JPH0453630B2 - - Google Patents

Description

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

This invention provides a workpiece that is a thin film photoelectric conversion substrate used as a solar cell, and a predetermined pattern is formed on the thin film processing surface by irradiating a laser beam onto the processing surface of the workpiece and performing laser scribing processing. 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, laser scribing is performed at a predetermined position using the first groove as a reference to form a second groove in the semiconductor film and patterning is performed. After forming a second conductive film on the semiconductor film, a third groove is formed at a predetermined position by laser scribing using the second groove as a reference, and patterning of the circuit is performed. A thin film patterning method using a laser beam is known. Next, a block diagram of a conventional laser processing apparatus for performing the above-mentioned laser scribing process will be described with reference to FIG. 6. In Fig. 6, 1 is an
- Y table, 3 is a laser oscillator of, for example, a YAG laser, 4 is a collimator lens, 5 is a reflection mirror, 6 is a condensing lens, and 7 is a computer for operation control. When processing with this configuration, the laser oscillator 3 is activated by executing a program on the computer 7.
The more oscillated laser beam 8 is passed through the collimator lens 4,
The processing surface of the workpiece 2 is irradiated via the reflection mirror 5 and the condensing lens 6, and on the other hand, the X-
As Y table 1 follows a predetermined pattern,
The movement is controlled in the axial and Y-axis directions, so that the focused spot of the laser beam scans the surface to be processed and performs laser scribing, thereby forming an open groove 9 along a predetermined circuit pattern. By the way, the beam spot of the laser beam oscillated and output from the laser oscillator 3 in the above configuration is usually circular, and in the conventional laser scribing process, the laser beam is directly irradiated onto the surface to be processed through a collimator lens and a condensing lens. In this laser processing method, the shape of the laser beam focusing spot is
As shown in A in the figure, it has a circular shape, and the light intensity distribution in the direction of the condensing diameter has the highest energy density at the center of the condensing spot, as shown in B in the figure.
It exhibits a kind of Gaussian distribution in which the energy density rapidly decreases toward the periphery of the spot. However, as mentioned above, the laser beam convergence spot is circular and the light intensity distribution exhibits a Gaussian distribution.The convergence spot of the pulsed laser beam is directly irradiated onto the workpiece surface, and a predetermined pattern is formed. Therefore, the conventional processing method that performs laser scribing processing while scanning has the following problems. In other words, the circular condensing spot is scanned directly over the surface to be machined to form an open groove 9 with a uniform width over the entire area.
In order to form , it is necessary to repeatedly irradiate the open groove along 9 by scanning in the direction of arrow Y while finely overlapping the repeated pulses of the condensing spot toy as shown in Figure 8. The loss due to the overlapping of the condensing spots becomes large, and the processing speed for forming the opening 9 becomes slow. On the other hand, if the overlapping width of the focused spots of the repeated pulses is reduced as shown in FIG. 9 in order to increase the processing speed, the side edges of the groove portion 9 will take on a wavy shape, forming an groove with a uniform width. This becomes difficult. Furthermore, as mentioned above, since the light intensity distribution of the condensing spot is a Gaussian distribution with a high energy density in the central part, as shown in FIG. After layering the first conductive film 11 thereon and laser scribing the first grooves 12, laser scribing the second grooves 14 on the amorphous semiconductor film 13 layered thereon. When formed by machining, the machined surface of the groove bottom of the open groove part 14 is not flat due to the light intensity distribution of the laser beam condensing spot described above, and the machined depth of the groove diagram as shown in the figure is not flat. The groove becomes locally excessive and extremely deep in the center of the groove, and the machining depth reaches the first conductive coating 11.
In addition to causing machining damage to 1, the machining depth is insufficient at the side edges of the open groove, and molten residue 15 remains. Also, the open groove portion 14
Protrusions 16 and scattered objects 17 are likely to adhere to the edge of the opening. Moreover, when a thin film such as a photoelectric conversion element formed as a thin film laminate is processed as a thin film laminate as shown in the figure, and when selectively forming grooves therein to separate the laminated regions, the grooves 14 as described above are processed. If non-uniformity of the machined surface or processing damage to the underlying film occurs, it will lead to short circuits in the laminated area, increase in resistance, lowering photoelectric conversion efficiency, etc. This will increase the dispersion of product characteristics and reduce the product yield. This will lead to a problem of deterioration.

[Purpose of the invention]

The present invention has been made in consideration of the above points, and eliminates the drawbacks of the conventional laser processing method described above, prevents processing damage to the open groove part, and improves the open groove part. It is an object of the present invention to provide a laser processing device that enables selective processing of thin films and laser scribing of grooves of uniform width at high speed.

