JP2023003563A - Processing method for wafer - Google Patents

Abstract

To suppress a crack from reaching a device when forming a laser processing groove by performing ablation processing on a wafer using green laser beams.SOLUTION: The present invention relates to a processing method for a wafer for processing with pulsed green laser beams the wafer comprising a device region where a plurality of devices is formed and an outer peripheral excessive region enclosing the device region on a front face side and having absorbability with respect to the green laser beams. The processing method for the wafer includes: a first laser processing step of forming an annular first laser processing groove or a first laser processing hole in the outer peripheral excessive region; and a second laser processing step of forming a plurality of second laser processing grooves by irradiating the wafer with the green laser beams of lower output than output of the green laser beams in the first laser processing step so as to pass the first laser processing groove or the first laser processing hole along each predetermined dividing line.SELECTED DRAWING: Figure 2

Description

The present invention relates to a wafer processing method for processing a wafer that absorbs a green laser beam with a pulsed green laser beam.

A laser beam is applied to an oxide single crystal wafer in which a plurality of planned division lines are set in a grid pattern on the surface and devices such as SAW (Surface Acoustic Wave) filters are formed in each region partitioned by the plurality of planned division lines. A method has been proposed in which laser processing grooves are formed along each planned division line by performing ablation processing (see, for example, Patent Document 1).

In the above document, a single crystal wafer of lithium niobate (LiNbO ₃ , hereinafter abbreviated as LN) is irradiated with a pulsed laser beam having a wavelength (266 nm) absorbed by the single crystal wafer. A method of performing an ablation process is described.

Further, a single crystal wafer of lithium tantalate (LiTaO ₃ , hereinafter abbreviated as LT) is irradiated with a pulsed laser beam having a wavelength (193 nm) absorbed by the single crystal wafer to perform ablation. It also describes how to do it.

Thus, single crystal wafers such as LN and LT are usually ablated using a pulsed laser beam having a wavelength in the ultraviolet (UV) band. As the pulsed laser beam having a wavelength in the ultraviolet band, the third harmonic (wavelength 355 nm) of Nd:YAG laser may be used.

By the way, when a wafer is to be ablated, a wafer unit is prepared in which the wafer is supported by a metal annular frame through a resin protective tape, and the wafer is sucked by a chuck table through the protective tape. In some cases, the wafer is ablated while being held.

However, when a pulsed ultraviolet laser beam as described above is used to divide the wafer by ablation, the laser beam reaches the protective tape and burns out the protective tape.

Therefore, in order to suppress damage to the protective tape, it is conceivable to use a green laser beam corresponding to the second harmonic of the Nd:YAG laser (having a wavelength of 532 nm, which is in the visible light band).

However, single-crystal wafers such as LN and LT have a lower absorptance for green laser beams than UV laser beams, so it is difficult to form laser-processed grooves by ablation. If the output of the green laser beam is increased, a laser-processed groove can be formed, but there is a problem that the crack extends from the laser-processed groove and reaches the device.

JP-A-10-305420

The present invention has been made in view of such problems, and an object of the present invention is to suppress cracks from reaching a device when laser processing grooves are formed by performing ablation processing on a wafer using a green laser beam. do.

According to one aspect of the present invention, a device region in which a device is formed in each region partitioned by a plurality of planned division lines set on a surface, and an outer peripheral surplus region surrounding the device region are arranged on the surface side. A wafer processing method for processing a wafer with a pulsed green laser beam that absorbs a green laser beam, wherein the green laser beam is applied to the wafer along the outer periphery of the wafer. A first laser processing step of irradiating to form an annular first laser processing groove or a first laser processing hole in the outer peripheral surplus region, and after the first laser processing step, along each planned division line, irradiating the wafer with the green laser beam at an output lower than the output of the green laser beam in the first laser processing step so as to pass through one laser-processed groove or first laser-processed hole, and a plurality of second lasers and a second laser processing step of forming a processed groove.

Preferably, in the wafer processing method, after the second laser processing step, a cutting blade having a blade thickness smaller than the width of each second laser processing groove is used to cut the wafer along the plurality of second laser processing grooves. It further comprises a dividing step of dividing the .

Also preferably, the wafer has a lithium tantalate single crystal substrate, and in the first laser processing step, the first laser processing groove or the first laser processing hole is formed in the single crystal substrate, In the second laser processing step, the plurality of second laser processing grooves are formed in the single crystal substrate.

