阅读说明：本技术 使用带电粒子显微镜检查样品的方法 (Method for examining a sample using a charged particle microscope ) 是由 T.图玛 J.赫拉迪尔 P.赫拉文卡 于 2019-08-19 设计创作，主要内容包括：本发明涉及一种使用带电粒子显微镜检查样品的方法。该方法包括以下步骤：使用第一检测器,响应于扫描过样品的区域的光束,检测来自样品的第一类型的发射。然后,使用所检测的第一类型的发射的光谱信息将所述样品的扫描区域的至少一部分分成多个区段。根据本发明,在所述多个区段中的至少一个区段中沿着扫描的不同位置处的第一类型的发射可以被组合以产生在所述多个区段的所述一个中的样品的组合光谱。在一个实施方案中,第二检测器用于检测第二类型的发射,并且这用于将样品的区域划分为多个区域。第一检测器可以是EDS,第二检测器可以基于EM。这样,EDS数据和EM数据可以有效地组合以产生彩色图像。(The present invention relates to a method of inspecting a sample using a charged particle microscope. The method comprises the following steps: a first type of emission from the sample is detected in response to the beam of light scanning across an area of the sample using a first detector. At least a portion of the scanned area of the sample is then divided into a plurality of segments using the detected spectral information of the first type of emission. According to the invention, the first type of emission at different positions along the scan in at least one of the plurality of segments may be combined to produce a combined spectrum of the sample in said 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 areas. The first detector may be an EDS and the second detector may be EM based. In this way, the EDS data and the EM data may be effectively combined to produce a color image.)

1. A method of inspecting a sample using a charged particle microscope, comprising:

-detecting a first type of emission from the sample in response to the beam of light scanning across the area of the sample using a first detector;

-dividing at least a portion of the scanned area of the sample into a plurality of sections using the detected spectral information of the first type of emission;

-combining the first type of emission at different positions along the scan in at least one of the plurality of segments to produce a combined spectrum of the sample in said one of the plurality of segments.

2. The method of claim 1, further comprising:

-dividing at least one of the plurality of segments into a plurality of sub-segments using the detected spectral information of the first type of emission;

-combining the first type of emission 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 said one of the plurality of sub-segments.

3. The method of claim 1 or 2, further comprising:

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

-dividing the scan area of the sample into a plurality of areas using the second type of emission;

-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.

4. The method of claim 3, wherein the step of dividing a scanned area of the sample into a plurality of regions is performed before the step of dividing at least a portion of the scanned area of the sample into a plurality of segments.

5. The method according to claim 3 or 4, wherein said step of dividing at least a part of a scanned area of said sample into a plurality of sections is performed for dividing at least one of said plurality of areas.

6. A method according to claim 3, 4 or 5, wherein the second detector is arranged for detecting charged particles, in particular electrons.

7. The method according to any of the preceding claims, wherein the first detector is arranged for detecting particles, in particular photons, such as x-ray photons.

8. A method according to any one of the preceding claims, comprising the step of additionally scanning at least a partial region of a sample to be examined, and detecting the first type of emission in response to the additional scanning using the first detector.

9. A method according to any preceding claim, when dependent on claim 3, comprising the step 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.

10. The method according to claims 2 and 9, wherein the color image is provided using section information and sub-section information.

11. The method of claim 9 or 10, wherein the color space of the color image comprises hue, value, and chroma, wherein:

-a first type of emission is used to define at least one of hue and chroma of the color image; and

-a second type of emission is used to define the values of the color image.

12. The method of claim 11, wherein hue is used to define a material property of a sample to be inspected, and wherein the chroma is used to define a measure of confidence in the material property.

13. Charged particle microscope for examining a sample using a method according to one or more of the preceding claims and comprising:

-an optical column comprising a charged particle source, a final probe forming lens and a scanner for focusing a beam of charged particles emitted from the charged particle source onto a sample;

-a sample stage located downstream of the final probe-forming lens and arranged for holding the sample;

-a first detector for detecting a first type of emission from the sample in response to incidence of charged particles emitted from the charged particle source;

-a control unit and a processing device connected to the first detector;

wherein the charged particle microscope is used for performing the method according to one or more of the preceding claims.

