Method and device for flushing an abrasion front

Abstract

The invention relates to a method for flushing an ablation front (4) on a hollow structure (2) formed by material-removing machining in a workpiece, preferably in a substrate for an EUV mirror, comprising: supplying a fluid (6) to the ablation front (4) by means of a preferably flexible fluid supply (7). In the method, the fluid supply (7) for supplying the fluid (6) to the ablation front (4) and / or for removing the fluid (6) from the ablation front (4) has at least one outer structure that is periodic in at least one spatial direction, preferably a helical outer structure (9a, b). The invention also relates to an associated device for flushing an ablation front (4).

Description

Background of the invention

[0001] The invention relates to a method for flushing an ablation front at a hollow structure formed by material-removing, typically contactless machining in a workpiece, preferably in a substrate for an EUV mirror. The method comprises: supplying a fluid to the ablation front by means of a preferably flexible fluid supply. The invention also relates to a device for flushing an ablation front at a hollow structure formed by material-removing, typically contactless machining in a workpiece, preferably in a substrate for an EUV mirror, comprising: a preferably flexible fluid supply for supplying a fluid to the ablation front. The material of the workpiece is typically glass or a glass-ceramic.

[0002] WO 2023 / 110816 A2 describes a method for creating a hollow structure in a workpiece in the form of a substrate for a mirror by material-removing machining using pulsed laser radiation. In this method, an ablation front is formed which, during the creation of the hollow structure, is moved within the workpiece and brought into contact with a fluid or rinsed with a fluid. The fluid is used to transport the ablation products generated during the material-removing machining away from the ablation front by means of a permanent fluid flow in sufficient concentration, thus ensuring homogeneous ablation. During the movement of the ablation front in the workpiece, the fluid is guided along the ablation front by means of a fluid supply which is introduced at least partially into the hollow structure. The fluid supply can have a flexible fluid line.

[0003] The hollow structure through which the flexible fluid line is routed to flush the ablation front can have bends and / or curves to achieve optimal performance when a temperature control medium, for example in the form of water, flows through it during operation of the EUV mirror. The cross-sections of hollow structures designed as temperature control channels are usually on the order of a few millimeters. The flexible, typically tubular fluid lines that are inserted into such temperature control channels require sufficient rigidity to be conveyed longitudinally. The fluid lines must also typically be flexible enough to be routed through any bends and curves present in the hollow structure.Any curvature, as well as the length and roughness of the cooling channels, poses a challenge for the tracking of the flexible fluid line, as it can cause kinking, jamming, or damage to the flexible fluid line. This can lead to insufficient purging of the removal front and possibly forced process interruptions or component damage.

[0004] For the reasons mentioned above, it has proven difficult to guide the fluid supply, especially in the form of a flexible fluid line, along the ablation front within the workpiece. If the fluid supply not only supplies the fluid to the ablation front but also removes it from the ablation front, the fluid supply can become clogged by larger ablation products, such as slugs or the like. Object of the invention

[0005] The object of the invention is to improve the efficiency and / or reliability of a method and a device for flushing an abrasion front. Subject of the invention

[0006] According to a first aspect, this object is achieved by a method of the type mentioned at the outset, in which the fluid supply for supplying the fluid to the removal front and / or for removing the fluid from the removal front has at least one outer structure which is periodic in at least one spatial direction, preferably a helical outer structure.

[0007] The inventors have recognized that a fluid supply with an outer structure that is periodic in at least one spatial direction, in particular with a helical outer structure, can be guided more easily along the removal front than is the case with a fluid supply designed in the manner of a hose with a smooth outer geometry or a smooth outer surface. Furthermore, the at least one outer structure that is periodic in at least one spatial direction can be used to supply the fluid to the removal front and / or to guide the fluid away from the removal front.

[0008] In one variant, the fluid supply has a preferably solid core which is surrounded by the at least one periodic outer structure. The core, which can be designed, for example, in the manner of a rigid wire or possibly in the form of a hose or the like, can serve as a stable basic framework which simplifies the introduction of the fluid supply into the hollow structure and improves it compared to a flexible fluid line without such a basic framework. The periodic, in particular helical, outer structure likewise simplifies or improves the tracking or introduction of the fluid supply into the hollow structure. The use of a helical outer structure enables, in particular, the fluid supply to be screwed into the hollow structure.

[0009] In a further development of this variant, the core is surrounded by at least two periodic outer structures, with which the fluid is supplied to the ablation front and removed from the ablation front. In this case, the fluid is not guided within the core; rather, the fluid is supplied to the ablation front and also removed from the ablation front with the aid of the at least two periodic, in particular helical, outer structures. The fluid supply can, in particular, have precisely two helical outer structures that form a double helix and enable a separation between the supply and removal of the fluid.

[0010] In a further development of this variant, the helical outer structures are web-shaped and separate at least a first helical channel, via which the fluid is supplied to the removal front, from at least a second helical channel, via which the fluid is discharged from the removal front. Two or more helical, i.e. screw-shaped, wound channels can be separated from one another by the web-shaped helical or spiral outer structures, in order to separate the fluid supplied to the removal front from the fluid discharged from the removal front. The helical channels between the web-shaped helical outer structures can be closed off from the environment by a casing on the outside of the fluid supply, but this is not absolutely necessary. The web-shaped helical outer structures can be made from a plastic material, for example.

[0011] In a further development, the helical channels are open to the outside of the fluid supply and are preferably laterally delimited by a lateral surface of the hollow structure when supplying the fluid to the removal front and when removing the fluid from the removal front. In this case, the circumferential lateral surface of the hollow structure, which in this case is typically designed in the manner of a channel, forms the lateral boundary of the helical channels. The web-shaped helical outer structures lie against the lateral surface of the hollow structure or are slightly spaced from it. Supporting the fluid supply on the lateral surface of the hollow structure simplifies tracking. In this case, the fluid supply is preferably guided along the removal front in the form of a combination of a feed and a rotational movement.

[0012] In an alternative development, the periodic external structures are designed as fluid lines through which the fluid is supplied to the removal front and discharged from the removal front. In this case, at least two external structures conducting the fluid, typically in the form of flexible hoses, for example in a multiple helix shape, in particular in a double helix shape, are wound around the rigid core of the fluid supply. The fluid supply with the helical external structures has a diameter that is typically slightly smaller than the diameter of the hollow structure, which in this case is generally designed in the form of a channel. The fluid supply can be supported on the lateral surface of the hollow structure via the periodic, in particular helical, external structures in the form of the fluid lines, which simplifies the tracking of the fluid supply.

