Method and device for correcting an imaging error of a particle beam during sample processing

Abstract

This case relates to a method (800, 900) and apparatus (100) for correcting at least one imaging error of a particle beam (105) during sample (105) processing. The method (800, 900) includes the steps of: (a) determining (step 920) at least one imaging error of the particle beam (127) after at least one interruption in the processing of the sample (105); and (b) correcting (step 930) the determined at least one error if the determined at least one imaging error of the particle beam (127) exceeds a specified threshold value.

Description

Method and device for correcting particle beam imaging errors during sample processing [Cross-reference] This patent application claims priority to German patent application No. DE 10 2023 208 993.9 filed with the German Patent and Trademark Office on September 15, 2023, entitled "Verfahren und Vorrichtung zum Korrigieren eines Abbildungsfehlers eines Teilchenstrahls während einer Probenbearbeitung", which is incorporated by reference in its entirety into this application. The present invention relates to a method and apparatus for correcting at least one imaging error of a particle beam during sample processing. As integration density in microelectronics steadily increases, photolithography masks must image increasingly smaller structures into the photoresist layer of the wafer. To meet these requirements, the exposure wavelength is shifting to shorter wavelengths. Currently, argon fluoride (ArF) excimer lasers, which emit at a wavelength of 193 nm, are primarily used for exposure. Intensive work is underway on light sources emitting in the extreme ultraviolet (EUV) wavelength range (10 nm to 15 nm) and corresponding EUV photomasks. The simultaneous development of multiple variants of conventional binary photolithography masks is increasing the resolution capabilities of wafer exposure processes. Examples include phase or phase-shift masks and masks for multiple exposures. Due to the ever-decreasing size of structural elements, lithography masks, reticles, or simple masks cannot always be produced on the wafer without visible or printable defects. Due to the high cost of producing reticles, defective masks must be repaired whenever possible. This also applies to microscopic samples or components such as stamps for nanoimprint lithography. Two important types of defects in lithography or photolithography masks are dark defects. These defects are areas where absorbers and / or phase-shifting materials are present, but not where they should be. These defects are preferably repaired by removing excess material using a localized etch process. Secondly, there are so-called transparent defects. These are defects on the photomask that, during optical exposure in a wafer stepper or scanner, have a higher light transmittance than an identical, defect-free reference location. During the photomask repair process, these defects can be corrected by depositing a material with appropriate optical properties. Ideally, the optical properties of the repair material should correspond to those of the absorber or phase-shifting material. The layer thickness at the repair location can then be adapted to the dimensions of the surrounding absorber or phase-shifting material layer. Typically, both types of defects are localized, often with sizes in the submicron range. These defects are typically repaired using particle beam-induced localized chemical processes. To repair localized defects in a sample, at least one process gas or precursor gas is provided at a processing location on the sample, where a focused particle beam induces a localized chemical reaction. To locally remove excess material from the sample, the process gas includes at least one etching gas. In the case of depositing missing material, the precursor gas includes at least one deposition gas. In the following, masks, masks for nanoimprint lithography, wafers, and various types of components to be repaired, such as micro-electro-mechanical systems (MEMS), nano-electro-mechanical systems (NEMS), or photonic integrated circuits (PICs), are grouped together under the term sample. In contrast to mechanical processes such as sputtering, chemical processes are generally slow-moving processes. When processing a defect, the sample may heat up locally. Furthermore, the micromanipulator used to align the sample with the focused particle beam may drift over a longer period of time. In addition, local irradiation of the sample with a charged particle beam can cause local static electricity in the sample. In addition to sample processing, these effects also occur when inspecting the sample using a focused particle beam. As a result, the charged particle beam cannot be incident on the intended location of the sample. All the effects outlined ultimately lead to drift between the intended processing location on the sample and the incident particle beam. This will lead to a deterioration in the lateral resolution of the particle beam relative to the defect surface of the sample. This leads to a deterioration in the (imaging) quality of the sample and also reduces the quality of the sample repair. This problem can be alleviated by placing one or more drift correction markers on the sample near the defect to be repaired. The drift correction marker(s) can be used as a reference during sample processing to determine the extent of drift, and then the drift can be corrected based on this information. For example, WO 2012 / 146 647 A1 describes depositing reference marks on a photomask using a particle beam, a process gas, and an additional gas (which may be an oxidizing gas). WO 2005 / 017 9 949 A2 describes depositing material on a photomask using an electron beam and tetraethyl orthosilicate (TEOS) or an organic or inorganic precursor gas. In addition to the translation of the beam position due to the drift process, the beam shape or beam geometry of a focused particle beam may also change over a longer period of time. Temperature changes and changes in the relevant materials, or in the case of semiconductor components, their functions, can affect the beam shape of the particle beam. In addition, the use of a precursor gas can accelerate the change of the beam geometry. For example, some precursor gases and / or their reaction products can penetrate a microscope column, such as the barrel of an electron beam microscope, and change the beam geometry of the particle beam. In addition, hysteresis effects can also affect the beam geometry, which may occur in magnetic lenses. However, during a defect treatment process, changes in the beam shape of the particle beam lead to a deterioration of the lateral process resolution and therefore ultimately reduce the quality of the defect repair performed. In addition, changes in the beam shape of the particle beam make it difficult to determine its drift, which has a negative impact on its correction. It is therefore an object of the present invention to provide a method and a device for correcting imaging errors of a particle beam during sample processing, which allow improved sample processing. According to an exemplary embodiment of the present invention, this object is achieved at least in part by the subject matter of independent claims 1 and 17 of the present application. A number of exemplary embodiments are described in the dependent claims. In one embodiment, the method for correcting at least one imaging error of a particle beam during a sample processing process includes the following steps: (a) determining at least one imaging error of the particle beam after at least one interruption in the sample processing; and (b) correcting the determined at least one error if the determined at least one imaging error of the particle beam exceeds a specified critical value. Generally, imaging errors or aberrations are considered to refer to deviations from ideal particle optical imaging caused by a real optical or particle optical system. In the present application, imaging errors or aberrations do not relate to ideal particle optical imaging, but rather to the best possible imaging of a real particle optical system. An image recorded with a particle optical system having the best possible settings is hereinafter referred to as a reference image. Even if the reference image exhibits a small amount of aberration, the reference image is used as a reference variable in the present application. Therefore, the reference variable is not an ideal image representation of a reference element, but rather the best possible image representation of a real particle optical system. In the present application, sample processing includes, for example, a controlled sample change. However, sample processing may also include a sample inspection or sample analysis, wherein a sample is imaged and / or the material composition of the sample is analyzed. It is not necessary to (substantially) change the sample or material composition. A process for treating a sample can be interrupted, for example, at any time or in a periodically repetitive manner. During the interruption of the process, it is determined whether the beam shape or beam geometry of the particle beam changes during the processing time. If this is not the case, or if the change in the beam shape is less than a specified critical value, the process (such as treating or repairing defects in the sample) will continue without changing the geometry of the particle beam. On the other hand, if the change in the beam shape of the particle beam exceeds a specified critical value, the beam shape of the particle beam is corrected in a manner that corrects imaging errors caused by the changed beam geometry. This can prevent deterioration of (imaging) quality and / or deterioration of the lateral process resolution of the process. Therefore, the consistent quality of sample processing can be ensured, that is, quality that is not affected by inspection time and / or processing time. Interrupting sample processing and determining at least one imaging error can be performed automatically, and correcting the at least one imaging error can be performed manually. However, interrupting sample processing and / or determining at least one imaging error can also be performed by human interaction, and correcting the at least one imaging error can be performed automatically. In a preferred embodiment, all steps of a method according to the present invention are performed fully automatically. The magnitude of an imaging error can be determined by determining one or more parameters used in image processing. For example, the widening of a structure's edge can be used as a metric or error measure. When considering edge contours, the magnitude of first- and / or second-order derivatives can be used. Alternatively and / or additionally, variables in Fourier space can be used to determine at least one imaging error. In other exemplary embodiments, the method for correcting at least one imaging error of a particle beam during sample processing may alternatively or additionally include the following steps: processing the sample after optimizing the particle beam and recording at least one reference image of one or more structural elements near the location of the sample to be processed; determining at least one imaging error of the particle beam at least partially during or after sample processing; and correcting the determined at least one error if the determined at least one imaging error of the particle beam exceeds a specified threshold value. Processing the sample includes processing the sample using a particle beam. Thus, the particle beam can serve a dual purpose. It can be used to image a sample, for example, defects within the sample and / or reference elements within the sample. Furthermore, the particle beam can be used to induce localized chemical reactions. As previously noted, the performance of this second function can accelerate changes in the beam shape of the particle beam, for example, through the action of a process gas or precursor gas and / or through temperature changes caused by sample processing. By implementing the method according to the present invention, changes in the beam geometry of the particle beam can be corrected regardless of their cause. Alternatively, however, the particle beam may not actively participate in sample processing, but rather be configured to make sample processing visible. In this embodiment