Method for separating a workpiece

Abstract

The invention relates to a method for segmenting a workpiece (104) having a transparent material (102), in which: a plurality of focus elements (120) are provided by means of an input laser beam (108); loading the material (102) with the focal element (120); forming a material modification (138) in the material (102) along a predefined processing line (128) by applying the material (102) with the focal element (120); the material (102) is cut along the processing line (128) by means of an etching process using a wet chemical solution, the temperature of the wet chemical solution being at least 100 DEG C and / or at most 150 DEG C during the etching process.

Description

Technical Field

[0001] The invention relates to a method for separating workpieces comprising a transparent material. Background Art

[0002] DE 10 2019 218 995 A1 discloses a method for laser beam modification of a material that is at least substantially transparent to the laser beam, wherein a single pulse of the laser beam interacts with the material in an elongated focusing region extending in the beam propagation direction, and wherein, through the interaction of the single pulse with the material, a channel with a channel width dimension of a maximum of 1 μm is generated, penetrating the material from a first end face to a second end face.

[0003] A method for cutting a transparent material by means of an elongated focal zone of a laser beam is known from EP 3 597 353 A1.

[0004] WO 2016 / 089799 A1 discloses a method for cutting a transparent material by means of a plurality of parallel non-diffracting laser beams.

[0005] JP 2020 004 889 A discloses a method for segmenting and in particular beveling a transparent material, wherein a plurality of focal spots for laser processing of the material are generated by means of a spatial light modulator.

[0006] US 2020 / 0147729 A1 and US 2020 / 0361037 A1 each disclose a method for forming an edge region having a chamfer on a transparent material by means of a laser beam.

[0007] DE 10 2018 110 211 A1 discloses a method for producing a cavity in a substrate made of a hard and brittle material, preferably glass or glass ceramic, wherein filamentary damage is produced in the volume of the substrate by means of a laser beam and wherein the substrate is exposed to an etching medium which removes material of the substrate at a removal rate of between 2 μm and 20 μm per hour.

[0008] WO 2017 / 062798 A1 discloses a method for forming a through hole in a glass-based substrate, wherein a plurality of etching paths are generated and etching / etching is performed along the etching paths by means of a hydroxide-based etching material. The etching rate along the etching path is at least 12 times greater than the etching rate outside the etching path.

[0009] WO 2018 / 162385 A1 discloses a method for introducing at least one recess into a transparent or transmissive material, wherein the material is selectively modified along a beam axis by means of electromagnetic radiation and the recess is subsequently produced by one or more etching steps, wherein different etching rates occur in modified and unmodified areas. Summary of the invention

[0010] The object of the present invention is to provide a method as described above which is able to separate workpieces at the highest possible speed and / or in the shortest possible time.

[0011] According to the invention, this object is achieved by a method as described above, wherein a plurality of focus elements are provided by means of an input laser beam, material is loaded with these focus elements, a material modification is formed in the material along a predetermined processing line by loading the material with these focus elements, and the material is divided along the processing line by means of an etching process using a wet chemical solution, wherein during the etching process the temperature of the wet chemical solution is at least 100° C. and / or at most 150° C.

[0012] By keeping the temperature of the wet chemical solution in the mentioned range during the etching process, the material can be etched at a particularly high etching rate at material modifications arranged along the processing line, wherein the etching rate outside the material modification is lower than the etching rate at the material modification along the processing line. This allows selective etching at a particularly high etching rate at the material modification along the processing line. This results in an etching process duration that is as short as possible in order to separate the material along the processing line. The method can thus be carried out at an increased speed.

[0013] In particular, after the material has been charged with the focal element and / or after the material modification has been formed along the processing line, an etching process for separating the material is carried out.

[0014] By impinging the material of the workpiece with the focal elements, material modifications are formed which are arranged in the material at positions and / or spacings associated with the focal elements. In particular, the spacing of adjacent focal elements corresponds to the spacing of adjacent material modifications formed in the material of the workpiece by means of these focal elements. However, in principle, it is also possible to form a plurality of material modifications and / or elongated material modifications by means of the focal elements, for example in the case of a Bessel-like shape of the focal elements.

[0015] In particular, the focal elements arranged along the processing line are spaced apart and / or have such a strength that a material modification formed along the processing line by means of the focal elements allows separation of the material by etching by means of a wet chemical solution.

[0016] In particular, the provided focal elements are respectively arranged at different spatial positions in the material. A determined spatial position of a focal element is to be understood in particular as the position of the center point of the corresponding focal element.

[0017] Providing a plurality of focus elements by means of at least one input laser beam may be understood in particular to mean providing these focus elements simultaneously. However, this may also be understood to mean that one or more focus elements are provided in a time-staggered manner, that is to say, for example, at a certain point in time, at least one focus element is provided for laser processing of a workpiece at a certain position, while at another point in time, at least one further focus element is provided for laser processing of a workpiece at another different position.

[0018] It may be advantageous if the wet chemical solution is an aqueous KOH solution having a concentration of at least 15% by weight and / or at most 50% by weight. This enables selective etching of the material at material modifications located along the processing line.

[0019] For the same reasons, it may be advantageous if the wet chemical solution is an aqueous NaOH solution having a concentration of at least 15% by weight and / or at most 50% by weight.

[0020] In particular, it can be provided that the temperature of the wet chemical solution remains constant over time during the etching process. This allows selective etching to be achieved at an at least approximately constant etching rate. This also allows the etching process to be carried out in a manner that is as controlled as possible.

[0021] In particular, the temperature is selected such that the etching rate of the material at the material modification is maximized and the wet chemical solution does not evaporate or evaporates only slightly. For example, in the case of KOH or NaOH solutions, the boiling temperature of the wet chemical solution is related to the corresponding KOH or NaOH concentration.

[0022] The temperature of the wet chemical solution is kept constant over time, which is to be understood in particular to mean that during the etching process the actual temperature of the wet chemical solution deviates from a predefined (constant over time) temperature (or setpoint temperature) by less than the difference mentioned in the following paragraphs.

[0023] In particular, the temperature is adjusted to a time-constant target temperature of at least 100° C. and / or at most 150° C., wherein during the etching process the actual temperature of the wet chemical solution deviates from the target temperature by less than 7 K, in particular less than 5 K, in particular less than 3 K, in particular less than 1 K.

[0024] In particular, it can be provided that the wet chemical solution is an aqueous KOH solution or an aqueous NaOH solution, wherein the concentration of the solution is selected such that the boiling temperature of the solution is at least 5%, in particular at least 10%, in particular at least 15% higher than the desired temperature of the wet chemical solution which is constant over time during the etching process.

[0025] For example, the duration of the etching process is at least 5 minutes and / or at most 180 minutes, and preferably at least 10 minutes and / or at most 90 minutes.

