Method, computer program product and control device for determining a repair shape for a defect of a microlithographic photomask and method of particle beam-induced processing of a defect of a microlithographic photomask

Abstract

A method for determining a repair shape (406) for a defect (D) of a microlithographic photomask (100), including the steps of: a) providing (S1) an image (400) of at least a portion of the photomask (100), b) determining (S2) at least one section of an edge line (408) of the defect (D) on the basis of the image (400) and e) correcting (S5) the at least one section of the edge line (408) on the basis of a curvature (K1) of the at least one section of the edge line (408).

Description

[0001] Carl Zeiss SMT GmbH

[0002] 1

[0003] METHOD, COMPUTER PROGRAM PRODUCT AND CONTROL DEVICE FOR DETERMINING A REPAIR SHAPE FOR A DEFECT OF A MICROLITHOGRAPHIC PHOTOMASK AND METHOD OF PARTICLE BEAM-INDUCED PROCESSING OF A DEFECT OF A MICROLITHOGRAPHIC PHOTOMASK

[0004] The present invention relates to a method, a computer program product and a control device for determining a repair shape for a defect of a microlithographic photomask. The present invention also relates to a method of particle beam-induced processing of a defect of a microlithographic photomask.

[0005] The content of the priority application DE 102025 104509.7 is incorporated by reference in its entirety.

[0006] Microlithography is used to produce microstructured components, for instance integrated circuits. The microlithography process is carried out using a lithography apparatus having an illumination system and a projection system. The image of a mask (reticle) illuminated by means of the illumination system is projected here by means of the projection system onto a substrate, for example a silicon wafer, which is coated with a light-sensitive layer (photoresist) and is arranged in the image plane of the projection system, in order to transfer the mask structure to the light-sensitive coating of the substrate.

[0007] Driven by the desire for ever smaller structures in the production of integrated circuits, EUV lithography apparatuses that use light at a wavelength in the range of 0.1 nm to 30 nm, in particular 13.5 nm, are currently under development.

[0008] The photomasks used in microlithography (i.e. lithography masks) have microstructures that are projected onto the substrate in reduced scale. TheCarl Zeiss SMT GmbH

[0009] 2

[0010] structures of the photomasks themselves are already very small and have dimensions of a few micrometres to a few nanometres, for example. In order to fabricate microstructured components with high accuracy by microlithography, the structures on the photomasks used also have to be manufactured very precisely, and the photomasks have to be free of defects (e.g. defective structures and contaminations). Another reason why a defect-free microlithographic photomask is very important is because a photomask is typically used for a multitude of exposures. Therefore, a high degree of time and effort goes into examining photomasks for defects and repairing defects found.

[0011] Typical defects of photomasks are the lack of envisaged structures and the presence of non-envisaged structures. Such defects may be caused by e.g. an unsuccessful etching process, for example owing to it having advanced too quickly or acted on an incorrect location. These defects can be eliminated by selective etching of excess material or by selective removal (depositing) of additional material at the appropriate positions. For example, this is possible in a very targeted manner by particle beam -induced processing (e.g. focused electron beam-induced processing, FEBIP), as describedin e.g. DE 10 2017 208 114 A1. This involves providing a particle beam and a process gas (e.g. etching gas or deposition gas) at a location on the photomask to be processed. The particle beam activates a local chemical reaction between a material of the photomask and the process gas, as a result of which material is locally removed from or deposited on the photomask.

[0012] In the particle beam-induced processing of a photomask, the accurate determination of a repair shape for the defect is of crucial importance for the processing operation. US 11,079,674 B2 has disclosed the practice of correcting a determined pre-repair shape for a defect of a photomask by taking account of a position of a wanted structure on the photomask relative to the defect of the photomask.Carl Zeiss SMT GmbH

[0013] 3

[0014] Against this background, a problem addressed by the present invention is that of better determining a repair shape for a defect of a microlithographic photomask.

[0015] According to a first aspect, a method is proposed for determining a repair shape for a defect of a microlithographic photomask. The method comprises the steps of:

[0016] a) providing an image of at least a portion of the photomask,

[0017] b) determining at least one section of an edge line of the defect on the basis of the image,

[0018] c) determining a curvature of the at least one section of the edge line at at least one position in the at least one section of the edge line,

[0019] d) determining at least one correction value for the at least one position on the basis of the determined curvature and

[0020] e) determining at least one corrected section of the edge line by correcting the at least one section of the edge line on the basis of the at least one determined correction value.

[0021] Labelling the steps a) to e) does not necessarily presuppose a sequence in which these steps are carried out. A different sequence is also possible. Furthermore, carrying out steps a), b) and e) does not necessarily presuppose steps c) and / or d) being carried out.

[0022] Furthermore, steps c) and / or d) are optional. Moreover, step e) may also be: correcting the at least one section of the edge line on the basis of a curvature of the at least one section of the edge line.

[0023] By determining the repair shape on the basis of the curvature of the edge line of the at least one section of the edge line (e.g. an edge line of a pre-repair shape for the defect), it is possible to determine an improved repair shape for a defect of a photomask. Hence, a defect of the photomask can be better processed and repaired. For example, an unwanted structure in the region of the defect can be better (e.g.Carl Zeiss SMT GmbH

[0024] 4

[0025] fully) removed and / or damage to neighbouring regions (e.g. an adjacent capping layer) can be avoided and / or reduced. Alternatively, a missing structure in the region of the defect may be better (e.g. fully) augmented.

[0026] To the extent that the following refers to determining a pre-repair shape for the defect,

[0027] an edge line of the pre-repair shape, a curvature of the edge line of the pre-repair shape and determining the repair shape by correcting the pre-repair shape, this may accordingly also mean determining at least one section of an edge line of the defect (i.e. without determining the entire pre-repair shape), at least one section of an edge line of the defect, a curvature of the at least one section of the edge line and determining of the repair shape by correcting the at least one section of the edge line.

[0028] To process the defect of the photomask, the repair shape is for example divided into a number m of pixels. Moreover, for example, a particle beam is provided at each pixel of the repair shape (e.g. for a predetermined dwell time). In the process, the particle beam is directed at a centre of a pixel, for example. For example, the particle beam has a Gaussian intensity distribution, the intensity of which has dropped to a predetermined intensity by the edge of the pixel. Owing to the Gaussian intensity distribution, the intensity of the particle beam is also greater than zero for pixels neighbouring the pixel. In other words, when the particle beam is provided for a specific pixel, a (residual) particle beam dose also acts on neighbouring pixels.

[0029] At the edge line of the pre-repair shape, pixels of the pre-repair shape that are intended to be processed are arranged next to pixels outside the pre-repair shape that are not intended to be processed. In a concave edge region of the pre-repair shape, pixels outside the pre-repair shape that are not intended to be processed are surrounded by particularly many pixels of the edge line of the pre-repair shapeCarl Zeiss SMT GmbH

[0030] 5

[0031] that are intended to be processed. Given a concave edge region of the pre-repair shape, this may result in an excessive particle beam dose for the neighbouring pixels that should not be processed, leading to an elevated risk of damage to neighbouring regions (e.g. a neighbouring capping layer).

[0032] Analogously, only a few pixels to be processed are present in a convex edge region of the pre-repair shape, and so the particle beam dose in the region of the convex shape of the pre-repair shape may be insufficient for complete processing of the defect at this location. In the case of etching processing in particular, this may give rise to material that should be removed not being removed (i.e. so-called residues may remain).

[0033] By determining the at least one correction value based on the curvature of the edge line of the pre-repair shape and correcting the pre-repair shape on the basis of the at least one determined correction value for determining the repair shape, it is possible to counteract the above-described unfavourable particle beam dose in the edge region of the repair shape.

[0034] For example, the microlithographic photomask is a photomask for an EUV lithography apparatus. EUV here stands for "extreme ultraviolet" and denotes a wavelength of the operating light of between 0.1 nm and 30 nm, in particular 13.5 nm. Within an EUV lithography apparatus, a beam shaping and illumination system is used to guide EUV radiation onto a photomask (also referred to as "reticle"), which in particular is in the form of a reflective optical element (reflective photomask). The photomask has a structure which is imaged onto a wafer or the like in a reduced fashion by means of a projection system of the EUV lithography apparatus.

[0035] For example, the microlithographic photomask can also be a photomask for a DUV lithography apparatus. DUV here stands for "deep ultraviolet" and denotes aCarl Zeiss SMT GmbH

[0036] 6

[0037] wavelength of the operating light of between 30 nm and 250 nm, in particular 193 nm or 248 nm. Within a DUV lithography apparatus, a beam shaping and illumination system is used to guide DUV radiation onto a photomask, which in particular is in the form of a transmissive optical element (transmissive photomask).

[0038] For example, the microlithographic photomask comprises a substrate and a structure formed on the substrate by way of a coating. For example, the photomask is a reflective photomask for use in EUV lithography, in the case of which the pattern to be imaged is realized in the form of an absorbing (i.e. opaque or partly opaque) coating on a reflective substrate. In an alternative, the photomask, especially for use in DUV lithography, may also be e.g. a transmissive photomask in which the pattern to be imaged is realized in the form of an absorbing coating on a transparent substrate. The photomask may also be a mask for nanoimprint lithography (NIL).

[0039] In the case of a photomask for an EUV lithography apparatus, the substrate for example comprises an alternating sequence of molybdenum and silicon layers. In the case of a transmissive photomask for DUV lithography, the substrate may also comprise, for example, silicon dioxide (SiO2), e.g. quartz glass. For example, the structured coating comprises chromium, chromium compounds, tantalum compounds and / or compounds made of silicon, nitrogen, oxygen and / or molybdenum. The substrate and / or the coating may also comprise other materials.

