Process for processing high-purity ultrafine monocrystalline silicon powder

Abstract

This invention relates to the field of monocrystalline silicon powder processing technology, specifically: a high-purity ultrafine monocrystalline silicon powder processing technology, comprising the following steps: Step 1, selecting monocrystalline silicon rods as initial raw materials and analyzing the impurity content in the raw materials by secondary ion mass spectrometry (SIMS); Step 2, performing surface pretreatment on the monocrystalline silicon rods to remove the oxide layer and contaminants present on the surface, and placing the monocrystalline silicon rods in a hydrofluoric acid (HF) solution for chemical etching; Step 3, using a high-precision multi-wire cutting device to cut the monocrystalline silicon rods into thin slices; Compared with the prior art, in this invention, the surface pretreatment of the monocrystalline silicon rods and the chemical etching using a hydrofluoric acid (HF) solution can effectively remove the oxide layer and contaminants on the surface, and the precise control of the particle size of the monocrystalline silicon powder is achieved by combining low-temperature planetary ball milling and media stirring grinding.

Description

Technical Field

[0001] This invention relates to the field of single-crystal silicon powder processing technology, and in particular to a high-purity ultrafine single-crystal silicon powder processing technology. Background Technology

[0002] Monocrystalline silicon is a core material in the modern electronics and photovoltaic industries. In electronics, monocrystalline silicon is the main raw material for manufacturing integrated circuit chips; the integrity and purity of its crystal structure directly determine the chip's performance, such as processing speed, power consumption, and reliability. In the photovoltaic industry, monocrystalline silicon is used to manufacture solar cells, and its quality has a crucial impact on photoelectric conversion efficiency. With the rapid development of information technology and the increasing demand for clean energy, the demand for high-purity, ultrafine monocrystalline silicon powder is constantly increasing.

[0003] The investigation revealed that traditional mechanical grinding methods struggle to precisely control particle size when preparing monocrystalline silicon powder. For example, during ball milling, the randomness of collisions between the milling balls and the material results in a wide particle size distribution in the monocrystalline silicon powder. Let the particle size distribution function of the ball-milled monocrystalline silicon powder be , where is the particle size. This function typically has a large standard deviation, meaning that the product contains many particles that do not meet the required particle size, failing to satisfy the stringent requirements for particle size uniformity in high-end applications. Summary of the Invention

[0004] To address the technical problem of accurately controlling particle size in the preparation of monocrystalline silicon powder using traditional mechanical pulverization methods, this invention provides a high-purity ultrafine monocrystalline silicon powder processing technology.

[0005] The technical solution adopted in this invention is: a high-purity ultrafine single-crystal silicon powder processing technology, specifically including the following steps:

[0006] Step 1: Select single-crystal silicon rods as initial raw materials and analyze the impurity content in the raw materials by secondary ion mass spectrometry (SIMS).

[0007] Step 2: Perform surface pretreatment on the single crystal silicon rod to remove the oxide layer and contaminants present on the surface, and place the single crystal silicon rod in a hydrofluoric acid (HF) solution for chemical etching.

[0008] Step 3: Use a high-precision multi-wire cutting device to cut the single crystal silicon rod into thin slices;

[0009] Step four: During the cutting process, the cutting force F and cutting speed v are monitored in real time through an online monitoring system. c According to the formula ΔE=F·v c Δt (where ΔE is the cutting energy per unit time Δt), and the thickness t of the cut sheet. s (Unit: mm) Between 0.3 and 0.8 mm;

[0010] Step 5: Use a jaw crusher to perform initial crushing of the cut sheets. Let the oscillation frequency of the moving jaw of the jaw crusher be f. j (Unit: Hz), the moving jaw stroke is s j (Unit: mm), according to the crushing energy formula (where m) s For the quality of single-crystal silicon wafers, v j =2πf j s j (To control the speed of the moving osprey), the crushing energy is controlled to break the monocrystalline silicon wafer into particles with a diameter of 3-8mm;

[0011] Step 6: Screen the initially crushed particles using a screening machine;

[0012] Step 7: Place the initially crushed monocrystalline silicon particles into a planetary ball mill for low-temperature ball milling. Use liquid nitrogen to cool the ball mill jar to keep the ball milling temperature between -50℃ and 100℃.

[0013] Step 8: During the ball milling process, monitor the temperature T inside the milling jar. b and pressure P b According to the ideal gas law PV = nRT (where P is pressure, V is the volume of the mill jar, n is the amount of gas, R is the ideal gas constant, and T is the temperature), the milling time t b Between 12 and 36 hours, single-crystal silicon powder with an average particle size of 0.5-2 μm was finally obtained.

[0014] Step 9: Use a media stirring and grinding equipment as an auxiliary grinding method to further refine the monocrystalline silicon powder. Select high-hardness and high-purity zirconia balls as grinding media and monitor the particle size distribution of the monocrystalline silicon powder in real time using a laser particle size analyzer.

[0015] Step 10: Use chemical vapor phase purification technology to remove impurities from monocrystalline silicon powder.

[0016] In one embodiment, in step one, the impurity content includes boron, phosphorus, arsenic, iron, copper, and nickel.

