DE102016120902B4 - Multibeam Teilchenmikroskop - Google Patents

Abstract

A multi-beam particle microscope comprising: a multi-beam particle source (300) configured to generate a plurality of primary particle beams (3); an objective lens (102) passing through beam paths of said plurality of primary particle beams (3) and configured to respectively direct and focus the plurality of primary particle beams (3) onto an object plane (101); a detector array (200) configured to sense intensities of a plurality of secondary particle beams (9) wherein each of the secondary particle beams (9) is producible by particles caused by one of the primary particle beams (3) on an object (7) which can be arranged in the object plane (101), wherein beam paths of the secondary particle beams (9) passing through the objective lens (102); a multi-aperture plate (11) disposed between the objective lens (102) and the object plane (101), which has a plurality of apertures (37), an electrode (21) arranged between the multi-beam particle source (300) and the multi-aperture plate (11) and having an opening, and a power supply system (27), wherein different openings (37) of the multi-aperture plate (37) 11) of beam paths of different primary particle beams (3) are interspersed, wherein different openings (37) of the multi-aperture plate (11) of beam paths of different secondary particle beams (9) are interspersed, wherein the opening of the electrode (21) of the beam paths of the plurality of primary particle beams (3) and of the beam paths of the plurality of secondary particle beams (9), wherein the power supply system (27) is configured to move a particle emitter of the multi-beam particle source (300) to a first electrical potential (U1). to set the electrode (21) to a second electrical potential (U2), the multi-aperture plate (11) to a third electrical P otential (U3), and to set an object (7) which can be arranged on the object plane (101) to a fourth electric potential (U4), and where: U1 is the first electric potential and U4 is the fourth electric potential.

Description

The invention relates to a multi-beam particle microscope.

Out WO 2012/041464 A1 For example, a multi-beam particle microscope is known in which a plurality of primary particle beams of a beam of primary particle beams are focused onto an object. The primary particle beams generate secondary electrons at the locations of their impact on the object which are accelerated away from the object by an electric field applied to the object and formed into secondary particle beams which are directed to a detector array having a plurality of detectors. In this case, each individual primary particle beam generates a secondary particle beam associated with the primary particle beam at the location of its impact on the object, and the secondary particle beam strikes at least one detector of the detector arrangement assigned to it, so that by detecting the at least one detector striking it Particle intensity information can be obtained to the location of the object on which the primary particle beam is directed. The bundle of primary particle beams can be deflected by the multi-beam particle microscope and the object can be displaced relative to the multi-beam particle microscope to systematically scan the surface thereof with the primary particle beams and from the thus detected intensities of secondary particle beams form an electron micrograph to win the object.

A further education from the WO 2012/041464 A1 known multi-beam particle microscope is in the DE 10 2014 008 383 A1 described.

Compared to a particle beam microscope which uses only one primary particle beam, the simultaneous use of the plurality of primary particle beams results in an increase in throughput. In this case, multi-beam particle microscopes are also used, for example, to obtain high-resolution three-dimensional data from biological objects using a technique known as "serial block-face scanning electron microscopy". However, it has been found that with a given design of particle beam optics of the multi-beam particle microscope for a bundle of many primary particle beams having a given diameter, the number of primary particle beams in the bundle can not be arbitrarily increased.

Out US 2010/0320382 A1 Further, a multi-beam particle microscope is known, which has a plurality of multi-aperture plates, which are arranged between a multi-beam particle source and an object plane and each having a plurality of openings which are interspersed by primary particle beams and secondary particle beams. The multiple multi-aperture plates act on the primary particle beams as objective lenses by applying electrical potentials to the multi-aperture plates such that the primary particle beams are focused at the object plane as they pass through the apertures of the multi-aperture plates.

It is an object of the present invention to propose a multi-beam particle beam microscope which makes it possible to use a comparatively large number of primary particle beams or a bundle of primary particle beams in which the primary particle beams are closely spaced from each other.

This object is achieved by providing a multi-beam particle beam microscope having the features specified in the accompanying claim 1. Advantageous embodiments of the invention are specified in the attached dependent claims.

A multi-beam particle microscope according to the present invention is a multi-beam particle source configured to generate a plurality of primary particle beams, an objective lens interspersed with beam paths of the plurality of primary particle beams and configured to each of the plurality of primary particle beams To focus and focus on an object plane, a detector array which is configured to detect intensities of a plurality of secondary particle beams, wherein each of the secondary particle beams can be generated by particles, which by one of the primary particle beams at an in the object plane can be caused object, wherein a beam path of the secondary particle beams passes through the objective lens.

In operation of the multibeam particle microscope, each of the primary particle beams generates a secondary particle beam emanating from the location of the impact of the primary particle beam on the object, the intensity of which is detectable by the detector arrangement. The plurality of primary particle beams impinge on the object at spaced locations, and the detected intensities of the secondary particle beams associated with the primary particle beams may provide information about the structure of the object at the points of incidence of the primary particle beams. Here, it is possible to deflect the plurality of primary particle beams by beam deflectors of the multi-beam particle microscope to direct the primary particle beams to different locations of the object and to scan the object with the primary particle beams, to obtain an electron microscopic image of the object. Alternatively or in addition to the deflection of the primary particle beams by beam deflectors, it is possible to displace the object relative to the multi-beam particle microscope in order to direct the primary particle beams also to different locations of the object.

The beam paths of the primary particle beams and the secondary particle beams in this case designate the areas in the space within which the particles which form the primary particle beams or the secondary particle beams can be encountered during the operation of the multi-beam particle microscope. Each of these beam paths is thus delimited by a surface in the form of a tube, the trajectories of the particles of the respective particle beam extending within this tube. The arrangement of the beam paths in the space within the multi-beam particle microscope can be determined by technical considerations and simulations on the basis of technical specifications of the multi-beam particle microscope, without the multi-beam particle microscope must be in operation. It is also possible here to supplement the basis for the technical considerations and simulations with experimental findings which are obtained on the basis of a multi-beam particle microscope in operation.

The multi-beam particle microscope according to the invention further comprises a arranged between the objective lens and the object plane multi-aperture plate having a plurality of openings, wherein different openings of the multi-aperture plate of beam paths of different primary particle beams are interspersed, wherein different openings of the multi-aperture plate of beam paths of different secondary particle beams and a number of the primary particle beams passing through a same opening of the plurality of openings of the multi-aperture plate is smaller than a number of the primary particle beams. The number of primary particle beams here is the total number of those primary particle beams which are generated during operation of the multi-beam particle microscope by the multi-beam particle source, reach the object plane and for generating secondary particle beams whose intensities are detected by the detector arrangement, be used. In particular, the number of primary particle beams passing through a common aperture of the plurality of apertures of the multi-aperture plate is less than 0.1 times, more preferably less than 0.05 times, and most preferably less than 0.01, for all apertures times the number of primary particle beams.

