WO2013010713A1

WO2013010713A1 - Laser head

Info

Publication number: WO2013010713A1
Application number: PCT/EP2012/060535
Authority: WO
Inventors: Armin TRAEGER; Paul PHILIPP; Andreas LOESEL; Daniel Kray; Sven Kleinschmidt
Original assignee: Rena Gmbh
Priority date: 2011-07-20
Filing date: 2012-06-04
Publication date: 2013-01-24
Also published as: TW201313373A; DE102011107982A1

Abstract

The invention relates to a method and a device for the heat-based and fluid-based treatment of a workpiece. The method comprises the following steps: - introducing fluid (F) through a fluid feed zone (6) arranged in a wet zone (4); - creating a fluid jet by discharging the fluid (F) through a nozzle (7), likewise arranged in the wet zone (4), in the direction of the workpiece surface (2'); - emitting a focused laser beam (L) from a dry zone (5) through a transparent separation layer separating the dry zone (5) from the wet zone (4) into the nozzle (7) in the direction of the workpiece surface (2'); - adjusting the machining distance (3) between tool head (1) and workpiece surface (2'); the fluid jet being surrounded, over a first portion of the entire length thereof, by the nozzle (7), and the machining distance (3) being adjusted such that a machining gap (3') forms between the nozzle end face (7') and workpiece surface (2'), which gap is filled at least in the region of the at least one laser beam (L) with a fluid film (F'), such that the fluid jet is surrounded and protected over the remaining portion thereof by said fluid film (F'), characterised in that the processing distance (3) is controlled by the pressure of the fluid (F).

Description

LASER HEAD

introduction

The invention relates to an apparatus and a method for the laser and liquid-based processing of materials. In particular, the invention relates to a method and apparatus in which the laser beam is directed to the workpiece within a fluid jet and to an apparatus and method for protecting the fluid jet.

State of the Art and Disadvantages The processing of materials by means of laser radiation has long been state of the art in many areas of material processing. The energy needed to process the material is provided by a high energy, focused and coherent light radiation of a particular wavelength on the workpiece, where it causes a strong superficial heating. Depending on the amount of energy provided at the site of action, the heat treatment may consist of a surface modification or a melt of material to be ablated.

Often it can be helpful if such a treatment is liquid-based. The liquid can only serve to cool the immediate environment of the site of action. The laser can only heat up supportive, whereas the actual process takes place due to a heat-induced chemical reaction. The heat energy can then lead to a localized chemical reaction of the material with a treatment liquid, for example in the context of laser-assisted chemical treatment (LCP, Laser Chemical Processing). Another object of the liquid may be to guide the laser beam, similar to an optical fiber. From the prior art, various devices for Processing of materials by means of a liquid-guided laser beam known.

The guiding of a focused laser beam through a liquid jet is shown for example in document EP 0 762 947 B1. Here, the liquid serves as a medium for guiding the laser beam, which allows the processing of a workpiece due to its high energy.

The liquid jet must be laminar according to the teaching of this document in order to obtain a good treatment result. Otherwise, the laser beam to disturbances of the outer shell, where locally and temporarily no total reflection occurs, leave the same radially. In order to obtain a laminar liquid jet, the pressure and thus the flow velocity of the jet is set high. Due to the high speed, however, the beam sucks perturbations such as e.g. at the outlet forming droplets or particles, downright. This in turn has a negative effect on the uniformity of the outer shell.

The document DE 10 2006 003606 and the document DE 10 2006 003607, which is based on the same applicant, disclose a device suitable for chemical treatment and a method in which a laser beam is guided by means of a laminar flowing liquid jet. The laser is coupled through a window into the liquid. The liquid includes a process medium, for example an etching liquid or a dopant dissolved in liquid. Due to the total reflection, the laser beam does not leave the liquid jet and heats it up at the site of action, that is to say the surface of the substrate, so that the desired chemical reaction can either take place at all or accelerate at any rate. This solution also has the disadvantage that the liquid jet is "free", ie laterally adjacent to the ambient air. Droplets that form when the liquid exits the nozzle can affect its shape when recombined with the jet. Inhomogeneities in the beam, as can be caused by particles or concentration fluctuations of the etching medium, also have an unfavorable effect on the beam shape. This results in energy losses due to an early exit of the laser light from the liquid jet, so that at the site of action only insufficient energy for the process is available for a short time.

