Microgroove structure neutron detector based on 4H-SiC material and preparation method thereof

Abstract

The invention discloses a 4H-SiC material-based micro-groove structure neutron detector and a preparation method thereof, the neutron detector comprises a 4H-SiC substrate, at least one N + layer, an I + layer and at least one P + layer from bottom to top, the lower part of the 4H-SiC substrate is provided with a cathode, and the upper part of the P + layer is provided with an anode; wherein the I + layer adopts a 3-5-layer structure with different doping concentrations, and the 4H-SiC doping concentration between the layers is gradually reduced in a gradient manner; the P + layer adopts a 3-5-layer structure with different doping concentrations, and the 4H-SiC doping concentrations among the layers are gradually increased in a gradient manner; 7 to 10 layers of gradient doped micro grooves are etched in a PI region of the neutron detector, and each groove is filled with a neutron conversion material 6LiF; wherein the PI region is formed by a P + layer and an I + layer; the neutron detector has the advantages of micro groove, deep etching, large sensitive area, small electric leakage, radiation resistance, high temperature resistance, high energy resolution, high detection efficiency and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor neutron detection, and in particular to, but not limited to, a micro-groove structure neutron detector based on 4H-SiC material and a preparation method thereof. Background Art

[0002] The demand for neutron detection technology is growing in fields such as nuclear energy and aerospace. Traditional semiconductor neutron detectors suffer from low effective detection efficiency and high leakage current, especially in extreme environments such as high temperature and strong radiation, where their performance degrades significantly. 4H-SiC, as a wide-bandgap semiconductor material, offers advantages such as high-temperature resistance, radiation resistance, and high breakdown electric field strength, making it ideal for the fabrication of high-performance neutron detectors. However, existing 4H-SiC neutron detectors still require improvement in structural design and fabrication process to further enhance neutron detection efficiency and reduce leakage current. Summary of the Invention

[0003] In view of this, an embodiment of the present invention provides a micro-groove structure neutron detector based on 4H-SiC material and a preparation method thereof, aiming to effectively improve the neutron detection efficiency and effectively reduce the leakage problem when etching the gradually doped PIN-type groove.

[0004] The technical solution of the embodiment of the present invention is achieved as follows: An embodiment of the present invention provides a micro-groove structure neutron detector based on 4H-SiC material, which includes, from bottom to top, a 4H-SiC substrate, at least one N+ layer, an I+ layer, and at least one P+ layer. A cathode is provided at the bottom of the 4H-SiC substrate, and an anode is provided at the top of the P+ layer. The I+ layer adopts a 3-5 layer structure with different doping concentrations, and the 4H-SiC doping concentration between each layer decreases gradually from bottom to top. The P+ layer adopts a 3-5 layer structure with different doping concentrations, and the 4H-SiC doping concentration between each layer increases gradually from bottom to top. A plurality of gradually doped micro-grooves are etched in the PI region of the neutron detector, and each groove is filled with a neutron conversion material. 6 LiF; wherein the PI region is composed of a P+ layer and an I+ layer.

[0005] In a specific embodiment, the total thickness of the P+ layer is 5 to 15 μm, and it is composed of 3 to 5 layers of uniform thickness. From bottom to top, the doping concentration of the first layer is 10 17 to 10 18 cm -3 , the doping concentration of the second layer is 10 18 to 10 19 cm -3 , the doping concentration of the third layer is 10 19 to 10 20 cm-3 , the doping concentration of the fourth layer is 10 19 to 10 20 cm -3 , the doping concentration of the fifth layer is 10 19 to 10 20 cm -3 .

[0006] In a specific embodiment, the total thickness of the I+ layer is 80 to 100 μm, and it is composed of 3 to 5 layers of uniform thickness. From bottom to top, the doping concentration of the first layer is 10 15 to 10 16 cm -3 , the doping concentration of the second layer is 10 14 to 10 15 cm -3 , the doping concentration of the third layer is 10 13 to 10 14 cm -3 , the fourth layer doping concentration is 10 13 to 10 14 cm -3 , the doping concentration of the fifth layer is 10 13 to 10 14 cm -3 .

[0007] In a specific embodiment, the thickness of the N+ layer is 10 to 20 μm, and the doping concentration is 10 17 to 10 19 cm -3 .

[0008] In a specific embodiment, the grooves are in the shape of a cuboid; the groove width and spacing are both 5 to 10 μm, and the groove depth is 50 to 80 μm.

[0009] In a specific embodiment, the neutron conversion material 6 The purity of LiF is greater than or equal to 90%; 6 The particle size of LiF is less than or equal to 5 μm.