The multi-aperture plate has a structure extending in a plane in the area where the plurality of openings are provided. The openings therein are spaced apart. The multi-aperture plate may, for example, be formed of a plate material, such as silicon, into which the openings have been introduced, for example by etching. The multi-aperture plate may, for example, also be formed as a grid which, for example, has intertwined or non-intertwined, intersecting grid bars which define or delimit the openings. The shape of the openings can be arbitrary. Exemplary shapes of openings are oval openings, in particular circular openings, rectangular openings, in particular square openings, hexagonal openings and the like.

By providing the multi-aperture plate between the objective lens and the object plane, various advantages can be achieved. For example, the multi-aperture plate results in an electric field arising immediately above the object, which is also used to accelerate the particles of secondary particle beams away from the object, acting much more uniformly on all primary particle beams than such a field as it does could be generated if the multi-aperture plate was not available. As a result, the primary particle beams are not deflected directly above the object by any components of electric fields which are oriented transversely to the beam direction of the primary particle beams or parallel to the object plane, from their intended trajectories, whereby the primary particle beams do not would hit the object at the intended positions. Furthermore, the secondary particle beams accelerated away from the object are accelerated essentially perpendicularly away from the object plane, resulting in small cross sections of the secondary particle beams whose intensities can be detected individually by the detector arrangement without particles of a secondary particle beam being detected by a detector Detector array can be detected, which is associated with another secondary particle beam. Further, the multi-aperture plate may protect the object from damage by electrical flashovers, which could occur without the presence of the multi-aperture plate between the objective lens and the object, and especially between the objective lens and the edge of some objects when strong electric fields are used to expose the particles of the secondary lens. Accelerating particle beams away from the object.

According to exemplary embodiments, the number of primary particle beams is greater than 50, and the number of primary particle beams, the the same aperture of the plurality of apertures of the multi-aperture plate is smaller than 10, in particular smaller than 5 and in particular equal to 1. If the number of primary particle beams passing through the same aperture of the multi-aperture plate is 1, then each is the primary one Particle beams assigned their own opening of the multi-aperture plate. In particular, the number of openings of the multi-aperture plate may be equal to the number of primary particle beams. However, it is also possible that the number of openings of the multi-aperture plate is larger than the number of primary particle beams. In particular, in this case openings can be provided in the multi-aperture plate, which are arranged between such openings, which are penetrated by directly adjacent primary particle beams. In this case, in particular, a secondary particle beam generated by a primary particle beam can pass through a plurality of openings of the multi-aperture plate.

The multi-beam particle microscope of the present invention further comprises an electrode disposed between the multi-beam particle source and the multi-aperture plate having an opening interspersed with the beam paths of the plurality of primary particle beams and the plurality of secondary particle beams. For example, this electrode may be formed by a component of the objective lens or may be formed as a component which is not part of the objective lens, which is disposed near the objective lens. A potential difference between the potential of this electrode and the potential of the multi-aperture plate determines an electric field which accelerates particles of the secondary particle beams which have penetrated openings of the multi-aperture plate toward the detector array and particles of the primary particle beams before passing through the openings of the multi-aperture plate and delays the impact on the object.

The multi-beam particle microscope of the present invention further includes a power supply system configured to set a particle emitter of the multi-beam particle source to a first electric potential, set the electrode to a second electric potential, set the multi-aperture plate to a third electric potential, and to set an object that can be arranged on the object plane to a fourth electrical potential. In this case, it is possible for one or more of the mentioned electrical potentials to be a ground potential of the multi-beam particle microscope.

Here, the potential difference between the particle emitter of the multi-beam source and the object, which potential difference determines the landing energy of the particles of the primary particle beam, is between 50 V and 3 kV.

According to further exemplary embodiments, the potential difference between the particle emitter of the multi-beam particle source and the electrode, which potential difference determines the kinetic energy of the particles of the primary particle beam before they are decelerated in an electric field between the electrode and the multi-aperture plate, is greater than 5 kV ,

According to further exemplary embodiments, the potential difference between the electrode and the multi-aperture plate is greater than 3 kV, greater than 5 kV, greater than 8 kV, greater than 10 kV, or greater than 20 kV.

According to further exemplary embodiments, the potential difference between the electrical potential of the electrode and the electrical potential of the multi-aperture plate is greater than a 50-fold, in particular greater than a 100-fold, the potential difference between the electric potential of the multi-aperture plate and the electrical potential of the object.

According to further exemplary embodiments, the multi-aperture plate is disposed a first distance from the electrode, such that this first distance and the potential difference between the multi-aperture plate and the electrode determine an electric field strength E1 at an electrode facing surface of the multi-aperture plate. Furthermore, the multi-aperture plate is arranged at a second distance from the object plane, such that the second distance and a potential difference between the multi-aperture plate and the object determine an electric field strength E2 at a surface of the multi-aperture plate that assigns to the object plane. According to exemplary embodiments, the electric field strengths E1 and E2 are as follows: $$0.7<\left|\text{E1}/\text{E2}\right|<\mathrm{1.5.}$$

Accordingly, assuming a sufficiently thin multi-aperture plate, a difference between the electric fields on both sides of the multi-aperture plate is not very large, so that the apertures of the plate have little focusing or defocusing effect on the particle beams passing through the apertures and these on their way towards the object or away from the object by the multi-aperture plate are only slightly influenced.

According to exemplary embodiments, the electric field strength E1 at the electrode facing surface of the multi-aperture plate is greater than 500 V / mm or greater than 1500 V / mm or even greater than 3000 V / mm.

According to exemplary embodiments, the electric field strength E2 at the surface of the multi-aperture plate facing the object plane is in a range of 500 V / mm to 1500 V / mm or in a range of 500 V / mm to 3000 V / mm or in a range of 500 V / mm up to 5000 V / mm.

According to exemplary embodiments, the distance between the multi-aperture plate and the object plane is less than 200 μm and greater than 50 μm or 1 μm, in particular less than 50 μm and greater than 30 μm or 1 μm, in particular less than 30 μm and greater than 20 μm or 1 μm, in particular less than 20 μm and greater than 10 μm or 1 μm and in particular less than 10 μm and greater than 1 μm. Such a small distance between the multi-aperture plate and the object causes the particles of the primary particle beam after passing through the multi-aperture plate to travel only a very short distance before they hit the object. Therefore, the locations of incidence of the primary particle beams on the object may differ only slightly from their desired positions due to any inhomogeneities of electric fields between the multi-aperture plate and the object.

According to exemplary embodiments, a minimum distance of two adjacent primary particle beams ("pitch") on the multi-aperture plate is less than 50 μm, in particular less than 30 μm, in particular less than 20 μm and in particular less than 12 μm.

According to further exemplary embodiments, the thickness of the multi-aperture plate in an environment around at least one of the openings or in the area where the plurality of openings is provided in the multi-aperture plate is less than 40 μm, in particular less than 20 μm and in particular less than 5 μm ,

The multi-beam particle microscope may include an object support configured to support the object, wherein an actuator assembly configured to displace and position the object support relative to the objective lens is provided. The positioning can be set independently, in particular in three spatial directions, so that the distance of the object from the multi-aperture plate is adjustable and the object is displaceable in two independent directions laterally relative to the direction of the primary particle beams striking the object.

