Device and method for preparing high-purity silicon film based on vacuum degree control electrolytic silicon purification

Abstract

The application belongs to the technical field of metallurgy, and particularly relates to a device and method for preparing high-purity silicon film based on vacuum degree control electrolytic silicon purification. The device creates a closed environment through a vacuum cabin, and utilizes a connected vacuumizing mechanism and a vacuum degree adjusting device to accurately control the vacuum degree in the cabin. A material storage mechanism is used for storing silicon materials, and is composed of a corundum crucible and a graphite crucible sleeved outside the corundum crucible. A heating mechanism heats the materials through electromagnetic induction. The method first heats impurity-containing electrolytic silicon in a vacuum environment in a deimpurification mode, so that impurities with higher saturated vapor pressure are preferentially volatilized and deposited on the inner wall of the cabin, thereby realizing preliminary purification. Then, in an evaporation mode, the purified silicon material is heated to a volatilization temperature again, so that it is vapor-deposited on the upper base material to directly form a high-purity silicon film. The scheme integrates the purification and film forming processes, and simplifies the process.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, and particularly relates to an apparatus and method for preparing high-purity silicon films by electrolytic silicon purification based on vacuum degree control. Background Technology

[0002] Currently, the preparation of semiconductor-grade and solar-grade high-purity silicon mainly relies on the Siemens process. This process uses metallurgical-grade silicon with a purity of approximately 98–99 wt.% as raw material, generates trichlorosilane through a gas-phase reaction, and after multiple distillations for purification, high-purity silicon is obtained by reduction deposition on silicon seed rods at high temperatures. Although the Siemens process is a mature technology capable of achieving ultra-high purity for electronic applications and suitable for large-scale production, its process flow is extremely cumbersome, energy consumption is extremely high (approximately 50–100 kWh / kg-Si), and costs are expensive. It also generates corrosive waste gases, putting pressure on the environment. Furthermore, considering the processing of silicon-based solar cells and silicon wafers, whether using early internal circular cutting machines or the current mainstream diamond wire cutting machines, the cutting blades or wire saws themselves have physical thickness. During cutting, this material is directly lost, resulting in significant waste. To reduce energy consumption and costs, molten salt electrolytic silicon technology has become a research hotspot. While this method holds promise for its green and low-carbon nature, its electrolysis products generally suffer from surface residues or inclusions of molten salt, and their purity is highly dependent on the purity of the raw material, silica. Regarding Si... 4+ Metal impurities with similar reduction potentials (such as Al) 3+ It is difficult to effectively separate these materials through electrolysis, resulting in an electrolytic silicon purity of only 95–98 wt.%, which cannot meet the stringent purity requirements of high-end applications such as solar cells and semiconductors.

[0003] Therefore, existing technologies face a dilemma: the Siemens process offers high purity and quality but is energy-intensive and costly, and subsequent processing and molding result in significant material waste; the molten salt electrolysis method is less expensive but produces products with insufficient purity and cannot accurately control the product morphology. A novel technological approach that can balance high purity, low energy consumption, and low cost is lacking.

[0004] In summary, existing technologies cannot achieve low-energy consumption, low-cost, and green large-scale production while ensuring high purity. Therefore, there is an urgent need for an apparatus and method for preparing high-purity silicon films or silicon plates based on vacuum-controlled electrolytic silicon purification to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide an apparatus and method for preparing high-purity silicon films by electrolytic silicon purification based on vacuum degree control, so as to solve the above-mentioned problems.

[0006] To achieve the above objectives, the present invention provides the following solution: An apparatus for preparing high-purity silicon films by vacuum-controlled electrolytic silicon purification includes: A material storage mechanism is placed inside a vacuum chamber, and the vacuum chamber is connected to a vacuum pumping mechanism and a vacuum degree regulating device. It also includes a heating mechanism for heating the materials stored in the material storage mechanism; When in the impurity removal mode, the material containing impurities is placed in the material storage mechanism, the vacuum degree of the vacuum chamber is adjusted to a preset value, and the material containing impurities is heated by the heating mechanism, so that the impurities are transformed into a gas phase and deposited on the inner wall of the vacuum chamber; When in vapor deposition mode, the vapor deposition material holder is fixed above the material storage mechanism, and the vapor deposition material is installed on the vapor deposition material holder. The purified material is placed in the material storage mechanism, the vacuum degree of the vacuum chamber is adjusted to a preset value, and the purified material is heated by the heating mechanism to cause the material to undergo phase change and be deposited on the vapor deposition material.

[0007] Optionally, the vacuum cavity includes a vacuum chamber, which is connected to the vacuum pumping mechanism and the vacuum degree adjustment device.

[0008] Optionally, the vacuuming mechanism includes a vacuum valve and a vacuum pump system, and the vacuum chamber is connected to the vacuum pump system through the vacuum valve.

[0009] Optionally, the vacuum regulating device includes an argon cylinder and a venting valve; Both the argon cylinder and the venting valve are connected to the vacuum chamber.

[0010] Optionally, the material storage mechanism includes a graphite crucible and a corundum crucible. The corundum crucible is used to store materials, and the graphite crucible is coaxially sleeved on the outside of the corundum crucible. The graphite crucible is fixed inside the vacuum chamber.

