Method and apparatus for forming a hollow structure

Abstract

The invention relates to a method for forming a hollow structure (2) by machining a workpiece (1), preferably a substrate for an optical element, by means of pulsed laser radiation (3), the method comprising: forming an ablation front (4) by irradiating the material of the workpiece (1) with the pulsed laser radiation (3), wherein, during the irradiation, the pulsed laser radiation (3) is radiated into the workpiece (1) through a beam entry surface (1a) and is focused in a focus region (F); and flushing the ablation front (4) by arranging a free end (8) of a preferably flexible fluid line (7) in the region of the ablation front (4). In the method, in order to flush the ablation front (4), a fluid (6) is fed to the ablation front (4) through an intermediate space (9) between an outer side (10) of the fluid line (7) and a lateral surface (5) of the hollow structure (2) and is discharged from the ablation front (3) inside the fluid line (7). The invention also relates to an associated apparatus (20) for forming a hollow structure (2) by machining, the apparatus being designed in particular for carrying out the method.

Description

[0001] Stuttgart, December 1st, 2025 SZ00402PCT Rp / pt

[0002] Method and apparatus for forming a hollow structure

[0003] Reference to related registration

[0004] This application claims priority over German patent application DE 102024211939.3 of 13.12.2024, the entire disclosure content of which is incorporated by reference into this application.

[0005] Background of the invention

[0006] The invention relates to a method for forming a hollow structure by material removal from a workpiece, preferably a substrate for an optical element, using pulsed laser radiation, the method comprising: forming a removal front by irradiating the material of the workpiece with the pulsed laser radiation, wherein the pulsed laser radiation is irradiated into the workpiece through a beam entry surface and focused in a focus area, and rinsing the removal front by arranging a free end of a preferably flexible fluid line in the area of ​​the removal front.The invention also relates to a device for forming a hollow structure by material removal in a workpiece, preferably in a substrate for an optical element, by means of pulsed laser radiation, comprising: a laser fluid for generating the pulsed laser radiation, a focusing device for focusing the pulsed laser radiation in a focus area, a holder for receiving the workpiece, a scanner optic designed for irradiating the pulsed laser radiation onto a radiation entry side of the workpiece received by the holder and for moving the focus area, and a device for rinsing the.

[0007] 2024PF00878WO 01.12.25 SZ00402PCT Removal front comprising a preferably flexible fluid line with a free end for arrangement in the area of ​​the removal front.

[0008] Material removal from a workpiece, particularly through laser ablation using pulsed laser radiation, allows for the structuring of a workpiece's surface, for example, by adding surface textures or contours. Material removal can also be used to create hollow structures within the workpiece material. When creating these hollow structures using pulsed laser radiation, the workpiece material is typically largely transparent to the wavelength of the incident laser radiation.The pulsed laser radiation, for example in the form of a pulsed laser beam, especially an ultrashort pulse laser beam, is directed into the workpiece through a beam entry surface, propagates through the workpiece material, which is essentially transparent to the pulsed laser radiation, and is focused in a focal region. In this case, the workpiece material is often glass or a similar material, such as a glass-ceramic.

[0009] In material removal processes used to create a hollow structure, a material removal front is formed within the workpiece material by moving the focal area of ​​the pulsed laser beam, typically using a scanner optic. To create the hollow structure, the material removal front is moved through or within the workpiece. To support the ablation process, for example through cavitation, and / or to remove particles from the material removal front, it is typically necessary to flush the front. For this purpose, a fluid, usually a liquid, is introduced into and then removed from the material removal front to create a fluid flow within the area of ​​the material removal front.

[0010] 2024PF00878WO 01.12.25 SZ00402PCT W02023 / 0110816A2 describes a method for creating a hollow structure in a workpiece by material removal using pulsed laser radiation. In this method, a material removal front is formed, which, during the creation of the hollow structure, moves within the workpiece and is brought into contact with or flushed with a fluid. As the material removal front moves within the workpiece, the fluid is fed to it by a fluid supply that is at least partially inserted into the hollow structure. The fluid supply can have a flexible fluid line. To supply the fluid to the material removal front, the flexible fluid line, for example, in the form of a flexible hose, can have a nozzle at its free end, which is located in the area of ​​the material removal front, for the fluid to exit.

