Detector and measurement device

Abstract

Provided is a detector (5) comprising: a plurality of light-emitting elements (10a, 10b, 10c) that emit light as a result of the collision of quanta emitted from a sample upon irradiation of the sample with a beam; light-receiving elements (12a, 12b, 12c) that receive, on a light-receiving surface, the light generated by the light-emitting elements (10a, 10b, 10c); and light guides (11a, 11b, 11c) that propagate the light emitted from the light-emitting elements (10a, 10b, 10c) to the light-receiving elements (12a, 12b, 12c). The detector is characterized in that: the light-emitting elements (10a, 10b, 10c) are planar and have a transparent part (10s) and a light-emitting layer (10e); the transparent part (10s) is thicker than the light-emitting layer (10e); light emitted by the light-emitting layer (10e) is emitted to the transparent part (10s); and in the transparent part (10s), if a surface having a normal line parallel to a normal line of the light-emitting layer (10e) and facing the light-emitting layer (10e) is defined as a facing surface and a surface having a normal line in a direction parallel to the light-emitting layer (10e) is defined as a side surface, at least one of the following configurations is established, a first configuration in which light is incident on the light guides (11a, 11b, 11c) from the side surface of the transparent part (10s), and a second configuration in which the light-emitting elements (10a, 10b, 10c) are disposed so as to be inclined with respect to a surface perpendicular to an irradiation direction of the beam, and light is incident on the light guides (11a, 11b, 11c) from both the side surface and the facing surface of the transparent part (10s).

Description

Detectors and Measuring Devices

[0001] The present disclosure relates to detectors and measurement devices.

[0002] Detectors are used to convert particle beams such as electrons and ions, and radiation such as X-rays and gamma rays, into electrical signals. When the detection target is charged particles, they are called charged particle detectors, and when the detection target is radiation, they are called radiation detectors. For example, in charged particle beam devices that use charged particle beams such as electrons, such as scanning electron microscopes (SEMs), the signals to be detected are charged particles such as electrons, and they are equipped with a charged particle detector for detecting the charged particles. An SEM irradiates a sample to be observed with an electron beam generated by an electron source, and then detects the electrons emitted from the sample with a detector. The charged particle detector outputs an electrical signal corresponding to the amount of detected electrons. An SEM image is formed by two-dimensionally displaying the relationship between this electrical signal and the position of the electron beam irradiation on the sample.

[0003] Many of these charged particle detectors are composed of a light-emitting element that converts detected electrons into photons, a light-receiving element that detects the photons from the light-emitting element and converts them into an electrical signal, and a light guide that delivers the light emitted by the light-emitting element to the light-receiving element. The light-receiving element may be a photomultiplier tube (PMT) or a silicon photomultiplier (SiPM). A similar configuration can also be used as a radiation detector by changing the type of light-emitting element. In other words, a radiation detector uses a light-emitting element that converts detected radiation into light of a wavelength that can be detected by the light-receiving element, and delivers the light from the light-emitting element to the light-receiving element via a light guide.

[0004] In recent years, detectors have been required to have various performance characteristics. For example, in order to improve the S / N ratio of SEM images, it has become important to have a detector whose output signal does not saturate when the electron beam irradiation dose is increased. Patent Document 1 proposes a detector that has a light-emitting element, a light guide, and a photodetector, and whose photodetection surface has a larger area than the detection surface of the light-emitting element, in order to obtain an observation image with accurate contrast without saturation.

[0005] International Publication No. 2021 / 176513

[0006] When an electron beam is irradiated onto a sample, signal electrons are emitted radially from an irradiation area (hereinafter referred to as an observation point) having a width of several tens of micrometers. In order to efficiently capture these signal electrons, it is preferable that the light-emitting element has an isotropic shape such as a circular ring. If the light-emitting element has a circular ring shape, the emission surface that emits light from the light-emitting element will also be circular.

[0007] On the other hand, the light-receiving surface of a light-receiving element is generally rectangular. Therefore, to efficiently capture signal electrons and convert them into signals in the light-receiving element, a light guide is required to illuminate the square light-receiving surface with light emitted from the annular light-emitting element's emission surface. If the light-receiving surface is sufficiently large relative to the area of ​​the emission surface of the light-emitting element and the light-receiving surface and the light-emitting element are sufficiently far apart, a light guide connecting the two can be created, although this results in a large structure. However, a large detector size limits its placement within the SEM. In particular, detectors placed near the sample to acquire more signals require thin and compact detectors, which is incompatible with the large structure described above. As a result, it is not possible to achieve high-efficiency detection of radially emitted signal electrons.

[0008] Therefore, the challenge is to provide a detector configuration that is thin, surrounds the observation point with a light-emitting element, efficiently captures signal electrons, and delivers the emitted light to the light-receiving element with low loss.

[0009] Patent Document 1 does not mention that the loss of light propagation due to the difference in shape between the light-emitting surface and the light-receiving surface is an issue. Because it does not acknowledge this as an issue, it does not mention a method for optically coupling between a circular light-emitting element and a rectangular light-receiving element.

[0010] Although the description has been given with respect to a charged particle detector, the above-mentioned problems arise even when the signal is not an electron but a radiation signal.

[0011] Another issue is that increasing the current of the electron beam irradiating the sample saturates the detector output signal. As the electron beam quantity increases, the number of signal electrons emitted from the sample and detected by the detector increases, improving the S / N ratio of the SEM image. Therefore, there is a demand for an increased electron beam quantity (higher current). At this time, the energy of the signal electrons is converted into photons by the light-emitting element, and the number of photons incident on the light-receiving element also increases.

[0012] However, as the incident photon density relative to the area of ​​the detection surface increases, the photodetector becomes saturated and is no longer able to output an electrical signal accurately proportional to the number of incident photons. For example, a SiPM (e.g., manufactured by Hamamatsu Photonics K.K., model: S13360-3050VE) has a rectangular detection surface with sides of 3 mm and is covered with minute rectangular detection pixels with sides of approximately 50 μm. When a photon is incident on each detection pixel, a current pulse signal is generated for each pixel, and each pixel's current pulse signal represents the detection of one photon. However, as the incident photon density increases and multiple photons are incident on the same detection pixel simultaneously, the proportional relationship between the number of incident photons and the output current is disrupted, making it impossible to obtain an accurate SEM image. This is the problem of photodetector saturation that occurs when the electron beam current is increased.

[0013] The problem will now be explained in more detail. Signal electrons fly from the observation point to the detector, but the position at which the signal electrons enter the light-emitting element is concentrated on the surface of the light-emitting element close to the observation point. In particular, since the light-emitting element cannot be made larger in a detector placed near the sample, the area on which the signal electrons enter becomes very small, resulting in a high incidence density. For this reason, when the current is increased, the large number of photons generated from the very small area of ​​the light-emitting element, that is, the saturation of the light-receiving element by the high-density photons, becomes a serious issue.

[0014] Countermeasures are needed to address the issue of signal saturation caused by high-density light emission from this minute region. This issue is not limited to charged particle detectors, but also applies to radiation detectors in which the radiation generation position and detection position are close to each other.

[0015] The problems described above are similar to those in International Application PCT / JP2023 / 010097 by the same applicant. This application provides a configuration that solves the problems associated with using a planar light-emitting element. Examples of light-emitting elements include scintillators in which a semiconductor layer is formed on a sapphire substrate. Scintillators using a semiconductor layer as a light-emitting layer are characterized by a response time of 10 ns or less, from the time signal electrons are incident to the time light emission begins and ends. A short response time of a light-emitting element shortens the time it takes to detect signal electrons and convert them into a signal, thereby enabling, for example, SEM images to be generated in a short time, thereby reducing imaging time. However, since the semiconductor scintillator is planar, it is not easy to realize a configuration in which the light-emitting element surrounds the observation point, efficiently captures signal electrons, and delivers the emitted light to a light-receiving element with low loss.

[0016] The detector structure, which places the detector close to the observation point and uses planar light-emitting elements to surround the observation point and efficiently detect signal electrons, and the structure that suppresses signal saturation are each important on their own, but by combining them together, the observation and measurement accuracy of measuring devices such as SEMs is greatly improved.

[0017] Therefore, the present disclosure provides a detector, a measuring device, and a charged particle beam device that can efficiently detect signal electrons emitted from an observation point and output an electrical signal without saturation even when the amount of signal electrons or radiation incident on a detector that uses a planar light-emitting element increases.

[0018] In order to solve the above problems, the detector of the present disclosure is a detector comprising: a plurality of light-emitting elements that emit light due to collisions of quanta emitted from a sample when the sample is irradiated with a beam; a light-receiving element that receives the light generated by the light-emitting elements on a light-receiving surface; and a light guide that propagates the light emitted by the light-emitting elements to the light-receiving element, wherein the light-emitting elements are planar and have a transparent portion and a light-emitting layer, the transparent portion is thicker than the light-emitting layer, and emits light emitted in the light-emitting layer to the transparent portion; the transparent portion has a normal parallel to a normal to the light-emitting layer, a surface facing the light-emitting layer is defined as an opposing surface, and a surface having a normal in a direction parallel to the light-emitting layer is defined as a side surface; the detector has at least one of a first configuration in which light is incident on the light guide from the side surface of the transparent portion, or a second configuration in which the light-emitting elements are arranged at an angle with respect to a plane perpendicular to the irradiation direction of the beam, and light is incident on the light guide from both the side surface and the opposing surface of the transparent portion.

[0019] Further features related to the present disclosure will become apparent from the description of this specification and the accompanying drawings. Also, aspects of the present disclosure are achieved and realized by the elements and combinations of various elements and the aspects of the following detailed description and the appended claims. The description of this specification is merely exemplary and does not limit the scope or application of the claims of the present disclosure in any way.

[0020] According to the technique of the present disclosure, it is possible to efficiently detect signal electrons emitted from the observation point. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments.

[0021] 1 is a schematic diagram of a charged particle beam device (SEM) according to a first embodiment. FIG. 1 is a perspective view showing a configuration example of a detector 5 according to the first embodiment. FIG. 2 is a bottom view (i) and a cross-sectional view (ii) of the detector 5. FIG. 3 is a front view of a light-emitting element 10. FIG. 4 is a perspective view of the light-emitting element 10. FIG. 5 is a cross-sectional view of the light-emitting element 10. FIG. 6 is a graph showing measurement results of the distance dependence from the side surface 10os of the light emission amount of a stealth-diced GaN scintillator. FIG. 7 is a graph showing the emission angle distribution of light from the GaN scintillator. FIG. 8 is a cross-sectional view showing a configuration example when the GaN scintillator is not tilted. FIG. 9 is a cross-sectional view showing a configuration example when the GaN scintillator is tilted. FIG. 10 is a graph showing the relationship between the angle of incidence on the light-emitting element and the amount of signal electrons that do not escape and are absorbed in the light-emitting element. FIG. 11 is a perspective view of a light guide 11 as seen from the sample 7 side. FIG. 12 is a perspective view of a light guide 11 as seen from the side where an electron beam is irradiated. FIG. 13 is a bottom view of a SiPM as seen from the light-receiving surface 12i side. FIG. 14 is a cross-sectional view of a SiPM. FIG. 15 is a diagram showing an example of a circuit for obtaining a signal from a SiPM. 1 is a cross-sectional view showing a light-emitting element 10, a light guide 11, and a light-receiving element 12 according to a first modification of the first embodiment. FIG. 2 is a perspective view showing a configuration example of a detector 5 according to a second embodiment. FIG. 3 is a bottom view (i) and a cross-sectional view (ii) of the detector 5 according to the second embodiment. FIG. 4 is a perspective view of a detection element 5e of the detector 5 according to the second embodiment. FIG. 5 is a cross-sectional view of the detection element 5e according to the second embodiment. FIG. 6 is a cross-sectional view of the detection element 5e according to the second embodiment. FIG. 7 is a cross-sectional view of the detection element 5e according to the second embodiment. FIG. 8 is a cross-sectional view of the detection element 5e according to the second embodiment. FIG. 9 is a cross-sectional view of another example of the means for making light incident on the side surface 10os of the light-emitting element 10. FIG. 10 is a cross-sectional view of another example of the means for making light incident on the side surface 10os of the light-emitting element 10. FIG. 11 is a cross-sectional view of another example of the means for making light incident on the side surface 10os of the light-emitting element 10. FIG. 12 is a perspective view showing a configuration example of a detector 5 according to a third embodiment. FIG. 13 is a bottom view (i) and a cross-sectional view (ii) showing a configuration example of the detector 5 according to the third embodiment. FIG. 14 is a perspective view of one detection element group 5g according to the third embodiment. FIG. 15 is a cross-sectional view of the detection element group 5g according to the third embodiment. FIG. 16 is a perspective view of the detection element group 5g according to a first modification of the third embodiment. 10 is a cross-sectional view of a detection element group 5g according to a first modified example of the third embodiment;FIG. 11 is a perspective view of a light-emitting element 10a according to a first modified example of the third embodiment;FIG.1 is a side view of a light-emitting element 10a according to a first modified example of the third embodiment. FIG. 2 is a perspective view showing a configuration example of a detector 5 according to a second modified example of the third embodiment. FIG. 3 is a bottom view (i) and a cross-sectional view (ii) showing a configuration example of a detector 5 according to a second modified example of the third embodiment. FIG. 4 is a partially enlarged view of a detection element group 5g according to a second modified example of the third embodiment. FIG. 5 is a perspective view of a detector 5 according to a fourth embodiment as seen from the sample side. FIG. 6 is a perspective view of a detector 5 according to a fourth embodiment as seen from the electron source side. FIG. 7 is a bottom view of a detector 5 according to a fourth embodiment as seen from the sample side. FIG. 8 is a side view of a detector 5 according to a fourth embodiment. FIG. 9 is a view showing in detail a part of a detector according to a fourth embodiment. FIG. 10 is a view showing in detail a part of a detector according to a fourth embodiment. FIG. 11 is a view showing in detail a part of a detector according to a fourth embodiment. FIG. 12 is a view showing in detail a part of a detector according to a fourth embodiment. FIG. 13 is a view showing in detail a part of a detector according to a fourth embodiment. FIG. 14 is a view showing in detail a part of a detector according to a fourth embodiment. FIG. 15 is a view showing in detail a part of a detector according to a fourth embodiment. FIG. 16 is a view showing in detail a part of a detector according to a fourth embodiment. FIG. 17 is a view showing in detail a part of a detector according to a fourth embodiment. 10 is a perspective view of one detecting element according to a modified example of the fourth embodiment. FIG. 11 is a side view of one detecting element according to a modified example of the fourth embodiment. FIG. 12 is a perspective view of a light receiving element 12a according to a modified example of the fourth embodiment. FIG. 13 is a front view of a light receiving element 12a according to a modified example of the fourth embodiment. FIG. 14 is a side view showing an example of the configuration of a detector 5 according to a modified example 2 of the first embodiment. FIG. 15 is a side view showing an example of the configuration of a detector 5 according to a modified example 3 of the first embodiment. FIG. 16 is a diagram for explaining an example of the configuration of a measuring device according to a fifth embodiment. FIG. 17 is a diagram showing a voltage signal Sv generated in a detection circuit 15. FIG. 18 is a diagram showing an example of a graphical user interface 16 (GUI) when improving visibility by energy discrimination (pulse height discrimination). FIG. 19 is a cross-sectional view showing an example of a detector according to prior art.

[0022] In this specification, particle beams such as electrons or ions, and beams such as X-rays or gamma rays that are irradiated onto a sample are collectively referred to as simply "beams," or the irradiated quantum is specified and referred to as an electron beam, etc. When a beam is irradiated onto a sample, particles such as electrons or ions, photons, and radiation (high-energy photons) such as X-rays and gamma rays are emitted from the sample depending on the energy and type of the beam and the type of sample. These particles and photons (including radiation) are collectively referred to as "quantums." A light-emitting element (commonly called a scintillator) is an element that emits light when a quantum is incident on it.

[0023] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Hereinafter, an electron microscope using an electron beam, particularly a scanning electron microscope, will be described as an example of a charged particle beam device, but the present disclosure is not limited to this. For example, a scanning ion microscope using an ion beam is also included as a charged particle beam device. It goes without saying that the present disclosure can also be applied to semiconductor pattern measurement devices, inspection devices, observation devices, and the like that use a scanning electron microscope.

[0024] The technology of the present disclosure is not limited to the embodiments described below, and various modifications are possible within the scope of the technical concept. Corresponding parts in the drawings used to explain the embodiments described below are denoted by the same reference numerals, and duplicated explanations will be omitted.

[0025] [First embodiment] <Configuration example of a charged particle beam device> Fig. 1 is a schematic diagram of a charged particle beam device 1 (SEM). The SEM functions as a measurement device. As shown in Fig. 1, the charged particle beam device 1 has a scanning deflector 3 and an objective lens 4 arranged on the trajectory of an electron beam 101 (generally called a primary electron or a primary electron beam in an SEM) extracted from an electron source 2.

