A device and method for measuring beam spots of multiple electron beams

Abstract

The present invention relates to the technical field of measuring the beam spot of multiple electron beams, and provides a device and method for measuring the beam spot of multiple electron beams. The device includes a vacuum chamber and multiple electron beams formed in the vacuum chamber, and at least includes: a blade piece, which is movably arranged in the vacuum chamber and located on the irradiation path of the multiple electron beams, and the blade piece has a blade suitable for the electron beam to pass through, and the blade piece can shield at least part of the electron beams in the multiple electron beams during the movement; an electron beam collecting structure, which is located in the vacuum chamber and downstream of the blade piece, and is suitable for collecting the electron beams emitted from the blade and converting them into electrical signals; a data processing module, which is connected to the electron beam collecting structure signal, is suitable for receiving the electrical signal, and obtains the beam spot distribution and beam spot size of each electron beam according to the electrical signal. The measuring device can obtain the beam spot distribution and beam spot size of each electron beam to meet the needs of observation and measurement.

Description

Technical Field

[0001] The invention relates to the technical field of multi-beam electron beam spot measurement, and in particular to a multi-beam electron beam spot measurement device and method. Background Art

[0002] Focused electron beams are widely used in electron microscopes, electron beam exposure machines, electron beam detection systems and electron spectrometers. At present, multi-beam electron microscopes, multi-beam electron beam exposure systems and multi-beam electron beam detection systems have received extensive attention and development. Among them, the porous multi-layer electrostatic lens with multi-beam focusing function plays an important role, which focuses multiple sub-beams obtained by the porous beam splitter plate onto the same plane at the same time. Therefore, the performance of the porous multi-layer electrostatic lens directly affects the performance indicators of the entire multi-beam system.

[0003] How to evaluate the performance of porous multi-layer electrostatic lenses is crucial. The only feasible way is to analyze the performance of the electrostatic lenses mentioned above by measuring multiple focused electron beam spots, including the beam spot diameter and beam current distribution. However, the beam spots of multiple electron beams are characterized by small beam spots and small spacing. The beam spot diameter is generally a few microns to tens of microns, which cannot be directly observed and measured. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is that the beam spots of multiple electron beams in the prior art are characterized by small beam spots and small spacing. The beam spot diameter is generally several microns to tens of microns in size and cannot be directly observed and measured, thereby providing a device and method for measuring the beam spots of multiple electron beams.

[0005] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0006] A device for measuring beam spots of multiple electron beams comprises a vacuum chamber and multiple electron beams formed in the vacuum chamber, and at least comprises: a knife-edge piece, movably arranged in the vacuum chamber and located on the irradiation path of the multiple electron beams, the knife-edge piece having a knife edge suitable for the electron beam to pass through, and the knife-edge piece being able to shield at least part of the electron beams in the multiple electron beams during movement; an electron beam collecting structure, located in the vacuum chamber and downstream of the knife-edge piece, suitable for collecting the electron beams emitted from the knife edge and converting them into electrical signals; a data processing module, signal-connected to the electron beam collecting structure, suitable for receiving the electrical signal, and calculating the beam spot distribution and beam spot size of each electron beam according to the electrical signal.

[0007] Furthermore, the electron beam collection structure includes a Faraday cup and an ammeter; the light entrance of the Faraday cup is located on the irradiation path of multiple electron beams; the ammeter is connected to the Faraday cup and is suitable for displaying the current value corresponding to the electron beam when the electron beam irradiates the inner wall of the Faraday cup, and the ammeter is connected to the data processing module signal to feed back the current value to the data processing module.

[0008] Furthermore, when the data processing module obtains the beam spot distribution and beam spot size of each electron beam, it first obtains a first curve of the relationship between the blade position and the current value, and then mathematically fits the first curve to obtain a second curve of the relationship between the blade position and the electron beam current intensity.

[0009] Furthermore, the device for measuring the beam spots of multiple electron beams also includes an electron gun assembly and a beam splitting structure arranged in the vacuum chamber; the electron gun assembly includes a planar cathode, a grid, an anode and a first electrostatic lens arranged in sequence along the irradiation direction of the electron beam, and the first electrostatic lens is used to collimate the electron beam emitted by the planar cathode so that the electron beam is emitted parallel to the optical axis; the beam splitting structure is arranged downstream of the electron gun assembly, and is suitable for splitting the passing electron beam into multiple electron beams; the knife edge is located downstream of the beam splitting structure.

[0010] Furthermore, the beam splitting structure includes a stacked beam splitting plate, a second electrostatic lens and an insulating layer; the beam splitting plate is provided with a plurality of first beam splitting holes in an array on its surface; the second electrostatic lens includes three electrodes, the three electrodes of the second electrostatic lens are arranged in parallel and spaced apart, and an insulating layer is sandwiched between every two adjacent electrodes; each electrode on the second electrostatic lens is provided with an array of second beam splitting holes corresponding to the first beam splitting holes, and the aperture of the second beam splitting holes is larger than the aperture of the first beam splitting holes; each insulating layer is provided with a through hole suitable for the passage of the electron beam.

