METHOD AND DEVICE FOR PRODUCEING A THREE-DIMENSIONAL STRUCTURE IN A LITHOGRAPHIC FLUID

Description

[0001] The invention relates to a method for generating a three-dimensional target structure in a lithography fluid using a lithography apparatus. The invention also relates to a lithography apparatus adapted and configured for the method.

[0002] In the lithography techniques considered here, a structure is written primarily by directing a writing beam along an optical axis into a lithographic material in such a way that the material is locally solidified in a focal region of the beam, thus defining a structural region or "voxel." For example, it is conceivable that the lithographic material is locally hardened or polymerized in the focal region by the writing beam. To write a two- or three-dimensional overall structure, the focal region is shifted (scanned) within the lithographic material so that a plurality of volume elements ("voxels") are sequentially defined, which together form the overall structure.

[0003] A corresponding technique utilizing the physical principle of two-photon polymerization, or more generally, multi-photon polymerization, is described, for example, in DE 10 2017 110 241 A1. Such techniques are particularly useful in the production of micro- or nanostructures in areas where high precision and, at the same time, design freedom for the structure to be produced are desired.

[0004] In the described techniques, the lithographic material is generally a liquid or viscous lithographic fluid provided in a lithographic bath. To create a target structure in the lithographic fluid, the writing beam can then be directed through a surface of the lithographic fluid into the lithographic bath, for example, via a suitably adapted air objective. It is also possible for the writing beam to be directed directly into the lithographic fluid via an immersion objective immersed in the fluid (so-called "dip-in" technology, see, for example, DE 10 2011 012 484 A1).

[0005] US 5,922,364 A describes a system for stereolithography for depositing a layer of liquid medium along an upper surface of a bath containing a liquid medium.

[0006] DE 44 14 775 A1 discloses a device for producing a three-dimensional object using stereolithography. A liquid material is solidified by the action of electromagnetic radiation.

[0007] EP 1 769 901 A2 shows a manufacturing system for the rapid production of prototypes.

[0008] The invention addresses the problem of improving the reliability and quality of structuring in the lithography techniques described above. In particular, it aims to enable the high-precision writing of structures with a large extent along the optical axis.

[0009] This problem is solved by a method according to claim 1. This method is a lithography method for producing a target structure in a volume of lithography fluid or in a volume filled with lithography fluid.

[0010] The process is carried out using a lithography apparatus. The lithography apparatus includes a receiving chamber for the lithography fluid. The receiving chamber, in particular, provides a receiving volume into which lithography fluid can be introduced, especially poured. The receiving chamber can be provided by a container of the lithography apparatus (see below). It is also conceivable that the receiving chamber is a receiving volume provided between a substrate and an exit optic (see below) of the lithography apparatus. The lithography apparatus also includes a radiation source for emitting a writing beam. In particular, the radiation source is a laser source for emitting a laser beam (writing laser beam).The lithography apparatus also includes a beam guidance device for defining a beam path for the writing beam from the radiation source to the lithographic fluid. The beam guidance device comprises an exit optic with an exit surface through which the writing beam exits along an optical axis and, in particular, is subsequently directed into the lithographic fluid. For example, the exit optic can include an exit aperture with an exit lens. In this case, an outer surface of the exit lens facing the lithographic fluid can form the exit surface. It is also conceivable that the exit optic has a radiolucent end window and that a surface of this end window facing the lithographic fluid provides the exit surface.As explained in more detail below, the exit optics can, in particular, include focusing optics for focusing the writing beam in a focal region, and in particular, be formed by these optics. The focusing optics can, in turn, include an exit aperture, in particular comprising an exit lens element. The exit surface can then be formed by a surface of the exit lens element facing the lithographic fluid in the exit aperture. The lithographic device is designed such that the exit optics and / or the receiving chamber, or a container providing the receiving chamber, are movable along the optical axis, so that the relative position of the exit optics and the receiving chamber can be changed. The lithographic device is thus, in particular, designed such that a focal region of the writing beam within the lithographic fluid is movable along the optical axis.

[0011] The lithography apparatus also includes a fill level adjustment device, which is designed to change the fill level of the lithography fluid in the receiving chamber such that the distance between the surface of the lithography fluid, i.e., the air-lithography fluid interface, and the exit surface of the exit optics can be adjusted. In other words, the fill level adjustment device is designed to set a distance between the surface of the lithography fluid and the exit surface of the exit optics by changing the fill level of the lithography fluid.

[0012] The advantages and features described below with regard to the lithography device as such can also serve to design the lithography device according to claim 1. To avoid repetition, reference is therefore made to the disclosure below.

[0013] According to the proposed method, a lithographic fluid is first provided in the recording chamber. The lithographic fluid is specifically tailored to the radiation source, particularly to a specific wavelength and / or intensity of the emitted radiation, such that solidification of the lithographic fluid occurs only in a focal region of the writing beam, particularly by utilizing a multi-photon process.

[0014] To create or write the target structure, the writing beam is directed into the lithographic fluid and, particularly by utilizing multi-photon absorption, the lithographic fluid is locally solidified in a focal region of the writing beam. Specifically, an exposure dose can be directed into the lithographic fluid in the focal region of the writing beam in such a way that the lithographic fluid is locally modified, preferably by utilizing multi-photon absorption, and thus a structural region is created or written. The lithographic fluid is therefore locally structured, particularly by utilizing multi-photon absorption. In particular, the lithographic fluid is chemically and / or physically modified by the exposure dose of the laser writing beam, for example, it is hardened or polymerized. The exposure dose is, in particular, a volume dose of radiation energy.

[0015] To generate three-dimensional structures, the focal area of ​​the writing beam can traverse a scan manifold through the lithographic fluid. In the simplest case, the scan manifold can be a scan curve, but it can also be more complex. In this respect, the focal area of ​​the writing beam can be shifted by the lithographic fluid. For this purpose, the writing beam can be controlled within a writing area of ​​the lithographic apparatus with the precision required for structuring, for example, by being deflected in a controlled manner using a beam guidance device. Alternatively, the lithographic fluid, or a container holding the lithographic fluid, can be shifted relative to the writing beam in a controlled manner using a positioning device.

