Method and apparatus for particle beam induced treatment of defects in microlithography photomasks

Abstract

A method for particle beam induced treatment of defects (D, D') in a microlithography photomask (100), comprising the steps of: a) providing (S1) an image (300) of at least a portion of the photomask (100); b) determining (S2) a geometric shape of the defect (D, D') in the image (300) as a repair shape (302, 302'), the repair shape (302, 302') comprising n pixels (304); and c) subdividing (S3) the repair shape (302, 302') into k partial repair shapes (306) in a computer implemented manner, the i-th of the k partial repair shapes (306) being has m pixels (304), which is a subset of the n pixels (304) of the repair shapes (302, 302'); d) providing (S4) an activating particle beam (202) and a process gas at each of the m pixels (304) of a first of the partially repaired shapes (306) for processing the first of the partially repaired shapes (306); e) repeating (S5) step d) for the first of the partially repaired shapes (306) for j repeat periods; and f) repeating (S6) steps d) and e) for each further partially repaired shape (306).

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for particle beam induced treatment of defects in microlithography photomasks. [Background technology]

[0002] Microlithography is used to manufacture microstructured components, such as integrated circuits. Microlithographic processes are carried out using a lithography apparatus having an illumination system and a projection system. An image of a photomask (reticle), illuminated by the illumination system, is projected by the projection system onto a substrate, e.g., a silicon wafer, which in this case is coated with a photosensitive layer (photoresist) and positioned in the image plane of the projection system, in order to transfer the mask structure into a photosensitive coating on the substrate.

[0003] To achieve small structure sizes and thus increase the integration density of microstructure components, light with very short wavelengths, for example deep ultraviolet (DUV) or extreme ultraviolet (EUV), is increasingly being used, DUV having a wavelength of, for example, 193 nm and EUV having a wavelength of, for example, 13.5 nm.

[0004] In this case, microlithographic photomasks have structure sizes ranging from a few nanometers to hundreds of nanometers. The manufacture of such photomasks is highly complex and therefore costly. This is especially true because the photomask must be defect-free; otherwise, it is impossible to ensure that the structures produced on the silicon wafer by the photomask exhibit the desired functionality. In particular, the quality of the structures on the photomask determines the quality of the integrated circuits produced on the wafer by this photomask.

[0005] For this reason, microlithography photomasks are checked for the presence of defects, and any defects found are repaired in a targeted manner. Typical defects include the absence of expected structures, for example, due to an unsuccessful execution of an etching process, or the presence of unexpected structures, for example, due to an etching process that proceeded too quickly or took effect in the wrong location. These defects can be repaired by targeted etching of excess material at the appropriate locations, or by targeted deposition of additional material; for example, this is possible in a very targeted manner by electron beam induced processing (FEBIP, "focused electron beam induced processing").

[0006] DE 10 2017 208 114 A1 describes a method for particle-beam-induced etching of photolithography masks. In this case, a particle beam, in particular an electron beam, and an etching gas are applied to the location on the photolithography mask to be etched. The particle beam activates a local chemical reaction between the material of the photolithography mask and the etching gas, resulting in local ablation of material from the photolithography mask.

[0007] It has been determined that for large area defects, the composition of the provided process gas, e.g., etching gas, may change adversely as the size of the defect increases, which can seriously impair the treatment of the defect. For example, the etching rate may be significantly reduced due to the adverse gas composition, so that the defect cannot be completely removed or can only be completely removed with a higher electron beam dose (i.e., for example, a longer etching duration). Summary of the Invention

[0008] Against this background, it is an object of the present invention to provide an improved method and apparatus for particle beam-induced processing of defects in microlithography photomasks.

[0009] Therefore, a method is proposed for particle beam induced treatment of defects in microlithography photomasks. a) providing an image of at least a portion of a photomask; b) determining the geometric shape of the defect in the image as a repair shape, the repair shape comprising n pixels; c) subdividing the repair shape into a number k of sub-repair shapes, the i-th of which is m i pixels, which are a subset of n pixels of the inpainting shape; d) m of the first of the partial repair shapes for the purpose of processing the first of the partial repair shapes. i providing an activating particle beam and a process gas at each of the pixels; e) repeating step d) for a first of the partial repair shapes for a number j of repetition cycles; f) repeating steps d) and e) for each further partial repair shape; Includes:

[0010] In particular, n, k, and m i and j is an integer greater than or equal to 2. Furthermore, i is an integer that specifies a counter that runs from 1 to k.

[0011] The repair shape is subdivided into multiple partial repair shapes, so that the processing time for one of the partial repair shapes is shorter than the processing time for the entire repair shape. As a result, the gas composition of the process gas required and / or optimal for processing the defect can be better ensured during processing of the partial repair shape. As a result, the defect can be better processed. For example, the proposed method also enables processing repair shapes with large areas and / or repair shapes with many pixels using advantageous and / or optimal gas compositions of the process gas.

[0012] The treatment of the defect may in particular involve etching the defect, within which material is locally ablated from the photomask, or depositing material on the photomask in the area of ​​the defect. By way of example, the proposed method may allow excess structures in the area of ​​the defect to be better etched away, or may allow missing structures in the area of ​​the defect to be better extended.

[0013] An image of at least one portion of the photomask is recorded, for example, by a scanning electron microscope (SEM). For example, the image of at least one portion of the photomask has a spatial resolution on the order of a few nanometers. The image can also be recorded using a scanning probe microscope (SPM), such as, for example, an atomic force microscope (AFM) or a scanning tunneling microscope (STM).

[0014] The method may include, inter alia, capturing an image of at least one portion of the photomask using a scanning electron microscope and / or a scanning probe microscope.

[0015] As an example, a microlithography photomask is a photomask for an EUV lithography tool. In this case, EUV stands for "extreme ultraviolet" and refers to the wavelength of the working light, which is between 0.1 nm and 30 nm, specifically 13.5 nm. Within an EUV lithography tool, a beam shaping and illumination system is used to direct EUV radiation onto a photomask (also called a "reticle"), which typically takes the form of a reflective optical element (a reflective photomask). The photomask has structures that are imaged, at reduced size, onto a wafer or the like using the projection system of the EUV lithography tool.

[0016] By way of example, a microlithography photomask can be a photomask for a DUV lithography system. In this case, DUV stands for "deep ultraviolet" and refers to a working light wavelength of 30 nm to 250 nm, particularly 193 nm or 248 nm. Within a DUV lithography system, a beam shaping and illumination system is used to direct the DUV radiation onto a photomask, typically in the form of a transmissive optical element (transmissive photomask). The photomask has a structure that is imaged, at reduced size, onto a wafer or the like using the projection system of the DUV lithography system.

[0017] For example, a microlithography photomask comprises a substrate and a structure formed on the substrate by a coating. For example, the photomask is a transmissive photomask, in which the imaged pattern is realized in the form of an absorbing (i.e., opaque or partially opaque) coating on a transparent substrate. Alternatively, the photomask can be a reflective photomask, particularly for use in EUV lithography.

[0018] By way of example, the substrate comprises silicon dioxide (SiO2), e.g., quartz glass. By way of example, the structured coating comprises chromium, a chromium compound, a tantalum compound, and / or a compound made from silicon, nitrogen, oxygen, and / or molybdenum. The substrate and / or coating can also comprise other materials.

[0019] In the case of a photomask for an EUV lithography tool, the substrate may include an alternating sequence of molybdenum and silicon layers.

[0020] The proposed method allows for the identification, location, and repair of defects in a photomask, in particular defects in the structured coating of this photomask. In particular, the defects are (absorbent or reflective) coatings of the photomask that have been incorrectly applied to the substrate. The method can be used to extend the coating in places on the photomask where it is missing. Furthermore, the coating can be removed from places on the photomask where it has been incorrectly applied.

[0021] For this purpose, the geometry of the defect is determined in the recorded image of at least one portion of the photomask. For example, the two-dimensional geometry of the defect is determined. The determined geometry of the defect is hereinafter referred to as the repair geometry.

