Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B33/00—Severing cooled glass
  • C03B33/09—Severing cooled glass by thermal shock
  • C03B33/091—Severing cooled glass by thermal shock using at least one focussed radiation beam, e.g. laser beam
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/0006—Working by laser beam, e.g. welding, cutting or boring taking account of the properties of the material involved
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
  • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
  • B23K26/0604—Shaping the laser beam, e.g. by masks or multi-focusing by a combination of beams
  • B23K26/0613—Shaping the laser beam, e.g. by masks or multi-focusing by a combination of beams having a common axis
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
  • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
  • B23K26/062—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam
  • B23K26/0622—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam by shaping pulses
  • B23K26/0624—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam by shaping pulses using ultrashort pulses, i.e. pulses of 1ns or less
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
  • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
  • B23K26/064—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
  • B23K26/0648—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms comprising lenses
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
  • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
  • B23K26/067—Dividing the beam into multiple beams, e.g. multifocusing
  • B23K26/0676—Dividing the beam into multiple beams, e.g. multifocusing into dependently operating sub-beams, e.g. an array of spots with fixed spatial relationship or for performing simultaneously identical operations
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
  • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
  • B23K26/073—Shaping the laser spot
  • B23K26/0738—Shaping the laser spot into a linear shape
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/36—Removing material
  • B23K26/40—Removing material taking account of the properties of the material involved
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/50—Working by transmitting the laser beam through or within the workpiece
  • B23K26/53—Working by transmitting the laser beam through or within the workpiece for modifying or reforming the material inside the workpiece, e.g. for producing break initiation cracks
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/50—Working by transmitting the laser beam through or within the workpiece
  • B23K26/55—Working by transmitting the laser beam through or within the workpiece for creating voids inside the workpiece, e.g. for forming flow passages or flow patterns
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B33/00—Severing cooled glass
  • C03B33/02—Cutting or splitting sheet glass or ribbons; Apparatus or machines therefor
  • C03B33/0222—Scoring using a focussed radiation beam, e.g. laser
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K2103/00—Materials to be soldered, welded or cut
  • B23K2103/50—Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P40/00—Technologies relating to the processing of minerals
  • Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping
  • Y02P40/57—Improving the yield, e-g- reduction of reject rates
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24355—Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24355—Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
  • Y10T428/24471—Crackled, crazed or slit

Definitions

• the present invention relates to a method for laser-based processing of preferably flat substrates according to the preamble of
• the method and the device have in particular the goal of separating flat substrates such as semiconductor wafers, glass elements, ... (in particular from brittle materials) into several parts (separating the wafers or glass elements).
• generally pulsed lasers having a wavelength for which the materials are substantially transparent are used.
• laser methods for cutting through brittle materials which function via a targeted, laser-induced cracking.
• a trace is first heated strongly on the surface by the laser and immediately thereafter this trace is cooled down so rapidly (eg by means of a water jet) that the thermal stresses achieved thereby lead to cracking, which can be propagated through the thickness of the material (mechanical stress) to sever the material.
• a laser is used at the wavelength of which the material is substantially transparent so that a focal point can be created inside the material.
• the intensity of the laser must be so high that internal damage takes place at this inner focal point in the material of the irradiated substrate.
• the method according to the invention generates for each laser pulse a laser focal line (as opposed to a focal point) by means of a suitable laser optics (hereinafter also referred to as optical arrangement).
• the focal line determines the zone of interaction between laser and material of the substrate. If the focal line falls into the material to be separated, so
• the laser parameters may be selected to interact with the material that produces a crack zone along the focal line in accordance with the invention.
• Important laser parameters here are the wavelength of the laser, the pulse duration of the laser, the pulse energy of the laser and possibly also the polarization of the laser.
• the pulse duration of the laser is preferably chosen such that within the
• the pulse energy of the laser is preferably selected such that the intensity in the interaction zone, ie in the focal line, produces an induced absorption which leads to local heating of the material along the focal line, which in turn leads to crack formation along the focal line of the thermal stress introduced into the material.
• the polarization of the laser influences both the surface interaction (reflectivity) and the type of interaction within the material in the induced absorption.
• the induced absorption can take place via induced, free charge carriers (typically electrons), either after thermal excitation, or via multiphoton absorption and internal photoionization, or via direct field ionization (field strength of the light breaks down electron binding directly).
• the manner of generating the charge carriers may be e.g. be judged by the so-called Keldysh parameter (reference), but this does not matter for the application of the method according to the invention.
• the polarization should be favorably selected by the user for the separation of the respective material via suitable optics (phase plates), eg simply in a heuristic manner.
• suitable optics phase plates
• the polarization and the orientation of the polarization vector can be chosen so that form as desired only one focal line and not two of them (ordinary and extraordinary rays). In optically isotropic materials, this does not matter.
