Method for determining the position of the tip of a manipulator of a charged particle beam device

Abstract

The object of the invention is a method of determining the position of the tip of a manipulator of a charged particle beam device, using the acquisition of two images with different directions of incidence of the charged particles beam on a sample. The tip of the manipulator located at a certain distance above the sample appears on the obtained images as the object which is most displaced in each image when these images are evaluated.

Description

[0001] Method for determining the position of the tip of a manipulator of a charged particle beam device

[0002] Field of Art

[0003] The present invention relates to a method for finding (i.e., determining the position of) the tip of a charged particle beam device manipulator, specifically, e.g., the tip of a manipulator used in a FIB-SEM system.

[0004] Background Art

[0005] Charged particle beam devices, such as a scanning electron microscope (SEM) or a system combining scanning electron microscopy and focused ion beam (FIB-SEM), are currently typically equipped with manipulators. These manipulators have a wide range of uses in various practical applications, and with regard to the scale at which they operate and the fineness of the manipulation they provide, the term nanomanipulators is often used in practice.

[0006] One of the practical cases of using a nanomanipulator is its use in the production of a lamella for a transmission electron microscope (TEM). In this field, a lamella is understood to be a sufficiently thin sample allowing the passage of an electron beam. For the production of TEM lamellas, a focused ion beam is most often used, which serves to sputter the surrounding material, either separately (FIB) or within a combined FIB-SEM system. After the material is sputtered away, the lamella is picked up and fixed on a sample holder using a nanomanipulator equipped with a tip. In order to perform the entire process automatically, it is necessary to first find the tip of the manipulator, i.e. determine its position. This generally applies to any other automated movement of the manipulator and in other applications.

[0007] There are several approaches to determining the position of the tip of a manipulator, however, tip detection is typically performed with a centered beam. In this configuration, two images are taken while either the tip of the manipulator or the sample is moved, and from the change in these images it can be determined which element in the images corresponds to the tip of the manipulator. The disadvantage of this solution consists precisely in the need to move the tip of the manipulator orthe sample. Furthermore, the detection and subsequent navigation of the tip of the manipulator in a plane perpendicular to the optical axis of the charged particle beam device (this plane is usually referred to as the xy plane) is complicated by the fact that the images may have different brightness and contrast.

[0008] Furthermore, it is known to obtain so-called anaglyphs, while in this field of technology this term refers to images composed of two partial images taken at different inclinations of the charged particle beam. When obtaining individual images, the charged particle beam is typically at an angle with respect to the axis of optimal centering of the lens of the charged particle beam device first to one side (e.g. to the left when looking at the system from a predetermined perspective) and then to the other side (i.e. to the right). The creation of anaglyphs is described, for example, in patent documents US9012842B2, US8143573B2 and CZ298798B6, but none of these documents describe any use of anaglyphs for finding the tip of a manipulator.

[0009] It would therefore be desirable to provide a solution that would allow finding the tip of a manipulator without the need to move the tip of the manipulator or to move the sample.

[0010] Summary of the invention

[0011] The above-mentioned drawbacks are to some extent eliminated by a method of determining the position of the tip of a manipulator of a charged particle beam device. The method comprises the steps of:

[0012] - acquiring a first image, wherein the first image is acquired by irradiating a sample with a charged particle beam which is focused and directed to an area of interest on the sample and which is incident on the sample in a first direction, wherein when the first image is acquired, the tip of the manipulator is located in the field of view of the charged particle beam device and at a certain distance above the sample,

[0013] - acquiring a second image, wherein the second image is acquired by irradiating the sample with a charged particle beam which is directed to the same area of interest and focused to the same location on the sample as in the step of obtaining the first image and which is incident on the sample in a second direction different from the first direction, wherein in the step of acquiring the second image the position of the tip of the manipulator and the sample relative to the chamber of the charged particle beam device is the same as in the step of acquiring the first image, and

[0014] - evaluating at least the first image and the second image, wherein based on the evaluation of the at least first image and second image, the position of the tip of the manipulator in a plane perpendicular to the optical axis of the column of the charged particle beam device is determined as the position of the object that is most displaced between the images.

