Method for operating a mask inspection device, control system for a mask inspection device, mask inspection device, computer program product

Abstract

A method for operating a mask inspection device, wherein a photomask (17) illuminated with EUV radiation (15) is projected onto an image sensor (24) of an EUV camera (23) by a projection lens (22). The photomask (17) is carried by a positioning system (26), the positioning system (26) being configured to change the position of the photomask (17) relative to the projection lens (22). The photomask (17) is moved relative to the projection lens (22) during an exposure process of the EUV camera (23) so that an image line (40, 41) is acquired. An image structure (35) contained in the image line (40, 41) is compared with a reference structure (34) and, in the event of a deviation between the image structure (35) and the reference structure (34), the positioning system (26) is controlled to perform a correction movement (33) of the photomask (17).The invention also relates to a mask inspection device, a control system and a computer program product.

Description

[0001] The invention relates to a method for operating a mask inspection device, a control system for a mask inspection device, a mask inspection device and a computer program product.

[0002] Photomasks are used in microlithographic projection exposure systems for the fabrication of integrated circuits with extremely small structures. The photomask, illuminated with very short-wavelength, extreme ultraviolet (EUV) radiation, is projected onto a lithography object to transfer the mask structure.

[0003] For high-quality images produced on lithographic objects, the photomask must be dimensionally accurate and free from impurities. It is known to inspect photomasks before use in a microlithographic projection exposure system or during downtime. For this purpose, a so-called aerial image of a section of the photomask is generated using a mask inspection device. In this image, the photomask is projected not onto a lithographic object, but onto the image sensor of an EUV camera. Based on the image on the sensor, an assessment can be made as to whether the photomask is free of defects and impurities.

[0004] DE 10 2014 204 876 A1 discloses an inspection method in which a sample containing a plurality of chip patterns is virtually subdivided. An optical image of the chip pattern is captured along several strip-shaped paths. DE 10 2023 110 173 B3 discloses a measuring device for inspecting photomasks, in which a pellicle is supported by a frame component and in which EUV radiation reflected from the photomask passes through the pellicle. DE 10 2023 123 098 A1 discloses a handling system for microlithographic photomasks, in which a photomask held by an alignment device is rotated about a vertical axis in a first movement sequence and then flipped about a horizontal axis in a second movement sequence. In DE 10 2023 129 754 B3 a transport and test system for a camera is described in which a vacuum flange for connection to a vacuum housing is formed on the camera housing.The vacuum flange allows an interior space to be enclosed in a vacuum-tight manner.

[0005] During operation, heat is supplied to the projection lens of the mask inspection device, which can lead to thermal expansion of its components. This thermal deformation can cause the image on the image sensor to drift. This drift can shift image lines relative to each other, potentially resulting in a photomask image composed of these lines that is not of optimal quality.

[0006] The invention is based on the objective of presenting a method for operating a mask inspection device, a control system for a mask inspection device, a mask inspection device, and a computer program product, with which the aforementioned disadvantages are reduced. This objective is achieved by the features of the independent claims. Advantageous embodiments are specified in the dependent claims.

[0007] In a method according to the invention for operating a mask inspection device, a photomask illuminated with EUV radiation is projected onto an image sensor of an EUV camera by a projection lens. The photomask is carried by a positioning system, which is designed to change the position of the photomask relative to the projection lens. During an exposure of the EUV camera, the photomask is moved relative to the projection lens so that an image line is acquired. A structure acquired in an image line is compared with a reference structure, and if there is a deviation between the structure and the reference structure, the positioning system is controlled to perform a corrective movement of the photomask.

[0008] In a mask inspection device, the image field corresponding to the area of ​​the image sensor on the surface of the photomask is small in relation to the photomask's area. A scanning movement of the positioning system moves the photomask relative to the image sensor during an exposure. This makes it possible to capture an image line extending across the length of the photomask in a single, continuous exposure. However, unlike an image line composed of individual exposures, such a continuously exposed image line offers no way to infer any drift of the projection lens from deviations between adjacent individual exposures.While drift in multiple individual images results in misalignment at the edges, in a continuously acquired image line it is impossible to distinguish whether a structure skewed in the image line is actually skewed or whether a structure that is actually straight on the photomask only appears skewed due to drift in the image line. Therefore, conventional image correction methods cannot be used in connection with a mask inspection device according to the invention.

