Method and apparatus for etching a lithography mask

Abstract

Method for particle beam-induced etching of a lithography mask (100), comprising the steps: a) providing (S1) the lithography mask (100) in a process atmosphere (ATM), b) irradiating (S2) a focused particle beam (110) onto a target position (ZP) on the lithography mask (100), c) supplying (S3) at least one first gaseous component (GK1) to the target position (ZP) in the process atmosphere (ATM), wherein the first gaseous component (GK1) can be converted into a reactive form by activation, wherein the reactive form reacts with a material of the lithography mask (100) to form a volatile compound, and d) supplying (S4) at least one second gaseous component (GK2) to the target position (ZP) in the process atmosphere (ATM), so that the process atmosphere (ATM) comprises the first and the second gaseous component (GK1, GK2) when step b) is carried out, wherein the second gaseous component (GK2) forms a deposit comprising a compound of silicon with oxygen, nitrogen and / or carbon under predetermined process conditions under the action of the particle beam (110).

Description

The present invention relates to a method for etching a lithography mask.Microlithography is used for producing microstructured components, such as integrated circuits. The microlithography process is carried out with a lithography apparatus which has 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, for example a silicon wafer, coated with a photosensitive layer (photoresist) and arranged in the image plane of the projection system, in order to transfer the mask structure to the photosensitive coating of the substrate.In order to achieve small structure sizes and thus to increase the integration density of the microstructured components, light having very short wavelengths is increasingly used, which is referred to, for example, as deep ultra-violet (DUV) or extreme ultra-violet (EUV). DUV has, for example, a wavelength of 193 nm and EUV has, for example, a wavelength of 13.5 nm. The lithography masks themselves have structure sizes which are in the range of 5-100 nm. The production of such lithography masks is very complicated and therefore expensive, in particular since the lithography masks have to be defect-free, since otherwise it is not ensured that a structure produced with the lithography mask has the desired function. For this reason, lithography masks are verified, for example, that is to say the defect freedom of the lithography mask is checked. Defects are thereby detected and localized, which enables a targeted repair of the defects. Typical defects are the absence of provided structures, since, for example, an etching process did not successfully take place, or provided structures are present, since, for example, an etching process has advanced too quickly or acted on at a wrong location. These defects can be eliminated by selective etching of excess material or selective deposition of additional material at the corresponding positions, which is possible very selectively, for example, by means of Focused Electron Beam Induced Processing (FEBIP).DE 10 2017 208 114 A1 discloses a method for particle beam-induced etching of a photolithographic mask, comprising the steps of: providing an activating particle beam at a location to be etched; and providing an etching gas at the location to be etched, wherein the etching gas comprises a first gaseous component and water vapor as a second gaseous component, and wherein the first gaseous component comprises nitrogen, oxygen and chlorine in a compound.DE 10 2013 203 995 A1 discloses a method and an apparatus for protecting a substrate during processing with at least one particle beam. The method comprises the following steps: applying a locally delimited protective layer on the substrate; etching the substrate and / or a layer arranged on the substrate by the particle beam and at least one gas and / or depositing material on the substrate by the particle beam and at least one precursor gas; and removing the locally delimited protective layer from the substrate.US 2012 / 0 328 974 A1 discloses an apparatus and a method for correcting opaque or transparent defects of a lithography mask using an ion beam which is irradiated onto the defect of the lithography mask. In addition to the irradiation of the ion beam, a process gas may be supplied that contributes to increasing an etching rate of an opaque defect. For correcting a transparent defect, a deposition gas may be supplied to deposit a transparent layer. It is also proposed to irradiate an electron beam in addition to the ion beam in order to avoid positive charging of the machined position.DE 10 2019 201 468 A1 discloses an apparatus and a method for processing a lithography mask in a particle beam-induced deposition or etching process with the supply of a suitable precursor gas. The apparatus comprises a means for changing the mean angle of incidence of the particle beam on the surface to be processed, which makes it possible to adapt an edge steepness of a processed structure.DE 103 38 019 A1 discloses a method for etching a chromium layer in a vacuum chamber. Furthermore, a method for the high-resolution production of a metal layer and / or a metal oxide layer and / or an insulator is disclosed. The method comprises the steps of arranging a substrate in a vacuum chamber, introducing at least one inorganic, organic or organometallic precursor into the vacuum chamber and depositing the precursor on the substrate.Against this background, it is an object of the present invention to improve the processing of a lithography mask.According to a first aspect, a method for particle beam-induced etching of a lithography mask, in particular a non-transmissive EUV lithography mask, is proposed. In a first step a), the lithography mask is provided in a process atmosphere. In a second step b), a focused particle beam is irradiated onto a target position on the lithography mask. In a third step c), at least one first gaseous component is supplied to the target position in the process atmosphere, wherein the first gaseous component can be converted into a reactive form by activation, wherein the reactive form reacts with a material of the lithography mask to form a volatile compound. In a fourth step d), at least one second gaseous component is supplied to the target position in the process atmosphere, such that the process atmosphere has the first and the second gaseous component when step b is carried out, wherein the second gaseous component forms a deposit comprising a compound of silicon with oxygen, nitrogen and / or carbon under predetermined process conditions under the action of the particle beam.This method has the advantage that the etching process which takes place is better controlled and can therefore be carried out in a more targeted and specific manner. Overall, the process resolution of the etching process can thus be increased. This allows lithography masks with smaller structures to be processed in a targeted manner and / or defects with a smaller size can be processed.The indicated sequence of the individual method steps, in particular steps b)- d), does not necessarily have to take place in the indicated sequence, but rather the steps can be carried out simultaneously, alternately and / or in another combination or temporal sequence.The particle beam-induced etching advantageously takes place substantially at the position at which the particle beam impinges on the surface of the lithography mask to be processed. The spatial limitation or resolution of the etching process depends, for example, on the type of particle beam. The particle beam can comprise photons, ions, protons, neutrons or also electrons, for example. The use of an electron beam is particularly advantageous since, on the one hand, it can be focused on a very small incident surface and, on the other hand, the electrons do not cause any substantial damage to the irradiated surface. Therefore, the achievable resolution with an electron beam is particularly high.In principle, the etching process proceeds on a molecular level in such a way that the particle beam impinges on the surface to be processed and there triggers, for example, secondary electrons which emerge, for example, from the surface in the region of the impingement surface. These secondary electrons have an energy that may be sufficient to dissociate molecules. If such a secondary electron encounters an as yet non-activated etching gas molecule which is adsorbed on the surface, for example, this can dissociate and thus be brought into a reactive form. The reactive form reacts, for example, to form a volatile compound having an atom or molecule in the surface of the material. In this way, the surface is therefore eroded. The exact physicochemical processes which take place in this case are very diverse and complex and the subject of current research.Relevant parameters which substantially influence the etching