DE102024115927A1 - Structured glass element and method for its manufacture - Google Patents

Abstract

Glass element (1) with two opposing side surfaces (2, 3), which has a web (5) with wall surfaces (50) connecting the side surfaces (2, 3), wherein the web (5) in plan view of one of the side surfaces (2, 3) has a width of less than 3 mm at least along a section (7), wherein this section (7) of the web (5) has a recess (9) in one of the side surfaces (2, 3), such that the thickness of the glass element (1) given by the distance of the side surfaces (2, 3) is reduced in the area of the recess (9), wherein the recess (9) has wall surfaces (90) and a bottom surface (92), and wherein the wall surfaces (90) and the bottom surface (92) of the recess (9), as well as the wall surfaces (50) of the web (5), have an etched surface structure.

Description

Background of the invention

The invention relates generally to the production of glass elements with a structured surface. In particular, the invention relates to glass elements whose surface is structured by etching.

Indentations in glass can be created by removing glass through mechanical or chemical processes, or by bonding two glass panes together, with one pane containing the corresponding recess. However, ensuring high surface accuracy between the individual panes when positioning the indentation is challenging. Furthermore, achieving precise and homogeneous depth control can be difficult. Some processes can cause damage (cracks, damage to the back surface) to the glass. Etching processes can also result in undesirably large radii of curvature, even on the order of the depth of the indentation, at the edges.

A process for the fine structuring of glass, in which filament-shaped defects are created in the glass with a laser and these are subsequently expanded in an etching medium, is described by the DE 10 2018 100 299 A1 . From the DE 102018 110 211 A1 A method for creating a cavity in a glass substrate is known in which the laser beam of an ultrashort pulse laser is concentrated into an elongated focus within the substrate using focusing optics. The energy of the laser beam generates filament-shaped defects within the substrate's volume, extending to a predetermined depth but not penetrating the substrate. The substrate is then exposed to an etching medium, which expands and connects the filament-shaped defects, thus creating a cavity. Among other applications, this method can be used to produce glass components for microfluidic cells.

The glass components produced in this way have a disc-shaped basic form, with the cavities being formed in the side surfaces. However, with increasing miniaturization or the production of components at the wafer level, it may be desirable to produce more intricate structures. This objective is achieved by the subject matter of the independent claims. Advantageous embodiments of the invention are specified in the respective dependent claims.

Summary of the invention

The invention provides a glass element with two opposing side surfaces, which has a web with wall surfaces connecting the side surfaces. The web, viewed from above on one of the side surfaces, has a width of less than 3 mm at least along a section, wherein this section of the web has a recess in one of the side surfaces, such that the thickness of the glass element, determined by the distance between the side surfaces, is reduced in the area of the recess, wherein the recess has wall surfaces and a bottom surface, and wherein the wall surfaces and the bottom surface of the recess, as well as the wall surfaces of the web, have an etched surface structure.

• - der gepulste Laserstrahl eines Ultrakurzpulslasers auf eine der Seitenflächen des Ausgangselements gerichtet und
• - mit einer Fokussierungsoptik zu einem langgezogenen Fokus im Ausgangselement konzentriert wird, wobei
• - durch die eingestrahlte Energie des Laserstrahls eine filamentförmige Schädigung im Volumen des Ausgangselements erzeugt wird, wobei
• - der Laserstrahl über das Ausgangselement entlang eines Pfades entsprechend der Kontur des Glaselements bewegt wird, so dass
• - entlang dieses Pfades nebeneinander filamentförmige Schädigungen erzeugt werden, wobei
• - die Kontur einen Steg mit einem Abschnitt mit einer Breite von kleiner als 3 mm umfasst, und wobei
• - mit dem Ultrakurzpulslaser innerhalb dieses Abschnitts eine Vielzahl von weiteren filamentförmigen Schädigungen eingefügt werden, welche im Volumen innerhalb des Ausgangselements enden, und wobei
• - das Ausgangselement einem Ätzmedium ausgesetzt wird, welches die filamentförmigen Schädigungen aufweitet, so dass diese sich entlang der Kontur miteinander verbinden und dadurch das Glaselement herausgearbeitet wird, und wobei die Vielzahl der im Volumen innerhalb des Ausgangselements endenden filamentförmigen Schädigungen sich durch Aufweitung ebenfalls verbinden und eine Vertiefung im Steg innerhalb des Abschnitts, der eine Breite kleiner als 3 mm aufweist, bilden.

A suitable method for manufacturing such a glass element involves providing a starting element made of glass, and

• - the pulsed laser beam of an ultrashort pulse laser is directed onto one of the side surfaces of the output element and
• - is concentrated with a focusing optic to an elongated focus in the output element, whereby
• - the energy emitted by the laser beam creates filament-shaped damage in the volume of the starting element, whereby
• - the laser beam is moved across the output element along a path corresponding to the contour of the glass element, so that
• - filament-shaped damage is generated side by side along this path, whereby
• - the contour includes a bridge with a section less than 3 mm wide, and wherein
• - using the ultrashort pulse laser, a multitude of further filament-shaped defects are introduced within this section, which terminate in the volume within the original element, and wherein
• - the starting element is exposed to an etching medium which expands the filament-shaped defects so that they connect along the contour and thereby create the glass element, and wherein the multitude of filament-shaped defects ending in the volume within the starting element also connect by expansion and form a depression in the web within the section which has a width of less than 3 mm.

This method also makes it possible to create indentations in a section of a web that has a width of less than 1 mm, or even less than 0.6 mm, or even less than 0.3 mm. In particular, the thickness of the glass element can also be greater than the width of the web, or of the section of this web containing the indentation.

