much as possible. Thereby, the steps and the magnitude of unevenness on the peeling surface 32 generated by the peeling in the peeling layer 25 are favorably suppressed, the processing cost of grinding and polishing on the peeling surface 32 is reduced, and the occurrence of peeling failure is favorably suppressed. In addition, the cycle time for forming the peeling layer 25 can be shortened. Therefore, according to the present embodiment, it is possible to improve the manufacturing efficiency as compared with the prior art.

[0034] FIG. 6 shows the locus of the relative movement of the central position in the in-plane direction of the light condensing device 42 with respect to the ingot 2. The "central position in the in-plane direction of the light condensing device 42" is typically, for example, the central position in the array of a plurality of laser beams B. As shown in FIGS. 4A and 6, in this embodiment, the ingot 2 is oriented such that the facet region RF is located on the "low off-angle side", and the laser beam B is irradiated from the C-plane side to perform the peeling layer formation step. The "low off-angle side" means the side with a low inclination on the C-plane, that is, the (0001) plane Pc, when the ingot 2 is oriented such that the ingot C-plane 21, which is one main surface, becomes the upper surface. On the other hand, the "high off-angle side" means the side with a high inclination on the C-plane, that is, the (0001) plane Pc, when the ingot 2 is oriented such that the ingot C-plane 21 becomes the upper surface.

[0035] As will be described later, by applying a unidirectional load for peeling the wafer precursor 26 from the ingot 2 at one end on the "high off-angle side" of the ingot 2, extremely good wafer peeling is achieved. Here, an assumed example will be considered in which, after setting the orientation of the ingot 2 such that the facet region RF is located on the "high off-angle side" and irradiating the laser beam B from the Si-plane side, a unidirectional load is applied at one end on the "high off-angle side" of the ingot 2. In this regard, the end portion of the ingot 2 close to the facet region RF is less likely to crack in the first place. Therefore, in such an assumed example, since the peeling start position is the end portion close to the facet region RF where cracks are less likely to occur, the success rate of the wafer peeling process may be low. On the other hand, in this embodiment, the ingot 2 is oriented such that the facet region RF is located on the "low off-angle side", and after irradiating the laser beam B from the C-plane side, a unidirectional load is applied at one end on the "high off-angle side" of the ingot 2. In this case, the peeling start position is a portion 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.

[0036] Incidentally, it is known that the intensity of the laser beam B reaching the condensing point BP is higher in the non-faceted region RN than in the faceted region RF. Therefore, in the present embodiment, in the peeling layer formation step, the laser beam B is irradiated onto the main surface of the ingot 2 such that the energy application density by the irradiation of the laser beam B is higher in the faceted region RF than in the non-faceted region RN. The "energy application density" referred to here is the energy application density in the plane along the main surface of the ingot 2. The following means can be used alone or in combination. Specifically, for example, in the faceted region RF, the output of the laser beam B is made higher than that in the non-faceted region RN. Alternatively, for example, the laser beam B is irradiated onto the main surface of the ingot 2 such that the irradiation frequency of the laser beam B is higher in the faceted region RF than in the non-faceted region RN. More specifically, for example, in the faceted region RF, the repetition frequency of the laser beam B is made higher than that in the non-faceted region RN, or the scanning speed is decreased while the repetition frequency is constant to narrow the irradiation interval in the scanning direction Ds. When making the output higher in the faceted region RF than in the non-faceted region RN, the output in the faceted region RF is preferably 1.5 times the output in the non-faceted region RN. When narrowing the irradiation interval in the scanning direction Ds or the line feed direction Df in the faceted region RF compared to the non-faceted region RN, the irradiation interval in the faceted region RF is preferably 2 / 5 of the irradiation interval in the non-faceted region RN. Alternatively, for example, separately from the irradiation of the laser beam B on the entire region including the faceted region RF and the non-faceted region RN, the laser beam B is irradiated on the faceted region RF. When irradiating the laser beam B on the faceted region RF, the laser beam B can also be irradiated on the region in the non-faceted region RN adjacent to the faceted region RF.

[0037] According to the release layer formation process according to this embodiment, it is possible to favorably form the release layer 25 over the entire region including the faceted region RF and the non-faceted region RN. In particular, even without using the distance adjustment in the Z-axis direction between the condenser device 42 on the irradiation side of the laser beam B and the chuck table 41 that supports the ingot 2, the formation of the release layer 25 for the faceted region RF can be performed in the same manner as for the non-faceted region RN. Therefore, according to this embodiment, it is possible to improve the manufacturing efficiency as compared with the conventional case.

[0038] Referring to FIGS. 4A and 6, in the release layer formation process, there are a forward scan Sc1 in which the irradiation position PR when the laser beam B is irradiated moves in the same direction as the off-angle direction Dθ on the main surface of the ingot 2, and a return scan Sc2 in which the irradiation position PR when the laser beam B is irradiated moves in the direction opposite to the off-angle direction Dθ on the main surface of the ingot 2. That is, in the forward scan Sc1, the scan direction Ds is the same as the off-angle direction Dθ. On the other hand, in the return scan Sc2, the scan direction Ds is the direction opposite to the off-angle direction Dθ. The forward scan Sc1 and the return scan Sc2 are performed alternately.

[0039] After one forward scan Sc1 is completed and before the next forward scan Sc1 starts, the relative position of the condenser device 42 with respect to the ingot 2 moves by a predetermined amount in the line feed direction Df. However, regarding the period from when one forward scan Sc1 is completed until the return scan Sc2 performed immediately thereafter starts, the relative position of the condenser device 42 in the line feed direction Df may or may not move. The same applies to the period from when one return scan Sc2 is completed until the subsequent forward scan Sc1 starts. The relative movement amount in the line feed direction Df at each stage can be appropriately set according to the irradiation conditions of the laser beam B and the like.

[0040] 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, while moving the irradiation position PR in the scanning direction Ds, which is the same direction as the off-angle direction Dθ on the main surface of the ingot 2, the main surface of the ingot 2 is irradiated with the laser beam B. Thereby, a scanning line Ls is formed across both ends of the ingot 2 in the scanning direction Ds. In contrast, in the return scan Sc2, the laser beam B may 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 on only a part of the ingot 2, rather than the entire width in the scanning direction Ds.