According to exemplary embodiments, the multi-beam particle microscope includes a controller configured to drive that actuator assembly so that the object is a predetermined distance from the multi-aperture plate. This predetermined distance may be less than a 10-fold, in particular less than a 5-fold and in particular less than 1.5 times a minimum distance of two adjacent primary particle beams ("pitch") on the multi-aperture plate. According to exemplary embodiments, the predetermined distance is less than 200 μm, in particular less than 50 μm, in particular less than 30 μm, in particular less than 20 μm and in particular less than 10 μm.

According to exemplary embodiments, the multi-beam particle microscope includes a distance measurement module configured to provide a measurement signal representing the instantaneous distance of the multi-aperture plate from the object, wherein the controller is capable of driving the actuator assembly in response to the measurement signal by the predetermined distance to set the object and the multi-aperture plate.

According to exemplary embodiments, the distance measuring module comprises a radiation source and a radiation detector, wherein the radiation source is configured to emit radiation of a predetermined wavelength and direct it into a gap between the multi-aperture plate and the object, the radiation detector being spaced from the radiation source and to is configured to detect radiation emitted by the radiation source into the gap, and wherein the measurement signal represents a radiation intensity detected by the radiation detector. The measurement principle may be based on the fact that the gap between the object and the multi-aperture plate is considered as a waveguide for electromagnetic radiation and correspondingly a cutoff frequency or a maximum wavelength of the electromagnetic radiation exists, which can propagate in this gap. For a given wavelength of radiation emitted by the radiation source, based on the measurement signal, a predetermined distance between the multi-aperture plate and the object which is close to the distance at which the wavelength of the radiation is the cut-off wavelength can then be set relatively accurately.

According to exemplary embodiments, the multi-aperture plate is attached to the objective lens. According to alternative embodiments, the multi-aperture plate is not attached to the objective lens and can be arranged in the beam paths of the primary particle beams and the secondary particle beams or removed from these beam paths by means of an actuator to which the multi-aperture plate or a holder of the multi-aperture plate is attached , Regardless of whether the multi-aperture plate or its holder is attached to the objective lens or whether the multi-aperture plate from the Beams is removable, a stop body may be provided which, when the multi-aperture plate is arranged in the beam paths, between the objective lens and a component of the objective lens and the multi-aperture plate or the holder of the multi-aperture plate and the position of the multi-aperture plate relative to the objective lens Are defined. This abutment body may comprise an insulating material, so that it is possible to set the objective lens or the component of the objective lens and the multi-aperture plate to different electrical potentials.

According to exemplary embodiments, the multi-beam particle microscope includes at least one electron beam deflector arranged in the beam path of the primary particle beams between the multi-beam particle source and the multi-aperture plate, which is configured to deflect the primary particle beams. This makes it possible to vary the locations of incidence of the primary particle beams on the object and to scan the object with the primary particle beams.

When the multi-aperture plate is fixed relative to the objective lens, the diameter of the openings of the multi-aperture plate penetrated by the primary particle beams limits the amount of deflection of the primary particle beams for scanning the object. According to exemplary embodiments, it is hereby provided that the multi-beam particle microscope comprises an actuator which is configured to shift the multi-aperture plate back and forth in a direction oriented parallel to a plane of the multi-aperture plate relative to the objective lens. A control module may then be configured to commonly control the actuator for reciprocating the multi-aperture plate and the electron beam deflector so that the multi-aperture plate is displaced such that any given primary particle beam has the same aperture in the multi-aperture plate independent of one through the electron beam deflector generated deflection of the primary particle beam interspersed and in particular substantially centrally penetrated. In this embodiment, it is then possible to further reduce the diameter of the openings of the multi-aperture plate.

• 1 eine schematische Darstellung zur Erläuterung einer Funktionsweise eines Vielstrahl-Teilchenmikroskops gemäß einer Ausführungsform;
• 2 eine schematische Darstellung eines Teils des Vielstrahl-Teilchenmikroskops der 1;
• 3 eine schematische Darstellung eines Teils eines Vielstrahl-Teilchenmikroskops gemäß einer weiteren Ausführungsform;
• 4 eine schematische Darstellung zur Erläuterung von Strahlengängen bei einem herkömmlichen Vielstrahl-Teilchenmikroskop;
• 5 eine schematische Darstellung zur Erläuterung eines Verfahrens zum Abrastern einer Oberfläche eines Objekts mit einem anhand der 1 bis 3 erläuterten Vielstrahl-Teilchenmikroskop; und
• 6 eine schematische Darstellung zur Erläuterung eines weiteren Verfahrens zum Abrastern einer Oberfläche eines Objekts mit einem anhand der 1 bis 3 erläuterten Vielstrahl-Teilchenmikroskop.

Embodiments of the invention are explained below with reference to figures. Hereby shows:

• 1 a schematic representation for explaining an operation of a multi-beam particle microscope according to an embodiment;
• 2 a schematic representation of a portion of the multi-beam particle microscope of 1 ;
• 3 a schematic representation of a portion of a multi-beam particle microscope according to another embodiment;
• 4 a schematic representation for explaining beam paths in a conventional multi-beam particle microscope;
• 5 a schematic representation for explaining a method for scanning a surface of an object with a reference to the 1 to 3 illustrated multi-beam particle microscope; and
• 6 a schematic representation for explaining a further method for scanning a surface of an object with a reference to the 1 to 3 explained multi-beam particle microscope.

1 is a schematic representation of a multi-beam particle microscope, which uses multiple particle beams. The multi-beam particle microscope generates a plurality of primary particle beams which strike an object to be examined to generate electrons emanating from the object and formed into secondary particle beams, which are subsequently detected. The multi-beam particle microscope 1 is of the scanning electron microscope (SEM) type, which uses electron beams 3 as primary particle beams in places 5 on a surface of the object 7 hit and produce there several electron beam spots or spots. The object 7 to be examined may be of any type, including, for example, a semiconductor wafer, a biological sample, and an array of miniaturized elements or the like. The surface of the object 7 is in an object plane 101 an objective lens 102 an objective lens system 100 arranged.

The enlarged detail I _{1 of} the 1 shows a plan view of the object plane 101 with a regular rectangular field 103 of impact locations 5 of primary particle beams 3 which is in the plane 101 be formed. In 1 is the number of places of incidence 25 which are arranged as a 5 × 5 array 103. The number 25 at points of incidence is a small number chosen for the purpose of simplified presentation. In practice, the number of beams or spots of incidence may be much larger, such as 20x30, 100x100, and the like.

In the illustrated embodiment, the field is 103 of impact locations 5 a substantially regular rectangular field with a constant distance p1 between adjacent points of incidence. Exemplary values of the distance p1 are 50 μm, 30 μm or 10 μm. However, it is also possible that the field 103 has other symmetries, such as a hexagonal symmetry.

