Preparation method and doping control method of doping agent for silicon carbide crystal growth

Abstract

The invention belongs to the technical field of semiconductors, and particularly relates to a preparation method and a doping control method of a doping agent for silicon carbide crystal growth. The preparation method of the doping agent for silicon carbide crystal growth comprises the following steps: pretreatment of a diatom template, surface modification of the diatom template, preparation of a metal ion precursor solution, dipping doping reaction, high-temperature calcination crystallization and formation of the doping agent for silicon carbide crystal growth. Diatom is adopted as a template, and the modified diatom template accurately locates positively charged metal ions through electrostatic adsorption, so that the metal ions are uniformly distributed on nano-scale pore walls; meanwhile, SDBS molecules increase active sites on the surface of the diatom template, promote chemical binding between the diatom template and metal ions, and form a protective film on the surface of the diatom template to prevent the diatom template from being damaged in subsequent reaction. The performance of the silicon carbide crystal is greatly optimized by synergistically doping three metal ions, i.e., Nb5 +, Dy < 3 + > and Li < + >, and combining with an accurately controlled preparation process.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor technology, and in particular relates to a method for preparing a dopant for silicon carbide crystal growth and a doping control method thereof. Background Art

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

[0003] At present, commonly used dopants in silicon carbide crystal growth include nitrogen (N), aluminum (Al), boron (B) and other elements. These dopants are usually introduced into the crystal growth system in the form of gas, liquid or solid. However, the preparation and doping control methods of dopants in the prior art have the following problems: insufficient purity of dopants; poor doping uniformity; inaccurate doping concentration control; In view of the above problems, the prior art has adopted gas phase doping technology to improve doping uniformity, or prepared high-purity dopants by sol-gel method. However, these methods still have problems such as insufficient dopant purity and inaccurate doping control, which are difficult to meet the needs of high-performance silicon carbide crystals. Therefore, it is of great practical significance and application value to develop a new method for preparing dopants for silicon carbide crystal growth and a doping control method thereof to solve the problems of low dopant purity, uneven doping, and inaccurate concentration control in the prior art. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a method for preparing a dopant for silicon carbide crystal growth and a doping control method thereof. The present invention uses diatoms as templates and pre-modifies the diatoms. The modified diatom templates accurately locate positively charged metal ions through electrostatic adsorption, so that they are evenly distributed on the nanoscale pore walls, and a highly ordered microscopic doping structure is constructed; at the same time, the SDBS molecules increase the active sites on the surface of the diatom templates, promote the chemical bonding between the diatom templates and the metal ions, and form a protective film on the surface of the diatom templates to prevent them from being destroyed in subsequent reactions. Nb 5+ 、Dy 3+ , Li + The synergistic doping of 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+ As an n-type dopant to provide additional electrons, Li +Adjusting the hole concentration, the two achieved precise control of the carrier concentration of silicon carbide crystals under precise preparation conditions, significantly improving its electrical properties. This preparation method combines the biological template method with precise chemical control, which not only gives the dopant a unique microstructure, but also implements the concept of green environmental protection, providing a feasible solution for large-scale industrial production of dopants for high-performance silicon carbide crystal growth.

