JP5361916B2 - Laser scribing method - Google Patents

Description

  The present invention relates to a laser scribing method, and more particularly to a laser scribing method in which a brittle material substrate is irradiated with a pulsed laser beam for scribing.

  A light emitting element such as a light emitting diode is formed by stacking a nitride semiconductor on a sapphire substrate. On a semiconductor wafer composed of such a sapphire substrate or the like, a plurality of elements such as light emitting diodes are formed by being partitioned by a division planned line. A laser scribing method is used to divide the semiconductor wafer along the division line.

  The laser scribing method is a method of scribing by irradiating a substrate such as a semiconductor with laser light, and is disclosed in Patent Document 1, for example. In the method disclosed in Patent Document 1, the position of the condensing point of the laser beam is adjusted to the back surface of the substrate, and the laser beam is scanned along the planned dividing line. Thereafter, the condensing point of the laser beam is moved in the thickness direction of the substrate, and similarly, the laser beam is scanned along the planned dividing line.

  Further, Patent Document 2 discloses a method in which a silicon substrate, a glass substrate, or the like is irradiated with pulsed laser light to form a modified region inside the substrate and scribe. In the method disclosed in Patent Document 2, the condensing point of the pulse laser beam is adjusted so as to be located inside the substrate. Then, after the pulse laser beam is irradiated onto the substrate, it is scanned in the horizontal direction without changing the position of the condensing point, and the next pulse laser beam is irradiated. By repeating such laser irradiation, a plurality of modified regions extending obliquely from the back surface side to the front surface side of the substrate are periodically formed along the planned dividing line.

JP 2007-21557 A JP 2007-167875 A

  Here, in particular, when a light emitting diode is formed by stacking semiconductors on a sapphire substrate, in order not to deteriorate the quality of the light emitting diode as a final product, the modified region (processing trace) by laser irradiation should be as small as possible preferable. Further, in order not to impair the strength such as the end face strength, it is preferable that the number of the modified regions is small. On the other hand, when the reforming region is small, a larger dividing force is required in the dividing process after scribing, and in some cases, the dividing cannot be performed.

  Therefore, in laser scribing, it is necessary to form a small (narrow) modified region that can be easily divided in a subsequent process. In order to achieve such an object, it is considered that a plurality of linear modified regions (hereinafter referred to as linear processing marks) extending in the thickness direction of the substrate are periodically formed along the planned dividing line. It is done. Such a linear processing mark can be formed by the method shown in Patent Documents 1 and 2.

  However, when forming a linear processing mark by the laser scribing method disclosed in Patent Document 1, after setting the laser beam condensing point at a certain position and scanning, then changing the position and scanning. Need to be repeated. In order to change the position of the condensing point to a plurality of positions, the processing becomes complicated and the apparatus configuration is complicated and expensive.

  In the method disclosed in Patent Document 2, it is not necessary to change the position of the condensing point, but the laser irradiation conditions such as the threshold value of the beam intensity are not shown at all, and the linear processing trace is stabilized. Cannot be formed. For this reason, a surface modified region with a large area instead of a linear shape is formed on the front and back surfaces of the substrate, and conversely, the linear processing traces are reduced and a large dividing force is required in the dividing step. It may become. Further, in Patent Document 2, since a processing mark of 300 μm is formed by one pulse, a linear processing mark cannot be formed on a substrate having a thickness of about 100 μm.

  An object of the present invention is to enable formation of a modified region having an appropriate width with a simple apparatus configuration when a brittle material substrate such as a sapphire substrate is scribed by laser light.

  A laser scribing method according to a first invention is a method of irradiating a brittle material substrate with a pulsed laser beam and scribing along a planned cutting line, and includes a first step and a second step. The first step is to irradiate the brittle material substrate with a pulsed laser beam and scan along the planned cutting line, and form a modified layer along the planned cutting line inside the front and back surfaces of the brittle material substrate. It is a process to do. The second step is to irradiate the pulse laser beam with adjusted beam intensity from the surface side of the brittle material substrate, and to divide the beam by fixing the height of the focal position while maintaining the same irradiation condition of the pulse laser beam. By scanning along the line and repeatedly irradiating the next pulsed laser beam to the position that overlaps the processing mark formed by the previously irradiated pulsed laser beam, the surface of the brittle material substrate starts from the modified layer. This is a step of periodically forming a plurality of linear processing traces that progress diagonally toward a depth that does not reach the surface of the brittle material substrate along the planned dividing line.

