Wafer manufacturing process

Abstract

A wafer manufacturing method for producing a hexagonal single-crystal wafer (27) from a hexagonal single-crystal ingot (11) having a first surface (11a), a second surface (11b) opposite the first surface (11a), a c-axis extending from the first surface (11a) to the second surface (11b), and a c-plane perpendicular to the c-axis, the wafer manufacturing method comprising: a separation start point formation step comprising setting a focal point of a laser beam having a transmission wavelength for the ingot (11) to a predetermined depth (D1) inside the ingot (11) from the first surface (11a), the depth (D1) corresponding to a thickness of the wafer (27) to be produced, and next applying the laser beam to the first surface (11a) while relatively moving the focal point and the ingot (11), thereby forming a modified layer (23) parallel to the first surface (11a) and cracks (25) extending from the modified layer (23) along the c-plane, thus forming a separation start point; and a wafer separating step of separating a plate-shaped member having a thickness corresponding to the thickness of the wafer (27) from the ingot (11) at the separation start point after performing the separation start point forming step, so as to manufacture the wafer (27) from the ingot (11); where the separation start point formation step includes: a modified layer (23) forming step comprising relatively moving the focal point of the laser beam in a first direction perpendicular to a second direction where the c-axis is inclined by a deviation angle (α) with respect to a normal to the first surface, and the deviation angle (α) is formed between the first surface (11a) and the c-plane, thereby linearly forming the modified layer (23) extending in the first direction, and a dividing step of relatively moving the focal point in the second direction to thereby advance the focal point by a predetermined amount; wherein the separation start point forming step further includes a protective member attaching step of attaching a protective member (29) to the first surface (11a) of the hexagonal single crystal ingot (11) after forming the separation start point in the ingot (11); and the wafer separating step includes the steps of immersing the ingot (11) in water after performing the protective member (29) attaching step and then applying ultrasonic vibration to the ingot (11) to thereby separate the plate-shaped member with the protective member (29) from the ingot (11) to produce the hexagonal single crystal wafer (27).

Description

BACKGROUND OF THE INVENTIONField of the InventionThe present invention relates to a wafer manufacturing method for slicing a hexagonal single crystal ingot to manufacture a wafer.Description of the Related ArtVarious devices such as ICs and LSIs are formed by forming a functional layer on the front surface of a wafer formed of silicon or the like and dividing this functional layer into a plurality of regions along a plurality of crossing division lines. The division lines of the wafer are processed by a processing device such as a dicing device and a laser processing device, to thereby divide the wafer into a plurality of individual device chips corresponding to the devices, respectively. The device chips thus obtained are widely used in a variety of equipment such as mobile phones and personal computers. Further, power devices or optical devices such as LEDs and LDs are formed by forming a functional layer on the front side of a wafer formed of a hexagonal single crystal such as SiC and GaN and dividing this functional layer into a plurality of regions along a plurality of intersecting division lines.Generally, the wafer on which the devices are to be formed is manufactured by cutting an ingot with a wire saw. Both sides of the wafer obtained above are polished to mirror, see, for example, Japanese Patent Laid-Open Publication No. 2000-94,221 A. This wire saw is configured in such a manner that a single wire having a diameter of about 100 to 300 μm like a piano wire is wound around many grooves, which are usually formed on two to four guide rollers, to form a plurality of cutting portions spaced parallel to each other at a predetermined pitch. The wire is actuated to travel in one direction or opposite directions, thereby slicing the ingot into a plurality of wafers.However, when the ingot is cut by the wire saw and both sides of each wafer are polished to obtain the product, 70 to 80% of the ingot becomes scrap, which poses the problem of poor economics. In particular, for example, a hexagonal single crystal ingot made of SiC or GaN has a high Mohs hardness, so that it is difficult to cut this