[0016] Both relocation concepts can also be applied together.

[0017] According to the proposed method, the fill level of the lithography fluid in the recording chamber is changed, in particular depending on a relative position of the recording chamber and the exit optics, by means of the fill level adjustment device.

[0018] This design allows for easy and precise adjustment of the distance between the exit surface of the exit optics and the surface of the lithographic fluid by changing the fill level. In particular, depending on the relative position of the exit optics and the recording chamber, the fill level of the lithographic material can be readjusted so that the distance between the exit surface and the surface of the lithographic fluid can be kept constant or at least within a tolerance range around a target distance (see details below). This improves writing quality, especially for structures with a large extent along the optical axis.

[0019] For example, the exit optics can include an air lens that provides the exit surface (see below). In this case, the exit surface can be positioned outside the lithographic fluid during the writing process, so that the writing beam is directed from the outside through the surface of the lithographic fluid into the fluid. The distance between the exit surface and the surface of the lithographic fluid then corresponds, in particular, to the thickness of the air gap between the exit surface and the lithographic fluid. With such an arrangement, aberration effects can occur due to different optical paths through regions with different refractive indices (air gap and lithographic fluid, respectively). This can lead to local artifacts in the written structure, especially if the distance between the exit surface and the surface of the lithographic fluid changes during the writing process.The proposed method now makes it possible to reduce such artifacts by adjusting the fill level of the lithographic fluid, thus maintaining a constant distance between the exit surface and the surface of the lithographic fluid, even when the relative position of the recording space and exit surface changes. Furthermore, the proposed method enables the writing of comparatively high structures with high precision, even when using air lenses. This is because the fill level can increase with the structure height, meaning that the maximum achievable structure height is no longer limited by the working distance of the air lens.As part of another advantageous aspect, the distance between the exit surface and the surface of the lithographic fluid can be adjusted so that the focal area of ​​the writing beam is located directly below the surface of the lithographic fluid during writing, which makes it possible to structure even highly absorbent lithographic fluids.

[0020] The exit optics can also include an immersion objective, which provides the exit surface. In this case, the exit surface can be immersed in the lithographic fluid during normal use ("dip-in"). The distance between the exit surface and the surface of the lithographic fluid is then a measure of how deeply the immersion objective is immersed in the lithographic fluid. With such configurations, adjusting the fluid level can prevent the immersion objective from being immersed too deeply in the lithographic fluid, thus, for example, partially protecting the immersion objective from contamination. It is also conceivable that the exit optics include an air objective onto which an immersion attachment, e.g., in the form of a cap, is mounted. In this case, the air objective with the immersion attachment is immersed in the lithographic fluid.It is also conceivable that the exit optics comprise an immersion objective onto which an immersion attachment, e.g., in the form of a cap, is mounted, and that an immersion medium is provided between the immersion objective and the immersion attachment. In particular, when used with an air objective or an immersion objective, the immersion attachment can include a beam-transparent exit window, e.g., a glass pane or a flexible film, through which the writing beam exits. The exit surface can then be provided by an outer surface of the exit window (e.g., a glass pane or flexible film) facing the lithographic fluid. The exit window or exit surface is thus transparent to the writing beam, especially to laser light.

[0021] In the context of the foregoing considerations, it has proven particularly advantageous to adjust the fill level, and in particular to coordinate the fill level and the relative position of the exit surface and the surface of the lithographic fluid, such that during the injection of the writing beam into the lithographic fluid for solidification (i.e., during the actual writing of the target structure or during the solidification of the lithographic fluid), the distance between the surface of the lithographic fluid and the exit surface of the exit optics always remains within a predetermined or predefinable tolerance range around a target distance along the optical axis. In other words, the fill level is preferably adjusted such that the distance between the surface of the lithographic fluid and the exit surface of the exit optics does not fall below a first threshold and does not exceed a second threshold.In this way, the aberration artifacts mentioned above can be reduced.

[0022] In this context, it has proven advantageous for the tolerance range to be between 0.04 mm and 40 mm, particularly between 0.21 mm and 18 mm. In particular, the tolerance range is less than 10 mm, more specifically less than 5 mm, further specifically less than 4 mm, further specifically less than 3 mm, further specifically less than 2 mm, and further specifically less than 0.5 mm. In other words, the fill height is adjusted such that the distance between the surface of the lithography fluid and the exit surface of the exit optics is changed by a maximum of 40 mm, more specifically a maximum of 18 mm, further specifically a maximum of 10 mm, further specifically a maximum of 5 mm, further specifically a maximum of 4 mm, further specifically a maximum of 3 mm, and further specifically a maximum of 2 mm during the actual writing of the target structure or a structural section of the target structure.The tolerance range can be selected in particular depending on a numerical aperture and / or a working distance (distance from focus to exit surface) of the exit optics, especially focusing optics.

[0023] However, it is particularly preferred if the fill level is adjusted such that the distance between the surface of the lithographic fluid and the exit surface of the exit optics remains essentially constant, preferably constant, during the actual writing of the target structure. In this way, any aberration effects that may occur also remain constant, so that no locally varying structural artifacts arise.

[0024] To write three-dimensional structures extending along the optical axis, the relative position of the exit optics and the receiving chamber, and thus the position of a focal region of the writing beam in the lithographic fluid along the optical axis, is changed. This can be achieved by repositioning the exit optics and / or the receiving chamber, or a container providing it, along the optical axis. In this context, it can be advantageous if the fill level is changed, particularly continuously, during a change in the relative position of the exit optics and the receiving chamber. Preferably, the fill level is changed such that a distance between the surface of the lithographic fluid and the exit surface of the exit optics remains constant.

