Method for simultaneously drawing multiple crystal bars

Abstract

A method for simultaneously drawing a plurality of crystal bars relates to the field of artificial crystal preparation, and comprises the steps of material loading, material melting, slag extraction, welding and seeding, shouldering, equal-diameter growth, crystal extraction, re-feeding and the like, more than 20 cylindrical silicon cores with the diameter of more than 8mm can be simultaneously produced at a time, the obtained silicon cores can be directly used for a polycrystalline silicon reduction furnace, and the production cost is reduced. The high-purity cylindrical silicon core can be drawn at the same time without stopping the furnace, the production efficiency is high, the resistivity of the head and the tail of the produced silicon core is stable, the uniformity of the head and the tail of the diameter of the silicon core is good, and meanwhile, external impurities are not introduced into the silicon core, so that a plurality of high-purity cylindrical silicon cores can be drawn at the same time without stopping the furnace; and meanwhile, the produced silicon core does not need to be subjected to cutting processing and pickling operation, can be directly used for growth of a high-purity polycrystalline silicon raw material, and has the characteristics of lower cost, higher efficiency and the like.

Description

Technical Field

[0001] The present invention relates to the field of artificial crystal preparation, and specifically relates to a method for simultaneously pulling multiple crystal rods. Background Art

[0002] It is known that in the field of artificial crystal preparation, how to improve the pulling efficiency of crystal rods and make them meet the usage requirements is one of the key technologies. Taking the preparation of poly / single crystal silicon as an example, during the entire production process of poly / single crystal silicon, the consumption of columnar silicon cores with a diameter of 8 mm to 12 mm is very large. In the actual production process, it is found that the waste materials generated during the preparation of columnar silicon cores, the accidentally broken silicon cores, and the scraps generated by poly / single crystal silicon production enterprises in the processes such as cutting and crushing are very cumbersome to handle. Many enterprises, for the sake of convenience, directly discard the above-mentioned scraps or store them in the warehouse for a long time. There are also some enterprises that recycle the above-mentioned scraps, pull them into silicon rods through a Czochralski furnace, and then cut the silicon rods into a plurality of columnar silicon rods with dimensions of 8 mm * 8 mm or 10 mm * 10 mm by a multi-wire cutting machine. Using this method, multiple silicon cores can be cut from one large-diameter single crystal silicon rod. However, it takes about 3 days to pull one large-diameter silicon rod, and there is a large material loss during the cutting process. Impurities will inevitably be introduced during the cutting process, affecting the purity of the silicon cores, and the stress generated during cutting will also remain in the silicon cores, thus affecting the quality of the produced high-purity polycrystalline silicon raw materials. Therefore, how to recycle the broken silicon materials has become a long-term technical demand of those skilled in the art.

[0003] In order to solve the above technical problems, those skilled in the art put the broken silicon materials into a crucible. After the silicon materials in the crucible are melted into a molten liquid, the upper shaft drives the seed crystal clamping device to descend. When the lower end of the seed crystal clamped on the seed crystal clamping device contacts and melts with the molten liquid, the upper shaft drives the seed crystal clamping device to ascend. When the molten liquid follows the seed crystal to ascend and gradually begins to solidify as the temperature decreases, a new columnar crystal rod formed at this time is the required silicon core. When pulling the crystal rod, choosing a suitable pulling process method is one of the key technologies, that is, how to achieve simultaneous pulling of multiple cylindrical silicon cores without stopping the furnace; at the same time, how to ensure that the produced silicon cores do not require further cutting and pickling operations, thereby reducing the production cost of enterprises and improving the production efficiency of enterprises are technical problems that those skilled in the art urgently need to solve.

[0004] In summary, how to provide a method for simultaneously pulling multiple crystal rods has become a long-term technical demand of those skilled in the art. Summary of the Invention

[0005] In order to overcome the deficiencies in the background art, the present invention provides a method for simultaneously pulling multiple crystal bars. The present invention can realize the simultaneous pulling of multiple high-purity cylindrical silicon cores without stopping the furnace. The produced silicon cores do not need to be cut and pickled, and can be directly used for the growth of high-purity polysilicon raw materials, with the characteristics of lower cost and higher efficiency, etc.

