CN115206756B - A device and method for measuring beam spots of multiple electron beams - Google Patents
A device and method for measuring beam spots of multiple electron beams Download PDFInfo
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- CN115206756B CN115206756B CN202210842745.7A CN202210842745A CN115206756B CN 115206756 B CN115206756 B CN 115206756B CN 202210842745 A CN202210842745 A CN 202210842745A CN 115206756 B CN115206756 B CN 115206756B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/02—Details
- H01J37/244—Detectors; Associated components or circuits therefor
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
- H01J2237/245—Detection characterised by the variable being measured
- H01J2237/24507—Intensity, dose or other characteristics of particle beams or electromagnetic radiation
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- H01J2237/24542—Beam profile
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Abstract
The invention relates to the technical field of multi-beam electron beam spot measurement, and provides a multi-beam electron beam spot measurement device and a multi-beam electron beam spot measurement method, wherein the device comprises a vacuum chamber and a plurality of electron beams formed in the vacuum chamber, and at least comprises a knife edge piece, a knife edge and a measuring device, wherein the knife edge piece is movably arranged in the vacuum chamber and positioned on an irradiation path of the plurality of electron beams, a knife edge suitable for the passage of the electron beams is arranged on the knife edge piece, and the knife edge piece can shade at least part of the electron beams in the plurality of electron beams in the moving process; the data processing module is in signal connection with the electron beam collecting structure and is suitable for receiving the electric signals and acquiring the beam spot distribution and the beam spot size of each electron beam according to the electric signals. The measuring device can acquire the beam spot distribution and the beam spot size of each electron beam, and meets the requirements of observation and measurement.
Description
Technical Field
The invention relates to the technical field of multi-beam electron beam spot measurement, in particular to a device and a method for measuring multi-beam electron beam spots.
Background
Focused electron beams have found wide application in electron microscopes, electron beam exposure machines, electron beam detection systems, and electron spectrometers. Currently, a multi-beam electron microscope, a multi-beam electron beam exposure system, and a multi-beam electron beam detection system are widely focused and developed. Among them, a multi-aperture multi-layered electrostatic lens having a multi-beam focusing function plays an important role in simultaneously focusing a plurality of beamlets obtained by a multi-aperture beam-splitting plate onto the same plane. Therefore, the performance of the porous multi-layer electrostatic lens directly affects the performance index of the entire multibeam system.
How to evaluate the performance of porous multilayer electrostatic lenses is of paramount importance. The only viable approach is to analyze the performance of the electrostatic lens described above by measuring a plurality of focused electron beam spots, including spot diameter and beam current distribution. But the multi-beam electron beam spot has the characteristics of small beam spot and small interval, and the diameter of the beam spot is generally from a few micrometers to tens of micrometers, and cannot be directly observed and measured.
Disclosure of Invention
Therefore, the technical problem to be solved by the invention is that the multi-beam electron beam spot in the prior art has the characteristics of small beam spot and small space, and the diameter of the beam spot is generally from a few micrometers to tens of micrometers, and cannot be directly observed and measured, so that the device and the method for measuring the multi-beam electron beam spot are provided.
In order to solve the technical problems, the technical scheme of the invention is as follows:
The measuring device for the beam spots of the multiple electron beams comprises a vacuum chamber and the multiple electron beams formed in the vacuum chamber, at least comprises a knife edge piece and a data processing module, wherein the knife edge piece is movably arranged in the vacuum chamber and is positioned on an irradiation path of the multiple electron beams, a knife edge suitable for the electron beams to pass through is arranged on the knife edge piece, the knife edge piece can shade at least part of the electron beams in the multiple electron beams in the moving process, an electron beam collecting structure is positioned in the vacuum chamber and is positioned at the downstream of the knife edge piece and is suitable for collecting the electron beams emitted from the knife edge and converting the electron beams into electric signals, and the data processing module is in signal connection with the electron beam collecting structure and is suitable for receiving the electric signals and calculating and obtaining the beam spot distribution and the beam spot size of each electron beam according to the electric signals.
The electronic beam collecting structure comprises a Faraday cup and an ammeter, wherein a light inlet of the Faraday cup is positioned on an irradiation path of a plurality of electronic beams, the ammeter is communicated with the Faraday cup and is suitable for displaying a current value corresponding to the electronic beams when the electronic beams irradiate on the inner wall of the Faraday cup, and the ammeter is in signal connection with the data processing module so as to feed back the current value to the data processing module.
