Method of wafer generation

Abstract

The present application provides a wafer production method that shortens the peeling time when a wafer is produced by peeling from a SiC ingot. The wafer production method includes a wafer production step of peeling a wafer from an ingot by spraying ultrasonic water to an end surface of the ingot on which a peeling layer is formed, thereby producing the wafer. Therefore, compared with a structure in which ultrasonic vibrations are simultaneously transmitted to the entire surface of the end surface of the ingot to peel the wafer, the peeling time can be shortened, and the ultrasonic water spraying nozzle and the ultrasonic vibration plate of the ultrasonic water spraying nozzle can be downsized. Thus, efficiency and cost reduction related to wafer peeling can be achieved.

Description

Technical Field

[0001] The present invention relates to a method for producing a wafer. Background Art

[0002] In the conventional techniques disclosed in Patent Documents 1 and 2, a SiC ingot is irradiated with laser light of a wavelength that is transmissive to the SiC ingot. This creates a delamination layer at a depth equivalent to the thickness of the wafer from one surface of the SiC ingot. This delamination layer comprises a modified portion and cracks extending from the modified portion along the c-plane. Delamination is then performed starting from the delamination layer to produce a SiC wafer.

[0003] Debonding can be achieved by transmitting ultrasonic vibrations to the debonding layer, thereby bonding the debonding layer. To transmit the ultrasonic vibrations to the debonding layer, after forming the debonding layer, one surface of the SiC ingot is immersed in water. The ultrasonic vibrations oscillated from the ultrasonic vibration plate are then transmitted from the one surface of the SiC ingot to the debonding layer via the water. This allows the wafer to be debonded.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2018-133485

[0005] Patent Document 2: Japanese Patent Application Publication No. 2019-096751

[0006] However, conventional exfoliation methods immerse one surface of the SiC ingot in water to simultaneously transmit ultrasonic vibrations to the entire surface. This requires a large ultrasonic vibration plate, resulting in poor efficiency. Furthermore, exfoliation of the entire surface takes time. Furthermore, the exfoliation process contaminates the water, necessitating replacement of the water. Summary of the Invention

[0007] Therefore, an object of the present invention is to provide a method for producing a wafer capable of shortening the peeling time when producing a wafer by peeling from a SiC ingot.

[0008] According to the present invention, a method for producing a wafer is provided, wherein the wafer is produced from a single-crystal SiC ingot, the single-crystal SiC ingot having a flat end face, a c-axis, and a c-plane perpendicular to the c-axis, wherein the method for producing the wafer comprises the following steps: a peeling layer forming step, wherein a focal point of a laser beam having a wavelength that is transparent to single-crystal SiC is positioned at a depth in the single-crystal SiC ingot corresponding to the thickness of the wafer to be produced, i.e., the wafer depth, and the laser beam is irradiated onto the flat end face of the single-crystal SiC ingot, and the single-crystal SiC ingot and the focal point are aligned along the direction parallel to the end face. The invention relates to a process for producing a single crystal SiC ingot comprising: a first step of moving the single crystal SiC ingot relative to the end face of the single crystal SiC ingot in a direction parallel to the c-plane, thereby forming a peeling layer, the peeling layer comprising a modified portion and cracks isotropically formed from the modified portion along the c-plane; and a chip generating process, wherein after the peeling layer forming process is implemented, ultrasonic water propagating ultrasonic vibrations is sprayed from an ultrasonic water jet nozzle toward the end face of the single crystal SiC ingot on the side where the chip is to be generated, and the single crystal SiC ingot and the ultrasonic water jet nozzle are moved relative to each other in a direction parallel to the end face, thereby peeling the chip with the peeling layer as an interface, thereby generating a chip.

[0009] Preferably, in the single crystal SiC ingot, the c-axis is tilted at a deviation angle relative to the perpendicular to the end face, and the angle formed by the c-face and the end face is the deviation angle, and the peeling layer forming process includes the following actions: alternately repeating the action of moving the focal point of the laser light irradiated to the end face linearly along a second direction perpendicular to the direction forming the deviation angle, i.e., the first direction, thereby continuously forming the peeling layer including the modified portion and the crack along the second direction, and the action of relative feeding the single crystal SiC ingot and the focal point along the first direction within a range not exceeding the width of the crack, thereby sequentially generating a plurality of the peeling layers along the second direction.