14. The charged particle microscope of claim 13, further comprising a second detector for detecting a second type of emission from the sample in response to incidence of charged particles emitted from the charged particle source.

15. Charged particle microscope according to claim 14, further comprising 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 for outputting a color image, wherein a 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 hue and chroma of the color image; and

-a second type of emission is used to define the values of the color image.

Technical Field

The present invention relates to a method of inspecting a sample using a charged particle microscope, comprising the steps of: detecting a first type of emission from the sample in response to the beam of charged particles scanning across an area of the sample using a first detector, and inspecting the sample using spectral information of the detected first type of emission.

Background

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 microscopy has evolved into a number of well-known classes of devices, such as Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Scanning Transmission Electron Microscopy (STEM), as well as various sub-classes, such as so-called "dual beam" devices (e.g., FIB-SEM), which additionally employ "machining" of a Focused Ion Beam (FIB), allowing supporting activities such as, for example, ion beam milling or Ion Beam Induced Deposition (IBID). The skilled person will be familiar with different kinds of charged particle microscopy.

The emission of "secondary" radiation from the sample is accelerated by irradiating the sample with a scanning electron beam, 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 the emitted radiation may be detected and used for sample analysis.

Typically, in an SEM, backscattered electrons are detected by a solid state detector, where each backscattered electron is amplified in the semiconductor detector producing many electron-hole pairs. When scanning the beam, the backscattered electron detector signals are used to form an image, and as the main beam is moved over the sample, the brightness of each image point is determined by the number of backscattered electrons detected at the corresponding point on the sample. The image provides only information about the topology of the sample to be examined.

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

One disadvantage of EDS is that it takes a considerable amount of time to accumulate the X-ray spectra of the sample. Typically, a grid with discrete analysis points is used. When the EDS detector records X-rays, the electron beam stays on each analysis spot. Once sufficient X-ray counts have been recorded, the beam moves to the next analysis point. The signals from the EDS detector are fed to a signal processing unit which establishes an x-ray spectral curve for each analysis point which can be matched against a wide library of known minerals to select the best match for that analysis point.

Disclosure of Invention

It is therefore an object of the present invention to provide an improved method of inspecting a sample using a charged particle microscope, wherein spectral information of the detected emissions is used to inspect the sample. In particular, it is an object of the present invention to provide a method and apparatus for more quickly and/or more accurately obtaining information about a sample.

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

Thus, spectral information of the detected first type of emission is collected during a light beam scan in an area of the sample. The emission detected by the first detector may be associated with a particular scanning beam position, i.e. may be associated with a particular position on the sample. This means that spectral information of corresponding locations on the sample can also be collected and/or determined. The obtained spectral information of different locations can be compared with each other. In particular, where the spectral information associated with two or more different locations is substantially the same, this means that the points on the sample may be similar, for example in terms of chemical composition, and thus related to each other. Thus, information relating to these two or more different locations but having similar characteristics may be used to group these locations together and define a first section of the sample being examined. Likewise, two or more other different locations having substantially the same or similar spectral information may also be combined together to define a second section of the sample being examined.

Instead of collecting the complete spectral information of different analysis points and then transferring to the next analysis point, in the method according to the invention a light beam is used to scan the sample and simultaneously collect spectral information of a plurality of analysis points. The scanning of the beam is relatively fast and can be continuous or semi-continuous 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 actually provide information, while other analysis points may 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 invention can provide more qualitative information for the entire sample more quickly. In addition, in case of multiple scans of the sample, the accuracy of the method according to the invention is further improved, since the sparsity of the collected data will be reduced. Thus, it can be seen from the above that the objects of the invention are achieved.

Further embodiments of the invention are in accordance with the dependent claims. Details of these further embodiments will be explained below.

Detailed Description

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

In one embodiment, the method further comprises the steps of:

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

-dividing the scan area of the sample into a plurality of areas using the second type of emission;

-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.

In this embodiment, an additional detector is used to detect the second type of emission. These second types of transmissions are different from the first types of transmissions. Information relating to these second types of emissions is used to define the area of the sample. These regions are then used to generate a combined spectrum of the sample in the region using the first type of emission.

