TW202412981A - Segmentation method of single crystal substrate and manufacturing method of device wafer - Google Patents

Abstract

[Topic] Suppress the decrease in yield rate by improving the processing quality of single crystal substrates. [Solution] A method for dividing a single crystal substrate is provided, wherein the single crystal substrate is cleaved for division. The method for dividing a single crystal substrate comprises the following steps: a holding step, wherein the single crystal substrate is held by a work clamp of a laser processing device, wherein a plurality of predetermined division lines along a first direction are provided on one side of the single crystal substrate in a manner along a predetermined crystal orientation for cleaving the single crystal substrate; a laser beam irradiation step, wherein after the holding step, a laser beam is irradiated from a laser beam irradiation unit of the laser processing device along each predetermined division line, thereby intermittently forming a promotion region for promoting the cleavage of the single crystal substrate along each predetermined division line; and a division step, wherein after the laser beam irradiation step, an external force is applied to the single crystal substrate, thereby cleaving the single crystal substrate along each predetermined division line, thereby dividing the single crystal substrate.

Description

Single crystal substrate dividing method and device chip manufacturing method

The present invention relates to a method for dividing a single crystal substrate by cleaving the single crystal substrate and a method for manufacturing a device chip by cleaving the single crystal substrate to manufacture a plurality of device chips.

When manufacturing light-emitting device chips such as LEDs (light emitting diodes) and LDs (laser diodes), a workpiece (i.e., a wafer) having a single crystal substrate may be used. After light-emitting elements are formed in each area demarcated by a plurality of predetermined dividing lines arranged in a grid pattern on the wafer, the wafer is divided along each predetermined dividing line.

As the material of the single crystal substrate, for example, sapphire, silicon carbide, and gallium nitride can be used. In addition, when dividing the wafer, a scriber having a blade portion formed of a high-hardness material such as diamond (i.e., a diamond scriber) can be used.

The following method is known: using this scriber to form scribe grooves along each predetermined dividing line, and then applying external force to the scribe grooves to divide the wafer (see, for example, Patent Document 1).

In addition, the following method has been proposed: when splitting a single crystal substrate, after setting the predetermined crystal orientation and the predetermined splitting line to be roughly parallel, after forming a score line groove along the predetermined splitting line, the single crystal substrate is split along each predetermined splitting line to split the wafer (see, for example, Patent Document 2). However, when the score line groove is formed relatively shallowly, even if an external force is applied to the single crystal substrate, an unsplit area will still be generated, and there is a problem that the single crystal substrate cannot be completely split.

On the other hand, when the scoring grooves are formed relatively deep, it is difficult to generate undivided areas when external force is applied to the single crystal substrate. However, when the scoring grooves are formed relatively deep, if the length direction of the scoring grooves deviates from the predetermined crystal orientation used for cleavage, cracks may occur in a direction obliquely intersecting the length direction of the predetermined splitting line. Prior art literature Patent literature

Patent document 1: Japanese Patent Publication No. 2015-207579 Patent document 2: Japanese Patent Publication No. 2012-119479

Invention Problems to be Solved

If cracks in such an inclined direction occur beyond the predetermined splitting line, the light-emitting device chip will be poorly manufactured, and the yield rate will be reduced. The present invention is made in view of the above-mentioned problem, and its purpose is to suppress the reduction of the yield rate by improving the processing quality of the single crystal substrate. Means for solving the problem

According to one aspect of the present invention, a method for splitting a single crystal substrate can be provided, wherein the splitting is performed by splitting the single crystal substrate, and the method for splitting the single crystal substrate comprises the following steps: A holding step, wherein the single crystal substrate is held by a work clamp of a laser processing device, wherein a plurality of predetermined splitting lines along a first direction are provided on one side of the single crystal substrate in a manner along a predetermined crystal orientation for splitting the single crystal substrate; A laser beam irradiation step, wherein after the holding step, a laser beam is irradiated from a laser beam irradiation unit of the laser processing device along each predetermined splitting line, thereby intermittently forming a promotion region for promoting the splitting of the single crystal substrate along each predetermined splitting line; and The splitting step, after the laser beam irradiation step, applies external force to the single crystal substrate to split the single crystal substrate along each predetermined splitting line, thereby splitting the single crystal substrate.

Preferably, in the holding step, the work clamp holds the other surface of the single crystal substrate on the opposite side to the one surface, and in the laser beam irradiation step, a laser beam having a wavelength that can be absorbed by the single crystal substrate is irradiated to intermittently form processing grooves having a depth that does not completely cut the single crystal substrate along each predetermined dividing line to serve as the promotion area.

Furthermore, it is preferred that, in the laser beam irradiation step, a first processing groove having a first depth is formed from the one surface at one end portion in the first direction of each predetermined dividing line as the promotion region, and a second processing groove having a second depth shallower than the first depth is intermittently formed in an area other than the one end portion of each predetermined dividing line as the promotion region, and in the dividing step, the single crystal substrate is divided by sequentially pushing a pressing blade from the one end portion toward the other end portion located on the opposite side of the one end portion.

Furthermore, preferably, in the laser beam irradiation step, a laser beam having a wavelength that penetrates the single crystal substrate is irradiated to intermittently form a weak region with reduced strength of the single crystal substrate along each predetermined dividing line as the promotion region.

Furthermore, it is preferred that, in the laser beam irradiation step, a first fragile region having a first depth is formed from the one surface at one end in the first direction of each predetermined splitting line as the promotion region, and a second fragile region having a second depth shallower than the first depth is intermittently formed in the region outside the one end of each predetermined splitting line as the promotion region, and in the splitting step, the single crystal substrate is split by sequentially pushing a pressing blade from the one end toward the other end located on the opposite side of the one end.

Furthermore, it is preferred that a plurality of predetermined splitting lines are further provided on the one surface of the single crystal substrate along a second direction orthogonal to the first direction, and in the laser beam irradiation step, when the promotion region is intermittently formed along each of the predetermined splitting lines along the first direction, the promotion region is formed in each of a plurality of intersection regions where the plurality of predetermined splitting lines along the first direction intersect with the plurality of predetermined splitting lines along the second direction.

Furthermore, it is preferred that a plurality of predetermined splitting lines are further provided on the one surface of the single crystal substrate along a second direction orthogonal to the first direction, and in the laser beam irradiation step, when the promotion region is intermittently formed along each predetermined splitting line along the first direction, the promotion region is formed in a region other than a plurality of intersection regions where the plurality of predetermined splitting lines along the first direction intersect with the plurality of predetermined splitting lines along the second direction.

According to other aspects of the present invention, a method for manufacturing a device chip can be provided, which is to manufacture a plurality of device chips by splitting a single crystal substrate, and the manufacturing method of the device chip has the following steps: A holding step, holding the single crystal substrate with a work clamp of a laser processing device, wherein the single crystal substrate is: a plurality of predetermined splitting lines arranged in a grid along a first direction and a second direction that intersect each other, and a plurality of predetermined splitting lines along the first direction are set on one side in a manner along a predetermined crystal orientation that can split the single crystal substrate; A first laser beam irradiation step, after the holding step, irradiating a laser beam from a laser beam irradiation unit of the laser processing device along each predetermined splitting line in the first direction, and intermittently forming a promotion area for promoting the splitting of the single crystal substrate along each predetermined splitting line in the first direction; A second laser beam irradiation step, after the holding step, irradiating the single crystal substrate with a laser beam from the laser beam irradiation unit along a plurality of predetermined splitting lines in the second direction, and forming a splitting starting point along each predetermined splitting line in the second direction; A first splitting step, after the first laser beam irradiation step and the second laser beam irradiation step, applying an external force to the promotion region of the single crystal substrate, so that the single crystal substrate is split along each predetermined splitting line in the first direction; and A second splitting step, after the first laser beam irradiation step and the second laser beam irradiation step, applying an external force to the splitting starting point of the single crystal substrate, so as to split the single crystal substrate, After the first splitting step and the second splitting step, the single crystal substrate is split into the plurality of device chips.

