Wafer fabrication methods

Abstract

[Problem] A wafer fabrication method is provided that can efficiently perform chamfering on the outer periphery of the wafer when fabricating it from a crystal ingot. [Solution] The wafer fabrication method includes: a release layer forming step, in which a focal point of a laser beam with a wavelength that has penetrability to the crystal ingot is positioned from a first end face of the crystal ingot at a depth equivalent to the thickness of the wafer to be fabricated, and the laser beam is irradiated onto the crystal ingot to form a release layer; a first chamfer forming step, in which a laser beam with an absorptive wavelength is irradiated from the first end face side to the remaining area of ​​the outer periphery of the wafer to form a first chamfer; a peeling step, in which the wafer to be fabricated is peeled off; and a second chamfer forming step, in which a laser beam with an absorptive wavelength is irradiated from the peeled surface side of the wafer to form a second chamfer.

Description

Technical Field

[0001] This invention relates to a method for generating a wafer by processing a crystal ingot. Prior Technology

[0002] ICs, LSIs, LEDs, and other components are formed by depositing functional layers on the front side of a wafer using materials such as Si (silicon) or Al₂O₃ (sapphire) and then dividing it by predetermined dicing lines. Similarly, power devices and LEDs are formed by depositing functional layers on the front side of a wafer using SiC (silicon carbide) and then dividing it by predetermined dicing lines. The wafers containing these components are then processed using cutting equipment or laser processing equipment to cut the predetermined dicing lines and divide them into individual component chips. These diced component chips are then used in electronic devices such as mobile phones or personal computers.

[0003] The wafers used to form components are generally produced by thinly cutting cylindrical crystal rods with a wire saw. The front and back sides of the produced wafers can be mirror-polished by grinding (see, for example, Patent Document 1).

[0004] However, if the crystal ingot is cut with a wire saw and the front and back sides of the cut wafer are ground, most of the crystal ingot (70-80%) will be discarded, which is uneconomical. In particular, SiC crystal ingots are hard and difficult to cut with a wire saw, requiring a considerable amount of time, resulting in poor productivity. Furthermore, the unit price of the crystal ingot is high, posing a challenge in efficiently forming wafers.

[0005] Therefore, the applicant proposes a technique in which the focal point of a laser beam with a wavelength that is penetrable to SiC is positioned inside the SiC crystal rod and the laser beam is irradiated onto the SiC crystal rod to form a release layer on a predetermined cutting surface, and the wafer is peeled off from the SiC crystal rod along the predetermined cutting surface where the release layer is formed (see, for example, Patent Document 2). [Known Technical Literature] [Patent Literature]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2000-94221 [Patent Document 2] Japanese Patent Application Publication No. 2016-111143 Summary of the Invention

[0007] [The problem that the invention aims to solve] However, the processing steps for separating the wafer from the ingot have not yet been established, leading to problems with inefficient wafer processing. In particular, when performing chamfering on wafers made from high-hardness materials such as SiC, it takes a long time to apply a grinding stone against the outer periphery of the wafer, resulting in poor productivity.

[0008] The aforementioned problems also occur in the following technology: a wafer-forming technology that focuses a laser beam of wavelength that is penetrable to silicon, sapphire, etc., inside the crystal rod, irradiates the crystal rod with the laser beam, and forms a release layer on a predetermined cut surface.

[0009] Therefore, the object of the present invention is to provide a method for generating a wafer, which can efficiently perform chamfering on the outer periphery of the wafer when generating the wafer from a crystal ingot.

[0010] [Methods for solving the problem] According to one aspect of the present invention, a method for generating a wafer is provided, which processes a crystal ingot to generate a wafer, and includes: a release layer forming step, wherein a focal point of a laser beam with a wavelength that is penetrable to the crystal ingot is positioned from a planarized first end face of the crystal ingot at a depth equivalent to the thickness of the wafer to be generated, and the laser beam is irradiated onto the crystal ingot to form a release layer; In the first chamfering step, a laser beam of an absorptive wavelength corresponding to the generated wafer is irradiated from the first end face side onto the remaining area of ​​the outer periphery of the wafer, thereby forming a first chamfer on the first end face; The stripping step, which peels the resulting wafer from the stripping layer; and The second chamfering step involves irradiating the remaining area on the outer periphery of the wafer's peeling surface with a laser beam of a wavelength that absorbs the wafer, thereby forming the second chamfer.

