Aberration correction reflector device, aberration correction system and aberration correction method

Abstract

The invention relates to the field of optics, in particular to an aberration correction reflector device and an aberration correction system and method.The aberration correction reflector device comprises a reflector and a transmission electrode set coaxially arranged on one side of the reflector at intervals, and the transmission electrode set comprises four or more transmission electrodes coaxially arranged at intervals; the reflector comprises a reflector body, a first through hole penetrating through the upper surface and the lower surface of the reflector body and used for electrons to pass through is formed in the center of the reflector body, and the reflector further comprises a cover body covering the side face, away from the transmission electrode set, of the first through hole and protruding towards the side face, away from the transmission electrode set, of the first through hole. Each transmission electrode comprises a transmission electrode body, and a second through hole which penetrates through the upper surface and the lower surface of the transmission electrode body and is used for electrons to pass through is formed in the center of the transmission electrode body. The correction system adopting the aberration correction reflector device can correct chromatic aberration, third-order spherical aberration and fifth-order spherical aberration at the same time.

Description

Technical Field

[0001] The present invention relates to the field of optics, and in particular to an aberration correction reflector device, an aberration correction system and a method. Background Art

[0002] In the nearly 100 years of development of electronic optical instruments, aberration has always been the decisive factor affecting the function of the instrument. Reducing and eliminating aberrations is the core issue of instrument design. Before the development of aberration correction technology, aberration control was mainly achieved by reducing the number of aberrations by improving the symmetry of lenses and systems and optimizing the geometry of lenses to reduce lens aberrations. The highest symmetry of lenses is rotational symmetry, so electronic optical instruments with low electron energy (roughly speaking, kinetic energy not exceeding 3MeV) generally use lenses with rotational symmetry to focus electrons. This type of lens is also called a circular lens. In 1936, the German Scherzer (O.Scherzer) proved a famous theorem (Scherzer's theorem) that the chromatic aberration and third-order spherical aberration of a circular lens will not change sign under any circumstances. The most important conclusion of this theorem is that the chromatic aberration and third-order spherical aberration of an instrument composed of rotationally symmetric lenses cannot be corrected. Correction of chromatic aberration and third-order spherical aberration can only be achieved through a reflector that does not have rotational symmetry or is rotationally symmetric. Although in theory, alternating electromagnetic fields or space charges may also be able to correct chromatic aberration and third-order spherical aberration, this approach is not adopted due to its poor stability.

[0003] Aberration correction technology (including aberration correctors) has been developed in the past 30 years and has played an important role in improving the spatial resolution of transmission electron microscopes, scanning electron microscopes, photoelectron microscopes and low-energy electron microscopes. These aberration correctors can be divided into the following three categories according to their functions: the first category is to correct only the third-order spherical aberration, the second category is to correct chromatic aberration and third-order spherical aberration at the same time, and the third category is to correct the third-order and fifth-order spherical aberrations at the same time. Among them, the third type of corrector is generally only suitable for scanning transmission electron microscopes (in principle, it can also be used on scanning electron microscopes). Due to the limitations of the aberration correction mirror device, the existing aberration correction technology cannot correct chromatic aberration, third-order spherical aberration and fifth-order spherical aberration at the same time, so that the spatial resolution of transmission electron microscopes, scanning electron microscopes, photoelectron microscopes and low-energy electron microscopes that have corrected chromatic aberration and third-order spherical aberration is limited by the fifth-order spherical aberration, and the spatial resolution of scanning transmission electron microscopes that have corrected third-order and fifth-order spherical aberrations is limited by chromatic aberration.

[0004] Therefore, the prior art needs to be improved. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide an aberration correction mirror device, an aberration correction system and a method, aiming to solve the problem that the existing aberration correction technology cannot simultaneously correct chromatic aberration, third-order spherical aberration and fifth-order spherical aberration due to the limitations of the aberration correction mirror device.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A first aspect of the present invention provides an aberration correction reflector device, comprising a reflector and a transmission electrode group coaxially spaced on one side of the reflector, wherein the transmission electrode group comprises four or more transmission electrodes coaxially spaced;

[0008] The reflector includes a reflector body, a through hole for electrons to pass through the center of the reflector body, and the through hole penetrates the upper and lower surfaces of the reflector body. The reflector also includes a cover body that covers the through hole and is away from the side of the transmission electrode group and protrudes toward the side away from the transmission electrode group.