[0011] Supplying the fluid to the machining front via a fluid line is relatively easy to implement. However, if hollow structures with a comparatively small cross-section are to be introduced into the workpiece, this type of supply can prove problematic because the fluid line and nozzle fill a large portion of the hollow structure's cross-section. This results in a comparatively small remaining cross-section of the hollow structure through which the particle-laden fluid is to flow back and be discharged from the workpiece's interior. Consequently, the material removal process can be limited in terms of the usable removal mechanisms and the resulting process efficiency.

[0012] Object of the invention

[0013] The object of the invention is to provide a method and a device for producing a hollow structure by material removal machining, which facilitates or enables the removal of comparatively large removed particles from the machining front.

[0014] 2024PF00878WO 01.12.25 SZ00402PCT Subject of the invention

[0015] This problem is solved by a method of the type mentioned above, in which a fluid, preferably a liquid, is supplied to the removal front through an intermediate space between an outer surface of the fluid line and a lateral surface of the hollow structure of the removal front for rinsing the removal front and is discharged from the removal front within the fluid line.

[0016] According to the invention, it is proposed that the fluid of the ablation front is not supplied via a fluid line, as described in W02023 / 0110816A2, but rather discharged via the fluid line. The advantage of discharging the fluid and the ablation particles contained therein within the fluid line is the stability of the ablation process at comparatively low flow rates. Therefore, the necessary free surface area or the diameter of the space can be reduced to a minimum, and the diameter of the fluid line, in particular its inner diameter, can be maximized depending on the required flow rate. This type of flushing of the ablation front, in which the flow direction is reversed compared to the flushing of the ablation front described in W02023 / 0110816A2, offers advantages, especially for the removal of larger particles, e.g., in hollow structures with a comparatively small diameter.Clod-like erosion particles from the erosion front.

[0017] As described in detail in W02023 / 0110816A2, when forming the hollow structure, the pulsed laser radiation is directed through a beam entry surface into the workpiece, which is made of a material that is essentially transparent to the pulsed laser radiation. The pulsed laser radiation is focused in a focal area located at the ablation front. During irradiation, the pulsed laser radiation passes through the material of the workpiece.

[0018] 2024PF00878WO 01.12.25 SZ00402PCT The pulsed laser radiation typically first emerges from the workpiece material in the region of the ablation front, i.e. the pulsed laser radiation typically propagates between the beam entry surface of the workpiece and the ablation front within the workpiece material, with no cavity between the beam entry surface and the ablation front.

[0019] In one variant, the hollow structure has a diameter of 15 mm or less, preferably 3 mm or less, and particularly preferably 2 mm or less. As described above, discharging the fluid within the fluid line is particularly advantageous when the diameter of the hollow structure is comparatively small. The hollow structure may have a circular cross-section, but this is not mandatory. If the cross-section of the hollow structure does not have a circular geometry, the diameter of the hollow structure is understood to be the equivalent diameter, i.e., the diameter of a circle whose area corresponds to the non-circular cross-section of the hollow structure in this case. The hollow structure may, for example, consist of a temperature control channel or have one or more temperature control channels.

[0020] In another variant, at least one undercut is created in the workpiece during the formation of the hollow structure. When forming the hollow structure through material removal using pulsed laser radiation, a hollow structure with virtually any geometry can be created. Accordingly, the hollow structure can also have undercuts or undercut sections that do not run in a direct line of sight to the surface of the workpiece. For example, a first section of the hollow structure, which runs in a direct line of sight to a surface of the workpiece and is, for example, perpendicular or below a constant

[0021] 2024PF00878WO 01.12.25 SZ00402PCT If the angle to the surface is aligned, a second, undercut section emerges. It is understood that the hollow structure can have not just one, but a multitude of undercuts or undercut sections.

[0022] In one variant, the fluid is drawn into the fluid line at the free end during rinsing; that is, active suction occurs. In the simplest case, a suction effect can be created by reversing the pumping direction of a fluid supply, as described, for example, in W02023 / 0110816A2, so that the fluid does not exit the free end of the fluid line but is drawn into it. As the fluid is drawn into the free end of the fluid line, it can then flow towards the ablation front in the space between the outer surface of the fluid line and the outer surface of the hollow structure, thus generating the desired fluid flow in the area of ​​the ablation front.

