Ingot processing method and processing apparatus

Abstract

To provide an ingot processing method and processing device which allow a user to three-dimensionally confirm facet regions with different impurity densities in an ingot.SOLUTION: An ingot processing method comprises: a fluorescence detection step 1 of detecting fluorescence generated from an upper surface of an ingot by irradiating with exciting light; a storage step S2 of storing the distribution of the photon number of fluorescence on the upper surface of the ingot in association with the XY coordinate position as two-dimensional data and storing the Z coordinate position where the two-dimensional data is acquired; a laser beam irradiation step 3 of performing irradiation by positioning the light condensing point of the laser beam at the depth equivalent to the thickness of a wafer from the upper surface of the ingot and forming a peeling layer; a wafer generation step 4 of separating the wafer from the ingot with the peeling layer as a starting point; and a three-dimensional data generation step 5 of generating the three-dimensional data indicating the distribution of the photon number of fluorescence in the entire ingot on the basis of the two-dimensional data at the Z coordinate position of each ingot.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for processing an ingot.

Background Art

[0002] Conventionally, as a method for manufacturing a semiconductor wafer, a method of cutting out a wafer from a columnar ingot using a wire saw is known. However, cutting with a wire saw has a problem in that most of the ingot is lost as kerf loss, so it is not economical. In addition, since a single crystal of SiC used as a power device has a high hardness, there is a problem in that it takes a long time to cut and the productivity is poor. To solve this problem, a method has been proposed in which the focal point of a laser beam is positioned inside the ingot and the focal point is scanned to slice a plate-like workpiece from the ingot (see Patent Document 1).

[0003] By the way, impurities such as nitrogen are generally doped into a SiC single crystal ingot in order to impart conductivity. For example, in a region called a facet region formed during the growth process of a SiC single crystal, which is a flat region at the atomic level, nitrogen is relatively more likely to be incorporated than other parts, so the nitrogen concentration becomes higher than that of other regions. When there are regions with different impurity concentrations like this, when a wafer is cut out from the ingot, variations in resistivity occur within the wafer surface, which causes a decrease in the yield of the device. Therefore, various techniques for controlling the facet region and growing the crystal have been proposed (see Patent Documents 2 and 3).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

[0005] However, since these impurities are not uniformly doped throughout the ingot, it is difficult to accurately evaluate the internal state of the ingot after crystal growth, and there is a challenge in providing appropriate feedback to the crystal growth process.

[0006] This invention has been made in view of the above problems, and its purpose is to provide an ingot processing method and processing apparatus that can three-dimensionally confirm facet regions with different impurity concentrations inside the ingot. [Means for solving the problem]

[0007] To solve the above-mentioned problems and achieve the objective, the present invention provides an ingot processing method comprising: a fluorescence detection step of irradiating the ingot with excitation light of a predetermined wavelength from above and detecting the number of fluorescent photons generated from the upper surface of the ingot; a storage step of storing the distribution of the number of fluorescent photons on the upper surface of the ingot detected in the fluorescence detection step as two-dimensional data linked to the XY coordinate position on an XY plane perpendicular to the height direction of the ingot, and storing the Z coordinate position, which is the height direction of the ingot where the two-dimensional data was obtained, linked to the two-dimensional data; and, after the storage step, generating a focal point of a laser beam with a wavelength that is penetrating to the ingot from the upper surface of the ingot. The process includes: a laser beam irradiation step in which the laser beam is positioned and irradiated at a depth corresponding to the thickness of the wafer, and the focusing point and the ingot are moved relative to each other in the XY direction to form a delamination layer on the ingot; a wafer generation step in which the wafer is separated from the ingot starting from the delamination layer formed in the laser beam irradiation step; a three-dimensional data generation step in which, after repeatedly performing the fluorescence detection step, the storage step, the laser beam irradiation step and the wafer generation step to generate multiple wafers from the ingot, three-dimensional data showing the distribution of the number of fluorescent photons in the entire ingot based on the two-dimensional data at the Z coordinate position of each ingot stored in the storage step; and The ingot is made of SiC. The present invention is characterized by the following: In addition, in the ingot processing method of the present invention, after the wafer generation step, the process returns to the fluorescence detection step, and the fluorescence detection step, the storage step, the laser beam irradiation step, and the wafer generation step are repeatedly performed in order until multiple wafers are generated from the ingot, thereby accumulating two-dimensional data at the Z coordinate position of each ingot, and then the three-dimensional data generation step is performed. In the laser beam irradiation step, the height of the focusing lens that focuses the laser beam is changed based on the two-dimensional data stored in the storage step so that the position of the focal point in the thickness direction of the ingot remains constant. do Preferably .

[0008] Furthermore, the ingot processing method of the present invention may further include a display step of displaying the three-dimensional data.

[0009] Furthermore, in the ingot processing method of the present invention, in the storage step, regions where the number of fluorescent photons detected in the fluorescence detection step is greater than or equal to a predetermined value are designated as non-faceted regions, and regions where the number of fluorescent photons is less than the predetermined value are designated as faceted regions, and the XY coordinate positions of the non-faceted regions and the faceted regions are stored, and in the display step, the boundary between the faceted regions and non-faceted regions in the entire ingot may be displayed.

