An intrinsic diamond based thermal neutron detector and fabrication process

Abstract

The application discloses a hot neutron detector based on intrinsic diamond and a preparation process. The hot neutron detector based on intrinsic diamond comprises an intrinsic diamond substrate, groove structures which are distributed at intervals on the intrinsic diamond substrate, a hot neutron conversion layer which is filled in the groove structures, a top electrode which is formed on the surface of the intrinsic diamond substrate and forms a Schottky contact with the intrinsic diamond substrate, a P-type heavily doped diamond epitaxial layer which is formed on the back surface of the intrinsic diamond substrate, and a bottom electrode which is formed on the back surface of the P-type heavily doped diamond epitaxial layer and forms an ohmic contact with the P-type heavily doped diamond epitaxial layer.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, specifically to a thermal neutron detector based on intrinsic diamond and its fabrication process. Background Technology

[0002] Diamond, a fourth-generation semiconductor and also known as the ultimate semiconductor, boasts an ultra-wide bandgap of 5.47 eV, a high breakdown electric field, high carrier saturation drift velocity, and extremely high thermal conductivity. Compared to traditional silicon-based devices, diamond exhibits superior performance under extreme conditions such as high temperature, high pressure, and intense radiation, meeting the requirements of fields such as power electronics, aerospace, high-energy physics experiments, and boron neutron capture therapy.

[0003] Traditional thermal neutron detectors are planar devices, utilizing planar... 6 LiF or 10 Materials such as B are used as thermal neutron conversion layers. Thermal neutrons generate high-energy particles that are emitted in opposite directions. One of these particles enters the detector and generates a signal. However, since only one type of particle can be detected, and the high-energy particles deposit some energy in the thick thermal neutron conversion layer, the detection efficiency is low. The high-energy particles also cause defects in the material, leading to a decrease in detector performance and lifespan.

[0004] Diamond has a higher displacement threshold energy and strong radiation resistance, giving it a natural advantage in high-energy particle detection. Summary of the Invention

[0005] To address the aforementioned problems, this invention discloses a thermal neutron detector based on intrinsic diamond, comprising: an intrinsic diamond substrate; trench structures spaced apart on the intrinsic diamond substrate; a thermal neutron conversion layer filling the trench structures; a top electrode formed on the surface of the diamond substrate and forming a Schottky contact therewith; a p-type heavily doped diamond epitaxial layer formed on the back side of the intrinsic diamond substrate; and a bottom electrode formed on the back side of the p-type heavily doped diamond epitaxial layer and forming an ohmic contact therewith.

[0006] In the intrinsic diamond-based thermal neutron detector of the present invention, it is preferable that it further includes an oxygen termination interface formed on the surface of the intrinsic diamond substrate.

[0007] In the intrinsic diamond-based thermal neutron detector of the present invention, preferably, the doping concentration of the p-type heavily doped diamond epitaxial layer is greater than 1e19cm. -3 .

[0008] In the intrinsic diamond-based thermal neutron detector of the present invention, preferably, the depth of the trench structure is greater than 50 micrometers.

[0009] In the intrinsic diamond-based thermal neutron detector of the present invention, preferably, the thermal neutron conversion layer is...6 LiF, 10 B or a combination of both.

[0010] This invention also discloses a fabrication process for a thermal neutron detector based on intrinsic diamond, comprising the following steps: forming a P-type heavily doped diamond epitaxial layer on an intrinsic diamond substrate; forming a trench structure spaced apart on the intrinsic diamond substrate; filling the trench structure with a thermal neutron conversion layer; growing a bottom electrode on the surface of the P-type heavily doped diamond epitaxial layer and annealing to form an ohmic contact; forming a top electrode on the surface of the intrinsic diamond substrate to form a Schottky contact.

[0011] In the fabrication process of the intrinsic diamond-based thermal neutron detector of the present invention, preferably, the following step is included before forming the top electrode: forming an oxygen termination interface on the surface of the intrinsic diamond substrate.

[0012] In the fabrication process of the intrinsic diamond-based thermal neutron detector of the present invention, preferably, the doping concentration of the p-type heavily doped diamond epitaxial layer is greater than 1e19cm. -3 .

[0013] In the fabrication process of the intrinsic diamond-based thermal neutron detector of the present invention, preferably, the depth of the trench structure is greater than 50 micrometers.

