KR101326569B1 - Laser scribe method and laser processing apparatus - Google Patents

Abstract

<Problem> When scribing a sapphire board | substrate etc. with a laser beam, a simple apparatus structure can make it possible to form a modified area of suitable width | variety, and also suppresses the damage to the element formed in the board | substrate. do.
<Method of solving> This method is a method of irradiating a pulsed laser beam to a brittle material board | substrate, and scribing along a dividing scheduled line, Comprising: A 1st process and a 2nd process are provided. A 1st process is a process of irradiating a pulse laser beam to a board | substrate, and scanning along a dividing scheduled line, and forming the modified layer along a dividing scheduled line in the inside separated from the front surface and the back surface of a board | substrate. The second step is to irradiate the substrate with the adjusted pulse laser light of beam intensity, fix the focal position of the pulse laser light and scan it along the division scheduled line, and make the modified layer the starting point on the surface of the substrate. It is a process of forming a plurality of linear process traces which progress to the depth which does not reach | perform periodically along the division planned line.

Description

LASER SCRIBE METHOD AND LASER PROCESSING APPARATUS}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser scribe method, and more particularly, to a laser scribe method in which a pulsed laser beam is irradiated onto a brittle material substrate. Moreover, this invention relates to the laser processing apparatus, especially the laser processing apparatus which irradiates a brittle material board | substrate to a brittle material board | substrate, and scribes a brittle material board | substrate along the dividing line.

Light emitting elements such as light emitting diodes are formed by laminating nitride semiconductors on a sapphire substrate. In a semiconductor device composed of such a sapphire substrate or the like, a plurality of elements such as light emitting diodes are divided and formed by a division scheduled line. And a laser scribe method is used in order to divide a semiconductor device along the division schedule line.

The laser scribing method is a method of irradiating a laser beam to a work such as a substrate and scribing, and is shown in Patent Document 1, for example. In the method shown in this patent document 1, the position of the converging point of a laser beam is adjusted to the back surface of a board | substrate, and a laser beam is scanned along the dividing scheduled line. Thereafter, the light converging point of the laser beam is moved in the thickness direction of the substrate, and the laser beam is similarly scanned along the division scheduled line.

In addition, Patent Document 2 discloses a method of scribing a modified region by irradiating a pulsed laser light to a silicon substrate or a glass substrate to form the inside of the substrate. In the method shown in this patent document 2, the condensing point of a pulsed laser beam is adjusted so that it may be located in a board | substrate. Then, after the pulsed laser light is irradiated onto the substrate, it is scanned in the lateral direction without changing the position of the light collecting point, and the next pulsed laser light is irradiated. By repeating such laser irradiation, a plurality of modified regions extending obliquely from the back surface side of the substrate toward the surface side are periodically formed along the division scheduled line.

Patent Document 1: Japanese Patent Application Laid-Open No. 2007-21557 Patent Document 2: Japanese Patent Application Laid-Open No. 2007-167875

Here, especially in the case of forming a light emitting diode by laminating semiconductors on a sapphire substrate, in order not to deteriorate the quality of the light emitting diode as a final product, a modified region by laser irradiation (hereinafter referred to as laser processing trace) (Or simply write a processing mark) is preferably less. Moreover, in order not to impair the intensity | strength, such as cross-sectional strength, it is preferable that the modified area | region is few. On the other hand, when there are few modified regions, larger division force is needed in the division | segmentation process after scribing, and in some cases, division | segmentation may not be possible.

Therefore, in laser scribing, it is necessary to scribe by forming a small (narrow) modified region easily in the subsequent step, and furthermore. In order to attain such an object, it is conceivable to periodically form a plurality of linearly modified regions (hereinafter referred to as linearly processed traces) extending in the thickness direction of the substrate along the scheduled division lines. Such linearly processed traces can be formed by the methods shown in Patent Documents 1 and 2.

However, when forming a linear processing mark by the laser scribing method shown in patent document 1, it is necessary to set the condensing point of a laser beam in a some position, and to scan a laser beam along a dividing line for every said some position. In such a method, the processing becomes complicated and the device configuration is complicated and expensive.

In addition, in the method shown in patent document 2, although it is not necessary to change the position of a light converging point, laser irradiation conditions, such as a beam intensity, do not appear at all. Therefore, even a person skilled in the art cannot refer to this patent document 2, and can stably form a linear process trace. For this reason, when the surface modification surface of a large area rather than linear shape is formed in the surface or back surface of a board | substrate, On the contrary, linear process traces become small, and a large division force is needed in a dividing process. There is. Furthermore, in this patent document 2, since 300 micrometers of processing traces are formed by 1 pulse, linear processing marks cannot be formed in the board | substrate about 100 micrometers in thickness.

An object of the present invention is to make it possible to form a modified region having an appropriate width with a simple device configuration when scribing a brittle material substrate such as a sapphire substrate with a laser beam.

The laser scribing method according to the first aspect of the invention is a method of irradiating a brittle material substrate with a pulsed laser beam and scribing along a division scheduled line, and includes a first step and a second step. A 1st process is a process of irradiating a pulsed laser beam to a brittle material board | substrate, and scanning along a division | segmentation scheduled line, and forming the modified layer along a division | segmentation scheduled line inside the surface and back surface of a brittle material substrate. . In the second step, the pulse laser light with the adjusted beam intensity is irradiated from the surface side of the brittle material substrate, the height of the focal position of the pulse laser light is fixed and scanned along the scheduled division line, and the first pulse laser light is irradiated. By repeatedly irradiating the next pulsed laser light at a position overlapped with the processing trace formed by the above, it proceeds toward the surface of the brittle material substrate with the modified layer as a starting point and does not reach the surface of the brittle material substrate. It is a process of forming a plurality of linear process traces periodically along the scheduled division 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 device configuration and has already filed a patent application (Japanese Patent Application No. 2010-193220). In this laser scribing method, linearly processed traces of a predetermined length are formed from the rear surface of the brittle material substrate toward the surface, and furthermore, the linearly processed traces are periodically formed along the predetermined line to be divided.

By the way, for example, in a light emitting diode, a semiconductor is laminated | stacked on the sapphire substrate and the element is formed. And when applying the laser scribe method of a source to such a light emitting diode, in order not to damage an element, a laser beam is irradiated from the surface (surface) in which the element is not formed. Then, in the method of a source, the modified area | region which becomes a starting point of a linear process trace is formed in the surface (back surface) in which the element was formed. In this case, the element formed in the one surface (rear surface) of a board | substrate may receive damage.

Therefore, in the present invention, a modified layer is formed inside the front and back surfaces of the brittle material substrate, and the linearly processed traces are formed using the modified layer inside the substrate as a starting point.

Here, since a scribe line can be formed in a small modification area, deterioration of quality and strength of the final product can be suppressed. In addition, it can segment relatively easily in the division | segmentation in a post process. In addition, since the modified layer is formed inside the substrate, and the linearly processed trace moves forward with the modified layer as a starting point, the damage to the device is suppressed even when the element is formed on one surface of the substrate. can do.

