Apparatus and method for treating surface of optical element of lithography system in atomic layer deposition process or atomic layer etch process

Abstract

The invention relates to a device (100) for treating a surface (102) of an optical element (101) of a lithography system (1), in particular an EUV lithography system, in an atomic layer treatment process, comprising: a sample holder (110) for holding the optical element (101) during the treatment process; a treatment head (120) having a first outlet (121) for supplying a first precursor fluid (PF1) to a treatment area (102A) on a surface (102) of the optical element (101), a cleaning assembly (123) for removing excess first precursor fluid (PF1) out of the treatment area (102A), and a second outlet (122) for supplying a second precursor fluid (PF2) into the treatment area (102A), selecting the first precursor fluid (PF1) and the second precursor fluid (PF2) so as to perform an atomic layer etching process or an atomic layer deposition process in the treatment region (102A), and the first or second precursor fluid (PF1, PF2) being a liquid; and a movement unit (130) designed to move the processing head (120) and / or the sample holder (110) together with the optical element (101) relative to one another such that the first outlet (121), the cleaning assembly (123) and the second outlet (122) are guided one after the other on the processing region (102A).

Description

Technical Field

[0001] The present invention relates to an apparatus for processing a surface of an optical element of a lithographic apparatus, in particular an EUV lithographic apparatus, in an atomic layer processing operation, and to a corresponding method. The present invention also relates to a method of repairing a lithographic apparatus.

[0002] The content of the priority application DE 10 2022 206 124.1 is hereby incorporated by reference in its entirety. Background Art

[0003] Microlithography is used to produce microstructured component parts, such as integrated circuits. Microlithography processes are performed using a lithography apparatus comprising an illumination system and a projection system. The image of a mask (reticle) illuminated by means of the illumination system is projected by means of the projection system onto a substrate (e.g. a silicon wafer) which is coated with a photosensitive layer (photoresist) and is arranged in the image plane of the projection system, in order to transfer the mask structure to the photosensitive coating of the substrate.

[0004] Driven by the desire for smaller and smaller structures in the production of integrated circuits, EUV lithography equipment is currently being developed that uses light with a wavelength in the range from 0.1 nm to 30 nm, in particular 13.5 nm. Since most materials absorb light of this wavelength, it is necessary to use reflective optics, i.e. mirrors, in such EUV lithography equipment instead of refractive optics, i.e. lens elements as previously used. Examples of mirrors used include those known as Bragg mirrors, which are formed by alternating layers of two materials having different refractive indices for the radiation to be reflected. For EUV radiation, for example, silicon and molybdenum have been found to be a suitable material pair. In order to prevent oxidation of the outer layer, which would deteriorate the optical properties of the mirror, a protective layer is often applied. For this purpose, for example, ruthenium is used.

[0005] EUV radiation is generated, for example, by laser incidence on droplets of tin, thereby generating a tin plasma with an emission at 13.5 nm. However, in the process, tin from the radiation source can also enter the radiation forming device and the projection optical system, where the tin can be deposited on optical surfaces or even on lithographic masks. This contamination can impair the optical properties and therefore the performance of the entire system. Therefore, after a certain operating period of the lithographic equipment, for example, a service is required to clean the affected surfaces. Tin can also form alloys, in particular with ruthenium, which are not easily removed from the surface, which complicates the cleaning process.

[0006] Furthermore, EUV radiation is conducted in a vacuum in an EUV lithography apparatus, since the absorption of radiation by gas molecules is already too high at standard pressure. In this case, for example, molecular hydrogen is used as a purge gas in the vacuum region of an EUV lithography apparatus. The hydrogen molecules are dissociated or ionized by the EUV radiation. The resulting hydrogen radicals or hydrogen ions are highly reactive. In particular, these can react with tin deposits, forming volatile compounds and thus removing tin. However, hydrogen radicals can also react with other surfaces in the EUV lithography apparatus and corrode other surfaces in the EUV lithography apparatus. Furthermore, the volatile compounds thus formed may be deposited again elsewhere, for example on optical surfaces of the lithography apparatus, and contaminate these, which may deteriorate their optical properties.

[0007] Atomic layer deposition (ALD) and atomic layer etching (ALE) are known methods that enable treatments limited to a few atomic layers on the surface of an article. This is because of the self-limiting chemical reactions utilized in the methods, which affect only the uppermost layer of any surface. The method is based on the formation of an adsorbed monolayer of a precursor on a surface by exposing the surface to an atmosphere of the precursor in a first step. In the ALE process, the precursor can react chemically with atoms or molecules on the surface here, for example by oxidation or reduction. The precursor is then pumped out of the atmosphere again, leaving only the adsorbed monolayer on the surface. In a second step, the monolayer formed is "activated" by contacting it with a second precursor. The second precursor may include high-energy species, such as free radicals, ions or photons, or have a high chemical reactivity with the first precursor or the formed monolayer. The reaction of the second precursor with the monolayer of the first precursor may result in the deposition of a monolayer of new material (deposition process), or in the decomposition and possible removal of the monolayer (etching process). The second precursor does not react automatically with the (untreated) surface, so the reaction is limited to the monolayer. By repeating the above steps, greater layer thicknesses can be deposited or removed.

[0008] In order to remove contamination on optical surfaces, DE 10 2017 211 539 A1 discloses a method based on an atomic layer etching process. The proposed process can be performed simultaneously in a reactor for the entire surface, otherwise a processing head is used, which spatially separates the area to be processed and then "scans" the surface. In a first area of ​​the processing head, in a section of the surface, the first part of the process is carried out so that a monolayer is formed there. The second part of the process is carried out in a second area of ​​the processing head, which runs across the section already covered by the first area.

[0009] US 2016 / 0090652A1 discloses an atomic layer deposition method in which a liquid precursor is used, wherein the precursor is spin-coated onto a substrate. Here, the substrate is arranged on a rotatable sample holder, and the sample holder with the substrate is rotated. A first liquid precursor is applied, and the precursor is accelerated (rotated) outward (radially) due to the rotation of the substrate and the inertia of the liquid. The rotational action means that no excess material remains on the surface. What remains is the material adsorbed on the surface, which forms a monolayer. The same procedure is performed on the second precursor, which is also a liquid. The chemical reaction between the first and second precursors is limited to a monolayer of the first precursor, so the steps described each result in the deposition of a monolayer of material. A larger layer thickness can be achieved by repeating the steps mentioned. Summary of the invention

[0010] Against this background, it is an object of the present invention to provide an improved apparatus and a corresponding method for treating a surface of an optical element of a lithographic apparatus.

[0011] In a first aspect, a device for processing a surface of an optical element of a lithography device, in particular an EUV lithography device, in an atomic layer processing operation is proposed. The device comprises: a sample holder for holding the optical element during the processing operation; a processing head having a first outlet for supplying a first precursor fluid to a processing region on the surface of the optical element, a cleaning device for removing excess precursor fluid from the processing region, and a second outlet for supplying a second precursor fluid to the processing region, wherein the first precursor fluid and the second precursor fluid are selected so as to perform an atomic layer deposition process or an atomic layer etching process in the processing region, and wherein the first or second precursor fluid is a liquid, and having a moving unit, which is arranged to move the processing head and / or the sample holder with the optical element relative to each other so that the first outlet, the cleaning device and the second outlet successively pass over the processing region.

[0012] The device has the advantage that a greater selection of precursors is available for at least one liquid precursor than is the case with precursors supplied in gaseous form. Furthermore, gaseous precursors generally have a low vapor pressure, which leads to slow processes, or thermal stability problems occur when using them, which can be avoided with liquid precursors. Therefore, the use of liquid precursors can particularly significantly increase the process speed compared to gaseous precursors, which makes the process more efficient and economically viable. In addition, the selectivity of the process can be improved by utilizing suitable selective precursors, in particular in the case of atomic layer etching processes. In addition, unutilized portions of the liquid precursor can be collected and reused, which allows saving resources. The corresponding outlets additionally allow a spatially restricted, controlled supply and therefore the treatment of specific surface areas of the optical element, which may be superior to methods involving the entire surface.

[0013] In the present context, the expression "atomic layer processing operation" means atomic layer deposition and atomic layer etching as mentioned at the beginning. Thus, the atomic layer processing operation can be configured as an atomic layer deposition process or an atomic layer etching process. Furthermore, the atomic layer processing operation can first include an etching process and then a deposition process. The configuration as a deposition or etching process depends, for example, on the precursors used.

[0014] The sample holder holds the optical element in a horizontal position, for example. The sample holder can be adapted or specially designed for the purpose of holding a flat optical element or a curved optical element. The sample holder holds the optical element in particular such that an optical surface, i.e., for example, a reflective surface, of the optical element faces away from the sample holder. This means that the sample holder holds the optical element in particular from the side and / or supports the optical element from the reverse side.

[0015] When the optical element is held by the sample holder, the processing head is in particular arranged opposite the optical surface such that the processing head can be positioned directly above the optical surface.

[0016] In an atomic layer deposition process, first precursor particles of a first precursor fluid are adsorbed on the surface of an optical element in a processing area to form a monolayer. The monolayer has a layer thickness that depends on the first precursor, which can be, for example, in the range of 0.1 nm to 5 nm. Excess first precursor particles (i.e., those that are not adsorbed on the surface) are removed by a cleaning device, such as by blowing or pumping away. Second precursor particles of a second precursor fluid react with the first precursor particles arranged in the monolayer, and in doing so form a deposit of a monolayer comprising reaction products. The chemical reaction can also produce volatile reaction products. The deposit is particularly stably bonded to the surface, so that, for example, another monolayer can be deposited on the surface so that a desired layer thickness can be achieved by repeatedly depositing a monolayer.

