Method for examining samples using a charged particle microscope

Abstract

The present invention relates to a method for examining a sample using a charged particle microscope, comprising the following steps: providing a charged particle beam and a sample, and scanning the charged particle beam over the sample. A first detector is used to detect a first type of emission from the sample in response to the beam being scanned over the sample; using spectral information of the detected first type of emission, a plurality of mutually different phases are assigned to the sample. An image representation of the sample is provided, wherein the image representation contains different tones. The tones are selected from a preselected continuous tones range in such a way that the selected tones are contained in mutually corresponding intervals within the preselected continuous tones range.

Description

Technical Field

[0001] The present invention relates to a method for examining a sample using a charged particle microscope.

[0002] The invention also relates to a charged particle microscope for examining a sample using such a method. Background Art

[0003] Charged particle microscopy is a well-known and increasingly important technique for imaging microscopic objects, especially in the form of electron microscopy. Historically, the basic class of electron microscopes has evolved into many well-known device species, such as transmission electron microscopes (TEM), scanning electron microscopes (SEM) and scanning transmission electron microscopes (STEM), and also into various subspecies, such as so-called "dual beam" devices (e.g. FIB-SEM), which additionally employ a "processing" focused ion beam (FIB), allowing support activities such as, for example, ion beam milling or ion beam induced deposition (IBID). The skilled person will be familiar with the different species of charged particle microscopy.

[0004] By irradiating the specimen with a scanning electron beam, the emission of "auxiliary" radiation from the specimen in the form of secondary electrons, backscattered electrons, X-rays, and cathodoluminescence (infrared, visible, and / or ultraviolet photons) is accelerated. One or more components of this emitted radiation can be detected and used for sample analysis.

[0005] Typically, in a SEM, backscattered electrons are detected by a solid-state detector, where each backscattered electron is amplified as it generates many electron-hole pairs in a semiconductor detector. When the beam is scanned, the backscattered electron detector signal is used to form an image, with the brightness of each image point being determined by the number of backscattered electrons detected at the corresponding point on the sample as the main beam moves across the sample. The image only provides information about the topology of the sample being examined.

[0006] In a process called "energy dispersive x-ray spectroscopy," or "EDS," the sample's x-ray response to the energy of the electron beam is measured and plotted in a histogram to form a material-specific spectrum. The measured spectrum can be compared to known spectra of various elements to determine which elements and minerals are present in the sample.

[0007] It is known to provide a set of color images containing EDS information, wherein each color image represents a different phase using a different hue. In this so-called elemental mapping technique, the user selects one or more phases associated with the sample and assigns a desired hue to each of these phases. This results in a set of images, each containing information about the associated phase in a different hue. The set of color images can be compared with the SEM image to identify areas of interest. However, it is relatively difficult for the user to interpret these images in a meaningful and consistent manner. To this end, attempts have been made to combine the different phases and corresponding colors into a single color image. However, selecting phases and assigning hues in a meaningful and consistent manner is difficult and quite time consuming. Summary of the invention

[0008] It is therefore an object of the present invention to provide an improved method for examining a sample, wherein in particular the method provides an image of the sample with improved phase information.

[0009] To this end, a method according to claim 1 is provided. The method as defined herein comprises the steps of providing a charged particle beam and a sample, and scanning the charged particle beam over the sample. A first type of emission emanating from the sample in response to scanning the charged particle beam over the sample is detected using a first detector. A plurality of mutually different phases are then assigned to the sample, wherein spectral information of the detected first type of emission is utilized. As an example, the above-mentioned EDS method can be used in this step to form a material specific spectrum and determine which elements and minerals (i.e. phases) are present in the sample. Other methods of obtaining and using spectral information can also be used.

[0010] As defined herein, the method further comprises the following steps: with reference to the HSV color space, a corresponding plurality of different hues are associated with the plurality of mutually different phases. This means that different hues (e.g., green, red, orange, blue) are assigned to different phases (e.g., elements, chemicals, minerals, etc.). The HSV color space is a color space that describes the properties of a particular color using hue (commonly referred to as "color", such as red, green, blue), saturation (commonly referred to as the intensity or purity of the color), and value (commonly referred to as the lightness or darkness of the color). The HSV color space can be represented by a cylindrical geometry, whose hue and angular dimensions start from the red primary at 0°, pass through the green primary at 120° and the blue primary at 240°, and then wrap around to red at 360°. The central vertical axis contains neutral, achromatic, or gray, ranging from black with a bottom value of 0 to white with a top value of 1. As the radius increases, the saturation of the color increases.

[0011] In principle, any color can be described in the HSV color space, regardless of the actual color space used. Therefore, the method described herein is not limited to the use of a specific color space, and can also be applied to the RGB color space (because all RGB colors can also be described with reference to the HSV color space) or other color spaces.

[0012] According to the method, the control unit is arranged to provide an image representation of the sample, wherein the image representation contains the associated different tones. Thus, the control unit is arranged to provide information of the phase to the user, wherein the information is encoded in the different tones. The image representation may be a single image, although it is also conceivable to use a plurality of images or a data table containing image representations or the like. The image representation preferably also contains different values ​​and / or different saturations.