In the laser scribing method according to the second invention, in the laser scribing method of the first invention, in the second step, the beam intensity of the pulsed laser light exceeds 8.8 × 10 ¹² W / m ² in the modified layer to the surface. In the board | substrate, it adjusts to be less than 8.8 * 10 <^12> W / m <^2> .

)(8.8 × 10¹²W/m²)를 넘기 때문에, 펄스 레이저광을 주사하면, 레이저 가공흔은 개질층을 기점(起点)으로 하여 표면을 향하여 비스듬히 상방(上方)으로 진행한다. 그리고, 표면까지의 기판 내부에 있어서, 빔 강도는 역치(8.8 × 10¹²W/m²)를 하회하기 때문에, 역치를 하회한 시점에서 선상 가공흔의 상방으로의 진행은 멈추고, 다시 개질층에 레이저 가공흔이 형성된다. 이상의 반복에 의하여, 개질층으로부터 표면에 도달하지 않는 깊이까지 연장되는 선상 가공흔이 분단 예정 라인을 따라 주기적으로 형성된다.Here, the beam intensity of the pulsed laser light in the modified layer inside the substrate is a threshold value (

(8.8 × 10 ¹² W / m ² ), when the pulsed laser beam is scanned, the laser processing trace proceeds upward obliquely toward the surface with the modified layer as the starting point. In the substrate to the surface, the beam intensity is lower than the threshold (8.8 × 10 ¹² W / m ² ), and therefore, the progression above the linear processing marks stops at the time when the threshold is lowered, and then is applied to the modified layer. Laser processing marks are formed. By the above repetition, linear processing traces extending from the modified layer to a depth not reaching the surface are periodically formed along the division scheduled line.

In the laser scribing method according to the third invention, in the laser scribing method of the second invention, in the second step, in the brittle material substrate, the energy absorbed per unit volume is 2.0 × 10 ¹⁰ J / m ³ or less. Laser irradiation and scanning conditions are controlled.

In laser irradiation and scanning, if the energy of the second invention and the energy absorbed per unit volume exceeds 2.0 × 10 ¹⁰ J / m ³ , planar processing traces such as adjacent linear processing traces are formed and are modified. The area cannot be made small. Therefore, here, laser irradiation and scanning conditions are adjusted so that the energy absorbed per unit volume may be 2.0 * 10 <^10> J / m <^3> or less.

The laser scribing method according to the fourth invention is the laser scribing method according to any one of the first to third inventions, wherein the brittle material is sapphire.

The laser scribing method which concerns on 5th invention is a method of irradiating a pulverizing material substrate to a brittle material board | substrate, and includes the following processes.

1st process: The process mark formed by the pulse laser beam irradiated previously by irradiating the pulse laser beam with the adjusted beam intensity to a brittle material board | substrate, and fixing the height of a focal position, and scanning along a division planned line. By repeatedly irradiating the next pulsed laser light at a position overlapping with each other, a linear laser processing trace that advances in the thickness direction of the brittle material substrate is formed.

2nd process: When a linear laser processing trace progresses to a predetermined position in the substrate thickness direction, repeated irradiation of a pulsed laser beam to the brittle material substrate is stopped.

3rd process: In the state in which irradiation of the pulse laser beam to the brittle material board | substrate was stopped, when irradiation position of a pulse laser beam moves a predetermined distance in a scanning direction by scanning, irradiation of a pulse laser beam to a brittle material board | substrate is restarted.

Repetition process: A plurality of linear laser processing traces are periodically formed along the division scheduled line by repeatedly performing irradiation and scanning of a laser beam to a brittle material board | substrate, stopping of irradiation, and restarting of irradiation.

In this laser scribing method, pulsed laser light is irradiated onto a brittle material substrate and scanned along a division scheduled line. Thereby, the linear processing trace extended in the board | substrate thickness direction is formed. And when the linear process trace progresses to a predetermined position in the substrate thickness direction, irradiation of the laser beam to the substrate is stopped. For this reason, the progress of the linear processing trace is also stopped. In addition, the injection continues. After the irradiation of the laser light is temporarily stopped, the irradiation of the laser light onto the substrate is resumed at a timing at which the irradiation position of the laser light is moved by a predetermined distance in the scanning direction, whereby a linear laser processing mark is formed again. By repeating irradiation and stop of the above laser beam to a board | substrate, several linear process traces are formed periodically along a division planned line.

As described above, for example, in a light emitting diode, semiconductors are stacked on the back surface of a sapphire substrate to form an element. Therefore, it is not desirable to form a modified region on the back surface of the substrate. On the other hand, when the element is not formed in the surface of the board | substrate, the one where the linear process trace is formed even in the vicinity of a surface can divide a board | substrate easily with little force at the time of the division | segmentation in a post process.

However, in the laser scribing method by the source (Japanese Patent Application No. 2010-193220) by the inventor of the present invention, since the degree (length) of the progress of the linear processing trace is determined by the laser irradiation conditions, the length of the linear processing trace It is difficult to manage the traces accurately to reach the near-surface processing traces.

Therefore, in this invention, irradiation of a laser beam to a board | substrate is temporarily stopped when the linear processing trace progresses to a predetermined position, and the progress of the linear processing trace is stopped. For this reason, it becomes easy to advance and stop a linear processing trace to a desired position, and can form a linear processing trace to the surface vicinity of a brittle material board | substrate without strictly managing a laser irradiation condition.

The laser scribing method according to the sixth invention is the laser scribing method according to the fifth invention, wherein the third step is performed when the irradiation position of the laser light is moved to a position which does not overlap with the laser processing trace already formed.

When resuming the irradiation after stopping the laser light, if the already formed laser processing trace overlaps with the newly irradiated laser light, the already formed linear processing trace is further advanced to reach the surface of the substrate, and the surface processing trace is not linear. It may be formed. Such planar processing marks are not preferable because the modified region becomes very wide.

Therefore, in this sixth invention, the irradiation of the laser beam onto the substrate is resumed at the timing at which the laser irradiation position is moved to a position which does not overlap with the already formed laser processing trace. As a result, the surface processing traces can be prevented from forming and the linear laser processing traces can be formed surely.

In the laser scribing method according to the seventh invention, in the laser scribing method according to the fifth or sixth invention, the irradiation conditions of the pulsed laser light are such that the starting point of the linear laser processing trace is the back surface of the brittle material substrate. Is set.

Here, the linear processing trace extending from the back surface of the brittle material substrate to the vicinity of the surface can be easily formed, and the substrate can be more easily divided in the later step.

The laser scribing method according to the eighth invention is the laser scribing method according to the fifth or sixth invention, wherein the laser beam has a starting point of a linear laser processing mark in which the substrate is separated from the back surface and the surface of the brittle material substrate. The laser irradiation condition is set so as to be.