Further, when the data processing module obtains the beam spot distribution and the beam spot size of each electron beam, a first curve of the relation between the knife edge position and the current value is obtained first, and then mathematical fitting is carried out on the first curve, so that a second curve of the relation between the knife edge position and the electron beam current intensity is obtained.
The measuring device for the multi-beam electron beam spots further comprises an electron gun assembly and a beam splitting structure, wherein the electron gun assembly and the beam splitting structure are arranged in the vacuum chamber, the electron gun assembly comprises a planar cathode, a grid electrode, an anode and a first electrostatic lens which are sequentially arranged along the irradiation direction of the electron beams, the first electrostatic lens is used for collimating the electron beams emitted by the planar cathode and enabling the electron beams to be emitted parallel to an optical axis, the beam splitting structure is arranged at the downstream of the electron gun assembly and suitable for splitting the passing electron beams into the multi-beam electron beams, and the knife edge piece is arranged at the downstream of the beam splitting structure.
The beam splitting structure comprises a beam splitting plate, a second electrostatic lens and an insulating layer, wherein the beam splitting plate is arranged in a stacked mode, a plurality of first beam splitting holes are formed in the surface array of the beam splitting plate, the second electrostatic lens comprises three electrodes, the three electrodes of the second electrostatic lens are arranged in parallel at intervals, one insulating layer is arranged between every two adjacent electrodes in a clamped mode, second beam splitting holes corresponding to the first beam splitting holes are formed in each electrode of the second electrostatic lens in an array mode, the aperture of each second beam splitting hole is larger than that of each first beam splitting hole, and through holes suitable for passing of electron beams are formed in each insulating layer.
Further, marking gratings suitable for alignment are arranged on the beam splitting plate, the three electrodes of the second electrostatic lens and the insulating layer.
The measuring device for the multi-beam electron beam spots further comprises a sleeve structure and an electron beam imaging structure, wherein one end of the sleeve structure extends into the vacuum chamber and is positioned at the downstream of the beam splitting structure and is suitable for converting the split electron beams into multi-beam light beams and leading the multi-beam light beams 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 multi-beam light beams into spots visible to naked eyes.
The sleeve structure comprises a cylinder body, lead glass and a YAG fluorescent screen, wherein one end of the cylinder body extends into the vacuum chamber, the lead glass is arranged in the cylinder body, the surface of the lead glass is perpendicular to the irradiation path of the electron beam so as to isolate the external atmosphere from vacuum in the vacuum chamber, and the YAG fluorescent screen is arranged on the surface of the lead glass and is positioned on one side of the lead glass facing the beam splitting structure.
The measuring device for the multi-beam electron beam spots further comprises a first fixing piece and a second fixing piece, wherein a first through hole suitable for passing the electron beam is formed in the first fixing piece, the first fixing piece stretches into the cylinder and abuts against the surface of the lead glass, the first fixing piece is suitable for limiting the movement of the lead glass along the irradiation direction parallel to the electron beam so as to play a role of sealing, a second through hole suitable for passing the electron beam is formed in the second fixing piece, and the second fixing piece stretches into the first through hole and abuts against the surface of the YAG fluorescent screen and is suitable for limiting the movement of the YAG fluorescent screen along the irradiation direction parallel to the electron beam.
The electron beam imaging structure comprises a first lens sleeve, a second lens sleeve and an objective lens, wherein the first lens sleeve is clamped between the first lens sleeve and the second lens sleeve, the camera is arranged at one end, far away from the sleeve lens, of the first lens sleeve, the objective lens is arranged at one end, far away from the sleeve lens, of the second lens sleeve, 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.
Further, the measuring device for the multi-beam electron beam spot further comprises a displacement table which is arranged in the vacuum chamber and is suitable for bearing and driving the knife edge piece and the electron beam collecting structure to move.
A method for measuring beam spots of multiple electron beams includes enabling one row of electron beams of the split electron beams to pass through a knife edge, recording current values of an ammeter, moving the knife edge, recording the current values and the knife edge positions until the current values are 0, obtaining a first curve of the relation between the knife edge positions and the current values, obtaining a second curve of the relation between the knife edge positions and the beam intensity of the electron beams according to the first curve, and obtaining beam spot distribution and beam spot size of each electron beam according to calculation of the second curve.
