Methods for characterizing defects in scanning electron microscopes.

Abstract

A method for characterizing a defect in a scanning electron microscope (100), the scanning electron microscope (100) being suitable for analyzing and / or processing a sample (10), in particular a lithography mask, using an electron beam (106), the method comprising the steps of: a) bringing the scanning electron microscope (100) to an equilibrium state (S1); b) introducing a trigger event (S2) into the scanning electron microscope (100) that disturbs the equilibrium state; c) detecting a response behavior of the scanning electron microscope (100) to the trigger event (S3); and d) comparing the detected response behavior with an expected response behavior for characterizing the defect (S4).

Description

[Technical Field]

[0001] The present invention relates to a method, apparatus, and computer program product for characterizing defects in a scanning electron microscope.

[0002] The content of priority application DE 10 2022 119 752.2 is incorporated by reference in its entirety. [Background technology]

[0003] Microlithography is used, for example, in the manufacture of microstructured components 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 (also called a reticle mask or lithography mask) illuminated by the illumination system is projected by the projection system onto a substrate, for example a silicon wafer, which is coated with a photosensitive layer (photoresist) and placed in the image plane of the projection system, to transfer the mask structure into the photosensitive coating of the substrate.

[0004] Masks are used for many exposures. Therefore, it is very important that they are free of defects. Significant efforts are accordingly made to inspect masks for defects and to repair any defects that are identified. Such mask defects can be on the scale of a few nanometers. Repairing such defects requires equipment that provides very high spatial resolution for the repair process.

[0005] Suitable devices for this purpose are those that activate local etching or deposition processes based on particle beam-induced processes, such as those disclosed in EP 1 587 128, where a chemical process is triggered using an electron beam from an electron microscope.

[0006] Such electron microscopes, particularly the electron beam columns of scanning electron beam microscopes (hereinafter "scanning electron microscopes" or "SEMs"), must regularly meet certain stability criteria to ensure the high-precision inspection and processing of lithography masks described above. Stability criteria include, for example, the beam position or beam profile of the generated electron beam. The stability of the electron beam column can be degraded by various external and internal disturbances. External disturbances include, for example, temperature and pressure fluctuations, vibrations, or the influence of magnetic fields. Internal disturbances can be caused by changes in the magnetic or electric fields within the electron beam column. Changes in the electric field are usually due to contamination, which can alter the charge.

[0007] Identifying and mitigating such faults can be complex in practice and can take several days, especially when the scanning electron microscope is already in use with a customer and the microscope manufacturer has limited access to it. Summary of the Invention

[0008] Against this background, the present invention aims to provide an improved method for characterizing lesions in a scanning electron microscope, in particular a rapid and targeted method.

[0009] Accordingly, there is provided a method for characterizing defects in a scanning electron microscope, the scanning electron microscope being suitable for analyzing and / or processing a sample (also called a "probe"), in particular a lithography mask, using an electron beam, the method comprising the steps of a) introducing a trigger event into the scanning electron microscope, b) detecting a response behavior of the scanning electron microscope to the trigger event, and c) comparing the detected response behavior with an expected response behavior for characterization of the defect.

[0010] In this way, it is possible to quickly and easily characterize the lesions in a scanning electron microscope.

[0011] Herein, any focused particle beam system can be used instead of a scanning electron microscope, for example a helium ion microscope.

[0012] For example, the method, or a method according to a further aspect, may comprise one or more of the following steps: i) recording an SEM image of a reference object that does not move within the chamber of the electron beam column; ii) calculating the offset of the recorded SEM images (the image offset corresponds to a change in the position of the electron beam); iii) comparing the image sharpness of the recorded SEM images; iv) calculating changes in parameters of the electron beam column such as focus, stigmator, or aperture (where appropriate, by optimizing these parameters by what are called automatic functions); and v) introducing a trigger event and repeating steps i) to v).

[0013] In one embodiment, prior to step a), the scanning electron microscope is brought to equilibrium and the trigger event in step a) is such that it disturbs the equilibrium.

[0014] The inventors have surprisingly found that faults can be visualized particularly efficiently by removing the scanning electron microscope, and in particular its electron beam column, from equilibrium and detecting and analyzing the response behavior. One advantage of this approach is that it simplifies the control of the scanning electron microscope, since it is always possible to record an image of, for example, a reference object. In contrast, if one simply introduces a trigger event into the scanning electron microscope without previously bringing the scanning electron microscope into equilibrium, such an image is only available or can be used, if at all, with difficulty as a basis for analyzing the response behavior.

[0015] An equilibrium state in this context is understood to mean a state of a scanning electron microscope in which the electron dose in the beam path of the electron beam column is constant over time. This means that the electron dose at location O1 at time t1 corresponds to the electron dose at location O1 at another time t2, which are the same or essentially the same, or in the case of a cyclic process, the electron dose in the beam path of the electron beam column is constant on average over time. The electron dose is determined as a function of current and voltage.

[0016] The sample is in particular a lithography mask, i.e. a mask intended for use in a lithography tool. This may in particular be an EUV or DUV lithography tool. EUV stands for "extreme ultraviolet" and refers to a working light wavelength between 0.1 nm and 30 nm. DUV stands for "deep ultraviolet" and refers to a working light wavelength between 30 nm and 250 nm.

[0017] In one embodiment, N images are recorded to bring the system into equilibrium, where N is preferably greater than 3, and more preferably greater than 10.

[0018] By recording N images (especially of a reference object), the equilibrium state of the scanning electron microscope can be easily established and maintained. For example, an image can be taken every 2 minutes for 10 seconds. During this time, the electron beam reaches the reference object. For the remaining time, i.e., 1 minute 50 seconds, the electron beam is directed towards the aperture of the scanning electron microscope using, for example, an electrostatic or magnetic deflector. In particular, the period envisaged for recording each of the N images may be shorter than the period between two consecutive images.

[0019] Reference objects are, for example, lithography masks, dissolved samples or other samples with structures in the nm range, Faraday cups with structures in the nm range or shielding elements for charge compensation (in particular meshes as described, for example, in DE 10 2020 124 306) which prevent charging of samples (in particular lithography masks) in normal operation.

[0020] In a further embodiment, bringing the system to equilibrium comprises recording the position and / or sharpness of the electron beam as a function of time and comparing it to a threshold value, and initiation of step a) is dependent on this comparison.

[0021] From the comparison of the above parameters with the threshold value, it can be concluded that the scanning electron microscope is indeed in an equilibrium state. In this case, a trigger event can be initiated. Alternatively, the step of bringing the system to equilibrium can consist of a predefined action (e.g., recording the aforementioned image) followed by a predefined waiting time. In this way, it is also possible to ensure that an equilibrium state has been reached. Only then is step a) initiated.

[0022] In a further embodiment, the response behavior detected in step b) is in particular the position, sharpness, focus, stigmator and / or coma of the electron beam as a function of time.