[0010] Preferably, the ultrasonic water jet nozzle used in the chip forming process includes: a dome-shaped ultrasonic vibration plate, which receives high-frequency power and oscillates ultrasonic vibrations; an annular plate, which extends outward from the outer periphery of the ultrasonic vibration plate; and a box, which has a water storage portion, a water supply port and a spray port, the water storage portion supports the annular plate and stores water on the recessed surface side of the ultrasonic vibration plate, the water supply port supplies water to the water storage portion, and the spray port is opposite to the recessed surface of the ultrasonic vibration plate and sprays the water from the water storage portion, and the chip forming process includes the following action: forming a focusing point of the ultrasonic vibration oscillated from the ultrasonic vibration plate by supplying high-frequency power to the ultrasonic vibration plate at the spray port.

[0011] Preferably, the chip generation method further includes the following steps: a separation step, in which the chip peeled in the chip generation step is separated from the single crystal SiC ingot by a separation unit; and a cleaning step, in which the peeled surface of the chip is cleaned using the ultrasonic water jet nozzle after the separation step is implemented.

[0012] According to the present invention, a wafer can be separated from a single-crystal SiC ingot by spraying ultrasonic water onto the end face of the ingot, where a separation layer has been formed. Therefore, compared to conventional structures that separate wafers by immersing one surface of the ingot in water while transmitting ultrasonic vibrations to the entire end face of the ingot, separation time can be shortened, and the ultrasonic water jet nozzle can be miniaturized. This improves efficiency and reduces costs associated with wafer separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 (a) is the main view of a single crystal SiC ingot. Figure 1 (b) is a top view of a single crystal SiC ingot.

[0014] Figure 2 (a) is a perspective view showing the structure of the main part of the laser processing device and the modified portion formed by the laser processing device, Figure 2 (b) is a side view showing a modified portion formed by a laser processing device.

[0015] Figure 3 (a) is a top view showing a single crystal SiC ingot on which a peeling layer is formed, Figure 3 (b) is Figure 3 Cross-sectional view along line BB in (a).

[0016] Figure 4 It is a perspective view showing a peeling device.

[0017] Figure 5 It shows Figure 4 A cross-sectional view of an ultrasonic water jet nozzle of a peeling device is shown.

[0018] Figure 6 It is a perspective view showing the peeling process.

[0019] Figure 7 It is a perspective view showing the cleaning process.

[0020] Description of labels

[0021] 1: Peeling device; 2: Ultrasonic water jet nozzle; 3: Ultrasonic vibration plate; 10: Holding table; 11: Holding surface; 12: Frame; 13: Holding table rotation mechanism; 14: Spindle; 15: Motor; 20: Box; 21: Bottom plate; 22: Top plate; 23: Side wall; 221: First chamber; 222: Second chamber; 231: Water supply port; 25: First electrode plate; 26: Second electrode plate; 27: Piezoelectric element; 261: Radiation surface; 29: High-frequency power supply; 30: Dome; 31: Shoulder; 32: Annular plate; 24: Nozzle; 241: Jet port; 41: Water supply pipe; 42: Joint; 43: First motor; 44: Water supply source; 45: Rotating shaft; 46: Rotating motor; 47: Lifting unit; 48: Holding component; 49: Housing; 500: Water; 501: Ultrasonic water; 600: Ultrasonic vibration; 50: Wafer holding portion; 51: Transfer pad; 52: Rotating arm; 53: Connecting portion; 64: Laser processing device; 66: Chuck table; 68: Condenser; 400: Laser beam; 401: Converging point; 100: Wafer; 101: Peeling surface; 200: Ingot; 201: First end face; 202: Second end face; 203: Peripheral surface; 204: Modified portion; 205: Crack; 206: Peeling layer; 211: First orientation plane; 212: Second orientation plane; 215: Vertical line; 216: C-axis; 217: C-plane; α: Deviation angle. DETAILED DESCRIPTION

[0022] The wafer production method according to an embodiment of the present invention is a method for producing a wafer from a single crystal SiC ingot having a c-axis and a c-plane perpendicular to the c-axis. The wafer production method according to this embodiment includes a peeling layer forming step, a wafer production step, a separation step, and a cleaning step.

[0023] First, the structure of a single crystal SiC ingot is described. Figure 1 As shown in (a) of FIG. 1 , a single crystal SiC ingot (hereinafter referred to as the ingot) 200 is formed into an overall cylindrical shape. Ingot 200 has a flat first end face 201 and a second end face 202 opposite first end face 201. First end face 201 of ingot 200 serves as the end face irradiated with laser light. A peripheral surface 203 is located between first end face 201 and second end face 202.