[0017] In one embodiment, in step one, the concentration of impurity element i in the single-crystal silicon is set to C. i (Unit: atoms / cm) 3 ), calculate the volume of the single-crystal silicon rod based on its diameter D (unit: cm) and length L (unit: cm). Therefore, the mass of the single-crystal silicon rod is determined to be m = ρV (where ρ is the density of single-crystal silicon, 2.33 g / cm³). 3 ).

[0018] In one embodiment, in step two, the concentration of hydrofluoric acid is set to C.HF (Unit: mol / L), corrosion time is t corr (Unit: s), Corrosion rate formula (where k is the reaction rate constant and n is the reaction order);

[0019] In one embodiment, in step three, let the diameter of the cutting line be d. w (Unit: μm), the tension of the cutting wire is T (unit: N), and the cutting speed is v. c (Unit: m / s), according to the cutting force formula F = μT (where μ is the friction coefficient between the cutting line and the single crystal silicon) and the material removal rate formula Q = v c h c w c (where h) c For the cutting depth, w c (This refers to the cutting width).

[0020] In one embodiment, in step six, based on the equivalent diameter d of the particle... p (Unit: mm) and the aperture d of the screening mesh in the screening machine m (Unit: mm), using the formula (where η) s For screening efficiency, N pass N represents the number of particles that pass through the sieve. t (total is the total number of particles).

[0021] In one embodiment, in step seven, the rotational speed of the ball mill is set to n. b (Unit: rpm), the diameter of the grinding ball is d. b (Unit: mm), ball-to-material ratio is R b (Dimensionless) Formula for Energy of Ball-Grinding Collision (where m) b For the mass of the grinding ball, v b =πd b n b The formulas for the ball speed (linear velocity of the grinding ball) and grinding efficiency η are: b =k b R b t b (where k) b t is a coefficient related to the material. b (For ball milling time).

[0022] In one embodiment, in step nine, the diameter of the grinding media is set to d. z (Unit: mm), the stirring speed is n s (Unit: rpm), according to the grinding shear force formula F s=τA (where τ is the shear stress and A is the contact area between the grinding media and the single-crystal silicon powder) and grinding rate formula Where m is the mass of the single-crystal silicon powder, and k s (where n is the grinding rate constant), controlling the grinding process, and adjusting the agitator speed n according to the change in particle size distribution function f(d). s and grinding time t s The average particle size reaches 0.1-1 μm.

[0023] In one embodiment, step ten involves using chemical vapor deposition (CVD) to remove impurities from the monocrystalline silicon powder, as detailed below:

[0024] Single-crystal silicon powder is placed in a high-temperature reactor, and high-purity hydrogen gas (H2) and hydrogen halide gas are introduced. The reactor temperature is set to T. CVP (Unit: °C), gas flow rates are respectively (unit: sccm) and Q HCl (Unit: sccm);

[0025] According to the chemical reaction equilibrium constant formula (for the reaction) ) and impurity removal rate formula (where m) b efore and m after (These are the masses of impurities before and after purification, respectively), and the reaction conditions are controlled.

[0026] In the CVP process, according to the gas diffusion equation (where J is the diffusion flux, D is the diffusion coefficient, C is the impurity concentration, and x is the diffusion distance), allowing hydrogen halide gas to react with impurities in single-crystal silicon powder and carrying the generated volatile compounds out of the reaction system;

[0027] The purification of monocrystalline silicon powder is carried out using ion exchange resin. The monocrystalline silicon powder is dispersed in a prepared solution to ensure sufficient contact with the ion exchange resin. Let the exchange capacity of the ion exchange resin be Q. ex (Unit: mg / g), the concentration of impurity ions in single-crystal silicon powder is C. imp (Unit: mmol / L), according to the ion exchange equilibrium formula (for ion exchange reactions) Where R represents resin, A and B represent ions, and the formula for impurity removal is m. removed =Q ex m resin (where m) resin To ensure the quality of the ion exchange resin, the ion exchange process must be controlled.

[0028] By monitoring the changes in the concentration of impurity ions in the solution, the formula ΔC = C0 - Ct (where C0 is the initial impurity ion concentration, C t (where t is the impurity ion concentration at time t), ensuring that impurities in the monocrystalline silicon powder are removed through ion exchange.

[0029] This also includes vacuum high-temperature purification, as detailed below:

[0030] The monocrystalline silicon powder, after chemical vapor deposition and ion exchange purification, is placed in a vacuum high-temperature furnace for further purification. A vacuum is drawn to pressure P. vac (Unit: Pa) at 10 -4 -10 -3 Between Pa;

[0031] The heating rate is r T (Unit: °C / min), heat to treatment temperature T vac (Unit: °C), between 1000-1200 °C;

[0032] According to the impurity diffusion equation (where D is the diffusion coefficient, D0 is the diffusion constant, and E) a (where R is the activation energy, T is the ideal gas constant, and T is the temperature) Under high temperature and vacuum conditions, the remaining impurities in the single crystal silicon powder are further removed by diffusion.

[0033] The furnace temperature T is monitored through an online monitoring system. vac Pressure P vac And the impurity concentration C in monocrystalline silicon powder vac According to the formula (where k) vac (where n is the reaction rate constant for vacuum high-temperature purification and n is the reaction order), and the purification time t is controlled. vac (Unit: h), between 4 and 8 hours.

