Detector device, electron beam device and method for inspecting and / or imaging a sample

Abstract

A detector apparatus (10) for detecting signal electrons in an electron beam apparatus (100) is described. The detector device (10) comprises an electron detector (120) having a central opening (23) for the passage of a primary electron beam (105) and having one or more radially inner detector sections (21) and one or more radially outer detector sections (22) at least partially surrounding the central opening. The detector device is configured to amplify, at a first amplification intensity, one or more first detector signals caused by a first set of signal electrons incident on the one or more radially inner detector sections (21), at the same time, one or more second detector signals caused by a second set of signal electrons incident on the one or more radially outer detector sections (22) are amplified at a second amplification intensity higher than the first amplification intensity. Further described is an electron beam apparatus having the detector apparatus described herein, and a method of imaging and / or inspecting a sample with an electron beam apparatus as described herein.

Description

Technical Field

[0001] Embodiments described herein relate to detector devices for detecting signal electrons, such as secondary electrons (SE) and backscattered electrons (BSE), in an electron beam device, for example, in a scanning electron microscope configured to inspect and / or image a sample. Embodiments described herein relate in particular to electron detectors and electron beam devices having electron detectors for detecting signal electrons, in particular BSE. In particular, an electron beam device for inspecting a sample having a 3D structure by detecting BSE is described. Embodiments further relate to methods for inspecting and / or imaging a sample using an electron beam device. Background Art

[0002] Charged particle beam devices have many functions in a variety of industrial fields, including but not limited to critical dimension setting of semiconductor devices, defect review of semiconductor devices, inspection of semiconductor devices, exposure systems for lithography, imaging of various samples, detection equipment and test systems. Therefore, there is a high demand for structuring, testing and inspection of samples or specimens at the micrometer and nanometer scale.

[0003] Micrometer and nanometer scale process control, inspection or structuring are usually performed with charged particle beams, in particular electron beams, which are generated and focused in charged particle beam equipment, such as electron beam devices, in particular electron microscopes. Due to their short wavelength, charged particle beams provide better spatial resolution, for example compared to photon beams.

[0004] In recent years, there has been increasing interest in inspecting and / or imaging samples with 3D structures or structures with large aspect ratios (such as large depth to opening width ratios). Devices like 3D FinFETs and 3D NANDs have structures with large aspect ratios that are difficult to image in a scanning electron microscope (SEM) when using secondary electrons (SE), i.e., low energy signal electrons generated at the sample surface when the primary electron beam strikes the sample surface. SEs can hardly escape from structures with high aspect ratios and deeper sample layers and are generally not detectable with a reasonable signal-to-noise ratio. In particular, critical dimension (CD) measurements of high aspect ratio trenches, contact holes, and buried layers or structures are a challenge. Image modes using backscattered electrons (BSE), i.e., high energy electrons backscattered from the sample, are often used to improve the quality of imaging and / or inspection, especially in the semiconductor industry.

[0005] In modern charged particle beam inspection systems, it will be beneficial to detect backscattered electrons with high detection efficiency. This will allow to accurately check the sample surface extending substantially in the xy plane and both 3D structures with depth or burial in the z direction with high resolution. In some systems, the backscattered electrons leaving the sample at different angles relative to the optical axis are mainly detected by a detector device arranged near the sample (e.g., between the object lens and the sample, or near the object lens). Secondary electrons (SE) can be mainly detected by an electronic detector arranged at a distance farther from the sample (e.g., between the beam source and the object lens in a "through lens detection setting", or laterally relative to the optical axis of the system). However, particularly for the high energy BSE carrying valuable sample information that can be released from the sample at a large angle relative to the optical axis, it is difficult to reach a high BSE detection efficiency.

[0006] In view of the above, it would be beneficial to provide a detection device suitable for efficiently detecting backscattered electrons and an electron beam device having such a detection device. In addition, it would be beneficial to provide methods for inspecting and / or imaging topographic sample structures or buried sample layers that overcome at least some of the above problems. Summary of the invention

[0007] In view of the above, according to the independent claims, a detector device, an electron beam apparatus and a method of examining and / or imaging a sample with an electron beam are provided. Further aspects, advantages and features are apparent from the dependent claims, the description and the drawings.

[0008] According to one aspect, a detector device for detecting signal electrons in an electron beam device is provided. The detector device includes an electron detector having: a central opening for a primary electron beam to pass through; one or more radially inner detector segments, the one or more radially inner detector segments at least partially surrounding the central opening; and one or more radially outer detector segments, the one or more radially outer detector segments at least partially surrounding the central opening. The detector device is configured to amplify one or more first detector signals caused by a first group of signal electrons incident on the one or more radially inner detector segments with a first amplification intensity, while amplifying one or more second detector signals caused by a second group of signal electrons incident on the one or more radially outer detector segments with a second amplification intensity higher than the first amplification intensity.

[0009] In some embodiments, the detector device comprises an electronic detector and an amplification device, in particular a preamplifier, integrated with the electronic detector or arranged adjacent to the electronic detector. One or more first amplification circuits of the amplification device may be connected to one or more radially inner detector segments, and one or more second amplification circuits of the amplification device may be connected to one or more radially outer detector segments. The one or more first amplification circuits are configured to amplify one or more first detector signals with a first amplification strength, and the one or more second amplification circuits are configured to amplify one or more second detector signals with a second amplification strength higher than the first amplification strength.

[0010] According to a further aspect, an electron beam apparatus, in particular a scanning electron microscope, is provided, comprising a detector device as described herein.

[0011] The electron beam device may include: an electron source for generating a primary electron beam propagating along an optical axis; a sample stage for supporting a sample to be inspected; an objective lens for focusing the primary electron beam onto the sample to release signal electrons; and a detector device as described herein. The detector device is configured to amplify one or more first detector signals caused by a first group of signal electrons incident on one or more radially inner detector segments at a first amplification intensity, while amplifying one or more second detector signals caused by a second group of signal electrons incident on one or more radially outer detector segments at a second amplification intensity higher than the first amplification intensity.

[0012] According to another aspect, a method of imaging and / or inspecting a sample, in particular with an electron beam device as described herein, is provided.

[0013] The method includes: generating a primary electron beam propagating along an optical axis; focusing the primary electron beam onto a sample to cause emission of a first set of signal electrons and a second set of signal electrons, the second set of signal electrons propagating at a greater distance from the optical axis than the first set of signal electrons. The method further includes: amplifying one or more first detector signals caused by the first set of signal electrons incident on one or more radially inner detector segments of the electron detector at a first amplification intensity; and amplifying one or more second detector signals caused by the second set of signal electrons incident on one or more radially outer detector segments of the electron detector at a second amplification intensity higher than the first amplification intensity.

[0014] Embodiments also relate to apparatus for performing the disclosed methods and include apparatus parts for performing each of the described method features. The method features may be performed by hardware components, computers programmed by appropriate software, any combination of the two, or any other means. In addition, embodiments also relate to methods of making the apparatus, methods of using the apparatus to examine and / or image a sample, and methods of operating the apparatus. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to be able to understand the above features of the present disclosure in detail, the above brief summary can be described in more detail by referring to the embodiments. The accompanying drawings relate to the embodiments of the present disclosure and are described below:

[0016] Figure 1 is a schematic diagram of an electron beam apparatus with a detector device according to an embodiment described herein;

[0017] Figure 2 is a more detailed view of a detector apparatus as described herein;

[0018] Figure 3A shows a schematic perspective view of a detector apparatus with a segmented electron detector as described herein;

[0019] Figure 3B Shows Figure 3A a schematic top view of a detector device; and

[0020] Figure 4 is a flow chart of a method for imaging and / or inspecting a sample using an electron beam apparatus according to embodiments described herein. DETAILED DESCRIPTION

[0021] Reference will now be made in detail to various embodiments, one or more examples of which are illustrated in the accompanying drawings. In the following description, like reference numerals denote like parts. Generally, only the differences with respect to various embodiments are described. Each example is provided by way of explanation, but this is not meant to be limiting. Further, features illustrated or described as part of one embodiment may be used on other embodiments or used in conjunction with other embodiments to produce yet another embodiment. This specification is intended to include such modifications and changes.

[0022] The detector devices and electron beam arrangements described herein are configured for detecting signal electrons. Signal electrons particularly encompass secondary electrons (SE) and / or backscattered electrons (BSE), in particular both secondary electrons and backscattered electrons.