[0006] To achieve the above-mentioned invention object, the present invention adopts the following technical solutions: A method for simultaneously pulling multiple crystal bars, the method specifically includes the following steps: The first step, loading materials: Load silicon materials into the crucible, install multiple single crystal seeds on the upper crystal bar lifting device, and the upper lifting steel wire rope drives the crystal bar lifting device to perform up and down movements. After closing the furnace, evacuate and detect leaks. The second step, melting materials: Simultaneously turn on the side heater and the lower heater or turn on the side heater and the lower heater at intervals. Turn on the lower shaft rotation mechanism to drive the crucible to rotate, uniformly melt the silicon materials into a molten liquid, and after all are melted, reduce the power of the side heater to the seeding power. The third step, removing slag: Synchronously lower the seed crystal and the crystal cooling mechanism, so that the surface impurities are welded to the bottom of the seed crystal. Adjust the power of the side heater to gradually crystallize the surface of the molten zone. After reaching a suitable diameter, lift out the crystallized impurities. The fourth step, melting and seeding: Adjust the power of the side heater, measure the liquid surface temperature of the molten liquid by the CCD imaging system. When the liquid surface temperature reaches the welding temperature, turn on the rotation motor on the crystal bar lifting device to make the seed crystal rotate. Lower the seed crystal to contact the surface of the molten liquid to weld the seed crystal with the molten liquid. After welding, the crystal bar lifting device drives the seed crystal to rise, and the crucible rises synchronously, and pull a silicon core with a diameter basically equal to the outer diameter of the seed crystal at a certain speed. The fifth step, shoulder forming: Lift the seed crystal upward at a certain speed, so that the diameter of each seed crystal gradually becomes the silicon core diameter. The sixth step, equal-diameter growth: After shoulder forming is completed, measure the diameter of the pulled silicon core by the CCD imaging system, give the best pulling speed through internal analysis of the CCD imaging system, and at the same time perform power and temperature compensation to achieve continuous and stable pulling; make the diameters of multiple silicon cores consistent through the crystal cooling mechanism placed above the molten liquid and increase the crystal pulling speed. The seventh step, crystal lifting: After the silicon core grows to a predetermined length with equal diameter, start to lift the crystal. The silicon core and the crystal cooling mechanism are synchronously lifted to the upper auxiliary furnace chamber, close the valve, lift and rotate the auxiliary furnace chamber to the crystal taking position, lower the silicon core to the welding place and then perform a shearing process. The eighth step, recharging: The lifting arm is suspended with an external re-feeding cylinder. The quartz feeding cylinder filled with crystalline silicon re-feed is driven by an upper lifting mechanism. After evacuating and washing the furnace of the external re-feeding device, the valve is opened, and the quartz feeding cylinder is lowered to add the crystalline silicon re-feed into the crucible. After remelting, the drawing of multiple silicon cores can be achieved without stopping the furnace.

[0007] For the method of simultaneously drawing multiple crystal rods, the evacuation and leak detection in the first step include: starting the vacuum pump to evacuate to 3 - 5 Pa and then performing leak detection. The overall leak rate is < 0.27 pa / min within 2 - 4 minutes. After passing the inspection, argon is introduced.

[0008] For the method of simultaneously drawing multiple crystal rods, the flow rate of the argon is 30 L / min - 150 L / min.

[0009] For the method of simultaneously drawing multiple crystal rods, when uniformly melting the silicon material into a molten liquid in the second step, the power of the side heater is set to rise to 70 - 100 KW within 90 min - 120 min, and the power of the lower heater is set to rise to 30 - 60 KW within 90 min - 120 min and then keep the temperature constant for 4 - 12 h to ensure that all the silicon material is melted.

[0010] For the method of simultaneously drawing multiple crystal rods, the slag lifting in the third step includes: lowering the crystal rod lifting device equipped with the seed crystal and the crystal cooling mechanism to the lower limit position of the crystal cooling mechanism at a speed of 300 - 500 mm / min, and then continuing to lower the crystal rod lifting device equipped with the seed crystal at a speed of 30 - 50 mm / min until the seed crystal contacts the surface of the molten liquid. The temperature is reduced to make the impurities floating on the surface of the molten liquid cool and crystallize. After reaching the appropriate diameter, the crystal rod lifting device and the crystal cooling mechanism are lifted synchronously to lift out the crystallized impurities.

[0011] For the method of simultaneously drawing multiple crystal rods, the optimal melting and seeding temperature in the fourth step is 1400 °C - 1500 °C; when drawing a section of silicon core with a diameter basically equal to the outer diameter of the seed crystal, the diameter of this section of silicon core is 6 - 15 mm and the length is 10 - 120 mm.