[0009] The invention proposes to perform a comparison between an image structure contained in an image line and a reference structure, and to control the positioning system based on the degree of deviation, so that the positioning system performs a corrective movement counteracting the deviation. An image structure is information about a structure of the photomask contained in the image data. The corrective movement can be performed, in particular, to correct drift resulting from thermal deformation of the projection lens. The drift can be determined by comparison with the reference structure. Alternatively or additionally, the drift can be determined from a stitching method. The stitching method can be configured to generate an at least partially contiguous image of the mask from temporal sequences of images from the EUV camera.

[0010] Multiple image lines can be acquired. The image lines can collectively cover the entire area of ​​a photomask under inspection. Overlap can occur between any two adjacent image lines. Adjacent image lines can extend parallel to each other longitudinally. Overlap can also occur transversely. The overlap can extend over the entire length of the image lines involved. For example, between 50 and 1000 image lines, preferably between 100 and 500, can be acquired when inspecting a single photomask. The inspection of the photomask can, for example, extend over a period of between 3 and 10 hours. The acquisition of a single image line can, for example, take between 1 and 5 minutes.

[0011] The majority of image lines can be acquired sequentially. For example, the directions of a movement of the photomask relative to the EUV camera can be controlled to acquire every second image line, except for influences from The correction movement may be identical, although the directions of the movements of the photomask relative to the EUV camera for capturing successive image lines may preferably be opposite, except for influences from the correction movement.

[0012] The plane of the photomask is called the XY plane. To capture one image line, the photomask is moved in the X direction by the positioning system. To switch between two image lines, the positioning system moves in the Y direction. The correction movement can involve movement within the XY plane. It can also involve a translation within the XY plane and / or a rotation about an axis perpendicular to the XY plane.

[0013] The positioning system can have one or more additional degrees of freedom, either in addition to or as an alternative to degrees of freedom within the XY plane. These degrees of freedom can include linear movement in the Z direction. The positioning system can also include tilting movements. The tilting axis can be an axis parallel to the photomask. The positioning system can have two mutually orthogonal tilting axes. The positioning system can have a total of six degrees of freedom. The correction movement can be a superposition of movements that lie within the XY plane and movements that extend beyond the XY plane.

[0014] The projection lens can form a mechanical unit. This mechanical unit can include a frame that supports the optical elements of the projection lens. These optical elements can be mirrors with high reflectivity for EUV radiation. To enable the desired image from the photomask onto the image sensor of the EUV camera, the photomask must be positioned appropriately relative to the projection lens. The positioning system can be a separate mechanical unit that allows the photomask to be moved relative to the projection lens.

[0015] The mask inspection device can include a measuring device for detecting the position of the photomask relative to the projection lens. This measuring device can be an optical measuring device, for example, in the form of an interferometer. The measuring device can be designed to detect the distance to one or more reference points. In one embodiment, the measuring device is mounted on the projection lens, and the reference points are in a known spatial relationship to the photomask. The reference points can, for example, be located on the photomask itself or on a component of the positioning system. Alternatively, it is also possible that the measuring device is in a known spatial relationship to the photomask, for example, by being mounted on the positioning system, and that the reference points are located on the projection lens.

[0016] The measured values ​​supplied by the measuring device can be evaluated to obtain information about the actual position of the photomask relative to the projection lens. The actual position can be compared with a target position. If there is a deviation between the actual and target positions, the positioning system can be controlled with an initial control signal to reduce the difference. The movement of the positioning system can include translation and / or rotation. All degrees of freedom of the positioning system can be utilized during this movement.

[0017] Such a correction based on measured values ​​from the measuring device cannot correct imaging errors resulting from drift within the projection lens, such as those caused by thermal deformation. Even if the photomask is correctly positioned relative to the projection lens with respect to the measured values, imaging errors can still occur. Therefore, the invention proposes processing an additional input variable when controlling the positioning system.

