CN118402043A

CN118402043A - Wafer manufacturing method

Info

Publication number: CN118402043A
Application number: CN202280081607.XA
Authority: CN
Inventors: 安田浩一朗; 高木亮汰; 河津知树; 野村飒大; 白井秀彰; 巴赫曼·苏丹尼; 傍岛骏介
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2021-12-08
Filing date: 2022-11-08
Publication date: 2024-07-26

Abstract

A laser beam (B) having permeability is irradiated to a surface on one end side in the height direction of the ingot, whereby a release layer is formed at a depth corresponding to the thickness of the wafer. In the formation of the peeling layer, laser scanning is performed a plurality of times while changing the position in the second direction (Df), the laser scanning being laser scanning in which the laser beam is irradiated while moving the irradiation Position (PR) of the laser beam in the first direction (Ds). A plurality of laser beams (B1, B2, B3) having different irradiation positions in the first direction and the second direction are irradiated by one laser scanning.

Description

Wafer manufacturing method

Cross Reference to Related Applications

The present application claims priority from Japanese patent application No. 2021-199576 to application No. 12/8/2022 and Japanese patent application No. 2022-128099 to application No. 8/10/2021, the contents of which are incorporated herein by reference in their entirety.

Technical Field

The present disclosure relates to wafer fabrication methods.

Background

Patent document 1 provides a wafer generation method capable of efficiently generating wafers from ingots. Specifically, the wafer generation method described in patent document 1 includes a separation start point forming step and a wafer peeling step. The separation start point forming step positions a converging point of a laser beam having a wavelength that is transparent to the hexagonal single crystal ingot to a depth from the surface corresponding to the thickness of the wafer to be produced, and irradiates the surface with the laser beam by moving the converging point relative to the ingot. Thus, a modified layer parallel to the surface and a crack extending from the modified layer are formed, and a separation origin is formed. The wafer separation step separates a plate-like object corresponding to the thickness of the wafer from the ingot from the separation start point, thereby producing a hexagonal single crystal wafer. In the separation start point forming step, the converging point of the laser beam is positioned at two or more positions at a predetermined interval in the direction of forming the off angle, and two or more linear modified layers are formed at the same time.

Patent document 1: japanese patent No. 6482389

In the method for producing a wafer described in patent document 1, a modified layer is simultaneously formed by forming each of a plurality of laser beams having different irradiation positions in the direction of the off angle. In this case, there is a possibility that the depth of each of the plurality of modified layers formed at the same time and having different positions in the direction in which the off angle is formed may vary. If the depth of the modified layer varies, a step is generated on the separation surface, and the grinding and polishing process is consumed more, or a separation failure is generated, which deteriorates the manufacturing efficiency.

Disclosure of Invention

The present disclosure has been made in view of the above-exemplified circumstances and the like. That is, the present disclosure provides, for example, a wafer manufacturing method having higher manufacturing efficiency than conventional methods.

According to one aspect of the present disclosure, a wafer manufacturing method is a method of obtaining a wafer from an ingot, comprising the following sequence, procedure, or process, i.e., comprising:

A peeling layer formed by irradiating a surface of one end side in a height direction of the ingot with a laser beam having permeability, and forming a peeling layer at a depth corresponding to a thickness of the wafer from the surface;

Wafer peeling, wherein the peeling layer peels a wafer precursor, which is a portion between the surface and the peeling layer, from the ingot; and

Wafer planarization, which planarizes the main surface of the plate-like peeled body obtained by peeling the wafer,

The peeling layer is formed by performing laser scanning on the surface a plurality of times while changing a position of the peeling layer in a second direction orthogonal to a first direction along the surface and along the surface, forming a scanning line which is a trace of irradiation of the laser beam in a plurality of lines along the first direction along the second direction, the laser scanning being a laser scanning in which the irradiation position of the laser beam on the surface is moved in the first direction while irradiating the surface with the laser beam,

A plurality of 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 by one laser scanning.

In such a wafer manufacturing method, first, the laser beam having permeability is irradiated to the surface of the one end side in the height direction of the ingot, and the release layer is formed at a depth corresponding to the thickness of the wafer from the surface. The formation of such a release layer is performed as follows. The laser beam is irradiated to the surface while moving the irradiation position of the laser beam on the surface in the first direction along the surface. That is, the laser beam is scanned in the first direction on the surface. The laser scanning is performed a plurality of times while changing a position on the surface in the second direction orthogonal to the first direction and along the surface. Thereby, the plurality of scanning lines, which are irradiation traces of the laser beam in the first direction, are formed along the second direction, thereby forming the peeling layer. Next, the wafer precursor is peeled off from the ingot at the peeling layer at a portion between the surface of the ingot and the peeling layer. Next, the wafer is obtained by flattening the main surface of the plate-like peeled body obtained by peeling the wafer precursor from the ingot.

In such a wafer manufacturing method, a plurality of laser beams having different irradiation positions in the first direction and the second direction are irradiated onto the surface by one laser scanning, thereby forming a plurality of scanning lines. This can shorten the cycle time for forming the release layer. One of the two adjacent laser beams included in the plurality of laser beams, which is located on the first direction side, is referred to as a "first beam" and the other is referred to as a "second beam". In this case, the first light beam travels in the first direction before the second light beam. In this case, the irradiation position of the second beam may overlap with the irradiation mark formed by the first beam and a crack formed around the irradiation mark. If the crack exists at the irradiation position of the second beam on the rear surface based on the irradiation trace of the first beam, the absorptivity of the second beam is improved. Therefore, the irradiation mark by the second beam after the irradiation mark by the first beam is easily generated at the depth substantially equal to the depth of the crack and the irradiation mark by the first beam before the irradiation mark. Thus, the two irradiation marks and the crack, which are formed at one time by the first beam and the second beam and are adjacent to each other in the second direction, are easily generated at substantially the same depth by the laser scanning at one time. That is, two scan lines constituting the peeling layer adjacent to each other in the second direction are easily generated at substantially the same depth.

In this way, in such a wafer manufacturing method, the variation in the depth of the scanning line constituting the peeling layer can be suppressed as much as possible. This can favorably suppress the level difference and the size of the irregularities on the release surface due to the release of the release layer, thereby reducing the grinding and polishing process consumption on the release surface, and favorably suppressing the occurrence of peeling failure. In addition, the cycle time when the release layer is formed can be shortened. Therefore, according to such a wafer manufacturing method, the manufacturing efficiency can be improved as compared with the conventional one.

In each column in the specification, a bracketed reference numeral may be added to each element. In this case, reference numerals are given to only one example of the correspondence between the elements and the specific configuration described in the embodiment described below. Accordingly, the present disclosure is not limited in any way by reference to the description of the reference numerals.

Drawings

Fig. 1 is a side view showing a schematic structure of a wafer, an ingot, and a separator in a wafer manufacturing method according to an embodiment of the present disclosure.

Fig. 2 is a schematic process diagram showing a wafer manufacturing method according to an embodiment of the present disclosure.

Fig. 3A is a side view showing a schematic structure of an ingot having undergone the step of forming a release layer shown in fig. 2.

Fig. 3B is a top view of the ingot shown in fig. 3A.

Fig. 4A is a schematic side view showing the step of forming a release layer shown in fig. 2, and a release layer forming apparatus used in the step.

Fig. 4B is a schematic front view showing the step of forming a release layer shown in fig. 2, and a release layer forming apparatus used in the step.

Fig. 5A is a schematic view showing a step of forming the release layer shown in fig. 4A and 4B.

Fig. 5B is a schematic diagram showing the step of forming the release layer shown in fig. 4A and 4B.

Fig. 6 is a schematic plan view showing the step of forming the release layer shown in fig. 4A and 4B.

Fig. 7 is a diagram showing the laser beams shown in fig. 4A and 4B enlarged in the vicinity of the focal point.

Fig. 8A is a schematic side view showing the step of forming the release layer shown in fig. 4A.

Fig. 8B is a schematic side view showing a step of forming a release layer in another example.

Fig. 9 is a schematic side view showing the step of forming the release layer shown in fig. 4A.

Fig. 10 is a schematic side view showing the step of forming the release layer shown in fig. 4A.

Fig. 11 is a schematic side view showing the wafer peeling step shown in fig. 2 and a peeling apparatus used in the step.

Fig. 12 is a plan view showing a modification of the arrangement of the plurality of laser beams shown in fig. 5A.

Fig. 13 is a plan view showing another modification of the arrangement of the plurality of laser beams shown in fig. 5A.

Fig. 14 is a schematic process diagram showing a wafer manufacturing method according to a modification.

Fig. 15 is a plan view showing an example of a method of setting a measurement position in the wafer optical measurement shown in fig. 14.

Fig. 16 is a plan view showing a scanning pattern of a measurement position in the wafer optical measurement shown in fig. 14.

Fig. 17 is a graph showing the change in the absorption coefficient based on the measurement position calculated from the transmittance measured by scanning the measurement position shown in fig. 16.

Fig. 18A is a different side cross-sectional view showing the position of generation of the modified layer in the step of forming the release layer, which is the laser dicing shown in fig. 14, based on transmittance.

Fig. 18B is a different side cross-sectional view based on transmittance showing the modified layer generation position in the release layer forming step, which is the laser dicing shown in fig. 14.

Fig. 18C is a different side cross-sectional view based on transmittance showing the modified layer generation position in the release layer forming step, which is the laser dicing shown in fig. 14.

