Polycrystalline diamond beam loss detector and preparation process thereof
By using optical grade polycrystalline diamond beam loss detectors to prepare polycrystalline diamond thin films, the cost and radiation resistance of diamond detectors in strong current accelerators are solved, and low-cost and efficient beam loss monitoring is achieved.
Patent Information
- Application Number
- CN202411316242.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-20
- Publication Date
- 2025-01-07
AI Technical Summary
In the prior art, the application of beam current loss monitoring in strong current heavy ion accelerators is limited by cost and radiation resistance, especially the high price of electronic-grade diamond films and the difficulty in procurement.
Using low-cost optical grade polycrystalline diamond films, polycrystalline diamond beam loss detectors are prepared through polishing, cleaning, oxidation treatment and coating technologies to form detectors with low cost and high performance.
It greatly reduces the cost of beam loss monitoring on strong current heavy ion accelerators, provides efficient beam loss detection capabilities, and is suitable for use in high-energy irradiation environments.
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Figure CN119277833A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of photoelectric detection, and in particular to a polycrystalline diamond beam loss detector and a preparation process thereof. Background Art
[0002] Heavy ion accelerators are devices that use artificial methods to generate high-speed ion beams. They are important tools for exploring fundamental interactions, material structure, and the evolution of the universe. They are also platforms for developing advanced nuclear technologies related to economic and social development and national security. High current, high energy, and high bunch power are the development trends of heavy ion accelerators.
[0003] Since the 21st century, with the comprehensive development of science and technology, nuclear science has also faced new development opportunities. The United States and Europe have formulated medium- and long-term development plans for nuclear physics research, pointing out that the frontier areas of heavy ion nuclear physics research are atomic nuclear structure and nuclear astrophysics, properties of strongly interacting matter, and new physics beyond the standard model. Driven by these scientific goals, countries around the world are building large-scale heavy ion accelerator research facilities, such as the Facility for Antiproton and Ion Research (FAIR) in Germany, the Facility for Rare-isotope Beams (FRIB) in the United States, and the Système de Production d'Ions Radioactifs en Ligne-2 (SPIRAL2) in France. The High Intensity heavy-ion Accelerator Facility (HIAF) of the Institute of Modern Physics, Chinese Academy of Sciences integrates the advantages of a new generation of heavy-ion accelerators in its design. It can provide high current, wide energy range, a rich variety of stable nuclear and radioactive ion beams, and high-power heavy ion bunches.
[0004] During the operation of a high-current accelerator, an important issue is the need to monitor the beam loss of the device in real time throughout the entire section. Once a device in the accelerator device fails, it may cause the beam that is normally accelerated or transmitted along the center of the beam line to deviate from the center, thereby hitting other equipment and causing damage to the equipment. When the beam deviates from the center, a large number of secondary particles will be generated due to the beam hitting the accelerator vacuum pipe or other equipment. By measuring the change in the counting rate of secondary particles, it can be determined that the accelerator beam is abnormal, and a signal is given to cut off the beam from the front end to achieve the purpose of protecting the experimental equipment and accurately locate the accelerator fault. Therefore, it is necessary to install a beam loss detector in the entire accelerator section for real-time monitoring of the beam loss, to determine whether the accelerator device is operating normally, and to protect the experimental equipment. The beam loss detector is an important component to ensure the normal operation of the high-current accelerator device.
