Method of positioning an object in a particle beam microscope and computer program product

Abstract

The invention relates to a method for positioning a movable object in a sample chamber of a particle beam microscope, which is carried out by means of a flexible particle beam barrier. The particle beam microscope comprises at least one particle beam column for generating a charged particle beam, and a sample chamber, a detector for detecting interaction signals and a control and evaluation unit. In the method, initially an object is provided in the sample chamber. Next, a barrier region is defined, which is subsequently scanned using the charged particle beam. Interaction signals generated during the scan are detected. The object is moved towards the barrier region, wherein the detected interaction signals are monitored and signal changes are registered, so that the time at which the object enters or leaves the barrier region can be detected.

Description

Technical Field

[0001] This invention relates to a method for positioning a movable object in the sample chamber of a particle beam microscope. Background Technology

[0002] For inspections or sample processing performed using particle beam microscopy, it is often necessary to move and precisely position objects within the sample chamber in a controlled manner. Particle beam microscopy is understood to refer to a microscope system that operates using a beam of charged particles, such as a scanning electron microscope or an ion beam microscope.

[0003] For example, the object can be an electron microscope sample, such as a TEM slide. TEM slides are typically prepared from a sample block (the original sample), then separated from the sample block using a lift and held by a transfer device (such as a micromanipulator).

[0004] Next, the extracted TEM slice is transferred to a suitable container device, such as a grid finger. In other words, the TEM slice must be moved in three-dimensional space in a targeted, precise, and controlled manner within the sample chamber. This process includes actual sample extraction (sample removal) as well as the transfer and attachment of trace amounts of sample to the target sample container.

[0005] In recent years, this lifting procedure has been automated in many ways. The most important of these is bringing the micromanipulator closer to the trace sample to be prepared for extraction, and also bringing the trace sample already attached to the micromanipulator closer to the target sample container.

[0006] To control this proximity procedure, image recognition methods have been proposed. For this purpose, particle beam images are recorded, showing, for example, TEM slices and grid fingers held by a manipulator. The lifting procedure can be performed under the visual supervision of the user. The disadvantage here is the need for image recording, which requires a certain amount of time. Furthermore, during image recording, the sample may be modified or damaged due to irradiation.

[0007] In addition, various other methods for automating TEM sample preparation are known.

[0008] However, it is not typically only microsamples that must be positioned within the sample chamber. Displaceable detectors are often used, moving back and forth between at least two positions, particularly a working position and a resting position. Furthermore, the sample stage of a particle beam microscope typically moves in at least three spatial directions to allow examination of the recorded sample. For this purpose, a special sample holder is typically mounted on the sample stage to receive the sample. Depending on the specific application, a wide variety of sample holders are available. Therefore, the sample stage can accommodate various structural designs, and there is a permanent risk of the structure colliding with other components in the sample chamber, such as objectives.

[0009] To avoid such collisions, it has been proposed to use laser equipment to position the sample below the objective lens and focus it on the sample.

[0010] The downside here is that additional laser equipment must be provided and the positioning only involves a very small spatial area.

[0011] Another known system is the light barrier system, in which a light source and a light sensor can detect when a movable obstacle interrupts the light beam. Light barriers can also be designed as light grids or light curtains.

[0012] Furthermore, it is known that any contact between the sample stage and the objective lens (touch alarm) can be detected electrically, allowing the movement of the sample stage to be stopped. The drawback here is that movement only stops upon contact.

[0013] Therefore, it is desirable to be able to reliably monitor the movement or approach of such an object in the sample chamber of a particle beam microscope without contact. This would be particularly advantageous if it could be achieved using equipment that is standard in particle beam microscopes.

[0014] The following documents should be considered prior art: - US 10,088,401 B2 (Uemoto et al.) - EP 1 812 945 B1 (Moore and Zaykova-Feldman) - US 7,414253 B2 (Moore et al.) - US 7,208,724 B2 (Moore et al.) - US 9,601,313 B2 (Brogden et al.) - DE 10 2006 047 729 A1 (Albiez) Summary of the Invention

[0015] The purpose of this invention is to provide a method for determining the position of a movable object in the sample chamber of a particle beam microscope.

[0016] This objective is achieved by means of a method having the features described below.

[0017] This invention relates to a method for positioning a movable object in a sample chamber of a particle beam microscope, wherein the method is performed using a particle beam microscope including a particle beam column for generating a charged particle beam, a sample chamber, a detector for detecting interaction signals, and a control and evaluation unit; the method includes the following steps: a) Provide movable objects in the sample chamber; b) Define the barrier area; c) Use the charged particle beam to scan the barrier region; d) Use the detector to detect interaction signals; e) Move the object along the direction of the barrier area; f) Monitor the detected interaction signals and register signal changes.

[0018] Advantageous improvements to this method are presented below.

[0019] Preferably, the registration of the signal change causes the movement of the object to stop.

[0020] Preferably, at least one of steps b) to f) is repeated.

[0021] Preferably, multiple detectors are used to detect the signal.

[0022] Preferably, the visualized image is recorded at the desired time.

[0023] Preferably, at least two barrier regions are used.

