Manufacturing method of wafer

Abstract

To manufacture a wafer, in which a device is formed, with high productivity.SOLUTION: A manufacturing method of a wafer for manufacturing a wafer from an ingot includes: a separate layer formation step of positioning a convergence point of a laser beam of a wavelength transmitted through the ingot inside of the ingot, irradiating the ingot with the laser beam while relatively moving the ingot and the convergence point, and forming a separate layer inside of the ingot; a separation step of imparting an external force to the ingot after the separate layer formation step and dividing the ingot with the separate layer defined as an origin, thereby obtaining the wafer as a divided piece; and a mark formation step of forming a mark indicating a crystal azimuth of a constituent of the wafer on the wafer after the separation step.SELECTED DRAWING: Figure 12

Description

[Technical field]

[0001] The present invention relates to a wafer manufacturing method for manufacturing a disk-shaped wafer from a cylindrical ingot. [Background technology]

[0002] Device chips to be mounted on electronic devices can be formed by arranging devices such as ICs (Integrated Circuits), LSIs (Large Scale Integration), and LEDs (Light Emitting Diodes) on the surface of a wafer made of semiconductor material and then dividing the wafer into individual devices. When manufacturing a disk-shaped wafer, first, a mass called an ingot obtained through a crystal growth process is cylindrically ground to form a cylindrical shape. Then, the ingot is thinly sliced ​​using a wire saw to obtain a disk-shaped wafer (see Patent Document 1).

[0003] However, in the method using a wire saw, a large amount of constituent material is lost in the process of dividing the ingot, and the number of wafers obtained is small compared to the size of the raw ingot. In addition, when an ingot is divided using a wire saw, undulations are formed on the front and back surfaces of the resulting wafer. Therefore, in order to remove the undulations, the front and back surfaces of the wafer must be polished, and further constituent material is lost during polishing. Therefore, the method using a wire saw has a problem of low productivity.

[0004] Therefore, a method of cutting an ingot using a laser beam with a wavelength that is transparent to the constituent material of the ingot (a wavelength that transmits through semiconductor materials) is known. In this method, a separation surface is set at a predetermined depth position from the surface of the ingot, and a laser beam is focused along the separation surface to form a separation origin (separation layer) inside the ingot that includes a modified layer and a crack extending from the modified layer. Then, the ingot is divided at the separation origin (separation layer) to form a wafer (see Patent Document 2).

[0005] Meanwhile, a mark called an orientation flat or a mark called a notch, which indicates the crystal orientation of the constituent material, is provided on the outer periphery of the wafer. The crystal orientation of the constituent material is specified in the ingot before it is cut into wafers. For example, the crystal orientation of the constituent material of the ingot is specified by X-ray diffraction (XRD), and a mark such as an orientation flat indicating the specified crystal orientation is formed on the ingot (see Patent Document 3). In this case, when the ingot is cut, a wafer having a mark indicating the crystal orientation is obtained. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2001-272359 A [Patent Document 2] JP 2016-127186 A [Patent Document 3] JP 2005-219506 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the process of cylindrical grinding an ingot and forming marks such as an orientation flat, a large amount of components is removed from an ingot that is much larger than a wafer. In addition, in these processes, not only must the workpiece be processed with a relatively large processing strength, but also large-scale dedicated equipment is required, resulting in high costs. Therefore, there is room for improvement in the wafer manufacturing process, and further improvement in the productivity of the manufacturing process is desired.

[0008] The present invention has been made in view of the above problems, and an object of the present invention is to provide a wafer manufacturing method capable of manufacturing wafers on which devices are formed with high productivity. [Means for solving the problem]

[0009] According to one aspect of the present invention, there is provided a wafer manufacturing method for manufacturing wafers from an ingot, comprising: a separation layer forming step of positioning a focal point of a laser beam having a wavelength that transmits through the ingot inside the ingot, and irradiating the ingot with the laser beam while moving the ingot and the focal point relatively to each other to form a separation layer inside the ingot; a separation step, after the separation layer forming step, of applying an external force to the ingot to divide the ingot starting from the separation layer to obtain the wafer as divided pieces; and a mark forming step, after the separation step, of forming marks on the wafer indicating the crystal orientation of components of the wafer.

[0010] Preferably, prior to the separation step, the method further includes a crystal orientation measurement step of measuring characteristics related to the crystal orientation of the constituent material, and the formation position and shape of the mark formed on the wafer in the mark formation step are determined based on the characteristics measured in the crystal orientation measurement step.

[0011] More preferably, in the mark forming step, the mark is formed on the wafer by laser processing an outer periphery of the wafer.

[0012] According to another aspect of the present invention, there is provided a wafer manufacturing method for manufacturing wafers from an ingot, comprising: a separation layer forming step of positioning a focal point of a laser beam having a wavelength that transmits through the ingot inside the ingot, and irradiating the ingot with the laser beam while moving the ingot and the focal point relatively to each other to form a separation layer inside the ingot; a separation step of applying an external force to the ingot after the separation layer forming step, and dividing the ingot starting from the separation layer to obtain divided pieces of the wafer; and a contour shaping step of shaping the contour of the wafer after the separation step.

[0013] Preferably, after the separation step, the method further comprises a mark forming step of forming a mark on the wafer indicating a crystal orientation of a component member of the wafer.

[0014] More preferably, the method further includes a crystal orientation measurement step prior to the separation step, in which characteristics related to the crystal orientation of the constituent material are measured, and the formation position and shape of the mark formed on the wafer in the mark formation step are determined based on the characteristics measured in the crystal orientation measurement step.

[0015] More preferably, after the separation step and before the contour shaping step, the method further includes an inspection step of inspecting the wafer to determine whether or not the wafer has a crystal defect and the location of the crystal defect, and if the inspection step determines that the wafer has the crystal defect, the contour shaping step removes the crystal defect by shaping the contour of the wafer. Effect of the Invention

[0016] In a wafer manufacturing method according to one aspect of the present invention, a focal point is positioned inside an ingot, a laser beam is irradiated onto the ingot to form a separation layer inside the ingot, and the ingot is divided from the separation layer to obtain wafers. Then, marks indicating the crystal orientation of the components of the wafer are formed on the wafer, and the wafer is shaped.

[0017] In processing individual wafers, the intensity of the processing performed on the workpiece is smaller than that in processing an ingot. In addition, the equipment used for processing can be small-scale, and there is no need to use dedicated equipment, and general-purpose equipment can be used. Furthermore, processing conditions, etc. can be selected in detail so that appropriate processing is performed in response to the individual state of the wafer, and each workpiece can be processed with high precision. Therefore, the cost required for wafer manufacturing can be reduced, high-quality wafers can be manufactured, and the productivity of the wafer manufacturing process can be increased.