[0022] n pixels are defined in the repair shape for particle beam-induced processing of the repair shape. Throughout steps d) to f) of the method, a particle beam is directed to each of the n pixels of the repair shape. In particular, an intensity maximum of the electron beam is directed to each center of each of the n pixels. In other words, the n pixels of the repair shape represent a raster, in particular a two-dimensional raster, of the repair shape for particle beam-induced processing. By way of example, the n pixels of the repair shape correspond to the incident area of ​​the particle beam during particle beam-induced processing of the defect. By way of example, the pixel size is selected so that the intensity distribution of the electron beam directed to the center of the pixel drops to a predetermined intensity at the edge of the pixel due to the Gaussian intensity distribution of the electron beam. The predetermined intensity can correspond to a drop to half of the intensity maximum, or otherwise to any other percentage of the intensity maximum of the electron beam. By way of example, the pixel size and / or the electron beam half-width are in the sub-nanometer range or on the order of a few nanometers.

[0023] For example, the process gas may be a precursor gas and / or an etching gas. For example, the process gas may be a mixture of multiple gas components, i.e., a process gas mixture. For example, the process gas may be a mixture of multiple gas components, each having only certain molecular types.

[0024] In particular, alkyl compounds of main group elements, metals or transition elements can be considered as suitable precursor gases for the deposition or growth of elevated structures. Examples of this are (cyclopentadienyl)trimethylplatinum (CpPtMe3Me=CH4), (methylcyclopentadienyl)trimethylplatinum (MeCpPtMe3), tetramethyltin (SnMe4), trimethylgallium (GaMe3), ferrocene (Cp2Fe), bisarylchromium (AR2Cr), and / or carbonyl compounds of main group elements, metals or transition elements, such as chromium hexacarbonyl (Cr(CO)6), molybdenum hexacarbonyl (Mo(CO)6), tungsten hexacarbonyl (W(CO)6), dicobalt octacarbonyl (Co2(CO)8), triruthenium dodecacarbonyl (Ru3(CO) 12 ), iron pentacarbonyl (Fe(CO)5), and / or alkoxide compounds of main group elements, metals, or transition elements, such as tetraethoxysilane (Si(OC2H5)4), tetraisopropoxytitanium (Ti(OC3H7)4), and / or halide compounds of main group elements, metals, or transition elements, such as tungsten hexafluoride (WF6), tungsten hexachloride (WC16), titanium tetrachloride (TiCl4), boron trifluoride (BF3), silicon tetrachloride (SiCl4), and / or complexes containing main group elements, metals, or transition elements, such as bis(hexafluoroacetylacetonato) copper (Cu(CF6HO2)2), dimethyl gold trifluoroacetylacetonate (Me2Au(CF3H4O2)), and / or organic compounds, such as carbon monoxide (CO), carbon dioxide (CO2), aliphatic and / or aromatic hydrocarbons, etc.

[0025] By way of example, the etching gas may include xenon difluoride (XeF), xenon dichloride (XeCl), xenon tetrachloride (XeCl), steam (H2O), heavy water (DO), oxygen (O2), ozone (O3), ammonia (NH3), nitrosyl chloride (NOCl), and / or one of the following halogen compounds: XNO, XONO2, X2O, XO2, X2O2, X2O4, and X2O6, where X is a halogen compound. Additional etching gases for etching one or more of the deposited test structures are specified in commonly owned U.S. Patent Application Serial No. 13 / 0103281.

[0026] The process gas can contain additional additive gases, such as oxidizing gases, such as hydrogen peroxide (HO), nitrous oxide (NO), nitric oxide (NO), nitrogen dioxide (NO), nitric acid (HNO), and other oxygen-containing gases, and / or halogen compounds, such as chlorine (Cl), hydrogen chloride (HCl), hydrogen fluoride (HF), iodine (I), hydrogen iodide (HI), bromine (BR), hydrogen bromide (HBr), phosphorus trichloride (PCl), phosphorus pentachloride (PCl), phosphorus trifluoride (PF), and other halogen-containing gases, and / or reducing gases, such as hydrogen (H), ammonia (NH), methane (CH), and other hydrogen-containing gases. These additive gases can be used, for example, for etching processes, as buffer gases, as passivation media, etc.

[0027] For example, the activation particle beam may include a particle beam source for generating a particle beam and a pixel m of each partial repair feature of the photomask. ia particle beam directing device (e.g., a scanning unit) configured to direct a particle beam at a specific focal point; a particle beam shaping device (e.g., electron or beam optical element) configured to shape the particle beam at a specific focal point; at least one containment vessel configured to store a process gas or at least one gas component of the process gas; and a gas supply unit configured to supply the process gas or at least one gas component of the process gas at a predetermined gas quantity flow rate to pixels m of each partial repair shape. i and at least one gas providing device configured to provide

[0028] For example, the energetic particle beam includes an electron beam, an ion beam and / or a laser beam.

[0029] Illustratively, the electron beam is provided using a modified scanning electron microscope. Illustratively, an image of at least one portion of the photomask is recorded using the same modified scanning electron microscope that provides the activating electron beam.

[0030] The activated particle beam specifically activates a local chemical reaction between the material of the photomask and the process gas, which leads to the local deposition of material onto the photomask from the gas phase or the local transfer of material of the photomask into the gas phase.

[0031] The activation particle beam is directed, for example, by a particle beam steering device, to the m of each part repair shape. i In step d) of the method, the activation particle beam is applied to each of the pixels m over a predetermined dwell time. i The dwell time is 100 ns.

[0032] In particular, steps d) to f) are performed without interruption in a single repair sequence, i.e. the particle beam is in particular provided at the last pixel of a first (or further) of the partial repair shapes and then immediately provided at the first pixel of the partial repair shape to be next processed.

[0033] According to an embodiment, the activated particle beam and the process gas are applied to the first of the partially repaired shapes in step d). i is provided only at each of the pixels.

[0034] In other words, the activated particle beam and the process gas are provided in step d) only at the pixels of the first partially repaired shape, but not at the pixels of the further partially repaired shapes, and it can be said that the partially repaired shapes are processed successively in steps d) to f).

[0035] According to a further embodiment, the repair shape is subdivided in step c) into k sub-repair shapes based on a threshold value.

[0036] For example, the repair shape is a shape where all the partial repair shapes have the same size and the same number of pixels m i For example, the repair shape is divided into a plurality of partial repair shapes having a pixel number m i may also be subdivided into multiple partial restoration shapes such that differ from each other by less than 30%, 20%, 10%, 5%, 3% and / or 1%.

[0037] For example, the repair shape may be subdivided into a plurality of partial repair shapes based on a threshold value, such that the determination of whether step c) is performed is performed based on the threshold value. In other words, the repair shape may be subdivided into a plurality of partial repair shapes based on a threshold value, such that, for example, above the threshold value, subdivision into the plurality of partial repair shapes is performed, whereas below the threshold value, subdivision of the repair shape is not performed.

[0038] By way of example, the repair shape is subdivided into a plurality of sub-repair shapes, such that the number k of sub-repair shapes into which the repair shape is subdivided is determined based on a threshold value.

[0039] The thresholds may also include a first (eg, upper) and a second (eg, lower) threshold (ie, parameter range).

[0040] According to a further embodiment, the threshold value is an empirically determined value and is determined before step a).

[0041] As a result, a threshold value for particle beam-induced processing of defects can be defined prior to application of the method. For example, the threshold value can be determined in advance within a separate method for determining the threshold value by the manufacturer of the device for performing the method. As a result, the method for processing defects on a photomask can be more easily implemented by the user.

[0042] According to a further embodiment, the particle beam induced processing includes etching of the defect or deposition of material on the defect, and the threshold is determined from an empirical value of the etching rate or deposition rate based on a number n of pixels of the repair feature.

[0043] As a result, the achievement of a desired etching or deposition rate can be ensured in the case of a defect in a photomask corresponding to a repair feature having n pixels.

