Method for preparing CZT high energy resolution radiation chip

Abstract

The present invention discloses a method for preparing a CZT high-energy resolution radiation chip, belonging to the field of electrical component production technology, comprising: S1. growing a CZT crystal; S2. preparing a desired CZT sheet using the CZT crystal; S3. injecting a certain dose of fluoride ions into the CZT sheet; S4. performing an annealing process on the CZT sheet after the fluoride ion injection to uniformly diffuse the fluoride ions in the CZT sheet, thereby improving lattice defects during CZT crystal growth; S5. injecting indium ions into the cathode surface layer of the CZT sheet to increase the resistivity of the CZT sheet and change the energy band structure of the CZT sheet to generate a stronger radiation signal; S6. performing an annealing process again to make the indium ions more uniformly distributed on the surface layer of the CZT sheet; S7. platinum-plating the cathode surface of the CZT sheet and indium-plating the anode surface of the CZT sheet; S8. connecting the CZT sheet to the cathode and anode of a detector, respectively, and then encapsulating the CZT sheet in a housing. The present invention has the advantages of improving lattice defects and increasing the carrier migration lifetime product.

Description

Technical Field

[0001] The invention belongs to the technical field of electrical component production, and in particular relates to a method for preparing a CZT high-energy resolution radiation chip. Background Art

[0002] CZT (cadmium zinc telluride) radiation detection material is an important semiconductor material widely used in radiation detectors, particularly for X-ray, gamma-ray, and neutron detection. This material possesses unique physical properties that give it significant advantages in radiation detection. Energy resolution is a key performance indicator for detectors, influenced by factors such as bulk resistivity, carrier-pulling lifetime product, and surface leakage current. During the growth process of CZT materials, lattice defects (such as vacancies and dislocations) often appear. These defects cause carrier scattering and reduce mobility. To address this issue, existing techniques employ doping during the CZT growth process to fill these defects or modify their properties, thereby reducing carrier scattering and improving electron mobility and carrier lifetime. However, during the growth of CZT crystals, the dopant element exhibits a segregation effect with varying segregation coefficients, resulting in uneven distribution of the dopant element in the CZT crystal both horizontally and vertically. This results in poor consistency in detectors made using this CZT crystal. In order to improve the uniformity of doping element distribution, fill lattice defects, and improve electron mobility and carrier lifetime, a method for preparing CZT high-energy resolution radiation chip is proposed. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art.

[0004] To this end, the present invention proposes a method for preparing a CZT high-energy resolution radiation chip, which has the advantages of improving lattice defects and increasing the carrier migration lifetime product.

[0005] The method for preparing a CZT high energy resolution radiation chip according to an embodiment of the present invention comprises the following steps:

[0006] S1. Growth of CZT crystals;

[0007] S2. Prepare the desired CZT sheet using a CZT crystal;

[0008] S3. injecting a certain dose of fluoride ions into the CZT sheet;

[0009] S4. Annealing the CZT sheet after fluoride ion implantation to uniformly diffuse the fluoride ions in the CZT sheet to improve lattice defects during CZT crystal growth;

[0010] S5. Implanting indium ions into the cathode surface of the CZT sheet to increase the resistivity of the CZT sheet and change the band structure of the CZT sheet, thereby generating a stronger radiation signal.

[0011] S6. Performing an annealing process again to make the indium ions more evenly distributed on the surface of the CZT sheet;

[0012] S7. Platinum is plated on the cathode surface of the CZT sheet and indium is plated on the anode surface of the CZT sheet;

[0013] S8. Connect the CZT sheet to the cathode and anode of the detector respectively, and then package them in a shell.

[0014] According to one embodiment of the present invention, in S3, the ion implantation energy is 30-50 keV; the ion implantation causes the concentration of fluorine (F) ions in the CZT wafer to reach 30 ppm.

[0015] According to one embodiment of the present invention, in S4, the annealing process temperature is 650° and maintained for 12 hours, and the atmosphere is an oxygen-free environment using an inert gas to avoid oxidation.

[0016] According to one embodiment of the present invention, in S5, indium ions are implanted into the surface layer of the CZT sheet to a depth of 200-500 nm, and the concentration of indium ions in the surface layer of the CZT sheet is 20 ppm.

