A preparation method of dopant for silicon carbide crystal growth and its doping control method

Abstract

The present invention belongs to the field of semiconductor technology, and particularly relates to a preparation method of a dopant for silicon carbide crystal growth and a doping control method thereof. The preparation method of the dopant for silicon carbide crystal growth according to the present invention comprises the following steps: diatom template pretreatment, diatom template surface modification, metal ion precursor solution preparation, impregnation doping reaction, high-temperature calcination crystallization, and formation of the dopant for silicon carbide crystal growth; using diatoms as templates, the modified diatom templates precisely locate positively charged metal ions through electrostatic adsorption, enabling them to be uniformly distributed on the nano-scale pore walls; at the same time, SDBS molecules increase the surface active sites of the diatom templates, promote the chemical bonding between the diatom templates and metal ions, and form a protective film on the surface of the diatom templates to prevent them from being damaged in subsequent reactions. The co-doping of three metal ions, namely Nb<supgt;5+< / supgt;, Dy<supgt;3+< / supgt;, and Li<supgt;+< / supgt;, combined with the precisely controlled preparation process, greatly optimizes the performance of silicon carbide crystals.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology, and particularly relates to a preparation method of a dopant for growing silicon carbide crystals and a doping control method thereof. Background Art

[0002] As a wide-bandgap semiconductor material, silicon carbide (SiC) crystals have excellent properties such as high thermal conductivity, high breakdown electric field, and high electron saturation drift rate, and have broad application prospects in the fields of power electronics, radio frequency devices, optoelectronic devices, etc. However, during the growth process of silicon carbide crystals, the introduction and control of dopants are one of the key factors affecting crystal performance. The type, concentration, uniformity, etc. of dopants directly determine the electrical properties, thermal properties, and crystal quality of silicon carbide crystals.

[0003] Currently, common dopants used in the growth of silicon carbide crystals include elements such as nitrogen (N), aluminum (Al), and boron (B). These dopants are usually introduced into the crystal growth system in the form of gases, liquids, or solids. However, the existing preparation and doping control methods of dopants have the following problems: insufficient dopant purity; poor doping uniformity; inaccurate doping concentration control; In response to the above problems, gas-phase doping technology has been used in the prior art to improve doping uniformity, or high-purity dopants have been prepared by sol-gel methods. However, these methods still have problems such as insufficient dopant purity and inaccurate doping control, and it is difficult to meet the requirements of high-performance silicon carbide crystals. Therefore, developing a new preparation method of a dopant for growing silicon carbide crystals and a doping control method thereof to solve the problems of low dopant purity, uneven doping, and inaccurate concentration control in the prior art has important practical significance and application value. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides a preparation method of a dopant for growing silicon carbide crystals and a doping control method thereof. The present invention uses diatoms as templates and modifies the diatoms in advance. The modified diatom templates precisely locate positively charged metal ions through electrostatic adsorption, making them evenly distributed on the pore walls at the nanoscale, and constructing a highly ordered microscopic doping structure; at the same time, SDBS molecules increase the surface active sites of the diatom templates, promote the chemical combination between the diatom templates and metal ions, and form a protective film on the surface of the diatom templates to prevent them from being damaged in subsequent reactions. Nb 5+ 、Dy 3+ 、Li + The co-doping of three metal ions, combined with a precisely controlled preparation process, greatly optimizes the performance of silicon carbide crystals. In terms of electrical properties, Nb 5+ acts as an n-type dopant to provide extra electrons, Li +By adjusting the hole concentration, under precise preparation conditions, the carrier concentration of silicon carbide crystals was accurately regulated, significantly improving their electrical properties. This preparation method combines the biological template method with precise chemical control, not only endowing the dopant with a unique microstructure but also practicing the concept of green environmental protection, providing a feasible solution for the large-scale industrial production of dopants for high-performance silicon carbide crystal growth.

