Electron beam microscope

Abstract

An electron beam microscope comprises an electron beam source for generating an electron beam, a specimen holder, and an electron detector 41. The electron detector includes a scintillator assembly 60 with a scintillator body 61 and a light detector 63 for detecting light generated by the scintillator body 61. The scintillator body 61, viewed in cross-section along an axis 29 along which the electron beam travels, has a conical shape tapering towards the axis 29.

Description

[0001] The present invention relates to electron beam microscopes.

[0002] The invention relates in particular to electron beam microscopes comprising an electron beam source, a magnetic objective lens, a specimen holder, and an electron detector. The electron beam source generates an electron beam whose electrons are accelerated and which is focused by the magnetic objective lens into a plane of the specimen. The specimen holder holds the specimen to be examined in the plane of the specimen such that the focused electron beam strikes the surface of the specimen. The electron beam striking the specimen generates electrons that exit the specimen, such as secondary electrons and backscatter electrons. These electrons are detected by the electron detector. The detected electron intensity allows conclusions to be drawn about the structure of the specimen at the point where the electron beam strikes the specimen.The electron detector comprises a scintillator array with a scintillator body onto which the electrons generated at the object strike, producing light. The electron detector also includes a light detector that detects the light generated by the scintillator array and converts it into electrical signals representing the intensity of the electrons generated at the object by the incident electron beam. These signals can be evaluated by the control unit of the electron microscope.

[0003] In some situations, it is desirable to detect a large proportion of the backscattered electrons generated by the object. These electrons have a higher kinetic energy than the secondary electrons that are also generated when they exit the object. To detect as many of these backscattered electrons as possible, it is advantageous to position the scintillator body of the scintillator array close to the object plane.

[0004] From US 9,029,766 B2, an electron beam microscope of this type is known, which has a scintillator arrangement with a scintillator body located close to the object. The light generated by electrons striking the scintillator body is guided by an optical fiber extending through the poles of a magnetic objective lens to a light detector located outside the objective lens.

[0005] It has become apparent that this conventionally known electron beam microscope does not meet certain expectations.

[0006] Accordingly, it is an object of the present invention to propose an electron beam microscope comprising an electron beam source, a magnetic objective lens and a scintillator arrangement with a scintillator body close to an object plane, and exhibiting improved properties.

[0007] According to the invention, an electron beam microscope is proposed, comprising an electron beam source, a specimen holder, a magnetic objective lens, and an electron detector. The electron beam source generates an electron beam whose electrons are accelerated and pass through the magnetic objective lens. The magnetic objective lens focuses the electron beam in a plane of the object. The magnetic objective lens generates a focusing magnetic field by means of a magnetic coil and a yoke with a first pole and a second pole, each extending around an axis of symmetry of the magnetic objective lens. The specimen holder can hold the object under investigation such that a surface of the object is positioned in the plane of the object, allowing the electrons of the focused electron beam to strike a location on the object's surface and generate electrons there.The electron detector comprises a scintillator array and a light detector. The scintillator array includes a scintillator body positioned such that some of the electrons generated at the object can strike the scintillator body. Specifically, the scintillator is positioned along the axis of symmetry between an edge of the magnet coil that supplies the electron source and the plane of the object. The scintillator body is made of a scintillator material that emits light when these electrons strike it. The light detector is configured to detect the light emitted by the scintillator body and to generate corresponding electrical signals.

[0008] According to exemplary embodiments, the light detector is arranged along the axis of symmetry between the scintillator body and the object plane. The light detector is thus positioned closer to the object plane than the scintillator body whose light the light detector detects. For example, the light detector is arranged close to the scintillator body in such a way that the distance of the light detector from the axis of symmetry is less than ten times, and particularly less than five times, the distance of the scintillator body from the axis of symmetry. For example, the distance of the light detector from the axis of symmetry is less than 5 mm. In particular, the electron detector does not have a light guide or the like that penetrates the magnet coil or the yoke of the objective lens.

[0009] In exemplary embodiments, the light detector is mounted on one of the two poles of the objective lens. In exemplary embodiments herein, the first pole of the yoke of the objective lens is arranged closer to the object plane than the second pole, and the light detector is mounted on the first pole.

[0010] This configuration makes it possible, firstly, to position the scintillator near the object plane by placing it between the edge of the magnet coil that supplies the electron source and the first pole end, i.e., within the objective lens. Secondly, this configuration allows for efficient detection of the light generated by the scintillator with the light detector, as the light detector is positioned close to the scintillator. Furthermore, the focusing magnetic field generated by the magnetic objective lens can exhibit high symmetry about the axis of symmetry, since the magnet coil and the yoke can also exhibit high symmetry about the axis of symmetry, unaffected by an optical fiber penetrating the magnet coil or the yoke.

[0011] According to exemplary embodiments, the scintillator assembly has a light-emitting surface from which the light generated by the scintillator body exits into a vacuum chamber of the electron beam microscope, and the light detector has a light-receiving surface through which the light generated by the scintillator body enters the light detector from the vacuum chamber. In this configuration, the scintillator assembly and the light detector are spaced apart. It is therefore possible to mount the scintillator assembly and the light detector on components of the electron beam microscope whose electrical potentials are different from each other.

[0012] According to exemplary embodiments herein, the light-emitting surface is provided directly on the scintillator body. The light generated in the scintillator body thus exits the scintillator body directly into the vacuum space, without first passing through another component, such as a light guide.

[0013] According to alternative embodiments, the scintillator arrangement comprises a light guide that is optically coupled to the scintillator body, so that at least part of the light generated by the scintillator body can enter the light guide, pass through the light guide and exit the light guide into the vacuum space at the light exit surface then provided on the light guide.