[0023] The samples, samples or wafers referred to herein include, but are not limited to, semiconductor wafers, semiconductor workpieces, and other workpieces, such as storage disks, etc. "Sample" may specifically be any workpiece that is structured or on which a material is deposited. Samples, samples or wafers may include surfaces to be inspected and / or imaged, such as surfaces that are structured or on which a layer or material pattern has been deposited. For example, a sample may be a substrate or wafer on which a plurality of electronic devices to be inspected are provided. The sample may have several layers, for example, a layer stack and / or one or more lower layers buried under one or more upper layers. According to some embodiments, the apparatus and methods described herein relate to electron beam inspection (EBI), critical dimension measurement, and defect review applications, wherein the apparatus and methods described herein may be beneficially used to obtain increased throughput and improved detection accuracy. According to some embodiments, electron beam inspection (EBI), critical dimension (CD) measurement tools, and / or defect review (DR) tools may be provided, in which high resolution, large field of view, and high scanning speed may be achieved.

[0024] Figure 1 A schematic diagram of an electron beam apparatus 100 for imaging and / or inspecting a sample 140 according to embodiments described herein is shown. The electron beam apparatus 100 comprises a detector device 10 having an electron detector 120 for detecting signal electrons emitted from the sample. Figure 2 A top view of the detector device 10 is shown to illustrate further details.

[0025] In some embodiments, the electron beam device 100 is a scanning electron microscope (SEM) comprising one or more scanning deflectors. The electron beam device 100 comprises an electron source 150 for generating a primary electron beam 105 propagating along an optical axis A. The primary electron beam 105 is directed to a sample 140 along the optical axis A to release signal electrons from the sample upon incidence. The sample 140 may be placed on a sample stage 50 comprising a sample support surface for supporting the sample 140, the sample support surface extending substantially in an xy plane. Optionally, the sample stage 50 may be moved in the xy plane and / or in the z direction to change the distance between the sample and the objective lens.

[0026] The electron source 150 may include, for example, a cold field emitter (CFE), a Schottky emitter, a thermal field emitter (TFE), or a high current and / or high brightness electron emitter.

[0027] The electron beam device 100 may include a number of further beam optical components not shown in the figures, such as but not limited to one or more condenser lenses, one or more beam deflectors, one or more beam aberration correctors, a beam splitter and / or one or more scanning deflectors.

[0028] The electron beam device 100 includes an objective lens 110 for focusing the primary electron beam 105 onto a sample 140, such as a magnetic objective lens, an electrostatic objective lens, or a magnetic-electrostatic composite objective lens.

[0029] The primary electron beam 105 passes through a column of the electron beam device 100 before striking a sample 140 to be imaged and / or inspected. The interior of the column may be evacuated, i.e., the electron beam device typically comprises a vacuum chamber 101, so that the primary electron beam propagates through a column having a sub-atmospheric pressure (e.g., 1 mbar or lower, in particular 1×10 -5 mbar or lower, or even 1×10 -8 The electron source 150 and the objective lens 110 may be arranged in a vacuum chamber 101 of the electron beam device.

[0030] According to some embodiments described herein, the electron beam device 100 is suitable for guiding the primary electron beam 105 along the optical axis A to the sample 140 to generate signal electrons. As used herein, the signal electrons emitted from the sample may include secondary electrons (SE) and / or backscattered electrons (BSE). When the primary electron beam is incident on the sample, the secondary electrons are emitted from the surface of the sample. Backscattered electrons are electrons of the primary electron beam backscattered from the sample. Compared with secondary electrons, backscattered electrons generally have higher energy. The signal electron beam including BSE may have a large energy spread and / or a large angle spread when leaving the sample. Backscattered electrons, for example, may have a particle energy higher than 50eV (e.g., 1keV or higher, 5keV or higher, 10keV or higher, or even 20keV or higher), and the secondary electrons may have a particle energy lower than 50eV. "Off-axis" signal electrons are emitted from the sample at a certain angle relative to the optical axis (e.g., in an angle range from 5° to 90° relative to the optical axis). "Axial" signal electrons are emitted from the sample substantially along the optical axis (eg, at an angle less than 5°).

[0031] BSEs are typically reflected from the sample at different angles relative to the optical axis A, and the signal electron beam including backscattered electrons may have a considerable angular spread. The signal electron energy and the number of backscattered electrons depend on the landing energy (LE) of the primary electron beam, and a high energy primary electron beam typically produces a high energy BSE signal electron beam with a large energy distribution. Whether signal electrons emitted from the sample at a large angle relative to the optical axis are still incident on the detector surface of the detector device and can be detected depends on the electron energy of the signal electrons (and therefore indirectly on the landing energy of the primary electron beam). For example, low energy signal electrons emitted from the sample at a large angle relative to the optical axis may still be redirected to the detector surface and thus be detected; whereas high energy signal electrons emitted from the sample at a large angle relative to the optical axis can no longer be detected due to the high electron energy (which makes it more difficult to be redirected to the detector).

[0032] As used herein, "a first set of signal electrons" refers to signal electrons that propagate within a first radial distance range from the optical axis in a plane defined by the electron detector, such that the first set of signal electrons are incident on a radially inner detector section of the detector device. As used herein, "a second set of signal electrons" refers to signal electrons that propagate within a second radial distance range from the optical axis in a plane defined by the electron detector, the second set of signal electrons being further from the optical axis than the first set of signal electrons, such that the second set of signal electrons are incident on a radially outer detector section of the detector device. The first set of signal electrons may specifically include low energy signal electrons and medium energy signal electrons that are redirected to a propagation path closer to the optical axis, and higher energy signal electrons that are emitted at an angle relatively close to the optical axis (such as incident on an inner detector section). The second set of signal electrons may specifically include higher energy signal electrons emitted off-axis from the sample, such that the higher energy signal electrons are incident on the detector device where the radially outer detector section is located at a distance farther from the optical axis.

[0033] The first group of signal electrons is also referred to herein as "small-angle BSEs" (see Figure 1 , and the second set of signal electrons is also referred to herein as “large-angle BSEs” (see Figure 1 ). In the context, "small angle" and "large angle" refer to the solid angle / acceptance angle of the electron detector. The first group of signal electrons can be detected by one or more radially inner detector segments of the electron detector 120, and the second group of signal electrons can be detected by one or more radially outer detector segments. Specifically, the first group of signal electrons propagate upward from the sample at a closer distance to the optical axis than the second group of signal electrons, so that the first group of signal electrons are incident on the radially inner detector segment, while the second group of signal electrons are incident on the radially outer detector segment.

[0034] In general, a high landing energy of the primary electron beam results in a greater number of signal electrons propagating back from the sample to a greater distance from the optical axis than a low landing energy. For example, if the primary electron beam has a landing energy of 10 keV or less, only signal electrons in the range from 1% to 10% may be incident on the radially outer segment, because low-energy BSEs, even if reflected from the sample at larger angles, can be redirected to a propagation path close enough to the optical axis. If the primary electron beam has a landing energy above 30 keV, the number of off-axis signal electrons incident on the radially outer segment may rise to 10% or more, because high-energy, large-angle BSEs (if still detectable) are typically redirected to a propagation path far from the optical axis.

[0035] Backscattered electrons may carry valuable information about the topography or geometry of the sample to be inspected and / or about buried layers or structures beneath the sample surface. Therefore, it would be beneficial to detect backscattered electrons, including high energy backscattered electrons released from the sample at large angles with high detection efficiency. However, if detected with a conventional electron detector, the detection efficiency of off-axis signal electrons released from the sample at large angles relative to the optical axis A may become low, especially if a high landing energy of the primary electron beam is used. One reason is that the typically weak detector signal caused by off-axis signal electrons emitted at large angles is not fully accounted for, or is lost in the background due to the high signal intensity caused by signal electrons propagating closer to the optical axis.

[0036] According to the embodiments described herein, a detector device 10 is provided, which is suitable for detecting off-axis signal electrons emitted at large angles with good detection efficiency even with high landing energies of the primary electron beam and / or for improving the signal-to-noise ratio (SNR) of the detector signal caused by off-axis signal electrons emitted at large angles. In particular, high-energy BSEs emitted from a sample at large angles relative to the optical axis can also be reliably detected, and the signals generated by such "large-angle BSEs" can be analyzed and considered during sample testing, sample inspection, sample analysis or sample imaging.

[0037] like Figure 1 and Figure 2Schematically depicted, the detector device 10 comprises an electron detector 120 with a segmented detection surface, in particular a segmented semiconductor electron detector, more particularly a segmented PIN diode. The electron detector 120 has a central opening 23, through which the primary electron beam 105 can pass through the electron detector 120 to the sample. The electron detector 120 comprises: one or more radially inner detector segments 21, which are arranged, for example, in an annular manner, at least partially surrounding the central opening; and one or more radially outer detector segments 22, which are arranged, for example, in an annular manner, at least partially surrounding the central opening. For example, as Figure 2 As shown, one or more radially inner detector segments 21 may be arranged in an annular manner surrounding the central opening 23 , and one or more radially outer detector segments 22 may be arranged in an annular manner surrounding the one or more radially inner detector segments 21 .

