Ultrafast efficient electron detector based on nano polycrystalline boron nitride

Abstract

The invention relates to the field of electronic detectors, and discloses an ultrafast and efficient electronic detector based on nano polycrystalline boron nitride, which comprises a nano polycrystalline boron nitride scintillator, a light guide and a photomultiplier, and is characterized in that the nano polycrystalline boron nitride scintillator and the photomultiplier are respectively connected with the front end and the rear end of the light guide, a nano polycrystalline boron nitride material of the nano polycrystalline boron nitride scintillator is prepared by taking a sapphire single crystal wafer as a substrate, using NH3 and BCl3 or NH3 and BF3 as raw material gases and adopting a chemical vapor deposition furnace for epitaxial growth. In the invention, the nano polycrystalline boron nitride scintillator has short electron decay time and high scintillation light yield, and can realize ultrafast and efficient electron radiation detection when being applied to an electron detector. The electron detector can be applied to secondary electron and backscattered electron detection in an electron beam detection system, and a new choice is provided for the electron beam detection technology.

Description

Technical Field

[0001] The invention relates to the field of electronic detectors, and in particular to an ultrafast and efficient electronic detector based on nano-polycrystalline boron nitride. Background Art

[0002] Semiconductor wafer inspection technology is an important part of ensuring the quality and performance of semiconductor devices. It not only includes the detection of physical defects on the wafer surface, but also involves the precise measurement of key dimensions. Electron beam inspection technology plays an irreplaceable role in this field due to its high precision and high resolution. For example, electron beam defect inspection equipment (EBI) can detect the defect status of semiconductor wafers in real time, especially electrical defects in internal circuits. Critical dimension scanning electron microscope (CD-SEM) monitors key process parameters by measuring key dimensions of electron beam microscopic images.

[0003] In these electron beam detection systems, electron detectors convert secondary electrons or backscattered electron signals into visible light signals for detection. Electron scintillators are key components for efficient electron detection. They need to have the following characteristics: high light yield to ensure sufficient signal intensity, short decay time to achieve fast signal response, low afterglow to avoid image tailing, and excellent radiation resistance to maintain long-term stability. Currently, the commonly used electron scintillator materials are YAG:Ce (Ce-doped Y3Al5O 12 ) and YAP:Ce (Ce-doped YAlO3) single crystals. These materials are widely used due to their relatively simple preparation process and low cost. However, most YAG:Ce scintillators used to date have problems with long decay time and high afterglow, which limits their performance in certain fast and high-precision applications. YAP:Ce scintillators have a fast decay capability of about 30ns, which can improve the efficiency of electron detection. Nevertheless, in order to further promote the advancement of electron beam detection technology and the expansion of applications, it is still of great significance to continuously explore and develop new electron scintillators. Summary of the invention

[0004] In view of the above background technology, the present invention provides an ultrafast and efficient electron detector based on nano-polycrystalline boron nitride and a method for preparing nano-polycrystalline boron nitride, which has a shorter decay time and higher luminous efficiency than the existing YAP:Ce scintillator.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0006] The first aspect of the present invention provides an ultrafast and efficient electron detector based on nano-polycrystalline boron nitride, comprising a nano-polycrystalline boron nitride scintillator, a light guide, and a photomultiplier tube, wherein the nano-polycrystalline boron nitride scintillator and the photomultiplier tube are connected to the front end and the rear end of the light guide, respectively; wherein:

[0007] The nano-polycrystalline boron nitride scintillator is used to receive electron irradiation and generate nanosecond-level ultrafast high-brightness scintillation light by utilizing the carrier confinement effect of its nano-polycrystalline structure under electron excitation;

[0008] The nano-polycrystalline boron nitride scintillator is made of a sapphire single crystal wafer as a substrate, NH3 and BCl3, or NH3 and BF3 as raw material gases, and is epitaxially grown in a vertical chemical vapor deposition furnace;

[0009] The light guide is used to transmit the scintillation light to the photomultiplier tube;

[0010] The photomultiplier tube is used to receive the scintillation light transmitted by the light guide and record the photon information.

[0011] Furthermore, a layer of metal aluminum with a thickness of 50 to 60 nm is plated on the surface of the nano-polycrystalline boron nitride scintillator using magnetron sputtering technology.

[0012] Furthermore, the electron detector also includes a Faraday cage device installed at the front end of the nano-polycrystalline boron nitride scintillator, which is used for secondary electron detection in the electron beam detection system.