[0014] According to exemplary embodiments, the light-receiving surface of the light detector faces the electron beam source, and a surface normal of the light-receiving surface of the light detector forms an angle of less than 20° with the axis of symmetry. In particular, the surface normal of the light-receiving surface can be oriented parallel to the axis of symmetry.

[0015] According to exemplary embodiments, a mirror is provided whose reflective surface lies in a beam path of a portion of the light generated by the scintillator body between the scintillator body and the light detector. For example, a portion of the light generated by the scintillator body can then pass directly to the light detector via a beam path that does not include the reflective surface, in order to be detected by it. The amount of detected light is increased by the light generated by the scintillator body that reaches the light detector via the beam path that includes the mirror.

[0016] According to exemplary embodiments, the electron beam microscope comprises a beam tube having an electrically conductive inner lining into which the electron beam enters at a first end of the beam tube and from which the electron beam exits at a second end of the beam tube. The electron beam microscope further comprises a potential supply system configured to supply a first electrical potential U1 to an electron emitter of the electron beam source, a second electrical potential U2 to the specimen holder, a third electrical potential U3 to the beam tube, and a fourth electrical potential U4 to the scintillator body.

[0017] The scintillator body can be mechanically mounted to the nozzle. For example, the electrically conductive inner lining of the nozzle can be self-supporting if the nozzle is made of metal and this metal provides the electrically conductive inner lining. The scintillator body can be mounted to this metal part of the nozzle. In this case, the scintillator body can be electrically connected to the electrically conductive inner lining of the nozzle or insulated from it. Alternatively, the electrically conductive inner lining can be non-self-supporting, for example, if an electrically conductive layer is applied to a supporting structure made of a non-conductive material, such as ceramic or plastic, which then provides the electrically conductive inner lining of the nozzle.The scintillator body can be mechanically held in place by this supporting structure and electrically connected to or insulated from the electrically conductive inner sheath.

[0018] According to exemplary embodiments, U2 > U1, U3 > U1, and U3 > U2. This means that the electrons of the electron beam are accelerated on their path between the electron emitter and the first end of the beam tube, traverse the beam tube rapidly between the first and second ends, exit the beam tube at the second end, and are decelerated on their path between the second end of the beam tube and the plane of the object. The kinetic energy of the electrons of the electron beam upon impact with the object corresponds to the difference between U3 and U1.

[0019] In exemplary embodiments, |U4 - U3| < 2 kV. For example, U4 = U3. In this case, the scintillator body can be electrically connected to the electrically conductive inner lining of the beam tube. If U4 is not equal to U3, the scintillator body is electrically insulated from the electrically conductive inner lining of the beam tube. The electrical potential of the scintillator body can be chosen to be different from the electrical potential of the electrically conductive inner lining of the beam tube in order to provide an electric field between the scintillator body and the beam tube that influences the trajectories of electrons in the electron beam on their way to the object plane and / or the trajectories of electrons generated at the object on their way to the scintillator body or to other components of the electron beam system.

[0020] According to a further embodiment, the electron beam microscope, for the latter purpose, also comprises a first ring electrode with a bore symmetrical to the axis of symmetry, which is arranged along the axis of symmetry between the second end of the beam tube and the object location. The potential supply system can be configured to supply the first ring electrode with a fifth electrical potential U5, for which |U5 - U2| < 2 kV.

[0021] In exemplary embodiments, the light detector is mounted on the first ring electrode. In further exemplary embodiments, the light detector is electrically connected to the first ring electrode, such that the light detector is at the same electrical potential as the first ring electrode. In further exemplary embodiments, the first ring electrode is mounted on or provided by the first pole end. This can be achieved, for example, by the ring electrode being a component integrally connected to the first pole end or being provided by the first pole end.

[0022] According to exemplary embodiments, the electron beam microscope further comprises a second ring electrode with a bore symmetrical to the axis of symmetry, arranged along the axis of symmetry between the scintillator body and the first ring electrode. The potential supply system can be configured to supply the second ring electrode with a sixth electrical potential U6, for which |U6 - U4| < 2 kV. The second ring electrode can provide an electric field between the scintillator body and the beam tube, which influences the trajectories of the electrons of the electron beam on their way to the object plane and / or the trajectories of the electrons generated at the object on their way to the scintillator body or to other components of the electron beam system.

[0023] According to further exemplary embodiments, the electron microscope further comprises a second electron detector configured to detect electrons generated by the electron beam at the object. The second electron detector comprises a scintillator arrangement with a scintillator body arranged along the axis of symmetry between an edge of the magnet coil facing the electron beam source and the object location, such that the electrons generated at the object strike the scintillator body. The scintillator body is made of a scintillator material capable of generating light upon contact with incident electrons. The second electron detector further comprises a light detector configured to detect light generated by the scintillator body and convert it into electrical signals.The light detector of the second electron detector is arranged along the axis of symmetry between the electron source and the scintillator body of the second light detector.

[0024] According to exemplary embodiments, the scintillator body of the second electron detector is mounted on the scintillator assembly of the first electron detector. This places the scintillator bodies of the first and second electron detectors close to each other but offset from one another. Light generated by the scintillator body of the first electron detector can be detected by the light detector of the first electron detector, and light generated by the scintillator body of the second electron detector can be detected by the light detector of the second electron detector. Because the two scintillator bodies are relatively close to each other but offset from one another, electrons emitted from the point of impact of the electron beam on the object with different energies and / or in different directions strike the two scintillator bodies.By detecting the light generated by the two scintillator bodies, it is thus possible to selectively detect groups of electrons generated on the object that differ in terms of their kinetic energy and / or direction.

