JP2011201200A - Laser beam machining method of brittle material substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser beam machining method that, in parting a brittle material substrate, has a great latitude of a condition setting width as well as a wider processing window and that excels in end face quality.SOLUTION: The method includes: (a) a laser scribing process for forming a scribe line on a substrate, in which the substrate is locally heated by relatively moving, on the first face of the substrate, a first beam spot for a first laser irradiation along a planned parting line, and in which the substrate is locally cooled by jetting a cooling medium while relatively moving the cooling medium to a part where the first beam spot has just passed; and (b) a laser breaking process for completely parting the substrate, in which the substrate is heated by relatively moving a second beam spot for a second laser irradiation, along the scribe line, from the second face side opposite from the first face of the substrate, and in which the substrate is cooled by jetting the cooling medium while relatively moving the cooling medium to a part where the second beam spot has just passed.

Description

  The present invention relates to a laser processing method for cutting a brittle material substrate such as glass, ceramic, and semiconductor by scanning a laser beam, and more specifically, a high-quality divided section along a scribe line formed by laser scribing in advance. The present invention relates to a laser processing method for dividing a substrate by the above method.

When the glass substrate is irradiated while scanning with a laser beam, a compressive stress is generated in a region where the beam spot of the laser beam passes and is locally heated. And a refrigerant | coolant is sprayed to the position immediately after the beam spot passes, and a local stress is produced | generated in a cooled area | region (cooling spot). Thus, a stress gradient is formed by forming a region where compressive stress is generated on the substrate and a region where tensile stress is generated close to each other.
By using this stress gradient to form a crack in a glass substrate, a processing technique for performing laser scribing on the surface of the substrate (see, for example, Patent Document 1) or performing full cut processing is used (for example, (See Patent Documents 2 and 3).

  Here, the laser scribing process is mainly performed in the depth direction by performing local heating by laser irradiation and local cooling by refrigerant injection immediately after that while performing relative movement along a scheduled cutting line set on the substrate. This refers to a process of developing cracks that do not penetrate the substrate by using thermal stress distribution (distribution in which the substrate surface side is tensile stress and the substrate inner side is compressive stress). The crack formed by laser scribing forms a scribe line with the tip in the depth direction of the crack (the deepest part of the crack) remaining in the substrate. Therefore, in order to completely divide the substrate along the scribe line, after the laser scribe, a break process for allowing the cracks to penetrate in the depth direction and reaching the back surface is separately required.

  For convenience of explanation, “progress” of a crack means that the crack grows in the forward direction of the substrate. Further, “penetration” of the crack means that the crack is formed deeply in the thickness direction (depth direction) of the substrate.

  For the break treatment after laser scribing, mechanical breaks are performed by mechanically applying stress along the scribe line formed on the substrate, or after the laser scribe, thermal stress is applied again by laser irradiation along the scribe line. One of the laser breaks that is given and divided is performed.

  On the other hand, when the thickness of the substrate to be processed is reduced, a temperature difference in the depth direction of the substrate is less likely to occur when a laser beam is scanned on the substrate, and therefore the stress distribution difference in the depth direction is also reduced. The thermal stress difference in the front-rear direction in which the beam spot moves greatly contributes to the thermal stress difference in the depth direction of the substrate. As a result, the substrate is suddenly completely divided without forming a scribe line. This is called full cut processing. Full-cut processing is the same as laser scribing in that the substrate is divided using the stress gradient caused by laser irradiation, but cracks that form a full-cut state mainly develop due to the stress difference in the longitudinal direction of the laser beam. Therefore, it is the division | segmentation by a mechanism different from the laser break after a laser scribe.

  Generally, the processing end face (divided section) formed by full-cut processing is difficult to control the direction in which the crack propagates, and therefore has better linearity than the processing end face formed by laser break after laser scribing. Rather, the end face quality is clearly inferior.

  Therefore, “laser break” as used in this specification refers to a break process in which a scribe line is once formed and then divided by laser irradiation along the scribe line. It is assumed that a full cut process that suddenly completely divides without forming a scribe line is not included in the “laser break” in this specification.

