Wien filters and charged particle beam imaging equipment

Abstract

This invention belongs to the field of detection technology, specifically relating to Wien filters and related charged particle beam detection instruments and imaging equipment. The Wien filter includes an electric deflector and a magnetic deflector; the electric deflector includes at least one set of opposing arc-shaped electrode pairs, each set of electrode pairs being coaxially and circularly arranged, and each electrode pair being excited by a voltage to generate its own electric field; the magnetic deflector includes at least one set of opposing arc-shaped magnetic pole pairs, each set of magnetic pole pairs being coaxially and circularly arranged, and distributed coaxially but circumferentially with the electric deflector, the magnetic pole pairs being excited by coils wound on the magnetic pole pairs to generate their own magnetic fields; at least one set of electrode pairs provides an electric field in a single direction, while the magnetic field directions provided by the remaining magnetic pole pairs are adjustable to satisfy the orthogonality condition with the electric field direction; alternatively, at least one set of magnetic pole pairs provides a magnetic field in a single direction, while the electric field directions provided by the remaining electrode pairs are adjustable to satisfy the orthogonality condition with the magnetic field direction. This invention can eliminate the third harmonic component of the deflection field in a charged particle optical system.

Description

Technical Field

[0001] This invention belongs to the field of detection technology, and specifically relates to Wien filters and related charged particle beam detection instruments and imaging equipment. Background Technology

[0002] The Wien filter mainly consists of a set of coaxial composite electric and magnetic deflectors. By changing the electrode voltage or coil excitation current, it generates orthogonal electric and magnetic fields in the off-axis space to adjust or balance the electric and magnetic forces acting on the passing charged particles, thereby controlling the trajectory of the charged particles. Since the magnetic force is also related to mass and velocity, it can achieve the separation of ions with specific masses or ions with specific energies. It is widely used in energy dispersive spectrometers or mass spectrometers in the field of detection instruments. In the field of electron microscopy, it is also used to achieve monochromatic filtering of the main electron beam and off-axis detection of signal electrons (including secondary electrons and backscattered electrons).

[0003] Due to the requirements of non-destructive testing in semiconductor processes and other scientific research and production fields, low-energy high-resolution electron microscopes based on repulsive field objectives have been rapidly developed. As the core of imaging, the signal electron detector needs to be placed inside the electron optics tube. The detector must avoid the main optical axis, that is, the downward channel of the main electron beam, and be placed on one side of the optical axis or around the optical axis. Accordingly, in order to detect the signal electrons traveling upward along the axis, a Wien filter is introduced in front of the detector to deflect the upward signal electrons off the axis. According to the principle of the Wien filter, electromagnetic excitation can be driven and matched so that the electromagnetic force on the downward main electron beam is canceled out and is not affected by the Wien filter. The Wien filter only affects the upward signal electrons, so that they are subjected to electromagnetic force in the same direction and reach the detector for detection and imaging.

[0004] Currently, Wien filters used for electron detection of auxiliary signals in electron microscopy generally have two main problems:

[0005] 1. How to reduce the third harmonic component of the deflection field. In order to ensure the uniformity of the field generated by the two-dimensional orthogonal deflector and reduce the third harmonic component of the deflection field, the industry usually adopts an 8-pole or 12-pole structure (see "Katsushige Tsuno 1, Damaschin Ioanoviciu 2, Advances in Imaging and Electron Physics, Volume 176, 2013, Pages 127-150" for details). Among them, the 8-pole deflector requires a power supply to provide four outputs of ±V and ±αV, which is complex. Although the 12-pole deflector only requires two outputs of ±V (see US Patent US13292455), it increases the number of electrodes and makes it more difficult to control the precision of processing and assembly.

[0006] Electrical deflectors are typically designed as a pair of orthogonal deflectors. By adjusting the voltage component ratio on the two pairs of plates in the orthogonal direction of the deflectors, the direction of the synthesized field can be adjusted to match the requirement of orthogonality with the magnetic deflection field. Since traditional Wien filters are based on the design concept of arbitrary-angle deflectors, possessing deflection capabilities controllable at any angle, they impose strict limitations on the symmetry of the deflector structure. The most common example is the evenly distributed four-electrode structure disclosed in patent CN110660633B, where the angle of a single electrode is <π / 2, and the third harmonic corresponding to a half-angle of π / 4 is sin(3π / 4)≠0. This patent reduces the third harmonic by changing the shape of the electrode cross-section, disrupting the conventional rotationally symmetric circular arc structure, but it suffers from high manufacturing difficulty and is relatively difficult to implement. Furthermore, the electrodes of this electrical deflector are made of magnetic material, also serving as magnetic poles, and are fitted with saddle-shaped coils, with a half-angle also less than <π / 4. The advantage of this structure is space saving, but the disadvantage is that the third harmonic corresponding to the magnetic pole is sin(3π / 4)≠0. Therefore, the above-mentioned technical problems cannot be solved by using traditional Wien filters.

[0007] 2. How to control the axial distribution of magnetic and electric fields to achieve conformal magnetic and electric fields? The ideal Wien filter must meet the following conditions. Also known as the direct-axis condition of the Wien filter, it means that the shapes of E(z) and B(z) (taking their normalized distribution) are perfectly matched, where v is the velocity of the charged particle. In practice, the edge field distributions at the inlet and outlet of the Wien filter are difficult to match, which has a significant impact on the performance of the main electron beam under strong excitation. Patents CN110660633B and US13292455 both introduce magnetic rings along the axial direction to compress and adjust the isomorphic matching of the magnetic and electric field distributions on the axis; however, the magnetic ring is also an electrode, and adjusting the magnetic field will inevitably affect the electric field, making it difficult to quickly adjust the coupling between the two to obtain a suitable isomorphic field distribution. Summary of the Invention

[0008] The first objective of this invention is to provide a Wien filter to eliminate the third harmonic component of the deflection field of a charged particle optical system in an imaging detection device, thereby reducing aberrations.

[0009] The present invention is achieved through the following technical solutions:

[0010] A Wien filter includes an electrical deflector and a magnetic deflector; the electrical deflector includes at least one set of opposing arc-shaped electrode pairs, each set of electrode pairs being coaxially and circumferentially arranged, and the electrode pairs being excited by voltage to generate their respective electric fields; the magnetic deflector includes at least one set of opposing arc-shaped magnetic pole pairs, each set of magnetic pole pairs being coaxially and circumferentially arranged, and coaxially but circumferentially distributed with respect to the electrical deflector, and the magnetic pole pairs being excited by coils wound on the magnetic pole pairs to generate their respective magnetic fields;

[0011] The electrode pairs and magnetic pole pairs comprise at least three pairs; the magnetic pole pairs provide a magnetic field with a constant direction, while the electric field directions provided by the remaining electrode pairs are adjustable to satisfy the orthogonality condition with the magnetic field; each electrode pair includes one or more main electrode pairs, with the electrodes on the same side of the main electrode pairs symmetrically arranged around the X-axis, the X-axis being located within the cross-section of the electric deflector and passing through the axis of the electric deflector; an insulating gap is provided between the electrodes on the same side of the main electrode pairs, and the full electrode opening angle α1 of the main electrode pairs is 120°±Δ, where the full electrode opening angle α1 represents the angle corresponding to the arc length of the total arc length of a single main electrode and the sum of the insulating gap between the main electrodes on that side relative to the axis, and Δ is a tolerance value.

[0012] Preferably, the magnetic pole pair provides a magnetic field B in a second direction;

[0013] The main electrode pairs are arranged orthogonally to the magnetic pole pairs. The electrodes on the same side of the main electrode pairs are applied with the same polarity voltage, and the electrodes on opposite sides of the axis are applied with the opposite polarity voltage. After the voltage is applied to each group of main electrode pairs, they generate a component electric field E1i, i = 1, 2, ..., which is at an angle to the expected first direction. The resultant electric field of each component electric field E1i is E1. The intensity of the resultant electric field E1 is adjusted by the amplitude of the excitation voltage V1i of each main electrode pair. The direction of the resultant electric field E1 is adjusted by the polarity of the excitation voltage of each main electrode pair and the relative ratio V11 / V12 / V13... / V1i, so that the direction of the resultant electric field E1 is ideally orthogonal to the direction of the magnetic field B near the axis.

[0014] Furthermore, the electrode pair also includes one or more auxiliary electrode pairs, wherein the electrodes on the same side of the auxiliary electrode pairs are symmetrically arranged with the Y-axis as the center, and the auxiliary electrode pairs are located between the main electrode pairs on opposite sides, wherein the Y-axis is perpendicular to the X-axis, and the Y-axis is located within the cross-section of the electric deflector and passes through the axis of the electric deflector; the main electrode pairs and the auxiliary electrode pairs do not overlap.