[0025] In exemplary embodiments, the electron beam microscope further comprises a third electron detector configured to detect electrons generated by the electron beam at the object, wherein the third electron detector includes a semiconductor detector configured to generate electrical signals from the electrons generated at the object. In exemplary embodiments, the semiconductor detector of the third electron detector and the light detector of the first electron detector are jointly supported on a mount. In exemplary embodiments, this common mount is provided by the first pole end of the objective lens yoke.

[0026] Furthermore, the semiconductor detector of the third electron detector can have an electron receiving surface facing the object plane, and the light detector of the first electron detector can have a light entry surface facing away from the object plane. This allows the back side of the first electron detector's light detector—that is, a side of the light detector that does not form the light entry surface—to be advantageously utilized by attaching the semiconductor detector of the third electron detector to it, in order to detect additional electrons generated at the object by the incident electron beam. Furthermore, the semiconductor detector of the third electron detector and the light detector of the first electron detector can also be implemented as a single, integrated component.

[0027] According to exemplary embodiments, the scintillator body of the first electron detector, viewed in a cross-section containing the axis of symmetry, has a conical shape that tapers towards the axis of symmetry. This shape can be advantageous for the following reason: conventional scintillator bodies of electron detectors are usually formed from a scintillator material with a plane-parallel plate shape. For example, they have the shape of a circular ring made of the plate material, centered on the axis of symmetry of the focusing lens. The electrons to be detected strike one of the main surfaces of the circular ring and generate light in it, which is transported radially outwards in the scintillator body and strikes a light detector at the outer edge of the ring or passes into an optical waveguide leading to a light detector.The scintillator body itself thus acts as a light guide, directing the generated light from its point of origin to a surface of the scintillator body that the light must pass through on its way to the light detector. The light passing through the scintillator body is reflected one or more times at its inner surfaces. Only a portion of the generated light is reflected at these inner surfaces in such a way that it can reach the light detector. The previously described conical shape can increase this proportion of light by directing one or more reflections of the light from the conical shape more and more towards the surface of the scintillator body that the light must pass through on its way to the light detector. Thus, the conical shape of the scintillator body increases the proportion of the generated light that can be detected by the light detector.

[0028] According to the invention, an electron beam microscope is therefore further proposed, comprising an electron beam source, a specimen holder, and an electron detector. The electron detector comprises a scintillator arrangement with a scintillator body arranged such that the electrons generated at the specimen strike the scintillator body, the scintillator body being formed from a scintillator material that emits light upon contact with the incident electrons. The electron detector further comprises a light detector configured to detect light generated by the scintillator body and convert it into electrical signals. The scintillator body of the electron detector, viewed in cross-section along an axis along which the electron beam travels, has a conical shape tapering towards the axis.

[0029] Embodiments of the invention are explained in more detail below with reference to figures. Fig. Figure 1 shows a schematic sectional view of an electron beam microscope according to a first embodiment. Fig. 2 shows a partial view of the in Fig. 1 Electron beam microscope details of an objective lens and an electron detector. Fig. Figure 3 shows a schematic sectional view of a partial view of an electron beam microscope according to a second embodiment. Fig. Figure 4 shows a schematic sectional view of a partial view of an electron beam microscope according to a third embodiment.

[0030] Fig. Figure 1 shows a schematic sectional view of an electron beam microscope 1 according to a first embodiment. The electron beam microscope 1 comprises an electron beam source 3 with an electron emitter 5 and an extractor electrode 7, between which an electrical voltage is applied to extract electrons from the electron emitter 5, forming an electron beam 9. An electrical potential U1 is applied to the electron emitter 5, which is provided by a potential supply system 11. The potential supply system 11 is part of a control unit 12 of the electron beam microscope 1. The electron beam 9 emerges from a Fig. The electron beam enters the beam tube 15 at its upper end 13, passes through it, and exits at its lower end 17 before striking an object 19 to be examined. The beam tube 15 has an electrically conductive inner lining that is at an electrical potential U3 provided by the potential supply system 11. The potential difference U3 - U1 is, for example, 8 kV or more, so that the electrons of the electron beam 9 pass rapidly through the beam tube 15 between the first end 13 and the second end 17 with increased kinetic energy.

[0031] Object 19 is held on an object holder 21, to which an electrical potential U2 is supplied by the potential supply system 11, so that object 19 is also at the potential U2. The potential difference U2 - U1 defines the kinetic energy with which the electrons of the electron beam 9 strike object 19. Here, the difference U2 - U1 is smaller than the potential difference U3 - U1, so that the electrons of the electron beam 9 are decelerated between the second end 17 of the beam tube 15 and the surface of object 19.

[0032] The electron beam microscope 1 further comprises a magnetic objective lens 23 to focus the electron beam 9 in an object plane 25. The object holder 21 positions the object 19 such that its surface essentially coincides with the object plane 25, so that the electron beam 9 is focused at an object location 27 on the surface of the object 19.

[0033] The magnetic objective lens 23 comprises a symmetry axis 29 and a magnetic coil 31 surrounding the symmetry axis 29 of the objective lens 23, to which an excitation current is supplied by the control unit 12 to generate a magnetic field. The magnetic coil 31 is surrounded by a yoke 33, which has a cross-section of Fig. 1 has a first pole end 35 and a second pole end 37. The yoke 33 and the pole ends 35 and 37 surround the axis of symmetry 29 in a ring-like manner. The pole ends 35 and 37 are arranged at a distance from each other, so that the current flowing in the magnet coil 31 generates a magnetic field in the vicinity of the pole ends 35 and 37 that is symmetrical with respect to the axis of symmetry 29 and that has a focusing effect on the electron beam 9.

