A photodetector

Abstract

This invention relates to a photodetector, belonging to the field of photodetector technology, capable of simultaneously detecting cathodoluminescence and electron signals, and greatly improving the collection efficiency of fluorescence signals. The photodetector includes an electron source, an accelerating electrode, an objective lens, a reflective grating, a CL fluorescence detector, and a BSE detector. The electron source is positioned at the top center to generate an electron beam. The accelerating electrode is positioned below the electron source. The objective lens is positioned below the accelerating electrode. The BSE detector is positioned below the objective lens. The sample to be scanned is positioned at the bottom. The accelerating electrode, the objective lens, and the BSE detector are coaxially arranged, and the electron beam passes through them sequentially before irradiating the surface of the sample. The BSE detector receives backscattered electrons reflected from the sample. The reflective grating and the CL fluorescence detector are both positioned around the BSE detector and reflect photons transmitted from the upper surface of the sample to the CL fluorescence detector.

Description

Technical Field

[0001] This invention relates to the field of photodetector technology, and more particularly to a photodetector. Background Technology

[0002] Cathodoluminescence (CL) spectroscopy is a technique that utilizes electron beams to bombard sample materials, causing electron transitions at band gaps or defect sites, resulting in the emission of ultraviolet, visible, or infrared light. When CL spectroscopy is combined with electron microscopy, the electron beam spot is extremely small, thus achieving nanometer-level spatial resolution. This offers significant advantages for studying sub-nanometer-level defect distribution, carrier dynamics, interface contrast analysis, stress-strain analysis, and band structure in materials. Therefore, CL spectroscopy can analyze and reflect the inherent physical properties of materials.

[0003] Simultaneous detection of electron beam-excited cathodoluminescence signals and scanning electron microscopy imaging is currently difficult to achieve. Simultaneous imaging would make it easier to detect defects on the sample surface. Currently, cathodoluminescence detection is achieved using a side-mounted cathodoluminescence detector, but this method has several drawbacks:

[0004] 1. Side-mounted cathodoluminescence detectors have a small receiving angle and low collection efficiency;

[0005] 2. Side-mounted cathodoluminescence detectors occupy a large space and block the paths of reflected electrons such as secondary electrons and backscattered electrons, making it impossible for scanning electron microscopes to detect cathodoluminescence and signal electrons simultaneously.

[0006] 3. The traditional method of use is a flat insertion method, which has a collection efficiency of only 20%.

[0007] 4. The flat-side insertion method used in Chinese patent CN113675060A uses PD mirrors as reflectors, mainly ellipsoidal mirrors and rimmed mirrors. They are heavy, difficult to polish, difficult to install, occupy a lot of space, have a single fixed angle, and the reflection efficiency is not high enough.

[0008] Therefore, it is necessary to study a photodetector to address the shortcomings of existing technologies and to solve or mitigate one or more of the aforementioned problems. Summary of the Invention

[0009] In view of this, the present invention provides a photodetector that can simultaneously detect cathode fluorescence signals and electronic signals, and greatly improves the collection efficiency of fluorescence signals.

[0010] This invention provides a photodetector, which includes an electron source, an accelerating electrode, an objective lens, a reflective grating, a CL fluorescence detector, and a BSE detector;

[0011] The electron source is positioned at the top center, generating a vertical electron beam; the accelerating electrode is positioned below the electron source; the objective lens is positioned below the accelerating electrode; the BSE detector is positioned below the objective lens; and the sample to be scanned is positioned at the bottom.

[0012] The accelerating electrode, the objective lens, and the BSE detector are coaxially arranged, and the electron beam passes through the accelerating electrode, the objective lens, and the BSE detector in sequence before irradiating the surface of the sample;

[0013] The BSE detector receives backscattered electrons reflected from the sample;

[0014] Both the reflective grating and the CL fluorescence detector are disposed around the BSE detector, and reflect photons transmitted from the upper surface of the sample onto the CL fluorescence detector.

[0015] In addition to the aspects described above and any possible implementations, a further implementation is provided in which the reflective grating is disposed below the objective lens and above the BSE detector; and the CL fluorescence detector is disposed below the reflective grating.

[0016] In addition to the aspects described above and any possible implementations, a further implementation is provided in which the reflective grating is disposed below the BSE detector and above the sample; and the CL fluorescence detector is disposed above the reflective grating.

[0017] In addition to the aspects and any possible implementations described above, a further implementation is provided in which a plurality of arc-shaped surfaces are formed on the reflective surface of the reflective grating.