Hereinafter, a processing method for cutting a substrate by excluding full-cut processing and performing break processing in a separate process after laser scribing will be described.
In the case of laser scribe processing, as described above, in order to finally divide the substrate, a break process is performed along the formed scribe line. In this break process, conventionally, mechanical breaks have been performed in which a substrate is bent and broken by pressing with a break bar or by pressing and rolling a break roller. With mechanical breaks, the load applied to the machining end face (divided cross section) is large, and even if a scribe line with high end face quality is formed by laser scribing, defects such as chipping may occur on the end face during breaks, or chipping (small fragments) ) Occurred.

  Therefore, after laser scribing by local heating by the first laser irradiation and local cooling by refrigerant injection immediately after that, laser processing that deeply penetrates the crack by performing the second laser irradiation along the formed scribe line is disclosed. (See, for example, Patent Document 4). According to this, it scans in order of the 1st beam spot by laser irradiation, the cooling spot by coolant injection, and the 2nd beam spot by laser irradiation, and both the 1st and 2nd beam spots are only in the edge part near the cooling spot. It is disclosed that a deep crack can be formed with a large stress gradient by irradiating with a spot shape having a special energy cloth having a maximum energy intensity.

  In addition, after the laser scribing by the first elliptical laser irradiation and the cooling immediately after the refrigerant injection, the second laser irradiation is performed along the formed scribe line, and the beam spot shape at this time (energy source) A method of dividing a substrate by optimizing its shape and arrangement) (see, for example, Patent Document 5) is disclosed. According to this, it is disclosed that the elliptical laser beam can be divided by optimizing the ratio between the major axis and the minor axis, making the beam asymmetrical, and making the minor axis have a special energy distribution.

International Publication Number WO03 / 008352 JP 2004-155159 A JP 2001-170786 A International publication number WO03 / 013816 JP 2003-117721 A

  According to the invention described in Patent Literature 4 and Patent Literature 5, after forming a scribe line by laser scribe processing, a second laser irradiation is performed along the scribe line to deeply penetrate the scribe line (crack). In addition, it can penetrate until it reaches the back surface and can be completely divided. And since it is the process by non-contact using a thermal stress, the process end surface (divided surface) can be made the quality excellent.

On the other hand, as the beam spot shape is limited, the degree of freedom of the processing condition setting width (process window) is narrow, and the beam spot shape and cooling spot shape affect the success or failure of the processing. It is difficult to optimize the processing conditions including.
For example, Patent Document 5 describes that the long axis length and the short axis length in the first and second laser irradiations cannot be divided unless the relationship is within an appropriate range. Further, it is disclosed that when excessive energy is applied when the cutting is not performed, a scorching phenomenon in which the surface is burnt by heat occurs.

Even if the processing conditions are optimized, the success or failure of the processing is affected depending on the material of the substrate. Specifically, in chemically strengthened soda glass having a large linear expansion coefficient, the first sliver is heated by laser irradiation in the form of an elongated elliptical beam spot, and a scribe line is formed by jetting a refrigerant immediately after heating, By performing the second laser irradiation (laser break) with a beam shape different from the first time, that is, a wide and short beam spot shape, the substrate can be divided.
However, even under the same processing conditions, for a non-alkali glass having a small linear expansion coefficient (for example, Corning glass product name: Eagle 2000), the second laser is processed under the same processing conditions as the above-described chemically strengthened soda glass. Even if irradiation is performed, it cannot be divided. In this case, if the heating amount is increased and the substrate is forcibly divided, the substrate is altered by heat, and if the heating amount is reduced, the scribe line does not change at all.

  Therefore, an object of the present invention is to provide a laser processing method that can be surely divided even when alkali-free glass having a small linear expansion coefficient is divided, and that has excellent end face quality.

  In addition, the present invention has a large degree of freedom in the condition setting range when a scribe line is formed by laser scribing processing on a brittle material substrate such as glass and then the substrate is divided by executing laser break processing. Accordingly, it is an object of the present invention to provide a laser processing method with a wide process window and excellent end face quality.

