Improved sample damage avoidance in devices and methods for sample processing and sample repair

Abstract

A method for potential determination related to a sample includes positioning a probe over the sample; applying at least a first DC voltage offset and a second DC voltage offset each from the first range; applying an AC voltage to the probe to cause mechanical oscillation of the probe; determining a first inductive deflection of the probe for the first DC voltage offset and a second inductive deflection of the probe for the second DC voltage offset; and determining a potential outside an interval spanned by the first DC voltage offset and the second DC voltage offset based at least in part on the first deflection and the second deflection. A method of causing proximity of a probe toward a sample includes causing proximity of the probe toward the sample; repeatedly determining the deflection of the probe during the process of causing the proximity; and determining an approach termination condition for avoiding damage to the sample based at least in part on the deflection of the probe or the oscillation frequency thereof.

Description

[0001] Related applications

[0002] This application claims priority to German patent application No. 102024132213.6, filed on November 5, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to a method for determining the potential of a sample, a method for causing a probe to approach the sample, a method for processing a sample, and corresponding apparatus and computer programs. Background Technology

[0004] Due to the ever-increasing integration density in microelectronics, substrates (such as photomasks, mask blanks, or wafers) require increasingly better surface finishes. For example, photomasks are designed to image smaller structural elements onto the photoresist layer of a wafer. The same applies to templates used in nanoimprint lithography. To meet these requirements, exposure wavelengths are being shifted to shorter wavelengths. The trend is towards increasingly shorter wavelengths extending into the extreme ultraviolet (EUV) wavelength range (10 nm to 15 nm) and towards corresponding EUV masks.

[0005] A common occurrence is that defects appear in mask production due to the continuous reduction in the size of structural components. Because production is associated with high costs, defective photomasks, lithography masks, and similarly, templates used in nanoimprint lithography are repaired whenever possible.

[0006] In photomask restoration, portions of the absorber pattern present in locations on the mask not intended in the design can be removed. Alternatively, even if the mask design includes absorber pattern elements, absorber material can be deposited on locations on the mask where no absorber material is present. Both types of restoration processes can generate debris or particles that may settle at opaque, transparent, or reflective sites on the photomask, leading to imaging aberrations visible in photolithography exposures on structured wafers.

[0007] Another issue is that particles from the environment can settle on the surface of the mask or another substrate, or on components of the photolithography system. Furthermore, handling of the mask during its production and / or operation can generate particles that can be deposited on the mask.

[0008] In the case of photolithography exposure systems operating with electromagnetic radiation in the EUV wavelength range, two additional difficulties exist. First, there is currently no satisfactory protection (e.g., a surface coating) for the surfaces of EUV masks that support structural components. Therefore, EUV masks are particularly susceptible to particle deposition on these structured surfaces. Second, EUV radiation sources typically use tin plasma to generate EUV radiation. Particles from the thermal plasma can deposit on components of the EUV exposure system, particularly on its optical parts or elements, including the EUV mask, and can impair its function.

[0009] The reduction in the structural size of photolithography masks increases the difficulty of the cleaning process. In addition, due to the reduction in exposure wavelength, increasingly smaller foreign matter particles or dirt particles adhering to the surface of the mask or optical components of the exposure system become visible on the wafer during the exposure process.

[0010] Given the increasingly smaller structures, customized solutions are becoming increasingly important for the handling and cleaning of masks and—more generally—substrates. In particular, it may be necessary to eliminate various defects on the same substrate at an acceptable level of cost and inconvenience. Surface treatment, especially particle movement and the lifting and / or removal of individual particles from the surface, is often a difficult and time-consuming process. External constraints can limit the available tools and treatment options. Furthermore, completely removing particles adhering to the substrate surface can be expensive and inconvenient.

[0011] Typically, processing a sample requires bringing the probe closer to the sample, although this is not always without problems, for the following reasons:

[0012] During processes used to load samples into a vacuum, such as evacuation and measurement, the sample can become electrostatically charged. Similarly, during the observation of samples in a scanning electron microscope (SEM) (e.g., using a photomask), the sample can be charged by both the introduction of electrons from the primary beam and secondary electrons (SE). The charging behavior here can depend primarily on the SE yield (SEY). Samples with large conductive structures that are not electrically contacted or cannot be electrically contacted are critical in both cases. These include, for example, the so-called "chromium on the glass blank" used for particle monitoring tests and EUV masks. EUV masks, as a high-end mask type, are particularly expensive and, due to their small structure, are especially sensitive to particulate contamination and electrostatic discharge (ESD).

[0013] For example, if a probe (such as an AFM tip) comes into contact with or is directed to the vicinity of a charged sample, the sample may be discharged via the tip (in a so-called ESD event), which could damage the sample as well as the probe.

[0014] Therefore, the present invention is based on the aim of at least partially improving the corresponding methods, apparatus and computer programs. Summary of the Invention

[0015] This objective is achieved, at least in part, through the aspects described herein.

[0016] A first aspect of the invention relates to a method for determining the potential of a sample, wherein the method includes: positioning a probe over the sample; applying at least a first DC voltage offset and a second DC voltage offset, each from a first range; applying an AC voltage to the probe to induce mechanical oscillation of the probe; determining a first induced deflection of the probe with respect to the first DC voltage offset and a second induced deflection of the probe with respect to the second DC voltage offset; and determining a potential (also referred to herein as the sample potential or the potential of the sample) outside the range traversed by the first DC voltage offset and the second DC voltage offset, based at least in part on the first deflection and the second deflection.

[0017] The inventors have recognized that the current situation is suitable for utilizing the following physical relationship: finite potential differences spaced apart from each other in the z-direction. There is an electric current between the two objects

[0018]

[0019] With capacitor The corresponding force gradient is

[0020]

[0021] If a DC voltage offset is applied This makes the potential difference If it disappears, then it has no effect. .

[0022] If a DC voltage offset is applied and time-variable AC voltage This typically results in time-variable forces.