[0026] In particular, it can be provided that the material is loaded with a wet chemical solution for carrying out the etching process. In particular, the material is partially or completely loaded with the wet chemical solution. In particular, the material is partially or completely introduced into the wet chemical solution. In particular, the material is partially or completely surrounded by the wet chemical solution.

[0027] It can be provided that the etching process is carried out in an ultrasonically assisted manner. For example, the etching process is carried out in an ultrasonically assisted etching bath. This simplifies the material separation in particular. In addition, the speed of the etching process can be further increased.

[0028] It can be provided that for the purpose of dividing the material, mechanical stresses and / or mechanical forces are additionally applied to the material, and / or for the purpose of dividing the material, heat is additionally applied to the material, thereby making it possible in particular to achieve an optimized dividing of the material.

[0029] Advantageously, the spacing between adjacent focal elements is at least 3 μm and / or at most 70 μm and preferably at least 5 μm and / or at most 10 μm, thereby enabling an etching process at the material modification formed by means of the focal elements to be carried out selectively with a particularly high etching rate.

[0030] For the same reasons, it can be advantageous if the spacing of adjacent material modifications is at least 3 μm and / or at most 70 μm, and preferably at least 5 μm and / or at most 10 μm. The spacing of adjacent material modifications within the stated value range relates to a spacing direction oriented parallel to the feed direction of the movement of the focal element relative to the material during laser processing of the material and / or to a spacing direction in a plane oriented perpendicular to the feed direction. In particular, this spacing relates to a spacing direction in the processing plane on which the material modification is arranged.

[0031] It may be advantageous if the input laser beam and / or the laser beam from which the focal element is formed is a pulsed laser beam and in particular an ultrashort pulsed laser beam. By impinging the material with the focal element, in particular the laser pulses (and in particular the ultrashort laser pulses) are introduced into the material. This makes it possible, for example, to form a type III material modification in the material, which enables the material to be separated.

[0032] For the same reasons, it may be advantageous to assign a pulse energy of at least 0.5 μJ and / or at most 10 μJ and preferably at least 1 μJ and / or at most 5 μJ to a specific focal element.

[0033] For example, the wavelength of the input laser beam and / or of the laser beam from which the focus element is formed is at least 300 nm and / or at most 1500 nm. For example, the wavelength is 515 nm or 1030 nm.

[0034] In particular, the input laser beam and / or the laser beam from which the focal element is formed has an average power of at least 1 W to 1 kW. For example, the laser beam comprises pulses with a pulse energy of at least 10 μJ and / or at most 50 mJ. It can be provided that the laser beam comprises a single pulse or a pulse train, wherein the pulse train has 2 to 20 sub-pulses and in particular has a time interval of about 20 ns.

[0035] In particular, the input laser beam and / or the laser beam from which the focus element is formed has a diffractive beam profile and / or a Gaussian beam profile.

[0036] In particular, the focal element has a diffraction beam profile and / or is designed in a diffraction-limited manner. For example, one or more focal elements have a Gaussian shape and / or a Gaussian intensity profile.

[0037] In principle, it is also possible for one or more focus elements to have a Bessel-like shape and / or a quasi-non-diffracting intensity profile and / or a Bessel-like intensity profile. For example, a Bessel-like beam profile is then assigned to the input laser beam.

[0038] The focal elements provided for forming the material modifications along the processing line may, but do not necessarily have to, have the same shape and / or the same intensity profile.

[0039] It can be advantageous to split the input laser beam into a plurality of sub-beams by means of a beam splitter element and to form focal elements by focusing the sub-beams coupled out of the beam splitter element. The focal elements can thus be formed, for example, as copies of one another. In particular, the focal elements can thereby be introduced into the material of the workpiece in a technically simple manner at different positions and / or at different distances.

[0040] For the same reasons, it may be advantageous to split the input laser beam by means of a beam splitting element by applying a phase shift to the beam cross section of the input laser beam. This is achieved or includes impressing a phase on the beam cross section of the input laser beam.

[0041] For example, the beam-splitting element is designed as a 3D beam-splitting element or comprises a 3D beam-splitting element.

[0042] For example, the beam splitting element comprises a plurality of components and / or functions. It may be provided that the beam splitting element comprises both a 3D beam splitting element and a polarization beam splitting element.

[0043] It can be provided that the splitting of the input laser beam is achieved solely by impressing a phase on the beam cross section of the input laser beam.

[0044] In particular, the phase is impressed in a transverse direction of the input laser beam. The transverse direction lies in a plane oriented perpendicularly to the beam propagation direction of the input laser beam.

[0045] Alternatively or additionally, it can be provided that the splitting of the input laser beam by means of the beam splitting element is realized by polarization splitting or includes polarization splitting. For example, mutually adjacent focal elements can then each be formed with a different polarization state. In particular, interference of mutually adjacent focal elements can thereby be prevented. Thus, mutually adjacent focal elements can be arranged, for example, at a particularly small distance from one another.

[0046] In principle, it is possible to split the input laser beam both by means of phase imposition and by means of polarization splitting.

[0047] It may be advantageous if the machining line is formed spatially continuously in the thickness of the material of the workpiece and / or in the thickness of the workpiece section to be separated from the workpiece, thereby making it possible, for example, to separate the workpiece into two parts or to separate workpiece sections from the workpiece.

[0048] In particular, the processing line extends from the outer side of the workpiece into the inner region of the material.

[0049] The outer side of the workpiece is to be understood as meaning, in particular, the outer side of the material of the workpiece into which the focal element is introduced.

[0050] For example, the processing line extends in particular spatially continuously from a first outer side of the workpiece, through which the focal element and / or the laser beam for forming the focal element is coupled into the material, to a second outer side of the workpiece spaced apart in the thickness direction of the workpiece.

[0051] In particular, material modifications and / or cracks are respectively assigned to the processing lines, which extend from the inner region of the material to the outer side of the workpiece, so that wet chemical solutions can be coupled into these material modifications or cracks of the processing lines on the outer side.

[0052] In particular, the shape of the processing line is associated with the shape and / or cross-sectional shape of the dividing surface to be or formed by dividing the material, and in particular with the desired shape and / or desired cross-sectional shape of the dividing surface. Thus, the edge geometry and / or cross-sectional geometry of the dividing surface produced by dividing the material, and in particular the desired edge geometry and / or desired cross-sectional geometry of the dividing surface, can be defined by means of the processing line.

[0053] For example, the total length of at least one processing line is between 50 μm and 5000 μm, and preferably between 100 μm and 1000 μm. Workpieces having a thickness in the aforementioned range can thereby be processed (and in particular separated).

[0054] For example, the thickness of the material of the workpiece is between 50 μm and 5000 μm, and preferably between 100 μm and 1000 μm, for example about 500 μm.