[0040] Using the proposed method, it is possible to detect and locate a defect of a photomask, in particular a defect of a structured coating of the photomask, in an image. In particular, a defect is an (e.g. absorbing or reflecting) coating of the photomask that has been applied incorrectly to the substrate.Carl Zeiss SMT GmbH

[0041] 7

[0042] To determine the repair shape for the defect, an image of at least a portion of the photomask is provided in step a).

[0043] The image of the at least one portion of the photomask is produced by means of a scanning electron microscope (SEM), for example. For example, the image of the at least one portion of the photomask has a spatial resolution of the order of a few nanometres. The image may also be produced using a scanning probe microscope (SPM), such as an atomic force microscope (AFM) or a scanning tunnelling microscope (STM).

[0044] The method may in particular include a step of capturing the image of the at least one portion of the photomask, e.g. by means of a scanning electron microscope and / or a scanning probe microscope.

[0045] In step b), a geometric shape (e.g. a two-dimensional geometric shape) of the defect is determined on the basis of the provided image of the at least one portion of the photomask. For example, the geometric shape is determined in the image provided or in an image (e.g. difference image) that is determined on the basis of the image provided. The geometric shape of the defect determined in step b) is referred to herein as a so-called pre-repair shape. The pre-repair shape corrected by the proposed method is referred to herein as a so-called repair shape (final repair shape).

[0046] Determining the geometric shape of a defect on the basis of the image in step b) may include subtracting the image or a partial section of the image from a reference image for the purpose of determining a difference image. In particular, the image or the partial section of the image and the reference image have the same structures apart from the defect. That is to say, a geometric shape of structures in the image or partial section of the image corresponds to a geometric shape of structures in the reference image. For example, the photomaskCarl Zeiss SMT GmbH

[0047] 8

[0048] comprises recurring structures (e.g. absorber structures), and a partial section of the image provided, which contains the defect, is compared with a further partial section of the image provided, which contains the same structure pattern but no defect. In this case, the further partial section of the image provided forms the reference image. However, the reference image may also be provided in a different manner in other examples. A difference image that only images the defect is obtained by subtracting the reference image from the image or the partial section of the image with the defect. The geometric shape of the defect is thereupon determined, for example in the difference image.

[0049] Determining the geometric shape of the defect for example comprises edge detection in the image provided and / or in the difference image.

[0050] A determined and / or detected edge of the defect forms the edge line of the pre¬ repair shape in particular. In particular, the edge line is a circumferential (e.g. closed) edge line. An area enclosed by the edge line is an area of the pre-repair shape in particular. In particular, the edge line is a boundary line of the pre-repair shape.

[0051] The determined edge line of the pre-repair shape may for example be smoothed in step b). In that case, step c) in particular may be carried out for the smoothed edge line.

[0052] The curvature of the edge line is determined at at least one position on the edge line in step c). The curvature of the edge line may also be determined at multiple positions on the edge line and / or for the entire edge line.

[0053] Herein, the curvature denotes a mathematical curvature of the edge line. In particular, curvature in this case means a deviation of the edge line from a straight line. The curvature may have a (mathematical) absolute value of the curvature (i.e.Carl Zeiss SMT GmbH

[0054] 9

[0055] a measure of curvature) and a direction of the curvature (positive or negative). Herein, a direction of the curvature is considered in relation to a profile of the edge line in an anticlockwise sense. The greater the absolute value of the curvature, the greater the curvature.

[0056] The edge line has a negative second derivative in the case of a negative curvature of the edge line (anticlockwise to the right). Furthermore, the pre-repair shape has a concave section in the region of the negative curvature of the edge line.

[0057] The edge line has a positive second derivative in the case of a positive curvature of the edge line (anticlockwise to the left). Moreover, the pre-repair shape has a convex section in the region of the positive curvature of the edge line.

[0058] For example, a (mathematical) absolute value of the curvature of the edge line is determined at the at least one position in step c). Moreover, whether the determined absolute value of the curvature at the at least one position is greater than zero (i.e. a curvature is present) and / or greater than a predetermined threshold value is for example determined in step c). In this case, steps d) and e) are for example only carried out if the determined absolute value of the curvature is greater than zero and / or greater than the predetermined threshold value.

[0059] Determining the curvature of the edge line at at least one position on the edge line in step c) is based for example on known methods and / or algorithms of image analysis for detecting contours, for detecting edges and for determining curvature. For example, the determination of the curvature of the edge line is based on known methods in programming language libraries and numerical programs.

[0060] For the analytic or numerical determination of contours, it is also possible herein to apply a method which extracts one or more contours from a pre-repair shape such that the extracted contours are available in the form x(t) and y(t). In thatCarl Zeiss SMT GmbH

[0061] 10

[0062] case, the functions x(t) and y(t) can be filtered e.g. using a second order Savitzky-Golay filter. The derivatives x'(t), x"(t) and y'(t), y"(t) are obtained therefrom. In that case, a curvature may be calculated e.g. from the known formula for a plane curve:

[0063] << / (<) ■. HO / / U)

[0064] - 7- y-

[0065]

[0066] U(0?• “

[0067] In step d), the at least one correction value for the at least one position on the edge line is determined on the basis of the determined curvature of the edge line at the at least one position. For example, the at least one correction value for the at least one position on the edge line indicates how (e.g. to what extent and in what direction) the edge line of the pre-repair shape should be displaced at the at least one position on the basis of the curvature present there in order to determine the repair shape (final repair shape). For example, the correction value is a real number whose mathematical absolute value specifies the extent of the displacement and whose sign indicates a direction of the displacement.

[0068] In step e), the pre-repair shape is corrected in order to determine the repair shape (final repair shape). In particular, a new edge line which encircles the repair shape (final repair shape) is determined in step e).

[0069] Steps a) to e) are carried out in computer-implemented fashion in particular.

[0070] According to an embodiment:

[0071] a geometric shape of the defect is determined in step b) on the basis of the image as a pre-repair shape with an edge line having the at least one section of the edge line,

[0072] a curvature of the edge line is determined at at least one position on the edge line in step c),Carl Zeiss SMT GmbH

[0073] 11

[0074] at least one correction value for the at least one position is determined in step d) on the basis of the determined curvature and

[0075] the repair shape is determined in step e) by correcting the pre-repair shape on the basis of the at least one determined correction value.

[0076] According to a further embodiment, the at least one correction value specifies a displacement of the edge line at the at least one position in a direction substantially perpendicular to a tangent to the edge line at the at least one position.

[0077] The direction substantially perpendicular to the tangent to the edge line at the at least one position for example comprises a direction which deviates by ±30° or less, ±20° or less, ±10° or less and / or ±5° or less from a direction exactly perpendicular to the tangent.

[0078] If a curvature equal to zero is determined at a position on the edge line, then this means that no curvature of the edge line is determined at this position. For example, step d) (and step e) are not carried out in that case, or the correction value determined in step d) is equal to zero, whereby a displacement of the edge line is also equal to zero.

[0079] If a curvature whose (mathematical) absolute value is less than a predetermined threshold value is determined at a position on the edge line, then this for example means that no significant curvature of the edge line is determined at this position. In that case, step d) (and step e), for example, will not be carried out.

[0080] According to a further embodiment, an absolute value and a sign of the curvature of the edge line at the at least one position on the edge line are determined in step c). Moreover, the at least one correction value for the at least one position on theCarl Zeiss SMT GmbH

[0081] 12

[0082] edge line is determined in step d) on the basis of the determined absolute value and the determined sign of the curvature.

[0083] As a result, the pre-repair shape can be corrected to a greater extent at the at least one position on the edge line, the greater an absolute value of the curvature of the edge line at this position. Moreover, a sign of the curvature is taken into account in the correction.

[0084] The absolute value of the curvature is in particular a mathematical absolute value, i.e. a magnitude, of the edge line. The sign of the curvature results from a value of the second derivative of the edge line at the at least one position. If the second derivative of the edge line at the at least one position has a negative value, then the curvature has a negative sign, and the curve bends to the right. If the second derivative of the edge line at the at least one position has a positive value, then the curvature has a positive sign, and the curve bends to the left.

[0085] According to a further embodiment, a second derivative of the edge line of the pre¬ repair shape is determined in step c). Furthermore, an absolute value of the curvature of the edge line is determined at the at least one position in step c) on the basis of the second derivative.

[0086] In this case, a derivative (e.g. second derivative) is understood to mean a mathematical derivative with respect to the spatial coordinate.

[0087] In particular, the second derivative of the edge line specifies a measure of the curvature of the edge line.

[0088] In particular, an absolute value of the curvature of the edge line at the at least one position is determined on the basis of a value of the second derivative at the at least one position.Carl Zeiss SMT GmbH

[0089] 13

[0090] According to a further embodiment, a second derivative of the edge line of the pre¬ repair shape is determined in step c). Furthermore, a sign of the curvature of the edge line is determined at the at least one position in step c) on the basis of the second derivative.

[0091] In particular, the second derivative of the edge line specifies a sign (positive or negative) of the curvature of the edge line.

[0092] In particular, a sign of the curvature of the edge line at the at least one position is determined on the basis of a value of the second derivative at the at least one position.

[0093] If the second derivative of the edge line at the at least one position on the edge line is negative, i.e. less than zero, then the curvature at the at least one position is negative.

[0094] If the second derivative of the edge line at the at least one position on the edge line is positive, i.e. greater than zero, then the curvature of the edge line at the at least one position is positive.