[0034] The electron microscope 1 comprises beam deflectors 38, which are controlled by the control unit 12 to deflect the electron beam 9 and thus move the object location 27, where the electron beam 9 strikes the object 19, for example, line by line across a region of the object 19, thereby scanning this region of the object 19 with the electron beam 9. The electrons of the electron beam 9 striking the object 19 at the object location 27 generate electrons through a reaction with the object 19, which exit the object and are detected by a first electron detector 41 and a second electron detector 43. During the scanning of the object 19 with the electron beam 9, the signal intensities detected by the electron detectors 41 and 43 are recorded by the control unit in order to ultimately generate an electron microscopic image of the scanned region of the object 19.

[0035] A trajectory 45 represents, by way of example, an electron emerging from object 19 at object location 27, which hits the first electron detector 41 to be detected by it, and a trajectory 47 represents, by way of example, an electron emerging from object 19 at object location 27, which hits the second electron detector 43 to be detected by it.

[0036] The second electron detector 43 comprises a scintillator body 49, which is formed from a scintillator material that generates light upon contact with electrons. The scintillator body 49 is attached to an optical fiber 51 that guides the light generated by the scintillator body 49, which exits the scintillator body 49 and enters the optical fiber 51, to a light detector 53. Lines 55 represent such light. The light detector 53 generates electrical signals from the detected light, which can be evaluated by the control unit 12 of the electron beam microscope 1. These electrical signals represent the intensity of the electrons generated by the electron beam 9 at the object location 27, which exit the object 19 in such directions and with such kinetic energy that they can strike the scintillator body 49.The scintillator body 49 and the light guide 51 have a bore 57 to allow the passage of the electron beam 19.

[0037] The first electron detector 41 comprises a scintillator assembly 60 and a light detector 63. The scintillator assembly 60 includes a scintillator body 61, onto which electrons 45 strike and generate light 65. This light propagates within the scintillator body 61, exits the scintillator body 61 into the vacuum at a light exit surface 67, and strikes a light entry surface 69 of the light detector 63 to be detected. The light detector 63 generates electrical signals that are transmitted from the objective lens 23 to the control unit 12 of the electron beam microscope 1 via conductors 70 located within the objective lens 23. The control unit can evaluate these electrical signals.These electrical signals represent the intensity of electrons generated by the electron beam 9 at the object location 27 and exiting the object 19 with such energy and in such directions that they can hit the scintillator body 61.

[0038] The light detector 63 is mounted at the first pole end 35 of the yoke 33 of the magnetic objective lens 23. The light-entry surface 69 of the light detector points away from the object plane 25 and towards the electron beam source 3. In particular, a surface normal of the light-entry surface 69 is defined in the Fig. In the example shown, the magnetic objective lens 23 is oriented parallel to the axis of symmetry 29. However, the light detector can also be oriented differently, such that the surface normal of the light-entry surface 69 is oriented at a non-zero angle to the axis of symmetry 29, which is, for example, less than 20°.

[0039] The first electron detector 41 further comprises a mirror 71 with a reflective surface 72, which is provided on the yoke 33 of the magnetic objective lens 23. The reflective surface 72 surrounds the electron beam 9 in a ring-like manner and symmetrically about the axis of symmetry 29. At the reflective surface 72, a portion of the light emerging from the light-exit surface 67 of the scintillator body 61, which does not directly strike the light detector 63, is reflected such that the light reflected at the reflective surface 72 strikes the light-intake surface 69 of the light detector 63 to be detected by it. An exemplary light beam 73 is shown in Fig. Figure 1 shows the mirror 71 increasing the detection probability of electrons 45 striking the scintillator body 61 by the light detector 63.

[0040] The scintillator body 61 is arranged along the axis of symmetry 29 between one edge 75 of the magnet coil 31, which assigns the electron beam source 3, and the object plane 25. In other words, the scintillator body 61 is in the Fig. 1, in which the axis of symmetry 29 extends vertically, is arranged further down and closer to the object plane 25 than the upper edge 75 of the magnetic coil 31. Furthermore, in this view, the light detector 63 with its light-entry surface 69 is arranged between the scintillator body 61 and the object plane 25. Thus, in other words, the light detector 63 is arranged further down and closer to the object plane 25 than the scintillator body 61.

[0041] Fig. Figure 2 is a sectional view of part of the electron beam microscope 1, showing magnified details of the objective lens 23 and the first electron detector 41.

[0042] The light detector 63 is embedded in a recess 77 provided in the first pole piece 35. The light detector 63 is at an electrical potential U5, which is equal to the electrical potential of the first pole piece 35 and is provided by the potential supply system 11. An inner edge 79 of the first pole piece 35, which is aligned with the axis of symmetry 29, extends symmetrically around the electron beam 9 with respect to the axis of symmetry 29. The first pole piece 35, which is at the electrical potential U5, thus forms a ring electrode 89, the bore of which is defined by the inner edge 79. The electrical potential U5 of the ring electrode 89 can be equal to or different from the electrical potential U2 of the object 19. In particular, the potential U5 and / or the potential U2 can be equal to the ground potential. The first ring electrode 89 is arranged closer to the object plane 25 than the second end 17 of the beam tube 15.

[0043] The scintillator body 61 is mounted at the second end 17 of the beam tube 15. The scintillator body 61 is electrically connected to the beam tube 15 such that an electrical potential U4 of the scintillator body 61 is equal to the electrical potential U3 of the beam tube 15. An inner rim 91 of the scintillator body 61, which aligns with the axis of symmetry 29, extends symmetrically around the electron beam 9. The scintillator body 61 thus forms a ring electrode 93, the bore of which is defined by the inner rim 91 of the scintillator body 61. The materials suitable for forming the scintillator body 61 are generally not electrically conductive.For this reason, the scintillator body 61 is at least partially provided with an electrically conductive layer, firstly to avoid a local electrical charging of the scintillator body 61 by incident electrons and secondly to be able to provide a uniform electrical potential over the essential parts of the surface of the scintillator body 61, so that the scintillator body 61 can act as part of the ring electrode 93 to define, together with other components of the electron microscope 1, the electric fields that influence the trajectories of the electrons of the electron beam 9 and of the electrons generated and detected at the object.

