DE102023005452A1 - multipole element, image error corrector and particle beam system - Google Patents

Abstract

The present invention relates to a multipole element (1). In particular, the invention relates to a multipole element (1) for generating a magnetic multipole field or for generating an electric-magnetic multipole field for a particle beam system, such as a scanning electron microscope. The multipole element (1) comprises a tube (3) which surrounds a central axis (5) of the multipole element (1); an outer space assembly (7) arranged outside the tube (3) and a vacuum space assembly (9) arranged inside the tube (3). The outer space assembly (7) comprises: a peripheral pole piece (11) which is magnetically conductive and surrounds the tube (3); a plurality of nozzles (13) which are magnetically conductive, are arranged distributed around the central axis (5) and extend from the peripheral pole piece (11) to an outer wall surface (15) of the tube (3); and a plurality of coils (17). The vacuum chamber assembly (9) comprises a plurality of pole pieces (19) which are magnetically conductive, are arranged distributed around the central axis (5) and extend from the tube (3) in the direction of the central axis (5).

Description

The present invention relates to a multipole element, an image aberration corrector with the multipole element and a particle beam system with the multipole element. In particular, the invention relates to a multipole element for generating a magnetic multipole field or for generating an electric-magnetic multipole field for a particle beam system, such as a scanning electron microscope.

Particle beam systems refer to systems in which a beam of electrically charged particles (e.g. electrons or ions) is generated and directed at a sample in order to analyze the sample or to process the sample. The particle beam can be scanned over the sample for this purpose. In an electron beam microscope, interaction products generated by the interaction of the electron beam with the sample (e.g. backscattered electrons, secondary electrons, electromagnetic radiation, light, etc.) are detected in order to analyze the sample. In an ion beam processing device, the ion beam is directed at the sample in order to process the sample, for example to remove material from the sample or to deposit or deposit it on the sample.

In such particle beam systems, multipole elements are used to manipulate or deflect the particle beam. Examples of conventional multipole elements are stigmators and aberration correctors.

In multipole elements for generating a magnetic multipole field, the magnetic multipole field is generated by coils. The coils are formed by a large number of turns of an insulated wire line. During operation, the insulation of the wire line outgasses. The particle beam is guided in a vacuum region and the outgassing of the insulation of the wire line in the vacuum region affects a vacuum generated in the vacuum region during operation of the multipole element. Encapsulations for the coils in the vacuum region are complex and expensive. It is therefore advantageous to arrange the coils outside the vacuum region.

However, for coils arranged outside the vacuum region, magnetic fluxes generated by the coils must be guided into the vacuum region so that a magnetic multipole field generated by the magnetic fluxes can act on the particle beam. EP 0 379 690 A1 discloses a multipole element in which pole pieces penetrate a partition wall of the vacuum area and are sealed by vacuum seals. However, this configuration has the problem that sealing the pole pieces is complex and the pole pieces must be provided with electrical (and thus also magnetic) insulation at another location if the magnetic multipole element is to be expanded to an electro-magnetic multipole element.

It is therefore an object of the present invention to provide a multipole element which overcomes the above-mentioned disadvantages of the prior art.

The problem is solved by a multipole element according to the independent claim. Advantageous developments of the multipole element are defined in the dependent claims. The multipole element comprises: a tube which surrounds a central axis of the multipole element; an outer space assembly which is arranged outside the tube with respect to a radial direction which is perpendicular to the central axis, and a vacuum space assembly which is arranged inside the tube with respect to the radial direction. The outer space assembly comprises: a circumferential pole piece which is magnetically conductive and surrounds the tube in a circumferential direction, wherein the circumferential direction is oriented perpendicular to the central axis and to the radial direction; a plurality of nozzles which are magnetically conductive, are arranged distributed around the central axis and extend from the circumferential pole piece counter to the radial direction to an outer wall surface of the tube; and a plurality of coils. The vacuum chamber assembly comprises: a plurality of pole pieces which are magnetically conductive, are arranged distributed around the central axis and extend from the tube in the opposite radial direction.

In the multipole element, the coils are arranged in an external space which is located outside the tube in the radial direction. During operation, a vacuum is generated in a vacuum region which is located inside the tube in the radial direction, in which a particle beam propagates, for example. Since the coils are arranged in the external space, outgassing of the coils does not affect the vacuum in the vacuum region.

The coils excite magnetic fluxes in the peripheral pole piece and the nozzles, which flow through the tube and further through the pole pieces. The magnetic flux exits the pole pieces at gaps between the pole pieces, forming a magnetic multipole field. Neither the pole pieces nor the nozzles penetrate the tube in the radial direction. It is therefore not necessary to use vacuum seals to transfer the magnetic fluxes excited in the outer space into the vacuum region to generate the magnetic multipole field. If the tube is also electrically non-conductive, the pole pieces of the vacuum assembly can easily be placed at different, high electrical potentials.

The multipole element can be used in various particle beam devices. For example, the multipole element can be used in an electron beam device, such as an electron beam microscope, or in an ion beam device, such as an ion beam processing device.

Further aspects of the invention are an image error corrector comprising at least one multipole element of the type described herein, and a particle beam system comprising at least one image error corrector of the type described herein.

character description

• 1 eine schematische Querschnittsansicht eines Multipolelements;
• 2 eine perspektivische Schnittansicht des Multipolelements;
• 3 eine schematische Querschnittsansicht eines ersten Beispiels eines Polstücks des Multipolelements;
• 4 eine schematische Querschnittsansicht eines zweiten Beispiels eines Polstücks des Multipolelements;
• 5 eine schematische Darstellung zur Erläuterung der Form von Polstücken;
• 6 eine schematische Querschnittsansicht eines dritten Beispiels eines Polstücks des Multipolelements;
• 7 eine schematische Querschnittsansicht eines vierten Beispiels eines Polstücks des Multipolelements;
• 8 eine schematische Darstellung einer Oktupol-Wicklung des Multipolelements;
• 9 eine schematische Darstellung von Quadrupol-Wicklungen des Multipolelements;
• 10 eine schematische Darstellung von Dipol-Wicklungen des Multipolelements;
• 11 eine schematische Querschnittsansicht eines weiteren Multipolelements;
• 12 eine schematische Darstellung eines Teilchenstrahlsystems.

Embodiments of the invention are explained in more detail below with reference to figures. Here:

• 1 a schematic cross-sectional view of a multipole element;
• 2 a perspective sectional view of the multipole element;
• 3 a schematic cross-sectional view of a first example of a pole piece of the multipole element;
• 4 a schematic cross-sectional view of a second example of a pole piece of the multipole element;
• 5 a schematic diagram explaining the shape of pole pieces;
• 6 a schematic cross-sectional view of a third example of a pole piece of the multipole element;
• 7 a schematic cross-sectional view of a fourth example of a pole piece of the multipole element;
• 8 a schematic representation of an octupole winding of the multipole element;
• 9 a schematic representation of quadrupole windings of the multipole element;
• 10 a schematic representation of dipole windings of the multipole element;
• 11 a schematic cross-sectional view of another multipole element;
• 12 a schematic representation of a particle beam system.

With reference to the 1 and 2 A multipole element according to an embodiment of the invention is described below. The multipole element 1 is a magnetic multipole element. This means that the multipole element is configured to generate a magnetic multipole field. Magnetic north poles and magnetic south poles are generated in equal numbers.

The geometry of the multipole element 1 is described by means of a cylindrical coordinate system, which is defined by a longitudinal direction, a radial direction R and a circumferential direction U. To simplify the description, it is assumed that the longitudinal direction coincides with a central axis 5 of the multipole element 1. The radial direction R is perpendicular to the longitudinal direction (central axis 5). The radial direction R starts perpendicularly from the central axis 5 and runs away from the central axis 5. The circumferential direction U is always perpendicular to the longitudinal direction and to the radial direction R and is parameterized by an angle of rotation around the longitudinal direction.

1 shows a schematic cross-sectional view of the multipole element 1 in a cross-sectional plane oriented perpendicular to the central axis 5. The central axis 5 and the longitudinal direction are in 1 represented by a cross in the middle of the multipole element 1. The central axis 5 and the longitudinal direction are perpendicular to the plane of the 1 . 2 shows a perspective sectional view of the multipole element 1, wherein the section is made in a plane which is spanned by the central axis 5 and the radial direction R.

The multipole element 1 comprises a tube 3 which surrounds the central axis 5 of the multipole element 1. The multipole element 1 is substantially symmetrical about the central axis 5. The tube 3 has an upper opening 6a at an upper end of the tube 3 in the longitudinal direction and has a lower opening 6b at a lower end of the tube 3 in the longitudinal direction. The tube 3 consists of a wall which encloses the central axis 5 at a distance from the central axis 5 in the circumferential direction and is elongated in the longitudinal direction. A space region which lies within the tube 3 and is completely enclosed by the upper opening 6a, the lower opening 6b and an inner wall surface 16 of the tube 3 in the radial direction is referred to as a vacuum space. During operation, a vacuum is generated in the vacuum space. A space area which lies outside the pipe 3 and is limited by the upper opening 6a, the lower opening 6b and an outer wall surface 15 of the pipe 3 in the radial direction is referred to as the outer space. In operation there is ambient pressure in the outside space (no vacuum).

