TW201803676A - Laser processing method and laser processing device for brittle material substrate inhibiting the thermal damage in the vicinity of the surface of the brittle material substrate and increasing the processing depth along the thickness direction - Google Patents

Abstract

An object of the present invention is to provide a laser processing method for a brittle material substrate that is capable of inhibiting the thermal damage in the vicinity of the surface of the brittle material substrate and increasing the processing depth along the thickness direction. In the present invention, the focus of the laser beam is varied along the thickness direction from the surface of a brittle material substrate, and the output of the laser beam is increased while the focus is further away from the surface of the brittle material substrate, thereby the laser beam irradiates the brittle material substrate to form a hole in the thickness direction from the surface of the brittle material substrate by the irradiation of the laser beam.

Description

Laser processing method and laser processing device for brittle material substrate

The present invention relates to a method for processing a brittle material substrate using a laser, and more particularly, to processing in a thickness direction.

It is widely used when processing brittle material substrates, such as glass substrates, sapphire substrates, and alumina substrates, in the thickness direction (depth direction), such as through-hole or non-through-hole opening processing. Lasers are used as processing devices. As one aspect of such a hole-making process using a laser, a laser beam having a larger diameter than a laser beam spot diameter (focus beam diameter, condensing diameter) is formed by irradiating the laser concentrically. The processing technology of holes or non-through holes is well known (for example, refer to Patent Document 1). [Prior Art Document] [Patent Document] [Patent Document 1] Japanese Patent Laid-Open No. 2013-146780

[Problems to be Solved by the Invention] In the case where a through-hole or non-through-hole is formed in a thickness direction of a brittle material substrate by laser, previously, the larger the target formation depth, the larger the output laser light. . However, if the output of laser light is too large, there is a problem that thermal damage (cracks and cracks) near the surface of the brittle material substrate becomes significant. On the other hand, at the depth that can be processed, there is a limit (threshold value) corresponding to the output of the laser light, and there is also a problem that no deep processing can be performed no matter how long the irradiation time is extended. The present invention was made in view of the above problems, and an object thereof is to provide a laser processing method for a brittle material substrate, which can suppress thermal damage near the surface of the brittle material substrate and increase the processing depth in the thickness direction. [Technical means to solve the problem] In order to solve the above problem, the invention of claim 1 is characterized in that it is a laser processing method for a brittle material substrate in which holes are formed in the thickness direction from the surface of the brittle material substrate by irradiating a laser beam. And while changing the focal point of the laser beam from the surface of the brittle material substrate in the thickness direction, and the further away from the surface of the brittle material substrate with the focal point, the output of the laser beam is increased, The laser beam is irradiated onto the brittle material substrate. The invention of claim 2 is the laser processing method for a brittle material substrate according to claim 1, wherein the focus is sequentially moved from the surface of the brittle material substrate in the thickness direction by a specific distance, and the above The plurality of discrete locations in the thickness direction sequentially irradiate the laser beam to the brittle material substrate, and the farther the focal point is from the surface of the brittle material substrate, the more the output increases. The invention of claim 3 is a laser processing method for a brittle material substrate as described in claim 2, characterized in that the holes formed are circular holes, and the concentric circles are drawn with the focus at each of the plurality of positions. The trajectory method scans the laser beam. The invention of claim 4 is the laser processing method for the brittle material substrate according to any one of claims 1 to 3, wherein the laser beam is a picosecond UV laser or a picosecond green laser. . The invention of claim 5 is characterized in that it is a device for processing a brittle material substrate by a laser beam, and is provided with: a stage on which the brittle material substrate is fixed; a light source that emits the laser beam; and a head The laser beam emitted from the light source is irradiated on the brittle material substrate placed on the stage; and the focal point of the laser beam is shifted from the above by moving the stage relative to the head relatively. The surface of the brittle material substrate changes in the thickness direction, and the farther the surface is from the surface of the brittle material substrate with the focus, the more the output of the laser beam emitted from the light source is increased, and the laser beam is The brittle material substrate is irradiated to form a hole in the thickness direction from the surface of the brittle material substrate. The invention of claim 6 is the laser processing apparatus according to claim 5, characterized in that the stage is moved relative to the above by sequentially moving a specific distance from the surface of the brittle material substrate in the thickness direction with the focus. Relative movement of the head, and sequentially irradiating the laser beam to the brittle material substrate at a plurality of positions discrete in the thickness direction, and the farther the focus is from the surface of the brittle material substrate, the more the The output of the laser beam emitted from the light source increases. The invention of claim 7 is the laser processing device according to claim 6, characterized in that the hole formed is a circular hole, and the head is at each of the plurality of positions, and the concentric circles are drawn with the focus. The trajectory method scans the laser beam. The invention of claim 8 is the laser processing device according to any one of claims 5 to 7, wherein the laser beam is a picosecond UV laser or a picosecond green laser. [Effects of the Invention] According to the inventions of the first to the eighth inventions, in the opening processing of the brittle material substrate in the thickness direction, the height position of the focal point and the laser output are gradually different by the accompanying processing, It can suppress the thermal damage on the surface of the brittle material substrate and form deep holes.

