High energy glass cutting

Abstract

The invention relates to a method for separating at least partially transparent material (1), wherein a single laser pulse and / or an ultrashort laser pulse comprising a plurality of sub-laser pulses is focused into the material (1) such that a modification zone (602) produced and elongated in the direction of beam propagation enters into the material (1) and penetrates at least one surface (14) of the material, wherein a material modification (3) is thereby introduced into the material (1), wherein a plurality of material modifications (3) are introduced into the material (1) along a separation line (2), and wherein the material (1) is subsequently separated along the separation line (2) by means of a separation step, and wherein the pulse energy of the single laser pulse or the sum of the pulse energies of the sub-laser pulses is in the range from 500 µJ to 50 mJ.

Description

Technical Field

[0001] The present invention relates to a method for separating at least partially transparent materials. Background Technology

[0002] In recent years, the development of lasers with very short pulse lengths, especially those less than nanoseconds, and high average power, particularly in the kilowatt range, has led to a new type of materials processing. The short pulse length and high peak power, or high pulse energy of several hundred microjoules, can cause nonlinear absorption of the pulse energy in materials, making it possible to process virtually transparent or essentially transparent materials using the laser wavelength employed.

[0003] US10421683 describes a separation method based on introducing laser pulses into a material. The problem with this prior art method is that good separability is difficult or impossible to achieve, particularly for thicker materials with a thickness greater than 1 mm, especially glass or layered systems. "Good separability" is generally understood to mean that the material can be reliably separated along a pre-defined separation line. Summary of the Invention

[0004] Based on known prior art, the objective of this invention is to provide an improved method.

[0005] This task is accomplished by a method for separating at least partially transparent materials, having the features of claim 1. Advantageous extensions are derived from the dependent claims, the description, and the drawings.

[0006] Accordingly, a method for separating at least partially transparent materials is proposed, wherein an ultrashort laser pulse, in the form of a single laser pulse and / or a pulse train comprising multiple sub-laser pulses, is focused into the material, such that a modified region, generated and elongated in the beam propagation direction, enters the material and penetrates at least one surface of the material, thereby introducing a material-modified portion into the material, wherein multiple material-modified portions are introduced into the material along a separation line, and wherein the material is subsequently separated along the separation line by means of a separation step. According to the invention, the pulse energy of the single laser pulse or the sum of the pulse energies of the sub-laser pulses is in the range of 500 μJ to 50 mJ.

[0007] The material can be a metal, semiconductor, insulator, or a combination thereof. In particular, it can also be glass, glass-ceramic, polymer, or a semiconductor wafer, such as a silicon wafer. The material can also be a glass substrate and / or a stacked substrate system and / or a silicon wafer. Preferably, the thickness L of the material is... M Greater than 1mm.

[0008] The material is partially transparent to the wavelength of the laser, where "partially transparent" means that 50% or more of the incident light at the wavelength is transmitted through the material.

[0009] Ultrashort pulse lasers provide ultrashort laser pulses. Here, "ultrashort" can mean a pulse length, for example, between 500 picoseconds and 1 femtosecond, particularly between 100 picoseconds and 10 femtoseconds. Ultrashort pulse lasers are also capable of providing pulse trains (so-called Bursts) consisting of multiple ultrashort laser pulses, where each pulse train includes the emission of multiple sub-laser pulses. Here, the time interval between the sub-laser pulses can be between 10 picoseconds and 500 nanoseconds, particularly between 10 nanoseconds and 80 nanoseconds. Time-shaped pulses with significant amplitude variations in the range of 50 femtoseconds to 5 picoseconds are also considered ultrashort laser pulses. In the following text, the terms "pulse" or "laser pulse" are used repeatedly. In this context, time-shaped laser pulses are also included, even if not explicitly defined separately. The ultrashort laser pulses emitted by the ultrashort pulse laser correspondingly form laser beams.

[0010] The laser beam is focused into the material in such a way that it has an elongated focal region along the beam propagation direction. This means that the focal region of the laser beam along the beam propagation direction is larger than the extension of the laser beam perpendicular to the beam propagation direction. A general definition of the extension of the focal region is given below.

[0011] The elongated modification region describes the area of ​​the laser beam where the intensity exceeds the material's processing threshold, enabling material processing within the laser's modification region. The geometry of the laser's modification and focusing regions is thus correlated on a scale with the laser intensity.

[0012] The elongated modified region can penetrate at least one surface. This means that the surface of the material intersects with the elongated modified region. In particular, the intensity of the laser beam on this surface is greater than that on the surface not penetrated by the elongated modified region. In particular, it is possible that the laser beam can emit pulsed energy into the volume of the material.

[0013] The elongated modified region can also penetrate more than one surface. In particular, the elongated modified region can also penetrate two opposing surfaces, resulting in a near-uniform intensity distribution between the two surfaces caused by the laser.

[0014] One or more laser pulses are at least partially absorbed by the material, causing the material to locally heat up or transition to a temporary plasma state. This absorption can be based on linear or nonlinear absorption. The size of the processed area is determined by the beam geometry, particularly by the modified region and beam cross-section of the laser beam. In particular, a modified material portion, which can be created by elongating the modified region in the beam propagation direction, can, for example, reach the entire thickness of the material.

[0015] Such material modification sections, spanning the entire thickness of the material, can be generated, for example, directly using a single laser pulse train containing a single pulse or sub-laser pulse. Therefore, the material modification section is introduced into the material through the localized action of the laser.

[0016] Here, the material modification can typically be a modification of the material's structure, particularly its crystalline and / or amorphous and / or mechanical structure. For example, the material modification introduced into an amorphous material can involve altering the network structure of the material only in that specific region through localized heating. For instance, the bond angles and lengths of the network structure can be changed through modification. The material modification can particularly be a localized density change, which can also include regions without material, and this localized density change can also depend on the material chosen.

[0017] Depending on specific material properties and laser settings, such as pulse energy, pulse duration, and repetition rate, other types of material modification can be achieved. For example, the laser can be configured in one way to provide a laser beam that induces an isotropic refractive index change in the material. However, the laser can also be configured in another way to provide a laser beam that induces a birefringent refractive index change in the material, thereby giving the material localized birefringent properties.

[0018] In particular, at high pulse energies, so-called micro-explosions can occur, in which highly excited, thus gaseous material is forced from the focal region into the surrounding material, creating a less dense region or an empty core surrounded by compressed material. The size of the heated region is determined here by the beam geometry, especially by the modified region of the laser beam and the beam cross-section.

[0019] Unlike the material modification section, the material modification region here includes the entire area where the effects of the laser pulse are measurable, for example, based on tensile and compressive stresses. This is especially true of the region where, spatially viewed from the material modification section, the material transitions back to its initial state as an untreated region of the material.