In this case, since the linearly processed traces are formed from the inside of the brittle material substrate and the back surface as a starting point, the linearly processed traces extend from the interior away from the back surface of the substrate to the surface side. For this reason, when an element is formed in the back surface of a board | substrate, the damage to an element can be suppressed.

In the laser scribing method according to the ninth invention, in the laser scribing method according to the fifth or sixth invention, the laser beam has a beam intensity of 8.8 × 10 ¹² W in a region where linear processing marks are to be formed on a brittle material substrate. It is adjusted to exceed / m ² .

In this case, since the beam intensity of the laser beam exceeds the threshold (8.8 × 10 ¹² W / m ² ) at the position where it becomes the starting point of the linear processing trace, the laser processing trace is the starting point when the laser beam is scanned. To the surface. And since irradiation of a laser beam to a board | substrate is temporarily stopped at the predetermined timing, progress of a linear process trace stops at a desired position. Then, irradiation of a laser beam is restarted and a linear process mark is again formed from a starting point. By the above repetition, a plurality of linearly processed traces are periodically formed along the division scheduled line.

The laser scribing method according to the tenth invention is the laser scribing method according to the ninth invention, wherein the laser beam is irradiated so that the energy absorbed per unit volume is 2.0 × 10 ¹⁰ J / m ³ or less in the brittle material substrate. And injection conditions are controlled.

In laser irradiation and scanning, when the conditions of the eighth invention and the energy absorbed per unit volume exceed 2.0 x 10 ¹⁰ J / m ³ , planar processing marks, such as adjacent linear processing marks, are formed and modified. The area cannot be made small. Therefore, here, laser irradiation and scanning conditions are adjusted so that the energy absorbed per unit volume may be 2.0 * 10 <^10> J / m <^3> or less.

In the laser scribing method according to the eleventh invention, in the laser scribing method according to the fifth or sixth invention, the brittle material is sapphire.

A laser processing apparatus according to a twelfth invention is a device for irradiating a brittle material substrate with a laser beam and scribing the brittle material substrate along a segmented scheduled line, the laser beam oscillating unit, a transmission optical system, a condenser lens, and a table And a moving control unit and a processing control unit. The laser beam oscillation unit includes a laser beam oscillator and a laser controller for adjusting the beam intensity of the laser beam, and emits laser light. The transmission optical system guides the laser light emitted from the laser beam oscillation unit in a predetermined direction. The condenser lens is a lens for condensing laser light from the transmission optical system. The table allows relative movement within a plane perpendicular to the laser beam from the condenser lens, and mounts a brittle material substrate to which the laser beam from the condenser lens is irradiated (raising another on the object). The movement control unit relatively moves the laser beam from the condenser lens and the table. The processing control unit controls the laser control unit and the movement control unit to periodically form a plurality of linear laser processing traces extending in the thickness direction of the brittle material substrate placed on the table along the division scheduled line. Moreover, the process control part is equipped with the 1st function, the 2nd function, and the 3rd function. The first function is applied to the processing traces formed by the pulse laser light irradiated by the irradiation of the pulse laser beam with the adjusted beam intensity by scanning the brittle material substrate together with fixing the focus position and scanning along the division scheduled line. By repeatedly irradiating the next pulsed laser light at the overlapping position, a linear laser processing trace that advances in the thickness direction of the brittle material substrate is formed. A 2nd function stops irradiation of a pulsed laser beam to a brittle material board | substrate when a linear laser processing trace progresses to a predetermined position in a board | substrate thickness direction. The third function resumes the irradiation of the pulsed laser light to the brittle material substrate when the irradiation position of the pulsed laser light in the scanning direction is moved by a predetermined distance while the irradiation of the laser beam to the brittle material substrate is stopped. And the process control part forms a plurality of linear laser processing traces along a predetermined division line periodically by repeatedly performing each function mentioned above.

By this laser processing apparatus, it is easy to advance and stop the linear processing trace to a desired position similarly to the above, and form the linear processing trace near the surface of the brittle material substrate without strictly managing the laser irradiation conditions. can do.

In the present invention as described above, when scribing brittle material substrates such as sapphire substrates, a modified region having an appropriate width can be formed with a simple device configuration. Moreover, when an element is formed in a board | substrate, the damage to an element can be suppressed. Furthermore, the progress length of the linear laser processing trace can be managed easily.

1 is an external perspective view of a wafer segmented by a processing method according to an embodiment of the present invention.
2 is a schematic configuration diagram of a laser processing apparatus for performing a processing method according to an embodiment of the present invention.
3A shows a micrograph of a modified layer formed inside a substrate.
3B shows a micrograph of a modified layer formed inside a substrate.
4 is a diagram showing a micrograph of a linear processing mark formed inside a substrate.
5 is a view for explaining a mechanism for forming a linear processing mark.
6 is a device configuration diagram for examining a threshold value at which linear processing marks are formed.
FIG. 7 is a diagram illustrating a relationship between a beam radius and a focal position in a sapphire substrate having a thickness of 150 μm. FIG.
FIG. 8 is a diagram showing a micrograph of the inside of a substrate in which a processing mark is formed only on the surface thereof.
FIG. 9 is a diagram showing a comparison between an experimental result and a result predicted from the simulation result of FIG. 7. FIG.
10 is a diagram showing a relationship between a beam radius and a focal position in a sapphire substrate having a thickness of 200 μm.
It is a figure which shows the microscope picture in the inside of a board | substrate with a process trace formed on the back surface.
FIG. 12 is a diagram showing a comparison between an experimental result and a result predicted from the simulation result of FIG. 10. FIG.
It is a figure which shows the microscope picture inside a board | substrate for demonstrating the boundary of a back surface process and a linear process.
14 is a diagram showing a relationship between energy absorbed per unit volume and a processing state;
15A is a diagram for explaining a mechanism for forming a linear processing mark;
15B is an explanatory diagram illustrating the formation mechanism of the linear processing mark.
Fig. 16A is a diagram for explaining the relationship between on and off distances of laser oscillation and linear processing marks.
It is a figure for demonstrating the relationship between the on-off distance of a laser oscillation, and a linear processing trace.
Fig. 16C is a diagram for explaining the relationship between the on and off distances of laser oscillation and linear processing marks.
FIG. 17 is a view for explaining a specific example 1 in which laser oscillation is temporarily stopped to form a linearly processed trace of a desired length; FIG.
FIG. 18 is a diagram showing a beam radius inside the substrate in the example of FIG. 17. FIG.
FIG. 19 is a view for explaining a specific example 2 in which laser oscillation is temporarily stopped to form a linearly processed trace of a desired length; FIG.
20 is a diagram showing a beam radius in the substrate in the example of FIG. 19;
Fig. 21A is a diagram for explaining the relationship between linear processing marks formed by adjusting and adjusting the on and off distance of laser oscillation.
Fig. 21B is a diagram for explaining the relationship between linear processing marks formed by adjusting and adjusting the on and off distance of laser oscillation;
Fig. 21C is a diagram for explaining the relationship between linear processing marks formed by adjusting and adjusting the on and off distance of laser oscillation.
The schematic diagram of the linear processing trace formed from the modified layer inside a board | substrate as a starting point.