[0009] Each transmission electrode comprises a transmission electrode body, and a through hole 2 for electrons to pass through the transmission electrode body is arranged at the center of the transmission electrode body.

[0010] Optionally, the aberration-correcting reflector device further comprises a connecting tube coaxially arranged on through hole 2 on a free end surface of a transmission electrode away from the reflector.

[0011] Optionally, the distance between the reflector body and the transmission electrode group is 2-6 mm.

[0012] Optionally, the distance between two adjacent transmissive electrode bodies is 2-6 mm.

[0013] Optionally, the thickness of the transmissive electrode body is 2-6 mm.

[0014] Optionally, the radius of the through hole 1 is 2-6 mm, the radius of the through hole 2 is 3-10 mm, and the inner diameter of the connecting tube is 3-10 mm.

[0015] Optionally, the inner surface of the cover is a cylindrical surface, a conical surface or a spherical surface protruding toward a side away from the transmissive electrode group.

[0016] Specifically, the radius of the spherical surface is 5.6 mm.

[0017] According to a second aspect of the present invention, there is provided an aberration correction system, comprising a magnetic deflector, a first matching mirror, a second matching mirror, a third matching mirror and the aberration correction reflector device, wherein the first matching mirror, the magnetic deflector and the second matching mirror are coaxially arranged in sequence along the optical path direction; the third matching mirror is arranged on one side of the vertical optical path of the magnetic deflector, and the aberration correction reflector device is arranged on the side of the third matching mirror away from the magnetic deflector.

[0018] The third aspect of the present invention is an aberration correction method, wherein the aberration correction system is installed in sequence, the transmission electrode group includes 4 coaxially spaced transmission electrodes, the voltage of the reflector is set to 3.5-5.5kV, and the voltages of the transmission electrodes starting from the reflector are 1.5-17kV, 14-17.5kV, 5.5-10kV and 5.0-15.0kV respectively.

[0019] Compared with the prior art, the present invention has the following beneficial effects: the correction system using the aberration correction mirror device of the present invention can not only correct chromatic aberration, third-order spherical aberration and fifth-order spherical aberration at the same time; but also improve the spatial resolution of the electron optical system and the transmittance of electrons. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic structural diagram of the aberration correction mirror device of Example 1 of the present invention.

[0021] Figure 2 It is a cross-sectional schematic diagram of the aberration-correcting reflecting mirror device of Example 1 of the present invention.

[0022] Figure 3 It is a cross-sectional schematic diagram of the aberration-correcting reflecting mirror device of Example 2 of the present invention.

[0023] Figure 4 It is a cross-sectional schematic diagram of the aberration-correcting reflecting mirror device of Example 3 of the present invention.

[0024] Figure 5 It is a cross-sectional schematic diagram of the aberration-correcting reflecting mirror device of Example 4 of the present invention.

[0025] Figure 6 It is a cross-sectional schematic diagram of the aberration-correcting reflecting mirror device of Example 5 of the present invention.

[0026] Figure 7 It is a structural schematic diagram of an aberration correction system according to Example 6 of the present invention.

[0027] Figure 8 1 is a graph showing the change in spatial resolution with half angle according to Example 6 of the present invention. DETAILED DESCRIPTION

[0028] The present invention provides an aberration correction mirror device, an aberration correction system and a method. To make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] Due to the limitations of the aberration correction mirror device, the existing aberration correction technology cannot correct chromatic aberration, third-order spherical aberration and fifth-order spherical aberration at the same time, so that the spatial resolution of transmission electron microscopes, scanning electron microscopes, photoelectron microscopes and low-energy electron microscopes that have corrected chromatic aberration and third-order spherical aberration is limited by the fifth-order spherical aberration, and the spatial resolution of scanning transmission electron microscopes that have corrected third-order and fifth-order spherical aberrations is limited by chromatic aberration.

[0030] like Figure 1 As shown, this embodiment provides an aberration correction reflector device, comprising a reflector 1 and a transmission electrode group coaxially spaced on one side of the reflector 1, wherein the transmission electrode group comprises more than four transmission electrodes 2-1 coaxially spaced;

[0031] The reflector 1 comprises a reflector body 1-1, a through hole 1-2 for electrons to pass through the center of the reflector body 1-1 and penetrating the upper and lower surfaces of the reflector body 1-1, and the reflector 1 further comprises a cover 1-3 which is arranged on a side of the through hole 1-2 away from the transmission electrode group and protrudes toward the side away from the transmission electrode group.