[0025] The target structure can be generated by sequentially creating several substructures that together approximate the target structure. For this purpose, the target structure can, for example, be computationally decomposed into substructures, and each substructure can be written by a preferably contiguous set of structural regions (voxels). To write structures extending along the optical axis, a first substructure can be created in a first subvolume of the recording space, followed by a second substructure in a second subvolume of the recording space. The first and second subvolumes are offset along the optical axis, and in particular, they are superimposed along the optical axis. Specifically, after creating a first substructure, a second substructure can be created that is offset from the first substructure, particularly along the optical axis.This does not preclude the possibility that further substructures may be written before the substructure referred to here as the first substructure and / or after the substructure described here as the second substructure has been written.

[0026] The substructures preferably have a certain extent along the optical axis. In particular, the substructures can themselves be generated by sequentially writing several structure layers.

[0027] In the configurations with substructures described above, the fill level of the lithographic fluid can be increased or decreased by a predetermined amount, particularly discretely, after the creation of the first substructure and before the writing of the second substructure. This does not necessarily mean that the fill level is changed after the creation of each substructure. For example, it is conceivable that several substructures are written sequentially without the fill level being changed by the fill level adjustment device, and that the fill level is only changed after the creation of selected substructures (referred to here as the "first substructure"). The change in the fill level can occur before or after a change in the relative position of the exit optics and the receiving area for writing the second substructure.In this context, it has proven advantageous to increase or decrease the fill level by an amount between 0.04 mm and 40 mm, particularly between 0.21 mm and 18 mm, and further, particularly between 1 mm and 5 mm, and further, particularly between 1 mm and 3 mm. In particular, the fill level is not changed by the fill level adjustment device during the writing of a respective substructure. Therefore, it can be advantageous if the substructures are designed such that, for the creation of a respective substructure, the relative position of the receiving chamber and the exit optics along the optical axis is changed only to the extent that, with a constant fill level of the lithographic fluid, the distance between the surface of the lithographic fluid and the exit surface does not exceed or fall below the aforementioned tolerance range.According to a general principle, the writing beam can exhibit an intensity distribution, particularly an elongated one, within the focal region. An advantageous further development can consist of adjusting the fill level such that, during the injection of the writing beam into the lithographic fluid for solidification (i.e., during the actual writing process), a first part of the intensity distribution of the writing beam is located below the surface of the lithographic fluid within the focal region, and a second part of the intensity distribution is located above the surface of the lithographic fluid, particularly in the air. This can improve resolution.

[0028] It is conceivable that the fill level of the lithographic fluid in the receiving chamber can be changed by altering the volume of the receiving chamber. For example, the receiving chamber could be provided by a container, and to change the fill level, a displacer could be immersed in (increasing the fill level) or withdrawn from (decreasing the fill level) the lithographic fluid contained in the container. Alternatively or additionally, it is also conceivable that the receiving chamber, or receiving volume, provided by the container could be altered, in particular reduced or increased, by deformation or displacement of a container wall.

[0029] Preferably, the fill level of the lithographic fluid in the receiving chamber is changed by adding or removing lithographic fluid from the receiving chamber. In this respect, the fill level adjustment device can include a fluid conveying device for adding and / or removing lithographic fluid (see below).

[0030] The fill level adjustment device can also be used to supply or discharge different lithographic fluids sequentially or simultaneously into or out of the receiving chamber. In an advantageous further development, for example, a first lithographic fluid can be supplied to the receiving chamber and locally solidified by the application of the printing beam, and then a second lithographic fluid, particularly one different from the first, can be supplied to the receiving chamber and subsequently locally solidified by the application of the printing beam. This makes it possible to produce different areas of the target structure from different materials, for example, according to an expected mechanical load (multi-material printing).

[0031] The first and second lithographic fluids can be supplied, in particular, by feeding the respective lithographic fluids into the receiving chamber using the fill level adjustment device. To avoid potentially undesirable mixing of the first and second lithographic fluids, it can be advantageous if, after the first lithographic fluid has solidified locally and before supplying, in particular feeding, the second lithographic fluid, at least a subset of the first lithographic fluid, in particular substantially the entire volume of the first lithographic fluid, is removed from the receiving chamber by means of the fill level adjustment device, in particular by suction. For this purpose, the lithographic apparatus can include a fluid conveying device designed to supply at least two lithographic fluids to the receiving chamber independently of one another and to discharge them again from it (see below).

[0032] As part of an advantageous further development, it is also conceivable that, after the local solidification of the first lithographic fluid and before the preparation of the second lithographic fluid, and especially after at least partial removal of the first lithographic material, an intermediate development step is carried out, in particular that a developer medium is provided in the receiving chamber, preferably by means of the fill level adjustment device. In this way, the structure written with the first lithographic fluid can, for example, be solidified.

[0033] In the 3D writing method used here, it can be particularly advantageous to introduce the exposure dose by means of multi-photon absorption. For this purpose, the lithography fluid is preferably designed and the writing beam, in particular a writing laser beam, is tuned to the lithography fluid in such a way that a change in the lithography fluid (e.g., local polymerization) is only possible by means of the absorption of multiple photons. For this purpose, for example, the wavelength of the writing beam can be selected (and thus the associated quantum energy dimensioned) such that the energy input required for the change in the lithography fluid is achieved only through the simultaneous absorption of two or more quanta. The probability of such a process is non-linearly intensity-dependent and significantly increased in the focus region compared to the rest of the writing beam.Fundamental considerations show that the probability of absorbing two or more quanta can depend on the square or a higher power of the radiation intensity. The mechanism of multi-photon absorption therefore makes it possible to introduce the desired exposure dose and locally modify the lithographic fluid even within a volume of lithographic fluid, i.e., even relatively deep below its surface.