[0011] Optionally, the heating mechanism includes an electromagnetic induction heating device, which includes an electromagnetic induction heating coil and a hot coil circulating water cooling device. The pipes of the electromagnetic induction heating coil and the hot coil circulating water cooling device are coaxially sleeved on the outside of the graphite crucible, and a working fluid flows in the pipes of the hot coil circulating water cooling device. The electromagnetic induction heating coil and the circulating water cooling device of the heating coil work together to control the temperature of the material inside the corundum crucible.

[0012] Optionally, an infrared temperature measuring device may also be included, which is used to measure the temperature of the material inside the corundum crucible.

[0013] Optionally, a vacuum monitoring system may also be included, which is connected to the vacuum chamber.

[0014] Optionally, the vacuum monitoring system includes a vacuum gauge and a vacuum resistance gauge.

[0015] The method for preparing high-purity silicon films based on vacuum-controlled electrolytic silicon purification, using the aforementioned apparatus for preparing high-purity silicon films based on vacuum-controlled electrolytic silicon purification, includes the following steps: When in impurity removal mode, the material containing impurities is placed in the material storage mechanism and then placed in the vacuum chamber. The vacuum degree of the vacuum chamber is adjusted using the vacuum pumping mechanism and the vacuum degree adjustment device. The heating mechanism is used to heat the material containing impurities to a preset temperature, causing the impurities to undergo a gas phase transformation and deposit on the inner wall of the vacuum chamber; After the vacuum chamber has cooled down, remove the material storage mechanism and clean the inner wall of the vacuum chamber. When in vapor deposition mode, the vapor deposition material is installed on the vapor deposition material fixing frame and fixed above the material storage mechanism that stores the purified material. The vapor deposition material, the vapor deposition material fixing frame and the material storage mechanism are placed in the vacuum chamber at the same time. The vacuum degree of the vacuum chamber is adjusted using the vacuum pumping mechanism and the vacuum degree adjustment device. The heating mechanism is used to heat the purified material to a preset temperature, causing the material to undergo a phase change and be vapor-deposited on the vapor deposition material. After the vacuum chamber has cooled down, the vapor-deposited material containing the product is removed.

[0016] Compared with the prior art, the present invention has the following advantages and technical effects: This invention achieves selective removal of residual molten salt and co-deposited metal impurities in molten salt electrolytic silicon by synergistically controlling vacuum and temperature, utilizing the difference in volatilization characteristics between impurities and silicon. This significantly improves the purity of the silicon material. This process integrates the traditional multi-step purification and material forming process into a single, continuous unit, reducing intermediate steps and material waste, and lowering production costs. Furthermore, this method provides a feasible technical route for directly preparing high-purity silicon films suitable for high-end applications using low-grade electrolytic silicon raw materials, offering considerable application flexibility. The entire process is conducted in a closed system, which is environmentally friendly and aligns with the direction of green production. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1This is a schematic diagram of the device structure of the present invention.

[0018] Figure 2 This is a schematic diagram of the method flow of the present invention.

[0019] Figure 3 This is the ICP element content detection data for the electrolytic silicon raw material of this invention.

[0020] Figure 4 The data provided are ICP-detected elemental content of the purified silicon material under the conditions of Example 1 of this invention, and SEM and EDS elemental distribution data of the prepared silicon film.

[0021] Figure 5 The data provided are ICP-detected elemental content of the purified silicon material under the conditions of Example 2 of this invention, and SEM and EDS elemental distribution data of the prepared silicon film.

[0022] Figure 6 The data provided are ICP-detected elemental content of the purified silicon material under the conditions of Example 3 of this invention, and SEM and EDS elemental distribution data of the prepared silicon film.

[0023] The components include: 1. Vacuum chamber; 1-1. Vacuum pump system; 1-2. Vacuum valve; 1-3. Vacuum monitoring system; 2. Electromagnetic induction heating device; 2-1. Electromagnetic induction heating coil; 2-2. Heating coil circulating water cooling device; 2-3. Infrared temperature measuring device; 3. Vacuum degree regulating device; 3-1. Argon cylinder; 3-2. Air rupture valve; 4. Evaporation material fixing frame; 5. Graphite crucible; 6. Corundum crucible. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Reference Figures 1 to 6 This invention discloses an apparatus for preparing high-purity silicon films through vacuum-controlled electrolytic silicon purification, comprising: The material storage mechanism is placed inside a vacuum chamber, which is connected to a vacuum pumping mechanism and a vacuum degree adjustment device 3. It also includes a heating mechanism, which is used to heat the materials stored in the material storage mechanism; When in the impurity removal mode, the material containing impurities is placed in the material storage mechanism, the vacuum degree of the vacuum chamber is adjusted to the preset value, and the material containing impurities is heated by the heating mechanism, so that the impurities are transformed into a gas phase and deposited on the inner wall of the vacuum chamber. When in vapor deposition mode, the vapor deposition material holder 4 is fixed above the material storage mechanism, and the vapor deposition material is installed on the vapor deposition material holder 4. The purified material is placed in the material storage mechanism, the vacuum degree of the vacuum chamber is adjusted to the preset value, and the purified material is heated by the heating mechanism to cause the material to undergo phase change and be deposited on the vapor deposition material.

