WO2005063432A1

WO2005063432A1 - Device for machining a workpiece using laser light

Info

Publication number: WO2005063432A1
Application number: PCT/EP2004/013712
Authority: WO
Inventors: Vitalij Lissotschenko
Original assignee: Hentze-Lissotschenko Patentverwaltungs Gmbh & Co. Kg
Priority date: 2003-12-20
Filing date: 2004-12-02
Publication date: 2005-07-14
Also published as: DE112004002394D2

Abstract

The invention relates to a device (1) for machining a workpiece (2), comprising at least one laser light source (3) for generating at least one laser-light bundle (30, 31) and means for generating at least one lateral focus pattern (21, 22, 23, 24) of at least one laser light-bundle (30, 31) on a surface (20) of the workpiece (2). According to the invention, the means for generating the lateral focus pattern (21, 22, 23, 24) comprise at least one lens mask (10) containing a plurality of structured lens segments (100, 101, 102, 103, 104, 105).

Description

"Device for processing a workpiece with laser light"

The present invention relates to a device for machining a workpiece, comprising at least one laser light source for generating at least one laser light bundle and means for generating at least one lateral focus pattern of the at least one laser light bundle on a surface of the workpiece.

Laser technology has developed into one of the standard techniques for machining workpieces. Novel processes such as laser welding, laser cutting or laser drilling have become indispensable in the field of material processing and processing.

One of the special advantages of laser processing is that the thermal energy introduced into the workpiece can be adequately determined. With a short exposure time of the workpiece, only the workpiece surface is heated, whereas a longer exposure time leads to continuous heating of the workpiece.

Various laser beam processes are also used in microelectronics. In laser lithography, for example, a photoresist of a wafer is specifically irradiated with laser light. Then, depending on the type of photoresist used, the irradiated or unirradiated areas are detached. The surface structured in this way is then coated, etched or doped over a large area.

It is known from the prior art, for example, small optical fiber elements, which can optionally be bent, to be arranged side by side in such a way that a lateral focus pattern of the laser light is generated on the surface of the workpiece.

Such a mask, which consists of a large number of optical fibers, is relatively difficult to manufacture.

This is where the present invention comes in.

The object of the present invention is to provide a device for machining a workpiece of the type mentioned at the outset, which is easier to manufacture and more flexible to handle.

The solution to this problem is provided by a device of the type mentioned with the characterizing features of the main claim.

In the solution according to the invention it is proposed that the means for generating the lateral focus pattern comprise at least one lens mask which has a plurality of structured lens segments. The lens segments are structured in such a way that they focus the at least one laser light beam on the surface of the workpiece in such a way that the desired lateral focus pattern is generated there. The device according to the invention can be used, for example, to selectively remove material from the surface, so that the surface is structured. Only in the areas of the surface on which the at least one laser light bundle is focused is the thermal energy density so high that material can be removed from the surface in these areas. The device can also be used, for example, to join two or more workpieces together in the area of a joint joint weld. A lateral focus pattern is generated by means of the lens mask, which corresponds to the desired contour of the weld seam that connects the at least two workpieces. Conventional laser light sources, which can optionally be pulsed, can be used as the laser light source.

In a particularly preferred embodiment, the structured lens segments have an optically functional interface, which is concavely shaped at least in sections, on a first side facing the surface of the workpiece during operation of the device. This means that these lens segments have a negative focal length. The essentially parallel laser light beam striking the lens mask is consequently imaged in the further beam path as if it had its origin in a virtual focal point which lies in front of the laser light entry surface of the lens mask. This in particular simplifies the further construction of the device according to the invention, since the position of the virtual focal point of the structured lens segments makes it very easy to predict where the workpiece and possibly further optically imaging elements of the device must be arranged so that the at least one laser light bundle for generating the lateral focus pattern is focused on the surface and can, for example, remove material there or weld workpieces to one another.

A particularly preferred embodiment provides that the lens mask in sections comprises essentially concave-cylindrical lens segments for generating a partially linear lateral focus pattern on the surface. The lens mask can also have sections of essentially plano-concave cylindrical lens segments for generating the focus pattern which is essentially linear in sections include. The side of the lens segments from which the laser light beam emerges is structured in sections in these concave-cylindrical or plano-concave-cylindrical lens segments in a channel-like manner. Each of these individual concave-cylindrical or plano-concave-cylindrical lens segments can, in sections, produce an essentially linear lateral focus pattern on the surface of the workpiece. It is clear that the length of these essentially linear lateral focus patterns depends on the one hand on the dimensioning of the concave-cylindrical or plano-concave-cylindrical lens segments and on the other hand on the number of lens segments of this type which are lined up.

