Aberration corrector and charged particle beam device

Abstract

The utility model provides an aberration corrector and a charged particle beam device. The aberration corrector includes a first plurality of magnetic elements, each magnetic element including a magnetic pole and a corresponding magnetic bar for providing a magnetic field to the magnetic pole. The first plurality of magnetic elements comprises at least a first magnetic element, and the first magnetic element comprises a first magnetic pole; the first magnetic rod is provided with a near end adjacent to the first magnetic pole and a far end opposite to the near end; the near end is provided with a tip end, and the tip end is provided with a hemispherical tip end surface; and the contact point of the tip surface contacts the first magnetic pole.

Description

Technical Field

[0001] Embodiments described herein relate to aberration correctors and charged particle systems including aberration correctors. Background Art

[0002] In charged particle beam devices such as microscopes, micro-machining devices, semiconductor manufacturing devices, etc., single-stage or multi-stage multipoles (quadrupoles, hexapole, octopole, etc.) are used in deflectors or aberration correctors. The machining accuracy of the above devices can be in the range of about 10 microns. The device can perform observations with an accuracy in the nanometer range or even below the nanometer range.

[0003] For such applications, the resolution of the device is beneficial in the range below nanometers. The performance of the charged particle beam device can be improved by the aberration correction of the multipole corrector. Such aberration corrector includes one or more multipole stages. The quality of the correction depends on the accuracy of the multipole field on the axis. The tolerance between the poles causes the magnetic field distribution on the optical axis to be disturbed.

[0004] In particular, in aberration correctors (such as spherical aberration correctors and chromatic aberration correctors), where the multipole fields involved can be strong, inaccuracies in such correctors can lead to imperfections in the electric and magnetic field profiles, which in turn produce residual aberrations that limit the performance achievable by the device.

[0005] Accordingly, high accuracy in manufacturing and assembly is beneficial. For example, in an aberration corrector, the positioning accuracy of the poles and other components that make up the magnetic circuit is advantageous. This is because such positioning inaccuracies lead to parasitic multipole fields, which in turn lead to blurring of the beam. In addition, solutions to improve accuracy often involve increased complexity, which has a negative impact on reproducibility and cost, especially in large-scale production.

[0006] Accordingly, it would be beneficial to provide an aberration corrector and method of reducing or minimizing magnetic field deviations from pole to pole. Utility Model Content

[0007] In view of the above, a utility model as defined by the claims is provided. According to the aspects described herein, an aberration corrector and a charged particle beam apparatus are provided.

[0008] According to one embodiment, an aberration corrector is provided. The aberration corrector includes a first plurality of magnetic elements, each magnetic element including a magnetic pole and a corresponding magnetic rod for providing a magnetic field to the magnetic pole. The first plurality of magnetic elements includes at least a first magnetic element, the first magnetic element including a first magnetic pole; a first magnetic rod having a proximal end adjacent to the first magnetic pole and a distal end opposite to the proximal end; the proximal end having a tip, the tip having a tip surface in the shape of a hemisphere; and a contact point of the tip surface contacts the first magnetic pole.

[0009] In some embodiments, the contact point of the tip surface contacts the first magnetic pole at the contact surface of the first magnetic pole, and the contact surface has a curvature that is less than the tip curvature of the tip surface. The curvature may be zero.

[0010] In some embodiments, the first magnetic element includes a first excitation coil disposed on a first magnetic bar. In particular, the first excitation coil is wound on a first carrier, and the first carrier electrically insulates the first excitation coil from the first magnetic bar.

[0011] In some embodiments, the first magnetic element comprises a first electrical connector connected to the first magnetic bar adjacent to the distal end. In particular, the first magnetic element comprises a spring at the proximal end contacting the first magnetic pole to provide an electrical connection between the first magnetic bar and the first magnetic pole.

[0012] In some embodiments, the aberration corrector further comprises a ring magnetically connecting the first plurality of magnetic elements to each other. In particular, the aberration corrector further comprises a foil positioned between the ring and the first plurality of magnetic elements, wherein the foil electrically insulates the ring from the first plurality of magnetic elements.

[0013] In some embodiments, the aberration corrector further comprises a support configured to support at least the first magnetic bar. In particular, the support comprises a vacuum feedthrough for the first magnetic bar.

[0014] In some embodiments, the aberration corrector further includes a pressing element configured to adjust a contact force between the first magnetic bar and the first magnetic pole.

[0015] In some embodiments, each pole of the first plurality of magnetic elements is attached to an assembly ring.

[0016] In some embodiments, the first plurality of magnetic elements includes 8 magnetic elements forming 8 poles or 12 magnetic elements forming 12 poles.

[0017] In some embodiments, the aberration corrector includes a second stage, the second stage includes a second plurality of magnetic elements, each of the second plurality of magnetic elements includes a magnetic pole and a corresponding magnetic rod for providing a magnetic field to the magnetic pole, wherein the first stage includes the first plurality of magnetic elements and the second stage is stacked above the first stage.

[0018] According to one embodiment, a charged particle beam device is provided. The charged particle beam device includes: a sample stage; a charged particle source, suitable for generating a charged particle beam; and a charged particle beam manipulation system, including an aberration corrector. The aberration corrector includes: a first plurality of magnetic elements, each magnetic element including a magnetic pole and a corresponding magnetic rod for providing a magnetic field to the magnetic pole, the first plurality of magnetic elements including at least a first magnetic element. The first magnetic element includes: a first magnetic pole; a first magnetic rod, having a proximal end adjacent to the first magnetic pole and a distal end opposite to the proximal end; the proximal end has a tip, the tip has a tip surface in the shape of a hemisphere; and a contact point of the tip surface contacts the first magnetic pole.

[0019] According to one embodiment, a charged particle beam apparatus is provided. The charged particle beam apparatus comprises: a sample stage; a charged particle source adapted to generate a charged particle beam; and a charged particle beam manipulation system comprising an aberration corrector according to any of the embodiments described herein.

[0020] Further advantages, features, aspects and details which can be combined with the embodiments described herein are apparent from the dependent claims, the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to be able to understand in detail the manner in which the above-mentioned features of the present invention are used, a more particular description of the embodiments briefly summarized above may be made with reference to the embodiments. The accompanying drawings relate to one or more embodiments and are described below.