[0044] At locations where it is desired that photons generated within the scintillator body should exit so that they can be detected by a dedicated light detector, the electrically conductive layer is transparent. Conversely, there may be locations on the surface of the scintillator body where, due to the geometric relationship between these locations and a light detector, exiting photons cannot be detected, or can only be detected with a low probability. In such cases, it can be advantageous for the electrically conductive layer to be light-reflecting, so that the photons are reflected through the layer and reach another location on the surface of the scintillator body, where they can exit and be detected with a higher probability.In the embodiment described here and in the further embodiments, electrically conductive layers on surfaces of scintillator bodies are not shown separately in the figures and are usually not explained again in the accompanying description.

[0045] The ring electrodes 93 and 89 and the surface of object 19 determine the electric fields in the region between the second end 17 of the beam tube 15 and object 19. These electric fields are traversed by the electron beam 9 on its path to object 19 and by the electrons leaving object 19 that may be detected. These electric fields thus influence the trajectories of these electrons. For example, these electric fields also have a focusing effect on the electron beam 9, and they can further be adjusted to optimize the impact of electrons generated at object 19 on the scintillator bodies 61 and 49 of the two electron detectors 41 and 43, respectively, according to specific criteria.

[0046] An inner edge 78 of the light detector 63, which is assigned to the axis of symmetry 29, is located close to the inner edge 79 of the first pole piece 35 and at a greater distance from the axis of symmetry 29 than the inner edge 91 of the scintillator body, so that the pole piece 35, which accommodates the light detector 63, does not completely shading the scintillator body 61 as seen from the object location 27, and electrons 45 generated at the object location 27 can strike the scintillator body 61. Nevertheless, the light detector 63 is arranged close to the scintillator body 61 so that the light 65 does not strike it at too large an angle to a surface normal of the light-entry surface 69 of the light detector 63. For example, the distance of the inner edge 78 of the light detector 63 from the axis of symmetry 29 is less than ten times, and in particular less than five times, the distance of the inner edge 91 of the scintillator body 61 from the axis of symmetry 29.

[0047] The scintillator body 61 has in the cross-sectional view of the Fig. 2 a polygonal shape. The light generated in the scintillator body 61 exits the scintillator body 61 at the light-emitting surface 67. The electrons 45 coming from the object 19 strike an electron-receiving surface 95 of the scintillator body 61. A surface 97 of the scintillator body 61 located between the electron-receiving surface 95 and the light-emitting surface 67 can be mirrored to reflect generated light in the scintillator body 61 towards the light-emitting surface 67. Likewise, a surface 99 of the scintillator body 61 extending between the light-emitting surface 67 and the inner edge 91 of the scintillator body 61 is mirrored to reflect light towards the light-emitting surface 67.

[0048] As can be seen from the cross-sectional representation containing the axis of symmetry 29 of the Fig. As can be seen in Figure 2, the electron receiving area 95 and the surface 99 of the scintillator body 61 extend at an acute angle to each other, so that the scintillator body 61 in this cross-sectional view has a shape that tapers conically towards the axis of symmetry 29, at least in some areas. Reference numeral 101 is used in Fig. 2 denotes a light beam that is reflected multiple times within the scintillator body 61 between the electron receiving surface 95 and the surface 99 of the scintillator body 61. Due to the acute angle between the two surfaces 95 and 99, the direction of the light beam 101 is directed more strongly towards the light emission surface 67 with each reflection, so that a larger proportion of the light generated by the scintillator body 61 reaches the light detector 63 through the light emission surface 67.

[0049] Further embodiments of the electron beam microscope are described below. Components are described that, in terms of their structure and / or function, are similar to those of the models based on the Fig. 1 and Fig. The components described in section 2 correspond to the first embodiment, provided with the same reference numerals, supplemented by an additional letter. Sufficiently similar components are not described again, and their understanding can be understood by referring to the preceding description, including the introductory section.

[0050] Fig. Figure 3 is a sectional view of a part of an electron beam microscope according to a second embodiment, showing magnified details of an objective lens and electron detectors of the electron beam microscope.

[0051] The electron beam microscope 1a comprises an objective lens 23a with a yoke 33a having a first pole end 35a and a second pole end 37a, which extend symmetrically around an axis of symmetry 29a of the objective lens 23a. A beam tube 15a extends in the illustration of the Fig. 3 from above into the objective lens, such that a lower end 17a of the beam tube 15a is located in a region between the poles 33a and 37a. The beam tube 15a comprises an electrically insulating support 111, on the inner wall of which an electrically conductive layer 113 is provided, extending from the first end of the beam tube 15a to the lower second end 17a of the beam tube 15a. The electrical potential U3 is supplied to the electrically conductive layer 113 by a potential supply system of the electron microscope 1a.

[0052] The electron beam microscope 1a further comprises a first electron detector 41a, which includes a scintillator body 61a and a light detector 63a. The scintillator body 61a is arranged closer to the object plane 25a than an edge of a magnetic coil of the objective lens 23 facing the electron source. The scintillator body 61a is also arranged closer to the object plane 25a than the second end 17a of the beam tube 15a.

