Integrated process for preparing high-purity silicon and growing monocrystalline silicon based on silane decomposition method

Abstract

The invention relates to the technical field of silicon material preparation and semiconductor process, and discloses a high-purity silicon preparation and monocrystalline silicon growth integrated process based on a silane decomposition method, which comprises the following steps: carrying out silane synthesis in a silicon carbide-lined fluidized bed reactor, separating a reaction product by a cyclone separator at the top of the reactor, and drying the reaction product; industrial silicon powder and high-purity hydrogen react under set conditions to generate silane gas, the synthesized silane gas is introduced into a three-section type vertical pyrolyzing furnace and sequentially passes through a preheating zone, a main reaction zone and a cooling zone, silane is gradually decomposed in the preheating zone and the main reaction zone to generate high-purity silicon powder, undecomposed gas is recycled after being condensed and adsorbed, and the high-purity silicon powder is obtained. High-purity silicon powder is molten in a molten silicon liquid tank, molten silicon liquid is formed through electromagnetic induction heating, the molten silicon liquid is drawn into monocrystalline silicon through a continuous straight-pulling single crystal furnace, and the growth diameter of crystals is controlled in real time through a laser range finder, so that efficient preparation of high-purity silicon and monocrystalline silicon is achieved, and the production requirement of semiconductor-grade monocrystalline silicon is met.

Description

Technical Field

[0001] The present invention relates to the field of silicon material preparation technology and semiconductor process technology, specifically to an integrated process for preparing high-purity silicon and growing single crystal silicon based on a silane decomposition method. Background Art

[0002] In the production process of high-purity silicon and single-crystal silicon, the traditional silane decomposition method has many problems. On the one hand, the recycling rate of hydrogen in the traditional process is low, resulting in high hydrogen consumption per unit, which increases production costs. It also limits the conversion rate of silicon powder, resulting in high overall energy consumption. On the other hand, the structural design of the traditional pyrolysis furnace is relatively simple, and the purity of the silane decomposition product is difficult to reach 9N level. The oxygen content of the single crystal is high, and the crystal defect rate is also relatively high, which makes it difficult to meet the production needs of semiconductor-grade and special-specification single-crystal silicon. In addition, the equipment integration level of the single crystal growth link in the traditional process is low, the crystal diameter tolerance is large, the material utilization rate is low, the production cost is high, and efficient and stable single-crystal silicon production cannot be achieved. Summary of the Invention

[0003] (1) Technical problems solved

[0004] In response to the shortcomings of the existing technology, the present invention provides an integrated process for preparing high-purity silicon and growing single crystal silicon based on the silane decomposition method, which has the advantages of efficient recycling of hydrogen, stable preparation of high-purity silicon materials, integrated integration and precise diameter control. It solves the problems of low hydrogen recycling rate, insufficient purity of silane decomposition products, low equipment integration in the single crystal growth link, large crystal diameter tolerance, low material utilization rate and high production cost in traditional processes.

[0005] (2) Technical solution

[0006] To achieve the above objectives, the present invention provides the following technical solution: an integrated process for preparing high-purity silicon and growing single crystal silicon based on a silane decomposition method, comprising the following steps:

[0007] Step 1: Silane synthesis: Silane synthesis is carried out in a fluidized bed reactor lined with silicon carbide using a double-layer gas distribution plate and a 30° cone section structure. A cyclone separator is installed on the top of the reactor to separate the reaction products. Industrial silicon powder is then reacted with high-purity hydrogen under set conditions to generate silane gas.

[0008] Step 2: Silane graded pyrolysis: The synthesized silane gas is introduced into a three-stage vertical pyrolysis furnace and sequentially passes through the preheating zone, main reaction zone, and cooling zone. In the preheating zone and main reaction zone, the silane is gradually decomposed to produce high-purity silicon powder. The undecomposed gas is condensed and adsorbed and then recycled;

[0009] Step 3: Single crystal growth integration: High-purity silicon powder is melted in a molten silicon liquid tank, heated by electromagnetic induction to form molten silicon liquid, and a continuous vertical single crystal pulling furnace is used to pull the molten silicon liquid into single crystal silicon. The crystal growth diameter is controlled in real time by a laser rangefinder.

[0010] Preferably, the industrial silicon powder in step 1 has a particle size of 100-200 mesh, a particle diameter of 75-150 μm, contains Fe ≤ 30 ppm, and contains Al ≤ 20 ppm.

[0011] Preferably, the purity of hydrogen in step 1 is ≥99.9999% and its dew point is <-70°C.

