KR20180013679A - Method and apparatus for laser processing substrate of brittle material - Google Patents

Abstract

Provided are a laser processing method and apparatus of a brittle material substrate to reduce a processing time while suppressing thermal damage in comparison to a conventional method. When a plurality of holes are formed in a thickness direction from the surface of the brittle material substrate by irradiating a laser beam, a machining target spot is switched at one height position whenever the irradiation of the laser beam to one machining target spot at one height position is finished. The focus of the laser beam is shifted from the surface of the brittle material substrate by a predetermined distance in the thickness direction whenever the irradiation of the laser beam is finished at all machining target spots at one height position. So, the plurality of holes is gradually formed.

Description

METHOD AND APPARATUS FOR LASER PROCESSING SUBSTRATE OF BRITTLE MATERIAL BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of processing a brittle material substrate using a laser, and more particularly to processing in a thickness direction at a plurality of locations.

For example, a brittle material substrate represented by a glass substrate, a sapphire substrate, an alumina substrate, or the like may be used as a processing means for performing processing in the thickness direction (depth direction), such as a perforation or non- A method of using a laser is widely practiced.

In such a form of such a laser drilling process, the laser is radially concentrically irradiated to form a through hole or a non-through hole with a diameter larger than the beam spot diameter of the laser (beam diameter at the focus position, condensed diameter) (For example, refer to Patent Document 1).

Japanese Patent Application Laid-Open No. 2013-146780

When a through hole or a non-through hole is formed in a thickness direction by laser with a plurality of portions of a brittle material substrate, conventionally, the formation of each through hole or non-through hole is sequentially performed. However, in such a method, there is a problem that thermal damage (occurrence of chipping and chipping) is likely to occur in the vicinity of the region, since the same region is continuously irradiated with the laser until the formation of the hole is completed.

In addition, when the depth of the hole to be formed is deep, the brittle material substrate needs to be moved in the thickness direction every time the individual hole is formed, so that there is also a problem that it takes time to process.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a laser machining method of a brittle material substrate capable of shortening a machining time while suppressing thermal damage in the case of performing machining in a thickness direction at a plurality of locations on a brittle material substrate The purpose is to provide.

According to a first aspect of the present invention, there is provided a laser processing method for a brittle material substrate for forming a plurality of holes in a thickness direction from a surface of a brittle material substrate by irradiating a laser beam, Each time the irradiation of the laser beam at the height position ends, the portion to be processed at the one height position is switched, and every time the irradiation of the laser beam at all of the processing target portions at the one height position is finished The focal point of the laser beam is moved from the surface of the brittle material substrate by a predetermined distance in the thickness direction, and the focal point is moved to a new height position, thereby gradually forming the plurality of holes.

According to a second aspect of the present invention, there is provided a laser machining method for a brittle material substrate according to the first aspect, characterized in that the output of the laser beam is increased each time the focal point reaches a new height position.

According to a third aspect of the present invention, there is provided a laser machining method for a brittle material substrate according to claim 2, characterized in that the plurality of holes are round holes and the laser beam is scanned so that the focal point forms a locus of concentric circles at the machining object .

The invention of claim 4 is a laser machining method of a brittle material substrate according to any one of claims 1 to 3, characterized in that the laser beam is a picosecond UV laser or a picosecond green laser.

According to a fifth aspect of the present invention, there is provided a laser machining apparatus for machining a brittle material substrate with a laser beam, comprising: a stage on which the brittle material substrate is mounted and fixed; a light source for emitting the laser beam; And a head for irradiating a brittle material substrate mounted on the stage, wherein, each time the irradiation of the laser beam at one height position in one machining target position is completed, the head is moved from the one height position to the machining target And the stage is moved relative to the head every time the irradiation of the laser beam at all of the machining target positions at the one height position is completed so that the focus of the laser beam is focused on the brittle material substrate Repeatedly moving the focal point to a new height position by moving a predetermined distance in the thickness direction from the surface Thereby gradually forming a plurality of holes.

According to a sixth aspect of the present invention, in the laser machining apparatus according to the fifth aspect, the output of the laser beam emitted from the light source increases every time the focal point becomes a new height position.