[0018] The additional input parameter is determined by comparing an image structure acquired in an image line with a reference structure. This reference structure can extend along the photomask in the X-direction, i.e., in the direction in which the photomask moves when capturing an image line. With error-free imaging, such an image structure should extend in a direction corresponding to the X-direction of the captured image line. If the longitudinal direction of the image line corresponds to the X-direction, then the image structure in question extends parallel to the longitudinal direction of the image line with error-free imaging. The reference structure can be oriented and positioned as expected for the image structure with error-free imaging. If there is a deviation between the image structure and the reference structure, the positioning system can be controlled to reduce the deviation.

[0019] The invention is not limited to a specific method of representing the reference structure. The reference structure can be derived from a reference image and be in the form of image data. The reference structure can be defined by suitable coordinate specifications. In one embodiment, the reference structure is obtained by pattern recognition. For example, if it is known that a specific pattern has a specific position on the photomask, this pattern can be searched for in the image row, and a deviation between the orientation of the pattern in the image row and the orientation of the reference pattern can be determined.

[0020] In the method according to the invention, it is important that structures aligned in the X-direction on the photomask extend parallel to each other in the image projected onto the image sensor, so that a complete image of the photomask can be generated from several adjacent image lines. The image lines can be captured such that there is an overlap between two adjacent image lines in the Y-direction. The image lines can be joined together in such a way that the image structures of the adjacent image lines match each other within the overlap area. In particular, the image lines can be shifted relative to each other in the X-direction for this purpose. A drift that has an effect in the X-direction therefore does not necessarily mean that the image lines can no longer be joined to form an error-free image.Regardless, the procedure can be carried out in such a way that deviations in the X-direction are also detected and corrected by appropriate control of the positioning system. The corrective movement can include a translation and / or a rotation of the photomask. The corrective movement can utilize all degrees of freedom of the positioning system.

[0021] Imaging errors that manifest in the Y-direction can cause the width of the overlap area to change. If the imaging error becomes so large that there is no longer any overlap between adjacent image lines, a seamless image of the photomask can no longer be generated. The method according to the invention can be carried out in such a way that an overlap area is maintained between two adjacent image lines along their entire length. Since very large amounts of data, for example on the order of several tens of gigabytes per second, are generated during the operation of the mask inspection device, it is desirable to keep the overlap area as small as possible. The width of the overlap area can be less than 10%, preferably less than 5%, and more preferably less than 2% of the width of an image line.

[0022] A correction movement of the positioning system triggered by a deviation between an image structure and a reference structure can be performed discretely in time. For example, a drift that occurred during the acquisition of a preceding image line can be detected during or after the acquisition of that line. A transition phase between the acquisition of the image line and the acquisition of an immediately subsequent image line can be used to execute a correction movement to correct the drift. The correction movement can be completed before the acquisition of the subsequent image line. A corresponding sequence of determining the necessary correction movement and executing the correction movement can be performed for multiple pairs of consecutive image lines, in particular for all pairs of consecutive image lines.This approach has the advantage that an image line can be captured without the capture being superimposed by a correction movement.

[0023] It is also possible to perform a photomask correction while an image line is being acquired. For this, it is advantageous to obtain information about the temporal evolution of any drift by comparing an image structure with a reference structure. If the temporal evolution of the drift is known, this information can be used to control a continuous correction movement of the positioning system. The correction movement can extend continuously over the entire duration of the acquisition of an image line. In this way, a correction that occurred during the acquisition of a previous image line can also be applied to the acquisition of a subsequent image line.

[0024] An image sensor is exposed when EUV radiation strikes it, and the sensor generates charge carriers based on the incident EUV radiation. These charge carriers can then be read out to obtain image data. According to the invention, an image is generated from image data when the image data is provided in a form that allows inferences to be drawn about structures present on the photomask. Generating an image does not require that the image be physically produced or presented in a form perceptible to humans.