Further, the obtaining the second curve of the relation between the knife edge position and the electron beam intensity according to the first curve specifically includes;
The first curve is segmented into a plurality of areas, and the curve of each area is fitted according to the following formula:
wherein It is the maximum value of the current, w is a coefficient, and x is displacement;
the curve fitted to each region is differentiated according to the following formula:
A second curve is obtained.
The method comprises the steps of adjusting the vacuum degree of a vacuum chamber to a target range, emitting an electron beam, adjusting a first electrostatic lens to enable the electron beam to be emitted parallel to an optical axis, observing an electron beam spot after beam splitting in an electron beam imaging structure, changing the voltage of an intermediate electrode applied to the second electrostatic lens if the size of the electron beam spot is consistent with the size of a first beam splitting hole, and enabling the second electrostatic lens to function normally if the size of the electron beam spot is observed to be consistent with the size of a first beam splitting hole, and changing the voltage of an intermediate electrode applied to the second electrostatic lens if the size of the electron beam spot is unchanged.
The technical scheme of the invention has the following advantages:
The measuring device for the beam spots of the multiple electron beams is provided with a knife edge piece, the knife edge piece is provided with a sharp knife edge, the multiple electron beams which are smaller after splitting can be selectively shielded, electrons of one or more electron beams which can pass through the knife edge are collected through an electron beam collecting structure and are converted into electric signals, and finally the electric signals are analyzed and processed through a data processing module, so that the beam spot distribution and the beam spot size of each electron beam can be obtained, and the requirements of observation and measurement are met.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of an overall structure of a measuring apparatus for multi-beam electron beam spot in an embodiment of the present invention;
FIG. 2 is a schematic view of an electron gun assembly in a multi-beam spot measurement apparatus according to an embodiment of the present invention;
FIG. 3 is a schematic view of a beam splitting structure in a measuring apparatus for multi-beam electron beam spots according to an embodiment of the present invention;
FIG. 4 is a cross-sectional view of FIG. 3;
FIG. 5 is a schematic view of an electron beam imaging structure in a measuring apparatus for multi-beam spot in an embodiment of the present invention;
FIG. 6 is a schematic view of a sleeve structure of a measuring device for multi-beam electron beam spots according to an embodiment of the present invention;
FIG. 7 is an enlarged schematic view of the partial structure of FIG. 6;
FIG. 8 is a schematic view of a knife edge member and Faraday cup in a multi-beam electron beam spot measurement apparatus according to an embodiment of the invention;
FIG. 9 is a cross-sectional view of FIG. 8;
FIG. 10 is a schematic view of a knife edge member in an initial position in a multi-beam spot measurement apparatus according to an embodiment of the present invention;
FIG. 11 is a schematic view of a first curve of a multi-beam spot measurement apparatus according to an embodiment of the present invention;
FIG. 12 is a schematic diagram of a second curve in the multi-beam spot measuring apparatus according to the embodiment of the present invention;
Fig. 13 is a flowchart of a method for measuring beam spots of a multi-beam electron beam in an embodiment of the present invention.
1. A vacuum chamber; 2, an electron gun assembly, 3, a beam splitting structure;
4. a displacement table, a sleeve structure, an electron beam imaging structure and a sleeve structure;
7. Pipeline, 8, mechanical dry pump, 9, molecular pump;
10. a planar cathode, 11, a grid, 12, an anode;
13. 14, marking grating 15, first beam splitting hole;
16. The beam splitter plate, the second electrostatic lens, the insulating layer and the first electrostatic lens are arranged on the beam splitter plate;
19. a second beam splitting aperture 20, a camera 21, a first lens sleeve;
22. A sleeve lens, 23, a second lens sleeve, 24, an objective lens;
25. 26 parts of cylinder, 27 parts of lead glass and a first fixing piece;
28. 29, YAG fluorescent screen 30, sealing ring;
31. knife edge piece 32, knife edge 33 and Faraday cup.