[0018] Therefore, the present invention provides a wafer manufacturing method capable of manufacturing wafers on which devices are formed with high productivity. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1(A) is a perspective view that typically shows an ingot, and FIG. 1(B) is a cross-sectional view that typically shows an ingot. [Diagram 2] FIG. 2 is a perspective view showing a schematic diagram of an ingot in a crystal orientation measuring step. [Diagram 3] FIG. 2 is a plan view illustrating the ingot in a crystal orientation measuring step. [Figure 4] 4(A), 4(B), 4(C), 4(D) and 4(E) are plan views each showing a schematic diagram of a strength reduced portion. [Diagram 5] FIG. 2 is a side view showing a schematic diagram of an optical system of a laser irradiation unit of the laser processing apparatus. [Figure 6] FIG. 6(A) is a perspective view that typically shows the separation layer forming step, and FIG. 6(B) is a cross-sectional view that typically shows the separation layer forming step. [Figure 7] FIG. 2 is a plan view showing a schematic diagram of an ingot on which a separation layer is formed. [Figure 8] FIG. 8(A) is a cross-sectional view that typically shows an ingot in a first stage of the separation step, and FIG. 8(B) is a cross-sectional view that typically shows an ingot in a second stage of the separation step. [Figure 9] FIG. 9(A) is a perspective view that typically shows a wafer before its outer shape is shaped, and FIG. 9(B) is a plan view that typically shows a wafer before its outer shape is shaped. [Figure 10] FIG. 10(A) is a plan view that typically shows a wafer before marks are formed thereon, and FIG. 10(B) is a plan view that typically shows a wafer after marks are formed thereon. [Figure 11] FIG. 11 is a plan view illustrating a wafer on which a mark according to a modified example is formed. [Figure 12]FIG. 12(A) is a flowchart showing the flow of each step of a method for manufacturing a wafer according to one example, and FIG. 12(B) is a flowchart showing the flow of each step of a method for manufacturing a wafer according to another example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the wafer manufacturing method according to the present embodiment, a wafer used for manufacturing devices mounted on electronic equipment is manufactured.

[0021] A wafer is a disk-shaped substrate made of, for example, silicon (Si), silicon carbide (SiC), gallium nitride (GaN), GaAs (gallium arsenide), or other semiconductors. Multiple devices such as ICs, LSIs, and LEDs are arranged in a matrix on the surface of the wafer, and the wafer is divided into individual devices to form individual device chips. Disk-shaped wafers are manufactured by cutting cylindrical ingots.

[0022] In recent years, SiC wafers have been attracting attention as wafers used in manufacturing device chips equipped with power devices capable of high-temperature operation and high-voltage resistance, LSIs, etc. Disc-shaped SiC wafers are formed by cutting an ingot 11 (e.g., a hexagonal single crystal ingot) made of cylindrical SiC as shown in Fig. 1(A) and other figures.

[0023] When the ingot 11 is a SiC ingot, the ingot 11 is produced by epitaxial growth so that the c-axis of the single crystal SiC is slightly inclined with respect to the perpendicular line to the front surface 11a and the back surface 11b. For example, the angle between the c-axis and the perpendicular line (off angle) is 1° to 6° (typically 4°).

[0024] FIG. 1(A) is a perspective view that typically shows an ingot 11, and FIG. 1(B) is a cross-sectional view that typically shows the ingot 11. The ingot 11 manufactured through a crystal growth process has a minute uneven shape on the outer periphery 11c before the outer shape is shaped, as shown in FIG. 1(A) and FIG. 1(B), etc. Therefore, the produced ingot 11 is generally shaped into a cylindrical shape by cylindrical grinding. Here, the lump of constituent material both before and after cylindrical grinding is called an ingot.

[0025] Generally, the ingot 11 formed through the crystal growth process is cylindrically ground and then cut. This produces a disk-shaped SiC wafer. Figure 10(B) shows a schematic diagram of an example of a wafer 21 produced by the wafer production method according to the present embodiment.

[0026] When the constituent material of the wafer 21 is single crystal SiC, two marks indicating the crystal orientation of the constituent material, single crystal SiC, are formed on the wafer 21. That is, a first orientation flat 27 and a second orientation flat 29 perpendicular to the first orientation flat 27 are formed on the wafer 21. The length of the first orientation flat 27 is formed to be longer than the length of the second orientation flat 29.

[0027] In general, the first orientation flat 27 (also called the primary orientation flat, etc.) is formed along a specific direction that is advantageous for the mobility of electrons when forming semiconductor elements such as MOSFETs on single crystal SiC, and the second orientation flat 29 (also called the secondary orientation flat, etc.) is formed along the inclination direction of the c-axis with respect to the perpendicular line to the front surface 21a and back surface 21b of the wafer 21 (the direction of the off-angle).

[0028] When cutting the ingot 11, for example, a laser beam having a wavelength that transmits through the material that constitutes the ingot 11 is irradiated onto the ingot 11. At this time, the focal point of the laser beam is positioned at a predetermined depth position corresponding to the thickness of the wafer 21 to be manufactured, and the laser beam is irradiated onto the ingot 11 while the focal point is relatively moved horizontally. Then, a separation layer (modified layer) that serves as a peeling starting point is formed inside the ingot 11. Then, the ingot 11 is cut using the separation layer (modified layer) as a starting point to obtain the wafer 21.

[0029] Conventionally, the crystal orientation of the material constituting the ingot 11 is measured, and a mark such as a notch or an orientation flat indicating the crystal orientation is formed in the ingot 11. In this case, the mark remains on the wafer 21 manufactured by cutting out the ingot 11, so the crystal orientation of the wafer 21 can be confirmed by referring to the mark.

[0030] However, in the process of cylindrical grinding the ingot 11 formed through the crystal growth process and the process of forming marks such as an orientation flat, a large amount of components are lost at once. Moreover, in these processes, not only must the workpiece be processed with a relatively large processing strength, but also large-scale dedicated equipment is required, resulting in high costs. Therefore, there is a problem in that the productivity of the wafer 21 is low.

[0031] Therefore, in the wafer manufacturing method according to this embodiment, the focal point is positioned inside the ingot 11, a laser beam is irradiated onto the ingot 11 to form a separation layer inside the ingot 11, and the ingot 11 is divided starting from the separation layer to obtain the wafer 21. After that, marks indicating the crystal orientation of the components of the wafer 21 are formed on the wafer 21, and the outer shape of the wafer 21 is shaped.

[0032] In processing an individual wafer 21, the intensity of the processing performed on the workpiece is smaller than that in processing an ingot 11. In addition, the equipment used for processing can be small-scale, and general-purpose equipment can be used without the need for dedicated equipment. Furthermore, processing conditions, etc. can be selected in detail so that appropriate processing is performed in response to the individual state of the wafer 21, and each workpiece can be processed with high precision.

[0033] Therefore, it is possible to reduce the cost required for manufacturing the wafer 21, and to manufacture high-quality wafers 21, thereby improving the productivity of the manufacturing process of the wafer 21. Next, an overview of a wafer manufacturing method according to this embodiment for manufacturing the wafer 21 from the ingot 11 will be described.

[0034] In the wafer manufacturing method according to this embodiment, a separation layer forming step S20 is performed to form a separation layer inside the ingot 11, followed by a separation step S30 to obtain wafers 21 as divided pieces by dividing the ingot 11 from the separation layer as a starting point. After the separation step S30, one or both of a mark forming step S41 is performed to form marks on the wafer 21 indicating the crystal orientations of the components of the wafer 21, and an outer shape shaping step S42 to shape the outer shape of the wafer 21 is performed.

[0035] Each step of the wafer manufacturing method according to this embodiment will be described in detail below. Fig. 12(A) is a flow chart for explaining the flow of each step of the wafer manufacturing method according to this embodiment when the mark forming step S41 is performed. Fig. 12(B) is a flow chart for explaining the flow of each step of the wafer manufacturing method according to this embodiment when the outer shape shaping step S42 is performed.