[0024] like Figure 1 As shown in (a), the ingot 200 has a c-axis 216 (<0001> direction) and a c-plane 217 ({0001} plane) perpendicular to the c-axis 216. The c-axis 216 is tilted at an offset angle α relative to the perpendicular 215 of the first end face 201 from the first end face 201 to the second end face 202. Therefore, the c-plane 217 is tilted at an offset angle α relative to the first end face 201. That is, the angle between the c-plane 217 and the first end face 201 is the offset angle α. Figure 1(a) and Figure 1 In (b), the direction forming the deviation angle α, that is, the first direction 300 is indicated by an arrow.

[0025] The number of c-planes 217 in the ingot 200 is countless at the molecular level of the ingot 200. In this embodiment, the off angle α is, for example, 1°, 3°, or 6°. The off angle α can be freely set within the range of, for example, 1° to 6°.

[0026] In addition, if Figure 1 As shown in (b), a rectangular first orientation flat surface 211 and a second orientation flat surface 212 are formed on the peripheral surface 203 of the ingot 200, indicating the crystal orientation. The first orientation flat surface 211 is parallel to the direction forming the deviation angle α, and the second orientation flat surface 212 is perpendicular to the direction forming the deviation angle α.

[0027] like Figure 1 As shown in (b) of FIG. 2 , when viewed from above, the length L2 of the second orientation flat surface 212 is shorter than the length L1 of the first orientation flat surface 211 ( L2 < L1 ).

[0028] [Peeling Layer Forming Step]

[0029] In the peeling step of the wafer production method of this embodiment, such an ingot 200 is irradiated with laser light to form a peeling layer inside the ingot 200. Therefore, in this embodiment, a peeling layer is used. Figure 2 (a) and Figure 2 The laser processing device 64 shown in (b).

[0030] The laser processing device 64 includes a chuck table 66 that holds the ingot 200 , and a condenser 68 that irradiates the ingot 200 held by the chuck table 66 with a laser beam 400 .

[0031] The chuck table 66 is rotated about an axis extending in the Z-axis direction by a rotation mechanism (not shown). Furthermore, the chuck table 66 is advanced and retracted in the X-axis direction by an X-axis movement mechanism (not shown), and advanced and retracted in the Y-axis direction by a Y-axis movement mechanism (not shown). The plane defined by the X-axis and Y-axis directions (XY plane) is substantially horizontal.

[0032] The condenser 68 includes a condenser lens (not shown) for condensing a pulsed laser beam 400 having a wavelength transparent to single crystal SiC emitted from a laser oscillator (not shown) of the laser processing device 64 and irradiating the laser beam 400 onto the ingot 200 .

[0033] When forming a peeling layer in the ingot 200, the operator first places the ingot 200 on the upper surface of the chuck table 66 with the first end surface 201 of the ingot 200 facing upward, and the ingot 200 is suctioned and held by the chuck table 66. Alternatively, an adhesive (e.g., an epoxy resin adhesive) may be sandwiched between the second end surface 202 of the ingot 200 and the upper surface of the chuck table 66 to secure the ingot 200 to the chuck table 66.

[0034] Next, an imaging unit (not shown) of the laser processing device 64 captures an image of the ingot 200 from above. Based on the image of the ingot 200 captured by the imaging unit, the chuck table 66 is moved and rotated using the X-axis movement mechanism, Y-axis movement mechanism, and rotation mechanism of the laser processing device 64. This adjusts the orientation of the ingot 200 to a predetermined orientation, and adjusts the positional relationship between the ingot 200 and the condenser 68 on the XY plane.

[0035] When the orientation of the ingot 200 is adjusted to a predetermined orientation, as shown in FIG. Figure 2 As shown in (a), the second orientation plane 212 is aligned with the X-axis direction. Thus, the direction perpendicular to the first direction 300 forming the deviation angle α (the second direction 301) is aligned with the X-axis direction, and the first direction 300 forming the deviation angle α is aligned with the Y-axis direction.

[0036] Next, the focusing point position adjustment mechanism (not shown) of the laser processing device 64 is used to raise and lower the focusing device 68. Figure 2 As shown in (b), by irradiating the first end face 201 of the ingot 200 with a laser beam 400 of a wavelength that is transmissive to single crystal SiC, the focal point 401 of the laser beam 400 can be positioned at the wafer depth, which is a depth in the ingot 200 corresponding to the thickness of the wafer to be generated (the depth from the first end face 201).

[0037] Next, a peeling layer forming process is performed by relatively moving the focal point 401 and the ingot 200 in the second direction. In the peeling layer forming process of this embodiment, the chuck table 66 is moved in the X-axis direction, which is aligned with the second direction 301 perpendicular to the first direction 300 forming the offset angle α, using the X-axis direction movement mechanism.