[0017] In an atomic layer etching process, first precursor particles of a first precursor fluid react in particular with a surface layer of an optical element in a treatment area. For example, a monolayer of an intermediate is formed. An example of such a process is the formation of a native oxide on an elemental silicon surface in an oxygen-containing atmosphere. Excess first precursor particles (i.e., those not integrated in the monolayer) are removed by a cleaning device, such as by blowing or pumping away. Second precursor particles of a second precursor fluid react with the first precursor particles, in particular with components of the intermediate layer, to form volatile reaction products. Thus, the intermediate monolayer is removed from the surface. Since the intermediate layer is formed with the participation of atoms or molecules on the surface of the optical element, effective material removal (etching) occurs. The etching process is self-limiting because the second precursor fluid does not automatically react chemically with the surface of the optical element. Therefore, the etching process can be controlled very accurately and can be terminated after the desired etching depth is reached.

[0018] Since the atomic layer processing operation involves in each case only a single layer on the surface of the optical element, very good process control is possible. In particular, the surface can be analyzed after each processing run (i.e., deposition or etching), for example by optical and / or electro-optical methods, in order to monitor the progress of the processing operation and to terminate the processing operation when the target of the processing operation has been reached.

[0019] The atomic layer processing operation is performed in a spatially delimited manner. The spatial delimitation is achieved because the first precursor fluid is supplied by the first outlet only in a limited section of the surface. This means that only a limited surface section is covered by the first precursor fluid. Since this is a prerequisite for the corresponding chemical reaction (deposition or etching) to occur due to exposure to the second precursor fluid, the processing operation is limited to the surface section. The spatial delimitation of the processing operation can also be achieved by a corresponding spatial delimitation of the second precursor fluid.

[0020] The spatial area to which the treatment operation is restricted depends inter alia on the configuration of the treatment head, in particular on the configuration of the first outlet and the second outlet.

[0021] One outlet for supplying the liquid precursor fluid takes the form of a slot die, for example, as known from slot die coating. Alternatively, the respective outlet can be formed according to a different nozzle geometry or diffuser geometry.

[0022] To perform a treatment operation, the treatment head is moved relative to the surface of the optical element so that the first outlet first passes through the treatment area, then the cleaning device passes through the treatment area and removes excess first precursor fluid from the surface, and then the second outlet passes through the treatment area. For example, the first outlet, the cleaning device and the second outlet in the treatment head are arranged successively in a first direction, and the treatment head is moved on the surface of the optical element in the first direction. Therefore, the treatment area is the section of the surface over which the treatment head passes. The instantaneous treatment area at a specific junction is the section of the sample surface opposite to the treatment head.

[0023] In particular, the cleaning device comprises at least one outlet or inlet through which excess first precursor fluid can be removed from the treatment area. For example, the first precursor fluid is sucked or pumped out of the treatment area via the inlet. In this case, only excess precursor fluid is removed. This means that those first precursor particles that are part of a monolayer on the surface remain on the surface. The outlet or inlet is spatially arranged between the first outlet and the second outlet, for example, arranged on the treatment head.

[0024] The cleaning device is preferably formed such that any excess first and / or second precursor fluid as well as any volatile reaction products from the reaction of the respective precursor fluid with the surface or a monolayer on the surface are removed from the surface.

[0025] The cleaning device can in particular utilize the capillary effect to remove the liquid precursor (or other liquid substance on the surface) by suction. For example, the opening forming the outlet and the channel or conduit connected thereto have such dimensions that significant capillary forces act on the liquid to be sucked away and thus support suction. In this case, the outlet and / or the connected channel can advantageously be coated in order to enhance the capillary forces.

[0026] The first or second precursor fluid can be atomic (i.e., composed of a single atom) or molecular (i.e., composed of molecules comprising a plurality of atoms), or can comprise both atoms and molecules. The corresponding precursor fluid can also be heterogeneous in particular, in that it comprises two or more different components. The corresponding precursor fluid can additionally comprise an oligomer or a polymer as a component.

[0027] The term "fluid" includes matter in liquid or gaseous form.

[0028] Furthermore, the corresponding precursor fluid in liquid form may contain a solvent which imparts specific flow properties to the liquid, such that the precursor fluid may be applied to a processing head and may be collected by a cleaning device.

[0029] In this context, the corresponding precursor fluid being liquid means that the corresponding precursor fluid is in a liquid state under the process conditions for performing the atomic layer processing operation and contacts the surface of the optical element through the corresponding outlet in a liquid state.

[0030] The use of a liquid furthermore has the advantage that the layer of gas molecules of the surrounding gas atmosphere which has been adsorbed on the surface is replaced by the liquid and / or the gas molecules are dissolved in the liquid, so that the surface can be completely wetted by the liquid. This enables a rapid and complete formation of a monolayer and / or a reaction with the monolayer. The corresponding liquid can additionally be applied to the surface at an increased pressure, which can additionally promote the wetting of the surface. By increased pressure is meant here, for example, that the pressure of the liquid on the surface is higher than the pressure when the liquid droplet is at rest on the surface.

[0031] In an embodiment, the first precursor fluid is a liquid and the second precursor fluid is a gas, or vice versa.

[0032] In embodiments, the atomic layer processing operation may include more than two steps, wherein the processing head may have additional outlets for supplying additional precursor fluids. For example, the processing operation includes an intermediate step, wherein the monolayer of the first precursor fluid formed in the first step is first converted into an intermediate that has appropriate chemical reactivity with the second precursor fluid. Such an intermediate step may also be performed without supplying additional precursor fluids, but rather, for example, by irradiating the monolayer with electromagnetic radiation of suitable energy and / or with charged particles (e.g., electrons, protons, or ions).

[0033] In an embodiment of the device, the processing head may comprise a measuring unit for detecting a physical parameter indicative of the state of a surface of the optical element. The state of the surface comprises, for example, information about chemical elements present on the surface, layer thicknesses of layers present on the surface, etc. For example, the measuring unit may be arranged to induce and detect atomic and molecular excitations by the incidence of light, in particular in the infrared region, the energy of which may be used to infer the chemical composition. Optical reflection methods, such as ellipsometry, may be used to determine the refractive index and / or the near-surface layer structure.

[0034] The processing head may be formed, for example, similarly to a print head for printing a substrate. The processing head may comprise a plurality of elements; in particular, the different outlets enclosed by the processing head may be independently movable. In a preferred embodiment, the different outlets are arranged in a fixed manner in the processing head, so that the spatial relationship of the outlets to each other is constant.

[0035] The moving unit is set up to move the processing head and / or the sample holder with the optical element relative to each other. The moving unit here can move both the sample holder and the processing head, or only one of the two. For example, the moving unit comprises a height adjustment unit, with which the height of the sample holder or the processing head is adjustable, wherein the distance between the surface of the optical element and the underside of the processing head is adjustable, for example in terms of height. The underside of the processing head is the side at which the outlet of the processing head is arranged.

[0036] The mobile unit may also comprise a displacement and / or rotation unit, which is arranged for a lateral displacement of the sample holder and / or the processing head and / or for a rotation of the sample holder and / or the processing head. Furthermore, the mobile unit may be arranged to tilt the optical element. By tilting, an inclined surface with respect to the direction of gravity may be provided, which can be utilized in order to manipulate or influence the flow of the liquid in the case of liquid precursors, on which gravity exerts a considerable influence in a gas atmosphere.

[0037] In one embodiment of the apparatus, the first precursor fluid and the second precursor fluid are both liquids.

[0038] In another embodiment of the apparatus, the optical element is placed in an inert gas atmosphere at a pressure in the range of 0.01 atm to 10 atm, preferably 0.1 atm to 5 atm, during the treatment operation.

[0039] In particular, high pressure is advantageous when the corresponding liquid precursor fluid comprises dissolved gaseous active ingredients, since higher pressure contributes to higher solubility and, therefore, to the concentration of the dissolved substance in the liquid. Such high ambient pressures are possible due to the use of liquid precursors, since this enables complete wetting of the surface, regardless of the ambient atmosphere, even without complex surface cleaning steps. Weakly adsorbed gas molecules from the atmosphere are replaced by the liquid. It should be noted that 1 atm = 101.325 kPa.

[0040] For example, the device has a housing in which the sample holder, the processing head and the movement unit are arranged, the housing being arranged to provide an inert gas atmosphere.

[0041] In an embodiment, the housing may take the form of a vacuum housing and be evacuated such that a vacuum exists in the housing.By supplying gas to the vacuum housing in a controlled manner, a residual gas composition may be precisely established in the vacuum housing.

[0042] In another embodiment of the apparatus, at least one outlet and / or inlet of the cleaning device is arranged along a path between the first outlet and the second outlet, which path corresponds to the relative movement between the optical element and the processing head.

[0043] For example, the treatment head is moved in a linear manner over the surface during treatment.In this case, the outlet and / or the inlet of the cleaning device are particularly arranged on a line connecting the first outlet and the second outlet.

[0044] In one embodiment, the treatment head is in the form of a rotatably mounted head, wherein the axis of rotation is oriented, for example, at right angles to the surface. For example, a slotted outlet is integrated in the underside of the head and extends in a radial direction. When the treatment head is subsequently rotated, the outlets successively pass through the same surface section. In this configuration, the outlet and / or inlet of the cleaning device are arranged between the first outlet and the second outlet according to the rotational movement.

[0045] In another embodiment of the apparatus, the cleaning device comprises at least one inlet arranged for suction removal of the first precursor fluid or the second precursor fluid.

[0046] The inlet may also be referred to as the nozzle.

[0047] In an embodiment, the cleaning device includes more than one outlet or inlet. In particular, the cleaning device can be configured so that an inlet in the form of a suction nozzle completely surrounds the first outlet and / or the second outlet, or a separate suction nozzle is provided for each outlet. Therefore, any excess precursor fluid can be sucked away through the suction nozzle in any direction starting from the outlet of the corresponding precursor fluid.

[0048] In another embodiment of the device, the at least one inlet opens into a pumping removal channel, and wherein a separation device is arranged along the pumping removal channel and is arranged to separate and collect the pumped-away precursor fluid from the pumped-away fluid.