[0012] Preferably, the setting conditions of the silane synthesis reaction in step 1 are: temperature 300-450°C, pressure 0.5-1.2 MPa, silicon powder conversion rate ≥85%, silane yield ≥89%, and the chemical reaction formula in the process is:

[0013] Si+2H2→SiH4

[0014] In the formula, industrial silicon powder and high-purity hydrogen react in a fluidized bed reactor at 300-450°C and 0.5-1.2MPa to generate silane. The reactor is equipped with a double-layer gas distribution plate and a 30° cone section.

[0015] Preferably, in the step 2, silane is graded and pyrolyzed: the silane gas passes through a 500-600° C. preheating zone, a 700-800° C. main reaction zone, and a 300-400° C. cooling zone to decompose and obtain 9N grade silicon powder.

[0016] Preferably, the parameters of the preheating zone in step 2 are: the porosity of the honeycomb ceramic filler is 75% to 80%, the temperature of the preheating zone is 500-600°C, and the silane decomposition rate is 10% to 15%. The chemical reaction formula in this process is:

[0017] SiH4→Si+2H2

[0018] In the formula, the decomposition rate of silane reaches 10% to 15% under the temperature condition of 500-600℃;

[0019] The parameters of the main reaction zone are: the roughness of the inner wall of the quartz glass furnace tube Ra ≤ 0.8μm, the pitch of the built-in spiral guide plate is 200-300mm, and the angle is 45°; the temperature of the main reaction zone is 700-800℃, and the decomposition rate is 80% to 85%. The chemical reaction formula in this process is:

[0020] SiH4→Si+2H2

[0021] In the formula, in the main reaction zone of the vertical pyrolysis furnace, the furnace tube is made of quartz glass, and the inner wall roughness is controlled at Ra≤0.8μm. In this main reaction zone, when the temperature is maintained at 700-800℃, the residence time of silane gas is 12-15 seconds, so that the silane decomposition rate reaches 80%-85%.

[0022] Preferably, the cooling zone parameters in step 2 are: diameter of the variable cross-section Φ300-500mm, and cooling zone temperature 300-400°C.

[0023] Preferably, the working process of the circulation system in step 2 is as follows: in the circulation system, the undecomposed gas is first condensed at a temperature below -10°C, then adsorbed by a molecular sieve, and finally returned to the reactor to continue to participate in the reaction. This process makes the recycling rate of hydrogen ≥95%, and at the same time controls the content of silane in the circulating gas so that it does not exceed 0.5%. In the silane synthesis stage, the molar ratio of hydrogen to silicon is maintained in the range of 8-12:1.

[0024] Preferably, in step 3, the high-purity silicon powder is injected into the single crystal furnace through a double-layer quartz tube after being melted in the molten silicon liquid tank. The outer layer of the quartz tube is provided with a spiral cooling water trough with a flow rate controlled at 5-8 L / min. The molten silicon liquid tank is heated by electromagnetic induction with a power of 50-100 kW and a frequency of 20-50 kHz, and is equipped with a double-layer quartz tube assembly, the inner layer of which has a diameter of Φ30 mm, a wall thickness of 3 mm, and a 15° groove at the outlet; the outer layer is a spiral cooling water trough;

[0025] The parameters of the continuous Czochralski single crystal furnace in step 3 are: the power density of the three-stage graphite heater is 15-20kW / m², the rotation speed of the magnetic fluid sealed seed crystal rod is 0-15rpm, and the accuracy of the laser rangefinder is ±0.05mm, and real-time control is performed.

[0026] Preferably, the process parameters for the single crystal growth integrated reaction in step 3 are: melting temperature 1300-1500° C., nitrogen pressure 0.05-0.1 MPa, and pressure fluctuation value ±0.002 MPa;

[0027] During the growth of the single crystal, the melting zone temperature is 1420±10°C, the growth zone temperature gradient is 5-8°C / cm, the pulling speed is 0.5-2 mm / min, and the crystal oxygen content is less than 3×10 16 atoms / cm³.

[0028] Compared with the prior art, the present invention provides an integrated process for preparing high-purity silicon and growing single crystal silicon based on silane decomposition, which has the following beneficial effects:

[0029] 1. The present invention achieves energy efficiency improvement through the coordinated design of a hydrogen circulation system and high-efficiency reaction equipment. By adopting a fluidized bed reactor with a double-layer gas distribution plate lined with silicon carbide and a 30° cone-segment structure and a three-stage vertical pyrolysis furnace with spiral guide plates and a variable-section cooling zone, combined with an unreacted gas condensation and adsorption circulation system, the hydrogen circulation utilization rate is greater than 95%. This not only reduces the unit hydrogen consumption, but also increases the silicon powder conversion rate, significantly reducing its overall energy consumption, while also reducing raw material waste and emissions.

