PARTICLE BEAM SYSTEM WITH MULTI-SOURCE SYSTEM AND MULTI-BEAM PARTICLE MICROSCOPE

Abstract

A particle beam system includes a multi-source system. The multi-source system comprises an electron emitter array as a particle multi-source. The inhomogeneous emission characteristics of the various emitters in this multi-source system are correctable, or pre-correctable for subsequent particle-optical imaging, via particle-optical components that are producible via MEMS technology. A beam current of the individual particle beams is adjustable in the multi-source system.

Claims

1. A particle beam system, comprising: a multi-source system, comprising: a particle multi-source configured to generate a multiplicity of charged individual particle beams via field emission; a first multi-aperture plate comprising a multiplicity of first openings configured to have the charged individual particle beams at least partly pass therethrough; a first multi-lens array comprising a multiplicity of individually adjustable particle lenses, the first multi-lens array downstream of the first multi-aperture plate along a beam path of charged individual particle beams so that the charged individual particle beams which pass through the first multi-aperture plate also pass through the first multi-lens array; a second multi-aperture plate comprising a multiplicity of second openings, the second multi-aperture plate downstream of the first multi-lens array along the beam path of charged individual particle beams so that the charged individual particle beams which pass through the first multi-lens array also pass through the second multi-aperture plate; a beam current-restricting multi-aperture plate comprising a multiplicity of beam current-restricting openings, the beam current-restricting multi-aperture plate downstream of the second multi-aperture plate along the beam path of charged individual particle beams so that the charged individual particle beams are partly incident on the beam current-restricting multi-aperture plate and absorbed there and partly pass through the openings in the beam current-restricting multi-aperture plate; and a controller configured to supply an individually adjustable voltage to the particle lenses of the first multi-lens array to individually adjust a focusing of the associated particle lens for each individual particle beam.

2. The particle beam system of claim 1, further comprising a beam-shaping system downstream of the multi-source system along the beam path of charged individual particle beams, wherein the beam-shaping system is configured to provide a final shape of the charged individual particle beams for subsequent optical imaging.

3. The particle beam system of claim 2, further comprising: a condenser lens system downstream of the multi-source system along the beam path of charged individual particle beams and upstream of the final beam-shaping system along the beam path of charged individual particle beams; a field lens system downstream of the final beam-shaping system along the beam path of charged individual particle beams; and an objective lens system downstream of the field lens system along the beam path of charged individual particle beams, wherein the particle beam system is configured to form an intermediate image plane between the beam-shaping system and the field lens system.

4. The particle beam system of claim 3, wherein the beam-shaping system comprises: a multi-aperture plate comprising a multiplicity of openings, the multi-aperture plate configured so that the charged individual particle beams are partly incident on the multi-aperture plate and absorbed there and partly pass through the openings in the multi-aperture plate; and a second multi-lens array comprising a multiplicity of adjustable particle lenses, the second multi-lens array arranged along the beam path of charged individual particle beams downstream of the multi-aperture plate so that the charged individual particle beams which pass through the multi-aperture plate substantially also pass through the second multi-lens array.

5. The particle beam system of claim 3, wherein the condenser lens system comprises condenser lenses.

6. The particle beam system of claim 3, wherein the condenser lens system comprises a condenser lens array which comprises a multiplicity of openings configured to have the charged individual particle beams pass therethrough.

7. The particle beam system of claim 3, wherein the objective lens system comprises a global magnetic objective lens.

8. The particle beam system of claim 3, wherein the objective lens system comprises an objective lens array which comprises a multiplicity of openings, the objective lens along the beam path of charged individual particle beam to have the charged individual particle beams pass through the openings in the objective lens array.

9. The particle beam system of claim 8, wherein the particle beam system is configured so that no cross over of the charged individual particle beams is provided between the field lens system and the object plane.