[0015] The full electrode angle α2 of the auxiliary electrode pair is 60°±Δ, where the full electrode angle α2 represents the angle corresponding to the arc length of the total arc length of the auxiliary electrode on one side and the insulation gap between the auxiliary electrodes on that side relative to the axis. The auxiliary electrode pair is used to compensate for the orthogonal deviation between the electric field of the main electrode pair and the magnetic field of the magnetic pole pair.

[0016] Preferably, each of the auxiliary electrode pairs generates a sub-electric field E2i, i = 1, 2..., after a voltage is applied. The combined electric field of each sub-electric field E2i is E2. The intensity of the combined electric field E2 is adjusted by the amplitude of the excitation voltage V2i of each main electrode pair. The deflection direction of the combined electric field E2 is adjusted by the polarity and relative ratio V21 / V22... / V2i of the excitation voltage of each auxiliary electrode pair. The intensity and direction of the combined electric field E of the electric field E1 generated by the main electrode pair and the electric field E2 generated by the auxiliary electrode pair can also be controlled, so that the direction of the combined electric field E is ideally orthogonal to the direction of the magnetic field B near the axis.

[0017] This application also provides another Wien filter, including an electric deflector and a magnetic deflector, wherein the electric deflector includes at least one set of opposing arc-shaped electrode pairs, each set of electrode pairs being arranged coaxially and circumferentially, and the electrode pairs being respectively excited by voltage to generate their own electric fields.

[0018] The magnetic deflector includes at least one set of opposing arc-shaped magnetic pole pairs. Each set of magnetic pole pairs is arranged coaxially and circumferentially, and is coaxially but circumferentially distributed with the electric deflector. The magnetic pole pairs are excited by coils wound on the magnetic pole pairs to generate their respective magnetic fields.

[0019] The sum of the electrode pairs and the magnetic pole pairs is at least three pairs; the electrode pairs provide an electric field in a constant direction, and the magnetic field provided by the remaining magnetic pole pairs is adjustable in direction to satisfy the orthogonality condition with the electric field;

[0020] The magnetic pole pair includes a main magnetic pole pair, which is orthogonally arranged with the main electrode pair. The full pole opening angle β1 of the main magnetic pole pair is 120°±Δ. When the coils of the same side of the main magnetic pole pair are not overlapped, the full pole opening angle β1 represents the angle corresponding to the arc length of the sum of the arc lengths of the coils on the same side with respect to the axis. When the coils of the same side of the main magnetic pole pair are overlapped, the full pole opening angle β1 is the arc length of each pair of coils with respect to the axis.

[0021] Preferably, the electrode pair provides an electric field E in a first direction;

[0022] After an excitation current is applied to the coils of each main magnetic pole pair, a sub-magnetic field B1i (i = 1, 2, ...) is generated at an angle to the expected second direction. The composite magnetic field of each sub-magnetic field B1i is B1. The intensity of the composite magnetic field B1 is adjusted by the intensity of the excitation currents I11, I12...I1i of each pair of coils. The direction of the composite magnetic field B1 is adjusted by the relative proportions I11 / I12... / I1i of the excitation currents on each pair of coils, so that the direction of the composite magnetic field B1 is ideally orthogonal to the direction of the electric field E near the axis.

[0023] Furthermore, the magnetic pole pair also includes one or more auxiliary magnetic pole pairs. The auxiliary magnetic pole pairs are close to the outside of the main pole pair and are symmetrically arranged with the same side magnetic poles around the X-axis. The auxiliary magnetic pole pairs are located between the main magnetic pole pairs on opposite sides. The main magnetic pole pairs and the auxiliary magnetic pole pairs may overlap or not overlap.

[0024] The full pole opening angle β2 of the auxiliary magnetic pole pair is 60°±Δ. When the coils of the auxiliary magnetic poles on the same side do not overlap, the full pole opening angle β2 represents the angle corresponding to the arc length of the auxiliary magnetic pole coils on the same side with respect to the axis. When the coils of the auxiliary magnetic poles on the same side overlap, the full pole opening angle β2 represents the angle corresponding to the arc length of the auxiliary magnetic pole coils on the same side with respect to the axis. The auxiliary magnetic pole pair is used to compensate for the orthogonal deviation between the magnetic field of the main magnetic pole pair and the electric field of the electrode pair.

[0025] Optionally, the coils of the main magnetic pole pair are arranged adjacent to each other on the circumference without overlapping, and / or the coils of the auxiliary magnetic pole pair are arranged adjacent to each other on the circumference without overlapping.

[0026] Each auxiliary magnetic pole pair generates a sub-magnetic field B2i, i = 1, 2..., after being excited by an excitation current. The combined magnetic field of each sub-magnetic field B2i is B2. The strength of the combined magnetic field B2 is adjusted by the strength of the excitation current I2i of each main magnetic pole pair. The deflection direction of the combined magnetic field B2 is adjusted by the polarity and relative ratio I21 / I22... / I2i of the excitation current of each auxiliary pole pair. The strength and direction of the combined magnetic field B of the magnetic field B1 generated by the main magnetic pole pair and the magnetic field B2 generated by the auxiliary magnetic pole pair can also be controlled, so that the direction of the combined magnetic field B is ideally orthogonal to the direction of the electric field E near the axis.

[0027] Optionally, the insulation gap is formed by radial division, or by successive radial and circumferential bending division.

[0028] Optionally, the excitation voltage applied to both the main electrode pair and the auxiliary electrode pair has a bias voltage V0.

[0029] Preferably, the coil of the magnetic pole pair is a saddle-shaped coil or a ring coil; the electric deflector and the magnetic deflector are wrapped by a magnetic core, and the magnetic core has openings at both ends along its axial direction.

[0030] Another objective of this application is to provide a Wien filter that controls the axial distribution of magnetic and electric fields to achieve conformal characteristics. The Wien filter includes an electric deflector and a magnetic deflector;

[0031] The electric deflector and the magnetic deflector are enclosed by a magnetic core. Openings are provided at both ends of the magnetic core along its axial direction. The openings are located near the inner side of the magnetic core. The sidewalls of the openings are provided with transition gaps to control the distribution pattern of the magnetic field along the axis.

[0032] Preferably, the transition gap includes an inner annular surface and an outer annular surface extending axially. The diameter of the inner annular surface is smaller than the diameter of the outer annular surface. The inner annular surface and the outer annular surface are connected and transitioned by a conical surface. The diameter of the conical surface gradually increases from one end of the inner annular surface to one end of the outer annular surface.

[0033] Furthermore, an electrode ring is embedded within the transition gap, the electrode ring being in close contact with the conical surface and the outer ring surface, and the minimum inner diameter of the electrode ring being not less than the diameter of the inner ring surface; the electrode ring is used to adjust the surrounding electric field distribution pattern.

[0034] Preferably, the exposed portion of the electrode ring includes an axially extending annular surface three and an annular surface four, with annular surface four located near the axis and recessed relative to the outer annular surface one, and annular surface three and annular surface four connected by an electrode conical surface.

[0035] Preferably, the electrode ring protrudes into the magnetic core relative to the outer ring, for fine-tuning the surrounding electric field distribution.

[0036] Furthermore, the magnetic core includes an annular magnetic core body and magnetic rings located at both ends of the magnetic core body, and the magnetic rings are provided with the transition gap; the coil of the magnetic deflector is wound on the magnetic core body, and the magnetic core body and the magnetic rings are isolated by an air gap or a non-magnetic material.

[0037] A third objective of this invention is to provide a charged particle beam imaging device including the Wien filter, which is configured to scan an incident and focused main charged particle beam onto the surface of a sample to be tested, and collect secondary charged particles excited at corresponding positions to generate an image of the sample surface morphology; the Wien filter is located between the sample and the secondary charged particle detector, the deflector of the Wien filter can eliminate the third harmonic, the orthogonality and edge field distribution matching can be finely adjusted to meet the direct axis condition, it has no deflection effect on the downward passing main charged particle beam, and applies a deflection force in a specific direction to the upward secondary charged particles, thereby achieving detection and imaging towards the detector.

[0038] The beneficial effects of this invention are as follows:

[0039] This invention application is based on the fact that detectors within electron microscope imaging lenses are mostly ring detectors, and that a single-direction off-axis deflection capability is sufficient to achieve off-axis detection of electrons. The Wien filter described prioritizes satisfying uniform field and straight-axis conditions, has a simple structure, is easy to implement, and introduces as few aberrations as possible.

