CN116646229B - Charged particle detection system, detection method and scanning electron microscope - Google Patents
Charged particle detection system, detection method and scanning electron microscope Download PDFInfo
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- CN116646229B CN116646229B CN202310893955.3A CN202310893955A CN116646229B CN 116646229 B CN116646229 B CN 116646229B CN 202310893955 A CN202310893955 A CN 202310893955A CN 116646229 B CN116646229 B CN 116646229B
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- 238000001514 detection method Methods 0.000 title claims abstract description 79
- 239000002245 particle Substances 0.000 title claims abstract description 49
- 238000010894 electron beam technology Methods 0.000 claims abstract description 65
- 239000004065 semiconductor Substances 0.000 claims description 23
- 230000003287 optical effect Effects 0.000 claims description 19
- 230000005684 electric field Effects 0.000 claims description 12
- 230000009471 action Effects 0.000 claims description 9
- 230000007246 mechanism Effects 0.000 claims description 6
- 230000001133 acceleration Effects 0.000 claims description 3
- 239000006185 dispersion Substances 0.000 claims description 3
- 238000001803 electron scattering Methods 0.000 claims description 3
- 230000005540 biological transmission Effects 0.000 claims 1
- 238000000034 method Methods 0.000 abstract description 18
- 230000008569 process Effects 0.000 abstract description 12
- 238000012545 processing Methods 0.000 abstract description 8
- 239000000523 sample Substances 0.000 description 84
- 230000000712 assembly Effects 0.000 description 5
- 238000000429 assembly Methods 0.000 description 5
- 238000005259 measurement Methods 0.000 description 5
- 238000010586 diagram Methods 0.000 description 3
- 238000009434 installation Methods 0.000 description 3
- 238000004364 calculation method Methods 0.000 description 2
- 238000000691 measurement method Methods 0.000 description 2
- 238000012544 monitoring process Methods 0.000 description 2
- 238000004626 scanning electron microscopy Methods 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 238000004630 atomic force microscopy Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000007480 spreading Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000004627 transmission electron microscopy Methods 0.000 description 1
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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
- 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
- H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement, ion-optical arrangement
- H01J37/10—Lenses
- H01J37/14—Lenses magnetic
- H01J37/141—Electromagnetic lenses
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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
- H01J37/20—Means for supporting or positioning the objects or the material; Means for adjusting diaphragms or lenses associated with the support
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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
- H01J37/26—Electron or ion microscopes; Electron or ion diffraction tubes
- H01J37/28—Electron or ion microscopes; Electron or ion diffraction tubes with scanning beams
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
- H01L22/10—Measuring as part of the manufacturing process
- H01L22/12—Measuring as part of the manufacturing process for structural parameters, e.g. thickness, line width, refractive index, temperature, warp, bond strength, defects, optical inspection, electrical measurement of structural dimensions, metallurgic measurement of diffusions
Abstract
The application relates to a charged particle detection system, a detection method and a scanning electron microscope; the charged particle detection system includes: the first detector component, the second detector component and the objective lens are sequentially arranged along the direction of the incident electron beam; the first detector component is used for receiving first signal electrons generated by the incident electron beam acting on the sample to be detected; the second detector component is used for receiving second signal electrons generated by the incident electron beam acting on the sample to be detected, and is provided with a first through hole, and the first signal electrons pass through the first through hole; the objective lens is an electromagnetic lens and is used for converging incident electron beams, the first signal electrons and the second signal electrons. Based on the scheme, the structure of the charged particle detection system is simplified, the processing difficulty of equipment is low, the processing cost of the charged particle detection system is reduced, and the debugging difficulty of the charged particle detection system in the using process is reduced.
Description
Technical Field
The present application relates to the field of scanning electron microscope technologies, and in particular, to a charged particle detection system, a detection method, and a scanning electron microscope.
Background
The semiconductor industry has grown increasingly, and the control of the process dimensions of integrated circuit devices has also required ever-increasing sophistication. The accurate and precise (precision <1 nm) measurement technique of nano-device Critical Dimensions (CD) plays a critical role in the development of the semiconductor industry and is also a very challenging task. Various measurement techniques such as scatterometry, atomic force microscopy, transmission electron microscopy and scanning electron microscopy have been developed in the market, wherein scanning electron microscopy is the most convenient and efficient method for real-time monitoring and line width measurement in semiconductor industry.