10. The particle beam system of claim 2, wherein the beam-shaping system comprises: a multi-aperture plate with a multiplicity of openings, the multi-aperture plate configured so that the charged individual particle beams are partly incident on the multi-aperture plate and absorbed there and partly pass through the openings in the multi-aperture plate; a multi-lens plate comprising a multiplicity of openings, the multi-lens plate downstream of the multi-aperture plate along the beam path of charged individual particle beams so that the charged individual particle beams which pass through the multi-aperture plate also pass through the multi-lens plate; and a first aperture plate comprising a single opening, the first aperture plate downstream of the multi-lens plate along the beam path of charged individual particle beams so that charged individual particle beams which pass through the multi-lens plate also pass through the opening in the at least first aperture plate, wherein the controller is configured to supply an adjustable excitation to the first aperture plate.

11. The particle beam system of claim 10, further comprising a second multi-deflector array upstream of the multi-aperture plate along the beam path of charged individual particle beams, wherein the controller is configured to supply individually adjustable excitations to the second multi-deflector array to individually deflect the charged individual particle beams.

12. The particle beam system of claim 2, wherein a deviation 6 of the individual beam currents from an arithmetic mean of the beam currents immediately after the beam current-restricting multi-aperture plate has been passed through is less than or equal to 5%.

13. The particle beam system of claim 1, wherein at least one of the following holds: the first multi-aperture plate comprises an extractor electrode; the second multi-aperture plate comprises a counter electrode; and the beam current-restricting multi-aperture plate comprises an anode.

14. The particle beam system of claim 1, wherein the particle beam system is configured to have an identical first voltage applied to the first multi-aperture plate and the second multi-aperture plate, and wherein the individually adjustable voltages at the first multi-lens array differ from the first voltage.

15. The particle beam system of claim 1, wherein a distance between the particle multi-source and the beam current-restricting multi-aperture plate is greater than or equal to 0.1 mm and less than or equal to 30 mm.

16. The particle beam system of claim 1, wherein the multi-source system further comprises a suppressor electrode.

17. The particle beam system of claim 1, wherein: the multi-source system comprises a second multi-lens array which comprises a multiplicity of individually adjustable and focusing particle lenses; the second multi-lens array is downstream of the beam current-restricting multi-aperture plate along the beam path of charged individual particle beams so that the particles of the charged individual particle beams which pass through the beam current-restricting multi-aperture plate substantially also pass through the second multi-lens array; and the controller is configured to supply an individually adjustable voltage to the particle lenses of the second multi-lens array to individually set a focusing of the associated particle lens for each individual particle beam.

18. The particle beam system of claim 1, wherein: the multi-source system further comprises a first multi-deflector array configured to have the charged individual particle beams pass therethrough; the multi-source array is downstream of the beam current-restricting multi-aperture plate along the beam path of charged individual particle beams; and the controller is configured to supply individually adjustable excitations to the first multi-deflector array to individually deflect the charged individual particle beams.

19. The particle beam system of claim 1, wherein: the multi-source system further comprises a multi-stigmator array configured to have the charged individual particle beams pass therethrough; and the controller is configured to supply an adjustable excitation to the multi-stigmator array.

20. The particle beam system of claim 1, wherein the multi-source system is manufactured at least in part via MEMS technology.

21. The particle beam system of claim 1, wherein the particle multi-source comprises at least one member selected from the group consisting of metallic emitters, silicon-based emitters, and carbon nanotubes-based emitters.

22. The particle beam system of claim 1, further comprising a magnetic field generation mechanism configured so that the particle multi-source is in a magnetic field generated by the magnetic field generation mechanism.

23. The particle beam system of claim 22, wherein the magnetic field generated by the magnetic field generation mechanism has a component perpendicular and/or a component parallel to an emission direction of the charged particles from the multi-source.

24. The particle beam system of claim 22, wherein the magnetic field generation mechanism is configured so that a start angular distribution of the charged particles caused by the magnetic field following the emergence of the charged particles from the particle source depends on the radial distance between the respective particle source and the optical axis of the particle beam system.

