A method for efficiently preparing low-oxygen-content single crystal silicon

Abstract

The application discloses a kind of high-efficiency preparation methods of low-oxygen-content monocrystalline silicon in the technical field of semiconductor materials;Rare earth-transition metal co-doped composite oxide porous ceramic material is used as oxygen vacancy control oxygen material, which is broken into thin pieces and loaded in boron nitride basket, and is laid in quartz crucible in sequence with gasket, zirconia block and silicon material.By stepwise heating and melting silicon material, and switching argon purging flow in stages, silicon melt is obtained after pre-adsorbing oxygen;Seed crystal is used for seeding, and seed crystal and crucible are counter-rotated, and overcooling degree is maintained by power regulation for isodiametric growth;After lifting crystal, slow cooling is carried out in stages and furnace pressure is recovered synchronously, and finally low-oxygen-content monocrystalline silicon is obtained.The application effectively reduces interstitial oxygen content in monocrystalline silicon through synergistic regulation of porous ceramic oxygen control, fine temperature control, airflow management and crystal growth parameters, and considers high production efficiency and crystal quality.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor materials technology, specifically relating to an efficient method for preparing low-oxygen-content single-crystal silicon. Background Technology

[0002] As the fundamental substrate material for semiconductor power devices and integrated circuits, the lattice integrity and electrical properties of monocrystalline silicon directly determine the final quality of the devices. Among numerous quality indicators, interstitial oxygen content is one of the key parameters affecting the performance of monocrystalline silicon. In the manufacturing process of power devices such as insulated-gate bipolar transistors, excessive interstitial oxygen will form thermal donors in subsequent heat treatment processes, leading to resistivity drift and severely affecting the breakdown voltage and reliability of the devices. In addition, the formation of oxygen deposits can induce secondary defects and reduce the integrity of the gate oxide layer. The current mainstream oxygen control technology mainly relies on the magnetically controlled Czochralski method, which suppresses melt convection by applying an external magnetic field to reduce oxygen dissolution from the quartz crucible wall. However, magnetically controlled equipment is extremely expensive and consumes a lot of energy, and the suppression effect of the magnetic field on large-sized melts has a physical limit. When the crystal diameter increases, convection in the melt edge region is still intense, leading to a deterioration in the radial oxygen concentration uniformity of the crystal. Another technical approach focuses on optimizing the thermal field design and crucible coating, but its reduction in oxygen content is limited and it is difficult to stably achieve extremely low oxygen levels.

[0003] To overcome the aforementioned technical bottlenecks, researchers have recently begun exploring the integration of oxygen trapping materials into silicon melts, attempting to capture and transfer oxygen within the melt through chemical adsorption or participation in oxygen transport. Among these, rare-earth and transition metal co-doped composite oxides, with their abundant oxygen vacancy structures, have shown great potential as solid-phase oxygen-controlling materials. These materials can be obtained from multi-metal-organic framework precursors through calcination and reduction treatment, where the internal oxygen vacancies can rapidly exchange and anchor with interstitial oxygen atoms in the molten silicon environment. However, in practical implementation, this technical route faces three major obstacles. First, the geometric dimensions of porous ceramic sheets lack precise definition; excessive thickness leads to limited mass transfer and a sharp decline in oxygen control efficiency, while insufficient thickness results in insufficient strength and brittleness, with fragments directly contaminating the entire melt and causing lattice dislocations. Second, the preparation and retention processes for oxygen vacancies are extremely demanding. If the material is exposed to air after reduction or undergoes improper cooling, the oxygen vacancies will be re-annihilated in the mid-temperature region, causing the material to completely lose its oxygen-controlling activity. Third, the introduction of porous ceramics into the melt alters the original thermal and flow field distributions. If the matching heating and melting regime, protective atmosphere management, and the synergistic relationship between rotation and temperature control parameters are unclear, it can easily lead to instability at the solid-liquid interface, resulting in crystal growth failure.

[0004] At the crystal growth process level, in the existing Czochralski single crystal preparation process, if a single rate is used during the heating and melting stage, the high-purity polycrystalline silicon raw material and the built-in porous ceramic sheet will be subjected to huge thermal shock during the liquid-solid phase transition, causing material fragmentation. The flow rate and timing of the protective gas purging need to be precisely controlled in segments according to the needs of different stages such as melting, pre-oxygen absorption, crystal pulling, and constant diameter growth. Flow rate mismatch at any stage will either destroy the oxygen vacancy trapping layer interface or disrupt the uniformity of the melt concentration field. In the crystal pulling and shoulder formation stages, the ratio of the rotational speed of the seed crystal to that of the crucible directly determines the morphology of the solid-liquid interface and the melt flow field. Without clear parameters, it is impossible to stably control the crystal diameter. More importantly, in the annealing and cooling stages after growth, if the cooling rate is too fast or not coordinated with furnace pressure recovery, dense slip dislocations will be generated inside the crystal, rendering all the results of the previous oxygen control processes useless. Therefore, from the precise preparation of porous ceramic oxygen-controlled materials to the refined process coordination of the entire crystal pulling process, there is an urgent need to build a complete, reproducible, and industrially applicable technical solution to efficiently and stably achieve extremely low interstitial oxygen content in monocrystalline silicon. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide an efficient method for preparing single-crystal silicon with low oxygen content.

[0006] In a first aspect, the present invention provides a highly efficient method for preparing low-oxygen-content monocrystalline silicon, comprising the following steps: S1. Under argon protection, crush and sieve 15-30 parts by weight of rare earth-transition metal co-doped composite oxide porous ceramic material, and load it into a boron nitride mesh basket to obtain a mesh basket containing rare earth-transition metal co-doped composite oxide porous sheets; at the center of the bottom of the quartz crucible, lay 1-2 parts of boron nitride pad, the mesh basket containing rare earth-transition metal co-doped composite oxide porous sheets, 6-10 parts of zirconium oxide ceramic block, 3-5 parts of polycrystalline silicon fragments, and 150-250 parts of high-purity polycrystalline silicon block material in a vertical order from bottom to top; lay 20-30 parts of high-purity polycrystalline silicon block material on the outermost ring of the quartz crucible to obtain a filled quartz crucible; S2. Place the filled quartz crucible into a single crystal furnace; introduce 100-200 parts of argon gas; raise the temperature from room temperature to 1090-1110℃ and hold; raise the temperature to 1370-1390℃ and hold; raise the temperature to 1410-1430℃ and hold to melt; purge with 1500-2500 parts of argon gas; adjust the temperature to 1418-1422℃ and hold to obtain silicon melt; S3. Adjust the temperature to 1408-1412℃, activate the seed crystal lifting mechanism, and move 5-10 oriented... <100> The silicon seed crystal descends to contact the silicon melt; the argon gas flow rate is adjusted to 30-50 L / min. -1The seed crystal rotates, and the crucible rotates in the opposite direction; the argon gas flow rate is adjusted to 80-120 L / min. -1 Maintain a supercooling of 1-2℃; grow crystals of constant diameter to obtain the grown crystals; S4. Lift the grown crystals off the liquid surface and keep them at 1290-1310℃; cool them down to 795-805℃; continue cooling them down to 595-605℃; let them cool naturally to room temperature.