[0011] Preferably, the method includes an ID formation step, in which, after the release layer formation step, a laser beam of an absorptive wavelength corresponding to the generated wafer is irradiated onto the remaining area of ​​the wafer to form the ID. Also preferably, the method includes a chamfer grinding step, in which the first chamfer and the second chamfer are ground. Furthermore, the method includes a wafer release surface planarization step, in which the release surface of the wafer is ground and planarized.

[0012] Furthermore, preferably, the method includes a mirror finishing step, which performs mirror finishing on the front and back sides of the wafer. Also preferably, the method includes a crystal rod release surface planarization step, in which, after the release step, the release surface of the crystal rod is ground and planarized. Furthermore, preferably, the crystal rod is a SiC crystal rod, and the wafer is a SiC wafer.

[0013] Furthermore, preferably, the c-plane of the SiC crystal rod is inclined relative to the vertical line of the first end face, and an angle is formed between the c-plane and the first end face. In this peel layer formation step, the peel band formation step and the indexing feed step are repeated to form the peel bands side by side in the Y-axis direction, thereby forming the peel layer. The stripping band formation step involves defining the X-axis as the direction orthogonal to the direction forming the deflection angle, and the Y-axis as the direction orthogonal to the X-axis. A laser beam with a wavelength penetrating the SiC crystal rod is focused at a depth equivalent to the thickness of the wafer to be formed. The laser beam is then directed onto the SiC crystal rod, and the SiC crystal rod is fed relative to the focused point along the X-axis. The modified portion, formed by separating Si and C from SiC, elongates along the c-plane, forming a strip-like stripping band. The indexing feed step involves indexing the SiC crystal rod relative to the focusing point in the Y-axis direction.

[0014] [Invention Benefits] Since the method for generating a wafer of a single state in this invention is configured as described above, it can efficiently perform chamfering on the outer periphery of the wafer generated from the crystal rod. Simple Explanation of the Diagram

[0015] Figure 1(a) is a perspective view of the crystal rod, Figure 1(b) is a top view of the crystal rod shown in Figure 1(a), and Figure 1(c) is a front view of the crystal rod shown in Figure 1(a). Figure 2(a) is a perspective view showing the state of the release layer formation step, Figure 2(b) is a front view of the state of the release layer formation step, and Figure 2(c) is a cross-sectional view of the crystal rod with the release layer formed. Figure 3 is a three-dimensional view showing the state of the ID formation process in progress. Figure 4(a) is a perspective view showing the state of the first chamfering step being performed, Figure 4(b) is a front view showing the state of the first chamfering step being performed, and Figure 4(c) is an enlarged view of part B shown in Figure 4(b). Figure 5 is a perspective view showing the state of the peeling process in progress. Figure 6(a) is a perspective view showing the state of the second chamfering step being performed, Figure 6(b) is a front view showing the state of the second chamfering step being performed, and Figure 6(c) is an enlarged view of part C shown in Figure 6(b). Figure 7(a) is a front view showing the state during the chamfer grinding step, and Figure 7(b) is a front view of the wafer after the chamfer has been ground. Figure 8 is a perspective view showing the state of the wafer stripping planarization step being performed. Figure 9 is a perspective view showing the state of the mirror finishing process in progress. Figure 10 is a perspective view showing the state of the crystal rod peeling surface planarization step being performed. Implementation

[0016] Hereinafter, the wafer fabrication method (wafer processing method) of the present invention will be described with reference to the accompanying drawings.

[0017] Figure 1 shows a crystal rod 2 that can be used in the wafer fabrication method, i.e., the wafer processing method of the present invention. Although the crystal rod 2 shown in the figure is formed of hexagonal single crystal SiC (silicon carbide), it can also be formed of silicon or sapphire.

[0018] The cylindrical crystal rod 2 has: a circular first end face 4, a circular second end face 6 opposite to the first end face 4, a circumferential surface 8 located between the first end face 4 and the second end face 6, a c-axis extending from the first end face 4 to the second end face 6, and a c-plane orthogonal to the c-axis. At least the first end face 4 is planarized to a degree that does not obstruct the incidence of the laser beam by grinding or polishing.

