Particle beam microscope

Abstract

A particle beam microscope 1 comprises a particle beam source 3, an objective lens 7, a first scintillator 51, a second scintillator 53, and a light detector 55, 57. A first beam path of light generated by the first scintillator 51 and a second beam path of light generated by the second scintillator 53 overlap each other. A scintillator body of the first scintillator 51 generates light 83 with a first spectral distribution, and the second scintillator 53 generates light with a second spectral distribution that is different from the first spectral distribution.

Description

[0001] The present invention relates to a particle beam microscope.

[0002] In particular, the invention relates to a particle beam microscope comprising a particle beam source, an objective lens, a scintillator, and a light detector. The particle beam source generates a particle beam by generating, accelerating, and forming charged particles, such as electrons or ions, into a particle beam. The objective lens focuses this particle beam into a small beam spot on the surface of an object. The particles of the particle beam striking the object interact with the object, with the type and extent of the interaction depending on the properties of the object at the point of impact of the particle beam. The scintillator and the light detector form a detection system for particles generated on the object as a result of the interaction. Based on the detection of these particles, it is possible to obtain information about the properties of the object, such as its structure and chemical composition.The detected particles include electrons, which are generated when the particles of the particle beam impact the object near its surface and then exit the object. These electrons exhibit widely varying directions and kinetic energies as they exit the object. The kinetic energies range from a few electron volts to the kinetic energy of the particles in the incident particle beam, which, depending on the application, can amount to several kiloelectron volts.

[0003] The electrons escaping from the object strike the scintillator, which is configured to generate light when an electron strikes or enters the scintillator. The intensity of the generated light increases with the intensity of the electrons striking the scintillator. A portion of the light generated by the scintillator is detected by the light detector and converted into electrical detection signals that can be read and analyzed by a controller of the particle beam microscope. The intensity of the detected light represents the intensity of the electrons generated by the particle beam on and escaping from the object and can provide valuable information about the properties of the object at the location of the particle beam impact.In addition to the intensity of the electrons generated on the object, their kinetic energy and the direction in which detected electrons exited the object are also of interest in order to obtain information about the object's properties. Conventionally, energy filters are used for this purpose, for example, which select the electrons generated on the object based on their kinetic energy before they are detected in order to be able to determine the intensity of the generated electrons as a function of their kinetic energy. Furthermore, particle beam microscopes are known which have several different detectors configured to selectively detect different types of electrons generated on the object. The different detectors differ from one another primarily in their spatial positioning within the particle beam microscope.

[0004] US 2020 / 0 312 609 A1 discloses a scintillator arrangement in which several layers of scintillators emitting light of different wavelengths are stacked. Electrons of different energies penetrate the stack to different depths and generate light of different wavelengths, the wavelength-dependent detection of which allows conclusions to be drawn about the energy of the detected electrons.

[0005] It is not easy to integrate several electron detectors at different spatial positions into a particle beam microscope because the space available for detectors and for the supply lines required for the operation of the detectors is limited.

[0006] Accordingly, it is an object of the present invention to propose a particle beam microscope with one or more detectors with which electrons can be selectively detected with regard to their kinetic energy and / or direction upon exiting the object.

[0007] This object is achieved by providing a particle beam microscope having the features of the appended independent claim 1 and a particle beam microscope having the features of the appended independent claim 8. Advantageous further developments are specified in the appended dependent claims.

[0008] The particle beam microscope comprises a particle beam source for generating a particle beam, an objective lens for focusing the particle beam in an object plane, at least one scintillator configured to generate light from electrons coming from the object, and at least one light detector configured to detect the light generated by the at least one scintillator.

[0009] In the scintillator, light is generated from the electrons by converting part of their kinetic energy into light in the scintillator material of a scintillator body of the scintillator, so that the kinetic energy of the electrons after the generation of light is lower and thus also their speed is lower than before.

[0010] The particle beam microscope comprises two scintillators, namely a first scintillator and a second scintillator, wherein the first scintillator comprises a scintillator body made of a first scintillator material, which generates light from electrons with a first spectral distribution, and wherein the second scintillator comprises a scintillator body made of a second scintillator material, which generates light from electrons with a second spectral distribution that is different from the first spectral distribution.

[0011] The scintillator bodies of the two scintillators can differ in their geometric arrangement relative to the object, so that electrons emitted by the object in different directions or with different kinetic energies strike the scintillator body of the first scintillator than the electrons emitted by the object of the second scintillator. Electrons emitted by the object in different directions or with different kinetic energies thus strike different scintillator bodies, which in turn generate light with different spectral distributions. The spectral distributions of the generated light can be used in subsequent detection with one or more light detectors to infer the directions or kinetic energies under which the detected electrons were emitted by the object by detecting the light generated by the different scintillators.Such directional information or information on kinetic energies can provide valuable clues about properties of the object, such as chemical composition and structure in the volume and on the surface of the object.

[0012] In this case, beam paths of the light generated by the scintillators can be arranged such that a beam path of the light generated by the first scintillator between the first scintillator and the at least one light detector and a beam path of the light generated by the second scintillator between the second scintillator and the at least one light detector partially overlap one another. This means that a construction space within the particle beam microscope which enables the transmission of light from the scintillators to the at least one light detector serves both for the transmission of the light generated by the first scintillator and for the transmission of the light generated by the second scintillator. Although the first and second beam paths geometrically overlap in this construction space, due to the different spectral distributions of the light generated by the first and second scintillators, it is not possible to achieve a uniform beam path between the first and second scintillators.Despite the light generated by the second scintillator, it is still possible to detect this light selectively with respect to wavelengths using the at least one light detector after it has passed through the installation space in which the two beam paths overlap, and thus to infer, for individual detected photons, the scintillator that most likely generated the detected light. In contrast to particle beam microscopes, in which the beam paths between several scintillators and the light detectors assigned to them are geometrically separated, the present detection of light generated by different scintillators allows for more efficient use of the available installation space and thus possibly improved integration of the detectors into the particle beam microscope.According to exemplary embodiments, the scintillator bodies of the two scintillators are arranged at a short distance from one another, measured along a main axis of the objective lens. The scintillator body of the first scintillator has at least one region that, viewed in the direction of the main axis, does not overlap with the scintillator body of the second scintillator, and the scintillator body of the second scintillator has at least one region that, viewed in the direction of the main axis, does not overlap with the scintillator body of the first scintillator, so that at least one region of the scintillator body of the first scintillator is arranged next to at least one region of the scintillator body of the second scintillator, viewed in the direction of the main axis.

[0013] A minimum distance, measured along the main axis of the objective lens, between the scintillator body of the first scintillator and the scintillator body of the second scintillator is less than 10 mm and in particular less than 5 mm. Furthermore, the scintillator body of the first scintillator has a surface area that, viewed in the direction of the main axis, does not overlap with the scintillator body of the second scintillator, so that electrons emitted by the object can strike both the scintillator body of the first scintillator and the scintillator body of the second scintillator.

[0014] According to exemplary embodiments, the two scintillator bodies of the first and second scintillators do not overlap with each other, as seen in the direction of the main axis, and the scintillator body of the first scintillator is arranged outside a beam path of the light generated by the second scintillator towards the at least one light detector, and the scintillator body of the second scintillator is arranged outside a beam path of the light generated by the first scintillator towards the at least one light detector.

[0015] According to another embodiment, a first part of the scintillator body of the first scintillator, viewed in the direction of the main axis, overlaps with the scintillator body of the second scintillator, and the first part of the scintillator body of the first scintillator is arranged within a beam path of the light generated by the second scintillator, between the second scintillator and the at least one light detector. The first part of the scintillator body of the first scintillator acts as a light guide for the light generated by the second scintillator. Electrons emitted by the object can strike a second part of the scintillator body of the first scintillator, which does not overlap with the scintillator body of the second scintillator, and generate light. This can enable simplified mounting of the two scintillator bodies, as they do not have to be mounted separately from one another on structures of the particle beam microscope.Rather, the scintillator body of the second scintillator may be mounted on the scintillator body of the first scintillator. According to exemplary embodiments herein, a surface of the scintillator body of the second scintillator is optically coupled to a surface of the scintillator body of the first scintillator.

[0016] According to further embodiments herein, the particle beam microscope comprises a light guide arranged in a beam path of the light generated by the first scintillator toward the at least one light detector and in a beam path of the light generated by the second scintillator toward the at least one light detector, wherein the surface of the first scintillator body is optically coupled to a surface of the light guide. Thus, the light generated in the second part of the scintillator body of the first scintillator can enter the light guide directly, while the light generated in the scintillator body of the second scintillator enters the second part of the scintillator body of the first scintillator, passes through it, and enters the light guide via it.