process and thus serve for controlling the same are, for example, the temperature, the composition of the process atmosphere, a local gas pressure at the target position and the partial pressures of the components and an intensity and energy of the particle beam. This list is not exhaustive.The process atmosphere is, for example, an atmosphere having a controlled composition and a controlled pressure which is, for example, in the range from 10 -2 to 10 -8 mbar. The process atmosphere is provided, for example, by an evacuated housing. However, the process atmosphere is subject to spatial and temporal fluctuations. In particular, the process atmosphere in the processing region can have a greater variation in its composition, since this depends on the supply of the process gases and on the chemical reactions. Further, the pressure of the process atmosphere may be several orders of magnitude higher during processing of the lithography mask compared to times when no processing occurs. Also, the pressure in the processing area may be several magnitudes different from the pressure elsewhere in the evacuated enclosure.The lithography mask is in particular an EUV lithography mask. EUV stands for extreme ultraviolet and denotes a wavelength of the working light in a range of 0.1-30 nm, in particular 13.5 nm. At these wavelengths, reflective optical elements must be used, as does the lithography mask. The lithography mask therefore has a layer which is reflective for the EUV radiation and is in particular embodied as a Bragg mirror, and a structured absorbing layer on the reflective surface. This is also referred to as binary lithography masks. The structured absorbing layer achieves a spatial modulation of the intensity of the reflected radiation, which ultimately leads to a targeted local variation in the exposure on the sample.The lithography mask therefore has, for example, regions which reflect as much of the total incident radiation as possible and, in addition, other regions which absorb a specific part of the radiation. The radiation does not have to be completely absorbed in these regions. The extent to which the residual intensity is allowed to be, which is still tolerable, depends on the respective lithography process. Preferably, less than 10% of the incident intensity is reflected.Any defect or defect in the structure of the patterned layer will result in an undesired exposure in the lithography process, which is why it is particularly important that the lithography mask has as few defects as possible. Defects present are determined by means of specific test methods and subsequently repaired in a targeted manner as far as possible. The method proposed here is particularly suitable for removing material that has remained at positions at which no material should be. This is also called an opaque defect, since the material absorbs the EUV radiation and therefore too low an intensity is present in the reflected radiation. These defects can be corrected by selective etching of the excess material.In a third step c), at least one first gaseous component is supplied to the target position in the process atmosphere. The first gaseous component forms the etching gas in the present case. This is distinguished in that it contains very reactive constituents in a comparatively low reactive compound. Suitable reactive constituents are, in particular, halogens, such as fluorine or chlorine. The etching gas can be decomposed by activation or otherwise converted into the reactive form.The etching gas is supplied as close as possible to the target position in the process atmosphere. The etching gas itself has, for example, a pressure in the range from 10 -3 to 10 -4 mbar. Individual molecules of the etching gas will adsorb on the surface of the lithography mask. In the adsorbed state, these molecules are bound to the surface at a small distance, but can also diffuse on the surface. In this way, for example, an adsorbed monolayer of the molecules can form on the surface of the lithography mask, preferably in the region of the target position. Due to the spatial proximity of the adsorbed molecules to the surface atoms of the lithography mask, the probability of a dissociated reactive molecule reacting with an atom of the surface is greatly increased.The etching gas is activated indirectly via the particle beam. As already described, the activation is triggered, for example, by secondary electrons triggered by the particle beam from the surface. The activation can also take place directly by the particles of the particle beam, but an effective cross section for such a reaction is very small, for which reason it makes only a small contribution. The effective cross section depends, for example, on the beam energy and can be influenced thereby.The reaction of the active species of the etching gas with a surface atom advantageously forms a volatile compound which can be pumped away from the target position via the process atmosphere.Although the particle beam-induced etching process already achieves a high process resolution as described above, undesirable side effects such as spontaneous reactions that have not been induced by the particle beam or etching reactions at positions other than the target position may also occur. In order to better control the etching process, it is therefore proposed to supply a second gaseous component to the target position in the process atmosphere. The second gaseous component comprises a chemical compound which, under predetermined process conditions, forms a deposit comprising a compound of silicon with oxygen, nitrogen and / or carbon under the action of the particle beam. The predetermined process conditions include in particular a pressure and a partial pressure of the second gaseous component at the target position and a further composition of the process atmosphere at the target position. It can also be said that the second gaseous component comprises a separation gas or a deposition gas.This is unusual because the goal of processing is removal of material and not build-up of material. However, the applicant has demonstrated in experiments that, by supplying such a deposition gas, the etching process can be carried out with improved control, in particular with respect to an etching rate, and with significantly reduced damage to the lithography mask both at the target position and at other positions.The second gaseous component is supplied to the target position in a manner corresponding to the first gaseous component in a manner as targeted as possible. The molecules of the second gaseous component can likewise adsorb on the surface of the lithography mask. The two gaseous components compete for the free sites on the surface. In equilibrium, for example, a distribution will be established which depends, inter alia, on the partial pressures of the two components in the gas phase, the tendency to adsorb on the respective surface and individual mobilities of the molecules.When a molecule of the second gaseous component adsorbed on the surface is activated, which can occur, for example, by a secondary electron, the molecule can decompose, whereby, for example, a molecule with silicon and oxygen, such as SiO or SiO 2, attaches to the surface. Preferably, the process conditions in the proposed etching method are set such that no deposit is formed or a deposit is formed only to an insignificant extent. This is understood to mean, for example, that a ratio of etched material to deposited material is at least 5:1, preferably 10:1, more preferably 20:1, even more preferably 50:1 and even more preferably 100:1.In order to control the etching process in a targeted manner, the individual gas flows of the first and second gaseous components are preferably controlled. The gas flow of the first gaseous component is, for example, in a range of 0.1 sccm-10 sccm (sccm=standard cubic centimeters). The gas flow of the second gaseous component is preferably adjusted with respect to the gas flow of the first component, for example a ratio of 100:1 up to 10,000:1 of the first gaseous component to the second gaseous component is adjusted. The ratio of the gas flows of the first and second components is particularly relevant, since this determines the stoichiometric ratio of the components in the region of the target position.In one embodiment, the second gaseous component comprises a silicate, a silane, a siloxane, a silazane, and / or a silicon isocyanate.Silicates are the salts and esters of ortho-silicic acid Si(OH 4). Silanes have a silicon backbone that is saturated with hydrogen. Siloxanes and silazanes are compounds derived from the silanes, with siloxanes having the general empirical formula R 3 Si-[O-SiR 2]n- O-SiR 3 (here R stands for a radical which can be a hydrogen atom or an alkyl radical) and silazanes having the general empirical formula R 3 Si-[NH-SiR 2]n- NH-SiR 3.An example of a silicate is tetraethyl orthosilicate Si(OC 2 H 5)4, an example of a silane is