WO2000013837A1

WO2000013837A1 - System for the multi-channel cutting and engraving of materials using laser beams

Info

Publication number: WO2000013837A1
Application number: PCT/DE1999/002424
Authority: WO
Inventors: Heinrich Jürgensen
Original assignee: Heidelberger Druckmaschinen Ag
Priority date: 1998-09-08
Filing date: 1999-08-04
Publication date: 2000-03-16
Also published as: DE19840936B4; DE19840936A1

Abstract

The invention relates to a system for processing materials using a laser, comprising a housing for receiving components of said system; a table (225) for receiving the material to be processed; servo-drives with which the table can be displaced in relation to a carriage along the space coordinates x, y, z and rotated at an angleζ-about an axis of rotation z which is substantially vertical to the surface to be processed; at least two fiber laser outputs for producing several processing traces which are positioned on a shaped rail and fitted with end pieces (26, 94) by means of which the laser beams can be directed at the surface (81) to be processed and focused. Said end pieces are arranged on the carriage in such away that the distance between the processing traces (224) produced by the end pieces can be modified. The system also comprises a cooling system, a control for the laser and a machine control for the drives which produce the relative and rotational movements.

Description

Arrangement for multi-channel cutting and scoring of materials using laser beams

The invention relates to an arrangement for multi-channel cutting and scribing of materials by means of laser beams. There is a great need in the semiconductor industry for new techniques for cutting and scribing and other processing of materials, in particular semiconductor materials.

For example, in the production of photovoltaic cells for generating electricity from solar energy, the so-called solar cells, there is a need to cut fine traces into the surface of the semiconductor material, as described in a special print of the magazine "Sonnenenergie & Wärmetechnik", 4/1997 by Dipl.-Ing. Stefan Müller, solar cells require contacts for the electrical connections. To lower the internal resistance of the cells and thus improve efficiency, such contacts are made at short intervals. In conventional solar cells, contact fingers are in one Screen printing process applied, a metal paste is pressed through a mask onto the pretreated silicon wafer. The contact fingers are about 200 μm wide. In the Saturn technology described in the aforementioned reference, this contact line is cut with a laser, the width is reduced thereby on about 20 μm. Since the contact lines are very narrow, you can afford to cut more lines into the solar cell. This reduces the ohmic losses when discharging the charge carriers. Around 60 contact fingers are printed on a conventional cell, while around 80 lines are cut into a Saturn cell. The total line width per cell is thus reduced from 12 mm (60x200 μm) to 1.6 mm (80x20 μm), although the number of contact lines has been increased. The area covered by the contact fingers is reduced accordingly, which leads to a higher energy yield.

In a known manner, the contact lines are usually cut in a step and repeat device with a YAG laser. One can easily see that such a single-channel cutting device will soon work at its performance limit and limit the production quantity. It is conceivable to have several such cutting devices work in parallel. However, this is associated with considerable costs. Another disadvantage is the cumbersome meandering movement of the slide on which the cells are attached. As a result of this meandering movement, the drive mechanism for the slide is exposed to severe mechanical wear.

The object of the invention is therefore to create a multi-channel scoring and cutting device which avoids the disadvantages mentioned and works precisely.

This object is achieved according to the invention by the arrangement for material processing according to claim 1. Advantageous developments of the invention emerge from subclaims 2 to 7.

