CN115963133A

CN115963133A - Photoelectric detector

Info

Publication number: CN115963133A
Application number: CN202211686334.XA
Authority: CN
Inventors: 何伟; 胡继闯; 陈志明; 张景龙; 张子豪; 牛辉
Original assignee: Nak Microbeam Beijing Co ltd
Current assignee: Nak Microbeam Beijing Co ltd
Priority date: 2022-12-27
Filing date: 2022-12-27
Publication date: 2023-04-14

Abstract

The invention relates to a photoelectric detector, which belongs to the technical field of photoelectric detectors, can realize the simultaneous detection of cathode fluorescence signals and electronic signals, and greatly improves the collection efficiency of the fluorescence signals; the photoelectric detector comprises an electron source, an accelerating electrode, an objective lens, a reflection grating, a CL fluorescent detector and a BSE detector; the electron source is arranged in the center of the top to generate an electron beam; the accelerating electrode is arranged below the electron source; the objective lens is arranged below the accelerating electrode; the BSE detector is arranged below the objective lens; the sample to be scanned is arranged at the bottommost part; the accelerating electrode, the objective lens and the BSE detector are coaxially arranged, and an electron beam sequentially penetrates through the accelerating electrode, the objective lens and the BSE detector and then irradiates the surface of a sample; the BSE detector receives the backscattered electrons reflected by the sample; the reflection grating and the CL fluorescence detector are both arranged at the periphery of the BSE detector, and reflect photons transmitted from the upper surface of the sample to the CL fluorescence detector.

Description

Photoelectric detector

Technical Field

The invention relates to the technical field of photoelectric detectors, in particular to a photoelectric detector.

Background

The cathode fluorescence spectroscopy is a technique of irradiating ultraviolet, visible or infrared light by electron transition in a band gap or a defect position after bombarding a sample material with an electron beam. When the cathode fluorescence spectrum (CL) is combined with an electron microscope, the electron beam spot is extremely small, so that the nm-level spatial resolution can be realized, and the method has great advantages for researching sub-nanometer-level defect distribution, carrier dynamics, interface contrast analysis, stress strain and energy band structure in the material. Therefore, the physical properties of the material itself can be analyzed and reflected by the cathode fluorescence spectrum (CL).

The detection of the electron beam excited cathode fluorescence signal and the simultaneous imaging of the scanning electron microscope are difficult to achieve at present, and the defects on the surface of a sample can be detected more easily if the simultaneous imaging is carried out. At present, the cathode fluorescence detection is realized by a side cathode fluorescence detector, and the method has the following defects:

1. the side-type cathode fluorescence detector has a small receiving space angle and low collection efficiency;

2. the side-type cathode fluorescence detector occupies a large space and shields paths of reflected electrons such as secondary electrons and backscattered electrons, so that the scanning electron microscope cannot detect cathode fluorescence and signal electrons simultaneously;

3. the traditional use mode is a horizontal insertion type, and the collection efficiency is only 20%;

4. the flat side insertion method used in the chinese patent CN113675060a, however, the PD mirror is used as a reflector, mainly an ellipsoidal mirror and a mirror with edge polishing, which have the disadvantages of heavy weight, hard polishing, large installation difficulty, large occupied space, single fixed angle, and insufficient reflection efficiency.

Accordingly, there is a need to address the deficiencies of the prior art by developing a photodetector that addresses or mitigates one or more of the problems discussed above.

Disclosure of Invention

In view of this, the present invention provides a photodetector, which can achieve simultaneous detection of a cathode fluorescence signal and an electronic signal, and greatly improve the collection efficiency of the fluorescence signal.

The invention provides a photoelectric detector, which comprises an electron source, an accelerating electrode, an objective lens, a reflection grating, a CL fluorescence detector and a BSE detector, wherein the electron source is connected with the accelerating electrode;

the electron source is arranged in the center of the top and generates a vertical electron beam; the accelerating electrode is arranged below the electron source; the objective lens is arranged below the accelerating electrode; the BSE detector is arranged below the objective lens; the sample to be scanned is arranged at the bottommost part;

the accelerating electrode, the objective lens and the BSE detector are coaxially arranged, and the electron beam sequentially passes through the accelerating electrode, the objective lens and the BSE detector and then irradiates the surface of the sample;

the BSE detector receives the backscattered electrons reflected by the sample;

the reflection grating and the CL fluorescence detector are both arranged at the periphery of the BSE detector, and reflect photons transmitted from the upper surface of the sample to the CL fluorescence detector.

The above aspects and any possible implementations further provide an implementation in which the reflection grating is disposed below the objective lens and above the BSE detector; the CL fluorescence detector is arranged below the reflection grating.

The above aspects and any possible implementations further provide an implementation in which the reflection grating is disposed below the BSE detector and above the sample; the CL fluorescence detector is arranged above the reflection grating.

