Method for examining blank of microlithographic photomask

Abstract

To provide a method for examining a blank of a microlithographic photomask.SOLUTION: The method for examining a blank of a microlithographic photomask, includes the steps of: a) arranging the blank on a first stage of a first examination apparatus such that a first and a second edge of the blank rest against stops of the first stage (S1); b) ascertaining an examination location on the blank in a first coordinate system by using the first examination apparatus (S2); c) arranging the blank on a second stage of a second examination apparatus having an image recording unit (S3); d) recording at least one image of the blank using the image recording unit such that the first and second edge are captured at least in part (S4); and e) ascertaining a transformation rule on the basis of the first and second edge captured in the at least one image, in order to transform the examination location captured in the first coordinate system into a second coordinate system of the second examination apparatus (S5).SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for inspecting a blank of a microlithography photomask.

[0002] The content of German Patent No. 102023130586.7 is incorporated herein by reference in its entirety.

Background Art

[0003] Microlithography is used to manufacture components with microstructures, such as integrated circuits. The microlithography process is carried out using a lithography apparatus having an illumination system and a projection system. An image of a mask (reticle or lithography mask) illuminated by the illumination system is projected by the projection system onto a substrate, such as a silicon wafer, coated with a photosensitive layer (photoresist) and disposed in the image plane of the projection system, in order to transfer the mask structure to the photosensitive coating of the substrate.

[0004] Mask blanks are processed for these purposes such that each mask structure is provided. The created mask structure is scaled down and projected onto the substrate. The mask structure itself is already very small, for example, having dimensions in the range of several micrometers to several nanometers. In order to generate components with microstructures very precisely using microlithography, the lithography mask structure must also be manufactured very precisely, and the mask must be free of defects (for example, defective structures and contamination). Since lithography masks are usually used for multiple exposures, defect-free lithography masks are also very important. Therefore, lithography masks are inspected at great expense with respect to defects. Subsequently, attempts are made to repair the identified defective structures or remove the contamination. The defects can also be extremely small, for example, having a size on the order of several nanometers. Therefore, the operations related to the inspection of lithography masks and blanks for lithography masks should be carried out with high spatial resolution and accuracy.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] Against such a background, an object of the present invention is to provide an improved method for inspecting a blank of a microlithography photomask.

MEANS FOR SOLVING THE PROBLEMS

[0006] Therefore, a method for inspecting a blank of a microlithography photomask is proposed. This method includes the following steps, namely, a) placing the blank on a first stage such that first and second edges of the blank abut against stoppers of the first stage of a first inspection apparatus; b) using the first inspection apparatus to determine inspection positions on the blank in a first coordinate system; c) placing the blank on a second stage of a second inspection apparatus having an image recording unit; d) using the image recording unit to record at least one image of the blank such that the first and second edges are at least partially captured; e) determining a conversion rule based on the first and second edges captured in the at least one image in order to convert the inspection positions captured in the first coordinate system into a second coordinate system of the second inspection apparatus and includes.

[0007] In the inspection of a photomask blank, the proposed method enables the use of two different inspection apparatuses (i.e., a first and a second inspection apparatus) having different coordinate systems (i.e., a first and a second coordinate system). For example, the blank has no structure for reproducibly arranging the blank on the stages of the two inspection apparatuses (i.e., a first and a second stage), e.g., no markers. If there is no structure or marker (a "registration marker") useful for reproducibly arranging the blank, or if these are not used, in the proposed method, on the first stage of the first inspection apparatus, it becomes possible to bring the first and second edges of the blank into contact with the stoppers of the first stage. Further, when the blank is arranged on the second stage of the second inspection apparatus, the positions of the first and second edges of the blank can be determined by image processing. Then, this can be used to determine a conversion rule for converting the spatial coordinates from the first coordinate system to the second coordinate system. As a result, the inspection positions (e.g., defect positions) on the blank determined by the first inspection apparatus can be converted to the second coordinate system of the second inspection apparatus. Thus, the inspection positions determined by the first inspection apparatus can be further inspected by the second inspection apparatus (e.g., with a higher spatial resolution compared to the first inspection apparatus).

[0008] Furthermore, the first and second edges of the blank that contact the stopper of the first inspection apparatus can be any desired edges of the blank. Further, the second inspection apparatus can also be provided with a stopper that serves to contact the edge of the blank. The proposed method does not require the stopper of the second inspection apparatus to contact the same edge and / or the same position on the corresponding edge as the stopper of the first inspection apparatus.

[0009] The blank is a blank for a lithography mask. For example, the blank is a blank for a transmissive lithography mask for DUV lithography (DUV: "deep ultraviolet", operating light wavelength in the range of 30 to 250 nm), or a blank for a reflective lithography mask for EUV lithography (EUV: "extreme ultraviolet", in the range of 1 to 30 nm, particularly an operating light wavelength of 13.5 nm).

[0010] The blank includes, for example, a substrate. For example, the substrate includes silicon dioxide (SiO2), such as quartz glass, and / or an alternating arrangement of a molybdenum layer and a silicon layer.

[0011] For example, in principle, the blank does not yet contain any structure (e.g., any absorber structure or phase shift structure) that is projected onto the substrate during the microlithography process. In particular, the blank does not contain any marker ("alignment marker") that serves for a reproducible placement of the blank on the stage of one or more inspection apparatuses.

[0012] For example, the blank is within a predetermined tolerance with respect to its outer dimensions. For example, the blank is within a predetermined tolerance with respect to its outer dimensions in accordance with the international standards for DUV lithography masks and / or EUV lithography masks. For example, the international standards for DUV lithography masks and / or EUV lithography masks are the international standard "SEMI P1" (e.g., SEMI P1 2008 Edition, July 2008) and / or the international standard "SEMI P37" ("Specification for Extreme Ultraviolet Lithography Substrates and Blanks"). As a mere example, a 6-inch blank according to the "SEMI P1" standard is within a tolerance of + / -400 μm with respect to width and length.

[0013] For example, the first inspection device is configured to recognize one or more blank defects, such as contamination. For example, the first inspection device is configured to create a list of the determined positions of the recognized defects. In this case, the inspection positions determined in step b) are, for example, the positions of the recognized defects.

[0014] The first inspection device has, for example, a spatial resolution in the range of 0.5 μm to 25 μm. The first inspection device includes, for example, an image recording device having a spatial resolution in the range of 0.5 μm to 25 μm. Alternatively or in addition, the first inspection device can be configured to detect blank defects, for example, by light scattering. In this case, the spatial resolution of the first inspection device is better than 0.5 μm and can be, for example, 100 nm or less and / or 50 nm or less.

[0015] For example, the first stage includes one or more elastic elements under tension in addition to stoppers configured to abut against the first and second edges of the blank. For example, one or more elastic elements press the blank against the stoppers of the first stage. For example, in step a), the first elastic element under tension is disposed on the third edge of the blank on the opposite side of the first edge. For example, the second elastic element under tension is disposed on the fourth edge of the blank on the opposite side of the second edge.

[0016] For example, the blank includes a main extension surface. Further, the first and second edges of the blank are disposed on the main extension surface. In particular, the first and second edges of the blank are edges of the blank that form an angle with each other and are, for example, (substantially) perpendicular to each other. For example, the first and second edges are adjacent edges. If the blank includes rounded and / or chamfered corners, for example, only the rounded and / or chamfered corners are disposed between the first edge and the second edge.

[0017] In particular, the first coordinate system is the coordinate system of the first inspection device. For example, both the first and second coordinate systems are right-handed orthogonal coordinate systems. For example, both the first coordinate system and the second coordinate system are two-dimensional coordinate systems. For example, both the first and second coordinate systems have a horizontal axis and a vertical axis arranged perpendicular to each other.