[0012] For the method of simultaneously drawing multiple crystal rods, the shoulder formation in the fifth step includes: lifting the seed crystal upward at a speed of 2 - 10 mm / min, turning on the rotation of the seed crystal, and making all the seed crystals rotate at a speed of 0.1 - 15 r / min to gradually enlarge the diameter of the seed crystal to be close to the required diameter of the silicon core, which is 6 - 30 mm.

[0013] The method of simultaneously pulling multiple crystal rods, the sixth step of equal-diameter growth includes: pulling the seed crystal upward at a speed of 3 to 15 mm / min, rotating the crucible at a speed of 0.1 to 15 r / min, and lifting it upward at a speed of 0.1 to 1 mm / min, keeping the crystal growth liquid level unchanged; and controlling the furnace pressure within the range of 800 Pa to 2666 Pa.

[0014] The method of simultaneously pulling multiple crystal rods, the seventh step of crystal lifting includes: after the silicon core grows to a predetermined length, crystal lifting begins, the lower shaft descends at a speed of 10 to 300 mm / min to separate the silicon core from the melt surface, and at the same time, the silicon core and the crystal cooling mechanism are synchronously lifted to the upper auxiliary furnace chamber at a speed of 100 to 800 mm / min.

[0015] The method for simultaneously drawing multiple crystal rods, the re-feeding in the eighth step includes: loading crystalline silicon re-feeding material into a quartz feeding tube, lifting it to the inside of the external re-feeding tube at a speed of 800-1500 mm / min through the upper pulling mechanism of the external re-feeding tube, after evacuating the external re-feeding device to clean the furnace, opening the valve, and lowering the quartz feeding tube at a speed of 600-1200 mm / min to allow the crystalline silicon re-feeding material to be added to the crucible.

[0016] Due to the adoption of the above-mentioned technical solution, the present invention has the following beneficial effects: The steps of loading, chemical processing, slag extraction, welding and seeding, shoulder release, equal diameter growth, crystal extraction, and re-investment in the present invention can simultaneously produce more than 20 cylindrical silicon cores with a diameter of more than 8 mm at a time. The obtained silicon cores can be directly used in a polysilicon reduction furnace without the need for cutting and pickling operations. The production efficiency is high, the resistivity of the produced silicon cores is stable at the head and tail, the diameter of the silicon cores in the same group is uniform, and no external impurities are introduced. The present invention can realize the simultaneous drawing of multiple high-purity cylindrical silicon cores without stopping the furnace. The silicon cores produced at the same time do not need to be cut and pickled, and can be directly used for the growth of high-purity polysilicon raw materials. It has the characteristics of lower cost and higher efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic structural diagram of an artificial lens pulling device in an embodiment of the present invention; In the figure: 1. Auxiliary furnace chamber; 2. Crystal cooling mechanism lifting device; 3. Crystal rod pulling device; 4. Silicon core; 5. Lifting arm; 6. Valve; 7. CCD imaging system; 8. Crystal cooling mechanism; 9. Furnace cover; 10. Main furnace chamber; 11. Side heater; 12. Melt; 13. Crucible; 14. Lower heater. Implementation

