JP2023085188A - Wafer manufacturing method - Google Patents

Abstract

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

Description

The present invention relates to a wafer manufacturing method.

Patent Literature 1 provides a wafer production method capable of efficiently producing wafers from ingots. Specifically, the wafer production method described in Patent Document 1 includes a separation starting point forming step and a wafer peeling step. In the separation starting point forming step, the focusing point of the laser beam having a wavelength that is transparent to the hexagonal single crystal ingot is positioned at a depth corresponding to the thickness of the wafer to be generated from the surface, and the focusing point and the ingot are separated. The surface is irradiated with a laser beam while moving relatively. As a result, a modified layer parallel to the surface and cracks extending from the modified layer are formed to form separation starting points. In the wafer peeling step, a plate-shaped object corresponding to the thickness of the wafer is peeled from the ingot from the separation starting point to generate a hexagonal single crystal wafer. In the separation starting point forming step, two or more converging points of the laser beam are positioned at predetermined intervals in the direction in which the off angle is formed, and two or more linear modified layers are simultaneously formed.

Japanese Patent No. 6482389

In the wafer production method described in Patent Document 1, modified layers are simultaneously formed by a plurality of laser beams having different irradiation positions in the direction in which the off-angle is formed. At this time, variations in depth may occur in each of the plurality of modified layers formed at the same time and having different positions with respect to the direction in which the off angle is formed. Variation in the depth of the modified layer causes a difference in level on the peeled surface, which increases the processing allowance for grinding or polishing, or causes poor peeling, thereby degrading the manufacturing efficiency. The present invention has been made in view of the circumstances exemplified above. That is, the present invention provides, for example, a wafer manufacturing method with higher manufacturing efficiency than conventional methods.

A wafer manufacturing method according to claim 1 is a method of obtaining a wafer (1) from an ingot (2), comprising the following procedures, steps or treatments:
A peeling layer (25) is formed from the surface to a depth corresponding to the thickness of the wafer by irradiating a surface (21) on one end side in the height direction of the ingot with a laser beam having transparency. , release layer formation, and
wafer peeling, wherein the wafer precursor (26), which is the portion between the surface and the peeling layer, is peeled from the ingot at the peeling layer;
Wafer flattening for flattening the main surface (32) of the plate-shaped peeled body (30) obtained by the wafer peeling;
including
Forming the release layer includes:
Laser scanning for irradiating the surface with the laser beam while moving the irradiation position (PR) of the laser beam on the surface in a first direction (Ds) along the surface is performed on the surface. In a second direction (Df) orthogonal to one direction and along the surface, scanning lines (Ls), which are irradiation traces of the linear laser beam along the first direction, are formed by performing a plurality of times while changing the position. , forming the release layer by forming a plurality of layers along the second direction;
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 in one laser scanning.

In this wafer manufacturing method, first, by irradiating the surface of the ingot on the one end side in the height direction with the laser beam having transparency, a depth corresponding to the thickness of the wafer from the surface is irradiated. Then, the release layer is formed. Formation of such a release layer is carried out as follows. The surface is irradiated with the laser beam 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 over the surface in the first direction. This laser scanning is performed a plurality of times while changing the position in the second direction perpendicular to the first direction on the surface and along the surface. As a result, the peeling layer is formed by forming a plurality of scanning lines, which are linear irradiation traces of the laser beam along the first direction, along the second direction. Next, the wafer precursor, which is the portion between the surface of the ingot and the release layer, is released from the ingot at the release layer. Subsequently, the wafer is obtained by flattening the main surface of the plate-shaped peeled body obtained by peeling the wafer precursor from the ingot.

Here, in such a wafer manufacturing method, in one laser scanning, by irradiating the surface with a plurality of laser beams having different irradiation positions in the first direction and the second direction, the scanning Form multiple lines. This can shorten the cycle time when forming the release layer. Further, of the two laser beams adjacent to each other included in the plurality of laser beams, one located on the first direction side is referred to as a "first beam", and the other one is referred to as a "second beam". called "Beam". In this case, the first beam travels in the first direction ahead of the second beam. At this time, the irradiation position of the second beam may overlap with the irradiation marks formed by the preceding first beam and cracks generated therearound. If the irradiation marks or cracks caused by the preceding first beam exist at the irradiation position of the following second beam, the absorptance of the second beam increases. For this reason, the irradiation mark by the following second beam is likely to occur at substantially the same depth as the irradiation mark and the crack by the preceding first beam. Therefore, two irradiation marks or cracks adjacent to each other in the second direction, which are formed at one time by the first beam and the second beam in one laser scanning, occur at substantially the same depth. easier to do. That is, the two scanning lines forming the release layer, which are adjacent to each other in the second direction, tend to occur at approximately the same depth.

Thus, in such a wafer manufacturing method, variations in the depth of the scanning lines forming the separation layer can be suppressed as much as possible. As a result, the size of steps and irregularities on the peeling surface caused by peeling of the peeling layer is well suppressed, the processing allowance for grinding and polishing on the peeling surface is reduced, and the occurrence of peeling defects is satisfactorily suppressed. be done. Also, the cycle time for forming the release layer can be shortened. Therefore, according to such a wafer manufacturing method, it is possible to improve the manufacturing efficiency more than conventionally.

In addition, in each column of the application documents, each element may be given a reference sign with parentheses. In this case, the reference numerals indicate only one example of the corresponding relationship between the same element and the specific configuration described in the embodiment described later. Therefore, the present invention is not limited in any way by the description of the reference numerals.

1 is a side view showing schematic configurations of a wafer, an ingot, and a separation body in a wafer manufacturing method according to one embodiment of the present invention; FIG. It is process drawing which shows the outline of the wafer manufacturing method which concerns on one Embodiment of this invention. FIG. 3 is a side view showing a schematic configuration of an ingot that has undergone a peeling layer forming step shown in FIG. 2; 3B is a plan view of the ingot shown in FIG. 3A; FIG. FIG. 3 is a side view schematically showing a release layer forming step shown in FIG. 2 and a release layer forming apparatus used therein; FIG. 3 is a front view showing the outline of the peeling layer forming step shown in FIG. 2 and the peeling layer forming apparatus used therein; 4A and 4B are diagrams schematically showing a release layer forming step shown in FIGS. 4A and 4B; FIG. 4A and 4B are diagrams schematically showing a release layer forming step shown in FIGS. 4A and 4B; FIG. FIG. 4C is a plan view schematically showing a release layer forming step shown in FIGS. 4A and 4B; FIG. FIG. 4B is an enlarged view of the laser beams shown in FIGS. 4A and 4B near a focal point; FIG. 4B is a side view schematically showing the release layer forming step shown in FIG. 4A; It is a side view which shows the outline of the peeling layer formation process in another example. FIG. 4B is a side view schematically showing the release layer forming step shown in FIG. 4A; FIG. 4B is a side view schematically showing the release layer forming step shown in FIG. 4A; FIG. 3 is a side view schematically showing the wafer peeling process shown in FIG. 2 and a peeling apparatus used therein; FIG. 5B is a plan view showing a modified example of the arrangement of a plurality of laser beams shown in FIG. 5A; FIG. 5B is a plan view showing another modified example of the arrangement of a plurality of laser beams shown in FIG. 5A; It is process drawing which shows the outline of the wafer manufacturing method which concerns on a modification. FIG. 15 is a plan view showing an example of a mode of setting measurement positions in the wafer optical measurement shown in FIG. 14; FIG. 15 is a plan view showing how the measurement position is scanned in the wafer optical measurement shown in FIG. 14; 17 is a graph showing how the absorption coefficient calculated from the transmittance measured by scanning the measurement positions shown in FIG. 16 changes depending on the measurement positions. FIG. 15 is a side cross-sectional view showing a difference in transmittance at a modified layer generation position in the laser slicing, that is, the peeling layer forming step shown in FIG. 14; FIG. 15 is a side cross-sectional view showing a difference in transmittance at a modified layer generation position in the laser slicing, that is, the peeling layer forming step shown in FIG. 14; FIG. 15 is a side cross-sectional view showing a difference in transmittance at a modified layer generation position in the laser slicing, that is, the peeling layer forming step shown in FIG. 14; FIG. 15 is a side cross-sectional view for explaining an example of a technique for setting laser beam irradiation conditions in the laser slicing, that is, the peeling layer forming step shown in FIG. 14; FIG. 10 is a plan view for explaining a method of deriving an absorption coefficient change amount shown in Equation (2); 21 is a graph showing how the absorption coefficient changes in the depth direction of the ingot at the in-plane center position shown in FIG. 20; 21 is a graph showing how the absorption coefficient changes in the depth direction of the ingot at the first end position shown in FIG. 20; 21 is a graph showing how the absorption coefficient changes in the depth direction of the ingot at the second end position shown in FIG. 20; 4 is a graph for explaining an example of a method of deriving an absorption coefficient; FIG. 15 is a side view showing a first generated body and a second generated body for setting laser beam irradiation conditions in the laser slicing, that is, the peeling layer forming step shown in FIG. 14; 15 is a graph showing how the absorption coefficient changes when the measurement pitch is reduced in the wafer optical measurement shown in FIG. 14;

(embodiment)
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described based on the drawings. It should be noted that if various modifications applicable to one embodiment are inserted in the middle of a series of explanations related to the embodiment, there is a risk that the understanding of the embodiment will be hindered. For this reason, the modification will not be inserted in the middle of the series of descriptions regarding the embodiment, and will be described collectively after that.