[0024] Preferably, the first barrier region is defined such that the movement of the object in the first direction of movement is detectable, and the second barrier region is defined such that the movement of the object in the second direction of movement is detectable.

[0025] Preferably, the first and second directions of movement are arranged orthogonally to each other.

[0026] Preferably, the at least two barrier regions are defined such that a path is specified in three-dimensional space and the movable object moves along the path in space.

[0027] Preferably, signals detectable in the multiple barrier areas are monitored simultaneously.

[0028] Preferably, the position of the movable object in three-dimensional space is monitored, and the particle beam microscope includes a first particle beam column for generating a first particle beam and a second particle beam column for generating a second particle beam, wherein the optical axes of these particle beam columns are arranged at a non-zero angle to each other, and wherein the first particle beam and / or the second particle beam is used to scan the barrier region.

[0029] Preferably, the barrier region comprises multiple partial regions arranged at intervals from each other, and the signals of the two partial regions are evaluated together.

[0030] Preferably, multiple barrier regions spaced apart from each other are used, and the signals of the barrier regions are evaluated individually.

[0031] Preferably, the movable object is in the form of a TEM sheet.

[0032] Preferably, the movable object is in the form of an electron beam lithography sample.

[0033] The present invention also relates to a computer program product comprising a sequence of control commands that cause a particle beam system to perform the methods described above.

[0034] When working with a particle beam microscope, it is often necessary to accurately position objects in the sample chamber, where vacuum conditions usually dominate during operation.

[0035] The object can be any article of manufacture, such as a microscopic sample to be examined held on a sample stage. However, within the sense of the invention, the object can also be a displaceable detector, a sample stage, a sample holder mounted on a sample stage, or any other desired component located in the sample chamber.

[0036] The "position" of an object is understood to refer to its location and spatial orientation. Here, "position" refers to the object's location in three-dimensional space, which can be described by specifying x, y, and z coordinates.

[0037] Spatial orientation is understood to refer to the arrangement of objects. Spatial orientation is usually specified relative to the optical axis of a particle beam microscope.

[0038] To detect the position of a movable object without contact, particle beam microscopy operates in a specific manner. This operating mode will be referred to below as a "particle beam barrier," similar to a known light barrier. However, unlike a light barrier, the "particle beam barrier" according to the invention uses a beam of charged particles instead of light. Furthermore, what is detected is not an interruption in the beam, but a specific change in the integrated signal, which occurs due to the interaction between the particle beam and the material of the object.

[0039] This invention is based on the discovery that the defined solid angle range can be sampled continuously or discretely using a particle beam, wherein the signal is continuously detected. A smoothed signal time profile is captured using one or more detectors to detect signal changes. In this way, the time it takes for an object, such as a trace sample, or a displaceable detector to move into or out of the sampled solid angle range can be detected.

[0040] The method according to the invention does not operate using the analysis of image data. Instead, the time curve of the average detector signal within an intentionally selected area or region is used to determine the location and the movement vector. For example, the time it takes for a moving object to pass through a threshold within the space can be detected.

[0041] To detect the aforementioned signal changes, a barrier region was specified for monitoring within the sample chamber. To specify the barrier region, the current position of the object should be known, for example, because the object's spatial coordinates are known. However, it's also possible to consider the inherent inaccuracies of the known object position when defining the barrier region.

[0042] The barrier region is a range of solid angles specified by the user, through which the particle beam continuously passes. It is particularly advantageous that the beam is a charged particle beam, such as an electron beam or an ion beam. However, it is also conceivable, alternatively, to scan the region with X-rays.

[0043] In other words, the barrier region is the area monitored by means of a particle beam barrier. In the process of the method according to the invention—depending on the intended application—the location (i.e., position and spatial orientation), size, and shape of the barrier region are defined.

[0044] During a single-pass particle beam scan of the barrier region, the signal is detected using a suitable detector. Advantageously, for this purpose, detectors already present in the particle beam microscope being used, such as secondary electron (SE) detectors and / or backscattered electron (BSE) detectors, are used.

[0045] A specific signal is detected when the movable object is not yet within the barrier area. However, once the movable object enters the barrier area, a change in the characteristic signal can be detected.

[0046] Furthermore, it is conceivable that changes in the characteristic signals can be observed when the object leaves the barrier area.

[0047] The location of the barrier region can be selected as needed. It is also possible to specify and monitor multiple barrier regions. If two particle beam columns are used, such as in a SEM-FIB combined microscope, a three-dimensional region can also be monitored.

[0048] This method not only detects the position of an object but also allows for targeted changes to that position. To this end, the position of the barrier region is repeatedly changed, and the object tracks the position of the barrier region progressively in each case.

[0049] Changes in a smoothed signal can be used not only to infer the position of an object, but also to deduce conclusions about the object's spatial orientation and / or shape.

[0050] The particle beam barrier according to the present invention can be applied flexibly.

[0051] The location, spatial orientation, size, and geometry of the barrier area can be freely selected and changed. In other words, the barrier area can be freely defined. Furthermore, it is conceivable to repeat this method and redefine the barrier area in each case.