[0018] In addition to the aspects described above and any possible implementation, a further implementation is provided in which a SiO2 film is coated on the arcuate surface of the reflective grating.

[0019] In addition to the aspects and any possible implementations described above, a further implementation is provided in which the lower end of the BSE detector is covered with a fluorescent reflective film;

[0020] The upper surface of the sample, the fluorescent reflective film, and the CL fluorescence detector are sequentially optically connected.

[0021] In addition to the aspects and any possible implementations described above, a further implementation is provided in which the fluorescent reflective film is a metal film, an aluminum film, or a silver film.

[0022] In addition to the aspects and any possible implementations described above, a further implementation is provided in which the CL fluorescence detector is a CL color fluorescence detector; the CL color fluorescence detector includes a plurality of PMT electron multipliers and a color filter disposed at the front end of the PMT electron multipliers.

[0023] In addition to the aspects and any possible implementations described above, a further implementation is provided in which the reflective grating is annular, and the longitudinal cross-section of the annular grating is triangular or plate-like.

[0024] In addition to the aspects described above and any possible implementation, a further implementation is provided in which the angle between the reflective surface of the reflective grating and the horizontal plane does not exceed 60°.

[0025] Compared with the prior art, one of the above technical solutions has the following advantages or beneficial effects: the setting angle of the reflective grating of the present invention can be adjusted according to the situation, and it has multiple arc-shaped reflective surfaces, which can reflect photons at different angles around the sample to the detector, realize large-scale photon collection, improve the collection efficiency of the photodetector, and the collection efficiency can reach 85%.

[0026] Of course, any product implementing this invention does not necessarily need to achieve all of the technical effects described above at the same time. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the overall structure of the first embodiment of the photodetector of the present invention;

[0029] Figure 2 This is a schematic diagram of the overall structure of the second embodiment of the photodetector of the present invention;

[0030] Figure 3 This is a schematic diagram of the overall structure of the third embodiment of the photodetector of the present invention;

[0031] Figure 4 This is a schematic diagram of the overall structure of the fourth embodiment of the photodetector of the present invention;

[0032] Figure 5 These are schematic diagrams of several reflective grating structures provided by the present invention;

[0033] Figure 6This is a top view of a photodetector provided in one embodiment of the present invention;

[0034] Figure 7 This is a top view of a photodetector provided in another embodiment of the present invention.

[0035] In the figure:

[0036] 1. Electron source; 2. Accelerating electrode; 3. Electron beam; 4. Objective lens; 5. Reflection grating; 6. CL fluorescence detector; 7. BSE detector; 8. Sample; 9. CL color fluorescence detector; 10. Color filter; 11. Deflection device. Detailed Implementation

[0037] To better understand the technical solution of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0038] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0039] To overcome the shortcomings of the prior art, this invention provides a photodetector composed of multiple arc-shaped gratings combined to form an angle-adjustable reflective grating. The reflective grating reflects photons from different angles around the sample onto the photon detector, achieving large-scale photon collection and resulting in very high collection efficiency for the photodetector.

[0040] The photodetector includes:

[0041] An electron source, used to generate an electron beam;

[0042] Accelerating electrodes are used to accelerate the electron beam emitted by an electron source.

[0043] Objective lens, used to focus the electron beam;

[0044] Backscattered electron (BSE) detector, used to receive electrons generated when an electron beam acts on the sample;

[0045] A CL fluorescence detector is used to receive photons generated when an electron beam acts on the sample.

[0046] A reflective grating is positioned below the backscattered electron (BSE) detector and above the CL fluorescence detector, or it can be positioned below both the BSE detector and the CL fluorescence detector. It is used to reflect photons generated on the sample onto the CL fluorescence detector.

[0047] The CL fluorescence detector can be a CL color fluorescence detector, used to detect light of a specific color, thus obtaining a colored CL. A CL color fluorescence detector can be implemented by mounting a color filter at the front end of the CL fluorescence detector, filtering out other electrons and creating a colored CL. The CL fluorescence detector can also be replaced with other detectors, such as a secondary electron detector.