[0013] As defined herein, the method comprises the additional step of providing a preselected continuous hue range. Relative to the HSV color space, the preselected continuous hue range is an increase or decrease in hue value, i.e., an increase or decrease in angular size, although they do not need to be provided or stored in an ordered manner during preselection. It should be noted that a complete angular range does not need to be provided, i.e., not all hues (red, purple, blue, green, yellow, orange [red] and / or intermediate colors) need to be used within the preselected color range. For example, it is conceivable to provide a preselected range of hues with limited angular values, such as red, orange, yellow (i.e., 0° to 60°). In another embodiment, different variations of a single hue are provided, i.e., cyan, green, and yellow-green (i.e., 90° to 150°).

[0014] Thus, the preselected continuous color range includes the angular hue range of the reference HSV color space. In one embodiment, the preselected continuous color range includes the entire angular hue range with reference to the HSV space. In another embodiment, the preselected range includes a limited angular hue range with reference to the HSV space.

[0015] According to the method, referring to the HSV color space, the step of associating the corresponding plurality of different hues with the plurality of mutually different phases comprises the following steps:

[0016] - selecting said plurality of different hues from said preselected range of continuous hues in such a way that the selected hues are contained in mutually corresponding intervals within said preselected range of continuous hues; and

[0017] - associating the selected hue with the plurality of mutually different phases.

[0018] In this way, the image representation of the sample contains the selected hues with similar hue spacing angles in the reference HSV color space. Hues are selected in such a way that the hue spacing angles between the hues finally associated and used are substantially equal from the starting hue to the ending hue, thereby ensuring that the legibility of the final image(s) is increased and that the user can quickly and reliably perform the interpretation of the results since the differences between the different phases are directly visible. This is particularly true in the case of providing a single image containing multi-phase information, and in particular when the number of phases displayed in the final image is relatively high.

[0019] It should be noted here that, in the case of using the entire angular range (0° to 360°), the hue spacing angle is approximately equal to 360° / n, where n is the number of hues used. In the case of using only a limited angular hue range, the spacing angle is determined accordingly, so that substantially equal spacing angles are used from the starting color to the ending color.

[0020] In one embodiment, a fixed hue spacing angle is used for each additional phase, where the fixed hue spacing angle is equal to the golden angle. By using the golden angle (approximately 137.5°) to select the additional hue for each additional phase, it is ensured that - regardless of how many phases need to be associated - all hues are selected in such a way that the next color is selected from the largest unused gap and that colors are not repeated for as long as possible given the model.

[0021] Thus, the above method can be used to map the topology of the HSV color space to a higher dimensional phase data space in a defined manner. Using the method, an information-rich, consistent, clearer color image can be created, which contains relevant information about the sample being inspected. By using this method, the image is also visually pleasing to the user. Thus, the purpose of the present invention is achieved.

[0022] Advantageous embodiments will be explained below.

[0023] In one embodiment, the step of selecting the plurality of different hues comprises using information about a plurality of mutually different phases as input variables. The information may contain the number of phases detected in the sample, which is useful for determining the hue spacing angle. The information may also contain different phase numbers, which means that similar or somewhat similar phases are grouped together and assigned a single hue or similar hues. Similar phases may be phases with similar composition because they contain one or more of the same chemical elements, such as noted above or compatible hues.

[0024] In one embodiment, the step of providing a preselected continuous hue range may include the step of assigning one or more preselected hues to the corresponding one or more phases. The step may be performed by a control unit. The step may be initiated by the control unit or by a user. In this way, it is possible, for example, to assign a blue hue to silicon, a purple hue to oxygen, and an orange hue to platinum. It is thus possible to determine certain boundary conditions for the hue that is ultimately used. This provides consistency between different samples and different experiments, by which the user can more easily interpret the results of the sample. The boundary condition of preassigning certain hues to different phases obviously sets some restrictions on the hue interval angles that can be obtained with this embodiment, which means that not all hue interval angles must be equal or similar. However, given these boundary conditions, the method preferably selects additional hues for additional phases in such a way that the selected hues are contained in corresponding intervals within the preselected continuous hue range.

[0025] In one embodiment, the method includes repeating the step of selecting the plurality of different hues and associating the reselected hues with the plurality of mutually different phases. The repetition step may be initiated by a control unit or by a user. For example, the reselection may be performed during data acquisition of a sample. As more data comes in, additional phases may be detected and the hues may be reselected based on the phases. For example, the reselection may be performed additionally or alternatively after a user sets or changes boundary conditions. For example, it is conceivable that, given the initial results, the user wishes to assign a certain hue to a certain phase (or composition), thereby requiring a change in other selected hues. This repetition step may also include the following steps: providing an additional preselected continuous hue range, wherein the preselected continuous hue range is different from the preselected continuous hue range initially provided. It is conceivable that, for example, a wider or smaller angular hue range is used during the repetition steps of selection and association.

[0026] In one embodiment, said emissions of said first type are used to encode different degrees of saturation within said image representation.

[0027] In one embodiment, a second detector is used to detect a second type of emission different from the first type. The emission of the second type may be, for example, secondary electrons and / or backscattered electrons. The emission of the second type is used to encode different values ​​within the image representation. In other words, the SEM is used to obtain a grayscale image of the inspected sample, and color (preferably on top of the image) is used to encode a first type of emission (preferably related to EDS) within the image representation.