[0034] In this context, lithographic fluid generally refers to substances whose chemical and / or physical properties can be altered by irradiation with a writing beam, for example, so-called lithographic resists. Depending on the type of changes induced by the writing beam, lithographic materials can be distinguished into so-called negative resists (in which irradiation causes local hardening or reduces solubility in a developer medium) and so-called positive resists (in which irradiation locally increases solubility in a developer medium).

[0035] The aforementioned problem is also solved by a lithography device according to claim 10. The lithography device is configured to generate a three-dimensional target structure in a lithography fluid, in particular by a multi-photon process. The lithography device is preferably configured and adapted to carry out the method described above. In this respect, the advantages and features of the lithography device explained with regard to the method can also serve to design the lithography device according to claim 10.

[0036] The lithography device comprises a receiving chamber for the lithography fluid. The receiving chamber can, in particular, be provided by a container. The container can preferably be open at least at one end. The lithography device also comprises a radiation source for emitting a writing beam. Preferably, the radiation source is a laser source for emitting a laser beam (writing laser beam). Furthermore, the lithography device comprises a beam guidance device for defining a beam path for the writing beam from the radiation source to the lithography fluid. The beam guidance device comprises an exit optic with an exit surface through which the writing beam exits along an optical axis. As already mentioned above with regard to the method, the exit optic can comprise an exit aperture with an exit lens.Then, an outer surface of the exit lens element facing the lithographic fluid can form the exit surface. It is also conceivable that the exit optics have a radiation-transmitting end window, with a surface of this end window facing the lithographic fluid forming the exit surface. As explained in more detail below, the exit optics can, in particular, include a focusing optic for focusing the writing beam in a focal region. The lithographic device is designed such that the exit optics and / or the recording space are movable along the optical axis, which enables the writing of three-dimensional structures extending along the optical axis. In this respect, the lithographic device is designed, in particular, such that the relative position of the exit optics and the recording space can be changed.For this purpose, the lithography device can include a displacement device for repositioning the exit optics or focusing optics along the optical axis. Alternatively or additionally, the lithography device can include a positioning device for repositioning the receiving chamber, in particular a container providing the receiving chamber. The lithography device also includes a fill level adjustment device configured to change the fill level of the lithography fluid in the receiving chamber in order to adjust the distance between the surface of the lithography fluid and the exit surface of the exit optics.

[0037] To avoid repetition, reference is made to the above description of the proposed method with regard to the advantages of such a lithography device with a fill level adjustment device.

[0038] The fill level adjustment device is preferably designed to decrease and / or increase the fill level of the lithography fluid in the recording chamber, particularly depending on a relative position of the recording chamber and the exit optics.

[0039] Preferably, the fill level adjustment device is configured to change the fill level by adding and / or removing lithographic fluid from the imaging chamber. In this respect, the fill level adjustment device can include a fluid conveying device for conveying lithographic fluid. The fluid conveying device can, in particular, be configured to add lithographic fluid to and / or remove it from the imaging area in order to change the fill level of the lithographic fluid in the imaging chamber. The fluid conveying device can, in particular, be configured to draw lithographic fluid from the imaging chamber to reduce the fill level. This makes it possible, for example, to continue the exposure of a structure at a "deeper" position in the lithographic material (viewed from the direction of the beam), a position that would otherwise be inaccessible due to the working distance of the exit optics, especially the focusing optics.

[0040] Specifically, the fluid conveying device can comprise at least one fluid line and at least one pumping device, in particular a pump. The at least one fluid line and the at least one pumping device are designed, in particular, for supplying lithographic fluid to the receiving chamber and / or for extracting lithographic fluid from the receiving chamber.

[0041] The fill level adjustment device, in particular the fluid delivery device, may also include at least one lithography fluid reservoir or lithography fluid tank. The lithography fluid reservoir can serve as an intermediate fluid storage tank to temporarily store lithography fluid drawn from the imaging chamber.

[0042] It is possible that the lithographic fluid is supplied to and extracted from the receiving chamber via the same fluid line. It is also possible that the fluid supply system comprises at least one fluid supply line for supplying lithographic fluid to the receiving chamber and at least one separate fluid discharge line for removing lithographic fluid from the receiving chamber.

[0043] In an advantageous further development, at least one fluid supply line and at least one fluid discharge line can be fluidically connected to a lithography fluid reservoir mentioned above, in particular such that the at least one fluid supply line and the at least one fluid return line, together with the receiving chamber and the lithography fluid reservoir, form a fluid circuit. This makes it possible to recycle lithography fluid, in particular to first discharge lithography fluid from the receiving chamber and then later return it to the receiving chamber. In particular, a pump device for conveying the lithography fluid within the fluid circuit can be provided.

[0044] In an advantageous further development, the fill level adjustment device can have a plurality of fluid supply lines and a plurality of fluid return lines. In particular, a first pair consisting of a fluid supply line and a fluid return line can be configured for supplying and removing a first lithography fluid, respectively, and a second pair consisting of a fluid supply line and a fluid return line can be configured for supplying and removing a second lithography fluid, respectively. The first pair can be connected to a first lithography fluid reservoir, preferably forming a first fluid circuit, and the second pair can be connected to a second lithography fluid reservoir, preferably forming a second fluid circuit. Such a configuration facilitates the aforementioned multi-material printing, since the different lithography fluids can be supplied to and removed from the receiving chamber separately.

[0045] Preferably, the receiving space is provided by a container. The container, in particular, comprises a container wall that defines the receiving space. The container can have at least one fluid connection for supplying and / or discharging lithographic fluid into and / or out of the receiving space. The fluid connections can then be connected to corresponding fluid lines of the fluid delivery system. In the simplest case, the fluid connections can be provided by local recesses in a container wall. However, it is also possible that the container is open on one side via a main opening (e.g., in the form of a bowl) and that the at least one fluid line of the fluid delivery system (e.g., in the form of a hose) is inserted into the receiving space through the main opening of the container. The fluid line can also be held in place on the container by a suitable retaining device.For example, it is conceivable that the fluid line is held against an inner wall of the container or is inserted into the container.