The multipole element 1 further comprises an outer space assembly 7 which is arranged outside the tube 3 with respect to the radial direction R, and a vacuum space assembly 9 which is arranged inside the tube 3 with respect to the radial direction R. Accordingly, the outer space assembly 7 is located in the outer space and the vacuum space assembly 9 is located in the vacuum space. This means that all elements of the outer space assembly 7 are arranged outside the tube 3 with respect to the radial direction R and that all elements of the vacuum space assembly 9 are arranged inside the tube 3 with respect to the radial direction R. The tube 3 provides a vacuum separation between the vacuum space assembly 9 and the outer space assembly 7 in the radial direction R. This means that a vacuum created in the vacuum space is maintained with respect to the outer space by the tube 3 with respect to the radial direction R. When the multipole element 1 is used in a particle beam system, the upper end of the tube 3 and the lower end of the tube 3 are connected to other components of the particle beam system, whereby the vacuum with respect to the outside space is maintained also with respect to the longitudinal direction.

The outer space assembly 7 comprises a circumferential pole piece 11 which surrounds the tube 3 in the circumferential direction U. This means that the circumferential pole piece 11 extends around the tube 3 along the circumferential direction U at a distance from the tube 3.

The outer space assembly 7 further comprises a plurality of nozzles 13 which are arranged distributed around the central axis 5 and extend from the circumferential pole piece 11 against the radial direction R to an outer wall surface 15 of the tube 3. This means that the nozzles 13 extend from the circumferential pole piece 11 towards the central axis 5. The nozzles 13 extend to the outer wall surface 15 of the tube 3. The nozzles 13 can penetrate into the tube 3 without completely penetrating the tube 3. This means that the nozzles 13 do not penetrate the tube 3 in the radial direction R.

Each nozzle 13 has an inner surface. The inner surface of the nozzle 13 faces the tube 3. This means that the inner surface of the nozzle 13 is opposite the tube 3 in the radial direction. Each nozzle 13 has an outer surface. The outer surface of the nozzle 13 faces the circumferential pole piece 11. This means that the outer surface of the nozzle 13 is opposite the circumferential pole piece 11 in the radial direction. Alternatively, the circumferential pole piece 11 and the nozzles 13 are made of one piece.

The outer assembly 7 further comprises a plurality of coils 17. The coils can be carried by the peripheral pole piece 11 and/or by the studs 13. Each of the studs 13 is associated with one of the coils 17.

The vacuum chamber assembly 9 comprises pole pieces 19 which are arranged distributed around the central axis 5 and extend from the tube 3 against the radial direction R. This means that the pole pieces 19 extend from the inner wall surface 16 of the tube 3 towards the central axis 5. The pole pieces 19 extend to the inner wall surface 16 of the tube 3. The pole pieces 19 can penetrate into the tube 3 without completely penetrating the tube 3. The pole pieces 19 do not touch the nozzles 13. This means that the pole pieces 19 do not penetrate the tube 3 in the radial direction R.

Each pole piece 19 has an inner surface 23 (see 3 ). The inner surface 23 faces the central axis 5. Each pole piece 19 has an outer surface 25. The outer surface 25 faces the tube 3. This means that the outer surface 25 faces the tube 3 in the radial direction. Each pole piece 19 has an upper surface. The upper surface faces the upper opening 6a of the tube 3. Each pole piece 19 has a lower surface. The lower surface faces the lower opening 6b of the tube 3. Each pole piece 19 has a first lateral surface 21 and a second lateral surface 22. The first lateral surface 21 faces a first other pole piece adjacent in the circumferential direction U. The second lateral surface 22 faces a second other pole piece adjacent in the opposite direction to the circumferential direction U. In the embodiment shown in 1 In the example shown, the inner surface 23 and the outer surface 25 are circular segments with a center on the central shank 5; and the side surfaces 21, 22 of the pole pieces 19 are flat surfaces. The pole pieces 19 are arranged longitudinally between an upper terminal pole piece 12a and a lower terminal pole piece 12b. The terminal pole pieces 12a, 12b are essentially shaped like thick-walled tubes and are magnetically conductive. This causes the magnetic multipole field to decay rapidly longitudinally outside the multipole element.

A propagation region 4 extends along the central axis 5 over the entire length of the multipole element 1, extends in the circumferential direction U over the full circumference of the multipole element 1 and extends in the radial direction R from the central axis 5 to pole pieces 19. The propagation region 4 is an empty space in which a particle beam can propagate through the multipole element 1. The magnetic multipole field is generated in the propagation region 4 and therefore acts on the particle beam in the propagation region 4. In particular, the propagation region 4 is limited by the upper opening 6a of the tube 3 and the lower opening 6b of the tube 3.

The tube 3 is magnetically non-conductive. This element therefore has a high magnetic resistance. The tube 3 is made of ceramic or a plastic, for example. An example of a suitable ceramic is aluminum oxide (Al2O3). An example of a suitable plastic is polyetheretherketone (PEEK).

The circumferential pole piece 11, the nozzles 13 and the pole pieces 19 are each magnetically conductive. These elements therefore have a low magnetic resistance. As a result, magnetic fluxes generated by the coils 17 can flow through these elements with little loss, and thus a magnetic multipole field can be efficiently generated in the propagation region 4.

Due to the configuration of the multipole element 1 described above, a magnetic multipole field can be efficiently generated in the propagation region 4, which is generated by the coils 17. A magnetic flux excited by the coils 17 flows from the coils 17 through the peripheral pole piece 11, through the nozzles 13, through the tube 3, through the pole pieces 19 and across a gap between the pole pieces 19. In addition, the coils 17 are arranged in the external space, which is under normal pressure during operation. Outgassing of wire insulation of the coils 17 therefore does not affect a vacuum generated in the vacuum space. In addition, the pole pieces 19 and the nozzles 13 can be electrically insulated from one another.

The tube 3 can be a one-piece body. The tube 3 can consist of exactly one material. An inner diameter DR of the tube 3 measured in the radial direction R (see 3 ) can have a value in the range from 20 mm to 200 mm. A length of the tube 3 measured along the central axis 5 can have a value in the range from 20 mm to 200 mm. A wall thickness TR of the tube 3 measured in the radial direction R (see 3 ) can be greater than zero. The wall thickness TR should be as thin as possible within the framework of acceptable stability in order to have the lowest possible magnetic resistance. The wall thickness TR should be less than 20% of the inner diameter DR of the tube 3. Preferably, the wall thickness TR should be less than 10% of the inner diameter DR of the tube 3. More preferably, the wall thickness TR should be less than 1% of the inner diameter DR of the tube 3. Furthermore or alternatively, the wall thickness TR should be less than 5 mm. Preferably, the wall thickness TR should be less than 2 mm. More preferably, the wall thickness TR should be less than 1 mm.

The tube 3 can have a symmetrical cross-section in a cutting plane oriented perpendicular to the central axis 5. The cross-section can in particular have the shape of a circular ring with a constant inner diameter DR and a constant outer diameter (see 3 ). Alternatively, the cross-section can have the shape of an elliptical ring with an inner diameter DR that varies in the circumferential direction. Further alternatively, the cross-section can have the shape of a (regular) polygon or the like. An example of a tube 3 whose cross-section has the shape of an octagon is shown in 4 The cross-section of the pipe 3 can be constant over the entire length of the pipe 3 in the longitudinal direction.

A diameter of the propagation region 4 measured in the radial direction R can have a value in the range of 1 mm to 20 mm. The diameter of the propagation region 4 is determined, for example, as the distance between inner surfaces 23 of two pole pieces 19 opposite each other via the central axis 5. A length of the propagation region 4 in the longitudinal direction corresponds to the length of the tube 3.

The circumferential pole piece 11 can be formed in one piece or can consist of several parts. The circumferential pole piece 11 provides a magnetic line between nozzles 13 that are adjacent to one another in the circumferential direction U. For this purpose, the circumferential pole piece 11 is in surface contact with the nozzles 13, for example.

The studs 13 and the circumferential pole piece 11 may be formed as one piece. In this case, the studs 13 are projections that protrude from the circumferential pole piece 11 opposite to the radial direction R. Alternatively, the studs 13 and the circumferential pole piece 11 may be formed as separate parts.

The nozzles 13 can rest against the outer wall surface 15 of the pipe 3. In this case, a distance measured in the radial direction R between the nozzles 13 and the pipe 3 is zero. Alternatively, the nozzles 13 can be have a distance measured in the radial direction R that is greater than zero. The distance should be less than 20% of the inner diameter DR of the tube 3 measured in the radial direction R. Preferably, the distance is less than 10% of the inner diameter DR of the tube 3. More preferably, the distance is less than 1% of the inner diameter DR of the tube 3. Furthermore or alternatively, the distance should be less than 5 mm. Preferably, the distance is less than 1 mm. More preferably, the distance is less than 0.1 mm.

In particular, the nozzles 13 are arranged symmetrically distributed in the circumferential direction U. This means that a difference between angles of rotation at which two nozzles 13 adjacent to one another in the circumferential direction U are arranged is 360°/(number of nozzles).

The pole pieces 19 can rest against the inner wall surface 16 of the tube 3. In this case, a distance D1 measured in the radial direction R (see 3 ) between the pole pieces 19 and the tube 3 is zero. Alternatively, the pole pieces 19 may have a distance D1, measured in the radial direction R, from the inner wall surface 16 of the tube 3 that is greater than zero. The distance D1 should be less than 20% of the inner diameter DR of the tube 3, measured in the radial direction R. Preferably, the distance D1 is less than 10% of the inner diameter DR of the tube 3. More preferably, the distance D1 is less than 1% of the inner diameter DR of the tube 3. Further or alternatively, the distance D1 should be less than 5 mm. Preferably, the distance D1 is less than 1 mm. More preferably, the distance D1 is less than 0.1 mm.

