Processing technology of high-purity superfine monocrystalline silicon powder

Abstract

The invention relates to the technical field of monocrystalline silicon powder processing technologies, in particular to a high-purity superfine monocrystalline silicon powder processing technology which specifically comprises the following steps: step 1, selecting a monocrystalline silicon rod as an initial raw material, and analyzing the impurity content in the raw material through secondary ion mass spectrometry (SIMS); 2, carrying out surface pretreatment on the single crystal silicon rod to remove an oxide layer and pollutants on the surface, and putting the single crystal silicon rod in a hydrofluoric acid (HF) solution for chemical corrosion; step 3, cutting the single crystal silicon rod into slices by adopting high-precision multi-wire cutting equipment; compared with the prior art, the method has the advantages that the silicon single crystal rod is subjected to surface pretreatment, the hydrofluoric acid (HF) solution is used for chemical corrosion, an oxide layer and pollutants on the surface can be effectively removed, and accurate control over the granularity of the silicon single crystal powder is achieved in the mode that low-temperature planetary ball milling and medium stirring grinding are combined.

Description

Technical Field

[0001] The invention relates to the technical field of single crystal silicon powder processing technology, in particular to a high-purity ultra-fine single crystal silicon powder processing technology. Background Art

[0002] Monocrystalline silicon is the core basic material of the modern electronic industry and photovoltaic industry. In the field of electronics, monocrystalline silicon is the main raw material for manufacturing integrated circuit chips. The integrity and purity of its crystal structure directly determine the performance of the chip, such as computing 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 the efficiency of photoelectric conversion. With the rapid development of information technology and the growing demand for clean energy, the demand for high-purity ultrafine monocrystalline silicon powder is increasing.

[0003] The investigation found that it is difficult to accurately control the particle size when preparing single crystal silicon powder using traditional mechanical crushing methods. For example, during the ball milling process, the collision between the ball milling balls and the material is relatively random, resulting in a wide particle size distribution of single crystal silicon powder. Suppose the particle size distribution function of the single crystal silicon powder after ball milling is, where is the particle size, and its standard deviation is usually large, which means that there are many particles in the product that do not meet the required particle size, and cannot meet the strict requirements of high-end applications for the uniformity of the particle size of single crystal silicon powder. Summary of the invention

[0004] Aiming at the technical problem that it is difficult to accurately control the particle size when preparing single crystal silicon powder by the traditional mechanical pulverization method, the present invention provides a high-purity ultra-fine single crystal silicon powder processing technology.

[0005] The technical solution adopted by the present invention is: a high-purity ultrafine single crystal silicon powder processing technology, which specifically includes the following steps:

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

[0007] Step 2: Pre-treat the surface of the single crystal silicon rod to remove the oxide layer and pollutants on the surface, and place the single crystal silicon rod in a hydrofluoric acid (HF) solution for chemical etching;

[0008] Step 3, using high-precision multi-wire cutting equipment to cut the single crystal silicon rod into thin slices;

[0009] Step 4: During the cutting process, the cutting force F and cutting speed v are monitored in real time through the online monitoring system. c , according to the formula ΔE=F·v c Δt (where ΔE is the cutting energy per unit time Δt), the thickness of the slice after cutting is t s (Unit: mm) between 0.3-0.8 mm;

[0010] Step 5: Use a jaw crusher to crush the slices. Suppose the swing frequency of the movable jaw of the jaw crusher is f. j (Unit: Hz), movable jaw stroke is s j (Unit: mm), according to the crushing energy formula (where m s is the mass of single crystal silicon wafer, v j =2πf j s j is the moving speed of the moving oscillator), controls the crushing energy, and crushes the single crystal silicon wafer into particles with a size of 3-8mm;

[0011] Step six, screening the particles after primary crushing by a screening machine;

[0012] Step 7: Place the primary crushed single crystal silicon particles into a planetary ball mill for low temperature ball milling, and use liquid nitrogen to cool the ball milling tank to control the ball milling temperature between -50°C and 100°C;

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

[0014] Step nine, using a medium stirring grinding device as an auxiliary grinding means to further refine the single crystal silicon powder, using high hardness and high purity zirconia balls as grinding media, and using a laser particle size analyzer to monitor the particle size distribution of the single crystal silicon powder in real time;

[0015] Step ten, using chemical vapor purification technology to remove impurities in the single crystal silicon powder.

