Methods and devices for determining the geometry of a measuring tip for a scanning probe microscope and for analyzing and / or processing a sample

Abstract

Method for determining a geometry of a measuring tip (100) for a scanning probe microscope, comprising the steps: a) Generating (S1) at least one test structure (200) which has raised areas (210) alternating with depressions (220) in a first direction (I), wherein the raised areas (210) and depressions (220) are aligned parallel to each other in a second direction (II) perpendicular to the first direction (I); b) Scanning (S2) the test structure (200) with the measuring tip (100) to determine a profile (300) of the test structure (200); and c) Determining (S3) the geometry of the measuring tip (100) depending on the determined profile (300), wherein in step a) at least two test structures (200) are generated which have a different aspect ratio (AV1, AV2) with respect to the depressions (220), wherein the aspect ratio (AV1, AV2) specifies a height (H) relative to a width (B1, B2) of the depression (220), and wherein in step b) the at least two test structures (200) are sequentially sampled one after the other with increasing or decreasing aspect ratio (AV1, AV2), the sampling being terminated when: In a sequence with decreasing aspect ratio (AV1, AV2), based on the determined profiles (300), it is determined that a lowest point of a depression (220) is reached, or In a sequence with increasing aspect ratio (AV1, AV2) based on the determined profiles (300), it is determined that a lowest point of a depression (220) is no longer reached.

Description

[0001] The present invention relates to a method and a testing device for determining the geometry of a measuring tip for a scanning probe microscope, as well as a method and a device for analyzing and / or processing a sample.

[0002] Microlithography is used to manufacture microstructured components, such as integrated circuits. The microlithography process is carried out using a lithography system, which includes an illumination system and a projection system. The image of a lithography mask (reticule) 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 positioned in the image plane of the projection system. This transfers the mask structure onto the photosensitive coating of the substrate.

[0003] To achieve small feature sizes and thus increase the integration density of microstructured devices, very short wavelength light is increasingly used, such as deep ultraviolet (DUV) or extreme ultraviolet (EUV). DUV, for example, has a wavelength of 193 nm, and EUV has a wavelength of 13.5 nm. The lithography masks themselves have feature sizes in the range of 5–100 nm. Manufacturing such lithography masks is very complex and therefore expensive, especially since the masks must be defect-free; otherwise, it cannot be guaranteed that a structure created with the mask will have the desired function. For this reason, lithography masks are verified, meaning their defect-free condition is checked.This process detects and locates defects, enabling targeted repair. Typical defects include the absence of intended structures, for example, due to an unsuccessful etching process, or the presence of unintended structures, such as an etching process that progressed too quickly or was applied to the wrong location. These defects can be eliminated by selectively etching away excess material or selectively depositing additional material at the affected locations. This can be achieved with high precision using focused electron beam induced processing (FEBIP).

[0004] During the repair process, the progress is preferably continuously monitored using a scanning electron microscope. The electron microscope offers a suitable spatial resolution for this purpose, on the order of a few nanometers. However, a disadvantage is that the surface under investigation can only be visualized based on contrasts resulting from the varying interactions of the electron beam with the surface atoms. Therefore, an electron microscope image typically contains no information about the surface height.

[0005] Scanning probe microscopy (SPM) is an imaging technique used to determine the height of a surface under investigation. This involves using a probe that interacts directly with the surface and scans across it. In atomic force microscopy (AFM), this interaction can be based on direct contact, vander-Waals interaction, or other physical interactions, as well as combinations thereof. For example, the interaction can be kept constant for each scan position of the probe by adjusting its height above the surface using a microactuator. The probe is also referred to as the tip. The tip's geometry significantly influences the interaction between the tip and the surface, especially for sharp structures.The result of such a measurement roughly corresponds to a convolution of the tip geometry with the surface geometry. Therefore, it is advantageous to know the tip geometry precisely in order to interpret the measurement result correctly.

[0006] The following publications deal with considering the influence of the geometry or shape of a scanning electron microscope (SPM) tip on SPM images of a sample surface: V. Bykov et al.: “Test structure for SPM tip shape deconvolution”, Appl. Phys. A 66, pp. 499–502 (1998); G. Reiss et al.: “Scanning tunneling microscopy on rough surfaces: Deconvolution of constant current images”, Appl. Phys. Lett. 57 (9), 27 August 1990, pp. 867–869; Y. Martin and HK Wickramasinghe: “Method of imaging sidewalls by atomic force microscopy”, Appl. Phys. Lett. 64 (19), 9 May 1984, pp. 2498–2500; L. Martinez et al.: “Aspectratio and lateral resolution enhancement in force microscopy by attaching nanoclusters generated by an ion cluster source at the end of a silicon tip,” Rev. Sci. Instrument. 82, (2011), pp. 02370-1 - 023710-7; X. Qian et al.: “Image simulation and surface reconstruction of undercut features in atomic force microscopy”, SPIE Proc. Vol. 6518, (2007), pp. 1-12; L. Udpa et al.: „Deconvolution of atomic force microscopy data for cellular and molecular imaging“, IEEE, Sig. Proc. Mag. 23, 73 (2006); Ch. Wong et al.: „Tip dilation and AFM capabilities in the characterization of nanoparticles“, J. O. Min. 59, 12 (2007); J.S. Villarrubbia: „Algorithms for scanned probe microscope image simulation, surface reconstruction, and tip estimation“, J. Res. Natl. Inst. Stand. Technol. 102, S. 425-454 (1997); X. Qian und J.S. Villarrubia: „General three-dimensional image simulation and surface reconstruction in scanning probe microscopy using a dexel representation“, Ultramicroscopy 1008 (2007), S. 29-42.

[0007] For example, by measuring test structures with known geometry using the measuring tip, the geometry of the tip can be deduced by "unfolding" the measurement signal with the known test structure geometry. The resulting known tip geometry can then be used to "unfold" the measurement signal of an unknown structure, thus allowing inferences to be drawn about its actual geometry. However, a measuring tip changes during use due to constant interaction with the surface, which is why the tip geometry should be checked regularly. This can be very time-consuming, especially if the measuring tip has to be moved to a separate test structure or even removed from the measuring device.It is therefore desirable to have a way to characterize the geometry of the measuring tip that is exact yet does not require much effort, especially little time.

[0008] DE 10 2016 223 659 A1 describes a method for providing a measuring tip for a scanning probe microscope. In a first step, at least one first and at least one second measuring tip are provided, wherein the first and the second measuring tip are arranged on a common measuring tip holder such that only the first measuring tip interacts with a sample to be examined. In a second step, the first measuring tip is irreversibly modified so that, after the irreversible modification, only the second measuring tip interacts with the sample to be examined.

[0009] DE 10 2018 221 304 A1 describes a device for determining in situ the process resolution of a particle beam-induced processing process of an element for photolithography. This device comprises a processing unit configured to generate at least two reference structures on the element within a process environment, which differ in at least one dimension, and an analysis unit configured to determine the dimensions of the at least two reference structures in the process environment in order to determine the process resolution of the particle beam-induced processing process.

[0010] DE 10 2017 211 957 A1 describes a method for examining a measuring tip of a scanning probe microscope, wherein a test structure is created and the measuring tip is examined using the created test structure.

[0011] The article by U. Hübner et al.: “Downwards to metrology in nanoscale: determination of the AFM tip shape with well-known sharp-edged calibration structures”, Appl. Phys. A 76, pp. 913-917, 2003, reveals another conventional test structure and method for characterizing a measuring tip.

[0012] Against this background, one object of the present invention is to improve the use of a measuring tip in processes for the analysis or processing of surfaces, in particular microstructured surfaces.

[0013] According to a first aspect, a method for determining the geometry of a probe tip for a scanning probe microscope is proposed. In a first step a), at least one test structure is generated, which has alternating protrusions and depressions in a first direction, wherein the protrusions and depressions are parallel to each other and oriented perpendicular to the first direction in a second direction. In a second step b), the test structure is scanned with the probe tip in the first direction and in a third direction perpendicular to the first and second directions to determine a profile of the test structure. In a third step c), the geometry of the probe tip is determined as a function of the determined profile.

[0014] This method offers the advantage that the geometry of the measuring tip can be determined quickly and easily using a comparatively simple test structure. Due to the parallel nature of the structures, it is reliably prevented that the measuring tip (partially) misses the test structure, as can happen with column-like protrusions or depressions, which can lead to measurement errors. This can be done in situ, for example, by creating the test structure specifically for this purpose on the surface of the sample under investigation. Because of the simple geometry of the test structure, it can be precisely generated or manufactured. Furthermore, relevant dimensions of the test structure can be easily determined and thus verified using supplementary measuring instruments, such as an electron microscope. Additionally, the proposed test structure allows the geometry of the measuring tip to be determined selectively on different flanks of the measuring tip.