[0022] Figure 1 is a cross-sectional view of an aberration corrector according to an embodiment described herein;

[0023] Figure 2A is a cross-sectional view of the tip of a magnetic rod of an aberration corrector according to an embodiment described herein;

[0024] Figure 2B is a cross-sectional view of the tip of a magnetic rod of an aberration corrector according to an embodiment described herein;

[0025] Figure 2C is a cross-sectional view of the tip of a magnetic rod of an aberration corrector according to an embodiment described herein;

[0026] Figure 3A is a cross-sectional view of a first magnetic element of an aberration corrector according to embodiments described herein;

[0027] Figure 3B is a cross-sectional view of a first magnetic element of an aberration corrector according to embodiments described herein;

[0028] Figure 4is a cross-sectional view of an aberration corrector including multiple stages each having multiple magnetic elements according to embodiments described herein;

[0029] Figure 5 is a schematic illustration of a charged particle beam apparatus according to embodiments described herein; and

[0030] Figure 6 is a flow chart illustrating a method of aligning an aberration corrector according to embodiments described herein.

[0031] Figure 7 is a flow chart illustrating a method of correcting aberrations of a charged particle beam using an aberration corrector according to embodiments described herein. DETAILED DESCRIPTION

[0032] Reference will now be made in detail to various embodiments, one or more examples of which are shown in the accompanying drawings. In the following description of the drawings, the same reference numerals refer to the same parts. In general, only the differences with respect to the various embodiments are described. Each example is provided by way of explanation and is not intended to be limiting. In addition, features shown or described as part of one embodiment may be used in other embodiments or used in conjunction with other embodiments to produce additional embodiments. The description is intended to include such modifications and variations.

[0033] In order to improve the resolution of, for example, an SEM column beyond the limits of a simple circular lens system, a multipole corrector can be used to correct aberrations, such as spherical aberration, chromatic aberration, coma and other aberrations. Such a multipole corrector typically comprises one or more stages of magnetic and / or electrostatic multipoles (MP), each MP comprising a number of poles. The poles may comprise electrodes and include magnetic elements, for example, 8 or 12 magnetic elements. Each magnetic element comprises a magnetic pole and a magnetic rod close to the optical axis of, for example, the SEM column. The magnetic rod may carry an excitation coil. The magnetic elements of the same multipole may be oriented in the same plane. The magnetic elements may be oriented in a star shape oriented around a central axis. The magnetic elements may have equal radial distances from the central axis and may have equal angles between each two adjacent magnetic elements. The magnetic elements may be aligned to form an opening of the aberration corrector, in particular the opening being concentric with the central axis. The opening may be aligned with the optical axis.

[0034] The quality of the correction depends on the accuracy of the MP quadrupole field on the axis. Advantageously, each magnetic pole provides a predetermined amount of magnetic field to the optical axis, in particular the same amount of magnetic field. The magnetic field may depend on the material properties, mechanical tolerances in the air gap of the magnetic circuit and mechanical tolerances of the pole-head shape. The magnetic field may depend on the alignment of the magnetic poles and the magnetic bars in each magnetic element. Tolerances may cause the magnetic field distribution on the optical axis to be disturbed, which may lead to undesired dipole fields and concomitant beam deflections.

[0035] According to an embodiment of the present disclosure, a joint design between a magnetic pole and a magnetic bar is provided that can compensate for machining and assembly tolerances and minimize or reduce deviations in pole-to-pole magnetic field transfer.

[0036] The on-axis magnetic field of each magnetic pole in the aberration corrector is determined by the connection between the yoke (also referred to as a ring in this disclosure), the magnetic bar and the magnetic pole, and other factors. Differences in the connection joints between the parts result in changes in the magnetic field transmitted to the optical axis.

[0037] The complexity of the assembly leads to angular and positional tolerances between the magnetic bar and the magnetic poles, i.e., angular and positional tolerances between the magnetic bar and the magnetic poles of each magnetic element. Solid connections (e.g., threads) may lead to mechanical stresses on the magnetic poles, which in turn may lead to unwanted physical movement of the magnetic poles. Mechanical stresses may further lead to unwanted changes in the magnetic properties of the poles, e.g., changes in the magnetic domain structure of the poles. Physical movement or different magnetic properties may affect the magnetic field on the shaft. Contactless connections lead to small gaps between the magnetic bar and the magnetic poles. Deviations in the gap between one magnetic element and another may also lead to deviations in the field between the magnetic poles.

[0038] According to an embodiment of the present disclosure, the magnetic bar has a hemispherical tip, in particular a hemispherical tip, which touches the magnetic pole on the flat surface. According to a further embodiment, the magnetic bar touches the magnetic pole on the surface with a larger radius (i.e. a smaller curvature) than the radius of the tip. With the connection joint according to an embodiment of the present disclosure, at each point on the surface of the bar tip, the distance between the bar and the pole head is similar from pole to pole (except for the machining tolerance of the radius), in particular independent of any angular or positional tolerances.

[0039] Embodiments advantageously overcome pole-to-pole deviations in magnetic field transmission between magnet bars and poles that may result from angular or positional tolerances of the system without introducing mechanical stresses to the poles. The amount of adjustment to compensate for a disturbed magnetic field distribution on the optical axis in a multipole may be reduced.

[0040] Correcting spherical and chromatic aberrations of a charged particle beam device may result in improvements in resolution or current density, and thereby generally improve the performance of the charged particle beam device, including an electron beam microscope, such as a scanning electron beam microscope (SEM).

[0041] According to one aspect, an aberration corrector is provided comprising a first plurality of magnetic elements. Each magnetic element comprises a magnetic pole and a corresponding magnetic rod for providing a magnetic field to the magnetic pole. The first plurality of magnetic elements comprises at least a first magnetic element, the first magnetic element comprising a first magnetic pole, a first magnetic rod having a proximal end adjacent to the first magnetic pole and a distal end opposite to the proximal end, the proximal end having a tip, the tip having a tip surface having a hemispherical shape, and a contact point of the tip surface contacts the magnetic pole. According to some embodiments, which can be combined with other embodiments described herein, the first magnetic rod or the further magnetic rod can be formed integrally, i.e. as one part, or can be formed from two or more parts, for example, a first rod part and a second rod part.