The glass of the glass element, or the starting element, is advantageously transparent to the laser beam so that the laser light can penetrate the glass. Preferably, the glass is selected such that less than 10% of the light is absorbed by linear absorption, i.e., for a weak light beam, when passing through the starting element. The absorption of the high-intensity ultrashort pulse laser beam, on the other hand, is caused by nonlinear effects, such as multiphoton absorption, and can therefore be greater. For the purposes of this disclosure, the term "glass" also includes glass ceramics.

The invention is explained in more detail below with reference to the figures. In the figures, identical reference numerals denote identical or corresponding elements.

Brief description of the characters

• 1 shows a device for laser processing of a starting element in preparation for subsequent etching.
• 2 shows a starting element with a contour of a glass element made up of inserted filament-shaped defects.
• 3 shows a glass element which is made from the in 2 The starting element shown was produced.
• 4 shows a section of another example of a starting element with inserted filament-shaped damage.
• 5 shows a white light interference image of the ground surface of a depression.
• 6 shows an exemplary embodiment of a glass element with laterally open recesses.
• 7 Another example shows a recess that is only open on one side.
• 8 shows a variant of the glass element with a bridge supported on one side.
• 9 and 10 Each shows composite elements with a glass element.
• 11 shows examples of how to access a cavity by means of a depression.
• 12 and 13 show composite elements with a combination of a recess and a through-opening.

Detailed description

In 1 An embodiment of a laser processing device 20 is shown, with which filament-shaped defects 32 can be introduced into a glass starting element 10 in order to subsequently introduce channels at the locations of the filament-shaped defects 32 in an etching process. The device 20 comprises an ultrashort pulse laser 30 with upstream focusing optics 23 and a positioning device 17. The positioning device 17 allows the point of impact 73 of the laser beam 27 of the ultrashort pulse laser 30 to be laterally positioned on the side surface 2 of a plate-shaped starting element 10 to be processed. In the illustrated example, the positioning device 17 comprises an xy-table on which the starting element 10 rests on a side surface 3. Alternatively or additionally, it is also possible to design the optics to be movable in order to move the laser beam 27, so that the point of impact 73 of the laser beam 27 can be moved while the output element 10 is held stationary.

The focusing optics 23 now focus the laser beam 27 to a focus elongated in the beam direction, i.e., accordingly transversely, and in particular perpendicularly to the irradiated side surface 2. Such a focus can be generated, for example, with a conical lens (a so-called axicon) or a lens with high spherical aberration. The in 1 The chosen representation of the focusing optics as a single lens is therefore only an exemplary sketch; the actual design of the optics may differ. The control of the positioning device 17 and the ultrashort pulse laser 30 is preferably carried out by means of a computer 15 programmed with a computer. In this way, predetermined patterns of filament-shaped defects 32 distributed laterally along the side surface 2 can be generated, in particular by reading in position data, preferably from a file or via a network. In particular, by moving the laser beam 27, or rather its point of impact 73, relative to the output element 10, a path corresponding to the contour of the glass element to be produced can be traced, so that filament-shaped defects 32 are generated side by side along this path. 1 Such adjacent filament-shaped defects 32 are shown. The corresponding direction of movement of the xy-table is indicated by an arrow. Also shown are several further filament-shaped defects 33 that terminate in the volume of the starting element 10. and serve to produce a depression. According to a preferred embodiment, these filament-shaped defects 33 begin on the side 2 of the starting element 10 facing the laser beam 27. For this purpose, the laser beam 27 is focused by the focusing optics 23 such that it already has sufficient intensity at the side surface 2 to modify the glass by nonlinear absorption. The correspondingly generated filament-shaped defects 33 are in 1 shown on the left side of the starting element 10. However, it is also possible to shift the focus so far into the glass that this threshold is only crossed within the glass. In this case, the filament-shaped defects 33 begin inside the starting element 10 and terminate in the rear side surface 3. Such filament-shaped defects 33 are in 1 drawn on the right side of the starting element 10.

It is apparent to those skilled in the art that the sequence for inserting the filament-shaped defects 32 along the contour of the glass element and the filament-shaped defects 33 terminating in the volume of the starting element is not fixed. These defects can also be inserted intermittently by changing the focus position while scanning the starting element 10. Generally, it is preferred if the filament-shaped defects 32 terminate along the contour at the two side surfaces 2, 3, or if they extend through the entire thickness of the glass. However, it would also be conceivable to have at least some of these filament-shaped defects 32 terminate or begin in the same way as the defects 33 for producing the depression in the glass. Furthermore, different layers and lengths of filament-shaped defects 32 can be combined, for example, to create a specific edge shape.

Suitable wavelengths for the ultrashort pulse laser are generally preferably in the range of 300 nm to 1905 nm; more preferably in the range of 505 nm to 1111 nm; particularly preferably in the range of 1000 nm to 1100 nm; and most preferably in the range of 1020 nm to 1070 nm. It is essential that the ultrashort pulse laser emits light of a wavelength for which the glass of the starting element 10 is transparent and which has sufficient intensity to deposit the energy of the light by exciting nonlinear effects in the glass. To reduce thermal and mechanical stresses in the glass, it is generally advantageous if the pulse duration of the laser pulses is less than 10 ps, preferably less than 3 ps, or even less than 1 ps. Pulse durations that are too short are also rather disadvantageous in this respect. Therefore, a pulse duration longer than 0.1 ps, preferably longer than 0.3 ps, and particularly preferably at least 0.5 ps, is preferred.

The laser light can be applied in individual pulses spaced at equal intervals. However, it is also possible, and preferred, to perform the insertion of the filament-shaped defects 32, 33 in so-called burst mode. In burst mode, the laser energy is not emitted as a single pulse, but as a sequence of pulses emitted in quick succession, which together form a pulse packet, a so-called burst. Such a pulse packet typically has a slightly higher energy than a single pulse in the usual single-shot operation. However, the individual pulses of a burst contain less energy than a single pulse. A burst mode with pulse packets of at most three, or with two pulses, is preferred.