In particular, the pole pieces 19 are arranged symmetrically distributed in the circumferential direction U. As a result, the generated multipole field has a high degree of symmetry. As in 1 As shown, the pole pieces 19 can be arranged opposite each other in pairs about the central axis 5.

In particular, the pole pieces 19 are free of recesses for holding the pole pieces 19. In particular, the pole pieces 19 are free of holes and internal threads. As a result, the magnetic resistance of the pole pieces 19 is lower and the magnetic flux through the pole pieces 19 remains undisturbed.

The number of pole pieces 19 and the number of nozzles 13 are generally the same, but may differ in special cases. However, the number of pole pieces 19 indicates the maximum number of poles of the magnetic multipole field.

The nozzles 13 are arranged relative to the pole pieces 19 such that a magnetic resistance from the nozzles 13 through the tube 3 into the pole pieces 19 is as low as possible. For example, the nozzles 13 form an extension of the pole pieces 19 in the radial direction R. For example, the nozzles 13 are opposite the pole pieces 19 in the radial direction R.

In the 1 In the example shown, the multipole element 1 is a magnetic octupole. This means that the multipole element 1 is configured to generate a magnetic octupole field. However, the multipole element 1 is not limited to a magnetic octupole. The multipole element 1 can be designed such that the magnetic multipole field has four poles (quadrupole element) or six poles (hexapole element) or 12 poles or 16 poles. With reference to 11 An example of a quadrupole element is described below.

As in 2 As shown, the multipole element 1 may further comprise a holder 27 for holding the pole pieces 19. In particular, the holder 27 is part of the vacuum chamber assembly 9. The holder 27 comprises, for example, an upper holding part arranged in the longitudinal direction above the pole pieces 19 (in 2 not shown to improve the clarity of the drawing) and a lower holding part arranged in the longitudinal direction below the pole pieces 19. The upper and lower holding parts can be attached to the tube 3 in any way. In this case, the tube 3 contributes to the holder 27 and is thus a component of the holder 27. In contrast to holders known from the prior art, in which the pole pieces 19 are held by screws, threads, retaining bolts, holes and the like introduced into the holders, the holder 27 has no negative influence on the magnetic conductivity of the pole pieces 19. The holder 27 thus enables efficient generation of the magnetic multipole field.

Alternatively, the holder 27 can also be provided entirely by the tube 3. The holder 27 can be formed by gluing, soldering, clamping and the like the pole pieces 19 to the tube 3. The holder 27 is made of a magnetically non-conductive material in order to minimize the magnetic flux from one pole piece 19 to another pole piece 19. The material of the holder 27 is furthermore electrically conductive or non-conductive as required. This means for a purely magnetic multipole element that the material of the holder 27 is preferably electrically conductive in order to set the electrical potentials of the pole pieces 19 to a common electrical potential. For an electro-magnetic multipole element, it is preferably electrically non-conductive in order to to enable different electrical potentials of the pole pieces 19.

When designing the shape of the pole pieces 19, it must be taken into account that high electrical currents in the coils 17 can lead to an uncontrolled change in the magnetic multipole field due to the power loss of the coils 17 (so-called drifting). A larger wire thickness reduces the power loss in the coils, but increases their volume. However, the installation space is limited, so the coils cannot be arbitrarily large. An efficient transmission of the magnetic fluxes from the nozzles 13 through the tube 3 to the pole pieces 19 is therefore particularly important. The efficiency can be influenced by the shape of the pole pieces 19.

With reference to the 3 and 4 special designs of the pole pieces 19 are described. 3 shows a schematic cross-sectional view of a first example of a pole piece 19A of the multipole element 1 in a cross-sectional plane oriented perpendicular to the central axis 5. 4 shows a schematic cross-sectional view of a second example of a pole piece 19B of the multipole element 1 in a cross-sectional plane oriented perpendicular to the central axis 5. In the 3 and 4 To simplify the explanation, only a single pole piece 19A or 19B is shown, although the multipole element 1 always comprises several pole pieces.

3 shows the pole piece 19A with its inner surface 23, its outer surface 25, its first lateral surface 21 and its second lateral surface 22. At a first edge k1, the first lateral surface 21 of the pole piece 19A abuts the inner surface 23 of the pole piece 19A. At a second edge k2, the second lateral surface 22 of the pole piece 19A abuts the inner surface 23 of the pole piece 19A. A first half-line h1 lies in the cross-sectional plane (drawing plane), starts from the central axis 5 and runs through the first edge k1. A second half-line h2 lies in the cross-sectional plane, starts from the central axis 5 and runs through the second edge k2. An acute angle between the first half-line h1 and the second half-line h2 is called the inner coverage angle α. To simplify the illustration, the first half-line h1 and the second half-line h2 were extended beyond the central axis 5 and the inner coverage angle α was plotted on the extended sections.

At a third edge k3, the first lateral surface 21 of the pole piece 19A abuts the outer surface 25 of the pole piece 19A. At a fourth edge k4, the second lateral surface 22 of the pole piece 19A abuts the outer surface 25 of the pole piece 19A. A third half-line h3 lies in the cross-sectional plane, starts from the central axis 5 and passes through the third edge k3. A fourth half-line h4 lies in the cross-sectional plane, starts from the central axis 5 and passes through the fourth edge k4. An acute angle between the third half-line h3 and the fourth half-line h4 is called the outer coverage angle β.

The special feature of the pole piece 19A is that the inner cover angle α and the outer cover angle β have different values from each other. This means, for example, that the inner cover angle α and the outer cover angle β differ from each other by at least 5°. In particular, the pole pieces 19 are shaped such that the inner cover angle α is larger than the outer cover angle β.

The inner coverage angle α influences the magnetic resistance between the inner surface 23 of the pole pieces 19 and the propagation region 4: As the inner coverage angle α increases, the magnetic resistance between the inner surface 23 of the pole pieces 19 and the propagation region 4 decreases. The lower the magnetic resistance, the lower the excitation power required to generate a desired magnetic field strength of the multipole field in the propagation region 4. In other words: the efficiency of generating the magnetic multipole field is higher the smaller the magnetic resistance between the inner surface 23 of the pole pieces 19 and the propagation region 4.

The outer coverage angle β influences the magnetic resistance between the outer surface 25 of the pole pieces 19 and the supports 13: As the outer coverage angle β increases, the magnetic resistance between the outer surface 25 of the pole pieces 19 and the supports 13 decreases. The lower the magnetic resistance, the lower the excitation power required to generate a desired magnetic field strength of the multipole field in the propagation region 4. In other words: the efficiency of generating the magnetic multipole field is higher the smaller the magnetic resistance between the outer surface 25 of the pole pieces 19 and the supports 13.

The distance between adjacent pole pieces 19 in the circumferential direction U, which is also influenced by the inner cover angle α and the outer cover angle β, influences the magnetic resistance between the pole pieces 19. This magnetic resistance is subordinate to the magnetic resistance that exists between the pole pieces 19 and the nozzles 13, and directs the magnetic field around the propagation region 4. Therefore, the lower the magnetic resistance between the pole pieces 19, the greater the excitation power required to generate a desired magnetic field strength of the multipole field in the propagation region 4. In other words: the efficiency of generating the magnetic multipole field is higher the greater the magnetic resistance between pole pieces 19 adjacent in the circumferential direction U.

The inventors have recognized that a clever choice of the inner coverage angle α and the outer coverage angle β leads to a particularly efficient generation of the magnetic multipole field.

4 shows an example of a tube 3 with an octagonal cross-section. The inner surface 23 and the outer surface 25 of the pole piece 19B are not circular segments, but flat surfaces. 4 In the pole piece 19B shown, the inner cover angle α and the outer cover angle β have different values from each other. The inner cover angle α is larger than the outer cover angle β.

Advantageous examples of pole piece shapes are characterized below using a sector width. The sector width is defined as the ratio of 360° to the number of pole pieces 19. For a quadrupole element, the sector width is 90°. For a hexapole element, the sector width is 60°. For an octupole element, the sector width is 45°.

For example, the pole pieces 19 are shaped such that a difference between the inner coverage angle α and the outer coverage angle β is at least 10% of the sector width, which corresponds to a difference of at least 9° for a quadrupole element and to a difference of at least 4.5° for an octupole element. Preferably, the difference between the inner coverage angle α and the outer coverage angle β is at least 20% of the sector width, which corresponds to a difference of at least 18° for a quadrupole element and to a difference of at least 9° for an octupole element.

For example, the pole pieces 19 are shaped such that a ratio of the inner coverage angle α to the sector width has a value in the range of 75% to 95%, which in the case of a quadrupole element corresponds to an inner coverage angle α in the range of 67.5° to 85.5° and in the case of an octupole element corresponds to an inner coverage angle α in the range of approximately 34° to approximately 43°. Preferably, the ratio of the inner coverage angle α to the sector width has a value in the range of 80% to 90%, which in the case of a quadrupole element corresponds to an inner coverage angle α in the range of 72° to 81° and in the case of an octupole element corresponds to an inner coverage angle α in the range of 36° to 40.5°.