[0023] Focus in this context is understood to mean the beam diameter of the electron beam. Stigmator describes the dispersion of the beam cross section in two mutually orthogonal directions. Coma describes the deformation of the electron beam resulting from its passage through a lens outside the optical axis. Changes in position over time are also called "drift".

[0024] Such response behavior can be easily detected, especially in images of a reference object generated by a scanning electron microscope. This response behavior can be generated via image information resulting from the imaging of a spatially invariant reference object. For this purpose, the positional changes are determined using the offset of individual elements in the image or of previous elements of the complete image or of another reference. To determine the parameters that change the image sharpness (focus, stigmata, coma), it is possible to use either a comparison of the changed images themselves or of processed images (e.g., evaluation of the Fourier spectrum), or to optimize the electron beam by recording multiple images with changed beam characteristics to find a new optimization.

[0025] In further embodiments, the trigger event comprises a change in sample current, a change in acceleration voltage, part of a switch-on sequence, a change in process gas composition or process gas pressure, and / or a change in electron beam cross section or position.

[0026] In principle, any adjustment of the electron microscope is a possible trigger if the change causes a change in electron dose or electron energy. This includes variations in lens currents due to electron expansion and focusing at any point in the system, variations in accelerating and other voltages in the system, or variations in electron deflection by electrostatic deflector coils, mechanical elements, and the emitter.

[0027] Sample current is understood to mean the current of the electron beam detected in the area of the sample.

[0028] Part of a switch-on sequence is understood to mean switching off and / or on acceleration voltages, closing / opening valves, etc.

[0029] Suitable process gases for the deposition of materials and growth of elevated structures are, in particular, alkyl compounds of main group elements, metals, or transition elements, such as (cyclopentadienyl)trimethylplatinum CpPtMe3 (Me=CH4), (methylcyclopentadienyl)trimethylplatinum MeCpPtMe3, tetramethyltin SnMe4, trimethylgallium GaMe3, ferrocene Cp2Fe, bis-allylchromium 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, triruthenium dodecacarbonyl Ru3(CO). 12 , iron pentacarbonyl Fe(CO)5, etc.), and / or alkoxide compounds of main group elements, metals, or transition elements (e.g., tetraethyl orthosilicate Si(OC2H5)4, tetraisopropoxytitanium Ti(OC3H7)4, etc.), and / or halide compounds of main group elements, metals, or transition elements (e.g., tungsten hexafluoride WF6, tungsten hexachloride WCl6, titanium tetrachloride TiCl4, boron trifluoride BF3, silicon tetrachloride SiCl4, etc.), and / or complexes containing main group elements, metals, or transition elements (e.g., copper bis(hexafluoroacetylacetonate) Cu(C5F6HO2)2, dimethyl gold trifluoroacetylacetonate Me2Au(C5F3H4O2), etc.), and / or organic compounds such as carbon monoxide CO, carbon dioxide CO2, aliphatic hydrocarbons, and / or aromatic hydrocarbons.

[0030] Suitable process gases suitable for etching materials are, for example, xenon difluoride XeF2, xenon dichloride XeCl2, xenon tetrachloride XeCl4, water vapor HO, heavy water DO, oxygen O2, ozone O3, ammonia NH3, nitrosyl chloride NOCl, and / or one of the following halogen compounds: XNO, XONO2, X2O, XO2, X2O2, X2O4, X2O6 (where X is a halide). Further process gases for etching materials are defined in the applicant's U.S. patent application Ser. No. 13 / 0103281.

[0031] In a further embodiment, steps a) to c) (which may include a step of bringing the system into equilibrium) are performed for a first trigger event and repeated for a second trigger event, the first and second trigger events being selected such that the electron dose at a first location in the beam path of the electron beam has a first value at the occurrence of the first trigger event and a second value different from the first value at the occurrence of the second trigger event, and the electron dose at a second location in the beam path of the electron beam has the first value at the occurrence of the first trigger event and a second value equal to the first value at the occurrence of the second trigger event, and in a step following step c), a fault is assigned to the first location depending on the comparison in step c) for the first and second trigger events.

[0032] In other words, this embodiment is based on the discovery that a fault can be localized in that two different trigger events are configured to cause a change in a target area (first location) due to the introduced electron dose, which has the effect of causing similar changes (secondary effects) in one or more other locations. In this way, the fault can be localized so that a targeted repair can be performed or, for example, the correct part of the electron beam column can be replaced.

[0033] In a further embodiment, the first trigger event includes focusing the electron beam with the anode aperture and / or aperture stop, and the sample current is collected in a Faraday cup, and the second trigger event includes trimming the electron beam with the anode aperture and / or aperture stop, and the sample current is also collected in a Faraday cup.

[0034] For example, an electron beam column may generate a sample current ("sample current" in this context means the electron current directed toward a reference object) by varying a lens current that focuses the beam through an aperture (high current) or expands the beam before the aperture (low current). In other systems, the electron beam is directed through smaller or larger apertures, such as aperture slides or multi-aperture apertures, or through electromagnetic deflectors that direct the beam toward the desired aperture.

[0035] In an embodiment, the use of a Faraday cup in the configuration allows for the electron dose to be varied in the system so that the electron beam for image recording is directed towards the edge of the Faraday cup, whereas in the case of triggering, the electrons are directed into the Faraday cup.

[0036] In a further embodiment, the first trigger event comprises a change in current in the electron source for generation of the electron beam, and the second trigger event comprises an increase in sample current using capacitor excitation.

[0037] In a further embodiment, the first trigger event comprises the electron beam passing through an aperture and the second trigger event comprises an increase in the sample current.

[0038] The term "aperture" here refers to a multi-aperture aperture in the case of a single condenser, and to a single-aperture aperture in the case of a double condenser, for example.

[0039] In a further embodiment, the first triggering event includes completely blocking the electron beam at the aperture, and the second triggering event includes focusing the electron beam on the Faraday cup.

[0040] The above variants show a clever selection of first and second trigger events that are of high importance to the location of the error or fault.

[0041] In a further embodiment, the response behavior in steps b) and / or c) comprises a vertical displacement, or a jump, and / or a damping characteristic, or a transient response.

[0042] The vertical displacement (particularly in terms of its magnitude) or the decay characteristics (eg the time it takes for the detected parameter to fall below a defined threshold) can be easily evaluated.

[0043] In one embodiment, steps a) through c) (which may include bringing the system to equilibrium) are fully automated.

[0044] This allows the scanning electron microscope manufacturer's customers to perform the method quickly, especially on-site.

[0045] According to a further aspect, there is provided a computer program product comprising instructions, the program, when executed by a computer, causing the computer to perform the above method.

[0046] The computer program product, e.g., a computer program medium, may for example be provided or supplied as a storage medium, e.g., a memory card, a USB stick, a CD-ROM, a DVD, or in the form of a file downloadable from a server over a network, e.g., in a wireless communications network, this may be achieved by transferring an appropriate file by means of the computer program product or computer program.