Fig. 19 is a side cross-sectional view for explaining an example of a method of setting the irradiation condition of the laser beam in the step of forming the release layer, which is the laser dicing shown in fig. 14.

Fig. 20 is a plan view for explaining a method of deriving the absorption coefficient variation amount shown in expression (2).

Fig. 21A is a graph showing the change in absorption coefficient in the depth direction of the ingot at the in-plane center position shown in fig. 20.

Fig. 21B is a graph showing the change in absorption coefficient in the depth direction of the ingot at the first end position shown in fig. 20.

Fig. 21C is a graph showing the change in absorption coefficient in the depth direction of the ingot at the second end position shown in fig. 20.

Fig. 22 is a graph for explaining an example of the method of deriving the absorption coefficient.

Fig. 23 is a side view showing a first product and a second product produced for setting irradiation conditions of a laser beam in the release layer forming step, which is a laser dicing shown in fig. 14.

Fig. 24 is a graph showing the change in absorption coefficient when the measurement pitch in a part of the region is thinned by the wafer optical measurement shown in fig. 14.

Detailed Description

(Embodiment)

Embodiments of the present disclosure will be described below based on the drawings. Further, if various modifications applicable to one embodiment are inserted in the middle of a series of descriptions related to the embodiment, there is a concern that understanding of the embodiment will be hindered. Therefore, the description will be focused on the following without inserting the modification in the middle of the series of descriptions related to this embodiment.

(Structure of wafer and ingot)

Referring to fig. 1, a wafer 1 manufactured by the wafer manufacturing method according to the present embodiment is a wafer obtained by slicing a substantially cylindrical ingot 2 in a side view, and is formed into a substantially circular thin plate in a plan view. That is, the wafer 1 and the ingot 2 have substantially cylindrical side surfaces or end surfaces surrounding the central axis L. The central axis L is a virtual straight line passing through the axial centers of the wafer 1 and the ingot 2 while being parallel to the substantially cylindrical side surfaces or end surfaces of the wafer 1 and the ingot 2. From the viewpoint of simplicity of illustration and description, illustration and description are omitted in the present specification with respect to a so-called orientation plane that is generally provided for the wafer 1 and the ingot 2.

In the present embodiment, the ingot 2 is a single crystal SiC ingot having c-axis Lc and (0001) plane Pc orthogonal to each other, and has an off angle exceeding 0 degrees. The c-axis Lc is a crystal axis represented by the direction index [0001 ]. (0001) The plane Pc is a crystal plane orthogonal to the C-axis Lc and is called "C-plane" in a strict crystallographic sense. The off angle θ is an angle formed between the central axis L and the c-axis Lc of the wafer 1 or the ingot 2, and is, for example, about 1 to 4 degrees. That is, the c-axis Lc in the wafer 1 and the ingot 2 is set in a state in which the central axis L is inclined to the off-angle direction dθ by an off-angle θ exceeding 0 degrees. The off-angle direction dθ is a direction in which a moving direction of a point on the central axis L on the side of the laser irradiation surface (i.e., upper surface or top surface in the figure) in the wafer 1 or the ingot 2 is mapped to the laser irradiation surface when the central axis L is rotated toward the c-axis Lc around the intersection of the central axis L and the c-axis Lc.

For simplicity of explanation, the right-handed XYZ coordinates are set as shown in fig. 1. In such right-handed XYZ coordinates, the off-angle direction dθ is the same direction as the positive X-axis direction. The X-axis and the Y-axis are parallel to the main surfaces of the wafer 1 and the ingot 2. The "main surface" is a surface of the plate-like object orthogonal to the plate thickness direction, and may be referred to as "upper surface", "bottom surface" or "plate surface". The "main surface" is a surface orthogonal to the height direction of the columnar material such as the ingot 2, and may be referred to as a "top surface" or a "bottom surface". The thickness direction of the wafer 1 and the height direction of the ingot 2 are parallel to the Z axis. Hereinafter, an arbitrary direction orthogonal to the Z axis may be referred to as an "in-plane direction".

Wafer 1 has a pair of main surfaces, wafer C surface 11 and wafer Si surface 12. In the present embodiment, the wafer 1 is formed such that the upper wafer C-plane 11 is inclined at an off-angle with respect to the (0001) plane Pc. Similarly, ingot 2 has a pair of main surfaces, i.e., ingot C surface 21 and ingot Si surface 22. The ingot 2 is formed with an ingot C-plane 21 as a top plane inclined by an off-angle with respect to a (0001) plane Pc. Hereinafter, an upstream end, which is one end of the ingot 2 in the departure angle direction dθ, is referred to as a first end 23, and a downstream end, which is the other end, is referred to as a second end 24. In fig. 1, the direction in which the wafer C-plane 11 and the ingot C-plane 21 face each other is indicated as the positive Z-axis direction.

In addition, ingot 2 has a facet region RF. The facet region RF can also be referred to as a "facet portion". The portion other than the facet region RF in the ingot 2 is hereinafter referred to as a non-facet region RN. Similarly, the non-facet region RN can also be referred to as a "non-facet region".

(Outline of wafer manufacturing method)

The wafer manufacturing method according to the present embodiment is a method for obtaining a wafer 1 from an ingot 2, and includes the following steps.

(1) A release layer forming step: by irradiating the ingot C surface 21, which is a main surface on one end side in the height direction of the ingot 2, with a laser beam having a predetermined degree of permeability to the ingot 2, the release layer 25 is formed at a depth corresponding to the thickness of the wafer 1 from the ingot C surface 21.

Here, the "predetermined degree of permeability" refers to a degree of permeability at which a converging point of the laser beam can be formed at a depth corresponding to the thickness of the wafer 1 inside the ingot 2. The "depth corresponding to the thickness of the wafer 1" is a dimension obtained by adding a thickness corresponding to predetermined processing consumption in a wafer planarization step or the like described later to the thickness (i.e., a target value of the thickness) of the wafer 1 as a finished product, and may be referred to as "depth corresponding to the thickness of the wafer 1".

(2) Wafer lift-off process: the wafer precursor 26 is peeled from the ingot 2 at a portion between the ingot C face 21, which is a laser light irradiation face, and the peeling layer 25 at the peeling layer 25.

Here, as expressed in the above-described "wafer peeling step", a plate-like object obtained by peeling the wafer precursor 26 from the ingot 2 can be referred to as a "wafer" in a social sense. However, in order to distinguish the final wafer 1 after the manufacture having the main surface with mirror-finished extension, such a plate-like object is hereinafter referred to as "peeled body 30".

The separator 30 has a pair of main surfaces, namely, a non-separation surface 31 and a separation surface 32. The non-release surface 31 is a surface on the side not constituting the release layer 25 before the wafer release step, and corresponds to the ingot C surface 21 before the release layer formation step and the wafer release step. The release surface 32 is a surface newly generated by the wafer release process, and constitutes the release layer 25 before the wafer release process. The release surface 32 has irregularities due to the roughness (i.e., the degree of grinding or polishing required) of the release layer 25 and the release of the wafer in the wafer release step.

(3) Wafer planarization process: by planarizing at least the release surface 32 out of the non-release surface 31 and the release surface 32 which are main surfaces of the release body 30, the final wafer 1 after production is obtained. In the wafer planarization step, ECMG and ECMP can be used in addition to general grinding and CMP. Furthermore, CMP is CHEMICAL MECHANICAL Polishing: the omission of chemical mechanical polishing. ECMG is Electro-CHEMICAL MECHANICAL GRINDING: the omission of electrochemical mechanical polishing. ECMP is Electro-CHEMICAL MECHANICAL Polishing: the omission of electrochemical mechanical polishing. The wafer planarization process can be performed by performing these plural types of planarization processes singly or in combination as appropriate.

(4) Ingot planarization step: the upper surface of the ingot 2 newly produced after the wafer precursor 26 is peeled off is planarized, that is, mirrored, so that it can be supplied again to the peeling layer forming process. In the ingot planarization step, ECMG and ECMP can be used in addition to general grinding and CMP. The ingot planarization process may be performed by performing these plural types of planarization processes singly or by appropriately combining them.

Fig. 2 is a process diagram showing an example of a typical implementation of the wafer manufacturing method according to the present embodiment. As shown in fig. 2, the epitaxial wafer 1 is completed by the following steps of the peeling body 30 peeled from the ingot 2 through the peeling layer forming step and the wafer peeling step.

Rough grinding of the release surface 32 to be the Si surface 12 of the wafer

ECMG grinding of the rough-ground release surface 32

ECMP grinding of the ECMG-ground release surface 32

Cleaning and rinsing

The ingot 2 remaining after the peeled body 30 is peeled from the ingot 2 through the peeling layer forming step and the wafer peeling step can be supplied again to the peeling layer forming step through the following steps.

Rough grinding of the ingot C-face 21 newly produced by the wafer peeling step

Refining of the rough-ground ingot C-face 21

Cleaning and rinsing

Hereinafter, each step will be described in detail with reference to fig. 1 and 2, as well as other drawings.

(Step of Forming a Release layer)

Fig. 3A and 3B show a schematic structure of the ingot 2 in a state where the release layer 25 and the wafer precursor 26 are formed in the release layer forming step. Fig. 4A and 4B show a schematic of the step of forming the release layer, and a schematic configuration of the release layer forming apparatus 40 used in such a step. The right-handed XYZ coordinates shown in fig. 3A to 4B are shown to match the right-handed XYZ coordinates shown in fig. 1.