[Key points of the invention]

In order to achieve the above object, according to the present invention,
Targeting the workpiece, which is a thin-film photoelectric conversion substrate, irradiates the processing surface of the workpiece with pulsed laser light oscillated by a laser oscillator through the laser optical system, and moves the X-Y table on which the workpiece is mounted. In the laser processing apparatus, which performs laser scribing of an open groove by scanning the condensing spot of the laser beam on the workpiece surface by operation, the laser optical system includes a laser beam on the processing surface of the workpiece. A field diaphragm means that forms the convergence spot of the irradiated laser beam into a rectangular convergence spot that is parallel to the scanning direction and exhibits a flat light intensity distribution, and a focal length of 10 mm to condense the laser beam onto the workpiece surface. or a 15 mm condensing lens, and the X-Y table is equipped with a drive system that scans the condensing spot so that the overlap rate of the condensing spot on the workpiece surface is reduced. shall be. This reduces the overlap rate of the focused spots due to the repeated pulses of the laser beam during laser scribe processing, making it possible to process grooves with uniform width at high speed.
In addition, it is possible to form uniform grooves with high machining depth accuracy along the machining pattern without causing machining damage to the grooves on the thin film processed surface.

[Embodiments of the invention]

FIG. 1 shows a block diagram of a laser processing apparatus according to an embodiment of the present invention, and the same members corresponding to those in FIG. 6 are given the same reference numerals. In other words, a laser processing device is broadly divided into a laser optical system, a drive system for an X-Y table on which a workpiece is mounted and whose movement is controlled, and a monitoring optical system that focuses the laser beam irradiation spot. . Here, the laser optical system includes a laser oscillator 3, a collimator lens 4, a dichroic mirror 5, a condenser lens 6,
It also includes a field diaphragm 18 and a motor drive mechanism 19 for focusing the condenser lens 6, which are newly added in this invention. As the condensing lens 6 described above, a lens with an extremely short focal length of, for example, about 10 to 15 mm is used. The field diaphragm 18 is centered on the optical axis of the laser beam 8 and is interposed between the collimator lens 4 and the mirror 5 on the front side of the condenser lens 6, and the diaphragm has a rectangular shape. Aperture hole 18
a is open. For example, the laser oscillator 3 has a wavelength of 1.06 μm and a repetition pulse frequency of 1 to
A YAG laser with a frequency of 40KHz and an output of 0.1 to 12W is used. On the other hand, the X-Y table drive system includes a pedestal 20, an X-Y table 1 installed on the pedestal 20 and driven and controlled by the computer 7, and a fine-adjustment table 1 installed on the X-Y table 1. Stage 21 and
and a vacuum suction type holding table 22 that is installed on the stage 21 and holds the workpiece 2, which is a thin film photoelectric conversion substrate mounted on the top surface, in a fixed position.
It is made up of etc. Note that this holding table 22 has a large number of suction holes opened on its upper surface that communicate with a vacuum pump 23, and by operating the vacuum pump 23 with the workpiece 2 mounted, the workpiece 2 can be moved onto the table. It is held in place by vacuum suction. The monitoring optical system includes an illumination lamp 24, an illumination lens 25, a dichroic mirror 26, and an imaging lens 2.
7. Crosshair 28 for positioning, TV camera 2
9, and a combination of a monitor television 30,
It is arranged above the condensing lens 6 of the laser optical system described above with its optical axis aligned. Further, a reference numeral 31 is located close to the condenser lens 6 facing the workpiece 2.
The vacuum pump 2 has a vacuum suction nozzle shown in
It is installed connected to 3. This suction nozzle 3
Reference numeral 1 is for sucking and removing debris that evaporates and scatters from the processing surface to the surroundings when laser processing the workpiece 2 to the outside of the system. Next, the processing procedure and processing operation using the laser processing apparatus with the above configuration will be explained. First, with the workpiece 2 mounted on the holding table 22, the vacuum pump 23 is started and the workpiece 2 is moved. Holding stand 22
Vacuum adsorb it to the upper position. Subsequently, the X-Y table 1 is set at the processing start position, the monitoring optical system is activated, and while the screen of the monitor television 30 is visually viewed, the condenser lens 6 is moved up and down by the motor drive mechanism 19 to perform focusing. At the same time, X-
The fine adjustment stage 21 of the Y table drive system is adjusted to correctly initialize the machining start position and horizontality of the workpiece. Next, a processing start command is given to the computer 7 to activate the laser oscillator 3, and at the same time
- Control the movement of the Y table 1 according to a predetermined machining pattern written in the computer in advance. As a result, the focused spot of the laser beam irradiated onto the processed surface of the workpiece 2 is scanned along a predetermined pattern with a small overlap ratio, and the processed surface is laser scribed to form an open groove. In this case, the spot shape of the laser beam immediately after it is oscillated from the laser oscillator 3 and transmitted through the collimator lens 4, and its light intensity distribution are shown in Figure 2a.