A diameter of the object plane 101 shaped beam spots can be small. Exemplary values of this diameter are 1 nm, 5 nm, 10 nm and 30 nm. Focusing the particle beams 3 for shaping the beam spots 5 takes place through the objective lens system 100 ,

The particles hitting the object, which in the example illustrated here are electrons, in turn generate particles which are essentially electrons and which from the surface of the object 7 out. The of the surface of the object 7 Outgoing particles are passed through the objective lens system 100 to secondary particle beams 9 which are electron beams in the example explained here. The multi-beam particle microscope 1 represents a secondary electron beam path 12 ready to the variety of secondary particle beams 9 a detection system 200 supply. The detection system 200 includes an electron optic with a projective lens system 205 to the secondary particle beams 9 to an electron multi-detector 209 to judge.

The section I ₂ in 1 shows a plan view of a plane 211 in which individual detection areas are arranged, to which the secondary particle beams 9 in places 213 incident. The place of arrival 213 form a second field 217 with a regular distance p2 of the places of impact from each other. Exemplary values of the distance p2 are 10 μm, 100 μm, 200 μm and 500 μm.

The primary particle beams 3 be through a multi-beam particle source 300 generates, which at least one electron source 301 with an electron emitter, at least one collimating lens 303 , a multi-aperture arrangement 305 and a field lens system 307 includes. The electron source 301 generates a divergent electron beam from electrons emitted by the electron emitter 309 passing through the collimating lens 303 is collimated to a beam 311 to form, which the multi-aperture arrangement 305 illuminated.

The section I ₃ in 1 shows a plan view of the multi-aperture arrangement 305. The multi-aperture arrangement 305 includes a multi-aperture plate 313 having a plurality of apertures formed therein 315 having. midpoints 317 the openings 315 are in a field 319 arranged which is the field 103 corresponds, which by the beam spots 5 in the object plane 101 is formed. A distance p3 of the centers 317 the apertures 315 one another may have exemplary values of 5 μm, 100 μm and 200 μm. The diameters D of the apertures 315 are smaller than the distance p3 of the centers of the apertures from each other. Exemplary values of the diameters D are 0.2 x p3, 0.4 x p3 and 0.8 x p3.

Electrons of the illuminating beam 311 enforce the apertures 315 and form electron beams 3 as primary particle beams. Electrons of the illuminating beam 311 which on the plate 313 meet, are intercepted by these and do not contribute to the formation of electron beams 3 at.

The multi-aperture arrangement 305 focuses the electron beams 3 such that in one plane 325 Strahlfoki 323 be formed. A diameter of the foci 323 may for example be 2 nm, 10 nm, 100 nm and 1 micron.

The field lens system 307 , a beam splitter 400 and the objective lens 102 provide a first imaging particle optic ready to the plane 325 in which the foci 323 be formed, via a primary beam path 10 to the object level 101 map, leaving a field there 103 of impact locations 5 or beam spots on the surface of the object 7 is formed.

The objective lens 102 , the beam splitter 400 and the projective lens system 205 provide a second imaging particle optic to the object plane 101 to the detection level 211 map. The objective lens 102 is thus a lens, which is both part of the first and the second particle optics, while the field lens system 307 only the first particle optics and the projective lens system 205 belongs only to the second particle optics. The objective lens 102 is thus penetrated both by the beam paths of the primary particle beams and by the beam paths of the secondary particle beams.

The beam splitter 400 is in the first particle optics between the multi-aperture array 305 and the objective lens system 100 arranged. The beam splitter 400 is also part of the second particle optics and is there between the objective lens system 100 and the detection system 200 arranged. The beam splitter 400 separates the beam paths of the primary particle beams from the beam paths of the secondary particle beams.

Further information on such multi-beam particle microscopes and components employed therein, such as particle sources, multi-aperture plates and lenses, may be found in International Patent Applications WO 2005/024881 A2 . WO 2007/028595 A2 . WO 2007/028596 A1 and WO 2007/060017 A2 and the patent applications US 2015/0083911 A1 . US 2015/0069235 A1 . DE 10 2014 008 383 A1 and US 6,946,655 B2 to be obtained, their disclosure respectively is fully incorporated by reference into the present application.

The multi-beam particle microscope 1 further includes one between the objective lens 102 and the object plane 101 arranged multi-aperture plate 11 , which is formed as a flat, thin plate and a plurality of openings 37 having. In the in 1 explained embodiment are in the multi-aperture plate 11 25 openings provided such that in operation of the multi-beam particle microscope 1, each of the openings 37 from a primary particle beam 3 and a secondary particle beam 9 is enforced.

The multi-aperture plate 11 has for the operation of the multi-beam particle microscope 1 an advantageous effect, which will be explained below. This is done first 4 Reference is made, which shows beam paths of primary particle beams and secondary particle beams in a multi-beam particle microscope, which does not have such a multi-aperture plate between the objective lens and the object plane.

4 is an enlarged schematic representation of a portion of a multi-beam particle microscope to effects, as in conventional multi-beam particle microscopes (see, for example WO 2012/041464 A1 ) can explain. The in 4 shown part of the multi-beam particle microscope includes inner ends of a lower pole piece 22 an objective lens 102 , an upper pole piece 21 the objective lens 102 , and a field separation electrode 18 , as well as an object holder 17 , The upper pole piece 21 and the lower pole piece 22 are at different electrical potentials to create an electric field which is present in the objective lens 102 delays the primary electrons and accelerates the secondary electrons. An object to be examined 7 is as a three-dimensional object on the object holder 17 arranged so that some of five exemplary primary particle beams 3 close to an edge 8th of the object 7 on a surface 14 of the object 7 meet the surface 14 in the object plane 101 of the multi-beam particle microscope is arranged, so that the primary particle beams 3 on the surface 14 of the object 7 are focused. Out 4 It can be seen that the three right-hand primary particle beams in the figure are substantially rectilinear to the surface 14 of the object 7 to run and impinge perpendicularly on this. Likewise, the right in the figure right three secondary particle beams 9 essentially perpendicular and straight from the surface 14 of the object 7 path. The Indian 4 left primary particle beam 3 does not run straight on the surface 14 of the object. Rather, this primary particle beam hits 3 to the left of his target point of incidence on the surface 14 of the object 7 on, wherein the target impact location at the intersection between the object plane 101 and a dashed line 3. ' , which is the beam path of the left primary particle beam 3 represents, if this is straight on the surface 14 of the object 7 to move. This deviation is due to the effect of the electric field over the surface of the object 7 near the edge 8th , This electric field is essentially determined by the geometries and the electrical potentials of the object 7 , the object holder 17 , the field separation electrode 18 and the pole shoes 21 . 22 certainly. On the one hand, this electric field brakes the particles of the primary particle beams 3 before their impact on the object 7 and on the other hand accelerates from the object 7 outgoing secondary particle beams 9 from the object 7 path. While these two desired effects are caused by the component of the electric field parallel to the axis 15 the objective lens is oriented causes the edge 8th of the three-dimensional object 7 also field components, which are oriented perpendicular to the axis 15 of the objective lens. These transverse components of the electric field lead to the deflection of the in 4 left illustrated primary particle beam 3 so that this is not at the intended location on the object 7 meets. Therefore, in such a situation with this primary particle beam, the multi-beam particle microscope generates information from a location of the object other than the location where the primary particle beam is supposed to be directed.

