Laser processing apparatus and wafer production method

Abstract

To provide a laser processing device that improves productivity when an SiC wafer is generated from an SiC ingot, and can reduce a disposal amount of the same.SOLUTION: Laser irradiation means 6 is constituted at least of: an oscillator 62 for oscillating a laser beam; and a condenser 61 for positioning a condensation point FP of a laser beam LB3 oscillated by the oscillator 62 at a depth corresponding to a thickness of an SiC wafer to be generated from an end face 12a of an Sic ingot 10 and radiating the laser beam. The oscillator 62 includes: a seeder 621 for oscillating a laser beam LB0 at prescribed pulse intervals; a branch part 622 for branching the laser beam LB0 oscillated by the seeder 621 into at least a first laser beam LB1 and a second laser beam LB2; a delay part 623 for delaying the first laser beam LB1 or the second laser beam LB2; a confluent part 624 for combining the first laser beam LB1 and the second laser beam LB2; and an amplifier 625.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a laser processing apparatus for generating a SiC wafer from a SiC ingot and a method for generating the wafer.

Background Art

[0002] A silicon (Si) wafer having a plurality of devices such as ICs and LSIs partitioned by a dicing line and formed on the surface is diced into individual device chips by a dicing apparatus or a laser processing apparatus and used in electric devices such as mobile phones and personal computers.

[0003] In addition, since SiC has a bandgap three times wider than that of silicon, SiC wafers are used when forming devices such as power devices and LEDs.

[0004] However, when applying a conventional wafer generation method to a SiC ingot and cutting it with an inner peripheral blade to form a wafer, only about 30% of the volume of the ingot is generated as a SiC wafer, and the remaining 70% is discarded, which is uneconomical (see, for example, Patent Document 1).

[0005] In addition, in order to reduce the amount of SiC to be discarded, a modified layer is formed by irradiating a condensing point of a laser beam having a wavelength permeable to the SiC ingot at a depth corresponding to the thickness of the SiC wafer to be generated, thereby generating a separation starting point for separating the SiC wafer from the SiC ingot. A method of generating a SiC wafer by peeling it from the SiC ingot with the separation starting point as a boundary has also been proposed (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

[0007] According to the technology described in Patent Document 2 mentioned above, it is possible to reduce the amount of waste compared to when an internal cutting edge is used to produce a SiC wafer from a SiC ingot. However, when a SiC wafer is produced using a modified layer formed by positioning the laser beam's focal point internally as the separation starting point, the modified layer formed by positioning the laser beam's focal point must be removed by grinding and polishing, resulting in poor productivity and still a large amount of waste, thus requiring further improvement.

[0008] The present invention has been made in view of the above facts, and its main technical problem is to provide a laser processing apparatus and a wafer production method that can improve productivity and reduce the amount of waste when producing SiC wafers from SiC ingots. [Means for solving the problem]

[0009] To solve the above-mentioned main technical problems, the present invention provides a laser processing apparatus for producing a SiC wafer from a SiC ingot, comprising at least a holding means for holding a SiC ingot, and a laser irradiation means for irradiating the SiC ingot held by the holding means with a laser beam of a wavelength that is penetrating, wherein the laser irradiation means comprises at least an oscillator for oscillating a laser beam, and a concentrator for positioning the focal point of the laser beam oscillated by the oscillator at a depth corresponding to the thickness of the SiC wafer to be produced from the end face of the SiC ingot, and irradiating the beam, wherein the oscillator comprises a seeder for oscillating a laser beam at a predetermined pulse interval, a branching section for branching the laser beam oscillated by the seeder into at least a first laser beam and a second laser beam, and by delaying the first laser beam or the second laser beam, the energy peak per pulse is suppressed, and the SiC is appropriately separated into Si and C to form a delamination layer. By forming a SiC wafer starting from the delamination layer, the delamination layer formed by irradiating with the first laser beam and the second laser beam becomes the delamination surface.A laser processing device is provided.