[0005] In order to achieve the above technical objectives, the technical solutions adopted by the present invention are as follows: The present invention provides a method for preparing a dopant for silicon carbide crystal growth, which is used for preparing 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 diatom, 1-3 parts of NbCl5, 1-3 parts of Dy(NO3)3·6H2O, 0.5-1 parts of LiCl, and 10-40 parts of SDBS (sodium dodecylbenzene sulfonate) solution; The method for preparing the dopant for silicon carbide crystal growth specifically comprises the following steps: A1, diatom template pretreatment: collect diatom samples, centrifuge, filter and separate diatom individuals with uniform size and complete structure, add anhydrous ethanol to wash the diatoms multiple times to remove surface impurities and organic matter, soak them in dilute nitric acid to further remove residual organic matter, and then dry them at low temperature to obtain dry diatom templates; A2, surface modification of diatom template: weigh SDBS solution, immerse the diatom template in the SDBS solution, stir ultrasonically for 30 min, then wash with deionized water several times, centrifuge, and dry to obtain a modified diatom template; The concentration of SDBS solution is 0.1-0.5 mol / L. A3, preparation of metal ion precursor solution: accurately weigh 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, with the ratio of NbCl5 to anhydrous ethanol being 1g:200 mL, and stir on a magnetic stirrer until completely dissolved to form a uniform metal ion precursor solution; A4, immersion doping reaction: immerse the modified diatom template in a metal ion precursor solution, stir at a certain temperature, and immerse at 50 °C for 12 h to allow the modified diatom template to fully contact with the metal ion precursor to obtain an immersion doped diatom template; A5, high temperature calcination and crystallization: the impregnated and doped diatom template is calcined and crystallized in a high temperature furnace. In a nitrogen atmosphere, it is heated from room temperature to 800 °C at a heating rate of 5 °C / min and kept at 800 °C for 2 h to allow the doping substance to further react and crystallize with the diatom template to obtain a dopant precursor. A6, formation of dopants for silicon carbide crystal growth: During the high-temperature calcination crystallization process, the organic components in the diatom template will be completely burned, 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.

[0006] The present invention also provides a method for controlling doping of a dopant for growing a silicon carbide crystal, comprising the following steps: (1) Pre-treating the dopant, treating the prepared silicon carbide crystal growth dopant through a jet mill to control the particle size to 1-3 µm; (2) Activate the surface of the silicon carbide crystal by heat treating it at 400 °C for 2 h in an argon / hydrogen mixed atmosphere with a volume ratio of argon to hydrogen of 95:5 to improve the wettability of the silicon carbide crystal; (3) mixing a dopant for silicon carbide crystal growth with silicon carbide crystals, accurately controlling the amount of the dopant, with the mass ratio of the dopant to the silicon carbide crystal being 1:1000, and mixing with a double cone mixer at 80-100 rpm for 45-60 min to obtain a mixture; (4) Loading the mixture into a PVT growth furnace, controlling the temperature to 2000-2350 °C in an argon atmosphere, and controlling the growth rate of the crystal by adjusting the heating power and cooling rate; (5) After the growth of the silicon carbide crystal is completed, gradient annealing is performed to eliminate the stress and defects inside the crystal. The temperature is lowered to 1500°C at 5°C / min and then to room temperature at 1°C / min.

[0007] Compared with the prior art, the present invention has the following beneficial effects: The present invention uses diatoms as templates and pre-modifies the diatoms. On the one hand, the modified diatom template allows a large number of SDBS molecules to be adsorbed on the surface of the diatoms, which are negatively charged and have a stronger electrostatic adsorption effect on positively charged metal ions, so that the metal ions can be accurately positioned in the pores and surfaces of the diatoms, and a highly ordered doping distribution can be achieved, so that the metal ions are evenly distributed on the nanoscale pore walls, and a microscopic doping structure is constructed; on the other hand, during the ultrasonic stirring process, the SDBS molecules can rise into the pores of the diatom template, increase the surface active sites, provide more reaction centers for the adsorption and chemical reaction of metal ions, and promote the chemical combination between the diatom template and the metal ions; and the SDBS molecules form a protective film on the surface of the diatoms, which effectively prevents the diatom template from being structurally damaged due to external forces or high temperatures during the immersion doping reaction and high-temperature calcination. Nb 5+ 、Dy 3+ , Li +The synergistic doping of 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+ As an n-type dopant to provide additional electrons, Li + Adjusting the hole concentration, under precise preparation conditions, the two realized the precise control of the carrier concentration of silicon carbide crystals, significantly improving its electrical properties; Dy 3+ By affecting the crystal structure and electron cloud distribution, it plays a unique role in magnetic and optical properties, can achieve efficient luminescence at a specific wavelength, and opens up a new path for the application of silicon carbide crystals in optoelectronic devices. The entire preparation process combines the biological template method with precise chemical control. The use of natural diatom templates not only gives the dopant a unique microstructure, but also embodies the green and environmentally friendly preparation concept. In each step, the refined control of parameters such as temperature, concentration, and time, as well as real-time monitoring and feedback adjustment mechanisms, 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

