Method and apparatus for particle beam-induced etching of defects in microlithographic photomask

Abstract

To improve particle beam-induced etching of a defect in a microlithographic photomask.SOLUTION: A method for particle beam-induced etching of a defect (D1) in a microlithographic photomask (100), comprises: a) Step (S1) of providing an activating particle beam (114) and a first gaseous component (116) activatable by the particle beam (114) at a surface (118) of the photomask (100) in a region (120) of the defect (D1) for etching the defect (D1); and subsequently b) Step (S2) of providing a second gaseous component (126) containing oxygen with spontaneous oxidizing action at the surface (118) of the photomask (100) in a passivation region (122) encompassing the region (120) of the defect (D1) for passivating the surface (118).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for particle beam induced etching of defects in microlithographic photomasks.

[0002] The content of priority application DE 102024110764.2 is incorporated in its entirety by reference. [Background technology]

[0003] Microlithography is used to create microstructured component parts, such as integrated circuits. The microlithography process is carried out using a lithography apparatus that includes an illumination system and a projection system. An image of a mask (reticle) illuminated by the illumination system is projected by the projection system onto a substrate, such as a silicon wafer, that is coated with a photosensitive layer (photoresist) and positioned in the image plane of the projection system to transfer the mask structure into a photosensitive coating on the substrate.

[0004] Driven by the desire for ever smaller features in the production of integrated circuits, EUV lithography tools using light having wavelengths in the range of 0.1 nm to 30 nm, particularly 13.5 nm, are currently under development.

[0005] Photomasks (i.e., lithography masks) used during microlithography have microstructures that are projected onto a substrate at reduced scale. The structures on the photomask themselves are already very small, e.g., with dimensions ranging from a few micrometers to a few nanometers. In order to create microstructured components very accurately using microlithography, the structures on the utilized photomask must also be manufactured with great precision, and the photomask must be free of defects (e.g., defective structures and contamination). Because photomasks are typically used in multiple exposures, defect-free microlithographic photomasks are also very important. Therefore, photomasks are inspected for defects at great expense, and any defects that are exposed are repaired.

[0006] Typical defects in a photomask include the absence of expected structures, for example because the etching process was not carried out successfully, or the presence of unexpected structures, for example because the etching process proceeded too quickly or caused its action to grow in the wrong places. These defects can be repaired by targeted etching of excess material or targeted deposition of additional material at the appropriate locations; for example, this can be achieved in a very targeted manner by electron beam induced processing (FEBIP, "focused electron beam induced processing").

[0007] German Patent No. 102017208114A1 describes a method for particle beam-induced etching of microlithographic photomasks. In this case, a particle beam, in particular an electron beam, and an etching gas are provided on the photomask at the site to be etched. The particle beam activates a local chemical reaction between the material of the photomask and the etching gas, resulting in local removal of material from the photomask. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] German patent no. 102024110764.2 [Patent Document 2] German patent no. 102017208114A1 Summary of the Invention

[0009] Against this background, the problem addressed by the present invention is to improve particle beam induced etching of defects in microlithographic photomasks.

[0010] According to a first aspect, a method is proposed for particle beam induced etching of defects in a microlithographic photomask, the method comprising: a) providing an active particle beam and a first gas component that can be activated by the particle beam at the surface of the photomask in the area of ​​the defect for the purpose of etching the defect, and then b) providing a spontaneously oxidizing oxygen-containing second gas component at the surface of the photomask in a passivation area encompassing the defect area, in order to passivate the surface; Includes.

[0011] In this specification, a "component having an oxidizing activity" should be understood to be an oxidizing agent that can oxidize another substance (e.g., the material on the surface of the photomask). In other words, the other substance (the material on the surface of the photomask) is oxidized by the component having an oxidizing activity.

[0012] As a result, defects in the photomask can be etched (i.e., ablated and / or removed) in a particle beam-induced manner in the first step a). Immediately thereafter, in a further step b) following the etching of the defects, the repaired site can be passivated with the aid of an oxygen-containing second gas component having spontaneous oxidation properties. For example, the surface of the photomask can be chemically modified in the passivation region with the aid of the second gas component. For example, a passivation layer (e.g., an oxygen-containing layer) can also be generated in the passivation region by chemical modification. In particular, passivation allows passivation, e.g., chemical modification, of the surfaces of structures (e.g., absorber structures) of the photomask exposed by the etching in step a). As a result, these structures are better protected during subsequent processes. Furthermore, spontaneous etching of the structures can occur at the surfaces exposed during etching without the supply of the second gas component. The spontaneous etching of the structures can be at least partially mitigated by the supply of the second gas component.

[0013] Within the passivation, reactive species (e.g., F, HF, F compounds) remaining around the repair site may be replaced on the surface of the photomask, for example, by adsorption of a second gas component. Further within the passivation, species that can act as a starting material for reactive compounds (e.g., TaO as a starting material for reactive fluorine compounds, e.g., HF) may be replaced on the surface of the photomask. a F b The oxyfluorotantalum species) can be passivated by chemical reaction with the second gas component. Furthermore, within the scope of passivation, molecules may be enriched with oxygen at the repair site, thereby sealing the surface at the repair site. For example, the oxyfluorotantalum produced at the repair site can be enriched with oxygen (e.g., Ta if the second gas component contains, for example, ozone (O). a O b F c +O3→Ta a O d F e, (d > b, e < b). This helps in the formation of Ta2O5, and thus the surface is sealed at the repair site.

[0014] For example, the exposed surface of the structure includes the surface of the sidewalls of the structure. The material of the structure includes, for example, tantalum, one or more tantalum compounds, tantalum nitride, and / or tantalum oxide.

[0015] In particular, step a) and step b) are two method steps that are temporally separated from each other. In other words, the repair step a) and the passivation step b) are two different processes that are not performed simultaneously. Thus, for example, at the end of the repair step a), the passivation step b) follows without a waiting time. Alternatively, a waiting time (for example, a few seconds) may be provided between the end of the repair step a) and the start of the passivation step b). For example, the waiting time is 60 seconds or less, 30 seconds or less, 10 seconds or less, and / or 1 second or less. The passivation step b), that is, the supply of the second gas component, is carried out, for example, over a time period of 120 seconds or less, 100 seconds or less, 80 seconds or less, and / or 60 seconds or less.