[0046] It is possible that the container has only one fluid connection through which lithographic fluid can be both supplied to and discharged from the receiving chamber. It is also possible that the container has at least one fluid supply connection for supplying lithographic fluid and at least one separate fluid discharge connection for removing lithographic fluid.

[0047] As mentioned at the outset, the beam guidance device includes, in particular, a focusing optic for focusing the writing beam in a focal area. In an advantageous embodiment, the focusing optic can comprise an air lens. Such air lenses have, in particular, a numerical aperture between 0.025 and 1.0. Specifically, the air lens provides the exit surface. For example, the air lens can have an exit aperture with an exit lens element, wherein an outer surface of the exit lens element facing the lithographic fluid provides the exit surface. The air lens is preferably arranged such that the exit surface is spaced apart from the lithographic fluid, i.e., in particular, located outside the lithographic fluid.Therefore, an air gap is formed between the exit surface and the surface of the lithographic fluid, the thickness of which defines the distance described above. The small numerical aperture associated with air lenses makes it possible to write even comparatively large structures quickly, which can be particularly advantageous in automated, industrial-scale processes.

[0048] In an alternative advantageous embodiment, the focusing optics can include, and in particular be formed by, an immersion objective. The exit surface can then be provided by the immersion objective, for example, by an outer surface of an exit lens element of an exit aperture of the immersion objective facing the lithographic fluid. For writing the target structure, the immersion objective can then be immersed in the lithographic fluid, such that the exit surface is located below a surface of the lithographic fluid (so-called "dip-in"). In such an embodiment, the distance described above between the exit surface of the exit optics and the surface of the lithographic fluid is a measure of how far the exit surface, and thus the immersion objective, is immersed in the lithographic fluid.

[0049] As mentioned above, it is also conceivable that the focusing optics comprise an air lens or an immersion lens onto which an immersion attachment, e.g., in the form of a cap, is mounted. In this case, the air lens or the immersion lens, along with the immersion attachment, is immersed in the lithographic fluid. When using an immersion lens, an immersion medium can be provided between the immersion lens and the immersion attachment. In particular, the immersion attachment can include a beam-transparent exit window, e.g., a glass plate or a flexible film, through which the writing beam exits. The exit surface can then be provided by an outer surface of the exit window facing the lithographic fluid. The exit window is thus transparent to the writing beam, especially a laser beam.

[0050] Preferably, the lithography device also includes a sensor device for detecting, and in particular monitoring, the fill level of the lithography fluid in the receiving chamber. This enables precise control of the fill level. In particular, the sensor device can interact with the fill level adjustment device. The sensor device can, for example, comprise one or more optical, mechanical, or electrical sensors.

[0051] Advantageously, the lithography device can also include a control unit for controlling the lithography device. The control unit can, in particular, interact with the fill level adjustment device and / or the sensor device, especially by controlling them. Preferably, the control unit can be configured to carry out the method described above.In particular, the control device can be configured to control the fill level adjustment device in such a way that it changes the fill level of the lithographic fluid in the recording space, in particular depending on a relative position of the exit optics and the recording space and / or a fill level of the lithographic fluid in the recording space detected by the sensor device, in particular such that during the injection of the writing beam into the lithographic fluid to solidify the lithographic fluid (i.e. during the actual writing of the target structure), a distance between the exit surface and the surface of the lithographic fluid remains within a predetermined or predeterminable tolerance range around a target distance along the optical axis, in particular is constant.

[0052] The invention will be explained in more detail below with reference to the figures. They show: Fig. 1 simplified schematic representation of a lithography device configuration; Figs. 2a-c simplified schematic representations to illustrate a writing process using the lithography device; Figs. 3a-b simplified schematic representations to illustrate the writing of a substructure; Fig. 4 simplified schematic representation to illustrate a configuration of the fill level adjustment device; Fig. 5 simplified schematic representation of a configuration of the container for the lithography fluid; and Fig. 6 simplified schematic representations to illustrate a writing process using an immersion lens.

[0053] In the following description and in the figures, the same reference symbols are used for identical or corresponding features.

[0054] The Fig. 1Figure 10 shows a schematic representation of an embodiment of a lithography device, which is designated in its entirety by reference numeral 10. The lithography device 10 comprises a radiation source 12, in particular a laser source, for emitting a writing beam 14, in particular a writing laser beam. The lithography device 10 also comprises a beam guidance device, designated in its entirety by reference numeral 16, for defining a beam path 18 for the writing beam 14 from the radiation source 12 to a lithography material 20 to be structured.

[0055] In the illustrated example, the beam guidance device 16 has several modules which fulfill optical and / or mechanical functions. For example, the beam path 18 can first pass through a beam shaping device 22.

[0056] The beam guidance device 16 also includes an exit optic 24 with an exit surface 26, through which the writing beam 14 is guided along an optical axis 28 (in Fig. 1 along the z-axis of the coordinate system shown there) exits the beam guidance device 16 (see also Fig. 2a The exit optics 24 preferably comprise a focusing optics 30 for focusing the writing beam 14 in a focus area 32. Specifically, the focusing optics 30 can comprise an exit aperture 34 with an exit lens means 36 (see Figure 1). Fig. 2a ). Then the exit surface 26 can be provided by an outer surface 38 of the exit lens medium 36 facing the lithography fluid 20.

[0057] In the Fig. 1 and 2In the illustrated embodiment, the focusing optics 30 are designed as an air lens 40, which is arranged at a distance from the lithographic fluid 20. The writing beam 14 thus first passes through an air gap after exiting the exit optics 24 and is then directed into the lithographic fluid 20 through a surface 42 of the lithographic fluid 20. The distance between the exit surface 26 and the surface 42 of the lithographic fluid 20 is indicated in the figures by the reference numeral 44.