[0038] Therefore, if Figure 3 (a) and Figure 3As shown in (b), a modified portion 204 is formed at a portion of the wafer depth from the first end face 201 of the ingot 200. This modified portion 204 is formed by the following process: the SiC ingot 200 is separated into Si (silicon) and C (carbon) by irradiation with the laser beam 400, and the subsequently irradiated laser beam 400 is absorbed by the previously formed C, causing a chain reaction of separation into Si and C.

[0039] In this manner, modified portion 204 is continuously formed in second direction 301, which is perpendicular to first direction 300 forming offset angle α. Furthermore, cracks 205 are generated, extending isotropically from modified portion 204 along the c-plane (cracks 205 formed isotropically on the c-plane). Consequently, delamination layer 206 is continuously formed along second direction 301. This delamination layer 206 includes modified portion 204 and cracks formed isotropically from modified portion 204 along the c-plane.

[0040] Following this peeling layer forming process, the light-converging point 401 and the chuck table 66 (i.e., the ingot 200) are indexed and fed relative to each other by a predetermined indexing amount Li in the Y-axis direction, which coincides with the first direction 300 forming the deviation angle α, within a range not exceeding the width of the crack 205. In this embodiment, the chuck table 66 is indexed and fed in the Y-axis direction using a Y-axis movement mechanism.

[0041] By repeating the peeling layer forming process and the indexing feeding alternately, a plurality of modified portions 204 extending continuously in a second direction 301 perpendicular to the first direction 300 forming the offset angle α can be formed at intervals of a predetermined indexing amount Li in the first direction 300 forming the offset angle α.

[0042] In addition, if Figure 3 As shown in (b), cracks 205 extending isotropically from the plurality of modified portions 204 along the c-plane are formed so that the cracks 205 extending from adjacent modified portions 204 in the first direction 300 overlap when viewed from the Z-axis direction.

[0043] In this manner, multiple peeling layers 206 can be sequentially generated along the second direction 301, including modified portions 204 and cracks 205, in a portion corresponding to the wafer depth from the first end face 201 of the ingot 200. These peeling layers 206 are portions whose strength is reduced by the modified portions 204 and cracks 205, and serve as interfaces for peeling the wafer from the ingot 200.

[0044] [Wafer production process]

[0045] In the wafer production process, the wafer is peeled off from the ingot 200 on which the peeling layer 206 is formed, using the peeling layer 206 as an interface, thereby producing a wafer. Figure 4The stripping device 1 is shown.

[0046] The peeling device 1 has a holding table 10 for Figure 3 The ingot 200 shown in (a) and (b) is held with the peeling layer 206 formed thereon; an ultrasonic water jet nozzle 2 that jets ultrasonic water toward the ingot 200 held by the holding table 10; and a housing (not shown) that surrounds the holding table 10.

[0047] The holding table 10 is formed in a disk shape. The holding table 10 has a holding surface 11 facing the second end surface 202 (see Figure 1 and a frame 12 supporting the holding surface 11. The holding surface 11 includes a porous member and is connected to a suction source (not shown) to suck and hold the second end surface 202 of the ingot 200 placed on the holding surface 11.

[0048] In the present embodiment, the peeling apparatus 1 peels the wafer by spraying ultrasonic water onto the entire upper surface, ie, the first end surface 201 , of the ingot 200 held by the holding surface 11 of the holding table 10 .

[0049] A holding table rotating mechanism 13 is provided below the holding table 10. The holding table rotating mechanism 13 includes a spindle 14, which serves as the rotation axis of the holding table 10, and a motor 15 for rotating the spindle 14. The motor 15 transmits a rotational driving force to the holding table 10 via the spindle 14. As a result, the holding table 10 rotates about the spindle 14, for example, in the direction indicated by arrow 302, while holding the ingot 200.

[0050] The ultrasonic water jet nozzle 2 jets ultrasonic water from above toward the first end surface 201 of the ingot 200 held by the holding surface 11 of the holding table 10. Figure 4 As shown, the ultrasonic water jet nozzle 2 is attached to the front end of a water supply pipe 41 that is rotatable above the holding table 10 .

[0051] The water supply pipe 41 extends horizontally and is connected to a water supply source 44 at its rear end via a joint 42. The water supply source 44 includes a pump and is configured to deliver water to the ultrasonic water jet nozzle 2 via the water supply pipe 41.

[0052] Furthermore, a first motor 43 is mounted at the rear end of the water supply pipe 41. The first motor 43 rotates the water supply pipe 41 and the ultrasonic water jet nozzle 2 about the axis of the water supply pipe 41. The water supply pipe 41 and the ultrasonic water jet nozzle 2 are rotated as indicated by arrow 303 by the first motor 43.