[0013] Furthermore, a circular hole is opened in the center of the nano-polycrystalline boron nitride scintillator to form a circular ring structure, which is used for backscattered electron detection in an electron beam detection system.

[0014] Furthermore, the light guide is any one of quartz optical fiber, glass optical fiber or plastic optical fiber.

[0015] Furthermore, the nano-polycrystalline boron nitride scintillator is prepared by the following preparation method, which comprises the following steps:

[0016] S1. Select a sapphire single crystal with a low lattice matching degree with boron nitride as a substrate, and select an aluminum polar surface that is easy to nucleate as a growth surface;

[0017] S2, fix the substrate with a graphite fixture, and place the graphite fixture and the substrate into a vertical chemical vapor deposition furnace, evacuate the furnace, and then heat the furnace sideways to the reaction temperature;

[0018] S3, NH3 and BCl3, or NH3 and BF3 raw material gases are introduced into the furnace, and N2 is used as a carrier gas;

[0019] S4, after ventilation, the gas flow rate is kept constant and the temperature is kept constant; finally, the power is turned off for cooling, and the boron nitride / sapphire is taken out of the furnace at room temperature with the furnace cooling, and the boron nitride falls off automatically to obtain a nano-polycrystalline boron nitride material;

[0020] S5. Cut the nano-polycrystalline boron nitride material into a preset size according to the detector requirements to obtain a nano-polycrystalline boron nitride scintillator.

[0021] Furthermore, step S5 of the method for preparing the nano-polycrystalline boron nitride scintillator further includes using magnetron sputtering to deposit metal aluminum with a thickness of 50 to 60 nm on the surface of the nano-polycrystalline boron nitride material, and then cutting it into a preset size.

[0022] Furthermore, in step S2 of the method for preparing the nano-polycrystalline boron nitride scintillator, lateral heating is used to a reaction temperature of 1300-1600° C. after vacuuming.

[0023] Furthermore, in step S3 of the method for preparing the nano-polycrystalline boron nitride scintillator, the gas volume ratio of the raw material gases NH3 and BCl3, or NH3 and BF3 is controlled at 1.2 to 1.5:1.

[0024] Furthermore, in step S4 of the method for preparing the nano-polycrystalline boron nitride scintillator (1), the temperature after ventilation is maintained at 1300-1600° C. and is kept warm for 240-360 minutes.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. Compared with YAP:Ce single crystal, the nano-polycrystalline boron nitride of the present invention has a shorter luminescence decay time and a faster response speed. This fast response characteristic helps to reduce image blur during electron beam imaging, thereby further improving image quality.

[0027] 2. Compared with the YAP:Ce single crystal, the nano-polycrystalline boron nitride film of the present invention exhibits higher luminescence efficiency, and its maximum luminescence quantum yield can be as high as 39.8%. It can be seen that the nano-polycrystalline boron nitride film of the present invention has excellent luminescence properties.

[0028] 3. In the present invention, the boron nitride scintillator produced by vertical chemical vapor deposition epitaxial growth is applied to the electron detector. Since the nano-polycrystalline boron nitride scintillator has a short electron decay time and a high scintillation light yield, the electron detector based on nano-polycrystalline boron nitride constructed by the present invention can achieve ultra-fast and efficient electron detection. The electron detector of the present invention can be applied to secondary electron and backscattered electron detection in the electron beam detection system, providing a new option for electron beam detection technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic structural diagram of a nano-polycrystalline boron nitride electron scintillator electron detector according to Example 1 of the present invention;

[0030] Figure 2 It is a structural schematic diagram and imaging comparison diagram of an electron detector based on nano-polycrystalline boron nitride that can be used for secondary electron detection according to Example 2 of the present invention;

[0031] Figure 3 This is a structural schematic diagram and imaging comparison diagram of an electron detector based on nano-polycrystalline boron nitride that can be used for backscattered electron detection according to Example 3 of the present invention;

[0032] Figure 4 The physical picture, growth schematic diagram and installation schematic diagram of nano-polycrystalline boron nitride according to Example 4 of the present invention;

[0033] Figure 5 This is a result diagram of the cross-sectional structure of nano-polycrystalline boron nitride photographed using a transmission electron microscope in Example 5 of the present invention;

[0034] Figure 6 This is a result diagram of comparative analysis of nano-polycrystalline boron nitride scintillator and commercial YAP:Ce scintillator under the same excitation conditions in Example 6 of the present invention.