[0041] Specifically, for example, in the return scan Sc2, the laser beam B may be irradiated only on the facet region RF and its peripheral portion. Thereby, it becomes possible to favorably form the release layer 25 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 on the end portion of the ingot 2 in the scanning direction Ds. In this case, in the return scan Sc2, while 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, a scanning line Ls is formed on the end portion of the ingot 2 in the scanning direction Ds. Thereby, the start of peeling in the wafer peeling process is favorably promoted, and the success rate of the wafer peeling process is improved. Further, in the return scan Sc2, the laser beam B may be irradiated only on the facet region RF and its peripheral portion and the end portion of the ingot 2 in the scanning direction Ds.

[0042] As shown in FIG. 7, in the present embodiment, the laser beam B has an intensity distribution such that the intensity is higher at the peripheral edge portion outside the central portion in the beam diameter direction, which is the direction extending radially from the axis center thereof. Specifically, the laser beam B has an annular or hollow shape on the front side of the focusing point BP, while having a beam shape that focuses into a dot 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 edge portions with high intensity in the laser beam B overlap each other.

[0043] In this way, the peeling layer forming apparatus 40 irradiates the ingot 2 with the annular laser beam B. Such an annular laser beam B and an apparatus for generating such a laser beam B and irradiating a workpiece therewith are already known or well-known at the time of filing of the present application (see, for example, Japanese Patent Application Laid-Open No. 2006-130691, Japanese Patent Application Laid-Open No. 2014-147946, etc.). Therefore, the details of the generating apparatus and generating method of such a laser beam B are omitted in this specification.

[0044] FIG. 8A shows a state in which an irradiation affected area RA including an irradiation mark RM is formed by the annular laser beam B according to the present embodiment. FIG. 8B shows, as another example different from the present embodiment, a state in which an irradiation affected area RA including an irradiation mark RM is formed by a non-annular or solid laser beam B.

[0045] As shown in Fig. 8B, when a solid laser beam B is used, an irradiation mark RM, which is a modified region formed by separating SiC into Si and C by the irradiation of the laser beam B, may be generated at a depth different from that of the beam waist BP. For this reason, the depth of the irradiation-affected region RA composed of the irradiation mark RM and the crack C developed from such irradiation mark RM may also be different from the depth of the beam waist BP. Specifically, for example, at a position shallower than the beam waist BP, the energy application density by the irradiation of the laser beam B may increase to such an extent that the irradiation mark RM can be generated. Then, the irradiation mark RM may be generated at a position shallower than the beam waist BP. The generation depth of the irradiation mark RM 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 condenser device 42, and the like. The region where the irradiation mark RM can be generated is shown as a modifiable range RC in the figure. Note that the irradiation mark RM corresponds to the "modified layer" in Patent Document 1.

[0046] On the other hand, as shown in Fig. 8A, when an annular laser beam B is used, the increase in the energy application density by the irradiation of the laser beam B to such an extent that the irradiation mark RM can be generated is limited to the depth near the beam waist BP. That is, for example, it is difficult to increase the energy application density by the irradiation of the laser beam B at a position shallower than the beam waist BP to such an extent that the irradiation mark RM can be generated as in the case of using a solid laser beam B. Therefore, the irradiation mark RM is stably generated at the depth near the beam waist 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 beam waist BP. For this reason, variations in the generation depth of the irradiation mark RM can be favorably suppressed. In other words, it becomes possible to form the peeling layer 25 as thin as possible, and the processing cost in grinding and polishing after peeling can be favorably reduced. Therefore, according to the present embodiment, it becomes possible to improve the manufacturing efficiency as compared with the prior art.

[0047] By the way, in the method described in Patent Document 1, the laser scanning direction is orthogonal to the direction in which the off-angle θ is formed (i.e., the off-angle direction Dθ in FIGS. 1 and 3A, etc.). For this reason, cracking is not stable and material loss increases. On the other hand, in the present embodiment, as shown in FIG. 4A, the scanning direction Ds, which is the moving direction of the condensing 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 forming step, 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 forming apparatus 40 forms the scanning line Ls along the off-angle direction Dθ by relatively moving the condensing device 42 with respect to the ingot 2 in the scanning direction Ds parallel to the off-angle direction Dθ and scanning the laser beam B. Then, as shown in FIGS. 9 and 10, the irradiation marks RM and the cracks C are formed along the (0001) plane Pc. Thereby, cracking in the peeling layer 25 during the wafer peeling step can be stabilized, and material loss is favorably reduced. Also, the processing cost in the wafer flattening step is favorably reduced, and thus the process time can be shortened as much as possible. Therefore, according to the present embodiment, it is possible to provide a wafer manufacturing method with higher manufacturing efficiency than in the prior art.

[0048] FIG. 9 shows an example in which the scanning direction Ds is the same as the off-angle direction Dθ. FIG. 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 FIG. 9, when the posture of the ingot 2 is set such that the C plane 21 of the ingot becomes the upper surface as shown in FIG. 4A, the irradiation position PR is moved from the higher side to the lower side in the (0001) plane Pc by laser scanning. On the other hand, in the example shown in FIG. 10, when the posture of the ingot 2 is set such that the C plane 21 of the ingot becomes the upper surface, the irradiation position PR is moved from the lower side to the higher side in the (0001) plane Pc by laser scanning.

[0049] For example, assume a situation where there is no irradiation influence region RA, i.e., irradiation mark RM or crack C, around the irradiation position PR in the in-plane direction. In such a situation, due to the irradiation of the laser beam B, the irradiation mark RM is likely to occur at a depth near the beam waist BP. On the other hand, in reality, the laser beam B moves in the scanning direction Ds while successively generating irradiation marks RM and cracks C. Therefore, the above situation mainly occurs when forming the irradiation mark RM corresponding to the starting point of the scanning line Ls, which is first formed in one laser scan. Thus, in most scenes during laser scanning, a situation occurs where there is an irradiation influence region RA around the irradiation position PR in the in-plane direction.

[0050] That is, as shown in FIGS. 9 and 10, there is usually an irradiation influence region RA formed previously (e.g., immediately before) at the current irradiation position PR. Then, in such an irradiation influence region RA, the absorption rate of the laser beam B increases. Also, such an irradiation influence region RA is formed along the (0001) plane Pc. For this reason, due to laser scanning, the irradiation mark RM is likely to progress along the (0001) plane Pc.