25. A multi-beam particle microscope, comprising: a particle beam system according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0081] The disclosure may be understood even better with reference to the accompanying figures. In the figures:

[0082] FIG. 1 shows a schematic illustration of a multi-beam particle microscope;

[0083] FIG. 2 shows a schematic illustration of a multi-source system according to the disclosure;

[0084] FIG. 3 shows a schematic illustration of a particle beam system comprising a multi-source system and further system components;

[0085] FIG. 4 shows a schematic illustration of a particle beam system comprising a multi-source system, an objective lens array and further system components;

[0086] FIG. 5 shows a particle beam system for correcting the direction of individual particle beams;

[0087] FIGS. 6A-6B shows magnetic field generation mechanism above a particle multi-source according to an example;

[0088] FIGS. 7A-7B shows magnetic field generation mechanism level with a particle multi-source according to an example; and

[0089] FIGS. 8A-8B shows magnetic field generation mechanism above a particle multi-source according to an example.

DETAILED DESCRIPTION

[0090] FIG. 1 is a schematic illustration of a particle beam system 1 in the form of a multi-beam particle microscope 1, which uses a multiplicity of particle beams. The particle beam system 1 generates a multiplicity of particle beams which strike an object to be examined in order to generate there interaction products, e.g. secondary electrons, which emanate from the object and are subsequently detected. The particle beam system 1 is of the scanning electron microscope (SEM) type, which uses a plurality of primary particle beams 3 which are incident on a surface of the object 7 at a plurality of locations 5 and generate there a plurality of electron beam spots, or spots, that are spatially separated from one another. The object 7 to be examined can be of any desired type, e.g. a semiconductor wafer or a biological sample, and comprise an arrangement of miniaturized elements or the like. 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.

[0091] The enlarged excerpt I.sub.1 in FIG. 1 shows a plan view of the object plane 101 having a regular rectangular field 103 of locations of incidence 5 formed in the first plane 101. In FIG. 1, the number of locations of incidence is 25, which form a 5×5 field 103. The number 25 of locations of incidence is a number chosen for reasons of simplified illustration. In practice, the number of beams, and hence the number of locations of incidence, can be chosen to be significantly greater, such as, for example, 20×30, 100×100 and the like.

[0092] In the embodiment illustrated, the field 103 of locations of incidence 5 is a substantially regular rectangular field having a constant pitch P.sub.1 between adjacent locations of incidence. Exemplary values of the pitch P.sub.1 are 1 micrometre, 10 micrometres and 40 micrometres. However, it is also possible for the field 103 to have other symmetries, such as a hexagonal symmetry, for example.

[0093] A diameter of the beam spots shaped in the first plane 101 can be small. Exemplary values of the diameter are 1 nanometre, 5 nanometres, 10 nanometres, 100 nanometres and 200 nanometres. The focusing of the particle beams 3 for shaping the beam spots 5 is carried out by the objective lens system 100.

[0094] The primary particles striking the object generate interaction products, e.g., secondary electrons, back-scattered electrons or primary particles that have experienced a reversal of movement for other reasons, which emanate from the surface of the object 7 or from the first plane 101. The interaction products emanating from the surface of the object 7 are shaped by the objective lens 102 to form secondary particle beams 9. The particle beam system 1 provides a particle beam path 11 for guiding the multiplicity of secondary particle beams 9 to a detector system 200. The detector system 200 comprises a particle-optical unit with a projection lens 205 for directing the secondary particle beams 9 at a particle multi-detector 209.

[0095] The excerpt I.sub.2 in FIG. 1 shows a plan view of the plane 211, in which individual detection regions of the particle multi-detector 209 on which the secondary particle beams 9 are incident at the locations 213 are located. The locations of incidence 213 lie in a field 217 with a regular pitch P.sub.2 with respect to one another. Exemplary values of the pitch P.sub.2 are 10 micrometres, 100 micrometres and 200 micrometres.