[0010] Furthermore, according to the present invention, a wafer production method for producing a SiC wafer from a SiC ingot comprises at least: a laser beam irradiation step of holding the SiC ingot in a holding means, positioning the focal point of a laser beam with a wavelength transparent to the SiC ingot at a depth corresponding to the thickness of the SiC wafer to be produced from the end face of the SiC ingot and irradiating it to form a delamination layer; and a wafer production step of separating the SiC wafer from the SiC ingot, wherein the oscillator that oscillates the laser beam oscillates at a predetermined pulse interval. The system comprises a seeder that emits a beam, a branching unit that splits the laser beam emitted by the seeder into at least a first laser beam and a second laser beam, a delay unit that delays the first laser beam or the second laser beam, a merging unit that merges the first laser beam and the second laser beam, and an amplifier. By delaying the first laser beam or the second laser beam, the energy peak per pulse is suppressed, and the SiC is appropriately separated into Si and C to form a delamination layer. By forming a SiC wafer starting from the delamination layer, the delamination layer formed by irradiating with the first laser beam and the second laser beam becomes the delamination surface. A method for generating wafers is provided.

[0011] In the laser beam irradiation process, it is preferable to repeatedly perform the following steps to form a delamination layer consisting of multiple adjacent delamination strips: a delamination strip formation step in which the laser beam is focused at a depth corresponding to the thickness of the SiC wafer to be produced, with the X-axis being the direction perpendicular to the direction in which the C-plane tilts with respect to the end face of the SiC ingot and the Y-axis being the direction perpendicular to the X-axis, and irradiating the wafer while processing and feeding it in the X-axis direction to form a strip-shaped delamination strip in which cracks extend along the C-plane from the region in which the SiC has separated into Si and C; and an indexing feed step in which the laser beam focus point is indexed and fed in the Y-axis direction to arrange the delamination strips in parallel in the Y-axis direction. Furthermore, when delaying the first laser beam or the second laser beam using the delay unit in the laser processing apparatus described above, the delay time is preferably set to 30 ns to 100 ns. Furthermore, when delaying the first laser beam or the second laser beam using the delay unit in the wafer production method described above, the delay time is preferably set to 30 ns to 100 ns. [Effects of the Invention]

[0012] The laser processing apparatus of the present invention includes at least a holding means for holding a SiC ingot, and a laser irradiation means for irradiating the SiC ingot held by the holding means with a laser beam having a wavelength that is penetrating, wherein the laser irradiation means comprises at least an oscillator for oscillating a laser beam, and a concentrator for irradiating the SiC wafer to be produced from the end face of the SiC ingot at a depth corresponding to the thickness of the SiC wafer to be produced, wherein the oscillator comprises a seeder for oscillating a laser beam at a predetermined pulse interval, a branching unit for branching the laser beam oscillated by the seeder into at least a first laser beam and a second laser beam, a delay unit for delaying the first laser beam or the second laser beam, a merging unit for merging the first laser beam and the second laser beam, and an amplifier. By delaying the first or second laser beam, the energy peak per pulse is suppressed, the SiC is appropriately separated into Si and C, and a delamination layer is formed. By forming a SiC wafer starting from this delamination layer, the delamination layer formed by irradiating with the combined first and second laser beams becomes the delamination surface. Therefore, compared to a configuration that irradiates without branching or delaying the laser beam, the energy peak per pulse is suppressed, allowing for proper separation of SiC into Si and C, and enabling the formation of a suitable delamination layer with less damage.

[0013] Furthermore, the wafer production method of the present invention includes at least a laser beam irradiation step of holding a SiC ingot in a holding means, positioning the focal point of a laser beam with a wavelength that is transparent to the SiC ingot at a depth corresponding to the thickness of the SiC wafer to be produced from the end face of the SiC ingot and irradiating it to form a delamination layer, and a wafer production step of separating the SiC wafer from the SiC ingot, wherein the oscillator that oscillates the laser beam includes a seeder that oscillates the laser beam at a predetermined pulse interval, a branching unit that branches the laser beam oscillated by the seeder into at least a first laser beam and a second laser beam, a delay unit that delays the first laser beam or the second laser beam, a merging unit that merges the first laser beam and the second laser beam, and an amplifier, wherein by delaying the first laser beam or the second laser beam... The energy peak per pulse is suppressed, and the SiC is appropriately separated into Si and C to form a delamination layer. By forming a SiC wafer starting from this delamination layer, the delamination layer formed by irradiating with the first laser beam and the second laser beam becomes the delamination surface.Compared to irradiating with a laser beam without branching or delaying, the energy peak per pulse is suppressed, allowing for proper separation of SiC into Si and C, and enabling the formation of a suitable delamination layer with minimal damage. [Brief explanation of the drawing]