[0051] Here, in the example shown in FIG. 9, due to laser scanning, when the irradiation mark RM progresses in the scanning direction Ds along the (0001) plane Pc, it is formed at a gradually deeper position and thus gradually moves away from the beam waist BP. Then, at approximately the same depth as the irradiation mark RM formed immediately before, the energy application density by 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 can no longer progress along the (0001) plane Pc. Then, as shown in FIG. 9, the newly formed irradiation mark RM is formed at a depth near the beam waist BP in the laser beam B irradiated this time. That is, a step occurs between the irradiation mark RM formed immediately before and the irradiation mark RM formed this time.

[0052] On the one hand, in the example shown in FIG. 10, during laser scanning, as the irradiation mark RM progresses in the scanning direction Ds along the (0001) plane Pc, it is formed at a gradually shallower position, thereby gradually moving away from the beam waist BP. When the energy application density by the laser beam B irradiated this time cannot be increased to a level that can generate a new irradiation mark RM at approximately the same depth as the immediately preceding irradiation mark RM, the irradiation mark RM can no longer progress along the (0001) plane Pc. Then, as shown in FIG. 10, the newly formed irradiation mark RM is formed at a depth near the beam waist BP in the laser beam B irradiated this time. However, in the example shown in FIG. 10, unlike the example shown in FIG. 9, the progression direction of the irradiation mark RM is a direction approaching 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 difference generated between the immediately preceding irradiation mark RM and the irradiation mark RM formed this time becomes larger than in the example shown in FIG. 9.

[0053] In this way, by setting the scanning direction Ds to the same direction as the off-angle direction Dθ and moving the irradiation position PR in the laser scanning from the higher side to the lower side on the C plane, the step difference between the immediately preceding irradiation mark RM and the irradiation mark RM formed this time can be reduced. Thereby, the peeling layer 25 can be formed as thin as possible, and thus the processing cost in grinding and polishing after peeling can be favorably reduced. Therefore, according to such an aspect, it is possible to further enhance the manufacturing efficiency compared to the conventional case.

[0054] (Wafer peeling process) FIG. 11 shows an overview of the wafer peeling process and the peeling apparatus 50 used in such a process. Note that the right-handed XYZ coordinates shown in FIG. 11 are shown to be consistent with the right-handed XYZ coordinates shown in FIG. 1.

[0055] 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 plane direction parallel to the C-plane 21 of the ingot, that is, the off-angle direction Dθ. The first end 23 is the end on the "higher off-angle side", that is, the higher end on the C-plane, that is, the (0001) plane Pc when the posture of the ingot 2 is set such that the C-plane 21 of the ingot becomes the upper surface. In the present embodiment, the peeling device 50 is configured to apply a static and / or dynamic load in the Z-axis direction in the drawing in a manner that separates the C-plane 21 of the ingot from the Si-plane 22 of the ingot at the first end 23 to the ingot 2. Specifically, in the present embodiment, the peeling device 50 includes a support table 51, a peeling pad 52, and a drive member 53.

[0056] 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 at the support suction surface 51a, which is the upper surface thereof, and is configured to adsorb the Si-plane 22 of the ingot 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 one end (i.e., the left side in the drawing) 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 shape that rises as it goes in the off-angle direction Dθ. That is, as shown in FIG. 11, the support table 51 is formed in a trapezoidal shape where the lower base is longer than the upper base in a side view.

[0057] The peeling pad 52 is provided above the support table 51 so as to be able to approach and separate along the Z-axis in the drawing with respect to the support table 51. That is, the peeling device 50 is configured such that the support table 51 and the peeling pad 52 can move relative to each other in the height direction of the ingot 2. The peeling pad 52 has a number of suction holes (not shown) that open at the pad suction surface 52a, which is the bottom surface thereof, and is configured to suction the C surface 21 of the ingot by air pressure at the pad suction surface 52a. The peeling 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 one end (i.e., the left side in the drawing) in the off-angle direction Dθ, has a pad end face 52d. The pad end face 52d is formed in an inclined surface shape that descends as it goes in the off-angle direction Dθ. That is, as shown in FIG. 11, the peeling pad 52 is formed in a trapezoidal shape in a side view, where the lower base is shorter than the upper base. The pad end face 52d is provided at a position corresponding to the table base end face 51d (i.e., directly above). When the C surface 21 of the ingot is fixed to the peeling pad 52 by suction and the Si surface 22 of the ingot is fixed to the support table 51 by suction, the state in which the ingot 2 is sandwiched between the support table 51 and the peeling pad 52 is hereinafter referred to as the "sandwiched state".

[0058] The driving member 53 is provided to apply an external force that relatively moves the support table 51 and the peeling pad 52 along the height direction of the ingot 2 in the clamped state to at least one of the support table 51 and the peeling pad 52. Specifically, the driving member 53 has a first driving end face 53a and a second driving end face 53b. The first driving end face 53a is formed in an inclined surface shape that descends as it goes in the off-angle direction Dθ. More specifically, the first driving end face 53a is provided parallel to the pad end face 52d. The second driving end face 53b is formed in an inclined surface shape that ascends as it goes in the off-angle direction Dθ. More specifically, the second driving end face 53b is provided parallel to the table base end face 51d. Further, the driving member 53 is provided such that in the clamped state, the first driving end face 53a contacts the pad end face 52d and the second driving end face 53b contacts the table base end face 51d. That is, as shown in FIG. 11, the driving member 53 is formed in a shape obtained by rotating a trapezoid, whose lower base is longer than its upper base in a side view, 90 degrees clockwise. And the driving member 53 is configured to be driven in the upward direction along the height direction of the ingot 2 and / or in the off-angle direction Dθ which is the direction approaching the ingot 2 by a driving means (not shown). That is, the driving member 53 is provided such that by being driven in the upward direction and / or the off-angle direction Dθ, a moment 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 acts on the ingot 2.

[0059] The wafer peeling process of 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 Si surface 22 of the ingot to the support adsorption surface 51a. The clamping process is a process of forming a clamped state by adsorbing the C surface 21 of the ingot 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 an end of one of the peeling pads 52 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 driving the driving member 53 upward and / or in the off-angle direction Dθ in the clamped state to press the second pad end 52c upward along the height direction of the ingot 2. Thereby, the wafer precursor 26, which is a part of the ingot 2, can be peeled from the ingot 2 with the peeling layer 25 as the interface.