[0019] In the crystal rod 2, the c-axis is inclined relative to the vertical line 10 of the first end face 4, and an angle α (e.g., α = 1, 3, or 6 degrees) is formed between the c-plane and the first end face 4. In Figure 1, the direction of forming the angle α is indicated by arrow A.

[0020] On the circumferential surface 8 of the crystal rod 2, a rectangular first orientation plane 12 and a second orientation plane 14 representing the crystal orientation are formed. The first orientation plane 12 is parallel to the direction A that forms the deflection angle α, and the second orientation plane 14 is orthogonal to the direction A that forms the deflection angle α. As shown in Figure 1(b), viewed from above, the length L2 of the second orientation plane 14 is shorter than the length L1 of the first orientation plane 12 (L2... <L1)。

[0021] (Steps for forming the peel layer) In the illustrated embodiment, firstly, a release layer forming step is performed, which involves positioning the focal point of a laser beam with a wavelength that has penetrability to the crystal rod 2 at a depth equivalent to the thickness of the wafer to be formed from the planarized first end face 4 of the crystal rod 2, and irradiating the crystal rod 2 with the laser beam to form a release layer.

[0022] The stripping layer formation step can be performed, for example, using the laser processing apparatus 16 shown in FIG. 2. The laser processing apparatus 16 includes: a chuck stage 18 that holds the crystal rod 2; a laser oscillator (not shown) that generates a pulsed laser beam LB with a wavelength that is penetrable to the crystal rod 2; and a concentrator 20 that focuses the pulsed laser beam LB generated by the laser oscillator and irradiates the pulsed laser beam LB onto the crystal rod 2 held in the chuck stage 18.

[0023] The chuck stage 18 is configured to rotate freely around an axis extending in the vertical direction, and is also configured to move freely in the X-axis direction (indicated by arrow X in Figure 2(a)) and the Y-axis direction (indicated by arrow Y in Figure 2(a)) which is orthogonal to the X-axis direction. The concentrator 20 irradiates the pulsed laser beam LB perpendicularly to the upper surface of the crystal rod 2. Furthermore, the XY plane defined by the X-axis and Y-axis directions is substantially horizontal.

[0024] Continuing the explanation with reference to FIG2, in the stripping layer formation step, firstly, the first end face 4 is facing upwards, and the crystal rod 2 is held by the upper surface of the chuck stage 18. Next, the crystal rod 2 is photographed from above by the camera unit (not shown) of the laser processing apparatus 16. Based on the image of the crystal rod 2 captured by the camera unit, the orientation of the crystal rod 2 is adjusted to a predetermined orientation, and the positional relationship between the crystal rod 2 and the condenser 20 is adjusted. When the orientation of the crystal rod 2 is adjusted to the predetermined orientation, as shown in FIG2(a), the second orientation plane 14 is aligned with the X-axis direction, the direction orthogonal to the direction A forming the deflection angle α is aligned with the X-axis direction, and the direction A forming the deflection angle α is aligned with the Y-axis direction.

[0025] Next, the focusing point FP (refer to Figure 2(b)) is positioned from the first end face 4 of the crystal rod 2 at a depth equivalent to the thickness of the wafer to be formed. Then, while the crystal rod 2 and the focusing point FP are being processed and fed relative to each other in the X-axis direction, a pulsed laser beam LB with a wavelength that can penetrate the crystal rod 2 is irradiated onto the crystal rod 2 from the focusing device 20. In this way, as shown in Figure 2(c), a strip-shaped peeling band 26, formed by elongating the crack 24 along the c-plane from the modified portion 22 (which can be separated from SiC into Si and C), is formed along the X-axis direction (peeling band formation step).

[0026] Next, the crystal rod 2 and the focusing point FP are indexed and fed relative to each other along the Y-axis (indexing feed step). The indexing feed amount Li is set to a length less than the width of the crack 24, such that adjacent cracks 24 overlap when viewed from above and below. Then, by alternately performing the peeling band formation step and the indexing feed step, the peeling bands 26 are arranged side by side in the Y-axis direction to form a peeling layer 28.