<Outline of Laser Processing Apparatus> FIG. 1 is a diagram schematically showing a configuration of a laser processing apparatus 100 used for processing a brittle material substrate W in an embodiment of the present invention. The laser processing apparatus 100 is roughly configured to irradiate a laser beam LB emitted from a light source 1 to a brittle material substrate W mounted and fixed on a stage 2 to specifically process the brittle material substrate W. Examples of the brittle material substrate W to be processed include a glass substrate, a sapphire substrate, and an alumina substrate. In addition to the light source 1 and the stage 2, the laser processing device 100 mainly includes: a head 3, which becomes a direct irradiation source of the laser beam LB to the fragile material substrate W; a shutter 4, which is attached to the light source 1 and is made from the light source The emission of the laser beam LB of 1 is ON / OFF; the mirror surface 5 sets the laser beam reaching the head 3 by reflecting the laser beam LB emitted from the light source 1 at a specific angle. An optical path of the light beam LB; and a control unit 10 that controls operations of the respective units of the laser processing apparatus 100. In addition, although two mirror surfaces 5 are provided in FIG. 1, these are only examples, and the number and arrangement positions of the mirror surfaces 5 are not limited to those shown in FIG. 1. The laser beam LB can be appropriately selected depending on the material of the brittle material substrate W to be processed, but is preferably, for example, a picosecond UV laser or a picosecond green laser. As the light source 1, it is sufficient to use a laser beam LB commensurate with the laser beam LB used for processing. The generation operation of the laser beam LB of the light source 1 and the ON / OFF operation of the shutter 4 are controlled by the control unit 10. The stage 2 is a portion on which the fragile material substrate W is fixed and fixed horizontally during processing. The stage 2 is free to move in the vertical direction by the driving mechanism 2m. By controlling the driving mechanism 2m by the control unit 10, in the laser processing apparatus 100, the brittle material substrate W can be moved up and down in the thickness direction during processing. In addition, the driving mechanism 2m can also movably mount the stage 2 in the horizontal one-axis direction or the two-axis direction, and also, at least the brittle material substrate W mounting portion of the stage 2 can be rotatably disposed in the horizontal plane. Thereby, adjustment or change of the processing position can be performed better. The fixing of the fragile material substrate W with respect to the stage 2 can be realized by various known aspects. For example, it may be a state of being fixed by suction, or a state of being fixed by holding an end portion of the brittle material substrate W with a specific holding device. The head 3 includes a galvanometer 3a and an fθ lens 3b. The galvanometer 3a can control the posture of the galvanometer 3a so that the incident laser beam LB can be emitted in an arbitrary direction within a specific range. An fθ lens 3b is arranged horizontally above the stage 2 so that the laser beam LB emitted from the galvanometer mirror 3a can be incident. The laser beam LB emitted from the galvanometer mirror 3a passes through the fθ lens 3b. On the other hand, a brittle material substrate W mounted and fixed on the stage 2 is irradiated horizontally from above. With this, in the laser processing apparatus 100, the position of the galvanometer 3a is continuously changed by the control of the control unit 10, so that the laser beam LB fixed on the brittle material substrate W fixed on the stage 2 can be placed. The irradiation position changes continuously. That is, the surface of the fragile material substrate W can be scanned by the laser beam LB. However, the irradiation range of the laser beam LB to the brittle material substrate W mounted on the stage 2 is set in advance according to the size or posture change range of the galvanometer mirror 3a. In the case of processing outside the irradiated range, it is necessary to move the stage 2 by the driving mechanism 2m to perform processing on a new irradiated range. Alternatively, instead of installing a driving mechanism 2m on the stage 2, a driving mechanism (not shown) may be provided on the head 3 to move the head 3 relative to the stage 2. The control unit 10 is implemented by, for example, a general-purpose computer. Since the control unit 10 executes a control program (not shown), various operations in the laser processing apparatus 100 are realized, for example, the laser beam LB is emitted from the light source 1, the stage 2 is moved, and the posture of the galvanometer 3a is changed. . <Punching Process> Next, a piercing process of the present embodiment performed on the brittle material substrate W using the laser processing apparatus 100 will be described. FIG. 2 is a diagram for explaining a scanning state of the laser beam LB processed by the hole-making process. In FIG. 2, the following situation is assumed: z = z0 is the position of the surface (upper surface) of the brittle material substrate W, since the position of z = z0 to z = z1 in the thickness direction (z direction) of the brittle material substrate W The laser beam LB is irradiated at different positions, and a substantially cylindrical non-through hole (round hole) having a specific depth of the diameter D is formed from the surface of the brittle material substrate W in the thickness direction. Here, the diameter D is a value larger than the diameter (beam spot diameter) d1 of the focal point (beam spot) F of the laser beam LB. Among them, in FIG. 2, for convenience of illustration, the diameter D is shown below z = z1. Hereinafter, the diameter D is a value of z = z0 on the