Sixth-order and above STEM multipole corrector

Abstract

Sixth-order and above corrected STEM multipole corrector. According to the present disclosure, a corrector for correcting the axial aberration of a particle optical lens in a charged particle microscope system comprises: a first primary multipole, which generates a first primary multipole field when a first excitation is applied to the first primary multipole; and a second primary multipole, which generates a second primary multipole field when a second excitation is applied to the second primary multipole. The first primary multipole is not imaged onto the second primary multipole, thereby generating a combined fourth-order aberration. The corrector further comprises a secondary multipole for correcting the fourth-order aberration and the sixth-order aberration. Such a corrector may further comprise a tertiary multipole for correcting the eighth-order aberration.

Description

Background Art

[0001] Particle optical microscopes utilize circular lenses to direct electron / charged particle beams to illuminate samples. However, circular lenses produce a positive spherical aberration coefficient, which limits wide angles and inhibits resolution and probe current. To address this issue, current particle optical microscopes incorporate multipole correctors to reduce and / or correct spherical aberration. For sextupole correctors, conventional practice is to carefully image the primary multipoles so that the fourth-order three-leaf aberration, D4, is zero. For example, the sextupole corrector invented by Rose in 1990 features two identical strong sextupoles. When the two strong sextupoles in the Rose corrector are carefully imaged onto each other at -1 magnification, this cancels their lowest-order effects (i.e., threefold astigmatism, A2) and also results in the fourth-order three-leaf aberration, D4, being null. For the Rose corrector, imaging the primary sextupole onto each other is equivalent to imaging the sextupole midplanes onto each other (i.e., the midplanes are perfectly conjugate).

[0002] However, imaging the mid-planes of the multipoles onto each other in this manner is not the only way to negate the D4 aberration in current practice. For example, with certain other sextupole corrector types (e.g., those that include more than two primary sextupole correctors), if the mid-planes of all the primary sextupole are completely conjugated to each other, a large D4 aberration will result. In such sextupole correctors, to negate D4, the mid-plane of one primary sextupole is conjugated to a plane that is adjacent to, but not identical to, the mid-plane of another primary sextupole.

[0003] Although the fourth-order three-leaf aberration D4 is zero for conventional multipole correctors, conventional multipole correctors also produce various higher-order aberrations (e.g., sixth-order three-leaf aberration D6, eighth-order three-leaf aberration D8, etc.) that limit the microscope's resolution. For example, the S-CORR corrector described in U.S. Patent No. 8,841,630 does not have sextuplicate astigmatism, but aberrations such as sixth-order three-leaf aberration D6 and eighth-order three-leaf aberration D8 are not eliminated. Therefore, even if current sextupole correctors (such as the Rose corrector and the S-CORR corrector) are mechanically perfect, current particle optical microscopes employing these sextupole correctors are still limited by sixth-order aberrations (i.e., sixth-order three-leaf aberration D6). Therefore, sixth-order aberrations are a fundamental obstacle limiting the imaging capabilities of current charged-particle optical microscopes employing sextupole correctors. Similarly, for similar reasons, charged-particle optical microscopes employing quadrupole-octupole correctors are limited by seventh-order aberrations. Therefore, it is desirable to reduce the higher-order aberrations of such Cs correctors. Summary of the Invention

[0004] According to the present disclosure, a corrector for correcting axial aberration of a particle optical lens in a charged particle microscope system includes: a first primary hexapole, which generates a first primary hexapole field when a first excitation voltage or current is applied to the first primary hexapole; and a second primary hexapole, which is positioned between the first primary hexapole and a lens that is a source of spherical aberration when the corrector is used within the charged particle microscope system. In the remainder of this document, this lens is sometimes referred to as the particle optical lens. Typically, the lens that is the primary source of spherical aberration is the lens that acts as an objective lens in the charged particle microscope system. When a second excitation is applied to the second primary hexapole, the second primary hexapole generates a second primary hexapole field. According to some embodiments of the present disclosure, the first primary hexapole is not carefully imaged onto the second primary hexapole. Instead, a combined fourth-order aberration is generated by slightly mismatching the image of the first primary hexapole on the second primary hexapole. In such embodiments, the corrector comprises a secondary sextupole for correcting the fourth-order and sixth-order aberrations, wherein when the corrector is used within the charged-particle microscope system, the secondary sextupole is positioned between the second primary sextupole and the particle-optical lens. Such a corrector may further comprise a tertiary sextupole positioned between the second primary sextupole and the particle-optical lens for correcting eighth-order aberrations.

[0005] In an alternative embodiment of the present disclosure, a corrector for correcting axial aberrations of a particle-optical lens may include: a first primary hexapole configured to generate a first primary hexapole field when a first excitation is applied to the first primary hexapole; and a second primary hexapole positioned between the first primary hexapole and the particle-optical lens when the corrector is used within a charged-particle microscope system. When a second excitation is applied to the second primary hexapole, the second primary hexapole generates a second primary hexapole field, and the first primary hexapole is imaged onto the second primary hexapole according to conventional practice. In such an embodiment, the corrector further includes a secondary hexapole positioned between the second primary hexapole and the particle-optical lens when the corrector is used within the charged-particle microscope system. The secondary hexapole is configured to generate a third hexapole field when a third excitation is applied to the secondary hexapole. The alternative further includes a tertiary hexapole positioned between the second primary hexapole and the particle-optical lens. The tertiary hexapole is configured to generate a fourth hexapole field when a fourth excitation is applied to the tertiary hexapole. The secondary hexapole and the tertiary hexapole are positioned and / or otherwise configured so that the third hexapole field and the fourth hexapole field correct the sixth-order aberration D6. In addition, a corrector according to the present disclosure may include other types of multipoles in place of hexapole, such as dipoles, quadrupoles, etc. For example, a corrector according to the present disclosure that uses quadrupole fields and octupole fields instead of hexapole can use similar phenomena as discussed above to correct intrinsic and parasitic higher-order aberrations. For example, the secondary and tertiary octupole fields can correct for 4x aberrations up to the 7th order. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The detailed description is described with reference to the accompanying drawings. In the drawings, the left-most digit(s) of a reference number identifies the drawing in which the reference number first appears. The same reference numbers in different drawings indicate similar or identical items.

[0007] Figure 1 An example multipole corrector for correcting sixth-order aberrations and / or higher aberrations according to the present invention is shown.

[0008] Figure 2 A collection of graphs 200 illustrating the optical behavior of the corrector transfer optics for a prior art corrector and a sixth-order corrected STEM multipole corrector system according to the present disclosure is shown.

[0009] Figure 3 An example charged particle microscope system for examining the composition of a sample 302 is shown, the optical column of which includes a sixth-order corrected STEM multipole corrector system 100 according to the present invention.

[0010] Figure 4An example charged particle microscope system is shown that includes a sixth-order corrected STEM multipole corrector system 100 having three primary multipoles, wherein at least two of the primary multipoles are not imaged onto each other.

[0011] Figure 5 is a graph showing the optical performance of a conventional corrector system.

[0012] Figure 6 is a graph showing the optical performance of a sixth-order corrected STEM multipole corrector system according to the present disclosure.

[0013] Figure 7 The optical performance of a corrected STEM multipole corrector system is shown, wherein the primary multipoles are not imaged onto each other and wherein the second primary multipole is asymmetrically displaced.

[0014] Figure 8 The optical performance of an example corrected STEM multipole corrector system with an asymmetric optical path is shown.

[0015] Figure 9 An example multipole corrector system for correcting sixth-order aberrations is shown, the multipole corrector system comprising at least one pair of primary multipoles imaged onto each other and a plurality of multipoles positioned downstream of the pair of primary multipoles, the plurality of multipoles positioned and / or otherwise configured to produce aberrations that combine to correct sixth-order aberrations or higher.

[0016] Figure 10 An example charged particle microscope system is shown that includes an example multipole corrector system for correcting sixth-order aberrations, the multipole corrector system comprising at least one pair of primary multipoles imaged onto each other.

[0017] Figure 11 is a diagram showing how the aberrations of the first primary multipole, the second primary multipole, and the secondary multipole of a sixth-order corrected STEM multipole corrector system are combined to correct sixth-order aberrations.

[0018] Figure 12 An example multipole imaging corrector system for correcting sixth-order aberrations is shown, the system comprising at least one pair of primary multipoles imaged onto each other and a plurality of multipoles positioned downstream of the pair of primary multipoles, the plurality of multipoles positioned and / or otherwise configured to produce aberrations that combine to correct sixth-order aberrations or higher.

[0019] Figure 13An example multipole corrector system for correcting sixth-order aberrations is shown, the multipole corrector system comprising at least one pair of primary multipoles imaged onto each other and a plurality of multipoles positioned downstream of the pair of primary multipoles, the plurality of multipoles positioned and / or otherwise configured to produce aberrations that combine to correct sixth-order aberrations or higher.

[0020] Figure 14 is a planar Ronchigram image produced by a microscope system with a conventional correction system, which is limited to D6.

[0021] Figure 15 is a planar Ronchigram image produced by a microscope system with a sixth-order corrected STEM multipole corrector system.

[0022] Figure 16 is a planar Ronchigram image produced by a microscope system with a sixth- and eighth-order corrected STEM multipole corrector system, where both D6 and D8 are strongly reduced.

[0023] Throughout the several views of the drawings, like reference numerals refer to corresponding parts. Generally, in the drawings, elements that may be included in a given example are shown in solid lines, while elements that are optional for a given example are shown in dashed lines. However, elements shown in solid lines are not required for all examples of the present disclosure, and elements shown in solid lines may be omitted from a particular example without departing from the scope of the present disclosure. DETAILED DESCRIPTION

[0024] Multipole correctors for correcting sixth-order and / or higher aberrations are encompassed herein. More specifically, the multipole correctors disclosed herein are configured to correct for a sixth-order, three-leaf D6 aberration in a charged particle microscope system. A multipole corrector according to some embodiments of the present invention includes at least one pair of primary multipoles that are not imaged onto each other, thereby producing a fourth-order combined aberration; and a secondary multipole positioned between the pair of primary multipoles and a lens that is a source of spherical aberration (e.g., an objective lens in the charged particle microscope system) when the corrector is used within the charged particle microscope system.

