Wafer manufacturing method

Abstract

To provide a wafer manufacturing method that can improve throughput while reducing material loss. [Solution] The wafer manufacturing method comprises: a separation point formation step 2, in which a separation point including a modified layer and cracks extending from the modified layer is formed on a plane parallel to a first surface by moving the focal point of a laser beam relative to the ingot along a predetermined processing feed direction while the focal point of the laser beam is positioned inside the ingot; a indexing feed step 3, in which the focal point is indexed and fed relative to the ingot; a full-surface processing step 1, in which separation points are formed on the entire interior surface of the ingot by repeatedly performing these steps; and a separation step 4, in which the wafer is separated from the ingot using the separation points as starting points. By forming multiple focal points of the laser beam in the depth direction of the ingot at intervals corresponding to the thickness of the wafer to be manufactured in the separation point formation step 2, multiple separation points are formed at different depth positions of the ingot in a single full-surface processing step 1.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a wafer.

Background Art

[0002] As a means for cutting out a wafer from a Si (silicon) ingot or a compound semiconductor ingot made of Si, etc., a wire saw is known. In a wire saw, a wire row is formed by winding a large number of cutting wires around a plurality of rollers, and the cutting wire is cut and fed with respect to the ingot to cut at the wire position (see Patent Document 1).

[0003] However, the wire saw has a relatively large cutting margin of around 300 μm, and since lapping, etching, and polishing are required to flatten the surface after cutting, the amount of material used as a wafer becomes about 1 / 3 of the original ingot, and there is a problem of poor productivity. Therefore, the present applicants have developed a method for efficiently manufacturing a Si substrate from a Si ingot by irradiating a laser beam (see Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The method of Patent Document 2 can reduce material loss, but there is a problem of a decrease in throughput due to single-piece processing.

[0006] This invention has been made in view of the above problems, and its purpose is to provide a wafer manufacturing method that can improve throughput while reducing material loss. [Means for solving the problem]

[0007] To solve the above-mentioned problems and achieve the objective, the present invention provides a wafer manufacturing method for manufacturing a wafer from an ingot having a first surface and a second surface opposite to the first surface, comprising: a separation origin formation step in which a separation origin is formed on a plane parallel to the first surface by moving the ingot relatively with respect to the focal point of a laser beam having a wavelength that penetrates the material constituting the ingot, with the focal point positioned inside the ingot from the side of the first surface; and a separation step in which a wafer is separated from the ingot using the separation origin as the origin, wherein in the separation origin formation step, a plurality of focal points of the laser beam are formed in the depth direction of the ingot, and each of the focal points is arranged inside the ingot at intervals corresponding to the thickness of the wafer to be manufactured, thereby forming a plurality of separation origins at different depth positions of the ingot in a single separation origin formation step.

[0008] Furthermore, in the wafer manufacturing method of the present invention, the plurality of focal points formed in the depth direction of the ingot may be arranged at different positions along the direction of progress in the processing feed direction, so that they are processed sequentially from the focal point located at the deepest position to the focal point located at the shallowest position.

[0009] Furthermore, in the wafer manufacturing method of the present invention, in the separation origin formation step, the separation origin, which includes the modified layer and cracks extending from the modified layer, may be formed on the entire interior surface of the ingot.

[0010] Furthermore, in the wafer manufacturing method of the present invention, the wafer may be separated from the ingot by applying ultrasound in the separation step. [Effects of the Invention]

[0011] This invention can improve throughput while reducing material loss. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a perspective view of the ingot to be processed according to the wafer manufacturing method of the embodiment. [Figure 2] Figure 2 is a top view of the ingot shown in Figure 1. [Figure 3] Figure 3 is a flowchart showing the flow of the wafer manufacturing method according to this embodiment. [Figure 4] Figure 4 is a schematic diagram showing an example of the separation point formation step shown in Figure 3. [Figure 5] Figure 5 is a perspective view showing one state of the overall machining step shown in Figure 3. [Figure 6] Figure 6 is a top view of the ingot shown in Figure 5. [Figure 7] Figure 7 is a side view showing a partial cross-section of an example of the separation step shown in Figure 3. [Figure 8] Figure 8 is a side view showing a partial cross-section of the first separation step in another example of the separation steps shown in Figure 3. [Figure 9] Figure 9 is a side view showing a partial cross-section of the second separation step in another example of the separation steps shown in Figure 3. [Figure 10] Figure 10 is a perspective view of the ingot to be processed in a modified wafer manufacturing method. [Figure 11] Figure 11 is a top view of the ingot shown in Figure 10. [Modes for carrying out the invention]

[0013] Embodiments for implementing the present invention will be described in detail with reference to the drawings. The present invention is not limited by the content described in the following embodiments. Further, the constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Also, various omissions, substitutions, or changes in the configuration can be made without departing from the gist of the present invention.