[0020] Due to the temperature gradient generated by localized pulsed action, stress can occur in the material-modified region during heating and / or cooling, and during the formation of the material-modified section. This stress promotes crack formation. In particular, tensile and compressive stresses can be generated in the material-modified region, which can be radially or orthoradially oriented, for example. Therefore, the material-modified section is preferably accompanied by effective crack formation, i.e., targeted damage to the material.

[0021] Depending on the selected pulse energy, the material modification section can generate slag on the surface of the material. This slag is a measure of the quality of the material modification section, and consequently, also a measure of the material's separability.

[0022] The slag here refers to the accumulation of material on the surface of the material, occurring around the location where the laser pulse for generating the material modification section is introduced. Specifically, "surface" means, relative to the direction of beam propagation, that it can be the upper and lower sides of the material. The slag is a result of heating the material, which emerges from its volume upon the introduction of the laser pulse. However, a portion of the volume may also be lost due to evaporation, etc., so the volume of material emerging from the material does not necessarily correspond precisely to the volume of material deposited in the slag around the material modification section.

[0023] The material modification section is introduced into the material along a desired separating line. Here, the separating line refers to the line along which the material should be separated or a portion of the material should be cut off.

[0024] By introducing material modification portions into the material along the separation line, the material is approximately perforated, such that the separation line defines a type of rated fracture site in the material. However, the perforation line does not typically cause the material to separate spontaneously. Instead, the material modification portions along the separation line, for example, are used for material weakening, such that when a subsequent separation step is applied (e.g., by applying thermal stress and / or by applying mechanical stress, preferably tensile or bending stress and / or by etching with the aid of at least one wet chemical solution), the material separates along the separation line.

[0025] The pulse energy of a single laser pulse or the sum of the pulse energies of sub-laser pulses is in the range of 500 μJ to 50 mJ. This achieves good separability, particularly for thick materials (e.g., with a material thickness greater than 1 mm).

[0026] The separation process may include applying thermal stress and / or mechanical stress, preferably tensile stress or bending stress, and / or etching with the aid of at least one wet chemical solution along the separation line.

[0027] Thermal stress can be achieved, for example, by heating the material along a separation line. For instance, the separation line can be heated using a continuous-wave CO2 laser, causing the material in the modified region to expand differently relative to the untreated or unheated material. Cracks promoted by the modified section thus undergo crack growth, enabling the formation of a continuous, non-hooked separation surface through which portions of the material separate from each other.

[0028] Tensile or bending stress can be generated, for example, by applying a mechanical load to material portions separated by a dividing line. For instance, tensile stress can be applied if at least two forces, pointing in opposite directions and respectively away from the dividing line, act at their respective points of application on material portions separated by the dividing line in a plane of the material. If these forces are oriented non-parallel or antiparallel to each other, this can contribute to the generation of bending stress. Once the tensile or bending stress exceeds the binding force of the material along the dividing line, the material is separated along the dividing line.

[0029] Materials can also be separated by etching using a wet chemical solution, wherein the etching process preferably etches the material at the modified portions, i.e., the targeted weakened portions. By preferably etching the weakened portions of the modified material, the materials separate along a separation line.

[0030] This has the advantage that an ideal separation method can be selected for the corresponding material, resulting in high-quality separation edges.

[0031] The laser pulses can have wavelengths between 0.3 μm and 1.5 μm, and / or the pulse length of a single laser pulse and / or sub-laser pulses can be between 0.01 ps and 50 ps, ​​preferably between 0.3 ps and 15 ps, and / or the average laser power at the laser output can be between 150 W and 15 kW.

[0032] This has the advantage of enabling optimization of methods for the corresponding materials over a large range of parameters. In particular, it increases the probability of finding a laser wavelength that can be used for the material, at which the material is partially transparent.

[0033] The laser beam formed by the laser pulse and the material can be moved relative to each other in a feed manner so as to introduce the plurality of material modification portions into the material along the separation line, wherein the laser beam and the material can preferably be oriented relative to each other at an angle, especially tilted and / or rotated.

[0034] "Being able to move relative to each other" means that the laser beam can translate relative to a material that is in a fixed position, the material can move relative to the laser beam, or both the material and the laser beam can move.

[0035] Therefore, it is particularly possible to place the focal point of the laser beam at different locations on the material to introduce material modification. In addition to translational motion along the X, Y, and Z axes, rotational motion is also particularly possible, especially the rotation of the material about the direction of beam propagation. This can include rotations about all Euler angles.

[0036] This allows the laser beam to be directed along the dividing line.

[0037] In a preferred embodiment, the elongated modified region is longer than the material thickness L in the beam propagation direction. M Longer, especially compared to 1.5×L M Length or ratio 2×(200μm)+L M long.

[0038] By making the elongated modified zone longer than the material thickness, the material modification section can be introduced across the entire material thickness. In particular, large focal position tolerances can be achieved, making it possible to ignore fluctuations in material thickness or material unevenness, especially in the case of large glass substrates with dimensions exceeding one square meter. However, it should be noted that the pulse energy required to introduce the material modification section increases linearly with the length of the focal zone.

[0039] In the modified region, the maximum diameter of the beam cross-section perpendicular to the beam propagation direction can be between 1 μm and 50 μm, preferably between 2 μm and 4 μm.

[0040] This allows for the creation of material modification sections with large lateral extension dimensions, thereby improving the separability of the material.

[0041] The laser beam formed by the laser pulse can be a quasi-non-diffractive beam or a coherent superposition of at least two quasi-non-diffractive beams, at least in the elongated focal region.

[0042] Non-diffractive beams satisfy the Helmholtz equation:

[0043]

[0044] Furthermore, it exhibits clear separability in the form of horizontal and vertical correlations:

[0045] U(x, y, z) = U t (x, y)exp(ik) z z).

[0046] Here, k = ω / c is the wave vector and has its transverse and longitudinal components k 2 =k z 2 +k t 2 And, U t(x, y) is an arbitrary complex-valued function that depends only on the transverse coordinates x and y. The z-correlation in the beam propagation direction of U(x, y, z) results in pure phase modulation, such that the corresponding intensity I of this solution is propagation invariant or non-diffractive.

[0047] I(x, y, z) = |U(x, y, z)| 2 =I(x, y)

[0048] This approach provides different categories of solutions in different coordinate systems, such as Mathieu beams in elliptical cylindrical coordinates or Bessel beams in cylindrical coordinates.

[0049] In experiments, a large number of non-diffracting beams can be realized as good approximations, namely quasi-non-diffracting beams. Contrary to theoretical constructions, they result only in finite power. Equally finite is the propagation invariance of the length L of these quasi-non-diffracting beams.

[0050] Based on the standard ISO 111461-3 for laser beam characterization, the beam diameter is determined by the so-called second-order moment. Here, the power or zeroth-order moment of the laser beam is defined as:

[0051] P = ∫dx dy I(x, y).