[0044] According to a further embodiment, the threshold value is an empirically determined value determined based on parameters selected from the group including the number n of pixels of the repair shape, the size of the pixel, the incident area of ​​the particle beam, the residence time of the activation particle beam at each pixel, the gas flow rate at which the process gas is provided, the composition of the process gas, and the gas flow rate ratio of the various gas components of the process gas.

[0045] This can be especially ensured whenever a subdivision of the repair shape into a plurality of partial repair shapes is performed in this way and the lack of such subdivision would result in a disadvantageous composition, gas amount and / or density of the process gas at the pixel of the repair shape being processed at the time that a particular pixel is to be processed.

[0046] In particular, the threshold is an empirically determined threshold that is determined so that the particle beam-induced process can repair, e.g., etch, defects in the photomask to at least a predetermined amount. For example, the quality of the repair can be determined by determining the smoothness of the repair site (e.g., etch smoothness), the width of the repair edge (e.g., etched edge), the speed of the repair (e.g., etching), and / or the etching rate or deposition rate.

[0047] In particular, the gas mass flow rate is a volumetric flow rate or a flow rate that specifies the amount of process gas transferred per unit time through a defined cross section, e.g., a valve of a gas supply unit. For example, the gas mass flow rate is defined by setting the temperature of the process gas. For example, the temperature of the process gas is set to a temperature in the range of -40°C to +20°C.

[0048] The dwell time is the time it takes for the m of the partial repair feature to initiate a local reaction (chemical, etching and / or material deposition reaction) in the photomask at the location of this pixel. i is the duration for which the activation particle beam is directed at one of the pixels.

[0049] According to a further embodiment, the repair shape is subdivided into a number of sub-repair shapes with the aid of the Voronoi approach.

[0050] The Voronoi method or Voronoi diagram facilitates easy subdivision of the defect geometry, i.e., repair geometry, into sub-repair geometries. In particular, defects with irregular shapes, and therefore repair geometries with irregular shapes, can be easily decomposed into sub-repair geometries.

[0051] According to a further embodiment, the partial repair shapes are determined in step c) as Voronoi regions starting from the Voronoi centers, each of which includes the pixel of the repair shape that corresponds to the associated Voronoi center and all pixels of the repair shape that are located closer to the associated Voronoi center than to any other Voronoi center of the repair shape.

[0052] In particular, the distance between Voronoi centers is predetermined based on a threshold in step c), and the Voronoi centers are determined based on the predetermined distance. As an example, the Voronoi centers are defined in the repair shape so as to be uniformly distributed over the repair shape.

[0053] According to a further embodiment, the repair shape is determined by m of each partial repair shape. i The pixels are subdivided into a plurality of partial repair shapes that are the same distance from each other in the scanning direction.

[0054] For example, the repair shape is a two-dimensional geometric shape that defines an XY plane. For example, n pixels of the repair shape are arranged in the X and Y directions. For example, the particle beam is guided in the X and Y directions with the aid of a particle beam steering device (scanning unit). For example, the scanning direction corresponds to the X and / or Y directions.

[0055] The pixels of each partial repair shape having the same distance from each other in the scanning direction avoid the need for the quantum beam to be directed over gaps in the partial repair shape, i.e., areas outside the partial repair shape, while the partial repair shape is being processed during scanning.

[0056] According to a further embodiment, the repair shape comprises at least two spaced apart regions. Further, the repair shape is subdivided into a plurality of partial repair shapes, each partial repair shape comprising at most one of the at least two spaced apart regions.

[0057] As a result, it is possible to avoid the quantum beam having to be moved back and forth between non-contiguous, i.e., spaced apart, regions during processing of the partially repaired shape, which is particularly advantageous as the partially repaired shape is processed by the particle beam over j repeat periods, which may be on the order of 100, 1000, 10,000, 100,000 or even a million.

[0058] According to a further embodiment, the method further comprises, before step d), the following step: directing the activated particle beam to m of a first of the partially repaired shapes, so that depletion of the process gas by chemical reactions activated by the activated particle beam is carried out uniformly over the partially repaired shapes. i The method includes calculating the sequence in which the pixels are consecutively provided.

[0059] In particular, the m of the partially repaired shape i A line-by-line scan of pixels can be avoided.

[0060] According to a further embodiment, the order in which steps d) and e) are performed in step f) for the further partial repair shapes is different from the row-wise and / or column-wise order and / or is randomly distributed.

[0061] In particular, the order in which the partial repair shapes are processed by steps d) and e) is different from the row-wise and / or column-wise order and / or is randomly distributed.

[0062] According to a further embodiment, the repair shape is subdivided in step c) by a number h of mutually different subdivisions into partial repair shapes, and further steps d) to f) are performed for each of the h subdivisions.

[0063] This avoids uneven treatment of defects at the boundaries between partial repair shapes, where h is an integer greater than or equal to 2.

[0064] For example, the first partial repair shapes of all h subdivisions may overlap each other, the second partial repair shapes of all h subdivisions may overlap each other, etc. That is, the ith partial repair shapes of all h subdivisions may overlap each other, where i=1 to k.

[0065] According to a further embodiment, steps d) to f) are performed for each of the h subdivisions over g repetition periods, where g is less than j, and / or over j / h repetition periods.

[0066] As a result, a total of j repeat periods can be subdivided among h subdivisions, where g is an integer greater than or equal to 2.

[0067] According to a further embodiment, the h subdivisions differ from one another by a displacement, in particular a lateral displacement, of the boundaries of the partial repair shape relative to the repair shape.

[0068] The calculation of further subdivisions of the repair shape can thus be realized particularly easily.

[0069] According to a further embodiment, steps d) to f) are repeated for p repetition periods, where p is an integer greater than or equal to 2.

[0070] As a result of the defect being only partially repaired rather than completely repaired during one iteration of steps d)-f), and complete repair of the defect being achieved only after p iteration periods, non-uniform treatment of the defect at the boundary between the partially repaired shapes can be avoided. This embodiment presents an alternative to, or can be applied in addition to, using h mutually different subdivisions.

[0071] According to a further aspect, an apparatus for particle beam induced treatment of defects in a microlithography photomask is proposed, the apparatus comprising: means for providing an image of at least a portion of a photomask; a computing device for determining a geometric shape of a defect in an image as a repair shape, the repair shape comprising n pixels, the computing device being configured to subdivide the repair shape into a plurality of sub-repair shapes in a computer-implemented manner; means for providing an activated particle beam and a process gas at each pixel of every partial repair shape over j repeating periods for processing each partial repair shape; Equipped with.

[0072] According to a further aspect, a computer program product is proposed for controlling an apparatus for particle beam induced treatment of defects in microlithography masks, the computer program product comprising instructions which, when executed by a computing device, prompt the apparatus to perform the method steps according to any one of claims 1 to 13.

[0073] For example, a computer program product such as a computer program means may be provided or supplied, for example as a storage medium, e.g. a memory card, USB stick, CD-ROM, DVD, etc., or else in the form of a file downloadable from a server in the network. For example in a wireless communication network, this may be effected by transferring an appropriate file using the computer program product or computer program means.

[0074] Each of the units mentioned above and below, e.g., computing device, control device, decision device, subdivision device, can be implemented in hardware and / or software. In the case of a hardware implementation, the corresponding unit can be embodied as a device or part of a device, e.g., a computer or microprocessor. By way of example, the device may include a central processing unit (CPU), a graphics processing unit (GPU), programmable hardware logic (e.g., field programmable gate array (FPGA)), an application specific integrated circuit (ASIC), etc. Furthermore, one or more units may be implemented together in a single hardware device and, e.g., may share memory, interfaces, etc. The units may also be realized in separate hardware components.