[0015] The above method allows to find the tip of the manipulator without having to move the manipulator or the sample. Furthermore, since the position of the tip of the manipulator and the sample relative to the chamber of the charged particle beam device is the same when both images are acquired, both images have substantially the same brightness and contrast, which facilitates the evaluation of the images for finding the tip of the manipulator. As mentioned above, the position of the manipulator tip in the plane perpendicular to the optical axis of the charged particle beam device column is determined as the position of the object that is most displaced between the images. Ideally, when the sample is not very topographically structured, the image of the sample itself remains unchanged and only the position of the manipulator tip in each image changes. If the sample is highly topographically structured, not only the image of the manipulator tip is shifted in each image, but there is also a certain shift in the image of the sample itself. The displacement of the image of the sample itself in the individual images is, however, smaller than the displacement of the image of the manipulator tip. The step of evaluating at least the first image and at least the second image preferably includes the step of creating a combined image, wherein the combined image is composed of at least the first image and the second image, which overlap each other. The position of the manipulator tip in a plane perpendicular to the optical axis of the charged particle beam device column is determined as the position of the object that is most displaced in the combined image. Thanks to the combined image, the so-called anaglyph, it is possible to obtain a more clear idea of the displacement of the image of the manipulator tip, or the evaluation of at least the first image and the second image in the form of a combined image may be simpler. However, creating a combined image is in principle not necessary to determine the position of the manipulator tip.

[0016] The charged particle beam incident on the sample in the first direction in the step of acquiring the first image is inclined at a first inclination angle with respect to the axis of optimal centering of the lens of the charged particle beam device and / or the charged particle beam incident on the sample in the step of acquiring the second image in the second direction is inclined at a second inclination angle with respect to the axis of optimal centering of the lens of the charged particle beam device. Tilting the charged particle beam by the first inclination angle and / or the second inclination angle, respectively, allows the manipulator tip above the sample to be captured from two different views, thereby acquiring images in which the image of the manipulator tip is shifted relative to each other. The inclination angle is set by moving the so-called pivot point in a plane perpendicular to the optical axis of the column of the charged particle beam device.

[0017] Preferably, the charged particle beam incident on the sample in the first direction in the step of acquiring the first image and the charged particle beam incident on the sample in the second direction in the step of acquiring the second image lie in one common plane, and the axis of optimal centering of the lens of the charged particle beam device also lies in this common plane. If the charged particle beam in both cases lies in a common plane with the axis of optimal centering of the lens of the charged particle beam device, it is computationally less demanding to determine the specific coordinates of the position of the manipulator tip in a plane perpendicular to the optical axis of the column of the charged particle beam device relative to the sample or relative to the chamber of the charged particle beam device.

[0018] Preferably, the charged particle beam incident on the sample in the first direction in the step of acquirng the first image is inclined with respect to the axis of optimal centering of the lens of the charged particle beam device by a first inclination angle to one side, and the charged particle beam incident on the sample in the second direction in the step of acquiring the second image is inclined with respect to the axis of optimal centering of the lens of the charged particle beam device by a second inclination angle to the opposite side. Due to the inclination of the charged particle beam in one plane gradually to each side, the (absolute) values of the individual inclination angles can be different, but also equal. Moreover, by tilting the charged particle beam in this way to opposite sides, a larger angle can be achieved between the individual directions of incidence even with relatively small inclination angles of the charged particle beam with respect to the axis of optimal centering of the lens of the charged particle beam device when obtaining the individual images.

[0019] The first inclination angle with respect to the axis of optimal centering of the lens of the charged particle beam device preferably has the same value as the second inclination angle with respect to the axis of optimal centering of the lens of the charged particle beam device. Therefore, if the charged particle beam when acquiring the first image and the charged particle beam when acquiring the second image lie in one common plane with the axis of optimal centering of the lens of the charged particle beam device, if they are inclined to mutually opposite sides with respect to the axis of optimal centering of the lens of the charged particle beam device and if the first inclination angle and the second inclination angle are of the same value, then it is true that the manipulator tip is located exactly in the middle between the two images of the manipulator tip on the individual images, or exactly in the middle between the two images of the manipulator tip on the combined image, if this combined image is created for the evaluation of at least the first image and the second image. The position of the manipulator tip in the plane perpendicular to the axis of the charged particle beam device column can then be calculated simply by averaging the coordinates of the first and second images of the manipulator tip on the individual images, or on the combined image. This is therefore the configuration that is computationally least demanding.

[0020] Preferably, at least one of the first inclination angle relative to the axis of optimal centering of the lens of the charged particle beam device and the second inclination angle relative to the axis of optimal centering of the lens of the charged particle beam device has a value in the range of 0.05° to 5°. Alternatively, the value of these angles may be slightly larger, e.g. it may be selected from the range of 0.05° to 10°. The specific value of the inclination angles is selected so that the inclination is as large as possible, i.e. so that the image of the manipulator tip is shifted as much as possible in individual images, but so that the image quality is not degraded too much. When selecting a specific value of the inclination angles, it depends, for example, on the scanning mode, acceleration voltage, charged particle beam current, column type, etc.