[0053] The scintillator body 61a is arranged at a distance in the direction of the axis of symmetry 29a from the second end 17a of the beam tube 15a. The scintillator body 61a is held at one end 115 of a metallic tube 117 near the object plane 25a, the other end 119 of which is attached to an outer wall 121 of the insulating body 111 of the beam tube 15a. An electrical potential U4 is supplied to the metallic tube 117 from the potential supply system via a conductor routed along the outer wall 121 of the insulating body 111. The electrical potentials U4 of the scintillator body 61a and the electrical potential U3 of the inner sheath 113 of the beam tube 15a can be the same or different. For example, U3 is 8 kV and U4 is 6 kV. According to another example, corresponding to a different operating state of the electron microscope 1a, U3 is equal to 8 kV and U4 is equal to 10 kV.

[0054] The light detector 63a of the first electron detector 41a is attached to an annular mount 119, which in turn is attached to the first pole 35a of the yoke 33a of the magnetic objective lens 23a. The light detector 63a is positioned closer to the object plane than the scintillator body 61a. Electrons 45a emanating from the object strike the scintillator body 61a and generate light 65a there, which can then reach the light detector 63a and be detected by it. It is possible to coat an inner region of the underside of the scintillator body 61a, near the axis of symmetry, so that light generated in this region must first increase its distance from the axis of symmetry 29a before it can exit towards the light detector 63a.

[0055] The electron microscope 1a comprises a second light detector 43a, which has a scintillator body 49a that is held at an inner edge of the scintillator body 61 of the first electron detector 41a. The scintillator body 49a of the second electron detector 43a also extends symmetrically around the axis of symmetry 29a in a ring-like shape. Electrons 47a coming from the object and striking the scintillator body 49a of the second electron detector 43a generate light within it, with some of this light being absorbed into Fig. 3 upwards, that is, in the direction towards an electron beam source of the electron beam microscope 1a. An exemplary light beam 55a of such light is in Fig. Figure 3 shows that this light can be detected by a light detector 56, which is provided along the axis of symmetry 29a between the electron beam source and the scintillator body 49a. For example, this light can enter an optical fiber, similar to the optical fiber 51 of the second light detector 43 of the first embodiment in Fig. 1 is arranged and the light is directed towards one in Fig. 3 light detectors not shown.

[0056] Electrons 45a emanating from the object and striking the scintillator body 61a of the first light detector 41a differ from electrons 47a emanating from the object and striking the scintillator body 49a of the second light detector 43a with respect to their kinetic energy and / or the direction in which they exit the object. It is therefore possible to detect different groups of electrons generated at the object using the two electron detectors 41a and 43a.

[0057] A semiconductor detector 123 of a third electron detector 125 is attached to a surface 121 of the light detector 63a opposite the light-receiving surface 69a of the light detector 63a, which is assigned to the object plane 25a. The semiconductor detector 123 extends symmetrically around the axis of symmetry 29a in a ring shape. The semiconductor detector 123 has an electron-receiving surface 127 that is assigned to the object plane 25a, onto which electrons generated at the object by the electron beam 9a can strike. An exemplary trajectory 129 of such electrons is shown in Fig. Figure 3 shows that these electrons are directly converted by the semiconductor detector 123 into electrical signals representing the intensity of the electrons generated at the object and striking the semiconductor detector 123. The electrical signals generated by the semiconductor detector 123 and the electrical signals generated by the light detector 63a can be fed to the control unit of the electron beam microscope 1a via conductors routed through and leading out of the objective lens 23a.

[0058] The electrons 129 generated at the object and striking the semiconductor detector 123 of the third electron detector 125 differ from the electrons striking the scintillator body 61a of the first electron detector 41a and the electrons striking the scintillator body 49a of the second electron detector 43a in their kinetic energy and / or the direction in which they emerge from the object. Thus, with the three electron detectors 41a, 43a, and 125 of the electron beam microscope 1a, it is possible to detect three groups of electrons that emerge from the object and differ in their direction and / or energy.

[0059] The inner edges of the light detector 63a and the semiconductor detector 123, which are aligned with the axis of symmetry 29a, are flush and form an inner edge 79a of a ring electrode 89a, which is formed by the outer surfaces 69a and 127 of the light detector 63a and the semiconductor detector 123. The potential U5 is supplied to this ring electrode via the holder 119 and the first pole piece 33a.

[0060] An inner edge 91a of the scintillator body 49a of the second electron detector 43a, which is aligned with the axis of symmetry 29a, defines a bore in a ring electrode 93a that is at potential U4. Thus, the electrically conductive inner lining of the beam tube 15a, which is at potential U3, the ring electrode 93a, which is at potential U4, the ring electrode 89a, which is at potential U5, and the object in the object plane 25a form a system of electrodes that determine the electric fields in the region between the second end 17a of the beam tube 15a and the object plane 25a. These fields, among other things, focus the electron beam 9a striking the object and influence the trajectories of the electrons that emerge from the object in different directions and with different energies.These potentials can be changed to alter the direction and energy of the groups of electrons detected by the three electron detectors 41a, 43a and 125.

[0061] Fig. Figure 4 shows a schematic sectional view of a partial view of an electron beam microscope of a third embodiment, which shows enlarged details of an objective lens and electron detectors of the electron beam microscope.