[0017] According to exemplary embodiments, the first scintillator body and / or the second scintillator body have the shape of a circular ring. The circular rings can, for example, be centered around the principal axis of the objective lens, so that the particle beam generated by the particle source passes through the hole in the circular ring to reach the object. The scintillator bodies of the two scintillators thus differ in terms of the distance from the principal axis at which the parts of the scintillator bodies that electrons impinge on are arranged. With such an arrangement, it is possible to discriminate between electrons based on the angle at which they exit the object with respect to the principal axis or based on their kinetic energy.

[0018] According to further embodiments, the scintillator bodies of the two scintillators have the shape of circular ring segments, so that their parts, which the detected electrons impinge on, are arranged at the same distance from the main axis but at different circumferential positions relative to the main axis. This makes it possible to discriminate electrons emerging from the object with respect to their emission direction in the circumferential direction around the main axis.

[0019] Alternatively, the particle beam microscope comprises a particle beam source for generating a particle beam, an objective lens for focusing the particle beam in an object plane, a scintillator, a wavelength shifter, and at least one light detector. The scintillator is configured to generate light from electrons coming from the object, wherein the scintillator comprises a scintillator body made of a scintillator material, in which light with a first spectral distribution can be generated from a portion of the kinetic energy of incoming electrons. The wavelength shifter is configured to convert the light generated by the first scintillator with the first spectral distribution into light with a second spectral distribution. The at least one light detector is configured to detect the light generated by the scintillator and the light generated by the wavelength shifter.

[0020] Here too, beam paths of the detected light can be arranged such that a beam path of the light generated by the scintillator between the scintillator and the at least one light detector and a beam path of the light converted by the wavelength shifter between the wavelength shifter and the at least one light detector partially overlap. This means that a space within the particle beam microscope that enables the transmission of light from the scintillator to the at least one light detector serves both for the transmission of the light generated by the scintillator and for the transmission of the light converted by the wavelength shifter. Although the beam paths in this space overlap geometrically, due to the different spectral distributions of the light generated by the scintillator and the light converted by the wavelength shifter,The light converted by the wavelength shifter still makes it possible to selectively detect this light with respect to wavelengths using at least one light detector after passing through the installation space in which the two beam paths overlap, thus determining for individual detected photons whether the detected light most likely originates directly from the scintillator or from the wavelength shifter. This design also allows for efficient use of the available installation space and thus potentially improved integration of electron detectors into the particle beam microscope.

[0021] According to exemplary embodiments herein, a first beam path exists between a first part of the scintillator body of the scintillator and the at least one light detector, wherein the wavelength shifter is arranged outside the first beam path and no further wavelength shifter is provided in the first beam path, so that the light generated in the first part of the scintillator body reaches the at least one light detector with the first spectral distribution.

[0022] According to exemplary embodiments, a surface of the wavelength shifter is optically coupled to a surface of a second part of the scintillator body that is different from the first part, so that the light generated in the second part of the scintillator body of the scintillator with the first spectral distribution can enter the wavelength shifter and is converted thereby into light with the second spectral distribution.

[0023] According to exemplary embodiments herein, the particle beam microscope further comprises a light guide arranged in a beam path of the light generated by the scintillator toward the at least one light detector and in a beam path of the light generated by the wavelength shifter toward the at least one light detector, wherein a surface of the wavelength shifter is optically coupled to a surface of the light guide. The wavelength shifter can also be mounted on the light guide, and the scintillator body of the scintillator can be mounted on the wavelength shifter.

[0024] As described above, the light having the first spectral distribution and the light having the second spectral distribution different from the first spectral distribution can be generated by a first scintillator and a second scintillator having scintillator bodies made of different scintillator materials or by a scintillator and a wavelength shifter.

[0025] According to exemplary embodiments, a center of gravity of the first spectral distribution lies at a first wavelength and a center of gravity of the second spectral distribution lies at a second wavelength, wherein an absolute value of a difference between the first wavelength and the second wavelength is greater than 50 nm. The center of gravity of the spectral distributions can be calculated in a conventional manner by integration over the appropriately normalized spectral distributions.

[0026] According to exemplary embodiments, the first wavelength is smaller than the second wavelength.

[0027] According to exemplary embodiments, an optical filter can be arranged in a beam path of the light with the first spectral distribution and the light with the second spectral distribution toward the at least one light detector, which optical filter allows the light with the first spectral distribution or the light with the second spectral distribution to pass through to the at least one light detector more effectively than the light with the other spectral distribution. The optical filter can be inserted into or removed from the beam path in order to selectively detect the light with the first spectral distribution and / or the second spectral distribution in temporal succession.

[0028] According to exemplary embodiments, the at least one light detector comprises a first light detector for detecting the light with the first spectral distribution and a second light detector for detecting the light with the second spectral distribution. In this case, a first optical filter is arranged in a beam path of the light with the first spectral distribution towards the first light detector, which filter allows the light with the first spectral distribution to pass through to the first light detector better than the light with the second spectral distribution, while a second optical filter is arranged in a beam path of the light with the second spectral distribution towards the second light detector, which filter allows the light with the second spectral distribution to pass through to the second light detector better than the light with the first spectral distribution.This makes it possible to selectively detect the light with the first spectral distribution and the light with the second spectral distribution simultaneously.

[0029] According to exemplary embodiments, the particle beam microscope comprises a dichroic beam splitter that provides the first optical filter and the second optical filter. For example, the light with the first spectral distribution is substantially reflected by the dichroic beam splitter, while the light with the second spectral distribution substantially passes through the dichroic beam splitter.

[0030] The scintillator body of the scintillator and / or the wavelength shifter can each have the shape of a circular ring and thus provide similar advantages for the particle microscope as the scintillator bodies of the previously described particle beam microscope with the first and second scintillator.

[0031] The scintillator body of the scintillator and the wavelength shifter can further have the shape of a circular ring segment and thus achieve the same advantages for the particle beam microscope as the scintillator bodies of the first and second scintillators of the particle beam microscope described above.

[0032] Embodiments of the invention are explained in more detail below with reference to figures. Fig. 1 shows a schematic representation of a particle beam microscope according to a first embodiment. Fig. 2 shows a schematic representation of a particle beam microscope according to a second embodiment. Fig. 3 is a schematic bottom view of a scintillator assembly used in the Fig. 1 or Fig. 2 shown particle beam microscope, according to a third embodiment. Fig. 4 is a schematic sectional view of the Fig. 3 shown scintillator arrangement. Fig. 5 is a view of the Fig. 4 corresponding schematic sectional view of another scintillator arrangement used in the particle beam microscope of Fig. 1 or the Fig. 2 can be used, according to a fourth embodiment. Fig. 6 is one of the Fig. 4 corresponding schematic sectional view of a scintillator arrangement used in the particle beam microscope of Fig. 1 or the Fig. 2 can be used, according to a fifth embodiment. Fig. 7 is one of the Fig. 5 corresponding schematic sectional view of a scintillator arrangement used in the particle beam microscope of Fig. 1 or the Fig. 2 can be used, according to a sixth embodiment. Fig. Figure 8 is a schematic view of a light detector arrangement used in the particle beam microscope of Fig. 1 or the Fig. 2 can be used, according to a seventh embodiment. Fig. 9 is a schematic view of a light detector arrangement used in the particle beam microscope of Fig. 1 or the Fig. 2 can be used, according to an eighth embodiment. Fig. 10 is a plan view of another scintillator assembly used in the Fig. 1 or Fig. 2, according to a ninth embodiment.

[0033] One in Fig. 1 schematically shown particle beam microscope 1 comprises a particle beam source 3 for generating a particle beam 5 and an objective lens 7 for focusing the particle beam 5 in an object plane 9. The particle beam microscope further comprises an object holder 11, which holds an object 13 to be examined such that its surface 15 is arranged in the object plane 9. The particle beam 5 striking the object 13 generates electrons at a location 17 where the particle beam 5 strikes the surface 15 of the object 13, which electrons emerge from the object 13 and are detected by the particle beam microscope 1, as described below.

[0034] The particle beam 5 generated by the particle beam source 3 is an electron beam, for which the particle beam source 3 has a cathode 19. A potential supply system 21, which is part of a controller 23 of the particle beam microscope 1, supplies an adjustable electrical potential to the cathode 19 via a connection 20. The object holder 11 is also supplied with an adjustable electrical potential by the potential supply system 21 via a connection 25. The electrical potential for the object holder 11 can, for example, be the ground potential. The difference between the potential of the object holder 11 and the potential of the cathode 19 determines the kinetic energy with which the electrons of the particle beam 5 impinge on the surface 15 of the object 13.