[0036] In the wafer manufacturing method according to the present embodiment, when the mark forming step S41 is performed later, it is preferable that the crystal orientation measuring step S10 for measuring the characteristics related to the crystal orientation of the constituent material is performed before the separation step S30. It is more preferable that the crystal orientation measuring step S10 is performed before the separation layer forming step S20. Here, the constituent material is the material that constitutes the ingot 11, and is also the material that constitutes the wafer 21 formed from the ingot 11.

[0037] The crystal orientation measurement step S10 will be described in detail. In the crystal orientation measurement step S10, the characteristics of the crystal orientation of the constituent material of the ingot 11 are measured by a known method such as X-ray diffraction. The characteristics of the crystal orientation of the constituent material obtained by the measurement are used when forming marks on the wafer 21 in a mark formation process described later. However, when the measurement is performed on the ingot 11 by the X-ray diffraction method, a relatively large and expensive measuring device is required, which is a factor in reducing the productivity of the wafer 21.

[0038] Therefore, in the wafer manufacturing method according to this embodiment, characteristics related to the crystal orientation of the constituent material may be measured by other methods in the crystal orientation measuring step S10. Here, the crystal orientation measuring step S10 will be described taking as an example a case where the measurement is performed using a laser processing device 2 shown in Fig. 2. Fig. 2 is a perspective view that typically shows the ingot 11 in the crystal orientation measuring step S10, and Fig. 3 is a plan view that typically shows the ingot 11 in the crystal orientation measuring step S10.

[0039] The laser processing device 2 includes a support table 4 that supports an ingot 11, and a laser irradiation unit 8 that irradiates a laser beam 12 onto the ingot 11 supported on the support table 4. The upper surface of the support table 4 serves as a support surface 6 that supports the ingot 11. This support surface 6 has an extremely high flatness so that measurements can be performed with high accuracy. The support table 4 is, for example, a chuck table that applies negative pressure to the ingot 11 placed on the support surface 6 to suction and hold the ingot 11.

[0040] The laser irradiation unit 8 also includes a processing head 10 that emits a laser beam 12. The laser irradiation unit 8 positions a focal point 14 of the laser beam 12 at a predetermined height, and focuses the laser beam 12, which has a wavelength that transmits through the constituent material of the ingot 11, at the focal point 14. The support table 4 and the processing head 10 of the laser irradiation unit 8 are relatively movable in a direction parallel to the support surface 6.

[0041] A focal point 14 is positioned at a height position a predetermined depth below the surface 11a of the ingot 11, and while the ingot 11 and the focal point 14 are moved relatively, a laser beam 12 having a wavelength that is transparent to the constituent material (SiC) is irradiated onto the ingot 11. At this time, a modified layer 16 is formed in the ingot 11 along the scanning direction of the focal point 14, and cracks extend from the modified layer 16. The modified layer 16 and the cracks become portions with reduced strength (strength-reduced portions).

[0042] For example, in the crystal orientation measuring step S10, the laser beam 12 is focused at the focal point 14 while linearly scanning the focal point 14. Next, the scanning direction is slightly changed and the laser beam 12 is focused at the focal point 14 while linearly scanning the focal point 14. In this manner, the scanning direction of the focal point 14 is sequentially changed each time the scanning of the focal point 14 of the laser beam 12 is repeated. In Figures 2 and 3, a plurality of modified layers 16 formed on the ingot 11 are indicated by dashed lines.

[0043] Here, when the scanning direction of the focal point 14 is parallel to the extension direction of the second orientation flat 29 to be formed on the ingot 11 (wafer 21), a continuous strength-reduced portion without a node is formed. This is considered to be because cracks are formed along the same c-plane from the modified layer 16. On the other hand, when the scanning direction of the focal point 14 is not parallel to the extension direction of the second orientation flat 29 to be formed, a node appears to be formed in the strength-reduced portion. This is considered to be because the focal point 14 moves across multiple c-planes whose positions are different in the depth direction. In other words, a step is generated between a crack formed on a certain c-plane and a crack formed on a different c-plane, and this is considered to be generated as a node in the strength-reduced portion.

[0044] Therefore, the extension direction of the second orientation flat 29 to be formed in the ingot 11 (wafer 21) can be specified by observing the modified layer 16 formed in the ingot 11 and checking the state of knot formation in the strength-reduced portion formed around the modified layer 16. In other words, the characteristics related to the crystal orientation of the constituent material of the ingot 11 (wafer 21) are measured.

[0045] A more detailed description will be given. In Fig. 3, five modified layers 16a, 16b, 16c, 16d, and 16e, which are formed in the ingot 11 by the irradiation of the laser beam 12 and have different elongation directions, are shown by dashed lines. Figs. 4(A) to 4(E) are plan views each showing a schematic view of the modified layers 16a, 16b, 16c, 16d, and 16e, and the strength-reduced portions 18a, 18b, 18c, 18d, and 18e, each including a crack formation region 20 where a crack is formed.

[0046] 4(A), nodes 22 are confirmed in the crack formation region 20 around the modified layer 16a. That is, nodes 22 are confirmed in the strength reduced portion 18a. Therefore, it can be seen that the scanning direction of the focal point 14 of the laser beam 12 when the modified layer 16a is formed is not parallel to the extension direction of the second orientation flat 29 to be formed.

[0047] Similarly, in the strength-reduced parts 18b, 18c, and 18e shown in Figures 4(B), 4(C), and 4(E), nodes 22 are confirmed in the crack formation regions 20 around the modified layers 16b, 16c, and 16e. Therefore, it is understood that the scanning direction of the focal point 14 of the laser beam 12 when the modified layers 16b, 16c, and 16e are formed is not parallel to the extension direction of the second orientation flat 29 to be formed.

[0048] 4(D), no knots 22 are observed in the crack formation region 20 formed around the modified layer 16d. That is, no knots 22 are observed in the strength reduced portion 18d. Therefore, it can be seen that the scanning direction of the focal point 14 of the laser beam 12 when the modified layer 16d is formed is parallel to the extension direction of the second orientation flat 29 to be formed.

[0049] When performing the crystal orientation measuring step S10 as described above using the laser processing device 2, the laser beam 12 is irradiated in each of a plurality of directions tilted at a predetermined angle (for example, 0.5 degrees) by moving and rotating the support table 4. In other words, the focal point 14 is repeatedly scanned while changing the scanning direction by a predetermined angle (for example, 0.5 degrees).

[0050] The irradiation of the laser beam 12 can be performed, for example, under the following processing conditions. Note that the defocus described below is the amount of movement of the focal point 14 of the laser beam 12 upward from the state in which the focal point 14 is positioned on the surface 11a of the ingot 11. Laser beam wavelength: 1064nm Repetition frequency: 80kHz Average output: 3.2W Pulse width: 3ns Focus spot diameter: φ10μm Condenser lens numerical aperture (NA): 0.65 Machining feed speed: 150mm / s Defocus: 90μm

[0051] According to the above-described method, the extension direction of the second orientation flat 29 to be formed in the ingot 11 (wafer 21) is specified. That is, according to the above-described method, the characteristics related to the crystal orientation of the constituent material of the ingot 11 (wafer 21) are measured. The characteristics related to the crystal orientation of the constituent material obtained by the measurement are used when forming a mark indicating the crystal orientation of the constituent material on the wafer 21, as described later.