[0021] Preferably, based on the position of the spot on the sample into which the charged particle beam is focused in the step of acquiring the first image and in the step of acquiring the second image, the position of the manipulator tip relative to the sample is determined in a plane perpendicular to the optical axis of the column of the charged particle beam device.

[0022] Preferably, based on the position of the spot on the sample onto which the charged particle beam is focused in the step of acquiring the first image and in the step of acquiring the second image, the position of the manipulator tip relative to the sample is determined in an axis determined by the optical axis of the column of the charged particle beam device. In other words, this means that when knowing the angles of inclination and displacement of the image of the manipulator tip in the individual images, the distance of the manipulator tip from the sample in an axis given by the optical axis of the column can be determined.

[0023] Description of the drawings

[0024] The invention is further illustrateded by examples of its embodiments, which are described using the attached drawings, wherein:

[0025] Fig. 1 schematically shows a charged particle beam device suitable for carrying out the method according to the present invention, with emphasis on illustrating the principle of tilting (inclining) the charged particle beam relative to the axis of optimal centering of the lens,

[0026] Fig. 2 schematically shows a sample, the tip of a manipulator and an incident charged particle beam in both configurations used in the method according to the present invention to acquire a first image and a second image,

[0027] Fig. 3 shows a flow chart of the method for finding the tip of the manipulator according to the present invention containing its basic steps,

[0028] Fig. 4a shows a partial image acquired in the method according to the present invention, i.e. the first image, or the second image,

[0029] Fig. 4b shows a combined image obtained in the method according to the present invention, and Fig. 5 schematically shows a combined image obtained in the method according to the present invention.

[0030] Examples

[0031] The invention will be further explained using examples of embodiments with reference to the corresponding drawings. A charged particle beam 3 device, suitable for carrying out the method according to the present invention, will be described first, and then the said method will be described.

[0032] The charged particle beam 3 device is schematically shown in Fig. 1 , whereby this schematic drawing, in the interest of clarity, only shows some parts of the charged particle beam device, in particular those parts that are important for describing the tilting (inclination) of the charged particle beam 3 relative to the axis 4 of optimal centering of the lens of the charged particle beam device, as will be described below. The charged particle beam device includes at least one source of charged particles (not shown in Fig. 1), by means of which charged particles are generated. The source of charged particles is, for example, an electron source. In another embodiment, the source of charged particles is an ion source.

[0033] The device further comprises at least one column and a chamber (these parts are also not shown in Fig. 1), the column being connected to the chamber, and the source of charged particles being located within the column. The optical axis 5 of the column of the charged particle beam device passes through the centre of the column. Elements for shaping and directing particles are further placed in the column, in particular electromagnetic lenses and scanning elements 6, for example scanning coils. In the case where the device comprises two columns connected to the chamber, these are connected so that the individual optical axes 5 of the column of the charged particle beam device form an angle greater than 0° and less than 180°. An example of such a device is a scanning electron microscope with a second column producing a focused ion beam. In an embodiment of the charged particle beam device, a device generating a photon beam is further connected to the chamber.

[0034] For the purposes of the description, the x, y and z axes are defined as follows. The z-axis is identical with the optical axis 5 of the column of the charged particle beam device. The x and y axes are perpendicular to each other and form the xy plane, which is perpendicular to the optical axis 5 of the column of the charged particle beam device.

[0035] The device further comprises an objective (lens) formed by an objective lens 7, wherein the objective lens 7 also belongs to the elements for shaping and directing particles. The source of charged particles then irradiates the space which is in its field of view, using the elements for shaping and directing particles, wherein the formed charged particle beam 3 passes through the objective lens 7. The charged particle beam 3 does not always have to irradiate the entire field of view, but can irradiate only a part of it, the so-called area of interest, or it can irradiate the entire field of view, but display only the area of interest, while the remaining part of the field of view can be used to compensate for, for example, a slight shift of the sample 2 due to drift. The optical axis 5 of the column of the charged particle beam device passes through the center of the objective lens 7.

[0036] The chamber further contains a movable stage 8 for receiving at least one sample 2. The stage 8 is arranged for movement along at least two mutually perpendicular axes. In an embodiment of the stage 8, the stage 8 is arranged for movement along three mutually perpendicular axes. In another embodiment of the stage 8, the stage 8 is further arranged for rotation around at least one axis and tilting around at least one axis. The embodiments of the stage 8 can be freely combined.