[0052] The design of the scanning area, that is, the design of the sampling solid angle, offers further possibilities for variation. On the one hand, the shape and size can vary. Therefore, various shapes are possible, such as simple geometric shapes like rectangles, circles, and triangles, but also complex multipart polygons, or even L-shapes. It is also conceivable that the barrier area could be designed as a straight line or curve, or in the form of a point.

[0053] Furthermore, beam and scanning parameters can be changed. For example, the focus, accelerating voltage, beam current, scanning speed, or the scanning mode used can be altered. Different repetition and averaging methods can also be considered in the evaluation of the detected signal.

[0054] Furthermore, different defined barrier regions can be used in the time series of this method, and therefore monitoring can be designed in a flexible manner. This method can be implemented using one barrier region or multiple differently defined barrier regions.

[0055] In principle, it is conceivable that the movement of a movable object using the method according to the invention can be performed continuously or alternatively discretely (i.e., in a stepwise manner). Similarly, monitoring using a particle beam barrier can be performed continuously or discretely.

[0056] For the purpose of recording the positioning method, a visualization image, such as an SEM image, may be recorded at the desired time. Attached Figure Description

[0057] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. For the purpose of illustrating the components, reference will be made to the entire preceding and following descriptions, respectively.

[0058] Figure 1 The principle of the method for positioning an object according to the present invention is illustrated in the form of a flowchart.

[0059] Figure 2 The time curves of the signals detected by the particle beam barrier are shown as an example when an object is brought into the barrier region of the particle beam barrier.

[0060] Figure 3 A first exemplary embodiment of the method is illustrated schematically, wherein the extracted TEM slice, held by a micromanipulator, is brought closer to the grid finger by means of a particle beam barrier.

[0061] Figure 4 A flowchart illustrating a first exemplary embodiment of the method is shown.

[0062] Figure 5 A second exemplary embodiment is shown, in which a flexible particle barrier is used to monitor the positioning of a structured sample stage.

[0063] Figure 6 Another exemplary embodiment is shown, in which a sample for electron beam lithography is positioned.

[0064] Figure 7 It demonstrates how to move objects in space in a targeted manner by repeatedly shifting the barrier area.

[0065] Figure 8 A FIB-SEM assembly suitable for performing the method according to the invention is shown. Detailed Implementation

[0066] Figure 1 The basic sequence of a method according to the invention for non-contact positioning of a movable object in a microscope system is illustrated. This method is performed by means of a particle beam microscope, i.e., a scanning electron microscope, an ion beam microscope, or a FIB-SEM combined microscope. The particle beam microscope includes a sample chamber in which vacuum conditions typically dominate during operation.

[0067] In the first step S1, the movable object to be positioned is provided in the sample chamber of the particle beam microscope.

[0068] The movable object can have various designs. For example, the movable object can be an extracted TEM slice held by a micromanipulator and movable by moving the micromanipulator. However, the movable object can also be a displaceable detector, such as a displaceable STEM (scanning transmission electron microscopy) detector. An STEM detector can be positioned in a working position within the sample chamber and can be moved to a resting position during work pauses.

[0069] What both examples have in common is that the movable object is designed to be positioned within the sample chamber. In the example of the displaceable STEM detector, care should be taken to move the STEM detector to its working position without colliding with other components in the sample chamber.

[0070] In step S2, a barrier region is defined to be scanned by the particle beam during the process according to the method of the invention. Therefore, the barrier region refers to the area of ​​the particle beam barrier that is scanned to detect objects entering or leaving this region.

[0071] For this purpose, the location and spatial orientation of the barrier region are specified. This is accomplished in such a way—depending on the specific application—that the defined volumetric region can be monitored. In this case, the barrier region should be advantageously positioned between the current position of the movable object and the desired position of the object. In this way, it is ensured that the object will pass through or at least come into contact with the barrier region during its movement in the direction of the desired position and can be captured by the particle beam barrier.

[0072] The barrier region can be defined as the scanning area scanned by the particle beam using the user interface of a particle beam microscope.

[0073] Alternatively, the location of the barrier region can be calculated using particle beam microscopy control software or determined based on 3D models or CAD data. Furthermore, it is conceivable to generate images of components within the sample chamber, such as STEM detectors intended to be positioned close to these components. The desired barrier region can then be specified based on these images.

[0074] Therefore, the barrier area can be defined manually by the user, automatically, or pre-specified. It is also conceivable that multiple barrier areas can be specified in step S2.

[0075] When selecting the location, spatial orientation, size, and geometry of the barrier region, it is advantageous to consider the object's moving speed, scanning speed, and other scanning parameters. It is also conceivable to bring the object closer step by step, with pauses between steps used to evaluate the corresponding acquired signal. Furthermore, the size of the object should be considered when specifying the size of the barrier region.

[0076] The size of the barrier region can be chosen based on the expected speed at which the object (i.e., a movable STEM detector) is moving. At low speeds, the barrier region can be chosen to be narrower; conversely, at higher speeds, the barrier region should be chosen to be wider.

[0077] When selecting the size and pose of this barrier region, the scanning speed and integration time of the detector used should also be taken into account.