[0016] According to one embodiment, the surface is passivated in step b) without providing an active particle beam. In particular, no particle beam-induced repair of the photomask occurs during passivation step b) (e.g., no particle beam-induced etching occurs). In other words, passivation step b) is a pure passivation step in which no particle beam-induced etching of the photomask occurs. For example, the first gas component is (no longer) supplied at the start of supplying the second gas component. However, for operational reasons, the first gas component may still be supplied to the surface of the photomask within a (short) gas transition time at the start of supplying the second gas component. However, after the gas transition time expires, the first gas component is no longer supplied, but the second gas component continues to be supplied. For example, even at the start of supplying the second gas component, the particle beam is (no longer) directed to the defect area and is no longer incident on the photomask in the defect area.

[0017] For example, the photomask is provided in a process atmosphere. For example, the process atmosphere may be of controlled composition and controlled (e.g., 10 -2 ~10 -8 The process atmosphere is, for example, an atmosphere having a pressure in the range of 1000 mbar (e.g., 1000 mbar). For example, the process atmosphere is provided in an evacuated housing. Furthermore, a first gas component that is supplied to the surface of the photomask in the region of the defect is, for example, provided in the process atmosphere. A second gas component that is supplied to the surface of the photomask in the passivation region is also, for example, provided in the process atmosphere. Hereinafter, the evacuated housing in which the process atmosphere is provided will further be referred to as a "vacuum chamber."

[0018] In particular, steps a) and b) are performed without the vacuum chamber being opened, and in particular, the photomask remains held within the vacuum chamber during steps a) and b).

[0019] The defect is etched in repair step a), i.e. material is locally removed from the photomask in the area of ​​the defect, as a result of which the etching can remove excess and / or unwanted structures (e.g. unwanted absorber structures) in the area of ​​the defect.

[0020] For example, before step a), a repair shape for the defect is identified based on an image of at least a portion of the photomask. In particular, the repair shape of the defect is the geometric shape of the defect in the image. For example, the repair shape is subdivided into several pixels. Furthermore, for example, the active particle beam is provided successively at each pixel of the repair shape, i.e., focused on each pixel, thus raster scanning over all pixels of the repair shape.

[0021] For example, the area of ​​the defect corresponds to the repair shape of the defect. For example, the particle beam is provided only within the area of ​​the defect (e.g., within the area of ​​the repair shape). Furthermore, for example, the first gas component is provided at least within the area of ​​the defect. This includes, for example, when the first gas component is provided to an expanded area of ​​the defect that includes and is larger than the area of ​​the defect (e.g., the repair shape).

[0022] The passivation region to which the second gas component is provided may, for example, completely encompass (i.e., include and / or cover) the region of the defect (e.g., the repair feature), e.g., the passivation region may be larger (i.e., have a larger area) than the region of the defect.

[0023] In step a), an active particle beam is emitted onto the surface of the photomask, particularly in the area of ​​the defect. For example, the particle beam may comprise electrons, ions, and / or protons. The use of an electron beam is particularly advantageous because, firstly, the electrons can be focused onto a very small incident surface, and, secondly, the electrons do not cause substantial damage to the emitting surface. Therefore, the achievable resolution is particularly high when an electron beam is used.

[0024] Furthermore, the first gas component is supplied in step a) to a surface of the photomask at least in the area of ​​the defect, in particular the surface of the photomask being a surface of the photomask configured for exposure in an EUV lithography apparatus.

[0025] In particular, the first gas component includes an etching gas, for example, the first gas component includes one or more of xenon difluoride (XeF), xenon tetrafluoride (XeF), sulfur hexafluoride (SF), sulfur tetrafluoride (SF), nitrogen trifluoride (NF), phosphorus trifluoride (PF), tungsten hexafluoride (WF), tungsten hexachloride (WCl), molybdenum hexafluoride (MoF), hydrogen fluoride (HF), nitrosyl fluoride (NOF), nitrosyl chloride (NOCl), and / or phosphorus trinitrogen hexafluoride (P3N3F6).

[0026] In addition to the etching gas, the first gas composition may further include other gases, such as additive gases, which may include oxygen-containing gases, halides (e.g., Cl, HCl, XeF, CF, HF, I, HI, Br, HBr, NOCl, PCl, PCl, PF, and other halogen-containing gases), and / or gases with reducing properties (e.g., H, NH, CH, and other hydrogen-containing gases).

[0027] The first gas component, e.g., an etching gas, is activated by the particle beam. As a result of this activation, the first gas component, e.g., an etching gas, is converted into a reactive form, which reacts with material (e.g., atoms or molecules) at the surface of the photomask to form volatile compounds. In this way, the surface of the photomask is eroded in the area of ​​the defect.

[0028] A microlithographic photomask is, for example, a photomask for use in an EUV lithography tool. In this case, EUV stands for "extreme ultraviolet" and refers to an operating light wavelength between 0.1 nm and 30 nm, in particular 13.5 nm. At these wavelengths, reflective optical elements must be used, and this also applies to photomasks. In an EUV lithography tool, a beam shaping and illumination system is used to direct EUV radiation onto a photomask ("reticle") in the form of a reflective photomask. The photomask thus includes a layer that reflects EUV radiation, e.g., in the form of a Bragg mirror, and a structured absorber layer ("absorber structures") on the reflective surface. Such a mask is also referred to as a binary lithography mask. The pattern of the structured absorber layer of the photomask (i.e., the pattern of the absorber structures) is imaged at reduced size onto a wafer by a projection system of the EUV lithography tool.

[0029] For example, a microlithographic photomask includes a substrate, a reflective multilayer coating disposed on the substrate, and a structured coating disposed on the reflective multilayer coating. Additionally, a capping layer may be further disposed, for example, between the multilayer coating and the structured coating.

[0030] For example, the substrate may include silicon dioxide (SiO2), such as fused silica, and / or a very low thermal expansion material. For example, the multilayer coating may include alternating molybdenum and silicon layers. For example, the structured coating may include tantalum, one or more tantalum compounds, tantalum nitride, tantalum boron nitride, tantalum boron oxide, and / or tantalum oxide. The substrate, multilayer coating, and / or structured coating (absorber structure) may further include other materials.

[0031] Thus, on its surface (i.e., on the surface suitable for exposure in a lithographic apparatus), the photomask comprises, for example, absorber regions with absorber structures and reflective regions without absorber structures. Furthermore, the defects are, for example, one or more of the unwanted absorber structures. With the presented method, such defects of the photomask, i.e., defects of the unwanted form of the photomask, i.e., in the form of extra absorber structures, are etched away and thus repaired.