[0026] The electron beam 101 is irradiated onto the sample 7 placed on the sample transfer stage 6, and signal electrons 102 are emitted from the sample 7. Here, the signal electrons 102 refer to electrons emitted from the sample, such as secondary electrons that are directly excited by the electron beam 101 and emitted into a vacuum, and backscattered electrons that are generated by the electron beam 101 being repeatedly scattered within the sample and then emitted back into a vacuum. Needless to say, when the signal electrons are incident on a reflector or the like and the generated secondary electrons and tertiary electrons are incident on a detector and become a signal, these secondary electrons and tertiary electrons are called signal electrons.

[0027] Generally, backscattered electrons are defined as signal electrons of 50 eV or more. When the electron beam 101 is irradiated, not only signal electrons 102 but also X-rays may be generated. In this embodiment, the signal electrons 102 are used as the quanta incident on the detector, but this is not limiting and the signal may also be X-rays.

[0028] A detector 5 for detecting signal electrons 102 is provided below the objective lens 4. An opening is provided in the center of the detector 5 to allow the electron beam 101 to pass through. The electron beam 101 emitted from the electron source 2 is controlled by the objective lens 4 and focused on the sample 7 so that the beam diameter is minimized. The scanning deflector 3 is controlled by a system control unit 8 so that the electron beam 101 scans a predetermined area of ​​the sample 7.

[0029] Signal electrons 102 generated from the position on the sample 7 where the electron beam 101 reaches are detected by the detector 5. In synchronization with a scanning signal sent from the system control unit 8 to the scanning deflector 3, the detected signal electrons 102 are processed to form an SEM image on the monitor 9.

[0030] <Configuration example of detector> Fig. 2A is a perspective view showing a configuration example of the detector 5. Fig. 2B(i) is a bottom view of the detector 5 as seen from the sample 7 side. Fig. 2B(ii) is a cross-sectional view taken along line AA shown in (i).

[0031] In the description of this embodiment, the direction away from the central axis C of the electron optical system of the charged particle beam device 1 (radial direction; for example, the x-axis direction in Figure 2B(i)) is sometimes referred to as the outward or outward direction, and conversely, the direction toward the central axis C is sometimes referred to as the inward or inward direction.

[0032] The detector 5 is composed of a light emitting element 10, a light guide 11, a light receiving element 12, and a mounting substrate 13 on which the light receiving element 12 is mounted. In Fig. 2B(i), the three-dimensional structure of the light emitting element 10 and the part of the light receiving element 12 that is hidden by the light guide 11 are also shown by dashed lines. In this embodiment, the light receiving element 12 is a 10 ６ The following describes the case where a SiPM, which is one of the smallest photodiodes in its class, is used. However, the photodiode is not limited to this. Various photodiodes can be used, such as a PMT (for example, a micro-PMT, which is a small PMT), an avalanche photodiode, and a PIN photodiode.

[0033] The center of the detector 5 is an opening 14 for passing the electron beam 101, and a hole is made in the mounting substrate 13, leaving an area free of components such as the light-emitting element 10. The electron beam 101 passes through the opening 14 and is incident on the sample 7.

[0034] 2B(ii) will be used to explain the process from irradiation of the electron beam 101 to reception of photons emitted by the signal electrons 102. In FIG. 2B(ii), the sample 7, the electron beam 101, the signal electrons 102, and rays Ray1 and Ray2, which are examples of rays of light emitted by the light-emitting element, are shown.

[0035] The signal electrons 102 are emitted from an observation point MP where the electron beam 101 is incident on the sample 7. Because the electron beam 101 is scanned, strictly speaking, the observation point MP moves within a certain range. However, this range is sufficiently small compared to the size of the detector, and therefore, in the description of this embodiment, it is assumed to be the point where the central axis C intersects with the sample 7, as shown in FIG. 2B(ii). In the case where the signal electrons 102 are backscattered electrons with high energy, the angle (polar angle θo) between the flight direction of the signal electrons 102 and the central axis C can be considered to fly while maintaining approximately the same emission angle as when they were emitted from the observation point MP. Hereinafter, the angle from the central axis C is referred to as the polar angle, and the angle in a plane perpendicular to the central axis C is referred to as the azimuthal angle φ. If necessary, a reference for the azimuthal angle can be set appropriately.

[0036] Most of the signal electrons 102 emitted from the sample 7 are incident on the incident surface 10i of the light-emitting element. The light-emitting element 10 of this embodiment is a GaN scintillator in which a layer containing GaN having a thickness of about several hundred nm to several tens of μm is formed on a sapphire substrate, and is a scintillator obtained by processing a plate-shaped GaN scintillator into a trapezoid.

[0037] The layer in which light emission occurs is referred to as the light-emitting layer. The light-emitting layer of a GaN scintillator is a layer containing GaN (details will be described later in this embodiment). The substrate on which the light-emitting layer is formed, such as a sapphire substrate, is referred to as the transparent substrate. The transparent substrate has a transparent portion through which light can propagate. This GaN scintillator is a planar light-emitting element having a transparent substrate and a light-emitting layer.

[0038] Here, "transparent" means that the light emitted in the light-emitting layer is transmitted through the substrate. The transparent substrate is not limited to being colorless or non-scattering, and may be a colored and scattering substrate, but it is a substrate that can transmit the light emitted in the light-emitting layer and emit it to the outside of the substrate. Examples of transparent substrates include a sapphire substrate, which is a single crystal of alumina, a translucent alumina ceramic substrate, YAG and Y ２ O ３ and glass substrates such as quartz.

[0039] The signal electrons 102 penetrate from the incident surface 10i of the light-emitting element to a depth of several tens of nanometers to several tens of micrometers depending on the energy of the electrons, and lose their energy. Meanwhile, the light-emitting layer of the light-emitting element 10 that has gained the energy emits light. When the current of the electron beam 101 is increased or the voltage for accelerating the electron beam is raised, and high-energy signal electrons 102 are generated and incident on the incident surface 10i, a large number of photons are generated from this thin, small-area light-emitting layer.

[0040] In this way, the light-emitting element 10 emits light due to the collision of quanta (signal electrons 102 in this embodiment, but may be other particle beams or radiation; the same applies to other embodiments) emitted from the sample 7 when a beam (electron beam 101 in this embodiment, but not limited to this) is irradiated onto the sample 7. FIG. 18 is a cross-sectional view showing an example of a detector according to conventional technology. Using the conventional detector shown in FIG. 18, we will explain the issues caused by the large amount of photons generated from a small area. In the case of a detector placed between the sample 7 and the SEM objective lens, the space between the mounting substrate 13 and the sample 7 is approximately 5 mm to ensure sufficient performance, such as SEM resolution. Therefore, there is almost no room for a light guide. Therefore, as shown in FIG. 18, the light-receiving element 12 is placed on the mounting substrate 13, and the light-emitting element 10 is placed opposite the light-receiving element 12. In this case, the distance between the observation point MP and the innermost light-emitting element 10n is approximately 1 to 3 mm.

[0041] On the other hand, although SiPMs are compact, if the light-receiving surface is too small, the light from the incidence of a single signal electron will quickly saturate, so a size of approximately 3 mm is required. Because of the size of approximately 3 mm, most of the signal electrons 102 will concentrate on the light-emitting element 10n closest to the electron beam 101, causing the problem of saturating the light-receiving element 12n. In this configuration, when the light-receiving element is a SiPM, saturation will occur even with an electron beam current value of approximately several tens of pA. On the other hand, to obtain an SEM image with a sufficient S / N ratio, a current of several nA or more is required, although this depends on the sample 7, for example, for semiconductor circuit patterns having a three-dimensional structure such as a trench portion.

[0042] In this embodiment, to solve this problem, a configuration is adopted in which most of the light generated in large quantities at the incident surface 10i is guided in a first direction intersecting the irradiation direction of the electron beam 101, and the light is diffused and the photon density is reduced by propagating the light in the first direction through an optical system consisting of the light emitting element 10 and the light guide 11. The first direction is, for example, a direction roughly directed radially outward from the electron beam 101, and may include a component in the axial direction of the electron beam 101 (the same direction as the traveling direction of the electron beam 101 or the opposite direction). The optical path that guides light in the first direction is referred to as the first optical path.

[0043] When the light is diffused to a certain extent, a second optical path continues from the first optical path, guiding the light toward the light-receiving surface of the light-receiving element, and the light reaches the light-receiving element. In this way, the detector 5 forms a first optical path and a second optical path. The first optical path is an optical path that guides light toward a first direction, and the second optical path is an optical path that guides the light arriving via the first optical path toward the light-receiving surface 12i of the light-receiving element 12 (see FIG. 2B(i)).

[0044] 2B(i), the light receiving element 12 has a light receiving surface 12i, and the light generated by the light emitting element 10 is received by this light receiving surface 12i. In this embodiment, the light receiving surface 12i is disposed at a position farther away from the electron beam 101 than the light emitting element 10. This makes it possible for many light receiving elements 12 to surround the electron beam 101 and receive diffused light. This configuration prevents saturation of the signal from the light receiving element 12.

[0045] In this embodiment, the light receiving element 12 may be a silicon photomultiplier (SiPM), which can suppress signal saturation according to the characteristics of the SiPM.

[0046] Note that the position of the light-receiving surface farther from the electron beam than the light-emitting element means, for example, in one definition, a configuration in which the distance between the electron beam and the part of the light-receiving surface closest to the electron beam is greater than the distance between the part of the light-emitting element closest to the electron beam and the electron beam. In another definition, a configuration in which the distance between the electron beam and the part of the light-receiving surface farthest from the electron beam is greater than the distance between the part of the light-emitting element farthest from the electron beam and the electron beam. A definition combining the conditions of these two definitions may also be used. In FIG. 2B(ii), all parts of the light-receiving surface 12i are positioned farther from the electron beam 101 than all parts of the light-emitting element 10.

[0047] In this embodiment, the light-receiving surface 12i is disposed in a direction perpendicular to the irradiation direction of the electron beam 101 (i.e., the normal to the light-receiving surface 12i is parallel to the irradiation direction of the electron beam 101). This allows the detector 5 to be configured to be thin (i.e., with a small axial dimension). Note that the light-receiving surface 12i does not need to be oriented strictly perpendicular to the irradiation direction of the electron beam 101; as long as it is oriented in a direction intersecting the irradiation direction of the electron beam 101, the axial dimension of the detector 5 can be reduced to an extent corresponding to the orientation.

[0048] The light emitting surface 10o of the light emitting element 10 is bonded to the light incident surface 11i of the light guide, and the light emitting surface 11o of the light guide 11 is bonded to the light receiving surface 12i of the light receiving element 12. In this manner, light is incident on the light guide 11 from the opposing surface of the transparent substrate (third configuration).

[0049] The light emitting element 10, light guide 11, and light receiving element 12 are mounted on the same mounting substrate 13. As shown in Fig. 2B(ii), the light guide 11 is configured to form a first optical path and a second optical path, which enables light to propagate from the light emitting element 10 mounted on the same substrate to the light receiving element 12. As a result of mounting the light emitting element 10 and the light receiving element 12 on the same substrate, the length of the light guide 11 can be shortened compared to when the light emitting element 10 and the light receiving element 12 are mounted on separate substrates, resulting in a structure that achieves high light utilization efficiency.

[0050] 2B(ii), the length of the light guide 11 in the first direction in a cross section including the central axis C can be made shorter than the width of four light receiving elements 12. If the light guide 11 can be made smaller, the entire detector 5 can be made smaller, which has the effect of enabling it to be placed in various installation locations and expanding the range of application.

[0051] In the above description, the light emitting element 10 and the light guide 11 are fixed by adhesive. However, the fixing method is not limited to this. They may be covered with a thin cover, or mechanically fixed to the mounting substrate 13 using screws or the like, or both adhesive and mechanical fixing may be used.

[0052] In Figure 2B(i), the arrangement of the light receiving elements 12 surrounding the electron beam 101 is best when it is circular (e.g., at each vertex of a regular polygon) because it allows for uniform light reception. Furthermore, a circular arrangement allows for the light receiving elements to be arranged at high density, which can accommodate large currents and improves light utilization efficiency because it allows for efficient reception without loss of propagating light. However, the arrangement of the light receiving elements 12 does not necessarily have to be circular, and various surrounding methods are possible, such as a rectangle or an ellipse with randomly spaced light receiving elements 12. The present disclosure does not limit the arrangement of the light receiving elements 12.

[0053] In the example of FIG. 2B(ii), the first direction can be defined as a direction perpendicular to the electron beam 101, for example, the direction of arrow D1. Although perpendicular in this example, the mounting substrate 13 may be tilted for mounting reasons within the SEM, or the electron beam 101 may be tilted to match the measurement target, and the first direction can be set appropriately. What is important is to diffuse light in a direction that is not parallel to the electron beam 101 (a direction intersecting the electron beam 101). An example of a configuration for guiding light in the first direction is a configuration in which the light-emitting element 10 and the light guide 11 are aligned in the first direction in a cross section including the central axis C, as shown in FIG. 2B(ii), and the optical path formed by these components is the first optical path.

[0054] In Figure 2B (ii), the second optical path is the radially outer portion of the light guide 11, i.e., the triangular region where the reflecting surface 11r is located. This is the region indicated by arrow D2. Because the amount of light directed toward the light-receiving surface 12i increases rapidly from the point where the reflecting surface 11r, which is inclined relative to the first direction, begins toward the radially outer side, the optical path from the position where the reflecting surface 11r begins can be referred to as the second optical path. Similarly, when the first optical path and the second optical path are formed by curved surfaces (e.g., when the light guide is tubular or serpentine), the position where the amount of light directed toward the light-receiving surface 12i begins to increase or the position where the inclination of the surface relative to the first optical path increases can be referred to as the second optical path.

[0055] The boundary between the first optical path and the second optical path may or may not be clearly defined. The downstream portion of the first optical path and the upstream portion of the second optical path may overlap, or another optical path may be formed between these optical paths. For example, the first optical path may be the portion including the optical path immediately after light is generated by the light-emitting element 10, and the second optical path may be the portion including the optical path immediately before the light is incident on the light-receiving surface 12i of the light-receiving element 12.

[0056] This will be explained in detail using light rays Ray1 and Ray2. Both emit light at the point where the signal electrons 102 are incident and begin to propagate. Light ray Ray1 is not reflected by the reflecting surface 11r, but propagates through the first optical path and the second optical path to enter the light receiving element. The light receiving surface 12i and the light guide exit surface 11o are connected with an adhesive, and light ray Ray1 is not reflected by the exit surface 11o and enters the light receiving surface 12i via the adhesive.

[0057] In particular, the light ray Ray1 is reflected twice in the first optical path. In this way, the first optical path is formed to include the following reflecting surfaces: - a surface that reflects light having a component in the first direction and a component in the opposite direction to the irradiation direction of the electron beam (upward component in the drawing) in a direction having a component in the first direction and a component in the irradiation direction of the electron beam (downward component in the drawing) (first reflection) - a surface that reflects light having a component in the first direction and a component in the irradiation direction of the electron beam (downward component in the drawing) in a direction having a component in the first direction and a component in the opposite direction to the irradiation direction of the electron beam (upward component in the drawing) (second reflection) By configuring the first optical path to include at least one of these surfaces, it is possible to propagate light in the first direction.

[0058] In this example, ray Ray2 travels substantially straight in the first direction, reflects off reflective surface 11r in the second optical path, and enters the light receiving element. For example, reflective surface 11r is a surface that reflects light arriving in a direction perpendicular to the irradiation direction of the electron beam (ray Ray2 arrives in approximately this direction) in a direction having a component opposite to the irradiation direction of the electron beam (upward component in the figure). With this configuration, light traveling in the first direction can be guided to light receiving surface 12i.

[0059] It is assumed that the reflection at the interfaces between the light emitting element 10 and the light guide 11 and the vacuum is total reflection. Therefore, light that does not satisfy the total reflection condition is emitted into the vacuum and is lost. To reduce loss, a reflective material such as an aluminum film may be formed on the surface of these components.

[0060] If there is no adhesive between the light receiving surface 12i and the light guide exit surface 11o and the light guide interface is air, there is a high probability that the light will be reflected by the exit surface 11o due to total reflection or Fresnel reflection. For example, light ray Ray1 has a high probability of being reflected because of its large angle of incidence on the exit surface 11o. The light reflected by the exit surface 11o may repeatedly reflect between the light receiving surface 12i and the reflecting surface 11r and then enter the light receiving surface 12i, or it may exit from the reflecting surface 11r to the outside of the detector and become stray light, resulting in loss. For this reason, it is preferable to provide an adhesive between the light receiving surface 12i and the light guide exit surface 11o, which has the effect of improving light utilization efficiency.

[0061] In Figure 2B(i), the spread of light in the azimuthal angle φ direction is explained using rays Ray1 to Ray4. For convenience, the circumferential position of the point at which the signal electron 102 is incident is taken as the reference for the azimuthal angle φ and is designated as the x-axis. Rays Ray1 and Ray2 in Figure 2B(i) are examples of light rays with an azimuthal angle φ of zero, which are incident on the light-receiving element 12 closest to the point at which the signal electron 102 is incident. Since light emission in the azimuthal angle direction is also isotropic, light also propagates in directions with large azimuthal angles, such as rays Ray3 and Ray4. Light diffuses when propagated in various azimuthal angles in this way.