[0034] In one embodiment, after step ten, the process further includes washing and dispersing, as well as drying and packaging, as detailed below:

[0035] Cleaning and Dispersion:

[0036] A multi-stage cleaning process is used to clean the purified monocrystalline silicon powder. First, ultrapure water is used for preliminary cleaning. Let the resistivity of ultrapure water be ρ. w (Unit: Ω·cm), cleaning time is t w1 (Unit: min), according to the cleaning efficiency formula η w 1 = 1 - exp(-k) w1 ρ w t w1 (where k) w1 (The cleaning coefficient) removes residual chemical reagents and impurities from the surface of monocrystalline silicon powder;

[0037] Then, a second cleaning is performed using an organic solvent such as ethanol, with the concentration of ethanol set at C. etj (Unit: v / v), cleaning time is t w2 (unit: min), based on the principle of like dissolves like and the cleaning effect formula η w2 =k w2 C eth t w2 (where k) w2 (This refers to the organic solvent cleaning coefficient).

[0038] After cleaning, the monocrystalline silicon powder was dispersed in a specific dispersant solution using ultrasonic dispersion technology, with the ultrasonic frequency set to f. ult (Unit: kHz), ultrasonic power is P ult (Unit: W), based on ultrasonic cavitation theory and dispersion effect formula (where k) disp m and n are parameters related to the dispersion system, ensuring uniform dispersion of monocrystalline silicon powder and preventing agglomeration;

[0039] Drying and Packaging:

[0040] The dispersed monocrystalline silicon powder was dried using vacuum freeze-drying technology. The monocrystalline silicon powder was frozen at a low temperature, and then the ice was directly sublimated in a vacuum environment. Let the freezing temperature be T. freeze (Unit: °C), vacuum degree is P freeze (Unit: Pa), drying time is t d ry (unit: h);

[0041] According to the formula for the sublimation rate of ice (where k) sub E is the sublimation rate constant. sub To enhance the activation energy, the drying process is controlled to ensure that the monocrystalline silicon powder does not agglomerate or undergo structural changes during the drying process. The dried monocrystalline silicon powder is then packaged in a dust-free and oxygen-free environment.

[0042] Multi-layer composite packaging materials are used, and the barrier performance parameter of the packaging materials is P. barrier (Unit: cm) 3 ·cm / cm 2 (·s·Pa), according to the gas permeation equation (where J) gas (where ΔP is the gas permeation flux, ΔP is the gas pressure difference between the inside and outside of the packaging, and L is the thickness of the packaging material).

[0043] The beneficial effects of this invention are as follows: Compared with the prior art, this invention firstly uses secondary ion mass spectrometry to analyze the impurity content in the raw material, which allows for precise control of the impurities in the monocrystalline silicon rod. Secondly, surface pretreatment of the monocrystalline silicon rod using hydrofluoric acid (HF) solution for chemical etching effectively removes the oxide layer and contaminants, ensuring the cleanliness of the monocrystalline silicon rod surface. Finally, a high-precision multi-wire cutting device is used to cut the monocrystalline silicon rod into thin slices, and parameters such as cutting force and material removal rate are calculated using relevant formulas to achieve precise cutting and ensure uniform slice thickness. Precise control of the monocrystalline silicon powder particle size is achieved through a combination of low-temperature planetary ball milling and media stirring grinding. During the low-temperature planetary ball milling process, the low-temperature environment reduces crystal defects, and the ball milling parameters are optimized based on the ball milling collision energy formula and grinding efficiency formula, resulting in finer monocrystalline silicon powder. Media stirring grinding further refines and homogenizes the particle size of the monocrystalline silicon powder, enabling precise control of particle size. Detailed Implementation

[0044] In the description of this invention, it should be noted that the terms "front", "up", "down", "left", "right", "vertical", "horizontal", etc., indicating orientation or positional relationship, are only for the convenience of describing this invention and simplifying the description, and do not 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.

[0045] To address the problems existing in the background technology, this application proposes the following technical solution: a high-purity ultrafine single-crystal silicon powder processing technology, specifically including the following steps:

[0046] Step 1: Select single-crystal silicon rods as initial raw materials and analyze the impurity content in the raw materials by secondary ion mass spectrometry (SIMS).

[0047] In step one, let the concentration of impurity element i in single-crystal silicon be C. i (Unit: atoms / cm) 3 ), calculate the volume of the single-crystal silicon rod based on its diameter D (unit: cm) and length L (unit: cm). Therefore, the mass of the single-crystal silicon rod is determined to be m = ρV (where ρ is the density of single-crystal silicon, 2.33 g / cm³). 3 );

[0048] In step one, the impurities include boron, phosphorus, arsenic, iron, copper, and nickel.

[0049] Step 2: Perform surface pretreatment on the single crystal silicon rod to remove the oxide layer and contaminants present on the surface, and place the single crystal silicon rod in a hydrofluoric acid (HF) solution for chemical etching.

[0050] In step two, the concentration of hydrofluoric acid is set to C. HF (Unit: mol / L), corrosion time is t corr (Unit: s), according to the corrosion rate formula (where k is the reaction rate constant, n is the reaction order), by controlling C HF and t corr This ensures that the oxide layer on the surface of the single-crystal silicon rod is completely removed, while avoiding excessive corrosion.