[0055] The processing line does not necessarily have to be designed to be spatially continuous, but can have different, spatially segmented sections. In particular, the processing line can have gaps and / or interruptions at which no focal element is arranged.

[0056] In particular, the processing line corresponds to the connecting line between focal elements adjacent to each other within the material.

[0057] In particular, it can be provided that the processing line is at least in sections a straight line and / or that the processing line is at least in sections curved and / or is curved.

[0058] By implementing the processing line as a curve, for example, rounded sections can be cut out from the workpiece. For example, rounded edges can be produced in this way.

[0059] In the case of a curved design of the processing line, a certain positioning angle range is assigned to the processing line, for example, which the processing line has with reference to the outer side of the workpiece.

[0060] In particular, it can be provided that the spacing of mutually adjacent focal elements has a non-zero spacing component which is oriented parallel to the thickness direction of the workpiece. In particular, the respective spacings of all mutually adjacent focal elements provided for laser processing of a workpiece have a non-zero spacing component which is oriented parallel to the thickness direction of the workpiece.

[0061] The thickness direction of the workpiece is to be understood in particular as a direction which is oriented transversely and in particular perpendicularly to the outer side of the workpiece through which the focal element and / or the laser beam for forming the focal element is coupled into the material.

[0062] In particular, the spacing component parallel to the thickness direction has a value which is greater than zero in magnitude.

[0063] An adjacent focus element is to be understood in particular as a focus element which is closest to a specific focus element.

[0064] In particular, it can be provided that the spacing of mutually adjacent focal elements has a non-zero spacing component which is oriented parallel to the beam propagation direction of the laser beam from which the focal element is formed. In particular, the respective spacings of all adjacent focal elements provided for laser processing of a workpiece have this non-zero spacing component.

[0065] Advantageously, it can be provided that the angle of attack / positioning between the processing line and the outer side of the workpiece, through which the focal element is coupled into the material of the workpiece, is at least 1° and / or at most 90°, at least in certain areas / sections. Depending on the selected positioning angle, the workpiece can thus be cut vertically, for example, or the workpiece can be chamfered at a certain angle.

[0066] The fact that a processing line has a certain positioning angle or a positioning angle range at least in sections is to be understood in particular to mean that the processing line has at least one section with this positioning angle or this positioning angle range.

[0067] In particular, the positioning angle can be at least 10° and / or at most 80°, preferably at least 30° and / or at most 60°, particularly preferably at least 40° and / or at most 50°.

[0068] In particular, it can be provided that the positioning angle of the processing line is constant at least in sections and / or that the processing line has a plurality of sections with different positioning angles.

[0069] The material modifications introduced into transparent materials by ultrashort laser pulses are subdivided into three different categories, see K. Itoh et al., “Ultrafast Processes for Bulk Modification of Transparent Materials”, MRS Bulletin, Vol. 31, p. 620 (2006): Type I isotropic refractive index changes; Type II is birefringent index changes; Type III is so-called voids or cavities. The resulting material modifications depend on the laser parameters of the laser beam from which the individual focus elements are formed (e.g. pulse duration, wavelength, pulse energy and repetition frequency of the laser beam), as well as on the material properties (e.g., electronic structure and thermal expansion coefficient, among others), and also on the numerical aperture (NA) of the focus.

[0070] The type I isotropic refractive index change is due to the locally confined melting and rapid resolidification of the transparent material by the laser pulse. For example, if the quartz glass is cooled rapidly from a higher temperature, the quartz glass has a higher material density and refractive index. Thus, if the material in the focal volume melts and then cools rapidly, the quartz glass has a higher refractive index in the region of the material modification than in the unmodified region.

[0071] The refractive index change of type II birefringence can occur, for example, due to the interference between an ultrashort laser pulse and the electric field of the plasma generated by the laser pulse. This interference leads to a periodic modulation in the electron plasma density, which leads to the birefringent properties of the transparent material (that is to say the direction-dependent refractive index) during solidification. For example, type II modifications are also accompanied by the formation of so-called nanogratings.

[0072] For example, voids (cavities) in type III modifications can be produced with the aid of high laser pulse energies. The formation of voids is attributed to the explosive expansion of highly excited, evaporated material from the focal volume into the surrounding material. This process is also known as a microexplosion. Since this expansion occurs within a mass of material, a microexplosion leaves behind a less dense or hollow core (void), or microscopic defects in the submicron range or in the atomic range, which are surrounded by a compressed material shell (Materialhülle). The compression at the shock wave front of the microexplosion generates stresses in the transparent material, which can lead to spontaneous crack formation or can promote crack formation.

[0073] In particular, the formation of voids can also be accompanied by type I and type II modifications. For example, type I and type II modifications can be produced in areas with less stress around the introduced laser pulse. Therefore, if it is mentioned that a type III modification is introduced, a lower density or hollow core (or defect) will be present in any case. For example, in sapphire, in the case of a type III modification, a lower density area is produced by microexplosions instead of a cavity. Since material stress is generated in the case of a type III modification, this modification is usually also accompanied by crack formation, or at least promotes crack formation. In the case of the introduction of a type III modification, the formation of type I and type II modifications cannot be completely prevented or avoided. Therefore, it is unlikely to find a "pure" type III modification.

[0074] At the high repetition rate of the laser beam, the material cannot completely cool between pulses, so that the accumulation effect of the heat introduced from pulse to pulse may affect the material modification. For example, the repetition frequency of the laser beam can be higher than the inverse of the thermal diffusion time of the material, so that heat accumulation can occur at the focal element by continuous absorption of laser energy until the melting temperature of the material is reached. In addition, through the heat transfer of thermal energy to the area around the focal element, a larger area than the focal element can be melted. After the introduction of the ultrashort laser pulse, the heated material cools rapidly, so that the density and other structural properties of the high temperature state are locked in the material to a certain extent.

[0075] It may be advantageous that, by loading the material with the focal element, material modifications are formed in the material, wherein these material modifications are type III material modifications and / or wherein these material modifications are accompanied by crack formation in the material. In particular, the material can be separated by etching, and in particular selective etching, with the aid of these material modifications.

[0076] In particular, it can be provided that the focal elements are moved relative to the material of the workpiece in the feed direction. Preferably, the focal elements are located at least approximately in a plane which is oriented, in particular, perpendicularly to the feed direction.

[0077] By the relative movement of the focal element with respect to the material of the workpiece, a processing surface is formed which is associated with the processing line and along which the material modification portion is arranged and / or along which the material of the workpiece can be divided.

[0078] In particular, during the singulation of the workpiece, the workpiece is divided into two or more workpiece sections, or during the singulation of the workpiece, at least one workpiece section is singulated from the workpiece.