[0013] In a further alternative development, the fluid is supplied to the removal front in the core and removed from the removal front via the at least one periodic outer structure, or vice versa. In this case, the fluid, usually in the form of fresh water, is typically supplied to the removal front through the hollow, usually flexible core of the fluid supply. The periodic, in particular helical, outer structure of the fluid supply is used to remove the fluid and removed material. This distinguishes the fluid supply from a flexible fluid line in the form of a double-walled hose, which has two chambers for supplying the fluid to the removal front and removing it from the removal front.

[0014] In a further development of this variant, the at least one periodic outer structure is web-shaped, and the fluid is discharged from the removal front in at least one helical channel between the core of the fluid supply and a lateral surface of the hollow structure, wherein the fluid supply is preferably rotated in the hollow structure to discharge the fluid. By rotating the fluid supply and thus also the helical channel, fluid, typically in the form of wastewater and removal material, can be actively conveyed away from the removal front in the manner of an Archimedean screw. The number of periodic, preferably helical, outer structures or helical channels can be selected practically freely and partially determines the return transport behavior of the fluid.

[0015] The rotary motion allows for mechanical comminution of the abrasive products, reducing the risk of clogging the fluid supply. For example, a threaded drive can be used to rotate the fluid supply, which rotates the fluid supply in idle mode without causing any feed.

[0016] In a further variant, the fluid supply is guided along the removal front by means of a threaded drive that engages the at least one helical outer structure. As described above, the threaded drive can be used in idle mode to rotate the fluid supply within the hollow structure, thus actively recirculating the fluid.

[0017] With the threaded drive, which is not operated in idle mode, the fluid supply can be advanced within the hollow structure to track the fluid supply to the removal front. A threaded drive enables precise insertion and tracking of the fluid supply, as well as precise position determination of the fluid supply within the workpiece. Furthermore, the tracking unit, or the unit used for this purpose, requires very little installation space. At the same time, the threaded drive can implement automatic rotation of the fluid supply and a back-slip protection.

[0018] A further aspect of the invention relates to a device of the type mentioned above, in which the fluid supply for supplying the fluid to the removal front and / or for removing the fluid from the removal front has at least one external structure that is periodic in at least one spatial direction, preferably a helical external structure. The fluid supply typically also has a tracking device that enables the fluid supply to be automatically tracked to the respective removal front. For this purpose, the tracking device generally has at least one drive.

[0019] In one embodiment, the fluid supply has a preferably solid core which is surrounded by the at least one periodic outer structure.

[0020] In a further development of this embodiment, the core is surrounded by at least two periodic outer structures designed to supply the fluid to the removal front and to discharge the fluid from the removal front. The helical outer structures are preferably web-shaped and separate at least one first helical channel, which serves to supply the fluid to the removal front, from at least one second helical channel, which serves to discharge the fluid from the removal front. In particular, the helical channels can be open on the outside of the fluid supply. In this case, the helical channels can be laterally delimited by a lateral surface of the hollow structure when supplying the fluid to the removal front and when discharging the fluid from the removal front.

[0021] In an alternative development, the periodic external structures are designed as fluid lines which serve to supply the fluid to the removal front and to remove the fluid from the removal front.

[0022] In a further alternative development, the device is designed to supply the fluid to the removal front via the core and to discharge the fluid from the removal front by means of the at least one periodic outer structure, or vice versa. The at least one periodic outer structure is preferably web-shaped in order to discharge the fluid from the removal front in at least one helical channel between the core of the fluid supply and a lateral surface of the hollow structure. The device is designed, in particular, to rotate the fluid supply in the hollow structure to discharge the fluid and has a suitable drive for this purpose.

[0023] In a further embodiment, the device comprises a threaded drive configured to engage the at least one helical outer structure in order to guide the fluid supply along the removal front. As described above in connection with the method, the threaded drive can be used in idle mode to rotate the fluid supply in the hollow structure and thus actively recirculate the fluid.

[0024] Instead of the periodic, particularly helical, outer structure described above, the fluid supply may optionally have other suitable outer structures or contours that improve the introduction into the hollow structure or the tracking to the removal front. For this purpose, other measures than providing outer contours on the fluid supply may also be implemented, which may be used alternatively or additionally in the method described above.

[0025] For example, by means of the particularly flexible fluid supply, a fluid flow can be directed onto a lateral surface of the hollow structure, which preferably exits the fluid supply at several outlet openings on the lateral side, or more precisely, from a jacket of the fluid supply. By directing a fluid flow onto the lateral surface of the hollow structure, which can exit simultaneously in the form of several partial flows from several outlet openings, the fluid supply can center itself in the hollow structure - particularly in the form of a temperature control channel. This is particularly the case when the fluid flow or the partial flows exiting the respective outlet openings exit radially with respect to a center of the fluid supply. In this way, the fluid supply can typically be prevented from getting caught on the lateral surface or on the walls of the hollow structure, similar to what is the case with a hydrodynamic plain bearing.This increases the robustness of the rinsing process and reduces the number of manual interventions required. Process interruptions can also generally be avoided, and a lower error rate, especially a lower scrap rate, can be achieved during the production of the hollow structure.

[0026] The shell-side outlet openings are preferably formed adjacent to a head end or an outlet end of the fluid supply, at which the fluid exits the front side toward the removal front. The additional fluid flow, which is directed toward the shell surface of the hollow structure, improves the self-positioning of the fluid supply within the cross-section of the hollow structure.

[0027] The outlet openings are usually created in the form of targeted perforations in the casing of the fluid supply in order to push the fluid supply away from all walls of the hollow structure, which is usually designed in the form of a channel. A sensible minimum number of outlet openings is four in order to cover all four quadrants of the channel cross-section. The geometry of the outlet openings can be freely selected; for example, they can be circles or cylinders, ellipses or cones, slots, etc. The partial streams of the fluid flow preferably exit the outlet openings at equal azimuthal intervals to facilitate centering. It is understood that the fluid flow exiting through the outlet openings should influence the fluid flow directed towards the ablation front as little as possible.To achieve this, the outlet openings must be dimensioned to ensure adequate irrigation of the ablation front and allow for sufficient backflow of the ablation products. The applicable pressures and flow rates must be taken into account.

[0028] It is not absolutely necessary for all outlet openings that generate the fluid flow directed toward the lateral surface to be arranged at the same distance from the front end of the fluid supply. For example, multi-stage perforations or outlet openings are possible, e.g., a first group of small outlet openings near the outlet end of the fluid supply and a second group of larger outlet openings at a greater distance from the outlet end of the fluid supply. The outlet openings of a respective group can, in particular, be arranged at the same distance from the outlet end of the fluid supply, e.g., along a circumferential ring on the lateral surface.