[0018] In step b), using the first inspection device, a plurality of inspection positions on the blank can also be determined in the first coordinate system. For example, in step b), one or more inspection positions are determined on the surface of the blank.

[0019] In particular, the second inspection device includes an image recording unit. For example, the second stage of the second inspection device can also be provided with one or more stoppers that serve to abut against the first edge, the second edge, the third edge (for example, arranged on the opposite side of the first edge), and / or the fourth edge (for example, arranged on the opposite side of the second edge) of the blank.

[0020] By the proposed method, for example, even when the stoppers of the second stage abut against different edges of the blank (for example, the third and fourth edges) from the stoppers of the first stage that abut against the first and second edges of the blank, an accurate coordinate transformation from the first coordinate system to the second coordinate system becomes possible.

[0021] The conversion rule is determined based on the first and second edges captured in at least one image. In particular, thereby, the positions of the first and second edges captured in at least one image can be determined in the second coordinate system of the second inspection device.

[0022] For example, step e) of the method includes the step of determining the positions of the first and second edges in both the first and second coordinate systems based on image processing of at least one image.

[0023] For example, the conversion rule is a mathematical conversion rule. For example, the conversion rule includes a conversion matrix and / or an affine conversion matrix. For example, the conversion rule includes rotation by a rotation angle and / or translation by a translation vector. The conversion rule is useful for, for example, two-dimensional coordinate conversion between a first coordinate system and a second coordinate system. For example, the conversion rule is used to perform a basis conversion between a first coordinate system and a second coordinate system.

[0024] According to one embodiment, the second inspection device includes a scanning microscope device, a scanning electron microscope device, a scanning probe microscope device, and / or an atomic force microscope device.

[0025] For example, a scanning microscope device, a scanning electron microscope device, a scanning probe microscope device, and / or an atomic force microscope device are configured to record at least one image of the blank. Using these devices, at least one image of the blank in which the first and second edges are at least partially captured can be recorded with high spatial resolution. As a result, the positions of the first and second edges (and / or the positions of the reference points on the first and second edges) can be determined more accurately, thereby enabling coordinate conversion according to the conversion rule to be performed with higher accuracy.

[0026] In particular, the scanning microscope device includes a scanning electron microscope (SEM), a scanning probe microscope (SPM), an atomic force microscope (AFM), and / or a scanning tunneling microscope (STM).

[0027] According to a further embodiment, the spatial resolution of the image recording unit of the second inspection device is 100 μm or less, 50 μm or less, 30 μm or less, 10 μm or less, 5 μm or less, 1 μm or less, 0.1 μm or less, 50 nm or less, 10 nm or less, 5 nm or less, and / or 3 nm or less.

[0028] The higher the spatial resolution used to record at least one image, the more accurately the positions of the first and second edges (and / or the positions of the reference points on the first and second edges) can be determined by image processing, and thus the conversion rule can be determined more accurately.

[0029] According to a further embodiment, one or more defects of the blank are inspected in the method. Further, the position of at least one defect of the blank is determined in a first coordinate system using a first inspection device in step b). Further, the determined conversion rule serves to convert the position of at least one defect detected in the first coordinate system into a position in a second coordinate system.

[0030] Thus, the position of one or more defects of the blank can be determined by the first inspection device. For example, a list of the positions of the defects of the blank can be created by the first inspection device. The position of one or more defects of the blank determined by the first inspection device, or the determined list of the positions of the defects of the blank, can be transmitted, for example, to a second inspection device.

[0031] As a result of the position of the defect determined by the first inspection device being converted into the second coordinate system of the second inspection device by the conversion rule, the defect can be found more easily by the second inspection device.

[0032] Furthermore, based on the data transmitted by the first inspection device, the defect can be inspected more accurately (e.g., with higher resolution) by the second inspection device.

[0033] According to a further embodiment, the method, after step e), includes the step of recording at least one image of at least one defect using an image recording unit of the second inspection device, the image recording unit being aligned based on the position of at least one defect converted into the second coordinate system.

[0034] For example, based on the position of at least one defect converted to the second coordinate system, the image details from the image recording unit are selected. For example, the position of at least one defect converted to the second coordinate system is located at the center of the image details.

[0035] For example, the second inspection device can also be configured to remove defects (e.g., particles) from the surface of the blank. For example, the second inspection device includes a micromanipulator and / or a nanomanipulator that serves to move and / or remove particles from the surface of the blank.

[0036] According to a further embodiment, the first stage includes first, second, and third stoppers. The blank is placed on the first stage such that the first edge abuts against the first and second stoppers and the second edge abuts against the third stopper, and as a result, the first, second, and third reference points of the blank are defined accordingly at the contact positions of the first, second, and third stoppers on the first and second edges. Further, in step d), an image of the blank is recorded for each reference point, and the corresponding reference point is captured in the image. Further, the conversion rule is determined based on the first, second, and third reference points captured in the recorded image.

[0037] That is, based on the recorded image, the positions of the first and second edges at the three reference points are determined, and the three stoppers of the first inspection device are in contact at the said reference points. This is advantageous when the edge of the blank (e.g., the first and / or second edge) deviates from a straight line (e.g., in relation to the resolution of the second inspection device). Therefore, even when the edge of the blank is not 100% straight (e.g., in relation to the resolution of the second inspection device), the conversion rule can be accurately determined.

[0038] In particular, the contact positions where the first edge of the blank abuts against the first and second stoppers of the first stage of the first inspection device respectively define the first and second reference points of the blank. Further, the contact position where the second edge of the blank abuts against the third stopper of the first stage defines the third reference point of the blank.

[0039] For example, step e) of the method includes determining the respective positions of the first, second and third reference points in each case of the first and second coordinate systems based on image processing for at least one image.

[0040] According to a further embodiment, the positions of the first and second reference points in the second coordinate system are determined based on image processing for the corresponding recorded images, and / or the position of the third reference point in the second coordinate system is determined based on image processing for the corresponding recorded images.

[0041] For example, here it is assumed that the first coordinate system of the first inspection device corresponds to the coordinate system of the blank. In other words, here it is assumed that either the blank is placed on the first stage without deviation with respect to the first coordinate system of the first inspection device in step a), or such a deviation is initially unknown and ignored for the sake of simplicity.

[0042] According to a further embodiment, the transformation rule includes rotation by a rotation angle and / or translation by a translation vector. Further, the rotation angle is determined based on the determined positions of the first and second reference points in the second coordinate system, and / or the vector components of the translation vector are determined based on the determined position of the third reference point in the second coordinate system and the determined positions of the first or second reference points in the second coordinate system.

[0043] For example, the first coordinate system of the first inspection device is twisted by a rotation angle (e.g., counterclockwise) with respect to the second coordinate system of the second inspection device. That is, the angle between a line arranged parallel to the first horizontal axis of the first coordinate system and a line arranged parallel to the second horizontal axis of the second coordinate system corresponds to the rotation angle. In that case, the rotation angle can be calculated from a right-angled inclined triangle formed by the line arranged parallel to the first horizontal axis and the line arranged parallel to the second horizontal axis. For example, the inclined triangle is formed such that the length of the opposite side Δy of this right-angled inclined triangle is given by the distance between the vertical coordinate positions of the first reference point and the second reference point in the second coordinate system. Further, the inclined triangle is formed such that, for example, the length of the adjacent side Δx of this right-angled inclined triangle is given by the distance between the horizontal coordinate positions of the first reference point and the second reference point in the second coordinate system. Further, the length Δu of the hypotenuse of the inclined triangle is given, in particular, by the distance between the horizontal coordinate positions of the first reference point and the second reference point in the first coordinate system.