[0040] The electrical or magnetic deflector in this Wien filter provides a field in a constant direction. Other magnetic or electrical deflectors can fine-tune the orthogonality of the deflecting magnetic and electric fields to satisfy the orthogonality condition between the magnetic and electric fields. The multi-pole structure of the electrical and magnetic deflectors, with the main electrode pair having a full opening angle of 120°±Δ and the auxiliary electrode pair having a full opening angle of 60°±Δ, eliminates the limitation of symmetry, prioritizing uniformity. For example, both the asymmetrical four-electrode structure and the symmetrical six-electrode design can meet the requirements for a uniform field to eliminate third harmonics and fine-tuning for orthogonality with the magnetic field. Similarly, the 120° full opening angle structure of the dual-pole coils and their symmetrical or asymmetrical layout can also meet the requirements for a uniform field to eliminate third harmonics and fine-tuning for orthogonality with the electric field.

[0041] This application proposes a Wien filter with a main and auxiliary deflector structure, and also proposes an electrode diameter variation design along the axis. Combined with the separation of auxiliary magnetic poles and electrodes and the combination design of irregular electrode rings, the axial distribution of magnetic and electric fields can be independently adjusted. The optimized design can obtain axial distributions of magnetic and electric fields with almost the same shape (normalized curve).

[0042] The Wien filter of this application solves the problems of orthogonality and conformal distribution of electric and magnetic fields. As long as a reasonable excitation is applied, it can filter particles with different energies and masses. For the intralens detection of electron signal electrons in an electron microscope, it can satisfy the direct axis condition while minimizing the aberrations introduced to the main electron beam. Attached Figure Description

[0043] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0044] Figure 1 This is a schematic diagram showing the distribution of three sets of main electrode pairs in an electric deflector.

[0045] Figure 2 This is a schematic diagram showing the distribution of two sets of auxiliary electrode pairs in an electric deflector.

[0046] Figure 3 yes Figure 1 main electrode pair and Figure 2 A schematic diagram of an electric deflector formed by the combination of auxiliary electrode pairs in the diagram.

[0047] Figure 4 This is a schematic diagram showing the distribution of two sets of main magnetic pole pairs in a magnetic deflector.

[0048] Figure 5 This is a schematic diagram showing the distribution of two sets of auxiliary magnetic pole pairs in a magnetic deflector.

[0049] Figure 6 yes Figure 4 The main magnetic pole pairs and Figure 5 A schematic diagram of a magnetic deflector formed by the combination of auxiliary magnetic pole pairs in the diagram.

[0050] Figure 7 yes Figure 3 Electrical deflector and Figure 6 A schematic diagram of the Wien filter structure formed by the combination of magnetic deflectors in the image;

[0051] Figure 8 This is a structural schematic diagram of the first specific embodiment of the Wien filter;

[0052] Figure 9 This is a structural schematic diagram of a second specific embodiment of the Wien filter;

[0053] Figure 10 This is a structural schematic diagram of the third specific embodiment of the Wien filter;

[0054] Figure 11 This is a structural schematic diagram of the fourth specific embodiment of the Wien filter;

[0055] Figure 12 This is a structural diagram illustrating the insulation gap division method on the Wien filter;

[0056] Figure 13 This is a schematic diagram of the equipotential lines distributed in the open cross-section of the Wien filter core, which adopts a straight-edge shape.

[0057] Figure 14 This is a schematic diagram of the equipotential line distribution of the open cross-section of the Wien filter core, which uses a transition notch.

[0058] Figure 15 It is the distribution of equipotential lines of electrode rings embedded in the transition gap of the magnetic core;

[0059] Figure 16 This is the matching effect of the deflection electric field and magnetic field along the axis distribution achieved by one embodiment of the present invention;

[0060] Figure 17 This is a cross-sectional view of the opening section of the Wien filter core with a transition notch;

[0061] Figure 18 This is a cross-sectional schematic diagram of the magnetic deflector of the Wien filter, which is a saddle-shaped coil, with an electrode ring embedded in the transition gap of the magnetic core.

[0062] Figure 19 This is a cross-sectional view of the Wien filter, where the magnetic deflector is a toroidal coil and an electrode ring is embedded in the transition gap of the magnetic core. Detailed Implementation

[0063] First, this article will use the following terms more frequently:

[0064] 300. Electrical deflector; 301. Main electrode pair; 3011. First electrode pair of the main electrode pair; 3012. Second electrode pair of the main electrode pair; 3013. Third electrode pair of the main electrode pair; 310. Half-angle of the main electrode pair; 3101. Half-angle of the first electrode pair of the main electrode pair; 3102. Half-angle of the second electrode pair of the main electrode pair; 302. Auxiliary electrode pair; 3021. First electrode pair of the auxiliary electrode pair; 3022. Second electrode pair of the auxiliary electrode pair; 320. Half-angle of the auxiliary electrode pair; 3201. Half-angle of the first electrode pair of the auxiliary electrode pair; 3202. Half-angle of the second electrode pair of the auxiliary electrode pair; 330. Insulation gap; 340. Angle between the electric fields of the main electrode pair and the auxiliary electrode pair;

[0065] 400. Magnetic deflector; 401. Main magnetic pole pair; 4011. First pair of magnetic poles of the main magnetic pole pair; 4012. Second pair of magnetic poles of the main magnetic pole pair; 4013. Third pair of magnetic poles of the main magnetic pole pair; 410. Half angle of the main magnetic pole pair; 4101. Half angle of the first pair of magnetic poles of the main magnetic pole pair; 4102. Half angle of the second pair of magnetic poles of the main magnetic pole pair; 402. Auxiliary magnetic pole pair; 4021. First pair of magnetic poles of the auxiliary magnetic pole pair; 4022. Second pair of magnetic poles of the auxiliary magnetic pole pair; 420. Half angle of the auxiliary magnetic pole pair; 4201. Half angle of the first pair of magnetic poles of the auxiliary magnetic pole pair; 4202. Half angle of the second pair of magnetic poles of the auxiliary magnetic pole pair; 430. Angle between the magnetic fields of the main magnetic pole pair and the auxiliary magnetic pole pair;

[0066] 500. Wien filter; 510. Angle between deflecting electric field and deflecting magnetic field;

[0067] 600. Magnetic core; 601. Magnetic core body; 602. Magnetic ring; 6021. Transition notch; 60211. Inner ring surface one; 60212. Outer ring surface one; 60213. Conical surface; 603. Electrode ring; 6031. Ring surface three; 6032. Ring surface four; 6033. Electrode conical surface; 604. Non-magnetic material; however, the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of the invention; interpreting them as any additional limitation would be contrary to the spirit of the invention.

[0068] In related technologies, such as charged particle beam imaging devices, Wien filters are used to deflect secondary charged particle beams. These Wien filters differ from those used in conventional scanning imaging; they require deflection in any direction, necessitating that the deflecting electrodes be evenly distributed circumferentially. However, this circumferential distribution sacrifices field uniformity. This application disregards the limitation of electrode even distribution, prioritizing field uniformity in its deflector design. For example, the electric deflector 300 provides a field in a constant direction, while the remaining magnetic deflectors 400 fine-tune the orthogonality of the deflecting magnetic and electric fields to satisfy the orthogonality condition between the magnetic and electric fields. Alternatively, the magnetic deflector 400 provides a field in a constant direction, while the remaining electric deflectors 300 fine-tune the orthogonality of the deflecting electric and magnetic fields to satisfy the orthogonality condition between the magnetic and electric fields. The Wien filter 500 of this application provides multiple options for fine-tuning the orthogonality of the deflecting electric and magnetic fields through combinations of multiple pairs of electrodes and magnetic poles.

[0069] For details, please refer to Figures 1 to 3 The Wien filter of this application includes an electrical deflector 300 and a magnetic deflector 400. The electrical deflector 300 includes opposing arc-shaped electrode pairs, each set of electrode pairs being coaxially and circumferentially arranged. When an excitation voltage is applied to each, each set of electrode pairs collaboratively generates its own electric field.

[0070] Please refer to Figures 4 to 6 The magnetic deflector 400 includes opposing arc-shaped magnetic pole pairs. Each set of magnetic pole pairs is arranged coaxially and circumferentially, and is distributed coaxially with the electric deflector. The magnetic pole pairs are located outside the circumference of the electrode pair. The magnetic pole pairs are excited by coils wound on the magnetic pole pairs to generate their respective magnetic fields.