Referring to fig. 3A and 3B, the peeling layer 25 is formed by forming a plurality of scanning lines Ls, which are irradiation traces of a linear laser beam along the X-axis, in the Y-axis direction. The scanning line Ls is a line in which the irradiation trace RM of the laser beam with respect to the ingot 2 is formed in a linear shape. In the present embodiment, the scanning line Ls is provided along the off-angle direction D. The plurality of scanning lines Ls are arranged in the line feed direction Df. The line feed direction Df is an in-plane direction orthogonal to the deviation angle direction dθ. That is, the feed direction Df is a direction orthogonal to the departure angle direction dθ and orthogonal to the height direction of the ingot 2.

Referring to fig. 4A and 4B, the peeling layer forming apparatus 40 includes a chuck table 41 and a light collecting device 42. The chuck table 41 is configured to hold the ingot 2 on the ingot Si surface 22 side as its bottom surface. Specifically, for example, the chuck table 41 includes an adsorption mechanism or the like for adsorbing the ingot Si surface 22 by air pressure or the like. As will be described later, the method of fixing the ingot 2 to the chuck table 41 is not limited to this method. The condensing device 42 is disposed so as to face the chuck table 41 in the beam axial direction, which is the irradiation direction of the laser beam B, and irradiates the spindle 2, which is the object to be processed fixed to the chuck table 41, with the laser beam B oscillated by a pulse laser oscillator, not shown. That is, the condensing device 42 is provided to irradiate the laser beam B from the upper surface of the ingot 2, that is, the ingot C-face 21 side toward the ingot 2. Specifically, the condensing device 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 from the ingot C surface 21 inside the ingot 2. The condensing device 42 may also be referred to as a "condenser", and includes an optical element (e.g., a lens) for forming a condensing point BP of the laser beam B at a predetermined position. The release layer forming apparatus 40 is configured to be capable of relatively moving the converging point BP of the laser beam B with respect to the ingot 2 at least in the in-plane direction, i.e., in the XY direction in the drawing. Here, the "in-plane direction" is a direction parallel to the upper surface of the ingot 2, i.e., the ingot C-plane 21.

The peeling layer forming apparatus 40 forms a scanning line Ls along the scanning direction Ds by "laser scanning" that scans the laser beam B in the scanning direction Ds (i.e., the first direction) on the ingot C face 21. That is, the "laser scanning" is to irradiate the laser beam B onto the ingot C surface 21 while moving the irradiation position PR of the laser beam B on the ingot C surface 21 as 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 thereto. Further, the peeling layer forming apparatus 40 forms the peeling layer 25 by performing laser scanning a plurality of times while changing the position in the line feed direction Df (i.e., the second direction), and forming a plurality of scanning lines Ls along the line feed direction Df. The line feed direction Df and the scanning direction Ds are in-plane directions (i.e., directions along the surface 21 of the ingot C) and are mutually orthogonal directions.

In the present embodiment, the peeling layer forming apparatus 40 scans the laser beam B on the ingot C surface 21 by relatively moving the chuck table 41 on which the ingot 2 is placed in the scanning direction Ds with respect to the condensing apparatus 42, and forms the scanning line Ls along the scanning direction Ds. After performing one laser scan, the peeling layer forming apparatus 40 moves the chuck table 41 by a predetermined amount relative to the light collecting apparatus 42 in the line feed direction Df. Then, the peeling layer forming device 40 scans the laser beam B again by relatively moving the chuck table 41 in the scanning direction Ds (i.e., the same direction as or opposite to the previous laser scanning) with respect to the condensing device 42 to form the scanning line Ls. In this way, the peeling layer forming apparatus 40 scans the laser beam B over substantially the entire width in the line feed direction Df, thereby forming a plurality of scanning lines Ls along the line feed direction Df. Thus, the peeling layer 25 is formed by providing a plurality of scanning lines Ls along the line feed direction Df. In addition, a wafer precursor 26 to be the wafer 1 in the future is formed on the ingot C surface 21 side compared to the release layer 25. As described above, in the present embodiment, the light collecting device 42 is fixedly provided in the in-plane direction, while the chuck table 41 for supporting the ingot 2 is provided so as to be moved at least in the in-plane direction by a scanning device such as an electric table device, not shown. On the other hand, as will be described later, the present disclosure is not limited to such a mode. That is, for example, there may be an embodiment in which the chuck table 41 for supporting the ingot 2 is fixedly provided in the in-plane direction, and the light collecting device 42 is movably provided in the in-plane direction by a scanning device not shown. However, in either of these modes, it appears to be apparent that the laser beam B or the irradiation position PR thereof moves in the in-plane direction on the main surface of the ingot 2, or that the laser beam B or the condensed point BP thereof moves in the in-plane direction within the ingot 2. For this reason, for simplicity of explanation, the explanation may be given below as to whether the laser beam B or the irradiation position PR thereof moves in the in-plane direction on the main surface of the ingot 2 or the laser beam B or the converging point BP thereof moves in the in-plane direction in the ingot 2. However, as will be described later, the present disclosure is not limited to such a mode.

As shown in fig. 4A and 4B, in the present embodiment, a plurality of laser beams B having different irradiation positions PR in the scanning direction Ds and the line feed direction Df are irradiated onto the ingot C surface 21 by one laser scanning. Specifically, as shown in fig. 5A and 5B, the irradiation position PR on the ingot C surface 21 is shifted along the scanning direction Ds by a plurality of laser beams B (i.e., the first beam B1 and the like) which are arranged obliquely to both the scanning direction Ds and the line feed direction Df in a plan view. Thereby, a plurality of scanning lines Ls are formed by one laser scanning. Therefore, the cycle time in the peeling layer forming process can be reduced satisfactorily.

In fig. 4A, 4B, and 5A, three examples of the laser beams B are illustrated as the plurality of laser beams B. However, this example is an example for reasons of simplification of the drawing, and the number of laser beams B is not particularly limited. However, for simplicity of explanation, the explanation will be continued below with the first beam B1, the second beam B2, and the third beam B3 being included at least as a plurality of laser beams B. The first beam B1 of the first, second and third beams B1, B2 and B3 is located at the forefront, i.e., closest to the scanning direction Ds side. On the other hand, the third beam B3 is located rearmost. The second light beam B2 is located between the first light beam B1 and the third light beam B3 in the scanning direction Ds and the line feed direction Df.

As shown in fig. 5A, the first light beam B1 travels in the scanning direction Ds before the second light beam B2. By irradiation with the first beam B1, as shown in fig. 5B, an irradiation affected area RA is generated at a predetermined depth from the ingot C surface 21 as the laser irradiation surface. The irradiation affected area RA includes an irradiation trace RM composed of a modified area formed by separating SiC into Si and C by irradiation of the laser beam B, and a crack C extending from such irradiation trace RM to the periphery thereof along the (0001) plane Pc. Therefore, the irradiation position PR of the second light beam B2 can overlap at least the slit C in the irradiation affected area RA formed by the previous first light beam B1 in the in-plane direction. If there are irradiation marks RM and cracks C included in the irradiation affected area RA of the previous first beam B1 at the irradiation position PR of the subsequent second beam B2, the absorptivity of the second beam B2 is improved by such irradiation affected area RA. Therefore, the irradiation trace RM by the second light beam B2 at the rear is easily generated at the depth substantially the same as the depth of the irradiation affected area RA by the first light beam B1 at the front. The same applies to the relationship between the second beam B2 and the third beam B3. As a result, three irradiation marks RM or irradiation affected areas RA adjacent to each other in the line feed direction Df, which are formed at one time by one laser scanning of the first to third light fluxes B1 to B3, are easily generated at substantially the same depth. That is, a plurality of scanning lines Ls constituting the peeling layer 25 adjacent in the line feed direction Df are easily generated at substantially the same depth.

As described above, in the present embodiment, the variation in the depth of the scanning line Ls, which is the irradiation trace RM constituting the release layer 25, can be suppressed as much as possible. This can favorably suppress the level difference and the size of the irregularities on the release surface 32 caused by the release of the release layer 25, and can reduce the grinding and polishing process consumption on the release surface 32, or favorably suppress the occurrence of peeling failure. In addition, the cycle time when the peeling layer 25 is formed can be shortened. Therefore, according to the present embodiment, the manufacturing efficiency can be improved as compared with the conventional one.

Fig. 6 shows a trajectory of the relative movement of the center position with respect to the ingot 2 in the in-plane direction of the condensing device 42. The "center position in the in-plane direction of the condensing device 42" is typically, for example, the center position of the arrangement of the plurality of laser beams B. As shown in fig. 4A and 6, in the present embodiment, the orientation of the ingot 2 is set such that the facet region RF is located on the "lower off angle side", and the laser beam B is irradiated from the C-plane side, thereby performing the peeling layer forming step. The "lower off angle side" refers to the side on which the inclination on the C-plane, i.e., the (0001) plane Pc is lower when the posture of the ingot 2 is set such that the ingot C-plane 21 as one main surface is the upper surface. On the other hand, the "side with a high off angle" refers to the side with a high inclination on the C-plane, i.e., the (0001) plane Pc when the posture of the ingot 2 is set such that the ingot C-plane 21 is the upper plane.