[0062] The electron beam microscope 1b comprises a Fig. 4 electron beam source (not shown) that generates an electron beam 9b which is directed at a in Fig. 4. An electron enters a beam tube 15b at its first end (not shown) and exits it at a second end 17b to strike an object. A magnetic objective lens 23b is provided to focus the electron beam 9. Some of the electrons generated by the electron beam 9 at the object can strike a scintillator body 61b of a first electron detector 41b of the electron microscope 1b, as shown by an exemplary trajectory 45b. Such electrons 45b generate light in the scintillator body 61b, some of which strikes a light-receiving surface 69b of a light detector 63b of the first electron detector 41b. An exemplary trajectory 65b of such light is shown in Fig. Figure 4 shows that the scintillator body 61b extends symmetrically around the axis of symmetry 29b in a ring-like shape. The scintillator body 61b is part of a scintillator assembly 60b of the first electron detector 41b. The scintillator assembly 60b further comprises an optical waveguide 131, which is optically coupled to an outer edge of the scintillator body 61b, so that light 65b generated in the scintillator body 61b can enter the optical waveguide 131. The optical waveguide 131 also has a truncated cone shape that is symmetrical with respect to the axis of symmetry 9b. The optical fiber 131 guides the light 65b to a light-emitting surface 67b of the scintillator arrangement 60b, where the light exits the scintillator arrangement 60b into the vacuum and can strike a light-receiving surface 69b of a semiconductor detector 63b. The semiconductor detector 63b is, similar to the one in Fig. In the first embodiment shown in Figure 2, the lens is embedded in a recess 77b, which is provided at a first pole end 35b of a yoke 33b of the objective lens 23b. A mirror 71b with two mirror surfaces 72b is also provided at the first pole end 35b, at which further light exiting the light guide 131 at the light exit surface 67b can be reflected to strike the light receiving surface 69b of the light detector 63b.

[0063] A ring body 135 of a ring electrode 93b is attached to an inner surface of the optical fiber 131. A surface 136 of the ring body 135 facing the first pole end 35b, a surface 137 of the ring body 135 facing the axis of symmetry 9b, and a surface 138 of the ring body 135 facing the scintillator body 61b are provided with an electrically conductive layer 139. This electrically conductive layer 139 is electrically connected to an electrically conductive layer 141, which is provided at the light-exit surface 67b of the optical fiber 131 and is transparent. The electrically conductive layer 141, in turn, is electrically connected to an electrically conductive layer 122 or an electrical conductor provided on an outer wall 121b of an electrically insulating body 111b, which forms the load-bearing component of the radiant tube 15b. The electrically conductive layer 122 orThe electrical potential U6 is supplied to the first end of the beam tube 15b by a potential supply system of the electron beam microscope 1b. Due to the electrical connection of the surfaces 141, 136, 137 and 138, a ring electrode 93b is formed by the surfaces 136, 137 and 139 on the ring body 135, the bore of which is defined by the surface 137 of the inner edge of the ring body 135 and which is at the electrical potential U6.

[0064] The scintillator body 61b is electrically connected to an electrically conductive layer 113b, which is provided on the inner wall of the beam tube 111b and defines the electrical potential U3 of the beam tube 15b. The scintillator body 61b is therefore also at the electrical potential U3.

[0065] Another ring electrode 89b is, similar to the one in Fig.2 in the embodiment shown, formed by the first pole end 35b of the magnetic objective lens 23b.

[0066] After exiting the beam tube 15b, the electron beam 9b first passes through the ring electrode 93b and then the ring electrode 89b before striking the object. As previously explained, the ring electrodes 93b and 89b, together with the object and a conductive coating on the scintillator body 61b, form the electric fields between the second end 17b of the beam tube 15b and the object. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 9 029 766 B2

[0004]

