Method and apparatus for calibrating motion relative to a photomask

Abstract

The present invention relates to a method and apparatus for calibrating operations on a mask. A method for generating correction marks on a lithographic object using a particle beam, in particular for calibrating operations, includes (a.) generating a first group of correction marks, (b.) generating a second group of correction marks, and (c.) a separation of the correction marks in the first group and in the second group is smaller than a separation between the correction marks from the first group and the correction marks from the second group.

Description

[Technical Field]

[0001] This patent application claims priority from German patent application DE 10 2021 213 163.8 entitled "Verfahren und Vorrichtung zur Kalibrierung eines Arbeitsvorgangs auf einer Photomaske", filed with the German Patent Office on November 23, 2021. German patent application DE 10 2021 213 163.8 is incorporated by reference in its entirety into this patent application.

[0002] The present invention relates to a method and apparatus for calibrating movements relative to a mask, in particular to a method for generating correction marks on a lithographic object, a method for calibrating movements, and corresponding apparatus and computer programs for carrying out the methods. [Background technology]

[0003] In the semiconductor industry, smaller and smaller structures are formed on wafers to ensure increased integration density. To form the structures, lithography methods are used, in particular, to image the structures onto the wafer. By way of example, lithography methods can include photolithography, UV lithography, DUV lithography, EUV lithography, X-ray lithography, nanoimprint lithography, etc. In this process, lithography typically utilizes a mask (e.g., a photomask, exposure mask, reticle, or stamp in the case of nanoimprint lithography) containing a pattern for imaging the desired structures onto the wafer.

[0004] As integration density increases, the demands on mask production also increase (e.g., as a result of a concomitant reduction in feature dimensions on the mask or as a result of higher material requirements in lithography). As a result, the mask production process becomes increasingly complex, time-consuming, and expensive, and it is not always possible to avoid mask errors (e.g., defects). Therefore, mask errors are typically repaired or repaired in further processing steps.

[0005] By way of example, mask errors can be repaired by a particle beam-based process, where the corresponding operations can include processing in a writing field and / or recording an image in an image field, in which a particle beam is typically scanned over a given writing or image field in a targeted manner (e.g., along a rectangular pixel raster).

[0006] Because masks are typically electrically insulating samples, scanning the mask with charged particles (e.g., electrons from an electron beam, ions from an ion beam) can result in electrostatic charging of the mask, which can cause the particle beam to unintentionally deviate from its intended point of incidence. This effect is called particle beam position drift or drift, and other mechanisms can also contribute to it.

[0007] Position drift manifests itself in the form of displacement, image distortion and / or distortion, which may significantly affect the predefined particle beam writing or image field. Therefore, it is usually necessary to correct or monitor the particle beam (i.e., drift correction / drift monitoring must be performed) to ensure that the particle beam is scanned along the desired working area.

[0008] The effect of relative displacement between the mask and the particle beam is often addressed by, for example, defining the repair relative to a reference marking in the particle beam image or scan area, tracking the position of the reference marking over the duration of the repair using image processing methods, and displacing the particle beam for repair by an offset. However, the marking or reference marking itself is subject to similar conditions as the defect being repaired, and therefore degrades during the repair process. Therefore, the marking is scanned as infrequently as possible, but as frequently as necessary.

[0009] US2002122992A discloses a method for correcting a photomask, in which rectangular reference holes are formed in a mask pattern by an ion beam. By determining the positions of the reference holes, it is possible to calculate the positional relationship between the reference holes and defects in the mask pattern, and the positional relationship is used to correct the defects.

[0010] US20090218488 discloses a method and apparatus for beam correction of beam drift. The beam position is aligned using a marker close enough to the working area so that an image of the marker can be recorded without moving the positioning stage. The particle beam is corrected during processing by using a model that predicts drift.

[0011] However, known techniques do not always perform satisfactorily, especially when repairing or inspecting large defects or defects having a large area (eg, greater than about 400×400 nm).

[0012] First, for defects with such large areas, the efficiency of the repair process is reduced due to the different behavior of the absorption and diffusion processes of the process gases involved. In addition, even for defects with such large areas, in conventional approaches, the process time increases with increasing defect size, requiring the fiducial marks to be scanned more frequently, resulting in further degradation of the fiducial marks. Such degraded fiducial marks cause greater noise in the position determination, ultimately impairing the quality of the repair or even interrupting the repair. Furthermore, the distance of the fiducial marks from the critical edge of the mask (or other relevant structures) increases. As a result, the accuracy of edge positioning decreases due to increased nonlinear effects caused by charging.

[0013] The present invention is therefore based on the object of specifying a method and an apparatus that provide improved possibilities for inspecting and / or processing lithographic objects (e.g. masks), in particular for inspecting and / or processing large area defects (e.g. having a diameter of more than several hundred nm) on such objects. Summary of the Invention

[0014] This objective is at least partially achieved by various aspects of the present invention.

[0015] A first aspect of the present invention relates to a method for generating correction marks on a lithography object (e.g., a mask) using a particle beam, particularly for calibrating operations. The method can include the following steps: (a.) generating a first group of correction marks; and (b.) generating a second group of correction marks, where a separation of the correction marks within the first group and within the second group is less than a separation between correction marks from the first group and correction marks from the second group. In this case, the first group includes two or more correction marks, and the second group similarly includes two or more correction marks.

[0016] In this case, the separation between two correction marks results from the conventional method of determining the distance between two geometric objects. For example, this distance can be defined by the length of the shortest connecting line between two points, each point belonging to a different correction mark. For example, the points in this case can include points on the edge of the correction mark (e.g., the outer or inner edge of the correction mark) and / or any point that can be assigned to the area / geometry of the correction mark. For this reason, the correction marks within a group are strictly spaced from each other (e.g., placed next to each other) so that they are always closer to each other than the correction marks of each other group.

[0017] In this case, the separation of correction marks within a group can be referred to as the intra-group separation, while the separation between correction marks from the first and second groups can be referred to as the extra-group separation. In this case, the intra-group separation includes all possible separations of correction marks within a group. The extra-group separation includes all possible separations between any (desired) correction mark from the first group and any (desired) correction mark from the second group. Therefore, no intra-group separation should be greater than the extra-group separation.

[0018] Known methods for generating correction marks on a mask have not previously relied on this type of geometric arrangement of the correction marks. Therefore, operations on the mask that require correction marks for a specific purpose were previously only possible with multiple disadvantages. In this case, the operations could include, for example, (particle beam-based) processing of the mask, inspecting the mask (e.g., with the electron beam of a scanning electron microscope, with an ion beam, etc.), locating the working area, calibrating the particle beam, etc.

[0019] In particular, optimized placement of the correction marks can serve to improve the determination of particle beam position drift, thereby enabling optimized inspection and / or repair of errors on the mask (e.g., mask defects). Mask errors represent deviations of the mask from corresponding target values ​​and can occur, for example, during mask production. Common mask defects are sites or areas where too much or too little absorber material is present and can be repaired, for example, by localized etching with the particle beam or material deposition while the corresponding precursor gas is introduced.

[0020] In particular, since the marks are thus provided locally (in the form of a first or second group), calibration can be performed on the basis of the marks. Thus, when a mark of the first (second) group wears out, it is possible to resort to, for example, a further mark of the first (second) group instead, which is arranged nearby and can therefore be used for further calibration of operations over a relatively long period of time (e.g., when processing and / or imaging relatively large defects). Alternatively, the marks of a group can also be used in a rotating manner, for example, in order to distribute wear over the marks and thereby maintain all marks for as long as possible.

[0021] By way of example, the particle beam may be a beam of particles that have mass (e.g., an electron beam or an ion beam), or may otherwise be a massless particle beam (e.g., a photon beam).

[0022] The optimized operation enabled by the generation of groups according to the invention is explained in more detail in the second aspect of the invention.

[0023] In a further example, the first group and / or the second group include correction marks having at least partially the same form. For example, it is possible to generate correction marks of similar geometric types in the two groups (i.e., geometrically similar correction marks), which can then be used for the same function within an operation. This concept facilitates the existence of redundancy and / or dispersion in the manifestation of wear, for example, when correction markers wear out, fall off, and / or become no longer technically usable during an operation for technical reasons. In this case, the functions of the correction marks can include reference marks for calibrating an operation, for example, marks for determining particle beam drift, focusing marks for focusing a particle beam, location marks for locating a working area, alignment marks for aligning an operation (e.g., for aligning a mask for processing), verification marks for verifying an operation, etc. In this case, both the geometry and material of the correction marks can be designed to be optimized for the specific function intended to be employed by the correction marks. In this case, any material that can be (additionally) attached to the mask can be considered as material (e.g., metals such as platinum, tungsten, etc., and / or insulating materials), and the correction marks can likewise be defined from the mask material and / or the associated substrate (e.g., the correction marks can be formed from chromium, tantalum nitride, molybdenum disilicide, the absorber material of the mask, etc.). Possible geometric shapes include, for example, circular, spherical, oval, triangular, or rectangular correction markers, but also more complex geometric shapes such as crosses, frames, polygons, etc. As an example, a group of cross-shaped correction markers can be designed for a first localization of the working area, while a group of circular correction markers can serve for calibration of the operation.

[0024] In a further example, the correction marks can be positioned next to each other. For example, the correction marks can be attached to the mask in an array of rows and / or styles (e.g., in a field having multiple adjacent rows of correction marks). In another example, only geometrically similar correction marks are generated in the first group and / or the second group, and similar correction marks can be used for multiple functions during operation.