[0078] Then (step S3) scanning begins, during which the barrier region is scanned continuously or repeatedly using a charged particle beam. The particle beam used (primary particle beam) can be an electron beam or an ion beam. Additionally, it is conceivable—depending on the specific application—that different scanning parameters will vary, such as dwell time, pixel pitch, pixel size, line spacing, or scanning mode.

[0079] Step S4 marks the beginning of detecting the interaction products using a suitable detector, which are generated when the particle beam is incident on the material. That is, the average signal from the detector is continuously recorded within the scanning region.

[0080] If there are no obstructions (i.e., no objects) within the barrier area, a specific signal value is detected. For example, the signal could be secondary electrons released when a primary particle beam strikes the wall of the sample chamber or other components of the microscope system. This signal appears only to a small extent and should be considered noise.

[0081] However, once the object to be located enters the barrier region (step S5), it is irradiated with a particle beam. A noticeable signal change can then be detected. It is also conceivable that a signal change would be detected when the object leaves the barrier region. Therefore, in principle, entry into and exit from the barrier region can be determined based on the signal curve.

[0082] In this case, the detector signal is independent of location. Instead, the time curve of the average detector signal is captured.

[0083] It has been shown that performing steps S3, S4 and S5 simultaneously is particularly advantageous.

[0084] A suitable detector is one of several types that can capture the different interaction signals between the primary particle beam and the irradiated material. For example, an in-lens detector or an SE (secondary electron) detector arranged in the sample chamber could be used. It is also conceivable to use a BSE detector to detect backscattered electrons (BSE).

[0085] Use EDX detectors that capture X-ray quanta whenever possible. Therefore, for example, it is conceivable that objects containing gold (Au) atoms could be well detected using an EDX detector and located using this method.

[0086] Using multiple detectors simultaneously or one after another may be particularly advantageous because different detector types may have different applicability depending on the characteristics of the moving object.

[0087] If a primary particle beam is, for example, directly incident on one of the detectors (or on the conversion surface of the detector), then the shadowing effect of the primary particle beam can even be utilized in a targeted manner.

[0088] If a significant signal change is detected, the position of the moving object is known. The moving object is at least partially located within the barrier area. Therefore, the position of the object can be registered (step S6).

[0089] Figure 2 An example illustrating the change of the detector signal over time during the scanning barrier region is shown schematically. The integrated detector signal (vertical axis) is plotted against time (horizontal axis).

[0090] Curves 20 and 20' represent the time curves of the detector signal. Initially, the movable object is not located in the barrier area, and therefore the detector signal has the first curve 20.

[0091] The captured detector signal can be averaged in various ways. One approach is to generate an average gray value for each scan run through the barrier region. In this case, one scan run produces one signal value. Alternatively, multiple average gray values ​​can be computationally combined such that the scan run is incorporated into only a portion of the signal value.

[0092] At a specific time 21, the object enters the scanned barrier area, and as a result, the amplitude of the detector signal changes and the detector signal has a second curve 20'.

[0093] However, the signal curve shown, indicating an increase in signal when an object enters the barrier area, should be considered merely an example. It is also conceivable that the signal decreases or increases when using the first detector, and decreases when using the second detector.

[0094] Regardless, the curve of the detected signal will be monitored. In other words, the signal is analyzed to reliably detect and register any significant signal changes. For this purpose, various suitable methods can be used, such as smoothing or differentiation.

[0095] It can be assumed that every object entering the barrier region will produce a typical time signal curve, that is, it has a typical signature.

[0096] If the system used is known, a typical signature can be detected when an object passes through the barrier area.

[0097] The signature can depend on various parameters, such as the object's moving speed, the size and shape of the barrier area, and the detector used. In particular, the selected detector settings will come into play, such as brightness and contrast settings.

[0098] It is also conceivable to use multiple detectors simultaneously for signal detection, and then capture the relevant signatures simultaneously in different detector systems.

[0099] Figure 3 A first specific exemplary embodiment of the method is illustrated schematically, which can be used to locate the extracted TEM slice.

[0100] A TEM slide is understood to be an electron microscope sample that is essentially a flattened cuboid shape. In at least one region, the sample cuboid must be thin enough that electrons can radiate through it. Electrons that pass through the TEM slide (called transmitted electrons) can then be detected by a suitable detector and used to generate an image of the sample (called a transmission image or diffraction image).

[0101] To prepare TEM slices, slices are initially extracted from the original sample and separated from the original sample by lifting. For further processing and inspection purposes, the TEM slices are then transferred to a grid finger, that is, transferred to a sample container device.

[0102] Then, by means of the particle beam barrier according to the invention, the extracted TEM sheet 32 ​​held by the micromanipulator 31 is brought closer to the grid finger 35, so that the TEM sheet 32 ​​can be fixed to the grid finger 35 in a later step.

[0103] Initially, a grid finger 35 was provided in the sample chamber of the particle beam apparatus. Figure 3 a) The first barrier region 33 is located near the grid finger 35. The first barrier region 33 is located between the current position of the TEM sheet 32 ​​and the grid finger 35. In order to define the first barrier region 33, an image containing the imaging region 34 can be recorded. However, such image recording is not mandatory.