In a development of the present invention, it is proposed that the lens mask in sections comprises essentially concave-toroidal lens segments for generating a focus pattern that is curved in sections. Furthermore, the lens mask can also comprise, in sections, essentially plano-concave toroidal lens segments for generating the focus pattern, which is curved in sections.

In a particularly preferred embodiment, the lens mask is composed of a plurality of lens segments in the manner of a mosaic. These can be lens segments that are used to generate a linear lateral focus pattern and / or are used to generate a curved lateral focus pattern. This makes it clear that the mosaic-like structure of the lens mask from a plurality of lens segments, which in sections produce curved and / or linear focus patterns on the surface, is suitable for generating any desired lateral focus patterns within certain limits, for example, in a targeted and well-defined manner and way material from the To remove the surface of the workpiece or to join two or more workpieces along a joint seam.

To improve the beam quality of the at least one laser light bundle, the device can have at least one homogenizer for homogenizing the at least one laser light bundle, which is arranged between the laser light source and the lens mask.

In an advantageous embodiment, it is proposed that the means for generating the lateral focus pattern have at least one first, at least sectionally convex lens means, which is arranged between the lens mask and the workpiece. In a further development it is proposed that the means for generating the lateral focus pattern have at least a second, at least sectionally convex lens means, which is arranged between the first lens means and the workpiece.

In a particularly advantageous embodiment, the focal length of the first lens means is greater than the focal length of the second lens means, so that the arrangement of the lens mask and the first and second lens means essentially corresponds to a conventional telescope arrangement. The beam path of the device according to the invention thus forms the desired structure to be produced on the surface in the form of a reduced lateral focus pattern on the surface of the workpiece or in the region of a joint seam of two or more workpieces to be connected to one another.

Overall, the present invention provides a device for machining a workpiece that is simple can be produced and adapted to any lateral focus pattern within certain limits.

Further features and advantages of the present invention will become clear from the following description of a preferred exemplary embodiment with reference to the accompanying figures. Show in it

Figure 1 is a schematic representation of the beam path of an inventive device for machining a workpiece.

FIG. 2 shows a view of the surface of the workpiece in the direction of arrow II of FIG. 1 with a representation of lateral focus patterns and a section of a lens mask of the device according to the invention;

Fig. 3 is a view of the lens mask in the direction of arrow I I I of Figure 1, which is constructed in sections from plano-concave-cylindrical lens segments and plano-concave-toroidal lens segments.

4a is a view of a plano-concave cylindrical lens segment in the direction of arrow IVa of FIG. 4b;

4b shows a plan view of the plano-concave cylindrical lens segment according to FIG. 4a;

5a shows a view of a plano-concave-toroidal lens segment in the direction of the arrow Va from FIG. 5b;

5b shows a plan view of the plano-concave-toroidal lens segment according to FIG. 5a. First, reference is made to FIG. 1, in which the beam path of a device 1 according to the invention for machining a workpiece 2 is shown schematically.

The device 1 comprises a laser light source 3, which is not explicitly shown here, for generating laser light bundles 30, 31. Before the laser light bundles 30, 31 meet the entry surface of a lens mask 10, they first preferably pass through a homogenizer for homogenizing the laser light bundles 30, 31, which is also not explicitly shown here. The homogenizer can comprise, for example, an array of crossed cylindrical lenses. The laser light bundles 30, 31 then strike the lens mask 10, which has a plurality of structured lens segments 100, 101, 102, 103, 104, 105, which will be discussed in more detail later. It can be seen that the lens segments 100, 101, 102, 103, 104, 105 of the lens mask 10 have partially concave-shaped optically functional interfaces 1000 on their exit side, that is to say on their side facing the surface 20 of the workpiece 2. The entry surfaces 1001 of the lens segments 100, 101, 102, 103, 104, 105, through which the laser light bundles 30, 31 enter the lens mask 10, on the other hand, are essentially planar in this exemplary embodiment.