[0095] According to a further embodiment, the repair shape is established in such a way in step e) that:

[0096] for a position on the edge line of the pre-repair shape for which a positive curvature is determined, the edge line is displaced at this position in such a way that the pre-repair shape is enlarged at this position, and

[0097] for a position on the edge line of the pre-repair shape for which a negative curvature is determined, the edge line is displaced at this position in such a way that the pre-repair shape is reduced in size at this position.Carl Zeiss SMT GmbH

[0098] 14

[0099] A positive curvature of the edge line of the pre-repair shape at the at least one position means that the pre-repair shape has a convex section in this region. In particular, a convex section of the pre-repair shape is a section which protrudes outward in relation to the pre-repair shape. For an outwardly protruding section of the pre-repair shape, it is advantageous to enlarge the pre-repair shape at this location in order to achieve a sufficient particle beam dose during particle beam processing.

[0100] It could also be said that, given a position on the edge line of the pre-repair shape for which a positive curvature is determined, the edge line is displaced outwardly at this position in relation to the pre-repair shape.

[0101] In particular, a correction value is determined in step d) for a position on the edge line for which a positive curvature of the edge line is determined, said correction value specifying a displacement of the edge line at this position which leads to an enlargement of the repair shape during correction of the pre-repair shape in step e).

[0102] A negative curvature of the edge line of the pre-repair shape at the at least one position means that the pre-repair shape has a concave section in this region. In particular, a concave section of the pre-repair shape is a section which is hollowed out inwardly in relation to the pre-repair shape and / or which has a recess. For a concave section of the pre-repair shape, it is advantageous to reduce the size of the pre-repair shape at this location in order to prevent an excessive particle beam dose during particle beam processing at this location.

[0103] It could also be said that, given a position on the edge line of the pre-repair shape for which a negative curvature of the edge line is determined, the edge line is displaced inwardly at this position in relation to the pre-repair shape.Carl Zeiss SMT GmbH

[0104] 15

[0105] In particular, a correction value is determined in step d) for a position on the edge line for which a negative curvature of the edge line is determined, said correction value specifying a displacement of the edge line at this position which leads to a reduction in size of the repair shape during correction of the pre-repair shape in step e).

[0106] According to a further embodiment, an absolute value of the curvature of the edge line at the at least one position is determined in step c). Furthermore, whether the absolute value of the curvature is greater than zero and / or greater than a predetermined threshold value is determined in step c). Moreover, the repair shape is determined in such a way in step e) that for a position on the edge line of the pre-repair shape for which the determined absolute value of the curvature is greater than zero and / or greater than the predetermined threshold value, the edge line at this position is displaced by an extent which is a mathematical function of the absolute value of the curvature at this position.

[0107] For example, the edge line at the relevant position is displaced by an extent that is a linear function of the absolute value of the determined curvature at this position and / or that is proportional to a power of the absolute value of the determined curvature (i.e. a monomial with the absolute value of the determined curvature as variable) at this position.

[0108] For example, the at least one correction value for the at least one position on the edge line can be determined on the basis of the following equation:

[0109] X = A • B • Cn.

[0110] In this equation, X denotes the correction value for a position on the edge line, B denotes a sign of the curvature at this position on the edge line (i.e. B mayCarl Zeiss SMT GmbH

[0111] 16

[0112] assume the values +1 or -1) and C denotes an absolute value of the curvature at this position on the edge line.

[0113] Moreover, in the equation above, the parameter A is a scaling factor, and the parameter n is a scaling exponent. The scaling factor A and the scaling exponent n are both positive real numbers in particular. For n=1, the equation simplifies to X = A • B • C, and the correction value X is directly proportional (constant of proportionality A) to the curvature (B • C), i.e. it is a linear function of the curvature (B • C). For n≠1, the equation is X = A • B • Cn, and the correction value X is directly proportional (constant of proportionality A) to a power n of the absolute value C of the curvature.

[0114] According to a further embodiment, the at least one correction value is determined in step d) on the basis of one or more scaling parameters determined in advance and specifying a dependence of an extent of a displacement of the edge line at the at least one position on an absolute value of the determined curvature at the at least one position.

[0115] The one or more scaling parameters determined in advance for example are the above-described scaling factor A and / or the above-described scaling exponent n.

[0116] According to a further embodiment, the one or more scaling parameters determined in advance include a scaling factor determined in advance and / or a scaling exponent determined in advance.

[0117] The scaling factor determined in advance specifies a linear dependence of the extent of the displacement of the edge line at the at least one position on the absolute value of the determined curvature at the at least one position.Carl Zeiss SMT GmbH

[0118] 17

[0119] The scaling exponent determined in advance specifies a dependence of the extent of the displacement of the edge line at the at least one position on the absolute value of the determined curvature at the at least one position, in such a way that the extent of the displacement is proportional to a power of the determined absolute value of the curvature.

[0120] For example, the one or more scaling parameters determined in advance may — in addition to the curvature of the edge line — also depend on parameters of the photomask, e.g. a photomask material, and on processing parameters, e.g. an acceleration voltage of the particle beam column, etc.

[0121] According to a further embodiment:

[0122] the determined pre-repair shape is divided into a number k of pixels, the pixels of the pre-repair shape which are touched and / or intersected by the edge line form edge pixels of the pre-repair shape,

[0123] the at least one position on the edge line corresponds to a position on at least one edge pixel, and

[0124] the repair shape is corrected in step e) on the basis of the at least one determined correction value by adding or removing one or more pixels to or from the pre-repair shape at a position neighbouring the at least one edge pixel.

[0125] For particle beam-induced processing of the repair shape, k pixels are defined in the pre-repair shape, and / or m pixels are defined in the repair shape. For example, dividing the pre-repair shape into the number k of pixels and dividing the repair shape into the number m of pixels is based on the same grid. For example, the image provided or an image section thereof, each larger than the pre-repair shape in particular, is divided into a number 1 of pixels using a predetermined grid. In this case, the k pixels of the pre-repair shape and the m pixels of the repair shape for example each form a subset of the 1 pixels of the image provided or of the imageCarl Zeiss SMT GmbH

[0126] 18

[0127] section thereof. That is to say, in particular, the number 1 is greater than the number k and greater than the number m.

[0128] If the pre-repair shape is reduced in size overall during the correction in step d), then the repair shape is smaller than the pre-repair shape, and the number m of pixels of the repair shape is smaller than the number k of pixels of the pre-repair shape. By contrast, if the pre-repair shape is enlarged overall during the correction in step d), then the repair shape is larger than the pre-repair shape, and the number m of pixels of the repair shape is greater than the number k of pixels of the pre-repair shape.

[0129] During particle beam-induced processing of the repair shape, the particle beam is subsequently directed at each of the m pixels of the repair shape (e.g. for a predetermined dwell time). In particular, an intensity maximum of the particle beam is directed at each centre point of each of the m pixels of the repair shape. In other words, the m pixels of the repair shape represent a grid, in particular a two- dimensional grid, of the repair shape for the particle beam-induced processing. For example, the m pixels of the repair shape correspond to areas of incidence of the particle beam during the particle beam-induced processing of the defect. For example, a pixel dimension of the m pixels (e.g. also of the aforementioned k pixels and of the 1 pixels) is chosen in such a way that an intensity distribution of a particle beam directed at a centre of a pixel drops to a predetermined intensity value at the edge of the pixel on account of the particle beam's (e.g. Gaussian) intensity distribution. The predetermined intensity value may for example correspond to a drop (i.e. a decrease) to half of the intensity maximum or else a drop to any other fraction of the intensity maximum of the particle beam. For example, a pixel dimension and / or a particle beam full width at half maximum is in the subnanometre range or of the order of a few nanometres.Carl Zeiss SMT GmbH

[0130] 19

[0131] The pixels of the pre-repair shape located on the edge line (i.e. touched and / or intersected by the edge line) form edge pixels of the pre-repair shape.

[0132] The at least one position on the edge line corresponds to a position on at least one edge pixel. The position on the at least one edge pixel includes e.g. a centre / centre point of the at least one edge pixel. The position on the at least one edge pixel may also include a centre point of a section of the edge line which is covered by the at least one edge pixel.

[0133] Then, one or more pixels is / are added to the pre-repair shape or removed from the pre-repair shape in step e). In particular, the added or removed pixels are neighbouring (e.g. adjacent to) the at least one edge pixel for which the curvature was determined.

[0134] According to a further embodiment, for an edge pixel for which a negative curvature is determined, this edge pixel and / or further neighbouring pixels is / are removed from the pre-repair shape in step e) in a direction substantially perpendicular to a tangent to the edge line at this edge pixel. Moreover, for an edge pixel for which a positive curvature is determined, one or more further pixels is / are added to the pre-repair shape in a direction substantially perpendicular to the tangent to the edge line at this edge pixel.

[0135] According to a second aspect, a method is proposed for particle beam-induced processing of a defect of a microlithographic photomask. The method includes determining a repair shape for the defect according the above-described method according to the first aspect,

[0136] dividing the determined repair shape into a number m of pixels and providing a particle beam at each of the m pixels of the repair shape for the purpose of processing the defect.Carl Zeiss SMT GmbH

[0137] 20

[0138] For example, an activating particle beam and a process gas are provided at each of the m pixels of the repair shape.

[0139] For example, the processing of the defect comprises an etching of the defect, within the scope of which material is locally removed from the photomask, or a deposition of material on the photomask in the region of the defect. For example, the proposed method allows a superfluous structure in the region of the defect to be better etched away, or a missing structure in the region of the defect to be better augmented. In particular, the proposed method allows edge regions of the defect to be etched away better and more accurately, can prevent neighbouring regions from being inadvertently damaged during an etching process and / or allows a missing structure in the edge region of the defect to be augmented better and more accurately.

[0140] Using the proposed method, it is possible to identify, locate and repair a defect of a photomask, in particular a defect of a structured coating of the photomask. For example, the method can be used to augment a coating of the photomask at locations at which it is missing. Furthermore, the method allows the coating to be removed from locations on the photomask at which it has been applied incorrectly.