[0010] Furthermore, the present invention relates to a processing apparatus for producing a plurality of wafers from an ingot, comprising: a holding unit having a holding surface for holding the ingot; a fluorescence detection unit that irradiates the ingot with excitation light of a predetermined wavelength from above and detects the number of photons of fluorescence generated from the upper surface of the ingot; a laser beam irradiation unit that positions the focal point of a laser beam with a wavelength that is transparent to the ingot at a depth corresponding to the thickness of the wafer to be produced from the upper surface of the ingot and irradiates it to form a peel layer; and the holding unit and the focal point of the laser beam relative to each other in the XY direction parallel to the holding surface. The device includes a moving unit for moving the ingot and a control unit, the control unit storing the distribution of the number of fluorescent photons on the upper surface of the ingot detected by the fluorescence detection unit as two-dimensional data linked to the XY coordinate position on an XY plane parallel to the holding surface, and a storage unit that stores the Z coordinate position, which is the height position of the ingot from which the two-dimensional data was acquired, linked to the two-dimensional data, and a three-dimensional data generation unit that generates three-dimensional data showing the distribution of the number of fluorescent photons in the entire ingot based on the two-dimensional data at each Z coordinate position of the ingot stored in the storage unit. Furthermore, the ingot is made of SiC. The present invention is characterized by the following: In the processing apparatus of the present invention, the control unit stores the two-dimensional data and the Z coordinate position in the storage unit, then controls the laser beam irradiation unit and the moving unit to form the delamination layer on the wafer, and after the wafer has been separated from the delamination layer, the fluorescence detection unit detects the number of photons of fluorescence on the new upper surface of the ingot, and stores a plurality of the two-dimensional data and the Z coordinate position in the storage unit. death, Based on the two-dimensional data stored in the memory unit, the height of the focusing lens that focuses the laser beam is changed so that the position of the focal point in the thickness direction of the ingot remains constant. ru Preferably .

[0011] Furthermore, the processing apparatus of the present invention may further include a display unit for displaying the three-dimensional data.

[0012] Furthermore, in the apparatus of the present invention, the storage unit may store the XY coordinate positions of the non-faceted region and the faceted region, with the region where the number of fluorescent photons detected by the fluorescence detection unit is greater than or equal to a predetermined value being a non-faceted region and the region where the number of fluorescent photons is less than the predetermined value being a faceted region, and the display unit may display the boundary between the faceted region and the non-faceted region in the entire ingot. [Effects of the Invention]

[0013] This invention makes it possible to three-dimensionally identify facet regions within an ingot that have different impurity concentrations. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a perspective view of the ingot to be processed by the ingot processing method according to the embodiment. [Figure 2] Figure 2 is a side view of the ingot shown in Figure 1. [Figure 3] Figure 3 is a perspective view showing an example of the configuration of the processing apparatus according to the embodiment. [Figure 4] Figure 4 is an explanatory diagram illustrating the schematic configuration of the fluorescence detection unit of the processing device shown in Figure 3. [Figure 5] Figure 5 is a flowchart showing the flow of the ingot processing method according to the embodiment. [Figure 6] Figure 6 is a perspective view showing the fluorescence detection step shown in Figure 5. [Figure 7] Figure 7 shows an example of the XY coordinate positions where fluorescence was detected in the fluorescence detection step shown in Figure 5. [Figure 8]FIG. 8 is a diagram showing an example of two-dimensional data stored in the storage step shown in FIG. 5. [Figure 9] FIG. 9 is a perspective view showing the laser beam irradiation step shown in FIG. 5. [Figure 10] FIG. 10 is a side view of FIG. 9. [Figure 11] FIG. 11 is a diagram showing a state of the wafer generation step shown in FIG. 5. [Figure 12] FIG. 12 is a diagram showing a state after FIG. 11 of the wafer generation step shown in FIG. 5. [Figure 13] FIG. 13 is a schematic diagram of a plurality of two-dimensional data accumulated before the three-dimensional data generation step shown in FIG. 5. [Figure 14] FIG. 14 is a schematic diagram of the three-dimensional data generated in the three-dimensional data generation step shown in FIG. 5.

BEST MODE FOR CARRYING OUT THE INVENTION

[0015] A mode (embodiment) for carrying out the present invention will be described in detail while referring to the drawings. The present invention is not limited by the content described in the following embodiments. Further, the constituent elements described below include those that can be easily assumed by those skilled in the art and substantially the same ones. Furthermore, the configurations described below can be combined as appropriate. Also, various omissions, substitutions, or changes in the configuration can be made without departing from the gist of the present invention.

[0016] 〔Embodiment〕 A method for processing the ingot 10 and a processing apparatus 100 according to an embodiment of the present invention will be described based on the drawings. The method for processing the ingot 10 in the embodiment uses the processing apparatus 100 shown in FIGS. 3 and 4 to generate a plurality of wafers 30 shown in FIGS. 1 and 13 from the ingot 10 shown in FIGS. 1 and 2, and to generate three-dimensional data of the facet region 21 inside the ingot 10 shown in FIG. 14.

[0017] (Ingot) First, the configuration of the ingot 10 to be processed by the ingot 10 processing method according to an embodiment of the present invention will be described. Figure 1 is a perspective view of the ingot 10 to be processed by the ingot 10 processing method according to an embodiment. Figure 2 is a side view of the ingot 10 shown in Figure 1.

[0018] The ingot 10 in the embodiment shown in Figures 1 and 2 is made of SiC (silicon carbide) and is formed in a cylindrical shape overall. In this embodiment, the ingot 10 is a hexagonal single crystal SiC ingot. The ingot 10 has a first face 11, a second face 12, a circumferential face 13, a first orientation flat 14, and a second orientation flat 15.