[0096] The primary particle beams 3 are generated in a beam generation apparatus 300 comprising at least one particle source 301 (e.g., an electron source), at least one collimation lens 303, a multi-aperture arrangement 305 and a field lens 307, or a field lens system made of a plurality of field lenses. The particle source 301 generates at least one diverging particle beam 309, which is collimated or at least substantially collimated by the at least one collimation lens 303 in order to shape a beam 311 which illuminates the multi-aperture arrangement 305.

[0097] The excerpt I.sub.3 in FIG. 1 shows a plan view of the multi-aperture arrangement 305. The multi-aperture arrangement 305 comprises a multi-aperture plate 313, which has a plurality of openings or apertures 315 formed therein. Midpoints 317 of the openings 315 are arranged in a field 319 that is imaged onto the field 103 formed by the beam spots 5 in the object plane 101. A pitch P.sub.3 between the midpoints 317 of the apertures 315 can have exemplary values of 5 micrometres, 100 micrometres and 200 micrometres. The diameters D of the apertures 315 are smaller than the pitch P.sub.3 between the midpoints of the apertures. Exemplary values of the diameters D are 0.2× P.sub.3, 0.4× P.sub.3 and 0.8× P.sub.3.

[0098] Particles of the illuminating particle beam 311 pass through the apertures 315 and form particle beams 3. Particles of the illuminating beam 311 which strike the plate 313 are absorbed by the latter and do not contribute to the formation of the particle beams 3.

[0099] On account of an applied electrostatic field, the multi-aperture arrangement 305 focuses each of the particle beams 3 in such a way that beam foci 323 are formed in a plane 325. Alternatively, the beam foci 323 can be virtual. A diameter of the beam foci 323 can be, for example, 10 nanometres, 100 nanometres and 1 micrometre.

[0100] The field lens 307 and the objective lens 102 provide a first imaging particle-optical unit for imaging the plane 325, in which the beam foci 323 are formed, onto the first plane 101 such that a field 103 of locations of incidence 5 or beam spots arises there. Should a surface of the object 7 be arranged in the first plane, the beam spots are correspondingly formed on the object surface.

[0101] The objective lens 102 and the projection lens arrangement 205 provide a second imaging particle optical unit for imaging the first plane 101 onto the detection plane 211. The objective lens 102 is thus a lens that is part of both the first and the second particle optical unit, while the field lens 307 belongs only to the first particle optical unit and the projection lens 205 belongs only to the second particle optical unit.

[0102] A beam switch 400 is arranged in the beam path of the first particle-optical unit between the multi-aperture arrangement 305 and the objective lens system 100. The beam switch 400 is also part of the second optical unit in the beam path between the objective lens system 100 and the detector system 200.

[0103] Further information relating to such multi-beam particle beam systems and components used therein, such as, for instance, particle sources, multi-aperture plate and lenses, can be obtained from the international patent applications WO 2005/024881 A2, WO 2007/028595 A2, WO 2007/028596 A1, WO 2011/124352 A1 and WO 2007/060017 A2 and the German patent applications DE 10 2013 016 113 A1 and DE 10 2013 014 976 A1, the disclosure of which in the full scope thereof is incorporated by reference in the present application.

[0104] The multiple particle beam system furthermore comprises a computer system 10 configured both for controlling the individual particle-optical components of the multiple particle beam system and for evaluating and analysing the signals obtained by the multi detector 209. In this case, the computer system 10 can be constructed from a plurality of individual computers or components. It can also contain the controller according to the disclosure.

[0105] FIG. 2 shows a schematic illustration of a multi-source system 500 according to the disclosure. In this case, the multi-source system 500 comprises a particle multi-source, which is illustrated in the illustrated example by the particle sources 501, 502, 503 and 504. The particle multi-source is an electron emitter array, which was manufactured using MEMS technology. The emitted charged particles are electrons which are produced by field emission, for example. They form the individual particle beams 3. The individual particle beams 3 are pre-shaped in the multi-source system 500 since the luminance of the individual sources 501, 502, 503 and 504 can deviate from one another. Specifically, the beam current strength of the individual particle beams 3 is set via the multi-source system 500. Further (coarse or preliminary) beam shaping is also possible or illustrated schematically.