[0079] The workpiece sections formed by dividing the workpiece can be useful sections and / or good sections, and the useful sections and / or good sections can have a dividing surface with a shape associated with the shape of the processing line and / or the processing surface. In addition, the workpiece sections formed by dividing the workpiece can be waste sections and / or waste sections.

[0080] In particular, by dividing the workpiece along the machining plane, workpiece segments are produced which have a dividing plane whose geometry corresponds to the machining plane.

[0081] A transparent material is to be understood in particular as a material which is transparent to the input laser beam and / or to the laser beam from which the focal element is formed. In particular, a transparent material is to be understood as a material through which at least 70% and in particular at least 80% and in particular at least 90% of the laser energy of the input laser beam and / or of the laser beam from which the focal element is formed is transmissive.

[0082] In particular, a focus element is to be understood as a focused radiation region of the input laser beam, which has in particular a certain spatial extension and / or is designed to be in particular spatially continuous. In order to determine the spatial size of a certain focus element (for example the diameter of this focus element), only intensity values ​​that exceed a certain intensity threshold are taken into account. The intensity threshold is selected, for example, in this case, so that intensity values ​​below the intensity threshold have such low intensities that they are no longer relevant for the interaction with the material to form a material modification. For example, the intensity threshold is 50% of the global intensity maximum value of the focus element.

[0083] In particular, a specific focal element is assigned a corresponding spatial interaction region in which it interacts with the material of a workpiece when it is introduced into the material.

[0084] In particular, the focal elements introduced into the material interact with the material via nonlinear absorption, ie the laser radiation assigned to these focal elements interacts with the material via nonlinear absorption. In particular, due to this interaction between the focal elements and the material, material modifications are formed in the material.

[0085] In particular, it can be provided that, according to the above definition, the maximum spatial extension of the respective focal element is at least 0.5 μm and / or at most 60 μm, preferably at least 2 μm and / or at most 10 μm. In particular, the maximum spatial extension of the interaction region associated with a specific focal element, which interacts with the material of the workpiece, is at least 0.5 μm and / or at most 60 μm, preferably at least 2 μm and / or at most 10 μm.

[0086] A determined maximum spatial extension of a focal element is to be understood in particular as the maximum spatial extension of the focal element in any spatial direction.

[0087] In particular, the expression "at least approximately" or "approximately" is to be understood as generally meaning a deviation of at most 10%. Unless otherwise indicated, the expression "at least approximately" or "approximately" is to be understood as meaning in particular that actual values ​​and / or spacings and / or angles deviate from ideal values ​​and / or spacings and / or angles by no more than 10%. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] The following description of the preferred embodiments serves to explain the present invention in more detail with reference to the accompanying drawings.

[0089] In the attached picture:

[0090] Figure 1 A schematic illustration of an exemplary embodiment of an apparatus for laser processing of a workpiece is shown;

[0091] Figure 2 A schematic cross-sectional view of a section of material of a workpiece is shown in which section a separation of the material along a processing line is provided;

[0092] Figure 3 Shown according to Figure 2 A schematic cross-sectional view of a section of , wherein material is loaded with a plurality of focal elements for forming a material modification portion;

[0093] Figure 4 shows a schematic cross-sectional view of a section of a material in which material modifications are produced by loading the material with focal elements, which material modifications are accompanied by crack formation in the material;

[0094] Figure 5 A cross-sectional view showing a simulated intensity distribution of a focal element for laser processing of a workpiece;

[0095] Figure 6a shows a schematic perspective view of a workpiece having a material modification formed thereon, wherein the workpiece is arranged in an etching bath for performing an etching process; and

[0096] Figure 6b Shown according to Figure 6a Schematic perspective view of two workpiece sections formed by dividing a workpiece.

[0097] In all figures, elements which are identical or have equivalent functions are provided with the same reference symbols. DETAILED DESCRIPTION

[0098] One embodiment of an apparatus for laser processing of a workpiece is Figure 11 and denoted here by 100. With the aid of the device 100, localized material modifications (e.g. defects in the submicrometer range or atomic range) that lead to material weakening can be produced in the material 102 of the workpiece 104. The workpiece 104 can be separated at these material modifications. For example, a workpiece section can be separated from the workpiece 104 with the aid of the produced material modifications.

[0099] In particular, material modifications can be introduced into the material 102 at a set angle by means of the device 100 , so that edge regions of the workpiece 104 can be chamfered or beveled by singulating corresponding workpiece sections from the workpiece 104 .

[0100] The device 100 comprises a beam splitting element 106 into which an input laser beam 108 is coupled. The input laser beam 108 is provided, for example, by means of a laser source 110. The input laser beam 108 is, for example, a pulsed laser beam and / or an ultrashort pulsed laser beam.

[0101] In particular, the input laser beam 108 is to be understood as a beam bundle that includes a plurality of (in particular parallel-running) beams. The input laser beam 108 has in particular a transverse beam cross section 112 and / or a transverse beam extent with which the input laser beam 108 impinges on the beam splitter element 106.

[0102] In particular, the input laser beam 108 impinging on the beam-splitting element 106 has an at least approximately flat wave front 114 .

[0103] The input laser beam 108 is split into a plurality of sub-beams 116 and / or sub-beam bundles by means of the beam splitting element 106. Figure 1 In the example shown in FIG. 2 , two sub-beams 116 a and 116 b that are different from each other are schematically shown.

[0104] The sub-beam 116 (or the sub-beam bundle) coupled out of the beam-splitting element 106 has, in particular, a diverging beam profile. In particular, the beam-splitting element 106 is designed as a far-field beam-shaping element.

[0105] In order to focus the sub-beams 116 coupled out of the beam splitting element 106, the device 100 comprises a focusing lens 118, into which the sub-beams 116 are coupled. In particular, the sub-beams 116 that differ from one another impinge on the focusing lens 118 with a positional and / or angular offset.

[0106] For example, the focusing optical device 118 has one or more lens elements. For example, the focusing optical device 118 is configured as a microscope objective. For example, the focusing optical device 118 has a focal length between 5 mm and 50 mm.

[0107] For example, the beam splitting element 106 is arranged at least approximately in a rear focal plane of the focusing optics 118 .

[0108] The sub-beams 116 are focused by means of focusing optics 118 to form a plurality of focus elements 120 which are each arranged at different spatial positions. In principle, it is possible for different and / or adjacent focus elements 120 to overlap spatially in sections.

[0109] For example, one or more sub-beams 116 and / or sub-beam bundles are respectively assigned to a specific focus element 120. For example, the respective focus element 120 is formed by focusing one or more sub-beams 116 and / or sub-beam bundles.