[0019] The first surface 11 is circular and is one end face of the cylindrical ingot 10. The first surface 11 corresponds to the top surface of the ingot 10. The second surface 12 is circular and is the end face of the cylindrical ingot 10 opposite to the first surface 11. The second surface 12 corresponds to the bottom surface of the ingot 10. The circumferential surface 13 is a surface that connects the outer edge of the first surface 11 and the outer edge of the second surface 12.

[0020] The first orientation flat 14 is a plane formed on a portion of the circumferential surface 13 to indicate the crystal orientation of the ingot 10. The second orientation flat 15 is a plane formed on a portion of the circumferential surface 13 to indicate the crystal orientation of the ingot 10. The second orientation flat 15 is perpendicular to the first orientation flat 14. The length of the first orientation flat 14 is longer than the length of the second orientation flat 15.

[0021] Furthermore, the ingot 10 has a c-axis 18 that is inclined at an off-angle of 20 in a direction 17 toward the second orientation flat 15 with respect to the perpendicular 16 of the first face 11, and a c-face 19 that is perpendicular to the c-axis 18. The direction 17 of inclination of the c-axis 18 from the perpendicular 16 is perpendicular to the extension direction of the second orientation flat 15 and parallel to the first orientation flat 14. The c-face 19 is inclined at an off-angle of 20 with respect to the first face 11 of the ingot 10.

[0022] The c-face 19 is set infinitely many times in the ingot 10 at the molecular level. In the embodiment, the off-angle 20 of the ingot 10 is set to 1°, 4°, or 6°, but in the present invention, it may be manufactured with the off-angle freely set in the range of, for example, 1° to 6°. The first face 11 of the ingot 10 is ground by a grinding device and then polished by a polishing device to form a mirror surface on the first face 11.

[0023] Furthermore, the ingot 10 of the embodiment is mainly formed as a hexagonal single crystal SiC ingot, but a localized facet region 21 exists. The facet region 21 is formed in a columnar shape from the first face 11 to the second face 12 of the ingot 10 (see Figure 14). Compared to the non-facet region 22 other than the facet region 21, nitrogen is relatively more easily incorporated into the facet region 21, so the nitrogen concentration is higher than in other regions.

[0024] (processing device) Next, the configuration of the processing apparatus 100 according to an embodiment of the present invention will be described. Figure 3 is a perspective view showing an example of the configuration of the processing apparatus 100 according to an embodiment. Figure 4 is an explanatory diagram illustrating the schematic configuration of the fluorescence detection unit 120 of the processing apparatus 100 shown in Figure 3. In the following description, the X-axis direction is one direction in the horizontal plane. The Y-axis direction is a direction perpendicular to the X-axis direction in the horizontal plane. The Z-axis direction is a direction perpendicular to both the X-axis and Y-axis directions. The processing apparatus 100 of the embodiment includes a holding unit 110, a fluorescence detection unit 120, a laser beam irradiation unit 140, a moving unit 150, a display unit 160, and a control unit 170.

[0025] The holding unit 110 holds the ingot 10 on its holding surface 111. The holding surface 111 is a disc shape formed from porous ceramic or the like. In this embodiment, the holding surface 111 is a plane parallel to the horizontal direction. The holding surface 111 is connected to a vacuum suction source, for example, via a vacuum suction path. The holding unit 110 holds the ingot 10 placed on the holding surface 111 by suction.

[0026] The holding unit 110 is rotated by the rotating unit 112 around an axis parallel to the Z-axis direction. The rotating unit 112 is supported by the X-axis direction moving plate 113. The rotating unit 112 and the holding unit 110 are moved in the X-axis direction by the moving unit 150 via the X-axis direction moving plate 113. The rotating unit 112 and the holding unit 110 are moved in the Y-axis direction by the moving unit 150 via the X-axis direction moving plate 113 and the Y-axis direction moving plate 114.

[0027] The fluorescence detection unit 120 is a unit that irradiates the ingot 10, which is held on the holding surface 111 of the holding unit 110, with excitation light 121 of a predetermined wavelength from above the ingot 10, and detects fluorescence 122 generated from the upper surface of the ingot 10. Part of the fluorescence detection unit 120 is supported at the tip of a support beam 103 that extends horizontally from the upper end of a vertical wall 102 erected from the main body of the apparatus 101. As shown in Figure 4, the fluorescence detection unit 120 includes an excitation light source 123, a focusing lens 124, an excitation light reflector 125, a light receiving unit 126, a bandpass filter 127, and a fluorescence reflector 128.

[0028] The excitation light source 123 irradiates the ingot 10 with excitation light 121 having a wavelength absorbed by the ingot 10. The excitation light source 123 has, for example, a GaN (gallium nitride) light-emitting element.

[0029] The focusing lens 124 focuses the excitation light 121 irradiated from the excitation light source 123 toward the upper surface (first surface 11) of the ingot 10 held on the holding surface 111 of the holding unit 110. In this embodiment, the focusing lens 124 is positioned between the excitation light reflector 125 and the ingot 10, but in this invention, it may be positioned between the excitation light source 123 and the excitation light reflector 125.

[0030] The excitation light reflector 125 reflects the excitation light 121 irradiated from the excitation light source 123 and guides it toward the upper surface (first surface 11) of the ingot 10 held on the holding surface 111 of the holding unit 110. In this embodiment, the excitation light reflector 125 also reflects the excitation light 121 irradiated from the excitation light source 123 toward the focusing lens 124.