cyclopentasilane H 10 Si 5, an example of a siloxane is pentamethyldisiloxane C 5 H 15 OS 12, an example of a silazane is 1,1,3,3-tetramethyldisilazane (CH 3)2( SiH) 2 O, and an example of a silicon isocyanate is tetraisocyanatosilane C 4 N4O4Si. The composition which comprises any deposit formed also depends in particular on the further additional gases which are fed in in the processing process. For example, a deposit containing silicon nitride could be formed in the case of a silane in conjunction with ammonia NH 3.According to a further embodiment, a deposit formed during the etching process by the second gaseous component is removed in a wet chemical cleaning step of the lithography mask.This has the advantage that the deposit which has a protective effect during the particle beam-induced etching process is removed without residue and therefore exerts no influence in a lithography process carried out with the processed lithography mask.According to a further embodiment, the first gaseous component comprises one of xenon difluoride XeF 2, sulfur hexafluoride SF 6, sulfur tetrafluoride SF 4, nitrogen trifluoride NF 3, phosphorus trifluoride PF 3, tungsten hexafluoride WF 6, tungsten hexafluoride WCl 6, molybdenum hexafluoride MoF 6, hydrogen fluoride HF, nitrogen oxygen fluoride NOF, and / or triphosphorus trinitrogen hexafluoride P 3 N 3 F6.According to a further embodiment, the feeding of the second gaseous component takes place temporally before and / or after the irradiation of the particle beam onto the target position.The second gaseous component is conducted, for example, via a line system to the target position. Valves or similar control devices for adjusting a volume or mass flow of the second gaseous component can be provided in the line system in order to control the supply of the second gaseous component exactly. For example, the second gaseous component is supplied before the irradiation of the target position by opening a corresponding valve. The valve is then closed and the particle beam is irradiated. Depending on the line length from the valve to a nozzle at the target position, a decreasing gas flow into the process atmosphere still results even when the valve is closed. In addition, gas molecules adsorbed on the surface remain adsorbed on the surface for a while, and thus the positive effect is obtained even though the second gaseous component is no longer supplied during irradiation. It can also be said that a partial pressure or a stoichiometric proportion of the second gaseous component in the process atmosphere in the region of the target position is still sufficiently high for a specific duration to achieve the positive effect even after the valve has been closed.According to a further embodiment, the feeding of the second gaseous component takes place during the irradiation of the particle beam onto the target position.According to a further embodiment, a third gaseous component comprising an oxidizing agent and / or a reducing agent is additionally supplied.The third gaseous component can take place temporally before, during and / or after the irradiation of the particle beam onto the target position. The third gaseous component can be supplied to the first and / or the second gaseous component temporally before, during and / or after the supply of the first and / or the second gaseous component and / or intermittently. Intermittent is understood here to mean that the respective components are supplied alternately.Examples of oxidizing agents are hydrogen peroxide H 2 O 2, nitrous oxide N 2 O. Examples of reducing agents are nitrogen oxide NO, nitrogen dioxide NO 2, nitric acid HNO 3, hydrogen H 2, ammonia NH 3, and / or methane CH 4. It should be noted that oxidizing agents can also act as reducing agents and reducing agents can also act as oxidizing agents, depending on the extent to which the oxidizing or reducing ability of the respective other component is oxidized or reduced.The etching process can be controlled even better by a third gaseous component by creating additional reaction paths and / or by favorably influencing a chemical equilibrium of an equilibrium reaction.In embodiments, a chemically inert buffer gas may additionally be supplied, which may contribute in particular to a stabilization of the etching process, such as a substantially spatially and temporally homogeneous etching rate. Suitable buffer gases are preferably noble gases, such as argon.According to a further embodiment, the supplying of the first gaseous component, the second gaseous component and / or the third gaseous component comprises providing a solid or liquid phase of the respective component, adjusting a temperature of the solid or liquid phase of the respective component such that a predefined vapor pressure of the respective component is achieved above the solid or liquid phase, and supplying the respective gaseous component into the process atmosphere via a respective supply line.This embodiment is particularly advantageous with respect to the control of the individual gas flows of the respective component. For example, for each component being supplied, a separate container or tank is provided in which the respective solid or liquid phase is stored. Each tank is assigned a temperature control medium, with which the temperature of the tank contents can be adjusted. The temperature control medium comprises, for example, electrothermal elements, such as a Peltier element, which can be used for cooling or for heating. Cooling circuits can also be provided in order to achieve a temperature of significantly below 0° C.The vapor pressure of the solid or liquid phase of a respective component can be controlled very accurately via the temperature. Due to the low pressure of the process atmosphere, a pressure gradient is present from a respective tank into the process atmosphere, which causes a flow of the respective gaseous component from the tank via the feed line into the process atmosphere.The separate gas flows of the plurality of gaseous components are mixed with one another, for example, in a common mixing chamber into which the respective feed lines end and from which a further feed line leads into the process atmosphere, so that a homogeneous mixture is produced.According to a further embodiment, a line cross section of the respective feed line is adjusted for controlling a mass flow and / or volume flow of the respective gaseous component and / or a duty cycle of a closing valve is controlled.In this way, on the one hand, the gas flow quantity can be controlled even more accurately, and on the other hand, fast variations in a gas flow can be achieved. For example, a first gas flow ratio of the first and second gaseous components is selected before the irradiation of the particle beam, a second gas flow ratio is selected during the irradiation and a third gas flow ratio is selected after the irradiation. The respective time durations are in the range of minutes here. The temperature of the solid or liquid phase of the respective component cannot be changed rapidly, since the heat-conducting processes themselves proceed on a time scale in the range of several minutes.For example, a respective feed valve for controlling the mass flow and / or the volume flow of the respective gaseous component is arranged in the respective feed line, wherein the respective feed valve is configured for setting a predetermined line cross section.Alternatively or additionally, the valve may be switched between a closed position and an open position according to a predetermined duty cycle between 0 and 100. The duty cycle here indicates the ratio of a closing time of the feed valve to an opening time of the feed valve, where 0= always open and 100= always closed. For example, when 1 second is selected as the basic interval, that is, the shortest possible opening or closing time is 1 second, a duty cycle of 10 means that the supply valve is opened for one second and then closed for ten seconds. This method, also referred to as "chopping", only leads to a negligible fluctuation of the partial pressure of the respective gaseous component in the process atmosphere, in particular since the volume of the feed line in the manner of a buffer maintains a gas flow even when the valve is closed.According to a further embodiment, the particle beam consists of charged particles, in particular of electrons.Electrons have the advantage that they cause no damage, or only very little damage, to the irradiated surface, since they do not penetrate deeply into the material and can flow off easily as current. On the other hand, electron beams can be focused on very small irradiation surfaces having a diameter in the range of 10 nm, so that the resolution of the etching process is particularly high.According to a further embodiment, the lithography mask is configured for use in EUV lithography.EUV lithography masks have a fundamentally different structure than lithography masks which can be used transmissively, such