Advantageously, for the purposes of the invention, a laser radiation source is used, such as that used in the parallel German patent application "Process and arrangement for material processing by means of laser beams", filed by the applicant 98/1035, and in the parallel one, simultaneously with the present application with the present application filed German utility model application "laser radiation source high power density and high energy for material processing", sign of the applicant 98/1036 GM, is described. This laser radiation source consists of several diode-pumped fiber lasers, also called fiber lasers, the output beams of which impinge on the processing site next to one another and / or one above the other or in a point or bundle and thus generate a processing spot that is specifically variable in shape and size even at very high laser powers and extremely high power densities enables. The material to be processed can be located on a plane that the laser radiation source or its output radiation is guided relatively past. Furthermore, in the parallel patent application filed at the same time as the present application, "end piece for optical fibers" is the sign of the applicant 98/1037, and in the parallel German utility model application "End piece for optical fibers", filed by the applicant 98/1037 GM, filed at the same time with the present application, a end piece which enables the beams of the individual lasers with defined values in The beam diameter, beam divergence, centering and angular direction can be grasped precisely and permanently in order to obtain a production and service-oriented arrangement and to guide the laser radiation in a targeted manner. The beams can, depending on the application, for. B. are coupled out as parallel laser beams, diverge or, for example, be focused at a certain distance from the exit point. The end pieces can be attached directly to the output of the fiber laser or to the output of coupled fibers or fiber fusion couplers, with which the radiation from one or more fiber lasers can be split or combined. With a design of the end pieces that is spatially small in accordance with the invention and that can also be strung together in a particularly simple manner, it becomes possible to combine the beams of several outputs of the fiber lasers at intervals of less than 2.5 mm, so that the object is achieved is and at the same time economical production and cost-effective maintenance of the laser radiation source is made possible. The invention is explained in more detail below with reference to FIGS. 1 to 7. Show it:

1 is a schematic diagram of the laser radiation source,

2 shows a schematic diagram of a fiber laser (prior art),

2a shows an abbreviated representation of the fiber of the fiber laser (prior art), FIG. 3 shows an example of an embodiment of an end piece with a conical fit for use in a holder, FIG. 4 shows a modular embodiment of the fiber of the fiber laser according to FIG. 1, 5 shows an example of the coupling of the pump energy into the fiber of the fiber laser according to FIG. 13, FIG. 6 shows a basic arrangement of the cutting and scoring device, FIG. 6a further details on FIG. 6, Fig. 6b is a sectional drawing of Fig. 6a and

Fig. 7 shows an embodiment of the cutting and scoring device.

1 shows a laser radiation source 1 which consists of a plurality of diode-pumped fiber lasers (fiber lasers) (2) which are preferably designed as modules according to the invention and which are supplied with electrical energy by a preferably modular supply 32, some of which is converted into laser radiation becomes. Furthermore, a controller 33 is provided, via which the radiation is modulated and which ensures the interaction of the laser radiation source with its periphery. The output beams of the lasers enter an optical unit 8 at the radiation input 9 and exit from the optical unit at the radiation output 10. The task of the optical unit 8 is to shape the laser radiation into a processing spot 24 on a processing surface 81, but the laser radiation can also be directed directly onto the processing surface without an optical unit, for example by means of the end pieces 26, 94. The laser radiation source is preferably accommodated in a housing, which also ensures the required laser safety. The laser radiation source is preferably cooled by a cooling system.

The basic structure of a fiber laser (also called fiber laser) arrangement 2 is shown in FIGS. 2 and 2a. In Fig. 2, the energy of a pump source such. B. a laser diode, here called pump source 18, formed via a coupling optics 3 to a suitable pump leak 4 and coupled into the laser fiber 5. Such pump sources are described, for example, in the German patent application running in parallel with the file number P 196 03 704. Typical pump cross sections of the laser fibers are between 100 μm and 600 μm in diameter, the numerical aperture is around 0.4. The laser fiber 5 is provided on the coupling-in side 6 with a coupling-in mirror 7 which allows the pump radiation to pass through unhindered, but has a 100% reflection for the laser radiation. The coupling mirror 7 can be attached to the fiber end with a suitable holder or by gluing, but it can also be attached directly vapor a suitable layer, such as is used in coupling mirrors for lasers, can be realized on the fiber end.

On the coupling-out side 11 of the laser fiber 5 there is a coupling-out mirror 12 which is partially transparent to the laser radiation and through which the laser radiation 13 is coupled out. The decoupling mirror for the pump radiation advantageously has a 100% reflection. As a result, the remaining pump radiation is reflected back into the optical fiber, which is advantageous since the pump energy is better utilized and also does not interfere with the use of the laser radiation. As with the coupling mirror, the coupling mirror can also be produced by vapor deposition.