In the first laser processing step according to one aspect of the present invention, the first laser-processed groove or the first laser-processed hole is formed by irradiating the peripheral surplus region with a green laser beam of a predetermined output. At this time, in the vicinity of the first laser-processed groove or the first laser-processed hole, an altered region is formed in which the absorptivity of the green laser beam is improved compared to before processing.

In the second laser processing step after the first laser processing step, the ablation process progresses starting from the altered region near the first laser-processed groove or the first laser-processed hole. Therefore, by irradiating the green laser beam so as to pass through the first laser processing groove, the device region can be ablated even if the output of the green laser beam is lowered compared to the first laser processing step.

Therefore, in the second laser processing step of performing ablation processing along the dividing line, it is possible to prevent cracks from reaching the device. For example, compared to performing the second laser processing step with the same output as the first laser processing step, the device is not damaged, the number of cracks is small, and the length of the cracks is short (i.e., processing quality A second laser-machined groove (better) can be formed in the device region.

1 is a perspective view of a wafer; FIG. 1 is a flowchart of a wafer processing method; FIG. It is a figure which shows the 1st laser processing step. FIG. 4 is a cross-sectional view of a first laser-processed groove; FIG. 10 is a diagram showing a second laser processing step; FIG. 6(A) is a cross-sectional view of a wafer in which two laser-processed grooves are formed per one planned division line, and FIG. FIG. 6C is a cross-sectional view of the wafer after the second laser processing step; FIG. It is a perspective view which shows a division step. FIG. 4 is a cross-sectional view showing a dividing step; It is a figure which shows the 1st laser processing step which concerns on 2nd Embodiment.

An embodiment according to one aspect of the present invention will be described with reference to the accompanying drawings. First, the wafer 11 to be processed will be described. FIG. 1 is a perspective view of a wafer 11. FIG. The wafer 11 of this embodiment has a disk-shaped single crystal substrate 13 made of TL (lithium tantalate).

The diameter of the single-crystal substrate 13 is, for example, approximately 150 mm (6 inches), and the thickness from the front surface 13a to the rear surface 13b of the single-crystal substrate 13 is, for example, approximately 200 μm. However, the diameter and thickness of the single crystal substrate 13 are not limited to this example.

The front surface 13 a of the single crystal substrate 13 corresponds to the front surface 11 a of the wafer 11 , and the back surface 13 b of the single crystal substrate 13 corresponds to the back surface 11 b of the wafer 11 . A plurality of planned division lines (street) 15 are set in a grid pattern on the surface 11a.

A plurality of devices 17 each functioning as a SAW filter are formed in each of the rectangular regions partitioned by the plurality of planned dividing lines 15 . Around the device region 17a, there is a substantially flat peripheral surplus region 17b in which the device 17 is not formed so as to surround the device region 17a.

Thus, on the front surface 11a side of the wafer 11, there are a device region 17a having a plurality of devices 17 and an outer peripheral surplus region 17b. In addition, in FIG. 1, the boundary between the device region 17a and the peripheral surplus region 17b is indicated by a dashed line for the sake of convenience.

Before processing the wafer 11, the central portion of a circular dicing tape 19 made of resin (see FIG. 6A, etc.) is attached to the rear surface 11b side of the wafer 11. As shown in FIG. Also, on the outer peripheral portion of the dicing tape 19, one surface of a metal annular frame (not shown) having an opening with a diameter larger than that of the wafer 11 is attached.

In this manner, a wafer unit is formed in which the wafer 11 is supported by the annular frame via the dicing tape 19 . Then, the wafer 11 is ablated by irradiating the front surface 11a with a green laser beam L (see FIG. 3).

FIG. 2 is a flowchart of the method for processing the wafer 11. As shown in FIG. In the first laser processing step S10, the laser processing device 2 (see FIG. 3) is used. As shown in FIG. 3, the laser processing device 2 has a disc-shaped chuck table 4 .

The chuck table 4 has a disk-shaped metal frame. A disk-shaped recess is formed in the frame, and a disk-shaped porous plate (not shown) made of porous ceramics is fixed to the recess.

A negative pressure from a suction source (not shown) such as an ejector is applied to the porous plate through a channel (not shown) formed in the frame. The upper surface of the porous plate and the upper surface of the frame are substantially flush with each other, forming a holding surface 4a (see FIG. 6A) for holding the wafer 11 by suction.