According to a seventh aspect of the present invention, there is provided a laser machining apparatus as set forth in the sixth aspect, wherein the plurality of holes are round holes, and the head scans the laser beam so that the focal point forms a locus of concentric circles at the processing target spot do.

The invention of claim 8 is the laser machining apparatus according to any one of claims 5 to 7, wherein the laser beam is a picoseco UV laser or a picosecond green laser.

According to the first to eighth aspects of the present invention, the perforation of the surface of the brittle material substrate at a plurality of locations in the thickness direction is carried out by a gradual processing method in which a plurality of holes are formed in parallel with each other in small increments, And the machining time can be shortened as compared with the case of sequential machining in which individual holes are sequentially formed.

Fig. 1 is a diagram schematically showing a configuration of a laser machining apparatus 100. Fig.
Fig. 2 is a view for explaining the scanning form of the laser beam LB in the drilling process.
3 is a diagram for explaining the sequence of sequential machining.
Fig. 4 is a diagram for explaining the order of gradual processing.
Fig. 5 is a picked-up image of a glass substrate on which a plurality of round holes are formed by gradual processing and sequential processing, from above the round holes.

<Outline of Laser Processing Apparatus>

Fig. 1 is a diagram schematically showing a configuration of a laser machining apparatus 100 used for processing a brittle material substrate W in an embodiment of the present invention. The laser processing apparatus 100 roughly irradiates the brittle material substrate W with the laser beam LB emitted from the light source 1 by irradiating the brittle material substrate W fixedly mounted on the stage 2, So as to execute machining.

Examples of the brittle material substrate W to be processed include a glass substrate, a sapphire substrate, and an alumina substrate.

The laser processing apparatus 100 includes a head 3 which is a direct irradiation source of a laser beam LB to a brittle material substrate W and a head 3 which is a light source 1 And a laser beam LB emitted from the light source 1 is reflected at a predetermined angle so as to be incident on the head 3 And a control section 10 for controlling the operation of each part of the laser processing apparatus 100. The laser processing apparatus 100 includes a mirror 5 for determining the optical path of the laser beam LB, In FIG. 1, two mirrors 5 are provided, but this is only an example, and the number and arrangement of the mirrors 5 are not limited to those shown in FIG.

The laser beam LB may be appropriately selected depending on the material of the brittle material substrate W to be processed, and for example, a picosecond UV laser or a picosecond green laser is suitable. As the light source 1, a laser beam LB used for processing may be employed. The operation of generating the laser beam LB in 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 where the brittle material substrate W is horizontally mounted and fixed at the time of processing. The stage 2 is constructed so as to be movable in the vertical direction by the driving mechanism 2m. The driving mechanism 2m is controlled by the control unit 10 so that the brittle material substrate W can be moved up and down in the thickness direction during processing in the laser processing apparatus 100. [ The driving mechanism 2m may be provided so that the stage 2 can be moved in the horizontal uniaxial direction or the biaxial direction and at least the mounting position of the brittle material substrate W among the stages 2 can be rotated It may be installed as much as possible. As a result, the machining position can be adjusted or changed appropriately.

The fixing of the brittle material substrate W to the stage 2 may be achieved by various known methods. For example, it may be fixed by suction, or it may be fixed by sandwiching an end portion of the brittle material substrate W by a predetermined holding means.

The head 3 has a galvanometer mirror 3a and an f? Lens 3b. The galvanometer mirror 3a is controlled in its posture by the control unit 10 so that the incident laser beam LB can be emitted within a predetermined range in an arbitrary direction. The f? Lens 3b is horizontally disposed above the stage 2 and is arranged so that the laser beam LB emitted from the galvanometer mirror 3a can enter the galvanometer mirror 3a, The laser beam LB is irradiated vertically above the brittle material substrate W horizontally mounted and fixed to the stage 2 by passing through the f? Lens 3b. Thereby, in the laser machining apparatus 100, the attitude of the galvanometer mirror 3a is continuously changed in accordance with the control by the control unit 10, whereby the laser beam from the brittle material substrate W mounted on the stage 2, The irradiating position of the laser beam LB can be continuously varied. As a result, the brittle material substrate W can be scanned from above by the laser beam LB.