[0044] Therefore, the length Δy of the opposite side of this right-angled inclined triangle can be calculated from the distance between the determined vertical coordinate positions of the first and second reference points in the second coordinate system.

[0045] Furthermore, assuming that the rotation is very small, the length Δx of the adjacent side of this right triangle can be assumed to be approximately the same as the length Δu of the hypotenuse of this right triangle.

[0046] For example, the distance between the first reference point and the second reference point in the first coordinate system, i.e., the length of the hypotenuse Δu, can be determined from the pre-determined structural data of the first inspection device. For example, the pre-determined structural data of the first inspection device includes the pre-determined distance between the first stopper and the second stopper of the first stage of the first inspection device. Further, the first reference point of the blank corresponds to the first stopper of the first stage of the first inspection device. Further, the second reference point of the blank corresponds to the second stopper of the first stage. Therefore, the distance between the first reference point and the second reference point of the blank in the first coordinate system can be determined based on the pre-determined distance between the first stopper and the second stopper of the first stage of the first inspection device.

[0047] Next, the rotation angle Θ can be approximately obtained from the arctangent of the quotient of the opposite side Δy and the adjacent side Δx (assuming that the adjacent side is approximately the same size as the hypotenuse Δu as described above).

Number

[0048] Alternatively, the rotation angle Θ can also be directly obtained from the arcsine of the quotient of the opposite side Δy and the hypotenuse Δu.

Number

[0049] As a result, using the determined rotation angle Θ, the distance Δx between the first reference point and the second reference point in the second coordinate system can be calculated based on the cosine of the rotation angle Θ. Δx = ΔucosΘ

[0050] Alternatively, the distance Δx between the first reference point and the second reference point in the second coordinate system can also be calculated based on the Pythagorean theorem.

Number

[0051] Optionally, the calculation of the distance Δx between the first reference point and the second reference point in the second coordinate system can also be determined based on multiple iterations.

[0052] In the next calculation step, the position of the first origin of the first coordinate system can be determined in the second coordinate system. In particular, it is applicable that the first straight line connecting the first origin and the third reference point R3 is arranged perpendicular to the second straight line connecting the first reference point R1 and the second reference point R2. In other words, the first vector V1 pointing from the first origin to the third reference point R3 is arranged perpendicular to the second vector V2 pointing from the first reference point R1 to the second reference point R2. Therefore, it holds that the scalar product of the first and second connection vectors is zero. V1·V2 = 0 (R3 - 0)·(R2 - R1) = 0

[0053] Furthermore, the parametric form of the second connection straight line passing through the first and second reference points R1, R2 can be formulated such that a parameter lambda is assigned to each point on the second connection straight line. O = R1 + λ(R2 - R1)

[0054] Inserting this parametric form of the second connection straight line into the above formula including the scalar product, the following formula is obtained. (R3 - R1 - λ(R2 - R1))·(R2 - R1) = 0

[0055] This formula can be solved for lambda, and thus the parameter lambda can be calculated.

[0056] By inserting the parameter lambda thus determined into the above parametric form of the second connection straight line, the origin O can be calculated.

[0057] According to a further embodiment, the conversion rule includes a conversion matrix according to the following formula.

Number

[0058]

Equation

[0059] According to a further embodiment, the determination of the conversion rule is such that the origin of coordinates of the first coordinate system is located on a first straight line, and the first and second reference points are also located on this straight line, and the first straight line is arranged perpendicular to a second straight line on which the origin of coordinates of the first coordinate system and a third reference point are located including determining the origin of coordinates of the first coordinate system based on this condition.

[0060] As a result, even when the corners of the blank are rounded and / or chamfered, the origin of coordinates of the first coordinate system can be determined.

[0061] In an embodiment, steps a) to e) are repeatedly executed so as to be able to determine an averaged conversion rule.

[0062] In an embodiment, steps a) to e) are precisely repeatedly executed for a plurality of different first inspection apparatuses. In particular, steps a) to e) are executed (at least once) for each of the plurality of different first inspection apparatuses. For example, the plurality of different first inspection apparatuses are different from each other in that their stoppers abut against a blank at different contact positions. Accordingly, a plurality of different conversion rules are determined, and then these are averaged. The thus determined averaged conversion rule can be used for coordinate conversion regardless of which of the plurality of first inspection apparatuses is used.

[0063] According to a further embodiment, before step a), the step of placing a blank on a second stage of a second inspection apparatus, and the step of creating a plurality of markers on the blank according to a predetermined nominal position in a second coordinate system using the second inspection apparatus are included.

[0064] Furthermore, in step b), the positions of the plurality of markers in the first coordinate system are determined using the first inspection apparatus. Furthermore, in step e), a correction rule is determined that serves to correct the conversion rule based on the deviation between the position of the marker in the first coordinate system determined using the first inspection apparatus and the nominal position of the marker in the second coordinate system.

[0065] As a result, the markers on the blank are created by the second inspection apparatus (i.e., in the second coordinate system), and these created markers are detected by the first inspection apparatus (i.e., in the first coordinate system). Using this, a conversion rule for converting the first coordinate system to the second coordinate system can be determined. Furthermore, thereby, a correction rule for correcting the conversion rule determined based on the image representations of the first and second edges can be determined.

[0066] For example, at least three markers are created on the blank using the second inspection apparatus.

[0067] According to a further embodiment, a plurality of markers are created by particle beam induced deposition and / or etching, and / or by embossing on a blank.

[0068] For example, the second inspection apparatus includes an apparatus for particle beam induced processing (e.g., deposition and / or etching) of a blank. For example, the apparatus for particle beam induced processing includes a particle beam supply unit for supplying a particle beam (e.g., an electron beam, an ion beam). Further, the apparatus for particle beam induced processing includes, for example, a gas supply unit for supplying a process gas (e.g., a deposition gas, an etching gas).

[0069] For example, the process gas is a deposition gas and / or an etching gas. For example, the process gas can be a mixture of a plurality of gaseous components, i.e., a process gas mixture. For example, the process gas can be a mixture of a plurality of gaseous components each having only a specific molecular type.

[0070] In particular, alkyl compounds of typical elements, metals or transition elements are considered deposition gases suitable for the deposition or growth of raised structures. Examples thereof include cyclopentadienyl(trimethyl)platinum (CpPtMe 3 Me = CH 4 ), methylcyclopentadienyl(trimethyl)platinum (MeCpPtMe 3 ), tetramethyltin (SnMe 4 ), trimethylgallium (GaMe 3 ), ferrocene (Cp 2 Fe), bisarylchromium (Ar 2 Cr), and / or, for example, chromium hexacarbonyl (Cr(CO) 6 ), molybdenum hexacarbonyl (Mo(CO) 6 ), tungsten hexacarbonyl (W(CO) 6 ), dicobalt octacarbonyl (CO 2 (CO) 8)、triruthenium dodecacarbonyl (Ru 3 (CO) 12 )、iron pentacarbonyl (Fe(CO) 5 ) and other carbonyl compounds of typical elements, metals or transition elements, and / or, for example, tetraethoxysilane (Si(OC 2 H 5 ) 4 )、tetraisopropoxytitanium (Ti(OC 3 H 7 ) 4 ) and other alkoxide compounds of typical elements, metals or transition elements, and / or, for example, tungsten hexafluoride (WF 6 )、tungsten hexachloride (WCl 6 )、titanium tetrachloride (TiCl 4 )、boron trichloride (BCl 3 )、silicon tetrachloride (SiCl 4 ) and other halogenated compounds of typical elements, metals or transition elements, and / or, for example, copper bis(hexafluoroacetylacetonate) (Cu(C 5 F 6 HO 2 ) 2 )、dimethylgold trifluoroacetylacetonate (Me 2 Au(C 5 F 3 H 4 O 2 )) and other complexes of typical elements, metals or transition elements, and / or, for example, organic compounds such as carbon monoxide (CO), carbon dioxide (CO 2 )、aliphatic and / or aromatic hydrocarbons are included.