[0023] In a further development, the fluid line has at least one external structure that supports the fluid line against the outer surface of the hollow structure. If the fluid is actively drawn in at the free end of the fluid line, contact between the free end of the fluid line and the material surrounding the hollow structure or the outer surface should be avoided, as otherwise advancement or guidance of the fluid line is not possible.

[0024] To prevent the free end of the fluid line from coming into contact with the material surrounding the hollow structure, it is advantageous for the fluid line to have at least one outer structure that serves to support the fluid line against the workpiece material. This outer structure can, for example, be in the form of a collar, ring, or similar feature extending from the outside of the fluid line to the outer surface of the hollow structure. The outer structure can be ring-shaped, but it is also possible for it to consist of three or more sections.

[0025] 2024PF00878WO 01.12.25 SZ00402PCT has struts or the like that are supported essentially at points on the outer surface of the hollow structure. The material of the outer structure can be a relatively flexible material that allows the fluid line to slide along the outer surface of the workpiece when being guided.

[0026] In a further development, the outer structure has at least one opening for the passage of fluid. As described above, the outer structure can be in the form of a collar, a ring, or the like, which surrounds the fluid conduit in a ring-like fashion. Openings, e.g., in the form of holes or the like, can be incorporated into the outer structure to allow fluid to flow through the space between the openings, while the fluid conduit is supported by the outer structure against the outer surface of the hollow structure.

[0027] In another variant, the workpiece is fully or partially immersed in the fluid contained in a fluid reservoir, and the fluid flows from the reservoir into the space between the outer surface of the fluid line and the outer surface of the hollow structure. In this variant, the fluid is typically actively drawn in at the free end of the fluid line. The fluid in the reservoir, however, is static; that is, no active fluid flow is generated within the reservoir. The fluid reservoir could be, for example, a basin or similar container into which the workpiece is fully or partially immersed.

[0028] In another variant, the hollow structure formed in the workpiece is sealed with a plug that has at least one opening through which the fluid flows into the space between the outer surface of the fluid line and the workpiece's outer surface. By providing a plug that seals the hollow structure during its manufacture, the complete or partial immersion of the workpiece in the fluid can be avoided.

[0029] 2024PF00878WO 01.12.25 SZ00402PCT can be omitted. Even in the case described here, the fluid can be drawn from a fluid reservoir without actively supplying the fluid. The fluid line, which serves to remove the fluid from the erosion front, typically also passes through the plug.

[0030] During further processing, the fluid is pumped through at least one opening into the space between the outer surface of the fluid line and the outer surface of the hollow structure. In this case, the fluid is actively fed into the space by creating overpressure using a pump or similar device to generate a fluid flow into the space. If the fluid is also actively extracted by being drawn into the fluid line, a particularly effective flushing of the ablation front can be achieved.

[0031] In another variant, the focus area is moved to form the ablation front, and the ablation front is moved within the workpiece to form the hollow structure. At the ablation front, material from the workpiece is removed across a surface. To form the ablation front for this surface material removal, the pulsed laser beam is moved along a motion pattern, as described, for example, in WO 2023 / 110816A2. The ablation front forms an interface between the workpiece material and the already formed part of the hollow structure. The surface of the already formed part of the hollow structure adjoins the ablation front, or more precisely, a boundary contour of the ablation front.

[0032] The movement of the hollow structure within the workpiece involves a relative movement between the pulsed laser radiation and the workpiece. For the movement of the ablation front within the workpiece, a slow movement of the workpiece, compared to the scanning movement, can be superimposed on the typically scanning movement of the laser beam used to create the ablation front. Alternatively, the ablation front can be moved...

[0033] 2024PF00878WO 01.12.25 SZ00402PCT by changing the position of the movement pattern within the scan field of a scanner optic that serves to move the pulsed laser radiation in the case of a stationary workpiece.