[0052] The first-order spatial moment describes the centroid of the intensity distribution and is defined as follows:

[0053]

[0054]

[0055] Based on the above equations, the second-order spatial moment of the lateral intensity distribution can be calculated:

[0056]

[0057]

[0058]

[0059] Using this fully defined second-order spatial moment of the laser beam, the beam diameter, or the size of the focal region along the principal axis, can be determined. The principal axis here refers to the direction in which the minimum and maximum extension scales of the transverse beam profile always align orthogonally to each other, i.e., the intensity distribution perpendicular to the beam propagation direction. Thus, the focal region d of the laser beam is obtained as follows:

[0060]

[0061]

[0062] in,

[0063]

[0064] In particular, through the value d x and d y The long and short principal axes of the lateral focal region are obtained.

[0065] Therefore, the focal region of a Gaussian beam is determined by the second moment of the beam. Specifically, the size d of the transverse focal region is thus obtained. GF x，y And the longitudinal extension scale of the focal region, Rayleigh length z R Rayleigh length z R By z R =π(d GF x，y ) 2 / 4λ is given. It describes the distance along the beam propagation direction from the location of maximum intensity, where the area of ​​the focal region increases by a factor of 2. In the case of a symmetric Gaussian beam, d applies to the focal region. GF 0 = d GF x =d GF y .

[0066] Furthermore, as in the quasi-non-diffractive ray d ND For the lateral focal diameter in case 0, we define the lateral dimension of the local maximum intensity as twice the shortest distance between the maximum intensity and the intensity that drops to 25% from that point.

[0067] The focal region of a quasi-non-diffractive beam is also determined by the second moment. Specifically, the focal region is determined by the size d of the transverse focal region. ND x，y The longitudinal extension scale of the focal region (i.e., the so-called characteristic length L) is generated. The characteristic length L of the quasi-non-diffractive ray is defined by the intensity decreasing from the local intensity maximum to 50% along the beam propagation direction. In particular, the size of the focal region is normalized with respect to the total laser power as shown above, and is therefore independent of the maximum power transmitted through the beam.

[0068] Just when for d ND x，y ≈d GF x，y That is, when the lateral dimensions are similar, and the characteristic length L significantly exceeds the Rayleigh length of the corresponding Gaussian focus, for example, when L > 10z R Only when this occurs can a quasi-non-diffractive beam exist.

[0069] As a subset of quasi-non-diffractive beams, quasi-Bessel beams or quasi-Bessel beams (also referred to here as Bessel beams) are known. Here, the transverse field distribution U near the optical axis... t (x, y) follows a good approximation to an nth-order Bessel function of the first kind. Another subset of this type of beam forms a Bessel-Gaussian beam, which is widely used due to its ease of generation. Illuminating an axis prism using a collimated Gaussian beam in the form of refraction, diffraction, or reflection allows the formation of a Bessel-Gaussian beam. The corresponding transverse field distribution near the optical axis here follows a good approximation to a 0th-order Bessel function of the first kind surrounded by a Gaussian distribution.

[0070] Accordingly, it is advantageous to use quasi-non-diffractive beams, especially Bessel beams, to process materials, as this allows for large focal position tolerances.

[0071] A typical Bessel-Gaussian beam used for processing materials has, for example, a size of d. ND x，y A lateral focusing region of 2.5 μm is possible, but the feature length can be 50 μm. However, for a region with a size of d... GF x，y A Gaussian beam with a lateral focusing region of λ = 2.5 μm has a Rayleigh length in air of only z when λ = 1 μm. R ≈5μm. However, in cases related to material processing, L >> 10z R It is applicable.

[0072] The coherent superposition of quasi-non-diffractive radiation is generated, in particular, by the superposition of at least two quasi-non-diffractive beams. This allows for the generation of additional beam profiles and thus the shape of the material-modified portion.

[0073] The laser beam can have a non-radial symmetrical beam cross section perpendicular to the beam propagation direction, wherein the beam cross section, or the envelope of the beam cross section, is preferably elliptical.

[0074] Here, "non-radial symmetry" means, for example, that the lateral focusing region is stretched in one direction. However, "non-radial symmetric focusing region" can also mean that the focusing region is, for example, cross-shaped, triangular, or N-sided, such as pentagonal. Furthermore, non-radial symmetric focusing regions can include rotationally symmetric and mirror-symmetric beam cross-sections.

[0075] For example, an elliptical focusing region perpendicular to the propagation direction can exist, where the ellipse has a major axis d. x and minor axis d y Therefore, when the ratio d x / d y When greater than 1, especially d x / d yWhen = 1.5, an elliptical focusing region exists. The elliptical focusing region of a specific beam can correspond to an ideal mathematical ellipse. However, the current specific focusing region of a quasi-non-diffracting beam can also have only the aforementioned ratio of the long principal axis to the short principal axis, but with different contours—for example, an approximate mathematical ellipse, a dumbbell shape, or other symmetrical or asymmetrical contours surrounded by a mathematically ideal ellipse.

[0076] In particular, elliptical quasi-diffractive beams can be generated using quasi-diffractive beams. Elliptical quasi-diffractive beams possess special characteristics derived from the analysis of beam intensity. For example, an elliptical quasi-diffractive beam has a principal maximum value that coincides with the center of the beam. The center of the beam is given by the position where the principal axes intersect. In particular, an elliptical quasi-diffractive beam can be generated by the superposition of multiple intensity maximum values, where only the envelope of the participating intensity maximum values ​​is elliptical. Furthermore, each intensity maximum value need not necessarily have an elliptical intensity profile.

[0077] The submaximum closest to the principal maximum, derived from the solution of the Helmholtz equation, has a relative intensity exceeding 17%. Therefore, depending on the laser energy transmitted in the principal maximum, the laser energy guided in the submaximum can also be sufficient for material processing. Furthermore, the closest submaximum always lies on a straight line perpendicular to the long principal axis or parallel to the short principal axis and passing through the direction of the principal maximum.

[0078] In particular, the profile of the beam cross-section has locations with varying radii of curvature. For example, in an elliptical beam cross-section, the radius of curvature is particularly large at the intersection of the shorter semi-axis and the ellipse, while it is particularly small at the intersection of the longer semi-axis and the ellipse. For instance, at points with small radii of curvature, such as peaks and corners, there is a possibility of material stress relaxation, leading to induced crack formation. Controlled crack propagation between modified material sections can improve the separability of the material along the separation line.

[0079] The major axis of a non-radially symmetric beam cross section can be oriented perpendicularly to the beam propagation direction along the separation line and / or along the feed direction.