[0025] In some embodiments, when the corrector is used within a charged particle microscope system, the lens can be the primary source of spherical aberration (i.e., the source of the largest spherical aberration in the system, the source of a significant amount of spherical aberration in the system). The secondary multipoles are configured to correct fourth-order aberrations and sixth-order aberrations. Aberration correction according to the present disclosure corresponds to the positive aberrations being offset by negative aberrations such that their sum is zeroed, substantially zeroed, and / or reduced to an optimal value (e.g., reduced to a value such that their sum is combined with one or more other aberrations to balance / correct for higher-order aberrations). Additionally, the terms "multipole," "quadrupole," "hexapole," "quadrupole-octupole," and the like are used herein to describe multipole fields, quadrupole fields, hexapole fields, quadrupole-octupole fields, and the like, rather than physical devices configured to generate the fields.

[0026] That is, embodiments of the disclosed invention correct aberrations through the generation of novel aberrations that, when combined, correct for sixth-order aberrations. Additionally, as disclosed below, in some embodiments of the disclosed invention, combinations of generated aberrations can be combined to correct for eighth-order aberrations. Specifically, a pair of primary multipoles that are not imaged onto each other generate large fourth-order aberrations that, when combined with the aberrations generated by the novel secondary multipoles, result in the cancellation of both fourth-order and sixth-order aberrations.

[0027] In addition, a multipole corrector according to some other embodiments of the present invention comprises: at least one pair of primary multipoles that are imaged or substantially imaged onto each other according to conventional practice; and a plurality of multipoles that, when the corrector is used within a charged particle microscope system, are positioned between the pair of primary multipoles and the particle optical lens. The plurality of multipoles are positioned and / or otherwise configured to produce aberrations that combine to correct for sixth-order aberrations or higher. That is, the individual multipoles positioned between the pair of primary multipoles and the particle optical lens can be positioned and set to specific excitation energy levels so that they produce aberrations that combine with other aberrations produced by the corrector system to offset aberrations up to sixth or eighth order.

[0028] The following discussion demonstrates the performance of example corrector systems according to the present disclosure. Specifically, the following discussion demonstrates the performance of a probe hexapole corrector according to the present disclosure having (i) parallel (or nearly parallel) input and output beams, (ii) identical geometry between the primary hexapole, (iii) only two primary hexapole, and (iv) a corrector upstream of the particle optical lens (as in a SEM or STEM). However, as described below, correctors according to the present disclosure are not limited to such embodiments, and correctors having other characteristics (e.g., quadrupole-octupole instead of hexapole, with additional primary hexapole, for use in microscopy systems other than STEM, designed to be positioned downstream of the sample from the system's charged particle source, non-parallel output beams, asymmetric hexapole correctors, asymmetric optical path lengths, etc.) can be constructed according to the present disclosure, the correctors operating according to similar phenomena. For example, in cases where an example corrector system according to the present disclosure is designed to be positioned downstream of a sample from a system charged particle source (e.g., a corrector for a TEM system), the arrangement of the hexapole in the corrector is reversed (i.e., one or more secondary hexapole are closer to the charged particle source than the primary hexapole, while the second hexapole is still positioned between the first hexapole and the one or more secondary hexapole).

[0029] For example, the case of a corrector with two primary sextupoles is discussed in detail. When fringe fields are neglected, the scalar magnetic potential of the sextupoles is given by:

[0030] ; (1)

[0031] here, Indicates radial position The complex hexapole excitation parameters of the component hexapole of the embodiment of the present invention are k Defined as

[0032] , (2)

[0033] in ,and is the relativistic potential, e is a single electron charge, and m is the mass of the particle. For the two sextupole corrector system, the optical properties are calculated in the Larmor reference frame, taking into account the rotation of the magnetic lens, in which case it can be assumed that the fields of the individual sextupole k However, in a three-sextupole rectifier system, the individual values ​​of the individual hexapole fields are k The value can be real or imaginary. In addition, in the plane parallel to the Gaussian beam, the phase function is given by The slope aberration is derived from:

[0034] (3)

[0035] The phase function for all terms allowed by the 3-fold symmetry up to order 7 of the sextupole of the system disclosed herein is given by:

[0036]

[0037] (4)

[0038] The subscript "s" indicates that the coefficient corresponds to the slope aberration. A is ignored here. 5S and D 6S Very small anisotropy values ​​of the aberrations (i.e., all aberration coefficients are assumed to be real in the Larmor reference frame).

[0039] The action of each primary sextupole in a pair of primary sextupole is approximated by:

[0040] ; (5)

[0041] And the action of one or more secondary hexapole is approximated by:

[0042] . (6)

[0043] here, and is defined asymptotically in the hexapole midplane. In the embodiment where the intermediate hexapole is positioned between a pair of primary hexapole, its modest effect on D6 is neglected in the following calculations in order to correct for A5. The excitation of the upstream primary hexapole in the pair of primary hexapole is k , and the excitation parameter of the downstream sextupole in a pair of primary sextupole is + ,in k Much greater than The excitation of the secondary sextupole is , which is also much smaller than k .

[0044] Consider the case where a parallel beam enters the first primary sextupole and the complex transverse position of the electrons in the beam = According to the invention, the intermediate result in the asymptotic mid-plane of the downstream primary sextupole ( , ) for (in The highest is level 4):

[0045] ; and (7)

[0046]

[0047] . (8)

[0048] This includes the action of the downstream primary hexapole, is the physical offset of the primary sextupole (e.g. Figure 2 offset shown in ).

[0049] When following When equation (8) is rewritten, it becomes ,in:

[0050] , (9)

[0051] It is characterized by the slope aberration, as shown in equation (4), In equation (9), the and The resulting corrector strength minor changes and in the remainder Set equal to From here, there are two ways of performing the calculations to show that the respective embodiments of the disclosed invention correct for sixth-order (and in some cases eighth-order or higher) aberrations.

[0052] In the first method, the drift distance between the downstream primary sextupole and the second sextupole is equal to d In the case of , and a back extrapolation is applied to the center of the downstream primary sextupole. This leads to the following relationship:

[0053] (10)

[0054] in ,and .

[0055] ( , ) allows the Taylor series inversion of Written as ( , ), which leads to the relationship ,in:

[0056]

[0057] (11)

[0058] Therefore, the triple aberration coefficient of the embodiment of the present invention can be written as:

[0059] ; (12)

[0060] ; and (13)

[0061] ; (14)

[0062] in is the intrinsic corrector aberration of the corrector without mechanical and / or electrical errors. Then, using equations (12) and (13), it can be shown that when = and = hour, and are all equal to 0. Rewrite the sixth-order spherical aberration using these values When I found that:

[0063] . (15)

[0064] Equation (15) can be converted into the position aberration at the sample:

[0065] , (16)

[0066] At the sample, is the spherical aberration of the lens outside the corrector, which is primarily caused by the spherical aberration of the objective lens ( ) decided, and is the effective focal length of the transfer lens and the objective lens. The relationship between the effective focal length is:

[0067] , (16.1)

[0068] where x is the position in the corrector exit plane, and is the corresponding angle in the sample plane.

[0069] Using these relationships, a corrector according to the present disclosure can be constructed that corrects for sixth-order three-leaf D6 aberrations in a charged particle microscope system. That is, a corrector having a secondary multipole sextupole downstream of a pair of primary sextupoles can be positioned and / or otherwise configured such that the corrector corrects for sixth-order aberrations. For example, in When the aberration is equal to 3 mm, the above relationship shows that 、 and Sextupole offset = 0.5 mm for correction, where L = 16 mm, = 1.4 mm, d = 35 mm and = 1.6 mm. As will be discussed further below, the hexapole offset This can be achieved by physically displacing a pair of primary hexapole so that they are not imaged onto each other; or changing the excitation of two transfer lenses between the primary hexapole so that the pair of primary hexapole are not imaged onto each other; or a combination thereof.

[0070] In the second approach, which proceeds from equations (1) to (9) to equations (12, 13, 14), a probe corrector with a parallel beam in the exit plane and with many multipoles treated in the thin lens approximation is considered. In free space downstream of the corrector, the phase function ( ) is governed by the eikonal equation described as Equation 2.21 in Harald Rose: Geometrical Charged-Particle Optics, Springer, 2009, where the electric potential is constant and the vector potential is zero. Therefore, the following ratio The scaled free-space phase function can be written as:

[0071] (17)

[0072] And the corresponding optical path can be written as:

[0073] , and (18)

[0074] . (19)

[0075] On the right side of Equation 17, the term -1 is added to eliminate components of no interest S = z Phase function is expanded in a sequence similar to Equation (4) with z-dependent aberration coefficients such as Therefore, Equation (17) can be rewritten as a set of nonlinear differential equations for these coefficients (e.g., and ). Using these differential equations, starting from Equation 9, at the drift distance Propagate the above coefficients 、 、 , which is then extrapolated back to the corrector exit plane (i.e., using, for example, and The corresponding inverse of equation (17) is The following triple aberration is obtained:

[0076] ; (20)

[0077] ; (twenty one)

[0078] ; and (22)

[0079] . (twenty three)

[0080] here, and is an inherently corrected aberration. In some embodiments of the corrector system according to the present invention, Corresponds to the distance between the most downstream primary multipole of the corrector and the downstream secondary multipole of the corrector.

[0081] Using the relations (20) to (22), a corrector according to the present disclosure can be constructed that corrects the sixth-order trifoliate aberration in a charged particle microscope system. That is, since the relations (20) to (22) contain three degrees of freedom (i.e., The increment of - incentive k2, causing The incentive k3 and the of These three degrees of freedom allow a corrector system according to the present disclosure to be designed with a pair of primary sextupoles having a certain sextupoles offset and including one or more secondary sextupoles located downstream of the pair of primary sextupoles, the one or more secondary sextupoles being positioned and / or otherwise configured such that the combined aberration of the corrector system reaches (i.e., correction for second-, fourth-, and sixth-order trifoliate aberrations).