[0034] A further aspect of the invention relates to a device of the type mentioned at the outset, in which the device for flushing the ablation front is configured to supply the ablation front with fluid through a space between an outer surface of the fluid line and a lateral surface of the hollow structure, and to discharge the fluid from the ablation front within the fluid line. The device can be used in particular for carrying out the method described above and enables flushing of the ablation front by generating a fluid flow in the region of the ablation front.

[0035] In one embodiment, the device for rinsing the ablation front has a suction port at the free end of the fluid line for drawing in the fluid. The suction port serves to generate a vacuum that draws the fluid into the fluid line at the free end. To achieve the required flow rate for rinsing the ablation front, a pressure or pressure differential of several bar may be necessary for suction, even with a relatively small diameter of the hollow structure and the fluid line.

[0036] When using a flexible fluid line, e.g., in the form of a hose or similar, it must be ensured that the flexible fluid line does not collapse when a vacuum is applied. This can be achieved, for example, by appropriately stiffening the hose material without excessively impairing its flexibility.

[0037] In another embodiment, the fluid line has at least one external structure for support against the outer surface of the hollow structure. As described above, this is particularly important during fluid intake.

[0038] 2024PF00878WO 01.12.25 SZ00402PCT It is advantageous for the free end of the fluid line to not come into contact with the outer surface of the hollow structure and become stuck there, as this makes guiding the fluid line difficult. It is advantageous if the external support structure for the fluid line, or at least one of them, is located near the free end of the fluid line to prevent contact between the free end and the outer surface of the hollow structure.

[0039] In another embodiment, the outer structure has at least one opening for the passage of fluid. If the outer structure is annular and, for example, shaped like a ring or collar, it typically has several openings to allow the fluid to pass through to the removal front. If the outer structure is not annular and is supported, for example, by several radially extending struts, the fluid can pass through the spaces between the struts.

[0040] In a further embodiment, the device for rinsing the ablation front comprises a fluid reservoir, in particular a basin, for immersing the workpiece during rinsing of the ablation front. The fluid can flow from the fluid reservoir into the space between the outer surface of the hollow structure and the outside of the fluid line without the need for a pump or similar device.

[0041] In a further embodiment, the device for rinsing the ablation front has a plug for closing the hollow structure formed in the workpiece, the plug having at least one opening for the fluid to flow into the space between the outside of the fluid line and the workpiece's outer surface. In this embodiment,

[0042] 2024PF00878WO 01.12.25 SZ00402PCT The plug must be connected to a suitable fluid supply through which the fluid is supplied to the cavity. For this purpose, a double-walled hose can be used, for example: The inner hose can serve to drain the fluid from the cavity, and the outer hose can supply the fluid to the cavity via the at least one opening in the plug. The fluid supply can, for example, connect the cavity to a fluid reservoir, which is also part of the device.

[0043] In a further development of this embodiment, the device includes a pump for pumping the fluid into the space between the outer surface of the fluid line and the outer surface of the hollow structure via the opening of the plug. As described above in connection with the method, the fluid can thus be actively supplied to the ablation front.

[0044] It is understood that the device may include further components for flushing the machining front, for example, a tracking device that serves to guide the fluid line as the machining front moves within the workpiece. When using a flexible fluid line, the tracking device may, for example, include a roller or the like from which the fluid line is unwound.

[0045] In a further embodiment, the device comprises a positioning device for moving the machining front within the workpiece, wherein the positioning device is configured to move, preferably to displace, the workpiece and / or the scanner optics. For this purpose, the positioning device typically acts on the workpiece holder or on the housing of a machining head in which the scanner optics are arranged. The positioning device can have one or more drives, e.g., in the form of linear motors or the like, which in particular perform a superimposed movement or displacement of the workpiece.

[0046] 2024PF00878WO 01.12.25 SZ00402PCT The workpiece or scanner optics can be positioned in two or three different spatial directions. It is also possible for the positioning device to rotate the workpiece or scanner optics, or to generate a superimposed displacement and rotation of the workpiece or scanner optics.

[0047] For moving the ablation front within the workpiece, the workpiece can be stationary, and the scanner optics or a corresponding housing, which may also contain a device for adjusting the position of the focus area in the direction of the pulsed laser beam (e.g., a zoom lens), is moved over the workpiece by means of the positioning device. For this purpose, the positioning device can, for example, have a movable gantry to which the scanner optics are attached. By moving the gantry, the scanner optics, and thus the scan field, can be moved over the workpiece. It is understood that the movement, and in particular the displacement, of the scanner optics can also be combined with the movement, and in particular the displacement, of the workpiece.