[0060] Thus, in this embodiment, the wafer peeling process is performed 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 upper surface of the ingot 2 (that is, the C surface 21 of the ingot in the example of FIG. 11). Then, a moment with the first end 23 as the fulcrum PP and the action point WP acts on the ingot 2.

[0061] In this regard, in the wafer peeling process described in Japanese Patent No. 6678522, the action point WP and the fulcrum PP were provided inside the ingot 2, that is, inside the outer edge of the peeling layer 25 in the in-plane direction. In such a comparative example, in order to generate good peeling with the peeling layer 25 as the interface, a much larger load was required than in this embodiment. In addition, since a load is applied over a wide area of the peeling layer 25, the peeling crack position is not determined, and partial unpeeled portions or breakage in the taken-out wafer 1 may occur. Furthermore, there was a problem that the peeling cross-section became rough and the processing cost of grinding and polishing increased. Therefore, in the comparative example, there was room for improvement in terms of reducing the load and improving the yield.

[0062] On the other hand, in the wafer peeling process according to the present embodiment, in order to peel the wafer precursor 26 from the ingot 2 with 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 such one end as the fulcrum PP and the point of action WP acts on the ingot 2. As a result, peeling proceeds from a crack formed at one end side of the ingot 2 in the off-angle direction Dθ, so that breakage can proceed stably over the entire surface of the peeling layer 25 while reducing the applied load. Further, by stably setting the breakage occurrence location, it is possible to reduce the surface roughness of the peeling surface 32 and the ingot C surface 21 in the peeled body 30 generated after peeling. In particular, by setting the first end 23, which is the starting point of breakage occurrence, as one end on the "higher off-angle side" in the off-angle direction Dθ, breakage occurs smoothly and splitting becomes even more stable. For this reason, the defective occurrence rate in the wafer peeling process and the processing cost in grinding and polishing the ingot 2 and the peeled body 30 after the wafer peeling process can be favorably reduced. Therefore, according to the present embodiment, it is possible to provide a wafer manufacturing method with higher manufacturing efficiency than before.

[0063] (Modification example) The present invention is not limited to the above embodiment. Therefore, the above embodiment can be appropriately changed. Hereinafter, typical modification examples will be described. In the description of the following modification examples, the differences from the above embodiment will be mainly described. Also, in the above embodiment and the modification examples, the same reference numerals are given to parts that are identical or equivalent to each other. Therefore, in the description of the following modification examples, for components having the same reference numerals as those in the above embodiment, the description in the above embodiment can be appropriately incorporated as long as there is no technical contradiction or special additional explanation.

[0064] The present invention is not limited to the specific configurations shown in the above embodiments. That is, for example, there are no particular limitations on the outer diameter or planar shape (such as the presence or absence of a so-called orientation flat) of the wafer 1 or the ingot 2. There are also no particular limitations on the magnitude of the off-angle θ. Further, in the above embodiments, the C-plane 11 of the wafer and the C-plane 21 of the ingot do not coincide with the C-plane in the strict crystallographic sense, i.e., the (0001) plane Pc. However, even in such a case, since the use of the term "C-plane" is socially acceptable, the expression "C-plane" is used. However, the present invention is not limited to such an aspect. That is, the C-plane 11 of the wafer and the C-plane 21 of the ingot may coincide with the C-plane in the strict crystallographic sense, i.e., the (0001) plane Pc. In other words, the off-angle θ may be 0 degrees.

[0065] 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 plurality of laser beams B irradiated in one laser scan can also be appropriately modified from the specific mode 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 plurality of laser beams B can be arranged in a W shape or a staggered shape. According to such an arrangement of the plurality of laser beams B, by forming the next modified layer at an interval wider than the length of the crack generated by the previously processed modified layer, it is possible to suppress the interference between the crack and the modified layer. Also, for example, even when irradiating the entire width of the ingot 2 in the scanning direction Ds with the laser beam B in the return scan Sc2 in the same manner as in the forward scan Sc1, the irradiation conditions of the two may be made different. Specifically, for example, the distance from the laser irradiation surface of the condenser 42, that is, the distance from the ingot C surface 21 (i.e., the irradiation distance) may be changed between the forward scan Sc1 and the return scan Sc2.

[0066] Depending on the irradiation conditions and scanning conditions of the laser beam B, the peeling surface 32 may have a surface state that can be ground or polished well even when directly subjected to the ECMG process. For this reason, the rough grinding process of the peeling surface 32 shown in FIG. 2 may be omitted. The same applies to the rough grinding of the upper surface of the ingot 2 after the wafer peeling process.

[0067] The peeling layer forming apparatus 40 shown in FIGS. 4A and 4B is a simplified schematic diagram for briefly 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 actually realized industrially does not necessarily coincide with the exemplary configuration shown in FIGS. 4A and 4B. Specifically, for example, the chuck table 41 may be configured to hold the ingot 2 by a method other than the air pressure adsorption mechanism. Further, the chuck table 41 may be configured to be relatively movable with respect to the condensing device 42 at least in the in-plane direction, that is, in the XY direction in the figure. Alternatively, the peeling layer forming apparatus 40 may include a scanning device configured to relatively move the condensing point BP of the laser beam B in the XYZ directions in the figure with respect to the ingot 2. Alternatively, in the above embodiment, the peeling layer forming apparatus 40 is configured such that the chuck table 41 that supports the ingot 2 is movable at least in the in-plane direction, while the condensing device 42 is fixedly provided in the in-plane direction. However, the present invention is not limited to such an aspect. That is, for example, the peeling layer forming apparatus 40 may be configured such that the chuck table 41 that supports the ingot 2 is fixedly provided in the in-plane direction, while the condensing device 42 moves in the in-plane direction by a scanning device (not shown). Further, depending on whether it is the faceted region RF or the non-faceted region RN, or regardless of this, performing distance adjustment in the Z-axis direction between the condensing device 42 on the irradiation side of the laser beam B and the chuck table 41 that supports the ingot 2 is an optional matter in the present invention. In addition, the specific configuration of the peeling layer forming apparatus 40 actually realized industrially can be appropriately changed from the exemplary configuration shown in FIGS. 4A and 4B.

[0068] In the above embodiment, the peeling layer 25 was formed on the ingot C surface 21 side by "C surface side irradiation" in which the laser beam B was irradiated onto the ingot C surface 21. However, the present invention is not limited to such an aspect. That is, the present invention is also applicable to "Si surface side irradiation" in which the laser beam B is irradiated onto the ingot Si surface 22 to form the peeling layer 25 on the ingot Si surface 22 side.