A rotary drive source (not shown) is provided below the chuck table 4, and this rotary drive source rotates the chuck table 4 along a predetermined rotation axis substantially parallel to the height direction A3 ₍ for example, the vertical direction). is rotatable around

A ball screw type first movement mechanism (for example, an X-axis direction movement mechanism) is provided below the rotational drive source. A ball screw type second movement mechanism (for example, a Y-axis direction movement mechanism) is provided between the first movement mechanism and the rotational drive source.

The second moving mechanism integrally moves the chuck table 4, the rotational driving source and the like in the indexing feed direction _A2 , and the first moving mechanism integrally moves the chuck table 4, the rotational driving source, the second moving mechanism and the like. Move in the processing _feed direction A1. The machining feed direction A ₁ , the indexing feed direction A ₂ and the height direction A ₃ are orthogonal to each other.

A laser beam irradiation unit 6 is provided above the chuck table 4 . The laser beam irradiation unit 6 has a laser oscillator (not shown). The laser oscillator contains Nd:YAG as a laser medium.

A pulsed laser beam emitted from a laser oscillator is converted into a second harmonic by a nonlinear crystal such as KTP (KTiOPO ₄ ) crystal, LBO (LiB ₃ O ₅ ), etc., and pulsed green having a central wavelength of 532 nm. becomes a laser beam L.

In this embodiment, the green laser beam L having a center wavelength of 532 nm is used, but the present invention is not limited to this, and a green laser beam L having a predetermined center wavelength of 501 nm or more and 561 nm or less may be used.

The laser beam irradiation unit 6 has a head portion 8 housing a mirror, a condenser lens, etc. (not shown). The green laser beam L is irradiated toward the holding surface 4a through the head portion 8. As shown in FIG. In the vicinity of the head section 8, a microscope camera unit 10 including a condensing lens, an imaging device, and the like is provided.

Although the wafer 11 has an absorptivity to the green laser beam L, the absorptance of the green laser beam L is lower than that of the UV laser beam. Therefore, it is generally difficult to use the green laser beam L to perform ablation processing.

Therefore, it is conceivable to increase the output of the green laser beam L in order to form laser-processed grooves by ablation. However, if the output of the green laser beam L is increased to the extent that the laser-processed groove can be formed, there is a problem that the crack extends from the formed laser-processed groove.

If the crack reaches device 17, device 17 will be damaged. Faced with such a problem, the applicant searched for a processing method for reducing the number and length of cracks formed in the device region 17a while forming laser-processed grooves in the device region 17a.

The applicant performs ablation with a relatively high output to form a laser-processed groove, and a crack extends from the laser-processed groove. Note the formation of an altered region with enhanced absorption.

By forming an altered region with a relatively high output in the outer peripheral surplus region 17b and then irradiating the line to be divided 15 with a relatively low output green laser beam L starting from the altered region, cracks are formed in the device region 17a. The inventors have come to believe that it is possible to form laser-processed grooves while reducing the number and length of grooves.

A processing method of this embodiment embodying the concept will be described. First, using a protective film forming unit (not shown), a protective film (not shown) containing a water-soluble resin is uniformly formed on the front surface 11a side of the wafer 11, and then the back surface 11b side of the wafer 11 is placed on the holding surface 4a. to hold.

Next, in a state where the condensing point of the green laser beam L is substantially positioned in the height direction A3 at a location located at a predetermined distance B (see FIG. ₃ ) from the outer peripheral edge of the wafer 11 in the outer peripheral surplus region 17b, the chuck is moved. The table 4 is rotated in a predetermined direction (first laser processing step S10).

For example, the annular first laser-processed groove 21 is formed by rotating the chuck table 4 once. FIG. 3 is a diagram showing the first laser processing step S10. Note that the dicing tape 19, the annular frame, and the like are omitted in FIG. Processing conditions in the first laser processing step S10 are set as follows, for example.

Center wavelength: 532nm
Repetition frequency: 50 kHz
Pulse width: 110ns
Average output: 2.5W
Peripheral speed at condensing point: 100mm/s
Defocus amount: 0.1 mm (amount of deviation of the condensing point to the upper side of the surface 11a)

FIG. 4 is a cross-sectional view showing an example of the first laser-processed groove 21 formed along the outer periphery of the wafer 11. As shown in FIG. The first laser-processed groove 21 has, for example, a depth 21a of approximately 9 μm and a width 21b of approximately 20 μm.