• the intensity over the pulse duration, the pulse energy and the focal line diameter should be chosen so that no ablation or melting takes place, but only a cracking in the structure of the solid. This requirement is most easily met for typical materials such as glass or transparent crystals with pulsed lasers in the sub-nanosecond range, in particular with pulse durations of e.g. between 10 and 100 ps. See also Figure 1: Over scale lengths of about one micron (0.5 to 5.0 microns, see center) acts for poor heat conductors such as glasses, the heat conduction to the sub-microsecond range (see the area between the two lines), while for good heat conductors how crystals and semiconductors heat conduction is effective from nanoseconds.
• the essential process for the present invention extending to the substrate level cracking in the material is mechanical stress that exceeds the structural strength of the material (compressive strength in MPa).
• the mechanical stress is achieved here by rapid, inhomogeneous heating (thermally induced stress) by the laser energy.
• the cracking according to the invention starts, assuming a corresponding positioning of the substrate realtivly to the focal line (see below) naturally at the surface of the substrate, since there the deformation is highest. This is because there is no material in the half space above the surface which can absorb forces.
• This argument also applies to materials with hardened or tempered surfaces, as long as the thickness of the hardened or tempered layer is large compared to the diameter of the abruptly heated surface. material along the focal line. (See also FIG. 2 described below.)
• the type of interaction can be adjusted via the fluence (energy density in joules per cm 2 ) and the laser pulse duration with selected focal line diameter that 1) preferably no melt on the surface or in volume and 2) preferably no ablation with particle formation at the Surface takes place.
• fluence energy density in joules per cm 2
• laser pulse duration with selected focal line diameter that 1) preferably no melt on the surface or in volume and 2) preferably no ablation with particle formation at the Surface takes place.
• induced absorption are known: a) In semiconductors and insulators with a low band gap, for example, a low residual absorption (by traces of impurities in the material or by at the temperature before laser processing already thermally excited charge carriers) rapid warming within a first fraction of the laser pulse duration lead to thermal excitation of other charge carriers, which in turn leads to increased absorption and, as a result, to an avalanche-like increase in the laser absorption in the focal line.
• the interaction with the material according to the invention produces a single, continuous (in the direction perpendicular to the substrate surface) crack zone in the material along a focal line per laser pulse.
• a sequence of these crack zones per laser pulse is set so close to each other along the desired separation line that a lateral connection of the cracks to a desired crack surface / contour in the material results.
• the laser is pulsed at a certain repetition rate.
• the spot size and spacing are chosen such that a desired, directional crack pattern is applied to the surface along the line of laser spots. education.
• the distance of the individual crack zones along the desired separation surface results from the movement of the focal line relative to the material within the time span from laser pulse to laser pulse. See also Fig. 9 described below.
• either the pulsed laser light with a parallel to the substrate plane (and possibly also perpendicular thereto) movable optical arrangement can be moved over the stationary material, or the material itself with a movable cinnamon at the stationary optical Arrangement moved over so that the desired Trennline is formed.
• the orientation of the focal line to the surface of the material may be either fixed or via a rotatable optical arrangement (hereinafter also referred to simply as optics) and / or a rotatable beam path of the laser along the desired
• the focal line for forming the desired separation line in up to five separate movable axes are guided through the material: two spatial axes (x, y), which set the puncture point of the focal line in the material, two angular axes (theta, phi), the Determine orientation of the focal line from the piercing point into the material, and another spatial axis ( ⁇ ', not necessarily orthogonal to x, y), which determines how deep the focal line extends from the piercing point at the surface into the material.
• ⁇ ' not necessarily orthogonal to x, y
• the orientation of the angles in theta and phi can only be done as far as the refraction of the laser light in the material allows (smaller than the angle of total reflection in the material), and the penetration depth of the laser focal line is limited by the available laser pulse energy and the laser optics chosen accordingly, which only forms a focal line length which can generate the crack zone according to the invention with the available laser pulse energy.
• One possible embodiment for moving the focal lines in all five axes may be, for example, moving the material on a driven axis table in the coordinates x, y, while the focal line via a Galvo scanner and a non-telecentric F-theta lens in the Field of the lens is moved relative to the lens center in the coordinates x ', y' and tilted by the angle theta, phi.
• the coordinates x and x 'and y and y' can be calculated so that the focal line is directed to the desired impact point of the material surface.
• Galvoscanner and F-theta lens are further attached to a z-axis orthogonal to the x, y plane of the axis table, which determines the position of the focal line perpendicular to the material (depth of the focal line in the material).
• the separation of the material along the generated crack surface / contour takes place either by internal stress of the material, or by introduced forces, e.g. mechanical (tensile) or thermal (non-uniform heating / cooling). Since, according to the invention, no material is ablated, there is generally no continuous gap in the material at first, but only a highly disrupted fracture surface (micro-cracks), which interlocks with one another and may u.U. still connected by bridges. As a result of the subsequently introduced forces, the remaining bridges are separated via lateral (parallel to the substrate plane) crack growth and the toothing is overcome so that the material can be separated along the separating surface.