[0005] Commonly used beam loss monitoring detectors (BLM) include ionization chambers, PIN photodiodes, scintillators + PMTs, scintillators + SiPMs, silicon semiconductor detectors, etc. Ionization chambers are the most commonly used beam loss monitoring detectors. Ionization chambers have a slow response time and a time resolution of 50us. Although plastic scintillator detectors have a fast response time, their radiation resistance is too poor and they cannot be used for a long time. Silicon semiconductor detectors can also be used as beam loss monitors, but their radiation resistance is worse than that of scintillators and their service life is short. In recent years, diamond detectors, as a new type of nuclear radiation detector, have also been widely used in beam loss monitoring. They have the following unique advantages: (1) High temperature and high pressure resistance and low noise. The diamond bandgap width is 5.47eV, it is insensitive to visible light, and its breakdown electric field is as high as 10MV / cm; it has ultra-high thermal conductivity and can work stably at a high temperature of 120°C. (2) Strong radiation resistance. Diamond SP3 hybrid CC bond binding energy is very high, lattice bonding is strong, even under high-dose high-energy heavy ion irradiation, its lattice loss is very small, and it has strong radiation resistance. (3) Fast time response, time resolution is less than 60ps. (4) High counting rate, the diamond detector time signal width is less than 10ns, so its counting rate is as high as 10 8 -10 9 pps. Ideally suited as a beam loss detector on high current devices.
[0006] Although diamond detectors have excellent performance in irradiation detection, their application in beam loss monitoring of high-current heavy ion accelerators is restricted by many practical reasons. The first is that they are relatively expensive. In order to accurately monitor beam loss, at least several hundred beam loss monitors are required on the HIAF device.
[0007] In order to obtain a diamond beam loss detector, in addition to purchasing finished products, you can also use diamond film to develop it yourself. Diamond film has different classifications according to its application, but in the application of irradiation detectors, it can be roughly divided into electronic grade diamond film and optical grade diamond film. The main difference between the two grades of diamond film lies in the content of N and B impurities. The content of N and B in electronic grade diamond film is at the ppb level, while the content of N and B elements in optical grade diamond film is at the ppm level. To make a high-performance diamond detector, an electronic grade diamond film substrate is required. Although detector-grade diamond film has been commercially produced in many foreign countries, due to the relatively backward semiconductor industry in my country, electronic grade diamond film cannot be grown in China at present. Foreign electronic grade diamond film is not only very expensive, but also too expensive to use in the production of diamond beam loss detectors, and difficult to purchase. Summary of the invention
[0008] The invention provides a preparation process of a polycrystalline diamond beam loss detector. The detector is based on an inexpensive optical-grade polycrystalline diamond film, has low production cost, simple structure and is easy to process.
[0009] In a first aspect, the present invention provides a process for preparing a polycrystalline diamond beam loss detector, comprising the following steps:
[0010] Selecting an optical grade polycrystalline diamond film as a wafer, and polishing both sides of the wafer;
[0011] Cleaning both sides of the wafer to remove organic grease and graphite layer on the surface;
[0012] Using strong oxidizing acid or oxygen plasma etching technology to oxidize the surface of the wafer;
[0013] A Cr film or a Ti film is plated on the surface of the wafer by using a magnetron sputtering coating technology, and an Au film is plated on the outer side of the Cr film or the Ti film. After the coating is completed, vacuum annealing is performed to form a contact electrode on the surface of the wafer;
[0014] A wafer with contact electrodes formed on the surface is packaged in a shielding shell to form a polycrystalline diamond beam loss detector, and a ceramic circuit board is used as a lead-out circuit board of the polycrystalline diamond beam loss detector.
[0015] In some implementations, cleaning both sides of the wafer includes:
[0016] The wafer was boiled in a saturated solution of H2SO4+KNO3 for 2 hours to remove the organic layer and graphite on the surface;
[0017] After taking out the wafer, boil it in H2SO4 solution for 30 minutes to remove KNO3 crystals produced on the surface of the wafer;
[0018] Boiling the wafer in aqua regia for 30 minutes to oxidize the surface of the wafer;
[0019] The wafer was ultrasonically cleaned using deionized water and dried under an inert gas environment.
[0020] In some implementations, cleaning both sides of the wafer includes:
[0021] The wafer was ultrasonically cleaned for 5 minutes using acetone, anhydrous ethanol, and deionized water to remove surface contaminants;
[0022] The wafer was boiled in aqua regia for 20 minutes, and then ultrasonically cleaned with ionized water for 5 minutes.
[0023] The wafer was cleaned in a solution of H2SO4:HNO3=3:2 for 20 minutes, and then ultrasonically cleaned in deionized water for 5 minutes.