[0069] The peeling device 50 shown in FIG. 11 is a simplified schematic diagram for briefly explaining the outline of the wafer peeling process according to the present invention. Therefore, the specific configuration of the peeling device 50 actually realized industrially does not necessarily coincide with the exemplary configuration shown in FIG. 11. Specifically, for example, the support table 51 may be configured to adsorb the ingot Si surface 22 on the support adsorption surface 51a using a method other than the air pressure adsorption mechanism (for example, wax, adhesive, etc.).

[0070] The optical properties, i.e., transmittance and refractive index, of the obtained wafer 1 or the peeled body 30 may be measured at a plurality of 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 such measurement results. FIG. 14 shows an outline of such an aspect. In the figure, "loading / unloading" indicates the process of loading and unloading the peeled body 30 and the ingot 2, which are workpieces. "Laser slicing" indicates the peeling layer formation process. "Peeling" indicates the wafer peeling process. "Rough grinding" indicates the process of roughly grinding the main surfaces of the ingot 2 and the peeled body 30. Rough grinding can be performed, for example, using a grinding material with a grit size of about #800. "Finish grinding" indicates the process of finish grinding the surface. Finish grinding can be performed, for example, using a grinding material with a grit size of about #30000. "Wafer optical measurement" indicates the process of measuring the optical properties (i.e., transmittance and refractive index) of the peeled body 30 that has undergone finish grinding at a plurality of positions in the scanning direction Ds and the line feed direction Df. "Ingot cleaning" indicates the process of cleaning the ingot 2 after finish grinding. The arrow on the left side of the block indicating each process shows the processing flow of the ingot 2, and the arrow on the right side shows the processing flow of the wafer 1 or the peeled body 30 that can be referred to as a "wafer" in the common social concept.

[0071] Referring to FIG. 14, first, the ingot 2 is put into a wafer manufacturing apparatus including a release layer forming apparatus 40. Next, a release layer forming process is performed on the input ingot 2 by irradiating it with a laser beam B. Subsequently, in the wafer peeling process, the peeled body 30 is peeled off from the ingot 2 that has undergone the release layer forming process. The upper surface of the ingot 2 newly generated after the wafer peeling process is flattened by rough grinding and finish grinding. Thereafter, the ingot 2 is washed and then subjected to the release layer forming process again. Note that the ingot 2 that has undergone the release layer forming process or the ingot washing process is discharged from the wafer manufacturing apparatus when its height becomes less than a predetermined value.

[0072] The peeled body 30 peeled off from the ingot 2 by the wafer peeling process is subjected to rough grinding and finish grinding and then used for optical measurement, that is, measurement of transmittance and refractive index. The measurement results are used to determine the irradiation conditions (for example, irradiation energy and / or irradiation distance) of the laser beam B in the next release layer forming 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 C-plane 21 of the ingot in the next release layer forming process are controlled. Thereby, it becomes possible to finely change the irradiation conditions corresponding to the variation in the optical characteristics for each location in the in-plane direction, and thus it becomes possible to reduce material loss. This is particularly effective when the ingot 2 has a facet region RF. Note that the measurement of transmittance and refractive index may be only one of them. Alternatively, the measurement of transmittance and refractive index may be performed on the finally obtained epitaxial wafer 1. Also, depending on the conditions of rough grinding (for example, in the case of ECMG), finish grinding may not be necessary. That is, rough grinding and finish grinding can be integrated.

[0073] FIG. 15 shows an example of the setting mode of the optical measurement position in the generated body 100. The generated body 100 is an object of optical measurement and corresponds to the wafer 1 or the peeled body 30 whose surface is flattened to a certain extent after being peeled from the ingot 2. In this example, the optical measurement positions are set at a constant pitch (for example, 3 mm) for 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. Also, the Y-axis direction is parallel to the line feed direction Df shown in FIG. 6 and the like. Here, as shown in FIG. 16, the state of 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 is shown in FIG. 17. The measurement line Lx is a virtual straight line passing through the center in the in-plane direction of the generated body 100 and the facet region RF and parallel to the X-axis. The absorption coefficient is obtained or 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 generated body 100, and T represents the transmittance.

Equation

[0074] In FIG. 17, the horizontal axis represents the measurement position when the center in the in-plane direction of the generated body 100 is set as the origin, i.e., "0". As shown in FIG. 17, the absorption coefficient is not constant in the in-plane direction and 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, even in the non-facet region RN where the absorption coefficient is lower than that in the facet region RF, there is a distribution in the in-plane direction, i.e., the radial direction. The "radial direction" is a direction extending radially from the center in the in-plane direction of the generated body 100. Specifically, in the example of FIG. 17, there is a region with a low absorption coefficient on the left side, i.e., the outer side, from the center position.

[0075] Figures 18A to 18C show the state of change in the position where the modified layer is generated, accompanying the change in the transmittance, that is, the absorption coefficient. The position where the modified layer is generated is the position where the modified layer, that is, the irradiated influence region RA is generated by 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, it is the direction opposite to the height direction of the ingot 2 (that is, the negative Z-axis direction in FIG. 1 etc.). In the figure, the circle indicated by the dashed-dotted line beside the irradiated influence region RA shows the focusing state of the laser beam B, that is, the beam diameter, at the position where the modified layer is generated.

[0076] First, referring to FIG. 18A, as the laser beam B travels in the depth direction within the ingot 2, it converges while attenuating according to the absorption coefficient. Then, when the energy density rises to a certain level due to the focusing, the processing threshold is reached, and a modified layer, that is, an irradiated influence region RA is formed. Here, when the transmittance is low (that is, the absorption coefficient is high), since the attenuation amount is large, as shown in FIG. 18B, at a deeper position where the focused cross-sectional area becomes smaller, the energy density corresponding to the processing threshold is reached and modification occurs. On the other hand, when the transmittance is high (that is, the absorption coefficient is low), since the attenuation amount is small, as shown in FIG. 18C, even at a shallow position where the focused cross-sectional area is larger, the energy density corresponding to the processing threshold is reached and modification occurs. Thus, when the position where the modified layer is generated fluctuates due to the difference in the transmittance, that is, the absorption coefficient, the surface of the generated body 100 after peeling becomes rough, and the processing cost, that is, the material loss for grinding and polishing becomes large.