Furthermore, it is off 4 seen that in the 4 Left secondary particle beam shown on the left 9 which is directed towards the detector (not shown in FIG 4 ) has a more curved trajectory. This can cause this secondary particle beam 9 does not meet or not completely on the detector, which is intended to detect this secondary particle beam. Also for this reason, the information which passes through this secondary particle beam over the object 7 won, falsified.

These transverse components of the electric field between the objective lens 102 and the object 7 be through the multi-aperture plate 11 (see 1 ), which between the objective lens 102 and the object plane 101 near the object plane 101 arranged, greatly reduced. The 2 and 3 explain possible structures of this multi-aperture plate 11 whose arrangement relative to the objective lens 102 and possibilities, the various components of the multi-beam particle beam microscope 1 to set to different electrical potentials.

2 shows a simplified schematic representation of an objective lens 102 which one bobbins 19 , an upper pole piece 21 and a lower pole piece 22 so as to form a gap therebetween, at which a magnetic field focusing the primary particle beams is generated. The multi-aperture plate 11 is via an electrically insulating holder 31 at the lower pole piece 22 the objective lens 102 held and attached to these. Alternatively to the attachment of the multi-aperture plate 11 at the objective lens 102 is it possible for an actuator 23 is provided, which the aperture plate from the area between the objective lens 102 and the object plane 101 can selectively remove or arrange there, with the multi-aperture plate 11 when placed between the objective lens 102 and the object plane 101 by a suitable mechanism against the holder acting as a spacer 31 is pressed. The actuator 23 is via a control line 25 through a controller 27 of the multi-beam particle microscope 1 controlled.

The control 27 further comprises a power supply system to the particle emitter of the particle source 301 to set to a first electrical potential U1, the upper pole piece 21 the objective lens 102 to put on a second electrical potential U2, the multi-aperture plate 11 to put on a third electric potential U3, the object holder 17 with the object arranged thereon 7 to put on a fourth electric potential U4 and the lower pole piece 22 the objective lens 102 to put on a fifth electric potential U5. For supplying the electrical potentials U1, U2, U3, U4 and U5 to the particle emitter of the particle source 301 , the upper pole piece 21 , the multi-aperture plate 11 , the object holder 17 and the lower pole piece 22 are potential supply lines 29 between these components and the controller 27 intended.

One between the end of the upper pole piece 21 and the end of the lower pole piece 22 extending in the objective lens extending magnetic iron is through an electrical insulator 24 separated, which makes it possible to set the upper and lower pole piece to different electrical potentials U2 and U5. The insulator 24 This is designed so that the two to the insulator 24 geometrically overlap adjacent parts of the iron circle to achieve a low resistance to the magnetic flux.

The difference between the potentials U1 and U4 determines the kinetic energy with which the particles of the primary particle beam strike the object. This difference can, for example, assume values between 50 V and 3 kV.

In the beam path of the primary particle beams 3 can be in the particle source 301 or subsequently an electrode (anode) to accelerate the particles to a high kinetic energy so that they travel the distance to the objective lens 102 and travel through them quickly. This electrode can also be set to the second electrical potential U2. The difference between U1 and U2 then determines the kinetic energy of the particles between the multi-beam particle source and the objective 102 and may advantageously be greater than 5 kV, greater than 15 kV, or greater than 25 kV. Between the upper pole piece 21 which is set to the second electric potential U2 and the lower pole piece 22 , which is set at the fifth electric potential U5, then there is an electric field, which the primary particles on their way to the object 7 delayed and the secondary particles accelerated on their way to the detector. Further, the multi-aperture plate 11 set to the third electric potential U3. The potentials U2, U5 and U3, the distances between the upper pole piece 21 and the lower pole piece 22 along the axis 15 and the lower pole piece 22 and the multi-aperture plate 11 along the axis 15 and the diameters of the openings in the upper pole piece 21 and the lower pole piece 22 determine the strength and course of an electric field above the multi-aperture plate, which has a field strength E1 (z) on the optical axis 15. This electric field delays the particles of the primary particle beams before passing through the multi-aperture plate 11 , For example, a difference between U2 and U3 may be greater than 3 kV, greater than 5 kV, greater than 8 kV, greater than 10 kV, or greater than 20 kV. The electric field strength E1 (z) may be, for example, at a location z close above the multi-aperture plate 11 greater than 500 V / mm, greater than 1500 V / mm or greater than 3000 V / mm.

Due to a difference between the electrical potentials U3 and U4 arises between the multi-aperture plate 11 and the object 7 an electric field with a mean field strength E2, which is the kinetic energy of the particles of the primary particle beams before their impact on the object 7 further reduced. For example, the field strength E2 may be greater than 500 V / mm and less than 1500 V / mm, less than 3000 V / mm, or less than 5000 V / mm.

The field strength E1 (z) of the electric field near above the multi-aperture plate 11 can equal the average field strength E2 of the electric field between the multi-aperture plate 11 and the object 7 or, for example, these two field strengths may differ by less than 30% or less than 50% from each other, which is also approximately equal by the relation 0.7 <| E1 / E2 | <1.5 can be expressed. In this case, the primary particle beams undergo a very thin multi-aperture plate as they pass through the openings 11 no or just a little focusing or defocusing effect. For example, the magnitude of the difference between U2 and U3 may be greater than a 50-fold or greater than a 100-fold of the magnitude of the difference between U3 and U4.

3 is one of the 2 similar, enlarged view of the area around the multi-aperture plate 11 to explain geometric relations. The multi-aperture plate 11 has a central portion of a lateral extent D1, in which the openings 37 are provided, which are enforced by the primary particle beams. In the sectional view of 3 This central area contains five openings in the sectional plane of the figure 37 , each of which is a primary electron beam 3 to be interspersed. In practice, this number can be much larger. The extent D1 can be, for example, 50 μm to 3000 μm and in particular 100 μm to 1000 μm. In the area of the extent D1, in which the of the primary particle beams 3 interspersed openings 37 are provided has the multi-aperture plate 11 a thickness of, for example, less than 40 microns, less than 20 microns and especially less than 5 microns. In this area extends the object plane 101 assigning surface of the multi-aperture plate 11 along a plane, leaving all openings 37 the multi-aperture plate 11 with an equal distance h1 from the object plane 101 or the surface 14 of the object 7 are arranged. This distance h1 can have, for example, values of 200 μm, 50 μm, 30 μm, 20 μm and 10 μm.

The area with the openings 37 which of the primary particle beams 3 can be interspersed, of additional openings 38 in the multi-aperture plate 11 which, for example, is a periodic continuation of a pattern of the primary particle beams 3 interspersed openings 37 can form.