[0008] Figure 1 The present invention is a flow chart of the preparation of a dopant for growing silicon carbide crystals; Figure 2 This is a SEM image of silicon carbide prepared by the dopant used for silicon carbide crystal growth of the present invention. DETAILED DESCRIPTION

[0009] In order to make the technical solution of the present invention better understood by the technical personnel in the field, and to make the above-mentioned features, purposes and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with the embodiments. The embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0010] Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to those described herein may be applied to the present invention. The preferred implementation methods and materials described herein are for demonstration purposes only and are not intended to limit the content of this application.

[0011] In the following examples, unless otherwise specified, conventional methods are used; the materials used in the following examples, unless otherwise specified, are all new materials purchased from the market, among which NbCl5, item number N837024, 99.999%, was purchased from Shanghai MacLean Reagent Co., Ltd.; Dy(NO3)3·6H2O, 99.90%, was purchased from Shandong Desheng New Materials Co., Ltd.; LiCl, item number 767295, 99.995%, was purchased from Shanghai MacLean Reagent Co., Ltd.; diatoms were purchased from Lanshe Diatom New Materials Co., Ltd.

[0012] according to Figure 1 The preparation flow chart of the dopant for growing silicon carbide crystal prepared by the present invention provides the following examples: 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, wherein 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; The method for preparing the dopant for silicon carbide crystal growth specifically comprises the following steps: A1, diatom template pretreatment: diatom samples were collected, centrifuged, filtered to separate diatom individuals of uniform size and complete structure, and the diatoms were washed 5 times with anhydrous ethanol to remove surface impurities and organic matter, and then soaked in 5% dilute nitric acid to further remove residual organic matter, and then low-temperature dried at 40 °C to obtain a dry diatom template; A2, surface modification of diatom template: weigh SDBS solution with a concentration of 0.1 mol / L, stir and dissolve, immerse the diatom template in the SDBS solution, stir ultrasonically for 30 min, then wash with deionized water several times, centrifuge and dry to obtain a modified diatom template; A3, preparation of metal ion precursor solution: accurately weigh 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, with the ratio of NbCl5 to anhydrous ethanol being 1g:200 mL, and stir on a magnetic stirrer until completely dissolved to form a uniform metal ion precursor solution; A4, immersion doping reaction: immerse the modified diatom template in a metal ion precursor solution and stir and immerse at 50 °C for 12 h to allow the modified diatom template to fully contact with the metal ion precursor to obtain an immersion doped diatom template; A5, high temperature calcination and crystallization: the impregnated and doped diatom template is calcined and crystallized in a high temperature furnace. In a nitrogen atmosphere, it is heated from room temperature to 800 °C at a heating rate of 5 °C / min and kept at 800 °C for 2 h to allow the doping substance to further react with the diatom template and crystallize. A6, formation of dopants for silicon carbide crystal growth: During the high-temperature calcination crystallization process, the organic components in the diatom template will be completely burned, and the silicon dioxide structure of the diatom will react with the doping substance to form a dopant precursor. The dopant precursor is cooled, ground, and other processes to obtain a dopant for silicon carbide crystal growth.