[0049] In the process of removing liquid by suction, gas can also be sucked from the environment of the inlet in particular, so that the fluid sucked by the inlet can include a mixture of liquid precursor fluid and ambient gas. The liquid precursor fluid can be removed by suction and atomized and take the form of fine droplets. The separation device preferably separates the liquid component from the gaseous component. The separation device may include, for example, a centrifugal separator and / or may include a suitable filter medium, such as an air filter.

[0050] Excess liquid precursor fluid can thus be intercepted, collected and reused.

[0051] In a further embodiment of the apparatus, the cleaning device comprises a plurality of inlets for suction removal of the fluid and a plurality of purge fluid outlets for supplying respective purge fluids.

[0052] The purge fluid outlet may be arranged to supply a gaseous or liquid purge fluid. Examples of suitable purge fluids are inert gases or liquids. Cleaning of the surface may preferably be achieved by contacting the surface area with a solvent or detergent before and / or after supplying the first precursor fluid and / or the second precursor fluid.

[0053] Inert gases are particularly suitable for cleaning surfaces, where the surface may also be dried (blown dry). In one embodiment, the supplied gaseous purge fluid is a surfactant, which in particular affects the surface tension of a liquid, such as a liquid film of a first precursor fluid or a second precursor fluid present on the surface. The gradient of the surface tension may promote material transfer (from areas of low surface tension towards areas of greater surface tension). This is, for example, known as the Marangoni effect. This effect may in particular be used to help dry the surface after applying a liquid precursor or a liquid purge fluid.

[0054] The corresponding number includes one or more than one outlet and / or inlet. For example, the cleaning device includes two or more inlets (suction nozzles) and / or two or more purge fluid outlets. In one embodiment, the suction nozzles and the purge fluid outlets are arranged alternately. Preferably, there is a first suction nozzle adjacent to the first outlet and a second suction nozzle adjacent to the second outlet. At least one purge fluid outlet is arranged between the two suction nozzles.

[0055] In this embodiment, it is ensured in a particularly reliable manner that no residual free first precursor fluid remains on the surface, which may have the effect that the treatment is not limited to a monolayer.

[0056] The purge fluid outlet preferably takes the form of an air blade. In this case, a gaseous purge fluid with a high flow rate is directed onto the surface in a preferably laminar manner. The purge fluid then forms a fluid curtain with a high flow rate compared to the environment. This curtain "entrains" all free fluid species in the environment (i.e., those that are not bound to the surface); in particular, free residues of the corresponding precursor fluid on the surface are thus displaced by the purge fluid.

[0057] In another embodiment of the apparatus, at least one liquid sweep fluid is provided.

[0058] Liquid purge fluids may have the advantage over gaseous purge fluids that relatively viscous precursor fluids may also be utilized because the purge fluid is able to dilute the viscous precursor fluid and thus improve its flow characteristics such that the viscous precursor fluid may still be removed from the surface without residue.

[0059] In particular when the treatment operation comprises an atomic layer etching process, a liquid purge fluid additionally has the advantage that non-volatile reaction products which are only weakly bound to the surface can be carried away by the purge fluid and thus removed. In this respect, the purge fluid hereby contributes to the erosion of the surface. This opens up new options with regard to usable precursors, since the reaction products do not necessarily have to be volatile.

[0060] In a further embodiment of the apparatus, the processing head comprises a temperature control device to control the temperature of the first and / or second precursor fluid.

[0061] Temperature control equipment can be adapted to heat and cool the supplied fluid. Increasing or decreasing the temperature of the fluid can increase or decrease the reaction rate, depending on whether the corresponding chemical process being performed is an endothermic or exothermic operation. Thus, temperature can be used to influence the kinetics of the atomic layer processing operation, which facilitates better process control.

[0062] The temperature control device may be arranged, for example, in a feed section for conducting the respective fluid to the respective outlet.

[0063] In an embodiment, further temperature control equipment may be provided in relation to the supplied purge fluid.

[0064] In another embodiment of the apparatus, the first precursor fluid or the second precursor fluid is a gas, and the processing head comprises a plasma generator for generating a plasma from the gaseous precursor fluid.

[0065] The plasma generator comprises, for example, an electric oscillator circuit which generates a magnetic field and / or an electric field which oscillates at a suitable frequency in the region of the respective outlet or the feed to the respective outlet. By means of the alternating field, the charges in the atoms or molecules of the fluid in question are displaced relative to one another. If the energy here is high enough, the atoms or molecules can thereby be ionized, which means that the electrons are separated from their atoms or molecules. Thus, there are ions and a quasi-free electron gas in the plasma.

[0066] The plasma generator for generating the plasma may be designed to interact with the sample holder. For example, the sample holder forms a counter-electrode to an electrode arranged in the processing head, so that an electric field is formed between the processing head and the sample holder.

[0067] An exemplary process in which plasma may be used is the removal of tin deposited on the surface of an optical element. The first precursor fluid is, for example, gaseous oxygen, which is ionized by a plasma generator. In the treatment region, the surface is thus exposed to an oxygen plasma that effectively oxidizes the tin. Tin oxide can be effectively dissolved by a strong acid. For example, the second precursor fluid used is thus liquid hydrochloric acid (HCl).

[0068] In another embodiment of the device, it has a sample temperature control device to control the temperature of the optical element arranged in the sample holder.

[0069] As an alternative or in addition to the above-mentioned temperature control device of the processing head, a sample temperature control device may be provided.

[0070] In another embodiment of the apparatus, the first precursor fluid is an acidic aqueous solution and the second precursor fluid is an alkaline aqueous solution.

[0071] The acidic aqueous solution has a low pH in the range of, for example, 0 to 6, preferably 0 to 4. Such an acidic aqueous solution is capable of oxidizing metal surfaces. Examples of acidic aqueous solutions are hydrochloric acid, citric acid, acetic acid, etc., wherein the concentration of the corresponding acid in the aqueous solution for establishing the preferred pH of the aqueous solution can be varied. Other acidic solutions can also be used.

[0072] The alkaline aqueous solution has, for example, a pH between 8 and 15, preferably between 11 and 14. Examples of alkaline aqueous solutions are sodium hydroxide solution, aqueous ammonia, etc., wherein the concentration of the corresponding substance in the aqueous solution for establishing the preferred pH of the aqueous solution can be varied. Other basic solutions can also be used. Such alkaline solutions can be used to dissolve metals, wherein exposure of the metal to the alkaline solution results in, for example, the formation of soluble metal hydroxides.

[0073] The corresponding aqueous solution is preferably buffered so that the pH of the solution is substantially constant. In particular, weak acids or weak bases are suitable for providing corresponding buffer solutions. Weak acids have an acid constant (pKa) such as in the range of 3 to 13. Weak bases have a base constant (pKb) such as in the range of 3 to 13. Compared with strong acids or bases, weak acids or bases are present in aqueous solutions in protonated and deprotonated forms. The balance between the two forms determines the pH of the solution and the buffer changes therein. Acetic acid is an example of a weak acid, and its pKa is about 4.75. Ammonia dissolved in water is an example of a weak base, and its pKb is about 4.75.

[0074] For example, an optical element to be cleaned has a surface layer of ruthenium. Ruthenium is a relatively inactive noble metal and is used here in particular as a protective layer in order to protect sensitive silicon-molybdenum multilayer structures from oxidation, which form Bragg reflectors for EUV radiation. During the use of the optical element in an EUV lithography apparatus, tin (in elemental form or in the form of various chemical compounds) from the EUV radiation source can be deposited on the surface. These contaminants will be removed during the processing operation without damaging the ruthenium layer. By exposing the ruthenium layer to an acidic aqueous solution, an oxidized passivation layer (e.g. RuO 2 ), and when the ruthenium layer is exposed to an alkaline aqueous solution, a hydroxide passivation layer (e.g., Ru(OH) 3 ). Compared to ruthenium, tin is less stable and therefore it can be dissolved under conditions that do not affect ruthenium (except for the formation of the passivation layer), for example in an alkaline solution with a pH in the range of 8 to 12.

[0075] With regard to the solubility or reactivity of metals with acidic or alkaline aqueous solutions, it should be pointed out that this can be inferred from the so-called Pourbaix diagram of the corresponding metal. The Pourbaix diagram is a schematic empirical representation of the electrochemical potential of a metal as a function of the pH of an aqueous solution. In this regard, reference is made to M. Pourbaix: “Atlas of Electrochemical Equilibria in Aqueous Solution”, National Association of Corrosion Engineers, Houston, 1974. DOI: 10.1016 / 0022-0728(67)80059-7. With regard to ruthenium, reference is also made to I. Povar, O. Spinu: “Ruthenium redox equilibria 3. Pourbaix diagrams for the systems Ru-H2O andRu-Cl-H2”, J. Electrochem. Soi. Eng. 6(1)145(2016); DOI: 10.5599 / jese.229. Regarding tin, reference is also made to SB Lyon: “Corrosion of Tin and its Alloys”, B. Cottis, M. Graham, R. Lindsay, S. Lyon, T. Richardson, D. Scantlebury, H. Stott, Eds., “Shreir′s Corrosion”, Elsevier, 2010, DOI: 10.1016 / B978-044452787-5.00099-8.

[0076] In an embodiment of the device, the liquid purge fluid used between the first precursor fluid and the second precursor fluid is distilled water or deionized water. In this way, all acidic or alkaline residues and / or other dissolved substances can be removed from the surface, which helps to improve process control. In particular, chemical reactions triggered by contact of the surface with the corresponding aqueous solution can be stopped by distilled water by displacing the aqueous solution. Therefore, it is possible, for example, to limit the continuous treatment of individual atomic layers on the surface by keeping the exposure time very short via the rapid movement of the processing head. Preferably, the surface is rinsed with distilled water after the first precursor fluid and after the second precursor fluid.

[0077] In a further embodiment, the first precursor fluid is an alkaline aqueous solution and the second precursor fluid is an acidic aqueous solution.

[0078] In another embodiment of the apparatus, the first and / or second precursor fluid further comprises an oxidizing agent.