[0025] In a further example, at least one correction mark from the first group and / or the second group is composed of multiple geometric shapes. For example, the correction mark can be composed of multiple separate, geometrically similar shapes (e.g., identical circular / spherical dots) generated very closely next to each other, thus forming the correction mark. For example, the generation can be performed so that, at a certain magnification required to read the correction mark by image processing, a uniform, continuous correction mark recess results from the (e.g., very small) dimensioned separate shapes. The procedure according to the present invention for generating a correction mark from multiple separate shapes can be advantageous from a process-technical perspective for processing lithographic masks. First, the variability of process conditions (and therefore susceptibility to errors) can be minimized, resulting in optimized process control in the generation of this type of correction mark. This is due to the fact that the generation of the correction mark can be achieved by multiple similar (separate) individual processes, each of which generates the same geometric shape on the mask and therefore requires the same process parameters to a large extent. Only locations on the mask where the same geometric shapes should be applied need to be adapted for each step. This reduces process complexity, minimizes process variations, and increases process stability, resulting in the generation of correction marks that reliably have the same characteristics on the mask over a relatively long manufacturing period. This ensures that the correction marks function reliably, for example, for operations based on the correction marks. Furthermore, the multiple distinct geometric shapes allow for a simplified process for removing the correction marks, since a smaller area of ​​the correction mark is connected to the mask. In addition, removal may be easier, for example, because gaps with mask material are exposed as a result of the multiple distinct connection areas of the multiple geometric shapes to the mask in the correction mark. Therefore, removal processes (e.g., cleaning with a wet chemical process, a plasma process, etc.) can act more uniformly on the correction marks, for example, because even the edges of the geometric shapes in the correction mark can be uniformly eroded.This minimizes residue following the removal process.

[0026] In a further example, the correction marks can be made up of multiple more complex geometric shapes that are not necessarily geometrically similar. By way of example, rectangles in a frame, circular structures in a circular frame, reticles, etc. are conceivable in this case. This allows, for example, the creation of correction mark shapes required for a particular image processing method.

[0027] In an example, the number of correction marks from the first group and / or the second group is at least three, preferably at least four. This is particularly advantageous, for example, for operations based on the correction marks, since it provides adequate redundancy and / or adequate wear distribution. In this case, the number of correction marks can be optimized for operations based thereon so that as many correction marks as necessary but as few as possible are generated. This avoids the unnecessary generation of correction marks, for example, to minimize residues during removal.

[0028] In an example, the separation of the correction marks within the first group and / or the second group is smaller than the separation between the correction marks from the first group and the correction marks from the second group, by at least a factor of 5, preferably at least a factor of 10, and particularly preferably at least a factor of 20. As a result of the above-mentioned difference in separation by several orders of magnitude, for example, rapid group assignment of two correction marks can be performed during operation. The working area of ​​a correction mark-based operation can be located, for example, within the area spanned by the separation between the correction marks from the first group and the correction marks from the second group (i.e., due to the outer group separation). In this case, the characteristics of the correction marks can be varied depending on the selected or generated dimensions of the outer group separation, for example, to optimize correction mark readout. For example, if the separation of correction marks within a group (i.e., the inner group separation) is at least a factor of 20 smaller than the outer group separation, the group can have a correspondingly larger correction mark area. In contrast, if the inner group separation is a factor of 5 smaller than the outer group separation, the group can have a correction mark with a smaller area, for example. This can also be assumed for the type of correction mark (eg, its material, geometric shape, etc., as explained above) that is chosen and generated depending on the size of the outer group separation.

[0029] In an example, the generation of the correction mark is based at least in part on a particle beam-induced deposition process and / or a particle beam-induced etching process. In this context, a particle beam-induced deposition process can include, for example, an electron beam-induced and / or an ion beam-induced deposition process. By way of example, the deposition process can be based on deposition (e.g., chemical and / or physical vapor deposition) that is induced or supported in a targeted manner by a particle beam. In this case, for example, it is possible to locally deposit any desired geometric shape of a correction mark made of a suitable material on a mask by targeted guidance of a particle beam and a suitable gas atmosphere. Suitable methods known to those skilled in the art include, for example, (focused) electron beam-induced deposition ((F)EBID), (focused) ion beam-induced deposition ((F)IBID), etc.

[0030] Particle beam-induced etching processes can include, for example, electron beam-induced and / or ion beam-induced etching processes. In this context, the etching process can, for example, occur in an etching environment (e.g., etching gas, etching plasma, etc.), and the etching process can be induced or assisted in a targeted manner by a particle beam. By way of example, any desired geometric shape of the correction mark can be locally etched into a mask material (e.g., an absorber material of the mask, a substrate) by targeted guidance of a particle beam in the etching environment. By way of example, (focused) electron beam-induced etching ((F)EBIE) is a suitable method.

[0031] Furthermore, particle beam induced (e.g., ion beam induced) milling processes can also be used in examples, within which, for example, there is localized material ablation by the induction of a particle beam. For example, ion beam milling is a suitable method.

[0032] In a further example, the method further comprises generating at least one third group of correction marks, wherein the separation of the correction marks within each group is smaller than the separation between correction marks from two different groups. Thus, the concept according to the invention is extended by at least one additional group. The generation of at least one fourth group of correction marks and / or at least a fifth group of correction marks, etc., is likewise conceivable in the examples.

[0033] In this case, the separation of correction marks within a group can again be referred to as the intra-group separation, whereas the separation between correction marks from two different groups (e.g., the first and third groups, the first and fourth groups, the fourth and fifth groups, etc.) can be referred to as the extra-group separation. In this case, the intra-group separation includes all possible separations of correction marks within a group. The extra-group separation includes all possible separations between (any) two correction marks from two different groups. The outline according to the present invention is therefore based on the fact that the intra-group separation is not greater than the extra-group separation, even in the case of multiple groups (e.g., three and / or four groups of correction marks).

[0034] In particular, in an example, four groups can be generated. These can be generated in an at least partially quadrilateral arrangement (e.g., in the form of a square or rectangle). The quadrilaterals can be arranged around the working area (e.g., the defect), i.e., the (geometric) centroids of the correction marks of the individual groups can form corners of a quadrilateral that surrounds the working area. In another example, the arrangement can be performed such that at least one rectangle, within which the working area is located, can be formed, for example, from four correction marks from four different groups.

[0035] A working area can be considered to be an area of ​​an object intended to be inspected or processed during operation. For example, this can be an area where defective material is located. Within the scope of the present invention, a working area can particularly refer to an area of ​​an object intended to be inspected / processed uniformly, i.e., an area that is not inspected or processed in multiple procedures that can be considered independent of each other. A working area of ​​a photomask is particularly a localized area that does not encompass the entire photomask. For example, a working area can represent or include a localized defect that does not, for example, resolve into multiple completely separate partial defects or that can be subdivided into completely separate partial defects. In this case, a "localized" defect can mean, for example, small compared to the size of the object, e.g., the mask. For example, a working area or a defect contained therein can have one or more lateral dimensions of less than 1 mm, less than 100 μm, less than 10 μm, less than 2 μm, less than 1 μm, or less than 500 nm. The working area or local defect can be fitted to a (virtual) square with side lengths of, for example, 1 mm, 100 μm, 10 μm or 2 μm or 1 μm or 500 nm.

[0036] In this case, the work area can be bounded by a peripheral edge or contour, and everything within this edge or contour can be considered the work area. In metaphorical terms, imagine a “lasso” thrown around a defect and tightened until it “captures” the defect at a minimum length. The “lasso” then represents the outer edge of the work area. (Alternatively, consider an elastic band thrown around the defect and tightened around it, where the band, due to its width (e.g., on the order of the typical diameter of the fiducial markings discussed herein), defines a marginal strip around the work area rather than a linear edge.) By way of example, the work area can be defined as an envelope of one or more areas to be repaired, e.g., a convex sleeve, and a group of correction marks can be positioned to enclose the work area.

[0037] In a further example, the first and second groups of correction marks can be generated such that the envelope, e.g., the convex sleeve, of at least one of the groups of correction marks does not intersect the working area (or such that the convex sleeve of at least one group of correction marks does not represent and / or form a subset of the working area (e.g., of a defect)). By way of example, the groups of correction marks can be positioned such that the convex sleeve of the first group and the convex sleeve of the second group do not intersect the working area (e.g., a defect). This can further be interpreted as the area defined by the convex sleeve of the groups of correction marks not forming part of the working area (e.g., a defect).

[0038] The rectangular arrangement can be designed as a calibration window for calibration of an operation, for example for distortion compensation of a writing or image field processed with a particle beam, where the rectangular arrangement facilitates, for example, digital data processing or suitable image processing required for distortion compensation.

[0039] In further examples, the calibration window may be provided in the form of a triangle (i.e., with three generated groups) and / or with different types of polygons (i.e., as an m-polygon, where m is the number of generated groups).

[0040] In a further example, the generated groups surround the working area of ​​operation such that, in each case, a connecting line between two correction marks in different groups can surround the working area without intersecting the working area. By way of example, the working area can be a mask error (e.g., a mask defect), and a connecting line between two correction marks in different groups does not intersect the mask error. This can also be formulated such that a connecting line defining an outer group separation does not intersect the working area. This is advantageous, for example, because it ensures that the working area is completely surrounded by the groups (and the correction marks located therein). By way of example, this allows a calibration window (e.g., as described above for distortion compensation) to completely encompass the mask error so that the entire working area can be interpolated across the calibration window without reducing the accuracy of the edge position. For example, measurement errors that may occur during the determination of the position of the correction marks (e.g., which may increase the extrapolation area) are consequently not amplified during distortion compensation.

[0041] In a further example of the method, the mask is first analyzed (e.g., by being scanned with a particle beam) to find and / or locate the working areas on the mask. By way of example, this can include image processing-assisted detection of mask errors (e.g., by methods of defect monitoring using pattern recognition). Information about the locations of the working areas can then be used to attach the groups according to one of the examples described above.