In order to improve the beam quality of a liquid jet carrying a laser, the European publication EP 1 657 020 proposes the additional use of an "admission gas" which surrounds the liquid flow on the shell side and thus protects it against environmental influences. The gas accompanies the liquid jet on a dependent of the gas pressure route. Preferably, a protective gas such as helium is used as the gas. Investigations have shown, however, that the surrounding of the liquid jet with a gas jacket solves the above-described problems only inadequately. The pressure in the gas supply must not be too high, otherwise the gas flow disturbs the liquid jet. A lower pressure leads to a short reach of the gas mantle, which is thus limited in both directions. In the field of gas injection, additional disturbances can arise, since the liquid jet can form droplets already on leaving the nozzle, which then accumulate in the area of the gas injection to form even larger droplets. One possible consequence is the temporary total failure of the jet when such drops enter the exit of the gas injection. In addition, high costs arise when using a protective gas as jacket gas. Another problem in the use of liquid-guided laser radiation is the document EP 1 940 579 B1. It proposes to increase the machining energy at the site of action to direct the laser beam not exclusively by total reflection to this, but first by means of an optical device to focus so that its focal plane is sufficiently far from the nozzle opening of the surrounding liquid jet. Particular attention is also paid to the exact location at which the focal plane of the laser beam coupled into the liquid should lie. At this point according to the document a laminar flow must be present. However, the focusing plane is also not in the plane of the active site, ie on the workpiece surface, but will be guided in the further course again by total reflection through the liquid jet. According to the document, a gas jacket is generated, which surrounds the liquid jet and to keep the lateral surface smoother. Proposed solutions to the above-mentioned problems does not offer this document.

OBJECT OF THE INVENTION AND SOLUTION The object of the present invention is therefore to avoid the problems known from the prior art.

In particular, the invention is intended to ensure that a liquid jet which encloses a laser beam is insensitive to external disturbances, such as, for example, droplet formation when leaving the liquid from the nozzle or against particles of ambient air entering the surface of the liquid jet. High costs due to the use of a protective gas should be avoided. The flow velocity of the liquid jet should be largely independent of its beam quality. Furthermore, the size of the site of action on the surface of the workpiece should be as independent as possible of the size, in particular the cross section, of the liquid jet.

The object is achieved by a method according to the main claim and by a device according to claim 7. Preferred embodiments are given in the respective subclaims, the following description and the figure.

description

The process according to the invention will first be described below. This is followed by a detailed description of the device according to the invention with direct reference to FIG. 1.

The method according to the invention serves for the laser-based and liquid-based heat treatment of a workpiece with a tool head which is arranged at a machining distance from the workpiece surface. For this it includes the following steps:

- introducing liquid through a liquid feed area arranged in a wet area; - Generating a liquid jet by discharging the liquid through a likewise arranged in the wet area nozzle in the direction of the workpiece surface;

- Injecting at least one focused laser beam from a drying area in the nozzle in the direction of the workpiece surface;

- Setting the machining distance between the tool head and workpiece surface.

The irradiation of the laser beam preferably takes place through a transparent separating layer which separates the dry area from the wet area. The axis of the laser beam runs parallel, and particularly preferably collinear with the axis of the liquid ^¬ beam and with the longitudinal axis of the nozzle.

