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. The method comprises the following steps: using a first detector, in response to a light beam scanning over an area of ​​the sample, detecting a first type of emission from the sample. Then, at least a portion of the scanned area of ​​the sample is divided into a plurality of segments using spectral information of the detected first type of emission. According to the present invention, the first type of emission at different positions along the scan in at least one of the plurality of segments can be combined to produce a combined spectrum of the sample in the one of the plurality of segments. In one embodiment, a second detector is used to detect the second type of emission, and this is used to divide the area of ​​the sample into a plurality of regions. The first detector can be EDS and the second detector can be based on EM. In this way, the EDS data and the EM data can be effectively combined to produce a color image.

Description

Technical Field

[0001] The present invention relates to a method for examining a sample using a charged particle microscope, comprising the steps of detecting a first type of emission from the sample using a first detector in response to a charged particle beam scanning over an area of ​​the sample, and examining the sample using spectral information of the detected first type of emission. Background Art

[0002] Charged particle microscopy, particularly in the form of electron microscopy, is a well-known and increasingly important technique for imaging microscopic objects. Historically, the basic class of electron microscopes has evolved into many well-known device species, such as the transmission electron microscope (TEM), the scanning electron microscope (SEM) and the scanning transmission electron microscope (STEM) as well as various subspecies, such as the 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.

[0003] By irradiating the sample with a scanning electron beam, emission of "auxiliary" radiation from the sample is accelerated, for example in the form of secondary electrons, backscattered electrons, X-rays, and cathodoluminescence (infrared, visible, and / or ultraviolet photons). One or more components of this emitted radiation can be detected and used for sample analysis.

[0004] 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 primary beam moves across the sample. The image provides only information about the topology of the sample to be examined.

[0005] In a process called "energy dispersive x-ray spectroscopy," or "EDS," the energy of the x-rays from the sample in response to 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.

[0006] One disadvantage of EDS is that it takes a considerable amount of time to accumulate the X-ray spectrum of a sample. Typically, a grid with discrete analysis points is used. The electron beam dwells on each analysis point while the EDS detector records the X-rays. Once enough X-ray counts have been recorded, the beam moves to the next analysis point. The signal from the EDS detector is fed to a signal processing unit which builds an X-ray spectral profile for each analysis point, which can be matched against an extensive library of known mineral phases to select the best match for that analysis point. Summary of the invention

[0007] Therefore, it is an object of the present invention to provide an improved method for examining a sample using a charged particle microscope, wherein spectral information of the detected emission is used to examine the sample. In particular, it is an object of the present invention to provide a method and apparatus for obtaining information about a sample more quickly and / or more accurately.

[0008] To this end, the present invention provides a method for examining a sample using a charged particle microscope as defined in claim 1. The method comprises the following steps: using a first detector, in response to a light beam scanning over an area of ​​the sample, detecting a first type of emission from the sample. The method also comprises collecting spectral information of the detected emission of the first type. The spectral information of the detected first type of emission is used to divide at least a portion of the scanned area of ​​the sample into a plurality of segments. According to the present invention, the first type of emission at different positions along the scan in at least one of the plurality of segments is combined to produce a combined spectrum of the sample in the one of the plurality of segments.

[0009] Therefore, during the scanning of the light beam in the area of ​​the sample, spectral information of the detected emission of the first type is collected. The emission detected by the first detector can be associated with a specific scanning light beam position, that is, it can be associated with a specific position on the sample. This means that spectral information of the corresponding position on the sample can also be collected and / or determined. The spectral information obtained at different positions can be compared with each other. In particular, in the case where the spectral information associated with two or more different positions is substantially the same, this means that these points on the sample may be similar, for example in terms of chemical composition, and are therefore related to each other. Therefore, information associated with these two or more different positions but having similar characteristics can be used to combine these positions together and define a first section of the inspected sample. Similarly, two or more other different positions with substantially the same or similar spectral information can also be combined together to define a second section of the inspected sample.

