Particle beam system and method for particle optical inspection of objects

Abstract

The present invention relates to a particle beam system. The particle beam system has a multi-particle beam generator, which is configured to generate a plurality of partial particle beams, which are spaced apart in space and at least include a first partial particle beam and a second partial particle beam. The particle beam system has a lens, which is configured to focus the incident partial particle beam in a first plane, so that the first area in the first plane where the first partial particle beam strikes is separated from the second area where the second partial particle beam strikes. The particle beam system includes a detector system with a plurality of detection zones and a projection system, which is configured to project interaction products onto the detector system. The projection system is matched with the plurality of detection zones, so that the interaction products originating from the first zone of the first plane are projected onto the first detection zone, and the interaction products originating from the second zone of the first plane are projected onto the second detection zone different from the first detection zone. The detector system includes a filter device.

Description

[0001] This application is a divisional application of Chinese patent application No. 201910426923.6, whose application date is February 3, 2016 and whose invention name is “Particle beam system and method for particle optical inspection of objects”. Technical Field

[0002] The present invention relates to a particle beam system operating using multiple particle beams. Background Art

[0003] WO 2005 / 024881 A2 has disclosed a multi-particle beam system in the form of an electron microscopy system, which uses a plurality of electron beams to operate so as to scan the object to be inspected in parallel by means of a clustered electron beam. This clustered electron beam is produced by means of an electron beam produced by an electron source, and this clustered electron beam is directed to a porous plate with a plurality of holes. Some electron impacts of electron beam are on the porous plate and are absorbed there, and another part of this electron beam passes these holes of the porous plate, thereby making to form an electron beam in the electron beam path behind each hole, the cross section of this electron beam being limited by the cross section of the hole. In addition, the suitably selected electric field provided in the upstream and / or downstream of the porous plate in the electron beam path causes each hole in the porous plate to play the role of a lens to the electron beam passing through the hole, and therefore described electron beam is focused in the plane at a distance from the porous plate. This plane (wherein forming the focus of the electron beam) is imaged on the surface of the object to be inspected by subsequent optics, thereby making these independent electron beams impact on the object as a primary electron beam focusing. There, they generate backscattered electrons or secondary electrons from the object, which are formed for forming a secondary electron beam and guided by further optics to a detector. On the detector, each secondary electron beam impinges on a separate detector element, so that the electron intensity detected therewith provides information about the object at the position where the corresponding primary electron beam was incident on the object. These focused primary electron beams are systematically scanned over the surface of the object in order to produce an electron microscopic image of the object in the conventional manner of scanning electron microscopy. Summary of the invention

[0004] The object of the present patent application is to develop such a multi-beam particle beam system and in particular to further improve the contrast generation in such a multi-beam particle beam system. A further object is to specify a developed method for particle optical inspection of objects.

[0005] The indicated objects are firstly achieved by a particle beam system having the features as discussed below. A further object is achieved by a method for particle microscopic inspection of an object as discussed below. Advantageous embodiments emerge from the features as discussed below.

[0006] According to one embodiment, the particle beam system comprises a particle source, which is configured to produce a first charged particle beam. In addition, the particle beam system comprises a multi-particle beam generator, which is configured to produce a plurality of partial particle beams from a first incident charged particle beam, and these partial particle beams are spatially spaced apart in a direction perpendicular to the propagation direction of these partial particle beams. Here, these plurality of partial particle beams at least comprise a first partial particle beam and a second partial particle beam. The particle beam system further comprises an object lens, which is configured to focus the incident partial particle beams in a first plane in a manner such that a first region incident thereon of the first partial particle beam is separated from a second region incident thereon of the second partial particle beam in the first plane. In addition, the particle beam system comprises a detector system and a projection system, and the detector system comprises a plurality of detection regions. The projection system is configured to project the interaction product leaving the first plane due to these incident partial particle beams onto the detection region of the detector system. Here, the projection system and the plurality of detection areas are matched to one another in such a way that interaction products from the first area of ​​the first plane are projected onto a first detection area of ​​the detector system, and interaction products from the second area of ​​the first plane are projected onto a second detection area. Here, the second detection area is different from the first detection area. In addition, the detector system comprises a filter device for filtering the interaction products according to the trajectories to which the interaction products correspond.

[0007] By appropriately filtering the interaction products according to their corresponding trajectories, the contrast of the image created by combining the output signals of the detector system for different detection areas to form an overall image can be increased. Filtering should not be limited to masking or suppressing interaction products whose trajectories extend in outer areas away from the optical axis of the projection system.

[0008] The charged particles may be electrons and / or ions. Specifically, these interaction products may be secondary electrons or backscattered electrons. However, these interaction products may also be primary particles that may undergo reverse motion due to the deceleration between the objective lens and the object, without the physical scattering process between the primary particles and the object.

[0009] In one embodiment, the filter device has a plurality of first detection fields, which are associated with the first detection area. In addition, the filter device has a plurality of second detection fields, which are associated with the second detection area. Here, each first detection field and each second detection field are implemented to detect the interaction products incident on the corresponding detection field in a manner independent of the interaction products incident on the other detection fields. In other words, each detection area of ​​this detector has a plurality of detection fields, which detect the interaction products independently of each other in each case. Such instruments are known from light microscopy in documents US8705172B2 and DE 102010049627 A1, and the unpublished German patent application No. 10 2013 218795.5.

[0010] The particle beam system may include a controller in addition, which is implemented to read out detector signals separately from these multiple detection fields of the associated detection area and process them. Important additional information can be obtained by evaluating the associated detector signals generated from different detection fields. By way of example, the detector signal of each detection field is analyzed so that it is possible to establish whether the associated primary partial particle beam is incident on the object surface in a focused manner, that is, whether the surface of the object coincides with the first plane at the position of the incident partial particle beam. This information can be used to start an automated adjustment system subsequently, such as an autofocus system, a detector adjustment system or a filter adjustment system, so as to achieve the ideal focusing of the partial particle beam on the object surface. In addition, the detector signals of the detection fields belonging to the same detection area can be compared to obtain the additional information related to the topography of the object that can be obtained at the position where the associated partial particle beam is incident on the object. In addition, averaging the detector signals belonging to the multiple detection areas or belonging to the entire image allows obtaining information related to the inclination of the sample in the area limited by the averaged detection area (object area) on the surface of the object. Moreover, the overall geometry of the object within the area on the object surface defined by the evaluated detector signals can be determined by evaluating the detector signals belonging to the multiple detection areas, and this information can be used to correct the focus and / or correct the astigmatism in object areas adjacent to the evaluated object area.