[0071] The deposition gas can also contain styrene, hexacarbonyl, ethylene, styrene, pyrene, cetane, formic acid, acrylic acid, propionic acid and / or methyl methacrylate.

[0072] For example, the etching gas is xenon difluoride (XeF 2 )、xenon dichloride (XeCl 2 )、xenon tetrachloride (XeCl 4 )、water vapor (H2 O), heavy water (D 2 O), oxygen (O 2 ), ozone (O 3 ), ammonia (NH 3 ), nitrosyl chloride (NOCl), and / or one of the following halogenated compounds, namely, XNO, XONO 2 , X 2 O, XO 2 , X 2 O 2 , X 2 O 4 , X 2 O 6 O, where X is a halide. Further etching gases for etching one or more of the deposited test structures are described in Applicant's U.S. Patent Application No. 13 / 0103281.

[0073] The process gas may further include additional gases such as hydrogen peroxide (H 2 O 2 ), nitrous oxide (N 2 O), nitrogen oxides (NO), nitrogen dioxide (NO 2 ), nitric acid (HNO 3 ) and other oxygen-containing gases such as oxidation gases, and / or chlorine (Cl 2 ), hydrogen chloride (HCl), hydrogen fluoride (HF), iodine (I 2 ), hydrogen iodide (HI), bromine (Br 2 ), hydrogen bromide (HBr), phosphorus trichloride (PCl 3 ), phosphorus pentachloride (PCl 5 ), phosphorus trifluoride (PF 3 ) and other halide-containing gases such as halides, and / or hydrogen (H 2 ), ammonia (NH 3 ), methane (CH 4 ) and other reducing gases such as hydrogen-containing gases. These additional gases can be used, for example, as buffer gases, passivation media, etc. for the etching process.

[0074] According to a further embodiment, the plurality of markers have a circular form and / or a diameter of 10 nm or more, 50 nm or more, 100 nm or more and / or 300 nm or more.

[0075] When circular markers are used, the first inspection device can more easily detect the markers and better determine their positions. In particular, the center of the markers can be more easily determined.

[0076] However, other shapes than circular can also be used for the markers.

[0077] By setting the minimum size to 10 nm, the first inspection device can reliably detect the markers. Furthermore, the larger the markers, the better and more reliably they can be detected by the first inspection device. For example, the maximum size of the markers is 50 μm.

[0078] According to a further embodiment, the plurality of markers are created in a regular pattern and / or a regular grid on the blank, or in an irregular pattern.

[0079] For example, the plurality of markers are created in a regular or irregular pattern / grid that completely covers the surface of the blank.

[0080] An example of a regular pattern is a regular grid with a uniform distance between the nodes of the grid.

[0081] An example of an irregular pattern is the distribution of markers created on the surface of the blank with a density increasing towards the edge of the blank.

[0082] According to a further embodiment, one or more defects of the blank are inspected in the method, and the position of the defect arranged between the created markers is determined by interpolating the positions of the markers determined by the first inspection device.

[0083] As a result, the position of a defect that does not lie on any of the created markers can also be easily converted from the first coordinate system to the second coordinate system.

[0084] For example, the position of a defect disposed between the coordinates of the created markers is determined by interpolating the positions of the markers determined by the first inspection apparatus.

[0085] For example, the interpolation includes triangulation, Delaunay triangulation, radial basis functions, and / or any other interpolation method.

[0086] In an embodiment, a reference blank including a plurality of markers at corresponding predetermined nominal positions can also be provided. The plurality of markers can have one or more of the aforementioned characteristics of the markers described above. Next, the reference blank is placed on the second stage of the second inspection apparatus. Further, the positions of the plurality of markers of the reference blank are determined in the second coordinate system using the second inspection apparatus. Furthermore, a correction rule is determined that serves to correct the conversion rule based on the deviation between the position of the marker in the second coordinate system determined using the second inspection apparatus and the nominal position of the marker.

[0087] "A(n)" should not necessarily be understood as being limited to exactly one element in this case. Rather, a plurality of elements, for example two, three or more elements, can also be provided. Also, any other numbers used in this specification should not be understood to be limited to the precisely described number of elements. Rather, deviations above and below the numerical value are possible unless otherwise indicated.

[0088] Further possible embodiments of the present invention also include combinations of features or embodiments not explicitly mentioned above or below with respect to the exemplary embodiments. In this case, those skilled in the art can also add individual aspects as improvements or supplements to each basic form of the present invention.

[0089] Further advantageous configurations and aspects of the present invention are the subject matter of the dependent claims and also of the exemplary embodiments of the present invention described below. Hereinafter, the present invention will be described in detail based on the preferred embodiments with reference to the accompanying drawings.

Brief Description of the Drawings

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Modes for Carrying Out the Invention

[0091] Unless otherwise indicated, in the figures, the same or functionally identical elements are denoted by the same reference numerals. Also, note that the illustrations in the figures are not necessarily to scale.

[0092] A method for inspecting a blank 100 for a microlithography photomask according to an embodiment will be described below.

[0093] In a first step S1 of the method, the blank 100 for the microlithography photomask is placed in a first inspection apparatus 102 as shown in FIG. 1. The blank 100 has a main extension plane 104 (uv plane in FIG. 1). The blank 100 further includes a first edge 106, a second edge 108, a third edge 110, and a fourth edge 112. In particular, the edges 106, 108, 110, 112 of the blank 100 are arranged parallel to its main extension plane 104. The first edge 106 and the second edge 108 form an angle with each other, and in particular, are arranged substantially perpendicular to each other. The third edge 110 is arranged on the opposite side of the first edge 106. Further, the fourth edge 112 is arranged on the opposite side of the second edge 108.

[0094] In particular, the first inspection apparatus 102 includes a first stage 114 for attaching the blank 100. The first stage 114 includes a plurality of stoppers 116, 118, 120 against which the blank 100 abuts. In particular, the blank 100 is placed on the first stage 114 in the first step S1 such that the first and second edges 106, 108 abut against the stoppers 116, 118, 120 of the first stage 114.

[0095] In the example shown in FIG. 1, the first stage 114 includes a first stopper 116, a second stopper 118, and a third stopper 120. Further, in this example, the blank 100 is placed on the first stage 114 such that the first edge 106 of the blank 100 abuts against the first and second stoppers 116, 118. Further, the second edge 108 of the blank 100 abuts against the third stopper 120.

[0096] The contact position A1 where the first edge 106 abuts against the first stopper 116 defines the first reference point R1 of the blank 100. Similarly, the contact position A2 where the first edge 106 abuts against the second stopper 118 defines the second reference point R2 of the blank 100. Further, the contact position A3 where the second edge 108 abuts against the third stopper 120 defines the third reference point R3 of the blank 100.

[0097] In the example shown in FIG. 1, the first stage 114 also includes an elastic element 122 under tension that presses the blank 100 in the direction of the stoppers 116, 118, 120. The first elastic element 122 is shown by way of example and presses the third edge 110 of the blank 100. Further, a second elastic element 122 is shown by way of example and presses the fourth edge 112 of the blank 100. Instead of the two elastic elements 122, more or fewer elastic elements can also be used.