In one embodiment, said step of dividing the scanned area of the sample into a plurality of regions is performed before said step of dividing at least a portion of the scanned area of the sample into a plurality of segments. In particular, the second type of transmission may provide a higher information rate than the first type of transmission. In other words, the process of detecting the important signals related to the second type of transmission is much faster than the process of detecting the important signals related to the first type of transmission. Thus, additional detectors may be used to provide that the sample is initially divided into regions that may have similar properties, and then the first type of emission is grouped for these regions. This improves the quality and speed of the method as described herein.

In one embodiment, said step of dividing at least a portion of the scanned area of the sample into a plurality of sections is performed for dividing at least one of the plurality of areas. Thus, information relating to the second type of transmission is used to create the areas, and information relating to the first type of transmission is used to subdivide at least one of the areas into a plurality of sections.

In an embodiment, the second detector is arranged for detecting charged particles, in particular electrons, e.g. backscattered electrons. It is also conceivable that the first detector is arranged for detecting particles, in particular photons, for example x-ray photons.

The backscattering of electrons depends on the atomic number of the elements in the surface and the geometrical relationship between the surface, the main beam and the detector. Therefore, the backscattered electron image shows contour information, i.e. the boundaries between areas of different composition and topological information. Obtaining a backscattered electron image requires collecting only a sufficient number of electrons at each point to produce 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 of an electron causing a characteristic X-ray emission at a particular frequency. It typically takes less than a microsecond to obtain enough backscattered electron image data at a single dwell point, while it typically takes more than a millisecond to obtain enough X-rays to obtain an analyzable spectrum at a single dwell point.

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 exhibiting the same elemental composition from contrast. The beam is then scanned over the sample, at least over one or more identified regions, and preferably a plurality of scans, to collect an X-ray spectrum representative of the region and divide the region into a plurality of segments, and subsequently into a plurality of subsections. The X-rays generated during the backscatter electron detector scan can advantageously be used to already obtain information that can be used in subsequent segments.

As previously mentioned, the method may comprise the step of additionally scanning at least a part of the area of the sample to be examined, and detecting said first type of emission in response to said additional scanning using said first detector. By repeating the scanning in a continuous or semi-continuous manner, more information about the first type of emission can be obtained to further improve the acquired information.

Advantageously, the steps of using a first type of emission and using a second type of emission may be used to provide a single colour 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 EDS data, as it allows-typically a grey-scale-backscattered electron image to be combined with the colour information produced by the EDS data.

In particular when using the segmentation information and the sub-segmentation information for providing the color image, a fast method for providing a color image of a sample to be examined is obtained, wherein the color image simultaneously provides meaningful information of the sample. In particular, the color image may be rendered in real time, i.e. may be generated in a few seconds or even less. In this way, the user can examine the sample faster, e.g. he can identify the region of interest on the sample faster.

The color information may 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 hue and chroma of the color image; the second type of emission is used to define the values of the color image. Thus, in one embodiment, the EDS data is used to define the color and color intensity of the image, while the EM data is used as grayscale data.

In one embodiment, the color tone is used to define the material properties of the sample to be tested. For example, the combined spectrum of the sample in the one of the plurality of segments may be converted to a hue value, e.g., red, blue, yellow, green, etc., and the hue value may be used as a representation of the chemical composition of the segment. Thus, for example, regions having atoms of, for example, C, O, Al, Si, Mn, Fe, and Ag can be identified because each atom can be set in advance to correspond to a different color. In this sense, it is conceivable that the color shade, i.e. the saturation of the color, is used to define a confidence measure for the material property. For example, when the confidence is low, the rendered image may be a full grayscale image (no chroma). As the data relating to the first type of emission increases, the confidence also increases and therefore a grayer image can be presented. After some time, the confidence will be maximum and therefore a full color, i.e. a fully saturated image, can be presented. In this way, the available color space (hue, value, chroma) is fully used to represent valuable information to the user.