[0075] According to a further embodiment, a method for determining a threshold value is proposed, which serves to subdivide a repair shape into k sub-repair shapes based on the threshold value during particle beam induced processing of defects of a microlithography photomask. i) performing particle beam-induced processing of a first test defect on a photomask using predetermined processing parameters, the first test defect having a first size; ii) determining the quality of the treatment of the first test defect; iii) repeating steps i) and ii) for the changed processing parameters until a processing parameter quality is determined, wherein the determined quality is equal to or greater than a predetermined quality; and iv) performing particle beam-induced processing of additional test defects on the photomask using the determined processing parameters, each additional test defect having a size different from a size of the other additional test defects and different from a size of the first test defect; v) determining the quality of the treatment for each further test defect; vi) determining a threshold value based on the determined qualities of the first and further test defects; Includes:

[0076] The predetermined and determined processing parameters include, for example, the dwell time of the electron beam at the pixel (e.g., 100 ns, 10 ns, or several μs); the interruption period during which the pixel is not "exposed" to the electron beam to ensure that sufficient adsorbed process gas is again present on the surface near the repair site (e.g., values ​​of 100 μs to 5000 μs); the type of guidance (scan) of the electron beam over the pixels of the repair shape (e.g., line scan, serpentine scan, random homing in at pixels, and / or incremental homing in at pixels), and / or the gas flow rate of the process gas (e.g., the gas flow rate is defined by setting the temperature of the process gas, the temperature being, for example, -40°C to +20°C).

[0077] By way of example, the quality of the repair can be determined by determining the smoothness of the repair site (e.g., the smoothness of the etched or deposited material), the width of the repair edge (e.g., the etched edge or the deposited edge), the speed of the repair (e.g., the etch or deposition), and / or the etch rate or the deposition rate. By way of example, the predetermined quality can be a predetermined value of the smoothness of the repair site, the width of the repair edge, the speed of the repair, the etch rate, and / or the deposition rate.

[0078] Features and advantages described with respect to the method for particle beam induced processing apply correspondingly to the apparatus, the computer program product and the method for determining a threshold, and vice versa.

[0079] "One" in this instance should not be understood as necessarily limiting to exactly one element. Rather, a plurality of elements, e.g., two, three, or more, may be provided. Any other number used herein should not be understood as indicating that there is a strict constraint on the stated number of elements. Rather, upward and downward numerical deviations are possible unless otherwise specified.

[0080] Further possible implementations of the present invention also include combinations not expressly mentioned of any features or embodiments shown above or below with respect to the exemplary embodiments, in which case the skilled person will also add individual aspects as improvements or supplements to the respective basic form of the invention.

[0081] Further advantageous refinements and aspects of the invention are the subject of the dependent claims and also of the exemplary embodiments of the invention described below. In the following text, the invention is explained in more detail on the basis of preferred embodiments with reference to the attached drawings. [Brief explanation of the drawings]

[0082] [Figure 1] 1A and 1B schematically illustrate details of a microlithography photomask having defects in a structured coating according to one embodiment. [Figure 2] 2 illustrates an apparatus for particle beam induced treatment of defects in the photomask from FIG. 1 according to one embodiment. [Figure 3] 10 illustrates a further example of a defect in the photomask from FIG. 1 in which the defect geometry has been subdivided into multiple partial repair shapes. [Figure 4] An enlarged detail of FIG. 3 is shown. [Figure 5]4 shows a diagram similar to FIG. 3 in which the defect geometry has been subdivided into multiple partial repair geometries by two mutually different subdivisions. [Figure 6] 1. Further examples of defects in the photomask of FIG. 1 are shown. [Figure 7] 1. Further examples of defects in the photomask of FIG. 1 are shown. [Figure 8] 2 shows a flowchart of a method for particle beam induced treatment of defects in the photomask of FIG. 1 according to one embodiment. [Figure 9] 10 shows a flowchart of a method for determining a threshold value according to one embodiment, where the threshold value determined in the process is applicable to the method of FIG. 8. [Figure 10] 10 shows images of five repaired test defects repaired and evaluated in the method of FIG. 9. [Figure 11] 11 shows a plot of etch rate as a function of defect size for the test defects from FIG. DETAILED DESCRIPTION OF THE INVENTION

[0083] Unless otherwise indicated, elements that are the same or functionally the same are provided with the same reference numerals in the drawings. It should also be understood that the figures in the drawings are not necessarily to scale.

[0084] 1 shows a schematic view of a microlithography photomask 100 in detail. In the example shown, the photomask 100 is a transmissive photolithography mask 100. The photomask 100 includes a substrate 102. The substrate 102 is optically transmissive, particularly at the wavelengths to which the photomask 100 is exposed. By way of example, the material of the substrate 102 includes fused silica.

[0085] A structured coating 104 (pattern elements 104) is applied to the substrate 102. In particular, the coating 104 is a coating made of an absorbing material. For example, the material of the coating 104 includes a chromium layer. For example, the thickness of the coating 104 ranges from 50 nm to 100 nm. The feature size B of the structures formed by the coating 104 on the substrate 102 of the photomask 100 can be different at various positions on the photomask 100. For example, in FIG. 1, the width B of the region is plotted as the feature size. For example, the feature size B is in the range of 20 to 200 nm. The feature size B can also be greater than 200 nm, for example, on the order of several micrometers.

[0086] In other examples, materials other than those mentioned above can be used for the substrate and coating. Furthermore, the photomask 100 can be a reflective photomask rather than a transmissive photomask. In this case, a reflective layer is applied in place of the absorbing layer 104.

[0087] Occasionally, defect D can occur during photomask fabrication, for example, because the etching process is not performed exactly as intended. In FIG. 1, such defect D is represented by a diagonal line. This defect is due to excess material resulting from not removing coating 104 from two adjacent coating regions 104, even though these regions were considered separate in the template for the photomask 100. Defect D can also be said to form a web. In this case, the size of defect D corresponds to the feature size B. Other defects smaller than feature size B, for example, on the order of 5 to 20 nm, are also known. Defects such as defect D shown in FIG. 1 or other defects must be repaired to ensure that the structures fabricated in the lithography apparatus using the photomask have the desired shape on the wafer and that the semiconductor components fabricated in this manner fulfill their desired functionality. In this example, it is necessary to remove the web in a targeted manner, for example, by particle-beam-induced etching.

[0088] Figure 2 shows an apparatus 200 for particle-beam-induced treatment of defects in microlithography photomasks, such as defect D in photomask 100 from Figure 1. Figure 2 shows a schematic cross-sectional view through several components of apparatus 200 that can be used for particle-beam-induced repair, in this example, etching, of defect D in photomask 100. Additionally, apparatus 200 can also be used for imaging of photomasks, in particular imaging of structured coating 104 of mask 100 and defect D, before, during, and after the repair process.

[0089] The apparatus 200 shown in Figure 2 represents a modified scanning electron microscope 200. In this case, a particle beam 202 in the form of an electron beam 202 is used to repair the defect D. Using an electron beam 202 as the activation particle beam has the advantage that the electron beam 202 can substantially not damage, or only slightly damage, the photomask 100, and in particular its substrate 102.

[0090] In embodiments, a laser beam can be used instead of or in addition to the electron beam 202 to activate a local particle beam-induced repair process for the photomask 100 (not shown in FIG. 2). Additionally, instead of the electron beam and / or laser beam, an ion beam, an atomic beam, and / or a molecular beam can be used to activate a local chemical reaction (not shown in FIG. 2).

[0091] The apparatus 200 is largely located in a vacuum housing 204 that is maintained at a certain gas pressure by a vacuum pump 206 .

[0092] By way of example, the apparatus 200 is a repair tool for microlithography photomasks, such as photomasks for DUV or EUV lithography tools.

[0093] The photomask 100 to be processed is placed on a sample stage 208. By way of example, the sample stage 208 is configured to set the position of the photomask 100 in three spatial directions and in three rotational axes with an accuracy of a few nanometers.

[0094] The apparatus 200 includes an electron column 210. The electron column 210 includes an electron source 212 for providing an activating electron beam 202. Furthermore, the electron column 210 includes electron or beam optics 214. The electron source 212 generates the electron beam 202, and the electron or beam optics 214 focuses and directs the electron beam 202 toward the photomask 100 at the output of the column 210. The electron column 210 further includes a deflection unit 216 (scanning unit 216) configured to guide, i.e., scan, the electron beam 202 over the surface of the photomask 100.