[0042] In a further example, a method for generating correction marks on an object for lithography can include the following step: generating at least a local group of spaced-apart correction marks. By way of example, it is possible to generate exactly one local group of spaced-apart correction marks; it is not necessary that two groups be generated. It is conceivable that the correction marks of the local group are generated in a local accumulation, with the dimensions of the envelope of the correction mark (e.g., the extent of the correction mark envelope) being an order of magnitude smaller (e.g., shorter) than the dimensions of the envelope of the working area. By way of example, the dimensions of the envelope of the correction marks of the exactly one local group can be at least one-quarter, preferably at least one-tenth, and most preferably at least one-twentieth of the dimensions of the envelope of the working area. In a further example, the convex sleeve of the local group of correction marks does not intersect the working area (or, for example, the convex sleeve is not a subset of the working area of ​​the operation). In this case, the separation of the correction marks in the local group can be designed in such a way that it is advantageous for the second aspect of the invention (which will be described in more detail below). If only one local group is envisaged, this method can be combined with the further steps described herein, however, it is also possible to generate more than one local group independently of this.

[0043] A second aspect of the present invention relates to a method for calibrating operations on a lithography object (e.g., a mask) using at least one local group of spaced-apart correction marks using a particle beam, the method comprising the following sequences: (S1.) selecting a sequence tuple, the sequence tuple including a subset of the correction marks of at least one group; (S2.) performing a calibration based at least in part on the sequence tuple; and (S3.) performing at least some of the operations based at least in part on the performed calibration.

[0044] By way of example, the second aspect of the present invention may be based, at least in part, on at least one local group being a group generated according to any one of the above-described examples (i.e., a group generated according to the first aspect of the present invention). In an example, the second aspect of the present invention may include the first aspect of the present invention (or, for example, the first aspect of the present invention may also include the second aspect). By way of example, the method of the second aspect of the present invention may include that correction marks are generated (or have been generated) according to the first aspect of the present invention. It is equally conceivable that (naturally) existing structures on the mask (e.g., one or more prominent points, structural transitions, various lithographic marks, etc.) may be used as local groups of correction marks.

[0045] At least one group is localized and therefore located in a spatially delimited area on the mask. The spatial delimitation or extent can be provided, for example, by an envelope around the outer contour of the correction marks of the at least one localized group. In this case, the spatial delimitation can be related to the spatial extent of the operation (for example, the at least one localized group of correction marks can extend to a range that is technically perceptible for the operation). Furthermore, the spatial extent of the localized group can be constrained, for example, to a continuous area, with the following area dimensions possible: 30 nm x 30 nm or less (or 9 x 10 -16 m 2 or less), 100nm x 100nm or less (or 10 -14 m 2 or less), and / or 1mm x 1mm or less (or 10 -6 m 2 Moreover, the spatial extent of the local group can be, for example, the total area A of the mask. M For example, the spatial extent of a local group can be defined as the ratio of its area to its area. -14 ×A M Below, 10 -12 ×A M Below, 10 -9 ×A M Below and / or 10-6 ×A M It may be as follows: By way of example, the spatial extents mentioned above may also apply to the generated groups described in the context of the first aspect of the invention. Local groups may also be distinguished in that the dimensions of the envelope of the correction marks (e.g., the perimeter of the envelope around the correction marks) are an order of magnitude smaller than the dimensions of the envelope of the working area. By way of example, the dimensions of the envelope of the correction marks of a local group may be at least a quarter, preferably at least a tenth, and most preferably at least a twentieth, of the dimensions of the envelope of the working area.

[0046] In this case, the sequence of the method according to the present invention can be repeated multiple times within the overall operation. Therefore, calibration can be performed for different parts of the operation (i.e., sequence operations) to ensure stable parameters during the operation (i.e., within the sequence). The (overall) operation in this case includes the overall (i.e., self-contained) processing of the mask, while parts of the operation can be partial steps of the (overall) operation. In this case, the operation can include a particle beam-based procedure, for example, recording an image of an image field or processing a writing field using a particle beam. In this case, image recording can include, for example, recording by a scanning electron microscope, while processing a writing field can include a particle beam-induced etching or deposition process. In this case, the working area can include the writing or image field. For example, calibration can be used to calibrate or correct particle beam parameters for the operation.

[0047] To date, particle beam calibration has been known to involve, for example, defining operations relative to identical correction marks. During calibration, a suitable correction mark is typically scanned (e.g., with respect to a recorded image) using a particle beam. However, the corresponding correction mark and its immediate vicinity may significantly deteriorate over time during an operation or the entire operation, which may lead to an increasingly poor calibration. This is because the correction mark being calibrated may be exposed to the same process effects of the operation (e.g., particle beam-induced deposition or etching process conditions still exist). A disadvantage of previously known procedures is that continuously reliable calibrations are limited, in particular, by the processing duration of the operation. For longer processing operations (e.g., for relatively large work areas, work areas that can only be processed at low speeds, complex work areas, etc.), it is usually necessary to perform calibration more frequently, which may cause the correction mark and its surroundings to deteriorate to a substantially greater extent. The accuracy with which the locations of the correction marks are determined by image processing may decrease significantly over time (e.g., as a result of reduced contrast, correction marks appearing washed out, etc.) Additionally, permanent damage (e.g., defects) can remain on the mask following degradation behavior around the correction marks.

[0048] The concept according to the present invention improves upon the known disadvantages of sequence tuples that include a subset of correction marks from a group of correction marks selected for each sequence. This subset can then be used for calibration within the sequence. Therefore, the calibration of a sequence is based on a targeted selection of a subset of correction marks selected with a view to optimal calibration. In this case, the subset can include at least one correction mark (however, multiple correction marks from, for example, a group are also conceivable). As a result, it is possible to select multiple correction marks (or one correction mark) appropriate for a sequence. As a result, it is not necessary to rely on fixed correction marks for calibration, for example, where the correction marks may already be significantly deteriorated, but it is possible to use a subset of correction marks that function well for calibration. This ensures that the calibration-based operation (part of the operation) can be performed optimally and / or without any untoward effects, since incorrect calibration of the operation is avoided.

[0049] In an example, the selection of the sequence tuple is based at least in part on the evaluation of a predetermined criterion associated with at least one correction mark of at least one group. In this case, the predetermined criterion can provide an indication of the degree of deterioration of the correction mark or can be designed to minimize the degree of deterioration. By way of example, the criterion can include the number of times the correction mark (or sequence tuple) has been used during the method (which can correspond to an estimate of the degree of wear of the mark). In particular, it is possible to evaluate how often the sequence tuples have been selected consecutively. In a further example, the criterion can be evaluated by physical analysis (e.g., by recording an image of the correction mark using a particle beam).

[0050] In an example, the predetermined criteria include at least one of the following criteria: a degree of wear of the at least one correction mark; a contrast of the at least one correction mark; a gradient image of the at least one correction mark; an autocorrelation function of an image of the at least one correction mark; a cross-correlation function of at least two images of the at least one correction mark.

[0051] By way of example, the above-mentioned criteria can be determined based on a recorded image (e.g., a scanned electron image) of the correction mark (or the criteria can be determined based on a basic signal generated by scanning the correction mark with a particle beam). By way of example, the degree of wear can be measured or evaluated automatically by image processing (and / or manually by an operator). By way of example, a gradient image can be obtained by (digital) processing of the correction mark image (or basic signal) and can contain information about the correction mark's edges. By way of example, this allows for a good assessment of edge degradation, which can flatten over time. Similarly, the characteristics of the correction mark's autocorrelation function can be determined from the correction mark image (or basic signal). By way of example, a wider autocorrelation function can be associated with a higher degree of degradation, so that the corresponding correction mark can no longer be used for calibration above a given threshold. Furthermore, there can be a cross-correlation function of the correction mark based on the correction mark image (or basic signal) at two different times (e.g., from two different sequences). This allows for analytical evaluation of the relative changes in the correction mark.

[0052] In a further example, the sequence is repeated at least once, and in the process, at least two sequence tuples containing different subsets of correction marks are selected. As a result, for the entire operation (e.g., including at least two sequences), the same correction marks do not need to be used consecutively for calibration. This can significantly minimize both the occurrence of correction mark degradation and mask damage caused by calibration, since all correction marks (or always the same correction marks) do not need to be exposed to the particle beam for every sequence. This ensures reliable operation of the calibration, even with relatively long processing times, which may occur, for example, in the case of a large number of sequences.

[0053] In an example, a sequence tuple is selected to include a subset of correction marks from each of at least m groups of correction marks, where m is 2 or greater (e.g., m=4), and the separation of correction marks within an individual group is less than the separation between correction marks from two different groups. By way of example, this example can be based at least in part on at least m groups, which are groups generated according to the first aspect of the present invention (an example of which is described above). By way of example, four groups can be arranged in a rectangle on the mask, each group including, for example, at least three correction marks. This allows a particular sequence tuple to be chosen for sequence calibration from a large number of possible sequence tuples. By way of example, each tuple can include (exactly) one correction mark from each of the m groups.

[0054] In an example, the selection of a sequence tuple is based at least in part on the expected number of sequences in the operation. For example, this can be based on the expected number of calibrations and / or portions of the operation. The number (of sequences, calibrations, and / or portions of the operation) can be determined by, among other things, analyzing the working area. For example, this can include analyzing mask defects, where several parameters of the mask defects, such as defect area, defect type, defect material, mask type, etc., can be observed to determine the number.

[0055] In examples, the selection of sequence tuples over a sequence of operations is performed according to a predetermined order. The order can be defined so that the occurrence of wear (or deterioration) on the correction marks is minimized or uniformly distributed. In this regard, as a result of the skilled ordering of the sequence tuples, in examples, physical analysis of the correction marks can be omitted (e.g., by evaluating appropriate criteria, as presented in some examples). Similarly, examples can be envisioned in which the sequence minimizes (and / or uniformly distributes) the occurrence of wear, but there is accidental physical analysis of the correction marks (e.g., by recording an image for subsequent analysis).

