Groove silicon carbide neutron detector structure with high detection efficiency

Abstract

The invention discloses a high-detection-efficiency groove silicon carbide neutron detector structure, and relates to the technical field of semiconductor neutron detection, a plurality of groove groups are etched on the top surface of a SiC substrate, and each groove group comprises groove units which are sequentially connected along the direction of a first central plane of the SiC substrate; each groove unit comprises a first groove and a second groove which are symmetrically arranged, and the bottom faces of the first grooves and the bottom faces of the second grooves are parallelograms which are symmetrically arranged. According to the neutron detector, the groove structure of a traditional neutron detector is improved, the filling area of the neutron conversion material is increased due to the arrangement of the through groove groups, meanwhile, the contact area of the neutron conversion material and the SiC region is also increased, the self-absorption effect of secondary particles is reduced, and the detection efficiency of the detector is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor neutron detection, and particularly to a trench silicon carbide neutron detector structure with high detection efficiency. Background Art

[0002] With the continuous development of deep space exploration, nuclear technology, and strategic weapon technology, the importance of neutron detection in the fields of radiation protection, nuclear facility safety monitoring, nuclear explosion detection, etc. has become increasingly prominent. Although traditional gas detectors (such as 3 He proportional counters) have relatively high detection efficiency, due to 3 the scarcity of

[0003] Semiconductor detectors, especially detectors based on silicon carbide (SiC) materials, have become a research hotspot in the field of neutron detection due to their excellent properties such as wide bandgap, high temperature resistance, and radiation resistance.

[0004] Existing SiC neutron detectors are mostly planar structures or straight-groove structures. However, the planar structure has a low detection efficiency, and the straight-groove structure theoretically has a higher detection efficiency than the planar structure. However, after filling the conversion material, the conversion material cannot fully react, and there is a self-absorption effect. In addition, due to the underdevelopment of existing trench etching technology, the actual detection efficiency is much lower than the theoretical value. Summary of the Invention

[0005] The present invention discloses a trench silicon carbide neutron detector structure with high detection efficiency to overcome the above technical problems.

[0006] To achieve the above object, the technical solution of the present invention is:

[0007] A trench silicon carbide neutron detector structure with high detection efficiency, comprising: an SiC substrate, a P-type ohmic contact electrode, an N-type ohmic contact electrode, and a neutron conversion material;

[0008] A plurality of trench groups are etched on the top surface of the SiC substrate;

[0009] Each trench group includes a plurality of trench units connected in sequence along the direction of the first central plane of the SiC substrate;

[0010] Each trench unit includes a first trench and a second trench;

[0011] The first trench and the second trench are symmetrically arranged with respect to a symmetry plane; the symmetry plane is parallel to the second central plane of the SiC substrate; the bottom surfaces of the first trench and the second trench are parallelograms symmetrically arranged with respect to the symmetry plane;

[0012] A P-type ohmic contact electrode is provided on the top surface of the SiC substrate, as well as on the inner wall surfaces and bottom surfaces of the first trench and the second trench;

[0013] A P-region doping region is formed between the P-type ohmic contact electrode and the SiC substrate;

[0014] An N-type ohmic contact electrode is provided at the bottom of the SiC substrate;

[0015] An N-region doping region is formed between the SiC substrate and the N-type ohmic contact electrode;

[0016] The first trench and the second trench are both filled with neutron conversion material.

[0017] Furthermore, the thickness of the SiC substrate is between 350 μm and 400 μm; the depth of the first trench and the second trench is between 20 μm and 50 μm.

[0018] Furthermore, the width of the first trench and the second trench is 4 μm to 20 μm.

[0019] Furthermore, the included angle between the central plane of the first trench / second trench and the first central plane of the SiC substrate is 30° to 85°.

[0020] Furthermore, the thickness of the P-region doping region does not exceed 0.5 μm; the thickness of the N-region doping region does not exceed 0.5 μm.

[0021] Furthermore, the P-type ohmic contact electrode and the N-type ohmic contact electrode are formed into Ti / Au electrodes through ion implantation and metal evaporation processes, with a thickness of 50 nm to 200 nm.

[0022] Furthermore, the filling rate of the neutron conversion material is 50% to 100%.