[0038] The terms "radially inner detector segment" and "radially outer detector segment" refer to the radial position of the respective detector segment being closer or further away in the radial direction from the central detector opening (i.e. from the optical axis). In other words, in the detection plane of the detector, the "radially inner detector segment" is typically arranged closer to the central opening than the "radially outer detector segment". The terms "radially inner" and "radially outer" do not refer to the shape of the respective detector segments. In particular, the radially inner and / or outer detector segments may have an inner / outer contour having a circular ring shape as depicted in the accompanying drawings, but the radially inner and / or outer detector segments may also have other shapes or contours, such as an octagon, a polygon, an ellipse, etc., as long as the radially outer segment is typically arranged further away from the central detector opening in the radial direction than the radially inner detector segment. Typically, the inner detector segment and the outer detector segment are provided on a detector body and are arranged in a detection plane perpendicular to the optical axis.

[0039] exist Figure 1 and Figure 2 In the exemplary embodiment of the present invention, the electron detector 120 includes an (annular) inner detector section surrounding the central opening 23 and an (annular) outer detector section surrounding the inner detector section. Figure 3A and Figure 3B As schematically depicted in FIG. 1 , more than one radially inner detector segment and / or more than one radially outer detector segment may be provided for improving topography inspection. Figure 3A and Figure 3BAs shown, providing several inner and / or several outer azimuth detector segments can enable more reliable inspection of sample topography with high accuracy. For example, the topography detector may include two, four or eight radially inner detector segments and two, four or eight radially outer detector segments in a four-quadrant configuration.

[0040] Back to Figure 1 and Figure 2 , the detector device 10 is configured to amplify one or more first detector signals caused by a first set of signal electrons incident on one or more radially inner detector segments 21 with a first amplification strength (G1, representing "first gain" or "first amplification factor"), and to amplify one or more second detector signals caused by a second set of signal electrons incident on one or more radially outer detector segments 22 with a second amplification factor (G2, representing "second gain" or "second amplification factor") that is higher than the first amplification strength. Therefore, the large-angle BSE generates a higher detector output signal per BSE compared to the small-angle BSE. For example, the second amplification strength G2 can be two or more times, three or more times, four or more times, or even five or more times higher than the first amplification strength G1.

[0041] As used herein, "amplification strength" relates to the output signal strength provided by the detector device 10 per current or per number of signal electrons impinging on the detection surface of the electron detector. Specifically, the detector device may provide an output signal (in [V]) that depends on the number of signal electrons (in amperes [A]) impinging on the detection surface of the electron detector (i.e., a large number of signal electrons results in a high output signal of the detector device, and a small number of signal electrons results in a small output signal of the detector device). If the "amplification strength" of a detector segment is high, the detector device provides a high output signal for each signal electron incident on the detector segment.

[0042] Therefore, a second amplification intensity G2 that is higher than the first amplification intensity G1 means that the detector device provides a higher output signal (e.g., in [V]) for each signal electron incident on one or more radially outer detector segments 22 compared to each signal electron incident on one or more radially inner detector segments 21. In one example, for one or more first detector signals caused by a first group of signal electrons incident on the radially inner detector segments, the first amplification intensity G1 (= first gain) can be from 30 kV / A to 60 kV / A. In other words, 1 ampere of signal electrons incident on the inner segments will cause an output signal of the detector device for the corresponding inner segment in the range between 30 kV and 60 kV. For one or more second detector signals caused by a second group of signal electrons incident on the radially outer detector segments, the second amplification intensity G2 (= second gain) can be from 200 kV / A to 300 kV / A. In other words, 1 ampere of signal electrons incident on an outer segment will cause an output signal of the detector device for the respective outer segment to be between 200 kV and 300 kV.

[0043] In some embodiments, which may be combined with other embodiments described herein, the detector device 10 comprises an electronic detector 120 and an amplification device 121, in particular a preamplifier. The amplification device 121 is connected to one or more radially inner detector segments 21 and one or more radially outer detector segments 22. The amplification device 121 may be configured to amplify one or more first detector signals provided by the one or more radially inner detector segments and caused by the first set of signal electrons with a first amplification intensity G1, and to amplify one or more second detector signals provided by the one or more radially outer detector segments and caused by the second set of signal electrons with a second amplification intensity G2. The second amplification intensity G2 is higher than the first amplification intensity G1. Therefore, large-angle signal electrons propagating far from the optical axis cause a higher detector output signal than small-angle signal electrons propagating closer to the optical axis.

[0044] The amplification device 121 may include one or more first amplification circuits 31 connected to one or more radially inner detector segments and providing a first amplification strength G1 (specifically, one amplification circuit connected to each of the inner detector segments). The amplification device 121 may include one or more second amplification circuits 32 connected to one or more radially outer detector segments and providing a second amplification strength G2 (specifically, one amplification circuit connected to each of the outer detector segments).

[0045] like Figure 2As schematically illustrated in FIG. 1 , one or more radially inner detector segments 21 may provide one or more first detector signals (e.g., in amperes [A]) amplified by one or more first amplification circuits 31 at a first amplification strength G1, respectively, to provide one or more first detector output signals (e.g., in voltage [V]). The first amplification strength G1 may, for example, be 30 kV / A or greater and 60 kV / A or less. One or more radially outer detector segments 22 may provide one or more second detector signals (e.g., in amperes [A]) amplified by one or more second amplification circuits 32 at a second amplification strength G2, respectively, to provide one or more second detector output signals (e.g., in voltage [V]). The second amplification strength G2 may, for example, be 200 kV / A or greater and 300 kV / A or less.

[0046] The first group of signal electrons incident on the one or more radially inner detector segments 21 result in the generation of one or more first detector signals (one first detector signal for each inner segment), and the one or more first detector signals can be amplified with a first amplification strength G1 by one or more first amplification circuits 31 of the amplification device 121. The second group of signal electrons incident on the one or more radially outer detector segments 22 result in the generation of one or more second detector signals (one second detector signal for each outer segment), and the one or more second detector signals can be amplified with a second amplification strength G2 by one or more second amplification circuits 32 of the amplification device 121.

[0047] Thus, the second set of signal electrons including the large-angle BSEs generates one or more second detector signals of higher amplification intensity compared to one or more first detector signals generated by the first set of signal electrons (including the small-angle BSEs). Reliable detection of large-angle BSEs is often challenging, particularly if the large-angle BSEs have high electron energies (e.g., if the landing energy of the primary electron beam is high). By amplifying the detector signals caused by the large-angle BSEs with a higher amplification intensity, the contribution of the large-angle BSEs to sample inspection and image generation may be increased, and / or the signal-to-noise ratio of the (typically small) portion of the output signal of the detector caused by the large-angle signal electrons may be improved. The valuable information provided by the large-angle signal electrons, particularly by the large-angle BSEs having high electron energies, is more reliably retrieved, enabling more accurate 3D imaging and inspection of complex sample morphologies and / or buried layer morphologies.

[0048] In some implementations, one or more first amplification circuits 31 apply a first amplification intensity G1, while simultaneously one or more second amplification circuits 32 apply a second amplification intensity G2 on the corresponding detector signal. Thus, one signal electron beam emitted from the sample causes different detector signals, which are (simultaneously) amplified with different amplification intensities, depending on whether the signal electrons belong to the first group and are incident on the inner detector segment or to the second group and are incident on the outer detector segment.

[0049] In some implementations, one or more first amplification circuits 31 and / or one or more second amplification circuits 32 are or belong to transimpedance amplification circuits (TIA). For example, one or more first amplification circuits 31 connected to one or more radially inner detector segments 21 include one or more first TIAs, one or more first TIAs characterized by a first current and voltage gain, and in particular characterized by a first feedback resistor. One or more second amplification circuits 32 connected to one or more radially outer detector segments 22 may include one or more second TIAs, one or more second TIAs characterized by a second current and voltage gain greater than the first current and voltage gain, and in particular characterized by a second feedback resistor different from the first feedback resistor.

[0050] In some embodiments, the first amplification strength G1 and the second amplification strength G2 are constant. In particular, the amplification device 121 may have fixed amplification strengths (the first amplification strength G1 and the second amplification strength G2) that cannot be modified or changed. Specifically, the first amplification circuit 31 and the second amplification circuit 32 may be configured for fixed amplification strengths, respectively, which may be defined by one or more corresponding resistors. Amplifiers with variable amplification gains are typically slower than fixed gain amplifiers, so that the achievable detection speed and signal-to-noise ratio will be negatively affected by providing variable gain amplification within the detector device 10.