[0042] An aberration corrector according to embodiments described herein comprising a first magnetic element allows minimizing or reducing deviations in the magnetic field provided by the magnetic pole towards the optical axis. This is achieved by minimizing deviations during positional alignment of the first magnetic bar with the first magnetic pole.

[0043] Figure 1 A view of an aberration corrector 100 according to an embodiment described herein is illustrated. The aberration corrector 100 includes a first plurality of magnetic elements 105 and a ring 180. The plurality of magnetic elements are evenly distributed around a central axis 110. The first plurality of magnetic elements can be arranged in the same plane or in a common plane. The distribution can be such that the magnetic elements have the same angle between every two magnetic elements and are centered around the central axis 110. In particular, the magnetic elements can be arranged in a star shape oriented around the central axis 110. The magnetic elements have equal radial distances from the central axis and can, for example, have equal angles between every two adjacent magnetic elements. The magnetic elements can be aligned to form an opening of the aberration corrector, in particular wherein the opening is concentric with the central axis. The opening can be aligned with the optical axis of a charged particle beam device, a SEM and / or an objective lens.

[0044] The aberration corrector may include a first plurality of magnetic elements 105, such as 8 magnetic elements for 8 poles or 12 magnetic elements for 12 poles. The aberration corrector may include any number n of magnetic elements to form n poles, for example, 4, 6, 8, 10, 12 or more magnetic elements. Throughout the present application, the individual magnetic elements of the first plurality of magnetic elements 105 are further numbered with letters to provide better distinguishability of the individual magnetic elements. For example, the magnetic elements of the 8 poles may be indicated as magnetic elements 105a, 105b, 105c, 105d, 105e, 105f, 105g and 105h, and the magnetic elements of the 12 poles may be indicated as 105a, 105b, 105c, 105d, 105e, 105f, 105g, 105h, 105i, 105j, 105k and 105l. In the present disclosure, one magnetic element, namely the magnetic element 105a, is referred to as the first magnetic element. The additional magnetic elements may be referred to as the second magnetic element 105b, the third magnetic element 105c, the fourth magnetic element 105d, and so on. In particular, the magnetic elements of the first plurality of magnetic elements 105 other than the first magnetic element 105a are referred to as additional magnetic elements 105x. In the present disclosure, reference will be made to the first magnetic element 105a, and the first magnetic element 105a will be described in detail. It will be understood that the additional magnetic elements 105x may be similar to the first magnetic element 105a, in particular have the same construction.

[0045] The first magnetic element 105a includes a first magnetic pole 120 and a first magnetic bar 130. The first magnetic bar 130 contacts the first magnetic pole 120. A magnetic field may be provided from the first magnetic bar 130 to the first magnetic pole 120. The first magnetic bar 130 has a first axis 135 in a length direction of the first magnetic bar 130. The first magnetic bar 130 may be arranged such that the extension of the first axis 135 crosses the central axis 110. The first excitation coil 170 may be provided on the first magnetic bar 130. A magnetic field may be provided by the first excitation coil 170. A magnetic field may be provided to the first magnetic bar 130.

[0046] The first plurality of magnetic elements 105 provide a magnetic circuit. The magnetic circuit can be closed by a ring 180. The ring 180 can be understood as a yoke. The ring 180 can surround the first plurality of magnetic elements 105. In one embodiment, a foil 185 is placed between the ring 180 and each magnetic element in the plurality of magnetic elements. The foil 185 electrically isolates the ring and each magnetic element in the first plurality of magnetic elements from each other. The magnetic element can be in direct contact with the foil 185, and the foil can be in direct contact with the ring 180 to provide a constant alignment of the magnetic element with the ring 180. The first magnetic bar 130 can be in direct contact with the foil 185 and the first magnetic pole. The first magnetic bar 130 can be fixed between the foil 185 and the first magnetic bar 130. In particular, the first magnetic bar 130 can be clamped between the foil 185 and the first magnetic pole. In another embodiment, the ring is placed with an air gap between each magnetic element and the ring 180. The air gap may be on the order of millimeters. The air gap may be constant for each magnetic element in the plurality of magnetic elements. In one embodiment, which can be combined with other embodiments described herein, the aberration corrector further comprises a ring magnetically connecting the first plurality of magnetic elements 105 to each other. The ring magnetically connects the first magnetic element 105a and the further magnetic element 105x to each other.

[0047] The magnetic elements in the first plurality of magnetic elements 105 provide magnetic n-poles, where n may be 4, 6, 8, 10, 12, or higher. That is, the magnetic elements in the first plurality of magnetic elements 105 may provide magnetic 4-pole, 6-pole, 8-pole, 10-pole, 12-pole, or higher order poles. Figure 1 An aberration corrector comprising 12 magnetic elements forming 12 poles is illustrated. The magnetic n-pole comprises a central opening, in particular a central opening corresponding to the opening of the aberration corrector. The central opening is configured to be aligned with the optical axis 109. The first magnetic element 105a can be arranged so that the extension of the first axis 135 spans the central axis 110. The further magnetic element 105x can be arranged so that the further axis spans the central axis 110. The magnetic elements are oriented together with the magnetic poles toward the center of the star shape. The magnetic elements have a constant angle α with each other. The constant angle depends on the number of magnetic elements and can be determined by the formula α=360° / n. In one embodiment that can be combined with other embodiments described herein, the first plurality of magnetic elements comprises 8 magnetic elements forming 8 poles or 12 magnetic elements forming 12 poles. The first plurality of magnetic elements can include 6 magnetic elements forming 6 poles.

[0048] The magnetic field provided by the first magnetic bar 130 to the first magnetic pole 120 depends on the alignment of the first magnetic bar 130 with the first magnetic pole 120. The first magnetic bar 130 has a proximal end 140 adjacent to the first magnetic pole 120 and a distal end 150 opposite the proximal end. The proximal end 140 has a tip 200 contacting the first magnetic pole 120. Figure 2Ais a detailed view of the tip 200 contacting the first magnetic pole 120. The tip 200 has a tip surface 210 in the shape of a hemisphere. In the present application, the term hemisphere generally refers to any sphere having a polar angle less than 360°, ie not a complete sphere.

