A photon counting detector crystal surface plasma treatment method and photon counting detector

Abstract

This invention belongs to the field of photon counting detector manufacturing technology, specifically relating to a plasma treatment method for the crystal surface of a photon counting detector and the resulting photon counting detector. The treatment method employs a step-by-step plasma surface modification process. First, the crystal wafer surface is bombarded with plasma generated by the ionization of an inert gas. Then, a secondary bombardment is performed using plasma generated by the ionization of reactive gases such as oxygen and hydrogen. Simultaneously, key process conditions such as process gas flow rate, wafer orientation bias, processing time, cavity vacuum, radio frequency power, plasma parameters, and wafer spacing are systematically controlled. This step-by-step modification process achieves nanoscale modification of the crystal surface, effectively repairing surface damage caused by processing and forming a uniformly distributed surface modification layer. Photon counting detectors fabricated using this method can significantly reduce device leakage current, improve withstand voltage performance, optimize energy resolution, and improve photon counting rate and counting stability.

Description

Technical Field

[0001] This invention belongs to the field of photon counting detector manufacturing technology, specifically relating to a method for plasma treatment of the crystal surface of a photon counting detector and a photon counting detector. Background Technology

[0002] Cadmium zinc telluride (CZT) and cadmium telluride (CT) crystals, as core crystal materials for photon counting detectors, have been widely studied and applied in various fields such as nuclear radiation detection, medical imaging, and industrial non-destructive testing due to their advantages such as high detection efficiency at room temperature and excellent energy resolution potential. Photon counting detector devices based on CZT / CT crystals have become an important carrier for achieving high-precision detection in related detection fields. Their performance directly determines the overall working effect of the detection system. Therefore, improving the performance level of CZT / CT-based detectors is an important research direction in related technical fields.

[0003] In the process of fabricating CZT / CT crystals into photon counting detector devices, the surface quality of the crystal is a key factor affecting the final performance of the device. After surface treatment processes such as cutting, grinding, and cleaning, the surface of the crystal may still have extended defects or impurities. These surface problems will lead to the degradation of the detector device's performance, becoming a bottleneck restricting the further optimization and improvement of the performance of CZT / CT-based detectors. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for plasma treatment of the crystal surface of a photon counting detector and a photon counting detector itself. The purpose of this invention is to solve the problem of detector performance degradation caused by defects in the surface treatment of existing cadmium zinc telluride and cadmium telluride crystals, thereby improving the overall performance of photon counting detectors.

[0005] The first aspect of this invention provides a method for plasma treatment of the crystal surface of a photon counting detector, comprising two steps of plasma surface modification treatment: Step 1: The surface of the wafer to be processed is bombarded with plasma generated by the ionization of the first process gas, which is an inert gas. The second step involves bombarding the wafer surface after the first step with plasma generated by the ionization of a second process gas, which is one or more of O2, H2, N2, and F2.

[0006] As a further optimization of the above-mentioned plasma treatment method, the first process gas is selected from one or more of Ar, He, and Ne.

[0007] As a further optimization of the above-mentioned plasma processing method, the wafer to be processed is cadmium zinc telluride crystal or cadmium telluride crystal.

[0008] As a further optimization of the above-mentioned plasma treatment method, the flow rates of both the first process gas and the second process gas are controlled within the range of 1~100 sccm.

[0009] As a further optimization of the above-mentioned plasma treatment method, in the first step and / or second step of the treatment, a directional bias voltage of 1~100V is applied to the wafer through the stage to drive the plasma to directionally bombard the wafer surface.

[0010] As a further optimization of the above-mentioned plasma treatment method, in the first step of the treatment, the ion bombardment treatment time is 1~1000s; in the second step of the treatment, the ion bombardment treatment time is 1~1000s.

[0011] As a further optimization of the above-mentioned plasma treatment method, before and / or between and / or after the first step of the treatment, the cavity of the plasma treatment equipment is evacuated to a pressure below 20 Pa; in the first step and / or the second step, the power of the radio frequency power supply used to generate the plasma is set to 10~1000W.

[0012] As a further optimization of the above-mentioned plasma treatment method, in the first step and / or the second step, the plasma density is controlled to be greater than 5.1E+11cm⁻³ and the plasma energy is 0.1~10eV.

[0013] As a further optimization of the above-mentioned plasma processing method, the buffer device between the wafer to be processed and the plasma generation chamber and the process execution chamber maintains a distance of 1~20cm.

[0014] A second aspect of the present invention provides a photon counting detector, which is prepared by plasma treatment of the surface of a zinc cadmium telluride crystal or a cadmium telluride crystal using the above-described method.