Because the multi-aperture plate 11 in the region with the openings penetrated by the primary particle beams 3 37 is very thin and very close to the object plane 101 is arranged, it may be advantageous to this area through a mounting portion 33 of the multi-aperture plate 11 to surround, which with a greater distance h2 from the object plane 101 is arranged and may have a greater thickness to provide greater mechanical stability. In this area 33 is also the stop element 31 on the multi-aperture plate 11 on which the multi-aperture plate 11 relative to the lower pole piece 22 the objective lens 102 supported.

Between the central area where the openings 37 . 38 are arranged and the mounting area 33 can be a transition area 35 be arranged, in which the thickness of the multi-aperture plate 11 towards the mounting area 33 increases and / or the distance to the object plane 101 increases. This transition region extends in a ring between the central region with the diameter D2 and the inner edge of the support region 33 with a diameter D3. For example, D2 may be one and a half times greater, two times greater, or three times greater than D1.

The distance P1 from centers of adjacent openings 37 the multi-aperture plate 11 ("Pitch") was already related to 1 explained. The distance h1 of the multi-aperture plate 11 from the object plane 101 For example, it may be less than 10 times, less than 4 times, or less than 1.5 times the distance P1 of the openings 37 be from each other.

The multi-beam particle microscope comprises an actuator 39 which the object holder 17 relative to the objective lens 102 relocated. This actuator is via a control line 41 to a controller (in 3 not shown).

By controlling the actuator 39 The controller can be the object holder 17 and with it the object 7 in three spatial directions relative to the objective lens shift. This makes it possible, in particular, the distance h1 of the surface 14 of the object 7 from the multi-aperture plate 11 to set to a desired value. For this purpose, it is desirable to measure the current value of the distance h1 and to perform the control of the actuator in dependence on the measured value of the distance h1, which is why the multi-beam particle microscope 1 may further comprise a distance measuring module.

In the basis of the 3 explained embodiment, the distance measuring module comprises a radiation source 43 and a radiation detector 45 , which via a signal line 46 to the controller 27 connected. The radiation source 43 emits radiation 44 into the gap between the multi-aperture plate 11 and the object 7 , where this radiation 44 from the radiation detector 45 is detected after passing through the gap. The one from the detector 45 Detected radiation intensity depends on the width of the gap, ie the distance h1 between the multi-aperture plate 11 and the surface of the object 7 from. In particular, the propagation of radiation in the gap is for wavelengths of radiation 44 , which are greater than a cut-off wavelength equal to twice h1, not possible. Therefore, it is possible to set the distance h1 with high sensitivity to be equal to 0.5 times the wavelength of the radiation 44 is. The radiation source 43 is then advantageously selected as a function of the desired distance h1. For example, the radiation source 43 a CO2 laser whose emitted radiation has a wavelength of 10.6 microns.

Alternatively and additionally, the distance h1 can be measured in the following manner: The controller first operates the multi-beam particle microscope in such a way that one or more or all of the particle beams are respectively separated by the opening associated with the particle beam 37 the multi-aperture plate 11 through to the surface 14 of the object 7 to meet. There, the particle beams are focused. The focusing can be done, for example, by scanning a small field on the surface of the object containing the particle beams, which contains structures. These structures are then recognizable in the electron micrograph of this field. The focusing of the particle beams can be changed individually or jointly until a sharpness of the structures in the image becomes maximum. It can be assumed that in this case the focusing of the particle beam (s) is optimal. The focusing of the particle beams can be automated with the aid of a suitable autofocus routine. Based on the recorded images, it is possible to assess automatically at which setting the focus is maximum. Determining this setting is part of the method used to measure the distance. Other strategies for focusing the particle beams are conceivable. To change the focusing of the particle beams, for example, adjustments of focusing lens excitations in the beam path of the particle beams or of accelerating or retarding electric fields in the beam paths of the particle beams and the like can be changed. The adjustments of the excitations and / or electric fields and / or other effects affecting the particle beams, in which the focusing of the particle beam (s) on the object is achieved, are stored.

Thereafter, the controller operates the multi-beam particle microscope so that one or more of the particle beams in addition to the respective particle beam associated opening are directed to the multi-aperture plate itself and focused there according to the method explained above. As a structure whose image sharpness can be evaluated in an electron microscopic image, for example, the edge or the edge of an opening 37 in the multi-aperture plate 11 serve, or it may be suitable structures by engraving or etching or the like on the object 7 groundbreaking surface of the multi-aperture plate 11 be targeted. This focusing of the particle beams can also be automated with the aid of a suitable autofocus routine, as has been explained above. Based on recorded images, it is again possible to assess automatically at which setting the focus is maximum. Determining this setting is another part of measuring the distance h1 between the multi-aperture plate 11 and the object 7 performed procedure. The two settings for focusing the particle beam (s) on the multi-aperture plate and for focusing the particle beams on the object are different and can be compared. If properly calibrated, these settings and their differences can be used to determine the distance h1 of the multi-aperture plate 11 from the surface 14 of the object 7 be determined. Sets of values indicating the two settings, or sets of values indicating the differences between the two settings, or values already indicating the distance h1 between the multi-aperture plate and the object in a suitable unit length, are themselves a result of the distance measurement and are therefore suitable for providing a distance measurement signal. The activation of the actuator 39 can therefore be done based on this distance measurement signal, which is determined from the setting of the multi-beam particle microscope when focusing the particle beam on the object and the setting of the multi-beam particle microscope when focusing the particle beam on the multi-aperture plate. The distance measuring module can thus be embodied in the control of the multi-beam particle microscope, which controls the operation of the multi-beam particle microscope.

To deal with the multi-beam particle microscope 1 an electron microscopic image of the object 7 The places of arrival must win 5 the primary particle beams 3 systematically over the surface 14 of the object 7 be moved, ie the surface 14 of the object 7 must be with the primary particle beams 3 be scanned. This includes the multi-beam particle microscope 1 deflector 49 (please refer 2 ), which, for example, within the objective lens 102 may be arranged to the bundle of primary particle beams 3 distract, as is common in Scanning Electron Microscopes. Because the primary particle beams are the openings 37 in the multi-aperture plate 11 have to push through to the surface 14 of the object 7 to arrive, is the maximum beam deflection through the diameter of the openings 37 limited. Accordingly, the areas of the surface can 14 of the object 7 which are not below the openings 37 the multi-aperture plate 11 are arranged, not completely scanned. However, it is possible the object 7 using the actuator 39 relative to the objective lens 102 shift laterally to the surface 14 gradually scrape the object completely, as will be explained below with reference to Figures 5 and 6.