[0016] In one embodiment, in step 1, the impurity content includes boron, phosphorus, arsenic, iron, copper and nickel.

[0017] In one embodiment, in step 1, the concentration of the impurity element i in the single crystal silicon is C i (Unit: atoms / cm 3 ), calculate the volume based on the diameter D (unit: cm) and length L (unit: cm) of the single crystal silicon rod Then determine the mass of the single crystal silicon rod m = ρV (where ρ is the density of single crystal silicon, 2.33g / cm 3 ).

[0018] In one embodiment, in step 2, the concentration of hydrofluoric acid is CHF (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 3, the diameter of the cutting line is d w (unit: μm), the tension of the cutting line 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 wire and the single crystal silicon) and the material removal rate formula Q = v c h c w c (where h c is the cutting depth, w c is the cutting width).

[0020] In one embodiment, in step 6, according to 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 n s is the screening efficiency, N pass is the number of particles passing through the sieve, N t otal is the total number of particles).

[0021] In one embodiment, in step 7, the speed of the ball mill is n b (Unit: rpm), the diameter of the ball mill is d b (Unit: mm), ball-to-material ratio is R b (dimensionless), ball mill collision energy formula (where m b is the mass of the ball mill, v b =πd b n b is the ball milling ball linear velocity) and the grinding efficiency formula η b =k b R b t b (where k b is the coefficient related to the material, t b is the ball milling time).

[0022] In one embodiment, in step nine, the diameter of the grinding medium is d z (Unit: mm), the speed of the stirrer 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 medium and the single crystal silicon powder) and the grinding rate formula Where m is the mass of single crystal silicon powder, k s is the grinding rate constant), controls the grinding process, and adjusts the speed of the agitator n according to the change of the particle size distribution function f(d). s and grinding time t s , the average particle size reaches 0.1-1μm.

[0023] In one embodiment, in step 10, chemical vapor purification technology is used to remove impurities in the single crystal silicon powder, as follows:

[0024] The single crystal silicon powder is placed in a high temperature reactor, and high purity hydrogen (H2) and hydrogen halide gas are introduced. The reactor temperature is set to T CVP (Unit: °C), gas flow rates are (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 fore and m after are the masses of impurities before and after purification, respectively), to control the reaction conditions;

[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 the hydrogen halide gas to react with the impurities in the single crystal silicon powder and taking the generated volatile compounds out of the reaction system;

[0027] The single crystal silicon powder is purified by using ion exchange resin, and the single crystal silicon powder is dispersed in a set solution so that it is fully in contact with the ion exchange resin. The exchange capacity of the ion exchange resin is Q ex (Unit: mmmol / g), the impurity ion concentration in single crystal silicon powder is C imp (Unit: mmol / L), according to the ion exchange equilibrium formula (For ion exchange reactions Where R is resin, A and B are ions) and the impurity removal formula m removed =Q ex m resin (where m resin is the quality of ion exchange resin), control the ion exchange process;

[0028] By monitoring the change of impurity ion concentration in the solution, according to the formula ΔC=C0-Ct (where C0 is the initial impurity ion concentration, C t is the impurity ion concentration at time t), ensuring that impurities in the single crystal silicon powder are removed through ion exchange;

[0029] It also includes vacuum high temperature purification, as follows:

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

[0031] The heating rate is r T (Unit: °C / min), heated to the 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, E a is the activation energy, R is the ideal gas constant, and T is the temperature), and the remaining impurities in the single crystal silicon powder are further removed by diffusion under high temperature and vacuum environment;

[0033] Monitor the furnace temperature T through the online monitoring system vac 、Pressure P vac and the impurity concentration C in the single crystal silicon powder vac , according to the formula (where k vac is the vacuum high temperature purification reaction rate constant, n is the reaction order), controls the purification time t vac (Unit: h), between 4-8h.