[0048] Further features and advantages of the invention will become apparent from the following description of exemplary embodiments of the invention, with reference to the figures in the drawing, which show details essential to the invention, and from the claims. The individual features can be implemented individually or in any combination in a variant of the invention.

[0049] drawing

[0050] Examples of implementation are shown in the schematic drawing and are explained in the following description. It shows

[0051] 2024PF00878WO 01.12.25 SZ00402PCT Fig. 1 a schematic representation of a workpiece during the supply of a fluid to a machining front of a hollow structure by means of a fluid line,

[0052] Fig. 2 is a schematic representation analogous to Fig. 1, in which the fluid is drawn into the fluid line at a free end, as well as

[0053] Fig. 3a, b schematic representations analogous to Fig. 2, in which the fluid flows into an intermediate space between the hollow structure and an outer surface of the fluid line from a basin or is supplied to the intermediate space via a plug that closes the hollow structure.

[0054] In the following description of the drawings, identical reference symbols are used for identical or functionally equivalent components.

[0055] Fig. 1 shows a detail of a substrate 1 for an EUV mirror, which in the example shown is made of titanium-doped quartz glass. The EUV mirror is used in a projection lens of an EUV lithography system (not shown). During the manufacturing of the EUV mirror, a reflective coating is applied to one surface of the substrate 1, which is not shown in Fig. 1. The reflective coating serves to reflect radiation in the EUV wavelength range.

[0056] A material removal process using pulsed laser radiation is carried out on substrate 1, as described in the aforementioned WQ2023 / 0110816A2, which is incorporated in its entirety into this application by reference. Using this process, a hollow structure 2 in the form of a cooling channel is formed in substrate 1 in the example shown, which has a comparatively low,

[0057] 2024PF00878WO 01.12.25 SZ00402PCT constant diameter D on the order of a few or some

[0058] millimeters, where in the example shown: D = 2 mm.

[0059] In this process, the substrate 1 material is irradiated with pulsed laser radiation in the form of a pulsed laser beam 3, forming an ablation front 4 that longitudinally delimits the hollow structure 2, which forms the cooling channel, during its fabrication. The ablation front 4 can be, for example, a flat surface or a partially flat surface, forming an interface between the hollow structure 2 and the substrate 1 material. The hollow structure 2 is circumferentially bounded by a lateral surface 5, which, in the example shown, has a cylindrical shape.

[0060] The pulsed laser beam 3 enters the substrate 1 through a beam entry surface 3 and is focused within a focus region F in the substrate 1. In the example shown, the ablation front 4 is formed by moving the focus region F along the interface between the hollow structure 2 and the substrate 1. The hollow structure 2 is formed by moving the ablation front 4 within the workpiece 1.

[0061] The material ablated by the pulsed laser beam 3 is washed away with the aid of a fluid 6, which is supplied to the ablation front 4 via a fluid feed in the form of a flexible fluid line 7. The fluid 6 is represented in Fig. 1 by an arrow illustrating the flow direction of the fluid 6. The fluid 6 exits the flexible fluid line 7 at an opening at the end face of a free end 8. In the example shown, the fluid 6 is a liquid, more precisely water. However, another liquid or, if necessary, a gas can also be used as the fluid 6.

[0062] In the example shown in Fig. 1, the fluid 6 is conveyed via a space 9 between the outer surface 5 of the hollow structure 2 and an outer surface 10 of the

[0063] 2024PF00878WO 01.12.25 SZ00402PCT flexible fluid line 7 from the machining front 4. During material removal, elongated, slab-like material particles 11 can form at the machining front 4, which must be removed via the space 9 between the outer surface 5 of the hollow structure 2 and the outer surface 10 of the flexible fluid line 7. Due to the fact that the hollow structure 2 has a diameter D of approximately 2 mm in the example shown, the space 9 in Fig. 1 has a small radial extent, on the order of approximately 400 pm. The maximum particle size that can be removed from the machining front 4 via the space 9 without the material particles 11 becoming wedged and clogging the space 9 is therefore also on the order of approximately 400 pm. It is irrelevant along which main axis the 400 pm of the ablation particle 11 is exceeded.Therefore, needle-like abraded particles 11, which are broken out of the substrate 1 material, can particularly hinder efficient process control. The removal of larger abraded particles 11 from the abraded surface 4 is therefore problematic with the rinsing concept shown in Fig. 1.