[0080] Typically, crack formation occurs along the primary direction (Vorzugsrichtung) of a non-radial symmetric beam cross-section. For example, crack propagation occurs primarily along the longer extension scale of the beam cross-section, and this crack propagation is associated with a small radius at the outer contour edge of the beam cross-section profile in the primary direction.

[0081] In particular, targeted crack guidance can be facilitated by rotating a non-radially symmetric beam section and / or material, such that the primary direction of rotating the non-radially symmetric beam section is always oriented along the split line.

[0082] If the feed direction between the laser beam and the material is perpendicular to, for example, the axis along which the preferred crack propagation occurs, then the meeting of cracks in adjacent material-modified sections is impossible. Conversely, if the feed direction is parallel to the preferred crack propagation axis, then it is possible for adjacent material-modified sections to meet and merge. By rotating the beam cross-section and / or the workpiece, even in the case of an arc-shaped separation line, targeted crack guidance along the entire length of the separation line can be ensured. This allows for the separation of material along arbitrarily shaped separation lines.

[0083] The major axis of a non-radially symmetric beam cross section can have an intensity that disappears or does not disappear, and preferably has an interference contrast of less than 0.9 in the case of an intensity that does not disappear.

[0084] Here, the elliptical quasi-non-diffractive beam can maintain a non-vanishing intensity along the long principal axis, especially with an intensity of I. max -I min / (I max +I min With an interference contrast of less than 0.9, the laser beam transmits laser energy throughout the long principal axis.

[0085] I max Here is the maximum beam intensity along the long principal axis, while I min It is the minimum beam intensity. If I min =0, then complete interference occurs along the long principal axis, resulting in an interference contrast of 1. If I min If the value is greater than 0, then only partial interference or no interference will occur along the long principal axis, resulting in an interference contrast of less than 1.

[0086] If, for example, the interference contrast along the long principal axis is less than 0.9, then complete interference does not occur along the long principal axis, but only partial interference. This partial interference will not lead to a minimum intensity I. min The laser intensity at the location is completely lost. This is the case if the quasi-non-diffractive beam is generated using a birefringent element, such as a Quartz Angle Displacer or a Quartz Beam Displacer, or a combination thereof.

[0087] However, elliptical quasi-diffractive beams can also exhibit vanishing intensity and interference contrast of 1 along the long principal axis, preventing the beam from propagating laser energy everywhere along the long principal axis. This is the case, for example, if the quasi-diffractive beam is generated using a modified axial prism.

[0088] A laser beam formed by a laser pulse can be directed onto the material surface at a processing angle, which is preferably not a right angle. Specifically, the processing angle is less than 20° for a material thickness of less than 2 mm and less than 10°, especially less than 5°, for a material thickness of more than 2 mm.

[0089] Because the laser beam strikes the material surface at an angle, it refracts as it enters the material. Correspondingly, the material modification is not perpendicular to the surface but introduced at a refraction angle determined according to Snell's law of refraction. This results in the material not having edges shaped as right angles. For example, sloping edges can be produced, and the material can be combined and, for example, joined along said sloping edges. For example, this allows for lateral joining of the materials.

[0090] In particular, the processing angle of the modified zone in the material that still achieves good separability depends on the material thickness.

[0091] A single laser pulse and / or pulse train can be triggered by a laser system via position-controlled pulse triggering, wherein the position is preferably given by the position of the laser beam formed by the laser pulse on the material.

[0092] Position-controlled pulse triggering can be achieved through a detector that reads the position of the material or feed device, or the position of the feed vector and the laser beam.

[0093] This allows the material-modified portions to be introduced into the material at equal intervals along the dividing line. This particularly helps to avoid overlap of the material-modified portions, which can occur when the laser pulse rate is constant and the feed rate varies. Attached Figure Description

[0094] Further preferred embodiments of the invention will be described in detail below with reference to the accompanying drawings. Herein lies:

[0095] Figure 1A , 1B 1C is a schematic diagram for executing this method;

[0096] Figure 2A , 2B These are microscope images and cross-sections of the material modification section, showing slag.

[0097] Figure 3A , 3B3C, 3D, 3E, and 3F are schematic diagrams of the beam cross-sections of quasi-non-diffractive beams;

[0098] Figure 4A , 4B 4C and 4D are analyses of the beam cross-section of a non-diffractive beam;

[0099] Figure 5 This is a schematic diagram of a combined elliptical quasi-non-diffractive beam.

[0100] Figure 6A , 6B 6C is another schematic diagram used to perform this method;

[0101] Figure 7A , 7B Figures 7C and 7D are schematic diagrams of the elliptical beam cross section and the material modification section and its orientation at the separation line;

[0102] Figure 8A , 8B This is a schematic diagram of the device used to perform the method;

[0103] Figure 9A , 9B This is a schematic diagram for executing the method; and

[0104] Figure 10 These are microscope images of the modified material section produced according to this method. Detailed Implementation

[0105] Preferred embodiments will now be described with reference to the accompanying drawings. Here, identical, similar, or functionally identical elements in different drawings are given the same reference numerals, and repeated descriptions of these elements are omitted in part to avoid redundancy.

[0106] Figure 1 schematically illustrates the separation method described herein for separating at least partially transparent material 1.

[0107] To separate material 1, an ultrashort pulse laser 6 (see example) will be used. Figure 8A A laser pulse is focused onto material 1. The laser pulse propagates as a laser beam 60, which is at least partially absorbed by material 1 in the modified region 602 of the laser beam 60, so as to introduce the material-modified portion 3 into material 1 in this way. Here, the shaded plane shows the plane below the separating line 2, along which it separates material 1. Ideally, this plane corresponds to the subsequent separating surface 20.

[0108] By means of linear and / or nonlinear absorption of laser pulses in material 1, a material modification section 3 can be generated. For example, the general structure or density of material 1 can be altered in this way to form the material modification section 3.

[0109] However, it is also possible that a so-called micro-explosion occurs due to the absorption of the laser pulse, in which case the material 1 suddenly evaporates in the modified region 602 of the laser beam. The highly excited, and thus gaseous, material 1 is forced into the surrounding material 1 under high pressure, causing the material 1 to be compressed at the impact front. As a result, a less dense or empty core (void) is created in the region of modified region 602, which is surrounded by the compressed material. In particular, the micro-explosion can also cause a portion of the material from modified region 602 to permeate outward, depositing on the surface of material 1 and forming slag 300.

[0110] These modifications produce a material modification section 3. A material modification region 30 is formed around the material modification section 3. Within the material modification region 30, as the material is observed further away from the material modification section 3, the material gradually transitions from its state as the material modification section 3 to its original state. This original state can be, for example, the unprocessed state of the material, which exists, for example, at adjacent points in the material 1. However, here, the state of the material 1 before the introduction of the material modification section 3 is also understood as the "original state".