  Here, the inventor of the present application has developed a laser scribing method capable of forming a modified region having an appropriate width with a simple apparatus configuration and has already filed an application (Japanese Patent Application No. 2010-193220). In this laser scribing method, a linear processing trace having a predetermined length is formed from the back surface to the front surface of the brittle material substrate, and the linear processing trace is periodically formed along a line to be divided.

  By the way, in a light emitting diode, for example, a semiconductor is stacked on a sapphire substrate to form an element. And when applying the laser scribing method of the prior application to such a light emitting diode, in order not to damage the element, the laser beam is irradiated from the surface (surface) where the element is not formed. Become. Then, in the method of the prior application, a modified region serving as a starting point of the linear processing trace is formed on the surface (back surface) on which the element is formed. In this case, an element formed on one surface (back surface) of the substrate may be damaged.

  Therefore, in the present invention, a modified layer is formed inside the brittle material substrate away from the front and back surfaces, and a linear processing mark is formed starting from the modified layer inside the substrate.

  Here, since the scribe line can be formed with a small number of modified regions, the quality and strength deterioration of the final product can be suppressed. Moreover, it can divide comparatively easily in the division | segmentation in a post process. In addition, the modified layer is formed inside the substrate, and the linear processing traces progress from the modified layer as a base point. Therefore, even when the element is formed on one surface of the substrate, damage to the element can be suppressed. .

The laser scribing method according to the second invention is the laser scribing method according to the first invention. In the second step, the beam intensity of the pulse laser beam exceeds 8.8 × 10 ¹² W / m ² in the modified layer, and reaches the surface. It is adjusted to be lower than 8.8 × 10 ¹² W / m ² inside the substrate.

Here, since the beam intensity of the pulse laser beam exceeds the threshold value (8.8 × 10 ¹² W / m ² ) in the modified layer inside the substrate, when the pulse laser beam is scanned, the laser processing trace starts from the modified layer. It progresses diagonally upward toward the surface. And since the beam intensity is below the threshold value (8.8 × 10 ¹² W / m ² ) inside the substrate up to the surface, when the value falls below the threshold value, the upward progress of the linear processing trace stops, and again Laser processing marks are formed in the modified layer. By repeating the above, linear processing traces extending from the modified layer to a depth that does not reach the surface are periodically formed along the planned dividing line.

A laser scribing method according to a third invention is the laser scribing method according to the second invention, wherein in the second step, the energy absorbed per unit volume in the brittle material substrate is 1.5 × 10 ¹⁰ J / m ³ or less. The laser irradiation and scanning conditions are adjusted.

In laser irradiation and scanning, if the energy absorbed per unit volume under the conditions of the second invention exceeds 2.0 × 10 ¹⁰ J / m ³ , surface processing traces that are connected by adjacent linear processing traces Thus, the modified region cannot be reduced. Therefore, here, the laser irradiation and scanning conditions are adjusted so that the energy absorbed per unit volume is 2.0 × 10 ¹⁰ J / m ³ or less.

  A laser scribing method according to a fourth invention is the laser scribing method of the first to third inventions, wherein the brittle material is sapphire.

  The laser scribing method according to a fifth aspect of the present invention is the laser scribing method of the first aspect, wherein in the second step, the laser irradiation and scanning conditions are adjusted so that the pulsed laser beams repeatedly irradiated overlap.

  In the present invention as described above, when a brittle material substrate such as a sapphire substrate is scribed, a modified region having an appropriate width can be formed with a simple apparatus configuration. Further, when an element is formed on the substrate, damage to the element can be suppressed.

1 is an external perspective view of a semiconductor wafer divided by a processing method according to an embodiment of the present invention. The schematic block diagram of the laser processing apparatus for enforcing the processing method by one Embodiment of this invention. The figure which shows the microscope picture of the modified layer formed in the inside of a board | substrate. The figure which shows the microscope picture of the linear process trace formed in the inside of a board | substrate. The figure for demonstrating the formation mechanism of a linear process trace. The apparatus block diagram for examining the threshold value in which a linear process trace is formed. The figure which shows the relationship between the beam radius and focus position in a 150-micrometer-thick sapphire substrate. The figure which shows the microscope picture inside the board | substrate with which the process trace was formed only in the surface. The figure which shows the comparison with the result estimated from the simulation result of FIG. 7, and an experimental result. The figure which shows the relationship between the beam radius and focus position in a 200-micrometer-thick sapphire substrate. The figure which shows the microscope picture inside the board | substrate with which the process trace was formed in the back surface. The figure which shows the comparison with the result estimated from the simulation result of FIG. 10, and an experimental result. The figure which shows the microscope picture inside a board | substrate for demonstrating the boundary of back surface processing and linear processing. The figure which shows the relationship between the energy absorbed per unit volume, and a processing state.