[0013] This embodiment also provides a doping control method for a dopant for growing a silicon carbide crystal, comprising the following aspects: (1) pre-treating the dopant for silicon carbide crystal growth, treating the prepared dopant for silicon carbide crystal growth by a jet mill, controlling the particle size to be 1 µm, and obtaining a pre-treated dopant; (2) Activating the surface of the silicon carbide crystal by placing the silicon carbide crystal in a mixed atmosphere of argon / hydrogen with a volume ratio of argon to hydrogen of 95:5 and heat treating it at 400 °C for 2 h to improve the wettability of the silicon carbide crystal and form activated silicon carbide; (3) mixing the pretreated dopant with the activated silicon carbide, precisely controlling the amount of the dopant, the mass ratio of the dopant to the silicon carbide crystal being 1:1000, and mixing with a double cone mixer at 80 rpm for 45 min to obtain a mixture; (4) loading the mixture into a PVT growth furnace, controlling the temperature at 2000 °C in an argon atmosphere, and controlling the growth rate of the silicon carbide crystal by adjusting the heating power and cooling rate; (5) After the growth of the silicon carbide crystal is completed, gradient annealing is performed to eliminate the stress and defects inside the crystal. The temperature is lowered to 1500°C at 5°C / min and then to room temperature at 1°C / min.

[0014] 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, wherein the dopant for silicon carbide crystal growth is prepared from the following raw materials in parts by weight: 80 parts of diatom, 2 parts of NbCl5, 2 parts of Dy(NO3)3·6H2O, 0.8 parts of LiCl, and 25 parts of SDBS solution; The method for preparing the dopant for silicon carbide crystal growth specifically comprises the following steps: A1, diatom template pretreatment: collect diatom samples, centrifuge, filter and separate diatom individuals of uniform size and complete structure, add anhydrous ethanol to wash the diatoms 5 times to remove surface impurities and organic matter, soak them in dilute nitric acid with a mass concentration of 5-10% to further remove residual organic matter, and then dry them at 50 °C to obtain a dry diatom template; A2, surface modification of diatom template: weigh SDBS solution with a concentration of 0.2 mol / L, stir and dissolve to form an SDBS solution, immerse the diatom template in the SDBS solution, stir ultrasonically for 30 min, then wash with deionized water several times, centrifuge, and dry to obtain a modified diatom template; A3, preparation of metal ion precursor solution: accurately weigh 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, with the ratio of NbCl5 to anhydrous ethanol being 1g:200 mL, and stir on a magnetic stirrer until completely dissolved to form a uniform metal ion precursor solution; A4, immersion doping reaction: immerse the modified diatom template in a metal ion precursor solution and stir and immerse at 50 °C for 12 h to allow the modified diatom template to fully contact with the metal ion precursor to obtain an immersion doped diatom template; A5, high temperature calcination and crystallization: the impregnated and doped diatom template is calcined and crystallized in a high temperature furnace. In a nitrogen atmosphere, it is heated from room temperature to 800 °C at a heating rate of 5 °C / min and kept at 800 °C for 2 h to allow the doping substance to further react with the diatom template and crystallize. A6, formation of dopants for silicon carbide crystal growth: During the high-temperature calcination crystallization process, the organic components in the diatom template will be completely burned, and the silica structure of the diatom will react with the doping substance to form a dopant and precursor. The dopant precursor is cooled, ground, and other processes to obtain a dopant for silicon carbide crystal growth.

[0015] This embodiment also provides a doping control method for a dopant for growing a silicon carbide crystal, comprising the following aspects: (1) pre-treating the dopant for silicon carbide crystal growth, treating the prepared dopant for silicon carbide crystal growth by a jet mill, controlling the particle size to be 2 µm, and obtaining a pre-treated dopant; (2) Activating the surface of the silicon carbide crystal by heat treating it at 400 °C for 2 h in an argon / hydrogen mixed atmosphere with a volume ratio of argon to hydrogen of 95:5 to improve the wettability of the silicon carbide crystal and form activated silicon carbide; (3) mixing the pretreated dopant with the activated silicon carbide, precisely controlling the amount of the dopant, the mass ratio of the dopant to the silicon carbide crystal being 1:1000, and mixing for 60 min at 90 rpm using a double cone mixer to obtain a mixture; (4) Loading the mixture into a PVT growth furnace, controlling the temperature at 2320 °C in an argon atmosphere, and controlling the growth rate of the crystal by adjusting the heating power and cooling rate; (5) After the growth of the silicon carbide crystal is completed, gradient annealing is performed to eliminate the stress and defects inside the crystal. The temperature is lowered to 1500°C at 5°C / min and then to room temperature at 1°C / min.