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

According to an aspect of the present invention, there is provided a charged particle microscope for inspecting a sample using the above method. The device according to the invention comprises:

-an optical column comprising a charged particle source, a final probe forming lens and a scanner for focusing a beam of charged particles emitted from the charged particle source onto a sample;

-a sample stage located downstream of the final probe-forming lens and arranged for holding the sample;

-a first detector for detecting a first type of emission from the sample in response to incidence of charged particles emitted from the charged particle source; and

-a control unit and a processing device connected to the first detector.

According to the invention, the charged particle microscope arrangement is used for carrying out the method according to the invention. Thus, in particular, the apparatus is arranged for detecting a first type of emission from the sample using said first detector in response to the beam of charged particles scanning over the sample area. The detected first type of emission is collected into spectral information, for example by the processing device, and the spectral information is used to divide at least a portion of the scanned area of the sample into a plurality of segments. In addition, the apparatus is arranged to combine the emissions 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 said one of the plurality of segments. In particular, the processing device is arranged to combine the emissions to produce a combined spectrum of the sample in the respective section. Thus, with this device, spectral information of relevant sections 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. And (4) point. Hereby, a device is obtained with which information about a sample can be acquired in a faster and/or more accurate manner. Thus, the object of the present invention is achieved.

In one embodiment, the apparatus further comprises a second detector for detecting a second type of emission from the sample in response to incidence of charged particles emitted from the charged particle source. In particular, the second type of data acquisition rate may be greater than the first type of data acquisition rate. In other words, the second detector may provide information faster than the first detector, and the processor may be arranged for processing data of the first detector using said data of the second detector. As already described in relation to the method, it is conceivable that information relating 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 respective region. According to the method of the invention, the region may then be subdivided into a plurality of sections, and a combined spectrum may be generated for each of the plurality of sections.

In an 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 for outputting a color image, wherein a color space of said color image comprises hue, value and chroma. Here, the first type of emission may be used to define at least one of a hue and a chroma of the color image; the second type of emission may be used to define the values of the color image.

The second detector may in one embodiment be a backscattered electron detector. In one embodiment, the first detector may be an EDS detector. The combination of a backscattered electron detector with an EDS detector can rapidly provide an informative image of the sample to be detected, such as a color image of the sample containing EM information and chemical composition information. It will of course be appreciated that other detectors may be used and that the use of such detectors may also provide particular advantages.

The invention will now be described in detail in terms of exemplary embodiments and the accompanying schematic drawings in which:

fig. 1-shows a longitudinal cross-sectional view of a charged particle microscope according to a first embodiment of the invention;

fig. 2-shows a longitudinal cross-sectional view of a charged particle microscope according to a second embodiment of the invention;

figure 3-shows a schematic diagram of an embodiment of the method according to the invention;

figure 4-shows a schematic diagram of another embodiment of the method according to the invention;

figure 5-shows a schematic diagram of another embodiment of the method according to the invention;

figure 6-shows a schematic view of yet another embodiment of the method according to the invention;

FIG. 1 (not to scale) is a highly schematic depiction of one embodiment of a charged particle microscope M according to one embodiment of the invention. More particularly, it shows a transmission microscope M, which in this case is a TEM/STEM (although, in the context of the present invention, it may effectively be a SEM only (see fig. 2), or e.g. an ion-based microscope). In fig. 1, within a vacuum enclosure 2, an electron beam B generated by an electron source 4 propagates along an electron-optical axis B' and passes through an electro-optical illuminator 6, directing/focusing the electrons onto selected portions of a sample S (e.g., it may be (locally) thinned/planarized). Also depicted is a deflector 8 which (among other things) can be used to achieve a scanning motion of the electron beam B.

The sample S is fixed on a sample holder H, which can be placed with multiple degrees of freedom by a positioning device/table a, which moves the cradle a' into the (detachably) attached holder H; for example, the sample holder H may comprise a finger that can be moved (among other things) in the XY plane (see the Cartesian coordinate system depicted; generally, motion parallel to Z and tilt about X/Y is also possible). This movement allows different parts of the sample S to be illuminated/imaged/inspected by the electron beam B travelling along the B' axis (in the Z direction), (and/or allows the scanning movement to be performed as an alternative to beam scanning). An optional cooling device (not depicted) can be brought into intimate thermal contact with sample holder H, if desired, for example, to maintain it (and sample S thereon) at cryogenic temperatures.