[0034] In one embodiment, after step 10, washing and dispersing, as well as drying and packaging are further included, and the specific steps are as follows:

[0035] Cleaning and dispersing:

[0036] The purified single crystal silicon powder is cleaned using a multi-stage cleaning process. Ultrapure water is first used for preliminary cleaning. The resistivity of ultrapure water is 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 is the cleaning coefficient), to remove the chemical reagents and impurities remaining on the surface of the single crystal silicon powder;

[0037] Then use an organic solvent such as ethanol for secondary cleaning. Suppose the concentration of ethanol is C etj (Unit: v / v), cleaning time is t w2 (unit: min), according to the principle of like dissolves like and the cleaning effect formula η w2 =k w2 C eth t w2 (where k w2 is the organic solvent cleaning coefficient);

[0038] After cleaning, the single crystal silicon powder is dispersed in a specific dispersant solution using ultrasonic dispersion technology, and the ultrasonic frequency is set to f ult (unit: kHz), ultrasonic power is P ult (Unit: W), according to the ultrasonic cavitation theory and dispersion effect formula (where k disp , m, n are parameters related to the dispersion system), ensuring that the single crystal silicon powder is evenly dispersed to prevent agglomeration;

[0039] Drying and packaging:

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

[0041] According to the sublimation rate formula of ice (where k sub is the sublimation rate constant, E sub (sublimation activation energy) to control the drying process to ensure that the single crystal silicon powder will not agglomerate or change in structure during the drying process. The dried single crystal silicon powder is packaged in a dust-free and oxygen-free environment;

[0042] Use multi-layer composite packaging materials, and assume that the barrier performance parameter of the packaging material is P barrier (Unit: cm 3 cm / cm 2 ·s·Pa), according to the gas permeability equation (Where J gas is the gas permeation flux, ΔP is the gas pressure difference inside and outside the package, and L is the thickness of the packaging material).

[0043] The beneficial effects of the present invention are as follows: compared with the prior art, in the present invention, firstly, the impurity content in the raw material is analyzed by secondary ion mass spectrometry, so that the impurity situation in the single crystal silicon rod can be accurately grasped; secondly, the surface of the single crystal silicon rod is pretreated, and a hydrofluoric acid (HF) solution is used for chemical corrosion, which can effectively remove the oxide layer and pollutants on the surface, and ensure the cleanliness of the surface of the single crystal silicon rod; finally, the single crystal silicon rod is cut into thin slices by a high-precision multi-wire cutting device, and the parameters such as the cutting force and the material removal rate are calculated by the relevant formula, so that accurate cutting can be achieved, and the thickness of the thin slice is ensured to be uniform; by combining low-temperature planetary ball milling and medium stirring grinding, the particle size of the single crystal silicon powder is accurately controlled. In the process of low-temperature planetary ball milling, the low temperature environment is used to reduce crystal defects, and the ball milling parameters are optimized according to the ball milling collision energy formula and the grinding efficiency formula, so as to obtain finer single crystal silicon powder. The particle size of the single crystal silicon powder is further refined and homogenized by medium stirring grinding, and the particle size can be accurately controlled. DETAILED DESCRIPTION

[0044] In the description of the present invention, it should be noted that the terms "front", "up", "down", "left", "right", "vertical", "horizontal" and the like to indicate directions or positional relationships are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0045] In order to solve the problems existing in the background technology, the present application proposes the following technical solution: a high-purity ultrafine single crystal silicon powder processing process, specifically comprising the following steps:

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

[0047] In step 1, the concentration of impurity element i in single crystal silicon is C i (Unit: atoms / cm 3 ), calculate the volume based on the diameter D (unit: cm) and length L (unit: cm) of the single crystal silicon rod Then determine the mass of the single crystal silicon rod m = ρV (where ρ is the density of single crystal silicon, 2.33g / cm 3 );

[0048] Wherein, in step 1, the impurity content includes boron, phosphorus, arsenic, iron, copper and nickel.

[0049] Step 2: Pre-treat the surface of the single crystal silicon rod to remove the oxide layer and pollutants on the surface, and place the single crystal silicon rod in a hydrofluoric acid (HF) solution for chemical etching;

[0050] Wherein, in step 2, 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 and n is the reaction order), by controlling C HF and t corr , ensuring that the oxide layer on the surface of the single crystal silicon rod is completely removed while avoiding excessive corrosion.