[0062] As described above, when the photodetectors 12 are arranged to surround the electron beam 101 as in this embodiment, light diffused in the azimuthal direction can also be received. In other words, this configuration, in which the light-emitting element 10 is arranged in the center so as to surround the central axis and the photodetectors 12 are arranged on the periphery so as to surround the central axis, and light is propagated in a first direction and then in a second direction, diffuses light emitted in a small region near the center in the azimuthal direction to reduce the photon density, and receives the light with the multiple photodetectors 12 surrounding the periphery, thereby reducing the amount of light entering each photodetector and suppressing saturation. By increasing the circumference of the photodetectors 12 according to the amount of electron beam 101, a detector 5 can be provided that does not saturate even when the signal electrons 102 increase.

[0063] <Regarding the Light-Emitting Element> In this embodiment, a GaN scintillator is used as an example of the light-emitting element 10. As mentioned above, GaN is a semiconductor material with a short response time from light emission to extinction. The response time can be 10 ns or less, depending on the structure. The semiconductor material is formed as a layer of approximately 100 nm to several tens of μm on a transparent substrate, and this layer serves as the light-emitting layer. A detailed example of the light-emitting layer of a GaN scintillator will be described. A GaN layer, primarily made of GaN, is formed on a sapphire substrate serving as a transparent substrate, and a quantum well structure is formed thereon. The quantum well structure is a structure in which multiple layers containing InGaN and multiple layers containing GaN are alternately stacked. Strictly speaking, light emission is considered to occur in the quantum well structure, but in this disclosure, the GaN layer formed on the transparent substrate through the quantum well structure will be referred to as the light-emitting layer. Other examples of semiconductor materials include ZnO. Needless to say, this disclosure is not limited by the material of the light-emitting element.

[0064] Fig. 3A is a front view of the light emitting element 10. Fig. 3B is a perspective view of the light emitting element 10. Fig. 3C is a cross-sectional view taken along line AA' in Fig. 3A.

[0065] In the cross-sectional view of Figure 3C, the transparent substrate 10s is a sapphire substrate with a thickness of 430 μm in this example. The light-emitting layer 10e has a thickness of approximately 100 nm to several tens of μm, and signal electrons can be detected only through this thin layer. A metal layer 10m is formed on the surface of the light-emitting layer 10e to prevent charging due to incident signal electrons. The surface of this metal layer 10m serves as the incident surface 10i for signal electrons. Examples of materials for the metal layer 10m include Al, ITO, and Ag, and the thickness is approximately 100 nm.

[0066] The signal electrons lose a small amount of energy in the metal layer 10m and enter the light-emitting layer 10e, where they lose and absorb a portion of the remaining energy. The light-emitting layer 10e generates photons according to the absorbed energy. Some of the generated photons are absorbed by the light-emitting layer 10e and the metal layer 10m, but most of the remaining photons are incident on the sapphire substrate 10s and then emitted from the sapphire substrate 10s. The light (photon) emission surface 10o consists of an opposing surface 10oc facing the planar light-emitting layer 10e and a side surface 10os that is substantially perpendicular to the light-emitting layer 10e.

[0067] As shown in Figures 3A and 3B, the GaN scintillator serving as the light-emitting element 10 is processed into a trapezoidal shape. As shown in Figure 2B(ii), the incident surface 10i of the light-emitting element is arranged so as to three-dimensionally cover the observation point MP, i.e., to have the range of the light-emitting element 10 in not only the radial direction of the electron beam 101 but also the irradiation direction. As shown in Figure 2B(ii), in order to achieve three-dimensional coverage by combining planes, the incident surface 10i is inclined with respect to a plane perpendicular to the irradiation direction of the beam, and the planar shape of the incident surface 10i of the light-emitting element is a trapezoid with the side facing the sample 7 being longer. Although other shapes such as a hexagon are possible, a trapezoid is the best shape for surrounding the observation point MP without gaps and aligning the heights of the upper and lower surfaces of the light-emitting element 10, and it is also a practical shape that is easy to process.

[0068] The reason for arranging the light-emitting elements 10 so that their upper surfaces are aligned will be explained. If there is a partial protrusion on the upper surface in any circumferential direction (azimuthal direction), it becomes necessary to make the light-emitting element smaller overall so that the protrusion does not enter the opening 14, and the amount of detected signal electrons decreases. In order to suppress this decrease in the signal amount, it is advisable to align the upper surfaces of the light-emitting elements 10.

[0069] Next, the reason for arranging the light-emitting elements 10 so that their bottom surfaces are aligned will be explained. If there is a partial protrusion on the bottom surface anywhere in the circumferential direction, it becomes necessary to make the light-emitting element smaller overall to prevent the protrusion from approaching the sample 7, which reduces the amount of signal electrons detected. In order to suppress this reduction in the signal amount, it is advisable to align the bottom surfaces of the light-emitting elements 10.

[0070] In other words, by making the light-emitting element 10 trapezoidal and arranging it at an angle with respect to a plane perpendicular to the beam irradiation direction, the observation point MP is covered three-dimensionally using a planar semiconductor scintillator with a short response time, and the upper and lower surfaces of the light-emitting element are aligned, thereby suppressing a decrease in signal level.

[0071] In the configuration of this embodiment, the observation point MP is three-dimensionally covered by four trapezoidal light-emitting elements 10, but three or more elements can be used to three-dimensionally cover the observation point MP. The number of light-emitting elements 10 can be determined appropriately. Since gaps are likely to occur between the light-emitting elements 10, when there are three light-emitting elements 10, the gaps can be minimized and the efficiency of detecting signal electrons can be maximized.

[0072] A method for processing the light-emitting element 10 will be described. Normally, the light-emitting layer 10e is sufficiently thin, so it is sufficient to process the transparent substrate. Methods for processing sapphire or Si substrates include cutting using a blade (blade dicing), laser ablation processing in which a laser is irradiated to melt and process the surface of the object to be processed, and stealth dicing (registered trademark) processing in which a laser is used to form cracks in the transparent substrate and divide it. Details of stealth dicing are described in the following literature and URL.

[0073] Literature: Damage-Less Singulation of Ultra-Thin Wafers using Stealth Dicing (2020 IEEE 70th Electronic Components and Technology Conference (ECTC)) URL: https: / / www.hamamatsu.com / jp / ja / product / lasers / laser-related-products / stealth-dicing-technology.html

[0074] Any of the processing methods can process the light emitting element 10 into a trapezoid shape, but stealth dicing is the best in terms of the effective light emitting area 10eff.

[0075] Here, the effective light-emitting region will be described. In the case of a light-emitting element 10 of the type in which a semiconductor layer is formed on a transparent substrate, when the light-emitting element 10 is cut into a trapezoidal shape from a circular wafer, the amount of light emitted decreases in an area a certain distance inward from the side surface 10os. For example, if the effective light-emitting region is defined as an area in which the amount of light emitted is 80% or more compared to the amount of light emitted near the center, then the area a certain distance Doff inward from the side surface 10os (the area within the dotted line 10eff in Figure 3A) becomes the effective light-emitting region.

[0076] In the case of blade dicing, the distance Doff is several tens of μm or more due to chipping, etc. On the other hand, in the case of stealth dicing, the distance Doff is close to zero.

[0077] 3D is a graph showing the measurement results of the distance dependency from the side surface 10os of the light emission amount of a stealth diced GaN scintillator. The vertical axis shows the relative light emission amount when the light emission amount near the center is set to 100. The horizontal axis shows the distance from the side surface 10os to the position where the electrons were incident on the GaN scintillator. It can be seen that even at a position 10 μm from the side surface 10os, the light emission amount is 91%, and the distance Doff is less than 10 μm.

[0078] Therefore, when processing a planar scintillator into a trapezoid to three-dimensionally cover the observation point MP, stealth dicing is extremely useful because it can increase the effective light-emitting area. Furthermore, because stealth dicing is a laser process, it is easy to divide the component into smaller pieces. The trapezoidal upper base of the light-emitting element 10 measures, for example, 0.1 mm to 3 mm, and the lower base measures, for example, 0.2 mm to 5 mm, and this can be processed using a laser.

[0079] Therefore, it is possible to process trapezoidal light-emitting elements 10 using laser processing, and furthermore, by using a laser to create cracks in the light-emitting elements (stealth dicing), the effective light-emitting area can be enlarged. When a transparent substrate is processed using stealth dicing, the cracked portions of the cut (divided) surface become rough, while the remaining portions become mirror-like. This also has the effect of reducing optically unnecessary scattering compared to cut surfaces processed using blade dicing or laser ablation. Furthermore, when a transparent substrate is processed using stealth dicing, stripes of laser-focused traces (modified layer (SD layer)) are present on the cut surface (see the URL above). This modified layer may exist in multiple layers along the thickness direction of the transparent substrate, or only a single layer may exist.

[0080] 2A and 2B(ii), the incident surface 10i of the light-emitting element 10 is tilted so that the normal to the surface faces the observation point MP. This configuration has two advantages. One is that it increases the amount of light emitted from the light-emitting element 10 that is guided in the first direction. The other is that it absorbs as much energy as possible of the incident signal electrons to increase the amount of light emission. These advantages will be explained in order.

[0081] The following describes how to increase the amount of light guided in the first direction. Fig. 3E is a graph showing the emission angle distribution of light from the GaN scintillator. This graph shows the results of simulation calculations using an optical model of the GaN scintillator shown in Fig. 3C. The vertical axis represents the relative intensity of the emitted light. The horizontal axis represents the angle from the normal to the emission surface 10oc. It can be seen that there is strong emission in the normal direction.

[0082] 3F is a cross-sectional view showing an example of the configuration when the GaN scintillator is not tilted. When the GaN scintillator is not tilted as in Fig. 3F, light enters the light guide as shown by ray Ray5 and exits from the surface opposite to the incident surface, resulting in loss.

[0083] 3G is a cross-sectional view showing an example of a configuration when the GaN scintillator is tilted. When the GaN scintillator is tilted as in FIG. 3G , as the tilt angle θis increases, the amount of light that is reflected and guided by the upper and lower surfaces of the light guide, as shown by light ray Ray6, increases. The amount of light that is guided increases most when the incident surface 10i of the GaN scintillator is perpendicular to the first direction. Therefore, with regard to increasing the amount of light guided in the first direction, it is effective if the incident surface 10i is tilted with respect to the first direction.

[0084] Next, we will explain how to increase the amount of energy absorbed by signal electrons. When the incident angle of the signal electrons onto the light-emitting element increases, the signal electrons that have once entered the light-emitting element are repeatedly scattered within the light-emitting element and escape from the light-emitting element into the vacuum again. This mechanism is a conclusion reached through experiments and electron trajectory simulations.

[0085] 3H is a graph showing the relationship between the angle of incidence on the light-emitting element and the amount of signal electrons absorbed within the light-emitting element without escaping. The horizontal axis is the angle of incidence θi. The vertical axis is the amount of signal electron absorption relative to 0 degrees. The amount of signal electron absorption is maximum when the angle of incidence θi is zero and drops sharply when it exceeds 30 degrees. In other words, when the angle of incidence θi of the signal electrons on the light-emitting element exceeds 30 degrees, the amount of energy absorption of the signal electrons decreases significantly, and therefore the amount of light emission also decreases significantly. Therefore, by positioning the light-emitting element so that the angle of incidence θi is 30 degrees or less, the effect of suppressing the decrease in the amount of light emission (i.e., the amount of signal) can be achieved.

[0086] From this perspective, the tilt angle θis of the light-emitting element 10 of this embodiment is set to 45 degrees. This angle allows for efficient detection of signal electrons emitting at angles of 15 degrees from the normal to the sample 7, as well as signal electrons emitting at angles of 75 degrees. Because signal electrons emitting at angles less than 15 degrees often travel through the aperture 14 toward the electron source 2, it is sufficient to be able to detect them up to about 15 degrees. Furthermore, detecting signal electrons up to about 75 degrees allows for detection of most of the signal electrons. Therefore, tilting the light-emitting element 10 so that the tilt angle θis is about 45 degrees provides the effect of detecting most of the signal electrons. Tilting the light-emitting element 10 also provides the effect of increasing the amount of light guided in the first direction, as described with reference to Figures 3E to 3G.

[0087] 2B , the light-receiving element 12 is positioned farther away from the electron beam 101 than the light-emitting element 10, and the two are connected by the light guide 11, separating the detection of signal electrons in a minute area from the reception of the emitted light, and the light-emitting element is trapezoidal. That is, even if the light-receiving element 12 has a free shape, the light guide 11 extending in the first direction eliminates the influence of the shape (the influence of the difference in shape between the light-emitting element and the light-receiving surface 12i), allowing the emitted light to propagate efficiently to the light-receiving surface 12i. In addition, the trapezoidal shape allows the observation point to be covered three-dimensionally by combining flat surfaces, making it easy to form by laser processing.

[0088] <About the Light Guide> FIG. 4A is a perspective view of the light guide 11 as seen from the sample 7 side. FIG. 4B is a perspective view of the light guide 11 as seen from the side where the electron beam is irradiated. FIG. 4A shows the reflecting surface 11r and the incident surface 11i facing the exit surface 10o of the light-emitting element. FIG. 4B shows the surface 11rc opposite the reflecting surface 11r, and the surface of that surface facing the light-receiving surface 12i of the light-receiving element is the exit surface 11o (see FIG. 2B(i) for a bottom view). In this embodiment, the light guide 11 is fixed to the mounting substrate 13 by bonding to the light-receiving surface 12i with an adhesive whose refractive index is close to that of the material of the light guide 11, and is fixed via the light-receiving element 12. While mechanical fixation using screws or the like is also possible, adhesive bonding improves light utilization efficiency.

[0089] When light reaches the exit surface 11o at an angle of incidence greater than or equal to total reflection, it is reflected and does not enter the light-receiving element, but becomes stray light and is largely lost. If the light guide 11 is made of a resin such as acrylic or quartz, the refractive index is approximately 1.5, so light with an incident angle of 42 degrees or greater is totally reflected. However, if a resin or glass adhesive with a similar refractive index is used, total reflection does not occur between the light guide 11 and the adhesive, and most of the light that reaches the exit surface 11o is incident on the light-receiving surface 12i. Therefore, an adhesive with roughly the same refractive index serves as a component that extracts light from the light guide 11 to the light-receiving element 12.

[0090] From the viewpoint of total reflection, the refractive index of the adhesive can be equal to or greater than the refractive index of the light guide 11 and equal to or less than the refractive index of the light-receiving surface. For example, the light-receiving surface and the adhesive can be made of epoxy resin (refractive index: approximately 1.55), and the light guide 11 can be made of acrylic resin (refractive index: approximately 1.49) taking transparency into consideration.

[0091] The adhesive as a light extracting member can be applied so as to cover the entire light receiving surface 12i shown by the dashed line in Fig. 2B(i). By using the adhesive, the transmittance of light emitted to the outside of the light guide increases only at the emission surface 11o facing the light receiving surface 12i on the surface 11rc opposite the reflection surface 11r, increasing the amount of light received at the light receiving surface 12i, and correspondingly reducing the amount of light lost by emitting into a vacuum from the surface 11rc that does not face the light receiving surface 12i.

[0092] Furthermore, increasing the transmittance to the light-receiving surface 12i only at the exit surface 11o also increases the probability that light propagating in the azimuthal direction toward a direction other than the light-receiving surface 12i will be repeatedly scattered and enter the light-receiving surface 12i, thereby improving the light utilization efficiency of light emitted in the azimuthal direction toward a direction other than the light-receiving surface 12i.

[0093] However, materials other than adhesives can also be considered as the light extraction member. A gel-like material may be sandwiched between the light guide 11 and the light-receiving surface 12i. Alternatively, a light extraction structure may be provided in which the light-emitting surface 11o facing the light-receiving surface 12i is a finely structured surface such as a roughened or uneven surface. Such a configuration can also improve light utilization efficiency. A light extraction member such as an adhesive may be used in combination with a light extraction structure.

[0094] On the other hand, adhesive can also be used to fix the light guide 11 and the light emitting element 10 together, since this improves light utilization efficiency for the same reason of suppressing total reflection. In other words, the adhesive guides light from the light emitting element 10 to the light guide 11, and also functions as a member that guides light in the first direction.

[0095] <Regarding the Light-Receiving Element> The SiPM as the light-receiving element 12 will be described using Figures 5A to 5C. Figure 5A is a bottom view of the SiPM as seen from the light-receiving surface 12i side. Figure 5B is a cross-sectional view taken along line A-A in Figure 5A. Figure 5C is a diagram showing an example of a circuit for obtaining a signal from the SiPM.