ingot with the wire saw. Accordingly, a considerable time is required for slicing the ingot, causing a decrease in productivity. That is, there is a problem in efficiently manufacturing a wafer with the related art.A technique for solving this problem is described in Japanese Patent Application Laid-Open No. 2013-49 161. This technique includes the steps of adjusting the focal point of a laser beam having a transmission wavelength for SiC to the inside of a hexagonal single crystal ingot, next applying the laser beam to the ingot upon scanning the laser beam on the ingot to thereby form a modified layer and cracks in a separation plane inside the ingot, and next applying an external force to the ingot to thereby break the ingot along the separation plane where the modified layer and the cracks are formed, and thus separating a wafer from the ingot. In this technique, the laser beam is scanned spirally or linearly along the parting plane so that a first application point of the laser beam and a second application point of the laser beam closest to the first application point have a predetermined positional relationship with each other. As a result, the modified layer and the cracks are formed with a very high density in the separation plane of the ingot.In addition, WO 2012 / 108 055 A1 discloses a method for providing a monocrystalline substrate, with which a monocrystalline substrate of this type can be produced relatively large and thin by forming a modified layer in the interior of a starting substrate. DE 10 2005 022 530 A1 proposes a method for dividing a wafer with functional elements by forming a decomposed layer along dividing lines.SUMMARY OF THE INVENTIONHowever, in the ingot slicing method described in the above-mentioned Laid-Open Patent Publication JP 2013-49 161 A, the laser beam is scanned spirally or linearly across the ingot. In the case of linearly scanning the laser beam, the scanning direction of the laser beam is not determined. In the ingot slicing method described in Japanese Patent Application Laid-Open No. 2013-49 161, the pitch, i.e., the distance, between the first application point and the second application point of the laser beam is set to 1 to 10 μm as mentioned above. This pitch corresponds to the pitch of the cracks extending from the modified layer along a c-plane defined in the ingot.In this way, the pitch of the application points of the laser beam to be applied to the ingot is very small. Accordingly, regardless of whether the laser beam is scanned spirally or linearly, the laser beam needs to be applied with a very small pitch, and the improvement in productivity is not yet sufficient.It is therefore an object of the present invention to provide a wafer manufacturing method that can efficiently manufacture a wafer from an ingot.According to an aspect of the present invention, there is provided a wafer manufacturing method for manufacturing a hexagonal single crystal wafer from a hexagonal single crystal ingot having a first surface, a second surface opposite to the first surface, a c-axis extending from the first surface to the second surface, and a c-plane perpendicular to the c-axis, the wafer manufacturing method including: a separation start point forming step of setting a focal point of a laser beam having a transmission wavelength to the ingot to a depth predetermined from the first surface inside the ingot, the depth corresponding to a thickness of the wafer to be manufactured, and next applying the laser beam to the first surface upon relatively moving the focal point and the ingot, Thereby, to form a modified layer parallel to the first surface and cracks extending from the modified layer along the c-plane so as to form a separation start point; and a wafer separating step of separating a plate-shaped member having a thickness corresponding to the thickness of the wafer from the ingot at the separation start point after performing the separation start point forming step so as to produce the wafer from the ingot. The separation start point forming step includes: a modified layer forming step of relatively moving the focal point of the laser beam in a first direction perpendicular to a second direction where the c-axis is inclined by an off angle with respect to a perpendicular to the first surface and the off angle is formed between the first surface and the c-plane, thereby linearly forming the modified layer extending in the first direction; and a dividing step of relatively moving the focal point in the second direction, thereby advancing the focal point by a predetermined amount. The separation start point forming step further includes a protection member attaching step