Electronic detector

Abstract

An electron detector comprises a light guide and a scintillator. Wherein the light guide is provided with a front end part, the surface of the front end part comprises a first surface of a quarter spherical surface structure and a second surface of a plane structure, and the surface of the scintillator comprises a light emergent surface and an electron incident surface which are opposite to each other; the light emitting surface is attached to the second surface, so that a light signal generated by the scintillator enters the front end part, and the first surface reflects the light signal. The first surface of the spherical structure is used as a reflecting surface for reflecting an optical signal in the light guide for the first time, so that the incident angle of the next reflection of the reflected light can be effectively controlled, and support is provided for ensuring that the optical signal can be totally reflected in the light guide; the purposes of reducing light loss and improving transmission efficiency by increasing total reflection in the light guide process are achieved; meanwhile, the front end part adopts a spherical surface structure, so that the processing difficulty of the light guide is simplified, and the optimal light transmission efficiency can be obtained by adjusting and determining the position of the scintillator at the front end part.

Description

Technical Field

[0001] The invention relates to the technical field of scanning electron microscopes, and in particular to an electron detector. Background Art

[0002] Scanning Electron Microscope (SEM), also known as SEM, is a microscopic analysis device that uses various physical signals stimulated by a focused electron beam scanning the surface of a sample to modulate imaging. Compared with traditional optical imaging, SEM can provide nanometer or even sub-nanometer resolution, and plays an indispensable role in defect detection and dimension measurement in the production process of semiconductor devices.

[0003] In scanning electron microscopes, a scintillator plus light guide in-tube electron detection scheme is often used to detect secondary electrons or backscattered electrons generated based on sample surface characteristics (such as morphology, material, etc.); compared with other detection schemes, the scintillator plus light guide electron detector not only has relatively fast response speed, relatively low noise level, relatively long life, etc., but can also be made into a multi-quadrant in-tube electron detector as needed. However, due to the limitations of the optical properties and processing technology of scintillators and light guides, the relevant electron detectors have problems such as large light energy loss and low light energy transmission efficiency in the process of detecting secondary electrons or backscattered electrons to form images, which also affects the quality of imaging. Summary of the invention

[0004] The main technical problem solved by the present invention is to provide an electronic detector which can improve the light transmission efficiency and reduce the difficulty of processing and assembly process.

[0005] In one embodiment, an electron detector is provided, comprising a light guide and a scintillator, wherein the light guide has a front end portion, the surface of the front end portion comprises a first surface and a second surface, the first surface is a quarter spherical structure, the second surface is a plane structure, and the surface of the scintillator comprises a light exit surface and an electron incident surface which are opposite to each other in the direction of the central axis of the scintillator; The light emitting surface is attached to the second surface so that the light signal generated by the scintillator enters the front end portion; and the first surface is used to reflect the light signal.

[0006] In one embodiment, the front end portion is a quarter sphere, and the second surface is a semicircular plane structure connected to the first surface; wherein, within the plane where the second surface is located, the scintillator is located at a position that enables the light signal reflected by the first surface to be totally reflected in the light guide.

[0007] In one embodiment, the scintillator has a first through hole, and the first through hole is arranged along the central axis to penetrate the light exit surface and the electron incident surface; the light exit surface is an annular plane structure surrounding the first through hole, and the diameter of the arc edge of the light exit surface is smaller than the radius of the arc edge of the second surface; In the direction of the axis of symmetry of the second surface, the position of the scintillator is between the first position and the second position; wherein the first position is the position where the arc edge of the first through hole is circumscribed to the arc edge of the second surface, and the second position is the position where the center axis, the axis of symmetry and the straight edge of the second surface intersect.

[0008] In one embodiment, in the direction of the symmetry axis, the scintillator is located at a position where the arc edge of the light emitting surface is inscribed in the arc edge of the second surface.

[0009] In one embodiment, the front end portion has a second through hole, the second through hole is arranged to penetrate the first surface and the second surface in a direction perpendicular to the second surface, the second through hole is coaxially connected to the first through hole to form an electron beam channel; a shielding tube is passed through the electron beam channel, or the channel wall of the electron beam channel is covered with a shielding film.