[0104] The first barrier region 33 is then scanned using a beam of charged particles. Signals generated during this process, such as secondary electrons (SE) and / or backscattered electrons (BSE), are detected in a position-independent manner using a suitable detector 30.

[0105] The TEM sheet 32 ​​then moves along a first moving direction 38, indicated by arrow 38, along the direction of the grid pointer 35, and therefore also along the direction of the first barrier region 33. For example, the first movement 38 can occur in the horizontal direction.

[0106] When the TEM sheet 32 ​​enters the first barrier region 33 ( Figure 3 At point b), a noticeable and detectable signal change will occur. It is particularly advantageous to immediately stop the movement of the TEM sheet 32 ​​when the signal change is detected.

[0107] The location of TEM sheet 32 ​​is known because at least a portion of the TEM sheet is located within the area of ​​barrier 33.

[0108] Then, define the second barrier region 36 ( Figure 3c), which is closer to the grid finger 35 than the first barrier region 33, so that the TEM sheet 32 ​​is closer to the grid finger 35. Assume that in this case the TEM sheet 32 ​​continues to move toward the grid finger 35.

[0109] Then, the signal change that occurred as described above when the TEM sheet 32 ​​entered the second barrier region 36 was detected again.

[0110] Furthermore, it is conceivable that the movement of the TEM sheet 32 ​​occurs in the second...

[0111] The movement direction is 39, and correspondingly, a third barrier area 37 is designated, such as... Figure 3 ( Figure 3 As shown in d). Figure 3 In the illustration, for example, the second direction of movement 39 is vertical movement.

[0112] Furthermore, it is conceivable that different barrier regions are pre-defined. Here, the direction of movement of the object (i.e., the TEM sheet) must be considered separately.

[0113] Figure 4 A first exemplary embodiment is shown as a flowchart.

[0114] Initially, in step S40, a TEM slide is provided in the sample chamber of the particle beam microscope. The TEM slide has been extracted from the original sample and is held by the tip of a micromanipulator. Alternatively, different transfer devices, such as nanogrippers, can be used. The transfer device should be designed to allow for targeted movement of the held slide.

[0115] Then, optionally, images of the grid finger and its surrounding environment can be recorded (step S41). Imaging of the TEM slice is not necessary here. Instead, the focus is on specifying the location of the barrier region near the grid finger.

[0116] If the desired location can be defined in a different way (step S43), for example by calculation or based on existing CAD data, then step S41 can also be omitted.

[0117] Then, the TEM sheet is positioned near the grid finger in the sample chamber by moving the micromanipulator (step S42).

[0118] In step S43, the location, size, and geometry of the first barrier region are specified.

[0119] Next, the barrier region is scanned using a charged particle beam (step S44).

[0120] Starting from step S45, the signal is detected using a suitable detector. Different suitable averaging methods can be used to analyze the captured signal. For example, time averaging is conceivable, but it could also be a combination of calculations from multiple scans, where one scan is considered as a single scan encompassing the barrier region.

[0121] The TEM slice is then moved toward the barrier region (step S46). Simultaneously, the barrier region is scanned (i.e., sampled continuously or intermittently) and analyzed. Once the TEM slice enters the barrier region, the detected signal changes. This signal change is monitored and recorded. When a signal change is detected, the movement of the TEM slice can be stopped to determine its exact location, specifically at the edge of the barrier region. Alternatively, the movement of the TEM slice can be altered when a signal change is detected.

[0122] In step S48, it is inquired whether additional positioning steps are needed. If so (S48 inquires: Yes), steps S42 to S46 can be repeated to bring the TEM sheet closer to the grid finger. If no additional steps are needed (S48 inquires: No), the TEM sheet can be secured to the grid finger in subsequent step S49. Therefore, it is conceivable that some or all of the steps mentioned in the described method can be repeated until the object is positioned as needed. In particular, it has proven advantageous to repeat steps S44 (scanning), S45 (detecting the signal), S46 (moving the sheet), and S47 (monitoring the detected signal).

[0123] Optionally, in an additional step S47, which is performed in parallel with steps S40 to S48, a visualization image may be recorded. For example, this visualization image may be an SEM image. The visualization image is generated independently of the rest of the localization method and is used solely for process observation and documentation. That is, such a visualization image can be recorded at each stage of the method so that the user can visually track the progress of the method.

[0124] Figure 3 and Figure 4 The exemplary embodiments shown are not limited to using a grid finger to receive trace samples. Instead, different types of container devices can be used, such as in-situ STEM holders or special holders for APT (atomic probe tomography) analysis.

[0125] Additionally, it is conceivable that this method could be used in a modified form to transfer TEM slides from the original sample to a transfer device (so-called lifting). This is because, even in this case, the movable object, which is the transfer device, must be positioned (i.e., close to the slide). For example, the transfer device could be a micromanipulator, a nanogripper, etc.

[0126] It is also conceivable that, Figure 3 and Figure 4 The method described in the paper has been modified so that the lattice finger itself is moved and brought close to the TEM sheet by means of a particle beam barrier. Furthermore, the method can also be used to bring two movable objects close to each other.