As will be described later, by applying a unidirectional load for peeling the wafer precursor 26 from the ingot 2 to one end of the ingot 2 on the side where the "off angle is high", extremely good wafer peeling is achieved. Here, an example of a virtual case in which the attitude of the ingot 2 is set so that the facet region RF is located on the "high off angle side" and the laser beam B is irradiated from the Si surface side, and then a unidirectional load is applied to one end of the ingot 2 on the "high off angle side" will be examined. In this regard, the end portion of the ingot 2 near the facet region RF is not easily cracked. In this way, in such a virtual example, the peeling start position is an end portion near the facet region RF where cracking is unlikely to occur, and therefore there is a possibility that the success rate of the wafer peeling process is low. In contrast, in the present embodiment, the attitude of the ingot 2 is set such that the facet region RF is located on the "side with a low off angle", the laser beam B is irradiated from the C-plane side, and then a unidirectional load is applied to one end of the ingot 2 on the "side with a high off angle". In this case, the peeling start position is a portion farther from the facet region RF where cracking is relatively easy to occur. Therefore, according to the present embodiment, the success rate of the wafer separation process is improved.

However, the intensity of the laser beam B reaching the converging point BP of the non-facet region RN is known to be stronger than the facet region RF. Therefore, in the present embodiment, in the release layer forming step, the laser beam B is irradiated onto the main surface of the ingot 2 so that the energy application density of the irradiation of the laser beam B in the facet region RF is higher than that in the non-facet region RN. The "energy application density" referred to herein is the energy application density in the plane along the main surface of the ingot 2. The following methods can be used alone or in combination. Specifically, for example, in the facet region RF, the output of the laser beam B is increased compared to the non-facet region RN. Or for example, the laser beam B is irradiated onto the main surface of the ingot 2 so that the irradiation frequency of the laser beam B in the facet region RF is increased compared to the non-facet region RN. More specifically, for example, in the facet region RF, the repetition frequency of the laser beam B is increased, or the scanning speed is decreased in a state where the repetition frequency is constant, as compared with the non-facet region RN, so that the irradiation interval in the scanning direction Ds is narrowed. When the output is higher in the facet region RF than in the non-facet region RN, the output in the facet region RF is preferably 1.5 times the output in the non-facet region RN. When the irradiation interval in the scanning direction Ds or the line feed direction Df is made narrower in the facet region RF than in the non-facet region RN, the irradiation interval in the facet region RF is preferably 2/5 of the irradiation interval in the non-facet region RN. Or, for example, irradiation of the laser beam B for the facet region RF is performed separately from irradiation of the laser beam B for the entire region including the facet region RF and the non-facet region RN. In addition, in the irradiation of the laser beam B to the facet region RF, the laser beam B may be irradiated to a region close to the facet region RF in the non-facet region RN.

According to the release layer forming step of the present embodiment, the release layer 25 can be formed well over the entire region including the facet region RF and the non-facet region RN. In particular, the separation layer 25 for the facet region RF can be formed in the same manner as the non-facet region RN without using the adjustment of the distance in the Z-axis direction between the light converging device 42 on the irradiation side of the laser beam B and the chuck table 41 supporting the ingot 2. Therefore, according to the present embodiment, the manufacturing efficiency can be improved as compared with the conventional one.

Referring to fig. 4A and 6, in the peeling layer forming step, an outgoing scan Sc1 in which the irradiation position PR in the case where 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 in the case where the laser beam B is irradiated moves in the opposite direction to the off-angle direction dθ on the main surface of the ingot 2 are generated. That is, in the forward scan Sc1, the scan direction Ds and the off-angle direction dθ are the same direction. In contrast, in the loop scan Sc2, the scan direction Ds and the off-angle direction dθ are opposite to each other. The outgoing scan Sc1 and the return scan Sc2 are alternately performed.

The relative position of the light collecting device 42 with respect to the ingot 2 is moved by a predetermined amount in the line feed direction Df from the end of one forward scan Sc1 to the start of the next forward scan Sc 1. However, the relative position of the condenser 42 in the line feed direction Df may or may not be shifted from the end of the one-pass scan Sc1 to the start position of the loop scan Sc2 immediately after the end of the one-pass scan. The same applies to the period from the end of the primary loop scan Sc2 to the start of the next forward scan Sc 1. The relative movement amount in the line feed direction Df of each stage can be appropriately set according to the irradiation condition of the laser beam B, and the like.

In the forward scan Sc1, the laser beam B is irradiated over the entire width of the ingot 2 in the scan direction Ds. That is, in the forward scanning Sc1, the irradiation position PR is moved in the scanning direction Ds, which is the same direction as the departure angle direction dθ, on the main surface of the ingot 2, and the laser beam B is irradiated onto the main surface of the ingot 2. Thereby, a scanning line Ls is formed between both ends in the scanning direction Ds of the ingot 2. In contrast, in the loop scan Sc2, the laser beam B may be irradiated over the entire width of the ingot 2 in the scan direction Ds, or the laser beam B may not be irradiated over the entire width of the ingot 2 in the scan direction Ds. Alternatively, in the loop scan Sc2, the laser beam B may be irradiated to a part of the entire width of the ingot 2 in the scan direction Ds.

Specifically, for example, in the loop scan Sc2, only the facet region RF and the peripheral portion thereof may be irradiated with the laser beam B. Thus, the release layer 25 can be favorably formed over the entire region including the facet region RF and the non-facet region RN. Alternatively, for example, in the loop scan Sc2, only the end of the ingot 2 in the scan direction Ds may be irradiated with the laser beam B. In this case, in the loop scan Sc2, the irradiation position PR is moved in the scan direction Ds, which is the direction opposite to the off-angle direction dθ, on the main surface of the ingot 2, and a scan line Ls is formed at the end in the scan direction Ds of the ingot 2. This can favorably promote the start of the separation in the wafer separation step, and the success rate of the wafer separation step can be improved. In the loop scan Sc2, the laser beam B may be irradiated only to the facet region RF and the peripheral portion thereof and the end portion of the ingot 2 in the scan direction Ds.

As shown in fig. 7, in the present embodiment, the laser beam B has an intensity distribution such that the intensity of the laser beam B is increased at the outer peripheral portion than the central portion in the beam radial direction, which is the direction extending radially from the axial center thereof. Specifically, the laser beam B has a beam shape that is annular, i.e., hollow, at the front side of the converging point BP, and is converged in a spot shape at the converging point BP. At the condensed point BP, the laser beam B has the smallest beam diameter, i.e., condensed diameter dc. The intersection range RX shown in fig. 7 is a predetermined range around the converging point BP in the beam axis direction, in which the peripheral portions of the laser beam B having high intensity are superimposed.

Thus, the peeling layer forming apparatus 40 irradiates the ingot 2 with the annular laser beam B. Such a ring-shaped laser beam B and a device for generating such a laser beam B and irradiating the workpiece are known or well known at the time of application of the present application (for example, refer to japanese patent application laid-open publication No. 2006-130691, japanese patent application laid-open publication No. 2014-147946, and the like). Therefore, in the present specification, the details of the generation device and the generation method of the laser beam B will be omitted.

Fig. 8A shows the state in which the irradiation affected area RA including the irradiation trace RM is formed by the annular laser beam B of the present embodiment. Fig. 8B shows, as another example different from the present embodiment, a case where an irradiation affected area RA including an irradiation trace RM is formed by a laser beam B which is not annular, i.e., solid.

As shown in fig. 8B, in the case where the solid laser beam B is used, there is a possibility that irradiation mark RM, which is a modified region formed by dividing SiC into Si and C by irradiation of the laser beam B, is generated at a depth different from the condensed point BP. Therefore, the depth of the irradiation affected area RA composed of the irradiation trace RM and the crack C that progresses from such irradiation trace RM may be different from the depth of the converging point BP. Specifically, for example, the energy application density by the irradiation of the laser beam B may be increased to such an extent that the irradiation mark RM can be generated at a position shallower than the converging point BP. In this way, the irradiation mark RM may be generated at a position shallower than the condensed point BP. The depth of generation of the irradiation trace RM may vary due to variations in irradiation energy of the laser beam B, variations in refractive index of the ingot 2, variations in optical system in the condensing device 42, and the like. The area where the irradiation trace RM may be generated is shown as a modifiable range RC in the drawing. The irradiation trace RM corresponds to the "modified layer" in patent document 1.

In contrast, as shown in fig. 8A, when the annular laser beam B is used, the application density of the energy by the irradiation of the laser beam B is increased to a depth at which the irradiation mark RM is generated to be limited to the vicinity of the converging point BP. That is, for example, as in the case of using the solid laser beam B, it is not easy to increase the application density of the energy based on the irradiation of the laser beam B at a position shallower than the condensed point BP to such an extent that the irradiation mark RM can be generated. Thereby, the irradiation trace RM is stably generated at a depth in the vicinity of the converging point BP. That is, unlike the case where the solid laser beam B is used, the modifiable range RC is limited to a narrow depth range centered on the depth of the converging point BP. Therefore, the variation in the depth of the irradiation trace RM can be favorably suppressed. In other words, the release layer 25 can be formed as thin as possible, and the processing consumption in grinding or polishing after the release can be reduced satisfactorily. Therefore, according to the present embodiment, the manufacturing efficiency can be improved as compared with the conventional one.