[0027] In the impurity removal mode, after the chamber is closed, the vacuum pumping mechanism connected to the chamber is activated to create a vacuum, and inert gas is introduced into the chamber using the vacuum adjustment device 3 to precisely control the vacuum level to the preset range. Subsequently, the heating mechanism is activated to heat the material, causing it to melt. At the set vacuum level and temperature, the difference in volatilization temperatures of different substances is utilized to cause low-boiling-point impurities in electrolytic silicon to undergo preferential phase transformation and deposit on the inner wall of the lower-temperature vacuum chamber, thereby achieving efficient impurity removal.

[0028] After impurity removal and chamber cleaning, the device switches to vapor deposition mode. At this time, the vapor deposition material holder 4 is fixedly installed above the material storage mechanism, and the vapor deposition substrate material is securely mounted on the holder. The previously purified high-purity silicon material is placed back into the material storage mechanism, and the vacuuming and precise control process of the vacuum degree adjustment device 3 is repeated. The heating mechanism is restarted, but the temperature is raised to a higher silicon volatilization temperature, causing the high-purity silicon material to undergo phase change evaporation. The silicon vapor is transported in a linear motion in the high vacuum and eventually deposited on the surface of the cooler vapor deposition substrate material above, cooling and growing to form a high-purity, uniform silicon film. This device, through flexible switching between two modes, achieves integrated, efficient, and low-carbon preparation from low-grade raw materials to high-end silicon film products, significantly simplifying the process and reducing energy consumption.

[0029] As an optional implementation, the vacuum chamber includes a vacuum chamber 1, which is connected to a vacuum pumping mechanism and a vacuum degree regulating device 3.

[0030] The device uses vacuum chamber 1 as its core cavity. Through its connection with vacuum pump system 1-1, vacuum valve 1-2, and vacuum degree adjustment device 3, it can precisely control the vacuum degree inside the chamber, creating a critical and controllable vacuum environment for subsequent heating, impurity removal, and vapor deposition processes.

[0031] As an optional implementation, the vacuuming mechanism includes a vacuum valve 1-2 and a vacuum pump system 1-1, with the vacuum chamber 1 connected to the vacuum pump system 1-1 via the vacuum valve 1-2.

[0032] When evacuating, open vacuum valve 1-2 and start vacuum pump system 1-1. The two work together to efficiently establish and maintain the vacuum environment required for the process in vacuum chamber 1.

[0033] As an optional implementation, the vacuum regulation device 3 includes an argon cylinder 3-1 and a venting valve 3-2; Argon cylinder 3-1 and venting valve 3-2 are both connected to vacuum chamber 1.

[0034] In the process, argon cylinder 3-1 injects argon gas into vacuum chamber 1 to fine-tune and maintain a precise process vacuum, while venting valve 3-2 introduces air after the operation to safely and quickly break the vacuum, facilitating the removal of the product.

[0035] As an optional implementation, the material storage mechanism includes a graphite crucible 5 and an alumina crucible 6. The alumina crucible 6 is used to store materials, and the graphite crucible 5 is coaxially sleeved on the outside of the alumina crucible 6. The graphite crucible 5 is fixed inside the vacuum chamber 1.

[0036] During device operation, the electrolytic silicon material to be processed is stored in an alumina crucible 6, which is enclosed by a graphite crucible 5 coaxially fitted on its outside, and the entire structure is fixed in the heating zone within the vacuum chamber 1. This structure allows the graphite crucible 5 to efficiently absorb electromagnetic energy and generate high temperatures during induction heating, and to uniformly transfer the heat to the internal alumina crucible 6, thereby melting or evaporating the silicon material. At the same time, the alumina material effectively prevents contamination of the material at high temperatures.

[0037] As an optional implementation, the heating mechanism includes an electromagnetic induction heating device 2, which includes an electromagnetic induction heating coil 2-1 and a hot coil circulating water cooling device 2-2. The pipes of the electromagnetic induction heating coil 2-1 and the hot coil circulating water cooling device 2-2 are coaxially sleeved on the outside of the graphite crucible 5, and a working fluid flows in the pipes of the hot coil circulating water cooling device 2-2. The electromagnetic induction heating coil 2-1 and the hot coil circulating water cooling device 2-2 work together to control the temperature of the material inside the corundum crucible 6.

[0038] During the heating process, the electromagnetic induction heating coil 2-1 of the electromagnetic induction heating device 2 is wrapped around the outside of the graphite crucible 5 and an alternating current is passed through it, causing it to generate eddy currents and rapidly heat up. At the same time, the heating coil circulating water cooling device 2-2 continuously introduces cooling medium into the coil pipeline, effectively removing the coil's own heat and preventing it from overheating and being damaged. The two work together to achieve rapid, uniform, and precise temperature control of the material in the corundum crucible 6 inside the graphite crucible 5, providing a stable and reliable thermal environment for silicon melting, impurity removal, and subsequent evaporation.

[0039] As an optional implementation, an infrared temperature measuring device 2-3 is also included, which is used to measure the temperature of the material inside the corundum crucible 6.