[0052] However, a small number of nodes 22 may be formed in the crack formation region 20 (strength reduced portion) around the modified layer 16 along the direction specified as the extension direction of the second orientation flat 29 to be formed. For example, the number of nodes 22 present per unit length (e.g., 10 mm) of the modified layer 16 may be measured, and the extension direction of the modified layer 16 when the crack formation region 20 (strength reduced portion) in which the number of nodes 22 is zero is formed may be determined as this specified direction.

[0053] Alternatively, when multiple modified layers 16 are formed along different directions, the extension direction of the modified layer 16 having the fewest number of nodes 22 formed in the surrounding crack formation region 20 may be identified as the extension direction of the second orientation flat 29 to be formed.

[0054] Alternatively, for example, two modified layers 16 that have a small number of nodes 22 formed in the surrounding crack formation region 20 are selected from among a plurality of modified layers 16 extending along different directions. Then, a direction between the extension directions of the two selected modified layers 16 may be specified as the extension direction of the second orientation flat 29 to be formed.

[0055] In the wafer manufacturing method according to this embodiment, before or after the crystal orientation measuring step S10, a separation layer forming step S20 is performed to form a separation layer inside the ingot 11. Next, the separation layer forming step S20 will be described. The separation layer forming step S20 is performed, for example, by a laser processing device 24 shown in Fig. 5 and Fig. 6(A).

[0056] The laser processing device 24 includes a chuck table 26, the upper surface of which serves as a holding surface 28 for suction-holding the workpiece, and a laser irradiation unit 30 for irradiating a laser beam 40 onto the workpiece held by the chuck table 26 to perform laser processing of the workpiece. The chuck table 26 has an internal suction path one end of which is connected to the holding surface 28, and the other end of the suction path is connected to a suction source such as a pump. When the suction source is operated, a negative pressure can be applied to the workpiece placed on the holding surface 28, and the workpiece can be suction-held.

[0057] 5 shows a side view of the simplest example of the configuration of the optical system of the laser irradiation unit 30. The laser irradiation unit 30 includes a laser oscillator 32 that emits a laser beam 40, and an attenuator 34 that adjusts the output of the laser beam 40. The laser irradiation unit 30 further includes a mirror 36 that reflects the laser beam 40, and a focusing lens 38 that focuses the laser beam 40 emitted by the laser oscillator 32. However, the optical system of the laser irradiation unit 30 is not limited to this. The laser irradiation unit 8 of the above-mentioned laser processing device 2 is configured in the same manner as the laser irradiation unit 30, for example.

[0058] 6(A), the laser irradiation unit 30 of the laser processing device 24 has a processing head 42 that houses a part or the whole of the optical system. In the laser processing device 24, the processing head 42 and the chuck table 26 can move relatively along a direction parallel to the holding surface 28. This allows the focal point 44 of the laser beam 40 to scan the ingot 11 held by the chuck table 26.

[0059] Fig. 6(A) is a perspective view that typically shows the separation layer forming step S20, and Fig. 6(B) is a cross-sectional view that typically shows the separation layer forming step S20. Fig. 6(A) and Fig. 6(B) typically show an ingot 11 in the process of forming a modified layer 13 that constitutes the separation layer to be formed. Fig. 7 is a schematic plan view of the ingot 11 on which the modified layer 13 (separation layer 15) has been formed.

[0060] In the separation layer forming step S20, first, the ingot 11 is placed on the holding surface 28 of the chuck table 26 of the laser processing device 24, and the suction source of the chuck table 26 is activated to suck and hold the ingot 11 on the chuck table 26. Next, the laser irradiation unit 30 is moved above the ingot 11, and the optical system of the laser irradiation unit 30 is adjusted or the height of the laser irradiation unit 30 is adjusted to position the focal point 44 of the laser beam 40 at a predetermined height.

[0061] Here, the predetermined height at which the focal point 44 of the laser beam 40 is located is a height position at which the laser beam 40 is focused so as to form a separation layer 15 (see FIG. 8, etc.) at a predetermined height position inside the ingot 11. Note that the height position of the focal point 44 does not need to coincide with the predetermined height position at which the separation layer 15 is planned to be formed.

[0062] The separation layer 15 is a layer formed parallel to the surface 11a inside the ingot 11, and is a layer where the ingot 11 is to be divided. The separation layer 15 is a layer separated from the surface 11a of the ingot 11 by a depth corresponding to the thickness of the wafer 21 produced from the ingot 11.

[0063] In the separation layer forming step S20, a focal point 44 of a laser beam 40 having a wavelength that is transparent to the ingot 11 is positioned at a predetermined height position inside the ingot 11. Then, the ingot 11 is irradiated with the laser beam 40 while the chuck table 26 and the processing head 42 are moved relatively to each other, that is, while the ingot 11 and the focal point 44 are moved relatively to each other.

[0064] More specifically, in the separation layer formation step S20, a process of relatively moving the ingot 11 and the focal point 44 in a first direction to form a linear modified layer 13, and a process of relatively moving them in a second direction are repeated.

[0065] Here, when the constituent material of the ingot 11 is single crystal SiC, the first direction is preferably a direction perpendicular to the direction in which the off angle is formed and parallel to the surface 11a. The second direction is preferably a direction in which the off angle is formed and parallel to the surface 11a. When the crystal orientation measurement step S10 is performed before the separation layer formation step S20, the first direction and the second direction may be specified based on the characteristics related to the crystal orientation of the constituent material obtained in the crystal orientation measurement step S10.

[0066] When the laser beam 40 is focused inside the ingot 11, a modified layer 13 is formed near the focusing point 44. Furthermore, cracks (not shown) extend from the formed modified layer 13. Then, when the modified layer 13 is formed along the surface 11a of the ingot 11 and the cracks are extended from each modified layer 13, a separation layer 15 composed of the modified layer 13 and the cracks is formed parallel to the surface 11a of the ingot 11.

[0067] 6(A), 6(B), and 7, for ease of explanation, the modified layer 13 formed inside the ingot 11 is shown by a dashed line, and cracks are omitted. The ingot 11 becomes more likely to separate from the separation layer 15 constituted by the modified layer 13 and the cracks.

[0068] Here, a description will be given of the irradiation conditions of the laser beam 40. For example, when the ingot 11 is a SiC ingot, the laser beam 40 may be irradiated onto the ingot 11 under the following irradiation conditions. However, the irradiation conditions are not limited to the following. Laser beam wavelength: 1064nm Repetition frequency: 60kHz Average power output: 1.5W Pulse width: 4ns Focus spot diameter: φ3μm Condenser lens numerical aperture (NA): 0.65 Machining feed speed: 200mm / s Index amount: 250~400μm Focusing depth from surface: 300μm

[0069] In the wafer manufacturing method according to this embodiment, after the separation layer forming step S20, a separation step S30 is performed in which an external force is applied to the ingot 11 to divide the ingot 11 starting from the separation layer 15 to obtain wafers 21 as divided pieces. In the separation step S30, for example, ultrasonic vibration is applied to the ingot 11 having the separation layer 15 formed therein to divide the ingot 11. However, the method of dividing the ingot 11 is not limited to this. When the ingot 11 is divided starting from the separation layer 15, a wafer is obtained.