[0016] Example 3: 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, wherein the dopant for silicon carbide crystal growth is prepared from the following raw materials in parts by weight: 100 parts of diatom, 3 parts of NbCl5, 3 parts of Dy(NO3)3·6H2O, 1 part of LiCl, and 40 parts of SDBS solution; The method for preparing the dopant for silicon carbide crystal growth specifically comprises the following steps: A1, diatom template pretreatment: collect diatom samples, centrifuge, filter and separate diatom individuals of uniform size and complete structure, add anhydrous ethanol to wash the diatoms 5 times to remove surface impurities and organic matter, soak them in dilute nitric acid with a mass concentration of 5-10% to further remove residual organic matter, and then dry them at 60 ° C to obtain a dry diatom template; A2, surface modification of diatom template: weigh SDBS solution with a concentration of 0.5 mol / L, stir and dissolve to form an SDBS solution, immerse the diatom template in the SDBS solution, ultrasonically stir for 30 min, then wash with deionized water several times, centrifuge, and dry to obtain a modified diatom template; A3, preparation of metal ion precursor solution: accurately weigh 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, with the ratio of NbCl5 to anhydrous ethanol being 1g:200 mL, and stir on a magnetic stirrer until completely dissolved to form a uniform metal ion precursor solution; A4, immersion doping reaction: immerse the modified diatom template in a metal ion precursor solution and stir and immerse at 50 °C for 12 h to allow the modified diatom template to fully contact with the metal ion precursor to obtain an immersion doped diatom template; A5, high temperature calcination and crystallization: the impregnated and doped diatom template is calcined and crystallized in a high temperature furnace. In a nitrogen atmosphere, it is heated from room temperature to 800 °C at a heating rate of 5 °C / min and kept at 800 °C for 2 h to allow the doping substance to further react with the diatom template and crystallize. A6, formation of dopants for silicon carbide crystal growth: During the high-temperature calcination crystallization process, the organic components in the diatom template will be completely burned, and the silica structure of the diatom will react with the doping substance to form a dopant and precursor. The dopant precursor is cooled, ground, and other processes to obtain a dopant for silicon carbide crystal growth.

[0017] This embodiment also provides a doping control method for a dopant for growing a silicon carbide crystal, comprising the following aspects: (1) pre-treating the dopant for silicon carbide crystal growth, treating the prepared dopant for silicon carbide crystal growth by a jet mill, controlling the particle size to be 3 µm, and obtaining a pre-treated dopant; (2) Activating the surface of the silicon carbide crystal by heat treating it at 400 °C for 2 h in an argon / hydrogen mixed atmosphere with a volume ratio of argon to hydrogen of 95:5 to improve the wettability of the silicon carbide crystal and form activated silicon carbide; (3) mixing the pretreated dopant with the activated silicon carbide, precisely controlling the amount of the dopant, the mass ratio of the dopant to the silicon carbide crystal being 1:1000, and mixing for 60 min at 100 rpm using a double cone mixer to obtain a mixture; (4) Loading the mixture into a PVT growth furnace, controlling the temperature at 2350 °C in an argon atmosphere, and controlling the growth rate of the crystal by adjusting the heating power and cooling rate; (5) After the growth of the silicon carbide crystal is completed, gradient annealing is performed to eliminate the stress and defects inside the crystal. The temperature is lowered to 1500°C at 5°C / min and then to room temperature at 1°C / min.

[0018] The difference between Comparative Example 1 and Example 1 is that the diatom template is not modified, and the rest is exactly the same as Example 1.

[0019] The difference between Comparative Example 2 and Example 1 is that no NbCl5 is added, and the rest is exactly the same as Example 1.

[0020] 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.

[0021] Experimental Example: Using the dopant for silicon carbide crystal growth prepared by the present invention, a physical vapor transport method (PVT method) was used to grow silicon carbide crystals, and the carrier velocity, resistivity and crystal growth rate of the grown silicon carbide crystals were measured.