Currently available detection systems for scanning electron microscopes for measuring line widths of semiconductors generally include two or more laterally pressurized scintillator detectors that are required to be used in conjunction with special wien filters, reverse electric fields, objective lenses, and to filter or collect the corresponding signal electrons. In the application of measuring the line width of a semiconductor, because the energy of secondary electrons and back scattered electrons serving as signal electrons is relatively fixed, the measuring capability of a scanning electron microscope with a complex structure is far greater than the requirement of actually measuring the line width of the semiconductor, and the excessive complex structure causes more complex processing, high installation and debugging difficulty and high equipment cost. Accordingly, it is desirable to provide a charged particle detection system, method and scanning electron microscope suitable for measuring semiconductor linewidths.
Disclosure of Invention
The application provides a charged particle detection system, a detection method and a scanning electron microscope, which are used for solving the technical problems of higher equipment cost, high installation and debugging difficulty and complex processing caused by the fact that the structure of the traditional scanning electron microscope for semiconductor measurement is too complex.
In a first aspect, the present application provides a charged particle detection system comprising:
the first detector component, the second detector component and the objective lens are sequentially arranged along the direction of the incident electron beam;
the first detector component is used for receiving first signal electrons generated by the incident electron beam acting on a sample to be detected;
the second detector component is used for receiving second signal electrons generated by the incident electron beam acting on the sample to be detected, and is provided with a first through hole, and the first signal electrons pass through the first through hole;
the objective lens is an electromagnetic lens and is used for converging the incident electron beam, the first signal electrons and the second signal electrons.
Optionally, the first detector component is provided with a second through hole, the aperture of the second through hole is smaller than that of the first through hole, and the second through hole, the first through hole and the objective lens are coaxial and can enable the incident electron beam to pass through in sequence.
Optionally, the first signal electrons are secondary electrons and the second signal electrons are backscattered electrons.
Optionally, the first detector assembly comprises a semiconductor detector or a microchannel plate detector for detecting secondary electrons and the second detector assembly comprises a scintillator detector for detecting backscattered electrons.
Optionally, a sample stage for placing the sample to be tested is further arranged below the objective lens;
the sample stage is capable of applying a reverse voltage for decelerating the incident electron beam and for accelerating and converging the secondary electrons and the backscattered electrons.
Optionally, an axial distance between the first and second probe assemblies is no greater than 25mm; the distance between the second detector assembly and the sample stage ranges from 135mm to 145mm.
Optionally, the aperture of the first through hole is 3.5 mm-4 mm; the aperture of the second through hole is 0.2 mm-1 mm.
Optionally, the aperture of the first via is greater than the propagation diameter of the first signal electrons at the first via and less than the propagation diameter of the second signal electrons at the first via when the second signal electron scattering angle is at a minimum;
the aperture of the second via is greater than the propagation diameter of the incident electron beam and less than the propagation diameter of the first signal electron scattering angle at the second via.
In a second aspect, the present application also provides a detection method, the detection method being suitable for the charged particle detection system according to any one of the first aspects, the sample to be detected being a nano-device sample, the first signal electrons being secondary electrons and the second signal electrons being backscattered electrons, the first detector assembly comprising a semiconductor detector or a microchannel plate detector for detecting secondary electrons, the second detector assembly comprising a scintillator detector for detecting backscattered electrons; the detection method comprises the following steps: applying a reverse voltage to the sample stage to form a reverse electric field between the sample stage and the objective lens;
controlling the incident electron beam to reach the objective lens, and acting on the nano device sample after converging to generate the secondary electrons and the back scattered electrons; controlling the objective lens and the reverse voltage to enable the secondary electrons and the back scattered electrons to be converged at different positions in the objective lens under the acceleration convergence action of the reverse electric field, and then to be scattered out of the objective lens at different angles, wherein the scattering angle of the back scattered electrons is larger than that of the secondary electrons;
the secondary electrons are received by the corresponding semiconductor detector or microchannel plate detector after passing through the first through hole of the scintillator detector outside the objective lens, and the back scattered electrons are received by the corresponding scintillator detector outside the objective lens.
In a third aspect, the present application also provides a scanning electron microscope, the scanning electron microscope at least comprising the charged particle detection system according to any one of the first aspect, and an electron optical column, the first detector assembly and the second detector assembly being fixed to a wall of the electron optical column by respective mounting members, the objective lens being provided at a bottom of the electron optical column;
a sample stage is arranged below the objective lens, and the reverse voltage which can be applied by the sample stage is-10 kV-0;
the sample table is provided with a plurality of nail tables for placing different samples to be tested, and the bottom of the sample table is provided with a high-precision five-axis mechanism for driving the sample table to move within a preset distance range under any five-axis coordinate system;
the electron optical lens further comprises a Schottky thermal field emission type electron gun arranged at the top of the electron optical lens barrel and used for generating the incident electron beam.