The further optical structure of the device 1 essentially corresponds to that of a conventional telescope arrangement. This means that in the further beam path behind the lens mask 10, a first lens means 11, which has at least one convexly shaped optically functional interface 110, and a second lens means 12, which also has at least one convexly shaped optically functional interface 120, are arranged. In this embodiment, both the first lens 11 and the second lens 12 are made plano-convex. The The diameter of the first lens means 1 1 is larger than that of the second lens means 12. Furthermore, in the telescope arrangement shown here, the focal length of the first lens means 1 1 is larger than that of the second lens means 12. The first lens means 1 1 thus acts like a lens and the second lens means 12 like an eyepiece of a conventional telescope arrangement.

It can be seen that the laser light bundles 30, 31 are focused on the surface 20 of the workpiece 2 by means of the lens mask 10 and the first lens means 11 and the second lens means 12. Depending on the geometry of the individual lens segments 100, 101, 102, 103, 104, 105 of the lens mask 10, a lateral focus pattern 21 is generated on the surface 20 of the workpiece 2. In the area of this lateral focus pattern 21, the energy density of the laser light bundles 30, 31 striking the surface 20 of the workpiece 2 is so great that material can be removed from the surface 20 of the workpiece 2 there.

In the field of microsystem technology, the surface 20 of the workpiece 2 can comprise, for example, a layer that can be removed in a targeted manner by means of the device 1 according to the invention, in order to structure the surface 20 before further processing.

The macroscopic geometric structure of the lens mask 10 from individual, differently structured lens segments 100, 101, 102, 103, 104, 105 corresponds to the lateral focus pattern 21 to be generated on the surface 20. The beam path of the device 1 according to the invention thus depicts the desired structure to be produced on the surface 20 in the form of a reduced lateral focus pattern 21 on the surface 20 of the workpiece 2. With the help of the device according to the invention For example, achieve lateral resolutions in the order of magnitude between approximately 1 μm and 10 μm.

2 shows an example of a top view of the surface 20 of the workpiece 2 after processing by means of the device 1 according to the invention. Furthermore, several lateral focus patterns 21, 22, 23, 24, 25 generated on the surface 20 are shown. An essentially oval lateral focus pattern 21, two circular lateral focus patterns 22 and two multiply curved lateral focus patterns 23, 24, which consist of straight and curved sections, are shown here by way of example.

Based on the essentially oval shaped lateral focus pattern 21, an example will be explained below with further reference to FIG. 3, in which way such a focus pattern can be generated on the surface 20 of the workpiece 2 using the device 1 according to the invention. In order to obtain the oval focus pattern 21, as shown in FIG. 2, a lens mask 10 is used, which is composed of a total of six individual structured lens segments 100, 101, 102, 103, 104, 105.

Of these six lens segments 100, 101, 102, 103, 104, 105, two lens segments 100, 101 are essentially plano-concave cylindrical in order to produce sections of essentially linear focus patterns on the surface 20 of the workpiece.

The remaining lens segments are plano-concave-toroidal lens segments 102, 103, 104, 105, which produce sections that are curved and thus curve-like focus patterns on the surface 20 of the workpiece 2. Already on the basis of these considerations it becomes clear that, for example, the circular lateral focus patterns 22 likewise shown in FIG. 2 can each be generated with the aid of a lens mask 10 which has a total of four plano-concave-toroidal lens segments 102, 103, 104, 105.

Any other focus patterns within certain limits, such as the lateral focus patterns 23, 24 consisting of sections of straight and curved areas, can consequently be generated by means of a lens mask, which is built up in sections from plano-concave-toroidal and plano-concave cylindrical lens segments.

A section of the lens mask 10, which is used to generate the oval focus pattern 21, is shown again in FIG. 3 in a view in the direction of the arrow I M in FIG. 1. Two plano-concave-toroidal lens segments 102, 104 can be seen, between which a plano-concave-cylindrical lens segment 100 is arranged. Plano-concave-toroidal lens segments 103, 105, in turn, adjoin the two plano-concave-toroidal lens segments 102, 104, between which a plano-concave-cylindrical lens means is arranged.

It is clear that with the aid of a lens mask 10, which has sections of plano-concave cylindrical and / or plano-concave toroidal lens segments, largely arbitrarily shaped lateral focus patterns 21, 22, 23, 24 can be produced on the surface 20 of the workpiece 2.

The device according to the invention can be used, for example, for laser lithography or also for welding or soldering two or more different workpieces. Depending on the structure of the lens mask 10 from individual lens segments 100, 101, 102, 103, 104, 105, the lateral contour of a weld seam, for example, can be predetermined.