The coupling process of the pump radiation into the pump cross section 14 of the laser fiber 5 is shown in more detail in FIG. 2a. The energy in the pump spot 4 excites the laser radiation in the core 15 of the laser fiber 5 on its way through the fiber. The pump core 16 is surrounded by a jacket 17. The approximately 5 μm to 10 μm thick core of the laser fiber is mainly doped with rare earths. The relatively large pump cross section 14 simplifies the coupling of the pump energy and enables the use of an easily detachable connection between the pump source and the laser fiber, as is shown in FIGS. 4 and 5. The end piece of the laser fiber on the pump source side can be identical to the end piece on the outcoupling side, but it does not have to be. A precise plug connection between the pump source and laser fiber offers considerable advantages in the manufacture of fiber lasers and in the event of service. The laser fiber can, however, also be permanently connected to the pump source to form a laser module. As a result of the deliberately produced, very small fiber core diameter, the fiber laser delivers a practically diffraction-limited laser radiation 13 at the exit. According to the invention, this enables a very large depth of field; For example, with a size of the processing spot of 20 μm, a depth of field range of about 0.5 to 1 mm can be achieved, which is particularly advantageous if the material surfaces are uneven or cannot be positioned exactly, which is the case especially with large areas . In principle, possible output powers of up to 100 W are mentioned in the literature for fiber lasers. Passive optical fibers 28 can also be coupled to the active output of fiber lasers. The excitation current of the pump source is supplied by the supply 32. If no excitation current flows through the pump source, the fiber laser does not emit any radiation. The pump sources are only switched on if laser energy is required in the processing spot. A safety circuit permanently switches off the pump sources if there is a danger. As explained in more detail in FIGS. 4 and 5, the laser fibers 5 and the pump sources 18 can be connected to one another via a detachable connection.

FIG. 3 shows a preferred embodiment of a terminating piece 26 (terminator) for a fiber. Such end pieces can advantageously be used for coupling out the laser radiation from a fiber, as described in the German patent application "End piece for optical fibers", sign of the applicant 98/1037, filed in parallel with the present application, and in the parallel one, simultaneously with the present application filed German utility model application "end piece for optical fibers", sign of the applicant 98/1037 GM is described. This end piece 26 can in principle be used for all applications in which it is important to precisely couple the rays of light emerging from a fiber 28 or a laser fiber 5 belonging to a fiber laser with a detachable connection. It is also the task of the end piece to enable a precisely detachable connection of the fiber laser or the fiber with the rest of the optics. The end piece consists of an elongated housing 132 which has a continuous, cylindrical opening 130 which extends in the axial direction. The housing is preferably made of prefabricated, for example drawn material. The laser fiber 5 of the fiber laser is preferably freed from its cladding at its last end and roughened on its outer surface, so that the remaining pump radiation leaves the laser fiber before the laser fiber enters the end piece. The laser fiber can additionally be surrounded by a protective cover 131 which is connected to the housing 132 of the end piece. The housing 132 has fits 134 with which the Housing in a socket 29 can be used exactly. The end of the fiber 28 or the laser fiber 5 is received at one end of the housing 132 and guided in the opening 130 within the housing. A short focal length lens 133 is attached to the other end of the housing 132. Means for adjusting the position of the fiber 28 or laser fiber 5 within the closure piece can be provided in order to adjust the position of the fiber 28 or laser fiber 5 relative to the lens 133 within the closure piece and with respect to the fits 134. The position of the lens relative to the fiber can also be adjusted. The adjustments are advantageously carried out using an adjusting device. Adjustment screws 135 (FIG. 3b) or balls 137 can be provided for adjusting the position of the fiber 28 or the laser fiber 5 in the housing 132. The fiber 28 or laser fiber 5 can also be axially displaced within the opening 130 or within the adjusting screws or balls. The lens 133 can also be either correctly assembled with respect to the fits 134 during assembly or adjusted and fixed axially and / or radially by suitable means, not shown, with respect to the fibers 5, 28 held in position by the opening 130. The aim of the adjustment is to ensure that the beam 144 emerging from the lens 133 is brought into a predetermined axis and focus position with a defined cone.

