JPS62168688A - Laser beam machining device - Google Patents

Abstract

PURPOSE:To improve the work accuracy by projecting laser light on the body to be worked via an optical fiber and condensing lens and by arranging the field diaphragm body which forms a square restriction at the laser light projection end of the optical fiber as well. CONSTITUTION:The X-Y table loading the body 2 to be worked is provided on a laser machining device and the laser light incident end 20 of an optical fiber 18 is connected to a laser light oscillator 3 as well and the projection end thereof is arranged by setting a condensing lens 6 and the optical axis. Moreover, a field diaphragm body 19 is arranged between the condensing lens 6 and the body 2 to be worked by setting the center position to the optical axis of laser light 8 and a square restriction is opened in parallel to the scanning direction of the laser light. With this mechanism, the light intensity distribution of the laser light 8 becomes flat and is converted into a rectangular beam by the field diaphragm body 19. Consequently, the laser light machining accuracy and product yield are improved.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

This invention uses a thin film type photoelectric conversion substrate as a workpiece, for example, as a solar cell, and performs laser scribing by irradiating the workpiece surface with laser light, thereby forming a predetermined pattern on the thin film processing surface. The present invention relates to a laser processing device for forming open grooves.

[Prior art and its problems]

Targeting the photoelectric conversion substrate mentioned above, the first conductive film layered on the insulating substrate is laser scribed to form a first groove of a predetermined shape and patterned, and then patterned as described above. After layering an amorphous semiconductor film on the conductive film, a second open groove is formed in the semiconductor film by applying a Zaskura f-cut process to a predetermined position using the first open groove as a reference, and patterning is performed. After forming a second conductive film on the semiconductor film, the second conductive film described above is applied.
There is known a method of baking using a laser beam, in which circuit patterning is performed by forming a third groove at a predetermined position using the groove as a reference by laser scribing. Next, a conventional laser processing apparatus for performing the above-described laser scribing process will be described with reference to FIG. 6. 6th
In the figure, 1 is an X-Y table on which a workpiece 2 such as the optical Tk conversion board mentioned above is mounted, 3 is a laser oscillator, for example, a YAG laser, 4 is a collimator lens, 5 is a reflection mirror, and 6 is a prefectural optical lens. , 7 is an operation control device. With this configuration, during processing, the operation control device 7 controls the laser beam 8 oscillated by the laser oscillator 3 to be passed through the collimator lens 4, the reflection mirror 5. The processing surface of the workpiece 2 is irradiated via the condensing lens 6, and on the other hand, the X-Y table 1 is
is the X axis according to a predetermined pattern. The movement is controlled in the Y-axis direction, whereby the irradiation spot of the laser beam scans the surface to be processed to perform laser scribe processing, thereby forming an open groove 9 corresponding to a predetermined circuit pattern. By the way, the beam spot of the laser light oscillated and output from the laser oscillator 3 in the above configuration is usually circular,
In the conventional laser processing method, in which laser scribing is performed by directly irradiating the laser beam onto the surface to be processed through a collimator lens and a condensing lens, the shape of the focused spot of the laser beam is shown in Fig. 7 (A). As shown in the figure (b), the energy density is highest in the center of the focused spot, and the energy density decreases toward the periphery of the spot, as shown in the figure (b). It exhibits a kind of Gaussian distribution with a sharp attenuation. However, as mentioned above, the focused spot of the pulsed laser light is circular and the light intensity density distribution exhibits a Gaussian distribution, and the focused spot of the pulsed laser light is directly irradiated onto the workpiece surface, and a predetermined pattern is formed. The conventional processing method in which laser scribe processing is performed while scanning according to the following problems occurs. In other words, in order to form a groove 9 with a uniform width by irradiating a focused spot of the same shape onto the surface to be machined and scanning the irradiation spot on the surface to be machined, it is necessary to scan the irradiation spot along the groove 9 as shown in FIG. The repeated pulses of the irradiation spot (A) must be scanned in the Y direction while finely overlapping the irradiation spot (A) to repeatedly irradiate the irradiation spot, and as a result, the loss due to the overlapping of the irradiation spot becomes large and an open groove 9 is formed. The machining speed becomes slower. On the other hand, if the pitch interval between the repeated pulse irradiation spot and the next irradiation spot is increased as shown in FIG. 9 to increase the laser processing speed and the overlapping width of the irradiation spots is narrowed, the side edges of the open groove 9 As a result, it becomes difficult to form grooves of uniform width. In addition, if the number of repeated pulses is increased to increase the processing speed, there is a laser oscillation characteristic in which the energy per pulse decreases, so there is a limit to increasing the number of repeated pulses, and the light intensity density decreases. The output of a laser oscillator whose distribution exhibits a Gaussian distribution is at most 1
Up to about 2W, the increase in output energy per pulse cannot be expected as much. Therefore, the method of increasing the number of repetitive pulses does not necessarily contribute to increasing the speed of laser scribing. Furthermore, as mentioned above, since the light intensity distribution of the irradiation spot is a Gaussian distribution exhibiting a high energy density in the central part, as shown in FIG. After layering the first conductive film 11 and laser scribing the first grooves 12, laser scribing the second grooves 14 on the amorphous semiconductor film 13 layered thereon. When forming the open grooves 14 using a laser beam, the groove bottom machined surface of the open grooves 14 is not flat due to the light intensity distribution of the laser beam irradiation spot described above, and the machined depth of the open grooves 14 is smaller than that of the grooves as shown in the figure. The machining depth is locally excessive and extremely deep in the center, and the machining depth is the first.
It reaches the conductive coating 11 of the coating 11, causing machining damage to the coating 11, and opening) 1. On the other hand, the machining depth is insufficient at the side edge portion inside -, and the melted residue 15 remains. In addition, protrusions 16 and scattered objects 17 are likely to adhere to the opening edges of the grooves 14. Moreover, as shown in the figure, when a thin film such as a photoelectric conversion element formed as a thin film laminate is processed as a workpiece and a groove is selectively formed therein to separate the laminated region, the groove 14 as described above is processed. If surface unevenness or processing damage to the underlying film occurs, the product characteristics will vary greatly, such as short circuits in the laminated region, increased resistance, and lower photoelectric conversion efficiency. This will lead to problems such as a decrease in yield. In addition, in the conventional laser processing apparatus shown in FIG. If the irradiation spot size on the workpiece surface changes even slightly, it becomes extremely difficult to control the movement of the laser optical system and scan the laser beam.As a result, conventional laser beam transmission methods In this case, the laser optical system must be fixed and the workpiece 2 must be relatively moved and controlled by the XY table 1 to scan the irradiated laser beam. However, with this method, for example, 400 x 12
When laser scribing a thin film photoelectric conversion substrate with a large size of about 0.00 mm, the maximum stroke of the X-Y table must be at least 2400 mm, which increases the footprint of the processing equipment. And X
-The large Y table makes high-speed machining difficult, making it unsuitable for mass production of product machining.

[Purpose of the invention]

The present invention has been made in consideration of the above points, and it eliminates the drawbacks of the conventional laser processing method described above, prevents the occurrence of machining damage of open grooves for thin film workpieces, and also enables processing along the machining evaporation turn. An object of the present invention is to provide a laser processing device that can laser scribe an open groove of uniform width at a high processing speed.

[Key points of the invention]