[0031] The light-receiving unit 126 detects the number of photons of fluorescence 122 emitted from the upper surface of the ingot 10. The light-receiving unit 126 includes a highly sensitive photodetector that converts light energy into electrical energy using, for example, the photoelectric effect, and also has a current amplification (electron multiplication) function. The light-receiving unit 126 is, for example, placed in a vacuum region partitioned by a glass tube, and receives photoelectrons (photons) of fluorescence 122 that have passed through the glass tube, and outputs an electrical signal indicating the number of photons of fluorescence 122. The photoelectrons of fluorescence 122 received by the light-receiving unit 126 generate secondary electrons one after another through photoelectron collisions, thereby amplifying the current.

[0032] The bandpass filter 127 is positioned before the light-receiving unit 126. The bandpass filter 127 allows light of a predetermined wavelength from the fluorescence 122 generated from the upper surface of the ingot 10 to pass through, and removes light of wavelengths other than the fluorescence 122 of the predetermined wavelength. Therefore, for example, even if some of the excitation light 121 is scattered and directed towards the light-receiving unit 126, the excitation light 121 is removed by the bandpass filter 127.

[0033] The fluorescent reflector 128 reflects the fluorescence 122 emitted from the upper surface of the ingot 10 toward the light receiving unit 126. The fluorescent reflector 128 is a spheroidal mirror whose reflective surface 129 is made up of a part of the surface of a spheroid obtained by rotating an ellipse 130, which has a major axis 131 extending vertically and a minor axis 132 perpendicular to the major axis 131, around the major axis 131.

[0034] Elliptic mirrors are known to have two foci, and light emitted from one focal point is reflected by the inner surface of the elliptic mirror before reaching the other focal point. The elliptic mirror forming the spheroid in this embodiment has a first focal point 133 and a second focal point 134. At the position of the first focal point 133, a portion of the upper surface of the ingot 10 is positioned to be irradiated with excitation light 121. A light-receiving unit 126 is positioned at the second focal point 134.

[0035] With this configuration, when excitation light 121 is shone toward the upper surface of the ingot 10 located at the first focal point 133, fluorescence 122 is emitted from the upper surface of the ingot 10 by the excitation light 121. The fluorescence 122 is reflected by a reflective surface 129 which is part of a spheroid, focused toward the second focal point 134, and received by a light-receiving unit 126 located at the second focal point 134.

[0036] Therefore, the fluorescence 122 emitted from the upper surface of the ingot 10 can be efficiently guided via the reflective surface 129 to the light-receiving unit 126 located at the second focal point 134, thereby reducing the loss of weak fluorescence 122. Furthermore, in this embodiment, since the light-receiving unit 126 is located at the second focal point 134, detection sensitivity can be improved even for fluorescence 122 of low intensity.

[0037] The laser beam irradiation unit 140 shown in Figure 3 is a unit that irradiates an ingot 10 held on the holding surface 111 of the holding unit 110 with a pulsed laser beam 141 (see Figure 9, etc.) of a predetermined wavelength. Part of the laser beam irradiation unit 140 is supported at the tip of a support beam 103 that extends horizontally from the upper end of a vertical wall 102 erected from the main body 101 of the apparatus. The irradiation section of the laser beam irradiation unit 140 is provided adjacent to the irradiation section of the fluorescence detection unit 120.

[0038] The laser beam irradiation unit 140, for example, positions the focal point 142 (see Figure 9, etc.) of a laser beam 141 with a wavelength that is transparent to the ingot 10 at a depth corresponding to the thickness of the wafer 30 (see Figure 11, etc.) to be produced from the top surface of the ingot 10 and irradiates it, thereby forming a delamination layer 24 (see Figure 10, etc.).

[0039] The moving unit 150 is a unit that moves the holding unit 110 and the focal point 142 of the laser beam 141 emitted from the laser beam irradiation unit 140 relative to the holding surface 111 in the XY direction. The moving unit 150 includes an X-axis moving unit 151 and a Y-axis moving unit 152.

[0040] The X-axis movement unit 151 is a unit that moves the holding unit 110 and the focal point 142 of the laser beam 141 irradiated from the laser beam irradiation unit 140 relative to each other in the X-axis direction, which is the processing feed direction. In the embodiment, the X-axis movement unit 151 moves the holding unit 110 in the X-axis direction. In the embodiment, the X-axis movement unit 151 is installed on the main body 101 of the processing apparatus 100. The X-axis movement unit 151 supports the X-axis movement plate 113 so as to be movable in the X-axis direction.

[0041] The Y-axis movement unit 152 is a unit that moves the holding unit 110 and the focal point 142 of the laser beam 141 irradiated from the laser beam irradiation unit 140 relative to each other in the Y-axis direction, which is the indexing and feeding direction. In the embodiment, the Y-axis movement unit 152 moves the holding unit 110 in the Y-axis direction. In the embodiment, the Y-axis movement unit 152 is installed on the main body 101 of the processing device 100. The Y-axis movement unit 152 supports the Y-axis movement plate 114 so that it can move freely in the Y-axis direction.

[0042] The X-axis movement unit 151 and the Y-axis movement unit 152 each include, for example, a well-known ball screw, a well-known pulse motor, and a well-known guide rail. The ball screw is rotatably mounted around its axis. The pulse motor rotates the ball screw around its axis. The guide rail of the X-axis movement unit 151 is fixed to the Y-axis movement plate 114 and supports the X-axis movement plate 113 so as to be movable in the X-axis direction. The guide rail of the Y-axis movement unit 152 is fixed to the device body 101 and supports the Y-axis movement plate 114 so as to be movable in the Y-axis direction.

[0043] The moving unit 150 may further include a Z-axis moving unit that moves the holding unit 110 and the focal point 142 of the laser beam 141 emitted from the laser beam irradiation unit 140 relative to each other in the Z-axis direction, which is the focusing direction. The Z-axis moving unit moves the condenser of the laser beam irradiation unit 140 in the Z-axis direction.