In summary, the application provides a charged particle detection system, a detection method and a scanning electron microscope: compared with the existing detection system, the charged particle detection system can detect a sample to be detected by arranging two groups of detectors to receive two corresponding electrons, special Wen filters and other equipment are not needed, the receiving quality and efficiency of signal electrons are improved through the special detection system, the structure of the charged particle detection system is simplified on the premise of detecting the sample to be detected, the processing difficulty of equipment is low, the processing cost of the charged particle detection system is reduced, and the debugging difficulty of the charged particle detection system in the use process can be reduced due to the simple structure of the charged particle detection system. Particularly in the field of measuring critical dimensions of nano devices, the detection method of the application ensures that secondary electrons and back scattered electrons are accelerated and converged respectively under the action of a reverse electric field and are emitted at different angles and are respectively received by corresponding detector components, thereby completing the measurement of the critical dimensions, avoiding the need of excessively complex debugging process in the process and improving the detection accuracy and precision. In addition, the scanning electron microscope provided by the application can randomly move the position of the sample to be detected through the five-axis mechanism, so that the real-time monitoring and the accurate measurement of different samples at different positions are realized.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description, serve to explain the principles of the application.
In order to more clearly illustrate the embodiments of the application or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, and it will be obvious to a person skilled in the art that other drawings can be obtained from these drawings without inventive effort.
FIG. 1 is a schematic diagram of a charged particle detection system according to an embodiment of the present application;
fig. 2 is a schematic structural diagram of still another charged particle detection system according to an embodiment of the present application.
Reference numerals:
11. a first detector assembly; 12. a second detector assembly; 13. an objective lens; 14. a sample to be tested; 15. a sample stage; 16. an electron source; 17. an electron optical lens barrel; 18. a mounting member; 100. incident electron beams; 200. a first signal electron; 300. a second signal electron; 111. a second through hole; 121. a first through hole.
Detailed Description
In order that the above objects, features and advantages of the application will be more clearly understood, a further description of the application will be made. It should be noted that, without conflict, the embodiments of the present application and features in the embodiments may be combined with each other.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application, but the present application may be practiced otherwise than as described herein; it will be apparent that the embodiments in the specification are only some, but not all, embodiments of the application.
The charged particle detection system, the charged particle detection method and the scanning electron microscope according to the embodiments of the present application are described below with reference to the accompanying drawings.
Fig. 1 is a schematic structural diagram of a charged particle detection system according to the present application, including: a first detector assembly 11, a second detector assembly 12 and an objective lens 13, which are sequentially arranged along the direction of an incident electron beam 100; wherein the first detector assembly 11 is configured to receive first signal electrons 200 generated by the incident electron beam 100 acting on the sample 14 to be measured; the second detector assembly 12 is configured to receive the second signal electrons 300 generated by the incident electron beam 100 acting on the sample 14 to be measured, and the second detector assembly 12 is provided with a first through hole 121, and the first signal electrons 200 pass through the first through hole 121; the objective lens 13 is an electromagnetic lens for converging the incident electron beam 100 and the first signal electrons 200, 300.
Illustratively, the charged particle detection system referred to in the embodiments of the present application may refer to a functional device for measuring a semiconductor linewidth. In some embodiments, the first signal electrons 200 may be secondary electrons generated after the incident electron beam 100 acts on the surface of the sample 14 to be measured, the second signal electrons 300 may be back-scattered electrons generated after the incident electron beam 100 acts on the sample 14 to be measured, the first detector assembly 11 may be a semiconductor detector or a microchannel plate (Microchannel Plate) detector, the second detector assembly 12 may be a scintillator detector, and the objective lens 13 may be an electron lens for converging the incident electron beam 100 while converging the first signal electrons 200 and the second signal electrons 300 such that the first signal electrons 200 and the second signal electrons 300 propagate to the first detector assembly 11 and the second detector assembly 12, respectively.