[0035] In the figure:

[0036] 1-nano polycrystalline boron nitride scintillator; 2-light guide; 3-photomultiplier tube; 4-Faraday cage; 5-circular hole. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Example 1: Ultrafast and efficient electron detector based on nano-polycrystalline boron nitride

[0039] This embodiment is used to provide an ultrafast and efficient electron detector based on nano-polycrystalline boron nitride of the present invention. Figure 1 As shown, an ultrafast and efficient electron detector based on nano-polycrystalline boron nitride includes a nano-polycrystalline boron nitride scintillator 1, a light guide 2, and a photomultiplier tube 3. The nano-polycrystalline boron nitride scintillator 1 and the photomultiplier tube 3 are connected to the front end and the rear end of the light guide 2 respectively; wherein,

[0040] Nano-polycrystalline boron nitride scintillator 1, which is made by high-temperature chemical vapor deposition for rapid film growth, is used to receive electron irradiation and, under electron excitation, utilizes the carrier confinement effect of its nano-polycrystalline structure to produce nanosecond-level ultrafast high-brightness scintillation light;

[0041] A light guide 2, used for transmitting the scintillation light to the photomultiplier tube 3, wherein the light guide 2 is specifically one of quartz optical fiber, glass optical fiber or plastic optical fiber;

[0042] The photomultiplier tube 3 is used to receive the scintillation light transmitted by the light guide 2 and record the photon information.

[0043] When working, the nano polycrystalline boron nitride scintillator 1 generates scintillation light after receiving electron irradiation, and the light guide 2 transmits the scintillation light to the photomultiplier tube 3. After receiving the scintillation light signal, the photomultiplier tube 3 records the photon information and then reads it out.

[0044] In order to avoid the accumulation of charges on the surface of the nano-polycrystalline boron nitride scintillator 1 due to electron impact, in this embodiment, a layer of 50-60nm thick metal aluminum is plated on the surface of the nano-polycrystalline boron nitride scintillator 1 by magnetron sputtering technology. This layer of metal aluminum can not only effectively prevent charge accumulation, but also serve as a reflection layer to reflect the scintillation light propagating in the reverse direction, thereby improving the light output capacity of the scintillator. In addition, in this embodiment, the nano-polycrystalline boron nitride scintillator 1 can also be cut to a preset size according to the requirements of the electronic detector.

[0045] Since the nano-polycrystalline boron nitride scintillator 1 has a short decay time and a high light yield, combined with the light guide 2 and the photomultiplier tube 3 matched therewith in the back-end design, the electronic detector of the present invention can achieve faster time resolution and higher detection efficiency.

[0046] Example 2: Electron detector based on nano-polycrystalline boron nitride for secondary electron detection

[0047] Based on Example 1, this example is used to provide a modified electron detector that can be used for secondary electron detection in an electron beam detection system.

[0048] Figure 2 a and Figure 2 b are the structural schematic diagram and imaging comparison diagram of the secondary electron detector based on nano-polycrystalline boron nitride in this embodiment. Figure 2As shown in a, on the basis of Example 1, the electron detector that can be used for secondary electron detection in this embodiment also includes a Faraday cage device installed at the front end of the nano-polycrystalline boron nitride scintillator 1. Since the energy of secondary electrons is relatively weak, they are easily affected by the electric field and deflected. During the operation of the secondary electron detector, the Faraday cage with applied voltage can attract and accelerate scattered secondary electrons from all directions. Once these accelerated electrons hit the nano-polycrystalline boron nitride scintillator 1, they will cause it to emit light, and the generated scintillation light is then transmitted through the light guide 2 and finally collected and recorded by the photomultiplier tube 3. Since the nano-polycrystalline boron nitride of the present invention has faster and more efficient electron scintillation performance, compared with existing secondary electron detectors, the use of a secondary electron detector based on nano-polycrystalline boron nitride can significantly shorten the time for scanning electronic signals to acquire images, thereby achieving faster and more efficient detection of samples (see Figure 2 b).

[0049] Example 3: Electron detector based on nano-polycrystalline boron nitride for backscattered electron detection

[0050] Based on Example 1, this example is used to provide a modified electron detector that can be used for backscattered electron detection in an electron beam detection system.