For example, the pole pieces 19 are shaped such that a ratio of the outer coverage angle β to the sector width has a value in the range of 35% to 75%, which in the case of a quadrupole element corresponds to an outer coverage angle β in the range of 31.5° to 67.5° and in the case of an octupole element corresponds to an outer coverage angle β in the range of approximately 16° to approximately 34°. Preferably, the ratio of the outer coverage angle β to the sector width has a value in the range of 50% to 70%, which in the case of a quadrupole element corresponds to an outer coverage angle β in the range of 45° to 63° and in the case of an octupole element corresponds to an outer coverage angle β in the range of approximately 22.5° to approximately 31.5°.

For pole pieces 19 with rounded edges k1 to k4, the determination of the inner cover angle α and the outer cover angle β according to the above definition can be difficult. Therefore, an alternative or more general definition for the inner cover angle α and the outer cover angle β is given below with reference to 5 explained.

The upper part in 5 shows an exemplary pole piece 19 with rounded edges in a cross-sectional plane that is oriented perpendicular to the central axis 5. The central axis 5 is perpendicular to the plane of the 5 . A radius-dependent coverage angle Φ(r) indicates an acute angle between a first half-line h1 and a second half-line h2. The first half-line h1 lies in the cross-sectional plane oriented perpendicular to the central axis 5, starts from the central axis (5) and runs through a first intersection point S1(r). The second half-line h2 lies in the cross-sectional plane, starts from the central axis 5 and runs through a second intersection point S2(r). The first intersection point S1(r) and the second intersection point S2(r) are (radius-dependent) intersection points of the surface of the pole piece 19 with a circle which lies in the cross-sectional plane, has the radius r and whose center lies on the central axis 5. This means that the coverage angle Φ(r) has different values depending on the radius r of the (imaginary) circle, which depend on the specific shape of the pole piece 19.

The inner coverage angle α shall exceed the coverage angle Φ(r) in a region close to the inner surface 23 or in the vicinity of the propagation region 4. For this purpose, the inner coverage angle α is defined, for example, as follows: The inner coverage angle α is the largest radius-dependent coverage angle Φ(r) in a range RO≤r<RO+20%L, where R0 is the smallest distance measured in the radial direction R between the surface of the pole piece 19 and the central axis 5, and where L is the maximum length of the pole piece 19 measured in the radial direction R. The range R0≤r<R0+20%L designates a range for the radius r with a lower limit at R0 and an upper limit at R0+20%L. An example of this definition is given in the lower part of the 5 , whereby the half-lines h1 and h2 are shown extended beyond the central axis 5 to improve the clarity of the figure. The half-lines h1 and h2, which define the inner cover angle α, are shown as dash-dotted lines. To show the range R0≤r<R0+20%L, 5 a circle with radius R0 around the central axis 5 and a circle with radius R0+20%L around the central axis 5 are shown.

The outer coverage angle β is intended to indicate the coverage angle Φ(r) in a region near the outer surface 25 or near the tube 3. For this purpose, the outer coverage angle β is defined, for example, as follows: The outer coverage angle is the largest radius-dependent coverage angle Φ(r) in a range DR/2-20%L<r≤DR/2, where DR is the inner diameter of the tube 3, and where L is the maximum length of the pole piece 19 measured in the radial direction R. The range DR/2-20%L<r≤DR/2 indicates a range for the radius r with a lower limit at DR/2-20%L and an upper limit at DR/2. An example of this definition is given in the lower part of the 5 The half-lines h1 and h2, which define the outer cover angle β, are shown as dashed lines. To show the range DR/2-20%L<r≤DR/2, 5 a circle with radius DR/2-20%L around the central axis 5 and a circle with radius DR/2 around the central axis 5 are shown.

The above values and value ranges for the inner cover angle α and the outer cover angle β apply in particular to pole pieces 19 whose lateral surfaces 21, 22 are flat surfaces. However, the above values and value ranges for the inner cover angle α and the outer cover angle β can also apply to pole pieces 19 whose lateral surfaces 21, 22 are curved or kinked.

With reference to the 6 and 7 Further special designs of the pole pieces 19 are described. 6 shows a schematic cross-sectional view of a third example of a pole piece 19C of the multipole element 1 in a cross-sectional plane oriented perpendicular to the central axis 5. 7 shows a schematic cross-sectional view of a fourth example of a pole piece 19D of the multipole element 1 in a cross-sectional plane oriented perpendicular to the central axis 5. In the 6 and 7 To simplify the explanation, only a single pole piece 19C or 19D is shown (and a pole piece adjacent to this in the circumferential direction U is indicated in dashed lines), although the multipole element 1 always comprises several pole pieces.

The pole piece 19C is characterized in that the two side surfaces 21, 22 of the pole piece 19C are not flat surfaces. Instead, the two side surfaces 21, 22 of the pole piece 19C are curved. Instead of a curved shape, the side surfaces 21, 22 can also be kinked.

Due to this shape of the lateral surfaces 21, 22 of the pole pieces 19, a distance between pole pieces 19 adjacent in the circumferential direction U is larger in large areas of the lateral surfaces 21, 22 than in the case of lateral surfaces 21, 22 with a shape of flat surfaces. As a result, the local magnetic resistance of a space between adjacent pole pieces that have curved or bent lateral surfaces is larger than the local magnetic resistance of a space between adjacent pole pieces that have lateral surfaces in the shape of flat surfaces. As a result, a smaller proportion of a magnetic flux guided in the pole piece escapes via the lateral surfaces 21, 22 between pole pieces that have curved or bent lateral surfaces. This increases the proportion of the magnetic flux guided in the pole piece that exits via the inner surface 23, which leads to a stronger magnetic multipole field with the same excitation (current through the coils 17). The efficiency of generating the magnetic multipole field is thus increased by the curved or bent side surfaces 21, 22 of the pole pieces 19.

A measure of this efficiency is the course of the coverage angle Φ(r) as a function of the radius r. For this purpose, a center coverage angle γ is defined as follows: The center coverage angle is the smallest radius-dependent coverage angle Φ(r) in a range R0+20%L<r<DR/2-20%L, where R0 is the smallest distance measured in the radial direction R between the surface of the pole piece 19 and the central axis 5, where DR is the inner diameter of the tube 3, and where L is the maximum length of the pole piece 19 measured in the radial direction R. The range R0+20%L<r<DR/2-20%L denotes a range for the radius r with a lower limit at R0+20%L and an upper limit at DR/2-20%L.

A significant increase in the efficiency of generating the magnetic multipole field by curved or bent side surfaces occurs when the center coverage angle γ is smaller than both the inner coverage angle α and the outer coverage angle β. The outer coverage angle β can also assume values greater than 75% of the sector width. The inner coverage angle α and the outer coverage angle β can have different values or can have the same values.

Below, details of the coils 17 of the multipole element 1 are given with reference to the 8 to 10 Each of the coils 17 can have one or more windings. Each winding consists of at least one turn. A turn is a loop of wire. Normally, each winding consists of a plurality of turns. The number of turns per winding is typically several tens to several thousand turns. As the number of turns increases, a current that must flow through the winding to generate a certain magnetic flux decreases.

When a coil 17 has multiple windings, the multiple windings are arranged such that the magnetic fluxes generated by the multiple windings spatially overlap. Multiple windings are electrically isolated from each other and are powered by separate power sources. One winding can extend over multiple of the coils 17.

8 shows a schematic representation of an octupole winding 41 of the multipole element 1. For the sake of clarity, the circumferential pole piece 11 is not shown (as in the 9 and 10 ). The octupole winding 41 has two connections 42 at which the octupole winding 41 can be connected to a power source. The octupole winding 41 consists of a single electrical conductor (for example a wire or a bundle of wires). The electrical conductor of the octupole winding 41 extends over all eight coils 17 of the multipole element 1 designed as an octupole element. The number of turns of the octupole winding 41 on each of the coils 17 (ie the number of turns of the octupole winding 41 wound around each of the supports 13 or sections of the circumferential pole piece 11) is the same and is, for example, 200. In each of the supports 13, an arrow is shown which is oriented either in the radial direction R or against the radial direction R. The orientation of the arrow indicates the winding direction of the turns of the octupole winding 41 on the respective coil 17. For example, the tip of the arrow indicates the position of the magnetic north pole and the beginning of the arrow indicates the magnetic south pole. As can be seen from the orientations of the arrows in 8 As shown, the winding directions of each pair of coils 17 adjacent in the circumferential direction U are opposite to each other. Accordingly, the arrows in the circumferential direction U are oriented alternately in the radial direction R and opposite to the radial direction R. With the octupole winding 41 it is possible to generate a magnetic octupole field in the propagation region 4.

9 shows a schematic representation of quadrupole windings of the multipole element 1. A first quadrupole winding 43 is shown by a solid line. The first quadrupole winding 43 has two connections 44 to which the first quadrupole winding 43 can be connected to a power source. The first quadrupole winding 43 consists of a single electrical conductor. The electrical conductor of the first quadrupole winding 43 extends over four of the eight coils 17 of the multipole element 1 designed as an octupole element. When counting continuously in the circumferential direction, the first quadrupole winding 43 extends over all odd-numbered coils 17 of the multipole element 1. The winding directions of each pair of coils 17 adjacent in the circumferential direction U, over which the first quadrupole winding 43 extends, are opposite to each other, as indicated by corresponding arrows in 9 The number of turns of the quadrupole winding 43 on each of the coils 17 is the same and is, for example, 1000. With the first quadrupole winding 43 it is possible to generate a first magnetic quadrupole field in the propagation region 4.