• mechanical tensile
• thermal non-uniform heating / cooling
• Claim 1 describes the essential features of a method according to the invention
• claim 11 describes the essential components of a trained for performing the method according to the invention device.
• the substrate is separated or singled out into the several parts by the crack formation according to the invention (induced absorption along the focal line extending perpendicular to the substrate plane) in the substrate plane.
• the crack formation according to the invention thus takes place perpendicular to the substrate plane into the substrate or into the interior of the substrate (longitudinal cracking).
• a multiplicity of individual laser beam focal lines must as a rule be introduced into the substrate along a line on the substrate surface, so that the individual parts of the substrate can be separated from one another.
• the substrate can be moved parallel to the substrate plane relative to the laser beam or to the optical arrangement or, conversely, the optical arrangement can be moved parallel to the substrate plane relative to the stationary substrate.
• the features of at least one of the dependent method or apparatus claims are additionally realized.
• the features of several dependent claims can be realized in any combination.
• the extended portion of induced absorption in the interior of the substrate extends from (or beyond) a surface of the substrate to a defined depth of the substrate.
• the extended portion of induced absorption may include the entire depth of the substrate from one surface to the other. It is also possible to generate elongated sections of the induced absorption only inside the substrate (without also including the surfaces of the substrate).
• the layer thickness d is in each case measured perpendicular to the two opposite substrate surfaces of the planar substrate (even with oblique irradiation of the laser radiation at an angle ß> 0 ° to the normal to the substrate surface, ie at oblique incidence).
• the induced absorption is advantageously produced according to claim 4. This is done by means of the setting of the already described, hereinafter explained in the context of examples and also in the dependent claims 5 to 7 mentioned laser parameters, the parameters of the optical arrangement and the geometric parameters of the arrangement of the individual elements of the device according to the invention. Basically, any combination of features of parameters, as they are called in the claims 5-7 possible.
• ⁇ « ⁇ 2 / means that ⁇ is less than 1%, preferably less than 1% o, of ⁇ 2 / ⁇ .
• the pulse duration! at 10 ps (or even below), between 10 and 100 ps or even over 100 ps.
• an Er: YAG laser having a wavelength between 1.5 and 1.8 ⁇ m is preferably used.
• a laser having a wavelength which is selected such that the photon energy is smaller than the band gap of the semiconductor is preferably used for semiconductor substrates.
• the additional process steps which may still be necessary for the final separation or for separating the substrate into its several parts are described in the dependent claims 9 and 10.
• either the substrate is relative to the optical arrangement (including laser) or the optical arrangement (including laser) moves relative to the substrate.
• the crack formation mentioned in claim 10 is (as opposed to the inventively essential, induced crack formation) to be understood as a transverse crack, ie as a lateral crack formation in a direction lying in the plane of the substrate (corresponding to the course of the line along which the substrate should be separated).
• An article of glass with one or more surface (s) (in particular: one or more surface ⁇ )). Along at least one of the one or more surface (s) is / are in each case a plurality of material modifications, each of the material modifications has a length in the range between 0.1 mm and 100 mm and an average diameter in the range between 0.5 ⁇ and 5 ⁇ has ,
• an article of glass with one or more surface (s) (in particular: one or more surface ⁇ )). Along each of at least one of the one or more surfaces is / are a plurality of material modifications.
• the present invention has a number of significant advantages over those known in the art on.
• the cut formation can be set either perpendicular (seen to the substrate plane) or at a desired angle ß by the user relative to the substrate normal. According to the invention, no very high average laser power is necessary, nevertheless comparatively high separation speeds can be achieved. It is essential that the invention generates one laser beam focal line per laser pulse (or per burst pulse) (and not only a focal point that is not or only very locally extended). For this purpose, the laser optics shown below are used in detail. The focal line thus determines the
• the laser parameters can be selected such that an interaction with the material takes place, which according to the invention has a crack zone along the entire focal line (or along the entire extended section) the laser beam focal line falling into the substrate) is generated.
• Selectable laser parameters are, for example, the wavelength of the laser, the pulse duration of the laser, the pulse energy of the laser and possibly also the polarization of the laser.
• the present invention has the particular advantage that a significantly higher Aspect ratio of the cut can be achieved. Problems of such known methods, which occur due to less directed cracking, especially with thicker substrates, are thus avoided.
• the processing speed is more punctiform, in particular in the case of thicker substrates (in which, at a defined position in the substrate plane, a multiple setting is more punctiform
• Burning line is adjusted relative to the substrate so that the inventive method from the surface of the substrate into the interior of the substrate for the inventive extended induced absorption and cracking ensures). In this case, therefore, the first (intentional) damage takes place directly on the surface and continues in a defined manner along the cracking zone by induced absorption into the substrate depth.