[0051] Figure 3 a and Figure 3 b are the structural schematic diagram and imaging comparison diagram of the backscattered electron detector based on nano-polycrystalline boron nitride in this embodiment. Figure 3 As shown in a, based on Example 1, the electron detector of this embodiment that can be used for backscattered electron detection has a circular hole in the center of the nano-polycrystalline boron nitride scintillator 1 to form a circular ring structure. The purpose of this geometric setting is to allow the incident electron beam to directly reach the sample surface, thereby exciting backscattered electrons. Although the incident electron beam can simultaneously excite secondary electrons and backscattered electrons, due to the low energy of the secondary electrons, they will not produce significant scintillation light after reaching the backscattered electron detector, while the high-energy backscattered electrons can effectively excite the scintillator to emit light. The light emitted by the scintillator is transmitted through the light guide 2 and is also collected and recorded by the photomultiplier tube 3. Since nano-polycrystalline boron nitride has faster and more efficient electron scintillation performance, compared with existing backscattered electron detectors, the backscattered electron detector based on nano-polycrystalline boron nitride of this embodiment can significantly shorten the time for scanning electronic signals to obtain images, thereby achieving faster and more efficient detection of samples (see Figure 3 b).

[0052] Example 4: Preparation method of nano-polycrystalline boron nitride scintillator in electronic detector

[0053] This embodiment is used to provide a method for preparing the nano-polycrystalline boron nitride scintillator in the electron detector described in embodiments 1 to 3. In this embodiment, the nano-polycrystalline boron nitride is prepared by epitaxial growth using a 6-inch sapphire single crystal wafer as a substrate, NH3 and BCl3 (or NH3 and BF3) as raw material gases, and a vertical chemical vapor deposition furnace. The preparation method of the nano-polycrystalline boron nitride material includes the following steps:

[0054] S1. Select a 6-inch sapphire single crystal with a low lattice matching degree with boron nitride as a substrate, and select an aluminum polar surface that is easy to nucleate as a growth surface;

[0055] In this embodiment, since the aluminum polar surface of sapphire has a higher surface energy, which is conducive to adsorption and nucleation, the aluminum surface of the substrate is selected for the growth of nano-polycrystalline boron nitride.

[0056] S2. Use a graphite clamp to fix the substrate, and put the graphite clamp and the substrate into a vertical chemical vapor deposition furnace. After vacuuming, use lateral heating to the reaction temperature of 1500°C.

[0057] S3, feed the raw gas NH3 and BCl3 (or NH3 and BF3) into the furnace, use N2 as the carrier gas, so that the gas mixing reaction quickly generates boron nitride on the substrate and promotes its continuous growth; S4, keep the gas flow unchanged, and control the gas volume ratio of the raw gas NH3 and BCl3 (or NH3 and BF3) at 1.2:1 to promote the generation of boron nitride; after ventilation, the temperature is maintained at 1500°C and kept warm for 300 minutes, during which time, the boron nitride grains nucleate on the sapphire substrate and gradually grow to form a nano-polycrystalline structure; finally, turn off the power for cooling, and the boron nitride / sapphire is taken out of the furnace at room temperature with the furnace cooling, and the boron nitride automatically falls off to obtain the nano-polycrystalline boron nitride material of the present invention;

[0058] S5, depositing metal aluminum with a thickness of 50 to 60 nm on the surface of the nano-polycrystalline boron nitride material by magnetron sputtering technology, and cutting the nano-polycrystalline boron nitride material into a preset size according to the detector requirements, to obtain the nano-polycrystalline boron nitride scintillator of the present invention;

[0059] In this embodiment, the metal aluminum can not only effectively prevent charge accumulation, but also serve as a reflective layer to reflect the scintillation light propagating in the reverse direction, thereby improving the light output capacity of the scintillator.

[0060] S6. Install the cut nano-polycrystalline boron nitride scintillator at the front end of the light guide to obtain the electron detector based on nano-polycrystalline boron nitride of the present invention.

[0061] The growth diagram, physical diagram and installation diagram of the nano-polycrystalline boron nitride prepared in this embodiment are as follows: Figure 4 As shown, Figure 4a is a physical picture of nano-polycrystalline boron nitride. Figure 4 b is a schematic diagram of the growth of nano-polycrystalline boron nitride. Figure 4 c is a schematic diagram of the installation of nano-polycrystalline boron nitride scintillator.

[0062] Example 5: Transmission electron microscope analysis of the cross-sectional structure of nano-polycrystalline boron nitride

[0063] The lattice matching between sapphire and boron nitride is low, and the boron nitride film reaches the micron level, which usually causes the grown boron nitride film to automatically fall off the sapphire substrate. The cross-sectional structure was photographed using a transmission electron microscope (TEM), and the results are as follows: Figure 5 As shown, Figure 5 a is a low magnification TEM image, Figure 5 b is the diffraction pattern of selected area electrons, Figure 5 c is a high-resolution TEM image.