[0077] Therefore, in this modified example, the transmittance is measured at a plurality of positions in the in-plane direction, and based on such measurement results, the irradiation conditions of the laser beam B are controlled at each of the plurality of positions. Specifically, in this modified example, the absorption coefficient is obtained, that is, calculated, based on the transmittance measured in the generated body 100 generated in the past including the previous time. Then, in this modified example, the irradiation energy of the laser beam B is determined based on the change tendency of the absorption coefficient in the depth direction of the ingot 2 for each different position in the plane.

[0078] A specific example of controlling the irradiation conditions of the next laser beam B based on the optical measurement results of the previously obtained product 100 will be described below. First, using a transmittance measuring device, the transmittance and the like of the previously obtained product 100 are measured. At this time, the workpiece thickness is also measured. Based on the measured transmittance, workpiece thickness, and the above formula (1), the absorption coefficient is calculated. 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, I0 represents the input energy, I represents the energy required for the processing point, that is, the minimum applied energy required for modification, z represents the depth, and k represents the change amount of the absorption coefficient in the depth direction, that is, the change tendency of the absorption coefficient in the depth direction of the ingot 2.

Equation

[0079] A method for deriving the change amount of the absorption coefficient will be described below. As shown in FIG. 20, the center in the in-plane direction of the ingot 2 is defined as the in-plane center position Ma. Further, at a position on the measurement line Lx parallel to the X-axis passing through the in-plane center position Ma and located within the facet region RF, the end position of the ingot 2 is defined as the first end position Mb. Further, at a position on the measurement line Lx and on the side opposite to the first end position Mb, the position is defined as the second end position Mc. The second end position Mc is a position that is substantially symmetric to the first end position Mb with the in-plane center position Ma as the center. FIG. 21A shows the state of change of the absorption coefficient in the depth direction of the ingot 2 at the in-plane center position Ma. FIG. 21B shows the state of change of the absorption coefficient in the depth direction of the ingot 2 at the first end position Mb. FIG. 21C shows the state of change of the absorption coefficient in the depth direction of the ingot 2 at the second end position Mc. As shown in FIGS. 21A to 21C, it can be seen that the change of the absorption coefficient in the depth direction of the ingot 2 has a certain specific tendency and is different for each in-plane position. Based on the change tendency of the absorption coefficient in the depth direction for each in-plane position, the change amount of the absorption coefficient is derived, and the value obtained by adding or multiplying this to the absorption coefficient obtained previously can be applied to the determination of the input energy in the next processing.

[0080] For example, as shown in FIG. 22, based on the change amount between the absorption coefficient α n-1 obtained previously and the absorption coefficient α n-2 obtained the time before last, it is possible to obtain or calculate the estimated absorption coefficient α n for use in the current processing. Specifically, for example, the difference between the absorption coefficient α n-1 obtained previously and the absorption coefficient α n-2 obtained the time before last is used as the change amount of the absorption coefficient, and by adding this to the absorption coefficient α n-1 obtained previously, the estimated absorption coefficient α n can be calculated. Then, based on such an estimated absorption coefficient α n , it is possible to determine the irradiation energy of the laser beam B. Note that, when calculating the change amount of the absorption coefficient, statistical processing using a so-called "annealing filter" or the like may be performed.

[0081] Also, as shown in FIG. 23, a first generated body 101 and a second generated body 102 are generated. The first generated body 101 is a generated body 100 obtained from one end side in the height direction of the ingot 2, that is, the C surface 21 side of the ingot. The second generated body 102 is a generated body 100 obtained from the other end side in the height direction of the ingot 2, that is, the Si surface 22 side of the ingot. Next, a first absorption coefficient which is the absorption coefficient in the first generated body 101 and a second absorption coefficient which is the absorption coefficient in the second generated body 102 are acquired. And it is possible to determine the irradiation condition of the laser beam B, that is, the irradiation energy, with the higher value of the first absorption coefficient and the second absorption coefficient as the upper limit value of the absorption coefficient. In other words, it is also possible to use a coefficient setting with the absorption coefficient obtained from the generated body 100 on the side with the higher absorption coefficient, that is, the wafer, as the upper limit value and not change it further.

[0082] Regarding the measurement pitch of the optical measurement, it may be measured at an equal pitch as shown in FIG. 15, but it can be changed as appropriate. That is, for example, different pitches may be used in the X-axis direction and the Y-axis direction. Or, for example, in a region where the change in the absorption coefficient is larger than that in other regions, such as the region surrounded by the dashed rectangle in FIG. 24, the measurement pitch may be made finer. Specifically, such a region is, for example, the boundary region between the non-faceted region RN and the faceted region RF. That is, in such a boundary region, the measurement pitch may be made finer than in other regions. Note that the region where the measurement pitch is made finer may include the entire faceted region RF. More specifically, for example, referring to FIG. 24, in the region where the measurement position is to the right of 40 mm, the measurement pitch may be made finer than in the region where the measurement position is to the left of 40 mm. In other words, in a predetermined region composed of the non-faceted region RN and the boundary region between the non-faceted region RN and the faceted region RF, the measurement pitch may be made finer than in the region outside such a predetermined region.

[0083] The above content was experimentally verified for its effectiveness. The laser beam B used in the experiment is a pulsed laser with a wavelength of 1064 nm, a pulse width of 7 ns, and an oscillation frequency of 25 kHz. Also, the laser beam B is a ring-shaped beam with an outer diameter of 4.85 mm and an inner diameter of 2.82 mm. Such a laser beam B was incident on a lens with an NA of 0.65, and processing was performed with an irradiation pitch (i.e., the irradiation interval in the scanning direction Ds) of 8 μm and a scanning interval (i.e., the interval between the 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 and was used. The transmittance was measured for the wafer 1 with a thickness of 0.385 mm cut previously at a pitch of 3 mm. The input energy was set such that an energy of 20 μJ was input at a depth of 0.4 mm at the center of the ingot 2. At this time, when processing was performed with a constant output, the height difference in the in-plane position where the modified layer was generated was 61 μm. On the other hand, by performing output correction according to the in-plane absorption coefficient change, the height difference in the position where the modified layer was generated was improved to 18 μm. This indicated that material loss could be reduced.