[0082] Additionally, in some embodiments, a corrector system according to the present invention may include a plurality of secondary multipoles that, when used in a charged particle microscope, are positioned between a pair of primary multipoles and an objective lens. For example, the corrector system may include a first secondary multipole positioned downstream of the pair of primary multipoles and a second secondary multipole positioned downstream of the first secondary multipole. To determine the triple aberration of such a system, the following procedure may be performed twice: using the propagation coefficients of equation (17) 、 、 , which is then extrapolated back to the corrector exit plane using the inverse of Equation (17). In the first iteration, the drift distance associated with the first secondary multipole can be These two calculations are performed on , and in the second iteration, the drift distance associated with the second secondary multipole can be The calculation is performed on Figure 9 An example visualization of this process is shown in FIG. Additionally, it should be noted that the following discussion corresponds to not activating lenses 908 and 910 (in Figure 9 In other cases, the principle remains the same, but the analytical calculations are different. This double iteration of the process results in the following triple aberration in the corrector system:

[0083] ; (twenty four)

[0084] ; (25)

[0085] ; and (26)

[0086] . (27)

[0087] These relationships indicate that a corrector system according to the present disclosure can be designed with a pair of primary sextupoles having a certain sextupoles offset, and including two or more secondary sextupoles located downstream of the pair of primary sextupoles, the two or more secondary sextupoles being positioned and / or otherwise configured such that the combined aberration of the corrector system reaches (i.e., correction for second-, fourth-, sixth-, and eighth-order trifoliate aberrations).

[0088] Alternatively, using these relationships for the triple aberration of such a corrector system, a corrector system according to the present disclosure can be constructed that has a pair of primary multipoles imaged onto each other while still correcting for sixth-order three-leaf aberrations. This has the advantage that second-order off-axis astigmatism is less than in embodiments where not all primary sextupoles are imaged onto each other. In this case, , i.e., it is no longer a degree of freedom. When a pair of primary multipoles are imaged onto each other, relations (24) to (26) allow correction of these three leaf aberrations. This is because relations (24) to (26) have three degrees of freedom (i.e., they cause 、 、 ), allowing the design of such corrector systems (i.e., with two specially positioned and / or configured secondary multipoles downstream of a pair of primary multipoles) that can correct triplet aberrations up to the sixth order without relying on the sextupole offset as an additional variable (i.e., ).

[0089] Figure 1 is a diagram of an example multipole corrector 100 for correcting sixth-order aberrations and / or higher aberrations in accordance with the present invention. Figure 1The description and arrows in the figure are specific to a probe corrector in a SEM or STEM system. The example multipole corrector 100 includes at least a first primary multipole 102 and a second primary multipole 104. The multipole is used to generate a display. n / 2 Optical elements with a multiple rotational symmetry of the electromagnetic field, where n is an even integer. Thus, examples of multipoles include dipoles, quadrupoles, hexapole, etc. For example, a multipole with 8 yokes / electrodes can generate dipole fields, quadrupole fields, and hexapole fields in any direction.

[0090] During operation of the SEM or STEM system, the charged particle beam 106 is directed toward the first end 110 of the multipole corrector along a central axis 108. When the corrector is used within a charged particle microscope system, the second primary multipole 104 is positioned between the first primary multipole 102 and the particle optical lens. For example, Figure 1 104 is shown positioned downstream of the first primary multipole 102 (i.e., the charged particle beam 106 interacts with the first primary multipole 102 before interacting with the second primary multipole 104). An excitation is applied to each of the first primary multipole 102 and the second primary multipole 104 so that they generate an electromagnetic field that guides the charged particle beam 106 to be incident on the sample. In an embodiment where the collimator 100 is designed for operation within a TEM system, the collimator 100 will be positioned downstream of the sample, and the charged particle beam 108 will interact with the second primary multipole 104 before interacting with the first primary multipole 102.

[0091] According to the present invention, the contributions of the first primary multipole 102, the second primary multipole 104, and the transfer optical components therebetween produce a significant 3-fold astigmatism A2 and a significant fourth-order 3-leaf aberration D4. In various embodiments, the reasons for not negating A2 and D4 may be: the excitation applied to the second primary multipole 104 is greater than the excitation applied to the first primary multipole 102; the lengths of the first primary multipole 102 and the second primary multipole 104 (i.e., L 1 and L 2) are different; the beam radii of the first primary multipole 102 and the second primary multipole 104 are different; the yoke sizes of the first primary multipole 102 and the second primary multipole 104 are different; an asymmetry of the transfer lens 118 between the first primary multipole 102 and the second primary multipole 104; an asymmetry of the optical path of the charged particle beam 106 between the first primary multipole 102 and the second primary multipole 104; an exit of the transfer optics between the primary multipoles so that the multipoles are not imaged onto each other; or a combination thereof. In contrast, according to the present invention, one or more of the aspects of the corrector described herein are adjusted and / or employed so that sixth-order aberrations and / or higher aberrations are corrected. As used herein, the term "excitation" applied to a multipole refers to an excitation voltage or an excitation current applied to the corresponding multipole. For example, in an embodiment where the corrector 100 is used in an electron microscope column, the excitation may refer to a current applied to a particular multipole that causes the particular multipole to generate a multipole field.

[0092] In prior art correctors 100, the component multipoles are imaged onto each other to prevent aberrations. However, in an example multipole corrector 100 for correcting sixth-order aberrations and / or higher aberrations, the first primary multipole 102 is not imaged onto the second primary multipole 104, thereby generating combined aberrations. For example, where both the first primary multipole 102 and the second primary multipole 104 are sextupoles, this will result in large fourth-order aberrations. In some embodiments, the first primary multipole 102 that is not imaged onto the second primary multipole 104 corresponds to one or more of the multipole mid-planes of the first primary multipole 102 and the multipole mid-planes of the second primary multipole 104 that are displaced along the central axis 108. For example, each of the first primary multipole 102 and the second primary multipole 104 can be displaced in opposite directions along the central axis 108 by 0.1 mm, 0.5 mm, 1 mm, 0.1%, 0.5%, 1% or more of the distance between the two primary sextupoles. Additionally, the charged particle beam 106 may enter the first primary multipole 102 at an angle that is non-parallel to the central axis 108. For example, an excitation may be applied to one or more lenses upstream of the example multipole corrector 100 such that the one or more lenses cause the charged particle beam to enter the first primary multipole 102 at an angle that is non-parallel to the central axis 108.

[0093] Figure 1The example multipole corrector 100 is further shown to include a secondary multipole 112 that, when used within a charged particle microscope system, is positioned between the second primary multipole 104 and the particle optical lens (e.g., downstream of the second primary multipole 104 in an SEM / STEM system and upstream of the second primary multipole 104 in a TEM system). The secondary multipole 112 is positioned, energized, and / or otherwise configured such that the multipole field generated by the secondary multipole 112 corrects (i) aberrations generated by the first primary multipole 102 that are not imaged onto the second primary multipole 104 and (ii) higher-order aberrations. For example, where the secondary multipole 112 is a hexapole, the secondary multipole is positioned, energized, and / or otherwise configured such that the multipole field generated by the secondary multipole 112 corrects (i) fourth-order aberrations generated by the first primary multipole 102 that are not imaged onto the second primary multipole 104 and (ii) sixth-order aberrations.

[0094] For example, the excitation variation between the first multipole 102 and the second multipole 104 acts as a first degree of freedom, the offset Serves as a second degree of freedom (which causes the D4 aberration to scale linearly with offset), and the excitation of the secondary multipole 112 serves as a third degree of freedom. By adjusting these values, the example multipole corrector 100 is able to produce controlled A2 and D4 aberrations (i.e., A2 depends on the excitation value of the secondary multipole 112 and the excitation variation between the first multipole 102 and the second multipole 104, while D4 depends on the excitation value of the secondary multipole 112 and the offset). Adjusting the values ​​also allows for the generation of additional aberrations that depend on the excitation value of the secondary multipole 112, when compared to D 6,cor When combined, this corrects the D6 aberration of the system.In this way, these values ​​of the example multipole corrector 100 cause second, fourth, and sixth order aberrations to be corrected.

[0095] In this manner, during operation of such a charged particle microscope, when the example multipole corrector 100 includes a sextupole, the example multipole corrector 100 corrects for a sixth-order three-leaf D6 aberration. In some embodiments, the example multipole corrector 100 may optionally include a tertiary multipole 114 that is positioned between the secondary multipole 112 and the particle optical lens when the corrector is used within a charged particle microscope system. Such a tertiary multipole 114 is positioned, excited, and / or otherwise configured such that the multipole field generated by the tertiary multipole 114 corrects even higher-order aberrations (e.g., if the tertiary multipole 114 is a sextupole, it can correct for an eighth-order aberration).

[0096] According to the present disclosure, the contributions of the first primary hexapole 102 , the second primary hexapole 104 , the secondary multipole 112 , and the optional tertiary multipole 114 to the triple astigmatism A2 add up to zero.

[0097] In some embodiments, the example multipole corrector 100 may include an intermediate multipole 116 and / or one or more transfer lenses 118. Additionally, although not shown in FIG. Figure 1 , but the example multipole corrector 100 may also optionally include a third primary multipole. Such a third primary multipole may be positioned upstream of the first multipole 102, downstream of the second multipole 104, or between the first multipole 102 and the second multipole 104. In some embodiments, in the Larmor reference frame, each of the generated sextupole fields is at xy Alternatively, in other embodiments, one or more of the generated hexapole fields are oriented in the same direction. xy Plane and / or xy They may not be in the same orientation in the plane.

[0098] exist Figure 1 In FIG, multipole corrector 100 is shown as a box containing multiple optical components (i.e., multipoles and lenses). In various embodiments, these optical components may be enclosed or partially enclosed by a protective and / or support structure. Additionally, in embodiments that include such a structure, one or more of the optical components may not be within the structure. Figure 1 Also shown is at least one additional primary multipole 120. Each of the at least one additional primary multipole 102 can be positioned: upstream of the first primary multipole 102; downstream of the second primary multipole 104; between the first and second primary multipole 102, 104; or a combination thereof.

[0099] Figure 2 is a collection of graphs 200 illustrating the optical behavior of the corrector transfer optics for a prior art corrector and a sixth-order corrected STEM multipole corrector system according to the present disclosure. Specifically, graphs 210 and 230 illustrate the optical behavior for accounting for aberrations present in the prior art corrector and the sixth-order corrected STEM multipole corrector 100, respectively.