[0051] Step 3, using high-precision multi-wire cutting equipment to cut the single crystal silicon rod into thin slices;

[0052] In step 3, let the diameter of the cutting line be d w (unit: μm), the tension of the cutting line 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 wire and the single crystal silicon) and the material removal rate formula Q = v c j c w c (where j c is the cutting depth, w c is the cutting width);

[0053] The above technical solution is explained as follows: by analyzing the impurity content in the raw materials through secondary ion mass spectrometry (SIMS), the impurity situation in the single crystal silicon rod can be accurately grasped. Secondly, the surface of the single crystal silicon rod is pretreated and chemically corroded with hydrofluoric acid (HF) solution, which can effectively remove the surface oxide layer and pollutants, ensure the cleanliness of the surface of the single crystal silicon rod, and help improve the quality of subsequent processing and product performance. Finally, the single crystal silicon rod is cut into thin slices using high-precision multi-wire cutting equipment, and the parameters such as cutting force and material removal rate are calculated through relevant formulas, which can achieve precise cutting and ensure the uniform thickness of the thin slices.

[0054] Step 4: During the cutting process, the cutting force F and cutting speed v are monitored in real time through the online monitoring system. c , according to the formula ΔE=F·v c Δt (where ΔE is the cutting energy per unit time Δt), ensuring a smooth cutting process and uniform thickness of the cut sheet. The thickness of the cut sheet is t s (Unit: mm) between 0.3-0.8 mm;

[0055] Step 5: Use a jaw crusher to crush the slices. Suppose the swing frequency of the movable jaw of the jaw crusher is f. j (Unit: Hz), movable jaw stroke is s j (Unit: mm), according to the crushing energy formula (where ms is the mass of single crystal silicon wafer, v j =2πf j s j is the moving speed of the moving oscillator), controls the crushing energy, and crushes the single crystal silicon wafer into particles with a size of 3-8mm;

[0056] The above technical solution is explained as follows: In step 4, the cutting force and cutting speed are monitored in real time through the online monitoring system, and the cutting process is ensured to be smooth and the thickness of the cut piece is uniform according to the formula, which helps to improve the cutting accuracy and efficiency, and ensure that the thickness of the cut slice is between 0.3-0.8mm, which can meet the requirements of subsequent processing for the consistency of the slice thickness and reduce product defects caused by uneven thickness. In step 5, a jaw crusher is used to initially crush the cut slices, and the crushing energy is controlled according to the crushing energy formula to crush the single crystal silicon slices into particles with a particle size of 3-8mm. This precise control can ensure that the size of the crushed particles meets the requirements of the subsequent processing steps and provide a suitable raw material particle size for further grinding and other operations. The online monitoring system is an existing technology and can be developed.

[0057] Step six, screening the particles after primary crushing by a screening machine;

[0058] Among them, in step 6, according to 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 n s is the screening efficiency, N pass is the number of particles passing through the sieve, N t otal is the total number of particles), ensuring that the primary crushed particles meet the requirements of subsequent processing;

[0059] Step seven: Place the crushed single crystal silicon particles into a planetary ball mill for low-temperature ball milling. Use liquid nitrogen to cool the ball milling tank so that the ball milling temperature is controlled between -50°C and 100°C to reduce crystal structure defects caused by the temperature increase during the grinding process.

[0060] Among them, in step 7, the speed of the ball mill is set to n b (Unit: rpm), the diameter of the ball mill is d b (Unit: mm), ball-to-material ratio is R b (dimensionless), according to the ball mill collision energy formula (where m b is the mass of the ball mill, v b =πd b n b is the ball milling ball linear velocity) and the grinding efficiency formula η b =k bR b t b (where k b is the coefficient related to the material, t b is the ball milling time), and the ball milling parameters were optimized.

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

[0062] The above technical solution is explained as follows: In step six, the particles after primary crushing are screened by a screening machine, and the screening efficiency is calculated using a formula to ensure that the primary crushed particles meet the requirements of subsequent processing, which helps to screen out particles of suitable particle size and ensure the quality and efficiency of subsequent processing. In step seven, the single crystal silicon particles are placed in a planetary ball mill for low-temperature ball milling, and liquid nitrogen is used for cooling, which can effectively control the grinding temperature and reduce the crystal structure defects caused by the increase in temperature, thereby improving the quality of the single crystal silicon powder. The grinding effect can be further improved by accurately setting and optimizing the parameters such as the rotation speed of the ball mill, the diameter of the ball mill, and the ball-to-material ratio. In step eight, the temperature and pressure in the ball mill tank are monitored during the ball milling process, and the ball milling environment is ensured to be stable according to the ideal gas state equation to prevent safety problems, and finally a single crystal silicon powder with an average particle size of 0.5-2μm is obtained.