[0053] The lower end of the first motor 43 is connected to a rotating shaft 45 of the water supply pipe 41. The rotating shaft 45 rotates while holding the ultrasonic water jet nozzle 2, the water supply pipe 41, and the first motor 43. The rotating shaft 45 extends in the Z-axis direction, and the first motor 43 is mounted on its upper end. A rotary motor 46 is mounted on the lower end of the rotating shaft 45 for rotating the rotating shaft 45 around its axis. Rotating the rotating shaft 45 by the rotary motor 46 causes the water supply pipe 41 and the ultrasonic water jet nozzle 2 to rotate as indicated by arrow 304.

[0054] The water supply pipe 41 has a length from the first motor 43 at the upper end of the rotating shaft 45 to the center of the holding table 10. Thus, the rotating shaft 45 can move the ultrasonic water jet nozzle 2 provided at the front end of the water supply pipe 41 from the outer periphery to the center of the ingot 200 held by the holding table 10.

[0055] Furthermore, the rotary motor 46 is mounted on the lifting unit 47. The lifting unit 47 includes a housing 49 having a groove 491 and a holding member 48 that holds the rotary motor 46. The holding member 48 is mounted on a driving member (not shown) within the housing 49 and protrudes from the housing 49 via the groove 491. The holding member 48 moves in the Z-axis direction along the groove 491 while holding the rotary motor 46.

[0056] The lifting unit 47 allows the rotary shaft 45 , the first motor 43 , the water supply pipe 41 , and the ultrasonic water jet nozzle 2 to move in the Z-axis direction.

[0057] The ultrasonic water jet nozzle 2 is a nozzle for jetting ultrasonic water that has propagated ultrasonic vibrations onto the first end surface 201 of the ingot 200 (see Figure 3 (a) and (b)). Figure 5 As shown, the ultrasonic water jet nozzle 2 includes: a tank 20 that temporarily stores water 500 supplied from a water supply source 44; a jet port 241 formed on the lower surface of the tank 20; and an ultrasonic vibration plate 3 disposed in the tank 20 opposite to the jet port 241.

[0058] The box 20 is formed in a substantially cylindrical shape, for example, and includes a bottom plate 21 , a top plate 22 facing the bottom plate 21 in the Z-axis direction, and a substantially cylindrical side wall 23 connecting the bottom plate 21 and the top plate 22 .

[0059] The interior of the box 20 is divided into two upper and lower chambers by the ultrasonic vibration plate 3: a first chamber 221 located above the ultrasonic vibration plate 3 and a second chamber 222 located below the ultrasonic vibration plate 3. A water supply port 231 is formed on the side wall 23 of the lower second chamber 222 and penetrates the side wall 23.

[0060] The water supply port 231 is used to supply water 500 to the second chamber 222 between the ultrasonic vibration plate 3 and the injection port 241 in the tank 20. The water supply port 231 is connected to the water supply pipe 41. Therefore, the water 500 supplied from the water supply source 44 is temporarily stored in the second chamber 222 of the tank 20.

[0061] A nozzle portion 24 is formed on the bottom plate 21, protruding toward the -Z direction. The nozzle portion 24 gradually tapers in diameter toward the front end. Furthermore, the nozzle portion 24 has a spray port 241 at the front end for spraying water 500 stored in the second chamber 222 of the tank 20. Alternatively, the nozzle portion 24 may not taper toward the spray port 241.

[0062] The ultrasonic vibration plate 3 is dome-shaped and configured to oscillate ultrasonic vibrations upon receiving high-frequency power. The ultrasonic vibration plate 3 transmits ultrasonic vibrations 600 to the water 500 stored in the second chamber 222 of the tank 20. The ultrasonic vibration plate 3 is positioned within the tank 20 opposite the injection port 241. The ultrasonic vibration plate 3 has an arcuate cross-section and is concave toward the injection port 241. Specifically, the injection port 241 faces the concave surface of the ultrasonic vibration plate 3.

[0063] The ultrasonic vibration plate 3 includes a dome portion 30 and a shoulder portion 31 extending radially outward from the outer periphery of the dome portion 30. Furthermore, the ultrasonic vibration plate 3 includes an annular plate 32 extending radially outward from the outer periphery of the shoulder portion 31. Specifically, the annular plate 32 is provided so as to extend outward from the outer periphery of the ultrasonic vibration plate 3.

[0064] The dome portion 30 includes a first electrode plate 25 , a piezoelectric element 27 , and a second electrode plate 26 , which overlap with each other along the Z-axis direction.

[0065] The first electrode plate 25 and the second electrode plate 26 are formed of, for example, a piezoelectric element which is a type of ceramic. The first electrode plate 25, the piezoelectric element 27, and the second electrode plate 26 are formed to have a dome shape.