Laser light sources which provide a sufficiently high energy density on the surface 20 in order to remove or melt material there can be used as the laser light source 3. Depending on the field of application, pulsed or continuously operated laser light sources can be used.

FIGS. 4a, 4b or 5a and 5b show an example of a plano-concave-cylindrical lens segment 100, 101 and a plano-concave-toroidal lens segment 102 in a side view (FIGS. 4a, 5a) or in a top view (FIGS. 4b and 5b).

It can be seen that the plano-concave-cylindrical lens segment 100, 101 has an essentially concave-shaped optically functional interface 1000 on one side, whereas the optically functional interface 1001 opposite this side is essentially planar. With the aid of this plano-concave-cylindrical lens segment 100, 101, essentially linear lateral focus patterns can be generated in sections on the surface 20 of the workpiece 2.

The plano-concave-toroidal lens segment 102 shown in FIGS. 5a and 5b, as shown in FIG. 5b, likewise has a substantially concave-shaped optically functional interface 1000. Starting from the side marked by an arrow in FIG. 5b, the plano-concave-toroidal lens segment 102 has a curvature extending to the right, so that when in use this lens segment 102 in the lens mask 10 on the surface 20 of the workpiece 2 a leftward, curved section of a focus pattern is generated.

It becomes clear that a mosaic-like or pixel-like construction of a lens mask 10 from a plurality of plano-concave-cylindrical lens segments 100, 101 and / or plano-concave-toroidal lens segments 102, 103, 104, 105 largely generates any lateral focus pattern on the surface 20 of the workpiece 2 enables.

Furthermore, the lens mask 10 can be exchanged very simply by another lens mask, by means of which a different focus pattern can be generated on the surface. Such a lens mask is considerably more flexible than those which have hitherto become known from the prior art, so that the device according to the invention can be used in a particularly advantageous manner, in particular in laser lithography or in laser welding.

Claims

claims:

1 . Device (1) for processing a workpiece (2), comprising: at least one laser light source (3) for generating at least one laser light bundle (30, 31),

Means for generating at least one lateral focus pattern (21, 22, 23, 24) of the at least one laser light bundle (30, 31) on a surface (20) of the workpiece (2), characterized in that the means for generating the lateral focus pattern (21 , 22, 23, 24) comprise at least one lens mask (10) which has a plurality of structured lens segments (100, 101, 102, 103, 104, 105).

2. Device according to claim 1, characterized in that the structured lens segments (100, 101, 102, 103, 104, 105) on a first, the surface (20) of the workpiece (2) facing during operation of the device (1) Side have an optically functional interface (1000) which is concavely shaped at least in sections.

3. The device according to claim 2, characterized in that the lens mask (10) comprises sections of essentially concave cylindrical lens segments for generating a sectionally essentially linear lateral focus pattern (21, 22, 23, 24) on the surface (20).

4. The device according to claim 3, characterized in that the lens mask (10) in sections essentially plano-concave cylindrical lens segments (100, 101) for generating the sectionally substantially linear focus pattern (21, 22, 23, 24).

5. Device according to one of claims 2 to 4, characterized in that the lens mask (10) in sections comprises essentially concave-toroidal lens segments for generating a sectionally curved lateral focus pattern (21, 22, 23, 24).

6. The device according to claim 5, characterized in that the lens mask (10) comprises sections of essentially plano-concave toroidal lens segments (102, 103, 104, 105) for generating the sectionally curved lateral focus pattern (21, 22, 23, 24).

7. Device according to one of claims 1 to 6, characterized in that the lens mask (10) is composed like a mosaic from a plurality of lens segments (100, 101, 102, 103, 104, 105).

8. Device according to one of claims 1 to 7, characterized in that the device (1) has at least one homogenizer for homogenizing the at least one laser light bundle (30, 31), which is arranged between the laser light source (3) and the lens mask (10) is.

9. Device according to one of claims 1 to 8, characterized in that the means for generating the lateral focus pattern (21, 22, 23, 24) have at least a first, at least partially convex lens means (1 1), which between the lens mask ( 10) and the workpiece (2) is arranged.

0. The device according to claim 9, characterized in that the device (1) have at least a second, at least partially convex lens means (12) which is arranged between the first lens means (1 1) and the workpiece (2). 1 . Apparatus according to claim 10, characterized in that the focal length of the first lens means (1 1) is greater than the focal length of the second lens means (12).