[0064] Ideally, boron nitride should exhibit a layered structure. However, Figure 5 As shown in a, in the low-magnification TEM image, the structure of the grown boron nitride film appears to be relatively disordered. Figure 5 In b, the selected area electron diffraction pattern reveals that it mainly grows along the c-axis direction, with the main crystal plane being the (002) plane, showing polycrystalline characteristics. Through in-depth analysis of high-resolution TEM images, it can be seen that the atomic arrangement of the grown boron nitride film is not uniform, the lattice is distorted, and a nanocluster structure is formed (see Figure 5 c). In the local area of ​​nanometer scale, boron nitride maintains an ordered layered structure, but it shows polycrystalline properties as a whole, which is defined as a nano-polycrystalline (NP) structure. The formation of this structure is attributed to the low lattice matching between the boron nitride layer and the sapphire substrate, which leads to the island growth phenomenon; on the other hand, due to the large reaction gas flow rate used in the growth process, the growth rate is accelerated, resulting in uneven lattice arrangement and local distortion. Therefore, in this embodiment, nano-polycrystalline boron nitride (NPBN) was successfully grown by chemical vapor deposition.

[0065] Example 6: Comparative Analysis of Nano-polycrystalline Boron Nitride Scintillator and Commercial YAP:Ce Scintillator

[0066] The comparative analysis of electron beam imaging of nano-polycrystalline boron nitride (NPBN) film scintillator and commercial YAP:Ce single crystal scintillator under the same excitation conditions is shown in the following results. Figure 6 As shown, Figure 6 a is the luminescence time response of NPBN and YAP:Ce under the same excitation conditions. Figure 6 b is the result diagram of the comparison of luminescence quantum yield. Figure 6 c and Figure 6d are the results of grayscale photos of the luminescence of NPBN and YAP:Ce under 2MeV electron beam excitation. Figure 6 e and Figure 6 f are the simulations of electron penetration depth distribution of NPBN and YAP:Ce under 2MeV electron beam excitation.

[0067] As shown in the figure, the luminescence decay time of NPBN (9.4ns) is significantly shorter than that of YAP:Ce (40.6ns), and has a faster time response. This fast response characteristic helps to reduce image blur during electron beam imaging and further improve image quality (see Figure 6 a). In addition, the peak wavelength of NPBN is around 385nm, which is similar to the peak wavelength of YAP:Ce, and it also does not require the use of a photomultiplier tube with increased sensitivity in the long-wave region. Further luminescence quantum yield (PLQY) test results also confirmed that NPBN exhibits higher luminescence efficiency than YAP:Ce, and its maximum luminescence quantum yield can be as high as 39.8% (see Figure 6 b) The strong luminescence comes from the carrier confinement effect caused by the nano-polycrystalline structure of boron nitride. Since the excited carriers are confined by the structure, they are more inclined to radiative recombination, thereby enhancing the luminescence ability. These results prove the excellent luminescence properties of NPBN.

[0068] In order to further observe the light yield of NPBN electron scintillation, this example took luminescence photos of NPBN and YAP:Ce scintillators under electron beam excitation. When the electron beam (energy is 2MeV) hits the scintillator vertically, the generated light is first deflected by the reflector at an angle of 90° and then captured by the camera. The luminescence image of the scintillator is taken while maintaining the same electron beam pulse frequency and camera integration time. Figure 6 c and Figure 6 d shows the grayscale photos of the blinking light of 100 μm thick NPBN and 500 μm thick YAP:Ce, respectively. As shown in the figure, under the same excitation conditions, the 100 μm thick NPBN exhibits a higher contrast, that is, a higher blinking light yield, compared with the 500 μm thick commercial YAP:Ce.

[0069] Furthermore, this embodiment also uses Casino software to simulate the penetration depth of the electron beam into the NPBN and YAP:Ce scintillators under these conditions. The simulation results show that under these conditions, the electron beam can easily penetrate the 100μm thick NPBN and the 500μm thick YAP:Ce (see Figure 6 e and Figure 6 f). NPBN can maintain high scintillation light yield even at thin thickness, which further confirms the great potential of NPBN as an electronic scintillator.

[0070] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the application should be included in the protection scope of the present application.