[0011] In a further embodiment, the detection system may further comprise a dispersion-generating element. The dispersion-generating element then causes the interaction products associated with the detection area to split according to their corresponding kinetic energy. By comparing the detector signals of the detection fields belonging to the same detection area, the kinetic energy of the interaction products when they are emitted from the object can be inferred. Thus, a voltage contrast can be generated. Here, voltage contrast should also be understood to mean that for secondary electrons from object areas with different charges of the object, the secondary electrons are emitted from the object with different potentials. An example of this is contact holes in semiconductor structures, which establish contact between different planes of a conductor track structure. If there is no connection between the two planes in such a contact hole, irradiation with charged particles (e.g., electrons) will cause charging in the contact hole, because the charge cannot dissipate. The inelastically scattered particles (e.g., electrons) or secondary electrons then start with a different potential than the contact hole in contact. Due to the fact that the electrons can be distinguished from one another due to their different kinetic energies, which lead to different trajectories due to the dispersion-generating elements, untouched contact holes can be detected at a significantly higher speed, since the signal-to-noise ratio is greatly increased.

[0012] As an alternative to the embodiment with a dispersion-generating element, the filter device can also be a dispersion-generating imaging energy filter. The detected interaction products can be split and selected according to their kinetic energy with the aid of such an energy filter. This embodiment can also be used to generate voltage contrast.

[0013] According to a further embodiment, the projection system comprises an intersection plane, and the filter device is implemented as an aperture arranged near this intersection plane. In particular, the aperture can have an annular aperture. What can be achieved by means of the annular aperture is to detect only those interaction products from the object under inspection that emerge from the object in a specific virtual starting angle range. Due to the annular aperture, selection is made according to the vector component of the initial velocity of the interaction products from the object pointing parallel to the surface of the object. Thus, additional information about the morphology of the surface of the object or the material at the surface of the object at the position where the associated partial particle beam is incident can be obtained. In particular, the energy distribution of the interaction products passing through the aperture can be partially filtered by the annular aperture. Since the energy distribution of the interaction products (especially in the case of secondary electrons as interaction products) also depends on the local surface potential and the number of emitted secondary electrons, the atomic mass number of the atoms at the position where the secondary electrons emerge from the object, to the extent that assumptions can be made about the sample surface, additional information about the material composition of the object at the corresponding position on the surface of the object can therefore be obtained.

[0014] According to a further embodiment, the projection system may comprise a plurality of particle beam lenses arranged in series one behind the other, which lenses produce at least two intersecting planes one behind the other. Then, an aperture may be arranged in each of the at least two intersecting planes, respectively. By way of example, the first aperture may have a central hole, through which only the interaction products whose trajectories extend sufficiently close to the optical axis of the projection system may pass. Using such a "bright field stop", crosstalk between different detection areas may be prevented. In other words, what may be prevented by means of a "bright field stop" is that the interaction products from the first area of ​​the first plane hit the detection area associated with the different areas in the first plane. Once again, an aperture with an annular hole may be arranged in the second intersecting plane. Similar to the embodiments already described above, additional information relating to the atomic mass number at the surface of the object may then be obtained and / or additional morphological contrast may be generated. This may preferably be performed using a dark field stop.

[0015] By changing the focal length of the particle beam lens, the filtering effect obtained by the apertures can be changed. Therefore, in a further embodiment the focal length of the particle beam lens is variable.

[0016] These particle beam lenses can be implemented as magnetic lenses or electrostatic lenses, or they can be implemented as combined lenses with overlapping magnetic and electrostatic fields.

[0017] According to a further embodiment, the particle beam system additionally comprises a particle beam deflection system, which is implemented to deflect the first particle beam and the second particle beam perpendicular to their propagation direction. In this case, the controller is additionally implemented to merge detector signals belonging to the different deflections of the partial particle beams to different detection areas to form an image. By deflecting these partial particle beams, each partial particle beam can scan the entire first area, and the image information generated by the scanning of these multiple partial particle beams can be merged to form an overall image.

[0018] According to a further embodiment, the present invention relates to a method for particle microscopic inspection of an object, the method comprising the following steps:

[0019] - the object is irradiated simultaneously in a plurality of mutually separated field regions respectively using a primary charged particle beam.

[0020] - collecting the interaction products emerging from the object as a result of these incident primary particle beams,

[0021] - projecting the interaction products onto a plurality of detection areas of a detector in such a way that interaction products from two different field areas are projected onto different detection areas of the detector, and

[0022] - Filtering these interaction products in a way that depends on the trajectories to which they correspond.

[0023] Specifically, the interaction products may be filtered according to their kinetic energy.

[0024] As already described further above, in one embodiment, these interaction products can be filtered by means of a detector which comprises a plurality of mutually independent detection fields sensitive to the interaction products per detection area. In this case, the signals of these detection fields belonging to the same detection area can be evaluated relative to one another in order to generate images with improved voltage contrast, improved topographic contrast or improved material contrast, for example. In addition, specifically aligned edges can be highlighted or height profiles of the object surface can be generated.

[0025] In a further embodiment of the method for particle microscopic inspection of an object, the particle beam system is operated in so-called reflection mode. In this method, an electrostatic potential is applied to the object to be inspected, and the potential corresponds substantially to the potential of the particle beam generator or these particle beam generators (particle sources). Due to the electrostatic potential applied to the object, as in the case of an electrostatic reflector, a primary particle beam slows down to zero kinetic energy before reaching the object but very close to the surface of the object, and accelerates back in the reverse direction, i.e., in the direction returning to the object lens. Those charged particles that experience reverse motion due to the electrostatic potential of the object are collected, and subsequently the charged particles collected are projected onto a plurality of detection areas of a detector in a manner such that the charged particles collected from two different field regions of the object plane are projected onto the different detection areas of the detector. In this embodiment of the method according to the invention, there is also the path corresponding to the collected particles to filter these particles. Here, the collected particles can be filtered by means of a detector, and each detection area of ​​the detector has a plurality of independent detection fields that are sensitive to the collected particles.