2 Figure 1 shows a schematic embodiment of a starting element 10, which has been processed with an ultrashort pulse laser 30, in a top view of a side surface 2. As can be seen, the filament-shaped defects 32 are arranged next to each other and form a contour 100. Specifically, in this example, the contour 100 comprises two circumferential, or ring-shaped, closed structures that are spaced apart from each other, leaving a bridge 5 between them. For the purposes of this disclosure, a ring-shaped closed structure is understood to mean not only a circular structure, but any structure of an arbitrary shape that follows a closed path. Thus, in the example shown, the 2 Ring-shaped closed structures in the form of rectangular paths are provided. According to this disclosure, the web 5 has a section 7 along which the width of the web 5 is less than 3 mm. In the example shown, the web 5 has a constant width, so that the length of the section 7 is equal to the length of the web 5. In addition, in this example, a series of further filament-shaped defects 33 has been inserted in the middle of the web 5. While the filament-shaped defects 32 preferably extend along the path following the contour 100 of the glass element to be produced and thus terminate in both opposite side surfaces 2, 3, the filament-shaped defects 33 terminate within the glass.

3 shows a glass element 1 in perspective view, which is made from the in 2 The starting element shown was produced by exposing the starting element 10 to an etching medium. The etching medium expands the filament-shaped defects 32, causing them to connect along the contour 100, thereby forming the glass element 1 in its desired contour. Simultaneously, during etching with the etching medium, the numerous filament-shaped defects 33 terminating in the volume within the starting element 10 connect by expansion. and thus form a depression 9 in the bridge 5 within section 7.

Etching can be carried out with an acidic etching medium, such as aqueous solutions of HF, HCl, _H₂SO₄ , _{HNO₃ ,} or other acids. Etching with a basic, particularly alkaline, etching medium, such as potassium hydroxide (KOH) or sodium hydroxide (NaOH), is preferred. According to a further development, etching is carried out in an alkaline etching medium with a pH value greater than 12 and a complexing agent. The complexing agent can complex one of the components of the glass. Thus, as in the WO 2022/268585 A1 As described, complexing agents are used that form complexes with alkaline earth metal ions, preferably calcium ions ( ^Ca²⁺ ). Suitable complexing agents include phosphates, preferably ATMP (nitrilotris(methylenephosphonic acid)), phosphonic acids, salts of hydroxycarboxylic acids, preferably alkali gluconates, EDTA, and/or transition metal salts, especially _CrCl₃ . The above measures can advantageously counteract local inhibition of the etching process by complexing released components. Furthermore, a self-stabilizing or even self-enhancing effect on the etching rate can occur within the structures to be produced.

Furthermore, an etching solution containing a silicate, preferably an alkali silicate, particularly preferably water glass, in dissolved form can also be used.

When using etching solutions containing dissolved silicates, the etching rate can be significantly increased. This effect is particularly noticeable at high silicate concentrations in the etching solution. Especially at high silicate concentrations, the silicates also act as alkali carriers, thus increasing the mobility of the hydroxide ions. This is particularly advantageous in embodiments with very high hydroxide concentrations in the etching solution. For example, the ion mobility of hydroxide ions decreases with increasing concentration in highly concentrated alkalis, which also affects the etching rate. However, this effect can be at least partially compensated for by adding silicates as alkali carriers. Complexing agents and the addition of silicates can be helpful in maintaining a sufficient etching rate within the well 9 being produced, with only minimal exchange of the etching medium, and in achieving the most perpendicular possible walls of the well 9.

According to a preferred embodiment, the etching depth can be adjusted to the spacing of the filamentous defects 33 for the formation of the recess 9. Generally, without limiting oneself to specific examples, it is particularly recommended that the total etching depth by the etching medium in the radial direction of the filamentous defects 33 be adjusted to be in the range of 0.5 to 1.5 times the spacing of the filamentous defects 33. Preferably, the etching depth is in the range of 0.7 to 1.3 times, and particularly preferably in the range of 0.9 to 1.1 times the spacing of the filamentous defects 33. This ensures that the etching process is not carried out significantly longer than the time required for the filamentous defects 33 to connect with each other through radial expansion. In any case, it is advantageous to prevent the etching depth from becoming so great that the bottom of the recess 9 reaches the opposite side surface. The etching process can be influenced and adjusted by various parameters. These parameters include the composition of the glass, the temperature of the etching medium, its composition, its concentration, and its pH value.

Due to the etching process, the wall surfaces 90 and the bottom surface 92 of the recess 9, as well as the wall surfaces 50 of the web 5, exhibit an etched surface structure. The side surfaces 2, 3 may also be exposed to the etching medium when the filament-shaped defects 32, 33 widen. Typically, the topography of the wall surfaces 50, 90 of the web 5 and recess 9, as well as the bottom surface 92 of the recess 9, differs significantly from the topography of the side surfaces 2, 3. The latter remain smooth, particularly when using a basic etching medium, while the etched surfaces of the wall surfaces 50, 90 exhibit a distinct structure. Without being limited to the specific examples and embodiments described herein, glass elements 1 according to this disclosure can be characterized by the fact that, alternatively or additionally to the feature of an etched surface structure, the wall surfaces 50, 90 and the bottom surface 92 exhibit a higher roughness than the side surfaces 2, 3.