In order to achieve the above object, the present invention irradiates a workpiece with a laser beam oscillated by a laser oscillator via an optical fiber and a condensing lens, and also irradiates a workpiece with a laser beam on the downstream side of the laser beam output end of the optical fiber. A field diaphragm body with a rectangular aperture hole parallel to the scanning direction of the light condensing spot is installed. By first guiding the oscillated laser light of the laser oscillator, whose light intensity distribution exhibits a Gaussian distribution, to the optical core/C bar, the optical fiber changes the light intensity distribution in the beam radial direction as the laser light propagates within the core. It exhibits characteristics that flatten the surface. Note that such characteristics apply even if the oscillation mode of the laser oscillator used is a single mode laser beam.
Alternatively, multimode laser light also shows a similar tendency to be flattened. Therefore, by irradiating the surface of the workpiece with a laser beam transmitted through an optical fiber through a condensing lens, laser scribing with a uniform processing depth can be performed, and the bottom surface of the open groove is also flat, resulting in the generation of melted residue. Therefore, damage caused by processing damage to the processed surface of the thin film as described in FIG. 10 can be minimized. Furthermore, in combination with the above-mentioned optical fiber, a rectangular field diaphragm parallel to the scanning direction of the laser beam is interposed in the middle of the laser beam path, so that the laser beam irradiated onto the workpiece surface during laser scribing is repeated. By selecting a small overlapping ratio of pulse widths, it is possible to form grooves with high precision and uniform width along the processed evaporation turn at high speed.

[Embodiments of the invention]