[0141] For example, the process gas is a precursor gas and / or an etching gas. For example, the process gas can be a mixture of multiple gaseous components, i.e. a process gas mixture. For example, the process gas can be a mixture of multiple gaseous components, of which each has only a certain molecule type.

[0142] In particular, alkyl compounds of main group elements, metals or transition elements can be considered as precursor gases suitable for the deposition or for growing of elevated structures. Examples thereof include cyclopentadienyl(trimethyl)platinum (CpPtMes Me = CH4), methylcyclopentadienyl (trimethyl)platinum (MeCpPtMes), tetramethyltinCarl Zeiss SMT GmbH

[0143] 21

[0144] (SnMe4), trimethylgallium (GaMe3), ferrocene (Cp2Fe), bis arylchromium (Ar2Cr), and / or carbonyl compounds of main group elements, metals or transition elements, such as for example 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 for example tetraethoxysilane (Si(OC2H5)4), tetraisopropoxytitanium (Ti(OC3H7)4), and / or halide compounds of main group elements, metals or transition elements, such as for example tungsten hexafluoride (WF6), tungsten hexachloride (WCl6), titanium tetrachloride (TiCl4), boron trifluoride (BCl3), silicon tetrachloride (SiCl4), and / or complexes with main group elements, metals or transition elements, such as for example copper bis(hexafluoroacetylacetonate) (Cu(C5F6HO2)2), dimethylgold trifluoroacetylacetonate (Me2Au(C5F3H4O2)), and / or organic compounds such as carbon monoxide (CO), carbon dioxide (CO2), aliphatic and / or aromatic hydrocarbons, and the like.

[0145] For example, the etching gas may comprise: xenon difluoride (XeF2), xenon dichloride (XeCl2), xenon tetrachloride (XeCl4), steam (H2O), heavy water (D2O), oxygen (O2), ozone (O3), ammonia (NH3), nitrosyl chloride (NOCI) and / or one of the following halide compounds: XNO, XONO2, X2O, XO2, X2O2, X2O4, X2O6, where X is a halide. Further etching gases for etching one or more of the deposited test structures are specified in the applicant’s US patent application with the number 13 / 0 103281.

[0146] The process gas can comprise further added gases, for example oxidizing gases such as hydrogen peroxide (H2O2), nitrous oxide (N2O), nitrogen oxide (NO), nitrogen dioxide (NO2), nitric acid (HNO3) and other oxygen-containing gases, and / or halides such as chlorine (Cl2), hydrogen chloride (HCl), hydrogen fluoride (HF), iodine (I2), hydrogen iodide (HI), bromine (Br2), hydrogen bromide (HBr),Carl Zeiss SMT GmbH

[0147] 22

[0148] phosphorus trichloride (PCI3), phosphorus pentachloride (PCI5), phosphorus trifluoride (PF3) and other halogen-containing gases, and / or reducing gases, such as hydrogen (H2), ammonia (NH3), methane (CH4) and other hydrogen-containing gases. These added gases can be used, for example, for etching processes, as buffer gases, as passivating media and the like.

[0149] For example, the particle beam is provided with the aid of an apparatus for particle beam-induced processing of a microlithographic photomask. The apparatus may comprise: a particle beam source for producing the particle beam; a particle beam guiding device (e.g. scanning unit) configured to direct the particle beam at a pixel m of the repair shape of the photomask; a particle beam shaping device (e.g. electron or beam optics) configured to shape, in particular focus, the particle beam; optionally at least one supply container configured to store the process gas or at least one gaseous component of the process gas; optionally at least one gas provision device configured to provide the process gas or the at least one gaseous component of the process gas with a predetermined gas quantity flow rate to the pixel m of the repair shape.

[0150] For example, the particle beam comprises an electron beam and / or an ion beam. In addition to a particle beam, a laser beam may also be provided (e.g. at each pixel of the repair shape).

[0151] For example, an electron beam is provided with the aid of a modified scanning electron microscope. For example, the image of the at least one portion of the photomask is recorded using the same modified scanning electron microscope that provides the electron beam. However, a particle beam other than an electron beam may also be used to process the photomask.

[0152] For example, the particle beam activates a local chemical reaction between a material of the photomask and the process gas, which leads locally to a depositionCarl Zeiss SMT GmbH

[0153] 23

[0154] of material on the photomask from the gas phase or to a transition of material of the photomask into the gas phase.

[0155] The particle beam is provided in succession at each of the m pixels of the repair shape, for example by means of the particle beam guiding device. For example, the particle beam remains on each of the m pixels for a predetermined dwell time. For example, the dwell time is 100 ns. After the particle beam has been provided at all m pixels of the repair shape, this process may be repeated with one or more repetition cycles.

[0156] According to an embodiment of the second aspect, the one or more scaling parameters are determined empirically by analysing and processing a microlithographic test photomask.

[0157] For example, the test photomask comprises a defect whose outline, as it appears in at least one image of the test photomask, has an edge line with different curvatures in different sections. Alternatively, the test photomask may also comprise multiple defects with the different curvatures. For example, the various curvatures cover a range of curvatures between a predetermined negative curvature (e.g. (B C) = -2) and a predetermined positive curvature (e.g. (B C) = +2) at uniform intervals (e.g. A(B C) = 0.5). However, other values than those mentioned by way of example may also be used.

[0158] Thereupon, multiple mutually different values of the one or more scaling parameters determined in advance are applied to each of the multiple mutually different curvatures of the edge line during the determination of the correction values and the repair shape. Subsequently, each repair shape determined in this way is processed with the aid of a particle beam (and e.g. process gas). Next, a result of the processing (e.g. the repair) of the corresponding defect and / or of the corresponding section of the defect is examined. Then the value of the one or moreCarl Zeiss SMT GmbH

[0159] 24

[0160] scaling parameters determined in advance which yields the optimal result of the processing of the corresponding defect (e.g. greatest degree of removal of an excess structure with the least amount of etching into a substrate of the photomask or greatest degree of completion of a missing structure) is determined as the optimal value.

[0161] For example, the empirical determination of the one or more scaling parameters determines the result of the processing (e.g. the repair) even for test photomasks which have different materials from one another and / or for defects of the test photomask made of different materials (e.g. absorber materials). Furthermore, it is also possible to vary one or more parameters of the particle beam processing (e.g. a type of the one or more process gases used in the process, one or more parameters of the particle beam used, one or more parameters of the rastering of the pre-repair shape or repair shape, etc.) when empirically determining the one or more scaling parameters.

[0162] According to a third aspect, a computer program product is proposed. The computer program product comprises instructions that, upon execution of the program by at least one computer, cause the latter to carry out the abovedescribed method for determining a repair shape for a defect of a microlithographic photomask and / or the above-described method of particle beam-induced processing of a defect of a microlithographic photomask.

[0163] A computer program product, such as e.g. a computer program means, can be provided or supplied for example as a storage medium, such as e.g. a memory card, a USB stick, a CD-ROM, a DVD, or else in the form of a downloadable file from a server in a network. For example, in a wireless communications network, this can be effected by transferring an appropriate file comprising the computer program product or the computer program means.Carl Zeiss SMT GmbH

[0164] 25

[0165] According to a fourth aspect, a control device is proposed for determining a repair shape for a defect of a microlithographic photomask. The control device comprises^ a provision unit for providing an image of at least a portion of the photomask, a first determination unit for determining at least one section of an edge line of the defect on the basis of the image,

[0166] a second determination unit for determining a curvature of the at least one section of the edge line at at least one position in the at least one section of the edge line,

[0167] a third determination unit for determining at least one correction value for the at least one position on the basis of the determined curvature and

[0168] a fourth determination unit for determining at least one corrected section of the edge line by correcting the at least one section of the edge line on the basis of the at least one determined correction value.

[0169] For example, the control device is part of an apparatus for particle beam-induced processing of a microlithographic photomask.

[0170] In particular, the control device is configured to carry out the above- described method according to the first aspect for determining a repair shape for a defect of a microlithographic photomask.

[0171] Each of the units mentioned above and below, e.g. the control device, the provision unit and the determination units, can be implemented in hardware and / or software. In the case of an implementation as hardware, the corresponding unit can be embodied as an apparatus or as part of an apparatus, for example as a computer or as a microprocessor. For example, the apparatus may comprise a central processing unit (CPU), a graphical processing unit (GPU), a programmable hardware logic (e.g. a field-programmable gate array, FPGA), an application-specific integrated circuit (ASIC) or the like. Moreover, the one or more units may be implemented together in a single hardware apparatus,Carl Zeiss SMT GmbH

[0172] 26

[0173] and they can for example share a memory, interfaces and the like. The units can also be realized in separate hardware components.

[0174] " A(n) / one" should not necessarily be understood as a restriction to exactly one element in the present case. Rather, multiple elements, for example two, three or more, may also be provided. Any other numeral used here should also not be understood as a restriction to exactly the stated number of elements. Rather, unless indicated otherwise, numerical deviations upward and downward are possible.

[0175] The embodiments and features described for the subject matter according to the first aspect are correspondingly applicable to the subject matter proposed according to the second to fourth aspects and vice versa.

[0176] Further possible implementations of the invention also comprise combinations, not explicitly mentioned, of features or embodiments described hereinabove or hereinafter with regard to the exemplary embodiments. A person skilled in the art will also add individual aspects as improvements or supplementations to the respective basic form of the invention.

[0177] Further advantageous configurations and aspects of the invention are the subject of the dependent claims and of the exemplary embodiments of the invention that are described hereinafter. The invention will be explained in more detail hereinafter on the basis of preferred embodiments with reference to the appended figures.