[0035] The particle beam source 3 further comprises an extractor 27, to which an electrical potential is supplied via a connection 28 from the potential supply system 21, which electrical potential is selected such that electrons are extracted from the cathode 19. The cathode 19 can also be Fig. 1. The electrons extracted from the cathode 19 pass through a hole in the extractor 27 and form the particle beam 5. The electrons are accelerated towards an anode 29, which is supplied with a corresponding anode potential via a connection 30 from the potential supply system 21. The anode 29 forms an upper end of a beam tube 31, near the particle beam source 3, through which the particle beam 5 passes. A lower end of the beam tube 31 is arranged near the object plane 9, so that the electrons of the particle beam 5, with the kinetic energy with which they enter the beam tube 31 accelerated through the anode 29, reach close to the object 13.Between the lower end of the beam tube 31, which is at the potential of the anode 29, and the object 13, which is at the potential of the object holder 11, the electrons are decelerated so that they hit the surface of the object 13 with the kinetic energy determined by the potential difference between the cathode 19 and the object holder 11.

[0036] Before impinging on the object 13, the particle beam 5 is focused by the objective lens 7. Additional particle-optical devices not shown in the figure, such as a condenser lens, an aperture stop, and a stigmator, can be provided between the particle beam source 13 and the objective lens 7 to influence and shape the particle beam 5 so that the spot illuminated by the particle beam 5 on the surface 15 of the object 13 is as small as possible. A finely focused particle beam 5 illuminating a small beam spot enables high spatial resolution of the particle beam microscope 1.

[0037] The objective lens 7 provides a magnetic field for focusing the particle beam 5. For this purpose, the objective lens 7 comprises a magnetic yoke 33, which is arranged rotationally symmetrically around a main axis 35 of the objective lens 7. In the example explained here, the main axis 35 of the objective lens 7 coincides with a main axis of the particle beam microscope 1, with respect to which other components, such as the particle beam source 19, are centered. The beam path of the particle beam 5 extends essentially along the main axis 35 and thus passes through the objective lens 7 along this main axis 35. The magnetic yoke 33 comprises an upper pole end 37 and a lower pole end 39 and surrounds a magnetic coil 41, to which an electrical excitation current is supplied by the controller 23.This current generates a magnetic field which essentially runs in the magnetic yoke 33 and exits the magnetic yoke 33 at the pole ends 37, 39 and acts on the particle beam 5 in such a way that it is focused.

[0038] The lower pole end 39 is arranged near the object plane 9 and has a central hole through which the particle beam 5 passes. The lower pole end 39 is also at an adjustable electrical potential, which is supplied to the magnetic yoke 33 via a connection 43 from the potential supply system 21. The potential of the lower pole end 39 can be the same as or different from the potential of the object holder 11. However, the electrons of the particle beam 5 are decelerated on their path between the lower end of the beam tube 31 and the surface 15 of the object 13, as described above. This deceleration is caused by an electric field, which is determined, among other things, by the potential difference between the beam tube 31 and the lower pole end 39 or the object holder 11.This electric retarding field also has a focusing effect on the particle beam 5, so that it is focused by the combined effects of the magnetic field and this electrostatic field.

[0039] In the area of the objective lens 7, Fig. 1, electrostatic or magnetic beam deflectors (not shown) are provided, which are excited by the controller 23 to deflect the particle beam 5 so that the point of impact 17 of the particle beam 5 on the surface 15 of the object 13 can be varied in a targeted manner. In particular, the controller 23 can scan or raster the point of impact 17 over a specific area of the surface 15 of the object 13 by controlling the beam deflectors, wherein the particles to be detected are created at the respective points of impact 17 due to the interaction of the particles of the particle beam 5 with the object 13 during the raster scanning. These particles to be detected include electrons that emerge from the object 13 with different kinetic energies. According to a conventional classification, a distinction is made between secondary electrons and backscattered electrons.The secondary electrons have kinetic energies of a few electron volts, for example up to 50 eV, upon exiting the surface 15 of the object 13, while the backscattered electrons typically have a much higher kinetic energy, which can be equal to the kinetic energy with which the electrons of the particle beam 5 impact the object 13. Both types of electrons should be able to be effectively detected with the particle beam microscope 1.

[0040] For this purpose, the particle beam microscope 1 comprises a first scintillator arrangement 51 and a second scintillator arrangement 53 as well as a first light detector arrangement 55 and a second light detector arrangement 57. The first and second scintillator arrangements 51, 53 and the first and second light detector arrangements 55, 57 are described below with reference to the Fig. 1 to 10 are described in more detail.

[0041] The first scintillator arrangement 51 may have a shape approximating a plate shape, with a main surface 45 facing the object plane 9 and a main surface 46 facing the particle beam source 3. It may have a circular outer circumference or an outer circumference of a different shape and a hole centered with respect to the main axis 35, through which the particle beam 5 passes. In the Fig. 1, the first scintillator arrangement 51, viewed along the beam path of the particle beam 5, is arranged between the end of the beam tube 31 near the object plane 9 and the object plane 9. In particular, the lower pole end 39 of the objective lens 7 is also arranged between the first scintillator arrangement 51 and the object plane 9. The first scintillator arrangement 51 has a connection 52, via which the first scintillator arrangement 51 and thus its surfaces 45 and 46 can be brought by the potential supply system 21 to an adjustable potential relative to the potentials of the beam tube 31, the object holder 11, and the lower pole end 39. In the embodiment shown in Fig. In the embodiment of the particle beam microscope 1 shown in Figure 1, a ring electrode 56 with an opening centered on the main axis 35 is provided between the first scintillator arrangement 51 and the object plane 9, as viewed along the beam path of the particle beam 5. The ring electrode 56 is also supplied with an adjustable electrical potential by the potential supply system 21 via a connection 58. The electrical potentials of the beam tube 31, the first scintillator arrangement 51, the ring electrode 56, the lower pole end 39, and the object holder 11 influence, on the one hand, the electrons of the particle beam 5 on their path toward the object 13, but also the secondary electrons and backscattered electrons that emerge from the object 13 at the point of impact 17 of the particle beam 5.In particular, these electric fields accelerate the secondary electrons emerging from the object 13, which initially have a relatively low kinetic energy, in such a way that they are guided away from the object 13 and accelerated to such an extent that their kinetic energy is sufficiently large to penetrate into scintillator materials of the first scintillator arrangement 51 and the second scintillator arrangement 53 and generate light there, which is detectable by the light detector arrangements 55 and 57.

[0042] If the electrical potential supplied to the object holder 11 via connection 25 is designated V1, the potential supplied to the first scintillator arrangement 51 via connection 52 is designated V2, and the electrical potential supplied to the beam tube 31 via connection 30 is designated V3, the electrical potentials V1, V2, and V3 can advantageously be selected such that they satisfy the following relationships: V2 > V1, V3 > V1, and V2 > V3. Furthermore, if the electrical potential supplied to the ring electrode 56 via connection 58 is designated V4, it can further advantageously be selected such that the relationships V4 > V1 and V4 > V2 are satisfied.

[0043] Electrons which emerge from the object 13 with comparatively low kinetic energy, i.e. primarily the so-called secondary electrons, are accelerated in the previously described electrostatic fields above the object 13 away from the object 13 towards the particle beam source 3, pass through the central opening in the first scintillator arrangement 51 and enter the beam tube 31 via the lower end. The reference numeral 61 represents such an electron as an example and in a simplified manner by its trajectory. In fact, the shape of the trajectory deviates from a straight line because the electrostatic and magnetic fields of the objective lens 7 also act on the electrons in directions transverse to the main axis 35. This electron 61 moves so far away from the main axis 35 that it strikes the second scintillator arrangement 53 and generates light therein.

[0044] The second scintillator arrangement 53 has a bore 63 centered on the main axis 35, through which the beam path of the particle beam 5 extends. Before entering the second scintillator arrangement 53, the electron 61 passes through a mirror layer 65, which is described below. At an interaction site 67 within the second scintillator arrangement 53, the electron 61 generates light. Such light is designated by the reference numeral 69 in the Fig. 1 is shown as an example by a trajectory.

