Method of manufacturing wafer and separating apparatus

Abstract

To provide a method of manufacturing a wafer, with which at least one of a wafer or an ingot can be made less probable to be broken when ultrasonic waves are applied through a layer of liquid to the ingot for separating the ingot in a plurality of separation layers to thereby produce a wafer and then the wafer is separated from the ingot.SOLUTION: After ultrasonic waves have been applied through a layer of liquid to an ingot for separating the ingot in a plurality of separation layers to thereby produce a wafer, the wafer and the ingot are moved relatively to each other along a predetermined direction, that is, a direction in which the separation layers each extend, to thereby separate the wafer and the ingot from each other.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a wafer manufacturing method and a separation apparatus for manufacturing wafers from an ingot. [Background technology]

[0002] Semiconductor device chips are generally manufactured using wafers made of single crystals of silicon (Si), silicon carbide (SiC), gallium nitride (GaN), lithium tantalate (LiTaO3:LT), lithium niobate (LiNbO3:LN), etc. These wafers are manufactured, for example, by separating an ingot using a laser beam with a wavelength that is transmitted through the material of the ingot (see, for example, Patent Document 1).

[0003] Specifically, in this method, first, the focal point where the laser beam is focused is positioned inside the ingot, and the relative movement between the ingot and the focal point along a predetermined direction and the relative movement between the ingot and the position where the focal point is formed along a direction perpendicular to the predetermined direction are alternately repeated, whereby a plurality of separation layers each along the predetermined direction and each including a modified portion and a crack extending from the modified portion are formed inside the ingot.

[0004] In this method, an external force is applied to the ingot so as to further extend the crack. As a result, the ingot is separated into a plurality of separation layers to produce wafers. As a method for applying an external force to the ingot in this manner, a method has been proposed in which ultrasonic waves are applied to the ingot through a liquid layer to produce wafers, and then the wafer and the ingot are pulled apart in a direction perpendicular to the interface between them (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2016-111143 A [Patent Document 2] JP 2019-102513 A Summary of the Invention [Problem to be solved by the invention]

[0006] When ultrasonic waves are applied to an ingot having a plurality of separation layers formed therein through a liquid layer, the liquid penetrates each of the separation layers, and therefore when the ingot is separated at the separation layers to produce wafers, a liquid layer remains between the wafer and the ingot.

[0007] In this case, when the wafer and the ingot are separated in a direction perpendicular to the interface between them, a strong resistance due to the surface tension of the liquid layer acts on each of the wafer and the ingot, and there is a risk that at least one of them may be damaged.

[0008] In view of this, an object of the present invention is to provide a wafer manufacturing method and separation apparatus that can reduce the probability of damage to at least one of a wafer or an ingot when the wafer and ingot are separated from each other by applying ultrasonic waves to the ingot through a liquid layer so as to separate the ingot at multiple separation layers to produce wafers. [Means for solving the problem]

[0009] According to one aspect of the present invention, there is provided a wafer manufacturing method for manufacturing wafers from an ingot, the method comprising: a separation layer forming step of forming a plurality of separation layers inside the ingot, each of which is aligned along the predetermined direction and each of which includes a modified portion and a crack extending from the modified portion, by alternately repeating a relative movement between the ingot and a focal point at which a laser beam having a wavelength that transmits through the material of the ingot is focused, the relative movement between the ingot and a position where the focal point is formed in a direction perpendicular to the predetermined direction, after which the relative movement between the ingot and a position where the focal point is formed is positioned inside the ingot; an ultrasonic wave applying step of applying ultrasonic waves to the ingot through a liquid layer so as to separate the ingot at the plurality of separation layers to produce the wafer, after which the ultrasonic wave applying step of separating the wafer and the ingot by moving the wafer and the ingot relatively along the predetermined direction.

[0010] According to another aspect of the present invention, there is provided a wafer manufacturing method for manufacturing a wafer from an ingot having a plurality of separation layers formed therein, each of which is aligned in a predetermined direction and each of which includes a modified portion and a crack extending from the modified portion, the method comprising: an ultrasonic application step of applying ultrasonic waves to the ingot through a liquid layer so as to separate the ingot at the plurality of separation layers to produce the wafer; and a separation step of separating the wafer and the ingot by moving the wafer and the ingot relatively along the predetermined direction after the ultrasonic application step.