[0026] When operating a particle beam system in reflection mode to inspect a non-conductive object, it is possible to almost completely avoid the local charging of the object caused by the incident primary particle beam because the primary particles of these partial particle beams do not penetrate into the object, if the radiation parameters are appropriately selected. If the object potential changes, the object potential when the primary particles fall on the surface of the object without kinetic energy can be determined. Thus, the potential of the object charge can be determined. If this is performed for multiple different points on the surface of the object, the potential profile near the surface of the object can be determined. Due to the above-mentioned filtering of the interaction product, the trajectory of the interaction product can be determined. These trajectories allow the form of the local potential profile near the surface of the object to be inferred, and the local morphology of the surface of the object can be inferred accordingly. Due to this "non-contact" sensing of the surface, the charge compensation method can be largely omitted. Specifically, the sample morphology can be determined from multiple data records with higher accuracy by different parameters (such as the object potential or the focal position of the multi-beam particle beam system). Therefore, the method may further include the following steps: changing the electric potential of the object, determining the electric potential profile near the surface of the object, and determining the local topography of the surface of the object from the local electric potential profile near the surface of the object.

[0027] In a further embodiment of a method for performing particle microscopic inspection of an object using a multi-beam particle beam system, the interaction products emitted from the object due to the incident primary particle beam are initially collected using a first suction field and projected onto multiple detection areas of a detector in such a way that the interaction products from two different field areas are incident on different detection areas of the detector. Subsequently, the interaction products emitted from the object due to these incident primary particle beams are collected by means of a second suction field different from the first suction field, and the interaction products collected by the second suction field are then also projected onto multiple detection areas of the detector in such a way that the secondary particles from two different field areas of the object are projected onto different detection areas of the detector. Subsequently, the detector signals belonging to different suction fields but belonging to the same detection area are combined with each other by calculation in such a way that a data signal rich in the morphological effects of the object is generated, which data signal is then used to generate and depict an image. This method can be similarly performed for three, four or more different suction fields so as to achieve higher accuracy when combined by calculation. If the suction field can penetrate into the object, this approach can also be used to image structures beneath the surface of the object that are not visible in the image alone.

[0028] In the above-mentioned method in which the interaction products are detected with different suction fields, the interaction products can also be filtered before the detection of the interaction products in a manner that depends on the trajectory to which the interaction products correspond. As described above, the filtering can be implemented as Fourier filtering in the cross plane using an aperture with a circular or annular aperture that is transmissive for the interaction products. As an alternative and as also described further above, the interaction products can be filtered with the aid of a detector, each detection area of ​​which has a plurality of mutually independent detection fields that are sensitive to the interaction products. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The details of the above and further embodiments are explained below based on the accompanying drawings. In detail:

[0030] Figure 1 : A schematic diagram of an embodiment of a multi-beam particle beam instrument is shown.

[0031] Figure 2 : A schematic diagram of the detector system in the first embodiment is shown.

[0032] Figure 3 : Shows a top view of the aperture with an annular aperture.

[0033] Figure 4 : A schematic diagram of a second embodiment of a detector system is shown.

[0034] Figure 5 : A schematic diagram of a further embodiment of a detector system is shown.

[0035] Figure 6 : Shows a top view of an aperture with a circular hole.

[0036] Figure 7 : A schematic diagram of an embodiment of a detector system with a detector having multiple detection fields per detection area is shown.

[0037] Figure 8 : shows a top view of a detector with a plurality of detection areas, on which the intensity distribution of the interaction products incident on these detection areas is indicated in a schematic manner.

[0038] Fig. 9 : shows a top view of a detector with a plurality of detection areas, on which the intensity distribution of the interaction products incident on these detection areas is indicated in a schematic manner.

[0039] Fig.10 : shows a schematic diagram of the detector system with energy filter.

[0040] Fig.11: shows a schematic diagram of a detector system with a dispersive element.

[0041] Fig.12 : Shows a top view of a multi-aperture with multiple bright field holes and dark field holes.

[0042] Fig.13 : A schematic diagram of a further embodiment of a detector system is shown.

[0043] Fig.14 : shows a further top view of the detector with a plurality of detection areas, on which the intensity distribution of the interaction products incident on the detection areas is indicated in a schematic manner.

[0044] Fig.15 : Shows Fig.14 A further top view of the detector with a modified assignment between detection fields and detection areas.

[0045] Fig.16 : A flow chart showing a method for amplifying topography effect. DETAILED DESCRIPTION

[0046] Figure 1 1 is a schematic diagram of a particle beam system 1 using multiple particle beams. The particle beam system 1 produces multiple particle beams, which are incident on an object to be inspected so as to generate interaction products there, such as secondary electrons, which come from the object and are subsequently detected. The particle beam system 1 belongs to the "scanning electron microscope" (SEM) type, which uses multiple primary partial particle beams 3, which impact multiple positions 5 on the surface of an object 7 and produce multiple spatially separated beam spots there. The object 7 to be inspected can be of any type, for example, including arrangements of semiconductor wafers, biological samples, miniaturized components, etc. The surface of the object 7 is arranged in a first plane 101 (object plane) of an objective lens 102 of an objective lens system 100.

[0047] Figure 1 The enlarged section I1 in FIG. 1 shows a top view of the object plane 101 , wherein a regular rectangular field 103 of impact locations 5 is formed in the first plane 101 . Figure 1 In , the number of impact positions is 25, which forms a 5×5 field 103. The number of impact positions 25 is a small number chosen to simplify the description. In practice, the number of particle beams or impact positions can be chosen to be significantly larger, such as 20×30, 100×100, etc.

[0048] In the embodiment shown, the field 103 of impact locations 5 is a substantially regular rectangular field with a constant distance P1 between adjacent impact locations 5. Exemplary values ​​of the distance P1 are 1 micron, 10 microns and 40 microns. However, the field 103 may also have a different symmetry, such as, for example, a hexagonal symmetry.

[0049] The diameter of the beam spot formed in the first plane 101 can be relatively small. Exemplary values ​​of this diameter are 1 nanometer, 5 nanometers, 10 nanometers, 100 nanometers and 200 nanometers. The particle beam 3 is focused to form the beam spot 5 by the objective lens system 100 .

[0050] The primary particles impinging on the object produce interaction products, such as secondary electrons, backscattered electrons or primary particles that undergo reversal motion for other reasons from the surface of the object 7 or from the first plane 101. These interaction products from the surface of the object 7 are formed into secondary particle beams 9 by the objective lens 102. The particle beam system 1 provides a particle beam path 11 so that the multiple secondary particle beams 9 are fed to the detector system 200. The detector system 200 includes a particle optical device with a projection lens 205, which is used to guide these secondary particle beams 9 to a particle multi-detector 209.