[0040] Throughout the heating process, the infrared temperature measuring device 2-3 performs non-contact real-time temperature measurement of the molten pool inside the corundum crucible 6 through the quartz window on the vacuum chamber 1, providing key feedback for precise control of the input current of the electromagnetic induction heating device 2, thereby ensuring that the temperature remains stable within the range required by the process.

[0041] As an optional implementation, a vacuum monitoring system 1-3 is also included, which is connected to the vacuum chamber 1.

[0042] As an optional implementation, the vacuum monitoring system 1-3 includes a vacuum gauge and a vacuum resistance gauge.

[0043] During the operation of the device, the vacuum monitoring system 1-3, installed on top of the vacuum chamber 1, includes a vacuum gauge and a vacuum resistance gauge. This system provides operators with key process parameters, enabling them to precisely control the operating status of the vacuum pump system 1-1 and the vacuum degree regulating device 3 based on the readings, thereby ensuring that the entire purification and evaporation process is reliably carried out in a preset, stable vacuum environment.

[0044] The method for preparing high-purity silicon films based on vacuum-controlled electrolytic silicon purification, using the aforementioned apparatus for preparing high-purity silicon films based on vacuum-controlled electrolytic silicon purification, includes the following steps: When in the impurity removal mode, the material containing impurities is placed in the material storage mechanism and then placed in the vacuum chamber. The vacuum degree of the vacuum chamber is adjusted by the vacuum pumping mechanism and the vacuum degree adjustment device 3. The heating mechanism is used to heat the material containing impurities to a preset temperature, causing the impurities to undergo a gas phase transformation and deposit on the inner wall of the vacuum chamber; After the vacuum chamber has cooled down, remove the material storage mechanism and clean the inner wall of the vacuum chamber. When in vapor deposition mode, the vapor deposition material is installed on the vapor deposition material fixing frame 4 and fixed above the material storage mechanism containing the purified material. The vapor deposition material, the vapor deposition material fixing frame 4 and the material storage mechanism are placed in the vacuum chamber at the same time. The vacuum degree of the vacuum chamber is adjusted by the vacuum pumping mechanism and the vacuum degree adjustment device 3. The purified material is heated to a preset temperature using a heating mechanism, causing the material to undergo a phase change and be vapor-deposited onto the vapor deposition material. After the vacuum chamber has cooled down, the vapor-deposited material containing the product is removed.

[0045] The implementation of this method is closely dependent on the apparatus and consists of two core modes: impurity removal and vapor deposition. In the impurity removal mode, the operation begins by placing the electrolytic silicon material containing residual molten salt and metallic impurities into a material storage mechanism consisting of a corundum crucible 6 and a graphite crucible 5, and then placing it inside a vacuum chamber, i.e., vacuum chamber 1. Subsequently, a vacuum pumping mechanism is used to evacuate the chamber, and the vacuum degree is precisely controlled to a preset range using a vacuum degree adjustment device 3. This process is monitored in real time by a vacuum monitoring system 1-3. Next, the heating mechanism is activated, and the material is heated to a preset temperature by observing the readings of infrared thermometers 2-3. Under this high-temperature vacuum environment, utilizing the difference in volatilization temperatures of different substances, impurities preferentially undergo phase transformation and volatilize, depositing on the cooler inner wall of vacuum chamber 1, thus being effectively removed. After the chamber cools down, the material storage mechanism is removed, and the volatiles on the inner wall are cleaned.

[0046] The process is then switched to vapor deposition mode. The vapor deposition substrate material is mounted on the vapor deposition material holder 4 and fixed directly above the material storage mechanism containing the purified silicon material, with the entire assembly placed inside the vacuum chamber 1. The vacuuming and vacuum adjustment steps are repeated to create the required vacuum environment. The heating mechanism is restarted, this time heating the purified silicon material to a higher preset temperature to cause phase transition evaporation. The silicon vapor moves linearly in the high vacuum and eventually deposits on the low-temperature vapor deposition substrate above, forming a high-purity silicon film. After the chamber cools down, the vapor deposition material with the silicon film product can be removed. This method, through precise two-stage control, continuously and efficiently purifies electrolytic silicon and directly prepares high-purity silicon films within the same device. The process is simple, energy-efficient, and produces high-purity products.

[0047] Specifically, this invention promotes the volatilization and removal of molten salt and metallic impurities by controlling the vacuum level and melting temperature. Subsequently, vacuum phase deposition technology is used to achieve efficient purification of electrolytic silicon and direct preparation of ultra-high purity silicon films. This approach not only overcomes the limitations of insufficient purity in traditional electrolytic silicon but also simplifies the process, improves material utilization, and enhances environmental performance.