[0014] [Figure 1] This is an overall perspective view of the laser processing apparatus of this embodiment. [Figure 2] (a) Plan view of a SiC ingot, (b) Side view of a SiC ingot. [Figure 3] (a) A block diagram showing the schematic of the optical system of the laser irradiation means installed in the laser processing apparatus shown in Figure 1, and (b) A conceptual diagram showing the pulse waveform of the laser beam LB3 generated by the laser irradiation means shown in (a). [Figure 4] (a) A perspective view showing an embodiment of the laser beam irradiation process, and (b) A cross-sectional view showing the laser beam irradiation process in progress. [Figure 5] This is a perspective view showing an embodiment of the wafer manufacturing process. [Modes for carrying out the invention]

[0015] Hereinafter, embodiments relating to a laser processing apparatus and a wafer production method configured based on the present invention will be described in detail with reference to the attached drawings.

[0016] Figure 1 shows an overall perspective view of a laser processing apparatus 1 capable of carrying out the wafer production method of this embodiment. The laser processing apparatus 1 includes at least a holding means 3 for holding a SiC ingot 10 as shown in Figure 1, and a laser irradiation means 6 for irradiating the SiC ingot 10 held by the holding means 3 with a laser beam of a wavelength that is penetrating.

[0017] The laser processing apparatus 1 includes a base 2 on which a holding means 3 and a laser irradiation means 6 are disposed, a moving means 4 for moving the holding means 3 in the X-axis direction and in the Y-axis direction orthogonal to the X-axis direction, an imaging means 7 for performing alignment, a wafer peeling means 8, and a display means 9.

[0018] As shown in FIG. 1, the holding means 3 includes a rectangular X-axis direction movable plate 31 mounted on the base 2 so as to be movable in the X-axis direction, a rectangular Y-axis direction movable plate 32 mounted on the X-axis direction movable plate 31 so as to be movable in the Y-axis direction, and a holding table 33 disposed on the Y-axis direction movable plate 32 and having a flat holding surface 33a configured to be rotatable by including a pulse motor inside.

[0019] The moving means 4 includes an X-axis moving means 41 for moving the holding table 33 in the X-axis direction and a Y-axis moving means 42 for moving the holding table 33 in the Y-axis direction. The X-axis moving means 41 converts the rotational motion of a motor 43 into linear motion via a ball screw 44 whose end is supported by a bearing block 44a and transmits it to the X-axis direction movable plate 31. The X-axis direction movable plate 31 is moved in the X-axis direction along a pair of guide rails 2a, 2a disposed along the X-axis direction on the base 2. The Y-axis moving means 42 converts the rotational motion of a motor 45 into linear motion via a ball screw 46 and transmits it to the Y-axis direction movable plate 32, and moves the Y-axis direction movable plate 32 in the Y-axis direction along a pair of guide rails 35, 35 disposed along the Y-axis direction on the X-axis direction movable plate 31.

[0020] The laser processing apparatus 1 includes a frame body 5 composed of a vertical wall portion 5a erected on the side of the X-axis moving means 41 and the Y-axis moving means 42 on the base 2 and a horizontal wall portion 5b extending horizontally from the upper end portion of the vertical wall portion 5a. Inside the horizontal wall portion 5b of the frame body 5, an optical system constituting the above-described laser irradiation means 6 and an imaging means 也 are accommodated.

[0021] The wafer peeling means 8 of this embodiment is disposed on a stationary base 2 and is installed near the end of the guide rails 2a, 2a (on the bearing block 44a side). The wafer peeling means 8 comprises a peeling unit case 81, a peeling unit arm 82 which is partially housed within the peeling unit case 81 and supported so as to be able to move up and down in the Z-axis direction (vertical direction), a peeling pulse motor 83 disposed at the tip of the peeling unit arm 82, and a suction means 84 located below the peeling pulse motor 83 which is rotatably supported by the peeling pulse motor 83 and has a plurality of suction holes on its lower surface. The peeling unit case 81 is equipped with a Z-axis moving means (not shown) for controlling the movement of the peeling unit arm 82 in the Z-axis direction. The peeling unit case 81 is equipped with a Z-axis position detection means (not shown) for detecting the position of the peeling unit arm 82 in the Z-axis direction, and the position signal is sent to the control means described above.