[0028] In one embodiment, the method comprises the step of selecting and associating the plurality of different hues using an algorithm.

[0029] In one embodiment, the algorithm may include one or more of the following steps:

[0030] - Provide an initial color scheme;

[0031] - provide one or more adjustment variables;

[0032] - generating a final color scheme and providing a pictorial representation of the sample using the final color scheme.

[0033] The adjustment variables may include one or more preferences, such as global preferences and / or user preferences. The adjustment variables may also include negative adjustment values ​​and positive adjustment values ​​used to change one or more preferences. For example, the composition of the sample may be used to generate adjustment values ​​that change the global preferences to the final preferences, thereby generating the final color scheme.

[0034] It should be noted that the above algorithm utilizes a preselected continuous hue range (i.e., an initial color scheme) and selects related colors (i.e., a final color scheme) based on one or more adjustment variables as boundary conditions for selecting the final color scheme. The selected colors may provide hue interval angles that correspond to each other, although it is conceivable that the hue interval angles do not substantially correspond. Therefore, according to one aspect, a method for examining a sample using a charged particle microscope comprises the following steps:

[0035] - Provide charged particle beam and sample;

[0036] - scanning the charged particle beam over the sample;

[0037] - detecting, using a first detector, emissions of a first type from the sample in response to the beam being scanned over the sample;

[0038] - using spectral information of the detected emission of the first type, assigning a plurality of mutually different phases to the sample;

[0039] - associating, with reference to the HSV color space, a corresponding plurality of different hues with the plurality of mutually different phases; and

[0040] - providing, by a control unit, a graphical representation of said sample, wherein said graphical representation contains said associated different shades;

[0041] It is characterized by the following steps:

[0042] - Provides a pre-selected continuous tone range;

[0043] - using at least spectral information of the detected emissions of the first type to provide one or more adjustment variables;

[0044] - selecting said plurality of different hues from said preselected continuous hue range based on said adjustment variable; and

[0045] - associating the selected hue with the plurality of mutually different phases.

[0046] By using such algorithms, it is possible to ensure that appropriate color schemes are used to create relevant, informative, consistent, and clearer color image representations. Many modifications of such algorithms are conceivable, and some embodiments will be described with the aid of the embodiments in the accompanying drawings. However, first, several other embodiments of the methods disclosed herein will be described.

[0047] In one embodiment, the method comprises the step of selecting and associating the plurality of different hues using an artificial neural network (ANN).ANNs can advantageously be used to select and associate related hues based on available data and are relatively efficient in this regard.

[0048] In one embodiment, the method comprises the step of using a Self-Organizing Map (SOM) as the artificial neural network.

[0049] In one embodiment, different nodes of the ANN represent different phases. The outer edge of the ANN may correspond to the preselected continuous hue range. With reference to the HSV color space, the ANN contains at least information with respect to hue and saturation. It is also conceivable that the method comprises the step of initializing the ANN to include a plurality of preselected phases as corresponding preselected nodes.

[0050] In one embodiment, the method comprises a step of training the ANN, wherein the training step comprises in particular a step of matching the ANN to a plurality of mutually different phases of the assignment.

[0051] In one embodiment, the method comprises the step of pre-assigning specific hues to specific phases.

[0052] In one embodiment, the method comprises the step of normalizing the color characteristic based on information about a plurality of mutually different phases.

[0053] According to one aspect, there is provided a charged particle microscope for examining a sample, wherein the charged particle microscope comprises:

[0054] - an optical column comprising a charged particle source, a final probe-forming lens and a scanner for focusing the charged particle beam emitted from said charged particle source onto a specimen;

[0055] - a specimen stage located downstream of the final probe forming lens and arranged to hold the specimen;

[0056] - a first detector that detects emissions of a first type originating from the specimen in response to incident charged particles emitted from the charged particle source; and

[0057] - A control unit and a processing device connected to the first detector.

[0058] As defined herein, the charged particle microscope is arranged for performing a method as described above, in particular in that the control unit and / or the processing unit are arranged for performing at least parts of the method.

[0059] In one embodiment, the charged particle microscope further comprises a second detector for detecting a second type of emission originating from the specimen in response to the incident charged particles emitted from the charged particle source.

[0060] In one embodiment, the charged particle microscope further comprises an output device for outputting a combination of the processed information of the first detector and the processed information of the second detector. In particular, the output device is arranged for outputting a color image, wherein the color space of the color image comprises hue, value and saturation, and wherein:

[0061] - the first type of emission (eg EDS data) is used to define at least one of hue and saturation of the color image; and

[0062] - Emission of the second type (eg SEM data) is used to define at least values ​​of the color image. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The invention will now be described in detail based on exemplary embodiments and the accompanying schematic diagrams, in which:

[0064] Figure 1 - shows a longitudinal cross-sectional view of a charged particle microscope according to a first embodiment of the present invention;

[0065] Figure 2 - shows a longitudinal cross-sectional view of a charged particle microscope according to a second embodiment of the present invention;

[0066] Figure 3 - shows a representation of the HSV color space;

[0067] Figure 4 - shows a first embodiment of selecting and assigning hues to phases;

[0068] Figure 5 - shows the use of artificial neural networks to select and assign hues to phases;