Claims

1. An ultrafast and efficient electron detector based on nano-polycrystalline boron nitride, characterized in that: The invention comprises a nano polycrystalline boron nitride scintillator (1), a light guide (2), and a photomultiplier tube (3), wherein the nano polycrystalline boron nitride scintillator (1) and the photomultiplier tube (3) are respectively connected to the front end and the rear end of the light guide (2); wherein: The nano-polycrystalline boron nitride scintillator (1) is used to receive electron irradiation and, under electron excitation, utilize the carrier confinement effect of its nano-polycrystalline structure to generate nanosecond-level ultrafast high-brightness scintillation light; The nano-polycrystalline boron nitride scintillator (1) is made of a sapphire single crystal wafer as a substrate, NH3 and BCl3, or NH3 and BF3 as raw material gases, and is produced by epitaxial growth in a vertical chemical vapor deposition furnace; The light guide (2) is used to transmit the scintillation light to the photomultiplier tube (3); The photomultiplier tube (3) is used to receive the scintillation light transmitted by the light guide (2) and record photon information.

2. The ultrafast and efficient electron detector based on nano-polycrystalline boron nitride according to claim 1, characterized in that: The surface of the nano-polycrystalline boron nitride scintillator (1) is plated with a layer of metal aluminum with a thickness of 50 to 60 nm using magnetron sputtering technology.

3. The ultrafast and efficient electron detector based on nano-polycrystalline boron nitride according to claim 1, characterized in that: The electron detector further comprises a Faraday cage device (4) installed at the front end of the nano-polycrystalline boron nitride scintillator (1) and used for secondary electron detection in an electron beam detection system.

4. The ultrafast and efficient electron detector based on nano-polycrystalline boron nitride according to claim 1, characterized in that: A circular hole (5) is provided at the center of the nano-polycrystalline boron nitride scintillator (1) to form a circular ring structure, which is used for backscattered electron detection in an electron beam detection system.

5. The ultrafast and efficient electron detector based on nano-polycrystalline boron nitride according to claim 1, characterized in that: The optical fiber (2) is any one of a quartz optical fiber, a glass optical fiber or a plastic optical fiber.

6. The ultrafast and efficient electron detector based on nano-polycrystalline boron nitride according to claim 1, characterized in that: The nano polycrystalline boron nitride scintillator (1) is prepared by the following preparation method, which comprises the following steps: S1. Select a sapphire single crystal with a low lattice matching degree with boron nitride as a substrate, and select an aluminum polar surface that is easy to nucleate as a growth surface; S2, fix the substrate with a graphite fixture, and place the graphite fixture and the substrate into a vertical chemical vapor deposition furnace, evacuate the furnace, and then heat the furnace sideways to the reaction temperature; S3, NH3 and BCl3, or NH3 and BF3 raw material gases are introduced into the furnace, and N2 is used as a carrier gas; S4, after ventilation, the gas flow rate is kept constant and the temperature is kept constant; finally, the power is turned off for cooling, and the boron nitride / sapphire is taken out of the furnace at room temperature with the furnace cooling, and the boron nitride falls off automatically to obtain a nano-polycrystalline boron nitride material; S5. Cut the nano-polycrystalline boron nitride material into a preset size according to the detector requirements to obtain a nano-polycrystalline boron nitride scintillator.

7. The ultrafast and efficient electron detector based on nano-polycrystalline boron nitride according to claim 6, characterized in that: Step S5 of the method for preparing the nano-polycrystalline boron nitride scintillator (1) further comprises using magnetron sputtering to deposit metal aluminum with a thickness of 50 to 60 nm on the surface of the nano-polycrystalline boron nitride material, and then cutting it into a preset size.

8. The ultrafast and efficient electron detector based on nano-polycrystalline boron nitride according to claim 6, characterized in that: In step S2 of the method for preparing the nano-polycrystalline boron nitride scintillator (1), lateral heating is performed to a reaction temperature of 1300-1600° C. after vacuuming.

9. The ultrafast and efficient electron detector based on nano-polycrystalline boron nitride according to claim 6, characterized in that: In step S3 of the method for preparing the nano-polycrystalline boron nitride scintillator (1), the gas volume ratio of the raw material gases NH3 and BCl3, or NH3 and BF3, is controlled within a range of 1.2 to 1.5:

1.

10. The ultrafast and efficient electron detector based on nano-polycrystalline boron nitride according to claim 6, characterized in that: In step S4 of the method for preparing the nano-polycrystalline boron nitride scintillator (1), the temperature after ventilation is maintained at 1300-1600° C. and is kept warm for 240-360 minutes.

Images