A second quadrupole winding 45 is shown by a dashed line. The second quadrupole winding 45 has two connections 46, to which the second quadrupole winding 45 can be connected to a power source. The second quadrupole winding 45 consists of a single electrical conductor. The electrical conductor of the second quadrupole winding 45 extends over four of the eight coils 17 of the multipole element 1 designed as an octupole element. When counting continuously in the circumferential direction, the second quadrupole winding 45 extends over all even-numbered coils 17 of the multipole element 1. The winding directions of each pair of coils 17 adjacent in the circumferential direction U, over which the second quadrupole winding 45 extends, are opposite to one another, as indicated by corresponding arrows in 9 With the second quadrupole winding 45 it is possible to generate a second magnetic quadrupole field in the propagation region 4. The first magnetic quadrupole field and the second magnetic quadrupole field effectively result in a magnetic quadrupole field that can be rotated in the circumferential direction U.

10 shows a schematic representation of dipole windings of the multipole element 1. A first dipole winding 47 has two connections 48; a second dipole winding 49 has two connections 50. The two dipole windings 47 and 49 can thus be connected to separate power sources. The dipole windings 47 and 49 each consist of a single electrical conductor.

The first dipole winding 47 has a plurality of turns on each of the nozzles 13. The number of turns of the first dipole winding 47 on a respective nozzle 13 is schematically represented by the thickness of the first dipole winding 47 on the respective nozzle 13. The orientation of the turns of the first dipole winding 47 on a respective nozzle 13 is schematically represented by an arrow (inward in the radial direction R) on the respective nozzle 13. For example, the turns of the first dipole winding 47 have the following configuration: +100, +100, +41, -41, -100, -100, -41, +41, where the sign indicates the orientation of the turn and the number indicates the number of turns on the respective nozzle 13, starting with the nozzle 13 shown in the middle at the top and ordered clockwise.

The second dipole winding 49 has a plurality of turns on each of the nozzles 13. The number of turns of the second dipole winding 49 on a respective nozzle 13 is schematically represented by the thickness of the second dipole winding 49 on the respective nozzle 13. The orientation of the turns of the first second dipole winding 49 on a respective nozzle 13 is schematically represented by an arrow (outward in the radial direction R) on the respective nozzle 13. For example, the turns of the second dipole winding 49 have the following configuration: -41, +41, +100, +100, +41, -41, -100, -100, where the sign indicates the orientation of the turn and the number indicates the number of turns on the respective nozzle 13, starting with the nozzle 13 shown in the middle at the top and ordered clockwise. With the dipole windings 47 and 49 it is possible to generate an arbitrarily rotatable magnetic dipole field in the propagation region 4.

Such dipole fields can also be generated with other configurations of the number of turns and winding orientations. The present embodiment shows only one embodiment for implementing a dipole winding.

With reference to 11 A further multipole element 1A according to an embodiment of the invention is described below. In contrast to the multipole element 1 described above, the multipole element 1A is an electro-magnetic multipole element. This means that the multipole element 1A is configured to generate a magnetic multipole field and an electric multipole field. Magnetic north poles and magnetic south poles of the magnetic multipole field are generated in equal numbers; and positive poles and negative poles of the electric multipole field are generated in equal numbers. Furthermore, the number of poles of the magnetic multipole field is equal to the number of poles of the electric multipole field. The magnetic multipole field and the electric multipole field are generated in particular in such a way that they are spatially superimposed on one another.

In further difference to the multipole element 1, which is an octupole element, the multipole element 1A is a quadrupole element with four pole pieces 19 and four studs 13. The maximum number of poles of the electric field is four and the maximum number of poles of the magnetic field is four. In further embodiments, the multipole element 1A can have a different number of poles, pole pieces 19 and studs 13, e.g. six, eight or more.

The tube 3 has a low magnetic conductivity and is in particular magnetically insulating. The tube 3 is also electrically insulating in order to electrically insulate the pole pieces 19 and the nozzles 13 from one another. In addition, the pole pieces 19 are electrically conductive. This means that a high electrical potential can be applied to the pole pieces 19, while the nozzles 13 are kept at ground potential. The pole pieces 19 in the electro-magnetic multipole element 1A thus also serve as electrodes for generating the electrical multipole field. However, this also means that the pole pieces 19 are kept electrically insulated in the holder 27 of the multipole element 1A; the material of the holder 27 is in this case (at least partially) electrically non-conductive.

The wall thickness TR of the tube 3 should be sufficiently large to maintain electrical insulation of the pole pieces 19 from the nozzles 13 even in the presence of a high electrical potential difference between them. For example, the wall thickness TR of the tube 3 should be such that the tube 3 has a breakdown voltage of at least 20 kV. The breakdown voltage is the smallest difference in magnitude between the electrical potential of the pole pieces 19 and the electrical Potential of the nozzle 13 at which the electrical insulation of the pipe 3 fails.

For applying externally generated electrical potentials to the pole pieces 19, the multipole element 1A further comprises a plurality of first electrical lines 29 which electrically connect the pole pieces 19 to electrical connections 31 in the external assembly 7. In 11 As an example, two first electrical lines 29 are shown. In 11 a region 33 of the tube 3 is highlighted with hatching. The region 33 of the tube 3 borders on the pole pieces 19 and the nozzles 13 in the radial direction R. In other words, the region 33 of the tube 3 is a region which is opposite the pole pieces 19 and the nozzles 13 in the radial direction R. In the region 33, the tube 3 has no opening (for a vacuum feedthrough) which penetrates the tube 3 as well as the nozzle 13 and the peripheral pole piece 11 in the radial direction R. In contrast to the prior art, in which an opening is provided in the region 33, which in turn requires a vacuum seal, the configuration of the present embodiment does not require an opening in the region 33, which simplifies the construction of the tube 3. In contrast, the tube 3 outside the region 33 has a vacuum feedthrough 37 which maintains the vacuum in the vacuum space in the radial direction R. The first electrical lines 29 pass through the tube 3 through the vacuum feedthrough 37. That is, the first electrical lines 29 pass through the tube 3 in the radial direction R outside the region 33. Alternatively, the first lines 29 can be guided through the upper opening 6a of the tube 3 or the lower opening 6b of the tube 3. Further alternatively, a part of the first electrical lines 29 can be guided through the vacuum feedthrough 37 outside the region 33 and another part of the first electrical lines 29 can be guided through the upper opening 6a of the tube 3 or the lower opening 6b of the tube 3.

In the 2 and 11 In the examples shown, the vacuum feedthrough 37 is at a position which lies in the circumferential direction U between two pole pieces 19. A possible position of the vacuum feedthrough 37 in the longitudinal direction is shown in 2 From there, an adjacent pole piece 19 can be easily contacted. Additionally or alternatively, a vacuum feedthrough 37 can be arranged in the longitudinal direction above or below a pole piece 19. The number of vacuum feedthroughs 37 is not limited to one. That is, the multipole element 1A can have several vacuum feedthroughs 37 for passing through the first lines 29.

In the 11 In the example shown, the multipole element 1A has the two first lines 29, which are electrically connected to two different pole pieces 19. In order to be able to apply an external electrical potential to the other two pole pieces 19 of the multipole element 1A, the multipole element 1A also has several second electrical lines 35, which electrically connect at least some of the pole pieces 19 to one another in groups. Specifically, the multipole element 1A has a second electrical line 35, which 11 top-mounted pole piece 19 with the pole piece opposite it via the central axis 5 (ie, the pole piece in the 11 pole piece 19) arranged below. In addition, the multipole element 1A has a further second electrical line 35, which connects the 11 right-hand pole piece 19 with the pole piece opposite it via the central axis 5 (ie, the pole piece in the 11 left-hand pole piece 19). Thus, each pair of pole pieces 19 opposite each other via the central axis 5 is directly electrically connected to each other. In this example, each pair of pole pieces 19 opposite each other via the central axis 5 forms a group in the sense of the "group-wise" electrical connection. Such a configuration reduces a negative influence of undesirable fluctuations in the external electrical potentials. The second lines 35 can be connected as in the example of the 11 be parts of the vacuum chamber assembly. Alternatively, the second lines 35 can be parts of the external chamber assembly. In a further embodiment, however, it is also possible for the pole pieces 19 to be individually supplied with externally generated electrical potentials via the first electrical lines 29.

In operation, the coils 17, the studs 13 and the circumferential pole piece 11 may remain at ground potential, whereas the pole pieces 19 are at high voltage. An electrical potential difference between an average electrical potential of the pole pieces 19 and an electrical potential of the studs 13 is, for example, at least 2 kV, preferably at least 6 kV. Furthermore or alternatively, an electrical potential difference between an average electrical potential of the pole pieces 19 and an electrical potential of the circumferential pole piece 11 is at least 2 kV, preferably at least 6 kV. Furthermore or alternatively, a maximum electrical potential difference between electrical potentials of adjacent pole pieces 19 is at least 200 V, preferably at least 1 kV.

With reference to 12 An exemplary particle beam system 100 is described below. The particle beam system 100 can be, for example, an electron beam microscope or a focused ion beam processing system.

The particle beam system 100 comprises, for example, a particle source 101 for providing charged particles of a particle beam 102, for example electrons or ions, an acceleration electrode 103 for accelerating the particles of the particle beam 102, a beam tube 104 through which the particle beam 102 passes within the particle beam system 100, an image error corrector 105 which comprises at least one of the multipole elements 1, 1A described herein, deflection coils 106 and/or deflection electrodes 107 for deflecting the particle beam 102 and an objective lens 109 for focusing the particle beam 102 into a focal plane FP. The beam tube 104 can, for example, extend from the acceleration electrode 103 to the objective lens 109. The beam pipe 104 can be interrupted, for example by the image aberration corrector 105 (the multipole element 1). Some components of the particle beam system 100, for example the image aberration corrector 105 (the multipole element 1) and the deflection electrodes 107, can be arranged entirely or partially within the beam pipe 104.