[0010] In one embodiment, the scintillator is a truncated cone, the light emitting surface is the lower bottom surface of the truncated cone, the electron incident surface is the upper bottom surface of the truncated cone, and the inclination angle of the truncated cone is less than 55°.

[0011] In one embodiment, the light guide further comprises a transition portion and a rear end portion, wherein the transition portion is connected between the front end portion and the rear end portion; wherein: The transition portion is a half cylinder, the surface of the transition portion includes a third surface with a semicircular curved surface structure and a fourth surface with a planar structure, the rear end portion is a cylinder, the surface of the cylinder includes a fifth surface with a full circular curved surface structure, the third surface is connected between the first surface and the fifth surface, and the second surface is connected to the fourth surface; the radius of the front end portion, the radius of the transition portion and the radius of the rear end portion are equal; Or the light guide also has a rear end portion connected to the front end portion, the rear end portion is a cylinder, the surface of the rear end portion includes a fifth surface with a full circular curved structure, the fifth surface is connected to the first surface, and the radius of the rear end portion is equal to the radius of the front end portion.

[0012] In one embodiment, the ratio of the diameter of the front end portion to the diameter of the light emitting surface is between 1.4 and 4.3.

[0013] In one embodiment, the first surface, the area of ​​the second surface not attached to the light exit surface, and the surface of the scintillator connected between the light exit surface and the electron incident surface are covered with a first film layer, and the first film layer is used to reflect light signals; And / or the electron incident surface is covered with a second film layer, and the second film layer is used to allow electrons to pass through and reflect light signals.

[0014] In one embodiment, the thickness of the second film layer is smaller than the thickness of the first film layer.

[0015] The electronic detector according to the above embodiment includes a light guide and a scintillator; wherein the light guide has a front end portion, the surface of the front end portion includes a first surface of a quarter spherical structure and a second surface of a planar structure, and the surface of the scintillator includes a light exit surface and an electron incident surface opposite to each other; the light exit surface is attached to the second surface so that the light signal generated by the scintillator enters the front end portion, and the first surface reflects the light signal. By using the first surface of the spherical structure as the reflection surface where the light signal is first reflected in the light guide, the incident angle of the next reflection of the reflected light can be effectively controlled, and support is provided to ensure that the light signal can be fully reflected in the light guide, so as to achieve the purpose of reducing light loss and improving transmission efficiency by increasing total reflection in the light guiding process; at the same time, the front end portion adopts a spherical structure, which is not only conducive to simplifying the processing difficulty of the light guide, but also can obtain the best light transmission efficiency by adjusting and determining the position of the scintillator in the front end portion. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The figure is a schematic diagram of the planar structure of an electronic detector according to an embodiment.

[0017] Figure 2 This is a schematic diagram of the three-dimensional structure of an electronic detector of an embodiment after omitting the shielding tube.

[0018] Figure 3 A schematic diagram of the structural decomposition of a scintillator and a front end portion of an electron detector in an embodiment.

[0019] Figure 4 Schematic diagram of the optical signal transmission principle of an electronic detector according to an embodiment (I).

[0020] Figure 5 Schematic diagram of the optical signal transmission principle of an electronic detector according to an embodiment (II).

[0021] Figure 6 A schematic diagram of the relative position relationship between the scintillator and the front end of an electron detector in an embodiment.

[0022] Figure 7 A simulation chart (I) of light transmission efficiency data of an electronic detector according to an embodiment of the present invention.

[0023] Figure 8 This is a simulation chart (2) of light transmission efficiency data of an electronic detector according to an embodiment of the present invention.

[0024] In the figure: 10. light guide; 11. front end; 11a. first surface; 11b. second surface; 11c. second through hole; 12. rear end; 12a. fifth surface; 12b. axial front end surface; 13. transition portion; 13a. third surface; 13b. fourth surface; 20, scintillator; 20a, light emitting surface; 20b, electron incident surface; 20c, first through hole; 30. Shielding tube; 40. Sealing rubber ring; L1. Center axis; L2. Symmetrical axis; A. First position; B. Second position. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below by specific embodiments in conjunction with the accompanying drawings. Wherein similar elements in different embodiments adopt associated similar element numbers. In the following embodiments, many detailed descriptions are for making the present application better understood. However, those skilled in the art can easily recognize that some features can be omitted in different situations, or can be replaced by other elements, materials, methods. In some cases, some operations related to the present application are not shown or described in the specification, this is to avoid the core part of the present application being overwhelmed by too much description, and for those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations according to the description in the specification and the general technical knowledge in the art.