[0014] 〔Embodiment〕 A method for manufacturing a wafer 30 according to an embodiment of the present invention will be described based on the drawings. The method for manufacturing the wafer 30 in the embodiment is a method for manufacturing the wafer 30 shown in FIGS. 4 and the like from an ingot 10 shown in FIGS. 1 and 2.

[0015] (Si single crystal ingot) First, the configuration of the ingot 10 to be processed in the method for manufacturing the wafer 30 according to an embodiment of the present invention will be described. FIG. 1 is a perspective view of the ingot 10 to be processed in the method for manufacturing the wafer 30 according to the embodiment. FIG. 2 is a top view of the ingot 10 shown in FIG. 1.

[0016] The ingot 10 in the embodiment shown in FIGS. 1 and 2 is a single crystal Si ingot made of Si and formed in a cylindrical shape as a whole. The ingot 10 has a first surface 11, a second surface 12, a peripheral surface 13, and an orientation flat 14.

[0017] The first surface 11 is circular and is one flat end face of the ingot 10 formed in a cylindrical shape. The second surface 12 is circular and is a flat end face on the opposite side of the first surface 11 of the ingot 10 formed in a cylindrical shape. The second surface 12 corresponds to the bottom surface of the ingot 10. The peripheral surface 13 is a surface that connects the outer edge of the first surface 11 and the outer edge of the second surface 12. The orientation flat 14 is a plane formed on a part of the peripheral surface 13 to indicate the crystal orientation of the ingot 10.

[0018] In the ingot 10, the first face 11 is a crystal plane {100}, and the orientation flat 14 is a crystal plane {011}. In this specification, Miller indices are indicated by placing a minus sign "-" before the index if the index is negative.

[0019] (Method of manufacturing wafer 30) Next, a method for manufacturing a wafer 30 according to an embodiment of the present invention will be described. Figure 3 is a flowchart showing the flow of the method for manufacturing a wafer 30 according to an embodiment. The method for manufacturing a wafer 30 includes a full-surface processing step 1 and a separation step 4. The full-surface processing step 1 includes a separation starting point formation step 2, which is performed repeatedly a predetermined number of times, and an indexing feed step 3.

[0020] In the following description, the X-axis direction is a unidirectional direction in the horizontal plane. The Y-axis direction is perpendicular to the X-axis direction in the horizontal plane. In the embodiment, the X-axis direction is the machining feed direction and the crystal orientation is

[0010] . In the embodiment, the Y-axis direction is the indexing feed direction and the crystal orientation is

[0001] .

[0021] Figure 4 is a schematic diagram showing an example of the separation point formation step 2 shown in Figure 3. Figure 5 is a perspective view showing one state of the full-surface processing step 1 shown in Figure 3. Figure 6 is a top view of the ingot 10 in Figure 5. The full-surface processing step 1 is a step in which separation points 18 are formed on the entire interior surface of the ingot 10 by repeatedly performing the separation point formation step 2 and the indexing feed step 3.

[0022] Step 1 of the embodiment is performed using the laser processing apparatus 100 shown in Figures 4 and 5. The laser processing apparatus 100 includes a holding table 110, a laser beam irradiation unit 120, a moving unit (not shown) that moves the holding table 110 and the laser beam irradiation unit 120 relative to each other, and an imaging unit (not shown).

[0023] The holding table 110 holds the ingot 10 on its holding surface 111. The holding surface 111 is a disc shape formed from porous ceramic or the like. In this embodiment, the holding surface 111 is a plane parallel to the horizontal direction. The holding surface 111 is connected to a vacuum suction source, for example, via a vacuum suction path. The holding table 110 holds the second surface 12 side of the ingot 10 placed on the holding surface 111 by suction.