[0051] Step 3: Use a high-precision multi-wire cutting device to cut the single-crystal silicon rod into thin slices;

[0052] In step three, let the diameter of the cutting line be d. w (Unit: μm), the tension of the cutting wire is T (unit: N), and the cutting speed is v. c (Unit: m / s), according to the cutting force formula F = μT (where μ is the friction coefficient between the cutting line and the single crystal silicon) and the material removal rate formula Q = v c j c w c (where j) c For the cutting depth, w c (for cutting width);

[0053] The above technical solution is explained as follows: First, by analyzing the impurity content in the raw material using secondary ion mass spectrometry (SIMS), the impurity situation in the monocrystalline silicon rod can be accurately determined. Second, surface pretreatment of the monocrystalline silicon rod using hydrofluoric acid (HF) solution for chemical etching effectively removes the oxide layer and contaminants from the surface, ensuring the cleanliness of the monocrystalline silicon rod surface and contributing to improved quality and product performance in subsequent processing. Finally, a high-precision multi-wire cutting device is used to cut the monocrystalline silicon rod into thin slices. Parameters such as cutting force and material removal rate are calculated using relevant formulas to achieve precise cutting and ensure uniform slice thickness.

[0054] Step four: During the cutting process, the cutting force F and cutting speed v are monitored in real time through an online monitoring system. c According to the formula ΔE=F·v c Δt (where ΔE is the cutting energy per unit time Δt) ensures a smooth cutting process and uniform blade thickness, with the resulting blade thickness t. s (Unit: mm) Between 0.3 and 0.8 mm;

[0055] Step 5: Use a jaw crusher to perform initial crushing of the cut sheets. Let the oscillation frequency of the moving jaw of the jaw crusher be f. j (Unit: Hz), the moving jaw stroke is s j (Unit: mm), according to the crushing energy formula (where m)s For the quality of single-crystal silicon wafers, v j =2πf j s j (To control the speed of the moving osprey), the crushing energy is controlled to break the monocrystalline silicon wafer into particles with a diameter of 3-8mm;

[0056] The above technical solution is explained as follows: In step four, the cutting force and cutting speed are monitored in real time through an online monitoring system. Based on the formula, the cutting process is ensured to be stable and the thickness of the cut sheet is uniform. This helps improve cutting accuracy and efficiency, ensuring that the thickness of the cut sheet is between 0.3-0.8mm, meeting the requirements of subsequent processing for consistent sheet thickness and reducing product defects caused by uneven thickness. In step five, a jaw crusher is used to initially crush the cut sheet, and the crushing energy is controlled according to the crushing energy formula to crush the monocrystalline silicon wafer into particles with a particle size of 3-8mm. This precise control ensures that the particle size after crushing meets the requirements of subsequent processing steps, providing suitable raw material particle size for further grinding and other operations. The online monitoring system is existing technology and can be further developed.

[0057] Step 6: Screen the initially crushed particles using a screening machine;

[0058] In step six, based on the equivalent diameter d of the particle... p (Unit: mm) and the aperture d of the screening mesh in the screening machine m (Unit: mm), using the formula (where η) s For screening efficiency, N pass N represents the number of particles that pass through the sieve. t (total is the total number of particles) to ensure that the initially crushed particles meet the requirements for subsequent processing;

[0059] Step 7: Place the pre-crushed monocrystalline silicon particles into a planetary ball mill for low-temperature ball milling. Use liquid nitrogen to cool the ball mill jar, keeping the ball milling temperature between -50℃ and 100℃ to reduce crystal structure defects caused by temperature rise during the grinding process.

[0060] In step seven, the rotational speed of the ball mill is set to n. b (Unit: rpm), the diameter of the grinding ball is d. b (Unit: mm), ball-to-material ratio is R b (dimensionless), based on the formula for energy of ball-mill collision. (where m) b For the mass of the grinding ball, v b =πd b n b The formulas for the ball speed (linear velocity of the grinding ball) and grinding efficiency η are: b =k bR b t b (where k) b t is a coefficient related to the material. b (For ball milling time), optimize ball milling parameters.

[0061] Step 8: During the ball milling process, monitor the temperature T inside the milling jar. b and pressure P b According to the ideal gas law PV = nRT (where P is pressure, V is the volume of the mill jar, n is the amount of gas, R is the ideal gas constant, and T is temperature), a stable milling environment is ensured to prevent safety issues caused by abnormal temperature and pressure. Milling time t b Between 12 and 36 hours, single-crystal silicon powder with an average particle size of 0.5-2 μm was finally obtained.

[0062] The above technical solution is explained as follows: In step six, the initially crushed particles are sieved using a screening machine, and the sieving efficiency is calculated using a formula to ensure that the initially crushed particles meet the requirements of subsequent processing. This helps to screen out particles of suitable size, ensuring the quality and efficiency of subsequent processing. In step seven, the monocrystalline silicon particles are placed in a planetary ball mill for low-temperature ball milling, cooled with liquid nitrogen. This effectively controls the grinding temperature, reduces crystal structure defects caused by temperature rise, and thus improves the quality of the monocrystalline silicon powder. By precisely setting and optimizing parameters such as the ball mill speed, the diameter of the grinding balls, and the ball-to-material ratio, the grinding effect can be further improved. In step eight, the temperature and pressure inside the ball mill jar are monitored during the ball milling process. The ideal gas law is used to ensure a stable ball milling environment and prevent safety issues, ultimately obtaining monocrystalline silicon powder with an average particle size of 0.5-2μm.