[0011] Furthermore, in the wafer manufacturing method of the present invention, it is preferable that the multiple separation layers are formed so that the modified portions contained in each are positioned on the same imaginary plane, and that the cracks extend so as to be inclined relative to the imaginary plane.

[0012] According to yet another aspect of the present invention, there is provided a separation apparatus for producing wafers from an ingot having a plurality of separation layers formed therein, each of which is aligned in a predetermined direction and each of which includes a modified portion and a crack extending from the modified portion, the separation apparatus including a first holding unit for holding the ingot, a second holding unit for holding the wafer, an ultrasonic wave applying unit for applying ultrasonic waves to the ingot held by the first holding unit through a liquid layer, a moving mechanism for relatively moving the first holding unit and the second holding unit along the predetermined direction, and a moving mechanism for moving the first holding unit, the second holding unit, the ultrasonic wave applying unit, and the moving mechanism. and a controller for controlling a moving mechanism, wherein the controller controls the first holding unit to hold the ingot, and then controls the ultrasonic application unit to apply ultrasonic waves to the ingot through the liquid layer so as to separate the ingot at the multiple separation layers to produce the wafer, and then controls the first holding unit to hold the ingot, and controls the second holding unit to hold the wafer, and controls the moving mechanism to move the first holding unit and the second holding unit relatively along the predetermined direction so that the wafer and the ingot are separated.

[0013] Furthermore, the separating apparatus of the present invention preferably further comprises an identifying unit for identifying the predetermined direction. Effect of the Invention

[0014] In the present invention, ultrasonic waves are applied to the ingot through a liquid layer so as to separate the ingot at a plurality of separation layers to produce wafers, and then the wafer and ingot are separated from each other by moving the wafer and ingot relatively in a predetermined direction, i.e., along the direction in which each of the plurality of separation layers extends.

[0015] In this case, the resistance caused by the surface tension of the liquid layer is weaker than when the wafer and the ingot are separated in a direction perpendicular to the interface between them, and therefore, in the present invention, it is possible to reduce the probability that at least one of the wafer and the ingot will be damaged during the separation. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1(A) is a perspective view that shows a schematic diagram of an example of an ingot, and FIG. 1(B) is a side view that shows a schematic diagram of the ingot shown in FIG. 1(A). [Diagram 2] FIG. 2 is a flow chart that illustrates a schematic example of a wafer manufacturing method for manufacturing a wafer from an ingot. [Diagram 3] FIG. 3 is a perspective view that illustrates the separation layer forming step. [Figure 4] FIG. 4 is a flow chart that illustrates the operation of the laser processing device when forming a plurality of separation layers inside an ingot. [Diagram 5] FIG. 5 is a partially enlarged cross-sectional view showing a schematic view of the ingot after the separation layer forming step. [Figure 6] FIG. 6 is a perspective view that illustrates a schematic example of a separation device capable of performing the ultrasonic application step and the detachment step. [Figure 7] FIG. 7 is a side view that illustrates the ultrasonic wave application step. [Figure 8] FIG. 8 is a partially enlarged cross-sectional view that illustrates a schematic view of the ingot after the ultrasonic wave application step and a wafer produced from the ingot. [Figure 9] 9(A) and 9(B) are side views each showing a schematic view of the separation step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] An embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1(A) is a perspective view showing an example of an ingot, and Fig. 1(B) is a side view showing the ingot shown in Fig. 1(A). The ingot 11 shown in Fig. 1(A) and Fig. 1(B) is made of, for example, a single crystal of SiC, and has a cylindrical shape including a front surface 11a and a back surface 11b that are approximately parallel to each other.

[0018] The ingot 11 is manufactured by epitaxial growth. In order to reduce lattice defects formed inside the ingot 11, the ingot 11 is manufactured so that the c-axis 11c of SiC is slightly tilted with respect to the perpendicular line 11d of the front surface 11a and the back surface 11b. For example, the angle (off angle) α between the c-axis 11c and the perpendicular line 11d is 1° to 6° (typically 4°).

[0019] Furthermore, two flat portions for indicating the crystal orientation of SiC, namely, a primary orientation flat 13 and a secondary orientation flat 15, are formed on the side surface of the ingot 11. The primary orientation flat 13 is longer than the secondary orientation flat 15. The secondary orientation flat 15 is formed so as to be parallel to an intersection line where a plane parallel to the c-plane 11e of SiC intersects with the front surface 11a or the back surface 11b.

