KR20130094173A - Method for dividing brittle material substrate - Google Patents

Abstract

The first scribing line 52a made of the vertical cracks 53a and the second scribing line 52b made of the vertical cracks 53b are formed by the irradiation of the laser beam LB and the injection of the cooling medium from the cooling nozzle 37, Thereby forming a line 52b. The laser beam LB is irradiated again on the second scribe line 52b to extend the vertical crack 53b and cut the substrate 50 to the second scribe line 52b. Then, the intersection region of the dividing line 54 and the first scribing line 52a is covered with the glass plate 61 or the liquid 62. Next, The laser beam LB is again irradiated on the first scribe line 52a except for the intersection area to extend the vertical crack 53a and cut the substrate 50 to the first scribe line 52a. Accordingly, when the brittle material substrate is cut in two directions intersecting with each other by using a laser, the generation of cracks at the intersection portion is suppressed.

Description

[0001] METHOD FOR DIVIDING BRITTLE MATERIAL SUBSTRATE [0002]

The present invention relates to a method of irradiating a brittle material substrate with a laser beam to divide a brittle material substrate along two directions intersecting with each other.

BACKGROUND ART Conventionally, as a breaking method of a brittle material substrate such as a glass substrate, a scribing line is formed by rolling a cutter wheel or the like, and then an external force is applied to the substrate along a scribe line from a vertical direction, It is widely practiced.

Generally, when scribing a brittle material substrate using a cutter wheel, defects of the substrate are likely to occur due to mechanical stress applied to the brittle material substrate by the cutter wheel, and when the brittle material substrate is broken, And the like.

Therefore, in recent years, a method of cutting a brittle material substrate using a laser has been put to practical use. In this method, a substrate is cooled by a cooling medium after irradiating the substrate with a laser beam to a temperature lower than the melting temperature, thermal stress is generated on the substrate, and the thermal stress is applied to the substrate in a substantially vertical direction Thereby forming a crack. In the breaking method of a brittle material substrate using the laser beam, since the thermal stress is used, the cutting edge is a smooth surface with less cracks or the like, without contacting the tool directly with the substrate, and the strength of the substrate is maintained.

Also, for example, Patent Document 1 proposes a method of cutting a brittle material substrate in two directions intersecting with each other using a laser. In this proposed method, a first crack in a half-cut state is formed by irradiating a brittle material substrate with a laser beam, and then a laser beam is irradiated in the same way to form a half-cut state A second crack is formed, and then the laser beam is irradiated again to the first crack and the second crack to perform a full-cut.

(Patent Document 1) Japanese Laid-Open Patent Publication No. 2001-130921

Incidentally, when the laser beam is irradiated to the first crack and the second crack again to crack the brittle material substrate like in the proposed method, cracks may occur at the intersection of the first crack and the second crack. When cracks occur at the intersections of the brittle material substrates which become corner portions after the cutting, the dimensional precision of the brittle material substrate after the cutting is lowered, and the generated cullet sticks to the surface of the substrate. do.

SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and it is an object thereof to provide a method for suppressing occurrence of breakage at an intersection portion when cutting a brittle material substrate in two directions intersecting with each other using a laser .

According to the present invention, there is provided a brittle material substrate comprising: a first scribing line and a second scribing line which are perpendicular to each other and which intersect with each other, the first scribing line and the second scribing line being formed on a brittle material substrate; A first scribe line and / or a second scribe line; and a step of extending the vertical cracks to divide the substrate into a first scribe line and a second scribe line, wherein the first scribe line and / Therefore, when irradiating the laser beam, the irradiation amount of the laser beam to the intersection region of the first scribe line and the second scribe line is made smaller than the irradiation amount of the laser beam other than the intersection region. do.

Here, it is preferable that the laser beam irradiation amount to the intersection region of the first scribe line and the second scribe line is 50% or less of the laser beam irradiation amount other than the intersection region.

Further, in order to reduce the irradiation amount of the laser beam to the intersection region of the first scribe line and the second scribe line from other portions, it may be done by controlling the laser beam output. The intersection region of the first scribe line and the second scribe line is covered with a covering member or liquid that absorbs or reflects the laser beam so that the laser beam irradiation amount to the intersection region of the first scribe line and the second scribe line .

It is preferable that the intersection area for reducing the irradiation amount of the laser beam has a width of 5 mm or less on the upstream side and the downstream side of the direction of relative movement of the laser beam from the intersection of the first scribe line and the second scribe line .