I: Processing object

1 is an example of a wafer to which a laser scribing method according to an embodiment of the present invention is applied. The wafer 1 shown in FIG. 1 is formed by stacking nitride semiconductors on a sapphire substrate 2, and is formed by partitioning a light emitting element 3 such as a plurality of light emitting diodes by a division scheduled line 4. It is.

II: Laser processing device

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 is a transmission including a pulsed laser beam oscillation unit 6 including a laser beam oscillator 6a and a laser controller 6b and a plurality of mirrors for guiding the laser beam in a predetermined direction. The optical system 7 and the condenser lens 8 for condensing laser light from the transmission optical system 7 are included. The pulse laser beam oscillation unit 6 emits pulse laser light (hereinafter simply referred to as laser light) whose irradiation conditions such as beam intensity are controlled. The wafer 1 is placed on the table 9. The table 9 is drive-controlled by the drive control part 20, and can move in a horizontal plane. That is, the laser beam irradiated from the wafer 1 and the condenser lens 8 placed on the table 9 can be relatively moved in the horizontal plane. In addition, the condenser lens 8 and the table 9 on which the wafer 1 is placed can be moved in the vertical direction relatively. The laser control unit 6b and the drive control unit 20 are controlled by the machining control unit 21. [

The processing control part 21 is comprised with the microcomputer, and controls the laser control part 6b and the drive control part 20. FIG.

III ： Laser scribe method (1)

The 1st laser scribe method using the above laser processing apparatus 5 is as follows.

[First process]

First, in the pulse laser beam oscillation unit 6, processing conditions, such as the output power of a laser beam, are controlled. This laser light is irradiated onto the sapphire substrate 2 to form a modified region inside the sapphire substrate 2 away from the front and back surfaces thereof. In addition, a laser beam is a transmission laser which permeate | transmits a board | substrate. Furthermore, this laser beam is scanned along the line to be divided. As a result, a modified layer along the division scheduled line is formed inside the substrate.

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

-Example 1-

The laser irradiation conditions of FIG. 3A are as follows.

Wavelength: 1064 nm

Pulse Width: 20ps

Pulse Energy: 1.4μJ

Scan Speed: 500mm / s

Laser irradiation direction: from the surface

Focal Position: z = -100μm

In this example 1, the modification layer M1 is formed in the substantially middle part of the thickness direction of a board | substrate.

-Example 2-

The laser irradiation condition of FIG. 3B is as follows.

Wavelength: 1064 nm

Pulse Width: 20ps

Pulse energy: 1.0μJ

Scan Speed: 50mm / s

Laser irradiation direction: from the surface

Focus position: z = -140μm

In this example 2, the modified layer M2 is formed in the area | region near the back surface inside a board | substrate.

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

[The second process]

Next, processing conditions, such as the output power of a laser beam, are controlled (it mentions later), and this laser beam is irradiated to the sapphire substrate 2. Thereafter, the laser beam is relatively moved along the divisional scheduled line and scanned while the position of the focus of the laser beam (here, the same as the "condensing point") is fixed. Thereby, as shown in FIG. 4 which is the microscope picture of the inside of a board | substrate, several linear laser processing traces 10 as a modified area | region are periodically formed along a dividing scheduled line. In this way, the wafer 1 is scribed along the dividing line. In addition, in FIG. 4, although the linear process trace was formed on the back surface of a board | substrate as a starting point, in this invention, linear processing is carried out using the modified layer formed in the 1st process as a starting point instead of the back surface of a board | substrate. A scar is formed.

After the periodic linear processing marks 10 are formed in the substrate as described above, the wafer 1 is easily moved along the scribe line by adding a bending stress to the portion where the linear processing marks 10 are formed. It can be divided.

[Formation mechanism of linear processing trace]

The formation mechanism of the linear processing trace in a 2nd process is demonstrated using FIG. As shown in Fig. 5A, the laser irradiation conditions are set so that the focal position is near the modified layer M inside the substrate, and the laser beam is irradiated. In addition, the conditions of a laser beam are mentioned later. When the laser beam is irradiated, the processed trace 10a is formed in the modified layer M by a certain laser pulse (hereinafter, simply referred to as "pulse") as shown in the same figure (b).

The laser beam is scanned while maintaining the laser irradiation conditions under the same conditions including the focal position (Fig. 5 (c)). Then, the laser pulses overlap, and the next pulse is irradiated onto the previous processing trace 10a, whereby the new processing is in contact with the previous processing trace 10a as shown in the drawing (d). A scar 10b is formed. By repeating the above process, as shown to the same figure (e)-(g), the linear process trace 10 is formed.

Since the laser beam always has its focal point set near the modified layer M inside the substrate, the diameter of the laser beam is widened as the laser beam is moved upward in the substrate, whereby the beam intensity per unit area is weakened. And before the process trace 10 formed in order reaches the board | substrate surface, if the beam intensity falls below a certain value at a predetermined depth position, the process trace 10 will not rise any further, and the modified layer M will again rise. The processing mark 10c is formed. This state is shown in FIG. 5 (h) (i).

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

[Threshold value where linear processing trace is formed]

Next, the threshold value of the beam intensity at which the linear processing marks as described above are formed will be described. Here, the result of having calculated the beam diameter in the inside of a sapphire substrate on the following calculation conditions is shown after FIG. In addition, the beam diameter in the inside of a board | substrate is d shown in FIG. 6, and after FIG. 7, the beam radius in the inside of a board | substrate is shown. In addition, since the starting point of the linear processing trace is made into the back surface of a board | substrate for convenience of description after FIG. It is a modified layer M formed inside. For this reason, the "substrate back surface" in the following description corresponds to the "modified layer in a board | substrate" of this invention.

<Calculation condition>

Laser Wavelength: 355nm

Incident beam diameter (Do in FIG. 6): 5 mm

M square: 1.2

Focus of the condenser lens 8: 20 mm

Sapphire Refractive Index: 1.76

<Calculation Result 1: Substrate Thickness 150 μm>

In FIG. 7, the beam radius and the height (substrate surface is shown) when the focal position is changed to 7 steps from +50 μm to -250 μm with the focal position as "0" in a sample (sapphire substrate) having a thickness of 150 μm. The calculation result of "it was set to" 0 "is shown. In addition, FIG. 7 shows only one side of a beam, and the beam shape of an actual laser beam becomes symmetrical across beam radius "0". For example, in the focal position "-50 µm", the beam is focused at a position of -100 µm, but this is because the laser beam is refracted inside the sapphire substrate, and the focal position is that the laser beam has advanced in the air. To show the value of.

In the condition of FIG. 7, the following is assumed.

Assumption 1: The formation of processing traces is possible with the beam intensity at the beam radius of 8 m or less.