[0023]

[0024] in This represents the contact potential or sample potential, which corresponds to the work function difference between the two aforementioned objects. Potential difference divided by elementary charge: .

[0025] The two objects mentioned above in this article can be, for example, a sample and a probe.

[0026] like Figure 1a As schematically shown, the force acting on the probe can be well approximated by the harmonic function 110. Specifically, Figure 1a The sample and probe are shown (see Figure 1b The force, a function of the voltage (DC voltage offset and AC voltage) between the two voltages, follows a parabola. It can be discerned here that applying a DC voltage offset of 121 results in... Corresponding to the vertex of the parabola. As described in this article, the constant... Corresponding to the contact potential or potential of the sample to be determined, and This corresponds to the applied DC voltage offset. At the vertex, the parabola has a gradient that is approximately zero, therefore the applied voltage with frequency f... mod The AC voltage 131 cannot induce a strong force 141 between the probe and the sample. Instead, the latter tends towards zero. Furthermore, due to the zero-crossing of the applied voltage 131 (and the associated sign change), the frequency with which the induced force occurs (the amplitude tends towards zero) is 2·f. mod The effect is that, since this frequency is far from the probe's resonant frequency, the probe cannot be excited (or can only be excited very difficultly) to oscillate there, which further contributes to the force amplitude and oscillation amplitude approaching zero.

[0027] At different (e.g., higher) DC voltage offsets of 122, In this case, the applied AC voltage 132 (e.g., with the same or different amplitude and / or frequency) results in a relatively large deflection or amplitude of the induced oscillation 142. This is evident from the fact that the parabola has a non-zero gradient at all points except its vertex.

[0028] Previously known methods have so far only been able to determine sample potentials for voltage ranges within which voltages can also be applied. Therefore, if one wishes to measure / determine the potential of a sample, such as the potential of a mask voltage, using these conventional methods, for example, within the technically generally relevant range of -63 V to +63 V, this would require "scanning" across that voltage range, for example, from -75 V to +75 V (or at least from -63 V to +63 V in any case) (i.e., applying a DC voltage offset and / or systematically changing them within a predetermined range, e.g., continuously or in discrete steps, as described more in detail herein). This would be problematic from three angles: First, such a wide range of DC voltage offsets requires additional amplifiers and compatible mixers for higher voltages. This complicates the method and the corresponding apparatus, increases costs, and makes the method more susceptible to damage. Second, typical controllers exhibit only a breakdown strength of up to 42 V, which could lead to (irreparable) damage to probes, samples, apparatus, etc., if a short circuit is present. Third, values ​​above 50 V indicate a departure from the ultra-low voltage range, which is safety-related and requires additional certification. The present invention avoids all these problems. The present invention, through the steps described herein, determines the potential outside the interval traversed by the first and second DC voltage offsets, which simplifies the method, makes it safer, speeds up the process, and reduces costs.

[0029] Tests show that the method according to the invention can cover the DC voltage offset range of -200 V to +200 V very well, and only less than ~10% error is obtained in the process.

[0030] Therefore, the shortcomings of traditional methods regarding the following problems can be addressed: First, the sample potential is often not precisely known, so a larger accessible measurement range may be helpful. Second, if the potential difference between the sample and the probe is too large, both the probe and the sample will be damaged (usually irreparably). This is especially true for expensive samples (e.g., EUV masks), where even a very small voltage difference (~20V) due to sample loading can be sufficient to cause irreparable damage. Such voltage differences can be reliably determined.

[0031] In a preferred embodiment, a first DC voltage offset can be applied at a first time point, and a second DC voltage offset can be applied at a second time point (different from the first time point), e.g., before or after the first time point in time. Applying at least the first and second DC voltage offsets can include a “scan”:

[0032] The applied voltage varies / changes during a so-called “scan.” The applied voltage can typically vary continuously or in discrete (e.g., equidistant) steps from a minimum to a maximum (or vice versa) within an interval predefined and / or determined by the user or device. Therefore, during or within a “scan,” multiple voltages (e.g., DC voltage offsets in this document) are applied continuously over time. A so-called “scan” can be performed, for example, with first and second DC voltage offsets applied as follows: in one example, the first DC voltage offset corresponds to the minimum value of the scan interval, and the second DC voltage offset corresponds to the maximum value of the scan interval. As described herein, a first DC voltage offset can be applied at a first time point, and a second DC voltage offset can be applied at a second time point (different from the first time point) (e.g., before or after the first time point). During the time between the first and second time points, the applied voltage can be scanned, that is, it can vary continuously or in discrete steps from the first DC voltage offset to the second DC voltage offset (or vice versa).

[0033] For example, the application of an AC voltage can be performed at two time points. In this regard, for example, a first DC voltage offset and an AC voltage can be applied at the first time point, and a second DC voltage offset and an AC voltage can be applied at the second time point.

[0034] In one embodiment, deflection may include the amplitude and / or phase of a mechanical oscillation.

[0035] The inventors have realized that, precisely, the amplitude and phase of the oscillation are suitable for performing a process of determining the potential with particularly high accuracy and reliability.

[0036] For example, the first deflection and the second deflection may include in-phase components and / or quadrature components.

[0037] The use of in-phase and / or quadrature components can further simplify or make the method more efficient. Instead of analyzing, for example, the demodulated amplitude signal, one can analyze (e.g., fit) in-phase and / or quadrature components, where each component can exhibit a very good linear profile. This can greatly simplify and accelerate subsequent analysis steps and / or improve its accuracy and / or reliability.

[0038] In one example, determining the first deflection and the second deflection may include locking the amplification.

[0039] This can be particularly advantageous when combined precisely with the use of in-phase and / or quadrature components as described herein, since the in-phase and / or quadrature components can be directly provided by conventional lock-in amplifiers. Although conventional methods do not use signals available by means of the operating mode of a lock-in amplifier, the inventors have recognized that these signals are helpful, for example, in subsequent evaluations (e.g., fitting).