According to the invention it is ensured that the liquid jet is enclosed on a first portion of its entire length from the nozzle. According to the invention, the machining ^distance is further adjusted such that a machining gap is formed between the nozzle end face and the workpiece surface, which is filled with a liquid film at least in the area of the at least one laser beam, so that the liquid jet is surrounded and protected on its remaining portion by this liquid film is, wherein the machining distance (3) on the pressure of the liquid (F) is regulated. According to another embodiment, the gap is completely filled with a liquid film. In other words, there is no free jet of liquid between the nozzle end face and the surface of the workpiece, but the liquid jet is completely guided to and surrounded by the nozzle until immediately before the site of action. The last piece of the liquid jet is then enclosed by the liquid film and thus protected. As a result, the nozzle effectively shields the surface of the liquid jet from environmental influences. Between the nozzle end face and the workpiece surface, a machining gap filled with a liquid film forms in any case in the region of the laser beam. Thus, at this point, no impairment of the processing caused by environmental influences. It should be noted that the liquid film according to the invention typically has an extension in the beam direction that is significantly smaller than perpendicular to the beam direction. A known from the prior art "free jet", however, has an extension in the beam direction, which is significantly greater than or equal to the extension perpendicular to the beam direction. In addition, a "free jet" has a On the outer surface, which is more or less precisely defined, whereas the film has no clearly defined lateral surface.

An alternative formulation would therefore also be the concept of a "liquid column" which comprises the jet located in the nozzle and its end section located beyond the nozzle end face, and which is always protected on all sides by nozzle or liquid film from environmental influences. The laser beam is therefore passed through the liquid column.

In particular, even for the typical case that the tool head moves parallel to the workpiece surface, it must always be ensured that there is a sufficiently large lateral distance between the laser beam (s) and lateral edge of the liquid film protecting the end section of the liquid jet. A sufficient value is a distance of 1 to 2 mm from the laser beam. It is irrelevant if the outer edge of the surface described by the liquid film is not on a circular path, and / or the laser beam does not pass through exactly the center of area of this surface.

For further information, reference is made to the description of the device according to the invention and the figure.

The invention thus also relates to a method for protecting a liquid jet from environmental influences in the context of the laser and liquid-based treatment of the workpiece surface of a workpiece with at least one focused laser beam. This is passed through a nozzle of a tool head as described above in the direction of the workpiece surface through the liquid jet. The term "directed" must be delimited from the term "led". When "guiding" the laser beam uses the walls of the liquid jet, where it is reflected by total reflection. By contrast, in the case of "conduction", the laser beam passes through the liquid column of the liquid jet, without its walls to interact. Accordingly, the quality of the walls, unlike in the prior art, also irrelevant to the treatment result, if the laser beam is always surrounded on all sides by liquid. Therefore, it is envisaged that the protection in the area of the tool head is provided by the walls of the nozzle, and beyond the tool head by the liquid film surrounding the liquid jet.

The protection is thus initially achieved by a nozzle which is so long that it comes as close as possible to the workpiece surface. Thus, no "free jet" is formed, as known from the prior art. An influence of the protected by the nozzle walls lateral surface of the liquid ^¬ jet by splashes is excluded.

Further, the protection outside the nozzle, more specifically, beyond the nozzle face, is provided by the liquid jet itself. In order to avoid the problem of a free jet (see above), the outflowing liquid in the machining gap forms a liquid film which encloses the laser beam on all sides in the area of the action location, ie on the workpiece surface. A gas to protect the lateral surface of the liquid jet is obsolete, since the exact geometry of the lateral surface of the liquid film is irrelevant. The protection is provided beyond the nozzle solely by liquid which has flowed through the nozzle, more preferably by the treatment liquid itself.

In summary, the method according to the invention has the following steps:

Introducing the treatment liquid into the nozzle,

Shaping a first section of a liquid jet running inside the nozzle, Shaping a liquid film arranged in the machining gap between the nozzle end face and the workpiece surface,

Forming a remaining section of the liquid jet in the machining gap, so that this section is enclosed by the liquid film,

- Passing a focused laser beam through both portions of the nozzle walls or liquid film protected liquid jet to the workpiece surface.

According to a preferred embodiment, the focal plane of the laser beam is adjusted so that the laser beam passes directly to the action surface lying on the workpiece surface without reflection on the liquid jet. This means that the cross-section of the active site is independent of the cross-section of the liquid jet. A further advantage is that the quality of the guided laser beam in the liquid jet does not depend on the quality of the lateral surface of the liquid ^¬ beam, as it no longer interacts with this.