[0011] Furthermore, the beam splitter plate, the three electrodes of the second electrostatic lens and the insulating layer are all provided with marking gratings suitable for alignment.

[0012] Furthermore, the device for measuring the beam spot of multiple electron beams also includes a sleeve structure and an electron beam imaging structure; one end of the sleeve structure extends into the vacuum chamber and is located downstream of the beam splitting structure, suitable for converting the split electron beams into multiple light beams and leading them out of the vacuum chamber; the input end of the electron beam imaging structure is inserted into the sleeve structure, and the output end of the electron beam imaging structure is suitable for converting the multiple light beams into light spots visible to the naked eye.

[0013] Furthermore, the sleeve structure includes a cylinder, lead glass and a YAG fluorescent screen; one end of the cylinder extends into the vacuum chamber; the lead glass is arranged in the cylinder, and the surface of the lead glass is arranged perpendicular to the irradiation path of the electron beam to isolate the external atmosphere from the vacuum in the vacuum chamber; the YAG fluorescent screen is arranged on the surface of the lead glass and is located on the side of the lead glass facing the beam splitting structure.

[0014] Furthermore, the device for measuring the beam spots of multiple electron beams also includes a first fixing member and a second fixing member; a first through hole suitable for the passage of the electron beam is arranged on the first fixing member; the first fixing member extends into the cylinder and abuts against the surface of the lead glass, suitable for limiting the movement of the lead glass along the irradiation direction parallel to the electron beam to play a sealing role; a second through hole suitable for the passage of the electron beam is arranged on the second fixing member; the second fixing member extends into the first through hole and abuts against the surface of the YAG fluorescent screen, suitable for limiting the movement of the YAG fluorescent screen along the irradiation direction parallel to the electron beam.

[0015] Furthermore, the electron beam imaging structure includes a camera, a first lens sleeve, a sleeve lens, a second lens sleeve and an objective lens; the sleeve lens is clamped between the first lens sleeve and the second lens sleeve; the camera is arranged at an end of the first lens sleeve away from the sleeve lens; the objective lens is arranged at an end of the second lens sleeve away from the sleeve lens; wherein the objective lens corresponds to the input end of the electron beam imaging structure, and the camera corresponds to the output end of the electron beam imaging structure.

[0016] Furthermore, the device for measuring the beam spots of multiple electron beams also includes a translation stage, which is arranged in the vacuum chamber and is suitable for carrying and driving the knife edge member and the electron beam collecting structure to move.

[0017] A method for measuring beam spots of multiple electron beams comprises the following steps: passing one row of electron beams of a split electron beam through a knife edge and recording the current value of an ammeter; moving the knife edge and recording the current value and the knife edge position until the current value is 0; obtaining a first curve of the relationship between the knife edge position and the current value; obtaining a second curve of the relationship between the knife edge position and the electron beam current intensity according to the first curve; and calculating and obtaining the beam spot distribution and beam spot size of each electron beam according to the second curve.

[0018] Furthermore, the second curve of the relationship between the knife edge position and the electron beam current intensity obtained according to the first curve specifically includes:

[0019] The first curve is segmented into several regions, and the curve of each region is fitted according to the following formula:

[0020]

[0021] Where It is the maximum current, w is the coefficient, and x is the displacement;

[0022] The fitted curve of each zone is differentiated according to the following formula:

[0023]

[0024] Obtain the second curve.

[0025] Furthermore, before allowing one row of the split electron beam to pass through the knife edge and recording the current value of the ammeter, the function of the second electrostatic lens is verified; specifically, the following steps are included: adjusting the vacuum degree of the vacuum chamber to the target range; emitting the electron beam; adjusting the first electrostatic lens so that the electron beam is emitted parallel to the optical axis; observing the beam spot of the split electron beam in the electron beam imaging structure; if the size of the electron beam spot is consistent with the size of the first beam splitting hole, changing the voltage of the middle electrode applied to the second electrostatic lens, and if a change in the size of the electron beam spot in the electron beam imaging structure is observed, the function of the second electrostatic lens is normal; if the size of the electron beam spot is consistent with the size of the first beam splitting hole, and the size of the electron beam spot in the electron beam imaging structure does not change after changing the voltage of the middle electrode applied to the second electrostatic lens, the function of the second electrostatic lens is abnormal.

[0026] The technical solution of the present invention has the following advantages:

[0027] The device for measuring the beam spots of multiple electron beams provided by the present invention is provided with a knife-edge piece, on which a sharp knife-edge can selectively block multiple electron beams that are smaller after beam splitting; and collects electrons of one or more electron beams that can pass through the knife-edge through an electron beam collecting structure, and converts them into electrical signals; finally, the electrical signal is analyzed and processed by a data processing module, so that the beam spot distribution and beam spot size of each electron beam can be obtained, meeting the needs of observation and measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 Schematic diagram of the overall structure of a device for measuring beam spots of multiple electron beams in an embodiment of the present invention;

[0030] Figure 2is a schematic diagram of an electron gun assembly in a device for measuring beam spots of multiple electron beams in an embodiment of the present invention;