[0020] Ingot 11 may be made of a single crystal of a material other than SiC (e.g., Si, GaN, LT, or LN, etc.). Ingot 11 may not have one or both of primary orientation flat 13 and secondary orientation flat 15 formed on its side surface, and may have a notch formed instead to indicate the crystal orientation of the material constituting ingot 11.

[0021] 2 is a flow chart that shows a schematic example of a wafer manufacturing method for manufacturing a wafer from an ingot 11. In this method, first, a plurality of separation layers each extending in a predetermined direction and each including a modified portion and a crack extending from the modified portion are formed inside the ingot 11 (separation layer forming step S1). Note that this predetermined direction is, for example, a direction parallel to the above-mentioned intersection line, i.e., a direction parallel to the secondary orientation flat 15.

[0022] Fig. 3 is a perspective view showing a schematic view of the separation layer forming step S1. Note that the X-axis direction and the Y-axis direction shown in Fig. 3 are directions perpendicular to each other on a horizontal plane, and the Z-axis direction is a direction perpendicular to the X-axis direction and the Y-axis direction (vertical direction). This separation layer forming step S1 is performed by the laser processing device 2 shown in Fig. 3.

[0023] The laser processing apparatus 2 includes a holding unit 4 for holding an ingot 11. The holding unit 4 includes a chuck table 4a having a circular holding surface substantially parallel to a horizontal plane, and a suction mechanism (not shown) in communication with the chuck table 4a.

[0024] The suction mechanism includes, for example, an ejector. When the suction mechanism operates, a suction force acts on the space near the holding surface of the chuck table 4a. Therefore, when the suction mechanism operates with the ingot 11 placed on the holding surface of the chuck table 4a, the ingot 11 is held on the holding surface.

[0025] The chuck table 4a is connected to a rotation mechanism (not shown). The rotation mechanism includes, for example, a pulley and a motor. When the rotation mechanism operates, the chuck table 4a rotates about a rotation axis that is a straight line passing through the center of the holding surface along the Z-axis direction. For example, the rotation mechanism rotates the chuck table 4a so that the secondary orientation flat 15 of the ingot 11 held on the holding surface of the chuck table 4a is parallel to the X-axis direction.

[0026] A head 8 of the laser beam irradiation unit 6 is provided above the chuck table 4a. This head 8 is provided at the tip of a cylindrical housing 10 extending along the Y-axis direction. The head 8 houses an optical system such as a condenser lens (for example, a condenser lens with a numerical aperture (NA) of 0.65) and a mirror, and the housing 10 houses an optical system such as a mirror and / or a lens.

[0027] The base end of the housing 10 is connected to a moving mechanism. This moving mechanism has, for example, a ball screw and a motor. When the moving mechanism operates, the head 8 and the housing 10 move along the X-axis direction, the Y-axis direction, and / or the Z-axis direction. The laser beam irradiation unit 6 also has a laser oscillator (not shown) including a laser medium such as Nd:YAG.

[0028] This laser oscillator generates a pulsed laser beam (e.g., a pulsed laser beam with a frequency of 60 kHz and a pulse width of 4 ns) with a wavelength (e.g., 1064 nm) that is transparent to the material of the ingot 11. Then, the output (power) of the laser beam is adjusted by an attenuator (e.g., adjusted so that the average output is 1.5 W), and then the laser beam is emitted directly downward from the head 8 via the housing 10 and an optical system contained in the head 8.

[0029] Furthermore, an imaging unit 12 capable of capturing an image of the area directly below is provided on the side of the housing 10. The imaging unit 12 has, for example, a light source such as an LED (Light Emitting Diode), an objective lens, and an imaging element such as a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor.

[0030] When performing the separation layer forming step S1 in the laser processing device 2, first, the ingot 11 is placed on the holding surface of the chuck table 4a with the surface 11a facing up. Next, the suction mechanism is operated so that the ingot 11 is held on this holding surface. Next, based on an image of the surface 11a of the ingot 11 formed by imaging by the imaging unit 12, etc., the rotation mechanism rotates the chuck table 4a so that a predetermined direction (i.e., a direction parallel to the secondary orientation flat 15) is parallel to the X-axis direction.