[0007] In this invention, the preparation mechanism of low-oxygen-content single-crystal silicon is based on the synergistic control of solid-liquid interface physicochemistry and crystal growth kinetics. During the thermal assembly stage, thin sheets of rare-earth-transition-metal co-doped composite oxide porous ceramic material containing oxygen vacancies are loaded into a pyrolytic boron nitride basket. A boron nitride gasket at the bottom of the quartz crucible acts as a chemically inert isolation layer, preventing direct contact between the rare-earth oxides and the quartz crucible, which could lead to the formation of a low-melting-point rare-earth silicate eutectic at high temperatures. The density of the dense zirconia ceramic block laid on top of the boron nitride basket is much higher than that of liquid silicon. The downward force generated by the density difference presses the boron nitride gasket, basket, and porous ceramic sheet together firmly against the bottom of the crucible, preventing the components from being rolled up by the Marangoni convection of the melt and causing heterogeneous nucleation and dislocations at the single-crystal growth interface. The high-purity polycrystalline silicon fragment buffer layer laid on top of the zirconia ceramic block has the same chemical composition as the high-purity polycrystalline silicon block. During the heating process, it softens before the large silicon block, absorbing the mechanical stress generated by the thermal expansion of the solid phase of the large silicon block, thus protecting the porous ceramic sheet from breakage. After the buffer layer completely melts, it integrates into the melt without introducing heterogeneous phases. The filled quartz crucible is placed in a single-crystal furnace and filled with high-purity argon gas. A three-step slow heating melting curve is used to achieve overall temperature homogenization of the solid silicon and balance the temperature gradient inside and outside the porous ceramic sheet, preventing the sheet from breaking due to sudden temperature changes during the liquid-solid phase transition. After the silicon material is completely melted into a silicon melt, the inner wall of the SiO2 in the quartz crucible reacts with the silicon melt (SiO2 + Si → 2SiO↑), continuously releasing dissolved oxygen into the melt. Oxygen vacancies on the surface of the porous ceramic sheet at the bottom act as highly active chemisorption sites, chemically bonding with dissolved oxygen diffused from the melt to the sheet surface, capturing and fixing oxygen atoms within the crystal lattice. Simultaneously, high-purity argon gas is introduced into the furnace to purge the liquid surface, carrying gaseous SiO away from the melt surface and out of the furnace, thus forming a dual-channel deoxidation mechanism synergistically involving bottom solid-phase chemisorption and surface gas-phase volatilization. During the crystal seeding and constant-diameter growth stages, the silicon seed crystal is lowered to contact the surface of the slightly supercooled silicon melt, and silicon atoms move along the seed crystal at the solid-liquid interface. <100> Orientation-driven epitaxial growth enables ordered crystallization; the rotation of the seed crystal and the opposite rotation of the crucible break the natural convection boundary layer of the melt, homogenizing the melt concentration field. Due to continuous oxygen adsorption at the bottom, the concentration of dissolved oxygen transported to the growth interface is significantly reduced, inhibiting the nucleation of oxygen-related micro-defects (including oxygen precipitation and stacking faults). After the crystal detaches from the liquid surface, it enters a programmed cooling stage, first undergoing long-term annealing in a high-temperature region, and then cooling in segments at a low rate through the main stress-relieving temperature region, allowing the internal thermal stress of the crystal to be fully released, thus obtaining a single-crystal silicon product with low oxygen content and low dislocation density.

[0008] According to a preferred embodiment of the present invention, in step S1, the boron nitride mesh basket is pre-cleaned with deionized water by ultrasonic cleaning and vacuum dried at 148-152°C; the purity of the high-purity polycrystalline silicon block is above 99.9999%.

[0009] According to a preferred embodiment of the present invention, in step S2, the time for heating to 1410-1430°C and holding for melting is 30-60 minutes.

[0010] According to a preferred embodiment of the present invention, in step S3, the time for constant diameter growth is 30-32 hours.

[0011] According to a preferred embodiment of the present invention, in step S4, the heat preservation time at 1290-1310℃ is 4-6 hours.

[0012] According to a preferred embodiment of the present invention, the preparation steps of the rare earth-transition metal co-doped composite oxide porous ceramic material include: A1. By weight, dissolve 40-50 parts of cerium nitrate hexahydrate, 15-20 parts of lanthanum nitrate hexahydrate, 10-15 parts of zirconium nitrate pentahydrate, and 6-13 parts of yttrium nitrate hexahydrate in 450-550 parts of deionized water, and stir at 58-62℃; evaporate by rotary evaporation to obtain a concentrated solution; add 48-52 parts of anhydrous N,N-dimethylformamide to the concentrated solution, azeotropically at 80-82℃, and add 150-200 parts of anhydrous N,N-dimethylformamide to obtain a premixed solution; dissolve 90-110 parts of terephthalic acid in 300-350 parts of anhydrous N,N-dimethylformamide. In N,N-dimethylformamide, a ligand solution was obtained by ultrasonic treatment at 38-42℃. 50-65 parts of 4-dimethylaminopyridine were dissolved in 150-200 parts of anhydrous N,N-dimethylformamide and added dropwise to the ligand solution to react, yielding a mixture. The premixed solution was mixed with the mixture and transferred to a reaction vessel for solvothermal treatment at 118-122℃. The mixture was centrifuged to obtain a solid. The solid was washed with N,N-dimethylformamide and anhydrous methanol, followed by supercritical carbon dioxide extraction. The solid was then vacuum dried at 58-62℃ to obtain a rare-earth-transition-metal multi-metal-organic framework precursor. A2. The rare earth-transition metal multi-metal organic framework precursor is placed in a tube furnace and heated from room temperature to 148-152℃ and held; then heated to 198-202℃ and held; then heated to 348-352℃ and held; then heated to 798-802℃ and held; cooled to room temperature to obtain a composite powder; the composite powder is dispersed in 300-500 parts of deionized water, ultrasonically treated, and centrifuged to obtain a precipitate; the precipitate is washed with anhydrous ethanol and vacuum dried at 78-82℃ to obtain a dry powder; A3. Press the dried powder to obtain a green body; place the green body in a tube furnace, introduce an argon atmosphere, and heat to 1098-1102℃ and hold. A4. Switch to a mixed atmosphere of hydrogen and argon, and maintain the temperature at 1098-1102℃; cool down to 398-402℃ and maintain the temperature thereafter; continue cooling to obtain a thin sheet; load the thin sheet into a transfer container pre-filled with argon; connect the transfer container to the glove box transition chamber, evacuate the transition chamber and clean it with argon; transfer the thin sheet into the main compartment of the glove box and seal it in an aluminum-plastic composite vacuum bag.