[0017] According to one embodiment of the present invention, in S6, the annealing process temperature is 550°, the temperature holding time is 1-2 hours, and the atmosphere is an oxygen-free environment using inert gas.

[0018] According to one embodiment of the present invention, after step S6, photoresist is used to protect the cathode surface and the anode surface of the CZT sheet, while exposing the four side surfaces of the CZT sheet. Then, an insulating layer is formed on the four side surfaces of the CZT sheet to reduce surface leakage of the CZT sheet and improve the accuracy of subsequent detection data.

[0019] According to one embodiment of the present invention, the insulating layer is a silicon dioxide layer, and the thickness of the insulating layer is 500 nm.

[0020] According to one embodiment of the present invention, the insulating layer is prepared by chemical vapor deposition, and the deposition temperature is 300° C. - 400° C.

[0021] According to one embodiment of the present invention, in S2, a CZT sheet is cut according to the orientation of the CZT crystal, the size of the CZT sheet is 10 mm x 10 mm x 1 mm, and then the CZT sheet is ground and polished to make the surface roughness of the CZT sheet reach Ra ≤ 0.5 µm.

[0022] According to one embodiment of the present invention, in S7, both indium plating and platinum plating are performed using a magnetron sputtering process with a sputtering power of 50-200 W. The thickness of the platinum layer after sputtering is 500 nm, and the thickness of the indium layer after sputtering is 500 nm-1 µm.

[0023] The beneficial effects of the present invention are that the present invention improves the lattice defects during the growth of the CZT crystal by implanting fluorine ions into the CZT sheet, eliminates the deep energy levels in the CZT sheet, and increases the carrier migration lifetime product in the CZT sheet;

[0024] By injecting indium ions into the surface of the CZT sheet to a certain depth, the resistivity of the CZT sheet is increased, and the energy band structure of the CZT sheet is changed, thereby generating a stronger radiation signal.

[0025] During the production process, a silicon dioxide layer is prepared on the four side walls of the CZT sheet, which reduces the contact between the CZT sheet and impurity ions before packaging, thereby reducing leakage current and improving the accuracy of subsequent detection data.

[0026] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention.

[0027] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0029] Figure 1 Schematic diagram of the influence of F doping on the energy resolution of CZT in the present invention;

[0030] Figure 2 Schematic diagram of the effect of In doping on the energy resolution of CZT according to the present invention;

[0031] Figure 3 2 is a schematic cross-sectional view of the chip structure of the present invention;

[0032] Reference numerals:

[0033] 1. Cathode conductive layer; 2. Anode conductive layer; 3. Insulation layer; 5. CZT sheet. DETAILED DESCRIPTION

[0034] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0035] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, features defined as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0036] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0037] The following describes in detail a method for preparing a CZT high energy resolution radiation chip according to an embodiment of the present invention with reference to the accompanying drawings.

[0038] like Figure 3 As shown, the method for preparing a CZT high energy resolution radiation chip according to an embodiment of the present invention includes the following steps:

[0039] S1. CZT crystals are grown using a liquid phase method, wherein the zinc content is 10%. No other elements are doped during this process to reduce the uneven distribution of dopants in the CZT crystals due to different segregation effect coefficients during CZT crystal growth. The growth temperature range of the CZT crystals includes but is not limited to 1100°C, and the cooling rate is 1°C / h - 2°C / h. Steady cooling is maintained to reduce internal stress.

[0040] S2. Prepare the desired CZT sheet 5 using a CZT crystal; cut the CZT sheet 5 according to the orientation of the CZT crystal to a size of 10 mm x 10 mm x 1 mm, and accurately slice the sheet to facilitate subsequent electrode deposition. Grind and polish the CZT sheet 5 to a surface roughness of Ra ≤ 0.5 µm.

[0041] S3. Implant a certain dose of fluoride ions into the CZT sheet 5 ; the ion implantation energy is 30-50 keV; and the ion implantation is performed so that the concentration of fluoride (F) ions in the CZT sheet 5 reaches 30 ppm.