[0064] Fig. 2 shows the substrate 1 from Fig. 1, in which, for rinsing the ablation front 4, the fluid 6 is not supplied to the ablation front 4 through the fluid line 7, but rather discharged from the ablation front 4 through the fluid line 7. In this way, the free diameter available for removing ablation particles 11 from the ablation front 4 is increased by more than 100%, since the inner diameter of the hose 7 is approximately 1 mm. Therefore, even lump-like ablation particles 11 with significantly larger dimensions than approximately 400 pm can be removed from the ablation front 4 within the hose 7.

[0065] The supply of fluid 6 to the removal front 4 can be carried out in different ways in the flushing concept described in connection with Fig. 2, as described below by way of example with reference to Fig. 3a, b.

[0066] 2024PF00878WO 01.12.25 SZ00402PCT, which shows a device 20 for producing the hollow structure 2 by material removal machining of the workpiece 1 using pulsed laser radiation 3, which includes a device 12 for rinsing the removal front 4.

[0067] The device 20 comprises a laser source 21 for generating the pulsed laser radiation 3 in the form of a pulsed laser beam, more precisely an ultrashort pulse laser beam. In the example shown, the laser source 21 serves to generate laser pulses with pulse durations in the picosecond range, e.g., less than 10 ps, ​​with peak pulse powers in the megawatt range. The device 20 also comprises a laser processing head 22, to which the pulsed laser beam 3 is fed. In the example shown, the laser processing head 22 comprises a scanner optic 23 and a focusing device 24.

[0068] The scanner optics 23 serve to direct the pulsed laser beam 3 onto the beam entry surface 1a of the substrate 1, which in the example shown is oriented perpendicular to the pulsed laser beam 3. The scanner optics 23 serve to move the focus area F within the substrate 1 in the X-direction and in the Y-direction of an XYZ coordinate system and, for this purpose, includes one or more scanner mirrors. For moving the focus area F in the Z-direction of the XYZ coordinate system, which is oriented perpendicular to the beam entry surface 1a and corresponds to the propagation direction of the pulsed laser beam 3, the scanner optics 23 includes a dynamic zoom lens. In the example shown, the focusing device 24 is designed as a telecentric F-theta lens to correct field curvature when the scanner mirror(s) are oriented differently.

[0069] The device 20 also includes a holder 25 for receiving the substrate 1, as well as a positioning device 26 that acts on the holder 25 to move the substrate 1. In the example shown, the positioning device 26 is configured to move the substrate 1 in all three spatial directions.

[0070] 2024PF00878WO 01.12.25 SZ00402PCT Positioning device 26 serves in the example shown to move the removal front 4 within the substrate 1, which is required to form the hollow structure 2.

[0071] The positioning device 26 can be configured to move the scanner optics 23, which projects the pulsed laser beam 3 onto the substrate 1, either as an alternative or in addition to doing so. For this purpose, the positioning device 26 can, for example, have a movable portal arranged above the substrate 1, to which the scanner optics 23 are attached. In this way, the scanner optics 23 can be moved across the substrate 1 in at least one spatial direction, typically in both directions X and Y. The positioning device 26 can also be configured to move, or in particular shift, the scanner optics 23 in the Z-direction perpendicular to the beam entry surface 1a.

[0072] Fig. 3a shows the substrate 1 with a hollow structure 2, which differs from the hollow structure 2 shown in Figs. 1 and 2 in that the hollow structure 2 has two sections oriented at an angle of 90° to each other. The first section runs parallel to the Z-direction, starting from an opening on the underside of the substrate 1, while the second, undercut section runs in the X-direction perpendicular to the first section. In this case as well, the flexible hose 7 can be guided along the ablation front 4 as it moves within the substrate 1. For this purpose, the device 12 has a tracking device (not shown) for guiding the hose 7. In the example shown, the device 12 has a suction device 13 in the form of a pump that draws in the fluid 6 at the free end of the hose 7.