The first scribing line and the second scribing line irradiate the substrate while relatively moving the laser beam so as to heat the substrate to below the melting temperature and then cool the substrate by spraying the cooling medium to cool the substrate, It is preferable to form it by the generated thermal stress.

According to the breaking method of the brittle material substrate according to the present invention, when the brittle material substrate is cut in two directions intersecting with each other, it is possible to suppress the occurrence of cracks at the crossing portions. As a result, the dimensional accuracy of the brittle material substrate after cutting is improved, and the problem caused by the cullet is remarkably suppressed.

1 is a schematic explanatory view showing an example of a demolition apparatus capable of carrying out demolition method according to the present invention.
2 is a view for explaining an operation state of the laser scribe.
3 is a process diagram showing an example of a breaking method according to the present invention.
4 is a diagram showing an example of adjustment of the irradiation amount to the intersection region of the laser beam LB and a laser irradiation amount in the intersection region.
5 is a diagram showing an example of adjustment of the irradiation amount to the intersection region of the laser beam LB and a laser irradiation amount in the intersection region.
Fig. 6 is a diagram showing an example in which the irradiation amount of the laser beam LB to the intersection region is adjusted by the cover member.
Fig. 7 is a diagram showing an example in which the irradiation amount adjustment to the intersection region of the laser beam LB is performed with a liquid.

(Mode for carrying out the invention)

Hereinafter, the breaking method of the brittle material substrate according to the present invention will be described in detail, but the present invention is not limited to these embodiments.

Fig. 1 is a schematic explanatory view showing an example of a demultiplexer used in the demultiplexing method according to the present invention. The cutting device of this figure is composed of a slide table 12 which is movable on a stand 11 in a direction perpendicular to the paper surface (Y direction), and a slide table 12 on which movement in the left and right directions (X direction) A free pedestal 19 and a rotating mechanism 25 provided on the pedestal 19. A brittle material substrate 50 is mounted and fixed on a rotary table 26 provided on the rotating mechanism 25, Are freely moved in the horizontal plane by their moving means.

The slide table 12 is movably mounted on a pair of guide rails 14 and 15 arranged in parallel with a predetermined distance on the upper surface of the mount 11. A ball screw 13 is provided between the pair of guide rails 14 and 15 in parallel with the guide rails 14 and 15 so as to be capable of forward and reverse rotation by a motor not shown. A ball nut 16 is provided on the bottom surface of the slide table 12. The ball nut (16) is screwed to the ball screw (13). The ball nut 16 is moved in the Y direction so that the slide table 12 to which the ball nut 16 is attached is moved in the X direction on the guide rails 14 and 15 In the Y direction.

The pedestal 19 is also movably supported on a pair of guide members 21 arranged on the slide table 12 at a predetermined distance in a straight line. A ball screw 22 is provided between the pair of guide members 21 so as to be rotatable in both the forward and reverse directions by a motor 23 in parallel with the guide member 21. A ball nut 24 is provided on the bottom surface of the pedestal 19 and is screwed with the ball screw 22. [ The ball nut 22 moves forward or backward so that the ball nut 24 moves in the X direction so that the pedestal 19 together with the ball nut 24 moves the pair of guide members 21 Therefore, it moves in the X direction.

On the pedestal 19, a rotating mechanism 25 is provided. Then, a rotary table 26 is provided on the rotary mechanism 25. The brittle material substrate 50 to be cut is fixed on the rotary table 26 by vacuum suction. The rotary mechanism 25 rotates the rotary table 26 around the central axis in the vertical direction.

The support table 31 is supported by a holding member 33 that is downwardly extended from the attachment table 32 so as to be opposed to the rotary table 26 so as to be opposed to the rotary table 26. [ The support 31 includes a cutter wheel 35 for forming a trigger crack on the surface of the brittle material substrate 50, an opening (not shown) for irradiating the brittle material substrate 50 with a laser beam, A cooling nozzle 37 for cooling the surface of the material substrate 50 is provided.

The cutter wheel 35 is supported by the chip holder 36 so as to be able to ascend and descend in a position in contact with the brittle material substrate 50 in a noncontact position and forms a trigger crack to be the starting point of the scribe line The brittle material substrate 50 is brought into pressure contact with the brittle material substrate 50. The formation position of the trigger crack is preferably formed on the inner side of the surface side edge of the brittle material substrate 50 in order to suppress the unstable fracture in which cracks are generated in the unpredictable direction from the trigger crack.