[0010] In a specific embodiment, the cathode is an ohmic contact, and the material is any one metal or a stack of multiple metals of Ni, Ti, Al, and Au, and the thickness of the cathode is 50 to 150 μm; the anode is a Schottky contact, and the material is any one or more metal stacks of Ni and Au, and the thickness of the anode is 50 to 150 μm.

[0011] A second aspect of the present invention provides a method for preparing a micro-groove structure neutron detector based on 4H-SiC material, comprising the following steps: S1. Clean the 4H-SiC substrate using the industrial standard wet cleaning process RCA; S2, growing an N+ layer on the top of the 4H-SiC substrate using a low-pressure chemical vapor deposition (LPCVD) process, with a doping concentration of 10¹ 7 to 10¹ 9 cm⁻³, growth temperature is 1500 to 1600℃, mainly doped with nitrogen or phosphorus, and gas flow rate is controlled at 30 to 100ppm; S3. Using an LPCVD process to grow a graded-doped I+ layer on top of the N+ layer, the I+ layer consists of 3 to 5 layers, each layer has a thickness of 15 to 30 μm, and the doping concentration decreases gradually from bottom to top. The growth temperature is 1500 to 1600° C. The doping gas is ammonia NH3 or phosphine PH3, and the gas flow rate is controlled to be 10 to 20 ppm. S4. Using an LPCVD process to form a graded doped P+ layer on top of the I+ layer, the P+ layer consists of 3 to 5 layers, each layer is 2 to 4 μm thick, the doping concentration increases gradually from bottom to top, the growth temperature is 1500 to 1600° C., the doping is mainly boron or aluminum, and the gas flow rate is controlled at 40 to 100 ppm; S5. Place the grown first device in acetone, isopropyl alcohol, or a deionized water solution and clean it with an ultrasonic cleaner for 10 to 20 minutes; wherein the first device is composed of a 4H-SiC substrate to a P+ layer; S6. Spin-coat the cleaned first device with a negative photoresist having a thickness of 1 to 2 μm, and soft-dry the device at a temperature of 80 to 120° C. for 30 to 60 seconds. Then, use photolithography pattern design software to design a groove pattern according to the detector size. Place the first device in a photolithography machine, and use deep ultraviolet light to expose the groove pattern according to a preset pattern. After development, dry the device at a temperature of 110 to 130° C. for 1 to 2 minutes. Immerse the first device in a developer for 1 to 2 minutes to develop the groove pattern. S7. Depositing a top contact based on a stack of either Ni or Au metals or both using electron beam evaporation technology, immersing the first device in a stripping solution to strip the photoresist to expose the P+ layer, cleaning the device with deionized water, and annealing the device at 400 to 500° C. with nitrogen gas N2 for 5 to 8 minutes to form a Schottky contact as an anode; S8. Deposit a bottom metal layer of any one or more metal stacks of Ni, Ti, Al, and Au by electron beam evaporation again, and anneal at 850 to 900° C. for 10 to 15 minutes in nitrogen gas N2 to complete the bottom ohmic contact electrode as the cathode, thereby forming a second device; the second device consists of an anode, a cathode, and a 4H-SiC substrate to a P+ layer; S9. The second device is again cleaned using an industrial standard wet cleaning process (RCA), and a 1 to 2 μm thick negative photoresist is spin-coated. The device is soft-dried at 80 to 120° C. for 30 to 60 seconds, and then exposed to a groove pattern according to a preset pattern using deep ultraviolet light. After development, the device is post-dried at 110 to 130° C. for 1 to 2 minutes, and the second device is immersed in a developer for 1 to 2 minutes to develop the groove pattern. The second device shown is composed of an anode, a cathode, and a 4H-SiC substrate to a P+ layer. S10, using plasma enhanced chemical vapor deposition (PECVD) technology to grow a SiO2 passivation layer on the top of the anode with a thickness of 50 to 100 nm, placing the second device after the SiO2 growth in a stripping solution, and stripping off the remaining photoresist to expose the window P+ layer; S11, etching the window P+ layer using dry etching or wet etching technology, etching the groove depth to the I+ layer to form multiple gradient doping micro-grooves; S12, removing the photoresist SiO2 passivation layer to expose the anode, forming a micro-groove structure neutron detector of 4H-SiC material; S13, will 6 LiF powder is filled into multiple gradient doping micro-grooves by wet centrifugation; S14, coating the surface of the micro-groove structure neutron detector of the filled 4H-SiC material with shadowless glue and curing it, thereby completing the packaging of the micro-groove structure neutron detector of the 4H-SiC material.