[0049] The tip surface 210 is in the shape of a hemisphere. The tip may be a convex tip, in particular, in the shape of a convex hemisphere. The center 215 of the hemisphere may be located on the first axis 135 of the first magnetic bar 130. The hemisphere has a first semi-axis a, a second semi-axis b, and a third semi-axis c. Figure 2A As shown, the first semi-axis and the third semi-axis c are in the plane of the paper and are perpendicular to each other. The second semi-axis b (not shown) is outside the plane of the paper and is perpendicular to the first semi-axis a and the third semi-axis c. The lengths of the first semi-axis a and the second semi-axis b are the same. The third semi-axis c is aligned with the axis 135. In an embodiment, the hemispherical body is a hemisphere, and the length of the third semi-axis c is equal to the length of the first semi-axis a and the second semi-axis b.

[0050] The opening angle of the hemisphere may be equal to 180°. Then, the radius of the first magnetic bar 130 adjacent to the tip 200 is equal to the length of the first semi-axis a. The center of the opening is located at the contact plane of the tip 200 and the first magnetic bar 130. The opening angle of the hemisphere may be less than 180°. Then, the radius of the first magnetic bar 130 adjacent to the tip 200 is less than the length of the first semi-axis a. The center 215 is located inside the first magnetic bar 130. The hemisphere may have an opening angle greater than 180°. Then, the radius of the first magnetic bar 130 adjacent to the tip 200 is less than the length of the first semi-axis a. The center 215 is located inside the tip 200.

[0051] The contact point 220 of the tip surface contacts the magnetic pole 120. The contact point 220 contacts the magnetic pole 120 on the contact surface 230. The contact point 220 is the point where the tip surface 210 contacts the contact surface 230. The contact surface is a surface having an area provided for the contact point 220 of the magnetic bar and the magnetic pole, e.g. Figure 2A The flat surface shown or having Figure 2B The contact surface is given by Figure 2A and Figure 2B The first bar magnet 130 has a first axis 135. The first pole 120 having a contact surface 230 has a surface normal 125. The surface normal is determined at the point on the contact surface 230 where the contact point 220 contacts the contact surface 230. The surface normal is determined at the contact point 220. Figure 2AAs shown in detail view AA in FIG. 1 , the first bar magnet 130 may have a deviation angle δ from the first magnetic pole 120. The deviation angle δ is determined as the angle of the first axis 135 and the surface normal 125. For a deviation angle δ equal to 0°, the contact point 220 is at the intersection of the first axis 135 and the tip surface 210, referred to as the vertex 225 of the tip. For δ not equal to 0, the contact point 220 will be offset from the vertex 225. Although detail view AA is two-dimensional, it will be understood that in a second direction, such as in a direction into the drawing plane, the first bar magnet 130 may have a further angular deviation from the first magnetic pole.

[0052] As can be seen in detail view AA, for small deviation angles δ, the hemispherical shaped tip can compensate for the angular deviation. The first magnetic bar 130 contacts the first magnetic pole 120 in a contact point 220. Two points located diametrically opposite the contact point have the same distance from the surface of the first magnetic pole 120. For deviation angles δ up to 0.5°, up to 1° or up to 2°, the tip can compensate for the angular deviation.

[0053] like Figure 2A As shown in the detailed view AA, the contact surface 230 of the first magnetic pole 120 may have zero curvature (0 1 / m), that is, the contact surface 230 of the first magnetic pole 120 may be flat. The contact surface 230 of the first magnetic pole may have a curvature of Figure 2B In an embodiment which can be combined with other embodiments described herein, a contact point of the tip surface contacts the magnetic pole at a contact surface of the magnetic pole, and the contact surface has a curvature that is less than a tip curvature of the tip surface.

[0054] Figure 2B An embodiment including a contact surface 230 having a curvature is illustrated. The curvature of the contact surface 230 is at least 3 times the curvature of the tip surface 210. The cross-sectional area of ​​the contact surface may have an area of ​​a circular shape having a radius greater than the length of the first semi-axis a. The cross-sectional area of ​​the contact surface may be other shapes with similar dimensions.

[0055] The contact surface 230 may be in the shape of a hemisphere. In particular, the contact surface 230 may be in the shape of a concave hemisphere. The tip surface 210 may have the shape of a hemisphere, and the contact surface 230 may have the shape of a hemisphere. The tip surface 210 may have the shape of a hemisphere, and the contact surface 230 may have the shape of a hemisphere. The tip surface may have the shape of a hemisphere, and the contact surface may have the shape of a hemisphere. The tip surface may have the shape of a hemisphere, and the contact surface may have the shape of a hemisphere.

[0056] The curvature of the contact surface 230 can provide guidance for the contact point of the tip surface. The contact surface may include a vertex corresponding to the point of the contact surface 230 that is farthest inside the first magnetic pole. The first magnetic bar 130 that contacts the first magnetic pole 120 including the hemispherical contact surface 230 can be guided to the vertex of the contact surface. The hemispherical contact surface 230 advantageously provides that the contact point of the first magnetic bar 130 can be guided to a predetermined position, i.e., the vertex of the contact surface. The contact point 220 of the first magnetic bar 130 contacts the first magnetic pole 120 close to the vertex of the contact surface or at the vertex of the contact surface.

[0057] Typical embodiments of the first magnetic element 105a and the further magnetic element 105x include a tip surface in the shape of a hemisphere and a contact surface in the shape of a hemisphere. The geometry of the tip surface and the contact surface advantageously provides alignment of the first magnetic bar 130 with the first magnetic pole 120. In particular, the geometry of the tip surface provides automatic alignment of the first magnetic pole 130 with the first magnetic pole 120 for the tilt angle of the first magnetic pole 130 with the first magnetic pole 120. The first magnetic bar 130 contacts the first magnetic pole 120 in the contact point 220. Two points located opposite the contact point on the diameter have the same distance from the surface of the first magnetic pole 120. For a deviation angle δ of up to 0.5°, up to 1° or up to 2°, the tip can compensate for the angular deviation.