(wafer and ingot structure)
Referring to FIG. 1, a wafer 1 manufactured by the wafer manufacturing method according to the present embodiment is obtained by slicing an ingot 2 having a substantially cylindrical shape in side view, and having a substantially circular shape in plan view. It is formed in a thin plate shape. That is, the wafer 1 and the ingot 2 have substantially cylindrical side surfaces or end surfaces surrounding the central axis L. As shown in FIG. A central axis L is an imaginary straight line that is parallel to the substantially cylindrical side or end face of the wafer 1 or ingot 2 and passes through the axial center of the wafer 1 or ingot 2 . From the viewpoint of simplification of illustration and explanation, the illustration and explanation of the so-called orientation flat which is usually provided on the wafer 1 and the ingot 2 are omitted in this specification.

In this embodiment, the ingot 2 is a single-crystal SiC ingot having a c-axis Lc and a (0001) plane Pc perpendicular to each other, and has an off angle θ exceeding 0 degree. The c-axis Lc is the crystallographic axis indicated as [0001] by the orientation index. The (0001) plane Pc is a crystal plane that is perpendicular to the c-axis Lc and is called a “C plane” in a strict crystallographic sense. The off angle θ is an angle between the central axis L of the wafer 1 or ingot 2 and the c-axis Lc, and is, for example, about 1 to 4 degrees. That is, the c-axis Lc of the wafer 1 and the ingot 2 is provided in a state in which the central axis L is inclined in the off-angle direction Dθ by an off-angle θ exceeding 0 degrees. The off-angle direction Dθ is the laser-irradiated surface of the wafer 1 or ingot 2 (that is, the upper surface or It is a direction obtained by mapping the movement direction of a point on the center axis L located on the top surface side to the laser irradiation surface.

For simplification of explanation, right-handed XYZ coordinates are set as shown in FIG. In the right-handed XYZ coordinates, the off-angle direction Dθ and the X-axis positive direction are assumed to be the same direction. Also, the X-axis and the Y-axis are assumed to be parallel to the main surfaces of the wafer 1 and the ingot 2 . A "principal surface" is a surface of a plate-like object perpendicular to the plate thickness direction, and may also be referred to as a "top surface", a "bottom surface", or a "plate surface". Alternatively, the “principal surface” is a surface perpendicular to the height direction of a columnar object such as the ingot 2, and can also be called a “top surface” or a “bottom surface”. Furthermore, it is assumed that the thickness direction of the wafer 1 and the height direction of the ingot 2 are parallel to the Z-axis. An arbitrary direction orthogonal to the Z-axis may be hereinafter referred to as an “in-plane direction”.

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

Ingot 2 also has facet regions RF. Facet region RF may also be referred to as a "facet portion". A portion of the ingot 2 other than the facet region RF is hereinafter referred to as a non-facet region RN. Similarly, the non-facet region RN may also be referred to as a "non-facet portion".

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

(1) Peeling layer forming step: A laser beam having a predetermined degree of transparency to the ingot 2 is irradiated to the ingot C surface 21, which is the main surface on one end side in the height direction of the ingot 2. A release layer 25 is formed at a depth corresponding to the thickness of the wafer 1 from the surface 21 .
Here, the “predetermined level of transparency” is a level of transparency that enables formation of a focal point of the laser beam at a depth corresponding to the thickness of the wafer 1 inside the ingot 2 . In addition, the "depth corresponding to the thickness of the wafer 1" is the thickness of the finished wafer 1 (that is, the target value of the thickness) plus the thickness corresponding to the predetermined processing allowance in the wafer flattening process, etc., which will be described later. , and may also be referred to as "a depth corresponding to the thickness of the wafer 1".

(2) Wafer peeling process: The wafer precursor 26 between the ingot C surface 21 , which is the laser irradiation surface, and the peeling layer 25 is peeled from the ingot 2 at the peeling layer 25 .
Here, as in the expression "wafer peeling process" above, the plate-like object obtained by peeling the wafer precursor 26 from the ingot 2 may be called a "wafer" in socially accepted terms. However, in order to distinguish from the final wafer 1 after manufacture which has the main surface epiready mirror-finished, such a plate-like object is hereinafter referred to as a "separate body 30".
The peeling body 30 has a non-peeling surface 31 and a peeling surface 32, which are a pair of main surfaces. The non-peeling surface 31 is a surface on which the peeling layer 25 was not formed before the wafer peeling process, and corresponds to the ingot C surface 21 before the peeling layer forming process and the wafer peeling process. The peeling surface 32 constitutes the peeling layer 25 before the wafer peeling process, and is a surface newly generated by the wafer peeling process. The peeling surface 32 has rough (that is, grinding or polishing required) irregularities resulting from the peeling of the peeling layer 25 and the wafer peeling process.

(3) Wafer flattening step: At least the peeled surface 32 of the non-peeled surface 31 and the peeled surface 32, which are the main surfaces of the peeled body 30, is flattened to obtain the final wafer 1 after manufacturing. In the wafer flattening process, ECMG and ECMP can be used in addition to general grindstone polishing and CMP. CMP is an abbreviation for Chemical Mechanical Polishing. ECMG is an abbreviation for Electro-Chemical Mechanical Grinding. ECMP is an abbreviation for Electro-Chemical Mechanical Polishing. The wafer flattening process can be performed by using these plural types of flattening processes singly or by appropriately combining them.

(4) Ingot planarization step: After detaching the wafer precursor 26, the newly formed upper surface of the ingot 2 is planarized or mirrored so that it can be subjected to the delamination layer forming step again. Also in the ingot flattening process, ECMG and ECMP can be used in addition to general grindstone polishing and CMP. The ingot flattening process can also be performed by using these plural types of flattening processes singly or by appropriately combining them.

FIG. 2 is a process chart showing a typical example embodying the wafer manufacturing method according to the present embodiment. As shown in FIG. 2, the separated body 30 separated from the ingot 2 through the separation layer forming process and the wafer separation process is finished as an epi-ready wafer 1 through the following processes.
・Rough grinding of the peeled surface 32 to be the wafer Si surface 12 ・ECMG grinding of the peeled surface 32 after rough grinding ・ECMP polishing and cleaning of the peeled surface 32 after ECMG grinding

Further, the ingot 2 remaining after the separation body 30 is separated from the ingot 2 through the separation layer forming process and the wafer separation process can be subjected to another separation layer forming process through the following processes.
・Rough grinding of the ingot C-side 21 newly generated by the wafer peeling process/finish grinding/cleaning of the ingot C-side 21 after rough grinding

Details of each step will be described below using other figures in addition to FIGS. 1 and 2. FIG.

(Peeling layer forming step)
3A and 3B show the schematic configuration of the ingot 2 in which the release layer 25 and the wafer precursor 26 are formed by the release layer forming step. 4A and 4B show an outline of the peeling layer forming process and a schematic configuration of the peeling layer forming apparatus 40 used in this process. It is assumed that the right-handed XYZ coordinates shown in FIGS. 3A to 4B are displayed so as to match the right-handed XYZ coordinates shown in FIG.

3A and 3B, the release layer 25 is formed by forming a plurality of scanning lines Ls, which are linear laser beam irradiation traces along the X-axis, in the Y-axis direction. The scanning line Ls is a line-shaped irradiation mark RM of the laser beam on the ingot 2 . In this embodiment, the scanning line Ls is provided along the off-angle direction Dθ. A 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 off-angle direction Dθ. That is, the line feed direction Df is a direction perpendicular to the off-angle direction Dθ and the height direction of the ingot 2 .

4A and 4B, the release layer forming apparatus 40 includes a chuck table 41 and a light collector 42. As shown in FIG. The chuck table 41 is configured to hold the ingot 2 on the ingot Si surface 22 side, which is the bottom surface thereof. Specifically, for example, the chuck table 41 has a suction mechanism or the like that suctions 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 aspect. The light condensing device 42 irradiates the laser beam B oscillated by a pulsed laser oscillator (not shown) to the ingot 2 that is the workpiece fixed to the chuck table 41 , so that the beam axis, which is the irradiation direction of the laser beam B, is radiated. It is arranged facing the chuck table 41 in the direction. That is, the light collecting device 42 is provided so as to irradiate the ingot 2 with the laser beam B from the ingot C surface 21 side, which is the upper surface of the ingot 2 . Specifically, the focusing device 42 is configured to form a focusing point BP of the laser beam B inside the ingot 2 at a depth corresponding to the thickness of the wafer 1 from the ingot C surface 21 . . The focusing device 42 may also be referred to as a "focusing device" and includes an optical element (for example, a lens) for forming the focal point BP of the laser beam B at a predetermined position. The peeling layer forming apparatus 40 is configured so that the focal point BP of the laser beam B can be moved relative to the ingot 2 at least in the in-plane direction, that is, in the XY directions in the figure. Here, the “in-plane direction” is a direction parallel to the ingot C surface 21 that is the upper surface of the ingot 2 .