[0030] 2. This invention achieves the stable preparation of high-purity silicon materials through graded pyrolysis and impurity control technology. By using a three-stage pyrolysis furnace with zoned temperature control, combined with a quartz glass furnace tube and spiral guide plates, and strictly controlling the Fe / Al content in the silicon powder, the purity of the silane decomposition product reaches 9N level, the oxygen content of the single crystal is reduced, and the crystal defect rate is reduced.

[0031] 3. This invention improves material utilization and product stability through an integrated process and precise diameter control technology. By directly connecting the molten silicon tank to the continuous Czochralski single crystal pulling furnace and equipping it with a laser rangefinder and a magnetic fluid-sealed seed crystal rod, the crystal diameter tolerance is reduced. This improves material utilization, reduces production costs, and significantly reduces the diameter tolerance of the final product, thus meeting the requirements of semiconductor-grade to special specifications. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a process flow chart of the present invention;

[0033] Figure 2 This is the structure of the fluidized bed reactor of the present invention. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] See also Figure 1-Figure 2 The integrated process for preparing high-purity silicon and growing single crystal silicon based on silane decomposition method includes the following steps:

[0036] Step 1: Silane synthesis (fluidized bed reaction): Silane synthesis is carried out in a fluidized bed reactor lined with silicon carbide using a double-layer gas distribution plate and a 30° cone section structure. A cyclone separator is installed on the top of the reactor to separate the reaction products. Industrial silicon powder is then reacted with high-purity hydrogen under set conditions to generate silane gas.

[0037] Step 2: Silane graded pyrolysis (vertical pyrolysis furnace): The synthesized silane gas is introduced into a three-stage vertical pyrolysis furnace and passes through the preheating zone, main reaction zone, and cooling zone in sequence. In the preheating zone and main reaction zone, the silane is gradually decomposed to produce high-purity silicon powder. The undecomposed gas is condensed and adsorbed and then recycled;

[0038] Step 3: Single crystal growth integration: High-purity silicon powder is melted in a molten silicon liquid tank, heated by electromagnetic induction to form molten silicon liquid, and then pulled into single crystal silicon using a continuous vertical single crystal pulling furnace. The crystal growth diameter is controlled in real time using a laser rangefinder to ensure the quality of the single crystal silicon.

[0039] The advantages are: the present invention improves material utilization and product stability through integrated integration process and precise diameter control technology. It directly connects the molten silicon liquid tank to the continuous vertical pulling single crystal furnace, and is equipped with a laser rangefinder and a magnetic fluid sealed seed crystal rod, which effectively reduces the crystal diameter tolerance, improves material utilization, and reduces production costs. The diameter tolerance of the final product is greatly reduced, thereby meeting the production needs of single crystal silicon from semiconductor grade to special specifications.

[0040] Specifically, in step 1, the industrial silicon powder has a particle size of 100-200 mesh, a particle diameter of 75-150 μm, contains Fe ≤ 30 ppm, and contains Al ≤ 20 ppm.

[0041] Specifically, in step 1, the purity of hydrogen is ≥99.9999%, its dew point is <-70°C, and its hydrogen-to-silicon ratio (H2 / Si molar ratio) is between 8-12:1.

[0042] Specifically, the silane synthesis reaction conditions in step 1 are: temperature 300-450°C, pressure 0.5-1.2 MPa, silicon powder conversion rate ≥85%, silane yield ≥89%. The chemical reaction formula in this process is:

[0043] Si+2H2→SiH4

[0044] In the formula, industrial silicon powder and high-purity hydrogen react in a fluidized bed reactor at 300-450°C and 0.5-1.2MPa to produce silane. The reactor is equipped with a double-layer gas distribution plate (upper layer aperture 0.5mm, lower layer aperture 1.0mm) and a 30° cone section.

[0045] Specifically, in step 2, silane is graded and pyrolyzed: the silane gas passes through a 500-600°C preheating zone, a 700-800°C main reaction zone (with a built-in spiral guide plate and a pitch of 200-300mm), and a 300-400°C cooling zone to decompose and obtain 9N grade silicon powder.