of attaching a protection member to the first surface of the hexagonal single crystal ingot after forming the separation start point in the ingot. The wafer separating step includes the steps of immersing the ingot in water after performing the protection member attaching step and then applying ultrasonic vibration to the ingot, thereby separating the plate-shaped member having the protection member from the ingot to form the hexagonal single crystal wafer.According to the wafer manufacturing method of the present invention, the modified layer is formed at the predetermined depth from the first surface of the ingot, and the cracks propagate along the c-plane on the opposite sides of the modified layer. As a result, the modified layer and another modified layer adjacent thereto are joined by the cracks. Accordingly, when the ingot is immersed in the wafer and then an ultrasonic vibration is applied to the ingot, the plate-shaped member having a thickness corresponding to the thickness of the wafer can be easily separated from the ingot at the separation start point, to thereby produce the wafer.Further, since the protection member is provided on the upper surface (first surface) of the plate-shaped member to be separated from the ingot, the plate-shaped member can be separated from the ingot without causing damage. Accordingly, productivity can be sufficiently improved and the amount of scrap from the ingot can be sufficiently reduced to about 30%.The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the appended drawings showing a preferred embodiment of the invention.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a perspective view of a laser processing apparatus suitable for use in carrying out a wafer manufacturing method of the present invention; FIG. 2 is a block diagram of a laser beam generation unit; FIG. 3A is a perspective view of a hexagonal single crystal ingot; FIG. 3B is a view of the ingot shown in FIG. 3A ; FIG. 4 is a perspective view for illustrating a separation start point forming step; FIG. 5 is a plan view of the ingot shown in FIG. 3A ; FIG. 6 is a schematic sectional view for illustrating a modified layer forming step; FIG. 7 is a schematic plan view for illustrating the modified layer forming step; FIG. 8A is a schematic plan view for illustrating an indexing step; FIG. 8B is a schematic plan view for illustrating an amount of division;FIGS. 9A and 9B are perspective views for illustrating a protective member attaching step with attaching a protective member to the upper surface of the ingot; FIG. 10 is a perspective view for illustrating a wafer separating step; FIG. 11 is a perspective view of a hexagonal single crystal wafer manufactured; andFIGS. 12A and 12B are perspective views for illustrating a protection member attaching step of attaching protection members to the upper and lower surfaces of a thin hexagonal single crystal ingot.DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTA preferred embodiment of the present invention will now be described in detail with reference to the drawings. Referring to FIG. 1, there is shown a perspective view of a laser processing apparatus 2 suitable for use in carrying out a wafer manufacturing method of the present invention. The laser processing apparatus 2 includes a stationary base 4 and a first slide block 6 mounted on the stationary base 4 so as to be movable in the X direction. The first link block 6 is moved in a feeding direction or in the X direction along a pair of guide rails 14 by a feeding mechanism 12 composed of a ball screw 8 and a stepping motor 10.A second link block 16 is mounted on the first link block 6 so as to be movable in the Y direction. The second link block 16 is moved in an indexing direction or in the Y direction along a pair of guide rails 24 by an indexing mechanism 22 constructed of a ball screw 18 and a stepping motor 20. A support table 26 is mounted on the second slide block 16. The support table 26 is movable in the X direction and the Y direction by the feeding mechanism 12 and the indexing mechanism 22, and is also rotatable by a motor housed in the second link block 16.A column 28 is provided on the stationary base 4 so as to project upward therefrom. A laser beam applying mechanism (laser beam applying means) 30 is mounted on the column 28. The laser beam applying mechanism 30 is configured of a housing 32, a laser beam generating unit 34 (see FIG. 2 ) housed in the housing 32, and a focusing means (laser head) 36 movably mounted on the front end of the housing 32 in the Z direction. An imaging unit 38 including a microscope and a camera is also mounted on the front end of the housing 32 so as to be