The peeling layer forming apparatus 40 forms scanning lines Ls along the scanning direction Ds by “laser scanning” in which the laser beam B is scanned on the ingot C surface 21 in the scanning direction Ds (that is, the first direction). That is, "laser scanning" is to irradiate the ingot C surface 21 with the laser beam B while moving the irradiation position PR of the laser beam B on the ingot C surface 21, which is the laser irradiation surface, in the scanning direction Ds. is. In the present embodiment, the scanning direction Ds is a direction along the off-angle direction Dθ, specifically, the same direction as or opposite to the off-angle direction Dθ. Then, the peeling layer forming apparatus 40 performs laser scanning a plurality of times while changing the position in the line feeding direction Df (that is, the second direction), and forms a plurality of scanning lines Ls along the line feeding direction Df. 25 is formed. Both the line feed direction Df and the scanning direction Ds are in-plane directions (that is, directions along the ingot C surface 21) and directions orthogonal to each other.

In the present embodiment, the release layer forming apparatus 40 moves the chuck table 41 on which the ingot 2 is placed relative to the light collector 42 in the scanning direction Ds, and scans the ingot C surface 21 with the laser beam B. Thus, a scanning line Ls is formed along the scanning direction Ds. After one laser scan, the release layer forming device 40 moves the chuck table 41 relative to the light collecting device 42 by a predetermined amount along the line feed direction Df. Then, the release layer forming device 40 again scans the laser beam B by moving the chuck table 41 relative to the light collecting device 42 in the scanning direction Ds (that is, the same or opposite direction as the previous laser scanning). By doing so, a scanning line Ls is formed. In this way, the release layer forming device 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. In this manner, the peeling layer 25 is formed by a plurality of scanning lines Ls provided along the line feed direction Df. Further, a wafer precursor 26 to be the wafer 1 in the future is formed on the ingot C surface 21 side of the separation layer 25 . As described above, in this embodiment, the light collecting device 42 is fixed in the in-plane direction, while the chuck table 41 that supports the ingot 2 is moved by a scanning device such as an electric stage device (not shown). It is provided to move at least in the in-plane direction. On the other hand, as will be described later, the present invention is not limited to such an aspect. That is, for example, there may be an embodiment in which the chuck table 41 that supports the ingot 2 is fixed in the in-plane direction, while the condensing device 42 is movably provided in the in-plane direction by a scanning device (not shown). However, in any of these modes, the laser beam B and its irradiation position PR apparently move on the main surface of the ingot 2 in the in-plane direction, and the laser beam B and its focal point BP move inside the ingot 2. It seems to move in the in-plane direction. Therefore, for simplification of explanation, hereinafter, the laser beam B and its irradiation position PR will move on the main surface of the ingot 2 in the in-plane direction, There are times when explanations such as moving inward are given. However, as described below, the invention is not limited to such embodiments.

In this embodiment, as shown in FIGS. 4A and 4B, a plurality of laser beams B with different irradiation positions PR in the scanning direction Ds and the line feed direction Df are applied to the ingot C surface by one laser scanning. 21 is irradiated. Specifically, as shown in FIGS. 5A and 5B, the irradiation positions PR on the ingot C surface 21 are arranged to be inclined with respect to both the scanning direction Ds and the line feed direction Df in plan view. A plurality of laser beams B (that is, the first beam B1, etc.) moves along the scanning direction Ds. 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 favorably shortened.

4A, 4B, and 5A show an example of three laser beams B as the plurality of laser beams B. FIG. However, this is for convenience of illustration simplification, and the number of laser beams B is not particularly limited. However, in order to simplify the explanation, the explanation will be continued below assuming that the plurality of laser beams B includes at least the first beam B1, the second beam B2 and the third beam B3. Among the first beam B1, the second beam B2, and the third beam B3, the first beam B1 is the most leading, that is, the first beam B1 is positioned closest to the scanning direction Ds. On the other hand, the third beam B3 is assumed to be the most trailing. The second beam B2 is positioned between the first beam B1 and the third beam B3 in the scanning direction Ds and the line feed direction Df.

As shown in FIG. 5A, the first beam B1 travels in the scanning direction Ds ahead of the second beam B2. By the irradiation of 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, which is the laser irradiation surface. The irradiation-affected region RA consists of an irradiation mark RM consisting of a modified region formed by separating SiC into Si and C by irradiation with the laser beam B, and the (0001) plane Pc from the irradiation mark RM around it. and a crack C extending along. Therefore, the irradiation position PR of the second beam B2 may overlap at least the crack C in the irradiation affected area RA formed by the preceding first beam B1 in the in-plane direction. If the irradiation marks RM and cracks C included in the irradiation affected area RA by the preceding first beam B1 exist at the irradiation position PR of the following second beam B2, the absorption rate of the second beam B2 is changed by the irradiation affected area RA. increases. For this reason, the irradiation mark RM by the following second beam B2 is likely to occur at substantially the same depth as the depth of the irradiation affected area RA by the preceding first beam B1. The same applies to the relationship between the second beam B2 and the third beam B3. Therefore, three adjacent irradiation marks RM or irradiation affected regions RA in the line feed direction Df, which are formed at once by the first beam B1 to the third beam B3 in one laser scanning, occur at approximately the same depth. easier to do. That is, the plurality of scanning lines Ls forming the release layer 25, which are adjacent in the line feed direction Df, tend to occur at approximately the same depth.

As described above, in the present embodiment, variations in the depth of the irradiation marks RM, ie, the scanning lines Ls, forming the peeling layer 25 can be suppressed as much as possible. As a result, the size of steps and irregularities on the peeling surface 32 caused by the peeling of the peeling layer 25 can be suppressed satisfactorily. be suppressed. Also, the cycle time for forming the release layer 25 can be shortened. Therefore, according to this embodiment, it is possible to improve the manufacturing efficiency more than the conventional one.

FIG. 6 shows the trajectory of relative movement of the central position of the light collecting device 42 in the in-plane direction with respect to the ingot 2 . The “central position in the in-plane direction of the condensing device 42” is typically the central position in the arrangement of the multiple laser beams B, for example. As shown in FIGS. 4A and 6, in this embodiment, the ingot 2 is oriented such that the facet region RF is positioned on the "lower off-angle side", and the laser beam B is directed from the C-plane side. The release layer forming step is performed by irradiation. The “lower off-angle side” refers to the lower inclination side of the C-plane, that is, the (0001) plane Pc when the orientation of the ingot 2 is set so that the C-plane 21 of the ingot, which is one principal plane, faces upward. shall be said. On the other hand, the “higher off-angle side” refers to the higher inclination side of the C-plane, that is, the (0001) plane Pc when the ingot 2 is oriented so that the C-plane 21 of the ingot faces upward. shall be

As will be described later, by applying a unidirectional load for peeling the wafer precursor 26 from the ingot 2 at one end of the "higher off-angle side" of the ingot 2, extremely good wafer peeling is achieved. Here, after setting the attitude of the ingot 2 so that the facet region RF is positioned on the “higher off-angle side” and irradiating the laser beam B from the Si surface side, the “higher off-angle side” of the ingot 2 is Consider the hypothetical example of applying a unidirectional load at one end. In this respect, the edge of the ingot 2 adjacent to the facet region RF is less prone to cracking in the first place. Therefore, in such a hypothetical example, since the peeling start position is the edge close to the facet region RF where cracks are less likely to occur, the success rate of the wafer peeling process may decrease. On the other hand, in the present embodiment, the ingot 2 is oriented such that the facet region RF is positioned on the “lower off-angle side”, and after the laser beam B is irradiated from the C surface side, the ingot 2 is “off-angled”. A unidirectional load is applied at one end of the high corner. In this case, the separation starting position is a portion far from the facet region RF where cracks are relatively likely to occur. Therefore, according to this embodiment, the success rate of the wafer peeling process is improved.