[0037] The chamber further contains a movable manipulator. The end of the manipulator has the shape of a tip, and therefore contains a tip 1 of the manipulator. In an alternative embodiment of the manipulator, the end of the manipulator is formed by a needle detachably connected to the manipulator and forming the tip 1 of the manipulator. In an embodiment of the manipulator movement options, the manipulator is movable along three axes, which are in some embodiments mutually perpendicular. In another embodiment of the manipulator movement options, the manipulator further allows rotation around one axis and tilting (i.e., inclining) around one axis.

[0038] The charged particle beam device further comprises at least one detector of signal particles. The signal particles are in particular secondary or back-reflected particles, or other particles emitted by the sample 2 due to its interaction with the incident charged particle beam. The detector of signal particles may also be an absorbed current detector. The detector of signal particles may be located in the chamber or in the column. By detecting the signal particles, an image is acquired, whereby the image shows the area of interest to which the charged particle beam 3 is directed, and which the charged particle beam 3 is therefore scanning. As shown in Fig. 1 , the charged particles are first deflected away from the optical axis 5 of the column of the charged particle beam device by means of the particle shaping and directing elements. The charged particles are subsequently deflected back towards the optical axis 5 of the column of the charged particle beam device. The charged particle beam 3 then passes through the objective lens 7, which focuses it to a specific location on the sample 2. This location is shown in Fig. 1 by a black dot on the surface of the sample 2.

[0039] Furthermore, Fig. 1 shows by further black dots the so-called pivot point, which is located inside the objective lens 7. The charged particle beam 3 passes through this pivot point when scanning the area of interest, and in Fig. 1 the charged particle beam 3 is shown by three dashed lines that cross precisely at this pivot point. Two of these lines correspond to the extreme deflection of the charged particle beam 3, when the charged particle beam 3 falls on the edge of the area of interest, and the remaining line in the middle corresponds to the incidence of the charged particle beam 3 on a specific location on the sample 2 located inside the area of interest. For the purpose of clarity, the reference sign is placed only on this middle dashed line. It should be noted that the charged particle beam 3 is represented by lines, as is common in drawings in this field of technology, although in reality it does not have such a shape in the column and falls on the sample 2 in the shape of a cone. The individual lines thus correspond to the central axis of the charged particle beam 3.

[0040] Specifically, Fig. 1 shows two charged particle beams 3, but in one of them (indicated by dotted lines) its central axis is marked as the axis 4 of optimal centering of the lens of the charged particle beam device, since it corresponds to the case when the charged particle beam 3 is optimally centered. In this case, the pivot point is located on the optical axis 5 of the column of the charged particle beam device. Therefore, these are not two different charged particle beams 3 that would be present in the chamber at the same time, but it is one charged particle beam 3 in two different cases, which are drawn together in Fig. 1 for greater clarity. In the second case, the charged particle beam 3 is inclined relative to the axis 4 of optimal centering of the lens of the charged particle beam device by a certain inclination angle, which is indicated as a in Fig. 1 . It is also evident from Fig. 1 that in this second case the pivot point is not located on the optical axis 5 of the column of the charged particle beam device, but it is shifted in a plane perpendicular to the optical axis 5 of the column of the charged particle beam device.

[0041] The pivot point is shifted in a plane perpendicular to the optical axis 5 of the column of the charged particle beam device, and thus the inclination of the charged particle beam 3 relative to the axis 4 of optimal centering of the lens of the charged particle beam device, is performed by changing the setting of the raster elements 6. Specifically, if these raster elements 6 are, for example, raster coils, a current with two components - a so-called offset (direct current component) and a changing value (alternating current component) - is supplied to the raster coils from at least one current source. The pivot point is then shifted specifically by changing the offset of the raster coils, while the changing value serves for scanning by the charged particle beam 3. Changing this changing value also ensures that when the charged particle beam 3 is inclined relative to the axis 4 of optimal centering of the lens of the charged particle beam device, the entire image is not shifted; i.e., to irradiate the same area of interest on the sample 2 and to focus the inclined charged particle beam 3 by means of the objective lens 7 to the same location on the sample 2 as in the case of optimal centering of the objective. Preferably, for example, a prominent point on the sample, such as a reference mark, can be used to align the image.

[0042] In another embodiment of the scanning elements 6, these scanning elements 6 are electrodes to which a voltage with a direct and alternating component is supplied from at least one voltage source. Inclining the charged particle beam 3 relative to the axis 4 of optimal centering of the lens of the charged particle beam device is then performed analogously to the use of scanning coils.

[0043] The device further comprises an evaluation unit containing software for performing the method.