[0026] In addition, the features, operations or characteristics described in the specification can be combined in any appropriate manner to form various implementations. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment and are not meant to be a required sequence, unless otherwise specified that a certain sequence must be followed.

[0027] The serial numbers assigned to the components herein, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" and "coupling" mentioned in this application, unless otherwise specified, include direct and indirect connections (couplings).

[0028] See also Figures 1 to 6An embodiment of the present application provides an electron detector that can be used in a scanning electron microscope to detect and process signals (such as secondary electrons, backscattered electrons, etc.) generated by the interaction between an electron beam and a sample, so that the scanning electron microscope can image the sample based on the signal output by the electron detector; the electron detector includes a light guide 10, a scintillator 20, and other functional components (such as a photomultiplier tube) that exist as needed, which are described in detail below.

[0029] See also Figure 1 The scintillator 20 is arranged at the front end of the light guide 10, and the rear end of the light guide 10 is used to connect to a photomultiplier tube (not shown in the figure); wherein, the scintillator 20 is used to generate a light signal, and the light guide 10 is used to transmit the light signal; specifically, the light signal generated by the scintillator 20 due to electron impact can enter the light guide 10 from the front end of the light guide 10, and then reach the rear end of the light guide 10 after multiple reflections in the light guide 10, and finally be received by the photomultiplier tube and converted into an electrical signal output.

[0030] For ease of distinction and description, the front end of the light guide 10 (i.e., the structural portion of the light guide 10 for receiving light signals or cooperating with the scintillator 20) is defined as the front end 11, and the rear end of the light guide 10 (i.e., the structural portion of the light guide 10 for emitting light signals or cooperating with the photomultiplier tube) is defined as the rear end 12.

[0031] In one embodiment, see Figures 1 to 3 The contour shape of the front end portion 11 is roughly a quarter sphere. For the convenience of description, the spherical part of the quarter sphere surface is defined as the first surface 11a, and the plane part of the quarter sphere surface is defined as the second surface 11b; that is: the first surface 11a is a quarter spherical structure, the second surface 11b is a semicircular plane structure, and the surface of the front end portion 11 is formed by connecting the first surface 11a and the second surface 11b.

[0032] As for the scintillator 20, the scintillator 20 is attached and fixed to the second surface 11b, for example, optical glue is arranged between the scintillator 20 and the second surface 11b to bond and fix the scintillator 20 to the front end portion 11; for the convenience of description, the surface of the scintillator 20 attached to the second surface 11b is defined as the light emitting surface 20a, and the surface opposite to the light emitting surface 20a in the direction of the central axis L1 of the scintillator 20 is defined as the electron incident surface 20b.

[0033] The electrons generated by the interaction between the electron beam and the sample can be incident from the electron incident surface 20b and hit the scintillator 20, so that the light signal generated by the scintillator 20 is refracted into the front end portion 11 through the light exit surface 20a and the second surface 11b to be reflected by the first surface 11a, and after the light signal is reflected multiple times in the optical waveguide 10, it can finally be transmitted through the rear end portion 12 and projected to the photomultiplier tube; wherein, with respect to the relative position of the scintillator 20 and the front end portion 11, the scintillator 20 can be located in the plane where the second surface 11b is located, and can be located at a position that enables the light signal (for example, most of the light signal) reflected by the first surface 11a to emit total reflection in the optical waveguide 10.

[0034] As for the contour shape of the scintillator 20 , different contour shapes can be adopted according to the overall processing complexity and overall performance requirements of the electronic detector.

