JP2015157293A - Parting method and laser processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heighten productivity when parting a substrate.SOLUTION: A parting method includes step (a) and step (b). In the step (a), the depth position of a focal point of laser light is changed in each scanning, and the laser light is used for scanning along a parting projected line in a plurality of times. In the step (b), after the step (a), the depth position of the focal point of laser light in each scanning is set in the same state, and the laser light is used for scanning along the parting projected line in a plurality of times.

Description

  The present invention relates to a cutting method and a laser processing apparatus.

  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 light-emitting elements such as light-emitting diodes are defined by dividing lines. A plurality of light emitting elements and the like are formed by dividing such a semiconductor wafer along a planned dividing line.

  Patent Document 1 discloses a method of dividing a substrate such as the above-described semiconductor wafer with a laser beam. In the method disclosed in Patent Document 1, first, a laser beam is scanned along a planned division line in a state where the laser beam is irradiated on the inside of the substrate. As a result, a modified region is formed inside the substrate along the division line. Then, a knife edge is pressed against the modified region formed in this way, and a tensile stress is applied to the modified region to divide the substrate.

JP 2006-231413 A

  In the cutting method described in Patent Document 1, it is necessary to press the substrate using a knife edge after the modified region is once formed by a laser.

  An object of the present invention is to increase productivity when dividing a substrate.

  The dividing method according to the first aspect of the present invention is a method for dividing a substrate along a planned dividing line. This dividing method includes step (a) and step (b). In step (a), the depth position of the condensing point of the laser beam is changed for each scan, and the laser beam is scanned a plurality of times along the planned dividing line. In step (b), after step (a), the laser beam is scanned a plurality of times along the planned dividing line with the same depth position of the condensing point of the laser beam for each scan.

  According to this method, the substrate can be divided by executing step (b) after executing step (a). That is, since the substrate can be divided only by scanning the laser beam, the substrate can be divided efficiently, and as a result, productivity can be increased.

  Preferably, the laser light is irradiated in a direction from the first surface side of the substrate toward the second surface side of the substrate. In step (a), the depth position of the condensing point is changed for each scan so as to move in the direction from the second surface toward the first surface. According to this method, it is possible to irradiate the inside of the substrate with laser light more efficiently.

  Preferably, the pulse energy of the laser beam in step (a) is lower than the pulse energy of the laser beam in step (b).

  Preferably, the scanning speed of the laser beam in step (a) is the same as the scanning speed of the laser beam in step (b). And the output of the laser beam in step (a) is lower than the output of the laser beam in step (b). According to this method, production efficiency can be improved.

  Preferably, the laser light in step (a) has pulse energy that does not divide the substrate.

  Preferably, the total length in the thickness direction of the processing marks formed by each scan in step (a) is not less than 70% and not more than 100% of the thickness of the substrate. According to this configuration, the division quality can be further improved.

  Preferably, the wavelength of the laser beam in step (a) and step (b) is not less than 355 nm and not more than 1064 nm. In addition, the pulse width of the laser beam in step (a) and step (b) is not less than 0.1 ns and not more than 10 ns.

  Preferably, the substrate is a tempered glass having a tempered layer with compressive stress on the surface.

  The laser processing apparatus according to the second aspect of the present invention is a laser processing apparatus that divides a substrate along a scheduled cutting line. This laser processing apparatus includes a light source, a transmission optical system, a condensing lens, a table, and a scanning control unit. The light source oscillates laser light. The transmission optical system guides the laser light in a predetermined direction. The condensing lens condenses the laser light from the transmission optical system. A substrate is placed on the table. The scanning control unit controls scanning of the laser beam. The scan control unit changes the depth position of the condensing point of the laser beam for each scan, and scans the laser beam a plurality of times along the planned dividing line. Next, the scanning control unit scans the laser light a plurality of times along the planned division line with the same depth position of the condensing point of the laser light for each scanning.