of a method according to the present invention, sample processing can be performed, for example, via the probe of a scanning probe microscope or, more generally, via a micromanipulator. For example, the particle beam makes it possible to track sample processing in real time and, if necessary, intervene in automated processing. Alternatively, a first particle beam (such as an electron beam) can be used to observe or image a sample repair process performed by a second particle beam. In this case, the second particle beam can induce a localized chemical process and / or alter a sample through its sputtering effect. The particle beam can include a charged particle beam. The particle beam can include a focused particle beam. The particle beam can include an element selected from the group consisting of a photon beam, an electron beam, an ion beam, an atomic beam, and a molecular beam. Both electron beams and photon beams (particularly photon beams in the deep ultraviolet (DUV) and extreme ultraviolet (EUV) wavelength ranges) can be finely focused, enabling the localized chemical reaction of at least one precursor gas induced by an electron beam and / or a photon beam to occur over a very small area. This allows for high spatial resolution when repairing localized transparent and / or dark defects. The resolution of an electron beam can range from 0.4 nm to 10 nm, preferably from 0.5 nm to 8 nm, more preferably from 0.6 nm to 6 nm, and most preferably from 0.7 nm to 4 nm. Furthermore, the energy of the electron beam can range from 0.01 keV to 50 keV, preferably from 0.02 keV to 20 keV, more preferably from 0.04 keV to 5 keV, and most preferably from 0.1 keV to 2 keV. Furthermore, the beam current of the electron beam can range from 5 pA to 5000 pA, preferably from 10 pA to 1000 pA, more preferably from 15 pA to 300 pA, and most preferably from 20 pA to 100 pA. These values ​​apply both to recording images by scanning the electron beam over the structure and to sample processing using the electron beam and at least one precursor gas. In particular, material analysis of a defective sample region (eg X-ray analysis) requires high beam currents, ie electron currents in the nanoampere range. The dwell time of the electron beam during sample processing can range from 10 ns to 0.1 s, preferably from 100 ns to 10 ms, more preferably from 1 μs to 1 ms, and most preferably from 10 μs to 0.1 ms. In addition, the repetition time of the electron beam (repetition time; the period during which the electron beam strikes the same site of the sample) can range from 1 μs to 1 s, preferably from 10 μs to 0.5 s, more preferably from 0.1 s to 0.2 s, and most preferably from 1 ms to 0.1 s. Sample processing includes providing at least one precursor gas onto the sample. Preferably, providing at least one precursor gas includes locally providing at least one precursor gas at a processing location on the sample (e.g., at a processing location of a sample defect). A sample processing process may include a localized etching process and / or a localized deposition process. Sample processing can repair defects in the sample. Interruption of sample processing may include at least interruption of the supply of at least one precursor gas. Furthermore, interruption of sample processing may include changing at least one parameter of the particle beam before performing its secondary function. However, if a defect repair rate is low, i.e., the sample repair time is long compared to the time required to determine and correct particle beam imaging errors, then changing the gas supply can be omitted. Determining at least one imaging error of the particle beam can include recording at least one image of at least one reference element of the sample using the particle beam. Recording at least one image of at least one reference element may require changing one or more parameters of the imaging particle beam compared to the processing particle beam. Recording at least one image of at least one reference element of the sample may include scanning the particle beam over the reference element. Recording the at least one image can be accomplished without providing a precursor gas. The at least one reference element may include at least one element selected from the group consisting of: at least one structural element of the sample, at least one drift correction mark, or at least one defect of the sample. If a structural element can be used as a reference element already present on the sample, the process steps of producing the reference element and removing it from the sample after sample processing are complete can be omitted. This also applies if a first defect has a contour and can therefore be used as a reference element when removing a second defect from the sample. The sample may include a lithographic mask, and the at least one structural element may include at least one element selected from the following group: at least one absorption and / or phase shifting element of a pattern of the lithographic mask, at least one mark (registration mark) of the lithographic mask, or at least one defect of the lithographic mask. Typically, the pattern elements and / or markings on the mask have contours suitable for using these elements as reference elements. The mask can include a transmissive or reflective mask. A mask can include any mask type. A method according to the present invention may further comprise the step of depositing a sacrificial layer on the sample and / or depositing a protective layer around the processing site of the sample using a particle beam and a precursor gas in the form of at least one deposition gas. Depositing a protective layer on the sample around, or at least partially around, a defect to be treated or corrected protects the sample area surrounding the defect from negative effects of sample processing. If the defect is corrected by depositing material, the protective layer prevents unintended deposition of material outside the defect. The same applies to defects treated by a localized etching process. In this case, a protective layer around the defect prevents etching, thereby preventing unintended changes to the sample outside the defect. Depositing a sacrificial layer near the processing site provides an additional degree of freedom when depositing drift correction markers. For example, the material composition of the marker can be selected regardless of the sample material. Additionally, the sacrificial layer protects the sample from potential removal effects caused by scanning a particle beam over the sample to record an image of a reference element to determine at least one imaging error and / or drift. Generating the sacrificial layer and / or the protective layer may include performing a particle beam induced localized chemical reaction. A sacrificial layer and / or a protective layer may be composed of a material that allows for easy removal of the layer(s) after sample processing is complete. The height of the sacrificial layer and / or protective layer may range from 5 nm to 2000 nm, preferably from 10 nm to 1000 nm, more preferably from 20 nm to 500 nm, and most preferably 50 nm. The lateral dimensions of the sacrificial layer may exceed the lateral dimensions of the drift correction mark by 1.2 times, preferably 1.5 times, more preferably 2 times, and most preferably 5 times. The smaller lateral dimension of the protective layer may range from 5 nm to 1000 nm, preferably from 10 nm to 500 nm, more preferably from 20 to 300 nm, and most preferably from 30 nm to 200 nm. Deposition of sacrificial layers, protective layers, and / or materials on defects where material is missing can be performed at a rate of 0.01 nm / s to 1 nm / s, preferably 0.02 nm / s to 0.5 nm / s, more preferably 0.04 nm / s to 0.3 nm / s, and most preferably 0.05 nm / s to 0.15 nm / s. Etching of sacrificial layers, protective layers, and / or excess defective materials can be performed at a rate of 0.01 nm / s to 1 nm / s, preferably 0.02 nm / s to 0.5 nm / s, more preferably 0.04 nm / s to 0.3 nm / s, and most preferably 0.05 nm / s to 0.15 nm / s. The particle beam that treated the sample can be used to deposit the sacrificial layer and / or the protective layer. However, a different particle beam can also be used for this purpose. The sacrificial layer and the protective layer can be deposited using a single deposition gas or a combination of deposition gases. However, conversely, a specific deposition gas or a specific combination of deposition gases can also be used to deposit each layer. At least one deposition gas used to deposit the sacrificial and / or protective layers may contain carbon. Layers containing significant amounts of carbon can be removed from the sample using wet chemical processes. Such cleaning processes are typically used to clean the sample after processing. At least one reference element may have a material contrast relative to the sample and / or the sacrificial layer. At least one drift correction marker may have a material composition different from the material composition of the sample and / or the sacrificial layer. A drift correction mark may contain molybdenum (Mo), carbon (C), and oxygen (O) as main components. If an electron beam is used as a particle beam, a mark having this material composition provides not only a topographic contrast but also a material contrast, typically relative to both a sample and a sacrificial layer located below the mark. For example, in the absence of an oxidizing agent during the deposition of the drift correction mark, the mark may have the following material composition: Mo 10%-15% C7 0%-75% O 15% When an effective oxidant is used, a deposited marker for drift correction may essentially consist of MoO 3. This shows that a marker used for drift correction usually always contains at least as much carbon or oxygen as molybdenum. The term "substantially" in this context means (as indicated in this specification) that a measured variable is within the usual error limits where measurement techniques according to the state of the art are used to measure the variable. The multiple drift correction markers can have many different shapes. Small markers with clearly defined contours, such as cylindrical or conical structures, are preferred. Markers with easily shaped topography, such as rectangular parallelepipeds or cubes, are also useful. Preferably, a plurality of drift correction markers are arranged around a sample location to be repaired. From an economical perspective, a number of two to five markers has also proven to be advantageous. The height of the mark used for drift correction can range from 1 nm to 1000 nm, preferably from 5 nm to 500 nm, more preferably from 20 nm to 300 nm, and most preferably from 40 nm to 100 nm. The lateral dimensions of the mark used for drift correction are preferably smaller than the structural elements of the sample. This means that for a reticle used as a sample, the lateral dimensions of a mark should be smaller than the smallest dimension of the pattern elements of the reticle. The lateral dimensions of the mark used for drift correction can range from 1 nm to 500 nm, preferably from 2 nm to 250 nm, more preferably from 5 nm to 150 nm, and most preferably from 10 nm to 75 nm. A reference element and / or a marker used for drift correction always has a topographical contrast in the particle beam image relative to the sample or sacrificial layer on which the marker is placed. If the drift correction reference element or marker has a different material composition than the sample or sacrificial layer, the image recorded by the particle beam also contains this material contrast. This makes it easier to determine particle beam imaging errors. At least one mark used for drift correction may have a material contrast relative to the sample and / or the sacrificial layer. At least one reference element may be positioned within a scanning region of the particle beam. The particle beam-induced localized chemical process can generate at least one drift correction mark within the scanning region of the particle beam. A maximum scanning region is considered to be an area with dimensions below the micrometer range, approximately 20 μm by 20 μm or 50 μm by 50 μm. When configuring or positioning a reference element, two boundary conditions must be observed. If the distance between the reference element and the processing site is too small, the reference element may be negatively affected by the sample