[0010] Instead of collecting complete spectral information for different analysis points and then moving on to the next analysis point, in the method according to the present invention, a light beam is used to scan the sample and collect spectral information for multiple analysis points simultaneously. The scanning of the light beam is relatively fast and can be scanned continuously or semi-continuously over the area of ​​the sample to be examined. After one or more scans, the spectral information obtained may be sparse, meaning that some analysis points may indeed provide information, while other analysis points do not. However, by combining similar analysis points into segments, and combining the first type of emission at the analysis points in each segment to produce a combined spectrum in the segment, the method according to the present invention is able to provide more qualitative information for the entire sample more quickly. In addition, in the case of multiple scans of the sample, the accuracy of the method according to the present invention is further improved because the sparsity of the collected data will be reduced. Therefore, it can be seen from the above that the purpose of the present invention is achieved.

[0011] Further embodiments of the invention are according to the dependent claims. The details of these further embodiments will be explained below. DETAILED DESCRIPTION

[0012] In one embodiment, the method comprises the additional step of dividing at least one of the plurality of segments into a plurality of sub-segments. In particular, the spectral information of the detected emission of the first type is used to divide one of the plurality of segments into a plurality of sub-segments. In this way, for example, information obtained during repeated scanning with the light beam is used to further refine the segment into smaller sub-segments. For these smaller sub-segments, the emission of the first type at different positions along the scan can be combined to produce a combined sub-spectrum of the sample in the one of the plurality of sub-segments. In this way, more accurate and detailed information about the sample can be obtained.

[0013] In one embodiment, the method further comprises the following steps:

[0014] - detecting a second type of emission from the sample using a second detector in response to the light beam being scanned over the area of ​​the sample;

[0015] - using the second type of emission, dividing the scanned area of ​​the sample into a plurality of areas;

[0016] - combining the emissions of the first type at different positions along the scan in at least one of the plurality of regions to produce a combined spectrum of the sample in that region.

[0017] In this embodiment, an additional detector is used to detect the emission of the second type. These second types of emission are different from the emission of the first type. Information related to these second types of emission is used to define the area of ​​the sample. These areas are then used to generate a combined spectrum of the sample in the area using the emission of the first type.

[0018] In one embodiment, the step of dividing the scanning area of ​​the sample into a plurality of regions is performed before the step of dividing at least a portion of the scanning area of ​​the sample into a plurality of segments. In particular, the second type of emission can provide a higher information rate than the first type of emission. In other words, the process of detecting important signals associated with the second type of emission is much faster than the process of detecting important signals associated with the first type of emission. Therefore, an additional detector can be used to provide an initial division of the sample into regions that may have similar properties, and then grouping the first type of emission for these regions. This improves the quality and speed of the method as described herein.

[0019] In one embodiment, the step of dividing at least a portion of the scanned area of ​​the sample into a plurality of segments is performed for dividing at least one of the plurality of regions. Thus, information related to the second type of emission is used to create the regions, and information related to the first type of emission is used to subdivide at least one of the regions into a plurality of segments.

[0020] In one embodiment, the second detector is arranged for detecting charged particles, in particular electrons, such as backscattered electrons. It is also conceivable that the first detector is arranged for detecting particles, in particular photons, such as x-ray photons.

[0021] The backscattering of electrons depends on the atomic number of the elements in the surface and the geometric relationship between the surface, the primary beam and the detector. Therefore, the backscattered electron image shows contour information, i.e. the boundaries between regions of different composition and topological information. Obtaining a backscattered electron image requires collecting only a sufficient number of electrons at each point to produce a reasonable contrast between points with different characteristics, and is therefore much faster than obtaining a sufficient number of X-rays at each point to compile a complete spectrum. Moreover, the probability of electron backscattering is greater than the probability that the electron causes characteristic X-ray emission of a specific frequency. It usually takes less than a microsecond to obtain sufficient backscattered electron image data at a single dwell point, while it usually takes more than a millisecond to obtain enough X-rays to obtain an analyzable spectrum at a single dwell point.

[0022] In one embodiment of the invention, an image is first acquired using a backscattered electron detector, and then the image is processed to identify regions that show the same elemental composition from the contrast. The beam is then scanned over the sample, at least over one or more identified regions, and preferably multiple times, to collect an X-ray spectrum representative of the region and to divide the region into a plurality of segments and subsequently into a plurality of sub-segments. The X-rays generated during the scanning of the backscattered electron detector can be advantageously used to already obtain information that can be used in subsequent segmentation.