[0063] Step 9: Use a media stirring and grinding equipment as an auxiliary grinding method to further refine the monocrystalline silicon powder. Select high-hardness and high-purity zirconia balls as grinding media and monitor the particle size distribution of the monocrystalline silicon powder in real time using a laser particle size analyzer.

[0064] In step nine, let the diameter of the grinding media be d. z (Unit: mm), the stirring speed is n s (Unit: rpm), according to the grinding shear force formula F s =τA (where τ is the shear stress and A is the contact area between the grinding media and the single-crystal silicon powder) and grinding rate formula Where m is the mass of the single-crystal silicon powder, and k s (where n is the grinding rate constant), controlling the grinding process, and adjusting the agitator speed n according to the change in particle size distribution function f(d). s and grinding time t s This ensures that the particle size uniformity of monocrystalline silicon powder is further improved, with an average particle size of 0.1-1μm;

[0065] The above technical solution is explained as follows: A media stirring and grinding device is used as an auxiliary grinding method, and high-hardness, high-purity zirconia balls are selected as the grinding media to further refine the monocrystalline silicon powder. The particle size distribution of the monocrystalline silicon powder is monitored in real time using a laser particle size analyzer, and the grinding process is controlled according to the grinding shear force formula and grinding rate formula, ensuring the scientific nature and precision of the grinding operation. Adjusting the stirrer speed and grinding time based on the change in the particle size distribution function helps to further improve the particle size uniformity of the monocrystalline silicon powder, achieving an average particle size of 0.1-1 μm.

[0066] Step 10: Use chemical vapor phase purification technology to remove impurities from monocrystalline silicon powder.

[0067] In step ten, chemical vapor deposition (CVD) is used to remove impurities from the monocrystalline silicon powder, as detailed below:

[0068] Single-crystal silicon powder is placed in a high-temperature reactor, and high-purity hydrogen gas (H2) and hydrogen halide gas are introduced. The reactor temperature is set to T. CVP (Unit: °C), gas flow rates are respectively (unit: sccm) and Q HCl (Unit: sccm);

[0069] According to the chemical reaction equilibrium constant formula (for the reaction) ) and impurity removal rate formula (where m) b efore and m after (These are the masses of impurities before and after purification, respectively), and the reaction conditions are controlled.

[0070] In the CVP process, according to the gas diffusion equation (where J is the diffusion flux, D is the diffusion coefficient, C is the impurity concentration, and x is the diffusion distance), allowing hydrogen halide gas to react with impurities in single-crystal silicon powder and carrying the generated volatile compounds out of the reaction system;

[0071] The purification of monocrystalline silicon powder is carried out using ion exchange resin. The monocrystalline silicon powder is dispersed in a prepared solution (hydrochloric acid solution) to ensure full contact with the ion exchange resin. Let the exchange capacity of the ion exchange resin be Q. ex (Unit: mg / g), the concentration of impurity ions in single-crystal silicon powder is C. imp (Unit: mmol / L), according to the ion exchange equilibrium formula (for ion exchange reactions) Where R represents resin, A and B represent ions, and the formula for impurity removal is m. removed =Q ex m resin(where m) resin To ensure the quality of the ion exchange resin, the ion exchange process must be controlled.

[0072] By monitoring the changes in the concentration of impurity ions in the solution, the formula ΔC = C0 - C t (where C0 is the initial impurity ion concentration, C t (where t is the concentration of impurity ions at time t), ensuring that impurities in the monocrystalline silicon powder are removed through ion exchange, thereby further improving the purity of the monocrystalline silicon powder;

[0073] The above technical solution is explained as follows: By introducing high-purity hydrogen and hydrogen halide gas into a high-temperature reactor and precisely controlling the reactor temperature and gas flow rate, and operating according to the chemical reaction equilibrium constant formula and impurity removal rate formula, impurities in monocrystalline silicon powder can be effectively removed. During the CVP process, according to the gas diffusion equation, hydrogen halide gas reacts fully with the impurities in monocrystalline silicon powder, and the generated volatile compounds are carried out of the reaction system, further ensuring the impurity removal effect and significantly improving the purity of monocrystalline silicon powder.

[0074] This also includes vacuum high-temperature purification, as detailed below:

[0075] The monocrystalline silicon powder, after chemical vapor deposition and ion exchange purification, is placed in a vacuum high-temperature furnace for further purification. A vacuum is drawn to pressure P. vac (Unit: Pa) at 10 -4 -10 -3 Between Pa;

[0076] The heating rate is r T (Unit: °C / min) Reheat to the treatment temperature T vac (Unit: °C), between 1000-1200 °C;

[0077] According to the impurity diffusion equation (where D is the diffusion coefficient, D0 is the diffusion constant, and E) a (where R is the activation energy, T is the ideal gas constant, and T is the temperature) Under high temperature and vacuum conditions, the remaining impurities in the single crystal silicon powder are further removed by diffusion.