[0031] Next, a plurality of separation layers are formed inside the ingot 11. Fig. 4 is a flow chart that shows a schematic operation of the laser processing device 2 when a plurality of separation layers are formed inside the ingot 11. Specifically, first, the moving mechanism moves the head 8 and the housing 10 along the X-axis direction and / or the Y-axis direction so that a region of the ingot 11 slightly inside the secondary orientation flat 15 is positioned in the X-axis direction as seen from the head 8 in a plan view.

[0032] Next, the moving mechanism moves the head 8 and the housing 10 along the Z-axis direction so that the focal point where the laser beam emitted from the head 8 is focused (for example, a focal point with a diameter of 3.0 μm) is positioned at a predetermined depth (for example, a depth of 300 μm from the surface 11a) from the surface 11a of the ingot 11. Next, while emitting a laser beam from the head 8, the moving mechanism moves the head 8 and the housing 10 along the X-axis direction at a predetermined speed (for example, 200 mm / s) so that the focal point where the laser beam is focused passes from one end to the other end of the ingot 11 in the X-axis direction.

[0033] That is, in a state where the focal point where the laser beam is focused is positioned inside the ingot 11, the ingot 11 and the focal point are moved relatively along the X-axis direction (laser beam irradiation step S11). As a result, a modified portion 17 where the crystal structure of the material of the ingot 11 (here, SiC) is disturbed is formed inside the ingot 11 with the focal point where the laser beam is focused as the center.

[0034] Then, in a situation where irradiation of the entire area of ​​the ingot 11 with the laser beam has not been completed (step S12: NO), the ingot 11 and the position where the focal point is formed are moved relatively along the Y-axis direction (indexing and feeding step S13). Specifically, the moving mechanism moves the head 8 and the housing 10 along the Y-axis direction by a predetermined index amount (e.g., 250 μm to 400 μm) so that the head 8 is positioned in the X-axis direction when viewed in a plan view from a region slightly farther from the secondary orientation flat 15 than the region already irradiated with the laser beam.

[0035] Next, the ingot 11 is irradiated with the laser beam as described above (i.e., the laser beam irradiation step S11). Furthermore, the indexing step S13 and the laser beam irradiation step S11 are alternately repeated until the laser beam is irradiated onto the region of the ingot 11 farthest from the secondary orientation flat 15 and irradiation of the entire region of the ingot 11 with the laser beam is completed. This completes the separation layer formation step S1.

[0036] 5 is a partially enlarged cross-sectional view showing a schematic diagram of the ingot 11 after the separation layer forming step S1. In the separation layer forming step S1, a plurality of modified portions 17 are formed, each of which extends along a predetermined direction (here, the X-axis direction) and has its center located at a predetermined depth from the surface 11a of the ingot 11.

[0037] In other words, in the separation layer formation step S1, a plurality of modified portions 17 are formed at equal intervals in a direction perpendicular to the predetermined direction (here, the Y-axis direction) and positioned on an imaginary plane roughly parallel to the surface 11a of the ingot 11. Furthermore, when the modified portions 17 are formed inside the ingot 11, the volume of the ingot 11 expands, causing internal stress in the ingot 11.

[0038] This internal stress is relieved by the extension of cracks 19 from each of the multiple modified regions 17. The cracks 19 extend along the c-plane 11e that is inclined with respect to the front surface 11a of the ingot 11. Therefore, the cracks 19 extend so as to be inclined with respect to an imaginary plane on which the multiple modified regions 17 are positioned.

[0039] As a result, in the separation layer formation step S1, a plurality of separation layers 21 are formed inside the ingot 11, each extending along a predetermined direction and each including a modified portion 17 and a crack 19 propagating from the modified portion 17.

[0040] After the separation layer formation step S1, ultrasonic waves are applied to the ingot 11 through a liquid layer so as to separate the ingot 11 at a plurality of separation layers 21 to produce wafers (ultrasonic wave application step S2), and the wafer and ingot 11 are then moved relatively along a predetermined direction to separate the wafer and ingot 11 (separation step S3).