[0048] The detailed steps are as follows: S1: Place the silicon prepared by molten salt electrolysis into the corundum crucible 6, and cover the outside of the corundum crucible 6 containing silicon material with a graphite crucible 5; then place the two crucibles in the center of the electromagnetic induction heating coil 2-1 and close the cover of the vacuum chamber 1. S2: Open vacuum valve 1-2 and vacuum pump system 1-1 to evacuate the inside of vacuum chamber 1. When the evacuation is complete, close vacuum valve 1-2 and then close vacuum pump system 1-1. Adjust the vacuum level of the chamber by inputting argon gas into the chamber through argon cylinder 3-1. S3: Start the circulating water cooling device 2-2 of the electromagnetic induction heating coil, then start the electromagnetic induction heating device 2. Adjust the electromagnetic induction input current value by observing the reading of the infrared thermometer 2-3 to control the temperature of the molten pool and achieve the purpose of impurity removal. This process mainly relies on the mechanism of molten salt, alloy impurities or solid solution impurities in silicon diffuse from the crystal lattice to the surface of the melt during vacuum heating. This is mainly due to the thermal activation migration of atoms / ions under high temperature melting conditions and the concentration gradient-driven diffusion induced by the vacuum environment. Specifically, when silicon is heated to above its melting point (>1414 ℃), its crystal structure is destroyed and it transforms into a molten state. This provides impurity atoms with higher degrees of freedom, allowing them to detach from solid solution sites such as interstitial spaces or substitution sites and diffuse into the interior of the melt. At the same time, the high temperature environment significantly enhances the kinetic energy of impurity atoms, promoting their random thermal motion and diffusion behavior, and impurities migrate from high concentration areas to low concentration areas.

[0049] Furthermore, under vacuum conditions, the difference in impurity vapor pressure at the melt surface plays a crucial role: impurities such as Ca, Al, or P have higher saturated vapor pressures than silicon, causing them to preferentially evaporate from the surface, forming a low-concentration region. This creates a concentration gradient from the melt interior to the surface, driving internal impurities to continuously diffuse towards the surface to compensate for evaporation losses, ultimately achieving selective removal. At room temperature, this diffusion is difficult to occur because the rigidity of the solid silicon lattice restricts impurity migration, and there is a lack of sufficient thermal energy and evaporation driving force.

[0050] Furthermore, the volatilization temperatures of each substance under different vacuum levels were calculated using the Clausius-Clapeyron equation, as follows: lgp=A−B / T Where A and B are substance-specific constants, p is the vapor pressure (Torr), and T is the temperature (K). The volatilization temperatures of various substances at different vacuum levels, calculated using the Clausius-Clapeyron equation, are shown in the table below: Table 1. Volatilization temperatures of various substances under different vacuum levels. The data in this table can be used to set different vacuum levels. It should be noted that the volatilization temperature of Si cannot be lower than the melting temperature of 1414 ℃, otherwise the silicon will directly sublimate in a molten state.

[0051] S4: After maintaining for a certain period of time, turn off the electromagnetic induction heating device 2. After the vacuum chamber 1 cools down, take out the corundum crucible 6 and the graphite crucible 5 and clean the vacuum chamber. After cleaning, place the corundum crucible 6 and the graphite crucible 5 in the center of the electromagnetic induction heating coil 2-1. Place the vapor deposition material fixing frame 4 on the upper part of the corundum crucible 6 and the graphite crucible 5 and fix the vapor deposition material to the vapor deposition material fixing frame 4. S5: Open vacuum valve 1-2 and vacuum pump system 1-1 to evacuate the inside of vacuum chamber 1. When the evacuation is complete, close vacuum valve 1-2 and then close vacuum pump system 1-1. Adjust the vacuum level of the chamber by inputting argon gas into the chamber through argon cylinder 3-1. S6: Start the electromagnetic induction heating coil circulating water cooling device 2-2, then start the electromagnetic induction heating device 2. Adjust the electromagnetic induction input current value by observing the reading of the infrared temperature measuring device 2-3 to control the molten pool temperature, reach the silicon volatilization temperature, and cool and grow on the vaporized material. This process primarily relies on physical vapor deposition (PVD) technology. The principle involves heating an evaporation source in a high-vacuum environment to sublimate or evaporate the coating material, such as metals or compounds, into atomic, molecular, or ionic forms. These particles travel in a straight line with a large path of freedom towards the substrate surface, where they condense, nucleate, and grow into a thin film at low temperatures. The key role of vacuum conditions is to lower the material's boiling point, prevent oxidation and contamination, and ensure high particle transport efficiency, thereby achieving uniformity and high purity in the film.

[0052] S7: After maintaining this position for a certain period of time, turn off the electromagnetic induction heating device 2. After the vacuum chamber 1 has cooled down, remove the product.

[0053] In a preferred embodiment, the silicon raw material used in step S1 before purification is silicon prepared by molten salt electrolysis, and the preparation scheme of this silicon material refers to the preparation method of patent CN101967649A. In a preferred embodiment, in steps S2 and S5, the vacuum level range is 10. −1 -10 −3 Torr; In a preferred embodiment, in steps S3 and S6, the heating temperature is set to 1414–1600 °C. It is worth noting that the temperature setting needs to refer to the vacuum degree value. The specific parameter selection is based on the data in Table 1. The selection of this parameter requires that the silicon material melts under the set vacuum degree and the impurity elements reach the volatilization temperature.