processing, which reduces its function as a reference for correcting imaging errors of the particle beam and / or for drift correction. On the other hand, if the distance of the mark from the processing site is too large, that is, outside a scanning range of the particle beam, position-related aberrations such as coma and / or field curvature cannot be correctly detected and corrected because the sample must be displaced relative to the particle beam in order to scan the mark. The displacement of the sample relative to the particle beam has a negative impact on the accuracy with which at least the drift of the particle beam can be determined. In addition, a large distance between the reference element(s) and the defect sample position may have a negative impact on the positioning accuracy. A favorable distance range is from 0.2 µm to 100 µm. Generating at least one drift correction mark can include at least one element selected from the group consisting of: depositing at least one drift correction mark on the sample, depositing at least one drift correction mark on the sacrificial layer, etching at least one drift correction mark into the sample, and etching at least one drift correction mark into the sacrificial layer. The drift correction mark etched into the sacrificial layer and / or the sample can have similar dimensions to the mark deposited on the sample and / or the sacrificial layer. If a mark is created on an absorptive pattern element of a photomask whose lateral dimensions are significantly smaller than the smaller lateral dimension of an absorptive pattern element, and if the mark can be deposited in the center of the pattern element, the mark can remain on the sample after sample processing, as it does not substantially interfere with the operation of the photomask. In all other cases, it is advantageous to apply the at least one drift correction mark to a sacrificial layer that is designed to be easily removable from the sample (e.g., photomask), for example, by a wet chemical cleaning process. This allows the at least one drift correction mark to be removed from the sample along with the sacrificial layer. This can be accomplished particularly simply if the mark is created as a structure etched into the sacrificial layer. A method according to the present invention may further comprise the following steps: performing a localized particle beam-induced localized chemical reaction to generate at least one drift-corrected marker. A particle beam with corrected imaging errors can be used to generate at least one drift-corrected marker. However, a particle beam with different types of particles can also be used to generate at least one drift-corrected marker. For example, the imaging errors of an electron beam used for sample processing can be corrected, and a sacrificial layer, a protective layer, and / or at least one drift-corrected marker can be deposited with the aid of a photon beam or an ion beam. The sample may include a lithographic mask, and the at least one structural element may include at least one element selected from the group consisting of a pattern element of the lithographic mask or an alignment mark of the lithographic mask. Furthermore, the sample may include an imprint stamp for nanoimprint lithography, and the at least one reference element may include a structural element of the imprint stamp. Determining at least one imaging error may include analyzing at least one recorded image relative to at least one reference. The at least one reference element may include at least one element selected from the following group: at least one reference image of the at least one reference element; stored data determined from at least one reference image of the at least one reference element; at least one reference image recorded by a particle beam; stored data determined from at least one reference image recorded by a particle beam; a database having at least two images of the at least one reference element, the at least two images being recorded by a particle beam having at least one defined imaging error, or a database having stored data, the stored data being determined from at least two images of the at least one reference element, the at least two images being recorded using a particle beam. A reference image of a reference element is an image generated by a particle beam from the reference element in which imaging error(s) are minimized. The at least one reference image of the at least one reference element may comprise a reference image similar to that recorded using the particle beam. This means that a reference image of the at least one reference element can be recorded by another (e.g., a second) particle beam and transformed into a reference image similar to the reference image recorded by the particle beam. A method according to the invention may further comprise systematically varying at least one parameter of the particle beam before recording at least one of the at least two images of at least one reference element, the at least one reference element being adapted to generate at least one defined imaging error. Multiple images of a reference element can be stored in a database, wherein one or more parameters of the particle beam are systematically varied during the recording process. This modifies the beam shape of the particle beam in a defined manner, so that the particle beam generates an image of the reference element with defined imaging errors. The database can contain images of individual imaging errors of varying severity. Furthermore, the database can contain multiple images of combinations of two or more aberrations of varying severity that were present during the recording process. For these images, it is known that the parameter variation(s) associated with the best possible settings generate the corresponding images. When an image of the reference element is to be recorded again, by determining the image stored in the database that is closest to the measured image of the reference element, the parameter variation(s) that eliminates the imaging error can be determined, so that the particle beam with the modified parameter settings generates a reference image of the reference element. A database can be created before sample processing. During the processing, all that is required is image comparison to determine the parameters for correcting particle beam imaging errors. Therefore, this type of imaging error correction has no impact on the progress of the processing process. Correcting the determined at least one imaging error may include using at least one element selected from the group consisting of: an auto-correction function and a machine learning training model. The automatic correction function may comprise at least one algorithm configured to determine imaging error(s) of the particle beam by comparing the recorded image of the at least one reference element with a reference image of the at least one reference element. The algorithm that performs the automatic correction function is computationally intensive and therefore takes time. It must be executed during sample processing. Specifically, only after the algorithm has been executed can a decision be made whether beam correction is actually necessary. Therefore, this method of correcting imaging errors can extend sample processing time. The machine learning training model may include as input data at least one element from the following group: a sample's material composition, a sample processing type, a particle beam type, at least one particle beam parameter, at least one component of at least one precursor gas used, or at least one sample processing environment parameter. Furthermore, the machine learning model can be trained using data from the same or similar processing or repair processes. The environmental parameter may include at least one element selected from the group consisting of: temperature of the sample processing site, pressure of the sample processing site, or humidity of the sample processing site. The machine learning training model can determine the time interval of a sample processing loop. The loop time interval can include the time interval between the start of sample processing and the first interruption of sample processing, or generally, the nth time interval can include the time interval between the (n-1)th and nth interruptions of sample processing. The machine learning training model can determine the nth time interval from n-1 input data from previous sample processing. Training a machine learning model can include training a machine learning model using a plurality of images with imaging errors having associated input data and a plurality of reference images having associated input data. A machine learning model generates knowledge from experience. A machine learning model learns from multiple examples presented to the model in the form of training or learning data during a learning or training phase. Using this approach, the model's internal variables (e.g., parameters of a parameterized mapping) are populated with appropriate values ​​to describe the relationships in the training data. Therefore, machine learning models typically do not simply memorize the training data during training, but rather recognize patterns and / or regularities in the training data. The quality of the learned relationship is typically evaluated against validation data to assess the generalization ability of the trained model to new data (i.e., data unknown during training). A trained machine learning model can be applied to correct for particle beam imaging errors to predict the potential effects of beam shape variations in an image of a reference element unknown to the machine learning model when provided with relevant input data. Therefore, a successfully trained or learned machine learning model (i.e., a machine learning model with good generalization) can be evaluated on unknown images of reference elements after the training phase when provided with relevant input data. A machine learning model can include at least one element from the following group: parameter mapping, an artificial neural network (ANN), a deep neural network (DNN), a time-delay neural network, a convolutional neural network (CNN), a recurrent neural network (RNN), a long short-term memory (LSTM) network, and a generative model. Correction of the specific imaging error may include changing at least one parameter of the particle beam such that when recording an image of the at least one reference element, the particle beam with the at least one changed parameter substantially produces a reference image. At least one imaging error of the particle beam can be determined by recording and analyzing one or more images (such as reference markers). To minimize disruption to the processing process by determining the imaging error, the recording time of the one or more images should be as short as possible. Furthermore, the time required to analyze the image(s) to determine the imaging error should be as short as possible. Therefore, an automated calibration process requiring a small number of steps is preferred. A method according to the invention may further comprise the steps of continuing sample processing without correcting the particle beam if the imaging error is less than a specified critical value, or correcting at least one imaging error of the particle beam and continuing sample processing with at least one particle beam having modified parameters if the imaging error is greater than or equal to a specified critical value. For example, a critical value can be defined as the percentage of deterioration of the image presentation compared to that recorded using the best possible settings of the particle beam. The deterioration of the imaging may be associated with an increase in imaging errors, such as the main imaging error, or with two or more types of different imaging errors, such as defocus, astigmatism, coma, etc. For example, a critical value can be defined as the doubling of the imaging error presented in the image relative to the reference image presentation, i.e., at the best possible settings of the parameters of the particle beam. The at least one imaging error of the particle beam may include at least one element selected from the group consisting of focus variation, astigmatism variation, and coma variation. Imaging errors can manifest as deviations from the best possible settings in at least two directions. For example, a focus change can mean