[0063] Step nine, using a medium stirring grinding device as an auxiliary grinding means to further refine the single crystal silicon powder, using high hardness and high purity zirconia balls as grinding media, and using a laser particle size analyzer to monitor the particle size distribution of the single crystal silicon powder in real time;

[0064] In step nine, the diameter of the grinding medium is assumed to be d z (Unit: mm), the speed of the stirrer 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 medium and the single crystal silicon powder) and the grinding rate formula Where m is the mass of single crystal silicon powder, k s is the grinding rate constant), controls the grinding process, and adjusts the speed of the agitator n according to the change of the particle size distribution function f(d). s and grinding time t s , ensuring that the particle size uniformity of single crystal silicon powder is further improved, and the average particle size reaches 0.1-1μm;

[0065] The above technical solution is explained as follows: using medium stirring grinding equipment as an auxiliary grinding means, and selecting high-hardness, high-purity zirconia balls as grinding media, can further refine the single crystal silicon powder. The particle size distribution of the single crystal silicon powder is monitored in real time by a laser particle size analyzer, and the grinding process is controlled according to the grinding shear force formula and the grinding rate formula to ensure the scientificity and accuracy of the grinding operation. Adjusting the speed and grinding time of the agitator according to the change of the particle size distribution function helps to further improve the particle size uniformity of the single crystal silicon powder, so that the average particle size reaches 0.1-1μm.

[0066] Step ten, using chemical vapor purification technology to remove impurities in the single crystal silicon powder.

[0067] Among them, in step ten, chemical vapor purification technology is used to remove impurities in the single crystal silicon powder, as follows:

[0068] The single crystal silicon powder is placed in a high temperature reactor, and high purity hydrogen (H2) and hydrogen halide gas are introduced. The reactor temperature is set to T CVP (Unit: °C), gas flow rates are (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 fore and m after are the masses of impurities before and after purification, respectively), to control the reaction conditions;

[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 the hydrogen halide gas to react with the impurities in the single crystal silicon powder and taking the generated volatile compounds out of the reaction system;

[0071] The single crystal silicon powder is purified by using ion exchange resin, and the single crystal silicon powder is dispersed in a set solution (hydrochloric acid solution) so that it is fully in contact with the ion exchange resin. The exchange capacity of the ion exchange resin is Q ex (Unit: mmmol / g), the impurity ion concentration in single crystal silicon powder is C imp (Unit: mmol / L), according to the ion exchange equilibrium formula (For ion exchange reactions Where R is resin, A and B are ions) and the impurity removal formula m removed =Q ex m resin(where m resin is the quality of ion exchange resin), control the ion exchange process;

[0072] By monitoring the change of impurity ion concentration in the solution, according to the formula ΔC=C0-C t (where C0 is the initial impurity ion concentration, C t is the impurity ion concentration at time t), ensuring that impurities in the single crystal silicon powder are removed through ion exchange, further improving the purity of the single crystal 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 accurately controlling the reactor temperature and gas flow rate, and operating according to the chemical reaction equilibrium constant formula and the impurity removal rate formula, the impurities in the single crystal silicon powder can be effectively removed. In the CVP process, the hydrogen halide gas is allowed to fully react with the impurities in the single crystal silicon powder according to the gas diffusion equation, and the generated volatile compounds are taken out of the reaction system, further ensuring the impurity removal effect, so that the purity of the single crystal silicon powder is significantly improved.

[0074] It also includes vacuum high temperature purification, as follows:

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

[0076] The heating rate is r T (Unit: °C / min), and then heated 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, E a is the activation energy, R is the ideal gas constant, and T is the temperature), and the remaining impurities in the single crystal silicon powder are further removed by diffusion under high temperature and vacuum environment;

[0078] Monitor the furnace temperature T through the online monitoring system vac 、Pressure P vac and the impurity concentration C in the single crystal silicon powder vac , according to the formula (where k vac is the vacuum high temperature purification reaction rate constant, n is the reaction order), controls the purification time t vac (Unit: h), between 4-8h, ensuring that the purity of single crystal silicon powder reaches an extremely high level.