[0046] Specifically, the parameters of the preheating zone in step 2 are: the porosity of the honeycomb ceramic filler is 75% to 80%, the preheating zone temperature is 500-600°C, and the silane decomposition rate is 10% to 15%. The chemical reaction formula in this process is:

[0047] SiH4→Si+2H2

[0048] In the formula, the decomposition rate of silane reaches 10% to 15% under the temperature condition of 500-600℃.

[0049] Specifically, the parameters of the main reaction zone in step 2 are: the inner wall roughness of the quartz glass furnace tube Ra ≤ 0.8 μm, the pitch of the built-in spiral guide plate is 200-300 mm, and the angle is 45°; the temperature of the main reaction zone is 700-800°C, and the decomposition rate is 80% to 85%. The chemical reaction formula in this process is:

[0050] SiH4→Si+2H2

[0051] In the formula, in the main reaction zone of the vertical pyrolysis furnace, the furnace tube is made of quartz glass, and the inner wall roughness is controlled at Ra≤0.8μm. In this main reaction zone, when the temperature is maintained at 700-800℃, the residence time of silane gas is 12-15 seconds, so that the silane decomposition rate reaches 80%-85%.

[0052] Specifically, the cooling zone parameters in step 2 are: a variable cross-section diameter of Φ300-500 mm, a cooling zone temperature of 300-400° C.; and a polytetrafluoroethylene bag dust collector with a collection efficiency of ≥99.9%.

[0053] Specifically, the working process of the circulation system in step 2 is as follows: in the circulation system, the undecomposed gas is first condensed at a temperature below -10°C, then adsorbed by a molecular sieve, and finally returned to the reactor to continue participating in the reaction. This process makes the recycling rate of hydrogen ≥95%, and at the same time controls the content of silane in the circulating gas so that it does not exceed 0.5%. In the silane synthesis stage, the molar ratio of hydrogen to silicon (H2 / Si) is maintained in the range of 8-12:1 to ensure the efficient progress of the reaction.

[0054] The advantages are: energy efficiency is improved through the coordinated design of the hydrogen circulation system and high-efficiency reaction equipment. By adopting a fluidized bed reactor with a double-layer gas distribution plate lined with silicon carbide + a 30° cone-segment structure and a three-stage vertical pyrolysis furnace with a spiral guide plate + a variable-section cooling zone, combined with an unreacted gas condensation adsorption circulation system, the hydrogen circulation utilization rate is greater than 95%, which not only reduces the unit consumption of hydrogen, but also increases the silicon powder conversion rate, greatly reduces its overall energy consumption, and at the same time reduces raw material waste and emissions.

[0055] Specifically, in step 3, the high-purity silicon powder is melted in the molten silicon liquid tank and injected into the single crystal furnace through a double-layer quartz tube. The outer layer of the quartz tube is provided with a spiral cooling water trough with a flow rate control of 5-8 L / min. The molten silicon liquid tank is heated by electromagnetic induction with a power of 50-100 kW and a frequency of 20-50 kHz, and is equipped with a double-layer quartz tube assembly with an inner tube diameter of Φ30 mm, a wall thickness of 3 mm, and a 15° groove at the outlet; the outer layer is a spiral cooling water trough; the parameters of the continuous vertical single crystal pulling furnace are: the power density of the three-stage graphite heater is 15-20 kW / m², the rotation speed of the magnetic fluid sealed seed crystal rod is 0-15 rpm, and the accuracy of the laser rangefinder is ±0.05 mm, for real-time control.

[0056] The advantages are: through graded pyrolysis and impurity control technology, stable preparation of high-purity silicon materials is achieved. Through zoned temperature control of the three-stage pyrolysis furnace, combined with quartz glass furnace tubes and spiral guide plates, and strict control of the Fe / Al content in the silicon powder, the purity of the silane decomposition product reaches 9N level, the oxygen content of the single crystal is reduced, and the crystal defect rate is reduced.

[0057] Specifically, the process parameters for the integrated reaction of single crystal growth in step 3 are as follows: melting temperature 1300-1500°C, nitrogen pressure 0.05-0.1 MPa, and pressure fluctuation value ±0.002 MPa; melting zone temperature 1420±10°C during single crystal growth, growth zone temperature gradient 5-8°C / cm, pulling speed 0.5-2 mm / min, crystal oxygen content <3×10 16 atoms / cm³.

[0058] The advantages are: through integrated integration process and precise diameter control technology, the material utilization rate and product stability are improved. The molten silicon liquid tank is directly connected to the continuous vertical single crystal furnace, equipped with a laser rangefinder and a magnetic fluid sealed seed crystal rod to reduce the crystal diameter tolerance, thereby improving material utilization, reducing production costs, and significantly reducing the diameter tolerance of the final product, thereby meeting the requirements of semiconductor level to special specifications.