over- or underfocusing. It's often difficult to detect which direction of deviation is responsible for the detected aberration(s). However, this is necessary to correct the imaging errors. In this case, the images stored in the database can help determine the parameter(s) of the particle beam that are needed to correct the detected particle beam aberration(s). The at least one imaging error comprises a drift of the particle beam relative to the sample and the device selected from the group consisting of focus variation, astigmatism variation, and coma variation. Recording a single image of at least one reference element allows determining both the severity of particle beam aberrations and their drift relative to the sample. Implementation of a method according to the invention can therefore significantly improve the quality of sample processing. The at least one precursor gas may include at least one element selected from the following group: at least one etching gas, at least one deposition gas, or at least one additive gas. The at least one precursor gas may include a first deposition gas for depositing at least one drift correction mark, at least one sacrificial layer, and / or at least one protective layer. The at least one first deposition gas may include at least one element selected from the group consisting of a metal alkyl, a transition element alkyl, a main group alkyl, a metal carbonyl, a transition element carbonyl, a main group carbonyl, a metal alkoxide, a transition element alkoxide, a main group alkoxide, a metal complex, a transition element complex, a main group complex, or an organic compound. The at least one precursor gas may include a second deposition gas for generating at least one marker for drift correction. The at least one second deposition gas may include at least one element selected from the group consisting of tetraethyl orthosilicate (Si(OC 2H 5) 4) Metal carbonyl, transition element carbonyl or main group carbonyl. The at least one metal carbonyl may comprise at least one element selected from the group consisting of: chromium hexacarbonyl (Cr(CO) 6) Molybdenum hexacarbonyl (Mo(CO) 6) Tungsten hexacarbonyl (W(CO) 6) Dicobalt octacarbonyl (Co 2(CO 8)), triruthenium dodecacarbonyl (Ru 3(CO) 12 ) and iron pentacarbonyl (Fe(CO) 5). The at least one main group element alkoxide may include at least one element selected from the following: tetraethyl orthosilicate (Si(OC 2H 5) 4, TEOS), tetramethyl orthosilicate (Si(OCH 3) 4, TMOS) or titanium tetraisopropoxide (Ti(OCH(CH 3) 2) 4). The at least one precursor gas may include at least one additive gas selected from the group consisting of an oxidizing agent, a halide, and a reducing agent. The oxidant may comprise at least one element selected from the following group: oxygen (O 2) Ozone (O 3) Water vapor (H 2O), hydrogen peroxide (H 2O 2) Nitrous oxide (N 2O), nitric oxide (NO), nitrogen dioxide (NO 2) or nitric acid (HNO 3). The halide may include at least one element selected from the following group: chlorine (Cl 2), hydrochloric acid (HCl), xenon difluoride, hydrofluoric acid (HF), iodine (I 2), hydrogen iodide (HI), bromine (Br2), hydrogen bromide (HBr), nitrosyl chloride (NOCl), phosphorus trichloride (PCl 3) Phosphorus pentachloride (PCL 5) or phosphorus trifluoride (PF 3). The reducing agent may comprise at least one element selected from the following groups: hydrogen (H 2) Ammonia (NH 3) or methane (CH 4). The first deposition gas may contain molybdenum hexacarbonyl (Mo(CO) 6), the at least one additional gas may contain nitrogen dioxide (NO 2), and the second deposition gas may include tetraethyl orthosilicate (Si(OC 2H 5) 4) or chromium hexacarbonyl (Cr(CO) 6). The at least one reference element may include at least one marker for drift correction, and a method according to the present invention may further include the step of removing the at least one marker for drift correction from the sample. The removal of the at least one sacrificial layer and the at least one mark for drift correction can be achieved in a common process step. The removal of the at least one sacrificial layer and / or the at least one mark for drift correction can be achieved during a wet chemical cleaning process of the sample. A computer program may include a plurality of instructions. When a computer system executes the computer program, the computer system is caused to perform the method steps of the aforementioned aspect of a method according to the present invention. A computer-implemented method for correcting at least one imaging error during sample processing comprises: (a) receiving at least one image of at least one reference element; (b) comparing the at least one received image of the at least one reference element with at least one or more stored images of the at least one reference element to automatically determine at least one imaging error; and (c) automatically changing at least one parameter of a particle beam such that the imaging error of the particle beam with the at least one changed parameter is less than a specified threshold. A method according to the present invention can be implemented in a manner that requires no human interaction. Thus, a method according to the present invention can be objectified, i.e., freed from subjective human evaluation. Furthermore, the method can be integrated into a sample processing process with minimal extension of sample processing time. In one embodiment, an apparatus for correcting at least one imaging error of a particle beam during a sample processing process includes: (a) means for determining at least one imaging error of the particle beam after at least one interruption in the sample processing; and (b) means for correcting the determined at least one error if the determined at least one imaging error of the particle beam exceeds a specified threshold. The device may further include at least one element selected from the following groups: a component for providing at least one precursor gas on the sample, a component for guiding and controlling the gas flow rate of the at least one precursor gas, a component for generating, focusing and scanning a particle beam, a component for adjusting the focus, a component for correcting the astigmatism and coma errors of the particle beam, a component for adjusting the objective lens for focusing the particle beam, a component for moving the sample in the beam direction of the particle beam, a component for adjusting the astigmatism device, a component for positioning the particle beam relative to a porous aperture, a component for positioning the porous aperture relative to the particle beam, or a component for positioning the particle beam inside and / or outside the particle beam column. A device according to the present invention may further comprise an astigmatist for varying the astigmatism of the particle beam. The astigmatism device may comprise at least one electric and / or magnetic multipole element, which is oriented substantially perpendicularly to the beam direction of the particle beam. The electric and / or magnetic multipole elements of the astigmatism device are capable of generating a quadrupole field. The electric and / or magnetic multipole elements may include quadrupole, hexapole, octapole and / or dodecapole elements. Coma error can be corrected by positioning the beam inside the beam column. Drift in the beam's incident position on the sample can be corrected by positioning the beam outside the beam column. A device according to the invention may also have a multi-aperture aperture for generating a defined particle flow. The multi-aperture diaphragm may include two to ten, preferably three to nine, more preferably four to eight, and most preferably five to seven apertures. The apertures of the multi-aperture diaphragm may have different opening widths. The particle beam can be shaped by selecting an aperture with a corresponding opening width through which the particle beam passes. The opening width of at least one of the plurality of apertures of the multi-aperture aperture can be adjusted within a range of 0.1 μm to 1000 μm, preferably 0.2 μm to 500 μm, more preferably 0.5 μm to 200 μm, and most preferably 1 μm to 100 μm. The multi-aperture diaphragm can be positioned in the microscope column upstream of the objective lens along the beam direction and can be used to adjust the size of the particle beam. A device according to the invention may also have an extractor diaphragm and / or an anode diaphragm at the output of the particle gun. The apparatus may be configured to perform the method steps according to any of the preceding aspects. The device may further include a computer system having the aforementioned computer program. Additionally, the device may include one or more algorithms configured to interrupt sample processing, determine imaging errors, and correct the determined imaging errors. The one or more algorithms can be implemented using hardware, software, firmware, or a combination thereof. A currently preferred embodiment of a device for correcting imaging errors and / or particle beam drift during sample processing according to the present invention will now be explained in more detail using the example of a modified scanning electron microscope. However, the device according to the present invention is not limited to the example described below. Those skilled in the art will readily appreciate that, instead of using the scanning electron microscope discussed below, any scanning particle microscope using, for example, a focused ion beam and / or a focused photon beam as an energy source may be employed. Furthermore, a method according to the present invention is not limited to the use of, for example, the photomask discussed below as a sample. Rather, it can be used to repair any lithography photomask. Furthermore, the application of a method according to the present invention is not limited to applications on photomasks. Rather, it can be used to repair nanoimprint lithography stamps or templates, or generally to correct microstructured components such as wafers, MEMS, NEMS, or PICs. Furthermore, in addition to or independently of sample processing, the device according to the present invention can also be used to analyze the material composition of a sample. For example, some analytical methods, such as energy-dispersive X-ray spectroscopy (EDX), require a large, high-resolution electron count or electron dose to be provided over a longer period of time in order to obtain spatially resolved information about the material composition of the sample. FIG1 schematically illustrates the basic components of an apparatus 100 that can be used to correct imaging errors of a particle beam and / or to correct drift of a particle beam during a processing step of a sample 105. Sample 105 can be any microstructured component or structural member. For example, sample 105 can include a transmission or reflection mask and / or a template for nanoimprint lithography. Furthermore, apparatus 100 can be used to process, for example, integrated circuits, wafers, microelectromechanical systems (MEMS), nanoelectromechanical systems, and / or photonic integrated circuits (PICs) that exhibit defects, such as missing material and / or excess material. In the example explained below, sample 105 is a lithography mask. 1 is a modified scanning electron microscope (SEM). An electron gun 115 generates an electron beam 127 that is directed by elements 120 and 125 as a focused electron beam 127 onto a lithography mask disposed on a sample stage 110. The sample stage 110 has multiple micromanipulators (not shown in FIG. 1 ) that enable the location of defects on the reticle 105 to be brought below the point of incidence of the electron beam 127 on the reticle 105. Furthermore, the sample stage 110 can be displaced in height (i.e., along the beam direction of the electron beam 127) so that the focus of the electron beam 127 remains on the surface of the reticle (also not shown in FIG. 1 ). The electron beam 127 can be focused by adjusting the height of the sample stage 110. However, this also means that slippage or drift in the height adjustment of the sample stage 110 can cause defocusing of the electron beam 127. The height of the sample 105 can change in both directions—upward or downward—which can lead to over- or underfocusing. In addition to adjusting the height of the sample stage 110, the focus of the electron beam 127 can also be reversed or adjusted by changing