[0015] A scanning probe microscope can be operated in various modes. Besides serving as an imaging instrument for capturing the three-dimensional structure of a surface, the probe tip can also be used as a micromanipulator. All measurement modes share the common feature of scanning the sample surface with the probe tip. For each measurement point, defined, for example, by a tuple of (x, y) coordinates, a height value, i.e., a value of a z-coordinate, is determined. The horizontal and vertical resolution of a scanning probe microscope is in the range of less than one nanometer. The scanning probe microscope is, for example, configured as an atomic force microscope.

[0016] The measuring tip is, for example, located at a free end of a cantilever. The end of the cantilever opposite the free end is held by a probe holder or measuring head, which can be moved in all three spatial directions, for example, by means of a piezoelectric actuator. Additionally, the probe holder may be mounted to rotate and / or tilt. The basic resolution of the scanning probe microscope is determined, for example, by the piezoelectric actuator, as it is responsible for precisely moving to the measuring points arranged in a grid. The cantilever with the measuring tip attached to it can be referred to collectively as the measuring probe. The cantilever is made, for example, of single-crystal silicon; however, depending on the application, other materials and / or material combinations may also be used.

[0017] Several types of scanning probe microscopes are known, such as scanning tunneling microscopes and atomic force microscopes. In scanning tunneling microscopes, a voltage is applied between the probe tip and the sample surface, and the current flowing without direct contact between the tip and the surface (the "tunnel current") is measured. The current intensity is an indicator of the distance between the probe tip and the sample surface. In atomic force microscopes, the probe tip interacts directly with the sample surface at the atomic level. This is explained in more detail below.

[0018] To measure the height of the sample surface at a given measurement point, the measuring tip interacts with the sample surface. For example, the measuring tip is brought into contact with the sample surface. To do this, the probe is approached from above. As soon as a bend in the cantilever is detected, which is determined, for example, optically by the deflection of a laser beam reflected from the top of the cantilever, contact is established. The measuring tip is then kept in contact with the surface and moved across it (scanned). The bend in the cantilever is a measure of the surface height at each scan point. In this mode, for example, the height of the probe holder is kept constant. Alternatively, the bend in the cantilever can be kept constant by controlling the height of the probe holder using a suitable control loop.The probe holder's position in the z-direction then corresponds to the height of the sample surface. Besides the contact mode, in which the measuring tip wears relatively quickly, other measurement modes are possible, such as a non-contact mode or an intermittent mode, which differ primarily in the way the measuring tip interacts with the surface. In these modes, the cantilever is, for example, set into a forced oscillation at a predetermined frequency, preferably close to the cantilever's resonance frequency. The oscillation is excited such that the free end of the cantilever vibrates with the measuring tip in the z-direction. The resonance frequency depends particularly on the properties of the cantilever and any existing interaction between the measuring tip and the sample surface.As soon as the interaction changes, the resonance frequency, and thus the amplitude of the forced oscillation at the specified frequency, also changes. For example, a closed-loop control system adjusts the probe holder in the z-direction to maintain the oscillation, ensuring that the probe holder's movement in the z-direction corresponds to the height of the sample surface. These exemplary measurement methods can be extended and / or modified in various ways. Furthermore, several other measurement methods are possible.

[0019] The measuring tip itself, for example, has a pyramid-like or needle-like shape. Depending on the application, a particularly fine measuring tip is advantageous, for instance, when very fine structures with a high aspect ratio are to be measured. The geometry of the measuring tip has a significant influence on the profile of a sample surface captured by the measuring tip, which is why it is advantageous to know the geometry as precisely as possible.

[0020] Depending on the geometry of a probe tip, measurement results can be inaccurate or incomplete. Here are two examples. A probe tip with a diameter of, for example, 60 nm cannot detect a depression, such as a trench or hole in the sample surface, with a width or diameter of only 30 nm, because the probe tip cannot penetrate the depression. Similarly, a probe tip with a length of 50 nm cannot fully detect a depression with a height of 100 nm.

[0021] The geometry of the measuring tip can be characterized by various parameters. For example, a diameter and length can completely characterize a rod-shaped measuring tip. If the measuring tip has a different basic shape, such as conical or pyramidal, the opening angle of the cone or pyramid can also be a helpful parameter. A measuring tip can also have different geometries on different flanks, so the geometry of the measuring tip is preferably determined with respect to each individual flank. Such geometry-characterizing parameters can be determined by scanning the test structure and subsequently analyzing the profile captured.

[0022] The test structure is generated, for example, on the surface of a sample under investigation. The surface of the sample on which the test structure is generated is preferably flat and smooth. "Flat" means, in particular, that the surface lies in the plane defined by the first and second directions, at least in the area of ​​the test structure. "Smooth" means, in particular, that the surface has no significant irregularities or structures deviating from this plane before the test structure is generated. "Significant irregularities" are, for example, irregularities that represent more than 10% of the structure size of the test structure. For example, if the test structure has a raised area with a height of 20 nm and a width of 10 nm, then the boundary between insignificant and significant would be 2 nm in height and 1 nm in width.Depending on the application, the expert understanding of what is essential or inessential may differ from this example.

[0023] The test structure at least one features alternating elevations and depressions in a first direction, which are parallel to each other and perpendicular to the first direction in a second direction. The elevations are, for example, raised structures relative to a lower point in a depression, and the depressions are, for example, hollows relative to an upper point of a elevation. This means that the terms elevation and depression are to be understood relative to each other. For example, elevations and depressions can be represented as at least one trench in a smooth surface. Then the surface adjacent to the depression (the trench) corresponds to an elevation. Conversely, with respect to a ridge that represents an elevation relative to the surface, the surface adjacent to the ridge can form a depression.The raised and recessed areas preferably extend in the direction of a surface normal relative to the surface bearing the test structure. However, deviations from this are also possible.

[0024] The alternating arrangement of the raised and recessed areas means, in particular, that when the test structure is cut along the first direction, raised and recessed areas are found in alternating sequence. The various raised and recessed areas can have different characteristics, such as variations in width, height, flank angle, and so on. Preferably, the test structure is designed to be periodic, at least in sections, so that several successive pairs of raised and recessed areas in the first direction are identical, i.e., they have the same geometry. Such a regular test structure makes it possible to determine the profile with statistically significant data at measurement points for determining the geometry of the measuring tip.

[0025] The fact that the elevations and depressions are parallel to each other and oriented in a second direction perpendicular to the first direction means, in particular, that a tangent drawn to an edge between an elevation and the adjacent depression extends in the second direction. The elevations and depressions can therefore have a curvilinear shape, in the sense that the tangents of two points spaced apart at the edge do not necessarily have to be parallel to each other.

[0026] Preferably in step b) the test structure is scanned with the measuring tip in the first direction and in a third direction perpendicular to the first and second directions to determine a profile of the test structure.

[0027] The scanning process is carried out as described above in step b), such that the probe holder scans the test structure with the measuring probe. A height value is determined at each grid point. This height value describes the distance of the point on the test structure corresponding to the grid point to a reference level, which is defined, for example, by a surface of a sample supporting the test structure, in a third direction orthogonal to the first and second directions. This third direction is subsequently also referred to as the z-direction.

[0028] The probe tip preferably scans the test structure in a line-like manner, for example along the first direction, but other directions are also possible. A line comprises, for example, 1000 grid points and extends over a distance of 1 µm. This gives a grid point resolution of 1 nm along the first direction. Each line is preferably scanned in both forward and reverse directions, so that each grid point is captured twice. A height value is assigned to each grid point. Once a first line has been captured, the probe tip is moved perpendicular to the first line by one grid point, and a second line, parallel to the first, is scanned. In this way, for example, a 1 µm 2 large area of ​​the test structure with a spatial resolution of 1 nm 2 scanned. The resulting profile thus comprises 10 6(One million) measurement points. Depending on the application, the resolution can be varied along the different directions. For example, the deflection along the first and / or second direction can be up to 10 µm or up to 100 µm. Furthermore, in some embodiments, a profile can comprise only a few lines, for example, ten lines, down to just a single line. Fewer lines are captured in a shorter time, which can be advantageous. On the other hand, there are then fewer measurement points available to determine the geometry of the measuring tip. It is also possible to use a varying resolution, employing a higher resolution in an area of ​​interest where, for example, a sharp edge of the test structure is located, than in other areas where the test structure is flat.