Detailed Description
The following description of the embodiments of the present invention will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, unless explicitly stated or limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected, mechanically connected, electrically connected, directly connected, indirectly connected via an intervening medium, or in communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
In addition, the technical features of the different embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
Fig. 1 is a schematic diagram of the overall structure of a device for measuring multiple beam spots in an embodiment of the present invention, fig. 8 is a schematic diagram of a knife edge member and a faraday cup in the device for measuring multiple beam spots in an embodiment of the present invention, fig. 9 is a cross-sectional view of fig. 8, and as shown in fig. 1, 8 and 9, the embodiment provides a device for measuring multiple beam spots, including a vacuum chamber 1 and multiple beam spots formed in the vacuum chamber 1, for example, one side of the vacuum chamber 1 may be connected to a mechanical dry pump 8 and a molecular pump 9 through a pipeline 7, and when vacuum pumping is required, air in the vacuum chamber 1 may 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 manner in which the plurality of electron beams are formed in the vacuum chamber 1 will be described in detail later.
Wherein the knife-edge piece 31 is movably arranged in the vacuum chamber 1 and is positioned on the irradiation path of a plurality of electron beams, and the knife-edge piece 31 is provided with a knife edge 32 which is suitable for the electron beams to pass through. For example, the knife edge piece 31 can be made of silicon wafer, the knife edge 32 is formed on the knife edge piece 31 by micro-nano processing technology, such as wet etching or dry etching, the edge of the knife edge 32 is sharper, and then the metal Mo with the thickness of 20nm is plated on the two sides of the knife edge piece 31, so that the knife edge piece 31 is conductive, thereby the knife edge piece 31 has conductivity, and the accuracy of measurement is guaranteed. The length and width of the knife edge 32 can be designed according to the beam spot spacing of the multiple electron beams.
The knife-edge member 31 is capable of shielding at least part of the electron beams in the plurality of electron beams during movement, that is, a part of the electron beams passing through the knife-edge 32 can be controlled, and the rest of the electron beams are irradiated to the surface of the knife-edge member 31, and the part of the electrons are transferred out by the knife-edge member 31 having conductivity.
Wherein an electron beam collecting structure is located in the vacuum chamber 1 downstream of the knife-edge member 31, adapted to collect the electron beam emitted from the knife-edge 32 and convert it into an electrical signal.
The data processing module is in signal connection with the electron beam collecting structure and is suitable for receiving the electric signals and acquiring the beam spot distribution and the beam spot size of each electron beam according to the electric signals. The data processing module may be a computer and related software.
The measuring device for the multi-beam electron beam spots is provided with the knife edge piece 31, the knife edge piece 31 is provided with the sharp knife edge 32, the multi-beam electron beams which are smaller after splitting can be selectively shielded, electrons of one or more electron beams which can pass through the knife edge 32 are collected through the electron beam collecting structure and converted into electric signals, and finally the electric signals are analyzed and processed through the data processing module, so that the spot distribution and spot size of each electron beam can be obtained, and the requirements of observation and measurement are met.
The electron beam collecting structure comprises a Faraday cup 33 and an ammeter, wherein an optical inlet of the Faraday cup 33 is positioned on an irradiation path of a plurality of electron beams, and is suitable for displaying a current value corresponding to the electron beams when the electron beams irradiate on the inner wall of the Faraday cup 33, and the ammeter is in signal connection with the data processing module so as to feed the current value back to the data processing module. Wherein the ammeter may be connected to faraday cup 33 by a lead wire, and may be placed outside vacuum chamber 1 for reading.
Fig. 11 is a schematic diagram of a first curve in a measuring device for beam spots of multiple beams in an embodiment of the present invention, fig. 12 is a schematic diagram of a second curve in a measuring device for beam spots of multiple beams in an embodiment of the present invention, as shown in fig. 11 and 12, where when a data processing module obtains beam spot distribution and beam spot size of each electron beam, a first curve of a relationship between a position of a knife edge 32 and a current value is obtained first, and then the first curve is subjected to regional mathematical fitting, so as to obtain a second curve of a relationship between a position of the knife edge 32 and beam intensity of the electron beam.