[0029] The fluid flow or the partial flows of the fluid flow can be directed perpendicular to the fluid supply, more precisely to its circumference or shell, or away from the removal front onto the shell surface of the hollow structure. In the latter case, the fluid flow is directed away from an end of the fluid supply adjacent to the removal front, i.e. the fluid flow exits at an obtuse outflow angle (> 90°) with respect to the end of the fluid supply adjacent to the removal front. If the outlet openings are installed at an obtuse outflow or inclination angle, both the advance of the fluid line and the return flow of the fluid from the removal front can be specifically supported. The fluid flow directed towards the removal front, which typically exits at the head end of the fluid supply, generally has a larger volume flow than the fluid flow directed towards the shell surface of the hollow structure.

[0030] It is also possible for the flexible fluid supply to be designed in the form of a double-walled or multi-lumen hose, i.e., a hose with multiple chambers. Instead of taking the fluid for the fluid flow directed toward the lateral surface from the main chamber, thereby disrupting the fluid flow directed toward the ablation front, the fluid used to stabilize the fluid supply is guided through an outer or secondary chamber. At the end of the hose, the transition between the outer and inner chambers can be freely designed, ensuring that the primary function of flushing is still maintained and can be optimized for the ablation front.

[0031] Another option for implementing the outlet openings is to attach a generally rigid end cap in the form of a nozzle or sleeve to the end of the flexible fluid supply line, into which the outlet openings are inserted to direct the fluid flow onto the lateral surface. The nozzle or end cap can be manufactured, for example, using a 3D printing process, particularly by 2-photon polymerization, which enables the production of very fine and small components. To optimize flow at the ablation front and to stabilize the fluid supply in the cavity, the nozzle or end sleeve can be attached to the end of a flexible hose. This solution is also applicable to the multi-lumen hoses described above.

[0032] The perforations or exit openings can be introduced into the generally flexible material of the sheath in a variety of ways. One possibility is to perform a laser ablation process, in which the diameter of the exit openings can be selected virtually freely. In this case, the angle of inclination of the exit openings can be specified using a suitable mount. In addition to a conventional scanner lens setup, drilling optics, such as a helical drilling optic or a trepanning optic, can be used to perform the laser ablation process. An optical setup using an axicon is also possible.

[0033] Another - much simpler - manufacturing method is based on a cigar cutter, in which the outlet openings are created by mechanically punching, cutting, or scoring the jacket. Instead of a blade like in a cigar cutter, in this case needles or cutting edges can be located on a ring of a corresponding device, which, when a suitable mechanism is actuated, mechanically remove the hose substrate. The removal can be carried out by cutting or abrasion. To fix the flexible fluid supply or the jacket, a ring holder with corresponding openings for aligning the needles or cutting edges can be used. Another holding element can be inserted into the head end of the flexible fluid line to protect the hose jacket from kinking when the cutting edges or needles penetrate, as the holding element significantly increases the rigidity of the jacket. The ring with the cutting edges orNeedles can also be designed in such a way that the needles insert the outlet openings into the hose surface at the appropriate outflow angle.

[0034] The options described above for inserting or attaching the outlet openings to the fluid supply are generally applicable to any type of flushing hose substrate.

[0035] The outlet openings described above or the fluid flow directed towards the lateral surface generally only enable the fluid supply in the hollow structure to be stabilized in the case of hollow structures that have a comparatively small diameter, as is typically the case when they are intended for the flow of a temperature control fluid. However, it is also possible for the hollow structure or part of the hollow structure to be a cavity that serves a different purpose, for example to dampen mechanical stresses exerted on the substrate by add-on parts, e.g. bushings or the like, which are attached to the rear side of the substrate, for example. In this way, the mirror surface provided on the front side of the substrate can be protected from the mechanical stresses being pushed through.

[0036] This generally requires that the cavity, viewed from above, completely conceals any interfering contours, such as a bonded bushing on the rear side. To create such a generally large-volume cavity in the substrate, access to the cavity is required, i.e., a connection to one side of the substrate. A hollow structure such as a channel, such as that used in a temperature control channel for the flow of a temperature control fluid, can be used as access. Both the channel-shaped access and the large-volume cavity can be created using the material removal method described above.

[0037] Since the hollow structure in this case requires only one access, this serves both as an inlet for supplying the rinsing fluid or the corresponding fluid supply into the hollow structure and for the outflow of the rinsing fluid and the ablation products from the hollow structure. Since the hollow structure or the large-capacity cavity, as described above, should conceal the entire interference contour on the outside of the substrate, it is necessary for the hollow structure to expand laterally from a channel-shaped section with a diameter of usually a few millimeters to a few tens of mm. At the ablation front, which is formed during the production of such a hollow structure, the ablation products must also be transported away and removed from the cavity or hollow structure in the large-volume, flat cavity across the entire width and height of the ablation front, which corresponds to the width and height of the cavity in a respective cross-section.

[0038] For flushing such a large-volume cavity with a correspondingly large-area removal front, the typically used fluid supply systems in the form of flexible hoses are not readily suitable. It is therefore advantageous or necessary to modify the fluid supply system to enable flushing of removal fronts in large-volume cavities without creating inhomogeneities or damage to the substrate. Various options exist for this purpose: In a method for forming a hollow structure having a large-volume cavity and a channel-shaped access to the large-volume cavity by material-removing machining of a workpiece, preferably a substrate for an EUV mirror, in one variant of an ablation front formed in the large-volume cavity, a fluid is simultaneously supplied via several, preferably flexible, fluid feeds guided in the channel-shaped access and extending into the large-volume cavity.

[0039] In this variant, a fluid is supplied to the removal front in the large-volume cavity via several fluid supplies that are guided simultaneously in the channel-shaped access. The fluid supplies can be guided in the channel-shaped access in the manner of a bundle. To flush the removal front, the fluid supplies protrude into the large-volume cavity with their outlet ends. In order to flush the removal front as homogeneously as possible, the outlet ends of the fluid supplies in the cavity are aligned to different positions of the removal front. In this variant, it is necessary to select the diameter of the channel-shaped access to the large-volume cavity so that several flexible fluid supplies, particularly in the form of an array of fluid supplies, can be guided through the channel-shaped access into the large-volume cavity.

[0040] In an alternative variant, a fluid is supplied to the removal front in the large-volume cavity via an outlet end of the fluid supply, said fluid having a flat jet nozzle or an adjustable nozzle. The nozzle can be attached to the flexible fluid supply, for example, in the manner of an attachment or the like. In the case of a flat jet nozzle, the fluid can be optimally distributed in the cavity in order to completely rinse a substantially flat removal front if the outlet end of the flat jet nozzle is positioned at a sufficient distance from the removal front. An adjustable nozzle makes it possible to vary the jet properties of the fluid stream, which is directed onto the removal front. For example, the opening angle of the fluid stream can be changed using an adjustable nozzle.In this case, one and the same fluid supply can be used to create the channel-shaped access and the large-volume cavity, provided the opening angle of the fluid flow is selected to be comparatively small in the channel-shaped access and comparatively large in the large-volume cavity to flush the removal front. In this way, a concentrated fluid flow directed forward can be generated in the channel-shaped access, and a broad flushing of the cavity volume can occur in the large-volume cavity. For example, a variable flushing head can be used as a variable nozzle, such as those used—in a correspondingly modified form—in the form of sprayers for watering gardens or the like.