[0047] Embodiments or features described above for the method are correspondingly applicable to the apparatus (described below) and computer program, and vice versa.

[0048] In this case, "a" or "an" should not necessarily be understood as being limited to exactly one element. Instead, a plurality of elements, e.g., two, three, or more, may be provided. Also, any other number used herein should not be understood as being limited to the exactly specified number of elements. Instead, unless otherwise specified, numerical deviations above and below are possible. Furthermore, described method steps may be performed in different orders, e.g., first step b) and then step a), unless otherwise specified.

[0049] Further possible implementations of the invention also include combinations not explicitly mentioned of the features or embodiments mentioned above or below with respect to the exemplary embodiments, in which case a person skilled in the art would also add individual aspects as improvements or supplements of the respective basic form of the invention.

[0050] Further advantageous structures and aspects of the invention are the subject of the dependent claims and the exemplary embodiments of the invention described below. The invention is elucidated in more detail below on the basis of preferred embodiments with reference to the attached drawings. [Brief explanation of the drawings]

[0051] [Figure 1] 1 shows a schematic diagram of a processing arrangement for checking and / or repairing lithographic masks. [Figure 2] 2 shows an electron beam column in the processing configuration of FIG. 1. [Figure 3] 1 shows a flow diagram of a method according to one embodiment. [Figure 4] 1 shows a flow diagram of a further method according to an embodiment. [Figure 5] 1 shows a diagram of a wafer inspection or metrology system for 3D volume inspection using a dual beam device. [Figure 6] 1 shows a diagram of a slice and image method for volume inspection of a wafer. [Figure 7] 1 illustrates a wafer inspection system according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0052] In the figures, identical or functionally identical elements are given the same reference symbols, unless one is specified. It should also be noted that the representative figures are not necessarily drawn to scale.

[0053] 1 shows a schematic diagram of an embodiment of a processing arrangement 100 (herein also referred to as "apparatus"), for example in the form of a scanning electron microscope. The processing arrangement 100 has the function of checking and / or repairing a sample, for example a lithography mask 10. The lithography mask 10 is intended for use in, for example, an EUV or DUV lithography apparatus (not shown).

[0054] The processing arrangement 100 comprises an electron beam column 102, which has an electron source 104 that generates an electron beam 106. The electron beam 106 impinges on the lithography mask 10. Backscattered electrons are detected by a detector unit 108 of the electron beam column 102. It is therefore possible to create a high-resolution image of the lithography mask 10 (electron beam microscope).

[0055] The electron beam column 102 is disposed within a vacuum housing 110, as is the lithography mask 10, which is disposed on a sample stage 112 below the electron beam column 102. A vacuum is created within the vacuum housing 110 using a vacuum pump 114. For example, -7 millibars ~ 10 -8 There is a residual gas pressure of millibars.

[0056] The electron beam column 102 can interact with a supplied process gas that is supplied externally by a gas supply unit 116 via a gas conduit 118 to the region of the focus of the electron beam 106, for example, to perform electron beam-induced processing (EBIP) operations, including, in particular, depositing or etching material onto or from the lithography mask 10. In particular, a control computer 120 of the processing arrangement 100 is configured to control the electron beam column 102, the sample stage 112, and the gas supply unit 116 in a manner suitable for this purpose.

[0057] In particular, the control computer 120 has stored thereon a computer program 122 which operates the processing arrangement 100 to carry out the method described in more detail below in connection with FIG.

[0058] FIG. 2 shows the electron beam column 102 of FIG. 1 in more detail. Compared to FIG. 1, FIG. 2 also shows that the electron beam column 102 of the electron source 104 includes an anode aperture 200 arranged downstream in the beam path. After the anode aperture 200, an aperture stop 202 with a single opening follows in the beam path. A first capacitor 206 of a double capacitor 208 is assigned to a beam path section 204 between the anode aperture 200 and the aperture stop 202. The aperture stop 202 is followed by a further aperture 210. A beam path section 212 between the aperture stop 202 and the further aperture 210 (which may be, for example, a pressure stage aperture) is surrounded by a second capacitor 212 of the double capacitor 208. After the aperture 210, the beam path is followed by the detector unit 108 already described in relation to FIG. 1. In particular, an energy-selective backscatter (ESB) detector 214 and a secondary electron (SE) detector 216 may be included, with a filter grid 220 disposed between the two. A further beam path section 218 following the detector unit 108 is surrounded by a magnetic lens 221. The electron beam 106 finally emerges from the electron beam column 102 and is directed towards the lithography mask 10 (or reference object 10′ in the manner described below) via a scan coil 222 and an electrostatic lens 226, which are responsible for scanning the lithography mask 10.

[0059] The above-described structure of the electron beam column 102 should be considered purely exemplary and various areas may have different designs, for example, a single capacitor may be provided instead of the double capacitor 208.

[0060] A flow diagram illustrating one embodiment of a processing sequence is described below with reference to Figure 3. This processing sequence may be carried out, inter alia, by the computer program 122 described in relation to Figure 1 within the processing arrangement 100.

[0061] In optional step S1, the scanning electron microscope 100 is brought to equilibrium. This can be achieved, for example, by having the scanning electron microscope 100 record N images using the detector unit 108, particularly of the reference object 10′, within the chamber of the scanning electron microscope 100 (not shown in detail), where N is preferably greater than 3, and more preferably greater than 10. The time taken to record an image can be, for example, 10 seconds, with an interval between images of 1 minute 50 seconds. These values are merely exemplary and can be adapted to the respective application. Typically, the scanning electron microscope 100 reaches equilibrium after recording 3 to 10 images.

[0062] In step S1, it can be checked that such an equilibrium state has indeed been reached by detecting the position and / or sharpness of the electron beam 106 (see Figures 1 and 2) as a function of time and comparing them with a threshold value: for example, if the drift is below a defined threshold, this ensures that an equilibrium state has been achieved and the method can proceed to step S2.

[0063] In step S2, a trigger event that disturbs the equilibrium state is introduced into the scanning electron microscope 100. This means that the scanning electron microscope 100, or in particular the electron column 102, is taken out of equilibrium. This means, for example, as follows:

[0064] 2 is constant over time or is constant during the recording of each of the N images (meaning, for example, that the electron dose at beam path section 204 during the recording of the first of the N images is equal to the electron dose at beam path section 204 during the recording of the second of the N images), but when the equilibrium is disturbed, the electron dose at a particular beam path section 204, 212, 218 changes over time. For a particular section, the electron beam dose can be calculated, for example, from the electron current and electron voltage.

[0065] Possible trigger events are, for example, a change in sample current, a change in acceleration voltage, part of a switch-on sequence, a change in process gas composition or process gas pressure, or a change in electron beam cross section or electron beam position.