[0096] A detection surface 12d that converts light into an electrical signal is provided within the frame 12f, and a transparent resin or quartz cover is provided to protect the detection surface 12d. A matrix of detection pixels constitutes the detection surface 12d. In this embodiment, the light receiving surface 12i is a resin or quartz surface facing the detection surface 12d.

[0097] In the case of SiPM, the dynamic range is maximized when uniform light is irradiated onto the detection surface 12d, and saturation can be suppressed. For this reason, as in this embodiment, the reflective surface 11r of the light guide 11 reflects light onto the entire light-receiving surface 12i, so it is configured to cover the entire light-receiving surface 12i rather than just a portion of it. This configuration has the effect of suppressing saturation.

[0098] The SiPM has an anode and a cathode, a high voltage is applied to the cathode, and the current value output from the anode is read and used as a signal. Although other circuit examples are possible, this circuit example is adopted in this embodiment.

[0099] The presence of multiple SiPMs poses the problem of a large number of wiring connections. Meanwhile, the voltage applied to the cathode electrode controls the magnitude of the electrical signal output from the SiPM, determining the multiplication rate, defined as the number of electrons generated within the SiPM when a single photon is detected. Generally, the voltage required to achieve the same multiplication rate varies from SiPM to SiPM, requiring individual control. However, by properly selecting individual SiPMs, the voltage required to achieve the same multiplication rate can be kept within, for example, 0.5 V, allowing the operating voltage applied to the electrodes of multiple SiPMs to be the same (e.g., by sharing common wiring). For example, by sharing the same voltage across all SiPMs, the number of wiring connections can be halved.

[0100] However, simply selecting individual SiPMs can result in different current values ​​output from the same number of photons, which can affect the SEM image. It is desirable to reduce this effect by adjusting the effect for each SiPM using downstream circuits or signal processing.

[0101] 5C is a diagram showing an example of a circuit related to the light receiving element 12. For simplicity, the case where three SiPMs are used as the light receiving element 12 is shown. As described above, each SiPM has an anode electrode 12AE and a cathode electrode 12CE, and current signals Isig1 to Isig3 are output from each anode electrode 12AE. It is desirable to read these signals individually and perform signal processing. Needless to say, if the effect is small, wiring can be connected and the sum of the currents can be read, and any appropriate configuration can be used.

[0102] A bias voltage Vbias is applied to the cathode electrode 12CE as an operating voltage that determines the multiplication rate. In addition, a capacitor 12Cs may be connected to the same mounting substrate 13 to suppress fluctuations in the operating voltage applied to the cathode electrode 12CE.

[0103] 5C, the cathode electrodes 12CE of all SiPMs are connected to wiring that supplies a bias voltage Vbias, making the voltage applied to the SiPMs common, and reducing the number of wirings to one. If there were three SiPMs and the bias voltage Vbias were to be supplied individually, a total of three wirings would be required for the cathode electrodes 12CE. However, by commonizing the voltage applied to the SiPMs, two wirings can be reduced. A configuration that can reduce the number of wirings reduces the size of the connectors, making it suitable for a configuration in which a detector is installed in a narrow space, as in this embodiment.

[0104] Note that, for noise suppression or other reasons, circuit components such as resistors may be inserted between the cathode electrode 12CE and the wiring supplying the bias voltage Vbias, but this is not a problem as long as they are within a range that can be considered to be the same operating voltage. For example, this range may be a range in which the signal output from the anode electrode 12AE can be corrected by signal processing (e.g., a range that does not saturate the downstream circuit). Preferably, the operating voltage applied to the cathode electrode 12CE is within a ±10% range of the specified voltage. For example, when the specified operating voltage Vbias is 55V, the operating voltage should be within a range of approximately 50 to 60V.

[0105] From another perspective, this configuration can be called a configuration in which a certain wiring on the mounting substrate 13 branches and is connected to a plurality of cathode electrodes 12CE, thereby reducing the number of wirings.

[0106] The light-emitting element 10 and the light-receiving element 12 are separated in position in the first direction by disposing the light-receiving surface 12i of the light-receiving element at a position farther away from the light-emitting element 10 in the first direction with respect to the electron beam 101. This creates a space between the light-emitting element 10 and the light-receiving element 12 where light can diffuse, thereby achieving the effect of enabling a large current to be passed through.

[0107] At the same time, by separating the light emitting element 10 in the first direction and making the light emitting element trapezoidal, the incident surface 10i of the light emitting element 10 can be tilted with respect to the first direction, which has the effect of absorbing as much energy as possible of the incident signal electrons to increase the amount of light emitted (improved energy absorption efficiency) and the effect of increasing the amount of light emitted from the light emitting element 10 that is guided in the first direction (improved light utilization efficiency).

[0108] Furthermore, after the light is propagated in the first direction along the first optical path, the light arriving via the first optical path is propagated toward the light-receiving surface 12i by a reflecting surface or the like, thereby enabling the light to be uniformly irradiated onto the light-receiving surface 12i, which has a larger area than the light-emitting surface 10o of the light-emitting element. In other words, the difference in shape between the light-emitting surface 10o and the light-receiving surface 12i is eliminated by the second optical path.

[0109] In general, the light receiving surface 12i of the light receiving element is positioned farther away in a first direction from the electron beam 101 than the light emitting element 10, and after propagating light in the first direction, the light is propagated along a second optical path toward the light receiving surface 12i via a reflecting surface or the like, thereby simultaneously achieving the effects of increasing the current of the electron beam 101, improving the energy absorption efficiency of the signal electrons, improving the light utilization efficiency, and uniform light incidence on the light receiving surface.

[0110] [Modification 1 of First Embodiment] Fig. 6 is a cross-sectional view showing a light emitting element 10, a light guide 11, and a light receiving element 12 according to Modification 1 of the first embodiment. Fig. 6 shows a cross section of a part of the detector taken along line A-A in Fig. 2B(i). Note that a description of the same configuration as in the first embodiment will be omitted.

[0111] The difference between this first modification and the first embodiment is that there are two light incidence paths from the light-emitting element 10 to the light guide 11, and the shape of the incidence surface of the light guide 11 is different to provide the two paths. As in the first embodiment, the first incidence path is a path in which the light guide's incidence surface 11i1 faces the opposing surface 10oc (corresponding to the only exit surface 10o of the light-emitting element 10 in the first embodiment) that faces the incidence surface 10i of the light-emitting element 10. As indicated by the light ray Ray7, light enters the incidence surface 11i1 from the opposing surface 10oc, propagates through the light guide, and reaches the light-receiving element 12. The second incidence path is a path via the side surface 10os of the light-emitting element 10. The trapezoidal light-emitting element 10 has four side surfaces 10os. A second incidence surface 11i2 of the light guide is provided facing the side surface 10os closest to the sample 7, and light also enters the light guide from this surface and propagates to the light-receiving element 12. That is, this is a configuration (second configuration) in which light is incident on the light guide 11 from both the side surface and the opposing surface of the transparent substrate of the light emitting element 10. This is a point that differs from the first embodiment.

[0112] Ray Ray8 is an example of a ray that propagates through the second incident path. Signal electrons 102 enter the light-emitting element 10 and emit light, but the direction of the emitted light is determined isotropically and randomly, so it does not necessarily propagate toward the opposing surface 10oc. Simulations have shown that when the incident surface 11i2 is not present, a certain amount of light also exits from the side surfaces and is lost.

[0113] The normal to the surface has two directions, one inside and one outside the surface, but if the outward direction is defined as the normal direction, the normal Ns of the side surface 10os closest to the sample 7 among the four side surfaces 10os is inclined toward the first direction D1. Therefore, light transmitted through this surface is refracted in the direction D1. Therefore, by arranging the second incident surface 11i2 of the light guide opposite this side surface 10os, it becomes possible to propagate light in the first direction D1.

[0114] By allowing light to enter the light guide from both the side surface 10os and the opposing surface 10oc of the light-emitting element, the amount of light reaching the light-receiving element 12 is increased (light utilization efficiency is improved). The light guide 11 has a surface 11i2 onto which light from the side surface 10os is incident, as a means for efficiently allowing light from the side surface 10os to enter. This provides the effect of improving light utilization efficiency. The opposing surface 10oc and the incident surface 11i1, and the side surface 10os and the incident surface 11i2 are bonded, respectively. As described in the first embodiment, bonding reduces total reflection and Fresnel reflection, thereby providing the effect of increasing the amount of light incident from the light-emitting element 10 to the light guide 11.

[0115] [Second embodiment] Fig. 7A is a perspective view showing an example of the configuration of a detector 5 according to a second embodiment. Fig. 7B(i) is a bottom view of the detector 5 according to the second embodiment. Fig. 7B(ii) is a cross-sectional view taken along line A-A in Fig. 7B(i).

[0116] A description of the second embodiment's configuration that is the same as that of the first embodiment will be omitted. Differences between the second embodiment and the first embodiment will be described below. One difference from the first embodiment is that the exit surface 11o and the reflecting surface 11r of the light guide 11 are divided to correspond to the light receiving surface 12i. This configuration enhances the effect of adhesion described in the first embodiment using FIGS. 2A and 2B (the effect of suppressing light that is lost as stray light due to light exiting from a position different from the exit surface 11o on the surface 11rc opposite the reflecting surface 11r).

[0117] This will be explained using the light ray Ray9 shown in Figure 7B(i). By dividing the reflecting surface 11r corresponding to the light-receiving surface 12i and using the side surfaces of the divided portions as reflecting surfaces 11rs, light traveling in the azimuthal direction toward an area where there is no light-receiving element 12, as with the light ray Ray9, can be reflected by the reflecting surface 11rs and returned to the area where the light-receiving surface 12i (12ia, 12ib, 12ic) is located. This provides the effect of suppressing light that is lost as stray light by emitting from a position on the surface 11rc opposite the reflecting surface 11r that is different from the exit surface 11o. Furthermore, in this configuration, there is almost no area on the surface 11rc opposite the reflecting surface 11r that is different from the exit surface 11o, which also provides the effect of suppressing light loss (improving light utilization efficiency).

[0118] Another difference from the first embodiment is that a plurality of light receiving surfaces 12i (12ia, 12ib, 12ic) of the light receiving elements are arranged along a first direction that intersects with the irradiation direction of the electron beam 101. When viewing the bottom view of Fig. 7B(i), the light receiving surfaces 12i of the plurality of light receiving elements 12 (12a, 12b, 12c) are arranged along the radial direction (first direction, the direction of arrow D1 in Fig. 7B(ii)) from the central axis C.

[0119] In the light-emitting element 10, the point where the signal electron 102 is incident becomes the light-emitting point, and tens to hundreds of photons are generated per signal electron. In the configuration of the first embodiment, these photons could diffuse freely in the azimuthal direction, but the configuration of the second embodiment is more spatially restricted than the configuration of the first embodiment due to the reflecting surface 11rs. For this reason, the configuration of the second embodiment is configured so that many photons can more easily reach the light-receiving element 12, which is closer to the light-emitting point, than the configuration of the first embodiment. Therefore, a configuration is provided that can disperse and acquire photons emitted in a specific azimuthal direction.

[0120] As shown in Figures 7A and 7B, three light-receiving surfaces 12i of the light-receiving elements are arranged along the first direction, and divided reflecting surfaces 11r are installed in each azimuth angle direction to cover them. Each of the light guide's exit surfaces 11o (11oa, 11ob, 11oc) faces a light-receiving surface 12i and is fixed to the opposing light-receiving surface 12i with an adhesive. With this configuration, while the first embodiment requires one light-receiving element 12 to receive light in each divided direction, three light-receiving elements receive light. This reduces the number of photons incident on one light-receiving surface by a simple calculation to one-third. Therefore, this configuration eliminates light loss due to emission from surfaces 11rc other than the exit surface 11o, improving light utilization efficiency, and also increases the light-receiving surface 12i, thereby suppressing saturation of the light-receiving elements 12.

[0121] Next, the second optical path will be described. In Fig. 7B(ii), there are multiple second directions (arrows D2) toward the light receiving surface. The second optical path is formed by the point in the light guide 11 where the surface begins to tilt from the first direction (arrows D1), that is, the area radially outward from the radial position where the reflecting surface 11r begins. The reflecting surface 11r begins at a position inside the innermost light receiving surface 12ai so that the same amount of light is incident on all light receiving elements 12.

[0122] Although it may be difficult to strictly separate the first and second optical paths depending on the shape of the light guide, the optical path through which many rays propagate in the first direction (the direction intersecting the electron beam 101) may be defined as the first optical path, and the optical path through which many rays propagate in the second direction (the direction toward the light-receiving surface 12i of the light-receiving element 12) may be defined as the second optical path. The second optical path may be defined as an optical path through which many light rays have components in the upward and downward directions in the drawing (directions parallel to the irradiation direction of the beam).

[0123] In this embodiment, the light receiving elements 12 are arranged along the first direction, and the corresponding light guides 11 are linear when viewed from the bottom. As shown in FIG. 7B(i), the width W ＬＧＰis constant from the radial position DP where division begins in the azimuthal angle direction to the outermost position in the radial direction. If there is a portion where the width of the light guide 11 narrows in the direction in which light propagates, the angle of incidence becomes small when the light is reflected by the reflecting surface 11rs, and the total reflection condition is broken, resulting in light leakage from the light guide 11 into the vacuum and loss. In order to suppress loss due to this light leakage, the light guide 11 is structured so that its width does not narrow along the first direction from the radial position DP where division begins.

[0124] For reasons of manufacturing the light guide 11, the width W ＬＧＰ However, the variation due to such variations is considered to be approximately constant. ＬＧＰ When the radial dimension of the light guide 11 is short, the light leakage is small. For example, when the radial length of the light guide 11 is approximately three light receiving elements as shown in FIG. 7B(i), the width W ＬＧＰ The decrease in is small and can be considered to be approximately constant.

[0125] As described above, the light receiving elements 12 are arranged along the first direction, and the light guide 11 is provided with the reflecting surfaces 11rs corresponding to the light receiving elements 12, and the width W ＬＧＰ By configuring the size of the light source so as not to be reduced, it is possible to suppress light leakage and improve light utilization efficiency.

[0126] In this embodiment, the width W of the light guide 11 ＬＧＰ and the width W of the light receiving surface 12i ＲＳ For example, the width W of the light guide 11 is approximately the same as that of the light guide 11. ＬＧＰ is the width W of the light receiving surface 12i. ＲＳ The ratio may be 1 or less, 1.1 or less, 1.2 or less, 1.3 or less, 1.4 or less, or 1.5 or less. If the ratio is 1.5 or less, the above-mentioned effect can be obtained to a substantial extent.

[0127] Another difference from the first embodiment is that the light guide 11 is configured to be completely separated in the azimuthal direction (circumferential direction). In the first and second embodiments, the detector 5 is configured by combining divided trapezoidal light emitting elements 10 to surround the observation point with a planar light emitting element 10. The divided light emitting element 10, light guide 11, and light receiving element 12 form an independent detection element 5e that functions as a single detector. In other words, when signal electrons 102 are incident on the light emitting element 10, the emitted light passes through the light guide 11 and reaches the light receiving element 12, which functions as a detector, outputting an electrical signal corresponding to the signal electrons 102. In the configuration of this embodiment, 12 detection elements (5e1 to 5e12) are arranged to surround the central axis C. This allows each detection element to measure the signal electrons 102 individually.

[0128] In this configuration, by identifying the detection element from which the signal was obtained, it is possible to determine the azimuthal direction in which the incoming signal electrons were detected. In other words, this configuration not only prevents saturation of the signal amount in the light-emitting element 10, but also makes it possible to discriminate signals based on azimuthal angles. Hereinafter, discriminating signals based on azimuthal angles will be referred to as azimuthal angle discrimination.

[0129] In particular, in the case of semiconductor inspection equipment, the observation of three-dimensional structures has become important because semiconductor structures in recent years have become three-dimensional. The human eye recognizes three-dimensional objects by viewing them from two directions. This structure improves the visibility of three-dimensional structures by using signals from 12 directions.

[0130] Fig. 7C is a perspective view of the detecting element 5e of the detector 5 according to the second embodiment. Fig. 7D is a cross-sectional view of the detecting element 5e taken along line A-A in Fig. 7B(i). Ray Ray10 in Fig. 7D is an example of a light beam reflected by surface 11g1 of the light intensity adjuster 11g located between the light receiving elements 12a and 12b and incident on the inner light receiving surface 12ia. Ray Ray11 is an example of a light beam reflected by surface 11g2 and incident on the light receiving surface 12ic. As surfaces 11g1 and 11g2 become more perpendicular to the exit surface 11o, the amount of reflection inward and outward increases, respectively.

[0131] An aluminum film or the like can be vapor-deposited on the surfaces 11g1 and 11g2. If the surface 11g2 is parallel to the light-emitting surface 11o and does not have a reflective material such as aluminum, light will leak from this surface. Therefore, tilting the surface 11g2 also serves to suppress light leakage. Therefore, the light amount adjustment unit 11g has the effect of uniforming the amount of light incident on the light-receiving element 12 in the first direction. Furthermore, the fact that the aluminum film is vapor-deposited on the surfaces 11g1 and 11g2 and that the surface 11g2 is tilted relative to the light-emitting surface also suppresses light leakage between the light-receiving elements 12, thereby improving light utilization efficiency.