5 shows an enlarged section I ₁ of 1 corresponding plan view of the object level 101 wherein collision points of the primary particle beams, which are not deflected by deflectors in the objective lens or other deflectors, are crossed 5 are shown. Also in 5 For simplicity of illustration, only 5x5 = 25 primary beams are shown. As explained above, this number can be much larger. It is assumed that the openings 37 in the multi-aperture plate 11 are so large that by deflecting the particle beams an object field 1151 in the vicinity of the place of impact 5 of the undeflected particle beam can be scanned, wherein for only two particle beams the object fields 1151 in 5 are shown. In the embodiment of 5 is the edge length of the object fields 1151 a little more than half of that in the enlarged section I ₁ in 1 shown distance p1. It can be seen that with such a small object field 115 ₁ with the particle beams only a fraction of the in 5 represented area of the object plane 101 can be scanned when the object 7 not relative to the objective lens 102 is relocated. Therefore, after scanning the object fields 115 ₁ and extracting the particle microscopic information from these object fields 115 _1, the object becomes 7 relative to the objective lens 102 so shifts that in 5 fields of the object labeled 1152 are arranged such that the locations of incidence 5 the undeflected particle beams in the center of the fields 1152 lie. These fields 1152 then coincide with the object fields of the respective particle beams and can be scanned. This process is repeated by moving the object 7 relative to the objective lens 102 subsequently the 1153 fields and then 1154 fields of the object 7 be scanned. Since this process is carried out in parallel with all 25 particle beams, then the area below the multi-aperture plate is completely scanned. Then the object becomes 7 relative to the objective lens 102 moved far to next, so far untracked fields 1155 arrange so that the place of impact 5 the undeflected particle beams in the respective centers of the fields 1155 are arranged so that the fields 1155 can coincide with the object fields of the respective particle beams and can be scanned. It can be seen that in this way the surface 14 of the object 7 can be completely scanned with particle beams. The object fields 115 preferably have overlapping edge regions (in 5 not shown). This reduces the positioning accuracy requirements when moving the object 7 relative to the objective lens 102 , The object fields 115 are joined with the aid of the imaged structures of the overlapping edge regions in a position corrected manner.

In the basis of the 5 The method is described, the object relative to the objective lens three times in succession by a small step, the increment of which is a fraction of the distance between two adjacent particle beams in the plane of the multi-aperture plate 11 is shifted to scan successively the areas 115 ₁ , 1152, 1153 and 1154, whereupon the object is displaced by a large step to scan the fields 115 _5, etc. The displacement of the object relative to the objective lens thus occurs stepwise, in FIG different sized steps and steps in different directions. It should be noted that in cases where the size of the openings 37 in the multi-aperture plate 11 requires smaller object fields, rather than the in 5 shown four fields 115 ₁ , 115 ₂ , 115 ₃ and 115 ₄ a larger number of fields, for example, 3 × 3 = 9 fields or 3 × 4 = 12 fields, with shifts in small steps can be scanned to the object 7 completely rasterize.

A method by which large portions of the surface of the object can be scanned with substantially uniform movement of the object relative to the objective lens will be described below with reference to FIGS 6 explained. 6 is one of the 5 corresponding representation that a plan view of the object plane 101 is shown and places of incidence of undeflected particle beams by crosses 5 are shown. The place of arrival 5 The undeflected particle beams are arranged in a rectangular grid whose grating vectors in 6 represented by arrows x and y. The displacement of the object relative to the objective lens takes place in a direction which is represented by an arrow v, which is oriented at an angle α relative to the grating vector x. While the uniform motion of the object 7 relative to the objective lens 102 is performed, the particle beams are each deflected in a direction perpendicular to the vector v, so that each particle beam, a band-shaped surface area 119 a width b of the surface 14 of the object 7 scans. The angle α is dimensioned such that for a given width b of the band-shaped surface areas 119 the particle beam through the left particle beam of the lowest row of particle beams in 6 scanned band-shaped surface area 119 at the band-shaped surface area scanned from below by the right particle beam in the second row 119 connects or slightly overlapped with it. In 6 For the sake of clarity, only four of the band-shaped surface areas are 119 however, it will be appreciated that with uniform movement of the object relative to the objective lens, a strip of the object may be scanned whose width is approximately the extent of the field of impact locations 5 corresponding to unexposed particle beams. Several such juxtaposed or slightly overlapping stripes can be scanned one after the other to rasterize the surface of an arbitrarily extended object.

The maximum deflection of the primary particle beams 3 is in particular by the diameter of the openings 37 limited when the multi-aperture plate 11 relative to the objective lens 102 is fixed. In 3 an alternative to this is shown schematically, which is a lateral displacement of the multi-aperture plate 11 together with the deflection of the primary particle beams through the beam deflectors 49 allows. On via a control line 51 from the controller 27 controlled actuator 53 is at the bracket area 33 the multi-aperture plate 11 coupled to these with respect to the objective lens 102 to shift laterally back and forth, as in 3 by a double arrow 54 is indicated. Such a shift of the multi-aperture plate 11 is especially possible in embodiments that support the 31 which the mounting area 33 the multi-aperture plate 11 relative to the lower pole piece 22 the objective lens 102 supports, not exhibit. The control 27 then controls the lateral displacement of the multi-aperture plate 11 such that the openings 37 the multi-aperture plate 11 which of the primary particle beams 3 be penetrated, in their deflection by the Strahlablenker 49 be moved. It is then possible, the diameter of the openings 37 to choose smaller.

Claims (24)

A multi-beam particle microscope comprising: a multi-beam particle source (300) configured to generate a plurality of primary particle beams (3); an objective lens (102) interspersed with beam paths of the plurality of primary particle beams (3) and configured to direct and focus the plurality of primary particle beams (3), respectively, on an object plane (101); a detector array (200) configured to detect intensities of a plurality of secondary particle beams (9), each of the secondary particle beams (9) being producible by particles passing through one of the primary particle beams (3) an object (7) which can be arranged in the object plane (101), beam paths of the secondary particle beams (9) passing through the objective lens (102); a multi-aperture plate (11) disposed between the objective lens (102) and the object plane (101) having a plurality of apertures (37), an electrode (21) interposed between the multi-beam particle source (300) and the multi-aperture plate (11) is arranged and has an opening, and a power supply system (27); wherein different openings (37) of the multi-aperture plate (11) of beam paths of different primary particle beams (3) are interspersed, wherein various openings (37) of the multi-aperture plate (11) of beam paths of different secondary particle beams (9) are interspersed, wherein the opening of Electrode (21) is penetrated by the beam paths of the plurality of primary particle beams (3) and by the beam paths of the plurality of secondary particle beams (9), wherein the power supply system (27) is configured to form a particle emitter of the multi-beam particle source (300 ) to set a first electrical potential (U1), to set the electrode (21) to a second electrical potential (U2), to set the multi-aperture plate (11) to a third electrical potential (U3), and an object level (U3) 101) to be placed on a fourth electric potential (U4), and where: $$50\text{V <}\left|\text{U1}-\text{U4}\right|<3\text{kV}.$$

where U1 is the first electrical potential and U4 is the fourth electrical potential. Multibeam particle microscope after Claim 1 wherein the number of primary particle beams is greater than 50 and the number of primary particle beams (3) passing through the same opening (37) of the plurality of openings of the multi-aperture plate (11) is less than 10, in particular less than 5 and in particular is equal to 1. Multibeam particle microscope after Claim 1 or 2 where: $$5\text{kV <}\left|\text{U}1-\text{U}2\right|$$