[0054] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0055] Example 1: The flowchart of the method for preparing ultra-high purity silicon films by purifying silicon materials under microvacuum using molten salt electrolysis is shown below. Figure 2As shown, the elemental composition of the electrolytic silicon raw material used in Example 1 is 95.83 wt.% Si, with 3.22 wt.% CaCl2 adhering to its surface that is difficult to remove, 0.58 wt.% Al co-deposited, and 0.38 wt.% other impurities. The specific steps are as follows: S1: Place the silicon prepared by molten salt electrolysis into the corundum crucible 6, and cover the outside of the corundum crucible containing silicon with a graphite crucible 5; then place the two crucibles in the center of the electromagnetic induction heating coil 2-1 and close the vacuum chamber cover. S2: Open vacuum valve 1-2 and vacuum pump system 1-1 to evacuate the inside of vacuum chamber 1. When the evacuation is complete, close vacuum valve 1-2 and then close vacuum pump system 1-1. Adjust the vacuum level of the chamber to 1 Torr by controlling the argon gas cylinder 3-1 to input argon gas into the chamber. S3: Start the electromagnetic induction heating coil circulating water cooling device 2-2, then start the electromagnetic induction heating device 2. Adjust the electromagnetic induction input current value by observing the reading of the infrared temperature measuring device 2-3 to control the molten pool temperature to 1600 ℃. S4: After maintaining for a certain period of time, turn off the electromagnetic induction heating device 2. After the vacuum chamber 1 cools down, take out the corundum crucible 6 and the graphite crucible 5 and clean the vacuum chamber. After cleaning, place the corundum crucible 6 and the graphite crucible 5 in the center of the electromagnetic induction heating coil 2-1. Place the vapor deposition material fixing frame 4 on the upper part of the corundum crucible 6 and the graphite crucible 5, and fix the carbon sheet to the vapor deposition material fixing frame 4. The carbon sheet is fixed 3 cm above the mouth of the graphite crucible. S5: Open vacuum valve 1-2 and vacuum pump system 1-1 to evacuate the inside of vacuum chamber 1. Once evacuation is complete, close vacuum valve 1-2 and then turn off vacuum pump system 1-1. Adjust the vacuum level of the chamber to 1×10⁻⁶ by injecting argon gas into the chamber through argon cylinder 3-1. −2 Torr; S6: Start the electromagnetic induction heating coil circulating water cooling device 2-2, then start the electromagnetic induction heating device 2. Adjust the electromagnetic induction input current value by observing the reading of the infrared temperature measuring device 2-3 to control the molten pool temperature to reach 1700 ℃, and cool and grow on the vapor-deposited material. S7: After maintaining this position for a certain period of time, turn off the electromagnetic induction heating device 2. After the vacuum chamber 1 has cooled down, remove the product.

[0056] Results Analysis: The elemental contents of purified electrolytic silicon in the three parallel experiments during the electrodeposition process in step S3 were as follows: Group A: 99.9908 wt.% Si, 0.0032 wt.% Ca, 0.0017 wt.% Al, and 0.0043 wt.% other impurities; Group B: 99.9876 wt.% Si, 0.0014 wt.% Ca, 0.0057 wt.% Al, and 0.0053 wt.% other impurities; Group C: 99.9821 wt.% Si, 0.0023 wt.% Ca, 0.0063 wt.% Al, and 0.0093 wt.% other impurities; the impurity content was significantly reduced compared to the raw material electrolytic silicon. SEM and EDS data analysis of the silicon film deposited in step S6 showed that the sample surface had a rough, porous, sheet-like texture and obvious layering, indicating that a thin film was deposited on the carbon substrate without significant mixing.

[0057] Example 2: The flowchart of the method for preparing ultra-high purity silicon films by purifying silicon materials under microvacuum using molten salt electrolysis is shown below. Figure 2 As shown, the elemental composition of the electrolytic silicon raw material used in Example 1 is 96.71 wt.% Si, 2.04 wt.% CaCl2 which is difficult to remove from its surface, 0.76 wt.% Al co-deposited, and 0.49 wt.% other impurities. The specific steps are as follows: S1: Place the silicon prepared by molten salt electrolysis into the corundum crucible 6, and cover the outside of the corundum crucible containing silicon with a graphite crucible 5; then place the two crucibles in the center of the electromagnetic induction heating coil 2-1 and close the vacuum chamber cover. S2: Open vacuum valve 1-2 and vacuum pump system 1-1 to evacuate the inside of vacuum chamber 1. Once evacuation is complete, close vacuum valve 1-2 and then turn off vacuum pump system 1-1. Adjust the vacuum level of the chamber to 1×10⁻⁶ by injecting argon gas into the chamber using argon cylinder 3-1. −2 Torr; S3: Start the electromagnetic induction heating coil circulating water cooling device 2-2, then start the electromagnetic induction heating device 2. Adjust the electromagnetic induction input current value by observing the reading of the infrared temperature measuring device 2-3 to control the molten pool temperature to 1500 ℃. S4: After maintaining for a certain period of time, turn off the electromagnetic induction heating device 2. After the vacuum chamber 1 cools down, take out the corundum crucible 6 and the graphite crucible 5 and clean the vacuum chamber. After cleaning, place the corundum crucible 6 and the graphite crucible 5 in the center of the electromagnetic induction heating coil 2-1. Place the vapor deposition material fixing frame 4 on the upper part of the corundum crucible 6 and the graphite crucible 5 and fix the vapor deposition material to the vapor deposition material fixing frame 4. The vapor deposition material is fixed 4 cm above the mouth of the graphite crucible. S5: Open vacuum valve 1-2 and vacuum pump system 1-1 to evacuate the inside of vacuum chamber 1. Once evacuation is complete, close vacuum valve 1-2 and then turn off vacuum pump system 1-1. Adjust the vacuum level of the chamber to 1×10⁻⁶ by injecting argon gas into the chamber through argon cylinder 3-1. −3 Torr; S6: Start the electromagnetic induction heating coil circulating water cooling device 2-2, then start the electromagnetic induction heating device 2. Adjust the electromagnetic induction input current value by observing the reading of the infrared temperature measuring device 2-3 to control the molten pool temperature to reach 1500 ℃, and cool and grow on the vapor-deposited material. S7: After maintaining this position for a certain period of time, turn off the electromagnetic induction heating device 2. After the vacuum chamber 1 has cooled down, remove the product.