aligned with the focusing means 36 in the X direction.As shown in FIG. 2, the laser beam generating unit 34 includes a laser oscillator 40 for generating a pulsed laser beam such as a YAG laser and a YVO4laser, repetition frequency setting means 42 for setting the repetition frequency of the pulsed laser beam to be generated by the laser oscillator 40, pulse width setting means 44 for setting the pulse width of the pulsed laser beam to be generated by the laser oscillator 40, and power setting means 46 for setting the power of the pulsed laser beam to be generated by the laser oscillator 40. Although not particularly shown, the laser oscillator 40 has a Brookfield window, so that the laser beam generated by the laser oscillator 40 is a laser beam of linearly polarized light. After the power of the pulsed laser beam is adjusted to a predetermined power by the power adjusting means 46 of the laser beam generating unit 34, the pulsed laser beam is reflected by a mirror 48 belonging to the focusing means 36, and next focused by a focusing lens 50 incorporated in the focusing means 36. The focusing lens 50 is positioned such that the pulsed laser beam is focused inside a hexagonal single crystal ingot 11 as a workpiece fixed to the support table 26.Referring to FIG. 3A, a perspective view of the hexagonal single crystal ingot 11 is shown as a workpiece to be processed. FIG. 3B is a view of the hexagonal single crystal ingot 11 shown in FIG. 3A. The hexagonal single crystal ingot 11, hereinafter simply referred to as an ingot, is selected from a SiC single crystal ingot or a GaN single crystal ingot. The ingot 11 has a first surface (upper surface) 11 aand a second surface (lower surface) 11 bopposing the first surface 11 a. The first surface 11 aof the ingot 11 is polished to mirror finish beforehand because the laser beam is applied to the first surface 11A.The ingot 11 has a first alignment plane 13 and a second alignment plane 15 perpendicular to the first alignment plane 13. The length of the first alignment plane 13 is greater than the length of the second alignment plane 15. the ingot 11 has a c-axis 19 inclined with respect to a perpendicular 17 to the upper surface 11 aby an off angle α towards the second alignment plane 15, and also has a c-plane 21 perpendicular to the c-axis 19. The c-plane 21 is inclined with respect to the upper surface 11a by the off angle α. In general, in the hexagonal single crystal ingot 11, the direction perpendicular to the extension direction of the shorter second orientation plane 15 is the inclination direction of the c-axis 19. the c-plane 21 is incountibly set on the molecular plane of the ingot 11. In this preferred embodiment, the off angle α is set to 4°. However, the off angle α is not limited to 4° of the present invention. For example, the off angle α can be freely set to a range of 1° to 6° when manufacturing the ingot 11.Referring again to FIG. 1, a column 52 is fixed to the left side of the stationary base 4. The column 52 is formed with an elongated opening 53 extending in the vertical direction, and a pressing mechanism 54 is mounted movably in the vertical direction on the column 52 so as to protrude from the opening 53.As shown in FIG. 4, the ingot 11 is fixed to the upper surface of the support table 26 using a wax or an adhesive in the state where the second orientation plane 15 of the ingot 11 is parallel to the X direction. In other words, the formation direction of the off angle α is indicated by an arrow Y 1 as shown in FIG. 5. That is, the direction of the arrow Y 1 is the direction in which the intersection 19 ais present between the c-axis 19 and the upper surface 11 aof the ingot 11 with respect to the perpendicular 17 to the upper surface 11 a. Further, the direction perpendicular to the direction of the arrow Y1 is shown by an arrow A. Then, the ingot 11 is fixed to the support table 26 in the state where the direction of the arrow A becomes parallel to the X direction.Accordingly, the laser beam is scanned in the direction of the arrow A perpendicular to the direction of the arrow Y 1 or the formation direction of the off angle α. In other words, the direction of the arrow A perpendicular to the direction of the arrow Y 1 where the off angle α is formed is defined as a feeding direction of the support table 26.In the wafer manufacturing method of the present invention, it is important that the scanning direction of the laser beam to be applied from the focusing means 36 is set to the direction of the arrow A perpendicular to the direction of the arrow Y 1 where the off angle α of the ingot 11 is formed. That is, it has been found that by setting the scanning