[0023] As previously mentioned, the method may include the step of additionally scanning at least a portion of the area of ​​the sample to be inspected, and detecting the first type of emission using the first detector in response to the additional scanning. By repeating the scanning in a continuous or semi-continuous manner, more information about the first type of emission may be obtained to further improve the information obtained.

[0024] Advantageously, the steps of using the first type of emission and using the second type of emission may be used to provide a single color image of the sample to be examined. In particular, the color image may contain data representing the first type and the second type of emission. This is particularly advantageous when the backscattered electron image data is used in conjunction with the EDS data, as it allows the - typically greyscale - backscattered electron image to be combined with the color information generated by the EDS data.

[0025] In particular, when using segment information and subsegment information for providing the color image, a fast method for providing a color image of the sample to be examined is obtained, wherein the color image can simultaneously provide meaningful information about the sample. In particular, the color image can be presented in real time, i.e. can be generated within a few seconds or even less. In this way, the user can examine the sample faster, for example, he can identify the area of ​​interest on the sample faster.

[0026] Color information can be encoded in a color space that includes hue, value, and chroma. The first type of emission is used to define at least one of the hue and chroma of the color image; the second type of emission is used to define the value of the color image. Thus, in one embodiment, EDS data is used to define the color and color intensity of the image, while EM data is used as grayscale data.

[0027] In one embodiment, hue is used to define the material properties of the sample to be detected. For example, the combined spectrum of the sample in one of the multiple sections can be converted into a hue value, such as red, blue, yellow, green, etc., and the hue value can be used as a representation of the chemical composition of the section. In this way, for example, regions with atoms such as C, O, Al, Si, Mn, Fe and Ag can be identified because each atom can be preset to correspond to different colors. In this sense, it is conceivable that chromaticity, i.e., the saturation of color, is used to define the confidence measure of the material properties. For example, when the confidence is low, the image presented can be a complete grayscale image (no chromaticity). As the data associated with the first type of emission increases, the confidence also increases, so a more gray image can be presented. After a period of time, the confidence will be the largest, so a full color, i.e., a fully saturated image can be presented. In this way, the available color space (hue, value, chromaticity) is completely used to represent valuable information to the user.

[0028] According to the present invention, the emission of the first type is used to identify multiple segments, and for those multiple segments, the emission of the first type is combined to establish a combined spectrum of the corresponding segment. In addition, in one embodiment, when more data related to the emission of the first type is available, those multiple segments are further divided into sub-segments. This means that more information is obtained during scanning, and this information is used to further subdivide the segment into smaller sub-segments. In other words, the granularity increases. This can be used to present a color image to the user, wherein the emission of the first type is used to represent the hue and / or chroma (i.e., color information), and wherein the emission of the second type is used to represent the value (i.e., a normal EM image in grayscale). The emission of the second type has a relatively fast information rate, which means that the grayscale image can be presented to the user almost immediately. The emission of the first type has a relatively slow information rate, which means that it takes more time to obtain information of the entire scan area of ​​the sample. By grouping similar information together, and presenting the grouped information as hue and chroma on the grayscale image obtained by the EM data, the relevant information (i.e., EM data) is presented to the user immediately and more information is gradually added to it over time (i.e., on the order of seconds). Furthermore, due to the fact that the segments are subdivided into sub-segments and information is grouped together, the quality of the data also gradually increases over time. In summary, the user is presented with a gradually changing color image, which provides a very user-friendly experience.

[0029] According to one aspect of the present invention, there is provided a charged particle microscope for examining a sample using the above method. The apparatus according to the present invention comprises:

[0030] - 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 the sample;

[0031] - a sample stage located downstream of said final probe forming lens and arranged to hold said sample;

[0032] - a first detector for detecting a first type of emission originating from the sample in response to incident charged particles emitted from the charged particle source; and

[0033] - A control unit and a processing device connected to said first detector.