[0100] Figure 210 shows a general scheme for a prior art corrector, where a first primary hexapole 202 is imaged onto a second primary hexapole 204. Figures 210 and 230 each show xz Axial ray 206 of charged particle beam 106 in a plane, where zThe axis corresponds to the central axis 108 of the example multipole corrector 100. Graph 210 shows axial rays 206 of the charged particle beam 206, which are parallel to the central axis 108 when the charged particle beam enters the incident plane 208 of the first hexapole 202 and when it exits the exit plane 210 of the second hexapole 204. Graph 210 further shows that the multipole midplane of the first hexapole 202 is at position 212 and the multipole midplane of the second hexapole 204 is at position 214, such that the first hexapole 202 is imaged onto the second hexapole 204.

[0101] FIG. 230 shows an embodiment of a sixth-order corrected STEM multipole corrector system in which the first primary hexapole 202 and the second primary hexapole 204 are both mechanically offset along the central axis 108 from their standard positions (i.e., the position where the first hexapole 202 is imaged onto the second hexapole 204, as shown in FIG. 230 ). Δz That is, the diagram 230 shows the multipole mid-plane of the first primary hexapole 102 at position 216 and the multipole mid-plane of the second primary hexapole 104 at position 218. However, as described above, in other embodiments, only one of the primary multipoles may be offset. Alternatively or in addition, as described above, the offset may also be effectively generated or supplemented by adjusting the transfer lens 118 and optionally in combination with the following operations: Δz : The excitation of one or more optical elements upstream of the sixth-order corrected STEM multipole corrector system is changed so that the charged particle beam 206 enters the first primary hexapole 102 at an angle that is non-parallel to the central axis 108. In such embodiments, in conventional practice, one or both of the first primary hexapole 202, the second primary hexapole 204, or both may not be mechanically offset from conventional primary hexapole positions.

[0102] Figure 2 The corrector system of FIG230 is further shown to include a secondary multipole 112 positioned downstream of the second primary hexapole 104. Each of the first hexapole 102, the second primary multipole 104, and the secondary hexapole 112 are positioned separately and excited by respective excitations such that the aberrations produced by the sixth-order corrected STEM multipole corrector system depicted in FIG230 combine to correct aberrations up to at least sixth order.

[0103] Figure 3 is a diagram of one or more example charged particle microscope systems 300 for examining the composition of a sample 302, the optical column of which includes a sixth-order corrected STEM multipole corrector system 100 according to the present invention. That is, Figure 3One or more charged particle microscope systems 300 are shown that include a STEM multipole corrector system 100, which includes a hexapole as a component multipole. One or more example charged particle microscope systems 300 can include an electron microscope (EM) setup or an electron lithography setup that is configured to irradiate and / or otherwise impact a sample 302 with a charged particle beam 304 (typically an electron beam or an ion beam). In various embodiments, the charged particle microscope system 300 can be or include one or more different types of EM and / or charged particle microscopes, such as, but not limited to, a scanning electron microscope (SEM), a scanning transmission electron microscope (STEM), a transmission electron microscope (TEM), a charged particle microscope (CPM), a dual-beam microscope system, and the like. Additionally, in some embodiments, a TEM can also be operated as a STEM. Figure 3 One or more example charged particle microscope systems 300 are shown as STEM systems 306 .

[0104] One or more example charged particle microscope systems 300 include a charged particle source 308 (e.g., a thermionic electron source, a Schottky emission source, a field emission source, a liquid metal ion source, a plasma ion source, etc.) that emits a charged particle beam 304 along an emission axis 310 and toward an accelerator lens 312. The emission axis 310 is a central axis running from the charged particle source 308 through the sample 302 along the length of the one or more example charged particle microscope systems 300.

[0105] The accelerator lens 312 accelerates / decelerates, focuses, and / or directs the charged particle beam 304 toward a focusing column 314. The focusing column 314 focuses the charged particle beam 304 so that it is incident on the sample 302. In addition, the focusing column 314 corrects and / or adjusts aberrations (e.g., geometric aberrations, chromatic aberrations) of the charged particle beam 304. Figure 3 , a focusing column 314 is shown as including a sixth-order corrected STEM multipole corrector system 100 according to the present invention, a transfer lens 318, and an objective lens 320. The sixth-order corrected STEM multipole corrector system 100 includes a first primary multipole 102 and a second primary multipole 104 that are not imaged onto each other. The sixth-order corrected STEM multipole corrector system 100 is also shown as including a secondary multipole 112 that is positioned and / or otherwise configured so that it produces aberrations that combine with other aberrations produced by the first primary multipole 102 and the second primary multipole 104 to correct for triple aberration up to the sixth order. Figure 3 The sixth-order corrected STEM multipole corrector system 100 is also shown as including an intermediate multipole 116 and a pair of transfer lenses 118 .

[0106] Objective lens 320 is an optical element that focuses charged particle beam 304 to a point on sample 302. Objective lens 320 may include a single pole lens, an electromagnetic electrostatic compound lens, an electrostatic detector objective lens, or another type of objective lens.

[0107] Figure 3 The example charged particle microscope system 300 is further shown as including a sample holder 322 for holding a sample 302. One or more example charged particle microscope systems 300 are also shown as including a detector 334 configured to detect charged particles 336 that pass through the sample 302 as a result of the charged particle beam 304 being incident on the sample 302. Additionally, one or more example charged particle microscope systems 300 are also shown as including astigmatism correction and scanning coils 338 for scanning the charged particle beam 304 across the surface of the sample 302. For example, by operating the scanning coils 338, the direction of the charged particle beam 304 can be shifted so that it illuminates different locations of the sample 302. One or more example charged particle microscope systems 300 further include one or more projection lenses 340 positioned between the sample 302 and the detector 334.

[0108] Figure 3 One or more example charged particle microscope systems 300 are further shown as optionally including one or more computing devices 342. One skilled in the art will appreciate that Figure 3 The computing device 342 depicted in FIG. 3 is illustrative only and is not intended to limit the scope of the present disclosure. Computing systems and devices may include any combination of hardware or software capable of performing the indicated functions, including computers, network devices, internet appliances, PDAs, wireless phones, controllers, oscilloscopes, amplifiers, and the like. Computing device 342 may also be connected to other devices not shown, or may operate as a standalone system.

[0109] Figure 4 One or more example charged particle microscope systems 400 are shown that include a sixth-order corrected STEM multipole corrector system 100 having three primary multipoles, wherein at least one of the primary multipoles is offset from its normal position (by physical translation and / or other adjustments described herein) to produce a large fourth-order aberration. That is, Figure 4 One or more charged particle microscope systems 400 are shown that include a STEM multipole corrector system 100 that includes a hexapole as a component multipole.

[0110] One or more example charged particle microscope systems 400 include a charged particle source 404 that emits a charged particle beam 406 along an emission axis 408 and toward an accelerator lens 410. The accelerator lens 410 accelerates / decelerates, focuses, and / or directs the charged particle beam 406 toward a focusing column 412, which is configured to focus the charged particle beam 406 so that it is incident on a sample 414. Additionally, the focusing column 412 corrects and / or adjusts for aberrations (e.g., geometric aberrations, chromatic aberrations) of the charged particle beam 416.

[0111] exist Figure 4 , a focusing column 412 is shown containing a sixth-order corrected STEM multipole corrector system 100 according to the present invention, a transfer lens 416, and an objective lens 418. Figure 4 The sixth-order corrected STEM multipole corrector system 100 shown in FIG includes three primary multipoles (i.e., a first primary multipole 420, a second primary multipole 422, and a third primary multipole 424), wherein at least two of the primary multipoles are not imaged onto each other. Specifically, in Figure 4 , the second primary multipole 422 is not imaged onto the third primary multipole 424. However, in other embodiments, any other pairing of three primary multipoles may also not be imaged onto each other. The sixth-order corrected STEM multipole corrector system 100 is also shown to include a secondary multipole 426, which is positioned and / or otherwise configured so that it produces an aberration that combines with other aberrations produced by the first primary multipole 420, the second primary multipole 422, and the third primary multipole 424 to correct for triple aberrations up to the sixth order. In embodiments where the three primary sextuples are oriented differently in the Larmor reference frame, their mutual imaging conditions must be adjusted so that the resulting complex aberration coefficient D4 is consistent with D 6,cor have the same phase, i.e. D4 / D 6,cor = (D 4r + i D 4i ) / ( D 6r,cor + iD 6i,cor ) = real value. Figure 4 The sixth-order correcting STEM multipole corrector system 100 is also shown to include an optional transfer lens pair 428 and an optional tertiary multipole 430. In embodiments including the tertiary multipole 430, the tertiary multipole 430 can be positioned and / or excited so that it produces aberrations that combine with the accumulated aberrations produced by the other multipoles of the sixth-order correcting STEM multipole corrector system 100 to correct for eighth-order aberrations, provided that D 6,cor / D 8,cor is close to the real value, and the primary six-pole D4 is adjusted so that D4 / D 6,cor = real value. Figure 4Transfer lens 416 is shown positioned between secondary multipole 426 and tertiary multipole 430 , however, in other embodiments, transfer lens 416 may be positioned between third primary multipole 424 and secondary multipole 426 or downstream of tertiary multipole 430 .

[0112] Figure 4 The example charged particle microscope system 400 is further shown as including a sample holder 432 that holds a sample 414. One or more example charged particle microscope systems 400 are also shown as including a detector 434 that is configured to detect charged particles that pass through the sample 414 due to the charged particle beam 406 being incident on the sample 414. Additionally, one or more example charged particle microscope systems 400 are also shown as including astigmatism correction and scanning coils 436 for scanning the charged particle beam 406 across the surface of the sample 414.

[0113] For example, by operating the scan coils 436, the direction of the charged particle beam 416 can be shifted so that it illuminates different locations of the sample 414. One or more example charged particle microscope systems 400 further include one or more projection lenses 438 positioned between the sample 414 and the detector 434. Figure 4 The one or more example charged particle microscope systems 400 are further shown as optionally including one or more computing devices 440 .