[0058] In further embodiments, it is also possible that the focusing optics 30 are designed as an immersion lens 46 and that this is immersed in the lithography fluid 20 to write a structure (hereinafter referred to as Fig. 6(described in more detail below). In embodiments not shown, it is also conceivable that the focusing optics comprise an air lens onto which an immersion attachment, e.g. in the form of a cap, is placed, and that the air lens with the immersion attachment is immersed in the lithography fluid 20 to write a structure.

[0059] The lithography device 10 preferably also includes a displacement device (not shown) for displacement of the focusing optics 24 along the optical axis 28. The beam guidance device 16 can also include a scanning device 48 by means of which the focus area 32 of the writing beam 14 can be displaced within the lithography fluid 20 with the precision required for structuring. For example, the scanning device 48 can include a beam guidance module, which may, for example, comprise a galvanometer scanner unit for controlled deflection of the writing beam 14.

[0060] As in Fig. 1 As shown in the sketch, the lithography device 10 comprises a container 50 with a container wall 51, which defines a receiving chamber 52 for receiving the lithography fluid 20. The container 50 can be fixed in position. The container 50 can also be moved with precise positioning relative to the focus area 32 of the writing beam 14 by means of an optional positioning device (not shown), in particular along the optical axis 28. The positioning device can preferably be configured to move the container in all three spatial directions x, y, z, and optionally also to tilt it about a first tilting axis parallel to the x-axis and / or about a second tilting axis parallel to the y-axis.

[0061] The lithography device 10 also includes a level adjustment device 54, which will be described in detail below, for changing the level 56 of the lithography fluid 20 in the container 50. In the example, the level adjustment device 54 includes a fluid conveying device 58 for supplying and discharging lithography fluid 20 into the container 50 (see details below).

[0062] The lithography device 10 preferably also includes a control unit (not shown) for controlling the lithography device 10. The control unit preferably includes a computing unit and a non-volatile memory.

[0063] An advantageous embodiment of a method for generating a target structure 60 using the lithography device 10 described above will be described below with reference to the Figures 2a to 2c explained.

[0064] In the described lithography device 10, a target structure 60 is fundamentally defined by shifting the focus area 32 of the writing beam 14 through the volume of lithography fluid 20 (surrounding the entire structure), in particular by means of the scanning device 48 and / or by shifting the focusing optics 30 and / or the container 50. In the focus area 32 of the writing beam 14, a writing exposure dose is locally irradiated into the lithography fluid 20, so that structural regions are defined locally, in particular by utilizing multi-photon absorption, which together approximate the target structure 60.

[0065] The Figures 2a to 2c The figures exemplify various stages of a writing process for writing a target structure 60 extending along the optical axis 28. As in a comparison of the Figures 2a to 2cAs can be seen, the focus area 32 is moved along the optical axis 28 relative to the lithography fluid 20 to write such a structure 60, so that structural areas along the optical axis 28 are locally solidified one after the other, which together then form the target structure 60. In particular, it is conceivable that the target structure 60 is composed of a plurality of substructures 62-1, 62-2, 62-3 (in Fig. 2 (example indicated by dashed lines), which are superimposed along the optical axis 28 and themselves have a certain extension along the optical axis 28.

[0066] The displacement of the focus area 32 along the optical axis 28 is preferably achieved by displacing the focusing optics 30, e.g. by means of the aforementioned displacement device, and / or the container 50, e.g. by means of the aforementioned positioning device, along the optical axis 28 relative to each other.

[0067] According to the proposed method, the fill level 56 of the lithography fluid 20 in the container 50 is adjusted as a function of the relative position of the focusing optics 30 and the container 50 such that the distance 44 between the exit surface 26 of the focusing optics 30 and the surface 42 of the lithography fluid 20 is constant or at least does not exceed or fall below a predetermined tolerance range (explained in detail below). In the example according to Figs. 2a to 2c As the height of the structure 60 increases, the filling height 56 ​​or the fill level of the lithographic fluid 20 in the container 50 is increased.

[0068] For this purpose, lithography fluid 20 is supplied to the receiving chamber 52 by means of the filling level adjustment device 54 or the fluid delivery device 58. This can be done continuously by changing the relative position of the focusing optics 30 and the container 50 along the optical axis 28, in particular such that the distance 44 always remains constant.

[0069] It is also possible for the fill level 56 to be changed in discrete steps. For example, it is possible for the target structure 60 to be composed of several substructures 62-1, 62-2, 62-3, and for the fill level 56 to be increased or decreased by a predetermined amount 64 after writing the first substructure 62-1 and before writing the next substructure 62-2.

[0070] In such a configuration, it is conceivable that the fill level 44 is not changed by the fill level adjustment device 54 during the writing of a respective substructure 62-1, 62-1, 62-3, i.e., in particular, no lithographic fluid 20 is actively supplied to or removed from the receiving chamber 52. Therefore, the distance 44 between the exit surface 26 and the surface 42 of the lithographic fluid 20 can change during the writing of a respective substructure 62-1, 62-2, 62-3, especially if the substructures 62-1, 62-2, 62-2 themselves have a certain extent along the optical axis 28, e.g., if they are formed from several superimposed layers (cf. Figures 3a and 3bThe substructures 62-1, 62-2, 62-3 are then preferably chosen such that the distance 44 is not changed beyond a predetermined tolerance range 66 when writing the substructure 62-1, 62-2, 62-3, within which a change in distance is acceptable (see above, in the Fig. 3a and 3b (shown schematically).

[0071] In particular, the amount 64 by which the fill height 56 ​​is increased or decreased can correspond to a width 68 of the tolerance range 66, i.e., a maximum permissible change in the distance 44. This ensures that the distance 44 does not fall below a first threshold 70 and does not exceed a second threshold 72 during the writing of the target structure 60 (see...). Fig. 3a and 3b , which exemplify the two extreme positions for the first substructure 62-1).