[0056] In examples, the selection (of sequence tuples) is performed according to a cyclic order of sequence tuples, a randomized order of sequence tuples, and / or rows of the same sequence tuple. For example, multiple different sequence tuples (T1, T2, ... Tm) may be available on the mask. In the cyclic order, a certain cyclic order of sequence tuples is "rotated" across multiple sequences of methods. For example, if three sequence tuples are available (e.g., T1, T2, T3), an exemplary cyclic order is given by T1-T2-T3, and the corresponding cyclic order across the sequence of methods is, for example, T1-T2-T3-T1-T2-T3-T1-T2-T3-... etc. In the case of three sequence tuples, the randomized order includes a random order of sequence tuples across multiple sequences of methods (e.g., T3-T1-T3-T3-T2-T1-T1-T2-T2-... etc.).

[0057] When selecting sequence tuples according to the rows of the same sequence tuple, an exemplary sequence (in the case of three sequence tuples) can be determined in the process as follows: T1-T1-T1-...-T2-T2-T2-...-T3-T3-...-T3. In particular, when selecting sequence tuples according to the rows of the same sequence tuple, there may be an additional evaluation of the predetermined criterion (as described above in the exemplary format), which is also conceivable for other orders. For example, the evaluation of the predetermined criterion can be performed after a predetermined number of sequences using the same sequence tuple to verify the status of the correction mark of the sequence tuple. Depending on the status of the correction mark of the sequence tuple, it is possible to change to a different sequence tuple in subsequent sequences (to ensure optimal calibration) or continue using the sequence tuple (for example, due to the absence of wear-out manifestations).

[0058] In an example, the method further includes determining a transformation of particle beam parameters associated with the two sequence tuples and performing a calibration based at least in part on the determined transformation. In principle, at least two sequence tuples must be available for this concept, and therefore the specified procedure can be performed for all possible sequence tuples (e.g., when more than two sequence tuples are available).

[0059] As an example, the method may include determining initial positions of correction marks of (possible) sequence tuples that can be selected for the method. In this case, the determination may be performed, for example, before the first sequence of the method. A mask may be electrostatically charged when the mask (e.g., correction marks of a sequence tuples) is irradiated with a particle beam in the method. As a result, system disturbances exist that may affect the desired trajectory of the particle beam. Typically, the desired trajectory can be adjusted both dynamically and statically by particle beam parameters (e.g., acceleration voltage, deflection voltage, adjustments to particle beam optical elements, etc.). As a result of the above-mentioned disturbances, the positions of the (possible) sequence tuples may appear displaced relative to their initial positions during the method (e.g., when additional images are recorded by the particle beam). In this case, these "new" positions may be referred to as current positions. In this case, the offsets of the (possible) sequence tuples are not necessarily uniform, and the correction marks may be or appear to be displaced independently of each other (e.g., due to different charging). As an example, the correction marks of the (possible) sequence tuples may initially be positioned next to each other in a row so that their centers of gravity form a straight line. However, during the course of the method, the correction marks may be displaced during image recording so that their centers of gravity no longer form a straight line (e.g., in a first perspective, each correction mark may appear to be randomly offset in space). These (e.g., nonlinear) effects can affect the calibration of the particle beam so that a previously desired trajectory (e.g., across the working area) is no longer traversed. Therefore, according to the present invention, it is possible to perform a transformation that considers the initial position of one (or both) of the two sequence tuples relative to the current position of this and / or the other of the two sequence tuples. The transformation can thus reestablish the correct relationship between the two sequence tuples, which is no longer given graphically as a result of a disturbance in the system.In-sequence calibration can further consider the transformation information so that the particle beam can then be calibrated accordingly. This allows the particle beam trajectory to be independent of changes in the sequence tuple chosen in the method. This can ensure that the same work area is at least partially traversed by the particle beam. Because the edges of the work area are not optimally processed in the case of missing transformations (e.g., flatter sidewall angles may occur in etched and / or deposited structures), the transformation allows the quality of the edges of the work area in particular to be optimized.

[0060] In an example, the method further includes: determining a transformation of particle beam parameters associated with the selected sequence tuple and / or the selected sequence tuple in the preceding sequence, and / or performing a calibration based at least in part on the determined transformation. By way of example, the transformation may be performed for each sequence change. In another example, the transformation may be performed when changing a sequence tuple during the method (e.g., when changing a sequence tuple due to a chosen order, as described above).

[0061] In an example, determining the transformation includes at least one of the following: determining relative positions of the correction marks of the different sequence tuples relative to each other and / or determining relative positions of the correction marks of the different sequence tuples relative to one or more structures of the lithography object (e.g., mask). In this case, the relative positions (or position differences) may be determined, for example, in the style of a vector (e.g.,<x,y> ) can be defined as

[0062] As an example, the relative positions between the initial positions of the correction marks of (possible) sequence tuples can be determined (e.g., in each case between two correction marks of sequence tuples from different groups). Furthermore, the relative positions between the current positions of the correction marks of (possible) sequence tuples can also be determined. A transformation can then be determined from the different relative positions that allows changing one sequence tuple to another, minimizing the above-mentioned errors in the process. Furthermore, it is also possible to determine the relative positions between the initial positions of a sequence tuple and the current positions of different sequence tuples. Similarly, it is also possible to determine the relative positions between the initial position of a sequence tuple and the current position of this sequence tuple.

[0063] Furthermore, the above-described determination of the relative positions of the correction marks of various sequence tuples with respect to one or more structures considers at least one third "fixed point" that includes one or more structures (e.g., of a mask). Thus, a transformation can be identified by determining the position of a (characteristic) structure with respect to the position of a first sequence tuple and determining the position of a (characteristic) structure with respect to the position of a second sequence tuple. Thus, for example, there can be a transformation from a first sequence tuple to a second sequence tuple via the third "fixed point."

[0064] In examples, the calibration includes determining drift of the particle beam and / or correcting for the drift of the particle beam. In this case, the calibration can include determining an offset associated with the determined drift of the particle beam. The offset can then be used to correct for the drift of the particle beam so that the desired trajectory of the particle beam is constant or maintained during the method.

[0065] In an example, the action includes repairing a defect. In this case, the defect may include, for example, a mask defect, and the defect may be treated such that the defect is at least partially repaired by a deposition or etching process (as described in the example above). Here, the working area may include the defect or may be defined by its dimensions (e.g., by its outline).

[0066] It is emphasized that the first and second aspects described herein can also be combined with each other, i.e. the generation of the correction marks described herein can be followed by the calibration method described herein, which is aided by the generated correction marks.

[0067] A third aspect of the present invention relates to an apparatus for generating correction marks on a mask and / or calibrating operations using a particle beam, the apparatus comprising: (a.) means for (automatically) executing one of the methods described herein; and (b.) means for executing a computer program. In this case, the apparatus may include an apparatus suitable for performing a particle beam-based process. In this case, the apparatus may include, for example, an electron beam system and / or an ion beam system configured for a particle beam-induced deposition and / or etching process. Processing is also conceivable in a particle beam system capable of controlling at least one electron beam and also at least one ion beam in a targeted manner (e.g., a dual beam system or a cross beam system).

[0068] A fourth aspect of the invention relates to a computer program comprising instructions which, when executed, cause the apparatus described above to perform the method steps according to one of the methods described herein.

[0069] A further aspect relates to the above-mentioned device having a memory containing a computer program. Furthermore, the device can have means for executing the computer program. Alternatively, the computer program can be stored elsewhere (e.g., in the cloud), and the device can only have means for receiving instructions resulting from the execution of the program elsewhere. In any case, this can allow the method to be performed in an automated or autonomous manner within the device. As a result, for example, operator intervention can be minimized, thereby minimizing both cost and complexity when processing masks. Furthermore, the method can also be in written form (e.g., in an instruction manual for the above-mentioned device) to communicate targeted instructions regarding the method steps to an operator.

[0070] The following detailed description describes technical background information and exemplary embodiments of the present invention with reference to the drawings. [Brief explanation of the drawings]

[0071] [Figure 1] 1 illustrates an aspect of a problem that arises when using an electron beam to inspect and / or process photolithographic objects, where the elements have charged surfaces. [Figure 2] FIG. 1A is a diagram illustrating a top view of an exemplary repair situation of a defect in a photolithography mask as described in the prior art. [Figure 3] 1 is a graph that schematically illustrates compensation of drift of an electron beam relative to a marking caused by electrostatic charging, according to the prior art; [Figure 4] 3 is a graph reproducing the displacement of the markings relative to the x-axis and y-axis during repair of the defect of FIG. 2. [Figure 5a] 5a and 5b show schematic diagrams of various aspects of the invention, in this case an example of correction marks according to the invention, for calibrating movement relative to a mask; [Figure 5b]Figures 5a and 5b show schematic diagrams of various aspects of the present invention: Figure 5a illustrates the selection of sequence tuples for operation; [Figure 5c] 5a-5c show various aspects of the present invention in a simplified manner, and FIG. 5c illustrates the topic of particle beam parameter transformation in the present invention. [Figure 6] Finally, it shows a schematic diagram of some components of an apparatus for carrying out the method according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0072] Some technical background information and possible embodiments of the method and apparatus according to the invention will be explained in more detail below on the basis of the inspection of photolithographic masks and the treatment of defects in photolithographic masks.

[0073] The methods and devices according to the present invention can be used primarily to inspect and / or process all types of transmissive and reflective photomasks. Furthermore, the methods and devices according to the present invention can also be used to inspect and / or process templates and / or wafers for nanoimprint lithography. Furthermore, the devices and methods according to the present invention are not even limited in principle to inspecting and / or processing (photo)lithography objects. Rather, they can generally be used to analyze and / or process non-conductive or only slightly conductive samples using a charged particle beam.

[0074] However, for the sake of clarity and to avoid ambiguity, the following embodiments will relate throughout to the example of a photolithography mask, but this always encompasses, and therefore should also always be taken into consideration, other possible uses of the aspects of the invention described.