[0051] However, it should be noted that the (optional) main amplifier 160 configured to further amplify the preamplified signal provided by the amplification device 121 may (optionally) provide a variable amplification strength. Once preamplified by the preamplifier within the detector device 10, in particular directly after the electronic detection of the signal, and preferably without the signal being transmitted at a distance from the detector surface, the signal is more robust and can be transmitted outside the vacuum chamber 101 for further amplification and / or processing, for example by the main amplifier 160 and / or the signal evaluation module 170. The main amplifier 160 optionally has a variable gain. Unlike the (optional) main amplifier 160, which is considered to be a separate component, the amplification device 121 described herein is a part of the detector device 10, which is integrated with the electronic detector or arranged close to the electronic detector.

[0052] In some embodiments, which may be combined with other embodiments described herein, the second amplified intensity G2 is 2 or more times, in particular 5 or more times, greater than the first amplified intensity G1. Thus, signal electrons incident on the radially outer detector segment cause a detector output signal whose amplitude is at least twice the amplitude of the detector output signal caused by signal electrons incident on the radially inner detector segment.

[0053] In some embodiments, which may be combined with other embodiments described herein, the detector device is a segmented lens in-detector, in particular a segmented lens in-BSE detector. In particular, the detector device may be arranged near the objective lens, for example near the magnetic lens gap of a magnetic objective lens, or between the objective lens and the sample stage. The detector device may, for example, be installed at a position directly downstream of the objective lens in the propagation direction of the primary electron beam. The position of the detector device close to the sample stage increases the angular range of signal electrons that can be "captured" by the electron detector. In particular, high energy signal electrons emitted from the sample at an angle greater than, for example, 45° or even greater than 65° may impact the detection surface of the electron detector (at the radially outer detector section) and may be detected.

[0054] In some embodiments, the central opening 23 may be arc-shaped or circular and may be partially or completely surrounded by one or more radially inner detector segments 21. For example, the central opening 23 may have a first radius (R1) of 500 μm or more, in particular 1 mm or more and / or 3 mm or less. The primary electron beam (typically with a beam diameter of less than 500 μm) may propagate through the central opening 23 toward the sample without being negatively affected by the electron detector. Optionally, axial signal electrons 103 and / or signal electrons emitted from the sample close to the optical axis may propagate through the central opening in a direction opposite to the propagation direction of the primary electron beam 105. An optional second electron detector ( Figure 1The axial signal electrons, in particular the SE, are detected, for example, in a "through the lens" detection arrangement with one or more optional secondary electron detectors.

[0055] In some embodiments that may be combined with other embodiments described herein, the detector device 10 comprises an electron detector 120 and an amplifying device 121, in particular a preamplifier, wherein the amplifying device 121 is connected to the electron detector 120, in particular integrated with the electron detector 120 or arranged directly adjacent to the electron detector 120. For example, the electron detector and the preamplifier may be integrated in the same detector housing, arranged on a common support and / or in the same chip or circuit board. In some implementations, the amplifying device 121 is at least one of the following: (i) integrated with the electron detector, (ii) arranged directly adjacent to the electron detector 120 inside the vacuum chamber 101 of the electron beam device, and / or (iii) fixedly mounted in the vacuum chamber 101 of the electron beam device. Specifically, the detector device 10 may include an electron detector 120 and an amplifying device 121 (the amplifying device may be a preamplifier) ​​integrated with each other to provide a compact and integrated detector device, which may be placed, for example, close to an objective lens in a vacuum chamber. The small transmission distance of the detector signal between the electronic detector and the preamplifier improves the signal integrity and signal-to-noise ratio, especially if a large amplification strength is used for the outer detector section. For example, a small detector signal caused by a BSE propagating far from the optical axis can be amplified directly after the signal generation, which improves the signal quality.

[0056] In an arrangement in which the amplifying device 121 is "adjacent" the electron detector 120, the distance between the detection surface of the electron detector and the amplifying device may be 5 cm or less, in particular 3 cm or less, more in particular 2 cm or less. Both the amplifying device and the electron detector may be arranged in a vacuum chamber of the electron beam device, for example within a column or near one end of the column. Fixedly mounting the amplifying device at a position near the electron detector may be understood as a substantially immovable positioning of the amplifying device at a position near the electron detector and means a distinction from other solutions in which the detector device may be pivoted or moved towards or away from a detection position near the sample in the sample chamber (i.e. outside the column).

[0057] In some embodiments, the detector device 10 comprises a support, such as a plate or a housing, on which both the electron detector 120 and the amplifying device 121 are mounted. The support may be arranged adjacent to the downstream end of the column of the electron beam device, for example fixed at the objective lens 110. In particular, the electron detector 120 and the amplifying device 121 may be provided as an integrated detector module, comprising the amplifying device integrated with the electron detector on a common support of the detector device 10 or even on a single chip. In some embodiments, the detector device 10 comprises a common support, which supports both the electron detector 120 and the amplifying device 121 at a close distance (e.g. 3 cm or less).

[0058] It is beneficial to arrange the amplification device close to the electron detector, in particular within the vacuum housing of the electron beam device (e.g., within or near the column), and / or integrate the amplification device 121 and the electron detector 120 to provide an integrated detector module, because the detection speed and detection efficiency can be improved. Fixedly mounting the amplification device at a position close to the electron detector improves the signal-to-noise ratio and improves the detection efficiency and the maximum detection speed. For example, by mounting the amplification device 121 at a position close to the electron detector 120, an increased signal strength can be achieved. This can achieve fast imaging / detection speeds with high scan rates of, for example, 10Mhz or faster or 20MHz or faster.

[0059] In some embodiments, the amplification device 121 may be an electronic amplifier, in particular an operational amplifier. In some embodiments, the electronic detector 120 may be a solid-state or semiconductor detector, in particular including a PIN diode. The electronic detector 120 may provide an electrical signal (e.g., a current signal) pre-amplified by the amplification device 121, for example to provide a voltage signal. The amplification device may include a TIA. The pre-amplified signal from the amplification device 121 may then be forwarded to the signal evaluation module 170.

[0060] In some implementations, in addition to the amplification device 121, a main amplifier 160 may be provided. The amplification device 121 may be a preamplifier arranged in the vacuum chamber of the electron beam device, in particular integrated with or in close proximity to the electron detector, and the preamplified signal provided by the preamplifier may be further amplified by the main amplifier 160, which may be arranged outside the vacuum chamber of the electron beam device. The main amplifier 160 may forward the amplified signal to the signal evaluation module 170. The main amplifier 160 may optionally have a variable gain. The main amplifier 160 is considered to be a component separate from the detector device 10, which is connected to the detector device, for example, by a connection extending through the wall of the vacuum chamber of the electron beam device via a vacuum feedthrough or a signal cable.

[0061] In some embodiments, which may be combined with other embodiments described herein, one or more radially inner detector segments extend from a first radius (R1) to a second radius (R2), and one or more radially outer detector segments extend from the second radius (R2) to a third radius (R3), such as Figure 2 . The second radius (R2) may be 6 mm or more and 11 mm or less, for example 9 mm or more and 10 mm or less, and / or the third radius may be greater than 12 mm, for example about 13 mm. The third radius may be greater than 12 mm and less than 20 mm. Such a segment size enables reliable detection of small-angle BSE and large-angle BSE and allows the detector device to operate in different operating modes depending on the landing energy of the primary electron beam, as explained in further detail below.

[0062] In some embodiments, the first radius (R1) may be 500 μm or more and 3 mm or less, for example between 1 mm and 2 mm. The first radius (R1) defines the size of the central detector opening and enables the primary electron beam and optional axial signal electrons to propagate through the electron detector without being negatively affected.

[0063] In some implementations, one or more radially inner detector segments 21 may cover a first surface area, such as a substantially annular surface area, and one or more radially outer detector segments may cover a second surface area, such as a substantially annular surface area. The ratio between the second surface area and the first surface area may be from 0.7 to 2, in particular from 0.9 to 1.1. In particular, the first surface area and the second surface area may have substantially the same size. For example, the first surface area may be 200 mm 2 With 400mm 2 Between, for example, from 250mm 2 Up to 300mm 2 , and / or the second surface area may be 200mm 2 With 400mm 2 Between, for example, from 250mm 2 Up to 300mm 2 The large second surface area increases the number of detectable large-angle BSEs. If the second surface area substantially corresponds in size to the first surface area or is larger in size than the first surface area, the contribution of the large-angle BSEs to the overall detector output signal may be increased. Furthermore, the detector device may be operated in different operating modes, as explained in further detail below.