Assumption 2: In the region where the processed traces of the substrate and the surface are not formed, the processed traces are not formed even at strengths above the threshold. Even if the beam intensity is 8 μm or less, the linearly processed traces are not formed from the inside of the substrate, but linearly processed traces are formed from the rear surface of the substrate (corresponding to the “modified layer inside the substrate”).

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

+ 50μm: × (non-processable)

 0: × (non-processable)

-50μm: ○ (surface processing)

-100μm: ◎ (Linear processing)

-150μm: × (non-processable)

-200μm: × (processing impossible)

-250μm-

Here, "surface processing" is the processing in which the beam intensity of a laser is strong in the whole area | region (full thickness) inside a board | substrate in the formation mechanism of the process mark shown in FIG. 5, and a process trace reaches a board | substrate surface. Specifically, when looking at the beam shape of the focal position "-50 micrometers" of FIG. 7, the beam radius is 8 micrometers or less in the whole thickness inside a sample (substrate). For this reason, beam intensity | strength is high in the whole area | region inside a board | substrate, and a process trace reaches to the surface.

In this manner, in the surface processing in which the processing trace reaches the substrate surface, all energy is absorbed in the shallow range of the substrate surface. When the energy absorbed per unit volume exceeds a certain threshold, as shown in FIG. 8, a layer 12 of a modified region having a uniform depth is formed on the substrate surface. In such surface processing, the target linear process trace is not formed.

In addition, "impossible to process" is a process in which the beam intensity of a laser is low in the whole area | region (full thickness) inside a board | substrate, and a process trace is formed nonuniformly on a surface, a back surface, etc. without forming a linear process trace.

And in the focal position "-100 micrometers" of FIG. 7, a beam radius is 8 micrometers or less from the back surface of a board | substrate to the intermediate position (about -75 micrometers) of substantially substrate thickness. Therefore, it is estimated that the linear process trace is formed from the back surface of a board | substrate to almost half depth.

In FIG. 9, the result estimated by the above simulation and an experiment result (laser output 3.2W) are shown. As apparent from this Fig. 9, in 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 is formed) is formed. Therefore, it turns out that the assumption which made "beam radius 8 micrometer" threshold value was correct under the laser irradiation conditions mentioned above.

<Calculation result 2: board thickness 200μm>

In FIG. 10, in the 200-micrometer-thick sapphire board | substrate, the beam radius and height (when the board | substrate surface is "0") when the focal position is changed in seven steps from +50 µm to -250 µm with the substrate surface position as "0". The calculation result of FIG. In addition, also in the conditions of FIG. 10, hypotheses 1 and 2 are assumed in the same manner as described above.

In this case, it is estimated from the beam radius inside the board | substrate of FIG. 10 that the relationship of a focal position and a processing trace becomes as follows (state predicted from a calculation result).

+ 50μm: × (non-processable)

0: × (non-processable)

-50μm: ○ (surface processing)

-100μm: ◎ (Linear processing)

-150μm: △ (backside processing)

-200μm: × (processing impossible)

-250μm-

Here, the "back surface processing" is a mechanism in which the processing traces shown in FIG. 5 have a low height at which the processing traces are raised, and all energy is absorbed in a narrow range on the back surface, so that the back surface of the substrate ("modified layer inside the substrate"). It is the process of forming the layer of the modified region of uniform depth in the vicinity. In addition, in the present invention, as described above, the starting point of the linear processing marks is not the back surface of the substrate, but the modified layer M formed inside the substrate. For this reason, "back surface processing" is processing by which the process trace is formed in planar vicinity in the vicinity of the modified layer formed in the 1st process.

Specifically, when looking at the beam shape of the focal position "-150 micrometer" of FIG. 10, only the vicinity of the back surface inside a sample (substrate) is a beam radius of 8 micrometers or less. For this reason, the processing trace does not rise like linear processing, and as shown in FIG. 11, the layer (surface processing trace) 13 of the modified area | region of uniform depth (thickness) is formed in the back surface of a board | substrate. Also in this case, the target linear processing trace is not formed.

And in the focal position "-100 micrometers" of FIG. 10, a beam radius is 8 micrometers or less from a board | substrate back surface to a height of about -75 micrometers, and it is estimated that a linear process trace is formed over this range.

In Fig. 12, the results estimated from the above simulation and the experimental results (laser output 3.2W) are shown. As is apparent from this FIG. 12, in 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 value of "beam radius of 8 m" is set under the same laser beam conditions is correct.

<Cleanup>

From the above, when the laser traces are irradiated with overlapping processing traces, the beam intensity of the laser beam in which new processing traces are formed in contact with the previous processing traces has an output of 3.2 W, a frequency of 120 MHz, a pulse width of 15 ps, and a beam radius of 8 μm. , 8.8 × 10 ¹² W / m ² .

That is, when the beam intensity exceeds the threshold at the portion of the modified layer M which becomes the starting point of the linear processing marks, the processing marks rise. Then, if the beam intensity falls below the threshold until the linearly processed trace reaches the substrate surface, the rise of the processed trace is stopped at that position, and the processed trace is formed again from the modified layer M. As a result, the periodic linearly processed trace The modified layer M is formed as a starting point.

[Threshold between linear processing trace and surface processing trace]

Here, as described above, in the "rear processing", the linear processing traces are not formed periodically, but in the vicinity of the modified layer inside the substrate, planar processing traces such as linear processing traces adjacent to the scanning direction are formed. Is formed. The boundary between the "planar processing" in which such planar processing traces are formed and the "linear processing" in which the linear processing traces are formed are examined below.

FIG. 13 is a micrograph of the inside of a substrate when a sapphire substrate having a thickness of 200 μm is set to a position of a light converging point at −150 μm, and the laser beam is scanned at a scanning speed of 200 mm / s. In addition, other laser irradiation conditions are the same as the above-mentioned conditions.

In this FIG. 13, it is observed that the linear processing trace is formed partially during the back surface processing (planar processing) trace. That is, it is estimated that the conditions in the process shown by this FIG. 13 are conditions of the boundary of surface processing and linear processing. 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) × Modified Layer Size (m) × Beam Diameter (m))

Specifically, in the example of FIG. 12, the energy absorbed per unit volume is

3.2 (J / s) / (200 (mm / s) × 72 (μm) × 14.6 (μm)) = 1.5 × 10 ¹⁰ (J / m ³ )

. 14 shows the results of calculating the energy absorbed per unit volume with respect to various processing results. From this FIG. 14, when surface processing is performed, it turns out that the energy absorbed per unit volume is 2.0 * 10 <^10> (J / m <^3> ) or more. From the above, the processing state changes with the energy absorbed per unit volume of 2.0 × 10 ¹⁰ (J / m ³ ) as the threshold value, and linear processing marks are formed below the threshold value. It can be considered that planar processing marks are formed.

[theorem]

Summarizing the above, in order to form a periodic linear process trace inside the sapphire substrate, it is necessary to process on the following conditions.