[0111] The laser pulse can have a wavelength between 0.3 μm and 1.5 μm, and / or, the pulse length of the laser pulse can be between 0.01 ps and 50 ps, ​​preferably between 0.3 ps and 15 ps, and / or, the average power of the laser can be between 150 W and 15 kW. Laser energy can be introduced into the material in the form of a single laser pulse, wherein the repetition rate of the single laser pulse is between 1 kHz and 2 MHz. However, laser energy can also be introduced into the material in the form of a pulse train comprising multiple sub-laser pulses, wherein the repetition frequency of the sub-laser pulses in the pulse train is between 2 MHz and 100 GHz, particularly between 12.5 MHz and 100 MHz, and further wherein a pulse train preferably comprises 2 to 20 sub-laser pulses and / or the total pulse energy of the sub-laser pulses in a pulse train is between 500 μJ and 50 mJ.

[0112] For example, the material modification part 3 can be generated using a laser with a wavelength of 1 μm, a pulse duration of 1 ps, and an average power of 1000 W. The laser pulse can be introduced into the material 1 in the form of a single pulse, wherein the repetition rate of the laser is, for example, 100 kHz.

[0113] Localized stresses can be generated in the material modification section 3 and the material modification region 30, and these localized stresses can promote crack formation. For example, material 1 can have a different density, such as a lower density, due to localized heating, and thus compressive stress can be generated in the material modification region 30. However, a higher density may also exist in the heated region, and thus tensile stress can be generated in the material modification region 30. If the tensile stress and / or compressive stress become too large, for example, greater than the tensile or compressive strength of the untreated material, cracks may spontaneously occur.

[0114] As shown in Figure 1, multiple material modification sections 3 are introduced into material 1. A material modification region 30 is formed around each material modification section 3. The material modification sections 3 are placed here along a desired separation line 2. The separation line 2 is an imaginary line along which material 1 should be separated.

[0115] By introducing a material modification portion 3 into the material 1 along the separation line 2, the material 1 is approximately perforated, such that the separation line 2 defines a type of nominal fracture site in the material 1. However, the perforation line does not typically cause the material 1 to break spontaneously. More specifically, the material modification portion 3 along the separation line 2 is used, for example, for targeted material weakening and / or targeted introduction of cracks 32, which cause material weakening along the separation line 2.

[0116] After the material modification part 3 is introduced into the material 1 using the laser beam 6, the material 1 can be physically separated, for example, in a subsequent separation step, by applying a tensile force FZ to the material halves 10 and 12 that are separated from each other by the separation line 2. In particular, it is also possible to separate the material 1 (not shown) by applying bending stress to the material halves 10 and 12.

[0117] exist Figure 1B A similar method is shown, in which material halves are separated in a separation step not by mechanical force, but by applying thermal stress.

[0118] After introducing the material modification section 3, a thermal gradient 620 can be generated on these material modification sections 3. In order to introduce the thermal gradient 620, a continuous wave CO2 laser 62 can be used, for example.

[0119] To generate the thermal gradient 620, the focus of the continuous-wave CO2 laser 62 can be positioned, for example, a few micrometers below the surface 14, allowing the separation of the material 1 to proceed with minimal damage and forming a smooth fracture edge, or separation surface 20. However, the focus can also be positioned at other distances from the surface. Generally, most of the continuous-wave CO2 laser radiation is already absorbed a few nanometers below the surface of the material, making at least no strong dependence on the positioning of the focus of the continuous-wave CO2 laser 62.

[0120] Since absorption occurs primarily near the upper surface 14 of the material, where the temperature is higher than at the lower surface, a thermal gradient T(z) is generated. Because the thermal expansion of material 1 is linear with respect to temperature in a first-order approximation, material 1 expands more dramatically at the upper surface 14 than at the lower surface. This results in material stresses of varying intensities along the Z-axis.

[0121] Different material stresses penetrate the introduced material modification section 3. These stresses relax there, leading to crack formation. Crack formation occurs between adjacent different material modification sections 3. That is, a crack forms, which eventually separates material 1 into two material halves 10 and 12.

[0122] exist Figure 1C Another similar method is shown, in which material halves 10 and 12 are separated in a separation step by means of a wet chemical reaction. For this purpose, material 1 with perforated wires made of material-modified portion 3 is placed in a chemical bath 11. Chemical bath 11 contains a solution capable of ablating and etching material 1. In particular, the etching process occurs in the previously introduced material-modified portion 3, because the material weakening is particularly significant there, and the changes in physical and / or chemical properties at the location of the material-modified portion 3 particularly favorably allow the reaction to proceed. To some extent, the material-modified portion 3 can act as a catalyst for the etching reaction. The reaction occurs in… Figure 1C The diagram is schematically illustrated by the reaction bubbles 110 formed in the chemical bath 11.

[0123] Once material 1 is etched through, it is separated into two material halves 10 and 12. If material 1 is not separated after chemical bath 11 (e.g., because chemical bath 11 only etches away the material modification part 3), then material 1 has been further targeted along the separation line 2, so that material 1 can be separated into material halves 10 and 12, for example, by applying tensile or bending stress.

[0124] exist Figure 2A The image shows a microscope image of the surface of the processed material 1. Circular material modification portions 3 have been introduced into the material 1 at intervals of dM = 5 μm along the dividing line 2. The material modification portions 3 are in the form of porous channels, wherein the material on the outer periphery of the porous channels has been compressed due to micro-explosions during the introduction of the material modification portions 3. Circular slag 300 is generated on the surface of the material 1 around the circular opening of the material modification portions 3, or the porous channels. These slag 300 have an outer diameter dA. The outer diameter of the slag 300 is 3 μm in this case.

[0125] exist Figure 2B The passage shown Figure 2AThe thickness of the cross section. It can be clearly seen that the slag extends beyond the surface of material 1 by 50 nm to 200 nm. The diameter and height of the slag 300 are pre-defined here by the pulse energy and beam cross section of the laser beam. In particular, it can be seen that the material modification section 3 begins at the upper surface 14. This is a result of the elongated modification zone 602 penetrating the surface 14, and thus a common cutting surface exists in particular.

[0126] exist Figure 3A The image shows the intensity profile and beam cross-section 4 of a quasi-non-diffractive laser beam. Specifically, the quasi-non-diffractive beam is a Bessel-Gaussian beam. In beam cross-section 4 in the xy-plane, the Bessel-Gaussian beam exhibits radial symmetry, such that the intensity of the laser beam depends only on the distance from the optical axis. In particular, the transverse beam diameter d... ND x，y The size ranges from 0.25 μm to 10 μm.

[0127] exist Figure 3B The diagram shows the longitudinal beam section 4, i.e., the beam section 4 in the beam propagation direction. Beam section 4 has an elongated focusing region, the size of which is approximately 3 mm. Therefore, the focusing region is significantly larger than beam section 4 in the propagation direction, resulting in an elongated focusing region 600.