In some possible scenarios, the first signal electrons 200 and the second signal electrons 300 may also be other types of signal electrons, such as characteristic X-rays, auger electrons, and the like. If the first signal electronics 200 and the second signal electronics 300 are other types of signal electronics, the first detector assembly 11 and the second detector assembly 12 in the embodiment of the present application may also be corresponding devices for receiving other types of signal electronics, which are not described herein. That is, the first signal electronic component 200 and the second signal electronic component 300 in the embodiment of the present application may be any signal electronic component capable of detecting the sample 14 to be detected, and the first detector assembly 11 and the second detector assembly 12 in the embodiment of the present application may also be any functional device capable of receiving the corresponding signal electronic component to detect the sample 14 to be detected.
Based on the scheme, the charged particle detection system can detect a sample to be detected by arranging two groups of detectors to receive two corresponding electrons, and special wien filters and other equipment are not needed, so that the structure of the charged particle detection system is simplified on the premise of being capable of detecting the sample to be detected, the processing difficulty of equipment is lower, the processing cost of the charged particle detection system is reduced, and the debugging difficulty of the charged particle detection system in the use process can be reduced due to the simple structure of the charged particle detection system.
With continued reference to fig. 1, in some possible embodiments, the incident electron beam 100 reaches the objective lens 13, is focused, impinges on the surface of the sample 14 to be measured, and upon acting on the sample 14 to be measured, generates the second signal electrons 300, and generates the first signal electrons 200. The first signal electrons 200 and the second signal electrons 300 may propagate in a direction opposite to the direction of the incident electron beam 100 and are collected by the objective lens 13, and the first signal electrons 200 and the second signal electrons 300 of different energies are collected to different positions and then dispersed. The energy of the second signal electrons 300 is larger than that of the first signal electrons 200, the scattering angle alpha 1 of the first signal electrons 200 with smaller energy is smaller than that of the second signal electrons 300 with larger energy, and the first signal electrons 200 are received by the first detector assembly 11 through the first through hole 121 on the second detector 12 after passing through the objective lens 13 due to the fact that the position of the first detector assembly 11 is higher than that of the second detector 12. The second, larger-energy signal electrons 300 cannot pass through the first through-hole 121, but are received by the second detector assembly 12, so that the first detector assembly 11 and the second detector assembly 12 detect the sample 14 to be measured based on the first signal electrons 200 and the second signal electrons 300, respectively.
In some embodiments, the first detector assembly 11 is provided with a second through hole 111, the aperture of the second through hole 111 is smaller than that of the first through hole 121, and the second through hole 111, the first through hole 121 and the objective lens 13 are coaxial and enable the incident electron beam 100 to pass through in sequence.
With continued reference to fig. 1, in some embodiments, the charged particle detection system may further include an electron source 16 disposed along the direction of the incident electron beam 100, the electron source 16 being disposed on a side of the first detector assembly 11 remote from the second detector assembly 12. The electron source 16 may be used to emit an incident electron beam 100 toward the sample 14 to be measured.
Illustratively, the electron source 16 may be a functional device (e.g., a thermal field emission electron gun system) for emitting an incident electron beam 100 towards the incident electron beam 100, the first detector assembly 11 being provided with a second through-hole 111 for passing the incident electron beam 100; in some embodiments, the through hole centers of the first through hole 121 and the second through hole 111 are on the same axis as the incident electron beam, so that the incident electron beam 100 can pass directly through the first through hole 121 and the second through hole 111 to reach the surface of the sample 14 to be measured.
Illustratively, the first through-hole 121 may be for passing through the incident electron beam 100 and the first signal electrons 200, and the second through-hole 111 may be for passing through the incident electron beam 100. In order for the first detector assembly 11 to receive as many first signal electrons 200 as possible and for the second detector assembly 12 to receive as many second signal electrons 300 as possible, the aperture of the first via 121 needs to be larger than the propagation diameter of the first signal electrons 200 at the first via 121, while the aperture of the first via 121 is smaller than the propagation diameter at the first via 121 when the second signal electrons 300 spread out at a minimum angle. The incident electron beam 100 may be considered as a parallel beam with a smaller propagation diameter, and the dispersion angle of the incident electron beam 100 may be approximately considered as zero, the second through-hole 111 being used only for passing the incident electron beam 100, the aperture of the second through-hole 111 being larger than the propagation diameter of the incident electron beam 100 and smaller than the propagation diameter of the first signal electrons 200 at the second through-hole 111 when the dispersion angle of the first signal electrons 200 is at a minimum. Since the propagation diameter of the incident electron beam 100 at the position of the first through hole 121 is smaller than the propagation diameter of the first signal electron 200 at the position of the first through hole 121, the aperture of the second through hole 111 should be smaller than the aperture of the first through hole. Based on the above arrangement, the aperture sizes of the first and second detector assemblies 11 and 12 can be reduced on the premise that the incident electron beam 100 can penetrate the first and second through holes 121 and 111 and the first signal electrons 200 can penetrate the first through hole 121, so that the detection areas of the first and second detector assemblies 11 and 12 can be increased, the volumes of the first and second detector assemblies 11 and 12 can be reduced, and the omission of the first and second signal electrons 200 and 300 can be reduced or avoided.