[0070] Fig. 8(A) is a cross-sectional view showing an ingot in a first stage of the separation step S30, and Fig. 8(B) is a cross-sectional view showing an ingot in a second stage of the separation step S30. Figs. 8(A) and 8(B) include a side view showing a separation device 46 used in the separation step S30. Here, the separation device 46 will be described. The separation device 46 includes a support table 48 on which the ingot 11 is placed, and a suction pad 54 arranged above the support table 48.

[0071] The support table 48 is, for example, a chuck table that can suction and hold the ingot 11 placed thereon. However, the support table 48 is not limited to a chuck table. The suction pad 54 is supported by a support shaft 52 that can be raised and lowered. The lower surface of the suction pad 54 serves as a suction surface that suction-holds an object that comes into contact with it. A suction path is formed inside the suction pad 54, one end of which reaches the suction surface, and the other end of the suction path is connected to a suction source such as a pump.

[0072] In the separating device 46, at least one of the support table 48 and the suction pad 54 has an ultrasonic vibration unit built in. The ultrasonic vibration unit has an ultrasonic vibrator such as a piezoelectric element, and can generate ultrasonic vibrations by operating the ultrasonic vibrator.

[0073] In the first stage of the separation step S30, the ingot 11 on which the separation layer 15 has been formed is placed on the support table 48. At this time, the back surface 11b of the ingot 11 faces the upper surface of the support table 48. Then, the front surface 11a of the ingot 11 is exposed upward. Next, the support shaft 52 is lowered above the support table 48, and the lower surface (suction surface) of the suction pad 54 is brought into contact with the front surface 11a of the ingot 11.

[0074] Then, in the second stage of the separation step S30, the ultrasonic vibration unit of the separation device 46 is operated to generate ultrasonic vibrations and apply the ultrasonic vibrations to the ingot 11. Then, the ingot 11 is separated from the separation layer 15 by the impact of the ultrasonic vibrations. Also, before and after the ultrasonic vibrations are applied to the ingot 11, a suction source connected to the suction surface of the suction pad 54 is operated to apply negative pressure to the surface 11a of the ingot 11. Then, the ingot 11 is suction-held by the suction pad 54.

[0075] When ultrasonic vibration is applied to the ingot 11 to separate the ingot 11, and the suction pad 54 applying negative pressure to the surface 11a of the ingot 11 is raised, the portion of the ingot 11 above the separation layer 15 is pulled up by the suction pad 54. Meanwhile, the portion of the ingot 11 below the separation layer 15 remains on the support table 48.

[0076] 8(B) is a schematic diagram showing how a portion above separation layer 15 separated from ingot 11 is pulled up by suction pad 54. The portion separated from ingot 11 becomes wafers 17. That is, when ingot 11 is divided at separation layer 15, wafers 17 are obtained as divided pieces.

[0077] The remaining portion of the ingot 11 remaining on the support table 48 is used to manufacture the next wafer 17. That is, a new separation layer 15 is formed inside the ingot 11 at a height position a predetermined depth below the newly exposed surface 11a of the ingot 11, and the ingot 11 is divided at the new separation layer 15, and a new wafer 17 is manufactured.

[0078] In the wafer manufacturing method according to this embodiment, when a shaping step S42 is performed later, an inspection step S31 may be further performed after the separation step S30 and before the shaping step S42. In the inspection step S31, the wafer 17 is inspected to identify the presence or absence of crystal defects in the wafer 17 and the positions of the crystal defects. Fig. 9(A) is a perspective view that typically shows the wafer 17 before the outer shape is shaped, and Fig. 9(B) is a plan view that typically shows the wafer 17 before the outer shape is shaped.

[0079] Ingot 11, which is made of single crystal SiC or the like, may have partial crystal defects during the growth process. Therefore, when wafer 17 is manufactured from ingot 11, wafer 17 may include a portion where crystal defects have occurred. Figures 9(A) and 9(B) show a schematic diagram of wafer 17 in which crystal defect region 19a has partially occurred. In Figures 9(A) and 9(B), crystal defect region 19a is hatched for ease of explanation.

[0080] Even if a device is formed in the crystal defect region 19a of the wafer 17, the device may not have the specified characteristics. Therefore, it is preferable to remove the portion where the crystal defects are generated from the wafer 17 manufactured from the ingot 11. In the inspection step S31, the presence or absence of crystal defects in the wafer 17 and the positions of the crystal defects are identified in order to remove the crystal defect region 19a of the wafer 17 later in the outer shape shaping step S42.

[0081] The detection of the crystal defect region 19a of the wafer 17 is performed by, for example, any one of a photoluminescence (PL) method, observation using an optical microscope, observation using an electron microscope such as SEM or STEM, observation using an X-ray topograph, Raman spectroscopy, etc. However, the inspection step S31 is not limited to this, and the crystal defect region 19a of the wafer 17 may be detected by other methods.

[0082] In the inspection step S31, in addition to the crystal defect region 19a, regions of the wafer 17 that are unsuitable for device formation may be detected. For example, cracks 19b generated in the wafer 17 may be detected.

[0083] A contour shaping step S42 for shaping the contour of the wafer 17 is performed after the separation step S30. When the inspection step S31 is performed in the wafer manufacturing method according to this embodiment, the contour shaping step S42 is preferably performed after the inspection step S31.

[0084] In the outer shape shaping step S42, unnecessary regions are removed by processing the wafer 17 separated from the ingot 11. For example, if the wafer 17 is identified to have a crystal defect in the inspection step S31, the outer shape of the wafer 17 is shaped in the outer shape shaping step S32 to remove the crystal defect.

[0085] In the outer shape shaping step S32, first, a boundary 23 between a region to be cut out and a region to be left in the wafer 17 separated from the ingot 11 is determined. The boundary 23 is determined, for example, so that the crystal defect region 19a and the cracks 19b are excluded from the wafer 17. The boundary 23 is set to a circle having as large an area as possible. Alternatively, the boundary 23 is set to a circle having a specific size selected from the specifications of the wafer used to form the device.

[0086] 9(A) and 9(B), the circular boundary 23 thus determined is shown typically by a dashed line. In the contour shaping step S32, the outside of the boundary 23 of the wafer 17 separated from the ingot 11 is removed. For example, the contour of the wafer 17 is shaped by cylindrically grinding the wafer 17 from the outer periphery 17c side or by cutting the wafer 17 along the boundary 23.

[0087] When cylindrically grinding the wafer 17 from the outer periphery 17c, a relatively wide area of ​​the wafer 17 is processed, which may result in low processing efficiency. Therefore, it is preferable to cut the wafer 17 along the boundary 23. Cutting the wafer 17 along the boundary 23 is performed by a laser processing device 24 shown in, for example, Fig. 5, Fig. 6(A), etc.

[0088] In the outer shape shaping step S32, the wafer 17 is placed on the chuck table 26 of the laser processing device 24, and the wafer 17 is suction-held by the chuck table 26. At this time, for example, the back surface 17b of the wafer 17 is made to face the holding surface 28, and the front surface 17a of the wafer 17 is exposed upward.