[0018] The present invention can be more specifically explained by the following embodiments. The object of the present invention is to protect all changes and improvements within the scope of the present invention, and the present invention is not limited to the following embodiments; In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "lateral", "length", "width", "height", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "side", etc. is based on the Figure 1 orientation or positional relationship shown, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0019] In the description of the present invention, it should also be noted that unless otherwise clearly specified and defined, the terms "set", "install", "connect", and "couple" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0020] Combined with the Figure 1 A method for simultaneously pulling multiple single crystal rods, the method specifically includes the following steps: First step, loading materials: Load silicon materials into the crucible 13, install multiple single seeds on the upper single crystal rod pulling device 3, and the upper pulling steel wire rope drives the single crystal rod pulling device 3 to move up and down. After the furnace is closed, evacuate and leak check. During implementation, the evacuating and leak checking includes: starting the vacuum pump to evacuate to 3 - 5 Pa and then perform leak checking. The overall leak rate is < 0.27 pa / min within 2 - 4 minutes. After passing the check, introduce argon gas; the flow rate of the argon gas is 30 L / min - 150 L / min; Second step, melting materials: Turn on the side heater 11 and the lower heater 14 simultaneously or turn them on alternately. Turn on the lower shaft rotation mechanism to drive the crucible 13 to rotate, uniformly melt the silicon material into the molten liquid 12, and after complete melting, reduce the power of the side heater 11 to the seeding power. During implementation, the side heater 11 and the lower heater 14 can be turned on simultaneously or separately, and the interval time between them can be selected as 5 minutes or 10 minutes. The specific interval time can be selected according to the situation of melting the material. When uniformly melting the silicon material into the molten liquid 12, set the power of the side heater 11 to rise to 70 - 100 KW within 90 min - 120 min, and set the power of the lower heater 14 to rise to 30 - 60 KW within 90 min - 120 min and then keep it at a constant temperature for 4 - 12 h to ensure complete melting of the silicon material. Step 3, slag removal: Synchronously lower the seed crystal and the crystal cooling mechanism 8 to weld the surface impurities to the bottom of the seed crystal. Adjust the power of the side heater 11 to gradually crystallize the surface of the molten zone, and lift out the crystallized impurities after reaching the appropriate diameter. During implementation, the slag removal includes: lowering the crystal rod lifting device 3 equipped with the seed crystal and the crystal cooling mechanism 8 to the lower limit position of the crystal cooling mechanism 8 at a speed of 300 - 500 mm / min, and then continuing to lower the crystal rod lifting device 3 equipped with the seed crystal at a speed of 30 - 50 mm / min until the seed crystal contacts the surface of the molten liquid 12, reducing the temperature to cool and crystallize the impurities floating on the surface of the molten liquid 12. After reaching the appropriate diameter, synchronously lift the crystal rod lifting device 3 and the crystal cooling mechanism 8 to lift out the crystallized impurities. Step 4, melting and seeding: Adjust the power of the side heater 11, measure the liquid surface temperature of the molten liquid 12 by the CCD imaging system 7. When the liquid surface temperature reaches the welding temperature, turn on the rotation motor on the crystal rod lifting device 3 to rotate the seed crystal, lower the seed crystal to contact the surface of the molten liquid 12, and weld the seed crystal with the molten liquid 12. After welding, the crystal rod lifting device 3 drives the seed crystal to rise, and the crucible 13 rises synchronously to draw a silicon core with a diameter basically equal to the outer diameter of the seed crystal at a certain speed. During implementation, the optimal melting and seeding temperature is 1400°C - 1500°C; when drawing a silicon core with a diameter basically equal to the outer diameter of the seed crystal, the diameter of this section of the silicon core is 6 - 15 mm and the length is 10 - 120 mm. Step 5, shoulder formation: Lift the seed crystal upward at a certain speed to gradually increase the diameter of each seed crystal to the diameter of the silicon core. During implementation, the shoulder formation includes: lifting the seed crystal upward at a speed of 2 - 10 mm / min, turning on the rotation of the seed crystal, and rotating all the seed crystals at a speed of 0.1 - 15 r / min to gradually enlarge the diameter of the seed crystal to be close to the required diameter of the silicon core, which is 6 - 30 mm. Step 6, equal - diameter growth: After the shoulder is formed, the diameter of the drawn silicon core 4 is measured by the CCD imaging system 7, and the optimal drawing speed is given through internal analysis of the CCD imaging system 7. At the same time, power-temperature compensation is performed to achieve continuous and stable drawing. The diameter of multiple silicon cores is made consistent and the crystal drawing speed is increased by the crystal cooling mechanism 8 placed above the melt 12. The isodiametric growth includes: the seed crystal is lifted upward at a speed of 3-15 mm / min, the crucible 13 rotates at a speed of 0.1-15 r / min, and is lifted upward at a speed of 0.1-1 mm / min, keeping the crystal growth liquid level unchanged. The furnace pressure is controlled within the range of 800 Pa - 2666 Pa. Step 7, crystal lifting: After the isodiametric growth of the silicon core 4 reaches the predetermined length, crystal lifting starts. The silicon core 4 and the crystal cooling mechanism 8 are synchronously lifted into the upper secondary furnace chamber 1. The valve 6 is closed, the secondary furnace chamber 1 is lifted and rotated to the crystal taking position, and the silicon core is lowered to the welding point and then cut off. During implementation, the crystal lifting includes: after the isodiametric growth of the silicon core reaches the predetermined length, crystal lifting starts, the lower shaft descends at a speed of 10-300 mm / min to separate the silicon core 4 from the surface of the melt 12, and at the same time, the silicon core 4 and the crystal cooling mechanism 8 are synchronously lifted into the upper secondary furnace chamber 1 at a speed of 100-800 mm / min. Step 8, recharging: The lifting arm suspends the external recharging cylinder. The quartz charging cylinder filled with crystalline silicon recharging material is driven by the upper lifting mechanism. After evacuating and flushing the external recharging device, the valve 6 is opened, and the quartz charging cylinder is lowered to add the crystalline silicon recharging material into the crucible 13. After remelting, the drawing of multiple groups of silicon cores can be realized without stopping the furnace. During implementation, the crystalline silicon recharging material can be polysilicon recharging material or monocrystalline silicon recharging material. The recharging includes: the quartz charging cylinder is filled with crystalline silicon recharging material, and is lifted into the internal part of the external recharging cylinder at a speed of 800-1500 mm / min by the upper lifting mechanism of the external recharging cylinder. After evacuating and flushing the external recharging device, the valve 6 is opened, and the quartz charging cylinder is lowered at a speed of 600-1200 mm / min to add the crystalline silicon recharging material into the crucible 13.