[0048] The reflective grating is generally ring-shaped. Figure 6 and Figure 7 The image shows a ring-shaped top view of the reflective grating. Its reflective surface has several reflective arc surfaces, which can be obtained through grinding or etching. Each reflective arc surface of the grating is coated with a SiO2 film to intercept and reflect photons, preventing electrons from penetrating the oxide layer and thus avoiding the generation of new electronic signals. The reflective grating can have a certain thickness, such as... Figure 5 The three reflective grating structures shown are as follows: the top and bottom groups are reflective grating structures with a certain thickness and a longitudinal section resembling a triangle; the middle one is a plate-like reflective grating structure without thickness. The reflecting surface of the reflective grating can be one of the aforementioned curved surfaces, or it can be... Figure 5 The bottom group shows a stepped structure. The overall thickness of the reflective grating can be determined according to the actual situation; it can be made very thin, occupying little space, easy to operate, and less prone to collision with other detectors. The angle between the reflective surface of the grating and the horizontal line can be determined according to the actual situation and can be any angle. In use, the reflective grating is inserted horizontally, the angle is adjustable, and collision with the sample is avoided when approaching. The outer direction of the overall reflective surface of the grating has an angle of no more than 60° with the horizontal plane.

[0049] The present invention provides a reflective structure with several reflective arc surfaces, in which the reflective grating is placed at an angle, which can reflect photons at different angles onto the CL fluorescence detector, thereby increasing the collection efficiency.

[0050] Example 1:

[0051] like Figure 1 and Figure 2 As shown, these are two types of photodetectors provided in this embodiment.

[0052] In this embodiment, electron source 1 is positioned at the top center, generating a vertical electron beam 3. Accelerating electrode 2 is positioned below electron source 1. Objective lens 4 is positioned below accelerating electrode 2. BSE detector 7 is positioned below objective lens 4. Sample 8 is positioned at the bottom center. Accelerating electrode 2, objective lens 4, and BSE detector 7 are coaxially arranged. Electron beam 3 passes sequentially through accelerating electrode 2, objective lens 4, and BSE detector 7 before irradiating the surface of sample 8. Backscattered electrons reflected by sample 8 are received by BSE detector 7, achieving backscattered electron detection.

[0053] A reflective grating 5 is arranged around the BSE detector 7, and a CL fluorescence detector 6 is arranged below the reflective grating 5. The reflective grating 5 reflects the photons generated on the sample 8 to the CL fluorescence detector 6 for reception and detection.

[0054] The BSE detector 7 is circular in shape, as are the CL fluorescence detector 6 and the reflection grating 5. The BSE detector 7, the reflection grating 5, and the CL fluorescence detector 6 are coaxial, with the axis being the center of the principal optical axis of the electron beam generated by the electron source 1.

[0055] This embodiment achieves wide-area photon collection by placing a reflective grating 5 composed of multiple arc-shaped rings above the sample 8, reflecting photons from around the sample 8 onto the CL fluorescence detector 6. The CL fluorescence detector 6 has high receiving efficiency. Furthermore, the lower surface of the reflective grating is coated with a SiO2 film, which intercepts electrons, preventing them from penetrating the oxide layer and generating new electron signals that would affect the quality of the received signal. The CL fluorescence detector 6 is ring-shaped and can be formed by connecting multiple sub-photon detectors. These sub-photon detectors are connected sequentially to form a ring-shaped CL fluorescence detector 6 with a central through-hole, through which the electron beam passes to irradiate the sample.

[0056] 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. The CL fluorescence detector 6 is horizontally positioned below the reflective grating 5, precisely receiving photons reflected by the reflective grating 5 to achieve detection. Figure 1 The reflective grating 5 in the image has a triangular cross-section and several arc-shaped reflective surfaces. Figure 2 The reflective grating 5 in the image is a plate-like structure with several arc-shaped reflective surfaces. During the fabrication of the triangular-shaped reflective grating, a cuboid reflective grating body is first polished with a grinding machine to create a bevel. Then, at least two arc-shaped surfaces are polished on this bevel. All arc-shaped surfaces are annular in shape. These arc-shaped surfaces can reflect photons incident from various angles, thereby increasing the photon collection range of the CL fluorescence detector 6 and improving the receiving efficiency.

[0057] Electron source 1 is divided into field emission source and thermal emission source. Field emission source is further divided into hot field and cold field types, while thermal emission source can be tungsten filament, lanthanum hexaboride, etc. In this invention, electron source 1 can be any type of electron source 1 used to generate an electron beam. Electron beam 3 acting on sample 8 will generate secondary electrons, backscattered electrons, Auger electrons, cathodoluminescence, and X-rays. CL fluorescence detector 6 is used to receive the cathodoluminescence generated by the electron beam acting on the sample.