[0032] Following the etching of the defects, a passivation step is performed in step b). To this end, a second gas component is supplied to the surface of the photomask in the passivation region in order to passivate the surface of the photomask in the passivation region. The second gas component is an oxygen-containing gas component with spontaneous oxidation action. It can also be said that the second gas component causes spontaneous oxidation of the material on the surface of the photomask. That is, the second gas component induces a spontaneous chemical reaction with the material on the surface of the photomask. A spontaneous chemical reaction is a chemical reaction that occurs without external coercion, particularly without further activation (e.g., at room temperature and / or at a temperature between 20°C and 22°C and / or at 21°C). In particular, the second gas component does not need to be activated by a particle beam to achieve its passivation effect.

[0033] This is an advantage over non-oxidizing species as passivation gases, which form deposits or cause chemical modifications of the substrate only under the influence of the particle beam. An example of a non-oxidizing species as a passivation gas is TEOS gas (here TEOS corresponds to tetraethylorthosilicate (Si(OC2H5)4), further referred to as tetraethoxysilane), which forms deposits, e.g., silicon dioxide, only under the influence of the particle beam.

[0034] For example, the photomask includes a metal-containing material on its surface, and the second gas component spontaneously passivates the metal-containing material (e.g., by spontaneous chemical adsorption). Thus, the second gas component is a strongly oxidizing species that can spontaneously (i.e., without further activation, particularly without activation by the particle beam) oxidize the metal-containing material (e.g., transfer oxygen elements to the metal-containing surface). This is an advantage over, for example, TEOS as a passivation gas, which cannot spontaneously oxidize the metal-containing material.

[0035] For example, the structured coating (absorber structure) of the photomask includes a metal-containing material (e.g., a tantalum compound). For example, the capping layer of the photomask includes a metal-containing material (e.g., ruthenium).

[0036] According to one embodiment, in step a) at least one edge of the structured coating of the photomask is exposed, and further in step b) at least one exposed edge is passivated.

[0037] In particular, at least one edge of the structured coating exposed in step a) is at least partially further exposed at the end of step a).

[0038] In particular, at least one edge of the structured coating is at least one edge that is disposed substantially perpendicular to the major extension surface of the photomask, where "substantially perpendicular" includes an angle of 60° or more, 70° or more, 80° or more, 85° or more, and / or approximately exactly 90° between the at least one edge of the photomask and the major extension surface of the photomask.

[0039] At least one edge of the structured coating includes, for example, at least one sidewall of the structured coating.

[0040] According to a further embodiment, in step a) the defects are completely etched and / or completely removed.

[0041] Therefore, defects, i.e., undesired structures (e.g., geometrically continuous undesired structures), can be completely removed in step a), and thus defects in the photomask are completely repaired, especially at the repair site, before the surface of the photomask is passivated.

[0042] According to a further embodiment, the second gas component passivates the surface of the photomask with the aid of spontaneous chemisorption.

[0043] That is, the second gas component is chemically adsorbed onto the surface material of the photomask. In other words, a chemical reaction occurs between the second gas component and the surface material of the photomask. Thus, the surface material of the photomask is chemically modified. Chemical adsorption is also referred to as "chemisorption."

[0044] In particular, for example, the second gas component is chemisorbed onto the material of the surface of the photomask, and then the surface of the photomask is oxidized by the chemisorbed second gas component, thereby irreversibly bonding at least one oxygen atom to the surface of the photomask.

[0045] Chemisorption differs from physical adsorption ("physisorption") in that chemisorption involves a chemical reaction between the adsorbate (in this case, the second gas component) and the adsorbent (in this case, the surface material of the photomask). That is, the adsorbate and / or adsorbent are chemically modified. In contrast, during physisorption, only a physical bond between the adsorbate (second gas component) and the adsorbent (the surface material of the photomask) is created. That is, the adsorbate and adsorbent are not chemically modified in this process; instead, they are bound to each other by physical forces. For example, this physical bond is based on weak, and therefore easily releasable, van der Waals forces. An example of physisorption is found in the accumulation of TEOS gas on the surface of a photomask. TEOS contains one or more oxygen-containing compounds that form nonvolatile oligomers on the mask. The nonvolatile oligomers are macromolecules formed from individual TEOS molecules, i.e., linkages between TEOS molecules (rather than linkages with the surface of the photomask). Due to their larger aggregates (compared to individual TEOS molecules), TEOS oligomers can physisorb to the surface of the photomask for longer periods of time.

[0046] According to a further embodiment, the method comprises: c) removing the second gas component from the surface of the photomask by pumping.

[0047] For example, the second gas component is pumped out of the process atmosphere.

[0048] For example, steps a), b), and c) are performed without opening the vacuum chamber, and in particular, the photomask remains in the vacuum chamber and in the process atmosphere during steps a), b), and c).

[0049] According to a further embodiment, in step a), a first defect in the photomask is etched in a first area of ​​the photomask. Following step c), the method further comprises the further step a), in which a second defect in the photomask is etched in a second area of ​​the photomask.

[0050] Following etching of the first defect, the surface of the photomask is passivated with the aid of the second gas component, and as a result, the surface of the photomask is protected for subsequent processing steps. In particular, this can prevent undesired continuation of the etching procedure at the repair site of the first defect during etching of the second defect when the etching gas is used again (i.e., during the repetition of step a) on the second defect).

[0051] In particular, the first and second regions of the corresponding first and second defects are disjoint regions of the photomask, which means, among other things, that the first and second regions do not overlap each other and are not contiguous with each other.

[0052] For example, the first and second regions of the corresponding first and second defects may be geometrically continuous regions by themselves, respectively.

[0053] Following the repetition of step b) for the second defect, step c) may be performed again.

[0054] Steps a) and b) and / or a)-c) may be repeated any desired number of times for further defects on the photomask, the further areas of the further defects being in each case disjoint to each other and to the first and second areas of the first and second defects.

[0055] For example, the method may be used to etch (e.g., repair) n defects in a photomask, where n is a natural number greater than 1. Thus, steps a) through c) may be performed for each of the first (n-1) defects, steps a) and b) may be performed for the nth defect, and the photomask may then be removed from the process atmosphere (e.g., removed and / or lowered from the vacuum chamber).

[0056] According to a further embodiment, the second gas component is ozone (O), atomic oxygen (O), excited oxygen (O * ), hydroperoxyl (HOO), hydroxyl (HO), nitrate radical (NO3), one or more oxygen radicals, and / or one or more neutral oxygen radicals.

[0057] Ozone (O3) is a strong oxidizing agent that develops its oxidizing activity even at room temperature. Due to its strong oxidizing activity, the gas is already unstable at room temperature. The atomic oxygen produced during molecular decomposition (decomposition reaction: O3 → O2 + O) is highly reactive and oxidizing, and it is this atomic oxygen that causes the action of ozone. Therefore, as the so-called "active oxygen," ozone is a carrier of this reactive atomic oxygen. For example, ozone can transfer oxygen atoms to metal surfaces. For example, ozone can further oxidize halides to halogens. Furthermore, ozone has a dipole moment of 0.5337 D, which promotes surface adsorption.