[0051] Figure 1 The section I2 in FIG. 2 shows a top view of a plane in which the individual detection areas of the particle multi-detector 209 are located and on which the secondary particle beam 9 impinges at positions 213. The impingement positions 213 are located in the field 217 at regular distances P2 from each other. Exemplary values ​​of the distance P2 are 10 micrometers, 100 micrometers and 200 micrometers.

[0052] These primary particle beams 3 are generated in a particle beam generating device 300, which comprises at least one particle source 301 (e.g. an electron source), at least one collimating lens 303, a multi-aperture arrangement 305 and a field lens 307. The particle source 301 generates a divergent particle beam 309, which is collimated by the collimating lens 303, or collimated to a large extent, to form a particle beam 311 which irradiates the multi-aperture arrangement 305.

[0053] Figure 1 The section I3 in FIG. 3 shows a top view of the multi-aperture arrangement 305. The multi-aperture arrangement 305 comprises a multi-aperture plate 313 having a plurality of openings or holes 315 formed therein. The center points 317 of the holes 315 are arranged in a field 319 corresponding to the field 103 formed in the object plane 101 by the beam spot 5. The distance P3 at which the center points 317 of the holes 315 are spaced from each other may have exemplary values ​​of 5 micrometers, 100 micrometers, and 200 micrometers. The diameter D of the holes 315 is smaller than the spacing P3 between the center points of the holes. Exemplary values ​​of the diameter D are 0.2×P3, 0.4×P3, and 0.8×P3.

[0054] Particles in the illumination particle beam 311 pass through the holes 315 and form the partial particle beams 3. Particles in the illumination particle beam 311 that impinge on the plate 313 are captured by the plate and do not contribute to the formation of the partial particle beams 3.

[0055] The porous arrangement 305 focuses each partial particle beam 3 due to the applied electrostatic field in such a way that a particle beam focus 323 is formed in a plane 325. By way of example, the diameter of the particle beam focus 323 may be, for example, 10 nanometers, 100 nanometers and 1 micrometer.

[0056] The field lens 307 and the objective lens 102 provide a first imaging particle optical device for imaging the plane 325 in which the particle beam focus is formed onto the first plane 101 so that a field 103 of impact locations 5 or beam spots is created in the first plane. To the extent that the surface of the object 7 is arranged in the first plane, the beam spot is correspondingly formed on the object surface.

[0057] The objective 102 and the projection lens arrangement 205 provide a second imaging particle optics for imaging the first plane 101 on a detection plane. Thus, the objective 102 is part of both the first and second particle optics, whereas the field lens 307 belongs only to the first particle optics and the projection lens 205 belongs only to the second particle optics.

[0058] The particle beam switch 400 is arranged in the particle beam path of the first particle optics between the multi-aperture arrangement 305 and the objective system 100. The particle beam switch 400 is also part of the second particle optics in the particle beam path between the objective system 100 and the detector system 200.

[0059] Further information about such multi-beam particle beam systems and components used therein (e.g., particle sources, porous plates, and lenses) can be obtained from international patent applications WO 2005 / 024881, WO 2007 / 028595, WO 2007 / 028596, WO2011 / 124352 and WO 2007 / 060017 and German patent applications with application numbers DE 10 2013016 113.4 and DE 10 2013 014976.2, the disclosures of which are incorporated by reference in their entirety into the present application.

[0060] In addition, the detector system 200 has a filter device 208, with the help of which the interaction products (for example, the electron beam 9) from the object 7 or the first plane 101 are filtered according to their trajectory. Figure 2-15Examples of detection devices with different filter arrangements are described in more detail.

[0061] The multi-beam particle beam system further has a controller 10, which is implemented both for controlling the individual particle optical components of the multi-beam particle beam system and for evaluating and analyzing the detector signals obtained by the multi-detector 209. In addition, the controller 10 is implemented so that the detector signals generated by the multi-detector 209 in turn generate an image of the object surface on a reproduction device (e.g., a display).

[0062] In addition to the projection lens 205 and the multi-detector 209, Figure 2 The detector system 200 in has two further particle beam lenses 210,211.First further particle beam lens 210 forms intersection in intersection plane 214.In this intersection plane 214, the track of the interaction product that leaves first plane 101 (object plane) in different regions overlaps.Second additional particle beam lens 211 is operated into its mode for making its focal plane basically in the intersection plane 214 of first additional particle beam lens 210.Interaction products from different regions in first plane 101 are then separated from each other again behind second additional particle beam lens 211 and they are projected to different detection areas 215 of multi-detector 209 by projection lens 205.

[0063] An aperture 213 is arranged in or near the intersection plane 214 , ie between the two additional particle beam lenses 210 and 211 , with the help of which the interaction products can be filtered as desired according to their corresponding trajectories. Figure 3 and Figure 6 Two exemplary apertures 213 are depicted in FIG. Figure 3 The aperture 213 depicted in FIG. 1 has a central region 220 and a peripheral region, both of which do not transmit the interaction products. Between the central region 220 and the peripheral region, the aperture 213 has an annular region that transmits the interaction products, which in the depicted embodiment is composed of three annular segments 221, 222, 223. The webs that exist between these annular segments 221, 222, 223, which separate these annular segments from one another, serve only to connect the central region 220 and the peripheral region to one another. With the help of such annular apertures, the interaction products can be filtered according to their starting angle when emerging from the object 7 or when leaving the first plane 101. Thus, only those interaction products that leave the first plane 101 in a specific angular region can pass through the aperture in one of the three annular segments 221, 222, 223 that are transparent for the interaction products. With the help of such an aperture, the topographic contrast can be increased, because the interaction products (e.g. secondary electrons) emerge mainly at the edge of the object surface at a large inclination angle relative to the incident partial particle beam.

[0064] Since the aperture 213 is arranged in the intersection plane 214 of the detector system, only a single annular aperture is required for all partial particle beams of the multi-particle beam system. In this way, the interaction products generated from the object 7 by all partial particle beams of the particle beam system undergo the same filtering.

[0065] exist Figure 2 In the exemplary embodiment of FIG. 2 , the two further particle beam lenses 210 , 211 together with the aperture 213 and the projection lens 205 form a projection system.