[0021] The specific implementation of the present invention is as follows: Figure 1 The structural schematic diagram of the artificial crystal drawing device or the artificial crystal furnace according to the embodiment of the present invention is shown.

[0022] As Figure 1As shown in the figure, this artificial crystal furnace can draw multiple crystal rods simultaneously. This artificial crystal furnace includes a secondary furnace chamber 1, a crystal cooling mechanism 8 with multiple drawing holes, a crystal cooling mechanism lifting device 2 for lifting the crystal cooling mechanism 8, a crystal rod lifting device 3 (i.e., a seed crystal chuck for driving the rotation of the seed crystal), a silicon core 4, a lifting arm 5, a valve 6, a CCD imaging system 7 (i.e., a diameter measuring instrument), a furnace lid 9, a main furnace chamber 10, a side heater 11, a melt 12, a crucible 13, a lower heater 14, and a control device.

[0023] The furnace lid 9 is arranged above the main furnace chamber 10, and a valve 6 is arranged above the furnace lid 9. The secondary furnace chamber 1 is arranged above the valve 6, and a crystal cooling mechanism lifting device 2 for lifting the crystal cooling mechanism 8 is arranged on the secondary furnace chamber 1. The crystal cooling mechanism lifting device 2 drives the lifting arm 5 to lift. The lifting arm 5 is connected to the crystal cooling mechanism 8. The lifting arm 5 can drive the crystal cooling mechanism 8 to move up and down within the secondary furnace chamber 1 and the main furnace chamber 1. Below the crystal cooling mechanism 8, a crucible 13 is arranged in the main furnace chamber 1. A side heater 11 is arranged around the crucible 13, and a lower heater 14 that can move up and down is arranged below the crucible 13. The upper shaft lifting device of the artificial crystal is connected to the crystal rod lifting device 3 and drives the crystal rod lifting device 3 to move up and down.

[0024] The CCD imaging system 7 is arranged on the furnace lid 9. During the drawing process, the CCD imaging system 7 can measure the diameter of at least one newly drawn silicon core 4 on the outer circle or the inner circle in real time. At the same time, the CCD imaging system 7 can also monitor the temperature of the melt 12 liquid surface. The control device can obtain the corresponding diameter change based on the comparison of the diameter of at least one crystal rod obtained by the CCD imaging system 7 with the parameter value or based on the comparison of the diameters of at least one crystal rod measured at different positions by the CCD imaging system 7, and control the crystal rod lifting device 3 through this diameter change. The crystal rod lifting device 3 lifts or lowers the drawn crystal rods in different circles at different speeds according to the instructions from the control device, so as to obtain crystal rods with diameters meeting the requirements. It should be noted that the crystal rod lifting device 3 can realize the differential lifting of the inner and outer circle seed crystals. This technical solution has been separately applied for a patent by the applicant, and its specific structure will not be elaborated here.