direction of the laser beam to the direction of the arrow A as mentioned above in the wafer manufacturing method of the present invention, cracks propagating from a modified layer formed inside the ingot 11 by the laser beam extend very long along the c-plane 21.In carrying out the wafer manufacturing method according to this preferred embodiment, a separation start point forming step is carried out in such a manner that the focal point of the laser beam having a transmission wavelength such as 1064 nm for the hexagonal single crystal ingot 11 fixed to the support table 26 is set to a predetermined depth inside the ingot 11 from the first surface 11 a(upper surface) corresponding to the thickness of a wafer to be manufactured, and the laser beam is next applied to the upper surface 11 ain a relative movement of the focal point and the ingot 11 to thereby form a modified layer 23 parallel to the upper surface 11 aand cracks 25 extending from the modified layer 23 along the c-plane 21 to form a separation start point (separation plane), where the modified layer 23 and the cracks 25 are formed.This separation start point forming step includes a modified layer forming step of relatively moving the focal point of the laser beam in the direction of the arrow A perpendicular to the direction of the arrow Y 1 where the c-axis 19 is inclined by the off angle α with respect to the perpendicular 17 to the upper surface 11 aand the off angle α is formed between the c-plane 21 and the upper surface 11 a, thereby forming the modified layer 23 inside the ingot 11 and the cracks 25 extending from the modified layer 23 along the c-plane 21, and further including a dividing step of relatively moving the focal point in the forming direction of the off angle α, i.e., in the Y-direction, to thereby form the focal point, As shown in FIG. 7 and FIGS. 8A and 8B, advance by a predetermined amount.As shown in FIGS. 6 and 7, the modified layer 23 is linearly formed to extend in the X direction so that the cracks 25 extend from the modified layer 23 in opposite directions along the c-plane 21. In the wafer manufacturing method according to this preferred embodiment, the separation start point forming step further includes an indexing amount setting step of measuring the width of the cracks 25 formed on one side of the modified layer 23 along the c-plane 21, and then setting the indexing amount of the focus according to the above width measurement. With W 1 indicating the width of the cracks 25 formed on one side of the modified layer 23 so as to propagate from the modified layer 23 along the c-plane 21, the focus adjustment amount W 2 is more specifically set in the range of W 1 to 2W 1.For example, the separation start point forming step is performed under the following laser processing conditions.Light source: pulsed Nd:YAG laserWavelength: 1064 nmRepetition frequency: 80 kHz Average power: 3.2 WPulse width: 4 nsSpot diameter: 10 μmnumerical aperture (NA) of the focusing lens: 0,45Scheduling amount: 400 μmIn the above-mentioned laser processing conditions, the width W 1 of the cracks 25 propagating from the modified layer 23 along the c-plane 21 in a direction seen in FIG. 6 is set to about 250 μm, and the division amount W 2 is set to 400 μm. However, the average power of the laser beam is not limited to 3.2 W. When the average power of the laser beam was set to 2 to 4.5 W, good results were obtained in the preferred embodiment. In the case where the average power was set to 2 W, the width W 1 of the cracks 25 was about 100 μm. In the case where the average power was set to 4.5 W, the width W 1 of the cracks 25 was about 350 μm.In the case where the average power is less than 2 W or greater than 4.5 W, the modified layer 23 cannot be formed well within the ingot 11. Accordingly, the average power of the laser beam to be applied is preferably set in a range of 2 to 4.5 W. For example, the average power of the laser beam to be applied to the ingot 11 was set to 3.2 W in this preferred embodiment. As shown in FIG. 6, the depth D 1 of the focal point for forming the modified layer 23 was set to 500 μm from the upper surface 11 a.Referring to FIG. 8A, a schematic plan view for illustrating the scanning direction of the laser beam is shown. The separation start point forming step is performed on a forward path X 1 and a backward path X 2 as shown in FIG. 8A. That is, the modified layer 23 is formed in the hexagonal single crystal ingot 11 on the forward path X 1. Thereafter, the focal point of the laser beam is advanced by the predetermined amount. Thereafter, the modified layer 23 is formed on the reverse path X 2 in the ingot 11 again.Further, in the