[0098] In the second step S2 of the method, the inspection position B on the blank 100 is determined using the first inspection device 102. For example, the inspection position B is a position on the surface 124 of the blank 100. The inspection position B of the blank 100 is a position that is first inspected by the first inspection device 102 and subsequently inspected by the second inspection device 126 (FIG. 2).

[0099] The first inspection device 102 has a first coordinate system 128. As is clear from FIG. 1, the first horizontal axis 130 of the first coordinate system 128 is labeled using the reference symbol u. The first vertical axis 132 of the first coordinate system 128 is labeled using the reference symbol v. The reference symbol 134 labels the first coordinate origin of the first coordinate system 128.

[0100] In step S2, the inspection position B on the blank 100 is determined in the first coordinate system 128 using the first inspection device 102. In this process, for example, the u coordinate u B and the v coordinate v B of the inspection position B are determined in the first coordinate system 128.

[0101] For example, the present method can be useful for inspecting one or more defects D on the blank 100. For example, the defect D can be a particle, such as a foreign object and / or a dust particle. In this case, in step S2, the position B of one or more defects D on the blank 100 is determined in the first coordinate system 128.

[0102] The blank 100 can be output from the first inspection device 102 at the end of step S2.

[0103] In the third step S3 of the present method, the blank 100 is placed in the second inspection device 126 as shown in FIG. 2.

[0104] The second inspection device 126 includes a second stage 136 for attaching the blank 100. The second stage 136 can also include one or more stoppers 138, 140. In the example shown in FIG. 2, the second stage 136 includes a stopper 138 that abuts against the third edge 110 of the blank 100. Further, the second stage 136 includes, by way of example, a further stopper 140 that abuts against the fourth edge 112 of the blank 100. The second stage 136 can include more or fewer stoppers than the two stoppers 138, 140 shown. This includes the case where the second stage 136 does not include a stopper. Further, the stoppers 138, 140 of the second stage 136 can abut against edges different from the third and fourth edges 110, 112 of the blank 100.

[0105] The second inspection device 126 has a second coordinate system 142. The second coordinate system 142 has a second horizontal axis 144 labeled with the reference sign x, a second vertical axis 146 labeled with the reference sign y, and a coordinate origin 148.

[0106] As shown in FIG. 2, the blank 100 is disposed on the second stage 136 of the second inspection device 126 in a twisted and displaced state with respect to the second stage 136 and the second coordinate system 142. For example, such twisting and / or displacement is caused by defects due to tolerances in the mechanical structure. For example, the aforementioned displacement is in the range of several micrometers (μm) to several millimeters (mm). Further, the aforementioned twist is, for example, in the range of several microradians (μrad) to several milliradians (mrad). Note that this twist and displacement are exaggerated in FIG. 2 and subsequent figures for the purpose of explanation.

[0107] The coordinates u B and v B of the inspection position B in the first coordinate system 128 are determined by the first inspection device 102. This inspection position B = (u B , v B) should then be found in the second coordinate system 142 of the second inspection device 126. With respect to the second coordinate system 142 of the second inspection device 126, the inspection position B appears at the coordinates x B and y B in it.

[0108] For the sake of clarity, the inspection position B = (u B , v B ) found in the first coordinate system 128 by the first inspection device 102 is labeled with the reference sign B. Further, the inspection position B' = (x B , y B ) found in the second coordinate system 142 by the second inspection device 126 is labeled with the reference sign B', even if this position is simply the same position with different coordinates.

[0109] In order to enable the second inspection device 126 to find and inspect the inspection positions B, B', the position B = (u B , v B ) determined by the first inspection device 102 needs to be converted into the second coordinate system 142 of the second inspection device 126.

[0110] In the fourth step S4 of this method, at least one image 152, 154, 156 (FIG. 3) of the blank 100 is recorded using the image recording unit 150 of the second inspection device 126. The image recording unit 150 is only schematically shown in FIG. 2. In particular, the image recording unit 150 is a high-resolution image recording unit having a spatial resolution of, for example, 50 μm or less, for example, a spatial resolution of several nanometers. For example, the image recording unit 150 is a scanning microscope, for example, a scanning electron microscope as described in detail in the context of FIG. 9.

[0111] In particular, at least one image 152, 154, 156 of the blank 100 is recorded using the image recording unit 150 such that the first and second edges 106, 108 of the blank 100 are at least partially captured in at least one image 152, 154, 156.

[0112] Preferably, separate images 152, 154, 156 (first to third images 152 - 156) are recorded for each reference point R1, R2, R3 of the blank 100, and the images capture the corresponding reference points R1, R2, R3 at the corresponding edges 106, 108, and a portion of the corresponding edges 106, 108, as is apparent from FIG. 3. Exemplary image details 158, 160, 162 of the images 152, 154, 156 are labeled in FIG. 2.

[0113] In the fifth step S5 of the method, the conversion rule is determined. The conversion rule serves to convert the inspection position B captured in the first coordinate system 128 to the inspection position B' in the second coordinate system 142 of the second inspection device 126. The conversion rule is determined based on the first and second edges 106, 108 captured in at least one image 152, 154, 156.

[0114] In particular, the positions P1, P2, P3 of the first and second edges 106, 108 in the first coordinate system 128, and the positions P1', P2', P3' of the first and second edges 106, 108 in the second coordinate system 142 are determined based on image processing for at least one image 152, 154, 156. For example, the positions P1, P2, P3 of the first and second edges 106, 108 are determined at three reference points R1, R2, R3 of the first coordinate system 128 based on image processing for at least one image 152, 154, 156. For example, the positions P1', P2', P3' of the first and second edges 106, 108 are further determined at three reference points R1, R2, R3 of the second coordinate system 142 based on image processing for at least one image 152, 154, 156.

[0115] FIGS. 4 and 5 label the rotation 164 of the first coordinate system 128 by the rotation angle Θ with respect to the second coordinate system 142. Further, FIG. 6 shows the translation vector with respect to the second coordinate system 142

Number

[0116] Regarding the description of FIGS. 4 and 6 and the determination of the conversion rules, assume that the coordinate system of the blank 100 corresponds to the first coordinate system 128 of the first inspection device 102. In other words, when the blank 100 is placed in step S1, the possible deviation with respect to the first coordinate system 128 of the first inspection device 102 is ignored.

[0117] As shown in FIG. 4, the first reference point R1 has a position P1 = (u 1 , v 1 ) in the first coordinate system 128 and a position P1' = (x 1 , y 1 ) in the second coordinate system 142. Further, the second reference point R2 has a position P2 = (u 2 , v 2 ) in the first coordinate system 128 and a position P2' = (x 2 , y 2 ) in the second coordinate system 142. Further, the third reference point R3 has a position P3 = (u 3 , v 3 ) in the first coordinate system 128 and a position P3' = (x 3 , y 3 ) in the second coordinate system 142.

[0118] In step S5, based on the image analysis of the image 154 (FIG. 3), for example, for the first and second reference points R1, R2, the respective vertical coordinate positions y 1 , y 2 in the second coordinate system 142 are determined. Further, based on the image analysis, for example, for the third reference point R3, the horizontal coordinate position x 3 in the second coordinate system 142 is determined.

[0119] In the examples of FIGS. 4 to 6, the first coordinate system 128 of the first inspection device 102 is twisted by a rotation angle Θ with respect to the second coordinate system 142 of the second inspection device 126. That is, the first horizontal axis 130 of the first coordinate system 128 is rotated by the rotation angle Θ with respect to the second horizontal axis 144 of the second coordinate system 142.