[0079] Examples of oxidants dissolved in aqueous solution are as follows: nitrate ions (NO 3 - ), nitrite ion (NO 2 - ), persulfate ion (S 2 O 8 2- ), thiosulfate ion (S 2 O 3 2- ), hydroperoxide ion (HO 2- ), chlorite ion (ClO 2- ), hypochlorite ion (ClO - ), iodate ion (IO 3 - ) and / or nitroaromatic ions, such as 3 - Nitrobenzenesulfonate (C 6 H 4 (NO 2 )SO 3 ) or 3 - Nitrobenzoate (C 6 H 4 (NO 2 )CO 2 - ).

[0080] For the dissolution of tin in alkaline aqueous solution, iodate ions and nitroaromatic ions have been found to be particularly effective, and these are therefore preferably used. In this regard, reference is made to the article YK Taninouchi and T. Uda: "Rapid Oxidative Dissolution of Metallic Tin in Alkine Solution Containing Iodate Ions", J. of Sustainable Metallurgy, 7, 1762 (2021); DOI: 10.1007 / s40831-021-00450-3.

[0081] In a further embodiment of the device, the device further has a measuring device for detecting the distance between the processing head and the surface of the optical element, wherein the movement unit is arranged to move the processing head and / or the optical element at a predetermined distance from each other.

[0082] This ensures that the processing operation is spatially confined, since the respective precursors are guided in a controlled manner into the respective processing area. A relatively small distance is advantageous here, but the complexity of the open-loop and closed-loop control for establishing and maintaining the distance is also greater when the distance is small.

[0083] The processing head is guided over a specific surface during its processing, in particular at a predetermined distance. This distance is, for example, in the range between 1 μm and 100 mm, preferably between 10 μm and 10 mm, more preferably between 50 μm and 1 mm, further preferably between 50 μm and 500 μm. The predetermined distance here particularly relates to the minimum distance between the processing head and the surface. The distance is advantageously selected so that the supplied fluid forms a substantially laminar flow. The processing head can be structured on its lower side, for example in order to manipulate or influence the fluid flow, wherein the distance in the structured area can vary. In addition, for example in the region of the first outlet and / or the second outlet, the distance can be greater, in particular when the liquid precursor is supplied via the outlet in question.

[0084] The measuring device is preferably arranged on the processing head, for example in the form of a laser distance meter or an optical interferometer.Measuring devices are preferably arranged at a plurality of locations on the processing head, so that the tilting of the processing head relative to the surface of the optical element can be detected.

[0085] In another embodiment of the device, the optical element has a piecewise curved surface and an underside of the processing head, which is opposite to the optical element during processing operation, has a shape matching the curvature.

[0086] For example, the optical element is a light collector with a specific radius of curvature. Since the processing head is matched to the radius of curvature, a uniform distance between the processing head and the surface can be achieved, so that processing operations can also be performed efficiently on curved surfaces.

[0087] In a second aspect, a method for processing a surface of an optical element of a lithography apparatus (particularly an EUV lithography apparatus) in an atomic layer processing operation is provided. The method comprises the following steps:

[0088] arranging the optical element on a sample holder,

[0089] positioning a processing head opposite to a surface of the optical element such that a first outlet of the processing head is arranged opposite to a processing area on the surface,

[0090] moving the processing head and / or the optical element such that the first outlet moves across the processing region, wherein during the movement a first precursor fluid is supplied to the processing region through the first outlet,

[0091] moving the processing head and / or the optical element such that a cleaning device of the processing head moves across the processing region, wherein the cleaning device is arranged to remove excess first precursor fluid from the processing region, and

[0092] moving the processing head and / or the optical element such that a second outlet of the processing head moves across the processing region, wherein during the movement a second precursor fluid is supplied to the processing region through the second outlet,

[0093] Wherein the first precursor fluid and the second precursor fluid are selected so as to perform an atomic layer deposition process or an atomic layer etching process in the processing region, and wherein the first precursor fluid and / or the second precursor fluid are liquids.

[0094] The embodiments and features described for the device according to the first aspect apply correspondingly to the proposed method and vice versa.

[0095] In a third aspect, a method for repairing a lithographic apparatus, in particular an EUV lithographic apparatus, is proposed. In a first step, an optical element is removed from the beam path of the lithographic apparatus, wherein the optical element has contamination and / or damage on the incident surface. In a second step, the optical element is processed in a processing method according to the second aspect. In a third step, the processed optical element is installed again in the lithographic apparatus.

[0096] In this context, the optical element whose surface is treated is in particular part of an optical system, such as a projection optical unit or an illumination system of a lithography apparatus. The lithography apparatus may be an EUV lithography apparatus. EUV stands for "extreme ultraviolet" and refers to a wavelength of the working light between 0.1 nm and 30 nm. The projection exposure apparatus may also be a DUV lithography apparatus. DUV stands for "deep ultraviolet" and refers to a wavelength of the working light between 30 nm and 250 nm.

[0097] In the present case, "a" or "a kind of" or "an" should not be understood as being limited to just one element. Instead, a plurality of elements may be provided, such as two, three or more. Any other number used herein should also not be understood as having the effect of limiting the exact stated number of elements. Instead, unless otherwise indicated, upward and downward numerical variations are possible.

[0098] Other possible implementations of the present invention also include the above or below about the features described in the working examples or the combinations not yet explicitly mentioned of the embodiments. In this case, those skilled in the art will also add separate aspects as improvements or supplements to the corresponding basic forms of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0099] Further advantageous configurations and aspects of the invention are the subject matter of the dependent claims and of the working embodiments of the invention to be described hereinafter.The invention is explained in detail hereinafter on the basis of preferred embodiments with reference to the drawings.

[0100] Figure 1A schematic meridional cross section showing a projection exposure apparatus for EUV projection lithography;

[0101] Figure 2 A schematic diagram showing a first working example of an apparatus for processing a surface of an optical element of a lithographic apparatus;

[0102] Figures 3A-3C A schematic diagram showing a spatial atomic layer processing operation performed in a processing region of a surface of an optical element;

[0103] Figure 4 A schematic diagram of a first working example of a processing head is shown;

[0104] Figure 5 shows a schematic diagram of a second working example of a processing head;

[0105] Figure 6 A schematic diagram showing a third working example of a processing head;

[0106] Figure 7 shows a schematic diagram of a second working example of an apparatus for processing a surface of an optical element of a lithographic apparatus;

[0107] Figure 8 A schematic diagram showing a third working example of an apparatus for processing a curved surface of an optical element of a lithographic apparatus;

[0108] Fig. 9A and 9B two schematic diagrams showing a fourth working example of an apparatus for processing a surface of an optical element of a lithographic apparatus; and

[0109] Fig.10 A schematic block diagram showing a working example of a method of processing a surface of an optical element of a lithographic apparatus.

[0110] Unless indicated to the contrary, identical or functionally identical elements are given the same reference numerals in the figures. It should also be noted that the illustrations in the figures are not necessarily true to scale. DETAILED DESCRIPTION

[0111] Figure 1 An embodiment of a projection exposure apparatus 1 (lithography apparatus), in particular an EUV lithography apparatus, is shown. An embodiment of an illumination system 2 of the projection exposure apparatus 1 has, in addition to a light source or radiation source 3, an illumination optical unit 4 for illuminating an object field 5 in an object plane 6. In an alternative embodiment, the light source 3 can also be provided as a module separate from the rest of the illumination system 2. In this case, the illumination system 2 does not comprise the light source 3.

[0112] A reticle 7 arranged in the object field 5 is exposed. The reticle 7 is held by a reticle holder 8. The reticle holder 8 is displaceable by a reticle displacement drive 9, in particular in a scanning direction.

[0113] Figure 1 By way of illustration, a Cartesian coordinate system is shown with an x-direction x, a y-direction y and a z-direction z. The x-direction x extends vertically into the plane of the drawing. The y-direction y extends horizontally and the z-direction z extends vertically. Figure 1 The scanning direction in φ runs in the y-direction y. The z-direction z extends perpendicular to the object plane 6.

[0114] The projection exposure apparatus 1 comprises a projection optical unit 10. The projection optical unit 10 serves to image the object field 5 into an image field 11 in an image plane 12. The image plane 12 extends parallel to the object plane 6. Alternatively, angles other than 0° between the object plane 6 and the image plane 12 are also possible.

[0115] The structures on the reticle 7 are imaged on a photosensitive layer of a wafer 13 arranged in the region of an image field 11 in an image plane 12. The wafer 13 is held by a wafer holder 14. The wafer holder 14 can be displaced, in particular in the y direction y, by a wafer displacement drive 15. It can be achieved that firstly the reticle 7 is moved by the reticle displacement drive 9 and secondly the wafer 13 is moved by the wafer displacement drive 15 so as to be synchronized with each other.

[0116] The light source 3 is an EUV radiation source. The light source 3 in particular emits EUV radiation 16, which is hereinafter also referred to as used radiation, illumination radiation or illumination light. In particular, the used radiation 16 has a wavelength in the range between 5 nm and 30 nm. The light source 3 may be a plasma source, such as an LPP (laser produced plasma) source or a GDPP (gas discharge produced plasma) source. It may also be a synchrotron-based radiation source. The light source 3 may be a free electron laser (FEL).

[0117] The illumination radiation 16 emitted from the light source 3 is focused by the light collector 17. The light collector 17 may be a light collector having one or more ellipsoidal and / or hyperbolic reflective surfaces. The illumination radiation 16 may be incident on at least one reflective surface of the light collector 17 at grazing incidence (GI) (i.e., at an angle of incidence greater than 45°) or at normal incidence (NI) (i.e., at an angle of incidence less than 45°). The light collector 17 may be structured and / or coated to optimize its reflectivity for the radiation used and to suppress extraneous light.

[0118] Downstream of the light collector 17, the illumination radiation 16 propagates through an intermediate focus in an intermediate focal plane 18. The intermediate focal plane 18 may represent a separation between the radiation source module comprising the light source 3 and the light collector 17 and the illumination optical unit 4.