[0059] The process of the present invention was tested against the traditional Siemens method and the conventional silane method, and the following test data were obtained:

[0060] Table 1

[0061] index Process of the present invention Traditional Siemens method Conventional silane method Test standards Hydrogen recycling rate 95.2% (±0.8%) 32.5% (±2.1%) 68.7% (±1.5%) GB / T 34537-2017 Comprehensive energy consumption 28 kWh / kg-Si 65 kWh / kg-Si 48 kWh / kg-Si SEMI PV22-0812 Silicon powder conversion rate 89.3% (±1.2%) - 72.5% (±2.0%) ASTM E1941-2018 Pyrolysis energy consumption 9.8 MJ / kg-Si 22.4 MJ / kg-Si 15.6 MJ / kg-Si ISO 16948:2015 Hydrogen replenishment amount 4.3 Nm³ / kg-Si 18.7 Nm³ / kg-Si 9.2 Nm³ / kg-Si GB / T 34542-2017

[0062] As shown in Table 1, the process of the present invention is superior to the traditional Siemens method and the conventional silane method in many key indicators. In terms of hydrogen recycling rate, the present invention reaches 95.2% (±0.8%), far exceeding the 32.5% (±2.1%) of the traditional Siemens method and 68.7% (±1.5%) of the conventional silane method; the comprehensive energy consumption is only 28 kWh / kg-Si, which is significantly lower than the 65 kWh / kg-Si of the traditional Siemens method and 48 kWh / kg-Si of the conventional silane method; the silicon powder conversion rate is as high as 89.3% (±1.2%), which is better than the 72.5% (±2.0%) of the conventional silane method; the pyrolysis energy consumption is 9.8 MJ / kg-Si, which is lower than the 22.4 MJ / kg-Si of the traditional Siemens method and 15.6 MJ / kg-Si of the conventional silane method; the hydrogen supplement amount is only 4.3 Nm³ / kg-Si, which is significantly less than 18.7 Nm³ / kg-Si of the traditional Siemens method and 9.2 Nm³ / kg-Si of the conventional silane method. In summary, the process of the present invention has obvious advantages in resource utilization efficiency and energy consumption control, and has higher economic benefits and technical competitiveness.

[0063] Example 1 (Production of Semiconductor-Grade Single Crystal Silicon)

[0064] S1. Silane synthesis: 200 kg of industrial silicon powder (150 mesh, Fe = 25 ppm) was added to a fluidized bed reactor, and 99.9999% hydrogen (hydrogen:silicon ratio 10:1) was introduced. The reaction was maintained at 400°C and 0.8 MPa for 6 hours. The silane yield was 89%. Unreacted silicon powder was recovered by a cyclone separator (recovery rate 98%).

[0065] S2, Silane graded pyrolysis: Silane gas passes through the 580℃ preheating zone (staying for 8s, decomposition rate 13%), the 760℃ main reaction zone (staying for 15s, turbulence intensity N under the action of spiral guide plate) in sequence. t =2.5, decomposition rate 83%), 350℃ cooling zone, 9N grade silicon powder (particle size 2μm) was obtained, and the bag dust collector collection efficiency was 99.95%;

[0066] S3, Single crystal growth: Silicon powder is heated to 1480℃ by electromagnetic induction and melted. It is then injected into the single crystal furnace through a double-layer quartz tube under nitrogen pressure (0.08MPa). The oxygen content in the melting zone is 0.8ppma.

[0067] The crystal pulling parameters are: crystal orientation <100>, pulling speed 1.2mm / min, solid-liquid interface temperature gradient 6℃ / cm, finished product diameter 300mm (tolerance ±0.08mm), resistivity 1200Ω・cm, and compliance with SEMI standards.

[0068] Example 2 (Photovoltaic-grade monocrystalline silicon production)

[0069] S1. Silane synthesis: 180 kg of industrial silicon powder (120 mesh, Fe = 28 ppm) was added to a fluidized bed reactor, and 99.9999% hydrogen (hydrogen-silicon ratio 9:1) was introduced. The reaction was maintained at 380°C and 0.7 MPa for 7 hours. The silane yield was 88%. Unreacted silicon powder was recovered by a cyclone separator (recovery rate 97.5%).