The electron beam B will interact with the sample S such that various types of "stimulated" radiation are emitted from the sample 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 by means of an analysis device 22, which may be, for example, a combined scintillator/photomultiplier tube or an EDX (energy dispersive X-ray spectrometer) module; in this case, the image can be constructed using substantially the same principle as in the SEM. However, alternatively or additionally, electrons may be studied that pass through (pass through) the sample S, exit/emanate therefrom and continue to propagate (substantially, although typically with some deflection/scattering) along the axis B'. This flux of transmitted electrons enters an imaging system (projection lens) 24, which typically will include various electrostatic/magnetic lenses, deflectors, correctors (e.g., stigmators), and the like. In a normal (non-scanning) TEM mode, the imaging system 24 can focus the flux of transmitted electrons onto the phosphor screen 26, which can be retracted/withdrawn (as indicated by arrow 26 ') to move it away from the B' axis, if desired. 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 an appropriate part of the wall of the housing 2. For example, the retraction mechanism of the screen 26 is mechanical and/or electrical in nature and is not depicted here.

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

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

STEM camera 32. The output from camera 32 may be recorded as a function of the (X, Y) scan position of beam B on sample S, and an image may be constructed that is a "map" of the output from camera 32 as a function of X, Y. Camera with a camera module32 may comprise individual pixels of diameter, for example, 20mm, as opposed to the pixel matrix characteristically present in the camera 30. Further, camera 32 will typically have a larger (e.g., 10 per second) than camera 30²Individual images) at a much higher acquisition rate (e.g., 10 per second⁶A point). Again, camera 32 may be retracted/removed (as schematically shown by arrow 32 ') away from axis B' when not needed (although such retraction is not necessary in the case of, for example, an annular dark field camera 32; in such a camera, the central aperture would allow flux to pass when the camera is not in use).

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

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

In the illustrated embodiment, the 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 observed along different lines of sight using a source and a (diametrically opposed) detector in order to obtain a penetrating view of the sample from various angles.

Note that the controller (computer processor) 20 is connected to the various illustrated components by 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). It goes without saying that the controller 20 (schematically depicted) may be (partially) internal or external to the casing 2 and may have an integral or composite structure as desired.

The skilled artisan will appreciate that the interior of the housing 2 need not be maintained at a strict vacuum; for example, in the so-called "ambient 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 this may be advantageous: the volume of the housing 2 is limited so that it substantially surrounds the axis B', where possible, in the form of a small tube (e.g. of the order of 1cm in diameter) through which the electron beam used passes, but is widened to accommodate structures such as the source 4, sample holder H, screen 26, camera 30, camera 32, spectroscopic apparatus 34, etc.

A charged particle microscope M according to the invention, an embodiment of which is shown in fig. 1, thus comprises an optical column O comprising a charged particle source 4, a final probe forming lens 6 and a scanner 8 for focusing a beam B of charged particles emitted from said charged particle source 4 onto a sample. The apparatus further comprises a sample stage A, H located downstream of the final probe-forming lens 6 and arranged to hold the sample S. The apparatus further comprises a first detector 22 for detecting a first type of emission from the sample in response to incidence of charged particles B emitted from the charged particle source 4. In the illustrated embodiment, the first detector 22 is an analytical device 22, which as previously described may be a combined scintillator/photomultiplier tube or EDS (energy dispersive X-ray spectrometer) module. In a preferred embodiment, the first detector is an EDS. Furthermore, the apparatus according to the invention comprises a control device 20, which is connected (via a line 20') to said first detector 22 (schematically shown). According to the invention, the charged particle microscope M is used to carry out the method according to the invention, which will be explained later with the aid of fig. 3 to 5.