• different materials in particular glass panes, sapphire disks, semiconductor wafers
• Both individual layers of corresponding materials and layer composites can be processed.
• the focal line can be positioned and aligned so that only a defined layer is separated in the interior of a layer stack.
• Different sandwich constructions of layer stacks can be processed: glass-air-glass composites, glass-film-glass composites, glass-glass composites.
• the selective cutting of individual layers is also possible within a stack as well as the cutting of intermediate layers (for example, films or adhesive film).
• Coated materials eg AR coated, TCO coated stratified
• unidirectionally non-transparently printed substrates are processed and separated according to the invention.
• cutting is possible virtually without a cutting gap: only a material damage is generated, which is generally in the range between 1 and 10 ⁇ m in extent. In particular, no loss of cut in relation to material or surface is generated. This is particularly advantageous when cutting semiconductor wafers since kerf losses would reduce the active area of the wafer.
• the inventive method of focal line cutting thus results in an increased area yield.
• the lack of material loss is also advantageous, in particular, when cutting gemstones (for example diamond): If the field of application of the present invention is preferably the cutting or cutting of flat substrates, non-planar substrates or workpieces can also be processed according to the invention.
• the method according to the invention can also be used in in-line operation of production processes. This is particularly advantageous in production processes that take place in a roll-to-roll process.
• single-pulse lasers can be used as well as lasers that generate burst pulses.
• the use of lasers in continuous wave mode is conceivable.
• the focal line is only partially inserted into the interior of the substrate material, so that it begins at the surface and stops in front of the taped film (on the back surface of the substrate remote from the laser): For example, about 10% of the material are not separated. The film thus remains intact because the focal line in front of the film "stops."
• the semiconductor wafer can then be separated by mechanical forces (or thermal forces, see example below with the C0 2 laser) over the remaining 10%.
• Cutting coated materials examples include Bragg reflectors (DBR) or metal-coated sapphire wafers. Processed silicon wafers to which the active metal or metal oxide layers have already been applied can also be cut according to the invention. Further examples are the processing of ITO or of AlZnO, with which substrates are coated, which are needed, for example, for the production of touch screens or smart windows. Because of the very extensive focal line (compared to its diameter), part of the focal line will remove the metal layer (or other layer), the remainder of the focal line will penetrate and cut into the transparent material. This has the particular advantage that correspondingly coated substrates can be separated in a one-step process, ie in a process in which the coating and substrate are separated in one process.
• Particularly advantageous according to the invention is the cutting of very thin materials (for example substrates made of glass with thicknesses of less than 300 ⁇ , less than 100 ⁇ or even less than 50 ⁇ ). These can only be processed with great difficulty using conventional mechanical methods. However, in the mechanical processes, edges, damage, cracks, spalling, which can either render the substrates unusable or involve costly reworking necessary. On the other hand, in thin materials, cutting in accordance with the present invention offers the advantages of avoiding edge damage and cracks, so that no post-processing is necessary, of very high cutting speeds (> 1 m / s) from a high yield and performing the process in one Step.
• the method according to the invention can also be used in particular in the production of thin film glasses which are produced with a continuous glass drawing process in order to trim the film edges.
• Figure 1 shows the relationship between the heat diffusion constant a, the linear expansion in the material (scale length, denoted here by d) and a period of time ⁇ such as the laser pulse duration for different materials.
• FIG. 2 shows the principle of the inventive positioning of a focal line, that is to say the processing of a material which is transparent to the laser wavelength on the basis of the induced absorption along the focal line.
• FIG. 3 a shows a first optical arrangement which can be used according to the invention.
• Figure 3b different ways of processing the substrate by different positioning of the laser beam focal line relative to the substrate.
• FIG. 4 shows a second optical arrangement which can be used according to the invention.
• FIGS. 5a and 5b show a third optical arrangement which can be used according to the invention.
• FIG. 6 shows a fourth optical arrangement which can be used according to the invention.
• Figure 7 shows a structure according to the invention for performing the method using the example of the first usable optical arrangement of Figure 3a (instead of this optical arrangement, the other shown opti see arrangements of Figures 4, 5 and 6 can be used in the context of the arrangement shown by the 7 is replaced by one of these arrangements).
• FIG. 8 shows the generation according to the invention of a focal line in detail.
• FIG. 9 shows a microscope image of the surface (top view of the substrate plane) of a glass pane processed according to the invention.
• FIG. 2 outlines the basic procedure of the machining method according to the invention.
• a laser beam 2 emitted from the laser 3, not shown here (see Fig. 7), which is designated at the beam input side of the optical device 6 by the reference numeral 2a, is irradiated to the optical device 6 of the invention (see the following embodiments thereto).