1 and 2 each show a configuration diagram of a laser processing apparatus according to a different embodiment of the present invention, and the same members corresponding to those in FIG. 6 are given the same reference numerals. First of all
In the figure, the laser processing device is equipped with an X
-Y table, laser optical system described below, and operation control device N
It consists of 7. The laser optical system here includes a laser oscillator 3, an optical fiber 18 connected to the laser oscillator, a condenser lens 6, and a field diaphragm 19. Here, the optical fiber 18 has a laser beam input end 20 connected to the laser oscillator 6, and a laser beam output end 21 facing the condenser lens 6 with the optical axis aligned. Further, a field diaphragm 19 is interposed between the condenser lens 6 and the workpiece 2 with its center aligned with the optical axis of the laser beam 8, and the field diaphragm 19 is provided as shown in FIG. As shown, a rectangular aperture hole 19a is opened parallel to the scanning direction of the laser beam irradiated onto the workpiece. On the other hand, the laser oscillator 3 has a wavelength of 1.06 μm, a repetition pulse frequency of 1 to 99 K Ilz, and an output of 0.1 to 100 W, for example.
A YAG laser is used. Further, the oscillation mode of the laser oscillator is not necessarily limited to a single mode, but also a multimode that can oscillate a higher output than a single mode. With the above configuration, the pulsed laser beam oscillated by the laser oscillator 3 enters the laser beam input end 20 of the optical fiber 18, propagates through the optical fiber 18, reaches the output end 21, and from there the condenser lens 6, Aperture hole 19 of field aperture body 19
The beam passes through the beam a and is irradiated onto the processing surface of the workpiece 2. on the other hand,
In conjunction with the laser beam irradiation, the X-Y table 1 on which the workpiece 2 is mounted is controlled to move in the X- and Y-axis directions along a predetermined machining evaporator under the control of the operation control device 7. As a result, the irradiation spot of the laser beam scans the surface to be processed, laser scribing is performed, and the open groove 9 is formed along a predetermined patterned pattern. In this case, the laser beam oscillated by the laser oscillator 3 is transmitted through the optical fiber 18, so that the laser beam emitted from the laser beam output end 20 has a flat distribution of light intensity density, and is transmitted through the field diaphragm 19. In the process, as shown in FIG. 3, the laser beam, which has a circular beam cross section, has its peripheral area trimmed and turns into a rectangular beam. Note that by varying the ratio of vertical and horizontal dimensions of the aperture hole 19a of the field diaphragm 19, the beam spot shape of the laser beam can be selected from various shapes such as rectangular and square. In this case, the field diaphragm J9 is oriented so that the two parallel sides of the diaphragm hole 19a are aligned with the scanning direction of the laser beam. Note that this field diaphragm 19 is connected to the condenser lens 6 as in the illustrated embodiment.
In addition to interposing the device between the laser beam emitting end 21 of the optical fiber 18 and the condensing lens 6, the same effect can be obtained (H7). As described above, by selecting a small overlap rate of the 1W repeated pulses of the laser beam during laser scribing, it becomes possible to form grooves of uniform width along a predetermined machining turn at high speed.Next, as described above. The overlapping state accompanying the scanning of the irradiation spot on the work surface by this method is shown in Fig. 4(a) and (bl) in comparison with the conventional apparatus shown in Fig. 6. Figure (al indicates the case using a conventional device; in the figure, the overlap rate of repeated pulses when scanning a circular irradiation spot with a radius r centered at 0 by moving the repeated pulses by a pitch interval β along the scanning direction Y) ρ is p = (1-I!/2r) x100%----