[0005] To achieve the above technical objectives, the technical solutions adopted by the present invention are as follows:

[0006] The present invention provides a preparation method for a dopant for silicon carbide crystal growth, which is used to prepare a dopant for silicon carbide crystal growth. The dopant for silicon carbide crystal growth is prepared from the following raw materials in parts by weight: 50 - 100 parts of diatoms, 1 - 3 parts of NbCl5, 1 - 3 parts of Dy(NO3)3·6H2O, 0.5 - 1 part of LiCl, and 10 - 40 parts of an SDBS (sodium dodecylbenzenesulfonate) solution;

[0007] The preparation method of the dopant for silicon carbide crystal growth specifically includes the following steps:

[0008] A1, Pretreatment of the diatom template: Collect diatom samples, centrifuge, and filter to separate diatom individuals with uniform size and complete structure. Add anhydrous ethanol to wash the diatoms multiple times to remove surface impurities and organic substances. Soak them in dilute nitric acid to further remove residual organic substances, and then dry them at low temperature to obtain a dried diatom template;

[0009] A2, Surface modification of the diatom template: Weigh the SDBS solution, immerse the diatom template in the SDBS solution, stir ultrasonically for 30 min, then wash it multiple times with deionized water, centrifuge, and dry to obtain a modified diatom template;

[0010] The concentration of the SDBS solution is 0.1 - 0.5 mol / L,

[0011] A3, Preparation of the metal ion precursor solution: Accurately weigh a certain amount of NbCl5, Dy(NO3)3·6H2O, and LiCl, and then add NbCl5, Dy(NO3)3·6H2O, and LiCl to anhydrous ethanol in sequence. The dosage ratio of NbCl5 to anhydrous ethanol is 1 g:200 mL, and stir on a magnetic stirrer until completely dissolved to form a uniform metal ion precursor solution;

[0012] A4, Impregnation doping reaction: Immerse the modified diatom template in the metal ion precursor solution, stir at a certain temperature, stir and soak at 50 °C for 12 h to make the modified diatom template fully contact with the metal ion precursor, and obtain an impregnation-doped diatom template;

[0013] A5, High-temperature calcination crystallization: The diatom template after impregnation doping is subjected to calcination crystallization treatment in a high-temperature furnace. Under a nitrogen atmosphere, starting from room temperature, it is heated to 800 °C at a heating rate of 5 °C / min and held at 800 °C for 2 h, so that the doping substance reacts further with the diatom template and crystallizes to obtain a dopant precursor;

[0014] A6, Formation of dopant for silicon carbide crystal growth: During the high-temperature calcination crystallization process, the organic components in the diatom template will be completely burned out, and the silicon dioxide structure of the diatom will react with the doping substance to obtain a dopant precursor. The dopant precursor is cooled and ground to obtain a dopant for silicon carbide crystal growth.

[0015] The present invention also provides a doping control method for a dopant for silicon carbide crystal growth, including the following steps:

[0016] (1) Pretreat the dopant. The prepared dopant for silicon carbide crystal growth is processed by a jet mill to control the particle size to be 1-3 µm;

[0017] (2) Activate the surface of the silicon carbide crystal. In a mixed atmosphere of argon / hydrogen, the volume ratio of argon to hydrogen is 95:5, and it is heat-treated at 400 °C for 2 h to improve the wettability of the silicon carbide crystal;

[0018] (3) Mix the dopant for silicon carbide crystal growth with the silicon carbide crystal, precisely control the dosage of the dopant, and the mass ratio of the dopant to the silicon carbide crystal is 1:1000. Use a double-cone mixer to mix at 80-100 rpm for 45-60 min to obtain a mixture;

[0019] (4) Load the mixture into a PVT growth furnace. Under an argon atmosphere, control the temperature to be 2000-2350 °C, and control the crystal growth rate by adjusting the heating power and cooling rate;

[0020] (5) After the growth of the silicon carbide crystal is completed, perform gradient annealing to eliminate the internal stress and defects of the crystal. Cool down to 1500 °C at 5 °C / min and then to room temperature at 1 °C / min.