[0042] S4. Anneal the CZT sheet 5 after fluoride ion implantation at a temperature of 650°C for 12 hours in an oxygen-free atmosphere using an inert gas to prevent oxidation. The inert gas, including but not limited to nitrogen or argon, allows the fluoride ions to diffuse evenly throughout the CZT sheet 5, thereby improving lattice defects during CZT crystal growth. During CZT growth, the saturated vapor pressure of cadmium (Cd) is high, which easily forms cadmium vacancies during crystal growth. This results in carrier signals being absorbed by defects during transmission after generation. Fluoride ion implantation can significantly eliminate deep energy levels in the CZT sheet 5, thereby increasing the carrier migration lifetime product within the CZT sheet 5.

[0043] S5. Indium ions are injected into the cathode surface of the CZT sheet 5 to a depth of 200-500 nm, and the concentration of indium ions in the surface of the CZT sheet 5 is 20 ppm, so as to increase the resistivity of the CZT sheet 5 and change the band structure of the CZT sheet 5 to generate a stronger radiation signal.

[0044] S6. Perform the annealing process again to make the indium ions more evenly distributed on the surface of the CZT sheet 5; the annealing process temperature is 550°, the temperature holding time is 1-2 hours, and the atmosphere is an oxygen-free environment using inert gas; the temperature holding time in this process is only 1-2 hours, so as to improve the uniform distribution of indium ions on the surface of the CZT sheet 5 while reducing the diffusion of indium ions into the deep layer of the CZT sheet 5; at the same time, the annealing process also realizes the repair of the damaged lattice during the ion implantation process.

[0045] S61. Use photoresist to protect the cathode and anode surfaces of the CZT sheet 5 to prevent the subsequent insulating layer 3 from covering the cathode and anode surfaces; at the same time, the four sides of the CZT sheet 5 are exposed, and then an insulating layer 3 is formed on the four sides of the CZT sheet 5 to reduce the surface leakage of the CZT sheet 5; the insulating layer 3 is a silicon dioxide layer, and the thickness of the insulating layer 3 is 500 nm; the insulating layer 3 is prepared by chemical vapor deposition, and the deposition temperature is 300°C - 400°C; during the production process, the CZT sheet 5 is very easy to adhere to impurity ions, such as sodium ions and chloride ions on the hands or gloves of the producer. The impurity ions will cause a large surface leakage current of the CZT sheet 5. Usually, when the CZT sheet 5 is applied to the detector, a certain compensation will be preset for the detection data according to the leakage current situation, but the compensation has a certain error with the actual leakage current, which will lead to the imprecision of the detection data. By preparing the silicon dioxide layer during the production process, the contact between the CZT sheet 5 and the impurity ions before packaging is reduced, thereby improving the accuracy of the subsequent detection data.

[0046] S7. Platinum is plated on the cathode surface of the CZT sheet 5 to form a cathode conductive layer 1, and indium is plated on the anode surface of the CZT sheet 5 to form an anode conductive layer 2. Both the indium plating and the platinum plating are performed using a magnetron sputtering process with a sputtering power of 50-200 W. The thickness of the platinum layer after sputtering is 500 nm, and the thickness of the indium layer after sputtering is 500 nm-1 µm.

[0047] S8. Use precision welding technology to weld the cathode and anode leads of the detector to the appropriate contact points of the CZT sheet 5, and then use a resin shell to encapsulate it to ensure its mechanical stability and prevent environmental pollution. The encapsulation can use sealant or other high-strength adhesive materials to ensure the long-term stability of the detector performance.

[0048] By simply growing CZT crystals and then using ion implantation, the CZT sheet 5 is prepared into a composite electrode structure to give full play to the advantages of different doping elements. The implantation of fluorine ions improves the lattice defects during CZT crystal growth, eliminates deep energy levels in the CZT sheet 5, and increases the carrier migration lifetime product in the CZT sheet 5. Injecting indium ions to a certain depth into the surface layer of the CZT sheet 5 increases the resistivity of the CZT sheet 5 and changes the energy band structure of the CZT sheet 5, thereby generating a stronger radiation signal. In addition, by preparing a silicon dioxide layer on the four side walls of the CZT sheet 5 during the production process, the contact between the CZT sheet 5 and impurity ions before packaging is reduced, thereby reducing leakage current and improving the accuracy of subsequent detection data.

[0049] like Figure 1 As shown in the figure, when the In concentration is fixed at 50 ppm, the energy resolution decreases from 2.0% to 1.6% as the F concentration increases from 0 to 200 ppm, indicating that F doping helps to improve the energy resolution.