[0024] The laser beam irradiation unit 120 irradiates the ingot 10, held on the holding surface 111 of the holding table 110, with a laser beam 121 having a wavelength that penetrates the material constituting the ingot. The focal point 127 formed by the laser beam irradiation unit 120 and the holding table 110 are relatively movable by a moving unit (not shown). Alternatively, instead of a moving unit, the focal point 127 and the holding table 110 may be moved relatively by a scanning unit that scans the laser beam 121. As shown in Figure 4, the laser beam irradiation unit 120 includes an oscillator 122, a condenser 123, an output adjustment unit 124, a branching unit 125, and a mirror 126.

[0025] The oscillator 122 emits a laser beam 121 having a predetermined wavelength for processing the ingot 10. The laser beam 121 that the laser beam irradiation unit 120 irradiates towards the ingot 10 is a laser beam with a wavelength that penetrates the material constituting the ingot.

[0026] The light concentrator 123 includes a focusing lens that focuses the laser beam 121 emitted from the oscillator 122 onto the ingot 10 held on the holding surface 111 of the holding table 110, and irradiates the ingot 10. The focal point 127 of the laser beam 121 focused by the light concentrator 123 is located inside the ingot 10. Furthermore, the focal point 127 of the laser beam 121 focused by the light concentrator 123 is formed at at least two different height positions by the branching unit 125, which will be described later.

[0027] The output adjustment unit 124 is located in the optical path between the oscillator 122 and the branching unit 125 and adjusts the output of the laser beam 121 passing through it. The output adjustment unit 124 includes, for example, an attenuator comprising a λ / 2 wave plate, a beam splitter, and a beam damper. The λ / 2 wave plate changes the linear polarization direction of the incident laser beam 121 according to its rotation angle. The beam splitter reflects the laser beam 121 that has passed through the λ / 2 wave plate toward the beam damper, and transmits the laser beam 121 that has a linear polarization direction other than the predetermined linear polarization direction.

[0028] The branching unit 125 is located in the optical path between the output adjustment unit 124 and the light concentrator 123, and branches the laser beam 121 so that the passing laser beam 121 forms at least two focal points 127. The branching unit 125 includes, for example, a diffractive optical element or a spatial light modulator. The diffractive optical element has the function of branching the incident laser beam 121 to form multiple focal points 127 by utilizing the diffraction phenomenon. The spatial light modulator modulates the laser beam 121 by electrically controlling the spatial distribution of the amplitude, phase, polarization, etc., of the laser beam 121 incident on a display unit that displays a predetermined pattern.

[0029] The direction in which the laser beam 121 is branched by the branching unit 125 is in the depth direction of the ingot 10. In addition, the branched laser beam 121 also branches slightly in the processing feed direction. That is, each focal point 127 of the branched and focused laser beam 121 by the focuser 123 is positioned slightly differently along the direction of progression in the processing feed direction so that the processing proceeds sequentially from the focal point 127 located at the deepest position to the focal point 127 located at the shallowest position. "Slightly" means that the distance between adjacent focal points 127 in the processing feed direction is about 30% of the beam diameter irradiated onto the first surface 11 of the ingot 10. For example, if the beam diameter on the first surface 11 is about 200 μm, the distance between adjacent focal points 127 in the processing feed direction is set to 60 μm.

[0030] The mirror 126 reflects the laser beam 121 that has passed through the branching unit 125 toward the concentrator 123. In other words, the mirror 126 reflects the laser beam 121 toward the ingot 10 held on the holding surface 111 of the holding table 110.

[0031] The separation initiation step 2 is a step in which a separation initiation point 18 is formed in a plane parallel to the first surface 11 (crystal plane {100}), including a modified layer 16 and a crack 17 extending from the modified layer 16. In separation initiation step 2, multiple separation initiations 18 are formed at different depth positions in the ingot 10.

[0032] In the separation starting point formation step 2, first, the second surface 12 side of the ingot 10 is held by suction against the holding surface 111 of the holding table 110. Next, the ingot 10 held on the holding table 110 is imaged using an imaging unit (not shown) to perform alignment, which aligns the laser beam irradiation unit 120 with the ingot 10.

[0033] At this time, the angle between the orientation flat 14 of the ingot 10 and the processing feed direction (X-axis direction) is set to 45°, and the processing feed direction is adjusted to be parallel to the crystal orientation

[0010] . In addition, the light concentrator 123 of the laser beam irradiation unit 120 is positioned above one end of the outer edge of the ingot 10 in the X-axis direction, which is the processing feed direction.