[0035] For example, see Figures 1 to 3 The outline shape of the scintillator 20 is roughly a truncated cone, the upper bottom surface of the truncated cone serves as the electron incident surface 20b, and the lower bottom surface of the truncated cone serves as the light exit surface 20a; the scintillator 20 in the form of a truncated cone can effectively improve the photon collection efficiency of the scintillator 20.

[0036] At the same time, from Figure 7 It can be seen from the optical simulation data shown that when the inclination angle of the truncated cone (i.e., the scintillator 20) increases from 15° to about 40°, the transmission efficiency of the optical signal is relatively stable; when the inclination angle of the truncated cone increases from 55° to 90°, the transmission efficiency of the optical signal will be significantly reduced. Therefore, in some embodiments, the inclination angle of the truncated cone can be set to less than 55° according to actual needs. It should be noted that the inclination angle mentioned here refers to the angle between the side surface and the bottom surface of the truncated cone.

[0037] Exemplarily, the contour shape of the scintillator 20 is roughly cylindrical, and the two end faces of the cylinder opposite to each other in the direction of its axial line are respectively the light exit surface 20a and the light incident surface 20b; the use of a cylindrical scintillator 20 can make the scintillator 20 easier to process and manufacture, providing support for reducing or simplifying the overall processing difficulty of the electronic detector.

[0038] On the one hand, by using the first surface 11a of the spherical structure as the reflection surface for the first reflection of the light signal in the light guide 10, the geometric shape of the first surface 11a can be fully utilized to adjust and control the incident angle of the next reflection of the light signal in the light guide 10, thereby ensuring that most of the light signal can be totally reflected at the next reflection after the first reflection, which is beneficial to increase the number of total reflections of the light signal in the light guide 10, thereby achieving the purpose of reducing light loss and improving the transmission efficiency of the light signal.

[0039] On the other hand, the use of other special-shaped surfaces (such as parabolic surfaces, ellipsoidal surfaces, and polyhedrons) at the front end of the light guide may improve the light transmission efficiency, but the light guide 10 is difficult to process, and the optimal matching parameters of the light guide 10 and the scintillator 20 are difficult to determine; in comparison, the front end 11 of the light guide 10 adopts a quarter sphere, and the reflection surface of the light guide 10 used for the first reflection of the light signal is simplified into a spherical surface, which can not only greatly simplify or reduce the processing complexity and difficulty of the light guide 10, but also make it easier to obtain the best light transmission efficiency or optimize the matching parameters of the scintillator 20 and the light guide 10 by adjusting the relative position of the scintillator 20 and the front end 11.

[0040] In other embodiments, the front end portion 11 may also adopt other suitable geometric shapes having a first surface 11a with a quarter-spherical structure and a second surface 11b with a planar structure. The spherical shape of the first surface 11a and the attachment relationship between the second surface 11b and the scintillator 20 provide support for the electronic detector to maintain the required optical signal transmission efficiency; details will not be elaborated here.

[0041] In one embodiment, see Figure 2 and Figure 3 , the scintillator 20 has a first through hole 20c for facilitating the downward electron beam to pass through the scintillator 20, the first through hole 20c is arranged along the central axis L1 of the scintillator 20, and passes through the light exit surface 20a and the electron incident surface 20b, the light exit surface 20a is an annular plane structure surrounding the first through hole 20c; exemplarily, the scintillator 20 is a cylinder or a truncated cone having the first through hole 20c. Among them, the second surface 11b is a semicircular plane structure (that is, the front end 11 is a quarter sphere), the light exit surface 20a is a circular plane structure, and the diameter of the arc edge of the light exit surface 20a is set to be smaller than the radius of the arc edge of the second surface 11b.

[0042] For the relative position of the scintillator 20 and the front end portion 10, please refer to Figure 6 , in the direction of the symmetry axis L2 of the second surface 11b, the position of the scintillator 20 is between the first position A and the second position B; wherein the first position A refers to the position where the arc edge of the first through hole 20c is circumscribed to the arc edge of the second surface 11b, and the second position B refers to the position where the central axis L1 of the scintillator 20, the symmetry axis L2 of the second surface 11b and the straight edge of the second surface 11b intersect. It can be understood that the second surface 11b adopts a semicircular plane structure, and the line between the midpoint (or vertex) of the semicircular arc edge and the midpoint of the semicircular straight edge is the symmetry axis L2.