[0114] Figure 5 is a graphical representation of the optical performance of a conventional corrector system. Figure 5 The optical performance of a conventional corrector system is shown, in which a pair of primary multipoles are imaged onto each other. Figure 5 The optical path of an axial ray 502 of the charged particle beam and the optical path of an off-axis ray 504 of the charged particle beam are shown, intersecting at the center of the primary hexapole of the system operating at a specific accelerating voltage. Figure 5-8 In each of the figures, line 506 shows the axial magnetic field of the respective system. When line 506 is not zero, this indicates the presence of a magnetic lens, such as transfer lens 118.

[0115] Figure 6 8 is a graphical representation of the optical performance of a corrected STEM multipole corrector system according to the present disclosure. Figure 6 The optical performance of a corrective STEM multipole corrector system for correcting eighth-order aberrations with a tertiary multipole 114 positioned downstream of the secondary multipole 112 is shown. Figure 6The optical path of an axial ray 602 of a charged particle beam and an optical path of an off-axis ray 604 of a charged particle beam are shown, wherein the system is operated at a specific accelerating voltage. As can be seen in the exploded image 606 of the first primary multipole 102, the off-axis ray 604 does not pass through the central axis 108 of the system at the multipole midplane of the first primary multipole 102. Instead, the off-axis ray 604 passes through the central axis 108 with a displacement from the multipole midplane of the first primary multipole 102 of Δ z As described above, the shift in the primary multipole compared to a conventional corrector can be generated by varying the excitation of the transfer lens 118, or a combination thereof. Δz In addition, the lens upstream of the corrector can be adjusted to produce a non-parallel incident light beam. In other embodiments, the off-axis light ray 604 passes through the central axis 108 at the multipole mid-plane of the second primary multipole 102, but does not pass through the central axis 108 at the multipole mid-plane of the second primary multipole 104.

[0116] Figure 7 The optical performance of a corrected STEM multipole corrector system is shown, wherein the primary multipoles are not imaged onto each other and wherein the second primary multipole is asymmetrically displaced. Figure 7 The optical path of an axial ray 702 of a charged particle beam and the optical path of an off-axis ray 704 of a charged particle beam are shown, wherein the system is operated at a specific accelerating voltage.

[0117] As can be seen in the exploded image 706, the length L1 of the second primary multipole 104 in the illustrated embodiment is different from the length L2 of the conventional multipole 708 in the conventional corrector system. Figure 7 , the length L2 of the first primary multipole 102 is different from the length L1 of the second primary multipole 104 . Figure 7 Depicts the positional offset of the multipole mid-plane 703 of the second primary multipole 104 from the multipole mid-plane 705 of a conventional multipole 708 in a conventional corrector system Δz .exist Figure 7 The offset depicted in Δz is asymmetric. That is, Figure 7 An embodiment is shown in which only one primary multipole is displaced so that the symmetry of the corrector in the mid-plane is abandoned. The values ​​of the following can be adjusted: Δz , the length L1 of the second multipole 104, the position of the secondary multipole 112, the excitation applied to the secondary multipole 112, or a combination thereof, to correct for high-order aberrations. For example, where the multipole is a hexapole, the combination of values ​​can be set such that A2 = D4 = D6 = 0 (or one or more different optimal values) for an appropriate primary hexapole excitation level.

[0118] In some embodiments, the length of the first primary multipole 102 is less than the length L1 of the secondary multipole 104. In such embodiments, the values ​​of the length difference between the first primary multipole 102 and the second primary multipole 104, the offset Δz , the length L1 of the second primary multipole 104, the position of the secondary multipole 112, the excitation applied to the secondary multipole 112, or a combination thereof, thereby correcting even higher-order aberrations. For example, in the case of a sextupole, a combination of values ​​can be set such that, for an appropriate primary sextupole excitation energy level, A2 = D4 = D6 = D8 = 0 (or one or more different optimal values). In other words, the length difference between the first primary multipole 102 and the second primary multipole 104 enables the corrector according to the present disclosure to correct the eighth-order aberration D8 without requiring a tertiary multipole 114.

[0119] Figure 8 The optical performance of a corrected STEM multipole corrector system with an asymmetric optical path is shown. Figure 8 The optical path of an axial ray 802 of a charged particle beam and the optical path of an off-axis ray 804 of a charged particle beam are shown, wherein the system is operated at a specific accelerating voltage. Figure 8 As can be seen, the excitation of the lens 118, the offset of the second primary multipole 104 Δz One or more of A2, D4, D6, or a combination thereof, may be used to cause the path of the axial light ray 802 as it passes through the corrector to be asymmetric. These values, as well as the other values ​​discussed above, may be adjusted so that for appropriate primary hexapole excitation energy levels, A2 = D4 = D6 = 0 (or one or more different optimal values).

[0120] Figure 9 is an illustration of an example multipole corrector system 900 for correcting sixth-order aberrations, the multipole corrector system comprising at least one pair of primary multipoles and a plurality of multipoles positioned downstream of the pair of primary multipoles, the plurality of multipoles being positioned and / or otherwise configured to produce aberrations that combine to correct sixth-order aberrations or higher.

[0121] Specifically, Figure 9 A corrector according to the present disclosure is shown that includes a pair of primary multipoles 102 and 104, a secondary multipole 112, and a tertiary multipole 114. As described above, the inclusion of the tertiary multipole 114 enables the multipole corrector system 900 to correct for three-leaf aberrations up to the sixth order when the pair of primary multipoles 102 and 104 are imaged onto each other. Alternatively, the tertiary multipole 114 allows the multipole corrector system 900 to correct for three-leaf aberrations up to the eighth order when the first primary multipole 102 and the second primary multipole 104 are not imaged onto each other.

[0122] As described above, the multipoles may correspond to any of a dipole, a quadrupole, a hexapole, an octupole, etc. For example, where the multipoles 104, 112, and / or 114 correspond to a hexapole field, the methods described herein may be used to design and / or configure a multipole corrector system 900 that negates 3x aberrations (intrinsic and / or parasitic) of any orientation up to the sixth order (in some embodiments, up to the sixth order). As another example, where the multipoles correspond to an octupole field, the methods described herein may be used to design and / or configure a multipole corrector system 900 that negates 4x aberrations (intrinsic and / or parasitic) of any orientation up to the seventh order.

[0123] In some embodiments, the example multipole corrector system 900 can include additional primary multipoles in addition to the pair of primary multipoles 102 and 104. For example, in some embodiments, the example multipole corrector system 900 can include four or six primary multipoles (e.g., a quadrupole octopole corrector). In such embodiments, the second multipole 104 corresponds to the primary multipole closest to the secondary multipole 112.

[0124] Figure 9 A charged particle beam 902 is shown directed by an objective lens 906 onto a sample 904 . Figure 9 Also shown are transfer lens 910 and optional transfer lens 908, which allow the microscope system to be operated with objective lens 906 closed (and the first upstream lens acting as a probe forming lens), for example, for studying samples in an environment without a magnetic field, such as a Lorentz microscope.

[0125] Figure 10 One or more example charged particle microscope systems 1000 are shown, including an example multipole corrector system 900 for correcting sixth-order aberrations. Figure 10 The example charged particle microscope system 1000 shown in FIG. 1 is an SEM system 1002 capable of operating in a standard mode of operation and a Lorentz mode of operation. That is, the path of the charged particle beam 1004 changes depending on the operating mode of the example charged particle microscope system 1000.

[0126] One or more example charged particle microscope systems 1000 include a charged particle source 1008 that emits a charged particle beam 1004 along an emission axis 1010 and toward an accelerator lens 1012, which accelerates / decelerates, focuses, and / or directs the charged particle beam 1004 toward a focusing column 1014 that focuses the charged particle beam 1004 so that it is incident on a sample 1016. The focusing column 1014 is shown as including an arrangement of the example multipole corrector system 900 and a plurality of lenses 1018. In some embodiments, when the example charged particle microscope system 1000 is operated in Lorentz mode, the objective lens 1020 is turned off. In such embodiments, the Lorentz lens 1022 acts like an objective lens and focuses the charged particle beam 1004 onto the sample 1016.

[0127] Figure 10 The example charged particle microscope system 1000 is further shown as including a sample holder 1024 that holds the sample 1016. One or more example charged particle microscope systems 1000 are also shown as including a detector 1026 that is configured to detect charged particles emitted and / or reflected by the sample 1016 as a result of the charged particle beam 1004 being incident on the sample 1016. Additionally, one or more example charged particle microscope systems 1000 are also shown as including astigmatism correction and a scanning coil 1028 for scanning the charged particle beam 1004 across the surface of the sample 1016. Figure 10 One or more example charged particle microscope systems 1000 are further shown as optionally including one or more computing devices 1030 .

[0128] Figure 11 1100 is a diagram illustrating how the primary aberrations of the first primary multipole, the second primary multipole, and the secondary multipole of a sixth-order corrected STEM multipole corrector system are combined at various stages to correct for sixth-order aberrations. Graph 1100 illustrates a first excitation energy level 1102 applied to each of the first primary multipole 102 and the second primary multipole 104, a second excitation energy level 1104 cumulatively applied to the second primary multipole 104, and a third excitation energy level 1106 applied to the secondary multipole 112. Graph 1100 also illustrates the primary aberrations 1108 generated by applying these excitation energy levels, as well as a relationship 1110 regarding how these aberrations are used to correct for second-order triplet astigmatism.

[0129] The different multipoles in Figure 1110 are positioned at different locations in the optical path. These different positions lead to combined aberrations through the following effects:

[0130] First multipole Change the direction of the ray by an amount which, in the lowest order, is related to its principal aberration Proportional.

[0131] When the light propagates to the second multipole This change in direction causes an additional deflection of the light at the second multipole. (i.e., any offset that may already exist due to the converging or diverging paths of the light beams). The additional offset and is proportional to the distance between the two multipoles. Proportional to ( ).

[0132] described The second multipole will also cause additional deflection of the light (i.e., additional to the action that the second multipole would do in the absence of the first). and and the main aberrations of the second multipole are proportional to ( ). The additional called multipolar and The combined aberration of M 1 and M 2 The lowest-order effects arise and can therefore be classified as primary combination aberrations.

[0133] In a similar manner, the second lowest order effects of the first multipole will produce a shift in the second multipole. , which can be classified as secondary composite aberration .