surface of the brittle material substrate W. First, adjust the height position of the stage 2 on which the fragile material substrate W is mounted in such a manner that the focal point F is consistent with the surface (z = z0) of the fragile material substrate W, and output the laser beam LB from the light source 1 (Laser output below) is set to a specific value (initial value) E0. Thereafter, the laser beam LB is scanned by controlling the posture of the galvanometer 3a, and drawing a plurality of concentric circular trajectories coaxial with the diameter D and different in diameter with the center C of the focal point F in z = z0. In other words, the diameters are made different and a plurality of circumferential scans are performed. In the following, the trajectory of the center C of the focal point F may be simply referred to as the trajectory of the laser beam LB. If it is the situation shown in FIG. 2, the four concentric trajectories TR1, TR2, TR3, and TR4 are respectively drawn in a counterclockwise rotation from the outside in order to scan the laser beam LB with the laser output E0. By this scanning, the vicinity of the surface of the brittle material substrate W is processed to form a recessed portion. In addition, four trajectories TR1, TR2, TR3, and TR4 are separately recorded in FIG. 2. However, in actual processing, the output state of the laser beam LB can be maintained at a point when a circumferential scan of the laser beam LB is substantially completed. Unchanged and transition to the next round scan. In the above aspect, when the scanning of the laser beam LB at z = z0 is completed, after the stage 2 is raised by a certain distance Δz, that is, the position of the focal point F of the laser beam LB is shifted from z = z0 toward After the brittle material substrate W is displaced in the depth direction by a distance Δz, the same concentric circle-shaped scan is performed as described above. In addition, the depth and the pitch Δz of the first formed concave portion may be different. Hereinafter, the movement of the stage 2 and the scanning of the concentric circle of the laser beam LB are repeated until the focal point F of the laser beam LB reaches the position z = z1, and the scanning of the concentric circle of the position is performed. In other words, at each height position, a plurality of circumferential scans are completed in a concentric circle shape. The values of Δz and z1 are set according to the material of the brittle material substrate W or the depth of the circular hole to be formed. Usually, the position of z = z1 is set to a position shallower than the position of the bottom of the round hole. In this case, each time the height of the focal point F is made different, the laser output is gradually increased. In the case shown in Figure 2, when the laser output (final value) of z = z1 is set to E = E1 (> E0), the lightning is strengthened in stages from the initial value E = E0 to E = E1. Shoot output. That is, in the drilling process of this embodiment, by moving the height position of the focal point F from the surface of the brittle material substrate W by a specific distance in the thickness direction, the laser beam LB is irradiated to the brittle material substrate W in the The plural discrete positions in the thickness direction are sequentially performed, and the farther away from the surface of the brittle material substrate W the focus position F is, the more the laser output is increased. With this, each time the concentric circular scanning of the laser beam LB at a different depth position is repeated, the concave portion of the brittle material substrate W in the thickness direction is advanced to form a circular hole of a desired depth. Here, the maximum diameter of the scanning trajectory of the laser beam LB (the diameter of the trajectory TR1) d2 and the number of the scanning trajectories (i.e., the number of scans) are only based on the diameter D of the circular hole to be formed, the beam spot diameter d1, and the current detection. The posture change range of the mirror 3a can be set experimentally or empirically in advance. For example, if the diameter of the circular hole to be formed is 50 μm and the beam spot diameter d1 is 15 μm, then by setting d2 = 30 μm and performing 5 concentric circular scans, the desired circular hole can be formed. . The initial value E0 of the laser output may be set experimentally or empirically based on the range of laser output that can form the above-mentioned recessed portion without generating thermal damage (crack or chipping, etc.) around the recessed portion. The initial value E0 set in this case can also be selected based on the range that cannot be processed to a desired depth when the value is maintained to be processed in a certain depth direction. On the other hand, the final value E1 of the laser output is processed on the surface of the brittle material substrate W by keeping the value constant. As long as it can be processed to the target depth, it will be generated on the surface of the brittle material substrate W. The range of laser output for thermal damage can be set in advance by experiment or experience. In addition, in FIG. 2, a plurality of concentric circles are scanned sequentially from the outside, but instead, they may be sequentially performed from the inside. Or, the scanning order may be changed every time the depth position of the focus F is changed. In the case shown in FIG. 2, by changing the height position of the focal point F by Δz one by one, the surrounding scanning portion is also separated by a distance Δz in the thickness direction. However, it can also be replaced as follows. Sample (spiral scan): While the height position of the focal point F is continuously changed and the focal point F is moved by a distance Δz in the thickness direction, a plurality of rounds equivalent to the above-mentioned multiple concentric