• the optical arrangement 6 forms an extended laser beam focal line 2b on the output side of the irradiated laser beam over a defined expansion region along the beam direction (length I of the focal line). At least in sections, overlapping the laser beam focal line 2b of the laser radiation 2, the substrate 1 to be processed, here flat, is positioned in the beam path after the optical arrangement.
• the reference numeral 1a denotes the surface of the planar substrate facing the optical arrangement 6 or the laser
• the reference symbol 1b the back surface lb of the substrate 1 which is usually parallel
• the substrate thickness (perpendicular to the surfaces 1a and 1b, that is to say Substrate level measured) is denoted by the reference numeral d.
• FIG. 2 a shows, here the substrate 1 is oriented perpendicular to the beam longitudinal axis and thus to the focal line 2 b generated in the space by the optical arrangement 6 behind the latter (the substrate is perpendicular to the plane of the drawing) and positioned relative to the focal line 2 b seen along the beam direction. that the focal line 2 b starts in the beam direction before the surface la of the substrate and in front of the surface 1 b of the substrate, ie still within the substrate, ends.
• the extended laser beam focal line 2b thus generates (with a suitable laser intensity along the laser beam focal line 2b, which is ensured by the focusing of the laser beam 2 on a section of length I, ie by a line focus of length I) in the coverage area of the laser beam focal line 2b with the substrate 1
• a suitable laser intensity along the laser beam focal line 2b which is ensured by the focusing of the laser beam 2 on a section of length I, ie by a line focus of length I
• the substrate 1 in the material of the substrate which is swept by the focal line 2b, viewed along the beam longitudinal direction extended section 2c, along which an induced absorption in the material of the substrate is generated, which induces cracking along the portion 2c in the material of the substrate.
• the cracking occurs not only locally, but over the entire length of the extended portion 2c of the induced absorption.
• the length of this section 2c (ie ultimately the length of the overlap of the laser beam focal line 2b with the substrate 1) is here provided with the reference symbol L.
• This average extent D corresponds here essentially to the mean diameter ⁇ of the laser beam focal line 2 b.
• FIG. 2 a shows, for the wavelength .lambda
• FIG. 2 b outlines that the heated material ultimately expands, so that a correspondingly induced voltage results in microcracking according to the invention, the stress on the surface 1 a being greatest.
• the individual focal lines to be positioned along the parting line 5 on the surface of the substrate be formed as described with the subsequent optical arrangements (Figs optical arrangement is alternatively referred to below as laser optics).
• the roughness results in particular from the spot size or the spot diameter of the focal line.
• certain requirements for the numerical aperture of the laser optical system 6 are generally required. These requirements are met by the laser optics 6 described below.
• the laser beam must illuminate the optics to the required opening, which is typically accomplished by beam expansion by means of telescopes telescope between laser and focusing optics.
• the spot size should not vary too much for a uniform interaction along the focal line. This can be ensured, for example, by the (see example below) that the focusing optics is illuminated only in a narrow, annular area by then naturally change the beam aperture and thus the numerical aperture only small percentage.
• the laser radiation 2a emitted by the laser 3 is first directed to a circular diaphragm 8, which is completely non-transparent to the laser radiation used.
• the aperture 8 is oriented perpendicular to the beam longitudinal axis and centered on the central beam of the beam 2a shown.
• the diameter of the diaphragm 8 is selected so that the near the center of the beam 2a and the central beam lying beam (here with 2aZ) impinge on the aperture and are completely absorbed by this. Only rays lying in the outer peripheral region of the radiation beam 2a (marginal rays, here denoted 2aR) are not absorbed due to the aperture size reduced in comparison to the beam diameter, but pass laterally through the diaphragm 8 and hit the edge regions of the bi-ground here. convex lens 7 trained focusing optical
• the centered on the central beam lens 6 is here consciously formed as uncorrected, bi-convex focusing lens in the form of a conventional spherically ground lens.
• the spherical aberration of such a lens is deliberately exploited.
• ideal-corrected systems may use different aspheres or multiple lenses that do not form an ideal focus point but rather a pronounced, elongated focus line of defined length (ie lenses or systems that no longer have a single focal point).
• the zones of the lens thus focus just as a function of the distance from the center of the lens along a focal line 2b.
• the diameter of the aperture 8 transverse to the beam direction here is about 90% of the diameter of the beam (beam diameter defined by the extent to the drop to 1 / e) and about 75% of the diameter of the lens of the optical assembly. 6
• the focal line 2b of a non-aberration-corrected spherical lens 7 is used, which was produced by hiding the beam in the middle. Shown is the section in a plane through the central ray, the complete three-dimensional bundle is obtained by rotating the rays shown around the focal line 2b.