[0070] S2, Silane Graded Pyrolysis: Silane gas passes through a 560°C preheating zone (residence time 7 seconds, decomposition rate 12%), a 740°C main reaction zone (residence time 14 seconds, turbulence intensity Nt = 2.3 under the action of spiral guide plates, decomposition rate 82%), and a 330°C cooling zone, obtaining 9N grade silicon powder (particle size 2.2 μm). The bag filter collection efficiency is 99.9%;

[0071] S3, Single crystal growth: Silicon powder is heated to 1450℃ by electromagnetic induction and melted. It is then injected into the single crystal furnace through a double-layer quartz tube under nitrogen pressure (0.07MPa). The oxygen content in the melting zone is 0.9ppma.

[0072] The crystal pulling parameters are: crystal orientation <111>, pulling speed 1.0mm / min, solid-liquid interface temperature gradient 5.5℃ / cm, finished product diameter 200mm (tolerance ±0.07mm), and resistivity 800Ω・cm, which meet photovoltaic industry standards.

[0073] Example 3 (Production of Monocrystalline Silicon of Special Specifications)

[0074] S1. Silane synthesis: 220 kg of industrial silicon powder (180 mesh, Fe = 23 ppm) was added to a fluidized bed reactor, and 99.9999% hydrogen (hydrogen-silicon ratio 11:1) was introduced. The reaction was maintained at 420°C and 0.9 MPa for 5.5 hours, resulting in a silane yield of 90%. Unreacted silicon powder was recovered by a cyclone separator (recovery rate 98.5%).

[0075] S2, Silane Graded Pyrolysis: Silane gas passes through a 600°C preheating zone (residence time 9 seconds, decomposition rate 14%), a 780°C main reaction zone (residence time 16 seconds, turbulence intensity Nt = 2.7 under the action of spiral guide plates, decomposition rate 84%), and a 370°C cooling zone, producing 9N grade silicon powder (particle size 1.8 μm). The bag filter collection efficiency is 99.98%.

[0076] S3, Single crystal growth: Silicon powder is heated to 1500℃ by electromagnetic induction and melted. It is then injected into the single crystal furnace through a double-layer quartz tube under nitrogen pressure (0.09MPa). The oxygen content in the melting zone is 0.7ppma.

[0077] The crystal pulling parameters are: crystal orientation <100>, pulling speed 1.5mm / min, solid-liquid interface temperature gradient 7℃ / cm, finished product diameter 150mm (tolerance ±0.06mm), and resistivity 1300Ω・cm, meeting special application requirements.

[0078] Comparative Example 1 (Traditional Process Reference)

[0079] S1. Silane synthesis: A conventional fluidized bed reactor was used. 200 kg of industrial silicon powder (150 mesh, Fe = 25 ppm) was added, and 99.99% hydrogen (hydrogen-silicon ratio 8:1) was introduced. The reaction was maintained at 400°C and 0.8 MPa for 6 hours. The silane yield was 75%. No high-efficiency recovery device was installed.

[0080] S2. Silane pyrolysis: Using a single-stage pyrolysis furnace, silane gas reacts at 700°C, the purity of silicon powder only reaches 6N level, and there is no gas circulation system;

[0081] S3. Single crystal growth: conventional equipment is used, the melting temperature of silicon powder is 1400℃, the crystal pulling process fluctuates greatly, the finished product diameter is 300mm (tolerance ±0.3mm), the oxygen content is 8×10 16 atoms / cm³, resistivity 600Ω・cm.

[0082] Comparative Example 2 (parameter deviation control)

[0083] S1. Silane synthesis: 200 kg of industrial silicon powder (150 mesh, Fe = 25 ppm) was added to a fluidized bed reactor, and 99.9999% hydrogen (hydrogen-silicon ratio 6:1) was introduced. The reaction was maintained at 300°C and 0.5 MPa for 6 hours. The silane yield was 78% and the silicon powder conversion rate was 70%.

[0084] S2, Silane graded pyrolysis: preheating zone temperature 450 ° C, main reaction zone temperature 650 ° C, silane decomposition rate is low, silicon powder purity 7N grade;

[0085] S3, single crystal growth: melting temperature 1300℃, pulling speed 2.5mm / min, the crystal has many defects, oxygen content 7×10 16 atoms / cm³, resistivity 700Ω・cm.

[0086] Comparative Example 3 (Simplified Equipment Comparison)

[0087] S1. Silane synthesis: A single-layer gas distribution plate fluidized bed reactor was used. 200 kg of industrial silicon powder (150 mesh, Fe = 25 ppm) was added, and 99.9999% hydrogen (hydrogen-silicon ratio 10:1) was introduced. The reaction was maintained at 400°C and 0.8 MPa for 6 hours. The silane yield was 82%, and the gas-solid contact efficiency was low.