case where the amount of division of the focal point of the laser beam is set in a range from W to 2W, where W is the width of the cracks 25 formed on one side of the modified layer 23 along the c-plane 21, the amount of division of the focal point is preferably set to W or less until the modified layer 23 is formed for the first time after the setting of the focal point of the laser beam to the inside of the ingot 11.In the case where the indexing amount of the focal point of the laser beam is 400 μm, for example, the indexing amount is set to 200 μm until the modified layer 23 is formed inside the ingot 11 for the first time, and then the laser beam is scanned a plurality of times with this indexing amount of 200 μm, as shown in FIG. 8B. That is, a first part of the plurality of scanning phases of the laser beam is idle, and when it is determined that the modified layer 23 has been formed inside the ingot 11 for the first time, the division amount is set to 400 μm, and then the modified layer 23 is formed inside the ingot 11.In this way, the focal point of the laser beam is successively advanced to form a plurality of modified layers 23 at the depth D 1 in the entire region of the ingot 11 and also to form the cracks 25 extending from each modified layer 23 along the c-plane 21. Thereafter, a wafer separating step is performed in such a manner that an external force is applied to the ingot 11 to thereby separate, at the separation start point consisting of the modified layers 23 and the cracks 25, a plate-shaped member having a thickness corresponding to the thickness of the wafer to be formed from the ingot 11, thereby producing a hexagonal single crystal wafer 27 shown in FIG. 11.Before performing the wafer separating step, a protection member 29 is attached to the upper surface of the hexagonal single crystal ingot 11 by forming the modified layers 23 and the cracks 25 in the separation start point forming step as shown in FIGS. 9A and 9B (protection member attaching step). This wafer separating step is carried out in the following manner. As shown in FIG. 10, an ultrasonic vibration generating device 62 is installed in a water tank 60, and the hexagonal single crystal ingot 11 is fixed to the ultrasonic vibration generating device 62 via a support table 26. At this time, the separation start point has already been formed in the ingot 11, and the protection member 29 has already been attached to the upper surface of the ingot 11. Thereafter, the water tank 60 is filled with pure water 64 to submerge the hexagonal single crystal ingot 11 in the pure water 64. Thereafter, a voltage is applied to the ultrasonic vibration generating device 62, thereby generating an ultrasonic vibration having a frequency of, for example, 50 kHz.This ultrasonic vibration is transmitted to the hexagonal single crystal ingot 11, thereby separating the plate-shaped member having a thickness corresponding to the thickness of the wafer from the ingot 11 at the separation start point formed inside the ingot 11. Accordingly, a hexagonal single crystal wafer 27 as shown in FIG. 11 can be manufactured from the hexagonal single crystal ingot 11. Although pure water 64 is contained in water tank 60 in this preferred embodiment, any other type of container is usable.For example, as the ultrasonic vibration generating device 62 for generating ultrasonic vibration, an AS Ultrasonic Cleaner US-2R provided by AS ONE Corporation may be used. In this case, the ultrasonic vibration generating device 62 can generate an ultrasonic vibration having a frequency of 40 kHz and a power of 80 W. The ultrasonic vibration to be applied in the wafer separating step preferably has a frequency of 30 to 50 kHz, and more preferably 35 to 45 kHz.In the wafer separating step according to this preferred embodiment, the protection member 29 is preliminarily provided on the upper surface of the hexagonal single crystal ingot 11. Accordingly, the plate-shaped member having a thickness corresponding to the thickness of the wafer can be easily separated from the ingot 11 at the separation start point without causing damage to the hexagonal single crystal wafer 27 to be manufactured.FIGS. 12A and 12B show a protective member mounting step using a thin hexagonal single crystal ingot 11A having a thickness two times the thickness of the hexagonal single crystal wafer 27 to be manufactured. Before performing the wafer separating step using the water tank 60 shown in FIG. 10 and the ultrasonic vibration generating device 62, as shown in FIGS. 12A and 12B, protective members 29 and 31 are attached to the upper and lower surfaces of the hexagonal single crystal ingot 11A, respectively. For