Claims

[1] Electron beam microscope, comprising: an electron beam source (3) configured to produce an electron beam (9); an object holder (21) configured to hold an object (19) at an object location (27) on which the electron beam (9) hits; a magnetic objective lens (23) for focusing the electron beam (9) in an object plane (25), wherein the magnetic objective lens (23) has a magnetic coil (31) and a yoke (33) with a first pole end (35) and a second pole end (37), each extending around an axis of symmetry (29) of the magnetic objective lens (23); and a first electron detector (41) configured to detect electrons produced by the electron beam (9) at the object (19); the first electron detector (41) comprises: a scintillator arrangement (60) with a scintillator body (61) arranged such that electrons generated at the object location (27) collide with the scintillator body (61), wherein the scintillator body (61) is formed from a scintillator material which generates light (65) with incident electrons (45), and a light detector (63) configured to detect light (65) generated by the scintillator body (61) and convert it into electrical signals; and wherein the light detector (63) is arranged along the axis of symmetry (29) between the scintillator body (61) and the object plane (25). [2] Electron beam microscope according to claim 1, wherein the scintillator body (61) is arranged along the axis of symmetry (29) between an edge of the magnet coil (31) assigning to the electron beam source (3) and the object plane (25). [3] Electron beam microscope according to claim 1 or 2, wherein the distance of the light detector (63) from the axis of symmetry (29) is less than ten times, and in particular less than five times, the distance of the scintillator body (61) from the axis of symmetry (29), and / or where the distance of the light detector (63) from the axis of symmetry (29) is less than 5 mm. [4] Electron beam microscope according to any one of claims 1 to 3, wherein the scintillator arrangement (60) has a light-emitting surface (67) from which the light (65) generated by the scintillator body (61) emerges into a vacuum chamber of the electron beam microscope (1); and wherein the light detector (63) has a light receiving surface (69) through which this light (65) from the vacuum space enters the light detector (63). [5] Electron beam microscope according to claim 4, wherein the light emission surface (67) is provided on the scintillator body (61). [6] Electron beam microscope according to claim 4, wherein the scintillator arrangement (60b) comprises an optical fiber (131) which is optically coupled to the scintillator body (61b) so that the light (65b) generated by the scintillator body (61b) can enter the optical fiber (131); and wherein the light emission surface (67b) is provided on the light guide (131). [7] Electron beam microscope according to one of claims 4 to 6, wherein the light receiving surface (69) of the light detector (63) faces the electron beam source (3) and a surface normal of the light receiving surface forms an angle of less than 20° with the axis of symmetry. [8] Electron beam microscope according to any one of claims 1 to 7, wherein the first pole end (35) is located closer to the object plane (25) than the second pole end (37); and wherein the light detector (63) is held at the first pole end (35). [9] Electron beam microscope according to claim 8, wherein the first pole end (35) carries a mirror (71) whose mirror surface (72) lies in a beam path of the light (73) generated by the scintillator body (61) between the scintillator body (61) and the light detector (63). [10] Electron beam microscope according to any one of claims 1 to 9, further comprising a beam tube (15) having an electrically conductive inner lining into which the electron beam (9) enters at a first end (13) of the beam tube (15) and from which the electron beam (9) exits at a second end (17) of the beam tube (15). [11] Electron beam microscope according to claim 10, wherein the scintillator body (61) is held on the beam tube (15). [12] Electron beam microscope according to claim 10 or 11, further comprising a potential supply system (11) configured to supply a first electric potential (U1) to an electron emitter (5) of the electron beam source (3), to supply a second electric potential (U2) to the specimen holder (21), to supply a third electric potential (U3) to the beam tube (15) and to supply a fourth electric potential (U4) to the scintillator body (61). [13] Electron beam microscope according to claim 12, where: U2>U1,U3>U1 and U3>U2; where U1 represents the first electric potential, U2 represents the second electric potential, and U3 represents the third electric potential. [14] Electron beam microscope according to claim 13, where: |U4−U3|<2 kV; where U4 represents the fourth electrical potential. [15] Electron beam microscope according to claim 14, wherein: U4=U3. [16] Electron beam microscope according to any one of claims 12 to 15, further comprising a first ring electrode (89) with a bore (79) symmetrical to the axis of symmetry (29), which is arranged along the axis of symmetry (29) between the second end (17) of the beam tube (15) and the object plane (25); wherein the potential supply system (11) is configured to supply a fifth electrical potential (U5) to the first ring electrode (89). [17] Electron beam microscope according to claim 16, where: |U5−U2|<2 kV; where U5 represents the fifth electrical potential. [18] Electron beam microscope according to one of claims 16 or 17, wherein the light detector (63) is mounted on the first ring electrode (89). [19] Electron beam microscope according to one of claims 16 to 18, wherein the first ring electrode (89) is held at the first pole end (35). [20] Electron beam microscope according to any one of claims 16 to 19, further comprising a second ring electrode (93b) with a bore symmetrical to the axis of symmetry (29b) which is arranged along the axis of symmetry (29b) between the scintillator body (61b) and the first ring electrode (89b); wherein the potential supply system is configured to supply a sixth electrical potential (U6) to the second ring electrode (93b). [21] Electron beam microscope according to claim 20, where: |U6−U4|<2 kV; where U6 represents the sixth electrical potential. [22] Electron beam microscope according to claim 20 or 21, wherein the second ring electrode (93b) is supported on the beam tube. [23] Electron beam microscope according to one of claims 20 to 22, wherein a surface of the scintillator body (61a) of the first electron detector (41a) provides at least a part of a surface of the second ring electrode (93a). [24] Electron beam microscope according to one of claims 1 to 23, wherein the scintillator body (61) is arranged along the axis of symmetry (29) between an edge of the magnet coil (31) assigning the object plane (25) and the object plane (25). [25] Electron beam microscope according to any one of claims 1 to 24, further comprising: a second electron detector (43a) configured to detect electrons (47a) generated by the electron beam (9a) at the object; the second electron detector (43a) comprises: a scintillator arrangement with a scintillator body (49a) arranged along the axis of symmetry (29a) between an edge of the magnet coil directing the electron beam source and the object location such that the electrons (47a) generated at the object strike the scintillator body (49a), wherein the scintillator body (49a) is formed from a scintillator material which generates light with incident electrons, and a light detector (56) configured to detect light (55a) generated by the scintillator body (49a) and convert it into electrical signals; and wherein the light detector (56) of the second electron detector (43a) is arranged along the axis of symmetry (29a) between the electron source and the scintillator body (49a) of the second electron detector (43a). [26] Electron beam microscope according to claim 25, wherein the scintillator body (49a) of the second electron detector (43a) is held on the scintillator body (61a) of the first electron detector (41a). [27] Electron beam microscope according to any one of claims 1 to 26, furthermore comprehensive: a third electron detector (125) configured to detect electrons (129) generated by the electron beam at the object; wherein the third electron detector (125) comprises a semiconductor detector (123) configured to generate electrical signals by means of the electrons (129) generated at the object. [28] Electron beam microscope according to claim 27, wherein the semiconductor detector (123) of the third electron detector (125) and the light detector (63a) of the first electron detector (41a) are jointly mounted on a support. [29] Electron beam microscope according to claim 28, wherein the first pole end (35a) provides the common support. [30] Electron beam microscope according to one of claims 27 to 29, wherein the semiconductor detector (123) of the third electron detector (125) has an electron receiving surface (127) that assigns itself to the object plane; and wherein the light detector (63a) of the first electron detector (41) has a light entry surface (69a) pointing away from the object plane. [31] Electron beam microscope according to one of claims 1 to 30, wherein the scintillator body (61) of the first electron detector (41), seen in a cross-section containing the axis of symmetry (29), has a conical shape tapering towards the axis of symmetry (29). [32] Electron beam microscope, in particular in combination with the electron beam microscope according to any one of claims 1 to 31, comprising: an electron beam source configured to produce an electron beam; an object holder configured to hold an object at an object location where the electron beam strikes; and a first electron detector configured to detect electrons generated by the electron beam at the object; the first electron detector comprises: a scintillator arrangement with a scintillator body arranged such that the electrons generated at the object strike the scintillator body, the scintillator body being formed from a scintillator material which generates light upon contact with incident electrons, and a light detector configured to detect light generated by the scintillator body and convert it into electrical signals; and wherein the scintillator body of the first electron detector, seen in a cross-section along an axis along which the electron beam travels, has a conical shape tapering towards the axis.

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