(1) Irradiate a transparent pulsed laser beam to a board | substrate.

(2) The laser pulses should overlap in the scanning direction.

(3) In the modified layer inside the substrate, the beam intensity should be 8.8 × 10 ¹² W / m ^{2 or} more.

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

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

By processing a sapphire substrate on the conditions mentioned above, a periodic linear process trace can be formed along a division planned line. And by forming such a linear process trace, the division | segmentation in a post process can be performed easily, without remarkably degrading the intensity | strength of a board | substrate. In addition, deterioration of the quality of the sapphire substrate can be suppressed, and the processing trace area can be reduced to a small size, and when a light emitting diode is formed as a final product, for example, an element having good luminous efficiency can be formed.

In particular, since a modified layer is formed inside the substrate and the linearly processed trace is formed using the modified layer as a starting point, damage to the element formed on the surface or the rear surface of the substrate can be suppressed.

IV ： Laser scribe method (2)

Next, a second laser scribe method will be described. In this method, the processing control unit 21 executes the following processing.

(1) Modification of irradiating the adjusted laser beam of beam intensity to the substrate 2, fixing the focal position of the laser beam and scanning along the division scheduled line 4, and advancing in the thickness direction of the substrate 2 The linear laser processing trace as a region is formed.

(2) When the linear laser processing trace progresses to a predetermined position in the substrate thickness direction, irradiation of the laser beam to the substrate 2 is stopped. In addition, scanning (moving of the table 9) continues.

(3) The table 9 is moved, and the irradiation of the laser beam to the substrate 2 is resumed at the timing at which the irradiation position of the laser beam is moved to a position which does not overlap with the already formed linear processing trace.

(4) By repeating each of the above processes, a plurality of linear laser processing traces are periodically formed along the division scheduled line 4.

In addition, irradiation of the laser beam to the board | substrate 2 and stop of irradiation are performed by turning on and off of laser oscillation.

Each part is controlled by the processing control part 21 as mentioned above, and a laser scribe is performed in the following method.

First, in the laser beam oscillation unit 6, processing conditions, such as the output power of a laser beam, are controlled. The laser beam is then irradiated onto the substrate 2 to form a modified region on the back surface of the substrate 2. In addition, the laser beam is irradiated from the surface of the board | substrate 2 in which the element 3 is not formed. The laser beam is a transmission laser that transmits the substrate 2.

Thereafter, the laser beam is relatively moved along the divisional scheduled line and scanned while the position of the focus of the laser beam (here, the same as the "condensing point") is fixed. Thereby, as shown in FIG. 4 which is the micrograph of the inside of a board | substrate, the linear laser processing trace 10 as a modified area | region moves to the surface side by making the back surface of a board | substrate into a starting point.

Next, when the linear laser processing mark 10 advances to a desired position in the substrate thickness direction, laser oscillation is stopped and irradiation of the laser beam to the substrate 2 is stopped. Thereby, the rise of the linear processing trace 10 also stops.

When the irradiation position of a laser beam is moved to the position which does not overlap with the already formed linear processing trace 10, laser oscillation is started and irradiation of a laser beam to the board | substrate 2 is resumed. As a result, another linear processing mark 10 is formed with the substrate back surface as a starting point.

By repeating the above process, a plurality of linear processing marks 10 as shown in FIG. 4 are periodically formed along the division scheduled line.

After the plurality of linear processing marks 10 are formed in the substrate as described above, the wafer 1 is easily moved along the scribe line by adding a bending stress to the portion where the linear processing marks 10 are formed. It can be divided.

[Formation mechanism of linear processing trace]

The formation mechanism of the linear processing trace by this 2nd method is demonstrated using FIG. 15A and FIG. 15B. As shown in Fig. 15A, laser irradiation conditions are set so that the focal position is near the substrate back surface, and the laser beam is irradiated. When the laser beam is irradiated, as shown in the same figure (b), the process mark 10a is formed in the back surface of a board | substrate by a certain laser pulse.

The laser beam is scanned while maintaining the laser irradiation conditions under the same conditions including the focal position (Fig. 5 (c)). Then, the laser pulses overlap, and the next laser pulse is irradiated onto the previous processing trace 10a, thereby contacting the previous processing trace 10a as shown in the drawing (d). The processing mark 10b is formed. By repeating the above process, as shown to the same figure (e)-(g), the linear process trace 10 is formed.

As shown in FIG. 15B, the laser oscillation is stopped at the timing at which the linear processing trace 10 has advanced to a desired height. When the laser oscillation is stopped, the rise of the linear processing mark 10 also stops.

Next, after the laser beam irradiation position advances a predetermined distance in the scanning direction, laser oscillation is resumed. As a result, the processing marks are formed with the back surface of the substrate as the starting point, and the linear processing marks 10 are raised.

As described above, as shown in FIG. 15B, a plurality of linearly processed traces 10 are periodically formed along the division scheduled line.

[Threshold value where linear processing trace is formed]

The threshold value at which the linear processing marks are formed by the second method is the same as the threshold value in the first method.

That is, when the laser trace overlaps the processed trace, the beam intensity of the laser beam in which a new processed trace is formed in contact with the previous processed trace is 8.8 × 10 ¹² W / m ² . Here, when the beam intensity exceeds the threshold value on the back surface of the substrate, the processing mark rises. And when the linear processing mark rises to a predetermined position, when laser oscillation is turned off and irradiation of a laser beam to a board | substrate is stopped and a beam intensity will be less than 8.8 * 10 <^12> W / m <^2> , the rise of linear processing mark will become Stop. Further, when the laser oscillation is turned on after the irradiation position of the laser beam is shifted by a predetermined distance, the irradiation of the laser beam onto the substrate is resumed, and linearly processed traces are formed with the back surface of the substrate as a starting point. By repeating the above process, a plurality of linearly processed traces are periodically formed along the division scheduled line.

[Threshold between line processing and surface processing (backside processing)]

The boundary between the planar processing (back surface processing) and the linear processing in the second scribing method is the same as the result examined in the first scribing method.

That is, from FIG. 13 and FIG. 14, when surface processing or back surface processing is performed, the energy absorbed per unit volume is 2.0x10 <^10> (J / m <^3> ) or more. Therefore, the processing state changes with the energy absorbed per unit volume of 2.0 × 10 ¹⁰ (J / m ³ ) as the threshold value, and linear processing marks are formed below the threshold value, and when the threshold value is exceeded, the surface is the same as that of adjacent linear processing marks. It can be considered that the processing marks of.

[Distance to stop laser oscillation]

Next, using FIG. 16A, FIG. 16B, and FIG. 16C, the distance which stops laser oscillation, ie, the time of "laser oscillation off" in FIG. 15B, is examined. In addition, FIG. 16A shows the case where the distance to stop laser oscillation is long enough, and FIG. 16B and FIG. 16C show the case where the distance to stop laser oscillation is relatively short.