[0029] In the third step c), the geometry of the measuring tip is determined based on the calculated profile. It is important to note that the profile obtained through scanning does not represent the height profile of the test structure, but rather a fold of the test structure geometry with the measuring tip geometry. However, by unfolding the profile, either the test structure geometry or the measuring tip geometry can be determined from it. For this to work, the other geometry should be known as precisely as possible. In this case, the test structure is generated according to precise specifications, so its geometry is known. Therefore, the geometry of the measuring tip can be determined from the calculated profile.

[0030] Steps b) and c) can be repeated repeatedly, for example, before and after scanning a structure under investigation with the measuring tip. This allows changes in the geometry of the measuring tip that affect the measurement result to be detected early and taken into account accordingly.

[0031] According to one embodiment of the method, an electron microscope image of the at least one test structure is acquired, and a structure size of the at least one test structure is determined from the acquired electron microscope image. In step c), the geometry of the measuring tip is determined as a function of the determined profile and the determined structure size.

[0032] This embodiment has the advantage that the structural size of the generated test structure is verified using a reliable method. The electron microscope image of the test structure makes it possible to precisely determine the dimensions of the test structure in the plane defined by the first and second directions. Thus, the structural size of the test structure is known accurately in at least two dimensions. The structural parameters determined from the electron microscope image are referred to, for example, as length and width. A distinction must be made here between the overall length / width, which describes the test structure as a whole, and the length / width of individual protrusions or depressions that are part of the test structure. The structural size refers specifically to the length / width of individual protrusions or depressions.

[0033] In step a) of the procedure, at least two test structures are generated, each exhibiting a different aspect ratio with respect to the elevations or depressions, where the aspect ratio specifies the height relative to the width of the elevation or depression. In step b), the at least two test structures are scanned with the measuring tip to determine a respective profile.

[0034] By varying the aspect ratio, the geometry of the measuring tip can be determined very precisely. For example, a first test structure has rectangular protrusions / depressions with a height of 50 nm and a width of 25 nm. The aspect ratio is therefore 2:1. The second test structure has rectangular protrusions / depressions with a height of 50 nm and a width of 10 nm. The aspect ratio is therefore 5:1. If, when scanning these two test structures, it is determined, for example, that the profile of the first test structure has a height of 50 nm between the upper point of a protrusion and the lower point of a depression, then the measuring tip has a leading edge with a length of over 50 nm and a diameter (along the scanning direction, which here lies along the first direction) of less than 25 nm.Further geometric details of the front section of the measuring tip can be determined from the steepness of the profile's flanks at the transition from a raised area to a depression and vice versa. In contrast, the profile of the second test structure exhibits a maximum height of only 10 nm between the upper point of a raised area and the lower point of a depression. This indicates that the measuring tip cannot fully penetrate the depressions and does not reach their bottom. It can also be deduced, for example, that the first ten nanometers of the measuring tip have a diameter of less than ten nanometers.

[0035] By combining a variety of different test structures with diverse aspect ratios, the geometry of the measuring tip can be determined very precisely.

[0036] The aspect ratio is a measure of how "fine" or "thin" a structure is. However, the aspect ratio alone does not define the geometry of a test structure; one of the two dimensions, either the height or the width, must also be specified.

[0037] The at least two test structures are scanned sequentially, one after the other, with increasing or decreasing aspect ratios. Scanning is terminated when, in a sequence with a decreasing aspect ratio, the determined profiles indicate that the deepest point of a depression has been reached, or when, in a sequence with an increasing aspect ratio, the determined profiles indicate that the deepest point of a depression is no longer reached.

[0038] This sequential approach is advantageous for efficiently determining a limit value that can still be measured or detected accurately with the measuring tip. The sequence with a decreasing aspect ratio can have the advantage of characterizing the front section of the measuring tip very precisely or in detail. The sequence with an increasing aspect ratio can have the advantage that, at smaller aspect ratios that are easily resolved by the measuring tip, fundamental properties of the measuring tip can be determined, and the successful generation of the test structures can also be verified.

[0039] As an alternative to a sequentially increasing or decreasing aspect ratio of the test structures to be scanned successively, an alternating scheme is also possible, whereby a series comprising every second test structure to be scanned has a sequentially increasing aspect ratio or sequentially decreasing aspect ratio, and a series with the intervening test structures to be scanned also has a sequentially increasing aspect ratio or sequentially decreasing aspect ratio.

[0040] According to a further embodiment of the method, in step a) at least a first test structure and a second test structure are having raised areas alternating with depressions in a first direction, wherein the first direction of the first test structure forms an angle other than 0° with the first direction of the second test structure, in particular an angle in the range of 45° - 90°. In step b) the at least two test structures are scanned with the measuring tip to determine a respective profile.

[0041] This embodiment has the advantage that the geometry of the measuring tip can be determined even more precisely. In particular, the flank geometry of different flanks of the measuring tip can be precisely determined.

[0042] For example, the first test structure is scanned along its first direction, which in this example is called the x-direction. The probe holder moves the measuring tip back and forth along the x-direction. The trajectory of the measuring tip in the x-direction therefore intersects an edge between a protrusion and a depression perpendicularly. In this case, the geometry of the leading or trailing edge of the measuring tip is crucial for the determined profile. The second test structure is also scanned along its first direction, which, however, is perpendicular to the first direction of the first structure, which is therefore called the y-direction. The probe holder moves the measuring tip back and forth along the y-direction. The measuring tip also intersects an edge between a protrusion and a depression perpendicularly in this case.If the measuring tip or probe holder has the same orientation as before, then the lateral flanks of the measuring tip are now decisive for the determined profile.

[0043] Other or different flank areas can also be determined more precisely, for example, by rotating the probe holder by a certain angle, so that a different flank area is decisive for the determined profile when the measuring tip approaches an edge.

[0044] According to another embodiment of the method, steps a) and b) are carried out in the same vacuum chamber and / or without breaking the vacuum.

[0045] The test structure is therefore generated in-situ and subsequently scanned without breaking the vacuum. This eliminates the need for the complex process of introducing a test structure and / or the measuring tip into a process environment. A process environment is characterized, in particular, by an atmosphere with very precisely controlled physicochemical properties, such as pressure, temperature, and composition, especially the partial pressure of various species present in the atmosphere.

[0046] According to a further embodiment of the method, step a) comprises generating the at least one test structure using a focused particle beam, in particular an electron beam, and at least one precursor gas or etching gas.

[0047] The generation of structures using particle beam-induced processes is possible with very high accuracy, particularly high spatial resolution. Therefore, test structures with very small feature sizes, on the atomic scale, can be produced. These test structures can, for example, exhibit raised areas with a width of 1 nm alternating with depressions, also with a width of 1 nm, and an aspect ratio of 10:1 or even higher. This is particularly advantageous using electron beam-induced processes (EBIP).

[0048] Suitable precursor gases for the deposition or growth of raised structures include, in particular, alkyl compounds of main group elements, metals, or transition elements. Examples include cyclopentadienyl trimethylplatinum (CpPtMe3, Me = CH4), methylcyclopentadienyl trimethylplatinum (MeCpPtMe3), tetramethyltin (SnMe4), trimethylgallium (GaMe3), ferrocene (Cp2Fe), bis-aryl chromium (Ar2Cr), and / or carbonyl compounds of main group elements, metals, or transition elements, such as chromium hexacarbonyl (Cr(CO)6), molybdenum hexacarbonyl (Mo(CO)6), tungsten hexacarbonyl (W(CO)6), dicobalt octacarbonyl (Co2(CO)8), and triruthenium dodecacarbonyl (Ru3(CO)6). 12), iron pentacarbonyl (Fe(CO)5), and / or alkoxide compounds of main group elements, metals or transition elements, such as tetraethoxysilane (Si(OC2H5)4), tetraisopropoxytitanium (Ti(OC3H7)4), and / or halide compounds of main group elements, metals or transition elements, such as tungsten hexafluoride (WF6), tungsten hexachloride (WCl6), titanium tetrachloride (TiCl4), boron trifluoride (BCl3), silicon tetrachloride (SiCl4), and / or complexes with main group elements, metals or transition elements, such as copper bishexafluoroacetylacetonate (Cu(C5F6HO2)2), dimethyl gold trifluoroacetylacetonate (Me2Au(C5F3H4O2)), and / or organic compounds such as carbon monoxide (CO), carbon dioxide (CO2), aliphatic and / or aromatic hydrocarbons, and the like.