Fig. 2 is a schematic view of an electron gun assembly in a measuring device for multi-beam spot in an embodiment of the present invention, as shown in fig. 2, wherein the measuring device for multi-beam spot further includes an electron gun assembly 2 and a beam splitting structure 3 disposed in a vacuum chamber 1, the electron gun assembly 2 may be mounted on a top wall of the vacuum chamber 1 through a vacuum seal, and an emitting end of the electron gun assembly 2 is disposed in the vacuum chamber 1 and adapted to emit an electron beam. For example, for the electron gun assembly 2, it mainly includes a planar cathode 10, a grid electrode 11, an anode 12, and a first electrostatic lens 13 for focusing and collimation, wherein the first electrostatic lens 13 may be provided with three planar electrodes at intervals along the optical axis direction, each electrode thickness of the first electrostatic lens 13 may be 2mm, and the center hole diameter may be 3mm. The material of the planar cathode 10 may be lanthanum hexaboride and the diameter of the emission plane may range between 0.2 and 0.5mm, for example, 0.4mm. The metal grid cap with the central hole is used as a grid electrode 11, the diameter of the central hole is 1.2mm, an anode 12 is arranged below the grid electrode 11, and the distance between the anode 12 and the grid electrode 11 is 1.2mm. The planar cathode 10 mainly emits relatively uniform electron beams, a cross spot is formed at the front end of the emitting surface, and then the electron beams enter the first electrostatic lens 13 for collimation, and the electron beams can be emitted uniformly and parallel to the optical axis after collimation adjustment.
Wherein a beam splitting structure 3 is arranged downstream of the electron gun assembly 2 and adapted to split the passing collimated electron beam into a plurality of electron beams, and a knife-edge member 31 is arranged downstream of the beam splitting structure 3.
Fig. 3 is a schematic view of a beam splitting structure in a measuring device for multiple beam spots of an embodiment of the present invention, fig. 4 is a cross-sectional view of fig. 3, and as shown in fig. 3 and 4, the beam splitting structure 3 includes a beam splitting plate 16, a second electrostatic lens 17 and an insulating layer 18 that are stacked, where a plate surface array of the beam splitting plate 16 is provided with a plurality of first beam splitting holes 15, for example, a hole diameter of each first beam splitting hole 15 may be 10-15 μm. The second electrostatic lens 17 is a porous multilayer electrostatic lens, and comprises three electrodes, wherein the three electrodes are arranged in parallel at intervals, an insulating layer 18 is arranged between every two adjacent electrodes, the electrode positioned in the middle on the second electrostatic lens 17 can be connected with positive high voltage or negative high voltage and is connected with a voltage source through a metal lead so as to load voltage, and the other two electrodes are grounded. The three electrodes on the second electrostatic lens 17 are each provided with a second beam splitting aperture 19 corresponding to the first beam splitting aperture 15 in an array, and the aperture of the second beam splitting aperture 19 is larger than that of the first beam splitting aperture 15, for example, the aperture of each second beam splitting aperture 19 may be 30-50 μm. Each insulating layer 18 is provided with a through hole suitable for passing the electron beam, the size of the through hole can be designed according to the requirement, and the through hole is not smaller than the whole area where the second beam splitting hole 19 is located. In use, a single larger electron beam is split into a plurality of smaller electron beams after passing through the beam splitter plate 16, and focused onto the same plane after passing through the third stage of the second electrostatic lens 17. The focal plane and the beam spot size of the multiple electron beams can be adjusted by adjusting the voltage of the electrode located in the middle on the second electrostatic lens 17. The insulating layer 18 is used for separating two adjacent electrodes of the second electrostatic lens 17 for insulation, the second electrostatic lens 17 positioned at the top layer and the bottom layer is grounded, and the second electrostatic lens 17 in the middle is connected with a high-voltage power supply to realize the focusing function.
Wherein, the beam splitter plate 16, the three electrodes of the second electrostatic lens 17 and the insulating layer 18 are respectively provided with a marking grating 14 which is suitable for alignment. For example, the marking grating 14 may be L-shaped for precise alignment to enhance beam splitting and focusing effects.
Fig. 5 is a schematic view of an electron beam imaging structure in a measuring device for a multi-beam spot according to an embodiment of the present invention, fig. 6 is a schematic view of a sleeve structure in the measuring device for the multi-beam spot according to an embodiment of the present invention, and as shown in fig. 5 and 6, the measuring device for the multi-beam spot further 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, and is suitable for converting the split multi-beam electron beam into a multi-beam, an input end of the electron beam imaging structure 6 is inserted into the sleeve structure 5, and an output end of the electron beam imaging structure 6 is suitable for converting the beam into a visible light spot.