[0034] According to the invention, the charged particle microscope is arranged for performing the method according to the invention. Therefore, in particular, the device is arranged for detecting the emission of the first type from the sample using the first detector in response to the charged particle beam scanning over the sample area. The emission of the first type detected is collected into spectral information, for example by the processing device, and the spectral information is used to divide at least a part of the scanning area of ​​the sample into a plurality of segments. In addition, the device is arranged for combining the emission of the first type at different positions along the scan in at least one of the plurality of segments to produce a combined spectrum of the sample in the one of the plurality of segments. In particular, the processing device is arranged for combining the emission to produce a combined spectrum of the sample in the respective segments. Therefore, with the device, spectral information of the relevant segments can be collected and combined, which provides relevant information in a relatively fast manner, i.e. in a faster manner than collecting complete spectral information of different analysis points and then proceeding to the next analysis point. Point. Therefore, a device is obtained, with which information about the sample can be obtained in a faster and / or more accurate manner. Therefore, the object of the invention is achieved.

[0035] In one embodiment, the device further comprises a second detector for detecting a second type of emission originating from the sample in response to the incident charged particles emitted from the charged particle source. In particular, the data acquisition rate of the second type can be greater than the data acquisition rate of the first type. In other words, the second detector can provide information faster than the first detector, and the processor can be arranged to use the data of the second detector to process the data of the first detector. As already described with respect to the method, it is conceivable that information related to the second type of data is used to provide regions of the sample, which are then used to generate a combined spectrum of the first type of emission of the sample in the corresponding region. According to the method of the present invention, the region can then be subdivided into a plurality of segments, and a combined spectrum can be generated for each of the plurality of segments.

[0036] In one embodiment, the apparatus further comprises an output device for outputting a combination of the processed first detector information and the processed second detector information, in particular wherein the output device is arranged to output a color image, wherein the color space of the color image comprises hue, value and chroma. Here, the first type of emission can be used to define at least one of the hue and chroma of the color image; the second type of emission can be used to define the value of the color image.

[0037] The second detector may be a backscattered electron detector in one embodiment. In one embodiment, the first detector may be an EDS detector. The backscattered electron detector combined with the EDS detector can quickly provide an information image of the sample to be detected, such as a color image of the sample containing EM information and chemical composition information. Of course, it is understood that other detectors may also be used, and the use of these detectors may also provide specific advantages.

[0038] The present invention will now be described in detail based on exemplary embodiments and the accompanying schematic diagrams, in which:

[0039] Figure 1 - shows a longitudinal cross-sectional view of a charged particle microscope according to a first embodiment of the invention;

[0040] Figure 2 - shows a longitudinal cross-sectional view of a charged particle microscope according to a second embodiment of the invention;

[0041] Figure 3 - a schematic diagram showing an embodiment of the method according to the invention;

[0042] Figure 4 - a schematic diagram showing another embodiment of the method according to the invention;

[0043] Figure 5 - a schematic diagram showing another embodiment of the method according to the invention;

[0044] Figure 6 - a schematic diagram showing a further embodiment of the method according to the invention;

[0045] Figure 1 (not to scale) is a highly schematic depiction of one embodiment of a charged particle microscope M according to one embodiment of the present invention. More specifically, it shows 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 figure, within the vacuum housing 2, an electron beam B generated by an electron source 4 propagates along an electro-optical axis B' and passes through an electro-optical illuminator 6, directing / focusing the electrons onto a selected portion of a sample S (e.g., which may be (locally) thinned / planarized). A deflector 8 is also depicted, which may be used (among other things) to achieve a scanning motion of the electron beam B.

[0046] The sample S is fixed to a sample holder H, which can be positioned 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 sample holder H may include a finger that can move (among other things) in the XY plane (see the Cartesian coordinate system depicted; typically, movement parallel to Z and tilting about X / Y are also possible). This movement allows different parts of the sample S to be illuminated / imaged / inspected by an electron beam B traveling along the B' axis (in the Z direction), (and / or allows scanning movements to be performed as an alternative to beam scanning). If desired, an optional cooling device (not depicted) can be brought into close thermal contact with the sample holder H, for example to maintain it (and the sample S thereon) at cryogenic temperatures.