Referring now first to fig. 2, another embodiment of the device according to the present invention is shown. FIG. 2 (not to scale) is a highly schematic view of a charged particle microscope M according to the invention; more specifically, it shows an embodiment of a non-transmission microscope M, which in this case is a SEM (although, in the context of the present invention, it may just as effectively be an ion-based microscope, for example). In this figure, parts corresponding to items in fig. 1 are denoted with the same reference numerals and are not discussed separately here. The (special) additions to fig. 1 are the following:

-2 a: a vacuum port which can be opened to introduce/remove an article (component, standard) to/from the interior of the vacuum chamber 2, or on which auxiliary equipment/modules, for example, can be mounted. If desired, the microscope M may include a plurality of such ports 2 a;

-10a, 10 b: schematically depicting the lens/optical element in the light emitter 6;

-12: a voltage source, allowing the sample holder H, or at least the sample S, to be biased (floating) to a potential relative to ground, if required;

-14: displays, such as FPDs or CRTs;

-22a, 22 b: segmented electron detector 22a, which comprises a plurality of individual detection segments (e.g. quadrants) arranged around central aperture 22B (allowing passage of light beam B). Such a detector may for example be used to study (the angular dependence of) the output (second or backscattered) flux of electrons exiting from the sample S.

Thus, the charged particle microscope M as shown in fig. 2 comprises an optical column O comprising a charged particle source 4, final probe forming lenses 6, 10a, 10B and a scanner 8 for focusing a beam B of charged particles emitted from said charged particle source 4 onto a sample S. The apparatus further comprises a sample stage A, H located downstream of the final probe-forming lens 6 and arranged to hold the sample S. The apparatus further comprises a first detector 22 for detecting a first type of emission from the sample in response to 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 mentioned may be a combined scintillator/photomultiplier tube or EDS (energy dispersive X-ray spectrometer) module. In an alternative embodiment, the first detector 22 may be a segmented detector 22a, 22 b. In a preferred embodiment, the first detector is an EDS. Furthermore, the apparatus according to the invention comprises said control device 20, which is connected (via a line 20') to said first detector 22.

The device shown in fig. 1 and 2 can be used for examining samples with the method according to the invention. Several embodiments of the method according to the invention are shown in fig. 3 to 5. Generally, these methods all comprise the steps of:

detecting a first type of emission from the sample in response to the beam B scanning across the area 50 of the sample S using the first detector 22.

-dividing at least a part of the scanning area 50 of the sample into a plurality of sections 51 using the detected spectral information G of the first type of emission; 61. 62, a first step of mixing; 81-87; and

-in said plurality of sectors 51; 61. 62, a first step of mixing; at least one of 81-87 combines the first type of emission at different locations along the scan to produce a combined spectrum of the sample in said one of the plurality of segments.

Referring now to fig. 3, a first embodiment of the method according to the present invention is schematically shown. Fig. 3 schematically shows on the left a region 50 of the sample to be examined with acquired data 54a, 54b and on the right a representation 150 of the acquired data.

A region 50 of the sample is scanned with a beam of charged particles. A first detector, such as the EDS detector described with reference to fig. 1 and 2, is used to scan over an area 50 of the sample in response to the light beam to detect a first type of emission from the sample. These emissions are schematically represented by data points 54a (white dots) and 54b (black dots) in fig. 3. Data point 54a represents a different emission than data point 54b, meaning that the detector detects different signals at these different locations. This may be the result of, for example, a white dot 54a representing a first material and a black dot 54b representing a second material (different from the first material). As shown in the left hand side sequence, from top to bottom, the data information 54a, 54b is relatively sparse at the beginning and increases as the scan continues. In the topmost step, the spectral information of the detected first type of emission 54a, 54b is used to divide the scanning area 50 of the sample into a plurality of sections 51. Here, the scanning area 50 is divided into four regular rectangular sections 51, although such a shape and such a rule are not necessary, as will be described later with reference to fig. 4-6.

Referring now to the right side of figure 3, which shows a representation 150 of the acquired data, it can be seen that for each sector 51, the first type of emission at different locations along the scan in each sector 51 is combined to produce a combined spectrum for that sector 51. In the embodiment shown, this means that if there are substantially only black dots in the segment 51, the segment is represented as a black segment 154 b. If there is essentially only a white point, the field is indicated as white field 154 a. In other words, the area 150 of the sample is divided into sections 51, and each section is given a representative value 154a, 154b according to the data points assigned in the respective section 51. Those skilled in the art will appreciate that the acquired data 54a, 54b may in principle have many values (not only black or white), and the representative values may be arbitrarily selected depending on the desired application. The illustrated example is merely illustrative of a single possibility and is not intended to be limiting.