However, in the method described in patent document 1, the laser scanning direction is a direction orthogonal to the "direction forming the off angle (i.e., the off angle direction dθ in fig. 1, 3A, and the like)". Thus, the crack is unstable and the material loss increases. In contrast, in the present embodiment, as shown in fig. 4A, the scanning direction Ds, which is the moving direction of the converging point BP of the laser beam B inside the ingot 2, is parallel to the departure 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 scans the laser beam B by relatively moving the light condensing apparatus 42 with respect to the ingot 2 in the scanning direction Ds parallel to the off-angle direction dθ, thereby forming the scanning line Ls along the off-angle direction D. As a result, as shown in fig. 9 and 10, the irradiation trace RM and the crack C are formed along the (0001) plane Pc. This stabilizes the crack in the release layer 25 in the wafer release process, and can reduce the material loss satisfactorily. In addition, since the processing consumption in the wafer planarization process can be reduced well, the process time can be reduced as much as possible. Therefore, according to the present embodiment, a wafer manufacturing method having higher manufacturing efficiency than the conventional one can be provided.

Fig. 9 shows an example in which the scanning direction Ds and the off-angle direction dθ are in the same direction. Fig. 10 shows an example in which the scanning direction Ds and the off-angle direction dθ are opposite directions. That is, in the example shown in fig. 9, as shown in fig. 4A, when the posture of the ingot 2 is set such that the ingot C surface 21 is the upper surface, the irradiation position PR is moved from the higher side to the lower side of the (0001) surface Pc by laser scanning. In contrast, in the example shown in fig. 10, when the posture of the ingot 2 is set such that the ingot C surface 21 is the upper surface, the irradiation position PR is moved from the lower side to the higher side of the (0001) surface Pc by laser scanning.

For example, it is assumed that the irradiation mark RM and the crack C, which are irradiation influence areas RA, are not present around the irradiation position PR in the in-plane direction. In such a case, irradiation marks RM are easily generated at a depth in the vicinity of the converging point BP by irradiation of the laser beam B. On the other hand, in reality, the laser beam B moves in the scanning direction Ds while generating the irradiation trace RM and the crack C one by one. Therefore, the above-described situation occurs mainly when the irradiation trace RM corresponding to the start point of the scanning line Ls is formed at the first time of one laser scanning. As a result, in most cases in laser scanning, there is a situation in which the irradiation influence area RA exists around the irradiation position PR in the in-plane direction.

That is, as shown in fig. 9 and 10, the irradiation influence area RA formed previously (for example, immediately before) is generally present at the current irradiation position PR. In this way, in such irradiation affected area RA, the absorptivity of the laser beam B increases. In addition, such an irradiation influence area RA is formed along the (0001) plane Pc. Therefore, the irradiation trace RM is liable to develop along the (0001) plane Pc by laser scanning.

Here, in the example shown in fig. 9, when the irradiation trace RM is developed along the (0001) plane Pc in the scanning direction Ds by laser scanning, it is formed at a position gradually deepened so as to be gradually distant from the condensed point BP. In this way, the energy application density of the laser beam B irradiated this time may not be increased to such an extent that a new irradiation mark RM can be generated at substantially the same depth as the irradiation mark RM formed immediately before. In this case, the irradiation trace RM cannot further develop along the (0001) plane Pc. Thus, as shown in fig. 9, a newly formed irradiation trace RM is formed at a depth in the vicinity of the converging point BP of the laser beam B irradiated this time. That is, a step is generated between the irradiation trace RM formed immediately before and the irradiation trace RM formed this time.

On the other hand, in the example shown in fig. 10, when the irradiation trace RM is advanced in the scanning direction Ds along the (0001) plane Pc by laser scanning, it is formed at a position gradually shallower so as to be gradually distant from the converging point BP. If the energy application density of the laser beam B irradiated at this time is not increased to such an extent that a new irradiation mark RM can be generated at substantially the same depth as the irradiation mark RM formed immediately before, the irradiation mark RM cannot further develop along the (0001) plane Pc. Thus, as shown in fig. 10, a newly formed irradiation trace RM is formed at a depth in the vicinity of the converging point BP of the laser beam B irradiated this time. However, in the example shown in fig. 10, unlike the example shown in fig. 9, the direction of the irradiation trace RM is a direction closer to the light source side of the laser beam B, i.e., the laser irradiation surface side of the ingot 2. Thus, in the example shown in fig. 10, the irradiation trace RM is likely to develop longer than in the example shown in fig. 9. Therefore, in the example shown in fig. 10, compared with the example shown in fig. 9, the step difference generated between the irradiation trace RM formed immediately before and the irradiation trace RM formed this time increases.

In this way, by moving the irradiation position PR in the laser scanning from the higher side to the lower side in the C-plane by making the scanning direction Ds and the off-angle direction dθ the same, the step difference between the irradiation mark RM formed immediately before and the irradiation mark RM formed this time can be reduced. This enables the release layer 25 to be formed as thin as possible, and therefore, the processing consumption in grinding and polishing after the release can be reduced satisfactorily. Therefore, according to this aspect, the manufacturing efficiency can be further improved than in the prior art.

(Wafer peeling step)

Fig. 11 shows a schematic of a wafer peeling step and a peeling apparatus 50 used in such a step. Further, the right-hand XYZ coordinates shown in fig. 11 are shown as matching the right-hand XYZ coordinates shown in fig. 1.

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

The support table 51 is provided to support the ingot 2 from below. Specifically, the support table 51 has a plurality of suction holes, not shown, opened to the upper support suction surface 51a, and the ingot Si surface 22 is sucked 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 as both ends in the deviation angle direction dθ. The second table end 51c, which is an end on one side (i.e., 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 toward the off-angle direction D. That is, as shown in fig. 11, the support table 51 is formed in a trapezoidal shape having a lower bottom longer than an upper bottom in a side view.

The peeling pad 52 is provided above the support table 51 so as to be capable of approaching and separating from the support table 51 along the Z axis in the drawing. That is, the stripping device 50 is configured such that the support table 51 and the stripping pad 52 are relatively movable in the height direction of the ingot 2. The release pad 52 has a plurality of suction holes, not shown, opened to a pad suction surface 52a as a bottom surface thereof, and sucks the ingot C surface 21 to the pad suction surface 52a by air pressure. The release pad 52 has a first pad end 52b and a second pad end 52c as both end portions in the deviation angle direction dθ. The second pad end portion 52c, which is an end portion on one side (i.e., left side in the drawing) in the off-angle direction dθ, has a pad end face 52D. The pad end surface 52D is formed in an inclined surface shape that decreases toward the off-angle direction dθ. That is, as shown in fig. 11, the peeling pad 52 is formed in a trapezoid shape having a lower bottom shorter than an upper bottom in a side view. The pad end surface 52d is provided at a position corresponding to (i.e., directly above) the table base end surface 51 d. Hereinafter, a state in which the ingot C surface 21 is fixed by being adsorbed to the peeling pad 52 and the ingot Si surface 22 is fixed by being adsorbed to the support table 51, and the ingot 2 is clamped between the support table 51 and the peeling pad 52 will be referred to as a "clamped state".

The driving member 53 is provided to apply an external force to at least one of the support table 51 and the peeling pad 52 to move the support table 51 and the peeling pad 52 relative to each other in the height direction of the ingot 2 in the clamped state. Specifically, the driving member 53 has a first driving end surface 53a and a second driving end surface 53b. The first driving end surface 53a is formed in an inclined surface shape that decreases toward the off-angle direction dθ. In more detail, the first driving end surface 53a is disposed parallel to the pad end surface 52 d. The second driving end surface 53b is formed in an inclined surface shape that rises toward the deviation angle direction dθ. In more detail, the second driving end surface 53b is disposed parallel to the table base end surface 51 d. In addition, the driving member 53 is provided such that in the clamped state, the first driving end surface 53a abuts against the pad end surface 52d and the second driving end surface 53b abuts against the table base end surface 51 d. That is, as shown in fig. 11, the driving member 53 is formed in a shape in which a trapezoid having a longer lower base than an upper base is rotated clockwise by 90 degrees in a side view. The driving means 53 is configured to drive the ingot 2 in the direction along the upper side of the height direction of the ingot 2 and/or in the direction approaching the ingot 2, that is, in the off-angle direction dθ by a driving method not shown. That is, the driving member 53 is provided to drive in the upward and/or yaw angle direction dθ so that a moment acts on the ingot 2 with the second pad end portion 52c as the force point FP and the first end 23 as the fulcrum PP and the action point WP.

The wafer peeling step of peeling the wafer precursor 26 from the ingot 2 includes a stage fixing step, a clamping step, and a peeling force applying step. The stage fixing step is a step of fixing the ingot 2 to the support stage 51 by sucking the ingot Si surface 22 to the support sucking surface 51 a. The sandwiching step is a step of adsorbing the ingot C surface 21 to the pad adsorption surface 52a to fix the ingot 2 to the peeling pad 52 in a sandwiched state. The peeling force applying step is a step of applying a static or dynamic load to the second pad end portion 52c, which is the end portion of the peeling pad 52 on one side in the deviation angle direction dθ, as the force point FP in a sandwiched state, thereby applying a moment about the first end 23 as the fulcrum PP to the ingot 2. Specifically, the peeling force applying step is a step of driving the driving member 53 upward and/or in the off-angle direction dθ in the sandwiched state to push the second pad end portion 52c upward in 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 an interface.

As described above, in the present embodiment, the wafer separation step is performed by unidirectionally applying a load to 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 (i.e., the ingot C surface 21 in the example of fig. 11). In this way, a moment is applied to the ingot 2 with the first end 23 as the fulcrum PP and the point of application WP.