As demonstrated by 3 It is also evident that the thickness of the glass element 1, and thus also of the web 5, is greater than its width in section 7. Accordingly, the wall surfaces 50 also have a larger total area than the areas of the parts of the side surfaces 2, 3 on the web 5, or section 7. Therefore, the web 5 in section 7 has a rectangular cross-section, with the long sides of the rectangle formed by the wall surfaces 50. The depth of the recess 9 is, in principle, without being limited to the example shown, less than the thickness of the glass element 1. In principle, there are There is no limitation regarding the depth of the recess 9, as long as a minimum residual glass height is selected such that damage to the back of the recess, or to the side surface 3 opposite the base surface 92, is avoided. In general, however, it is advantageous if the thickness of the glass between the base surface 92 of the recess 9 and the opposite side surface 3 of the glass element, or the distance between the base surface 92 and the opposite side surface 3, is at least 200 µm, preferably at least 300 µm, and particularly at least 400 µm. This distance corresponds to the thickness of the glass element 1 minus the depth of the depression 9. More generally, and also valid for glasses thinner than 200 µm, the distance and length L of the filamentous defects 33 can be adjusted so that a minimum residual glass thickness RD remains, for which: GD = RD+0.5*s + L, where s is the distance of the filamentous defects 33 and GD is the original thickness of the starting element.

As already mentioned 2 As described, contour 100 comprises two circumferential, or ring-shaped, closed structures that are spaced apart from each other, leaving the bridge 5 between them. These ring-shaped paths of filamentous damage 32 lead to the dissolution of internal parts during the etching process, so that, as described in 3 As shown, complementary cutouts 40 remain in the glass element 1, between which the web 5 runs. Particularly preferably, the glass element 1 is formed from the starting element 10 by inserting filament-shaped defects 32 along one or more paths and subsequent etching, such that the glass element 1 has at least one cutout 40 which is bounded by the web 5. With the method described here, particularly delicate yet stable glass elements 1 can be produced, which have large-area cutouts 40 on the one hand and thin webs 5 which also have at least one recess 9 on the other. The cutouts 40 thus have a large surface area of the glass element 1. Without being limited to specific examples, a preferred embodiment provides that the glass element 1 has at least one cutout 40 in the form of a through opening, wherein the web 5 limits the cutout 40 or forms an edge of the cutout 40, the total area of the cutout(s) 40 comprising at least 40% of the area enclosed by the outer contour of the glass element 1. Preferably, the total area of the one or more cutouts 40 is even at least 57%, or even at least 65%, or at least 65%, or even at least 73%, or even at least 82% of the area enclosed by the outer contour of the glass element 1. In the case of the 3 In the example of a rectangular glass element 1 shown, the area enclosed by the outer contour 11 is given by the product of the side dimensions. The sum of the two cutouts 40 separated by the web 5 is therefore at least 40% of the area calculated by the product of the side dimensions.

To produce the delicate structures, especially the webs 9, which themselves have further recesses, it is advantageous for the glass to exhibit minimal stress after laser processing. This can also be generally achieved using glasses with lower coefficients of thermal expansion. In a further development of the method and the glass element 1, a glass is used that has a linear coefficient of thermal expansion of less than 10 ppm (α < 10 × ^{10⁻⁶ K⁻¹} ), preferably less than 8 ppm (α < 8 × ^{10⁻⁶ K⁻¹} ), and particularly preferably less than 4 ppm (α < 4 × ^{10⁻⁶ K⁻¹} ). For the same reason, glasses with a low modulus of elasticity are also preferred. In a further alternative or additional embodiment, the glass of the glass element 1 has a modulus of elasticity of less than 73 GPa, preferably less than 70 GPa.

In the example of the 2 and 3 The depression 9 was created using only a single row of filament-shaped defects 33. This also defines the minimum structure width, without being limited to the examples shown. The width of such a depression 9 is determined by twice the radial etching depth. Thus, for example, if an etching depth of 20 µm is performed, depressions 9 with a width of 40 µm or more can be produced.

In general, however, a grid of filament-shaped defects 33 is introduced to create correspondingly wider depressions 9. For this purpose, the laser beam is guided over the output element 10 in several adjacent tracks or rows. This results in two spacings of the filament-shaped defects 33: the spacing within a track and the spacing between the tracks themselves. 4 Figure 1 shows a section of the side surface 2 of a correspondingly machined starting element 10. Specifically, a section is shown which has the filament-shaped defects 32 arranged along contour 100 for machining section 7 of a web 5 with a width of less than 3 mm, preferably less than 1 mm. Within this contour 100 in the shown section are also the not completely through The starting element 10 is inserted through filament-shaped defects 33 to form a recess 9 in the web 5. As can be seen from the illustration, the spacing 36 of filament-shaped defects 33 along a row 35 differs from the row spacing 37. In this example, the spacing 36 is smaller than the row spacing 37. These spacings 36, 37 can significantly influence the strength of a delicate web 5 with a recess 9. Spacings in the range of up to 10 µm are usually chosen to achieve rapid production and good contour accuracy. However, for producing a recess 9 on a section 7 of a web 5 with a width of less than 3 mm or even less than 1 mm, it has proven advantageous to choose larger spacings. Spacings that are too small can lead to microcracks in the glass due to stresses introduced by light exposure, which can quickly lead to breakage in these delicate structures.

In a preferred embodiment of the method, the filament-shaped defects 33 for producing the depression 9 are inserted successively in several adjacent rows 35, wherein the speed at which the laser beam 27 is moved over the output element 10, the repetition rate at which the ultrashort pulse laser 30 is operated, and a row spacing 37 between two adjacent rows 35 are selected such that the average distance between adjacent filament-shaped defects 33 is at least 20 µm. A mean distance between adjacent filament-shaped defects 33 of at least 25 µm, and optionally at least 30 µm, is further preferred. Adjacent filament-shaped defects are both the nearest neighbors within a row 35, i.e., the filament-shaped defects 33 inserted immediately before and after a given filament, and the nearest filament-shaped defects 33 in adjacent rows 35. However, excessively large average distances are disadvantageous due to the need to maintain the contour accuracy of the recess 9 and the duration of the etching process. Therefore, according to a further development of the method, the filament-shaped defects 33 are designed to have an average distance of at most 50 µm, preferably at most 40 µm.