The irradiation range of the laser beam LB with respect to the brittle material substrate W mounted and fixed on the stage 2 is predetermined in accordance with the size and attitude change range of the galvanometer mirror 3a. It is necessary to move the stage 2 by the driving mechanism 2m to perform the machining on the new irradiable range.

Instead of installing the drive mechanism 2m on the stage 2, a drive 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. A control program not shown is executed in the control unit 10 to perform various operations in the laser machining apparatus 100 such as the emission of the laser beam LB from the light source 1 or the movement of the stage 2, The attitude change of the mirror 3a is realized.

<Drilling>

Next, the boring process according to the present embodiment, which is performed using the laser machining apparatus 100 described above with respect to the brittle material substrate W, will be described as an example in which machining is performed at one place. Fig. 2 is a view for explaining a scanning form of the laser beam LB in such drilling.

In Fig. 2, z = z0 is the position of the surface (upper surface) of the brittle material substrate W, and z = z0 to z = z1 in the thickness direction (z direction) Through holes (round holes) of a predetermined depth and a diameter D in the thickness direction from the surface of the brittle material substrate W are formed by changing the irradiation position of the brittle material substrate W. Here, the diameter D is larger than the diameter (beam spot diameter) d1 of the focal spot (beam spot) F of the laser beam LB. In Fig. 2, the diameter D on the circumferential surface is shown below z = z1. Hereinafter, it is assumed that the diameter D is a value at the surface of the brittle material substrate W, that is, at z = z0.

First, the height position of the stage 2 on which the brittle material substrate W is mounted and fixed is adjusted so that the focal point F coincides with the surface (z = z0) of the brittle material substrate W, And sets the output (hereinafter, laser output) of the laser beam LB to a predetermined value (initial value, E0). Thereafter, by controlling the attitude of the galvanometer mirror 3a, the center C of the focus F is coaxial with the diameter D at z = z0, and a plurality of concentric circles of different diameters The beam LB is scanned. In other words, a plurality of rounds of scanning are performed with different diameters. In the following description, the locus of the center C of the focus F is simply referred to as the locus of the laser beam LB.

In the case shown in Fig. 2, the laser beam LB is scanned with the laser output E0 such that four concentric trajectories TR1, TR2, TR3 and TR4 are sequentially drawn from the outside in the counterclockwise direction. The vicinity of the surface of the brittle material substrate W is processed by such a scan to form a concave portion. In FIG. 2, four trajectories TR1, TR2, TR3, and TR4 are described independently. However, at the time of actual machining, when one round of scanning by the laser beam LB is almost completed, LB may be maintained while maintaining the output state of the next main scan.

When scanning with the laser beam LB at z = z0 is completed in the above-described mode, the stage 2 is raised by the predetermined pitch DELTA z, that is, the position of the focus F of the laser beam LB Is shifted in the depth direction of the brittle material substrate W by the distance DELTA z at z = z0, and then the concentric scanning as described above is executed. In addition, the depth of the concave portion formed first and the pitch [Delta] z may not always coincide with each other. Thereafter, until the focal point F of the laser beam LB reaches the position z = z1 and the movement of the stage 2 and the concentric circular shape by the laser beam LB are performed until the concentric scanning at this position is performed Is repeated. In other words, a plurality of main scanning is performed concentrically at the respective height positions. The values of DELTA z and z1 are determined according to the material of the brittle material substrate W and the depth of the round hole to be formed. Usually, the position where z = z1 is set at a position shallower than the position where the bottom of the round hole becomes.

However, in this case, the laser output is gradually increased every time the height of the focus F is made different. In the case shown in FIG. 2, when the laser output (final value) at z = z1 is E = E1 (> E0), the laser output is increased stepwise from the initial value E = E0 to E = E1.

That is, in the drilling process described here, the irradiation of the laser beam LB to the brittle material substrate W is carried out by moving the height position of the focus F by a predetermined distance in the thickness direction from the surface of the brittle material substrate W, And the laser output is increased as the height position of the focus F is further away from the surface of the brittle material substrate W. [

Thereby, every time the concentric scanning of the laser beam LB at the different depth positions is repeated, the formation of the recess in the thickness direction of the brittle material substrate W progresses, and finally, .