• a disadvantage of this focal line is that the conditions (spot size, intensity of the laser) along the focal line, and thus along the desired depth in the material, change, and thus the desired type of interaction (no melting, induced absorption, thermo-plastic deformation until crack formation) may only occur within a part of the focal line leaves. Conversely, this means that if necessary only a part of the irradiated laser light is absorbed in the desired manner.
• the efficiency of the process is degraded
• laser light may be applied to undesired, deeper places (adhering to the substrate parts or
• FIG. 3 b shows (not only for the optical arrangement in FIG. 3 a but in principle also for all other usable optical arrangements 6) that the laser beam focal line 2 b is formed by suitable positioning and / or alignment of the optical arrangement 6 relative to the substrate 1 and by suitable choice of the Parameter of the optical assembly 6 can be positioned differently: As the first line outlined in Figure 3b, the
• Length I of the focal line 2b can be adjusted so that it exceeds the substrate thickness d (here by a factor of 2). If one places the substrate 1 centrally in the beam longitudinal direction to the focal line 2 b, then an extended portion of induced absorption 2 c is generated over the entire substrate thickness d.
• a focal length 2b of length I is generated which corresponds approximately to the extent of the substrate d. Since the substrate 1 is positioned relative to the line 2 so that the line 2b starts at a point in front of, ie, outside, the substrate, the length L of the extended induced absorption portion 2c (which is here derived from the surface of the substrate)
• Substrate extends into a defined substrate depth, but not to the back surface lb) here smaller than the length I of the focal line 2b.
• the fourth line in FIG. 3b shows the case in which the focal line length I produced is smaller than the substrate thickness d, so that when centric positioning of the substrate relative to the focal line in FIG
• the focal line positioning in such a way that at least one of the surfaces 1a, 1b is swept by the focal line, thus the portion of the induced absorption 2c begins on at least one surface.
• the portion of the induced absorption 2c begins on at least one surface.
• FIG. 4 shows another optical arrangement 6 that can be used according to the invention.
• the basic structure follows that described in FIG. 3 a, so that only the differences are described below.
• the optical arrangement shown is based on the idea of using a lens with a non-spherical free surface shaped to form the focal line 2 b so that a focal line of defined length I is formed.
• 6 aspheres can be used as optical elements of the optical arrangement.
• a so-called cone prism which is often referred to as axicon, used.
• An axicon is a special, conically ground lens that forms a point source along a line along the optical axis (or also transforms a laser beam into an annular shape).
• the structure of such an axicon is basically known to the person skilled in the art; the cone angle is here, for example, 10 °.
• the axicon designated here by the reference numeral 9 is aligned with its cone tip counter to the direction of irradiation and centered on the beam center. Since the focal line 2 b of the axicon 9 already begins within the same, the substrate 1 (which is arranged here perpendicular to the main beam axis) can be positioned in the beam path immediately after the axicon 9. As FIG. 4 shows, due to the optical properties of the axicon, a displacement of the substrate 1 along the beam direction is also possible without leaving the region of the focal line 2b. The extended portion of the induced absorption 2 c in the material of the substrate 1 thus extends over the entire substrate depth d.
• the structure shown has the following limitations: Since the focal line of the axicon 9 already begins within the lens, a finite working distance between the lens and the material makes up a significant part of the laser beam. Energy is not focused in the part 2c of the focal line 2b, which lies in the material. Furthermore, with the available refractive indices and cone angles of the axicon 9, the length I of the focal line 2b is linked to the beam diameter, which is why with relatively thin materials (a few millimeters) the focal line is too long in total, which in turn means that the laser energy can not be deliberately focused into the material ,
• an improved optical arrangement 6 can be used according to the invention if it comprises both an axicon and a focusing lens.
• FIG. 5a shows such an optical arrangement 6 in which, in the beam path of the laser 3 along the beam direction, first a first optical element with a non-spherical free surface, which is formed to form an extended laser beam focal line 2b, is positioned.
• this first optical element is a 5 ° cone angle axicon 10, which is positioned perpendicular to the beam direction and centered on the laser beam 3.
• the cone tip of the axicon points against the beam direction.
• a second, focusing optical element here a plano-convex lens 11 (the curvature pointing to the axicon) positioned.
• the distance z1 is chosen here with about 300 mm so that the laser radiation formed by the axicon 10 is incident annularly on the outer regions of the lens 11.
• the lens 11 focuses the radiation incident on the ring at the beam exit side at a distance z 2 from here about 20 mm from the lens 11 to a focal line 2 b of defined length of 1.5 mm here.
• the effective focal length of the lens 11 is here 25 mm.
• the annular transformation of the laser beam by the axicon 10 is provided here with the reference symbol SR.
• FIG. 5b shows the design of the focal line 2b or of the induced absorption 2c in the material of the substrate 1 according to FIG. 5a in detail.