Fig. 4 shows an application example for the end piece 26, 94 in a fiber 28 or a laser fiber 5, which are provided at both ends with a respective end piece according to the invention. It is fundamentally possible to combine several of the end pieces described above in several tracks next to one another and in several levels one above the other to form a package. It is also possible to design the shape of the end pieces differently than shown in FIG. B. that a cylindrical shape according to Fig. 3 receives trapezoidal or rectangular fits.

5 shows a coupling of the laser fiber 5 to a pump source by means of the end piece 26 via the housing 152, in which the pump source 18 is preferably accommodated in an airtight manner in a recess 153. Through a seal 146 It is ensured that the end piece 26 is also airtight, so that no dirt particles can penetrate into the recess from outside and it can be evacuated or filled with a protective gas if necessary. A constant flow of a protective gas can also flow through the recess 153, in particular when the end piece 26 is temporarily removed. The radiation from the pump source 18 is focused on the pump cross section of the laser fiber 5 via a lens 154. The pump source can consist of one or more laser diodes, but it can also consist of an arrangement of one or more lasers, in particular also fiber lasers, the output radiation of which has been combined with suitable means so that a suitable pump leak occurs.

6 shows a possible embodiment of the laser radiation source according to the invention, as can be used for the multi-channel cutting and scribing of, for example, semiconductor materials. The end pieces 26, 94 of the fibers or fiber lasers F _a to F _n have beams 144 which are focused by means of the lens 133 at a predetermined distance from the end piece. The diameter of the processing points B. to B _n is, for example, 20 μm, but it can also be below or above. Furthermore, the end pieces are arranged on a profile rail 256 described in more detail in FIGS. 6a and 6b in such a way that their mutual distance "A" can be set to any values until the end pieces abut one another. The profile rail is preferably attached to an arm of a robot (FIG. 7) and can be moved, for example, in the directions x, y, z relative to a table 225 by means of actuators which are shown in FIG. 7. In addition, the profile rail can be rotated relative to the table by an angle φ with the axis z '(FIG. 7), which can also be used to determine the mutual distance between the machining tracks. Furthermore, the table can be moved in the x, y, z directions and rotated through an angle φ with the axis z. The material to be processed, for example one or more so-called “wafers” separated from a drawn semiconductor ingot, can be fastened on the table 225 by means of clamping or suction devices, not shown. By means of the laser energy in the individual processing points B ^ is B-, for example, in the semiconductor material Cut fine parallel tracks, such as those required for contacting photovoltaic cells. However, fine bores can also be made in the semiconductor material or cut by means of the laser in order to separate electrical circuits, for example. An arrangement for removing the material removed from the processing surface is arranged separately for each processing track 224 or for several processing tracks 224 together according to the invention near the processing surface 81. If the profile rail with the end pieces is rotated relative to the table in order to change the distance between the processing tracks, it is expedient according to the invention that the distortion of the pattern to be recorded caused by the relative rotation by predistortion of the pattern to be applied and / or a timing of the To compensate for data flow.

The parallel arrangement of several fiber laser outputs can considerably reduce the time required for processing, for example 10 laser outputs can be used in parallel for scoring the photovoltaic elements, which increases the output by a factor of 10.

The described arrangement for cutting and scribing is not only suitable for the processing of semiconductor materials, but can also be used for all materials in which the precise generation of patterns, such as e.g. arrives at the printing plate production.