[0047] 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 can be detected with the aid of an analysis device, which may be, for example, a combined scintillator / photomultiplier tube or an EDX (energy dispersive X-ray spectrometer) module; in this case, an image can be constructed using essentially the same principles as in a SEM. Alternatively or additionally, however, electrons that pass (through) the specimen S, exit / emit therefrom and continue to propagate along the axis B' (basically, although usually with some deflection / scattering) can be studied. This transmitted electron flux enters an imaging system (projection lens) 24, which will typically include various electrostatic / magnetic lenses, deflectors, correctors (such as an stigmator), etc. In normal (non-scanning) TEM mode, this imaging system 24 can focus the transmitted electron flux onto a screen 26, such as a phosphor screen, which can be retracted / withdrawn (as indicated by arrow 26') if desired, so that it is away from the B' axis. An image (or diffraction pattern) of (a portion of) the sample S will be formed by the imaging system 24 on the screen 26, and this can 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 is mechanical and / or electrical in nature and is not depicted here, for example.

[0048] As an alternative to viewing the image on the screen 26, use can instead be made of the fact that the depth of focus of the electron flux leaving the imaging system 24 is typically quite large (e.g. of the order of 1 meter). Therefore, various other types of analysis equipment can be used downstream of the screen 26, such as:

[0049] -TEM camera 30. At camera 30, the electron flux can form a static image (or diffraction pattern) which can be processed by controller / processor 20 and displayed on a display device (not shown), such as a flat panel display, for example. When not needed, camera 30 can be retracted / withdrawn (as indicated by arrow 30') to move it away from the B' axis.

[0050] - STEM camera 32. The output from camera 32 can be recorded as a function of the (X,Y) scanning position of beam B on sample 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 include a single pixel of, for example, 20 mm in diameter, as opposed to the matrix of pixels characteristically present in camera 30. Furthermore, camera 32 will typically have a higher resolution than camera 30 (e.g., 10 pixels per second). 2 images per second) at much higher acquisition rates (e.g., 10 6 Again, when not needed, the camera 32 can be retracted / withdrawn (as schematically indicated by arrow 32') to move it away from the axis B' (although in the case of, for example, an annular dark field camera 32, such retraction is not necessary; in such a camera, the central hole would allow flux to pass when the camera is not in use).

[0051] As an alternative to imaging using cameras 30 or 32 , it is also possible to call upon a spectroscopic device 34 , which can be an EELS module, for example.

[0052] It should be noted that the order / position of items 30 , 32 and 34 is not strict and many possible variations can be envisaged. For example, the spectroscopic device 34 can also be integrated into the imaging system 24 .

[0053] 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 sample is viewed along different lines of sight using a source and (diametrically opposed) detectors to obtain penetrating views of the sample from a variety of angles.

[0054] Note that a controller (computer processor) 20 is connected to the various illustrated components via control lines (buses) 20'. This controller 20 may provide various functions, such as synchronizing actions, providing set points, processing signals, performing calculations, and displaying messages / information on a display device (not shown). 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.

[0055] The skilled person will appreciate that the interior of the housing 2 need not 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' where possible, in the form of a small tube (e.g., of the order of 1 cm in diameter) through which the electron beam used passes, but widened to accommodate structures such as the charged particle source 4, the sample holder H, the screen 26, the camera 30, the camera 32, the spectroscopic device 34, etc.

[0056] The charged particle microscope M according to the present invention is implemented as follows Figure 1 As shown, it therefore 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 sample. The device also comprises a sample stage A, H, which is located downstream of the final probe forming lens 6 and is arranged to hold the sample S. The device also comprises a first detector 22 for detecting a first type of emission originating from the sample 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, 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 present invention comprises a control device 20, which is connected to the first detector 22 (schematically shown) (via line 20'). According to the present invention, the charged particle microscope M is used to perform the method according to the present invention, which will be described later with the aid of Figures 3 to 5 Explain it.