The particle beam system 100 further comprises a vacuum chamber 111 in which a sample table 113 is arranged. The sample table 113 is configured to support a sample 115. The sample table 113 may be configured to translate and rotate the sample 115.

The particle beam system 100 further comprises a detector 117 for detecting interaction products 118 which are generated by interaction of the particle beam 102 with the sample 115. Interaction products can be, for example: secondary electrons, backscattered electrons, secondary ions, backscattered ions, light, radiation, etc.

The particle beam system 100 further comprises a controller 125 for control and data processing. The controller 125 controls the particle source 101, the acceleration electrode 103, the image aberration corrector 105, the deflection electrodes 107 and the objective lens 109 via a communication line 121. The controller 125 controls the sample table 113 via a communication line 114. The controller 125 controls the detector 117 and obtains data from the detector 117 via a communication line 119. An input device 127 is connected to the controller 125 to receive inputs from a user or a data carrier. An output device 129 is connected to the controller 125 to output outputs of the controller 125 to a user or a data carrier. The controller 125 is connected to a data storage 131 for storing data.

The particle beam system 100 further comprises one or more current sources and/or one or more voltage sources, which are not shown in the figures. The current sources or voltage sources are configured to supply the components of the particle beam system 100, in particular electrodes for generating electric fields and coils for generating magnetic fields, with suitable electrical voltages and electrical currents. The current sources and the voltage sources are controlled by the controller 125.

During operation, the beam tube 104 may be at high voltage. In particular, the same high voltage may be applied to the beam tube 104 as to the pole pieces 19. For example, an electrical potential difference between the beam tube 104 and the sample 115 is at least 2 kV or at least 6 kV.

Examples of subject matter of the present disclosure

Some examples of subject matter of the present disclosure are described below.

• ein Rohr (3), welches eine Zentralachse (5) des Multipolelements (1, 1A) umgibt;
• eine Außenraumbaugruppe (7), welche bezüglich einer Radialrichtung (R), die von der Zentralachse (5) senkrecht ausgeht, außerhalb des Rohres (3) angeordnet ist, und eine Vakuumraumbaugruppe (9), welche bezüglich der Radialrichtung (R) innerhalb des Rohres (3) angeordnet ist,
• wobei die Außenraumbaugruppe (7) umfasst:
  • ein Umfangspolstück (11), welches magnetisch leitend ist und das Rohr (3) in einer Umfangsrichtung (U) umgibt, wobei die Umfangsrichtung (U) zu der Zentralachse (5) und zu der Radialrichtung (R) senkrecht orientiert ist,
  • mehrere Stutzen (13), welche magnetisch leitend sind, um die Zentralachse (5) herum verteilt angeordnet sind und sich von dem Umfangspolstück (11) entgegen der Radialrichtung (R) bis zu einer äußeren Wandoberfläche (15) des Rohres (3) erstrecken; und
  • mehrere Spulen (17);
• wobei die Vakuumraumbaugruppe (9) umfasst:
  • mehrere Polstücke (19), welche magnetisch leitend sind, um die Zentralachse (5) herum verteilt angeordnet sind und sich von dem Rohr (3) entgegen der Radialrichtung (R) erstrecken.

Example 1 relates to a multipole element (1, 1A) comprising:

• a tube (3) surrounding a central axis (5) of the multipole element (1, 1A);
• an external space assembly (7) which is arranged outside the tube (3) with respect to a radial direction (R) extending perpendicularly from the central axis (5), and a vacuum space assembly (9) which is arranged inside the tube (3) with respect to the radial direction (R),
• wherein the exterior assembly (7) comprises:
  • a circumferential pole piece (11) which is magnetically conductive and surrounds the tube (3) in a circumferential direction (U), wherein the circumferential direction (U) is oriented perpendicular to the central axis (5) and to the radial direction (R),
  • a plurality of nozzles (13) which are magnetically conductive, are arranged distributed around the central axis (5) and extend from the peripheral pole piece (11) against the radial direction (R) to an outer wall surface (15) of the tube (3); and
  • several coils (17);
• wherein the vacuum chamber assembly (9) comprises:
  • several pole pieces (19), which are magnetically conductive, distributed around the central axis (5) are arranged and extend from the tube (3) against the radial direction (R).

Example 2 relates to a multipole element (1, 1A) according to Example 1,
wherein a distance measured in the radial direction (R) between the pipe (3) and each of the nozzles (13) is at least zero.

Example 3 relates to a multipole element (1, 1A) according to Example 1 or 2,
wherein a distance measured in the radial direction (R) between the pipe (3) and each of the nozzles (13) is less than 20% of an inner diameter (DR) of the pipe (3) measured in the radial direction (R) and/or less than 5 mm.

Example 4 relates to a multipole element (1, 1A) according to one of Examples 1 to 3,
wherein a distance (D1) measured in the radial direction (R) between each of the pole pieces (19) and the tube (3) is at least zero.

Example 5 relates to a multipole element (1, 1A) according to one of Examples 1 to 4,
wherein a distance (D1) measured in the radial direction (R) between each of the pole pieces (19) and the tube (3) is less than 20% of an inner diameter (DR) of the tube (3) measured in the radial direction (R) and/or less than 5 mm.

Example 6 relates to a multipole element (1, 1A) according to one of examples 1 to 5, wherein a wall thickness (TR) of the tube (3) measured in the radial direction (R) is greater than zero.

Example 7 relates to a multipole element (1, 1A) according to one of examples 1 to 6, wherein a wall thickness (TR) of the tube (3) measured in the radial direction (R) is less than 20% of an inner diameter (DR) of the tube (3) measured in the radial direction (R) and/or less than 5 mm.

Example 8 relates to a multipole element (1, 1A) according to any one of Examples 1 to 7,
wherein the nozzles (13) do not penetrate the pipe (3) in the radial direction (R),
wherein the pole pieces (19) do not penetrate the tube (3) in the radial direction (R).

Example 9 relates to a multipole element (1, 1A) according to any one of Examples 1 to 8,
wherein the tube (3) provides a vacuum separation in the radial direction (R) between the vacuum space assembly (9) and the outer space assembly (7).

Example 10 relates to a multipole element (1, 1A) according to any one of Examples 1 to 9,
wherein the tube (3) is magnetically non-conductive.

Example 11 relates to a multipole element (1, 1A) according to any one of Examples 1 to 10,
wherein the pole pieces (19) are each shaped such that an inner cover angle (α) and an outer cover angle (β) have different values from each other,
where a radius-dependent coverage angle (Φ(r)) indicates an acute angle between a first half-line (h1) and a second half-line (h2),
wherein the first half-line (h1) lies in a cross-sectional plane oriented perpendicular to the central axis (5), starts from the central axis (5) and passes through a first intersection point (S1(r)),
wherein the second half-line (h2) lies in the cross-sectional plane, starts from the central axis (5) and passes through a second intersection point (S2(r)),
wherein the first intersection point (S1(r)) and the second intersection point (S2(r)) are intersection points of the surface of the respective pole piece (19) with a circle which lies in the cross-sectional plane, has the radius r and whose center lies on the central axis (5),
where the inner coverage angle (α) is defined as the largest radius-dependent coverage angle (Φ(r)) in a range R0≤r<R0+20%L,
where the outer coverage angle (β) is defined as the largest radius-dependent coverage angle (Φ(r)) in a range DR/2-20%L<r≤DR/2,
where R0 is the smallest distance measured in the radial direction R between the surface of the respective pole piece (19) and the central axis (5),
where DR is the inner diameter of the pipe (3),
where L is the maximum length of the respective pole piece (19) measured in the radial direction (R).

Example 12 relates to a multipole element (1, 1A) according to Example 11,
where a sector width is defined as the ratio of 360° to the number of pole pieces;
wherein the pole pieces (19) are shaped such that the inner cover angle (α) is greater than the outer cover angle (β); and/or
wherein the pole pieces (19) are shaped such that a difference between the inner cover angle (α) and the outer cover angle (β) is at least 10% of the sector width; and/or
wherein the pole pieces (19) are shaped such that a ratio of the inner cover angle (α) to the sector width has a value in the range of 75% to 95%; and/or
wherein the pole pieces (19) are shaped such that a ratio of the outer coverage angle (β) to the sector width has a value in the range of 35% to 75%.

Example 13 relates to a multipole element (1, 1A) according to Example 11 or 12,
wherein the pole pieces (19) are each shaped that a center coverage angle (γ) of the respective pole piece (19) is smaller than both the inner coverage angle (α) of the respective pole piece (19) and the outer coverage angle (β) of the respective pole piece (19),
where the center coverage angle (γ) is defined as the smallest radius-dependent coverage angle (Φ(r)) in a range R0+20%L<r<DR/2-20%L.