[0089] Then, the chuck table 26 and the processing head 42 of the laser irradiation unit 30 are moved relatively in a direction parallel to the holding surface 28 to position the processing head 42 above the boundary 23. Thereafter, the focal point 44 is positioned at a predetermined height position between the front surface 17a and the back surface 17b of the wafer 17, and the chuck table 26 and the processing head 42 are moved relatively while irradiating the laser beam 40 to the focal point 44. As a result, the laser beam 40 is irradiated onto the wafer 17 along the boundary 23.

[0090] Here, a description will be given of the irradiation conditions of the laser beam 40. For example, when the wafer 17 is a SiC wafer, the laser beam 40 may be irradiated onto the wafer 17 under the following irradiation conditions. However, the irradiation conditions are not limited to the following. Laser beam wavelength: 532nm Repetition frequency: 60kHz Average power output: 3.0W Pulse width: 10ns Condenser lens numerical aperture (NA): 0.6 Machining feed speed: 100mm / s Focusing depth from surface: 150μm

[0091] When the laser beam 40 is irradiated onto the wafer 17 along the boundary 23, a modified layer or the like that will become the starting point of division is formed on the wafer 17 along the boundary 23. Thereafter, when an impact or the like is applied to the wafer 17, the wafer 17 is cut starting from the modified layer, and a wafer 21 (see FIG. 10(A)) is obtained from which unnecessary regions have been removed. In other words, a wafer 21 with a shaped outer shape is obtained.

[0092] In this manner, if it is determined in the inspection step S31 that the wafer 17 has crystal defects, the crystal defects are removed by shaping the wafer 17 in the contour shaping step S42.

[0093] It should be noted that the contour shaping step S42 does not have to be performed by the laser processing device 24. For example, the contour shaping step S42 may be performed by a cutting device (not shown) capable of cutting the workpiece with a cutting blade having an annular cutting edge. In this case, the cutting device cuts the wafer 17 along the boundary 23, and a cut groove along the boundary 23 is formed in the wafer 17.

[0094] Here, in the multiple wafers 17 formed by being separated from the ingot 11, the positions and sizes of the crystal defect regions 19a and the cracks 19b are not necessarily the same in each wafer 17. Therefore, the boundary 23 is set individually for each wafer 17, and each wafer 17 is cut or otherwise processed along the individually set boundary 23.

[0095] As a result, in the wafer manufacturing method according to this embodiment, it is possible to set a mutually different optimal boundary 23 for each wafer 17, and the wafer 17 can be cut along the mutually different optimal boundary 23. Therefore, according to the wafer manufacturing method according to this embodiment, it is possible to manufacture a plurality of wafers 21 each having an outer shape shaped under optimal conditions.

[0096] Also, unlike the wafer manufacturing method according to the present embodiment, when the wafers 17 are cut out from the ingot 11 after the ingot 11 is cylindrically ground, a boundary is set on the ingot 11 so that unnecessary regions can be removed from all the wafers 17. Then, outside the boundary, the ingot 11 is cylindrically ground from the outer periphery 11c.

[0097] Therefore, even if a useful region of one wafer 17 overlaps with an unnecessary region of another wafer 17, in order to remove the unnecessary region by cylindrical grinding, the useful region is also removed by cylindrical grinding. In other words, this method does not fully utilize the useful constituent material.

[0098] In contrast, in the wafer manufacturing method according to the present embodiment, the boundary 23 can be set individually for each of the multiple wafers 17 obtained from the ingot 11 so that the maximum useful area remains. In other words, it is not necessary to remove the useful area of ​​the wafer 17 because it overlaps with the unnecessary area of ​​another wafer 17 in the ingot 11. Therefore, the constituent material of the ingot 11 can be utilized as effectively as possible.

[0099] In addition, since the ingot 11 is extremely thick compared to the wafer 17, it is difficult to cut the ingot 11 using a laser processing device 24 or a cutting device. Therefore, a dedicated cylindrical grinding device must be used to shape the outer shape of the ingot 11.

[0100] In contrast, in the wafer manufacturing method according to the present embodiment, the outer shape of the wafer 17 can be shaped using processing equipment such as a laser processing equipment 24 or a cutting equipment that can be used for various purposes. Therefore, the wafer 21 with a shaped outer shape and a trimmed outer periphery 21c can be easily and inexpensively obtained. Therefore, according to the wafer manufacturing method according to the present embodiment, a high-quality wafer 21 with a shaped outer shape can be manufactured with high efficiency.

[0101] Incidentally, the outer periphery 17c of the wafer 17 may have an uneven shape caused during the manufacturing process of the ingot 11. However, in the wafer manufacturing method according to the present embodiment, the outer periphery 17c with the uneven shape is removed by performing the outer shape shaping step S32. That is, by performing the outer shape shaping step S32, unnecessary regions of the wafer 17 can be removed and the outer shape of the wafer 17 can be shaped.

[0102] Furthermore, in the wafer manufacturing method according to this embodiment, the outer shape shaping step S32 may be performed only for the purpose of removing uneven shapes generated on the outer periphery 17c of the wafer 17 due to the manufacturing process of the ingot 11. In this case, the inspection step S31 for inspecting the wafer 17 separated from the ingot 11 may not be performed. Moreover, even if the inspection step S31 is performed and no crystal defects or the like are found in the wafer 17, it is preferable to perform the outer shape shaping step S32.

[0103] In the wafer manufacturing method according to this embodiment, instead of the contour shaping step S42 after the separation step S30, or after the contour shaping step S42, a mark forming step S41 may be performed. In the mark forming step S41, a mark indicating the crystal orientation of the components of the wafer 17, 21 is formed on the wafer 17, 21. The mark indicating the crystal orientation is, for example, a notch or an orientation flat.

[0104] Fig. 10(A) is a plan view that typically shows the wafer 21 before marks are formed, and Fig. 10(B) is a plan view that typically shows the wafer 21 after marks are formed. For example, when the wafer 21 is a single crystal SiC wafer, two marks are formed on the wafer 21 in the mark forming step S41. That is, a first orientation flat 27 and a second orientation flat 29 that is perpendicular to the first orientation flat 27 are formed as marks on the wafer 21.

[0105] Here, the positions and shapes of the marks formed on the wafers 17, 21 in the mark forming step S41 may be determined based on the characteristics relating to the crystal orientation of the constituent materials measured in the crystal orientation measuring step S10.

[0106] In this case, the orientation of the wafers 17, 21 must be continuously identified until marks are formed on the wafers 17, 21 so that the meaning of the characteristics related to the crystal orientation of the constituent materials is not lost after the wafers 17 are separated from the ingot 11 in the separation step S30. That is, even after the wafer 17 is separated from the ingot 11, it must be continuously identified which orientation the wafer 17 had in the ingot 11 before it was separated from the ingot 11.

[0107] Also, even when the outer shape shaping step S42 is performed and the wafer 17 is cut along the boundary 23 to obtain the wafer 21, it is necessary to continue to identify the orientation of the wafer 21 until a mark is formed on the wafer 21. In other words, even after the wafer 21 is cut from the wafer 17, it is necessary to continue to identify which orientation the wafer 21 had in the ingot 11 when it was originally included in the ingot 11.