[0120] Next, the rotation angle Θ can be calculated from a right-angled inclined triangle 168 formed based on the first and second horizontal axes 130, 144. In particular, the length Δy of the opposite side of this right-angled triangle 168 is the determined vertical coordinate positions y 1 、y 2 from the first and second reference points R1, R2 in the second coordinate system 142, and Δy = y 2 -y 1 can be calculated as.

[0121] Furthermore, it can be assumed that the length Δx of the adjacent side of this right-angled triangle 168 is approximately the same size as the length Δu of the hypotenuse of this right-angled triangle 168. In particular, the length Δu is the distance between the first reference point R1 and the second reference point R2 in the first coordinate system. For example, the length Δu is determined based on the pre-determined structural data of the first inspection device 102, and in particular, based on the pre-determined distance between the first stopper 116 and the second stopper 118 of the first stage 114 of the first inspection device 102.

[0122] Next, the rotation angle Θ is approximately obtained from the arctangent of the quotient of the opposite side Δy and the adjacent side Δx according to the following formula.

Equation

[0123] In the examples shown in FIGS. 4 and 6, the first coordinate system 128 of the first inspection device 102 is a translation vector

Equation

[0124] [Number] so as to be displaced with respect to the second coordinate origin 148 of the second coordinate system 142.

[0125] For example, the conversion rule includes a conversion matrix T (for example, an affine conversion matrix) that follows the following equation. [Number]

[0126] In the above equation, u and v represent the coordinates of the position (for example, inspection position B) in the first coordinate system 128, x and y represent the coordinates of the position (for example, inspection position B') in the second coordinate system 142, Θ represents the rotation angle of the rotation of the first coordinate system 128 with respect to the second coordinate system 142, and t x and t y are the translational vectors

[0127] [Number] represent the vector components of.

[0128] As described above, the rotation angle Θ can be calculated from Δx and Δy.

[0129] Based on the determined position P3 (especially x 3 ) of the third reference point R3 in the second coordinate system 142 and the determined positions P1, P2 (especially y 1 , y 2 ) of the first or second reference points R1, R2 in the second coordinate system 142, the translational vector [Number] vector components t ofx and t y can be determined.

[0130] In particular, the above conversion rules can be rewritten as follows by matrix multiplication. x = u cos Θ - v sin Θ + t x y = u sin Θ + v cos Θ + t y

[0131] Therefore, for the reference point R2, it is as follows. y 2 = u 2 sin Θ - v 2 cos Θ + t y

[0132] Therefore, for the reference point R3, it is as follows. x 3 = u 3 cos Θ - v 3 sin Θ + t x

[0133] These two equations can be solved respectively for t x and t y The position y of the reference point R2 2 and the position x of the reference point R3 3 are determined by image processing from the recorded images 154, 156 (see also FIG. 4), and u 1 and u 2 are known from the structural data of the first inspection device 102. Therefore, t x and t y can be determined respectively from the equations solved for t x and t y The determined rotation angle Θ and the translation vector

[0134]

Number

Number

[0135] When this method is used, for example, to inspect one or more defects D on the blank 100, the first inspection device 102 can determine the position B = (u B , v B ) in the first coordinate system. The first inspection device 102 can further transmit the determined position B = (u B , v B ) to the second inspection device 126. The computing device of the second inspection device 126 (not shown in FIG. 2, but for example, the control device 242 in FIG. 9) can then apply the transformation rule using the transformation matrix T to transform the transmitted position B = (u B , v B ) into the corresponding position B' = (x B , y B ) in the second coordinate system 142 of the second inspection device 126. Therefore, the defect D on the blank 100 can be easily found by the second inspection device 126 and inspected in detail, for example, with high spatial resolution.

[0136] For example, when the purpose is to inspect a plurality of defects D or a plurality of positions B, B' on the blank 100, it may be sufficient to determine the transformation rule using the transformation matrix T only once. This is especially true when the blank 100 does not move within the second inspection device 126. Then, a plurality of positions B = (u B , v B ) transmitted by the first inspection device 102 can be transformed into the corresponding plurality of positions B' = (x B , y B ) in the second coordinate system 142 of the second inspection device 126 by applying one transformation rule.

[0137] FIG. 7 shows a case where the blank 100' for a lithography mask has a rounded corner 172.

[0138] In this case, as described above, assume that the coordinate system of the blank 100' corresponds to the first coordinate system 128. In the case of the rounded corner 172 of the blank 100', or in the case of the chamfered corner (not shown) of the blank 100', the coordinate origin 134 of the first coordinate system 128 can be determined based on the conditions described below. As is clear from FIG. 7, first, the coordinate origin 134 of the first coordinate system 128 is located on the first straight line 174 on which the first and second reference points R1 and R2 are also located. Next, a second straight line 176 is defined by the coordinate origin 134 of the first coordinate system 128 and the third reference point R3. The first straight line 174 is perpendicular to the second straight line 176. Therefore, the coordinate origin 134 of the first coordinate system 128 can be determined even in the case of the rounded corner 172 and / or the chamfered corner of the blank 100'.

[0139] Optionally, steps S1 to S5 can be repeatedly executed to determine the averaged conversion rule (statistical average) with higher accuracy.

[0140] Optionally, steps S1 to S5 can also be repeatedly executed so as to be executed for a plurality of different first inspection devices 102. For example, the plurality of different first inspection devices 102 are different from each other in that the stoppers 116 to 120 contact the blank 100 at different contact positions A1 to A3. By executing steps S1 to S5 at least once for each of the plurality of different first inspection devices 102, a plurality of different conversion rules are determined in step S5. These determined plurality of different conversion rules are then averaged. By applying the thus created averaged conversion rule, this conversion rule can be applied to any desired first inspection device 102 for the purpose of coordinate conversion.

[0141] In any sixth step S6 of the method, at least one image 170 (FIG. 8) of at least one defect D is recorded using the second inspection device 126. In this case, the image recording unit 150 is aligned based on the position B’ = (x B , y B ) transformed into the second coordinate system 142. In particular, the image recording unit 150 is controlled such that the position B’ = (x B , y B ) transformed into the second coordinate system 142 is captured in the image 170. For example, the image recording unit 150 is controlled such that the position B’ = (x B , y B ) is imaged at the center of the image 170.

[0142] In any further step of the method, the defect D is removed from the blank 100 by the second inspection device 126.

[0143] FIG. 9 shows a further exemplary embodiment of a second inspection device 200 that can be used in the above and / or below methods. The second inspection device 200 in FIG. 9 is a device for inspecting (i.e., analyzing) a sample 202, such as a blank 100 (FIG. 1). The second inspection device 200 can also be further configured as a device for processing a sample 202, such as a blank 100.

[0144] For example, the device 200 includes a housing 204. The housing 204 can be evacuated, for example, by a vacuum pump 206 (e.g., to a residual gas pressure of 10 -5 ~10 -9 mbar).

[0145] The device 200 also includes a particle beam supply unit 208 that is disposed in the housing 204 and serves to supply a particle beam 210. For example, the particle beam supply unit 208 is embodied as an electron column 212 for supplying an electron beam 210.

[0146] The particle beam supply unit 208, for example an electron column 212, can be designed in particular as an electron microscope 212 (scanning electron microscope). The scanning electron microscope 212 is an example of the image recording unit 150 (FIG. 2).

[0147] (As an example of a second inspection apparatus) The apparatus 200 includes, for example, a sample stage 214 (as an example of a second stage) for attaching a sample 202 (for example, a blank 100). The sample stage 214 can further include a positioning unit 216 (not shown individually), whereby the sample stage 214 can be displaced relative to the base 218 in, for example, three spatial directions x, y, and z, and can be rotated, for example, about at least one axis (for example, an axis arranged parallel to the z direction in FIG. 9). The reference numeral 220 represents a sample stage apparatus including the sample stage 214, the base 218, and the positioning unit 216.