[0075] Diagram 100 of Figure 1 shows a schematic cross-sectional view of a charged mask 110 and the output 165 of a scanning electron microscope 160. The mask 110 has a distribution of surface charges on its surface 120 that causes a potential distribution or electrostatic charging of the mask 110. In image portion 105 on the left, the mask surface 120 has a positive charge 140. In image portion 195 on the right, the mask surface 120 exhibits an excess negative charge 150. Hereinafter, reference numerals 140 and 150 will be used to indicate both the distribution of surface charges on the mask surface 120 and the potential distribution caused by the charged surface.

[0076] Charging 140, 150 on the mask surface 120 can be caused by a beam 170 of charged particles, for example, the electron beam 170 of a scanning electron microscope (SEM) 160. Electrostatic charging 140, 150 on the mask surface 120 can be caused by scanning the mask 110 as part of an inspection process, or can occur as a result of a processing process. For example, electrostatic charging can be caused during processing of the mask 110 with an electron beam or an ion beam. Additionally, electrostatic charging 140, 150 on the mask 110 can be caused, for example, by handling the mask 110.

[0077] In the portion of the mask 110 represented in the schematic diagram 100 of Figure 1, the distribution of surface charges 140, 150 has a uniform density, however, this is not a necessary condition for the explanations given herein.

[0078] 1, a deflection system 175 deflects and scans the electron beam 170 over the mask surface 120 to determine the dimensions of the structural elements 130 of the mask 110. By way of example, the structural elements 130 can be pattern elements of absorber structures of the mask.

[0079] As shown in the left image portion 105 of the schematic diagram 100, as a result of the attractive effect of the positive charge 140 on the mask surface 120, the electron beam 170 scanning the structural element 130 is deflected near the mask surface 120 toward the optical axis 172 and follows a trajectory 174. Without the potential distribution 140, the electron beam 170 would follow a path 176. In the SEM image produced by the electron beam 170, the scanned dimension 178 appears larger than the actual dimension 180 of the structural element 130.

[0080] 1 shows the repulsive effect of the negatively charged (150) mask surface 120 on the path 184 of electrons 170 of electron beam 170. Without potential distribution 150, electron beam 170 would follow path 186. As a result of the electrostatic charge 150, and as a result of the further deflection of electron beam 170 directed away from beam axis 172 near mask surface 120, measured dimension 188 of structure element 130 in an SEM image generated from the scan data appears to have a smaller dimension than the actual dimension 180 of structure element 130.

[0081] Scanning the structural element 130 by the electron beam 170, or more generally with the charged particle beam 170, can result in local heating of the mask 110 and therefore changes in the extent of the mask 110. Even if these changes in the length of the mask 110 are only on the order of nanometers, these changes should be taken into account in the treatment process of the mask 110 so as not to jeopardize the success of the treatment process. Furthermore, thermal effects of the SEM 160 and / or the mask 110, or the specimen mount (not shown in FIG. 1), can again cause the point of incidence of the electron beam 170 on the mask 110 to drift in the double-order nanometer range as a function of time.

[0082] FIG. 2 shows a portion of a top view of a mask 200, which can be, for example, the mask 110 in FIG. 1. The photomask 200 includes a substrate 210. Two pattern elements 220 and 230 in the form of absorbent strips are arranged on the substrate 210 of the mask 200. In the pattern element 220, the mask 200 has a defect 250 in the form of excess material. To correct the defect 250, in the example shown in FIG. 2, a marking 240 is applied to the pattern element 220. The marking 240 (which can also be called a correction mark) is used to determine and compensate for drift or displacement of the electron beam 170 relative to the defect 250 during the repair process of the defect 250.

[0083] The marking 240 is deposited after identification of the defect 250 on the mask 200, for example, using an electron beam induced deposition (EBID) process, i.e., by supplying at least one precursor or process gas onto the mask 200. This is advantageous if the precursor gas is selected such that the marking 240 has a different material composition than the pattern elements 220, 230 of the mask 200. In the SEM 160 image, the marking 240 further distinguishes itself by material contrast in addition to topological contrast.

[0084] To remove defect 250, for example, by supplying additional precursor or process gas (or gas mixture), an etching reaction is triggered due to the electron beam or particle beam at the location of defect 250, thereby removing defect 250. In line with this, and in line with what was stated above regarding the meaning of the term "working area," working area 260 in FIG. 2 is substantially defined by the extent of defect 250 and is bounded or surrounded by contour line 265. The working area is shown here in FIG. 2 only in highly schematic form. However, as can be clearly seen, in FIG. 2 showing the prior art, marking 240 is located outside working area 260.

[0085] For example, material deposition to correct specific imperfections in the mask 200 is also possible.

[0086] FIG. 3, by way of example, schematically illustrates compensation for the drift or displacement of the electron beam 170 relative to the marking 240 during the repair process of the defect 250 according to the prior art. The local electrostatic charging of the mask 200 is difficult to define mathematically. This also applies to the thermal drift between the electron beam 170 and the marking 240. Therefore, the effect of the electrostatic charging of the mask 200 and / or its displacement relative to the point of incidence of the electron beam 170 relative to the marking 240 is measured and corrected at periodic time intervals. The solid curve 310 in FIG. 3 schematically illustrates the change, displacement, fluctuation, or drift of the marking 240 as a function of time during the repair process of the defect 250.

[0087] At the start of the repair process, a reference position 330 of marking 240 is determined. Reference position 330 can be specified relative to a reference marking on mask 200 or absolutely relative to the coordinate system of mask 220. In a second step, a position of a repair shape is defined relative to marking 240. In this case, the repair shape can be designed to cover defect 250 within working area 260. In an example, the repair shape can correspond (at least in part) to the spatial dimensions of defect 250 (e.g., the area, shape, and / or contour of the repair shape can correspond to corresponding characteristics of defect 250). In a further example, the repair shape can correspond to working area 260 (e.g., the repair shape can be identical to working area 260). Inspection or treatment of defect 250 can be performed, for example, such that an electron beam is scanned along the repair shape, resulting in or causing inspection or treatment of the working area or defect in a manner known per se. The repair shape may be known in advance, for example, from inspection or processing of similar work areas or defects (eg, work areas or defects having generally the same size, generally the same shape, material properties, defect class, etc.).

[0088] Repair of defect 250 is then initiated. To this end, as already mentioned, one or more etching gases are supplied to the location of defect 250 in Figure 2, and electron beam 170 is scanned over defect 250 through working area 260, shown schematically in Figure 2, as predefined by the repair shape.

[0089] After a specific time interval 320 has elapsed, the repair process is interrupted at regular or irregular time intervals 340, but the supply of precursor gas is not interrupted, in order to scan the marking 240 with the electron beam 170. A displacement, drift, or change 350 in the marking relative to a reference position 330 or relative to a previous measurement of the marking 240 is determined from an SEM image of the marking 240. The position of the repair feature relative or absolute to the marking 240 is then corrected based on the change 350 in the marking, and the repair process of the defect 250 continues.

[0090] FIG. 4 illustrates a further example of the displacement or drift of the marking 240 during the repair process of the defect 250 according to the prior art. The x-axis of the graph 400 in FIG. 4 plots time in arbitrary units. The horizontal axis of the graph 400 can also represent the number of measurements of the marking 240 during the repair process. The time interval between two scanning processes can range from 1 second to 50 seconds. The example shown in FIG. 4 illustrates a time range of approximately 1000 seconds. The y-axis of the graph 400 represents the total displacement or drift of the marking 240 in arbitrary units relative to the reference position 330 of the marking 240. By way of example, the drift can be specified as the number of pixels scanned by the electron beam 170 in one direction. Depending on the focus of the electron beam, the pixels can have dimensions ranging from 0.1 nm to 10 nm. The ordinate of the graph 400 includes a position change of approximately 120 nm.

[0091] The drift of marking 240 in the x-direction is represented by curve 410 in graph 400, and the displacement of marking 240 in the y-direction is represented by curve 420. A large position change or displacement of marking 240 results from switching between two process or precursor gases. This is indicated by arrow 440 in FIG. 4. A smaller oscillation or jump in position change results from, for example, switching between different repair shapes to repair defect 250 (see arrow 430).

[0092] 2-4 may be adequate for small defects such as defect 250. (Note that the extent of defect 250 is smaller than the dimensions of lines 220, 230 and the space between them, i.e., typically a few nanometers.) However, for larger area defects (e.g., in the range of hundreds of nanometers), the situation changes dramatically.

[0093] 5a to 5c show diagrammatically various aspects of the invention. Proceeding from the situation known from the prior art, the invention makes it possible, inter alia, to increase the accuracy and efficiency of mask inspection and / or processing, especially in the case of large area, continuous defects.

[0094] In this case, FIG. 5a shows an example of a correction mark according to the present invention for calibrating an operation on a mask and an associated working area (which may also be referred to as a marking, a reference marking, etc.). In this case, the working area 500 may include a defect on the mask to be repaired. The operation may serve to repair the defect on the mask, and a particle-beam-based process is conceivable here (e.g., a particle-beam-induced deposition or etching process). In this context, the working area 500 may initially be located at an initial step. For this purpose, for example, conventional methods for defect recognition on a mask may be used. For example, the mask may be scanned using an electron beam so that a scanning electron image is generated. Image processing may then analyze the scanning electron image to locate the defect and, in addition, define the working area 500. For example, image processing may be part of a method for automatic defect control and may include pattern recognition of the associated defect. The working area 500 may be considered as a writing field (i.e., for physical processing of the mask) and / or an image field (i.e., for the purpose of recording an image of the working area).