[0031] Figure 3 is a schematic diagram of a beam splitting structure in a device for measuring beam spots of multiple electron beams in an embodiment of the present invention;

[0032] Figure 4 for Figure 3 A cross-sectional view of

[0033] Figure 5 is a schematic diagram of an electron beam imaging structure in a device for measuring beam spots of multiple electron beams in an embodiment of the present invention;

[0034] Figure 6 is a schematic diagram of a sleeve structure in a device for measuring beam spots of multiple electron beams in an embodiment of the present invention;

[0035] Figure 7 for Figure 6 A magnified schematic diagram of the local structure;

[0036] Figure 8 Schematic diagram of a knife-edge member and a Faraday cup in a device for measuring beam spots of multiple electron beams in an embodiment of the present invention;

[0037] Fig. 9 for Figure 8 A cross-sectional view of

[0038] Fig.10 It is a schematic diagram of a knife edge member in a device for measuring beam spots of multiple electron beams in an embodiment of the present invention when the knife edge member is located at an initial position;

[0039] Fig.11 is a schematic diagram of a first curve in a device for measuring beam spots of multiple electron beams in an embodiment of the present invention;

[0040] Fig.12 is a schematic diagram of a second curve in the device for measuring beam spots of multiple electron beams in an embodiment of the present invention;

[0041] Fig.13 The figure is a flow chart of a method for measuring beam spots of multiple electron beams in an embodiment of the present invention.

[0042] 1. Vacuum chamber; 2. Electron gun assembly; 3. Beam splitting structure;

[0043] 4. Translation stage; 5. Sleeve structure; 6. Electron beam imaging structure;

[0044] 7. Pipeline; 8. Mechanical dry pump; 9. Molecular pump;

[0045] 10. Planar cathode; 11. Grid; 12. Anode;

[0046] 13. first electrostatic lens; 14. marking grating; 15. first beam splitting hole;

[0047] 16. beam splitter; 17. second electrostatic lens; 18. insulating layer;

[0048] 19. Second beam splitting hole; 20. Camera; 21. First lens tube;

[0049] 22. Tube lens; 23. Second lens tube; 24. Objective lens;

[0050] 25. cylinder; 26. lead glass; 27. first fixing member;

[0051] 28. second fixing member; 29. ​​YAG fluorescent screen; 30. sealing ring;

[0052] 31. Knife edge; 32. Knife edge; 33. Faraday cup. DETAILED DESCRIPTION

[0053] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0055] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0056] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0057] Figure 1 Schematic diagram of the overall structure of a device for measuring beam spots of multiple electron beams in an embodiment of the present invention; Figure 8 Schematic diagram of a knife-edge member and a Faraday cup in a device for measuring beam spots of multiple electron beams in an embodiment of the present invention; Fig. 9 for Figure 8 A cross-sectional view of Figure 1 , Figure 8 as well as Fig. 9 As shown, this embodiment provides a device for measuring beam spots of multiple electron beams, including a vacuum chamber 1 and multiple electron beams formed in the vacuum chamber 1. For example, one side of the vacuum chamber 1 can be connected to a mechanical dry pump 8 and a molecular pump 9 through a pipeline 7. When vacuuming is required, the air in the vacuum chamber 1 can be pumped out through the mechanical dry pump 8 and the molecular pump 9 until the vacuum degree in the vacuum chamber 1 reaches a target range. The formation method of the multiple electron beams in the vacuum chamber 1 will be described in detail in the subsequent content.

[0058] The blade piece 31 is movably arranged in the vacuum chamber 1 and is located on the irradiation path of the multiple electron beams. The blade piece 31 has a blade edge 32 suitable for the electron beam to pass through. For example, the blade piece 31 can be made of a silicon wafer, and a blade edge 32 is formed on the blade piece 31 through micro-nano processing technology, such as wet etching or dry etching. Such a blade edge 32 has a sharper edge, and then a metal Mo with a thickness of 20nm is plated on both sides of the blade piece 31 to make the blade piece 31 conductive, so that the blade piece 31 has conductivity, which is conducive to ensuring the accuracy of the measurement. The length and width of the blade edge 32 can be designed according to the beam spot spacing of the multiple electron beams.

[0059] The blade 31 can block at least part of the multiple electron beams during movement; that is, a part of the electron beams can be controlled to pass through the blade 32, and the remaining electron beams are irradiated to the surface of the blade 31, and these electrons are transferred out by the conductive blade 31.

[0060] The electron beam collecting structure is located in the vacuum chamber 1 and downstream of the blade 31 , and is suitable for collecting the electron beam emitted from the blade 32 and converting it into an electrical signal.

[0061] The data processing module is connected to the electron beam collecting structure signal, is suitable for receiving the electrical signal, and obtains the beam spot distribution and beam spot size of each electron beam according to the electrical signal. The data processing module can be a computer and its related software.

[0062] The device for measuring the beam spots of multiple electron beams provided in the present embodiment is provided with a knife-edge piece 31, on which there is a sharp knife-edge 32, which can selectively block the multiple electron beams that are smaller after splitting; and collect the electrons of one or more electron beams that can pass through the knife-edge 32 through the electron beam collecting structure, and convert them into electrical signals; finally, the electrical signal is analyzed and processed by the data processing module, so as to obtain the beam spot distribution and beam spot size of each electron beam, thereby meeting the needs of observation and measurement.