[0072] The fluid conveying device 58 includes in the examples according to Fig. 1 to 3Each fluid line 74 opens into the receiving chamber 52 of the container 50 via a corresponding fluid connection 76 (simplified in the figures as an opening in the container wall 51). As mentioned above, in embodiments not shown, the fluid line 74 may also be in the form of a hose inserted from above into the receiving chamber 52 of the container 50. The fluid conveying device 58 preferably also includes a pump device 78 (see Figure 5). Fig. 1 , in the Figs. 2a to 2c (not shown) for the promotion of lithography fluid 20.

[0073] The fluid conveying device 58 thus makes it possible to lower the fill level 56 again after writing a substructure 62-1, 62-2, 62-2 or a first target structure 60, so that a subsequently written substructure or second target structure can be written at a lower level along the optical axis 28.

[0074] The Figure 4 Figure 1 shows a simplified schematic view of another exemplary embodiment of the fluid conveying device 58, which comprises a fluid supply line 80 for supplying lithographic fluid 20 into the receiving chamber 52 and a separate fluid discharge line 82 for removing lithographic fluid 20 from the receiving chamber 52. As shown in Figure 1, the fluid conveying device 58 is further exemplified by a fluid supply line 80 for supplying lithographic fluid 20 into the receiving chamber 52. Figure 4 As can be seen, the container 50 then includes, for example, corresponding fluid connections 76. The fluid connections 76 are located in the Figure 4In the example shown, the fluid connections are arranged on opposite sides of the container wall 51. However, it is also possible for the fluid connections 76 to be arranged on the same side.

[0075] In the example shown, the fluid supply line 80 and the fluid discharge line 82 are connected to a lithography fluid reservoir 84, so that together with the receiving chamber 52 a fluid circuit is formed. The fluid conveying device 58 according to Fig. 4 This includes, in particular, a pump unit 78 (not shown) for conveying the lithography fluid 20 along the fluid circuit. The in Figure 4 The illustrated design makes it possible to extract lithography fluid 20 from the recording chamber 52 and, for example at a later time, to return it to the recording chamber 52.

[0076] The Figure 5Figure 1 shows a further embodiment of a container 50 designed for multi-material printing. In the illustrated example, a total of four fluid connections 76 are provided on the container 50, which are connected to corresponding fluid lines 74-1, 74-2, 74-3, 74-4. Preferably, two fluid lines 74-1, 74-3 form fluid supply lines 80-1, 80-2 and two fluid lines 74-2, 74-4 form fluid discharge lines 82-1, 82-2. In particular, one fluid supply line 80-1, 80-2 and one fluid discharge line 82-1, 82-2 can each be equipped with a lithography fluid reservoir analogous to the one shown in Figure 1. Fig. 4 The illustrated configuration may be connected. In this respect, two fluid circuits can be provided. In particular, each fluid circuit can carry a different lithography fluid 20, so that the target structure 60 can be manufactured from different materials.

[0077] The Figures 6a and 6bFigure 1 schematically shows an embodiment of the lithography device 10 in which the focusing optics 30 are designed as an immersion lens 46. In this embodiment, the exit surface 26 is immersed in the lithography fluid 20 for writing the target structure 60. A distance 44 between the exit surface 26 and the surface 42 of the lithography fluid 20 defines a measure of how far the immersion lens 46 is immersed in the lithography fluid 20. As shown in the Figs. 6a and 6b As shown schematically, the filling level 56 of the lithography fluid 20 is preferably adjusted such that sensitive areas 86 of the immersion objective 46 do not come into contact with the lithography fluid 20.

Claims

1. Method for producing a three-dimensional target structure (60) in a lithography fluid (20) by means of a lithography apparatus (10), the lithography apparatus (10) comprising - a receiving space (52) for lithography fluid (20); - a radiation source (12) for emitting a writing beam (14) ; - a beam guiding device (16) for defining a beam path (18) for the writing beam (14) from the radiation source (12) to the lithography fluid (20), comprising an exit optical system (24) having an exit surface (26) through which the writing beam (14) exits along an optical axis (28), wherein the exit optical system (24) and / or the receiving space (52) are displaceable along the optical axis (28); - a filling level adjustment device (54) for changing a filling level (56) of the lithography fluid (20) in the receiving space (52), the method comprising the steps of: - providing a lithography fluid (20) in the receiving space (52); - irradiating the writing beam (14) into the lithography fluid (20) and locally solidifying the lithography fluid (20) in a focus region (32) of the writing beam (14), - changing the filling level (56) of the lithography fluid (20) in the receiving space (52) by means of the filling level adjustment device (54) in order to adjust a distance (44) between a surface (42) of the lithography fluid (20) and the exit surface (26) of the exit optical system (24).

2. Method according to claim 1, wherein the filling level (56) of the lithography fluid (20) in the receiving space (52) is changed depending on a relative position of the receiving space (52) and the exit optical system (24) .

3. Method according to any of the preceding claims, wherein the filling level (56) is changed such that during the irradiation of the writing beam (14) into the lithography fluid (20) for solidifying the lithography fluid (20), the distance (44) between the surface (42) of the lithography fluid (20) and the exit surface (26) of the exit optical system (24) is within a predetermined or predeterminable tolerance range (66) around a target distance, and is preferably substantially constant.

4. Method according to claim 3, wherein a width (68) of the tolerance range (66) is between 0.04 mm and 40 mm, in particular between 0.21 mm and 18 mm, more particularly less than 10 mm, more particularly less than 5 mm, in particular less than 4 mm, more particularly less than 3 mm, more particularly less than 2 mm, more particularly less than 0.5 mm.