as, for example, lithography masks for DUV lithography (DUV: deep ultraviolet, working light wavelength, for example 193 nm). DUV lithography masks have, for example, a transparent quartz substrate and a likewise transparent but phase-influencing structured layer, such as, for example, silicon nitride. The chemistry of an EUV lithography mask is fundamentally different from this, since the optical properties of materials at EUV wavelengths are fundamentally different.For example, the EUV lithography mask has a layer-like structure, wherein a carrier or substrate, which can consist for example of quartz glass or of silicon, forms the base. On the side which is later irradiated with the working light during operation, a Bragg mirror or multilayer mirror is arranged which is formed specifically for the respective wavelength of the working light. In this case, layers having a high and a low refractive index, based on the wavelength of the working light, and having a layer thickness of approximately half the wavelength of the working light are arranged alternately one above the other. For example, the working light has a wavelength of 13.5 nm. A multilayer mirror comprising a plurality of double layers, for example made of molybdenum and silicon, each having a layer thickness of 6.75 nm would then be suitable as a Bragg mirror (in the case of perpendicular light incidence). The multilayer mirror can be produced by means of known deposition processes, such as chemical vapor deposition (CVD) or the like. An etch stop layer is disposed on the multilayer mirror. The etch stop layer has the function, on the one hand, of stopping etching processes used during the structuring of the structured layer, so that the multilayer mirror is not attacked. On the other hand, the etch stop layer itself is a component of the multilayer mirror. The etch stop layer therefore has, in particular, a layer thickness adapted accordingly to the working light. The etch stop layer is made of ruthenium or another noble metal, for example. The patterned layer on the etch stop layer absorbs the EUV radiation and is thus the layer that induces modulation in the spatial illumination intensity of the radiation.The requirements for surface homogeneity are particularly high in EUV lithography masks. In particular, a surface roughness of the reflective surfaces in the sub-nanometer range is to be controlled, since otherwise scattering losses occur and thus impair the lithography process.According to a further embodiment, the lithography mask has an etch stop layer, on the front side of which a patterned layer made of a material which has an absorbing effect for the radiation used in a lithography process is arranged, wherein an etching rate of the activated first gaseous component with respect to the etch stop layer is lower than the etching rate with respect to the patterned layer by at least a factor of 2, preferably by a factor of 5, further preferably by a factor of 10.The patterned layer includes, in particular, tantalum compounds such as tantalum nitride TaN, tantalum oxide TaO, tantalum oxynitride TaNO, tantalum boron nitride TaN, and the like. However, other materials having an absorbing effect for the radiation used for the exposure in the lithography process are likewise possible here. The etch stop layer comprises in particular a noble metal, such as ruthenium. The etching process can be better controlled by the etching selectivity.According to a further embodiment, the lithography mask comprises a mirror layer formed as a multilayer mirror made of a plurality of bilayers, wherein a respective bilayer comprises a first layer made of a first chemical composition and a second layer made of a second chemical composition, wherein a respective layer thickness of the first and the second layer is in a range of 3-50 nm, preferably 3-20 nm, preferably 5-10 nm, more preferably 5-8 nm, even more preferably 6-7 nm.The optical properties of the first chemical composition and of the second chemical composition, in particular a refractive index, differ with respect to the radiation used in a lithography process.For example, the multilayer mirror comprises a number of 50-100 bilayers, i.e. 100-200 monolayers. The multilayer mirror can additionally have further intermediate layers which, for example, reduce diffusion of atoms from one layer into the adjacent layer within the multilayer stack. Such intermediate layers preferably have an optically substantially imperceptible layer thickness, for example a few atomic layers.The respective combination of the first and second chemical compositions is preferably selected on the basis of a refractive index contrast of the two chemical compositions. The respective layer thickness is preferably selected such that the optically effective thickness of the layer corresponds to approximately half a wavelength, taking into account the angle of incidence. A slight deviation therefrom, for example in order to compensate intermediate layers, can be provided.According to a further embodiment, the particle beam has an energy of 1 eV-100 keV, preferably of 3 eV-30 keV, preferably of 10 eV-10 keV, further preferably of 30 eV-3 keV, even more preferably of 100 eV-1 keV.The beam energy is preferably selected such that as many of the incident particles of the beam as possible result in activation of a molecule of the first gaseous component. For this purpose, a rather reduced beam energy is advantageous. On the other hand, charging effects of the lithography mask, which can occur as a result of the charge carriers supplied via the particle beam, can lead to a deflection of the particle beam and thus to a reduction in the resolution. In order to keep this effect low, a higher beam energy is advantageous.For example, the particle beam consists of electrons, wherein the electron beam has a current of 1-1000 pA, preferably in a range of 1-100 pA, preferably in a range of 10-70 pA, more preferably in a range of 20-40 pA. A higher current can lead to a higher reaction rate and thus to an acceleration of the etching process, on the other hand a higher current also leads to a stronger charging of the surface.According to a second aspect, a lithography mask, in particular a non-transmissive EUV lithography mask, is proposed, which has been produced with a method according to the first aspect.A device usable in the proposed method for particle beam-induced etching of a lithography mask, in particular a non-transmissive EUV lithography mask, comprises a housing for providing a process atmosphere and a means for the focused irradiation of a particle beam at a target position on the lithography mask. Furthermore, a means for providing a first gaseous component at the target position in the process atmosphere is provided, wherein the first gaseous component can be converted into a reactive form by activation, wherein the reactive form reacts with a material of the lithography mask to form a volatile compound. Furthermore, a means for providing a second gaseous component at the target position in the process atmosphere is provided, wherein the second gaseous component forms a deposit comprising a compound of silicon with oxygen, nitrogen and / or carbon under predetermined process conditions under the action of the particle beam.This apparatus is preferably operated according to the method of the first aspect.The embodiments and features described for the proposed method apply to the device accordingly and vice versa.For example, the apparatus comprises an electron column arranged in a vacuum housing, which is configured for the focused irradiation of an electron beam onto a sample arranged on a sample holder. This can be, for example, a modified electron microscope. The vacuum housing advantageously provides the process atmosphere, wherein, for example, a pressure in the range of 10 -5- 10-8 mbar is provided. The pressure in the process atmosphere may be subject to spatial and temporal fluctuations. The respective means for providing the first and second gaseous components comprises in particular a container or tank in which a large amount of the respective component is stored. If the respective component is stored in gaseous form, it is preferably a high-pressure container which keeps the gas available under a pressure of several hundred bar. Advantageously, a liquid or solid phase of the respective component is provided in the container, wherein the vapor pressure of the component is controlled via the temperature. Individual gas molecules evaporate or sublime from the liquid or solid phase directly into the gas phase. The respective means also comprises a feed line which ends in a nozzle as close as possible to the target position. In this way, the respective gaseous component is supplied very close and in a targeted manner to the target position on the lithography mask. The feed line can in this case comprise valves and / or other process engineering devices."An" is not necessarily to be understood