[0058] The first magnetic bar 130 and the first magnetic pole are magnetically connected, in particular at the contact point 220, and a magnetic field can be provided by the first magnetic bar 130 to the first magnetic pole 120. The first magnetic bar 130 and the first magnetic pole 120 can be electrically connected through the contact point 220. A voltage can be provided to the first magnetic bar 130. The first magnetic bar can provide a voltage to the first magnetic pole 120 through the contact point 220. An additional electrical connection between the first magnetic bar 130 and the first magnetic pole 120 can be provided.

[0059] According to some embodiments, which can be combined with other embodiments described herein, a voltage can be applied to the first magnetic rod and the further magnetic rod to provide a voltage to the plurality of magnetic rods. In particular, the plurality of magnetic poles can provide a plurality of electrodes, which can be biased by a voltage. The plurality of electrodes biasing the aberration corrector can form an electrostatic multipole.

[0060] Figure 2C An embodiment comprising a spring 240 is illustrated. Additional electrical connection may be provided by the spring. The spring 240 is arranged on the proximal end 140 of the first magnetic bar 130. The spring may be arranged between the contact surface 230 and the protruding portion 250 of the first magnetic bar. In the present disclosure, a spring is understood to be an elastic object that stores mechanical energy, i.e. any elastic connector. In particular an elastic connector that allows the position between the bar and the pole to be adapted while maintaining an electrical connection. The spring advantageously has a high electrical conductivity.

[0061] When the first magnetic bar 130 contacts the first magnetic pole 120, the spring 240 is tightened between the contact surface 230 and the protrusion 250. The spring 240 may be preloaded between the contact surface 230 and the protrusion 250. The preloaded spring provides an electrical connection between the first magnetic bar 130 and the first magnetic pole 120. The preloaded spring advantageously allows for reliable and / or continuous contact of the spring with the protrusion 250 and the contact surface 230. The preloaded spring 240 provides a reliable and continuous electrical connection between the first magnetic bar 130 and the first magnetic pole 120.

[0062] In an embodiment, which can be combined with other embodiments described herein, the first magnetic element comprises a spring at a proximal end of a surface contacting the magnetic pole to provide an electrical connection between the magnetic bar and the magnetic pole.

[0063] Figure 3A 3 is a cross-sectional view of the first magnetic element 105a. The first magnetic element 105a includes a first magnetic pole 120 and a first magnetic bar 130. As can be seen in FIG3 , the first magnetic bar 130 contacts the first magnetic pole 120. The contact point 220 of the tip 200 of the first magnetic bar 130 contacts the first magnetic pole 120. The contact point 220 contacts the contact surface of the first magnetic pole 120. The distal end of the first magnetic bar 130 contacts the foil 185 placed between the first magnetic bar 130 and the ring 180.

[0064] The first magnetic bar 130 may be formed by a first rod element 130a and a second rod element 130b. The first rod element 130a and the second rod element 130b may have a threaded connection. The first rod element 130a may have an external thread, and the second rod element 130b may have an internal thread. The first rod element 130a may have an internal thread, and the second rod element 130b may have an external thread. The first rod element 130a and the second rod element 130b may be unscrewed. The contact force F on the magnetic pole and the foil 185 may be adjusted. 接触 . Contact force F 接触 It may be in the range of 5N to 500N, in particular in the range of 10N to 100N.

[0065] Figure 3B is with Figure 3A The first magnetic bar 130 is formed integrally, and the contact force is provided by the pressing element 360. The pressing element 360 is configured to apply a pressing force F to the first magnetic bar. 按压 The first magnetic bar has a contact force F 接触 Contact with the first magnetic pole. Contact force F 接触 Can be basically equal to the pressing force F 按压 The pressing element 360 may be configured to adjust the contact force F 接触. The pressing element may include a thread (not shown). The pressing element may include other methods for adjusting the contact force, for example, the pressing element may clamp the first magnetic bar 130 and apply a force along the axis 135 to adjust the contact force. The magnetic bar 130 may be in contact with the foil 185 at the distal end of the magnetic bar. The magnetic bar in contact with the foil has the advantage of defined magnetic properties that can be well controlled. Alternatively, an air gap may be provided between the magnetic bar 130 and the ring 180. In one embodiment that may be combined with other embodiments described herein, the aberration corrector includes a pressing element configured to adjust the contact force between the first magnetic bar and the first magnetic pole. In particular, the pressing element may be configured to adjust the contact force between the first magnetic bar and the first magnetic pole within a range of 5N to 500N, in particular within a range of 10N to 100N. A pressing element 360 may be provided for each magnetic element in the first plurality of magnetic elements 105.

[0066] refer to Figure 3A , the first magnetic bar 130 is supported in the support structure 320. The support structure 320 supports the first magnetic bar 130. The support structure 320 fixes the position of the first magnetic bar 130 in the aberration corrector 100. The support structure 320 can fix the position of the first magnetic bar 130 relative to the position of the first magnetic pole 120. Additional support structures can be provided for additional magnetic elements 105x. The pressing element 360 can be formed integrally with the support structure 320. For example, the support structure and the magnetic bar can have a threaded connection to adjust the contact force.

[0067] The support structure 320 may be formed integrally with the further support structure. The integrally formed support structure 320 fixes the positions of the first magnetic bar 130 of the first magnetic element 105a and the further magnetic bar of the further magnetic element 105x to each other. For example, for 8 poles or 12 poles, the integrally formed support structure may provide the magnetic bars as a star-shaped structure, with equal angles between each magnetic bar, 45° or 30° respectively, and an opening provided in the center of the star. In one embodiment, which may be combined with other embodiments described herein, the aberration corrector comprises a support configured to support at least the first magnetic bar.

[0068] The support structure 320 may be made of plastic, ceramic, glass or any other non-magnetic and electrically isolating material. The support structure 320 may provide a vacuum feedthrough 340. In particular, an integrally formed support structure may provide a vacuum feedthrough. The first magnetic pole 120 may be located inside the vacuum housing. In addition, the magnetic poles of each magnetic element may be located inside the vacuum housing. The vacuum feedthrough may include a sealant ring 330, particularly near the proximal end 140. The sealant ring 330 may be located in a recessed portion of the protrusion 250 or the first magnetic bar. The sealant ring 330 may be located in a recessed portion of the support structure. The sealant ring 330 may contact the inner wall of the vacuum feedthrough 340 and provide a vacuum seal. Additional vacuum feedthroughs may be provided for additional magnetic bars of multiple magnetic elements. In one embodiment that may be combined with other embodiments described herein, the aberration corrector includes a support configured to support at least a first magnetic bar, and the support includes a vacuum feedthrough for the first magnetic bar.