[0022] Carrier rate determination: square slices with a side length of 5-10 mm were cut from the prepared silicon carbide crystals. The sample surface was treated to a mirror finish by combining mechanical polishing and chemical mechanical polishing to reduce the influence of surface scattering on carrier transport. Metal electrodes were prepared on the sample surface by vacuum evaporation or magnetron sputtering. Aluminum (Al) was selected as the electrode material. The electrode shape was an ohmic contact electrode. The electrode layout of the four-probe method was adopted. The four electrodes were arranged in a straight line. The electrode spacing was precisely controlled at 1-2 mm. The prepared sample was placed in a cryostat, and the electrodes were connected to the high-precision current source and voltage measuring instrument test equipment. The sample test temperature was precisely controlled by the cryostat. The test was first carried out at room temperature to study the influence of temperature on the carrier rate. A high-precision current source was used to inject a stable current into the sample. The current size was adjusted according to the characteristics of the sample and the test requirements. At the same time, a voltage measuring instrument was used to measure the voltage drop across the sample. According to Ohm's law and the carrier mobility formula, the carrier mobility was calculated by measuring the current, voltage and the geometric dimensions (thickness, length, etc.) of the sample. Carrier velocity = carrier mobility × electric field strength, where the electric field strength can be calculated based on the applied voltage and sample length. The injection current was changed multiple times, and the measurements and calculations were repeated. The average value was taken to improve the test accuracy. The average value is recorded in Table 1.

[0023] Resistivity test: The silicon carbide crystal was cut into 200 μm thick silicon carbide single crystals, and the resistivity test was performed using the non-contact eddy current method. The eddy current resistivity tester was calibrated using a standard silicon carbide sample with a known resistivity to ensure the accuracy of the test equipment. The resistivity value of the standard sample should cover the expected resistivity range of the sample to be tested. The sample was placed on the test bench of the eddy current resistivity tester, and the parameters of the tester, such as the excitation frequency and magnetic field strength, were adjusted to suit the sample characteristics. The tester was started to obtain the resistivity data of the sample. To ensure the reliability of the test, three measurements were performed at different locations of the sample, with an interval of 5 mm between each measurement location. Finally, the average value was taken as the resistivity of the sample, and the results are recorded in Table 1.

[0024] Crystal growth rate test: The system for growing silicon carbide crystals using the physical vapor transport method (PVT method) is equipped with a high-precision temperature control system in the growth furnace with a temperature control accuracy of ±1°C, as well as a pressure monitoring and regulation device with a pressure control accuracy of ±0.1kPa. The crucible containing high-purity silicon carbide micropowder raw materials is placed in the growth furnace, the seed crystal is fixed in a suitable position, the growth furnace is sealed, and the vacuum is pumped to 10 -3 -10 -4Pa, and then fill with high-purity argon as a protective atmosphere, and the gas pressure is maintained at 5-10 kPa. Start heating the growth furnace, raise the temperature to 2300 ℃ 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 laser interferometer to monitor the growth of the crystal in real time. The growth interface of the crystal can be directly observed through an optical microscope. Every 1 hour, the growth length of the crystal in a certain direction is recorded; the laser interferometer accurately calculates the change in the growth thickness of the crystal by measuring the change in the interference fringes. According to the recorded growth time and crystal growth length or thickness data, the crystal growth rate is calculated, and the results are recorded in Table 1.

[0025] Table 1

[0026] From the results in Table 1, it can be seen that the carrier rates of Examples 1-3 are significantly higher than those of Comparative Examples 1-3, indicating that the dopant for silicon carbide crystal growth prepared by the present invention is beneficial to improving the carrier rate, indicating that the added dopant can construct an ordered structure and reduce scattering; the resistivity of the embodiment reaches 0.06 Ω·cm, indicating that the addition of the dopant can effectively reduce the resistivity and enhance the conductivity of silicon carbide; from the perspective of crystal growth rate, the addition of the dopant prepared by the present invention has a significant promoting effect on the growth of silicon carbide crystals.