[0132] The configuration described in the first embodiment, such as the improvement of light utilization efficiency by the adhesive, can also be applied to the second embodiment as appropriate, and the same effects can be obtained.

[0133] [Modification of the Second Embodiment] Fig. 8A is a perspective view of a detection element 5e according to a modification of the second embodiment. Fig. 8B is a cross-sectional view of the detection element 5e according to the modification of the second embodiment taken along line A-A in Fig. 7B(i). Note that a description of the same configuration as that of the second embodiment in this modification will be omitted.

[0134] The difference from the second embodiment is that there are two paths of light incident from the light emitting element to the light guide, and the shape of the light incident surface of the light guide is different to accommodate the two paths. Note that the configuration in Fig. 8 for making light incident from the light emitting element 10 to the light guide 11 is the same as the configuration described using Fig. 6 (Modification 1 of the first embodiment).

[0135] As in the second embodiment, the first incident path is a path in which the incident surface 11i1 of the light guide is opposite the opposing surface 10oc (which corresponds to the only exit surface 10o of the light-emitting element 10 in the second embodiment) that faces the incident surface 10i of the light-emitting element 10, and as shown by the light ray Ray12, light enters the incident surface 11i1 from the opposing surface 10oc, propagates through the light guide, and reaches the light-receiving element 12.

[0136] The second incident path is a path via the side surface 10os of the light-emitting element 10. The trapezoidal light-emitting element 10 has four side surfaces 10os. A second incident surface 11i2 of the light guide is provided opposite the side surface 10os closer to the sample 7, and light also enters the light guide from this surface and propagates to the light-receiving element 12. This is a difference from the second embodiment.

[0137] Ray Ray 13 is an example of a ray propagating along the second path. Signal electrons 102 enter the light-emitting element 10 and emit light, but the direction of the emitted light is determined isotropically and randomly, so it does not necessarily travel toward the opposing surface 10oc. Simulations have shown that when the incident surface 11i2 is not present, a certain amount of light also exits from the side surfaces and is lost.

[0138] The normal to the surface has two directions, one inside and one outside the surface, but if the outward direction is defined as the normal direction, the normal Ns of the side surface 10os closest to the sample 7 among the four side surfaces 10os is inclined toward the first direction D1. Therefore, light transmitted through this surface is refracted in the direction D1. For this reason, by arranging the second incident surface 11i2 of the light guide opposite this side surface 10os, it is possible to propagate light in the first direction D1.

[0139] By allowing light to enter the light guide 11 from both the side surface 10os and the opposing surface 10oc of the light-emitting element, the amount of light reaching the light-receiving element 12 is increased (improved light utilization efficiency). The light guide 11 has a surface 11i2 onto which light from the side surface 10os is incident, as a means for efficiently allowing light from the side surface 10os to enter. This provides the effect of improving light utilization efficiency.

[0140] 9A to 9C are cross-sectional views showing other examples of means for directing light incident on the side surface 10os of the light-emitting element 10. FIG. 9A shows a case where the second incident surface 11i2 of the light guide is not parallel to the side surface 10os of the light-emitting element 10. Even when these surfaces are not parallel, it is possible to capture light, such as ray Ray14. In particular, in FIG. 9A, the normal to the second incident surface 11i2 is generally parallel to the first direction D1. Light incident from a surface perpendicular to the first direction D1 tends to continue to be guided in the direction D1 due to the relationship between the angle of incidence and the angle of total reflection (in the case of a rectangular parallelepiped, light is guided forever) when the light guide material has a refractive index of approximately 1.5 or higher, such as PMMA, epoxy, or quartz. Therefore, by providing the second incident surface 11i2 that is generally perpendicular to the first direction D1, light can more easily reach the light-receiving element 12, improving light utilization efficiency.

[0141] By attaching a highly reflective side cover 11m (tape) between the light guide 11 and the light emitting element 10, light emitted from the side surface 10os, such as light ray Ray 15, can be returned to the light guide. The light incident surface 10i of the light emitting element is a metal surface, as shown in FIG. 3C , to prevent charging due to signal electrons. This surface must be connected to an electrode that supplies charge, such as ground. Therefore, by using conductive tape for the side cover 11m, charging due to signal electrons in the light emitting element 10 can also be suppressed. Examples of side cover 11m include aluminum or silver tape, which have high reflectivity and conductivity.

[0142] 9B shows a possible configuration when the light emitting element 10 is sufficiently thin. In particular, if the thickness of the light emitting element 10 of the first embodiment is 430 μm, the thickness of the light emitting element 10 of FIG. 9B is less than half that (less than 215 μm), or less than 100 μm. In this configuration, the incident surface 11i1 of the light guide 11 is extended downward from the area facing the light emitting element 10, and a second incident surface 11i2 is provided between the lower surface of the light guide 11 and the side surface 10os. Light is incident on the light guide 11 as a light ray Ray16. The distance between the lower surface of the light guide 11 and the side surface 10os is defined as W ｉ２Ｌ and this distance W ｉ２Ｌis equal to or greater than the thickness of the light-emitting element 10 (the distance between the incident surface 10i and the opposing surface 10oc), this extended surface effectively functions as the second incident surface 11i2.

[0143] 9C shows a configuration in which the incident surface 11i1 of the light guide 11 is extended upward and downward from the region facing the light emitting element 10, and second incident surfaces 11i2 are provided on the upper and lower sides. Light is incident on the light guide 11 as rays Ray17 and Ray18. The distances between the upper and lower surfaces of the light guide 11 and the side surface 10os are respectively distances W ｉ２Ｕ , distance W ｉ２Ｌ In this case, when the respective distances are equal to or greater than the thickness of the light emitting element 10, these extended surfaces effectively function as the second light entrance surface 11i2.

[0144] In this modified example, a configuration has been described in which the light utilization efficiency is improved by providing two paths for the light to enter the light guide 11 from the light emitting element 10. That is, this is a configuration (second configuration) in which light enters the light guide 11 from both the side surface and the opposing surface of the transparent substrate of the light emitting element 10.

[0145] In this modified example, as an example of a means for making light incident on the light guide 11 from the side surface 10os of the light-emitting element, a configuration has been described in which the second incident surface 11i2 of the light guide 11 is provided opposite the side surface 10os closer to the sample 7. However, it has also been explained that the second incident surface 11i2 does not necessarily have to face the side surface 10os to have the effect of improving light utilization efficiency.

[0146] In particular, when the light emitting element 10 is thin, it has been explained that the light utilization efficiency can be improved by extending the incident surface 11i1 of the light guide 11 upward and downward from the region facing the light emitting element 10 by a distance greater than the thickness of the light emitting element 10, thereby providing second incident surfaces 11i2 on the upper and lower sides. It is also possible to improve the light utilization efficiency by introducing a side cover that reflects light onto the second incident surface 11i2. Various combinations of side covers and second incident surfaces 11i2 can be considered, and these may be applied as appropriate.

[0147] It goes without saying that the various configurations for improving the light utilization efficiency described in the modified example of the second embodiment can be appropriately applied to the configuration of the light emitting element and light guide of the first embodiment.

[0148] [Third embodiment] Fig. 10A is a perspective view showing an example of the configuration of a detector 5 according to a third embodiment. Fig. 10B(i) is a bottom view showing an example of the configuration of a detector 5 according to the third embodiment. Fig. 10B(ii) is a cross-sectional view taken along line A-A in Fig. 10B(i). Figs. 10C and 10D are partial enlarged views of a detection element group 5g of a detector 5 according to the third embodiment.

[0149] The third embodiment is an example in which the configuration of the second embodiment is modified, and a description of the same configuration as that of the second embodiment will be omitted. The difference from the second embodiment is that a plurality of light-emitting elements 10 (10a, 10b) are arranged in the irradiation direction of the electron beam 101, a light guide 11 (11a, 11b) is provided for each of the light-emitting elements 10, and each light guide 11 has a first optical path that guides light in a first direction and a second optical path that guides light toward each of a plurality of light-receiving surfaces 12i (12ia, 12ib) arranged along the first direction.

[0150] The light-emitting element 10a, light guide 11a, and light-receiving element 12a form an independent detection element that functions as a single detector. That is, when a signal electron 102 is incident on the light-receiving element 12a, the emitted light passes through the light guide 11a and reaches the light-receiving element 12a, which outputs an electrical signal corresponding to the signal electron 102. Similarly, the light-emitting element 10b, light guide 11b, and light-receiving element 12b form an independent detection element.

[0151] Each detector element has the characteristics of the detector described in the first embodiment and achieves the same effects. That is, the signal electrons 102 are detected on a tiny incident surface 10i near the center, and the light emitted there propagates and diffuses in a first direction, and is received on a light-receiving surface 12i that has an area sufficiently larger than that of the incident surface 10i, resulting in a detector configuration in which the signal does not saturate even when the beam amount increases.

[0152] Figure 10D is a cross-sectional view of the detector group 5g taken along line A-A in Figure 10B(i). Ray Ray19 is shown as an example of a ray of light propagating within a detector element. When signal electrons 102 are incident on the incident surface 10ib of the light-emitting element, the light emitted at this point of incidence propagates in a direction intersecting the electron beam 101 (the direction of arrow D1). The optical path propagating in this direction can be defined as the first optical path. The light guide 11b bends midway toward the light-receiving element 12b, and the light propagating inside propagates toward the corresponding light-receiving surface 12ib. The section from this bending point to the exit surface 11ob of the light guide 11b can be defined as the second optical path.

[0153] The detector 5 comprises two types of detector elements that form one detector element group 5g. FIG. 10C is a perspective view of one detector element group 5g. The incident surface 10ia of the light-emitting element 10a and the incident surface 10ib of the light-emitting element 10b are both trapezoidal. As shown in FIG. 10B(i), the detector element groups (5g1 to 5g12) are arranged around the central axis C. Each detector element group 5g is configured to divide the space among multiple detector elements to detect signal electrons and to precisely control the amount of light incident on each light-receiving surface 12i (12ia, 12ib).

[0154] The amount of light can be controlled by adjusting the size of the incident surfaces (10ia, 10ib) of the light-emitting elements and adjusting the amount of signal electrons 102 incident on the incident surface 10i. By using this configuration and adjusting the size of the incident surface 10i so that light is uniformly incident on each light-receiving surface 12i, it is possible to suppress saturation of all light-receiving elements 12 in the detector 5 due to an increase in the amount of signal.

[0155] This effect is obtained in addition to the effect of suppressing saturation described in the first and second embodiments. The configuration of the second embodiment also has the effect of suppressing saturation due to large current, but by using the detection element group 5g as in this embodiment, an additional effect is achieved in that the amount of light incident on each light-receiving surface 12i can be controlled, and light can be controlled so as to be uniformly incident on the light-receiving surface.

[0156] Although the first embodiment also mentioned various arrangements of the light receiving elements, the arrangement of the detecting elements and the detecting element group 5g relative to the central axis C is not limited to that shown in the figure. They do not necessarily have to completely surround the central axis C, and may be arranged in a partial circumferential region (the same applies to each of the above-mentioned embodiments). Even if there is only one detecting element group 5g, various effects can be achieved. In other words, the detecting elements and the detecting element group 5g alone have the effect of suppressing saturation due to large currents.

[0157] Furthermore, by arranging a plurality of light-emitting elements 10 in the irradiation direction of the electron beam 101 and configuring the system so that signals can be acquired individually corresponding to each light-emitting element, it becomes possible to discriminate signals in the polar angle θo direction as well. Discriminating signals in the polar angle direction is referred to as polar angle discrimination. Like azimuthal angle discrimination, polar angle discrimination also has the effect of improving the visibility of three-dimensional structures.

[0158] The direction in which signal electrons are emitted varies depending on the material and shape of the sample, but even for a sample that is isotropic in azimuth, differences can occur in polar angle. For this reason, by detecting the exit polar angle of the signal electrons from the sample, more information about the material and shape of the sample can be obtained. The detector 5 of this embodiment has the above-described configuration, and is structured to be able to calculate the polar angle θo from information about the incident detection element, thereby achieving the effect of obtaining information about the material and shape of the sample.

[0159] 10B to 10D, the incident surfaces 10i (10ia, 10ib) of the light-emitting elements are planes (inclined surfaces) with different inclinations for each incident surface so that the normal to the surface faces the observation point MP. For the purpose of improving the detection efficiency of signal electrons as described in the first embodiment, these incident surfaces are all inclined so that the incident angle θi is 30 degrees or less. Note that when multiple light-emitting elements 10 are arranged in the beam irradiation direction, gaps are generated between the light-emitting elements in the beam irradiation direction. Therefore, when each incident surface is viewed from the observation point MP, the light-emitting element closest to the sample 7 in each gap conceals the gap from the observation point MP to prevent signal electrons 102 from entering the gap.

[0160] The detector 5 has two types of detection elements, each of which has a different configuration for making light incident from the light emitting element 10 into the light guide 11 .

[0161] The light-emitting element 10b closer to the sample 7 emits light into the light guide 11b from the opposing surface 10ocb of the transparent substrate of the light-emitting element 10b. This configuration is the same as the configuration described with reference to FIG. 2 or FIG. 7. In the configurations of FIG. 2 or FIG. 7, the tilt angle θis of the light-emitting element 10 with respect to a plane perpendicular to the beam irradiation direction is approximately 45 degrees. The example of FIG. 10B shows a case where the tilt angle θis of the light-emitting element 10 with respect to a plane perpendicular to the beam irradiation direction is 85 degrees. As described in the first embodiment, when the tilt angle θis is large, the amount of light incident from the opposing surface of the light-emitting element 10 into the light guide 11 increases, so the detection element of this embodiment is configured to improve light utilization efficiency. In other words, when the tilt angle θis is large, the surface that mainly emits light in the first direction D1 is the opposing surface 10ocb, and therefore, a configuration in which light enters the light guide 11 from this opposing surface 10ocb is configured to improve light utilization efficiency.

[0162] The light-emitting element 10a on the electron source side emits light into the light guide 11b from both the opposing surface 10oca and the side surface 10osa of the transparent substrate of the light-emitting element 10a. This configuration is the same as the configuration described using Figures 6 and 8. The tilt angle θis of the light-emitting element 10 is 40 degrees, which is close to the tilt angle θis in the configurations of Figures 6 and 8. This is because this configuration is likely to improve light utilization efficiency when the tilt angle θis is approximately 45 degrees. In other words, when the tilt angle θis is approximately 45 degrees, the surfaces that mainly emit light in the first direction D1 are the opposing surface 10oca and the side surface 10osa, so a configuration in which light enters the light guide 11 from both of these surfaces improves light utilization efficiency. Needless to say, it is possible to appropriately combine this configuration with various light utilization efficiency-improving configurations described in Figure 9.

[0163] The emission angle θo of the signal electrons 102 incident on the light-emitting element 10b closer to the sample 7 is larger than that of the light-emitting element 10a on the electron source side. Therefore, the tilt angle θis of each light-emitting element is set so that the average incident angle of the signal electrons on each light-emitting element becomes small. With this setting, the tilt angle of the light-emitting element 10b closer to the sample 7 becomes larger than the tilt angle of the light-emitting element 10a.

[0164] The configuration for illuminating light from the light-emitting element into the light guide is such that, depending on the respective tilt angles, the configuration closer to the sample 7 is configured so that light enters the light guide from the opposing surface of the light-emitting element, while the configuration on the electron source side is configured so that light enters the light guide from both the opposing surface and the side of the light-emitting element, thereby improving light utilization efficiency.

[0165] As shown in Figure 10B(i), multiple light-receiving elements 12 are aligned in a row in the radial direction from the central axis C. Furthermore, the light-emitting elements 10 and light-receiving elements 12 are aligned in a row in the same azimuthal direction, and the shape of the light guide is linear when viewed from the bottom, minimizing the distance between the light guide's entrance surface 11i and exit surface 11o. A linear light guide maximizes light utilization efficiency. Furthermore, a shorter distance reduces light loss, resulting in greater light utilization efficiency with this configuration. Therefore, lining up the light-receiving elements 12 and making the light guide 11 linear when viewed from the sample side has the effect of improving the light utilization efficiency of the light guide.

[0166] However, there are various methods for arranging the light receiving elements 12 and for arranging the light emitting elements in the irradiation direction of the beams, and the present disclosure is not limited to the arrangement method. The configurations described in the first and second embodiments, such as the improvement of light utilization efficiency by the adhesive, can also be applied to the third embodiment as appropriate, and similar effects can be obtained.

[0167] The effect of this embodiment, which allows polar angle discrimination in a thin structure, is particularly great. This point will be explained below.