[0106] Specifically, the electrons leave the tips of the sources 501, 502, 503 and 504, the tips 511, 512, 513 and 514 being indicated by the tip of the “V”.

[0107] Following the emission, the individual particle beams 3 pass through the first multi-aperture plate 521, to which a voltage U.sub.1 has been applied in the illustrated example. In this case, the first multi-aperture plate 521 serves as an extractor electrode. Here, the openings in the first multi-aperture plate 521 are chosen in such a way that the first aperture plate 521 blocks parts of the emitted individual particle beams.

[0108] A first multi-lens array 523 is arranged in the beam path downstream of the first multi-aperture plate 521. It has a multiplicity of individually adjustable particle lenses, which are indicated in FIG. 2 by the flat cylinders. By way of example, these can be ring electrodes. A voltage U.sub.2+V.sub.i is applied to the first multi-lens array 523 in the example shown. In this case, the particle lenses of the first multi-lens array 523 can be controlled by way of the controller 10. The controller 10 is set up to supply an individually adjustable excitation to the particle lenses and thus individually adjust the focusing of the associated particle lens for each individual particle beam 3. A second multi-aperture plate 522 is arranged in the beam path downstream of the first multi-lens array 523. Substantially the voltage U.sub.1 is applied thereto in turn in the example shown. Consequently, the first multi-aperture plate 521, the first multi-lens array 523 and the second multi-aperture plate 522 form a sequence of Einzel-lenses for the individual particle beams 3. Overall, a focusing effect on the individual particle beams arises.

[0109] The focusing effect on the individual particle beams differs depending on how big the voltage V.sub.i is chosen to be. They are focused differently or expanded to different extents. This is evident when the beam current-restricting multi-aperture plate 524, which is arranged downstream of the second multi-aperture plate 522 in the beam path, is considered. The openings in the beam current-restricting multi-aperture plate 524 are smaller in terms of diameter than the openings in the second multi-aperture plate 522 and in the first multi-lens array 523. In general all plates or arrays are arranged in such a way that their openings are located above one another in centred fashion. According to an alternative embodiment of the disclosure, the second multi-aperture plate 522 and the beam current-restricting multi-aperture plate 524 can also be functionally combined or brought together with one another.

[0110] In the example shown, the voltage V.sub.1 is chosen in such a way that the associated lens is strongly excited or the individual particle beam 3 is strongly focused. In the process, it passes almost in full through the beam current-restricting multi-aperture plate 524. By contrast, the second and the fourth lens of the first multi-lens array 523 are less strongly excited and the individual particle beam 3 passing therethrough is expanded to a greater extent. As a consequence, a greater proportion of the associated individual particle beams 3 is blocked by the beam current-restricting multi-aperture plate 524. The third lens in the first multi-lens array 523 is strained the least and the associated individual particle beam 3 is expanded to the greatest possible extent. Accordingly, large parts of the individual particle beam 3 are blocked at the beam current-restricting multi-aperture plate 524 in this case. The voltages at the lenses in the first multi-lens array 523 can now be chosen in a targeted manner such that the beam current strength of the individual particle beams 3 is approximately the same following the passage through the beam-current restricting multi-aperture plate 524. In this way, the different luminance levels of the sources 501, 502, 503 and 504 can be corrected or can be pre-corrected for the subsequent particle-optical imaging. The following relationship can apply to deviations δ of the individual beam currents from an arithmetic mean of the beam currents immediately after the beam current-restricting multi-aperture plate 524 has been passed through: δ≤5%, such as δ≤2%, for example δ≤1%.