By the way, it is known that the intensity of the laser beam B reaching the focal point BP is higher in the non-facet region RN than in the facet region RF. Therefore, in the present embodiment, in the separation layer forming step, the laser beam B is applied to the ingot 2 so that the energy application density due to the laser beam B irradiation is higher in the facet region RF than in the non-facet region RN. Irradiate the main surface. The “energy application density” referred to here is the energy application density in the plane along the main surface of the ingot 2 . The following means can be used singly or in combination. Specifically, for example, the output of the laser beam B is made higher in the facet region RF than in the non-facet region RN. Alternatively, for example, the main surface of the ingot 2 is irradiated with the laser beam B so that the facet region RF is irradiated with the laser beam B more frequently than the non-facet region RN. More specifically, for example, in the facet region RF, the repetition frequency of the laser beam B is set higher than that in the non-facet region RN, or the scanning speed is lowered while the repetition frequency is constant, and irradiation in the scanning direction Ds is performed. Close the gap. In making the output in the facet region RF higher than that 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. In making the irradiation interval in the scanning direction Ds or the line feed direction Df narrower in the facet region RF than in the non-facet region RN, the irradiation interval in the facet region RF should be 2/5 of the irradiation interval in the non-facet region RN. preferable. Alternatively, for example, the facet region RF is irradiated with the laser beam B separately from the irradiation of the laser beam B onto the entire region including the facet region RF and the non-facet region RN. When irradiating the facet region RF with the laser beam B, the laser beam B may also irradiate a region adjacent to the facet region RF in the non-facet region RN.

According to the release layer forming process according to the present embodiment, the release layer 25 can be satisfactorily formed in the entire region including the facet region RF and the non-facet region RN. In particular, the separation layer 25 can be formed on the facet region RF without adjusting the distance in the Z-axis direction between the focusing device 42 on the irradiation side of the laser beam B and the chuck table 41 supporting the ingot 2. , can be done similarly to the non-faceted regions RN. Therefore, according to this embodiment, it is possible to improve the manufacturing efficiency more than the conventional one.

4A and 6, in the release layer forming step, forward scanning Sc1 in which the irradiation position PR when irradiated with the laser beam B moves on the main surface of the ingot 2 in the same direction as the off-angle direction Dθ; A backward scan Sc2 occurs in which the irradiation position PR when the laser beam B is irradiated moves on the main surface of the ingot 2 in the direction opposite to the off-angle direction Dθ. That is, in forward scanning Sc1, the scanning direction Ds is the same as the off-angle direction Dθ. On the other hand, in the backward scanning Sc2, the scanning direction Ds is opposite to the off-angle direction Dθ. The forward scanning Sc1 and the backward scanning Sc2 are alternately performed.

The relative position of the light collecting device 42 with respect to the ingot 2 moves by a predetermined amount in the line feed direction Df between the end of one forward scan Sc1 and the start of the next forward scan Sc1. However, the relative position of the light collecting device 42 in the line feed direction Df may move between the end of one forward scan Sc1 and the start of the backward scan Sc2 immediately thereafter. and do not need to move. The same applies to the period from the end of one backward scan Sc2 to the start of the subsequent forward scan Sc1. The amount of relative movement in the line feed direction Df at each stage can be appropriately set according to the irradiation conditions of the laser beam B and the like.

In the forward scan Sc1, the laser beam B is irradiated over the entire width of the ingot 2 in the scanning direction Ds. That is, in the forward scan Sc1, the main surface of the ingot 2 is irradiated with the laser beam B while the irradiation position PR is moved on the main surface of the ingot 2 in the scanning direction Ds that is the same direction as the off-angle direction Dθ. Thereby, a scanning line Ls is formed between both ends of the ingot 2 in the scanning direction Ds. On the other hand, in the backward scanning Sc2, the laser beam B may be irradiated over the entire width of the ingot 2 in the scanning direction Ds, or the laser beam B may not be irradiated over the entire width of the ingot 2 in the scanning direction Ds. may Alternatively, in the backward scanning Sc2, the laser beam B may be irradiated not only on the entire width of the ingot 2 in the scanning direction Ds but on a part thereof.

Specifically, for example, in the backward scanning Sc2, the laser beam B may be applied only to the facet region RF and its periphery. This makes it possible to form the release layer 25 satisfactorily over the entire region including the facet region RF and the non-facet region RN. Alternatively, for example, in the backward scanning Sc2, the laser beam B may be applied only to the end of the ingot 2 in the scanning direction Ds. In this case, in the backward scanning Sc2, while the irradiation position PR moves on the main surface of the ingot 2 in the scanning direction Ds, which is the direction opposite to the off-angle direction Dθ, a scanning line is formed on the end of the ingot 2 in the scanning direction Ds. Ls is formed. As a result, the start of delamination in the wafer delamination process is favorably promoted, and the success rate of the wafer delamination process is improved. Further, in the backward scanning Sc2, the laser beam B may be irradiated only to the facet region RF and its peripheral portion, and the end portion of the ingot 2 in the scanning direction Ds.

As shown in FIG. 7, in this embodiment, the intensity of the laser beam B is increased at the peripheral edge portion outside the center portion in the beam radial direction, which is the direction radially extending from the center of the axis. intensity distribution. Specifically, the laser beam B has a beam shape that is ring-shaped or hollow in front of the condensing point BP and converges into a point at the condensing point BP. At the condensing point BP, the laser beam B has a condensed diameter dc, which is the minimum beam diameter. The intersection range RX shown in FIG. 7 is a predetermined range centered on the focal point BP in the beam axis direction in which the peripheral edges of the laser beam B having high intensity overlap each other.

Thus, the release layer forming apparatus 40 irradiates the ingot 2 with the annular laser beam B. As shown in FIG. Such a ring-shaped laser beam B and an apparatus for generating such a laser beam B and irradiating it to a workpiece are already known or well-known at the time of filing of the present application (for example, Japanese Patent Application Laid-Open No. 2006-130691). Japanese Patent Laid-Open No. 2014-147946, etc.). For this reason, the detailed description of the generation device and generation method of the laser beam B is omitted in this specification.

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

As shown in FIG. 8B, when a solid laser beam B is used, irradiation marks RM, which are modified regions formed by separating SiC into Si and C by irradiation with the laser beam B, are formed. , may occur at different depths than the focal point BP. Therefore, the depth of the irradiation affected area RA, which is composed of the irradiation marks RM and the cracks C developed from the irradiation marks RM, can also be different from the focal point BP. Specifically, for example, at a position shallower than the focal point BP, the energy application density due to the irradiation of the laser beam B may increase to such an extent that the irradiation mark RM can be generated. Then, the irradiation mark RM can occur at a position shallower than the focal point BP. The depth of the irradiation mark RM may vary due to variations in the irradiation energy of the laser beam B, variations in the refractive index of the ingot 2, variations in the optical system of the light collecting device 42, and the like. A region in which irradiation marks RM may occur is shown as a modifiable range RC in the figure. Note that the irradiation mark RM corresponds to the “modified layer” in Patent Document 1.

On the other hand, as shown in FIG. 8A, when the annular laser beam B is used, the energy application density due to the irradiation of the laser beam B increases to the extent that the irradiation mark RM can be generated. Limited to the depth near the focal point BP. That is, for example, as in the case of using a solid laser beam B, the energy application density due to the irradiation of the laser beam B at a position shallower than the focal point BP increases to the extent that irradiation marks RM can be generated. becomes difficult. Therefore, the irradiation mark RM is stably generated at a depth near the focal 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 focal point BP. Therefore, variations in the depth of the irradiation mark RM can be suppressed satisfactorily. In other words, the peeling layer 25 can be formed as thin as possible, and the processing allowance in grinding and polishing after peeling can be favorably reduced. Therefore, according to this embodiment, it is possible to improve the manufacturing efficiency more than the conventional one.

By the way, in the method described in Patent Document 1, the laser scanning direction is a direction orthogonal to "the direction in which the off-angle θ is formed (that is, the off-angle direction Dθ in FIGS. 1, 3A, etc.)". For this reason, cleavage is not stable, and 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 focal point BP of the laser beam B inside the ingot 2, is parallel to the off-angle direction Dθ. be. 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 device 40 scans the laser beam B by moving the light collecting device 42 relative to the ingot 2 in the scanning direction Ds parallel to the off-angle direction Dθ, thereby turning off the scanning line Ls. It is formed along the angular direction Dθ. Then, as shown in FIGS. 9 and 10, irradiation marks RM and cracks C are formed along the (0001) plane Pc. As a result, the cleavage of the peeling layer 25 during the wafer peeling process can be stabilized, and the material loss can be favorably reduced. Also, the processing allowance in the wafer flattening process can be favorably reduced, so that the process time can be shortened as much as possible. Therefore, according to this embodiment, it is possible to provide a wafer manufacturing method with higher manufacturing efficiency than the conventional one.

FIG. 9 shows an example in which the scanning direction Ds is the same direction as the off-angle direction Dθ. FIG. 10 shows an example in which the scanning direction Ds is opposite to the off-angle direction Dθ. That is, in the example shown in FIG. 9, when the attitude of the ingot 2 is set so that the C surface 21 of the ingot faces upward as shown in FIG. , (0001) plane Pc from the high side to the low side. On the other hand, in the example shown in FIG. 10, when the attitude of the ingot 2 is set so that the C surface 21 of the ingot is the top surface, laser scanning causes the irradiation position PR to be a low point on the (0001) surface Pc. Move from the side to the high side.