[0073] To prevent the free end 8 of the hose 7 from coming into contact with the outer surface 5 of the hollow structure 2 and becoming stuck to it, the hose 7 has an outer structure on its outside 10 in the example shown.

[0074] 2024PF00878WO 01.12.25 SZ00402PCT 14 in the form of an annular collar, which serves to support the hose 7 on the outer surface 5 of the hollow structure 2 or as a spacer. To allow the fluid 6 to flow through the space 9 to the removal front 4, the outer structure 14 has several openings.

[0075] 15 for the fluid 6. It is understood that the outer structure 14 can also be designed in a manner other than that shown. The outer structure 14, more precisely its outer edge, slides along the outer surface 5 of the hollow structure 2 as the hose 7 is guided.

[0076] For the supply of the fluid 6 into the space 9, the device 12 in the example shown in Fig. 3a has a fluid reservoir in the form of a basin.

[0077] Basin 16, which is filled with fluid 6 and into which substrate 1 is partially immersed during material removal. The fluid 6 can flow from basin 16 into the space 9 without requiring an active fluid supply.

[0078] Fig. 3b shows a device 12 comprising a plug 17 that seals the hollow structure 2 in the substrate 1. A hose 7, which serves to drain the fluid 6 from the removal front 4 and is connected to a suction device 13 for this purpose, runs through a central opening in the plug 17. In the example shown in Fig. 3b, the plug 17, which seals the hollow structure 2 in a fluid-tight manner, has several openings 18 through which the fluid 6 enters the space 9. The device 12 also includes a pump 19 that allows the fluid 6 to flow into the space 9 via the openings 18. In the example shown, the pump 19 and the suction device 13 form a single unit. It may be possible to omit the suction device when actively supplying the fluid 6 to the removal front 4 via the space 9.

[0079] It goes without saying that the method described above is not limited to the production of hollow structures 2 in the form of temperature control channels,

[0080] 2024PF00878WO 01.12.25 SZ00402PCT but can be used to produce hollow structures of virtually any shape. In particular, the hollow structures do not need to be designed for fluid flow; that is, they can simply open at one end onto the outside of the substrate. Such hollow structures can, for example, serve to hold components or the like within the workpiece.

[0081] The workpiece in which the hollow structure is formed does not necessarily have to be a substrate for an optical element, such as a mirror or a transmitting optical element, e.g., in the form of a lens. Rather, the workpiece can also be an attachment of an optical element, for example, in the form of a bushing or the like.

[0082] The workpiece can also be a non-optical component, such as a wafer holder, a mask, or similar item. Such holders may be made entirely or partially from materials that can be machined in the manner described above, i.e., by ablation using pulsed laser radiation. The machined workpiece may be a component used in semiconductor manufacturing equipment, but this is not mandatory.

[0083] 2024PF00878WO 01.12.25 SZ00402PCT

Claims

Patent claims 1. Method for forming a hollow structure (2) by material removal from a workpiece (1), preferably a substrate for an optical element, using pulsed laser radiation (3), the method comprising: Forming a material removal front (4) by irradiating the material of the workpiece (1 ) with the pulsed laser radiation (3), wherein the pulsed laser radiation (3) is irradiated into the workpiece (1 ) through a beam entry surface (1a) and focused in a focus area (F), as well as Flushing the removal front (4) by arranging a free end (8) of a preferably flexible fluid line (7) in the area of ​​the removal front (4), characterized in that a fluid (6), preferably a liquid, is supplied through an intermediate space (9) between an outer surface (10) of the fluid line (7) and a lateral surface (5) of the hollow structure (2) of the removal front (4) for flushing the removal front (4) and is discharged from the removal front (4) within the fluid line (7).

2. The method according to claim 1, wherein the hollow structure (2) has a diameter (D) of 15 mm or less, preferably 3 mm or less, particularly preferably 2 mm or less.

3. Method according to claim 1 or 2, wherein at least one undercut is created in the workpiece (1) when forming the hollow structure (2).