[Processing target]
FIG. 1 is an example of a semiconductor wafer to which a laser scribing method according to an embodiment of the present invention is applied. A semiconductor wafer 1 shown in FIG. 1 is formed by laminating nitride semiconductors on a sapphire substrate 2, and is formed by dividing a plurality of light emitting elements 3 such as light emitting diodes by dividing lines 4. Yes.

[Laser processing equipment]
FIG. 2 shows a schematic configuration of a laser processing apparatus 5 for performing a processing method according to an embodiment of the present invention. The laser processing apparatus 5 includes a laser beam oscillation unit 6 including a laser beam oscillator and a control unit, a transmission optical system 7 including a plurality of mirrors for guiding the laser beam in a predetermined direction, and a laser beam from the transmission optical system 7. And a condensing lens 8 for condensing the light. The wafer 1 is placed on the table 9, and the laser beam and the table 9 on which the wafer 1 is placed can move relatively in the vertical direction and can move relatively in the horizontal plane. It has become.

[Laser scribing method]
The laser scribing method using the laser processing apparatus 5 as described above is as follows.

<First step>
First, the laser beam oscillation unit 6 controls processing conditions such as the output power of the pulse laser beam. Then, this pulsed laser beam is irradiated onto the sapphire substrate 2 to form a modified region inside the sapphire substrate 2 away from the front and back surfaces. Note that the pulse laser beam is a transmissive laser that passes through the substrate. Further, this pulsed laser beam is scanned along the planned dividing line. As a result, a modified layer is formed in the substrate along the planned dividing line.

  3A and 3B show specific examples of the modified layer formed inside the substrate. In each example, a sapphire substrate having a thickness of 330 μm is used as a sample.

-Example 1-
The laser irradiation conditions in FIG. 3 (a) are as follows.
Wavelength: 1064 nm
Pulse width: 20 ps
Pulse energy: 1.4μJ
Scanning speed: 500 mm / s
Laser irradiation direction: Focus position from the surface: z = -100 μm
In this example 1, the modified layer M1 is formed in the almost middle part in the thickness direction of the substrate.

-Example 2-
The laser irradiation conditions in FIG. 3 (b) are as follows.
Wavelength: 1064 nm
Pulse width: 20 ps
Pulse energy: 1.0μJ
Scanning speed: 50 mm / s
Laser irradiation direction: Focus position from surface: z = −140 μm
In Example 2, the modified layer M2 is formed in a region near the back surface inside the substrate.

  In Examples 1 and 2, the repetition frequency, output, and scanning speed are changed in addition to the focal position, but the position (depth) at which the modified layer is formed is changed by changing only the focal position. Is possible.

<Second step>
Next, processing conditions such as the output power of the pulse laser beam are controlled (details will be described later), and the sapphire substrate 2 is irradiated with this pulse laser beam. Thereafter, the laser beam is moved relatively along the planned dividing line while the position of the focus of the laser beam (similar to the “condensing point” here) is fixed, and scanning is performed. As a result, as shown in FIG. 4 which is a micrograph of the inside of the substrate, a plurality of linear laser processing marks 10 as the modified regions are periodically formed along the planned dividing line. In this way, the wafer 1 is scribed along the planned cutting line. FIG. 4 shows an example in which linear processing marks are formed starting from the back surface of the substrate. However, in the present invention, linear processing is performed starting from the modified layer formed in the first step, not the back surface of the substrate. A scar is formed.

  As described above, after the periodic linear processing marks 10 are formed inside the substrate, bending stress is applied to the portion where the linear processing marks 10 are formed, so that it can be easily performed along the scribe line. The wafer 1 can be divided.

[Mechanism of formation of linear processing marks]
The formation mechanism of the linear processing marks in the second step will be described with reference to FIG. As shown in FIG. 5A, the laser irradiation conditions are set so that the focal position is in the vicinity of the modified layer M inside the substrate, and the laser beam is irradiated. The laser light conditions will be described later. When the laser beam is irradiated, a processing mark 10a is formed in the modified layer M by a certain laser pulse (hereinafter also simply referred to as “pulse”) as shown in FIG.