[0110] A focus element 120 is to be understood in particular as a focused radiation region, such as a focus spot, a focus point or a focus line. In particular, these focus elements 120 each have a certain geometry and / or a certain intensity profile, wherein a geometry is to be understood as meaning, for example, a spatial shape and / or a spatial extension of the respective focus element 120.

[0111] The determined geometry and / or intensity profile of the focus elements 120 is referred to below as focus distribution 121 of the focus elements 120. The focus distribution 121 is characteristic of the respective focus element 120 and describes the shape and / or intensity profile of the respective focus element 120. In particular, a plurality of focus elements 120 or all formed focus elements 120 have the same focus distribution.

[0112] The focus profile of the formed focal element 120 is defined by the input laser beam 108, which is formed by splitting the input laser beam 108 by means of the beam splitting element 106. If the input laser beam 108 is focused before it is coupled into the beam splitting element 106, for example, a single focal element with a focus profile assigned to the input laser beam 108 is formed.

[0113] For example, input laser beam 108 has a Gaussian beam profile if it is provided, for example, by means of laser source 110. By focusing input laser beam 108, a focus element is formed in this case which has a focus distribution with a Gaussian shape and / or a Gaussian intensity profile.

[0114] Alternatively to this, it can be provided, for example, that a quasi-non-diffraction and / or Bessel-like beam profile is assigned to the input laser beam 108, so that by focusing the input laser beam 108 a focal element is formed which has a focusing distribution with a quasi-non-diffraction or Bessel-like shape and / or a quasi-non-diffraction or Bessel-like intensity profile.

[0115] The focusing distribution of the input laser beam 108 is assigned to the sub-beams 116 and / or the sub-beam bundles formed by splitting the input laser beam 108 by means of the beam splitting element 106 in such a way that a focal element 120 is formed by focusing the sub-beams 116, which has the focusing distribution and / or has a focusing distribution based on the focusing distribution.

[0116] exist Figure 1 In the example shown, the input laser beam 108 has a Gaussian beam profile, i.e. a focus distribution having a Gaussian shape and / or a Gaussian intensity profile is assigned to the input laser beam 108. The focus elements 120 then each have, for example, a focus distribution 121 having this Gaussian shape and / or this Gaussian intensity profile or having a shape or intensity profile that is based on this Gaussian shape and / or this Gaussian intensity profile (see Figure 5 ).

[0117] For example, if a Bessel-like beam profile is assigned to the input laser beam 108, the focal elements 120 formed for the laser processing of the workpiece 104 each have a focus profile 121 having the Bessel-like beam profile or having a beam profile based on the Bessel-like beam profile. Thus, the focal elements 120 can be designed, for example, to each have a focus profile having an elongated shape and / or an elongated intensity profile.

[0118] It can be provided that the device 100 has a beam shaping device 122 (e.g. Figure 1 For example, the beam shaping device 122 is arranged upstream of the beam splitting element 106 with reference to a beam propagation direction 124 of the input laser beam 108 and / or between the laser source 110 and the beam splitting element 106 .

[0119] A beam propagation direction is to be understood to mean, in particular, a main beam propagation direction and / or an average propagation direction of the laser beam.

[0120] In particular, a certain focus distribution and / or a certain beam profile can be assigned to the input laser beam 108 by means of the beam shaping device 122. In particular, a focus distribution 121 of a focal element 120 can be defined by means of the beam shaping device 122.

[0121] The beam shaping device 122 can be configured, for example, to form a laser beam having a quasi-non-diffraction and / or Bessel-like beam profile from a laser beam having a Gaussian beam profile. The quasi-non-diffraction and / or Bessel-like beam profile is then assigned to the input laser beam 108 coupled into the beam splitting element 106. Accordingly, the focal element 120 is then formed to have the quasi-non-diffraction and / or Bessel-like beam profile or to have a beam profile based on the beam profile.

[0122] For example, the beam shaping device 122 may include an axicon element for forming a laser beam having a quasi-non-diffractive and / or Bessel-like beam profile. In order to couple the beam coupled out of the beam shaping device 122 into the beam splitting element 106, for example, one or more lens elements (not shown) may be provided.

[0123] For the definition and implementation of quasi-non-diffraction and / or Bessel-like beams, refer to the book "Structured Light Fields: Applications in Optical Trapping, Manipulation and Organisation", M. Springer Science and Business Media (2012), ISBN 978-3-642-29322-1, and also reference is made to the scientific publications by I Chremmos et al. “Bessel-like optical beams with arbitrary trajectories”, Optics Letters, Vol. 37, No. 23, 1 December 2012, and by K. Chen et al. “Generalized axicon-based generation of nondiffracting beams”, arXiv:1911.03103v1 [physics.optics], 8 November 2019.

[0124] As a result of the beam splitting by means of the beam splitting element 106 , the focus elements 120 are in particular each designed to be identical to one another and / or to be copies of one another.

[0125] Figures 2 to 4 Schematic cross-sections of workpiece 104 and material 102 are shown, wherein the cross-sectional plane is oriented parallel to a thickness direction 126 and / or a depth direction of the workpiece (in the example shown, thickness direction 126 is oriented parallel to the z-direction).

[0126] It is provided that, after laser processing has been completed by means of the device 100, the workpiece 104 is separated along predefined processing lines 128. The processing lines 128 are associated with the cross-sectional geometry in which the workpiece 104 is to be separated.

[0127] In order to perform laser processing, these focus elements 120 are introduced into the material 102 of the workpiece 104 ( Figure 3 ). It is provided that focal elements 120 introduced into material 102 of workpiece 104 move relative to material 102 in feed direction 130. The movement of these focal elements 120 relative to material 102 is carried out in feed direction 130, in particular at a defined feed speed.

[0128] Each of the formed focus elements 120 is assigned a specific position x0, z0, and each focus element 120 is arranged at the specific spatial position x0, z0 with reference to the material 102 of the workpiece 104. For example, the specific position of a focus element 120 ( Position) is to be understood as the position of the center point and / or center of gravity of focus element 120 in space.

[0129] In particular, the specific position x0 , z0 of the respective focal element 120 lies in a plane oriented perpendicularly to the feed direction 130 , wherein in particular all focal elements 120 formed for laser processing of the workpiece 104 lie in this plane.

[0130] In particular, a certain intensity I is assigned to each of the focus elements 120 formed.

[0131] The specific position x0 , z0 of the individual focal elements 120 and in particular also their intensity I can be adjusted by means of the beam-splitting element 106 .

[0132] In particular, the respective spacings d and / or the respective positional offsets between mutually adjacent focal elements 120 can be adjusted by means of the beam splitter element 106. The spacing direction of the spacing d adjustable by means of the beam splitter element 106 preferably lies in a plane that is oriented transversely and in particular perpendicularly to the feed direction 130. For example, the beam splitter element 106 can be used to adjust the spacings d in two spatial directions (in the plane that forms the plane or lies in the plane) to the respective focal elements 120 adjacent to each other. Figure 3 In the example shown, the spacing d is adjusted component-wise in the x-direction and the z-direction.