For example, it is assumed that there is no radiation affected area RA, that is, no radiation marks RM or cracks C around the radiation position PR in the in-plane direction. In such a situation, the irradiation of the laser beam B tends to cause the irradiation mark RM at a depth near the focal point BP. On the other hand, in reality, the laser beam B moves in the scanning direction Ds while successively producing irradiation marks RM and cracks C. As shown in FIG. Therefore, the situation as described above mainly occurs when forming the irradiation mark RM corresponding to the starting point of the scanning line Ls, which is formed first in one laser scanning. Therefore, in most situations during laser scanning, a situation occurs in which an irradiation influence area RA exists around the irradiation position PR in the in-plane direction.

That is, as shown in FIGS. 9 and 10, the current irradiation position PR usually has an irradiation affected area RA formed earlier (for example, immediately before). Then, the absorptivity of the laser beam B increases in the irradiation affected area RA. Also, the irradiation affected area RA is formed along the (0001) plane Pc. Therefore, the laser scanning causes the irradiation mark RM to easily develop along the (0001) plane Pc.

Here, in the example shown in FIG. 9, the irradiation mark RM is gradually formed at a deeper position by the laser scanning as it progresses in the scanning direction Ds along the (0001) plane Pc. Gradually move away from the light spot BP. Then, at a depth almost identical to that of the irradiation mark RM formed immediately before, the energy application density of the laser beam B to be irradiated this time may not be increased to the extent that a new irradiation mark RM can be generated. . In this case, the irradiation mark RM can no longer progress along the (0001) plane Pc. Then, as shown in FIG. 9, a newly formed irradiation mark RM is formed at a depth near the focal point BP of the laser beam B irradiated this time. That is, a step occurs between the irradiation mark RM formed immediately before and the irradiation mark RM formed this time.

On the other hand, in the example shown in FIG. 10, the laser scanning causes the irradiation mark RM to be gradually formed at a shallower position as it progresses along the (0001) plane Pc in the scanning direction Ds. Gradually move away from point BP. At a depth almost identical to that of the irradiation mark RM formed immediately before, if the energy application density of the laser beam B irradiated this time is no longer increased to the extent that a new irradiation mark RM can be generated, irradiation will occur. The mark RM can no longer progress along the (0001) plane Pc. Then, as shown in FIG. 10, a newly formed irradiation mark RM is formed at a depth near the focal point BP of the laser beam B irradiated this time. However, in the example shown in FIG. 10, unlike the example shown in FIG. 9, the direction in which the irradiation mark RM grows is the direction closer to the light source side of the laser beam B, that is, the laser-irradiated surface side of the ingot 2. . Therefore, in the example shown in FIG. 10, the irradiation mark RM tends to grow longer than in the example shown in FIG. Therefore, in the example shown in FIG. 10, the step between the previously formed irradiation mark RM and the currently formed irradiation mark RM is larger than in the example shown in FIG.

In this way, by making the scanning direction Ds the same as the off-angle direction Dθ and moving the irradiation position PR in the laser scanning from the higher side toward the lower side of the C plane, the irradiation mark RM formed immediately before and the current irradiation mark RM It is possible to reduce the step between the formed irradiation marks RM. As a result, the peeling layer 25 can be formed as thin as possible, so that the processing allowance in grinding and polishing after peeling can be reduced satisfactorily. Therefore, according to this aspect, it is possible to further improve the manufacturing efficiency as compared with the conventional art.

(Wafer peeling process)
FIG. 11 schematically shows a wafer peeling process and a peeling apparatus 50 used in this process. It is assumed that the right-handed XYZ coordinates shown in FIG. 11 are displayed so as to match the right-handed XYZ coordinates shown in FIG.

The peeling device 50 applies a load in one direction at the first end 23 , which is one end of the ingot 2 , in the in-plane direction parallel to the ingot C surface 21 , that is, the off-angle direction Dθ, thereby separating the wafer precursor 26 from the peeling layer 25 . It is configured to separate from the ingot 2 at . The first end 23 is the end on the “high side of the off-angle”, that is, the end on the high side of the C-plane, that is, the (0001) plane Pc when the ingot 2 is oriented so that the C-plane 21 of the ingot faces upward. is. In this embodiment, the peeling device 50 applies a static and/or dynamic load in the Z-axis direction in the figure in such a manner as to separate the ingot C surface 21 from the ingot Si surface 22 at the first end 23. It is configured to be applied to the ingot 2 . Specifically, in this embodiment, the peeling device 50 includes a support table 51 , a peeling pad 52 , and a driving member 53 .

The support table 51 is provided to support the ingot 2 from below. More specifically, the support table 51 has a large number of suction holes (not shown) that open on a support attraction surface 51a, which is the upper surface of the support table 51, so that the ingot Si surface 22 is attracted to the support attraction surface 51a by air pressure. is configured to The support table 51 has a first table end portion 51b and a second table end portion 51c, which are both end portions in the off-angle direction Dθ. A second table end portion 51c, which is an end portion on one side (that is, the left side in the drawing) in the off-angle direction Dθ, has a table base end surface 51d. 51 d of table base end surfaces are formed in the shape of an inclined surface which rises toward the off-angle direction D(theta). That is, as shown in FIG. 11, the support table 51 is formed in a trapezoidal shape in which the lower base is longer than the upper base when viewed from the side.

The stripping pad 52 is provided above the support table 51 so as to be able to approach and separate from the support table 51 along the Z-axis in the figure. That is, the peeling device 50 is configured such that the support table 51 and the peeling pad 52 are relatively movable in the height direction of the ingot 2 . The stripping pad 52 has a large number of suction holes (not shown) that open at a pad adsorption surface 52a, which is the bottom surface of the stripping pad 52, and is configured to adsorb the ingot C surface 21 to the pad adsorption surface 52a by air pressure. . The peeling pad 52 has a first pad end portion 52b and a second pad end portion 52c, which are both ends in the off-angle direction Dθ. The second pad end portion 52c, which is the end portion on one side (that is, the left side in the drawing) in the off-angle direction Dθ, has a pad end surface 52d. The pad end surface 52d is formed in an inclined surface shape that descends toward the off-angle direction Dθ. That is, as shown in FIG. 11, the stripping pad 52 is formed in a trapezoidal shape in which the lower base is shorter than the upper base when viewed from the side. 52 d of pad end surfaces are provided in the position corresponding to 51 d of table base end surfaces (that is, right above). The ingot C surface 21 is fixed to the peeling pad 52 by suction and the ingot Si surface 22 is fixed to the support table 51 by suction, so that the ingot 2 is sandwiched between the support table 51 and the peeling pad 52. , hereinafter referred to as a "sandwiched state".

The drive member 53 applies an external force to at least one of the support table 51 and the stripping pad 52 to relatively move the support table 51 and the stripping pad 52 along the height direction of the ingot 2 in the clamping state. It is arranged to be applied to one side. Specifically, the drive member 53 has a first drive end face 53a and a second drive end face 53b. The first drive end surface 53a is formed in an inclined surface shape that descends toward the off-angle direction Dθ. More specifically, the first drive end face 53a is provided parallel to the pad end face 52d. The second driving end surface 53b is formed in an inclined surface that rises toward the off-angle direction Dθ. More specifically, the second driving end surface 53b is provided parallel to the table base end surface 51d. Further, the driving member 53 is provided so that the first driving end surface 53a contacts the pad end surface 52d and the second driving end surface 53b contacts the table base end surface 51d in the sandwiched state. That is, as shown in FIG. 11, the driving member 53 is formed in a trapezoidal shape whose lower base is longer than its upper base and which is rotated clockwise by 90 degrees when viewed from the side. The driving member 53 is configured to be driven upward along the height direction of the ingot 2 and/or in the off-angle direction Dθ, which is the direction toward the ingot 2, by a driving means (not shown). there is That is, the driving member 53 is driven upward and/or in the off-angle direction Dθ to apply a moment to the ingot 2 with the second pad end 52c as the force FP and the first end 23 as the fulcrum PP and action point WP. designed to work.

A wafer peeling process for peeling the wafer precursor 26 from the ingot 2 includes a table fixing process, a clamping process, and a peeling force applying process. The table fixing step is a step of fixing the ingot 2 to the support table 51 by adsorbing the ingot Si surface 22 to the support adsorption surface 51a. The sandwiching step is a step of attaching the ingot C surface 21 to the pad adsorption surface 52 a to fix the ingot 2 to the peeling pad 52 to form a sandwiched state. In the step of applying a peeling force, the second pad end, which is the end of the peeling pad 52 on one side in the off-angle direction Dθ, is applied to the ingot 2 so that a moment with the first end 23 as the fulcrum PP acts on the ingot 2 in the sandwiched state. This is a step of applying a static or dynamic load using the portion 52c as the force point FP. Specifically, in the peeling force applying step, the driving member 53 is driven upward and/or in the off-angle direction Dθ in the sandwiched state, thereby moving the second pad end portion 52 c upward along the height direction of the ingot 2 . It is a step of pressing to As a result, the wafer precursor 26, which is a part of the ingot 2, can be separated from the ingot 2 using the separation layer 25 as an interface.