• the optical properties of the two elements 10, 11 and the positioning of the same takes place here such that the extension I of the focal line 2 b exactly matches the thickness d of the substrate 1 in the beam direction. Accordingly, accurate positioning of the substrate 1 along the beam direction is necessary to, as shown in Figure 5b, the focal line 2b exactly between the two To position surfaces la and lb of the substrate 1.
• the focal line is formed at a certain distance from the laser optics, and the majority of the laser radiation is focused to a desired end of the focal line.
• This can be achieved as described by illuminating a mainly focusing element 11 (lens) only in a ring on a desired zone, whereby the desired numerical aperture and thus the desired spot size are realized on the one hand and the desired focal line on the other hand 2b, the circle of confusion loses intensity over a very short distance in the middle of the spot, as a substantially annular spot is formed.
• crack formation in the sense of the invention is stopped within a short distance at the desired depth of the substrate.
• a combination of axicon 10 and focus lens 11 fulfills this requirement.
• the axicon 10 acts in two ways: through the axicon 10, a usually round laser spot is sent annularly onto the focusing lens 11 and the asphericity of the axicon 10 causes a focal line to form outside the focal plane instead of a focal point in the focal plane of the lens.
• the length I of the focal line 2b can be adjusted via the beam diameter on the axicon.
• the numerical aperture along the focal line in turn, can be adjusted via the distance zl axicon lens and the cone angle of the axicon. In this way, thus the entire laser energy can be concentrated in the focal line.
• the annular illumination still has the advantage that on the one hand the laser power is used optimally, since a large part of the laser light remains concentrated in the desired length of the focal line, on the other hand through the annular illuminated zone, together with the desired aberration set by the other optical functions, a uniform spot size along the focal line, and thus a uniform separation process according to the invention along the focal line can be achieved.
• a focusing meniscus lens or other higher corrected focusing lens may also be used (Asphere, Mehrlinser) are used.
• a collimating lens 12 (FIG. 6): through this further positive lens 12, the annular illumination of the focusing lens 11 can be set very narrow.
• the focal length f of the collimating lens 12 is chosen so that the desired ring diameter d r at a distance zla from the axicon to the collimating lens 12, which is equal to f, results.
• the desired width b r of the ring can be selected via the distance zlb (collimating lens 12 to focusing lens 11). Purely geometrically follows now from the small width of the annular lighting a short focal line. A minimum can be achieved in the
• the optical arrangement 6 shown in FIG. 6 is thus based on that shown in FIG. 5a, so that only the differences will be described below.
• axicon 10 which is here with its cone tip opposite to the beam direction
• plano-convex lens 11 on the other hand here also as a plano-convex lens (with its curvature opposite to the beam direction facing) trained collimating lens 12
• the distance of the collimating lens 12 from the axicon 10 is here designated zla, the distance from the focusing lens 11 of the collimating lens 12 with zlb and the distance of the focal line 2b generated by the focusing lens 11 with z2 (each viewed in the beam direction).
• FIG. 6 shows, the annular radiation SR incident on the collimating lens 12 and under the ring diameter d r , formed by the axicon 10 along the distance zlb at at least approximately constant annular diameter d r to the desired ring width b r at the location of Focusing lens 11 is set.
• a very short focal line 2 b is to be produced so that the ring width b r of approximately 4 mm at the location of the lens 12 is reduced by the focusing properties of the latter to approximately 0.5 mm at the location of the lens 11 (ring diameter d r here, for example 22) mm).
• a focal line length I of less than 0.5 mm can be achieved.
• Borosilicate or Sodalime glasses 1 without any other colorations are optically transparent from about 350 nm to about 2.5 ⁇ m. Glasses are generally poor heat conductors, which is why laser pulse durations of a few nanoseconds already allow no significant heat diffusion from a focal line 2b out. Nevertheless, even shorter laser pulse durations are advantageous because with sub-nanosecond or picosecond
• Pulse a desired induced absorption via non-linear effects is easier to achieve (intensity much higher).
• Suitable for the separation of flat glasses according to the invention is, for example, a commercially available picosecond laser 3, which has the following parameters: wavelength 1064 nm, pulse duration of 10 ps, pulse repetition frequency of 100 kHz, average power (measured directly after the laser) of up to 50 W.
• the laser beam initially has a beam diameter (measured at 13% of the peak intensity, ie l / e 2 diameter of a Gauss beam) of about 2 mm, the beam quality is at least M 2 ⁇ 1.2 (determined according to
• the theoretical diameter ⁇ of the focal line varies along the beam axis, therefore it is advantageous for the creation of a homogeneous crack surface if the substrate thickness d is less than about 1 mm (typical thicknesses for display glasses are 0.5 mm to 0.7 mm). With a spot size of about 2 ⁇ and a distance from spot to spot of 5 ⁇ results in a speed of 0.5 m / sec, with which the focal line on the substrate 1 out 5 (see Fig. 9) can be.