[0014] In the fabrication process of the intrinsic diamond-based thermal neutron detector of the present invention, preferably, the step of filling the thermal neutron conversion layer in the trench structure includes: ... 6 LiF powder or 10 Powder B or a mixture thereof is placed in deionized water to form a liquid or colloidal state; it is then placed in a centrifuge with a diamond substrate, and centrifugal force is used to fill the trenches in the diamond substrate; it is then dried to remove the liquid in the thermal neutron conversion layer and solidify it into a solid state.

[0015] Beneficial effects:

[0016] Compared to traditional semiconductor materials, diamond has stronger radiation resistance and can work stably for a long time in strong radiation environments. Schottky electrodes and ohmic electrodes are fabricated on the top and bottom surfaces of the wafer, respectively. The vertical structure makes the electric field lines parallel to the trench, eliminating the problem of carrier aggregation caused by low electric field in the trench of traditional silicon and silicon carbide pin trench structures. Diamond has an atomic number similar to that of human tissue, making it more suitable for medical testing and significantly reducing the workload required for detector calibration. Diamond has high thermal conductivity and low dark current properties, and can work in special environments such as high temperature. A fabrication process for diamond grooved thermal neutron detectors is proposed, making the fabrication processes of diamond SBDs and thermal neutron detectors compatible. Attached Figure Description

[0017] Figure 1 This is a flowchart of the fabrication process for a thermal neutron detector based on intrinsic diamond.

[0018] Figures 2-8 This is a schematic diagram of the various stages of the fabrication process for a thermal neutron detector based on intrinsic diamond. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for explaining this invention and are not intended to limit this invention. The described embodiments are merely some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0020] In the description of this invention, it should be noted that the terms "upper," "lower," "vertical," and "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0021] Furthermore, many specific details of the invention, such as the structure, materials, dimensions, processing techniques, and methods of the device, are described below to provide a clearer understanding of the invention. However, as those skilled in the art will understand, the invention may be implemented without adhering to these specific details. Unless specifically indicated below, various parts of the device may be made of materials known to those skilled in the art, or may employ materials with similar functionality developed in the future.

[0022] Figure 1 This is a flowchart illustrating the fabrication process of a thermal neutron detector based on intrinsic diamond. (For example...) Figure 1 As shown, the fabrication process of the intrinsic diamond-based thermal neutron detector includes the following steps: Step S1: Select an intrinsic single-crystal diamond substrate 100 (a polycrystalline diamond substrate is used for large areas), and epitaxially grow a 1 μm thick P-type heavily doped diamond epitaxial layer 101, resulting in the structure shown below. Figure 2 As shown. The thickness of the diamond substrate is 100-500 micrometers. The doping concentration of the p-type heavily doped diamond epitaxial layer is greater than 1e19cm.-3 .

[0023] Step S2: Place the P-type heavily doped diamond epitaxial layer 101 on the back side, and prepare a thick metal layer as a hard mask layer 102 on the front side of the device using methods such as PVD.

[0024] Photoresist is spin-coated to etch trench patterns, which can be elongated trenches, round holes, square holes, hexagonal holes, etc. The metal hard mask layer 102 is etched using dry or wet etching processes, followed by removal of the photoresist. The resulting structure is as follows: Figure 3 As shown.

[0025] The diamond substrate 100 was deeply etched using RIE etching technology to a depth greater than 50 micrometers, forming a trench structure with spaced distribution. After etching, the remaining metal hard mask layer 102 was removed using wet etching, resulting in the structure shown below. Figure 4 As shown.

[0026] Step S3, will 6 LiF powder or 10 Powder B, or a mixture thereof, is placed in deionized water (or anhydrous ethanol, etc.) and ultrasonically stirred to form a liquid or colloidal state. Then, it is placed with diamond in a centrifuge, and centrifugal force is used to fill the trench structure of the diamond substrate. Finally, it is dried to remove the liquid within the thermal neutron conversion layer, solidifying it into a solid state to form the thermal neutron conversion layer thermal 103. The resulting structure is as follows: Figure 5 As shown.

[0027] Step S4: Using electron beam evaporation (EBE) or physical vapor deposition (PVD) processes, a metal such as Ti / Pt / Au is grown on the back side of the device, i.e., the P-type heavily doped diamond epitaxial layer 101, as a bottom electrode 104. Annealing is then performed to form an ohmic contact between the electrode and the P-type heavily doped diamond epitaxial layer 101. The resulting structure is as follows: Figure 6 As shown.

[0028] Step S5: Perform oxygen plasma RIE treatment on the front side of the device, i.e., the surface of the diamond substrate 100 (CMP surface polishing can be selectively performed before treatment) to form an oxygen terminal interface on the surface and increase the Schottky barrier height of the device.