A laser output device 34 is provided on the mounting table 32. The laser beam LB emitted from the laser output device 34 is reflected downward from the reflection mirror 44 and is guided from the opening formed in the support table 31 through the optical system supported in the support member 33 to the rotary table 26 to the brittle material substrate 50 fixed thereon.

Water as a cooling medium is ejected together with the air toward the brittle material substrate 50 from the cooling nozzles 37 provided in the vicinity of the openings through which the laser beam LB exits. The position on the brittle material substrate 50 from which the cooling medium is ejected is on the line to be cut 51 and on the back side of the irradiation area of the laser beam LB (see Fig. 2).

A pair of CCD cameras 38 and 39 for recognizing alignment marks preliminarily imprinted on the brittle material substrate 50 are provided on the attachment base 32. [ When the positional deviation of the brittle material substrate 50 during the setting of the brittle material substrate 50 is detected by the CCD cameras 38 and 39 and the brittle material substrate 50 is deviated by the angle? When the brittle material substrate 50 is shifted Y, the slide table 12 is moved by -Y.

In the case of removing the brittle material substrate 50 in the demolishing device having such a configuration, first, the brittle material substrate 50 is placed on the rotary table 26 and fixed by the suction means. Then, the CCD cameras 38 and 39 pick up an alignment mark provided on the brittle material substrate 50, and position the brittle material substrate 50 at a predetermined position based on the image pickup data as described above .

Subsequently, as described above, a trigger crack is formed in the brittle material substrate 50 by the wheel cutter 35. [ Then, the laser beam LB is emitted from the laser output device 34. The laser beam LB is irradiated by a reflecting mirror 44 substantially perpendicularly to the surface of the brittle material substrate 50 as shown in Fig. At the same time, water as a cooling medium is jetted from the cooling nozzle 37 in the vicinity of the rear end of the laser beam irradiation area. By irradiating the brittle material substrate 50 with the laser beam LB, the brittle material substrate 50 is heated to a temperature lower than the melting temperature in the thickness direction so that the brittle material substrate 50 tries to thermally expand but does not expand because of local heating And the compressive stress is generated around the irradiation point. Immediately after the heating, the surface of the brittle material substrate 50 is cooled by water, so that the brittle material substrate 50 is contracted at this time and tensile stress is generated. By the action of the tensile stress, a vertical crack 53 is formed on the brittle material substrate 50 along the line to be cut 51 with the trigger crack as the starting point.

The vertical cracks 53 are extended to form the scribe lines 52 in the brittle material substrate 50 by relatively moving the laser beam LB and the cooling nozzles 37 along the line 51 to be cut. In this embodiment, the slide table 12, the pedestal 19, the rotation mechanism 25 of the rotary table 26, and the like are fixed with the laser beam LB and the cooling nozzle 37 in a predetermined position, The brittle material substrate 50 is moved. Of course, the laser beam LB and the cooling nozzle 37 may be moved while the brittle material substrate 50 is fixed. Or both the brittle material substrate 50 and the laser beam LB and the cooling nozzle 37 may be moved.

Next, a breaking method according to the present invention will be described. Fig. 3 shows a process drawing showing an example of the breaking method of the present invention. As shown in the drawing, by moving the laser beam LB and the cooling nozzle 37 relatively along the planned destruction line 51a as described above, a trigger crack (not shown) And the first scribe line 52a is formed on the brittle material substrate 50. The first scribe line 52a is formed in the brittle material substrate 50. [

The laser beam LB to be used here is not particularly limited and may be appropriately determined from the material and the thickness of the substrate, the depth of vertical cracks to be formed, and the like. In the case where the brittle material substrate is a glass substrate, a laser beam having a wavelength of 9 to 11 mu m having a large absorption at the surface of the glass substrate is suitably used. As such a laser beam, a CO ₂ laser can be mentioned. As the irradiation shape of the laser beam to the substrate, it is preferable that the laser beam has a long and thin elliptical shape in the relative movement direction of the laser beam. The irradiation length L in the relative movement direction is in the range of 10 to 60 mm, A range of 5 mm is suitable.