According to a particularly preferred embodiment, the focal plane of the laser beam is adjusted so that it lies on the workpiece surface. This means that the maximum available laser energy is currently focused on the Werkstückoberflä ^¬ che. In this way, the most efficient utilization of the laser as an energy source at the site of action is ensured. This also means that the adjustment of the size of the action location on the workpiece surface can be done exclusively by means of the focusing of the laser beam. As already mentioned, this is possible because, according to the invention, the laser beam and the liquid jet are independent in their cross-section, as long as the former is not larger (wider) than the latter. In the case of a non-round, in particular slit-shaped cross section of the nozzle, the adaptation of the size of the site of action additionally or alternatively also by a scanning, "scanning" movement of the laser beam. For this purpose, a galvo head is preferably to be used.

Preferably, the adjustment of the laser energy, and in particular of the energy which the laser unfolds at the site of action, by means of variation of the pulse length of the laser beam. Such a setting is particularly easy to implement. Additionally or alternatively, the setting can also be effected by means of a change in the focal plane, a weakening of the beam path, or an adaptation of the electrical power generated by the laser beam generating laser.

The invention can be implemented particularly advantageously if the following dimensions are maintained: width of the machining gap between 0.01 and 5 mm, preferably between 0.1 and 0.5 mm, particularly preferably 0.2 mm; or width of the machining gap between 5% and 500%, preferably between 20% and 100%, particularly preferably 50% of the smallest nozzle cross-sectional dimension, measured at the nozzle outlet. This is for the case of a round nozzle the diameter, and in the case of a slit-shaped nozzle, the shorter of the two sides, which form the rectangle of the cross section. However, it is clear that the invention can also be realized with other values. It is only essential that the above-mentioned, at least partially filled with liquid machining gap can form during operation. It is further preferred that the liquid flows in from all sides under the same pressure from the liquid feed area into the nozzle. In this way, a uniform and possibly laminar liquid jet can be realized.

As already mentioned, compliance with the correct processing distance is essential for the method according to the invention. In principle, active, ie measuring, methods can be used for distance control. However, preferred are passive Method in which the machining distance automatically adjusts, for example when an uneven surface is processed. According to the invention therefore the Bearbeitungsab ^¬ is regulated by the pressure of the liquid. This means that as the pressure increases, the machining distance increases and decreases with decreasing pressure. As the machining distance changes, so will the backpressure with which the tool head seeks to repel the workpiece surface. If the tool head is suspended, for example, by means of springs, it will automatically approach the workpiece surface as far as it will go or be removed from it until counter-pressure and spring pressure hold the balance. By changing the spring tension or the Ausströmdruckes the Bearbeitungsab ^¬ stand can be actively changed. According to a particularly preferred embodiment, the tool head moves during the treatment along the Werkstückoberflä ^¬ che. Such a movement is well known from the prior art and therefore need not be further elaborated. The method according to the invention is provided in particular for wet-chemical processing of workpiece surfaces. Accordingly, the liquid is an etching liquid. The method can be used particularly advantageously for structuring a surface comprising silicon. Thus, the method is for example advantageous for microstructuring of thin silicon nitride layers, which serve as an antireflection coating in commercial solar cells used. However, layers which can be processed, for example, with phosphoric acid are preferably processable by the process according to the invention. The corresponding substrate may for example consist of silicon, glass, metal, ceramic or plastic and optionally be provided with a wet-processable layer. According to another embodiment, the liquid contains at least one dopant, and the method according to the invention is used for doping a surface comprising silicon. The surface of the substrate can thus be doped locally in a simple manner. By using a metal-containing liquid, a thin metal layer on the workpiece upper surface ^¬ can be generated which for example can serve as a seed layer for subsequent electroplating.

The invention further discloses a tool head for carrying out the method according to the invention for the laser and liquid-based treatment of a workpiece according to the above embodiments. For explanation, reference is made to the following, with reference to FIG 1 Description. In summary, the invention provides a liquid jet which encloses a laser beam, the liquid jet being insensitive to external disturbances, such as droplet formation upon exiting the liquid from the nozzle. High costs due to the use of an inert gas are effectively avoided because a corresponding gas is not needed. The flow rate of the liquid jet is largely independent of its jet quality, that is, the flow rate can be varied within wide limits without affecting the quality of the liquid jet.