[0050] like Figure 2 As shown in the figure, when the F concentration is fixed at 100 ppm, as the In concentration increases from 0 to 100 ppm, the energy resolution decreases from 2.2% to 1.6%, indicating that In doping also has a similar optimization effect.

[0051] By injecting indium ions only into the surface layer of the CZT sheet 5, the signal is prevented from propagating deep into the CZT sheet 5 (indium doping will form indium-tellurium clusters that absorb the generated signal). Therefore, during the signal transmission process, the signal mainly passes through the F-doped area, thereby ensuring the intensity of the signal propagating deep into the CZT sheet 5 and reducing the energy resolution of the CZT sheet 5 from 2-1.5% to below 1%.

[0052] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative uses of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0053] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A method for preparing a CZT high energy resolution radiation chip, characterized in that: The following steps are involved: S1. Growth of CZT crystals; S2. Prepare the required CZT sheet (5) using CZT crystal; S3. injecting a certain dose of fluoride ions into the CZT sheet (5); S4. performing an annealing process on the CZT sheet (5) after the fluorine ions are injected, so that the fluorine ions are uniformly diffused in the CZT sheet (5) to improve the lattice defects during the growth of the CZT crystal; S5. Injecting indium ions into the cathode surface layer of the CZT sheet (5) to increase the resistivity of the CZT sheet (5) and change the band structure of the CZT sheet (5); S6. performing an annealing process again to make the indium ions more evenly distributed on the surface of the CZT sheet (5); S7. Plating platinum on the cathode surface of the CZT sheet (5) and plating indium on the anode surface of the CZT sheet (5); S8. Connect the CZT sheet (5) to the cathode and anode of the detector respectively, and then use a shell to package it.

2. The method for preparing a CZT high energy resolution radiation chip according to claim 1, wherein: In S3, the ion implantation energy is 30-50 keV; the fluorine ion concentration in the CZT sheet (5) reaches 30 ppm by ion implantation.

3. The method for preparing a CZT high energy resolution radiation chip according to claim 2, characterized in that: In S4, the annealing process temperature is 650° and maintained for 12 hours, and the atmosphere is an oxygen-free environment using an inert gas.

4. The method for preparing a CZT high energy resolution radiation chip according to claim 3, wherein: In S5, indium ions are implanted into the surface layer of the CZT sheet (5) to a depth of 200-500 nm, and the concentration of indium ions in the surface layer of the CZT sheet (5) is 20 ppm.

5. The method for preparing a CZT high energy resolution radiation chip according to claim 4, characterized in that: In S6, the annealing process temperature is 550°, the temperature holding time is 1-2 hours, and the atmosphere is an oxygen-free environment using an inert gas.

6. The method for preparing a CZT high energy resolution radiation chip according to claim 5, characterized in that: After step S6, a photoresist is used to protect the cathode surface and the anode surface of the CZT sheet (5), while exposing the four side surfaces of the CZT sheet (5). Then, an insulating layer (3) is formed on the four side surfaces of the CZT sheet (5) to reduce surface leakage of the CZT sheet (5).

7. The method for preparing a CZT high energy resolution radiation chip according to claim 6, wherein: The insulating layer (3) is a silicon dioxide layer, and the thickness of the insulating layer (3) is 500 nm.

8. The method for preparing a CZT high energy resolution radiation chip according to claim 7, wherein: The insulating layer (3) is prepared by chemical vapor deposition, and the deposition temperature is 300°C - 400°C.

9. The method for preparing a CZT high energy resolution radiation chip according to claim 8, wherein: In S2, the CZT sheet (5) is cut according to the orientation of the CZT crystal, the size of the CZT sheet (5) is 10 mm x 10 mm x 1 mm, and then the CZT sheet (5) is ground and polished so that the surface roughness of the CZT sheet (5) reaches Ra ≤ 0.5 µm.

10. The method for preparing a CZT high energy resolution radiation chip according to claim 9, wherein: In S7, both indium and platinum plating are performed using magnetron sputtering technology with a sputtering power of 50-200 W. The thickness of the platinum layer after sputtering is 500 nm, and the thickness of the indium layer after sputtering is 500 nm-1 µm.

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