[0058] Oxygen radicals are reactive oxygen species (ROS), particularly, for example, oxygen-containing molecules. As used herein, oxygen radicals further include atomic oxygen.

[0059] According to a further embodiment, the second gas component comprises ozone generated with the aid of an ozone generator, where the oxygen is induced through an electric field or exposed to ultraviolet light so that ozone is generated from the oxygen. The generated ozone is supplied to the surface of the photomask through a supply line of the ozone generator and / or through a supply line fluidly connected to the ozone generator.

[0060] Oxygen can be supplied to the ozone generator as pure oxygen (O2) or as a molecule (e.g., H2O) or a component of a mixture (e.g., air).

[0061] For example, an ozone generator comprises a chamber through which oxygen is guided and within which an electric field or ultraviolet light acts on the oxygen.

[0062] For example, the supply line of the ozone generator is fluidly connected (e.g., directly) to the chamber, e.g., at its end opposite the chamber, the supply line includes a nozzle through which ozone is directed onto the surface of the photomask.

[0063] For example, the ozone generator provides an O3 flow of 0.1 to 4 standard cubic centimeters per minute at its output nozzle and / or at the surface of the photomask. This relatively low O3 flow ensures compatibility with vacuum systems.

[0064] According to a further embodiment, the second gas component contains one or more neutral oxygen radicals generated with the aid of a plasma-based gas generating device, the plasma-based gas generating device comprising a plasma generating source and a selection device fluidly connected to the plasma generating source, wherein the one or more neutral oxygen radicals are separated from the plasma generated in the plasma generating source by the selection device and supplied to the surface of the photomask through a supply line of the plasma-based gas generating device and / or through a supply line fluidly connected to the selection device.

[0065] A plasma source (remote plasma source) and selection equipment can be used to provide, for example, atomic oxygen (O), hydroperoxyl (HOO), hydroxyl (HO), and / or nitrate radical NO as the neutral oxygen radical and thus the second gas component.

[0066] The plasma-based gas generating device, particularly the plasma generating source, may comprise, for example, a chamber in which the plasma is generated. The selection device may be disposed, for example, at an outlet opening of the chamber. Furthermore, a supply line of the plasma-based gas generating device may be fluidly connected (e.g., directly) to the selection device. For example, at its end opposite the selection device, the supply line may comprise a nozzle through which oxygen radicals are directed onto the surface of the photomask.

[0067] According to a further embodiment, the first gas composition contains at least one etching gas component for etching defects and at least one passivation gas component for passivating the surface of the photomask in a first passivation step, and the surface of the photomask is passivated in step b) with the aid of a second gas component in a second passivation step.

[0068] In this embodiment, in addition to the passivation step b) with the aid of the second gas component, a further passivation step is already performed during the etching step a). In other words, the defect is etched with the aid of the first gas component in step a) and the repair site is simultaneously passivated in the first passivation step. After that, a second passivation step is performed in step b) with the aid of the second gas component.

[0069] In particular, it may be the case that the first passivation step performed during step a) does not lead to a complete passivation of the surface of the photomask. For example, the passivation may be incomplete at the edges of the absorber structure. Therefore, the passivation of the surface may be improved and / or completed with a subsequent second passivation step b).

[0070] In this embodiment, the passivation gas component included in the first gas component includes, for example, one or more of the following substances: oxygen (O), ozone (O), water (H), hydrogen peroxide (H), nitrous oxide (N), nitric oxide (NO), nitrogen dioxide (NO), nitric acid (HNO), and an additional oxygen-containing gas.

[0071] According to a further embodiment, step b) comprises the steps of: providing a third gas composition at the surface of the photomask in the passivation region; a third gas component passivating the photomask in the passivation region by physical adsorption; The second and third gas components are provided simultaneously in a single passivation step or sequentially in two corresponding passivation steps separated in time from each other. Includes.

[0072] In this embodiment, in addition to the passivation step with the aid of the second gas component, a further passivation step with the aid of a third gas component is carried out in step b). The passivation step with the aid of the second gas component is passivation by chemisorption, while the further passivation step with the aid of the third gas component includes passivation by physisorption. As a result, the passivation of the surface of the photomask can be further improved.

[0073] When the second and third gas components are provided simultaneously in a single passivation step, the second and third gas components may, for example, be provided as a gas mixture.

[0074] When the second and third gas components are provided successively in two corresponding passivation steps separated from each other in time, the third gas component for physical passivation is provided, for example, first, followed by the second gas component for chemical passivation.

[0075] If further passivation steps are additionally carried out in step a), the method may comprise three mutually different passivation steps, for example with three mutually different gases.

[0076] The third gas component includes, by way of example only, NO2 and / or TEOS, however, the third gas component may further include one or more of other gases.

[0077] According to a further embodiment, the photomask includes an absorber region having an absorber structure and a reflective region without an absorber structure; the defects include one or more of the absorber structures that are undesired and are etched in step a) with the aid of the first gas component; a fourth gas component is provided at the surface of the photomask in step b); The reflective areas of the photomask are protected from passivation by the second gas component with the aid of the fourth gas component; The photomask is passivated in the absorber region with the aid of a second gas component.

[0078] With the aid of the fourth gas component, the reflective region of the photomask can be protected from passivation by the second gas component. For example, the reflective region of the photomask includes a capping layer. For example, the capping layer includes ruthenium ("Ru capping layer"). The capping layer can be damaged by the second gas component, which has a strong oxidizing effect. To prevent this, with the aid of the fourth gas component, the reflective region of the photomask can be protected from passivation (i.e., oxidation) by the second gas component. The fourth gas component is adsorbed, for example, physically adsorbed, on the reflective region of the photomask.

[0079] For example, the fourth gas component may include TEOS, tetrafluoromethane (CF4), and / or nitrogen dioxide (NO2). The fourth gas component may further include one or more other substances.

[0080] According to a second aspect, an apparatus for particle beam induced etching of defects in a microlithographic photomask is presented. a first providing device for providing an active particle beam at a surface of the photomask in the area of ​​the defect; a second providing device for providing a first gas component activatable by the particle beam at the surface in the region of the defect for the purpose of etching the defect; a third providing device for providing a second gaseous component containing oxygen having spontaneous oxidizing properties at the surface in the passivation area of ​​the photomask, including the area of ​​the defect, for the purpose of passivating the surface; Equipped with.