[0012] In a specific embodiment, step S11 includes three stages: S111, first stage: ICP power is maintained at 700 to 800W, bias voltage power is maintained at 80 to 100W, SF6 and O2 gas flow ratio is 20:5, etching is carried out for 25 to 30 minutes, sidewall angle is maintained at 85 to 90°, and 20 to 25μm deep trenches are etched; S112, second stage: increasing the ICP power to 750 to 850 W, while reducing the bias voltage power to 80 to 90 W, the gas flow ratio of SF6 and O2 is 20:5, etching for 25 to 35 minutes, and the etching depth is 15 to 20 μm; S113, the third stage: increase the ICP power to 800 to 900 W, and at the same time reduce the bias voltage power to 70 to 80 W, adjust the gas flow ratio of SF6 and O2 to 20:8, the etching time is 15 to 20 minutes, the etching depth is about 5 to 10 μm, and finally etch out a groove with a width of 5 to 10 μm, a spacing of 5 to 10 μm, and a depth of 50 to 80 μm.

[0013] In a specific embodiment, step S13 includes the following steps: S131, take some 6The LiF sample was ground into nano-scale powder in a grinder, and the powder was mixed with anhydrous ethanol at a ratio of 1g:10ml and then dispersed in an ultrasonic cleaner. 6 LiF powder particles, so that the particle size is less than or equal to 5μm, will be evenly mixed 6 The LiF solid-liquid mixture is coated in the groove of the PI area and placed in a centrifuge tube. The initial speed of the centrifuge is 3500 to 4000 r / min and it works for 1 to 2 minutes. In the second stage, the speed is adjusted to 8000 to 10000 r / min and it works for 1 to 2 minutes. This operation is repeated 3 to 5 times to fill the centrifuge tube. 6 The gaps between the LiF powders were cleared and the micro-groove structure neutron detector of 4H-SiC material was placed on a heating table and heated for 3 to 5 minutes at a temperature of 80 to 120°C.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention proposes a micro-groove structure neutron detector based on 4H-SiC material and its preparation method, which has the advantages of micro-grooves, deep etching, large sensitive area, small leakage, radiation resistance, high temperature resistance, high energy resolution and high detection efficiency. The effective sensitive area of 4H-SiC substrate is 25mm 2 In the preparation of the detector, a groove structure with simple process and high theoretical detection efficiency was selected. First, the optimal groove width and spacing parameters were simulated. Combined with the actual manufacturing process level and particle range, the groove width and spacing were selected to be 5 to 10 μm and the depth to be 50 to 80 μm. The energy of secondary particles generated by the reaction between neutrons and materials was determined. 6 LiF is used as the neutron conversion material. The device adopts a PIN junction structure, combined with the secondary particle range, and the sensitive layer is set to 75 to 150μm. The gradient space doping process GDSM-JTE terminal structure is introduced to reduce leakage. Through the relatively mature and easy-to-control ICP etching process, the ICP power, bias voltage and gas ratio are dynamically adjusted to etch the preset groove, and the liquid phase centrifugal method is used to fill the groove. 6 LiF powder is etched with gold on the PCB and soldered with micron-level gold wire as the signal lead. The test results show that the neutron detector proposed by this invention shows that the leakage current is less than 80nA at 0-1000V and the capacitance is stable at 22pA / cm at 0-100V. 2 , the carrier density is evenly distributed, indicating that the overall electrical characteristics of the detector are stable. In the temperature sensitivity test of 10℃-50℃, the event count rate recorded by the energy spectrum acquisition device in the same time period has little difference, indicating that the detector performance is less affected by temperature. Neutron tests were carried out in the BL-20 beamline test room of the China Spallation Neutron Source. The experimental results showed that the detector had a maximum count of 235cps and an absolute neutron detector efficiency of 3.16%. After 24 hours of high-flux neutron beam irradiation, the test No obvious shift in the energy spectrum peak was found, and the event count rate decreased by 0.6 cps, which is within the theoretical range. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive work, among which: Figure 1 A schematic cross-sectional view of a neutron detector with a micro-groove structure based on 4H-SiC material provided in an embodiment of the present invention; Figure 2 Filling provided by the embodiment of the present invention 6 Schematic diagram of the cross-sectional structure of a micro-groove structure neutron detector made of 4H-SiC material, a LiF neutron conversion material; Figure 3 Filling provided by the embodiment of the present invention 6 A front view of the gradient doping trench in the PI region of the LiF neutron conversion material; Figure 4 Filling provided by the embodiment of the present invention 6 Top view of the graded doping trench in the PI region of the LiF neutron conversion material.