[0066] Figure 6 The aperture 213 in FIG. 1 has only a circular hole that transmits the interaction product. Figure 2 Such a "bright field stop" in the intersection plane 214 of the detector system 200 can avoid crosstalk of detection signals between detection areas of the detector 209. Crosstalk between detection areas 215 may occur when interaction products from field areas in the first plane 101 impinge on detection areas 215 that are not assigned to this field area. Figure 6 By appropriately selecting the diameter of the circular aperture, the aperture 213 can be ensured to filter out and absorb interaction products that, due to their trajectories, will impinge on a detection area that is not associated with the corresponding field area. The trajectories of those interaction products that have a combination of a large starting angle and a large starting energy when emitted from the object extend in the outer region of the intersection plane in terms of radial direction. The bright field aperture can reduce crosstalk between adjacent particle beams. Moreover, the bright field aperture can affect contrast, such as edge contrast, for example.

[0067] To be able to produce different filtering, the diaphragms 213 can be arranged in an interchangeable manner in the detector system 200 and multiple diaphragms can be provided with different hole diameters, ring diameters and ring widths. As an alternative to interchangeable diaphragms with only one diaphragm opening, multiple diaphragms can also be used. Fig.12 A top view of a multi-aperture 803 with multiple aperture holes 803a-803d is depicted in FIG. Fig.12 In the multi-aperture depicted in FIG, two apertures 803a, 803b each have an annular aperture transparent for the interaction product, wherein the inner and outer diameters of the annular apertures are different. Two further apertures 803c, 803d are circular and have different aperture diameters. However, other aperture arrangements with more or fewer different apertures are possible.

[0068] Fig.13 An exemplary embodiment of a detector system is shown, which is designed with Figure 2The detector system once again comprises a first additional particle beam lens 210, which produces a crossover in the crossover plane. The second additional particle beam lens 211 is once again operated in such a way that its focal plane coincides with the crossover plane formed by the first further particle beam lens 210. The interaction products from different areas in the first plane 101 then propagate separately from each other again after the second additional particle beam lens 211 and they are projected onto different detection areas 215 of the multi-detector 209 via the projection lens 205. Figure 2 An exemplary embodiment of Fig.13 In the exemplary embodiment of the present invention, a first double deflection system 801, 802 is arranged between the first additional particle beam lens 210 and the intersection plane, and a second double deflection system 804 is arranged between the intersection plane and the second further particle beam lens. Fig.12 By means of two double deflection systems 801, 802, 804, one of the holes of the multi-aperture 803 can be selected in this exemplary embodiment, wherein Fig.13 Only two apertures 803a, 803b of the multi-aperture are depicted in FIG. Thus, depending on the excitation thereof, it is possible to switch between different contrasts with the aid of the multi-aperture with the aid of a dual deflection system. The two dual deflection systems 801, 802, 804, 805 thus act as aperture selectors.

[0069] exist Fig.13 In the embodiment of FIG. 2 , two further particle beam lenses 210 , 211 together with an aperture 213 , a double deflection system 801 , 802 , 804 , and a projection lens 205 form a projection system.

[0070] In addition to the projection lens 205 and the multi-detector 209, Figure 4 The detector system 200 in FIG. 1 has six further particle beam lenses 230, 231, 232, 233, 235, 236. Two first further particle beam lenses 230, 231 form a first intersection in a first intersection plane 238, and two subsequent further particle beam lenses 232, 233 form a second intersection in a second intersection plane 239. Two further particle beam lenses 235, 236 behind the second intersection plane 239 re-collect the particle beams of the interaction products from the second intersection plane 239 in such a way that the interaction products from different field regions in the first plane 101 are projected again into different detection regions 215 of the multi-detector 209 by means of the projection lens 205 on the multi-detector 209.

[0071] In this embodiment of the detector system 200, two different apertures 237, 234 may be used simultaneously in the first and second intersection planes 238 and 239. By way of example, Figure 6 The bright field aperture 213 depicted in FIG. 2 can be arranged in the first intersection plane 238, and Figure 3 The aperture with the annular aperture depicted in can be arranged in the second intersection plane 239. In this embodiment, suppression of crosstalk between the detection regions 215 and targeted filtering of the interaction products depending on their starting angle in the first plane 101 are simultaneously performed.

[0072] Attention is drawn here to the fact that the two apertures 237 , 234 can also be arranged in an interchangeable manner such that the aperture with the annular aperture is arranged in the first intersection plane 238 and the aperture with the central aperture is arranged in the second intersection plane 239 .

[0073] By changing the excitation of the further particle beam lenses 230, 231, 232, 233, 235, the trajectories of the interaction products can be set independently of each other in the two intersection planes 238, 239. By changing the trajectories in the intersection planes 238, 239, different aperture radii and aperture diameters can be simulated without mechanically replacing the aperture for this purpose. In this case, the trajectories when entering the detector system 200 and when entering the projection lens 205 can be kept consistent, so that the correlation between the field area in the first plane 101 and the detection area of ​​the multi-detector 209 can be maintained. The object field transmitted by all partial particle beams of the interaction products in the first plane 101 remains unchanged and constant in the process.

[0074] In this case, the further particle beam lenses 230 , 231 , 232 , 233 , 235 , 236 may be magnetic lenses or electrostatic lenses.

[0075] exist Figure 4 In the exemplary embodiment of FIG. 2 , six further particle beam lenses 230 , 231 , 232 , 233 , 235 , 236 together with two apertures 234 , 237 and the projection lens 205 form a projection system.

[0076] Figure 5 The embodiment of the detector system 200 in FIG. Figure 4 Specifically, except for the projection lens 205 and the multi-detector 209, Figure 5The detector system 200 in the embodiment of the present invention again has a total of six further particle beam lenses 230, 231, 232, 233, 235, 236, of which the first two further particle beam lenses 230, 231 again produce a first intersection in a first intersection plane 238, and the subsequent two further particle beam lenses 232, 233 again produce a second intersection in a second intersection plane 239. Figure 4 In the embodiment, Figure 5 The detector system 200 in FIG. 2 has a deflection system 240, 244 respectively before and after the first intersection plane 238. The detector system 200 also has a deflection system 241, 242 respectively before and after the second intersection plane 239. Due to the different excitation of the deflection systems before and after the respective intersection planes 238, 239 (with a stop 237 located therebetween), edge effects in the signals detected by the multi-detector 209 can be amplified and shadow effects can be generated. It is important here that the deflection experienced by the deflection system 244, 241 respectively arranged before the intersection plane is compensated again by the deflection system 240, 242 arranged after the respective intersection plane. Since the intersection plane is located between the two deflection systems respectively assigned to each other, this means that the deflection system 244, 241 arranged before the intersection plane and the deflection system 240, 242 arranged after the same intersection plane can produce exactly the same deflection in certain configurations.