[0041] Fig. 6 is a perspective view showing a schematic example of a separation device capable of performing the ultrasonic wave application step S2 and the separation step S3. Note that the U-axis direction and the V-axis direction shown in Fig. 6 are directions perpendicular to each other on a horizontal plane, and the W-axis direction is a direction (vertical direction) perpendicular to the U-axis direction and the V-axis direction. Also, in Fig. 6, some components of the separation device are shown as blocks.

[0042] 6 includes a first holding unit 16 for holding the ingot 11. The first holding unit 16 includes a chuck table 16a having a circular holding surface substantially parallel to a horizontal plane, and a suction mechanism (not shown) in communication with the chuck table 16a.

[0043] The suction mechanism includes, for example, an ejector. When the suction mechanism operates, a suction force acts on the space near the holding surface of the chuck table 16a. Therefore, when the suction mechanism operates with the ingot 11 placed on the holding surface of the chuck table 16a, the ingot 11 is held on the holding surface.

[0044] The chuck table 16a is connected to a rotation mechanism (not shown). The rotation mechanism includes, for example, a pulley and a motor. When the rotation mechanism operates, the chuck table 16a rotates about a rotation axis that is a straight line passing through the center of the holding surface along the W-axis direction. For example, the rotation mechanism rotates the chuck table 16a so that the secondary orientation flat 15 of the ingot 11 held on the holding surface of the chuck table 16a is parallel to the V-axis direction.

[0045] The chuck table 16a is also connected to a W-axis direction moving mechanism. This W-axis direction moving mechanism has, for example, a ball screw and a motor. When the W-axis direction moving mechanism operates, the chuck table 16a moves along the W-axis direction, that is, the chuck table 16a moves up and down. For example, the W-axis direction moving mechanism raises the chuck table 16a so that the ingot 11 held on the holding surface of the chuck table 16a approaches the ultrasonic wave application unit 30 or the second holding unit 42, which will be described later.

[0046] A V-axis direction moving mechanism 18 is provided diagonally above the chuck table 16a. The V-axis direction moving mechanism 18 extends along the V-axis direction and has a rectangular prism-shaped frame body 20 with an opening 20a formed on the side surface on the chuck table 16a side. A first ball screw (not shown) and a second ball screw (not shown) are housed in the frame body 20.

[0047] The base end of the screw shaft of the first ball screw is connected to the motor 22 through a through hole formed in one end (rear end) of the frame body 20. Similarly, the base end of the screw shaft of the second ball screw is connected to the motor 24 through a through hole formed in the other end (front end) of the frame body 20. Furthermore, the base end of the first moving plate 26 and the base end of the second moving plate 28 are inserted into the opening 20a of the frame body 20.

[0048] The base end of the first moving plate 26 is fixed to the nut of the first ball screw. Similarly, the base end of the second moving plate 28 is fixed to the nut of the second ball screw. Therefore, when at least one of the motor 22 and the motor 24 operates, at least one of the first moving plate 26 and the second moving plate 28 moves along the V-axis direction without contacting each other.

[0049] The tip of the first moving plate 26 is provided with an ultrasonic application unit 30 for applying ultrasonic waves through a liquid layer to the ingot 11 held by the first holding unit 16, and an imaging unit (identification unit) 40 for forming an image for identifying the direction (predetermined direction) in which each of the multiple separation layers 21 formed in the ingot 11 extends.

[0050] The ultrasonic wave applying unit 30 has a cylindrical vibration member 32 having a lower surface that can face the upper surface (e.g., surface 11a) of the ingot 11 held by the first holding unit 16. The vibration member 32 has an ultrasonic vibrator built in, and the vibration of the ultrasonic vibrator causes the entire vibration member 32 to vibrate.

[0051] Moreover, a tip (lower end) of a connection part 34 is fixed to the central region of the upper surface of the vibration member 32. And, this connection part 34 is fixed to the lower surface side of the tip part of the first moving plate 26. Moreover, a cylindrical water supply port 36 is provided at a corner of the upper surface of the first moving plate 26, through which liquid (e.g., water) is supplied from a liquid supply source (not shown) via a pipe (not shown) and a valve (not shown), etc.

[0052] The liquid supplied to this water supply port 36 is supplied to a liquid nozzle 38 provided at a position adjacent to the vibration member 32 and the connection part 34 in the V-axis direction. The liquid also passes through a flow path in the liquid nozzle 38 and is supplied to the lower surface of the vibration member 32 from an opening provided in the lower surface thereof.