[0128] exist Figure 3C In, similar to Figure 3A The diagram illustrates a non-diffractive beam with a non-radial symmetric beam cross-section 4. In particular, the beam cross-section 4 appears to be stretched in the y-direction, approximately elliptical.

[0129] exist Figure 3D The diagram shows the longitudinal focusing region 600 of the Bessel beam, which has an extension dimension of approximately 3 μm. Correspondingly, the Bessel beam also has a focusing region that is elongated in the beam propagation direction.

[0130] exist Figure 3E The diagram illustrates the coherent superposition of different quasi-diffractive beams. By superimposing multiple quasi-diffractive beams, beam profiles that cannot be achieved using a single laser beam can be generated. The illustration of the maximum intensity in the xy-plane illustrates the rounded intensity distribution relative to the total intensity.

[0131] exist Figure 3FThe diagram illustrates the intensity profiles in the z-direction of two laser beams with different laser powers but the same Gaussian-Bessel cross-section. Both beam profiles have the same characteristic length L, defined by the laser intensity decreasing to 50% of its maximum value. However, the material itself has a defined intensity threshold IS, from which it can be processed. The length of the modified region 602 defines a length at which the laser beam intensity exceeds the material's intensity threshold IS. Thus, for high laser power, a large modified region 602 is produced, while for low laser power, a small modified region 602 is produced. The size of the modified region 602 of the laser beam therefore depends on the transmitted laser power.

[0132] Figure 4 shows the difference from Figure 3C Detailed analysis of beam cross section 4 of D. In Figure 4A The transverse intensity distribution of the laser beam 60 is shown, where the principal maximum and secondary maximum values ​​are derived from the solutions to the Helmholtz equation.

[0133] exist Figure 4B The text shows information from... Figure 4A The intensity distribution is represented by so-called isointense lines, where lines are drawn at relative intensities of the laser beam of 25%, 50%, and 75%. It can be clearly seen that the principal maximum 41 of the intensity distribution has an approximately elliptical shape, where the extension scale along the x-axis is significantly larger than the extension scale along the y-axis. In particular, two kidney-shaped secondary maximums 43 with significantly lower relative intensities are adjacent to the principal maximum.

[0134] exist Figure 4C The text shows information from... Figure 4A The intensity distribution is a cross-section along the x-axis passing through the center of the principal maximum value. At the center of the principal maximum value 41, the intensity distribution has its maximum value, where the relative intensity is defined here as 100%. The intensity distribution decreases along the positive and negative x-directions until it reaches the minimum value in the relative intensity distribution at approximately 0.003 mm; however, this minimum value is not 0%. Therefore, laser energy is also transmitted between the principal maximum value 41 and the secondary maximum value 43 of the laser beam 60.

[0135] exist Figure 4D The text shows information from... Figure 4A The intensity distribution is along the y-axis through a cross section at the center of the primary maximum value 41. Here, the maximum intensity value can again be found at the center; however, the intensity decreases significantly faster along the y-direction, resulting in a minimum intensity value at approximately 0.002 mm. Here, the minimum intensity value is precisely zero because complete interference exists for the laser beam 60. In particular, a secondary maximum value 43 can be found again at larger values ​​on the y-axis, which, for example, is higher than 25% of the relative intensity value. And from... Figure 4CThis is not the case in the x-axis section. Therefore, the characteristics of the elliptical beam section 4 differ along different propagation directions.

[0136] In particular, Figure 4C and 4B The diagram shows the measurement of the major semi-axis a, from the center of the principal maximum to the point where the relative intensity decreases to 50%. Similarly, the measurement of the minor semi-axis b, from the center of the principal maximum to the point where the relative intensity decreases to 50%, is also shown. Here, the major and minor semi-axis are perpendicular to each other.

[0137] exist Figure 5 As shown, an elliptical quasi-non-diffractive beam can be generated by the superposition of multiple intensity maxima, wherein, in this case, only the envelopes of the participating intensity maxima are elliptical. In particular, the individual intensity maxima do not necessarily have elliptical intensity profiles.

[0138] In the current case, the beam cross-section has two kidney-shaped sub-maximums 43 in addition to the significant primary maximum 41. Up to 17% of the laser energy of the primary maximum 41 is transmitted in the sub-maximums. If the laser pulse energy is high enough, the laser pulse energy transmitted in the sub-maximums 43 is also sufficient to cause material modification in the material modification section 3. Therefore, the geometry of the modification region 602 can be influenced by selecting the laser pulse energy.

[0139] For example, the laser pulse energy can be selected such that the material modification section can be introduced into the region above the 25% isointense line. Here, the main maximum value 41 and the two secondary maximum values ​​43 respectively form, for example, overlapping material modification regions 30, resulting in an overall elliptical material modification section 3, the major axis of which extends in the y-direction. Therefore, crack formation along the y-direction is expected.

[0140] In particular, based on this, an elliptical material modification section 3 is also produced, the major axis of which is similarly oriented along the y-axis.

[0141] Figure 6A , 6B This demonstrates that the elongated modified region 602 can be introduced into material 1 in different ways. Figure 6A In this process, the elongated modified region 602 has a length greater than the thickness of the material. Specifically, the elongated modified region 602 is greater than 1.5 × L. M Therefore, it is possible to position the modified region 602 such that it penetrates both the upper and lower surfaces 14. This is particularly likely to be the case throughout the entire material thickness L. M The material modification section 3 is introduced. This results in a smaller separation force required during the subsequent separation process and thus a lower roughness of the separation surface 20.

[0142] exist Figure 6B As shown, material 1 can be composed of different layers 1', 1"', and 1"'. Each layer has its own material thickness, where the total material thickness L... M It is the sum of the thicknesses of all layers. In particular, each layer can also have its own refractive index, but each layer is partially transparent to the wavelength of the laser. Here, the elongated modified region 602 is also greater than the total thickness of the material.

[0143] exist Figure 6C As shown, the elongated modified region 602 can also be introduced into the material 1 such that only one material surface 14 is penetrated by the elongated modified region 602. In the present case, the upper surface 14 is penetrated. However, it is also possible to introduce other types of material modified parts 3 into the material 1 by means of the laser beam 6.

[0144] exist Figure 7A The diagram shows an elliptical material modification section 3 in material 1. The material modification section 3 is introduced into material 1 by a laser beam 60 from laser 6. Here, the shape of the material modification section 3 is predetermined by the beam cross-section 4 of the laser beam 60, especially its modification region 602. A material modification region 30 is formed around the material modification section 3, in which the laser beam 60 directly acts on material 1 during the laser pulse duration. This material modification region corresponds in shape to the introduced material modification section 3, or the beam cross-section 4 of the laser beam 6.