the focusing effect of the objective lens of the apparatus 100. Furthermore, the sample stage 110 may include a device for adjusting and controlling the temperature to allow the reticle to reach and remain at a specified temperature (not specified in FIG1 ). Furthermore, the temperature and other parameters of the environment of the characterization apparatus 100 and / or the interior of the particle beam column containing its electronic components, such as air pressure and / or humidity, can be measured and regulated. For this purpose, a liquid cooling system and / or a chiller can be used. The apparatus 100 typically includes a plurality of apertures 182, 184, or an aperture system 180. An extractor aperture and an anode aperture are mounted in the column of the apparatus 100 after the electron gun 115, indicated by reference numeral 182 in FIG1 . In the exemplary apparatus 100 shown in FIG1 , the aperture system 180 further includes an aperture 184 having a plurality of openings of varying diameters. Typically, the aperture 184, or multi-aperture aperture 184, is fixedly mounted in the microscope column. A first deflection system guides the electron beam 127 through corresponding openings of the multi-aperture aperture 184, depending on the desired operating point (e.g., sampling current, and, if desired, resolution and / or depth of field). One or more second deflection systems, positioned below the multi-aperture aperture 184, deflect the electron beam 127 away from corresponding openings of the multi-aperture aperture 184, causing the electron beam to pass through the center of the objective lens 125. The first and second deflection systems, or the first and second deflection systems, may include, for example, electric and / or magnetic deflection systems. The deflection system is suppressed in Figure 1. The coma aberration of the electron beam 127 can be reduced by passing the electron beam 127 through the center of the objective lens 125. However, in an alternative embodiment, the multi-aperture diaphragm 184 can be designed to be movable perpendicular to the beam direction. By moving the multi-aperture diaphragm 184 in a plane perpendicular to the beam direction of the electron beam 127, the electron beam 127 or particle beam 127 can be directed through an opening of the multi-aperture diaphragm 184 of a corresponding width or diameter. The lateral displacement of the at least one first deflection system and the at least one second deflection system and / or the multi-aperture diaphragm can be adjusted by the control unit 145 of the apparatus 100. The size of the particle stream can be adjusted via the selected opening width of the multi-aperture diaphragm 184. By directing the electron beam 127 through the center of the objective lens 125 independently of the electron beam intensity, its coma aberration can be reduced. The distance between apertures 182 (extractor aperture and / or anode aperture) and multi-aperture aperture 184 of aperture system 180 in the beam direction of electron beam 127 can be 1 cm, preferably 2 cm, more preferably 5 cm, and most preferably 10 cm. The number of apertures can vary from 2 to 20. Currently, five to seven apertures of multi-aperture aperture 184 are preferred. The opening diameter of multi-aperture aperture 184 preferably has a value in the range of 1 μm to 50 μm. It is advantageous to guide the precisely positioned particle beam 127 through the openings of multi-aperture aperture 184 so that it passes through the optical center of downstream objective lens 125. This allows for a virtually coma-free image of particle beam 127 incident on sample 105. Furthermore, the apparatus 100 has an astigmatism filter, which is not shown in Figure 1. The astigmatism filter comprises an octupole element that generates a quadrupole electric field. The astigmatism filter is used to correct the aberration of the electron beam 127 in the form of astigmatism. The apparatus 100 of FIG. 1 uses an electron beam 127 as an energy source 127 to induce a localized chemical reaction in a precursor gas or a mixture of two or more precursor gases. An electron beam 127 can be focused to a small focal spot with a diameter of less than 10 nm, preferably less than 5 nm. Furthermore, the electrons incident on the reticle surface cause virtually no damage to the reticle 105, even if their kinetic energy varies over a wide energy range. However, the apparatus 100 and method presented herein are not limited to the use of an electron beam 127. Rather, any particle beam capable of locally inducing a chemical reaction in a precursor gas at the point of impact of the particle beam on the surface of a sample 105 (such as a reticle 105) and generating image data from the sample surface can be used. Examples of alternative particle beams include ion beams, atomic beams, molecular beams, and / or photon beams. Furthermore, two or more particle beams can be used in parallel. Specifically, an electron beam 127 and a photon beam or an ion beam can be used simultaneously as the energy source 127 (not shown in FIG. 1 ). The electron beam 127 can be used to record an image of the reticle, particularly the locations of defects in the reticle. A detector 130 for detecting backscattered electrons (BSE) and / or secondary electrons (SE) provides a signal proportional to the surface profile and / or composition of the reticle. A computer system 140 of apparatus 100 can generate an image of the reticle by scanning electron beam 127 across the reticle with the aid of a control unit 145. Specifically, under optimal possible parameter settings for electron beam 127, a reference image of one or more reference elements present on sample 105 (i.e., the reticle in FIG1 ) can be recorded by scanning the electron beam 127 across the reticle before a processing step on the sample 105 (i.e., the reticle in FIG1 ) begins. The optimal possible parameter settings for electron beam 127 are those that result in a focused electron beam 127 with the minimum imaging error or aberration permitted by apparatus 100. In addition to recording reference images of one or more reference elements present on the sample 105, a database containing images of one or more reference elements with a defined aberration ratio can be generated by a system parameter mismatch before sample processing begins. The aberrations of the images in this database can then be reversed by reversing the defined parameter mismatch, with the result that the images in the database are converted back to corresponding reference images. The generated database can thus be used to correct aberrations "acquired" by a particle beam during sample processing. To achieve this, the computer system 140 performs a quantification of image characteristics, which is used to determine the imaging error(s) of the particle beam 127. Control unit 145 can be part of computer system 140, as shown in FIG1 , or can be designed as a separate unit (not shown in FIG1 ). Computer system 140 can include algorithms implemented using hardware, software, firmware, or a combination thereof, and can extract an image of defects in a reference component and / or sample 105 from the measurement data from detector 130. A screen (not shown in FIG1 ) of computer system 140 can display the calculated image. Furthermore, computer system 140 can store the measurement data from detector 130 and / or the calculated image. Control unit 145 of computer system 140 can also control electron gun 115 and the beam path through device 100's beam imaging and beam shaping elements 120 and 125. Control signals from control unit 145 can further control the movement of sample stage 110 via a micromanipulator (not shown in FIG1 ). Furthermore, the computer system 140 and / or the control unit 145 may include one or more algorithms stored in a non-volatile memory (not shown in FIG. 1 ) of the computer system 140 and / or the control unit 145. Such algorithms can determine aberrations of the electron beam 127 by comparing a recorded image of one or more reference elements with a reference image of one or more reference elements. The algorithm(s) can also determine parameter changes that reduce aberrations of the electron beam 127. Thus, the one or more algorithms can be considered an automatic correction function that minimizes imaging errors of the electron beam 127. Electron beam 127 incident on the reticle can electrostatically charge the reticle. This can cause electron beam 127 to deflect and reduce spatial resolution during image recording of a reference element or defect, and during defect repair. To reduce electrostatic charging of the reticle, an ion gun 135 can be used to irradiate the reticle surface with ions of low kinetic energy. For example, argon ions with a kinetic energy of approximately 100 eV can be used to neutralize the reticle 105. Alternatively and / or additionally, a conductive grid mounted at the output of the column can be used for charge compensation. To process the sample 105 or reticle placed on the sample stage 110, or to repair defects therein, the apparatus 100 includes at least three storage containers for three different process gases, process gases, or precursor gases. A first storage container 150 stores a first precursor gas in the form of a deposition gas. For example, a main-group element alkoxide, such as TEOS, can be stored in the first storage container 150, which can be used to repair defects in the reticle, such as missing material from the reticle blank. The second storage container 155 stores an etching gas, such as xenon difluoride (XeF 2). Other examples of etching gases that can be stored in the second storage container are: a halogen, such as chlorine (Cl 2) Fluorine (F 2) Bromine (Br 2) or iodine (I 2) Oxygen (O 2) Ozone (O 3) and nitrosyl chloride (NOCl). The third storage container 160 stores an oxidant. The oxidant can include, for example, an element selected from the following group: oxygen (O 2) Ozone (O 3) Water vapor (H 2O), hydrogen peroxide (H 2O 2) Nitrous oxide (N 2O), nitric oxide (NO), nitrogen dioxide (NO 2) Nitric acid (HNO 3) and other oxygen-containing compounds. The fourth optional storage container 165 can, for example, store a reducing agent such as hydrogen (H 2) Ammonia (NH 3) and methane (CH 4). The fifth optional storage container 170 can also store a carbon-containing precursor gas. The precursor gas stored in the fifth storage container 170 can be, for example, a metal carbonyl, such as chromium hexacarbonyl (Cr(CO) 6) or molybdenum hexacarbonyl (Mo(CO) 6). Metal carbonyls can be used to deposit a protective layer around the defects to be treated. In addition, during sample processing, a metal carbonyl can be used to deposit one or more markers that serve as reference elements for drift correction. In addition, a metal carbonyl, preferably Mo(CO) can be used. 6. As a deposition gas for depositing a sacrificial layer and / or a protective layer. Finally, the sixth optional storage container 175 can contain a second etching gas. This second etching gas can be used to repair excess material defects (dark defects) on the photomask. Furthermore, the etching gas stored in the sixth container 175 can be used to remove reference elements in the form of marks used for drift correction, a sacrificial layer, and / or a protective layer from the photomask. Each storage container 150, 155, 160, 165, 170, 175 has its own control valve 151, 156, 161, 166, 171, 176 to control the amount of the corresponding gas provided per unit time, that is, the gas flow rate at the incident point of the electron beam 127 on the sample 105. The control valves 151, 156, 161, 166, 171, and 176 are controlled and monitored by the control unit 145 of the computer system 140. Therefore, the partial pressure ratio of the gas provided at the processing site can be set within a wide range. Furthermore, in the exemplary apparatus 100, each storage container 150, 155, 160, 165, 170, 175 has its own gas supply system 152, 157, 162, 167, 172, 177, with a nozzle at the end near the point of incidence of the electron beam 127 on the reticle 105. In an alternative embodiment (not shown in FIG. 1 ), a gas supply line system is used to bring several or all of the process gases in a common flow to the surface of the sample 105. In the example shown in FIG1 , valves 151, 156, 161, 166, 171, and 176 are positioned adjacent to corresponding containers 150, 155, 160, 165, 170, and 175. In an alternative arrangement, control valves 151, 156, 