In addition, the size of the site of action on the surface of the workpiece is practically independent of the size, in particular the cross section, of the liquid jet.

DESCRIPTION OF THE FIGURES The tool head according to the invention is explained in detail below with reference to the single FIGURE 1, in FIG which its essential components are shown roughly schematically.

The tool head 1 according to the invention serves for the laser and liquid-based treatment of a workpiece 2. It is clear that the workpiece 2 itself is not part of the device. Typically, it is arranged on a transport device in a transport plane (not shown in each case). This transport device is not a mandatory part of the invention, this but possibly assigned functionally. Optionally, this transport device provides a transport direction into which the workpiece 2 can be transported. As transporting means are in particular tapes, belts, holders or even based on air or liquid flow fluid cushion into consideration. Preferably, the beam axis of the laser beam L and thus typically the liquid jet is perpendicular to the workpiece surface 2 '. For the typical case that the workpiece 2 is present as a flat substrate, the beam axes are thus also perpendicular to the transport plane. The tool head 1 is arranged at a machining distance 3 from the workpiece surface 2 '. Furthermore, it is divided into a wet area 4 lying in the picture below and a dry area 5 lying in the picture above.

In the wet area 4 liquid F, indicated in the picture by a wavy hatching, by a ^{Flüssigkeitszuführbe ¬} rich 6 with a liquid chamber 10 can be entered. This is shown open on both sides in the figure, it being understood that the openings are only the inflow of liquid F. The exact arrangement of the liquid chamber is irrelevant; Thus, according to an embodiment not shown, it can also be arranged directly at the end of the nozzle 7 and / or formed from a plurality of smaller chambers or channels. The liquid F leaves the wet area 4 again by a likewise arranged in the wet area 4 nozzle 7 in the direction of the workpiece surface 2 '. In cases not shown, more than one nozzle may be present in the tool head 1. From the drying area 5, at least one focused laser beam L can be introduced into the nozzle 7. The irradiation, as shown, preferably takes place through a transparent separating layer 8 separating the drying area 5 from the wet area 4. In certain cases, not shown, on the other hand, it is possible to dispense with the separating layer 8, or the separating layer 8 consists of air or another gas (mixture). An arrangement of the laser source within the wet area 4 is conceivable. The contour of the laser beam L is indicated in the figure by the dashed line. The axis of the laser beam runs parallel, and particularly preferably collinear with the axis of the liquid jet and with the longitudinal axis of the nozzle. It is clear that the contour of the laser beam L should be adapted to the cross section of the nozzle 7. Accordingly, in the case of a round nozzle 7, the laser beam may be round or fan-shaped in the case of a slot-shaped nozzle, with a galvo head preferably being used to form a linear laser beam L. In the case of a slot-shaped nozzle, the same can preferably also transmit through a plurality of laser beams L (not shown) standing parallel to one another, for example. The transparent material of the separating layer 8 is indicated by the dotted hatching. It is clear that the separating layer 8 does not have to be horizontally formed horizontally but, as shown, can be incorporated into the beam path as an insert in a non-transparent frame. The focusing takes place in the illustrated embodiment by means of a lens 9. This can be part of the tool head 1, or this only be assigned functionally. It is clear that in addition corresponding holding devices must be present to the lens 9 to fix, which are not shown for reasons of clarity.

If, as shown, liquid F flows through the nozzle 7, a liquid jet can be formed therewith, by means of which the laser beam L can be enclosed within the nozzle 7.