  The laser beam is scanned while maintaining the same laser irradiation condition including the focal position ((c) in the figure). Then, the laser pulses overlap, and the next processing mark 10a is irradiated with the next pulse, thereby forming a new processing mark 10b in contact with the previous processing mark 10a as shown in FIG. Is done. By repeating the above processing, a linear processing mark 10 is formed as shown in FIGS.

  Since the focal position of the laser beam is always set in the vicinity of the modified layer M inside the substrate, the diameter of the laser beam becomes wider in the substrate as it goes upward, so that the beam intensity per unit area is weak. Become. Then, before the processing marks 10 that are formed one after another reach the substrate surface, if the beam intensity falls below a certain value at a predetermined depth position, the processing marks 10 will not rise any further, and again become the modified layer M. A machining mark 10c is formed. This state is shown in FIGS. 5 (h) and (i).

  By repeating the processing as described above, as shown in FIG. 5 (j), a plurality of linear processing marks 10 are periodically formed along the planned cutting line.

[Threshold for forming linear processing marks]
Next, a description will be given of the threshold value of the beam intensity at which the linear processing trace as described above is formed. Here, the results of calculating the beam diameter inside the sapphire substrate under the following calculation conditions are shown in FIG. The beam diameter inside the substrate is d shown in FIG. In FIG. 7 and subsequent figures, for convenience of explanation, the starting point of the linear processing trace is the back surface of the substrate. However, in the present invention, the starting point of the linear processing trace is formed inside the substrate in the first step, not the back surface of the substrate. The modified layer M. Therefore, the “substrate back surface” in the following description corresponds to the “modified layer inside the substrate” of the present invention.

<Calculation conditions>
Laser wavelength: 355nm
Incident beam diameter (Do in FIG. 6): 5 mm
M Square: 1.2
Focus point of condenser lens 8: 20mm
Sapphire refractive index: 1.76
<Calculation result 1: Substrate thickness 150 μm>
FIG. 7 shows the beam radius and height when the focus position is changed from +50 μm to −250 μm in seven steps with the substrate surface position set to “0” in a sample (sapphire substrate) having a thickness of 150 μm (the substrate surface is “ The calculation result is “0”. FIG. 7 shows only one side of the beam, and the actual beam shape of the laser beam is symmetric with respect to the beam radius “0”. For example, at the focal position “−50 μm”, the beam is focused at a position of −100 μm because the laser light is refracted inside the sapphire substrate, and the laser light is in the air at each focal position. It shows the value when progressing.

  Under the conditions of FIG. 7, the following is assumed.

  Assumption 1: A processing mark can be formed with a beam intensity with a beam radius of 8 μm or less.

  Assumption 2: No processing trace is formed in the substrate or on the surface where the processing trace is not formed, even if the strength is higher than the threshold value. Even if the beam intensity is 8 μm or less, no linear processing marks are formed from the inside of the substrate, but linear processing marks are formed from the back surface of the substrate (corresponding to “modified layer inside the substrate”). .

  Under the assumptions as described above, it is presumed that the relationship between the focal position and the processing mark is as follows from the beam radius inside the substrate in FIG. 7 (state predicted from the calculation result).

+ 50μm: × (Cannot be processed)
0: × (cannot be processed)
-50μm: ○ (Surface processing)
−100μm: ◎ (Linear processing)
-150μm: × (Cannot be processed)
-200μm: × (Cannot be processed)
−250μm −
Here, the “surface processing” is processing in which the laser beam intensity is strong in the entire area (total thickness) inside the substrate and the processing trace reaches the substrate surface in the mechanism for forming the processing marks shown in FIG. . Specifically, looking at the beam shape at the focal position “−50 μm” in FIG. 7, the beam radius is 8 μm or less in the entire thickness inside the sample (substrate). For this reason, the beam intensity is high throughout the substrate, and the processing trace reaches the surface.

  As described above, in the surface processing in which the processing trace reaches the substrate surface, all energy is absorbed in a shallow range of the substrate surface. When the energy absorbed per unit volume exceeds a certain threshold value, a modified region layer 12 having a uniform depth is formed on the substrate surface as shown in FIG. In such surface processing, the intended linear processing trace is not formed.

  In addition, “unprocessable” means that the laser beam intensity is low in the entire area (total thickness) inside the substrate, linear processing traces are not formed, and processing traces are formed unevenly on the front surface or the back surface. It is processing.