[0023] Beneficial effects: A trench-type silicon carbide neutron detector structure with high detection efficiency according to the present invention has several trench groups etched on the top surface of the SiC substrate. Each trench group includes trench units connected in sequence along the direction of the first central plane of the SiC substrate. The trench units include a first trench and a second trench symmetrically arranged, and the bottom surfaces of the first trench and the second trench are parallelograms symmetrically arranged. The present invention improves the trench structure of the traditional neutron detector. Through the setting of the trench groups, the filling area of the neutron conversion material is increased, and at the same time, the contact area between the neutron conversion material and the SiC region is also increased, reducing the self-absorption effect of secondary particles and significantly improving the detection efficiency of the detector. Description of the Drawings

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0025] Figure 1 Top view of the high-detection-efficiency trench silicon carbide neutron detector structure of the present invention;

[0026] Figure 2 Left view of the high-detection-efficiency trench silicon carbide neutron detector structure of the present invention;

[0027] Figure 3 Top view of the existing straight-groove type neutron detector structure in the embodiment of the present invention;

[0028] Figure 4 Schematic diagram of the relationship between the detection efficiency of the silicon carbide neutron detector structure of the present invention and the angle α between the parallelepiped of the constituent unit and the Y-axis under different conversion materials;

[0029] Figure 5 Relationship between the detection efficiency of the straight-groove type detector and the ratio of the groove width to the unit size under different unit sizes in the embodiment of the present invention;

[0030] Figure 6 Energy deposition spectrum diagram of the silicon carbide neutron detector structure in the embodiment of the present invention;

[0031] Figure 7 Neutron conversion material in the embodiment of the present invention 6 LiF and neutron conversion material 10 Schematic diagram of the detection efficiency of the detector under different filling rates of B.

[0032] Wherein: 1, SiC substrate; 2, P-region doping area; 3, P-type ohmic contact electrode; 4, N-type ohmic contact electrode; 5, trench unit; 51, first trench; 52, second trench; 6, N-region doping area; 7, neutron conversion material; A, first central plane; B, second central plane. Detailed implementation manners

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0034] This embodiment introduces a high-detection-efficiency trench silicon carbide neutron detector structure, as Figure 1 and Figure 2 shown, including: a SiC substrate 1 made of 4H-SiC material, a P-type ohmic contact electrode 3, an N-type ohmic contact electrode 4, a neutron conversion material 7, and an N-region doping region 6;

[0035] A plurality of trench groups are etched on the top surface of the SiC substrate 1;

[0036] The trench group includes a plurality of trench units 5 connected in sequence along the direction of the first central plane A of the SiC substrate 1;

[0037] The trench unit 5 includes a first trench 51 and a second trench 52;

[0038] The first trench 51 and the second trench 52 are symmetrically arranged with respect to a symmetry plane 53; the symmetry plane 53 is parallel to the second central plane B of the SiC substrate 1; the bottom surfaces of the first trench 51 and the second trench 52 are parallelograms symmetrically arranged with respect to the symmetry plane 53;

[0039] P-type ohmic contact electrodes 3 are arranged on the top surface of the SiC substrate 1, the inner wall surfaces and the bottom surfaces of the first trench 51 and the second trench 52;

[0040] A P-region doping region 2 is formed between the P-type ohmic contact electrode 3 and the SiC substrate 1;

[0041] An N-type ohmic contact electrode 4 is arranged at the bottom of the SiC substrate 1;

[0042] An N-region doping region 6 is formed between the SiC substrate 1 and the N-type ohmic contact electrode 4;

[0043] The first trench 51 and the second trench 52 are both filled with a neutron conversion material 7.

[0044] Specifically, in this embodiment, a number of groove groups are etched on the top surface of the SiC substrate 1; the bottom surfaces of the first groove 51 and the second groove 52 are parallelograms symmetrically arranged, and the side wall surfaces of the first groove 51 and the second groove 52 are perpendicular to the bottom surface, forming a phase hexahedron-shaped groove; through the spatial phase arrangement of the hexahedron basic unit, a triangular waveform surface structure is formed; as Figure 1 and Figure 2 shown; wherein, the groove width of the phase hexahedron-shaped groove is T, W cell is the unit size, Tg is the groove spacing, L is the unit length, H is the groove depth, and α is the groove angle;

[0045] Preferably, the thickness of the SiC substrate 1 is between 350 μm and 400 μm; the depth of the first groove 51 and the second groove 52 is between 20 μm and 50 μm;

[0046] In this embodiment, the neutron conversion material 7 filled inside the first groove 51 and the second groove 52 is 6 LiF and 10 B.