[0021] Compared with the prior art, the beneficial effects obtained by the present invention are as follows:

[0022] The present invention uses diatoms as templates and modifies the diatoms in advance. On the one hand, the modified diatom templates enable a large number of SDBS molecules to be adsorbed on the diatom surface, carrying negative charges, and having a stronger electrostatic adsorption effect on positively charged metal ions. This can accurately locate the metal ions in the diatom voids and on the surface, achieving a highly ordered doping distribution, and making the metal ions evenly distributed on the nano-scale pore walls to construct a microscopic doping structure. On the other hand, during the ultrasonic stirring process, the SDBS molecules can enter the pores of the diatom templates, increasing the surface active sites, providing more reaction centers for the adsorption and chemical reactions of metal ions, and promoting the chemical bonding between the diatom templates and the metal ions. Moreover, the SDBS molecules form a protective film on the diatom surface, effectively preventing the structural damage of the diatom templates due to external forces or high temperatures during the impregnation doping reaction and high-temperature calcination processes. Nb 5+ 、Dy 3+ 、Li + The co-doping of these three metal ions, combined with the precisely controlled preparation process, greatly optimizes the performance of silicon carbide crystals. In terms of electrical properties, Nb 5+ acts as an n-type dopant to provide extra electrons, and Li + regulates the hole concentration. Under precise preparation conditions, the two achieve precise control of the carrier concentration of silicon carbide crystals, significantly improving their electrical properties. Dy 3+ plays a unique role in magnetic and optical properties by affecting the crystal structure and electron cloud distribution, and can achieve efficient luminescence at specific wavelengths, opening up new ways for the application of silicon carbide crystals in optoelectronic devices. The entire preparation process combines the biological template method with precise chemical control, using natural diatom templates, which not only endows the dopants with unique microscopic structures but also reflects the concept of green and environmentally friendly preparation. In each step, the fine control of parameters such as temperature, concentration, and time, as well as the real-time monitoring and feedback adjustment mechanism, ensure the stability and controllability of the preparation process, improve production efficiency and product quality, and provide a feasible solution for large-scale industrial production of dopants for high-performance silicon carbide crystal growth. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the preparation flow chart of the dopant for silicon carbide crystal growth of the present invention;

[0024] Figure 2 is the SEM image of silicon carbide prepared by the dopant for silicon carbide crystal growth of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] In order to enable those skilled in the art to better understand the technical solutions of the present invention and make the above features, objectives, and advantages of the present invention clearer and more understandable, the present invention will be further described below with reference to embodiments. The embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0026] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to the described content can be applied to the present invention. The preferred implementation methods and materials described in the text are for illustrative purposes only and do not limit the content of this application.

[0027] In the following examples, unless otherwise specified, all are conventional methods; the materials used in the following examples, unless otherwise specified, the raw materials are newly purchased on the market. Among them, NbCl5, product number N837024, 99.999%, was purchased from Shanghai Macklin Biochemical Co., Ltd.; Dy(NO3)3·6H2O, 99.90%, was purchased from Shandong Desheng New Materials Co., Ltd.; LiCl, product number 767295, 99.995%, was purchased from Shanghai Macklin Biochemical Co., Ltd.; diatom was purchased from Lanshe Diatom New Materials Co., Ltd.

[0028] According to Figure 1 The preparation flow chart of the dopant for silicon carbide crystal growth prepared according to the present invention gives the following examples:

[0029] Example 1: This example provides a method for preparing a dopant for silicon carbide crystal growth, which is used to prepare a dopant for silicon carbide crystal growth. The dopant for silicon carbide crystal growth is prepared from the following raw materials in parts by weight: 50 parts of diatom, 1 part of NbCl5, 1 part of Dy(NO3)3·6H2O, 0.5 part of LiCl, and 10 parts of SDBS solution;

[0030] The preparation method of the dopant for silicon carbide crystal growth specifically includes the following steps:

[0031] A1, Diatom template pretreatment: Collect diatom samples, centrifuge, and filter to separate diatom individuals with uniform size and complete structure. Add anhydrous ethanol to wash the diatoms 5 times to remove surface impurities and organic substances. Soak them in dilute nitric acid with a mass concentration of 5% to further remove residual organic substances, and then perform low-temperature drying at a temperature of 40 °C to obtain a dried diatom template;

[0032] A2, Surface modification of the diatom template: Weigh the SDBS solution with a concentration of 0.1 mol / L, stir and dissolve it to form a solution. Immerse the diatom template in the SDBS solution, stir ultrasonically for 30 min, then wash it with deionized water multiple times, centrifuge, and dry to obtain a modified diatom template;