[0148] The apparatus 200 can optionally also include a process gas supply unit 224 for supplying a process gas 226. The process gas supply unit 224 can be used together with the particle beam supply unit 208 to perform a particle beam induced processing process on the sample 202 (for example, a blank 100). For this purpose, for example, the process gas 226 is supplied by the process gas supply unit 224 and irradiated by the particle beam 210.

[0149] The apparatus 200 can optionally also include a manipulator unit 228 (for example, a micromaniplulator unit and / or a nanomanipulator unit) for performing operations on the sample 202 or the surface 222 of the sample 202 (for example, the surface 124 of the blank 100 in FIG. 2).

[0150] As an example, the manipulator unit 228 includes an atomic force microscope 230. The atomic force microscope 230 includes a probe 232 for analyzing and / or processing the sample 202. The probe 232 is disposed on a cantilever 234 that is movably fixed to a positioning unit 236 (a moving unit). In particular, the cantilever 234 includes a first end 238 (a base end 238) to which the cantilever 234 is movably fixed to the positioning unit 236. Further, the cantilever 234 includes a second end 240 (a free end 240) on which the probe 232 is disposed. Using the positioning unit 236, the probe 232 can be moved in three spatial directions x, y, and z (translation in the x, y, and z directions). Movement in the x direction and / or the y direction is referred to herein as lateral movement. In this specification, movement in the z direction is referred to as the approach of the sample 202 by the probe 232 (negative z direction) and the withdrawal / separation movement of the probe 232 from the sample 202 (positive z direction).

[0151] The atomic force microscope 230 can be used to perform operations on the sample 202. For example, the probe 232 can be used to pick up (i.e., lift) the particles D (FIGS. 1 and 2) adhering to the sample surface 222 of the sample 202. For this purpose, the probe 232 is correspondingly moved, for example, by the positioning unit 236. Additionally, the sample stage 214 can also be displaced by its positioning unit 216. The pickup (i.e., lifting) of the particles D by the probe 232 can be monitored live, for example, using the electron microscope 212. Thereafter, the probe 232 is moved, for example, by the positioning unit 236 to a storage unit (not shown), and the particles D are transferred from the probe 232 to the storage unit.

[0152] In addition to or instead of the operations, the atomic force microscope 230 can also be configured to record an image.

[0153] The apparatus 200 further comprises, for example, a control device 242 for controlling a manipulator unit 228 (e.g., a positioning unit 236), a sample stage 214 or a further positioning unit 216, a particle beam supply unit 208 and / or a process gas supply unit 224.

[0154] A method for inspecting a blank 300 of a microlithography photomask according to a further embodiment will be described below with reference to FIGS. 10 and 12.

[0155] In a first step S101 of the method according to a further embodiment (FIG. 12), the blank 300 is placed on a second stage 136 of a second inspection device 126 (FIG. 2).

[0156] In a second step S102 of the method according to a further embodiment, a plurality of markers 302 are created on the blank 300 using the second inspection device 126. In FIG. 10, as an example, a part of the markers 302 is labeled.

[0157] For example, the plurality of markers 302 are created by particle beam induced deposition and / or etching. For example, the embodiment of the second inspection device shown in FIG. 9 can be used for this purpose.

[0158] For example, the process gas 226 is supplied to the surface of the blank 300 (e.g., to the surface 222 of the sample 202 in FIG. 9) by the gas supply unit 224. Further, the particle beam supply unit 208 (e.g., an electron column 212) supplies an activated particle beam 210 (e.g., an electron beam) to the surface of the blank 300. Thereby, a chemical reaction is caused, and material is deposited from the gas phase of the process gas 226 onto the surface of the blank 300 (in the case of a deposition gas), or material is etched away from the blank (in the case of an etching gas).

[0159] In an alternative form, the markers 302 can also be created on the surface of the blank 300 by embossing.

[0160] Preferably, each of the plurality of markers 302 has a circular form 304, as is apparent in FIG. 10. As a result, the position of the marker 302, particularly the center of the marker 302, can be more easily determined by the first inspection device 102 in the subsequent step S2'.

[0161] Furthermore, each of the plurality of markers 302 has a diameter 306 of at least 10 nm or more, for example. The larger the diameter 306 of each individual marker 302, the easier it is to be detected by the first inspection device 102 in the subsequent step S2'.

[0162] In the example of FIG. 10, the plurality of markers 302 are arranged in a regular pattern 308, particularly in a regular grid 310. In particular, the markers 302 are arranged on the nodes of the regular grid 310. Furthermore, the nodes are arranged at regular distances from each other.

[0163] Although not shown in the figure, the markers 302 can also be created in an irregular pattern on the blank 300.

[0164] In the example of FIG. 10, a large number of created markers 302 are shown. However, in other examples, using the second inspection device 126, it is also possible to create a number of markers on the blank 300 that is more or less than the number of markers 302 shown in FIG. 10. For example, it is also possible to create only three markers 302 on the blank 300.

[0165] The plurality of markers 302 are created on the blank 300 according to a predetermined nominal position P in the second coordinate system 142 in step S102. N As an example, the nominal position P in the second coordinate system 142 N =(x N , y N ) is labeled to one of the markers 302 shown in FIG. 10.

[0166] Similar to the case of FIG. 2, the blank 300 may be disposed in a slightly twisted and / or displaced manner on the second stage 136 of the second inspection device 126. Then, as shown in FIG. 10, markers 302 are created on the blank 300 according to the inaccurate placement of the blank 300 on the stage 136. Therefore, the created markers 302 contain information regarding the inaccurate placement of the blank 300 on the stage 136 of the second inspection device 126.

[0167] Subsequent to step S102, steps S1' to S5' (FIG. 12) corresponding to steps S1 to S5 of the above-described method (FIG. 11) are executed.

[0168] In this case, in step S2', using the first inspection device 102, the positions P of the plurality of created markers 302 in the first coordinate system 128 M are determined. Further, the positions P of the markers 302 in the first coordinate system 128 determined using the first inspection device 102 M and the nominal positions P of the markers 302 in the second coordinate system 142 N are determined.

[0169] Subsequently, steps S3' and S4' are executed in the same manner as steps S3 and S4.

[0170] Next, step S5' is executed. Following the determination of the conversion rule, the markers 302 detected by the first inspection device 102 in S2' are used to further improve the determined conversion rule. In particular, the positions P of the markers 302 in the first coordinate system 128 from the nominal positions P of the markers 302 in the second coordinate system 142 determined in step S2' N are used to determine a correction rule for correcting the conversion rule. M

[0171] In particular, the method can be applied such that marker 302 is applied to the (e.g., single) blank to be inspected, and thus the deviation is determined once. The deviation thus determined can be applied when inspecting different blanks, and in particular, it is possible to perform corresponding corrections.

[0172] A situation that can occur when using this method to inspect one or more defects D of blank 300 is that defect D is located at the coordinates of one of markers 302. Therefore, the position of defect D can be easily determined. However, if the position of defect D is located between the coordinates of the created markers 302, interpolation 312 can be applied between the positions P of markers 302 determined by the first inspection device 102, which is shown in FIG. 10. M It is possible to apply interpolation 312 therebetween, which is shown in FIG. 10.

[0173] Although the present invention has been described based on exemplary embodiments, the present invention can be modified in various ways.