[0034] In the separation point formation step 2, the focal point 127 of the laser beam 121 is then positioned inside the ingot 10 from the first surface 11 side. At this time, the focal points 127 of the laser beam 121, which has been branched into multiple beams, are arranged in the depth direction inside the ingot 10 at intervals corresponding to the thickness 31 of the wafer 30 to be manufactured. The thickness 31 of the wafer 30, i.e., the distance between the focal points 127, is, for example, 200 μm.

[0035] In the separation point formation step 2, with multiple focal points 127 of the laser beam 121 positioned inside the ingot 10, the laser beam 121 is irradiated towards the ingot 10 while the light concentrator 123 and the holding table 110 of the laser beam irradiation unit 120 are moved relative to each other along the processing feed direction (X-axis direction).

[0036] As a result, a modified layer 16 is formed inside the ingot 10 at the depth where the focusing point 127 is located, along the crystal orientation

[0010] which is the processing feed direction, and a crack 17 is formed extending from the modified layer 16 along a planar direction substantially parallel to the first surface 11. That is, the crack 17 extends in the indexing feed direction (Y-axis direction). In this way, the separation initiation step 2 forms a separation initiation point 18 that includes the modified layer 16 and the crack 17 formed from the modified layer 16 along a planar direction substantially parallel to the first surface 11.

[0037] In the separation starting point formation step 2, once the modified layer 16 is formed across one end and the other end of the outer edge in the processing feed direction (X-axis direction), the irradiation of the laser beam 121 from the laser beam irradiation unit 120 is temporarily stopped, and the process proceeds to the indexing feed step 3.

[0038] Indexing feed step 3 is a step in which the focal point 127 of the laser beam 121 is indexed and fed in a direction perpendicular to the machining feed direction (X-axis direction) (Y-axis direction). In indexing feed step 3, the holding table 110 is moved in the indexing feed direction (Y-axis direction) and also in the machining feed direction (X-axis direction). In indexing feed step 3, when the concentrator 123 of the laser beam irradiation unit 120 is positioned adjacent to the position where the modified layer 16 has already been formed on the ingot 10, and above one end of the outer edge of the ingot 10 in the X-axis direction, which is the machining feed direction, the process returns to separation starting point formation step 2.

[0039] In the returned separation point formation step 2, similar to the previous separation point formation step 2, with multiple focal points 127 of the laser beam 121 positioned inside the ingot 10, the laser beam 121 is irradiated towards the ingot 10 while the light concentrator 123 of the laser beam irradiation unit 120 and the holding table 110 are moved relative to each other along the processing feed direction (X-axis direction).

[0040] As a result, a separation starting point 18 is formed, which includes a modified layer 16 formed adjacent to the indexing feed direction and along the processing feed direction relative to the modified layer 16 formed in the previous separation starting point formation step 2, and a crack 17 extending from this modified layer 16 along the indexing feed direction. Once the separation starting point 18 is formed across the entire interior of the ingot 10, the entire processing step 1, which includes the separation starting point formation step 2 and the indexing feed step 3, is completed, and the process proceeds to the separation step.

[0041] In addition, in the full-surface processing step 1, the relationship between the processing direction and the crystal orientation is not limited to the crystal orientation described above, but can be any equivalent crystal orientation. That is, the processing feed direction (X-axis direction) for forming the modified layer 16 is not limited to a direction parallel to the crystal orientation

[0100] , but can be any equivalent crystal orientation. <100> It is sufficient if the direction is parallel to the direction.

[0042] Figure 7 is a side view showing a partial cross-section of an example of separation step 4 shown in Figure 3. Separation step 4 is performed after full-surface processing step 1 is carried out. Separation step 4 is a step in which the wafer 30 is separated from the ingot 10 starting from the separation starting point 18.

[0043] The separation step 4 shown in Figure 7 is performed using an ultrasonic device 200. The ultrasonic device 200 comprises a liquid tank 210, a holding table 220, an ultrasonic unit 230, and a moving unit (not shown) for raising and lowering the ultrasonic unit 230. The liquid tank 210 contains a liquid 211. The liquid 211 is, for example, pure water.