  At the focal position “−100 μm” in FIG. 7, the beam radius is 8 μm or less from the back surface of the substrate to the middle position of the substrate thickness (about −75 μm). Accordingly, it is presumed that a linear processing mark is formed from the back surface of the substrate to almost half the depth.

  FIG. 9 shows the results inferred from the above simulation and the experimental results (laser output 3.2 W). As can be seen from FIG. 9, at the focal position “−100 μm”, even if the scanning speed is changed, a linear processing mark (in the table, “◎” indicates that a linear processing mark was formed). Is formed. Therefore, it can be seen that the assumption that the “beam radius of 8 μm” is the threshold value under the laser irradiation conditions as described above was correct.

<Calculation result 2: Substrate thickness 200 μm>
FIG. 10 shows the beam radius and height when the focus position is changed from +50 μm to −250 μm in seven steps with the substrate surface position set to “0” in a sapphire substrate having a thickness of 200 μm (the substrate surface is set to “0”). The calculation result is shown. Note that assumptions 1 and 2 are also assumed under the conditions of FIG.

  In this case, it is estimated from the beam radius inside the substrate in FIG. 10 that the relationship between the focal position and the processing mark is as follows (state predicted from the calculation result).

+ 50μm: × (Cannot be processed)
0: × (cannot be processed)
-50μm: ○ (Surface processing)
−100μm: ◎ (Linear processing)
-150μm: △ (Back side processing)
-200μm: × (Cannot be processed)
−250μm −
Here, the “back surface processing” means that the processing mark formation mechanism shown in FIG. 5 has a low rising height of the processing marks, and all energy is absorbed in a narrow range of the back surface, and the substrate back surface (“substrate This is a process in which a layer of a modified region having a uniform depth is formed in the vicinity. As described above, in the present invention, the starting point of the linear processing trace is the modified layer M formed inside the substrate, not the back surface of the substrate. For this reason, the “back surface processing” is precisely processing in which a processing mark is formed in a planar shape in the vicinity of the modified layer formed in the first step.

  Specifically, when the beam shape at the focal position “−150 μm” in FIG. 10 is viewed, only the vicinity of the back surface inside the sample (substrate) has a beam radius of 8 μm or less. For this reason, the processing trace does not rise like the linear processing, and as shown in FIG. 11, a layer (planar processing trace) 13 of a modified region having a uniform depth (thickness) is formed on the back surface of the substrate. The Also in this case, the intended linear machining trace is not formed.

  Then, at the focal position “−100 μm” in FIG. 10, the beam radius is 8 μm or less from the back surface of the substrate to a height of about −75 μm, and it is estimated that a linear processing mark is formed over this range.

  FIG. 12 shows the results inferred from the above simulation and the experimental results (laser output 3.2 W). As is apparent from FIG. 12, at the focal position “−100 μm”, a linear processing mark is formed even if the scanning speed is changed. Therefore, it can be seen that the assumption that the threshold of “beam radius 8 μm” was used under the laser beam conditions as described above was correct.

<Summary>
From the above, when laser pulses overlap and irradiate the processing trace, the beam intensity of the laser beam that forms a new processing trace in contact with the previous processing trace is output 3.2 W, frequency 120 MHz, pulse width 15 ps, Since the beam radius is 8 μm, it can be seen that it is 8.8 × 10 ¹² W / m ² .

  That is, when the beam intensity exceeds the threshold value in the portion of the modified layer M that is the starting point of the linear processing trace, the processing trace rises. When the beam intensity falls below the threshold before the linear processing trace reaches the substrate surface, the processing trace stops rising at that position, and the processing trace is formed again from the modified layer M. As a result, Periodic linear processing marks are formed starting from the modified layer M.

[Threshold between linear machining trace and planar machining trace]
Here, as described above, in “back surface processing”, linear processing marks are not periodically formed, but linear processing marks adjacent in the scanning direction are connected in the vicinity of the modified layer inside the substrate. A planar processing trace is formed. The boundary between “planar processing” in which such planar processing traces are formed and “linear processing” in which linear processing traces are formed will be discussed below.

  FIG. 13 is a micrograph of the inside of the substrate when the sapphire substrate having a thickness of 200 μm is scanned by irradiating a laser at a scanning speed of 200 mm / s with the focal point position set to −150 μm. Other laser irradiation conditions are the same as those described above.