[0063] The electron beam collection structure includes a Faraday cup 33 and an ammeter; the light inlet of the Faraday cup 33 is located on the irradiation path of the multiple electron beams, and is suitable for displaying the current value corresponding to the electron beam when the electron beam irradiates the inner wall of the Faraday cup 33, and the ammeter is connected to the data processing module signal to feed back the current value to the data processing module. The ammeter can be connected to the Faraday cup 33 by a lead wire, and the ammeter can be placed outside the vacuum chamber 1 for reading.

[0064] Fig.11 is a schematic diagram of a first curve in a device for measuring beam spots of multiple electron beams in an embodiment of the present invention; Fig.12 is a schematic diagram of a second curve in the device for measuring beam spots of multiple electron beams in an embodiment of the present invention; Fig.11 and Fig.12 As shown, when the data processing module obtains the beam spot distribution and beam spot size of each electron beam, it first obtains a first curve of the relationship between the position of the blade 32 and the current value, and then performs partition mathematical fitting on the first curve to obtain a second curve of the relationship between the position of the blade 32 and the electron beam current intensity.

[0065] Figure 2 FIG. 1 is a schematic diagram of an electron gun assembly in a device for measuring beam spots of multiple electron beams in an embodiment of the present invention; Figure 2As shown, the measuring device for the beam spot of the multi-beam electron beam also includes an electron gun assembly 2 and a beam splitting structure 3 arranged in a vacuum chamber 1; the electron gun assembly 2 can be installed on the top wall of the vacuum chamber 1 through a vacuum seal, and the emission end of the electron gun assembly 2 is located in the vacuum chamber 1, suitable for emitting electron beams. For example, for the electron gun assembly 2, it mainly includes a planar cathode 10, a grid 11, an anode 12, and a first electrostatic lens 13 for focusing and collimation, wherein the first electrostatic lens 13 can be provided with three planar electrodes spaced along the optical axis direction, and each electrode of the first electrostatic lens 13 can be 2mm thick and the center hole diameter can be 3mm. The material of the planar cathode 10 can be lanthanum hexaboride, and the emission plane diameter ranges from 0.2 to 0.5mm, for example, it can be 0.4mm. Among them, a metal grid cap with a center hole is used as the grid 11, and the center hole diameter is 1.2mm; the anode 12 is below the grid 11, and the distance between the grid 11 and the anode 12 is 1.2mm. The planar cathode 10 mainly emits a relatively uniform electron beam, which first forms a cross spot at the front end of the emission surface and then enters the first electrostatic lens 13 for collimation. After collimation adjustment, the electron beam can be emitted uniformly and parallel to the optical axis.

[0066] The beam splitting structure 3 is arranged downstream of the electron gun assembly 2 and is suitable for splitting the collimated electron beam passing through into multiple electron beams; the knife edge piece 31 is located downstream of the beam splitting structure 3 .

[0067] Figure 3 is a schematic diagram of a beam splitting structure in a device for measuring beam spots of multiple electron beams in an embodiment of the present invention; Figure 4 for Figure 3 A cross-sectional view of Figure 3 and Figure 4As shown, the beam splitting structure 3 includes a stacked beam splitting plate 16, a second electrostatic lens 17 and an insulating layer 18; the beam splitting plate 16 is provided with a plurality of first beam splitting holes 15 in an array on the plate surface, for example, the aperture of each first beam splitting hole 15 can be 10-15 μm. The second electrostatic lens 17 is a porous multi-layer electrostatic lens, including three electrodes, and the three electrodes are arranged in parallel and spaced apart, and an insulating layer 18 is sandwiched between each two adjacent electrodes. The electrode located in the middle of the second electrostatic lens 17 can be connected to a positive high voltage or a negative high voltage, and is connected to a voltage source through a metal lead to load a voltage; the remaining two electrodes are grounded. The three electrodes on the second electrostatic lens 17 are all provided with a second beam splitting hole 19 corresponding to the first beam splitting hole 15 in an array, and the aperture of the second beam splitting hole 19 is larger than the aperture of the first beam splitting hole 15, for example, the aperture of each second beam splitting hole 19 can be 30-50 μm. Each insulating layer 18 is provided with a through hole suitable for the passage of electron beams. The size of the through hole can be designed as needed, and the through hole is not smaller than the area where the entire second beam splitting hole 19 is located. When in use, a single larger electron beam is split into multiple smaller electron beams after passing through the beam splitter plate 16, and then is focused onto the same plane after passing through the third-level second electrostatic lens 17. By adjusting the voltage of the middle electrode on the second electrostatic lens 17, the focal plane and beam spot size of the multiple electron beams can be adjusted. Among them, the insulating layer 18 is used to separate the two adjacent electrodes of the second electrostatic lens 17 for insulation. The second electrostatic lenses 17 located at the top and bottom layers are grounded, and the middle second electrostatic lens 17 is connected to a high-voltage power supply to achieve the focusing effect.