[0025] The image sensor can comprise a large number of pixels, thus spanning a pixel array with a large number of pixel rows. The pixel rows can extend in a direction corresponding to the X-direction, meaning that a movement of the photomask in the X-direction corresponds to a movement parallel to the longitudinal direction of the pixel rows. It is also possible for the pixel rows to enclose an angle other than 0° with the X-direction. This angle can be less than 5°, preferably less than 2°, and more preferably less than 1°. The pixel sensor can be designed to be read out row by row. The width of an image row can be determined by the image data acquired from multiple pixel rows, in particular by the data acquired from all pixel rows together.

[0026] The method can be carried out by shifting charge carriers generated by incident EUV radiation within the image sensor from pixel to pixel within a pixel row before the number of charge carriers is read out. The displacement speed of the charge carriers can be matched to the speed at which the photomask is moved in the X-direction. This makes it possible to sum the charge carriers generated by the image, which has a beneficial effect on the accuracy and signal-to-noise ratio of the acquired data. The image sensor can be designed as a CCD sensor (charge-coupled device) or as a CMOS sensor (complementary metal-oxide semiconductor). In one embodiment, the image sensor is designed as a TDI sensor (time-delay and integration).

[0027] The photomask can have an aspect ratio between 1:1 and 1:3, preferably between 1:1 and 1:2, and most preferably between 1:1 and 1:2. The photomask can be substantially rectangular. The photomask can preferably be 5 to 7 inches (12.7 cm to 17.8 cm) long and wide, and most preferably 6 inches (15.2 cm) long and wide. Alternatively, the photomask can be 5 to 7 inches (12.7 cm to 17.8 cm) long and 10 to 14 inches (25.4 cm to 35.6 cm) wide, and more preferably 6 inches (15.2 cm) long and 12 inches (30.5 cm) wide.

[0028] The invention also relates to a control system for a mask inspection device, wherein the control system is designed to control an image sensor and a positioning system such that, during an exposure process of the image sensor, a photomask carried by the positioning system is moved relative to a projection lens, thereby capturing an image line. The control system is further designed to generate a control signal for the positioning system by comparing an image structure contained in the image line with a reference structure, so that the positioning system performs a corrective movement of the photomask. The invention further relates to a mask inspection device equipped with such a control system.

[0029] The invention also relates to a computer program product or a set of computer program products comprising program parts which, when loaded into a computer or into interconnected computers connected to a control system according to the invention, are designed to carry out the method according to the invention.

[0030] The disclosure includes further developments of the method with features that are described in connection with the control system according to the invention.

[0031] The invention is described below by way of example with reference to the accompanying drawings and advantageous embodiments. The drawings show: Fig. 1: a schematic representation of a mask inspection device; Fig. 2: a schematic representation of a photomask; Fig. 3: a schematic representation of aspects of an EUV camera; Fig. 4: a schematic representation of a projection lens of the mask inspection system; Fig. 5: a schematic representation of the image lines on a photomask without drift correction according to the invention; Fig. 6: a schematic representation of a comparison between an image structure and a reference structure; Fig. 7: a schematic representation of the projection lens of the mask inspection device with control system according to the invention; Fig. 8: a schematic representation of the image lines on a photomask with drift correction according to the invention.

[0032] With a Fig. Microlithographic photomasks 17 can be examined using the mask inspection device shown in Figure 1.

[0033] Microlithographic photomasks 17 are generally intended for use in a microlithographic projection exposure system (not shown). In the microlithographic projection exposure system, the photomask 17 is illuminated with extreme ultraviolet (EUV) radiation with a wavelength of, for example, 13.5 nm to image a structure formed on the photomask 17 onto the surface of a lithographic object in the form of a wafer. The wafer is coated with a photoresist that reacts to the EUV radiation. The mask inspection device is used to check whether the photomask meets the specifications and is free of contaminants.

[0034] The mask inspection device is designed according to Fig. 1. The photomask 17 is arranged such that an EUV beam path 15 emanating from an EUV radiation source 14 is directed onto the photomask 17 via an illumination system 16. The illumination system 16 shapes the EUV radiation into a beam that illuminates an inspection area 20 on the surface of the photomask 17 with uniform brightness. The inspection area 20, which is small in relation to the area of ​​the photomask 17, is shown in a representation not to scale in Fig. Figure 2 shows that the illuminated area 20 can, for example, have dimensions of 0.5 mm x 0.8 mm. A field stop is arranged in the illumination system 16, which limits the illuminated area to the examination field 20 on the surface of the photomask 17. An XY positioner 26 can be used to move the photomask in the XY plane 18 in order to bring different examination fields 20 into the area of ​​the EUV beam path 15.