[0066] In a further method step S3, the response behavior of the electron beam microscope 100 or the electron beam column 102 is detected. For example, the position, focus, stigmator, and / or coma of the electron beam 106 can be detected using the detector unit 108 (see FIGS. 1 and 2). In particular, it is also possible to detect or calculate derivatives of the aforementioned parameters in step S3. In the subsequent step S4, the detected response behavior is compared with an expected response behavior. The fault is characterized based on this comparison.

[0067] The expected response behavior may be recorded, for example, in a test preceding the method according to steps S1-S4, particularly before the scanning electron microscope 100 is delivered to a customer. A specific fault can be concluded by comparing the detected response behavior with the expected response behavior. This correlation can then be verified, for example, by experiment, prior to performing the method according to steps S1-S4, particularly before delivering the scanning electron microscope to a customer. This empirical knowledge can be included in the fault determination in step S4. For example, the fault may be a contamination in one of the beam path sections 204, 212, or 218. Such contamination has a predetermined effect on the response behavior of the electron beam column 102. In particular, in step S4, it is possible to verify the response behavior related to vertical displacement and / or collapse characteristics.

[0068] By carefully selecting the trigger event, the location of the fault can also be identified. For this purpose, the method according to steps S1-S4 is performed for a first trigger event and then repeated for a second trigger event, as shown in method step S5. The first and second trigger events are selected, for example, so that the electron dose in beam path section 204 (FIG. 2) has different values. In contrast, the electron dose in the other beam path sections of electron beam column 102 (identified here by reference numbers 212 and 218, for example) remains constant. In method step S6 following method step S4, if a fault is detected for the first trigger event of method step S4 but no such fault is detected for the second trigger event (in step S4 in the repetition of steps S1-S4), it can be concluded that the fault or its cause must be in beam path section 204. This is because the conditions (electron beam dose) in the other sections of electron beam column 102 remain unchanged. Therefore, a charge reversal must have occurred in electron beam section 204. Therefore, the corresponding evaluation shown in tabular form below can be carried out in method step S6.

[0069] [Table 1]

[0070] The second trigger event is also referred to as an identifier because it serves to classify the fault detected in the first trigger event, for example, as an actual fault, no fault, or an invalid measurement, and to assign the fault detected in the first trigger event to a specific location in the electron beam column 102.

[0071] The inventors have discovered that subsequent triggering events provide surprisingly good results in terms of localization of the fault.

[0072] For example, in the first trigger event, the electron beam 106 is focused through the anode aperture 200 (see FIG. 2) or the aperture stop 202. The sample current 228 does not strike the sample 10 but is instead collected in the Faraday cup 10′. Because of the focusing of the electron beam 106, the anode aperture 200 or the aperture stop 202 is not trimmed. In contrast, the second trigger event assumes trimming of the electron beam 106 by the anode aperture 200 and / or the aperture stop 202. The sample current 228 is similarly collected in the Faraday cup. This ultimately changes only the electron dose in the beam path section 204 (comparing the first trigger event to the second trigger event). In contrast, the electron dose in sections 212, 218, and all other regions remains constant within the electron beam column 102.

[0073] A further advantageous trigger event (first trigger event) has been found to be a change in the current of the electron source 104. The second trigger event in this case involves an increase in the sample current 228 by means of a capacitor. For this purpose, the electron beam is focused by the aperture 210, for example by means of a condenser lens (particularly the first one).

[0074] A further first trigger event assumes that the electron beam 106 passes through the aperture 210. A second trigger event increases the sample current 228. For example, the sample current is changed using a multi-aperture aperture with different diameters, or the beam diameter is changed as it passes through the aperture 210 (e.g., via increased excitation in a condenser lens).

[0075] In a further variation, the first trigger event involves completely blocking the electron beam 106 at the aperture 210. At the second trigger event, the electron beam 106 is focused into a Faraday cup.

[0076] 4 shows one possible implementation of the method described in relation to FIG. 3. In the method according to FIG. 4, in step T1, a repair or standby mode of the electron beam microscope 100 is initiated. In step T2, the electron beam microscope 100, in particular the electron beam column 102, is initialized. In step T3, an image of the sample 10 is recorded using the detector unit 108. In step T4, the sharpness of the detected image is measured. In step T5, the image offset is measured. In step T6, it is decided whether to initiate a trigger event according to step T7. This is done if the electron microscope 100 is found to be in an equilibrium state ("Yes"). If this is not yet the case ("No"), this is awaited in step T8. In step T9, a decision is made whether the process is complete. If not, it is repeated.

[0077] One embodiment of a wafer inspection system 1000 for 3D volume inspection is shown in Figure 5. The coordinate system is chosen so that the wafer surface 55 coincides with the XY plane.

[0078] To investigate the volume of a 3D inspection volume within a semiconductor wafer, a slicing and imaging method applicable to the inspection of the volume within the wafer has been proposed. In one embodiment, a 3D volume image is generated from the inspection volume within the wafer by a so-called "wedge-cut" approach or wedge-cut geometry without the need to remove a sample piece from the wafer. The slicing and imaging method is applied to inspection volumes with dimensions of a few microns (e.g., lateral lengths of 5 μm to 10 μm for a 200 mm or 300 mm diameter wafer). The lateral lengths can be longer, reaching up to 30 or 50 microns. V-shaped grooves or edges are milled into the top surface of the integrated semiconductor wafer to allow access to cross-sectional surfaces angled relative to the top surface. The 3D volume images of the inspection volume are acquired at a limited number of inspection locations, e.g., at a process control monitor (PCM), e.g., at representative locations on the die, or at locations identified by other inspection tools. The slicing and imaging method only locally destroys the wafer, allowing other dies to remain usable, or the wafer to be used for further processing. A method and inspection system with 3D volume imaging is described in WO2021 / 180600, which is incorporated herein by reference in its entirety.

[0079] The wafer inspection system 1000 is configured for a slicing and imaging method under a wedge-cut geometry using a dual beam system 1. For a wafer 8, multiple inspection locations, including inspection locations 6.1 and 6.2, are defined in a location map or inspection list generated from an inspection tool or design information. The wafer 8 is placed on a wafer support 15. The wafer support 15 is mounted on a stage 155 equipped with actuators and position control. Means for precise control of the wafer stage, such as actuators or laser interferometers, are known in the art. A control unit 16 is configured to control the wafer stage 155 and adjust the inspection location 6.1 of the wafer 8 at the intersection 43 of the dual beam device 1. The dual beam device 1 includes a focused ion beam (FIB) column 50 (having an FIB optical axis 48) and a charged particle beam (CPB) imaging system 40 (having an optical axis 42). At the intersection 43 of the optical axes of both the FIB and CPB imaging systems, the wafer surface 55 is disposed at a tilt angle GF relative to the FIB axis 48. The FIB axis 48 and the CPB imaging system axis 42 form an angle GFE, and the CPB imaging system axis forms an angle GE with the normal to the wafer surface 55. In the coordinate system of FIG. 5, the normal to the wafer surface 55 is given by the z-axis. A focused ion beam (FIB) 51 is generated by the FIB column 50 and impinges on the surface 55 of the wafer 8 at an angle GF. A tilted cross-sectional surface is milled into the wafer by ion beam milling at the inspection station 6.1 under approximately the tilt angle GF. In the example of FIG. 5, the tilt angle GF is approximately 30°. The actual tilt angle of the tilted cross-sectional surface may deviate from the tilt angle GF by up to 1° to 4° due to the beam divergence of a focused ion beam, e.g., a gallium ion beam. The FIB column 50 can be, for example, a gallium FIB or a FIB with a gas field ion source (GFIS) with other types of ion species such as xenon ions or argon ions. The charged particle beam imaging system 40 is tilted under an angle GE with respect to the wafer normal and an image of the milled surface is acquired.5, the tilt angle GE is approximately 15°, but other configurations are possible, for example, with GE=GF so that the CPB imaging system axis 42 is perpendicular to the FIB axis 48, or with GE=0° so that the CPB imaging system axis 42 is perpendicular to the wafer surface 55.