[0134] This concept of combined aberrations can be applied not only to the combination of one multipole with another, but also to the combination of a set of optical elements (such as a sextupole corrector consisting of two sextupoles and two transfer lenses—the primary aberration is negative spherical aberration) with a multipole, or the combination of one set of optical elements with another set of optical elements. In this disclosure, the general term combined aberrations is intended to refer to any primary, secondary, tertiary, and / or combinations thereof.

[0135] Diagram 1100 also illustrates primary combined aberrations 1112 generated by the applied excitation energy levels, and a relationship 1114 for how the primary combined aberrations are used to correct for the fourth-order triplet aberration. Finally, diagram 1100 also depicts secondary combined aberrations 1116 generated by the applied excitation energy levels, which correct for the sixth-order three-leaf aberration of the microscope system when the sixth-order corrective STEM multipole corrector system is optimally configured.

[0136] Figure 12is an illustration of an example multipole corrector system 1200 for correcting sixth-order aberrations, the multipole corrector system comprising at least one pair of primary multipoles and a plurality of multipoles positioned downstream of the pair of primary multipoles, the plurality of multipoles being positioned and / or otherwise configured to produce aberrations that combine to correct sixth-order aberrations or higher.

[0137] Specifically, Figure 12 A multipole corrector system 1200 according to the present disclosure is shown, comprising a triplet of primary multipoles 1202 (two of which correspond to primary multipoles 102 and 104), a secondary multipole 112, and an optional tertiary multipole 114. As described above, the inclusion of the tertiary multipole 114 enables the multipole corrector system 1200 to correct for three-leaf aberrations up to the sixth order when the triplet of primary multipoles 1202 are imaged onto each other (they do not produce D4). Alternatively, the tertiary multipole 114 allows the multipole corrector system 1200 to correct for three-leaf aberrations up to the eighth order when the triplet of primary multipoles 1202 are not imaged onto each other. Alternatively, the mutual imaging conditions of the primary multipoles 1202 and the excitation of the secondary multipoles 112 and 114 can be adjusted so that all three-leaf aberrations up to the sixth order are corrected and second-order off-axis astigmatism is zero.

[0138] Figure 12 The multipole corrector system is further shown as optionally including a plurality of weak sextupoles 1204 (eg, weak sextupoles). In some embodiments, the plurality of weak multipoles may include two pairs of antisymmetric weak multipoles to correct for off-axis coma. Figure 12 Further shown is a charged particle beam 1206 directed by an objective lens 1210 onto a sample 1208 .

[0139] Figure 13 is an illustration of an example multipole corrector system 1300 for correcting sixth-order aberrations, the multipole corrector system comprising a pair of primary multipoles, a plurality of transfer lenses including a weak circular transfer lens, and a plurality of multipoles positioned downstream of the pair of primary multipoles, the plurality of multipoles being positioned and / or otherwise configured to produce aberrations that combine to correct sixth-order aberrations or higher.

[0140] Specifically, Figure 13A multipole corrector system 1300 according to the present disclosure is shown, comprising a triplet transfer lens multipole 1302 (corresponding to the central transfer lens of a weak circular transfer lens), a secondary multipole 112, and an optional tertiary multipole 114. As described above, the inclusion of the tertiary multipole 114 enables the multipole corrector system 1300 to correct for three-leaf aberrations up to the sixth order when a pair of primary multipoles 102 and 104 are imaged onto each other. Alternatively, the tertiary multipole 114 allows the multipole corrector system 1300 to correct for three-leaf aberrations up to the eighth order when the first primary multipole 102 and the second primary multipole 104 are not imaged onto each other. In some embodiments, the length of the first primary multipole 102 can be different from the length of the second primary multipole 104, such that the first primary multipole 102 and the second primary multipole 104 are not imaged onto each other. Figure 13 Further shown is the charged particle beam 106 directed by the objective lens 1306 onto the sample 1304.

[0141] Figure 14-16 These are the plane Ronchigram images produced by microscope systems equipped with conventional, sixth-order, and eighth-order corrected STEM multipole correctors, respectively. A Ronchigram is a projected image (pattern) of a specimen formed in the diffraction plane, where a converging incident electron beam is focused near the specimen by a probe-forming lens. Plane Ronchigrams are used to illustrate corrector performance in microscope systems. Figure 14 and Figure 15-16 Comparisons show that the aberration-free regions produced by the sixth-order corrected STEM multipole corrector system and the eighth-order corrected STEM multipole corrector system (i.e., ~100 mrad at half angle) are larger than those produced by the conventional corrector system correcting up to 5 orders (i.e., less than 80 mrad).

[0142] Examples of inventive subject matter according to the present disclosure are described in the following enumerated paragraphs.

[0143] A1. A corrector for correcting axial aberration in a charged particle system, the corrector comprising:

[0144] a first primary hexapole for generating a first primary hexapole field when a first excitation is applied to the first primary hexapole;

[0145] a second primary sextupole for generating a second primary sextupole field when a second excitation is applied to the second primary sextupole, wherein the second primary sextupole is positioned between the first primary sextupole and a lens that is a source of spherical aberration when the corrector is used within a charged particle system, and wherein the first primary sextupole is not imaged onto the second primary sextupole, thereby generating a combined fourth-order aberration; and

[0146] A secondary sextupole for correcting the fourth-order aberration and the sixth-order aberration, wherein the secondary sextupole is positioned between the second primary sextupole and the lens when the corrector is used within the charged particle system.

[0147] A1.0.1. A corrector according to paragraph A1, wherein the lens that is the source of spherical aberration is a particle optical lens.

[0148] A1.0.2. A corrector according to any of paragraphs A1 to A1.0.1, wherein the lens acts as an objective lens when the corrector is used within the charged particle system.

[0149] A1.0.3. A corrector according to any of paragraphs A1 to A1.0.2, wherein the lens is the primary source of spherical aberration when the corrector is used within the charged particle microscope system.

[0150] A1.0.4. A corrector according to any of paragraphs A1 to A1.0.3, wherein the charged particle system is a charged particle microscope system.

[0151] A1.0.5. A corrector according to any of paragraphs A1 to A1.0.4, wherein the charged particle system is an electron microscope system.

[0152] A1.1. A corrector according to any of paragraphs A1 to A1.0.5, wherein the secondary hexapole is configured such that when a third excitation is applied to the secondary hexapole, it produces a third hexapole field.

[0153] A1.1.1. A corrector according to paragraph A1.1, wherein the third hexapole field produces one or more aberrations that correct the fourth-order aberration and the sixth-order aberration.

[0154] A1.2. A corrector according to any one of paragraphs A1 to A1.1.1, further comprising a tertiary sextupole for correcting eighth-order aberrations, wherein when the corrector is used within the charged particle system, the tertiary sextupole is positioned between the secondary sextupole and the lens.

[0155] A1.2.1. A corrector according to paragraph A1.2, wherein the three-level hexapole is configured such that when a fourth excitation is applied to the three-level hexapole, it produces a fourth hexapole field.

[0156] A1.2.1.1. A corrector according to paragraph A1.2.1, wherein the fourth sextupole field produces one or more aberrations that correct the eighth-order aberrations.

[0157] A1.2.1.1.1. A corrector according to paragraph A1.2.1.1, wherein the fourth sextupole field produces one or more combined aberrations (eg, primary combined aberrations, secondary combined aberrations, etc.) that correct the eighth-order aberrations.

[0158] A2. A corrector according to any of paragraphs A1 to A1.2.1.1, wherein the secondary sextupole produces second-order aberrations that produce first combined aberrations that correct the fourth-order aberrations.

[0159] A2.1. A corrector according to paragraph A2, wherein the first combined aberration includes or corresponds to a primary combined aberration.

[0160] A2.2. A corrector according to paragraph A2, wherein the first combined aberration includes or corresponds to a secondary combined aberration.

[0161] A3. A corrector according to any one of paragraphs A1 to A2.2, wherein the secondary sextupole is configured such that, when positioned in the optical column of a charged particle microscope, the positional aberration produced by the drift space between the corrector and the objective lens is combined with the additional aberration produced by the secondary sextupole to form a second combined aberration that corrects the sixth-order aberration.

[0162] A3.1. A corrector according to paragraph A3, wherein the second combined aberration includes or corresponds to the primary combined aberration.

[0163] A3.2. A corrector according to paragraph A3, wherein the second combined aberration includes or corresponds to a secondary combined aberration.

[0164] A4. A corrector according to any of paragraphs A1 to A3.2, wherein the contribution of the first primary hexapole, the contribution of the second primary hexapole, and the contribution of any transfer optics between the first primary hexapole and the second primary hexapole do not cancel.

[0165] A4.1. A corrector according to paragraph A4, wherein the first excitation corresponds to an excitation voltage that, when applied to the first primary hexapole, causes the first primary hexapole to generate a first primary hexapole field.

[0166] A4.2. A corrector according to paragraph A4, wherein the first excitation corresponds to an excitation current that, when applied to the first primary hexapole, causes the first primary hexapole to generate a first primary hexapole field.

[0167] A4.3. A corrector according to any of paragraphs A4 to A4.2, wherein the second excitation is greater than the first excitation.

[0168] A4.4. A corrector according to any of paragraphs A4 to A4.3, wherein the contribution of the first primary sextupole, the contribution of the second primary sextupole, and the contribution of any transfer optical devices between the first primary sextupole and the second primary sextupole produce 3x astigmatism A2 and a fourth-order 3-leaf aberration D4.

[0169] A5. A corrector according to any of paragraphs A1 to A4.4, wherein the first primary hexapole not being imaged onto the second primary hexapole corresponds to a first displacement of the first primary hexapole along the axis from the position where the first primary hexapole is imaged onto the second primary hexapole.

[0170] A5.1. A corrector according to paragraph A5, wherein the first displacement is 0.1 mm, 0.5 mm, 1 mm or greater.

[0171] A5.2. A corrector according to paragraph A5, wherein the first displacement is 0.1%, 0.5%, or 1% or more of the distance between the two primary hexapole.

[0172] A6. A corrector according to any of paragraphs A1 to A5.2, wherein the first primary hexapole not being imaged onto the second primary hexapole corresponds to a second displacement of the second primary hexapole along the axis from the position where the first primary hexapole is imaged onto the second primary hexapole.