The mean distances between adjacent filament-shaped defects 33 within a row 35 and to adjacent rows are preferably similar in order to avoid damage or loss of strength due to stresses in the glass. According to a further embodiment, the distance between the filament-shaped defects 33 within a row 35 is 0.5 to 2 times the row spacing 37, preferably 0.7 to 1.4 times, and particularly 0.9 to 1.1 times the row spacing. The aforementioned preferred distances between the filament-shaped defects 33 also result in a comparatively flatter bottom surface 92 of the depression 9.

The regular arrangement of the filament-shaped defects 33 can also be observed on the etched surface of the extracted glass element 1. Specifically, a regular arrangement of depressions or dimples is found on the bottom surface 92 of the depression 9 at the positions of the filament-shaped defects 33. These depressions presumably arise from the anisotropic etching rate at the defects and in the areas between them.

• - der Abstand benachbarter Mulden 94 beträgt im Mittel mindestens 20 µm, vorzugsweise im Mittel mindestens 25 µm,
• - die Mulden 94 weisen einen mittleren Abstand von höchstens 50 µm, bevorzugt höchstens 40 µm auf,
• - der Abstand der Mulden 94 innerhalb einer Reihe 35 liegt beim 0,5-fachen bis zweifachen des Reihenabstands 37, bevorzugt beim 0,7-fachen bis 1,4-fachen, insbesondere beim 0,9-fachen bis 1,1-fachen des Reihenabstands 37,
• - der Abstand benachbarter Mulden 94 liegt im Bereich von 25 µm bis 35 µm.

An example of such a structured ground surface 92, a depression 9 with hollows 94, shows 5 The scales at the edge of the image show the dimensions of the image in micrometers. Accordingly, it shows 5 a section measuring 370 µm x 370 µm. The in 5 The colors, shown only as shades of gray, correspond to the local elevation coordinate. The depth of the depressions 94 relative to the mean elevation varies in the illustrated example from approximately -17 µm to +23 µm. In the illustrated example, a row spacing 37 of 30 µm and a spacing 36 of filamentous defects 33 along a row 35 of 20 µm were chosen. These dimensions are close to the particularly preferred range of 25 µm to 35 µm for both spacings. Accordingly, a spacing of adjacent filamentous defects in the range of 25 µm to 35 µm is generally particularly preferred. With distances between adjacent filamentous defects 33, preferably in the preferred range between 20 µm and 50 µm, general roughness values of the floor surface ⁹² for a measurement window of 370 x 370 µm can be determined, evaluable by white light interferometry, with _Sq < 6 µm and _Sa < 6 µm. _Sq represents the root mean square of the ordinate values within the defined area. _Sq is thus equivalent to the standard deviation of the heights. _Sa is the extension of the roughness value Ra (arithmetic mean height of a line) to a surface. As an absolute value, _Sa indicates the mean height difference of each point compared to the arithmetic mean of the surface. With the preferred method parameters, very flat floor surfaces 92 can thus be produced in a depression 9. As can be seen from the discussion above, such a depression 9 is characterized first and foremost by the fact that its bottom surface 92 has a regular arrangement of depressions 94. This regularity means in particular that the depressions 94 are oriented in relation to each other. The recesses 94 are arranged in spaced rows 35, with the recesses 94 within a row 35 having a uniform spacing. Preferably, the rows 35 are also spaced uniformly apart from each other by a distance 37, as in the illustrated examples. In accordance with the preferred parameters described above with regard to the method, a further embodiment of this design provides that at least one of the following features applies to the arrangement of the recesses 94:

• - the distance between adjacent troughs 94 is on average at least 20 µm, preferably on average at least 25 µm,
• - the troughs 94 have an average spacing of at most 50 µm, preferably at most 40 µm,
• - the spacing of the recesses 94 within a row 35 is 0.5 to 2 times the row spacing 37, preferably 0.7 to 1.4 times, in particular 0.9 to 1.1 times the row spacing 37,
• - the distance between adjacent troughs 94 is in the range of 25 µm to 35 µm.

These distances refer to the center-to-center distance.

In a further embodiment, the filament-shaped defects 33 can also be inserted along intersecting rows 35, particularly in rows 35 running at an angle of 120° to each other. In this case, for example, a regular arrangement of depressions 94 in a triangular or hexagonal pattern can be achieved. Such an arrangement can offer further advantages with regard to the strength of the glass element 1 at the depression 9. The features concerning the center-to-center spacing can also be applied to this embodiment, where several sets of intersecting rows are present. The center-to-center spacing in the range of 25 µm to 35 µm is also independent of whether the depressions are arranged in rows and is equally applicable to a hexagonal or triangular pattern.

To achieve a particularly flat base surface 92, it is advantageous if the scattering of the position at which the filamentary defects in the glass end or begin is as low as possible. An advantage here is that the absorption process of the laser beam is inherently nonlinear, so that even a certain scattering of the individual intensities of the pulses or bursts locally has less of an impact on falling below the modification threshold at similar axial coordinates when the intensity decreases. Additionally, it is advantageous if the axial intensity profile of the laser beam is such that there is a large change in intensity in the axial direction at the axial position within the glass where the filamentary defects end or begin. The steeper the increase or decrease in intensity in the axial direction, the lower the scattering of the axial coordinate of the boundary of the material modification of the glass. This can be achieved with suitable optics. In a further development of the method, the laser beam 23 is focused by means of a suitable laser processing device 20, in particular its focusing optics 23, such that at least 80% of the total intensity of the elongated focus lies within the axial region between the points where the light intensity exceeds half the maximum value. According to yet another embodiment, at least 60% or even at least 80% of the total light intensity can lie between the points where the light intensity exceeds 80% of the maximum value. According to an alternative or additional embodiment, the maximum intensity of the radial intensity profile varies over 85% of the length of the elongated focus by no more than 40%, preferably by no more than 20%, of the mean maximum intensity. A suitable device for this purpose is, for example, from the US 10 522963 B2 known.