[0033] A3, Preparation of metal ion precursor solution: Weigh accurately a certain amount of NbCl5, Dy(NO3)3·6H2O and LiCl. Then add NbCl5, Dy(NO3)3·6H2O and LiCl to anhydrous ethanol in sequence. The dosage ratio of NbCl5 to anhydrous ethanol is 1 g:200 mL. Stir on a magnetic stirrer until completely dissolved to form a uniform metal ion precursor solution;

[0034] A4, Impregnation doping reaction: Immerse the modified diatom template in the metal ion precursor solution and stir and immerse at 50 °C for 12 h to ensure full contact between the modified diatom template and the metal ion precursor, obtaining the impregnated and doped diatom template;

[0035] A5, High-temperature calcination and crystallization: Conduct calcination and crystallization treatment on the impregnated and doped diatom template in a high-temperature furnace. Under a nitrogen atmosphere, starting from room temperature, heat at a heating rate of 5 °C / min to 800 °C and hold at 800 °C for 2 h to enable further reaction and crystallization between the doped substances and the diatom template;

[0036] A6, Formation of dopant for silicon carbide crystal growth: During the high-temperature calcination and crystallization process, the organic components in the diatom template will be completely burned out, and the silicon dioxide structure of the diatom will react with the doped substances to form a dopant precursor. After cooling, grinding and other treatments on the dopant precursor, the dopant for silicon carbide crystal growth is obtained.

[0037] This embodiment also provides a doping control method for the dopant for silicon carbide crystal growth, including the following aspects:

[0038] (1) Pretreat the dopant for silicon carbide crystal growth. Process the prepared dopant for silicon carbide crystal growth with an air jet mill to control the particle size to be 1 µm, obtaining the pretreated dopant;

[0039] (2) Activate the surface of the silicon carbide crystal. Place the silicon carbide crystal in a mixed atmosphere of argon / hydrogen with the volume ratio of argon:hydrogen being 95:5, and conduct heat treatment at 400 °C for 2 h to improve the wettability of the silicon carbide crystal and form activated silicon carbide;

[0040] (3) Mix the pretreated dopant with the activated silicon carbide, precisely control the dosage of the dopant, with the mass ratio of the dopant to the silicon carbide crystal being 1:1000. Use a double-cone mixer to mix at 80 rpm for 45 min to obtain a mixture;

[0041] (4) Load the mixture into a PVT growth furnace. Under an argon atmosphere, control the temperature to be 2000 °C, and control the growth rate of the silicon carbide crystal by adjusting the heating power and cooling rate;

[0042] After the growth of the silicon carbide crystal is completed, gradient annealing is carried out to eliminate the stress and defects inside the crystal. The temperature is decreased to 1500 °C at a rate of 5 °C / min, and then further decreased to room temperature at a rate of 1 °C / min.

[0043] Example 2: This example provides a method for preparing a dopant for silicon carbide crystal growth, which is used to prepare a dopant for silicon carbide crystal growth. The dopant for silicon carbide crystal growth is prepared from the following raw materials in parts by weight: 80 parts of diatoms, 2 parts of NbCl5, 2 parts of Dy(NO3)3·6H2O, 0.8 part of LiCl, and 25 parts of SDBS solution.

[0044] The preparation method of the dopant for silicon carbide crystal growth specifically includes the following steps:

[0045] A1, pretreatment of diatom template: Collect diatom samples, centrifuge, and filter to separate diatom individuals with uniform size and complete structure. Add anhydrous ethanol to wash the diatoms 5 times to remove surface impurities and organic substances. Immerse them in dilute nitric acid with a mass concentration of 5-10% to further remove residual organic substances, and then perform low-temperature drying at a temperature of 50 °C to obtain a dried diatom template.

[0046] A2, surface modification of diatom template: Weigh the SDBS solution with a concentration of 0.2 mol / L, stir and dissolve it to form an SDBS solution. Immerse the diatom template in the SDBS solution, stir ultrasonically for 30 min, then wash it with deionized water multiple times, centrifuge, and dry to obtain a modified diatom template.