[0108] Then, in the mark forming step S41, for example, marks (first orientation flat 27, second orientation flat 29) are formed on the wafer 17, 21 by laser processing the outer periphery of the wafer 17, 21. In Fig. 10(A), a planned cutting point 25 set on the wafer 17, 21 to form the marks is shown typically by a broken line. In the mark forming step S41, the wafer 17, 21 is cut at the planned cutting point 25 to form the marks.

[0109] For example, the wafers 17 and 21 are cut by a laser processing device 24. The procedure for cutting the wafers 17 and 21 by the laser beam 40 is similar to the procedure for laser processing performed in the outer shape shaping step S42. Therefore, details of the procedure for cutting the wafers 17 and 21 at the intended cutting location 25 by the laser processing device 24 will be omitted.

[0110] When the mark forming step S41 is performed, marks (first orientation flat 27, second orientation flat 29) indicating the crystal orientations of the components of the wafers 17, 21 are formed on the wafers 17, 21. Note that, instead of the laser processing device 24, a cutting device that cuts a workpiece with an annular cutting blade may be used to cut the wafers 17, 21.

[0111] In the wafer manufacturing method according to the present embodiment, marks can be formed on the outer periphery of the wafer 17, 21 using a processing device such as a laser processing device 24 or a cutting device that can be used for various purposes. Therefore, the wafer 17, 21 on which marks indicating the crystal orientation of the constituent material are formed can be obtained easily and inexpensively. Therefore, according to the wafer manufacturing method according to the present embodiment, high-quality wafers 17, 21 on which marks are formed can be manufactured with high efficiency.

[0112] In the wafer manufacturing method according to the present embodiment described above, the separation layer 15 is formed inside the ingot 11, and the ingot 11 is divided at the separation layer 15 to obtain the wafers 17 and 21. Thereafter, marks indicating the crystal orientations of the components of the wafers 17 and 21 are formed on the wafers 17 and 21, and the outer shapes of the wafers 17 and 21 are shaped.

[0113] In processing the individual wafers 17, 21, the intensity of the processing performed on the workpiece is smaller than that in processing the ingot 11. In addition, the equipment used for processing can be small-scale, and there is no need to use dedicated equipment, and general-purpose equipment can be used. Furthermore, processing conditions, etc. can be selected in detail so that appropriate processing is performed in response to the individual state of the wafers 17, 21, and each workpiece can be processed with high precision. Therefore, the cost required for manufacturing the wafers 17, 21 can be reduced, high-quality wafers 17, 21 can be manufactured, and the productivity of the manufacturing process of the wafers 17, 21 can be increased.

[0114] The present invention is not limited to the above embodiment, and can be modified in various ways. For example, in the above embodiment, the mark forming step S41 is described as forming two orientation flats 27, 29 on the wafers 17, 21 as marks indicating the crystal orientation of the constituent materials. However, the method for manufacturing a wafer according to one aspect of the present invention is not limited to this.

[0115] That is, in the mark forming step S41 in the wafer manufacturing method according to one aspect of the present invention, only one mark may be formed on the wafer 17, 21. Also, the mark formed on the wafer 17, 21 may be a cutout portion called a notch.

[0116] Furthermore, in the mark forming step S41, dot-like marks may be formed on the wafers 17 and 21 as marks indicating the crystal orientations of the constituent materials. Fig. 11 is a plan view showing a wafer 21 on which two types of marks 31 and 33 according to a modified example are formed.

[0117] The first mark 31 is formed on the wafer 21 in place of the first orientation flat 27 (see FIG. 10(B)). Also, the second mark 33 is formed on the wafer 21 in place of the second orientation flat 29 (see FIG. 10(B)). For example, the first mark 31 and the second mark 33 formed on the wafer 21 are distinguished by the number of dots that constitute them.

[0118] For example, the first mark 31 is composed of two points aligned along the extension direction of the first orientation flat 27 when the first orientation flat 27 is formed on the wafer 21. More specifically, a straight line connecting the centers of the two points constituting the first mark 31 and the center of the wafer 21 is perpendicular to the extension direction. As a result, the first mark 31 indicates the same crystal orientation as the crystal orientation indicated by the first orientation flat 27.

[0119] Also, for example, the second mark 33 is composed of one point. More specifically, a straight line connecting the point constituting the second mark 33 and the center of the wafer 21 is perpendicular to the extension direction of the second orientation flat 29 when the second orientation flat 29 is formed on the wafer 21. As a result, the second mark 33 indicates the same crystal orientation as the crystal orientation indicated by the second orientation flat 29.

[0120] Here, for example, the two points constituting the first mark 31 and the one point constituting the second mark 33 are affected regions formed in a circular shape with a diameter of 3 mm. The distance between the two points (affected regions) constituting the first mark 31 is set to 5 mm. The two points (affected regions) constituting the first mark 31 and the one point (affected region) constituting the second mark 33 are formed on the wafer 21 at positions about 5 mm inward from the outer periphery 21c of the wafer 21.

[0121] The points (altered regions) constituting the first mark 31 and the points (altered regions) constituting the second mark 33 are formed on the wafer 21 by, for example, laser processing using the laser processing device 24. The irradiation conditions of the laser beam 40 at this time are as follows. The focal point 44 of the laser beam 40 is positioned on the front surface 21a of the wafer 21. In other words, the focal depth is set to 0 μm. However, the irradiation conditions of the laser beam 40 are not limited to this. Laser beam wavelength: 1064nm Repetition frequency: 60kHz Average power output: 0.3W Pulse width: 4ns Focus spot diameter: φ3μm Condenser lens numerical aperture (NA): 0.65

[0122] Compared with the case where orientation flats 27, 29 are formed on the wafer 21, when marks 31, 33 consisting of dot-like affected regions are formed on the front surface 21a of the wafer 21, extremely little constituent material of the wafer 21 is lost from the wafer 21. Therefore, the constituent material of the wafer 21 can be used efficiently and more devices can be formed on the wafer 21, thereby improving the manufacturing efficiency of chips manufactured from the wafer 21.

[0123] Furthermore, when the marks 31, 33 composed of point-like affected regions are formed on the front surface 21a of the wafer 21, the amount of processing required is also extremely small. Therefore, the marks 31, 33 composed of point-like affected regions are formed on the wafer 21 extremely easily and efficiently. This improves the manufacturing efficiency of the wafer 21.

[0124] In the above embodiment, the crystal orientation measuring step S10 is performed before the separation step S30, and the ingot 11 is irradiated with a laser beam 12 as shown in Fig. 2 and the like to measure the characteristics related to the crystal orientation of the constituent material from the shape of the formed strength reduced portion. However, the wafer processing method according to one aspect of the present invention is not limited to this. In the crystal orientation measuring step S10, the characteristics related to the crystal orientation of the constituent material may be obtained by measurement using X-ray diffraction (XRD).

[0125] Furthermore, the crystal orientation measuring step S10 may be performed after the separation step S30, and the measurement of characteristics related to the crystal orientation of the constituent materials may be performed on the wafers 17, 21 instead of the ingot 11.

[0126] For example, in the crystal orientation measuring step S10, the characteristics related to the crystal orientation of the constituent materials of the wafers 17 and 21 may be obtained by measuring using an X-ray diffraction method (XRD). Also, for example, in the crystal orientation measuring step S10, the wafers 17 and 21 may be irradiated with a laser beam 12 instead of the ingot 11, and the characteristics related to the crystal orientation of the constituent materials may be measured from the shape of the formed strength reduction portion.