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

[0080] As another embodiment, after step 10, washing and dispersing, as well as drying and packaging are further included, and the specific steps are as follows:

[0081] Cleaning and dispersing:

[0082] The purified single crystal silicon powder is cleaned using a multi-stage cleaning process. Ultrapure water is first used for preliminary cleaning. The resistivity of ultrapure water is 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 is the cleaning coefficient), to remove the chemical reagents and impurities remaining on the surface of the single crystal silicon powder;

[0083] Then use an organic solvent such as ethanol for secondary cleaning. Suppose the concentration of ethanol is C eth (Unit: v / v), cleaning time is t w2 (unit: min), according to the principle of like dissolves like and the cleaning effect formula η w2 =k w2 C eth t w2 (where k w2 is the organic solvent cleaning coefficient), further improving the cleanliness of single crystal silicon powder;

[0084] After cleaning, the single crystal silicon powder is dispersed in a specific dispersant solution using ultrasonic dispersion technology, and the ultrasonic frequency is set to f ult (unit: kHz), ultrasonic power is P ult (Unit: W), according to the ultrasonic cavitation theory and dispersion effect formula (where k disp, m, n are parameters related to the dispersion system), ensuring that the single crystal silicon powder is evenly dispersed to prevent agglomeration;

[0085] The above technical solution is explained as follows: a multi-stage cleaning process is used to clean the purified single crystal silicon powder. Ultrapure water is used for preliminary cleaning. According to the cleaning efficiency formula, the chemical reagents and impurities remaining on the surface of the single crystal silicon powder can be effectively removed to ensure the cleanliness of the surface of the single crystal silicon powder. Secondly, an organic solvent such as ethanol is used for secondary cleaning. According to the principle of like dissolves like and the cleaning effect formula, the cleanliness of the single crystal silicon powder can be further improved. This multi-stage cleaning process can more thoroughly remove pollutants on the surface of the single crystal silicon powder and ensure the high purity of the single crystal silicon powder. Finally, after cleaning, ultrasonic dispersion technology is used to disperse the single crystal silicon powder in a specific dispersant solution. According to the ultrasonic cavitation theory and the dispersion effect formula, the single crystal silicon powder can be evenly dispersed to prevent agglomeration. Uniformly dispersed single crystal silicon powder is helpful for subsequent processing and application.

[0086] Drying and packaging:

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

[0088] According to the sublimation rate formula of ice (where k sub is the sublimation rate constant, E sub (sublimation activation energy) to control the drying process to ensure that the single crystal silicon powder will not agglomerate or change in structure during the drying process. The dried single crystal silicon powder is packaged in a dust-free and oxygen-free environment;

[0089] Use multi-layer composite packaging materials, and assume that the barrier performance parameter of the packaging material is P barrier (Unit: cm 3 cm / cm 2 ·s·Pa), according to the gas permeability equation (Where J gas is the gas permeation flux, ΔP is the gas pressure difference inside and outside the package, and L is the thickness of the packaging material), to ensure that the packaged single crystal 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 single crystal silicon powder, prevent agglomeration and structural changes, and ensure its quality stability during storage and transportation, thereby meeting the strict requirements of single crystal silicon powder in high-end applications.

[0091] In summary, in the present invention, precise control of the particle size of single crystal silicon powder is achieved by combining low-temperature planetary ball milling and medium stirring grinding. In the process of low-temperature planetary ball milling, the low temperature environment is used to reduce crystal defects, and the ball milling parameters are optimized according to the ball milling collision energy formula and the grinding efficiency formula to obtain finer single crystal silicon powder. Medium stirring grinding is used to further refine and homogenize the particle size of the single crystal silicon powder. By real-time monitoring of the particle size distribution and adjusting the grinding parameters, the average particle size of the final single crystal silicon powder can be accurately controlled between 0.1-1μm, which solves the problem of uneven particle size in traditional pulverization methods. In the post-processing stage, ultrasonic dispersion technology is combined with vacuum freeze-drying technology to effectively prevent the agglomeration of single crystal silicon powder. Ultrasonic dispersion technology uses cavitation to evenly disperse the single crystal silicon powder in the dispersant solution, while vacuum freeze-drying technology avoids particle agglomeration caused by water evaporation.