[0047] A3, preparation of metal ion precursor solution: Accurately weigh a certain amount of NbCl5, Dy(NO3)3·6H2O, and LiCl, and then add NbCl5, Dy(NO3)3·6H2O, and LiCl to anhydrous ethanol in sequence. The dosage ratio of NbCl5 to anhydrous ethanol is 1 g:200 mL, and stir on a magnetic stirrer until completely dissolved to form a uniform metal ion precursor solution.

[0048] A4, impregnation doping reaction: Immerse the modified diatom template in the metal ion precursor solution, stir and soak at 50 °C for 12 h to make the modified diatom template fully contact with the metal ion precursor, and obtain an impregnation-doped diatom template.

[0049] A5, high-temperature calcination and crystallization: Perform calcination and crystallization treatment on the impregnation-doped diatom template in a high-temperature furnace. Under a nitrogen atmosphere, start from room temperature, heat to 800 °C at a heating rate of 5 °C / min, and keep it at 800 °C for 2 h to make the doping substance react and crystallize further with the diatom template.

[0050] A6. Formation of dopants for silicon carbide crystal growth: During the high-temperature calcination and crystallization process, the organic components in the diatom template will be completely burned out, and the silica structure of the diatoms will react with the doping substances to form dopants and precursors. The dopant precursors are processed through cooling, grinding, etc. to obtain dopants for silicon carbide crystal growth.

[0051] This embodiment also provides a doping control method for dopants for silicon carbide crystal growth, including the following aspects:

[0052] (1) Pretreat the dopants for silicon carbide crystal growth. The prepared dopants for silicon carbide crystal growth are processed by a jet mill to control the particle size to 2 µm, obtaining pretreated dopants.

[0053] (2) Activate the surface of the silicon carbide crystal. In a mixed atmosphere of argon / hydrogen, with the volume ratio of argon:hydrogen being 95:5, heat-treat at 400 °C for 2 h to improve the wettability of the silicon carbide crystal and form activated silicon carbide.

[0054] (3) Mix the pretreated dopants with the activated silicon carbide, precisely control the dosage of the dopants. The mass ratio of the dopants to the silicon carbide crystal is 1:1000, and use a double-cone mixer to mix at 90 rpm for 60 min to obtain a mixture.

[0055] (4) Load the mixture into a PVT growth furnace. In an argon atmosphere, control the temperature to 2320 °C, and control the crystal growth rate by adjusting the heating power and cooling rate.

[0056] (5) After the silicon carbide crystal growth is completed, perform gradient annealing to eliminate the internal stress and defects of the crystal. Cool down to 1500 °C at a rate of 5 °C / min, and then cool down to room temperature at a rate of 1 °C / min.

[0057] Example 3: This example provides a preparation method for dopants for silicon carbide crystal growth, which is used to prepare dopants for silicon carbide crystal growth. The dopants for silicon carbide crystal growth are prepared from the following raw materials in parts by weight: 100 parts of diatoms, 3 parts of NbCl5, 3 parts of Dy(NO3)3·6H2O, 1 part of LiCl, and 40 parts of SDBS solution.

[0058] The preparation method of the dopants for silicon carbide crystal growth specifically includes the following steps:

[0059] A1. Pretreatment of the diatom template: Collect diatom samples, centrifuge, and filter to separate diatom individuals with uniform size and complete structure. Add anhydrous ethanol to wash the diatoms 5 times to remove surface impurities and organic substances. Soak them in dilute nitric acid with a mass concentration of 5-10% to further remove residual organic substances, and then perform low-temperature drying at 60 °C to obtain a dried diatom template.

[0060] A2, Surface modification of the diatom template: Weigh the SDBS solution with a concentration of 0.5 mol / L, stir and dissolve it to form the SDBS solution. Immerse the diatom template in the SDBS solution, stir ultrasonically for 30 min, then wash it with deionized water multiple times, centrifuge, and dry to obtain the modified diatom template;

[0061] A3, Preparation of the metal ion precursor solution: Accurately weigh a certain amount of NbCl5, Dy(NO3)3·6H2O, and LiCl, and then add NbCl5, Dy(NO3)3·6H2O, and LiCl to anhydrous ethanol in sequence. The dosage ratio of NbCl5 to anhydrous ethanol is 1 g:200 mL. Stir on a magnetic stirrer until completely dissolved to form a uniform metal ion precursor solution;