[0064] In some embodiments that may be combined with other embodiments described herein, the electron beam device 100 may further include a deceleration field device for decelerating the primary electron beam before the primary electron beam is incident on the sample. The deceleration field device may include a proximity electrode 130 having at least one opening, the opening allowing the primary electron beam and the signal electrons, in particular the first group of signal electrons and the second group of signal electrons to pass through. In particular, the primary electron beam may pass through the opening of the proximity electrode 130 in a first direction, and the signal electrons may propagate through the (multiple) openings of the proximity electrode 130 in the opposite direction. The proximity electrode 130 may be set at a potential suitable for decelerating the primary electron beam when it hits the sample. In addition, the electric field generated by the proximity electrode 130 may accelerate the signal electrons away from the sample, in particular towards the detector device 10.

[0065] The proximity electrode 130 may be understood as the beam-affecting electrode closest to the sample or sample stage. In an example, the distance between the proximity electrode and the sample stage or sample is less than the distance between the objective lens and the sample stage or sample. According to some embodiments, the ability to detect large-angle backscattered particles with reduced detection losses is achieved by using a proximity electrode with an opening as an incident window for backscattered particle detection. The proximity electrode may further be used to decelerate the primary charged particle beam as a final component of a deceleration field device. The proximity electrode may further be capable of controlling the extraction field strength of the signal electrons.

[0066] Since the retarding field device can provide a significant potential difference between the sample and the column of the electron beam device, which is typically 5 keV or higher or even 30 keV or higher, the BSE passing through the opening close to the electrode is accelerated before reaching the detector device 10, which is advantageous for high efficiency detection. Optionally, the electron detector 120 can be used as an accelerating electrode and set at a corresponding potential. Accelerating the BSE is particularly beneficial when detecting backscattered particles at low landing energies (e.g., below 10 keV) or when the backscattered particles lose part of their energy when passing through the sample material. In the case where the column is at ground potential, detection with a semiconductor detector like a pin diode may be feasible, because the detector and the detector electronics can be set at ground potential.

[0067] In some embodiments, Figure 1As schematically depicted, the detector device 10 may be arranged between the proximity electrode 130 and the objective lens 110. The proximity electrode may, for example, be used to adjust the landing energy of the primary electron beam on the sample to, for example, 35 keV or less, 25 keV or less, or even 10 keV or less. The landing energy of the primary electron beam on the sample may affect the number of BSEs reflected from the sample. In addition, as described above, the landing energy of the primary electron beam on the sample affects the BSE energy and therefore the number of BSEs incident on the inner detector segment and the outer detector segment. In particular, a higher landing energy of the primary electron beam on the sample generally increases the number of BSEs that can be detected by the (multiple) radially outer detector segments.

[0068] The "maximum detection speed" of an electron detector defines the maximum scanning speed at which a sample can be scanned while the detector is still able to temporally resolve signal electrons originating from different points (or pixels) of the sample. The "maximum detection speed" of an electron detector may also be referred to as the "detector bandwidth" which constitutes a characteristic parameter of the electron detector. For example, an electron detector with a bandwidth greater than 20 MHz is able to achieve rapid scanning speeds, while an electron detector with a bandwidth less than 1 MHz is not very fast.

[0069] The maximum detection speed (or bandwidth) of a detector segment may depend on the amplification strength of the signal applied to the detector segment. Thus, a detector segment with a high amplification strength may operate at a lower bandwidth than a detector segment with a low amplification strength.

[0070] According to some embodiments described herein, one or more radially inner detector segments connected to an amplification circuit with a lower gain are configured for a first maximum detection speed, and / or one or more radially outer segments connected to an amplification circuit with a higher gain are configured for a second maximum detection speed, wherein the first maximum detection speed may be faster than the second maximum detection speed. In other words, the inner detector segments may have a higher bandwidth (i.e., may be operated at a faster scanning speed) than the outer detector segments. For example, the bandwidth of one or more radially outer detector segments may be from 5Mhz to 15Mhz, in particular about 10Mhz, and / or the bandwidth of one or more radially inner detector segments may be 15Mhz or more, in particular faster than 20Mhz, for example between 20Mhz and 50MHz.

[0071] In some embodiments, which may be combined with other embodiments described herein, the detector device 10 may be operated in (at least) two operating modes, in particular in a first operating mode, a second operating mode and / or a third operating mode. Each operating mode may be characterized by a corresponding (maximum) detection speed. In particular, the first operating mode and the third operating mode may be characterized by a slower detection speed (or detector bandwidth) than the second operating mode. In some embodiments, the detector device 10 may be operated in at least two of the three operating modes (e.g., in the first operating mode and the second operating mode), or in three operating modes (i.e., in the first operating mode, the second operating mode and the third operating mode).

[0072] In the first operating mode, both the first set of signal electrons and the second set of signal electrons are detected with the detector device 10, and the respective detector signals are amplified with respective amplification intensities G1 and G2. Since in the first operating mode the second set of signal electrons are detected with radially outer detector sections providing high amplification intensities but with lower bandwidth, the overall bandwidth of the detector device may be lower than in the second operating mode.

[0073] In the second operating mode, the first set of signal electrons is detected with the detector device and the corresponding detector signal is amplified with the first amplification intensity G1, but the second set of signal electrons is not detected. Specifically, only the radially inner detector segment(s) may be operated in the second operating mode, while the radially outer detector segment(s) are not operated. Because only the first set of signal electrons is detected with the radially inner detector segment(s) providing a lower amplification intensity but having a higher bandwidth, the overall bandwidth of the detector device (where the radially outer detector segment is not in operation, e.g., turned off) is increased in the second operating mode.

[0074] In the third operating mode, the second group of signal electrons are detected with the detector device and the corresponding detector signal is amplified with the second amplification intensity G2, but the first group of signal electrons are not detected. Specifically, only the (multiple) radially outer detector segments may be operated in the third operating mode, without operating the (multiple) radially inner detector segments. Because only the second group of signal electrons are detected with the radially outer detector segments that provide a higher amplification intensity but have a lower bandwidth, the total bandwidth of the detector device in the third operating mode (wherein the radially inner detector segments are not in operation, e.g., turned off) may be lower than in the second operating mode. Specifically, the detector bandwidth of the first operating mode may correspond to the detector bandwidth of the third operating mode (wherein the slower outer detector segments are operated), and the detector bandwidth of the second operating mode may be higher (because the slower outer detector segments are not operated in the second operating mode).

[0075] For example, in the first and third operating modes for detecting large-angle BSE, the detection speed (or bandwidth) may be from 5 MHz to 15 MHz. In the second operating mode for detecting only small-angle signal electrons incident on the radially inner detector segment, the detection speed (or bandwidth) may be higher than 15 MHz, for example, 25 MHz or higher.

[0076] The operating mode of the detector device can be selected based on the landing energy of the primary electron beam. For example, if the landing energy is below 15 keV, most of the signal electrons can be detected with the radially inner detector section. A second operating mode can be applied, in which only the radially inner detector section is operated, which is characterized by a high maximum detection speed. Therefore, fast BSE detection can be performed with the radially inner detector section.

[0077] If the landing energy is above 15 keV, for example 30 keV or more, a large amount of high energy BSEs will also be released from the sample which can be detected by the radially outer detector segment. A first operating mode can be applied, in which both the radially inner detector segment and the radially outer detector segment are operated. The first operating mode is characterized by a reduced maximum detection speed, because the radially outer detector segment is also in operation. Therefore, in applications with high energy BSE output at large emission angles with low signal intensity, high amplification at the radially outer detector segment is possible. The first operating mode can be applied, for example, when the landing energy of the primary electron beam is above 15 keV, for example 30 keV or more or even 50 keV or more. Alternatively, a third operating mode can be applied, in which only high angle BSEs are detected by (multiple) radially outer detector segments.

[0078] For the radially inner detector section, where most BSEs at landing energies up to 15 keV are detected, smaller amplification is sufficient, but higher bandwidths, for example of at least 20 MHz, are beneficial for fast defect detection.A wide range of defects can be detected quickly and reliably in the second operating mode.

[0079] For the radially outer detector section, where large angle BSEs at landing energies of 15 keV or higher can be detected, high amplification due to small BSE input current is beneficial so that large angle BSEs can still be detected with reasonable signal-to-noise ratio. Here, the detector bandwidth can be lower, for example 10 MHz. Due to the size of the radially outer detector section as specified herein, and the high gain applied to the detector signal from the radially outer detector section, detection of large angle BSEs in high landing energy applications is possible. Certain types of defects can be inspected.