[0080] During imaging, a beam of charged particles 44 is scanned along a scan path over the cross-sectional surface of the wafer 8 at the inspection location 6.1 by the scanning unit of the charged particle beam imaging system 40, generating secondary and scattered particles. For example, a secondary electron particle detector 17.1 collects at least a portion of the secondary and scattered particles and communicates the particle count to the control unit 19. Other detectors for other interaction products may be present. For example, an in-lens detector 17.2 may be present for collecting backscattered charged particles. The control unit 19 controls the charged particle beam imaging column 40, the FIB column 50, and is connected to the stage control unit 16 to control the position of the wafer 8 mounted on the wafer support 15 via the wafer stage 155. The control unit 19 communicates with the motion control unit 2. The motion control unit 2 triggers, for example, via wafer stage movement, the placement and alignment of the wafer 8 at the inspection location 6.1 at the intersection 43 and triggers repeated FIB milling, image acquisition, and stage movement operations.

[0081] Each new intersecting surface is milled by the FIB beam 51 and imaged by a charged particle imaging beam 44 (e.g., a scanning electron beam or a helium ion beam of a Helium-Ion-Microscope (HIM)). In one embodiment, the dual beam system comprises a first focused ion beam system 50 positioned at a first angle GF1 and a second focused ion column positioned at a second angle GF2, and the wafer is rotated between milling at the first angle GF1 and the second angle GF2 while imaging is performed by the imaging charged particle beam column 40 positioned, for example, perpendicular to the wafer surface 55.

[0082] The dual beam system 1 further includes a gas injection system (GIS) 79, in which gas nozzles are connected to at least one gas reservoir (not shown) via valves (not shown). This provides a controlled amount of precursor gas during milling and imaging, allowing for example, the creation of metal coatings. For example, alignment marks or fiducials can be created. For example, tungsten metal coatings can be created by providing tungsten hexacarbonyl. Metal coatings can be shaped by ion beam milling, where alignment markers or fiducials are formed near the inspection location. This allows for precise registration and image alignment of multiple cross-sectional images. Using specialized precursor gases can enhance milling with the FIB 51. For example, it can improve milling uniformity and reduce curtaining across different material compositions. The material composition in a semiconductor wafer can include silicon, silicon dioxide, silicon nitride, copper, aluminum, or other materials.

[0083] Preferred precursor gases include at least one of ammonia, ammonium hydroxide, ammonium carbamate, bromine, chlorine, hydrazine, hydrogen peroxide, hadacidin, iodine, diiodoethane, isopropanol, methyl difluoroacetate, nitroethane, nitroethanol, nitrogen, nitrogen tetroxide, nitrogen trifluoride, nitromethane, nitropropane, nitrobutane, oxygen, ozone, PMCPS, tungsten hexacarbonyl, water, or xenon difluoride. However, other gases are also possible, such as acetyl methoxy chloride, methyl acetate, methyl nitroacetate, ethyl acetate, ethyl nitroacetate, propyl acetate, propyl nitroacetate, ethyl nitroacetate, methyl methoxyacetate, and acetyl methoxy chloride, acetic acid or thiolacetic acid, hexafluoroacetylacetone, silazane, trifluoroacetamide, dicobalt octacarbonyl, molybdenum hexacarbonyl, and combinations thereof.

[0084] Additionally, the dual beam system 1 further comprises a contact pin 81 connected to, for example, a manipulator (not shown) for precise movement of the contact pin 81 under control of the charged particle beam 44 during image acquisition, so that structures present on the wafer surface can be contacted and electrically connected to the control device 19.

[0085] FIG. 6 illustrates a wedge-cut geometry for an example 3D memory stack. FIG. 6 illustrates the situation when surface 52 is the last milled cross-sectional surface milled by FIB 51. Cross-sectional surface 52 is scanned by SEM beam 44, which, for example, in the example of FIG. 6, is positioned at normal incidence to wafer surface 55, to generate high-resolution cross-sectional image slices. Cross-sectional surfaces 53.1...53.N are subsequently milled by FIB beam 51 at an angle GF of approximately 30° relative to wafer surface 55, although other angles GF (e.g., GF=20° to GF=60°) are also possible. The cross-sectional image slices include first cross-sectional image features formed by intersections with high aspect ratio (HAR) structures or vias (e.g., first cross-sectional image features of HAR structures 4.1, 4.2, and 4.3) and second cross-sectional image features formed by intersections with layers L.1...LM, e.g., including SiO2, SiN, or tungsten lines. Some of the lines are also called "word lines." The maximum number M of layers is typically greater than 50, e.g., greater than 100, or even greater than 200. The HAR structures and layers span most of the wafer volume but may contain gaps. The HAR structures typically have diameters less than 100 nm, e.g., about 80 nm, or 40 nm. Therefore, the cross-sectional image slices contain first cross-sectional image features as intersections or cross sections of the HAR structures at different depths (Z) at each XY location. In the case of a cylindrical vertical memory HAR structure, the resulting first cross-sectional image features are circular or elliptical structures at various depths determined by the structure's position on the inclined cross-sectional surface 52. The memory stack extends in the Z direction perpendicular to the wafer surface 55. The thickness d or minimum distance d between two adjacent cross-sectional image slices is typically adjusted to a value on the order of a few nm, e.g., 30 nm, 20 nm, 10 nm, 5 nm, 4 nm, or even smaller. Once a layer of material of a predetermined thickness d has been removed with the FIB, the next cross-sectional surface 53.i . . . 53.J is exposed and becomes accessible for imaging with the charged particle imaging beam 44.Repeated milling and imaging produces multiple cross sections and multiple cross-sectional images, which adequately sample an inspection volume of size LX × LY × LZ, allowing, for example, a 3D volume image to be generated. This limits damage to the wafer to inspection volume 160 plus a damage volume in the y-direction of length LYO. With an inspection depth LZ of approximately 10 μm, the additional damage volume in the y-direction is typically limited to less than 20 μm.