[0044] The method first comprises a step of acquiring a first image and a step of acquiring a second image, wherein the first image and the second image are acquired successively at different configurations of the charged particle beam device, namely at different directions of incidence of the charged particle beam 3. In the step of acquiring the first image, the charged particle beam 3 is incident on the sample 2 in a first direction, while in the step of acquiring the second image, the charged particle beam 3 is incident on the sample 2 in a second direction, which is different from the first direction. This is best shown in the schematic Fig. 2, where a first inclination angle (designated as a1) of the charged particle beam 3 with respect to the axis 4 of optimal centering of the lens of the charged particle beam device and a second inclination angle (designated as a2) of the charged particle beam 3 with respect to the axis 4 of optimal centering of the lens of the charged particle beam device are shown. The first inclination angle corresponds to the configuration in which the first image is acquired, and the second inclination angle corresponds to the configuration in which the second image is acquired. In the method according to the present invention, however, the charged particle beam 3 may be inclined with respect to the axis 4 of optimal centering of the lens of the charged particle beam device only in the step of acquiring the first image or only in the step of acquiring the second image. Thus, one of the inclination angles a1 and a2 may be zero.

[0045] The inclination of the charged particle beam 3 is performed by moving the pivot point in a plane perpendicular to the optical axis 5 of the column of the charged particle beam device, as described above in the description of the device.

[0046] The charged particle beam 3 in the step of acquiring the first image and the charged particle beam 3 in the step of acquiring the second image are both shown in Fig. 2 for the sake of greater clarity. Namely, when acquiring the second image, the position of the tip 1 of the manipulator and the sample 2 relative to the chamber of the charged particle beam device 3 is the same as when acquiring the first image. In both cases, the mutual position of the tip 1 of the manipulator and the sample 2 is also the same, which is reflected in Fig. 2. It can also be seen in Fig. 2 that the tip 1 of the manipulator is located at a certain distance above the sample 2, i.e. that it is not in contact with the sample 2. However, the angle at which the image is taken changes. In other words, the angle of inclination of the charged particle beam 3 relative to the axis 4 of optimal centering of the lens of the device with the charged particle beam 3 changes.

[0047] In a preferred embodiment of the method, the charged particle beam 3 incident on the sample 2 in the step of acquiring the first image and the charged particle beam 3 incident on the sample 2 in the step of acquiring the second image lie in one common plane, while the axis 4 of optimal centering of the lens of the charged particle beam device also lies in this common plane. The values of the first inclination angle and the second inclination angle may generally be different. In the event that the values of these angles are the same and the charged particle beam 3 in each case lies in one common plane with the axis 4 of optimal centering of the lens of the charged particle beam device, the charged particle beam 3 in the step of acquiring the first image must be inclined to one side with respect to the axis 4 of optimal centering of the lens of the charged particle beam device, and the charged particle beam 3 in the step of acquiring the second image must then be inclined to the opposite side with respect to the axis 4 of optimal centering of the lens of the charged particle beam device. However, if the values of the two inclination angles are different, the charged particle beam 3 in the step of acquiring the first image and the charged particle beam 3 in the step of acquiring the second image can be inclined to the same side with respect to the axis 4 of optimal centering of the lens of the charged particle beam device.

[0048] The specific value of the inclination angles is chosen so that the inclination is as large as possible, but at the same time there is no excessive deterioration of the image. Preferably, the value of the first inclination angle and the second inclination angle is selected from the range of 0.05° to 5°. In order to find the tip 1 of the manipulator, it is necessary that when acquiring the first image and when acquiring the second image, the tip 1 of the manipulator is located in the field of view of the charged particle beam device. This ensures that the image of the tip 1 of the manipulator is visible in the first image as well as in the second image.

[0049] It is also necessary that the charged particle beam 3 is directed to the same area of interest and focused on the same location on the surface of the sample 2 when the first image is acquired and when the second image is acquired. Due to the fact that the charged particle beam 3 is directed to the same area of interest and focused on the same location on the sample 2 when the first image and the second image are acquired, and at the same time due to the fact that the position of the tip 1 of the manipulator and the sample 2 relative to the chamber of the charged particle beam device does not change when the images are acquired, the image of the sample 2 itself does not change in the first image and the second image. Accordingly, in the case of a topographically structured sample, the image of the sample 2 may shift between individual images, since, for example, a protruding object will be irradiated by the charged particle beam from different sides. However, since the tip 1 of the manipulator is located at a certain distance above the sample 2, typically at a distance of tens of pm, the position of the tip 1 of the manipulator changes in the first and second images, or rather the image of the tip 1 of the manipulator shifts more in the individual images than the image of the sample 2 itself. To find the position of the tip 1 of the manipulator, it is necessary to evaluate the first and second images, and the position of the tip

[0050] 1 of the manipulator in the plane perpendicular to the optical axis 5 of the column of the charged particle beam device is determined as the position of the object that is most displaced between the individual images.