[0127] The method according to the invention can also be used to position or bring close to any desired object in the sample chamber of a particle microscope. The object may be a microsample (e.g., a TEM slide, an APT (Atomic Probe Tomography) sample, a lithographic sample), a container device for receiving the sample (e.g., a grid finger, a manipulator needle, a nanogripper), a displaceable detector, or another movable object.

[0128] therefore, Figure 5 A second exemplary embodiment of the method is shown, wherein a flexible particle beam barrier is used to monitor the positioning of a structured sample stage.

[0129] The schematic diagram illustrates the arrangement within the sample chamber 53 of the FIB-SEM assembly. The FIB-SEM assembly includes an electron beam column 50 with a first optical axis 51 and an ion beam column 58 with a second optical axis 59. Located within the sample chamber 53 is a movable sample stage 56, which can accommodate a sample holder 55 for holding the sample. Many types of sample holders 55 are known, and therefore, various sample holder structures can be mounted on the sample stage 56.

[0130] To minimize the risk of collision between the sample stage 56 or sample holder 55 and structural components of the microscope (e.g., electron beam column 50, ion beam column 58, or detector 54), barrier regions 52 and 57 are defined.

[0131] For example, a first barrier region 52 can be defined near the objective lens of the electron beam column 50. A second barrier region 57 can be positioned near the objective lens of the ion beam column 58. When the sample stage 56 or one of its structures enters one of the barrier regions 52, 57, the movement of the sample stage can be stopped immediately. Therefore, the particle beam barrier according to the invention can be used for protection against collisions.

[0132] Figure 6 Another exemplary embodiment is schematically illustrated. This other exemplary embodiment shows the precise positioning of a sample 61 for electron beam lithography.

[0133] Typically, the sample 61 used for electron beam lithography is coated with an electron beam resist that reacts to particle radiation.

[0134] Using the particle beam barrier according to the invention, the contact time between the photolithographic sample 61 and the previously defined region 60 can be determined. As described above, the barrier region 60 is initially specified ( Figure 6 a).

[0135] When the edge of the photolithographic sample 61 enters the barrier region 60 ( Figure 6 b) When moving the photolithographic sample 61, the movement can be stopped. This ensures that the particle beam irradiates only one edge of the photolithographic sample 61, thus avoiding undesirable irradiation effects. Therefore, the radiation dose incident on the structure of the photolithographic sample 61 can be kept low.

[0136] Furthermore, it is conceivable that the particle beam barrier according to the invention can be used to bring two movable objects closer to each other, for example, to bring a grid finger that moves by means of a sample stage closer to a manipulator (within a limited range).

[0137] Figure 7 This illustrates how a particle beam barrier according to the invention can be used to move an object 70 in space in a targeted manner by repeatedly displacing the barrier region 72.

[0138] Multiple spatial orientations can be monitored by progressively shifting and changing the geometry of barrier region 72 (or multiple barrier regions). Tracking paths can also be envisioned.

[0139] For this purpose, the barrier region 72 of the particle beam barrier is repeatedly adjusted along the desired path 74. Figure 7 a to Figure 7 b). Then, for example, the specific spatial region can be scanned using successive displacements and / or adjustments of the barrier region 72. The movable object 70 is tracked in each case and thus moves through space along the path 74. For example, this is how obstacle 73 can be handled ( Figure 7 d). This is based on the fact that registration can be made when an object enters or leaves the barrier area. Once such movement is registered, the barrier area can be shifted and / or altered.

[0140] Therefore, the method according to the invention can be used to monitor the movement of an object in two spatial directions, which are, for example, orthogonal to each other, and thus, the vertical and horizontal movement of the object can be monitored. For this purpose, a first barrier region is defined through which the movement of the object in the first spatial direction can be detected. Figure 7 a to Figure 7 c). Furthermore, a second barrier region is defined through which the movement of an object in a second spatial direction is detected. Figure 7 d).

[0141] Furthermore, this method can be used to locate objects with improved accuracy.

[0142] Furthermore, it is conceivable to repeatedly use multiple barrier areas of different shapes in this manner. In this case, the barrier areas could, of course, also have different sizes.

[0143] The method according to the invention can also be used to monitor and locate movable objects in three spatial dimensions. For this purpose, two particle beams are required, which are not parallel to each other. Both particle beams are used to scan the barrier region.

[0144] This embodiment of the method can be performed, for example, in an L-shaped FIB-SEM combination device. In a particular form of dual-beam device, the ion beam column and the electron beam column are arranged at right angles (90°) to each other, and thus the two optical axes are arranged in an L-shape.

[0145] Here, the optical axes of the electron beam columns are arranged parallel to the z-axis, therefore the position of an object on the z-axis cannot be detected using the electron beam columns. The electron beam columns can only detect positions along the x and y axes.

[0146] In addition, ion beam columns can be used to image positions along the z-axis and x-axis, with the optical axis of the ion beam column extending parallel to the y-axis because the ion beam columns are arranged perpendicular to the z-axis.