[0053] The imaging unit 40 has, for example, a light source such as an LED that irradiates light with a wavelength that passes through the ingot 11, an objective lens, and an imaging element such as a CCD image sensor or a CMOS image sensor, and is capable of imaging the area directly below it.

[0054] Further, a second holding unit 42 for holding wafers produced by separating the ingot 11 at the plurality of separation layers 21 is provided at the tip of the second moving plate 28. This second holding unit 42 has a suction plate 44 having a plurality of suction ports provided on its lower surface.

[0055] The plurality of suction ports communicate with a suction mechanism (not shown) such as an ejector via a flow path (not shown) provided inside the suction plate 44, and piping (not shown) and a valve (not shown) connected to the flow path. A tip (lower end) of a connection part 46 is fixed to the central region of the upper surface of the suction plate 44. The connection part 46 is fixed to the lower surface side of the tip part of the second moving plate 28.

[0056] Furthermore, the separation device 14 includes a controller 48 for controlling each component (e.g., the first holding unit 16, the V-axis direction moving mechanism 18, the ultrasonic application unit 30, the imaging unit 40, and the second holding unit 42, etc.). The controller 48 includes a processor 48a and a memory 48b.

[0057] The processor 48a is configured, for example, by a CPU (Central Processing Unit) etc. The memory 48b is configured, for example, by a volatile memory such as a DRAM (Dynamic Random Access Memory) or an SRAM (Static Random Access Memory) and a non-volatile memory such as an SSD (Solid State Drive) (NAND type flash memory) or an HDD (Hard Disk Drive) (magnetic storage device).

[0058] The memory 48b stores data, programs, etc. used by the processor 48a. The processor 48a also controls each component of the separation device 14 so as to read and execute the programs stored in the memory 48b.

[0059] When the ingot 11 on which the multiple separation layers 21 are formed is carried into the separation device 14, the ingot 11 is first placed on the holding surface of the chuck table 16a with its surface 11a facing up. Next, the controller 48 controls the first holding unit 16, specifically, the suction mechanism communicating with the chuck table 16a, so that the ingot 11 is held.

[0060] Next, the controller 48 controls the V-axis direction moving mechanism 18, specifically, the motor 22, so as to position the vibration member 32 directly above the ingot 11. Next, the controller 48 controls the W-axis direction moving mechanism connected to the chuck table 16a so as to raise the chuck table 16a until the lower surface of the vibration member 32 approaches the front surface 11a of the ingot 11.

[0061] Next, the controller 48 controls the ultrasonic wave applying unit 30 to apply ultrasonic waves to the ingot 11 through the liquid layer so that the ingot 11 is separated at the multiple separation layers 21 to produce wafers. That is, the ultrasonic wave applying step S2 is performed. Fig. 7 is a side view showing the ultrasonic wave applying step S2.

[0062] In the ultrasonic application step S2, the controller 48 controls the ultrasonic vibrator built into the vibration member 32 so as to vibrate the entire vibration member 32, while the controller 48 controls the liquid supply source so that liquid L is supplied from the liquid nozzle 38 to the underside of the vibration member 32.

[0063] At this time, the controller 48 may control a rotation mechanism connected to the chuck table 16a so as to rotate the chuck table 16a while vibrating the vibration member 32 and supplying the liquid L to the lower surface of the vibration member 32. In this way, ultrasonic waves are applied to the ingot 11 using the liquid L as a medium. This completes the ultrasonic wave application step S2.

[0064] 8 is a partially enlarged cross-sectional view showing the ingot 11 after the ultrasonic wave application step S2 and a wafer produced from the ingot 11. In the ultrasonic wave application step S2, the cracks 19 included in each of the multiple separation layers 21 extend. As a result, the number of cracks exposed on the side surface of the ingot 11 increases, and the cracks 19 included in a pair of adjacent separation layers 21 are connected.

[0065] At this time, the liquid L permeates into the ingot 11 through cracks 19 exposed on the side surface thereof. The ingot 11 is separated at a plurality of separation layers 21 to produce wafers 23. Therefore, a layer of the liquid L remains at the interface between the ingot 11 and the wafer 23.