  In FIG. 13, it is observed that a linear processing mark is partially formed in the back surface processing (planar processing) mark. That is, it is presumed that the conditions in the machining shown in FIG. 13 are the boundary conditions between the planar machining and the linear machining. The energy absorbed per unit volume of the processing in FIG. 13 can be obtained by the following equation.

Output (J / s) ÷ (scanning speed (m / s) x modified layer size (m) x beam diameter (m))
Specifically, in the example of FIG. 12, the energy absorbed per unit volume is
3.2 (J / s) / (200 (mm / s) x 72 (μm) x 14.6 (μm)) = 1.5 x 10 ¹⁰ (J / m ³ )
It becomes. FIG. 14 shows the results of calculating the energy absorbed per unit volume for various processing results. From FIG. 14, it can be seen that in the case of surface processing, the energy absorbed per unit volume is 2.0 × 10 ¹⁰ (J / m ³ ) or more. As described above, the machining state changes with the energy absorbed per unit volume of 2.0 × 10 ¹⁰ (J / m ³ ) as a threshold, and linear machining traces are formed below the threshold, exceeding the threshold. It is considered that a planar processing trace is formed in which linear processing traces adjacent to each other are connected.

[Summary]
In summary, in order to form periodic linear processing marks inside the sapphire substrate, it is necessary to perform processing under the following conditions.

  (1) Irradiate the substrate with a transmissive pulse laser.

  (2) To overlap laser pulses.

(3) On the back side of the substrate, the beam intensity must be 8.8 × 10 ¹² W / m ² or more.

(4) The beam intensity must be less than 8.8 × 10 ¹² W / m ² between the substrate surface.

(5) The energy absorbed per unit volume is 2.0 × 10 ¹⁰ (J / m ³ ) or less.

  By processing the sapphire substrate under the conditions as described above, periodic linear processing marks can be formed along the planned dividing line. By forming such a linear processing mark, it is possible to easily perform division in a subsequent process without significantly deteriorating the strength of the substrate. In addition, deterioration of the quality of the sapphire substrate can be suppressed, and the area of the processing trace can be reduced. For example, when a light emitting diode is formed as the final product, an element with high light emission efficiency can be formed.

  In particular, since the modified layer is formed inside the substrate and the linear processing marks are formed starting from the modified layer, damage to the elements formed on the front surface or the back surface of the substrate can be suppressed.

[Other Embodiments]
The present invention is not limited to the above-described embodiments, and various changes or modifications can be made without departing from the scope of the present invention.

  In the specific examples of the first step and the second step, the wavelength of the laser beam is changed in each step, but it is needless to say that the same wavelength is preferable in both steps.

  In the embodiment, the sapphire substrate has been described as an example of the substrate constituting the wafer. However, the present invention can be similarly applied to other brittle material substrates. However, the threshold value varies depending on the substrate material.

2 Sapphire substrate 4 Line to be cut 10 Laser processing mark M, M1 to M3 Modified layer

Claims (5)

A laser scribing method of irradiating a brittle material substrate with a pulsed laser beam and scribing along a planned cutting line,
A pulse laser beam is irradiated onto the brittle material substrate and scanned along the planned cutting line, and a modified layer is formed along the planned cutting line inside the brittle material substrate away from the front and back surfaces. 1 process,
A pulse laser beam with adjusted beam intensity is emitted from the surface side of the brittle material substrate , and the height of the focal position is fixed while keeping the pulse laser beam irradiation condition at the same condition , along the line to be divided. Scanning , and repeatedly irradiating the next pulsed laser beam to a position overlapping the processing mark formed by the previously irradiated pulsed laser beam , starting from the modified layer toward the surface of the brittle material substrate. And a second step of periodically forming a plurality of linear processing traces that proceed to a depth that does not reach the surface of the brittle material substrate along a line to be divided,
A laser scribing method comprising: In the second step, the beam intensity of the pulsed laser beam, wherein in the reforming layer exceed 8.8 × 10 ¹² W / m ^2, is adjusted to the substrate interior to the surface below 8.8 × 10 ¹² W / m ² The laser scribing method according to claim 1. ^{3. The} laser according to claim 2, wherein in the second step, laser irradiation and scanning conditions are adjusted so that energy absorbed per unit volume is 2.0 × 10 ¹⁰ J / m ³ or less in the brittle material substrate. Scribe method. The laser scribing method according to claim 1, wherein the brittle material is sapphire. In the second step, the pulsed laser beam is repeatedly irradiated is adjusted laser irradiation and scanning conditions such overlap, Les Zasukuraibu method according to Claim 1.

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