[0032] Each of the transmissive electrodes 2-1 includes a transmissive electrode body 2-11, and a through hole 2-12 for electrons to pass through the center of the transmissive electrode body 2-11 and penetrating the upper and lower surfaces of the transmissive electrode body 2-11 is provided.

[0033] The reflector 1 returns the electrons on the axis to their original path, making it possible to correct chromatic aberration, third-order spherical aberration, and fifth-order spherical aberration. The shape of the reflector 1 and each transmission electrode 2-1 affects the spatial distribution of the voltage on the electron path, thereby determining the overall values ​​of the chromatic aberration, third-order spherical aberration, and fifth-order spherical aberration. After the shapes of the reflector 1 and each transmission electrode 2-1 are determined, the spatial distribution of the voltage on the electron path is adjusted by adjusting the voltage of the reflector 1 and each transmission electrode 2-1. Therefore, the voltage of the reflector 1 and each transmission electrode 2-1 can be set on the voltage source as needed to achieve the purpose of adjusting the spatial distribution of the voltage on the electron path, thereby achieving the purpose of simultaneously correcting chromatic aberration, third-order spherical aberration, and fifth-order spherical aberration.

[0034] It should be noted that the cover body 1-3 can be integrally formed with the reflector body 1-1.

[0035] In one embodiment, the aberration correction reflector device further comprises a connecting tube 3 coaxially arranged on the through hole 2-12 of the free end surface of a transmission electrode 2-1 away from the reflector 1. The connecting tube 3 can be connected to the third matching mirror 7 below the magnetic deflector 4 to ensure that the region in the tube away from the lens electrode is an equal voltage region.

[0036] In some embodiments, the distance between the reflective mirror body and the transmissive electrode group is 2-6 mm, and can be any value within this range.

[0037] In some embodiments, the distance between two adjacent transmissive electrode bodies is 2-6 mm, and can be any value within this range.

[0038] In some embodiments, the thickness of the transmissive electrode body is 2-6 mm, and can be any value within this range.

[0039] In some embodiments, the radius of the through hole 1 is 2-6 mm, and can be any value within this range.

[0040] In some embodiments, the radius of the second through hole is 3-10 mm, which can be any value within this range.

[0041] In some embodiments, the inner diameter of the connecting tube is 3-10 mm, which can be any value within this range.

[0042] It should be noted that the distance between the reflective mirror body 1-1 and the transmissive electrode group may be different from the distance between two adjacent transmissive electrode bodies 2-11, and the distance between two adjacent transmissive electrode bodies 2-11 may also be unequal.

[0043] The thickness of the transmissive electrode body 2 - 11 may be different.

[0044] The inner pore diameters mentioned above are all the pore diameters at the smallest part of the pore.

[0045] In one embodiment, the inner surface of the cover 1 - 3 is a cylindrical surface, a conical surface or a spherical surface protruding toward a side away from the transmissive electrode group.

[0046] It should be noted that the inner surface of the cover body 1-3 is not limited to the above-mentioned shape, but can also be any other curved surface.

[0047] In one embodiment, the hole walls of the through hole 1-2 and the through hole 2-12 are parallel to the axis or protrude toward the center of the hole. When the hole walls are parallel to the axis, cylindrical holes are formed; when the hole walls protrude toward the center of the hole, two conical holes or round holes with a small middle and large ends can be formed, and the radius of the round hole is half the thickness of the mirror body.

[0048] It should be noted that the reflector 1 and each transmission electrode 2 - 1 , as well as each transmission electrode 2 - 1 , need to be connected with insulating materials due to different voltages, and the specific connection method has no effect on aberration correction.

[0049] The embodiment of the present invention also provides an aberration correction system, such as Figure 7 As shown, it includes a magnetic deflector 4, a first matching mirror 5, a second matching mirror 6, a third matching mirror 7 and the aberration correction reflector device. The first matching mirror 5, the magnetic deflector 4 and the second matching mirror 6 are coaxially arranged in sequence along the optical path direction (optical axis); the third matching mirror 7 is arranged on one side of the vertical optical path of the magnetic deflector 4, and the aberration correction reflector device is arranged on the side of the third matching mirror 7 away from the magnetic deflector 4.