[0147] By using two particle beams arranged in this manner to scan the barrier region, objects in space, that is, in all three spatial directions x, y, and z, can be observed. It is conceivable that, in each case, only a portion of the barrier region is scanned by the particle beams. The arrangement of objects in three-dimensional space is therefore deduced, and thus, objects can be positioned in three-dimensional space by means of the particle beam barrier according to the invention.

[0148] However, this embodiment is not limited to an L-shaped dual-beam device. Instead, it is conceivable that the two particle beam columns are arranged at different non-zero angles to each other, such as 56°, 52° or 48°.

[0149] Furthermore, it is conceivable that the barrier region has a discrete geometry. This is understood to mean that the barrier region has different partial regions that are discontinuous and spaced apart from each other. However, these partial regions are treated as single regions and evaluated as such in signal evaluation. This means that the detection signal of these partial regions is evaluated as a single data point for each scan.

[0150] Furthermore, two separate barrier regions arranged at intervals can be scanned and detected almost simultaneously and independently, with the signals from these regions analyzed separately. This provides two separate data points for these barrier regions. Therefore, two barrier regions can be observed and monitored in parallel.

[0151] Figure 8 An example of a FIB-SEM combination device 80 is shown, illustrating a particle beam microscope that can be used to perform the method according to the invention.

[0152] To enable the sample 95 to be examined for microscopic inspection or processing, the sample 95 is held by a sample holder 94 mounted on a sample stage 93 of the FIB-SEM assembly 80. Alternatively, the FIB-SEM assembly 80 may include other holding devices, such as grid fingers. Alternatively, the sample 95 may be held by a transfer device 102, such as a micromanipulator or nanogripper.

[0153] The sample stage 93 is arranged in the sample chamber 89 of the FIB-SEM assembly 80, where vacuum conditions dominate during operation.

[0154] It is particularly advantageous to design the sample stage 93 as a multi-axis sample stage, thus providing multiple translational and rotational degrees of freedom. This is the case, for example, if the sample stage 93 were implemented as a five-axis stage including translational axes x, y, and z and rotational axes R and T (tilt axes). In this case, the aforementioned translational axes are arranged perpendicular to each other in each case. The rotational axis R is typically arranged parallel to the z-axis, while the tilt axis T is typically arranged perpendicular to the rotational axis R. The sample 95 can therefore be moved via the multi-axis stage in three spatial directions x, y, and z to change the position of the sample 95.

[0155] The FIB-SEM assembly 80 includes two particle beam columns, specifically an electron beam column 81 for generating an electron beam and an ion beam column 101 for generating an ion beam. Both particle beams are directed at a sample 95, which is advantageously located at the point of overlap of the two particle beams.

[0156] During operation of the FIB-SEM assembly 80, primary electrons are generated in the electron source 82. These primary electrons are focused, parallelized, or scattered by the condenser lens system 83, 85 along the optical axis 84 of the electron beam column 81 and trimmed by at least one aperture stop 86. Furthermore, the electron beam column 81 includes a deflection system 87 that allows the primary electron beam to be guided onto the sample 95 in a grating manner, and also includes an objective lens 88 by means of which the primary electron beam can be focused onto the sample 95.

[0157] Furthermore, the FIB-SEM assembly 80 includes an ion beam column 101 with an ion source 99, a deflection system 97, an aperture stop 103, and lens element systems 96 and 100. The ion source 99 may be a liquid metal ion source (LMIS), for example, it operates using a gallium ion source.

[0158] Ions generated in ion source 99 are accelerated along the optical axis 98 of ion beam column 101 and focused onto sample 95 by means of objective lens system 100. Ions incident on sample 95 can be used to remove material from sample 95 and / or to image sample 95. Optionally, FIB-SEM assembly 80 may also have a gas injection system 92 for introducing process gases, thus enabling material removal and / or deposition.

[0159] Furthermore, the FIB-SEM combination device 80 includes at least one detector 90 for detecting interaction products of electrons and / or ions interacting with the material of the sample 95. As an example, the detector may be an SE detector or a BSE detector.

[0160] Furthermore, the FIB-SEM assembly 80 includes an evaluation and control unit 91. The evaluation and control unit 91 can execute control commands included in a computer program product sequentially and / or in parallel. The execution of the control commands enables the FIB-SEM assembly 80 to implement embodiments of the method according to the invention.

[0161] List of reference numerals

[0162] S1 provides the object in the sample chamber.

[0163] S2 defines the barrier area

[0164] S3 uses a particle beam to scan the barrier area.

[0165] S4 Detection and Evaluation Signals

[0166] S5 moves the object to the barrier area and detects signal changes.

[0167] S6 Register the position of the object

[0168] 20. The first curve of the detector signal

[0169] The second curve of the detector signal at 20'

[0170] 21. Time it takes for an object to enter the barrier area

[0171] 30 detectors

[0172] 31 Micromanipulator

[0173] 32 TEM thin section

[0174] 33 First Barrier Area

[0175] 34 Imaging Area

[0176] 35 grille refers to

[0177] 36 Second Barrier Area

[0178] 37 Third Barrier Area

[0179] 38 First direction of movement

[0180] 39 Second direction of movement

[0181] S40 offers thin sheets

[0182] S41 records an image of the grid pointer (optional)

[0183] S42 arranges the thin plates near the grid fingers.