[0044] In this embodiment, the irradiation section of the fluorescence detection unit 120 is provided adjacent to the irradiation section of the laser beam irradiation unit 140. Therefore, the moving unit 150 is also a unit that moves the holding unit 110 and the irradiation position of the excitation light 121 irradiated from the fluorescence detection unit 120 relative to each other in the XY direction parallel to the holding surface 111.

[0045] The display unit 160 is a display unit composed of a liquid crystal display device or the like. The display unit 160 displays, for example, the processing condition setting screen, the state of the ingot 10 captured by an imaging unit (not shown), the processing operation status, and two-dimensional and three-dimensional data generated by the control unit 170 (described later) on its display surface. The imaging unit includes, for example, a micro microscope and a macro microscope, and is provided adjacent to the fluorescence detection unit 120 and the irradiation section of the laser beam irradiation unit 140.

[0046] If the display surface of the display unit 160 includes a touch panel, the display unit 160 may also include an input unit. The input unit can accept various operations from the operator, such as registering processing content information. The input unit may also be an external input device such as a keyboard. The information and images displayed on the display surface of the display unit 160 can be switched by operations from the input unit, etc. The display unit 160 may also include a notification device. The notification device notifies the operator of the processing device 100 of predetermined notification information by emitting at least one of sound and light. The notification device may also be an external notification device such as a speaker or a light-emitting device.

[0047] The control unit 170 controls each of the above-mentioned components of the processing unit 100 to cause the processing unit 100 to perform processing operations on the ingot 10. The control unit 170 is a computer that includes an arithmetic processing unit as an arithmetic means, a memory device as a storage means, and an input / output interface device as a communication means.

[0048] The arithmetic processing unit includes, for example, a microprocessor such as a CPU (Central Processing Unit). The storage device has memory such as ROM (Read Only Memory) or RAM (Random Access Memory). The arithmetic processing unit performs various calculations based on a predetermined program stored in the storage device. The arithmetic processing unit outputs various control signals to the above-mentioned components via an input / output interface device according to the calculation results, thereby controlling the processing unit 100.

[0049] The control unit 170, for example, instructs the fluorescence detection unit 120 to irradiate the ingot 10, held by the holding unit 110, with excitation light 121 of a predetermined wavelength from above the ingot 10. The control unit 170, for example, acquires the number of photons of fluorescence 122 generated from the upper surface of the ingot 10 as detected by the fluorescence detection unit 120.

[0050] The control unit 170, for example, causes the moving unit 150 to position the focal point 142 of the laser beam 141 irradiated by the laser beam irradiation unit 140 at a depth corresponding to the thickness of the wafer 30 to be produced from the upper surface of the ingot 10 held by the holding unit 110. The control unit 170, for example, causes the laser beam irradiation unit 140 to irradiate the ingot 10 held by the holding unit 110 with a laser beam 141 of a wavelength that is penetrating. The control unit 170, for example, causes the moving unit 150 to move the focal point 142 of the laser beam 141 and the holding unit 110 that holds the ingot 10 relative to each other in the XY direction.

[0051] The control unit 170 causes the display unit 160 to display various information and processing results. The control unit 170 causes the display unit 160 to display two-dimensional data stored in the storage unit 171 (described later). The control unit 170 causes the display unit 160 to display three-dimensional data generated by the three-dimensional data generation unit 172 (described later). In this case, the control unit 170 causes the display unit 160 to display the boundary 25 (see Figure 14) between the facet region 21 and the non-facet region 22 of the entire ingot 10. The control unit 170 includes the storage unit 171 and the three-dimensional data generation unit 172.

[0052] The memory unit 171 stores the distribution of photons of fluorescence 122 on the upper surface of the ingot 10 detected by the fluorescence detection unit 120. At this time, the memory unit 171 stores the distribution of photons of fluorescence 122 as two-dimensional data, linked to the XY coordinate position on the XY plane parallel to the holding surface 111 of the holding unit 110. The memory unit 171 also stores the Z coordinate position, which is the height position of the ingot 10 from which the two-dimensional data was acquired, linked to the two-dimensional data.

[0053] The memory unit 171 stores the XY coordinate positions of the non-faceted region 22 and the faceted region 21, defining the region where the number of photons of fluorescence 122 detected by the fluorescence detection unit 120 is greater than or equal to a predetermined value as the non-faceted region 22, and the region where the number of photons of fluorescence 122 is less than or equal to a predetermined value as the faceted region 21.

[0054] The three-dimensional data generation unit 172 generates three-dimensional data showing the distribution of the number of photons of fluorescence 122 throughout the ingot 10, based on the two-dimensional data at each Z-coordinate position of the ingot 10 stored in the storage unit 171.

[0055] (How to process ingots) Next, a method for processing an ingot 10 according to an embodiment of the present invention will be described. Figure 5 is a flowchart showing the flow of the processing method for an ingot 10 according to an embodiment. The processing method for an ingot 10 includes a fluorescence detection step 1, a storage step 2, a laser beam irradiation step 3, a wafer generation step 4, a three-dimensional data generation step 5, and a display step 6. The fluorescence detection step 1, the storage step 2, the laser beam irradiation step 3, and the wafer generation step 4 are repeatedly performed while generating multiple wafers 30 from one ingot 10.

[0056] <Fluorescence detection step 1> Figure 6 is a perspective view showing the fluorescence detection step 1 shown in Figure 5. The fluorescence detection step 1 is a step in which excitation light 121 of a predetermined wavelength is irradiated onto the ingot 10 from above and the number of photons of fluorescence 122 generated from the upper surface of the ingot 10 is detected.