[0062] A4, Impregnation doping reaction: Immerse the modified diatom template in the metal ion precursor solution, stir and soak at 50 °C for 12 h to make the modified diatom template fully contact with the metal ion precursor, and obtain the impregnated and doped diatom template;

[0063] A5, High-temperature calcination and crystallization: Perform calcination and crystallization treatment on the impregnated and doped diatom template in a high-temperature furnace. Under a nitrogen atmosphere, start from room temperature, heat to 800 °C at a heating rate of 5 °C / min, and hold at 800 °C for 2 h to make the doped substance react and crystallize further with the diatom template;

[0064] A6, Formation of the dopant for silicon carbide crystal growth: During the high-temperature calcination and crystallization process, the organic components in the diatom template will be completely burned out, and the silicon dioxide structure of the diatom will react with the doped substance to form the dopant precursor. After cooling, grinding, etc. of the dopant precursor, the dopant for silicon carbide crystal growth is obtained.

[0065] This embodiment also provides a doping control method for the dopant for silicon carbide crystal growth, including the following aspects:

[0066] (1) Pretreat the dopant for silicon carbide crystal growth. Process the prepared dopant for silicon carbide crystal growth with a jet mill to control the particle size to 3 µm to obtain the pretreated dopant;

[0067] (2) Activate the surface of the silicon carbide crystal. In a mixed atmosphere of argon / hydrogen with a volume ratio of argon:hydrogen of 95:5, heat-treat at 400 °C for 2 h to improve the wettability of the silicon carbide crystal and form the activated silicon carbide;

[0068] (3) Mix the pre-treated dopant with activated silicon carbide, precisely control the dosage of the dopant, with the mass ratio of the dopant to the silicon carbide crystal being 1:1000. Use a double-cone mixer to mix at 100 rpm for 60 min to obtain a mixture.

[0069] (4) Load the mixture into a PVT growth furnace. In an argon atmosphere, control the temperature at 2350 °C, and control the crystal growth rate by adjusting the heating power and cooling rate.

[0070] (5) After the growth of the silicon carbide crystal is completed, perform gradient annealing to eliminate the internal stress and defects in the crystal. Cool down to 1500 °C at 5 °C / min, and then cool down to room temperature at 1 °C / min.

[0071] The difference between Comparative Example 1 and Example 1 is that the diatom template is not subjected to modification treatment, and the rest is exactly the same as Example 1.

[0072] The difference between Comparative Example 2 and Example 1 is that NbCl5 is not added, and the rest is exactly the same as Example 1.

[0073] The difference between Comparative Example 3 and Example 1 is that Dy(NO3)3·6H2O is not added, and the rest is exactly the same as Example 1.

[0074] Experimental Example: Using the dopant for silicon carbide crystal growth prepared by the present invention, grow silicon carbide crystals by physical vapor transport method (PVT method), and measure the carrier rate, resistivity, and crystal growth rate of the grown silicon carbide crystals.

[0075] Carrier Rate Measurement: Cut out square wafers with side lengths of 5 - 10 mm from the prepared silicon carbide crystals. Using a method that combines mechanical polishing and chemical mechanical polishing, the surface of the sample is processed to mirror finish to reduce the influence of surface scattering on carrier transport. On the surface of the sample, metal electrodes are prepared by vacuum evaporation or magnetron sputtering. The electrode material is aluminum (Al), and the electrode shape is an ohmic contact electrode. The electrode layout of the four-probe method is used, with the four electrodes arranged in a straight line, and the electrode spacing is precisely controlled at 1 - 2 mm. Place the prepared sample in a cryostat, connect the electrodes to a high-precision current source and a voltage measuring instrument testing equipment, and precisely control the sample testing temperature through the cryostat. First, conduct tests at room temperature to study the influence of temperature on the carrier rate. Inject a stable current into the sample using a high-precision current source, and adjust the current magnitude according to the characteristics of the sample and the testing requirements. At the same time, use the voltage measuring instrument to measure the voltage drop across the sample. According to Ohm's law and the carrier mobility formula, calculate the carrier mobility through the measured current, voltage, and the geometric dimensions (thickness, length, etc.) of the sample. Carrier rate = carrier mobility × electric field strength, where the electric field strength can be calculated based on the applied voltage and the sample length. Change the injected current magnitude multiple times, repeat the measurement and calculation, and take the average value to improve the testing accuracy. The average value is recorded in Table 1.