[0077] A 3D data record of the sample surface can be generated by recording a plurality of images with different deflection angles in intersecting planes and by evaluating the correspondingly occurring shadow effects in the controller 10 .

[0078] The deflection systems 240 , 244 , 241 , 242 can be implemented respectively as a single deflection system or as a double deflection system, wherein a single deflection system is sufficient for most applications.

[0079] exist Figure 5 In the exemplary embodiment, six further particle beam lenses 230 , 231 , 232 , 233 , 235 , 236 together with two apertures 237 , deflection systems 240 , 244 , 241 , 242 and the projection lens 205 form a projection system.

[0080] Figure 7A top view of a multiple detector 209 of a further embodiment of a detection system is shown. The detector 209 also has associated detection areas 215a, 215b, 215c for each field area of ​​the plane 101. However, in this detector 209, the detection areas 215a, 215b, 215c are each subdivided again into a plurality of detection fields 216a, 216b which detect independently of one another. Figure 7 In FIG. 1 , this subdivision of the detection areas 215a, 215b into detection fields 216a, 216b that are detected independently of one another is depicted only for one column of detection areas (via the detection areas 215b and 215c). Figure 7 20 detection fields 216a, 216b are depicted for each detection region 215b, 215c, respectively. However, the number of detection fields 216a, 216b per detection region 215b, 215c can also be a different number; in particular, each detection field can present more or fewer detection fields. The number of detection fields per detection region is preferably in the range between 3 and 64. A square or hexagonal arrangement of the detection fields is possible, but other symmetries are also possible. In cases where a high measuring speed is not so important, the number of detection fields per detection region can also be significantly larger.

[0081] In this embodiment of the detector system 200, the interaction products are filtered according to their corresponding trajectories only when the corresponding interaction products impinge on the multi-detector 209, and this filtering is achieved by keeping the output signals of the detection fields 216a, 216b belonging to the same detection area 215b, 215c not taken into account for generating the image in the subsequent evaluation performed by the controller 10, or by combining the output signals of these different detection fields belonging to the same detection area with each other by calculation in a suitable manner by the controller 10.

[0082] A corresponding multi-detector 209 with multiple detection fields 216a, 216b per detection area 215a, 215b, 215c can be implemented in many different ways. A first embodiment of such a multi-detector 209 can be a CCD camera with an upstream scintillator. Each pixel of the CCD camera then forms a detection field 216a, 216b and the multiple detection fields together form a detection area 215a, 515b, 215c respectively. In another embodiment, an optical cable can be arranged between the scintillator and the detector to transmit the light generated in the scintillator by the impact of the interaction product on the scintillator to the detector. The optical cable then has at least one optical fiber for each detection field 216a, 216b. And the detector also has a dedicated detector or a dedicated detector pixel for each detection field. However, alternatively, the corresponding detector 209 can also be a very fast pixelated electronic detector, which directly converts the incident electrons (interaction products, secondary electrons) into electrical signals. In this case, each detector pixel also forms a detection field. Combinations of the described embodiments are also possible. By way of example, the optical cable arranged behind the scintillator can be directed to the first group of detectors, and only each detection area of ​​this group of detectors has a single detector. By being arranged between the beam splitter of the entrance end of the scintillator and the optical cable, another part of the light produced in the scintillator can be directed to the second group of detectors, and each detection area of ​​this group of detectors has a plurality of detectors. Each detector associated with the same detection area then forms a detection field. Since the two groups of detectors have very different numbers of detectors, the two groups of detectors can then be read with the corresponding different clocks for the entire detector group. Since the second group of detectors usually has a lower clock because the number of detectors is larger, it is possible to obtain a signal that does not require a high data rate with this group of detectors, such as a signal for particle beam adjustment as a component, and use the first group of detectors to obtain a signal for producing an image.

[0083] Figure 8 and Fig. 9 A further top view of the corresponding multi-detector 209 is depicted respectively, with the intensity distribution of the corresponding particle beam of the interaction product incident on the corresponding detection area being simultaneously indicated within the detection area.

[0084] If the objective lens 102, the particle beam switch 400 and the projection lens 205 are completely aberration-free, and if the object surface is flat and charge-free, the interaction products from each field region in the plane 101 should be projected onto the detector 209 through the system made of the objective lens, the particle beam switch 400 and the projection lens 205 in such a way that the intensity distribution in each detection region 215 is rotationally symmetric, as for Figure 8, as indicated by the intensity distribution 515e in the detection area 215e in the image. However, due to different effects, the actual intensity distribution incident on the corresponding detection area deviates from this ideal situation. By way of example, such effects can be surface topography effects of the object that affect the starting conditions of the secondary electrons from the object, or other simple charge effects. Moreover, due to aberrations of the objective lens 102, the particle beam switch 400 and the projection lens 205, an intensity distribution that deviates from the rotational symmetry may appear in the detection area. This is in Fig. 9 In the detection area 215a, this is indicated by a cross 515a. If the deviations from the rotational symmetry caused by the aberrations are known in the ideal focusing situation, this information can be used to generate an autofocus signal. To this end, the interaction products detected in these individual detection fields of the same detection area and the detector signals derived therefrom can be analyzed with respect to their spatial distribution. If the established symmetry of the intensity distribution deviates from the known deliberate geometry, it is necessary to make adjustments, such as refocusing. Ideal focus is achieved when the symmetry of the intensity distribution in the detection area has the expected symmetry. An overall displacement or deformation of the intensity distribution of the interaction products at the detector relative to the expected position or the expected distribution allows conclusions to be drawn about the overall sample geometry, such as, for example, sample tilt, or the overall sample charge. Here, a sample characteristic is global if it spreads over the field area of ​​more than one individual particle beam.