------- (11. On the other hand, as shown in Figure 4 (bl), the manipulated pulse of the rectangular irradiation spot parallel to the laser beam scanning direction Y with the - side length 2r' is Expressing the overlapping rate ρ° of repetitive pulses when moving and scanning with a pitch pitch of ``p'', it is: /)' = (1-1l'/2r') xioo%
−・−(2). Here, in order to form an open groove with a uniform width almost on the processed surface, the radius of the condensed spot in Fig. 4(a) 2r = 7
5mm, it=15. If cr m is (
From equation 11, the overlap rate ρ of the focused spots is 80%,
If the frequency of the repetitive pulse is 4 KHz, the moving scanning speed of the laser beam is 15 / l m x 4000 Hz = 60 mm /
sec ------(3). On the other hand, in Fig. 4 (bl), the shape of the square focused spot is 75X75.cam, that is, 2 r '-75p.
If m + 71' -70 μm, the overlap rate ρ° of the focused spots is approximately 7% from equation (2), and if the frequency of the repetitive pulse is 4000 Hz, the moving scanning speed of the laser beam is 70 μ m 400011z
= 280mm / sec -------(4
1, and the scanning speed, that is, the laser scribing processing speed, can be increased to 4.7 times as compared to the result of equation (3) according to the conventional method. Furthermore, the rectangular condensing spot described above is, for example, 75×2.
00 μm, that is, 2r' = 200 μIl+, and the pitch interval of the irradiation spot ff' = 180 μm, the above (2
) formula, the overlap rate is ρ゛-10%, and if the frequency of the repetitive pulse is 10000Hz, the scanning speed of the laser beam is 200 μm x 10000Hz = 1800mm
/5ec=−−−−+51, and according to the conventional method (
3) It is possible to increase the scanning speed to about 30 times as compared to the result of formula. In this case, the shape of the aperture hole 19a of the field aperture body 19 is set to be a rectangle with a vertical to horizontal dimension ratio of 75:200. In addition, for such a large focal spot, a multi-mode laser oscillator should be used, or the laser oscillator should be processed at a position slightly away from the focal point of the focusing lens 6, as long as the irradiation energy density of the laser beam is not extremely reduced. easily obtained by positioning the surface. Here, an enlarged drawing of the cross section of the processed part when a thin film photoelectric conversion substrate is used as a workpiece and an open groove is actually formed by laser scribing using the laser processing apparatus shown in Fig. 1 is shown. It is shown in Figure 5. As is clear from this figure,
In a14, there are almost no melted residues, protrusions, or deposits seen in FIG. Damage was also kept to a negligible level. Next, a different embodiment of the present invention is shown in FIG. The difference between this embodiment and the embodiment shown in FIG.
The table 22 holding the laser beam emitting end 21 . Condensing lens 6 and field stop body 19
are collectively shown by reference numeral 24 on an X-Y plotter, and with the table 22 stopped at a predetermined machining position, the movement of the X-Y plotter 24 is controlled by the operation control device 7 to achieve a predetermined processing turn. The laser scribing process is performed by scanning the laser beam irradiation spot along the processing surface of the workpiece 2. Thus flexible as a transmission medium for laser light. Moreover, by employing the lightweight optical fiber 18, laser scribing of a predetermined pattern can be performed by controlling the movement of the laser optical system while the workpiece 2 is kept at a stopped position without using an X-Y table. Moreover, unlike X-Y table movement control, the X-Y
Since the movement is controlled by a plotter, the laser processing speed can be further increased. In addition, according to the method of this embodiment, the table 22 is arranged vertically, so that the floor space occupied by the equipment can be reduced. By supporting the workpiece 2 and scanning the laser beam irradiation spot on each workpiece by adopting a multi-beam method in which the laser beam oscillated by a high-output laser oscillator is branched into multiple branches using branching optical fibers, It is now possible to laser scribe multiple workpieces at the same time using the same laser oscillator.
It will also be easier to handle mass production of product processing.