[0022] The control means described above is composed of a computer and includes a central processing unit (CPU) that performs calculations according to a control program, a read-only memory (ROM) for storing the control program and the like, a read-write random access memory (RAM) for temporarily storing detected values, calculation results, etc., and an input interface and an output interface (details are not shown in the illustration). In addition to the laser irradiation means 6 described above, the control means is connected to and controls imaging means 7, X-axis movement means 41, Y-axis movement means 42, wafer peeling means 8, display means 9, etc.

[0023] In addition to Figure 1, Figures 2(a) and (b) show a SiC ingot 10 processed by the laser processing apparatus 1 described above to produce a SiC wafer. The illustrated SiC ingot 10 shows the state before the delamination layer described later is formed. The SiC ingot 10 is formed from hexagonal single crystal SiC and is formed in a substantially cylindrical shape overall. The SiC ingot 10 has a circular first end face 12a (upper surface), a second end face 12b (lower surface) opposite to the first end face 12a and placed on the holding surface 33a of the holding table 33 described above, a circumferential surface 13 located between the first end face 12a and the second end face 12b, and a C-axis 19( from the first end face 12a to the second end face 12b). <0001> It has a direction and a C-plane 20 ({0001} plane) perpendicular to the C-axis 19. In the illustrated SiC ingot 10, the C-axis 19 is inclined with respect to the perpendicular 18 passing through the center point 16 of the first end face 12a shown in Figure 2(a) as shown by α in the figure (see Figure 2(b)), and an off-angle α (for example, α = 1, 3, 6 degrees) is formed between the C-plane 20 and the first end face 12a.

[0024] The direction in which the off-angle α is formed is indicated by arrow R in Figures 2(a) and (b). Furthermore, a rectangular first orientation flat 14 and a second orientation flat 15, indicating the crystal orientation, are formed on the circumferential surface 13 of the SiC ingot 10. The first orientation flat 14 is parallel to the direction R in which the off-angle α is formed, and the second orientation flat 15 is perpendicular to the direction R in which the off-angle α is formed. The length of the second orientation flat 15 is set shorter than the length of the first orientation flat 14, thereby specifying the front and back sides of the SiC ingot 10 and the inclination direction of the off-angle α.

[0025] The optical system of the laser irradiation means 6, which is suitable for laser processing the SiC ingot 10 described above to produce a SiC wafer, will be explained with reference to Figure 3(a).

[0026] As shown in Figure 3(a), the laser irradiation means 6 consists of at least an oscillator 62 that emits a laser beam, and a focuser 61 that positions the focal point of the laser beam emitted by the oscillator 62 at a depth corresponding to the thickness of the wafer to be produced from the end face (first end face 12a in this embodiment) of the SiC ingot 10 held on the holding table 33, and irradiates it.

[0027] The oscillator 62 includes a seeder 621 that oscillates a laser beam LB0 at predetermined pulse intervals, a branching unit 622 that splits the laser beam LB0 oscillated by the seeder 621 into at least a first laser beam LB1 and a second laser beam LB2, a delay unit 623 that delays either the first laser beam LB1 or the second laser beam LB2, a merging unit 624 that combines the first laser beam LB1 and the second laser beam LB2 to generate a laser beam LB3, and an amplifier 625 that amplifies the laser beam LB3. The branching unit 622 and the merging unit 624 are made up of, for example, fiber couplers. The delay unit 623 is made of optical fiber, and a 48m optical fiber with a refractive index of 1.5 is used to set the delay time, which will be described later, to, for example, 80ns. The laser beam LB3 emitted from the oscillator 62 configured as described above is processed into a laser beam LB3 having a pulse waveform (horizontal axis represents time, vertical axis represents energy) as shown in Figure 3(b), the output is adjusted by the attenuator 63 and focused by the focusing lens 61a of the light concentrator 61, and irradiated from the first end face 12a side of the SiC ingot 10.

[0028] In the embodiment described above, the delay unit 623 delays the second laser beam LB2, but the first laser beam LB1 may also be delayed. In this embodiment, the predetermined pulse interval of the laser beam LB0 oscillated by the seeder 621 is 10 μs, and the pulse width is 10 nm. As shown in Figure 3(b), the laser beam LB3 generated by the oscillator 62 comprises a pulse P1 of the first laser beam LB1 and a pulse P2 of the second laser beam LB2, which is delayed relative to pulse P1 by the action of the delay unit 623.

[0029] The laser processing apparatus 1 of this embodiment has a configuration that is generally as described above, and an embodiment of the wafer production method carried out using this laser processing apparatus 1 will be described below.