[0040] In principle, lock-in amplifiers are advantageous, for example, for measuring weak signals that may be embedded in, for example, a high-noise background. A lock-in amplifier can be configured to extract the signal, for example, by mixing the signal with a reference frequency and analyzing the resulting components. These components can be or include the in-phase component (also referred to herein as "X") and the quadrature component (also referred to herein as "Y") as described herein.

[0041] For example, the AC voltage frequency can be approximately equal to or several times the resonant frequency of the probe.

[0042] To be precise, resonant excitation can be particularly suitable because it allows for high amplitudes and thus allows for large differences in deflection even when there are small differences in the DC voltage offset. This simplifies and speeds up the method and makes it more accurate.

[0043] In one exemplary embodiment, the first range can extend from -10 V to +10 V.

[0044] In view of the problems with conventional methods for potential determination as described herein, the range of -10 V to +10 V is particularly advantageous: instead of expanding the scan range to be able to check the maximum possible voltage range, the invention may include varying the DC voltage offset within a (relatively small) range of -10 V to +10 V, which corresponds to the typical output range of a controller for a corresponding device.

[0045] For example, determining the potential may include using a fitting function to fit a first data point that includes at least a first deflection and a first DC voltage offset, and a second data point that includes a second deflection and a second DC voltage offset.

[0046] This method may include, for example, fitting data points (e.g., 10 or more, 100 or more, etc.). The inventors have determined that a particularly suitable trade-off between accuracy and speed can be found within, for example, the range of 10 to 300 data points. In this respect, determining the sample potential in the manner described herein can be performed particularly robustly, reliably, and rapidly.

[0047] In one exemplary embodiment, determining the potential may further include extrapolation and / or determining the zeros of the fitted function.

[0048] The key feature here is that it enables not only good interpolation but also extrapolation, thus allowing the determination of the intersection points of the fitted function (e.g., a straight line) outside a first range (e.g., from -10 V to +10 V). The minimum deflection can be determined where the function intersects the abscissa, which in turn determines the sample potential. The inventors have recognized that surprisingly accurate potential determination can be achieved through this fitting, even for extrapolations far from the first range.

[0049] For example, the fitting function may include a linear function, and preferably includes a correction of a linear function based at least in part on the probe’s resonant frequency, oscillation quality and / or spring constant.

[0050] In initial testing, calculations, and simulations, the inventors recognized that, particularly for distances between the probe and sample less than 10 μm, the electrostatic force can be very strong, causing the resonant frequency to vary significantly during changes / application of the DC voltage offset (also known as "scanning" / "sweeping"), and the applied AC voltage can then correspond to a non-resonant excitation. As a result, the measured signal (e.g., deflection as a function of the applied DC voltage offset) can comprise a signal that is well approximated as either a linear or nonlinear signal. Therefore, in the nonlinear case, it may be advantageous to include a correction for a linear function in the fitting function or to use a nonlinear fitting function. In one exemplary embodiment, the fitting function can therefore be based at least in part on the distance between the sample and the probe.

[0051] In one exemplary embodiment, the probe and sample can be positioned such that the distance between them can be from 0.001 μm to 1000 μm, preferably from 50 μm to 150 μm. In some examples, minimum distances of 0.01 μm, 0.1 μm, 1 μm, or 10 μm can also be provided.

[0052] As described herein, the method has been found to be effectively implemented within these ranges: on the one hand, the distance between the sample and probe is small enough to satisfy, for example, the conditions provided for a linear relationship between deflection and DC voltage offset (described herein) or a reasonable estimate of the correction for a linear function (also outside the first range), and / or the force between the sample and probe is strong enough to reliably implement the method. On the other hand, the sample and probe are spaced far enough apart that collisions between the sample and probe can be excluded or avoided with a high probability. Possible nonlinearities may occur as described herein and generally become apparent outside the first range. However, by computational consideration, they can be similarly incorporated into the method described herein.

[0053] A second aspect of the invention relates to a method for inducing a probe to approach a sample, wherein the method includes: inducing the probe to approach the sample; repeatedly determining the deflection of the probe during the approach induction process; and determining an approach termination condition for avoiding sample damage based at least in part on the deflection of the probe.

[0054] The detection of excessively high mask potentials achieved through the first aspect can indeed be used to avoid damage to the sample, but it is not always sufficient to allow the sample to be repaired in subsequent steps, which is a practical goal. This problem is addressed by the second aspect. However, conventional methods assume, for example, that the sample surface is uniformly discharged after a discharge, and the inventors have recognized that even after such a discharge, local charges may still exist on the sample, resulting in the sample and probe not being able to safely approach each other. The inventors have recognized that such local charges may still be high enough that they can cause considerable damage to the sample and / or probe. This is exacerbated because most methods for measuring sample potentials involve large-area measurements, which typically produce an average over an area that is very large compared to the area addressed by the probe (e.g., equivalent to the cross-section of the probe tip). Such an average does not contain any information about the possible local charges. However, if the probe happens to approach or even contact the sample at or near such a local charge, damage to the sample and / or probe will generally occur even in the case of a previous large-area discharge of the sample. Even though such situations do not usually occur, it is highly desirable to be able to identify and avoid them at an early stage, especially in the case of very expensive samples (such as EUV masks).

[0055] For example, the determination can be performed using a real-time device configured to determine the near-termination condition within 2 ms or less, preferably 1 ms or less, particularly preferably 0.5 ms or less.

[0056] Determining the approach termination condition so quickly ensures that unwanted collisions can be avoided even at relatively high approach speeds that allow for rapid processing.

[0057] The method may also include, for example, terminating the process that causes the probe to approach the sample based at least in part on determining a proximity termination condition.

[0058] Defining near-termination conditions can provide an objective basis for decision-making, making the method safer and equally reliable, regardless of the user. For example, near-termination conditions can be determined automatically, which can simplify the user's work, speed up the method, and make it more reliable and secure.

[0059] In one exemplary embodiment, termination may be performed within 2 ms or less, preferably 1 ms or less, particularly preferably 0.5 ms or less, after the occurrence of a near-termination condition.