Example 14 relates to a multipole element (1, 1A) according to any one of Examples 1 to 10,
wherein the pole pieces (19) are each shaped such that a center coverage angle (γ) of the respective pole piece (19) is both smaller than an inner coverage angle (α) of the respective pole piece (19) and smaller than an outer coverage angle (β) of the respective pole piece (19),
where a radius-dependent coverage angle (Φ(r)) indicates an acute angle between a first half-line (h1) and a second half-line (h2),
wherein the first half-line (h1) lies in a cross-sectional plane oriented perpendicular to the central axis (5), starts from the central axis (5) and passes through a first intersection point (S1(r)),
wherein the second half-line (h2) lies in the cross-sectional plane, starts from the central axis (5) and passes through a second intersection point (S2(r)),
wherein the first intersection point (S1(r)) and the second intersection point (S2(r)) are intersection points of the surface of the respective pole piece (19) with a circle which lies in the cross-sectional plane, has the radius r and whose center lies on the central axis (5),
where the inner coverage angle (α) is defined as the largest radius-dependent coverage angle (Φ(r)) in a range R0≤r<R0+20%L,
where the outer coverage angle (β) is defined as the largest radius-dependent coverage angle (Φ(r)) in a range DR/2-20%L<r≤DR/2,
where the center coverage angle (γ) is defined as the smallest radius-dependent coverage angle (Φ(r)) in a range R0+20%L<r<DR/2-20%L,
where R0 is the smallest distance measured in the radial direction R between the surface of the respective pole piece (19) and the central axis (5),
where DR is the inner diameter of the pipe (3),
where L is the maximum length of the respective pole piece (19) measured in the radial direction (R).

Example 15 relates to a multipole element (1, 1A) according to any one of Examples 1 to 14,
wherein the pole pieces (19) each have two lateral surfaces (21, 22) each facing a pole piece of the pole pieces (19) adjacent in the circumferential direction (U);
wherein the lateral surfaces (21, 22) of the pole pieces (19) are curved or kinked.

Example 16 relates to a multipole element (1, 1A) according to any one of examples 1 to 15, wherein the vacuum space assembly (9) further comprises a holder (27) for holding the pole pieces (19).

Example 17 relates to a multipole element (1, 1A) according to Example 16, wherein the holder (27) is partially or completely provided by the tube (3).

• mehrere erste elektrische Leitungen (29), welche die Polstücke (19) mit elektrischen Anschlüssen (31) in der Außenraumbaugruppe (7) elektrisch verbinden.

Example 18 relates to a multipole element (1A) according to any one of Examples 1 to 17,
wherein the tube (3) is electrically insulating;
wherein the pole pieces (19) are electrically conductive and
wherein the multipole element (1) further comprises:

• a plurality of first electrical leads (29) which electrically connect the pole pieces (19) to electrical terminals (31) in the exterior assembly (7).

Example 19 relates to a multipole element (1A) according to Example 18,
wherein at least a part of the plurality of first electrical lines (29) is guided through an opening (6a, 6b) of the tube (3) located on the central axis (5).

Example 20 relates to a multipole element (1, 1A) according to any one of Examples 1 to 19,
wherein a region (33) of the tube (3) which adjoins the pole pieces (19) and the nozzles (13) in the radial direction (R) has no opening which penetrates the tube (3) in the radial direction (R).

Example 21 relates to a multipole element (1, 1A) according to any one of Examples 18 to 20,
wherein the plurality of first electrical lines (29) pass through the tube (3) in the radial direction (R) outside a region (33) of the tube (3) which adjoins the pole pieces (19) and the nozzles (13) in the radial direction (R).

• mehrere zweite elektrische Leitungen (35), welche zumindest einen Teil der Polstücke (19) gruppenweise miteinander elektrisch verbinden.

Example 22 relates to a multipole element (1, 1A) according to any one of Examples 18 to 21, further comprising:

• a plurality of second electrical lines (35) which electrically connect at least some of the pole pieces (19) to one another in groups.

Example 23 relates to a multipole element (1, 1A) according to Example 22, wherein the second electrical lines (35) each electrically connect a pair of the pole pieces (19) which are opposite to each other via the central axis (5).

Example 24 relates to a multipole element (1, 1A) according to any one of Examples 1 to 23,
where an electrical potential difference between an average electrical potential of the pole pieces (19) and an electrical potential of the nozzles (13) is at least 2 kV; and/or
wherein an electrical potential difference between an average electrical potential of the pole pieces (19) and an electrical potential of the peripheral pole piece (11) is at least 2 kV.

• eine Quadrupolfeld-Wicklung (43) zum Erzeugen eines magnetischen Quadrupolfeldes und mehrere getrennte Dipolfeld-Wicklungen (47, 49) zum Erzeugen von magnetischen Dipolfeldern.

Example 25 relates to a multipole element (1, 1A) according to any one of Examples 1 to 24,
wherein the multipole element (1, 1A) is a quadrupole element with four pole pieces (19) and four supports (13);
wherein the coils (17) comprise at least one winding from a group of windings, the group of windings comprising:

• a quadrupole field winding (43) for generating a magnetic quadrupole field and several separate dipole field windings (47, 49) for generating magnetic dipole fields.

• eine Oktupolfeld-Wicklung (41) zum Erzeugen eines magnetischen Oktupolfeldes, mehrere getrennte Quadrupolfeld-Wicklungen (43, 45) zum Erzeugen von magnetischen Quadrupolfeldern und mehrere getrennte Dipolfeld-Wicklungen (47, 49) zum Erzeugen von magnetischen Dipolfeldern.

Example 26 relates to a multipole element (1, 1A) according to any one of Examples 1 to 24,
wherein the multipole element (1, 1A) is an octupole element with eight pole pieces (19) and eight nozzles (13);
wherein the coils (17) comprise at least one winding from a group of windings, the group of windings comprising:

• an octupole field winding (41) for generating a magnetic octupole field, a plurality of separate quadrupole field windings (43, 45) for generating magnetic quadrupole fields and a plurality of separate dipole field windings (47, 49) for generating magnetic dipole fields.

Example 27 relates to an image aberration corrector (105) comprising at least one multipole element (1, 1A) according to any one of Examples 1 to 26.

• mindestens ein Multipolelement (1, 1A) gemäß einem der Beispiele 1 bis 26 oder mindestens einen Bildfehlerkorrektor (105) gemäß Beispiel 27.

Example 28 relates to a particle beam system (100) for analyzing or processing a sample (115), comprising:

• at least one multipole element (1, 1A) according to one of examples 1 to 26 or at least one image aberration corrector (105) according to example 27.

• ein Strahlrohr (104); und
• eine Spannungsquelle, welche konfiguriert ist, eine elektrische Potentialdifferenz zwischen dem Strahlrohr (104) und der Probe (115) zu erzeugen, welche mindestens 2 kV beträgt.

Example 29 relates to a particle beam system (100) according to Example 28, further comprising:

• a jet pipe (104); and
• a voltage source configured to generate an electrical potential difference between the beam tube (104) and the sample (115) which is at least 2 kV.

list of reference symbols

1, 1A

multipole element;

3

Pipe;

4

propagation area;

5

central axis;

6a, 6b

opening of the tube at the central axis;

7

outdoor assembly;

9

vacuum chamber assembly;

11

circumferential pole piece;

12a

upper end pole piece;

12b

lower end pole piece;

13

Support;

15

outer wall surface of the pipe;

16

inner wall surface of the pipe;

17

Wash;

19, 19A, 19B, 19C, 19D

pole pieces;

21, 22

side surfaces of a pole piece;

23

inner surface of a pole piece;

25

outer surface of a pole piece;

27

bracket;

29

first electrical line;

31

electrical connections;

33

area of the tube between pole piece and nozzle;

35

second electrical line;

37

vacuum feedthrough;

41

octupole winding;

42

connections of the octupole winding;

43

first quadrupole winding;

44

Connections of the first quadrupole winding;

45

second quadrupole winding;

46

Connections of the second quadrupole winding;

47, 49

dipole winding;

48, 50

connections of the dipole windings;

100

particle beam system;

101

particle source;

102

particle beam;

103

accelerating electrode;

104

jet pipe;

105

image error corrector;

106

deflection coils;

107

deflection electrodes;

109

objective lens;

111

vacuum chamber;

113

sample table;

114

communication link;

115

Sample;

117

Detector;

118

interaction products;

119

communication link;

121

communication link;

125

Steering;

127

input device;

129

output device;

131

data storage;

D1

Radial distance between pole piece and tube;

DR

inner diameter of the pipe;

FP

focal plane;

h1

first half-line;

h2

second half-line;

h3

third half-line;

h4

fourth half-line;

k1

first edge;

k2

second edge;

k3

third edge;

k4

fourth edge;

L

Length of a pole piece in radial direction;

R

radial direction;

R0

smallest distance between central axis and pole piece;

S1, S2

intersection point;

TR

Wall thickness of the pipe in radial direction;

TP

Thickness of the pole piece in the circumferential direction;

U

circumferential direction;

α

inner cover angle;

β

external cover angle;

Φ

coverage angle.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• EP 0 379 690 A1 [0005]

Claims (26)