[0173] A6.1. A corrector according to paragraph A6, wherein the second displacement is 0.1 mm, 0.5 mm, 1 mm or greater.

[0174] A6.2. A corrector according to paragraph A6, wherein the second displacement is 0.1%, 0.5%, or 1% or more of the distance between the two primary hexapole.

[0175] A7. When relying on A5 to A5.1, a corrector according to any of paragraphs A6 to A6.2, wherein the first displacement and the second displacement have the same magnitude.

[0176] A8. When relying on A5 to A5.1, a corrector according to any of paragraphs A6 to A7, wherein the first displacement is in opposite directions to the second displacement.

[0177] A9. A corrector according to any of paragraphs A1 to A4, wherein the first primary hexapole that is not imaged onto a hexapole corresponds to a light beam entering the first primary hexapole at a non-parallel angle.

[0178] A9.1. A corrector according to paragraph A9, wherein the first primary hexapole that is not imaged onto the hexapole corresponds to one or more lens excitations of a lens upstream of the corrector so that the light beam enters the first primary hexapole at the non-parallel angle.

[0179] A9.2. In the corrector of paragraph A9, the light beam entering the first primary hexapole at a non-parallel angle corresponds to the light beam entering the first primary hexapole at a diverging angle.

[0180] A10. The corrector of any of paragraphs A1 to A9.2, further comprising a set of one or more transfer lenses located between the first primary hexapole and the second primary hexapole.

[0181] A11. The corrector of any of paragraphs A1 to A9.1, further comprising a third hexapole positioned between the first primary hexapole and the second primary hexapole.

[0182] A11.1. The corrector of paragraph A1, further comprising a first set of one or more transfer lenses located between the first primary hexapole and the third hexapole, and a second set of one or more transfer lenses located between the third hexapole and the second primary hexapole.

[0183] A11.2. The corrector of any of paragraphs A11 to A11.1, wherein the third hexapole positioned between the first and second primary hexapole is a third primary hexapole.

[0184] A11.3. The corrector of any of paragraphs A11 to A11.2, wherein the third hexapole positioned between the first and second primary hexapole is a weak mid-hexapole.

[0185] A12. The corrector of any of paragraphs A1 to A12.4, further comprising a third hexapole positioned upstream of the first primary hexapole.

[0186] A12.1. A corrector according to paragraph A2, further comprising a first set of one or more transfer lenses located between the third hexapole and the first primary hexapole, and a second set of one or more transfer lenses located between the first primary hexapole and the second primary hexapole.

[0187] A13. The corrector of any of paragraphs A1 to A9.1, further comprising a third hexapole positioned between the second primary hexapole and the secondary hexapole.

[0188] A13.1. The corrector of paragraph A13, further comprising a first set of one or more transfer lenses located between the first primary hexapole and the second primary hexapole, and a second set of one or more transfer lenses located between the second primary hexapole and the third hexapole.

[0189] A14. A rectifier according to any of paragraphs A1 to A13.1, wherein a first length of the first primary hexapole is different from a second length of the second primary hexapole.

[0190] A14.1. The calibrator of paragraph A14, wherein the second length is greater than the first length.

[0191] A15. The corrector of any of paragraphs B1 to B14.1, further comprising one or more additional primary hexapole(s).

[0192] A15.1. A corrector according to paragraph B15, wherein when an additional excitation is applied to at least one of the one or more additional primary hexapole, an additional hexapole field is generated that helps to combine fourth-order aberrations.

[0193] B1. A corrector for correcting axial aberration in a charged particle system, the corrector comprising:

[0194] a first primary multipole for generating a first primary multipole field when a first excitation is applied to the first primary multipole;

[0195] a second primary multipole for generating a second primary multipole field when a second excitation is applied to the second primary multipole, wherein the second primary multipole is positioned between the first primary multipole and a lens that is a source of spherical aberration when the corrector is used within the charged particle system, wherein the first primary multipole is not imaged onto the second primary multipole, thereby generating a combined fourth-order aberration; and

[0196] A secondary multipole for correcting the fourth-order and sixth-order aberrations, wherein the secondary multipole is positioned between the second primary multipole and the lens when the corrector is used within the charged particle system.

[0197] B1.0.1. A corrector according to paragraph B1, wherein the lens that is the primary source of spherical aberration is the particle optical lens.

[0198] B1.0.2. A corrector according to any of paragraphs B1 to B1.0.1, wherein the lens acts as an objective lens when the corrector is used within the charged particle system.

[0199] B1.0.3. A corrector according to any of paragraphs B1 to B1.0.2, wherein the lens is the primary source of spherical aberration when the corrector is used within the charged particle system.

[0200] B1.0.4. A corrector according to any of paragraphs B1 to B1.0.3, wherein the charged particle system is a charged particle microscope system.

[0201] B1.0.5. A corrector according to any of paragraphs B1 to B1.0.4, wherein the charged particle system is an electron microscope system.

[0202] B1.1. A corrector according to any of paragraphs B1 to B1.0.1, wherein the secondary multipole is configured such that when a third excitation is applied to the secondary multipole, it generates a third multipole field.

[0203] B1.1.1. A corrector according to paragraph B1.1, wherein the third multipole field produces one or more aberrations that correct the fourth-order aberration and the sixth-order aberration.

[0204] B1.2. The corrector of paragraph B1, further comprising a tertiary multipole for correcting eighth-order aberrations, wherein the tertiary multipole is positioned between the secondary multipole and the lens when the corrector is used within the charged particle system.

[0205] B1.2.1. A corrector according to paragraph B1.2, wherein the three-level multipole is configured such that when a fourth excitation is applied to the three-level multipole, it generates a fourth multipole field.

[0206] B1.2.1.1. A corrector according to paragraph B1.2.1, wherein the fourth multipole field produces one or more aberrations that correct the eighth-order aberration.

[0207] B1.2.1.1.1. A corrector according to paragraph B1.2.1.1, wherein the fourth sextupole field produces one or more combined aberrations (eg, primary combined aberrations, secondary combined aberrations, etc.) that correct the eighth-order aberrations.

[0208] B2. A corrector according to any of paragraphs B1 to B1.1.1, wherein the secondary multipoles produce second-order aberrations that produce first combined aberrations that correct the fourth-order aberrations.

[0209] B2.1. A corrector according to paragraph B2, wherein the first combined aberration includes or corresponds to a primary combined aberration.

[0210] B2.2. A corrector according to paragraph B2, wherein the first combined aberration includes or corresponds to a secondary combined aberration.

[0211] B3. A corrector according to any one of paragraphs B1 to B2.2, wherein the secondary multipole is configured such that, when positioned in the optical column of a charged particle microscope, the positional aberration produced by the drift space between the corrector and the objective lens is combined with the additional aberration produced by the secondary multipole to form a second combined aberration that corrects the sixth-order aberration.

[0212] B3.1. A corrector according to paragraph B3, wherein the first combined aberration includes or corresponds to a primary combined aberration.

[0213] B3.2. A corrector according to paragraph B3, wherein the first combined aberration includes or corresponds to a secondary combined aberration.

[0214] B4. A corrector according to any of paragraphs B1 to B3.2, wherein the contribution of the first primary multipole, the contribution of the second primary multipole, and the contribution of any transfer optical devices between the first primary multipole and the second primary multipole do not cancel.

[0215] B4.1. A corrector according to paragraph B4, wherein the first excitation corresponds to an excitation voltage that, when applied to the first primary multipole, causes the first primary multipole to generate a first primary multipole field.

[0216] B4.2. A corrector according to paragraph B4, wherein the first excitation corresponds to an excitation current that, when applied to the first primary multipole, causes the first primary multipole to generate a first primary multipole field.

[0217] B4.3. A corrector according to any of paragraphs B4 to B4.2, wherein the second excitation is greater than the first excitation.

[0218] B4.4. A corrector according to any one of paragraphs B4 to B4.3, wherein the contribution of the first primary multipole, the contribution of the second primary multipole, and the contribution of any transfer optical devices between the first primary multipole and the second primary multipole produce 3x astigmatism A2 and a fourth-order 3-leaf aberration D4.

[0219] B5. A corrector according to any one of paragraphs B1 to B4.4, wherein the first primary multipole not being imaged onto the second primary multipole corresponds to a first displacement of the first primary multipole along the axis from the position where the first primary multipole is imaged onto the second primary multipole.

[0220] B5.1. A corrector according to paragraph B5, wherein the first displacement is 0.1 mm, 0.5 mm, 1 mm or greater.

[0221] B5.2. A corrector according to paragraph B5, wherein the first displacement is 0.1%, 0.5%, or 1% or more of the distance between the two primary multipoles.

[0222] B6. A corrector according to any one of paragraphs B1 to B5.2, wherein the first primary multipole not being imaged onto the second primary multipole corresponds to a second displacement of the second primary multipole along the axis from the position where the first primary multipole is imaged onto the second primary multipole.

[0223] B6.1. A corrector according to paragraph B6, wherein the second displacement is 0.1 mm, 0.5 mm, 1 mm or greater.

[0224] B6.2. A corrector according to paragraph B6, wherein the first displacement is 0.1%, 0.5%, or 1% or more of the distance between the two primary multipoles.

[0225] B7. When relying on B5 to B5.1, a corrector according to any of paragraphs B6 to B6.2, wherein the first displacement and the second displacement have the same magnitude.

[0226] B8. When relying on B5 to B5.1, a corrector according to any of paragraphs B6 to B7, wherein the first displacement is in opposite directions to the second displacement.

[0227] B9. A corrector according to any of paragraphs B1 to B4, wherein the first primary multipole that is not imaged onto a multipole corresponds to a light beam entering the first primary multipole at one of a diverging angle or a converging angle.

[0228] B9.1. A corrector according to paragraph B9, wherein the first primary multipole that is not imaged onto the multipole corresponds to one or more lens excitations of a lens upstream of the corrector, so that the light beam enters the first primary multipole at one of a divergent angle or a convergent angle.

[0229] B9.2. In a corrector according to paragraph B9, the light beam entering the first primary multipole at a non-parallel angle corresponds to the light beam entering the first primary multipole at a diverging angle.