[0013] In this invention, the preparation mechanism of rare-earth-transition-metal co-doped composite oxide porous ceramic materials is based on the gradual evolution of coordination chemistry and solid-state thermodynamics. Cerium nitrate hexahydrate, lanthanum nitrate hexahydrate, zirconium nitrate pentahydrate, and yttrium nitrate hexahydrate dissociate in deionized water, respectively generating Ce. 3+ La 3+ Zr 4+ and Y 3+A cation. Terephthalic acid, acting as a bridging organic ligand, is dissolved in N,N-dimethylformamide solvent with ultrasonic assistance to form a clear ligand solution. 4-Dimethylaminopyridine, acting as a weak base deprotonating agent, deprotonates the carboxyl group of terephthalic acid to form a carboxylate anion, exposing the lone pair electrons on the carboxyl oxygen as a coordinating active site. Under solvothermal conditions, the deprotonated terephthalate anion bonds with the aforementioned metal cation through carboxyl-metal bonds, forming a multi-metal co-coordinated metal-organic framework precursor. The solid is alternately washed with N,N-dimethylformamide and anhydrous methanol to remove free unreacted substances and solvent from the surface; supercritical carbon dioxide extraction replaces residual N,N-dimethylformamide solvent molecules in the pores, avoiding pore structure collapse caused by capillary forces at the liquid-gas interface during atmospheric pressure drying. The dried precursor was calcined in a closed tube furnace under a high-purity air atmosphere in a multi-stage, slow-heating process: a low-temperature stage removed residual solvents; a medium-temperature stage oxidized and burned the organic ligands into carbon dioxide and water vapor, which then escaped; a high-temperature stage completely burned off the carbon skeleton and oxidized metal ions in situ into a multi-element metal oxide nanoparticle network, forming a hierarchical porous structure. The calcined product was ultrasonically cleaned with deionized water and washed with anhydrous ethanol before drying to obtain porous oxide powder. The dried powder was isostatically pressed into thin, circular blanks, which were then sintered for a long time in an argon atmosphere at the critical Taman temperature range. This process allowed the nanocrystals to form stable sintering necks through grain boundary diffusion and surface diffusion, giving the porous ceramic sheet sufficient mechanical strength to resist the shear flow of molten silicon, while retaining macroscopic channels for melt penetration. After the sintered framework is shaped, the gas path is switched to a mixed reducing atmosphere of hydrogen and argon in the same tube furnace. Initial high-temperature reduction is performed at 1100℃. Hydrogen dissociates and adsorbs on the surface of the metal oxide, reacting with oxygen on the lattice surface to generate water vapor, which is released and forms oxygen vacancies around the metal nodes. Subsequently, deep reduction is performed by continuously cooling at a low rate to 400℃ in a continuous hydrogen / argon reducing atmosphere. This allows the oxygen vacancies to be stably retained by the continuous hydrogen reduction flux as they cross the 600-700℃ annihilation temperature range. Finally, the ceramic sheet is cooled to below 80℃ in a reducing atmosphere. The cooled porous ceramic sheet is then transferred to the glove box transition chamber via a pre-purged, positively pressurized argon vacuum transfer tank. After the transition chamber is evacuated, it is purged with argon gas through circulation to remove residual air. The sheet is then introduced into the main compartment of the glove box and sealed in an aluminum-plastic composite vacuum bag to prevent surface deactivation caused by the reaction of moisture and carbon dioxide in the air with the oxygen vacancies at room temperature.

[0014] According to a preferred embodiment of the present invention, in step A1, the solvent heat treatment at 118-122°C is carried out for 24-30 hours.

[0015] According to a preferred embodiment of the present invention, in step A2, the time for holding the temperature at 798-802°C is 4-6 hours.

[0016] According to a preferred embodiment of the present invention, in step A3, the time for holding the temperature at 1098-1102°C is 16-20 hours.

[0017] According to a preferred embodiment of the present invention, in step A4, the time for cooling to 398-402°C and holding at that temperature is 3-5 hours.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention significantly improves the system stability of low-oxygen single crystal preparation by optimizing the thermal field layout. In the filling stage, a layered bottom layer and gravity counterweight structure is adopted. After the relative positions of the high-purity polycrystalline silicon block and the bottom component are strictly defined, the zirconia ceramic block firmly presses the boron nitride basket containing the active material, together with the bottom boron nitride pad, onto the bottom of the quartz crucible. This layout effectively resists the buoyancy of the high-temperature fluid generated during the silicon melting stage, preventing the component from floating and causing crystal dislocations. Homologous polycrystalline silicon fragments are laid as a flexible buffer layer between the large-size silicon block and the bottom brittle structure, fully absorbing the mechanical extrusion stress during the solid-phase thermal expansion stage and protecting the physical integrity of the porous thin sheet inside the basket. The stepped heating regime ensures a smooth transition of temperature difference changes in each stage, further reducing the risk of thin sheet breakage caused by thermal shock.

[0019] (2) This invention utilizes precise chemical assembly and thermodynamic control to construct a highly active rare-earth-transition-metal co-doped composite oxide porous ceramic material. The precursor synthesis uses cerium nitrate hexahydrate, lanthanum nitrate hexahydrate, zirconium nitrate pentahydrate, and yttrium nitrate hexahydrate as all-metal sources, with terephthalic acid as the ligand framework. The multi-metal-organic framework structure is obtained through solvothermal assembly, multiple rounds of washing with anhydrous methanol, and supercritical carbon dioxide extraction. During the calcination stage, the framework is first densified at high temperature under an inert atmosphere, then the atmosphere is switched to a hydrogen-argon mixed atmosphere and the temperature is lowered for reduction. This allows oxygen vacancies to be generated and retained on the framework surface, avoiding the vacancy annihilation window in the mid-temperature region. When the obtained rare-earth-transition-metal co-doped composite oxide porous ceramic material is placed at the bottom of a silicon melt, it continuously captures free oxygen atoms, blocking the diffusion and transport path of oxygen to the solid-liquid interface from the source.

[0020] (3) This invention achieves a refined upgrade of the entire chain in terms of crystal growth kinetic control and material microenvironment management. During the crystal growth stage, the purge gas flow rate is dynamically switched according to the process nodes: a low flow rate is used during the crystal contact period to maintain interface stability, and a high flow rate is switched during the constant diameter period to maintain the target supercooling range with power fine-tuning. After lifting off the liquid surface, segmented slow cooling is performed, and the furnace pressure is restored in a gradient manner to effectively release the radial residual thermal stress in the crystal and suppress the generation of slip dislocations. After the porous ceramic is reduced and activated in situ in a hydrogen-argon mixed atmosphere, it is connected to the glove box transition chamber through a vacuum-sealed transfer tank under positive pressure protection. After vacuuming and multiple gas cleaning, it enters the main chamber and is sealed in an aluminum-plastic composite vacuum bag, isolating air and water vapor throughout the process to ensure zero decay of oxygen vacancy activity. The above closed-loop process reduces the interstitial oxygen content of monocrystalline silicon while realizing the non-destructive recycling and reuse of functional materials in the furnace. Detailed Implementation