The sleeve structure 5 comprises 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 with the vacuum chamber 1 through a flange.
Wherein the lead glass 26 is disposed in the cylinder 25, and the surface of the lead glass 26 is disposed perpendicular to the irradiation path of the electron beam, for example, the wall of the sleeve may be provided with a stepped surface for placing the lead glass 26, the YAG phosphor screen 29 may be laid flat on the surface of the lead glass 26, and the YAG phosphor screen 29 is located on the side of the lead glass 26 facing the beam splitting structure 3. By such arrangement, sealing and light transmission are performed through the lead glass 26, when the beam spots of the multiple electron beams are irradiated to the YAG fluorescent screen 29, fluorescence is generated, the light is transmitted through the lead glass 26, then the light is imaged through the electron beam imaging structure 6, and the shape and the size change condition of the beam spots of the multiple electron beams can be obtained through image processing.
Fig. 7 is an enlarged schematic view of the partial structure of fig. 6, wherein the measuring device for multi-beam spot of electron beam further comprises a first fixing member 27 and a second fixing member 28, wherein the first fixing member 27 is provided with a first through hole suitable for passing electron beam, the first fixing member 27 extends into the cylinder 25 and abuts against the surface of the lead glass 26, is suitable for limiting the movement of the lead glass 26 along the irradiation direction parallel to the electron beam and plays a role in sealing, for example, a convex part can be arranged at one end of the first fixing member 27 facing the lead glass 26, and the convex part is matched with a step surface on the cylinder wall to press the edge of the lead glass 26. A groove may be provided on the surface of the step surface facing the lead glass 26, and a seal ring 30 may be placed in the groove. Similarly, a groove may be provided on the side of the protrusion facing the lead glass 26, and a seal ring 30 may be placed in the groove. By this arrangement, the overall sealing performance can be improved. Wherein the first fixing member 27 and the cylinder 25 can be connected by a screw.
The second fixing member 28 is provided with a second through hole for passing the electron beam, and the second fixing member 28 extends into the first through hole and abuts against the edge surface of the YAG screen 29, so as to limit the movement of the YAG screen 29 in a direction parallel to the irradiation direction of the electron beam. For example, a recess may be provided in the side of the second mount 28 facing the YAG phosphor screen 29 so that the rim of the YAG phosphor screen 29 may extend into the recess, preventing the YAG phosphor screen 29 from shifting relative to the lead glass 26. The edges of the first through hole and the second fixing piece are provided with grooves, and the second fixing piece 28 and the first fixing piece 27 can be fixed through a sliding block.
The electron beam imaging structure 6 comprises a camera 20, a first lens sleeve 21, a sleeve lens 22, a second lens sleeve 23 and an objective lens 24, wherein the sleeve lens 22 is clamped 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 far away from the sleeve lens 22, the objective lens 24 is arranged at one end of the second lens sleeve 23 far away from the sleeve lens 22, the objective lens 24 corresponds to an input end of the electron beam imaging structure 6, and the camera 20 corresponds to an output end of the electron beam imaging structure 6. The first lens sleeve 21 and the second lens sleeve 23 are telescopic lens sleeves, so that the focal length of the objective lens 24 can be adjusted. The electron beam imaging structure 6 is mounted on a three-axis displacement table, and the working distance between the objective lens 24 and the YAG screen 29 can be adjusted, thereby facilitating clearer imaging. For example, the camera 20 has a pixel size of 3.45 μm and a number of pixels 1440×1080, and has a color imaging function, and the objective lens 24 has a magnification of 10 times, a resolution of 1.1 μm, and a working distance of 10mm.
The measuring device for the multi-beam electron beam spot further comprises a displacement table 4, which is arranged in the vacuum chamber 1 and is suitable for carrying and driving the knife edge piece 31 and the electron beam collecting structure to move. The displacement table 4 can adopt a triaxial precision displacement table, so that the motion precision is improved. When in use, the Faraday cup 33 can be fixed on the displacement table 4, then the knife edge piece 31 is arranged on the Faraday cup 33, and when the displacement table 4 moves, the knife edge piece 31 and the Faraday cup 33 can be driven to synchronously move.