[0047] Preferably, the width T of the first groove 51 and the second groove 52 is 4 μm to 20 μm;

[0048] Preferably, the included angle between the central plane of the first groove 51 / second groove 52 and the first central plane A of the SiC substrate 1 is 30° to 85°.

[0049] Specifically, the P-region doping region 2 and the N-region doping region 6 of this embodiment are both formed by ion implantation. The ion implantation covers the side walls and the bottom surface of the groove, and a positive electrode is formed through metal evaporation. The thickness of the P-region doping region 2 does not exceed 0.5 μm. The thickness of the N-region doping region 6 does not exceed 0.5 μm.

[0050] Preferably, the P-type ohmic contact electrode 3 and the N-type ohmic contact electrode 4 are formed into Ti / Au electrodes through ion implantation and metal evaporation processes, and the thickness is 50 nm to 200 nm.

[0051] Preferably, the material filling rate of the neutron conversion material 7 is 50% to 100%. That is, the volume of the neutron conversion material filled in the first groove 51 and the second groove 52 accounts for the proportion of the groove volume.

[0052] Specifically, the first groove 51 / second groove 52 of this embodiment is a hexahedron-shaped groove. The first groove 51 and the second groove 52 together form a phase hexahedron corrugated configuration groove, as Figure 1 and Figure 2 shown. Through the spatial phase arrangement of the hexahedron basic unit, a triangular waveform surface structure is formed;

[0053] The cross-section of the phase hexahedron corrugated configuration groove formed by the first groove 51 and the second groove 52 is V-shaped. The depth, width, and included angle of the groove can all be optimized according to detection requirements. In this embodiment, the depth of the phase hexahedron corrugated configuration groove is 20 μm to 50 μm, the width is 4 μm to 20 μm, and the included angle between the central plane of the first groove 51 / the second groove 52 and the first central plane A of the SiC substrate 1 is between 30° and 85°;

[0054] In this embodiment, P-region doping regions 2 are formed between the neutron conversion material and the P-type ohmic contact electrode 3 in the first groove 51 and the second groove 52 and the SiC substrate 1. The P-region doping regions 2 therein are filled on the side walls and the bottom surface of the first groove 51 / the second groove 52 by ion implantation.

[0055] Specifically, the neutron conversion material filled in the phase hexahedron corrugated configuration groove in this embodiment is 6 LiF or 10 B. The conversion material undergoes a nuclear reaction with neutrons to generate secondary charged particles (such as alpha particles, tritium particles, etc.). The particles deposit energy in the SiC material to form an electrical signal that can be detected.

[0056] Specifically, since the structure of the traditional rectangular groove type neutron detector is relatively simple, as Figure 3 shown, only rectangular grooves are etched on the front surface of the SiC substrate, and then the neutron conversion material is backfilled into the grooves. Based on the traditional rectangular groove silicon carbide neutron detector, in this embodiment, the rectangular grooves are changed to two parallelepiped grooves arranged symmetrically, and P-region doping regions are formed in the grooves by ion implantation, which can greatly increase the utilization rate of the neutron conversion material and reduce the self-absorption effect of secondary charged particles, thereby greatly improving the neutron detection efficiency.

[0057] Specifically, the groove group in this embodiment is etched on the SiC substrate by plasma etching technology. During the etching process, the etching rate and the groove shape need to be controlled to ensure the uniformity and consistency of the grooves.

[0058] Example 1:

[0059] The Monte Carlo simulation is carried out on the phase hexahedron corrugated configuration silicon carbide neutron detector structure and the rectangular groove silicon carbide neutron detector in this embodiment by using the Monte Carlo software Geant4 to verify the advantages of the phase hexahedron corrugated configuration silicon carbide neutron detector structure in this embodiment. The electron incident path is as shown in the appendix Figure 2As shown, the measurement of the detector detection efficiency is based on the premise that the filling rate of the conversion material is 100%. The relationship between the detection efficiency of the phase hexahedron corrugated configuration silicon carbide neutron detector structure in this embodiment and the angle α between the constituent unit parallelepiped and the Y-axis is shown in the appendix Figure 4 , under different unit sizes, the relationship between the detection efficiency of the straight-groove type detector and the ratio of the groove width to the unit size is shown in the appendix Figure 5 . When the unit size W cell is 20μm, the groove depth is 40μm, the unit length L = 50μm, and the filling material in the groove is 6 LiF, and the angle α of the phase hexahedron corrugated configuration groove is 85°, the detection efficiency can reach 17.48%; when the unit size W cell is 20μm, the groove depth is 40μm, the unit length L = 50μm, and the filling material in the groove is 10 B, and the angle α of the phase hexahedron corrugated configuration groove is 85°, the detection efficiency can reach 47.87%. Under the same size, the detection efficiency of the straight-groove type silicon carbide neutron detector is shown in the appendix Figure 7 , with a maximum of 13.13%. Obviously, the detection efficiency of the phase hexahedron corrugated configuration silicon carbide neutron detector in this embodiment is greatly improved compared with that of the traditional straight-groove structure.