[0060] This rapid termination of the approach ensures that unwanted collisions can be avoided even at relatively high approach speeds that allow for quick processing.

[0061] The approach process induced by the probe can be carried out at a speed of, for example, 0.1 μm / s or higher, preferably 1 μm / s or higher, and particularly preferably 2 μm / s or higher.

[0062] This can reduce the processing time required for samples, thereby saving time and costs.

[0063] In one exemplary embodiment, the near-termination condition may include a predefined deflection of the probe.

[0064] The inventors have determined that, for a sufficiently large distance between the probe and the sample, the deflection (e.g., the amplitude of the oscillation, the bending of a portion of the probe, as measured, for example, using a photodiode and the beam reflected at the probe as described herein) remains within a predetermined range (e.g., within the range of vibrations induced by the surrounding environment). Therefore, exceeding the predefined deflection constitutes a particularly reliable proximity termination condition, which can be applied to both the static procedural approach (without induced probe oscillation) and the dynamic procedural approach (with induced probe oscillation) of the method as described herein.

[0065] The method may also include, for example, determining the resonant frequency of the probe during the process that induces proximity.

[0066] In one exemplary embodiment, the near-termination condition may include a predefined frequency shift exceeding the resonant frequency.

[0067] The inventors have recognized that the shift to lower (higher) frequencies occurs alongside attractive (repulsive) forces, and have taken advantage of this. Surprisingly, this procedural pathway has been found to be highly sensitive, allowing for near-termination to be achieved rapidly enough.

[0068] For example, near-termination conditions could include a resonant frequency below a predefined minimum frequency.

[0069] The electrostatic force, resulting from the potential difference between the sample and the probe, will generate an attractive force and thus a shift towards lower frequencies. Therefore, a minimum frequency can be defined, below which conditions can be used as termination criteria, which can be particularly simple and reliable.

[0070] A third aspect of the invention relates to a method for processing a sample, comprising: the steps of a method for potential determination as described herein; and the steps of a method for inducing a probe to approach the sample, as described herein, based at least in part on the potential determination.

[0071] The combination of the potential determination method and the method for inducing probe approach toward the sample is advantageous in many different respects: First, it can thus be ensured that approach is only induced from the outset if the potential determination indicates that it can be carried out safely with a high probability. Second, the probe whose approach is intended to be induced later is used for potential determination, which is a procedural approach that is particularly economical in terms of materials, time, and cost.

[0072] For example, the method described herein may also include discharging the sample at least partially based on potential determination.

[0073] Discharges may include, for example, those described in DE 10 2013 212 957 A1.

[0074] For example, the discharge can be performed at a potential of ±1 V or higher, preferably ±5 V or higher, and especially preferably ±10 V or higher.

[0075] In this context, "or greater" should be understood as an absolute value relative to the potential. Therefore, a potential of ±1 V or greater corresponds to, for example, a potential of -1 V or less or +1 V or greater. This ensures that discharge occurs whenever the potential becomes too high for possible subsequent method steps (e.g., causing the probe to approach the sample).

[0076] In one exemplary embodiment, the steps of the method for causing the probe to approach the sample may be performed only at a potential of ±20 V or lower, preferably ±15 V or lower, and particularly preferably ±10 V or lower.

[0077] Therefore, it can be ensured that the probe can safely approach the sample with a relatively high probability.

[0078] The sample may, for example, be at least partially charged. This can be caused by, for example, treating the sample with a particle beam (e.g., an ion and / or an electron beam) and / or observing the sample (e.g., using a transmission electron microscope and / or a scanning electron microscope).

[0079] For example, the probe may include the probe of a scanning probe microscope, the probe may include a probe arm and / or a measuring tip, and / or the deflection may be measured by a beam of light reflected at the probe.

[0080] Using probes (such as those in scanning probe microscopes), particularly for deflection measurements via reflected beams, offers numerous technical advantages: The measurement of probe arm deflection allows for extremely precise capture of the sample's surface structure. This results in very high spatial resolution, extending to the atomic level. The method is extremely sensitive to small forces and displacements. This allows for the detection of very fine morphology and mechanical properties of samples. Scanning probe microscopes can operate in various modes, such as contact, tap, and / or non-contact modes, depending on the specific requirements of the examination. This allows them to be used in different ways for a wide variety of samples and applications. Since the measurement of probe arm deflection typically does not cause any significant physical changes to the sample, sensitive or valuable samples can be examined without damage. In addition to morphological imaging, scanning probe microscopes can also measure other physical properties of samples, such as electrical, magnetic, or mechanical properties, using appropriate probes and measurement methods. Probe arm deflection can be measured and analyzed in real time, enabling immediate feedback on sample properties and facilitating adjustments to measurement parameters during experiments.

[0081] The sample may include, for example, an object for photolithography, preferably a photolithographic mask. The sample may be a photolithographic mask. The sample or photolithographic mask may have an aspect ratio between 1:1 and 1:4, preferably between 1:1 and 1:2, and particularly preferably 1:1 or 1:2. The sample or photolithographic mask may have a nearly rectangular shape. The sample or photolithographic mask may preferably have a length and width of 5 to 7 inches, particularly preferably 6 inches. Alternatively, the sample or photolithographic mask may also have a length of 5 to 7 inches and a width of 10 to 14 inches, preferably 6 inches in length and 12 inches in width.

[0082] The use of such a probe is particularly advantageous in the case of objects used for photolithography, because the aforementioned advantages are extremely relevant when handling the corresponding samples—especially when handling the samples gently without damaging them.

[0083] A fourth aspect of the invention relates to an apparatus for processing samples. The apparatus includes one or more components configured to automatically perform the steps of one or more methods described herein.

[0084] Automation enables the methods described in this paper to be performed consistently and reproducibly. This reduces human error and ensures high accuracy and reproducibility of results, which is particularly important in quality control and scientific research. Automation also allows complex and time-consuming processes, such as those described in this paper, to be performed more quickly and efficiently. This results in a significant reduction in processing time and enables higher productivity, which in turn reduces costs. Automated systems reduce the need for human intervention, thereby minimizing variability that may be caused by different operators. This leads to uniform, high-quality results and reduces the risk of operational errors, which increases the reliability and safety of the method.