[0066] The first electrode plate 25, the piezoelectric element 27, and the second electrode plate 26 are stacked with the recessed side facing the injection port 241. Electrodes (not shown) are attached to the first electrode plate 25 and the second electrode plate 26. A high-frequency power supply 29 is connected to the first electrode plate 25 and the second electrode plate 26 via these electrodes and wiring 28.

[0067] The high-frequency power supply 29 supplies high-frequency power to the ultrasonic vibration plate 3. Specifically, the high-frequency power supply 29 applies a high-frequency AC voltage to the first electrode plate 25 and the second electrode plate 26 of the dome portion 30 of the ultrasonic vibration plate 3. Thus, the high-frequency power supply 29 supplies high-frequency power to the ultrasonic vibration plate 3.

[0068] The upper surface of the convex side of the second electrode plate 26 is in close contact with the lower surface of the first electrode plate 25 via the piezoelectric element 27. The lower surface of the concave side of the second electrode plate 26 (i.e., the lower surface of the dome portion 30 facing the injection port 241) serves as a radiation surface 261 that radiates ultrasonic vibrations 600 toward the water 500 temporarily stored in the second chamber 222 of the tank 20.

[0069] In this embodiment, the radiating surface 261 of the ultrasonic vibration plate 3 is formed to have a dome shape similar to a portion of the inner surface of a sphere. Alternatively, the radiating surface 261 may be formed to have a dome shape similar to the inner surface of a mortar. In other words, the radiating surface 261 only needs to be configured so that the ultrasonic vibrations 600 are concentrated toward the ejection port 241.

[0070] A circular plate-shaped boss portion 31 integrally extends radially outward from the outer peripheral edge of the second electrode plate 26 of the dome portion 30. The boss portion 31, like the dome portion 30, is formed of a piezoelectric element or the like.

[0071] The annular plate 32 extends radially outward from the outer peripheral edge of the boss portion 31. The outer peripheral portion of the annular plate 32 is supported by the sidewall 23 of the second chamber 222 of the housing 20, thereby securing the dome portion 30 hollow within the housing 20. Thus, the second chamber 222 (and the housing 20) functions as a water reservoir that supports the annular plate 32 and stores water on the concave surface of the ultrasonic vibration plate 3.

[0072] The end portion of the outer peripheral portion of the annular plate 32 is supported by the side wall 23. The annular plate 32 amplifies the ultrasonic vibration 600 by the portion not supported by the side wall 23.

[0073] Next, the wafer production process using the above-mentioned peeling device 1 will be described. Figure 5 As shown, the operator places the ingot 200 on the holding surface 11 of the holding table 10 with the first end surface 201 facing upward, so that the center of the ingot 200 is roughly aligned with the center of the holding surface 11 of the holding table 10. Then, the suction force generated by the operation of the suction source (not shown) is transmitted to the holding surface 11, thereby attracting and holding the second end surface 202 of the ingot 200 by the holding surface 11 of the holding table 10.

[0074] Then, the distance between the ultrasonic water jet nozzle 2 and the first end surface 201 of the ingot 200 is adjusted by the lifting unit 47. Furthermore, the main spindle 14 rotates the holding table 10 holding the ingot 200 in the direction of arrow 302. Furthermore, the rotary motor 46 rotates the rotary shaft 45. As a result, the ultrasonic water jet nozzle 2 moves from its retracted position outside the holding table 10 to above the ingot 200, with the jet port 241 facing the first end surface 201 of the ingot 200.

[0075] Then, the pressurized water 500 is sent out from the water supply source 44. The water 500 passes through the water supply pipe 41 and is temporarily stored in the second chamber 222 of the tank 20 of the ultrasonic water jet nozzle 2.

[0076] When a predetermined amount of water 500 is stored in the second chamber 222 of the tank 20, and the pressure in the second chamber 222 increases, the water 500 is ejected downward from the ejection port 241. Furthermore, by continuously supplying water 500 from the water supply source 44, the amount of water 500 in the second chamber 222 is maintained at a predetermined amount.

[0077] At this time, high-frequency power source 29 supplies high-frequency power of a predetermined frequency (e.g., 20 kHz to 1 MHz) to ultrasonic vibration plate 3. Specifically, high-frequency power source 29 repeatedly turns voltage application on and off at a predetermined frequency. This causes vertical expansion and contraction of first electrode plate 25 and piezoelectric element 27. This expansion and contraction motion is converted into mechanical ultrasonic vibration 600. The amount of power supplied from high-frequency power source 29 to ultrasonic vibration plate 3 is, for example, 95 W.