According to another aspect of the present invention, a method for splitting a single crystal substrate can be provided, which is to split the single crystal substrate by splitting. The method for splitting the single crystal substrate comprises the following steps: A holding step, in which the single crystal substrate is held by a work clamp of a laser processing device, wherein the single crystal substrate has a plurality of predetermined splitting lines along a first direction on one side in a manner along a predetermined crystal orientation for splitting the single crystal substrate; A laser beam irradiation step, in which after the holding step, a laser beam is irradiated from a laser beam irradiation unit of the laser processing device along each predetermined splitting line, and a promotion region for promoting the splitting of the single crystal substrate is formed in a range from the one side to a predetermined depth at one end of the predetermined splitting line in the first direction; and The splitting step, after the laser beam irradiation step, applies external force to the single crystal substrate by sequentially pushing the pressing blade from the one end toward the other end located on the opposite side of the one end, so as to split the single crystal substrate along the predetermined splitting line, thereby splitting the single crystal substrate.

Preferably, the predetermined depth is greater than 15% and less than 80% of the thickness of the single crystal substrate from the one surface to the other surface located on the opposite side of the one surface, and in the laser beam irradiation step, the promotion region is formed at the one end in the range from the one surface to the predetermined depth. Effect of the invention

In the single crystal substrate dividing method and device chip manufacturing method of the present invention, a laser beam is irradiated from a laser beam irradiation unit of a laser processing device, and a promotion area (laser beam irradiation step, first laser beam irradiation step) for promoting the splitting of the single crystal substrate is intermittently formed along each predetermined dividing line in the first direction.

In this way, since the promotion region for promoting the cleavage of the single crystal substrate is formed using a laser processing device, the depth position of the promotion region in the single crystal substrate becomes easier to control than when a diamond scriber is used to form a scribe groove. Therefore, the occurrence of undivided regions when dividing the single crystal substrate can be suppressed.

After the laser beam irradiation step, an external force is applied to the single crystal substrate to cleave the single crystal substrate along each predetermined dividing line in the first direction, thereby dividing the single crystal substrate (dividing step, first dividing step).

The promotion region intermittently formed along the predetermined splitting line in the laser beam irradiation step functions as a guide when the single crystal substrate is cleaved in the splitting step. Therefore, even if the long side direction of the promotion region has deviated from the predetermined crystal orientation, the generation of cracks in the oblique direction beyond the predetermined splitting line can still be suppressed. Therefore, the reduction in the yield rate during the manufacture of the light-emitting device wafer can be suppressed.

Furthermore, in a single crystal substrate splitting method in other aspects of the present invention, a promotion region for promoting the splitting of the single crystal substrate is formed in a range from one surface to a predetermined depth at one end in the first direction of a predetermined splitting line by irradiating a laser beam from a laser beam irradiation unit of a laser processing device (laser beam irradiation step).

Thus, since the depth position of the promotion region in the single crystal substrate becomes easier to control than when a diamond scriber is used to form a scribe groove, it is possible to suppress the occurrence of undivided regions when dividing the single crystal substrate.

After the laser beam irradiation step, the single crystal substrate is split along a predetermined splitting line in the first direction by applying an external force to the single crystal substrate by sequentially pushing a pressing blade from one end toward the other end located on the opposite side of the one end (splitting step).

Although the promotion area formed at one end in the laser beam irradiation step will become the start of cleavage, the single crystal substrate can be cleaved sequentially at the pushing position of the pushing blade by sequentially pushing the pushing blade from one end to the other end. Therefore, compared with the case where the pushing blade is pushed substantially simultaneously in the range from one end to the other end, the generation of cracks in the oblique direction can be suppressed, and thus the reduction in the yield rate during the manufacture of the light-emitting device wafer can be suppressed.

The form used to implement the invention

Referring to the attached drawings, an embodiment of the present invention is described. FIG1 is a flow chart of a method for dividing a single crystal substrate 13 (see FIG2(A) etc.) of a workpiece 11 of the first embodiment, and a method for manufacturing a plurality of light emitting device chips (device chips) 33 (see FIG11) by dividing the single crystal substrate 13 (see FIG2(A) etc.).

First, the workpiece 11 to be divided will be described. Fig. 2(A) is a perspective view of the workpiece 11, and Fig. 2(B) is a cross-sectional view of the workpiece 11 taken along line A-A in Fig. 2(A). The workpiece 11 is a wafer having a single crystal substrate 13 in a disk shape.

The single crystal substrate 13 is used as a substrate for forming the light emitting element 15. Although the single crystal substrate 13 of the present embodiment is formed of gallium arsenide (GaAs), the single crystal substrate 13 may also be formed of other compound semiconductor materials having a cleavable crystal orientation (e.g., indium phosphide (InP) or gallium nitride (GaN)).

The single crystal substrate 13 includes a first crystal orientation [0-11] and a second crystal orientation [011] which are orthogonal to each other. The first crystal orientation [0-11] is parallel to the first direction 11a shown in FIG. 2(A), and the second crystal orientation [011] is parallel to the second direction 11b shown in FIG. 2(A). The first direction 11a and the second direction 11b are also orthogonal to each other.

Since cracks are more likely to occur in the first crystal orientation [0-11] than in the second crystal orientation [011], the single crystal substrate 13 is more likely to be cleaved. Furthermore, although cracks are less likely to occur in the second crystal orientation [011] than in the first crystal orientation [0-11], the single crystal substrate 13 can be cleaved along the second crystal orientation.

That is, although both the first crystal orientation [0-11] and the second crystal orientation [011] are crystal orientations that can cleave the single crystal substrate 13, the first crystal orientation [0-11] is relatively easier to cleave.

Furthermore, even when the single crystal substrate 13 is formed of other compound semiconductor materials, it is still possible to appropriately select a first crystal orientation that is easier to cleave and a second crystal orientation that is more difficult to cleave than the first crystal orientation.

The single crystal substrate 13 is thinned to a predetermined thickness 13c by grinding or the like. The single crystal substrate 13 of this embodiment has a thickness 13c of 90 μm. The thickness 13c is the length from the front surface 13a to the back surface (other surface) 13b located on the opposite side of the front surface 13a.

On the front surface (one surface) 13a of the single crystal substrate 13, a plurality of first planned dividing lines 17a along the first direction 11a of the single crystal substrate 13 and a plurality of second planned dividing lines 17b along the second direction 11b of the single crystal substrate 13 are arranged in a grid pattern.

2 (A), although the first dividing line 17a is shown to be parallel to the first direction 11a, as described later, sometimes the first dividing line 17a is slightly deviated from the first direction 11a (see, for example, FIG. 9 (A)).

That is, the so-called first predetermined splitting line 17a is along the first direction 11a, including the case where the first predetermined splitting line 17a is completely parallel to the first direction 11a, and the case where the first predetermined splitting line 17a deviates slightly (for example, about 1 to 2 degrees). The second predetermined splitting line 17b is also along the second direction 11b.

The first predetermined splitting line 17a and the second predetermined splitting line 17b are orthogonal (crossed). In this embodiment, the width of each of the first predetermined splitting line 17a and the second predetermined splitting line 17b (the length of the direction orthogonal to the length direction) is 20 μm, but the width of the predetermined splitting line (i.e., the cutting path) is not limited to this value.

Light emitting elements 15 such as LEDs and LDs are formed in each of the rectangular regions defined by the plurality of first predetermined dividing lines 17a and the plurality of second predetermined dividing lines 17b. The number of light emitting elements 15 is not limited to the example shown in FIG. 2(A) and the like.