In the example of the 3 The recess 9 is inserted such that the wall surfaces 90 form a closed contour. For this purpose, the filament-shaped defects 33 for the recess 9 are sufficiently far removed from the filament-shaped defects 32 located on the contour 100 of the glass element 1. It is therefore advisable to choose this distance to be greater than twice the radial etching depth. In the example of the 4 In contrast, the row spacing 37 of the filament-shaped defects 33 is greater than the distance to the contour 100, or to the filament-shaped defects 32 lying on the intended contour 100. Therefore, during etching, no wall surface 90 of the recess 9 will form in this area. Instead, a lateral opening will form in the wall surface 50 of the web 5. Generally, without being limited to specific examples, a further development of the glass element 1 provides that the recess 9 is open towards its wall surface 50 on at least one side of the web 5.

In 6 A perspective view shows a section of such a glass element 1 with laterally open recesses 9. The glass element 1 has a network of interconnected, narrow webs 5 compared to the thickness of the glass element 1. Accordingly, in this example as well, the thickness of the glass element 1 is greater than the width of the section 7 of the webs 5. Some of the webs 5 have recesses 9 that are open on both sides. The recesses 9 are open laterally, or towards the wall 50 of the web 5. A wall 90 of the recesses 9 is therefore only present at their ends. This embodiment has a very large area fraction of the cutouts 40, since the width of the webs 5 is considerably narrower than the dimensions of the cutouts 40. The area fraction of the cutouts 40 is well over 90% here. This can be a general feature of a further development of a glass element 1 according to this disclosure, not limited to the specific example shown.

7 Figure 1 shows a schematic example in which the recess 9 is open to the wall 50 on only one side of the web 5. In this example, the ends of the web 5 where it transitions into a frame-shaped section of the glass element 1 can also be thicker than 3 mm. Section 7 is thus shorter than the entire web 5. Here, too, the recess 9 extends within or at least into this section 7. As in the previously described examples, the web 5 is connected at its two ends 51, 52 to the remaining glass element 1, or other sections of the glass element 1. In other words, the web 5 forms a bridge here and generally in other embodiments. 8 Figure 1 shows a variant in which the bridge 5 is connected to the remaining glass element 1, or to further sections of the glass element 1, only at one end 51. In other words, the bridge 5 forms a cantilever. Such an embodiment can be used, for example, for sensory or actuator applications, with the bridge 5 forming a spring element. For this purpose, a material essential for the function of a sensor or actuator can be introduced into the recess 9. For example, a ferromagnetic material could be deposited there.

A glass element 1 according to this disclosure can preferably be used in a composite element. The glass element is connected to another element, preferably an element made of a brittle material, particularly preferably glass. For the purposes of this disclosure, the term "glass" generally includes glass ceramics. However, other materials, such as metals, are also conceivable for the other element. In this case, the composite element thus forms a glass-metal composite element. In an embodiment advantageous for many applications, the glass element 1 is connected to the other element via its side surface having the recess 9. Without limiting itself to specific embodiments and examples, this disclosure also relates to a composite element comprising a glass element 1 having at least one recess 9, as described herein, and another element, wherein the glass element 1 is connected to the other element such that the recess 9 is covered by a side surface 12 of the other element.

An example of such a composite element 4 shows 9 The glass element 1 has a cutout 40 forming a through-opening, which is bounded by a web 5. According to a further embodiment of a glass element 1, which is realized in this example, at least two recesses 9, 91, 93 can also be provided, which have different depths and which, in particular, merge into one another. In the illustrated example, three merged or laterally open recesses 9, 91, 93 are present in the side surface 2 of the glass element 1. The glass element 1 is connected, as described above, to a further element 6 via the side surface 2, which has the at least one recess 9, 91, 93, so that a composite element 4 is obtained. The recess 9, or the multiple recesses 9, 91, 93, are covered by the side surface 12 of the further element 6.

According to a preferred embodiment, which is also shown in the illustrated example of the 9 Once realized, a recess 9 is provided, which is similar to the examples in the 6 , 7 , 8 ) is open on at least one side of the bridge 5 towards its wall surface 50. In particular, the recess 9 is open towards the wall surface 50, which defines the cutout 40. The side surface 12 of the further element 6, which covers the recess 9, or the connected recesses 9, 91, 93, forms a lateral access opening to the cutout 40. In particular, a cavity 41 can be formed by the cutout 40 of the glass element 1 covered by the side surface 12 of the further element 6, with the recess 9, which opens towards the wall 50 that defines the cutout 40, forming an access point connecting the cavity 41. In the example shown, the cavity 41 is also open towards the side surface 3 of the glass element 1. If this side surface 3 is also closed with another element, this access point alone can then provide access to the surroundings.

In the embodiments shown so far, for example the 6 The recesses 9, if there are several, are all inserted into the same side surface. However, it is also possible to provide several recesses 9 that are inserted into both opposite side surfaces 2, 3. Without limiting oneself to specific examples, one embodiment provides that the glass element 1 has at least two recesses 9, one of which is inserted into one Side surface 2, the other being inserted into the opposite side surface 3 of the glass element 1. It is not even necessary to turn the glass element over to insert the filament-shaped defects 33 for both recesses 9. Rather, the position of the laser beam focus can simply be changed, as already described in 1 It has been shown that filament-shaped damage – viewed from the direction of the laser beam – can either end or begin within the glass. It is also still possible, as in the example of... 9 to connect these depressions. One such variant shows 10 Here, things are similar to in 9 Three interconnected recesses 9, 91, 93 are provided. In the example of the 10 However, the recesses 9 and 93 are inserted into side surface 2, and the recess 91 located between them is inserted into side surface 3. Furthermore, a connection is generally formed between the recesses 9, 91, and 93 at their respective bottom surfaces 94. This results in a meandering connection to cavity 41.