[0045] This light 69 exits the second scintillator arrangement 53 at a main surface 71 opposite the mirror layer 65 and enters a light guide 73. A first surface region 70 of the light guide 73 is in surface contact with the second scintillator arrangement 53 at its main surface 71 or is at a small distance from it, so that the light guide 73 is optically coupled to the second scintillator arrangement 53 and a large proportion of the light generated in the second scintillator arrangement 53 passes into the light guide 73. The light guide 73 has a second surface region 75 and further surface regions 76 at which the light is internally reflected and can reach the second light detector arrangement 57 to be detected thereby.

[0046] The second light detector arrangement 57 generates electrical signals representing the detected light and outputs the detection signals via one or more terminals 77 to the controller 23 of the particle beam microscope 1.

[0047] The second surface region 75 of the light guide 73 lies opposite the first surface region 70 of the light guide 73 and has a surface normal 78, which has an angle α to the beam direction of the particle beam 5. The angle α can, for example, be in a range from 0° to 70°. In particular, the angle α can be less than 45°. The light guide 73 also has a bore 79, which is aligned with the bore 63 of the scintillator 53 and through which the beam path of the particle beam 5 extends.

[0048] The reference number 81 in Fig. 1 shows an example of an electron with higher kinetic energy emerging from the object 13, for example a so-called backscattered electron, represented by its trajectory. Due to its higher kinetic energy, the electron 81 can move further away from the main axis 35 of the particle beam microscope 1 than the electron of lower energy, designated by reference numeral 61, which moves with only a small velocity component transverse to the main axis 35 and therefore passes through the central hole in the first scintillator arrangement 51. The electron 81 moves further away from the main axis 35 than corresponds to the radius of the central hole in the first scintillator arrangement 51 and strikes the first scintillator arrangement 51, generating light therein.

[0049] At an interaction site within the first scintillator arrangement 51, the electron 81 generates light. An exemplary trajectory of a resulting light beam is shown in Fig. 1 with the reference numeral 83. The light beam 83 strikes an inner wall 85 of the beam tube 31 and is reflected twice by this inner wall 85 before striking the surface of the mirror 65, where it is reflected again toward a light guide 86, into which the light beam 83 penetrates and is guided toward the first light detector arrangement 55. The first light detector arrangement 55 detects the light beam 83 and converts it into an electrical signal, which is output to the controller 23 of the particle beam microscope 1 via one or more terminals 87 of the first light detector arrangement 55.

[0050] The two reflections of the light beam 83 on the inner wall 85 of the beam tube 31 are exemplary. The number of reflections can be greater than two, and the light generated by the first scintillator arrangement 51 can also strike the mirror 65 directly or reach the mirror 65 after only one reflection on the inner wall 85 of the beam tube 31. To improve the reflection properties of the inner wall 85 of the beam tube 31, the inner wall is machined to be a mirror surface. This machining can include polishing the inner wall 85. In particular, the machining can be carried out such that an average surface roughness Ra of the inner wall is less than 0.4 µm.

[0051] As from the Fig. 1, the inner wall 85 of the beam tube 31 is formed as a surface with a conical shape in the region viewed along the beam path of the particle beam 5 between the second scintillator arrangement 53 or the mirror 65 and the first scintillator arrangement 51. In particular, the beam tube 31 has, at its end near the object plane 9 or the first scintillator arrangement 51, a cross-sectional area measured perpendicular to the main axis 35 that is more than twice smaller than the cross-sectional area of the beam tube in a cross-sectional plane 91 near the second scintillator arrangement 53. In particular, the cross-sectional area of the beam tube 31 increases continuously from its end near the object plane 9 toward the plane 91.

[0052] The conical design of the inner wall 85 of the beam tube 31 results in light rays emerging from the first scintillator arrangement 51 in a direction transverse to the main axis 35 being aligned more strongly in the direction of the main axis 35 with each reflection from the conical inner wall 85 and then, after reflection from the surface of the mirror 65, striking a surface 93 of the light guide 86 almost perpendicularly. The light striking the surface 93 of the light guide 86 almost perpendicularly is reflected to a lesser extent by the surface 93 than light striking it at a greater angle to the perpendicular to the surface 93. The conical shape of the inner wall 85 of the beam tube 31 thus increases the proportion of the light generated by the first scintillator arrangement 51 that penetrates the light guide 86, so that the probability of detecting electrons with the first scintillator arrangement 51 is also increased.

[0053] The surface of the mirror 65 is oriented relative to the main axis 35 such that a surface normal of the mirror 65 forms an angle β with the main axis 35, which in the example of the Fig. 1 is 40°. In general, the angle β can be in a range between 25° and 65° or 30° and 60°. In the Fig. In the example shown in Figure 1, a surface normal to the surface 93 of the light guide 86 is oriented at an angle of 90° to the main axis 35.

[0054] In the In Fig. In the example shown in Figure 1, the first surface region 70 of the light guide 73 is parallel to the surface of the mirror 65, so that the first surface region 70 of the light guide 73 is also oriented at an angle β to the main axis 35. Furthermore, the first surface region 70 is not far from the second surface region 75 of the light guide 73, so that the two surface regions 70 and 75 delimit a part of the light guide 73 that has a wedge-shaped configuration. A minimum distance between the first surface region 70 and the second surface region 75 is, for example, less than 5 mm or less than 3 mm. An aperture angle γ can be defined as an angle between a surface normal of the first surface region 70 and the surface normal of the second surface region 75. The aperture angle γ lies, for example, in a range between 15° and 55° and in particular in a range between 20° and 50°.

[0055] In the particle beam microscope 1, primarily secondary electrons pass through the central opening of the first scintillator arrangement 51 to the second scintillator arrangement 53, generating light therein, which is ultimately detected by the light detector arrangement 57. Essentially, backscattered electrons pass to the first scintillator arrangement 51, generating light therein. After one or more reflections on the inner wall 85 of the beam tube 31, the light detector arrangement 55 is reflected via the mirror 65 to the light detector arrangement 55, where it is detected. The first scintillator arrangement 51 is arranged relatively close to the object plane 9, so that backscattered electrons, which emerge from the surface 15 of the object 13 at the location 17 at a relatively large solid angle, strike the first scintillator arrangement 51.Thus, the particle beam microscope 1 has a comparatively high detection probability for backscattered electrons emerging from the object 13.

[0056] A further embodiment is described below with reference to Fig. 2. Here, components, the components of the based on the Fig. 1 in terms of their structure and / or function, are designated by the same reference numeral, but are provided with an additional letter for differentiation. To understand the individual components, the description of which is not repeated or only partially repeated, reference should be made to the description of the preceding embodiments and the introduction to the description.

[0057] One in Fig. The particle beam microscope 1a shown in Figure 2 has a similar structure to the one shown in Figure 1. Fig. The particle beam microscope illustrated in Figure 1 comprises a particle beam source 3a and an objective lens 7a for focusing a particle beam 5a generated by the particle beam source 3a into an object plane 9a. The particle beam source 3a also comprises a cathode 19a and an extractor 27a. The particle beam 5a also passes through a beam tube 31a, the lower end of which is arranged within the objective lens 7a. The objective lens 7a generates a magnetic field focusing the particle beam 5a with a coil 41a partially enclosed by a magnetic yoke 33a with an upper pole end 37a and a lower pole end 39a.

[0058] A first scintillator arrangement 51a is arranged between the lower end of the beam tube 31a and the object plane 9a. A ring electrode 56a can also be arranged between the first scintillator arrangement 51a and the object plane 9a. In addition to the first scintillator arrangement 51a, which is arranged close to the object plane 9a, the particle beam microscope 1a comprises a second scintillator arrangement 53a, which is arranged at a greater distance from the object plane 9a. The first scintillator arrangement 51a serves to generate light primarily from backscattered electrons 81a, while the second scintillator arrangement 53a serves primarily to generate light from secondary electrons that have passed through a central opening of the first scintillator arrangement 51a.

[0059] The Fig. The embodiment shown in Figure 2 differs from that of Fig. 1 essentially in that a common light detector arrangement 101 is provided for the detection of the light generated by the first scintillator arrangement 51a and for the detection of the light generated by the second scintillator arrangement 53a.

[0060] An electron emanating from an impact point 17a of the particle beam 5a on the surface of an object 13a and which is in Fig. 2 is shown exemplarily and simplified by a trajectory 61a, penetrates the second scintillator arrangement 53a and generates light at an interaction site 67a. An exemplary light beam generated from the electron 61a is shown in Fig. 2 with the reference numeral 69a. This light beam exits the second scintillator arrangement 53a at the surface 71a facing away from the object plane 9a and enters a light guide 103 that is optically coupled to the second scintillator arrangement 53a. The light beam 69a is reflected one or more times by internal surfaces of the light guide 103 before reaching the light detector arrangement 101, which detects the light and outputs a detection signal corresponding to the light via one or more connections 107 to a controller 23a of the particle beam microscope 1a.