After the workpiece 11 is thinned and before the workpiece 11 is subjected to laser processing, a workpiece unit 23 is formed in which the workpiece 11 is supported by a metal ring frame 21 through a resin protective tape 19 as shown in FIG. 3 .

Specifically, the workpiece unit 23 is formed by attaching the central portion of the circular protective tape 19 to the back surface 13 b side of the single crystal substrate 13 and attaching the outer peripheral portion of the protective tape 19 to one surface of the ring frame 21 .

Next, laser processing is performed on the single crystal substrate 13 of the workpiece unit 23 using the laser processing device 2 (see FIG. 3 ). Here, the laser processing device 2 is described with reference to FIG. 3 and FIG. 4 . The laser processing device 2 has a disk-shaped worktable 4 .

The work clamp 4 has a disc-shaped frame body formed of metal. A disc-shaped recess (not shown) is formed in the center of the frame body, and a disc-shaped porous plate (not shown) formed of porous ceramics is fixed to the recess.

The frame is connected to a suction source such as a vacuum pump (not shown). When the negative pressure from the suction source is transmitted to the porous plate through the frame, negative pressure is generated on the upper surface of the porous plate. The upper surface of the frame and the upper surface of the porous plate become roughly flush and function as a roughly flat holding surface for sucking and holding the workpiece 11.

The holding surface is arranged to be substantially parallel to the X-Y plane formed by the X-axis direction (processing feed direction) and the Y-axis direction (indexing feed direction). Furthermore, the X-axis direction, the Y-axis direction, and the Z-axis direction (vertical direction, up-down direction) are orthogonal to each other.

A plurality of clamping units (not shown) are provided at substantially equal intervals on the outer periphery of the work clamping table 4 along the circumferential direction of the work clamping table 4. Each clamping unit clamps the annular frame 21 of the workpiece unit 23.

The worktable 4 is supported by a worktable rotating mechanism (not shown) including a rotating drive source (not shown) such as a motor. When the rotating drive source is operated, the worktable 4 can be rotated around a predetermined rotating axis along the Z-axis direction.

The table rotation mechanism is supported by a horizontal movement mechanism (not shown). The horizontal movement mechanism includes a ball screw type X-axis movement mechanism and a Y-axis movement mechanism (both not shown).

The horizontal direction moving mechanism can move the worktable rotating mechanism and the work clamping table 4 along the X-axis direction and the Y-axis direction. That is, the horizontal direction moving mechanism can perform processing feeding and indexing feeding of the work clamping table 4.

The horizontal moving mechanism is fixed on the base (not shown) of the laser processing device 2. A column (not shown) is provided at one end of the base in the Y-axis direction. The column has its long side arranged along the Z-axis direction and its upper end is located above the horizontal moving mechanism.

A ball screw type Z-axis direction moving mechanism (not shown) is provided on the column. The Z-axis direction moving mechanism includes a moving plate (not shown) that can move along the Z-axis direction, and a laser beam irradiation unit 6 (refer to FIG. 4 ) is fixed on the moving plate.

The laser beam irradiation unit 6 has a laser oscillator (not shown). The laser oscillator includes, for example, Nd:YVO ₄ crystal as a laser medium. From the laser oscillator, a pulsed laser beam having a wavelength of 1064 nm can be emitted by Q-switch pulse oscillation.

The laser beam is irradiated to the workpiece 11 after its wavelength is converted according to the need. For example, the wavelength of the pulsed laser beam emitted from the laser oscillator is irradiated to the workpiece 11 after it is converted to a wavelength of 355nm (a wavelength that can be absorbed by the single crystal substrate 13) through the nonlinear optical crystal provided in the laser beam irradiation unit 6.

The wavelength-converted laser beam is incident on an acousto-optic modulator (hereinafter referred to as AOM) (not shown) provided in the laser beam irradiation unit 6. The AOM can be controlled by an electrical signal.

The AOM has a switching function for switching between irradiation of the laser beam to the workpiece 11 (output on state) and non-irradiation of the laser beam to the workpiece 11 (output off state) according to the designation formed by the input electrical signal.

The laser beam irradiation unit 6 has a cylindrical housing 8 arranged with its long side along the Y-axis direction. An irradiation head 10 is fixed to the front end of the housing 8. The irradiation head 10 accommodates a condenser lens (not shown) and the like.

From the irradiation head 10 of this embodiment, a pulsed laser beam L having a wavelength (e.g., 355 nm) that can be absorbed by the single crystal substrate 13 is irradiated toward the holding surface of the worktable 4 along the Z-axis direction via nonlinear optical crystal, AOM, etc.

A microscope camera unit 12 is fixed near the irradiation head 10. The microscope camera unit 12 includes an object lens and a CCD (charge-coupled device) image sensor and other photographing elements.

Furthermore, a light source such as an LED used for photographing is provided in the microscope camera unit 12. The housing 8, the irradiation head 10, the microscope camera unit 12, etc. can be integrally moved in the Z-axis direction by a Z-axis direction moving mechanism.

The actions of the work clamp 4, the suction source, the plurality of clamp units, the rotation drive source, the horizontal movement mechanism, the Z-axis movement mechanism, the laser beam irradiation unit 6, the microscope camera unit 12, etc. can be controlled by the control unit (not shown) of the laser processing device 2.

The control unit can be constituted by a computer, which includes a processor (processing device) represented by a CPU (Central Processing Unit), a main memory device such as DRAM (Dynamic Random Access Memory) and SRAM (Static Random Access Memory), and an auxiliary memory device such as a flash memory and a hard disk drive.

The auxiliary memory device stores software including a predetermined program. By operating the processing device and the like according to the software, the function of the control unit can be realized. Next, referring to FIG. 7 and FIG. 8, a breaking device 14 used when dividing the single crystal substrate 13 after laser processing is described.

The fracture device 14 has a support table 16 for supporting the workpiece 11 that has been laser processed. The support table 16 has a recess 16b on its upper surface 16a, and the recess 16b is formed so that the long side is along a predetermined direction (in the example shown in FIG. 8 , the depth direction of the paper surface) (refer to FIG. 8 ). The long side of the recess 16b is longer than the diameter of the single crystal substrate 13.

A pressing blade 18 is provided above the support table 16. The pressing blade 18 is arranged along a predetermined direction (in the example shown in FIG. 8 , the depth direction of the paper) so that a straight lower end 18a covers the longitudinal direction of the pressing blade 18 at the same height.

The length of the long side of the push blade 18 is longer than the diameter of the single crystal substrate 13, and a first ball screw type moving mechanism (not shown) for pushing the push blade 18 downward is provided on the upper portion of the push blade 18. By pushing the push blade 18 downward by the first moving mechanism, a downward external force can be applied to the single crystal substrate 13 disposed on the support table 16.

Next, a dividing method for dividing the single crystal substrate 13 by cleaving and a method for manufacturing a plurality of light emitting device chips 33 by dividing the single crystal substrate 13 will be described according to the flow chart shown in FIG. 1 .

First, the workpiece unit 23 is placed on the work table 4, and the back surface 13b of the single crystal substrate 13 is sucked and held by the holding surface of the work table 4 via the protective tape 19 (holding step S10). Fig. 3 is a diagram showing the holding step S10.

After step S10 is maintained, the microscope camera unit 12 is used to photograph the front side 13a to calculate the deviation of the first predetermined splitting line 17a from the X-axis direction (i.e., calibration is performed). Then, the direction of the work clamp 4 in the X-Y plane is adjusted so that the first predetermined splitting line 17a becomes approximately parallel to the X-axis direction.