[0030] In carrying out the wafer production method of this embodiment, first, a SiC ingot 10 having a predetermined thickness capable of producing multiple SiC wafers is prepared, and an adhesive (for example, an epoxy resin adhesive) is interposed between the second end face 12b (bottom surface) of the SiC ingot 10 and the holding surface 33a of the holding table 33 of the laser processing apparatus 1, thereby fixing the SiC ingot 10 to the holding table 33. Next, the moving means 4 described above is operated to move the holding table 33 below the imaging means 7, and the SiC ingot 10 is imaged by the imaging means 7.

[0031] Next, a laser beam irradiation step is performed to form a delamination layer by positioning the focal point FP of a laser beam LB3 with a wavelength that is transparent to the SiC ingot 10 at a depth corresponding to the thickness of the SiC wafer to be produced, from the first end face 12a of the SiC ingot 10, and irradiating it. The laser beam irradiation step of this embodiment includes a delamination strip formation step and an indexing feed step, which will be described below.

[0032] When performing the laser beam irradiation process, first, based on the image of the SiC ingot 10 captured by the imaging means 7, the moving means 4 is activated to move and rotate the holding table 33, thereby adjusting the orientation of the SiC ingot 10 to a predetermined orientation and adjusting the position of the SiC ingot 10 and the light concentrator 61 in the XY plane. When adjusting the orientation of the SiC ingot 10 to a predetermined orientation, as shown in Figure 4(a), the first orientation flat 14 is aligned in the Y-axis direction and the second orientation flat 15 is aligned in the X-axis direction. This aligns the direction R in which the off-angle α is formed in the Y-axis direction and the direction perpendicular to the direction R in which the off-angle α is formed in the X-axis direction.

[0033] Next, the light condenser 61 is raised and lowered by a light condenser position adjustment means (not shown in the figure) to position the light condenser FP at a depth corresponding to the thickness of the wafer to be produced from the first end face 12a, as can be understood from Figure 4(b), which is shown as the AA cross section in Figure 4(a). In this embodiment, this depth is set to 450 μm from the first end face 12a. Next, the X-axis moving means 41 of the moving means 4 is activated, and while processing the SiC ingot 10 in the X-axis direction which is aligned with the direction perpendicular to the direction R in which the off-angle α is formed, a laser beam LB3 with a wavelength that is transparent to SiC is irradiated from the light condenser 61 onto the SiC ingot 10. At this time, at the focal point FP, the SiC is separated into Si (silicon) and C (carbon) by irradiation with the laser beam LB3, and the next irradiated laser beam LB3 is absorbed by the previously formed C, creating a modified region 100 where the SiC is separated into Si and C in a chain reaction. Cracks 102 extend from the modified region 100 along the C plane to both sides of the modified region 100. As a result, a strip-shaped delamination zone 110 extending in the X-axis direction is formed by the modified region 100 and the cracks 102 (delamination zone formation step).

[0034] Once the delamination zone formation step is performed, the Y-axis moving means 42 of the moving means 4 is activated to index and feed the focal point FP of the laser beam LB3 by a predetermined index amount (250 μm in this embodiment) in the Y-axis direction in order to arrange the delamination zones 110 side by side in the Y-axis direction. Once the indexing and feeding step is performed in this manner, a new delamination zone 110 is formed adjacent to the delamination zone 110 that was previously formed by performing the delamination zone formation step described above. In this way, by performing the delamination zone formation step and the indexing and feeding step over the entire surface of the first end face 12a of the SiC ingot, a delamination layer 120 consisting of a plurality of adjacent delamination zones 110 is formed.

[0035] The laser processing conditions when performing the laser beam irradiation process described above are set, for example, as follows. Wavelength: 1064nm Repetition frequency: 100kHz Pulse width: 10ns Delay time: 30-100ns Average output: 4W *Energy per pulse when there is no branching = 0.00004 (J) Numerical aperture (NA) of the focusing lens: 0.7 Spot size: 6.7 μm Machining feed rate: 50~135mm / s Delamination layer location (depth): 450 μm Index amount: 250 μm

[0036] In the laser beam irradiation process described above, as shown in Figure 3(b), one pulse oscillated by the seeder 621 is divided into a pulse P1 formed by the first laser beam LB1 and a pulse P2 formed by the second laser beam LB2, and one of the pulses P2 is irradiated with a delay time by the delay unit 623. The delay time is set to be a small delay time such that the pulse P2 formed by the second laser beam LB2 is irradiated while the energy (heat) from the pulse P1 formed by the first laser beam LB1 remains in the SiC ingot 10, for example, it is set to 30 ns to 100 ns. As a result, compared to the case where irradiation is performed with one pulse without branching, the energy peak per pulse is suppressed, the effect of leakage light in the depth direction is suppressed, the SiC is appropriately separated into Si and C, and the modified region 100 and crack 102 are appropriately formed in the C-plane direction, forming an appropriate delamination layer 120 with less damage.