Wherein, 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 collinear.
Fig. 13 is a flowchart of a method for measuring beam spots of a multi-beam electron beam according to an embodiment of the present invention, and as shown in fig. 13, another embodiment of the present invention further provides a method for measuring beam spots of a multi-beam electron beam, which includes the steps of passing one row of the split electron beams through a knife edge 32 and recording the current value of an ammeter, moving the knife edge 32, recording the current value and the position of the knife edge 32 until the current value is 0, obtaining a first curve of the relation between the position of the knife edge 32 and the current value, obtaining a second curve of the relation between the position of the knife edge 32 and the beam intensity of the electron beam according to the first curve, obtaining the beam spot distribution and the beam spot size of each electron beam according to the second curve, and stopping the measurement if the function of the second electrostatic lens is abnormal.
Wherein, the second curve for obtaining the relation between the position of the knife edge 32 and the beam intensity of the electron beam according to the first curve specifically comprises;
the first curve is segmented into a plurality of areas, and the curve of each area is fitted according to the following formula:
Wherein I t is the maximum value of the current, w is a coefficient, and x is displacement;
the curve fitted to each region is differentiated according to the following formula:
A second curve is obtained.
The method specifically comprises the steps of adjusting the vacuum degree of the vacuum chamber 1 to a target range, emitting the electron beam, adjusting the first electrostatic lens to enable the electron beam to be emitted parallel to an optical axis, observing the beam spots in the electron beam imaging structure 6 after beam splitting, changing the voltage applied to the electrode positioned in the middle on the second electrostatic lens 17 if the size of the beam spots is consistent with the size of the first beam splitting hole 15, and enabling the second electrostatic lens 17 to function normally if the size of the beam spots in the electron beam imaging structure 6 is observed to change, wherein the subsequent measurement operation can be performed if the size of the beam spots is consistent with the size of the first beam splitting hole 15, and the function of the second electrostatic lens 17 does not stop when the size of the beam spots in the electron beam imaging structure 6 is unchanged after the voltage applied to the second electrostatic lens 17 is changed.
For illustration, a 3×3 beam spot distribution pattern is used, but the present application is not limited to a 3×3 beam spot distribution pattern, and can be applied to a larger number of n×n patterns.
The following is a detailed procedure for verifying whether the second electrostatic lens 17 is normal:
the mechanical pump is turned on to perform pre-evacuation, and when the pressure reaches 20pa or less, the molecular pump 9 is turned on to perform high-vacuum evacuation.
When the vacuum degree is 5×10 -5 Pa or lower, the planar cathode 10 is heated, and the current of the planar cathode 10 is gradually increased, so that the temperature of the planar cathode 10 is 1800K or higher.
The voltage of the grid electrode 11 is opened and adjusted to a preset value of-5V, the voltage of the anode 12 is opened and gradually increased to 5kV, and meanwhile, whether the image of the electron beam imaging structure 6 exists or not and whether the image changes or not are observed.
At this time, if a beam spot of a plurality of electron beams is observed, which means that the electron gun assembly 2 has normally emitted the electron beams, then the voltage of the intermediate electrode of the first electrostatic lens 13 is increased, adjusted to-3.2 kV, which is a value obtained by calculation and measurement in advance, and the electron beams are made to exit parallel to the optical axis and irradiated onto the beam splitting plate 16.
At this time, the beam spot of the plural electron beams split by the beam splitter 16 is observed in the electron beam imaging structure 6, and the size of the beam spot corresponds to the first beam splitter hole 15.
The intermediate electrode voltage of the second electrostatic lens 17 is applied, which is indicated to work well if a change in the beam spot size of the electron beam in the electron beam imaging structure 6 is observed.
The following is a detailed procedure of the method for measuring beam spots of a plurality of electron beams:
the mechanical pump is turned on to perform pre-evacuation, and when the pressure reaches 20pa or less, the molecular pump 9 is turned on to perform high-vacuum evacuation.
When the vacuum degree is 5×10 -5 Pa or lower, the planar cathode 10 is heated, and the current of the planar cathode 10 is gradually increased, so that the temperature of the planar cathode 10 is 1800K or higher.