According to the invention, the length of the nozzle 7 is dimensioned such that the liquid jet is enclosed on a first portion of its entire length by the nozzle 7, so that it can extend largely in its interior. Thus, the laser beam L does not leave the liquid inside the nozzle 7 at any time, nor does it come into contact with the surface of the liquid jet. Furthermore, the invention provides that at machining distance 3 between nozzle end face 7 'and workpiece surface 2', a machining gap 3 'is formed, which is completely filled during operation of the tool head 1 of a liquid film F', so that the liquid jet on its remaining portion of this liquid film 'F' is umbaren and protectable. The machining distance 3 is adjustable by means of variation of the liquid pulse, which results from the liquid F flowing out of the nozzle 7. The vertical height of the machining gap 3 'to be measured in the image corresponds to the machining distance 3. The liquid film F' typically extends, as indicated, beyond the width of the tool head 1 or at least the nozzle end face 7 '. However, it can also be smaller than the nozzle end face 7 ', as long as it is ensured that there is a sufficient, overall minimum distance between the laser beam (s) and the lateral edge of the liquid film.

By using a nozzle 7, which encloses the liquid jet on all sides and over its entire length, this is completely insensitive to external disturbances and thus solves due to this configuration, a significant problem, which is the basis of the invention. Droplets can not arise at all, since the nozzle end face 7 'in contrast to the known devices is suitable to reach almost directly to the workpiece surface 2'. The first section of the liquid jet thus ends at the outlet of the nozzle 7, ie at its nozzle end face 7 '. Also there, the remaining portion of the liquid jet does not come into contact with the ambient air, but dissolves in the machining gap 3 'in all directions and thus forms itself the liquid film F' protecting it. In this way, gas bubbles or processing residues that occur, for example, during an etching process, effectively rinsed. A gas jet, which encloses the liquid jet, in particular in the remaining section, ie beyond the nozzle end face 7 ', is neither necessary nor provided. This eliminates both the additional design effort and the media costs. The flow velocity of the liquid jet no longer plays a significant role in the quality of the jet. In particular, even low flow velocities are possible, which would result in a "free jet", ie a liquid jet extending at least partially outside, to no stable or very easily disturbing jet. At the same time, unnecessarily high media consumption or throughput is avoided.

According to a further, not shown embodiment, the device additionally has a workpiece support. The workpiece support serves to receive the workpiece 2. With it, the workpiece 2 can be positioned such that the liquid film F 'can form in the machining gap 3' between its workpiece surface 2 'and the nozzle end face 7'. For this purpose, the support distance between the nozzle end face 7 'and workpiece support is preferably adjustable. The support distance is therefore, at least for a flat, flat workpiece 2, the sum of the workpiece thickness and thickness of the liquid film F 'or machining gap 3'. As can be seen, the nozzle 7 is dimensioned according to the preferred embodiment shown in the figure such that it can be irradiated by the laser beam L in a direct way and thus without reflection thereof on its inner wall. "Sizing" means that the geometry of the nozzle, ie its length and cross section, and the geometry of the symbolized by the dashed thin line laser beam L are coordinated so that the "lateral surface" of the laser beam L in the nozzle 7 not with the lateral surface of the liquid jet interacts. It is clear that this can be done both by adjusting the nozzle geometry and the beam geometry. The exact configuration depends on the respective desired parameters such as flow velocity, viscosity, flow rate, cross section in the focal point, etc. It must therefore be adapted by the expert, but this will not pose any problems.