[0050] The embodiment of the present invention also provides an aberration correction method, wherein the aberration correction system is installed in sequence, the transmission electrode group includes four transmission electrodes 2-1 coaxially spaced apart, the voltage of the reflector 1 is set to 3.5-5.5 kV, and the voltages of the transmission electrodes 2-1 starting from the reflector 1 are set to 1.5-17 kV, 14-17.5 kV, 5.5-10 kV, and 5.0-15.0 kV in sequence. The voltages of the reflector 1 and each transmission electrode 2-1 are adjusted as needed. The voltage of the reflector 1 can be 3.5 kV, 4.5 kV, 5.5 kV, or any value within this range. The voltages of each transmission electrode 2-1 starting from the reflector 1 can be any value within the range in sequence.

[0051] Figure 1 The topmost transmission electrode 2-1 is connected to the connection tube 3 and is at the same voltage. Figure 7 As shown, the connecting tube 3 is connected to the third matching mirror 7, so the voltage of the transmission electrode 2-1 provided with the connecting tube 3 is not arbitrarily adjustable. Figure 1 The aberration correction reflector device in the invention includes four voltage adjustable parts (the second to fourth transmission electrodes and reflectors from the top respectively), and the voltages of these four parts can be used to adjust the values ​​of chromatic aberration, third-order spherical aberration, fifth-order spherical aberration and defocus. Since the four voltages and the four objective functions (chromatic aberration, third-order spherical aberration, fifth-order spherical aberration and defocus) are not orthogonal, that is, changing any voltage will cause the values ​​of all four objective functions to change, and the solution process requires multiple iterations. The solution process is not a problem to be solved by the present invention and will not be discussed in detail here.

[0052] The first matching mirror 5 is close to the sample end, the second matching mirror 6 is close to the detector end, an objective lens 8 should be provided between the first matching mirror 5 and the sample, and one or more projection mirrors 9 should be provided between the second matching mirror 6 and the detector.

[0053] The principle of the aberration correction system of this embodiment is as follows: Figure 7 As shown, the magnetic deflector 4 separates the electron trajectory of the incident aberration correction reflector device and the electron trajectory after being reflected by the aberration correction reflector device. The three matching mirrors adjust the path of the electrons to minimize the aberration of the magnetic deflector and the influence of the aberration correction reflector device on other aberrations. Specifically, the magnetic deflector 4 itself has mirror symmetry. The objective lens 8 and the first matching mirror 5 allow the on-axis electrons (green line in the figure) to be symmetrical about the midpoint of the magnetic deflector 4 when passing through the magnetic deflector 4 for the first time, and at the same time allow the off-axis electrons (red line in the figure) to be anti-symmetrical about the midpoint of the magnetic deflector 4 when passing through the magnetic deflector 4 for the first time. The third matching mirror 7 and the aberration correction reflector device allow the on-axis electrons to be symmetrical about the turning point when passing through the aberration correction reflector device, and at the same time allow the off-axis electrons to be anti-symmetrical about the turning point when passing through the aberration correction reflector device. The second matching mirror 6 forms an intermediate image upstream of the first projection mirror 9, which is finally detected by the detector.

[0054] It should be noted that the above coaxial setting is not a coaxial setting in the physical sense, but a coaxial setting in the electronic optical path.

[0055] Example 1

[0056] like Figure 2 As shown, an aberration correction reflector device of this embodiment includes a reflector 1 and a transmission electrode group coaxially spaced on one side of the reflector 1, wherein the transmission electrode group includes more than 4 transmission electrodes 2-1 coaxially spaced;

[0057] The reflector 1 comprises a reflector body 1-1, a through hole 1-2 for electrons to pass through the center of the reflector body 1-1 and penetrating the upper and lower surfaces of the reflector body 1-1, and the reflector 1 further comprises a cover 1-3 which is arranged on a side of the through hole 1-2 away from the transmission electrode group and protrudes toward the side away from the transmission electrode group.

[0058] Each of the transmissive electrodes 2-1 includes a transmissive electrode body 2-11, and a through hole 2-12 for electrons to pass through the center of the transmissive electrode body 2-11 and penetrating the upper and lower surfaces of the transmissive electrode body 2-11 is provided.

[0059] The aberration-correcting reflector device further comprises a connecting tube 3 coaxially arranged on a second through hole 2 - 12 on a free end surface of a transmission electrode 2 - 1 away from the reflector 1 .