[0021] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0022] Example 1 This embodiment provides a highly efficient method for preparing low-oxygen-content monocrystalline silicon, including the following steps: Step S1: In an argon-filled glove box, 23g of rare earth-transition metal co-doped composite oxide porous ceramic material (RTM-1) is crushed and sieved to obtain porous ceramic sheets with a thickness of 2.5mm and a transverse dimension of 12mm. These sheets are then placed into a boron nitride mesh basket that has been ultrasonically cleaned with deionized water and vacuum dried at 150℃. The purity of the high-purity polycrystalline silicon ingot used is above 99.9999%. At the center of the bottom of a 22-inch high-purity quartz crucible, the following materials are laid vertically from bottom to top: 1.5g of pyrolytic boron nitride pad, a mesh basket containing 18.5g of RTM-1 sheets, 8g of densified zirconia ceramic block, 4g of polycrystalline silicon fragments, and 200g of high-purity polycrystalline silicon ingot. Finally, 25g of high-purity polycrystalline silicon ingot is laid on the outermost ring of the crucible to complete the filling.

[0023] Step S2: Place the filled quartz crucible into the single crystal furnace, close the furnace chamber, evacuate to 10 Pa, and then fill with 150 g of high-purity argon gas. Repeat the evacuation and filling process three times until the furnace pressure is stabilized at 2.0 kPa. Then, reduce the pressure from room temperature to 5 °C / min. -1 Heat to 1100℃ and hold for 30 minutes, then reduce the temperature by 3℃·min. -1 Heat to 1380℃ and hold for 30 minutes, then reduce the temperature by 1.0℃·min. -1 The temperature was raised to 1420℃ and held for melting for 45 minutes, maintaining a furnace pressure of 2.0 kPa throughout the process; the argon flow rate was increased to 65 L·min. -1The furnace was continuously purged for 3.5 hours, with a total argon gas volume of 2000g introduced, while the furnace pressure remained controlled at 2.0 kPa. Subsequently, the argon gas flow rate was temporarily reduced to 40 L·min. -1 The heater power was finely adjusted to stabilize the temperature at 1420℃ and held for 20 minutes to obtain silicon melt.

[0024] Step S3: at 0.5℃·min -1 The temperature is slowly reduced to 1410℃, and the seed crystal lifting mechanism is activated to move 8g of oriented crystals. <100> Silicon seed crystals at 2 mm·min -1 Reduce the flow rate to 5 mm from the melt surface and preheat for 5 minutes, then slowly contact the melt surface and weld for 15 minutes; adjust the argon gas flow rate to 40 L / min. -1 The seed crystal rotates at 15 rpm, and the crucible rotates in the opposite direction at 8 rpm, at a speed of 0.5 mm / min. -1 The seed crystal was pulled at a high rate to develop shoulders until the crystal diameter reached 200 mm; then the argon gas flow rate was adjusted to 100 L·min. -1 Switch to automatic diameter control mode, at 0.3 kW·h -1 The rate was finely adjusted to reduce the heater power, maintaining a solid-liquid interface subcooling of 1.5°C, at a rate of 0.8 mm·min. -1 The crystals were grown at a constant diameter rate for 31 hours to obtain the grown crystals.

[0025] Step S4: After constant diameter growth, the crystal is grown at a speed of 5 mm·min. -1 The rate of detachment from the liquid surface is increased, while the argon flow rate is gradually reduced to 25 L·min. -1 The furnace pressure was maintained at 2.0 kPa; the crystal was annealed in situ at 1300℃ for 5 hours; and then annealed at 100℃·h. -1 The temperature was slowly reduced to 800℃; when the crystal temperature dropped to 800℃, the pressure was increased at 3 kPa·min. -1 The furnace pressure was uniformly restored from 2.0 kPa to 90 kPa at a rate of 100℃·h. -1 The temperature was further reduced to 600℃; the heating power was turned off, and the crystal was allowed to cool naturally to room temperature under argon protection. The furnace was then opened and the low-oxygen content monocrystalline silicon was removed.

[0026] Preparation steps of rare earth-transition metal co-doped composite oxide porous ceramic materials: Step A1: Weigh 45g of cerium nitrate hexahydrate, 18g of lanthanum nitrate hexahydrate, 13g of zirconium nitrate pentahydrate, and 9g of yttrium nitrate hexahydrate, dissolve them in 500g of deionized water, and stir at 300rpm in a 60℃ water bath; transfer the solution to a rotary evaporator and evaporate to 65% of the original volume at 60℃ and -0.09MPa to obtain a concentrated solution; add 50g of anhydrous N,N-dimethylformamide to the concentrated solution, and azeotropically evaporate the residual water in an 81℃ oil bath. Repeat the above operation of adding anhydrous N,N-dimethylformamide and azeotropically evaporating the residual water three times, with a total amount of anhydrous N,N-dimethylformamide added of 180g, to obtain a premixed solution; dissolve 100g of terephthalic acid in 330g of anhydrous N,N-dimethylformamide, and sonicate at 40℃ and 40kHz for 30min to obtain a ligand solution; add 58g of... 4-Dimethylaminopyridine was dissolved in 180 g of anhydrous N,N-dimethylformamide and stirred at 25 °C and 200 rpm at a rate of 1.0 mL / min. -1 The solution was added dropwise to the ligand solution using a peristaltic pump at a rate that allowed for continuous stirring for 1 hour after the addition was complete, resulting in a mixture. The premixed solution was then mixed with the ligand solution and transferred to a stainless steel reactor with a polytetrafluoroethylene liner. The mixture was subjected to solvothermal treatment at 120°C for 27 hours. After cooling to room temperature, the solid was separated by centrifugation at 8000 rpm for 10 minutes. The solid was washed three times with 250 g of N,N-dimethylformamide, with stirring for 10 minutes each time followed by centrifugation. The solid was then washed five times with 350 g of anhydrous methanol. Subsequently, the solid was placed in a supercritical carbon dioxide extraction vessel and extracted at 40°C and 20 MPa for 4.5 hours. After extraction, the solid was vacuum dried at 60°C and -0.1 MPa for 12 hours to obtain a rare earth-transition metal multi-metal organic framework precursor.

[0027] Step A2: Place the precursor obtained in step A1 in a tube furnace and heat at 200 mL / min. -1 High-purity air is introduced at a flow rate of 1.0℃·min from room temperature. -1 Heat to 150℃ and hold for 2 hours, then feed at a rate of 1.0℃·min. -1 Heat to 200℃ and hold for 2 hours, then cook at a rate of 2.0℃·min. -1 Heat to 350℃ and hold for 1 hour, at a rate of 1.0℃·min -1 The temperature was raised to 800℃ and held for 5 hours; the furnace was cooled to room temperature under a flowing air atmosphere, and the composite powder was obtained; the composite powder was dispersed in 400g of deionized water, ultrasonically treated with 100W power for 30 minutes, and then centrifuged at 8000rpm for 10 minutes to obtain a precipitate; the precipitate was washed three times with 250g of anhydrous ethanol and vacuum dried at 80℃ and -0.1MPa for 12 hours to obtain a dried powder.