[0058] Results Analysis: The elemental contents of purified electrolytic silicon in the three parallel experiments during the electrodeposition process in step S3 were as follows: Group A: 99.9808 wt.% Si, 0.0043 wt.% CaCl2, 0.0045 wt.% Al, and 0.0104 wt.% other impurities; Group B: 99.9702 wt.% Si, 0.0078 wt.% CaCl2, 0.0042 wt.% Al, and 0.00178 wt.% other impurities; Group C: 99.9725 wt.% Si, 0.0063 wt.% CaCl2, 0.0072 wt.% Al, and 0.0014 wt.% other impurities; the impurity content was significantly reduced compared to the raw material electrolytic silicon. SEM and EDS data analysis of the silicon film deposited in step S6 showed that there was obvious stratification on the sample surface, indicating that a thin film was deposited on the carbon substrate without significant mixing.

[0059] Example 3: The flowchart of the method for preparing ultra-high purity silicon films by purifying silicon materials under microvacuum using molten salt electrolysis is shown below. Figure 2 As shown, the elemental composition of the electrolytic silicon raw material used in Example 1 is 96.21 wt.% Si, with 2.41 wt.% CaCl2 adhering to its surface that is difficult to remove, 0.46 wt.% Al co-deposited, and 0.92 wt.% other impurities. The specific steps are as follows: S1: Place the silicon prepared by molten salt electrolysis into the corundum crucible 6, and cover the outside of the corundum crucible containing silicon with a graphite crucible 5; then place the two crucibles in the center of the electromagnetic induction heating coil 2-1 and close the vacuum chamber cover. S2: Open vacuum valve 1-2 and vacuum pump system 1-1 to evacuate the inside of vacuum chamber 1. Once evacuation is complete, close vacuum valve 1-2 and then close vacuum pump system 1-1. Adjust the vacuum level of the chamber to 10 by injecting argon gas into the chamber through argon cylinder 3-1. −3 Torr; S3: Start the electromagnetic induction heating coil circulating water cooling device 2-2, then start the electromagnetic induction heating device 2. Adjust the electromagnetic induction input current value by observing the reading of the infrared temperature measuring device 2-3 to control the molten pool temperature to 1420 ℃. S4: After maintaining for a certain period of time, turn off the electromagnetic induction heating device 2. After the vacuum chamber 1 cools down, take out the corundum crucible 6 and the graphite crucible 5 and clean the vacuum chamber. After cleaning, place the corundum crucible 6 and the graphite crucible 5 in the center of the electromagnetic induction heating coil 2-1. Place the vapor deposition material fixing frame 4 on the upper part of the corundum crucible 6 and the graphite crucible 5 and fix the vapor deposition material to the vapor deposition material fixing frame 4. The vapor deposition material is fixed 2 cm above the mouth of the graphite crucible. S5: Open vacuum valve 1-2 and vacuum pump system 1-1 to evacuate the inside of vacuum chamber 1. Once evacuation is complete, close vacuum valve 1-2 and then close vacuum pump system 1-1. Adjust the vacuum level of the chamber to 10 by injecting argon gas into the chamber through argon cylinder 3-1. −3 Torr; S6: Start the electromagnetic induction heating coil circulating water cooling device 2-2, then start the electromagnetic induction heating device 2. Adjust the electromagnetic induction input current value by observing the reading of the infrared temperature measuring device 2-3 to control the molten pool temperature to reach 1500 ℃, and cool and grow on the vapor-deposited material. S7: After maintaining this position for a certain period of time, turn off the electromagnetic induction heating device 2. After the vacuum chamber 1 has cooled down, remove the product.

[0060] Results Analysis: The elemental contents of purified electrolytic silicon in the three parallel experiments during the electrodeposition process in step S3 were as follows: Group A: 99.9932 wt.% Si, 0.0023 wt.% CaCl2, 0.0024 wt.% Al, and 0.0021 wt.% other impurities; Group B: 99.9803 wt.% Si, 0.0065 wt.% CaCl2, 0.0064 wt.% Al, and 0.0068 wt.% other impurities; Group C: 99.9834 wt.% Si, 0.0057 wt.% CaCl2, 0.0042 wt.% Al, and 0.0067 wt.% other impurities; the impurity content was significantly reduced compared to the raw material electrolytic silicon. SEM and EDS data analysis of the silicon film deposited in step S6 showed that there was obvious stratification on the sample surface, indicating that a thin film was deposited on the carbon substrate without significant mixing.