[0076] Resistivity Test: Cut the silicon carbide crystal into silicon carbide single crystal wafers with a thickness of 200 μm, and use the non-contact eddy current method for resistivity testing. Calibrate the eddy current resistivity tester using a standard silicon carbide sample with a known resistivity to ensure the accuracy of the testing equipment. The resistivity value of the standard sample should cover the expected resistivity range of the sample to be tested. Place the sample on the test bench of the eddy current resistivity tester, and adjust the parameters of the tester, such as the excitation frequency, magnetic field strength, etc., to adapt to the sample characteristics. Start the tester to obtain the resistivity data of the sample. To ensure the reliability of the test, conduct 3 measurements at different positions of the sample, with a spacing of 5 mm between each measurement position. Finally, take the average value as the resistivity of the sample, and the results are recorded in Table 1.

[0077] Crystal Growth Rate Measurement: Use a system for growing silicon carbide crystals by physical vapor transport method (PVT method). The growth furnace is equipped with a high-precision temperature control system with a temperature control accuracy of ±1°C, and a pressure monitoring and regulating device with a pressure control accuracy of ±0.1 kPa. Place the crucible containing high-purity silicon carbide micropowder raw materials in the growth furnace, fix the seed crystal in a suitable position, seal the growth furnace, and evacuate it to 10 -3 -10 -4Pa, and then fill it with high-purity argon as a protective atmosphere, and maintain the air pressure at 5-10 kPa. Start heating the growth furnace, raise the temperature to 2300 °C according to the set heating program, and maintain stable temperature and pressure conditions for crystal growth. During the growth process, use an optical microscope or a laser interferometer to monitor the crystal growth in real time. The growth interface of the crystal can be directly observed through the optical microscope. Every 1 h, record the growth length of the crystal in a certain direction; the laser interferometer calculates the change in the growth thickness of the crystal accurately by measuring the change in interference fringes. According to the recorded growth time and the crystal growth length or thickness data, calculate the crystal growth rate, and the results are recorded in Table 1.

[0078] Table 1

[0079]

[0080] It can be seen from the results in Table 1 that the carrier rates of Examples 1-3 are significantly higher than those of Comparative Examples 1-3, indicating that the dopant for the growth of silicon carbide crystals prepared by the present invention is beneficial to improving the carrier rate, which shows that the added dopant can construct an ordered structure and reduce scattering; the resistivity of the example reaches 0.06 Ω·cm, indicating that the resistivity can be effectively reduced after adding the dopant, enhancing the conductivity of silicon carbide; from the perspective of the crystal growth rate, adding the dopant prepared by the present invention has an obvious promoting effect on the growth of silicon carbide crystals.

[0081] Figure 2 The SEM image of silicon carbide prepared by the dopant for the growth of silicon carbide crystals of the present invention is shown. It can be seen that a glass phase gradually appears between the silicon carbide particles, forming a large number of neck connections. The increase in the number of neck connections greatly improves the flexural strength of the support, and there is no foaming phenomenon, indicating that the addition of the dopant has improved the oxidation resistance of silicon carbide crystals well.

[0082] In summary, the present invention shows many significant advantages through the modification of diatoms and the co-doping with specific metal ions. In terms of carrier rate, by means of the precise positioning of metal ions by the modified diatom template, an ordered microstructure is constructed, reducing carrier scattering, thereby improving the carrier mobility and optimizing the carrier transport performance of silicon carbide crystals; in terms of resistivity regulation, this doping method effectively increases the conductivity of silicon carbide crystals and reduces the resistivity, significantly improving its electrical conductivity characteristics; from the perspective of crystal growth rate, the dopant provides more active sites for crystal growth, optimizes the growth environment, and promotes the crystal growth process. The entire preparation process combines the biological template method with precise chemical control, not only achieving precise regulation of the structure and properties of silicon carbide crystals, but also reflecting the concept of green environmental protection, providing a highly valuable solution for the preparation of high-performance silicon carbide crystals and their applications in related fields, and is expected to promote the wide application and development of silicon carbide crystals in the fields of electronics, energy, etc.