[0060] The distance between the reflector body 1-1 and the transmissive electrode group in this embodiment is 2.681 mm. The distance here refers to the spacing between the two, that is, the spacing between the side of the reflector body 1-1 close to the transmissive electrode group and the side of the transmissive electrode group close to the reflector body 1-1.

[0061] The distance between two adjacent transmissive electrode bodies 2 - 11 is 2.681 mm.

[0062] The thickness of the transmissive electrode body 2 - 11 is 2.681 mm.

[0063] The radius of the through hole 1-2 is 3.805 mm, the radius of the through hole 2-12 is 3.805 mm, and the inner diameter of the connecting tube 3 is 3.805 mm.

[0064] The inner pore diameters mentioned above are all the pore diameters at the smallest part of the pore.

[0065] The inner surface of the cover body 1-3 of this embodiment is a spherical surface with a radius of 5.6 mm. Figure 2 shown.

[0066] The hole walls of the through hole 1-2 and the through hole 2-12 of this embodiment are parallel to the axis to form cylindrical holes. Figure 2 shown.

[0067] Example 2

[0068] like Figure 3 As shown, different from Example 1, the hole walls of the through hole 1-2 and the through hole 2-12 protrude toward the center of the hole to form a circular hole, and the radius of the circular surface of the circular hole is half the thickness of the mirror body.

[0069] Example 3

[0070] like Figure 4 As shown, different from Example 1, the hole walls of through hole 1-2 and through hole 2-12 protrude toward the center of the hole to form two conical holes that are small in the middle and large at both ends.

[0071] Example 4

[0072] like Figure 5 As shown, different from the embodiment 1, the cover 1-3 of this embodiment is a cylindrical surface protruding toward a side away from the transmissive electrode group.

[0073] Example 5

[0074] like Figure 6 As shown, different from the embodiment 1, the inner surface of the cover 1-3 is a conical surface protruding toward a side away from the transmissive electrode group.

[0075] Example 6

[0076] The aberration correction mirror device of Example 2 is applied to an aberration correction system, such as Figure 7As shown, the aberration correction system of this embodiment includes a magnetic deflector 4, a first matching mirror 5, a second matching mirror 6, a third matching mirror 7 and the aberration correction reflector device, wherein the first matching mirror 5, the magnetic deflector 4 and the second matching mirror 6 are coaxially arranged in sequence along the optical path direction; the third matching mirror 7 is arranged on a side of the vertical optical path of the magnetic deflector 4, and the aberration correction reflector device is arranged on a side of the third matching mirror 7 away from the magnetic deflector 4.

[0077] The first matching mirror 5 is close to the sample end, the second matching mirror 6 is close to the detector end, an objective lens 8 is provided between the first matching mirror 5 and the sample, and two projection mirrors 9 are provided between the second matching mirror 6 and the detector.

[0078] The transmission electrode group of this embodiment includes four transmission electrodes 2-1 coaxially arranged at intervals. The voltage of the reflector 1 is set to 3.6801493 kV, and the voltages of the transmission electrodes 2-1 starting from the reflector 1 are 16.8303078 kV, 14.0450711 kV, 5.9086491 kV, and 4.9840000 kV respectively.

[0079] In order to increase the range of the objective function, the distance between the third matching mirror 7 and the bottom surface of the cover body 1-3 is often used as a variable in the solution process. Therefore, the distance between the third matching mirror 7 and the bottom surface of the cover body 1-3 in this embodiment is between 450-600mm (513mm in this embodiment).

[0080] like Figure 7 As shown, the blue line is the optical axis, the red line is the off-axis electron, and the green line is the on-axis electron. The intersection of the green line and the blue line is the imaging point, and the plane perpendicular to the blue line is the image plane. The plane perpendicular to the blue line at the intersection of the red line and the blue line is the focal plane. The objective lens 8 images the sample at the entrance of the magnetic deflector 4, and the first matching mirror 5 images the focal plane at the midpoint (45° angle) of the first deflection of the magnetic deflector 4. The magnetic deflector 4 images the sample image at the entrance at the exit of the first deflection. The third matching mirror 7 images the focal plane at the turning point in the aberration correction reflector device, and the turning point is not far from the concave surface of the reflector on the central axis of the reflector 1 (about a few millimeters away). The aberration correction reflector device images the sample image at the exit of the first deflection of the magnetic deflector 4 at the entrance of the second deflection of the magnetic deflector 4 (and overlaps with the exit of the first deflection of the magnetic deflector 4 in space). Due to symmetry, the third matching mirror 7 images the focal plane at the midpoint (45° angle) of the second deflection of the magnetic deflector 4. The magnetic deflector 4 images the sample image at the entrance of the second deflection at the exit of the second deflection. The second matching mirror 6 images the sample image at the exit of the second deflection before the projection mirror 9, and the projection mirror 9 images the sample image on the detector, and the image is obtained as follows: Figure 8 The results are shown. Figure 8It can be seen that the aberration correction mirror device of the present invention, on the one hand, improves the spatial resolution (vertical axis, the smaller the number, the higher the spatial resolution) and the electron transmittance (horizontal axis, the larger the number, the higher the transmittance), and on the other hand, can simultaneously correct chromatic aberration, third-order spherical aberration and fifth-order spherical aberration.