As shown in Fig. 16A, when the laser oscillation is resumed, when the already formed linear processing trace 10 and the laser beam Lb do not overlap, the processing trace is formed with the back surface as a starting point. In addition, linear process traces can be formed again.

On the other hand, as shown in FIG. 16B, when laser oscillation is resumed, if the laser processing trace 10 already formed and the laser beam Lb overlap, the linear processing trace 10 already formed will rise further. There is a possibility. When the linear processing trace 10 rises and reaches the substrate surface, surface processing is formed in which planar processing traces are formed in the vicinity of the surface, and a plurality of linear processing traces cannot be formed periodically.

In addition, the example shown in FIG. 16C has a long distance for stopping laser oscillation compared with the example of FIG. 16B, and the output of the laser is low compared with the example of FIG. 16B. Although a part of laser beam Lb overlaps, it is an example in which the energy of the laser absorbed by the process mark already formed does not reach the magnitude | size which can form a linear process trace. In this case, the linear processing trace 10 already formed does not rise further. For this reason, as a condition for forming a plurality of linearly processed traces periodically, it is not an essential condition that already formed processing traces do not overlap with the laser beam which resumed oscillation. After the laser oscillation is resumed, if the laser light reaching the back surface of the substrate exceeds a predetermined value without being shielded by the already formed work mark, even if a part of the already formed linearly processed trace and the laser light overlap, the starting point is the back surface. As a base material, a process mark is formed and a linear process mark is formed again.

[Specific example of managing progress length to form linear processing trace]

<Example 1>

The processing conditions at the time of forming the linear process trace of 150 micrometers and width 25 micrometers from the back surface of a board | substrate as shown in FIG. 17 are shown below.

Laser oscillation distance l _on ： 25μm

Distance to stop laser oscillation l _off ：

When _off ≥ L / 2 + r _top , the laser light and the processing trace do not overlap when the laser oscillation is resumed.

L ： Processing mark size

r _top : Beam radius at machining stop

In Fig. 18, since the beam radius at the position of 150 mu m in height from the rear surface is 4 mu m, a plurality of linear processing marks can be formed by setting l _off ? 9 mu m in the case of L = 10 mu m.

<Example 2>

The processing conditions in the case of forming the linear processing trace of 100 micrometers and width 20 micrometers from the back surface of a board | substrate as shown in FIG. 19 are shown below.

Laser oscillation distance l _on ： 20μm

Distance to stop laser oscillation l _off ：

When _off ≥ L / 2 + r _top , the laser light and the processing trace do not overlap when the laser oscillation is resumed.

From FIG. 20, since the beam radius at the position of 100 micrometers in height from the back surface of a board | substrate is 2 micrometers, in case of L = 10 micrometers, several _off- line process traces can be formed by _setting l _{off more than} 7 micrometers.

In addition, even if l < _off <L / 2 + r _top, if the overlap of a process trace and a laser beam is small enough, as shown in FIG. 16C, it is possible to form a linear process trace.

In addition, since the inclination θ of the linear processing trace changes due to the ratio of the repetition frequency of the laser beam and the scanning speed, these conditions need to be appropriately set. Furthermore, the smaller the l _off for stopping the laser oscillation, the larger the absorbed energy per unit volume. Therefore, it is necessary to set it so as not to exceed the above-described energy threshold in order to prevent the surface processing traces from forming.

[Change of processing trace by adjustment of laser oscillation on, off]

Figure 21a, is shown in Figure 21b and Figure 21c, the laser oscillation on the distance (l _on), and a laser oscillation-off distance (l _off) the change in the processing marks the line of the case where a number of changes in the Fig.

21A is a schematic diagram of linear processing marks formed when the distance of laser oscillation on and the distance of laser oscillation off are set together to 25 µm.

21B is a schematic diagram of linear processing marks formed when the distance of laser oscillation on is 25 µm and the distance of laser oscillation off is 50 µm. In this example, the length of the linearly processed traces is the same as in the case of Fig. 21A, but the interval between the linearly processed traces adjacent to each other is widened. For this reason, compared with the case of FIG. 21A, the modified area | region as a whole board | substrate is narrow, and a big force is needed in a division process compared with the case of FIG. 21A.

21C is a schematic diagram of linear processing marks formed when the distance of laser oscillation on is 12.5 µm and the distance of laser oscillation off is 25 µm. In this example, the length of the linear processing marks is shorter than in the case of FIG. 21A. In addition, the space | interval of the linear processing trace adjacent to each other is the same as that of the case of FIG. In this example, similarly to Fig. 21B, the modified region as the whole substrate is narrower than in the case of Fig. 21A, and a large force is required in the dividing step as compared with the case of Fig. 21A.

[theorem]

In summary, in the second laser scribing method, in order to form a periodic linear processing mark inside the sapphire substrate, it is necessary to process under the following conditions.

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

(2) The laser pulses should overlap in the scanning direction.

(3) The beam intensity per unit time should be 8.8 × 10 ¹² W / m ^{2 or} more at the starting point of the linear processing mark.

(4) Stop the laser oscillation until the linear processing trace reaches the substrate surface so that the beam intensity is less than 8.8 × 10 ¹² W / m ² .

(5) The energy absorbed per unit volume in unit time should be 2.0 × 10 ¹⁰ (J / m ³ ) or less.

By processing a sapphire substrate on the conditions mentioned above, a periodic linear process trace can be formed along a division planned line. In particular, since the laser oscillation is stopped and the progress of the linear processing trace is stopped when the linear processing trace advances to a desired position, the formation of a planar processing trace can be prevented, and a plurality of linear processing traces can be surely formed. . Moreover, the advance position of a linear process trace can be arbitrarily controlled.

And by forming the above-mentioned linear process trace, the division | segmentation in a post process can be performed easily, without remarkably degrading the intensity | strength of a board | substrate. In addition, since the processing trace area can be reduced to a small extent, deterioration of the quality of the sapphire substrate can be suppressed, and when a light emitting diode is formed as a final product, for example, an element having good luminous efficiency can be formed.

V ： Laser scribe method (3)

For example, in a light emitting diode, a semiconductor is laminated on a sapphire substrate to form an element. When the second laser scribing method is applied to such a light emitting diode, laser light is irradiated from the surface where the device is not formed so as not to damage the device. Then, in the second method, a modified region serving as a starting point of the linear processing trace is formed on the back surface on which the element is formed. In this case, the element formed on the back surface of the substrate may be damaged.

Therefore, in the third laser scribing method, a modified layer is formed inside the substrate and separated from the front and rear surfaces thereof, and the linearly processed traces are formed using the modified layer inside the substrate as a starting point.

This laser scribe method is as follows. In addition, the structure of a laser processing apparatus is the same as that of the 2nd laser scribe method.

First, in the laser beam oscillation unit 6, processing conditions, such as the output power of a laser beam, are controlled. The laser beam is then irradiated onto the substrate 2 to form a modified region in the interior away from the front surface and the rear surface of the substrate 2. In addition, a laser beam is a transmission laser which permeate | transmits a board | substrate. Furthermore, this laser beam is scanned along the line to be divided. As a result, a modified layer along the division scheduled line is formed inside the substrate.