[0086] FIG. 7 illustrates a further embodiment of an improved wafer inspection system. The wafer inspection system 1000 includes a dual beam system 1. The dual beam system is illustrated in FIG. 5, and reference is also made to the description of FIG. 5. Basic features of the dual beam system 1 may include a first charged particle or FIB column 50 for milling and a second charged particle beam imaging system 40 for high-resolution imaging of cross-sectional surfaces. The dual beam system 1 includes at least one detector 17 for detecting secondary particles, which may be electrons or photons. In this embodiment, a first detector 17.1 is positioned near the interaction volume of the primary beam 44 with the wafer 8 and configured to attract and collect secondary electrons. A second in-lens detector 17.2 is positioned within the imaging charged particle beam system 40 and configured to collect backscattered electrons. The dual beam system 1 further includes a wafer stage 155 configured to hold the wafer 8 during use. The wafer stage 155 includes actuators for lateral and axial displacement or rotation of the wafer stage 155. For example, the wafer stage includes a long-stroke actuator for displacing the wafer 8 from the first inspection location 6.1 to the second inspection location 6.2 (see FIG. 5) and a high-precision short-stroke actuator for precise alignment of the wafer 8 at the inspection location. The degrees of freedom for positioning and movement of the wafer stage 155 can range from three (rotation about the x-, y-, and z-axes) to all six degrees of freedom. The dual beam system 1 further includes a control unit 19. The control unit 19 is configured with memory and logic for controlling the operation of the dual beam system 1.

[0087] The wafer stage 155 is positionally controlled by a stage control unit 16. The stage control unit 16 is connected to a precision position sensor 21 that is configured to measure the position of the wafer stage 155 relative to the charged particle beam imaging system 40 in at least two degrees of freedom (x, y) during use. In one embodiment, the charged particle beam imaging system 40 and the precision position sensor 21 are mounted to a rigid support or metrology frame 25 that serves as a reference for relative position measurements between the wafer stage 155 and the charged particle imaging beam 44. Examples of the precision position sensor 21 include a laser interferometer, a grid interferometer, a capacitance sensor, or a confocal sensor. The precision position sensor 21 is configured to make at least one position measurement 27 of the position of the wafer stage 155 relative to the metrology frame 25 during use.

[0088] In use, the charged particle beam source 31 generates charged particles. The dual beam system 1 further comprises a deflection scanner 29 for raster scanning the charged particle imaging beam 40. The dual beam system 1 further comprises an objective lens 33 for focusing the charged particle imaging beam 40 onto a cross-sectional surface 53. The deflection scanner 29 and the objective lens 33 are connected and controlled by the control unit 19.

[0089] 7 further includes a condition monitor 23 configured as a measurement system for measuring environmental influences during image acquisition. The condition monitor 23 includes at least one of a group of measurement systems including an electromagnetic field sensor, a vibration sensor, a temperature sensor, and a gravity sensor. The condition monitor 23 is connected to the control unit 19 and configured to provide a plurality of measurements of environmental influences during image scanning at a plurality of representative dwell points during image acquisition.

[0090] The wafer inspection system 1000 further includes an operation control unit 2. The operation control unit 2 includes at least one processing engine 201, which may be composed of multiple parallel processors including a GPU processor and a common integrated memory. The operation control unit 2 further includes SSD memory, disk memory, or storage 203 for storing data including, for example, training data, a trained machine learning algorithm, and multiple cross-sectional images. The operation control unit 2 further includes a user interface 205. The user interface 205 includes a user interface display 400 and a user command device 401 and is configured to receive input from a user and display quotes or results to the user. The operation control unit 2 further includes memory or storage 219 for storing process information for the image generation process of the dual beam device 1 and for storing software instructions 3 executable by the processing engine 201.

[0091] The motion control unit 2 is further connected to an interface unit 231. The interface unit 231 is configured to receive further commands or data, e.g., CAD data, from an external device or a network. The interface unit 231 is further configured to exchange information, e.g., receive instructions from an external device or provide measurement results to an external device, or store a set of training data, a trained machine learning algorithm, or a plurality of cross-sectional images in an external storage.

[0092] The motion control unit 2 is connected to the dual beam system 1 and configured to receive the plurality of two-dimensional images of the plurality of cross-sectional surfaces. The motion control unit 2 is configured to determine a three-dimensional (3D) volumetric image of the examination volume 160 from the plurality of two-dimensional images of the plurality of cross-sectional surfaces.

[0093] Wafer inspection system 1000 is configured to receive user information for the performance of a measurement task (e.g., including CAD information for a semiconductor object of interest, the location of an inspection site, or inspection results). Processing engine 201 is configured to calculate and display information via user display 400 and to receive user input via user interface 401.

[0094] All features, method steps, and advantages described herein with respect to apparatus 100 and steps S1-S6 apply equally to apparatus / system 1000 and steps S2'-S4, and vice versa. Faults can be characterized in the same or substantially the same manner in apparatus or system 100, 1000.

[0095] According to one embodiment, a method for characterizing defects in a scanning electron microscope 100 is provided, the scanning electron microscope 100 being suitable for analyzing and / or processing a sample 8, 10, in particular a wafer or a lithography mask, using an electron beam 106. The method comprises the following steps: Step S2' of introducing a trigger event into the scanning electron microscope 100 (see FIG. 3); Step S3 of detecting the response behavior of the scanning electron microscope 100 to the trigger event; and step S4 of comparing the detected response behavior with an expected response behavior for fault characterization.

[0096] Advantageously, this embodiment does not rely on a previous equilibrium state (step S1 of the previous embodiment). Nevertheless, all embodiments and features described above with respect to method steps S1 to S4 apply equally to this method (steps S2' to S4).

[0097] According to one embodiment, step S2 or S2' comprises introducing a sequence of trigger events into the scanning electron microscope 40, 100. By using the sequence, the fault can be characterized in a more reliable / safer way.

[0098] According to one embodiment, the trigger event or each trigger event in the sequence of trigger events is an event that occurs during operation of the scanning electron microscope 40, 100. This may be the normal operation of the scanning electron microscope. Advantageously, no "extra" triggers are required to characterize the system, but rather triggers that occur naturally during operation of the electron microscope 40, 100 can be used.

[0099] According to one embodiment, the operations preferably include one or more of the following: a start-up phase in which the scanning electron microscope 40, 100 is started up, which includes, in particular, opening the column isolation valve 230 (see FIG. 2) of the scanning electron microscope 40, 100 and / or applying an accelerating voltage to one or more electrodes 104 of the scanning electron microscope 40, 100; an analysis step in which the sample 8, 10 is analyzed using a scanning electron microscope 100, which in particular comprises recording one or more images of the sample 8, 10 using the scanning electron microscope 40, 100; a processing step in which the sample 8, 10 is processed using a scanning electron microscope 40, 100, which processing step includes, in particular, depositing material on and / or etching material from the sample 8, 10, and / or milling the sample 8 using an ion beam 51, and / or recording one or more images of the sample 8, 10 using the scanning electron microscope 40, 100; and / or A sample transfer stage in which a sample 8, 10 is moved (238) into or out of the scanning electron microscope 100, which includes, among other things, turning off the accelerating voltage applied to one or more electrodes 104 of the scanning electron microscope 40, 100, closing the column isolation valve 230 of the scanning electron microscope 40, 100, and / or opening a sieve 232 (see FIG. 2) in the vacuum housing 110 of the scanning electron microscope 40, 100 to move the sample 8, 10.