[0043] Since the relative position of the scintillator 20 and the optical waveguide 10 has an important influence on the transmission efficiency of the optical signal; on the one hand, limiting the position of the scintillator 20 between the first position A and the second position B can ensure that most of the optical signals reflected by the first surface 11a can be totally reflected at the next reflection, so that the optical waveguide 10 or the electronic detector as a whole maintains a high optical signal transmission efficiency; on the other hand, selecting the position of the scintillator 20 along the symmetry axis L2 of the second surface 11b makes it easier to determine the optimal position of the scintillator 20.

[0044] More specifically, please combine Figures 4 to 6 Through optical simulation calculation, it is known that when the arc edge of the light emitting surface 20a is just inscribed in the arc edge of the second surface 11b, most of the light signals reflected by the first surface 11a can be totally reflected at the next reflection (see Figure 4 ), the light signal transmission efficiency of the electronic detector reaches the maximum, at this time, the position of the scintillator 20 in the plane where the second surface 11b is located is the optimal position; and when the scintillator 20 is moved along the symmetry axis L2 between the optimal position and the first position A or between the optimal position and the second position B, part of the light signal reflected by the first surface 11a will be refracted out from the light guide 10 (see Figure 5 ), causing the optical signal transmission efficiency to gradually decrease.

[0045] Therefore, in some embodiments, please refer to Figures 1 to 4 In the direction of the symmetry axis L2, the scintillator 20 is located at a position where the arc edge of the light emitting surface 20a is inscribed in the arc edge of the second surface 11b, so as to ensure that the electronic detector has the highest light transmission efficiency. Of course, based on different needs, the position of the scintillator 20 can be selected between the first position A and the second position B along the symmetry axis L2, which will not be described in detail here.

[0046] For some examples, see Figures 1 to 3 The front end portion 11 has a second through hole 11c that allows the downward electron beam to pass through. The second through hole 11c is arranged to penetrate the first surface 11a and the second surface 11b in a direction perpendicular to the second surface 11b, and the second through hole 11c is coaxially connected with the first through hole 20c to form an electron beam channel. A shielding tube 30 is passed through the electron beam channel. The shielding tube 30 can be made of a completely demagnetized magnetic shielding material (such as Permalloy) or a weakly magnetic material (such as stainless steel).

[0047] In this way, the downward electron beam emitted by the electron gun of the scanning electron microscope can be projected onto the sample after passing through the electron detector (i.e., the light guide 10 and the scintillator 20) through the electron beam channel; and the downward electron beam can be protected by the shielding tube 30 to prevent the downward electron beam from being affected by the nearby electromagnetic field. Of course, a shielding film can also be coated on the channel wall of the electron beam channel to protect the downward electron beam and avoid stray electromagnetic fields.

[0048] It can be understood that whether to set the second through hole 11c depends on the position of the scintillator 20. For example, when the position of the scintillator 20 is the first position A, the second channel 11c can be omitted; when the position of the scintillator 20 is between the position where the arc edge of the first through hole 20c is inscribed in the arc edge of the second surface 11b and the second position B, the second through hole 11c needs to be set.

[0049] In one embodiment, see Figure 1 and Figure 2 The light guide 10 also has a transition portion 13, which can be understood as a structural portion of the light guide 10 that is connected between the front end portion 11 and the rear end portion 12; specifically, the front end portion 11 is a quarter of a sphere, the transition portion 13 is a half of a cylinder, and the surface of the transition portion 13 includes a third surface 13a with a semicircular curved surface structure and a fourth surface 13b with a planar structure, and the third surface 13a and the fourth surface 13b are connected to form a contour surface of the transition portion 13; the rear end portion 12 is a cylinder, and the surface of the rear end portion 12 includes a fifth surface 12a with a full circular curved surface structure, an axial front end surface 12b and an axial rear end surface (not marked in the figure).