[0071] In this configuration, at least one set of electrode pairs provides an electric field in a constant direction, while the magnetic field provided by the remaining magnetic pole pairs is adjustable in direction to satisfy the orthogonality condition with the electric field direction; or, at least one set of magnetic pole pairs provides a magnetic field in a constant direction, while the electric field provided by the remaining electrode pairs is adjustable in direction to satisfy the orthogonality condition with the magnetic field direction.

[0072] Figures 1 to 3 The diagram illustrates an electrical deflector comprising three pairs of main electrodes 301 and two pairs of auxiliary electrodes 302, where 3011, 3012, and 3013 represent the three pairs of electrodes in the main electrode pairs. Figure 1 The figure shows the half-angle 3101 of the first pair of electrodes of the main electrode pair and the half-angle 310 of the main electrode pair composed of three electrode pairs. Figure 2 The first and second pairs of electrodes 3021 and 3022 of the auxiliary electrode pair are shown, their electrode half-angles 3201 and 3202, and the half-angle 320 of the auxiliary electrode pair. Figure 3The electric field angle 340° between the main electrode pair and the auxiliary electrode pair is shown. An insulating gap 330° exists between each electrode. In this application, half-angles are all half of the corresponding full angles. The above-defined electrodes and their half-angles will aid in understanding the specific embodiments described below.

[0073] Figures 4 to 6 The diagram illustrates a magnetic deflector comprising two pairs of primary magnetic poles 401 and two pairs of secondary magnetic poles 402. The two pairs of primary magnetic poles are designated as the first and second pairs of poles 4011 and 4012, respectively. The diagram also shows the half-angle 410 of the primary pole pairs, the half-angle 4101 of the first pair of poles, and the half-angle 4102 of the second pair of poles; the first pair of poles 4021 and the second pair of poles 4022 of the secondary magnetic pole pairs, the half-angle 420 of the secondary magnetic pole pairs, the half-angle 4201 of the first pair of poles, and the half-angle 4202 of the second pair of poles; and the angle 430 between the magnetic fields of the primary and secondary pole pairs. The defined poles and their half-angles will aid in understanding the specific embodiments described below.

[0074] Figure 7 The layout structure after assembling and combining the above-mentioned electric deflector and magnetic deflector is shown.

[0075] In general, the sum of electrode pairs and magnetic pole pairs is at least three pairs. For example, in the first case, a magnetic pole pair with a constant orientation and at least two pairs of electrode pairs with finely adjustable electric field orientation are provided, or in the second case, an electrode pair with a constant orientation and at least two pairs of magnetic pole pairs with finely adjustable magnetic field orientation are provided.

[0076] For the first scenario, this application proposes a first specific embodiment. The coils of the magnetic pole pair are excited by an applied current to generate a magnetic field B in a constant direction, such as a second direction. The strength of the magnetic field B is adjustable. The aforementioned magnetic pole pair does not have an auxiliary magnetic pole pair 402 or the auxiliary magnetic pole pair 402 is not activated. The electrode pair includes at least two sets of main electrode pairs 301. The main electrode pairs 301 are not evenly divided into circumferences. The half-angle of the arc formed by the sum of the arc lengths of the electrodes on one side of the axis and the sum of the insulation gaps between the electrodes on that side, with respect to the axis center, forms half the electrode half-angle, i.e., the half-angle 310 of the main electrode pair. In some specific embodiments, the full angle α1 of the main electrode pair is 120°±Δ, where Δ is a tolerance value, i.e., considering the assembly requirements, material properties, and processing errors of the main electrode pair, as well as the small distance of the insulation gaps between the electrodes, the angle corresponding to the half-angle of the main electrode pair is approximately 60°. At this point, the electric deflection field near the paraxial axis satisfies sin(60°*3)=0, the third harmonic is almost zero, and it has better uniformity, that is, smaller third-order deflection aberration.

[0077] The main electrode pair 301 is arranged orthogonally to the magnetic pole pair. Orthogonal arrangement should be understood as treating the main electrode pair and the magnetic pole pair as a whole. The direction of the line connecting the main electrode pair to the axis is basically perpendicular to the direction of the line connecting the magnetic pole pair to the axis.

[0078] like Figure 1 As shown, a voltage ±V1i (i = 1, 2, 3...) is applied to the main electrode pairs. Electrodes on the same side of the main electrode pair are applied with the same polarity voltage, while adjacent electrodes on opposite sides are applied with opposite voltages. Each pair of main electrode pairs generates a component electric field E1i (i = 1, 2, 3...) at an angle to the expected first direction. The resultant electric field of each component electric field E1i is E1. The intensity of the resultant electric field E1 is adjusted by the amplitude of the excitation voltage V1i of each main electrode pair. The direction of the resultant electric field E1 is adjusted by the polarity and relative ratio V11 / V12 / V13… / V1i of the excitation voltage of each main electrode pair. A reasonable ratio of V11 / V12 / V13… / V1i exists such that the direction of the resultant electric field E (i.e., the first direction) is perpendicular to the magnetic field B in the second direction.

[0079] The following explanation uses i=2 as an example. The electrode pair consists of two main electrode pairs. After applying excitation voltages ±V11 and ±V12 to the main electrode pairs, they generate partial electric fields E11 and E12, respectively. Figure 8 As shown, with the second direction as a reference, the azimuth angle of the subfield E11 is 90°+θ1, and the azimuth angle of the subfield E12 is 90°-θ2, where θ1 is the angle corresponding to the half angle 3101 of the first pair of electrodes of the main electrode pair, and θ2 is the angle corresponding to the half angle 3102 of the second pair of electrodes of the main electrode pair.

[0080] The electric field components EI of the deflection fields E11 and E12 in the first direction are expressed as:

[0081] EI=E11*sin(90°+θ1)+E12*sin(90°-θ2)=E11*cos(θ1)+E12*cos(θ2);

[0082] The electric field in this direction is the field in the desired direction of the Wien filter, denoted by E in the figure;

[0083] The electric field components EII of the subfields E11 and E12 in the second direction are expressed as follows:

[0084] EII=E11*cos(90°+θ1)+E12*cos(90°-θ2)=E11*sin(θ1)-E12*sin(θ2);

[0085] The electric field in this direction is undesirable for Wien filters and needs to be minimized as much as possible. Therefore, the two sets of main electrode pairs are configured as follows:

[0086] When the two sets of main electrode pairs have the same shape and are ideally orthogonal to the magnetic pole pairs, then θ1 = θ2, and by adjusting E11 = E12, the electric field component EII is eliminated, and the resultant electric field E in the first direction is perpendicular to the magnetic field B in the second direction. The ideal orthogonal arrangement in this application should be understood as strictly orthogonal, meaning that the precision errors in the processing, assembly, excitation, and symmetry of the Wien filter are negligible.

[0087] When the two sets of main electrode pairs have different shapes, or when the two sets of main electrode pairs are arranged in a non-ideal orthogonal manner with the magnetic pole pairs, that is, considering the precision errors in the processing, assembly, excitation, and symmetry of the Wien filter, then θ1≠θ2. The azimuth angle of E1 is adjusted by changing the intensity of E1i: by adjusting the ratio of the excitation voltage V1i of each electrode pair, E11*sin(θ1)=E12*sin(θ2) is made, thereby eliminating the electric field component EII in the second direction and retaining the electric field component EI in the first direction, so that the combined electric field E is perpendicular to the magnetic field B in the second direction.

[0088] In response to the first scenario, this application proposes a second specific embodiment. The magnetic pole pair provides a magnetic field B with a constant direction in the second direction, and the strength of the magnetic field B is adjustable. The electrode pair includes a main electrode pair 301 and an auxiliary electrode pair 302. The main electrode pair 301 is not evenly divided into circumferences. The angle corresponding to the arc length formed by the sum of the arc lengths of the electrodes on one side of the main electrode pair 301 and the insulation gap 330 between the electrodes on that side with respect to the axis center forms the full electrode angle α1. The full electrode angle α2 formed by the arc lengths of the electrodes on one side of the auxiliary electrode pair with respect to the axis center is approximately the supplementary angle of the full electrode angle. In some specific embodiments, α1 is 120°±Δ and α2 is 60°±Δ.