Examples of the cooling medium ejected from the cooling nozzle 37 include water and alcohol. Further, an additive such as a surfactant may be added within a range that does not adversely affect the brittle material substrate after the cutting. The injection amount of the cooling medium is usually about several ml / min. Cooling of the substrate by the cooling medium is preferably a so-called water jet method in which water is jetted together with a base body (usually air) from the viewpoint of quenching the substrate heated by the laser beam. The cooling region by the cooling medium is preferably circular or elliptical with a long diameter of about 1 to 5 mm. It is preferable that the cooling region is formed such that the distance between the center of the cooling region and the center of the heating region is about several millimeters to several tens millimeters after the heating region in the relative movement direction by the laser beam.

The relative moving speed of the laser beam LB and the cooling nozzle 37 is not particularly limited and may be suitably determined from the depth of the vertical crack to be obtained. Generally, the more the relative movement speed is slowed, the deeper the vertical cracks are formed. Normally, the relative moving speed is about several hundreds of millimeters per second.

The depth of the vertical cracks 53a constituting the scribe line 52a is not particularly limited but may be a condition for irradiating a laser beam for cutting a brittle material substrate in a subsequent step such as a relative movement speed, In order to increase the margin, it is preferable to set the depth to 25% or more of the substrate thickness.

3B, the laser beam LB and the cooling nozzle 37 are relatively moved along the scheduled breaking line 51b perpendicular to the first scribing line 52a, (52b). Conditions for forming the second scribe line 52b may be the same as those for forming the first scribe line 52a.

Next, as shown in Fig. 5C, the laser beam LB is again irradiated along the second scribe line 52b. As a result, the vertical crack 53b extends in the substrate thickness direction, and the substrate 50 is cut by the second scribe line 52b to form the cut line 54. The vertical cracks 53b need not be extended to the depth at which the substrate 50 is removed without exerting an external force and need not necessarily reach the opposite surface side of the substrate 50.

The irradiation conditions of the laser beam LB for extending the vertical cracks 53b in the thickness direction of the substrate may be appropriately determined from the thickness of the substrate and the depth of the vertical cracks 53b, 52b are formed are also exemplified here.

Next, as shown to the same figure (b), the laser beam LB is irradiated again along the 1st scribe line 52a. As a result, the vertical cracks 53a are extended in the thickness direction of the substrate, and the substrate 50 is cut into the first scribe lines 52a. The depth of the vertical crack 53a after the extension of the substrate 50 in the thickness direction of the substrate is sufficient to extend to the depth at which the substrate 50 is removed without exerting an external force as in the case of the vertical crack 53b, ) On the opposite side.

What is important here is that when the laser beam LB is again irradiated along the first scribe line 52a, the laser beam LB to the intersection region of the first scribe line 52a and the break line 54 The irradiation dose may be lower than the irradiation dose of the other portion. By reducing the irradiation amount of the laser beam LB to the intersection region, it is possible to effectively suppress the breakage of the intersection portion which becomes the corner portion after the cutting. A more preferable laser beam irradiation amount in the intersection region is 50% or less, more preferably 10% or less, and more preferably 0% of the laser beam irradiation amount other than the intersection region.

In the embodiment described above, when the laser beam LB is again irradiated along the first scribe line 52a, the irradiation amount of the laser beam LB to the intersection area is reduced to be smaller than the irradiation amount of the other part, When irradiating the laser beam LB again along the scribe line 52b, the irradiation amount of the laser beam LB to the intersection area may be made smaller than the irradiation amount of the other part. Alternatively, when irradiating the laser beam LB again along the first scribe line 52a and again irradiating the laser beam LB along the second scribe line 52b, the laser beam LB LB may be made smaller than the irradiation amount of other portions.

Adjustment of the irradiation amount of the laser beam LB to the intersection area of the first scribing line 52a and the second scribing line 52b can be performed, for example, by controlling the laser beam output. When the irradiation spot of the laser beam is formed into a long and thin elliptical shape in the direction of relative movement of the laser beam by an optical system such as a cylindrical lens, as shown in Fig. 4 (a), the first scribe line A region where the laser beam LB is not irradiated is formed over a predetermined range on the downstream side from the upstream side of the relative movement direction of the laser beam LB with the center of the intersection of the first scribe line 52a and the second scribe line 52b do. The irradiation amount of the laser beam LB at this time is shown in Fig. 4 (b). As can be understood from Fig. 4 (b), the irradiation amount of the laser beam gradually decreases from the normal irradiation amount toward the intersection between the first scribing line 52a and the second scribing line 52b, becomes 0 at the intersection , And gradually increases to return to the normal irradiation dose. By reducing the irradiation amount of the laser beam LB to the intersection region of the first scribing line 52a and the second scribing line 52b in this manner, the occurrence of cracking at the intersection portion is suppressed.