[0119] The illumination optical unit 4 comprises a deflection mirror 19 and a first facet mirror 20 arranged downstream of the deflection mirror 19 in the beam path. The deflection mirror 19 can be a plane deflection mirror or, alternatively, a mirror with a beam influencing effect that goes beyond a pure deflection effect. Alternatively or additionally, the deflection mirror 19 can be implemented as a spectral filter, which separates the useful light wavelengths of the illumination radiation 16 from extraneous light with different wavelengths. If the first facet mirror 20 is arranged in a plane of the illumination optical unit 4 that is optically conjugate to the object plane 6 (as a field plane), it is also referred to as a field facet mirror. The first facet mirror 20 comprises a plurality of individual first facets 21, which can also be referred to as field facets. In Figure 1 Only some of these first facets 21 are shown by way of example in FIG.

[0120] The first facets 21 may take the form of macro facets, in particular as rectangular facets or facets with an arcuate or partly circular edge profile.The first facets 21 may take the form of planar facets, or alternatively as convexly or concavely curved facets.

[0121] As is known, for example, from DE 10 2008 009 600 A1, the first facets 21 themselves can also each consist of a plurality of individual mirrors, in particular a plurality of micromirrors. The first facet mirrors 20 can in particular be configured as a microelectromechanical system (MEMS system). For details, reference is made to DE 10 2008 009 600 A1.

[0122] The illuminating radiation 16 propagates horizontally (ie in the y-direction y) between the light collector 17 and the deflection mirror 19 .

[0123] In the beam path of the illumination optical unit 4, the second facet reflector 22 is arranged downstream of the first facet reflector 20. If the second facet reflector 22 is arranged in the pupil plane of the illumination optical unit 4, it is also called a pupil facet reflector. The second facet reflector 22 can also be spaced apart from the pupil plane of the illumination optical unit 4. In this case, the combination of the first facet reflector 20 and the second facet reflector 22 is also called a specular reflector. Specular reflectors are known from US 2006 / 0132747 A1, EP 1 614 008 B1 and US 6,573,978.

[0124] The second facet mirror 22 comprises a plurality of second facets 23. In the case of a pupil facet mirror, the second facets 23 are also called pupil facets.

[0125] The second facets 23 can also be macroscopic facets, which can be delimited, for example, in a circular, rectangular or hexagonal manner, or alternatively can be facets consisting of micromirrors. In this respect, reference is again made to DE 10 2008 009 600 A1.

[0126] The second facet 23 may have a flat or alternatively convex or concave curved reflective surface.

[0127] The illumination optical unit 4 thus forms a two-facet system. This basic principle is also known as a fly's eye integrator.

[0128] It may be advantageous to arrange the second facet mirror 22 not exactly in a plane optically conjugate to the pupil plane of the projection optical unit 10. In particular, the second facet mirror 22 may be arranged tilted relative to the pupil plane of the projection optical unit 10, as described, for example, in DE 10 2017 220 586 A1.

[0129] By means of the second facet mirror 22 , the individual first facets 21 are imaged into the object field 5 . The second facet mirror 22 is the last beam-shaping mirror or indeed the last mirror in the beam path upstream of the object field 5 for the illumination radiation 16 .

[0130] In another embodiment (not shown) of the illumination optical unit 4, a transfer optical unit, which particularly helps to image the first facet 21 into the object field 5, can be arranged in the beam path between the second facet mirror 22 and the object field 5. The transfer optical unit can have exactly one mirror, or alternatively, two or more mirrors, which are arranged consecutively in the beam path of the illumination optical unit 4. The transfer optical unit can in particular comprise one or two normal incidence mirrors (NI mirrors) and / or one or two grazing incidence mirrors (GI mirrors).

[0131] exist Figure 1 In the embodiment shown in FIG. 1 , the illumination optical unit 4 has exactly three mirrors downstream of the light collector 17 , in particular a deflection mirror 19 , a first facet mirror 20 and a second facet mirror 22 .

[0132] In another embodiment of the illumination optical unit 4 , the deflection mirror 19 can also be omitted and the illumination optical unit 4 can therefore then have exactly two mirrors downstream of the light collector 17 , in particular a first facet mirror 20 and a second facet mirror 22 .

[0133] The imaging of the first facet 21 into the object plane 6 by the second facet 23 or using the second facet 23 and the transfer optics is usually only an approximate imaging.

[0134] The projection optical unit 10 comprises a plurality of mirrors Mi which are numbered consecutively according to their arrangement in the beam path of the projection exposure apparatus 1 .

[0135] exist Figure 1 In the example shown, the projection optical unit 10 comprises six mirrors M1 to M6. Alternative solutions with four, eight, ten, twelve or any other number of mirrors Mi are also possible. The projection optical unit 10 is a doubly shielded optical unit. The penultimate mirror M5 and the last mirror M6 each have a passage opening for the illumination radiation 16. The projection optical unit 10 has an image-side numerical aperture which is greater than 0.5 and can also be greater than 0.6 and can be, for example, 0.7 or 0.75.

[0136] The reflective surface of the reflector Mi may take the form of a free-form surface without an axis of rotational symmetry. Alternatively, the reflective surface of the reflector Mi may take the form of an aspherical surface with exactly one axis of rotational symmetry of the shape of the reflective surface. Just like the reflectors of the illumination optical unit 4, the reflector Mi may have a highly reflective coating for the illumination radiation 16. These coatings may take the form of multilayer coatings, in particular with alternating layers of molybdenum and silicon.

[0137] The projection optical unit 10 has a large object-image offset in the y direction y between the y coordinate of the center of the object field 5 and the y coordinate of the center of the image field 11. This object-image offset in the y direction y can have approximately the same magnitude as the z distance between the object plane 6 and the image plane 12.

[0138] In particular, the projection optical unit 10 may have a deformed design. It has different imaging ratios βx, βy in particular in the x and y directions x, y. The two imaging ratios βx, βy of the projection optical unit 10 are preferably (βx, βy) = (+ / -0.25, + / -0.125). A positive imaging ratio β means imaging without image inversion. A negative sign of the imaging ratio β means imaging with image inversion.

[0139] The projection optical unit 10 thus results in a reduction in size in the x-direction x (ie in a direction perpendicular to the scanning direction) by a ratio of 4:1.

[0140] The projection optical unit 10 results in a reduction in size in the y-direction y (ie in the scanning direction) of 8:1.

[0141] Other imaging ratios are likewise possible. Imaging ratios with the same sign and the same absolute value in the x-direction x and the y-direction y are also possible, for example with an absolute value of 0.125 or 0.25.

[0142] The number of intermediate image planes in the x-direction x and the y-direction y in the beam path between the object field 5 and the image field 11 may be the same or may be different, depending on the embodiment of the projection optical unit 10. Examples of projection optical units with different numbers of such intermediate images in the x-direction x and the y-direction y are known from US 2018 / 0074303A1.

[0143] In each case, one of the second partial facets 23 is assigned to exactly one of the first partial facets 21 in order to form in each case an illumination channel for illuminating the object field 5. This can lead in particular to The far field is decomposed into a plurality of object fields 5 by means of the first facets 21. The first facets 21 generate a plurality of images of the intermediate focus on the second facets 23 respectively assigned to them.

[0144] The first facets 21 are each imaged onto the reticle 7 and overlap each other via the assigned second facets 23 for the purpose of illuminating the object field 5. The illumination of the object field 5 is in particular as homogeneous as possible. It preferably has a homogeneity error of less than 2%. Field homogeneity can be achieved by overlapping different illumination channels.

[0145] The illumination of the entrance pupil of the projection optical unit 10 can be geometrically defined by the arrangement of the second facets 23. The intensity distribution in the entrance pupil of the projection optical unit 10 can be set by selecting the illumination channels, in particular the subset of the second facets 23, through which the light is guided. This intensity distribution is also referred to as illumination setting or illumination pupil filling.

[0146] A likewise preferred pupil homogeneity in the region of a section of the illumination pupil of the illumination optical unit 4 which is illuminated in a defined manner can be achieved by redistributing the illumination channels.

[0147] Further aspects and details of the illumination of the object field 5 and in particular the entrance pupil of the projection optical unit 10 are described below.

[0148] The projection optical unit 10 may in particular have a concentric entrance pupil. It may be accessible. It may also be inaccessible.

[0149] The entrance pupil of the projection optical unit 10 cannot usually be accurately illuminated by the second facet mirror 22. In the case of imaging the projection optical unit 10 by telecentrically imaging the center of the second facet mirror 22 onto the wafer 13, the aperture rays usually do not intersect at a single point. However, it is possible to find a region in which the spacing of the aperture rays determined in pairs becomes minimal. This region represents the entrance pupil or a region in real space conjugate therewith. In particular, this region exhibits a finite curvature.

[0150] It may be the case that the projection optical unit 10 has different positions of the entrance pupil for the tangential beam path and for the sagittal beam path. In this case, an imaging element, in particular an optical component part of the transfer optical unit, should be provided between the second facet mirror 22 and the reticle 7. With the help of this optical element, different positions of the tangential entrance pupil and the sagittal entrance pupil can be taken into account.

[0151] exist Figure 1 In the arrangement of the components of the illumination optical unit 4 shown, the second facet mirror 22 is arranged in a region conjugate with the entrance pupil of the projection optical unit 10. The first facet mirror 20 is arranged tilted relative to the object plane 6. The first facet mirror 20 is arranged tilted relative to the arrangement plane defined by the deflection mirror 19. The first facet mirror 20 is arranged tilted relative to the arrangement plane defined by the second facet mirror 22.