The diameter D of the circular hole to be formed and the beam spot diameter d1 are set so that the maximum diameter of the trajectory of the laser beam LB (diameter of the trajectory TR1, d2) and the number of scan loci (i.e., And the attitude change range of the galvanometer mirror 3a may be determined experimentally or empirically in advance. For example, in the case where the diameter of a circular hole to be formed is 50 mu m and the beam spot diameter d1 is 15 mu m, five circular concentric scanning is performed with d2 = 30 mu m so that a desired circular hole can be formed do.

The initial value E0 of the laser output may be determined experimentally or empirically in advance from the range of the laser output capable of forming the concave portion and causing no thermal damage (such as cracking or chipping) around the concave portion . In this case, the initial value E0 determined in this case may be selected from a range in which machining to a desired depth can not be performed when processing is performed in the depth direction while the value is kept constant.

On the other hand, the final value E1 of the laser output can be machined up to the target depth when the value is kept constant from the surface of the brittle material substrate W, It may be determined experimentally or empirically in advance from the range of the laser output that causes thermal damage to the substrate. However, when the thickness of the brittle material substrate W is thin, the laser output may be kept constant (E1 = E0) as the initial value E0 is maintained.

In Fig. 2, a plurality of concentric circles are sequentially arranged from the outside, but they may be arranged in order from the inside instead. Or the scanning order may be changed every time the depth position of the focus F changes.

2, the positions where the main scanning is performed are spaced apart by the distance? Z in the thickness direction by making the height position of the focus F different by? Z, but instead of the height of the focus F (Spiral scanning) in which a plurality of times of main scanning corresponding to the main scanning in a plurality of concentric circles described above are continuously performed while the focus F is shifted by a distance DELTA z in the thickness direction by changing the position continuously. In such a case, the laser output may be continuously increased.

In the above description, the case of forming the non-through hole is described as an example, but the same method can be adopted even in the case of forming the through hole. That is, when the total movement distance of the focal point F of the laser beam LB from the surface of the brittle material substrate W is made sufficiently large, a through hole can be formed. In this case as well, the specific processing conditions may be determined in accordance with the thickness of the brittle material substrate W and the irradiation conditions of the laser beam LB, as in the case of forming the non-through holes.

In the above description, circular holes are formed by scanning the laser beam LB in the main scanning direction. However, in the case where the diameter D of the circular hole to be formed is small, the main scanning is not essential.

&Lt; Processing of multiple holes &

Next, processing for forming a plurality of holes in the thickness direction on the surface of one brittle material substrate W to be performed using the laser processing apparatus 100 will be described. Such processing of the plurality of holes can be realized simply by a method (hereinafter referred to as sequential processing) in which individual holes are sequentially formed by a method of perforating holes at one place described above, but in the present embodiment, It is carried out by the method called processing. Gradually, by using the above-described technique, while changing the portion to be processed each time the irradiation of the laser beam LB at one height position in one machining target position is completed, So that it is formed in small increments.

3 is a diagram for explaining the sequence of sequential machining. It is assumed that a plurality of round holes (non-through holes) having a depth h in the thickness direction of the brittle material substrate W are formed at pitch p. It should be noted that irradiation of the laser beam LB at one height position is performed by the main scanning described above. 3 (a) shows four adjacent areas a, b, c, and d among the individual round hole forming scheduled areas H0. In Fig. 3, only the planned formation regions H0 adjacent to each other in the direction of the oblique view are shown, but in the actual processing, the planned formation region H0 may be determined two-dimensionally.

In the sequential processing, first, the focal point F of the laser beam LB is adjusted to the height (z = z0) of the surface of the brittle material substrate W, and as shown in Fig. 3, And the shift of the height position of the focus F of the laser beam LB is repeated to execute the drilling process. 3 (c), when a round hole Ha is formed in the region a, the laser beam LB is focused on the laser beam LB in the same manner as in the case of the concentric circular main scanning in the region b The round holes Hb are formed in the region b repeatedly as shown in Fig. 3 (d). After the formation of the round hole Hb is completed, processing is then performed on all of the to-be-formed regions H0 in the order of region c → region d. Finally, as shown in FIG. 3 (e) A desired plurality of round holes H (Ha, Hb, Hc and Hd) are formed in the to-be-formed region H0 (regions a, b, c and d).