[0095] According to the present invention, at least two groups of correction marks can be generated around the working area 500. By way of example, the groups can be generated by a particle-beam-based process. In this case, particle-beam-induced deposition or etching processes, such as electron-beam-induced deposition, ion-beam-induced deposition, electron-beam-induced etching, ion-beam-induced milling, etc., are conceivable. The deposition or etching can be performed here on the mask material or on the mask substrate. The application of particle-beam-based processes can allow for a great degree of freedom when designing the correction marks with respect to their geometry, their material, and their position on the mask. Thus, the groups of correction marks around the working area 500 can be designed with various variants. By way of example, the correction marks can have any desired geometric shape, such as a circular structure, an amalgam of closely spaced circular structures, a polygon, a sphere, holes, grooves, etc. In this case, the geometry of the correction marks can crucially depend on the chosen deposition or etching process. By way of example, additional topologies can be generated by a deposition process, whereas structures can be generated by material ablation in an etching procedure. Similarly, the correction mark material can depend on the deposition or etching process selected. By way of example, in a deposition process, the material of the correction mark can include metals (e.g., platinum, tungsten, silver, gold, etc.), insulators (e.g., nitrides, oxides, polyimides, etc.), semiconductors, etc. Composite materials are also contemplated herein. In the case of an etching process, the correction mark material can include or be defined by the material of the mask and / or substrate. By way of example, the correction mark can be defined as an absorber strip of the mask, a hole (etched / milled) in the substrate of the mask, etc.

[0096] As shown in Figure 5a, for example, four groups of correction marks can be arranged around the working area. In this case, the first group can include correction marks A1, B1, and C1. The second group can include correction marks A2, B2, and C2. The third group can include correction marks A3, B3, and C3. The fourth group can include correction marks A4, B4, and C4. Each group can include the same number of correction marks (in this example, each group has three correction marks), but it is also conceivable that the groups can include different numbers of correction marks.

[0097] According to the present invention, a group is defined by a local accumulation of spatially separated correction marks from different groups of correction marks. In this case, the separation of correction marks within an individual group (i.e., intra-group separation) can be smaller than the separation between correction marks from two different groups (i.e., inter-group separation). By way of example, the following separations between correction marks occur within the first group: A1B1 (correction marks A1 to B1), A1C1 (correction marks A1 to C1), B1C1 (correction marks B1 to C1). In this case, the separations can be determined, for example, by the centroids, edges, arbitrary surface points, etc. of the correction marks. The separations between correction marks from two different groups are, for example, A1A3 (correction marks A1 to A3), C1A2 (correction marks C1 to A2), A1C4 (correction marks A1 to C4). As is clear from FIG. 5a, the separation between correction marks from two different groups is smaller than the separation (any separation) of correction marks within a single group (eg, A1A3>A1C1).

[0098] The groups arranged in this way can serve to optimize operations for processing the mask or for processing a working area of ​​the mask. As explained in relation to FIG. 3, calibration using the markings (or correction marks) must usually be performed multiple times for operations while the mask is being processed. By way of example, this can be compensation for drift or displacement of the particle beam, and the repair shape can be adapted accordingly. During calibration, the markings (or correction marks) must usually be measured using the particle beam to determine their position, and as a result, the markings (or correction marks) may deteriorate and / or wear (as explained above).

[0099] According to the present invention, not all markings (or correction marks) are necessarily provided for each calibration step of the (entire) processing of the mask (or the corresponding working area of ​​the mask), as previously known. The generated arrangement of groups of correction marks allows targeted selection of the desired correction marks for calibration (e.g., in the case of calibration during the repair of defects in the working area of ​​the mask, this can be calibrated, for example, by marking). In this case, the boundary condition for calibration may be that at least one correction mark from each group is used. Therefore, for calibration purposes, it is possible to select from a set of correction marks so that the calibration step is not limited to a single sequence tuple of correction marks. According to FIG. 5a, a large number of possible sequence tuples arise with the specified boundary conditions (four sequence tuples are listed in an exemplary format: A1, A2, A3, A4; A1, B2, C3, C4; B1, A2, C3, A4; B1, A2, A3, A4; ...). Thus, in more general terms, it is possible to choose from a large number of different tuples T1, T2, . . . Tm for calibration.

[0100] According to the present invention, the selection of sequence tuples allows minimizing or distributing the degradation of the correction marks during processing. For example, different sequence tuples can be used for the calibration step during the course of processing. In the process, the degradation can be minimized according to several principles.

[0101] First, a statistical distribution of sequence tuple usage can be assumed. As an example, a fixed number of sequence tuples (e.g., three tuples: T1, T2, T3) can be available. To ensure a uniform distribution, the sequence tuples can be used periodically across calibration steps in one variant. For example, it can be assumed that the order of the sequence tuples is periodically reused. In the case of three sequence tuples, the selection of sequence tuples across multiple calibration steps can be seen here as follows: T1-T2-T3-T1-T2-T3-T1-T2-T3-... As a result, each sequence tuple is stressed to roughly the same extent across the process. Furthermore, it can also be assumed that a randomized order of sequence tuples is selected. In this context, the type of order can be based on a mathematically uniform distribution, so that the sequence tuples used are used to roughly the same extent after multiple calibration steps.

[0102] Furthermore, it can be assumed that sequence tuples are always used consecutively until there is a change to a different sequence tuple. First, this can be designed so that there is a statistically uniform distribution of sequence tuple usage. In this case, the number of predicted measurements (or calibration steps) during mask processing can be estimated. As an example, it can be estimated that nine calibration steps are required for processing in one example. Thus, for example, in the case of three sequence tuples, the following order of calibration steps can be chosen to ensure a uniform distribution of sequence tuple usage: T1-T1-T1-T2-T2-T2-T3-T3-T3.

[0103] Second, it is possible to assume that sequence tuples are used continuously until significant wear occurs on the correction marks of the sequence tuples. If significant wear occurs, there may be a change to a different sequence tuple in the next calibration step. For example, significant wear can be verified by evaluating a quality criterion of the correction marks of the sequence tuples (e.g., a scanning electron image recording must be performed for this purpose). In an example, all correction marks of the sequence tuples can be evaluated against a quality criterion. For example, the quality criterion can be, for example, the contrast of the correction marks. For example, this can also be the difference in contrast between the correction mark and its immediate surroundings. In this case, an excessively strong or excessively weak contrast can prompt a trigger that initiates a change of the sequence tuple in the next calibration step. Furthermore, the quality criterion can be an evaluation of the gradient image of the correction marks. For example, if the gradient image indicates that the edges of the correction marks have deteriorated significantly, a trigger that initiates a change of the sequence tuple in the next calibration step can be prompted. Furthermore, it is also possible to analyze the characteristics of the autocorrelation function of the correction mark images. In this case, the threshold for prompting the trigger of a sequence tuple change can be the width of the autocorrelation function, which can provide information, for example, about the state of the edge of the correction mark. Furthermore, it is also possible to analyze the properties of the cross-correlation function of images of the correction mark at two different times. As a result, the correspondence of the images can be analytically evaluated and a measure of similarity of the images of the correction mark (at different times) can be determined. As an example, if the measure of similarity of the images (at different times) exceeds a threshold, it is possible to prompt a trigger that results in a sequence tuple change. Furthermore, it is also possible to analyze the properties of the cross-correlation function of images of different correction marks. As an example, there can be a cross-correlation between a correction mark of a sequence tuple and a correction mark of the same sequence tuple.Furthermore, there may be a cross-correlation between a correction mark of a sequence tuple and a correction mark not included in the (current) sequence tuple (e.g., this latter correction mark may be from a sequence tuple already used for calibration or from a sequence tuple not yet used for calibration). A combination of the autocorrelation and cross-correlation functions of one or more correction marks may also be used to evaluate the quality criterion. Furthermore, the quality criterion of a correction mark or its degree of wear can be estimated. By way of example, this estimate may be based on the number of calibration steps in which the correction mark has already been used during processing. By way of example, based on the process employed (e.g., an electron beam induced deposition process), it may be estimated that after the correction mark has been called 10 times (i.e., for 10 calibration steps), significant degradation of the correction mark can be expected, and therefore a change to a different sequence tuple should be made. By way of example, this estimate may be based on empirical values ​​and / or experiments.

[0104] FIG. 5b illustrates the selection of sequence tuples for an operation. In particular, three sequence tuples P1, P2, and P3 are shown. With reference to FIG. 5a, in this example, P1 is represented by correction marks A1, A2, A3, and A4 (the reference numbers of the correction marks are not shown in FIG. 5b). In this case, P2 is represented by correction marks A1, C2, A3, and B4. In this case, P3 is represented by A1, A2, A3, and A4. The connecting lines between the correction marks of the groups are presented using dashed lines for each sequence tuple, while the connecting lines between the correction marks from the second group and the correction marks from the fourth group are labeled in more detail (501, 502, 503). According to the present invention, the correction marks can be positioned such that the working area is located within a polygon (e.g., a triangle, a trapezoid, a rectangle, a pentagon, etc.) spanned by the sequence tuple. By way of example, the correction marks can be positioned such that their convex sleeves define (or contain) the working area. In this case, this can be done so that the working area is completely surrounded by the connecting lines and so that the connecting lines of the sequence tuples do not intersect the working area. As a result, this is the case where the calibration window (spanned by the correction marks of the sequence tuples) completely surrounds the envelope or contour of the working area 500. Thus, the entire working area, or the distortion of the particle beam relative to the working area, can be interpolated across the calibration window. By way of example, the calibration window can be used for distortion compensation, which can similarly measure and compensate for particle beam displacements as first-order aberrations. By way of example, these situations are given for sequence tuples P1 and P2 in FIG. 5b, but not for sequence tuple P3. In sequence tuple P3, the connecting line 503 from correction mark A4 to correction mark A2 intersects the working area 500, so intersection 533 is located outside the calibration window. By way of example, distortion compensation (performed by the calibration window) performs extrapolation in this case, which may reduce the accuracy of the edge location (e.g., of a defect). During processing of a work area (e.g., a defect), this may lead to the edges (or contours) of the work area (e.g., a defect) not being optimally traversed by the electron beam (e.g., not following the desired trajectory).These situations may further amplify measurement errors when determining mask positions. Therefore, the generation of correction marks in the style of sequence tuple P3 can be avoided. If such sequence tuples are nevertheless generated (e.g., due to manufacturing variations), this type of sequence tuple can preferably be filtered out by the calibration method or excluded from the formation of the calibration window. Alternatively, marks from one group can be selected based on marks chosen from another group, such that this type of sequence tuple is excluded.