[0111] A multi-deflector array 525 is provided in the beam path below the beam current-restricting multi-aperture plate 524. This multi-deflector array can likewise be excited by the controller 10. Here, it is possible to apply a voltage U.sub.2 in targeted and individual fashion to each opening in the array 525. The direction of the individual particle beams 3 can be corrected on the basis of the voltage applied and the direction of the electric field in the deflector. This can be relevant if the beam 3 is incident on the beam current-restricting multi-aperture plate 524 in a manner that is not exactly parallel to the optical axis Z (not illustrated here). This may be the case if the sequence of the plates is not exactly aligned; the precision when aligning the plates with respect to one another is limited in practice, for example leading to tilted beam axes. The correction function of the deflector of the multi-deflector array 525 is illustrated in exemplary fashion for the individual particle beam 3 far right, which originates from the source 504: In this case, the individual particle beam 3 is deflected significantly to the left.

[0112] Additionally, the multi-source system 500 comprises a multi-stigmator array 526 in the example shown.

[0113] All components of the multi-source system 500 can be controlled via the controller 10 in the example shown. In this case, the controller 10 can be identical to the overall controller of a multi-beam particle microscope 1. However, this could also be a separate controller 10.

[0114] Here, the dimensions of the multi-source system 500 are comparatively small in the direction of the optical axis Z (not plotted): In the illustrated example, the overall extent in the direction of the optical axis Z can be less than 20 mm.

[0115] FIG. 3 shows a schematic illustration of a particle beam system 1 comprising a multi-source system 500 and further system components. The beam paths are presented in a much-simplified fashion. Specifically, FIG. 3 shows the integration of the multi-source system 500 according to the disclosure in already existing particle beam systems 1. A multiplicity of individual particle beams 3 are produced via the multi-source system 500 and the individual particle beams 3 are subjected to pre-shaping. For example, the different luminance levels of the sources 501, 502, 503 is compensated in the process. A condenser lens system CL1 . . . N is arranged in the beam path downstream of the multi-source system 500. For example, this can be a multiple condenser lens system. However, it would also be possible to replace the global condenser lenses CL1 . . . N with a condenser lens array.

[0116] The final beam-shaping system 600 is arranged in the beam path downstream of the condenser lens system CL1 . . . N. The latter is only presented in a schematic and much-simplified fashion. It comprises the final multi-aperture plate. However, it can also still comprise further particle-optical components, such as a third multi-lens array or a stigmator array, for example. It is generally desirable that the final beam shaping for the individual particle beams 3, which allows high quality imaging, is implemented via the final beam-shaping system 600. In this case, the individual particle beams are clipped via the final multi-aperture plate and only the centrally arranged individual particle beam constituent parts pass through the final multi-aperture plate. This allows elimination or compensation in the further beam path of aberrations which occurred in the multi-source system 500 during the beam shaping or which are yet to arise in the further beam path. After passing through the final beam-shaping system 600, the individual particle beams 3 are focused into the intermediate image plane 325. In view thereof, the illustration in FIG. 3 is likewise very much simplified in order to ensure an appropriate level of clarity. The individual particle beams 3 focused into the intermediate image plane 325 are then imaged into the object plane 101 by the subsequent particle-optical imaging. To this end, they initially pass through a field lens system FL1 . . . N, via which the individual particle beams 3 are focused. The individual particle beams 3 cross in the cross over 401 before they are focused by the global objective lens 102, a global magnetic objective lens 102 in this case, and are imaged on the sample 7 in the object plane 101 at locations of incidence 5. Secondary electron beams 9 emanate from the locations of incidence 5 and these are separated from the primary beams 3 via a beam switch 400. The detection system 200 with a particle multi-detector 209 is not shown in FIG. 3 for reasons of simplicity.

[0117] In summary, FIG. 3 shows the combination of the multi-source system 500 according to the disclosure and the final beam-shaping system 600 with global lens elements.