[0066] The cracks 19 included in each of the multiple separation layers 21 extend along the c-face 11e inclined with respect to the surface 11a of the ingot 11. Therefore, the newly exposed surfaces of the ingot 11 and the wafer 23 each have an undulating shape in a direction perpendicular to the direction in which each of the multiple separation layers 21 formed in the ingot 11 extends (predetermined direction). In other words, these surfaces have a shape in which the maximum waviness height Wz in the predetermined direction is small, but the maximum waviness height Wz in the direction perpendicular thereto is large.

[0067] Next, the controller 48 controls the ultrasonic wave application unit 30 to stop the application of ultrasonic waves to the ingot 11 through the layer of liquid L. Specifically, the controller 48 controls the ultrasonic transducer, the liquid supply source, and the W-axis direction movement mechanism connected to the chuck table 16a to stop the vibration of the vibration member 32 and the supply of liquid L to the lower surface of the vibration member 32 and to lower the chuck table 16a.

[0068] Next, the controller 48 controls the V-axis direction moving mechanism 18, specifically the motor 22, so as to position the imaging unit 40 directly above the ingot 11. Next, the controller 48 controls the imaging unit 40 so as to form an image for identifying a predetermined direction. For example, the controller 48 controls the imaging unit 40 so as to form an image focused on the interface between the ingot 11 and the wafer 23.

[0069] In this case, by referring to this image, the waviness of the newly exposed surfaces of the ingot 11 and the wafer 23 can be grasped, and the predetermined direction can be specified. Next, the controller 48 controls the rotation mechanism connected to the chuck table 16a so that the predetermined direction specified by referring to this image becomes parallel to the V-axis direction.

[0070] Next, the controller 48 controls the V-axis direction moving mechanism 18, specifically, the motors 22, 24, so as to move the imaging unit 40 away from the ingot 11 in a plan view and to position the suction plate 44 directly above the ingot 11. Next, the controller 48 controls the W-axis direction moving mechanism connected to the chuck table 16a so as to raise the chuck table 16a until the lower surface of the suction plate 44 comes into contact with the wafer 23.

[0071] Next, the controller 48 controls the second holding unit 42 and the V-axis direction moving mechanism 18, specifically, the motor 24, so as to relatively move the wafer 23 and the ingot 11 in a predetermined direction, i.e., along the V-axis direction. That is, a separating step S3 is performed. Each of Figs. 9(A) and 9(B) is a side view that typically shows the state of the separating step S3.

[0072] In the separating step S3, first, the controller controls the second holding unit 42, specifically, the suction mechanism communicating with a plurality of suction ports provided on the lower surface of the suction plate 44, so that the wafer 23 is held by the second holding unit 42 (see FIG. 9(A)). Next, while the wafer 23 is held by the second holding unit 42, the controller 48 controls the V-axis direction moving mechanism 18, specifically, the motor 24, so that the wafer 23 and the ingot 11 are separated from each other along the V-axis direction (see FIG. 9(B)).

[0073] In the wafer manufacturing method shown in FIG. 2, ultrasonic waves are applied to the ingot 11 through a layer of liquid L so as to separate the ingot 11 at the multiple separation layers 21 to produce the wafer 23, and then the wafer 23 and the ingot 11 are moved relatively in a predetermined direction, i.e., along the direction in which each of the multiple separation layers 21 extends, thereby separating the wafer 23 from the ingot 11.

[0074] In this case, the resistance caused by the surface tension of the layer of the liquid L is weaker than when the wafer 23 and the ingot 11 are separated in a direction perpendicular to the interface between them. Therefore, this method can reduce the probability that at least one of the wafer 23 and the ingot 11 is damaged during the separation.

[0075] The above-mentioned content is one aspect of the present invention, and the present invention is not limited to the above-mentioned content. For example, the wafer manufacturing method of the present invention may be a wafer manufacturing method in which the separation layer forming step S1 is omitted from the wafer manufacturing method shown in Fig. 2. That is, the wafer manufacturing method of the present invention may be a wafer manufacturing method in which a wafer 23 is manufactured from an ingot 11 in which a plurality of separation layers 21 are already formed.

[0076] Furthermore, the separating apparatus of the present invention may be provided with a V-axis direction moving mechanism for moving the first holding unit 16 along the V-axis direction instead of or in addition to the V-axis direction moving mechanism 18 for moving the ultrasonic wave application unit 30 and the second holding unit 42 along the V-axis direction. That is, in the present invention, it is only necessary that the wafer 23 and the ingot 11 can be moved relatively along the above-mentioned predetermined direction, and there is no limitation on the structure for this purpose.