[0024] The wafer was cleaned in a solution of H2SO4:H2O2=5:1 for 20 minutes, and then ultrasonically cleaned in deionized water for 5 minutes.
[0025] Drying under inert gas environment;
[0026] The surface of the wafer is oxidized using oxygen plasma etching technology.
[0027] In some implementations, the contact electrode and the wafer are in ohmic contact.
[0028] In some implementations, the Au film has a thickness of 50 nm-200 nm; the Cr film or the Ti layer has a thickness of 50 nm-150 nm.
[0029] In some implementations, the cross-sectional shape of the contact electrode is rectangular or circular.
[0030] In some implementations, in the polishing process performed on both sides of the wafer, the polishing accuracy is less than 10 nm.
[0031] In a second aspect, the present invention also provides a polycrystalline diamond beam loss detector prepared by the above-mentioned preparation process, comprising a shell, wherein a high-frequency SMA connector, a ceramic lead-out circuit board and a diamond polycrystalline film are encapsulated in the shell, and the surface of the diamond polycrystalline film is plated with a contact electrode, and the high-frequency SMA connector is connected to the diamond polycrystalline film through the ceramic lead-out circuit board.
[0032] In some implementations, the structure of the detector is an MSM structure, and the MSM structure is a metal-semiconductor-metal structure.
[0033] In some implementations, the detector has a signal width of 3-4 ns and a rise time of 0.5-1.5 ns.
[0034] Beneficial effects of the present invention:
[0035] Compared with the currently expensive electronic-grade polycrystalline detectors, the present invention uses optical-grade polycrystalline diamond film to prepare a diamond beam loss detector, which greatly reduces the cost of beam loss monitoring on a high-current heavy ion accelerator. BRIEF DESCRIPTION OF THE DRAWINGS
[0036] Figure 1 is a structural diagram of a detector in an embodiment of the present invention;
[0037] Figure 2 is the Raman spectrum of the optical grade diamond polycrystalline film in the embodiment of the present invention;
[0038] Figure 3 : is the IV curve of the Cr / Au type contact electrode in the embodiment of the present invention;
[0039] Figure 4 It is a structural diagram of a ceramic lead-out circuit board in an embodiment of the present invention;
[0040] Figure 5 This is an overall packaging diagram of the detector in an embodiment of the present invention;
[0041] Figure 6 Schematic diagram of the time signal of the 241Am source in an embodiment of the present invention.
[0042] The numbers in the figure are as follows: 1-fixing screw holes of the detector housing, 2-upper housing of the detector, 3-high-frequency SMA connector, 4-ceramic lead circuit board, 5-diamond polycrystalline film, 6-lower housing of the detector.
[0043] The drawings are only used for illustrative purposes and should not be construed as limitations on this patent. In order to better illustrate this embodiment, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted. The same or similar numbers correspond to the same or similar parts. The terms describing the positional relationship in the drawings are only used for illustrative purposes and should not be construed as limitations on this patent. DETAILED DESCRIPTION
[0044] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.
[0045] Embodiment 1:
[0046] This embodiment provides a process for preparing a polycrystalline diamond beam loss detector, comprising the following steps:
[0047] The first step: polishing. Select an optical grade polycrystalline diamond film as the wafer and polish both sides of the wafer.
[0048] It should be noted that the polycrystalline diamond film used in the present invention is grown by microwave chemical vapor deposition (MWCVD). In the polycrystalline diamond film, starting from the growth substrate surface along the growth direction, the charge collection distance (CCD) and the charge collection efficiency (CCE) gradually increase. The closer to the growth substrate, the smaller the polycrystalline lattice size, and the smaller the CCD and CCE.