[0080] Figure 3A A schematic perspective view of a detector device 10 with a segmented electron detector as described herein is shown. Figure 3B Shows Figure 3A Schematic top view of a detector device. Figure 3A and Figure 3B The detector device is basically the same as Figure 2 Corresponding to the detector device, so please refer to the above explanation and no longer repeat it here.

[0081] In particular, the detector device 10 comprises an electron detector 120 and an amplification device 121. The electron detector 120 is an in-lens detector having a central opening 23 for the primary electron beam and having one or more radial detector segments 21 and one or more radial outer detector segments 22 surrounding the central opening 23.

[0082] The amplification device 121 is configured to amplify first detector signals of one or more radially inner detector segments 21 with a first amplification strength G1 while amplifying second detector signals of one or more radially outer detector segments 22 with a second amplification strength G2 higher than the first amplification strength G1.

[0083] The amplification device 121 may be a preamplifier connected to the electron detector 120. The preamplifier is at least one of: (i) integrated with the electron detector 120, (ii) arranged directly adjacent to the electron detector 120 inside the vacuum chamber of the electron beam device, and (iii) installed in the vacuum chamber of the electron beam device.

[0084] exist Figure 3A and Figure 3B In the illustrated embodiment, the electron detector 120 comprises a plurality of radially inner detector segments surrounding the central opening 23 in an annular arrangement, particularly in a four-quadrant arrangement, and a plurality of radially outer detector segments surrounding the plurality of radially inner segments in an annular arrangement, particularly in a four-quadrant arrangement.

[0085] In some embodiments, the one or more radially inner detector segments 21 include two or more inner segments, in particular four inner segments, arranged in an annular manner around the central opening. Alternatively or additionally, the one or more radially outer detector segments 22 include two or more outer segments, in particular four outer segments, or even eight outer segments, arranged in an annular manner around the central opening. Figure 3A and Figure 3B As schematically depicted, the one or more radially inner detector segments 21 may include four inner segments surrounding the central opening 23 in an annular four-quadrant configuration, and the one or more radially outer detector segments 22 may include four outer segments surrounding the four inner segments in an annular four-quadrant configuration.

[0086] The electronic detector 120 may be a segmented semiconductor detector, such as a PIN diode detector having a segmented detection surface 125, and the amplification device 121 may be a multi-channel transimpedance amplifier integrated with or arranged adjacent to the segmented semiconductor detector. A first subset of channels of the amplification device 121 may be configured to apply a first amplification intensity, and a second subset of channels of the amplification device may be configured to apply a second amplification intensity. Specifically, four first detector signals provided by four radially inner detector segments may be amplified at a first amplification intensity in four channels of the amplification device, and four second detector signals provided by four radially outer detector segments may be amplified at a second amplification intensity in four other channels of the amplification device. In particular, the multi-channel amplifier may have a first subset of channels connected to the radially inner detector segments and configured for amplification at a first amplification intensity and a second subset of channels connected to the radially outer detector segments and configured for amplification at a second amplification intensity higher than the first amplification intensity.

[0087] An (optional) main amplifier 160 may additionally be provided, which serves to amplify the pre-amplified signal provided by the amplification device 121. The main amplifier 160 may be arranged separately from the detector device 10, for example outside the vacuum chamber of the electron beam apparatus.

[0088] like Figure 3A and Figure 3B As depicted, the dual four-quadrant segmented detector enables signal electron detection that is differentiated based on both the emission angle of the corresponding signal electron relative to the optical axis (e.g., small angle BSE vs. large angle BSE) and the azimuth angle of the corresponding signal electron (e.g., via corresponding segments in top, bottom, right, and left directions). Thus, specific defects, surface gradients, surface topography and geometry, and / or details of the buried layer can be inspected and / or imaged. Weak signals at radially outer segments and strong signals at radially inner segments can be reliably detected with an improved signal-to-noise ratio.

[0089] According to a further aspect, a method of imaging and / or inspecting a sample, in particular with a detector device and / or an electron beam arrangement according to any of the embodiments described herein, is provided.

[0090] Figure 4 is a flow chart schematically illustrating a method as described herein. In block 410, a primary electron beam is generated that propagates along an optical axis.

[0091] In block 420, the primary electrons are focused onto the sample with an objective lens to cause emission of signal electrons, wherein the signal electrons include BSEs. In particular, a first set of signal electrons propagate within a first radial distance range from the optical axis in a plane of an electron detector, and a second set of signal electrons propagate within a second radial distance range further from the optical axis than the first set. The first set of signal electrons and the second set of signal electrons are detected with a detector device, as described herein, the detector device including an electron detector, in particular a semiconductor detector.

[0092] In block 430, one or more first detector signals caused by a first set of signal electrons incident on one or more radially inner detector segments of the electron detector are amplified with a first amplification strength, and one or more second detector signals caused by a second set of signal electrons incident on one or more radially outer detector segments of the electron detector are amplified with a second amplification strength. The second amplification strength (= second gain) for the outer detector segments is, for example, 2 or more times or 5 or more times the first amplification strength (= first gain) for the inner detector segments.

[0093] In some embodiments, the one or more first detector signals and the one or more second detector signals are amplified by a preamplifier, in particular by at least one transimpedance amplification circuit of the preamplifier, more particularly by a multi-channel transimpedance amplifier having two channel subsets. The preamplifier may be at least one of: integrated with the electron detector, and arranged adjacent to the electron detector in a vacuum environment.

[0094] In some embodiments, which may be combined with other embodiments described herein, the one or more radially inner detector segments include two or four inner detector segments arranged in an annular manner surrounding a central opening of the electron detector, and / or the one or more radially outer detector segments include two or four outer detector segments arranged in an annular manner surrounding the two or four inner detector segments. Each detector segment may have the shape of an annular segment, extending around the central opening at an angle of, for example, 180° or 90°, respectively.

[0095] The landing energy of the primary electron beam incident on the sample can be 15 keV or higher, in particular 30 keV or higher, more particularly 35 keV or higher, or even 50 keV or higher. Higher landing energies increase the number of high-energy BSEs reflected from the sample, which propagate farther from the optical axis if reflected off-axis. At a landing energy of, for example, 10 keV or lower, only a negligible number of BSEs may be incident on the radially outer detector segments. Therefore, the method described herein is particularly beneficial if the landing energy of the primary electron beam is higher than 15 keV. According to the method described herein, large-angle BSEs generated at high landing energies can be detected with a good signal-to-noise ratio.

[0096] In some embodiments, the detector device may be operated in at least a first operating mode and a second operating mode. As schematically depicted in block 430, in the first operating mode, both the first set of signal electrons and the second set of signal electrons are detected, and the corresponding detector signals are amplified with different amplification intensities. In the first operating mode, the primary electron beam may be incident on the sample at a first landing energy, wherein the first landing energy may be, for example, 15 keV or higher, so that large angle BSEs with high particle energy are also emitted from the sample.

[0097] In (optional) box 440, the method further includes switching the detector device from the first operating mode to a second operating mode or a third operating mode. In the second operating mode, the first group of signal electrons are detected, but the second group of signal electrons are not detected. For example, in the second operating mode, only one or more inner detector segments are operated, but not one or more outer detector segments. In the second operating mode, the primary electron beam can be incident on the sample at a second landing energy that is less than the first landing energy, in particular, where the second landing energy can be, for example, 10 keV or lower, so that no large number of large-angle BSEs are emitted from the sample. In the optional third operating mode, the second group of signal electrons are detected, but the first group of signal electrons are not detected. For example, the radially inner detector segment is not operated or turned off.

[0098] The first operating mode may be characterized by a second (maximum) detection speed (or detector bandwidth), and the second operating mode may be characterized by the first (maximum) detection speed (or detector bandwidth) being faster than the second (maximum) detection speed. In other words, when operating all detector segments in the first operating mode, the sample may be scanned at a slower maximum speed than in the second operating mode in which only radially inner detector segments are operated.

[0099] Specifically, the following embodiments are described herein:

[0100] Embodiment 1: A detector device (10) for detecting signal electrons, the detector device comprising: an electron detector (120), the electron detector having: a central opening (23) for a primary electron beam (105) to pass through; one or more radially inner detector segments, the one or more radially inner detector segments at least partially surrounding the central opening; and one or more radially outer detector segments, the one or more radially outer detector segments at least partially surrounding the central opening. The detector device is configured to amplify one or more first detector signals caused by a first group of signal electrons incident on the one or more radially inner detector segments with a first amplification intensity, and to amplify one or more second detector signals caused by a second group of signal electrons incident on the one or more radially outer detector segments with a second amplification intensity higher than the first amplification intensity.