[0049] The etching gas may, for example, comprise: xenon difluoride (XeF2), xenon dichloride (XeCl2), xenon tetrachloride (XeCl4), water vapor (H2O), heavy water (D2O), oxygen (O2), ozone (O3), ammonia (NH3), nitrosyl chloride (NOCl), and / or one of the following halide compounds: XNO, XONO2, X2O, XO2, X2O2, X2O4, X2O6, where X is a halide. Further etching gases for etching one or more of the deposited test structures are specified in the applicant's US patent application No. 13 / 0 103 281.

[0050] Other additive gases that can be used in the production of the test structure include, for example, oxidizing gases such as hydrogen peroxide (H₂O₂), nitrous oxide (N₂O), nitrogen oxide (NO), nitrogen dioxide (NO₂), nitric acid (HNO₃), and other oxygen-containing gases, and / or halides such as chlorine (Cl₂), hydrogen chloride (HCl), hydrogen fluoride (HF), iodine (I₂), hydrogen iodide (HI), bromine (Br₂), hydrogen bromide (HBr), phosphorus trichloride (PCl₃), phosphorus pentachloride (PCl₅), phosphorus trifluoride (PF₃), and other halogen-containing gases, and / or reducing gases such as hydrogen (H₂), ammonia (NH₃), methane (CH₄), and other hydrogen-containing gases. These additive gases can be used, for example, in etching processes, as buffer gases, as passivating agents, and the like.

[0051] According to a further embodiment of the method, the at least one test structure has a linear structure in plan view with a comb-like cross-section, wherein the comb-like cross-section in particular comprises a substantially rectangular profile.

[0052] Ideally, the test structure has a rectangular profile. Since the particle beam, for example, the electron beam, typically has a Gaussian beam profile, the edges of a constructed structure are not sharp at the atomic level, but rounded. Such structures with rounded corners are also considered "essentially rectangular." Which structures are still considered "essentially rectangular" depends on expert understanding using relevant measurement methods. A beam profile, for example, is defined as an intensity distribution along a cross-section through the particle beam perpendicular to its direction of propagation.

[0053] In further embodiments, the at least one test structure has a curvilinear profile when viewed from above. Curvilinear means, for example, that the first direction at a first position is different from the first direction at a second position that differs from the first. The radius of curvature of the curvilinear profile is preferably larger than the width of a protrusion or depression, in particular more than twice the radius of curvature and up to 20 times the radius of curvature. The protrusions and depressions can, for example, be arc-shaped, in particular circular arc-shaped. The parallelism criterion is maintained at every point of the test structure.

[0054] In further embodiments, the test structure has a regular arrangement of cubes or cuboids. From a top view, this test structure would resemble a chessboard, for example. This test structure corresponds to a superposition of two linear test structures with orthogonal alignment at the same position. This embodiment is particularly space-saving.

[0055] According to another embodiment of the method, in step c) a length of a front section of the measuring tip, the diameter of which is less than a width of the recess of the test structure, is determined.

[0056] According to a further embodiment of the method, before step a) a structure size of a sample to be measured or manipulated using the measuring tip is determined and in step a) the at least one test structure is generated depending on the determined structure size.

[0057] This embodiment is advantageous when the primary objective is to determine whether a given limit structure size can still be measured with the respective measuring tip. For example, if in an application it is sufficient for the measuring tip to accurately detect a structure with an aspect ratio of 1:1 and a height of 25 nm, then it may be sufficient to create a test structure with precisely these geometric properties and scan it with the measuring tip.

[0058] The measuring tip is specifically designed for measuring and / or manipulating a photomask for microlithography.

[0059] According to another embodiment of the method, the test structure generated in step a) is removed again after the geometry of the measuring tip has been determined.

[0060] Preferably, the test structure is removed by means of a particle beam-induced etching process using a suitable precursor gas. The precursor gas may, for example, comprise: xenon difluoride (XeF₂), xenon dichloride (XeCl₂), xenon tetrachloride (XeCl₄), water vapor (H₂O), heavy water (D₂O), oxygen (O₂), ozone (O₃), ammonia (NH₃), nitrosyl chloride (NOCl), and / or one of the following halide compounds: XNO, XONO₂, X₂O, XO₂, X₂O₄, X₂O₆, where X is a halide. Further etching gases for etching one or more of the deposited test structures are specified in the applicant's US patent application No. 13 / 0 103 281.

[0061] Such an etching process can advantageously be carried out in-situ, i.e. without having to break a vacuum and / or transfer the sample to another device.

[0062] According to a second aspect, a method for analyzing and / or processing a sample, in particular a photomask for microlithography, is proposed. In a first step a), the sample is analyzed and / or processed using a probe tip of a scanning probe microscope. In a step b), which can be performed before and / or after step a), a probe tip geometry is determined according to the method described in the first aspect.

[0063] According to one embodiment of the method, steps a) and b) are carried out in the same vacuum chamber and / or without breaking the vacuum.

[0064] According to a further embodiment of the method, in step b) at least one test structure is generated on the sample and / or a substrate within a vacuum chamber of the scanning probe microscope.

[0065] According to a third aspect, a test structure for determining the geometry of a scanning probe microscope's measuring tip is proposed. The test structure features alternating protrusions and depressions in a first direction, with the protrusions and depressions being parallel to each other and perpendicular to the first direction in a second direction.

[0066] The embodiments and features of the test structure described in the first aspect apply accordingly to the proposed test structure and vice versa.

[0067] The test structure features raised and recessed areas with a width ranging from 1 to 50 nm and a height ranging from 1 to 100 nm. This can also be described as a spatial frequency structure in the range of 10 / µm to 1000 / µm, which can be referred to as the test structure's resolution. The test structure can be designed such that the resolution varies spatially and two-dimensionally, for example, increasing or decreasing along the first direction. The function describing this variation can be, for example, a step function with piecewise constant resolution, or a continuous function. The resolution can increase linearly, logarithmically, or exponentially, and / or the function can exhibit a combination of different components.

[0068] The test structure can be designed such that the aspect ratio of the surveys and in-depth analyses varies along the first direction. For example, each survey-in-depth analysis pair may have a specific initial aspect ratio, and the following survey-in-depth analysis pair may have a different aspect ratio.

[0069] The test structure can further be designed such that the structural size of the elevations and depressions varies along the first direction while maintaining a constant aspect ratio. Each elevation-depression pair can have a specific initial structural size with a specific aspect ratio, and the following elevation-depression pair can have a different structural size with the same specific aspect ratio.

[0070] Such a variation in aspect ratio or structure size can be continuous according to a step function or a continuous function. Preferably, sections with constant geometry of the test structure along the first direction are larger than a lower limit. The lower limit can, for example, be determined such that each section comprises at least ten raised-depressed pairs.

[0071] The test structure is preferably produced by means of a particle beam-induced process, in particular with an electron beam in conjunction with a suitable precursor gas. Etching processes that remove material and / or deposition processes that deposit material can be used.

[0072] In embodiments, the test structure can further comprise a plurality of rounded, for example circular, column-like protrusions and / or depressions, which are preferably arranged regularly and have a specific aspect ratio.

[0073] According to a fourth aspect, the use of a test structure according to the third aspect is proposed for determining a geometry of a measuring tip of a scanning probe microscope.

[0074] According to a fifth aspect, a test device for determining the geometry of a probe tip for a scanning probe microscope is proposed. The test device comprises a generation unit for creating at least one test structure, which has alternating protrusions and depressions in a first direction, wherein the protrusions and depressions are parallel to each other and oriented perpendicular to the first direction in a second direction. Furthermore, the test device includes a scanning unit for scanning the test structure with the probe tip to determine a profile of the test structure. A determination unit of the test device is configured to determine the geometry of the probe tip as a function of the determined profile.

[0075] The embodiments and features described for the proposed method according to the first aspect apply accordingly to the proposed test device.

[0076] The test device is advantageously designed to carry out the procedure according to the first aspect.

[0077] The production unit is specifically designed to generate a test structure according to the third aspect.

[0078] The unit of definition can be implemented in hardware and / or software. In a hardware implementation, the unit of definition can be, for example, a computer or a microprocessor. In a software implementation, the unit of definition can be a computer program product, a function, a routine, an algorithm, a neural network, a part of program code, or an executable object.