At the bottom and side portions of the first laser-processed groove 21, a denatured region 21c (dotted in FIG. 4) that has been denatured due to heat during ablation processing is formed. In the vicinity of the first laser-processed groove 21, a crack 21d extending about 60 μm at maximum is formed starting from the bottom and side surfaces thereof.

However, the predetermined distance B (FIG. 3) from the inner peripheral side surface of the first laser-processed groove 21 to the edge of the device 17 closest to the outer peripheral edge is, for example, 1 mm or more, and the crack 21d reaches the device 17. There is nothing.

After the first laser processing step S10, alignment is first performed using the microscope camera unit 10, and the planned division line 15 in _one direction is positioned substantially parallel to the processing feed direction A1.

After that, while the focal point of the green laser beam L is positioned at a predetermined height in the height direction A3 _, the focal point passes through the first laser-processed groove 21 and moves along each division line 15. Then, the chuck table ₄ is moved in the processing feed direction A1.

Thereby, the second laser-processed grooves 23 (see FIG. 5) are formed along each dividing line 15 in one direction. After irradiating the green laser beam L along each dividing line 15 parallel to one direction, the chuck table 4 is rotated by 90 degrees.

As a result, the planned division lines 15 in the other direction orthogonal to the _one direction are made substantially parallel to the processing feed direction A1. Then, the green laser beam L is applied to each division line 15 along the other direction.

In this way, the second laser-processed grooves 23 are formed along each planned division line 15 (second laser-processed step S20). FIG. 5 is a diagram showing the second laser processing step S20. Processing conditions in the second laser processing step S20 are set as follows, for example.

Center wavelength: 532nm
Repetition frequency: 50 kHz
Pulse width: 110ns
Average output: 1.25W
Peripheral speed of condensing point: 100mm/s
Defocus amount: none (so-called just focus state)

Thus, the power of the green laser beam L in the second laser processing step S20 is made lower than the power of the green laser beam L in the first laser processing step S10. Let the average output in the second laser processing step S20 be a predetermined value of 25% or more and 50% or less of the average output in the first laser processing step S10.

If it is less than 25%, abrasion processing can hardly be performed. Moreover, when it exceeds 50%, although ablation processing can be performed, cracks may extend from the formed second laser-processed groove 23 and reach the device 17 . Therefore, it is preferable to use a predetermined value of 25% or more and 50% or less of the average output in the first laser processing step S10.

In the second laser processing step S20, the wafer 11 is not completely cut in the thickness direction of the wafer 11 in order to suppress the formation of cracks on the surface 11a. The cutting of the wafer 11 is performed using a cutting blade 22 (see FIG. 7) after the second laser processing step S20.

In the second laser processing step S20, by moving the condensing point of the green laser beam L a plurality of times along one planned division line 15, a width wider than the blade thickness 22a (see FIG. 8) of the cutting blade 22 is formed. A second laser processed groove 23 is formed.

In more detail, the second laser processing step S20 will be described. In the second laser processing step S20 of the present embodiment, a second laser processing groove 23 is formed in each division line 15 by a so-called π-cut method. The π-cut in the second laser processing step S20 will be described with reference to FIGS. 6(A) to 6(C).

In the π-cut, first, two laser-processed grooves 25 are formed for one dividing line 15 . FIG. 6A is a cross-sectional view of the wafer 11 in which two laser-processed grooves 25 are formed for one dividing line 15. FIG.

One laser-processed groove 25 has, for example, a depth 25a of approximately 5 μm and a width 25b of several μm to approximately 5 μm. A residual region 25c between two laser-processed grooves 25 is similarly removed by ablation processing.

When removing the residual region 25c, since cracks do not reach the device 17, the output of the green laser beam L may be increased compared to when forming one laser-processed groove 25. FIG.

FIG. 6B is a cross-sectional view of the wafer 11 from which the residual region 25c between the two laser-processed grooves 25 has been removed, and FIG. 6C shows the second laser processing after the second laser processing step S20. FIG. 4 is a cross-sectional view of wafer 11 including groove 23; The second laser-processed groove 23 has, for example, a depth 23a of approximately 5 μm and a width 23b of approximately 20 μm.