[0069] Figure 6- shows a second embodiment of selecting and assigning hues to phases;

[0070] Figure 7 - shows an embodiment using normalized color characteristics;

[0071] Figure 8 - shows an embodiment of an algorithm for selecting and assigning hues to phases;

[0072] Fig. 9 - shows a pictorial representation of a sample using the method disclosed herein. DETAILED DESCRIPTION

[0073] Figure 1 (not to scale) is a highly schematic depiction of an embodiment of a charged particle microscope M according to an embodiment of the present invention. More specifically, it shows one embodiment of a transmission type microscope M, which in this case is a TEM / STEM (although, in the context of the present invention, it may effectively just be a SEM (see Figure 2 ), or for example ion-based microscopy). Figure 1 In the vacuum housing 2, the electron source 4 generates an electron beam B. Beam B Propagates along electron optical axis B' and passes through electron optical illuminator 6 for directing / focusing the electrons onto a selected portion (eg, which may be (locally) thinned / planarized) of specimen S. A deflector 8 is also depicted, which may (among other things) be used to achieve a scanning motion of beam B.

[0074] The specimen S is held on a specimen holder H, which is positionable with multiple degrees of freedom by a positioning device / stage A, which moves a cradle A' into the (removably) attached holder H; for example, the specimen holder H may comprise fingers that are movable (among others) in the XY plane (see the depicted Cartesian coordinate system; typically, movements parallel to Z and tilts about X / Y are also possible). Such movements allow different parts of the specimen S to be illuminated / imaged / inspected by an electron beam B traveling along an axis B' (in the Z direction) (and / or to perform a scanning movement as an alternative to beam scanning). If desired, an optional cooling device (not depicted) may be brought into close thermal contact with the specimen holder H, in order to, for example, maintain it (and the specimen S thereon) at cryogenic temperatures.

[0075] The electron beam B will interact with the specimen S so that various types of "stimulated" radiation are emitted from the specimen S, including (for example) secondary electrons, backscattered electrons, X-rays and optical radiation (cathodoluminescence). If desired, one or more of these radiation types may be detected with the aid of an analysis device 22, which may be, for example, a combined scintillator / photomultiplier tube or an EDX or EDS (energy dispersive X-ray spectrometer) module; in this case, an image may be constructed using essentially the same principles as in a SEM. Alternatively or additionally, however, electrons that have traversed (passed through) the specimen S, exited / emitted therefrom and continue to propagate along the axis B' (essentially, although usually with some deflection / scattering) may be studied. Such a transmitted electron flux enters an imaging system (projection lens) 24, which typically comprises various electrostatic / magnetic lenses, deflectors, correctors (such as an stigmator), etc. In normal (non-scanning) TEM mode, this imaging system 24 may focus the transmitted electron flux onto a screen 26, which may be retracted / withdrawn if desired (as schematically indicated by arrow 26') so as to be away from the axis B'. An image (or diffraction pattern) of (a portion of) the specimen S will be formed by the imaging system 24 on a screen 26, and this may be viewed through a viewing port 28 located in a suitable portion of the wall of the housing 2. The retraction mechanism of the screen 26 may, for example, be mechanical and / or electrical in nature, and is not depicted here.

[0076] As an alternative to observing the image on the screen 26, one can instead exploit the fact that the depth of focus of the electron flux leaving the imaging system 24 is typically large (e.g., about 1 meter). Thus, various other types of analysis devices can be used downstream of the screen 26, such as:

[0077] - TEM camera 30. At camera 30, the electron flux may form a static image (or diffraction pattern) which may be processed by controller / processor 20 and displayed, for example, on a display device (not depicted) such as a flat panel display. When not needed, camera 30 may be retracted / withdrawn (as schematically indicated by arrow 30') to move it away from axis B'.

[0078] - STEM camera 32. The output from camera 32 can be recorded as a function of the (X,Y) scanning position of beam B on specimen S, and an image can be constructed, which is a "map" of the output from camera 32 as a function of X,Y. Camera 32 may contain a single pixel of, for example, 20 mm in diameter, as opposed to the matrix of pixels characteristically present in camera 30. Furthermore, the acquisition rate of camera 32 (e.g., 10 pixels per second) may be very high. 6 points) is usually faster than the camera 30 (e.g. 10 per second 2Again, when not needed, the camera 32 can be retracted / withdrawn (as schematically shown by arrow 32') to move it away from the axis B' (although such retraction is not necessary in the case of, for example, a donut-shaped annular dark field camera 32; in such cameras, the central hole will allow flux to pass when the camera is not in use).

[0079] As an alternative to imaging using the camera 30 or 32 , a spectroscopic device 34 can also be called upon, which can be, for example, an EELS module.

[0080] It should be noted that the order / position of items 30, 32 and 34 is not critical and many possible variations are conceivable. For example, spectroscopic device 34 may also be integrated into imaging system 24.

[0081] In the illustrated embodiment, microscope M also includes a retractable X-ray computed tomography (CT) module, generally indicated by reference numeral 40. In computed tomography (also known as tomographic imaging), a source and (diametrically opposed) detectors are used to observe a specimen along different lines of sight in order to obtain penetrating views of the specimen from a variety of angles.