[0049] In this embodiment, the efficiency of the detector increases linearly with the average lattice size of the crystal. Polishing the base surface can improve the performance of the detector; the growth orientation of polycrystalline is random, and this random growth mode will cause the roughness of the polycrystalline growth surface to be as high as 10% of the thickness of the diamond film, that is, the roughness of a 500um diamond film is 50um. The surface flatness of the diamond film will affect the contact between the metal electrode and the crystal, and thus also affect the performance of the detector. Therefore, in this embodiment, both sides of the diamond film need to be polished. In this implementation, the polishing accuracy of the domestic polycrystalline diamond film is less than 10nm.
[0050] Step 2: Diamond film cleaning: cleaning both sides of the wafer to remove organic grease and graphite layer on its surface.
[0051] It should be noted that in this embodiment, before using the diamond film to make the contact electrode, both sides of the diamond film need to be cleaned to remove the surface organic grease and the surface graphite layer, and the surface of the diamond film needs to be oxygen-terminated (the surface of the diamond film is oxidized using a strong oxidizing acid or oxygen plasma etching technology) to obtain a contact electrode with excellent performance.
[0052] In this embodiment, the specific steps for cleaning the diamond film are:
[0053] S1. First, boil the diamond film in a boiling saturated solution of H2SO4+KNO3 for 2 hours to effectively remove the organic layer and graphite on the surface;
[0054] S2. Take out the diamond film and boil it in a boiling pure H2SO4 solution for 30 minutes to remove KNO3 crystals that may have formed on the surface of the diamond film.
[0055] S3. Boil the diamond film in boiling aqua regia (3HCl+HNO3) for 30 minutes to oxidize the surface of the diamond film to facilitate the formation of a link between the metal and the surface of the diamond film.
[0056] S4. Ultrasonic clean the diamond film with deionized water and dry it in a clean room filled with argon or nitrogen.
[0057] Step 3: Make an ohmic electrode. Use strong oxidizing acid or oxygen plasma etching technology to oxidize the surface of the wafer; use magnetron sputtering coating technology to coat the surface of the wafer with a Cr film or a Ti film, and coat the outer side of the Cr film or the Ti film with an Au film. After the coating is completed, vacuum annealing is performed to form a contact electrode on the surface of the wafer.
[0058] It should be noted that in order to lead the electron-hole pairs generated in the diamond film to the external circuit and form an observable current signal, it is necessary to add contact electrodes to both ends of the diamond film. The contact between metal and semiconductor is a very important issue in the manufacture of semiconductor devices, which directly affects the performance of the device. The contact between metal and semiconductor is divided into Schottky contact and ohmic contact. The characteristic of ohmic contact is that the contact electrode does not produce obvious additional impedance in the device, and its IV curve is linear. Therefore, a good ohmic contact does not change the performance of the semiconductor device.
[0059] The detector structure in this embodiment is an MSM structure, such as Figure 1 shown.
[0060] In the present invention, the metal material of the ohmic electrodes on both sides of the detector is the same, which is Cr / Au electrode or Ti / Au electrode. Figure 3 The IV curve of the Cr / Au contact electrode shows that a good ohmic contact is formed. The specific manufacturing process is: fix the diamond film under a mask of different shapes, and use magnetron sputtering coating technology to coat the film with corresponding thickness of Cr / Au or Ti / Au. After coating, vacuum annealing is performed at a high temperature of 450-500℃ for 1 hour.
[0061] It should be noted that, in this embodiment, the shape of the prepared ohmic electrode can be rectangular, circular, or striped, etc., and a mask plate of a corresponding shape can be machined according to specific needs.
[0062] The ohmic electrode is composed of two layers of metal films. The first layer is a Cr or Ti layer with a thickness of about 50nm-150nm. The second layer is an Au layer with a thickness of about 50nm-200nm. The smaller the metal layer thickness, the smaller the dead layer thickness of the detector.
[0063] Step 4: Detector packaging: packaging the wafer with contact electrodes formed on the surface in a shielding shell to form a polycrystalline diamond beam loss detector, and using a ceramic circuit board as the lead-out circuit board of the polycrystalline diamond beam loss detector.