[0133] The feed direction 130 is oriented transversely and in particular perpendicularly with respect to the thickness direction 126 of the workpiece 104 .

[0134] Preferably, the beam splitter element 106 is designed as a 3D beam splitter element or comprises a 3D beam splitter element. Thus, the focal elements 120 can be designed, for example, such that they respectively correspond to one another and / or such that they respectively form copies of one another.

[0135] Regarding the technical implementation and characteristics of the beam splitting element 106 implemented as a 3D beam splitting element, refer to the scientific publication "Structured light for ultrafast laser micro-and nanoprocessing" by D. Flamm et al., arXiv:2012.10119v1[physics.optics], December 18, 2020.

[0136] To perform beam splitting, in one embodiment of the beam splitting element 106, for example, as a 3D beam splitting element, a defined transverse phase distribution is applied to a transverse beam cross section 112 of the input laser beam 108. A transverse beam cross section or a transverse phase distribution is to be understood in particular as a beam cross section or a phase distribution in a plane which is oriented transversely and in particular perpendicularly to a beam propagation direction 124 of the input laser beam 108.

[0137] The focal point elements 120 spaced apart from one another are formed by interference of the focused sub-beams 116 , wherein, for example, constructive interference, destructive interference or intermediate conditions thereof, such as partially constructive interference or partially destructive interference, may occur.

[0138] In order to form focal elements 120 at corresponding positions x0 , z0 and / or at corresponding spacings d, the phase distribution applied by means of the beam-splitting element 106 has a defined grating portion and / or optical lens portion for each focal element 120 .

[0139] Due to the grating portion, a corresponding position shift of the formed focus element 120 in a first spatial direction (e.g. in the x-direction) is produced after focusing of the sub-beams 116. Due to the optical lens portion, the sub-beams 116 or the sub-beam bundles impinge on the focusing optical device 118 at different angles or with different convergence or divergence, which results in a position shift in a second spatial direction (e.g. in the z-direction) after focusing has been completed.

[0140] These spatial positions x0 , z0 can therefore be defined by a corresponding design of the beam-splitting element 106 or a corresponding design of the phase distribution applied by means of the beam-splitting element.

[0141] The intensity I of each focal element 120 is determined by the phase position of the focused sub-beams 116 relative to one another. These phase positions can be defined by the mentioned grating parts and optical lens parts. When designing the beam splitter element 106, the phase positions of the focused sub-beams 116 relative to one another can be selected so that these focal elements 120 each have the desired intensity.

[0142] Alternatively or additionally to the above-described variants of the beam splitter element 106, it can be provided that the beam splitter element 106 is designed as a polarization beam splitter element or includes a polarization beam splitter element. In this case, the beam splitter element 106 is used to polarize the input laser beam 108 into a plurality of beams each having one of at least two different polarization states.

[0143] In particular, the aforementioned polarization states are to be understood as linear polarization states, wherein, for example, two different polarization states and / or polarization states oriented perpendicularly to one another are provided.

[0144] In particular, these polarization states are such that the electric field is oriented in a plane perpendicular to the beam propagation direction of the polarized beam (transverse electric).

[0145] For polarization beam splitting, the beam splitting element 106 comprises, for example, a birefringent lens element and / or a birefringent wedge element. For example, the birefringent lens element and / or the birefringent wedge element is made of or comprises a quartz crystal.

[0146] With regard to the function and embodiment of the beam splitting element 106 as a polarization beam splitting element (or with a polarization beam splitting element), reference is made to DE 10 2020 207 715 A1 and DE 10 2019 217 577 A1.

[0147] By means of the beam splitter element 106, in particular, sub-beams 116 with different polarization states can be formed. By focusing the sub-beams 116 by means of the focusing optical device 118, for example, the focus elements 120 can each be formed from a beam with a specific polarization state. Thus, a specific polarization state can be assigned to each of the focus elements 120.

[0148] In particular, it may be provided that focal elements 120 are arranged and formed by polarization splitting by means of beam-splitting element 106 in such a way that focal elements 120 adjacent to one another each have a different polarization state.

[0149] Focus elements 120 are coupled into material 102, for example, through first outer side 132 of material 102 of workpiece 104. For example, second outer side 134 of material 102 of workpiece 104 is arranged spaced apart from first outer side 132 in thickness direction 126 of workpiece 104.

[0150] The first outer side 132 and the second outer side 134 are oriented, for example, at least approximately parallel to one another. For example, the workpiece 104 is designed to be plate-shaped and / or sheet-shaped.

[0151] Material 102 of workpiece 104 has, for example, an at least approximately constant thickness D in thickness direction 126 .

[0152] The focal elements 120 formed are arranged along a processing line 128. The respective spacing d and strength I of the focal elements 120 arranged along the processing line 128 are selected such that a material modification 138 ( Figure 4 ), these material modifications 138 allow the material 102 to be separated along the processing line 128 and / or along the processing surface associated with the processing line 128 by etching with the help of a wet chemical solution.

[0153] The individual distances d of the focal elements 120 provided for laser processing of the workpiece 104 can be selected differently for different focal elements 120 and / or for different pairs of focal elements 120. However, it is also possible in principle for all focal elements 120 provided for laser processing of the workpiece 104 to have the same individual distances d.

[0154] In particular, for all focal elements 120 and / or for all pairs of focal elements 120 adjacent to one another, a distance component d of the distance d oriented parallel to the thickness direction 126 of the material 102 Z is non-zero. In particular, all adjacent focus elements 120 are separated by a non-zero spacing component d Z Spaced apart in the thickness direction 126 .

[0155] In accordance with Figure 3 and Figure 4 In the illustrations, focal elements or material modifications are shown only schematically with regard to number, geometry, extent and arrangement.

[0156] In particular, it may be provided that the processing line 128 extends between a first outer side 132 and a second outer side 134 of the workpiece 104 and in particular extends continuously and / or without interruption between the first outer side 132 and the second outer side 134 .

[0157] It can be provided that the processing line 128 has a plurality of different sections 140. For example, Figure 3 In the example shown, the processing line 128 has a first section 140a, a second section 140b and a third section 140c, wherein, with reference to the thickness direction 126, the second section 140b adjoins the first section 140a and the third section 140c adjoins the second section 140b.

[0158] The processing line 128 does not necessarily have to be designed to be continuous and / or differentiable. For example, the processing line 128 can have discontinuities. It can be provided that the processing line 128 has interruptions and / or gaps, at which in particular no focal element 120 is arranged.