[0118] FIG. 4 shows a further schematic illustration of a particle beam system 1 comprising a multi-source system 500 and further system components. The beam paths are presented in a much-simplified fashion. The same reference signs in the figures label the same elements. Only the differences between FIGS. 3 and 4 are discussed in more detail below. Unlike in FIG. 3, FIG. 4 contains an objective lens array 102a. The latter is illustrated schematically and can be realized, for example, by way of an Einzel-lens array. Unlike in FIG. 3, the particle beam system 1 does not have a cross over 401. The objective lens array 102a is arranged so high up or so early in the beam path of the particles that the objective lens array 102a is arranged upstream of the (theoretical) cross over 401. Dispensing with the cross over 401 is desirable in view of the suppression of the Coulomb effect. Thus, overall, FIG. 4 shows a combination of the multi-source system 500 according to the disclosure and of the final beam-shaping system 600, both with global lens elements (condenser lens system CL1 . . . N and field lens system FL1 . . . N) and with a further micro lens system, which is present in the form of the objective lens array 102a. Here, the objective lens array 102a can have different configurations. By way of example, it can comprise a plurality of sequentially arranged multi-aperture plates, to which voltages are applied in suitable fashion and, for example, via the controller 10. In addition or as an alternative thereto, the objective lens array 102a can comprise a further multi-lens array. In the embodiment illustrated in FIG. 4, it is also possible to provide a detection unit with segmented detectors in the region of the objective lens array 102a in place of the beam switch 400 in combination with the projection path to the detection unit (the latter two are not illustrated).

[0119] FIG. 5 shows a particle beam system 1 for correcting the direction of individual particle beams 3 in a schematic and much-simplified fashion. The multi-source system 500 with its sources 501, 502, 503 and 504 is illustrated in combination with the final beam-shaping system 600. The final beam-shaping system 600 comprises a final multi-lens plate 601, through which individual particle beams 3a, 3b, 3c and 3d pass. A final multi-aperture plate (not illustrated here) is arranged above the multi-lens plate 601. Moreover, the final beam-shaping system 600 comprises aperture plates 620, 630 and 640, it being possible to apply, e.g., global electric fields thereto. As a result, the electrostatic field can be shaped in targeted fashion in the region of the final beam-shaping system 600. As an alternative, it is also possible to use magnetic fields to this end.

[0120] Specifically, the electromagnetic fields also influence the extraction field close to the final multi-aperture plate: Depending on the application of voltages to the electrodes 620, 630, 640, the lens field in the multi-lens plate 601, and hence the focusing effect on the individual beams, can have different strengths. For example, suitable voltages at the electrodes 620-640 render it possible to let the lens field in the outer region (3a, 3d) have a weaker focusing effect on the individual particle beams than in the inner region (3b, 3c). Consequently, it is possible to compensate for a field curvature possibly present, the focal distribution of which in the image field having an opposite profile. However, the field distribution at the electrodes 620-640 also acts in size-reducing fashion on the intermediate image in this case; i.e., the beam pitch between the beams in the intermediate image plane becomes smaller. A multi-deflector array 610 arranged between the multi-source system 500 and the final beam-shaping system 600 contributes to correcting the beam pitch of the individual particle beams 3a, 3b, 3c and 3d in the intermediate image (not illustrated here). In the example shown, the individual particle beams 3a and 3b are each deflected to the left while the individual particle beams 3c and 3d are deflected to the right by way of an appropriate control of the deflectors in the multi-deflector array 610. With the aid of this embodiment it is possible to influence the pitch between the individual particle beams 3 in the intermediate image plane. Specifically, it is possible to produce negative field curvature in the intermediate image plane. The magnitude of this negative field curvature can be chosen in such a way that it exactly compensates a subsequently occurring (positive) field curvature during the particle-optical imaging from the intermediate image plane into the object plane. Thus, no further field curvature correction is involved any more in that case.