  According to the present invention, productivity when dividing a substrate can be increased.

Schematic of a laser processing apparatus. Schematic of the partial cross section of a substrate. The photograph which shows the divided cross section of the board | substrate divided | segmented in the Example.

  Hereinafter, embodiments of a laser processing apparatus and a cutting method according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a laser processing apparatus according to the present embodiment.

[Laser processing equipment]
As shown in FIG. 1, the laser processing apparatus 1 includes an apparatus main body 2, a table 3, and a scanning control unit 4. The apparatus main body 2 includes a pulse laser beam oscillation unit 21, a transmission optical system 22, and a condenser lens 23. The pulse laser light oscillation unit 21 includes a light source 21a and a control unit. The transmission optical system 22 includes a plurality of mirrors, and guides the laser light from the pulse laser light oscillation unit 21 to the condenser lens 23. The condensing lens 23 is a lens for condensing the laser light from the transmission optical system 22.

  On the table 3, a substrate S that is an object of laser processing is placed. The table 3 can move the substrate S in the vertical direction and the horizontal direction relative to the apparatus main body 2. That is, the apparatus body 2 may be moved in the vertical direction and the horizontal direction with respect to the table 3 with the table 3 fixed, or the table 3 may be moved with respect to the apparatus body 2 with the apparatus body 2 fixed. You may move to an up-down direction and a horizontal direction. Further, both the apparatus main body 2 and the table 3 may be movable in the vertical direction and the horizontal direction with respect to each other.

  The scanning control unit 4 controls scanning of laser light. Specifically, the scanning control unit 4 controls the movement of at least one of the apparatus main body 2 and the table 3. The scanning control unit 4 scans the laser beam as described below by moving at least one of the scanning main body 2 and the table 3.

[Division method]
A method for dividing the substrate S using the laser processing apparatus 1 described above will be described.

  First, as a first step, the laser beam is scanned a plurality of times along the planned dividing line while changing the depth position of the condensing point of the laser beam for each scan. Hereinafter, the first step will be described in detail. The first step corresponds to step (a) of the present invention.

  First, the laser light oscillation unit 21 controls the conditions of the pulsed laser light. For example, the output of the laser beam is preferably about 0.4 W or more and 0.6 W or less. The scanning speed is preferably about 400 mm / s to 600 mm / s.

  The pulse energy that is a value obtained by dividing the output (W) of the laser beam by the repetition frequency (Hz) is set to a pulse energy that does not divide the substrate S. Such pulse energy varies depending on the thickness and material of the substrate S, but can be set to, for example, about 10 μJ or more and 12 μJ or less.

  The wavelength of the pulse laser beam is a wavelength that is transmissive to the substrate S to be processed. For example, when the substrate S to be processed is a tempered glass having a tempered layer with compressive stress on the surface and the thickness is about 0.2 mm or more and 1.5 mm or less, the wavelength of the laser beam is 355 nm or more. The thickness is preferably about 1064 nm or less.

  The pulse width of the laser light is preferably about 0.1 ns to 10 ns.

  The laser beam controlled as described above is scanned with respect to the substrate S a plurality of times. In each scan, the depth position of the condensing point of the laser beam is changed. The depth position of this condensing point is adjusted by adjusting the position of the condensing lens 23 or adjusting the height of the table 3. The depth position of the laser beam means a position in the thickness direction of the substrate S. Further, the depth position of the condensing point is constant within one scan.

  Specifically, as shown in FIG. 2, first, in the first scanning, the laser light is adjusted so that the condensing point of the laser light is positioned at the first depth position, and the laser light is scanned. As a result, a first processing mark L1 is formed at the first depth position. FIG. 2 is a schematic view showing a sectional surface of the substrate S.

  When the first scan is completed, the laser light is then scanned by adjusting the condensing point of the laser light to be located at the second depth position. As a result, a second processing mark L2 is formed at the second depth position. Similarly, the third processing mark L3 is formed at the third depth position, and then the fourth processing mark L4 is formed at the fourth depth position. In this first step, the substrate S is not divided.