[0061] In addition to the secondary electrons 61a striking the second scintillator arrangement 53a, light rays 83a, which are generated by electrons in the first scintillator arrangement 51a, also pass through the space within the beam tube 31a and between the first scintillator arrangement 51a and the second scintillator arrangement 53a. These light rays 83a are optionally reflected one or more times on an inner wall 85a of the beam tube 31a before they strike the second scintillator arrangement 53a. However, the second scintillator arrangement 53a, unlike the second scintillator arrangement 53 in the embodiment of the Fig. 1, no mirror surface, so that the light 83a generated by the first scintillator arrangement 51a can pass through the second scintillator arrangement 53a and enter the light guide 103. The light guide 103 has a surface region 104 opposite the second scintillator arrangement 53a, as well as further surface regions 105. In the light guide 103, this light 83a is reflected one or more times by the surface regions 104, 105 of the light guide, to then be detected by the light detector arrangement 101.

[0062] A main surface 54 of the second scintillator arrangement 53a is oriented orthogonally to the direction of a main axis 35a of the objective lens 7a. Thus, an angle β between a surface normal on the surface 54 and the direction of the main axis 35a in the example of Fig. 2 0°, while the corresponding angle β in the embodiment of the Fig. 1 was 40°. Other possibilities for selecting the angle β in the design of the Fig. 2 are such that the angle β is greater than 0° but less than 20°, and in particular less than 10°. The light guide 103 also has a bore 79a, which is aligned with a bore 63a in the second scintillator arrangement 53a to allow the beam path of the particle beam 5a to pass through the light guide 103 and the second scintillator arrangement 53a.

[0063] The surface region 104 of the light guide 103 also functions as a mirror surface for the light 83a generated by the first scintillator arrangement 51a, which has passed through the second scintillator arrangement 53a to reflect it towards the light detector arrangement 101. The surface region 104 has a surface normal 78a, which has an angle α to the beam direction of the particle beam 5a. The angle α can, for example, be in a range between 15° and 55° and in particular in a range between 20° and 50° and in particular be less than 45°. As in the Fig. 1 also forms the embodiment of the Fig. 2, the light guide 103 forms a wedge whose opening angle γ can be defined as the angle between the surface normal 78a of the surface region 104 of the light guide 103 and the surface normal of the surface region of the light guide 103 coupled to the second scintillator 53a. The opening angle γ lies, for example, in a range between 15° and 55° and in particular in a range between 20° and 50°.

[0064] In the light guide 103, the beam path of the light generated by the first scintillator arrangement 51a toward the light detector arrangement 101 and the beam path of the light generated by the second scintillator arrangement 53a toward the light detector arrangement 101 overlap. In a simplified embodiment, the light detector arrangement 101 can detect the light generated by the scintillator arrangement 51a and the light generated by the scintillator arrangement 53a without discriminating between the two types of light. Advantageously, however, the first light detector arrangement 101 is designed such that the detection can discriminate between the light generated by the scintillator arrangement 51a and the light generated by the scintillator arrangement 53a. This is possible, for example, if the spectral distributions of the light generated by the scintillator arrangement 51a and the light generated by the scintillator arrangement 53a differ from each other.This can be achieved, for example, by using scintillator bodies made of different scintillator materials in the scintillator assembly 51a and the scintillator assembly 53a, which generate light with different spectral distributions from electrons. Examples of light detector assemblies suitable in this regard as the light detector assembly 101 are explained below.

[0065] In addition to the scintillator arrangements 51a and 53a, the particle beam microscope 1a also comprises a further detection system for electrons emerging from the object 13a. This detection system comprises an electron detector 111 and a first grid 113 and a second grid 115, which are arranged in the beam path of the electrons emitted by the object 13a between the object plane 9a and the detector 111. Electrons that have passed through the opening in the first scintillator arrangement 51a and the holes 63a and 79a in the second scintillator arrangement 53a and the light guide 103, respectively, can strike the electron detector 111 to be detected by it. The grids 115 and 113 are set to adjustable potentials by a potential supply system 21a. These potentials can be varied to select the energy of the electrons reaching the detector 111.A potential difference between the object and the grid 113 is used to set a minimum kinetic energy of the electrons that can be detected by the detector 111. By changing the potential at the grid 113, the kinetic energy of the electrons that reach the grid 113 and pass through it to be subsequently detected by the detector 111 can be selected.

[0066] Embodiments of scintillator arrangements are described below, which can be used as the first and / or the second scintillator arrangement of the Fig. 1 and Fig. 2 described particle beam microscopes. In addition, the scintillator arrangements described can also be used in other particle beam microscopes that have a different structure and provide different functions than those described in the Fig. 1 and Fig. 2 explained particle beam microscopes.

[0067] Fig. 3 is a schematic representation of a bottom view of a scintillator arrangement 201, which is particularly used as the first scintillator arrangement 51 in the particle beam microscope of Fig. 1 and as the first scintillator arrangement 51a in the particle beam microscope of Fig. 2 can be used. It is a view from below of the main surface 45 of the first scintillator arrangement 51 of the Fig. 1. Fig. 4 is a schematic sectional view of the Fig. 3 shown scintillator arrangement 201 along a line IV-IV in Fig. 3.

[0068] The scintillator assembly 201 comprises two scintillators configured to generate light from electrons coming from the object. The first scintillator has a scintillator body 203, and the second scintillator has a scintillator body 205. The two scintillator bodies 203, 205 each have, in the bottom view of the Fig. 3 the shape of a circular ring, which can be centered with respect to the main axis 35 of the objective lens 7, and in the sectional view of the Fig. 4 the shape of a flat plate. The two scintillator bodies 203, 205 are arranged at a small distance from each other, for example less than 5 mm apart. In the Fig. 3 and Fig. 4, the scintillator bodies 203, 205 lie against one another with their surfaces. The scintillator body 203 has a first region 207 which, viewed in the direction of the main axis 35, overlaps with the scintillator body 205. The scintillator body 203 further has a second region 209 which, viewed in the direction of the main axis 35, does not overlap with the scintillator body 205. Accordingly, the two scintillator bodies 203 and 205 are arranged with a small distance or without a distance from one another, measured in the direction of the main axis 35, but each of the scintillator bodies has at least one region which, viewed in the direction of the main axis 35 or in the bottom view of the Fig. 3, is arranged adjacent to at least one region of the other scintillator body.

[0069] The scintillator bodies 203, 205 are made of different scintillator materials, so that the scintillator body 205 generates light with a spectral distribution that differs from a spectral distribution of the light generated by the scintillator body 203. The spectral distributions of the light generated by the scintillator bodies 203, 205 each have a center of gravity at a specific wavelength, wherein the wavelengths of the centers of gravity differ by, for example, more than 50 nm. Examples of suitable scintillator material for the scintillator bodies 203 and 205 are single-crystal YAP scintillator material or powdered P47 scintillator material.

[0070] For example, the scintillator body 203 may be formed from single-crystal YAP scintillator material, while the scintillator body 205 is applied as a powder layer of P47 scintillator material to the underside of the scintillator body 203 in its first region 207.

[0071] A line 213 in Fig. Figure 4 shows a trajectory of an electron coming from the object, which strikes and penetrates the second region 209 of the scintillator body 203. At an interaction location 214 in the scintillator body 203, light is generated from the electron, which leaves the scintillator body and for which an exemplary trajectory in Fig. 4 is represented by an arrow 215.

[0072] A line 217 in Fig. 4 shows a trajectory of an electron coming from the object, which hits the scintillator body 205 and penetrates it. At an interaction site 218 in the scintillator body 205, light is generated from the electron, for which an exemplary trajectory is indicated by an arrow 219 in Fig. 4. The light exits the scintillator body 205 and enters the scintillator body 203, which is optically coupled to the scintillator body 205. This acts as a light guide for the light 219, so that the light 219 passes through the scintillator body 203 and into Fig. 4 exits upwards from this.

[0073] To prevent light emission by the scintillator body 203 due to absorption of light 219, the wavelength of the center of gravity of the spectral distribution of the light generated in the scintillator body 205 can be longer than the wavelength of the center of gravity of the spectral distribution of the light generated in the scintillator body 203. In addition, an optical filter between the scintillator bodies 205 and 203 in the beam path of the light 219 can clip the spectral distribution emitted by the scintillator body 205 in a spectral range in which it overlaps with the spectral distribution emitted by the scintillator body 203.