Explanation of Reference Numerals

[0174] 100, 100’ blank 102 inspection device 104 main extension plane 106 edge 108 edge 110 edge 112 edge 114 stage 116 stopper 118 stopper 120 stopper 122 elastic element 124 surface 126 inspection device 128 coordinate system 130 horizontal axis 132 vertical axis 134 coordinate origin 136 stage 138 stopper 140 stopper 142 coordinate system 144 Horizontal axis 146 Vertical axis 148 Coordinate origin 150 Image recording unit 152 Image 154 Image 156 Image 158 Image detail 160 Image detail 162 Image detail 164 Rotation 166 Translation 168 Triangle 170 Image 172 Angle 174 Straight line 176 Straight line 200 Inspection device 202 Sample 204 Housing 206 Pump 208 Particle beam supply unit 210 Particle beam 212 Electron microscope 214 Sample stage 216 Positioning unit 218 Base 220 Sample stage device 222 Surface 224 Process gas supply unit 226 Process gas 228 Manipulator unit 230 Atomic force microscope 232 Probe 234 Cantilever 236 Positioning unit 238 End 240 End 242 Control device 300 Blank 302 Marker 304 Shape 306 Diameter 308 Pattern 310 Grid 312 Interpolation Positions A1 - A3 Positions B, B’ D defect Δu length Δy length Θ angle R1 - R3 reference points P1 - P3 positions P1’ - P3’ positions P M position P N position

Number

Claims

1. A method for inspecting a microlithography photomask blank (100), comprising the steps of: a) placing the blank (100) on a first stage (114) of a first inspection device (102) such that first and second edges (106, 108) of the blank (100) abut against stops (116, 118, 120) of the first stage (114); b) determining (S2) an inspection location (B) on the blank (100) in a first coordinate system (128) using the first inspection device (102); c) placing (S3) said blank (100) on a second stage (136) of a second inspection device (126) having an image recording unit (150); d) recording (S4) at least one image (152, 154, 156) of said blank (100) using said image recording unit (150) such that said first and second edges (106, 108) are at least partially captured; e) determining (S5) a transformation rule based on the first and second edges (106, 108) captured in the at least one image (152, 154, 156) for transforming the inspection location (B) captured in the first coordinate system (128) into a second coordinate system (142) of the second inspection device (126); A method comprising:

2. The method of claim 1 , wherein the second inspection device (126) comprises a scanning microscope device (212), a scanning electron microscope device (212), a scanning probe microscope device, and / or an atomic force microscope device (230).

3. 3. The method of claim 1 or 2, wherein the spatial resolution of the image recording unit (150) of the second inspection device (126) is 100 μm or less, 50 μm or less, 30 μm or less, 10 μm or less, 5 μm or less, 1 μm or less, 0.1 μm or less, 50 nm or less, 10 nm or less, 5 nm or less, and / or 3 nm or less.

4. In said method, the blank (100) is inspected for one or more defects (D), a position (B) of at least one defect (D) in said blank (100) is determined in said first coordinate system (128) in step b) using said first inspection device (102), the determined transformation rule serves to transform the position (B) of the at least one defect (D) captured in the first coordinate system (128) to a position (B') in the second coordinate system (142); The method according to any one of claims 1 to 3.

5. After step e), a step (S6) of recording at least one image (152, 154, 156) of the at least one defect (D) using the image recording unit (150) of the second inspection device (126), the image recording unit (150) being aligned based on the position (B') of the at least one defect (D) transformed into the second coordinate system (142); The method of claim 4 , comprising:

6. the first stage (114) includes first, second and third stoppers (116, 118, 120); said blank (100) is placed on said first stage (114) such that said first edge (106) abuts said first and second stops (116, 118) and said second edge (108) abuts said third stop (120), so that first, second and third reference points (R1, R2, R3) of said blank (100) are accordingly defined at contact positions (A1, A2, A3) of said first, second and third stops (116, 118, 120) on said first and second edges (106, 108); For each reference point (R1, R2, R3) an image (152, 154, 156) of the blank (100) is recorded in step d) and the corresponding reference point (R1, R2, R3) is captured in the image, the transformation rule is determined based on the first, second and third reference points (R1, R2, R3) captured in the recorded images (152, 154, 156); The method according to any one of claims 1 to 5.

7. the positions (P1, P2) of the first and second reference points (R1, R2) in the second coordinate system (142) are determined based on image processing of the corresponding recorded images (152, 154); and / or a position (P3) of the third reference point (R3) in the second coordinate system (142) is determined based on image processing of the corresponding recorded image (156); The method according to claim 6.

8. The transformation rule may be a rotation (164) by a rotation angle (Θ) and / or a translation vector [0010] (166) including a translation by the rotation angle (Θ) is determined based on the determined positions (P1, P2) of the first and second reference points (R1, R2) in the second coordinate system (128, 142); and / or Based on the determined position (P3) of the third reference point (R3) in the second coordinate system (142) and the determined position (P1, P2) of the first or second reference point (R1, R2) in the second coordinate system (142), the translation vector [0025] The vector component (t x , t y ) is confirmed, The method of claim 7.

9. The transformation rules include a transformation matrix according to the following formula: [0030] where u and v represent the coordinates of a position (B) in the first coordinate system (128), x and y represent the coordinates of a position (B') in the second coordinate system (142), Θ represents the rotation angle (164) of the first coordinate system (128) relative to the second coordinate system (142), and t x and t y represents a translation (166) of said first coordinate system (128) relative to said second coordinate system (142); and / or The transformation rule includes a rotation (164) with a rotation angle Θ that satisfies the following formula: [0045] where Θ represents the rotation angle of the rotation (164) of the first coordinate system (128) relative to the second coordinate system (142), and Δx represents the abscissa (x θ) of the first reference point (R1) and the second reference point (R2) in the second coordinate system (142). 1 , x 2 ) and Δy represents the difference between the ordinate (y 1 , y 2 ) 9. The method according to claim 7 or 8.

10. The determining of the transformation rule defines a coordinate origin (134) of the first coordinate system (128) as: the coordinate origin (134) of the first coordinate system (128) is located on a first straight line (174) on which the first and second reference points (R1, R2) are also located; The first straight line (174) is disposed perpendicular to the coordinate origin (134) of the first coordinate system (128) and a second straight line (176) on which the third reference point (R3) is located. This includes determining the matter on the basis that: The method according to any one of claims 6 to 9.

11. Before step a), placing (S101) the blank (300) on the second stage (136) of the second inspection device (126); Using the second inspection device (126), a predetermined nominal position (P N (S102) creating a plurality of markers (302) on the blank (300) according to In step b), the first inspection device (102) is used to measure the positions (P M ) The position (P) of the marker (302) in the first coordinate system (128) determined using the first inspection device (102). M ) and the nominal position (P N determining a correction rule serving to correct said transformation rule in step e) based on the deviation between The method according to any one of claims 1 to 10, comprising:

12. The method of claim 11 , wherein the plurality of markers (302) are created by particle beam induced deposition and / or etching and / or by embossing on the blank (300).

13. The method of claim 11 or 12, wherein the plurality of markers (302) have a circular shape (304) and / or a diameter (306) of 10 nm or more, 50 nm or more, 100 nm or more, and / or 300 nm or more.

14. The method according to any one of claims 11 to 13, wherein the plurality of markers (302) are created on the blank (300) in a regular pattern (308) and / or a regular grid (310), or in an irregular pattern. 【Request 15】 The blank (300) is inspected for one or more defects (D) by the method, and the positions (B) of the defects (D) located between the created markers (302) are determined by the positions (P) of the markers (302) determined by the first inspection device (102). M The method of any one of claims 11 to 14, wherein the eigenvalues ​​are determined by interpolating (312)

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