[0178] Fig. 1 schematically shows a detail of a microlithographic photomask having a defect in a structured coating according to an embodiment;Carl Zeiss SMT GmbH

[0179] 27

[0180] Fig. 2 shows an apparatus for particle beam-induced processing of the defect of the photomask from Fig. 1 according to an embodiment;

[0181] Fig. 3 shows a flowchart of a method for determining a repair shape for a defect of a microlithographic photomask, according to an embodiment;

[0182] Fig. 4 shows an image of the photomask from Fig. 1 together with a reference image and a difference image according to an embodiment;

[0183] Fig. 5 shows an enlarged view of a pre-repair shape for the defect from the difference image of Fig. 4 according to an embodiment;

[0184] Fig. 6 illustrates an absolute value of a curvature of an edge line of the pre-repair shape from Fig. 5 together with a threshold value for the absolute value of the curvature according to an embodiment;

[0185] Fig. 7 shows a view similar to Fig. 5, wherein the pre-repair shape according to an embodiment is divided into a number k of pixels;

[0186] Fig. 8 shows a flowchart of a method of particle beam-induced processing of a defect of a microlithographic photomask; and

[0187] Fig. 9 shows a detail of a test photomask for ascertaining one or more scaling parameters which can be used within the scope of correcting the pre-repair shape from Fig. 5 according to an embodiment.

[0188] In the figures, identical or functionally identical elements have been provided with the same reference signs, unless indicated otherwise. It should also be noted that the illustrations in the figures are not necessarily true to scale.Carl Zeiss SMT GmbH

[0189] 28

[0190] Fig. 1 schematically shows a detail of a microlithographic photomask 100. In the example shown, the photomask 100 is a reflective photolithographic mask 100 for EUV lithography. The photomask 100 comprises a substrate 102. A surface of the substrate 102 and / or of a coating of the substrate 102 is optically reflective, especially at the wavelength with which the photomask 100 is exposed.

[0191] A structured coating 104 (pattern elements 104) has been applied to the substrate 102. In particular, the coating 104 is a coating made of an absorbing material. For example, a material of the coating 104 comprises a chromium layer. For example, a thickness of the coating 104 is in the range from 50 nm to 100 nm. A structure dimension G of the structure formed by the coating 104 on the substrate 102 of the photomask 100 may be different at different positions of the photomask 100. For example, the width G of a region is plotted as structure dimension in Fig. 1. For example, the structure dimension G is in a range from 20 to 200 nm. The structure dimension G may also be greater than 200 nm, for example be of the order of micrometres.

[0192] Other materials to those mentioned may also be used for the substrate and the coating in other examples. Furthermore, the photomask 100 may also be a transmissive photomask rather than a reflective photomask. In this case, the substrate 102 is optically transparent at the wavelength used.

[0193] Occasionally, defects D may arise during the production of photomasks 100, for example because etching processes do not run exactly as intended. Such a defect D is depicted in Fig. 1. In the example, this is an excess of material since the coating 104 has not been removed in a region of the defect D. To ensure that a structure produced in a lithography apparatus using the photomask 100 has the desired shape on a wafer and hence the semiconductor component produced in this way fulfils the desired function, it is necessary to repair defects, such as the defect D shown in Fig. 1 or else other defects. In the example of Fig. 1, it isCarl Zeiss SMT GmbH

[0194] 29

[0195] necessary to remove the defect D in a targeted manner, for example by particle beam-induced etching.

[0196] Fig. 2 shows an apparatus 200 for particle beam-induced processing of a defect of a microlithographic photomask, for example the defect D of the photomask 100 from Fig. 1. Fig. 2 shows schematically the section through a few components of the apparatus 200 which can be used for particle beam-induced repairing, in this case etching, of the defect D of the photomask 100. Moreover, the apparatus 200 can also be used for imaging the photomask 100, in particular the structured coating 104 of the mask 100 and of the defect D, before, during and after the implementation of a repair process.

[0197] The apparatus 200 shown in Fig. 2 represents a modified scanning electron microscope 200. In this case, a particle beam 202 in the form of an electron beam is used to repair the defect D. The use of an electron beam as activating particle beam 202 has the advantage that the electron beam substantially cannot damage, or can only slightly damage, the photomask 100, in particular the substrate 102 thereof.

[0198] However, in some examples, a different particle beam 202, e.g. an ion beam, an atomic beam and / or molecular beam (not shown), may be used instead of an electron beam to activate a local chemical reaction. Moreover, a laser beam may be used (not shown) in addition to the particle beam 202 to activate a local particle beam-induced repair process for the photomask 100.

[0199] The apparatus 200 is largely arranged in a vacuum housing 204, which is kept at a certain gas pressure by a vacuum pump 206.Carl Zeiss SMT GmbH

[0200] 30

[0201] For example, the apparatus 200 is a repair tool for microlithographic photomasks, for example for photomasks for a DUV or EUV lithography apparatus.

[0202] A photomask 100 to be processed is arranged on a sample stage 208. For example, the sample stage 208 is configured to set the position of the photomask 100 in three spatial directions x, y, z and in three axes of rotation around the spatial directions x, y, z with an accuracy of a few nanometres.

[0203] The apparatus 200 comprises a particle column 210 (e.g. an electron column). The particle column 210 comprises a particle source 212 (e.g. an electron source) for providing the activating particle beam 202 (e.g. the electron beam). Furthermore, the particle column 210 comprises electron or beam optics 214. The particle source 212 produces the particle beam 202 and the electron or beam optics 214 focus the particle beam 202 and direct the latter to the photomask 100 at the output of the column 210. The particle column 210 moreover comprises a deflection unit 216 (scanning unit 216) which is configured to guide, i.e. raster scan or scan, the particle beam 202 over the surface of the photomask 100.

[0204] The apparatus 200 furthermore comprises a detector 218 for detecting the secondary particles (e.g. secondary electrons and / or backscattered electrons) generated at the photomask 200 by the incident particle beam 202. For example, as shown, the detector 218 is arranged around the particle beam 202 in ringshaped fashion within the particle column 210. In an alternative to the detector 218 and / or in addition to that, the apparatus 200 may also comprise other / further detectors for detecting secondary particles (e.g. secondary electrons and / or backscattered electrons) (not shown).Carl Zeiss SMT GmbH

[0205] 31

[0206] Moreover, the apparatus 200 may comprise one or more scanning probe microscopes, for example atomic force microscopes, which can be used to analyse the defect D of the photomask 100 (not shown).

[0207] The apparatus 200 furthermore optionally comprises a gas provision unit 220 for supplying process gas to the surface of the photomask 100. For example, the gas provision unit 220 comprises a valve 222 and a gas line 224. The particle beam 202 directed at a location on the surface of the photomask 100 by the particle column 210 can carry out particle beam-induced processing (e.g. electron-beam induced processing, EBIP) in conjunction with the process gas supplied by the gas provision unit 220 from the outside by way of the valve 222 and the gas line 224. In particular, said processing comprises a deposition and / or an etching of material.

[0208] The apparatus 200 also comprises a computing apparatus 300, for example a computer. In the example of Fig. 2, the computing apparatus 300 is arranged outside of the vacuum housing 204. The computing apparatus 300 may also be arranged remotely from the rest of the apparatus 200, e.g. remotely from the vacuum housing 204.

[0209] For example, the computing apparatus 300 comprises a control device 302 for determining a repair shape 406 (Fig. 5) for a defect D of a microlithographic photomask 100. For example, the control device 302 comprises a provision unit 304 and multiple determination units 306 to 312.

[0210] For example, the computing apparatus 300 moreover comprises a further control device 314 for controlling the apparatus 200. In particular, the further control device 314 controls the provision of the particle beam 202 by controlling the particle column 210. For example, the further control device 314 controls the raster scanning of the particle beam 202 over the surface of the photomask 100Carl Zeiss SMT GmbH

[0211] 32

[0212] by controlling the scanning unit 216. The control device 314 may optionally also control the provision of the process gas by driving the gas provision unit 220.

[0213] Moreover, the computing apparatus 300 for example comprises an image generating device 316. For example, the image generating device 316 receives measured data from the detector 218 and / or other detectors of the apparatus 200 and creates images which can be displayed on a monitor (not shown) from the measured data. Moreover, images produced from the measured data can be stored in a memory unit (not shown) of the computing apparatus 300.

[0214] To check the photomask 100 and, in particular, the structured coating 104 of the photomask 100, the apparatus 200 is configured, in particular, to capture an image 400 of the photomask 100 (Fig. 1) or an image 400 of a detail of the photomask 100 from measured data from the detector 218 and / or other detectors of the apparatus 200. For example, a spatial resolution of the image 400 is of the order of a few nanometres.

[0215] The control device 302 is configured to detect and localize a defect D (Fig. 1) in the recorded image 400. Moreover, the control device 302 is configured to determine a geometric shape 402 of the defect D as a pre-repair shape 404 for the defect D. The determined geometric shape 402 of the defect D is a two- dimensional geometric shape in particular. Furthermore, the control device 302 is configured to correct the determined pre-repair shape 404 for the defect D in order to determine a repair shape 406 (final repair shape 406) for the defect D.

[0216] A method for determining a repair shape 406 (Fig. 5) for a defect D of a microlithographic photomask 100 is described below with reference to Fig. 3.

[0217] In a first step Si of the method, an image 400 (Fig. 1) of at least a portion of the photomask 100 is provided.Carl Zeiss SMT GmbH

[0218] 33

[0219] For example, a scanning electron microscope image 400 of a portion of the photomask 100 imaging a defect D of a structured coating 104 of the photomask 100 is captured by means of the apparatus 200 (Fig. 2).

[0220] In a second step S2 of the method, a geometric shape 402 of the defect D is determined on the basis of the image 400 as a pre-repair shape 404 with an edge line 408.