[0057] In fluorescence detection step 1, first, the second surface 12 side of the ingot 10 is held by attraction to the holding surface 111 of the holding unit 110. Next, the height of the fluorescence detection unit 120 is adjusted so that the first focal point 133 (see Figure 4) of the fluorescence detection unit 120 is positioned on the first surface 11 of the ingot 10, and the holding unit 110 is moved by the moving unit 150 so that the irradiation part of the fluorescence detection unit 120 faces the periphery of the first surface 11 of the ingot 10.

[0058] In this state, the rotating unit 112 rotates the holding unit 110 at a predetermined rotational speed (for example, 900° / sec) to rotate the ingot 10 in a predetermined direction (the direction of the arrow shown at the bottom of Figure 6). While continuously irradiating the fluorescence detection unit 120 with excitation light 121 toward the upper surface (first surface 11) of the ingot 10, the holding unit 110 is moved so that the fluorescence detection unit 120 moves radially (the direction of the arrow shown at the top of Figure 6) from the periphery to the center of the ingot 10, as shown in Figure 6. As a result, the fluorescence detection unit 120 passes through a spiral trajectory from the periphery to the center of the ingot 10.

[0059] In fluorescence detection step 1, the number of photons of fluorescence 122 generated from the upper surface of the ingot 10 is obtained, and the XY coordinate position of the location where the excitation light 121 was irradiated when the fluorescence 122 was obtained is also obtained.

[0060] <Memory Step 2> Figure 7 shows an example of the XY coordinate positions where fluorescence 122 was detected in fluorescence detection step 1 shown in Figure 5. Figure 8 shows an example of the two-dimensional data stored in storage step 2 shown in Figure 5. Storage step 2 is a step in which the distribution of the number of photons of fluorescence 122 on the upper surface of the ingot 10 detected in fluorescence detection step 1 is stored as two-dimensional data linked to the XY coordinate positions, and the Z coordinate position of the ingot 10 from which the two-dimensional data was acquired is stored linked to the two-dimensional data.

[0061] In memory step 2, for example, for detection positions 23-1, 23-2, 23-3, 23-4, and 23-5 shown in Figure 7, the XY coordinate positions and the number of photons (counts per second: cps) of fluorescence 122 detected at each position are stored as two-dimensional data 173, as shown in Figure 8. In memory step 2, the Z coordinate position of the ingot 10 from which the two-dimensional data 173 shown in Figure 8 was acquired is linked to the two-dimensional data 173 and stored in the memory unit 171 of the control unit 170.

[0062] In the storage step 2 of the embodiment, the XY coordinate positions of the facet region 21 and the non-facet region 22 are stored. The facet region 21 is the region in which the number of photons of fluorescence 122 detected in the fluorescence detection step 1 is less than a predetermined value. The non-facet region 22 is the region in which the number of photons of fluorescence 122 detected in the fluorescence detection step 1 is greater than or equal to a predetermined value. As shown in the embodiments in Figures 7 and 8, when the predetermined value is set to 4000, detection positions 23-3 and 23-4 are the facet region 21, and detection positions 23-1, 23-2, and 23-5 are the non-facet region 22.

[0063] <Laser beam irradiation step 3> Figure 9 is a perspective view showing the laser beam irradiation step 3 shown in Figure 5. Figure 10 is a side view of Figure 9. The laser beam irradiation step 3 is performed after the storage step 2. The laser beam irradiation step 3 is a step in which a delamination layer 24 is formed on the upper surface of the ingot 10 to a depth corresponding to the thickness of the wafer 30 to be produced.

[0064] In laser beam irradiation step 3, the second surface 12 side of the ingot 10 is held by attraction to the holding surface 111 of the holding unit 110, continuing from fluorescence detection step 1. In laser beam irradiation step 3, first, the focal point 142 of the laser beam 141 is positioned at a depth corresponding to the thickness of the wafer 30 (see Figure 11) to be produced from the upper surface of the ingot 10. The laser beam 141 is a pulsed laser beam with a wavelength that is penetrating to the ingot 10. Next, in laser beam irradiation step 3, the laser beam 141 is irradiated toward the ingot 10 while the focal point 142 and the ingot 10 are moved relative to each other in the XY direction.

[0065] In laser beam irradiation step 3, the SiC is separated into Si (silicon) and C (carbon) by irradiation with a pulsed laser beam 141. Then, the next pulsed laser beam 141 is absorbed by the previously formed C, and a modified region is formed inside the ingot 10 along the processing feed direction, in which the SiC is separated into Si and C in a chain reaction, and cracks are generated extending from the modified region along the c-plane 19 (see Figure 2). In this way, laser beam irradiation step 3 forms a delamination layer 24 including the modified region and the cracks formed from the modified region along the c-plane 19.

[0066] <Wafer Production Step 4> Figure 11 shows one state of wafer production step 4 shown in Figure 5. Figure 12 shows one state of wafer production step 4 after Figure 11. Wafer production step 4 is a step in which the wafer 30 is separated from the ingot 10, starting from the delamination layer 24 formed in laser beam irradiation step 3.

[0067] In wafer production step 4, the ultrasonic oscillation unit 180 applies ultrasonic waves to the ingot 10, and the peeling unit 190 peels the wafer 30 from the ingot 10. This peels off a portion of the ingot 10 on the first surface 11 side with the peeling layer 24 as the interface, and the peeled portion is produced as wafer 30. The ultrasonic oscillation unit 180 includes, for example, an ultrasonic power supply and an ultrasonic transducer formed from piezoelectric ceramics or the like to which a voltage is applied by the ultrasonic power supply.