[0060] Example 2:

[0061] The Geant4 software of Monte Carlo was used to count the energy and count of secondary particles deposited in SiC after nuclear reaction in the phase hexahedron corrugated configuration silicon carbide neutron detector structure of this embodiment. Under different angles α, the energy deposition spectrum of the detector filled with 6 LiF is shown in the appendix Figure 6 . The low-energy discriminator (LLD) of the system is set to 300 KeV. In the figure, an obvious 3 H particle peak (2.73 MeV) and a smaller α particle peak (2.05 MeV) can be seen. This is because 3 the penetration power of H particles is much stronger than that of α particles, and it is easier to enter the SiC region and be detected. Many high-energy peaks above 2.73 MeV are observed in the deposition spectrum. This is two secondary particles generated by one neutron 3Both H and α enter the SiC region to deposit energy and are counted, with the maximum energy reaching 4.78 MeV. As the angle of α increases, the count of particles in the energy range between 0.3 MeV and 1.0 MeV will slightly decrease, while the count in the energy range between 1.0 MeV and 1.5 MeV will significantly increase. Overall, as the angle increases, the energy spectrum will shift towards the high-energy end, proving that the energy deposited by particles in the SiC region has increased significantly, further proving the above view. Moreover, the increase in the count at the medium-energy end is greater than the decrease in the count at the low-energy end, and the total count of particles will increase. And compared with the energy deposition diagram of the straight-groove type SiC neutron detector, the count of the phase hexahedron corrugated configuration SiC neutron detector in this embodiment in the energy range between 1.0 MeV and 1.5 MeV is also significantly greater than that of the straight-groove type SiC neutron detector. Therefore, the detection efficiency of the phase hexahedron corrugated configuration SiC neutron detector in this embodiment has been greatly improved compared with that of the straight-groove type SiC neutron detector.

[0062] Example 3:

[0063] On the premise that the existing etching technology is underdeveloped, when the groove depth is fixed at 40 μm, explore whether the phase hexahedron corrugated configuration silicon carbide neutron detector in this embodiment can increase the reaction rate of the conversion material, reduce the self-absorption effect, and improve the detection efficiency of the device at different filling rates. The structure of the phase hexahedron corrugated configuration silicon carbide neutron detector in this embodiment is simulated and analyzed by the Monte Carlo software Geant4. At different 6 LiF / 10 B filling rates, the detection efficiency of the detector is as shown in the appendix Figure 7 shown. It can be seen that as the 6 LiF filling rate continuously decreases, the detection efficiency of the detector also decreases accordingly, and the two almost maintain a linear relationship. The change in the filling rate will cause the 6 LiF in the conversion layer unit volume to decrease, and the reaction rate between neutrons and the conversion material to decrease. This change is linearly changed with the decrease of the powder filling rate, resulting in the detection efficiency of the detector also changing linearly. However, compared with the detection efficiency of the straight-groove type silicon carbide neutron detector in the appendix Figure 7 when the structural parameters are the same, H = 40, L = 50 μm, T / Wcell = 0.8, and the filling rate is 100%, the detection efficiency of the phase hexahedron corrugated configuration silicon carbide neutron detector structure in this embodiment is 17.47%, while the detection efficiency of the straight-groove type silicon carbide neutron detector is 13.13%. There is still an improvement compared with it. For 10 B material, because 10The reaction rate of Material B with neutrons is very high. However, because the energy of the secondary particles generated by the reaction is relatively low, the particle range is prone to self-absorption effects. Appropriately reducing the material density can make it easier for the secondary particles to pass through the conversion material and reach the SiC region. Therefore, with a slight decrease in the filling rate, the detection efficiency of the detector will have a small increase. When the filling rate is 80%, the detection efficiency can reach 52.08%. This shows that when the filling material is 10 B, the detection efficiency of the phase hexahedron corrugated configuration silicon carbide neutron detector structure has been greatly improved compared to that of the straight-groove type silicon carbide detector. Based on the above multi-dimensional data analysis and comprehensive consideration, the phase hexahedron corrugated configuration silicon carbide neutron detector in this embodiment can significantly increase the reaction area of the conversion material, reduce the self-absorption effect, and further prove that the phase hexahedron corrugated configuration silicon carbide neutron detector structure in this embodiment has great advantages.