[0035] The edge lengths of the photomask 17 can, for example, be between 100 mm and 200 mm. The photomask can have an aspect ratio between 1:1 and 1:3, preferably between 1:1 and 1:2, and particularly preferably between 1:1 or 1:2. The photomask can be substantially rectangular. The photomask can preferably be 5 to 7 inches (12.7 cm to 17.8 cm) long and wide, and particularly preferably 6 inches (15.2 cm) long and wide. Alternatively, the photomask can be 5 to 7 inches (12.7 cm to 17.8 cm) long and 10 to 14 inches (25.4 cm to 35.6 cm) wide, and preferably 6 inches (15.2 cm) long and 12 inches (30.5 cm) wide.

[0036] The EUV beam path 15, reflected at the photomask 17, continues via a projection lens 22 to an EUV camera 23, which is equipped with an image sensor 24. The projection lens maps the inspection field 20 of the photomask 17 onto the image sensor 24 of the EUV camera 23. The EUV radiation source 14, the illumination system 16, the photomask 17, the projection lens 22, and the EUV camera 23 are arranged in a vacuum housing 40, in which a negative pressure is maintained during operation of the mask inspection device.

[0037] The EUV radiation source 14 is a plasma radiation source in which EUV radiation with a wavelength of 13.5 nm is emitted from a plasma. Tin is a medium suitable for generating a plasma for emitting such EUV radiation. To generate the plasma, a droplet of the medium can be exposed to a laser beam.

[0038] The illumination system 16 and the projection lens 22 can include mirrors that reflect the EUV radiation. These mirrors can be designed as EUV mirrors, exhibiting particularly high reflectivity for EUV radiation. The optical surface of the EUV mirrors can be formed by a highly reflective coating. This can be a multilayer coating, in particular a multilayer coating with alternating layers of molybdenum and silicon. With such a coating, approximately 70% of the incident EUV radiation can be reflected.

[0039] The projection lens 22 has a magnification factor of more than 100. In order to fully capture the image generated by the field of view 20 of the photomask 17, the area of ​​the image sensor 24 is larger than the area of ​​the field of view 20, corresponding to the magnification factor. The image sensor 24 can, for example, have dimensions on the order of 100 mm to 200 mm. The image sensor 24 comprises a plurality of parallel pixel rows 36, which span a pixel array 50. The image sensor 24 is oriented such that the longitudinal direction of the pixel rows 36 corresponds to the X-direction. When the photomask 17 moves in the X-direction, the image of the photomask 17 moves on the image sensor 24 parallel to the longitudinal direction of the pixel rows 36.

[0040] The EUV camera 23 includes, according to Fig. 3 A control unit 30 communicates with the image sensor 24. The control unit 30 controls the image sensor 24, among other things to determine the times at which the image sensor 24 is exposed to take an image. In each pixel 31, the amount of incident EUV radiation is then registered and converted into a corresponding number of free charge carriers. Image data can be obtained by reading the number of charge carriers for each pixel 31.

[0041] The image sensor 24 is read out by moving the charge carriers generated by a pixel 31 in each pixel row 36 from pixel to pixel in the scan direction 32. With each movement step, the charge carriers from the last pixel of a pixel row 36 are moved into a readout cell 37. The number of charge carriers is determined in the readout cell 37. Information about the number of charge carriers in a readout cell 37 is transmitted as image information to the control unit 30.

[0042] The image sensor 24 can be configured such that, in a single readout step, the charge carriers in all pixel rows 36 are simultaneously shifted by one pixel 31, so that charge carriers for each pixel row 36 are transferred to a corresponding readout cell 37. The image data acquired jointly from all pixel rows 36 spans the width of an image row 40. An image row 40 extends in the X direction over the entire length of the photomask 17. With several parallel image rows 40, an image of the entire photomask 17 is generated.