as limiting to exactly one element. Rather, a plurality of elements, such as two, three or more, can also be provided. Any other counting word used here is also not to be understood as being limited to exactly the number of elements mentioned. Instead, numerical deviations upwards and downwards are possible, unless indicated to the contrary.Further advantageous embodiments and aspects of the invention are the subject matter of the dependent claims and of the exemplary embodiments of the invention described below. The invention is explained in more detail below on the basis of preferred embodiments with reference to the enclosed figures. FIG. 1 schematically shows a section through a lithography mask which is subjected to a particle beam-induced processing process; FIG. 2 shows a schematic block diagram of an apparatus for particle beam-induced etching of a lithography mask; FIGS. 3 aand 3 b show an electron microscope image of a lithography mask before and after a particle beam-induced etching process; FIGS. 4 a- 4 c show a known particle beam-induced etching process of a lithography mask; FIGS. 5a-5c show a sequence of electron microscopic images of a lithography mask before and after etching with a known etching process; FIGS. 6a-6c show substrate damage caused by a known etching process; FIGS. 7 a- 7 c show a particle beam-induced etching process of a lithography mask according to the invention; FIGS. 8a-8c show a lithography mask processed with an etching process according to the invention; and FIG. 9 shows a schematic block diagram of a method for processing a lithography mask with a particle beam-induced etching process.In the figures, identical or functionally identical elements have been provided with the same reference symbols, unless indicated to the contrary. It should also be noted that the representations in the figures are not necessarily to scale.FIG. 1 schematically shows a section through a lithography mask 100 which is subjected to a particle beam-induced processing process. This is in particular a locally induced etching process, in which material is removed from the lithography mask 100. The etching process may also be applied to foreign objects such as dust particles deposited on the surface of the lithography mask 100 (not shown).The example illustrated for the lithography mask 100 is, for example, a mask suitable for EUV lithography, which is operated on a reflective basis. That is, the working light during operation is illuminated onto the lithography mask 100 and reflected back into the same half space. Here, EUV stands for "extreme ultra-violet" (EUV) and denotes a wavelength of the working light between 0.1 nm and 30 nm.In this example, the lithography mask 100 has a layer-like structure, wherein a carrier or substrate 102, which can consist of quartz glass, for example, forms the base. On the side which is later irradiated with the working light during operation, a multilayer mirror 104 is arranged, which is formed as a Bragg mirror specifically for the respective wavelength of the working light. Here, layers having a high and a low refractive index with respect to the wavelength of the working light and having a layer thickness of about half the wavelength of the working light multiplied by the sine value of the angle of incidence of the working light on the lithography mask 100 are alternately arranged one above the other. For example, the working light has a wavelength of 13.5 nm. Then, for an angle of incidence of 90°, a multilayer mirror 104 comprising a plurality of double layers of molybdenum and silicon, each having a layer thickness of 6.75 nm, would be suitable as Bragg mirror. In the case of oblique incidence of light, the layer thickness must be selected to be smaller. The multilayer mirror 104 comprises, for example, up to 100 such double layers. The multilayer mirror 104 may be manufactured using known deposition processes, such as chemical vapor deposition (CVD) or the like. An etch stop layer 106 is disposed on the multilayer mirror 104. This etch stop layer 106 has the function, on the one hand, of stopping etching processes used in the structuring of the structured layer 108, such that the multilayer mirror 104 or the substrate 102 are not attacked. On the other hand, the etch stop layer 106 itself is a component of the multilayer mirror 104 and thus forms the first layer of the multilayer mirror 104. The etch stop layer 106 therefore has, in particular, a layer thickness adapted accordingly to the working light. The etch stop layer 106 is made of ruthenium or another noble metal, for example.Such a layer structure achieves, for example, a reflectivity of approximately 70% of the radiated intensity in the case of EUV illumination. In order to achieve the local modulation in the illumination intensity necessary for lithography, the patterned layer 108 is arranged on the etch stop layer 106. The structured layer 108 comprises, for example, tantalum boron nitride TaB, tantalum nitride TaN, tantalum boron oxide TaBO and / or tantalum oxide TaO. In order to produce the structured layer 108, for example, a layer of TaN is first applied over the entire surface and then selectively etched. In regions where the TaN layer remains, the incident working light is greatly attenuated. Since a reflected beam passes twice through the TaB layer, less than about 10% of the incident intensity is reflected in the regions of the TaB layer.Defects may occur during the production of the lithography mask 100 (see, for example, FIG. 3 ). In the case of intensity-modulating lithography masks, a distinction is made in particular between clear and opaque defects. A clear defect results in too high an intensity in an exposure at a position at which no or only a low intensity should be present. An opaque defect causes the opposite, i.e. there is no or too low an intensity than desired at a respective position.In this example, possible sources of error are, in particular, errors in the construction of the multilayer mirror 104 including the etch stop layer 106 and errors in the structuring of the structured layer 108. The latter can be repaired very specifically, since these defects are located on the surface and are thus directly accessible. A suitable method for this is particle beam-induced processes, since these enable targeted local processing. Here, ions, electrons and photons (lasers or the like) are suitable as particles. Electron beams are particularly advantageous since, on the one hand, they can be focused on a very small target point and, on the other hand, they cause no damage or only very little damage, such as, for example, a structural change of the irradiated surfaces. This is also due in particular to the fact that electrons have a comparatively small penetration depth. In contrast thereto, ions in particular penetrate deeper into the material and lead there in part to doping and thus to a structure change of the material, which can have a negative effect. Laser beams, on the other hand, have the disadvantage compared to electron beams that they cannot be focused on such a small area, which is why the spatial selectivity and thus the resolution of the machining process is lower. In this example, it is an electron beam 110In this example, there is an opaque defect 112, which is an unremoved portion of the TaN layer of the structured layer 108. To remove the defect 112, a locally induced etching process is performed. For this purpose, on the one hand, the activating electron beam 110 (generally: particle beam 110) and, on the other hand, a first gaseous component GK 1 is required, which can be converted into a reactive form by activation.The focused electron beam 110 is rastered in particular over the target position ZP. For example, the target position ZP has an extent in the range of 5 nm-2 μm. The focused particle beam 110 preferably has an approximately Gaussian beam profile (in terms of intensity) with a half width in the range of 1-50 nm at the point of incidence. The focusing can be advantageously adjusted. The electron beam 110 is deflected in such a way that it irradiates a point of the size of the point of impingement for a predefined dwell time ("dwell time"). One can also refer to an image point or pixel. The target position ZP is divided into, for example, pixels which are successively irradiated by the electron beam 110. The dwell time is, for example, in the range of a few hundred picoseconds up to microseconds. Depending on the size of the target position ZP and of a pixel, a specific cycle time results for a complete pass. At 10 6 pixels and a dwell time of 1000 ps, the cycle time is, for example, 1 ms. In an etching process, for example, several million cycles are applied to a target position ZP, i.e., the electron beam 110 scans the target position ZP several million times.The first gaseous component GK 1, for example XeF 2, is preferably supplied in a targeted manner to the target position ZP. In this case, individual XeF 