[0089] Please refer to Figure 2 , Figure 3 and Figure 9 The main electrode pair 301 is orthogonally arranged to the magnetic pole pair, and the auxiliary electrode pair 302 is located between the electrodes on opposite sides of the main electrode pair 301. The electrodes on the same side of the auxiliary electrode pair 302 are applied with the same polarity voltage. After the voltage is applied to each set of auxiliary electrode pairs, they generate a component electric field E2i at an angle to the expected first direction. The resultant electric field of each component electric field E2i is E2. The intensity of the electric field E2 is adjusted by the amplitude of the excitation voltage V2i of each auxiliary electrode pair, and the direction of the electric field E2 is adjusted by the polarity and relative ratio V21 / V22 / V23… / V2i of the excitation voltage of each auxiliary electrode pair.

[0090] The following example illustrates the concept of an electrode pair consisting of a main electrode pair and a secondary electrode pair. Figure 9 As shown, corresponding excitation voltages ±V11 and ±V21 are applied to the main electrode pair 301 and the auxiliary electrode pair 302, respectively, and electric fields E1 and E2 are generated at angles to the expected first direction, respectively. The azimuth angles of E1 and E2 are as follows: Figure 9 As shown. Adjusting the excitation voltage ±V11 of the main electrode pair and the excitation voltage ±V21 of the auxiliary electrode pair can change the intensity and direction of the synthesized electric field E (adjusted to the first direction). There exists a reasonable ratio of V11 to V21 such that the first direction of the synthesized electric field E is perpendicular to the second direction where the deflecting magnetic field B is located.

[0091] With the second direction as a reference, the azimuth angle of the electric field E1 is 90° - θ3, and the azimuth angle of the electric field E2 is 180° - θ4, where θ3 is... Figure 9 The angle corresponding to the half-angle 3101 of the first pair of electrodes of the main electrode pair is θ4, and the angle corresponding to the half-angle 3201 of the first pair of electrodes of the auxiliary electrode pair is θ4.

[0092] The electric field components EI of the electric fields E1 and E2 in the first direction are expressed as follows:

[0093] EI=E1*sin(90°-θ3)+E2*sin(180°-θ4)=E1*cos(θ3)+E2*sin(θ4);

[0094] The electric field in this direction is the field in the direction desired by the Wien filter.

[0095] The electric field components EII of the electric fields E1 and E2 in the second direction are expressed as follows:

[0096] EII=E1*cos(90°-θ3)+E2*cos(180°-θ4)=E1*sin(θ3)-E2*cos(θ4);

[0097] The electric field component EII needs to be eliminated so that the first direction of the combined electric field E is perpendicular to the second direction of the magnetic field B. Since θ3 and θ4 are both very small, E1*sin(θ3) is usually very small, but cos(θ4) is close to 1. Therefore, the auxiliary electrode pair needs to provide a small E2, that is, the partial electric field of the auxiliary electrode pair does not need to be very strong.

[0098] When the main electrode pair and the magnetic pole pair are ideally orthogonal, θ3 = 0, so there is no need to use the auxiliary electrode pair, that is, E2 = 0, which satisfies that the first direction of the combined electric field E is perpendicular to the second direction of the magnetic field B.

[0099] When the main electrode pair and the magnetic pole pair are arranged in a non-ideal orthogonal manner, θ3≠0, the auxiliary electrode pair needs to be activated. The deflection voltages ±V11 and ±V21 of the main electrode pair and the auxiliary electrode pair are adjusted so that E2*cos(θ4) cancels the component E1*sin(θ3) of the main electrode pair in the same direction, and the deflection voltage ratio V11 / V21 that meets the target is determined. When the intensity of the electric field E is changed by adjusting the deflection voltages V11 and V21, this voltage excitation ratio is kept constant, and the electric field E in the first direction is always perpendicular to the magnetic field B in the second direction.

[0100] For the second scenario, this application proposes a third specific embodiment. The electrode pair provides a constant electric field E in a first direction, the intensity of which is adjustable. The electrode pair does not have an auxiliary electrode pair or the auxiliary electrode pair is not activated. The magnetic pole pair is arranged orthogonally to the electrode pair. The magnetic pole pair includes at least two sets of main magnetic pole pairs 401. The main magnetic pole pairs 401 do not evenly divide the circumference. The coils of the main magnetic pole pairs can overlap or not overlap. When the coils of the main magnetic pole pairs are adjacent and do not overlap, the full opening angle β1 of the main magnetic pole pair coils is the angle corresponding to the arc length formed by the sum of the circumferential spans of adjacent coils on one side with respect to the axis. When the main magnetic pole pair coils overlap, the full opening angle β1 is the angle corresponding to the arc length formed by the arc length of each pair of coils with respect to the axis. In some preferred embodiments, β1 is 120°±Δ. In one specific embodiment, the two pairs of magnetic poles of the main magnetic pole pair 401 are wound on one side with an overall winding half-angle of 60° relative to the axis. The two pairs of magnetic poles do not overlap and there is almost no gap between them. The magnetic deflection field has almost zero third harmonic near the paraxial direction, resulting in better uniformity, i.e. smaller third-order deflection aberration.

[0101] Please refer to Figure 4 The magnetic pole pair includes two sets of overlapping main magnetic pole pairs. After the coils of each set of main magnetic pole pairs 401 are subjected to excitation current I1i (i = 1, 2, ...), they generate sub-magnetic fields B1i (i = 1, 2, ...) that are at an angle to the expected second direction. The intensity of B1i is variable. The composite magnetic field of each sub-magnetic field B1i is B1. The intensity of the composite magnetic field B1 is adjusted by the intensity of the excitation currents I11, I12...I1i of each pair of coils. The direction of the composite magnetic field B1 is adjusted by the relative ratio of the excitation currents on each pair of coils I11 / I12... / I1i, so as to achieve orthogonality with the deflection electric field E in the first direction.

[0102] The following example illustrates the concept of a magnetic pole pair consisting of two adjacent but non-overlapping main magnetic pole pairs. Figure 10As shown, after the two sets of main magnetic pole pairs are subjected to excitation currents I11 and I12 respectively, they generate sub-magnetic fields B11 and B12. Taking the first direction of the electric field E as a reference, the azimuth angle of the sub-magnetic field B11 is (-90°-θ5), and the azimuth angle of the sub-magnetic field B12 is (-90°+θ6), where θ5 is the angle corresponding to the half-angle 4101 of the first pair of main magnetic poles, and θ6 is the angle corresponding to the half-angle 4102 of the second pair of main magnetic poles.

[0103] The magnetic field components BII of the subfields B11 and B12 in the second direction are represented as follows:

[0104] BII=B11*sin(-90°-θ5)+B12*sin(-90°+θ6)=-B11*cos(θ5)-B12*cos(θ6);

[0105] The magnetic field in this direction is what the Wien filter desires.

[0106] The magnetic field components BI of the magnetic fields B11 and B12 in the first direction are represented as follows:

[0107] BI=B11*cos(-90°-θ5)+B12*cos(-90°+θ6)=B11*sin(θ5)-B12*sin(θ6);

[0108] The magnetic field in this direction is undesirable for the Wien filter; by carefully selecting the strengths of B11 and B12, BI can be reduced to zero.

[0109] When the two sets of main magnetic pole pairs have the same shape and are ideally orthogonal to the electrode pairs, then θ5=θ6, adjust B11=B12, thereby eliminating the magnetic field component BI, and the combined magnetic field in the second direction is perpendicular to the electric field in the first direction.

[0110] When the two sets of main magnetic pole pairs have different shapes, or are arranged in a non-ideal orthogonal manner with the electrode pairs, then θ5≠θ6, and the excitation current ratio I11 / I12 of the main magnetic pole pairs is finely adjusted; when the strength of the magnetic field is changed by adjusting the excitation currents I11 and I12, this excitation current ratio is kept constant, and the magnetic field B in the second direction is always perpendicular to the electric field E in the first direction.

[0111] For the second scenario, this application proposes a fourth specific embodiment. The electrode pair provides a constant electric field E with a first direction, and the intensity of the electric field E is adjustable. The aforementioned electrode pair does not have an auxiliary electrode pair or the auxiliary electrode pair is not used. The magnetic pole pair includes a main magnetic pole pair 401 and an auxiliary magnetic pole pair 402. The main magnetic pole pair 401 is not evenly divided by the circumference, and the main magnetic pole pair 401 and the auxiliary magnetic pole pair 402 are orthogonally arranged on the circumference. The auxiliary magnetic pole pair 402 is closely attached to the outer side of the main electrode pair 401. The full opening angle β2 of the auxiliary magnetic pole pair is the angle corresponding to the arc length of its single-sided coil winding relative to the axis. In some specific embodiments, such as... Figure 11 As shown, the auxiliary magnetic pole pair 402 and the main magnetic pole pair 401 have the same magnetic pole shape, the windings overlap each other and the full opening angle β2 is about 120°. The third harmonics of the fields generated by the main magnetic pole pair and the auxiliary magnetic pole pair near the paraxial axis are almost zero. At this time, there is better uniformity, that is, smaller third-order deflection aberration.