  As described above, when the laser beam is irradiated in the direction from the upper surface side (an example of the first surface side) of the substrate S to the lower surface side, the depth position of the condensing point is the direction from the lower surface of the substrate S to the upper surface. It is changed at every scanning so as to move to.

  The total of the widths w1 to w4 of the first to fourth processing marks L1 to L4 formed as described above is preferably about 70% to 100% of the plate thickness w of the substrate S. Note that the width of each of the processing marks L1 to L4 means the width of the discolored portion in the divided section of the substrate S. In addition, the width of the processing mark means the length of the processing mark in the thickness direction. Note that the number of scans in the first step is not particularly limited because it is determined according to the thickness of the substrate S and the width of the processing mark, but can be, for example, about 2 to 7 times.

  Next, as a second step, the laser beam is scanned a plurality of times along the planned dividing line without changing the depth position of the condensing point of the laser beam. Hereinafter, the second step will be described in detail. The second step corresponds to step (b) of the present invention.

  First, the laser light oscillation unit 21 controls the conditions of the pulsed laser light. For example, the output of the laser beam is preferably about 1.8 W or more and 2.2 W or less. The scanning speed is preferably 400 mm / s to 600 mm / s.

  The pulse energy of the laser beam in the second step is preferably larger than the pulse energy in the first step described above. Although it varies depending on the thickness and material of the substrate S, for example, it can be set to about 35 μJ or more and 43 μJ or less.

  The wavelength and pulse width of the pulse laser beam are the same as in the first step.

  The laser beam controlled as described above is scanned with respect to the substrate S a plurality of times. The depth position of the condensing point of the laser beam in each scan is the same. That is, in the second step, the laser beam is scanned a plurality of times without changing the depth position of the condensing point.

  Although not particularly limited, the depth position of the condensing point of the laser beam in the second step is the depth position closest to the substrate upper surface of the condensing point of the laser beam in the first step, and the depth position in the first step. It is preferable to be positioned between the condensing point of the laser beam and the depth position closest to the lower surface of the substrate.

  For example, it is preferable that the depth position of the condensing point of the laser beam in the second step is a position from about 20% to 80% of the thickness of the substrate from the lower surface of the substrate S. By setting the focal position of the laser light within this range, the substrate S can be divided more efficiently.

  Scanning of the laser light along the planned dividing line is repeated a plurality of times until the substrate S is divided. The number of repeated scans (including the first scan) at this time varies depending on the output of the laser beam and the thickness w of the substrate S, but is generally about 3 to 7 times.

  As described above, the substrate S is divided by scanning the laser beam a plurality of times. In the first step and the second step, the scanning direction is not particularly limited. For example, all scanning may be performed in the same direction, or scanning that proceeds in the first direction and scanning that proceeds in the second direction, which is the reverse direction of the first direction, may be performed alternately.

[Feature]
The dividing method according to the present embodiment has the following characteristics.

  After executing the first step, the substrate S can be divided by executing the second step. That is, since the substrate S can be divided only by scanning the laser beam, the substrate S can be divided efficiently.

  Compared with the method of dividing the substrate S only in the first step, the dividing method according to the present embodiment has better dividing quality. Moreover, in order to improve the cutting quality when the substrate S is cut only in the first step, it is necessary to slow down the processing speed. However, in the cutting method according to the present embodiment, it is good without reducing the processing speed. Can be obtained with high quality.

[Modification]
As mentioned above, although embodiment of this invention was described, this invention is not limited to these, A various change is possible unless it deviates from the meaning of this invention.

  The present invention will be described more specifically with reference to the following examples. In addition, this invention is not limited to the following Example.