[0028] Step A3: The dried powder obtained in step A2 is loaded into a rubber mold and pressed under isostatic pressure of 200 MPa for 10 min to form a thin circular blank with a thickness of 2.5 mm; the blank is then placed in a tube furnace and heated at 80 mL / min. -1 Argon gas is introduced at a flow rate of 2.0℃·min. -1 The temperature was rapidly increased to 1100℃ and held for 18 hours, then cooled to 1100℃ in an argon atmosphere before use.

[0029] Step A4: In the same tube furnace, while maintaining a sealed furnace cavity, continuous argon gas flow, and a constant sample position, switch the gas route from argon to a flow rate of 80 mL / min. -1 The mixture was heated at 1100℃ for 2 hours in a 3% H2 / 97% Ar mixed atmosphere; subsequently, it was heated at 2.0℃·min under an H2 / Ar mixed atmosphere. -1 The temperature was lowered to 400℃ and held for 4 hours, then cooled at a rate of 2.0℃·min. -1 The furnace temperature was further reduced to below 80°C in an H2 / Ar mixed atmosphere to obtain a thin sheet. After the furnace temperature dropped to 80°C, the KF40 transfer valve connecting the tubular furnace and the glove box was opened, and the thin sheet was directly loaded into a vacuum-sealed transfer container pre-filled with argon to a positive pressure of 1.05 atm. The transfer container was then connected to the glove box transition chamber via a KF40 flange, and the transition chamber was evacuated to 10 Pa. Then, 80g of high-purity argon was introduced, and the evacuation-argon filling cycle was repeated three times. Finally, the transfer container was moved into the main chamber of the glove box (H2O < 0.1ppm, O2 < 0.1ppm), and the thin sheet was removed and sealed in an 8g aluminum-plastic composite vacuum bag to obtain a rare earth-transition metal co-doped composite oxide porous ceramic material, denoted as RTM-1.

[0030] Example 2 The difference between this embodiment and Embodiment 1 is that this embodiment provides a highly efficient method for preparing low-oxygen-content monocrystalline silicon, including the following steps: Step S1: Under argon protection, 15g of rare earth-transition metal co-doped composite oxide porous ceramic material (RTM-2) is crushed and sieved to obtain porous ceramic sheets with a thickness of 2mm and a transverse dimension of 8mm. These sheets are then placed into a boron nitride mesh basket to obtain a mesh basket containing the rare earth-transition metal co-doped composite oxide porous sheets. The boron nitride mesh basket is pre-cleaned with deionized water using ultrasonic cleaning and vacuum dried at 148℃. At the center of the bottom of the quartz crucible, 1g of boron nitride pad, the mesh basket containing 12.2g of rare earth-transition metal co-doped composite oxide porous sheets, 6g of zirconia ceramic block, 3g of polycrystalline silicon fragments, and 150g of high-purity polycrystalline silicon blocks with a purity of 99.9999% or higher are laid in a vertical order from bottom to top. 20g of high-purity polycrystalline silicon blocks with a purity of 99.9999% or higher are laid on the outermost ring of the quartz crucible to obtain a filled quartz crucible.

[0031] Step S2: Place the filled quartz crucible into the single crystal furnace; purge with 100g of argon gas; reduce temperature from room temperature to 4℃·min. -1 Heat to 1090℃ and hold at 2℃·min -1 Heat to 1370℃ and hold at that temperature for 0.8℃·min. -1 Heat to 1410℃ and hold for 30 minutes to melt; flow rate is 50 L / min. -1 Purge with 1500g of argon gas; temporarily adjust the argon gas flow rate to 30L·min. -1 The temperature was adjusted to 1418℃ and held to obtain a silicon melt.

[0032] Step S3: at 0.4℃·min -1 Adjust the rate and temperature to 1408℃, activate the seed crystal lifting mechanism, and move the 5g oriented crystal... <100> The silicon seed crystal descends to contact the silicon melt; the argon gas flow rate is adjusted to 30 L / min. -1 The seed crystal rotates at 14 rpm, and the crucible rotates in the opposite direction at 7 rpm; the flow rate of the introduced argon gas is adjusted to 80 L·min. -1 With 0.1 kW·h -1 The rate was finely adjusted to reduce the heater power, maintaining a subcooling of 1°C, and the crystal was grown at constant diameter for 30 hours to obtain the grown crystal.

[0033] Step S4: Lift the grown crystal off the liquid surface and gradually reduce the argon gas flow rate to 20 L·min. -1 Incubate at 1290℃ for 4 hours; at 80℃·h -1 The temperature was reduced to 795℃ at a rate of ≤5 kPa·min when the crystal temperature dropped below 800℃. -1 The furnace pressure was restored to 80 kPa at a rate of 80 °C / h. -1 The temperature was further reduced to 595°C; it was then allowed to cool naturally to room temperature, resulting in low-oxygen-content monocrystalline silicon.

[0034] Preparation steps of rare earth-transition metal co-doped composite oxide porous ceramic materials: Step A1: Weigh 40g of cerium nitrate hexahydrate, 15g of lanthanum nitrate hexahydrate, 10g of zirconium nitrate pentahydrate, and 6g of yttrium nitrate hexahydrate, dissolve them in 450g of deionized water, and stir at 58℃ to dissolve; rotary evaporate to 60% of the original volume to obtain a concentrated solution; add 48g of anhydrous N,N-dimethylformamide to the concentrated solution, and azeotropically distill off the residual water at 80℃. Repeat the above operation of adding anhydrous N,N-dimethylformamide and azeotropically distilling off the residual water three times, with a total amount of anhydrous N,N-dimethylformamide added being 150g, to obtain a premixed solution; dissolve 90g of terephthalic acid in 300g of anhydrous N,N-dimethylformamide, and sonicate at 38℃ to obtain a ligand solution; add 50g of... 4-Dimethylaminopyridine was dissolved in 150 g of anhydrous N,N-dimethylformamide and added dropwise to the ligand solution at a rate of 0.8 mL·min⁻¹ to react and obtain a mixture. The premixed solution was mixed with the mixture and transferred to a reaction vessel, where it was solvothermal treated at 118 °C for 24 h. After centrifugation, a solid was obtained. The solid was washed three times with 200 g of N,N-dimethylformamide and five times with 300 g of anhydrous methanol. Subsequently, it was extracted with 200 g of supercritical carbon dioxide for 4 h. After vacuum drying at 58 °C, a rare earth-transition metal multi-metal organic framework precursor was obtained.