In contrast, the spot shape and light intensity distribution after passing through the rectangular field diaphragm 18 described above are circular as shown by E and F in FIG. 2B. The peripheral area of the beam spot is trimmed and changed into a rectangular shape, and its light intensity distribution also changes from a Gaussian distribution to a flat distribution with high energy density and almost uniform light intensity over the entire beam spot. In addition, the above-mentioned field stop body 1
By varying the ratio of the vertical and horizontal dimensions of the diaphragm hole 18a of 8, the shape of the beam spot can be selected from various shapes such as square and rectangular. In this case, the orientation of the field diaphragm 18 is set so that the rectangular condensing spot irradiates the machined surface of the workpiece with its two parallel sides parallel to the scanning direction of the laser beam. Further, the light intensity distribution of the laser beam transmitted through the field stop 18 can be selected from the distributions shown in FIGS. 3a, b, and c by changing the beam diameter magnification by the collimator lens 4. The distributions in FIGS. 3a, b, and c are shown in descending order of beam diameter magnification. Further, according to the above-mentioned laser processing apparatus, first, the overlapping situation caused by repeated pulse scanning of the condensing spot that irradiates the processing surface of the workpiece 2 is as shown in FIG. As is clear from this figure, the focal spot of each pulse has a rectangular shape, and its scanning direction Y
Translate parallel along. This makes it possible to form the open groove portion 9 with a uniform width along the scanning direction Y even if the overlap width between the focal spot and the focal spot of the next pulse is small. As shown in Figure 9, without forming the wave-shaped grooves that occur when scanning with a pulsed laser beam that exhibits a circular condensing spot, we can increase the moving speed of the laser beam irradiation point and create grooves with a uniform width. can be processed, and the laser scribing processing speed can be increased accordingly. Regarding this point, according to a machining experiment conducted by the inventor, it is possible to laser scribe an opening groove of uniform width along the machining pattern on the machining surface by setting the aperture hole of the field diaphragm 18 in a square shape. It has been confirmed that the processing speed can be increased approximately 4.5 times compared to the conventional method of scanning a circular light spot. In this case, by selecting the shape of the aperture hole of the field diaphragm 18 as described above to be a horizontally long rectangle, and irradiating with the long side aligned with the scanning direction of the condensing spot, the processing speed can be further increased. It is easy to understand that this method can increase the processing speed, and as a result, the processing speed can be increased by about 10 times compared to the conventional method. Furthermore, depending on the overlap rate between the focal spots,
By appropriately selecting the intensity distribution of the laser beam from the above figures 3a, b, and c, the groove depth can be made uneven over the entire open groove, including the overlapping and non-overlapping parts of the condensing spots. It can be formed almost uniformly without causing. In addition, in the apparatus shown in FIG. 1, a short focal length lens with a focal length of about 10 to 15 mm is used as the condenser lens 6 as described above, so the depth of focus is extremely shallow, and the rectangular shape described above is used. By using the field diaphragm 18, the focused spot light intensity distribution is flat, so the laser can cut grooves with high precision and a uniform processing depth without creating any residue on the thin film processing surface. It can be formed by scribing, and in addition, the vacuum suction nozzle 31 shown in FIG. Processing damage, protrusions, deposits, etc. that damage the underlying layer at the bottom of the open groove as described in FIG. 10 can be effectively prevented, and even higher processing performance can be obtained. When processing a thin film used in a solar cell, which is the object of the present invention, for example, when the thin film is an amorphous semiconductor film, the film thickness is approximately 3000 to 7000.
〓 and thin. Therefore, a lens with a focal length as short as possible is suitable as a lens, but in this embodiment, a commercially available and practical lens with a focal length of 10 to 15 mm is used. FIG. 5 shows a photoelectric conversion substrate formed by laminating thin films as a workpiece, and a conductive film 11 and a semiconductor film 13 are layered on an insulating substrate 10 in the same manner as in FIG. 10. This is a cross-sectional view of the processed part when the open groove 14 is formed by laser scribing using the laser processing apparatus shown in FIG. The melting residues, protrusions, and deposits seen in the figure are hardly generated, and the processing depth of the open groove portion 14 is almost uniform in the width direction, and processing damage to the underlying conductive coating 11 can be ignored. I was able to keep it down to This means that the depth of focus of the condensing lens is extremely shallow and the light intensity distribution at the condensing spot is flat. This is because the irradiation energy of the laser beam is significantly attenuated outside the depth range.
In addition, the scattered particles, which are a type of fine evaporation material generated during laser processing, are immediately suctioned away from the spot by the vacuum suction nozzle 31, preventing the scattered particles from adhering to the surrounding area. Occurrence can be effectively prevented.