[0068] The beam splitter plate 16, the three electrodes of the second electrostatic lens 17 and the insulating layer 18 are all provided with a mark grating 14 suitable for alignment. For example, the mark grating 14 can be L-shaped for accurate alignment to improve the beam splitting and focusing effects.

[0069] Figure 5 is a schematic diagram of an electron beam imaging structure in a device for measuring beam spots of multiple electron beams in an embodiment of the present invention; Figure 6 FIG. 1 is a schematic diagram of a sleeve structure in a device for measuring beam spots of multiple electron beams in an embodiment of the present invention; Figure 5 and Figure 6 As shown, the measuring device for the beam spot of the multi-beam electron beam also includes a sleeve structure 5 and an electron beam imaging structure 6; one end of the sleeve structure 5 extends into the vacuum chamber 1 and is located downstream of the beam splitting structure 3, suitable for converting the split multi-beam electron beams into multi-beam light beams; the input end of the electron beam imaging structure 6 is inserted into the sleeve structure 5, and the output end of the electron beam imaging structure 6 is suitable for converting the light beam into a light spot visible to the naked eye.

[0070] The sleeve structure 5 includes a cylinder 25, lead glass 26 and a YAG fluorescent screen 29; one end of the cylinder 25 extends into the vacuum chamber 1, and the other end of the cylinder 25 can be connected to the vacuum chamber 1 through a flange.

[0071] Among them, the lead glass 26 is arranged in the cylinder 25, and the surface of the lead glass 26 is arranged perpendicular to the irradiation path of the electron beam. For example, the cylinder wall of the sleeve can be provided with a step surface for placing the lead glass 26; the YAG fluorescent screen 29 can be laid flat on the surface of the lead glass 26, and the YAG fluorescent screen 29 is located on the side of the lead glass 26 facing the beam splitting structure 3. In this arrangement, the lead glass 26 is used for sealing and light transmission. When the beam spots of the multiple electron beams are irradiated to the YAG fluorescent screen 29, fluorescence is generated, which passes through the lead glass 26 and is then imaged by the electron beam imaging structure 6. After image processing, the shape of the beam spots of the multiple electron beams and the change of the beam spot size can be obtained.

[0072] Figure 7 for Figure 6 A schematic diagram of the local structure of Figure 7 As shown, the measuring device for the beam spot of the multi-beam electron beam also includes a first fixing member 27 and a second fixing member 28; a first through hole suitable for the electron beam to pass through is provided on the first fixing member 27; the first fixing member 27 extends into the cylinder 25 and abuts against the surface of the lead glass 26, suitable for limiting the movement of the lead glass 26 in a direction parallel to the irradiation direction of the electron beam and plays a sealing role; for example, a convex portion can be provided at one end of the first fixing member 27 facing the lead glass 26, and the convex portion cooperates with the step surface on the cylinder wall to press the edge of the lead glass 26. In addition, a groove can be provided on the side of the step surface facing the lead glass 26, and a sealing ring 30 can be placed in the groove. Similarly, a groove can be provided on the side of the convex portion facing the lead glass 26, and a sealing ring 30 can be placed in the groove. Such a configuration can improve the overall sealing. Among them, the first fixing member 27 and the cylinder 25 can be connected by screws.

[0073] The second fixing member 28 is provided with a second through hole suitable for the electron beam to pass through; the second fixing member 28 extends into the first through hole and abuts against the edge surface of the YAG fluorescent screen 29, suitable for limiting the movement of the YAG fluorescent screen 29 in a direction parallel to the irradiation direction of the electron beam. For example, a groove can be provided on the side of the second fixing member 28 facing the YAG fluorescent screen 29, so that the edge of the YAG fluorescent screen 29 can extend into the groove, which can prevent the YAG fluorescent screen 29 from moving relative to the lead glass 26. The first through hole and the edge of the second fixing member are provided with grooves, and the second fixing member 28 and the first fixing member 27 can be fixed by a slider.

[0074] The electron beam imaging structure 6 includes a camera 20, a first lens sleeve 21, a sleeve lens 22, a second lens sleeve 23 and an objective lens 24; the sleeve lens 22 is sandwiched between the first lens sleeve 21 and the second lens sleeve 23; the camera 20 is arranged at one end of the first lens sleeve 21 away from the sleeve lens 22; the objective lens 24 is arranged at one end of the second lens sleeve 23 away from the sleeve lens 22; wherein the objective lens 24 corresponds to the input end of the electron beam imaging structure 6, and the camera 20 corresponds to the output end of the electron beam imaging structure 6. The first lens sleeve 21 and the second lens sleeve 23 are both retractable lens sleeves, so that the focal length of the objective lens 24 can be adjusted. The electron beam imaging structure 6 will be installed on a three-axis translation stage, which can adjust the working distance between the objective lens 24 and the YAG fluorescent screen 29, so as to facilitate clearer imaging. For example, the pixel size of the camera 20 is 3.45 μm, the number of pixels is 1440×1080, and it has a color imaging function; the objective lens 24 has a 10-fold magnification, a resolution of 1.1 μm, and a working distance of 10 mm.