[0050] The third surface 13a is connected between the first surface 11a and the fifth surface 12a, the fourth surface 13b is connected between the second surface 11b and the axial front end surface 12b, and the axial rear end surface is connected to the side of the fifth surface 12a away from the axial front end surface 12b, thereby forming the outer surface of the entire light guide 10. In addition, the radius of the front end portion 11, the radius of the transition portion 13, and the radius of the rear end portion 12 are equal.

[0051] First, by using the transition portion 13 of a half cylinder to make a structural transition between the front end 11 of the quarter sphere and the rear end 12 of the cylinder, the optical signal that has been totally reflected in the light guide 10 can almost be totally reflected again at the next reflection, thereby ensuring effective transmission of the optical signal.

[0052] Secondly, the radii of the front end portion 11 , the transition portion 13 and the rear end portion 12 are consistent, which can avoid the formation of complex curved surfaces, thus effectively simplifying the processing of the light guide 10 and reducing the processing difficulty.

[0053] Thirdly, the rear end portion 12 is a cylinder with a full circular curved surface, which can provide support for the airtight connection of the electronic detector. For example, the sealing rubber ring 40 can be stably placed on the rear end portion 12 to ensure airtightness.

[0054] For some examples, see Figure 1 and Figure 2 A circular arc transition is made between the fourth surface 13b of the transition portion 13 and the axial front end surface 12b of the rear end portion 12, for example, the fourth surface 13b and the axial front end surface 12b are connected with a rounded corner; this can avoid the appearance of sharp edges between the transition portion 13 and the rear end portion 12, ensure the smoothness of the surface of the light guide 10, and avoid light loss caused by the light signal being emitted from the light guide 10 at the connection between the fourth surface 13b and the axial front end surface 12b.

[0055] In some embodiments, the transition portion 13 may be omitted, that is, the first surface 11a is connected to the fifth surface 12a, and the second surface 11b is connected to the axial front end surface 12b; in this way, the rear end portion 12 of the cylinder can be used to provide support for the airtight connection of the light guide 10, and the front end portion 11 of the quarter sphere can be used to ensure the efficiency of optical signal transmission, avoid complex curved surfaces, and reduce the difficulty of processing the light guide 10.

[0056] See also Figure 8 ,from Figure 8 It can be seen from the optical simulation data shown that as the diameter of the quarter sphere (i.e., the quarter spherical surface corresponding to the first surface 11a) increases, the optical signal transmission efficiency also increases accordingly, but when the diameter of the quarter sphere exceeds a certain critical value, the optical signal transmission efficiency increases slowly.

[0057] In view of this, in some embodiments, the ratio of the diameter of the front end portion 11 to the diameter of the light emitting surface 20a is between 1.4 and 4.3. This can ensure the efficiency of optical signal transmission and help avoid the problems of the light guide 10 or the electronic detector being too large in size or occupying too much space, and it is convenient to select the most suitable size according to the actual installation space of the electronic detector to meet the overall application requirements of the light guide 10 or the electronic detector.

[0058] In one embodiment, although not shown in the figure, the first surface 11a, the area of ​​the second surface 11b that is not attached to the light exit surface 20a, and other surfaces of the scintillator 20 except the light exit surface 20a and the electron incident surface 20b (for example, the surface connected between the light exit surface 20a and the electron incident surface 20b, such as the circumferential side surface of a truncated cone or a cylinder) are all covered with a first film layer (for example, a total reflection film). The first film layer is mainly used to reflect light signals, that is, the first film layer enables the light signal to be reflected on the structural surface such as the first surface 11a, thereby reducing or even avoiding the light signal from being refracted out from the front end 11 or the scintillator 20, thereby reducing light loss.

[0059] In some embodiments, although not shown in the figure, the electron incident surface 20b is covered with a second film layer, which is mainly used to allow electrons to pass through and reflect light signals to improve the light reflection effect inside the scintillator 20 and prevent charge accumulation. In specific implementations, the thickness of the second film layer can be less than the thickness of the first film layer, and the second film layer should be thin enough to ensure that the second film layer does not block electrons from reaching the scintillator 20. Exemplarily, the second film layer can be an aluminum film with a thickness between 10nm and 100nm.