Then, the work table 4 is fed at a predetermined speed while the focal point of the laser beam L is positioned at a height position near the front surface 13a at one end of the first predetermined dividing line 17a. The processing conditions in the laser beam irradiation step S20 are set as follows, for example.

Wavelength: 355nm Average output: 0.5W Repetition frequency: 160kHz Processing feed speed: 10mm/sec Number of passes: 1

The number of passes means the number of times the single crystal substrate 13 is irradiated with the laser beam L at a predetermined processing feed speed along one first predetermined dividing line 17 a (or one second predetermined dividing line 17 b ).

For example, when the number of passes is 2, the focal point of the laser beam L is moved from one end to the other end at a predetermined processing feed speed (first pass), and then moved from the other end to one end at a predetermined processing feed speed (second pass).

In the laser beam irradiation step S20 of the present embodiment, the irradiation and non-irradiation of the laser beam L are controlled along the first predetermined splitting line 17a using the above-mentioned AOM, and processing grooves (promotion areas) 25a for promoting the cleavage of the single crystal substrate 13 are intermittently formed along the first predetermined splitting line 17a.

4 is a diagram showing the laser beam irradiation step (first laser beam irradiation step) S20. In the present embodiment, the processing grooves 25a are intermittently formed along the first planned dividing line 17a so as to avoid the side regions of the light emitting element 15.

Specifically, processing grooves 25a are formed in two end regions 13d and a plurality of intersection regions 13e. The end region 13d is a region located further outside the single crystal substrate 13 than the intersection region 13e of a first predetermined splitting line 17a and a second predetermined splitting line 17b located on the outermost side. The intersection region 13e is a region where a plurality of first predetermined splitting lines 17a and a plurality of second predetermined splitting lines 17b intersect.

After forming the processing groove 25a along one first predetermined dividing line 17a, the work clamp 4 is indexed and fed, and processing grooves 25a are intermittently formed along other first predetermined dividing lines 17a adjacent to the first predetermined dividing line 17a that has just been processed in the Y-axis direction.

In this way, processing grooves 25a are intermittently formed along all the first planned dividing lines 17a. As shown in FIG5, processing grooves 25a have a predetermined depth _25a1 that does not completely cut the single crystal substrate 13. The predetermined depth _25a1 is, for example, 5% or more and less than 15% of the thickness 13c of the single crystal substrate 13 from the front surface 13a.

In the present embodiment where the thickness 13c of the single crystal substrate 13 is 90 μm, the predetermined depth _25a1 is 10 μm (approximately 11%) from the front surface 13a. Fig. 5 is a cross-sectional view of the workpiece 11 after the laser beam irradiation step S20.

After the laser beam irradiation step S20, the microscope camera unit 12 is used to photograph the front side 13a, and then the direction of the work clamp 4 is adjusted so that the second predetermined dividing line 17b becomes substantially parallel to the X-axis direction.

Then, with the focal point _LP of the laser beam L (see FIG6) positioned at one end of a second planned dividing line 17b in the single crystal substrate 13, the worktable 4 is fed at a predetermined speed (second laser beam irradiation step S30).

Fig. 6 is a diagram showing the second laser beam irradiation step S30. The processing conditions in the second laser beam irradiation step S30 are set as follows, for example.

Wavelength: 355nm Average output: 1.5W Repetition frequency: 160kHz Processing feed speed: 10mm/sec Number of passes: 1

In the second laser beam irradiation step S30, the laser beam L is irradiated from the irradiation head 10 along each second planned dividing line 17b, thereby forming a processing groove (dividing starting point) 25b along each second planned dividing line 17b of the single crystal substrate 13.

In this embodiment, the processing groove 25b is formed continuously along the second planned dividing line 17b, but the processing groove 25b may be formed intermittently along the second planned dividing line 17b. The processing groove 25b has a predetermined depth _25b1 (see FIG. 10(B)) that does not completely cut the single crystal substrate 13.

The predetermined depth _25b1 is deeper than the predetermined depth _25a1 of the processed groove 25a. The predetermined depth _25b1 is not less than 15% and not more than 80% of the thickness 13c of the single crystal substrate 13, and preferably not less than 20% and not more than 50%.

As described above, the single crystal substrate 13 is more difficult to cleave in the second direction 11b than in the first direction 11a. Therefore, in this embodiment, the processing groove 25b is formed deeper than the processing groove 25a. This can suppress the generation of undivided areas in the second dividing step S50.

Furthermore, in the second laser beam irradiation step S30, although the average output of the laser beam L is increased, the processing feed speed may be set lower or the number of passes may be increased instead of or in addition to the increase in the average output.

If the processing feed speed is set to be slower, the energy irradiated per unit time in the unit area will increase, so the effect similar to the case of increasing the average output can be obtained. In addition, if the number of passes is increased, the time for irradiating the laser beam L in the unit area will increase, so the effect similar to the case of increasing the average output can be obtained.

Furthermore, in the present embodiment, although the second laser beam irradiation step S30 is performed after the laser beam irradiation step S20, the laser beam irradiation step S20 may also be performed after the second laser beam irradiation step S30.

After the laser beam irradiation step S20 and the second laser beam irradiation step S30, the single crystal substrate 13 is divided using the breaking device 14 (dividing step (first dividing step) S40).

FIG. 7 is a partial cross-sectional side view showing the segmentation step S40 , and FIG. 8 is a partial cross-sectional side view showing the segmentation step S40 when viewed from a direction 90 degrees different from that of FIG. 7 .

In the dividing step S40, first, the release paper 19a that was originally attached to the adhesive layer of the protective tape 19 is arranged on the front surface 13a side of the single crystal substrate 13. At this time, the release paper 19a is attached to the protective tape 19 by the adhesive layer exposed between the single crystal substrate 13 and the annular frame 21, and is integrated with the workpiece unit 23.

Next, the position of the single crystal substrate 13 on the upper side is adjusted so that the processing grooves 25a intermittently formed along one of the first predetermined dividing lines 17a are located on the recessed portion 16b. Furthermore, at this time, the single crystal substrate 13 is placed on the support table 16 with the front surface 13a facing downward and the back surface 13b facing upward.

Thereafter, by pushing the pressing blade 18 into the recess 16b, a downward external force is applied from the rear surface 13b to the single crystal substrate 13. Thus, the single crystal substrate 13 can be cleaved along one first planned dividing line 17a.

After the single crystal substrate 13 is cleaved along one of the first planned splitting lines 17a, external force is applied similarly along other first planned splitting lines 17a adjacent to the first planned splitting line 17a that has just been split. Thus, the single crystal substrate 13 is cleaved along other first planned splitting lines 17a. Similarly, the single crystal substrate 13 is cleaved along all the first planned splitting lines 17a.

In this embodiment, since the processing groove 25a for promoting the cleavage of the single crystal substrate 13 is formed by using the laser processing device 2, the depth position of the processing groove 25a in the single crystal substrate 13 can be more easily controlled compared to the case where a diamond scriber is used to form the scribe groove 29.

When a diamond scriber is used, the depth position of the processed groove 25a is relatively difficult to control due to the material, type and shape of the blade, the angle at which the blade contacts the front surface 13a, and the jumping and landing of the blade during processing (so-called jumping).

In contrast, in the case of the laser processing device 2, the depth of the processing groove 25a can be precisely controlled by parameters such as output and processing feed speed. Therefore, compared with the case of using a diamond scriber, the occurrence of undivided areas when dividing the single crystal substrate 13 can be suppressed.

Furthermore, the processing grooves 25a intermittently formed along each of the first predetermined splitting lines 17a function as guides when splitting the single crystal substrate 13 in the splitting step S40. Therefore, even if the processing grooves 25a are formed in a manner such that the long side direction deviates from the predetermined crystal orientation, the generation of cracks 31a (see FIG. 9(B)) that extend beyond the first predetermined splitting lines 17a can be suppressed.