[0064] In summary, the phase hexahedron corrugated configuration silicon carbide neutron detector structure in this embodiment has the following technical effects:

[0065] Compared with the traditional straight-groove type silicon carbide neutron detector, the phase hexahedron corrugated configuration silicon carbide neutron detector structure in this embodiment improves the structure of etching grooves on the substrate, can increase the filling area of the conversion material, and at the same time can also increase the contact area between the neutron conversion material and the SiC region, reducing the self-absorption effect of the secondary particles and significantly improving the detection efficiency of the detector to a certain extent. Since the chemical properties of SiC are stable and the etching difficulty is very high, but under the traditional theory, the neutron detection efficiency is proportional to the groove depth. Under the existing etching technology, the deep groove etching difficulty is relatively high. Therefore, without increasing the groove depth, the contact area of the conversion material is increased, the self-absorption effect is reduced, and the utilization rate of the conversion material is improved, thus greatly improving the detection efficiency.

[0066] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A trench silicon carbide neutron detector structure with high detection efficiency, characterized in that, Comprising: SiC substrate (1), P-type ohmic contact electrode (3), N-type ohmic contact electrode (4), neutron conversion material (7); A plurality of groove groups are etched on the top surface of the SiC substrate (1); The groove group includes a plurality of groove units (5) connected in sequence along the direction of the first central plane (A) of the SiC substrate (1); The groove unit (5) includes a first groove (51) and a second groove (52); The first groove (51) and the second groove (52) are symmetrically arranged with respect to the symmetry plane (53); the symmetry plane (53) is parallel to the second central plane (B) of the SiC substrate (1); the bottom surfaces of the first groove (51) and the second groove (52) are parallelograms symmetrically arranged with respect to the symmetry plane (53); P-type ohmic contact electrodes (3) are arranged on the top surface of the SiC substrate (1), the inner wall surfaces and the bottom surfaces of the first groove (51) and the second groove (52); A P-region doping region (2) is formed between the P-type ohmic contact electrode (3) and the SiC substrate (1); An N-type ohmic contact electrode (4) is arranged at the bottom of the SiC substrate (1); An N-region doping region (6) is formed between the SiC substrate (1) and the N-type ohmic contact electrode (4); The first groove (51) and the second groove (52) are both filled with neutron conversion material (7).

2. The structure of a trench silicon carbide neutron detector with high detection efficiency according to claim 1, characterized in that, The thickness of the SiC substrate (1) is between 350 μm and 400 μm; the depths of the first groove (51) and the second groove (52) are between 20 μm and 50 μm.

3. The structure of a trench silicon carbide neutron detector with high detection efficiency according to claim 1, characterized in that, The widths of the first groove (51) and the second groove (52) are 4 μm to 20 μm.

4. A high-detection-efficiency trench silicon carbide neutron detector structure according to claim 1, characterized in that, The included angle between the central plane of the first groove (51) / second groove (52) and the first central plane (A) of the SiC substrate (1) is 30° to 85°.

5. A high-detection-efficiency trench silicon carbide neutron detector structure according to claim 1, wherein The thickness of the P-region doping region (2) does not exceed 0.5 μm; the thickness of the N-region doping region (6) does not exceed 0.5 μm.

6. The structure of a trench silicon carbide neutron detector with high detection efficiency according to claim 1, characterized in that, The P-type ohmic contact electrode (3) and the N-type ohmic contact electrode (4) are formed into Ti / Au electrodes by ion implantation and metal evaporation processes, and the thickness is 50 nm to 200 nm.

7. The structure of a trench silicon carbide neutron detector with high detection efficiency according to claim 1, characterized in that The filling rate of the neutron conversion material (7) is 50% to 100%.

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