[0027] This stripping layer formation step can be performed, for example, using the following processing conditions. Furthermore, the defocusing described below refers to the amount of movement of the concentrator 20 towards the first end face 4, from the state where the focusing point FP of the pulsed laser beam LB has been positioned on the first end face 4 (upper surface) of the crystal rod 2. Wavelength of the pulsed laser beam: 1064nm Average output: 7~16W Repetition frequency: 30kHz Pulse width: 3ns Machining feed rate: 165 mm / s Defocus: 188μm Location of the peel layer from the first end face: 500μm

[0028] (ID formation steps) After the stripping layer formation step, the ID formation step is performed, which involves irradiating the remaining area of ​​the wafer with a laser beam of an absorptive wavelength to form the ID.

[0029] The ID formation step can be implemented, for example, using the laser processing apparatus 30 shown in FIG3. The laser processing apparatus 30 for implementing the ID formation step includes: a chuck stage 32 that holds the crystal rod 2; a laser oscillator (not shown) that generates a pulsed laser beam LB' with an absorptive wavelength corresponding to the wafer formed from the crystal rod 2; and a concentrator 34 that focuses the pulsed laser beam LB' generated by the laser oscillator and irradiates the crystal rod 2 held in the chuck stage 32 with the pulsed laser beam LB'.

[0030] The chuck stage 32 is configured to rotate freely around an axis extending in the vertical direction, and is also configured to move freely in the X-axis and Y-axis directions respectively. The concentrator 34 irradiates the pulsed laser beam LB' perpendicularly to the upper surface of the crystal rod 2.

[0031] Referring to Figure 3, in the ID formation step, firstly, the first end face 4 is facing upwards, and the crystal rod 2 is held by the upper surface of the chuck stage 32. Next, the crystal rod 2 is photographed, and the positional relationship between the crystal rod 2 and the condenser 34 is adjusted based on the image of the crystal rod 2. Then, the focusing point is positioned on the remaining area of ​​the unformed element (excluding the outer periphery) on the first end face 4 of the crystal rod 2.

[0032] Next, while appropriately moving the crystal rod 2 relative to the focusing point, a pulsed laser beam LB' of the wavelength corresponding to the absorption wavelength of the wafer generated from the crystal rod 2 is irradiated from the focusing device 34 onto the crystal rod 2. In this way, the remaining area where no element is formed can be ablated in the first end face 4 to form ID36 which can be constructed in the form of a barcode.

[0033] In the illustrated embodiment, although ID36 is formed along the second orientation plane 14, ID36 can also be formed along the first orientation plane 12 or along the arc-shaped perimeter, as long as it is the remaining area where no element is formed.

[0034] The ID36 formed during the ID formation process can contain information such as the ingot number of crystal ingot 2, the order in which wafers were generated from crystal ingot 2, the manufacturing date of the wafer, the wafer manufacturing plant, and the type of equipment used in wafer generation. Therefore, in cases where defects occur in components formed on the wafer, the manufacturing history of the wafer can be traced based on ID36 to investigate the cause of the defect, which can help prevent recurrence.

[0035] The ID formation step can be implemented, for example, using the following processing conditions. Wavelength of pulsed laser beam: 355nm Average output: 3W Repetition frequency: 10kHz Pulse width: 10ns Feed rate: 100mm / s

[0036] (Steps for forming the first chamfer) After the ID formation step, a first chamfer formation step is performed. This first chamfer formation step involves irradiating the remaining outer periphery of the wafer with a laser beam of an absorptive wavelength from the first end face 4 side, thereby forming a first chamfer on the first end face 4. Alternatively, the first chamfer formation step can be performed before the ID formation step.

[0037] For example, the first chamfering step can be performed using the laser processing apparatus 38 shown in FIG. 4. The laser processing apparatus 38 for performing the first chamfering step includes: a chuck stage 40 that holds the crystal rod 2; a laser oscillator (not shown) that generates a pulsed laser beam LB” with an absorptive wavelength corresponding to the wafer generated from the crystal rod 2; and a concentrator 42 that focuses the pulsed laser beam LB” generated by the laser oscillator and irradiates the pulsed laser beam LB” onto the crystal rod 2 held in the chuck stage 40.