[0078] The vibrations of the second electrode plate 26 and the first electrode plate 25 resonate, causing ultrasonic vibrations 600 to propagate from the radiation surface 261, which is a gently concave surface when viewed from the ejection port 241, toward the water 500 temporarily stored in the second chamber 222 of the tank 20. Furthermore, the ultrasonic vibrations 600 propagating from the concave radiation surface 261 toward the water 500 are concentrated toward the ejection port 241. In other words, the ultrasonic vibrations oscillated from the ultrasonic vibration plate 3 converge at the ejection port 241.

[0079] As a result of the propagation of such ultrasonic vibrations, ultrasonic water 501 propagating ultrasonic vibrations 600 is ejected from ejection port 241 of nozzle portion 24 toward the outside. Specifically, in this embodiment, ultrasonic water 501 is ejected from ejection port 241 of nozzle portion 24 toward first end surface 201, the end surface of ingot 200 on the side where a wafer is to be formed.

[0080] At this time, the ingot 200 and the ultrasonic water jet nozzle 2 are relatively moved in a direction parallel to the first end surface 201 of the ingot 200. In this embodiment, the rotary motor 46 rotates the rotary shaft 45, causing the ultrasonic water jet nozzle 2 to pass above the center of the ingot 200 and reciprocate at a predetermined angle above the ingot 200, which rotates along with the holding table 10. As a result, the ultrasonic water 501 is sprayed onto the entire surface of the first end surface 201 of the ingot 200.

[0081] By spraying ultrasonic water 501, multiple peeling layers 206 of ingot 200 arranged along first direction 300 are connected to each other, and the plate-shaped wafer is peeled from ingot 200 using these peeling layers 206 as interfaces. In addition, the first end surface 201 of ingot 200 is cleaned by spraying ultrasonic water 501.

[0082] [Separation process]

[0083] In the separation process, the wafers separated in the wafer production process are separated from the ingot 200 by the separation unit. Figure 6 The wafer holding portion 50 is shown as a separation unit.

[0084] The wafer holding portion 50 includes a transfer pad 51 having a downward holding surface parallel to the XY plane, a rotating arm 52 for rotating the transfer pad 51 , and a connecting portion 53 connecting the transfer pad 51 and the rotating arm 52 .

[0085] During the separation process, a rotating arm 52 is used to position a transfer pad 51 above the ingot 200 placed on the holding table 10 of the peeling apparatus 1. The transfer pad 51 is then lowered by a vertical movement unit (not shown), and the first end surface 201 of the ingot 200 is held by the transfer pad 51 under suction. The vertical movement unit then raises the transfer pad 51 as indicated by arrow 305. This separates the SiC wafer 100 from the ingot 200. The lower surface of the wafer 100 becomes the peeling surface 101, which is the surface to be peeled from the ingot 200.

[0086] [Cleaning process]

[0087] In the cleaning step, the separation surface 101 of the wafer 100 is cleaned using the ultrasonic water jet nozzle 2 .

[0088] Therefore, first of all, Figure 7 As shown, the ultrasonic water jet nozzle 2 is positioned below the wafer 100 that has been peeled from the ingot 200 and held on the transfer pad 51 of the wafer holding portion 50. Then, the water supply pipe 41 is rotated by the first motor 43 as indicated by arrow 303, thereby orienting the jet port 241 of the ultrasonic water jet nozzle 2 upward. As a result, the jet port 241 of the ultrasonic water jet nozzle 2 is positioned opposite the peeled surface 101 of the wafer 100.

[0089] Then, while the ultrasonic water jet nozzle 2 is appropriately rotated by the rotary shaft 45, ultrasonic water 501 is jetted from the jet port 241 of the ultrasonic water jet nozzle 2 toward the peeling surface 101 of the wafer 100. This cleans the peeling surface 101. After the peeling surface 101 is cleaned, the wafer 100 held by the transfer pad 51 is transported, for example, to a predetermined storage location, using the rotary arm 52 and the vertical movement unit. Furthermore, during cleaning, the high-frequency power supply 29 supplies high-frequency power of a predetermined frequency (e.g., 500 kHz to 1 MHz) to the ultrasonic vibration plate 3.

[0090] As described above, in this embodiment, while rotating the ingot 200 having the peeling layer 206 formed thereon, ultrasonic water 501 is jetted from the rotating ultrasonic water jet nozzle 2 toward the first end surface 201 of the ingot 200. This allows the wafer 100 to be peeled from the ingot 200 to form a wafer.