example, protective tapes can be used as the protective members 29 and 31.In performing the wafer separating step in this case, the hexagonal single crystal ingot 11A is attached to the upper and lower surfaces with the protective members 29 and 31 as shown in FIG. 12B by the support table 26 attached to the ultrasonic vibration generating device 62 installed in the water tank 60 shown in FIG. 10. Thereafter, the water tank 60 is filled with the pure water 64 to submerge the hexagonal single crystal ingot 11A in the pure water 64. Thereafter, a voltage is applied to the ultrasonic vibration generating device 62, thereby generating an ultrasonic vibration having a frequency of, for example, 40 kHz.This ultrasonic vibration is transmitted to the hexagonal single crystal ingot 11A, thereby dividing the ingot 11A into two at the separation start point formed inside the ingot 11. Accordingly, two hexagonal single crystal wafers can be manufactured in the state where the protection member 29 or 31 is attached to one side of each wafer. According to this preferred embodiment, the protection members 29 and 31 are preliminarily attached to the upper and lower surfaces of the hexagonal single crystal ingot 11A, respectively, so that the ingot 11A can be separated into two plate-shaped members (two wafers) without causing damage to the wafers.The present invention is not limited to the details of the preferred embodiments described above. The scope of the invention is defined by the appended claims.

Claims

A wafer manufacturing method for manufacturing a hexagonal single crystal wafer (27) from a hexagonal single crystal ingot (11) having a first surface (11a), a second surface (11b) opposite to the first surface (11a), a c-axis extending from the first surface (11a) to the second surface (11b), and a c-plane perpendicular to the c-axis, the wafer manufacturing method comprising: a separation start point forming step of setting a focus point of a laser beam having a transmission wavelength to the ingot (11) to a predetermined depth (D1) from the first surface (11a) inside the ingot (11), the depth (D1) corresponding to a thickness of the wafer (27) to be manufactured, and next, applying the laser beam to the first surface (11a) upon relatively moving the focal point and the ingot (11), thereby forming a modified layer (23) parallel to the first surface (11a) and cracks (25) extending from the modified layer (23) along the c-plane, so as to form a separation start point; and a wafer separating step of separating a plate-shaped member having a thickness corresponding to the thickness of the wafer (27) from the ingot (11) at the separation start point after performing the separation start point forming step, so as to produce the wafer (27) from the ingot (11); wherein the separation start point forming step includes: a modified layer forming step (23) of relatively moving the focal point of the laser beam in a first direction perpendicular to a second direction where the c-axis is inclined by an off angle (α) with respect to a perpendicular to the first surface and the off angle (α) is formed between the first surface (11a) and the c-plane, thereby linearly forming the modified layer (23) extending in the first direction; and a dividing step of relatively moving the focal point in the second direction, thereby further moving the focal point by a predetermined amount; wherein the separation start point forming step further includes a protection member attaching step of attaching a protection member (29) to the first surface (11 a) of the hexagonal single crystal ingot (11) after forming the separation start point in the ingot (11); and the wafer separating step includes the steps of immersing the ingot (11) in water after performing the protection member attaching step (29) and then applying an ultrasonic vibration to the ingot (11) to thereby separate the plate-shaped member having the protection member (29) from the ingot (11) to produce the hexagonal single crystal wafer (27).The wafer manufacturing method according to claim 1, wherein the hexagonal single crystal ingot (11) has a thickness that is twice the thickness of the plate-shaped member to be separated from the ingot (11), and the protection member attaching step includes the step of attaching a first protection member (29) to the first surface (11a) of the ingot and a second protection member (31) to the second surface (11b) of the ingot.The wafer manufacturing method according to claim 1 or 2, wherein the hexagonal single crystal ingot (11) is selected from a SiC single crystal ingot and a GaN single crystal ingot.

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