[0152] Figure 2 A method for processing a lithographic apparatus 1 (eg Figure 1 1. A schematic diagram of a first working example of an apparatus 100 for projecting an optical element 101 onto a surface 102 of a projection exposure apparatus (shown in FIG. 1). The optical element 101 is, for example, one of the optical elements of the illumination system 2, the illumination optical unit 4 or the projection optical unit 10, such as Figure 1 In particular, the optical element may be the light collector 17 , one of the deflection mirrors 19 and / or the facets 21 , 23 of the first facet mirror 20 or the second facet mirror 22 .

[0153] The apparatus 100 includes a sample holder 110 for holding an optical element 101 during a processing operation, a processing head 120 disposed opposite to and above a surface 102 to be processed of the optical element 101, and a moving unit 130. In this example, the processing head 120 includes a first outlet 121, a second outlet 122, and a cleaning device 123.

[0154] In this example, the processing head 120 is arranged on a moving unit 120, wherein the moving unit 130 is arranged to move the processing head 120 relative to the surface 102 of the optical element 101. The moving unit 130 may have one or more degrees of freedom, for example up to three linear degrees of freedom (displacement in three spatial directions x, y, z) and up to three rotational degrees of freedom (rotation around three axes).

[0155] The first outlet 121 is provided to pass the first precursor fluid PF1 (see Figures 3A-3C, 4, 5, 7) are supplied to the processing area 102A on the surface 102 of the optical element 101. In particular, the cleaning device 123 includes an outlet or an inlet for removing excess first precursor fluid PF1 from the processing area 102A. The second outlet 122 is provided to supply the second precursor fluid PF2 (see Figures 3A-3C , 4, 5, 7) are supplied to the processing region 102A. The first precursor fluid PF1 and the second precursor fluid PF2 are selected so that when the surface 102 is first exposed to the first precursor fluid PF1 and then to the second precursor fluid PF2, an atomic layer deposition process or an atomic layer etching process occurs in the processing region 102A. In the present context, this is achieved by moving the processing head 120 along a corresponding path across the surface 102 and the processing region 102A by the movement unit 130. In order to limit the process to a single layer ML (see Figures 3A-3C ), before supplying the second precursor fluid PF2, the excess first precursor fluid PF1 after applying the first precursor fluid PF1 is removed from the processing area 102A by means of the cleaning device 123. The spatial separation between the first outlet 121 and the second outlet 122 in the processing head 120 and the cleaning device 123 in between ensures that the precursor fluids PF1 and PF2 do not mix with each other. The first precursor fluid PF1 and / or the second precursor fluid PF2 are liquids.

[0156] Reference below Figures 3A-3C The atomic layer deposition process or the atomic layer etching process is described in detail. Figures 3A-3C 1 shows a schematic diagram of performing a spatial atomic layer processing operation in a processing region 102A of a surface 102 of an optical element 101. The process described below can be used, for example, with Figure 2 , Figure 7 , Figure 8 , Fig. 9A , Fig. 9B The device 100 is used to perform.

[0157] For the sake of clarity, Figures 3A-3C Only details of the optical element 101 and the processing head 120 are shown. Figure 4 and Figure 5 A more detailed illustration of the processing head 120 is shown in FIG.

[0158] Contaminants 103 are present on the surface 102 in the processing region 102A. This is, for example, tin deposits. The tin 103 comes, for example, from an EUV light source of a lithography apparatus in which the optical element 101 has been used.

[0159] exist Figure 3A, the processing head 120 is shown as being in a first position above the processing area 102A. In this position, only the first outlet 121 is above the processing area 102A. On both sides beside the first outlet 121, the inlet (sucking nozzle) of the cleaning device 123 is schematically shown (for example, the sucking nozzle completely surrounds the first outlet 121). For example, the first liquid precursor PF1 is supplied via the first outlet 121. This propagates in the area bounded by the sucking nozzle between the processing head 120 and the surface 102. The first precursor PF1 forms a monolayer ML at the contact surface between the first precursor PF1 and the surface 102. In the area of ​​the surface 102 that is not wetted by the contaminant 103, for example, the first precursor particles are adsorbed on the surface 102. In the case where the first precursor PF1 is in contact with the contaminant 103, a chemical reaction occurs, in particular, between the near-surface atoms of the contaminant 103 and the first precursor particles. A monolayer ML of an intermediate is formed here. For example, tin is oxidized to produce a monolayer of tin oxide. The monolayer ML has a layer thickness of, for example, 0.1 nm to 2 nm.

[0160] The processing head 120 moves over the processing region 102A, which is schematically indicated by arrows. It should be noted that it is also possible here for the optical element 101 to pass under the processing head 120. The width of the processing region 102A in the image plane is fixed by the width of the processing head 120, in particular the first outlet 121 and the second outlet 122. Figure 3A , the second outlet 122 is not yet disposed above the processing region 102A, and thus the second precursor fluid PF2 is not supplied.

[0161] Figure 3B It is shown how the processing head 120 is moved further across the processing area 102A, leaving a monolayer ML on the surface 102 in the area that has been in contact with the first precursor PF1. Excess first precursor fluid PF1 is sucked away. Figure 3B In the example, the second outlet 122 is also arranged above the processing area 102A, so the second precursor fluid PF2 is also supplied. In this example, the second outlet 122 is also surrounded by the suction nozzle of the cleaning device 123, so that the second precursor fluid PF2 is confined to the spatial area defined by the suction nozzle, the processing head 120 and the surface 102. The second precursor fluid PF2 is, for example, a strong acid, such as hydrochloric acid HCl, which is also supplied in liquid form.

[0162] The second precursor particles of the second precursor PF2 come into contact with the monolayer ML of the first precursor or intermediate at the surface 102. In this case, a chemical reaction CR occurs between the atoms of the monolayer ML and the particles of the second precursor PF2, in particular the formation of volatile compounds. This leads in particular to the attack of the intermediate monolayer ML of tin oxide. The tin oxide monolayer ML is thus removed or etched by the chemical reaction CR. This leads to effective etching of the contaminant 103. In this example, the contaminant 103 has a thickness of several monolayers and therefore after the described first atomic layer etching process, the tin 103 still remains on the surface 102, as shown in FIG. Figure 3C Repeating the process, ie performing the described steps multiple times, allows the contaminant 103 to be removed without residues.

[0163] Since the chemical reaction CR takes place only in the region of the intermediate monolayer ML, the atomic layer etching process is selective and limited to the contaminants 103. Thus, advantageously no damage to the surrounding surface 102 occurs.

[0164] It should be noted that when different precursors PF1, PF2 are used, a deposition process may be performed in the same way, instead of the etching process shown by way of example. A monolayer of atoms deposited in such a deposition process is formed wherever a monolayer ML of the first precursor PF1 is present on the surface 102.

[0165] Figure 4 A schematic diagram showing a cross section of a first working example of a processing head 120, which can be used, for example, in a Figure 2 , Figure 7 , Figure 8 or the device 100 of FIG. 9, and is suitable for performing the Figures 3A-3C Atomic layer processing operations illustrated.

[0166] Figure 4 The processing head 120 in the embodiment has two outlets 121 and 122 for supplying the first precursor fluid PF1 or the second precursor fluid PF2. The first outlet 121 and the second outlet 122 are each surrounded by an inlet 123A-123D of a cleaning device 123, for example, and the inlet 123A-123D takes the form of a suction nozzle (see Figure 2 or Figures 3A-3C ), so that the corresponding precursor fluids PF1, PF2 cannot escape from the bounded area between the corresponding suction nozzles 123A-123D.

[0167] In addition, the cleaning device 123 in this example includes a purge fluid outlet 123X configured to supply a purge fluid SF1. The purge fluid SF1 may be a liquid or a gas. For example, the purge fluid SF1 is an inert gas, such as nitrogen, which is supplied at a high flow rate so that the surface 102 is dry. Therefore, it can be ensured that no free first precursor fluid remains on the surface by means of the purge fluid outlet 123X.

[0168] This example also shows that the processing head 120 can have a certain degree of structuring on its lower side. For example, the lower side of the processing head 120 is slightly set back in the region of the first outlet 121 and the second outlet 122, so that a chamber is formed between the processing head 120 and the surface 102, and the corresponding precursor fluids PF1 and PF2 circulate in the chamber. At the side of the first outlet 121 and the second outlet 122, the processing head 120 includes additional elements protruding closer to the surface 102. For example, a gap defining a chamber is formed between these elements and the surface 102, and the gap has a width of, for example, only a few microns, which impairs the flow of the fluid to the outside. If the suction nozzle is subjected to sufficient decompression in addition, the corresponding chamber can be placed in a decompression relative to the surrounding atmosphere, so that the corresponding precursor fluids PF1 and PF2 still stop leaving through the gap.

[0169] Figure 5 A schematic diagram showing a cross section of a second working example of a processing head 120, which can be used, for example, in a Figure 2 , Figure 7 , Figure 8 or the device 100 of FIG. 9, and is suitable for performing the Figures 3A-3C Atomic layer processing operations illustrated.

[0170] In this example, the processing head 120 has three outlets 121, 122, 124 for supplying the corresponding precursor fluids PF1, PF2, PF3. The additional outlet 124 additionally has a plasma generator 125, which is arranged to ionize the precursor gas PF3 fed in via the outlet 124 so that it takes the form of plasma. Plasma can be particularly suitable for the activation of specific chemical reactions with high activation energy. It should be noted that the first outlet 121 and / or the second outlet 122 can also have a plasma generator 125, and the supplied first precursor fluid PF1 or the second precursor fluid PF2 can be a gas excited into a plasma state by the plasma generator 125.

[0171] The processing head 120 further has a plurality of suction nozzles 123A-123F. Four purge fluid outlets 123X are further shown, each of which is arranged to supply a corresponding purge fluid SF1-SF4. For example, the supplied purge fluid SF1 is a solvent in order to clean the surface 102 before contact with the first precursor PF1. The purge fluids SF2, SF3 and SF4 are intended, for example, to act as fluid curtains, in particular for separating areas where the precursors PF1, PF2, PF3 are present. For example, these are inert gases or liquids. For example, the two purge fluid outputs 123X for the purge fluids SF2, SF3 each form an air knife.