[0041] In a further variant, an outlet-side end of the fluid supply introduced into the large-volume cavity is preferably moved in an oscillating manner in order to supply the fluid to different positions of the removal front. In this variant, the flexible fluid supply or the nozzle described above is moved within the large-volume cavity and performs defined, in particular oscillating movements in order to flush the entire removal front. Through the defined, in particular oscillating movement, each position of the removal front is flushed from time to time, but there is no constant flushing of the entire removal front with a fluid. In the event that the large-volume cavity is a cavity with a planar cross-section that has a significantly greater width than height, the oscillating movement can take place in one plane.However, it is also possible for the outlet end of the fluid supply to perform a three-dimensional oscillating movement in the cavity in order to flush different positions of the removal front one after the other.

[0042] In a further variant, the fluid supply has at least one outlet unit for the fluid at its outlet end, which is moved, preferably pivoted, into an extended position upon introduction into the cavity in order to supply the fluid to the removal front. In this variant, the outlet unit is in a retracted position during the arrangement of the outlet end of the fluid supply in the channel-shaped access and is only moved or pivoted into the extended position when the outlet end of the fluid supply is located within the large-volume cavity.

[0043] The outlet unit can, for example, be designed as an attachment attached to the outlet end of the fluid supply. In the retracted position, typically no fluid emerges from the outlet unit, i.e., the fluid supply is used in the channel-shaped access like a conventional fluid supply. Only when the outlet end of the fluid supply has been inserted into the large-volume cavity is the outlet unit moved into the extended position, and the fluid is supplied to the removal front via the outlet unit, i.e., the flushing behavior of the fluid supply is changed.

[0044] The supply of fluid to the removal front via the outlet unit(s) generally occurs in addition to the outlet of the fluid from a front end of the fluid supply. In the extended position, the at least one outlet unit is preferably aligned at a predetermined, generally acute outflow angle to the center of the fluid supply in order to align the fluid with the removal front. The outlet unit(s) or the corresponding flushing head only unfolds in the cavity in order to flush a larger part of the removal front than would be possible with the outlet end of the fluid supply without the use of the outlet unit(s). Depending on the type of mechanism that causes the movement of the outlet unit(s), it may not be possible to move the outlet unit(s) from the extended to the retracted position. Pulling the fluid supply out of the cavity or from the hollow structure may therefore be necessary.This is not possible without damaging the outlet unit(s) or the fluid supply. Therefore, the outlet unit or the entire fluid supply may be a disposable product in this case.

[0045] In all variants described above, the flushing of the removal front can be coupled with process monitoring in order to be able to detect errors promptly and, if necessary, correct them.

[0046] The material removal machining of the workpiece is typically carried out in a process tank containing the fluid, or more precisely a liquid, into which the workpiece is fully or partially immersed for material removal. The process tank is typically supplied with the rinsing fluid, usually water, hereinafter also referred to as process water, using a first pump that pumps the rinsing fluid into the process tank. For this purpose, the first pump can take the water from a tank and pump it through a filter or the like, possibly in conjunction with a cooling system, into the process tank. Part of the water that has been pumped through the filter is pumped back into the tank via a bypass line.

[0047] Since the water in the process tank absorbs the ablation products, it is necessary to drain the process water from the process tank or to replace it. This can be achieved using a second pump, which returns a portion of the process water from the process tank to the tank in order to create a closed process water circuit. However, returning the process water from the process tank to the tank is problematic, as the process tank may run dry and thus air is sucked into the hose system of the second pump. This places special demands on the second pump, which is met by using a peristaltic pump. However, using a peristaltic pump poses the problem that the particles introduced into the process water during abrasive machining, particularly in the form of glass particles, can destroy the flexible hose used for the return. This leads to increased maintenance effort and, where appropriate,Process water leakage. If this defect is not detected in time, it will result in the process tank overflowing and possibly damaging the equipment used to perform the material removal process. Overflowing of the process tank can also occur if the first pump, i.e., the process water pump, is active and, for some reason, the second pump, i.e., the recirculation pump, is not active.

[0048] To avoid the problems described above, the second pump can be integrated into the bypass line to return a portion of the process water pumped by the first pump and can be designed as a water jet pump or a Venturi pump. The water jet pump is used to suck in the process water from the process tank via an intake pipe. The water jet pump has no moving parts, is low-maintenance, and is not prone to failure. The water jet pump in the bypass line is also coupled to the pumping output of the first pump. Therefore, it is not possible for the first pump to be running while the second pump is not active. An overflow of the process water in the process tank can therefore only occur if the return hose or the intake hose of the second pump, in the form of the water jet pump, is blocked.Another advantage of the water jet pump in the bypass line is that it does not require separate control. The passive process water recirculation described here requires a bypass line with a sufficiently large flow rate to drain the process water from the process tank.

[0049] 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 of the drawing, which illustrate details essential to the invention, and from the claims. The individual features can be implemented individually or in combination in a variant of the invention. drawing

[0050] Examples of embodiments are shown in the schematic drawing and are explained in the following description. Fig. 1 a schematic representation of a flexible fluid supply that follows a removal front in a tempering channel, Fig. 2a,b schematic representations of a fluid supply which has web-shaped helical outer structures for supplying and discharging the fluid, Fig. 3a,b schematic representations of a fluid supply system which has two helical outer structures in the form of fluid lines for supplying and discharging the fluid, Fig. 4a,b are schematic representations of a fluid supply system having a hollow core for supplying the fluid to the removal front and one or more helical outer structures for removing the fluid from the removal front, Fig. 5a-d are schematic representations of a fluid supply system having outlet openings or perforations for directing a fluid flow onto the surface of the temperature control channel, Fig. 6 a schematic representation of a device for producing the perforations by laser ablation, Fig. 7a,b schematic representations of a device for producing the perforations by mechanical processing, Fig. 8 a schematic representation of a substrate with a hollow structure having a large-volume cavity and a channel-like access, Fig. 9a-e schematic representations of fluid feeds for flushing a removal front formed in the large-volume cavity, as well as Fig. 10a,b schematic representations of a device for supplying and discharging process water to and from a process tank.

[0051] In the following description of the drawings, identical reference symbols are used for identical or functionally identical components.