[0145] Correspondingly, material stress can occur both in the material modification section 3 itself and in the material modification region 30, and this material stress promotes crack formation. For example, in the case of an elliptical material modification section 3, crack formation can be promoted at the following location on the ellipse: where the radius of curvature of the boundary line is particularly small. This small radius of curvature ensures that the stress introduced into the glass 1 by the material modification section 3 can decrease particularly rapidly in many different directions. Therefore, material stress relaxation is achieved with a higher probability at this location compared to locations where material stress can relax in only a few directions. Consequently, the portion of the material modification section 3 with a small radius of curvature in the material 1 is particularly unstable.

[0146] Here, the formation of crack 32 preferably occurs in the direction of the long axis of the elliptical material modified portion 3. Therefore, it is possible to control crack propagation by the orientation of the material modified portion 3. Therefore, it is particularly possible to control crack propagation from one material modified portion 3 to another.

[0147] exist Figure 7BIn this diagram, multiple material-modified sections 3 have been introduced into material 1. The material-modified sections 3 are again elliptical. Therefore, cracks 32 are particularly preferably formed along the major axis of the ellipse at the location of the minimum radius of curvature of the ellipse. The material-modified sections 3 are placed so close to each other in this diagram that the corresponding cracks of adjacent material-modified sections overlap. It is thus possible for cracks to fuse and form a common crack between two adjacent material-modified sections. In particular, this state can be achieved by crack growth, for example, by applying tensile force. In this way, for example, cracks 32 can be introduced into material 1 along any dividing line 2.

[0148] exist Figure 7C As shown, the long axes of both the material modification section 3 and the slag 300 are oriented along the dividing line 2. Since the long axis of the material modification section 3 is oriented along the dividing line 2, this also means that when the material modification section 3 is introduced, the long axis of the beam cross-section of the laser beam 60 is already oriented along the dividing line 2.

[0149] exist Figure 7D Correspondingly, it is shown that the long axis of the beam section 4 is oriented parallel to the feed velocity V, such that the long axis is always oriented parallel to the separation line 2.

[0150] exist Figure 8A The diagram illustrates a structure for performing this method. A laser beam 60 from an ultrashort pulse laser 6 is directed onto material 1 via a beam-shaping optics 9 and an optional reflector 70. Here, material 1 is arranged on a support surface of a feeding device, wherein the support surface strongly scatters laser energy that the material does not absorb, and preferably laser energy that the material neither reflects nor absorbs, back into the material.

[0151] In particular, the laser beam 60 can be coupled into the beam-shaping optical system 9 via a free-space path using a lens and mirror system. However, the laser can also be coupled into the beam-shaping optical system via a hollow fiber 65 having coupling and coupling-out optical systems, as in... Figure 8B As shown in the diagram.

[0152] The beam-forming fixture 9 can be, for example, a diffractive optical element or an axonometric prism that generates a non-diffractive laser beam 60 from a Gaussian-shaped laser beam 60. In the current example, the laser beam 60 is deflected by a mirror 70 toward the material 1 and focused onto or into the material 1 by a focusing fixture 72. In the material 1, the laser beam 60 causes a material modification portion 3. The beam-forming fixture 9 is particularly rotatable, such that, for example, the primary direction or axis of symmetry of the laser beam can be adapted to the feed trajectory.

[0153] Here, the feeding device 8 enables the material 1 to move under the laser beam 60 with a feed V, such that the laser beam 60 is introduced into the material modification section 3 along the desired separation line 2. In particular, in the figure shown, the feeding device 8 includes a first part 80 that enables the material 1 to move along an axis. In particular, the feeding device can also have a second part 82, which is configured to rotate the laser beam 60 about the z-axis, or about the beam propagation direction, such that the major axis of the beam section perpendicular to the beam propagation direction is always tangent to the desired separation line 2, thereby causing crack propagation along the separation line 2.

[0154] If the orientation of the major axis of the beam cross-section can be determined by both the beam-forming optics 9 and the second part 82 of the feeding device, it is also possible to use either the orientation possibilities of the beam-forming optics 9 or the orientation possibilities of the second part 82 of the feeding device. However, the two possibilities can also be used in a complementary manner.

[0155] For this purpose, the feeding device 8 can be connected to the control device 5, wherein the control device 5 translates user commands from the user of the device into control commands for the feeding device 8. In particular, predefined cutting patterns can be stored in the memory of the control device 5, and these processes can be automatically controlled by the control device 5.

[0156] The control device 5 can also be connected to the laser 6. Here, the control device 5 can adjust the laser pulse energy of the laser 6 or request or trigger the emission of laser pulses or laser pulse trains. The control device 5 can also be connected to all the aforementioned components and thus coordinate material processing.

[0157] In particular, this enables position-controlled pulse triggering, whereby, for example, the shaft encoder of the feed device 8 is read and the shaft encoder signal can be interpreted by the control device as a position indication. Therefore, it is possible, for example, that if the internal summing unit, which adds up the distance traveled, reaches a value and then resets to 0, the control device 5 automatically triggers the emission of a laser pulse or laser pulse train. Thus, for example, laser pulses or laser pulse trains can be automatically emitted towards the material 1 at regular intervals.

[0158] By also controlling the feed speed and feed direction in the control device 5, and thus the separation line 2, it is possible to automatically emit laser pulses or laser pulse trains.

[0159] The control device 5 can also calculate the spacing dM or the position where a laser pulse train or laser pulse should be emitted based on the measured speed and the fundamental frequency provided by the laser 6.

[0160] By emitting laser pulses or pulse trains in a position-controlled manner, the tedious programming of separate processes is eliminated. Furthermore, it is possible to simply implement processes with freely selectable speeds.

[0161] Figure 9 illustrates how these sub-laser beams, positioned behind the beam-forming fixture 9, introduce a quasi-non-diffractive beam into material 1. Figure 9A In this process, the sub-laser beams are symmetrically incident on the surface 14 of material 1 with respect to the surface normal 140. Therefore, the laser beams are generally incident on the surface 14 at right angles. Correspondingly, the elongated modified region 602 is oriented parallel to the surface normal 140, i.e., it does not undergo any refraction. Of course, the sub-laser beams do indeed incident on the material surface 14 at an angle, such that these sub-laser beams are refracted according to Snell's law of refraction. The length of the elongated modified region 602 in material 1 can be determined by the refractive index of material 1 and the incident angle of the sub-laser beams. Along the elongated modified region 602, the material modification portion 3 can be introduced into material 1.

[0162] exist Figure 9B The diagram illustrates a scenario where the sub-laser beam is introduced into material 1 not symmetrically with respect to the surface normal 140, but at an angle θ. This results in an elongated modified region 602 formed in the material, which does not extend parallel to the surface normal 140 but is refracted at an angle θ'. This makes it possible to introduce a material modified portion 3 that is not parallel to the direction of the surface normal 140 into material 1. Therefore, material 1 can be separated, for example, at an angle θ'.