161, 166, 171, and 176 can be incorporated adjacent to corresponding nozzles (not shown in FIG1 ). Unlike the schematic illustration shown in FIG1 , and not currently preferred, one or more gases stored in containers 150, 155, 160, 165, 170, and 175 can also be provided in a non-directional manner within the lower portion of the vacuum chamber 102 of the apparatus 100. In this case, a screen (not shown in FIG1 ) is installed between the lower reaction chamber 107 and the upper portion 102 of the apparatus 100. This screen provides the electron beam 127 to prevent vacuum depletion in the upper portion of the apparatus 100. Each of the storage containers 150, 155, 160, 165, 170, and 175 can have its own temperature setting element and control element capable of cooling and heating the corresponding storage container. This allows the precursor gases to be stored and supplied at relatively optimal temperatures (not shown in FIG. 1 ). This also allows the control valves 151, 156, 161, 166, 171, and 176 to be used as digital elements, with the gas flow or flow rate being controlled via a heater in the storage container 150, 170, 160, 165, 155, 175, i.e., via the vapor pressure of the precursor gas. Furthermore, each supply system 152, 157, 162, 167, 172, and 177 can include its own temperature setting element and temperature control element to provide all process gases or precursor gases at their optimal processing temperatures at the point of incidence of the electron beam 127 on the reticle 105 (also not shown in FIG. 1 ). The control unit 145 of the computer system 140 can control the temperature setting components and temperature control components of the storage containers 150 , 155 , 160 , 165 , 170 , 175 and the gas supply systems 152 , 157 , 162 , 167 . Apparatus 100 in FIG1 includes a pump system for generating and maintaining a desired vacuum (not shown in FIG1 ) in vacuum chamber 102 . A residual gas pressure of ≤10^-7 mbar is achieved in vacuum chamber 102 of apparatus 100 by closing control valves 151 , 156 , 161 , 166 , 171 , and 176 . The pump system may include separate pump systems for an upper portion 103 and a lower portion 107 of apparatus 100 for providing electron beam 127 , the lower portion including sample stage 110 with sample 105 . Furthermore, apparatus 100 may include a suction device near the processing point of electron beam 127 to establish a defined local pressure condition on the surface of sample 105 or reticle 105 (not shown in FIG1 ). The use of an additional suction device can largely prevent one or more volatile reaction products of one or more precursor gases (unwanted for localized deposition of the deposition material) from being deposited on the photomask 105 and / or within the vacuum chamber 102 or reaction chamber 107. Furthermore, the suction device can prevent particles formed during an etching process from being distributed within the vacuum chamber 102 of the apparatus 100. The functions of the pump system(s) and the additional suction device can also be controlled and / or monitored by the control unit 145 of the computer system 140. Furthermore, apparatus 100 may include one or more atomic force microscopes (AFMs) that allow for detailed analysis of sample defects (not shown in FIG1 ). Furthermore, one or more AFMs may be configured to perform sample processing, and focused electron beam 127 may be used for in-situ observation or monitoring of sample processing. For example, an AFM probe may be configured to remove defects caused by excess material through mechanical processing. Furthermore, one or more AFM probes may be configured to remove particles from sample 105. Furthermore, a probe may be configured to repair a transparent defect by depositing an absorbing material. Finally, the lower portion of FIG1 schematically shows a cleaning device 190 having a cleaning liquid 195 for cleaning a sample 105 during and / or after sample processing in the device 100. The cleaning liquid 195 can be adapted to the sample 105 to be cleaned. The cleaning liquid 195 can comprise water and / or an aqueous solution, such as dilute sulfuric acid or dilute hydrogen peroxide under the action of ultrasound or megasonic waves. Furthermore, the presence of ultraviolet (UV) or infrared (IR) light and a diluent gas such as hydrogen (H2) can also be used to clean the sample 105. 2) and / or oxygen (O 2) The presence of can enhance the cleaning effect of the cleaning liquid. In addition, the cleaning device 190 can be used to remove reference marks present as marks for drift correction from the sample 105. If the marks for drift correction, a sacrificial layer and / or a protective layer have been removed by means of, for example, the precursor gas Mo(CO) 6 deposition, these marks or layers can be removed from the sample 105 with a cleaning liquid containing a specific solution such as an inorganic acid, base or organic ligand. FIG2 schematically illustrates a detail view of a photomask as an example of sample 105. Detail 200 shows a defect 260 on a substrate 210 of the photomask that is intended to be repaired by a particle beam induced treatment process. Defect 260 can be a defect of missing material, excess material, or particles on the photomask substrate 210. In the example of FIG2 , a defect 260 is a defect of excess material on the photomask substrate 210, i.e., a dark defect 260. In the example of FIG2 , defect 260 is isolated, i.e., there are no pattern elements of the photomask in its vicinity that could function as a reference element or on which a reference element could be generated. In order to compensate for drift of the particle or electron beam 127 during sample processing, the detail 200 has a reference element 230 in the form of a marker 230 for drift correction. In the example shown in Figure 2, the marker 230 has a circular and / or cylindrical shape. To prevent damage to the marks 230 during multiple scans for drift correction, which is used to determine the position of the marks 230, the marks 230 or DC marks 230 (DC stands for drift correction) are deposited on a sacrificial layer 220 of the photomask blank 210. Furthermore, a defined material contrast of the electron beam 127 (e.g., particle beam 127) between the sacrificial layer 220 and the reference element 230 can be set through the sacrificial layer 220. Furthermore, the material composition of the sacrificial layer 220 can be selected so that it can be removed from the photomask 105 together with the reference element 230 after sample processing in a wet chemical cleaning step. In the exemplary embodiment of FIG. 2 , the sacrificial layer 220 has a rectangular shape. The double-headed arrow in FIG2 indicates a reference distance 240 of the DC mark 230 relative to the defect 260. The coordinates of the DC mark 230 at the start of sample processing (based on the coordinate system of the sample carrier 110) define a reference position 250 of the DC mark 230. The coordinate system of a two-dimensional vector describing the direction and absolute value of the drift between the electron beam 127 and the position of the defect 260 is referred to as the reference position 250 of the DC mark 230. The reticle detail 200 shown in FIG2 has a DC mark 230. Of course, two, three, four, or even more reference elements 230 can be generated on the reticle around the defect 260 and used to determine the drift and / or aberrations of the particle beam 127. 2 indicates the surface that is scanned by the focused electron beam 127 to determine the reference position 250 of the reference element 230 before the treatment process of the defect 260 of the sample 105 begins. In the example of FIG2 , the scanning range of the electron beam 127 is entirely located on the sacrificial layer 220. FIG3 shows a detail of the photomask 200 after a portion or a first portion of sample processing has been performed, i.e., a process for treating the defects 260. The dark defects 260 are treated by performing a particle beam induced localized chemical reaction in the form of an etching process, i.e., the dark defects 260 are removed from the photomask blank 210 by etching. For example, xenon difluoride (XeF 2) It can be used as an etching gas. Depending on the material composition of the defect 260, an additive gas, such as an oxidant, such as oxygen (O 2) or chlorine (Cl 2) Can be added to the etching gas. A combination of two or more etching gases can also be used to remove the defect 260. The sample treatment in the form of a local chemical reaction is a lengthy process that can last for several minutes, up to hours if large-scale defects occur. In addition, the sample treatment can lead to local variations in the temperature on the sample 105. Furthermore, the use of a precursor gas or a mixture of different precursor gases can change the focus of the focused electron beam 127, or more generally, change the beam shape of the focused electron beam 127. These effects of the sample treatment can lead to a drift of the electron beam 127 relative to the defect 260 to be treated. The correction of a drift is explained using Figures 3 and 4. In addition, the described effects can change the beam shape or beam geometry of the focused particle beam 127. The consequences of a beam variation and the elimination of beam variations are discussed below with reference to Figures 5 to 7. Due to the above-mentioned effects, sample processing is interrupted, and the focused electron beam 127 is displaced by the reference distance 240 to scan the DC mark 230 again without supplying a precursor gas. If the position of the alignment mark scanned by the focused electron beam 127 is approached and the imaging error of the focused electron beam 127 is determined within a short period of time, the interruption of the precursor gas supply can be avoided. This avoids the need to wait for a period of time after the gas flow is interrupted until the gas flow stabilizes after it is restarted. As shown by vector 350 in FIG3 , the DC mark 230 has moved within the scan range 270. This means that the processing window of the focused electron beam 127 has shifted relative to the defect 260 to be etched. To examine in detail the drift 350 of the DC mark 230 relative to its reference position 250, the scan range 270 of the electron beam 127 in this example is substantially displaced about the drift vector 350 and the DC mark 230 is scanned again. Starting from the new position of the DC mark 230, the focused electron beam 127 is again displaced by the reference distance 240 and processing of the defect 260 is continued. The process is illustrated in Figure 4. In Figures 3 and 4, defect 260 is reproduced in grayscale, while defect 260 in Figure 2 is shown in black. This indicates that defect 260 in Figures 3 and 4 has been partially removed by etching; that is, Figures 3 and 4 show a residual defect of original defect 260. If necessary, sample processing can be interrupted a second time, typically n times, to detect focused electron beam drift and / or aberrations at the end of the nth processing interval or at the end of the nth cycle. FIG5 shows an image 500 of a reference element 530 recorded using the best possible parameter settings for the electron beam 127, resulting in an image containing minimal aberrations. Image 500 thus represents a reference image 500 of the reference element 530. The reference element 530 has three cylindrical structures 505, 510, 515 arranged at the ends of an isosceles or equilateral triangle. The center of the center of gravity of the reference element 530 can be selected as a reference position 550 of the reference element 530. Like reference element 230, reference element 530 is not a pattern element present on sample 105 or the reticle. Instead, reference element 530 is a mark for drift correction. Reference element 530 may, for example, comprise reference element 230 of FIG. 2 . This means that reference element 530 can be deposited on a sacrificial layer 210 of the sample using a deposition gas or a deposition gas mixture through the components of an electron beam induced deposition process. However, reference element 530 or the mark 530 for drift correction can also be etched into sacrificial layer 210. Furthermore, DC mark 530 can be deposited directly on or etched into the reticle blank 210 of the reticle 105. 