2- molecules can adsorb on the surface of the lithography mask 100. In the adsorbed state, a comparatively strong interaction is present between the adsorbed molecules and the surface atoms. The molecules of the first gaseous component GK 1 are activated by the activating electron beam 110 and / or by secondary processes which are triggered by the electron beam 110 in the target point ZP, in particular by secondary electrons of atoms close to the surface. In the example of XeF 2 this is dissociated, for example, whereby the fluorine atoms or fluorine radicals formed react with surface atoms of the TaN layer and form volatile gaseous compounds which evaporate via the process atmosphere ATM. In this way, localized material removal takes place.Since XeF 2 is a comparatively reactive substance, in some cases even without activation by a particle beam 110 a spontaneous reaction with surface atoms occurs, which can lead to uncontrolled etching. This is highly dependent on the combination used of the first gaseous component GK1 (etching gas) and the free surface chemistry. In order to better control the etching process, various additive gases that perform a buffer function or a passivation function may be supplied. In this context, the use of water in an etching process which has a passivating effect is known. However, the problem with water is that the etch stop layer 106, which consists for example of ruthenium or another noble metal, can be attacked by the latter. As an alternative to water, in this example tetraethyl orthosilicate (Si(OC 2 H 5)4, also referred to as tetraethoxysilane, hereinafter TEOS for short) is supplied as the second gaseous component GK2. TEOS is known as deposition gas in particle beam-induced processes, it being used, for example, for the local generation of a silicon oxide layer. TEOS acts on the one hand as a passivating agent, so that spontaneous etching processes do not occur at all or do not occur substantially, and on the other hand the etch stop layer 106 is not attacked. TEOS can lead to a deposit comprising silicon oxide, silicon nitride and silicon carbide, and mixed phases of these compounds, under the action of the electron beam 110. This may contribute to the selectivity or control of the etching process. It should also be noted that silicon oxide, silicon nitride and silicon carbide attenuate EUV radiation only relatively slightly, such that a thin layer possibly arising here with silicon oxide, silicon nitride and silicon carbide is negligible.FIG. 2 shows a schematic block diagram of an apparatus 200 for particle beam-induced etching of a lithography mask 100, for example the EUV lithography mask 100 from FIG. 1. The apparatus 200 has a housing 210 which is evacuated by a vacuum pump 250 to a pressure in the range of 10 -2- 10-8 mbar in order to create a process atmosphere ATM in the housing 210. The apparatus 200 has a means 220 arranged in the vacuum housing 210 for providing a focused particle beam 110. The means 220 has a beam provision unit 222 and one or more beam-guiding and / or beam-shaping means 224, 225 which direct the particle beam 110 onto the target point ZP in the desired manner. For example, this is an electron column 220 which is configured to provide a focused electron beam 110. The beam-guiding and beam-forming elements 224, 225 are in this case in particular embodied as multipoles. In addition, a detector 226 is advantageously provided, which detects backscattered electrons and / or secondary electrons and is thus configured to detect an electron microscope image of the lithography mask 100. This allows a processing process of the lithography mask 100 to be tracked in situ.The apparatus 200 has a sample table 202 for holding and positioning the lithography mask 100 to be processed, which can preferably be actuated in two, preferably three, spatial directions. In addition, the sample table 202 can be mounted in a tiltable and rotatable manner in order to align the lithography mask 100 as perfectly as possible with respect to the means 220, in particular with respect to the particle beam 110 (not illustrated). The sample table 220 is advantageously mounted in a vibration-damped manner and is mechanically decoupled from the further structure (not shown).Outside the housing 210 there are arranged a means 230 for providing a first gaseous component GK 1 and a means 240 for providing a second gaseous component GK 2. The respective means 230, 240 are preferably designed such that they control a temperature of a solid or liquid phase of the respective component in order to set a vapor pressure of the respective gaseous component GK 1, GK 2. In this way, a gas flow of the respective gaseous component GK 1, GK 2 optimized for the respective process can be achieved advantageously without valves or the like. However, it is not excluded that valves or the like are additionally provided, since valves advantageously enable a very rapid change of the gas flows. Each of the means 230, 240 has a feed line 232, 242 into the housing 210 which leads into a respective nozzle. The nozzle is advantageously directed at the target point ZP, so that the supplied gas GK 1, GK 2 comes into contact with the surface of the lithography mask 100 in a targeted manner at the target point ZP. This increases process control and an efficiency of the etching process. In addition to the means 230, 240, further, identically designed means (not shown) can be provided in order to feed further gaseous components, such as buffer gases, oxidizing or reducing gases, into the process atmosphere ATM.In addition, a suction unit 260 is shown, which is configured to suck away excess gas and in particular volatile reaction products from the region of the target point ZP, which is carried out, for example, by means of a further vacuum pump 250. The composition of the process atmosphere ATM can thus be better controlled, in particular reaction products are prevented from settling elsewhere on the lithography mask 100 or further, unpredictable processes with excess gas take place.FIGS. 3 aand 3 b show an electron microscope image of a lithography mask 100 before and after a particle beam-induced etching process. The example illustrated here has parallel structures, but this is to be understood as merely exemplary and not restrictive. Other lithography masks may have various other geometric shapes. The lithography mask 100 illustrated is in particular an EUV lithography mask which has, for example, the layer structure illustrated in FIG. 1.FIG. 3 ashows the lithography mask 100 having a defect in the form of an absorbing region which is not provided at this location. The white dashed box serves to emphasize the defective area. The EUV lithography mask 100 is subjected to the proposed particle beam-induced etching process, for example, with the apparatus 200 of FIG. 2, wherein the region of the lithography mask 100 whose material is to be removed is defined as the target position ZP (see FIG. 1 ).FIG. 3 bshows the EUV lithography mask 100 after the etching process has been carried out. It can be seen that the defect has been successfully removed and the lines on the lithography mask 100 are now all separated from one another. The white box serves to emphasize the repair location. The lithography mask 100 now has the provided structure and can be used, for example, in an EUV lithography process.FIGS. 4 a- 4 cschematically illustrate a known particle beam-induced etching process of a lithography mask 100. With the known process, undesirable side effects occur, as will be explained below. FIG. 4 ashows the initial situation, wherein the lithography mask 100 is arranged in the process atmosphere ATM 1. A patterned layer 108 is etched, which is substantially made of a first material 108 a, for example tantalum nitride TaN. The surface of the layer 108 is made of another material 108 bcomprising, for example, tantalum oxide Ta and / or tantalum oxynitride TaON. Such a layer 108 b, which is close to the surface, can form spontaneously by itself, wherein the layer 108 bthen has a thickness of a few nanometers, or it can be deposited in a targeted manner, wherein the layer thickness can then be adjusted as desired, for example. The lithography mask 100 can have further layers, as shown in FIG. 1, the illustration of which has been omitted here for reasons of clarity. The etching process is carried out, for example, by means of the device 200 of FIG. 2.The process in FIGS. 4 a- 4 cis carried out with a process atmosphere ATM 1, which comprises, for example, as etching gas XeF 2 and H 2 O as passivation gas. For example, a defect 112 as shown in FIG. 3 ais to be removed. The defect 112 is bounded here by the dashed lines. The target position ZP is placed accordingly in the region of the defect 112.As illustrated in FIG. 4 b, the etching process is carried out in a targeted manner by the particle beam 110, wherein the layer 108 is removed in the target position ZP apart from the substrate 