[0052] Fig. Figure 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 manufacture of the EUV mirror, a reflective coating is applied to a surface of the substrate 1, which Fig. 1 is not shown. The reflective coating serves to reflect radiation in the EUV wavelength range.

[0053] A method for material-removing machining is performed on the substrate 1, as described in WO 2023 / 110816 A2 cited above, which is incorporated by reference in its entirety into this application. This method forms a hollow structure 2 in the form of a temperature control channel in the substrate 1. The hollow structure 2 has a comparatively small, constant diameter on the order of a few millimeters.

[0054] In this process, the material of the substrate 1 is irradiated with a pulsed laser beam 3, forming an ablation front 4 that defines the hollow structure 2 in the form of the temperature control channel in the longitudinal direction during its manufacture. The ablation front 4 is formed as a plane or a flat surface that represents an interface between the hollow structure 2 and the material of the substrate 1. The hollow structure 2 is circumferentially delimited by a lateral surface 5, which has a cylindrical shape in the example shown.

[0055] The material removed by the pulsed laser beam 3 is flushed away with the aid of a fluid 6, which is supplied to the removal front 4 by means of a fluid supply in the form of a flexible fluid line 7. For this purpose, the fluid line 7 is guided along the removal front 4, as shown in Fig. 1 is indicated by an arrow. The fluid 6 exits the flexible fluid line 7 at an opening on the front side of an outlet-side end 7a. In the example shown, the fluid 6 is a liquid, more precisely water. However, another liquid or possibly a gas can also be used as the fluid 6. In the example shown, the fluid 6 is discharged from the removal front 4 via the flexible fluid line 7, for which purpose the latter has two chambers or is designed as a double-walled hose. It is fundamentally also possible to supply the fluid 6 to the removal front 4 via the flexible fluid line 7 and to discharge it from the removal front 4 between the flexible fluid line 7 and the outer surface 5 of the hollow structure 2.

[0056] The Fig. The fluid supply 7 shown in Figure 1 in the form of the flexible fluid line can only be tracked with difficulty by the removal front 4 as it moves through the substrate 1. Fig. 2a,b show a fluid supply 7 which, for supplying the fluid 6 to the removal front 4 and for removing the fluid 6 from the removal front 4, has two web-shaped, helical outer structures 9a,b which are periodic in one spatial direction and surround a solid core 8 of the fluid supply 7. In the example shown, the solid core 8 is designed as a wire and forms the stable basic framework of the fluid supply 7, which enables the fluid supply 7 to be better introduced into the hollow structure 2 in the form of the temperature control channel and to rotate the fluid supply 7 in a defined manner within the hollow structure 2.

[0057] The two web-shaped helical outer structures 9a,b are wound in the manner of a double helix around the solid core 8. The helical outer structures 9a,b separate a first helical channel 10, through which the fluid 6 is supplied to the removal front 4, from a second helical channel 11, through which the fluid 6 is discharged from the removal front 4. As is particularly evident in Fig. 2b, which shows the fluid supply 7 in cross section, the helical channels 10, 11 are open on the outside of the fluid supply 7 and are delimited laterally, in the example shown in the radial direction, by a lateral surface 5 of the hollow structure 2 when the fluid 6 is supplied to the removal front 4 and when the fluid 6 is removed from the removal front 4.

[0058] When in Fig. 2a,b, the web-shaped helical outer structures 9a, 9b are in contact with the outer surface 5 of the hollow structure 2, but this may not be absolutely necessary. The web-shaped helical outer structures 9a, 9b are made of plastic in order to keep the fluid supply 7 flexible and to reduce the friction between the fluid supply 7 and the outer surface 5 of the hollow structure 2. It has proven advantageous if the fluid supply 7 is Fig. 2a,b is inserted or screwed into the hollow structure 2 with a screw movement.

[0059] Fig. 3a,b show a fluid supply 7, which differs from the one in Fig. 2a,b in that instead of two web-shaped helical outer structures 9a,b, two helical outer structures 9a, 9b in the form of fluid lines surround the solid core 8. The two fluid lines 9a, 9b are wound around the solid core 8 in the form of a double helix. The fluid 6 is supplied to the removal front 4 via the first helical fluid line 9a, and the fluid 6 is removed from the removal front 4 via the second helical fluid line 9b. As shown in the cross-sectional view of Fig. 3b, the two fluid lines 9a,b can be located on the outer surface 5 of the hollow structure 2 in the form of the temperature control channel, but it is also possible that the fluid lines 9a,b are slightly spaced from the outer surface 5 of the hollow structure 2, as shown in Fig. 3a is shown.

[0060] Fig. 4a,b show a fluid supply 7, which differs from the Fig. 2a,b and in Fig. 3a,b shown fluid feeds 7 in that the core 8 is not solid, but rather is designed as a hollow cylinder, which encloses a cylindrical cavity 12 in which the fluid 6 is fed to the removal front 4, as shown in Fig. 4a is indicated. To discharge the fluid 6 from the removal front 4, the fluid supply 7 of Fig. 4a has a web-shaped helical outer structure 9, which defines a helical channel 13 in which the fluid 6 is discharged from the removal front 4. The helical channel 13 is Fig. 4a radially inwardly from the core 8, more precisely from the outside of the core 8, and radially outwardly from the lateral surface 5 of the hollow structure 2, into which the fluid supply 7 is introduced, wherein the web-shaped helical outer contour 9 may optionally be slightly spaced from the lateral surface 5 of the hollow structure 2, as shown in Fig. 4a is indicated.

[0061] Fig. 4b shows the cross section of a fluid supply 7, which differs from the one shown in Fig. 4a in that, instead of a single web-shaped helical outer structure 9, it has a number of six web-shaped helical outer structures 9a-e, between which six helical channels 13a-e run, via which the fluid 6 is transported away from the removal front 4.

[0062] At the Fig. 4a,b, the fluid 6 is transported away from the removal front 4 by rotating the fluid supply 7 in the hollow structure 2. In this case, the fluid supply 7 functions in the manner of an Archimedean screw. For the rotation of the fluid supply 7, a Fig. 4a shows a threaded drive 14, indicated by a square, which engages the web-shaped helical outer structure(s) 9, 9a-e. To transport the fluid 6 away from the removal front 4, the threaded drive 14 can be operated in idle mode, whereby the fluid supply 7 is rotated in the hollow structure 2, but the fluid supply 7 is not advanced.

[0063] In order to guide the fluid supply 7 along the removal front 4, a "turn" of the threaded drive 14 can be used, which, in addition to rotation, causes the fluid supply 7 to advance in the hollow structure 2. It is understood that the number of web-shaped, helical outer structures can be selected practically freely, with the number of outer structures affecting the return transport behavior of the fluid 6 from the removal front 4.