In this regard, in the wafer peeling step described in japanese patent No. 6678522, the working point WP and the fulcrum PP are 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 an interface, a much larger load is required than in the present embodiment. Further, since a load is applied to a wide range of the release layer 25, the release crack position is not specified, and there are cases where a part of the non-release portion and the wafer 1 to be taken out are damaged. Further, there is a problem that the peeling section becomes rough and the grinding cost increases. Therefore, in the comparative example, there is room for improvement in terms of reduction in load, yield, and the like.

In contrast, in the wafer peeling step of the present embodiment, in order to peel the wafer precursor 26 from the ingot 2 at the peeling layer 25, a load is unidirectionally applied to 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. In this way, a moment is applied to the ingot 2 with such one end as the fulcrum PP and the point of application WP. In this way, since the peeling proceeds from the crack formed at the end portion on the one end side of the ingot 2 in the off-angle direction dθ, the crack can stably proceed over the entire surface of the peeling layer 25 while reducing the additional load. Further, by stably setting the fracture occurrence position, the surface roughness of the peeling surface 32 and the ingot C surface 21 in the peeled body 30 generated after peeling can be reduced. In particular, by making the first end 23, which is the starting point of the fracture generation, be the end of the "side with higher off angle" in the off angle direction dθ, the fracture is smoothly generated, and the crack is further stabilized. Therefore, the occurrence of defects in the wafer separation step, and the processing consumption in grinding and polishing the ingot 2 and the separator 30 after the wafer separation step can be reduced satisfactorily. Therefore, according to the present embodiment, a wafer manufacturing method having higher manufacturing efficiency than the conventional method can be provided.

(Modification)

The present disclosure is not limited to the above embodiments. Accordingly, the above-described embodiments can be appropriately modified. Representative modifications will be described below. In the following description of the modification, differences from the above-described embodiment will be mainly described. In the embodiment and the modification, the same or equivalent parts are given the same reference numerals. Therefore, in the following description of the modification, the description of the above-described embodiment can be appropriately referred to as long as there is no technical contradiction or special additional description for the constituent elements having the same reference numerals as those of the above-described embodiment.

The present disclosure is not limited to the specific configurations shown in the above embodiments. That is, for example, the outer diameter and the planar shape (for example, the presence or absence of a so-called orientation flat) of the ingot 2, which is the wafer 1, are not particularly limited. The magnitude of the off angle θ is not particularly limited either. In the above embodiment, the wafer C-plane 11 and the ingot C-plane 21 do not coincide with the (0001) plane Pc, which is the C-plane in strict crystallographic sense. However, even in such a case, the expression "C-plane" is used because it is also allowed to be called "C-plane" in the social sense. The present disclosure is not limited to such an approach. That is, the wafer C-plane 11 and the ingot C-plane 21 may be identical to the (0001) plane Pc, which is the C-plane in strict crystallographic sense. In other words, the off angle θ may be 0 degrees.

The irradiation conditions and scanning conditions of the laser beam B are not limited to the specific examples shown in the above embodiments. That is, the arrangement of the plurality of laser beams B irradiated by one laser scanning, for example, can also be changed appropriately from the specific manner shown in fig. 5A. Specifically, for example, as shown in fig. 12, the first light beam B1, the second light beam B2, and the third light beam B3, which are arranged at mutually 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 light beam B1, the second light beam B2, and the third light beam B3 are arranged in this order along the line feed direction Df. The second light beam B2 is disposed at a position protruding in the scanning direction Ds from the first light beam B1 and the third light 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 zigzag shape. According to the arrangement of the plurality of laser beams B, the next modified layer is formed at intervals larger than the length of the crack generated by the modified layer processed in the preceding step, whereby the crack and the modified layer can be suppressed from interfering. In addition, for example, in the case where the laser beam B is irradiated to the entire width of the ingot 2 in the scanning direction Ds in the loop scan Sc2 as in the forward scan Sc1, the irradiation conditions may be different between them. Specifically, for example, in the forward scan Sc1 and the return scan Sc2, the distance (i.e., the irradiation distance) from the laser irradiation surface of the condensing device 42, that is, the ingot C surface 21 may be changed.

Depending on the irradiation conditions and scanning conditions of the laser beam B, the release surface 32 may have a surface state of a degree that can be ground or polished well even if it is directly supplied to the ECMG process. Therefore, the rough grinding step of the separation surface 32 shown in fig. 2 may be omitted. The same applies to rough grinding of the upper surface of the ingot 2 after the wafer separation step.

The release layer forming apparatus 40 shown in fig. 4A and 4B is a simplified schematic diagram for simply explaining the outline of the release layer forming process of the present disclosure. Therefore, the specific configuration of the release layer forming apparatus 40 actually realized industrially does not necessarily coincide with the configuration illustrated in fig. 4A and 4B. Specifically, for example, the chuck table 41 may be configured to hold the ingot 2 by a means other than an adsorption mechanism by air pressure. The chuck table 41 may be configured to be movable relative to the light collecting device 42 at least in the in-plane direction, that is, in the XY direction in the drawing. Alternatively, the peeling layer forming apparatus 40 may be provided with a scanning device configured to be able to move the converging point BP of the laser beam B relative to the ingot 2 in XYZ directions in the drawing. Alternatively, in the above embodiment, the separation layer forming apparatus 40 is configured such that the chuck table 41 for supporting the ingot 2 is movable at least in the in-plane direction, and the light collecting apparatus 42 is fixedly provided in the in-plane direction. However, the present disclosure is not limited to such a manner. That is, for example, the separation layer forming apparatus 40 may be configured such that a chuck table 41 for supporting the ingot 2 is fixedly provided in the in-plane direction, and the light converging apparatus 42 is moved in the in-plane direction by a scanning apparatus not shown. In the present disclosure, it is an arbitrary matter to adjust the distance in the Z-axis direction between the light converging device 42 on the irradiation side of the laser beam B and the chuck table 41 supporting the ingot 2, depending on whether the facet region RF is not the facet region RN or not. In addition, the specific configuration of the release layer forming apparatus 40 actually realized in industry can be appropriately changed from the exemplary configurations shown in fig. 4A and 4B.

In the above embodiment, the release layer 25 is formed on the ingot C-face 21 side by irradiating the laser beam B to the "C-face side irradiation" of the ingot C-face 21. However, the present disclosure is not limited to such a manner. That is, the present disclosure can also be applied to "Si surface side irradiation" in which the laser beam B is irradiated to the ingot Si surface 22 to form the peeling layer 25 on the ingot Si surface 22 side.

The peeling apparatus 50 shown in fig. 11 is a simplified schematic diagram for simply explaining the outline of the wafer peeling process of the present disclosure. Therefore, the specific configuration of the peeling apparatus 50 actually realized in industry does not necessarily match the configuration illustrated 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 by a method other than the adsorption mechanism by air pressure (for example, paraffin, an adhesive, or the like).

The transmittance and refractive index of the optical characteristics of the wafer 1 or the separator 30 measured at a plurality of positions in the scanning direction Ds and the line feed direction Df may be controlled based on the measurement results, and the irradiation conditions of the laser beam B next may be controlled. Fig. 14 shows a schematic of such a method. In the figure, "input/discharge" means a step of inputting and discharging the peeled body 30 or the ingot 2 as the workpiece. "laser dicing" means a step of forming a release layer. "lift-off" refers to a wafer lift-off process. The "rough grinding" means a step of rough grinding the main surface of the ingot 2 or the separator 30. For example, grinding materials of about #800 are used for rough grinding. "refining" refers to the process of refining a surface. For example, grinding materials of about #30000 are used for the fine grinding. The "wafer optical measurement" means a process of measuring the optical characteristics (i.e., transmittance and refractive index) of the polished separator 30 at a plurality of positions in the scanning direction Ds and the line feed direction Df. "ingot cleaning" means a process of cleaning the refined ingot 2. The left arrow of the block showing each step shows the flow of the process of the ingot 2, and the right arrow shows the flow of the process of the wafer 1 or the separator 30 which can be called "wafer" in the social sense.

Referring to fig. 14, first, ingot 2 is put into a wafer manufacturing apparatus including a peeling layer forming apparatus 40. Next, the ingot 2 to be put into the ingot is subjected to a peeling layer forming step by irradiation with the laser beam B. Next, in the wafer peeling step, the peeled body 30 is peeled from the ingot 2 having undergone the peeling layer forming step. The upper surface of the ingot 2 newly produced on the ingot 2 subjected to the wafer peeling step is flattened by rough grinding and fine grinding. Thereafter, the ingot 2 is cleaned, and then supplied again to the peeling layer forming step. When the height of the ingot 2 subjected to the separation layer forming step or the ingot cleaning step is smaller than a predetermined value, the ingot is discharged from the wafer manufacturing apparatus.

The peeled body 30 peeled from the ingot 2 by the wafer peeling step is subjected to rough grinding and fine grinding, and is subjected to optical measurement, that is, measurement of transmittance and refractive index. The measurement result is used for determining the irradiation condition (e.g., irradiation energy and/or irradiation distance) of the laser beam B in the next step of forming the release layer. That is, the irradiation conditions for each position in the in-plane direction of the ingot C surface 21 in the next peeling layer forming step are controlled based on the measurement results of the transmittance and the refractive index for each position in the in-plane direction of the wafer 1. This allows a change in the detailed irradiation conditions corresponding to the variation in the optical characteristics at each position in the in-plane direction, and thus, the material loss can be reduced. In particular, it is effective in the case where the ingot 2 has a facet region RF. The transmittance and refractive index may be measured only by one of them. Alternatively, the transmittance and refractive index of the finally obtained epitaxial wafer 1 may be measured. In addition, depending on the conditions of the rough grinding (e.g., in the case of ECMG), no fine grinding may be required. I.e. coarse grinding and fine grinding can be integrated.