【Effect of the invention】

As described above, according to the present invention, the following effects are achieved as a result of employing the above configuration. By reducing the overlapping ratio of the light condensing spots, it is possible to significantly increase the processing speed when forming grooves of uniform width, thereby improving work efficiency. In addition to reducing the overlapping rate of the condensing spots, by using a lens with a focal length of 10 to 15 mm, the entire area of the groove where the condensing spots do not overlap can be formed more evenly and almost uniformly. can do. By reducing the overlapping rate of the condensing spots and using a lens with a focal length of 10 to 15 mm, it is possible to prevent processing damage in the open groove portion. According to the above, it is possible to reliably realize selective processing of the thin film in the groove portion of the thin film type photoelectric conversion substrate. As a result of the above, there is less variation in product characteristics.
It is possible to significantly improve the yield when mass producing products.

[Brief explanation of the drawing]

1 to 5 are embodiments of the present invention;
1 to 10 show diagrams corresponding to conventional apparatuses, and FIGS. 1 and 6 are block diagrams of an embodiment of the present invention and a conventional laser processing apparatus, and FIGS. 2a, b, and 2 are block diagrams, respectively. FIG. 7 is a spot shape of a laser beam and its light intensity distribution diagram, FIGS. 3 a to c are light intensity distribution diagrams of a condensing spot in the embodiment of FIG. The figures are explanatory diagrams showing the overlapping state of the condensing spot on the scanning method by repeated pulses applied to the processing surface of the workpiece, Fig. 5 and Fig. 1, respectively.
FIG. 0 is a cross-sectional view of an open groove portion when laser processing is performed using a thin film type photoelectric conversion substrate as a workpiece. In the figure, 1...X-Y table, 2...workpiece, 3...
...Laser oscillator, 4...Collimator lens, 6...
... Condensing lens, 8 ... Laser light, 9, 14 ... Groove formed by laser processing, 18 ... Field diaphragm body, 18a ... Aperture hole, 19 ... Motor drive mechanism, 22 ... Vacuum Adsorption type holding stand, 29...
Surveillance optical system TV camera, 30...Monitor TV, 31...Vacuum suction nozzle.

Claims (1)

[Claims] 1. For a workpiece that is a thin-film photoelectric conversion substrate, a pulsed laser beam oscillated by a laser oscillator is irradiated onto the processing surface of the workpiece through a laser optical system, and the workpiece is mounted. In the laser processing apparatus, the laser scribe processing is performed by scanning the focused spot of the laser light on the surface to be processed by moving the X-Y table, in which the laser optical system includes: A field diaphragm means for shaping the convergence spot of the laser beam irradiated onto the workpiece surface into a rectangular convergence spot parallel to the scanning direction and exhibiting a flat light intensity distribution; It is equipped with a condensing lens with a focal length of 10 mm to 15 mm, and the X-Y table scans the condensing spot so that the overlapping ratio of the condensing spot on the workpiece surface is small. A laser processing device characterized by comprising a drive system. 2. In the laser processing apparatus according to claim 1, the field stop means has a field of view having a rectangular aperture hole arranged in front of the condensing lens so as to align the optical axis with the laser beam oscillated by the laser oscillator. A laser processing device characterized by being a diaphragm body. 3. In the laser processing apparatus according to claim 1, the laser optical system is equipped with a motor drive mechanism for focusing the condensing lens, and is further equipped with a monitoring optical system for monitoring the focusing of the condensing lens. A laser processing device characterized by: 4. The laser processing apparatus according to claim 3, wherein the monitoring optical system is equipped with a television camera and a monitor television for imaging a condensed spot on the surface to be processed. 5. In the laser processing apparatus according to claim 1, a vacuum is provided in the vicinity of the condensing lens facing the workpiece to suck out scattered objects generated from the workpiece surface during laser processing and remove them from the system. A laser processing device characterized by being equipped with a type of suction nozzle. 6. The laser processing apparatus according to claim 1, wherein a vacuum suction type holding table is installed on the X-Y table to suction and hold the workpiece in a predetermined position. Device.