[0038] The chuck stage 40 is configured to rotate freely around an axis extending in the vertical direction as its center, and is also configured to move freely in the X-axis and Y-axis directions respectively. The concentrator 42 is tilted relative to the upper surface of the crystal rod 2 and irradiates the pulsed laser beam LB". The angle θ formed by the upper surface of the crystal rod 2 and the direction of irradiating the pulsed laser beam LB" (see Figure 4(b)) can be, for example, about 45°.

[0039] Referring to Figure 4, in the first chamfering step, firstly, the first end face 4 is facing upwards, and the crystal rod 2 is held by the upper surface of the chuck stage 40. Next, the crystal rod 2 is photographed, and the positional relationship between the crystal rod 2 and the condenser 42 is adjusted based on the image of the crystal rod 2. Then, the focusing point is positioned on the remaining area of ​​the outer periphery of the wafer to be formed on the first end face 4 of the crystal rod 2.

[0040] Next, as shown in Figures 4(a) and 4(b), while the chuck stage 40 is rotated at a predetermined speed, a pulsed laser beam LB” of the wavelength corresponding to the absorption wavelength of the wafer generated from the crystal rod 2 is irradiated onto the remaining peripheral area (outer periphery) on the first end face 4. In this way, the remaining peripheral area on the first end face 4 is ablated, and as shown in Figure 4(c), a first chamfer 44 can be formed on the first end face 4.

[0041] In the illustrated embodiment, the crystal rod 2 has first and second orientation planes 12 and 14. Therefore, when a pulsed laser beam LB” is irradiated along the first and second orientation planes 12 and 14, the focusing point is moved along the first and second orientation planes 12 and 14 by appropriately moving the chuck stage 40 in the X-axis and Y-axis directions. In this way, the pulsed laser beam LB” is irradiated to the entire circumference of the remaining outer peripheral area on the side of the first end face 4.

[0042] The first chamfering step can be performed, for example, using the following processing conditions. Wavelength of pulsed laser beam: 355nm Average output: 3W Repetition frequency: 10kHz Pulse width: 10ns Feed rate: 100mm / s

[0043] (Stripping step) After the first chamfering step is performed, a peeling step is performed, in which the wafer to be generated is peeled off from the peeling layer 28.

[0044] The stripping step can be performed, for example, using the stripping apparatus 46 shown in FIG. 5. The stripping apparatus 46 includes: a chuck stage 48 that attracts and holds the crystal rod 2; and a stripping means 50 that strips a portion of the crystal rod 2 that is attracted and held in the chuck stage 48.

[0045] The peeling means 50 includes: an arm 52, which extends substantially horizontally; and a motor 54 attached to the front end of the arm 52. A circular plate-shaped adsorption plate 56 is connected to the lower surface of the motor 54, and the adsorption plate 56 is rotatable with its vertically extending axis as the center. An ultrasonic vibration application unit (not shown) is built into the adsorption plate 56 on the upper surface of the adsorption rod 2 adsorbed on the lower surface of the adsorption plate 56 to apply ultrasonic vibration to the lower surface of the adsorption plate 56.

[0046] Referring to FIG5, in the stripping step, firstly, the first end face 4 is facing upwards, and the crystal rod 2 is held by the upper surface of the chuck stage 48. Next, the lifting mechanism (not shown) of the stripping device 46 lowers the arm 52, causing the lower surface of the adsorption sheet 56 to adhere to the first end face 4 of the crystal rod 2. Then, the ultrasonic vibration application unit is operated to apply ultrasonic vibration to the lower surface of the adsorption sheet 56, and the motor 54 is operated to rotate the adsorption sheet 56. In this way, the wafer 58 can be stripped from the stripping layer 28 of the crystal rod 2. Furthermore, the front side 58a of the wafer 58, which was the first end face 4 of the crystal rod 2, is flat, while the back side 58b of the stripping surface, i.e., the wafer 58, has irregularities.

[0047] (Steps for forming the second chamfer) After the stripping step, a second chamfering step is performed. This second chamfering step involves irradiating the remaining peripheral area of ​​the stripped surface of wafer 58 from the stripped surface side (back side 58b) of wafer 58 to form the second chamfer. The second chamfering step can be performed using the same laser processing apparatus 38 used in the first chamfering step.