On the other hand, Fig. 4 is a diagram for explaining the gradual processing procedure adopted in the present embodiment. Now, it is assumed that a plurality of round holes (non-through holes) having a depth h in the thickness direction of the brittle material substrate W are formed with pitch p as in the case of the sequential machining shown in Fig. 4A also shows four neighboring regions a, b, c, and d among the round hole formation scheduled regions H0. Of course, also in the case of processing gradually, the to-be-formed region H0 may be determined two-dimensionally.

First, as shown in Fig. 4 (b), the focal point F of the laser beam LB is adjusted to the height (z = z0) of the surface of the brittle material substrate W, (LB). As a result, a concave portion is formed in the region a as shown in Fig. 4 (c). Subsequently, unlike sequential machining, gradual machining is performed in the region b while keeping the height position of the focus F at z = z0. As a result, as shown in Fig. 4 (d), a recess is formed in the region b following the region a. Subsequently, main scanning is performed on the area c.

As shown in Fig. 4 (e), the main scanning in the state in which the height position of the focus F is maintained at z = z0 is performed for all the to-be-formed regions H0 (areas a, b, c, and d) to form recesses in the respective regions, the height position of the focus F is shifted by the distance DELTA z, and the main scanning is performed again for the region a. As a result, as shown in Fig. 4 (f), the formation of the recess in the region a proceeds. When the main scanning is completed, main scanning is performed on all the to-be-formed regions H0 in the order of region b? Region c? Region d without changing the height position of the focus F, As shown in Fig. Likewise, the main scanning in the order of the shift of the distance DELTA z at the height position of the focus F and the area a, the area b, the area c, and the area d is performed at a predetermined position z = Z1). Finally, a desired plurality of round holes H (Ha, Hb, Hc and Hd) are formed in the respective to-be-formed regions H0 (regions a, b, c and d) .

If the sequential processing and the gradual machining are compared, in the case of the sequential machining, the laser is continuously irradiated to the region until the formation of the hole in one planned region is completed, so that the temperature in the vicinity of the region rises Heat damage (cracking, occurrence of chipping) is likely to occur. On the other hand, in the case of gradual processing, the processing time per one time in each of the formation scheduled regions is short, and furthermore, the planned formation regions to be processed are sequentially changed, so that the temperature rise in each of the planned formation regions is unlikely to occur. Therefore, thermal damage (generation of cracks and chipping) is hard to occur.

In the case of progressive machining, the stage 2 is moved up and down every time the machining is performed in each of the machining target areas so that the focal point F of the laser beam LB is moved from the surface z = z0 to z = z1, while in the case of gradual processing, the movement of the focus F from the surface z = z0 to z = z1 is only intermittent from the start of machining to the end of machining. This means that the machining time is shorter than the gradual machining. In addition, the effect of shortening the time is remarkable as the number of holes to be drilled is larger.

As described above, according to the present embodiment, by perforating the surface of the brittle material substrate W at a plurality of locations in the thickness direction in a manner of gradually forming a plurality of holes in parallel, And the machining time can be shortened as compared with the case of performing sequential machining in which individual holes are sequentially formed.

<Modifications>

In the above-described embodiment, the description is given on the assumption that the hole is formed under a certain machining condition. However, the machining condition may be changed at the time the machining proceeds to the depth in the middle.

In the above-described embodiment, a description has been given of a mode in which the formation of a plurality of holes is sequentially performed by taking round holes as an example. However, the application of the sequential processing to the formation of a plurality of holes is not limited to a circular hole, It is also applicable to the case where machining is performed. For example, it can be applied to the formation of square holes and grooves. In the case of the former case, scanning of the laser beam LB at one height position may be carried out in a main scan so that loci of rectangular shapes of different sizes are formed coaxially, or a plurality of loci parallel to a predetermined pitch May be formed. In the latter case, a plurality of loci parallel to each other at a predetermined pitch may be formed.