  The laser processing method of the present invention made to solve the above-mentioned problems is a laser processing method for a brittle material substrate in which the substrate is divided by performing laser irradiation along a planned cutting line set on the brittle material substrate. (A) On the first surface of the substrate, the first beam spot for performing the first laser irradiation is relatively moved along the line to be divided to locally heat the substrate, and the first beam spot is A laser scribing step for forming a scribe line on the substrate by spraying while locally moving the coolant while moving the coolant relative to the portion immediately after passing, and (b) a second beam spot for performing a second laser irradiation, While the substrate is heated by moving relatively from the second surface side opposite to the first substrate along the scribe line, the second beam spot passes through. It was cooled by spraying while relatively moving the refrigerant to the site immediately after, and a laser breaking process of completely dividing the substrate.

  According to the present invention, after the scribe line is formed on the first surface by laser scribe processing by laser scribe processing, the second beam is formed along the scribe line from the second surface (back surface) side which is the opposite surface when viewed from the first surface. The spot is scanned and heated locally. At this time, compressive stress due to heating acts in the vicinity of the surface of the second surface, and tensile stress is applied to the first surface side by the reaction force, so that the scribe line (crack) penetrates in the depth direction. In the steps so far, the scribe line (crack) may reach the second surface to be completely divided, but the scribe line (crack) may not reach the second surface. Therefore, subsequently, a refrigerant is jetted immediately after the second beam spot to locally cool, so that a tensile stress acts near the surface on the second surface side. At this time, it was expected that the penetration of scribe lines (cracks) would be suppressed because the compressive stress acts as a reaction force on the first surface side, but in reality, the penetration of cracks was promoted contrary to expectations. The experimental results were obtained with 100% probability of complete fragmentation. Since the scribe line has already been penetrated sufficiently deep by local heating by the second beam spot, it is considered that the tensile stress on the second surface side worked effectively, and the compressive stress acting on the first surface side did not affect much. .

  According to the present invention, after the scribe line is formed by laser scribe processing on the first surface side, the scribe line can be infiltrated by local heating by laser irradiation on the second surface side, and further, by the refrigerant injection immediately after that. Since the local cooling is performed, the substrate can be surely completely divided.

(Means and effects for solving other problems)
In the above invention, it is preferable that the heating by the first beam spot in the laser scribing step and the heating by the second beam spot in the laser breaking step are performed under the same conditions. Here, “same conditions” means that the processing conditions of the beam spot shape, laser output, and laser scanning speed at the time of laser irradiation are the same, and the processing conditions are not changed between the first time and the second time. Say.
According to this, it is not necessary to change the machining conditions between the first time and the second time, and it is not necessary to optimize the second machining conditions. Further, when processing a plurality of substrates one after another, it is possible to process without concern even if the substrate for processing the first surface and the substrate for processing the second surface are mixed. .

In the above invention, after the laser scribe process, the laser break process may be performed by inverting the substrate.
According to this, if there is one laser device and a mechanism for injecting one refrigerant, the processing according to the method of the present invention can be executed.

It is a schematic block diagram of the laser processing apparatus used when enforcing the board | substrate processing method of this invention. It is a figure which shows the process operation procedure of the laser scribe process which forms a scribe line by the laser irradiation of the 1st time. It is a figure which shows the processing operation procedure of the laser break process which performs a laser break process by the 2nd laser irradiation. It is a figure which shows the board | substrate cross section in each process in a laser scribe process and a laser break process. It is sectional drawing of an alkali free glass substrate when laser scribe is performed from the front surface and laser break is performed from the back surface. It is sectional drawing of an alkali free glass substrate when laser scribe is performed from the surface and laser break is also performed from the surface.