[0084] It goes without saying that the elements constituting the above-described embodiments are not necessarily essential except in cases where it is explicitly stated that they are particularly essential or where they are considered to be clearly essential in principle. Also, when numerical values such as the number, amount, range, etc. of the components are mentioned, the present invention is not limited to those specific numerical values except in cases where it is explicitly stated that they are particularly essential or where they are clearly limited to specific numerical values in principle. Similarly, when the shape, direction, positional relationship, etc. of the components are mentioned, the present invention is not limited to those shape, direction, positional relationship, etc. except in cases where it is explicitly stated that they are particularly essential or where they are clearly limited to specific shape, direction, positional relationship, etc. in principle.

[0085] The modification examples are not limited to the above examples. That is, for example, in addition to those exemplified above, multiple embodiments can be combined with each other as long as they do not technically conflict. Similarly, multiple modification examples can be combined with each other as long as they do not technically conflict.

[0086] (Aspect of Disclosure) As is clear from the description of the embodiments and modifications as described above, at least the following aspects are disclosed in this specification. [Aspect 1] A wafer manufacturing method for obtaining a wafer (1) from an ingot (2) includes forming a release layer (25) at a depth corresponding to the thickness of the wafer from the surface by irradiating a laser beam having permeability with respect to one end surface (21) in the height direction of the ingot, which is release layer formation, peeling a wafer precursor (26), which is a portion between the surface and the release layer, from the ingot at the release layer, which is wafer peeling, and planarizing a main surface (32) of a plate-like peeled body (30) obtained by the wafer peeling, which is wafer planarization, and includes the release layer formation includes performing laser scanning in which the irradiation position (PR) of the laser beam on the surface is moved in a first direction (Ds) along the surface while irradiating the surface with the laser beam, and performing the laser scanning a plurality of times while changing the position in a second direction (Df) orthogonal to the first direction and along the surface, and forming a plurality of scanning lines (Ls), which are linear irradiation marks of the laser beam along the first direction, along the second direction to form the release layer, forming a plurality of the scanning lines by irradiating the surface with a plurality of the laser beams having different irradiation positions in the first direction and the second direction in one laser scanning, wafer manufacturing method. [Aspect 2] In Aspect 1, the release layer formation irradiates the surface with the laser beam such that the energy application density in the in-plane direction along the surface due to the irradiation of the laser beam is higher in the facet region (RF) than in the non-facet region (RN). [Aspect 3] In Aspect 1 or 2, The peeling layer formation is as follows: While moving the irradiation position in the first direction, a scanning line is formed across both ends of the surface in the first direction, and while moving the irradiation position in the direction opposite to the first direction, an irradiation mark is formed at the end of the surface in the first direction. [Viewpoint 4] In viewpoints 1 to 3, the peeling layer formation is as follows: a first scan in which a scanning line is formed across both ends of the surface in the first direction while moving the irradiation position in the first direction, and a second scan in which the distance from the surface of the condensing device (42) that irradiates the laser beam onto the surface is changed from the first scan, and while moving the irradiation position in the direction opposite to the first direction, a scanning line is formed across both ends of the surface in the first direction. [Viewpoint 5] In viewpoints 1 to 4, the ingot is a single-crystal SiC ingot having a c-axis (Lc) and a C-plane (Pc) orthogonal to each other, the c-axis is provided in a state where a central axis (L) orthogonal to the surface is inclined by an off-angle (θ) exceeding 0 degrees in an off-angle direction (Dθ), the wafer peeling is performed by applying a load in one direction at one end (23) of the ingot in the off-angle direction. [Viewpoint 6] In viewpoint 5, the one end of the ingot in the off-angle direction is the higher-side end on the C-plane when the posture of the ingot is set such that the surface is the upper surface. [Viewpoint 7] In viewpoint 5 or 6, the peeling layer formation is performed such that when the posture of the ingot is set such that the surface is the upper surface, the facet region (RF) is located on the lower side of the C-plane. [Viewpoint 8] In viewpoints 1 to 7, Measure the transmittance of the release body or the obtained wafer at a plurality of positions in the first direction and the second direction, Based on the measurement results of the transmittance, control the irradiation conditions of the laser beam at each of the plurality of positions in the first direction and the second direction. [Viewpoint 9] In viewpoint 8, Based on the transmittance, obtain the absorption coefficient of the laser beam, Based on the change tendency of the absorption coefficient in the depth direction of the ingot for each different position in the in-plane along the surface, determine the irradiation energy of the laser beam. [Viewpoint 10] In viewpoint 9, Based on the change tendency of the absorption coefficient in the depth direction of the ingot, obtain the change amount of the absorption coefficient in the depth direction, Based on the value obtained by adding or multiplying the absorption coefficient change amount to the previously obtained absorption coefficient, determine the irradiation energy of the laser beam. [Viewpoint 11] In viewpoints 9 and 10, Based on the absorption coefficient estimated value obtained based on the change amount between the previously obtained absorption coefficient and the absorption coefficient obtained the time before last, determine the irradiation energy of the laser beam. [Viewpoint 12] In viewpoints 9 to 11, Generate a first product (101) which is the release body or the wafer obtained from the ingot at one end side in the height direction, and a second product (102) which is the release body or the wafer obtained from the ingot at the other end side in the height direction, Obtain a first absorption coefficient which is the absorption coefficient in the first product and a second absorption coefficient which is the absorption coefficient in the second product, Use the higher value of the first absorption coefficient and the second absorption coefficient as the upper limit value of the absorption coefficient to determine the irradiation energy of the laser beam. [Viewpoint 13] In viewpoints 8 to 12, In a second region where the change in the absorption coefficient is greater than that in the first region, make the measurement pitch of the transmittance finer than that in the first region. [Viewpoint 14] In Viewpoint 13, the second region is a boundary region between the non-faceted region (RN) and the faceted region (RF). [Viewpoint 15] In Viewpoints 1 to 14, the plurality of laser beams include a first beam, a second beam, and a third beam that are arranged at different positions from each other in the second direction. [Viewpoint 16] In Viewpoint 15, the second beam is located between the first beam and the third beam in the first direction and the second direction. [Viewpoint 17] In Viewpoint 15, the first beam, the second beam, and the third beam are arranged in a V shape on the surface.