According to the illustrated, preferred embodiment, the nozzle 7 is dimensioned such that the focal plane, ie the plane in which the "focal spot" of the laser beam L lies, is positioned on the workpiece surface 2 '. This means that the laser beam L leads to a maximum heat development at the site of action. It is clear that the term "measured" also refers here to a tuning of the nozzle geometry and laser beam, as already described above. By using a laser beam L whose focal plane is at the site of action, ie the workpiece surface 2 ', it is possible that the adjustment of the size of the active site on the workpiece surface 2' exclusively by means of focusing the laser beam L. This is a significant advantage over known devices and methods of the prior art, in which a laser beam is guided by means occurring on the insides of a liquid jet total reflection, since here width of the liquid and laser beam Correlate or influence each other. If small site dimensions are desired, thin liquid jets must also be used. However, thin jets of liquid must flow rapidly to achieve sufficient stability, but this results in increased droplet formation on the (air contacting) nozzle tip. Since the size of such droplets does not decrease proportionally with increasing flow velocity, but remains essentially independent of the flow velocity, the size of the droplets and thus their interference increases relative to the thinning liquid jet, resulting in a deterioration of the beam quality of the liquid and thus the Laser beam leads at the site of action. This problem is effectively avoided with the present device. According to the illustrated preferred embodiment, the nozzle 7 is round or slit-shaped, and / or it has a plate-shaped end face 7 '. Studies have shown that even the very simple and easy to produce round (cylindrical or conically tapered) nozzle shape leads to good results, and that in particular nozzle shapes, which have a widening towards the output end, as are known in the prior art , can not lead to better or even worse results. The alternative slot-shaped configuration has an elongated channel with a rectangular cross-section, which has a short and a long side. The optional plate-shaped configuration of the end face 7 'of the nozzle 7, the formation of the homogeneous liquid film F' is supported. This should not only cover the immediate site of action (focal spot of the laser beam L), but at least the Querschnittsflä ^¬ surface of the nozzle 7 and thus the liquid jet have. In this way, it is ensured that the tip region of the laser beam L, which is no longer in the (substantially within the nozzle 7) liquid jet, but already in Machining gap 3 'is located (remaining portion of the liquid jet), protected from environmental influences.

In particular, in the case of a (not shown) slit-shaped configuration of the nozzle 7, it is preferred that not only a single, but that a plurality of laser beams L are coupled into the nozzle 7. These can fan out, similar to the tines of a rake, from a common location, which is located at the beginning of the nozzle 7, or which is arranged in the region of the lens 9 or a more complex optical unit. Alternatively, however, the laser beams L can also run parallel to one another through the nozzle 7, similar to the tines of a comb. In this way, it is possible to generate a line pattern in one operation and / or to achieve a surface treatment. By coupling the individual laser beams L with galvo heads (not shown), both non-linear line patterns can be generated in a simple manner, as can surfaces of variable width on the workpiece surface 2 '.

The preferred embodiment shown in the figure shows that the wet area 4 comprises a disk-shaped liquid chamber 10. It is preferably fed by a supply line (not shown) which surrounds this in a circular manner, via which the liquid F can flow symmetrically out of the liquid feed region 6 into the nozzle 7 beginning in the center of the liquid chamber 10 under the same pressure. In this way, a uniform, laminar as possible flow of the liquid jet can be achieved.

As mentioned above, the machining distance 3 is adjustable by means of variation of the liquid pulse, which results from the liquid F flowing out of the nozzle 7 and impinging on the workpiece surface 2 '. However, it must be ensured that the hydrodynamic paradox known as the "Bernoulli effect" may occur. After this effect will be below a minimum distance streamed body in the direction of him flowing nozzle moves. However, if desired, this effect can be used just to stabilize the machining distance 3. It is readily possible for the person skilled in the art to set the geometry and pressure conditions in such a way that the invention can be realized in the manner described, for which reason a detailed description of the corresponding possibilities is dispensed with.

According to a particularly preferred embodiment, the tool head 1 comprises a spring 11 shown symbolically in the figure above the separating layer 8 or an equivalent means which is fixed to an abutment (also not shown) likewise shown symbolically. On the spring 11 of the tool head is resiliently mounted. In this way it is particularly easy to realize the adjustability of the machining distance 3 described in the preceding paragraph.

FIG. 1 also shows schematically a preferred lens 9 which is used to focus the laser beam L. It is clear that, if necessary, corresponding holders are necessary, and that in addition to a simple lens 9, even more complex optical units can be part of the tool head 1. Alternatively, the optical components can be assigned functionally to the tool head 1 and coupled to it.