circular scans are continuously performed. scanning. In the description up to this point, although the case of forming a non-through hole is taken as an example, the same technique can be applied to the case of forming a through-hole. That is, when the total moving distance of the focal point F of the laser beam LB from the surface of the brittle material substrate W is set sufficiently large, a through hole can be formed. This case is also the same as the case of forming a non-through hole, and the specific processing conditions may be set according to the thickness of the brittle material substrate W and the irradiation conditions of the laser beam LB. In the description so far, the circular hole is formed by scanning the laser beam LB around, but the circular scanning is not necessary when the diameter D of the circular hole to be formed is small. As described above, according to the technique of this embodiment, in the hole-opening processing in the thickness direction of the brittle material substrate W, the height position of the focal point and the laser output can be changed in stages along with the progress of processing. Inhibits thermal damage to the surface of the brittle material substrate, and forms deeper round holes. In addition, only the laser output is gradually increased without changing the height position of the focal point F, and it may be difficult to advance the processing to a sufficient depth. The reason is that as the bottom of the recess is separated from the focal point F as the processing progresses, the beam spot diameter of the irradiation position of the laser beam LB becomes larger than the beam spot diameter d1 of the focal spot F, and the energy density at that position becomes It is smaller than the position of the focus F. In particular, as in the case where the laser beam LB is scanned at the outermost side of the concentric circle, that is, at the position of the track TR1, the energy density is further reduced when the irradiation position may become an inclined surface. On the other hand, the state of changing the height position of the focal point F while keeping the laser output constant is as described above. If the value is too small, it is difficult to process to the desired depth. <Modifications> In the above-mentioned embodiment, although the processing of round holes is taken as an example, the description has been made of the situation in which the hole is processed to a deeper position without thermal damage on the surface of the brittle material substrate, but the The technology of processing in the depth direction and deepening the focal position to increase the laser output can also be applied to processing in the depth direction with an arbitrary shape other than a circular hole. For example, it can also be applied to the formation of square holes or grooves. In addition, in the former case, scanning of a laser beam LB at a height position may be formed on the same axis for rectangular tracks of different sizes, and a plurality of parallel tracks may be formed at a specific pitch. In the latter case, it is only necessary to form a plurality of parallel tracks at a specific pitch. [Example] Three types of requirements for laser output are condition A (4 W), condition B (1 W), and condition C (phased increase in the range of 1 W to 4 W from the start of processing). The circular holes of the same size were processed under different conditions, and the quality of the formed circular holes was evaluated. Specifically, a glass substrate having a thickness of 1.1 mm was prepared as the brittle material substrate W, and the diameter D of the formed circular hole was 1000 μm. In addition, set the beam spot diameter d1 of the laser beam LB to 10 μm, the maximum diameter d2 of the scanning track of the laser beam LB to 1000 μm, the number of scans at one height position to 101 times, Δz to 10 μm, and the focus F toward the thickness The moving distance (z1-z0) in the direction is 400 μm. FIG. 3 is a photographed image from above and a magnified image near an end portion of a circular hole formed by processing under various conditions. Figures 3 (a), (b), and (c) are images related to condition A, condition B, and condition C, respectively. In addition, FIG. 4 is a photographic image related to a cross section of a circular hole obtained by cutting the glass substrate shown in FIG. 3 through a surface having a diameter D. Figures 4 (a), (b), and (c) are images related to condition A, condition B, and condition C, respectively. In the case of condition A, as shown in FIG. 4 (a), the processing is performed to the deepest position of 436 μm, but as shown by the arrow in the enlarged image of FIG. 3 (a), near the surface of the glass substrate, at Cracks occur at the ends of the round holes. In the case of condition B, it can be seen from FIG. 3 (b) that no thermal damage occurs, but as shown in FIG. 4 (b), the processing can be performed only to a position shallower than condition A at 346 μm. In contrast, in the case of condition C, it can be seen from FIG. 3 (c) that, as in the case of condition B, no thermal damage occurs, and, as shown in FIG. 4 (c), processing can be performed to a temperature of 377 μm. Deeper than Condition B. That is, in the case of condition C, while the laser output at the start of processing is made the same as the condition B that does not cause thermal damage, the laser output is gradually increased as the subsequent processing progresses, so that It can cause thermal damage to the surface of the substrate, and can be processed deeper than Condition B. In addition, although the final value of the laser output in condition C is the same as the value of the laser output in condition A, by setting the final value to a larger value, the moving distance of the focal point F in the thickness direction is further increased. (z1-z0), can be processed to deeper positions.