[0048] Referring to Figures 6(a), 6(b), and 6(c), in the second chamfering step, firstly, the wafer 58 is held with its peeling surface (back side 58b) facing upwards by the upper surface of the chuck stage 40. Next, the wafer 58 is photographed, and the positional relationship between the wafer 58 and the condenser 42 is adjusted based on the image of the wafer 58. Then, the focusing point is positioned on the remaining area of ​​the outer periphery of the peeling surface of the wafer 58.

[0049] Next, as shown in Figures 6(a) and 6(b), while the chuck stage 40 is rotated at a predetermined speed, a pulsed laser beam LB” of a wavelength that absorbs the wafer 58 is irradiated onto the remaining peripheral area (outer periphery) of the stripped surface of the wafer 58. This process ablation is performed on the remaining peripheral area of ​​the stripped surface of the wafer 58, and as shown in Figure 6(c), a second chamfer 60 is formed on the stripped surface of the wafer 58.

[0050] Similar to the first chamfering step, when the pulsed laser beam LB” is irradiated along the first and second orientation planes 12 and 14, the focusing point is moved along the first and second orientation planes 12 and 14 by appropriately moving the chuck stage 40 in the X-axis and Y-axis directions. This process irradiates the entire circumference of the remaining outer periphery of the wafer 58 on the peeling surface side with the pulsed laser beam LB”. Furthermore, the processing conditions for the second chamfering step can be the same as those for the first chamfering step.

[0051] (Chamfering process) After the second chamfering step is performed, a chamfering grinding step is performed, in which the first chamfering part 44 and the second chamfering part 60 are ground.

[0052] The chamfering grinding step can be performed, for example, using the grinding apparatus 62 shown in FIG7(a). The grinding apparatus 62 includes: a chuck stage 64 that holds the wafer 58; and a grinding unit 66 that grinds the outer periphery of the wafer 58 held in the chuck stage 64.

[0053] The chuck stage 64 is circular, as shown in Figure 7(a), and its diameter is smaller than that of the wafer 58. Furthermore, the chuck stage 64 is configured to rotate freely around an axis extending in the vertical direction as its center. The grinding unit 66 includes: a spindle 68 extending in the vertical direction; and a grinding stone 70 fixed to the lower end of the spindle 68.

[0054] The grinding stone 70 has: a cylindrical upper part 70a; a cylindrical lower part 70b; and a neck 70c located between the upper part 70a and the lower part 70b. As can be understood by referring to FIG7(a), the diameter of the neck 70c gradually decreases from the upper end toward the middle in the vertical direction, and gradually increases from the middle in the vertical direction toward the lower end. The cross-sectional shape of the outer periphery of the neck 70c is arc-shaped. Furthermore, the vertical dimension of the neck 70c is almost the same as the thickness of the wafer 58.

[0055] Referring to Figure 7(a) for further explanation, in the chamfering step, firstly, with the center of the wafer 58 aligned with the rotating chuck stage 64, the wafer 58 is held with its peeling surface (back side 58b) facing upwards by the upper surface of the chuck stage 64. Next, the chuck stage 64 is rotated in the direction indicated by arrow R1. Then, the grinding stone 70, together with the spindle 68, is rotated in the direction indicated by arrow R2.

[0056] Next, the grinding unit 66 is moved toward the chuck stage 64 by the moving mechanism (not shown) of the grinding apparatus 62, so that the neck 70c of the grinding stone 70 contacts the outer periphery of the wafer 58. Grinding water is then supplied to the outer periphery of the wafer 58 that contacts the grinding stone 70. After the grinding stone 70 contacts the outer periphery of the wafer 58, the grinding unit 66 is moved at a predetermined grinding feed speed by pushing the grinding stone 70 toward the wafer 58. Thus, as shown in FIG. 7(b), the first chamfer 44 and the second chamfer 60 can be smoothly ground.

[0057] In the illustrated embodiment, since the first and second chamfered portions 44 and 60 are formed on the outer periphery of the wafer 58 before the chamfering grinding step, the chamfering grinding step can be completed with a smaller grinding amount. Generally, if the material of the wafer 58 is hard, such as SiC, the grinding time will be longer. However, as described above, in the illustrated embodiment, even if the material of the wafer 58 is hard, the grinding can be completed with a smaller grinding amount, thus shortening the grinding time. Therefore, chamfering of the outer periphery of the wafer 58 can be performed efficiently.