4. Method according to one of the preceding claims, wherein the fluid (6) is drawn into the fluid line (7) at the free end (8) during rinsing. 2024PF00878WO 01.12.25 SZ00402PCT 5. Method according to one of the preceding claims, wherein the fluid line (7) has at least one outer structure (14) with which the fluid line (7) is supported on the outer surface (5) of the hollow structure (2).

6. Method according to claim 5, wherein the outer structure (14) has at least one opening (15) for the passage of the fluid (6).

7. Method according to any one of claims 1 to 6, wherein the workpiece (1 ) is wholly or partially immersed in the fluid (6) located in a fluid reservoir (16) and the fluid (6) flows from the fluid reservoir (16) into the space (9) between the outer surface (10) of the fluid line (7) and the outer surface (5) of the hollow structure (2).

8. Method according to any one of claims 1 to 6, wherein the hollow structure (2) formed in the workpiece (1 ) is closed with a plug (17) having at least one opening (18) through which the fluid (6) flows into the space (9) between the outside (10) of the fluid line (7) and the outer surface (5) of the workpiece (1 ).

9. Method according to claim 8, wherein the fluid (6) is pumped through the at least one opening (18) into the space (9) between the outside (10) of the fluid line (7) and the outer surface (5) of the hollow structure (2).

10. Method according to one of the preceding claims, wherein the focus area (F) is moved to form the removal front (4) and wherein the removal front (4) is moved within the workpiece (1) to form the hollow structure (2).

11. Device (20) for forming a hollow structure (2) by material removal in a workpiece (1), preferably in a substrate for an optical element, using pulsed laser radiation (3), in particular for 2024PF00878WO 01.12.25 SZ00402PCT Carrying out the method according to one of the preceding claims, comprising: a laser source (21) for generating the pulsed laser radiation (3), a focusing device (24) for focusing the pulsed laser radiation (3) in a focus area (F), a holder (25) for receiving the workpiece (1), a scanner optic (23) for irradiating the pulsed laser radiation (3) is designed for a radiation entry side (1a) of the workpiece (1) received by the holder (25) and for moving the focus area (F), and a device (12) for rinsing the ablation front (4), which comprises a preferably flexible fluid line (7) with a free end (8) for arrangement in the area of ​​the ablation front (4), characterized in that the device (12) is designed for rinsing the ablation front (4), supplying the fluid (6) to the ablation front (4) through an intermediate space (9) between an outer surface (10) of the fluid line (6) and a lateral surface (5) of the hollow structure (2) and discharging it within the fluid line (7) from the ablation front (4).

12. Device according to claim 11, wherein the device (12) for rinsing the removal front (4) has a suction (13) for drawing in the fluid (6) at the free end (8) of the fluid line (6).

13. Device according to claim 11 or 12, wherein the fluid line (6) has at least one outer structure (14) for support on the outer surface (5) of the hollow structure (2).

14. Device according to claim 13, wherein the outer structure (14) has at least one opening (15) for the passage of the fluid (6). 2024PF00878WO 01.12.25 SZ00402PCT 15. Device according to one of claims 11 to 14, wherein the device (12) for rinsing the removal front (4) further comprises: a liquid reservoir, in particular a basin (16), for immersing the workpiece (1) when rinsing the removal front (4).

16. Device according to one of claims 11 to 14, wherein the device (12) for rinsing the removal front (4) further comprises: a plug (17) for closing the hollow structure (2) formed in the workpiece (1), wherein the plug (17) has at least one opening (18) for the fluid (6) to flow into the space (9) between the outside (10) of the fluid line (7) and the outer surface (5) of the workpiece (1).

17. Device according to claim 16, wherein the device (12) for rinsing the removal front (4) further comprises: a pump (19) for pumping the fluid (6) into the space (9) between the outside (10) of the fluid line (7) and the lateral surface (5) of the hollow structure (2) via the at least one opening (18) of the plug (17).

18. Device according to one of claims 11 to 17, further comprising: a positioning device (26) for moving the removal front (4) within the workpiece (1), wherein the positioning device (26) is designed for moving, preferably for displacing, the workpiece (1) and / or the scanner optics (23). 2024PF00878WO 01.12.25 SZ00402PCT

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