[0159] The processing line 128 and / or the corresponding section 140 of the processing line 128 need not be configured as a straight line. For example, the processing line 128 and / or the section 140 can be configured as a straight line or a curve.

[0160] Furthermore, a certain positioning angle α and / or a positioning angle range is assigned to the processing line 128 and / or the corresponding section 140 of the processing line 128 , which the processing line 128 or the corresponding section 140 encloses with the first outer side 132 of the workpiece 104 .

[0161] In the exemplary embodiment shown, the positioning angle α of the first segment 140a and the third segment 140c is 45° in magnitude, and the positioning angle α of the second segment 140b is 90° in magnitude.

[0162] The material modifications 138 formed by the application of the focal elements 120 and / or introduction into the material 102 are arranged at specific, localized positions in the material 102. The specific positions of the material modifications 138 correspond at least approximately to the specific positions x0, z0 of the focal elements 120 in the material 102, by means of which the material modifications 138 are formed. By suitable selection of processing parameters, such as the respective spacings d between the focal elements 120, their respective intensities I, the feed speed oriented in the feed direction 130 and the laser parameters of the input laser beam 108, the material modifications 138 can be designed, for example, as type III modifications, which are accompanied in particular by the spontaneous formation of cracks 142 in the material 102 of the workpiece 104. In particular, the cracks 142 are formed between mutually adjacent material modifications 138.

[0163] It is provided that the material 102 of the workpiece 104 is separated along the processing line 128 (or along the processing plane associated with the processing line 128 ) by etching with the aid of a wet chemical solution.

[0164] For example, after forming the material modified portion 138, the workpiece 104 is introduced into a wet chemical solution for etching, wherein the wet chemical solution penetrates through the first outer side 132 and / or the second outer side 134 into the material modified portion 138 formed at the processing line 128 or the processing surface and, if necessary, can enter the material 102 through the crack 142.

[0165] Figure 5 A simulated intensity distribution is shown for a plurality of focus elements 120, wherein the spacing d is approximately 8.0 μm for these focus elements 120. In the gray value view shown, brighter areas represent higher intensity.

[0166] Laser processing of the workpiece 104 is performed as follows:

[0167] A focal element 120 is formed for laser processing of a workpiece 104 by means of the device 100 , for example, by splitting the input laser beam 108 by means of the beam-splitting element 106 and subsequently focusing the sub-beams 116 .

[0168] The material 102 of the workpiece 104 is acted upon with the formed focal element 120, i.e. the focal element 120 is introduced into the material 102, wherein the focal element 120 is positioned in the material 102 along a predetermined processing line 128. The focal element 120 is then moved relative to the material 102 in a feed direction 130 through the material 102.

[0169] In this case, the material 102 is a material that is transparent to the wavelength of the laser beam from which the focal element 120 is respectively formed, for example a glass material.

[0170] By loading material 102 with focal elements 120 , material modifications 138 are formed in material 102 at corresponding locations of these focal elements 120 .

[0171] The material modification 138 formed by means of the focal element 120 is arranged along the processing line 128 (see Figure 3 and Figure 6a ), which processing line 128 extends continuously over the entire thickness D of the material 102, for example. The focus element 120 or material modification 138 associated with the processing line 128 defines the cross-sectional geometry of the dividing surface resulting from the subsequent dividing of the material ( Figure 6b ).

[0172] The focal element 120 moves relative to the material 102 along a predetermined path 144, thereby forming a surface-based structure in the material 102. The material modification section 138 is arranged. Figure 6a In the example shown, the trajectory 144 is oriented parallel to the feed direction 130 .

[0173] By the relative movement of the focal element 120 relative to the material 102 along the trajectory 144 , a processing plane 146 associated with the processing line 128 is formed, on which the material modification portion 138 is arranged. In particular, the processing line 128 is located in the associated processing plane 146 .

[0174] The trajectory 144 can in principle have straight sections and / or curved sections. In the case of a curved section, the processing line 128 is particularly rotated during the relative movement between the workpiece 102 and the focal element 120 so that the processing line 128 is always located in a plane oriented perpendicularly to the feed direction 130. This can be achieved, for example, by a corresponding rotation of the beam splitter element 106 or by a relative rotation of the entire device 100 relative to the workpiece 104.

[0175] The distance between adjacent material modifications 138 in the advancing direction 130 can be defined, for example, by adjusting the pulse distance of laser pulses of the input laser beam 108 and / or by adjusting the advancing speed.

[0176] The material modification 138 formed along the processing line 128 or the processing surface 146 leads to a reduction in the strength of the material 102 , wherein the strength is reduced in particular due to the cracks 142 formed.

[0177] After the material modification 138 has been formed in the material 102, an etching process is performed with the aid of a wet chemical solution 148 in order to separate the material 102 along the processing lines 128 and / or the processing surfaces 146. For this purpose, the material 102 is introduced partially or completely into an etching bath 150 (by a wet chemical solution 148), for example. Figure 6a In particular, the material 102 is partially or completely introduced into the wet chemical solution 148, so that the wet chemical solution 148 partially or completely surrounds the material 102. The subsequent etching process is carried out at a determined temperature of the wet chemical solution 148 and for a determined duration.

[0178] The wet chemical solution penetrates on the outer sides 132, 134 into the material modification 138 and / or crack 142 associated with the processing line 128 and then penetrates along the processing line 128 into the inner region 152 of the material 102. The inner region 152 is in particular a region of the material 102 that is spaced apart from the respective outer sides 132, 134 parallel to the thickness direction 126.

[0179] In particular, etching by means of etching bath 150 can be performed with the aid of ultrasound.

[0180] The temperature of the wet chemical solution 148 is between 100° C. and 150° C. In particular, the temperature of the wet chemical solution 148 is kept at least approximately constant over the duration of the etching process, wherein the desired value for the temperature that is constant over time lies within the above-mentioned value range. For example, the etching process is carried out at a constant temperature of 130° C.

[0181] With regard to the temperature of wet chemical solution 148 , “at least approximately constant” is preferably to be understood as meaning that during the etching process the actual temperature of wet chemical solution 148 deviates by less than 7 K from a predefined (constant over time) desired value.

[0182] The wet chemical solution is preferably an aqueous KOH solution or an aqueous NaOH solution, each having a concentration between 15% (by weight) and 50% (by weight).

[0183] The duration of the etching process for singulating the material 102 depends on the type of material 102 and the positioning and shape of the process lines 128 in the material 102. The duration is typically between 5 minutes and 180 minutes.

[0184] By etching with the aid of the supplied wet chemical solution, the material 102 is divided at the processing surface 152 into two mutually different workpiece sections 154a, 154b ( Figure 6b ).

[0185] The workpiece section 154 b is a good section and / or a useful section and has a dividing surface 156 having a shape associated with the shape of the processing line 128 (or the processing surface 146 ).