Therefore, compared with the conventional method of forming the scoring grooves 29 along the planned dividing lines and then applying external force along the scoring grooves 29 to cleave the single crystal substrate 13, the yield rate of the light emitting device wafer 33 (see FIG. 11) can be suppressed from decreasing.

Here, the crack 31a in the oblique direction generated when the ruled groove 29 is formed along the first planned dividing line 17a as in the conventional method will be described using Fig. 9(A) and Fig. 9(B). Fig. 9(A) is a diagram showing the continuous ruled groove 29.

In Fig. 9(A) and Fig. 9(B), the first planned dividing line 17a is slightly offset from the first direction 11a (that is, the first crystal orientation [0-11]). The amount of offset is the same in Fig. 9(C) and Fig. 9(D) described later.

When an external force is applied by the breaking device 14 with the ruled groove 29 formed as shown in FIG8 , the single crystal substrate 13 is split along the first direction 11a, and the dividing groove 31 exceeds the first predetermined dividing line 17a and generates a crack 31a in an oblique direction (see FIG9(B)).

In FIG9(B), the dividing groove 31 is represented by a thicker line than the line groove 29. FIG9(B) is a diagram showing a situation where a crack 31a in an inclined direction is generated. If the dividing groove 31 exceeds the first predetermined dividing line 17a or reaches the light-emitting element 15 due to the crack 31a in the inclined direction, it will become a manufacturing defect of the light-emitting device wafer 33, and the yield rate will be reduced.

In contrast, FIG. 9(C) and FIG. 9(D) illustrate the intermittent processing grooves 25a formed by the laser beam irradiation step S20 of the present embodiment functioning as guides during cleavage.

Fig. 9(C) is a diagram showing the intermittent processing grooves 25a, and Fig. 9(D) is a diagram showing the intermittent processing grooves 25a as a guide to split the single crystal substrate 13. In Fig. 9(C) and Fig. 9(D), the first planned splitting line 17a is also slightly offset from the first direction 11a.

However, as shown in Fig. 9(D), since the dividing grooves 31 are formed so that the region between the two processing grooves 25a is connected to the processing grooves 25a, the dividing grooves 31 do not reach the light emitting element 15. Therefore, the yield of the light emitting device wafer 33 can be suppressed from decreasing.

After the dividing step S40, an external force is applied to each processing groove 25b of the single crystal substrate 13, thereby dividing the single crystal substrate 13 into a plurality of light emitting device wafers (device wafers) 33 (second dividing step S50).

FIG. 10(A) is a partial cross-sectional side view showing the second segmentation step S50, and FIG. 10(B) is a partial cross-sectional side view showing the second segmentation step S50 when viewed from a direction 90 degrees different from FIG. 10(A).

In the second splitting step S50, the same breaking device 20 as the breaking device 14 used in the splitting step S40 is used. However, in the breaking device 20, the lower end 22a of the pressing blade 22 is arranged to be inclined relative to the upper surface 16a of the support table 16.

More specifically, as shown in FIG. 10(A), the push blade 22 is arranged so that the height position of one end _22b1 of the lower end 22a of the push blade 22 becomes lower than the height position of the other end _22b2 . A first moving mechanism (not shown) of a ball screw type for pushing the push blade 22 downward is provided on the upper portion of the push blade 22, similarly to the breaking device 14.

When the first moving mechanism pushes the pressing blade 22 downward, the pressing blade 22 pushes sequentially from one end _17b1 of the second predetermined splitting line 17b toward the other end _17b2 . As described above, since cleavage is more difficult to occur in the second direction 11b than in the first direction 11a, it is difficult to split the single crystal substrate 13 on the second predetermined splitting line 17b.

However, in the second splitting step S50, by sequentially pushing the pressing blade 22 from one end _17b1 toward the other end _17b2 of the second predetermined splitting line 17b, it becomes easy to partially cleave the single crystal substrate 13 in the crystal orientation parallel to the second direction 11b while still splitting the single crystal substrate 13 at the pushed position of the lower end 22a of the pressing blade 22. Therefore, the single crystal substrate 13 can be split substantially parallel to the second predetermined splitting line 17b.

In this manner, the single crystal substrate 13 is divided into light emitting device wafers 33 using the breaking device 20. FIG11 is a perspective view of the light emitting device wafer 33. As shown in FIG11 , the single crystal substrate 13 is divided into light emitting device wafers 33. As shown in FIG11 , the light emitting device wafer 33 is shown in FIG11 .

In the second splitting step S50, since the pushing blade 22 is pushed sequentially from one end _17b1 toward the other end _17b2 , compared with the case where the pushing blade 22 is pushed approximately simultaneously in the range from one end _17b1 to the other end _17b2 , the occurrence of cracks in the oblique direction can be suppressed, thereby suppressing the reduction in the yield rate during the manufacture of the light-emitting device chip 33.

Furthermore, in the present embodiment, although the second segmentation step S50 is performed after the segmentation step S40, the segmentation step S40 may also be performed after the second segmentation step S50.

(Second Embodiment) Next, the second embodiment will be described with reference to Figures 12 to 14. Figure 12 is a cross-sectional view of the workpiece 11 after the laser beam irradiation step S20 in the second embodiment.

In the second embodiment, in the laser beam irradiation step S20 following the holding step S10, a first processing groove (promotion region) 25c having a first depth _25c1 is formed from the front surface 13a at one end _17a1 of each first predetermined dividing line 17a (see FIG. 12).

An end portion _17a1 refers to an area which is located on the outer peripheral side of the single crystal substrate 13 in the length direction of the first predetermined splitting line 17a, compared with the intersection area 13e of the second predetermined splitting line 17b located at the outermost periphery of the single crystal substrate 13 and the first predetermined splitting line 17a, and corresponds to one of the two end areas 13d mentioned above.

When forming the first processing groove 25c, the processing conditions used when forming the processing groove 25b described above can be applied. The first depth _25c1 of the first processing groove 25c is not less than 15% and not more than 80% of the thickness 13c of the single crystal substrate 13, preferably not less than 20% and not more than 50%.

In the present embodiment in which the thickness 13c of the single crystal substrate 13 is 90 μm, the first depth _25c1 is 30 μm (approximately 33%) from the front surface 13a.

Furthermore, in the second embodiment, in the area other than one end _17a1 of each first predetermined dividing line 17a (specifically, the other end _17a2 and each intersection area 13e), a second processing groove (promotion area) 25d having a second depth _25d1 shallower than the first depth _25c1 is intermittently formed.

When forming the second processing groove 25d, the processing conditions used when forming the processing groove 25a described above may be applied. The second depth _25d1 of the second processing groove 25d may be, for example, not less than 5% and not more than 10% of the single crystal substrate 13.

Furthermore, in the first planned dividing line 17a, the second processing groove 25d is not connected to the first processing groove 25c but is separated from the first processing groove 25c. It does not matter which of the first processing groove 25c and the second processing groove 25d is formed first.

Furthermore, in the splitting step S40, the breaking device 20 shown in FIG. 10(A) is used to sequentially push the pressing blade 22 from one end _17a1 toward the other end _17a2 of the first predetermined splitting line 17a (see FIG. 13(A) and FIG. 13(B)).

Thus, the single crystal substrate 13 can be split along the first predetermined splitting line 17a. Fig. 13(A) shows the state where the pressing blade 22 is pushed against one end _17a1 , and Fig. 13(B) shows the state where the pressing blade 22 is pushed toward the other end _17a2 side relative to the one end _17a1 .

Incidentally, in the splitting step S40, a breaking device 26 having an annular push blade 24 rotatable around a rotation axis 24a may be used instead of the push blade 22 whose lower end 22a is arranged obliquely with respect to the upper surface 16a of the support table 16.