[0221] For example, the geometric shape 402 is determined directly in the provided image 400. Alternatively, as depicted in Fig. 4, the geometric shape 402 of the defect D can also be determined in an image 412 that is derived from the provided image 400. For example, a reference image 410 is subtracted from the provided image 400 imaging the structures 104 of the photomask 100 and the defect D. The reference image 410 contains similar structures 104 to the provided image 400 but no defect D. The difference image 412 generated in this way only contains an image representation of the defect D. In this case, the geometric shape 402 of the defect D in the difference image 412 can be determined as the pre-repair shape 404.

[0222] In particular, determining the geometric shape 402 and hence the pre-repair shape 404 includes detecting edges of the imaged defect D in the image 400 or the image 412. Known edge detection algorithms may be used for this purpose.

[0223] An image representation of the defect D with a circumferential edge line 408 can be seen in the difference image 412 in Fig. 4.

[0224] A curvature K1 of the edge line 408 is determined at at least one position P1 on the edge line 408 in a third step S3 of the method, as illustrated in Fig. 5.Carl Zeiss SMT GmbH

[0225] 34

[0226] In particular, Fig. 5 shows the pre-repair shape 404 of the defect D determined in step S2 in an enlarged view. The edge line 408 encircling the pre-repair shape 404 includes different curvatures, of which the curvatures K1, K2, K3, K4 have been identified with a reference sign. It was established that when the pre-repair shape 404 is used for particle beam-induced processing of the defect, the defect D is inadequately repaired in edge regions with a strong curvature KI to K4. In particular, an insufficient particle beam dose is applied in convex regions Q1, Q2, Q4 of the pre-repair shape 404 (i.e. in a positively curved section of the edge line 408) when the uncorrected pre-repair shape 404 is used. Moreover, an excessive particle beam dose is applied in concave regions Q3 of the pre-repair shape 404 (i.e. in a negatively curved section of the edge line 408) when the uncorrected pre¬ repair shape 404 is used.

[0227] To improve the processing of the defect D of the photomask 100, a curvature K1 to K4 of the edge line 408 of the pre-repair shape 404 is taken into account in the present method (Fig. 3).

[0228] For example, a mathematical absolute value Cl and a sign Bl of the curvature KI are determined in step S3 at the at least one position Pl on the edge line 408. For example, an absolute value Cl of the curvature KI of the edge line 408 at the position Pl is determined on the basis of a second derivative F" (Fig. 5) of the edge line 408. Moreover, a sign Bl of the curvature KI of the edge line 408 at the position Pl, for example, is also determined on the basis of the second derivative F" of the edge line 408.

[0229] By way of example, Fig. 5 shows that a curvature K1, K2, K3, K4 is determined at four positions P1, P2, P3, P4 on the edge line 408, with an absolute value C1, C2, C3, C4 and a sign B1, B2, B3, B4 of the curvature K1, K2, K3, K4 being determined in each case.Carl Zeiss SMT GmbH

[0230] 35

[0231] Determining the curvature KI to K4 of the edge line 408 for example comprises a comparison with a predetermined threshold value SW, as illustrated in Fig. 6. Fig. 6 shows a diagram of an absolute value C of a curvature as a function of a position P. For example, whether an absolute value C1 of the determined curvature K1 of the edge line 408 at a predetermined position P1 is greater than the predetermined threshold value SW is determined in step S3. For example, steps S4 and S5 are subsequently only carried out for the predetermined position P1 if the absolute value C1 of the curvature K1 at this position P1 is determined to be greater than the predetermined threshold value SW in step S3.

[0232] At least one correction value X1 for the at least one position P1 on the edge line 408 is determined in a fourth step S4 of the method on the basis of the determined curvature K1. For example, the at least one correction value X1 is determined in step S4 on the basis of the determined absolute value C1 and the determined sign B1 of the curvature K1.

[0233] In particular, the at least one correction value X1 indicates a displacement V1 of the edge line 408 at the at least one position P1. In other words, the at least one correction value X1 indicates how the edge line 408 of the pre-repair shape 404 should be displaced at the at least one position P1 in order to improve the particle beam-induced processing of the defect D in view of the curvature K1 at this position P1.

[0234] The displacement VI of the edge line 408 at the at least one position Pl defined by the correction value XI is, in particular, a displacement of the edge line 408 at the position P1 in a direction substantially perpendicular to a tangent T1 to the edge line 408 at this position P1.

[0235] For the four exemplary positions Pl to P4 of the edge line 408, Fig. 5 accordingly plots the respective determined correction values X1, X2, X3, X4, the tangentsCarl Zeiss SMT GmbH

[0236] 36

[0237] T1, T2, T3, T4 and the displacements V1, V2, V3, V4 of the edge line 408 corresponding to the correction values.

[0238] For a position Pl, P2, P4 on the edge line 408 of the pre-repair shape 404 for which a positive curvature KI K2, K4 is determined (i.e. the second derivative F" > 0), the edge line 408 is displaced at this position Pl, P2, P4 in such a way that the pre-repair shape 404 is enlarged at this location, as illustrated in Fig. 5.

[0239] Moreover, for a position P3 on the edge line 408 of the pre-repair shape 404 for which a negative curvature K3 is determined (i.e. the second derivative F" < 0), the edge line 408 is displaced at this position P3 in such a way that the pre-repair shape 404 is reduced in size at this location P3.

[0240] Moreover, at a position P1 to P4 at which a curvature K1 to K4 of the edge line was determined (i.e. K1 to K4 > 0) and / or at which the ascertained curvature K1 to K4 is greater than the predetermined threshold value SW, the edge line 408 is displaced by an extent that depends on the determined absolute value C1 to C4 of the curvature K1 to K4. In other words, an extent of the displacement V1 to V4 is a function of the absolute value C1 to C4 of the curvature K1 to K4. Thus, the more pronounced the curvature of the edge line 408 at a position P1 to P4, the greater the displacement of the edge line 408 at this position in order to correct the pre-repair shape 404 and thus determine the repair shape 406.

[0241] For example, the edge line 408 is more strongly curved at the position P2 than at the position Pl in the example of Fig. 5. Hence, an absolute value B2 of the curvature K2 at the position P2 is greater than an absolute value B1 of the curvature K1 at the position P1. Consequently, the edge line 408 is displaced to a greater extent at the position P2 (displacement V2, correction value X2) than at the position P1 (displacement V1, correction value X1).Carl Zeiss SMT GmbH

[0242] 37

[0243] The at least one correction value XI is determined in step S4, for example on the basis of the following equation:

[0244] X1 = A - B1 • C1n.

[0245] In this equation, X1 denotes the correction value for the position P1 on the edge line 408, B1 denotes the sign of the curvature K1 at this position P1 (i.e. B1 can assume the values +1 or -1) and C1 denotes the absolute value of the curvature K1 at this position P1.

[0246] Moreover, the equation above contains two optional scaling parameters A, n. The scaling parameter A is a scaling factor A (constant of proportionality A). Further, the scaling parameter n is a scaling exponent. For example, the at least one correction value X1 may also be calculated on the basis of the scaling factor A only! in this case, only linear dependencies of the displacement V1 of the edge line 408 on the absolute value C1 of the curvature K1 are taken into account. If the correction value X1 is additionally calculated on the basis of the scaling exponent n, then nonlinear dependencies of the displacement V1 of the edge line 408 on the absolute value C1 of the curvature may also be taken into account.

[0247] A repair shape 406 (final repair shape 406) for the defect D is determined in a fifth step S5 of the method. In particular, the pre-repair shape 404 is corrected on the basis of the at least one determined correction value X1 in order to determine the repair shape 406 of the defect D. The solid edge line 408 of the pre-repair shape 404 can be seen in Fig. 5. Moreover, displacements V1 to V4 of the pre-repair shape 404 that lead to the corrected pre-repair shape, i.e. the final repair shape 406 (shown using dashed lines in Fig. 5), are shown at the positions P1 to P4.Carl Zeiss SMT GmbH

[0248] 38

[0249] As shown in Fig. 7, the pre-repair shape 404 may be divided into a number k of pixels 416. For reasons of clarity, only a few of the pixels 416 are provided with a reference sign in Fig. 7. Moreover, Fig. 7 plots the edge line 408 of the pre-repair shape 404. The pixels 416 of the pre-repair shape 404 located on the edge line 408 (i.e. touched and / or intersected by the edge line 408) form edge pixels 418 of the pre-repair shape 404. Some of the edge pixels 418 are provided with a reference sign in Fig. 7. It is evident from Fig. 7 that the edge pixels 418 form an encircling edge of the pre-repair shape 404. If the pre-repair shape 404 is divided into the pixels 416, then the at least one position P1 on the edge line 408 of the pre-repair shape 404 corresponds to a position on at least one edge pixel 416. In this case, the at least one correction value X1 indicates how many pixels 420 are added to the pre-repair shape 404 or how many pixels 422 are removed from the pixels 416 of the pre-repair shape 404 in order to correct the pre-repair shape 404.

[0250] In the method according to Fig. 3, steps S3 and / or S4 are optional in particular. Furthermore, step S5 may also be: correcting the at least one section of the edge line 408 on the basis of a curvature K1 of the at least one section of the edge line 408.

[0251] There follows a description, with reference to Fig. 8, of a method of particle beam-induced processing of a defect of a microlithographic photomask 100.

[0252] In a first step S 101 of the method according to Fig. 8, a repair shape 406 for the defect D is determined as described in connection with the method according to Fig. 3.

[0253] In a second step S102 of the method, the determined repair shape 406 is divided into a number m of pixels 416, 420 (Fig. 5).Carl Zeiss SMT GmbH

[0254] 39

[0255] In a third step S103 of the method, a particle beam 202 (Fig. 2) is provided at each of the m pixels 416, 420 of the repair shape 406 for the purpose of processing the defect D. Moreover, a process gas may be provided at each of the pixels 416, 420 of the repair shape 406 in step S103.