11 Figure 1 shows possible further connections to a cavity 41 formed by a cutout 40. The glass element 1 is shown in plan view of a side surface 2. The cavity 40 is bounded by webs 5 with a width of less than 3 millimeters. The webs 5 in turn have recesses 9, 91, 93, which are open towards the cavity 4. The geometry of these recesses, and thus the shape of such access points, can be shaped essentially arbitrarily using this method. For example, recess 9 forms an access point that tapers conically towards the cavity 41, and recess 93 forms an access point that tapers in a stepped fashion. Recess 91 is meandering and creates a corresponding access channel that has a length greater than the width of section 7 of web 5.

In the examples of 9 and 10 Various interconnected recesses 9, 91, 93 are provided. For example, to provide access to a cavity 41 formed by a cutout 40, a recess 9 can also be combined with a through-opening according to an alternative or additional embodiment. Such a through-opening ultimately also constitutes a cutout 40, but typically with a small opening cross-section. A through-opening can also be produced, like a cutout 40, by inserting filament-shaped defects 32 that extend through the glass and connect both side surfaces 2, 3, followed by etching. 12 Figure 4 shows a composite element with a combination of a recess 9 and a through-opening 8. Without limiting itself to the example shown, this embodiment is based on the fact that a through-opening 8 with an etched side wall is arranged in the web 5, in particular in its section 7 with a width of less than 3 mm, and which is connected to the recess 9. As can be seen from 12 As can be seen, such a combination of a through-opening 8 with a recess 9 can provide an L-shaped access to the cavity 41.

13 This shows another variant of a combination of a through-opening 8 with a recess 9. This variant also creates an L-shaped connecting channel to the cavity 41. In contrast to, for example, the 12 However, the through-opening 8 is located in the further element 6. The further element 6 is attached to the glass element 1 in such a way that the through-opening 8 is at least partially located on the recess 9 and establishes a gas-permeable connection to the cavity 41.

13 Figure 4 also shows a further processing of the composite element 4, in which a support element 19 for functional components, for example electro-optical functional elements 21, is connected to the composite element 4, so that the cavity 41 is closed by the support element 19. The cavity 41 now communicates with the environment via the connection to the recess 9 and the through-hole 8. This connection can be closed, for example, after filling with a controlled gas atmosphere.

It is obvious to those skilled in the art that the embodiments shown in the figures are merely exemplary and can be modified in many ways, in particular combined with one another. Thus, in the 9 until 13 Only one composite element 4 with a single cavity is shown. However, and preferably, corresponding elements with a multitude of cutouts 40 and webs 5 are produced, so that, for example, individual components can be separated by cutting the composite element. The method as described here is therefore particularly suitable for the production of components in wafer composites.

Furthermore, the recesses 9, 91, 93 of the illustrated examples have wall surfaces 90 that extend perpendicularly only with respect to the side surfaces 2, 3. This embodiment, with a deviation from the perpendicular direction of less than 5° in magnitude, is also preferred. However, it is also possible to produce differently oriented wall surfaces 90, such as inclined or stepped ones, very simply by changing the focus position while scanning the surface.

Reference symbol list

1

Glass element

2, 3

Side surfaces of 1

4

Composite element

5

web

6

further element

7

Section of bridge 5 with a width of less than 3 mm

8

Passage opening

9, 91, 93

in-depth

10

Output element

11

Outer contour of glass element 1

12, 13

Side surfaces of 6

15

Computer system

16

Access opening

17

Positioning device

19

Support element

20

Laser processing device

21

electro-optical component

23

Focusing optics

27

laser beam

30

Ultrashort pulse laser

32, 33

filamentous damage

35

Series of filamentous lesions 33

36

Spacing of filamentous damage 33 along a row 35

37

Row spacing

40

Excerpt in 1

41

cavity

50

Wall area of 5

51, 52

Ends of 5

73

Point of impact from 27 to 10

90

Wall area of 9

92

Floor area of 9

94

Mulde in 92

100

Contour of 1

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 10 2018 100 299 A1 [0003]
• DE 102018 110 211 A1 [0003]
• WO 2022/268585 A1 [0017]
• US 10 522963 B2 [0033]

Claims (15)