[0027] Figure 2 From the SEM image of silicon carbide prepared by the dopant for silicon carbide crystal growth of the present invention, it can be seen that a glass phase is gradually generated between the silicon carbide particles to form a large number of neck connections. The increase in the number of neck connections greatly improves the flexural strength of the support body, and no foaming occurs, indicating that the addition of the dopant greatly improves the antioxidant ability of the silicon carbide crystals.

[0028] In summary, the present invention shows many significant advantages by modifying diatoms and co-doping with specific metal ions. In terms of carrier rate, the modified diatom template accurately positions the metal ions to construct an ordered microstructure, reduce carrier scattering, thereby improving carrier mobility and optimizing the carrier transport performance of silicon carbide crystals; in terms of resistivity regulation, the doping method effectively increases the conductivity of silicon carbide crystals, reduces resistivity, and significantly improves its conductive properties; from the perspective of crystal growth rate, the dopant provides more active sites for crystal growth, optimizes the growth environment, and promotes the growth process of the crystal. The entire preparation process combines the biological template method with precise chemical control, which not only realizes the precise regulation of the structure and performance of silicon carbide crystals, but also embodies the concept of green environmental protection, and provides a valuable solution for the preparation of high-performance silicon carbide crystals and applications in related fields, and is expected to promote the wide application and development of silicon carbide crystals in electronics, energy and other fields.

[0029] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a dopant for silicon carbide crystal growth, for preparing a dopant for silicon carbide crystal growth, 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 diatom, 1-3 parts of NbCl5, 1-3 parts of Dy(NO3)3·6H2O, 0.5-1 parts of LiCl, and 10-40 parts of SDBS solution; The method for preparing a dopant for growing silicon carbide crystals comprises the following steps: A1, pretreatment of diatom template: weigh diatom, soak the diatom 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, ultrasonicate, 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 by weight, then add NbCl5, Dy(NO3)3·6H2O and LiCl to anhydrous ethanol in sequence, and stir until completely dissolved to form a metal ion precursor solution; A4, impregnation doping reaction: immersing the modified diatom template in a metal ion precursor solution, stirring and impregnating, to obtain an impregnation doped diatom template; A5, high temperature calcination and crystallization: calcining and crystallizing the impregnated and doped diatom template to obtain a dopant precursor; A6, formation of dopant for silicon carbide crystal growth: cooling and grinding the dopant precursor to obtain the dopant for silicon carbide crystal growth.

2. A method for preparing a dopant for silicon carbide crystal growth 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 method for preparing a dopant for silicon carbide crystal growth according to claim 1, characterized in that: In step A3, the ratio of NbCl5 to anhydrous ethanol is 1 g:200 mL; in step A4, the temperature of the stirring immersion is 50°C and the time is 12 h.

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

5. A method for controlling doping of a dopant for silicon carbide crystal growth prepared by the method for preparing a dopant for silicon carbide crystal growth according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) pre-treating a dopant for silicon carbide crystal growth, controlling the particle size of the prepared dopant for silicon carbide crystal growth, and obtaining a pre-treated dopant; (2) Activating the surface of the silicon carbide crystal by heat treatment in an argon / hydrogen mixed atmosphere to form activated silicon carbide; (3) mixing the pretreated dopant with the activated silicon carbide, precisely controlling the amount of the dopant to obtain a mixture; (4) placing the mixture in an argon atmosphere, controlling the temperature, and controlling the crystal growth rate by adjusting the heating power and cooling rate; (5) After the silicon carbide crystal growth is completed, gradient annealing is performed.

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

7. The method for controlling doping of a dopant for growing silicon carbide crystal 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 method for controlling doping of a dopant for growing silicon carbide crystal according to claim 5, characterized in that: In step (5), the gradient annealing is performed by cooling the temperature down to 1500°C at 5°C / min, and then cooling the temperature down to room temperature at 1°C / min.

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