The foregoing aspects and any possible implementations further provide an implementation, where the reflecting surface of the reflection grating is provided with a plurality of arc surfaces.

In accordance with the foregoing aspect and any one of the possible implementations, there is further provided an implementation in which the arc-shaped surface of the reflection grating is covered with SiO ₂ And (3) a membrane.

The above aspects and any possible implementations further provide an implementation in which the BSE detector is covered with a fluorescent reflecting film at a lower end thereof;

and the upper surface of the sample, the fluorescent reflection film and the CL fluorescent detector are sequentially connected in an optical mode.

The above aspects and any possible implementations further provide an implementation in which the fluorescent reflecting film is a metal film, an aluminum film, or a silver film.

The above aspects and any possible implementations further provide an implementation in which the CL fluorescence detector is a CL color fluorescence detector; the CL color fluorescence detector comprises a plurality of PMT electron multipliers and color filters arranged at the front ends of the PMT electron multipliers.

The above aspect and any possible implementation manner further provide an implementation manner that the reflection grating is annular, and a longitudinal cross section of the annular is triangular-like or plate-like.

The aspect described above and any possible implementation form further provide an implementation form, wherein an included angle between the reflection surface of the reflection grating and a horizontal plane is not more than 60 °.

Compared with the prior art, one of the technical schemes has the following advantages or beneficial effects: the setting angle of the reflection grating can be adjusted according to the situation, and the reflection grating is provided with a plurality of arc-shaped reflection surfaces, so that photons with different angles around the sample can be reflected to the detector, the photon collection in a large range is realized, the collection efficiency of the photoelectric detector is improved, and the collection efficiency can reach 85%.

Of course, it is not necessary for any one product in which the invention is practiced to achieve all of the above-described technical effects simultaneously.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic overall structure of a first embodiment of a photodetector of the present invention;

FIG. 2 is a schematic diagram of the overall structure of a second embodiment of the photodetector of the present invention;

FIG. 3 is a schematic diagram of the overall structure of a third embodiment of the photodetector of the present invention;

FIG. 4 is a schematic view of the overall structure of a fourth embodiment of the photodetector of the present invention;

FIG. 5 is a schematic diagram of several reflective grating structures provided by the present invention;

FIG. 6 is a top view of a photodetector provided in accordance with an embodiment of the present invention;

fig. 7 is a top view of a photodetector provided in accordance with another embodiment of the present invention.

Wherein, in the figure:

1. an electron source; 2. an accelerating electrode; 3. an electron beam; 4. an objective lens; 5. a reflective grating; 6. a CL fluorescence detector; 7. a BSE detector; 8. a sample; 9. a CL color fluorescence detector; 10. a color filter; 11. a deflection device.

Detailed Description

For better understanding of the technical solutions of the present invention, the following detailed descriptions of the embodiments of the present invention are provided with reference to the accompanying drawings.

It should be understood that the described embodiments are only some embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In order to overcome the defects of the prior art, the invention provides the photoelectric detector, the plurality of polished arc-shaped gratings are combined into the reflection grating with the adjustable angle, the reflection grating reflects photons from different angles around the sample to the photon detector, the photon collection in a large range is realized, and the collection efficiency of the photoelectric detector is very high.

The photodetector includes:

an electron source for generating an electron beam;

an acceleration electrode for accelerating the electron beam emitted from the electron source;

an objective lens for focusing the electron beam;

a backscattered electron (BSE) detector for receiving electrons generated by the electron beam acting on the sample;

a CL fluorescence detector for receiving photons generated by the electron beam acting on the sample;

and the reflection grating is arranged below the Back Scattered Electron (BSE) detector and above the CL fluorescence detector, and can also be arranged below the Back Scattered Electron (BSE) detector and the CL fluorescence detector and used for reflecting photons generated on the sample to the CL fluorescence detector.

Wherein the CL fluorescence detector may be a CL color fluorescence detector for detecting light of a specific color, thereby obtaining a color CL. The CL color fluorescence detector can be realized by assembling a color filter at the front end of the CL color fluorescence detector, filters out other electrons and can be made into color CL. The CL fluorescence detector may also be exchanged for other detectors, such as a secondary electron detector.