[0044] The holding table 220 is housed inside the liquid tank 210. The holding table 220 holds the ingot 10, on which the separation point 18 is formed, with its holding surface 221. The ingot 10 held on the holding table 220 is immersed in the liquid 211. The holding surface 221 is a disc shape formed from porous ceramic or the like. The holding surface 221 is a plane parallel to the horizontal direction. The holding surface 221 is connected to a vacuum suction source, for example, via a vacuum suction path. The holding table 220 suction-holds the second surface 12 side of the ingot 10 placed on the holding surface 221.

[0045] The ultrasonic application unit 230 includes an ultrasonic transducer 231 and a high-frequency power supply 232. The ultrasonic transducer 231 expands and contracts when alternating current is applied, generating ultrasonic vibrations. The ultrasonic transducer 231 is made of, for example, piezoelectric ceramics. The high-frequency power supply 232 applies alternating current to the ultrasonic transducer 231. The ultrasonic application unit 230 is movable from the position shown by the dashed line in Figure 7 to the position shown by the solid line by a movable unit (not shown). The surface of the ultrasonic application unit 230 facing the ingot 10 held on the holding table 310 is larger than the entire surface of the ingot 10 so as to cover the top of the ingot 10.

[0046] In separation step 4, first, the ingot 10 on which the separation starting point 18 has been formed is placed on the holding table 220 and immersed in the liquid 211 of the liquid tank 210. Next, the ultrasonic application unit 230 is moved from the position shown by the dashed line in Figure 7 to the position shown by the solid line and immersed in the liquid 211, so that it faces the first surface 11 of the ingot 10 on the holding table 220 via the liquid 211.

[0047] In separation step 4, a voltage is then applied to the ultrasonic transducer 231 from the high-frequency power supply 232 to cause the ultrasonic transducer 231 to vibrate ultrasonically. As a result, ultrasonic vibrations with a frequency corresponding to the vibration of the ultrasonic transducer 231 propagate within the liquid 211, and these ultrasonic vibrations generated within the liquid 211 are applied to the ingot 10.

[0048] In separation step 4 shown in Figure 7, ultrasonic vibrations are applied to the ingot 10 via the liquid 211 in the liquid tank 210, thereby separating a portion of the ingot 10 from the uppermost separation starting point 18 on the first surface 11 side as a wafer 30. Additionally, portions of the ingot 10 between the multiple separation starting points 18 formed in the depth direction of the ingot 10 are also separated as wafers 30. After performing separation step 4 shown in Figure 7, for example, a grinding step is performed to grind both sides of each wafer 30 to remove irregularities on the separated surface.

[0049] Thus, in the example of separation step 4 shown in Figure 7, multiple wafers 30 were peeled off at once starting from multiple separation starting points 18, but the wafers 30 may also be peeled off sequentially in a branch-like manner starting from the upper separation starting point 18. Figure 8 is a side view showing a partial cross-section of the first separation step in another example of separation step 4 shown in Figure 3. Figure 9 is a side view showing a partial cross-section of the second separation step in another example of separation step 4 shown in Figure 3.

[0050] The first separation step is to extend the crack 17 by applying ultrasound to the ingot 10. The first separation step is carried out using an ultrasound application device 300, as shown in Figure 8. The ultrasound application device 300 comprises a holding table 310, an ultrasound application unit 320, a liquid supply unit 330, and a moving unit (not shown) that moves the ultrasound application unit 320 and the liquid supply unit 330 relative to the holding table 310.

[0051] The holding table 310 holds the ingot 10, on which the separation starting point 18 is formed, with its holding surface 311. The holding surface 311 is a disc shape formed from porous ceramic or the like. The holding surface 311 is a plane parallel to the horizontal direction. The holding surface 311 is connected to a vacuum suction source, for example, via a vacuum suction path. The holding table 310 holds the second surface 12 side of the ingot 10 placed on the holding surface 311 by suction.

[0052] The ultrasonic application unit 320 includes an ultrasonic transducer 321 and a high-frequency power supply 322. The ultrasonic transducer 321 expands and contracts when alternating current is applied, generating ultrasonic vibrations. The ultrasonic transducer 321 is formed from, for example, piezoelectric ceramics. The high-frequency power supply 322 applies alternating current to the ultrasonic transducer 321. The ultrasonic application unit 320 is movable relative to the holding table 310 by a moving unit (not shown).