[0051] After the steps of acquiring the first image and the second image, and the order of these steps in the method according to the present invention does not matter, the step of evaluating at least the first image and the second image is performed. The step of evaluating at least the first image and the second image can be implemented in various ways, as long as it leads to determining the position of the tip 1 of the manipulator in a plane perpendicular to the optical axis 5 of the column of the charged particle beam device as the position of the object that is most displaced between the individual images.

[0052] In one embodiment of this step, the evaluation of at least the first image and the second image is implemented by creating a combined image composed of the first image and the second image. This combined image, also called an anaglyph, is created by overlapping the first image and the second image so that the combined image simultaneously includes elements of the first image and the second image. For example, the creation of the combined image is performed using software into which the individual images are loaded as input.

[0053] In the combined image, the image of the sample 2 itself remains unchanged (unless sample 2 is highly topographically fragmented, as explained above), while the image of the tip 1 of the manipulator is shifted in this combined image. This shift of the image of the tip 1 of the manipulator in the combined image occurs despite the fact that the tip 1 of the manipulator has not physically moved in any way relative to the sample 2, or indeed relative to the chamber of the charged particle beam device. The shift in the combined image is due to the fact that in the first image and the second image, the tip 1 of the manipulator is captured from different views, i.e., the charged particle beam 3 is incident on the sample

[0054] 2 in a generally different direction when the second image was acquired than when the first image was acquired.

[0055] The combined image is subsequently evaluated to determine the position of the tip 1 of the manipulator in a plane perpendicular to the axis 5 of the column of the charged particle beam device. The evaluation of the combined image includes recognizing the image of the tip 1 of the manipulator from the image of the sample 2 itself, whereby the object that appears to be the most displaced in the combined image is identified as the tip 1 of the manipulator. This displacement of the tip 1 of the manipulator is evident from Fig. 4b, which shows the combined image obtained in a real experiment, or in Fig. 5, which shows the combined image only schematically for greater clarity. Fig. 4a, on the other hand, shows a partial image, i.e. the first image or the second image, where no displacement of the image of the tip 1 of the manipulator occurs. The identification of the image of the tip 1 of the manipulator on the combined image to determine the position of the tip 1 of the manipulator can be implemented in various ways. For example, it may be implemented automatically using an algorithm that automatically determines the position of the significant point of the displaced object on the combined image, which therefore corresponds to the tip 1 of the manipulator. This significant point is, for example, the end-tip of the tip 1 of the manipulator. If the charged particle beam 3 when acquiring the first image and the charged particle beam 3 when acquiring the second image lie in one common plane with the axis 4 of optimal centering of the lens of the charged particle beam device, if they are inclined to mutually opposite sides with respect to the axis 4 of optimal centering of the lens of the charged particle beam device, and if the first inclination angle and the second inclination angle have the same value, then it is true that the tip 1 of the manipulator is located exactly in the middle between the first image of the tip 1 of the manipulator on the combined image and the second image of the tip 1 of the manipulator on the combined image. The position of the tip 1 of the manipulator in the plane perpendicular to the axis 5 of the column of the device with the charged particle beam 3 is then calculated simply by averaging the coordinates of the first image of the tip 1 of the manipulator on the combined image and the second image of the tip 1 of the manipulator on the combined image. If the value of the first inclination angle and the second inclination angle are not the same, or if the charged particle beams 3 do not lie in the said common plane, the calculation for determining the position of the tip 1 of the manipulator in the plane perpendicular to the axis 5 of the column of the charged particle beam device needs to be corrected.

[0056] In another embodiment of the evaluation of the combined image, the combined image is evaluated using artificial intelligence, which automatically recognizes the images of the displaced object in the combined image that correspond to the tip 1 of the manipulator.

[0057] In another embodiment of the step of evaluating at least the first image and the second image, a combined image is not created and the identification of the image of the manipulator tip is performed directly on the individual images. If, for example, artificial intelligence is used for image recognition, the individual images are processed using the artificial intelligence.

[0058] The specific type of artificial intelligence for evaluating at least the first and second images is chosen such that the input of the artificial intelligence is individual images or a combined image and the output is information leading to the determination of the position of the tip 1 of the manipulator or directly the position of the tip 1 of the manipulator.