[0095] Apparatus 200 further comprises a detector 218 for detecting secondary electrons and / or backscattered electrons generated at photomask 100 by incident electron beam 202. By way of example, as shown, detector 218 is arranged around electron beam 202 in a ring-shaped format within electron column 210. Alternatively or in addition to detector 218, apparatus 200 may also include other / further detectors for detecting secondary electrons and / or backscattered electrons (not shown in FIG. 2 ).

[0096] Additionally, the apparatus 200 may include one or more scanning probe microscopes, such as atomic force microscopes, that can be used to analyze defects D in the photomask 100 (not shown in FIG. 2).

[0097] The apparatus 200 further comprises a gas providing unit 220 for supplying a process gas to the surface of the photomask 100. By way of example, the gas providing unit 220 includes a valve 222 and a gas line 224. The electron beam 202 directed by the electron column 210 to a location on the surface of the photomask 100 can perform electron beam induced processes (EBIP) in conjunction with a process gas supplied by the gas providing unit 220 from outside via the valve 222 and the gas line 224. In particular, these processes include deposition and / or etching of materials.

[0098] The apparatus 200 further comprises a computing device 226, for example a computer having a control device 228, a determination device 230, and a segmentation device 232. In the example of Figure 2, the computing device 226 is located outside the vacuum housing 204.

[0099] The computing device 226, and in particular the control device 228, is responsible for controlling the apparatus 200. In particular, the computing device 226, and in particular the control device 228, controls the provision of the electron beam 202 by driving the electron column 210. In particular, the computing device 226, and in particular the control device 228, controls the scanning of the electron beam 202 over the surface of the photomask 100 by driving the scanning unit 216. Furthermore, the computing device 226 controls the provision of process gases by driving the gas provision unit 220.

[0100] Additionally, the computing device 226 receives measurement data from the detector 218 and / or other detectors of the device 200 and generates an image from the measurement data. This image can be displayed on a monitor (not shown here). Additionally, the image generated from the measurement data can be stored in a memory unit (not shown here) of the computing device 226.

[0101] To check photomask 100, and in particular structured coating 104 on photomask 100, apparatus 200 is configured to capture image 300 of photomask 100 (FIG. 1) or image 300 of a detail of photomask 100, in particular from measurement data from detector 218 and / or other detectors of apparatus 200. By way of example, the spatial resolution of image 300 is on the order of a few nanometers.

[0102] The computing device 226, in particular the determination device 230, is configured to recognize a defect D ( FIG. 1 ) in the recorded image 300, to locate the defect, and to determine a geometric shape 302 (repair shape 302) of the defect D. The determined geometric shape 302 of the defect D, i.e., the repair shape 302, is, for example, a two-dimensional geometric shape.

[0103] 3 shows a further example of defect D' in structured coating 104 of photomask 100. In this example, defect D', and therefore its repair shape 302', is a square.

[0104] The computing device 226, in particular the determination device 230, is configured to divide the device repair shape 302, 302′ (FIGS. 1 and 3) into a grid including n pixels 304. FIG. 3 plots some pixels 304 of the repair shape 302′ in an exemplary format. By way of example, the repair shape 302′ includes one million pixels 304 (n=1,000,000). By way of example, the side length a (FIG. 4) of the pixels 304 is a few nanometers, for example, 1.5 nm. By way of example, the pixels 304 have a size of 1.5 nm x 1.5 nm. During the repair method, the electron beam 202 is directed multiple times by the scanning unit 216 to the center of each pixel 304. In particular, the intensity maximum of the Gaussian intensity profile of the electron beam 202 is directed multiple times to the center of each pixel 304 over the course of the method.

[0105] The computing device 226, in particular the subdivision device 232, is configured to subdivide the repair shape 302, 302′ into a plurality of, in particular k, partial repair shapes 306, for example based on a threshold value W. By way of example, the computing device 226 is configured to subdivide the repair shape 302, 302′ if the number n of pixels 304 of the repair shape exceeds a predetermined threshold value W. By way of example, the total number k of partial repair shapes into which a given repair shape 302′ is subdivided is predefined based on the predetermined threshold value W. By way of example, the predetermined threshold value W is an empirically determined threshold value W.

[0106] In the example shown in Figure 3, the repair shape 302' is subdivided into nine partial repair shapes 306 (k=9). Each partial repair shape 306 has m i 304, which is a subset of the n pixels 304 of the repair shape 302′. In particular, m pixels 304 for i=1 to k i The sum over m is equal to n. In the example shown in FIG. 3, the partial repair shapes 306 all have the same size. In other words, each of the nine partial repair shapes 306 has the same number m i 304 (i.e., m i(i=1~9) In another example, m of the i-th partial repair shape 306 i The pixel 304 may also differ from one, some, or all of the other (k−1) partial repair shapes 306 .

[0107] FIG. 4 shows an enlarged detail view from FIG. 3 in which five pixels 304 of the first partially repaired shape 306 shown in an exemplary form in FIG. 3 are shown in an enlarged format. Each pixel 304 is a square with a side length a. As a result, the distance between two adjacent pixel centers M is also equal to a. A circle with a diameter c and designated by reference numeral 308 represents the incidence area of ​​the electron beam 202 on the surface of the photomask 100. In this case, the diameter c corresponds to the side length a. The electron beam 202 has a Gaussian intensity profile that is particularly symmetric in the radial direction. In particular, the electron beam 202 is directed toward the incidence area 308 or the center M of the pixel 304 so that the maximum value of its intensity distribution is incident on the center M within the technically possible range. By way of example, the incidence area 308 can correspond to the half-width of the intensity profile of the electron beam 202. However, the incidence area 308 can also correspond to any other intensity drop from the maximum of the intensity distribution of the electron beam 202.

[0108] As an example, the repair shape 302′ (FIG. 3) is subdivided into k partial repair shapes 306 by the Voronoi method (Voronoi diagram). In this case, the computing device 226, and in particular the subdivision device 232, is used to define the distance between Voronoi centers 310 in the repair shape 302′ (FIG. 3). The Voronoi centers (310) in the repair shape 302′ are determined based on this distance s using the computing device 226, and in particular the subdivision device 232.

[0109] Furthermore, the computing device 226, and in particular the subdivision device 232, in this example, is configured to determine the partial repair shapes 306 as Voronoi regions starting from the Voronoi center 310. Thus, each partial repair shape 306 so determined includes the pixel 304 of the repair shape 302′ that corresponds to the associated Voronoi center 310 and all pixels 304 of the repair shape 302′ that are located closer to the associated Voronoi center 310 than any other Voronoi center 310 of the repair shape 302′.

[0110] While Figure 3 shows a relatively simple repair shape 302', specifically a square, the Voronoi technique allows for suitable subdivision of more complex repair shapes into sub-repair shapes. Examples in this regard include honeycomb structures or more general two-dimensional polyhedra.

[0111] The computing device 226, in particular the control device 228, is configured to scan the repair shape 302' subdivided into the partial repair shape 306 by the electron beam 202 under the application of the process gas, so that the defect D' whose geometric shape is the repair shape 302' is treated and repaired. In this case, the activation electron beam 202 scans the m of the first partial repair shape 306. i=1 The electron beam 202 is directed sequentially to each of the pixels 304 of the first partial repair shape 306 for a predetermined dwell time. i=1 In this case, the chemical reaction of the process gas is caused by the electron beam 202 to cause the m of the first partially repaired shape 306 to dwell in each of the pixels 304. i=1 304. By way of example, the process gas includes an etching gas. By way of example, a chemical reaction will occur with the material of the defect D' being etched, which will produce volatile reaction products that are at least partially gaseous at room temperature and can be pumped away using a pumping system (not shown).

[0112] The electron beam 202 is i=1 Once each of the pixels 304 has been addressed (step d)), the procedure is repeated for j repetition periods (step e)).