1‧‧‧ light source
2‧‧‧ carrier
2m‧‧‧drive mechanism
3‧‧‧ head
3a‧‧‧ Galvanometer
3b‧‧‧fθ lens
4‧‧‧ shutter
5‧‧‧Mirror
10‧‧‧Control Department
100‧‧‧laser processing device
C‧‧‧Focus Center
d1‧‧‧beam spot diameter
d2‧‧‧Maximum diameter of scanning trajectory
D‧‧‧ diameter of round hole
E‧‧‧Laser output
E0‧‧‧ Initial value of laser output
Final value of E1‧‧‧laser output
F‧‧‧ Focus
LB‧‧‧laser beam
TR1 ～ TR4‧‧‧‧Concentric trajectory
W‧‧‧ Brittle material substrate
z = z0‧‧‧‧ Location of substrate surface of brittle material
z = z1‧‧‧A specific position corresponding to the depth of a specific circular hole Δz‧‧‧A specific distance

FIG. 1 is a diagram schematically showing the configuration of a laser processing apparatus 100. FIG. 2 is a diagram for explaining a scanning state of the laser beam LB processed by the hole-making process. 3 (a)-(c) are photographed images from above, and enlarged images near the ends of the circular holes formed by processing under the conditions of the examples. Figures 4 (a)-(c) are camera images related to the cross section of a circular hole.