[0061] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0062] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. An apparatus for preparing high-purity silicon films by vacuum-controlled electrolytic silicon purification, characterized in that, include: Material storage mechanism, the material storage mechanism is placed in a vacuum chamber, the vacuum chamber is connected to a vacuum pumping mechanism and a vacuum degree adjustment device (3). It also includes a heating mechanism for heating the materials stored in the material storage mechanism; When in the impurity removal mode, the material containing impurities is placed in the material storage mechanism, the vacuum degree of the vacuum chamber is adjusted to a preset value, and the material containing impurities is heated by the heating mechanism, so that the impurities are transformed into a gas phase and deposited on the inner wall of the vacuum chamber; When in vapor deposition mode, the vapor deposition material holder (4) is fixed above the material storage mechanism, and the vapor deposition material is installed on the vapor deposition material holder (4). The purified material is placed in the material storage mechanism, the vacuum degree of the vacuum chamber is adjusted to a preset value, and the purified material is heated by the heating mechanism to cause the material to undergo phase change and be deposited on the vapor deposition material.

2. The apparatus for preparing high-purity silicon films based on vacuum-controlled electrolytic silicon purification according to claim 1, characterized in that, The vacuum chamber includes a vacuum chamber (1), which is connected to the vacuum pumping mechanism and the vacuum degree adjustment device (3).

3. The apparatus for preparing high-purity silicon films based on vacuum-controlled electrolytic silicon purification according to claim 2, characterized in that, The vacuum pumping mechanism includes a vacuum valve (1-2) and a vacuum pump system (1-1), and the vacuum chamber (1) is connected to the vacuum pump system (1-1) through the vacuum valve (1-2).

4. The apparatus for preparing high-purity silicon films based on vacuum-controlled electrolytic silicon purification according to claim 2, characterized in that, The vacuum regulation device (3) includes an argon cylinder (3-1) and a venting valve (3-2). Both the argon cylinder (3-1) and the venting valve (3-2) are connected to the vacuum chamber (1).

5. The apparatus for preparing high-purity silicon films based on vacuum-controlled electrolytic silicon purification according to claim 2, characterized in that, The material storage mechanism includes a graphite crucible (5) and a corundum crucible (6). The corundum crucible (6) is used to store materials. The graphite crucible (5) is coaxially sleeved on the outside of the corundum crucible (6). The graphite crucible (5) is fixed inside the vacuum chamber (1).

6. The apparatus for preparing high-purity silicon films by vacuum-controlled electrolytic silicon purification according to claim 5, characterized in that, The heating mechanism includes an electromagnetic induction heating device (2), which includes an electromagnetic induction heating coil (2-1) and a hot coil circulating water cooling device (2-2). The pipes of the electromagnetic induction heating coil (2-1) and the hot coil circulating water cooling device (2-2) are coaxially sleeved on the outside of the graphite crucible (5). The working fluid flows in the pipe of the hot coil circulating water cooling device (2-2). The electromagnetic induction heating coil (2-1) and the circulating water cooling device (2-2) work together to control the temperature of the material inside the corundum crucible (6).

7. The apparatus for preparing high-purity silicon films based on vacuum-controlled electrolytic silicon purification according to claim 5, characterized in that, It also includes an infrared temperature measuring device (2-3), which is used to measure the temperature of the material inside the corundum crucible (6).

8. The apparatus for preparing high-purity silicon films by vacuum-controlled electrolytic silicon purification according to claim 2, characterized in that, It also includes a vacuum monitoring system (1-3), which is connected to the vacuum chamber (1).

9. The apparatus for preparing high-purity silicon films based on vacuum-controlled electrolytic silicon purification according to claim 8, characterized in that, The vacuum monitoring system (1-3) includes a vacuum gauge and a vacuum resistance gauge.

10. A method for preparing high-purity silicon films based on vacuum-controlled electrolytic silicon purification, using the apparatus for preparing high-purity silicon films based on vacuum-controlled electrolytic silicon purification as described in any one of claims 1-9, characterized in that... Includes the following steps: When in the impurity removal mode, the material containing impurities is placed in the material storage mechanism and then placed in the vacuum chamber. The vacuum degree of the vacuum chamber is adjusted using the vacuum pumping mechanism and the vacuum degree adjustment device (3). The heating mechanism is used to heat the material containing impurities to a preset temperature, causing the impurities to undergo a gas phase transformation and deposit on the inner wall of the vacuum chamber; After the vacuum chamber has cooled down, remove the material storage mechanism and clean the inner wall of the vacuum chamber. When in vapor deposition mode, the vapor deposition material is installed on the vapor deposition material fixing frame (4) and fixed above the material storage mechanism that stores the purified material. The vapor deposition material, the vapor deposition material fixing frame (4) and the material storage mechanism are placed in the vacuum chamber at the same time. The vacuum degree of the vacuum chamber is adjusted by the vacuum pumping mechanism and the vacuum degree adjustment device (3). The heating mechanism is used to heat the purified material to a preset temperature, causing the material to undergo a phase change and be vapor-deposited on the vapor deposition material. After the vacuum chamber has cooled down, the vapor-deposited material containing the product is removed.

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