In the second laser processing step S20 of the present embodiment, the ablation processing progresses starting from the altered region 21c of the first laser processing groove 21. As shown in FIG. Therefore, by irradiating the green laser beam L so as to pass through the first laser processing groove 21, the device region 17a can be ablated even if the output is lower than in the first laser processing step S10.

Therefore, cracks can be prevented from reaching the device 17 in the second laser processing step S20. For example, compared to the case where the second laser processing step S20 is performed with the same output as the first laser processing step S10, the device 17 is not damaged, the number of cracks is small, and the length of the cracks is short (i.e. , a second laser-processed groove 23 with good processing quality) can be formed in the device region 17a.

After the second laser processing step S20, the cutting device 12 (see FIG. 7) is used to cut the cutting blade 22 into the second laser processing groove 23 to divide the wafer 11 (dividing step S30). First, the cutting device 12 used in the dividing step S30 will be described.

The cutting device 12 has a disk-shaped chuck table 14 . Since the chuck table 14 is substantially the same as the chuck table 4 described above, detailed description thereof will be omitted. A rotary drive source (not shown) such as a motor is provided below the chuck table 14 .

A ball screw type third movement mechanism (for example, an X-axis direction movement mechanism (not shown)) is provided below the rotary drive source. The chuck table 14 and the rotary drive source are configured to be integrally movable along the processing feed direction A1 by _a third moving mechanism.

A cutting unit 16 is arranged above the holding surface 14a of the chuck table 14 (see FIG. 8). As shown in FIG. 8, the cutting unit 16 has a tubular spindle housing 18 whose longitudinal portion is arranged along the index feed direction _A2 .

A part of a cylindrical spindle 20 is rotatably accommodated in the spindle housing 18 . A rotational drive source such as a motor is provided at the base end of the spindle 20 . A distal end portion of the spindle 20 protrudes from the spindle housing 18, and a cutting blade 22 having an annular cutting edge is attached to the distal end portion of the spindle 20. As shown in FIG.

The cutting edge of the cutting blade 22 has a blade thickness 22a (eg, 15 μm) that is smaller than the width 23b (eg, 20 μm) of each second laser-processed groove 23 . The cutting blade 22 is, for example, a hubless type (washer type) composed only of a cutting edge.

A blade cover 24 is connected to the spindle housing 18 so as to cover the cutting blade 22 from above. The blade cover 24 is provided with a plurality of nozzles 26 for supplying cutting water such as pure water to the cutting blade 22 during cutting.

The spindle housing 18 is provided with a ball screw type fourth movement mechanism (for example, a Z-axis direction movement mechanism, not shown). The _fourth moving mechanism allows the spindle housing 18 to move along the height direction A3.

Further, the fourth moving mechanism is provided with a ball screw type fifth moving mechanism (for example, a Y-axis direction moving mechanism, not shown). The fifth movement mechanism allows the spindle housing 18 to move along the index feed direction _A2 .

In the division step S30, first, a microscope camera unit (not shown) fixed to the spindle housing 18 is used to position the second laser-processed groove 23 in _one direction substantially parallel to the processing feed direction A1.

After that, the lower end of the rotating cutting blade 22 is positioned at a height between the dicing tape 19 and the holding surface 14a, and the cutting edge of the cutting blade 22 is set to the width of the _second laser processing groove 23 in the index feed direction A2. positioned approximately in the center of

Next, by moving the chuck table ₁₄ along the processing feed direction A1, cutting grooves 27 are formed along the respective second laser processing grooves 23 in one direction, and the wafer 11 is cut.

FIG. 7 is a perspective view showing the dividing step S30, and FIG. 8 is a sectional view showing the dividing step S30. The processing conditions in the division step S30 are set as follows, for example.

Spindle speed: 32,000 rpm
Processing feed speed: 20mm/s
Flow rate of cutting water: 1 L/min

After cutting the wafer 11 along the second laser-processed grooves 23 parallel to one direction, the chuck table 14 is rotated by 90 degrees to cut the second laser-processed grooves 23 in the other direction orthogonal to the one direction. The wafer 11 is cut along . In this manner, wafer 11 is divided into device chips (not shown) each having device 17 .

Since the second laser-processed groove 23 has already been formed on the surface 11a side, the crack formed in the dividing step S30 does not reach the device 17. FIG. After the dividing step S30, a spinner cleaning device (not shown) is used to clean and remove the protective film, and each device chip is cleaned.