Fig. 15 shows an example of a setting method of the optical measurement position in the body 100. The product 100 is a target for optical measurement, and corresponds to the wafer 1, or a peeled body 30 having a surface flattened to a predetermined degree after being peeled from the ingot 2. In this example, the optical measurement positions are set at a constant pitch (for example, 3 mm) in each of the X-axis direction (i.e., the first direction) and the Y-axis direction (i.e., the second direction). The X-axis direction is parallel to the scanning direction Ds shown in fig. 6 and the like. The Y-axis direction is parallel to the line feed direction Df shown in fig. 6 and the like. Here, as shown in fig. 16, when optical measurement is performed at a plurality of measurement positions on the measurement line Lx, the change in the absorption coefficient of the laser beam B accompanying the change in the measurement positions is as shown in fig. 17. The measurement line Lx is a virtual straight line parallel to the X axis passing through the center and the facet area RF in the in-plane direction of the generation body 100. The absorption coefficient is calculated by the following expression (1). In the following expression (1), α represents an absorption coefficient, D represents a workpiece thickness, that is, a thickness of the product 100, and T represents a transmittance.

[ Number 1]

In fig. 17, the horizontal axis represents the measurement position when the center in the in-plane direction of the product 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, but changes with the change in the measurement position. Specifically, the region on the right end side in fig. 17 where the absorption coefficient is high corresponds to the facet region RF. In the non-facet region RN having a lower absorption coefficient than the facet region RF, the non-facet region RN also has a distribution in the in-plane direction, that is, in the radial direction. The "radial direction" is a direction extending radially from the center in the in-plane direction of the product 100. Specifically, in the example of fig. 17, a region having a lower absorption coefficient exists on the left side, i.e., the outer side, than the center position.

Fig. 18A to 18C show the change in the generation position of the modified layer with the change in the transmittance, that is, the absorption coefficient. The modified layer generation position is a position where the irradiation affected area RA, which is a modified layer, is generated by condensing the laser beam B, and can be represented by a dimension in the depth direction of the ingot 2 from the laser irradiation surface, i.e., the ingot C surface 21. Here, the depth direction of the ingot 2 is a direction parallel to the height direction of the ingot 2, and more specifically, is a direction opposite to the height direction of the ingot 2 (i.e., a negative Z-axis direction in fig. 1 and the like). In the figure, a circle indicated by a dot-dash line beside the irradiation affected area RA indicates a condensed state of the laser beam B at the modified layer generation position, i.e., a beam diameter.

Referring first to fig. 18A, the laser beam B attenuates and condenses according to the absorption coefficient as it travels in the depth direction thereof within the ingot 2. When the energy density increases to a predetermined level due to the light condensation, the processing threshold is reached, and a modified layer, that is, the irradiation affected area RA is formed. Here, when the transmittance is low (that is, the absorption coefficient is high), the attenuation is large, so that the energy density corresponding to the processing threshold is modified at a deep position where the light collection cross-sectional area is smaller as shown in fig. 18B. On the other hand, when the transmittance is high (that is, the absorption coefficient is low), the attenuation is small, so as shown in fig. 18C, the energy density corresponding to the processing threshold is also reached and the modification occurs at a shallow position where the light-condensing cross-sectional area is larger. In this way, if the modified layer is changed in position due to the difference in transmittance or absorption coefficient, the surface of the product 100 after peeling becomes rough, and the material loss, which is the processing consumption for grinding and polishing, increases.

Therefore, in this modification, the transmittance is measured at a plurality of positions in the in-plane direction, and the irradiation conditions of the laser beam B at each of the plurality of positions are controlled based on the measurement results. Specifically, this modification obtains, that is, calculates the absorption coefficient based on the transmittance measured on the product 100 including the last previous generation. The present modification determines the irradiation energy of the laser beam B based on the trend of the absorption coefficient in the depth direction of the ingot 2 for each different position in the plane.

A specific example of controlling the irradiation conditions of the laser beam B next based on the optical measurement result of the product 100 obtained last time will be described below. First, the transmittance of the product 100 obtained last time is measured using a transmittance measuring instrument. At this time, the thickness of the workpiece was also measured. Based on the measured transmittance, the workpiece thickness, and the above expression (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 expression (2). In the following formula (2) and fig. 19, I ₀ denotes input energy, I denotes energy required for a processing point, i.e., minimum applied energy required for modification, and z denotes depth. K represents the amount of change in the absorption coefficient in the depth direction, that is, the trend of change in the absorption coefficient in the depth direction of the ingot 2.

[ Number 2]

I_O＝k·I·e^αz…(2)

The method for deriving the absorption coefficient variation will be described below. As shown in fig. 20, the center in the in-plane direction of the ingot 2 is set as an in-plane center position Ma. The position on the measurement line Lx passing through the in-plane center position Ma and parallel to the X axis is set to be the first end position Mb, which is the end position of the ingot 2 located in the facet region RF. The position on the measurement line Lx and the position on the opposite side from the first end position Mb is referred to as the second end position Mc. The second end position Mc is a position substantially symmetrical to the first end position Mb about the in-plane center position Ma. Fig. 21A shows the change in the absorption coefficient of the ingot 2 in the depth direction at the in-plane center position Ma. Fig. 21B shows the change in the absorption coefficient in the depth direction of the ingot 2 at the first end position Mb. Fig. 21C shows the change in the absorption coefficient in the depth direction of the ingot 2 at the second end position Mc. As shown in fig. 21A to 21C, it is known that the change in the absorption coefficient in the depth direction of the ingot 2 has a specific tendency and differs in position from one plane to another. The amount of change in the absorption coefficient can be derived based on the trend of change in the absorption coefficient in the depth direction of each in-plane position, and the value obtained by adding or multiplying the absorption coefficient obtained last time to the absorption coefficient change amount can be applied to the determination of the input energy at the next processing.

For example, as shown in fig. 22, the estimated value α _n of the absorption coefficient used for this processing can be obtained, i.e., calculated, based on the amounts of change in the absorption coefficient α _n-1 obtained last time and the absorption coefficient α _n－2 obtained last time. Specifically, for example, the difference between the last acquired absorption coefficient α _n－1 and the last acquired absorption coefficient α _n－2 can be used as the absorption coefficient change amount, and the absorption coefficient estimated value α _n can be calculated by adding the absorption coefficient change amount to the last acquired absorption coefficient α _n－1. The irradiation energy of the laser beam B can be determined based on the absorption coefficient estimation value α _n. In addition, in the calculation of the absorption coefficient variation amount, statistical processing based on a so-called "smoothing filter" or the like may be performed.

As shown in fig. 23, a first generator 101 and a second generator 102 are generated. The first product 101 is a product 100 obtained from one end side in the height direction of the ingot 2, that is, the ingot C-face 21 side. The second product 102 is a product 100 obtained from the other end side in the height direction of the ingot 2, i.e., the ingot Si surface 22 side. Next, the first absorption coefficient, which is the absorption coefficient in the first generator 101, and the second absorption coefficient, which is the absorption coefficient in the second generator 102, are obtained. The irradiation condition of the laser beam B, that is, irradiation energy can be determined by using the higher one of the first absorption coefficient and the second absorption coefficient as the upper limit value of the absorption coefficient. In other words, the absorption coefficient obtained from the wafer, which is the product 100 on the side having the higher absorption coefficient, may be set as the upper limit value by using a coefficient that does not change further.

The measurement pitch of the optical measurement may be measured at an equal pitch as shown in fig. 15, but may be changed as appropriate. That is, for example, the X-axis direction and the Y-axis direction may be different from each other. Alternatively, for example, in a region surrounded by a rectangle with a dash-dot line in fig. 24, the measurement pitch may be reduced in a region where the change in absorption coefficient is larger than in other regions. Specifically, for example, such a region is a boundary region between the non-facet region RN and the facet region RF. That is, in such a boundary region, the measurement pitch may be reduced as compared with other regions. The area of reduced measurement pitch may include the entire facet area RF. More specifically, referring to fig. 24, for example, the measurement pitch may be reduced in a region on the right side of the measurement position of 40mm compared to a region on the left side of the measurement position of 40 mm. In other words, the measurement pitch may be reduced in a predetermined region including the non-facet region RN and the boundary region between the non-facet region RN and the facet region RF, as compared with a region outside such a predetermined region.

For the above, the effect was confirmed by experiments. The laser beam B used in the experiment was a pulse laser with a wavelength of 1064nm, a pulse width of 7ns and an oscillation frequency of 25kHz. The laser beam B was an annular beam having an outer diameter of 4.85mm and an inner diameter of 2.82 mm. Such a laser beam B is incident on a lens having NA0.65, and is processed at an irradiation pitch (i.e., an irradiation interval in the scanning direction Ds) of 8 μm and a scanning interval (i.e., an interval of the scanning line Ls in the line feed direction Df) of 120 μm. As the ingot 2 to be processed, an ingot having an outer diameter of 6 inches and an in-plane absorption coefficient difference of 2.49mm ^－1 was used. The transmittance of the wafer 1 having a thickness of 0.385mm cut from the front surface was measured at a pitch of 3 mm. The setting of the input energy was such that 20. Mu.J of energy was input at the center of the ingot 2 at a depth of 0.4 mm. In this case, when the processing is performed with a constant output, the step difference in the generation position of the modified layer in the plane is 61 μm. On the other hand, by performing output correction corresponding to the in-plane absorption coefficient change, the level difference of the generation position of the modified layer was improved to 18 μm. This shows that material loss can be reduced.