The first scribe line 52a and the second scribe line 52b and the second scribe line 52b are used as the intersecting area between the first scribe line 52a and the second scribe line 52b for reducing the irradiation amount of the laser beam LB, It is preferable that the width of the laser beam LB is maximum 5 mm on the upstream side in the direction of relative movement of the laser beam LB and 5 mm maximum on the downstream side.

When the irradiation spot of the laser beam LB is scanned by using a polygon mirror, a galvano mirror, a cylindrical reflector, or the like to form a long and thin elliptical shape in the direction of relative movement of the laser beam, The laser intensity in the irradiation spot becomes uniform and the laser irradiation amount over a predetermined range can be made zero. Fig. 5 (a) shows the irradiation state of the laser beam LB with passage of time. When the laser beam LB hits the intersection region of the first scribe line 52a and the second scribe line 52b, the laser oscillation is turned off during scanning within the intersection region, Turning the laser oscillation on when it goes out. Thus, as shown in Fig. 5 (b), the irradiation amount of the laser beam LB to the intersection region can be made zero.

6 shows another means for adjusting the irradiation amount of the laser beam LB to the intersection region of the first scribe line 52a and the second scribe line 52b. In the means shown in this figure, the intersection region of the first scribe line 52a and the second scribe line 52b is covered with the covering member 61, and the irradiation amount of the laser beam LB to the intersection region is reduced. According to this means, the amount of irradiation of the laser beam LB can be reduced by a simple operation of placing the covering member 61 without the necessity of on / off control of the laser oscillation as in the above embodiment.

The cover member 61 used in the present invention is not particularly limited as long as it is a member that absorbs or reflects the laser beam LB, and examples thereof include a glass plate, a metal plate such as aluminum, dry ice and the like. In the case of using a glass substrate, since the laser beam is absorbed by the glass substrate, the irradiation amount of the laser beam LB to the substrate 50 can be adjusted by the material and the thickness. Further, in the case of using a metal plate such as aluminum, since the laser beam LB is reflected by the metal plate, the irradiation amount to the substrate 50 becomes zero.

7 shows yet another means for adjusting the irradiation amount of the laser beam LB to the intersection region of the first scribe line 52a and the second scribe line 52b. In the means shown in this figure, the intersection region of the first scribe line 52a and the second scribe line 52b is covered with the liquid 62 to reduce the irradiation amount of the laser beam LB to the intersection region. According to this means, it is not necessary to control on / off of the laser oscillation as in the above embodiment, and the irradiation amount of the laser beam LB can be reduced by a simple operation such as dropping and coating of the liquid 62. [

The liquid 62 used in the present invention is not particularly limited as long as it is a member that absorbs or reflects the laser beam LB. For example, water or alcohol is suitably used. Attachment of the liquid 62 to the intersection region of the substrate 50 can be performed, for example, by coating with a dropper or the like. The amount of deposition of the liquid 62 may be suitably determined depending on the size of the intersection region, the type and output of the laser to be used, and the like, but when water is used, it is usually in the range of 0.01 ml to 0.05 ml.

In the above-described embodiments, the first scribing line 52a and the second scribing line 52b are formed to form a single substrate. However, the first scribing line 52a and the second scribing line 52b may be formed on the large- In the case where a plurality of second scribe lines 52b are formed and divided into a plurality of small area substrates, the disconnection method of the present invention can be naturally applied. In addition to the case where the two scribe lines are orthogonalized, the dividing method of the present invention can also be applied to the case of intersecting at a desired angle.

(Example)

Example 1

A plurality of scribe lines directly perpendicular to each other were formed on a chemical strengthened soda glass substrate having a thickness of 0.55 mm by using the breaking apparatus shown in Fig. 1 so that the number of intersections was 40, and a laser beam was irradiated along one scribe line After cutting the substrate, a glass plate (5 mm x 5 mm x 0.4 mm thick) was placed on the intersection area with the scribe line and the other scribe line. Then, a laser beam was irradiated along the other scribe line to divide the substrate into a plurality of scribe lines. The cutting of the glass substrate was carried out by the method shown in Fig. The results are shown in Table 1. The specific irradiation conditions of the laser beam are as follows.