[0101] Embodiment 2: The detector device of embodiment 1, further comprising an amplification device having one or more first amplification circuits connected to one or more radially inner detector segments and configured to amplify one or more first detector signals with a first amplification strength. The amplification device further has one or more second amplification circuits connected to one or more radially outer detector segments and configured to amplify one or more second detector signals with a second amplification strength.

[0102] Embodiment 3: The detector device according to embodiment 2, wherein the one or more first amplification circuits and the one or more second amplification circuits are or belong to transimpedance amplification circuits.

[0103] Embodiment 4: A detector device as described in Embodiment 2 or 3, wherein the amplification device is a preamplifier connected to the electron detector, in particular, wherein the preamplifier is at least one of the following: integrated with the electron detector, and arranged directly adjacent to the electron detector, in particular in a vacuum chamber of the electron beam device.

[0104] Embodiment 5: The detector device according to any one of embodiments 1 to 4, wherein the first amplification strength and the second amplification strength are constant. In particular, the detector device does not allow changing or switching the gain.

[0105] Embodiment 6: The detector device as described in any of embodiments 1 to 5, wherein the second amplification intensity is 2 times or more, in particular 3 times or more, or even 5 times or more, greater than the first amplification intensity.

[0106] Embodiment 7: A detector device as described in any of embodiments 1 to 6, wherein one or more radially inner detector segments cover a first surface area of ​​the electron detector and one or more radially outer detector segments cover a second surface area of ​​the electron detector, the ratio between the second surface area and the first surface area being from 0.7 to 2, in particular from 0.9 to 1.1. In particular, one or more radially inner detector segments cover 200 mm 2 or larger and 400mm 2 or smaller, especially from 250mm 2 Up to 300mm 2 A first area of ​​200 mm and / or one or more radially outer detector segments covering 200 mm 2 or larger and 400mm 2 or smaller, especially from 250mm 2 Up to 300mm 2 The second area.

[0107] Embodiment 8: A detector device as described in any of embodiments 1 to 7, wherein one or more radially inner detector segments extend from a first radius (R1) to a second radius (R2), and one or more radially outer detector segments extend from the second radius (R2) to a third radius (R3), in particular arranged in a ring, wherein the second radius (R2) is between 7 mm and 11 mm, and the third radius (R3) is greater than 12 mm. Optionally, the first radius (R1) can be 500 μm or more and 2 mm or less, and / or the third radius (R3) can be 12 mm or more and 20 mm or less.

[0108] Embodiment 9: A detector device as described in any of Embodiments 1 to 8, wherein one or more radially inner detector segments include two or more inner segments arranged in a ring around a central opening, and / or one or more radially outer detector segments include two or more outer segments arranged in a ring around a central opening.

[0109] Embodiment 10: A detector device as described in any of Embodiments 1 to 9, wherein one or more radially inner detector segments include four inner segments surrounding a central opening in an annular four-quadrant configuration, and one or more radially outer detector segments include four outer segments surrounding the four inner segments in an annular four-quadrant configuration.

[0110] Embodiment 11: A detector device as described in any of embodiments 1 to 10, wherein the electronic detector is a segmented semiconductor detector, in particular a PIN diode detector, the segmented semiconductor detector is connected to a multi-channel transimpedance amplifier, the multi-channel transimpedance amplifier having a first subset of channels configured to apply a first amplification strength and a second subset of channels configured to apply a second amplification strength. The multi-channel transimpedance amplifier can be integrated with the segmented semiconductor detector or arranged directly adjacent to the segmented semiconductor detector, for example, in a common detector housing and / or integrated on the same chip.

[0111] Embodiment 12: A detector device as described in any of Embodiments 1 to 11, wherein one or more radially inner detector segments are configured for a first maximum detection speed and one or more radially outer detector segments are configured for a second maximum detection speed, the first maximum detection speed being faster than the second maximum detection speed.

[0112] Embodiment 13: A detector device as described in any of embodiments 1 to 12, wherein the detector device is capable of operating in at least two different operation modes. In a first operation mode, both a first set of signal electrons and a second set of signal electrons are detected with the detector device at a second detection speed. In a second operation mode, the first set of signal electrons are detected with the detector device at a first detection speed that is faster than the second detection speed, but the second set of signal electrons are not detected. In some embodiments, the second (=slower) detection speed corresponds to a maximum detection speed of one or more radially outer detector segments, and / or the first (=faster) detection speed corresponds to a maximum detection speed of one or more radially inner detector segments. In some embodiments, the first operation mode or the second operation mode is selected based on the landing energy of the primary electron beam on the sample. Specifically, the first operation mode can be selected for a first landing energy range of the primary electron beam, and the second operation mode can be selected for a second landing energy range of the primary electron beam that is lower than the first range. Specifically, the first operation mode can be characterized by a slow (maximum) detection speed and the detection of both the first set of signal electrons and the second set of signal electrons, and the second detection mode can be characterized by a fast (maximum) detection speed and the detection of the first set of signal electrons but not the second set of signal electrons. In an optional third mode of operation, the second set of signal electrons are detected at a second (slower) detection speed with the detector device, but the first set of signal electrons are not detected.

[0113] Embodiment 14: An electron beam device, the electron beam device comprising: an electron source, the electron source is used to generate a primary electron beam propagating along an optical axis; a sample stage, the sample stage is used to support a sample; an objective lens, the objective lens is configured to focus the primary electron beam onto the sample to release signal electrons from the sample; and a detector device, the detector device comprising: an electron detector (120), the electron detector comprising a central opening (23) for the primary electron beam, one or more radially inner detector segments (21) at least partially surrounding the central opening, and one or more radially outer detector segments (22) at least partially surrounding the central opening. The detector device is configured to amplify one or more first detector signals caused by a first group of signal electrons incident on the one or more radially inner detector segments (21) with a first amplification intensity, and at the same time amplify one or more second detector signals caused by a second group of signal electrons incident on the one or more radially outer detector segments (22) with a second amplification intensity higher than the first amplification intensity.

[0114] Embodiment 15: An electron beam device as described in Embodiment 14, wherein one or more first detector signals and one or more second detector signals are amplified by a preamplifier of the detector device, the preamplifier is connected to the electron detector, and is at least one of the following: (i) integrated with the electron detector, (ii) arranged directly adjacent to the electron detector inside the vacuum chamber of the electron beam device, and (iii) installed in the vacuum chamber of the electron beam device.

[0115] Embodiment 16: The electron beam device as described in Embodiment 14 or 15, further comprising a main amplifier, which is used to amplify the pre-amplified detector signal provided by the preamplifier.

[0116] Embodiment 17: An electron beam device as described in any one of Embodiments 14 to 16, further comprising a deceleration field device for decelerating the primary electron beam before the primary electron beam is incident on the sample. The deceleration field device may include an approach electrode having an opening, which allows the primary electron beam and the first group of signal electrons and the second group of signal electrons to pass through. Optionally, a detector device may be arranged between the approach electrode and the objective lens. In some embodiments, the landing energy of the primary electron beam on the sample may vary with the deceleration field device, for example, in a range from 50keV or 35keV to, for example, 10keV or lower.

[0117] Example 18: A method for imaging and / or inspecting a sample, the method comprising: generating a primary electron beam propagating along an optical axis; focusing the primary electron beam onto the sample with an objective lens to cause emission of a first group of signal electrons and a second group of signal electrons, wherein the second group of signal electrons propagate at a greater distance from the optical axis in the plane of an electron detector than the first group of signal electrons; amplifying one or more first detector signals caused by the first group of signal electrons incident on one or more radially inner detector segments of the electron detector with a first amplification intensity; and amplifying one or more second detector signals caused by the second group of signal electrons incident on one or more radially outer detector segments of the electron detector with a second amplification intensity higher than the first amplification intensity.

[0118] Embodiment 19: A method as described in Embodiment 18, wherein one or more first detector signals and one or more second detector signals are amplified by a preamplifier, in particular, by a mutual impedance amplification circuit of the preamplifier, and the preamplifier is integrated with the electron detector or arranged adjacent to the electron detector in a vacuum environment.

[0119] Embodiment 20: A method as described in Embodiment 18 or 19, wherein one or more radially inner detector segments include two or four inner detector segments arranged in an annular manner surrounding a central opening in the electron detector, and one or more radially outer detector segments include two or four outer detector segments arranged in an annular manner surrounding the two or four inner detector segments, the method comprising: amplifying two or four first detector signals provided by the two or four inner detector segments with a first amplification intensity, and amplifying two or four second detector signals provided by the two or four outer detector segments with a second amplification intensity.

[0120] Embodiment 21: The method as described in any one of Embodiments 18 to 20, wherein the landing energy of the primary electron beam on the sample is 20 keV or higher, specifically 30 keV or higher, and more specifically 35 keV or higher.