[0029] Step S6: Aluminum, gold, platinum, or other metals are grown on the surface of the diamond substrate 100 as a top electrode 105, forming a Schottky junction with the diamond substrate 100. The resulting structure is as follows: Figure 7 As shown; a Schottky electrode pattern is photolithographically etched, the metal is etched and the resist is removed, and the metal on the surface of the trench structure is removed, resulting in the structure shown. Figure 8 As shown. The Schottky contact top electrode can also be fabricated directly using a lift-off process.

[0030] like Figure 8 As shown, the intrinsic diamond-based thermal neutron detector includes an intrinsic diamond substrate 100; trench structures spaced apart on the intrinsic diamond substrate 100; a thermal neutron conversion layer 103 filling the trench structures; a top electrode 102 formed on the surface of the diamond substrate 100 and forming a Schottky contact therewith; a p-type heavily doped diamond epitaxial layer 101 formed on the back side of the intrinsic diamond substrate 100; and a bottom electrode 104 formed on the back side of the p-type heavily doped diamond epitaxial layer 101 and forming an ohmic contact therewith.

[0031] A trench-type thermal neutron detector structure is employed to effectively increase thermal neutron detection efficiency and enhance the detection capability of two opposing high-energy particles. A vertical Schottky barrier diode structure generates a parallel-downward high-electric-field sensitive region within the detector, mitigating the low electric field problem on both sides of the trench caused by homogeneous electrodes in traditional PIN structures. Utilizing the inherent strong radiation resistance of diamond material, defects generated in the detector during high-energy particle incidence are effectively reduced, increasing the detector's lifespan. The high thermal conductivity of diamond is leveraged to address the adverse effects on device performance in high-temperature and other special application scenarios.

[0032] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A thermal neutron detector based on intrinsic diamond, characterized in that, include: Intrinsic diamond substrate; The trench structure is spaced out on the intrinsic diamond substrate; Thermal neutron conversion layer, filling the trench structure; The top electrode is formed on the surface of the intrinsic diamond substrate and forms a Schottky contact therewith; A p-type heavily doped diamond epitaxial layer is formed on the back side of an intrinsic diamond substrate; The bottom electrode is formed on the back side of the P-type heavily doped diamond epitaxial layer and forms an ohmic contact with it.

2. The intrinsic diamond-based thermal neutron detector according to claim 1, characterized in that, It also includes an oxygen terminal interface, formed on the surface of the intrinsic diamond substrate.

3. The intrinsic diamond-based thermal neutron detector according to claim 1, characterized in that, The doping concentration of the p-type heavily doped diamond epitaxial layer is greater than 1e19cm. -3 .

4. The intrinsic diamond-based thermal neutron detector according to claim 1, characterized in that, The depth of the trench structure is greater than 50 micrometers.

5. The intrinsic diamond-based thermal neutron detector according to claim 1, characterized in that, The thermal neutron conversion layer is 6 LiF, 10 B or a combination of both.

6. A fabrication process for a thermal neutron detector based on intrinsic diamond, characterized in that, Includes the following steps: A P-type heavily doped diamond epitaxial layer is formed on an intrinsic diamond substrate; A trench structure is formed at intervals on the intrinsic diamond substrate; Fill the trench structure with a thermal neutron conversion layer; A bottom electrode is grown on the surface of a p-type heavily doped diamond epitaxial layer and annealed to form an ohmic contact. A top electrode is formed on the surface of an intrinsic diamond substrate, forming a Schottky contact.

7. The fabrication process of the intrinsic diamond-based thermal neutron detector according to claim 6, characterized in that, The process before forming the top electrode also includes the following steps: forming an oxygen termination interface on the surface of the intrinsic diamond substrate.

8. The fabrication process of the intrinsic diamond-based thermal neutron detector according to claim 6, characterized in that, The doping concentration of the p-type heavily doped diamond epitaxial layer is greater than 1e19cm. -3 .

9. The intrinsic diamond-based thermal neutron detector according to claim 1, characterized in that, The depth of the trench structure is greater than 50 micrometers.

10. The fabrication process of the intrinsic diamond-based thermal neutron detector according to claim 6, characterized in that, The steps for filling the thermal neutron conversion layer in the trench structure include: Will 6 LiF powder or 10 When powder B or a mixture of both is placed in deionized water, it forms a liquid or colloidal state. The material and the diamond substrate were placed in a centrifuge, and centrifugal force was used to fill the grooves in the diamond substrate. The liquid in the thermal neutron conversion layer is removed by drying, causing it to solidify into a solid state.

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