[0057] 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 present invention; more particularly, it shows an embodiment of a non-transmission type microscope M, which in this case is a SEM (although, in the context of the present invention, it may just be effectively an ion-based microscope, for example). Figure 1 Corresponding parts of the items in FIG. 1 are denoted by the same reference numerals and will not be discussed separately here. Figure 1 In particular, the following components are:

[0058] 2a: a vacuum port which can be opened to introduce objects (components, samples) into / remove objects (components, samples) from the interior of the vacuum chamber 2, or on which, for example, auxiliary equipment / modules can be mounted. If necessary, the microscope M may include a plurality of such ports 2a;

[0059] - 10a, 10b: schematically depicting lenses / optical elements in the light emitter 6;

[0060] -12: Voltage source, allowing the sample holder H or at least the sample S to be biased (floated) to a potential relative to ground if necessary;

[0061] -14: Display, such as FPD or CRT;

[0062] 22a, 22b: Segmented electron detector 22a comprising a plurality of independent detection segments (e.g. quadrants) arranged around a central hole 22b (allowing the passage of light beam B). Such a detector can be used, for example, to study (the angular dependence of) the output (second or backscattered) flux of electrons emitted from the sample S.

[0063] Therefore, if Figure 2 The charged particle microscope M shown comprises an optical column O, which comprises 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 sample S. The device also comprises a sample stage A, H located downstream of the final probe forming lens 6 and arranged to hold the sample S. The device also comprises a first detector 22 for detecting a first type of emission originating from the sample in response to the incident charged particle B emitted from the charged particle source 4. In the embodiment shown, the first detector 22 is the analytical device, 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 present invention comprises the control device 20, which is connected to the first detector 22 (via line 20').

[0064] Figure 1 and Figure 2 The device shown in can be used to examine a sample using the method according to the invention. Figures 3 to 5 Several embodiments of the method according to the present invention are shown in FIG. Generally, these methods all comprise the following steps:

[0065] - using the first detector 22, in response to the light beam B being scanned over the area 50 of the sample S, detecting a first type of emission from the sample.

[0066] - using the spectral information G of the detected first type of emission, dividing at least a portion of the scanned area 50 of the sample into a plurality of segments 51; 61, 62; 81-87; and

[0067] - combining emissions of the first type at different positions along the scan in at least one of said plurality of sectors 51; 61, 62; 81-87 to produce a combined spectrum of the sample in said one of said plurality of sectors.

[0068] Reference now Figure 3 , schematically illustrating a first embodiment of the method according to the present invention. Figure 3 On the left side, a region 50 of a sample to be examined is schematically shown with acquired data points 54a, 54b, and on the right side, a representation 150 of the acquired data is shown.

[0069] A region of the sample is scanned with a charged particle beam 50. A first detector, such as a reference Figure 1 and Figure 2 The EDS detector described is used to detect emissions of a first type from the sample in response to a beam being scanned over a region 50 of the sample. These emissions are Figure 3 The data points 54a (white dots) and 54b (black dots) in are schematically represented. Data point 54a represents a different emission than data point 54b, meaning that the detector detects different signals at these different locations. For example, this can be the result of white data points 54a representing a first material and black data points 54b representing a second material (different from the first material). As shown in the left-hand sequence, from top to bottom, the data points 54a, 54b are relatively sparse at the beginning and increase as the scan continues. In the topmost step, the spectral information of the detected first type of emission data points 54a, 54b is used to divide the scan area 50 of the sample into multiple segments 51. Here, the scan area 50 is divided into four regular rectangular segments 51, although this shape and this regularity are not required, which will be referred to later. Figure 4-6 Give a description.

[0070] Reference now Figure 3 , which shows a representation 150 of the acquired data, it can be seen that for each segment 51, the first type of emission at different positions along the scan in each segment 51 is combined to produce a combined spectrum of the segment 51. In the embodiment shown, this means that if there are essentially only black dots in the segment 51, the segment is represented as a black segment 154b. If there are essentially only white dots, the segment is represented as a white segment 154a. In other words, the area 150 of the sample is divided into segments 51, and each segment is given a representation value 154a, 154b according to the data points assigned in the corresponding segment 51. Those skilled in the art will understand that the acquired data points 54a, 54b can in principle have many values ​​(not only black or white), and the representation value can be arbitrarily selected according to the desired application. The example shown is merely an illustration of a single possibility and is not intended to be limiting.