[0230] B10. The corrector of any of paragraphs B1 to B9.1, further comprising a group of one or more transfer lenses located between the first primary multipole and the second primary multipole.

[0231] B11. The corrector of any of paragraphs B1 to B9.1, further comprising a third multipole positioned between the first primary multipole and the second primary multipole.

[0232] B11.1. A corrector according to paragraph B1, further comprising a first set of one or more transfer lenses located between the first primary multipole and the third multipole, and a second set of one or more transfer lenses located between the third multipole and the second primary multipole.

[0233] B11.2. The corrector of any of paragraphs B11 to B11.1, wherein the third multipole positioned between the first primary multipole and the second primary multipole is a third primary multipole.

[0234] B11.3. A corrector according to any of paragraphs B11 to B11.2, wherein the third multipole positioned between the first primary multipole and the second primary multipole is a weak intermediate multipole.

[0235] B12. The corrector of any of paragraphs B1 to B11.3, further comprising a third multipole positioned upstream of the first primary multipole.

[0236] B12.1. A corrector according to paragraph B2, further comprising a first set of one or more transfer lenses located between the third multipole and the first primary multipole, and a second set of one or more transfer lenses located between the first primary multipole and the second primary multipole.

[0237] B13. The rectifier of any of paragraphs B1 to B9.1, further comprising a third multipole positioned between the second primary multipole and the secondary multipole.

[0238] B13.1. A corrector according to paragraph B13, further comprising a first set of one or more transfer lenses located between the first primary multipole and the second primary multipole, and a second set of one or more transfer lenses located between the second primary multipole and the third multipole.

[0239] B14. A corrector according to any of paragraphs B1 to B13.1, wherein the multipole is a hexapole.

[0240] B14. A rectifier according to any of paragraphs B1 to B13.1, wherein a first length of the first primary multipole is different from a second length of the second primary multipole.

[0241] B14.1. A corrector according to paragraph B14, wherein the second length is greater than the first length.

[0242] B15. The rectifier of any of paragraphs B1 to B14.1, further comprising one or more additional primary multipoles.

[0243] B15.1. A corrector according to paragraph B15, wherein when an additional excitation is applied to at least one of the one or more additional primary multipoles, an additional multipole field is generated that helps to combine fourth-order aberrations.

[0244] C1. A corrector for correcting axial aberration in a charged particle system, the corrector comprising:

[0245] a first primary multipole for generating a first primary multipole field when a first excitation is applied to the first primary multipole;

[0246] a second primary multipole for generating a second primary multipole field when a second excitation is applied to the second primary multipole, wherein the second primary multipole is positioned between the first primary multipole and a lens that is a source of spherical aberration when the corrector is used within the charged particle system, and wherein the first primary multipole is imaged onto the second primary multipole;

[0247] a secondary multipole for generating a third multipole field when a third excitation is applied to the secondary multipole, wherein the secondary multipole is positioned between the second primary multipole and the lens when the corrector is used within the charged particle system; and

[0248] A three-stage multipole for generating a fourth multipole field when a fourth excitation is applied to the three-stage multipole, wherein when the corrector is used within the charged particle system, the three-stage multipole is positioned between the secondary multipole and the lens, wherein the third multipole field and the fourth multipole field correct the sixth-order aberration.

[0249] C1.0.1. A corrector according to paragraph C1, wherein the lens that is the primary source of spherical aberration is the particle optical lens.

[0250] A corrector according to any of paragraphs C1 to C1.0.1, wherein the lens acts as an objective lens when the corrector is used within the charged particle system.

[0251] C1.0.3. A corrector according to any of paragraphs C1 to C1.0.2, wherein the lens is the primary source of spherical aberration when the corrector is used within the charged particle system.

[0252] C1.0.4. A corrector according to any of paragraphs C1 to C1.0.3, wherein the charged particle system is a charged particle microscope system.

[0253] C1.0.5. A corrector according to any of paragraphs C1 to C1.0.4, wherein the charged particle system is an electron microscope system.

[0254] C1.1. A corrector according to any one of paragraphs C1 to C1.0.1, further comprising a quadruple multipole for correcting eighth-order aberrations, wherein when the corrector is used in the charged particle microscope system, the quadruple multipole is positioned between the tertiary multipole and the particle optical lens.

[0255] C1.1.1. A corrector according to paragraph C1.1, wherein the quadrupole multipole is configured such that when a fifth excitation is applied to the quadrupole multipole, it generates a fifth multipole field.

[0256] C1.1.1.1. A corrector according to paragraph C1.1.1, wherein the fifth multipole field produces one or more aberrations that correct the eighth-order aberrations.

[0257] C2. The corrector of any of paragraphs C1 to C1.1.1.1, wherein the contribution of the first primary multipole, the contribution of the second primary multipole, and the contribution of any transfer optics between the first primary multipole and the second primary multipole do not cancel. C2.1. The corrector of paragraph C2, wherein the first excitation corresponds to an excitation voltage that, when applied to the first primary multipole, causes the first primary multipole to generate a first primary multipole field.

[0258] C2.2. A corrector according to paragraph C2, wherein the first excitation corresponds to an excitation current that, when applied to the first primary multipole, causes the first primary multipole to generate a first primary multipole field.

[0259] C2.3. A corrector according to any of paragraphs C2 to C2.2, wherein the second excitation is greater than the first excitation.

[0260] C2.4. A corrector according to any one of paragraphs C2 to C2.3, wherein the contribution of the first primary multipole, the contribution of the second primary multipole, and the contribution of any transfer optical devices between the first primary multipole and the second primary multipole produce 3x astigmatism A2 and a fourth-order 3-leaf aberration D4.

[0261] C3. A corrector according to any of paragraphs C1 to C2.4, further comprising a set of one or more transfer lenses located between the first primary multipole and the second primary multipole.

[0262] C4. The rectifier of any one of paragraphs C1 to C3, further comprising a third multipole positioned between the first primary multipole and the second primary multipole.

[0263] C5. A corrector according to any of paragraphs C1 to C5, wherein the multipole is a hexapole.

[0264] C6. A rectifier according to any of paragraphs C1 to C5, wherein a first length of the first primary multipole is different from a second length of the second primary multipole.

[0265] C6.1. A corrector according to paragraph C6, wherein the second length is greater than the first length.

[0266] D1. A charged particle microscope comprising: a charged particle source configured to emit a charged particle beam toward a sample; and an optical column configured to focus the charged particle beam onto the sample, wherein the optical column comprises a corrector according to any one of paragraphs A1–A13.1, B1–B14, or C1–C5.

[0267] E1. Use of a corrector according to any of paragraphs A1-A13.1, B1-B14, or C1-C5.

[0268] F1. A use of the charged particle microscope according to paragraph D1.

Claims

1. A corrector for correcting axial aberration in a charged particle system, the corrector comprising: a first primary multipole that generates a first primary multipole field when a first excitation is applied to the first primary multipole; a second primary multipole that generates a second primary multipole field when a second excitation is applied to the second primary multipole, wherein when used in the charged particle system, the second primary multipole is positioned between the first primary multipole and a lens that is a source of spherical aberration, wherein the first primary multipole is not imaged onto the second primary multipole, thereby generating a combined fourth-order aberration; and A secondary multipole is provided for correcting the fourth-order and sixth-order aberrations, wherein the secondary multipole is positioned between the second primary multipole and the lens when used in the charged particle system. 2 . The corrector of claim 1 , wherein the secondary multipole is further configured to correct for triple astigmatism A2.

3. The rectifier according to claim 1, wherein the secondary multipole is configured such that: When a third excitation is applied to the secondary multipole, the secondary multipole generates a third multipole field, and The third multipole field produces one or more aberrations that correct the fourth-order aberration and the sixth-order aberration.

4. The corrector of claim 1 , wherein the secondary multipoles generate second-order aberrations that produce combined aberrations that correct the fourth-order aberrations.

5. The corrector according to claim 1, wherein the first excitation and the second excitation are such that a first contribution to the threefold astigmatism A2 produced by the first primary multipole field and a second contribution to the threefold astigmatism A2 produced by the second primary multipole field are not cancelled.

6. The collimator of claim 1, wherein when the collimator is used, the first primary multipole that is not imaged onto the second primary multipole comprises a charged particle beam that enters the first primary multipole at one of a diverging angle or a converging angle.

7. A corrector according to claim 1, wherein the first primary multipole that is not imaged onto the second primary multipole includes one or more lens excitations of a lens upstream of the corrector so that when the corrector is used, the charged particle beam enters the first primary multipole at one of a diverging angle or a converging angle.

8. The corrector of claim 1, wherein the first primary multipole not imaged onto the second primary multipole corresponds to one or more lens excitations of a lens positioned between the first primary multipole and the second primary multipole.

9. The rectifier of claim 1, wherein the first primary multipole and the second primary multipole are both hexapole.

10. The corrector according to any one of claims 1 to 9, further comprising a tertiary multipole for correcting eighth-order aberrations, wherein when used in the charged particle system, the tertiary multipole is positioned between the secondary multipole and the lens.

11. The rectifier according to claim 10, wherein the three-stage multipole is configured such that: When a fourth excitation is applied to the three-level multipole, the three-level multipole generates a fourth multipole field; and The fourth multipole field produces one or more aberrations that correct the eighth-order aberrations.

12. A corrector according to any one of claims 1 to 9, wherein the first primary multipole not being imaged onto the second primary multipole corresponds to a first displacement of one of the first primary multipole or the second primary multipole along the central axis from the position where the first primary multipole is imaged onto the second primary multipole.

13. The corrector of claim 12 , wherein the first primary multipole not being imaged onto the second primary multipole further corresponds to a second displacement of the other of the first primary multipole or the second primary multipole along the central axis from a position at which the first primary multipole is imaged onto the second primary multipole. The rectifier of claim 13 , wherein the first displacement is in opposite directions to the second displacement.

15. A charged particle system comprising: a charged particle source configured to emit a charged particle beam toward the sample; and An optical column configured to focus the charged particle beam onto the sample, wherein the optical column comprises a corrector according to any one of claims 1 to 9 for correcting axial aberration of a lens as a source of spherical aberration.

Images