[0078] The furnace temperature T is monitored through an online monitoring system. vac Pressure P vac And the impurity concentration C in monocrystalline silicon powder vac According to the formula (where k) vac (where n is the reaction rate constant for vacuum high-temperature purification and n is the reaction order), and the purification time t is controlled. vac (Unit: h) The purity of the monocrystalline silicon powder is ensured to reach an extremely high level within 4-8 hours.

[0079] The above technical solution is explained as follows: Monocrystalline silicon powder, after chemical vapor deposition and ion exchange purification, is placed in a vacuum high-temperature furnace for further purification. By evacuating to extremely low pressure, impurity gases within the furnace can be effectively reduced, preventing the introduction of new impurities during the purification process. Secondly, under high temperature and vacuum conditions, according to the impurity diffusion equation, remaining impurities in the monocrystalline silicon powder can be further removed through diffusion. This high-temperature vacuum environment helps accelerate impurity diffusion, allowing impurities to escape more fully from the monocrystalline silicon powder, thereby improving its purity. By monitoring the furnace temperature, pressure, and impurity concentration in the monocrystalline silicon powder through an online monitoring system, and controlling the purification time according to relevant formulas, the purification process can be precisely controlled, ensuring that the purity of the monocrystalline silicon powder reaches a high level.

[0080] Alternatively, after step ten, the process may include washing and dispersing, as well as drying and packaging, as detailed below:

[0081] Cleaning and Dispersion:

[0082] A multi-stage cleaning process is used to clean the purified monocrystalline silicon powder. First, ultrapure water is used for preliminary cleaning. Let the resistivity of ultrapure water be ρ. w (Unit: Ω·cm), cleaning time is t w1 (Unit: min), according to the cleaning efficiency formula η w 1 = 1 - exp(-k) w1 ρ w t w1 (where k) w1 (The cleaning coefficient) removes residual chemical reagents and impurities from the surface of monocrystalline silicon powder;

[0083] Then, a second cleaning is performed using an organic solvent such as ethanol, with the concentration of ethanol set at C. eth (Unit: v / v), cleaning time is t w2 (unit: min), based on the principle of like dissolves like and the cleaning effect formula η w2 =k w2 C eth t w2 (where k) w2 (This is the organic solvent cleaning coefficient), further improving the cleanliness of monocrystalline silicon powder;

[0084] After cleaning, the monocrystalline silicon powder was dispersed in a specific dispersant solution using ultrasonic dispersion technology, with the ultrasonic frequency set to f. ult (Unit: kHz), ultrasonic power is P ult (Unit: W), based on ultrasonic cavitation theory and dispersion effect formula (where k) dispm and n are parameters related to the dispersion system, ensuring uniform dispersion of monocrystalline silicon powder and preventing agglomeration;

[0085] The above technical solution is explained as follows: A multi-stage cleaning process is used to clean the purified monocrystalline silicon powder. First, ultrapure water is used for initial cleaning. According to the cleaning efficiency formula, this effectively removes residual chemical reagents and impurities from the surface of the monocrystalline silicon powder, ensuring its cleanliness. Second, an organic solvent such as ethanol is used for secondary cleaning. Based on the principle of "like dissolves like" and the cleaning effect formula, this further improves the cleanliness of the monocrystalline silicon powder. This multi-stage cleaning process can more thoroughly remove contaminants from the surface of the monocrystalline silicon powder, ensuring its high purity. Finally, after cleaning, ultrasonic dispersion technology is used to disperse the monocrystalline silicon powder in a specific dispersant solution. Based on ultrasonic cavitation theory and the dispersion effect formula, this ensures uniform dispersion of the monocrystalline silicon powder and prevents agglomeration. Uniformly dispersed monocrystalline silicon powder facilitates subsequent processing and applications.

[0086] Drying and Packaging:

[0087] The dispersed monocrystalline silicon powder was dried using vacuum freeze-drying technology. The monocrystalline silicon powder was frozen at a low temperature, and then the ice was directly sublimated in a vacuum environment. Let the freezing temperature be T. freeze (Unit: °C), vacuum degree is P freeze (Unit: Pa), drying time is t d ry (unit: h);

[0088] According to the formula for the sublimation rate of ice (where k) sub E is the sublimation rate constant. sub To enhance the activation energy, the drying process is controlled to ensure that the monocrystalline silicon powder does not agglomerate or undergo structural changes during the drying process. The dried monocrystalline silicon powder is then packaged in a dust-free and oxygen-free environment.

[0089] Multi-layer composite packaging materials are used, and the barrier performance parameter of the packaging materials is P. barrier (Unit: cm) 3 ·cm / cm 2 (·s·Pa), according to the gas permeation equation (where J) gas (where ΔP is the gas permeation flux, ΔP is the gas pressure difference between the inside and outside of the packaging, and L is the thickness of the packaging material) to ensure that the packaged monocrystalline silicon powder is not contaminated by the external environment during storage and transportation.

[0090] The above technical solution is explained as follows: The drying and packaging steps can effectively maintain the purity of monocrystalline silicon powder, prevent agglomeration and structural changes, and ensure its quality stability during storage and transportation, thus meeting the stringent requirements of monocrystalline silicon powder in high-end applications.