[0082] Note that a controller (computer processor) 20 is connected to the various illustrated components via control lines (bus) 20'. This controller 20 may provide a variety of functions, such as synchronizing actions, providing set points, processing signals, performing calculations, and displaying messages / information on a display device (not depicted). Needless to say, the (schematically depicted) controller 20 may be (partially) inside or outside the housing 2 and may have an integral or composite structure as desired.

[0083] The skilled person will appreciate that the interior of the housing 2 need not necessarily be kept in a strict vacuum; for example, in a so-called "environmental TEM / STEM", a background atmosphere of a given gas is intentionally introduced / maintained within the housing 2. The skilled person will also appreciate that, in practice, it may be advantageous to limit the volume of the housing 2 so that it substantially surrounds the axis B', if possible, in the form of a small tube (e.g., of about 1 cm in diameter) through which the electron beam used passes, but widened to accommodate structures such as the source 4, the specimen holder H, the screen 26, the camera 30, the camera 32, the spectroscopic device 34, etc.

[0084] The charged particle microscope M according to the present invention and its embodiments are Figure 1, and thus comprises an optical column O, which includes a charged particle source 4, a final probe forming lens 6 and a scanner 8 for focusing a charged particle beam B emitted from the charged particle source 4 onto a specimen. The device also comprises a specimen stage A, H, which is located downstream of the final probe forming lens 6 and is arranged to hold the specimen S. The device also comprises a first detector 22, which detects a first type of emission originating from the specimen in response to the incidence of charged particles B emitted from the charged particle source 4. In the embodiment shown, the first detector 22 is an analysis device 22, which, as previously described, can be a combined scintillator / photomultiplier tube or an EDS (energy dispersive X-ray spectrometer) module. In a preferred embodiment, the first detector is an EDS. In addition, the device according to the invention comprises a control device 20, which is connected to the first detector 22 (schematically shown) (by means of a line 20'). According to the invention, the charged particle microscope M is arranged for performing a method according to the invention, which will be described later by means of Figures 3 to 8 Explain it.

[0085] Now first refer to Figure 2 , shows another embodiment of the device according to the present invention. Figure 2 (not to scale) is a highly schematic diagram of a charged particle microscope M according to the invention; more specifically, it shows an embodiment of a non-transmission type microscope M, which in this case is a SEM (although, in the context of the invention, it may just be useful, for example, as an ion-based microscope). Figure 1 Corresponding parts of the items in the same figure are indicated by the same reference numerals and will not be discussed separately here. Figure 1 Among them are (especially) the following parts:

[0086] - 2a: a vacuum port which can be opened to introduce / remove objects (components, specimens) into / from the interior of the vacuum chamber 2 or to which, for example, auxiliary devices / modules can be mounted. If necessary, the microscope M can comprise a plurality of such ports 2a;

[0087] - 10a, 10b: schematic representations of lenses / optical elements in the illuminator 6;

[0088] - 12: voltage source, allowing, if necessary, the specimen holder H or at least the specimen S to be biased (floated) to a potential relative to ground;

[0089] - 14: Display, such as FPD or CRT;

[0090] 22a, 22b: Segmented electron detector 22a comprising a plurality of independent detection segments (e.g. quadrants) arranged around a central aperture 22b (allowing the beam B to pass). Such detectors can be used, for example, to study (the angular dependence of) the output (second or backscattered) flux of electrons emerging from the specimen S.

[0091] Therefore, if Figure 2 The charged particle microscope M shown comprises an optical column O, which includes a charged particle source 4, a final probe forming lens 6, 10a, 10b and a scanner 8 for focusing a beam B of charged particles emitted from the charged particle source 4 onto a specimen S. The device also comprises a specimen stage A, H, which is located downstream of the final probe forming lens 6 and is arranged to hold the specimen S. The device also comprises a first detector 22, which detects a first type of emission originating from the specimen in response to the incidence of charged particles B emitted from the charged particle source 4. In the embodiment shown, the first detector 22 is the analysis device 22, which, as previously described, can be a combined scintillator / photomultiplier tube or an EDS (Energy Dispersive X-ray Spectrometer) module. In an alternative embodiment, the first detector 22 can be a segmented detector 22a, 22b. In a preferred embodiment, the first detector is an EDS. In addition, the device according to the invention comprises the control device 20, which is connected to the first detector 22 (by means of a line 20').

[0092] Figure 1 and Figure 2 The device shown in can be used to examine samples using the method according to the present invention. Generally, embodiments of the method all include the following general steps:

[0093] - scanning said charged particle beam B over said specimen S;

[0094] - detecting, using a first detector 22, emissions of a first type from the specimen S in response to the beam B being scanned over the specimen S;

[0095] - using spectral information of the detected emission of the first type, assigning a plurality of mutually different phases to the sample;

[0096] - associating, with reference to the HSV color space, a corresponding plurality of different hues with the plurality of mutually different phases; and

[0097] - providing, by the control unit 20, a graphic representation of said sample, wherein said graphic representation contains said associated different shades.

[0098] The method disclosed herein further comprises the following steps:

[0099] - Provides a pre-selected continuous tone range;

[0100] - selecting said plurality of different hues from said preselected range of continuous hues in such a way that the selected hues are contained in mutually corresponding intervals within said preselected range of continuous hues; and

[0101] - associating the selected hue with the plurality of mutually different phases.