[0064] In order to improve the tracking of the fluid supply 7, it is not absolutely necessary to use helical outer structures 9, 9a-e.

[0065] Fig. 5a-d show a fluid supply 7 having a flexible, tubular jacket 15 through which the fluid 6 is supplied to the removal front 4. For this purpose, the fluid 6 exits in the form of a fluid stream at a front opening of an outlet-side end 7a of the fluid supply 7. The fluid supply 7, more precisely the tubular jacket 15 of the fluid supply 7, has a plurality of perforations that form jacket-side outlet openings 16 for a fluid stream 6a, which is directed toward the jacket surface 5 of the hollow structure 2 in the form of the temperature control channel. In the example shown, the tubular jacket 15 has four outlet openings 16, which are aligned circumferentially at an angle of 90° to one another.The fluids flowing out through the four outlet openings 16 in a radial direction perpendicular to the center of the fluid supply 7 together form the fluid flow 6a, which pushes the fluid supply 7 radially away from the outer surface 5 of the hollow structure 2 and stabilizes or self-centers it within the hollow structure 2. In this way, the fluid supply 7 can typically be prevented from getting caught on the outer surface 5 of the hollow structure 2, similar to what happens with a hydrodynamic plain bearing. This increases the robustness of the flushing process and reduces the number of manual interventions in the flushing process.

[0066] As in Fig. As can be seen in Figure 5a, the jacket-side outlet openings 16 are arranged adjacent to the outlet-side head end 7a of the fluid supply 7, at which the fluid 6 exits at the front end in the direction of the ablation front 4. The outlet openings 16 are introduced in the form of targeted perforations in the jacket 15 of the fluid supply 7. The outlet openings 16 are dimensioned such that sufficient flushing of the ablation front 4 is still ensured and sufficient backflow of the ablation products is possible.

[0067] In the Fig. In the example shown in Figure 5a, the fluid flow 6a directed onto the shell surface 5 of the hollow structure 2 is oriented perpendicular to the fluid supply 7, more precisely perpendicular to its cylindrical shell 15. In the example shown in Fig. In the example shown in Fig. 5b, the fluid flow 6a is directed away from the removal front 4 or from the outlet-side end 7a of the fluid feed 7, ie the fluid flow 6a exits at an obtuse outflow angle (> 90°) with respect to the end 7a of the fluid feed 7 adjacent to the removal front 4. If the outlet openings 16 are introduced into the casing 15 at an obtuse outflow or inclination angle, both the advance of the fluid feed 7 and the return flow of the fluid 6 from the removal front 4 can be specifically supported, which in the Fig. 5a-d shown examples outside the fluid supply 7.

[0068] In the Fig. In the example shown in Figure 5c, the flexible fluid supply 7 is designed in the form of a double-walled or multi-lumen tube 15, i.e., in the form of a tube with multiple chambers. Instead of removing the fluid 6 for the fluid flow 6a directed toward the lateral surface 5 of the hollow structure 2 from the main chamber and thus disrupting the fluid flow 6 directed toward the removal front 4, the fluid 6 is used to stabilize the fluid supply in the Fig. 5c, the fluid is guided through an outer or secondary chamber of the hose 15. At the outlet end 7a of the fluid supply 7, the transition between the outer and inner chambers can be freely designed, so that the main function of the flushing is still ensured and can be optimized for the removal front 4.

[0069] Fig. Figure 5d shows another possibility for implementing the outlet openings 16, in which a rigid end cap 17 in the form of a nozzle or sleeve is attached to the outlet end 7a of the flexible fluid supply 7, into which the outlet openings 16 are inserted in order to direct the fluid flow 6a onto the lateral surface 5 of the hollow structure 2. In the example shown, the end cap 17 is manufactured by a 3D printing process, more precisely by 2-photon polymerization, which enables the production of very fine and small components. This in Fig. The solution shown in Figure 5b is also valid for the Fig. 5c shown multi-lumen tube 15 can be used.

[0070] The perforations or outlet openings 16 can be introduced into the flexible material of the casing 15 of the fluid supply 7 in various ways. One possibility is to perform a laser ablation process, in which the diameter of the outlet openings can be selected practically freely. Fig. 6 shows a device suitable for this purpose, which has a laser beam generator 18 for generating a laser beam 3. The laser beam generator 18 has a scanner for deflecting the laser beam 3 and an F-theta lens that focuses the laser beam 3 onto the casing 15 of the fluid supply 7. The fluid supply 7 rests on an inclined plane of a workpiece support 19, which is aligned at an angle α to the horizontal in order to create the outlet opening 16 with the desired angle of inclination to the casing of the fluid supply 7. The outlet-side end 7a of the fluid supply 7 rests against a stop 20 attached to the workpiece support 19.

[0071] Fig. 7a,b shows an alternative way of producing the outlet openings 16 mechanically, more precisely by punching. As in Fig. As can be seen in Figures 7a,b, the casing 15 of the fluid supply 7 is perforated by means of needles 21, which are attached to a ring 24 of a device for perforating the casing 15. To fix the casing 15 in the center of the device, an annular holder 22 is used, which is attached to the ring 24 and has openings for aligning the needles 21, as shown in Fig. 7a is indicated.

[0072] To fix the casing 15, a cylindrical holding element 23 is inserted into the casing 15. The holding element 23 serves to increase the rigidity of the casing 15 and prevents the casing 15 from buckling when drilled through with the aid of the needles 21. When the device is actuated, the needles 21 are moved radially towards the center of the casing 15, whereby the casing 15 is perforated and the outlet openings 16 are formed. It is understood that the ring 24 with the needles 21 can be designed such that the outlet openings 16 are introduced into the casing 15 of the flexible fluid supply 7 at a suitable angle. It is further understood that instead of needles 21, other mechanical tools, for example cutting edges or the like, can be used to form the outlet openings 16 in the casing 15 of the flexible fluid supply 7.

[0073] Fig. Figure 8 shows a substrate 1 with a hollow structure 2, which, unlike the hollow structures 2 described above, is not intended for the flow of a temperature control fluid, but serves to dampen mechanical stresses exerted on the substrate 1 by an attachment 25 in the form of a bushing. The attachment 25 in the form of the bushing is glued to a rear side 1b of the substrate 1. The mechanical stresses are intended to prevent the mechanical stresses from passing through from the rear side 1b of the substrate 1 to a front side 1a of the substrate 1, to which a reflective coating is applied to form the EUV mirror.

[0074] For this purpose, it is advantageous if the hollow structure 2 completely covers the attachment 25 in a plan view of the front side 1a of the substrate 1. To achieve this, a large-volume cavity 27 is required, which has a surface in a plane parallel to the front side 1a of the substrate 1 that corresponds at least to the surface of the attachment 25. The extension of the cavity 27 perpendicular to the front side 1a, however, can be selected to be small, ie the cavity 27 can have a relatively low height, as shown in Fig. 8 is indicated.