[0083] As described above, it is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes, should be covered by the protection scope of the present invention.

Claims

1. A preparation method of a dopant for silicon carbide crystal growth, which is used to prepare a dopant for silicon carbide crystal growth, and is characterized in that, The dopant for silicon carbide crystal growth is prepared from the following raw materials in parts by weight: 50 - 100 parts of diatoms, 1 - 3 parts of NbCl5, 1 - 3 parts of Dy(NO3)3·6H2O, 0.5 - 1 part of LiCl, and 10 - 40 parts of SDBS solution; The preparation method of the dopant for silicon carbide crystal growth includes the following steps: A1, pretreatment of diatom template: Weigh diatoms, soak the diatoms in dilute nitric acid solution, and dry at low temperature to obtain a diatom template; A2, surface modification of diatom template: Weigh SDBS solution, immerse the diatom template in the SDBS solution, perform ultrasonic treatment, then wash, centrifuge, and dry to obtain a modified diatom template; A3, preparation of metal ion precursor solution: Weigh NbCl5, Dy(NO3)3·6H2O, and LiCl according to parts by weight, and then add NbCl5, Dy(NO3)3·6H2O, and LiCl to anhydrous ethanol in sequence, stir until completely dissolved to form a metal ion precursor solution; A4, impregnation doping reaction: Immerse the modified diatom template in the metal ion precursor solution, stir and impregnate to obtain an impregnated and doped diatom template; A5, high-temperature calcination and crystallization: Calcinate and crystallize the impregnated and doped diatom template to obtain a dopant precursor; A6, formation of dopant for silicon carbide crystal growth: Cool the dopant precursor and grind to obtain the dopant for silicon carbide crystal growth.

2. The preparation method of the dopant for growing silicon carbide crystal according to claim 1, characterized in that, In step A1, the mass concentration of the dilute nitric acid solution is 5 - 10%, and in step A2, the concentration of the SDBS solution is 0.1 - 0.5 mol / L.

3. The preparation method of the dopant for silicon carbide crystal growth according to claim 1, wherein, In step A3, the dosage ratio of NbCl5 to anhydrous ethanol is 1 g:200 mL; in step A4, the temperature of the stirring and impregnation is 50 °C, and the time is 12 h.

4. The preparation method of a dopant for silicon carbide crystal growth according to claim 1, characterized in that In step A5, the calcination is carried out in a nitrogen atmosphere, starting from room temperature, heating to 800 °C at a heating rate of 5 °C / min, and holding at 800 °C for 2 h.

5. A doping control method for a dopant for silicon carbide crystal growth prepared by the preparation method of the dopant for silicon carbide crystal growth described in any one of claims 1-4, characterized in that, It includes the following steps: (1) Pretreat the dopant for silicon carbide crystal growth, control the particle size of the prepared dopant for silicon carbide crystal growth to obtain a pretreated dopant; (2) Activate the surface of the silicon carbide crystal, perform heat treatment in a mixed atmosphere of argon / hydrogen to form activated silicon carbide; (3) Mix the pretreated dopant with the activated silicon carbide, precisely control the dosage of the dopant to obtain a mixture; (4) Put the mixture into an argon atmosphere, control the temperature, and control the crystal growth rate by adjusting the heating power and cooling rate; (5) After the growth of the silicon carbide crystal is completed, perform gradient annealing.

6. The doping control method of the dopant for silicon carbide crystal growth according to claim 5, wherein, In step (2), the volume ratio of argon to hydrogen is 95:5, the heat treatment temperature is 400 °C, and the time is 2 h.

7. The doping control method of the dopant for silicon carbide crystal growth according to claim 5, characterized in that, In step (4), the controlled temperature is 2000 - 2350 °C, and the crystal growth rate is 0.9 - 1.2 mm / h.

8. The doping control method of the dopant for silicon carbide crystal growth according to claim 5, characterized in that, In step (5), the gradient annealing is to cool to 1500 °C at 5 °C / min and then cool to room temperature at 1 °C / min.

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