[0071] Now, as the number of data points 54a, 54b increases (in Figure 3 In the sequence of: from top to bottom), a segment 51 can be subdivided into a plurality of subsegments 52, and even smaller subsegments 53. The spectral information of the segment 51 and the subsegment 52 are used for this respectively. In one embodiment, this means that the total number of data points is used for the subdivision into one or more subsegments: once the total number of data points exceeds a certain threshold, the division into a segment, a subsegment or a further subsegment is performed.

[0072] For these sub-segments, the spectral information of the detected emission data points 54a, 54b of the first type in each of said sub-segments (or smaller sub-segments) is used to provide a combined sub-spectrum 155a, 155b, or a further sub-spectrum 156a, 156b of the sample can be used as a representative value (see Figure 3 ). It can therefore be seen that the granularity and precision of the represented data (right side) increases as more data points are acquired: the image becomes more detailed and contains more information.

[0073] Figure 4 As shown, in one embodiment, it is not necessary to divide each segment 51 into sub-segments at the same time. Figure 4 As shown, once enough data points 54a', 54b' are contained in the segment 51', the segment 51' can be divided into sub-segments 52'. If there are not enough data points, the segment is not divided into sub-segments. The same is true for dividing the sub-segment 52' into further sub-segments 53'. Figure 4 In the embodiment shown, the white data points are numerous and relatively close to each other, making the local division into sub-segments 52' and further sub-segments 53' very convenient. On the other hand, in the upper right segment, there is only one black data point, so no subdivision of this segment is performed.

[0074] Figure 5 It is shown that the segments and sub-segments do not have to have regular shapes. At the beginning, a region 50 of the sample is scanned, and the spectral information G s61 , G s62 The region 50 is divided into segments 61, 62. Here, the shapes of the segments 61, 62 are irregular, i.e., not square or rectangular. As more information is obtained during further scanning, further spectral information G s63 For adjusting the shape of the segments 61, 62 into adjusted segments 61', 62' and creating another segment 63. Additional segments 64, 65, 66 are also introduced. These segments 61-66 (including the adjusted segments 61', 62') can then be divided into sub-segments 61'a, 61'b, 62'a, 62'b, for example Figure 5A further division into other subsections (not shown) is also possible.

[0075] In one embodiment, if Figure 6 As shown, a second detector is used to provide an initial division of the region. Thus, using the second detector, a second type of emission from the sample 50 is detected in response to the scanning of the beam over the region of the sample, and the scanned region 50 of the sample is divided into a plurality of regions 71-78. Then, the emission of the first type (i.e., obtained using the first detector) at different positions along the scan in at least one of the plurality of regions 71-78 is combined to produce a combined spectrum 93 of the sample in the regions 71-78.

[0076] The second detector may be arranged to detect charged particles, in particular electrons. The first detector may be arranged to detect particles, in particular photons, such as x-ray photons (e.g., by EDS). For example, the EM data 91 may be used to initially partition regions 71-78, which are then used at least in part as boundaries for the EDS data 92 to group them into combined spectra for that region. In particular, the EM data 91 is well versed in providing profile information that may provide an indication of similar EDS data to be expected for a particular profile.

[0077] Figure 6 The first detector detects the first type of emissions and these emissions are used to define the regions 81-87 (with reference to FIG. 1 ). Figure 3-5 As more emissions are detected, the segments 81-87 can be redefined, resulting in a stacked set of segments 92. All information of the stacked set 92 can be used, or only a single piece of information, such as the latest information, can be used. The data 91 obtained in the first process is then combined 99 with the data 92 obtained in the second process to generate a combined data set 93, for example in the form of a color image 93. In the combined image, at least one region 77 is identified using the second type of emission, and in this region 77, the first type of emission is used to provide a combined spectrum 97. In this way, for example, a single image with improved accuracy can be obtained. As previously described, the single image can contain color information.

[0078] exist Figure 6In an embodiment, it is advantageous to perform a first process (top) including region segmentation before dividing the scanned region into segments. As an example: EM data can be used to define regions based on contours, and EDS data (or comparable data) is used to divide these regions into segments (and sub-segments, if applicable). Typically, relatively fast data can be used to perform a first segmentation of the regions, and relatively slow data can be used to divide these regions into segments and sub-segments.