[0088] S2, Silane graded pyrolysis: The main reaction zone is not equipped with spiral guide plates, the silane decomposition rate is 75%, and the silicon powder purity is 8N grade;

[0089] S3, single crystal growth: double-layer quartz tube assembly was not used, silicon liquid flow was unstable, finished product diameter was 300mm (tolerance ±0.2mm), oxygen content was 6×10 16 atoms / cm³, resistivity 850Ω・cm.

[0090] The embodiment and the comparative example were compared and tested, and the test data are shown in Table 1 below:

[0091] Table 1

[0092]

[0093] This process is tested in Table 1 by comparing Examples 1-3 with Comparative Examples 1-3, and the following information is obtained:

[0094] (1) In terms of process design, the embodiment adopts a fluidized bed reactor lined with silicon carbide, a three-stage vertical pyrolysis furnace and a matching continuous vertical single crystal pulling furnace. By optimizing the innovative design of the double-layer gas distribution plate and the spiral guide plate, efficient gas-solid contact and sufficient decomposition of silane are achieved. However, the comparative example 1 adopts traditional equipment and the comparative example 3 simplifies the equipment structure, resulting in low gas-solid contact efficiency and insufficient silane decomposition rate. The comparative example 2 deviates from the key process parameters, which greatly reduces the overall process performance.

[0095] (2) From the perspective of performance indicators, the hydrogen recycling rate of the examples exceeded 95%, the comprehensive energy consumption was reduced by 40%, the silicon powder conversion rate reached 88% to 90%, the purity of the silane decomposition product was stable at 9N level, and the oxygen content of the single crystal was less than 5×10 16 atoms / cm³, with a maximum resistivity of 1300Ω・cm and a crystal diameter tolerance of ±0.06-±0.08mm, far exceeding the comparative examples. Comparative Example 1 lacked a circulation system and efficient recovery equipment, resulting in high energy consumption and low silicon powder conversion rate. Comparative Example 2 experienced increased crystal defects due to improper parameters such as temperature and ratio. Comparative Example 3's simplified equipment resulted in insufficient purity and stability.

[0096] (3) In terms of economic benefits, the embodiment eliminates the polysilicon crushing and cleaning processes through integrated design, increases the material utilization rate from 80% to 98%, and reduces the production cost by 25% to 30%. However, the comparison example still maintains the traditional production model, and the cost remains high.

[0097] In summary, the integrated process of the present invention has achieved comprehensive breakthroughs in energy efficiency, purity, process and equipment, and has obvious technological advancement and industrial application value.

[0098] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. An integrated process for preparing high-purity silicon and growing single crystal silicon based on silane decomposition method, characterized in that: The following steps are involved: Step 1: Silane synthesis: Silane synthesis is carried out in a fluidized bed reactor lined with silicon carbide using a double-layer gas distribution plate and a 30° cone section structure. A cyclone separator is installed on the top of the reactor to separate the reaction products. Industrial silicon powder is then reacted with high-purity hydrogen under set conditions to generate silane gas. Step 2: Silane graded pyrolysis: The synthesized silane gas is introduced into a three-stage vertical pyrolysis furnace and sequentially passes through the preheating zone, main reaction zone, and cooling zone. In the preheating zone and main reaction zone, the silane is gradually decomposed to produce high-purity silicon powder. The undecomposed gas is condensed and adsorbed and then recycled; Step 3: Single crystal growth integration: High-purity silicon powder is melted in a molten silicon liquid tank, heated by electromagnetic induction to form molten silicon liquid, and a continuous vertical single crystal pulling furnace is used to pull the molten silicon liquid into single crystal silicon. The crystal growth diameter is controlled in real time by a laser rangefinder.

2. The integrated process for preparing high-purity silicon and growing single crystal silicon based on silane decomposition according to claim 1, characterized in that: The industrial silicon powder in step 1 has a particle size of 100-200 mesh, a particle diameter of 75-150 μm, contains Fe ≤ 30 ppm, and contains Al ≤ 20 ppm.

3. The integrated process for preparing high-purity silicon and growing single crystal silicon based on silane decomposition according to claim 1, characterized in that: In the step 1, the purity of hydrogen is ≥99.9999% and its dew point is <-70°C.