[0079] According to a sixth aspect, a device for analyzing and / or processing a sample, in particular a photomask for microlithography, is proposed. The device comprises an analysis and processing unit for analyzing and / or processing the sample using a measuring tip of a scanning probe microscope. Furthermore, the device comprises a testing device according to the fifth aspect, wherein the testing device is configured to determine the geometry of the measuring tip before and / or after analyzing and / or processing the sample.

[0080] The embodiments and features described for the proposed method according to the second aspect apply accordingly to the proposed device.

[0081] The device is advantageously designed to carry out the procedure according to the second aspect.

[0082] The term "one" here is not necessarily to be understood as restricting the number to exactly one element. Rather, it can also refer to multiple elements, such as two, three, or more. Similarly, every other counter used here should not be interpreted as restricting the number to the exact number stated. Instead, numerical deviations, both higher and lower, are possible unless otherwise specified.

[0083] Other possible implementations of the invention also include combinations of features or embodiments described previously or subsequently with regard to the exemplary embodiments, even if not explicitly mentioned. In such cases, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

[0084] Further advantageous embodiments and aspects of the invention are the subject of the dependent claims and the exemplary embodiments of the invention described below. The invention will be explained in more detail below with reference to preferred embodiments and the accompanying figures. Fig. Figure 1a shows a schematic view of a measuring probe for a scanning probe microscope; Fig. Figure 1b shows three different measuring tips with different geometries; Fig. Figure 2 shows a schematic view of a first embodiment of a test structure; Fig. Figure 3 schematically shows a scanning of a test structure with a measuring tip and a resulting profile; Fig. Figure 4 shows a schematic electron microscope image of a sample with several test structures; Fig. Figure 5 shows cross-sections through two test structures with different aspect ratios; Fig. Figure 6 shows a sequence with three test structures with decreasing aspect ratio and the corresponding profiles; Fig. Figure 7 shows an electron microscope image of a test structure and the corresponding profile; Fig. Figure 8 shows a diagram illustrating, by way of example, the penetration depth of a measuring tip as a function of a structural dimension of the test structure; Fig. Figure 9 shows an arrangement of several different test structures; Fig. Figure 10 shows three further different embodiments of test structures; Fig. Figure 11 schematically shows a sample to be analyzed; Fig. Figure 12 shows an exemplary block diagram of an embodiment of a device for analyzing and processing a sample with a test fixture; and Fig. Figure 13 shows a schematic block diagram of an embodiment of a method for determining the geometry of a measuring tip.

[0085] In the figures, identical or functionally equivalent elements have been labelled with the same reference symbols, unless otherwise indicated. Furthermore, it should be noted that the representations in the figures are not necessarily to scale.

[0086] Fig. Figure 1a shows a schematic view of a measuring probe 110 for a scanning probe microscope 514 (see Fig. 12) The measuring probe 110 has a retaining bar 120, commonly referred to as a cantilever, arranged on a mounting section 130. The measuring tip 100 is arranged at the free end of the cantilever 120. In this example, the measuring tip has two sections 101, 102. The front section 101 is particularly fine. For example, the front section 101 has a length of 200 nm and a diameter of 20 nm. Alternatively, the measuring tip 100 does not have such a division into different sections with different geometries.

[0087] The cantilever 110 and the measuring tip 100 can be manufactured as a single piece. For example, the cantilever 120 and the measuring tip 100 can be made of a metal, such as tungsten, cobalt, or iridium; a metal alloy; or a semiconductor, such as silicon, silicon nitride, silicon carbide, or silicon oxide. Preferably, the measuring tip 100 is grown on the cantilever 120 using a particle beam-induced process. The measuring tip 100 can also be made of different materials, for example, having a base made of one material and a tip made of a second material. It is also possible to manufacture the cantilever 110 and the measuring tip 100 as two separate components and then join them together. This can be done, for example, by bonding.

[0088] The Fig. Figure 1b, for example, shows three different measuring tips 100a, 100b, 100c with different geometries. In the left column of the Fig. 1b shows a side view of the respective measuring tip and in the right column of the Fig. Figure 1b shows the cross-section through the respective measuring tip at different positions.

[0089] The first measuring tip 100a, for example, has a conical geometry. This tapers conically towards the tip, with the cross-section being circular in each case, as the exemplary cross-sections C1, C2, C3 show.

[0090] The second measuring tip 100b, for example, has a pyramid-like geometry with a triangular base C1, C2, C3. Each corner of the triangular base forms a flank F1, F2, F3 of the measuring tip 100b. Flank F1 is essentially perpendicular to the cross-sections C1, C2, C3, while flanks F2 and F3 are tilted. This makes the measuring tip 100b suitable for detecting perpendicular edges of a structure when the measuring tip 100b is brought close to the structure with flank F1.

[0091] The third measuring tip 100c has a cylindrical shape, with the cross-section C1 being essentially constant along the length of the measuring tip 100c.

[0092] Fig. Figure 2 shows a schematic perspective view of a first embodiment of a test structure 200. In this example, the test structure 200 is arranged on a substrate 230, which can be, for example, a semiconductor substrate. The test structure 200 has a linear geometry in plan view with a comb-like cross-section. Here, protrusions 210 and depressions 220 are arranged alternately in a first direction I. The protrusions 210 and depressions 220 extend parallel to each other in a second direction II, which is perpendicular to the first direction I.

[0093] The test structure 200 was created in this example by depositing material at the positions of the protrusions 210. One could say that the protrusions 210 were grown. This growth occurred along the third direction III, which is perpendicular to the first direction I and the second direction II. The third direction III is, for example, parallel to a surface normal (not shown) of the substrate 230.

[0094] In this example, the raised areas 210 and the depressions 220 are uniformly shaped, meaning that the width of a raised area 210 and the width of a depression 220 are each the same. For example, the width is 10 nm and the height of the raised areas 210 above the substrate is 30 nm. Thus, the raised areas 210 and the depressions 220 have an aspect ratio of 3:1.

[0095] Fig. Figure 3 schematically shows the scanning of a test structure 200 with a measuring tip 100 and a resulting profile 300. For example, the measuring tip 100a of the Fig. 1b, which has a conical geometry, and the test structure 200 of the Fig. 2. On the left side of the Fig. Figure 3 shows schematically how the measuring probe 110 is mounted on a probe holder 140 (see Fig. 12) is held, and the test structure 200 is scanned to scan it. This example is an atomic force microscope.

[0096] The measuring probe 110 is moved back and forth parallel to the first direction I, whereby a control loop (not shown) keeps the interaction of the measuring tip 100 with the surface of the test structure 200 constant by adjusting the probe holder 140 with the measuring probe 110 in the third direction III. A schematic representation for easier understanding is shown in the Fig. Figure 3 shows the measuring tip 100 in contact with the test structure 200, although this is not necessarily the case in other operating modes of the atomic force microscope. At the time shown, the measuring tip 100 is located in a recess 220 of the test structure 200, with a leading edge of the measuring tip 100 just coming into contact with an edge between the recess 220 and the subsequent protrusion 210. If the measuring probe 110 is now advanced further, the probe holder 140 must be moved upwards in the third direction III. In this case, the angle of the probe holder 140's trajectory with respect to the horizontal direction corresponds to the angle of the leading edge of the measuring tip 100 with respect to the horizontal direction.

[0097] Therefore, the profile 300 shown in the diagram on the right is the result of the scan of the test structure 200. The dashed lines represent the actual geometry of the test structure 200. This example shows that the profile 300 determined by scanning does not correspond to the actual structure. Rather, profile 300 is a convolution of the geometry of the test structure 200 and the geometry of the measuring tip 100. If one geometry or the other is known, the other geometry can be determined by unfolding profile 300. Thus, if the geometry of the test structure 200 is known, the geometry of the measuring tip 100 can be determined.

[0098] By advantageously designing the test structure 200, various geometric parameters of the measuring tip 100, such as length, diameter as a function of length, angle of attack, flank of the measuring tip in different directions, and the like, can be determined in this way. Determining the geometry of the measuring tip, in this context, means that at least one of the geometric parameters is determined.