[0016] Figure 5 Schematic diagram of the manufacturing process flow of a micro-groove structure neutron detector based on 4H-SiC material provided in an embodiment of the present invention.

[0017] Reference numerals: 1, anode; 2, P+ layer; 3, I+ layer; 4, N+ layer; 5, 4H-SiC substrate; 6, cathode; 7, 6 LiF powder. DETAILED DESCRIPTION

[0018] In order to make the purpose, 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 in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0019] In the following description, reference is made to “some embodiments”, which describes a subset of all possible embodiments, but it will be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0020] It should be pointed out that the terms "first\second\third" involved in the embodiments of the present invention are only used to distinguish similar objects and do not represent a specific ordering of the objects. It can be understood that "first\second\third" can be interchanged with a specific order or sequence where permitted, so that the embodiments of the present invention described here can be implemented in an order other than that illustrated or described here.

[0021] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art in the art to which the embodiments of the present invention pertain. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art and, unless specifically defined as herein, should not be interpreted in an idealized or overly formal sense.

[0022] The present invention proposes a neutron detector with a micro-groove structure based on 4H-SiC material, which is applied to the detection of thermal neutrons. Example 1 See Figure 1 , Figure 1 This is a schematic cross-sectional view of a micro-trench neutron detector based on 4H-SiC material. The neutron detector provided in this embodiment comprises, from bottom to top, a 4H-SiC substrate, at least one N+ layer (heavily doped with pentavalent elements nitrogen and phosphorus to form N-type conductivity with electrons as majority carriers), an I+ layer (a low-doped intrinsic region between the P+ and N+ layers, typically consisting of a lightly doped N-type 4H-SiC N⁻ base region), and at least one P+ layer (heavily doped with trivalent elements boron or aluminum to form P-type conductivity with holes as majority carriers). A cathode is provided below the 4H-SiC substrate, and an anode is provided above the P+ layer. Among them, the I+ layer adopts a 3 to 5-layer structure with different doping concentrations, and the 4H-SiC doping concentration between each layer decreases gradually from bottom to top; the P+ layer adopts a 3 to 5-layer structure with different doping concentrations, and the 4H-SiC doping concentration between each layer increases gradually from bottom to top; 8 to 10 layers of gradient doping micro-grooves are etched in the P+ layer and the I+ layer in the PI area of the neutron detector, and each groove is filled with neutron conversion material. 6 LiF, see Figure 2 ; Wherein, the PI region includes 6 to 10 layers of I+ layer and P+ layer.

[0023] Specifically, the thickness of the 4H-SiC substrate is 300 to 400 μm, and the layer is placed below the N+ layer with a doping concentration of 10 17 to 10 18 cm -3 4H-SiC material is used as the substrate, which has the advantages of high temperature resistance, radiation resistance, high breakdown electric field strength, and can increase the sensitivity of the neutron detector. Its effective sensitive area is 25mm 2 .

[0024] Specifically, the thickness of the N+ layer is 10 to 20 μm, and the doping concentration is 10 17 to 10 19 cm -3 .

[0025] Specifically, the total thickness of the I+ layer is 80 to 100 μm, which is composed of 3 to 5 layers of uniform thickness. From bottom to top, the doping concentration of the first layer is 10 15 to 10 16 cm -3 , the doping concentration of the second layer is 10 14 to 10 15 cm -3 , the doping concentration of the third layer is 10 13 to 10 14 cm -3 , the fourth layer doping concentration is 10 13 to 10 14 cm -3 , the doping concentration of the fifth layer is 10 13 to 10 14 cm -3 .

[0026] Specifically, the total thickness of the P+ layer is 5 to 15 μm, which is composed of 3 to 5 layers of uniform thickness. The doping concentration of the first layer from bottom to top is 10 17 to 10 18 cm -3 , the doping concentration of the second layer is 10 18 to 10 19 cm -3 , the doping concentration of the third layer is 10 19 to 10 20 cm -3 , the fourth layer doping concentration is 10 19 to 10 20 cm -3 , the doping concentration of the fifth layer is 10 19 to 10 20 cm -3The PIN structure is formed by forming N+ layer, I+ layer and P+ layer from bottom to top. This structure helps to optimize the performance of the detector. When an external voltage is applied between the P+ layer and the N+ layer, an electric field is formed, which causes the charge carriers (electrons and holes) in the I+ layer (intrinsic layer) to separate and drift under the action of the electric field. When charged particles (such as 、 When a neutron (e.g., a particle) is incident on the detector, energy deposition ionizes the atoms or molecules within the detector, generating charge. This charge is then collected by the electric field, forming a measurable electrical signal. By using gradient spatial doping modulation to form the I+ and P+ layers, the problem of single-point electric field concentration at the main junction edge can be effectively alleviated, leakage current can be significantly reduced, and a higher bias voltage can be provided to expand the depletion region, thereby increasing the detector's sensitive area and improving neutron detection accuracy. This demonstrates that PIN-structured 4H-SiC detectors can maintain excellent performance even in harsh environments such as high temperature and high radiation.