[0186] exist Figure 6b In the example shown, the workpiece segment 154a is a defective segment and / or a scrap segment.

[0187] The optimal parameters of the etching process, such as the duration, the KOH or NaOH concentration of the wet chemical solution and its (time-constant) temperature, are in particular specific to the respective material 102 of the workpiece 104 used.

[0188] Preferably, these parameters are selected such that during the etching process, the material 102 is etched at the material modifications 138 arranged along the processing line 128 (or the processing surface 152) at the highest possible speed and / or etching rate, and at the same time, the unmodified areas of the workpiece 104 are eroded as little as possible. Therefore, it is preferred that the etching is selectively performed at the material modifications 138 and / or cracks 142 formed in the material 102 at the highest possible etching rate. This enables the etching process for separating the material 102 to be carried out in the shortest possible duration.

[0189] For example, the material 102 of the workpiece 104 is aluminosilicate glass. In order to form the material modification 138 as a type III modification, the laser beam from which the focal elements 120 are formed has, for example, a wavelength of 1030 nm and a pulse duration of 3 ps. Furthermore, the numerical aperture associated with the focusing optical system 118 is 0.4, and the pulse energy associated with the individual focal elements 120 is 500 nJ to 5000 nJ.

[0190] Reference numerals list

[0191] α positioning angle

[0192] d-spacing

[0193] d Z Spacing Component

[0194] DThickness

[0195] The position of x0 in the x direction

[0196] The position of z0 in the y direction

[0197] 100 devices

[0198] 102 Materials

[0199] 104 Workpieces

[0200] 106 beam splitter

[0201] 108 Input laser beam

[0202] 110 Laser source

[0203] 112 Beam cross section

[0204] 114 Wellenfront

[0205] 116 beamlets

[0206] 116a sub-beam

[0207] 116b subbeam

[0208] 118 Focusing optics

[0209] 120 Focus Elements

[0210] 121 Focus Distribution

[0211] 122 Beam shaping device

[0212] 124 Beam propagation direction

[0213] 126 Thickness direction

[0214] 128 Processing Line

[0215] 130 Feed direction

[0216] 132 First Outer Side

[0217] 134 Second outer side

[0218] 138 Material Modification Department

[0219] 140 Segment

[0220] 140a First section

[0221] 140b Second segment

[0222] 140c Section 3

[0223] 142 Crack

[0224] 144 Track

[0225] 146 Processing surface

[0226] 148 Wet Chemical Solutions

[0227] 150 Etching Pool

[0228] 152 Internal Area

[0229] 154a Workpiece section / waste section

[0230] 154b Workpiece section

[0231] 156 Split surface

Claims

1. A method for separating a workpiece (104) having a transparent material (102), in which: a plurality of focus elements (120) are provided by means of an input laser beam (108); the material (102) is impinged with the focus elements (120); a material modification (138) is formed in the material (102) along a predetermined processing line (128) by impinging the material (102) with the focus elements (120); and the material (102) is separated along the processing line (128) by means of an etching process using a wet chemical solution, wherein: During the etching process, the temperature of the wet chemical solution is at least 100°C and / or at most 150°C.

2. The method according to claim 1, It is characterized in that The wet chemical solution is an aqueous KOH solution having a concentration of at least 15% by weight and / or at most 50% by weight.

3. The method according to claim 1, It is characterized in that The wet chemical solution is an aqueous NaOH solution having a concentration of at least 15% by weight and / or at most 50% by weight.

4. The method according to any one of the preceding claims, It is characterized in that The temperature of the wet chemical solution is kept constant over time during the etching process, wherein, in particular, the temperature is adjusted to a desired temperature that is constant over time of at least 100° C. and / or at most 150° C., and wherein, during the etching process, the actual temperature of the wet chemical solution deviates from the desired temperature by less than 7 K and in particular less than 1 K.

5. The method according to claim 4, It is characterized in that The wet chemical solution is an aqueous KOH solution or an aqueous NaOH solution, wherein the concentration of the solution is selected such that the boiling temperature of the solution is at least 5% and in particular at least 10% higher than the desired temperature of the wet chemical solution which is constant over time.

6. The method according to any one of the preceding claims, It is characterized in that The duration of the etching process is at least 5 minutes and / or at most 180 minutes, and preferably at least 10 minutes and / or at most 90 minutes.

7. The method according to any one of the preceding claims, It is characterized in that In order to carry out the etching process, the material is exposed to the wet chemical solution, wherein the material is introduced in particular partially or completely into the wet chemical solution.

8. The method according to any one of the preceding claims, It is characterized in that The spacing (d) between mutually adjacent focal elements (120) is at least 3 μm and / or at most 70 μm, and preferably at least 5 μm and / or at most 10 μm, and / or The distance between mutually adjacent material modifications (138) is at least 3 μm and / or at most 70 μm, and preferably at least 5 μm and / or at most 10 μm.

9. The method according to any one of the preceding claims, It is characterized in that The input laser beam and / or the laser beam forming the focus element is a pulsed laser beam and in particular an ultrashort pulsed laser beam and is characterized in particular in that a pulse energy of at least 0.5 μJ and / or at most 10 μJ is assigned to a specific focus element.

10. The method according to any one of the preceding claims, It is characterized in that The input laser beam (108) is split into a plurality of sub-beams (116) by means of a beam splitting element (106), and the focal element (120) is formed by focusing the sub-beams (116) coupled out of the beam splitting element (106).

11. The method according to any one of the preceding claims, It is characterized in that The processing line (128) is formed spatially continuously over the thickness (D) of the material (102) of the workpiece (104) and / or over the thickness of workpiece sections to be separated from the workpiece (104).

12. The method according to any one of the preceding claims, It is characterized in that The spacing (d) between adjacent focus elements (120) has a non-zero spacing component (d Z ), the non-zero spacing component being oriented parallel to a thickness direction (126) of the workpiece (104).

13. The method according to any one of the preceding claims, It is characterized in that The positioning angle (α) between the processing line (128) and the outer side (132, 134) of the workpiece (104) through which the focal element (120) is coupled into the material (102) of the workpiece (104) is at least 1° and / or at most 90°, at least in sections.

14. The method according to any one of the preceding claims, It is characterized in that By loading the material (102) with the focal element (120), a material modification (138) is formed in the material (102), wherein the material modification (138) is a Type III material modification, and / or wherein the material modification (138) is accompanied by crack formation in the material (102).

15. The method according to any one of the preceding claims, It is characterized in that The focal element (120) moves in a feed direction (130) relative to the material (102) of the workpiece (104) and is particularly characterized in that the focal element (120) is at least approximately located in a plane oriented perpendicularly to the feed direction (130).

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