[0099] Fig. Figure 4 shows a schematic electron microscope image 400 of a sample 10 (see Fig. 11 or Fig. 12) with several different test structures 200a - d. In this example, four different test structures 200a - d are shown. All four test structures 200a - d have a linear structure with a comb-like cross-section, as can be seen from the Fig. 2 explained in detail. For example, the hatched bars represent elevations 210 (see Fig. 2) represents, but alternatively, it could also be depressions 220 (see Fig. 2) act. Without limiting the generality, in this example, test structures 200c and 200d each have three ridges / depressions, and test structures 200a and 200b each have four ridges / depressions. Test structures 200a and 200c have the same orientation, while test structures 200b and 200d have an orthogonal orientation. Furthermore, test structures 200a and 200b have a smaller structure size than their corresponding test structures 200c and 200d. As an example of the structure size, the width B1 of a ridge 210 and the width B2 of a depression 220 are shown for test structure 200a. It can be said that test structures 200a and 200c have different spatial resolutions or contain information at different spatial frequencies. The same applies to test structures 200b and 200d.The structure size or resolution of a respective test structure 200a - d can be advantageously determined from the electron microscope image 400.

[0100] Due to the different resolution of the test structures 200a, 200c or 200b, 200d, various geometry parameters of a measuring tip 100 can be determined (see Fig. 1a, Fig. 1b or Fig. 12) determine or certain geometric parameters can be determined with varying accuracy. Furthermore, the geometry of the measuring tip 100 with respect to different flanks F1 - F3 can be determined by the orthogonal alignment of any two of the test structures 200a - d (see Fig. 1b) determine more precisely. The respective test structure 200a - d is preferably scanned perpendicular to the respective line direction. For test structures 200a, 200c, for example, a front and a rear flank are decisive, so that from the profile 300 determined here (see Fig. 3) whose geometry can be determined, and for the test structures 200b, 200d the left and right flanks are decisive, so that their geometry can be determined from the profile 300 determined there.

[0101] Fig. Figure 5 shows cross-sections through two test structures 200a and 200b with different aspect ratios AV1 and AV2. Both test structures 200a and 200b have a comb-like cross-section. In this example, the aspect ratio AV1 and AV2, calculated as the quotient of the height H1 and H2 of the respective well 220 and the width B1 and B2 of the respective well 220, is shown for each well 220. In this example, the aspect ratio AV1 is greater than the aspect ratio AV2. The respective aspect ratio can be specified for the other uplifts 210 or further wells 220 of the respective test structures 200a and 200b. In this example, the test structures 200a and 200b are uniformly formed, meaning that the aspect ratio AV1 and AV2 is the same for each uplift 210 or well 220.

[0102] Fig. Figure 6 shows a sequence with three test structures 200a - c with decreasing aspect ratio AV1, AV2 (see Fig. 5) and corresponding profiles 300a - 300c. In this example, the respective test structure 200a - c has a linear structure with a comb-like cross-section. The hatched areas correspond to elevations 210 (see Fig. 2, Fig. 3, Fig. 5). These have a height H1, H2 (see Fig. 5) of 30 nm. The aspect ratio of the left test structure 200a is, for example, 3:1, meaning that the protrusions 210 / depressions 220 have a width B1, B2 (see Fig. 5) of 10 nm. The aspect ratio of the middle test structure 200b is, for example, 6:1, meaning that the raised areas 210 / depressions 220 have a width B1, B2 of 5 nm. The aspect ratio of the right test structure 200c is, for example, 10:1, meaning that the raised areas 210 / depressions 220 have a width B1, B2 of 3 nm.

[0103] The three test structures 200a - c shown are sequentially tested with increasing aspect ratio using a measuring tip 100 (see Fig. 1a, Fig. 1b, Fig. 3 or Fig. 12) is scanned to obtain a corresponding profile 300a-c. The scanning is performed along the first direction I of the respective test structure 200a-c. The profiles 300a-c shown in the diagrams are obtained as examples. The horizontal axis I corresponds to a position of the respective test structure 200a-c along the first direction I, and the vertical axis III corresponds, for example, to a height value at which the interaction of the measuring tip with the surface of the respective test structure 200a-c is constant. The left test structure 200a is completely covered by the measuring tip 100; in particular, the measuring tip 100 reaches the bottom of the depressions 210. A slight angle of attack of the measuring tip 100 may be discernible in the profile 300a at the edges between a protrusion 210 and a depression 220.In the middle test structure 200b, the measuring tip 100 just reaches the bottom of a depression 220 between two protrusions 210, which is recognizable by a short flat section in the profile 300b. In the right test structure 200c, however, the measuring tip 100 only penetrates a short distance into the depressions 220, and the bottom of the depressions 220 is no longer reached.

[0104] These three measurements clearly show that this probe tip 100 is not suitable for analyzing depressions with a diameter of 5 nm and an aspect ratio of 10:1. The feature size of the central test feature 200b could be considered the limiting factor for the suitability of probe tip 100. The rising flanks of profiles 300a–c indicate a geometry for the respective flanks F1–F3 (see Fig. 1b) of the measuring tip 100. From profile 300c, it can be deduced in particular that the measuring tip 100 has a diameter of 5 nm at the maximum penetration depth, since this is the width of the recesses 220. The penetration depth of the measuring tip 100 can be represented as a function of the width of the recesses 220, which is exemplified in the Fig. 8 is shown.

[0105] Fig. Figure 7 shows an electron microscope image of a test structure 200 and the corresponding profile 300, which was obtained by scanning the test structure 200 with a measuring tip 100 (see Fig. 1a, Fig. 1b, Fig. 3, Fig. 12) was recorded. In this example, the test structure 200 has a linear structure with a comb-like cross-section. The bright lines visible in the electron microscope image correspond to the protrusions 210, and the darker areas between them correspond to the depressions 220. The test structure 200 has, for example, an aspect ratio of 3:1, with a height of, for example, 60 nm for each protrusion. The test structure 200 was built up, for example, using tetraethoxysilane as the deposition gas with an electron beam. The protrusions 210 have, for example, a width of 20 nm, and the depressions 220 have a width of 60 nm. The test structure 200 was scanned with an atomic force microscope, thus recording the profile 300. The profile 300 shows rounded corners of the protrusions 210 and downwardly tapered depressions 220. Such a profile 300 is referred to here as being essentially rectangular.As already explained, the corners of the test structure 200 are often slightly rounded, for example, due to a Gaussian beam profile. This becomes more significant the narrower the protrusions or depressions are. Profile 300 shows that the measuring tip 100 reaches the substrate between the protrusions 210. From this, it can be deduced that the measuring tip 100 reaches the substrate at its front section 101 (see . Fig. 1a) has a diameter of less than 60 nm.

[0106] Fig. Figure 8 shows a diagram illustrating, by way of example, the penetration depth ΔH of a measuring tip 100 (see Fig. 1a, Fig. 1b, Fig. 3 or Fig. 12) as a function of a structural parameter B1 of the test structure 200 (see Fig. 2 - 7, 9, 10). The horizontal axis B1, for example, refers to a width B1 (see Fig. 5) a depression 220 (see Fig. 2, Fig. 3, Fig. 5) of the test structure 200. For example, twelve test structures 200 (each point in the diagram corresponds to a test structure) were used here, each with a different width B1 of the recesses 220, but with a constant height H1 (see Fig. 5) generated and scanned with a measuring tip 100. From the resulting profiles 300 (see Fig. 3, Fig. 6) A maximum penetration depth ΔH of the measuring tip was determined and entered into the diagram shown here. The height H of the depressions 220 is, for example, 70 nm. Instead of the width B1, the aspect ratio could also be plotted on the horizontal axis.

[0107] It can be seen that up to a width B1 of 20 nm, the penetration depth ΔH is essentially 0. From this, it can be concluded that the measuring tip 100 has a diameter of approximately 20 nm at its leading end. The penetration depth ΔH then increases steadily, and the diameter of the measuring tip 100 at a distance corresponding to the penetration depth ΔH from its leading end can be read from each value. This is illustrated as an example for the recess 220 with a width B1 of 40 nm. At a penetration depth ΔH of 20 nm, the measuring tip 100 thus has a diameter of 40 nm. From a width B1 of 70 nm, the measuring tip 100 reaches the bottom of the recess 220 at a penetration depth ΔH of 70 nm.

[0108] Fig. Figure 9 shows an arrangement of several different test structures 200a-f. These test structures are linear structures with a comb-like cross-section. Test structures 200a, 200c, and 200e have the same orientation but different structure sizes or aspect ratios. Test structures 200b, 200d, and 200f are oriented orthogonally to these and have correspondingly different structure sizes or aspect ratios. Fig. Figure 9 is an example of an arrangement of several test structures 200a - f with different orientations and a variation of the aspect ratio.