5. Method according to any of the preceding claims, wherein, in order to produce three-dimensional structures (60) extending along the optical axis (28), a relative position of the exit optical system (24) and the receiving space (52) is changed along the optical axis (28), wherein the filling level (56) is changed, in particular continuously, during a change in the relative position of the exit optical system (24) and the receiving space (52), in particular such that a distance (44) between the surface (42) of the lithography fluid (20) and the exit surface (26) remains substantially constant.

6. Method according to any of claims 1 to 4, wherein the target structure (60) is produced by sequentially producing a plurality of partial structures (62-1, 62-2, 62-3) which together approximate the target structure (60), wherein after producing a first partial structure (62-1), a second partial structure (62-2) is produced, which is offset with respect to the first partial structure (62-1), in particular along the optical axis (28), wherein the filling level (56) of the lithography fluid (20) is increased or decreased by a predetermined amount (64) after the production of the first partial structure (62-1), in particular wherein the amount (64) is between 0.04 mm and 40 mm, more particularly between 0.21 mm and 18 mm, more particularly between 1 mm and 5 mm, more particularly between 1 mm and 3 mm.

7. Method according to any of the preceding claims, wherein the filling level (56) is adjusted such that during the irradiation of the writing beam (14) into the lithography fluid (20) for solidifying the lithography fluid (20), a first portion of an, in particular elongate, intensity distribution of the writing beam in the focus region is arranged below the surface (42) of the lithography fluid (20), and a second portion is arranged above the surface (42) of the lithography fluid (20).

8. Method according to any of the preceding claims, wherein changing the filling level (56) of the lithography fluid (20) comprises supplying lithography fluid (20) into the receiving space (52) and / or removing lithography fluid (20) from the receiving space (52).

9. Method according to any of the preceding claims, wherein a first lithography fluid (20) is provided in the receiving space (52) and is locally solidified by irradiation of the writing beam (14), and wherein a second lithography fluid is then provided in the receiving space (52) and is locally solidified by irradiation of the writing beam (14).

10. Method according to the preceding claim, wherein after the local solidification of the first lithography fluid (20) and before the provision of the second lithography fluid, at least some of the first lithography fluid (20) is removed from the receiving space (52) by means of the filling level adjustment device (54).

11. Lithography apparatus (10) for producing a three-dimensional target structure (60) in a lithography fluid (20), according to a method according to any of the preceding claims, comprising - a receiving space (52) for the lithography fluid (20) ; - a radiation source (12) for emitting a writing beam (14) ; - a beam guiding device (16) for defining a beam path (18) for the writing beam (14) from the radiation source (12) to the lithography fluid (20), comprising an exit optical system (24) having an exit surface (26) through which the writing beam (14) exits along an optical axis (28), wherein the exit optical system (24) and / or the receiving space (52) are displaceable along the optical axis (52); - a filling level adjustment device (54) for changing a filling level (56) of the lithography fluid (20) in the receiving space (52) in order to adjust a distance (44) between a surface (42) of the lithography fluid (20) and the exit surface (26) of the exit optical system (24).

12. Lithography apparatus (10) according to the preceding claim, wherein the filling level adjustment device (54) is designed to reduce and / or increase the filling level (56) of the lithography fluid (20) in the receiving space (52), in particular depending on a relative position of the receiving space (52) and the exit optical system (24).

13. Lithography apparatus (10) according to claim 11 or claim 12, wherein the filling level adjustment device (54) comprises a fluid conveying device (58) which is designed to supply lithography fluid (20) to the receiving region (52) and / or to discharge lithography fluid from the receiving region (52).

14. Lithography apparatus (10) according to the preceding claim, wherein the fluid conveying device (58) comprises at least one fluid line (74) and at least one pumping device (78) for supplying lithography fluid (20) into the receiving space (52) and / or for suctioning lithography fluid (20) from the receiving space (52).

15. Lithography apparatus (10) according to claim 13 or claim 14, wherein the fluid conveying device (58) comprises at least one fluid supply line (80) for supplying lithography fluid (20) into the receiving space (52) and at least one fluid discharge line (82) for discharging lithography fluid (20) from the receiving space (52), wherein the at least one fluid supply line (80) and the at least one fluid discharge line (82) are connected to a lithography fluid reservoir (84), in particular wherein the at least one fluid supply line (80) and the at least one fluid return line (82) form a fluid circuit together with the receiving space (52) and the lithography fluid reservoir (84).

16. Lithography apparatus (10) according to any of claims 12 to 15, wherein a plurality of fluid supply lines (80-1, 80-2) and a plurality of fluid discharge lines (82-1, 82-2) are provided, wherein a first pair of a fluid supply line (80-1) and a fluid discharge line (82-2) is designed to supply and discharge a first lithography fluid (20) and wherein a second pair of a fluid supply line (80-2) and a fluid discharge line (82-2) is designed to supply and discharge a second lithography fluid.

17. Lithography apparatus (10) according to any of claims 11 to 16, wherein the receiving space (52) is provided by a container (50), wherein the container (50) has at least one fluid connection (76) for supplying and / or discharging lithography fluid (20), in particular at least one fluid connection (76) for supplying lithography fluid (20) and at least one separate fluid connection (76) for discharging lithography fluid (20).

18. Lithography apparatus according to any of claims 11 to 17, wherein the beam guiding device (16) comprises a focusing optical system (30) for focusing the writing beam (14) in a focus region (32), wherein the focusing optical system (30) comprises an air objective (40) which provides the exit surface (26) and is arranged such that the exit surface (26) is arranged outside the lithography fluid (20), or wherein the focusing optical system (30) comprises an immersion objective (46) which provides the exit surface (26) and is arranged such that the exit surface (26) is immersed in the lithography fluid (20).

19. Lithography apparatus (10) according to any of claims 11 to 18, further comprising a sensor device for detecting the filling level (56) of the lithography fluid (20) in the receiving space (52).

20. Lithography apparatus (10) according to any of claims 11 to 19, further comprising a control device for controlling the lithography apparatus (10), wherein the control device is configured to carry out a method according to any of claims 1 to 10.