[0075] The device for measuring the beam spot of the multi-beam electron beam further comprises a displacement stage 4, which is arranged in the vacuum chamber 1 and is suitable for carrying and driving the blade 31 and the electron beam collecting structure to move. The displacement stage 4 can adopt a three-axis precision displacement stage to improve the accuracy of the movement. When in use, the Faraday cup 33 can be fixed on the displacement stage 4, and then the blade 31 can be installed on the Faraday cup 33. When the displacement stage 4 moves, the blade 31 and the Faraday cup 33 can be driven to move synchronously.

[0076] When in use, the electron gun assembly 2, the beam splitter plate 16, the first electrostatic lens 17 and the electron beam imaging structure 6 are on the same straight line.

[0077] Fig.13 FIG. 1 is a flow chart of a method for measuring a multi-beam electron beam spot in an embodiment of the present invention. Fig.13 As shown, another embodiment also provides a method for measuring the beam spot of a multi-beam electron beam, including the following steps: passing one row of the split electron beam through the blade 32, and recording the current value of the ammeter; moving the blade 32, recording the current value and the position of the blade 32 until the current value is 0; obtaining a first curve of the relationship between the position of the blade 32 and the current value; obtaining a second curve of the relationship between the position of the blade 32 and the electron beam current intensity based on the first curve; obtaining the beam spot distribution and beam spot size of each electron beam based on the second curve; if the function of the second electrostatic lens is abnormal, stopping the measurement.

[0078] The second curve for obtaining the relationship between the position of the knife edge 32 and the electron beam intensity according to the first curve specifically includes:

[0079] The first curve is segmented into several regions, and the curve of each region is fitted according to the following formula:

[0080]

[0081] Among them, I t is the maximum current, w is the coefficient, and x is the displacement;

[0082] The fitted curve of each zone is differentiated according to the following formula:

[0083]

[0084] Obtain the second curve.

[0085] Among them, before allowing one row of the split electron beam to pass through the knife edge and recording the current value of the ammeter, the function of the second electrostatic lens is verified; specifically, the following steps are included: adjusting the vacuum degree of the vacuum chamber 1 to the target range; emitting the electron beam; adjusting the first electrostatic lens so that the electron beam is emitted parallel to the optical axis; observing the beam spot of the split electron beam in the electron beam imaging structure 6; if the size of the electron beam spot is consistent with the size of the first beam splitting hole 15, then changing the voltage applied to the middle electrode on the second electrostatic lens 17, if it is observed that the size of the electron beam spot in the electron beam imaging structure 6 changes, the function of the second electrostatic lens 17 is normal, and subsequent measurement operations can be performed at this time; if the size of the electron beam spot is consistent with the size of the first beam splitting hole 15, and after changing the voltage applied to the middle electrode on the second electrostatic lens 17, the size of the electron beam spot in the electron beam imaging structure 6 does not change, then the function of the second electrostatic lens 17 is abnormal, and subsequent measurement operations are stopped at this time.

[0086] For the purpose of illustration, a 3×3 beam spot distribution form is used. Of course, the present application is not limited to the 3×3 beam spot distribution form, but can also be applied to more n×n forms.

[0087] The following are detailed steps for verifying whether the second electrostatic lens 17 is normal:

[0088] Turn on the mechanical pump to perform pre-vacuuming. When the pressure reaches below 20 Pa, turn on the molecular pump 9 to perform high vacuum extraction.

[0089] When the vacuum degree reaches 5×10 -5 Pa, the planar cathode 10 is heated and the current of the planar cathode 10 is gradually increased to make the temperature of the planar cathode 10 reach above 1800K.

[0090] The voltage of the gate 11 is turned on and adjusted to a pre-designed value of -5V; the voltage of the anode 12 is then turned on and gradually increased to 5kV; at the same time, the presence or absence of an image of the electron beam imaging structure 6 is observed and whether it changes.

[0091] At this time, if beam spots of multiple electron beams are observed, it means that the electron gun assembly 2 has been emitting electron beams normally; then increase the voltage of the middle electrode of the first electrostatic lens 13 and adjust it to -3.2 kV, which is a value obtained by pre-calculation and measurement; make the electron beam emit parallel to the optical axis and irradiate the beam splitter plate 16.

[0092] At this time, beam spots of the multiple electron beams split by the beam splitter plate 16 can be observed in the electron beam imaging structure 6 , and the size of the beam spots is equivalent to the first beam splitter hole 15 .

[0093] When the voltage of the middle electrode of the second electrostatic lens 17 is applied, if a change in the size of the beam spot of the electron beam in the electron beam imaging structure 6 is observed, it indicates that the second electrostatic lens works well.

[0094] The following are the detailed steps of the multi-beam electron beam spot measurement method:

[0095] Turn on the mechanical pump to perform pre-vacuuming. When the pressure reaches below 20 Pa, turn on the molecular pump 9 to perform high vacuum extraction.

[0096] When the vacuum degree reaches 5×10 -5 Pa, the planar cathode 10 is heated and the current of the planar cathode 10 is gradually increased to make the temperature of the planar cathode 10 reach above 1800K.