[0035] Step A2: Place the precursor obtained in step A1 in a tube furnace and, under the protection of 100g of high-purity air, heat it from room temperature at a rate of 0.8℃·min. -1 Heat to 148℃ and hold; at a rate of 0.8℃·min -1 Heat to 198℃ and hold; at a rate of 1.8℃·min -1 Heat to 348℃ and hold; at a rate of 0.8℃·min -1 The temperature was raised to 798℃ and held for 4 hours; then cooled to room temperature to obtain composite powder; the composite powder was dispersed in 300g of deionized water, sonicated, and centrifuged to obtain precipitate; the precipitate was washed with 200g of anhydrous ethanol and vacuum dried at 78℃ to obtain dry powder.

[0036] Step A3: The dried powder obtained in step A2 is pressed into a thin, round sheet with a thickness of 2 mm under isostatic pressure of 200 MPa; the sheet is placed in a tube furnace, and an airflow of 50 mL / min is introduced. -1 In a 50g argon atmosphere at 1.8℃·min -1 The temperature was rapidly increased to 1098℃ and held for 16 hours.

[0037] Step A4: In the same tube furnace, while keeping the furnace cavity sealed and the sample position unchanged, switch the gas path to an inlet flow rate of 50 mL / min. -150g of a mixture of 3% H2 and 97% Ar was kept at 1098℃; then, under a mixed H2 / Ar atmosphere, the temperature was increased by 1.8℃·min. -1 Cool to 398℃ and hold for 3 hours; at a rate of 1.8℃·min -1 The temperature was further reduced to below 80°C in an H2 / Ar mixed atmosphere to obtain a thin sheet. After the thin sheet was cooled to 80°C in an H2 / Ar atmosphere, it was directly loaded into a 1g vacuum-sealed transfer container pre-filled with argon to a positive pressure of 1.04 atm through a transfer valve. The transfer container was connected to the glove box transition chamber through a KF40 flange. The transition chamber was evacuated to 8 Pa and then purged three times with 50g of argon. The thin sheet was then introduced into the main compartment of the glove box and sealed in a 5g aluminum-plastic composite vacuum bag to obtain a rare earth-transition metal co-doped composite oxide porous ceramic material, denoted as RTM-2.

[0038] Example 3 The difference between this embodiment and Embodiment 1 is that this embodiment provides a highly efficient method for preparing low-oxygen-content monocrystalline silicon, including the following steps: Step S1: Under argon protection, 30g of rare earth-transition metal co-doped composite oxide porous ceramic material (RTM-3) is crushed and sieved to obtain porous ceramic sheets with a thickness of 3mm and a transverse dimension of 15mm. These sheets are then placed into a boron nitride mesh basket to obtain a mesh basket containing 26.4g of rare earth-transition metal co-doped composite oxide porous sheets. The boron nitride mesh basket is pre-cleaned with deionized water using ultrasonic cleaning and vacuum dried at 152℃. At the bottom center of the quartz crucible, 2g of boron nitride pad, the mesh basket containing the rare earth-transition metal co-doped composite oxide porous sheets, 10g of zirconia ceramic block, 5g of polycrystalline silicon fragments, and 250g of high-purity polycrystalline silicon blocks with a purity of 99.9999% or higher are laid vertically from bottom to top. Finally, 30g of high-purity polycrystalline silicon blocks with a purity of 99.9999% or higher are laid on the outermost ring of the quartz crucible to obtain a filled quartz crucible.

[0039] Step S2: Place the filled quartz crucible into the single crystal furnace; purge with 200g of argon gas; reduce temperature from room temperature to 6℃·min. -1 Heat to 1110℃ and hold at 4℃·min -1 Heat to 1390℃ and hold at that temperature for 1.2℃·min. -1 Heat to 1430℃ and hold for 60 minutes to melt; flow rate is 80 L / min. -1 Purge with 2500g of argon gas; temporarily adjust the argon gas flow rate to 50L·min. -1 The temperature was adjusted to 1422℃ and held to obtain a silicon melt.

[0040] Step S3: at 0.6℃·min -1Adjust the rate and temperature to 1412℃, activate the seed crystal lifting mechanism, and move 10g of oriented... <100> The silicon seed crystal descends to contact the silicon melt; the argon gas flow rate is adjusted to 50 L / min. -1 The seed crystal rotates at 16 rpm, and the crucible rotates in the opposite direction at 9 rpm; the flow rate of the introduced argon gas is adjusted to 120 L·min. -1 With 0.5 kW·h -1 The rate was finely adjusted to reduce the heater power, maintaining a subcooling of 2°C, and the crystals were grown at constant diameter for 32 hours to obtain the grown crystals.

[0041] Step S4: Lift the grown crystal off the liquid surface and gradually reduce the argon gas flow rate to 30 L·min. -1 ; Keep warm at 1310℃ for 6 hours; at 120℃·h -1 The temperature was reduced to 805℃ at a rate of ≤5 kPa·min when the crystal temperature dropped below 800℃. -1 The furnace pressure was restored to 100 kPa at a rate of 120 °C / h. -1 The temperature was further reduced to 605°C; it was then allowed to cool naturally to room temperature, resulting in low-oxygen-content monocrystalline silicon.

[0042] Preparation steps of rare earth-transition metal co-doped composite oxide porous ceramic materials: Step A1: Weigh 50g of cerium nitrate hexahydrate, 20g of lanthanum nitrate hexahydrate, 15g of zirconium nitrate pentahydrate, and 13g of yttrium nitrate hexahydrate, dissolve them in 550g of deionized water, and stir at 62℃ to dissolve; rotary evaporate to 70% of the original volume to obtain a concentrated solution; add 52g of anhydrous N,N-dimethylformamide to the concentrated solution, and azeotropically distill off the residual water at 82℃. Repeat the above operation of adding anhydrous N,N-dimethylformamide and azeotropically distilling off the residual water a total of 4 times, with a total amount of anhydrous N,N-dimethylformamide added of 200g, to obtain a premixed solution; dissolve 110g of terephthalic acid in 350g of anhydrous N,N-dimethylformamide, and sonicate at 42℃ to obtain a ligand solution; dissolve 65g of 4-dimethylaminopyridine in 200g of anhydrous N,N-dimethylformamide, and distill at 1.2mL·min -1 The solution was added dropwise to the ligand solution at a certain rate to react and obtain a mixture. The premixed solution was mixed with the mixture and transferred to a reaction vessel for solvothermal treatment at 122°C for 30 h. The mixture was then centrifuged to obtain a solid. The solid was washed three times with 300 g N,N-dimethylformamide and five times with 400 g anhydrous methanol. It was then extracted with 300 g supercritical carbon dioxide for 5 h and dried under vacuum at 62°C to obtain a rare earth-transition metal multi-metal organic framework precursor.

[0043] Step A2: Place the precursor obtained in step A1 in a tube furnace and, under the protection of 200g of high-purity air, heat it from room temperature at a rate of 1.2℃·min.-1 Heat to 152℃ and hold; at a rate of 1.2℃·min -1 Heat to 202℃ and hold; at a rate of 2.2℃·min -1 Heat to 352℃ and hold; at a rate of 1.2℃·min -1 The temperature was raised to 802℃ and held for 6 hours; then cooled to room temperature to obtain composite powder; the composite powder was dispersed in 500g of deionized water, sonicated, and centrifuged to obtain precipitate; the precipitate was washed with 300g of anhydrous ethanol and vacuum dried at 82℃ to obtain dry powder.