Fig. 14(A) is a diagram showing a state when the pressing blade 24 of the breaking device 26 is pressed against one end _17a1 . Fig. 14(B) is a diagram showing a state when the pressing blade 24 is pressed against the other end _17a2 .

In this way, by moving the pressing blade 24 along the first planned dividing line 17a while rotating, the pressing blade 24 can be pressed sequentially from the one end _17a1 toward the other end _17a2 .

Furthermore, in the second embodiment, the light emitting device chip 33 can be manufactured by performing the second laser beam irradiation step S30 after the laser beam irradiation step S20, and then performing the dividing step S40 and the second dividing step S50.

(Third Embodiment) Next, the third embodiment will be described with reference to Fig. 15. Fig. 15 is a cross-sectional view of the workpiece 11 after the holding step S10 and the laser beam irradiation step S20 in the third embodiment.

In the holding step S10, as shown in Fig. 3, the work chuck 4 holds the back surface 13b side by suction so that the front surface 13a of the single crystal substrate 13 is exposed. However, the work chuck 4 may also hold the front surface 13a side by suction so that the back surface 13b is exposed.

Furthermore, when the front side 13a is held by suction by the work clamp 4, a holding plate (not shown) formed of substantially transparent glass and having a plurality of suction holes capable of transmitting negative pressure may be fixed to the recess of the work clamp 4. In addition, the front side 13a may be photographed from below by disposing the microscope camera unit 12 below the substantially transparent holding plate.

Furthermore, the substantially transparent retaining plate may be replaced by an infrared camera in the microscope camera unit 12 shown in Fig. 3. Thus, the front side 13a can be photographed from above by penetrating the back side 13b.

In the laser beam irradiation step S20 of the third embodiment, a laser beam L having a wavelength that can penetrate the single crystal substrate 13 is used instead of a wavelength that can be absorbed by the single crystal substrate 13 to perform so-called stealth dicing (SD).

In the present embodiment in which the single crystal substrate 13 is formed of gallium arsenide, a pulsed laser beam L having a wavelength of 1064 nm is irradiated to the single crystal substrate 13. This wavelength can be achieved by, for example, omitting wavelength conversion in the laser beam irradiation unit 6 described above.

In the laser beam irradiation step S20 of the third embodiment, the worktable 4 is fed at a predetermined speed while the focal point _LP of the laser beam L is positioned at a height position near the front surface 13a at one end of the first predetermined dividing line 17a.

Although the processing conditions in the laser beam irradiation step S20 can be set as follows, for example, they are not limited to the processing conditions of this example.

Wavelength: 1064nm Average output: 0.3W Repetition frequency: 160kHz Processing feed speed: 300mm/sec Number of passes: 1

In the laser beam irradiation step S20 of the present embodiment, the processing grooves 25a, 25b, the first processing groove 25c, and the second processing groove 25d are replaced, and a fragile area (promotion area) _25e of the single crystal substrate 13 whose strength is lower than that of the irradiation area of the laser beam L is formed in the range from the front surface 13a to a predetermined depth 25e1.

The fragile region 25e includes a region where crystallinity has been deteriorated due to multiphoton absorption, and cracks extending from the region toward the front surface 13a and the back surface 13b.

In the present embodiment, the irradiation and non-irradiation of the laser beam L along the first planned dividing line 17a are controlled, so that the fragile region 25e is intermittently formed along the first planned dividing line 17a.

In the second laser beam irradiation step S30 after the laser beam irradiation step S20, although the processing groove 25b can be formed in the single crystal substrate 13 by etching under the same processing conditions as the first embodiment, invisible cutting can also be performed under the following processing conditions.

Wavelength: 1064nm Average output: 0.3W Repetition frequency: 160kHz Processing feed speed: 300mm/sec Number of passes: 2

Furthermore, when the focal point _LP of the laser beam L in the first pass has been positioned at a predetermined depth, in the second pass, in order to suppress the scattering of the laser beam L on the fragile area 25e formed in the first pass, the focal point _LP of the laser beam L is positioned at a depth closer to the front surface 13a (or the back surface 13b when the back surface 13b is exposed upward) than the height position of the focal point _LP in the first pass.

By increasing the number of passes in this way, the single crystal substrate 13 can be easily cleaved in the second direction 11b, which is more difficult to cleave than in the first direction 11a. The number of passes is not limited to 2, and may be 3 or more.

By performing the dividing step S40 and the second dividing step S50 after the laser beam irradiation step S20 and the second laser beam irradiation step S30, the light emitting device wafer 33 can be manufactured. The contents described in the first and second embodiments can be applied to the dividing step S40 and the second dividing step S50.

(Fourth Embodiment) Next, the fourth embodiment will be described with reference to Fig. 16. Fig. 16 is a cross-sectional view of the workpiece 11 after the holding step S10 and the laser beam irradiation step S20 in the fourth embodiment.

In the fourth embodiment, in the laser beam irradiation step S20 subsequent to the holding step S10, a first fragile region (promotion region) 25f having a first depth _25f1 is formed at one end portion _17a1 of each first predetermined dividing line 17a from the front surface 13a.

When forming the first fragile region 25f, the processing conditions used when forming the above-mentioned two or more fragile regions 25e can be applied. The first depth _25f1 of the first fragile region 25f is not less than 15% and not more than 80% of the single crystal substrate 13, preferably not less than 20% and not more than 50%.

Furthermore, in the fourth embodiment, in the region other than the one end _17a1 of each first predetermined dividing line 17a (specifically, the other end _17a2 and each intersection region 13e), a second fragile region (promotion region) 25g having a second depth _25g1 shallower than the first depth _25f1 is intermittently formed.

When forming the second fragile region 25g, the processing conditions used when forming the above-mentioned fragile region 25e may be applied. The second depth _25g1 of the second fragile region 25g may be, for example, not less than 5% and not more than 10% of the single crystal substrate 13.

Furthermore, the second fragile region 25g which is closest to the first fragile region 25f in the first planned dividing line 17a is not connected to the first fragile region 25f but is separated from it.

In the splitting step S40 following the laser beam irradiation step S20 and the second laser beam irradiation step S30, the breaking devices 20 and 26 are used to sequentially push the pushing blades 22 and 24 from one end _17a1 of the first predetermined splitting line 17a toward the other end _17a2 (refer to Figures 13(A), 13(B), 14(A) and 14(B)).

Thus, the single crystal substrate 13 can be cleaved along the first planned dividing line 17a to be divided. By performing the second dividing step S50 after the dividing step S40, the light emitting device wafer 33 can be manufactured.

(Fifth Embodiment) Next, the fifth embodiment will be described with reference to Fig. 17. Fig. 17 is a diagram showing the laser beam irradiation step S20 after the holding step S10 in the fifth embodiment.

In the laser beam irradiation step S20 of the fifth embodiment, when the processing grooves 25a are intermittently formed along each first predetermined splitting line 17a, the processing grooves 25a are formed by etching in a plurality of non-intersecting areas 13f except for a plurality of intersecting areas 13e where a plurality of first predetermined splitting lines 17a intersect with a plurality of second predetermined splitting lines 17b.

The non-intersection region 13f includes a straight line region between adjacent intersection regions 13e and an end region 13d. In this embodiment, since a laser processing device is also used, it becomes easy to control the depth position of the processing groove 25a in the single crystal substrate 13. In addition, since the processing groove 25a is formed intermittently, the generation of cracks such as those exceeding the tilt direction of the first predetermined dividing line 17a can be suppressed.

In the fifth embodiment, after the laser beam irradiation step S20, the steps are sequentially performed from the second laser beam irradiation step S30 to the second dividing step S50 in the same manner as in the first embodiment, thereby manufacturing the light emitting device chip 33.