[Example]

The machining of a plurality of round holes having the same shape as each other was gradually carried out by both the machining and the sequential machining.

Specifically, a glass substrate (OA-10G manufactured by Nippon Electric Glass Co., Ltd.) having a thickness of 0.1 mm was prepared as a brittle material substrate W, and nine round holes having a diameter D of 1 mm were formed into a square pit To 1.5 mm. As the laser beam (LB), a picosecond UV laser was used. The specification of the picosecond UV laser is as follows.

Wavelength: 355 nm;

Repetition frequency: 300kHz;

Output: Initial value 1.5W → Final value 1.5W;

Scanning speed: 200 nm / s;

Pulse energy: 5 mu J;

Pulse fluence: 6.4 J / cm 2;

Pulse period: 0.67 mu m;

Pulse width: 50ps.

The beam spot diameter d1 of the laser beam LB is 10 m, the maximum diameter d2 of the scan locus of the laser beam LB is 1 mm, the number of scans at one height position is 20 ,? Z was 4 占 퐉, and the moving distance (z1-z0) of the focus F in the thickness direction was 36 占 퐉.

Fig. 5 is a picked-up image of a glass substrate on which a plurality of round holes are formed by respective machining methods from above the round hole. 5 (a) is an image in the case of gradual processing, and FIG. 5 (b) is an image in the case of progressive processing.

When two images are compared with each other, cracks are confirmed at points indicated by arrows in an image in the sequential processing shown in Fig. 5 (b), but cracks are not observed in the image in the gradual processing shown in Fig. 5 (a) .

In addition, the processing time per one hole in the processing was about 3.9 seconds, whereas the processing time per one hole in the sequential processing was about 4.4 seconds.

The above results indicate that the processing side is superior in terms of suppression of thermal damage and reduction of processing time, rather than sequential processing.

1 light source
2 stage
2m drive mechanism
3 head
3a Galvano Mirror
3b lens
4 Shutter
5 mirror
10 control unit
100 laser processing equipment
C Center of focus
D Diameter of round hole
F Focus
H0 (a, b, c, d) (round hole)
H (Ha, Hb, Hc, Hd) Round hole
LB laser beam
W brittle material substrate
d1 Beam spot diameter
h (depth of round hole)
p (pitch of round hole)

Claims (8)

A laser processing method for a brittle material substrate which forms a plurality of holes in a thickness direction from the surface of a brittle material substrate by irradiating a laser beam,
Each of the positions to be machined at the one height position is switched every time the irradiation of the laser beam at one height position in one machining target position ends, The focal point of the laser beam is moved from the surface of the brittle material substrate by a predetermined distance in the thickness direction every time the irradiation of the laser beam is finished, Of the brittle material substrate. The method according to claim 1,
And increases the output of the laser beam every time the focus becomes a new height position. 3. The method of claim 2,
Wherein the plurality of holes are round holes,
And the laser beam is scanned so that the focal point forms a locus of concentric circles in the portion to be processed. 4. The method 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 apparatus for processing a brittle material substrate with a laser beam,
A stage on which the brittle material substrate is mounted and fixed,
A light source for emitting the laser beam;
And a head for irradiating the laser beam emitted from the light source to a brittle material substrate mounted on the stage,
Each time the head irradiates a laser beam at one height position in one machining target position, the head switches the machining target spot at the one height position, and all the machining target points The focal point of the laser beam is moved a predetermined distance in the thickness direction from the surface of the brittle material substrate by moving the stage relative to the head every time the irradiation of the laser beam in the brittle material substrate is finished, And a plurality of holes are gradually formed by repeating the above-described steps. 6. The method of claim 5,
And increases the output of the laser beam emitted from the light source every time the focus becomes a new height position. The method according to claim 6,
Wherein the plurality of holes are round holes,
Wherein the head scans the laser beam so that the focal point draws a concentric trajectory on the portion to be processed. 8. The method according to any one of claims 5 to 7,
Wherein the laser beam is a picosecond UV laser beam or a picosecond green laser.

Images