[0043] By moving the photomask 17 relative to the image sensor 24 with the positioning system 26 during an exposure process of the image sensor 24, the field of investigation 20 is, as Fig. 5 schematically depicted, guided in the X-direction across the photomask 17, so that a first image line 40 is captured. This allows the first image line to be captured in a continuous exposure process. An image structure 35 extending in the X-direction on the photomask 17 has an orientation in an image line 40 captured by the image sensor 24 that is parallel to the longitudinal direction of the image lines 36.

[0044] The process then switches from the first image line 40 to a second image line 41 by moving the positioning system 26 in the Y direction. The second image line 41 has a scan direction opposite to the first image line 40, so the inspection field 20 is moved in the negative X direction over the photomask 17, thus capturing an image line 41. This process is repeated until the entire photomask 17 has been exposed.

[0045] To create a complete image of the photomask from the adjacent image lines, the image lines are captured in such a way that there is an overlap between neighboring image lines in the Y direction. Based on image structures in this overlapping area, the image lines can then be assembled into a complete image of the photomask.

[0046] The image quality on the image sensor depends on the precise positioning of the photomask 17. The relative position of the photomask 17 to the projection lens 22 is determined as shown in Fig. Figure 4 shows the measurement being taken with a measuring device 51 attached to the projection lens 22. The measuring device 51 is designed as an interferometer and measures the distance to several reference points of the photomask 17. A measurement signal from the measuring device 51 is used to control the positioning system 26 and to align the photomask 17 relative to the projection lens 22.

[0047] The projection lens 22 comprises several optical elements M1-M4, which guide the EUV beam path from the photomask to the EUV camera 23 and the image sensor 24. Thermal influences can cause drifts within the projection lens 22, leading to a change in the position of the optical elements M1-M4 of the projection lens 22. This can result in a shift of the field of view 20 on the photomask. These drifts within the projection lens 22 are not detected by the measuring device 51 and therefore are not corrected.

[0048] This means that the investigation area 20, as in Fig. Figure 5 schematically illustrates how, due to drift, the image is guided over the photomask in such a way that a first image line 43 and a second image line 44 are captured. The resulting image lines 43 and 44 are spaced apart in the Y direction such that there is no overlap between them. To ensure the required overlap of adjacent image lines for image quality, the drift-related deviations must be corrected according to the invention.

[0049] Such a drift error can be detected by comparing an image structure 35 recorded with image lines 43, 44 with a reference structure 34, see Fig. 6. The comparison reveals that the image structure 35 does not have the expected alignment within the image line 43, 44.

[0050] As in Fig. As shown in Figure 7, the image structures of the individual image lines 43, 44, captured by the EUV camera 23 with the image sensor 24, are evaluated by a computer 53 to perform a comparison between the image structure 35 and the reference structure 34. A signal 54 is generated from the deviation of the captured image structure 35 and the reference structure 34 and transmitted to a control unit 55. The control unit 55 controls the positioning system 26 of the photomask 17 such that the positioning system 26 performs a corrective movement so that the X-direction of the movement of the photomask 17 again corresponds to the longitudinal direction of the pixel rows 36.

[0051] Furthermore, deviations of the target position of the photomask relative to the projection lens 22, as detected by the measuring device 51, are transmitted to the control unit 55. The control unit 55 controls the positioning system 26 in such a way that the corrective movement compensates for both the deviations from the relative position of the photomask 17 to the projection lens 22 and deviations caused by drift.

[0052] In Fig.Figure 8 is a schematic representation of the image lines illuminated on the photomask 17 with a correction movement 33 of the positioning system 26. The field of investigation 20 is moved along image lines 40, 41, 45, 46, 47 by implementing the correction movements of the positioning system 26. Within the second image line 41, a drift 29 occurs, which is schematically indicated and is detected by a comparison between an image structure 35 and a reference structure 34. In a transition phase 39 between the second image line 41 and a subsequent image line 45, the positioning system 26 is controlled such that the photomask 17 within the XY plane 18 performs a correction movement 33 in the form of a rotation about an axis perpendicular to the XY plane, so that the X direction is again aligned with the longitudinal direction of the pixel lines 36.The resulting image lines 40, 41, 45, 46, 47 are laterally adjusted such that they overlap in the Y-direction within an overlap area 56. The width of the overlap area 56 is less than 2% of the width of an image line. The overlap areas of adjacent image lines are used to assemble the individual image lines into a complete image.