In particular, in the fifth embodiment, since the processing groove 25a is not formed in the intersection region 13e, the single crystal substrate 13 is divided only by pure cleavage without forming a processing mark of the etching process in the intersection region 13e.

Therefore, compared with the case where the single crystal substrate 13 is divided after the processing groove 25a is formed in the intersection region 13e, there is the following advantage: defects in the area corresponding to the intersection region 13e on the light-emitting device wafer 33 become difficult to occur.

Furthermore, in the laser beam irradiation step S20 of the present embodiment, as in the second embodiment (FIG. 12), a first processing groove 25c having a first depth _25c1 may be formed at one end _17a1 , and a second processing groove _25d having a second depth _25d1 shallower than the first depth _25c1 may be intermittently formed in each non-intersecting area 13f outside the one end 17a1.

Furthermore, in the splitting step S40 of the present embodiment, the pressing blades 22, 24 may be sequentially pushed from one end _17a1 toward the other end _17a2 of the first predetermined splitting line 17a as shown in the second embodiment (FIGS. 13(A), 13(B), 14(A) and 14(B)).

By the way, in the laser beam irradiation step S20 of the present embodiment, the method of forming the processing groove 25a by ablation processing can also be replaced by forming the fragile area 25e, or the first fragile area 25f and the second fragile area 25g by invisible cutting as shown in the third embodiment (Figure 15) and the fourth embodiment (Figure 16).

(Sixth embodiment) Next, the sixth embodiment is described with reference to Fig. 18(A). In the sixth embodiment, after the step S10 is maintained, a first processing groove (promotion region) 25c having a first depth 25c1 is formed from the front surface _13a at one end 17a1 of each first predetermined dividing line _17a in the same manner as in Fig. 12 (laser beam irradiation step S20).

However, in the laser beam irradiation step S20 of the sixth embodiment, the processing grooves 25a are not intermittently formed along the first predetermined dividing lines 17a, but the first processing grooves 25c are formed by etching only in the range from the front surface 13a to the first depth _25c1 (predetermined depth) in one end portion _17a1 .

Fig. 18(A) is a cross-sectional view of the workpiece 11 after the holding step S10 and the laser beam irradiation step S20 in the sixth embodiment. In the splitting step S40 after the laser beam irradiation step S20 and the second laser beam irradiation step S30, the breaking device 20 (Fig. 13(A)) or the breaking device 26 (Fig. 14(A)) is used.

That is, in the splitting step S40, the push blade 22 or the push blade 24 is sequentially pushed from one end _17a1 of each first predetermined splitting line 17a toward the other end _17a2 . Thus, an external force is applied to the single crystal substrate 13, so that the single crystal substrate 13 is split along each first predetermined splitting line 17a, thereby splitting the single crystal substrate 13.

In the sixth embodiment, since the first processing groove 25c is formed by using the laser processing device 2, the depth position of the first processing groove 25c in the single crystal substrate 13 can be controlled more easily than when a diamond scriber is used to form the scribe groove 29. Therefore, the occurrence of undivided areas when dividing the single crystal substrate 13 can be suppressed.

Furthermore, the first processing groove 25c formed at one end _17a1 in the laser beam irradiation step S20 will become the start of cleavage, and the single crystal substrate 13 will be cleaved along the straight line area pushed sequentially by the pushing blade 22 or the pushing blade 24 from one end _17a1 to the other end _17a2 .

In contrast, when the pressing blade 18 is pushed approximately perpendicularly against the back surface 13b of the single crystal substrate 13 having the ruled groove 29 formed therein, cracks 31a in an oblique direction may occur due to a slight deviation of the first predetermined dividing line 17a from the first direction 11a (see FIG. 8(B)).

However, as shown in this embodiment, by sequentially pressing the pressing blade 22 or the pressing blade 24 from one end _17a1 to the other end _17a2 , the single crystal substrate 13 can be cleaved sequentially at the pressing position of the pressing blade 22 or the pressing blade 24. Therefore, the generation of cracks 31a in the oblique direction can be suppressed.

In the sixth embodiment, the light emitting device chip 33 can be manufactured by performing the second dividing step S50 after the dividing step S40 in the same manner as in the first embodiment.

(Seventh Embodiment) Next, the seventh embodiment will be described with reference to Fig. 18(B). Fig. 18(B) is a cross-sectional view of the workpiece 11 after the holding step S10 and the laser beam irradiation step S20 in the seventh embodiment.

In the laser beam irradiation step S20 of the seventh embodiment, a first fragile region (promotion region) _25f having a first depth 25f1 is formed from the front surface 13a by invisible cutting only at one end _17a1 of each first predetermined dividing line 17a. Although the above point is different from the sixth embodiment, the other points are the same as the sixth embodiment.

Although the embodiments of the present invention are described above, the technical scope of the present invention is not limited to the scope described in the above embodiments. The structures and methods of the above embodiments can be appropriately modified and implemented as long as they do not deviate from the scope of the purpose of the present invention.

In the above embodiment, the case where the length direction of the first planned dividing line 17a is set along the first direction 11a, and the length direction of the second planned dividing line 17b is set along the second direction 11b is described.

However, in the second predetermined splitting line 17b, since the push blade 22 or the push blade 24 is pushed in sequence from one end _17b1 toward the other end _17b2 , it is easier to split it or to split it in a manner other than splitting, compared to the case where the push blade 18 is pushed substantially perpendicularly to the back surface 13b. Therefore, the length direction of the second predetermined splitting line 17b may not be set along the crystal orientation that can be split.

2: Laser processing device 4: Work clamp 6: Laser beam irradiation unit 8: Housing 10: Irradiation head 11: Workpiece 11a: First direction 11b: Second direction 12: Microscope camera unit 13: Single crystal substrate 13a: Front side (one side) 13b: Back side (other side) 13c: Thickness 13d: End area 13e: Intersection area 13f: Non-intersection area 14, 20, 26: Fracture device 15: Light emitting element 16: Carrier 16a: Upper surface 16b: Concave portion 17a: First predetermined splitting line 17a ₁ , 17b ₁ : One end 17a ₂ , 17b ₂ : other end 17b: second predetermined splitting line 18, 22, 24: pressing blade 18a, 22a: lower end 19: protective tape 19a: release paper 21: ring frame 22b ₁ : one end 22b ₂ : other end 23: workpiece unit 24a: rotation axis 25a: processing groove (promotion area) 25a ₁ , 25b ₁ , 25e ₁ : depth 25b: processing groove (starting point of splitting) 25c: first processing groove (promotion area) 25c ₁ : first depth (predetermined depth) 25d: second processing groove (promotion area) 25d ₁ , 25g ₁ : second depth 25e: fragile area (promotion area) 25f: first fragile area (promotion area) _25f1 : 1st depth 25g: 2nd fragile region (promotion region) 29: ruled groove 31: split groove 31a: crack in oblique direction 33: light emitting device wafer (device wafer) AA: line L: laser beam _LP : focal point S10: holding step S20: laser beam irradiation step (1st laser beam irradiation step) S30: 2nd laser beam irradiation step S40: splitting step (1st splitting step) S50: 2nd splitting step X, Y, Z: directions