[0112] When an excitation current is applied to the main magnetic pole pair 401 and the auxiliary magnetic pole pair 402, magnetic fields B1 and B2 are generated at an angle to the expected second direction, respectively. The direction of the combined magnetic field B is the second direction perpendicular to the first direction.

[0113] Please refer to Figure 5 In some specific implementations, the magnetic pole pair includes at least two sets of auxiliary magnetic pole pairs 402. Each set of auxiliary magnetic pole pair coils is subjected to an excitation current I2i (i = 1, 2, ...), generating a radial magnetic field B2i perpendicular to the axis. The radial magnetic fields B2i of adjacent auxiliary magnetic pole pair coils form a composite magnetic field B2. The strength of the composite magnetic field B2 is adjusted by the strength of the excitation current I2i of each auxiliary magnetic pole pair coil; the direction of the composite magnetic field B2 is adjusted by the polarity and relative ratio I21 / I22... / I2i of the excitation current of each auxiliary magnetic pole pair coil. Figure 5 The two sets of auxiliary magnetic pole pairs 402 are arranged close to each other and with minimal overlap.

[0114] Please refer to Figure 11 The following example illustrates the situation using a magnetic pole pair containing a set of auxiliary magnetic pole pairs. With the first direction of the electric field E as a reference, the azimuth angle of the magnetic field B1 of the main magnetic pole pair is (-90°-θ7), and the azimuth angle of the magnetic field B2 of the auxiliary magnetic pole pair is θ8. θ7 is the angle corresponding to the half-angle 41° of the main magnetic pole pair, and θ8 is the angle corresponding to the half-angle 42° of the auxiliary magnetic pole pair.

[0115] The magnetic field components BII of magnetic fields B1 and B2 in the second direction are represented as follows:

[0116] BII=B1*sin(-90°-θ7)+B2*sin(θ8)=-B1*cos(θ7)+B2*sin(θ8);

[0117] The magnetic field in this direction is what the Wien filter desires. Since angles θ7 and θ8 are limited by winding errors and are usually small, -B1*cos(θ7) is the primary deflection magnetic field and B2*sin(θ8) is the secondary deflection magnetic field.

[0118] The magnetic field components BI of magnetic fields B1 and B2 in the first direction are represented as follows:

[0119] BI=B1*cos(-90°-θ7)+B2*cos(θ8)=-B1*sin(θ7)+B2*cos(θ8);

[0120] The magnetic field in this direction is undesirable for the Wien filter because the angle θ7 is very small, i.e., -B1*sin(θ7) is very small. Therefore, B2 can be adjusted to reduce BI to zero. The primary and secondary pole pairs are configured as follows:

[0121] When the main magnetic pole pair 401 and the electrode pair are ideally orthogonal, θ7 = 0, and the orthogonal condition of the deflection electric field and the deflection magnetic field is satisfied without using the auxiliary magnetic pole pair.

[0122] When the main magnetic pole pair 401 and the electrode pair are not ideally orthogonal, θ7≠0. The magnetic field B1 generated by applying excitation I11 to the coil of a single main magnetic pole pair will not be orthogonal to the deflection electric field E. The auxiliary magnetic pole pair needs to be activated. The excitation current I21 of the auxiliary magnetic pole pair is adjusted so that the component of the magnetic field B2 in the expected first direction cancels the component of the main magnetic pole pair in the first direction. The current excitation ratio I11 / I21 that satisfies this goal is determined. When the intensity of the electric field B is changed by adjusting the excitation currents I11 and I21, this excitation ratio is kept constant, and the magnetic field B in the second direction is always perpendicular to the electric field E in the first direction.

[0123] In summary, the primary and secondary deflectors of this application feature combinations of multiple electrode and / or magnetic pole pairs, covering possibilities for general applications. For example, electrode pairs may have primary / secondary electrode pairs, or magnetic pole pairs may have primary / secondary magnetic pole pairs. Each electrode pair may also contain multiple electrode pairs, or each magnetic pole pair may also contain multiple magnetic pole pairs. In practical applications, the number of electrode pairs and magnetic pole pairs can be simplified. In the deflection electrode pairs or magnetic pole pairs used for fine-tuning, only one type of deflector needs to have a primary / secondary design, or have two or more electrode pairs, or two or more magnetic pole pairs to satisfy the orthogonal correction of the electric field E and magnetic field B.

[0124] In the above embodiments, the coil of the magnetic pole pair can be either a saddle-shaped coil or a toroidal coil; the coil has a magnetic core with soft magnetic properties or no magnetic core.

[0125] Magnetic pole pairs may partially overlap or not overlap. Since they are the main magnetic pole pairs, their field strength must be able to cancel the third harmonic. If there is one main magnetic pole pair, its half-angle is 60°; if there are multiple main magnetic pole pairs, each main magnetic pole pair's half-angle is 60°, and the sum of the half-angles of all main magnetic pole pairs is at least 120°. As for auxiliary magnetic pole pairs, if strict requirements dictate that they must also cancel the third harmonic, their half-angle is 60°. However, this would cause the auxiliary magnetic pole pair to overlap with the main magnetic pole pair coil on the circumference. Because the overlapping winding process is more complicated, and the field strength of the auxiliary magnetic pole pair is weaker, serving a fine-tuning function, the requirements can be lowered as needed. Complete elimination of the third harmonic is not required; in this case, the half-angle of its coil covers the remaining circumference, for example, 30°. This is the case where the auxiliary magnetic pole pair does not overlap with the main magnetic pole pair.

[0126] In the preferred embodiments described above, the full-width angle α1 of the main electrode pair is equal to the full-width angle β1 of the main magnetic pole pair coil. The full-width angles between the main electrode pair and the auxiliary electrode pair, or between the main magnetic pole pair and the auxiliary magnetic pole pair, may not be equal. The full-width angles of the electrodes referred to in this application all refer to the full-width angle from the inner surface of the electrode to the axis.

[0127] In some specific embodiments of the above examples, necessary insulating gaps 330 are provided between adjacent electrodes on the same side of the main electrode pair, and between the electrodes of the main electrode pair and the electrodes of the adjacent auxiliary electrode pair; the insulating gaps 330 can be formed by radial division, or by first dividing radially and then bending circumferentially, as shown below. Figure 12 As shown, the bent dividing groove can prevent electrons from directly bombarding and adhering to the device, thus avoiding affecting the device's function.

[0128] In some specific implementations of various embodiments, the voltage applied to the electrostatic deflection electrode pair may not be completely positive-negative dual, i.e., it may have a voltage bias. For example, +V11+Vo may be applied to one side of the main electrode pair's axis, and -V11+Vo may be applied to the other side of the axis, where Vo is the center potential of the deflector, or the bias voltage. In this case, the excitation signals on the main and auxiliary deflection electrodes of the electrode pair must have the same center potential Vo. If an electrode is not used as a deflection electrode, it also needs to have this center potential applied to it. Vo can be positive, negative, or zero / ground potential.

[0129] In some specific implementations of the various embodiments, the electric deflector 300 and the magnetic deflector 400 are externally enclosed by a magnetic core. Openings are provided at both axial ends of the magnetic core, with the center of these openings located on the axis of the electric deflector. From another perspective, the ends of the magnetic core extend in a ring-like shape towards the near-axial direction, serving as magnetic poles to compress the axial magnetic field distribution.

[0130] The relative permeability of the magnetic core is generally above several hundred, and the magnetic field is compressed. Since the core is placed at zero potential or a certain DC potential, it also affects the deflection electric field, which is also compressed. Therefore, it is impossible to simply change the core structure without altering the electric deflection field distribution; the two are closely coupled. Changing the core structure alone cannot make the normalized distribution curves of the electric and magnetic fields meet or approximate the requirements.

[0131] Therefore, another requirement for the direct-axis condition of the Wien filter is that the morphological matching of the deflection electric field and the deflection magnetic field along the axis must be identical. The conventional method of matching the morphological distribution of the field along the axis relies on adjusting the longitudinal cross-sectional shape of the deflection electrodes and magnetic poles, as seen in US Patent 13292455.