2 , a reference element 530 or a reference image 500 of a DC marker 530 can be used to determine a reference position 550 of the DC marker 530. The reference position 550 of the DC marker 530 can be determined with high accuracy based on the reference image 500. As explained in the context of FIG. 3 , after partial processing of defect 260, sample processing is interrupted and DC mark 230 is scanned again with focused electron beam 127, with or without interruption of precursor gas flow, to obtain an image of DC mark 230. FIG. 6 presents image 600 of DC mark 530 of FIG. 5 after sample processing is interrupted. In image 600 of FIG. 6 , DC mark 530 exhibits an increased amount of aberration compared to reference image 500 due to the defocusing of electron beam 127. The increased amount of aberration, represented by the magnified, blurred structures 605, 610, 615 of the cylindrical structures 505, 510, 515 of reference element 530, reduces the accuracy with which the position 650 of drift mark 530 can be determined. This reduces the accuracy of the determination of drift vector 350. Furthermore, the defocused electron beam 127 increases the lateral dimensions of the localized etching reaction used to remove defect 260, thereby reducing the lateral resolution of sample processing. By determining the degree of defocus and correcting for it, a reference image 500 of the DC mark 530 can be recorded again after an interruption in sample processing. As described in the context of Figures 3 and 4 , the degree of drift indicated by two-dimensional vector 350 can be optimally corrected, ignoring changes in the beam shape of the focused electron beam 127. Furthermore, the beam geometry can be optimized to perform a localized etching reaction for removing defects 260 to perform the second portion of sample processing. This prevents degradation of the processing resolution of a localized chemical reaction (a localized electron beam-induced etching reaction in the examples of Figures 2-4 ) during sample processing. The determination and correction of aberrations associated with defocusing the focused electron beam 127 have already been explained in the context of the apparatus 100. Furthermore, the apparatus 100 has been described as being able to correct for defocusing the electron beam 127. FIG7 illustrates a second type of aberration that degrades the image quality of focused electron beam 127 during sample processing. When recording image 700 of reference mark 530, focused electron beam 127 exhibits astigmatism. This astigmatism images elements 505, 510, 515 of DC mark 530 as blurred, enlarged ellipses 705, 710, 715. Determining the position 750 of DC mark 730 is subject to greater uncertainty. As already explained in the context of FIG6 , drift vector 350 can only be determined imprecisely, and the beam shape of focused particle beam 127 is only conditionally suitable for performing a localized etching reaction to remove excess material from defect 260. The astigmatism detector of the apparatus 100 generates an electric field or a magnetic quadrupole field that can be used to correct the astigmatism of the focused electron beam 127. The focused electron beam 127 uses the modified parameter settings of the astigmatism detector to correct its astigmatism to record an image of the DC mark 530 and generate a reference image 500 of the mark 530 for drift correction. After determining the degree of astigmatism and its correction by the astigmatism detector of the apparatus 100, the degree of drift 350 can be corrected in an optimal manner, and sample processing can continue using an optimized beam geometry of the focused particle beam 127. Coma, not shown here, is another type of aberration through which imaging errors of a focused particle beam 127 can be amplified during sample processing. This type of aberration is typically caused by the particle beam 127 passing obliquely through the objective lens 125 of the device 100. This type of aberration also reduces the accuracy with which the position of a DC marker 530 can be determined. By directing the particle beam 127 through the optical center of the objective lens 125 of the device 100, coma aberration of the focused particle beam 127 can be largely avoided, and the beam shape of the focused electron beam 127 can be optimized for other parts of the sample processing. FIG8 schematically illustrates a flow chart 800 of a method according to the present invention for correcting aberrations of a focused particle beam 127 relative to a defect 260 to be processed and drift of the particle beam 127 relative to the defect to be processed during sample processing. The method begins at step 805. First, at a decision step 810, a check is performed to determine whether one or more structural elements suitable for use as reference elements 230, 530 are present on the sample 105 to be processed. If not, step 815 generates one or more reference elements 230, 530 near the defect 260 to be processed. Typically, one or more reference elements 230, 530 for drift correction (in the form of one or more marks 230, 530) are generated by a particle beam-induced etching process and / or deposition process on the sample 105. In one possible embodiment of the method according to the present invention, in step 820, a database is created comprising images of at least one reference element 230, 530, wherein the focused particle beam 127 images the at least one reference element 230, 530 with a defined imaging error through a defined misalignment of the focused particle beam 127. Since the execution of step 820 is only necessary in certain embodiments, it is shown in dashed lines in FIG8 . In step 825, a reference image 500 of the at least one reference element 530 is generated by scanning the focused particle beam 127 over the reference element 530. This step is not required for all variants of the method according to the present invention and is therefore also represented as optional by dashed lines. For example, a reference image 500 of the at least one reference element 530 can be stored in a database. In step 830 , the actual sample processing begins with a combination of a focused particle beam 127 and at least one etching gas etching the defects 260 of FIGS. 2 to 4 . After a fixed or variable time interval, the sample processing or defect processing is interrupted at step 835. If necessary, the flow of the etching gas can be stopped. If necessary, one or more parameters of the focused particle beam 127 used to scan the reference element 230, 530 can also be changed. In step 840, the focused particle beam 127 records images 600, 700 of the reference elements 230, 530 by scanning over the reference element 530. In a next step 845, the reference image 500 of the reference element 530 is compared with the images 600, 700 of the reference element 530 at the end of the first portion of the sample processing. Based on this comparison, the imaging error of the focused particle beam 127 is determined at the end of the first cycle of the defect repair process. Other possible exemplary embodiments for determining the image aberration have been described above, such as using a database with a defined imaging error, using an automatic correction function, and / or using a machine learning training model. In decision step 850, it is then determined whether the specified imaging error is below or exceeds a specified threshold value. If the determined imaging error exceeds the threshold value, the imaging error is corrected and the method jumps back to step 840, where the image 500 of the reference element 530 is recorded again. The possibility of correcting various aberrations is explained in the discussion of FIG. 1 . If the imaging error(s) of the focused particle beam 127 are less than a specified threshold, a two-dimensional vector 350 is determined in step 860, wherein the two-dimensional vector 350 describes the drift of the focused particle beam 127 relative to the defect 260 to be processed during the first processing interval. If the drift is also less than the associated threshold, the method at decision step 875 jumps back to step 830, and the second part of the sample processing continues with the original parameter values ​​of the focused particle beam 127. On the other hand, if it is determined in decision step 875 that the absolute value of the drift vector 350 is greater than the threshold for drift correction, the drift of the particle beam 127 relative to the reference position 550 of the reference element 530 is corrected in step 875. Additionally, at decision step 880, it is determined whether defects 250 remain after the first loop, or whether the remaining defects exceed an acceptable threshold. If so, the method returns to step 830 and executes a second defect handling loop. On the other hand, if it is determined at decision step 880 that the remaining defects no longer interfere with the functionality of sample 105 in an unacceptable manner, the method ends at step 885. Finally, flowchart 900 of FIG9 presents the basic steps of a method for correcting imaging errors of particle beam 127 during sample processing. The method begins at step 910. In step 920, at least one imaging error of particle beam 127 is determined after at least one interruption in sample processing. This can be done, for example, by comparing reference image 500 of reference element 520 with images 600, 700 of reference element 530 recorded after the interruption in sample processing. Furthermore, the determination of the image error(s) can be performed based on a database of defined imaging errors and / or by using an automatic correction function. A machine learning training model can also be used. The method ends at step 940. 100: Device 102: Vacuum chamber; upper part 105: Sample 107: Lower reaction chamber 110: Sample stage / sample carrier 115: Electron gun 120: Component 125: Component 127: Electron beam 130: Detector 135: Ion gun 140: Computer system 145: Control unit 150: Container 151: Valve 152: Supply system 155: Container 156: Valve 157: Supply system 160: Container 161: Valve 162: Supply system 165: Container 166: Valve 167: Supply system 170: Container 171: Valve 172: Supply system 175: Container 176: Valve 177: Supply system 180: Aperture system 182: Aperture 184: Aperture 190: Cleaning device 195: Cleaning liquid 200: Fine Section 210: Substrate 220: Sacrificial Layer 230: Mark 240: Reference Distance 250: Reference Position 260: Defect 270: Dashed Rectangle 350: Vector; Drift 500: Image 505: Cylindrical Structure 510: Cylindrical Structure 515: Cylindrical Structure 530: Reference Element 550: Reference Position 600: Image 605: Blurred Structure 610: Blurred Structure 615: Blurred Structure 650: Position 700: Image 705: Enlarged Ellipse 710: Enlarged Ellipse 715: Enlarged Ellipse 750: Position 800: Flowchart 805-885: Steps 900: Flowchart 910-940: Steps The following embodiments will describe currently preferred exemplary embodiments of the present invention with reference to the accompanying drawings, in which: FIG. 1 schematically illustrates in an upper fragmentary diagram a block diagram of some important components of an apparatus capable of correcting one or more imaging errors of a particle beam during sample processing and also capable of determining and correcting particle beam drift, and in a lower fragmentary diagram a schematic cross-section of an apparatus for cleaning a sample; FIG2 is a schematic diagram showing a detail of a sample reticle having a defect of excess material on the reticle blank; FIG3 shows a detail from FIG2 after an interruption in defect processing and rescanning of the marker for drift correction to determine imaging errors and / or drift of the particle beam; FIG4 shows the detail from FIG3 after drift correction of the focused particle beam before continuing with sample processing; FIG5 shows a top view of three exemplary reference elements clearly depicting the form of dot-like structures; FIG6 shows the reference element of FIG5 , which records the imaging error of the focused particle beam in a defocused form; FIG7 shows the reference element of FIG5 , which records a focused particle beam having an imaging error in the form of astigmatism; FIG8 schematically illustrates an exemplary method for correcting imaging errors and drift of a focused particle beam during sample processing; and FIG9 is a flow chart showing a plurality of basic steps of a method for correcting at least one imaging error of a particle beam during sample processing. 530: Reference element 700: Image 705: Enlarge the ellipse 710: Enlarge the ellipse 715: Enlarge the ellipse 750: Location