[0081] For example, the apparatus is a repair apparatus for repairing microlithographic photomasks.For example, the apparatus is a modified scanning electron microscope.

[0082] The first providing device comprises, for example, a particle source (e.g., electron source) for generating a particle beam (e.g., electron beam), a particle beam directing device (e.g., scanning unit) configured to guide the particle beam to each pixel of the repair shape of the photomask, a particle beam shaping device (e.g., particle, electron and / or beam optics unit) configured to shape the particle beam, more specifically, to focus the particle beam, and at least one detector for capturing secondary electrons and / or backscattered electrons.

[0083] In particular, the second and third providing devices are second and third gas providing devices. For example, the second and third providing devices may each be part of an overall gas providing apparatus. Each of the second and third gas providing devices includes at least one storage container configured to store a corresponding gas component and / or a gas generating device configured to generate the corresponding gas component on-site; a gas flow rate setting unit (e.g., further including one or more valves) configured to provide the corresponding gas component at a predetermined gas flow rate at the surface of the photomask in the corresponding region; and a supply unit (e.g., having a supply line) configured to supply the corresponding gas component to the surface of the photomask.

[0084] In step a), an active particle beam is sequentially applied to each pixel of the repair shape, for example, using a particle beam directing device. The active particle beam remains at each pixel for a predetermined dwell time to initiate a chemical reaction between the first gas component and the mask material at the location of each pixel. For example, the dwell time is 100 nanoseconds. However, other dwell times may also be used.

[0085] According to an embodiment of the second aspect, the apparatus comprises: an ozone generator for generating ozone from oxygen, the ozone generator including a capacitor for generating an electric field or an ultraviolet light source for generating ultraviolet light; a supply line for supplying the generated ozone as a second gas component at the surface of the photomask; Equipped with.

[0086] According to a further embodiment of the second aspect, an apparatus includes a plasma-based gas generation device for generating the second gas component, the plasma-based gas generation device including a plasma generation source for generating a plasma, a selection device for separating one or more neutral oxygen radicals from the plasma, and a delivery line for providing one or more decoupled neutral oxygen radicals at a surface of the photomask.

[0087] For example, the plasma is generated from oxygen. In particular, the plasma is generated in a plasma chamber of the plasma generation source and exists only in the plasma chamber. Therefore, one or more neutral oxygen radicals are extracted from the plasma with the aid of a selective device.

[0088] An ozone generator or plasma-based gas generating device allows the second gas component to be generated in situ at the location of the apparatus for particle beam induced etching.

[0089] "A" or "an" in this instance should not necessarily be understood as a limitation to exactly one element. Rather, there may be a plurality of elements, e.g., two, three, or more. Any other numbers used herein should also not be understood as a limitation to the exact number of elements stated. Rather, unless otherwise indicated, upward and downward deviations in the numbers are permitted.

[0090] The embodiments and features described for the method apply equally to the presented device, and vice versa.

[0091] Further possible implementations of the present invention further include not explicitly mentioned combinations of features or embodiments described herein above or hereinafter with respect to the exemplary embodiments. Those skilled in the art will further add individual aspects as improvements or supplements to the respective basic forms of the invention.

[0092] Further advantageous embodiments and aspects of the invention are the subject of the dependent claims and 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 attached drawings. [Brief explanation of the drawings]

[0093] [Figure 1] 1A and 1B are schematic diagrams illustrating a cross section of a microlithographic photomask being subjected to a particle beam induced treatment process, according to one embodiment, where the top image shows a particle beam induced repair process for defects and the bottom image shows passivation of the repair site. [Figure 2] FIG. 1 illustrates a flowchart of a method for particle beam induced etching of defects in a microlithographic photomask, according to one embodiment. [Figure 3] FIG. 1 illustrates an apparatus for particle beam induced etching of defects in a microlithographic photomask, according to one embodiment. [Figure 4] 4 shows a gas generating device of the device from FIG. 3 according to one embodiment. [Figure 5] 4 shows a gas generating device of the apparatus from FIG. 3 according to a further embodiment. [Figure 6] FIG. 1 illustrates a top view of a microlithographic photomask, according to one embodiment. [Figure 7] 3 shows a variant of the method step of the method from FIG. 2; [Figure 8] FIG. 10 illustrates an apparatus for particle beam induced etching of defects in a microlithographic photomask according to a further embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0094] In the figures, identical or functionally identical elements are given the same reference numerals unless otherwise indicated. It should further be noted that the depictions in the figures are not necessarily to scale.

[0095] 1 shows a schematic cross-section of a photomask 100 being subjected to a particle beam induced treatment process. In particular, this process is a locally induced etching process in which material is removed from the photomask 100.

[0096] In the illustrated example of photomask 100, the mask is a reflection-based mask suitable for EUV lithography, i.e., in operation, operating light is emitted onto photomask 100 and reflected back into the same half-space. EUV stands for "extreme ultraviolet" (EUV) and refers to operating light wavelengths between 0.1 nm and 30 nm, specifically 13.5 nm.

[0097] In the example of FIG. 1 , the photomask 100 has a layer-like structure. The base of the photomask 100 is formed by a substrate 102, which may include, for example, quartz glass. The multilayer mirror 104 is disposed on the substrate 102. In particular, the multilayer mirror 104 is disposed on the side of the substrate 102 that is subsequently irradiated by the operating light during operation. For example, the multilayer mirror 104 as a Bragg mirror is specifically designed for each wavelength of the operating light. For example, the multilayer mirror 104 includes multiple bilayers made of molybdenum and silicon. The capping layer 106 is disposed on the multilayer mirror 104. For example, the capping layer 106 includes ruthenium or another noble metal. For example, the capping layer 106 is an etch stop layer configured to interrupt the etching process used in structuring the structured layer 108 so that the multilayer mirror 104 or the substrate 102 are not attacked during the process.

[0098] A structured layer 108 is disposed on the capping layer 106, and a pattern of the structured layer must be projected onto a wafer in the image plane of a projection system of a lithography apparatus. Reference numeral 110 denotes multiple structures of the structured layer 108. For example, the structured layer 108 may comprise tantalum boron nitride (TaBN), tantalum nitride (TaN), tantalum boron oxide (TaBO), and / or tantalum oxide (TaO). For example, a layer of TaBN may first be applied over the entire area and then selectively etched to create the structured layer 108. Incident operating light is significantly attenuated in areas where the TaBN layer remains.

[0099] Defect D1 can occur when photomask 100 is produced. Figure 1 shows opaque defect D1 in which absorber structure 112 is located on photomask 100 in a location where there should be no absorber structure. In other words, absorber structure 110 in Figure 1 is a desired absorber structure, but absorber structure 112 is an unwanted extra absorber structure.