[0102] The above method steps will be explained in further detail below.

[0103] Figure 3 1 shows an example of an HSV color space 101 used in the methods defined herein. The HSV color space 101 is a color space that describes the properties of a particular color using hue (commonly referred to as "color", e.g., red, green, blue), saturation (commonly referred to as the intensity or purity of a color), and value (commonly referred to as the lightness or darkness of a color). The HSV color space can be used as Figure 3 The cylindrical geometry shown represents the hue, angular dimensions of which start at the red primary at 0°, pass through the green primary at 120° and the blue primary at 240°, and then wrap around back to red at 360°. The central vertical axis contains the neutral, achromatic, or gray colors, ranging from black ( Figure 3 ) to a white value of 1 ( Figure 3 As the radius increases, i.e. from the center outwards, the saturation of the color increases. The details of the HSV color space itself are known to those skilled in the art of color spaces.

[0104] Figure 4 An embodiment is shown of how a plurality of different hues can be assigned to a plurality of mutually different phases. In this embodiment, a charged particle beam and a sample are provided, and the charged particle beam is scanned over the sample. A first type of emission, such as X-rays, of the sample is detected. Based on those detected emissions, mutually different phases oxygen (O), aluminum (Al), and silicon (Si) are assigned to the sample.

[0105] Figure 4 A schematic image representation of a portion of a color space 201 is shown, which color space can be used to provide an image representation of an inspected sample. It can be seen here that a preselected range 201 of a total of eight continuous tones 211-218 is provided, wherein the following tones are used:

[0106] 211 - red;

[0107] 212 – orange;

[0108] 213 – yellow;

[0109] 214 – green;

[0110] 215 – teal;

[0111] 216 – blue;

[0112] 217 – Violet; and

[0113] 218 – Purple.

[0114] Based on a preselected continuous hue range and the different phases available, a plurality of different hues can be selected. The selection is made in such a way that the selected hues are contained in mutually corresponding intervals within the preselected continuous hue range. In the illustrated embodiment, red 211, yellow 213 and blue 216 are selected. Within the preselected continuous hue range, these hues have substantially equal hue interval angles with reference to the HSV color space. In the illustrated embodiment, red 211 is then assigned to oxygen, yellow 213 to silicon and blue 216 to aluminum. As an alternative, it is conceivable to assign red 211 to aluminum, yellow 213 to oxygen and blue 216 to silicon.

[0115] For example, the algorithm (see also Figure 8 The selected hues are assigned to different phases randomly or in a more structured manner (described in the description of FIG. 1 ). It is conceivable that boundary conditions are provided, for example, by the control unit or by the user. These boundary conditions may include a desired hue for a specific phase, such as the hue red 211 needs to be assigned to oxygen (O). In this way, specific hues can be pre-assigned to specific phases. Based on these boundary conditions, additional colors can be selected from a list of pre-selected hues.

[0116] As an alternative, it is conceivable that, as the first color, any arbitrary hue is selected from the preselected continuous hue range. It is not necessary to select the first hue within the preselected continuous hue range. For example, it is conceivable that the hues orange 212, green 214 and purple 217 are selected for O, Si and Al, because these colors also exhibit substantially equal hue spacing angles.

[0117] As an alternative, it is conceivable to use subsequent hues within the preselected color range. For example, it is conceivable that the hues orange 212, yellow 213 and green 214 are used for Si, O and Al, since these hues also exhibit substantially equal hue spacing angles.

[0118] Figure 5 It is shown how an artificial neural network (ANN) can be used to select and associate multiple different hues. Figure 5A color space 301 generated by such an ANN is shown, which in one embodiment may be a self-organizing map (SOM). In this way, the chemical composition may be mapped onto a network of nodes (311-316, 321, 322) that respect their interdependencies given by the color model. The network may adapt according to the input data, i.e. when the detector detects additional data. Such ANNs, and in particular SOMs, may be used in general to generate and select tones to be used in image representations of samples. The main advantage is that ANNs may be used and programmed to reflect (dis)similarities in phase composition:

[0119] - Phases of similar composition should have similar colors;

[0120] - Overlapping phases should have adjacent colors on the color wheel so that they can be mixed;

[0121] - two different phases should not acquire similar colors; and

[0122] - Different phases (different from all other phases) should have different colors.

[0123] In addition, boundary conditions can be added to ensure that the ANN produces consistent results throughout the experiment. For example, a certain phase (such as copper) is expected to obtain the same color regardless of the surrounding environment. Therefore, it is possible to initialize the ANN to include multiple pre-selected phases as corresponding pre-selected nodes.

[0124] In addition, the ANN can be programmed to specifically adapt to the available data. In this way, for example, it is possible to prevent the allocation of colors when certain phases are not present in the scene, or to allocate them to different phases. Ultimately, it is desirable to utilize tones across the entire color space in the final image representation of the sample, because this provides a way to convey technical information to the user in the most clear and information-intensive way. Therefore, the ANN can be programmed to select the multiple different tones from the preselected continuous tones range in such a way that the selected tones substantially contain corresponding intervals within the preselected continuous tones range. Of course, it is conceivable that due to the presence of certain boundary conditions, not all tones have corresponding tones interval angles.