• burstpuls With 25 W average power on the substrate (measured after the focusing lens 7) results from the pulse repetition frequency of 100 kHz, a pulse energy of 250 ⁇ , which also in a structured pulse (rapid succession of individual pulses at a distance of only 20 ns, so-called. Burstpuls ) can be made from 2 to 5 sub-pulses.
• Unhardened glasses have essentially no internal stress, which is why the still entangled and connected with unseparated bridges fault zone holds without external action, the parts still together. If, however, a thermal stress is applied, the substrate separates completely and without further external force introduction along the loaded fracture surface 5.
• a C0 2 laser with up to 250 W average power is focused on a spot size of about 1 mm, and this spot with up to 0.5 m / s over the dividing line 5 out.
• the local thermal stress due to the introduced laser energy (5 J per cm of the dividing line 5) completely separates the workpiece 1.
• the threshold intensity for the process naturally has to be reached over a longer focal line I. Consequently follow higher required pulse energies and higher average power.
• the transection of approximately 3 mm thick glass succeeds.
• the annular aperture 8 is removed and, on the other hand, the distance lens 7 to substrate is corrected (increased in the direction of the nominal focal distance) so that a longer focal line is formed in the substrate.
• Sodium-containing glasses are hardened by exchanging sodium for potassium by immersion in liquid potassium salt baths on the glass surface. This leads to a considerable internal stress (compressive stress) in a 5-50 ⁇ m thick layer on the surfaces, which in turn leads to the higher stability.
• the process parameters when severing tempered glasses are similar to those for uncured glasses of comparable dimensions and composition.
• the tempered glass can burst much more easily due to the internal stress, namely due to undesired crack growth, which does not take place along the lasered predetermined breaking surface 5 but into the material. Therefore, the parameter field for the successful cutting of a particular tempered glass is narrower.
• the average laser power and the associated cutting speed must be kept fairly accurate, depending on the thickness of the cured layer. For a glass with 40 ⁇ thicker hardened layer and 0.7 mm total thickness results in the o.g. Construction e.g. the following parameters: cutting speed of Im / s at 100 kHz pulse repetition frequency, therefore a spot distance of 10 ⁇ , with an average power of 14 W.
• Very thin tempered glasses consist predominantly of strained material, ie front and back, for example, each 30 ⁇ depleted sodium and thus hardened, and only 40 ⁇ inside are uncured. This material shatters very easily and completely when one of the surfaces is injured. Such hardened glass sheets were previously unworkable in the prior art.
• the separation of this material by the method of the invention succeeds when a) the diameter of the focal line is very small, e.g. smaller than 1 ⁇ , b) the distance from spot to spot is small, e.g. between 1 and 2 ⁇ , and c) the separation speed is high enough that the crack growth can not precede the laser process (high laser pulse repetition frequency, for example 200 kHz at 0.2 to 0.5 m / s).
• sapphire crystals and sapphire glasses are visually similar (transparency and refractive index), they behave very differently mechanically and thermally. So sapphire is an excellent conductor of heat, is mechanically extremely resilient, and very hard and scratch resistant. Nevertheless, thin (0.3 mm to 0.6 mm) sapphire crystals and glasses can be cut through with the laser and optical assembly described above. Because of the high mechanical stability, it is particularly important that the remaining bridges between the parts to be separated are minimized, otherwise very high forces are required for final separation. The fault zone must be formed as completely as possible from entrance la to exit surface 1b of the substrate. As with thicker glasses, this can be achieved with higher pulse energy and thus higher average laser power. Furthermore, crystalline sapphire is birefringent.
• the cut surface must be perpendicular to the optical axis (so-called C-cut).
• C-cut For cutting through a crystalline sapphire wafer of 0.45 mm thickness, the following parameters can be used: an average laser power of 30 W at 100 kHz pulse repetition frequency, a spot size of 2 ⁇ , and a sports distance of 5 ⁇ , which a cutting speed of 0.5m / s in the mentioned Pulse repetition frequency corresponds.
• an average laser power of 30 W at 100 kHz pulse repetition frequency
• a spot size of 2 ⁇ a sports distance of 5 ⁇ , which a cutting speed of 0.5m / s in the mentioned Pulse repetition frequency corresponds.
• it can be required for complete separation to perform a subsequent heating of the cutting line 5, for example, with a C0 2 laser spot, so that forms the fault zone on the thermal stress crack growth to a complete, continuous, unhooked separation surface.
• FIG. 9 shows a microscope image of the surface of a glass pane processed according to the invention.
• the individual focal lines or extended sections of induced absorption 2c which are designated here by the reference symbols 2c-1, 2c-2... (In the depth of the substrate perpendicular to the illustrated surface), join along the line 5, along which the laser beam was passed over the surface 4 of the substrate, by cracking to a separation surface for the separation of the substrate parts.

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