[0092] While the embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-purity ultrafine single crystal silicon powder processing process, characterized in that: The specific steps include: Step 1: Select single crystal silicon rods as the initial raw material, and analyze the impurity content in the raw material by secondary ion mass spectrometry (SIMS); Step 2: Pre-treat the surface of the single crystal silicon rod to remove the oxide layer and pollutants on the surface, and place the single crystal silicon rod in a hydrofluoric acid (HF) solution for chemical etching; Step 3, using high-precision multi-wire cutting equipment to cut the single crystal silicon rod into thin slices; Step 4: During the cutting process, the cutting force F and cutting speed v are monitored in real time through the online monitoring system. c , according to the formula ΔE=F·v c Δt (where ΔE is the cutting energy per unit time Δt), the thickness of the slice after cutting is t s (Unit: mm) between 0.3-0.8 mm; Step 5: Use a jaw crusher to crush the slices. Suppose the swing frequency of the movable jaw of the jaw crusher is f. j (Unit: Hz), movable jaw stroke is s j (Unit: mm), according to the crushing energy formula (where m s is the mass of single crystal silicon wafer, v j =2πf j s j is the moving speed of the moving oscillator), controls the crushing energy, and crushes the single crystal silicon wafer into particles with a size of 3-8mm; Step six, screening the particles after primary crushing by a screening machine; Step 7: Place the primary crushed single crystal silicon particles into a planetary ball mill for low temperature ball milling, and use liquid nitrogen to cool the ball milling tank to control the ball milling temperature between -50°C and 100°C; Step 8: During the ball milling process, the temperature T b and pressure P b According to the ideal gas state equation PV = nRT (where P is pressure, V is the volume of the ball mill, n is the amount of gas, R is the ideal gas constant, and T is temperature), the ball milling time t b Between 12 and 36 hours, single crystal silicon powder with an average particle size of 0.5-2 μm is finally obtained; Step nine, using a medium stirring grinding device as an auxiliary grinding means to further refine the single crystal silicon powder, using high hardness and high purity zirconia balls as grinding media, and using a laser particle size analyzer to monitor the particle size distribution of the single crystal silicon powder in real time; Step ten, using chemical vapor purification technology to remove impurities in the single crystal silicon powder.

2. A high-purity ultrafine single crystal silicon powder processing process according to claim 1, characterized in that: In step one, the impurity content includes boron, phosphorus, arsenic, iron, copper and nickel.

3. A high-purity ultrafine single crystal silicon powder processing process according to claim 1, characterized in that: In step 1, the concentration of impurity element i in single crystal silicon is C i (Unit: atoms / cm 3 ), calculate the volume based on the diameter D (unit: cm) and length L (unit: cm) of the single crystal silicon rod Then determine the mass of the single crystal silicon rod m = ρV (where ρ is the density of single crystal silicon, 2.33g / cm 3 ).

4. A high-purity ultrafine single crystal silicon powder processing process according to claim 1, characterized in that: In step 2, 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).

5. A high-purity ultrafine single crystal silicon powder processing process according to claim 1, characterized in that: In step 3, let the diameter of the cutting line be d w (unit: μm), the tension of the cutting line 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 wire and the single crystal silicon) and the material removal rate formula Q = v c h c w c (where h c is the cutting depth, w c is the cutting width).

6. A high-purity ultrafine single crystal silicon powder processing process according to claim 5, characterized in that: In step 6, according to 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 n s is the screening efficiency, N pass is the number of particles passing through the sieve, N t otal is the total number of particles) to calculate the screening efficiency.

7. A high-purity ultrafine single crystal silicon powder processing process according to claim 6, characterized in that: In step 7, the speed of the ball mill is set to n b (Unit: rpm), the diameter of the ball is d b (Unit: mm), ball-to-material ratio is R b (dimensionless), ball mill collision energy formula (where m b is the mass of the ball mill, v b =πd b n b is the ball milling ball linear velocity) and the grinding efficiency formula η b =k b R b t b (where k b is the coefficient related to the material, t b is the ball milling time).

8. A high-purity ultrafine single crystal silicon powder processing process according to claim 7, characterized in that: In step nine, the diameter of the grinding medium is assumed to be d z (Unit: mm), the speed of the stirrer 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 medium and the single crystal silicon powder) and the grinding rate formula Where m is the mass of single crystal silicon powder, k s is the grinding rate constant), controls the grinding process, and adjusts the speed n of the agitator according to the change of the particle size distribution function fd. s and grinding time t s , average particle size 0.1-1μm.