[0256] In the method according to Fig. 8, one or more scaling parameters A, n used to determine the at least one correction value X1 (Fig. 5) when determining the repair shape 406 can optionally be determined empirically in a preceding step S100. For example, the empirical determination of the one or more scaling parameters A, n includes analysing a test photomask 500 (Fig. 9), the test photomask 500 having one or more defects D', D" (similar to the defect D in Fig. 1). For example, an image 502 (e.g. a SEM image) of at least one portion of the test photomask 500 is analysed. For example, the image 502 of the test photomask 500 is a difference image similar to the image 412 in Fig. 4.

[0257] Analysing the image 502 of at least a portion of the test photomask 500 serves in particular to determine a repair shape (similar to the repair shape 406 in Fig. 5) for the one or more defects D', D" of the test photomask 500. In this case, a pre¬ repair shape 504, 506 with an edge line 508, 510 of the corresponding defect D', D" is determined and corrected on the basis of correction values, similar to what is shown in Fig. 5 for the pre-repair shape 404 and the correction values XI to X4. For example, the test photomask 500 comprises one or more defects D', D" with multiple concave and convex edge sections with different curvatures K, as illustrated in Fig. 9 (e.g. K has values of -2; -1.5; -1; -0.5; +0.5; +1; +1.5; +2). The correction values for the various curvatures K are determined as described in connection with Fig. 5. Moreover, the correction values for the various curvatures K are determined on the basis of one or more scaling parameters A, n. In this case, a table of values is fully tested for the one or more scaling parameters A, n. That is to say, repair shapes for the one or more defects D', D" of the testCarl Zeiss SMT GmbH

[0258] 40

[0259] photomask 500 are used for multiple mutually different values of the one or more scaling parameters A, n.

[0260] Furthermore, empirically determining the one or more scaling parameters A, n for example includes particle beam-induced processing of the one or more defects D', D" of the test photomask 500 (e.g. using the apparatus 200 from Fig. 2). In particular, the one or more defects D', D" of the test photomask 500 are processed with the particle beam 202 on the basis of the repair shapes determined for the various values of the one or more scaling parameters A, n in order to assess a quality of a repair of the one or more defects D', D" of the test photomask 500 on the basis of the values of the one or more scaling parameters A, n. On the basis thereof, it is then possible to determine the one or more optimal scaling parameters A, n.

[0261] In summary, an improved repair shape 406 for a defect D of a photomask 100 can be determined using the described method for determining the repair shape 406 (Fig. 3), in which the curvature K1 of the edge line 408 of the pre-repair shape 404 is taken into account. As a result, a dose of a particle beam 202 acting on a surface of the photomask 100 can be set better when the photomask 100 is processed (method according to Fig. 8). Hence, a defect D of the photomask 100 can be better processed and repaired. For example, an unwanted structure in the region of the defect D may be better (e.g. fully) removed. Alternatively, a missing structure in the region of the defect D may be better (e.g. fully) augmented. Moreover, damage to neighbouring structures (e.g. to a capping layer) may be prevented and / or reduced (in the case of convex structures).

[0262] Further aspects of the invention are disclosed in the following clauses:

[0263] Clause 1. Method for determining a repair shape (406) for a defect (D) of a microlithographic photomask (100), including the steps of:Carl Zeiss SMT GmbH

[0264] 41

[0265] a) providing (Si) an image (400) of at least a portion of the photomask (100), b) determining (S2) at least one section of an edge line (408) of the defect (D) on the basis of the image (400),

[0266] c) determining (S3) a curvature (Kl) of the at least one section of the edge line (408) at at least one position (Pl) in the at least one section of the edge line (408), d) determining (S4) at least one correction value (Kl) for the at least one position (Pl) on the basis of the determined curvature (Kl) and

[0267] e) determining (S5) at least one corrected section of the edge line by correcting the at least one section of the edge line (408) on the basis of the at least one determined correction value (Kl).

[0268] Clause 2. Method according to Clause 1, wherein

[0269] a geometric shape (402) of the defect (D) is determined in step b) on the basis of the image (400) as a pre-repair shape (404) with an edge line (408) having the at least one section of the edge line (408),

[0270] a curvature (Kl) of the edge line (408) is determined at at least one position (Pl) on the edge line (408) in step c),

[0271] at least one correction value (Kl) for the at least one position (Pl) is determined in step d) on the basis of the determined curvature (Kl) and

[0272] the repair shape (406) is determined in step e) by correcting the pre-repair shape (404) on the basis of the at least one determined correction value (Kl).

[0273] Clause 3. Method according to Clause 1 or 2, wherein the at least one correction value (Kl) specifies a displacement (Vl) of the edge line (408) at the at least one position (Pl) in a direction substantially perpendicular to a tangent (Tl) to the edge line (408) at the at least one position (Pl).

[0274] Clause 4. Method according to any of Clauses 1 to 3, whereinCarl Zeiss SMT GmbH

[0275] 42

[0276] an absolute value (Cl) and a sign (Bl) of the curvature (Kl) of the edge line (408) are determined in step c) at the at least one position (Pl) on the edge line (408), and

[0277] the at least one correction value (Kl) for the at least one position (Pl) on the edge line (408) is determined in step d) on the basis of the determined absolute value (Cl) and the determined sign (Bl) of the curvature (Kl).

[0278] Clause 5. Method according to any of Clauses 2 to 4, wherein a second derivative (F") of the edge line (408) of the pre-repair shape (404) is determined in step c), and an absolute value (Cl) of the curvature (Kl) of the edge line (408) at the at least one position (Pl) is determined on the basis of the second derivative (F").

[0279] Clause 6. Method according to any of Clauses 2 to 5, wherein a second derivative (F") of the edge line (408) of the pre-repair shape (404) is determined in step c), and a sign (Bl) of the curvature (Kl) of the edge line (408) at the at least one position (Pl) is determined on the basis of the second derivative (F").

[0280] Clause 7. Method according to any of Clauses 2 to 6, wherein the repair shape (406) is determined in step e) in such a way that

[0281] for aposition (Pl) on the edge line (408) of the pre-repair shape (404) for which a positive curvature (Kl) is determined, the edge line (408) is displaced at this position (Pl) in such a way that the pre-repair shape (404) is enlarged at this position (Pl), and

[0282] for a position (P3) on the edge line (408) of the pre-repair shape (404) for which a negative curvature (K3) is determined, the edge line (408) is displaced at this position (P3) in such a way that the pre-repair shape (404) is reduced in size at this position (P3).

[0283] Clause 8. Method according to any of Clauses 2 to 7, whereinCarl Zeiss SMT GmbH

[0284] 43

[0285] an absolute value (Cl) of the curvature (Kl) of the edge line (408) at the at least one position (Pl) is determined in step c), and there is a determination as to whether the absolute value (Cl) of the curvature (Kl) is greater than zero and / or greater than a predetermined threshold value (SW), and

[0286] the repair shape (406) is determined in such a way in step e) that for a position (Pl) on the edge line (408) of the pre-repair shape (404) for which the determined absolute value (Cl) of the curvature (Kl) is greater than zero and / or greater than the predetermined threshold value (SW), the edge line (408) at this position (Pl) is displaced by an extent which is a mathematical function of the absolute value (C1) of the curvature (K1) at this position (P1).

[0287] Clause 9. Method according to any of Clauses 1 to 8, wherein the at least one correction value (Kl) is determined in step d) on the basis of one or more scaling parameters (A, n) determined in advance which specifies / specify a dependence of an extent of a displacement (Vl) of the edge line (408) at the at least one position (Pl) on an absolute value (Cl) of the determined curvature (Kl) at the at least one position (Pl).

[0288] Clause 10. Method according to Clause 9, wherein

[0289] the one or more scaling parameters (A, n) determined in advance include a scaling factor (A) determined in advance and / or a scaling exponent (n) determined in advance.

[0290] Clause 11. Method according to any of Clauses 2 to 10, wherein

[0291] the determined pre-repair shape (404) is divided into a number k of pixels (416),

[0292] the pixels (416) of the pre-repair shape (404) which are touched and / or intersected by the edge line (408) form edge pixels (418) of the pre-repair shape (404),Carl Zeiss SMT GmbH

[0293] 44

[0294] the at least one position (Pl) on the edge line (408) corresponds to a position (Pl) on at least one edge pixel (418), and

[0295] the repair shape (406) is corrected in step e) on the basis of the at least one determined correction value (Kl) by adding or removing one or more pixels (420, 422) to or from the pre-repair shape (404) at a position neighbouring the at least one edge pixel (418).

[0296] Clause 12. Method according to Clause 11, wherein in step e),

[0297] for an edge pixel (418) for which a positive curvature (Kl) is determined, one or more further pixels (420) is / are added to the pre-repair shape (404) in a direction substantially perpendicular to a tangent (Tl) to the edge line (408) at this edge pixel (418), and

[0298] for an edge pixel (418, 422) for which a negative curvature (K3) is determined, this edge pixel (418, 422) and / or further neighbouring pixels (422) is / are removed from the pre-repair shape (404) in a direction substantially perpendicular to a tangent (T3) to the edge line (408) at this edge pixel (418).

[0299] Clause 13. Method of particle beam-induced processing of a defect (D) of a microlithographic photomask (100), comprising

[0300] determining (S101) a repair shape (406) for the defect (D) according to any of Clauses 1 to 12,

[0301] dividing (S102) the determined repair shape (406) into a number m of pixels and

[0302] providing (S103) a particle beam (202) at each of the m pixels of the repair shape (406) for the purpose of processing the defect (D).

[0303] Clause 14. Method according to Clause 13 and Clause 9 or 10, wherein the one or more scaling parameters (A, n) is / are determined empirically by analysing and processing a test photomask (500).Carl Zeiss SMT GmbH

[0304] 45

[0305] Clause 15. Computer program product comprising instructions that, upon execution of the program by at least one computer, cause the latter to carry out a method according to any of Clauses 1 to 14.