[0027] Specifically, the cathode is an ohmic contact, and the material is any one metal or a stack of multiple metals of Ni, Ti, Al, and Au, and the thickness of the cathode is 50 to 150 μm; the anode is a Schottky contact, and the material is any one or more metal stacks of Ni and Au, and the thickness of the anode is 50 to 150 μm.

[0028] Specifically, the shape of the groove is a rectangular parallelepiped, the groove width and spacing are both 5 to 10 μm, and the depth is 50 to 80 μm. Figure 3 and Figure 4 This increases 6 The volume of LiF and the effective contact area with the neutron detector are reduced, and the problem of high process difficulty is solved.

[0029] Specifically, neutron conversion materials 6 The purity of LiF is greater than or equal to 90%; 6 The particle size of LiF is less than or equal to 5 μm. 6 LiF as a 6 Li compounds have stable chemical properties and relatively mature coating and filling processes. The neutron detector proposed in this invention is mainly used for thermal neutrons with an energy range of 0.025eV~0.5eV and a wavelength range of 0.1Å~5Å. It uses the nuclear reaction method to detect neutrons. 6 LiF is used as a neutron conversion material. Neutrons react with the material to produce 2.04MeV particles and 2.43MeV 3 H particles increase the utilization of three-dimensional space, which increases the filling volume and can directly improve the neutron and conversion material 6The reaction probability of LiF is increased, thereby improving the detection efficiency of the detector.

[0030] Example 2 See Figure 5 , Figure 5 The following is a schematic diagram of the process flow for preparing a micro-groove structure neutron detector based on 4H-SiC material, which includes the following steps: S1. Perform RCA cleaning on the 4H-SiC substrate using an industrial standard wet cleaning process.

[0031] Specifically, the 4H-SiC substrate is cleaned using RCA (Resist Cleaning and Stripping) to ensure that the surface is clean and free of impurities.

[0032] S2, growing an N+ layer on the top of the 4H-SiC substrate using a low-pressure chemical vapor deposition (LPCVD) process, with a doping concentration of 10¹ 7 to 10¹ 9 cm⁻³, the growth temperature is between 1500 and 1600℃, it is mainly doped with nitrogen or phosphorus, and the gas flow rate is controlled at 30 to 100ppm.

[0033] S3. A gradient-doped I+ layer is generated on the upper portion of the N+ layer using an LPCVD process. The I+ layer consists of 3 to 5 layers, each layer is 15 to 30 μm thick, and the doping concentration decreases gradually from bottom to top. The growth temperature is 1500 to 1600°C, and the doping gas is ammonia NH3 or phosphine PH3, with a gas flow rate controlled at 10 to 20 ppm.

[0034] S4. A gradually doped P+ layer is generated on the upper portion of the I+ layer using an LPCVD process. The P+ layer consists of 3 to 5 layers, each layer is 2 to 4 μm thick, and the doping concentration increases gradually from bottom to top. The growth temperature is 1500 to 1600°C, and the doping is mainly done with boron or aluminum elements. The gas flow rate is controlled at 40 to 100 ppm.

[0035] S5. Place the first device after growth in acetone, isopropyl alcohol or deionized water solution and clean it with an ultrasonic cleaner for 10 to 20 minutes to remove contamination on the surface of the material; wherein the first device is composed of a 4H-SiC substrate to a P+ layer.

[0036] S6. Spin-coat the cleaned first device with a negative photoresist having a thickness of 1 to 2 μm, and soft-dry the device at a temperature of 80 to 120° C. for 30 to 60 seconds. Then, use photolithography pattern design software to design a groove pattern according to the detector size. Place the first device in a photolithography machine, and use deep ultraviolet light to expose the groove pattern according to a preset pattern. After development, dry the device at a temperature of 110 to 130° C. for 1 to 2 minutes. Immerse the first device in a developer for 1 to 2 minutes to develop the groove pattern. S7. Use electron beam evaporation technology to deposit a top contact based on any one or two metal stacks of Ni, Au, immerse the first device in a stripping solution to strip off the photoresist to expose the P+ layer, use deionized water to clean the device, and introduce nitrogen N2 at 400 to 500°C for annealing for 5 to 8 minutes to form a Schottky contact as the anode.