Glass element (1) with two opposing side surfaces (2, 3), which has a web (5) with wall surfaces (50) connecting the side surfaces (2, 3), wherein the web (5) in plan view of one of the side surfaces (2, 3) has a width of less than 3 mm at least along a section (7), wherein this section (7) of the web (5) has a recess (9) in one of the side surfaces (2, 3), such that the thickness of the glass element (1) given by the distance of the side surfaces (2, 3) is reduced in the area of the recess (9), wherein the recess (9) has wall surfaces (90) and a bottom surface (92), and wherein the wall surfaces (90) and the bottom surface (92) of the recess (9), as well as the wall surfaces (50) of the web (5), have an etched surface structure. Glass element (1) according to the preceding claim, characterized by at least one of the following features: the section (7) of the web (5) with the recess (9) has a width of less than 1 mm, in particular less than 0.6 mm, and more preferably less than 0.3 mm; the thickness of the glass element (1) is greater than the width of the section (7) of the web (5) with the recess (9); the thickness of the glass between the bottom surface (92) of the recess (9) and the opposite side surface (3) of the glass element (1) is at least 200 µm, preferably at least 300 µm, and more preferably at least 400 µm; the glass of the glass element (1) has a linear coefficient of thermal expansion of less than 10 ppm, preferably less than 8 ppm, and more preferably less than 4 ppm; the glass of the glass element (1) has a modulus of elasticity of less than 73 GPa, preferably less than 70 GPa on. Glass element (1) according to one of the preceding claims, characterized in that the glass element (1) has at least one cutout (40) in the form of a through opening, wherein the web (5) limits the cutout (40), wherein the sum of the areas of the cutout(s) (40) constitutes at least 40%, preferably at least 57%, in particular at least 65%, or in particular at least 65%, even in particular at least 73%, or even at least 82% of the area enclosed by the outer contour of the glass element (1). Glass element (1) according to one of the preceding claims, characterized in that the bottom surface (92) of the depression (9) has a regular arrangement of troughs (94). Glass element according to the preceding claim, characterized by at least one of the following features: - the recesses (94) are arranged in spaced-apart rows (35), wherein the recesses (94) within a row (35) have a uniform distance (36) and wherein the rows (35) are spaced uniformly apart from each other by a distance (37), - the recesses (94) are arranged in a hexagonal pattern. Glass element according to one of the two preceding claims, wherein at least one of the following features applies to the arrangement of the troughs (94): - the center-to-center distance of adjacent troughs (94) is on average at least 20 µm, preferably on average at least 25 µm, - the troughs (94) have an average center-to-center distance of at most 50 µm, preferably at most 40 µm, - the center-to-center distance of the troughs (94) within a row (35) is 0.5 to 2 times the row spacing (37), preferably 0.7 to 1.4 times, in particular 0.9 to 1.1 times the row spacing (37), - the center-to-center distance of adjacent troughs (94) is in the range of 25 µm to 35 µm, - the roughness of the bottom surface (92) for a measuring window of 370 x 370 µm ² is _Sq < 6 µm and _Sa < 6 µm. Glass element (1) according to one of the preceding claims, characterized in that the recess (9) is open on at least one side of the web (5) towards its wall surface (50). Glass element (1) according to one of the preceding claims, characterized by at least one of the following features: - the web (5) is connected at one end (51) to the remaining glass element (1), or is connected at both ends (52) to the remaining glass element (1) and forms a bridge, - several interconnected recesses (9, 91, 93) are present, which have different depths, - the glass element (1) has at least two recesses (9), one of which is inserted into one side surface (2), the other into the opposite side surface (3) of the glass element (1), - in the web (5), in particular in its section (7) with a width of less than 3 mm, a through-opening (8) with an etched side wall is arranged, which is connected to the recess (9). Composite element (4) with a glass element (1) having at least one recess (9) according to one of the preceding claims, wherein the glass element (1) according to one of the preceding claims is connected to a further element (6) such that the recess (9) is covered by a side surface (12) of the further element (6). Composite element (4) according to the preceding claim, characterized in that a cavity (41) is formed by a cutout (40) of the glass element (1) covered by the side surface (12) of the further element (6), wherein the recess (9) is open to the wall (50) which limits the cutout (40) and forms an access connecting the cavity (41). A method for producing a glass element (1) according to one of the preceding claims, wherein a starting element (10) made of glass is provided, and - the pulsed laser beam (27) of an ultrashort pulse laser (30) is directed onto one of the side faces (2, 3) of the starting element (10) and - is concentrated by a focusing optic (23) to an elongated focus in the starting element (10), wherein - the incident energy of the laser beam (27) generates a filament-shaped damage (32) in the volume of the starting element (10), wherein - the laser beam (27) is moved over the starting element (10) along a path corresponding to the contour (100) of the glass element (1), such that - filament-shaped damage (32) is generated side by side along this path, wherein - the contour (100) comprises a ridge (5) with a section (7) having a width of less than 3 mm, and wherein - with the ultrashort pulse laser (30) within this section (7) a plurality of further filament-shaped defects (33) are introduced, which terminate in the volume within the starting element (10), and wherein - the starting element (10) is exposed to an etching medium which expands the filament-shaped defects (32) so that they connect along the contour (100) and thereby form the glass element (1), and wherein the plurality of the filament-shaped defects (33) terminating in the volume within the starting element (10) connect by expansion and form a depression (9) in the rib (5) within the section (7), which has a width of less than 3 mm. Method according to the preceding claim, characterized in that the etching removal by the etching medium in the radial direction of the filament-shaped defects (33) is adjusted such that it is in the range of 0.5 to 1.5 times the distance between the filament-shaped defects 33. Method according to one of the two preceding claims, wherein the glass element (1) is formed from the starting element (10) by inserting filament-shaped damage (32) along one or more paths and subsequent etching, such that the glass element (1) has at least one cutout (40) which is bounded by the web (5). A method according to one of the three preceding claims, wherein the filament-shaped defects (33) for producing the depression (9) are inserted successively in several adjacent rows (35), the speed at which the laser beam (27) is moved over the output element (10), the repetition rate at which the ultrashort pulse laser (30) is operated, and a row spacing (37) between two adjacent rows (35) are selected such that at least one of the following features is present: - the spacing of adjacent filament-shaped defects (33) is on average at least 20 µm, preferably on average at least 25 µm, - the filament-shaped defects (33) have an average spacing of at most 50 µm, preferably at most 40 µm, - the spacing of the filament-shaped defects (33) within a row (35) is 0.5 to 2 times the row spacing. (37), preferably at 0.7 to 1.4 times, in particular at 0.9 to 1.1 times the row spacing (37) - the spacing of adjacent filamentous defects (33) is in the range of 25 µm to 35 µm. Method according to one of the preceding claims, characterized in that the laser beam (23) is focused such that at least 80% of the total intensity of the elongated focus lies within the axial region between the points at which the light intensity exceeds half the maximum value.