[0044] Step A3: The dried powder obtained in step A2 is pressed into a thin circular sheet with a thickness of 3 mm under isostatic pressure of 200 MPa; the sheet is placed in a tube furnace, and an airflow of 100 mL / min is introduced. -1 100g of argon gas atmosphere at 2.2℃·min -1 The temperature was rapidly increased to 1102℃ and held for 20 hours.

[0045] Step A4: In the same tubular furnace, while keeping the furnace cavity sealed and the sample position unchanged, switch the gas path to an inlet flow rate of 100 mL / min. -1 100g of a mixture of 3% H2 / 97% Ar was kept at 1102℃; then, under a mixed H2 / Ar atmosphere, the temperature was increased at 2.2℃·min. -1 The temperature was lowered to 402℃ and held for 5 hours; then cooled at a rate of 2.2℃·min. -1 The temperature was further reduced to below 80°C in an H2 / Ar mixed atmosphere to obtain a thin film. After the thin film was cooled to 80°C in an H2 / Ar atmosphere, it was directly loaded into a 2g vacuum-sealed transfer container pre-filled with argon to a positive pressure of 1.06 atm through a transfer valve. The transfer container was connected to the glove box transition chamber through a KF40 flange. The transition chamber was evacuated to 12 Pa and then purged three times with 100g of argon. The thin film was then introduced into the main compartment of the glove box and sealed in a 10g aluminum-plastic composite vacuum bag to obtain a rare earth-transition metal co-doped composite oxide porous ceramic thin film, denoted as RTM-3.

[0046] Comparative Example 1 The difference between this comparative example and Example 1 is that, in step S1, the rare earth-transition metal co-doped composite oxide porous ceramic sheet and its matching boron nitride basket, boron nitride pad and zirconium oxide ceramic block are not laid. Instead, polycrystalline silicon fragments and high-purity polycrystalline silicon blocks are directly laid in sequence in the quartz crucible. The rest is the same as in Example 1.

[0047] Comparative Example 2 The difference between this comparative example and Example 1 is that in step A4, the blank after sintering in A3 is cooled to room temperature in the furnace and taken out, exposed to air for 24 hours, and then placed in another tube furnace for separate reduction treatment under a mixed atmosphere of hydrogen and argon. The rest is the same as in Example 1.

[0048] Comparative Example 3 The difference between this comparative example and Example 1 is that in step A4, after the wafer is cooled to below 80°C in a mixed H2 / Ar atmosphere, it is directly taken out from the tube furnace, placed in a regular self-sealing bag in a normal atmospheric environment and stored for 48 hours before proceeding with the preparation of single crystal silicon in steps S1 to S4. The vacuum-sealed transfer tank and glove box oxygen-free transfer packaging operation are not used. The rest is the same as in Example 1.

[0049] In accordance with national and industry standard testing specifications, a series of standardized tests were conducted on the low-oxygen-content monocrystalline silicon prepared in Examples 1-3 and Comparative Examples 1-3.

[0050] A 2 mm thick silicon wafer was cut from the prepared single-crystal silicon ingot at a point 20 mm from the tail, perpendicular to the crystal growth direction. After double-sided mechanical grinding and chemical mechanical polishing to a mirror finish, the interstitial oxygen content was measured using a Fourier transform infrared spectroscopy (FTIR) instrument at room temperature (20-25°C). Before measurement, the silicon wafer was placed on a clean polytetrafluoroethylene (PTFE) sample holder, and the spectrometer scanning parameters were set to a resolution of 4 cm⁻¹. -1 64 scans, wavenumber range 500-4000 cm⁻¹ -1 Wavenumber 1107 cm⁻¹ was selected. -1 The absorption peak of the silicon-oxygen-silicon antisymmetric stretching vibration is shown, and the reference background spectrum is taken from a high-purity zone-melted silicon wafer.

[0051] The interstitial oxygen concentration is calculated based on the product of the absorption coefficient and the calibration factor, which is taken as 3.14 × 10⁻⁶. 17 atoms·cm -3 For each sample, the center point and four symmetrical points 5 mm from the edge are measured, and the average value of the five points is taken as the final interstitial oxygen content.

[0052] Dislocation density detection employs a selective etching method: the same silicon wafer is immersed in Schimmel etching solution (chromium trioxide: hydrofluoric acid: water mass ratio of 1:2:1.5), etched at 25 ℃ for 300 s, rinsed with deionized water and dried, and the number of etching pits is observed and counted using an optical microscope at 200x magnification using a grid method. Five fields of view are selected for each wafer, and the average dislocation density is calculated.

[0053] The performance test data above are shown in Table 1.

[0054] Table 1 Performance Test Results ; As can be seen from the above, the interstitial oxygen content in Examples 1-3 is 2.3 × 10⁻⁶. 17 atoms·cm -3 2.8×10 17 atoms·cm -3 and 2.5×10 17 atoms·cm -3 The dislocation densities are all below 1×10 3 cm -2 In contrast, Comparative Example 1, which completely lacked the rare-earth-transition-metal co-doped composite oxide porous ceramic sheet and its associated bottom oxygen control component, exhibited an interstitial oxygen content as high as 1.2 × 10⁻⁶. 18 atoms·cm -3 This is about an order of magnitude higher than the previous example, and the dislocation density also increases significantly to 3.2 × 10⁻⁶. 3 cm -2 This indicates that without solid-phase oxygen trapping materials, oxygen in the silicon melt cannot be effectively captured and anchored. Oxygen atoms continue to diffuse towards the solid-liquid interface and eventually enter the interstitial positions of the lattice. At the same time, the oxygen precipitation caused by the high oxygen concentration induces a large number of secondary dislocations, which seriously degrades the crystal quality.

[0055] Comparative Example 2 involved exposing the sintered green body to air and then transferring it to another furnace tube for reduction treatment. The resulting monocrystalline silicon interstitial oxygen content was 8.9 × 10⁻⁶. 17 atoms·cm -3 The dislocation density increased by approximately 287% compared to Example 1, reaching 1.5 × 10⁻⁶. 3 cm -2 This indicates that the non-in-situ reduction operation caused the water vapor and oxygen adsorbed by the billet in the air to occupy the active sites, and subsequent individual reduction could not completely restore the oxygen vacancy concentration. The partial annihilation of oxygen vacancy directly weakened the material's ability to capture interstitial oxygen, confirming that in-situ continuous reduction and the same furnace non-transfer process are the key to maintaining the activity of oxygen vacancy.