[0113] All m of the first partial repair shape 306 i=1After the first partial repair shape 306 has been processed for j iteration periods in pixels 304, each further one of the remaining k−1 partial repair shapes 306 of repair shape 302′ is processed accordingly (step f)). In this case, the order in which the partial repair shapes 306 are processed may differ from a row-by-row and / or column-by-column order. In other words, in the example of FIG. 3 , the partial repair shapes 306 may also be processed in an order other than consecutively from top-left to bottom-right. By way of example, the order in which the partial repair shapes 306 are processed may be randomly distributed.

[0114] In an embodiment, steps d)-f) are repeated for a number p of repetition cycles, such that the total number of repetition cycles for each of m=1 pixels 304 is jxp.

[0115] To (completely) remove the coating 104 in the area of ​​the defect D', for example, a total of 100, 1000, 10,000, 100,000 or one million repeat periods j (or jxh) are applied to each pixel m i=1 is needed in

[0116] 3, the repair shape 302′ having n pixels is subdivided into multiple partial repair shapes 306 (k partial repair shapes 306, in this case, 9), each having n / k pixels, so that the processing time of one of the k partial repair shapes 306 is shorter than the processing time of the entire repair shape 302′. This is advantageous because the gas composition of the process gas required and / or optimal for treating defect D′ can be better ensured during the processing of the partial repair shape 306. As an example, the gas composition of the process gas can be updated for each partial repair shape 306, rather than for each repair shape 302′. As an example, this can avoid a significant reduction in etch rate due to an unfavorable gas composition of the process gas.

[0117] 3, the subdivision 312 of the repair shape 302′ into partial repair shapes 306, and the described scanning method with the electron beam 202, can result in undesirable attrition at boundary regions 314 between the partial repair shapes 306. By way of example, the boundary region 314 between the first and second partial repair shapes 306 is provided with a reference number in FIG. 3. At such boundary regions 314, processing with the electron beam 202 may lead to excessive or insufficient material ablation, or excessive or insufficient material deposition.

[0118] To avoid such intra-repair shape artifacts, the computing device 226, and in particular the subdivision device 232, may be configured to subdivide the repair shape 302' into h mutually distinct subdivisions 312, 316.

[0119] Figure 5 shows something very similar to Figure 3, but the subdivision 312 of the repair shape 302' into the partial repair shape 306 shown in Figure 3 is shown using dashed lines in Figure 5. Furthermore, Figure 5 shows a further subdivision 316 calculated by the computing apparatus 226, and in particular the subdivision device 232. As a result, Figure 5 illustrates the subdivision of the repair shape 302' into two mutually different subdivisions 312, 316.

[0120] 5, subdivision 316 differs from subdivision 312 in that the boundary 318 of the partial repair shape 306 resulting from the first subdivision 312 has been displaced laterally relative to the repair shape 302', and a new partial repair shape 306' has thus been determined. As can be seen in FIG. 5, the partial repair shapes 306' resulting from the second subdivision 316 have different sizes and different numbers of pixels m'. i It has.

[0121] When multiple subdivisions 312, 316 (h subdivisions, in this case two) are calculated for the repair shape 302′ for the purpose of avoiding intra-repair shape artifacts, for example, a predetermined number (or j×p) of repeat periods are divided between the multiple subdivisions 312, 316. For example, in the example of FIG. 5 , each partial repair shape 306 in the first subdivision 312 and each partial repair shape 306′ in the second subdivision 316 are processed by the electron beam 202 for g repeat periods, where g in each case is equal to j / h (or (j×p) / h). In other words, the predetermined number j (or j×p) of repeat periods are uniformly divided between the two subdivisions 312, 316.

[0122] In the case of more complex repair shapes, the computing device 226, and in particular the subdivision device 232, can be configured to perform subdivision of the repair shape while taking into account additional boundary conditions, as illustrated in Figures 6 and 7.

[0123] 6 shows a further example of a repair shape 402. The repair shape 402 has a recessed region 404 such that the electron beam 202 of the apparatus 200 repeatedly crosses gaps 408 present in the recessed region 404 in the scanning direction X. In such a case, the computing device 226, and in particular the subdivision device 232, may generate a subdivision m'' of each partial repair shape 406. i The repair shape 402 can be configured to be subdivided into multiple partial repair shapes 406 such that pixels have the same distance from each other in the scan direction X. In other words, the repair shape 402 is subdivided into multiple partial repair shapes 406 such that the electron beam 202 does not have to cross any gaps when processing the partial repair shapes 406 in the scan direction X.

[0124] Three pixels 410, 412, and 414 of the repair shape 402 are plotted in an exemplary format in FIG. 6. Pixels 410 and 412 belong to the first partial repair shape 406, and pixel 414 belongs to the second partial repair shape 406. It is clear that the two pixels 410 and 412 of the first partial repair shape 406 are located directly next to each other. In particular, there is no gap between them, even in the scanning direction X. In contrast, pixel 412 of the first partial repair shape and pixel 414 of the second partial repair shape are not located directly next to each other, but rather there is a distance e between them in the scanning direction X, which corresponds to the gap 408.

[0125] 7 shows a further example of a repair shape 502. In the example, the repair shape 502 has two spaced apart regions 504. In other examples, the repair shape 502 can have three or more spaced apart regions 504. To subdivide the repair shape 502, the computing device 226, and in particular the subdivision device 232, can be configured to subdivide the repair shape 502 into multiple partial repair shapes 506, such that each partial repair shape 506 includes at most one of the two spaced apart regions 504. In other words, the repair shape 502 is subdivided into multiple partial repair shapes 506 such that the electron beam 202 does not need to cross any gaps when processing the partial repair shapes 506 in the scan direction X.

[0126] 8 shows a flowchart of a method for particle-beam-induced treatment of defects in a microlithography photomask. Defects D, D' in photomask 100 (FIG. 1) can be treated by the method. By way of example, defects D, D' have repair shape 302 shown in FIG. 1, repair shape 302' shown in FIG. 3, repair shape 402 shown in FIG. 6, repair shape 502 shown in FIG. 7, or any other repair shape.

[0127] In step S1 of the method, an image 300 of at least a portion of the photomask 100 is provided. In particular, a scanning electron microscope image 300 of a portion of the photomask 100 is captured by the apparatus 200, and defects D, D' in the structured coating 104 of the photomask 100 are imaged in said image.

[0128] In step S2 of the method, the geometry of the defects D, D' in the image 300 is determined as the repair shapes 302, 302', 402, 502.

[0129] In step S3 of the method, the repair shape 302, 302′, 402, 502 is subdivided in a computer-implemented manner into a plurality of partial repair shapes 306, 406, 506. By way of example, this subdivision is performed based on a threshold W (e.g., an empirically determined threshold).

[0130] In step S4 of the method, an energetic particle beam 202 and a process gas are provided at each pixel of a first one of the partial repair shapes 306, 406, 506.

[0131] In step S5 of the method, step S4 is repeated for j iteration periods for a first of the partial repair shapes.

[0132] In step S6 of the method, steps S4 and S5 are repeated for each further one of the partial repair shapes.

[0133] In an embodiment, a method is performed to determine the threshold value W, as shown by the flowchart in Figure 9. In particular, the method is performed before the above-described method of particle beam-induced processing of defects in a microlithography photomask (Figure 8). The method according to Figure 9 is particularly a method for empirically determining the threshold value W.

[0134] In the example method for determining the threshold value W described in relation to FIG. 9, the determined threshold value W is a function of the repair feature size G S(Fig. 11), i.e., the defect size. In particular, the threshold W in this example is set to the maximum repair feature size G S The repair shape size G S can be specified in units of area or number of pixels.

[0135] In another example, the threshold W may also have a minimum repair feature size. In other words, the threshold W may also represent a range of repair feature sizes with a lower limit (minimum repair feature size) and an upper limit (maximum repair feature size).