Reference sign list

1 tool head

2 workpiece

2 'workpiece surface

3 machining distance

3 'machining gap

4 wet area

5 dry area

6 liquid feed area

7 nozzle

7 'nozzle face, face

8 separating layer

9 lens

10 fluid chamber

11 spring

F liquid

F 'liquid film

L laser beam

Claims

claims

Method for the laser and liquid-based treatment of a workpiece (2) with a tool head (1) which is arranged at a machining distance (3) from the workpiece surface (2 '), comprising the following steps:

- introducing liquid (F) through a liquid feed area (6) arranged in a wet area (4);

- Generating a liquid jet by discharging the liquid (F) by a likewise in the wet area (4) arranged nozzle (7) in the direction of the workpiece surface (2 ');

- irradiating at least one focused laser beam (L) from a drying area (5) into the nozzle (7) in the direction of the workpiece surface (2 ');

- Setting the machining distance (3) between the tool head (1) and workpiece surface (2 ');

wherein the liquid jet is enclosed on a first portion of its entire length by the nozzle (7), and the processing distance (3) is adjusted such that between the nozzle end face (7 ') and workpiece surface (2') a machining gap (3 '; ), which is filled at least in the region of the at least one laser beam (L) with a liquid film (F '), so that the liquid ^¬ keitsstrahl is surrounded on its remaining portion of this liquid film (F') and protected, characterized in that the machining distance (3) is regulated by the pressure of the liquid (F).

The method of claim 1, wherein the focal plane of the laser beam (L) is set such that the laser beam (L) directly on the way without reflection on the liquid jet comes to the workpiece surface (2 ') lying action.

The method of claim 1 or 2, wherein the focal plane of the laser beam (L) is set so that it lies on the workpiece surface (2 ').

Method according to one of the preceding claims, wherein the machining gap (3 ') is between 0.01 and 5 mm, and preferably between 0.1 and 0.5 mm, and particularly preferably 0.2 mm, or between 5% and 500%, and preferably between 20% and 100% of the smallest Düsenquerschnittsmaßes and is particularly preferably 50% of the smallest Düsenquer ^¬ cut measure.

Method according to one of the preceding claims, wherein the liquid (F) flows from the liquid feed region (6) into the nozzle (7) under the same pressure.

Method according to one of claims 1 to 5, wherein the liquid (F) is an etching liquid and the method is used to pattern a surface comprising silicon, or wherein the liquid (F) contains at least one dopant and the method for doping a silicon comprehensive surface is used.

Tool head (1) for carrying out the method for the ^laser- and liquid-based treatment of a workpiece (2) as defined in any one of claims 1 to 6.

Tool head (1) according to claim 7, comprising a wet section (4) in which liquid (F) through a fluid supply ^¬ lead-in area (6) entered and from which this liquid (F) by a likewise in the wet area (4) arranged nozzle (7 ) can be dispensed, and a drying area (5), from which at least one focused laser beam (L) in the nozzle (7) can be irradiated, so that with the nozzle (7) a liquid ^¬ keitsstrahl is malleable, by means of which the laser beam ( L) is encompassable, wherein the length of the nozzle (7) in such a way is dimensioned so that the liquid jet on a first portion of its entire length from the nozzle (7) is encompassed so that it can run completely in its interior, and wherein at the machining distance (3) between the nozzle end face (7 ') and workpiece surface ( 2 ') a machining ^¬ tung gap (3') is formable, which at least in the region of the at least one laser beam (L) from a liquid film (F 'can be filled), so that the liquid jet (on its remaining portion of this liquid film F') is umbar and protectable, characterized in that the machining distance (3) by means of variation of the liquid ^¬ pulse, which results from the nozzle (7) effluent liquid (F), is adjustable.

Tool head (1) according to claim 7 or 8, further comprising a workpiece support, wherein the support distance between the nozzle end face (7 ') and workpiece support is adjustable.

Tool head (1) according to one of claims 7 to 9, wherein the nozzle (7) has a plate-shaped end face (7 ').

Tool head (1) according to one of claims 7 to 10, wherein the wet area (4) comprises a disk-shaped liquid chamber (10) and this annularly surrounds Versorgungslei ^¬ tung, through which the liquid (F) on all sides the same pressure from the Flüssigkeitszuführbereich (6 ) can flow symmetrically into the beginning in the center of the liquid chamber (10) nozzle (7).

Tool head (1) according to one of claims 7 to 11, which is spring-mounted.