101. The target position ZP is divided into pixels, for example, wherein one pixel corresponds to the area of incidence of the focused particle beam 110 on the layer 108, and the particle beam 110 scans the target position pixel by pixel. In each cycle, some atomic layers of layer 108 are ablated. In this case, first the outer layer 108 band then the inner layer 108 aare exposed in sections.Undesired damage DMG 1, DMG 2 may occur during the etching process. For example, the substrate 101 of the lithography mask 100 may be damaged, as illustrated by the rough surface DMG 1. Since the etching process does not always proceed exactly the same speed at each pixel of the target position ZP, it occurs that the substrate 101 is already exposed at some pixels, but material is still to be removed at others. The etching process is therefore still continued, which can lead to damage DMG 1 by the particle beam 110 and by the aggressive etching gas, in particular in activated form, and / or by the water present as passivation gas in the process atmosphere ATM 1 in the regions in which the substrate 101 is already open.In addition, further damage DMG 2 can occur at an edge of the target position ZP, where a flank of the layer 108 is exposed as the etching process progresses. These are, for example, etching processes which attack the exposed flank of the layer 108, which can lead to degradation of the flank.After completion of this etching process at the illustrated target position ZP, an etching process is carried out (not shown), for example, at another position of the lithography mask 100. Meanwhile, the gases in the process atmosphere ATM 1 are still in direct contact with the exposed layer 108 a. In this case, spontaneous reactions can occur, in which the exposed material 108a is attacked. As a result, an unwanted etching process can proceed, which can lead to further damage DMG 3 in the form of under-etching of the surface layer 108 b, as illustrated in FIG. 4 c. This process, which takes place in an uncontrolled manner, can therefore be in the way of a targeted etching process. Damage DMG 3 occurs, for example, when the layer 108 btoward the surface is not attacked, or is only insignificantly attacked, by the first gaseous component GK 1, while the material 108 ais significantly attacked, on the other hand.FIGS. 5 a- 5 c show a sequence of electron microscope images of a lithography mask 100 before (FIG. 5 a ) and after (FIGS. 5 band 5 c ) a particle beam-induced etching with the etching process described with reference to FIGS. 4 a- 4 c. The lithography mask 100 has, for example, a structure as illustrated in FIG. 1.In the electron microscope images, the substrate 106 and the structured layer 108 are clearly recognizable. FIG. 5 ashows the target position ZP as a dashed box. The target position ZP is located on the substrate 106. The target position ZP is scanned with the focused particle beam 110 (see FIG. 1 or FIG. 2 ) as described with reference to FIG. 1.FIG. 5 bshows the processed region after the etching process, wherein the image was captured with an electron beam energy of 600 V. With this energy, topological structures can be detected in particular. In the region that the particle beam 110 has irradiated, a slight discoloration is detectable, which indicates that the substrate surface is damaged in this region. The damaged area is indicated by the broken line DMG 1. In addition, a comparison of the edges of the layer 108 with FIG. 5 ashows that they likewise have damage DMG 2 and are no longer as sharp.FIG. 5 cshows a further image of the processed region, wherein the image has been acquired with a higher electron beam energy, whereby material contrasts in particular become visible. The dark dots DMG1 indicate that the etch stop layer 106 has been completely etched away at these sites. At these points, even more serious damage, for example of the multilayer mirror 104 (see FIG. 1 ), cannot be ruled out.The damage DMG 1, DMG 2 illustrated lead, for example, to a reduced reflection of EUV radiation in a lithography process, which can lead to errors in the production of microstructured components. More radiation is scattered at the frayed edges, which can likewise impair an exposure process.FIGS. 6 a- 6 c show a further damage of an etch stop layer 106 of an EUV lithography mask 100 caused by a known etching process, which damage has, for example, the structure of the lithography mask illustrated in FIG. 1. Here, for example, an etching process was used in which XeF 2 was supplied as an etching gas, H 2 O as a passivating gas, and NO 2 as a buffer gas. The etching process was used to remove a column of material made of tantalum boron nitride TaB, which was located in the region of the target position ZP.FIG. 6 ashows an electron microscope image of the processed region of the lithography mask 100. In the region of the target position ZP, a distinct lightening is recognizable, which indicates damage DMG 1. Four position markings DC can also be seen. For reasons of clarity, only one is identified by a reference sign. The position marks DC serve to detect and compensate a relative displacement between the lithography mask 100 and the means 220 (see FIG. 2 ) for providing the focused particle beam 110 (see FIG. 1 or 2 ) during the irradiation. In this case, the position markings DC are regularly scanned during the etching process, for which reason a lightened, damaged region can also be seen around the latter.FIG. 6 bshows an image of the lithography mask 100 captured with actinic radiation. FIG. 6 b shows, for example, a two-dimensional intensity distribution of the reflected radiation, as would arise on the sample in a lithography process with the lithography mask 100. Brightness differences correspond to intensity differences. The reflected intensity is approximately 70% in the region of the etch stop layer 106 and less than 10% in the region of the structured layer 108. The damaged region DMG1 is likewise to be seen as lightening. An interest region ROI passing through the damaged region DMG 1 is illustrated. The intensity values of the region of interest ROI are plotted in FIG. 6 c as a function of the position, the markings ("z" and "0") coinciding with FIG. 6 c.The diagram of FIG. 6 cshows the reflected intensity R of the EUV radiation in the region of interest ROI as a function of the position. The positions "z" and "0" correspond to FIG. 6 b. The vertical axis shows the intensity I, which is normalized to the highest value, for example. The measurement shows that at position "z" there is a minimum of reflected intensity. This shows that the damage to the etch stop layer 106 leads to a poorer reflectivity of EUV radiation and thus to a poorer lithography process.FIGS. 7a-7c show, analogously to FIGS. 4a-4c, an etching process which is carried out here, however, according to the invention. The unwanted or uncontrolled secondary effects explained with reference to FIGS. 4a-4c are therefore substantially suppressed.In the example of FIGS. 7 a- 7 c, the process atmosphere ATM comprises, for example, XeF 2 as etching gas and TEOS as supplementary gas. The etching process proceeds in a targeted manner, as in the example of FIG. 4 b, as is illustrated in FIG. 7 b. In contrast to FIG. 4 b, however, the presence of TEOS in the process atmosphere ATM leads, for example, to the formation of a passivating layer 109 which consists, for example, essentially of silicon oxide or silicon dioxide. The passivating layer 109 can be produced here, for example, by the deposition of the second gaseous component GK 2 from the process atmosphere ATM and / or by chemical reactions of molecules of the second gaseous component GK 2 with the exposed material 108 a. The passivating layer 109 has the advantageous effect that the exposed surface of the substrate 101 and of the layer 108a is sealed or passivated, so that damage, as explained with reference to FIG. 3b, does not occur or occurs only insignificantly. It should be noted that the layer 109 may also be removed by the activated etching process. Therefore, a high layer thickness of the layer 109 is advantageously not formed. The process is controlled in particular by controlling the gas supply, which determines the composition of the process atmosphere ATM in the region of the target position ZP.The passivating layer 109 thus has the advantage that damage to the substrate 101 is reduced or completely suppressed. Moreover, spontaneous etching reactions are prevented, which can also restrict the quality of the lithography mask 100. This allows a very selective and clean etching process.FIGS. 8 a- 8 c show a lithography mask 100 processed with an etching process according to the invention. The lithography mask 100 has, for example, the layer structure explained with reference to FIG. 1. The patterned layer 108 and the etch stop layer 106 are partly visible on the top side. The lithography mask 100 was subjected to an etching process, wherein XeF 2 was