(Laser processing equipment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, an example of a laser processing apparatus used when carrying out the processing method of the present invention will be described. FIG. 1 is a schematic configuration diagram of a laser processing apparatus LS1 that can implement the processing method of the present invention. Here, a case where a glass substrate is processed will be described as an example. The target glass substrate is not particularly limited, but may be an alkali-free glass substrate in which laser break is difficult. Specifically, the present invention is particularly effective when processing non-alkali glass such as Corning's glass trade names: Eagle 2000, # 7059, # 1737, HOYA NA35, Nippon Electric Glass OA10, etc. .

  First, the overall configuration of the substrate processing apparatus LS1 will be described. A slide table 2 is provided that reciprocates in the front-rear direction (hereinafter referred to as the Y direction) of FIG. 1 along a pair of guide rails 3 and 4 arranged in parallel on a horizontal base 1. A screw screw 5 is disposed between the guide rails 3 and 4 along the front-rear direction, and a stay 6 fixed to the slide table 2 is screwed to the screw screw 5. The slide table 2 is formed so as to reciprocate in the Y direction along the guide rails 3 and 4 by forward and reverse rotation (not shown).

  A horizontal base 7 is arranged on the slide table 2 so as to reciprocate in the left-right direction (hereinafter referred to as X direction) in FIG. A screw screw 10 that is rotated by a motor 9 is threaded through a stay 10a fixed to the pedestal 7, and the pedestal 7 is moved along the guide rail 8 in the X direction by rotating the screw screw 10a forward and backward. Move back and forth.

  A table 12 that is rotated by a rotation mechanism 11 is provided on the pedestal 7, and the glass substrate A is mounted on the table 12 in a horizontal state. The rotation mechanism 11 rotates the table 12 around a vertical axis, and is formed so as to be able to rotate at an arbitrary rotation angle with respect to the reference position. Further, the glass substrate A is fixed to the table 12 by a suction chuck.

Above the table 12, the laser device 13 and the optical holder 14 are held by the mounting frame 15.
As the laser device 13, a general device for processing a brittle material substrate may be used. Specifically, an excimer laser, a YAG laser, a carbon dioxide gas laser, a carbon monoxide laser, or the like is used. For processing the glass substrate A, it is preferable to use a carbon dioxide gas laser that oscillates light having a wavelength with high energy absorption efficiency of the glass material.

  The laser beam emitted from the laser device 13 is irradiated on the glass substrate A with a beam spot having a preset shape by an optical holder 14 incorporating a lens optical system for adjusting the beam shape. As for the shape of the beam spot, a shape having a long axis (elliptical shape, oval shape, etc.) is excellent in that it can be efficiently heated along the line to be divided, but as long as local heating is possible along the line, the beam spot The shape of is not particularly limited. In the present embodiment, an elliptical beam spot is formed.

The mounting frame 15 is provided with a cooling nozzle 16 adjacent to the optical holder 14. A coolant is injected from the cooling nozzle 16. As the refrigerant, cooling water, compressed air, He gas, carbon dioxide gas, or the like can be used. In this embodiment, compressed air containing water is injected.
The cooling medium ejected from the cooling nozzle 16 is directed to a position slightly away from the left end of the beam spot so as to form a cooling spot on the surface of the glass substrate A.

  A cutter wheel 18 is attached to the attachment frame 15 via an elevating mechanism 17. The cutter wheel 18 is used so as to temporarily descend from above the glass substrate A when the initial crack Tr is formed in the glass substrate A. The cutter wheel 18 is not always necessary. That is, the initial crack Tr may be formed in advance in the previous step at the end of the division line of the substrate A.

  Further, the substrate processing apparatus LS1 is equipped with a camera 20 that can detect a positioning alignment mark preliminarily engraved on the glass substrate A. From the position of the alignment mark detected by the camera 20, the substrate is processed. A corresponding positional relationship between the position of the scheduled cutting line set on A and the table 12 is obtained so that the lowering position of the cutter wheel 18 and the irradiation position of the laser beam can be accurately positioned so that they are on the scheduled scribe line. It is.