9. A high-purity ultrafine single crystal silicon powder processing process according to claim 1, characterized in that: In step 10, chemical vapor purification technology is used to remove impurities in the single crystal silicon powder, as follows: The single crystal silicon powder is placed in a high temperature reactor, and hydrogen (H2) and hydrogen halide gas are introduced. The reactor temperature is set to T CVP (Unit: °C), gas flow rates are (unit: sccm) and Q HCl (Unit: sccm); According to the chemical reaction equilibrium constant formula And the impurity removal rate formula (where m before and m after are the masses of impurities before and after purification, respectively), to control the reaction conditions; 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 the hydrogen halide gas to react with the impurities in the single crystal silicon powder and taking the generated volatile compounds out of the reaction system; The single crystal silicon powder is purified by using ion exchange resin, and the single crystal silicon powder is dispersed in a set solution so that it is fully in contact with the ion exchange resin. The exchange capacity of the ion exchange resin is Q ex (Unit: mmmol / g), the impurity ion concentration in single crystal silicon powder is C imp (Unit: mmol / L), according to the ion exchange equilibrium formula And the impurity removal formula m removed =Q ex m resin (where m resin is the quality of ion exchange resin), control the ion exchange process; By monitoring the change of impurity ion concentration in the solution, according to the formula ΔC=C0-C t (where C0 is the initial impurity ion concentration, C t is the impurity ion concentration at time t), ensuring that impurities in the single crystal silicon powder are removed through ion exchange; It also includes vacuum high temperature purification, as follows: The single crystal silicon powder after chemical vapor purification and ion exchange purification is placed in a vacuum high temperature furnace for further purification. Vacuum to pressure P vac (Unit: Pa) at 10 -4 -10 -3 Between Pa; The heating rate is r T (Unit: °C / min), heated to the treatment temperature T vac (Unit: °C), between 1000-1200 °C; According to the impurity diffusion equation (Where D is the diffusion coefficient, D0 is the diffusion constant, E a is the activation energy, R is the ideal gas constant, and T is the temperature), and the remaining impurities in the single crystal silicon powder are further removed by diffusion under high temperature and vacuum environment; Monitor the furnace temperature T through the online monitoring system vac 、Pressure P vac and the impurity concentration C in the single crystal silicon powder vac , according to the formula (where k vac is the vacuum high temperature purification reaction rate constant, n is the reaction order), controls the purification time t vac (Unit: h), between 4-8h.

10. The high-purity ultrafine single crystal silicon powder processing process according to claim 1, characterized in that: After step 10, it also includes cleaning and dispersion, as well as drying and packaging. The specific steps are as follows: Cleaning and dispersing: The purified single crystal silicon powder is cleaned using a multi-stage cleaning process. Ultrapure water is first used for preliminary cleaning. The resistivity of ultrapure water is 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 is the cleaning coefficient), to remove the chemical reagents and impurities remaining on the surface of the single crystal silicon powder; Then use an organic solvent such as ethanol for secondary cleaning. Suppose the concentration of ethanol is C eth (Unit: v / v), cleaning time is t w2 (unit: min), according to the principle of like dissolves like and the cleaning effect formula η w2 =k w2 C eth t w2 (where k w2 is the organic solvent cleaning coefficient); After cleaning, the single crystal silicon powder is dispersed in a specific dispersant solution using ultrasonic dispersion technology, and the ultrasonic frequency is set to f ult (Unit: kHz), ultrasonic power is P ult (Unit: W), according to the ultrasonic cavitation theory and dispersion effect formula (where k disp , m, n are parameters related to the dispersion system), ensuring that the single crystal silicon powder is evenly dispersed to prevent agglomeration; Drying and packaging: The dispersed single crystal silicon powder is dried and vacuum freeze-drying technology is used to freeze the single crystal silicon powder at low temperature, and then the ice is directly sublimated in a vacuum environment. The freezing temperature is T freeze (Unit: °C), vacuum degree is P freeze (Unit: Pa), drying time is t d ry (unit: h); According to the sublimation rate formula of ice (where k sub is the sublimation rate constant, E sub (sublimation activation energy) to control the drying process to ensure that the single crystal silicon powder will not agglomerate or change in structure during the drying process. The dried single crystal silicon powder is packaged in a dust-free and oxygen-free environment; Use multi-layer composite packaging materials, and assume that the barrier performance parameter of the packaging material is P barrier (Unit: cm 3 cm / cm 2 ·s·Pa), according to the gas permeability equation (Where J gas is the gas permeation flux, ΔP is the gas pressure difference inside and outside the package, and L is the thickness of the packaging material).

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