[0132] The magnetic core opening of this application is located near the inner side of the magnetic core 600. The sidewall of the opening is provided with a transition notch 6021 for controlling the axial distribution of the magnetic field. The cross-section of this transition notch 6021 is an irregular structure, such as... Figure 17 As shown. Specifically, the transition gap 6021 includes an inner ring surface 60211 and an outer ring surface 60212 extending along the axial direction. The diameter of the inner ring surface 60211 is smaller than the diameter of the outer ring surface 60212. The inner ring surface 60211 and the outer ring surface 60212 are connected and transitioned by a conical surface 60213. The cone angle of the conical surface 60213 is set such that the diameter of the conical surface gradually increases from one end of the inner ring surface 60211 to one end of the outer ring surface 60212. Any one or more of the parameters of the inner ring surface 60211, the height of the outer ring surface 60211, and the cone angle of the conical surface can be adjusted to change the shape of the transition gap 6021 and finely adjust the shape of the axial distribution B(z) of the deflection magnetic field.

[0133] like Figure 18 As shown, an electrode ring 603 is adaptively embedded within the transition notch 6021 to adjust the surrounding electric field distribution. The electrode ring 603 is a non-soft magnetic metal electrode, therefore it does not affect the magnetic field distribution. The contact surfaces of the electrode ring 603 and the transition notch 6021 are in close contact with the conical surface 60213 and the outer ring surface 60212, facilitating the fixation of the electrode ring 603. The exposed portion of the electrode ring includes an axially extending ring surface 6031 and ring surface 6032. Ring surface 6031 is located near the axis and is recessed relative to the outer ring surface 60212. Ring surface 6031 and ring surface 6032 are connected by an electrode conical surface 6033. By controlling the shape of the exposed portion of the electrode ring, the surrounding electric field distribution is affected. The electrode ring 603 can also be configured such that ring surface 6032 slightly protrudes into the magnetic core, using this protrusion to fine-tune the electric field distribution.

[0134] Figure 13 The magnetic core's open cross-section uses straight-edged equipotential lines, and the corresponding on-axis field distribution is as follows: Figure 16 The dotted line in the diagram (illustrated as a), Figure 14 For an embodiment employing a transition gap, the equipotential line distribution and the corresponding on-axis magnetic field distribution are as follows: Figure 16 The dashed line in the diagram (illustrated as b). From Figure 16 As can be seen from the comparison of the on-axis magnetic field, the transition gap of the irregular structure in this application can achieve fine adjustment of the magnetic field distribution. Figure 15 To embed the equipotential line distribution of the electrode ring within the transition gap, such as Figure 16 The solid line (illustrated as c) shows the electric field distribution on the corresponding axis of the electrode ring embedded in the transition gap, and the shape of this distribution almost coincides with the magnetic field distribution on the axis shown by the dashed line b.

[0135] The magnetic core 600 includes an annular core body 601 and magnetic rings 602 located at both ends of the core body 601. The magnetic rings 602 have transition notches 6021. For example... Figure 18 As shown, when the coil of the magnetic deflector 400 is saddle-shaped, the saddle-shaped coil is wound around the outer surface of the electrode, and the magnetic core body 601 is in contact with the soft magnetic ring 602. Figure 19 As shown, when the coil of the magnetic deflector 400 is a ring, the ring coil is wound on the magnetic core body 601. The magnetic core body 601 and the magnetic ring 602 are isolated by an air gap or a non-magnetic material 604, and there is no direct magnetic circuit short circuit.

[0136] To adjust the electric and magnetic field distribution in accordance with the above structure, the deflection electrodes and deflection magnetic poles of the Wien filter in this application can both be set as equal-diameter cylindrical shapes, or set as... Figure 18 and Figure 19 The inner cylinder shown is a tapered shape with an inwardly convex diameter.

[0137] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A Wien filter, comprising an electrical deflector and a magnetic deflector; characterized in that: The electric deflector includes at least one set of opposing arc-shaped electrode pairs, each set of electrode pairs being arranged coaxially and around the same circumference, and each electrode pair being excited by voltage to generate its own electric field. The magnetic deflector includes at least one set of opposing arc-shaped magnetic pole pairs. Each set of magnetic pole pairs is arranged coaxially and circumferentially, and is coaxially but circumferentially distributed with the electric deflector. The magnetic pole pairs are excited by coils wound on the magnetic pole pairs to generate their respective magnetic fields. The electrode pairs and the magnetic pole pairs consist of at least three pairs, including: a magnetic pole pair providing a constant magnetic field direction and at least two pairs of electrode pairs with finely adjustable electric field directions to satisfy the orthogonality condition with the magnetic field; the electrode pairs include multiple sets of main electrode pairs, with the electrodes on the same side of the main electrode pairs symmetrically arranged around the X-axis, which is located within the cross-section of the electric deflector and passes through the axis of the electric deflector; an insulating gap is provided between the electrodes on the same side of the main electrode pairs; the full electrode opening angle α1 of the main electrode pairs is 120°±Δ, where the full electrode opening angle α1 represents the angle corresponding to the arc formed by the sum of the total arc length of the main electrode on one side and the insulating gap between the main electrodes on that side and the axis, and Δ is a tolerance value.

2. The Wien filter according to claim 1, characterized in that: The magnetic pole pair provides a magnetic field B in a second direction; The main electrode pair is arranged orthogonally to the magnetic pole pair. The electrodes on the same side of the main electrode pair are applied with the same polarity voltage, and the adjacent electrodes on opposite sides are applied with the opposite polarity voltage. After a voltage is applied to each of the main electrode pairs, a component electric field E1i, i=1,2... is generated at an angle to the expected first direction. The resultant electric field of each component electric field E1i is E1. The intensity of the resultant electric field E1 is adjusted by the amplitude of the excitation voltage V1i of each main electrode pair. The direction of the resultant electric field E1 is adjusted by the polarity and relative ratio V11 / V12 / V13... / V1i of the excitation voltage of each main electrode pair, so that the direction of the resultant electric field E1 is ideally orthogonal to the direction of the magnetic field B near the axis.

3. A Wien filter, comprising an electrical deflector and a magnetic deflector; characterized in that: The electric deflector includes at least one set of opposing arc-shaped electrode pairs, each set of electrode pairs being arranged coaxially and around the same circumference, and each electrode pair being excited by voltage to generate its own electric field. The magnetic deflector includes at least one set of opposing arc-shaped magnetic pole pairs. Each set of magnetic pole pairs is arranged coaxially and circumferentially, and is coaxially but circumferentially distributed with the electric deflector. The magnetic pole pairs are excited by coils wound on the magnetic pole pairs to generate their respective magnetic fields. The electrode pairs and the magnetic pole pairs consist of at least three pairs, including: a magnetic pole pair providing a constant magnetic field direction and at least two pairs of electrode pairs with finely adjustable electric field directions to satisfy the orthogonality condition with the magnetic field; the electrode pairs include main electrode pairs and auxiliary electrode pairs, the electrodes on the same side of the main electrode pairs are symmetrically arranged with the X-axis as the center, the X-axis is located in the cross-section of the electric deflector and passes through the axis of the electric deflector, an insulating gap is provided between the electrodes on the same side of the main electrode pairs, and the full electrode opening angle α1 of the main electrode pairs is 120°±Δ, where the full electrode opening angle α1 represents the angle corresponding to the arc formed by the sum of the total arc length of the main electrode on one side and the insulating gap between the main electrodes on that side and the axis, and Δ is the tolerance value; The auxiliary electrode pairs are one or more sets. The electrodes on the same side of the auxiliary electrode pairs are symmetrically arranged with the Y-axis as the center. The auxiliary electrode pairs are located between the main electrode pairs on opposite sides. The Y-axis is perpendicular to the X-axis. The Y-axis is located within the cross-section of the electric deflector and passes through the axis of the electric deflector. The main electrode pairs and auxiliary electrode pairs do not overlap. The full electrode angle α2 of the auxiliary electrode pair is 60°±Δ, where the full electrode angle α2 represents the angle corresponding to the arc length of the total arc length of the auxiliary electrode on one side and the insulation gap between the auxiliary electrodes on that side relative to the axis. The auxiliary electrode pair is used to compensate for the orthogonal deviation between the electric field of the main electrode pair and the magnetic field of the magnetic pole pair.

4. The Wien filter according to claim 3, characterized in that: Each auxiliary electrode pair generates a sub-electric field E2i, i=1, 2..., after a voltage is applied. The combined electric field of each sub-electric field E2i is E2. The intensity of the combined electric field E2 is adjusted by the amplitude of the excitation voltage V2i of each main electrode pair. The deflection direction of the combined electric field E2 is adjusted by the polarity and relative ratio V21 / V22... / V2i of the excitation voltage of each auxiliary electrode pair. The intensity and direction of the combined electric field E of the electric field E1 generated by the main electrode pair and the electric field E2 generated by the auxiliary electrode pair can also be controlled, so that the direction of the combined electric field E is ideally orthogonal to the direction of the magnetic field B near the axis.