[0058] (Wafer lift-off surface planarization step) After the chamfer grinding step, the wafer stripping surface planarization step is performed, which involves grinding and planarizing the stripping surface of wafer 58.

[0059] The wafer stripping planarization step can be performed, for example, using the grinding apparatus 72 shown in FIG8. The grinding apparatus 72 includes: a chuck stage 74 that holds the wafer 58; and a grinding unit 76 that grinds the wafer 58 held in the chuck stage 74.

[0060] The chuck table 74 is configured to rotate freely around an axis extending in the vertical direction. The grinding unit 76 includes: a spindle 78 extending in the vertical direction; and a circular wheel mount 80 fixed to the lower end of the spindle 78. An annular grinding wheel 84 is locked to the lower surface of the wheel mount 80 by bolts 82. A plurality of grinding stones 86 are fixed to the outer periphery of the lower surface of the grinding wheel 84, and the plurality of grinding stones 86 are arranged in a ring at intervals in the circumferential direction.

[0061] As shown in Figure 8, in the wafer stripping planarization step, firstly, the stripping surface (back side 58b) of wafer 58 is facing upwards, and wafer 58 is held by the upper surface of chuck stage 74. Next, chuck stage 74 is rotated in the R3 direction at a predetermined rotational speed (e.g., 300 rpm). Then, spindle 78 is rotated in the R4 direction at a predetermined rotational speed (e.g., 6000 rpm).

[0062] Next, the spindle 78 is lowered using the lifting mechanism (not shown) of the grinding apparatus 72, bringing the grinding stone 86 into contact with the stripping surface (back side 58b) of the wafer 58. Grinding water is then supplied to the portion in contact with the grinding stone 86. After the grinding stone 86 contacts the stripping surface of the wafer 58, the spindle 78 is lowered at a predetermined grinding feed rate (e.g., 1.0 μm / s). This process grinds and planarizes the stripping surface of the wafer 58.

[0063] (Mirror finishing steps) After performing the wafer stripping planarization step, a mirror finishing step is performed, which involves performing mirror finishing on the front side 58a and the back side 58b of the wafer 58.

[0064] The mirror finishing process can be performed, for example, using the polishing apparatus 88 shown in FIG9. The polishing apparatus 88 includes: a chuck stage 90 that holds the wafer 58; and a polishing unit 92 that polishes the wafer 58 held on the chuck stage 90.

[0065] The chuck stage 90 is configured to rotate freely around an axis extending in the vertical direction. The grinding unit 92 includes: a spindle 94 extending in the vertical direction; a circular plate-shaped base 96 fixed to the lower end of the spindle 94; and a grinding pad 98 fixed to the lower surface of the base 96. The grinding pad 98 can be formed, for example, from a foamed urethane sheet.

[0066] Referring to Figure 9, in the mirror finishing process, firstly, the front side 58a of the wafer 58 is facing upwards, and the wafer 58 is held by the upper surface of the chuck stage 90. Next, the chuck stage 90 is rotated in the R5 direction. Then, the spindle 94 is rotated in the R6 direction.

[0067] Next, while supplying slurry from the slurry supply source (not shown) of the polishing apparatus 88 between the front side 58a of the wafer 58 and the lower surface of the polishing pad 98, the lower surface of the polishing pad 98 is pushed against the front side 58a of the wafer 58. This allows the front side 58a of the wafer 58 to be polished and mirror-finished. Furthermore, the back side 58b of the wafer 58 is also mirror-finished in the same manner.

[0068] (Crystal rod release surface planarization step) Furthermore, after performing the above-described stripping step, a crystal rod stripping surface planarization step is performed in parallel with the aforementioned second chamfering processing step, wherein the crystal rod stripping surface planarization step involves grinding and planarizing the stripping surface of the crystal rod 2. The crystal rod stripping surface planarization step can be performed using the grinding apparatus 72 used in the wafer stripping surface planarization step.

[0069] As shown in Figure 10, in the crystal rod peeling surface planarization step, firstly, the peeling surface 4' of the crystal rod 2 is facing upwards, and the crystal rod 2 is held by the attraction of the upper surface of the chuck stage 74. Next, the chuck stage 74 is rotated in the R3 direction. Then, the spindle 78 is rotated in the R4 direction.