With continued reference to fig. 1, in some embodiments, a sample stage 15 for placing a sample 14 to be measured is further provided below the objective lens 13; the sample stage 15 is capable of applying a back voltage for decelerating the incident electron beam 100 and for accelerating and converging secondary electrons (first signal electrons 200) and backscattered electrons (second signal electrons 300).
Illustratively, the sample stage 15 may be connected by a preset negative power supply electrode, so that a reverse electric field is formed between the sample stage 15 and the objective lens 13, and a reverse voltage may be applied to secondary electrons (the first signal electrons 200) and back-scattered electrons (the second signal electrons 300), so as to energize, accelerate and collect the secondary electrons and the back-scattered electrons, so that the first signal electrons 200 and the back-scattered electrons may propagate in a direction opposite to the direction of the incident electron beam 100, and further propagate to the first detector assembly 11 and the second detector assembly 12 under the action of the objective lens 13, and are received by the first detector assembly 11 and the second detector assembly 12, respectively. In some embodiments, the energy of the backscattered electrons after the application of the back voltage by the sample stage 15 is greater than the energy of the secondary electrons, so the scatter angle α1 of the second secondary electrons accelerated to converge by the sample stage 15 and the objective lens 13 is smaller than the scatter angle α2 of the backscattered electrons. In some scenarios, the reverse voltage applied by the sample stage 15 may also slow down the incident electron beam 100 so that the incident electron beam may strike the surface of the sample 14 under test at different speeds.
With continued reference to FIG. 1, in some embodiments, the axial distance L1 between the first and second probe assemblies is no greater than 25mm (length units: millimeters).
In some embodiments, the distance L2 between the second detector assembly 12 and the sample stage 15 ranges from 135mm to 145mm. For example, if L1, L2 are too large, the propagation diameter of the secondary electrons and the backscattered electrons is larger when reaching the position of the detection surface of the corresponding detector assembly, and if the corresponding detector assembly can receive the secondary electrons and the backscattered electrons meeting the requirements, a larger detection surface is required, so that the volume of the corresponding detector assembly is increased. The minimum distance of L1 mainly considers that the disassembly and the maintenance are convenient, the installation interference problem is avoided, and the minimum distance of L2 mainly considers that the backscattered electrons are received by the corresponding detector assembly with optimal quality and efficiency. Based on this, the inventor obtains that the distance L1 between the first detector component 11 and the second detector component 12 is generally not more than 25mm through simulation calculation, and the distance L2 between the second detector component 12 and the sample stage 15 ranges from 135mm to 145mm. The detection area of the detection surface of the corresponding detector assembly is reduced when the received signal is optimal electronically, so that the volume of the corresponding detector assembly is reduced.
In some embodiments, through simulation calculation, the aperture of the first through hole is 3.5 mm-4 mm; the aperture of the second through hole is 0.2 mm-1 mm, and based on the arrangement, secondary electrons can pass through the first through hole to be received by the corresponding detector assembly with the best quality and efficiency, and back scattered electrons can be received by the corresponding detector assembly with the best quality and efficiency. In specific application, the method can be flexibly determined according to the setting relation of each electronic device and each part.
In some embodiments, the distance between the sample stage 15 and the pole piece of the objective lens 13 is no more than 3mm.
With continued reference to fig. 1, illustratively, an excessive distance L3 between the sample stage 15 and the pole piece of the objective lens 13 may result in an insufficient focusing of the incident electron beam acting on the sample to be measured, affecting the measurement result; meanwhile, secondary electrons (the first signal electrons 200) and back-scattered electrons (the second signal electrons 300) may not be better converged by the objective lens 13, and thus the sample 14 to be detected may not be better detected, so that the distance L3 between the sample stage 15 and the pole shoe of the objective lens 13 may be set to be not more than 3mm, so as to ensure that the objective lens 13 better converges.