[0053] The liquid supply unit 330 supplies liquid 331 between the upper surface (first surface 11) of the ingot 10 held on the holding table 310 and the surface of the ultrasonic application unit 320 facing the ingot 10. The liquid 331 is, for example, pure water.

[0054] In the first separation step shown in Figure 8, first, the second surface 12 of the ingot 10 on which the separation starting point 18 is formed is held by the holding surface 311 of the holding table 310. In the first separation step, next, the ultrasonic application unit 320 is positioned opposite the upper surface (first surface 11) of the ingot 10 held on the holding table 310 at a predetermined distance.

[0055] In the first separation step, liquid 331 is then supplied from the liquid supply unit 330 between the first surface 11 of the ingot 10 and the ultrasonic application unit 320. In the first separation step, while the surface of the ultrasonic application unit 320 facing the ingot 10 is immersed in the liquid 331, alternating current power is applied to the ultrasonic transducer 321 of the ultrasonic application unit 320 for a predetermined time to cause ultrasonic vibration. As a result, when ultrasonic vibration is applied to the first surface 11 of the ingot 10 via the liquid 331, the crack 17 extends due to the action of ultrasound from the ultrasonic application unit 320.

[0056] The second separation step is to peel the wafer 30 from the ingot 10, starting from the separation initiation point 18 where the crack 17 has been extended. The second separation step is carried out using a peeling device 400 shown in Figure 9. The peeling device 400 comprises a holding table 410, a peeling unit 420, and a moving unit (not shown) that moves the holding table 410 and the peeling unit 420 relative to each other.

[0057] The holding table 410 holds the ingot 10 after the first separation step has been performed on the holding surface 411. The holding surface 411 is a disc shape formed from porous ceramic or the like. The holding surface 411 is a plane parallel to the horizontal direction. The holding surface 411 is connected to a vacuum suction source, for example, via a vacuum suction path. The holding table 410 holds the second surface 12 side of the ingot 10 placed on the holding surface 411 by suction.

[0058] The peeling unit 420 is capable of suction-holding the first surface 11 (upper surface) of the ingot 10 that is in contact with the holding surface 421. The peeling unit 420 can also move closer to and away from the holding table 410 that holds the ingot 10 by a moving unit (not shown).

[0059] In the second separation step shown in Figure 9, the second surface 12 of the ingot 10 is held by the holding surface 411 of the holding table 410, and then the peeling unit 420 is brought closer to the holding table 410 and the first surface 11 (top surface) of the ingot 10 is held by suction on the holding surface 421.

[0060] In this state, when the peeling unit 420 is separated from the holding table 410, the ingot 10, which has been pulled vertically, separates starting from the separation starting point 18 located at the uppermost position, and a portion of the peeled-off first surface 11 (upper surface) of the ingot 10 is generated as a wafer 30.

[0061] The first and second separation steps are repeated for the number of separation points 18 formed in the depth direction of the ingot 10. That is, after peeling the wafer 30 from the first surface 11 (top surface) of the ingot 10 in the second separation step, the peeled surface of the ingot 10 is used as the first surface 11, a crack 17 is extended in the first separation step, and then peeled again as wafer 30 in the second separation step.

[0062] Furthermore, after performing the second separation step shown in Figure 9, a grinding step may be performed to grind the peeled surface of the wafer 30 peeled from the ingot 10 to remove irregularities on the peeled surface. Similarly, a grinding step may also be performed on the peeled surface of the ingot 10 after peeling the wafer 30 from all separation starting points 18 to remove irregularities on the peeled surface.

[0063] [Variation] Next, a method for manufacturing a wafer 30 according to a modified version of the present invention will be described based on the drawings. The modified method for manufacturing a wafer 30 is a method for manufacturing a wafer from the ingot 20 shown in Figures 10 and 11.

[0064] (GaN single crystal ingot) Figure 10 is a perspective view of the ingot 20 to be processed in the wafer 30 manufacturing method according to the modified example. Figure 11 is a top view of the ingot 20 shown in Figure 10. The ingot 20 to be processed in the wafer 30 manufacturing method of the modified example is a single-crystal GaN ingot made of GaN (gallium nitride) and formed in a cylindrical shape overall. In the modified example, the ingot 20 is a hexagonal single-crystal GaN ingot. The ingot 20 has a first surface 21, a second surface 22, a circumferential surface 23, a first orientation flat 24, and a second orientation flat 25.