The elements constituting the above embodiment are not necessarily essential, except for the case where essential elements are specifically and clearly shown, and the case where essential elements are regarded as being essential in principle. In addition, when numerical values such as the number, amount, and range of constituent elements are mentioned, the present disclosure is not limited to a specific numerical value except for the case where necessary numerical values are specifically and clearly limited to the specific numerical value in principle. Similarly, when referring to the shape, direction, positional relationship, etc. of the constituent elements, etc., the present disclosure is not limited to the shape, direction, positional relationship, etc. except for the case where the necessary shape, direction, positional relationship, etc. are specifically indicated and the case where the present disclosure is limited to a specific shape, direction, positional relationship, etc. in principle.

The modification is not limited to the above example either. That is, for example, in addition to the above-described examples, a plurality of embodiments may be combined with one another as long as they are not technically contradictory to one another. Similarly, a plurality of modifications can be combined with one another as long as they are not technically contradictory.

(Public opinion)

As is apparent from the description of the embodiments and the modifications described above, at least the following points are disclosed in the present specification.

[ Viewpoint 1]

A wafer manufacturing method for obtaining a wafer (1) from an ingot (2) includes:

A peeling layer (25) formed by irradiating a surface (21) on one side in the height direction of the ingot with a laser beam having a permeability, and forming the peeling layer at a depth from the surface corresponding to the thickness of the wafer;

wafer peeling, namely, peeling a wafer precursor (26) at a part between the surface of the peeling layer and the peeling layer from the ingot; and

The wafer is flattened, and the main surface (32) of a plate-like peeled body (30) obtained by peeling the wafer is flattened,

The peeling layer is formed by performing laser scanning on the surface a plurality of times while changing positions in a second direction (Df) orthogonal to a first direction along the surface and along the surface, forming a plurality of scanning lines (Ls) which are irradiation traces of the laser beam in a line shape along the first direction along the second direction, the laser scanning being performed by irradiating the surface with the laser beam while moving an irradiation Position (PR) of the laser beam on the surface in the first direction (Ds),

[ Viewpoint 2]

In the view point 1, the number of the light emitting elements,

The release layer is formed by irradiating the surface with the laser beam so that the irradiation of the laser beam in the facet Region (RF) causes a higher density of energy applied in the plane along the surface than in the non-facet Region (RN).

[ Viewpoint 3]

In either the point of view 1 or 2,

The peeling layer is formed such that the scanning line is formed between both end portions of the surface in the first direction while the irradiation position is moved in the first direction, and the irradiation trace is formed at an end portion of the surface in the first direction while the irradiation position is moved in a direction opposite to the first direction.

[ Viewpoint 4]

In the view points 1 to 3,

The above-mentioned release layer formation includes:

A first scanning step of forming the scanning line between both end portions of the surface in the first direction while moving the irradiation position in the first direction; and

And a second scanning unit for changing a distance from a condensing unit (42) for irradiating the laser beam to the surface from the first scanning unit, and forming the scanning line between both end portions of the surface in the first direction while moving the irradiation position in a direction opposite to the first direction.

[ Viewpoint 5]

In the viewpoints 1 to 4 of the present invention,

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 disposed in a state of being inclined by an offset angle (theta) exceeding 0 DEG in an offset angle direction (Dtheta) with respect to a central axis (L) orthogonal to the surface,

The wafer separation is performed by unidirectionally applying a load to one end (23) of the ingot in the direction of the off angle.

[ Viewpoint 6]

In the view point 5 of the present invention,

The one end of the ingot in the off-angle direction is the end on the higher side of the C-plane when the posture of the ingot is set such that the surface is the upper surface.

[ Viewpoint 7]

In either point of view 5 or 6,

The release layer is formed such that a facet Region (RF) is located on a lower side of the C-plane when the posture of the ingot is set such that the surface is the upper surface.

[ Viewpoint 8]

In the viewpoints 1 to 7 of the present invention,

The transmittance of the peeled body or the wafer obtained is measured at a plurality of positions in the first direction and the second direction,

Based on the result of the measurement of the transmittance, the irradiation conditions of the laser beam are controlled at each of a plurality of positions in the first direction and the second direction.

[ Viewpoint 9]

In the view point 8 of the present invention,

Based on the transmittance, the absorption coefficient of the laser beam is obtained,

The irradiation energy of the laser beam is determined based on the trend of the absorption coefficient in the depth direction of the ingot at each different position along the surface in-plane.

[ Viewpoint 10]

In the view point 9 of the present invention,

Based on the trend of the absorption coefficient in the depth direction of the ingot, the amount of change in the absorption coefficient in the depth direction is obtained,

The irradiation energy of the laser beam is determined based on a value obtained by adding or multiplying the absorption coefficient obtained last time by the absorption coefficient variation amount.

[ Viewpoint 11]

In the view points 9 and 10,

The irradiation energy of the laser beam is determined based on an estimated value of the absorption coefficient obtained based on the absorption coefficient obtained last time and the amount of change in the absorption coefficient obtained last time.

[ Viewpoint 12]

In the viewpoints of 9 to 11, the following are preferred,

Generating a first generating body (101) which is the peeled body or the wafer obtained from the ingot at one end side in the height direction and a second generating body (102) which is the peeled body or the wafer obtained from the ingot at the other end side in the height direction,

Acquiring a first absorption coefficient which is the absorption coefficient of the first product and a second absorption coefficient which is the absorption coefficient of the second product,

The irradiation energy of the laser beam is determined by using the higher one of the first absorption coefficient and the second absorption coefficient as the upper limit value of the absorption coefficient.

[ Viewpoint 13]

In the view points 8 to 12,

In the second region where the change in the absorption coefficient is larger than that in the first region, the measurement pitch of the transmittance is reduced as compared with that in the first region.

[ Viewpoint 14]

In the view point 13, the processing unit,

The second region is a boundary region between a non-facet Region (RN) and a facet Region (RF).

[ Viewpoint 15]

In the viewpoints from the point of view 1 to 14,

The plurality of laser beams include first, second, and third beams disposed at mutually different positions in the second direction.

[ Viewpoint 16]

In the view point 15 of the present invention,

The second light beam is located between the first light beam and the third light beam in the first direction and the second direction.

[ Viewpoint 17]

In the view point 15 of the present invention,

The first beam, the second beam, and the third beam are arranged in a V-shape on the surface.

Claims

1. A wafer manufacturing method for obtaining a wafer (1) from an ingot (2), comprising:

a peeling layer forming step of irradiating a surface (21) on one end side in the height direction of the ingot with a laser beam having a permeability to form a peeling layer (25) at a depth corresponding to the thickness of the wafer from the surface;

A wafer peeling step of peeling a wafer precursor (26) from the ingot at the peeling layer, the wafer precursor being a portion between the surface and the peeling layer; and

The wafer is flattened, and the main surface (32) of the plate-like peeled body (30) obtained by the wafer peeling step is flattened,

The peeling layer forming step of forming the peeling layer by performing laser scanning on the surface a plurality of times while changing a position of the peeling layer in a second direction (Df) orthogonal to a first direction along the surface and along the surface, forming a scanning line (Ls) which is a trace of irradiation of the laser beam in a line shape along the first direction along the second direction, the laser scanning being a laser scanning of irradiating the surface with the laser beam while moving an irradiation Position (PR) of the laser beam on the surface in the first direction (Ds),

2. The wafer manufacturing method according to claim 1, wherein,

The release layer forming step irradiates the surface with the laser beam so that the irradiation of the laser beam in the facet Region (RF) causes a higher density of energy to be applied in a plane along the surface than in the non-facet Region (RN).

3. The wafer manufacturing method according to claim 1, wherein,

The peeling layer forming step forms the scanning line between both end portions of the surface in the first direction while moving the irradiation position in the first direction, and forms the irradiation trace at an end portion of the surface in the first direction while moving the irradiation position in a direction opposite to the first direction.

4. The wafer manufacturing method according to claim 1, wherein,

The release layer forming step includes:

5. The wafer manufacturing method according to claim 1, wherein,

The wafer separation step is performed by unidirectionally applying a load to one end (23) of the ingot in the off-angle direction.

6. The wafer manufacturing method according to claim 5, wherein,

The one end of the ingot in the off-angle direction is a high-side end of the C-plane when the posture of the ingot is set such that the surface is the upper surface.

7. The wafer manufacturing method according to claim 5 or 6, wherein,

The release layer forming step is performed such that a facet Region (RF) is located on a lower side of the C-plane when the posture of the ingot is set such that the surface is the upper surface.

8. The wafer manufacturing method according to claim 1, wherein,

Based on the result of the transmittance measurement, the irradiation conditions of the laser beam at each of the plurality of positions are controlled.

9. The wafer manufacturing method according to claim 8, wherein,

10. The wafer manufacturing method according to claim 9, wherein,

11. The wafer manufacturing method according to claim 9, wherein,

12. The wafer manufacturing method according to claim 9, wherein,

13. The wafer manufacturing method according to claim 9, wherein,

14. The wafer manufacturing method according to claim 13, wherein,

15. The wafer manufacturing method according to claim 1, wherein,

16. The wafer manufacturing method according to claim 15, wherein,

17. The wafer manufacturing method according to claim 15, wherein,