[0070] Next, the spindle 78 is lowered so that the grinding stone 86 contacts the peeling surface 4' of the crystal rod 2. Grinding water is then supplied to the portion in contact with the grinding stone 86. After the grinding stone 86 contacts the peeling surface 4' of the crystal rod 2, the spindle 78 is lowered at a predetermined grinding feed rate. This process grinds and flattens the peeling surface 4' of the crystal rod 2.

[0071] In addition, after planarizing the stripping surface 4' of the crystal ingot 2, the same mirror processing as the mirror processing performed on the front side 58a and back side 58b of the wafer 58 can be applied to the stripping surface 4' of the crystal ingot 2.

[0072] Then, after performing the planarization step of the crystal rod peeling surface, by repeating the above steps, multiple wafers 58 can be generated from the crystal rod 2, and the outer periphery of the generated wafers 58 can be chamfered efficiently.

[0073] 2: Crystal rod 4: The first end face of the crystal rod α: Deflection angle A: The direction that forms the deflection angle 10: Vertical lines 22: Quality Improvement Department 24: Crack 26: Stripping band 28: Peeling layer 36:ID 44: First chamfer 58: Wafer 58a: Front side of the wafer 58b: Back side of the wafer 60: Second chamfer

Claims

1. A method for generating a wafer, comprising processing a crystal ingot to generate a wafer, and comprising: a release layer forming step, wherein a focal point of a laser beam of a wavelength having penetrability to the crystal ingot is positioned from a planarized first end face of the crystal ingot at a depth equivalent to the thickness of the wafer to be generated, and the laser beam is irradiated onto the crystal ingot to form a release layer; a first chamfer forming step, wherein a laser beam of a wavelength having absorption to the wafer to be generated is irradiated from the first end face side of the crystal ingot to the remaining peripheral area of ​​the wafer to be generated, thereby forming a first chamfer on the first end face of the crystal ingot; a peeling step, wherein the wafer to be generated is peeled off from the release layer; and a second chamfer forming step, wherein a laser beam of a wavelength having absorption to the wafer is irradiated from the peeled surface side of the wafer to the remaining peripheral area of ​​the peeled surface of the wafer to form a second chamfer.

2. The wafer fabrication method as described in Request 1, wherein, Includes: an ID formation step, which, after the stripping layer formation step, irradiates the remaining area of ​​the wafer with a laser beam of an absorbent wavelength to form an ID associated with the manufacturing history.

3. The wafer fabrication method as described in Request 1, wherein, Includes: a chamfering grinding step, which grinds the first chamfer and the second chamfer.

4. The wafer fabrication method as described in Request 1, wherein, Includes: a wafer stripping surface planarization step, which grinds and planarizes the stripping surface of the wafer.

5. The wafer fabrication method as described in request item 4, wherein, Includes: a mirror finishing step, which performs mirror finishing on the front and back sides of the wafer.

6. The wafer fabrication method as described in Request 1, wherein, Includes: a crystal rod stripping surface planarization step, which, after the stripping step, grinds and planarizes the stripping surface of the crystal rod.

7. The wafer fabrication method as described in Request 1, wherein, The crystal rod is a SiC crystal rod, and the wafer is a SiC wafer.

8. The wafer fabrication method as described in claim 7, wherein, The c-plane of the SiC crystal rod is inclined relative to the vertical line of the first end face, and an angle is formed by the c-plane and the first end face. In the peeling layer formation step, the peeling band formation step and the indexing feed step are repeatedly performed, so that the peeling bands are arranged side by side in the Y-axis direction to form the peeling layer. In the peeling band formation step, the direction orthogonal to the direction of forming the angle is set as the X-axis, and the direction orthogonal to the X-axis is set as the Y-axis. The focus point of the laser beam with a wavelength that has penetrability to the SiC crystal rod is positioned at a depth equivalent to the thickness of the wafer to be generated, and the laser beam is irradiated onto the SiC crystal rod. The SiC crystal rod and the focus point are processed and fed in the X-axis direction, and the modified part formed by separating SiC into Si and C forms a strip-shaped peeling band along the c-plane by crack elongation. The indexing feed step is to index and feed the SiC crystal rod and the focus point in the Y-axis direction.

Images