[0059] By determining the position of the tip 1 of the manipulator in a plane perpendicular to the axis 5 of the column of the charged particle beam device, the position of the tip 1 of the manipulator is determined sufficiently. Subsequently, given that the coordinates of the point on the surface of the sample 2, into which the charged particle beam 3 was focused, are known, the position of the tip 1 of the manipulator relative to the sample 2 or generally relative to the chamber of the charged particle beam device can also be calculated, namely in the xy plane. This data can be provided to the manipulator control element, which controls the movement of the manipulator, including the tip 1 of the manipulator, in the chamber of the charged particle beam device.

[0060] Furthermore, the position of the tip 1 of the manipulator in the z-axis belonging to a specific column of the charged particle beam device can also be determined. When the charged particle beam device has a plurality of columns, e.g. when it is designed as a FIB-SEM system, the position of the tip 1 of the manipulator in the z-axis of the first column (for example, the column of a scanning electron microscope) is determined using a focused ion beam, since the second column with the focused ion beam is inclined by a known angle relative to the column of the scanning electron microscope. Alternatively, instead of the focused ion beam, e.g. a laser or another scanning electron microscope can be used, if it is inclined relative to the first scanning electron microscope. In another embodiment of the determination of the position of the tip 1 of the manipulator in the z-axis, the determination of the position of the tip 1 of the manipulator in the z-axis is performed without using a focused ion beam, for example based on measuring the area occupied by the image of the tip 1 of the manipulator in individual images or in a combined image. In another embodiment of determining the position of the tip 1 of the manipulator in the z-axis, the position is determined based on the known change in the angle of inclination of the charged particle beam between individual images and the magnitude of the displacement of the tip 1 of the manipulator between individual images.

[0061] One specific exemplary embodiment of the method according to the present invention is further described below.

[0062] In this specific exemplary embodiment, the method of finding the tip 1 of the manipulator is performed using a charged particle beam device, which is a scanning electron microscope (SEM) further equipped with a focused ion beam (FIB). To acquire the first image and the second image, an electron beam is used, forthe inclining of which (the displacement of the pivot point in a plane perpendicularto the optical axis 5 of the column of the charged particle beam device, i.e. here the column of the scanning electron microscope) scanning coils are used as scanning elements 6. An objective lens 7 is also used as another element for shaping and directing the particles.

[0063] The charged particle beam 3 incident on the sample 2 in the step of acquiring the first image and the charged particle beam 3 incident on the sample 2 in the step of acquiring the second image lie in a common plane with the axis 4 of optimal centering of the lens of the charged particle beam device. Specifically, the charged particle beam 3 in the step of acquiring the first image is inclined relative to the axis 4 of optimal centering of the lens of the charged particle beam device by a first inclination angle to one side and the charged particle beam 3 in the step of acquiring the second image is inclined relative to the axis 4 of optimal centering of the lens of the charged particle beam device by a second inclination angle to the opposite side. The (absolute) value of the first inclination angle is the same as the value of the second inclination angle. In this particular embodiment, the value of the inclination angle is chosen to be 0.2°.

[0064] In orderto evaluate the first image and the second image, a combined image is created in this exemplary embodiment. The combined image is evaluated using artificial intelligence, which automatically recognizes two mutually displaced images of the tip 1 of the manipulator in the combined image and determines their position within the combined image. Subsequently, the position of the tip 1 of the manipulator in a plane perpendicular to the optical axis 5 of the column of the charged particle beam device is calculated; i.e. the position in a plane perpendicular to the optical axis of the column of the scanning electron microscope, since it is used to acquire the first and second images). Specifically, the position of the tip 1 of the manipulator in the said plane is calculated by averaging the coordinates of the first image of the tip 1 of the manipulator in the combined image and the second image of the tip 1 of the manipulator in the combined image. Based on the position of the spot on the sample 2 to which the charged particle beam 3 was focused in the step of acquiring the first image and in the step of acquiring the second image, the position of the tip 1 of the manipulator in the said plane relative to the sample 2 is subsequently determined. This data is provided to the control element of the manipulator, which controls the movement of the manipulator, whereby the navigation of the tip 1 of the manipulator in the said plane is performed.

[0065] The position of the tip 1 of the manipulator in the axis given by the optical axis 5 of the column of the charged particle beam device, here the optical axis of the column of the scanning electron microscope, is determined, which can be further used for navigation in this axis. Specifically, the position of the tip 1 of the manipulator in this axis is calculated from the known value of the inclination angles and from the displacement of the image of the tip 1 of the manipulator in the combined image. This information is provided to the control element of the manipulator, which controls the movement of the manipulator.