[0100] Hereinafter, a method for particle beam induced etching of defect D1 in microlithographic photomask 100 will be described with reference to FIGS. 1-8, and in particular FIG.

[0101] Defect D1 is etched in a particle-beam-induced process in a first step S1 of the method. First step S1 is shown in the upper image of FIG. 1. An active particle beam 114 (e.g., an electron beam) and a first gas component 116 that can be activated by particle beam 114 are provided at surface 118 of photomask 100 in region 120 of defect D1, specifically in step S1. In particular, first gas component 116 includes an etching gas, for example, XeF2.

[0102] For example, one or more edges 124 (FIG. 1, bottom) of structure 108 are exposed when defect D1 is etched in step S1.

[0103] For example, defect D1 may be completely etched, i.e. completely removed, in step S1, in which case undesired structure 112 is completely removed at the end of step S1.

[0104] In a second step S2 of the method, the surface 118 of the photomask 100 is passivated in passivation regions 122. In particular, the second step S2 is performed after the first step S1, in which the defect D1 is etched. The second step S2 is shown in the lower image of Figure 1, where the photomask 100 is seen without the defect D1, 112.

[0105] In particular, in step S2, a second gas component 126 is provided at the surface 118 of the photomask 100 in a passivation region 122 of the photomask 100. The passivation region 122 specifically completely encompasses the defect region 120 ( FIG. 1 , top), e.g., is larger than the defect region 120. The second gas component 126 is an oxygen-containing gas component with spontaneous oxidizing properties. The second gas component 126 includes highly reactive species, e.g., ozone or different oxygen radicals, and passivates the surface 118 of the photomask 100 without further activation, i.e., without activation by a particle beam (e.g., without the particle beam 114 shown in the upper image of FIG. 1 ). In particular, the second gas component 126 passivates the surface 118 of the photomask 100 by spontaneous chemisorption, and the surface 118 is chemically modified. In particular, the properties of the second gas component 126 are such that it can spontaneously oxidize (without activation by a particle beam) metal-containing materials on the surface 118 of the photomask 100, such as the metal-containing materials (e.g., tantalum alloys and / or tantalum) of the structured coating 108.

[0106] The passivation in step S2 makes it possible in particular to passivate the exposed surfaces 118' of the edges 124 of the structure 108 exposed during the etching in step S1.

[0107] FIG. 3 shows a schematic diagram of an apparatus 200 for particle-beam induced etching of a photomask 100, for example, the EUV photomask 100 from FIG.

[0108] The apparatus 200 is operated by a vacuum pump 204 to create a process atmosphere 206 within the housing 202. -2 ~10 -8 The apparatus 200 comprises a housing 202 evacuated to a pressure in the mbar range. The apparatus 200 further comprises a providing device 208 disposed within the evacuated housing 202 for providing the focused particle beam 114. The providing device 208 comprises a particle source 210 and one or more beam directing units 212 and / or beam shaping units 214 that steer the particle beam 114 onto the surface 118 of the photomask 100 as desired. For example, the providing device 208 is an electron column configured to provide the focused electron beam 114. The apparatus 200 further comprises one or more detectors 216, for example for detecting secondary electrons.

[0109] The apparatus 200 further comprises a sample stage 218 for holding and positioning the photomask 100 to be processed. The sample stage 218 is actuable in two, or preferably three, spatial directions. Furthermore, the sample stage 218 may be mounted in a tiltable and rotatable manner to position the photomask 100. In particular, the sample stage 218 is mounted with vibration damping and is mechanically isolated from the structure's mount (not shown).

[0110] The apparatus 200 further includes first and second gas-providing devices 220, 222 for providing the first and second gas components 116, 126, as appropriate. The first and second gas-providing devices 220, 222 are, for example, partially disposed outside the housing 202. Each of the first and second gas-providing devices 220, 222 includes at least one storage vessel 224, 226 or gas-generating device 224, 226. Each of the first and second gas-providing devices 220, 222 further includes means for setting a gas volume flow rate and means for starting and terminating the gas flow. Furthermore, each of the first and second gas-providing devices 220, 222 includes a supply line 228, 230 leading to the housing 202 and opening at its end into a respective nozzle. Additionally, further gas providing devices similar to the gas providing devices 220, 222 may be provided to provide further gas components, for example buffer gases, gases having an oxidizing or reducing effect on the process atmosphere 206.

[0111] 3 depicts an intake unit 232. The intake unit 232 is configured to suck out excess gases, particularly volatile reaction products, from the process atmosphere 206, and in particular from the surface 118 of the photomask 100. To this end, the intake unit 232 comprises, for example, a further pump 234. This allows for better control of the composition of the process atmosphere 206.

[0112] 4 and 5 illustrate embodiments of second gas generating devices 226′, 226″ for generating second gas components 126, 126′, 126″, respectively. In particular, second gas components 126, 126′, 126″ are highly reactive species that are preferably generated near their point of use.

[0113] FIG. 4 shows an ozone generator 236 for generating ozone O3 as the second gas component 126'. The ozone generator 236 includes a supply line 238 for supplying oxygen O2. The oxygen O2 can be supplied to the ozone generator 236 as pure oxygen O2 or as a component of a molecule (e.g., HO) or a mixture (e.g., air). The ozone generator 236 further includes a chamber 240 in which the oxygen O2 is exposed to, for example, a strong electric field E (capacitor 242), thereby forming ozone O3 from the oxygen O2. The ozone generator 236 further includes a supply line 244 for providing the formed ozone O3. For example, the supply line 244 is the supply line 230 shown in FIG. 3 for supplying the second gas component 126, 126' to the photomask 100. Alternatively, the supply line 244 is fluidly coupled to the supply line 230 of FIG. 3.

[0114] FIG. 5 shows a plasma-based gas generation apparatus 246 for generating one or more neutral oxygen radicals 248 as a second gas component 126″. The plasma-based gas generation apparatus 246 includes a supply channel 250 for supplying a working gas 251 (e.g., oxygen) to a chamber 252 including a plasma generation source 254 for generating a plasma, a selection apparatus 256 for extracting one or more neutral oxygen radicals 248 from the plasma, and a supply line 258 for providing the generated neutral oxygen radicals 248. For example, the supply line 258 is the supply line 230 shown in FIG. 3 for supplying the second gas component 126, 126″ to the photomask 100. Alternatively, the supply line 258 is fluidly connected to the supply line 230 of FIG. 3. For example, a plasma-based gas generating device 246 can be used to provide atomic oxygen (O), hydroperoxyl (HOO), hydroxyl (HO), and / or NO3 as neutral oxygen radicals 248 and thus as the second gas component 126''.