[0085] The aspects described in this article can be used with a variety of samples.

[0086] The samples mentioned in this application may include, for example, various types of substrates, such as semiconductor substrates, like semiconductor industry substrates. In some instances, the samples may contain objects for photolithography.

[0087] The samples mentioned in this article may also include masks (including, for example, various formats, such as 6×6 inch, 6×12 inch and 12×12 inch sizes, with or without a thin film), nanoimprint lithography (NIL) templates or molds, for example for nanoscale pattern replication.

[0088] Alternatively or concurrently, the aspects described herein may be used with, for example, samples of wafers. Wafers may be provided in various sizes and / or cuts. Wafers may include, for example, Si, SiO, sapphire, SiC, GaN, InP, Ge, GaAs, AlGaAs, ZnO, or CdS. Samples may also include wafers where each chip contains a unique or non-uniform structure, wafers with structured and unstructured regions, wafers that have undergone partial processing or preprocessing of one or more manufacturing steps, and / or diced wafers (e.g., mounted on a frame such as a 380mm frame). Other applicable substrate types include, for example, packaging substrates for semiconductor packaging processes, dies, interposers, circuit boards, substrates subjected to circuit editing applications, photonic integrated circuits, and hybrid electro-optic circuit substrates combining electronic and optical functions. The methods and apparatus described herein are also applicable to, for example, microfluidic systems, including lab-on-a-chip devices, metamaterial substrates (which can be characterized by engineering properties, such as negative refractive index), and substrates incorporating advanced nanomaterials, such as 2D materials, nanosheets, or topological insulators. In some possible examples, the sample can be a sample for quantum computing applications (e.g., a chip including one or more qubits or other quantum information processing elements) or a sample for artificial intelligence and machine learning applications, for example, in which a dedicated electronic circuit architecture is employed.

[0089] Another aspect of the invention relates to a computer program comprising instructions for performing steps of at least one of the methods described herein. The computer program may be written in any programming language, including compiled or interpreted languages, and may be provided in any form, including as a standalone program or as a module, component, subroutine, or other entity suitable for use in a computer environment.

[0090] The embodiments of the invention described herein, as well as the features and properties optionally mentioned therein, should also be understood to be disclosed in all combinations thereof. In particular, the description of features included in the embodiments—assuming no explicit contrary interpretation—should not be construed in the present context as meaning that such feature is indispensable or necessary for the functionality of the embodiments. Similarly, the features described herein with respect to the steps of a method can be implemented as instructions for a computer program and means of an apparatus, and vice versa. Attached Figure Description

[0091] Figure 1a A schematic diagram is shown showing the harmonic approximation of the force caused by the applied AC voltage as a function of the DC voltage offset.

[0092] Figure 1b A schematic diagram is shown of the probe and the sample, as well as the oscillations caused by the probe relative to the sample.

[0093] Figure 2 A schematic diagram of the deflection is shown, specifically the amplitude, in-phase component, quadrature component, and phase as a function of the applied DC voltage deflection.

[0094] Figure 3a A schematic diagram of those components that can be used for control and sample potential determination is shown.

[0095] Figure 3b An exemplary probe is shown, along with how to connect it to a source. Figure 3a Components.

[0096] Figure 4 An exemplary comparison of two cases is shown, in which probes with applied AC voltages at different distances from the sample have different resonant frequencies.

[0097] Figure 5 An exemplary flowchart of an exemplary method according to the present invention is shown, which combines several aspects described herein. Detailed Implementation

[0098] Figure 1bA schematic diagram is shown of probe 150 and sample 160, and the resulting oscillation 170 of probe 150 relative to sample 160. Probe 150 may be part of, for example, a device for processing sample 160. In this case, the probe has a probe arm 151, one end of which may be fixed to, for example, a moving platform (also referred to herein as a "platform"). The moving platform or platform may be configured to, for example, move probe 150 in the x, y, and / or z directions and / or rotate probe 150 along one or more angles. The moving platform may include, for example, a 6DOF moving platform, i.e., a moving platform with six degrees of freedom. Figure 1b In the example, a measurement tip 152 with a pointed end 153 is located at the other end of the probe arm 151. For example, the first and second DC voltage offsets described herein can be applied between the probe 150 and the sample 160. The measurement tip 152 with a pointed end 153 can be used to... Figure 1b The diagram shows a probe arm 151 that periodically bends or oscillates up and down to perform mechanical oscillations, indicated by a dashed double-headed arrow 170 (in a greatly magnified manner). As a result, the distance 154 between the measuring tip 152 or tip end 153 and the sample 160 changes periodically accordingly. This may correspond to the first deflection and / or the second deflection described herein.

[0099] Figure 2 A schematic diagram of the deflection is shown, in particular the amplitude 210, the in-phase component (X) 212, the quadrature component (Y) 211, and the phase 230 as functions of the applied DC voltage offset (U).

[0100] A lock-in amplifier is a device used to measure signals hidden in high-noise environments. It works using phase-sensitive detection to separate the signal from the noise. The in-phase component 212 and the quadrature component 211 are the two fundamental parts of this process.

[0101] The in-phase component (X component) 212 is the projection of the input signal onto a reference signal wave that is in phase with the input signal. It represents the portion of the signal that directly matches the reference phase. Mathematically, it is obtained by multiplying the input signal by a sinusoidal reference signal and then low-pass filtering. This component can provide information about the amplitude of the signal that is in phase with the reference. The quadrature component (Y component) 211 is the projection of the input signal onto a reference signal wave that is 90 degrees phase-shifted (i.e., orthogonal to the reference phase). It represents the portion of the signal that is 90 degrees phase-shifted relative to the reference phase. Mathematically, it is obtained by multiplying the input signal by a cosine reference signal and then low-pass filtering. This component can provide information about the amplitude of the signal that is orthogonal to the reference.