[0037] S8. Use electron beam evaporation again to deposit a bottom metal layer of any one or more metal stacks of Ni, Ti, Al, and Au, and introduce nitrogen N2 for annealing at 850 to 900°C for 10 to 15 minutes to complete the bottom ohmic contact electrode as the cathode to form a second device; the second device consists of an anode, a cathode and a 4H-SiC substrate to a P+ layer.

[0038] S9. The second device is again cleaned using the industrial standard wet cleaning process RCA, and a 1 to 2 μm thick negative photoresist is spin-coated. The device is then soft-dried at a temperature of 80 to 120° C. for 30 to 60 seconds. A groove pattern is exposed according to a preset pattern using deep ultraviolet light. After development, the device is post-dried at 110 to 130° C. for 1 to 2 minutes. The second device is immersed in a developer for 1 to 2 minutes to reveal the groove pattern.

[0039] S10. Using plasma enhanced chemical vapor deposition (PECVD) technology, a SiO2 passivation layer with a thickness of 50 to 100 nm is grown on the upper portion of the anode. The second device after the SiO2 growth is placed in a stripping solution to strip off the remaining photoresist to expose the window P+ layer.

[0040] S11. Etch the window P+ layer using dry etching or wet etching technology, and etch the groove depth to the I+ layer to form a plurality of gradient doping micro grooves.

[0041] Specifically, the step S11 includes three stages: S111, the first stage: the ICP power is maintained at 700 to 800 W, the bias voltage power is maintained at 80 to 100 W, the SF6 and O2 gas flow ratio is 20:5, the etching time is 25 to 30 minutes, the sidewall angle is maintained at 85 to 90 degrees, and a 20 to 25 μm deep trench is etched; S112, second stage: increasing the ICP power to 750 to 850 W, while reducing the bias voltage power to 80 to 90 W, with a flow ratio of SF6 to O2 gas of 20:5, etching for 25 to 35 minutes, and an etching depth of 15 to 20 μm; S113, the third stage: increase the ICP power to 800 to 900 W, while reducing the bias voltage power to 70 to 80 W, increase the SF6 and O2 gas flow ratio to 20:8, the etching time is 15 to 20 minutes, the etching depth is about 5 to 10 μm, and finally etch out a groove with a width of 5 to 10 μm, a spacing of 5 to 10 μm, and a depth of 50 to 80 μm.

[0042] S12, removing the SiO2 passivation layer to expose the anode, thereby forming a micro-groove structure neutron detector made of 4H-SiC material.

[0043] S13, will 6 LiF powder is filled into multiple gradient doping micro-grooves by wet centrifugation.

[0044] Specifically, the step S13 includes the following steps: S131, taking several 6 The LiF sample was ground into nano-scale powder in a grinder, and the powder was mixed with anhydrous ethanol at a ratio of 1g:10ml and then dispersed in an ultrasonic cleaner. 6 LiF powder particles, so that the particle size is less than or equal to 5μm, will be evenly mixed 6 The LiF solid-liquid mixture is coated in the groove of the PI area and placed in a centrifuge tube. The initial speed of the centrifuge is 3500 to 4000 r / min and it works for 1 to 2 minutes. In the second stage, the speed is adjusted to 8000 to 10000 r / min and it works for 1 to 2 minutes. This operation is repeated 3 to 5 times to fill the centrifuge tube. 6 The gaps between the LiF powders were cleared and the micro-groove structure neutron detector of 4H-SiC material was placed on a heating table and heated for 3 to 5 minutes at a temperature of 80 to 120°C.

[0045] S14, coating the surface of the micro-groove structure neutron detector of the filled 4H-SiC material with shadowless glue and curing it, thereby completing the packaging of the micro-groove structure neutron detector of the 4H-SiC material.

[0046] It should be understood that "one embodiment" or "an embodiment" mentioned throughout the specification means that the specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present invention. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner. It should be understood that in various embodiments of the present invention, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention. The serial numbers of the above-mentioned embodiments of the present invention are for description only and do not represent the advantages and disadvantages of the embodiments.

[0047] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0048] In the several embodiments provided herein, it should be understood that the disclosed methods can be implemented in other ways. The methods disclosed in the several method embodiments provided herein can be combined arbitrarily, unless they conflict, to produce new method embodiments. The features disclosed in the several method embodiments provided herein can be combined arbitrarily, unless they conflict, to produce new method embodiments.