[0015] Beneficial effects The present invention provides a plasma surface treatment method and a photon counting detector for a crystal surface. Based on plasma processing equipment, a step-by-step plasma surface treatment process for CZT / CT crystal wafers has been developed. By systematically controlling key parameters such as cavity pressure, process gas type and flow rate, and radio frequency power, combined with step-by-step ion bombardment of inert and reactive gases, nanoscale modification of the crystal surface is achieved, effectively improving surface damage caused by crystal processing, forming a uniformly distributed modified layer on the crystal surface, significantly reducing device leakage current, improving withstand voltage performance, optimizing energy resolution, and improving photon counting rate and counting stability. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the plasma processing device.

[0017] Figure 2 This is a schematic diagram of the structure of a wafer after undergoing two plasma surface modification treatments.

[0018] In the figure, 1 is the stage; 2 is the wafer to be processed; 3 is the plasma generation chamber; 4 is the plasma; 5 is the coil; 6 is the buffer device; and 7 is the process execution chamber. Detailed Implementation

[0019] The structure of the plasma processing device is as follows Figure 1 As shown, the entire structure consists of an interconnected plasma generation chamber 3 and a process execution chamber 7. The plasma generation chamber 3 serves as the source of plasma 4, and is surrounded by coils 5 connected to a high-frequency radio frequency power source. The alternating electromagnetic field generated after energization ionizes the introduced process gas. The process execution chamber 7 serves as the processing area, with a stage 1 horizontally positioned at its central axis to support the wafer 2 to be processed. A buffer device 6 is located at the junction of the generation chamber 3 and the execution chamber 7, positioned along the path of the plasma 4 flowing towards the wafer surface. This device improves airflow stability and optimizes ion distribution uniformity. In the actual process, the stage 1 establishes a directional bias voltage of 1~100V, driving the plasma 4 generated by the generation chamber 3 to pass through the buffer device 6 and directionally bombard the upper surface of the wafer 2 to be processed.

[0020] The plasma surface modification treatment method of the present invention, such as Figure 2 As shown, the modification and optimization of the wafer surface is achieved through a two-step plasma bombardment process. The specific process steps are as follows: S1. Place the wafer 2 to be processed horizontally on the stage 1 of the process execution chamber 7; keep the distance between the wafer 2 to be processed and the buffer device 6 at 1~20cm; S2. Close the chamber, open the evacuation valve, and perform vacuum treatment on the integral cavity formed by connecting the plasma generation chamber 3 and the process execution chamber 7 to reduce the internal pressure to below 20Pa, thereby eliminating the interference of air impurities on the plasma treatment effect. S3. Open the process gas valve and introduce one or more inert process gases of Ar, He, and Ne into the plasma generation chamber 3. Control the gas flow rate within the range of 1~100 sccm and continue to ventilate for more than 2 minutes. S4. Turn on the RF power supply and set the power to 10~1000W to ionize the inert process gas in plasma generation chamber 3 to form plasma 4. During the process, control the density of plasma 4 to be >5.1E+11cm. -3Plasma 4 has an energy of 0.1 to 10 eV; ions are driven by a bias voltage of 1 to 100 V and enter the process execution chamber 7 through the buffer device 6 to bombard the wafer surface placed on the stage 1 with ions for a bombardment time of 1 to 1000 s. S5. After completing the first round of ion bombardment, shut down the RF power supply and process gas valve, and once again perform vacuum treatment on the entire cavity that connects the plasma generation chamber 3 and the process execution chamber 7, reducing its internal pressure to below 20Pa. S6. Reopen the process gas valve and introduce one of the reaction process gases, namely O2, H2, N2, and F, into the plasma generation chamber 3. Control the gas flow rate within the range of 1~100 sccm and continue to ventilate for more than 2 minutes. S7. Turn the RF power on again and set the power to 10~1000W to ionize the process gas in plasma generation chamber 3 to form plasma 4. During the process, control the density of plasma 4 to be >5.1E+11cm. -3 The plasma energy is 0.1-10 eV; the ions enter the process execution chamber 7 through the buffer device 6 and continue to bombard the wafer surface with ions for 1-1000 s. S8. After completing the secondary reaction gas ion bombardment treatment, turn off the RF power supply and process gas valve, and evacuate the entire cavity that connects the plasma generation chamber 3 and the process execution chamber 7 to restore its internal pressure to below 20Pa. S9. Close the suction valve and open the inflation valve to restore the internal pressure of the entire cavity to normal pressure. Then, remove the wafer sample treated with plasma 4 to complete the entire plasma surface modification process. The invention is further illustrated below with specific embodiments. These embodiments are exemplary and intended to illustrate the problem and explain the invention, and are not intended to be limiting.