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

In this regard, in the wafer peeling process described in Japanese Patent No. 6678522, the point of action 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, a much larger load than that of the present embodiment was required in order to cause good peeling with the peeling layer 25 as the interface. In addition, since the load is applied to a wide area of the peeling layer 25, the position of the peeling crack may not be fixed, and a partial unpeeled portion or breakage of the removed wafer 1 may occur. Furthermore, there is a problem that the peeled cross-section becomes rough and the processing allowance for grinding and polishing increases. Therefore, in the comparative example, there is room for improvement in terms of load reduction, yield, and the like.

On the other hand, in the wafer peeling process according to the present embodiment, in order to peel the wafer precursor 26 from the ingot 2 by the peeling layer 25, a load is applied in one direction at one end of the ingot 2 in the off-angle direction Dθ. . That is, the load is concentrated on one end of the release layer 25 in the off-angle direction Dθ. Then, a moment having this one end as the fulcrum PP and the action point WP acts on the ingot 2 . As a result, since the crack formed at the end of the ingot 2 on the one end side in the off-angle direction Dθ is the starting point, the delamination progresses, so that the fracture progresses stably over the entire surface of the delamination layer 25 while reducing the applied load. be able to. In addition, by stably setting the fracture occurrence location, it is possible to reduce the surface roughness of the peeled surface 32 of the peeled body 30 and the ingot C surface 21 after peeling. In particular, by setting the first end 23, which is the starting point of the breakage, to be one end of the "higher off-angle side" in the off-angle direction Dθ, the breakage occurs smoothly and the cleavage is further stabilized. Therefore, the defect rate in the wafer peeling process and the processing allowance in grinding and polishing the ingot 2 and the peeled body 30 after the wafer peeling process can be favorably reduced. Therefore, according to this embodiment, it is possible to provide a wafer manufacturing method with higher manufacturing efficiency than the conventional one.

(Modification)
The present invention is not limited to the above embodiments. Therefore, the above embodiment can be modified as appropriate. A representative modified example will be described below. In the following description of the modified example, differences from the above embodiment will be mainly described. Moreover, in the above-described embodiment and modifications, the same reference numerals are given to parts that are the same or equivalent to each other. Therefore, in the description of the modification below, the description in the above embodiment can be used as appropriate for components having the same reference numerals as those in the above embodiment, unless there is a technical contradiction or special additional description.

The present invention is not limited to the specific configurations shown in the above embodiments. That is, for example, the outer diameter and planar shape of the wafer 1, that is, the ingot 2 (for example, whether or not there is a so-called orientation flat) are not particularly limited. The magnitude of the off angle θ is also not particularly limited. In the above embodiments, the wafer C-plane 11 and the ingot C-plane 21 do not coincide with the C-plane in the strict crystallographic sense, that is, the (0001) plane Pc. However, even in such a case, the term "C surface" is used because the term "C surface" is acceptable under social conventions. However, the present invention is not limited to such an aspect. That is, the wafer C-plane 11 and the ingot C-plane 21 may coincide with the C-plane in the strict crystallographic sense, that is, the (0001) plane Pc. In other words, the off angle θ may be 0 degrees.

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

Depending on the irradiation conditions and scanning conditions of the laser beam B, the peeled surface 32 may have such a surface condition that it can be satisfactorily ground or polished even if it is subjected to the ECMG process as it is. Therefore, the rough grinding step of the peeled surface 32 shown in FIG. 2 may be omitted. The same applies to the rough grinding of the upper surface of the ingot 2 after the wafer peeling process.

The release layer forming apparatus 40 shown in FIGS. 4A and 4B is a simplified schematic diagram for simply explaining the outline of the release layer forming process according to the present invention. Therefore, the specific configuration of the release layer forming apparatus 40 that is actually industrially implemented does not necessarily match the exemplary configuration shown in FIGS. 4A and 4B. Specifically, for example, the chuck table 41 may be configured to hold the ingot 2 by a method other than an air pressure adsorption mechanism. Also, the chuck table 41 may be configured to be relatively movable with respect to the light collector 42 at least in the in-plane direction, that is, in the XY directions in the drawing. Alternatively, the peeling layer forming device 40 may include a scanning device configured to allow the focal point BP of the laser beam B to move relative to the ingot 2 in the XYZ directions in the drawing. Alternatively, in the above-described embodiment, the peeling layer forming apparatus 40 is configured such that the chuck table 41 that supports the ingot 2 is movable at least in the in-plane direction, while the light collecting device 42 is fixedly provided in the in-plane direction. had been However, the invention is not limited to such aspects. That is, for example, the separation layer forming apparatus 40 has a configuration in which the chuck table 41 that supports the ingot 2 is fixed in the in-plane direction, while the light collecting device 42 is moved in the in-plane direction by a scanning device (not shown). may be In addition, depending on whether the faceted region RF or the non-faceted region RN, or regardless of this, the Z-axis between the condenser 42 on the irradiation side of the laser beam B and the chuck table 41 supporting the ingot 2 Making directional distance adjustments is optional in the present invention. In addition, the specific configuration of the release layer forming apparatus 40 that is actually industrially realized can be appropriately changed from the exemplary configuration shown in FIGS. 4A and 4B.

In the above-described embodiment, the release layer 25 is formed on the ingot C-plane 21 side by "C-plane irradiation" in which the laser beam B is irradiated onto the ingot C-plane 21 . However, the invention is not limited to such aspects. That is, the present invention is also applicable to “Si surface side irradiation” in which the Si surface 22 of the ingot is irradiated with the laser beam B to form the separation layer 25 on the Si surface 22 side of the ingot.

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

The optical properties, that is, the transmittance and refractive index of the obtained wafer 1 or peeled body 30 are measured at a plurality of positions in the scanning direction Ds and the line feed direction Df, and the next irradiation of the laser beam B is performed based on the measurement results. Conditions may be controlled. FIG. 14 shows a schematic of such an embodiment. In the figure, "insertion/ejection" indicates the step of inserting and ejecting the stripped body 30 and the ingot 2, which are the workpieces. "Laser slicing" indicates a release layer forming step. "Strip" indicates a wafer stripping process. “Rough grinding” indicates a step of rough grinding the main surfaces of the ingot 2 and the peeled body 30 . For rough grinding, for example, it is possible to use an abrasive of about #800. "Finish grinding" indicates a process of finishing the surface. For the finish grinding, for example, it is possible to use an abrasive of about #30000. "Wafer optical measurement" indicates a step of measuring the optical properties (that is, transmittance and refractive index) of the peeled body 30 that has undergone finish grinding at multiple positions in the scanning direction Ds and the line feed direction Df. "Ingot cleaning" indicates a process of cleaning the ingot 2 after finish grinding. The arrows on the left side of the block indicating each step indicate the flow of processing for the ingot 2, and the arrows on the right side indicate the flow of processing for the wafer 1 or the peeled body 30, which can be commonly called a "wafer". .

Referring to FIG. 14 , first, ingot 2 is put into a wafer manufacturing apparatus including peeling layer forming apparatus 40 . Next, a peeling layer forming step is performed by irradiating the laser beam B to the ingot 2 that has been thrown. Subsequently, in the wafer peeling process, the peeling body 30 is peeled off from the ingot 2 that has undergone the peeling layer forming process. The upper surface of the ingot 2 newly produced in the ingot 2 that has undergone the wafer peeling process is flattened by rough grinding and finish grinding. After that, the ingot 2 is subjected to the release layer forming step again after being washed. The ingot 2 that has undergone the separation layer forming process or the ingot cleaning process is ejected from the wafer manufacturing apparatus when the height thereof becomes less than a predetermined value.

The peeled body 30 peeled from the ingot 2 by the wafer peeling process is subjected to rough grinding and finish grinding, and is subjected to optical measurement, that is, measurement of transmittance and refractive index. The measurement results are used to determine irradiation conditions (for example, irradiation energy and/or irradiation distance) of the laser beam B in the next release layer forming step. That is, based on the measurement results of the transmittance and refractive index for each location in the in-plane direction of the wafer 1, the irradiation conditions for each location in the in-plane direction of the ingot C surface 21 in the next peeling layer forming step are controlled. . As a result, it becomes possible to finely change the irradiation conditions corresponding to the variation in the optical characteristics of each location in the in-plane direction, thereby reducing the material loss. This is particularly effective when the ingot 2 has facet regions RF. Only one of the transmittance and the refractive index may be measured. Alternatively, transmittance and refractive index measurements may be made on the finally obtained epi-ready wafer 1 . Also, depending on the conditions of rough grinding (for example, in the case of ECMG), finish grinding may not be necessary. That is, rough grinding and finish grinding can be combined.