[0102] In this case, the corresponding theoretical curve for amplitude 210 shows a V-shaped curve, and the quadrature component (Y component) 211 and the in-phase component (X component) 212 each show a linear curve, both having the same zero crossings or zero points, which theoretically correspond to the sample potential. Therefore, amplitude 210, quadrature component (Y component) 211 and / or in-phase component (X component) 212 can be fitted by corresponding functions to determine the zero points (e.g., for amplitude 210) or zero crossings (e.g., for quadrature component (Y component) 211 and / or in-phase component (X component) 212), i.e., thus determining the sample potential.

[0103] The phase has a 180° jump at the sample potential. The phase can be fitted using a corresponding function to determine the zero-crossing point, i.e., thus determining the sample potential.

[0104] exist Figure 2 In the example, the first range 221 is the range that includes measurement point 220. Exemplary multiple DC voltage offsets include a first DC voltage offset, a second DC voltage offset, and additional DC voltage offsets within the first range 220. Figure 2 In the example, only the measurement points for the in-phase component (X component) 212 are shown, and the dotted lines represent the fit of these measurement points 220. Extrapolation allows the determination of a zero point, i.e., the mask potential outside the interval (first range) spanned by multiple DC voltage offsets. In this case, the first range may be, for example, in the interval from -10 V to +10 V, and the determined mask potential may be, for example, at an absolute voltage value higher than 10 V.

[0105] Figure 3a A schematic diagram of those components 310, 320, 331, 332 of an exemplary device 300 that can be used for control and sample potential determination is shown.

[0106] in this case, Figure 3aThe exemplary device 300 includes a computer 310. In some embodiments, device 300 and / or the computer may include a data processor and a storage medium. The data processor may be configured to, for example, perform the method steps described herein and / or provide mechanical and / or electronic components relating to instructions for performing the steps. The storage medium may store the data, information, software 313, protocol 311, etc., described herein for performing the methods described herein. As its interface, for example, a COM server 314 may be provided. The COM server (Component Object Model Server) 314 may include, for example, software components based on COM technology and may provide services or functions for other applications. For example, this component may communicate with another unit 320 (e.g., a controller for the aforementioned mechanical and / or electronic components 331, 332) via IP and / or TCP protocols. In some embodiments, device 300 may include one or more computers 310 containing one or more data processors configured to execute one or more programs containing various instructions according to the principles described above. Each data processor may contain one or more processor cores, and each processor core may contain logic circuitry for data processing. For example, a data processor may include an arithmetic logic unit (ALU), a control unit, and various registers. Each data processor may include cache memory. Each data processor may include a system-on-a-chip (SoC), which includes multiple processor cores, random access memory (RAM), a graphics processor, one or more controllers, and one or more communication modules. Each data processor may contain millions or billions of transistors.

[0107] In an example of the invention, controller 320 may include, for example, one or more field-programmable gate arrays (FPGAs) 321, 322 and / or an operating system 323 inherent to the controller, to control, for example, photodiode 331 and / or platform 332 and / or receive data thereby recorded (e.g., deflection detected by photodiode 331). The recorded data may then be provided to computer 310, for example, via an IP / TCP interface.

[0108] The methods described in this document can be performed by one or more computers 310, which include one or more data processors for data processing, one or more storage media for data storage, and / or one or more computer programs including instructions that, when executed by the one or more computers, cause the process to be performed. The one or more computers may include one or more input devices, such as a keyboard, mouse, touchpad, and / or voice command module, and one or more output devices, such as a display and / or speakers. Therefore, a graphical user interface 312 may be provided, through which a user can start, stop, pause, and / or at least partially control or influence the execution of the methods described herein.

[0109] In some embodiments, one or more computing devices may include digital electronic circuits, computer hardware, firmware, software, or combinations thereof. Features for data processing may be implemented in a computer program product substantially embodied in an information carrier, such as a machine-readable storage medium, for execution by a programmable processor; and method steps may be executed by a programmable processor executing instructions to achieve the functions of the described embodiments. Alternatively or additionally, program instructions may be encoded in propagating signals, which are artificially generated signals, such as machine-generated electrical, optical, or electromagnetic signals, generated to encode information for transmission to a suitable receiving device for execution by a programmable processor.

[0110] As an example, one or more computers may be configured to execute computer programs, and they may include general-purpose and special-purpose microprocessors as well as any desired processor of any type of digital computer. Typically, the processor receives instructions and data from read-only memory or random access memory, or both. Elements of a computer system include one or more processors for executing instructions and one or more storage devices for storing instructions and data. Typically, a computer system also includes, or is operatively coupled thereto, a means to receive data from or transfer data to, or both of, one or more machine-readable storage media, such as hard disks, magnetic disks, solid-state drives, magneto-optical disks, or optical disks. Machine-readable storage media suitable for embodying computer program instructions and data include various forms of non-volatile memory, including, for example, semiconductor memory devices such as EPROMs, EEPROMs, flash memory devices, and solid-state drives; magnetic disks, such as internal hard disks or removable disks; magneto-optical disks; and CD-ROMs, DVD-ROMs, and / or Blu-ray discs.

[0111] In some implementations, the above processes can be performed by means of software executing on one or more mobile computing devices, one or more local computing devices, and / or one or more remote computing devices (which may be, for example, cloud computing devices). For example, the software method forms one or more computer programs executing on one or more programmed or programmable computer systems, said computer systems being mobile computing devices, local computing devices, or remote computing systems (which may include various architectures such as distributed systems, client / server systems, grid systems, or cloud systems), each computing system including at least one processor, at least one data storage system (including volatile and non-volatile storage devices and / or storage elements), at least one wired or wireless input device or port, and at least one wired or wireless output device or port.