[0115] In an optional third step S3 of the method, the second gas component 126 is removed from the surface 118, 118' of the photomask 100 by pumping. For example, a suction unit 232 with a further pump 234 as shown in Figure 3 may be used for this purpose.

[0116] In an optional fourth step S4 of the method, step S1 is performed again after step S3, but for a different second defect D2 (FIG. 6) on the photomask.

[0117] In particular, a first defect D1 in the photomask 100 in a first region 120 of the photomask 100 is etched during a first performance of step S1 (FIGS. 1 and 6). Additionally, a surface 118 of the photomask 100 (e.g., FIG. 1, surface 118' of the exposed edge 124 of the structure 108) is passivated during a first performance of step S2. Immediately thereafter, step S3 is performed, in which the second gas component 126 is pumped away from the surface 118, 118' of the photomask 100. Thereafter, a second defect D2 in the photomask 100 in a second region 130 of the photomask 100 (FIG. 6) is etched during a second performance of step S1.

[0118] Optionally, a new step S2 can then be performed to passivate the surface 118 of the photomask 100 on a second passivation region 132 (FIG. 6) including a second region 130 of the second defect D2.

[0119] Similarly, multiple additional defects (not shown) in the photomask 100 that are similar to defects D1 and D2 may be etched, and the corresponding repair sites may be passivated by repeatedly performing steps S1 and S2 or S1-S3.

[0120] Steps S1-S3, including possible repetition of steps S1 and S2 or S1 and S3 for additional defects, are performed, for example, without removing photomask 100 from process atmosphere 206. In other words, photomask 100 remains within vacuum chamber 202 during these method steps, and vacuum chamber 202 remains closed.

[0121] FIG. 7 shows a variant of method steps S1 and S2.

[0122] In a first variant of the method, method step S1 can include a passivation step S12 for passivating the surface 118 of the photomask 100 in addition to the above-mentioned etching step (hereinafter referred to as step S11). This means that the method includes passivation steps that are independent of each other. In particular, the method includes a pre-passivation step S12 with a pre-passivation gas 318 during etching S11 (FIG. 8) and a main passivation step S2 (or S22) with a main passivation gas 126 after etching S11.

[0123] In a first variant of the method, the first gas composition 316 (see apparatus 300 of FIG. 8 ) includes an etching gas 318 for etching defects D1 as well as at least one passivation gas 320 for passivating the surface 118 of the photomask 100. For example, the passivation gas 320 includes HO. For example, the passivation gas 320 is a passivation gas that has only a passivating effect upon activation by the particle beam 114.

[0124] In step S1 of this first variant of the method, the defect D1 is etched (by an etching gas 318) with the aid of a first gas component 316 (in particular in a partial step S11), and the repair site is simultaneously passivated (by a passivation gas 320) in a first pre-passivation step S12. A second passivation step is then carried out in step S2 with the aid of a second gas component 126.

[0125] In particular, if the pre-passivation step S12 does not result in complete passivation of the surfaces 118, 118' of the photomask 100 and, for example, passivation is incomplete at the edge 124 of the absorber structure 108 (Figure 1), passivation of the surface 118 can advantageously be completed using a second subsequent main passivation step S2.

[0126] In a second variant of the method, method step S2 can include a step S21 of generating the second gas component 126, 126', 126" . In particular, the second gas component 126, 126', 126" is in this case generated in situ at the location of the apparatus 200, 300. For example, the second gas component 126, 126', 126" is generated using an ozone generator 236 ( FIG. 4 ) or using a plasma-based gas generation device 246 ( FIG. 5 ).

[0127] In a third variant of the method, method step S2 can comprise a further passivation step S23. In this case, method step S2 comprises two passivation processes S22 and S23, such that in addition to the passivation process described above (hereinafter denoted S22) with the aid of the second gas component 126, 126', 126'', a further passivation process S23 is carried out with the aid of a third gas component 326.

[0128] In particular, a third gas component 326 is provided at the surface 118 of the photomask 100 in a passivation region 122 encompassing the defect region 120. The third gas component 326 passivates the photomask 100 in the passivation region 122 by physical adsorption. For example, the third gas component 326 includes NO and / or TEOS. Passivation of the surface 118 of the photomask 100 at the repair site can be even further improved by passivation with the help of the second gas component 126 based on chemisorption of the surface 118 and, additionally, by passivation with the help of the third gas component 326 based on physical adsorption.

[0129] In a third variant of the method, the second and third gas components 126, 326 may be provided simultaneously in a single passivation step S22+S23, for example as a gas mixture (e.g., 2 / 3 second gas component 126 and 1 / 3 third gas component 326, or a different mixture ratio). Alternatively, the second and third gas components 126, 326 may be provided consecutively in two corresponding passivation steps S22, S23 separated in time. For example, the third gas component 326 for physical passivation is provided first, followed by the second gas component 126 for chemical passivation. However, the reverse order is also feasible.

[0130] If a further passivation step S12 is additionally performed, the method may consequently comprise three different passivation processes / steps S12, S22, S23 with three different passivation gases 126, 320, 326.

[0131] In a fourth variant of the method, method step S2 can include step S24, in which a fourth gas component 426 is supplied to surface 118 of photomask 100 to protect regions R (FIG. 6) of photomask 100 that should not be passivated from passivation by second gas component 126.

[0132] In particular, the photomask 100 includes an absorber region A having an absorber structure 108 and a reflective region R (FIG. 6) lacking the absorber structure 108. For example, the reflective region R includes the surface 118″ (FIG. 1) of the capping layer 106. Furthermore, the defect D1 includes one or more of the absorber structures 108, 110, and in particular, the undesired absorber structures 112 (FIG. 1). These undesired absorber structures 112 are etched in step S1 with the aid of the first gas component 126. Then, both the first gas component 126 (in partial step S22) and the fourth gas component 426 (in partial step S24) are provided at the surfaces 118, 118′, 118″ of the photomask 100 in step S2. As a result, the reflective regions R of the photomask 100 are protected from passivation by the second gas component 126 with the aid of the fourth gas component 426, for example, as a result of physisorption of the fourth gas component 426 in the reflective regions R. Additionally, the photomask is passivated in the absorber regions A with the aid of the second gas component 126.

[0133] Individual, some or all of the first to fourth variants of the method may also be combined with one another.