[0081] The aberration-correcting mirror device of other embodiments can also achieve the same effect as the above-mentioned embodiment, which can further illustrate that the correction system using the aberration-correcting mirror device of the present invention can correct chromatic aberration, third-order spherical aberration and fifth-order spherical aberration at the same time.

[0082] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, they can be improved or transformed as described above. All these improvements and transformations should fall within the scope of protection of the claims attached to the present invention.

Claims

1. An aberration-correcting reflector device, characterized in that: It comprises a reflector (1) and a transmission electrode group coaxially spaced on one side of the reflector (1), wherein the transmission electrode group comprises more than four transmission electrodes (2-1) coaxially spaced; The reflector (1) comprises a reflector body (1-1), a through hole (1-2) for electrons to pass through the center of the reflector body (1-1) and penetrating the upper and lower surfaces of the reflector body (1-1), and the reflector (1) further comprises a cover (1-3) which is arranged on a side of the through hole (1-2) away from the transmission electrode group and protrudes toward the side away from the transmission electrode group. Each transmission electrode (2-1) of the transmission electrode group comprises a transmission electrode body (2-11), and a second through hole (2-12) for electrons to pass through the transmission electrode body (2-11) is provided at the center of the transmission electrode body (2-11).

2. An aberration-correcting reflector device according to claim 1, characterized in that: The aberration correction reflector device also includes a connecting tube (3) coaxially arranged on a second through hole (2-12) on the free end surface of a transmission electrode (2-1) away from the reflector (1).

3. The aberration-correcting reflector device according to claim 1, characterized in that: The distance between the reflector body (1-1) and the transmission electrode group is 2-6 mm.

4. The aberration-correcting reflector device according to claim 1, characterized in that: The distance between two adjacent transmission electrode bodies (2-11) is 2-6 mm.

5. The aberration-correcting reflector device according to claim 1, characterized in that: The thickness of the transmissive electrode body (2-11) is 2-6 mm.

6. The aberration-correcting reflector device according to claim 2, characterized in that: The radius of the through hole one (1-2) is 2-6 mm, the radius of the through hole two (2-12) is 3-10 mm; and the inner diameter of the connecting pipe (3) is 3-10 mm.

7. The aberration-correcting reflector device according to claim 1, characterized in that: The inner surface of the cover body (1-3) is a cylindrical surface, a conical surface or a spherical surface protruding toward a side away from the transmission electrode group.

8. The aberration-correcting reflector device according to claim 1, characterized in that: The hole walls of the through hole 1 (1-2) and the through hole 2 (2-12) are parallel to the hole axis or protrude toward the hole center.

9. An aberration correction system, characterized in that: The invention comprises a magnetic deflector (4), a first matching mirror (5), a second matching mirror (6), a third matching mirror (7) and an aberration correction reflector device as described in any one of claims 1 to 8, wherein the first matching mirror (5), the magnetic deflector (4) and the second matching mirror (6) are coaxially arranged in sequence along the optical path direction; the third matching mirror (7) is arranged on one side of the magnetic deflector (4) perpendicular to the optical path, and the aberration correction reflector device is arranged on the side of the third matching mirror (7) away from the magnetic deflector (4).

10. A method for correcting an aberration, characterized in that: The aberration correction system described in claim 9 is installed in sequence, the transmission electrode group includes four transmission electrodes (2-1) coaxially arranged at intervals, the voltage of the reflector (1) is set to 3.5-5.5 kV, and the voltages of the transmission electrodes (2-1) starting from the reflector (1) are 1.5-17 kV, 14-17.5 kV, 5.5-10 kV and 5.0-15.0 kV respectively.

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