[0112] In some implementations, the software may be provided on a medium such as, for example, a CD-ROM, DVD-ROM, Blu-ray disc, solid-state drive, or hard disk, which may be read by a general-purpose or special-purpose programmable computer, or may be transmitted via a network (in a manner encoded in a propagating signal) to the computer on which it is executed. These functions may be performed on a specific computer or by means of specific hardware (e.g., a coprocessor). The software may be implemented in a distributed manner, wherein different parts of the computation specified by the software are executed by different computers. Any such computer program is preferably stored or downloaded on a storage medium or storage device (e.g., solid-state memory or a storage medium or magnetic or optical medium) that may be read by a general-purpose or special-purpose programmable computer to configure and operate the computer system upon reading, thereby performing the methods described herein. The system according to the invention may also be considered a computer-readable storage medium configured with a computer program, wherein such a storage medium enables the computer system to perform the functions described herein in a specific and predefined manner.

[0113] Figure 3b An exemplary probe 350 is shown, for example, for processing sample 360, and how the probe can be connected to a device from... Figure 3a Components 331 and 332. In Figure 3b In the illustration, the probe is basically as follows Figure 1b The light source 340 is positioned above the sample 360, for example, by means of platform 332. The light source 340 is configured to guide the light beam to the probe, for example, on the top side of the reflective probe arm, so that the reflected signal can be recorded by photodiode 331 and forwarded to, for example, controller 320.

[0114] The photodiode 331 can be, for example, a four-quadrant photodiode (4Q photodiode) and / or can play an important role in measuring the deflection of the probe arm (e.g., in atomic force microscopy (AFM)): as described herein, the probe arm can reflect a light beam or laser beam such that the beam can illuminate the surface of the four-quadrant photodiode. The photodiode can be subdivided into four separate regions (quadrants), each of which can capture a portion of the reflected laser beam. These quadrants are typically designated A, B, C, and D. If the probe arm deflects due to interaction with the sample surface, the position of the reflected laser beam on the photodiode changes. This change results in different intensities of light illuminating the respective quadrants. The photodiode can generate, for example, an electrical signal proportional to the light intensity in each quadrant. By comparing the signals in different quadrants, the deflection of the probe arm in two dimensions (vertical and lateral) can be calculated: the signal difference between the upper quadrant (A + B) and the lower quadrant (C + D) represents the vertical deflection of the probe arm. The signal difference between the left quadrant (A + C) and the right quadrant (B + D) represents the lateral deflection of the probe arm.

[0115] Figure 4 An exemplary comparison of two scenarios is shown, in which probe 450, with applied AC voltages at different distances 454, 454' from the sample, has different resonant frequencies. These scenarios can occur, for example, in methods described herein for inducing probe 450 to approach sample 460.

[0116] exist Figure 4 In the upper region 410, the probe 450 is located at a first (maximum) distance 454 from the sample. To its right is shown a curve 411 depicting the amplitude of the resulting oscillation as a function of frequency. In this example, the frequency with the highest amplitude is approximately 300,000 Hz.

[0117] exist Figure 4 In the lower region 420, the probe 450 is at a second (smallest) distance 454' from the sample, for example, after or during the process that causes the probe 450 to approach the sample 460. To its right is shown a curve 421 of the amplitude of the resulting oscillation as a function of frequency. In this example, the frequency with the highest amplitude is at approximately 299,990 Hz, and is therefore redshifted relative to the case shown in the upper region 410.

[0118] therefore, Figure 4 The diagram illustrates how the frequency shift occurs as a function of the distances 454, 454' between the probe 450 and the sample.

[0119] Figure 5 An exemplary flowchart of an exemplary method according to the present invention is shown, which combines several aspects described herein.

[0120] Figure 5 The method can be further divided into three aspects: method 510 for determining the potential of the sample, method 520 for discharging the sample, and method 530 for causing the probe to approach the sample.

[0121] Method 510 for determining the potential of a sample includes steps 511 to 515: the method may be initiated by positioning a probe 511 above the sample. Then, at least a first DC voltage offset and a second DC voltage offset, each deviating from a first range, may be applied 512. As described herein, the first DC voltage offset may be applied at a first time point, and the second DC voltage offset may be applied at a second time point (different from the first time point) (e.g., before or after the first time point). Furthermore, method 512 includes applying an AC voltage to the probe to induce mechanical oscillation of the probe 513, and determining a first induced deflection of the probe relative to the first DC voltage offset and a second induced deflection of the probe relative to the second DC voltage offset 514. Based on this, a potential P outside the range traversed by the first and second DC voltage offsets may be determined at least in part based on the first and second deflections 515. The potential P determined in this way is determined based on whether it falls within the range “P…”. min <P <P max "Inside, the probe can then continue to approach the sample 531 or cause the sample to discharge 520. In this case, P..." min This can correspond to the lower threshold, P max This can correspond to an upper threshold, where a given potential P (of the sample) falls within the range P. min <P <P max Within (i.e., above the lower threshold P) min And below the upper limit threshold P max We can assume that safe access is possible. For example, P min It can be -1 V, -5 V, -10 V or -20 V and / or P max It can be 1 V, 5 V, 10 V, or 20 V. In other examples, P can also be used. min and / or P max Other predetermined values.

[0122] If the potential is within the range where the sample potential is assumed to be too high for the probe to safely approach (i.e., within [P]), min P max (Except for) the sample discharge, then it can be determined whether to discharge the sample: Figure 5In the example, the method for discharging the sample 520 only includes discharging the sample (e.g., according to known methods and / or the methods described herein). Specifically, the discharge can be based on a determined sample potential in terms of its duration, intensity, and execution. Specifically, parameters of the sample discharge can be set such that it can be assumed that the sample potential substantially disappears due to the discharge. Afterwards, the process can be repeated, for example as... Figure 5 Method 510 as described herein (starting with step 511 or, for example, step 512 (if the probe has been correctly positioned)). This cycle can occur frequently as needed until the sample potential is at [P]. min P max Within the range.