(Laser beam irradiation condition for forming the first scribe line)

Laser type: CO ₂ laser

Laser power: 100W

Relative movement speed: 100mm / sec

Laser Spot: Oval

(Laser beam irradiation condition for formation of the second scribe line)

Laser type: CO ₂ laser

Laser output: 120W

Relative movement speed: 200mm / sec

Laser Spot: Oval

(Laser beam irradiation condition of laser brake)

Laser type: CO ₂ laser

Laser power: 320W

Relative movement speed: 1500㎜ / sec

Laser Spot: Oval

Comparative Example 1

The substrate was cut off in the same manner as in Example 1 except that the glass plate was not placed on the intersection region. The results are shown in Table 1.

Table 1

"Broken": Broken part of the intersection occurred.

&Quot; Skip crossing ": A cut line did not extend from the intersection to the downstream side of the relative movement direction of the laser beam.

As can be understood from Table 1, in the break-away method of Example 1, only three intersections were good in all of the 40 intersections, whereas in the break-up method of Comparative Example 1, Cracking occurred.

Example 2

A glass substrate was prepared in the same manner as in Example 1, except that water (amount of deposition: 0.04 ml, diameter: 8 to 10 mm) was adhered to the glass plate. The results are shown in Table 2. The specific irradiation conditions of the laser beam are as follows.

(Laser beam irradiation condition for forming the first scribe line)

Laser type: CO ₂ laser

Laser power: 100W

Relative movement speed: 100mm / sec

Laser Spot: Oval

(Laser beam irradiation condition for formation of the second scribe line)

Laser type: CO ₂ laser

Laser power: 130W

Relative movement speed: 180mm / sec

Laser Spot: Oval

(Laser beam irradiation condition of laser brake)

Laser type: CO ₂ laser

Laser power: 240W

Relative movement speed: 1500㎜ / sec

Laser Spot: Oval

Comparative Example 2

Except that water droplets were not adhered to the intersection region, the substrate was cut off in the same manner as in Example 2. [ The results are shown in Table 2.

[Table 2]

As can be understood from Table 2, in the cutting method of Example 2 in which water droplets were adhered to the intersection region, all the intersections of 40 intersections were satisfactorily cleaned. In the cutting method of Comparative Example 2, however, And the remaining 38 intersections were broken.

According to the cutting method of the present invention, when a brittle material substrate is cut in two directions intersecting with each other by using a laser, it is possible to suppress the occurrence of cracking at an intersection portion, which is useful.

37: Cooling nozzle
50: brittle material substrate
51, 51a, and 51b:
52: scribe line
52a: 1st scribe line
52b: second scribe line
53, 53a, 53b: Vertical crack
61:
62: liquid
LB: Laser Beam

Claims (7)

Forming a first scribe line and a second scribe line composed of vertical cracks crossing each other on a brittle material substrate; and irradiating a laser beam along the first scribe line and the second scribe line with relative movement to irradiate the vertical crack. A method of cutting a brittle material substrate, the method comprising: stretching the substrate and cutting the substrate with a first scribe line and a second scribe line,
When irradiating a laser beam along the first scribe line and / or the second scribe line, the amount of laser beam irradiation to the intersection region of the first scribe line and the second scribe line is reduced than that of the laser beam other than the intersection region. A cutting method of a brittle material substrate, characterized in that. The method of claim 1,
And the laser beam irradiation amount to the intersection region of the first scribing line and the second scribing line is set to 50% or less of the laser beam irradiation amount other than the intersection region. 3. The method according to claim 1 or 2,
And controlling the laser beam output so as to reduce the irradiation amount of the laser beam to the intersection region of the first scribe line and the second scribe line. 3. The method according to claim 1 or 2,
Wherein the intersection region of the first scribe line and the second scribe line is covered with a covering member that absorbs or reflects the laser beam to reduce the amount of laser beam irradiation to the intersection region. 3. The method according to claim 1 or 2,
Wherein the intersection area of the first scribe line and the second scribe line is covered with the liquid absorbing or reflecting the laser beam to reduce the amount of laser beam irradiation to the intersection area. The method according to any one of claims 1 to 5,
Wherein the intersection region is a region having a width of 5 mm or less on the upstream side and the downstream side of the laser beam in the relative movement direction from an intersection point of the first scribe line and the second scribe line. 7. The method according to any one of claims 1 to 6,
The first scribing line and the second scribing line irradiate the substrate while relatively moving the laser beam so as to heat the substrate to below the melting temperature and then cool the substrate by spraying the cooling medium to cool the substrate, By the generated thermal stress.

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