[0064] It should be noted that in order to reduce the leakage current of the detector, the detector lead circuit board adopts a ceramic circuit board, such as Figure 4 As shown in the figure, the leakage current of the detector can be reduced to the pA level. In order to reduce noise, a shielding shell is also designed for the detector, as shown in the figure. Figure 5 As shown. Using the DBA-II fast preamplifier of miron company to measure 241 The time signal of the Am source, such as Figure 6 As shown, the signal width is about 3-4ns and the rise time is about 1ns.
[0065] Embodiment 2:
[0066] This embodiment provides a preparation process for a polycrystalline diamond beam loss detector. The preparation process of this embodiment 2 is basically the same as that of embodiment 1, and the main difference is that the method of cleaning the diamond film in the second step is different.
[0067] The method for cleaning the diamond film in this embodiment is:
[0068] S1. Use acetone, anhydrous ethanol and deionized water to ultrasonically clean the diamond film for 5 minutes to remove surface contaminants. Then boil the diamond film in boiling aqua regia (3HCl+HNO3) for 20 minutes, take it out and use deionized water to ultrasonically clean the diamond film for 5 minutes;
[0069] S2. The diamond film was placed in a heated H2SO4:HNO3=3:2 for 20 minutes, and then the diamond film was ultrasonically cleaned with deionized water for 5 minutes;
[0070] S3. The diamond film was cleaned in heated H2SO4:H2O2=5:1 for 20 minutes, and then ultrasonically cleaned with deionized water for 5 minutes.
[0071] S4. Ultrasonic cleaning of the diamond film with deionized water and drying in a clean room filled with argon or nitrogen;
[0072] S5. Oxidation treatment is performed on the surface of the diamond film using oxygen plasma etching technology.
[0073] Compared with the current expensive electronic-grade polycrystalline detectors, the detector prepared by the above method uses optical-grade polycrystalline diamond film to prepare diamond beam loss detectors, which greatly reduces the cost of beam loss monitoring on high-current heavy ion accelerators.
[0074] Embodiment 3:
[0075] The present embodiment provides a polycrystalline diamond beam loss detector. The polycrystalline diamond beam loss detector in the present embodiment selects an optical grade polycrystalline diamond film as a wafer, polishes both sides of the wafer; cleans both sides of the wafer to remove organic grease and graphite layer on the surface; oxidizes the wafer surface using a strong oxidizing acid or oxygen plasma etching technique; and utilizes magnetron sputtering coating technology to coat Cr / Au or Ti / Au of corresponding thickness on both sides of the wafer. After the coating is completed, vacuum annealing is performed at a high temperature of 450-500°C for 1 hour to form a contact electrode on the surface of the wafer; a ceramic circuit board is used as a lead-out circuit to connect to the wafer, and the ceramic circuit board and the wafer are packaged; thereby, the detector is prepared.
[0076] The polycrystalline diamond beam loss detector in this embodiment includes an upper housing 2 of the detector, a high-frequency SMA connector 3, a ceramic lead-out circuit board 4, a diamond polycrystalline film 5, and a lower housing 6 of the detector. The upper housing 2 of the detector is provided with a fixing screw hole 1 of the detector housing, and a fixing member can be used to package the upper housing 2 of the detector and the lower housing 6 of the detector through the fixing screw hole 1 of the detector housing. A high-frequency SMA connector 3, a ceramic lead-out circuit board 4, and a diamond polycrystalline film 5 are packaged between the upper housing 2 of the detector and the lower housing 6 of the detector. The surface of the diamond polycrystalline film is plated with a contact electrode, and the high-frequency SMA connector 3 is connected to the diamond polycrystalline film 5 through the ceramic lead-out circuit board 4.
[0077] Compared with the currently expensive electronic-grade polycrystalline detectors, the detector of Example 3 of the present invention utilizes optical-grade polycrystalline diamond film to prepare a diamond beam loss detector, which greatly reduces the cost of beam loss monitoring on high-current heavy ion accelerators.