[0123] If the sample potential is within the range [P] min P max Within (with or without pre-discharge 520), a method for inducing probe approach toward the sample 530 can be performed. This method includes steps 531-535: inducing probe approach toward the sample 531, and repeatedly determining probe deflection 532 during the approach induction process, for example, at a predefined rate. Based at least in part on the probe deflection, an approach termination condition 533 (or uncertain) for avoiding sample damage can be determined. If the approach termination condition is determined, the process of inducing probe approach toward the sample (534) can be terminated and / or the sample can be (partially) discharged 535. Because method 530 can determine a very localized sample potential during the approach induction process (compared to a relatively large area scan of the surface by method 510), sample potentials not detected in method 510 can be captured. After sample discharge 535, the process of approaching the sample 531 can continue (along with further steps 532-535). This cycle can occur frequently as needed until probe approach is induced toward the sample until a target distance (e.g., until contact) is reached.

Claims

1. A method (510) for determining the potential of a sample (160), wherein, The method includes: Position the probe (150) (511) above the sample (160); Apply (512) at least a first DC voltage offset and a second DC voltage offset (121, 122) respectively from the first range (221); An AC voltage (513) is applied to the probe (150) to cause mechanical oscillations (141, 142) in the probe (150). Determine (514) the first induced deflection (210, 211, 212, 230) of the probe (150) for the first DC voltage offset (121, 122) and the second induced deflection (210, 211, 212, 230) of the probe (150) for the second DC voltage offset (121, 122); and The potential outside the range spanned by the first DC voltage offset and the second DC voltage offset (121, 122) is determined (515) at least in part based on the first deflection and the second deflection (210, 211, 212, 230).

2. The method according to claim 1, wherein, The deflection (210, 211, 212, 230) includes the amplitude (210, 211, 212) of the mechanical oscillation (141, 142) and / or the phase (230) of the mechanical oscillation (141, 142).

3. The method according to claim 1 or 2, wherein, The first deflection and the second deflection (210, 211, 212, 230) include an in-phase component (212) and / or a quadrature component (211).

4. The method according to any one of the preceding claims, wherein, It is determined (514) that the first deflection and the second deflection (210, 211, 212, 230) include locked amplification.

5. The method according to any one of the preceding claims, wherein, The AC voltage frequency is substantially equal to the resonant frequency of the probe (150) or several times the resonant frequency of the probe (150).

6. The method according to any one of the preceding claims, wherein, The first range (221) extends from -10 V to +10 V.

7. The method according to any one of the preceding claims, wherein, Determining the potential includes using a fitting function to fit at least a first data point and a second data point, the first data point including the first deflection (210, 211, 212, 230) and the first DC voltage offset (121, 122), and the second data point including the second deflection (210, 211, 212, 230) and the second DC voltage offset (121, 122).

8. The method according to claim 7, wherein, Determining the potential also includes extrapolation and / or determining the zero point of the fitted function.

9. The method according to claim 7 or 8, wherein, The fitting function includes a linear function, and preferably includes a correction of the linear function based at least in part on the resonant frequency, oscillation mass and / or spring constant of the probe (150).

10. The method according to any one of the preceding claims, wherein, The positioning is performed such that the distance between the probe (150) and the sample (160) is 0.001 μm to 1000 μm, preferably 50 μm to 150 μm.

11. A method (530) for causing a probe (150) to approach a sample (160), wherein, The method includes: This causes the probe (150) to approach (531) the sample (160); During the process that causes approach (531), the deflection (210, 211, 212, 230) of the probe (150) is repeatedly determined (532); and The near-termination condition for avoiding sample damage is determined (533) based at least in part on the deflection (210, 211, 212, 230) of the probe (150).

12. The method according to claim 11, wherein, The determination (533) is performed by means of a real-time device configured to determine the near-termination condition within a time of 2 ms or less, preferably 1 ms or less, particularly preferably 0.5 ms or less.

13. The method according to claim 11 or 12, further comprising terminating (534) the process of causing the probe (150) to approach (531) the sample (160) based at least in part on determining (533) the proximity termination condition.

14. The method according to claim 13, wherein, After the near-termination condition is met, the termination is performed within 2 ms or less, preferably 1 ms or less, particularly preferably 0.5 ms or less.

15. The method according to any one of claims 11 to 14, wherein, The process of approaching (531) induced by the probe (150) is carried out at a speed of 0.1 μm / s or higher, preferably 1 μm / s or higher, particularly preferably 2 μm / s or higher.

16. The method according to any one of claims 11 to 15, wherein, The near-termination condition includes a predefined deflection (210, 211, 212, 230) exceeding that of the probe (150).

17. The method according to any one of claims 11 to 16, further comprising determining the resonant frequency of the probe (150) during the process of causing proximity (531).

18. The method according to claim 17, wherein, The near-termination condition includes a predefined frequency shift exceeding the resonant frequency.

19. The method according to claim 17 or 18, wherein, The near-termination condition includes the resonant frequency being lower than a predefined minimum frequency.

20. A method for processing a sample (160), comprising: The steps of the method for determining potential according to any one of claims 1 to 10; as well as The steps of the method for bringing the probe (150) toward the sample (160) (531) are determined at least in part based on the potential, according to any one of claims 11 to 19.

21. The method of claim 20, further comprising at least partially discharging the sample (160) (520) based at least in part on the potential.

22. The method of claim 21, wherein, Discharge at a potential of ±1 V or higher, preferably ±5 V or higher, and particularly preferably ±10 V or higher (520).

23. The method according to claim 21 or 22, wherein, The steps of the method according to any one of claims 11 to 19 are performed only for potentials of ±20 V or lower, preferably ±15 V or lower, particularly preferably ±10 V or lower.

24. The method according to any one of the preceding claims, wherein, The sample (160) is at least partially charged.

25. The method according to any one of the preceding claims, wherein, The probe (150) includes the probe (150) of a scanning probe microscope. The probe (150) includes a probe arm (151) and a measuring tip (152), and / or The deflection (210, 211, 212, 230) is measured by the light beam reflected at the probe (150).

26. The method according to any one of the preceding claims, wherein, The sample (160) includes an object for photolithography, preferably a photolithographic mask.

27. An apparatus for processing a sample (160), wherein, The apparatus includes devices configured to automatically perform the steps of the method according to any one of claims 1 to 26.

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