[0125] Furthermore, similar phases can be assigned similar, compatible colors. Thus, it is conceivable that in one embodiment, there are typically two different phases, namely phase A and phase B. For these two different phases, two opposite hues can be selected, such as orange and blue. Thus, phase A is represented by the hue blue, while phase B is represented by the hue orange. However, there are several variations of phase B in the sample, and these variations can be intuitively represented by selecting different orange hues for these different phase B variations. Thus, for example, it is possible to use hues orange-red to yellow (so-called compatible colors) for these phase B variations, while for phase A, a single blue-hue (so-called opposite color) is used. In this way, colors are still selected from the preselected continuous hue range in such a way that the selected colors are contained in mutually corresponding intervals within the preselected continuous hue range.

[0126] Still refer to Figure 5 , it can be seen that, referring to the HSV color space, the ANN contains information at least with respect to hue and saturation. Most saturated colors (e.g., the purest phase) are located at the border of the network, and less saturated colors (e.g., purer phases) are located at the center of the network.

[0127] Figure 6 An embodiment of the method disclosed herein is shown, compared to Figure 4 , an alternative approach was used. Figure 6 , a total of eight hues are provided (red 411, orange 412, yellow 413, green 414, cyan 415, blue 416, violet 417, and purple 418), where these colors are associated with specific elements. For example, silicon (Si) may be pre-associated with red hue 411, aluminum (Al) may be pre-associated with purple hue 418, and oxygen (O) may be pre-associated with green hue 414. Once the data comes in and it turns out that Si, Al, and O are present as elements in the sample, the corresponding red, purple, and green colors may be provided as pre-selected continuous hue ranges. In other words, in this case, only three possible hues red, purple, and green are provided. Now, as Figure 6 As shown, the triangle 401 is marked with an x, and different phases exist, and different hues can be selected from a preselected continuous hue range (red, purple, green) in such a way that the selected hues are contained in mutually corresponding intervals within the preselected continuous hue range. In this regard, a mixture or shifting of the hues is conceivable in order to establish mutually corresponding hue interval angles. For example, in Figure 6 As can be seen in the figure, the clusters of x-marks (each cluster represents a similar phase) are positioned within the triangle in such a way that there are substantially corresponding hue spacing angles between them. Therefore, the final image does have a corresponding hue spacing angle for each phase cluster present in the sample.

[0128] It is also conceivable that the method comprises a step of normalizing the color characteristic based on the information about a plurality of mutually different phases. Figure 6 It is shown that the color space is somewhat concentrated relative to the entire color space (the triangle). Figure 7 (left hand side) shows an example where the different phases are very concentrated between the B and C edges of the color space. By normalizing the color characteristics (which may include normalizing hue, value and / or saturation), it is possible to expand the use of color in the final image representation. In this regard, it is important to note that after normalization Figure 7 The colors (dots) used in (right hand side) provide an expansion in the color space. As a result, the image representation of the sample is more information dense and clearer for the user.

[0129] Figure 8 An embodiment of one aspect of the method disclosed herein is shown. Figure 8 An embodiment of an algorithm that can be used to assign hues to detected phases is schematically shown. Blocks U, V, W generally represent a user interface block U, a detector block V, and a processor block W. These blocks U, V, W provide inputs to an algorithm generally represented by algorithm blocks i-vi. Here, the algorithm comprises the following steps: generalizing an intermediate color scheme in algorithm block i, rendering a negative adjustment ii and a positive adjustment iv that generate preference adjustments in algorithm block iii, and using both the preference adjustments from processor block W and the global preferences to generate a final preference v. Using the final preference v, a color can be assigned to a phase vi, by which the intermediate color scheme i can be updated again. The intermediate color scheme generated in this way is output to the user interface block U to provide a final color scheme.

[0130] The user interface block U can provide user preferences for the intermediate color scheme i. The detector block V can provide information about the integral composition, phase overlap statistics, and / or other variables related to the detected characteristics of the sample to provide negative and / or positive adjustments ii, iv. The processor block W can provide global preferences to the algorithm.

[0131] In general, the algorithm may use the following steps:

[0132] 1. Place a "locked" element in the middle color scheme i, where the locked element is provided by the user through the user interface module U;

[0133] 2. Select the next unplaced element with the largest proportion in the sample;

[0134] 3. Reduce preference for occupied colors;

[0135] 4. Increased preference for colors that are compatible with the coexisting elements that have been placed, such as having the largest or corresponding hue separation angle;

[0136] 5. Combine these preference adjustments iii with the global preferences from the processor unit block W to generate the final preferences v;

[0137] 6. Pick the color based on your final preference ("Place Elements")vi;

[0138] 7. Repeat steps 2 to 6 until all detected elements or phases have been placed, wherein it is conceivable, for example, to carry out negative and / or positive adjustments by equalizing the weights as a function of the integral components.

[0139] Therefore, in Figure 8 In the illustrated embodiment, a preselected continuous tone range is provided, and at least the spectral information of the detected first type of emission is used to provide one or more adjustment variables. Based on these adjustment values, the plurality of different tones are selected from the preselected continuous tone range. Finally, the selected tones are associated with the plurality of mutually different phases.