or $$15\text{kV <}\left|\text{U}1-\text{U}2\right|$$

or $$25\text{kV <}\left|\text{U}1-\text{U}2\right|.$$

where U1 is the first electrical potential and U2 is the second electrical potential. Multibeam particle microscope according to one of the Claims 1 to 3 where: $$\text{3 kV <}\left|\text{U2}-\text{U3}\right|$$

or $$\text{5kV <}\left|\text{U2}-\text{U3}\right|$$

or $$\text{8kV <}\left|\text{U2}-\text{U3}\right|$$

or $$\text{10kV <}\left|\text{U2}-\text{U3}\right|$$

or $$\text{20kV <}\left|\text{U2}-\text{U3}\right|.$$

where U2 is the second electrical potential and U3 is the third electrical potential. Multibeam particle microscope according to one of the Claims 1 to 4 where: $$\text{50}<\left|\text{U2}-\text{U3}\right|/\left|\text{U3}-\text{U4}\right|$$

or $$\text{100}<\left|\text{U2}-\text{U3}\right|/\left|\text{U3}-\text{U4}\right|.$$

where U2 is the second electrical potential, U3 is the third electrical potential, and U4 is the fourth electrical potential. Multibeam particle microscope according to one of the Claims 1 to 5 wherein the multi-aperture plate (11) is disposed at a first distance from the electrode (21), the multi-aperture plate (11) is disposed at a second distance (h1) from the object plane (101), and the second, third and fourth electrical potential are coordinated so that the following relation is fulfilled: $$0.7<\left|\text{E1 / E2}\right|<1.5$$

wherein E1 is an electric field strength at a surface of the multi-aperture plate (11) facing the electrode (21), and E2 is an electric field intensity at a surface of the multi-aperture plate (11) facing the object plane (101). Multibeam particle microscope after Claim 6 where: $$500\text{V / mm}<\left|\text{E1}\right|$$

or $$1500\text{V / mm}<\left|\text{E1}\right|$$

or $$\text{3000V / mm}<\left|\text{E1}\right|,$$

Multibeam particle microscope according to one of the Claims 6 or 7 where: $$500\text{V / mm}<\left|\text{E2}\right|<1500\text{V / mm}$$

or $$500\text{V / mm}<\left|\text{E2}\right|<3000\text{V / mm}$$

or $$500\text{V / mm}<\left|\text{E2}\right|<5000\text{V / mm}\text{,}$$

Multibeam particle microscope according to one of the Claims 6 to 8th , wherein the second distance (h1) is less than 200 μm, in particular less than 50 μm, in particular less than 30 μm, in particular less than 20 μm and in particular less than 10 μm. Multibeam particle microscope according to one of the Claims 1 to 9 , wherein a minimum distance of two adjacent primary particle beams (3) on the multi-aperture plate (11) is less than 50 μm, in particular less than 30 μm, in particular less than 20 μm and in particular less than 12 μm. Multibeam particle microscope according to one of the Claims 1 to 10 wherein a thickness of the multi-aperture plate (11) in an environment around at least one of the openings (37) is less than 40 μm, in particular less than 20 μm, in particular less than 5 μm. Multibeam particle microscope according to one of the Claims 1 to 11 further comprising an object holder (17) configured to support the object (7) and an actuator assembly (39) configured to displace the object holder (17) relative to the objective lens (102). Multibeam particle microscope after Claim 12 , further comprising a controller (27) configured to drive the actuator assembly (39) such that the object (7) has a predetermined distance (h1) from the multi-aperture plate (11). Multibeam particle microscope after Claim 13 , wherein the predetermined distance (h1) is less than a 10-fold, in particular less than a 5-fold and in particular less than a 1.5-fold a minimum distance (p1) of two adjacent primary particle beams (3) on the multi-aperture plate (11). Multibeam particle microscope after Claim 13 or 14 , Wherein the predetermined distance (h1) is less than 200 .mu.m, in particular less than 50 .mu.m, in particular less than 30 .mu.m, in particular less than 20 .mu.m and in particular less than 10 .mu.m. Multibeam particle microscope according to one of the Claims 13 to 15 , further comprising a distance measuring module configured to provide a measurement signal representing the distance (h1) of the multi-aperture plate (11) from the object (7), and wherein the controller (27) controls the actuator assembly (39) in response to the Actuates measuring signal. Multibeam particle microscope after Claim 16 wherein the distance measuring module comprises a radiation source (43) and a radiation detector (45), wherein the radiation source (43) is configured to emit radiation (44) of a predetermined wavelength and into a gap between the multi-aperture plate (11) and the object ( 7), wherein the radiation detector (45) is spaced from the radiation source (43) and is configured to detect radiation (44) emitted into the gap from the radiation source (43), and wherein the measurement signal is one of Radiation detector (45) represents detected radiation intensity. Multibeam particle microscope after Claim 16 wherein the distance measuring module is configured to direct at least one of the primary particle beams (3) through one of the openings (37) of the multi-aperture plate (11) onto the object (7) and focus there by changing a setting of the multi-beam particle microscope to direct the primary particle beam (3) next to one of the openings (37) of the multi-aperture plate (11) to the multi-aperture plate (11) itself and to focus there by changing the setting of the multi-beam particle microscope, and the measurement signal based on the determined setting of the multi-beam particle microscope when focusing the particle beam on the object and the determined setting of the multi-beam particle microscope when focusing the particle beam on the multi-aperture plate provide. Multibeam particle microscope according to one of the Claims 1 to 18 , wherein on a the object plane (101) facing pole piece (22) of the objective lens (102) a stop body (31) is mounted on which a holder (33) of the multi-aperture plate (11). Multibeam particle microscope after Claim 19 wherein the stop body (31) comprises an insulating material. Multibeam particle microscope according to one of the Claims 1 to 20 further comprising an actuator (53) configured to reciprocate the multi-aperture plate (11) in a direction (54) oriented parallel to a plane of the multi-aperture plate (11) relative to the objective lens (102) relocate. Multibeam particle microscope after Claim 21 further comprising an electron beam deflector (49) disposed in the beam path of the primary particle beams (3) between the multi-beam particle source (300) and the multi-aperture plate (11) and configured to deflect the primary particle beams (3). Multibeam particle microscope after Claim 22 , further comprising a control module (27) configured to commonly drive the actuator (53) and the electron beam deflector (49) so as to displace the multi-aperture plate (11) such that each given primary particle beam (3) exposes the one the same opening (37) in the multi-aperture plate (11) regardless of a by the electron beam deflector (49) generated deflection of the primary particle beam (3) passes through and in particular substantially centrally penetrated. Multibeam particle microscope after Claim 23 wherein the deflection of the primary particle beam (3) by the electron beam deflector (49) is so large that in the plane of the multi-aperture plate (11) an area of a surface swept by the primary particle beam (3) is larger than a diameter of the opening (37) Multi-aperture plate (11).

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