[0077] Furthermore, the separating device of the present invention does not need to include the imaging unit 40. In this case, the above-mentioned predetermined direction is not specified by referring to an image formed by imaging with the imaging unit 40, but is specified, for example, by visually observing the secondary orientation flat 15.

[0078] In addition, the structures and methods according to the above-described embodiments can be modified as appropriate without departing from the scope of the present invention. [Explanation of symbols]

[0079] 2: Laser processing equipment 4: Holding unit (4a: chuck table) 6: Laser beam irradiation unit 8: Head 10: Housing 11: Ingot (11a: front surface, 11b: back surface) (11c: c-axis, 11d: perpendicular, 11e: c-plane) 12: Imaging unit 13: Primary orientation flat 14: Separation device 15: Secondary orientation flat 16: first holding unit (16a: chuck table) 17: Modification section 18:V-axis direction movement mechanism 19: Crack 20: Frame (20a: opening) 21: Separation layer 22: Motor 23: Wafer 24: Motor 26: First moving plate 28: Second moving plate 30: Ultrasonic application unit 32: Vibration member 34: Connection 36: Water inlet 38: Liquid nozzle 40: Imaging unit (specific unit) 42: Second holding unit 44: Suction plate 46: Connection 48: Controller (48a: processor, 48b: memory)

Claims

1. A wafer manufacturing method for manufacturing a wafer from an ingot, comprising: a separation layer forming step in which, with a focal point where a laser beam having a wavelength that transmits through the material of the ingot is focused, the ingot and a focal point are moved relative to each other along a predetermined direction while the focal point is positioned inside the ingot, and a relative movement between the ingot and a position where the focal point is formed along a direction perpendicular to the predetermined direction is repeated to form a plurality of separation layers within the ingot, each of which is aligned along the predetermined direction and each of which includes a modified portion and a crack extending from the modified portion; an ultrasonic wave applying step of applying ultrasonic waves to the ingot through a liquid layer so as to separate the ingot at the plurality of separation layers to produce the wafers after the separation layer forming step; a separating step of separating the wafer and the ingot by moving the wafer and the ingot relatively along the predetermined direction after the ultrasonic wave applying step; A method for manufacturing a wafer comprising the steps of:

2. A method for manufacturing a wafer from an ingot having a plurality of separation layers formed therein, each of which is aligned in a predetermined direction and each of which includes a modified portion and a crack extending from the modified portion, comprising: an ultrasonic wave applying step of applying ultrasonic waves to the ingot through a liquid layer so as to separate the ingot at the plurality of separation layers to produce the wafers; a separating step of separating the wafer and the ingot by moving the wafer and the ingot relatively along the predetermined direction after the ultrasonic wave applying step; A method for manufacturing a wafer comprising the steps of:

3. the plurality of separation layers are formed such that the modified portions included in each of the separation layers are positioned on the same imaginary plane; 3. The method for producing a wafer according to claim 1, wherein the crack extends so as to be inclined with respect to the imaginary plane.

4. A separation apparatus for manufacturing wafers from an ingot having a plurality of separation layers formed therein, each of which is aligned in a predetermined direction and each of which includes a modified portion and a crack extending from the modified portion, comprising: a first holding unit for holding the ingot; a second holding unit for holding the wafer; an ultrasonic wave applying unit for applying ultrasonic waves through a liquid layer to the ingot held by the first holding unit; a moving mechanism for relatively moving the first holding unit and the second holding unit along the predetermined direction; a controller for controlling the first holding unit, the second holding unit, the ultrasonic application unit, and the moving mechanism; The controller controls the ultrasonic application unit to apply ultrasonic waves to the ingot through the liquid layer while controlling the first holding unit to hold the ingot, so as to separate the ingot at the multiple separation layers to produce the wafer, and then controls the first holding unit to hold the ingot and the second holding unit to hold the wafer, while controlling the moving mechanism to move the first holding unit and the second holding unit relatively along the predetermined direction so that the wafer and the ingot are separated from each other.

5. The separating apparatus according to claim 4 , further comprising an identifying unit for identifying the predetermined direction.

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