FIG1 is a flow chart of the splitting method. FIG2(A) is a perspective view of the workpiece, and FIG2(B) is a cross-sectional view of the workpiece. FIG3 is a view showing the holding step. FIG4 is a view showing the laser beam irradiation step. FIG5 is a cross-sectional view of the workpiece after the laser beam irradiation step. FIG6 is a view showing the second laser beam irradiation step. FIG7 is a partial cross-sectional side view showing the splitting step. FIG8 is a partial cross-sectional side view showing the splitting step. FIG. 9(A) is a diagram showing continuous ruled grooves, FIG. 9(B) is a diagram showing the occurrence of cracks in an oblique direction, FIG. 9(C) is a diagram showing intermittent processing grooves, and FIG. 9(D) is a diagram showing the intermittent processing grooves as guides for dividing a single crystal substrate. FIG. 10(A) is a partial cross-sectional side view showing the second dividing step, and FIG. 10(B) is a partial cross-sectional side view showing the second dividing step. FIG. 11 is a three-dimensional view of a light-emitting device wafer. FIG. 12 is a cross-sectional view of a workpiece after the laser beam irradiation step in the second embodiment. FIG. 13(A) is a diagram showing the state of pushing a pressing blade against one end, and FIG. 13(B) is a diagram showing the state of pushing a pressing blade against the other end. FIG. 14(A) is a diagram showing a state when the pressing blade is pushed against one end, and FIG. 14(B) is a diagram showing a state when the pressing blade is pushed against the other end. FIG. 15 is a cross-sectional view of the workpiece after the laser beam irradiation step of the third embodiment. FIG. 16 is a cross-sectional view of the workpiece after the laser beam irradiation step of the fourth embodiment. FIG. 17 is a diagram showing the laser beam irradiation step of the fifth embodiment. FIG. 18(A) is a cross-sectional view of the workpiece after the laser beam irradiation step of the sixth embodiment, and FIG. 18(B) is a cross-sectional view of the workpiece after the laser beam irradiation step of the seventh embodiment.

S10: Keep step

S20: Laser beam irradiation step (first laser beam irradiation step)

S30: Second laser beam irradiation step

S40: Segmentation step (first segmentation step)

S50: Second segmentation step

Claims (10)

A method for splitting a single crystal substrate is to split the single crystal substrate. The method for splitting the single crystal substrate is characterized by comprising the following steps: A holding step, wherein the single crystal substrate is held by a work clamp of a laser processing device, wherein a plurality of predetermined splitting lines along a first direction are provided on one side of the single crystal substrate in a manner along a predetermined crystal orientation for splitting the single crystal substrate; A laser beam irradiation step, wherein after the holding step, a laser beam is irradiated from a laser beam irradiation unit of the laser processing device along each predetermined splitting line, thereby intermittently forming a promotion region for promoting the splitting of the single crystal substrate along each predetermined splitting line; and A splitting step, wherein after the laser beam irradiation step, an external force is applied to the single crystal substrate to split the single crystal substrate along each predetermined splitting line, thereby splitting the single crystal substrate. A method for dividing a single crystal substrate as claimed in claim 1, wherein in the holding step, the work clamp holds the other side of the single crystal substrate on the opposite side to the one side, and in the laser beam irradiation step, a laser beam having a wavelength that can be absorbed by the single crystal substrate is irradiated to intermittently form a processing groove having a depth that does not completely cut the single crystal substrate along each predetermined dividing line as the promotion area. A method for dividing a single crystal substrate as claimed in claim 2, wherein in the laser beam irradiation step, a first processing groove having a first depth is formed from the surface at one end in the first direction of each predetermined dividing line as the promotion region, and a second processing groove having a second depth shallower than the first depth is intermittently formed in the region other than the one end of each predetermined dividing line as the promotion region, In the dividing step, the single crystal substrate is divided by sequentially pushing a pressing blade from the one end toward the other end located on the opposite side of the one end. A method for dividing a single crystal substrate as claimed in claim 1, wherein in the laser beam irradiation step, a laser beam having a wavelength that penetrates the single crystal substrate is irradiated to intermittently form fragile areas of the single crystal substrate with reduced strength along each predetermined dividing line as the promotion area. A method for dividing a single crystal substrate as claimed in claim 4, wherein in the laser beam irradiation step, a first fragile region having a first depth is formed from the surface at one end in the first direction of each predetermined dividing line as the promotion region, and a second fragile region having a second depth shallower than the first depth is intermittently formed in the region other than the one end of each predetermined dividing line as the promotion region, In the dividing step, the single crystal substrate is divided by sequentially pushing a pressing blade from the one end toward the other end located on the opposite side of the one end. A method for dividing a single crystal substrate as claimed in any one of claims 1 to 5, wherein a plurality of predetermined dividing lines are further provided on the surface of the single crystal substrate along a second direction orthogonal to the first direction, and in the laser beam irradiation step, when the promotion region is intermittently formed along each predetermined dividing line along the first direction, the promotion region is formed in each of the plurality of intersection regions where the plurality of predetermined dividing lines along the first direction intersect with the plurality of predetermined dividing lines along the second direction. A method for dividing a single crystal substrate as claimed in any one of claims 1 to 5, wherein a plurality of predetermined dividing lines are further provided on the surface of the single crystal substrate along a second direction orthogonal to the first direction, and in the laser beam irradiation step, when the promotion region is intermittently formed along each predetermined dividing line along the first direction, the promotion region is formed in a region other than a plurality of intersection regions where the plurality of predetermined dividing lines along the first direction intersect with the plurality of predetermined dividing lines along the second direction. A method for manufacturing a device chip is to manufacture a plurality of device chips by splitting a single crystal substrate. The device chip manufacturing method is characterized in that: It has the following steps: A holding step, holding the single crystal substrate with a work clamp of a laser processing device, wherein the single crystal substrate is: a plurality of predetermined splitting lines arranged in a grid along a first direction and a second direction intersecting each other, and a plurality of predetermined splitting lines along the first direction are arranged on one side in a manner along a predetermined crystal orientation that can split the single crystal substrate; A first laser beam irradiation step, after the holding step, irradiating the laser beam from the laser beam irradiation unit of the laser processing device along each predetermined splitting line in the first direction, and intermittently forming a promotion area for promoting the splitting of the single crystal substrate along each predetermined splitting line in the first direction; A second laser beam irradiation step, after the holding step, irradiating the single crystal substrate with a laser beam from the laser beam irradiation unit along a plurality of predetermined splitting lines in the second direction, and forming a splitting starting point along each predetermined splitting line in the second direction; A first splitting step, after the first laser beam irradiation step and the second laser beam irradiation step, applying an external force to the promotion region of the single crystal substrate, so that the single crystal substrate is split along each predetermined splitting line in the first direction; and A second splitting step, after the first laser beam irradiation step and the second laser beam irradiation step, applying an external force to the splitting starting point of the single crystal substrate, so as to split the single crystal substrate, After the first splitting step and the second splitting step, the single crystal substrate is split into the plurality of device chips. A method for splitting a single crystal substrate is to split the single crystal substrate. The method for splitting the single crystal substrate is characterized by comprising the following steps: A holding step, wherein the single crystal substrate is held by a work clamp of a laser processing device, wherein the single crystal substrate has a plurality of predetermined splitting lines along a first direction on one side in a manner along a predetermined crystal orientation for splitting the single crystal substrate; A laser beam irradiation step, wherein after the holding step, a laser beam is irradiated from a laser beam irradiation unit of the laser processing device along each predetermined splitting line, and a promotion region for promoting the splitting of the single crystal substrate is formed in a range from the one side to a predetermined depth at one end of the predetermined splitting line in the first direction; and The splitting step, after the laser beam irradiation step, applies external force to the single crystal substrate by sequentially pushing the pressing blade from the one end toward the other end located on the opposite side of the one end, so as to split the single crystal substrate along the predetermined splitting line, thereby splitting the single crystal substrate. A method for dividing a single crystal substrate as claimed in claim 9, wherein the predetermined depth is greater than 15% and less than 80% of the thickness of the single crystal substrate from the one surface to the other surface located on the opposite side of the one surface, and in the laser beam irradiation step, the promotion region is formed at the end portion in the range from the one surface to the predetermined depth.

Images