Multipole element (1, 1A), comprising: an electrically insulating tube (3) which surrounds a central axis (5) of the multipole element (1, 1A); an outer space assembly (7) which is arranged outside the tube (3) with respect to a radial direction (R) which extends perpendicularly from the central axis (5), and a vacuum space assembly (9) which is arranged inside the tube (3) with respect to the radial direction (R), wherein the outer space assembly (7) comprises: a circumferential pole piece (11) which is magnetically conductive and surrounds the tube (3) in a circumferential direction (U), wherein the circumferential direction (U) is oriented perpendicularly to the central axis (5) and to the radial direction (R), a plurality of nozzles (13) which are magnetically conductive are arranged distributed around the central axis (5) and extend from the circumferential pole piece (11) counter to the radial direction (R) to an outer wall surface (15) of the tube (3); and a plurality of coils (17); wherein the vacuum space assembly (9) comprises: a plurality of pole pieces (19) which are magnetically conductive, electrically conductive, are arranged distributed around the central axis (5) and extend from the tube (3) counter to the radial direction (R); wherein the multipole element (1) further comprises: a plurality of first electrical lines (29) which electrically connect the pole pieces (19) to electrical connections (31) in the external space assembly (7); and a plurality of second electrical lines (35) which electrically connect at least some of the pole pieces (19) to one another in groups. Multipole element (1A) according to claim 1 , wherein at least a part of the plurality of first electrical lines (29) is guided through an opening (6a, 6b) of the tube (3) located on the central axis (5). Multipole element (1, 1A) according to claim 1 or 2 , wherein a region (33) of the tube (3) which adjoins the pole pieces (19) and the nozzles (13) in the radial direction (R) has no opening which penetrates the tube (3) in the radial direction (R). Multipole element (1, 1A) according to one of the Claims 1 until 3 , wherein the plurality of first electrical lines (29) penetrate the tube (3) in the radial direction (R) outside a region (33) of the tube (3) which adjoins the pole pieces (19) and the nozzles (13) in the radial direction (R). Multipole element (1, 1A) according to one of the Claims 1 until 4 , wherein the second electrical lines (35) each electrically connect a pair of the pole pieces (19) which are opposite to each other via the central axis (5). Multipole element (1, 1A) according to one of the Claims 1 until 5 , wherein a distance measured in the radial direction (R) between the pipe (3) and each of the nozzles (13) is at least zero. Multipole element (1, 1A) according to one of the Claims 1 until 6 , wherein a distance measured in the radial direction (R) between the pipe (3) and each of the nozzles (13) is less than 20% of an inner diameter (DR) of the pipe (3) measured in the radial direction (R) and/or less than 5 mm. Multipole element (1, 1A) according to one of the Claims 1 until 7 wherein a distance (D1) measured in the radial direction (R) between each of the pole pieces (19) and the tube (3) is at least zero. Multipole element (1, 1A) according to one of the Claims 1 until 8 , wherein a distance (D1) measured in the radial direction (R) between each of the pole pieces (19) and the tube (3) is less than 20% of an inner diameter (DR) of the tube (3) measured in the radial direction (R) and/or less than 5 mm. Multipole element (1, 1A) according to one of the Claims 1 until 9 , wherein a wall thickness (TR) of the tube (3) measured in the radial direction (R) is greater than zero. Multipole element (1, 1A) according to one of the Claims 1 until 10 , wherein a wall thickness (TR) of the pipe (3) measured in the radial direction (R) is less than 20% of an inner diameter (DR) of the pipe (3) measured in the radial direction (R) and/or less than 5 mm. Multipole element (1, 1A) according to one of the Claims 1 until 11 , wherein the nozzles (13) do not penetrate the tube (3) in the radial direction (R), wherein the pole pieces (19) do not penetrate the tube (3) in the radial direction (R). Multipole element (1, 1A) according to one of the Claims 1 until 12 , wherein the tube (3) provides a vacuum separation in the radial direction (R) between the vacuum space assembly (9) and the outer space assembly (7). Multipole element (1, 1A) according to one of the Claims 1 until 13 , wherein the tube (3) is magnetically non-conductive. Multipole element (1, 1A) according to one of the Claims 1 until 14 , wherein the pole pieces (19) are each shaped such that an inner cover angle (α) and an outer cover angle (β) have different values from one another, wherein a radius-dependent cover angle (Φ(r)) indicates an acute angle between a first half-line (h1) and a second half-line (h2), wherein the first half-line (h1) lies in a cross-sectional plane oriented perpendicular to the central axis (5), starts from the central axis (5) and runs through a first intersection point (S1(r)), wherein the second half-line (h2) lies in the cross-sectional plane, starts from the central axis (5) and runs through a second intersection point (S2(r)), wherein the first intersection point (S1(r)) and the second intersection point (S2(r)) are intersection points of the surface of the respective pole piece (19) with a circle which lies in the cross-sectional plane, has the radius r and whose center is on the central axis (5) wherein the inner coverage angle (α) is defined as the largest radius-dependent coverage angle (Φ(r)) in a range R0≤r<R0+20%L, wherein the outer coverage angle (β) is defined as the largest radius-dependent coverage angle (Φ(r)) in a range DR/2-20%L<r≤DR/2, wherein R0 is the smallest distance measured in the radial direction R between the surface of the respective pole piece (19) and the central axis (5), wherein DR is the inner diameter of the tube (3), wherein L is the maximum length of the respective pole piece (19) measured in the radial direction (R). Multipole element (1, 1A) according to claim 15 , wherein a sector width is defined as the ratio of 360° to the number of pole pieces; wherein the pole pieces (19) are shaped such that the inner coverage angle (α) is greater than the outer coverage angle (β); and/or wherein the pole pieces (19) are shaped such that a difference between the inner coverage angle (α) and the outer coverage angle (β) is at least 10% of the sector width; and/or wherein the pole pieces (19) are shaped such that a ratio of the inner coverage angle (α) to the sector width has a value in the range of 75% to 95%; and/or wherein the pole pieces (19) are shaped such that a ratio of the outer coverage angle (β) to the sector width has a value in the range of 35% to 75%. Multipole element (1, 1A) according to claim 15 or 16 , wherein the pole pieces (19) are each shaped such that a center coverage angle (γ) of the respective pole piece (19) is both smaller than the inner coverage angle (α) of the respective pole piece (19) and smaller than the outer coverage angle (β) of the respective pole piece (19), wherein the center coverage angle (γ) is defined as the smallest radius-dependent coverage angle (Φ(r)) in a range R0+20%L<r<DR/2-20%L. Multipole element (1, 1A) according to one of the Claims 1 until 14 , wherein the pole pieces (19) are each shaped such that a center coverage angle (γ) of the respective pole piece (19) is both smaller than an inner coverage angle (α) of the respective pole piece (19) and smaller than an outer coverage angle (β) of the respective pole piece (19), wherein a radius-dependent coverage angle (Φ(r)) indicates an acute angle between a first half-line (h1) and a second half-line (h2), wherein the first half-line (h1) lies in a cross-sectional plane oriented perpendicular to the central axis (5), starts from the central axis (5) and runs through a first intersection point (S1(r)), wherein the second half-line (h2) lies in the cross-sectional plane, starts from the central axis (5) and runs through a second intersection point (S2(r)), wherein the first intersection point (S1(r)) and the second intersection point (S2(r)) are intersection points the surface of the respective pole piece (19) with a circle which lies in the cross-sectional plane, has the radius r and whose center lies on the central axis (5), wherein the inner coverage angle (α) is defined as the largest radius-dependent coverage angle (Φ(r)) in a range R0≤r<R0+20%L, wherein the outer coverage angle (β) is defined as the largest radius-dependent coverage angle (Φ(r)) in a range DR/2-20%L<r≤DR/2, wherein the center coverage angle (γ) is defined as the smallest radius-dependent coverage angle (Φ(r)) in a range R0+20%L<r<DR/2-20%L, wherein R0 is the smallest distance measured in the radial direction R between the surface of the respective pole piece (19) and the central axis (5), wherein DR is the inner diameter of the tube (3), wherein L is the radius-dependent coverage angle (Φ(r)) in the radial direction (R) is the maximum length of the respective pole piece (19). Multipole element (1, 1A) according to one of the Claims 1 until 18 , wherein the pole pieces (19) each have two lateral surfaces (21, 22), each facing a pole piece of the pole pieces (19) adjacent in the circumferential direction (U); wherein the lateral surfaces (21, 22) of the pole pieces (19) are curved or kinked. Multipole element (1, 1A) according to one of the Claims 1 until 19 , wherein the vacuum chamber assembly (9) further comprises a holder (27) for holding the pole pieces (19). Multipole element (1, 1A) according to claim 20 , wherein the holder (27) is partially or completely provided by the tube (3). Multipole element (1, 1A) according to one of the Claims 1 until 21 , wherein the multipole element (1, 1A) is a quadrupole element with four pole pieces (19) and four studs (13); wherein the coils (17) have at least one winding from a group of windings, the group of windings comprising: a quadrupole field winding (43) for generating a magnetic quadrupole field and a plurality of separate dipole field windings (47, 49) for generating magnetic dipole fields. Multipole element (1, 1A) according to one of the Claims 1 until 21 , wherein the multipole element (1, 1A) is an octupole element with eight pole pieces (19) and eight studs (13); wherein the coils (17) have at least one winding from a group of windings, the group of windings comprising: an octupole field winding (41) for generating an octupole magnetic field, a plurality of separate quadrupole field windings (43, 45) for generating quadrupole magnetic fields and a plurality of separate dipole field windings (47, 49) for generating dipole magnetic fields. Image aberration corrector (105) comprising at least one multipole element (1, 1A) according to one of the Claims 1 until 23 includes. Particle beam system (100) for analyzing or processing a sample (115), comprising: at least one multipole element (1, 1A) according to one of the Claims 1 until 23 or at least one image error corrector (105) according to claim 24 . Particle beam system (100) according to claim 25 , further comprising: a beam tube (104); and a voltage source configured to generate an electrical potential difference between the beam tube (104) and the sample (115) that is at least 2 kV.

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