[0078] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. Similarly, in order to simplify the present invention and help understand one or more of the various inventive aspects, in the above description of exemplary embodiments of the present invention, the various features of the embodiments of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. Wherein, the claims that follow the specific embodiment are hereby expressly incorporated into the specific embodiment, wherein each claim itself is a separate embodiment of the present invention.
[0079] It should be noted that the above embodiments illustrate the present invention rather than limit the present invention, and those skilled in the art may design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference symbol between brackets shall not be construed as a limitation to the claims.
[0080] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.
Claims
1. A process for preparing a polycrystalline diamond beam loss detector, characterized in that: The steps include: Selecting an optical grade polycrystalline diamond film as a wafer, and polishing both sides of the wafer; Cleaning both sides of the wafer to remove organic grease and graphite layer on the surface; Using strong oxidizing acid or oxygen plasma etching technology to oxidize the surface of the wafer; A Cr film or a Ti film is plated on the surface of the wafer by using a magnetron sputtering coating technology, and an Au film is plated on the outer side of the Cr film or the Ti film. After the coating is completed, vacuum annealing is performed to form a contact electrode on the surface of the wafer; A wafer with contact electrodes formed on the surface is packaged in a shielding shell to form a polycrystalline diamond beam loss detector, and a ceramic circuit board is used as a lead-out circuit board of the polycrystalline diamond beam loss detector.
2. The process for preparing a polycrystalline diamond beam loss detector according to claim 1, characterized in that: The step of cleaning both sides of the wafer comprises: The wafer was boiled in a saturated solution of H2SO4+KNO3 for 2 hours to remove the organic layer and graphite on the surface; After taking out the wafer, boil it in H2SO4 solution for 30 minutes to remove KNO3 crystals produced on the surface of the wafer; Boiling the wafer in aqua regia for 30 minutes to oxidize the surface of the wafer; The wafer was ultrasonically cleaned using deionized water and dried under an inert gas environment.
3. The process for preparing a polycrystalline diamond beam loss detector according to claim 1, characterized in that: The step of cleaning both sides of the wafer comprises: The wafer was ultrasonically cleaned for 5 minutes using acetone, anhydrous ethanol, and deionized water to remove surface contaminants; The wafer was boiled in aqua regia for 20 minutes, and then ultrasonically cleaned with ionized water for 5 minutes. The wafer was cleaned in a solution of H2SO4:HNO3=3:2 for 20 minutes, and then ultrasonically cleaned in deionized water for 5 minutes. The wafer was cleaned in a solution of H2SO4:H2O2=5:1 for 20 minutes, and then ultrasonically cleaned in deionized water for 5 minutes. Drying under inert gas environment; The surface of the wafer is oxidized using oxygen plasma etching technology.
4. The process for preparing a polycrystalline diamond beam loss detector according to claim 1, characterized in that: The contact electrode and the wafer are in ohmic contact.
5. The process for preparing a polycrystalline diamond beam loss detector according to claim 1, characterized in that: The thickness of the Au film is 50nm-200nm; the thickness of the Cr film or the Ti film is 50nm-150nm.
6. The process for preparing a polycrystalline diamond beam loss detector according to claim 4, characterized in that: The cross-sectional shape of the contact electrode is rectangular or circular.
7. The process for preparing a polycrystalline diamond beam loss detector according to claim 1, characterized in that: In the polishing process for the two sides of the wafer, the polishing accuracy is less than 10 nm.
8. A polycrystalline diamond beam loss detector prepared by the preparation process according to any one of claims 1 to 7, characterized in that: The invention comprises a shell, wherein a high-frequency SMA connector, a ceramic lead-out circuit board and a diamond polycrystalline film are encapsulated in the shell, a contact electrode is plated on the surface of the diamond polycrystalline film, and the high-frequency SMA connector is connected to the diamond polycrystalline film through the ceramic lead-out circuit board.
9. The polycrystalline diamond beam loss detector according to claim 8, characterized in that: The structure of the detector is an MSM structure.
10. The polycrystalline diamond beam loss detector according to claim 9, characterized in that: The signal width of the detector is 3-4ns, and the rise time is 0.5-1.5ns.