Fig. 6a and the associated sectional drawing Fig. 6b show how the end pieces 26 of the individual fiber lasers F _a to F _{n are} attached. The profile rail 256 is fastened to a carrier 260 by means of connections 261, which can be the arm of a robot, for example. The end pieces 26 are received in sockets 257 and fixed with screws 259. The sockets 257 are provided with a profile that matches the profile rail 256, are lined up on the profile rail 256, are set at predetermined distances “A” from one another and are fixed by means of the screws 259. end pieces 26 and the mounts 257 a very small distance "A" is possible. By means of the robot, the profiled rail with the end pieces can be guided over the machining surface for the purpose of material processing, as shown in FIG. 6 and described in detail 6 can be carried out by the table 225 described in Fig. 6, but can also be carried out by the arm of the robot or in a combined form by both, preferably the arm of the robot can also be rotated about that with the axis of the end pieces make approximately parallel axis of rotation z 'of the arrangement With this rotation and a relative displacement between the arm of the robot and the table 225, it is possible to change the distance of the machining tracks generated on the machining surface 81, and preferably less set as it corresponds to the set dimension "A" right

7 shows an example of the robot as it can be assembled, for example, from components from Montech-Deutschland GmbH, Postfach 1949, 79509 Lörach. A horizontal linear unit 263 is fastened on a stand system “Quickset” 262, which in turn accommodates a vertical linear unit 264 with a rotary drive 265. The actual robot arm 260, to which the profile rail 256 is fastened by means of the connection 261, sits on the rotary drive Another horizontal linear unit is possible, but not shown .. The same elements can be used to implement the different directions of movement of the table 225, the directions of movement also being able to be assigned in part to the table and in part to the profile rail an arrangement is arranged for removing the material removed from the processing surface, as described in the applicant's patent application, filed concurrently with the present application, application number 98/1035.

In the figures, the housing for accommodating individual components, the cooling system, the control for the lasers, the pump sources for the fiber lasers, are from - - /.

which only the end pieces 26, 94 are shown and the machine control for the drives is not shown. If the profiled rail with the end pieces is rotated relative to the table in order to change the distance between the processing tracks, it is expedient according to the invention that the distortion of the pattern to be recorded resulting from the relative rotation by predistortion of the pattern to be applied and / or a temporal Compensate control of the data stream.

The arrangement for cutting and scoring is preferably carried out fully automatically under computer control, as is known from machine tools and / or industrial robots.

Claims

claims

1. Arrangement for material processing using laser beams, consisting of

a housing for receiving components of the arrangement,

a table (225) for receiving the material to be processed,

at least two fiber lasers for producing a plurality of processing tracks, which are arranged on a profile rail (256) and are provided with end pieces (26, 94) by means of which the lasers can be aligned and focused on the processing surface (81), the end pieces on the profile rail are arranged so that the mutual spacing of the machining tracks (224) generated by the end pieces can be changed,

Actuators with which the table can be moved relative to the profile rail along at least one of the spatial coordinates x, y, z and / or can be rotated through an angle φ about an axis of rotation z running approximately perpendicularly through the machining surface and / or actuators with which the profile rail is movable relative to the table along at least one of the spatial coordinates x, y, z,

a cooling system,

a controller for the lasers and

a machine control for the drives for generating the relative movements and the rotational movements.

2. Arrangement for processing material according to claim 1, characterized in that an arrangement for removing the material removed from the processing surface (249) is provided for each processing track.

3. Arrangement for material processing according to claim 1, characterized in that a common arrangement for removing the material removed from the processing surface (249) is provided for several processing tracks.

4. Arrangement for material processing according to claims 1 to 3, characterized in that the profile rail is arranged rotatable about an axis z 'to change the distance between the processing tracks.

5. Arrangement for material processing according to claims 1 to 4, characterized in that means for compensating for the distortions resulting from the distortion in the pattern to be recorded are provided, which consist of predistortion of the pattern to be applied and / or influence the timing of the data stream.

6. Arrangement for material processing according to claims 1 to 5, characterized in that the fiber lasers are designed as modules, each consisting of identical units that are connected to the pump sources (18).

7. Arrangement for material processing according to claims 1 to 6, characterized in that the pump sources (18) and the laser fibers (5) are connected by means of end pieces (26, 94).