[0109] Fig. Figure 10 shows three further examples of embodiments of test structures 200a-c. All three test structures 200a-c comprise protrusions 210 alternating with depressions 220 in a first direction I, wherein the protrusions 210 and depressions 220 are aligned parallel to each other in a second direction II perpendicular to the first direction I.

[0110] In test structure 200a, the protrusions 210 and depressions 220 have a circular arc shape, with each arc spanning an angle of 90°. Test structure 200a also features a variation in structure size, particularly in width B1, B2, which is shown as an example for two of the circular arcs, in the radial direction. The protrusions 210 and depressions 220, which are shaped as circular arcs, share a common center point. A tangent T is drawn at each of three edges between a protrusion 210 and a depression 220. Each tangent T refers to a point on the respective circular arc that corresponds to an intersection with a line I extending in the radial direction. With respect to this radial direction, the protrusions 210 and depressions 220 are aligned parallel to each other. The radial direction thus corresponds to the first direction I, and the tangential direction corresponds to the second direction II.

[0111] In addition to circular arc structures, the elevations 210 and depressions 220 may exhibit further curvilinear or curved contours.

[0112] The test structure 200b has a checkerboard-like arrangement of the protrusions 210 and depressions 220. This embodiment combines two orthogonally arranged test structures 200 in a small area. In this example, the structure size is uniform, but a variation of the structure size is also possible, for example, a row-wise increase or decrease in the structure size or the aspect ratio.

[0113] The test structure 200c has a linear structure with a comb-like cross-section, in which the width B1 of the recesses 220 is gradually reduced along the first direction I. This makes it possible to determine a limit value in a single scanning operation that can still be reliably detected with the respective measuring tip 100. This embodiment can therefore contribute to a faster determination of the geometry of the measuring tip 100.

[0114] Fig. Figure 11 schematically shows a sample 10 to be analyzed, for example, a section of a structured lithography mask. The lithography mask 10 has, in particular, a structure formed by a coating 14 on the substrate 12 of the sample 10. The structure size B of these structures can vary at different positions on the lithography mask 10. An example is shown in the Fig. Figure 11 shows the width B of a region as the structure size. The structure size B, for example, lies in a range of 20–200 nm. During the production of lithography masks, defects D occasionally occur because, for example, etching processes do not proceed exactly as intended. In the Fig. Figure 11 shows such a defect D as hatching. It represents an excess of material, as the coating 14 in this area was not removed, even though the two adjacent coating areas 14 are provided separately in the template for the lithography mask 10. The defect D can also be described as forming a bridge. In this case, the size of the defect D corresponds to the feature size B. Other defects smaller than the feature size B are also known, for example, in the range of 5–20 nm. Such defects D, and also defects of other types, can be repaired using suitable devices. In this example, it is necessary to selectively remove the bridge, for example, by particle beam etching. It is advantageous to monitor the defect area using imaging methods before, during, and / or after the etching process.To obtain a three-dimensional image, a scanning probe microscope, preferably an atomic force microscope, is particularly suitable.

[0115] As above based on the Fig. As described in section 3, for an accurate interpretation of the measurement data obtained, the profile 300 (see Fig. 3 and Fig. 6), the geometry of the measuring tip used 100 (see Fig. 1a, Fig. 1b, Fig. 3, and 12) should be known as precisely as possible. For this purpose, one of the test structures 200 described above (see above) can be advantageously used. Fig. 2 - 7, 9, 10 or 12). Depending on the type of defect D and how it is repaired, it may be sufficient to ensure that the measuring tip 100 does not exceed a certain limit regarding its width. In the example of the Fig. For example, it may be sufficient to determine that, after the defect D is removed, the substrate 12 is reached along a narrow line and that the two substrate areas 12 above and below the depicted defect D are connected. Therefore, it may be sufficient to generate the test structure 200 such that it has, for example, a structure size like that of the defect D, i.e., in particular a width B as shown here. For the lithography mask 10, the height of the coating 14 is fixed and constant; therefore, the width B also corresponds to an aspect ratio AV1, AV2 (see Fig. 5) defined. It can therefore be said that the test structure 200 is generated based on or depending on the structure size B of the sample 10. This means that determining the geometry of the measuring tip 100 used can be limited to one or a few test structures 200, which can result in time savings. The analysis of the defect D or the defect location after the defect D has been removed is thus also accelerated and possible with greater reliability.

[0116] Fig. Figure 12 shows an exemplary block diagram of an embodiment of a device 500 for analyzing and processing a sample 10 with a test device 510. The device 500 is largely arranged in a vacuum housing 501, which is maintained at a specific gas pressure by a vacuum pump 502.

[0117] The device 500 is particularly suitable for analyzing and processing lithography masks 10 (see Fig. 11) is set up. For example, it is a verification and / or repair tool for lithography masks, in particular for lithography masks for EUV (extreme ultraviolet) or DUV (deep ultraviolet) lithography. A sample 10 to be analyzed or processed is placed on a sample stage 11. The sample stage 11 is specifically designed to adjust the position of the sample 10 in three spatial directions and in three rotational axes to an accuracy of a few nanometers. The device 500 has an electron column 540. This includes an electron source 541 for providing an electron beam 542 and an electron microscope 543, which in this arrangement detects the electrons backscattered from the sample 10. A further detector for secondary electrons may also be provided (not shown).The electron column 540, in conjunction with supplied process gases introduced externally by a gas supply unit 530 via a valve 532 and a gas line 534 into the area of ​​a focal point of the electron beam 542 on the sample 10, can perform electron-beam induced processing (EBIP). This includes, in particular, the deposition and / or etching of material. The electron column 540, together with the gas supply unit 530, can, for example, be referred to as the generation unit 512. It should be noted that the electron microscope 543 is not strictly necessary for EBIP, but is advantageous for monitoring the processes.

[0118] The device 500 also includes an analysis and processing unit 520, which is configured here as an atomic force microscope. The atomic force microscope 520 comprises a scanning unit 514, which has a probe holder 140 that can be moved in at least three spatial directions by means of a plurality of piezo actuators (not shown). In addition, the probe holder 140 can be rotatably mounted in one or more axes to compensate for or deliberately induce tilting and / or to adjust a relative goniometric alignment with respect to the sample 10. The probe holder 140 is particularly suitable for receiving a measuring probe 110 (see Fig. 1) comprising a cantilever 120 and a measuring tip 100. The probe holder 140 is configured to scan a surface of the sample 10 with the measuring tip 100 in a grid pattern. For this purpose, the scanning unit 514 preferably includes a closed control loop (not shown) which, for example, keeps the interaction of the measuring tip 100 with the sample 10 constant. This allows, in particular, the acquisition of a height profile of the sample surface. To obtain the height profile from the raw measurement data, an assumption must be made, for example, about the geometry of the measuring tip 100.

[0119] To determine the geometry of the measuring tip 100 in-situ, a test structure 200 with a predefined geometry, in particular with a predetermined aspect ratio, can be generated using the generation unit 512. The test structure 200 can be generated as described above. Fig. 2 - 7, 9 or 10 can be configured as described. In this example, the test structure 200 is arranged on the sample 10 itself. The test structure 200 can be located on the substrate 12 (see Fig. 11) or on the coating 14 (see Fig. 11) be arranged on a lithography mask. The test structure 200 is preferably designed such that it can be removed without leaving any residue in a subsequent process step. As an alternative to the position on the sample 10, the test structure 200 can be produced on a position on the sample table specifically provided for this purpose or on a separate sample (not shown).

[0120] The device 500 also includes a determination unit 516, which here is designed as a component of a control computer 503 arranged externally to the vacuum housing 501. The determination unit 516 is used in particular for determining the geometry of the measuring tip 100 based on a profile 300 acquired with the measuring tip 100 (see Fig. 3 and Fig. 6) The test structure 200 is set up. The control computer 503 is set up to control the electron column 540 and the atomic force microscope 520.

[0121] The atomic force microscope 520 can also be used as a micromanipulator. For example, the measuring tip 100 is moved to a position on the sample 10 to be manipulated and brought into contact with the sample. In this way, for example, dirt adhering to the sample surface, such as dust particles, can be picked up by the measuring tip 100 and thus removed.

[0122] The test device 510 comprises at least the generating unit 512, the scanning unit 514 and the determining unit 516.