[0136] In another embodiment of the method for determining the threshold, the threshold W is set to a value greater than or equal to the repair feature size G S It can also be a different parameter.

[0137] The threshold value W is determined in the method of FIG. 9 such that, when the determined threshold value W is applied to the repair method of FIG. 8, defect D or D' (FIG. 1 or FIG. 3) in photomask 100 can be repaired, e.g., etched, by particle beam-induced processing, for example, to at least a specified amount. In the method for determining threshold value W of FIG. 9, test defects 602-610 (FIG. 10) similar to defect D or D' in photomask 100 in FIG. 1 or FIG. 3 are repaired for test purposes by particle beam-induced processing, for example, using apparatus 200 (FIG. 2). The quality of the repair is then determined.

[0138] For example, the quality of the repair is determined by detecting the smoothness of the etching, the width of the etching edge, and / or the etching speed. The quality depends on various parameters adjustable by the apparatus 200 (FIG. 2), such as the dwell time of the electron beam 202 (FIG. 2) at the pixel 304 (FIG. 3), the pause period between exposure of one pixel 304 and another pixel 304, the type of scanning of the electron beam 202 over the pixel 304 of the repair feature 302′ (e.g., line scanning or random homing at the pixel), and the gas flow rate of the process gas. Furthermore, the quality of the repair depends on the type of mask material of the photomask (e.g., photomask 100 of FIG. 1) and the selected process gas (e.g., process gas mixture). Furthermore, the quality of the repair depends on the repair feature being repaired (e.g., repair features 302, 302′, 402, 502 in FIGS. 1, 3, 6, and 7). In particular, the quality of the repair depends on the repair feature size (defect size) and, if the repair feature is subdivided into multiple sub-repair features (eg, 306 in FIG. 3), also on the sizes of these sub-repair features.

[0139] In the example method for determining threshold W described in connection with FIG. 9 , a first test defect (e.g., test defect 606 in FIG. 10 ) (similar to defect D or D′ in photomask 100 in FIG. 1 or FIG. 3 ) is determined for a given mask material (e.g., the mask material of photomask 100 in FIG. 1 ) and a first given defect size (e.g., a typical or average defect size G3, e.g., 300×400 nm 2 ) are repaired, eg, etched, by particle beam induced processing using apparatus 200 in step S1′.

[0140] In this case, the following restoration parameters are set that can be adjusted by the device 200: i) the dwell time of the electron beam 202 at the pixel (e.g., 100 ns, 10 ns, or a few μs); ii) a break period (e.g., 100 μs to 5000 μs) during which the pixel is “not exposed” to the electron beam 202 to ensure that sufficient adsorbed process gas is again present on the surface near the repair site; iii) the type of guidance (scanning) of the electron beam 202 over the pixels of the repair shape, e.g., line scan, serpentine scan, randomized homing in at pixels and / or incremental homing in at pixels (e.g., every xth pixel is homed in first, followed by pixels that have not yet been "exposed"); and iv) The gas mass flow rate of the process gas (for example, the gas mass flow rate is defined by setting the temperature of the process gas, the temperature being, for example, -40°C to +20°C).

[0141] 10 shows an image 600 (e.g., an SEM image) of multiple repaired test defects 602, 604, 606, 608, and 610. Accordingly, test defects 602-610 have different sizes G1-G5. Illustratively, sizes G1-G5 are specified as numbers of pixels. Illustratively, test defect 602 has a size G1 of 2500 pixels, test defect 604 has a size G2 of 40,000 pixels, test defect 606 has a size G3 of 160,000 pixels, test defect 608 has a size G4 of 360,000 pixels, and test defect 610 has a size G5 of 1,000,000 pixels.

[0142] However, the sizes of the test defects 602-610 can be specified in units other than pixels in other examples. Additionally, the test defects 602-610 can also have sizes G1-G5 other than those specified in the exemplary format. While Figure 10 also shows five test defects 602-610 in exemplary format, more or fewer than five test defects are also possible within the scope of the method for determining the threshold.

[0143] The first test defect to be repaired, e.g., etched, in step S1′ by particle beam-induced processing using apparatus 200 for testing purposes is test defect 606, e.g., having an average size G3. However, another of test defects 602-610 can be treated as the first test defect in step S1′.

[0144] In step S2′ of the method for determining threshold W, the quality of the repair, e.g., etching, of the first test defect 606 processed in step S1′ is determined. By way of example, the quality of the repair may be determined by determining the smoothness of the repair site (e.g., etch smoothness), the width of the repair edge (e.g., etch edge), the speed of the repair (e.g., etching), and / or the amount of material etched or deposited (e.g., etch rate or deposition rate).

[0145] 11 shows a plot of etch rate R against defect size G. As an example, for a first test defect 606 having a size G3, an etch rate R3 was determined in step S2'.

[0146] The quality of the repair of the first test defect 606 determined in step S2' is equal to or greater than a specified quality determined in step S3' of the method for determining the threshold W. As an example, there is a determination of whether the detected etch rate R3 of the repaired test defect 606 is sufficient. As an example, there is a determination of whether the detected etch rate R3 is equal to or greater than a predetermined etch rate R S There is a judgement as to whether it is greater than (Figure 11).

[0147] Steps S1'-S3' are repeated until the quality of the restoration determined in step S3' is equal to or greater than the specified quality. In particular, the parameters set in step S2' are varied in the process to determine the optimal parameter settings for the specified quality.

[0148] In step S4' of the method for determining the threshold W, a test series having different defect sizes, e.g., for test defects 602-610 shown in FIG. 10, sizes G1-G5, is run using the optimal parameter settings determined in steps S1'-S3' for a first test defect (e.g., 606 in FIG. 10). In particular, test series are run for defect sizes (e.g., G1, G2, G4, and G5) of additional test defects 602, 604, 608, and 610 that differ from the first specified defect size (e.g., G3). Within the test series, the additional test defects 602, 604, 608, and 610 are repaired, e.g., etched, by particle beam-induced processing.

[0149] In step S5′ of the method for determining threshold W, the quality of the repair is determined for each defect size G1, G2, G4, and G5 applied in step S4′ (i.e., for each test defect 602, 604, 608, and 610 repaired in step S4′). By way of example, etch rates R1, R2, R4, and R5 ( FIG. 11 ) are determined for each repaired test defect 602, 604, 608, and 610.

[0150] As is apparent from FIG. 11, the etch rates R1-R4 determined for test defects 602-608 (i.e., defect sizes G1-G4) are relatively constant, particularly for a given etch rate R S In other words, the etching procedure for these test defects 602-608 was completed with satisfactory results. However, the etch rate R5 was substantially lower for the larger test defect 610 (defect size G5) than for the other test defects 602-608, particularly for the given etch rate R S In other words, the etching procedure for this test defect 610 was completed with unsatisfactory results.

[0151] In step S6' of the method for determining the threshold value W, the threshold value W is determined based on the results of the test series. For example, the threshold value W is determined based on the maximum defect size (G4 in FIG. 11), where the repair quality determined in step S5' is equal to or greater than the specified quality. The threshold value W is determined based on the range of detection sizes (minimum defect size G min ~Maximum defect size G max , for example, G1 to G4 in FIG.

[0152] As an example, the threshold W may be determined based on the following formula:

[0153] W={x[(G max ) 0.5 -(G min ) 0.5 ]+(G min ) 0.5} 2 where x is a coefficient, for example 0.5 or 0.75, or 1 otherwise. In the example of FIG. 11, G max = G4 and G min =G1.

[0154] The thresholds determined in the above method (steps S1' to S6' in FIG. 9) before the actual mask repair (steps S1 to S6 in FIG. 8) can be used when performing the actual mask repair (FIG. 8). In particular, in step c) of the method for particle beam induced treatment of defects (FIG. 8), it is necessary to determine whether the size of the defects to be treated is larger than a predetermined threshold W (e.g., larger than the threshold W determined by the above formula and / or the maximum defect size G for which repair is still sufficient). max=G4), the repair shape (302, 302' in FIGS. 1 and 3, respectively) can be subdivided into partial repair shapes (306 in FIG. 3). Furthermore, the k partial repair shapes (306 in FIG. 3) into which the repair shape (302, 302' in FIGS. 1 and 3) is subdivided in step c) can be set based on the threshold W so that the size of each of the partial repair shapes (306 in FIG. 3) is equal to or smaller than a predetermined threshold W and / or so that the size of each of the partial repair shapes (306 in FIG. 3) is within a predetermined range of the defect size.