[0097] The voltage of the gate 11 is turned on and adjusted to a pre-designed value of -5V; then the voltage of the anode 12 is turned on and gradually increased to 5kV.

[0098] Next, the voltage of the middle electrode of the first electrostatic lens 13 is increased and adjusted to -3.2 kV, which is a value obtained by pre-calculation and measurement.

[0099] The electron beam is emitted parallel to the optical axis and irradiates the beam splitter plate 16 .

[0100] Since the beam spot of the split electron beam has been obtained in the previous method, the beam spot will not be checked again in this step because it will be blocked by the translation stage 4.

[0101] Adjust the position of the displacement stage 4 and the central axis so that the beam spots of one row of the multiple electron beams are located in the middle of the knife edge 32. Fig.10 As shown, at this time, the ammeter can read the beam current size of one line of electron beam.

[0102] Then, the translation stage 4 is moved, and the current value of the ammeter and the position of the translation stage 4 are recorded until the ammeter reading is 0. When moving the translation stage 4, you can choose to move left or right, and the moving direction cannot be changed after it is selected in a single test. Fig.10 Schematic diagram of a knife edge member in a device for measuring beam spots of multiple electron beams in an embodiment of the present invention when the knife edge member is located at an initial position; Fig.10 As shown, that is to say, at the initial position, the number of electron beams passing through the blade 32 is the largest, and the ammeter reading is the largest. Then, the translation stage 4 is moved in the selected direction. At this time, the number of electron beams passing through the blade 32 gradually decreases, and the ammeter reading also decreases accordingly, until the number of electron beams passing through the blade 32 is 0, and the corresponding ammeter reading is 0.

[0103] According to the relationship between the position of the displacement stage 4 and the recorded current value, a first curve is obtained, such as Fig.11 As shown, the horizontal axis represents the displacement of the blade 32, in μm, and the vertical axis represents the reading of the ammeter; Fig.11 The first curve in the figure is segmented into three regions: I, II and III. The curve of each region is fitted according to the following formula:

[0104]

[0105] The fitting curves for the above three regions are differentiated according to the following formula:

[0106]

[0107] The second curve can be obtained as Fig.12 As shown, the horizontal axis represents the displacement of the blade 32, in μm, and the vertical axis represents the beam intensity of the beam spot; according to the beam distribution of the beam spot in each area, the beam distribution and the beam spot size of each beam spot are finally obtained. For example, the size of the beam spot can be calculated according to the half-height width of the beam intensity of each beam spot.

[0108] In summary, the present application uses a precision translation stage 4, combined with a special blade 32 and a calculation method, to quickly obtain the beam current distribution and beam spot size of the multi-beam electron beam spot. Secondly, the electron beam is irradiated vertically to reduce the aberration effect caused by the deflected electron beam, and a more accurate beam spot calculation result can be obtained. In addition, through the electron beam imaging structure 6, it is possible to quickly and conveniently verify the changes in the multi-beam beam spot after the collimated electron beam is split and focused, and verify whether the function of the porous multi-layer electrostatic lens is reliable, which is conducive to optimizing the overall design.

[0109] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A device for measuring beam spots of multiple electron beams, comprising a vacuum chamber and multiple electron beams formed in the vacuum chamber, characterized in that: At least: A knife-edge member is movably arranged in the vacuum chamber and is located on the irradiation path of the multiple electron beams. The knife-edge member has a knife edge suitable for the electron beam to pass through, and the knife-edge member can shield at least part of the electron beams in the multiple electron beams during movement; an electron beam collecting structure, located in the vacuum chamber and downstream of the knife edge, adapted to collect the electron beam emitted from the knife edge and convert it into an electrical signal; A data processing module, connected to the electron beam collecting structure signal, adapted to receive the electrical signal and calculate the beam spot distribution and beam spot size of each electron beam according to the electrical signal; Also included is an electron gun assembly and a beam splitting structure disposed in the vacuum chamber; The electron gun assembly comprises a planar cathode, a grid, an anode and a first electrostatic lens arranged in sequence along the irradiation direction of the electron beam, wherein the first electrostatic lens is used to collimate the electron beam emitted by the planar cathode so that the electron beam is emitted parallel to the optical axis; The beam splitting structure is disposed downstream of the electron gun assembly and is adapted to split the passing electron beam into a plurality of electron beams; The knife-edge member is located downstream of the beam splitting structure; It also includes a sleeve structure and an electron beam imaging structure; One end of the sleeve structure extends into the vacuum chamber and is located downstream of the beam splitting structure, and is suitable for converting the split multiple electron beams into multiple light beams; The input end of the electron beam imaging structure is inserted into the sleeve structure, and the output end of the electron beam imaging structure is suitable for converting the multiple light beams into light spots visible to the naked eye.

2. The device for measuring the beam spots of multiple electron beams according to claim 1, characterized in that: The electron beam collection structure includes a Faraday cup and an ammeter; The light entrance of the Faraday cup is located on the irradiation path of the multiple electron beams; The ammeter is connected to the Faraday cup and is suitable for displaying the current value corresponding to the electron beam when the electron beam irradiates the inner wall of the Faraday cup. The ammeter is signal-connected to the data processing module to feed back the current value to the data processing module.