[0049] The above description is merely an embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A micro-groove structure neutron detector based on 4H-SiC material, characterized in that: The neutron detector includes a 4H-SiC substrate, at least one N+ layer, an I+ layer and at least one P+ layer from bottom to top. A cathode is provided at the bottom of the 4H-SiC substrate and an anode is provided at the top of the P+ layer. The I+ layer adopts a 3-5 layer structure with different doping concentrations, and the 4H-SiC doping concentration between each layer decreases gradually from bottom to top. The P+ layer adopts a 3-5 layer structure with different doping concentrations, and the 4H-SiC doping concentration between each layer increases gradually from bottom to top. A plurality of gradient doping micro-grooves are etched in the PI area of the neutron detector, and each groove is filled with neutron conversion material. 6 LiF; wherein the PI region is formed by a P+ layer and an I+ layer.

2. The micro-groove structure neutron detector according to claim 1, characterized in that: The total thickness of the P+ layer is 5 to 15 μm, which is composed of 3 to 5 layers of uniform thickness. The doping concentration of the first layer from bottom to top is 10 17 to 10 18 cm -3 , the doping concentration of the second layer is 10 18 to 10 19 cm -3 , the doping concentration of the third layer is 10 19 to 10 20 cm -3 , the doping concentration of the fourth layer is 10 19 to 10 20 cm -3 , the doping concentration of the fifth layer is 10 19 to 10 20 cm -3 .

3. The micro-groove structure neutron detector according to claim 1, characterized in that: The total thickness of the I+ layer is 80 to 100 μm, which is composed of 3 to 5 layers of uniform thickness. The doping concentration of the first layer from bottom to top is 10 15 to 10 16 cm -3 , the doping concentration of the second layer is 10 14 to 10 15 cm -3 , the doping concentration of the third layer is 10 13 to 10 14 cm -3 , the doping concentration of the fourth layer is 10 13 to 10 14 cm -3 , the doping concentration of the fifth layer is 10 13 to 10 14 cm -3 .

4. The micro-groove structure neutron detector according to any one of claims 1 to 3, characterized in that: The thickness of the N+ layer is 10 to 20 μm, and the doping concentration is 10 17 to 10 19 cm -3 .

5. The micro-groove structure neutron detector according to any one of claims 1 to 3, characterized in that: The grooves are in a rectangular parallelepiped shape; the groove width and spacing are both 5 to 10 μm, and the groove depth is 50 to 80 μm.

6. The micro-groove structure neutron detector according to any one of claims 1 to 3, characterized in that: The neutron conversion material 6 The purity of LiF is greater than or equal to 90%; 6 The particle size of LiF is less than or equal to 5 μm.

7. The micro-groove structure neutron detector according to claim 1, characterized in that: The cathode is an ohmic contact, and the material is any one metal or a stack of multiple metals such as Ni, Ti, Al, and Au, and the thickness of the cathode is 50 to 150 μm; the anode is a Schottky contact, and the material is any one or more metal stacks such as Ni and Au, and the thickness of the anode is 50 to 150 μm; the thickness of the 4H-SiC substrate is 300 to 400 μm, and the doping concentration is 10 17 to 10 18 cm -3 .