[0105] FIG. 5c illustrates the topic of particle beam parameter conversion in the present invention. Four groups of the aforementioned correction marks, applied to a mask for example, are shown (in a manner similar to FIGS. 5a and 5b). The mask can become electrostatically charged during irradiation with a particle beam (e.g., an electron beam). These charging phenomena, among other things, have nonlinear effects on the particle beam, so that, in the absence of technical adaptations, there will be an impact on the particle beam trajectory when the sequence tuples are changed during the process. As an example, FIG. 5c illustrates the corresponding trajectories associated with the sequence tuples. Without further intervention, these particle beam trajectories will be traversed during calibration. In this case, trajectory 510 is associated with sequence tuples C1, C2, C3, and C4, and trajectory 520 is associated with sequence tuples B1, B2, B3, and B4. Furthermore, trajectory 530 is associated with sequence tuples A1, A2, A3, and A4.

[0106] These effects do not necessarily lead to significant offsets of the particle beam (as shown diagrammatically in FIG. 5c). However, as diagrammatically represented by trajectories 510, 520, and 530, the edge quality of the etched or deposited structures in operation may be degraded due to the edges of the working area 500 not being traversed identically by the particle beam. For example, this can be noticeable by a flatter sidewall angle of the structure. This phenomenon can be addressed by determining a mathematical transformation for each sequence tuple, which compensates for the differences between the sequence tuples. This transformation can be further taken into account during calibration (e.g., in addition to distortion compensation of the repair shape). As a result, it is possible to ensure that the particle beam trajectory remains the same even in the case of calibrations using different sequence tuples. First, the global positions of all correction marks in the sequence tuples and / or the relative (initial) positions of all correction marks relative to each other can be determined for the establishment of the transformation. In addition, the corresponding positions of the characteristic mask structures can be determined. The relative position can be expressed in terms of vectors, e.g., by x and y distances (e.g.,<x,y> distance vector).

[0107] The transformation can then be determined in a number of ways, for example, by determining the relative positions of sequence tuple X and sequence tuple Y. As an example, sequence tuple Y may initially be known to have a vector separation from sequence tuple X of V1 = <50 nm, 0 nm> (e.g., defined by the separation between corresponding marks in the tuples). Initially, only sequence tuple X may be used within the scope of the present invention. However, when changing from sequence tuple X to sequence tuple Y during the course of the method, it may now be known that sequence tuple Y has a vector separation from sequence tuple X of V2 = <100 nm, 10 nm>. This information can be used for transformation such that the particle beam can adapt accordingly to provide a constant trajectory (to compensate for the apparently changed separation).

[0108] As an example, the transformation can also be established by establishing the position of the (characteristic) mask structure relative to the sequence tuple X and the sequence tuple Y. Initially, only the sequence tuple X can be used within the method. Initially, the separation of the (characteristic) mask structure from the sequence tuple X can be given by V3=<500 nm, 500 nm>, and from the sequence tuple Y by V4=<550 nm, 500 nm>. However, when changing from the sequence tuple X to the sequence tuple Y during the course of the method, it can now be determined, for example, that V3=<600 nm, 400 nm> and V4=<700 nm, 350 nm>. This information can be used for the transformation so that the particle beam can adapt accordingly to provide a certain trajectory.

[0109] Figure 6 shows, in cross-section, some components of an apparatus 600 in which embodiments of the method according to the invention for inspecting and / or processing a mask (or generally one of the objects mentioned in the introduction for which the invention can be used) can be carried out and implemented. By way of example, reference is made to Figure 6 and the following description is given to the mask 510 of Figures 5a-5c, although this should not be understood as limiting. Alternatively, other lithographic masks or objects can be used.

[0110] The apparatus 600 comprises a vacuum chamber 602 and a scanning particle microscope 620 therein. In the example of Fig. 6, the scanning particle microscope 620 is a scanning electron microscope (SEM) 620. An electron beam as particle beam has the advantage that the mask 510 to be inspected or processed cannot be substantially damaged by said beam, or can only be damaged to a small extent. However, other charged particle beams are also possible, for example an ion beam of a FIB (Focused Ion Beam) system (not shown in Fig. 6).

[0111] The SEM 620 essentially comprises a particle gun 622 and a column 624 in which an electron or beam optical unit 626 is disposed. The electron gun 622 generates an electron beam 628, which the electron or beam optical unit 626 focuses and directs at the output of the column 624 onto a mask 510 (or generally onto a lithography sample or object). The mask 510 has a surface 520 with one or more structures 530, as already described in detail above. Surface charges that may be present on the mask 510 are not shown in FIG. 6 .

[0112] The mask 510 is placed on a specimen stage 605. As symbolized by the arrows in Figure 6, the specimen stage 605 can move in three spatial directions relative to the electron beam 628 of the SEM 620.

[0113] The spectrometer-detector combination 640 distinguishes the secondary electrons generated by the electron beam 628 at the measurement point 635 and / or the electrons backscattered by the mask 510 based on their energy and then converts them into electrical measurement signals, which are then passed to an evaluation unit 676 of the computer system 670.

[0114] To separate the energies, the spectrometer-detector combination 640 can include a filter or filter system to differentiate electrons by energy (not shown in FIG. 6).

[0115] Similar to spectrometer-detector combination 640, the energy-resolving spectrometer can be located outside of column 624 of SEM 620. However, it is also possible to locate the spectrometer and associated detector within column 624 of SEM 620. In the example shown in Figure 6, spectrometer 645 and detector 650 are integrated within column 624 of SEM 620. In addition to or as an alternative to spectrometer-detector combination 640, spectrometer 645 and detector 650 can be used in apparatus 600.

[0116] 6 may optionally include a detector 655 for detecting photons generated by the incident electron beam 628 at measurement point 635. Detector 655 may, for example, spectrally resolve the energy spectrum of the generated photons, thereby allowing conclusions to be drawn regarding the composition of layers at or near surface 520 of mask 510.

[0117] Additionally, the apparatus 600 may include an ion source (not shown) that provides low-energy ions in the region of the measurement point 635 when the mask 510 or its surface 520 is electrically insulating or semiconductive and has a negative surface charge. The ion source may be used to reduce the negative charge on the mask surface 520 in a localized and controlled manner.

[0118] If the mask surface 520 has an undesirable distribution of positive surface charge, for example caused by handling of the mask 510, the electron beam 628 can be used to reduce the charging of the mask surface 520.

[0119] The computer system 670 includes a scanning unit 672 that scans the electron beam 628 over the mask 510, particularly over the markings 540, 580 and / or the defects 550. The scanning unit 672 controls deflection elements in the column 624 of the SEM 620, which are not shown in FIG. 6 . Furthermore, the computer system 670 includes a setting unit 674 for setting and controlling various parameters of the SEM 620. Parameters that can be set by the setting unit 674 can be, for example, the magnification, the focus of the electron beam 628, one or more settings of the astigmatism corrector, the beam displacement, the position of the electron source, and / or one or more apertures (not shown in FIG. 6 ).

[0120] The scanning unit 672 and / or the setting unit 674 may perform, control or contribute to the inspection and / or processing of the mask 510 in the working area 560, for example, by use of an embodiment of the method according to the invention.

[0121] Furthermore, the computer system 670 comprises a memory unit 676 in which instructions for carrying out, for example, one embodiment of the method according to the invention can be stored. The computer system 670 can include one or more processors designed to execute such instructions, i.e., to control and activate corresponding components of the apparatus 600 (e.g., the SEM 620, the scanning unit 672, the setting unit 674 and / or a gas supply system not yet described) according to commands. The processor can include, for example, a powerful graphics processor.

[0122] 6 may be integrated into device 600 or may take the form of a dedicated device. Computer system 670 may be embodied using hardware, software, firmware, or a combination thereof.

[0123] To treat the defect 550 in the mask 510 and / or to write the (first and / or second) fiducial markings 540 and / or 580 on the mask 510, the apparatus 600 of FIG. 6 preferably includes multiple different storage containers for different processes or precursor gases. In the apparatus 600 given as an example, two storage containers are shown. However, the apparatus 600 may also have three or more storage containers for treating the mask 510 and / or writing the fiducial markings 540, 580 on the mask 510. The first storage container 652 stores a precursor gas or deposition gas, which can be used in cooperation with the electron beam 628 of the SEM 620 to deposit material for generating the fiducial markings 540, 580 on the mask 510, for example. Furthermore, the electron beam 628 of the SEM 620 can be used to deposit, for example, a missing absorber material in one of the pattern elements of the mask 510. The second reservoir 662 contains an etching gas that can be used, for example, to etch the defect 550 .

[0124] Each storage vessel 652, 662 has its own valve 654, 664, respectively, for controlling the amount of gas particles supplied per unit time, or gas flow rate, at the point of incidence 635 of the electron beam 628 on the surface 520 of the mask 510. Furthermore, the two storage vessels 652, 662 have their own gas supply 656, 666, which terminate at nozzles 658, 668 near the point of incidence 635 of the electron beam 628 on the mask 510. In the exemplary apparatus 600 shown in FIG. 6 , the valves 654, 664 are integrated near the storage vessels. In an alternative embodiment, the valves 654, 664 can be located near the corresponding nozzles 658, 668, respectively (not shown in FIG. 6 ). Each storage vessel 652, 662 can have its own elements for individual temperature setting and control. The temperature setting allows for both cooling and heating of each precursor gas. Additionally, gas supplies 656, 666 may each similarly have their own elements for setting and monitoring the temperature at which each precursor gas is supplied at the reaction location (also not shown in FIG. 6).