[0056] Comparative Example 3 omits the vacuum-sealed transfer vessel and glove box oxygen-free sealing process, and directly exposes the reduced and activated sheet to the atmosphere for storage and reuse, with an interstitial oxygen content of 7.6 × 10⁻⁶. 17 atoms·cm -3 The dislocation density increased by approximately 230% compared to Example 1, reaching 1.1 × 10⁻⁶. 3 cm -2 This indicates that the oxygen vacancies on the surface of the reduced and activated porous ceramic are rapidly re-oxidized by water vapor and oxygen in a normal atmospheric environment and become inactive. Even if the melt is added immediately afterward, it cannot restore its original oxygen capture function, which verifies the necessity of oxygen-free transfer and encapsulation throughout the entire process from the end of reduction to the loading of materials.

[0057] The above data collectively demonstrate that Examples 1-3, through the synergistic implementation of rare-earth-transition-metal co-doped composite oxide porous ceramics, in-situ reduction and activation in the same furnace, and oxygen-free transfer within a completely vacuum-sealed process, effectively solved three progressive technical problems: the inability to capture oxygen in the melt due to the lack of solid-phase oxygen control materials, the irreversible annihilation of oxygen vacancies caused by non-in-situ reduction, and the re-oxidation of vacancies caused by exposure of the activation material to the atmosphere. Ultimately, this resulted in a stable interstitial oxygen content in single-crystal silicon below a certain level. And the dislocation density is controlled at Significant technical effects within.

Claims

1. A highly efficient method for preparing low-oxygen-content monocrystalline silicon, characterized in that, Includes the following steps: S1. Under argon protection, crush and sieve 15-30 parts by weight of rare earth-transition metal co-doped composite oxide porous ceramic material, and load it into a wire basket to obtain a wire basket containing rare earth-transition metal co-doped composite oxide porous sheets; at the center of the bottom of the crucible, lay 1-2 parts of a gasket, the wire basket containing rare earth-transition metal co-doped composite oxide porous sheets, 6-10 parts of zirconia ceramic blocks, 3-5 parts of polycrystalline silicon fragments, and 150-250 parts of high-purity polycrystalline silicon blocks in a vertical order from bottom to top; lay 20-30 parts of high-purity polycrystalline silicon blocks on the outermost ring of the crucible to obtain a filled crucible; S2. Place the filled crucible into a single crystal furnace; introduce argon gas; heat to 1090-1110℃ and hold; heat to 1370-1390℃ and hold; heat to 1410-1430℃ and hold to melt; purge with 1500-2500 parts of argon gas; adjust the temperature to 1418-1422℃ and hold to obtain silicon melt; S3. Adjust the temperature to 1408-1412℃ and orient 5-10 parts as follows: <100> The silicon seed crystal descends to contact the silicon melt; the seed crystal rotates, and the crucible rotates in the opposite direction; constant diameter growth is performed to obtain the grown crystal; S4. Lift the grown crystals off the liquid surface and keep them at 1290-1310℃; cool them down to 795-805℃; continue cooling them down to 595-605℃; let them cool naturally to room temperature.

2. The efficient preparation method of low-oxygen-content monocrystalline silicon according to claim 1, characterized in that, In step S1, the basket is pre-cleaned with deionized water by ultrasonic cleaning and vacuum dried at 148-152℃; the purity of the high-purity polycrystalline silicon block is above 99.9999%.

3. The efficient preparation method of low-oxygen-content monocrystalline silicon according to claim 1, characterized in that, In step S2, the time for heating to 1410-1430℃ and holding at that temperature to melt is 30-60 minutes.

4. The efficient preparation method of low-oxygen-content monocrystalline silicon according to claim 1, characterized in that, In step S3, the growth time for constant diameter is 30-32 hours.

5. The efficient preparation method of low-oxygen-content monocrystalline silicon according to claim 1, characterized in that, In step S4, the heat preservation time at 1290-1310℃ is 4-6 hours.

6. The efficient preparation method of low-oxygen-content monocrystalline silicon according to any one of claims 1-5, characterized in that, The preparation steps of the rare earth-transition metal co-doped composite oxide porous ceramic material include: A1. By weight, dissolve 40-50 parts of cerium nitrate hexahydrate, 15-20 parts of lanthanum nitrate hexahydrate, 10-15 parts of zirconium nitrate pentahydrate, and 6-13 parts of yttrium nitrate hexahydrate in 450-550 parts of deionized water, and stir at 58-62℃; evaporate by rotary evaporation to obtain a concentrated solution; add 48-52 parts of anhydrous N,N-dimethylformamide to the concentrated solution, azeotropically at 80-82℃, and add 150-200 parts of anhydrous N,N-dimethylformamide to obtain a premixed solution; dissolve 90-110 parts of terephthalic acid in 300-350 parts of anhydrous N,N-dimethylformamide. In N,N-dimethylformamide, a ligand solution was obtained by ultrasonic treatment at 38-42℃. 50-65 parts of 4-dimethylaminopyridine were dissolved in 150-200 parts of anhydrous N,N-dimethylformamide and added dropwise to the ligand solution to react, yielding a mixture. The premixed solution was mixed with the mixture and transferred to a reaction vessel for solvothermal treatment at 118-122℃. The mixture was centrifuged to obtain a solid. The solid was washed with N,N-dimethylformamide and anhydrous methanol, followed by supercritical carbon dioxide extraction. The solid was then vacuum dried at 58-62℃ to obtain a rare-earth-transition-metal multi-metal-organic framework precursor. A2. The rare earth-transition metal multi-metal organic framework precursor is placed in a tube furnace and heated from room temperature to 148-152℃ and held; then heated to 198-202℃ and held; then heated to 348-352℃ and held; then heated to 798-802℃ and held; cooled to room temperature to obtain a composite powder; the composite powder is dispersed in 300-500 parts of deionized water, ultrasonically treated, and centrifuged to obtain a precipitate; the precipitate is washed with anhydrous ethanol and vacuum dried at 78-82℃ to obtain a dry powder; A3. Press the dried powder to obtain a green body; place the green body in a tube furnace, introduce an argon atmosphere, and heat to 1098-1102℃ and hold. A4. Switch to a mixed atmosphere of hydrogen and argon, and maintain the temperature at 1098-1102℃; cool down to 398-402℃ and maintain the temperature thereafter; continue cooling to obtain a thin sheet; load the thin sheet into a transfer container pre-filled with argon; connect the transfer container to the glove box transition chamber, evacuate the transition chamber and clean it with argon; transfer the thin sheet into the main compartment of the glove box and seal it in an aluminum-plastic composite vacuum bag.

7. The efficient preparation method of low-oxygen-content monocrystalline silicon according to claim 6, characterized in that, In step A1, the solvothermal treatment at 118-122℃ takes 24-30 hours.

8. The efficient preparation method of low-oxygen-content monocrystalline silicon according to claim 6, characterized in that, In step A2, the temperature is raised to 798-802℃ and held for 4-6 hours.

9. The efficient preparation method of low-oxygen-content monocrystalline silicon according to claim 6, characterized in that, In step A3, the temperature is raised to 1098-1102℃ and held for 16-20 hours.

10. The efficient preparation method of low-oxygen-content monocrystalline silicon according to claim 6, characterized in that, In step A4, the temperature is lowered to 398-402℃ and held for 3-5 hours.