[0066] Industrial applicability

[0067] The method described herein above is particularly suitable for finding the tip of the manipulator in SEM and FIB systems. The method described herein above can also be used to find the tip of the manipulator in optical microscopes. The method of the invention is an important element in navigation of the manipulator.

[0068] List of reference signs

[0069] 1 - tip of the manipulator

[0070] 2 - sample

[0071] 3 - charged particle beam

[0072] 4 - axis of optimal centering of the lens of the charged particle beam device

[0073] 5 - optical axis of the column of the charged particle beam device

[0074] 6 - rastering element 7 - objective lens

[0075] 8 - stage

Claims

CLAIMS1 . A method of determining the position ofthe tip (1) of a manipulator of a charged particle beam device, which comprises the steps of:- acquiring a first image, wherein a first image is acquired by irradiating a sample (2) with a charged particle beam (3) which is focused and directed to an area of interest on the sample (2) and which is incident on the sample (2) in a first direction, wherein when the first image is acquired, the tip (1) of the manipulator is located in the field of view of the charged particle beam device and not touching the sample (2),- acquiring a second image, wherein a second image is acquired by irradiating the sample (2) with a charged particle beam (3) which is directed to the same area of interest and focused to the same area of interest on the sample (2) as in the step of acquiring the first image and which is incident on the sample (2) in a second direction different from the first direction, wherein in the step of acquiring the second image the position of the tip (1) of the manipulator and the sample (2) relative to the chamber of the charged particle beam device is the same as in the step of acquiring the first image, and- evaluating at least the first and the second images, wherein based on the evaluation of the at least first image and second image, the position of the tip (1) of the manipulator in a plane perpendicular to the optical axis (5) of the column of the charged particle beam device is determined as the position of the object that is most displaced between the images.

2. The method according to claim 1 , wherein the step of evaluating at least the first and second images includes the step of creating a combined image, wherein the combined image is composed of at least the first and second images, which overlap each other; and wherein the position of the manipulator tip (1) in a plane perpendicular to the optical axis (5) of the charged particle beam device column is determined as the position of the object that is most displaced in the combined image.

3. The method according to any one of the preceding claims, wherein the charged particle beam (3) incident on the sample in the first direction in the step of acquiring the first image is inclined with respect to the axis (4) of optimal centering of the lens of the charged particle beam device by a first inclination angle, and the charged particle beam incident on the sample in the second direction in the step of acquiring the second image is inclined with respect to the axis of optimal centering of the lens of the charged particle beam device by a second inclination angle.

4. The method according to any one of the preceding claims, wherein the charged particle beam (3) incident on the sample in the first direction in the step of acquiring the first image and the charged particle beam incident on the sample in the second direction in the step of acquiring the second image both lie in one common plane, and the axis (4) of optimal centering of the lens of the charged particle beam device also lies in this common plane.

5. The method according to claim 4, wherein the charged particle beam (3) incident on the sample in the first direction in the step of acquiring the first image is inclined with respect to the axis (4) of optimal centering of the lens of the charged particle beam device by a first inclination angle to one side, and the charged particle beam incident on the sample in the second direction in the step of acquiring the second image is inclined with respect to the axis of optimal centering of the lens of the charged particle beam device by a second inclination angle to the opposite side, and wherein the absolute values of the first and second inclination angles are the same or different.

6. The method according to any one of claims 3 to 5, wherein the absolute values of the first and second inclination angles are the same.

7. The method according to any one of the claims 3 to 6, wherein at least one of the first inclination angle relative to the axis of optimal centering of the lens of the charged particle beam device and the second inclination angle relative to the axis of optimal centering of the lens of the charged particle beam device has an absolute value in the range of 0.05° to 10°, preferably in the range of 0.05° to 5°.

8. The method according to any one of the preceding claims, wherein, based on the position of the area of interest on the sample (2) into which the charged particle beam (3) is focused in the step of acquiring the first image and in the step of acquiring the second image, the position of the manipulator tip (1) relative to the sample (2) in a plane perpendicular to the optical axis (5) of the column of the charged particle beam device is determined.

9. The method according to any one of the preceding claims, wherein, based on the position of the area of interest on the sample (2) onto which the charged particle beam (3) is focused in the step of acquiring the first image and in the step of acquiring the second image, the position of the manipulator tip (1) relative to the sample (2) in an axis given by the optical axis (5) of the column of the charged particle beam device is determined.

Images