[0037] Once the laser beam irradiation process described above has been performed to form the exfoliation layer 120, a wafer production process is carried out to separate the SiC wafer W from the SiC ingot 10, starting from the exfoliation layer 120.

[0038] When carrying out the wafer production process, first, the moving means 4 described above is activated to position the holding table 33 below the suction means 84 of the wafer peeling means 8. Next, the peeling unit arm 82 is lowered by a Z-axis moving means (not shown), and as shown in Figure 5, the lower surface of the suction means 84 is brought into close contact with the SiC ingot 10 and suction is performed. Next, an ultrasonic vibration applying means (not shown) is activated to apply ultrasonic vibration to the lower surface of the suction means 84, and the peeling pulse motor 83 repeatedly rotates the suction means 84 in clockwise and counterclockwise directions. In this way, the SiC wafer W can be peeled off starting from the peeling layer 120 formed on the SiC ingot 10. If a SiC wafer W is peeled from a SiC ingot 10, the top surface (new first end face 12a) of the SiC ingot 10 is polished, and then the laser beam irradiation process and the wafer generation process described above are repeated to form multiple SiC wafers W. The peeled surface of the SiC wafer W peeled from the SiC ingot 10 is also polished as needed to produce a SiC wafer W on which a device can be formed on one side.

[0039] As described above, in the laser beam irradiation process of this embodiment, the oscillator 62 suppresses the energy peak per pulse, and the SiC is appropriately separated into Si and C, forming a less damaged delamination layer 120. As a result, the amount of polishing required when polishing the new first end face 12a of the delaminated SiC ingot 10 and the delamination surface (bottom side) of the delaminated SiC wafer W can be reduced, thereby reducing the amount of SiC discarded from the SiC ingot 10. Consequently, production efficiency is improved, and the amount of SiC wafers produced from a SiC ingot 10 of the same thickness can be increased.

[0040] Furthermore, the present invention is not limited to cases where multiple SiC wafers W are extracted from a thick SiC ingot 10 as described above. For example, the present invention can also be applied to a thin SiC substrate with a thickness of about 1 mm as an ingot, and the wafer production method described above can be carried out to form a delamination layer 120 in the center in the thickness direction to produce two SiC wafers W.

[0041] Furthermore, as described above, the present invention is not limited to splitting the laser beam LB0 oscillated by the seeder 621 into only the first laser beam LB1 and the second laser beam LB2, but may also be split into three or more laser beams, so that three or more pulses are irradiated continuously with a predetermined delay time.

[0042] In the above embodiment, the laser beam irradiation process involves a delamination strip formation step in which the X-axis is defined as the direction perpendicular to the direction in which the C-plane tilts with respect to the first end face 12a of the SiC ingot 10 and forms an off-angle α, the Y-axis being defined as the direction perpendicular to the X-axis, the focal point FP of the laser beam LB3 is positioned at a depth corresponding to the thickness of the SiC wafer to be generated, and the material is irradiated and processed in the X-axis direction to form a strip-shaped delamination strip 110 in which cracks 102 extend along the C-plane from a modified region 100 in which the SiC is separated into Si and C, and an indexing feed step in which the focal point FP of the laser beam LB3 is indexed and fed in the Y-axis direction to arrange the delamination strips 110 side by side in the Y-axis direction, and these steps are repeated to form a delamination layer 120 consisting of a plurality of adjacent delamination strips 110. However, the present invention is not limited thereto, and for example, the delamination layer may be formed by irradiating the SiC ingot 10 with the laser beam LB3 in a spiral manner or by randomly dispersing and uniformly irradiating it. However, as described in the embodiment based on Figure 4, irradiating with the laser beam LB3 makes it possible to form the peeling zone 110 and the peeling layer 120 more appropriately, and is therefore more preferable. [Explanation of symbols]