FIG. 15 shows an example of how optical measurement positions are set in the generator 100 . The product 100 is an object of optical measurement, and corresponds to the stripped body 30 whose surface is flattened to a predetermined extent after being stripped from the wafer 1 or ingot 2 . In this example, the optical measurement positions are set at a constant pitch (eg, 3 mm) in each of the X-axis direction (ie first direction) and the Y-axis direction (ie second direction). The X-axis direction is parallel to the scanning direction Ds shown in FIG. 6 and the like. Also, the Y-axis direction is parallel to the line feed direction Df shown in FIG. 6 and the like. Here, as shown in FIG. 16, when optical measurement is performed at a plurality of measurement positions on the measurement line Lx, FIG. shown in The measurement line Lx is an imaginary straight line parallel to the X-axis passing through the center of the product 100 in the in-plane direction and the facet region RF. The absorption coefficient is obtained or calculated by the following formula (1). In the following equation (1), α represents the absorption coefficient, D represents the thickness of the workpiece, that is, the thickness of the product 100, and T represents the transmittance.

In FIG. 17, the horizontal axis indicates the measurement position when the center of the product 100 in the in-plane direction is the origin, that is, "0". As shown in FIG. 17, the absorption coefficient is not constant in the in-plane direction, but changes as the measurement position changes. Specifically, the region with a high absorption coefficient on the right end side in FIG. 17 corresponds to the facet region RF. Moreover, even in the non-facet region RN having a lower absorption coefficient than the facet region RF, there is a distribution in the in-plane direction, that is, in the radial direction. A “radial direction” is a direction radially extending from the center of the in-plane direction of the generator 100 . Specifically, in the example of FIG. 17, there is a region with a low absorption coefficient on the left side of the center position, that is, on the outer side.

18A to 18C show how the modified layer generation position changes as the transmittance, that is, the absorption coefficient changes. The position where the modified layer is generated is the position where the modified layer, that is, the irradiation affected area RA is generated by condensing the laser beam B. can be shown. Here, the depth direction of the ingot 2 is a direction parallel to the height direction of the ingot 2, and more specifically, the direction opposite to the height direction of the ingot 2 (that is, the Z-axis negative direction in FIG. 1 and the like). ). In the drawing, the circle indicated by the dashed line beside the irradiation affected area RA indicates the condensing state of the laser beam B at the position where the modified layer is generated, ie, the beam diameter.

First, referring to FIG. 18A, as the laser beam B travels in the depth direction of the ingot 2, it is focused while being attenuated according to the absorption coefficient. Then, when the energy density is increased to a predetermined level by condensing, the processing threshold value is reached, and the 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 as shown in FIG. Reforming occurs when the energy density is reached. On the other hand, when the transmittance is high (that is, the absorption coefficient is low), the attenuation is small. Therefore, as shown in FIG. and reformation occurs. As described above, if the modified layer generation position varies due to the difference in transmittance, that is, the absorption coefficient, the surface of the product 100 after peeling becomes rough, and the processing allowance for grinding and polishing, ie, the material loss 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, in this modified example, the absorption coefficient is obtained, that is, calculated based on the transmittance measured in the generated body 100 generated in the past including the previous time. In this modified example, the irradiation energy of the laser beam B is determined based on the change tendency of the absorption coefficient in the depth direction of the ingot 2 for each different position within the plane.

A specific example of controlling the irradiation conditions of the next laser beam B based on the optical measurement result of the product 100 obtained last time will be described below. First, the transmittance and the like of the product 100 obtained last time are measured using a transmittance measuring instrument. At this time, the workpiece thickness is also measured. The absorption coefficient is calculated based on the measured transmittance, the work thickness, and the above equation (1). Then, the input energy, which is the irradiation energy of the laser beam B, is derived using the following equation (2). In the following formula (2) and FIG. 19, _I0 indicates the input energy, I indicates the energy required at the processing point, that is, the minimum applied energy required for reforming, and z indicates the depth. k indicates the amount of change in the absorption coefficient in the depth direction, that is, the change tendency of the absorption coefficient in the depth direction of the ingot 2 .

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

For example, as shown in FIG. 22, based on the amount of change between the absorption coefficient α _n−1 acquired last time and the absorption coefficient α _n−2 acquired the time before last, the absorption coefficient estimated value used for the current processing is It is possible to obtain or calculate α _n . Specifically, for example, the difference between the absorption coefficient α _n−1 acquired last time and the absorption coefficient α _n−2 acquired last time before last is taken as the amount of change in absorption coefficient, and this is used as the absorption coefficient α _n− acquired last time. By adding to ₁ , the absorption coefficient estimate α _n can be calculated. Then, the irradiation energy of the laser beam B can be determined based on the estimated absorption coefficient α _n . Statistical processing using a so-called "smoothing filter" or the like may be performed when calculating the amount of change in absorption coefficient.

Also, as shown in FIG. 23, a first generator 101 and a second generator 102 are generated. The first product 101 is the product 100 obtained from one end side of the ingot 2 in the height direction, that is, the C surface 21 side of the ingot. The second product 102 is the product 100 obtained from the other end side of the ingot 2 in the height direction, that is, the side of the Si surface 22 of the ingot. Next, the first absorption coefficient, which is the absorption coefficient in the first generated body 101, and the second absorption coefficient, which is the absorption coefficient in the second generated body 102, are obtained. Then, it is possible to determine the irradiation condition of the laser beam B, that is, the irradiation energy, by using the higher one of the first absorption coefficient and the second absorption coefficient as the upper limit of the absorption coefficient. In other words, the absorption coefficient obtained from the generator 100 having the higher absorption coefficient, ie, the wafer, may be set as the upper limit, and the coefficient setting may be such that the absorption coefficient is not changed beyond that limit.

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

The effect of the above contents was confirmed by experiments. The laser beam B used in the experiment is a pulsed laser with a wavelength of 1064 nm, a pulse width of 7 ns, and an oscillation frequency of 25 kHz. Laser beam B is a ring-shaped beam with an outer diameter of 4.85 mm and an inner diameter of 2.82 mm. The laser beam B was made incident on a lens of NA 0.65, and processing was performed at an irradiation pitch (that is, an irradiation interval in the scanning direction Ds) of 8 μm and a scanning interval (that is, an interval between scanning lines Ls in the line feed direction Df) of 120 μm. The ingot 2 to be processed has an outer diameter of 6 inches and an in-plane absorption coefficient difference of 2.49 mm ⁻¹ . The transmittance measurements were performed at a 3 mm pitch on the previously cut wafer 1 having a thickness of 0.385 mm. The input energy was set to an output setting in which an energy of 20 μJ was input at a depth of 0.4 mm in the center of the ingot 2 . At this time, when the processing was performed under a constant output, the height difference of the in-plane modification layer generation position was 61 μm. On the other hand, by correcting the output according to the change in the in-plane absorption coefficient, the height difference at the modified layer generation position was improved to 18 μm. It was shown that this can reduce material loss.

Needless to say, the elements constituting the above-described embodiments are not necessarily essential, unless explicitly stated as essential or clearly considered essential in principle. In addition, when numerical values such as the number, amount, range, etc. of a constituent element are mentioned, unless it is explicitly stated that it is particularly essential, or when it is clearly limited to a specific numerical value in principle, the specific numerical value The present invention is not limited to Similarly, when the shape, direction, positional relationship, etc. of the constituent elements, etc. are mentioned, unless it is explicitly stated that it is particularly essential, or when it is limited to a specific shape, direction, positional relationship, etc. in principle , the shape, direction, positional relationship, etc., of which the present invention is not limited.

Modifications are also not limited to the above examples. That is, for example, a plurality of embodiments other than those exemplified above can be combined with each other as long as they are not technically inconsistent. Likewise, multiple variants may be combined with each other unless technically inconsistent.