The voltage of the grid electrode 11 is opened and adjusted to a preset value of-5V, and the voltage of the anode 12 is opened and gradually increased to 5kV.
Then the voltage of the intermediate electrode of the first electrostatic lens 13 is increased and adjusted to-3.2 kV, which is a value obtained by calculation and measurement in advance.
The electron beam is emitted parallel to the optical axis and irradiated onto the beam splitter plate 16.
Since the beam spot of the electron beam after splitting has been obtained in the previous method, the beam spot is not inspected any more in this step, because it is blocked by the displacement table 4.
The positions of the displacement table 4 and the central axis are adjusted so that one line of electron beam spots of the multiple electron beams are positioned in the middle of the knife edge 32, as shown in fig. 10, and at this time, the current meter can read the beam size of one line of electron beams.
Then, the displacement stage 4 is moved, and the current value of the ammeter and the position of the displacement stage 4 are recorded until the ammeter reading is 0. Wherein, when the displacement table 4 is moved, the displacement table can be moved leftwards or rightwards, and the direction of movement can not be changed after being selected in a single test. Fig. 10 is a schematic diagram of a measuring device for beam spots of multiple electron beams according to an embodiment of the present invention, in which the knife edge member is located at the initial position, as shown in fig. 10, that is, in the initial position, the electron beams passing through the knife edge 32 are the largest, the readings of the ammeter are the largest, and then the displacement table 4 is moved toward the selected direction, at this time, the number of electron beams passing through the knife edge 32 is gradually reduced, and the readings of the ammeter are also reduced until the number of electron beams passing through the knife edge 32 is 0, and at this time, the readings of the corresponding ammeter are 0.
According to the relation between the position of the displacement table 4 and the recorded current value, a first curve is obtained, as shown in fig. 11, the abscissa represents the displacement of the movement of the knife edge 32, the unit is μm, the ordinate is the reading size of an ammeter, the first curve in fig. 11 is segmented into I, II and III areas, and the curve of each area is fitted according to the following formula:
the fitted curve for the above three regions is differentiated according to the following formula:
a second curve is obtained, as shown in fig. 12, the abscissa represents the displacement of the knife edge 32, the unit is μm, and the ordinate represents the beam intensity of the beam spot, and the beam distribution and the beam spot size of each beam spot are finally obtained according to the beam distribution of each area. For example, the size of the beam spot may be calculated from the half-width of the beam intensity of each beam spot.
In summary, the application uses the precision displacement table 4, combines the special knife edge 32 and the calculation method, and can rapidly obtain the beam current distribution and the beam spot size of the multi-beam electron beam spot. Secondly, the electron beam irradiates vertically, so that the aberration influence caused by deflection of the electron beam is reduced, and a more accurate beam spot calculation result can be obtained. In addition, through the electron beam imaging structure 6, the change condition of a plurality of beam spots after the collimated electron beams are split and focused can be conveniently and quickly verified, and whether the functions of the porous multilayer electrostatic lens are reliable or not is verified, so that the optimization of the overall scheme design is facilitated.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the invention.
Claims (11)
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| US5382895A (en) * | 1992-12-28 | 1995-01-17 | Regents Of The University Of California | System for tomographic determination of the power distribution in electron beams |
| CN111579890A (en) * | 2019-02-19 | 2020-08-25 | Fei 公司 | Focused ion beam contaminant identification |
| WO2024129489A2 (en) * | 2022-12-14 | 2024-06-20 | Lam Research Corporation | Divergence measurement system for ion beam substrate processing systems |
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| US7479644B2 (en) * | 2006-10-30 | 2009-01-20 | Applied Materials, Inc. | Ion beam diagnostics |
| JP2018129559A (en) * | 2015-06-19 | 2018-08-16 | 江藤 剛治 | High-speed imaging device |
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| US5382895A (en) * | 1992-12-28 | 1995-01-17 | Regents Of The University Of California | System for tomographic determination of the power distribution in electron beams |
| CN111579890A (en) * | 2019-02-19 | 2020-08-25 | Fei 公司 | Focused ion beam contaminant identification |
| WO2024129489A2 (en) * | 2022-12-14 | 2024-06-20 | Lam Research Corporation | Divergence measurement system for ion beam substrate processing systems |
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