[0168] When the distance between the observation point MP and the light-emitting element 10 is about 1 to 3 mm, in the conventional configuration described in the first embodiment with reference to Fig. 18 , azimuthal angle discrimination is possible by arranging the light-receiving elements 12 so as to surround the central axis C, but polar angle discrimination is difficult. The reason for this is that most of the signal electrons 102 (for example, signal electrons emitted within a polar angle range of 10 to 60 degrees) are concentrated and incident on the inner light-emitting element 10 closest to the electron beam 101, making it impossible to discriminate them. In particular, to separate and detect signal electrons emitted within a polar angle range of 10 to 50 degrees, a very small incident surface of the light-emitting element is required, making polar angle discrimination quite difficult.

[0169] In this embodiment, a plurality of light-emitting elements are arranged in the beam irradiation direction, and light-receiving elements are positioned farther away from the electron beam than the light-emitting elements. The light emitted by each light-emitting element is individually converted into a signal by the light-receiving element. Furthermore, the light is propagated in a first direction and then in a second direction. This configuration divides the incident surface of each minute light-emitting element, enabling polar angle discrimination across almost the entire polar angle range, including signal electrons emitted at small polar angles.

[0170] In other words, this configuration gathers the light-emitting elements at the center and places the light-receiving elements at a distance in the first direction, so that the entire optical system from the light-emitting elements to the light-receiving elements can be housed within the limited space between the objective lens 4 and the sample 7, thereby achieving both reduced light loss by shortening the optical path and polar angle discrimination through high-density division in the center. The effect of realizing the polar angle discrimination function with this configuration at a position where many signal electrons can be detected is significant.

[0171] If multiple light-emitting elements are arranged in the irradiation direction of the beam, it is possible to achieve the above-mentioned effects of realizing polar angle discrimination and suppressing signal saturation due to an increase in the beam amount, and therefore it is sufficient to arrange multiple light-emitting elements in the irradiation direction of the beam. Furthermore, various modifications are possible within the scope of the idea that the signal electrons 102 are acquired on the minute incident surface 10i of the light-emitting element near the central axis C and the light is propagated and diffused in the first direction.

[0172] [Modification 1 of Third Embodiment] Fig. 11A is a perspective view showing a detection element group 5g according to Modification 1 of the third embodiment. Fig. 11B is a cross-sectional view of the detection element group 5g according to Modification 1 of the third embodiment taken along line A-A in Fig. 10B(i). Note that a description of the same configuration as in the third embodiment will be omitted.

[0173] The difference from the third embodiment is the shape of the light emitting element 10a on the electron source side and that light is incident on the light guide 11a from the side surface 10osa of the light emitting element 10a.

[0174] The tilt angle θis of the light-emitting element 10a on the electron source side is set to 10 degrees to efficiently detect signal electrons emitted at a low polar angle θo. When the tilt angle is less than approximately 10 degrees, the surface that mainly emits light in the first direction D1 is the side surface 10osa, and therefore a configuration in which light enters the light guide from this side surface 10osa improves light utilization efficiency. Note that this configuration is a configuration in which light enters the light guide from the side surface of the transparent substrate (first configuration). The detailed shape of the light-emitting element 10a that improves light utilization efficiency for the configuration of this modified example will be described below.

[0175] Fig. 12A is a perspective view of a light-emitting element 10a according to Modification 1 of the third embodiment. Fig. 12B is a side view of the light-emitting element 10a. The metal layer 10ma and the light-emitting layer 10ea are as described with reference to Fig. 3A. In this example, the shape of the incident surface 10ia is also trapezoidal as shown in Fig. 11A. The shape of the transparent substrate 10sa is different from the shape described with reference to Fig. 3A.

[0176] 12B, the left side surface 10osa is bonded to the light guide's incident surface 11ia, and light emitted from the light-emitting layer 10ea passes through this surface and enters the light guide 11a. The normal to this surface is approximately parallel to the first direction D1 (the angle between direction D1 and the normal is approximately 10 degrees, or the inclination angle θis in this example). Therefore, most of the light incident on this surface into the light guide propagates toward the light-receiving element 12 without destroying the total reflection condition, and therefore easily reaches the light-receiving element 12, improving light utilization efficiency.

[0177] As described in the first embodiment, the adhesion between the side surface 10 osa and the incident surface 11 ia reduces reflection at the interface, thereby increasing the amount of light incident from the light emitting element 10 to the light guide 11 .

[0178] Light emitted from the light-emitting layer 10ea to the transparent substrate 10sa has a high intensity in the normal direction of the light-emitting layer. Therefore, a reflective surface 10ra is provided opposite the light-emitting layer 10ea to reflect the light toward the side surface 10osa, which serves as the exit surface. As shown in FIG. 11B, the reflection from the reflective surface 10ra of the transparent substrate increases the number of light rays propagating toward the light-receiving element 12a. Simulations have shown that the light utilization efficiency is approximately doubled when this reflective surface is present compared to when it is not present. Therefore, when light is primarily incident on the light guide from the side, providing a reflective surface opposite the light-emitting layer 10ea effectively improves light utilization efficiency. This inclined surface configuration improves efficiency even more effectively when the light-emitting element is thick.

[0179] 11B, in order to efficiently detect signal electrons emitted at a low polar angle θo, the tilt angle θis is lowered to increase the amount of energy absorbed by the signal electrons. Furthermore, in this configuration, light is mainly incident on the light guide from the side of the transparent substrate, and a reflective surface is provided opposite the light-emitting layer to improve light utilization efficiency.

[0180] With respect to the light emitting element 10b and light guide 11b closer to the sample 7, since the tilt angle θis of the light emitting element is 70 degrees, light is incident on the light guide 11b from the opposing surface 10ocb of the transparent substrate of the light emitting element 10b, and this tilt angle θis improves the light utilization efficiency. None of the light guides of this modification have a second incident surface, which has the effect of making the light guides easier to fabricate.

[0181] As a configuration closer to the sample 7, a configuration in which light is incident on the light guide from both the opposing surface and the side surface of the light-emitting element is also possible, and it goes without saying that the configuration shown in Figure 9 of the second embodiment may be applied as appropriate.

[0182] [Modification 2 of Third Embodiment] Fig. 13A is a perspective view showing a configuration example of a detector 5 according to Modification 2 of the third embodiment. Fig. 13B(i) is a bottom view of the detector 5 according to Modification 2 of the third embodiment. Fig. 13B(ii) is a cross-sectional view taken along line A-A in Fig. 13B(i). Fig. 13C is a partial enlarged view of the detection element group 5g in Fig. 13B(ii).

[0183] Modification 2 is an example in which the configurations of the third embodiment and Modification 1 of the third embodiment are modified, and description of the same configurations as these will be omitted. The difference from the third embodiment and Modification 1 of the third embodiment is that three light-emitting elements 10 (10a, 10b, 10c) are arranged in the irradiation direction of the electron beam 101, light guides 11 (11a, 11b, 11c) are provided for each light-emitting element 10, and each light guide 11 has a first optical path that guides light in a first direction and a second optical path that guides light toward each of a plurality of light-receiving surfaces 12i (12ia, 12ib, 12ic) arranged along the first direction.

[0184] Increasing the number of light-emitting elements arranged in the beam irradiation direction has several effects, such as increasing the number of polar angle divisions (resolution) when polar angle discrimination is performed, suppressing signal saturation due to an increase in the number of light-receiving elements, and reducing the angle of incidence of signal electrons incident on each light-emitting element. However, the present disclosure is not limited to the number of light-emitting elements arranged in the irradiation direction or the number in the azimuthal angle direction.

[0185] 13B(ii) shows the first optical path D1 and the second optical path D2 of each detecting element. When signal electrons 102 are incident on the incident surface 10i of the light-emitting element, the light emitted at this incident point propagates in a direction intersecting the electron beam 101 (the direction of arrow D1). The optical path propagating in this direction can be defined as the first optical path. The light guide 11a becomes a reflective surface 11ra midway, and the light guides 11b and 11c bend midway, so that the light propagating therethrough propagates toward the corresponding light-receiving surfaces 12ib and 12ic. The section from the starting point or bending point of the reflective surface 11ra to the light guide's exit surfaces 11oa, 11ob, and 11oc can be defined as the second optical path.

[0186] 13B(ii) and 13C, the tilt angle θis of the light-emitting element 10 with respect to the plane perpendicular to the beam irradiation direction increases as the light-emitting element approaches the sample 7 from the electron source side. The tilt angles of the light-emitting elements 10a, 10b, and 10c are 0 degrees, 45 degrees, and 70 degrees, respectively. This configuration makes it possible to minimize the angle of incidence of signal electrons on each light-emitting element, thereby improving the amount of energy absorption of the signal electrons and improving detection efficiency.

[0187] 13C, the shape of the incident surface 10i of each light-emitting element 10 is trapezoidal, and the incident surface 10i is configured to cover the observation point MP. The effect of the trapezoidal shape is as described in the above embodiment.

[0188] In Figure 13B(ii), the configuration for light incident from the light-emitting element to the light guide is configured to improve light utilization efficiency depending on the tilt angle. The configuration of the detector elements (10a, 11a, 12a) closest to the electron source is the same as the detector elements closest to the electron source shown in Figure 11, where light is incident on the light guide from the side of the transparent substrate (first configuration). To efficiently emit light from the side to the light guide 11a, a slope is formed on the transparent substrate. The central detector elements (10b, 11b, 12b) are configured to input light into the light guide from both the side and the opposing surface of the transparent substrate (second configuration), similar to the configuration shown in Figure 9A (side cover 11m is not shown). The light guide has multiple surfaces through which light is incident. The detection elements (10c, 11c, 12c) closest to sample 7 have a configuration in which light is incident on the light guide from the opposing surface of the transparent substrate (third configuration), and this configuration is similar to the detection elements closest to sample 7 shown in Figure 10B(ii) and Figure 11B.

[0189] For a light-emitting element on which signal electrons are incident at a small polar angle of about 10 degrees, the tilt angle is reduced to form a first configuration. For a light-emitting element on which signal electrons are incident at a polar angle of about 45 degrees, the tilt angle is set to about 45 degrees to form a second configuration. For a light-emitting element on which signal electrons are incident at a larger polar angle, the tilt angle is set to a larger angle to form a third configuration. This improves the amount of energy absorption of the signal electrons and improves light utilization efficiency over the entire range of the emission angles of the signal electrons.

[0190] In the second modification, a configuration of a light emitting element and a light guide that is efficient according to the tilt angle θis of the light emitting element 10 has been described, but the present invention is not limited to this. For example, the configuration of the electron source side and the central detecting element may be the second configuration, or the configuration of the central detecting element and the detecting element on the sample side may be the second configuration. Furthermore, the configuration of the central detecting element and the detecting element on the sample side may be the third detecting element. All detecting elements may be of one of the configurations. These combinations are not limited, and any suitable configuration may be applied as appropriate.

[0191] [Fourth embodiment] Fig. 14A is a perspective view of a detector 5 according to the fourth embodiment, as seen from the sample side. Fig. 14B is a perspective view of a detector 5 according to the fourth embodiment, as seen from the electron source side. Fig. 14C is a bottom view of a detector 5 according to the fourth embodiment, as seen from the sample side. Fig. 14D is a side view of a detector 5 according to the fourth embodiment. Figs. 14E to 14M are views showing a part of the detector in detail. Descriptions of configurations similar to those of the first to third embodiments will be omitted.

[0192] In the fourth embodiment, a plurality (two) of light-emitting elements 10 (10a (10na, 10ca), 10b (10rb, 10lb)) are arranged in the irradiation direction of the electron beam 101. FIG. 14B shows the light-emitting elements 10a (10na, 10ca) on the electron source side and the light-receiving elements 12a (12na, 12ca) connected thereto. FIG. 14C shows the light-emitting elements 10b (10rb, 10lb) on the sample side and the light guides 11b (11rb, 11lb) and light-receiving elements 12b (12rb, 12lb) connected thereto.

[0193] In the configuration of the fourth embodiment, the light-emitting element 10a on the electron source side is connected to the light-receiving element 12a instead of a light guide. Instead of a light guide, the light is guided using a transparent substrate of the light-emitting element 10a. As can be seen from Fig. 14B, eight light-receiving elements 12a connected to the light-emitting element on the electron source side are arranged to surround the opening 14.

[0194] The four light-receiving elements 12na closest to the opening 14 are connected to light-emitting elements 10na, which are the light-emitting elements 10a on the electron source side and are mainly visible from the sample 7. In other words, these four elements are the light-emitting elements on the electron source side onto which signal electrons are mainly incident.

[0195] 14E, the region IA surrounded by the dotted line is the region where the signal electrons are incident on the light-emitting element 10a on the electron source side without being detected by the light-emitting element 10b on the sample side. As shown in FIGS. 14A and 14C, the light-emitting element 10ca is disposed at the corner of the region IA that cannot be covered by the light-emitting element 10na, and the light-receiving element 12ca is connected to it.

[0196] 18, in order to prevent many signal electrons from entering the light-emitting element 10a, in this embodiment, the light-emitting element 10a is partially hidden by the light-emitting element 10b on the sample side. By doing so, the number of incident signal electrons can be controlled to be approximately the same for the light-emitting element 10a and the light-emitting element 10b.

[0197] The detailed structures of the light-emitting element 10a and light-receiving element 12a on the electron source side are shown in Figure 14B. The light-receiving element 12a is both square. However, the shape of the light-emitting element 10 (10na, 10ca) differs from the square light-receiving surface shape (see Figure 5A) because it covers the incident area IA of the signal electrons, shown by the dotted line. This difference in shape is resolved by guiding light within the transparent substrate.

[0198] Fig. 14G is a perspective view of the light-emitting element 10na and the light-receiving element 12na. Fig. 14H is a side view of the light-emitting element 10na and the light-receiving element 12na. Fig. 14I is a perspective view of the light-emitting element 10ca and the light-receiving element 12ca. Fig. 14J is a side view of the light-emitting element 10ca and the light-receiving element 12ca.

[0199] For mounting reasons, a certain gap is required between the light-receiving elements 12a and between the opening 14 and the light-receiving element 12a. Therefore, as shown in Figures 14G to 14J, there is an area on the back surface of the light-emitting element 10a within the incident area IA that is not faced by a light-receiving surface. To propagate light from the area where the signal electrons 102 are incident to the light-receiving element 12, the transparent substrate of each light-emitting element has a reflective surface (10rna, 10rca). As shown by ray Ray21 in Figure 14H and ray Ray22 in Figure 14J, this reflective surface changes the propagation direction of the light, making it easier for the light to reach the light-receiving element 12, thereby improving light utilization efficiency.

[0200] 14F and 14K to 14M show the details of the light emitting element 10b, light guide 11b, and light receiving element 12b on the sample side. There are a total of eight detecting elements 5e (5er, 5el), two in each of the four directions.

[0201] The propagation of light is the same as that described in the first embodiment. A light ray Ray23 is shown in FIG. 14L. Light emitted by the light-emitting element 10rb enters the light guide 11rb, propagates in a first direction D1, is reflected by a reflecting surface 11rbr that is inclined with respect to the first direction D1, propagates in a second direction D2, and reaches the light-receiving element 12rb. The first optical path and the second optical path can be defined as described in the first embodiment.

[0202] 14F and 14K-L, the light-emitting elements 10rb and 10lb each have a shape obtained by dividing the trapezoidal light-emitting element 10 along the height direction at the center. The trapezoidal surface formed by the two light-emitting elements (10rb and 10lb) detects signal electrons flying in one direction (within a 90-degree azimuth angle range) among the directions obtained by dividing 360 degrees into four.

[0203] As described in the first embodiment, a trapezoid is the best way to surround the observation point MP three-dimensionally without any gaps and to align the heights of the upper and lower surfaces of the light-emitting element. In this example, the trapezoid is further divided into two, thereby reducing the amount of light incident on one light-receiving element and suppressing saturation of the output signal from the light-receiving element.

[0204] The two light-emitting elements (10rb, 10lb) form part of a trapezoid, and therefore are quadrilaterals with parallel upper and lower sides and sides tilted relative to the parallel upper and lower sides. In other words, one of the four corners is at an angle other than 90 degrees. Even when there are more than two light-emitting elements, when they are combined to form a trapezoid, the trapezoid is characterized by a quadrilateral with one corner at an angle other than 90 degrees.

[0205] As described in the first embodiment, the configuration shown in Figures 14F and 14K to 14L is a configuration in which light emitted in a small region near the center is diffused in the azimuthal direction to reduce the density of photons, and the light is received by multiple light-receiving elements 12 surrounding the periphery, thereby reducing the amount of light entering each light-receiving element and suppressing saturation.

[0206] The configuration of this embodiment is easy to realize when the light-emitting element 10 is planar. In the case of a planar configuration, the thickness is thin even when the light-receiving element 12a on the electron source side and the light-emitting element 10a are stacked. This makes it easy to arrange the light-emitting element 10b and light guide 11b tilted with respect to a plane perpendicular to the beam irradiation direction at a position closer to the sample 7 than the light-emitting element 10a. Furthermore, in order to prevent many signal electrons from entering the light-emitting element 10a, it is easy to realize a configuration in which the light-emitting element 10b on the sample side partially covers and conceals the light-emitting element 10a.