[0065] The first surface 21 is circular and is one flat end face of the cylindrical ingot 20. The second surface 22 is circular and is the flat end face of the cylindrical ingot 20 opposite to the first surface 21. The second surface 22 corresponds to the bottom surface of the ingot 10. The circumferential surface 23 is a surface that connects the outer edge of the first surface 21 and the outer edge of the second surface 22.

[0066] The first orientation flat 24 is a plane formed on a portion of the circumferential surface 23 to indicate the crystal orientation of the ingot 20. The second orientation flat 25 is a plane formed on a portion of the circumferential surface 23 to indicate the crystal orientation of the ingot 20. The second orientation flat 25 is perpendicular to the first orientation flat 24. The length of the first orientation flat 24 is longer than the length of the second orientation flat 25.

[0067] In the ingot 20, the first face 21 is a crystal plane (0001), the first orientation flat 24 is a crystal plane (-1100), and the second orientation flat 25 is a crystal plane (11-20).

[0068] The basic procedure for the wafer manufacturing method of the modified example is the same as that for the wafer manufacturing method of the embodiment. However, in the separation starting point formation step 2 of the wafer manufacturing method of the modified example, the processing feed direction (X-axis direction) is set to a direction parallel to the crystal orientation <11-20> of the ingot 20.

[0069] As described above, in the wafer manufacturing method of the embodiment and modified version, multiple focusing points 127 of the laser beam 121, which is branched into multiple strips, are positioned at different depths inside the ingots 10 and 20 to form the modified layer 16. As a result, multiple delamination layers, which serve as separation starting points, can be formed at different depths parallel to the flat surfaces of the ingots 10 and 20 with a single laser irradiation, thereby reducing material loss and improving throughput.

[0070] It should be noted that the present invention is not limited to the embodiments described above. That is, it can be implemented with various modifications without departing from the core principles of the present invention. For example, in the separation starting point formation step 2, the laser beam 121, which is branched in the depth direction and the processing feed direction (X-axis direction), may be further branched in the indexing feed direction (Y-axis direction).

[0071] Furthermore, the method of splitting the laser beam 121 is not limited to using a branching unit 125 such as a diffractive optical element or a spatial light modulator. For example, the beam may be split using a beam splitter and incident on different concentrators to form multiple focal points that are branched in the depth direction and the processing feed direction. [Explanation of Symbols]

[0072] 10, 20 ingots 11, 21 First side 12, 22 Second side 16 Modified layer 17 Crack 18 Separation starting point 30 wafers 31 Thickness 120 Laser beam irradiation unit 121 Laser beam 122 Oscillators 123 Light concentrator 125 Branch Unit 127 Focusing point 211, 331 liquid 230, 320 Ultrasonic Unit 330 Liquid supply unit 420 Peeling Unit

Claims

1. A wafer manufacturing method for producing a wafer from an ingot having a first surface and a second surface opposite to the first surface, A separation starting point formation step is performed by positioning the focal point of a laser beam with a wavelength that penetrates the material constituting the ingot from the first surface side to the interior of the ingot, and then moving the focal point and the ingot relative to each other to form a separation starting point on a plane parallel to the first surface. A separation step of separating the wafer from the ingot starting from the separation starting point, Equipped with, In the separation point formation step, multiple focal points of the laser beam are formed in the depth direction of the ingot, and each of these focal points is arranged at intervals corresponding to the thickness of the wafer to be manufactured inside the ingot, The method is characterized by forming multiple separation points at different depth positions in the ingot during a single separation point formation step. A method for manufacturing wafers.

2. Multiple light-gathering points formed in the depth direction of the ingot are The process is carried out sequentially, starting from the deepest point of focus and moving to the shallowest point of focus. Characterized by being arranged at different positions along the direction of travel in the processing feed direction, The method for manufacturing a wafer according to claim 1.

3. The separation initiation step is characterized by forming the separation initiation, which includes the modified layer and cracks extending from the modified layer, across the entire interior surface of the ingot. A method for manufacturing a wafer according to claim 1 or 2.

4. The separation step is characterized by separating the wafer from the ingot by applying ultrasound. A method for manufacturing a wafer according to claim 1 or 2.

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