[0043] 1: Laser processing equipment 2: Base 3: Holding means 31:X-axis movable plate 32: Y-axis movable plate 33: Holding Table 33a: Holding surface 4: Means of transportation 41:X-axis movement means 42: Y-axis movement means 5:Frame body 5b:Horizontal wall part 6: Laser irradiation means 61: Light concentrator 61a: Focusing lens 62: Oscillator 621: Cedar 622: Branching point 623: Delay section 624: Confluence 625: Amplifier 63: Attenuator 7: Imaging means 8: Wafer peeling method 82; Peeling unit arm 83: Pulse motor for stripping 84: Adsorption means 9:Display means 10: Ingot 12a: First end face 12b: Second end face 13: Peripheral surface 14: First Orientation Flat 15: Second Orientation Flat 18: Perpendicular line 19:C axis 20:C side 100: Modification area 102: Crack 110: Detachment zone 120: Exfoliation layer

Claims

1. A laser processing apparatus for producing SiC wafers from SiC ingots, The system includes at least a holding means for holding a SiC ingot, and a laser irradiation means for irradiating the SiC ingot held by the holding means with a laser beam of a wavelength that is penetrating, The laser irradiation means comprises at least an oscillator that emits a laser beam, and a focuser that positions the focal point of the laser beam emitted by the oscillator at a depth corresponding to the thickness of the SiC wafer to be produced from the end face of the SiC ingot and irradiates it. The oscillator comprises a seeder that emits a laser beam at predetermined pulse intervals, a branching unit that splits the laser beam emitted by the seeder into at least a first laser beam and a second laser beam, a delay unit that delays the first laser beam or the second laser beam, a merging unit that merges the first laser beam and the second laser beam, and an amplifier. A laser processing apparatus in which, by delaying the first laser beam or the second laser beam, the energy peak per pulse is suppressed, SiC is appropriately separated into Si and C to form a delamination layer, and a SiC wafer is formed starting from the delamination layer, so that the delamination layer formed by irradiating with the first laser beam and the second laser beam merge becomes the delamination surface.

2. A wafer manufacturing method for producing a SiC wafer from a SiC ingot, A laser beam irradiation step involves holding a SiC ingot in a holding means, positioning the focal point of a laser beam with a wavelength that is transparent to the SiC ingot at a depth corresponding to the thickness of the SiC wafer to be produced from the end face of the SiC ingot, and irradiating it to form a delamination layer. A wafer production process that separates SiC wafers from SiC ingots, It includes at least, The oscillator that generates the laser beam includes a seeder that generates a laser beam at a predetermined pulse interval, a branching unit that splits the laser beam generated by the seeder into at least a first laser beam and a second laser beam, a delay unit that delays the first laser beam or the second laser beam, a merging unit that merges the first laser beam and the second laser beam, and an amplifier. A method for producing a wafer in which, by delaying the first laser beam or the second laser beam, the energy peak per pulse is suppressed, the SiC is appropriately separated into Si and C, a delamination layer is formed, and a SiC wafer is formed starting from the delamination layer, thereby irradiating the wafer with the first laser beam and the second laser beam joined together, and the delamination layer formed becomes the delamination surface.

3. In the laser beam irradiation process, A delamination strip formation step is performed by positioning the focal point of a laser beam at a depth corresponding to the thickness of the SiC wafer to be generated, with the X-axis being the direction perpendicular to the direction in which the C-plane tilts with respect to the end face of the SiC ingot and the Y-axis being the direction perpendicular to the X-axis, and irradiating the wafer while processing and feeding it in the X-axis direction to form a strip-shaped delamination strip in which cracks extend along the C-plane from the region where the SiC has separated into Si and C, and the direction perpendicular to the X-axis is the Y-axis, and An indexing and feeding step in which the focal point of the laser beam is indexed and fed in the Y-axis direction to arrange the separation strips in parallel in the Y-axis direction, A method for producing a wafer according to claim 2, wherein the process is repeated to form a delamination layer consisting of a plurality of adjacent delamination zones.

4. The laser processing apparatus according to claim 1, wherein the delay time for delaying the first laser beam or the second laser beam by the delay unit is set to 30 ns to 100 ns.

5. The wafer production method according to claim 2, wherein the delay time for delaying the first laser beam or the second laser beam by the delay unit is set to 30 ns to 100 ns.

Images