[0069] Machining tolerances may result in a gap or yaw between the outer surface of the first magnetic bar 130 and the inner surface of the vacuum feedthrough. The gap or yaw may result in the first magnetic bar 130 being fixed at an angle to the first magnetic pole, thereby generating a deviation angle δ. The aberration corrector of the present application advantageously provides that the angular deviation between the first magnetic bar 130 and the first magnetic pole 120 is compensated by the geometry of the tip. The deviation of the magnetic field provided to the magnetic pole 120 and the optical axis 109 can be minimized.

[0070] The first excitation coil 170 may be mounted on the first magnetic bar 130. The first excitation coil 170 may provide a magnetic field to the first magnetic bar 130. The first excitation coil 170 is electrically isolated from the first magnetic bar 120. The first excitation coil 170 may be wound on a first carrier 350. The first carrier is electrically insulated. The first carrier may be made of polyetheretherketone (PEEK), ceramic, or any other suitable insulating material. The first carrier 350 may be mounted on the first magnetic bar 130. The first carrier 350 may be mounted so that the support structure 320 is between the proximal end and the first carrier along the axis 135. The first carrier 350 may be mounted so that the pressing element 360 is between the proximal end and the first carrier along the axis 135. The pressing element 360 may be formed integrally with the first carrier 350. The support structure 320, the first carrier 350, and the pressing element 360 may be formed integrally. The first carrier electrically isolates the first excitation coil 170 from the first magnetic bar 130. The first carrier does not magnetically isolate the first excitation coil 170 from the first magnetic bar 130. In particular, the first excitation coil 170 wound on the first carrier 350 and mounted on the first magnetic bar 130 provides a magnetic field to the first magnetic bar 130. In one embodiment that can be combined with other embodiments described herein, the first magnetic element includes a first excitation coil disposed on the magnetic bar. In particular, the first excitation coil is wound on the first carrier.

[0071] The first magnetic bar 130 may include a first electrical connector 370. The first electrical connector 370 may electrically connect the magnetic bar 130 to a voltage source. Voltage may be applied to the first magnetic bar 130 via the first electrical connector 370. The first electrical connector may be disposed on the first magnetic bar 130. The first electrical connector may be disposed adjacent to the distal end. The first electrical connector 370 may be disposed along the length of the bar between the first excitation coil and the distal end of the first bar. The first electrical connector may be a nut configured to provide an electrical connection to the magnetic bar. In one embodiment that may be combined with other embodiments described herein, the first magnetic element includes a first electrical connector that is connected to the first magnetic bar adjacent to the distal end.

[0072] An assembly ring 310 may be provided. The first magnetic pole 120 may be attached to the assembly ring 310 to support the first magnetic pole 120. The assembly ring may be rigid to fix the position of the first magnetic pole 120. Additional magnetic poles may be attached to the assembly ring 310. In particular, each magnetic pole of the first plurality of magnetic elements 105 may be attached to the assembly ring 310. The assembly ring 310 may support the first magnetic pole 120 and the additional magnetic poles. The assembly ring 310 may fix the positions of the first magnetic pole 120 and the additional magnetic poles to each other. In one embodiment that may be combined with other embodiments described herein, each magnetic pole of the first plurality of magnetic elements is attached to the assembly ring. The assembly ring 310 may be a ceramic ring. The first magnetic pole 120 may be attached to the ceramic ring by an adhesive connection. In particular, the first magnetic pole 120 may be bonded to the assembly ring 310. Additional magnetic poles may be attached to the ceramic ring by an adhesive connection, in particular bonded to the assembly ring. The assembly ring 310 may be a plastic composite ring. The first magnetic pole 120 may be molded into a plastic composite ring. Additional poles may be molded into the plastic compound.

[0073] The plastic compound 310 can arrange the magnetic poles of the first plurality of magnetic elements 105 in a star shape. In particular, in a star shape similar to the star shape of the magnetic bars arranged by the support structure 320. The plastic compound 310 can arrange the magnetic poles in a star shape, with equal angles between each pole, 45° or 30° for 8 poles or 12 poles, respectively, and centered around an opening in the center of the star shape. The opening in the center of the star shape can be configured to align with the optical axis 109. The plastic compound 310 molded with each magnetic pole of the first plurality of magnetic elements 105 can be placed inside the center opening of the star shape of the integrally formed support structure 320. Each magnetic pole can be aligned with the corresponding magnetic bar at the same time.

[0074] Figure 4An embodiment of an aberration corrector having an additional plurality of magnetic elements is illustrated. The aberration corrector includes a first plurality of magnetic elements 105 and additional plurality of magnetic elements 105', 105", and 105'" as described herein. The additional plurality of magnetic elements 105', 105", and 105'" may have a structure and arrangement similar or identical to the first plurality of magnetic elements. The first plurality of magnetic elements 105 and the additional plurality of magnetic elements 105', 105", and 105'" may be stacked on top of each other. The first plurality of magnetic elements may form a first magnetic n-pole, such as 4 poles, 6 poles, 8 poles, 10 poles, or 12 poles or higher order poles, aligned with the optical axis 109. The additional plurality of magnetic elements 105', 105", and 105'" may form a similar n-pole aligned with the optical axis 109.

[0075] In one embodiment that may be combined with other embodiments described herein, the aberration corrector comprises a second stage comprising a second plurality of magnetic elements, each of the second plurality of magnetic elements comprising a magnetic pole and a corresponding magnetic rod for providing a magnetic field to the magnetic pole, wherein the first stage comprises the first plurality of magnetic elements and the second stage is stacked above the first stage.