[0079] It is conceivable that the area 50 to be scanned is scanned multiple times to obtain the required amount of data. The multiple scans may include scanning only a portion of the area 50 of the sample. For example, it is conceivable that based on a first scan (or a first set of scans), an area of ​​interest and an area of ​​no interest are defined, and in a second scan (or a second set of scans) only the area of ​​interest is scanned. This increases the efficiency of the method. In particular, the data obtained from the second type of emission can be used to define the area of ​​interest, i.e., the EM data can be used to define the area of ​​interest that is scanned, in particular, to obtain EDS data.

[0080] The invention has been described above with reference to several embodiments. The protection desired is defined by the appended claims.

Claims

1. A method for examining a sample using a charged particle microscope, comprising: - detecting, using a first detector, emissions of a first type from the sample in response to the beam being scanned over an area of ​​the sample; - dividing at least a portion of the scanned area of ​​the sample into a plurality of segments using the spectral information of the detected first type of emission; - combining emissions of the first type at different positions along a scan in at least one of the plurality of segments to produce a combined spectrum of the sample in the one of the plurality of segments.

2. The method according to claim 1, further comprising: - using the spectral information of the detected emission of the first type, dividing at least one of the plurality of segments into a plurality of sub-segments; - combining emissions of the first type at different positions along the scan in at least one of the plurality of sub-segments to produce a combined sub-spectrum of the sample in the one of the plurality of sub-segments.

3. The method according to claim 1 or 2, further comprising: - detecting a second type of emission from the sample using a second detector in response to the light beam being scanned over the area of ​​the sample; - using the second type of emission, dividing the scanned area of ​​the sample into a plurality of areas; - combining the emission of the first type at different positions along the scan in at least one of the plurality of regions to produce a combined spectrum of the sample in that region.

4. The method according to claim 3, wherein the step of dividing the scanning area of ​​the sample into a plurality of areas is performed before the step of dividing at least a part of the scanning area of ​​the sample into a plurality of sections.

5. The method according to claim 3, wherein the step of dividing at least a portion of the scanning area of ​​the sample into a plurality of sections is performed for dividing at least one of the plurality of areas. The method of claim 3 , wherein the second detector is arranged to detect charged particles. The method of claim 6 , wherein the charged particles are electrons.

8. The method of claim 1 or 2, wherein the first detector is arranged to detect particles.

9. The method of claim 8, wherein the particles are photons.

10. The method of claim 9, wherein the photons are x-ray photons.

11. A method according to claim 1 or 2, comprising the step of additionally scanning at least a portion of the area of ​​the sample to be inspected, and detecting the first type of emission using the first detector in response to the additional scanning of at least a portion of the area of ​​the sample to be inspected.

12. A method according to claim 3, comprising the steps of using a first type of emission and using a second type of emission for providing a single colour image of the sample to be inspected.

13. The method of claim 2, wherein the segment information and the sub-segment information are used to provide a single color image.

14. The method of claim 12, wherein the color space of the color image includes hue, value, and chroma, and wherein: - a first type of emission is used to define at least one of a hue and a chroma of said color image; and - The second type of emission is used to define the value of said color image.

15. A method according to claim 14, wherein hue is used to define a material property of the sample to be inspected, and wherein the chromaticity is used to define a measure of confidence in the material property.

16. A charged particle microscope for examining a sample using a method according to any one 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 the charged particle beam emitted from said charged particle source onto the sample; - a sample stage located downstream of said final probe forming lens and arranged to hold said sample; - a first detector for detecting a first type of emission originating from the sample in response to incident charged particles emitted from the charged particle source; - 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 any one of claims 1-15.

17. The charged particle microscope of claim 16, further comprising a second detector for detecting a second type of emission originating from the sample in response to incident charged particles emitted from the charged particle source.

18. The charged particle microscope of claim 17, further comprising an output device for outputting a combination of the processed first detector information and the processed second detector information.

19. A charged particle microscope according to claim 18, wherein the output device is arranged to output a color image, wherein the color space of the color image comprises hue, value and chroma, and wherein: - a first type of emission is used to define at least one of a hue and a chroma of said color image; and - The second type of emission is used to define the value of said color image.

Images