[0091] Therefore, compared to the conventional structure in which one surface of the ingot is immersed in water while ultrasonic vibrations are transmitted to the entire surface of the ingot to peel the wafer, the peeling time can be shortened, and the ultrasonic water jet nozzle 2 and the ultrasonic vibration plate 3 of the ultrasonic water jet nozzle 2 can be miniaturized. As a result, the efficiency and cost of peeling the wafer 100 can be improved.

[0092] Furthermore, in this embodiment, the dome portion 30 generating the ultrasonic vibrations 600 is held by the side wall 23 of the tank 20 via the annular plate 32. Therefore, when high-frequency power is supplied to the ultrasonic vibration plate 3, the dome portion 30 readily vibrates. Consequently, the ultrasonic vibrations, having a large amplitude amplified by the annular plate 32, can be effectively propagated to the water 500.

[0093] Furthermore, in this embodiment, during the peeling layer forming process for forming the peeling layer 206 on the ingot 200, the ingot 200 is moved relative to the focal point 401 in a second direction 301 perpendicular to the first direction 300 forming the offset angle α. Furthermore, during the indexing process, the ingot 200 is moved relative to the focal point 401 in the first direction 300 forming the offset angle α. In this regard, the relative movement direction of the ingot 200 and the focal point 401 during the peeling layer forming process need not be the second direction 301 perpendicular to the first direction 300 forming the offset angle α. Furthermore, the relative movement direction of the ingot 200 and the focal point 401 during the indexing process need not be the first direction 300 forming the offset angle α.

Claims

1. A method for producing a wafer from a single crystal SiC ingot, wherein the single crystal SiC ingot has a flat end face, a c-axis, and a c-plane perpendicular to the c-axis, the c-axis being inclined at an offset angle relative to a perpendicular to the end face, and the angle between the c-plane and the end face being the offset angle, wherein: The wafer production method includes the following steps: a peeling layer forming step of positioning a converging point of laser light of a wavelength that is transmissive to single-crystalline SiC at a depth in the single-crystalline SiC ingot corresponding to the thickness of a wafer to be formed, i.e., a wafer depth, irradiating the flat end face of the single-crystalline SiC ingot with the laser light, and moving the single-crystalline SiC ingot and the converging point relative to each other in a direction parallel to the end face, thereby forming a peeling layer including a modified portion and cracks isotropically formed from the modified portion along the c-plane; and A chip generating process, after implementing the peeling layer forming process, jetting ultrasonic water that propagates ultrasonic vibrations from an ultrasonic water jet nozzle toward the end face of the single crystal SiC ingot on the side where the chip is to be generated, and moving the single crystal SiC ingot and the ultrasonic water jet nozzle relative to each other in a direction parallel to the end face, so that the multiple peeling layers of the single crystal SiC ingot arranged along the direction forming the deviation angle are connected to each other, thereby peeling the chip with the peeling layer as the interface, thereby generating a chip.

2. The method for producing a wafer according to claim 1, wherein: The peeling layer forming process includes the following steps: The actions of linearly moving the focal point of the laser light irradiated onto the end face in a second direction perpendicular to the first direction forming the deviation angle, thereby continuously forming the peeling layer including the modified portion and the crack along the second direction, and the action of relative shifting and feeding the single crystal SiC ingot and the focal point along the first direction within a range not exceeding the width of the crack are repeated alternately, thereby sequentially generating a plurality of peeling layers along the second direction.

3. The method for producing a wafer according to claim 1, wherein: The ultrasonic water jet nozzle used in the wafer production process includes: A dome-shaped ultrasonic vibration plate that receives high-frequency electricity and oscillates ultrasonic vibrations; a circular ring-shaped plate extending outward from the outer periphery of the ultrasonic vibration plate; and The box includes a water storage portion, a water supply port, and a spray port. The water storage portion supports the annular plate and stores water on the concave surface side of the ultrasonic vibration plate. The water supply port supplies water to the water storage portion. The spray port faces the concave surface of the ultrasonic vibration plate and sprays the water in the water storage portion. The wafer forming step includes forming a focusing point of ultrasonic vibration oscillated from the ultrasonic vibration plate by supplying high-frequency power to the ultrasonic vibration plate, at the ejection port.

4. The method for producing a wafer according to claim 1, wherein: The wafer production method also includes the following steps: a separation step of separating the wafer peeled in the wafer production step from the single crystal SiC ingot by a separation unit; and In the cleaning step, after the separation step is performed, the separation surface of the wafer is cleaned using the ultrasonic water jet nozzle.

5. The method for producing a wafer according to claim 3, wherein: The frequency of the high-frequency power supplied to the ultrasonic vibration plate is 20 kHz to 1 MHz.

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