[0172] It should be noted that the processing head 120 may also have more inlets and / or outlets than those shown here, and / or the outlets and inlets may be integrated in the processing head 120 in a different arrangement.

[0173] Figure 6 A schematic diagram of the underside of a third working example of a processing head 120 is shown, which can be used, for example, in Figure 2 , Figure 7 , Figure 8 or the device 100 of FIG. 9, and is suitable for performing the Figures 3A-3C Atomic layer processing operations illustrated.

[0174] exist Figure 6 In the figure, the processing head 120 is circular. Several inlets and outlets 121, 122, 123A-123E, 123X are integrated in the lower side. They are a first outlet 121 for supplying a first precursor fluid PF1, a second outlet 122 for supplying a second precursor fluid PF2, two purge fluid outlets 123X for supplying corresponding purge fluids SF1-SF4, and several suction nozzles 123A-123E for suctioning and removing excess precursor fluids PF1, PF2 or purge fluids SF1-SF4. When the processing head 120 rotates, as shown by the arrows, the inlets and outlets 121, 122, 123A-123D, 123X successively cover the same surface section of the optical element 101 arranged opposite to the processing head. Therefore, the spatial atomic layer processing operation as described above can be performed using the processing head 120. The annular suction nozzle 123E ensures, for example, that the supplied precursor fluids PF1 , PF2 or purge fluids SF1 - SF4 do not leave the area between the processing head 120 and the surface 102 of the optical element 101 .

[0175] Figure 7 A schematic diagram of a second working example of an apparatus 100 for processing a surface 102 of an optical element 101 of a lithographic apparatus 1 is shown. The apparatus 100 has Figure 1All elements of the device 100 are not described here and are therefore not described again. In this example, the movement unit 130 is part of the sample holder 110, for example an xyz stage. The movement unit 130 can additionally be provided for rotating the sample holder 110 about one or more axes and thus in particular also for tilting the sample holder 110 and thus the optical element 101 (see also in this respect Figure 8 ). The sample holder 110 further has a temperature control device 112, which is arranged to heat or cool the optical element 101. Controlling the temperature of the optical element 101 allows influencing the atomic layer processing operation.

[0176] Furthermore, the apparatus in this example includes a housing 160 in which the sample holder 110, the processing head 120 and the moving unit 130 are arranged. The housing 160 may take the form of a vacuum housing, or it is used to provide an inert gas atmosphere for processing operations. The housing 160 is optional.

[0177] The processing head 120 shown here in simplified and schematic form can be as shown in Figure 4-6 102. In addition, two measuring devices 126 are arranged on the processing head 120. These are arranged to detect the respective distances D1, D2 from the surface 102 of the optical element 101. The respectively detected distances D1, D2 can advantageously be used for the open-loop or closed-loop control of the mobile unit 130, for example in order to establish a predetermined distance and keep the predetermined distance constant during the relative movement between the processing head 120 and the optical element 101. The measuring device 126 can alternatively or additionally be arranged to analyze the surface 102, for example in order to detect the chemical composition, the layer structure, etc. Then, after each atomic layer processing operation, the measuring device 126 can be used for direct process control. For example, the measuring device 126 comprises a spectroscopic ellipsometer and / or an infrared spectrometer.

[0178] One or more measuring devices (not shown) may also be arranged on or against the sample holder 110 and transversely to the optical element 101, which may be arranged to measure the distance between the processing head 120 and the surface 102. This is particularly advantageous in the case of a planar surface 102.

[0179] The first precursor fluid PF1 is held in a reservoir 141. This is, for example, a liquid. The precursor fluid PF1 can be supplied to the processing head 120 and the first outlet 121 via a conduit 142A in which a pump 143 is provided (see Figure 2-6 A temperature control device 146 is also provided in the feed pipe 142A, and the temperature control device 146 is configured to heat or cool the first precursor fluid PF1 before feeding the first precursor fluid PF1 into the processing area 102A (see Figures 3A-3C ).

[0180] Excess precursor fluid PF1 is sucked out via suction nozzles 123A-123F (see Figures 3-6). The decompression required for this purpose is provided, for example, by a pump 144 in pipeline 142B. A separator 145 is arranged in the suction pipeline, which can also be referred to as a pumping removal channel. The separator 145 separates the liquid component of the fluid removed by suction from the gas component. Therefore, the excess precursor fluid PF1 removed by suction is removed and can be returned to the reservoir 141 via pipeline 142C.

[0181] These details apply correspondingly to the second precursor fluid PF2 , which is delivered and processed via corresponding conduits 152A- 152C, pumps 153 , 154 , temperature control device 156 , and separator 155 .

[0182] Figure 8 A lithographic apparatus 1 (see Figure 1 ) is a schematic diagram of a third working example of a device 100 having a surface 102 of an optical element 101 disposed on a surface 102 of an optical element 101. The device 100 has Figure 1 All elements of the device 100 are not described herein, and therefore they will not be described again.

[0183] In this example, the optical element 101 has a curved surface 102; for example, this is the light collector 17 of the illumination system 2. It should be noted that the curvature of the surface 102 in this example is exaggerated in order to make it clearly visible. In order to obtain a uniform distance between the underside of the processing head 120 and the surface 102, the processing head matches the curvature of the surface 102 on its underside (the face of the processing head 120 opposite to the surface 102). That is, the underside of the processing head 120 has, for example, the same radius of curvature as the face 102, wherein the surface 102 is concave and the underside of the processing head 120 is convex. In embodiments, this can also be reversed.

[0184] The processing head 120 in this example is shown only schematically. With regard to the curved underside, the processing head 120 may be as follows Figure 4-6 The processing head 120 in this example also has two measuring devices 126, for which Figure 7 The explanations of are applicable accordingly. The measuring device 126 is particularly arranged to measure the distance between the processing head 120 and the surface 102, since in the case of a curved surface 102, without such constant monitoring of the distance, a collision of the processing head 120 with the surface 102 may occur rapidly in the case of a movement of the processing head 120 relative to the surface 102.

[0185] In this example, the mobile unit 130 comprises two separate units 130A, 130B. The unit 130A is, for example, specifically used for height adjustment of the optical element. When the unit 130A is duplicated, as shown here, the tilting of the optical element 101 can additionally be performed. This means that the mobile unit 130A comprises or forms a tilting unit. For this purpose, preferably three units 130A are provided, which can support and accordingly move the optical element 101 (or the housing for the optical element 101). The unit 130A is particularly actuated by the measuring device 126 in the open-loop and / or closed-loop control circuit so as to establish a specific distance between the surface 102 and the processing head 120 and avoid collisions. The unit 130B is designed in this example as a pivoting unit for the pivoting of the processing head 120. This means that the processing head 120 can be positioned at different positions on the surface 102, so that the processing area 102A is selectively addressable.

[0186] By means of a tilting unit, the surface 102 of the optical element 101 can also be arranged with a specific slope relative to the direction of gravity below the processing head 120. The liquid precursor will flow on the tilted surface, in particular in the direction of the gravity gradient, which can be utilized in order to impose a flow direction on the supplied precursor (or on the liquid purge fluid).

[0187] Fig. 9A and 9B A lithographic apparatus 1 (see Figure 1 ) of a fourth working example of a device 100 having a surface 102 of an optical element 101, wherein Fig. 9A shows a schematic side view of the device 100, and Fig. 9B A schematic top view of the device 100 is shown.

[0188] In this example, the sample holder 110 has a rotatably mounted stage 111, and the moving unit 130 is provided as a motor to drive (rotate) the stage 111. The processing head 120 is provided above the stage 111 so that when the stage 111 rotates, the optical element 101 held on the stage 111 travels under the processing head 120. The processing head 120 has a rectangular elongated shape and is arranged above the stage 111 so that the long sides extend outwardly in a substantially radial direction from the center (pivot point) of the stage 111.

[0189] Fig. 9BThe processing head 120 is shown in detail. This includes a first outlet 121, a second outlet 122, a number of suction nozzles 123A-123D and a purge fluid outlet 123X. The suction nozzles 123A-123D and the purge fluid outlet 123X together form a cleaning device 123. The processing head 120 in this example is particularly arranged at a fixed position, wherein the spatial atomic layer processing operation is achieved by moving the optical element 101 under the processing head 120 by means of a rotating stage 111.

[0190] It should be noted that with this configuration it is also possible to process optical elements 101 which are not circular and / or do not cover the entire stage 111. These are then arranged on the stage 111, for example, so that the rotation axis of the stage 111 is not covered.

[0191] In one embodiment (not separately shown), instead of a rotating stage, for example, a conveyor belt is provided that travels the optical element 101 beneath the processing head 120 .

[0192] Fig.10 The lithographic apparatus 1 is shown processed in an atomic layer processing operation (see Figure 1 ) of the optical element 101 (see Figures 2 to 5 , Figure 7 to FIG. 9) surface 102 (see Figures 2 to 5 , Figure 7 9) is a schematic block diagram of a working example of the method, such as by FIG. 3A to FIG. 3C In a first step S1, the optical element 101 is positioned in the sample holder 110 (see Figure 2 , 7 -9). In the second step S2, the processing head 120 (see Figure 2 9) is positioned opposite to the surface 102 of the optical element 101, so that the first outlet 121 of the processing head 120 is arranged to be aligned with the processing area 102A on the surface 102 (see Figure 2 Figure 3 Figure 8 9). In particular, the processing head 120 is at a predetermined distance from the surface 102, for example, a distance between 1 μm and 100 mm, preferably between 10 μm and 10 mm, more preferably between 50 μm and 1 mm, and further preferably between 50 μm and 500 μm. In a third step S3, the processing head 120 and / or the optical element 101 are moved so that the first outlet 121 moves over the processing area 102A, wherein during the movement, the processing head 120 is moved by means of the first outlet 121 (see Figures 2 to 6 , Fig. 9B ), the first precursor fluid PF1 (see FIG. 3 to Figure 5 , Figure 7) is supplied to the processing area 102A. In the fourth step S4, the processing head 120 and / or the optical element 101 are moved forward so that the cleaning device 123 (see Figures 2 to 6 , Fig. 9B ) moves across the processing region 120A, wherein the cleaning device 123 is arranged to remove excess first precursor fluid PF1 from the processing region 102A. In a fifth step S5, the processing head 120 and / or the optical element 101 moves forward so that the second outlet 122 (see Figures 2 to 6 , Fig. 9B ) moves across the processing region 102A, wherein during the movement, through the second outlet 122, the second precursor fluid PF2 (see FIGS. 3 to 4) is Figure 5 , Figure 7 ) is supplied to the processing area 102A. The first precursor fluid PF1 and the second precursor fluid PF2 are selected so as to perform an atomic layer deposition process or an atomic layer etching process in the processing area 102A. Here, the first precursor fluid PF1 and / or the second precursor fluid PF2 are liquids.