[0121] Embodiment 22: A method as described in any of Embodiments 17 to 19, further comprising switching between a first operating mode and a second operating mode (or an optional third operating mode), wherein in the first operating mode, the primary electron beam is incident on the sample with a first landing energy, and both the first group of signal electrons and the second group of signal electrons are detected; and in the second operating mode, the primary electron beam is incident on the sample with a second landing energy less than the first landing energy, and the first group of signal electrons are detected, while the second group of signal electrons are not detected. In the second operating mode, the sample can be scanned at a first (fast) scanning speed, and the first group of signal electrons can be detected at a first (fast) detection speed. In the first operating mode, the sample can be scanned at a second (slow) scanning speed, and the first group of signal electrons and the second group of signal electrons can be detected at a second (slow) detection speed. The first detection speed is faster than the second detection speed. The first detection mode and the second detection mode can be selected depending on the landing energy of the primary electron beam.

[0122] Embodiment 23: A detector device for detecting signal electrons, the detector device comprising: an electron detector having: a central opening for passage of a primary electron beam; one or more radially inner detector segments, the one or more radially inner detector segments at least partially surrounding the central opening; and one or more radially outer detector segments, the one or more radially outer detector segments at least partially surrounding the central opening. The detector device further comprises an amplification device, the amplification device being configured to amplify one or more first detector signals of the one or more radially inner detector segments at a first amplification strength, while amplifying one or more second detector signals of the one or more radially outer detector segments at a second amplification strength higher than the first amplification strength.

[0123] While the foregoing is directed to embodiments, other and further embodiments may be devised without departing from the basic scope, and the scope of the embodiments is determined by the claims that follow.

Claims

1. A detector device for detecting signal electrons, the detector device comprising: An electronic detector, the electronic detector comprising: a central opening for passage of the primary electron beam; one or more radially inner detector segments at least partially surrounding the central opening; and one or more radially outer detector segments at least partially surrounding the central opening, Wherein the detector device is configured to amplify one or more first detector signals caused by a first group of signal electrons incident on the one or more radially inner detector segments with a first amplification intensity, and at the same time amplify one or more second detector signals caused by a second group of signal electrons incident on the one or more radially outer detector segments with a second amplification intensity higher than the first amplification intensity.

2. The detector device of claim 1 , wherein the detector device comprises an amplification device having one or more first amplification circuits connected to the one or more radially inner detector segments and configured to amplify the one or more first detector signals with the first amplification strength, and having one or more second amplification circuits connected to the one or more radially outer detector segments and configured to amplify the one or more second detector signals with the second amplification strength.

3. The detector device of claim 2, wherein the one or more first amplification circuits and the one or more second amplification circuits are transimpedance amplification circuits.

4. The detector device of claim 2, wherein the amplification device is a preamplifier connected to the electronic detector, wherein the preamplifier is at least one of: integrated with the electronic detector, and arranged adjacent to the electronic detector.

5. The detector device of any one of claims 1 to 4, wherein the first amplification intensity and the second amplification intensity are constant.

6. The detector device of any one of claims 1 to 4, wherein the second amplification intensity is 2 or more times greater than the first amplification intensity.

7. A detector device as described in any one of claims 1 to 4, wherein the one or more radially inner detector segments cover a first surface area and the one or more radially outer detector segments cover a second surface area, and the ratio between the second surface area and the first surface area is from 0.7 to 2.

8. A detector device as described in any one of claims 1 to 4, wherein the one or more radially inner detector segments extend from a first radius to a second radius, and the one or more radially outer detector segments extend from the second radius to a third radius, wherein the second radius is between 7 mm and 11 mm, and the third radius is greater than 12 mm.

9. A detector device as described in any one of claims 1 to 4, wherein the one or more radially inner detector segments include two or more inner segments arranged in a ring around the central opening, and the one or more radially outer detector segments include two or more outer segments arranged in a ring around the central opening.

10. A detector device as described in any one of claims 1 to 4, wherein the one or more radially inner detector segments include four inner segments surrounding the central opening in an annular four-quadrant configuration, and the one or more radially outer detector segments include four outer segments surrounding the four inner segments in an annular four-quadrant configuration.

11. A detector device as described in any one of claims 1 to 4, wherein the electronic detector is a segmented semiconductor detector, the segmented semiconductor detector is connected to a multi-channel transimpedance amplifier, the multi-channel transimpedance amplifier is integrated with the segmented semiconductor detector or arranged adjacent to the segmented semiconductor detector, the multi-channel transimpedance amplifier has a first channel subset configured to apply the first amplification intensity and a second channel subset configured to apply the second amplification intensity.

12. A detector device as described in any one of claims 1 to 4, wherein the one or more radially inner detector segments are configured for a first maximum detection speed and the one or more radially outer detector segments are configured for a second maximum detection speed, the first maximum detection speed being faster than the second maximum detection speed.

13. The detector device according to any one of claims 1 to 4, wherein the detector device is operable in at least two of the following operating modes: in a first operating mode, wherein both the first set of signal electrons and the second set of signal electrons are detected with the detector device at a second detection speed, in a second operating mode, wherein the first set of signal electrons is detected with the detector device at a first detection speed faster than the second detection speed, and the second set of signal electrons is not detected, and In an optional third operating mode, the second set of signal electrons are detected by the detector device at the second detection speed and the first set of signal electrons are not detected.

14. An electron beam device, comprising: an electron source for generating a primary electron beam propagating along an optical axis; A sample stage, the sample stage is used to support the sample; an objective lens configured to focus the primary electron beam onto the sample to release signal electrons; as well as A detector device, the detector device comprising: an electron detector comprising a central opening for the primary electron beam, one or more radially inner detector segments at least partially surrounding the central opening, and one or more radially outer detector segments at least partially surrounding the central opening, Wherein the detector device is configured to amplify one or more first detector signals caused by a first group of signal electrons incident on the one or more radially inner detector segments with a first amplification intensity, and at the same time amplify one or more second detector signals caused by a second group of signal electrons incident on the one or more radially outer detector segments with a second amplification intensity higher than the first amplification intensity.

15. An electron beam device as described in claim 14, wherein the one or more first detector signals and the one or more second detector signals are amplified by a preamplifier of the detector device, which is connected to the electron detector and is at least one of the following: (i) integrated with the electron detector, (ii) arranged directly adjacent to the electron detector inside the vacuum chamber of the electron beam device, and (iii) fixedly mounted in the vacuum chamber of the electron beam device.

16. The electron beam apparatus of claim 15, further comprising a main amplifier for amplifying the preamplified detector signal provided by the preamplifier.

17. A method of imaging and / or inspecting a sample, the method comprising: generating a primary electron beam propagating along an optical axis; focusing the primary electron beam onto the sample with an objective lens to cause emission of a first set of signal electrons and a second set of signal electrons, the second set of signal electrons propagating farther from the optical axis than the first set of signal electrons; amplifying one or more first detector signals caused by the first set of signal electrons incident on one or more radially inner detector segments of the electron detector at a first amplification intensity; as well as One or more second detector signals caused by the second set of signal electrons incident on one or more radially outer detector segments of the electron detector are amplified at a second amplification intensity that is higher than the first amplification intensity.

18. The method of claim 17, wherein the one or more first detector signals and the one or more second detector signals are amplified by a preamplifier, in particular by at least one mutual impedance amplification circuit of the preamplifier, the preamplifier being at least one of: integrated with the electron detector, and arranged adjacent to the electron detector in a vacuum environment.

19. The method of claim 17 or 18, wherein the one or more radially inner detector segments comprise two or four inner detector segments arranged in an annular manner surrounding a central opening in the electron detector, and the one or more radially outer detector segments comprise two, four or eight outer detector segments arranged in an annular manner surrounding the two or four inner detector segments, the method comprising: amplifying two or four first detector signals provided by the two or four inner detector segments at the first amplification strength, and The two or four second detector signals provided by the two or four outer detector segments are amplified at the second amplification strength.

20. The method of claim 17 or 18, wherein the landing energy of the primary electron beam on the sample is 15 keV or higher.

21. The method of claim 17 or 18, further comprising switching between the first operating mode and at least one of the second operating mode and the third operating mode, wherein in the first operating mode, the primary electron beam is incident on the sample at a first landing energy, and both the first set of signal electrons and the second set of signal electrons are detected; In the second operating mode, the primary electron beam is incident on the sample at a second landing energy that is less than the first landing energy, and the first set of signal electrons are detected while the second set of signal electrons are not detected; and In the third operating mode, the second set of signal electrons are detected and the first set of signal electrons are not detected.

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