[0091] In summary, this invention achieves precise control of the particle size of monocrystalline silicon powder by combining low-temperature planetary ball milling and media stirring grinding. During low-temperature planetary ball milling, the low-temperature environment reduces crystal defects, and the milling parameters are optimized based on the ball milling collision energy formula and grinding efficiency formula, resulting in finer monocrystalline silicon powder. Media stirring grinding further refines and homogenizes the particle size of the monocrystalline silicon powder. By monitoring the particle size distribution in real time and adjusting the grinding parameters, the average particle size of the final monocrystalline silicon powder can be precisely controlled between 0.1-1 μm, solving the problem of uneven particle size in traditional grinding methods. In the post-processing stage, ultrasonic dispersion technology combined with vacuum freeze-drying technology effectively prevents the agglomeration of monocrystalline silicon powder. Ultrasonic dispersion technology uses cavitation to uniformly disperse the monocrystalline silicon powder in the dispersant solution, while vacuum freeze-drying technology avoids particle agglomeration caused by moisture evaporation.

[0092] Although embodiments of the invention have been shown and described, the scope of the invention will be defined by the appended claims and their equivalents by those skilled in the art.

Claims

1. A processing technology for high-purity ultrafine single-crystal silicon powder, characterized in that, Specifically, the following steps are included: Step 1: Select single-crystal silicon rods as initial raw materials and analyze the impurity content in the raw materials by secondary ion mass spectrometry (SIMS). Step 2: Perform surface pretreatment on the single crystal silicon rod to remove the oxide layer and contaminants present on the surface, and place the single crystal silicon rod in a hydrofluoric acid (HF) solution for chemical etching. Step 3: Use a high-precision multi-wire cutting device to cut the single crystal silicon rod into thin slices; Step four: During the cutting process, the cutting force is monitored in real time through an online monitoring system. and cutting speed According to the formula (in unit of time (internal cutting energy), thickness of the cut sheet (unit: The thickness is between 0.3 and 0.8 mm. Step 5: Use a jaw crusher to perform initial crushing of the cut sheets. Assume the oscillation frequency of the moving jaw of the jaw crusher is... (unit: The stroke of the moving jaw is (unit: According to the energy formula for crushing (in For the quality of monocrystalline silicon wafers, (To control the speed of the moving osprey), the crushing energy is controlled to break the monocrystalline silicon wafer into particles with a diameter of 3-8mm; Step 6: Screen the initially crushed particles using a screening machine; Step 7: Place the initially crushed monocrystalline silicon particles into a planetary ball mill for low-temperature ball milling. Use liquid nitrogen to cool the ball mill jar to keep the ball milling temperature between -50°C and 100°C. Step 8: During the ball milling process, monitor the temperature inside the milling jar. and pressure According to the ideal gas law (in For pressure, For the volume of the ball mill jar, For the amount of gaseous substance, Let be the ideal gas constant. (temperature), ball milling time Between 12 and 36 hours, single-crystal silicon powder with an average particle size of 0.5-2 μm was finally obtained. Step 9: Use a media stirring and grinding equipment as an auxiliary grinding method to further refine the monocrystalline silicon powder. Select high-hardness and high-purity zirconia balls as grinding media and monitor the particle size distribution of the monocrystalline silicon powder in real time using a laser particle size analyzer. Step 10: Use chemical vapor phase purification technology to remove impurities from monocrystalline silicon powder.

2. The high-purity ultrafine single-crystal silicon powder processing technology according to claim 1, characterized in that, In step one, the impurities include boron, phosphorus, arsenic, iron, copper, and nickel.

3. The high-purity ultrafine single-crystal silicon powder processing technology according to claim 1, characterized in that, In step one, let impurity elements be defined. The concentration in monocrystalline silicon is (unit: ), based on the diameter of the single crystal silicon rod (unit: ) and length (unit: Calculate its volume This allows for the determination of the quality of the single-crystal silicon rod. (in The density of monocrystalline silicon, ).

4. The high-purity ultrafine single-crystal silicon powder processing technology according to claim 1, characterized in that, In step two, let the concentration of hydrofluoric acid be... (unit: ), corrosion time is (unit: Corrosion rate formula (in The reaction rate constant is... (Represents the reaction order).

5. The high-purity ultrafine single-crystal silicon powder processing technology according to claim 1, characterized in that, In step three, let the diameter of the cutting line be... (unit: The tension of the cutting wire is (unit: The cutting speed is (unit: According to the cutting force formula (in (The friction coefficient between the cutting line and the monocrystalline silicon) and the material removal rate formula. (in For cutting depth, (This refers to the cutting width).

6. The high-purity ultrafine single-crystal silicon powder processing technology according to claim 5, characterized in that, In step six, based on the equivalent diameter of the particles... (unit: ) and the aperture of the screening screen in the screening machine (unit: ), using formula (in For screening efficiency, The number of particles passing through the sieve. The screening efficiency is calculated based on the total number of particles.

7. The high-purity ultrafine single-crystal silicon powder processing technology according to claim 6, characterized in that, In step seven, let the rotational speed of the ball mill be... (Unit: rpm), the diameter of the grinding ball is (unit: ), the ratio of balls to material is (Dimensionless) Formula for Energy of Ball-Grinding Collision (in For the quality of the grinding ball, Formulas for ball mill linear velocity and grinding efficiency (in For material-related coefficients, (For ball milling time).