The reflection grating is annular as a whole (shown in fig. 6 and 7)The overlooking structure of the reflection grating is annular), a plurality of reflection arc surfaces are arranged on the reflection surface of the reflection grating, and the reflection arc surfaces can be obtained by polishing or etching. SiO is covered on the reflecting arc surface of the reflecting grating ₂ The film is used for intercepting the reflected photons of the electrons, so that the electrons cannot penetrate through the oxide layer and cannot generate new electronic signals. The reflection grating may have a certain thickness, such as three reflection grating structures shown in fig. 5, the upper group and the lower group are both reflection grating structures having a certain thickness and having a triangle-like longitudinal section; the middle part is a plate-like reflecting grating structure without thickness. The reflecting surface of the reflecting grating may be a plurality of cambered surfaces as described above, or may be a step shape as shown in the bottom group of fig. 5. The whole thickness of the reflection grating can be determined according to actual conditions, and the reflection grating can be made to be thin, occupies small space, is easy to operate and is not easy to collide with other detectors. The included angle between the reflecting surface of the reflection grating and the horizontal line can be determined according to actual conditions and can be any angle. When the device is used, the reflection grating is inserted in a flat mode, the angle is adjustable, and collision with a sample is avoided when the device is close to the angle. The outer side direction of the whole reflection surface of the reflection grating is at an included angle of not more than 60 degrees with the horizontal plane.

The inclined reflection structure with the plurality of reflection cambered surfaces of the reflection grating can reflect photons with different angles to the CL fluorescence detector, thereby increasing the collection efficiency.

Example 1:

as shown in fig. 1 and 2, two types of photodetectors are provided for the present embodiment.

In this embodiment, the electron source 1 is arranged at the center of the top, generating a vertically oriented electron beam 3. The accelerating electrode 2 is disposed below the electron source 1. The objective lens 4 is disposed below the accelerating electrode 2. The BSE detector 7 is arranged below the objective lens 4. Sample 8 is placed in the bottommost center. The accelerating electrode 2, the objective lens 4 and the BSE detector 7 are coaxially arranged, the electron beam 3 sequentially penetrates through the accelerating electrode 2, the objective lens 4 and the BSE detector 7 and then irradiates the surface of the sample 8, and backscattered electrons reflected by the sample 8 are received by the BSE detector 7 to realize backscattered electron detection.

The periphery of the BSE detector 7 is provided with a reflection grating 5, and a CL fluorescence detector 6 is arranged below the reflection grating 5. The reflection grating 5 reflects photons generated on the sample 8 to the CL fluorescence detector 6 for detection by the CL fluorescence detector 6.

The BSE detector 7 is in a circular ring shape as a whole, the CL fluorescence detector 6 is also in a circular ring shape as a whole, and the reflection grating 5 is also in a circular ring shape as a whole. The BSE detector 7, the reflection grating 5, and the CL fluorescence detector 6 are coaxial with each other, and the axis is the center of the main optical axis of the electron beam generated by the electron source 1.

According to the embodiment, the reflection grating 5 consisting of a plurality of cambered rings is arranged above the periphery of the sample to reflect photons around the sample 8 to the CL fluorescence detector 6, so that the photons are collected in a large range, and the CL fluorescence detector 6 is high in receiving efficiency. And the lower surface of the reflection grating is covered with SiO ₂ The membrane can not intercept electrons, can not penetrate an oxide layer, and can not generate new electronic signals, thereby influencing the quality of received signals. The CL fluorescence detector 6 is annular, the CL fluorescence detector 6 may be an annular formed by connecting a plurality of sub-photon detectors, the plurality of sub-photon detectors are connected in sequence to form the annular CL fluorescence detector 6 with a through hole in the middle, and the through hole in the middle allows an electron beam to pass through so as to irradiate on a sample.

In this embodiment, the CL fluorescence detector 6 is located between the electron source 1 and the sample 8, specifically, the CL fluorescence detector 6 is located below the BSE detector 7 and above the sample, and the CL fluorescence detector 6 is horizontally disposed and located below the reflection grating 5, and just receives photons reflected by the reflection grating 5 to realize detection. The reflection grating 5 in fig. 1 has a structure with a triangular-like cross section and a plurality of arc-shaped reflecting surfaces, and the reflection grating 5 in fig. 2 has a plate-like structure and a plurality of arc-shaped reflecting surfaces. When the cross-section is the preparation of triangle-like's reflection grating, polish out an inclined plane with the reflection grating body of cuboid earlier with the polisher, then polish out two at least arcwall faces on this inclined plane, the arcwall face is whole all to be the annular, and the arcwall face can reflect the photon that each angle incidence comes to increase CL fluorescence detector 6 collects the scope of photon, improves receiving efficiency.

The electron source 1 is divided into a field emission source and a thermal emission source, the field emission source is divided into a thermal field and a cold field, and the thermal emission source is divided into a tungsten filament, lanthanum hexaboride and the like. The electron source 1 in the present invention may be any one of the electron sources 1 for generating an electron beam. The electron beam 3 acting on the sample 8 generates secondary electrons, backscattered electrons, auger electrons, cathode fluorescence, X-rays, and the like. The CL fluorescence detector 6 is used to receive the cathode fluorescence generated by the electron beam acting on the sample.