The present application also provides a detection method, which is suitable for the charged particle detection system according to any one of the embodiments of the charged particle detection system, wherein the sample 14 to be detected is a nano device sample, and is placed on the sample stage 15, the first signal electrons 200 are secondary electrons, the second signal electrons 300 are back scattered electrons, the first detector assembly 11 at least comprises a semiconductor detector or a microchannel plate detector for detecting the secondary electrons, and the second detector assembly 12 at least comprises a scintillator detector for detecting the back scattered electrons; the detection method comprises the following steps:
applying a reverse voltage to the sample stage 15 to form a reverse electric field between the sample stage 15 and the objective lens 13;
controlling the incident electron beam 100 to reach the objective lens 13, and acting on the nano device sample to generate secondary electrons and back scattered electrons after converging; the objective lens 13 and the reverse voltage are controlled, so that secondary electrons and back scattered electrons are converged at different positions in the objective lens 13 under the acceleration convergence action of a reverse electric field, and then spread out of the objective lens 13 at different angles, wherein the spreading angle of the back scattered electrons is larger than that of the secondary electrons;
the secondary electrons are received by the corresponding semiconductor detector or microchannel plate detector above after passing through the first through hole 121 of the scintillator detector below outside the objective lens 13, and the backscattered electrons are received by the corresponding scintillator detector below outside the objective lens 13.
By way of example, the nano-device sample may be a chip wafer or the like, which may be desirable in some scenarios to measure semiconductor linewidths. Based on the above requirements, an operator can adopt the detection method provided by the application and use the charged particle detection system provided by the application to measure the semiconductor line width. For example, an operator may place and fix a chip wafer on a sample stage, then control the electron source 16 to emit an incident electron beam 100 toward the chip wafer, control the objective lens 13 to converge the incident electron beam 100, and control the sample stage 15 to apply a reverse voltage to the incident electron beam 100, and decelerate the incident electron beam 100 by a reverse electric field formed with the objective lens 13 to prevent the chip wafer from being damaged due to an excessively fast speed of the incident electron beam 100. The incident electron beam 100, after striking the wafer surface, may generate secondary electrons (i.e., first signal electrons 200) and backscattered electrons (i.e., second signal electrons 300), respectively. The back electric field can accelerate the secondary electrons and the back scattered electrons respectively, the secondary electrons and the back scattered electrons are scattered at different angles after being converged at different positions by the objective lens 13, the scattering angle alpha 2 of the back scattered electrons is larger, and the scattering angle alpha 1 of the secondary electrons is smaller. The backscattered electrons cannot pass through the first through hole 121 and are received by the scintillator detector (i.e. the second detector assembly 12), so as to detect the microstructure of the chip wafer, and the secondary electrons can pass through the first through hole 121 and are received by the semiconductor detector or the microchannel plate detector (i.e. the first detector assembly 11), so as to detect and analyze the surface morphology of the chip wafer, thereby completing the process of measuring the semiconductor linewidth of the chip wafer. In this process, the voltage applied by the electron source 16 may be fixed, and the operator need only adjust the reverse voltage applied by the sample stage 15 to enable the backscattered electrons to be received by the scintillator detector and the secondary electrons to be received by the semiconductor detector or microchannel plate detector to complete the probing of the chip wafer.
Compared with the existing detection method, the detection method provided by the application can control reverse voltage when detecting the sample to be detected, so that secondary electrons and back scattered electrons are accelerated and converged under the action of a reverse electric field respectively, and the first signal electrons and the second signal electrons are emitted again at different angles after being converged at different positions and are respectively received by the first detector assembly and the second detector assembly, so that the detection of the sample to be detected is finished, and a complicated debugging process is not needed.
FIG. 2 is a schematic view of a scanning electron microscope according to an embodiment of the disclosure; the scanning electron microscope comprises at least a charged particle detection system according to any of the above described charged particle detection system embodiments, and an electron optical column 17. The first detector component 11 and the second detector component 12 are fixed on the wall of the electron optical lens cone 17 through corresponding mounting pieces 18, and the objective lens 13 is arranged at the bottom of the electron optical lens cone 17;
a sample stage 15 is arranged below the objective 13, and the reverse voltage which can be applied by the sample stage 15 is 0-10 kV;
the sample stage 15 may be provided with a plurality of nail stages (not shown) for placing different samples 14 to be tested, and in specific application, different mounting positions can be designed on the sample stage 15 so as to detachably mount nail stages with different specifications, and the bottom of the sample stage 15 is provided with a high-precision five-axis mechanism (not shown) for driving the sample stage 15 to move within a predetermined distance range under any five-axis coordinate system;
the scanning electron microscope of the present application further includes a schottky thermal field emission type electron gun (i.e., electron source 16) disposed on top of the electron optical column 17 for generating an incident electron beam.