[0076] The second plurality of magnetic elements may be substantially similar to the first plurality of magnetic elements. The second plurality of magnetic elements may include the same number of magnetic elements as the first magnetic elements. The second plurality of magnetic elements may include a first magnetic element similar to a first magnetic element in the first plurality of magnetic elements. The first magnetic element in the second plurality of magnetic elements may include a first magnetic pole, a first magnetic bar having a proximal end adjacent to the magnetic pole and a distal end opposite to the proximal end, the proximal end having a tip, the tip having a tip surface in the shape of a hemisphere, and a contact point of the tip surface contacts the first magnetic pole. Additional magnetic elements in the second plurality of magnetic elements may be similar to the first magnetic element in the first plurality of magnetic elements. The second stage may be similar or identical to the first stage.

[0077] According to one aspect, a charged particle beam apparatus is described. The charged particle beam apparatus comprises a sample stage, a charged particle source adapted to generate a charged particle beam, and a charged particle beam manipulation system comprising an aberration corrector according to embodiments described herein.

[0078] See now Figure 5 , a schematic diagram of a charged particle beam device is illustrated. As shown, the charged particle beam device 507 includes a charged particle source 580, a sample stage 586, and a charged particle beam manipulation system 584 including an aberration corrector 100. As shown, the charged particle source 580 is suitable for generating a charged particle beam 582. As can be seen, the sample stage 586 is suitable for supporting a sample 588. An optical axis 109 is shown. The optical axis 109 can be understood to be the optical axis 109 of the charged particle beam device 507.

[0079] A method of aligning an aberration corrector is described. The method includes providing a plurality of magnetic poles having a predetermined alignment; and contacting the plurality of magnetic poles with a plurality of magnetic bars, wherein each of the plurality of magnetic bars is connected to a corresponding magnetic pole so that the predetermined alignment of the plurality of magnetic poles is substantially maintained or maintained.

[0080] For n magnetic poles, the predetermined alignment can be the shape of n poles. For example, for 4, 6, 8, 10, 12 magnetic poles, the predetermined alignment can be the shape of 4, 6, 8, 10, 12 magnetic poles. The predetermined alignment of the magnetic poles can be a star shape oriented around the central axis. The magnetic poles can have equal radial distances from the central axis and can have equal angles between every two adjacent magnetic poles. The magnetic poles can be aligned to form an opening of the aberration corrector, which is concentric with the central axis. Maintaining the predetermined alignment includes maintaining equal radial distances of each magnetic pole to the central axis and maintaining equal angles between every two adjacent magnetic poles.

[0081] See now Figure 6 , a flow chart showing a method of aligning an aberration corrector is illustrated. At step 610, a plurality of magnetic poles are provided, the magnetic poles having a predetermined alignment. The predetermined alignment may be an n-pole shape or a star shape. At step 620, the plurality of magnetic poles are contacted with a plurality of magnetic bars. Each of the plurality of magnetic bars is connected to a corresponding magnetic pole so that the predetermined alignment of the plurality of magnetic poles is maintained or substantially maintained.

[0082] The method for aligning the aberration corrector comprises pressing the tip surface of a hemispherical first magnetic bar onto the contact surface of a first magnetic pole. The hemispherical tip can compensate for a small deviation angle δ between the axis of the first magnetic bar and the surface normal of the first magnetic pole. Two points located diametrically opposite to the contact point have the same distance from the surface of the first magnetic pole.

[0083] A method for aligning an aberration corrector includes moving at least one of a plurality of magnetic bars during contact of corresponding magnetic poles, while the corresponding magnetic poles do not substantially move. For example, during installation of the magnetic bars constituting the corrector, the magnetic bars may be moved with an angular displacement. During installation of the plurality of magnetic bars, angular displacement of one or more magnetic bars may occur. According to an embodiment of the present disclosure, the effect of angular displacement of one or more magnetic bars on the magnetic field provided to the magnetic poles can be reduced or avoided. At least one magnetic bar is pressed forcefully against the corresponding magnetic pole to provide physical contact. The force causes the magnetic poles to not move. In particular, the radial distance from the central axis does not change, and the angle with the adjacent magnetic poles does not change.

[0084] A method of correcting aberrations of a charged particle beam using an aberration corrector according to embodiments described herein is described. The method includes directing the charged particle beam through an opening of the aberration corrector, and correcting the aberrations of the charged particle beam.

[0085] See now Figure 7 , illustrates a flow chart showing a method of correcting aberrations of a charged particle beam using an aberration corrector according to embodiments described herein. At step 710, a charged particle beam is directed through an opening of an aberration corrector. At step 720, aberrations of the charged particle beam are corrected.

[0086] The method of correcting aberrations of a charged particle beam comprises providing a magnetic field to a plurality of magnetic elements. According to further embodiments, the method of correcting aberrations of a charged particle beam comprises deflecting charged particles of the charged particle beam toward a central axis, wherein an opening of an aberration corrector is concentric with the central axis. According to further embodiments, the method of correcting aberrations of a charged particle beam comprises shaping the charged particle beam using a multipole field generated by applying a current and or voltage to an aberration corrector.

[0087] In view of the above, a number of embodiments are provided in the present disclosure, some of which are as follows:

[0088] Embodiment 1. An aberration corrector comprises: a first plurality of magnetic elements, each magnetic element comprising a magnetic pole and a corresponding magnetic rod for providing a magnetic field to the magnetic pole, the first plurality of magnetic elements comprising at least a first magnetic element, the first magnetic element comprising: a first magnetic pole; a first magnetic rod having a proximal end adjacent to the first magnetic pole and a distal end opposite to the proximal end; the proximal end having a tip, the tip having a tip surface in the shape of a hemisphere; and a contact point of the tip surface contacts the first magnetic pole.

[0089] Embodiment 2. An aberration corrector according to embodiment 1, wherein a contact point of the tip surface contacts the first magnetic pole at a contact surface of the first magnetic pole, and the contact surface has a curvature smaller than a tip curvature of the tip surface, in particular a curvature of zero.

[0090] Embodiment 3. An aberration corrector according to any one of embodiments 1-2, wherein the first magnetic element comprises a first excitation coil arranged on a first magnetic bar.

[0091] Embodiment 4. The aberration corrector according to embodiment 3, wherein the first exciting coil is wound on a first carrier, and the first carrier electrically insulates the first exciting coil from the first magnetic bar.

[0092] Embodiment 5. An aberration corrector according to any one of embodiments 1-4, wherein the first magnetic element includes a first electrical connector connected to a first magnetic rod adjacent to the distal end.