8. A method for preparing a micro-groove structure neutron detector based on 4H-SiC material, characterized in that: The following steps are involved: S1. Clean the 4H-SiC substrate using the industrial standard wet cleaning process RCA; S2, growing an N+ layer on the top of the 4H-SiC substrate using a low-pressure chemical vapor deposition (LPCVD) process, with a doping concentration of 10¹ 7 to 10¹ 9 cm⁻³, growth temperature is 1500 to 1600℃, mainly doped with nitrogen or phosphorus, and gas flow rate is controlled at 30 to 100ppm; S3. Using an LPCVD process to grow a graded-doped I+ layer on top of the N+ layer, the I+ layer consists of 3 to 5 layers, each layer has a thickness of 15 to 30 μm, and the doping concentration decreases gradually from bottom to top. The growth temperature is 1500 to 1600° C. The doping gas is ammonia NH3 or phosphine PH3, and the gas flow rate is controlled to be 10 to 20 ppm. S4. Using an LPCVD process to form a graded doped P+ layer on top of the I+ layer, the P+ layer consists of 3 to 5 layers, each layer is 2 to 4 μm thick, the doping concentration increases gradually from bottom to top, the growth temperature is 1500 to 1600° C., the doping is mainly boron or aluminum, and the gas flow rate is controlled at 40 to 100 ppm; S5. Place the grown first device in acetone, isopropyl alcohol, or a deionized water solution and clean it with an ultrasonic cleaner for 10 to 20 minutes; wherein the first device is composed of a 4H-SiC substrate to a P+ layer; S6. Spin-coat the cleaned first device with a negative photoresist having a thickness of 1 to 2 μm, and soft-dry the device at a temperature of 80 to 120° C. for 30 to 60 seconds. Then, use photolithography pattern design software to design a groove pattern according to the detector size. Place the first device in a photolithography machine, and use deep ultraviolet light to expose the groove pattern according to a preset pattern. After development, dry the device at a temperature of 110 to 130° C. for 1 to 2 minutes. Immerse the first device in a developer for 1 to 2 minutes to develop the groove pattern. S7. Depositing a top contact based on a stack of either Ni or Au metals or both using electron beam evaporation technology, immersing the first device in a stripping solution to strip the photoresist to expose the P+ layer, cleaning the device with deionized water, and annealing the device at 400 to 500° C. with nitrogen gas N2 for 5 to 8 minutes to form a Schottky contact as an anode; S8. Deposit a bottom metal layer of any one or more metal stacks of Ni, Ti, Al, and Au by electron beam evaporation again, and anneal at 850 to 900° C. for 10 to 15 minutes in nitrogen gas N2 to complete the bottom ohmic contact electrode as the cathode, thereby forming a second device; the second device consists of an anode, a cathode, and a 4H-SiC substrate to a P+ layer; S9. The second device is again cleaned using an industrial standard wet cleaning process (RCA), and a 1 to 2 μm thick negative photoresist is spin-coated. The device is then soft-dried at a temperature of 80 to 120° C. for 30 to 60 seconds. A groove pattern is exposed using deep ultraviolet light according to a preset pattern. After development, the device is post-dried at 110 to 130° C. for 1 to 2 minutes. The second device is immersed in a developer for 1 to 2 minutes to develop the groove pattern. S10, using plasma enhanced chemical vapor deposition (PECVD) technology to grow a SiO2 passivation layer on the top of the anode with a thickness of 50 to 100 nm, placing the second device after the SiO2 growth in a stripping solution, and stripping off the remaining photoresist to expose the window P+ layer; S11, etching the window P+ layer using dry etching or wet etching technology, etching the groove depth to the I+ layer to form multiple gradient doping micro-grooves; S12, removing the SiO2 passivation layer to expose the anode, forming a micro-groove structure neutron detector made of 4H-SiC material; S13, will 6 LiF powder is filled into multiple gradient doping micro-grooves by wet centrifugation; S14, coating the surface of the micro-groove structure neutron detector of the filled 4H-SiC material with shadowless glue and curing it, thereby completing the packaging of the micro-groove structure neutron detector of the 4H-SiC material.

9. The method for preparing a micro-groove structure neutron detector according to claim 8, characterized in that: The step S11 includes three stages: S111, first stage: ICP power is maintained at 700 to 800W, bias voltage power is maintained at 80 to 100W, SF6 and O2 gas flow ratio is 20:5, etching is carried out for 25 to 30 minutes, sidewall angle is maintained at 85 to 90°, and 20 to 25μm deep trenches are etched; S112, second stage: increasing the ICP power to 750 to 850 W, while reducing the bias voltage power to 80 to 90 W, the gas flow ratio of SF6 and O2 is 20:5, etching for 25 to 35 minutes, and the etching depth is 15 to 20 μm; S113, the third stage: increase the ICP power to 800 to 900 W, and at the same time reduce the bias voltage power to 70 to 80 W, adjust the gas flow ratio of SF6 and O2 to 20:8, the etching time is 15 to 20 minutes, the etching depth is about 5 to 10 μm, and finally etch out a groove with a width of 5 to 10 μm, a spacing of 5 to 10 μm, and a depth of 50 to 80 μm.

10. The method for preparing a micro-groove structure neutron detector according to claim 8 or 9, characterized in that: The step S13 includes: S131, take some 6 The LiF sample was ground into nano-scale powder in a grinder, and the powder was mixed with anhydrous ethanol at a ratio of 1g:10ml and then dispersed in an ultrasonic cleaner. 6 LiF powder particles, so that the particle size is less than or equal to 5μm, will be evenly mixed 6 The LiF solid-liquid mixture is coated in the groove of the PI area and placed in a centrifuge tube. The initial speed of the centrifuge is 3500 to 4000 r / min and it works for 1 to 2 minutes. In the second stage, the speed is adjusted to 8000 to 10000 r / min and it works for 1 to 2 minutes. This operation is repeated 3 to 5 times to fill the centrifuge tube. 6 The gaps between the LiF powders were cleared and the micro-groove structure neutron detector of 4H-SiC material was placed on a heating table and heated for 3 to 5 minutes at a temperature of 80 to 120°C.

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