(Machining operation procedure)
Next, a processing operation procedure by the substrate processing apparatus LS1 will be described. FIG. 2 is a diagram showing a processing operation procedure of a laser scribing process for forming a scribe line by the first laser irradiation, and FIG. 3 is a processing operation procedure of a laser breaking process for performing a laser breaking process by the second laser irradiation. FIG. 2 and 3, only the main part of FIG. 1 is shown. FIG. 4 is a view showing a cross section of the substrate at each step in FIGS.

  First, as shown in FIG. 2A, the glass substrate A is placed on the table 12 and fixed by a suction chuck. The alignment mark engraved on the glass substrate A is detected by the camera 20 (see FIG. 1), the position is adjusted based on the detection result, and the position of the line to be divided, the table 12, the slide table 2, and the base 7 is adjusted. Are related. Then, the table 12 and the slide table 2 are operated, and the position is adjusted so that the cutting edge direction of the cutter wheel 18 is aligned with the direction of the line to be cut. FIG. 4A is a cross section of the substrate at this time. Nothing is formed on either the first surface F or the second surface R.

  Subsequently, as shown in FIG. 2B, the cutter wheel is lowered by the elevating mechanism 17, the table 12 is moved, and the cutter wheel 18 is applied to the end surface A1 where the initial crack Tr of the glass substrate A is to be formed. Thus, the initial crack Tr is formed (in the case where the initial crack is previously formed in the substrate A, the operation of FIG. 2B can be omitted).

  Subsequently, as shown in FIG. 2C, the elevating mechanism 17 and the table 12 are returned to their original positions (positions shown in FIG. 2A), and the laser device 13 is operated to prepare for laser scribing. Irradiate the beam. Further, the coolant is injected from the cooling nozzle 16. The heating conditions such as the laser output P1, the laser scanning speed V1, the beam spot shape, the coolant injection amount, and the cooling conditions set at this time are set within a range in which no through cracks are generated in the substrate (that is, a full cut is not generated). These processing conditions are obtained in preliminary experiments.

  Subsequently, as shown in FIG. 2D, the table 12 is moved at the speed V 1, the first beam spot of the laser beam at the laser output P 1 formed on the substrate A, and the coolant from the cooling nozzle 16. The cooling spot is scanned at the speed V1 along the planned dividing line in this order. At this time, a compressive stress field is generated in the substrate and a tensile stress field is generated on the substrate surface due to the time difference depending on the scanning order on the substrate. Cracks Cr) are formed. FIG. 4B is a cross section of the substrate at this time. A scribe line is formed on the first surface F side. Since the compressive stress field suppresses the progress of cracks, the crack tip stops on the compressive stress field.

  With the above operation, a scribe line made of the crack Cr is reliably formed on the first surface F of the substrate A. (Needless to say, the laser heating conditions and the cooling conditions by the refrigerant are selected so that full cuts (through cracks) do not occur at this time).

Subsequently, as shown in FIG. 3A, the table 12 is returned to the original position (position of FIG. 2A). Then, the substrate A is inverted. In this embodiment, the substrate is reversed manually, but a substrate may be automatically reversed by installing a transfer robot arm. FIG. 4C shows the cross section of the substrate after inversion.
Furthermore, in preparation for laser break, the laser device 13 is operated to irradiate a laser beam. Further, the coolant is injected from the cooling nozzle 16. The heating conditions and cooling conditions such as the laser output P1, laser scanning speed V1, beam spot shape, and refrigerant injection amount set at this time are the same as the processing conditions (FIG. 2C) set at the time of laser scribing. . The laser output, the scanning speed, and the beam spot shape may be changed. However, since the process window of the present invention is sufficiently wide and can be processed without being changed, the processing conditions are used as they are.