8. The high-purity ultrafine single-crystal silicon powder processing technology according to claim 7, characterized in that, In step nine, let the diameter of the grinding media be... (unit: The speed of the stirrer is (Unit: rpm), according to the grinding shear force formula (in For shear stress, (The contact area between the grinding media and the single-crystal silicon powder) and the grinding rate formula. ,in For the quality of monocrystalline silicon powder, (where the grinding rate constant is the constant), controlling the grinding process based on the particle size distribution function. Adjust the stirrer speed according to the changes. and grinding time The average particle size is 0.1-1 μm.

9. The high-purity ultrafine single-crystal silicon powder processing technology according to claim 1, characterized in that, In step ten, chemical vapor phase purification technology is used to remove impurities from the monocrystalline silicon powder, as detailed below: Single-crystal silicon powder is placed in a high-temperature reactor, and hydrogen gas is introduced. ) and hydrogen halide gas, assuming the reactor temperature is (Unit: °) ), gas flow rates are respectively (unit: sccm) and (Unit: sccm); According to the chemical reaction equilibrium constant formula Formula for impurity removal rate (in and (These are the masses of impurities before and after purification, respectively), and the reaction conditions are controlled. In the CVP process, according to the gas diffusion equation (in For diffusion flux, Where is the diffusion coefficient. Impurity concentration, (For diffusion distance), allowing hydrogen halide gas to react with impurities in single-crystal silicon powder and carrying the generated volatile compounds out of the reaction system; The purification of monocrystalline silicon powder is achieved using ion exchange resin. The monocrystalline silicon powder is dispersed in a prepared solution to ensure sufficient contact with the ion exchange resin. The exchange capacity of the ion exchange resin is assumed to be... (unit: The concentration of impurity ions in single-crystal silicon powder is (unit: According to the ion exchange equilibrium formula Formula for impurity removal (in To ensure the quality of the ion exchange resin, the ion exchange process must be controlled. By monitoring changes in the concentration of impurity ions in the solution, according to the formula (in This represents the initial impurity ion concentration. for (the concentration of impurity ions at any given time) ensures that impurities in the monocrystalline silicon powder are removed through ion exchange. This also includes vacuum high-temperature purification, as detailed below: The monocrystalline silicon powder, after chemical vapor deposition and ion exchange purification, is placed in a vacuum high-temperature furnace for further purification; a vacuum is then drawn to pressure. (unit: )exist - Between Pa; The heating rate is (Unit: °) Heat to the processing temperature. (Unit: °) (), between 1000-1200°C; According to the impurity diffusion equation (in Diffusion coefficient It is the diffusion constant. For activation energy, Let be the ideal gas constant. (Temperature), under high temperature and vacuum conditions, the remaining impurities in the single crystal silicon powder are further removed by diffusion; The furnace temperature is monitored via an online monitoring system. ,pressure And the concentration of impurities in monocrystalline silicon powder According to the formula (in The rate constant for vacuum high-temperature purification reaction is... (Reaction order), controlling purification time (unit: (), between 4-8 hours.

10. The high-purity ultrafine single-crystal silicon powder processing technology according to claim 1, characterized in that, After step ten, the process also includes cleaning and dispersing, as well as drying and packaging, with the specific steps as follows: Cleaning and Dispersion: A multi-stage cleaning process is used to clean the purified monocrystalline silicon powder. First, ultrapure water is used for preliminary cleaning. The resistivity of ultrapure water is assumed to be... (unit: The cleaning time is (Unit: min), according to the cleaning efficiency formula (in (The cleaning coefficient) removes residual chemical reagents and impurities from the surface of monocrystalline silicon powder; Then, a second cleaning is performed using an organic solvent such as ethanol, assuming the ethanol concentration is [value missing]. (unit: The cleaning time is (unit: min), based on the principle of like dissolves like and the formula for cleaning effect. (in (This refers to the organic solvent cleaning coefficient). After cleaning, the monocrystalline silicon powder was dispersed in a dispersant solution using ultrasonic dispersion technology, with the ultrasonic frequency set at [frequency value missing]. (Unit: kHz), ultrasonic power is (unit: Based on ultrasonic cavitation theory and dispersion effect formula (in , , (Parameters related to the dispersion system) to ensure uniform dispersion of monocrystalline silicon powder and prevent agglomeration; Drying and Packaging: The dispersed monocrystalline silicon powder was dried using vacuum freeze-drying technology. The powder was frozen at a low temperature, and then the ice was directly sublimated in a vacuum environment. The freezing temperature was set to [temperature value missing]. (Unit: °) Vacuum degree is (unit: The drying time is (unit: ); According to the formula for the sublimation rate of ice (in Let be the sublimation rate constant. To enhance the activation energy, the drying process is controlled to ensure that the monocrystalline silicon powder does not agglomerate or undergo structural changes during the drying process. The dried monocrystalline silicon powder is then packaged in a dust-free and oxygen-free environment. Multi-layer composite packaging materials are used. The barrier performance parameters of the packaging materials are set as follows: (unit: According to the gas permeation equation (in For gas permeation flux, Due to the pressure difference between the inside and outside of the packaging, (For packaging material thickness).

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