[0163] exist Figure 10 The image shows a microscopic photograph of the material modification sections 3, which have been introduced into the material 1 for different pulse energies. For this purpose, elongated modification regions 602 penetrate the surface 14 of the material 1. Correspondingly, the material modification sections 3 shown begin at the surface 14. At a pulse energy of 700 μJ, a first elongated modification region 602 is generated, which is longer than the material thickness L. M Short. Correspondingly, the material modification section terminates before reaching the lower surface. To expand the elongated modification zone 602, the pulse energy is increased, as mentioned above, especially in... Figure 3F As shown in the figure. For example, at a pulse energy of 1400 μJ, a stretched modified region 602 twice the length at 700 μJ has been produced. However, in principle, a linear relationship between the length of the stretched modified region and the pulse energy is not necessary. However, it is possible that the relationship between the length of the stretched modified region and the pulse energy can be approximated piecewise by a linear relationship. Correspondingly, the resulting stretched modified region 602 is greater than 1.5 × L. MThis results in the formation of a material modification portion 3 extending between the two opposing material surfaces in material 1.

[0164] Where applicable, all individual features presented in the embodiments may be combined and / or interchanged with each other without departing from the scope of the invention.

[0165] List of reference numerals

[0166] 1. Materials

[0167] 10 First Material Half

[0168] 12 Second Material Half

[0169] 14 Surface

[0170] 140 Surface Normal

[0171] 2. Separate lines

[0172] 20 pieces

[0173] 3. Materials Modification Department

[0174] 30 Material Modification Area

[0175] 300 slag

[0176] 32 Cracks

[0177] 4. Beam cross section

[0178] 41 Main Rank

[0179] 43rd order

[0180] 5. Control equipment

[0181] 6. Laser

[0182] 60 laser beams

[0183] 600 Focus Area

[0184] 602 Modified Zone

[0185] 62 Continuous Wave CO2 Laser

[0186] 620 temperature gradient

[0187] 65 Hollow-core optical fiber

[0188] 7 Focusing Unit

[0189] 70 reflector

[0190] 72 Focusing Optical Tool

[0191] 8. Feeding equipment

[0192] The first part of the 80 feed device

[0193] 800 bearing surface

[0194] 82 The second part of the feed device

[0195] 9 Beam shaping optical tools

[0196] 11 chemical bath

[0197] 110 Reaction bubbles

[0198] L M Material thickness

[0199] dA Outer diameter of the slag

[0200] dM Spacing of the material modification section

[0201] FZ Tension

Claims

1. A method for separating at least partially transparent materials (1), wherein, An ultrashort laser pulse, in the form of a single laser pulse and / or a pulse train comprising multiple sub-laser pulses, is focused into the material (1), such that a modified region (602) generated and elongated in the beam propagation direction enters the material (1) and penetrates at least one surface (14) of the material, thereby introducing a material modification portion (3) into the material (1). In this process, multiple material modification sections (3) are introduced into the material (1) along the separation line (2). Furthermore, the material (1) is then separated along the separating line (2) using a separating step. Its features are, The pulse energy of the single laser pulse or the sum of the pulse energies of the sub-laser pulses is in the range of 500µJ to 50mJ, and the elongated modified region (602) is longer than the material thickness L in the beam propagation direction. M Longer than 1.5×L M Length or ratio 2×(200µm) + L M The laser beam is focused into the material such that the laser beam has an elongated focusing region in the beam propagation direction, wherein the laser beam (60) is a quasi-non-diffractive beam at least in the elongated focusing region (600), the laser beam (60) having a non-radially symmetrical beam cross section (4) perpendicular to the beam propagation direction, wherein the beam cross section (4), or the envelope of the beam cross section (4), is elliptical, and the major axis of the elliptical quasi-non-diffractive beam has a non-vanishing interference contrast of less than 0.

9.

2. The method according to claim 1, characterized in that, The separation step includes applying thermal stress along the separation line (2) and / or applying mechanical stress and / or etching with the aid of at least one wet chemical solution.

3. The method according to claim 1 or 2, characterized in that, The material (1) is a glass substrate and / or a stacked substrate system and / or a silicon wafer.

4. The method according to claim 1 or 2, characterized in that, - The laser pulse has a wavelength between 0.3µm and 1.5µm, and / or - The pulse length of the single laser pulse and / or the pulse length of the sub-laser pulse is from 0.01 ps to 50 ps, ​​and / or - The average power of the laser at the laser output is between 150W and 15kW.

5. The method according to claim 1 or 2, characterized in that, The laser beam (60) formed by the laser pulse and the material (1) are feedable relative to each other so as to introduce the plurality of material modification parts (3) into the material (1) along the separation line (2), wherein the laser beam (60) and the material (1) are oriented relative to each other.

6. The method according to claim 1 or 2, characterized in that, In the modified region (602), the maximum diameter of the beam cross section (4) perpendicular to the beam propagation direction is between 1µm and 50µm.

7. The method according to claim 2, characterized in that, The mechanical stress is either tensile stress or bending stress.

8. The method according to claim 3, characterized in that, The thickness of the material is greater than 1 mm.

9. The method according to claim 1 or 2, characterized in that, The major axis of the non-radially symmetrical beam section (4) perpendicular to the beam propagation direction is oriented along the separation line (2) and / or along the feed direction.

10. The method according to claim 4, characterized in that, The pulse length of the single laser pulse and / or the pulse length of the sub-laser pulse is from 0.3 ps to 15 ps.

11. The method according to claim 1 or 2, characterized in that, A laser beam (60) formed by the laser pulse is directed onto the material surface (14) at a processing angle, wherein the processing angle is less than 20° for a material thickness of less than 2 mm and less than 10° for a material thickness of greater than 2 mm.

12. The method according to claim 1 or 2, characterized in that, The single laser pulse and / or pulse train are triggered by position-controlled pulse triggering of the laser system (6).

13. The method according to claim 5, characterized in that, The laser beam (60) and the material (1) are tiltable and / or rotatable relative to each other.

14. The method according to claim 5, characterized in that, The laser beam (60) and the material (1) are oriented relative to each other at an angle.

15. The method according to claim 6, characterized in that, In the modified region (602), the maximum diameter of the beam cross section (4) perpendicular to the beam propagation direction is between 2µm and 4µm.

16. The method according to claim 11, characterized in that, The machining angle is not a right angle.

17. The method according to claim 11, characterized in that, The machining angle is less than 5° for materials with a thickness greater than 2mm.

18. The method according to claim 12, characterized in that, The position is given by the position of the laser beam (60) formed by the laser pulse on the material (1).

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