[0207] The optical system consisting of the light-emitting element 10b, the light guide 11b, and the light-receiving element 12b has the characteristics of the optical system described in the first embodiment, and is configured so that even if the shape and arrangement of the light-emitting element are free, the difference in shape between the light-emitting surface of the light-emitting element and the light-receiving surface of the light-receiving element is eliminated in the first optical path of the light guide. This optical system makes it possible to configure the light-emitting element 10b to partially cover and hide the light-emitting element 10a.

[0208] The configuration of this embodiment is smaller overall by the amount corresponding to the elimination of the light guide in the detection system on the electron source side. Because light is incident from the light-emitting element 10a to the light-receiving element 12a, the optical path is shorter, improving light utilization efficiency. Furthermore, the light guide 11b can be made shorter than the light guide 11b described in the third embodiment, improving light utilization efficiency. Therefore, this configuration offers the advantage of improving light utilization efficiency. Furthermore, the configuration of this embodiment is compact and simple, with no light guide in the detection system (10a, 12a) on the electron source side, which offers the advantage of easy assembly.

[0209] [Modification of Fourth Embodiment] Fig. 15A is a perspective view of a detector 5 according to a modification of the fourth embodiment. Figs. 15B to 15D show the detection system (10a, 12a) on the electron source side. Fig. 15B is a perspective view of the entire detection system. Fig. 15C is a perspective view of one detection element. Fig. 15D is a side view of one detection element. Note that a description of the same configuration as in the fourth embodiment will be omitted.

[0210] The difference from the fourth embodiment is that the shape of the light receiving element 12a has been changed from a square to a trapezoid, and the shape of the light emitting element 10a has also been changed to a trapezoid accordingly. By making the shape of the light emitting element 10a trapezoidal, more light emitting elements 10a can be arranged without gaps compared to the fourth embodiment. In addition, all the light emitting elements 10a have the same shape, allowing them to be arranged isotropically. This arrangement makes it possible to easily perform azimuth angle discrimination isotropically. Furthermore, since the shapes are the same, there is also the effect of reducing the number of types of parts.

[0211] For mounting reasons, there are gaps between the light receiving elements 12a and between the opening and the light receiving element 12a, and the light emitting element 10a is made larger than the light receiving element 12a, and the light emitting element 10a is also positioned opposite the gap, so that the signal electrons 102 flying toward the gap can also be detected.

[0212] As shown by ray Ray 24 in Figure 15D, when signal electrons are incident on a part of the light-emitting element 10a that is not facing the light-receiving element 12a, a portion of the light emitted at the point of incidence is reflected by the reflecting surface 10ra, propagates toward the light-receiving element 12a, and is received.

[0213] FIG. 15E is a perspective view of the light-receiving element 12a. FIG. 15F is a front view of the light-receiving element 12a. An example using a SiPM as the light-receiving element 12 is shown. In a SiPM, each detection pixel detects one photon, so the number of photons that can be detected at one time is proportional to the number of detection pixels. Therefore, a number of detection pixels corresponding to the number of photons generated by the signal electrons is required, and a certain area is required for the light-receiving surface 12ia. This required area is often larger than the incident area IA indicated by the dotted line.

[0214] When the light-receiving surface 12ia is approximately the same size as the incident area IA, the problem described with reference to Fig. 18 occurs. That is, the problem is that most of the signal electrons are incident on the light-emitting element connected to one light-receiving element. To solve this problem, in the fourth embodiment and this modification, the light-emitting element 10a is partially hidden by the light-emitting element (10rb, 10lb) on the sample side, thereby limiting the number of signal electrons incident on one light-emitting element 10a.

[0215] By making the light-receiving element 10a trapezoidal, even if the light-emitting element 12a is also trapezoidal, a configuration can be achieved in which the light utilization efficiency is hardly reduced, even without a light guide. The incident area IA formed by the light-emitting elements (10rb, 10lb) on the sample side allows signal electrons to be incident only on the tip of the trapezoid, thereby reducing the area occupied by one light-emitting element 10 within the incident area. This configuration has the effect of preventing the signal from saturating the light-receiving element 12.

[0216] Here, even if a signal electron is detected at the tip of the light-emitting element, the light emitted at the detection position propagates through the transparent substrate and is incident on the detection surface 12d (not shown, see FIG. 5B) from almost the entire light-receiving surface 12ia and converted into an electrical signal. In other words, the presence of a transparent portion through which light can propagate within the light-emitting element makes it possible to guide the light emitted at the tip and allow light from the entire light-receiving surface 12ia to be incident on the detection surface 12d, thereby preventing multiple photons from entering the detection pixel at the same time and preventing saturation of the output signal from the light-receiving element.

[0217] [Modification 2 of First Embodiment] FIG. 16A is a side view showing an example of the configuration of a detector 5 according to Modification 2 of the first embodiment. Note that a description of the same configuration as in the first embodiment will be omitted. In FIGS. 2A and 2B of the first embodiment, the light-receiving surface 12i and the first direction (arrow D1) are substantially parallel, but as mentioned above, they may be tilted. As an example of the maximum tilt, a configuration in which the light-receiving element is vertically oriented so that the first direction (arrow D1) and the light-receiving surface 12i are substantially perpendicular to each other is also conceivable. When the first direction and the light-receiving surface 12i are substantially perpendicular to each other, the concept of detecting the signal electrons 102 at the center and propagating and diffusing light in the first direction remains the same, and the same effects as those described in the first embodiment and the like are achieved. However, because the second direction coincides with the first direction, the configuration differs from that of the first embodiment.

[0218] 2A and 2B is that the light-receiving surface 12i of the light-receiving element 12 faces toward the center, and light propagates in a first direction to reach the light-receiving surface 12i. In other words, the normal to the light-receiving surface 12i can be said to be approximately parallel to the first direction, and can be said to face the direction in which the electron beam 101 is located (inward in the radial direction).

[0219] In this modified example, as in the above-described embodiments, the detector 5 transmits light emitted from the light-emitting element 10 at an incident surface 10i on which the signal electrons 102 are incident to the light-receiving surface 12i of the light-receiving element 12 via the light guide 11. The light-emitting element 10 and the light guide 11, and the light guide 11 and the light-receiving element 12 are bonded together, respectively, and the bonding improves the light detection efficiency.

[0220] 16A, the light receiving element 12 has electrodes on its side surfaces and is mounted on the mounting substrate 13 by solder or the like. Another mounting method is to mount it on the mounting substrate 13 via an L-shaped metal fitting or the like so that it stands perpendicular to the mounting substrate 13. When using an L-shaped metal fitting or the like, it is advisable to use lead wires for electrical connection.

[0221] In the configuration of this modification, the light propagating in the first direction reaches the light-receiving surface 12i without changing direction, which increases the light utilization efficiency. Furthermore, since there is no light-receiving element between the mounting substrate 13 and the first optical path, the detector can be made thinner (the dimension in the beam irradiation direction can be reduced).

[0222] 16A, the normal to the light-receiving surface 12i is parallel to the first direction, but it does not have to be parallel. For example, the normal to the light-receiving surface 12i can be configured to form an angle of 10 degrees or less, 20 degrees or less, 30 degrees or less, or 45 degrees or less with the first direction, and the light utilization efficiency can be improved depending on the angle. Note that, although it depends on the shape of the incident surface 10i, in many cases, the light utilization efficiency is highest when the normal to the light-receiving surface 12i is parallel to the first direction.

[0223] The position of the light receiving surface 12i may be located at a position farther away from the electron beam 101 than the light emitting element 10, and the present disclosure is not limited to other arrangements of the light receiving element, such as the angle, etc. For example, in Fig. 16A, the light receiving element 12 on the right side of the paper may be located diagonally to the upper right of the paper, and may be tilted with respect to the first direction so that the light receiving surface 12i faces generally toward the light emitting element 10, and a configuration may be adopted in which light is propagated in the first direction and toward the light receiving surface diagonally above right (second direction) as in the light guide 11c in Fig. 13C.

[0224] The incident surface 10i of the light-emitting element 10 is trapezoidal. As described in the first embodiment, by making the light-emitting element 10 trapezoidal and arranging it at an angle with respect to a plane perpendicular to the irradiation direction of the beam, the observation point MP is covered three-dimensionally using a planar semiconductor scintillator with a short response time, and the upper and lower surfaces of the light-emitting element are aligned to suppress a decrease in the signal amount.

[0225] Furthermore, the arrangement (and shape) of the light emitting element 10 and the shape of the light guide entrance surface 11i may be appropriately adapted to the configurations shown in FIGS.

[0226] For example, it may be combined with the structure of Fig. 14A, in which case a configuration based on this example may be applied to the detection element 5e (5er, 5el). In this way, it is possible to apply an appropriate combination of the various structures described in the first to fourth embodiments to the configuration of this modified example.

[0227] 16B is a side view showing a configuration example of the detector 5 according to Modification 3 of the first embodiment. The difference from Modification 2 of the first embodiment is that the light receiving element 12 is a photomultiplier tube PMT, and the PMT is placed in the atmosphere. Note that a description of the same configuration as Modification 2 of the first embodiment will be omitted.

[0228] The electron source 2, scanning deflector 3, objective lens 4, and light-emitting element 10 of the charged particle beam device 1 are disposed inside an electron optical column 60, which is kept in a vacuum state. In Fig. 16B, a portion of the side wall of the electron optical column 60 is shown by a dashed line. The area inside this dashed line (inside in the radial direction) is in a vacuum state. The light guide 11 has a separation flange 11f for separating the internal vacuum from the external atmosphere.

[0229] The separation flange 11f may or may not be present depending on the structure of the electron microscope 1. In this modified example, the light receiving element 12 is arranged outside the electron optical barrel 60, and the light emitting element 10 is arranged inside the electron optical barrel 60, so the separation flange 11f is provided on the light guide 11. The separation flange 11f can be pressed perpendicularly against the side wall of the electron optical barrel 60, and is configured to prevent air from entering the vacuum.

[0230] Since the PMT requires a high input voltage as its drive voltage, it is desirable to place it as far outside the electron optical column 60 as possible to avoid the need for insulation measures against discharge in a vacuum. The configuration of this example is one that allows the PMT to be easily used as the light receiving element 12 without the need for insulation measures. Furthermore, by placing the light receiving element 12 outside, it is possible to use a large light receiving element 12 that will not be saturated even when a large number of photons are incident on it.

[0231] In this configuration, the light receiving surface 12i is also positioned farther away from the electron beam 101 than the light emitting element 10, the signal electrons 102 are detected at the center, and the light is propagated and diffused in the first direction. As described in the second modification of the first embodiment, the present disclosure is not limited to the angle of the light receiving element, etc.

[0232] The incident surface 10i of the light-emitting element 10 is trapezoidal. As described in the first embodiment, by making the light-emitting element 10 trapezoidal and arranging it at an angle with respect to a plane perpendicular to the irradiation direction of the beam, the observation point MP is covered three-dimensionally using a planar semiconductor scintillator with a short response time, and the upper and lower surfaces of the light-emitting element are aligned to suppress a decrease in the signal amount.

[0233] 8, 9, and 13 may be applied as appropriate to the arrangement (and shape) of the light-emitting element 10 and the shape of the light guide incidence surface 11i. Furthermore, for example, when combined with the structure of FIG. 14A, the light-receiving elements 12rb and 12lb may be arranged as PMTs on the atmosphere side as shown in FIG. 16B. In this way, it is possible to apply an appropriate combination of the various structures described in the first to fourth embodiments to the configuration of this modification.

[0234] In the first to fourth embodiments, a detector was described that uses a planar light-emitting element to efficiently detect quanta such as signal electrons or radiation emitted from an observation point, and that can output an electrical signal without saturation even when the quanta of signal electrons or radiation incident on the detector increase. Further functions can be realized by using these detectors, and these functions will be described in the fifth embodiment.

[0235] The fifth embodiment is a measurement device including the detector of Modification 2 of the third embodiment. In the second embodiment, a detection element 5e is provided for each azimuth angle, enabling azimuth angle discrimination. Furthermore, in the third embodiment, a plurality of light-emitting elements 10 are arranged in the irradiation direction of the beam, and a detection element is provided for each polar angle, enabling polar angle discrimination in addition to azimuth angle discrimination. That is, in the fifth embodiment, a plurality of light-emitting elements 10 are arranged in the irradiation direction of the beam, and when the azimuth angle is defined with the irradiation direction of the beam as the central axis, a plurality of light-emitting elements 10 are also arranged in the azimuth angle direction.

[0236] The second embodiment uses 12 detection elements, and the second modification of the third embodiment uses 36 detection elements, which can individually output signals of the signal electrons 102. In this case, the number of signal electrons 102 incident on each detection element is 1 / 12 and 1 / 36 of the total number of signal electrons 102 incident on the detector, respectively. For example, when the number of signal electrons is 1 / 36, if the amount of the electron beam 101 is not increased and is used at about 1 nA or less, the interval between the signal electrons 102 incident on each detection element will be about several tens to several hundreds of nanoseconds.

[0237] On the other hand, when the light-emitting element 10 is a semiconductor scintillator, the response time from when the signal electrons 102 enter the light-emitting element 10 until light emission begins and ends is approximately several tens of nanoseconds. This response time is the detector response time required to detect one signal electron 102. By using elements capable of individual detection as in the second and third embodiments, it is possible to extend the interval at which the signal electrons 102 enter each detection element to be longer than the response time, and to detect the signal electrons 102 as discrete pulse signals. In other words, it becomes possible to count the number of signal electrons 102 as the number of pulse signals according to the irradiation position of the electron beam 101, making it possible to generate an SEM image by pulse counting (number of signal electrons), and improving visibility by providing a new observation image.

[0238] Furthermore, in the case of a detector in which the light utilization efficiency is sufficiently improved using the technology for improving light utilization efficiency described in this specification, the pulse height and the energy of the signal electrons 102 become roughly proportional. This makes it possible to measure the energy of the signal electrons 102 from the pulse height, and to discriminate signals according to the energy of the signal electrons 102. Discriminating signals according to their energy is referred to as energy discrimination. Alternatively, it may be called pulse height discrimination, since signals are discriminated according to the pulse height of the pulse signal.

[0239] If the light utilization efficiency is low, the probability that emitted photons will reach the light-receiving element 12 is low, resulting in a large variation in the number of photons that reach the light-receiving element 12. Since the number of photons from signal electrons with similar energies does not change much, if the light utilization efficiency is low, it becomes impossible to distinguish between the differences in the number of photons. In other words, if the light utilization efficiency is low, the energy resolution deteriorates and energy discrimination becomes impossible.

[0240] 17A to 17C are diagrams illustrating an example configuration of a measurement device according to the fifth embodiment. FIG. 17A shows a portion of the detector. Each light-receiving element 12 is wired so that it can individually send an electrical signal to the detection circuit 15. Generally, a current signal is output from the light-receiving element 12. The detection circuit 15 converts this current signal into an easily manageable voltage signal and amplifies it. The detection circuit 15 then digitizes the resulting voltage signal through analog-to-digital conversion and stores it in a storage device (not shown) in the system control unit 8 or elsewhere. The detection element group 5g described in Modification 2 of the third embodiment is shown as an example of the detection element group 5g.

[0241] 17B is a diagram showing the voltage signal Sv generated by the detection circuit 15. The vertical axis represents voltage, and the horizontal axis represents time. This diagram shows an example in which the amount of electron beam 101 is sufficiently low, and shows five pulse signals corresponding to five signal electrons 102.

[0242] The pulse width PW indicates the approximate response time of the detection element, and the pulse height PH indicates a quantity proportional to the energy of the signal electrons 102. Therefore, by measuring the pulse height PH, it is possible to measure the energy of the signal electrons 102. Strictly speaking, however, a histogram of the pulse height PH is created, and the noise on the low pulse side is removed and the vicinity of the peak of the histogram is fitted with a Gaussian distribution; the average of the peak values ​​is proportional to the energy of the signal electrons.

[0243] 17B, ​​the pulse height PH can be accurately measured when the pulse interval PI is longer than the response time of the detector element, i.e., the pulse width PW. When multiple signal electrons 102 are incident on the detector element within the response time, multiple pulse signals overlap. When the number of incident signal electrons within the response time is sufficiently large, the voltage signal Sv becomes a continuous curve, and each pulse becomes indistinguishable from the others.

[0244] As described in the second and third embodiments, a configuration is adopted in which multiple detection elements are arranged and electrical signals from each detection element can be output individually. This makes it possible to reduce the number of signal electrons incident on each detection element and extend the pulse interval PI at each detection element. If the number of detection elements in the detector is N, the interval PI between each detector is N times greater. This reduces pulse overlap, making it possible to measure the pulse height PH and the energy of the signal electrons 102. In other words, the configurations described in the second and third embodiments not only suppress saturation of the signal amount in the light-emitting element 10, but also enable energy discrimination even when N times as many signal electrons 102 are incident as compared to a detector with a single detection element.