[0075] To realize a large-volume cavity 27 in a monolithic substrate 1, an access 26 is required that connects it to one side of the substrate 1, which in the example shown is the back side 1b of the substrate 1. In the example shown, the access 26 is a channel-shaped access 26 that has a comparatively small diameter and, in the example shown, a cylindrical cross-section.

[0076] Both the channel-shaped access 26 and the large-volume cavity 27 are created using the material-removing machining process described above. The comparatively small cross-section or diameter of the channel-shaped access 26 must be expanded to match the comparatively large cross-section of the large-volume cavity 27. In the example shown, the access 26 has a diameter d of approximately 2 mm, and the maximum width b of the large-volume cavity 27 is approximately 10 mm. The height of the cross-section, on the other hand, only needs to be adjusted slightly. The width b of the removal front 4 during the formation of the cavity 27 increases, starting from the access 26, until the maximum width b of the cavity 27 is reached.

[0077] Even with the Fig. In the example shown in Figure 8, a fluid 6 is supplied to the ablation front 4 in order to flush it and to remove ablation products from the ablation front 4 and from the hollow structure 2. For flushing the large-volume cavity 27 with a correspondingly large-area ablation front 4, the typically used fluid supplies in the form of flexible hoses are not readily suitable.

[0078] Fig. 9a-e show fluid feeds 7 which have been modified to enable the flushing of such a removal front 4 without causing damage to the substrate 1.

[0079] In the Fig. In the example shown in Figure 9a, the fluid supply 7 has several flexible fluid lines to supply the fluid 6 to the removal front 4. As in Fig. As can be seen in Figure 9a, the flexible fluid lines are guided in the channel-shaped access 26 in the manner of a bundle. For flushing the removal front 4, the flexible fluid lines extend with their outlet ends into the large-volume cavity 27 and are aligned to different positions on the removal front 4, which are simultaneously flushed with the fluid 6. The outlet ends of the flexible fluid lines extend fan-shaped from the channel-shaped access 26 into the large-volume cavity 27.

[0080] In the Fig. In the example shown in Figure 9b, the fluid supply 7 has a flat jet nozzle 28 at its outlet end to supply the fluid 6 to the removal front 4. The flat jet nozzle 28 is attached in the form of an attachment to a flexible fluid line of the fluid supply 7. By means of the flat jet nozzle 28, the fluid 6 can be distributed homogeneously in the large-volume cavity 27 in order to flush the removal front 4 as homogeneously as possible over its entire width b, if the latter is arranged at a sufficient distance from the removal front 4, as shown in Fig. 9b is the case.

[0081] As an alternative to a flat jet nozzle 28, the fluid supply 7 can have an adjustable nozzle, i.e. a nozzle that makes it possible to change the jet properties of the fluid 6 flowing out of the nozzle. In this case, one and the same fluid supply 7 can be used to form the channel-shaped access 26 and the large-volume cavity 27, provided that the opening angle of the outflowing fluid 6 is selected to be comparatively small in the channel-shaped access 26 and comparatively large in the large-volume cavity 27. In this case, a concentrated fluid flow can be generated in the channel-shaped access 26, which is directed forward, and a broad flushing of the volume can take place in the large-volume cavity 27. For example, a variable flushing head can be used as the variable nozzle, as is also used in the form of sprayers for watering gardens or the like.

[0082] Fig. 9c shows a fluid supply 7, the outlet end of which is inserted into the large-volume cavity 27 and is moved in order to supply the fluid 6 to different positions of the removal front 4. In the Fig. In the example shown in Figure 9c, the outlet-side end of the fluid supply 7, optionally with the nozzle described above, is moved within the large-volume cavity 27 and performs defined oscillating movements in order to flush the entire removal front 4. Due to the defined oscillating movement, each position of the removal front 4 is flushed from time to time, but there is no constant flushing of the entire removal front 4 with the fluid 6. In the example shown, in which the cross-section of the cavity 27 has a significantly greater width b than height, the oscillating movement can take place in one plane, but it is also possible for the outlet-side end of the fluid supply 7 to perform a three-dimensional oscillating movement in the cavity 27 in order to flush different positions of the removal front 4 one after the other.

[0083] Fig. 9d and Fig. 9e shows a fluid supply 7 which, at its outlet end, has two outlet units 29a,b for the fluid 6, which, upon introduction into the cavity 27, are moved, or more precisely pivoted, into an extended position in order to supply the fluid 6 to the removal front 4. In this variant, the outlet units 29a,b are located in the channel-shaped access 26 during the arrangement of the outlet end of the fluid supply 7 (cf. Fig. 9d) in a retracted position and are only moved, or more precisely pivoted, into the extended position when the outlet-side end of the fluid supply 7 is located within the large-volume cavity 27 (cf. Fig. 9e).

[0084] The outlet units 29a,b are designed as attachments that are attached to the outlet end of the fluid supply 7. In the Fig. In the retracted position shown in Figure 9d, no fluid 6 exits the outlet units 29a,b, i.e., in the channel-shaped access, the fluid supply 7 is used like a conventional fluid line, at the outlet end of which the fluid 6 exits. Only when the outlet end of the fluid supply 7 has been introduced into the large-volume cavity 27 are the outlet units 29a,b moved into the extended position and the fluid 6 is additionally supplied to the removal front 4 via the outlet units 29a,b, i.e., the flushing behavior of the fluid supply 7 changes.

[0085] In the extended position, the outlet units 29a,b are aligned at an acute outflow angle to the center of the fluid supply 7 in order to flush a larger portion of the removal front 4 than would be the case without the use of the outlet units 29a,b. Depending on the mechanism used for movement between the retracted and extended positions, it is possible to change the exit angle of the outlet units 29a,b in order to flush different positions of the removal front 4. In the event that the mechanism does not allow movement from the extended position back to the retracted position, it may not be possible to withdraw the fluid supply 7 from the cavity 27 or from the hollow structure 2 without damaging the outlet units 29a,b or the fluid supply 7, i.e., they may not be reusable.

[0086] In all variants described above, the flushing of the removal front 4 can be coupled with process monitoring in order to be able to detect errors promptly and, if necessary, correct them.

[0087] Fig. 10a,b show a device 30 for supplying the fluid 6 used for the material-removing processing to a process tank 31 and for removing the fluid 6 from the process tank 31. The fluid 6 is water, which is also referred to below as process water 6. During the material-removing processing, the substrate 1 described above is placed in the process tank 31 and is immersed completely or partially in the process water 6.