[0184] S43 defines the location and geometry of the barrier area.

[0185] S44 begins using particle beam scanning of the barrier region.

[0186] S45 Start: Use a detector to capture the signal

[0187] S46 moves the thin film toward the barrier area until the signal changes.

[0188] S47 Records visualized images (optional)

[0189] S48 Inquiry: Are any additional steps required?

[0190] S49 secures the sheet to the grid finger.

[0191] 50 electron beam columns

[0192] 51 Optical axis of electron beam column

[0193] 52 First Barrier Area

[0194] 53 Sample Chamber

[0195] 54 detectors

[0196] 55 Sample Holder

[0197] 56 Sample Stage

[0198] 57 Second Barrier Area

[0199] 58 Ion Beam Column

[0200] 59 Optical axis of the ion beam column

[0201] 60 Barrier Area

[0202] 61 Photolithography Samples

[0203] 70 objects

[0204] 71 Micromanipulator

[0205] 72 Barrier Area

[0206] 73 Obstacles

[0207] 74 Paths

[0208] 80 FIB-SEM Combined Unit

[0209] 81 Electron Beam Column

[0210] 82 electronic sources

[0211] 83 First Condensing Lens System

[0212] 84 Optical axis of electron beam column

[0213] 85 Second Condensing Lens System

[0214] 86-aperture stop

[0215] 87 Deflection System

[0216] 88. Objective Lens System (SEM)

[0217] 89 Sample Chamber

[0218] 90 detectors

[0219] 91 Assessment and Control Unit

[0220] 92 Gas Injection System

[0221] 93 Sample Stage

[0222] 94 Sample Holder

[0223] 95 samples

[0224] 96 Lens System

[0225] 97 Deflection System

[0226] 98 Optical axis of ion beam column

[0227] 99 Ion Source

[0228] 100 Objective Lens System (FIB)

[0229] 101 Ion Beam Column

[0230] 102 Transfer equipment (e.g., micromanipulators)

[0231] 103 Aperture Stop

[0232] X x-axis

[0233] Y-axis

[0234] Z z-axis

[0235] R Rotation axis

[0236] T-axis

Claims

1. A method for positioning a movable object in the sample chamber of a particle beam microscope. in, The method is performed using a particle beam microscope, which includes a particle beam column for generating a beam of charged particles, a sample chamber, a detector for detecting interaction signals, and a control and evaluation unit. The method includes the following steps: a) Provide movable objects (32, 70, 95) in the sample chamber (S1, S40); b) Define the barrier region (S2, S43); c) Use the charged particle beam to scan the barrier region (S3, S44). d) Use the detector to detect the interaction signals (S5, S45); e) Move the object along the direction of the barrier area (S5, S46). f) Monitor the detected interaction signals and register signal changes (S5, S46).

2. The method according to claim 1, wherein, The registration of this signal change causes the object to stop moving.

3. The method according to any one of the preceding claims, wherein, Repeat at least one of steps b) through f).

4. The method according to claim 1 or 2, wherein, Multiple detectors (30, 54, 90) are used to detect the signal (20, 20').

5. The method according to claim 1 or 2, wherein, Record and visualize images at the desired time.

6. The method according to claim 1 or 2, wherein, Use at least two barrier regions (33, 36, 37).

7. The method according to claim 6, wherein, The first barrier region (33) is defined to make the movement of the object in the first direction of movement (38) detectable, while the second barrier region (37) is defined to make the movement of the object in the second direction of movement (39) detectable.

8. The method according to claim 7, wherein, The first and second moving directions (38, 39) are arranged orthogonally to each other.

9. The method according to claim 6, wherein, The at least two barrier regions (72) are defined such that a path (74) is specified in three-dimensional space and the movable object moves along the path (74) in space.

10. The method according to claim 6, wherein, Simultaneously monitor detectable signals in the multiple barrier regions (33, 36, 37).

11. The method according to claim 1 or 2, in, The particle beam microscope monitors the position of the movable object in three-dimensional space and includes a first particle beam column (81) for generating a first particle beam and a second particle beam column (101) for generating a second particle beam, wherein the optical axes of these particle beam columns are arranged at a non-zero angle to each other. Furthermore, the first particle beam and / or the second particle beam are used to scan the barrier region.

12. The method according to claim 1 or 2, wherein, The barrier area comprises multiple sections spaced apart from each other. Furthermore, the signals from these two regions are evaluated together.

13. The method according to claim 1 or 2, wherein, Using multiple barrier areas spaced apart from each other, Furthermore, the signals in the barrier areas are evaluated individually.

14. The method according to claim 1 or 2, wherein, The movable object is in the form of a TEM sheet (32).

15. The method according to claim 1 or 2, wherein, The movable object is in the form of an electron beam lithography sample (61).

16. A computer program product comprising a sequence of control commands that cause a particle beam system (80) to perform the method according to any one of claims 1 to 15.

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