Illustratively, the electron optical column 17 is a functional device for housing optics such as the first detector assembly 11, the second detector assembly 12, etc., within which the incident electron beam 100, the first signal electrons 200, and the second signal electrons 300 may propagate, and the first detector assembly 11, the second detector assembly 12 may be fixed to the inside of the electron optical column 17 by the mount 18. The objective lens 13 and the sample stage 15 may be fixed to each other with respect to the electron optical column 17, and the manner of fixing may be similar to the above-described embodiment by the mount 18, or may be fixed by any other means, and is not limited thereto. Based on the above arrangement, the whole structure of the charged particle detection system can be compact and stable, so that the propagation paths of the first signal electrons 200 and the second signal electrons 300 meet the requirements, the first detector assembly 11 and the second detector assembly 12 can better receive the first signal electrons 200 and the second signal electrons 300, and stable and accurate detection of the sample 14 to be detected is realized.
As a specific example, the first detector assembly 11 may be an MCP detector (micro channel plate detector), and the second detector assembly 12 may be a scintillator detector, where the second through hole 111 of the MCP detector and the first through hole 121 of the scintillator detector are coaxially arranged on the central axis of the incident electron beam. The aperture of the first through hole 121 may be 4mm, the aperture of the second through hole 111 may be 1mm, and the distance between the MCP detector and the scintillator detector may be 25mm. The scintillator detector is used for detecting back scattering electrons (namely the second signal electrons 300), and the scintillator detector is 135-145 mm away from the sample stage. The MCP detector is used to detect secondary electrons (i.e., first signal electrons 200). The MCP detector and the scintillator detector are fixed to the inner wall of the electron optical barrel 17 by the mount 18, respectively. The sample stage 15 is located 3mm below the pole piece of the objective 13, and a reverse voltage of-7 kV is added.
The incident electron beam 100 impinges on the sample 14 to be measured of the sample stage 15 with a predetermined beam current, generating backscattered electrons and secondary electrons. The secondary electron energy is less than or equal to 50eV, the secondary electron energy is about 7keV after being accelerated by-7 kV reverse voltage, and the back scattered electron energy is about 8keV. The secondary electrons and the backscattered electrons are accelerated and converged by the magnetic field of the objective lens 13 and the reverse voltage of the sample stage 15, are converged at different positions due to the difference in energy therebetween, and then are scattered. The back scattering electrons are larger in scattering angle, more than half of the back scattering electrons are distributed between the half opening angles of 5 degrees to 1.5 degrees, and the central axis distribution is small. The secondary electrons are scattered little, almost 100% are distributed at half-aperture angles of 0-0.7 degrees, and almost all the secondary electrons are concentrated near the center axis. Secondary electrons may pass through the first through-hole 121 to be received and detected by the upper MCP detector, and backscattered electrons may be received and detected by the lower scintillator detector. In some scenarios, the operator may also fix the sample 14 to be measured through different nail tables according to different types of the sample 14 to be measured, and may also move the position of the sample table 15 through a five-axis mechanism, so that the sample table 15 may freely move within a preset distance range, so that the sample 14 to be measured may freely move within the preset distance range, and the operator may detect more positions of the sample 14 to be measured.
Compared with the existing scanning electron microscope, the scanning electron microscope provided by the application can randomly move the position of the sample to be detected through the five-axis mechanism so as to realize detection of different samples and the positions of different samples, and the scanning electron microscope provided by the application has the same technical characteristics as the charged particle detection system provided by the application, so that the same technical effects as the charged particle detection system provided by the application can be realized.
It should be noted that in this document, relational terms such as "first" and "second" and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The foregoing is only a specific embodiment of the application to enable those skilled in the art to understand or practice the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown and described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. Charged particle detection system, characterized in that it comprises:
the first detector component, the second detector component and the objective lens are sequentially arranged along the direction of the incident electron beam;
the first detector component is used for receiving first signal electrons generated by the incident electron beam acting on a sample to be detected;
the second detector component is used for receiving second signal electrons generated by the incident electron beam acting on the sample to be detected, and is provided with a first through hole, and the first signal electrons pass through the first through hole;
the objective lens is an electromagnetic lens and is used for converging the incident electron beam, the first signal electrons and the second signal electrons;
the energy of the second signal electrons is larger than that of the first signal electrons, and the scattering angle of the first signal electrons is smaller than that of the second signal electrons;
the second detector assembly is inclined towards one surface of the first detector assembly, and the thickness of the second detector assembly at a position closer to the region where the incident electron beam transmission path is located is smaller.