[0155] Although the present invention has been described based on exemplary embodiments, it can be modified in various ways. [Explanation of symbols]

[0156] 100 Photomasks 102 Circuit Board 104 Coating 200 equipment 202 Particle Beam 204 Vacuum Housing 206 Vacuum Pump 208 Sample Stage 210 Electron Column 212 Electron source 214 Electron or beam optical elements 216 Scanning Unit 218 detector 220 Gas Supply Unit 222 Valve 224 Gas Line 226 Computing Devices 228 Control Device 230 Decision Device 232 Subdivision Device 300 statues 302, 302' Repair shape 304 pixels 306 Partial repair shape 310 Voronoi Center 312 Subdivision 314 Boundary area 316 Subdivision 318 Boundary 402 Repair Shape 404 Concave area 406 Partial repair shape 408 Gap 410 pixels 412 pixels 414 pixels 502 Repair Shape 504 Spaced Areas 506 Partial repair shape 600 statues 602 Test Defects 604 Test Defects 606 Test Defects 608 Test Defects 610 Test Defects a pixel size B Structure width c diameter D, D' defects E distance G size G1 size G2 size G3 size G4 size G5 size G S size M center R Etching rate R1 etch rate R2 Etch Rate R3 Etch Rate R4 Etch Rate R5 Etch Rate R S Etching rate s distance S1~S6 method steps S1'~S6' Method steps X direction W threshold

Claims

1. 1. A method for particle beam induced treatment of defects (D, D') in a microlithography photomask (100), comprising: a) providing an image (300) of at least a portion of said photomask (100); b) determining (S2) the geometric shape of the defect (D, D') in the image (300) as a repair shape (302, 302'), said repair shape (302, 302') comprising n pixels (304); c) subdividing (S3) said repair shape (302, 302') into k partial repair shapes (306) in a computer-implemented manner, wherein the i-th of said k partial repair shapes (306) is m i pixels (304) that are a subset of the n pixels (304) of the repair shape (302, 302'), where i is an integer specifying a count running from 1 to k; d) providing (S4) an activated particle beam (202) and a process gas at each of the m=1 pixels (304) of the first of the partially repaired shapes (306) for the purpose of processing the first of the partially repaired shapes (306); e) repeating step d) for the first of the partial repair shapes (306) for j iteration periods (S5); f) repeating steps d) and e) for each further partial repair shape (306) (S6); A method comprising:

2. 2. The method of claim 1, wherein the activated particle beam (202) and the process gas are provided only at each of the m=1 pixels (304) of the first one of the partially repaired shapes (306) in step d).

3. 3. The method of claim 1, wherein the repair shape (302, 302') is subdivided in step c) into the k partial repair shapes (306) based on a threshold value (W).

4. The method of claim 3 , wherein the threshold (W) is an empirically determined value and is determined prior to step a).

5. 4. The method of claim 3, wherein the particle beam induced processing comprises etching the defect (D, D′) or depositing material on the defect (D, D′), and the threshold (W) is determined from an empirical value of an etching rate (R) or a deposition rate based on a number n of pixels (304) of the repair shape (302, 302′).

6. 4. The method of claim 3, wherein the threshold value (W) is an empirically determined value determined based on parameters selected from the group including the number n of pixels (304) of the repair shape (302, 302'), the size (a) of the pixels (304), the incident area (308) of the particle beam (202), the residence time of the activated particle beam (202) at each pixel (304), the gas flow rate at which the process gas is provided, the composition of the process gas, and the gas flow rate ratio of various gas components of the process gas.

7. The method of claim 1 or 2, wherein the repair shape (302, 302') is subdivided into the plurality of partial repair shapes (306) with the aid of a Voronoi method.

8. 8. The method of claim 7, wherein the partial repair shapes (306) are determined in step c) as Voronoi regions starting from Voronoi centers (310), and each partial repair shape (306) includes the pixel (304) of the repair shape (302, 302′) that corresponds to the associated Voronoi center (310) and all pixels (304) of the repair shape (302, 302′) that are located closer to the associated Voronoi center (310) than any other Voronoi center (310) of the repair shape (302, 302′).

9. The repair shape (402) is m'' of each partial repair shape (406). i 3. The method of claim 1, wherein the plurality of partial repair shapes are subdivided such that pixels have the same distance from each other in the scanning direction.

10. 3. The method of claim 1, wherein the repair shape (502) includes at least two spaced apart regions (504), and the repair shape (502) is subdivided into a plurality of partial repair shapes (506) such that each partial repair shape (506) includes at most one of the at least two spaced apart regions (504).

11. 3. The method according to claim 1, further comprising, before step d), the following step: calculating an order in which the activation particle beam (202) is successively provided at the m=1 pixels (304) of the first of the partially repaired shapes (306) so that depletion of the process gas by chemical reactions activated by the activation particle beam (202) is uniformly performed over the partially repaired shapes (306).

12. 3. The method of claim 1, wherein steps d) and e) are performed in step f) for each further partial repair shape (306) such that for each further partial repair shape (306) the activated particle beam (202) and the process gas are provided at the pixels (304) of the corresponding further partial repair shape (306) in an order that is different from a row-by-row and / or column-by-column order and / or that is randomly distributed, the rows and columns corresponding to the rows and columns of the corresponding further partial repair shape (306).

13. 3. The method according to claim 1, wherein in step c) the repair shape (302, 302') is subdivided into partial repair shapes (306, 306') in h mutually different subdivisions (312, 316), and steps d) to f) are performed for each of the h subdivisions (312, 316).

14. 14. The method of claim 13, wherein steps d) to f) are performed for each of h subdivisions (312, 316) over g repetition periods, where g is less than j, and / or over j / h repetition periods.

15. 14. The method of claim 13, wherein the h subdivisions (312, 316) differ from one another by a displacement, in particular a lateral displacement, of a boundary (318) of the partial repair shape (306) relative to the repair shape (302, 302').

16. 3. The method of claim 1, wherein steps d) to f) are repeated for p repetition periods, where p is an integer greater than or equal to 2.

17. An apparatus (200) for particle beam induced treatment of defects (D, D') in a microlithography photomask (100), comprising: a means (210) for providing an image (300) of at least a portion of a photomask (100); A computing device (226) for determining a geometric shape of a defect (D'D) in an image (300) as a repair shape (302, 302'), the repair shape (302, 302') comprising n pixels (304), the computing device (226) configured to subdivide the repair shape (302, 302') into k partial repair shapes (306) in a computer-implemented manner, the i-th of the k partial repair shapes (306) being m i a computing device having n pixels (304) that are a subset of the n pixels (304) of the repair shape (302, 302'), where i is an integer specifying a count running from 1 to k; means (210, 220) for providing an activated particle beam and a process gas at each pixel (304) of all the partial repair shapes (306) over j repeating periods for processing each partial repair shape (306); Equipped with The computing device (226) d) providing an activated particle beam (202) and a process gas at each of the m=1 pixels (304) of the first of the partially repaired shapes (306) for processing the first of the partially repaired shapes (306); e) repeating step d) for said first one of said partial repair shapes (306) for j repetition periods; f) steps d) and e) are repeated for each further partial repair shape (306); configured to control the means (210, 220) for providing the activated particle beam and the process gas so that Device.

18. 10. A computer program product for controlling an apparatus (200) for particle beam induced treatment of defects in microlithography photomasks, the computer program product comprising instructions that, when executed by a computing device (226), prompt the apparatus (200) to perform the method steps of claim 1 or 2.

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