5. A Wien filter, comprising an electrical deflector and a magnetic deflector; characterized in that: The electric deflector includes at least one set of opposing arc-shaped electrode pairs, each set of electrode pairs being arranged coaxially and around the same circumference, and each electrode pair being excited by voltage to generate its own electric field. The magnetic deflector includes at least one set of opposing arc-shaped magnetic pole pairs. Each set of magnetic pole pairs is arranged coaxially and circumferentially, and is coaxially but circumferentially distributed with the electric deflector. The magnetic pole pairs are excited by coils wound on the magnetic pole pairs to generate their respective magnetic fields. The sum of the electrode pairs and the magnetic pole pairs is at least three pairs, including: an electrode pair providing a constant electric field direction and at least two pairs of magnetic pole pairs with finely adjustable magnetic field directions to satisfy the orthogonality condition with the electric field. The magnetic pole pair includes at least two sets of main magnetic pole pairs, which are orthogonally arranged with the electrode pair. The full pole opening angle β1 of the main magnetic pole pair is 120°±Δ. When the coils of the same side of the main magnetic pole pair are not overlapped, the full pole opening angle β1 represents the angle corresponding to the arc length of the sum of the arc lengths of the coils on the same side with respect to the axis. When the coils of the same side of the main magnetic pole pair are overlapped, the full pole opening angle β1 is the angle corresponding to the arc length of each pair of coils with respect to the axis.

6. The Wien filter according to claim 5, characterized in that: The electrode pair provides an electric field E in a first direction; After an excitation current is applied to the coils of each main magnetic pole pair, a sub-magnetic field B1i (i=1, 2, ...) is generated at an angle to the expected second direction. The resultant magnetic field of each sub-magnetic field B1i is B1. The intensity of the resultant magnetic field B1 is adjusted by the intensity of the excitation currents I11, I12...I1i of each pair of coils. The direction of the resultant magnetic field B1 is adjusted by the relative proportions I11 / I12... / I1i of the excitation currents on each pair of coils, so that the direction of the resultant magnetic field B1 is ideally orthogonal to the direction of the electric field E near the axis.

7. A Wien filter, comprising an electrical deflector and a magnetic deflector; characterized in that: The electric deflector includes at least one set of opposing arc-shaped electrode pairs, each set of electrode pairs being arranged coaxially and around the same circumference, and each electrode pair being excited by voltage to generate its own electric field. The magnetic deflector includes at least one set of opposing arc-shaped magnetic pole pairs. Each set of magnetic pole pairs is arranged coaxially and circumferentially, and is coaxially but circumferentially distributed with the electric deflector. The magnetic pole pairs are excited by coils wound on the magnetic pole pairs to generate their respective magnetic fields. The sum of the electrode pairs and the magnetic pole pairs is at least three pairs, including: an electrode pair providing a constant electric field direction and at least two pairs of magnetic pole pairs with finely adjustable magnetic field directions to satisfy the orthogonality condition with the electric field. The magnetic pole pair includes a main magnetic pole pair and an auxiliary magnetic pole pair. The main magnetic pole pair is orthogonally arranged to the electrode pair. The full pole opening angle β1 of the main magnetic pole pair is 120°±Δ. When the coils of the same side of the main magnetic pole pair are not overlapped, the full pole opening angle β1 represents the angle corresponding to the arc length of the sum of the arc lengths of the coils on the same side with respect to the axis. When the coils of the same side of the main magnetic pole pair are overlapped, the full pole opening angle β1 is the angle corresponding to the arc length of each pair of coils with respect to the axis. The auxiliary magnetic pole pairs are one or more sets. The auxiliary magnetic pole pairs are close to the outside of the electrode pairs and are symmetrically arranged with the same side magnetic poles around the X-axis. The auxiliary magnetic pole pairs are located between the main magnetic pole pairs on opposite sides. The main magnetic pole pairs and the auxiliary magnetic pole pairs may overlap or not overlap. The full pole opening angle β2 of the auxiliary magnetic pole pair is 60°±Δ. When the coils of the auxiliary magnetic poles on the same side do not overlap, the full pole opening angle β2 represents the angle corresponding to the arc length of the auxiliary magnetic pole coils on the same side with respect to the axis. When the coils of the auxiliary magnetic poles on the same side overlap, the full pole opening angle β2 represents the angle corresponding to the arc length of the auxiliary magnetic pole coils on the same side with respect to the axis. The auxiliary magnetic pole pair is used to compensate for the orthogonal deviation between the magnetic field of the main magnetic pole pair and the electric field of the electrode pair.

8. The Wien filter according to claim 7, characterized in that: The coils of the main magnetic pole pair are arranged close together on the circumference without overlapping, and / or the coils of the auxiliary magnetic pole pair are arranged close together on the circumference without overlapping.

9. The Wien filter according to claim 7, characterized in that: Each auxiliary magnetic pole pair generates a sub-magnetic field B2i, i=1, 2..., after being excited by an excitation current. The combined magnetic field of each sub-magnetic field B2i is B2. The strength of the combined magnetic field B2 is adjusted by the strength of the excitation current I2i of each main magnetic pole pair. The deflection direction of the combined magnetic field B2 is adjusted by the polarity and relative ratio I21 / I22... / I2i of the excitation current of each auxiliary magnetic pole pair. The strength and direction of the combined magnetic field B of the magnetic field B1 generated by the main magnetic pole pair and the magnetic field B2 generated by the auxiliary magnetic pole pair can also be controlled, so that the direction of the combined magnetic field B is ideally orthogonal to the direction of the electric field E near the axis.

10. The Wien filter according to any one of claims 1 to 4, characterized in that: The insulating gap is formed by radial division, or by successive radial and circumferential bending division; The main electrodes each have a bias voltage V0 in response to the applied excitation voltage.

11. The Wien filter according to any one of claims 3 to 4, characterized in that: The insulating gap is formed by radial division, or by successive radial and circumferential bending division; The auxiliary electrodes all have a bias voltage V0 in response to the applied excitation voltage.

12. The Wien filter according to any one of claims 1 to 9, characterized in that: The electric deflector and the magnetic deflector are enclosed by a magnetic core, and the magnetic core has openings at both ends along its axial direction. The opening is located near the inner side of the magnetic core, and the sidewall of the opening is provided with a transition gap for controlling the distribution pattern of the magnetic field along the axis.

13. The Wien filter according to claim 12, characterized in that: The transition gap includes an inner annular surface and an outer annular surface extending along the axial direction. The diameter of the inner annular surface is smaller than the diameter of the outer annular surface. The inner annular surface and the outer annular surface are connected and transitioned by a conical surface. The diameter of the conical surface gradually increases from one end of the inner annular surface to one end of the outer annular surface.

14. The Wien filter according to claim 13, characterized in that: An electrode ring made of non-soft magnetic material is embedded in the transition gap. The electrode ring is used to adjust the electric field distribution around it. The electrode ring is in close contact with the conical surface and the outer ring surface. The exposed portion of the electrode ring includes an axially extending annular surface three and an annular surface four. Annular surface four is located near the axis and is recessed relative to the outer annular surface one. Annular surface three and annular surface four are connected by an electrode conical surface.

15. The Wien filter according to claim 14, characterized in that: The electrode ring protrudes towards the inside of the magnetic core relative to the outer ring, and is used to fine-tune the surrounding electric field distribution.

16. The Wien filter according to any one of claims 13 to 15, characterized in that: The coil of the magnetic pole pair is a saddle-shaped coil or a toroidal coil; The magnetic core includes an annular magnetic core body and magnetic rings located at both ends of the magnetic core body, with the transition gaps provided on the magnetic rings; when the coil of the magnetic deflector is annular, the annular coil is wound on the magnetic core body, and the magnetic core body and the magnetic rings are isolated by an air gap or a non-magnetic material.

17. A charged particle beam imaging device, configured to scan an incident and focused main charged particle beam onto the surface of a sample to be tested, and to detect secondary charged particles excited at corresponding positions to form an image, characterized in that, The Wien filter, comprising any one of claims 1 to 16, is located between the sample and the secondary charged particle detector, the Wien filter being configured to have little or no deflection effect on the primary charged particle beam, deflect only the secondary charged particles emitted from the sample, and guide the secondary charged particles to the secondary charged particle detector.

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