【Effect of the invention】

As described above, according to the present invention, a laser beam oscillated by a laser oscillator is irradiated onto a workpiece via an optical fiber and a condensing lens, and a laser beam is emitted to the downstream side of the laser beam emitting end of the optical fiber. By configuring a laser processing device with a field diaphragm body with a rectangular aperture hole parallel to the scanning direction of the light condensing spot, the irradiation spot of the pulsed laser beam remains circular and remains on the workpiece surface. Compared to the conventional method in which laser scribe processing is performed by scanning, the laser processing speed when forming grooves of uniform width can be significantly increased, improving work efficiency. Moreover, since the light intensity distribution of the laser beam becomes flat due to the use of optical fibers, there is no possibility of machining damage to the bottom of the groove. Laser processing equipment with high practical effects, such as being able to laser scribe open grooves with high precision on the thin film processed surface of the workpiece, reducing variation in product characteristics and greatly improving product yield during mass production. can be obtained.

[Brief explanation of drawings]

1 and 2 are configuration diagrams of different embodiments of the present invention, FIG. 3 is a cross-sectional diagram of the laser beam before and after the field diaphragm in the embodiment, and FIG. 4 +81. (b
1 is an explanatory diagram showing a comparison of the overlapping state in the scanning direction of repeated pulse irradiation spots irradiated onto a processed surface by the conventional laser processing apparatus and the laser processing apparatus of the present invention, respectively, and FIG. 5 is for a thin film type photoelectric conversion substrate. FIG. 6 is an enlarged cross-sectional view of the processed part when laser scribing an open groove using the apparatus of the embodiment; FIG. 6 is a configuration diagram of a conventional laser processing apparatus; FIG.
The figure shows the shape of the laser beam irradiation spot and its light intensity distribution by the laser processing apparatus shown in Fig. 6, and Figs. 8 and 9 show the scanning state of the irradiation spot on the processed surface by the apparatus shown in Fig. 6, respectively. , FIG. 10 is an enlarged sectional view of a processed portion when laser scribing is performed using a conventional apparatus corresponding to FIG. 5. In each figure, 1: X-Y table, 2: Workpiece, 3: Laser oscillator, 6: Condensing lens, 8: Laser light, 9° 14: Open groove formed by laser processing, 18: Optical fiber , 19: field stop body, 19a: aperture hole, 20: laser beam input end of optical fiber, 21: laser beam output end of optical fiber, 22:
Workpiece conveyance table, 24: ((1)
(b) Figure 4 Figure 7 Figure 8 Figure 10

Claims (1)

[Claims] 1) For a thin film workpiece, a pulsed laser beam oscillated by a laser oscillator is irradiated onto the workpiece surface through an optical system, and the irradiation spot is scanned on the workpiece surface. In a laser processing apparatus that laser scribes an open groove using a laser oscillator, a laser beam oscillated from a laser oscillator is irradiated onto a workpiece via an optical fiber and a condensing lens, and the laser beam output from the optical fiber is A laser processing device characterized in that a field aperture body having a rectangular aperture hole opened parallel to the scanning direction of a laser beam condensed spot is interposed on the rear side of the end. 2) A laser processing apparatus according to claim 1, wherein a field diaphragm is interposed between the condenser lens and the workpiece. 3) A laser processing apparatus according to claim 1, characterized in that a field diaphragm is interposed between the output end of the optical fiber and the condenser lens. 4) In the laser processing apparatus according to claim 1, the laser beam emitting end of the optical fiber, the condensing lens, and the field stop body are collectively
- A laser processing device characterized by moving a Y plotter to scan a laser beam irradiation spot on a surface to be processed.