The substrate was cut by the cutting method described in the above embodiment. The substrate is tempered glass (manufactured by Corning, trade name “GORILLA glass” (“GORILLA” is a registered trademark of Corning)) and has a thickness of 0.7 mm. Various conditions are as follows.
Wavelength (first and second steps): 355 nm
Pulse width (first and second steps): 1 ns
Condensing diameter (first and second steps): 5.2 μm
Each processing mark width (first step): 150 μm
Output (first step): 0.56W
Output (second step): 1.96W
Repetition frequency (first and second steps): 50 kHz
Pulse energy (first step): 11.2 μJ
Pulse energy (second step): 39.2 μJ
Pulse interval (first and second steps): 10 μm
Scanning speed (first and second steps): 500 mm / s
Number of scans (first step): 4 times Number of scans (second step): 5 times Depth position of condensing point (first step): 150 μm (first time), 300 μm (second time), 450 μm (third time) 600μm (4th time)
Depth position of condensing point (second step): 350 μm
The depth position means the distance from the lower surface of the substrate.

  FIG. 3 shows a sectional view of the substrate divided in the above embodiment. In addition, the board | substrate was parted by the scanning frequency | count of the 2nd step 5th time. As shown in FIG. 3, there was no chipping or the like in the divided cross section of the substrate, and good cross section quality could be obtained. The flatness was 15 μm. In addition, as the flatness, the difference between the most protruding portion and the most recessed portion of the divided cross section of the substrate was measured.

DESCRIPTION OF SYMBOLS 1 Laser processing apparatus 21a Light source 22 Transmission optical system 23 Condensing lens 3 Table 4 Scan control part

Claims (10)

A method of dividing a substrate along a planned dividing line,
(A) changing the depth position of the condensing point of the laser beam for each scan, and scanning the laser beam a plurality of times along the planned dividing line;
(B) After the step (a), the step of scanning the laser light a plurality of times along the planned dividing line with the same depth position of the condensing point of the laser light for each scan;
Including cutting method. The laser beam is irradiated in a direction from the first surface side of the substrate toward the second surface side of the substrate,
In the step (a), the depth position of the condensing point is changed for each scan so as to move in the direction from the second surface toward the first surface.
The cutting method according to claim 1. The pulse energy of the laser beam in the step (a) is lower than the pulse energy of the laser beam in the step (b).
The cutting method according to claim 1 or 2. The scanning speed of the laser beam in the step (a) is the same as the scanning speed of the laser beam in the step (b),
The output of the laser beam in the step (a) is lower than the output of the laser beam in the step (b).
The cutting method according to any one of claims 1 to 3. The laser beam in the step (a) has a pulse energy that does not divide the substrate.
The cutting method according to any one of claims 1 to 4. The total length in the plate thickness direction of the processing marks formed by each scan in step (a) is 70% or more and 100% or less of the plate thickness of the substrate.
The cutting method according to any one of claims 1 to 5. The wavelength of the laser beam in the step (a) and the step (b) is not less than 355 nm and not more than 1064 nm.
The cutting method according to any one of claims 1 to 6. The pulse width of the laser beam in the step (a) and the step (b) is not less than 0.1 ns and not more than 10 ns.
The cutting method according to any one of claims 1 to 7.   The cutting method according to any one of claims 1 to 8, wherein the substrate is a tempered glass having a tempered layer having a compressive stress on a surface thereof. A laser processing apparatus for cutting the substrate along a cutting line,
A light source that oscillates laser light;
A transmission optical system for guiding the laser beam in a predetermined direction;
A condensing lens that condenses the laser light from the transmission optical system;
A table on which the substrate is placed;
A scanning control unit for controlling scanning of the laser beam;
With
The scanning control unit changes the depth position of the condensing point of the laser light for each scanning, scans the laser light a plurality of times along the planned dividing line, and then scans the laser light for each scanning. The laser beam is scanned a plurality of times along the planned dividing line with the same depth position of the condensing point.
Laser processing equipment.