[0125] The apparatus 600 of FIG. 6 may include a pumping system for generating and maintaining the required vacuum. The pumping system is not shown in FIG. 6 for clarity. Additionally, the apparatus 600 may include a suction extraction device (also not shown in FIG. 6). The pump or suction extraction device in combination with the pumping system allows fragments or components generated during decomposition of the precursor gases that are not required for the local chemical reaction to be extracted from the vacuum chamber 602 of the apparatus 600 substantially at their point of origin. Unwanted gas components are pumped out of the vacuum chamber 602 locally at the location of incidence of the electron beam 628 on the mask 510 before they can disperse and settle within the vacuum chamber 602 of the apparatus 600, thereby preventing contamination of the vacuum chamber 602. Further embodiments of the present invention are described below.

[0126] Embodiment 1 relates to a method for generating correction marks on a lithographic object using a particle beam, in particular for calibrating the operation, comprising: a. generating a first group of correction marks (A1, B1, C1); b. generating a second group of correction marks (A2, B2, C2); Including, c. The separation of the correction marks within the first group and within the second group is less than the separation between the correction marks from the first group and the correction marks from the second group.

[0127] Embodiment 2: The method according to embodiment 1, wherein the first group and / or the second group include correction marks having at least partly the same form.

[0128] Embodiment 3: The method according to any of embodiments 1-2, wherein at least one correction mark from the first group and / or the second group is composed of a plurality of geometric shapes.

[0129] Embodiment 4: The method according to any one of embodiments 1 to 3, wherein the number of correction marks from the first group and / or the second group is at least 3, preferably at least 4.

[0130] Embodiment 5: A method according to any one of embodiments 1 to 4, wherein the separation of the correction marks within the first group and / or within the second group is smaller than the separation between the correction marks from the first group and the correction marks from the second group by a factor of at least 5, preferably at least 10, particularly preferably at least 20.

[0131] Embodiment 6: The method according to any one of embodiments 1 to 5, wherein the production is based at least in part on a particle beam induced deposition process and / or a particle beam induced etching process.

[0132] Embodiment 7: The method according to any one of embodiments 1 to 6, further comprising generating at least one third group of correction marks (A3, B3, C3), wherein the separation of the correction marks within an individual group is smaller than the separation between correction marks from two different groups.

[0133] Embodiment 8: A method according to embodiment 7, wherein the generated groups surround the working area such that a connecting line between two correction marks of different groups in each case can surround the working area (500) of the operation without crossing it.

[0134] Embodiment 9 relates to a method for calibrating a movement on a lithographic object using at least one local group of spaced apart correction marks (A1, B1, C1; A2, B2, C2) using a particle beam, the method comprising the following sequence: S1. Selecting a sequence tuple (A1;A2), where the sequence tuple includes a subset of correction marks of at least one group; S2. Performing a calibration based at least in part on the sequence tuple (A1;A2); and S3. Performing at least some of the actions based at least in part on the performed calibration; and The present invention relates to a method, including:

[0135] Embodiment 10: The method according to embodiment 9, wherein the selection of the sequence tuple is based at least in part on an evaluation of a predetermined criterion associated with at least one correction mark of at least one group.

[0136] Embodiment 11: A method according to embodiment 10, wherein the predetermined criteria include at least one of the following criteria: degree of wear of the at least one correction mark, contrast of the at least one correction mark, gradient image of the at least one correction mark, autocorrelation function of an image of the at least one correction mark, cross-correlation function of at least two images of the at least one correction mark.

[0137] Embodiment 12: The method according to any one of embodiments 9 to 11, wherein the sequence is repeated at least once, and in the process at least two sequence tuples comprising different subsets of correction marks are selected.

[0138] Embodiment 13: The method according to any one of embodiments 9 to 12, wherein the sequence tuple is selected to include a subset of correction marks from each of at least m groups of correction marks, where m is greater than or equal to 2, and the separation of correction marks within an individual group is less than the separation between correction marks from two different groups.

[0139] Embodiment 14: The method according to embodiment 13, wherein the selection of the sequence tuple is based at least in part on the expected number of sequences in operation.

[0140] Embodiment 15: The method according to any one of embodiments 9 to 14, wherein the selection of sequence tuples over the sequence of operations is performed according to a predetermined order.

[0141] Embodiment 16: The method according to any one of embodiments 9 to 15, wherein the selection is performed according to a cyclic order of the sequence tuples, a randomized order of the sequence tuples, and / or rows of the same sequence tuple.

[0142] Embodiment 17: A method comprising: determining a transformation of particle beam parameters associated with the two sequence tuples; performing a calibration based at least in part on the determined transformation; and 17. The method according to any one of embodiments 9 to 16, further comprising:

[0143] Embodiment 18: Determining the transformation comprises: determining relative positions of correction marks of different sequence tuples with respect to each other; determining relative positions of correction marks of different sequence tuples with respect to one or more structures of the lithography object; 18. The method according to embodiment 17, comprising at least one of:

[0144] Embodiment 19: A method according to any one of embodiments 1 to 18, wherein the calibration includes determining drift of the particle beam and / or correcting drift of the particle beam.

[0145] Embodiment 20: The method according to any one of embodiments 1 to 19, wherein the operation includes repairing the defect.

[0146] Embodiment 21 is an apparatus for generating correction marks on a lithographic object and / or calibrating operations using a particle beam, comprising: a. Means for carrying out the method according to any one of claims 1 to 20; b. Means for executing a computer program; The present invention relates to an apparatus comprising:

[0147] Embodiment 22 relates to a computer program comprising instructions which, when executed, cause an apparatus according to embodiment 21 to perform the method steps of the method according to any one of embodiments 1 to 20.

[0148] Embodiment 23: An apparatus according to embodiment 21, having a memory containing a computer program according to embodiment 22.

Claims

1. 1. A method for calibrating a movement relative to a lithographic object using at least one local group of spaced apart correction marks (A1, B1, C1; A2, B2, C2) using a particle beam, comprising the following sequence: S1. Selecting a sequence tuple (A1; A2), said sequence tuple including a subset of correction marks of said at least one group; S2. Performing a calibration based at least in part on said sequence tuple (A1;A2); S3. Performing at least some of the operations based at least in part on the performed calibration; Including, the sequence is repeated at least twice to select at least two sequence tuples containing different subsets of correction marks; selecting a first sequence tuple from a first sequence; selecting a second sequence tuple from the second sequence; selecting the first sequence tuple from a third sequence; Including, the third sequence is executed subsequent to the second sequence; The method, wherein the second sequence is executed subsequent to the first sequence.

2. The method of claim 1 , wherein the selection of the sequence tuples is based at least in part on an evaluation of predetermined criteria associated with at least one correction mark of the at least one group.

3. The predetermined criteria are the following criteria:

3. The method of claim 2, wherein the at least one of the following is included: a degree of wear of the at least one correction mark; a contrast of the at least one correction mark; a gradient image of the at least one correction mark; an autocorrelation function of an image of the at least one correction mark; and a cross-correlation function of at least two images of the at least one correction mark.

4. 3. The method of claim 1, wherein the sequence tuple is selected to include a subset of correction marks from each of at least m groups of correction marks, where m is greater than or equal to 2, and wherein a separation of the correction marks within an individual group is less than a separation across correction marks from two different groups.

5. The method of claim 4 , wherein the selection of the sequence tuples is based at least in part on an expected number of sequences in the run.

6. The method of claim 1 or 2, wherein the selection of the sequence tuples over the sequence of operations is performed according to a predetermined order.

7. The method according to claim 1 or 2, wherein the selection is performed according to a randomized order of the sequence tuples and / or according to rows of the same sequence tuple.

8. determining a transformation of particle beam parameters associated with the two sequence tuples; performing the calibration based at least in part on the determined transformation; and 3. The method of claim 1 or 2, further comprising:

9. Determining the transformation comprises: determining relative positions of correction marks of different sequence tuples with respect to each other; determining the relative positions of correction marks of different sequence tuples with respect to one or more structures of a lithography object; The method of claim 8 , comprising at least one of:

10. 1. A method for producing correction marks on a lithographic object using a particle beam, in particular for calibrating the operation, comprising: a. generating a first group of correction marks (A1, B1, C1); b. generating a second group of correction marks (A2, B2, C2); c. generating at least one third group (A3, B3, C3) of correction marks; Including, the separation of the correction marks within an individual group is less than the separation between correction marks from two different groups; a separation of the correction marks within the first group and / or within the second group being at least 5 times smaller, preferably at least 10 times smaller, particularly preferably at least 20 times smaller, than a separation between a correction mark from the first group and a correction mark from the second group.

11. The method of claim 10 , wherein the first group and / or the second group include correction marks having at least partly the same form.

12. The method according to claim 10 or 11, wherein at least one correction mark from the first group and / or the second group is made up of a plurality of geometric shapes.

13. 12. The method according to claim 10 or 11, wherein the number of correction marks from the first group and / or the second group is at least three, preferably at least four.

14. The method of claim 10 or 11, wherein said generating is based at least in part on a particle beam induced deposition process and / or a particle beam induced etching process.

15. 11. The method of claim 10, wherein the generated groups surround a working area (500) of an operation such that a connecting line between two correction marks of different groups can surround the working area (500) without crossing the working area.

16. The method of claim 1 or 2, wherein the calibration comprises determining a drift of the particle beam and / or correcting a drift of the particle beam.

17. The method of claim 1 or 2, wherein the action comprises repairing a defect.

18. 1. An apparatus for generating correction marks on a lithographic object and / or calibrating operations using a particle beam, comprising: a. means for carrying out the method of claim 1; b. Means for executing a computer program; An apparatus comprising:

19. 20. A computer program comprising instructions which, when executed, cause an apparatus according to claim 18 to perform the method steps of the method according to claim 1.

20. 20. Apparatus according to claim 18, having a memory containing a computer program according to claim 19.

Images