[0140] It should be noted that the increase and decrease in steps 3 and 4 are similar to the previous Figure 8 Positive iv and negative ii adjustments mentioned.

[0141] Fig. 9 A black and white version of an image representation of a sample is shown, in this case platinum-rhodium particles on a ceramic (Si, Al, O). The image representation contains different hues selected by the method disclosed herein. The hues include blue-green for aluminum, blue for silicon, orange for platinum, purple for oxygen, and yellow for rhodium. Platinum and rhodium are similar phases and are assigned compatible hues of yellow and orange. Si, Al, and O are different phases and are assigned a blue-green hue to maximize the hue spacing angle used in the image representation. The result is that the Pt-Rh particles are clearly visible, giving more information about the sample.

[0142] Several embodiments of the method have been disclosed herein. The desired protection is determined by the appended claims.

[0143] References

[0144] Figure 7 – Adapted from: Pawlowsky-Glahn, Egozcue, Tolosana-Delgado: "Lecture Notes on Compositional Data Analysis" ( http: / / www.sediment.uni-goettingen.de / staff / tolosana / extra / CoDa.pdf , p. 36, referring to MARTIN-FERNÁNDEZ, Josep A. et al. "Variance measurement of compositional data based on difference measurement" in: Proceedings of IAMG. 1999. p.211-216.).

Claims

1. A method for examining a sample using a charged particle microscope, comprising the following steps: providing a charged particle beam and a sample; scanning the charged particle beam over the sample; detecting, using a first detector, emissions of a first type from the sample in response to the beam being scanned over the sample; assigning a plurality of mutually different phases to the sample using the detected spectral information of the first type of emission; Referring to the HSV color space, associating the corresponding plurality of different hues with the plurality of mutually different phases; and providing, by a control unit, a graphical representation of the sample, wherein the graphical representation contains the associated different tones; It is characterized by the following steps: Provides a pre-selected continuous tone range; selecting said plurality of different hues from said preselected continuous hue range in such a manner that said selected hues comprise mutually corresponding intervals within said preselected continuous hue range; selecting a fixed hue spacing angle within said preselected continuous hue range to select an additional hue for each additional phase so as to ensure that the next color is selected from the largest unused gap and that colors are not repeated for as long as possible given the model; and The selected hue is associated with the plurality of mutually different phases.

2. The method of claim 1, wherein the step of selecting the plurality of different hues comprises using information about the plurality of mutually different phases as an input variable.

3. A method according to claim 1 or 2, comprising repeating the step of selecting the plurality of different hues and associating the reselected hues with the plurality of mutually different phases.

4. A method according to claim 1 or 2, comprising the step of using an algorithm to select and associate the plurality of different hues. The method of claim 4 , wherein the algorithm is non-deterministic.

6. The method according to claim 1 or 2, comprising the step of selecting and associating the plurality of different hues using an artificial neural network.

7. The method according to claim 6, comprising the step of using a self-organizing map (SOM) as the artificial neural network.

8. The method according to claim 6, wherein different nodes of the artificial neural network represent different phases.

9. The method of claim 6, wherein an outer edge of the artificial neural network corresponds to the preselected continuous tone range.

10. The method of claim 6, wherein the artificial neural network contains information at least with respect to hue and saturation with reference to an HSV color space.

11. The method according to claim 6, comprising the step of initializing the artificial neural network to include a plurality of pre-selected phases as corresponding pre-selected nodes.

12. The method according to claim 6, comprising the step of training the artificial neural network, wherein the step of training the artificial neural network particularly comprises the step of matching the artificial neural network to the assigned plurality of mutually different phases.

13. The method according to claim 1 or 2, comprising the step of pre-assigning a specific hue to a specific phase.

14. The method according to claim 1 or 2, comprising the step of normalizing the color characteristics based on the information about the plurality of mutually different phases.

15. A method for examining a sample using a charged particle microscope, comprising the following steps: providing a charged particle beam and a sample; scanning the charged particle beam over the sample; detecting, using a first detector, emissions of a first type from the sample in response to the beam being scanned over the sample; assigning a plurality of mutually different phases to the sample using the detected spectral information of the first type of emission; Referring to the HSV color space, associating the corresponding plurality of different hues with the plurality of mutually different phases; and providing, by a control unit, a graphical representation of the sample, wherein the graphical representation contains the associated different tones; Features: Provides a pre-selected continuous tone range; using at least the detected spectral information of the first type of emissions to provide one or more adjustment variables; selecting the plurality of different hues from the preselected continuous hue range based on the adjustment variable; selecting a fixed hue spacing angle within the preselected continuous hue range to select an additional hue for each additional phase so as to ensure that the next color is selected from the largest unused gap and that colors are not repeated for as long as possible given the model; and The selected hue is associated with the plurality of mutually different phases.

16. A charged particle microscope for examining a sample using a method according to one or more of claims 1 to 15, and comprising: an optical column comprising a charged particle source, a final probe forming lens and a scanner for focusing a charged particle beam emitted from said charged particle source onto a specimen; a specimen stage located downstream of the final probe forming lens and arranged to hold the specimen; a first detector that detects a first Type of launch; a control unit and a processing device connected to said first detector; Wherein the charged particle microscope is arranged for performing the method according to one or more of claims 1-15.

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