[0068] In wafer production step 4, first, the second surface 12 side of the ingot 10 is held by suction against the holding surface 182 of the holding unit 181. Next, the ultrasonic transducer of the ultrasonic oscillation unit 180 is positioned opposite the first surface 11 of the ingot 10. Then, liquid 186 is supplied from the liquid supply unit 185 between the ultrasonic transducer and the ingot 10.

[0069] In this state, a voltage is applied from the ultrasonic power supply of the ultrasonic oscillation unit 180 to cause the ultrasonic transducer to vibrate ultrasonically, thereby propagating ultrasonic vibrations of a frequency corresponding to the vibration of the ultrasonic transducer into the liquid 186 and applying them to the ingot 10. By applying ultrasonic vibrations to the entire surface of the ingot 10, a portion of the first surface 11 side of the ingot 10 is peeled off with the peeling layer 24 formed in the laser beam irradiation step 3 as the interface.

[0070] In wafer production step 4, the second face 12 side of the ingot 10 is then held by suction to the holding surface 192 of the holding unit 191. Next, the first face 11 side of the ingot 10 is held by the peeling unit 190. Then, by pulling the peeling unit 190 upward, the ingot 10 is pulled vertically, and the ingot 10 is separated with the peeling layer 24 as the interface. As a result, the peeled portion of the first face 11 side of the ingot 10 is produced as wafer 30.

[0071] <3D Data Generation Step 5> Figure 13 is a schematic diagram of multiple two-dimensional data accumulated before the three-dimensional data generation step 5 shown in Figure 5. Figure 14 is a schematic diagram of the three-dimensional data generated in the three-dimensional data generation step 5 shown in Figure 5. The three-dimensional data generation step 5 is performed after generating multiple wafers 30 from the ingot 10 by repeatedly performing the fluorescence detection step 1, the storage step 2, the laser beam irradiation step 3, and the wafer generation step 4. The three-dimensional data generation step 5 is a step in which three-dimensional data showing the distribution of the number of photons of fluorescence 122 in the entire ingot 10 is generated based on the two-dimensional data at each Z-coordinate position of the ingot 10 stored in the storage step 2.

[0072] As shown in Figure 13, in the ingot 10 processing method of this embodiment, n wafers 30-1, 30-2, 30-3, ..., 30-n are produced by peeling off the ingot 10. The storage unit 171 of the control unit 170 stores, for each of the n wafers 30-1, 30-2, 30-3, ..., 30-n, the data of their respective Z coordinate positions and two-dimensional data (for example, the two-dimensional data 173 shown in Figure 8) linked together.

[0073] In step 5 of the three-dimensional data generation, the three-dimensional data generation unit 172 of the control unit 170 generates three-dimensional data showing the distribution of the number of photons of fluorescence 122 in the entire ingot 10 from the Z coordinate positions of each of the n wafers 30-1, 30-2, 30-3, ..., 30-n and the corresponding two-dimensional data.

[0074] In this embodiment, the storage unit 171 stores data for the XY coordinate positions of facet regions 21-1, 21-2, 21-3, ..., 21-n corresponding to the respective Z coordinate positions of n wafers 30-1, 30-2, 30-3, ..., 30-n. In this embodiment, three-dimensional data showing the boundary 25 between the facet region 21 and the non-facet region 22 is generated from the respective Z coordinate positions of the n wafers 30-1, 30-2, 30-3, ..., 30-n and the XY coordinate positions of the facet regions 21-1, 21-2, 21-3, ..., 21-n, as shown in Figure 14.

[0075] <Display Step 6> Display step 6 is a step in which three-dimensional data is displayed. In the embodiment, the three-dimensional data is displayed on the display surface of the display unit 160. In display step 6, the three-dimensional data is displayed visually, for example, as a three-dimensional model. In display step 6, for example, the boundary between the faceted region 21 and the non-faceted region 22 in the entire ingot 10 is displayed as a three-dimensional model, as shown in Figure 14.

[0076] As described above, the ingot 10 processing method according to the embodiment involves detecting the number of photons of fluorescence 122 when excitation light 121 is irradiated onto the upper surface of the ingot 10 before forming a peeling layer 24 for peeling the wafer 30 from the ingot 10, thereby obtaining the distribution of the number of photons of fluorescence 122 on the upper surface of the ingot 10. Then, each time multiple wafers 30 are repeatedly generated, the distribution of the number of photons of fluorescence 122 on the upper surface of the ingot 10 is obtained, thereby generating three-dimensional data showing the distribution of the number of photons of fluorescence 122 throughout the entire ingot 10.

[0077] Therefore, the ingot processing method of this embodiment allows for the cutting of multiple wafers 30 from the ingot 10, as well as the three-dimensional confirmation of facet regions 21 with different impurity concentrations within the ingot 10. This has the effect of enabling rapid and appropriate feedback to the crystal growth process.