[0058] In a preferred embodiment, the lower end of the BSE detector 7 is covered with a thin film such as a metal film, aluminum film, or silver film that can reflect fluorescence. Photons incident on the lower surface of the BSE detector 7 are reflected by the aforementioned reflective film to the CL fluorescence detector 6, thereby increasing the receiving efficiency of the CL fluorescence detector 6.

[0059] Accelerating electrode 2 serves as the anode, positioned along the electron beam emission direction to create an electric field that increases the electron beam's velocity. Objective lens 4 controls the beam current and direction of the electron beam emitted from electron source 1. Objective lens 4 focuses the electron beam onto the sample and performs scanning. The objective lens can be a magnetic lens, an electric lens, or an electromagnetic compound lens.

[0060] The photodetector of the present invention is further provided with a deflection device 11, which is used to change the direction of motion of the electron beam before it is incident on the sample, and can generate a scanning field with arbitrary deflection direction. The deflection device 11 can be a magnetic deflection device or an electric deflection device.

[0061] Example 2:

[0062] The difference between this embodiment and Embodiment 1 lies in the placement of the CL fluorescence detector 6 and the reflective grating 5. In this embodiment, as... Figure 3 As shown, the CL fluorescence detector 6 is located below the objective lens 4 and above the BSE detector 7. The horizontal positional relationship between the CL fluorescence detector 6 and the BSE detector 7 is that the CL fluorescence detector 6 is located outside the BSE detector 7. The reflective grating 5 is located below both the CL fluorescence detector and the BSE detector 7, and the overall reflective surface has an angle of no more than 60° with the horizontal plane.

[0063] Example 3:

[0064] The difference between this embodiment and Embodiment 1 is 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 an existing PMT electron multiplier, such as... Figure 4 As shown. Because the front end of the PMT electron multiplier has a layer of glass, it can filter electrons and collect only photons, thus improving the acquisition quality of the fluorescence image. In this embodiment, there can be multiple PMT electron multipliers, and the color filters 10 at the front end of different PMT electron multipliers are different colors, so that multiple photomultipliers can detect light of different colors, increasing collection efficiency and improving image resolution.

[0065] The foregoing has provided a detailed description of a photodetector provided in the embodiments of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this application; furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

[0066] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the product or system including said element. "Substantially" means within an acceptable margin of error, indicating that a person skilled in the art can resolve the technical problem and substantially achieve the technical effect within a certain margin of error.

[0067] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. In this application, the terms “upper,” “lower,” “left,” “right,” “inner,” “outer,” “horizontal,” and “vertical,” etc., indicate orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings. Some of the above terms may also be used to indicate other meanings besides orientation or positional relationships; for example, the term “upper” may in some cases indicate a dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application according to the specific circumstances. The term “and / or” used herein is merely a description of the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone. Additionally, the character “ / ” in this document generally indicates that the preceding and following related objects have an “or” relationship.

Claims

1. A photodetector, comprising: The photoelectric detector comprises an electron source, an acceleration electrode, an objective lens, a reflection grating, a CL fluorescence detector and a BSE detector; The electron source is arranged at the top center to generate a vertical electron beam; the acceleration electrode is arranged below the electron source; the objective lens is arranged below the acceleration electrode; the BSE detector is arranged below the objective lens; and the sample to be scanned is arranged at the bottom. The acceleration electrode, the objective lens and the BSE detector are coaxially arranged, and the electron beam sequentially passes through the acceleration electrode, the objective lens and the BSE detector and then irradiates the surface of the sample; The BSE detector receives 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 from the upper surface of the sample to the CL fluorescence detector; The reflection grating is arranged below the objective lens and above the BSE detector; and the CL fluorescence detector is arranged below the reflection grating. The reflection surface of the reflection grating is provided with a plurality of arc surfaces.

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

3. The photodetector of claim 1, wherein, The arc surface of the reflection grating is covered with a SiO2 film.

4. The photodetector of claim 1, wherein, The lower end of the BSE detector is covered with a fluorescent reflection film. The upper surface of the sample, the fluorescent reflection film and the CL fluorescence detector are sequentially optically connected.

5. The photodetector of claim 4, wherein, The fluorescent reflection film is a metal film, an aluminum film or a silver film.

6. The photodetector of claim 1, wherein, The CL fluorescence detector is a CL color fluorescence detector; and 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.

7. The photodetector of claim 1, wherein, The reflection grating is annular, and the longitudinal section of the annular reflection grating is triangular or plate-shaped.

8. The photodetector of claim 1, wherein, The included angle between the reflection surface of the reflection grating and the horizontal plane is not more than 60°.

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