[0021] Example 1 This embodiment describes a surface modification treatment for a 4-inch CZT wafer. The specific process steps are as follows: S1. Place 10 4-inch CZT (Cd0.9Zn0.1Te) wafers horizontally in the fixture box and manually push them into the process execution chamber 7 to place the wafers stably on the stage 1; keep the distance between the CZT wafers and the buffer device 6 at 20cm. S2. Close the chamber, open the evacuation valve, and evacuate the pressure inside the whole formed by the process execution chamber 7 and the plasma generation chamber 3 to 5Pa to eliminate air impurities. S3. Open the process gas valve and introduce Ar process gas into the plasma generation chamber 3. Control the gas flow rate to 80 sccm and continue to ventilate for 5 minutes. S4. Turn on the RF power supply and set the power to 500W to ionize the process gas in plasma generation chamber 3 to form plasma 4, and control the density of plasma 4 to be greater than 5.1E+11cm. -3 Plasma 4 has an energy of 5-10 eV; ions are driven by a 100V bias voltage and enter the process execution chamber 7 through the buffer device 6 to bombard the wafer surface. The ion bombardment treatment time is 120s. S5. Turn off the RF power supply, close the process gas valve, and pump the pressure in the entire chamber back to 5Pa. S6. Open the process gas valve and introduce O2 process gas into the plasma generation chamber 3. Control the gas flow rate to 100 sccm and continue to ventilate for 2 minutes. S7. Turn on the RF power supply and set the power to 200W to ionize the process gas in plasma generation chamber 3 to form plasma 4, and control the density of plasma 4 to be greater than 5.1E+11cm. -3 Plasma energy 8-10 eV; ion bombardment treatment time 300s; S8. Turn off the RF power supply and the process gas valve to restore the pressure in the entire chamber to 5Pa; S9. Close the extraction valve, open the inflation valve, and remove the wafer sample after plasma treatment 4 to complete the entire process.

[0022] After the wafers were processed by the plasma, they were fabricated into devices and the performance of the photon counting detector was tested. The results are shown in Table 1.

[0023] Table 1 Performance Test Results Leakage current nA / mm² (at +1000V) 4.3 Energy resolution 8% Maximum withstand voltage V 700 Surface element distribution uniformity deviation after treatment ±3% The above embodiments are exemplary and are intended to illustrate the technical concept and features of the present invention, so that those skilled in the art can understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for plasma treatment of the crystal surface of a photon counting detector, characterized in that: This includes two separate plasma surface modification treatments performed in stages: Step 1: The surface of the wafer to be processed is bombarded with plasma generated by the ionization of the first process gas, which is an inert gas. The second step involves bombarding the wafer surface after the first step with plasma generated by the ionization of a second process gas, which is one or more of O2, H2, N2, and F2.

2. The method for plasma treatment of the crystal surface of a photon counting detector according to claim 1, characterized in that: The first process gas is selected from one or more of Ar, He, and Ne.

3. The method for plasma treatment of the crystal surface of a photon counting detector according to claim 1 or 2, characterized in that: The wafer to be processed is cadmium zinc telluride crystal or cadmium telluride crystal.

4. The method for plasma treatment of the crystal surface of a photon counting detector according to claim 3, characterized in that: The flow rates of both the first process gas and the second process gas are controlled within the range of 1 to 100 sccm.

5. The method for plasma treatment of the crystal surface of a photon counting detector according to claim 3, characterized in that: During the first and / or second processing steps, a directional bias voltage of 1 to 100V is applied to the wafer via a stage to drive plasma to directionally bombard the wafer surface.

6. The method for plasma treatment of the crystal surface of a photon counting detector according to claim 3, characterized in that: In the first step of the process, the ion bombardment time is 1~1000s; in the second step of the process, the ion bombardment time is 1~1000s.

7. The method for plasma treatment of the crystal surface of a photon counting detector according to claim 3, characterized in that: Before and / or between and / or after the first step of the process, the cavity of the plasma processing equipment is evacuated to reduce its internal pressure to below 20 Pa; in the first step and / or the second step, the power of the radio frequency power supply used to generate the plasma is set to 10~1000W.

8. The method for plasma treatment of the crystal surface of a photon counting detector according to claim 3, characterized in that: In the first and / or second processing steps, the plasma density is controlled to be greater than 5.1E+11cm⁻³, and the plasma energy is 0.1~10eV.

9. The method for plasma treatment of the crystal surface of a photon counting detector according to claim 3, characterized in that: The buffer device between the wafer to be processed and the plasma generation chamber and the process execution chamber maintains a distance of 1~20cm.

10. A photon counting detector, characterized in that: It is prepared by plasma treatment of the crystal surface using the method described in any one of claims 1-10.

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