[0085] If a partial particle beam impinges on the edge of an object surface in the first plane 101, this generally causes a shift of the intensity distribution in the plane of the multi-detector 209 and a change in the form of the intensity distribution due to the different trajectories of the interaction products from the sample. Figure 8 215c and 215d. The changed intensity distribution form of the interaction product in the plane of the multi-detector 209 is caused by the surface topography of the object or by a corresponding change in the trajectory of the interaction product caused by other effects such as local charging. By evaluating the detection signals recorded with the individual detection fields, both the shift of the intensity distribution of the detected interaction product and the deviation of the intensity distribution from the rotational symmetry can be determined again. By evaluating this additional information, the image information subsequently presented to the user can be improved, for example by highlighting the edges.

[0086] In particular in reflection mode, the local secondary electron starting angle can be inferred by determining the position of the secondary electrons on the detector. It is advantageous to perform this evaluation more than once per image (frame), and it is particularly advantageous to perform this evaluation for each scanned pixel. The lateral form of these features can be calculated from the starting angle distribution together with further information about the object (such as material composition and / or the height of topographic features). To this end, the relative position of the brightness distribution generated by the secondary electrons can be analyzed, and the local relative particle beam form changes and particle beam position changes at the detector can be analyzed.

[0087] Charging of the object at the impact site of the primary particle beam also leads to a shift in the intensity distribution of the interaction products in the detector plane and to a change in the form of the intensity distribution of the interaction products. Fig.14 As depicted in FIG. 8 , charging of an object in a charging region 810 may result in a wider intensity distribution of the interaction product in a portion of the detection region 811. In other detection regions 812, 813, 818, the intensity distribution is displaced relative to the case of an uncharged object and is also partially elongated, resulting in an elliptical intensity distribution in the plane of the multi-detector 209. In other detection regions 814, 815, the location of these detection regions on the surface of the object is far enough away from the charging region that the charging of the object no longer has an effect and the intensity distribution has its predetermined form and position. In particular, detection signal crosstalk may be prone to occur in detection region 817, into which the intensity distribution of the adjacent detection region 812 is projected.

[0088] The charge contrast image can be generated in a targeted manner by evaluating the detector signals in the individual detection fields. By way of example, this can be caused by those points at which a specific intensity distribution form of the interaction product is detected, which points are depicted in a special way in the depicted image. In addition, crosstalk can be prevented by modifying the association between the detection area and the assigned detection field based on the intensity distribution determined with the aid of these detection fields. This is particularly useful in Fig.15 The detection areas 811a, 812a, and 818a are depicted in FIG. Fig.15 In the detection fields correspondingly depicted as squares are determined from the corresponding locally determined intensity distributions in these individual detection areas and recombined to form detection areas 811a, 812a, 818a in such a way that the corresponding intensity distributions of the interaction products are completely within the boundaries of the respective detection areas. By way of example, after the reassignment, Fig.14In the example, six detection fields are associated with the original detection region 811, while after reassignment of a different original detection region 812, a detection region 812a with ten detection fields appears. After the reassignment of the detection fields to the detection regions, the detector signals in all detection fields are then correspondingly added to one signal and associated with the corresponding object point on the object surface to form an image signal. Alternatively, the reassignment of the detection fields to the detection regions can be implemented during the evaluation of the detector signals of the individual image points on the object surface.

[0089] As mentioned above, charging or edge contrast is too large can cause crosstalk (crosstalk between detector channels) in a multi-detector with a single fixed detection area for each image detection area, because the detection signal is no longer uniquely associated with the detection area in part. Use a detector with multiple detection fields in each detection area (that is, wherein multiple detectors are available for each primary particle beam) just can reassociate the detection fields associated with each detection area, in a manner that depends on the particle beam position obtained after analyzing the particle beam position by finding a simple continuous area with increased signal intensity, firstly making it possible to reduce crosstalk and secondly making it possible to not lose detector signals in other channels. Particularly advantageously, this assessment is not just implemented once per frame, but is implemented multiple times per frame or even per pixel. The result is that the requirements for possible charge compensation systems or the morphology requirements for objects are greatly reduced.

[0090] Particularly in the case of charged objects, it is possible with the aid of this method to infer the local object structure in reflection mode as described above.

[0091] By integrating all detector signals of all detection fields belonging to the same detection area 215a, it is also possible to obtain image information under conditions where irradiation of the object with a primary particle beam causes local object charging.

[0092] Fig.10The detection system 200 in FIG. 2 has, in addition to the multi-detector 209 and the projection lens 205, a so-called imaging energy filter 600, such as an omega filter. By way of example, such an imaging energy filter is described in US 4740704A. The imaging energy filter 600 images the first input side plane 601 into the output image plane 602 in an achromatic manner. At the same time, the imaging energy filter images the second input side plane 603 into the second output image plane 604, the diffuse plane, in a diffuse manner. By arranging an aperture in the diffuse plane 604, in which the second input side plane 603 is imaged, the energy of those interaction products that can pass through the filter 600 can be changed. In this way, it can be achieved that only those interaction products from the object are detected by the multi-detector 209, which have an energy predetermined by the aperture in the diffuse plane 604. In this embodiment, the filtering of the interaction products is also achieved according to the corresponding trajectory of the interaction products in the projection system, even if the energy filter ensures that the trajectory of each interaction product depends on its kinetic energy in the filter. In this embodiment, the imaging energy filter 600 together with the projection lens 205 forms a projection system.

[0093] In the manner described above, a voltage contrast image can be produced using a multi-particle beam system because the energy of the interaction product is determined by the potential of the object at the location where the interaction product leaves the object.

[0094] Fig.11 A detector system 200 is depicted which, in addition to a multi-detector 209 and a projection lens 205, also has a dispersion generating element 700. By way of example, such a dispersion generating element may be a sector magnetic field. The interaction products entering the dispersion generating element 700 are split in the dispersion generating element 700 according to their kinetic energy. In this case, the multi-detector 209 (e.g. Figure 7 Each detector area has a plurality of detection fields 216a, 216b. The interaction products from the various field areas in the plane 101 thus impinge on different detection fields 216a, 216b in the same detection area 215b due to the dispersion in the dispersion generating element 700. Due to a suitable evaluation of the detector signals in these different detection fields, image information can again be obtained, which depends on the kinetic energy of the interaction products detected in the corresponding detection fields. Since the kinetic energy of the interaction products in turn depends on the electrostatic potential at the location where the interaction products leave the first plane 101, a voltage contrast image can be generated in this way.