[0074] The scintillator arrangement 201 thus generates light with two different spectral distributions from the electrons coming from the object, depending on which of the two scintillator bodies 203, 205 the respective electron coming from the object strikes. The areas of the scintillator bodies 203 and 205, which the electrons coming from the object can strike, are arranged at geometrically different positions relative to the object. The positions of the two scintillator bodies differ little in the direction of the main axis 35 of the objective lens 7, while they differ significantly in the direction perpendicular to it. The light 215, 219 generated by the two scintillators can subsequently be detected with a suitable light detector.On the way to the light detector, the beam paths of the light 215 generated by the scintillator body 203 and the light 219 generated by the scintillator body 205 overlap with each other. The beam paths of the two types of light overlap in the sense that, for example, there are locations along the two beam paths that are traversed by both light beams of the light generated by the scintillator body 203 and light beams of the light generated by the scintillator body 205. The light detector can be configured to detect selectively with respect to the wavelength of the light 215, 219, so that the detection signal of the light detector contains information regarding the impact location of the electron 213, 217 generating the light 215, 219.

[0075] The scintillator assembly 201 can be used in any suitable particle beam microscope. For example, the scintillator assembly 201 can be used as the first scintillator assembly 51 in the particle beam microscope 1 of Fig. 1. For this purpose, the two scintillator bodies 203 and 205 can be attached, for example, to the lower end of the beam tube 31, to the upper pole end 37 of the magnetic yoke 33, to the lower pole end 39 of the magnetic yoke 33, to the ring electrode 56, or to another component of the particle beam microscope 1. The light beams generated by the scintillator bodies 203 and 205 can, as shown by the exemplary light beam 83 in Fig. 1, reach the first light detector arrangement 55 to be detected thereby. Between the scintillator arrangement 51 and the first light detector arrangement 55, the beam path of the light generated by the scintillator body 203 and the beam path of the light generated by the scintillator body 205 overlap. The first light detector arrangement 55 can detect the light generated by the scintillator body 203 and the light generated by the scintillator body 205 without discriminating between the two types of light. Advantageously, the first light detector arrangement 55 is designed such that the detection can discriminate between the light generated by the scintillator body 203 and the light generated by the scintillator body 205. This is possible because the spectral distributions of the light generated by the scintillator body 203 and the light generated by the scintillator body 205 differ from each other.Examples of light detector arrangements suitable in this respect as the first light detector arrangement 55 are explained below.

[0076] The scintillator arrangement 201 can, for example, also be used as the second scintillator arrangement 53 in the particle beam microscope 1 of the Fig. 1. This is possible both for the particle beam microscope 1 with the first scintillator arrangement 51 and for embodiments without the first scintillator arrangement 51. For this purpose, the two scintillator bodies 203 and 205 can be attached, for example, to the light guide 73, and the mirror layer 65 can have the shape shown in the bottom view of the Fig. 3 cover the visible surfaces of the scintillator bodies 203 and 205. The light beams generated by the scintillator bodies 203 and 205 can then, as shown by the exemplary light beam 69 in Fig. 1, reach the second light detector arrangement 57 to be detected thereby. Between the second scintillator arrangement 53 and the second light detector arrangement 57, the beam path of the light generated by the scintillator body 203 and the beam path of the light generated by the scintillator body 205 overlap in the light guide 73. The second light detector arrangement 57 can also detect the light generated by the scintillator body 203 and the light generated by the scintillator body 205 without discriminating between the two types of light. Advantageously, the second light detector arrangement 57 is designed such that the detection can discriminate between the light generated by the scintillator body 203 and the light generated by the scintillator body 205.

[0077] In the example shown here, the scintillator bodies 203 and 205 of the two scintillators each have the shape of a circular ring. However, it is also possible for one, the other, or both scintillators to each have multiple scintillator bodies. For example, a scintillator can comprise multiple scintillator bodies arranged distributed around the main axis. Furthermore, the scintillators can comprise, for example, electrically conductive layers provided on surfaces of the scintillator bodies in order to prevent local electrostatic charges on the surfaces of the scintillator bodies. The electrically conductive layers can be light-reflecting, for example by consisting of a thin metal layer, or they can be light-transmitting, for example by being made of indium tin oxide.

[0078] Fig. 5 is one of the Fig. 4 shows a cross-sectional view of a scintillator arrangement 201b according to a further embodiment, corresponding to the viewing direction. The scintillator arrangement 201b has a scintillator body 223 with a circular ring shape and a wavelength shifter 225, also with a circular ring shape. The scintillator body 223 has a first region 227 which, viewed in the direction of the main axis 35, does not overlap with the wavelength shifter 225, and a second region 229 which, viewed in the direction of the main axis 35, overlaps with the wavelength shifter 225. The wavelength shifter 225 is optically coupled to the scintillator body 223 and is arranged at a slight distance from it or is directly adjacent to it.

[0079] For example, one of the previously described scintillator materials can be used as the scintillator material for the scintillator body 223. The scintillator body 223 generates light with a first spectral distribution from electrons. The wavelength shifter 225 converts light with the first spectral distribution into light with a second spectral distribution by absorbing the light with the first spectral distribution and re-emitting it with the second spectral distribution. A wavelength of the center of gravity of the second spectral distribution is greater than the wavelength of the center of gravity of the first spectral distribution. Examples of suitable scintillator materials for forming the wavelength shifter are: - POPOP (1,4-bis-[2-(5-phenyloxazolyl)]-benzene; C 24 H 16 N2O2) - Bis-MSB (1,4-bis(2-methylstyryl)benzene; C 24 H 22 ) - BBQ (Benzimidazo-Benzisoquinolin-7-one)

[0080] A line 213b in Fig. 5 shows a trajectory of an electron coming from the object, which strikes the first region 227 of the scintillator body 223 and penetrates into it. At an interaction location 214b in the scintillator body 223, light with the first spectral distribution is generated from the electron, which leaves the scintillator body 223 and for which an exemplary trajectory in Fig. 5 is represented by an arrow 215b.

[0081] A line 217b in Fig. 5 shows a trajectory of an electron coming from the object, which strikes the second region 229 of the scintillator body 223 and penetrates into it. At an interaction location 218b in the scintillator body 223, light with the first spectral distribution is generated from the electron, for which an exemplary trajectory is shown in Fig. 5 is represented by a line 221. The light 221 with the first spectral distribution leaves the scintillator 223 and enters the wavelength shifter 225 optically coupled to the scintillator 223. At an interaction location 222 in the wavelength shifter 225, the light with the first spectral distribution is converted into light with the second spectral distribution, which leaves the wavelength shifter 225 and for which an exemplary trajectory in Fig. 5 is represented by an arrow 219b.

[0082] The scintillator arrangement 201b can be used in any suitable particle beam microscope. For example, the scintillator arrangement 201b can be used as the first scintillator arrangement 51 in the particle beam microscope 1 of Fig. 1. For this purpose, the scintillator body 223 and the wavelength shifter 225 can be attached, for example, to the lower end of the beam tube 31, to the upper pole end 37 of the magnetic yoke 33, to the lower pole end 39 of the magnetic yoke 33, to the ring electrode 56, or to another component of the particle beam microscope 1. The light beams generated by the scintillator body 223 and the wavelength shifter 225 can, as shown by the exemplary light beam 83 in Fig. 1, reach the first light detector arrangement 55 to be detected thereby. Between the scintillator arrangement 51 and the first light detector arrangement 55, the beam path of the light generated by the scintillator body 223 and the beam path of the light generated by the wavelength shifter 225 overlap. The first light detector arrangement 55 can detect the light generated by the scintillator body 223 and the light generated by the wavelength shifter 225 without discriminating between the two types of light. Advantageously, the first light detector arrangement 55 is designed such that the detection can discriminate between the light generated by the scintillator body 223 and the light generated by the wavelength shifter 225. This is possible because the spectral distributions of the light generated by the scintillator body 223 and the light generated by the wavelength shifter 225 differ from each other.

[0083] Fig. Figure 6 is a schematic sectional view of an arrangement consisting of a light guide 233 and one of the Fig. 4 corresponding scintillator arrangement 201c, which in particular serves as the second scintillator arrangement 53 in the particle beam microscope of Fig. 1 and as the second scintillator arrangement 53a in the particle beam microscope of Fig. 2 can be used.