Now, as the number of data points 54a, 54b increases (in the sequence of FIG. 3: from top to bottom), the segment 51 may be subdivided into a plurality of subsections 52, and even smaller subsections 53. The spectral information of the section 51 and the sub-section 52, respectively, is used for this. In one embodiment, this means that the total number of data points is used for subdivision into one or more subsections: once the total number of data points exceeds a certain threshold, a division into sections, sub-sections or further sub-sections is made.

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

Fig. 4 illustrates that, in one embodiment, the division of sub-sections need not be done simultaneously for each section 51. As shown in fig. 4, once enough data points 54a ', 54b ' are contained in the segment 51 ', the segment 51 ' may be divided into subsections 52 '. If there are not enough data points, the section is not divided into subsections. The same is true for the division of the subsection 52 'into further subsections 53'. In the embodiment shown in fig. 4, the white data points are numerous and located relatively close to each other, so that local division into subsections 52 'and further subsections 53' is very convenient. On the other hand, in the upper right section, there is only one black data point, and therefore the section is not subdivided.

Fig. 5 shows that the segments and sub-segments do not necessarily have a regular shape. At the beginning, a region 50 of the sample is scanned, and spectral information G_s61、G_s62For dividing the area 50 into sections 61, 62. Here, the shape of the sections 61, 62 is irregular, i.e. not square or rectangular. Further spectral information G as more information is obtained during further scans_s63For adjusting the shape of the sections 61, 62 to the adjusted sections 61 ', 62' and creating a further section 63. Additional sections 64, 65, 66 are also introduced. These segments 61-66 (including adjusted segments 61 ', 62') may then be divided into subsections 61 'a, 61' b, 62 'a, 62' b, for example, as shown in FIG. 5. Further division into other subsections (not shown) is also possible.

In one embodiment, as shown in FIG. 6, a second detector is used to provide an initial partitioning of the area. Thus, using a second detector, a second type of emission from the sample 50 is detected in response to scanning of the beam over the area of the sample and the scanned area 50 of the sample is divided into a plurality of regions 71-78. The emissions of the first type (i.e., obtained with the first detector) at different locations along the scan in at least one of the plurality of regions 71-78 are then combined to produce a combined spectrum 93 of the sample in the regions 71-78.

The second detector may be arranged for detecting charged particles, in particular electrons. The first detector may be arranged for detecting 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 the regions 71-78, and then use these regions at least partially as boundaries for the EDS data 92 to group them into a combined spectrum for that region. In particular, the EM data 91 is very generic for providing contour information that can provide an indication that similar EDS data is expected for a particular contour.

Fig. 6 shows the use of a second type of emission detected by a second detector to identify regions 71-78 in a first procedure (top). In a second procedure (bottom), the first detector detects emissions of the first type and these are used to define the segments 81-87 (comparable to what was explained with reference to fig. 3-5). As more emissions are detected, the segments 81-87 may be redefined, thereby creating a stacked segment group 92. All of the information of stack group 92 may be used, or only a single piece of information, such as the most recent information, may 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, the second type of emission is used to identify at least one region 77, and in that 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 may be obtained. As previously described, the single image may contain color information.

In the embodiment of fig. 6, it is advantageous that the first process (top) comprising region division is performed before dividing the scanned region into segments. As an example: the EM data may be used to define regions based on contours, and the EDS data (or comparable data) is used to divide these regions into sections (and sub-sections, if applicable). In general, relatively fast data may be used to partition regions a first time, and relatively slow data may be used to partition the regions into sections and sub-sections.

It is contemplated that the area 50 to be scanned is scanned multiple times to obtain the desired amount of data. The multiple scans may include scanning only a portion of the area 50 of the sample. For example, it is conceivable to define a region of interest and a region of no interest on the basis of a first scan (or a first set of scans) and to scan only the region of interest in a second scan (or a second set of scans). This improves the efficiency of the process. In particular, data obtained from the second type of emission may be used to define a region of interest, i.e., EM data may be used to define a region of interest that is scanned, in particular, to obtain EDS data.

The present invention has been illustrated by the above several embodiments. The desired protection is defined by the appended claims.