[0060] It should be noted that Figure 1 and Figure 2 The bold dashed line in the figure is only used to indicate the approximate boundary between the front end portion 11 and the transition portion 13, and the approximate boundary between the transition portion 13 and the rear end portion 12; it can be understood that the bold dashed line is a virtual line customized to more clearly define the structure of the light guide.

[0061] The above specific examples are used to illustrate the present invention, which is only used to help understand the present invention and is not intended to limit the present invention. For those skilled in the art, according to the concept of the present invention, some simple deductions, modifications or substitutions can be made.

Claims

1. An electronic detector, characterized in that: The invention comprises a light guide and a scintillator, wherein the light guide has a front end portion, the surface of the front end portion comprises a first surface and a second surface, the first surface is a quarter spherical structure, the second surface is a plane structure, and the surface of the scintillator comprises a light emitting surface and an electron incident surface which are opposite to each other in the direction of the central axis of the scintillator; The light emitting surface is attached to the second surface so that the light signal generated by the scintillator enters the front end portion; and the first surface is used to reflect the light signal.

2. The electron detector according to claim 1, characterized in that The front end is a quarter sphere, and the second surface is a semicircular plane structure connected to the first surface; wherein, within the plane where the second surface is located, the scintillator is located at a position that enables the light signal reflected by the first surface to be totally reflected in the light guide.

3. The electron detector according to claim 2, characterized in that: The scintillator has a first through hole, and the first through hole is arranged along the central axis to penetrate the light exit surface and the electron incident surface; the light exit surface is an annular plane structure surrounding the first through hole, and the diameter of the arc edge of the light exit surface is smaller than the radius of the arc edge of the second surface; In the direction of the axis of symmetry of the second surface, the position of the scintillator is between the first position and the second position; wherein the first position is the position where the arc edge of the first through hole is circumscribed to the arc edge of the second surface, and the second position is the position where the center axis, the axis of symmetry and the straight edge of the second surface intersect.

4. The electron detector according to claim 3, characterized in that In the direction of the symmetry axis, the scintillator is located at a position where the arc edge of the light emitting surface is inscribed in the arc edge of the second surface.

5. The electron detector according to claim 3, characterized in that: The front end portion has a second through hole, which is arranged to penetrate the first surface and the second surface in a direction perpendicular to the second surface, and the second through hole is coaxially connected with the first through hole to form an electron beam channel; a shielding tube is passed through the electron beam channel, or the channel wall of the electron beam channel is covered with a shielding film.

6. The electron detector according to claim 2, characterized in that The scintillator is a truncated cone, the light emitting surface is the lower bottom surface of the truncated cone, the electron incident surface is the upper bottom surface of the truncated cone, and the inclination angle of the truncated cone is less than 55°.

7. The electron detector according to claim 2, characterized in that: The light guide further comprises a transition portion and a rear end portion, wherein the transition portion is connected between the front end portion and the rear end portion; wherein: The transition portion is a half cylinder, the surface of the transition portion includes a third surface with a semicircular curved surface structure and a fourth surface with a planar structure, the rear end portion is a cylinder, the surface of the cylinder includes a fifth surface with a full circular curved surface structure, the third surface is connected between the first surface and the fifth surface, and the second surface is connected to the fourth surface; the radius of the front end portion, the radius of the transition portion and the radius of the rear end portion are equal; Or the light guide also has a rear end portion connected to the front end portion, the rear end portion is a cylinder, the surface of the rear end portion includes a fifth surface with a full circular curved structure, the fifth surface is connected to the first surface, and the radius of the rear end portion is equal to the radius of the front end portion.

8. The electron detector according to claim 3, characterized in that: The ratio of the diameter of the front end portion to the diameter of the light emitting surface is between 1.4 and 4.

3.

9. The electron detector according to claim 1, characterized in that: The first surface, the area of ​​the second surface not attached to the light exit surface, and the surface of the scintillator connected between the light exit surface and the electron incident surface are covered with a first film layer, and the first film layer is used to reflect light signals; And / or the electron incident surface is covered with a second film layer, and the second film layer is used to allow electrons to pass through and reflect light signals.

10. The electron detector according to claim 9, characterized in that The thickness of the second film layer is smaller than the thickness of the first film layer.

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