Claims

1. A method (800, 900) for correcting at least one imaging error of one of the particle beams (127) during sample (105) processing, comprising: a. After at least one interruption in the processing of the sample (105), determine (step 920) the at least one imaging error of the particle beam (127), wherein the processing of the sample includes controlled modification of the sample; and b. If the determined at least one imaging error of the particle beam (127) exceeds a specified threshold, correct (step 930) the determined at least one error.

2. The method (800, 900) as described in claim 1, wherein the processing of the sample (105) includes processing the sample (105) using the particle beam (127).

3. The method (800, 900) as described in claim 1, wherein the treatment of the sample (105) includes providing at least one precursor gas on the sample (105).

4. The method (800, 900) as described in claim 1, wherein the interruption of the processing of the sample (105) includes at least the interruption of the supply of the at least one precursor gas.

5. The method (800, 900) as described in claim 1, wherein determining the at least one imaging error of the particle beam (127) comprises: using the particle beam (127) to record at least one image (500, 600, 700) of at least one reference element (230, 530) of the sample (105).

6. The method (800, 900) as described in claim 5, wherein the at least one reference element (230, 530) comprises at least one element selected from the group consisting of at least one structural element of the sample, at least one mark (230, 530) for drift correction, or at least one defect (260) of the sample (105).

7. The method (800, 900) as described in claim 1 further comprises the steps of: depositing a sacrificial layer (220) on the sample using a particle beam (127) and / or depositing a protective layer around a treatment site on the sample (105).

8. The method (800, 900) as described in claim 6, wherein determining the at least one imaging error comprises: analyzing the at least one recorded image relative to at least one reference (500) (600, 700).

9. The method (800, 900) as described in claim 8, wherein the at least one reference (500) comprises at least one element selected from the group consisting of: at least one reference image (500) of the at least one reference element (230, 530); stored data determined from the at least one reference image (500) of the at least one reference element (230, 530); at least one reference image (500) recorded by the particle beam (127); and stored data determined from the stored data recorded by the particle beam (127). The stored data determined by the reference image (500); a database having at least two images of the at least one reference element (230, 530) recorded by a particle beam (127) having at least one defined imaging error; or a database of stored data determined from at least two images of the at least one reference element (230, 530) recorded by a particle beam (127) having at least one defined imaging error.

10. The method (800, 900) as described in claim 9 further comprises: systematically changing at least one parameter of the particle beam (127) to generate the at least one defined imaging error before recording at least one of the at least two images of the at least one reference element (230, 530).

11. The method (800, 900) as described in claim 1, wherein the correction of the determined at least one imaging error comprises using at least one element selected from the group consisting of: an automatic correction function or a machine learning training model.

12. The method (800, 900) as claimed in claim 1, wherein the correction of the determined imaging error comprises changing at least one parameter of the particle beam (127) such that when an image (500, 600, 700) of the at least one reference element (230, 530) is recorded, the particle beam (127) having the at least one changed parameter substantially produces a reference image (500).

13. The method (800, 900) as described in claim 1, wherein the at least one imaging error comprises at least one element selected from the group consisting of: a focus change, an astigmatism change, or a coma change.

14. The method (800, 900) as described in claim 3, wherein the at least one precursor gas comprises at least one element selected from the group consisting of at least one etching gas, at least one deposition gas, or at least one additive gas.

15. The method (800, 900) as described in any of claims 5, wherein the at least one reference element (230, 530) includes at least one mark (230, 530) for drift correction, and the method further includes the step of removing at least one mark (230, 530) for drift correction from the sample (105).

16. A computer program comprising a plurality of instructions which, when executed by a computer system, cause the computer system to perform the method steps as described in claims 1 to 15.

17. An apparatus (100) for correcting at least one imaging error of a particle beam (127) during the processing of a sample (105), comprising: a. a determining member for determining at least one imaging error of the particle beam (127) after at least one interruption of the processing of the sample (105), wherein the processing of the sample includes controlled modification of the sample; and b. a correcting member for correcting the determined at least one error (110, 180) if the determined at least one imaging error of the particle beam (127) exceeds a specified threshold value.

18. The apparatus (100) as claimed in claim 17 further comprises at least one element selected from the group consisting of: a component for providing (150, 155, 160, 165, 170, 175) at least one precursor gas on the sample (105); a component for guiding (152, 157, 162, 167, 172, 177) and controlling (151, 156, 161, 166, 171, 176) the gas flow rate of at least one precursor gas; a component for generating (115), focusing (120, 125) and scanning the particle beam (127); and a component for adjusting... The components (110, 120, 125, 145, 180) for adjusting (145) the focus, astigmatism and coma of the particle beam (127); the components for adjusting (145) the objective lens (125) for focusing the particle beam (127); the components for moving the sample (105) in the beam direction of the particle beam (127); the components for adjusting (145) the astigmatism device; or the components for positioning (145) the particle beam (127) relative to a multi-aperture stop (184) and / or the components for positioning (145) the multi-aperture stop (184) relative to the particle beam (127).

19. The apparatus (100) as described in claim 17 further comprises: an astigmatist for altering the astigmatism of the particle beam (127).

20. The apparatus (100) as claimed in claim 17 further comprises: a porous aperture (184) for generating a specified particle stream.

21. The apparatus (100) as described in claim 17 further comprises: a computer system (140) having a computer program as described in claim 16.

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