In this embodiment, the device 17 is not damaged, the number of cracks is small, and the length of the crack is less than when the second laser processing step S20 is performed with the same output as the first laser processing step S10. Since the short second laser-processed groove 23 can be formed in the device region 17a, the non-defective product rate of device chips can be improved.

Next, a second embodiment will be described with reference to FIG. In the first laser processing step S10 of the second embodiment, a plurality of dot-shaped first laser processing holes 31 are annularly formed in the outer peripheral surplus region 17b. More specifically, the first laser-processed holes 31 are formed at both ends of one planned division line 15 (indicated by broken lines in FIG. 9).

FIG. 9 is a diagram showing the first laser processing step S10 according to the second embodiment. Each first laser-processed hole 31 is a cylindrical hole having a depth of about 9 μm and a diameter of about 20 μm. A denatured region (not shown) is formed along with the denaturation.

In the subsequent second laser processing step S20, from the first laser processing hole 31 formed at one end of the one scheduled division line 15, the first laser processing hole formed at the other end of the one scheduled division line 15 31, a second laser-processed groove 23 (see FIG. 5) is formed along the one scheduled division line 15 so as to pass through the first laser-processed hole 31 .

At the start of the second laser processing step S20, the focal point of the green laser beam L is positioned outside the wafer 11 from the first laser processing hole 31 formed at one end of one dividing line 15. good too.

Further, at the end of the second laser processing step S20, the focal point of the green laser beam L is positioned outside the wafer 11 with respect to the first laser processing hole 31 formed at the other end of one dividing line 15. may

In any case, in the second laser processing step S20, if the two first laser processing holes 31 formed at both ends of one dividing line 15 are scanned with the focal point, the second laser processing groove 23 can be formed. Also in the second embodiment, the second laser-processed groove 23 with good processing quality can be formed in the device region 17a.

In addition, the structures, methods, and the like according to the above-described embodiments can be modified as appropriate without departing from the scope of the present invention. For example, in the second laser processing step S20, the second laser processing groove 23 can be formed by a method other than the π-cut described above.

In addition, the wafer 11 having a single crystal substrate of silicon carbide (SiC), gallium arsenide (GaAs), or indium phosphide (InP) can also be processed according to the above-described processing method, without being limited to the single crystal substrate 13 of LT. .

2: laser processing device, 4: chuck table, 4a: holding surface 6: laser beam irradiation unit, 8: head unit, 10: microscope camera unit 11: wafer, 11a: front surface, 11b: back surface,
13: single crystal substrate, 13a: front surface, 13b: back surface, 15: planned dividing line 12: cutting device, 14: chuck table, 14a: holding surface 16: cutting unit, 18: spindle housing, 20: spindle 17: device, 17a: device region, 17b: outer peripheral surplus region 19: dicing tape 21: first laser processed groove 21a: depth, 21b: width, 21c: altered region, 21d: crack 22: cutting blade, 22a: blade thickness, 24: Blade cover, 26: Nozzle 23: Second laser-processed groove, 23a: Depth, 23b: Width 25: Laser-processed groove, 25a: Depth, 25b: Width, 25c: Remaining area 27: Cutting groove, 31: First Laser processing hole A ₁ : processing feed direction, A ₂ : indexing feed direction, A ₃ : height direction, B: predetermined distance L: green laser beam

Claims (3)

a device region in which a device is formed in each region partitioned by a plurality of planned division lines set on the surface; A wafer processing method for processing a wafer having an absorptive property with a pulsed green laser beam,
a first laser processing step of irradiating the wafer with the green laser beam along the outer periphery of the wafer to form an annular first laser-processed groove or first laser-processed hole in the outer peripheral surplus region;
After the first laser processing step, an output lower than the output of the green laser beam in the first laser processing step so as to pass through the first laser processing groove or first laser processing hole along each planned division line a second laser processing step of irradiating the wafer with the green laser beam to form a plurality of second laser processing grooves;
A wafer processing method comprising: After the second laser processing step, a dividing step of dividing the wafer along the plurality of second laser processing grooves with a cutting blade having a blade thickness smaller than the width of each second laser processing groove. 2. The method of processing a wafer according to claim 1, wherein: The wafer has a single crystal substrate of lithium tantalate,
In the first laser processing step, the first laser processing groove or the first laser processing hole is formed in the single crystal substrate,
3. The wafer processing method according to claim 1, wherein in the second laser processing step, the plurality of second laser processing grooves are formed in the single crystal substrate.

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