[0100] These are examples of stages where one or more trigger events occur naturally, i.e., as part of normal system operation. Any anomalies detected in step S4 are therefore indications that there may be a problem.

[0101] According to one embodiment, the triggering event or sequence of triggering events includes one or more of the following triggers: the introduction of a gas preferably containing a carbon compound or a tungsten precursor, for writing a pad 502 containing a layer preferably made of carbon and tungsten (thus ensuring a good contrast) and position marks 500 on the pad 502 (based on the position marks 500 the progress of the milling process, in particular the depth, can be determined; the position marks 500 in the different images taken with the SEM 40 make it easy to determine the progress of the milling process), retracting and / or extending a gas injection needle 79 (e.g., for injecting process gas); setting a sample current (228) to write a position mark 500 on a pad 502 (the sample current is preferably greater than 1 or 4 nanoamperes); Setting the irradiation energy (i.e., the energy at which particles are irradiated onto the sample 8, 10) (the irradiation energy can be, for example, low (e.g., in the range of 500 to 1000 eV) and / or high (e.g., in the range of 15,000 to 30,000 eV)); Beam blanking during imaging, for example at the end of a scan line (in this case a short beam blank can be used, for example using electrode 234 (see FIG. 2) to avoid contamination); Beam blanking during FIB processing (in this case, a long beam blank can be used, for example, using coil 234 (see FIG. 2) (instead of an electrode)); Turning off the accelerating voltage during FIB processing; Introducing an auxiliary gas during FIB processing (e.g., H2O, O2, N2, and / or XeF2), and / or FIB processing (e.g., emission of secondary electrons due to FIB processing interacting with the scanning electron microscope 40).

[0102] According to one embodiment, the method further comprises: If an unexpected response behavior is determined in the comparing step S4, one or more additional trigger events are searched for, and if such additional trigger events are detected, a warning is output, and / or steps S1 to S4 or S2' to S4 are repeated, and / or operation of the scanning electron microscope 100 is stopped or aborted.

[0103] Some trigger events are difficult to isolate and analyze in a running process because they are likely to occur simultaneously. Therefore, it may be advantageous to run the method in a separate module. For example, it can be run "online," searching for unexpected responses against a list of triggers that occur during the process, and issuing a warning (yellow light) indicating the need for a service call / complete procedure, or aborting the process (red light). It is also conceivable to evaluate partial data as "suspicious" if the system's response is abnormal (e.g., increased beam drift in mapping due to blanking for FIB processing).

[0104] For example, in steps S3 and / or S4, the position of the electron beam can be plotted as a function of time relative to the previously placed alignment mark 500 for a second imaging method that does not rely on an electron beam (e.g., a focused ion beam), or the sample position (i.e., the position of the sample stage 15, 112) can be determined. Simultaneous imaging with secondary ions and backscattered primary electrons can distinguish, for example, between beam drift and stage drift (e.g., missing or defective laser interferometer). However, simultaneous imaging of ions and electrons can create another trigger event.

[0105] Furthermore, the occurrence of image line jumps and ripples can be detected. Image line jumps are very fast, discrete position changes, as opposed to slow, global image drift. For example, image line jumps can be caused by micro-arcing (defective insulation distances), which can occur at very high voltages. Furthermore, deformations of the scanning field (e.g., magnification, trapezoidal / cushion, non-linear deformations) can be recorded. This can be due to charges under the scanning system, or temperature changes in the scanning system after setting the minimum / maximum magnification.

[0106] [Table 2]

[0107] According to a further aspect, there is provided an apparatus comprising: a charged particle beam imaging system 40, 100; a detector unit 17.2, 102 for detecting the response behavior of the charged particle beam imaging system 40, 100 to a trigger event; A control unit (2, 120) for comparing the detected response behavior with the expected response behavior for fault characterization.

[0108] According to one embodiment, the apparatus is configured as a mask repair system 100 or a wafer inspection system 1000 .

[0109] According to one embodiment, the charged particle beam imaging system includes a scanning electron microscope 40, 100, a FIB column 50, and / or a dual beam system 1.

[0110] According to a further aspect, there is provided an apparatus comprising: a charged particle beam imaging system 40, 100; and a control unit 2, 120 configured to implement the above method.

[0111] Although the present invention has been described with reference to exemplary embodiments, this may be varied in many ways.

[0112] List of Reference Numbers 10 Lithography Mask 10' Reference object 100 Processing Placement 102 Electron Column 104 Electron source 106 Electron Beam 108 Detector Unit 110 Vacuum housing 112 Sample Stage 114 Vacuum Pump 116 Gas Supply Unit 118 Gas Pipe 120 Control Computer 122 Computer Program Products 200 Anode aperture 202 Aperture diaphragm 204 Beam Path Section 206 Capacitor 207 Capacitor 208 double capacitor 210 aperture 212 Beam Path Section 214 ESB detector 216 SE detector 220 Filter Grid 221 Magnetic Lens 222 scanning coil 226 Electrostatic Lens 228 Sample Current 230 Column Isolation Valve 232 Three 234 Beam Guiding Means 236 particles 238 Sample Transfer 1 Dual Beam Device 2. Motion control unit 3 Software Instructions 4.1 HAR Structure 4.2 HAR Structure 4.3 HAR Structure 6.1 Inspection Location 6.2 Inspection Location 8 wafers 15 Wafer support stand 16 Stage Control Unit 17.1 Secondary Electron Particle Detectors 17.2 In-lens detector 19 Control Unit 21 High-precision position sensor 23 Condition Monitor 25 measurement frames 27 Measurement Frame 29 Deflection Scanner 31 Charged particle beam source 33 Objective Lens 40 Scanning Imaging System 42 CPB imaging system 43 Intersection 44 Charged Particle Beam 48 FIB axis 50 FIB columns 51 FIB ion beam 52 Cross section surface 53.i…53.j Cross section surface 55 Wafer surface 79 GIS 81 Contact pin 155 wafer stage 160 test volumes 201 Processing Engine 203 Storage 205 User Interface 219 Storage 231 Interface Unit 400 user displays 401 User Command Device 500 position mark 502 Pad 1000 Wafer Inspection System GE angle GFE angle GE angle L.1~LM layer S1~S6 method steps T1~T9 method steps

Claims

1. A method for characterizing defects in a scanning electron microscope (40, 100), said scanning electron microscope (40, 100) being suitable for analyzing and / or processing a sample (8, 10), in particular a wafer or a lithography mask, using an electron beam (106), said method comprising: a) equilibrating the scanning electron microscope (40, 100) (S1); b) introducing a trigger event into the scanning electron microscope (40, 100) that disturbs the equilibrium state (S2); c) detecting a response behavior of the scanning electron microscope (100) to the trigger event (S3); d) comparing the detected response behavior with an expected response behavior for characterizing the fault (S4); A method comprising:

2. 2. The method of claim 1, wherein in step a) N images are recorded, where N is preferably greater than 3, more preferably greater than 10.