In a preferred embodiment, a thin film capable of reflecting fluorescence, such as a metal film, an aluminum film, or a silver film, is coated on the lower end of the BSE detector 7, and photons incident on the lower surface of the BSE detector 7 are reflected to the CL fluorescence detector 6 through the reflection film, thereby increasing the receiving efficiency of the CL fluorescence detector 6.

The accelerating electrode 2 is an anode along the emission direction of the electron beam and is used for forming an electric field to increase the moving speed of the electron beam. The objective lens 4 is used for controlling the beam current size and the electron beam advancing direction of the electron beam emitted by the electron source 1. The objective lens 4 focuses the electron beam on the sample and scans it. The objective lens may be a magnetic lens, or an electric lens, or an electromagnetic compound lens.

The photodetector of the present invention is further provided with a deflection device 11 for changing the moving direction of the electron beam before being incident on the sample, and is capable of generating a scanning field in any deflection direction. The deflection means 11 may be magnetic deflection means or electrical deflection means.

Example 2:

this embodiment differs from embodiment 1 in the arrangement positions of the CL fluorescence detector 6 and the reflection grating 5. In this embodiment, as shown in fig. 3, the CL fluorescence detector 6 is located below the objective lens 4 and above the BSE detector 7, and the positional relationship between the CL fluorescence detector 6 and the BSE detector 7 in the horizontal direction is: the CL fluorescence detector 6 is located outside the BSE detector 7. The reflection grating 5 is positioned below the CL fluorescence detector and the BSE detector 7, and the integral reflection surface and the horizontal plane form an included angle of not more than 60 degrees.

Example 3:

this embodiment differs from embodiment 1 in that the CL fluorescence detector 6 is replaced with a CL color fluorescence detector 9. The CL color fluorescence detector 9 is implemented by placing a color filter 10 at the front end of the conventional PMT electron multiplier, as shown in fig. 4. Because the front end of the PMT electron multiplier is provided with a layer of glass, the PMT electron multiplier can play a role in filtering electrons, only collects the photons, and improves the acquisition quality of a fluorescence image. In this embodiment, the number of the PMT electron multipliers may be multiple, and the color filters 10 at the front ends of the different PMT electron multipliers are different in color, so that the multiple PMT electron multipliers can detect light of different colors, respectively, thereby increasing the collection efficiency and improving the image resolution.

The above provides a detailed description of a photodetector provided in the embodiments of the present application. The above description of the embodiments is only for the purpose of helping to understand the method of the present application and its core idea; meanwhile, for a person skilled in the art, according to the idea of the present application, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present application.

It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a good or system that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such good or system. Without further limitation, an element defined by the phrase "comprising a … …" does not exclude the presence of another identical element in a good or system that comprises the element. "substantially" means within an acceptable error range, that a person skilled in the art can solve the technical problem within a certain error range to substantially achieve the technical effect.

The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the description of the invention and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. In the present application, the terms "upper", "lower", "left", "right", "inner", "outer", "horizontal", "vertical", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings. Some of the above terms may be used to indicate other meanings in addition to orientation or positional relationship, for example, the term "on" may also be used to indicate some kind of dependency or connection relationship in some cases. The specific meaning of these terms in this application will be understood by those of ordinary skill in the art as appropriate. The term "and/or" as used herein is merely a relationship that describes an associated object, meaning that three relationships may exist, e.g., a and/or B, may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter associated objects are in an "or" relationship.

Claims

1. A photoelectric detector is characterized by comprising an electron source, an accelerating electrode, an objective lens, a reflection grating, a CL fluorescence detector and a BSE detector;

the BSE detector receives the backscattered electrons reflected by the sample;

2. The photodetector of claim 1, wherein the reflective grating is disposed below the objective lens and above the BSE detector; the CL fluorescence detector is arranged below the reflection grating.

3. The photodetector of claim 1, wherein the reflective grating is disposed below the BSE detector, above the sample; the CL fluorescence detector is arranged above the reflection grating.

4. The photodetector of claim 1, wherein the reflective surface of the reflective grating has a plurality of curved surfaces.

5. The photodetector of claim 4, wherein the curved surface of the reflective grating is covered with SiO ₂ And (3) a film.

6. The photodetector of claim 1, wherein the BSE detector is coated with a fluorescent reflective film at its lower end;

7. The photodetector according to claim 6, wherein the fluorescent reflecting film is a metal film, an aluminum film, or a silver film.

8. The photodetector of claim 1, wherein the CL fluorescence detector is a CL color fluorescence detector; the CL color fluorescence detector comprises a plurality of PMT electron multipliers and color filters arranged at the front ends of the PMT electron multipliers.

9. The photodetector of claim 1, wherein the reflective grating is annular, and a longitudinal cross-section of the annular shape is triangular-like or plate-like.

10. The photodetector of claim 4, wherein the angle between the reflective surface of the reflective grating and the horizontal plane is not more than 60 °.