[0078] It should be noted that the present invention is not limited to the embodiments described above. That is, it can be implemented with various modifications without departing from the core of the present invention. For example, in the laser beam irradiation step 3, processing may be performed with different laser processing conditions only for the facet region 21, based on the two-dimensional data stored in the storage step 2. For example, the height (Z-direction position) of the focusing lens that focuses the laser beam 141 may be changed between the facet region 21 and the non-facet region 22 so that the position of the focusing point 142 in the thickness direction of the ingot 10 remains constant. [Explanation of symbols]

[0079] 10 ingots 11 First face (top face) 12. The second side 21, 21-1, 21-2, 21-3, 21-n facet regions 22 Non-faceted regions 23-1, 23-2, 23-3, 23-4, 23-5 Detection location 24. Exfoliation layer 25 Boundary 30, 30-1, 30-2, 30-3, 30-n wafers 100 Processing Units 110 Holding Unit 111 Holding surface 120 Fluorescence Detection Unit 121 Excitation light 122 Fluorescence 140 Laser beam irradiation unit 141 Laser beam 142 Focusing points 150 Mobile Units 160 display units 170 Control Unit 171 Storage section 172 Three-dimensional data generation unit 180 Ultrasonic Oscillation Unit 185 Liquid supply unit 190 peeling unit

Claims

1. A method for processing ingots, A fluorescence detection step involves irradiating the ingot with excitation light of a predetermined wavelength from above the ingot and detecting the number of fluorescent photons generated from the upper surface of the ingot. A storage step is performed in which the distribution of the number of fluorescent photons on the upper surface of the ingot detected in the fluorescence detection step is stored as two-dimensional data linked to the XY coordinate position on the XY plane perpendicular to the height direction of the ingot, and the Z coordinate position, which is the height direction of the ingot from which the two-dimensional data was obtained, is stored linked to the two-dimensional data. After the storage step, a laser beam irradiation step is performed in which a laser beam with a wavelength that is transparent to the ingot is focused at a depth corresponding to the thickness of the wafer to be produced from the top surface of the ingot and irradiated, and the focus point and the ingot are moved relative to each other in the XY direction to form a delamination layer on the ingot. A wafer production step in which a wafer is separated from the ingot starting from the delamination layer formed in the laser beam irradiation step, After repeatedly performing the fluorescence detection step, the storage step, the laser beam irradiation step, and the wafer generation step to generate multiple wafers from the ingot, a three-dimensional data generation step is performed to generate three-dimensional data showing the distribution of the number of fluorescent photons in the entire ingot based on the two-dimensional data at the Z-coordinate position of each ingot stored in the storage step, It has, The ingot is made of SiC, and the method for processing the ingot.

2. After the wafer generation step, the process returns to the fluorescence detection step, and the fluorescence detection step, the storage step, the laser beam irradiation step, and the wafer generation step are repeated in sequence until multiple wafers are generated from the ingot, accumulating two-dimensional data at the Z-coordinate position of each ingot, and then the three-dimensional data generation step is performed. In the laser beam irradiation step, the height of the focusing lens used to focus the laser beam is changed based on the two-dimensional data stored in the storage step so that the position of the focal point in the thickness direction of the ingot remains constant. The method for processing an ingot according to claim 1.

3. The method further includes a display step for displaying the three-dimensional data. The method for processing an ingot according to claim 1 or 2.

4. In the storage step, regions where the number of fluorescent photons detected in the fluorescence detection step is greater than or equal to a predetermined value are designated as non-faceted regions, and regions where the number of fluorescent photons is less than the predetermined value are designated as faceted regions. The XY coordinate positions of the non-faceted regions and the faceted regions are then stored. The display step displays the boundary between the faceted region and the non-faceted region of the entire ingot. The method for processing an ingot according to claim 3.

5. A processing apparatus for generating multiple wafers from an ingot, A holding unit having a holding surface for holding the ingot, A fluorescence detection unit that irradiates the ingot with excitation light of a predetermined wavelength from above the ingot and detects the number of fluorescent photons generated from the upper surface of the ingot, A laser beam irradiation unit that positions the focal point of a laser beam with a wavelength that is transparent to the ingot at a depth corresponding to the thickness of the wafer to be produced from the top surface of the ingot and irradiates it to form a delamination layer, A moving unit that moves the holding unit and the focusing point of the laser beam relative to each other in the XY direction parallel to the holding surface, Control unit and It has, The control unit is, A storage unit stores the distribution of photons of fluorescence detected on the upper surface of the ingot as two-dimensional data, linked to the XY coordinate position on an XY plane parallel to the holding surface, and stores the Z coordinate position, which is the height position of the ingot from which the two-dimensional data was acquired, linked to the two-dimensional data. A three-dimensional data generation unit generates three-dimensional data showing the distribution of the number of fluorescent photons in the entire ingot based on two-dimensional data at each Z-coordinate position of the ingot stored in the memory unit, Includes, The processing apparatus is characterized in that the ingot is made of SiC.

6. The control unit is, After storing the two-dimensional data and the Z-coordinate position in the memory unit, the laser beam irradiation unit and the movement unit are controlled to form the delamination layer on the wafer, and the fluorescence detection unit is used to detect the number of photons of fluorescence on the new upper surface of the ingot after the wafer has been separated from the delamination layer, and a plurality of the two-dimensional data and the Z-coordinate position are stored in the memory unit. Based on the two-dimensional data stored in the memory unit, the height of the focusing lens that focuses the laser beam is changed so that the position of the focal point in the thickness direction of the ingot remains constant. The apparatus according to claim 5.

7. The system further includes a display unit for displaying the three-dimensional data. The apparatus according to claim 5 or 6.

8. The memory unit stores the XY coordinate positions of the non-faceted regions and the faceted regions, with the region where the number of fluorescent photons detected by the fluorescence detection unit is greater than or equal to a predetermined value being a non-faceted region and the region where the number of fluorescent photons is less than the predetermined value being a faceted region. The display unit displays the boundary between faceted and non-faceted regions in the entire ingot. The apparatus according to claim 7.

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