C‧‧‧Focus Center

d1‧‧‧beam spot diameter

d2‧‧‧Maximum diameter of scanning trajectory

D‧‧‧ diameter of round hole

E‧‧‧Laser output

E0‧‧‧ Initial value of laser output

Final value of E1‧‧‧laser output

F‧‧‧ Focus

LB‧‧‧laser beam

TR1 ~ TR4‧‧‧‧Concentric track

z = z0‧‧‧‧ Location of substrate surface of brittle material

z = z1‧‧‧ at a specific position corresponding to the depth of a specific circular hole

Δz‧‧‧Specific pitch

Claims (8)

A laser processing method for a brittle material substrate is characterized in that it forms a hole in the thickness direction from the surface of the brittle material substrate by irradiating a laser beam, and one side makes the focus of the laser beam from the brittle material substrate The surface changes in the thickness direction, and the farther the surface is from the surface of the brittle material substrate with the focus, the output of the laser beam is increased, and the laser beam is irradiated to the brittle material substrate. For example, the laser processing method for a brittle material substrate according to claim 1, wherein the focus is sequentially moved from the surface of the brittle material substrate in the thickness direction by a specific distance, and sequentially performed at a plurality of positions discrete in the thickness direction. The laser beam irradiates the brittle material substrate, and the farther the focal point is from the surface of the brittle material substrate, the more the output increases. For example, the laser processing method for a brittle material substrate according to claim 2, wherein the formed hole is a circular hole; and at each of the plurality of positions, the above-mentioned focus is used to draw a concentric circular trajectory to scan the laser beam. . The laser processing method for a brittle material substrate according to any one of claims 1 to 3, wherein the laser beam is a picosecond UV laser or a picosecond green laser. A laser processing device, characterized in that it is a device for processing a brittle material substrate by a laser beam, and includes: a stage on which the brittle material substrate is fixed; a light source that emits the laser beam; and A head part, which irradiates the laser beam emitted from the light source to a brittle material substrate placed on the carrier; and on the one hand, the focal point of the laser beam is caused by the relative movement of the carrier relative to the head The surface of the fragile material substrate changes in the thickness direction, and the farther the surface is from the surface of the fragile material substrate with the focus, the more the output of the laser beam emitted from the light source increases, and the laser beam is performed By irradiating the brittle material substrate, a hole is formed in the thickness direction from the surface of the brittle material substrate. The laser processing device according to claim 5, wherein the relative movement of the stage relative to the head is performed by sequentially moving a specific distance from the surface of the brittle material substrate in the thickness direction with the focus described above, and at the thickness The plurality of positions discrete in the direction sequentially perform irradiation of the laser beam on the brittle material substrate, and the farther the focal point is from the surface of the brittle material substrate, the more the output of the laser beam emitted from the light source is. For increase. For example, the laser processing device of claim 6, wherein the hole formed is a circular hole; and the head is scanned at each of the plurality of positions by drawing a concentric circular trajectory with the focus. The laser processing apparatus according to any one of claims 5 to 7, wherein the laser beam is a picosecond UV laser or a picosecond green laser.