[0084] The scintillator arrangement 201c in turn comprises a first and a second scintillator with a first scintillator body 203c and a second scintillator body 205c. The two scintillator bodies 203c, 205c have a configuration that corresponds to that of the scintillator bodies 203, 205 of the embodiment of the Fig. 4. In contrast to the embodiment of the Fig. 4 is the scintillator body 203c of the Fig. 6 is optically coupled over a short distance to a surface 231 of the light guide 233. The light guide 233 can, for example, be the light guide 103 of the Fig. 2 or the light guide 73 of the Fig. 1.

[0085] Fig. 6 shows the Fig. 4 corresponding exemplary trajectories of electrons and generated light, namely an electron 213c coming from the object, which generates light 215c at an interaction location 214c, which exits from the scintillator body 203c and enters the light guide 233 optically coupled to the scintillator body 203c, at the inner walls of which the light is reflected one or more times to reach a light detector arrangement, which in Fig. 6 is not shown and will be discussed below in connection with the Fig. 8 and Fig. 9. Furthermore, light 219c is generated from an electron 217c coming from the object at an interaction site 218c in the scintillator body 205c. This light 219c exits the scintillator body 205c, enters the scintillator body 203c, passes through it, and enters the light guide 233. After being reflected one or more times by the inner walls of the light guide, the light 219c can then be detected by the light detector arrangement.

[0086] When using the scintillator assembly 201c of Fig. 6 as the second scintillator arrangement 53a in the particle beam microscope 1a of Fig. 2, the following condition should be met: The spectral distribution of the light passing from the first scintillator arrangement 51a to the scintillator arrangement 201c should be substantially longer-wavelength than the spectral distribution of light emitted by elements of the second scintillator arrangement 201c. The elements of the second scintillator arrangement 201c are the scintillator bodies 203c and 205c. By meeting this condition, it is essentially avoided that light generated by electrons in the first scintillator arrangement 51a is converted in its spectral distribution by elements of the second scintillator arrangement 201c in such a way that it appears as if it had been generated by electrons in the second scintillator arrangement 201c. There are various ways to achieve this.Either the spectral distribution of the light emitted by the first scintillator arrangement 51a can be substantially longer-wave than the spectral distributions of the light emitted by the elements of the second scintillator arrangement 201c, and / or a wavelength shifter and / or a filter above the first scintillator 51a can ensure that the condition is met. Corresponding designs may also apply to other embodiments that comprise detector arrangements corresponding to the particle beam microscope of FIG. Fig. 2 include: The spectral distributions passing from the first scintillator arrangement 51a to the second scintillator arrangement 53a are preferably substantially longer wavelength than the spectral distributions of the light emitted by the second scintillator arrangement 53a.

[0087] Fig. Figure 7 is a schematic sectional view of an arrangement of a light guide 233d and a substantially Fig. 5 corresponding scintillator arrangement 201d, which in particular serves as the second scintillator arrangement 53 in the particle beam microscope of Fig. 1 and as the second scintillator arrangement 53a in the particle beam microscope of Fig. 2 can be used.

[0088] The scintillator assembly 201d in turn comprises a scintillator with a scintillator body 223d and a wavelength shifter 225d. The scintillator body 223d and the wavelength shifter 225d have a configuration substantially similar to that of the scintillator body 223 and the wavelength shifter 225 in the embodiment of the Fig. 5. In contrast to the embodiment of the Fig. 5 is the wavelength shifter 225d of the Fig. 7 is optically coupled over a short distance to a surface 231d of the light guide 233d. The light guide 233d can in turn be, for example, the light guide 73 of the Fig. 1.

[0089] The scintillator arrangement 201d further comprises an annular spacer 241, which is inserted next to the wavelength shifter 225d between the scintillator body 223d and the light guide 233d. In other embodiments, the spacer 241 can also be replaced, for example, by a vacuum or omitted by the scintillator body 223d being in direct contact with the surface 231d of the light guide 233d in this area. The elements of the scintillator arrangement 201d are accordingly the scintillator body 223d, the wavelength shifter 225d, and, if present, the spacer 241.

[0090] In other exemplary embodiments, the position of wavelength shifter 225d and spacer 241 is reversed, wherein wavelength shifter 225d may be configured as a narrow ring having an area of one-fifth or less compared to the area of spacer 241.

[0091] Fig. 7 shows the Fig. 5 corresponding exemplary trajectories of electrons and generated light, namely that of an electron 213d coming from the object, which generates light 215d with the first spectral distribution at an interaction location 214d, which exits the scintillator body 223d, passes through the spacer 241, and enters the light guide 233d to be guided to a light detector arrangement. Furthermore, light 221d with the first spectral distribution is generated from an electron 217d coming from the object at an interaction location 218d in the scintillator body 223d, which exits the scintillator body 223d and enters the wavelength shifter 225d. At an interaction site 222d in the wavelength shifter 225d, the light with the first spectral distribution is converted into light 219d with the second spectral distribution, which leaves the wavelength shifter 225d and enters the light guide 233d.The spacer 241 can be configured as an optical filter that cuts the light with the first spectral distribution in a spectral range where the first and second spectral distributions overlap. This allows for better signal separation.

[0092] Fig. Fig. 8 shows a schematic view of a light detector arrangement 251, which may be used, for example, as the first light detector arrangement 55 or the second light detector arrangement 57 in the particle beam microscope of Fig. 1 or the light detector arrangement 101 in the particle beam microscope of Fig. 2 can be used. The light detector arrangement 251 comprises a first light detector 253 for detecting light 215e with the first spectral distribution and a second light detector 255 for detecting light 219e with the second spectral distribution. For this purpose, the light detector arrangement 251 comprises a first light guide 257, which is optically coupled to a part of an end 259 of the light guide 233e and feeds light exiting through this part of the end 259 of the light guide 233e to the first light detector 253. In the beam path between the light guide 257 and the first light detector 253, a first optical filter 261 is provided, which allows light with the first spectral distribution to pass through to the first light detector 253 better than light with the second spectral distribution.

[0093] The light detector arrangement 251 further comprises a second light guide 263, which is coupled to another part of the end 259 of the light guide 233e and guides light exiting through this other part of the end 259 of the light guide 233e to the second light detector 255. A second optical filter 265 is arranged in the beam path between the light guide 263 and the second light detector 255, which allows light with the second spectral distribution to pass through to the second light detector 255 more effectively than light with the first spectral distribution. Due to the arrangement of the optical filters 261 and 265 in the beam path toward the first light detector 253 and the second light detector 255, respectively, it is possible to selectively detect the two types of light with the first and second spectral distributions with the two light detectors 253, 255.

[0094] The cutoff frequencies of the optical filters 261 and 265 are tuned to the spectral distributions of the light emitted by the scintillator bodies and, if applicable, also by the wavelength shifter of the scintillator arrays with which the light detector array is used. If another optical filter is included in the light-optical beam path, this is also tuned to the cutoff frequencies of the optical filters 261 and 265.

[0095] The Fig. 9 is a schematic view of a light detector arrangement according to another embodiment similar to Fig. 8. The light detector arrangement 251f also comprises a first light detector 253f for detecting light 215f with the first spectral distribution and a second light detector 255f for detecting light 219f with the second spectral distribution. In the beam path to the two light detectors 253f and 255f, a dichroic beam splitter 271 is provided in the light guide 233f, which reflects the light 215f with the first spectral distribution toward the first light detector 253f, while allowing the light 219f with the second spectral distribution to pass through to the second light detector 255f. The dichroic beam splitter 271 thus fulfills, to a certain extent, the functions of the first optical filter 261 and the second optical filter 265 of the light detector arrangement 251 of the Fig. 8. To further improve the discrimination of the signals, the optical filter 261 of the Fig. 8 can be arranged in the beam path between the dichroic beam splitter 271 and the light detector 253f, or / and the optical filter 265 of the Fig. 8 in the beam path between the dichroic beam splitter 271 and the light detector 255f.

[0096] Fig. 10 is like Fig. 3 a bottom view of a scintillator arrangement 201g, which can also be used as a scintillator arrangement, in particular as the first scintillator arrangement 51 or the second scintillator arrangement 53 in the particle beam microscope 1 of Fig. 1 or as the first scintillator arrangement 51a or the second scintillator arrangement 53a in the particle beam microscope 1a of Fig. 2. The scintillator arrangement 201g comprises a first scintillator with a first scintillator body 203g, which in the bottom view of the Fig. 10 has the shape of a circular ring, similar to the scintillator body 203 of the Fig. 4 or the scintillator body 203c of the Fig. 6. The scintillator arrangement 201g further comprises a second scintillator with a second scintillator body 205g, which forms a part of the scintillator body 203g in the bottom view of the Fig. 10 covered.