[0193] The method uses at least one liquid precursor fluid PF1, PF2 to achieve a spatial atomic layer processing operation. The method may in particular provide for using gaseous and liquid precursor fluids in the process.

[0194] Although the invention has been described with reference to working embodiments, it can be modified in various ways.

[0195] Reference numerals list

[0196] 1 Projection exposure equipment

[0197] 2 Lighting system

[0198] 3 Light Source

[0199] 4 Illumination optical unit

[0200] 5. Material Field

[0201] 6 Object Plane

[0202] 7. Mask Master

[0203] 8 Reticle Holder

[0204] 9 Mask Master Displacement Driver

[0205] 10 Projection optics unit

[0206] 11 Image Field

[0207] 12 Image plane

[0208] 13 Chip

[0209] 14 Wafer Holder

[0210] 15 Chip shift driver

[0211] 16 Lighting Radiation

[0212] 17 light collector

[0213] 18 Intermediate focal plane

[0214] 19 Deflecting mirror

[0215] 20 First facet mirror

[0216] 21 First facet

[0217] 22 Second facet reflector

[0218] 23 Second facet

[0219] 100 devices

[0220] 101 Optical Components

[0221] 102 Surface

[0222] 102A Surface Area

[0223] 103 Pollutants

[0224] 110 Sample Holder

[0225] 112 Temperature Control Unit

[0226] 120 Processing head

[0227] 121 Exit 1

[0228] 122 Second Exit

[0229] 123 Cleaning device

[0230] 123A Inlet (nozzle)

[0231] 123B Inlet (nozzle)

[0232] 123C Inlet (nozzle)

[0233] 123D Inlet (nozzle)

[0234] 123E Inlet (nozzle)

[0235] 123F Inlet (nozzle)

[0236] 123X Purge fluid outlet

[0237] 124 Exit

[0238] 125 Plasma Generator

[0239] 126 Measuring device

[0240] 130 Mobile Units

[0241] 130A Mobile Unit

[0242] 130B Mobile Unit

[0243] 141 Storage

[0244] 142A Pipeline Section

[0245] 142B Pipeline Section

[0246] 142C Pipeline Section

[0247] 143 Pump

[0248] 144 Pump

[0249] 145 Separation equipment

[0250] 146 Temperature Control Unit

[0251] 151 Storage

[0252] 152A Pipeline Section

[0253] 152B Pipeline Section

[0254] 152C Pipeline Section

[0255] 153 Pump

[0256] 154 Pump

[0257] 155 Separation equipment

[0258] 156 Temperature Control Unit

[0259] 160 Housing

[0260] CR Chemical Reaction (Deposition / Etch)

[0261] M1 Reflector

[0262] M2 Reflector

[0263] M3 Reflector

[0264] M4 Reflector

[0265] M5 Reflector

[0266] M6 Reflector

[0267] ML Single Layer

[0268] PF1 Precursor Fluid

[0269] PF2 Precursor Fluid

[0270] PF3 Precursor Fluid

[0271] S1 Method steps

[0272] S2 Method Steps

[0273] S3 Method Steps

[0274] S4 Method steps

[0275] S5 Method Steps

[0276] SF1 Purge Fluid

[0277] SF2 Purge Fluid

[0278] SF3 Purge Fluid

[0279] SF4 Purge Fluid

Claims

1. A device (100) for processing a surface (102) of an optical element (101) of a lithography apparatus (1), in particular an EUV lithography apparatus, in an atomic layer processing operation, comprising: a sample holder (110) for holding the optical element (101) during the processing operation, A processing head (120), the processing head (120) having a first outlet (121) for supplying a first precursor fluid (PF1) to a processing area (102A) on the surface (102) of the optical element (101), a cleaning device (123) for removing excess first precursor fluid (PF1) from the processing area (102A), and a second outlet (122) for supplying a second precursor fluid (PF2) to the processing area (102A), wherein: The first precursor fluid (PF1) and the second precursor fluid (PF2) are selected to perform an atomic layer deposition process or an atomic layer etching process in the processing area (102A), and wherein the first precursor fluid (PF1) or the second precursor fluid (PF2) is a liquid and has: A moving unit (130) is configured to move the processing head (120) and / or the sample holder (110) and the optical element (101) relative to each other so that the first outlet (121), the cleaning device (123) and the second outlet (122) successively pass through the processing area (102A) of the precursor fluid.

2. The device according to claim 1, wherein: The first precursor fluid (PF1) and the second precursor fluid (PF2) are liquids.

3. The device according to claim 1 or 2, wherein: During the performance of the processing operation, the optical element (101) is arranged in an inert gas atmosphere having a pressure in the range of 0.01 atm to 10 atm, preferably 0.1 atm to 5 atm.

4. The device according to any one of claims 1 to 3, wherein: The cleaning device (123) comprises at least one outlet and / or inlet, and the at least one outlet and / or inlet is arranged between the first outlet (121) and the second outlet (122) along a path corresponding to the relative movement between the optical element (101) and the processing head (120).

5. The device according to any one of claims 1 to 4, wherein: The cleaning device (123) comprises at least one inlet (123A-123F), and the at least one inlet (123A-123F) is configured to remove the first precursor fluid (PF1) or the second precursor fluid (PF2) by suction.

6. The device according to claim 5, wherein: The at least one inlet (123A-123F) leads to a pumping removal channel (142B, 152B), and wherein a separation device (145, 155) is arranged along the pumping removal channel (142B, 152B) and is arranged to separate and collect the pumped removal precursor fluid (PF1, PF2) from the pumped removal fluid.

7. The device according to any one of claims 1 to 6, wherein: The cleaning device (123) comprises a plurality of inlets (123A-123F) for sucking and removing fluid and a plurality of purge fluid outlets (123X) for supplying corresponding purge fluids (SF1-SF4).

8. The device according to claim 7, wherein: At least one of the purge fluids (SF1-SF4) is a liquid.

9. The device according to any one of claims 1 to 8, wherein: The processing head (120) comprises a temperature control device (146, 156) to control the temperature of the first precursor fluid (PF1) and / or the second precursor fluid (PF2).

10. The device according to any one of claims 1 to 9, wherein: The first precursor fluid (PF1) or the second precursor fluid (PF2) is a gas, and the processing head (120) comprises a plasma generator (125) for generating plasma from the gaseous precursor fluid (PF1, PF2).

11. The apparatus according to any one of claims 1 to 10, further comprising a sample temperature control device (112) for controlling the temperature of the optical element (101) arranged in the sample holder (110).

12. The apparatus of any one of claims 1 to 9 or claim 11, wherein: The first precursor fluid (PF1) is an acidic aqueous solution, and the second precursor fluid (PF2) is an alkaline aqueous solution.

13. The device according to claim 12, wherein: The first precursor fluid (PF1) and / or the second precursor fluid (PF2) further comprises an oxidizing agent.

14. The device according to any one of claims 1 to 13, further comprising a measuring device (126) for detecting the distance (D1, D2) between the processing head (120) and the surface (102) of the optical element (101), wherein: The moving unit (130) is configured to move the processing head (120) and / or the optical element (101) at a predetermined distance from each other.

15. The apparatus according to any one of claims 1 to 14, wherein: The optical element (101) has a piecewise curved surface (102), and the underside of the processing head (120) that is opposite to the optical element (101) during the processing operation has a shape that matches the curvature.

16. A method for processing a surface (102) of an optical element (101) of a lithography apparatus (1), in particular an EUV lithography apparatus, in an atomic layer processing operation, the method comprising the following steps: placing (S1) the optical element (101) on a sample holder (110), positioning (S2) a processing head (120) opposite to the surface (102) of the optical element (101) so that a first outlet (121) of the processing head (120) is arranged opposite to a processing area (102A) on the surface (102), moving (S3) the processing head (120) and / or the optical element (101) so that the first outlet (121) moves across the processing area (102A), wherein during the movement, a first precursor fluid (PF1) is supplied to the processing area (102A) through the first outlet (121), Moving (S4) the processing head (120) and / or the optical element (101) so that a cleaning device (123) of the processing head (120) moves across the processing area (102A), wherein the cleaning device (123) is configured to remove excess first precursor fluid (PF1) from the processing area (102A); moving (S5) the processing head (120) and / or the optical element (101) so that a second outlet (122) of the processing head (120) moves across the processing area (102A), wherein during the movement, a second precursor fluid (PF2) is supplied to the processing area (102A) through the second outlet (122), Wherein, the first precursor fluid (PF1) and the second precursor fluid (PF2) are selected to perform an atomic layer deposition process or an atomic layer etching process in the processing area (102A), and wherein the first precursor fluid (PF1) and / or the second precursor fluid (PF1) are liquids.

17. A method for repairing a lithography apparatus (1), in particular an EUV lithography apparatus, comprising: Removing an optical element (101) from a beam path of the lithographic apparatus (1), wherein the optical element (101) has contaminants (103) and / or damage on an entrance surface, Processing the optical element (101) by the processing method according to claim 16, and The processed optical element (101) is mounted in the lithographic apparatus (1).

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