Explanation of Reference Numerals

[0087] 1 Wafer 2 Ingot 21 Ingot C-plane (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

1. A wafer manufacturing method for obtaining a wafer (1) from an ingot (2), comprising: forming a release layer (25) at a depth corresponding to the thickness of the wafer from the surface by irradiating a laser beam having permeability to one end surface (21) in the height direction of the ingot, i.e., release layer formation; releasing a wafer precursor (26), which is a portion between the surface and the release layer, from the ingot at the release layer, i.e., wafer release; flattening a main surface (32) of a plate-like release body (30) obtained by the wafer release, i.e., wafer flattening; wherein the release layer formation includes: measuring the transmittance of the obtained release body or the wafer at a plurality of positions in a first direction (Ds) along the surface and a second direction (Df) orthogonal to the first direction and along the surface; acquiring the absorption coefficient of the laser beam based on the measurement result of the transmittance; determining the irradiation energy of the laser beam at each of a plurality of irradiation positions (PR) of the laser beam on the surface based on the change tendency of the absorption coefficient in the depth direction of the ingot for different positions in the in-plane direction along the surface; performing laser scanning a plurality of times while changing the position in the second direction, wherein the laser beam is irradiated on the surface while moving the irradiation position in the first direction, and forming a plurality of scanning lines (Ls), which are irradiation marks of the linear laser beam along the first direction, along the second direction to form the release layer; forming a plurality of the scanning lines by irradiating a plurality of laser beams having different irradiation positions in the first direction and the second direction on the surface in one laser scanning; A wafer manufacturing method.

2. A wafer manufacturing method for obtaining a wafer (1) from an ingot (2), comprising: forming a release layer (25) at a depth corresponding to the thickness of the wafer from the surface by irradiating a laser beam having permeability to one end surface (21) in the height direction of the ingot, i.e., release layer formation; releasing a wafer precursor (26), which is a portion between the surface and the release layer, from the ingot at the release layer, i.e., wafer release; flattening a main surface (32) of a plate-like release body (30) obtained by the wafer release, i.e., wafer flattening; wherein the release layer formation includes: While moving the irradiation position (PR) of the laser beam on the surface in a first direction (Ds) along the surface, laser scanning is performed to irradiate the surface with the laser beam. The laser scanning is performed a plurality of times while changing the position in a second direction (Df) orthogonal to the first direction and along the surface. By forming a plurality of scanning lines (Ls), which are irradiation marks of the linear laser beam along the first direction, along the second direction, the release layer is formed. In one laser scanning, a plurality of the laser beams having different irradiation positions in the first direction and the second direction are irradiated onto the surface, thereby forming a plurality of the scanning lines. The plurality of laser beams include a first beam, a second beam, and a third beam that are arranged at mutually different positions in the second direction. The first beam, the second beam, and the third beam are arranged in a V shape on the surface. Wafer manufacturing method.

3. For the release layer formation, the laser beam is irradiated onto the surface such that the energy application density in the in-plane direction along the surface due to the irradiation of the laser beam is higher in the facet region (RF) than in the non-facet region (RN). The wafer manufacturing method according to claim 1 or 2.

4. The release layer formation is as follows. While moving the irradiation position in the first direction, scanning lines are formed across between both ends in the first direction of the surface, and while moving the irradiation position in the direction opposite to the first direction, irradiation marks are formed only at the ends in the first direction of the surface. The wafer manufacturing method according to claim 1 or 2.

5. The release layer formation is as follows. A first scan in which scanning lines are formed across between both ends in the first direction of the surface while moving the irradiation position in the first direction, and a second scan in which the distance of a condensing device (42) that irradiates the surface with the laser beam from the surface is changed from the first scan, and scanning lines are formed across between both ends in the first direction of the surface while moving the irradiation position in the direction opposite to the first direction. The wafer manufacturing method according to claim 1 or 2.

6. The ingot is a single crystal SiC ingot having a c-axis (Lc) and a C-plane (Pc) orthogonal to each other. The c-axis is provided in a state where the central axis (L) perpendicular to the surface is inclined by an off-angle (θ) exceeding 0 degrees in the off-angle direction (Dθ). The wafer peeling is performed 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 1 or 2.

7. One end of the ingot in the off-angle direction is the higher side end on the C-plane when the posture of the ingot is set such that the surface becomes the upper surface. The wafer manufacturing method according to claim 6.

8. When the posture of the ingot is set such that the surface becomes the upper surface, the peeling layer formation is performed so that the facet region (RF) is located on the lower side of the C-plane. The wafer manufacturing method according to claim 6.

9. Measure the transmittance of the peeling body or the obtained wafer at a plurality of positions in the first direction and the second direction. Based on the measurement results of the transmittance, control the irradiation conditions of the laser beam at each of the plurality of positions. The wafer manufacturing method according to claim 2.

10. Based on the change tendency of the absorption coefficient in the depth direction of the ingot, obtain the change amount of the absorption coefficient in the depth direction. Based on the value obtained by adding or multiplying the absorption coefficient change amount to the previously obtained absorption coefficient, determine the irradiation energy of the laser beam. The wafer manufacturing method according to claim 1.

11. Based on the absorption coefficient estimated value obtained based on the change amount between the previously obtained absorption coefficient and the absorption coefficient obtained the time before last, determine the irradiation energy of the laser beam. The wafer manufacturing method according to claim 1.

12. Generate a first product (101) which is the peeling body or the wafer obtained from the ingot at one end side in the height direction, and a second product (102) which is the peeling body or the wafer obtained from the ingot at the other end side in the height direction. Obtain a first absorption coefficient which is the absorption coefficient in the first product and a second absorption coefficient which is the absorption coefficient in the second product. Determine the irradiation energy of the laser beam with the higher value of the first absorption coefficient and the second absorption coefficient as the upper limit value of the absorption coefficient. The wafer manufacturing method according to claim 1.

13. In a second region where the change in the absorption coefficient is greater than that in the first region, making the measurement pitch of the transmittance finer than that in the first region, The wafer manufacturing method according to claim 1.

14. The second region is a boundary region between a non-faceted region (RN) and a faceted region (RF). The wafer manufacturing method according to claim 13.

15. The plurality of laser beams include a first beam, a second beam, and a third beam arranged at mutually different positions in the second direction. The wafer manufacturing method according to claim 1.

16. The second beam is located between the first beam and the third beam in the first direction and the second direction. The wafer manufacturing method according to claim 15.

17. The first beam, the second beam, and the third beam are arranged in a V shape on the surface. The wafer manufacturing method according to claim 15.

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