[0093] Embodiment 6. An aberration corrector according to embodiment 5, wherein the first magnetic element includes a spring at a proximal end contacting the first magnetic pole to provide an electrical connection between the first magnetic bar and the first magnetic pole.

[0094] Embodiment 7. The aberration corrector of any one of embodiments 1-6, further comprising a ring magnetically connecting the first plurality of magnetic elements to each other.

[0095] Embodiment 8. The aberration corrector of embodiment 7, further comprising a foil positioned between the ring and the first plurality of magnetic elements, wherein the foil electrically insulates the ring from the first plurality of magnetic elements.

[0096] Embodiment 9. The aberration corrector according to any one of embodiments 1-8 further comprises: a support member configured to support at least the first magnetic rod.

[0097] Embodiment 10. An aberration corrector according to embodiment 9, wherein the support comprises a vacuum feedthrough for the first magnetic rod.

[0098] Embodiment 11. The aberration corrector according to any one of Embodiments 1 to 10 further comprises: a pressing element configured to adjust the contact force between the first magnetic bar and the first magnetic pole.

[0099] Embodiment 12. An aberration corrector according to any of Embodiments 1-11, wherein each pole of the first plurality of magnetic elements is attached to an assembly ring.

[0100] Embodiment 13. An aberration corrector according to any one of embodiments 1-12, wherein the first plurality of magnetic elements includes 8 magnetic elements forming 8 poles or 12 magnetic elements forming 12 poles.

[0101] Embodiment 14. An aberration corrector according to any one of embodiments 1-13, comprising a second stage, wherein the second stage comprises a second plurality of magnetic elements, each of the second plurality of magnetic elements comprises a magnetic pole and a corresponding magnetic rod for providing a magnetic field to the magnetic pole, wherein the first stage comprises a first plurality of magnetic elements, and the second stage is stacked above the first stage.

[0102] While the foregoing is directed to particular embodiments, other and further embodiments may be devised without departing from the basic scope thereof, and the scope of the same is determined by the following claims.

Claims

1. An aberration corrector characterized by the aberration corrector comprising: a first plurality of magnetic elements, each magnetic element comprising a magnetic pole and a corresponding magnetic bar for providing a magnetic field to the magnetic pole, the first plurality of magnetic elements comprising at least a first magnetic element, the first magnetic element include: first magnetic pole; a first magnetic bar having a proximal end adjacent to the first magnetic pole and a distal end opposite to the proximal end; The proximal end has a tip having a tip surface in the shape of a hemisphere; as well as The contact point of the tip surface contacts the first magnetic pole.

2. An aberration corrector according to claim 1, wherein the contact point of the tip surface contacts the first magnetic pole at a contact surface of the first magnetic pole, and the contact surface has a curvature smaller than a tip curvature of the tip surface.

3. The aberration corrector of claim 2, wherein the curvature is zero.

4. The aberration corrector according to claim 1, wherein the first magnetic element comprises a first exciting coil disposed on the first magnetic bar. 5 . The aberration corrector according to claim 4 , wherein the first exciting coil is wound on a first carrier, and the first carrier electrically insulates the first exciting coil from the first magnetic bar.

6. The aberration corrector of claim 1, wherein the first magnetic element comprises a first electrical connector connected to the first magnetic bar adjacent the distal end.

7. The aberration corrector of claim 6, wherein the first magnetic element comprises a spring at the proximal end contacting the first magnetic pole to provide an electrical connection between the first magnetic bar and the first magnetic pole.

8. The aberration corrector of claim 1, further comprising a ring magnetically coupling the first plurality of magnetic elements to one another.

9. The aberration corrector of claim 8, further comprising a foil positioned between the ring and the first plurality of magnetic elements, wherein the foil electrically insulates the ring from the first plurality of magnetic elements.

10. The aberration corrector according to claim 1, further comprising: include: The support member is configured to support at least the first magnetic bar.

11. The aberration corrector of claim 10, wherein the support comprises a vacuum feedthrough for the first magnetic bar.

12. The aberration corrector according to any one of claims 1 to 11, further comprising: include: The pressing element is configured to adjust the contact force between the first magnetic bar and the first magnetic pole.

13. The aberration corrector of any one of claims 1 to 11, wherein each pole of the first plurality of magnetic elements is attached to an assembly ring.

14. The aberration corrector of any one of claims 1 to 11, wherein the first plurality of magnetic elements comprises 8 magnetic elements forming 8 poles or 12 magnetic elements forming 12 poles.

15. An aberration corrector according to any one of claims 1 to 11, comprising a second stage, the second stage comprising a second plurality of magnetic elements, each magnetic element of the second plurality of magnetic elements comprising a magnetic pole and a corresponding magnetic bar for providing a magnetic field to the magnetic pole, Wherein a first stage includes the first plurality of magnetic elements, and the second stage is stacked above the first stage.

16. The aberration corrector according to any one of claims 1 to 3, wherein the first magnetic element comprises a first exciting coil provided on the first magnetic bar.

17. The aberration corrector of any one of claims 1 to 5, wherein the first magnetic element comprises a first electrical connector connected to the first magnetic bar adjacent the distal end.

18. The aberration corrector of any one of claims 1 to 7, further comprising a ring magnetically connecting the first plurality of magnetic elements to each other.

19. The aberration corrector according to any one of claims 1 to 9, further comprising: include: A support member is configured to support at least the first magnetic bar.

20. A charged particle beam apparatus, characterized by the charged particle beam apparatus comprising: Sample stage; a charged particle source adapted to generate a charged particle beam; as well as A charged particle beam manipulation system, comprising an aberration corrector, the aberration corrector comprising: a first plurality of magnetic elements, each magnetic element comprising a magnetic pole and a corresponding magnetic bar for providing a magnetic field to the magnetic pole, the first plurality of magnetic elements comprising at least a first magnetic element, the first magnetic element comprising: first magnetic pole; a first magnetic bar having a proximal end adjacent to the first magnetic pole and a distal end opposite to the proximal end; The proximal end has a tip having a tip surface in the shape of a hemisphere; and The contact point of the tip surface contacts the first magnetic pole.

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