supplied as the first gaseous component GK 1 (see FIG. 1 or 2 ) and TEOS was supplied as the second gaseous component GK 2 (see FIG. 1 or 2 ). No additional additional gases were used. The gas flow was controlled via the temperature of the respective liquid or solid phase of the component, wherein XeF 2 in this example was kept at a temperature of -20° C. and TEOS was kept at a temperature of -33° C. For activating the first gaseous component GK 1, a focused electron beam 110 (see FIG. 1 or 2 ) was used. The etching process was performed at two adjacent rectangular target positions ZP on the exposed etch stop layer 106.FIG. 8 a shows an electron microscope image of the processed region of the lithography mask 100, which was captured with an electron energy of 600 V, whereby surface structures can be easily recognized. In the region of the two target positions ZP, a very weak lightening is recognizable, which indicates a slight change in the surface structure, for example the surface roughness.FIG. 8 bshows an electron microscope image of the processed region of the lithography mask 100, which was acquired with a higher electron energy, resulting in strong material contrasts. In this image, it would be possible to see if a deposit had formed on the etch stop layer 106 or if the etch stop layer 106 had been etched away, as can be seen in FIG. 5 c. FIG. 8 bshows that substantially no deposit has formed and that the etch stop layer 106 has not been significantly attacked either during the etching process.FIG. 8 cshows an image of the lithography mask 100 recorded with actinic radiation, which image shows the reflected intensities. The reflected intensity is approximately 70% in the region of the etch stop layer 106 and less than 10% in the region of the structured layer 108. In the region of the target positions ZP, only very insignificant deviations can be seen in comparison with the remaining, non-irradiated surface of the etch stop layer 106.Compared to the conventional process which leads to damage (see FIGS. 5 a- 5 cand 6 a- 6 c), the etch stop layer 106 is not damaged here.FIG. 9 shows a schematic block diagram of a method for processing a lithography mask 100 (see FIGS. 1-8 ) with a particle beam-induced etching process. In a first step S 1, the lithography mask 100 is provided in a process atmosphere ATM (see FIGS. 1, 2 and 7 ). For example, lithography mask 100 is placed on sample stage 202 of device 200 and housing 210 is evacuated to a pressure of about 10 -6- 10-8 mbar. In a second step S 2, a focused particle beam 110 (see FIG. 1 or FIG. 2 ) is irradiated onto a target position ZP (see FIGS. 1-8 ) on the lithography mask 100. In a third step S 3, a first gaseous component GK 1 (see FIG. 1 or 2 ) is supplied to the target position ZP in the process atmosphere ATM. The first gaseous component GK 1 can be converted into a reactive form by activation, wherein the reactive form reacts with a material of the lithography mask 100 to form a volatile compound. The first gaseous component GK 1 is activated in particular by the particle beam 110 and / or by secondary effects triggered by the particle beam 110. In a fourth step S 4, at least one second gaseous component GK 2 (see FIGS. 1 and 2 ) is supplied to the target position ZP in the process atmosphere ATM. The second gaseous component GK 2 forms a deposit comprising a compound of silicon with oxygen, nitrogen and / or carbon under predetermined process conditions under the action of the particle beam 110. The process conditions of the etching process are preferably selected such that no deposit or only a very slight deposit is formed.Although the present invention has been described on the basis of exemplary embodiments, it can be modified in various ways.LIST OF REFERENCE CHARACTERS100 Lithography mask 101 substrate 102 substrate 104 multilayer mirror 106 etch stop layer 108 structured layer 108 alayer 108 blayer 109 layer 110 particle beam 112 defect 200 device 202 sample stage 210 housing 220 means 222 beam provision unit 224 beam guiding means 225 beam shaping means 226 detector 250 vacuum pump 260 suction unit ATM process atmosphere ATM 1 process atmosphere DC position marking DMG 1 damage DMG 2 damage DMG 3 damage GK 1 gaseous component GK 2 gaseous component I intensity POS position R reflected intensity ROI region of interest S 1 method step S 2 method step S 3 method step S 4 method step z position ZP target point

Claims

Method for particle beam-induced etching of a lithography mask (100), comprising the steps: a) providing (S1) the lithography mask (100) in a process atmosphere (ATM), b) irradiating (S2) a focused particle beam (110) onto a target position (ZP) on the lithography mask (100), c) supplying (S3) at least one first gaseous component (GK1) to the target position (ZP) in the process atmosphere (ATM), wherein the first gaseous component (GK1) can be converted into a reactive form by activation, wherein the reactive form reacts to form a volatile connection with a material of the lithography mask (100), and d) supplying (S4) at least one second gaseous component (GK2) to the target position (ZP) in the process atmosphere (ATM) such that the process atmosphere (ATM) has the first and the second gaseous component (GK1, GK2) when step b is carried out, wherein the second gaseous component (GK2) forms a deposit comprising a compound of silicon with oxygen, nitrogen and / or carbon under predetermined process conditions under the action of the particle beam (110).The method of claim 1, wherein the second gaseous component (GK2) comprises a silicate, a silane, a siloxane, a silazane, and / or a silicon isocyanate.Method according to Claim 1 or 2, wherein a deposit formed during the etching process by the second gaseous component (GK2) is removed in a wet chemical cleaning step of the lithography mask (100).The method according to any one of claims 1 to 3, wherein the first gaseous component (GK1) comprises one of xenon difluoride XeF 2, sulfur hexafluoride SF 6, sulfur tetrafluoride SF 4, nitrogen trifluoride NF 3, phosphorus trifluoride PF 3, tungsten hexafluoride WF 6, tungsten hexafluoride WCl 6, molybdenum hexafluoride MoF 6, hydrogen fluoride HF, nitrogen oxygen fluoride NOF, triphosphorus trinitrogen hexafluoride P 3 N 3 F6.Method according to one of Claims 1 to 4, wherein the feeding of the second gaseous component (GK2) takes place temporally before and / or after the irradiation of the particle beam (110) onto the target position (ZP).Method according to one of Claims 1 to 5, wherein the feeding of the second gaseous component (GK2) takes place during the irradiation of the particle beam (110) onto the target position (ZP).The method according to any one of claims 1 to 6, comprising: supplying a third gaseous component comprising an oxidizing agent and / or a reducing agent.The method according to any one of claims 1 to 7, wherein supplying the first gaseous component (GK1), the second gaseous component (GK2) and / or the third gaseous component comprises: providing a solid or liquid phase of the respective component, adjusting a temperature of the solid or liquid phase of the respective component such that a predetermined vapor pressure of the respective component is achieved above the solid or liquid phase, and supplying the respective gaseous component (GK1, GK2) into the process atmosphere (ATM) via a respective supply line (232, 242).Method according to Claim 8, wherein a line cross section of the respective feed line (232, 242) is adjusted and / or a duty cycle of a closing valve is controlled in order to control a mass flow and / or volume flow of the respective component.Method according to one of Claims 1 to 9, wherein the particle beam (110) consists of charged particles.The method according to any one of claims 1 to 10, wherein the lithography mask (100) is configured for use in EUV lithography.Method according to one of Claims 1 to 11, wherein the lithography mask (100) has an etch stop layer (106), on the front side of which a patterned layer (108) made of a material which acts to absorb the radiation used in a lithography process is arranged, wherein an etching rate of the activated first gaseous component (GK1) with respect to the etch stop layer (106) is lower than the etching rate with respect to the patterned layer (108) by at least a factor of 2.Method according to claim 11 or 12, wherein the lithography mask (100) has a mirror layer formed as a multilayer mirror (104) made of a plurality of bilayers, wherein a respective bilayer comprises a first layer made of a first chemical composition and a second layer made of a second chemical composition, and wherein a respective layer thickness of the first and the second layer is in a range of 3 - 50 nm.Method according to one of Claims 1 to 13, wherein the particle beam (110) has an energy of 1 eV - 100 keV.Lithography mask (100) produced by a method according to one of claims 1-14.

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