[0097] In contrast to the embodiments of the Fig. 4 and Fig. 6, the second scintillator body 205g does not have the shape of a circular ring, but rather the shape of a circular ring segment that covers the right half of the circular ring-shaped first scintillator body 203g. With regard to the generation of light with a first spectral distribution and a second spectral distribution from electrons coming from the object, the scintillator arrangement 201g corresponds to the scintillator arrangements of Fig. 4 and Fig. 6. Due to the fact that, compared to the scintillator arrangements of the Fig. 4 and Fig. 6 Due to the different geometry of the second scintillator body 205g, the scintillator arrangement 201g can discriminate electrons with respect to their emission direction in the circumferential direction around the main axis 35 of the objective lens 7. In particular, the scintillator arrangement 201g can image the object simultaneously from two different viewing directions.

[0098] It is possible to use the scintillator arrangement 201g with a view to implementing a scintillator arrangement with a wavelength shifter according to the embodiments of the Fig. 5 and Fig. 7 by designing the wavelength shifter as a circular ring segment arranged on a scintillator body with a circular ring shape.

[0099] Each of the light detector assemblies 55 and 57 of the Fig. 1 and the light detector arrangement 101 of the Fig. 2 can be configured to discriminate light with different spectral distributions, for example, by using multiple light detectors in the respective light detector arrangement, with wavelength-selective elements, such as optical filters or dichroic beam splitters, being arranged in the beam paths leading to these light detectors. In addition to the two different spectral distributions explained above, three or more pairwise different spectral distributions can be discriminated against and detected.

[0100] In the example of Fig. 2, the first scintillator arrangement 51a may comprise one or more scintillator bodies made of the same scintillator material, each generating light with a same first spectral distribution. Similarly, the second scintillator arrangement 53a may comprise one or more scintillator bodies made of the same scintillator material, each generating light with a same second spectral distribution that is different from the first spectral distribution. Furthermore, the first scintillator arrangement 51 of the Fig. 1 and the first scintillator arrangement 51a of the Fig. 2 each comprise a plurality of scintillator bodies that generate light with pairwise different spectral distributions. Similarly, the second scintillator arrangement 53 of the Fig. 1 and the second scintillator arrangement 53a of the Fig. 2 each comprise a plurality of scintillator bodies which generate light with pairwise different spectral distributions.

Claims

[1] Particle beam microscope, comprising: a particle beam source (3) for generating a particle beam (5); an objective lens (7) for focusing the particle beam (5) in an object plane (9); a first scintillator (51, 53) configured to generate light from electrons coming from the object plane (9); a second scintillator (51, 53) configured to generate light from electrons coming from the object plane (9); and at least one light detector (55, 57; 101) configured to detect light generated by the first scintillator (51, 53) and light generated by the second scintillator (51, 53); wherein a first beam path of the light generated by the first scintillator (51, 53) between the first scintillator (51, 53) and the at least one light detector (55, 57; 101) and a second beam path of the light generated by the second scintillator (51, 53) between the second scintillator (51, 53) and the at least one light detector (55, 57; 101) partially overlap each other; wherein the first scintillator (51, 53) comprises a scintillator body (203) made of a first scintillator material, which generates light (215) with a first spectral distribution from electrons (213); wherein the second scintillator (51, 53) comprises a scintillator body (205) made of a second scintillator material, which generates light (219) from electrons (217) with a second spectral distribution which is different from the first spectral distribution; and wherein a smallest distance measured along a main axis (35) of the objective lens (7) between the scintillator body (203) of the first scintillator and the scintillator body (205) of the second scintillator is less than 10 mm, in particular less than 5 mm; characterized by that, viewed in the direction of the main axis (35), the scintillator body (203) of the first scintillator has a surface area which does not overlap with the scintillator body of the second scintillator. [2] Particle beam microscope according to claim 1, wherein, viewed in the direction of the main axis, the scintillator body (203g) of the first scintillator does not overlap with the scintillator body (205g) of the second scintillator; wherein the scintillator body (203g) of the first scintillator is arranged substantially outside the second beam path, and wherein the scintillator body (205g) of the second scintillator is arranged substantially outside the first beam path. [3] Particle beam microscope according to claim 1, wherein, viewed in the direction of a main axis (35) of the objective lens (7), a first part (207) of the scintillator body (203) of the first scintillator overlaps with the scintillator body (205) of the second scintillator; and wherein the first part (207) of the scintillator body (203) of the first scintillator is arranged within a beam path of the light generated by the second scintillator (205) between the second scintillator and the at least one light detector. [4] A particle beam microscope according to claim 3, wherein a surface of the scintillator body (205) of the second scintillator is optically coupled to a surface of the scintillator body (203) of the first scintillator. [5] Particle beam microscope according to claim 4, further comprising at least one light guide (73; 103) in which the first beam path and the second beam path overlap each other; wherein the surface of the first scintillator body is optically coupled to a surface of the light guide. [6] Particle beam microscope according to one of claims 1 to 5, wherein the scintillator body (203) of the first scintillator has a shape of a circular ring; and / or wherein the scintillator body (205) of the second scintillator has a shape of a circular ring. [7] Particle beam microscope according to one of claims 1 to 5, wherein the scintillator body (203g) of the first scintillator has a shape of a circular ring segment; and / or wherein the scintillator body (205g) of the second scintillator has a shape of a circular ring segment. [8] Particle beam microscope, comprising: a particle beam source (3) for generating a particle beam (5); an objective lens (7) for focusing the particle beam (5) in an object plane (9); a scintillator configured to generate light from electrons coming from the object plane (9), the scintillator comprising a scintillator body (223) made of a scintillator material which generates light (215b, 221) having a first spectral distribution from electrons (213b, 217b); a wavelength shifter (225) configured to convert the light (221) generated by the scintillator into light (219b) having a second spectral distribution; and at least one light detector (55, 57; 101) configured to detect light (215b) generated by the scintillator and light generated by the wavelength shifter (225); wherein a first beam path exists between a first part (227) of the scintillator body (223) of the scintillator and the at least one light detector; and wherein the wavelength shifter (225) is arranged substantially outside the first beam path. [9] Particle beam microscope according to claim 8, wherein no wavelength shifter is provided in the first beam path. [10] Particle beam microscope according to one of claims 8 or 9, wherein a surface of the wavelength shifter (225) is optically coupled to a surface of a second part (229) of the scintillator body (223) of the scintillator. [11] Particle beam microscope according to one of claims 8 to 10, wherein the first beam path and a second beam path of the light converted by the wavelength shifter partially overlap each other between the wavelength shifter and the at least one light detector. [12] Particle beam microscope according to claim 11, further comprising at least one light guide (73; 103) in which the first beam path and the second beam path overlap each other; wherein the surface of the wavelength shifter is optically coupled to a surface of the light guide. [13] Particle beam microscope according to one of claims 1 to 12, wherein a center of gravity of the first spectral distribution lies at a first wavelength, wherein a center of gravity of the second spectral distribution lies at a second wavelength, and wherein an absolute value of a difference between the first wavelength and the second wavelength is greater than 50 nm. [14] A particle beam microscope according to claim 13, wherein the first wavelength is smaller than the second wavelength. [15] Particle beam microscope according to one of claims 1 to 7 and 11 to 14, wherein an optical filter (261) can be arranged in the first beam path, which allows the light (215) with the first spectral distribution to pass better to the at least one light detector (253) than the light (219) with the second spectral distribution. [16] Particle beam microscope according to one of claims 1 to 15, wherein the at least one light detector comprises a first light detector (253) for detecting the light (215e) having the first spectral distribution and a second light detector (255) different from the first light detector for detecting the light (219e) having the second spectral distribution; wherein a first optical filter (261) is arranged in the first beam path, which allows the light (215e) with the first spectral distribution to pass better to the first light detector (253) than the light (219e) with the second spectral distribution; and wherein a second optical filter (265) is arranged in the second beam path, which allows the light (219e) with the second spectral distribution to pass better to the second light detector (255) than the light (215e) with the first spectral distribution. [17] Particle beam microscope according to claim 16, further comprising a dichroic beam splitter (271) providing the first optical filter and the second optical filter. [18] Particle beam microscope according to one of claims 9 to 17, wherein the scintillator body of the scintillator has a shape of a circular ring; and / or wherein the wavelength shifter has a shape of a circular ring. [19] Particle beam microscope according to one of claims 9 to 17, wherein the scintillator body of the scintillator has a shape of a circular ring; and / or wherein the wavelength shifter has a shape of a circular ring segment.

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