4. The integrated process for preparing high-purity silicon and growing single crystal silicon based on silane decomposition according to claim 1, characterized in that: The setting conditions of the silane synthesis reaction in step 1 are: temperature 300-450°C, pressure 0.5-1.2MPa, silicon powder conversion rate ≥85%, silane yield ≥89%. The chemical reaction formula in this process is: Si+2H2→SiH4 In the formula, industrial silicon powder and high-purity hydrogen react in a fluidized bed reactor at 300-450°C and 0.5-1.2MPa to generate silane. The reactor is equipped with a double-layer gas distribution plate and a 30° cone section.

5. The integrated process for preparing high-purity silicon and growing single crystal silicon based on silane decomposition according to claim 1, characterized in that: In the step 2, the silane is graded and pyrolyzed: the silane gas passes through a preheating zone at 500-600° C., a main reaction zone at 700-800° C., and a cooling zone at 300-400° C. to decompose and obtain 9N grade silicon powder.

6. The integrated process for preparing high-purity silicon and growing single crystal silicon based on silane decomposition according to claim 1, characterized in that: The parameters of the preheating zone in step 2 are: the porosity of the honeycomb ceramic filler is 75% to 80%, the temperature of the preheating zone is 500-600°C, and the silane decomposition rate is 10% to 15%. The chemical reaction formula in this process is: SiH4→Si+2H2 In the formula, the decomposition rate of silane reaches 10% to 15% under the temperature condition of 500-600℃; The parameters of the main reaction zone are: the roughness of the inner wall of the quartz glass furnace tube Ra ≤ 0.8μm, the pitch of the built-in spiral guide plate is 200-300mm, and the angle is 45°; the temperature of the main reaction zone is 700-800℃, and the decomposition rate is 80% to 85%. The chemical reaction formula in this process is: SiH4→Si+2H2 In the main reaction zone of the vertical pyrolysis furnace, the furnace tube is made of quartz glass, and the inner wall roughness is controlled at Ra≤0.8μm. In this main reaction zone, when the temperature is maintained at 700-800℃, the residence time of silane gas is 12-15 seconds, so that the silane decomposition rate reaches 80%-85%.

7. The integrated process for preparing high-purity silicon and growing single crystal silicon based on silane decomposition according to claim 1, characterized in that: The parameters of the cooling zone in step 2 are: the diameter of the variable cross-section is Φ300-500mm, and the temperature of the cooling zone is 300-400°C.

8. The integrated process for preparing high-purity silicon and growing single crystal silicon based on silane decomposition according to claim 1, characterized in that: The circulation system workflow in step 2 is as follows: In the circulation system, the undecomposed gas is first condensed at a temperature below -10°C, then adsorbed by a molecular sieve, and finally returned to the reactor to continue the reaction. This process ensures a hydrogen recycling rate of ≥95%. At the same time, the silane content in the circulating gas is controlled to not exceed 0.5%. During the silane synthesis stage, the molar ratio of hydrogen to silicon is maintained in the range of 8-12:

1.

9. The integrated process for preparing high-purity silicon and growing single crystal silicon based on silane decomposition according to claim 1, characterized in that: In step 3, the high-purity silicon powder is melted in the molten silicon liquid tank and then injected into the single crystal furnace through a double-layer quartz tube. The outer layer of the quartz tube is provided with a spiral cooling water trough with a flow rate controlled at 5-8 L / min. The molten silicon liquid tank is heated by electromagnetic induction with a power of 50-100 kW and a frequency of 20-50 kHz. It is equipped with a double-layer quartz tube assembly, the inner tube diameter is Φ30 mm, the wall thickness is 3 mm, and the outlet is provided with a 15° groove; the outer layer is a spiral cooling water trough; The parameters of the continuous Czochralski single crystal furnace in step 3 are: the power density of the three-stage graphite heater is 15-20kW / m², the rotation speed of the magnetic fluid sealed seed crystal rod is 0-15rpm, and the accuracy of the laser rangefinder is ±0.05mm, and real-time control is performed.

10. The integrated process for preparing high-purity silicon and growing single crystal silicon based on silane decomposition according to claim 1, characterized in that: The process parameters for the single crystal growth integrated reaction in step 3 are: a melting temperature of 1300-1500° C., a nitrogen pressure of 0.05-0.1 MPa, and a pressure fluctuation of ±0.002 MPa; During the growth of the single crystal, the melting zone temperature is 1420±10°C, the growth zone temperature gradient is 5-8°C / cm, the pulling speed is 0.5-2 mm / min, and the crystal oxygen content is less than 3×10 16 atoms / cm³.

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