2. A charged particle detection system according to claim 1, wherein the first detector assembly is provided with a second through hole having a smaller aperture than the first through hole, the second through hole, the first through hole, the objective lens being coaxial and enabling the incident electron beam to pass in sequence.
3. A charged particle detection system according to claim 2 wherein the first signal electrons are secondary electrons and the second signal electrons are backscattered electrons.
4. A charged particle detection system according to claim 3, wherein the first detector assembly comprises a semiconductor detector or a microchannel plate detector for detecting secondary electrons and the second detector assembly comprises a scintillator detector for detecting backscattered electrons.
5. A charged-particle detection system according to claim 3, wherein a sample stage for placing the sample to be detected is further provided below the objective lens;
the sample stage is capable of applying a reverse voltage for decelerating the incident electron beam and for accelerating and converging the secondary electrons and the backscattered electrons.
6. The charged-particle detection system of claim 5, wherein an axial distance between the first detector assembly and the second detector assembly is no greater than 25mm; the distance between the second detector assembly and the sample stage ranges from 135mm to 145mm.
7. The charged-particle detection system of claim 6, wherein the aperture of said first through-hole is 3.5 mm-4 mm; the aperture of the second through hole is 0.2 mm-1 mm.
8. The charged-particle detection system of claim 2, wherein an aperture of the first via is greater than a propagation diameter of the first signal electrons at the first via and less than a propagation diameter of the second signal electrons at the first via at a minimum dispersion angle;
the aperture of the second via is greater than the propagation diameter of the incident electron beam and less than the propagation diameter of the first signal electron scattering angle at the second via.
9. A detection method, characterized in that the detection method is applied to the charged particle detection system according to any one of claims 1-8, the sample to be detected is a nano device sample, the first signal electrons are secondary electrons, the second signal electrons are back scattered electrons, the first detector assembly comprises a semiconductor detector or a microchannel plate detector for detecting the secondary electrons, and the second detector assembly comprises a scintillator detector for detecting the back scattered electrons; the detection method comprises the following steps: applying a reverse voltage to the sample stage to form a reverse electric field between the sample stage and the objective lens;
controlling the incident electron beam to reach the objective lens, and acting on the nano device sample after converging to generate the secondary electrons and the back scattered electrons; controlling the objective lens and the reverse voltage to enable the secondary electrons and the back scattered electrons to be converged at different positions in the objective lens under the acceleration convergence action of the reverse electric field, and then to be scattered out of the objective lens at different angles, wherein the scattering angle of the back scattered electrons is larger than that of the secondary electrons;
the secondary electrons are received by the corresponding semiconductor detector or microchannel plate detector after passing through the first through hole of the scintillator detector outside the objective lens, and the back scattered electrons are received by the corresponding scintillator detector outside the objective lens.
10. A scanning electron microscope, characterized in that the scanning electron microscope comprises at least a charged particle detection system according to any one of claims 1-8, and an electron optical column, the first detector assembly, the second detector assembly being fixed on the wall of the electron optical column by means of corresponding mounting elements, the objective being arranged at the bottom of the electron optical column;
a sample stage is arranged below the objective lens, and the reverse voltage which can be applied by the sample stage is-10 kV-0;
the sample table is provided with a plurality of nail tables for placing different samples to be tested, and the bottom of the sample table is provided with a high-precision five-axis mechanism for driving the sample table to move within a preset distance range under any five-axis coordinate system;
the electron optical lens further comprises a Schottky thermal field emission type electron gun arranged at the top of the electron optical lens barrel and used for generating the incident electron beam.
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| CN114256043A (en) * | 2020-12-02 | 2022-03-29 | 聚束科技（北京）有限公司 | Electron beam system |
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| EP0872873A2 (en) * | 1997-04-18 | 1998-10-21 | Hitachi, Ltd. | Scanning electron microscope |
| CN207425790U (en) * | 2017-11-21 | 2018-05-29 | 聚束科技（北京）有限公司 | A kind of low energy scanning electron microscope system |
| CN109300759A (en) * | 2017-11-21 | 2019-02-01 | 聚束科技（北京）有限公司 | Low energy scanning electron microscope system, scanning electron microscope system and sample detection method |
| CN110376229A (en) * | 2019-06-12 | 2019-10-25 | 聚束科技（北京）有限公司 | The scanning electron microscope and sample detection method for having combined type detection system |
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