[0088] For conveying the process water 6 to the process basin 31, the device 30 has a first pump 33. The first pump 33 draws the process water 6 from a tank 32 and pumps it through a filter 34, optionally in combination with a cooling system, into the process basin 31. A significant portion of the process water 6, which may be on the order of 95%, for example, is pumped back into the tank 32 via a bypass line 35.

[0089] During material-removing processing, the process water 6 in the process tank 31 absorbs ablation products of the substrate 1. In order to remove the ablation products as well as a part of the process water 6 from the process tank 31, the device 30 of Fig. 10a has a second pump 36 in the form of a peristaltic pump, which returns the process water 6 from the process basin 31 into the tank 32.

[0090] However, the return of the process water 6 from the process basin 31 to the tank 32 is problematic because the process basin 31 may run dry, thereby sucking air into the hose system of the second pump 36. Furthermore, with a second pump 36 in the form of a peristaltic pump, the particles introduced into the process water 6 during machining, particularly in the form of glass particles, can destroy the flexible hose used for the return. If this defect is not detected in time, it will result in the process basin 31 overflowing and possibly damaging the device 30. The process basin 31 may also overflow if the first pump 33 is active and the second pump 36 is not active for any reason.

[0091] To avoid the problems described above, the Fig.In the device 30 shown in Figure 10b, the second pump 36 is integrated into the bypass line 35 for returning a portion of the process water 6 pumped by the first pump 33 and is designed as a water jet pump or a Venturi pump. The second pump 36 in the form of a water jet pump serves to suck in the process water 6 from the process tank 31 via an intake pipe 37. The second pump 36 in the form of a water jet pump in the bypass line 35 is coupled to the pumping output of the first pump 34. Therefore, the situation cannot arise that the first pump 34 is running but the second pump 36 is not active. An overflow of the process water 6 in the process tank 31 can therefore only occur if the intake hose 37 or a return hose of the second pump 36 is blocked. A further advantage of the second pump 36 in the form of the water jet pump in the bypass line 35 is that it does not have to be controlled separately.For the passive return of the process water 6 described here, a bypass line 35 with a sufficiently large flow volume is required to drain the process water 6 from the process basin.

Claims

[1] Method for rinsing a removal front (4) on a hollow structure (2) formed by material-removing machining in a workpiece (1), preferably in a substrate for an EUV mirror, comprising: Supplying a fluid (6) to the removal front (4) by means of a preferably flexible fluid supply (7), characterized by , that the fluid supply (7) for supplying the fluid (6) to the removal front (4) and / or for removing the fluid (6) from the removal front (4) has at least one outer structure which is periodic in at least one spatial direction, preferably a helical outer structure (9a,b, 9; 9a-e). [2] Method according to claim 1, wherein the fluid supply (7) has a preferably solid core (8) which is surrounded by the at least one periodic outer structure (9a, 9b). [3] Method according to claim 2, wherein the core (8) is surrounded by at least two periodic outer structures (9a, 9b) with which the fluid (6) is supplied to the removal front (4) and removed from the removal front (4). [4] Method according to claim 3, in which helical outer structures (9a, 9b) are web-shaped and separate at least one first helical channel (10), via which the fluid (6) is supplied to the removal front (4), from at least one second helical channel (11), via which the fluid (6) is discharged from the removal front (4). [5] Method according to claim 4, wherein the helical channels (10, 11) are open on the outside of the fluid feed (7) and are preferably delimited laterally by a lateral surface (5) of the hollow structure (2) when feeding the fluid (6) to the removal front (4) and when removing the fluid (6) from the removal front (4). [6] Method according to claim 3, wherein the periodic external structures (9a, 9b) are designed as fluid lines through which the fluid (6) is supplied to the removal front (4) and removed from the removal front (4). [7] Method according to claim 2, wherein the fluid (6) is supplied to the removal front (4) in the core (8) and the fluid (6) is removed from the removal front (4) by means of the at least one periodic outer structure (9, 9a-e), or vice versa. [8] Method according to claim 7, in which the at least one periodic outer structure (9, 9a-e) is web-shaped and the fluid (6) is discharged from the removal front (4) in at least one helical channel (13a-e) between the core (6) of the fluid feed (7) and a lateral surface (5) of the hollow structure (2), wherein the fluid feed (7) is preferably rotated in the hollow structure (2) to discharge the fluid (6). [9] Method according to one of the preceding claims, in which the fluid supply (7) of the removal front (4) is guided by means of a threaded drive (14) which engages the at least one helical outer structure (9, 9a-e). [10] Device for rinsing a removal front (4) on a hollow structure (2) formed by material-removing machining in a workpiece (1), preferably in a substrate for an EUV mirror, comprising: a preferably flexible fluid supply (7) for supplying a fluid (6) to the removal front (4), characterized by , that the fluid supply (7) for supplying the fluid (6) to the removal front (4) and / or for removing the fluid (6) from the removal front (4) has at least one outer structure which is periodic in at least one spatial direction, preferably a helical outer structure (9a,b, 9; 9a-e). [11] Device according to claim 10, wherein the fluid supply (7) has a preferably solid core (8) which is surrounded by the at least one periodic outer structure (9a, 9b). [12] Device according to claim 11, wherein the core (8) is surrounded by at least two periodic outer structures (9a, 9b) which are designed to supply the fluid (6) to the removal front (4) and to remove the fluid (6) from the removal front (4). [13] Device according to claim 12, wherein the helical outer structures (9a, 9b) are web-shaped and separate at least one first helical channel (10), which serves to supply the fluid (6) to the removal front (4), from at least one second helical channel (11), which serves to discharge the fluid (6) from the removal front (4), wherein preferably the helical channels (10, 11) are open on the outside of the fluid supply (7). [14] Device according to claim 12, wherein the periodic external structures (9a, 9b) are designed as fluid lines which serve to supply the fluid (6) to the removal front (4) and to remove the fluid (6) from the removal front (4). [15] Device according to claim 11, which is designed to supply the fluid (6) to the removal front (4) via the core (8) and which is designed to discharge the fluid (6) from the removal front (4) by means of the at least one periodic outer structure (9, 9a-e), or vice versa, wherein the at least one periodic outer structure (9, 9a-e) is preferably web-shaped in order to discharge the fluid (6) in at least one helical channel (13a-e) between the core (6) of the fluid supply (7) and a lateral surface (5) of the hollow structure (2) from the removal front (4), wherein the device is designed in particular to rotate the fluid supply (7) in the hollow structure (2) in order to discharge the fluid (6). [16] Device according to one of claims 10 to 15, further comprising: a threaded drive (14) which is designed to engage the at least one helical outer structure (9, 9a-e) in order to guide the fluid supply (7) of the removal front (4).

Images