Subsequently, as shown in FIG. 3B, the table 12 is moved at the speed V1, and the second beam spot formed on the substrate A with the laser output P1 and the cooling spot by the coolant from the cooling nozzle 16 are formed. In this order, scanning is performed at a speed V1 along the line to be divided.
At this time, first, the second beam spot is irradiated, so that compressive stress is applied to the second surface R side as shown in FIG. 4D, but simultaneously, tensile stress is applied to the first surface F side as a reaction force. As a result, the scribe line (crack Cr) penetrates deeply. There may be cases where complete division occurs at this stage, but there are cases where complete division does not occur. In the latter case, when the cooling spot subsequently passes, tensile stress acts on the surface of the second surface R, and the tip of the deeply penetrated scribe line (crack Cr) further penetrates, resulting in complete fragmentation. (FIG. 4E).

(Example)
In order to verify the effect of the present invention, a case where a laser scribing process is performed on the surface of an alkali-free glass and then a laser breaking process is performed from the back surface is compared with a case where the laser breaking process is performed from the front surface.
The alkali-free glass used is Eagle 2000 manufactured by Corning, and the thickness of the glass is 0.7 mm.

FIG. 5 is a cross-sectional view when the laser breaking process is performed from the back side after the laser scribing process on the front surface.
Laser scribing was performed under the conditions of a laser output of 260 W and a scanning speed of 40 mm / sec, and a 215 μm crack was formed. Subsequently, when laser break was performed from the back surface under the same conditions of a laser output of 260 W and a scanning speed of 40 mm / sec, it was possible to completely divide. The end face was very clean.

FIG. 6 is a cross-sectional view when the laser breaking step is performed from the same surface side after the surface laser scribing step.
Furthermore, after laser scribing under the same irradiation conditions as in FIG. 5, even if a laser break was performed from the surface side under the same irradiation conditions as in FIG. 5, cracks did not penetrate at all and could not be divided, so cracks formed by laser scribing In order to keep the depth deep, the laser output was increased so that the crack caused by laser scribing was 300 μm. Under such laser output conditions, laser break was subsequently performed from the surface. However, cracks hardly penetrated, and an altered portion was generated on the surface due to overheating.

That is, even when laser break was performed from the same side as the surface on which laser scribing was performed, there was no effect of infiltrating the cracks, and the result was that when the applied irradiation energy was excessive, it was altered.
On the other hand, when laser break is performed from the back side opposite to the surface on which laser scribing is performed, there is an effect of infiltrating the crack, and it is understood that the crack can penetrate and be divided without giving excessive irradiation energy. It was.

(Modified embodiment)
In the embodiment described above, the first and second beam spots and the cooling spot are all formed from one side of the table 12 and the substrate is inverted. However, the table 12 is divided and the divided gaps are divided. If the beam spot and the cooling spot are formed also from below the part, the beam spot and the cooling spot can be formed from the vertical direction of the substrate without inverting the substrate.

  Although the glass substrate has been described as an example in the above-described embodiment, the present invention can be applied to other brittle material substrates such as ceramics and semiconductors as long as they are brittle material substrates capable of laser scribing.

  The present invention can be used for processing of completely dividing a brittle material substrate such as a glass substrate.

12 Table 13 Laser device 16 Cooling nozzle 18 Cutter wheel A Glass substrate (brittle material substrate)
Cr crack Tr initial crack

Claims (3)

A laser processing method for a brittle material substrate, wherein the substrate is processed by irradiating a laser along a planned cutting line set on the brittle material substrate,
(A) On the first surface of the substrate, the first beam spot for performing the first laser irradiation is relatively moved along the planned dividing line to locally heat the substrate, and the first beam spot has passed. A laser scribing process for forming a scribe line on the substrate by spraying the coolant while relatively moving the coolant to the site immediately after the local cooling,
(B) A second beam spot for performing the second laser irradiation is relatively moved from the second surface side opposite to the first substrate along the scribe line to heat the substrate. A laser processing method for a brittle material substrate, comprising: a laser break process in which a coolant is sprayed and cooled while moving relative to a portion immediately after the second beam spot passes to completely divide the substrate.   The laser processing method according to claim 1, wherein the heating by the first beam spot in the laser scribing step and the heating by the second beam spot in the laser breaking step are performed under the same conditions.   The laser processing method according to claim 1, wherein a laser break process is performed by inverting the substrate after the laser scribing process.