The specific example of the modified layer formed in the inside of a board | substrate is the same as that of FIG. 3A and 3B.

The processing after the modified layer is formed in the substrate as described above is the same as in the second laser scribe method. That is, a plurality of linearly processed traces are periodically formed along the division scheduled line with the modified layer formed inside the substrate as a starting point. In FIG. 22, the modified layer M formed by this 3rd method, and several linear process trace 10 are shown typically. In addition, in FIG. 22, "on" shows the distance (time) of laser oscillation on, and "off" shows the distance (time) of laser oscillation off.

After the plurality of linear processing marks 10 are formed in the substrate as described above, the wafer 1 is easily moved along the scribe line by adding a bending stress to the portion where the linear processing marks 10 are formed. It can be divided.

In this third method, since a scribe line can be formed in a small modification area, deterioration in quality and strength of the final product can be suppressed. In addition, it can segment relatively easily in the division | segmentation in a post process. In addition, since the modified layer is formed inside the substrate, and the linearly processed traces are advanced from the modified layer as a starting point, damage to the element can be suppressed when the element is formed on the back surface of the substrate. .

[Other Embodiments]

The present invention is not limited to the above embodiments, and various variations or modifications can be made without departing from the scope of the present invention.

Although the wavelength of a laser beam is changed in each process in the specific example of said 1st process and 2nd process, it is a matter of course that it is preferable to set it as the same wavelength in both processes.

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

2: sapphire substrate
4: line to be divided
10: laser processing mark
M, M1 ~ M3: modified layer

Claims (12)

A laser scribing method of irradiating a pulsed laser light to a brittle material substrate and scribing along a scheduled line for dividing,
And irradiating a pulsed laser beam to the brittle material substrate, and scanning along the division scheduled line, and forming a modified layer along the division scheduled line in the interior away from the front and back surfaces of the brittle material substrate. 1 process,
In addition to irradiating the pulsed laser light whose beam intensity is adjusted from the surface side of the brittle material substrate, the height of the focal position of the pulsed laser light is fixed and scanned along the predetermined division line, thereby formed by the previously irradiated pulsed laser light. By repeatedly irradiating the next pulsed laser light at a position overlapping the processing mark, the modified layer is set as a starting point toward the surface of the brittle material substrate and proceeds to a depth not reaching the surface of the brittle material substrate. A second step of periodically forming a plurality of linear processing traces to be formed along a scheduled line for dividing
Laser scribe method having a. The method of claim 1,
In the second step, control of the laser light beam intensity, exceeds 8.8 × 10 ¹² W / m ² in the modified layer, to 8.8 × 10 ¹² W / m ² to fall below (下廻) in the substrate to the surface Laser scribe method. 3. The method of claim 2,
In the second step, in the brittle material substrate, 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. 4. The method according to any one of claims 1 to 3,
And the brittle material is sapphire. A laser scribing method of irradiating a pulsed laser light to a brittle material substrate and scribing,
By irradiating the pulsed laser light whose beam intensity is adjusted to the brittle material substrate, and fixing the height of the focus position and scanning along the line to be divided, the position overlapped with the processing trace formed by the first irradiated pulsed laser light. A first step of forming a linear laser processed trace that advances in the thickness direction of the brittle material substrate by repeatedly irradiating the next pulsed laser light,
A second step of stopping the repeated irradiation of the pulsed laser beam onto the brittle material substrate when the linear laser processing trace has advanced to a predetermined position in the substrate thickness direction;
A method for resuming the irradiation of the pulsed laser beam to the brittle material substrate when the irradiation position of the pulsed laser beam is moved a predetermined distance in the scanning direction by the scanning while the irradiation of the pulsed laser beam to the brittle material substrate is stopped; With 3 processes,
By repeatedly performing the said 1st process, the said 2nd process, and the said 3rd process, a plurality of linear laser processing traces are formed periodically along a division scheduled line,
Laser scribe method. The method of claim 5,
The said 3rd process is a laser scribe method performed when the irradiation position of the said pulsed laser beam is moved to the position which does not overlap with the laser processing trace already formed. The method according to claim 5 or 6,
The said laser beam is a laser scribe method in which irradiation conditions are set so that the origin of a linear laser processing trace may become the back surface of a brittle material substrate. The method according to claim 5 or 6,
Irradiation conditions are set so that the said laser beam may be set so that the origin of a linear laser processing trace may become inside the board | substrate which is separated from the back surface and the surface of a brittle material substrate. The method according to claim 5 or 6,
The said laser beam is a laser scribing method in which the beam intensity is adjusted so that it may exceed 8.8 * 10 <^12> W / m <^2> in the planar process trace formation area | region in a brittle material board | substrate. 10. The method of claim 9,
The laser scribing method of the said laser beam is irradiated and a scanning condition adjusted so that the energy absorbed per unit volume may be 2.0 * 10 <^10> J / m <^3> or less in a brittle material substrate. The method according to claim 5 or 6,
And the brittle material is sapphire. It is a laser processing apparatus which irradiates a brittle material board | substrate to a brittle material board | substrate, and scribes a brittle material board | substrate along the dividing line.
A laser beam oscillator comprising a laser beam oscillator, a laser controller for adjusting the beam intensity of the laser beam, and emitting a pulsed laser light;
A transmission optical system for guiding the laser light emitted from the laser beam oscillation unit in a predetermined direction;
A condenser lens for condensing laser light from the transmission optical system;
A table for mounting relative to a brittle material substrate to which relative movement is possible in a plane perpendicular to the laser beam from the condensing lens and to which the laser light from the condensing lens is irradiated;
A movement control unit for relatively moving the laser beam from the condensing lens and the table;
The processing control part which controls the said laser control part and the said moving control part, and periodically forms along the division | segmentation line the several linear laser processing trace extended in the thickness direction of the brittle material board | substrate mounted on the said table.
And,
Wherein the machining control unit comprises:
By irradiating the pulsed laser light whose beam intensity is adjusted to the brittle material substrate, and fixing the height of the focus position and scanning along the line to be divided, the position overlapped with the processing trace formed by the first irradiated pulsed laser light. 1st function which forms the linear laser processing trace which advances in the thickness direction of a brittle material board | substrate by repeatedly irradiating the following pulse laser beam,
A second function of stopping the repeated irradiation of the pulsed laser beam onto the brittle material substrate when the linear laser processing trace has advanced to a predetermined position in the substrate thickness direction;
An irradiating of the pulsed laser light to the brittle material substrate when the irradiation position of the pulsed laser light is moved a predetermined distance in the scanning direction by the scanning while the irradiation of the pulsed laser light to the brittle material substrate is stopped; 3 functions
And,
By repeatedly performing the above functions, a plurality of linear laser processing traces are periodically formed along the division scheduled line,
Laser processing apparatus.

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