[0127] That is, in the crystal orientation measurement step S10, characteristics related to the crystal orientation of the constituent material are measured for either the ingot 11 or the wafers 17, 21. Here, the constituent material whose crystal orientation is to be measured is the material constituting the ingot 11 as well as the material constituting the wafers 17, 21 separated from the ingot 11. In other words, the constituent material of the ingot 11 is synonymous with the constituent material of the wafers 17, 21.

[0128] In addition, if the strength-reduced portion formed by irradiating the ingot 11 or the wafer 17, 21 with the laser beam 12 in the crystal orientation measurement step S10 remains in the ingot 11 etc., it may interfere with subsequent steps.

[0129] For example, if a reduced-strength portion remains in ingot 11, it is conceivable that the reduced-strength portion may hinder the formation of separation layer 15 by laser beam 40 in separation layer formation step S20, or that ingot 11 may crack starting from the reduced-strength portion in separation step S30. Furthermore, if a reduced-strength portion remains in wafers 17, 21, it is conceivable that problems resulting from the reduced-strength portion may occur in the formation of devices on wafers 17, 21, or in the manufacture of chips by dividing wafers 17, 21.

[0130] Therefore, in the wafer manufacturing method according to one aspect of the present invention, after the crystal orientation measuring step S10, a removing step may be performed in which the ingot 11 or the wafer 17, 21 is ground to remove the strength-reduced portion. In the removing step, for example, the ingot 11 is ground or polished from the front surface 11a to remove the strength-reduced portion. Alternatively, in the removing step, the wafer 17, 21 is ground or polished from the front surface 17a, 21a to remove the strength-reduced portion.

[0131] In the wafer manufacturing method according to one embodiment of the present invention, grinding (polishing) of the ingot 11 or the wafers 17, 21 may be performed for a purpose other than removing the strength-reduced portion, and may be performed in a state where no strength-reduced portion is formed in the ingot 11, etc. For example, grinding (polishing) may be performed to flatten the surface 11a of the ingot 11 or the surfaces 17a, 21a of the wafers 17, 21.

[0132] In the above embodiment, in the mark forming step S41, the formation positions and shapes of the marks formed on the wafers 17 and 21 are determined based on the characteristics measured and acquired in the crystal orientation measuring step S10. However, the wafer manufacturing method according to one aspect of the present invention is not limited to this.

[0133] For example, characteristics related to the crystal orientation of the constituent material of the ingot 11 may be measured and acquired before the wafer manufacturing method according to one aspect of the present invention is performed. In this case, in the mark forming step S41, the formation position and shape of the mark on the wafer 17, 21 may be determined based on the characteristics related to the crystal orientation of the constituent material that have been measured and acquired beforehand. That is, in the wafer manufacturing method according to one aspect of the present invention, the crystal orientation measuring step S10 does not need to be performed.

[0134] Furthermore, in the first place, in the wafer manufacturing method according to one aspect of the present invention, a mark indicating the crystal orientation of the constituent material may be formed in advance on the ingot 11. In this case, the wafers 17, 21 with the mark can be obtained by separating the wafers 17, 21 from the ingot 11. Therefore, in the wafer manufacturing method according to one aspect of the present invention, the crystal orientation measuring step S10 and the mark forming step S41 do not need to be performed.

[0135] To sum up the above explanation, in a wafer manufacturing method according to one embodiment of the present invention, as shown in Fig. 12(A), a crystal orientation measuring step S10, a separation layer forming step S20, a separation step S30, and a mark forming step S41 are performed. In a wafer manufacturing method according to another embodiment of the present invention, as shown in Fig. 12(B), a separation layer forming step S20, a separation step S30, an inspection step S31, and an outer shape shaping step S42 are performed.

[0136] The structures, methods, and the like according to the above-described embodiments can be modified as appropriate without departing from the scope of the object of the present invention. [Explanation of symbols]

[0137] 11 Ingot 11a,17a,21a surface 11b,17b,21b Back side 11c,17c,21c outer circumference 13 Modification layer 15 Separation layer 17 Wafers 19a Crystal defect region 19b Crack 21 Wafer 23 Boundary 25 Planned cutting location 27,29 Orientation Flat 31,33 marks 2 Laser processing equipment 4 Support table 6 Support surface 8 Laser irradiation unit 10 Processing head 12 Laser Beam 14 Focus point 16, 16a, 16b, 16c, 16d, 16e Modification layer 18a,18b,18c,18d,18e Decreased strength part 20 Crack formation area Verse 22 24 Laser processing equipment 26 Chuck Table 28 Holding surface 30 Laser irradiation unit 32 Laser Oscillator 34 Attenuator 36 Mirror 38 Condenser Lens 40 Laser Beam 42 Processing head 44 Focus point 46 Separation device 48 Support Table 52 Support shaft 54 Suction Pad

Claims

1. A wafer manufacturing method for manufacturing a wafer from an ingot, comprising: a separation layer forming step of positioning a focal point of a laser beam having a wavelength that transmits the ingot inside the ingot, and irradiating the ingot with the laser beam while moving the ingot and the focal point relatively to each other, thereby forming a separation layer inside the ingot; a separation step of applying an external force to the ingot after the separation layer forming step, and dividing the ingot at the separation layer to obtain the wafers as divided pieces; a mark forming step of forming marks on the wafer indicating crystal orientations of components of the wafer after the separating step.

2. The method further includes a crystal orientation measurement step of measuring a characteristic related to the crystal orientation of the constituent material prior to the separation step; 2. The method for manufacturing a wafer according to claim 1, wherein the position and shape of the mark formed on the wafer in the mark forming step are determined based on the characteristics measured in the crystal orientation measuring step.

3. 3. The method for manufacturing a wafer according to claim 1, wherein in the mark forming step, the mark is formed on the wafer by laser processing an outer periphery of the wafer.

4. A wafer manufacturing method for manufacturing a wafer from an ingot, comprising: a separation layer forming step of positioning a focal point of a laser beam having a wavelength that transmits the ingot inside the ingot, and irradiating the ingot with the laser beam while moving the ingot and the focal point relatively to each other, thereby forming a separation layer inside the ingot; a separation step of applying an external force to the ingot after the separation layer forming step, and dividing the ingot at the separation layer to obtain the wafers as divided pieces; a contour shaping step of shaping the contour of the wafer after the separation step.

5. 5. The method for producing a wafer according to claim 4, further comprising, after the separating step, a mark forming step of forming a mark on the wafer indicating a crystal orientation of a component member of the wafer.

6. The method further includes a crystal orientation measurement step of measuring a characteristic related to the crystal orientation of the constituent material prior to the separation step; 6. The method for manufacturing a wafer according to claim 5, wherein the position and shape of the mark formed on the wafer in the mark forming step are determined based on the characteristics measured in the crystal orientation measuring step.

7. After the separation step and before the contour shaping step, the method further includes an inspection step of inspecting the wafer to determine whether or not there is a crystal defect in the wafer and the location of the crystal defect; A method for manufacturing a wafer as described in any one of claims 4 to 6, characterized in that if the inspection step identifies that the wafer has the crystal defect, the contour shaping step removes the crystal defect by shaping the contour of the wafer.

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