[0306] Clause 16. Control device (302) for determining a repair shape (406) for a defect (D) of a microlithographic photomask (100), comprising

[0307] a provision unit (304) for providing an image (400) of at least a portion of the photomask (100),

[0308] a first determination unit (306) for determining at least one section t of an edge line (408) of the defect (D) on the basis of the image (400),

[0309] a second determination unit (308) for determining a curvature (Kl) of the at least one section of the edge line (408) at at least one position (Pl) in the at least one section of the edge line (408),

[0310] a third determination unit (310) for determining at least one correction value (Kl) for the at least one position (Pl) on the basis of the determined curvature (Kl) and

[0311] a fourth determination unit (312) for determining at least one corrected section of the edge line by correcting the at least one section of the edge line on the basis of the at least one determined correction value (Kl).

[0312] Although the present invention has been described on the basis of exemplary embodiments, it may be modified in a variety of ways.Carl Zeiss SMT GmbH

[0313] 46 LIST OF REFERENCE SIGNS

[0314] 100 Photomask

[0315] 102 Substrate

[0316] 104 Coating

[0317] 200 Apparatus

[0318] 202 Particle beam

[0319] 204 Housing

[0320] 206 Pump

[0321] 208 Sample stage

[0322] 210 Particle column

[0323] 212 Particle source

[0324] 214 Electron / beam optics 216 Deflection unit

[0325] 218 Detector

[0326] 220 Gas provision unit 222 Valve

[0327] 224 Gas line

[0328] 300 Computing apparatus 302 Control device

[0329] 304 Provision unit 306-312 Determination unit 314 Control device

[0330] 316 Image generating device 400 Image

[0331] 402 Shape

[0332] 404 Pre-repair shape

[0333] 406 Repair shape

[0334] 408 Edge line

[0335] 410 Reference imageCarl Zeiss SMT GmbH

[0336] 47

[0337] 412 Difference image 416 Pixel

[0338] 418 Pixel

[0339] 420 Pixel

[0340] 422 Pixel

[0341] 500 Test photomask 502 Image

[0342] 504, 506 Pre-repair shape 508, 510 Edge line

[0343] A Scaling parameter B1-B4 Sign

[0344] C, C1-C4 Absolute value D, D', D" Defect

[0345] F" Derivative

[0346] G Structure dimension K, K1-K4 Curvature

[0347] n Scaling parameter P1-P4 Position

[0348] Q1-Q4 Region

[0349] S1-S5 Method step

[0350] S100-S103 Method step

[0351] SW Threshold value T1-T3 Tangent

[0352] V1-V4 Displacement

[0353] X1-X4 Correction value x, y, z Direction

Claims

1. Carl Zeiss SMT GmbH48CLAIMS1. Method for determining a repair shape (406) for a defect (D) of a microlithographic photomask (100), including the steps of:a) providing (Si) an image (400) of at least a portion of the photomask (100), b) determining (S2) at least one section of an edge line (408) of the defect (D) on the basis of the image (400) ande) correcting (S5) the at least one section of the edge line (408) on the basis of a curvature (Kl) of the at least one section of the edge line (408).

2. Method according to Claim 1, including:c) determining (S3) a curvature (Kl) of the at least one section of the edge line (408) at at least one position (Pl) in the at least one section of the edge line (408) andd) determining (S4) at least one correction value (Kl) for the at least one position (Pl) on the basis of the determined curvature (Kl),wherein step e) includes: determining (S5) at least one corrected section of the edge line by correcting the at least one section of the edge line (408) on the basis of the at least one determined correction value (Kl).

3. Method according to Claim 1 or 2, whereina geometric shape (402) of the defect (D) is determined in step b) on the basis of the image (400) as a pre-repair shape (404) with an edge line (408) having the at least one section of the edge line (408), andthe repair shape (406) is determined in step e) by correcting the pre-repair shape (404) on the basis of the curvature (Kl) of the at least one section of the edge line (408).

4. Method according to Claim 2 or 3, wherein the at least one correction value (Kl) specifies a displacement (Vl) of the edge line (408) at the at least one positionCarl Zeiss SMT GmbH49(Pl) in a direction substantially perpendicular to a tangent (Tl) to the edge line (408) at the at least one position (Pl).

5. Method according to any of Claims 2 to 4, whereinan absolute value (Cl) and a sign (Bl) of the curvature (Kl) of the edge line (408) are determined in step c) at the at least one position (Pl) on the edge line (408), andthe at least one correction value (Kl) for the at least one position (Pl) on the edge line (408) is determined in step d) on the basis of the determined absolute value (Cl) and the determined sign (Bl) of the curvature (Kl).

6. Method according to any of Claims 3 to 5, whereina second derivative (F") of the at least one section of the edge line (408) is determined, and an absolute value (Cl) of the curvature (Kl) of the at least one section of the edge line (408) is determined on the basis of the second derivative (F"), and / ora second derivative (F") of the edge line (408) of the pre-repair shape (404) is determined in step c), and an absolute value (Cl) of the curvature (Kl) of the edge line (408) at the at least one position (Pl) is determined on the basis of the second derivative (F").

7. Method according to any of Claims 3 to 6, whereina second derivative (F") of the at least one section of the edge line (408) is determined, and a sign (Bl) of the curvature (Kl) of the at least one section of the edge line (408) is determined on the basis of the second derivative (F"), and / or a second derivative (F") of the edge line (408) of the pre-repair shape (404) is determined in step c), and a sign (Bl) of the curvature (Kl) of the edge line (408) at the at least one position (Pl) is determined on the basis of the second derivative (F").Carl Zeiss SMT GmbH508. Method according to any of Claims 3 to 7, wherein the repair shape (406) is determined in step e) in such a way thatfor aposition (Pl) on the edge line (408) of the pre-repair shape (404) for which a positive curvature (Kl) is determined, the edge line (408) is displaced at this position (Pl) in such a way that the pre-repair shape (404) is enlarged at this position (Pl), andfor a position (P3) on the edge line (408) of the pre-repair shape (404) for which a negative curvature (K3) is determined, the edge line (408) is displaced at this position (P3) in such a way that the pre-repair shape (404) is reduced in size at this position (P3).

9. Method according to any of Claims 3 to 8, whereinan absolute value (Cl) of the curvature (Kl) of the edge line (408) at the at least one position (Pl) is determined in step c), and there is a determination as to whether the absolute value (Cl) of the curvature (Kl) is greater than zero and / or greater than a predetermined threshold value (SW), andthe repair shape (406) is determined in such a way in step e) that for a position (Pl) on the edge line (408) of the pre-repair shape (404) for which the determined absolute value (Cl) of the curvature (Kl) is greater than zero and / or greater than the predetermined threshold value (SW), the edge line (408) at this position (Pl) is displaced by an extent which is a mathematical function of the absolute value (Cl) of the curvature (Kl) at this position (Pl).

10. Method according to any of Claims 2 to 9, wherein the at least one correction value (Kl) is determined in step d) on the basis of one or more scaling parameters (A, n) determined in advance and specifying a dependence of an extent of a displacement (Vl) of the edge line (408) at the at least one position (Pl) on an absolute value (Cl) of the determined curvature (Kl) at the at least one position (Pl).Carl Zeiss SMT GmbH5111. Method according to Claim 10, whereinthe one or more scaling parameters (A, n) determined in advance include a scaling factor (A) determined in advance and / or a scaling exponent (n) determined in advance.

12. Method according to any of Claims 3 to 11, whereinthe determined pre-repair shape (404) is divided into a number k of pixels (416),the pixels (416) of the pre-repair shape (404) which are touched and / or intersected by the edge line (408) form edge pixels (418) of the pre-repair shape (404),the at least one position (Pl) on the edge line (408) corresponds to a position (Pl) on at least one edge pixel (418), andthe repair shape (406) is corrected in step e) on the basis of the at least one determined correction value (Kl) by adding or removing one or more pixels (420, 422) to or from the pre-repair shape (404) at a position neighbouring the at least one edge pixel (418).

13. Method according to Claim 12, wherein in step e),for an edge pixel (418) for which a positive curvature (Kl) is determined, one or more further pixels (420) is / are added to the pre-repair shape (404) in a direction substantially perpendicular to a tangent (Tl) to the edge line (408) at this edge pixel (418), andfor an edge pixel (418, 422) for which a negative curvature (K3) is determined, this edge pixel (418, 422) and / or further neighbouring pixels (422) is / are removed from the pre-repair shape (404) in a direction substantially perpendicular to a tangent (T3) to the edge line (408) at this edge pixel (418).

14. Method of particle beam-induced processing of a defect (D) of a microlithographic photomask (100), comprisingCarl Zeiss SMT GmbH52determining (S 101) a repair shape (406) for the defect (D) according to any of Claims 1 to 13,dividing (S102) the determined repair shape (406) into a number m of pixels andproviding (S103) a particle beam (202) at each of the m pixels of the repair shape (406) for the purpose of processing the defect (D).

15. Method according to Claim 14 and Claim 10 or 11, wherein the one or more scaling parameters (A, n) is / are determined empirically by analysing and processing a test photomask (500).

16. Computer program product comprising instructions that, upon execution of the program by at least one computer, cause the latter to carry out the method according to any of Claims 1 to 15.

17. Control device (302) for determining a repair shape (406) for a defect (D) of a microlithographic photomask (100), comprising:a provision unit (304) for providing an image (400) of at least a portion of the photomask (100),a first determination unit (306) for determining at least one section of an edge line (408) of the defect (D) on the basis of the image (400) anda further determination unit (312) for correcting the at least one section of the edge line (408) on the basis of a curvature (Kl) of the at least one section of the edge line (408).

Images