[0245] In an electron microscope, signal electrons scattered at a deep position in the sample 7 lose a large amount of energy compared to before entering the sample 7. For this reason, the energy of the signal electrons contains information about the structure of the sample 7 in the depth direction. As mentioned above, particularly in the case of semiconductor inspection equipment, observation of three-dimensional structures has become important because semiconductor structures have become three-dimensional in recent years. For this reason, it is important to utilize energy information of the signal electrons 102 in order to obtain information in the depth direction. Furthermore, because the energy spectrum of the signal electrons 102 differs depending on the composition distribution of the sample, the energy of the signal electrons also contains information about the composition of the sample 7, making it possible to observe the composition distribution.

[0246] Pulse height discrimination using this detector having a plurality of detection elements capable of individually detecting the above-described signals has the effect of extracting energy information of the signal electrons and improving visibility when observing the depthwise structure and composition distribution of the sample 7. For example, if a measuring device such as an SEM has a plurality of detection elements each composed of at least a light-emitting element and a light-receiving element and capable of individually detecting signals, by generating an image based on information related to the energy or number of signal electrons, the user can better visualize the depthwise structure and the like in the image.

[0247] In the first to third embodiments, the incident surface 10i of the light-emitting element is inclined as a trapezoid to reduce the incident angle θi and sufficiently absorb the energy of the signal electrons, but these configurations are suitable for energy discrimination. This is because energy discrimination involves absorbing as much of the energy of the signal electrons as possible and measuring the energy from the amount of light emitted by that energy. However, if the amount of light emitted varies depending on the incident angle, it becomes unclear whether the discrimination is based on energy or angle. For this reason, when discriminating between energies, it is necessary to reduce the incident angle θi, and it is particularly suitable to configure the incident angle θi to be less than 30 degrees.

[0248] 17C is a diagram showing an example of a graphical user interface 16 (GUI) when improving visibility through energy discrimination (pulse height discrimination). This GUI is a GUI when energy discrimination is performed using the detector described in Modification 2 of the third embodiment. The azimuth angle direction is separated into 12 directions, and the polar angle direction is separated into three directions. At the top of the GUI, a filtered image 16a created by energy discrimination and an image 16b using all signals are displayed. Based on these images, the visibility of the filtered image can be improved, as described below.

[0249] This example shows a display example in which a 50 keV electron beam 101 is irradiated onto the sample 7, and the maximum energy of the signal electrons 102 is 50 keV, the same as the energy of the electron beam 101.

[0250] The three graphs in the middle of the GUI show the energy spectra of the detector elements, representing spectrum 16c, spectrum 16d, and spectrum 16e, respectively. In this example, spectrum 16c is the spectrum obtained by averaging the spectra detected by the detector elements located radially inward (on the electron source side in the beam irradiation direction) in 12 azimuthal directions. Similarly, spectra 16d and 16e are spectra corresponding to signal electrons detected by the detector element located at the middle position in the radial direction (the center in the beam irradiation direction) and the detector element located radially outward (on the sample side in the beam irradiation direction), respectively. In other words, spectrum 16c is the spectrum of the signal electrons 102 detected after arriving in a direction with a small polar angle, while spectra 16d and 16e are the spectra of the signal electrons detected after arriving in a direction with a medium polar angle and a direction with a large polar angle, respectively. Displaying the spectrum for each polar angle facilitates simultaneous energy discrimination and polar angle discrimination. Note that the graphs in the middle may be generated for each light-receiving element. Furthermore, numerical values ​​may be output as spectral data to a file or the like.

[0251] In all three graphs in the middle section of the GUI, the horizontal axis represents energy, and the vertical axis represents the frequency at which signal electrons corresponding to each energy level are detected. The horizontal axis can be considered to represent quantities related to energy, such as peak value. The solid and dashed lines in each graph represent the energy spectrum at the positions indicated by the circles and triangles in the filtered image. In this example, the sample materials differ at the circle and triangle positions.

[0252] This energy spectrum is used to select the energy band to be used for generating the filtered image. The energy band used for image generation is between the dotted line 16j and the dashed-dotted line 16k. In this example, since the frequency of circles (solid lines) is greater than the frequency of triangles (dashed lines) in all energy bands in spectra 16c and 16d, signals are acquired in all energy bands to increase contrast. In spectrum 16e, the dotted line 16j representing the lower limit is set to an energy greater than the intersection of the frequency of circles and the frequency of triangles, so that only the region where the frequency of circles is greater than the frequency of triangles is included. The dashed-dotted line 16k representing the upper limit is set to a value slightly smaller than the maximum energy value to exclude regions where the frequency difference is small.

[0253] Needless to say, the method of selecting the energy bands used for image generation is not limited to this, and various algorithms exist. These algorithms may be implemented as programs in the charged particle beam device 1, or a program (including a script, macro, etc.) describing the algorithm may be loaded and executed later. The charged particle beam device 1 may include a processor, and the processor may execute a program to cause the charged particle beam device 1 to realize the functions of each embodiment.

[0254] The check boxes 16f are used to select data to be displayed in the filtered image 16a. The letters "S," "M," and "H" that label the check boxes 16f indicate data sets corresponding to the spectra 16c, 16d, and 16e, respectively. When "H" is checked, the filtered image 16a is generated using the electrical signals of the signal electrons 102 that belong to the energy band sandwiched between the dotted line 16j and the dash-dotted line 16k in the spectrum 16e. When all the check boxes 16f are checked, the image 16a is generated using the electrical signals of the signal electrons 102 that belong to the energy band sandwiched between the dotted line 16j and the dash-dotted line 16k in all of the spectra 16c, 16d, and 16e.

[0255] The pull-down menu 16g allows the user to select the azimuth data processing method for generating the spectra 16c, 16d, and 16e. In FIG. 17C, "Average" is selected, which averages the spectra in 12 azimuth directions. Alternatively, it is possible to average only the spectra of some of the detector elements (e.g., the detector elements belonging to the detector element groups 5g6 to 5g8 in FIG. 11B), or to specify only the spectra of the detector elements belonging to the detector element group 5g1. In this way, various processes are possible using the pull-down menu 16g, allowing for settings to be made to appropriately improve the visibility of the image. The contents of the pull-down menu 16g can be appropriately set by those skilled in the art.

[0256] The text boxes 16h and 16i respectively indicate the minimum and maximum values ​​of the energy bands when generating the filtered image 16a, i.e., the values ​​of the dotted line 16j and the dashed-dotted line 16k in the spectra 16c, 16d, and 16e. When numerical values ​​are input into these text boxes, the charged particle beam device 1 may set the input values ​​as the minimum and maximum values ​​of the energy bands and display them in the text boxes. Alternatively, when a user moves the dotted line 16j and the dashed-dotted line 16k on the GUI, the charged particle beam device 1 may set the moved values ​​as the minimum and maximum values ​​of the energy bands and display them in the text boxes.

[0257] Using such a GUI to generate a filtered image 16a with good visibility is convenient, and the good visibility makes it easy to create an image with good visibility. In this example, the difference in signal amount (frequency difference) between the circle and triangle positions, that is, the increase in contrast, is used as an indicator of visibility. However, visibility is not limited to this, and may be appropriately set based on SNR (Signal-to-Noise Ratio) or CNR (Contrast-to-Noise Ratio), etc.

[0258] Furthermore, although much of the work in this GUI is done manually, it can be automated as appropriate, and when automating it, various optimization methods such as Bayesian optimization and AI (Artificial Intelligence) can also be used.

[0259] As in the second and third embodiments, in a measuring device having a detector that can detect pulses individually, quantities related to energy such as energy spectrum or wave height and items related to the control of those quantities are displayed, and by using a GUI that displays quantities related to the orientation and position of the detector and items related to the control of those quantities, it is possible to easily improve visibility through energy (wave height) discrimination and angle discrimination such as polar angle, thereby making it possible to construct an optimal image.

[0260] Needless to say, a GUI may be provided that creates a filtered image fully automatically by creating an algorithm in advance and omitting the display of a control GUI (check boxes, text boxes, pull-down menus, etc.). However, when creating an algorithm or fine-tuning visibility, it would be convenient to have such a control GUI or a function to output spectral data for each polar angle or to load a program.

[0261] The GUI described in this embodiment is an example, and various other forms are possible. For example, it may be a GUI specialized for polar angle discrimination, or a GUI specialized for energy discrimination.

[0262] [Other Modifications] In each embodiment of this specification, an electron microscope using an electron beam, particularly a scanning electron microscope, has been described as an example of a charged particle beam device, but as stated at the beginning of the embodiment, this is not limited to this. The quantum beam irradiated onto the sample is not limited to an electron beam, and may be a particle beam such as an ion beam, or a beam such as an X-ray or gamma ray. Furthermore, although a compact detector placed near the observation point provides better results, this is not a limitation.

[0263] The observation point is not limited to the beam irradiation position on the sample, but can also be the collision point of two beams. This technology is effective even for detectors placed far from the observation point, such as detectors installed in narrow spaces or detectors where the shape of the light-emitting element's exit surface and the shape of the light-receiving element's light-receiving surface are different, and various applications are possible.

[0264] The light-emitting elements described in the first to fourth embodiments and the modified examples of each embodiment are not limited to semiconductor scintillators in which a semiconductor layer is formed on a transparent substrate. The configurations described in these embodiments and modified examples are effective for planar (plate-shaped) light-emitting elements. Furthermore, if there is a transparent portion within the light-emitting element through which light can propagate, all of the effects described in the embodiments and modified examples can be achieved. In other words, the effects are achieved for planar light-emitting elements having a light-emitting layer, and even more so for planar light-emitting elements having a transparent portion and a light-emitting layer. The meaning of "transparent" is as described in the first embodiment.

[0265] Examples of planar light-emitting elements having a transparent portion and a light-emitting layer include the light-emitting elements described in each embodiment, such as a semiconductor scintillator formed on a sapphire substrate using GaN as the light-emitting layer material, as well as the following light-emitting elements.

[0266] An example of a light-emitting device using powder phosphor as a light-emitting layer is a light-emitting device in which a powder film (phosphor layer) is formed on a glass substrate as a transparent substrate. This light-emitting device is a planar light-emitting device having a transparent substrate as a transparent portion and a phosphor layer as a light-emitting layer. The powder film is formed by the adhesion of powder phosphor. Therefore, there is variation in thickness. The average thickness of the film is about several μm to several tens of μm. Light-emitting devices in which a film of powder phosphor is formed are characterized by high light extraction efficiency from the powder, and there are materials with high luminous intensity.

[0267] Such materials include, for example, YAP (YAlO ３ :Ce), YSO(Y ２ SiO ５ :Ce), YAG(Y ３ Al ５ O １２ :Ce), GGAG((Y, Gd) ３ (Al, Ga) ５ O １２ :Ce, (Y, Gd) ３ (Al, Ga) ５ O １２ :Tb), GOS(Gd ２ O ２ S: Pr, Gd ２ O ２ S: Ce, Gd ２ O ２ S:Tb), etc.

[0268] These YAP, YSO, YAG, GGAG, and GOS materials can be used not only as powders but also as single-crystal and polycrystalline planar light-emitting devices. In other words, planar light-emitting devices can be fabricated from these crystalline materials to achieve the configuration of the present disclosure and obtain various effects. The light-emitting layer in a crystalline material can be defined as the distance that signal electrons can penetrate. While this varies depending on the energy of the signal electrons, the light-emitting layer extends several tens of micrometers from the surface. Furthermore, while some crystalline material plates have scattering crystals, they are transparent in the sense of "transparency" described in the first embodiment. Therefore, in a crystalline material plate, the light-emitting layer extends several tens of micrometers from the surface on which the signal electrons are incident, and the remaining portion is a transparent portion. Planar light-emitting devices fabricated from these crystalline materials are also planar light-emitting devices having a transparent portion and a light-emitting layer.

[0269] The present disclosure is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present disclosure, and it is not necessary to include all of the described configurations. Furthermore, a part of one embodiment can be replaced with a configuration of another embodiment. Furthermore, a configuration of another embodiment can be added to a configuration of one embodiment. Furthermore, a part of the configuration of each embodiment can be added to, deleted from, or substituted for a part of the configuration of another embodiment.

[0270] [Regarding Related Applications] The disclosure of International Application PCT / JP2023 / 010097 by the same applicant is incorporated by reference as part of this specification.

[0271] DESCRIPTION OF SYMBOLS 1...Charged particle beam device (measurement device) 2...Electron source 3...Scanning deflector 4...Objective lens 5...Detector 6...Sample transfer stage 7...Sample 8...System control unit 9...Monitor 10...Light emitting element 11...Light guide 12...Light receiving element 13...Mounting board 14...Opening 15...Detection circuit 16...Graphical user interface 101...Electron beam 102...Signal electron C...Central axis φ...Azimuthal angle θo...Polar angle θis...Tilt angle D1...Arrow (first direction) D2...Arrow (second direction) MP...Observation point

Claims

1. A detector comprising: a plurality of light-emitting elements that emit light due to collisions of quanta emitted from a sample when the sample is irradiated with a beam; a light-receiving element that receives the light emitted by the light-emitting elements on its light-receiving surface; and a light guide that propagates the light emitted by the light-emitting elements to the light-receiving element, wherein the light-emitting elements are planar and have a transparent portion and a light-emitting layer, the transparent portion is thicker than the light-emitting layer and emits light emitted in the light-emitting layer to the transparent portion, and the transparent portion has a normal parallel to the normal to the light-emitting layer, the surface facing the light-emitting layer is the opposing surface, and the surface having a normal parallel to the light-emitting layer is the side surface, the detector has at least one of a first configuration in which light is incident on the light guide from the side surface of the transparent portion, and a second configuration in which the light-emitting elements are arranged at an angle with respect to a plane perpendicular to the irradiation direction of the beam, and light is incident on the light guide from both the side surface and the opposing surface of the transparent portion.

2. The detector according to claim 1, wherein the light-emitting element is an element in which a light-emitting layer is formed on a transparent substrate as the transparent portion.

3. The detector according to claim 1, further comprising a third configuration in which light is incident on said light guide from said opposing surface of said transparent portion.

4. The detector according to claim 1, wherein said light-emitting element is trapezoidal when viewed from a certain direction.

5. The detector according to claim 1, characterized in that the detector has both a light-emitting element having the first configuration and a light-emitting element having the second configuration, and the light-emitting element having the second configuration is closer to the sample than the light-emitting element having the first configuration.

6. A detector as described in claim 3, characterized in that the light-emitting element in the third configuration is closer to the sample than the light-emitting element in the first configuration or the light-emitting element in the second configuration.

7. The detector according to claim 1, wherein the light-emitting element in the first configuration has a transparent portion on which a slope is formed.

8. A detector according to claim 1, characterized in that said light emitting element and said light guide having said second configuration have means for receiving light from the side of said transparent portion.

9. The detector according to claim 8, wherein said light guide has a plurality of surfaces onto which light is incident.

10. A detector according to claim 1, characterized in that the angle of inclination of the beam with respect to a plane perpendicular to the irradiation direction of the beam increases as the light-emitting element is closer to the sample.

11. A detector comprising: a plurality of light-emitting elements that emit light due to the collision of quanta emitted from a sample when the sample is irradiated with a beam; a light-receiving element that receives the light emitted by the light-emitting elements on its light-receiving surface; and a light guide that transmits the light emitted from the light-emitting elements to the light-receiving element, wherein the light-emitting elements are planar and have a transparent portion and a light-emitting layer; the light-emitting elements are quadrilaterals with angles other than 90 degrees when viewed from a certain direction, and are arranged at an angle with respect to a plane perpendicular to the irradiation direction of the beam; the transparent portion is thicker than the light-emitting layer, and the light emitted from the light-emitting layer is emitted to the transparent portion and light from the transparent portion enters the light guide.

12. The detector according to claim 11, wherein the plurality of light-emitting elements are arranged so as to surround the beam.

13. The detector according to claim 11, wherein at least one of said plurality of light-emitting elements is trapezoidal when viewed from a certain direction.

14. The detector according to claim 13, wherein all of said light-emitting elements are trapezoidal when viewed from a certain direction.

15. A detector comprising: a plurality of light-emitting elements that emit light due to the collision of quanta emitted from a sample when the sample is irradiated with a beam; a light-receiving element that receives the light emitted by the light-emitting elements on its light-receiving surface; and a light guide that transmits the light emitted by the light-emitting elements to the light-receiving element, wherein the light-emitting elements are planar and have a transparent portion and a light-emitting layer; one of the light-emitting elements is arranged at an angle with respect to a plane perpendicular to the irradiation direction of the beam; the light emitted by the light-emitting element is incident on the light guide; and the other of the light-emitting elements is incident on the light-receiving element.

16. A measuring device comprising a detector according to claim 1.

17. A measuring device comprising a detector according to claim 11.

18. A measuring device comprising a detector according to claim 15.

19. A measuring device according to claim 16, comprising a plurality of said detecting elements, said measuring device generating an image based on information relating to the energy, number and emission angle of said quanta.

Images