[0123] Fig. Figure 13 shows a schematic block diagram of an embodiment of a method for determining the geometry of a measuring tip 100 (see Fig. 1a, Fig. 1b, Fig. 3 or Fig. 12). In a first step S1, at least one test structure 200 (see Fig. 2 - 7, 9, 10) generates which surveys 210 (see Fig. 2, Fig. 3, Fig. 5 or Fig. 10) alternating with depressions 220 (see Fig. 2, Fig. 3, Fig. 5 or Fig. 10) in a first direction I (see Fig. 2, Fig. 3 or Fig. 10) exhibits, with the elevations 210 and depressions 220 parallel to each other in a second direction II (see Fig. 2 and Fig. 10) are aligned perpendicular to the first direction I. The test structure 200, for example, has one of the features shown in the Fig. The structures shown are 2-7, 9 or 10. The test structure 200 is preferably provided by the generating unit 512 (see Fig. 12) of the test device 510 (see Fig. 12) or the device 500 (see Fig. 12). In a second step S2, the test structure 200 is used with the measuring tip 100 to determine a profile 300 (see Fig. 3 or Fig. 6) the test structure 200 is scanned. This is done in particular by means of the scanning unit 514 (see Fig. 12) the test device 510 or the device 500. In a third step S3, the geometry of the measuring tip 100 is determined as a function of the determined profile 300. This is done, for example, by the determination unit 516 (see Fig. 12) the test device 510 or the device 500.

[0124] Once the geometry of the measuring tip 100 is determined, the measuring tip 100 can be used to analyze and / or process a sample 10. In particular, the suitability of the measuring tip 100 for a specific analysis or processing task is then known. Profiles 300 determined with the measuring tip 100 can be converted into height profiles of the scanned surface with high reliability based on the known geometry of the measuring tip 100.

[0125] Advantageously, by repeatedly scanning the test structure 200 with the measuring tip 100, a change in the geometry of the measuring tip, which may occur, for example, due to wear or abrasion, can be detected, so that the actual geometry of the measuring tip 100 can be monitored and faulty measurements can be avoided.

[0126] Furthermore, the generated test structure 200 can be removed in-situ, i.e. without breaking the vacuum, for example by means of a particle beam-induced etching process.

[0127] Although the present invention has been described using exemplary embodiments, it can be modified in many ways. REFERENCE MARK LIST 10 Sample 11 Sample table 12 Substrat 14 Coating 100 measuring tips 100a - c Measuring tip Section 101 Section 102 110 measuring probe 120 Cantilever 130 fastening section 140 probe holders 200 test structure 200a - f Test structure 210 Survey 220 In-depth study 230 substrate 300 Profile 300a - c profile 400 electron microscope image 500 Device 501 Vacuum Housing 502 Vacuum pump 503 Tax Calculator 510 Test device 512 production units 514 scanning unit 516 Unit of determination 520 Analysis and processing unit 530 Gas Supply Unit 532 Valve 534 Line 540 electron column 541 Electron source 542 Electron beam 543 Electron microscope ΔH Penetration depth AV1 Aspect Ratio AV2 aspect ratio B Structure size B1 width B2 width C1 cut C2 cut C3 cut D defect structure H1 height H2 height I first direction II second direction III third direction S1 Procedure step S2 process step S3 process step T tangent

Claims

[1] Method for determining a geometry of a measuring tip (100) for a scanning probe microscope, comprising the steps: a) producing (S1) at least one test structure (200) which has elevations (210) alternating with depressions (220) in a first direction (I), wherein the elevations (210) and depressions (220) are aligned parallel to one another in a second direction (II) perpendicular to the first direction (I); b) scanning (S2) the test structure (200) with the measuring tip (100) to determine a profile (300) of the test structure (200); and c) determining (S3) the geometry of the measuring tip (100) depending on the determined profile (300), wherein in step a) at least two test structures (200) are produced which have a different aspect ratio (AV1, AV2) with respect to the depressions (220), wherein the aspect ratio (AV1, AV2) indicates a height (H) relative to a width (B1, B2) of the depression (220), and wherein in step b) the at least two test structures (200) are scanned sequentially one after the other with increasing or decreasing aspect ratio (AV1, AV2), wherein the scanning is terminated when: in a sequence with decreasing aspect ratio (AV1, AV2) it is determined on the basis of the determined profiles (300) that a deepest point of a depression (220) is reached, or in a sequence with increasing aspect ratio (AV1, AV2) it is determined on the basis of the determined profiles (300) that a deepest point of a depression (220) is no longer reached. [2] The method of claim 1, further comprising: Acquiring an electron microscope image (400) of the at least one test structure (200); Determining a structure size (B1, B2) of the at least one test structure (200) from the acquired electron microscope image (400); and Determining the geometry of the measuring tip (100) as a function of the determined profile (300) and the determined structure size (B1, B2) in step c). [3] A method according to claim 1 or 2, wherein: in step a) at least one first test structure (200) and one second test structure (200) comprising elevations (210) alternating with depressions (220) are produced in a first direction (I), wherein the first direction (I) of the first test structure (200) has an angle other than 0°, in particular in the range of 45° - 90°, with the first direction (I) of the second test structure (200); and in step b) the at least two test structures (200) are scanned with the measuring tip (100) to determine a respective profile (300). [4] Method according to one of claims 1-3, wherein steps a) and b) are carried out in the same vacuum chamber (501) and / or without breaking the vacuum. [5] Method according to one of claims 1-4, wherein step a) comprises generating the at least one test structure (200) using a focused particle beam (542), in particular with an electron beam, and at least one precursor gas or etching gas. [6] Method according to one of claims 1-5, wherein the at least one test structure (200) has a linear structure in plan view with a comb-like cross-section, wherein the comb-like cross-section in particular comprises a substantially rectangular profile. [7] Method according to one of claims 1-6, wherein in step c) a length of a front portion (101) of the measuring tip (100) whose diameter is less than a width (B1, B2) of the recess (220) of the test structure (200) is determined. [8] A method according to any one of claims 1-7, wherein: before step a) a structural size (B) of a sample (10) to be measured or manipulated using the measuring tip (100) is determined; and in step a) the at least one test structure (200) is generated as a function of the determined structure size (B). [9] Method according to one of claims 1-8, further comprising: Removing the test structure (200) created in step a) after the geometry of the measuring tip (100) has been determined. [10] Method for analyzing and / or processing a sample (10), in particular a photomask for microlithography, comprising the steps: a) analyzing and / or processing a sample (10) using a measuring tip (100) of a scanning probe microscope (520); and b) determining a geometry of the measuring tip (100) according to the method according to one of claims 1-9 before and / or after step a). [11] Method according to claim 10, wherein steps a) and b) are carried out in the same vacuum chamber (501) and / or without breaking the vacuum. [12] Method according to claim 10 or 11, wherein in step b) the at least one test structure (200) is produced on the sample (10) and / or a substrate within a vacuum chamber (501) of the scanning probe microscope (520). [13] Test device (510) for determining a geometry of a measuring tip (100) for a scanning probe microscope, comprising: a generating unit (512) for generating at least one test structure (200) which has elevations (210) alternating with depressions (220) in a first direction (I), wherein the elevations (210) and depressions (220) are aligned parallel to one another in a second direction (II) perpendicular to the first direction (I); a scanning unit (514) for scanning the test structure (200) with the measuring tip (100) to determine a profile (300) of the test structure (200); and a determination unit (516) for determining the geometry of the measuring tip (100) as a function of the determined profile (300), wherein the generation unit is configured to generate at least two test structures (200) having a different aspect ratio (AV1, AV2) with respect to the depressions (220), wherein the aspect ratio (AV1, AV2) indicates a height (H) relative to a width (B1, B2) of the depression (220), and wherein the scanning unit (514) is configured to scan the at least two test structures (200) sequentially one after the other with increasing or decreasing aspect ratio (AV1, AV2), and wherein the scanning unit (514) is configured to terminate the scanning when: in a sequence with decreasing aspect ratio (AV1, AV2) it is determined on the basis of the determined profiles (300) that a deepest point of a depression (220) is reached, or in a sequence with increasing aspect ratio (AV1, AV2) it is determined on the basis of the determined profiles (300) that a deepest point of a depression (220) is no longer reached. [14] Device (500) for analyzing and / or processing a sample (10), in particular a photomask for microlithography, comprising: an analysis and processing unit (520) for analyzing and / or processing the sample (10) using a measuring tip (100) of a scanning probe microscope; and a testing device (510) according to claim 13, wherein the testing device (510) is configured to determine a geometry of the measuring tip (100) before and / or after analyzing and / or processing the sample (10).

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