3. The device for measuring the beam spots of multiple electron beams according to claim 2, characterized in that: When the data processing module obtains the beam spot distribution and beam spot size of each electron beam, it first obtains a first curve of the relationship between the knife edge position and the current value, and then mathematically fits the first curve to obtain a second curve of the relationship between the knife edge position and the electron beam current intensity.

4. The device for measuring the beam spots of multiple electron beams according to claim 1, characterized in that: The beam splitting structure comprises a beam splitting plate, a second electrostatic lens and an insulating layer arranged in layers; The beam splitter plate has a plate array provided with a plurality of first beam splitter holes; The second electrostatic lens comprises three electrodes, the three electrodes of the second electrostatic lens are arranged in parallel and spaced apart, and an insulating layer is sandwiched between every two adjacent electrodes of the second electrostatic lens; Each electrode on the second electrostatic lens is arrayed with a second beam splitting hole corresponding to the first beam splitting hole, and the aperture of the second beam splitting hole is larger than the aperture of the first beam splitting hole; Each of the insulating layers is provided with a through hole suitable for the electron beam to pass through.

5. The device for measuring the beam spots of multiple electron beams according to claim 4, characterized in that: The beam splitter plate, the three electrodes of the second electrostatic lens and the insulating layer are all provided with marking gratings for alignment.

6. The device for measuring the beam spots of multiple electron beams according to claim 1, characterized in that: The sleeve structure includes a cylinder, lead glass and a YAG fluorescent screen; One end of the cylinder extends into the vacuum chamber; The lead glass is arranged in the cylinder, and the surface of the lead glass is arranged perpendicular to the irradiation path of the electron beam to isolate the external atmosphere from the vacuum in the vacuum chamber; The YAG fluorescent screen is arranged on the surface of the lead glass and is located on a side of the lead glass facing the beam splitting structure.

7. The device for measuring the beam spots of multiple electron beams according to claim 6, characterized in that: Also includes a first fixing member and a second fixing member; The first fixing member is provided with a first through hole suitable for the electron beam to pass through; the first fixing member extends into the cylinder and abuts against the surface of the lead glass, suitable for limiting the movement of the lead glass in a direction parallel to the irradiation direction of the electron beam to play a sealing role; The second fixing member is provided with a second through hole suitable for the electron beam to pass through; the second fixing member extends into the first through hole and abuts against the surface of the YAG fluorescent screen, suitable for limiting the movement of the YAG fluorescent screen along the irradiation direction parallel to the electron beam.

8. The device for measuring the beam spots of multiple electron beams according to claim 1, characterized in that: The electron beam imaging structure includes a camera, a first lens tube, a tube lens, a second lens tube and an objective lens; The sleeve lens is sandwiched between the first lens sleeve and the second lens sleeve; The camera is arranged at an end of the first lens tube away from the tube lens; The objective lens is arranged at an end of the second lens tube away from the tube lens; Wherein, the objective lens corresponds to the input end of the electron beam imaging structure, and the camera corresponds to the output end of the electron beam imaging structure.

9. The device for measuring the beam spots of multiple electron beams according to claim 1, characterized in that: It also includes a translation platform, which is arranged in the vacuum chamber and is suitable for carrying and driving the knife edge member and the electron beam collecting structure to move.

10. A method for measuring beam spots of multiple electron beams, characterized in that: The steps include: Make one row of the split electron beam pass through the knife edge and record the current value of the ammeter; Move the knife edge and record the current value and knife edge position until the current value reaches 0; Obtaining a first curve of the relationship between the knife edge position and the current value; Acquire a second curve of the relationship between the knife edge position and the electron beam current intensity according to the first curve; Calculate the beam spot distribution and beam spot size of each electron beam according to the second curve; The function of the second electrostatic lens is verified before one row of the split electron beam passes through the knife edge and the current value of the ammeter is recorded. The specific steps include: Adjust the vacuum degree of the vacuum chamber to a target range; emitting electron beams; Adjusting the first electrostatic lens so that the electron beam is emitted parallel to the optical axis; Observe the electron beam spot after beam splitting in the electron beam imaging structure; If the size of the electron beam spot is consistent with the size of the first beam splitter hole, the voltage applied to the electrode located in the middle of the second electrostatic lens is changed. If a change in the size of the electron beam spot in the electron beam imaging structure is observed, the function of the second electrostatic lens is normal; If the size of the electron beam spot is consistent with the size of the first beam splitter hole, and the size of the electron beam spot in the electron beam imaging structure does not change after changing the voltage applied to the middle electrode of the second electrostatic lens, the second electrostatic lens is not functioning properly.

11. The method for measuring the beam spots of multiple electron beams according to claim 10, characterized in that: Acquiring a second curve of the relationship between the knife edge position and the electron beam current intensity according to the first curve specifically comprises: The first curve is segmented into several regions, and the curve of each region is fitted according to the following formula: Among them, I t is the maximum current, w is the coefficient, and x is the displacement; The fitted curve of each zone is differentiated according to the following formula: Obtain the second curve.

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