[0095] By assessing the signal distribution in the detection field belonging to the same detection area, it is possible to draw a conclusion about the adjustment state of the entire system. These conclusions or this information can be used to readjust the system or activate the automated adjustment action in an automated manner. The signal distribution form or the signal offset in the inspection field belonging to the same detection area are assessed and can also be used to draw a conclusion about focusing parameters or other parameters (such as the inclination of the object surface). In addition or alternatively, the signal distribution in the inspection field belonging to the same detection area can be averaged over multiple detection fields and / or over a period of time. This then provides information about overall object characteristics, such as the overall inclination of the object surface relative to the optical axis of the particle beam system.

[0096] Fig.16 A method is described which can be implemented using a particle beam instrument and by which image information of an object surface with an amplified morphological effect can be obtained. In a first step, a primary charged particle beam is used in each case in a plurality of mutually separated field regions to simultaneously irradiate the surface of the object. Here, in step 902, the interaction products emitted from the object due to the incident primary particle beam are collected by means of a first suction field and the interaction products collected by the first suction field are projected onto a plurality of detection regions of a detector in such a way that the interaction products from two different field regions are projected onto different detection regions of the detector. Afterwards, in a further step 903, a primary charged particle beam is used again in the plurality of mutually separated field regions to simultaneously irradiate the surface of the object. Here, in step 904, the interaction products emitted from the object due to the incident primary particle beam are collected by means of a second suction field, wherein the second suction field is different from the first suction field. Here, the interaction products collected by the second suction field are further projected onto the multiple detection areas of the detector in such a way that the interaction products from two different field areas of the object are projected onto different detection areas of the detector. In the subsequent step 905, the signals detected under the two different suction field conditions are evaluated together, and in step 906, a data signal highlighting the topographic effect of the object is obtained from the detector signals obtained under the different suction field conditions. The two suction fields in steps 901 and 903 should be significantly different from each other in this case; specifically, at the surface of the object, the electric field strength of the stronger suction field should be at least 10% greater than the electric field strength of the weaker suction field, and even better, more than 20%. At the same time, the electric field strength of the stronger suction field should be at least 100V / mm greater than the electric field strength of the weaker suction field.

Claims

1. A detection system for use in a multi-beam charged particle system, comprising: a multi-detector comprising a plurality of detection fields for each of a plurality of detection regions; as well as Controller, configured as: acquiring a set of intensity signals from the plurality of detection fields; determining at least one single continuous region of the beam spot based on the set of intensity signals; as well as determining a detection field group of the plurality of detection fields within the beam spot based on the at least one single continuous area, wherein the controller is configured to determine an intensity value of the beam spot based on detector signals received from the detection field group, and to generate an image of the object based on the intensity value, wherein the controller is configured to analyze the intensity signal detected in the detection field of the detection area to obtain additional information, The additional information is at least one piece of information selected from the following information group: additional information about the topography of the object being examined at the location at which the associated partial particle beam impinges on the object, additional information about the material composition of the object at the corresponding location on the surface of the object, Additional information about the atomic mass number at the surface of the object, Additional information about the shift in the intensity distribution of the detected interaction products.

2. The detection system according to claim 1, wherein: The controller is configured to highlight an edge of the image based on the additional information.

3. The detection system according to claim 1, wherein: The multi-detector includes a CCD camera with an upstream scintillator.

4. The detection system according to claim 1, wherein: The multi-detector includes a scintillator and an optical cable comprising at least one optical fiber for each detection field.

5. The detection system according to claim 1, wherein: The multiple detectors include pixelated electronic detectors.

6. The detection system according to claim 1, wherein: The beam spot is generated by a charged particle beam, and the charged particle beam is generated by the multi-beam charged particle system.

7. The detection system according to claim 6, wherein: The intensity signal is generated by a product of interaction of the charged particle beam with an object in an object field of the multi-beam charged particle system.

8. A method for obtaining image information, comprising: projecting interaction products originating from a first region of a first plane onto a first detection region of a detector system; projecting interaction products originating from a second region of the first plane onto a second detection region of the detector system; as well as modifying an association between the first and second areas and first and second detection fields assigned to the first and second areas, Modifying the association includes: determining a local intensity distribution of the detection area; determining a detection field in an individual detection area from the determined local intensity distribution of the detection area; and The detection fields are combined to define two new detection regions such that for each of the two new detection regions the corresponding intensity distribution lies completely within the new detection region.

9. The method according to claim 8, further comprising: integrating all detector signals of all detection fields assigned to the same detection area to obtain image signals associated with corresponding points in the first plane.

10. The method according to claim 8, wherein: Each of the two new detection areas contains a different number of detection fields from the number of detection fields in each of the first detection area and the second detection area.

11. The method according to claim 8, wherein: Modifying the correlation involves finding simple contiguous regions of increased signal intensity and determining beam positions.

12. The method of claim 8, comprising modifying the association at least once per frame.

13. The method according to claim 8, further comprising: analyzing the intensity distribution detected in the detection field of the detection area to obtain additional information.

14. The method according to claim 13, wherein: The analysis includes determining the deviation of the intensity distribution from rotational symmetry or a displacement of the intensity distribution.

15. The method of claim 13, further comprising: evaluating the additional information, and improving the image information based on the additional information.

16. The method according to claim 15, wherein: Improving the image information includes highlighting edges of the image based on the image information.

17. The method of claim 14, further comprising generating an auto-focus signal based on the determined displacement of the intensity distribution or the deviation of the intensity distribution from rotational symmetry.

18. The method of claim 8, further comprising: using a multi-beam charged particle system to provide at least one charged particle beam, the at least one charged particle beam striking an object in a first region and a second region of the first plane to generate the interaction product.

19. A method for obtaining image information, comprising: a) detecting interaction products in individual detection fields of detection areas of the multiple detectors; b) analyzing the spatial intensity distribution of the interaction products by analyzing the detector signals emitted from the detection area; as well as c) determining a displacement of the spatial intensity distribution of the detected interaction product and a deviation of said spatial intensity distribution from rotational symmetry; as well as d) Based on c), generate an autofocus signal.

20. The method of claim 19, further comprising: simultaneously indicating intensity distributions of the particle beams of the interaction products within detection regions of the multiple detectors.

21. The method according to claim 19, wherein: The analyzing includes implementing additional information, and the method further includes: evaluating the additional information; and The image information is improved with the additional information.

Images