(Disclosure perspective)
As is clear from the description of the embodiments and modifications as described above, this specification discloses at least the following aspects.
[Viewpoint 1]
A wafer manufacturing method for obtaining a wafer (1) from an ingot (2), comprising:
A peeling layer (25) is formed from the surface to a depth corresponding to the thickness of the wafer by irradiating a surface (21) on one end side in the height direction of the ingot with a laser beam having transparency. , release layer formation, and
wafer peeling, wherein the wafer precursor (26), which is the portion between the surface and the peeling layer, is peeled from the ingot at the peeling layer;
Wafer flattening for flattening the main surface (32) of the plate-shaped peeled body (30) obtained by the wafer peeling;
including
Forming the release layer includes:
Laser scanning for irradiating the surface with the laser beam while moving the irradiation position (PR) of the laser beam on the surface in a first direction (Ds) along the surface is performed on the surface. In a second direction (Df) orthogonal to one direction and along the surface, scanning lines (Ls), which are irradiation traces of the linear laser beam along the first direction, are formed by performing a plurality of times while changing the position. , forming the release layer by forming a plurality of layers along the second direction;
A plurality of the scanning lines are formed by irradiating the surface with a plurality of the laser beams having different irradiation positions in the first direction and the second direction in one laser scanning.
Wafer manufacturing method.
[Viewpoint 2]
In aspect 1,
The release layer is formed such that the facet region (RF) has a higher energy application density in the plane along the surface due to the laser beam irradiation than the non-facet region (RN). is applied to the surface.
[Viewpoint 3]
In aspect 1 or 2,
Forming the release layer includes:
While moving the irradiation position in the first direction, forming the scanning line between both ends of the surface in the first direction,
While moving the irradiation position in a direction opposite to the first direction, the irradiation marks are formed on the end portion of the surface in the first direction.
[Viewpoint 4]
In terms of 1 to 3,
Forming the release layer includes:
a first scan for forming the scan line across both ends of the surface in the first direction while moving the irradiation position in the first direction;
While changing the distance from the surface of the condensing device (42) that irradiates the laser beam to the surface from the first scan and moving the irradiation position in the direction opposite to the first direction, the surface and a second scan forming the scan line between the ends in the first direction of the.
[Viewpoint 5]
In terms of 1 to 4,
The ingot is a single crystal SiC ingot having a c-axis (Lc) and a C-plane (Pc) perpendicular to each other,
The c-axis is provided in a state in which the central axis (L) orthogonal to the surface is inclined in the off-angle direction (Dθ) by an off-angle (θ) exceeding 0 degrees,
The wafer peeling is performed by applying a load in one direction at one end (23) of the ingot in the off-angle direction.
[Viewpoint 6]
In aspect 5,
The one end of the ingot in the off-angle direction is the high end of the C-plane when the ingot is oriented so that the surface faces upward.
[Viewpoint 7]
In aspect 5 or 6,
When the orientation of the ingot is set such that the surface faces upward, the release layer is formed such that the facet region (RF) is located on the lower side of the C plane.
[Viewpoint 8]
In terms of 1 to 7,
measuring the transmittance of the peeled body or the obtained wafer at a plurality of positions in the first direction and the second direction;
The irradiation conditions of the laser beam at each of the plurality of positions in the first direction and the second direction are controlled based on the measurement result of the transmittance.
[Viewpoint 9]
In aspect 8,
obtaining an absorption coefficient of the laser beam based on the transmittance;
The irradiation energy of the laser beam is determined based on the tendency of change in the absorption coefficient in the depth direction of the ingot for each different position in the plane along the surface.
[Viewpoint 10]
In aspect 9,
obtaining an amount of change in the absorption coefficient in the depth direction based on the tendency of change in the absorption coefficient in the depth direction of the ingot;
The irradiation energy of the laser beam is determined based on the value obtained by adding or multiplying the absorption coefficient change amount to the absorption coefficient obtained last time.
[Viewpoint 11]
In aspects 9 and 10,
The irradiation energy of the laser beam is determined based on the absorption coefficient estimated value obtained based on the amount of change between the absorption coefficient obtained last time and the absorption coefficient obtained last time before.
[Viewpoint 12]
In aspects 9-11,
A first product (101) that is the separated body or the wafer obtained from the ingot on one end side in the height direction, and the separation obtained from the ingot on the other end side in the height direction a second product (102), which is the body or the wafer;
obtaining a first absorption coefficient, which is the absorption coefficient in the first generated body, and a second absorption coefficient, which is the absorption coefficient in the second generated body;
The irradiation energy of the laser beam is determined using the higher one of the first absorption coefficient and the second absorption coefficient as the upper limit of the absorption coefficient.
[Viewpoint 13]
In aspects 8-12,
In the second region where the change in absorption coefficient is greater than in the first region, the measurement pitch of the transmittance is made finer than in the first region.
[Viewpoint 14]
In aspect 13,
The second area is a boundary area between the non-facet area (RN) and the facet area (RF).
[Viewpoint 15]
In aspects 1 to 14,
The plurality of laser beams has a first beam, a second beam, and a third beam arranged at different positions with respect to the second direction.
[Viewpoint 16]
In aspect 15,
The second beam is located between the first beam and the third beam with respect to the first direction and the second direction.
[Viewpoint 17]
In aspect 15,
The first beam, the second beam and the third beam are arranged in a V shape on the surface.

REFERENCE SIGNS LIST 1 wafer 2 ingot 21 ingot C surface (surface)
25 Release layer 26 Wafer precursor 30 Release body 32 Release surface (principal surface)
L central axis Lc c axis Pc (0001) plane

Claims (17)

A wafer manufacturing method for obtaining a wafer (1) from an ingot (2), comprising:
A peeling layer (25) is formed from the surface to a depth corresponding to the thickness of the wafer by irradiating a surface (21) on one end side in the height direction of the ingot with a laser beam having transparency. , release layer formation, and
wafer peeling, wherein the wafer precursor (26), which is the portion between the surface and the peeling layer, is peeled from the ingot at the peeling layer;
Wafer flattening for flattening the main surface (32) of the plate-shaped peeled body (30) obtained by the wafer peeling;
including
Forming the release layer includes:
Laser scanning for irradiating the surface with the laser beam while moving the irradiation position (PR) of the laser beam on the surface in a first direction (Ds) along the surface is performed on the surface. In a second direction (Df) orthogonal to one direction and along the surface, scanning lines (Ls), which are irradiation traces of the linear laser beam along the first direction, are formed by performing a plurality of times while changing the position. , forming the release layer by forming a plurality of layers along the second direction;
A plurality of the scanning lines are formed by irradiating the surface with a plurality of the laser beams having different irradiation positions in the first direction and the second direction in one laser scanning.
Wafer manufacturing method. The release layer is formed such that the facet region (RF) has a higher energy application density in the plane along the surface due to the laser beam irradiation than the non-facet region (RN). irradiating said surface with
A wafer manufacturing method according to claim 1 . Forming the release layer includes:
While moving the irradiation position in the first direction, forming the scanning line between both ends of the surface in the first direction,
While moving the irradiation position in a direction opposite to the first direction, forming the irradiation mark at an end portion of the surface in the first direction;
A wafer manufacturing method according to claim 1 . Forming the release layer includes:
a first scan for forming the scan line across both ends of the surface in the first direction while moving the irradiation position in the first direction;
While changing the distance from the surface of the condensing device (42) that irradiates the laser beam to the surface from the first scan and moving the irradiation position in the direction opposite to the first direction, the surface a second scan that forms the scan line between both ends in the first direction of
A wafer manufacturing method according to claim 1 . The ingot is a single crystal SiC ingot having a c-axis (Lc) and a C-plane (Pc) perpendicular to each other,
The c-axis is provided in a state in which the central axis (L) orthogonal to the surface is inclined in the off-angle direction (Dθ) by an off-angle (θ) exceeding 0 degrees,
The wafer peeling is performed by applying a load in one direction at one end (23) of the ingot in the off-angle direction.
A wafer manufacturing method according to claim 1 . The one end of the ingot in the off-angle direction is a high end of the C-plane when the ingot is oriented so that the surface faces upward.
A wafer manufacturing method according to claim 5 . When the orientation of the ingot is set so that the surface faces upward, the release layer is formed so that the facet region (RF) is positioned on the lower side of the C plane.
The wafer manufacturing method according to claim 5 or 6. measuring the transmittance of the peeled body or the obtained wafer at a plurality of positions in the first direction and the second direction;
controlling irradiation conditions of the laser beam at each of the plurality of positions based on the measurement result of the transmittance;
A wafer manufacturing method according to claim 1 . obtaining an absorption coefficient of the laser beam based on the transmittance;
determining the irradiation energy of the laser beam based on the change tendency of the absorption coefficient in the depth direction of the ingot for each different position in the plane along the surface;
A wafer manufacturing method according to claim 8 . obtaining an amount of change in the absorption coefficient in the depth direction based on the tendency of change in the absorption coefficient in the depth direction of the ingot;
Determining the irradiation energy of the laser beam based on the value obtained by adding or multiplying the absorption coefficient change amount to the absorption coefficient obtained last time,
A wafer manufacturing method according to claim 9 . determining the irradiation energy of the laser beam based on an estimated absorption coefficient obtained based on the amount of change between the absorption coefficient obtained last time and the absorption coefficient obtained last time before;
A wafer manufacturing method according to claim 9 . A first product (101) that is the separated body or the wafer obtained from the ingot on one end side in the height direction, and the separation obtained from the ingot on the other end side in the height direction a second product (102), which is the body or the wafer;
obtaining a first absorption coefficient, which is the absorption coefficient in the first generated body, and a second absorption coefficient, which is the absorption coefficient in the second generated body;
The irradiation energy of the laser beam is determined using the higher value of the first absorption coefficient and the second absorption coefficient as the upper limit of the absorption coefficient.
A wafer manufacturing method according to claim 9 . In a second region where the change in the absorption coefficient is larger than in the first region, the transmittance measurement pitch is made finer than in the first region.
A wafer manufacturing method according to claim 9 . The second region is a boundary region between a non-facet region (RN) and a facet region (RF),
14. A wafer manufacturing method according to claim 13. The plurality of laser beams has a first beam, a second beam, and a third beam arranged at different positions with respect to the second direction,
A wafer manufacturing method according to claim 1 . the second beam is located between the first beam and the third beam with respect to the first direction and the second direction;
16. A wafer manufacturing method according to claim 15. the first beam, the second beam, and the third beam are arranged in a V-shape on the surface;
16. A wafer manufacturing method according to claim 15.

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