[0134] Although the present invention has been described with reference to exemplary embodiments, it can be modified in many ways. [Explanation of symbols]

[0135] 100 Photomasks 102 Circuit Board 104 Multi-layer mirror 106 Capping Layer 108 layers 110, 112 Absorbent structure 114 Particle Beam 116 ingredients 118, 118', 118'' surface 120 areas 122 areas 124 Edge 126, 126', 126'' components 130 areas 132 areas 200 equipment 202 Housing 204 Vacuum Pump 206 Process atmosphere 208 Equipment provided 210 Particle Source 212, 214 units 216 detector 218 Sample Stage 220, 222 Gas supply equipment 224, 226 Storage vessels / gas generating equipment 226', 226'' Gas Generating Equipment 228 Supply Line 230 Supply Line 232 Inhalation Unit 234 Pump 236 Ozone Generator 238 Supply Line 240 Chamber 242 capacitor 244 Offering Line 246 Gas Generating Equipment 248 Oxygen Radical 250 Supply Channels 251 Working Gas 252 Chamber 254 Plasma Generation Source 256 Selected Devices 258 Offering Lines 300 equipment 316 ingredients 318 Gas 320 Gas 326, 426 ingredients Area A D1, D2 defects E electric field O2 oxygen R region S1~S4 Method steps S11, S12 method steps S21~S24 Method steps

Claims

1. 1. A method for particle beam induced etching of defects (D1) in a microlithographic photomask (100), comprising: a) providing (S1) an active particle beam (114) and a first gas component (116) that can be activated by said particle beam (114) at the surface (118) of said photomask (100) in the area (120) of said defect (D1) for the purpose of etching said defect (D1), and thereafter b) providing (S2) a spontaneously oxidizing oxygen-containing second gas component (126) at the surface (118) of the photomask (100) in a passivation area (122) encompassing the area (120) of the defect (D1) for the purpose of passivating the surface (118); A method comprising:

2. In step a), at least one edge (124) of the structured coating (108) of the photomask (100) is exposed; The method of claim 1, wherein in step b), the at least one exposed edge (124) is passivated.

3. 3. The method according to claim 1 or 2, wherein in step a) the defect (D1) is completely etched and / or completely removed.

4. The method of any one of claims 1 to 3, wherein the second gas component (126) passivates the surface (118) of the photomask (100) with the aid of spontaneous chemisorption.

5. The method of any one of claims 1 to 4, further comprising the step of: c) removing the second gas component (126) from the surface (118) of the photomask (100) by pumping (S3).

6. In step a), a first defect (D1) in the photomask (100) is etched in a first area (120) of the photomask (100), 6. The method of claim 5, further comprising the step a) after step c) of etching a second defect (D2) in the photomask (100) in a second region (130) of the photomask (100).

7. The second gas component (126) is ozone (O 3 ), atomic oxygen (O), excited oxygen (O 2 * ), hydroperoxyl (HOO), hydroxyl radical (HO), nitrate radical (NO 3 ), one or more oxygen radicals (248), and / or one or more neutral oxygen radicals (248).

8. The second gas component (126) is ozone (O 3 ) Ozone (O 3 ) is oxygen (O 2 ) to be generated from the oxygen (O 2 ) is induced in said ozone generator (236) through an electric field (E) or exposed to ultraviolet light; The generated ozone (O 3 8. The method of claim 1, wherein ozone is supplied to the surface of the photomask through a supply line of the ozone generator and / or through a supply line that is fluidly connected to the ozone generator.

9. the second gas component (126) contains one or more neutral oxygen radicals (248) generated with the aid of a plasma-based gas generating device (246); the plasma-based gas generation device (246) comprises a plasma generation source (254) and a selection device (256) fluidly connected to the plasma generation source (254); 9. The method of claim 1, wherein the one or more neutral oxygen radicals are separated from the plasma generated in the plasma generation source by the selection device and supplied to the surface of the photomask through a supply line of the plasma-based gas generation device and / or through a supply line fluidly connected to the selection device.

10. the first gas composition (316) contains at least one etching gas composition (318) for etching the defects (D1) and at least one passivation gas composition (320) for passivating the surface (118) of the photomask (100) in a first passivation step (S12); 10. The method according to any one of claims 1 to 9, wherein the surface (118) of the photomask (100) is passivated in step b) with the aid of the second gas component (126) in a second passivation step (S2).

11. In step b), providing a third gas composition (326) at the surface (118) of the photomask (100) within the passivation region (122); the third gas component (326) passivates the photomask (100) in the passivation region (122) by physisorption; 11. The method according to any one of claims 1 to 10, wherein the second and third gas components (126, 326) are provided simultaneously in a single passivation step or sequentially in two corresponding passivation steps (S22, S23) spaced apart in time.

12. the photomask (100) comprises an absorber region (A) having an absorber structure (108) and a reflective region (R) without the absorber structure (108); the defect (D1) comprises one or more of the absorber structures (108, 110) which are undesirably etched in step a) with the aid of the first gas component (116), a fourth gas component (426) is provided at the surface (118) of the photomask (100) in step b); the reflective area (R) of the photomask (100) is protected from passivation by the second gas component (126) with the aid of the fourth gas component (426); The method of any one of claims 1 to 11, wherein the photomask (100) is passivated in the absorber region (A) with the aid of the second gas component (126).

13. 1. An apparatus for particle beam induced etching of defects (D1) in a microlithographic photomask (100), comprising: a first providing device (208) for providing an active particle beam (114) at a surface (118) of the photomask (100) in a region (120) of the defect (D1); a second providing device (220) for providing a first gas component (116) activatable by the particle beam (114) at the surface (118) within the region (120) of the defect (D1) for the purpose of etching the defect (D1); a third providing device (222) for providing a spontaneously oxidizing oxygen-containing second gas component (126) at the surface (118) in a passivation area (122) of the photomask (100) that includes the region (120) of the defect (D1) for the purpose of passivating the surface (118); An apparatus comprising:

14. Oxygen (O 2 ) to ozone (O 3 an ozone generator (236) for generating an ozone gas (O), the ozone generator (236) including a capacitor (242) for generating an electric field (E) or an ultraviolet light source for generating ultraviolet light; The generated ozone (O 3 14. The apparatus of claim 13, further comprising a delivery line (244) for delivering HCl as the second gas component (126') at the surface (118) of the photomask (100).

15. 15. The apparatus of claim 13, further comprising a plasma-based gas generation device (246) for generating the second gas component (126''), the plasma-based gas generation device (246) comprising: a plasma generation source (254) for generating a plasma; a selection device (256) for separating one or more neutral oxygen radicals (248) from the plasma; and a delivery line (258) for providing the one or more decoupled neutral oxygen radicals (248) at the surface (118) of the photomask (100).

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