3. 3. The method according to claim 1, wherein in step a) the position and / or the visibility of the electron beam (106) are recorded as a function of time and compared with a threshold value, and the initiation of step b) depends on said comparison.

4. The method of any one of claims 1 to 3, wherein the response behavior detected in step c) is a position, focus, stigmator, and / or coma of the electron beam (106) as a function of time.

5. The method of any one of claims 1 to 4, wherein the trigger event comprises a change in sample current, a change in acceleration voltage, part of a switch-on sequence, a change in process gas composition or process gas pressure, and / or a change in electron beam cross section or position of the electron beam (106).

6. 6. The method according to claim 1, wherein steps a) to d) are performed for a first trigger event and repeated for a second trigger event (S5), the first and second trigger events being selected such that an electron dose at a first location (204) in the beam path of the electron beam (106) has a first value at the occurrence of the first trigger event and a second value at the occurrence of the second trigger event that is different from the first value, and an electron dose at a second location (212, 218) in the beam path of the electron beam (106) has a first value at the occurrence of the first trigger event and a second value equal to the first value at the occurrence of the second trigger event, and wherein in a step (S6) following step d), the fault is assigned to the first location (204) depending on the comparison in step d) for the first and second trigger events.

7. (i) the first trigger event comprises focusing the electron beam (106) with an anode diaphragm and / or aperture diaphragm (200, 202), with the sample current (228) being collected in a Faraday cup; and the second trigger event comprises trimming the electron beam (106) with the anode diaphragm and / or aperture diaphragm (200, 202), with the sample current (228) also being collected in the Faraday cup; (ii) the first trigger event comprises a change in current in the electron source (104) for generating the electron beam (106), and the second trigger event comprises an increase in the sample current (228) using capacitor excitation; (iii) the first trigger event comprises the electron beam (106) passing through an aperture (210), and the second trigger event comprises an increase in the sample current (228); and / or 7. The method of claim 6, wherein (iv) the first trigger event comprises completely blocking the electron beam at the aperture and the second trigger event comprises focusing the electron beam in a Faraday cup.

8. The method according to any one of claims 1 to 7, wherein the response behaviour in steps c) and / or d) comprises vertical displacement and / or damping characteristics.

9. The method according to any one of claims 1 to 8, wherein steps a) to d) are carried out in a fully automated manner.

10. A method for characterizing defects in a scanning electron microscope (100), said scanning electron microscope (100) being suitable for analyzing and / or processing a sample (8, 10), in particular a wafer or a lithography mask, using an electron beam (106), said method comprising: b1) introducing a trigger event into the scanning electron microscope (100) (S2'); c1) detecting a response behavior of the scanning electron microscope (100) to the trigger event (S3); d1) comparing the detected response behavior with an expected response behavior for characterizing the fault (S4); A method comprising:

11. The method of any one of claims 1 to 10, wherein step b) or b1) comprises introducing a sequence of trigger events into the scanning electron microscope (40, 100).

12. The trigger event or each trigger event in the sequence of trigger events is an event that occurs during operation of the scanning electron microscope (40, 100), said operation preferably including: a start-up phase in which the scanning electron microscope (40, 100) is started up, which includes in particular opening a column isolation valve (230) of the scanning electron microscope (40, 100) and / or applying an accelerating voltage to one or more electrodes (104) of the scanning electron microscope (40, 100); an analysis step in which the sample (8, 10) is analyzed using the scanning electron microscope (100), which step in particular comprises recording one or more images of the sample (8, 10) using the scanning electron microscope (40, 100); a processing stage in which the sample (8, 10) is processed using the scanning electron microscope (40, 100), in particular comprising depositing material on and / or etching material from the sample (8, 10) and / or milling the sample (8) using an ion beam (51) and / or recording one or more images of the sample (8, 10) using the scanning electron microscope (40, 100); and / or a sample transfer step in which the sample (8, 10) is transferred (238) into or out of the scanning electron microscope (100), comprising, in particular, switching off an accelerating voltage applied to one or more electrodes (104) of the scanning electron microscope (40, 100), closing a column isolation valve (230) of the scanning electron microscope (40, 100), and / or opening a slit (232) in the vacuum housing (110) of the scanning electron microscope (40, 100) to transfer the sample (8, 10); The method of any one of claims 1 to 11, comprising one or more of:

13. The trigger event or sequence of trigger events may include: Introduction of a gas preferably containing a carbon compound or a tungsten precursor for writing a pad (502) preferably containing a layer made of carbon and tungsten and a position mark (500) on said pad (502), Retracting and / or extending the gas injection needle (79); setting a sample current (228) to write a position mark (500) on the pad (502), said sample current preferably being greater than 1 or 4 nanoamperes; setting the irradiation energy, wherein the irradiation energy is e.g., low, including e.g., in the range of 500-1000 eV, and / or high, including e.g., in the range of 15,000-30,000 eV; Beam blanking during imaging, e.g., at the end of a scan line; Beam blanking during FIB processing; Turning off the accelerating voltage during FIB processing; introducing an auxiliary gas, e.g., H2O, O2, N2, and / or XeF2, during the FIB process; and / or For example, FIB processing, which is the emission of secondary electrons by interacting with the scanning electron microscope (40); The method of any one of claims 1 to 12, comprising one or more of:

14. 14. The method according to claim 1, further comprising, if in the comparing step (S4) an unexpected response behavior is determined, searching for one or more additional trigger events, and if such additional trigger events are detected, outputting a warning and / or repeating steps a) to d) or b1) to d1) and / or stopping operation of the scanning electron microscope (100).

15. a charged particle beam imaging system (40, 100); a detector unit (17.2, 102) for detecting the response behavior of the charged particle beam imaging system (40, 100) to a trigger event; a control unit (2, 120) for comparing the detected response behavior with an expected response behavior for fault characterization; An apparatus comprising:

16. The apparatus of claim 15, configured as a mask repair system (100) or a wafer inspection system (1000).

17. 17. The apparatus of claim 15 or 16, wherein the charged particle beam imaging system comprises a scanning electron microscope (40, 100), an FIB column (50), and / or a dual beam system (1).

18. a charged particle beam imaging system (40, 100); a control unit (2, 120) configured to implement the method according to any one of claims 1 to 14; An apparatus comprising:

19. A computer program product (3, 122) comprising instructions, which when executed by a computer, cause the computer to carry out the method of any one of claims 1 to 14.

Images