[0121] Generating a magnetic field in the region of the particle multi-source allows a generalized angular momentum to be impressed in a targeted manner on the emitted particles or electrons, the generalized angular momentum contributing overall to a telecentric incidence of the individual particle beams in the object plane 101 after passing through the particle beam system. It is possible to compensate a Larmor rotation caused by the magnetic immersion in the region of the objective lens. In this respect, FIGS. 6 to 8 show a few examples:

[0122] FIG. 6A shows magnetic field generation mechanism 700 for generating a divergent magnetic field. To this end, a multiplicity of coil windings 702 are provided in a pole shoe 701 with a rotationally symmetric embodiment about the optical axis Z. The magnetic field B is oriented as per reference sign 703. Projected onto the emitter plane of the multi-source system 500, the magnetic field B has a component perpendicular to the optical axis Z. At right angles to this radial direction, emitted electrons experience a corresponding start angle distribution. A start velocity vector projected onto the emitter plane is illustrated schematically in FIG. 6B using the arrows.

[0123] FIG. 7A shows magnetic field generation mechanism for generating a homogeneous magnetic field. This magnetic field has substantially no orthogonal component to the start direction of the emitted electrons. A corresponding start angle distribution is therefore punctual or not present (cf. FIG. 7B).

[0124] FIG. 8A shows a further example for shaping the magnetic field in order to impress onto the emitted electrons a dedicated start angle distribution in the magnetic field. Two concentric pole shoes 701 and 701a are illustrated; they each comprise a multiplicity of coil windings 702 and 702a, respectively. The direction of the magnetic field lines is indicated by 703. They are oriented in opposite directions between the two pole pots 701 and 701a. Accordingly, this also yields a start angle distribution running in opposite directions for the emitted electrons (cf. FIG. 8B).

[0125] In very general terms, the provision of a magnetic field impressed in a certain manner renders it possible to influence the start angle distribution for the electrons in a targeted fashion during the emission from the multi-sources in order to subsequently ensure telecentric conditions in the particle beam system 1 upon incidence on an object 7. This facilitates, for example, a good inspection of HAR structures.

LIST OF REFERENCE SIGNS

[0126] 1 Multi-beam particle microscope [0127] 3 Primary particle beams (individual particle beams) [0128] 5 Beam spots, locations of incidence [0129] 7 Object [0130] 9 Secondary particle beams [0131] 10 Computer system, controller [0132] 100 Objective lens system [0133] 101 Object plane [0134] 102 Objective lens [0135] 102a Objective lens array [0136] 103 Field [0137] 200 Detector system [0138] 205 Projection lens [0139] 209 Particle multi-detector [0140] 211 Detection plane [0141] 213 Locations of incidence [0142] 217 Field [0143] 300 Beam generation apparatus [0144] 301 Particle source [0145] 303 Condenser lens system [0146] 305 Multi-aperture arrangement [0147] 313 Multi-aperture plate [0148] 315 Openings in the multi-aperture plate [0149] 317 Midpoints of the openings [0150] 319 Field [0151] 307 Field lens system [0152] 309 Diverging particle beam [0153] 311 Illuminating particle beam [0154] 323 Beam foci [0155] 325 Intermediate image plane [0156] 400 Beam switch [0157] 401 Cross over [0158] 500 Multi-source system [0159] 501 First particle source [0160] 502 Second particle source [0161] 503 Third particle source [0162] 504 Fourth particle source [0163] 511 First tip [0164] 512 Second tip [0165] 513 Third tip [0166] 514 Fourth tip [0167] 520 Suppressor electrode [0168] 521 First multi-aperture plate, extractor [0169] 522 Second multi-aperture plate, counter electrode [0170] 523 First multi-lens array [0171] 524 Beam current-restricting multi-aperture plate [0172] 525 Multi-deflector array [0173] 526 Multi-stigmator array [0174] 600 Final beam-shaping system [0175] 601 Multi-lens plate [0176] 602 Third multi-lens array [0177] 610 Multi-deflector array [0178] 620 Aperture plate [0179] 630 Aperture plate [0180] 640 Aperture plate [0181] 650 Electric field lines [0182] 700 Magnetic field generation mechanism [0183] 701 Pole shoe [0184] 702 Coil [0185] 703 Magnetic field [0186] Z Optical axis