Claims

[1] Method for operating a mask inspection device, wherein a photomask (17) illuminated with EUV radiation (15) is imaged by a projection lens (22) onto an image sensor (24) of an EUV camera (23), wherein the photomask (17) is carried by a positioning system (26), the positioning system (26) being configured to change the position of the photomask (17) relative to the projection lens (22), the photomask (17) being moved relative to the projection lens (22) during an exposure process of the EUV camera (23) so that an image line (40, 41) is acquired, an image structure (35) contained in the image line (40, 41) being compared with a reference structure (34), and in the event of a deviation between the image structure (35) and the reference structure (34), the positioning system (26) being controlled to initiate a corrective movement (33) to perform the photomask (17). [2] Method according to claim 1, wherein a plurality of image lines (40, 41, 45, 46, 47) are recorded and wherein there is an overlap (56) between each two adjacent image lines. [3] Method according to claim 1 or 2, wherein the correction movement (33) comprises a movement within the XY plane (18), wherein the XY plane (18) corresponds to a plane spanned by the photomask (17). [4] Method according to claim 3, wherein the correction movement (33) comprises a translation within the XY plane (18). [5] Method according to claim 3 or 4, wherein the correction movement comprises a rotation about an axis perpendicular to the XY plane (18). [6] Method according to any one of claims 1 to 5, wherein the correction movement comprises a tilting movement about a tilting axis parallel to the photomask (17). [7] Method according to any one of claims 1 to 6, wherein the position of the photomask relative to the projection lens (22) is detected by a measuring device (51). [8] Method according to claim 7, wherein the measuring device (51) is designed as an optical measuring device, in particular as an interferometric measuring device. [9] Method according to any one of claims 1 to 8, wherein the image structure (35) contained in the image line (40, 41) depicts a structure which extends on the photomask (17) in the X direction, wherein the X direction corresponds to the direction in which the photomask (17) is moved during an exposure process of the EUV camera (23). [10] Method according to any one of claims 1 to 9, wherein a plurality of correction movements (33) of the photomask (17) is performed and wherein the correction movements (33) are performed discretely in time. [11] Method according to any one of claims 1 to 10, wherein in a transition phase (39) between the acquisition of a first image line (41) and the acquisition of an immediately following second image line (45) the correction movement (33) of the photomask (17) or part of the correction movement (33) of the photomask (17) is carried out. [12] Method according to any one of claims 1 to 11, wherein the correction movement (33) of the photomask (17) or part of the correction movement (33) of the photomask (17) is performed while an image line (40, 41) is being recorded. [13] Method according to any one of claims 1 to 12, wherein a drift (29) that occurred during the recording of a first image line (41) is determined and wherein a correction movement (33) of the photomask (17) is carried out to correct the drift (29) before the recording of a subsequent second image line (45). [14] Control system for a mask inspection device, wherein the control system is designed to control an image sensor (24) and a positioning system (26) such that during an exposure process of the image sensor (24) a photomask (17) carried by the positioning system (26) is moved relative to a projection lens (22) so that an image line (40, 41) is recorded, and wherein the control system is designed to generate a control signal for the positioning system (26) by comparing an image structure (35) contained in the image line (40, 41) with a reference structure (34) so ​​that the positioning system (26) performs a correction movement of the photomask (17). [15] Mask inspection device comprising an EUV camera (23), a positioning system (26) for a photomask and a projection lens (22) for imaging the photomask (17) onto an image sensor (24) of the EUV camera (23), wherein the positioning system (26) is designed to move the photomask (17) while the image sensor (24) is exposed so that an image line (40, 41) is captured, further comprising a control system according to claim 14 for controlling the positioning system (26). [16] Computer program product or set of computer program products, comprising program parts which, when loaded into a computer or into interconnected computers connected to a control system according to claim 14, are designed to carry out the method according to any one of claims 1 to 13.

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