[0025] The specific implementation method is as follows: The first step, loading materials: Initially load 170 kg of materials into the crucible 13, and then add another 50 kg after the silicon materials are melted. The silicon materials can be virgin polycrystalline materials, powder materials, edge skin materials, or head and tail materials; After loading the materials, evacuate and leak-check: Start the vacuum pump to evacuate to 5 Pa and then conduct a leak-check. The overall leak rate should be <0.27 pa / min within 3 minutes. After passing the check, introduce argon gas, and the argon gas flow rate is 30 L / min to 150 L / min. The furnace pressure is controlled within the range of 800 Pa to 2666 Pa; The second step, melting materials: Raise the power of the side heater 11 to 70 - 100 KW within 90 - 120 min, and raise the power of the lower heater 14 to 30 - 60 KW within 90 - 120 min. Then keep the temperature constant for 7 h to ensure that all the materials are melted. During implementation, conduct full melting stability: lower the power of the side heater 11 and the lower heater 14 to the seeding power, control the liquid surface temperature measured by the CCD imaging system 7 at the welding temperature, and keep the liquid surface temperature at the optimal seeding temperature of 1400℃ - 1500℃. The third step: slag removal During execution, lower the crystal rod lifting device 3 and the crystal cooling mechanism 8 to the lower limit position of the crystal cooling mechanism 8 at a speed of 300 - 500 mm / min, lower the seed crystal to contact the surface of the melt 12 at a speed of 30 - 50 mm / min, reduce the temperature, and cool and crystallize the impurities floating on the surface of the melt 12. After reaching the appropriate diameter, synchronously lift the crystal rod lifting device 3 and the crystal cooling mechanism 8 to lift out the crystallized impurities. After lifting to the secondary furnace chamber 1, close the valve 6 and remove the slag cover. This operation can be not executed or executed multiple times according to the cleanliness of the silicon material. The fourth step: melt and seed Adjust the power of the side heater 11 and the lower heater 14, measure the liquid surface temperature by the CCD imaging system 7 to the welding temperature, and the optimal seeding temperature is 1400℃ - 1500℃. Turn on the rotating motor on the crystal rod lifting device 3 to rotate the seed crystal, lower the seed crystal to contact the surface of the melt 12 at a speed of 30 - 50 mm / min, and weld the seed crystal with the silicon melt 12. After welding, turn on the crystal lift and lift upward at a speed of 1 - 10 mm / min, turn on the lower shaft to rise, and draw a silicon core with a diameter of 6 - 15 mm and a length of 10 - 120 mm. The fifth step: shoulder release Lift the seed crystal upward at a speed of 2 - 10 mm / min, turn on the rotation of the seed crystal, and make all the seed crystals rotate at a speed of 0.1 - 15 r / min to gradually enlarge the diameter of the seed crystal to be close to the required diameter of the silicon core of 6 - 30 mm. The sixth step: equal - diameter growth After the shoulder is formed, the seed crystal is lifted upward at a speed of 3 - 15 mm / min, the crucible 13 rotates at a speed of 0.1 - 15 r / min, and is lifted upward at a speed of 0.1 - 1 mm / min to keep the crystal growth liquid level unchanged; through furnace pressure control, the furnace pressure is controlled within the range of 800 Pa - 2666 Pa; the diameter of the drawn silicon core 4 is measured by the CCD imaging system 7, the optimal drawing speed is given through internal system analysis, and at the same time power temperature compensation is carried out to achieve continuous and stable drawing; the diameters of multiple silicon cores 4 are kept consistent and the crystal drawing speed is increased by the crystal cooling mechanism 8 placed above the melt 12; there are multiple sight glass observation ports on the equipment, and the CCD imaging system 7 can observe and measure the drawing situation in the furnace from different sight glass observation ports to ensure a constant crystal drawing crucible position and achieve temperature control; Step 7, Crystal lifting: After the silicon core grows with equal diameter to the predetermined length, crystal lifting begins. The lower shaft descends at a speed of 10 - 300 mm / min to separate the silicon core 4 from the surface of the melt 12. At the same time, the silicon core 4 and the crystal cooling mechanism 8 are synchronously lifted to the upper auxiliary furnace chamber 1 at a speed of 100 - 800 mm / min, the valve 6 is closed, the auxiliary furnace chamber 1 is lifted and rotated to the crystal taking position, and the silicon core is lowered to the welding place for shearing treatment; Step 8, Recharging: After a group of silicon cores are drawn, the remaining material in the crucible 13 is not enough to draw another group of silicon cores. At this time, the operation of recharging silicon material into the crucible 13 is required. 70 - 150 kg of recharged polysilicon material is added into the quartz feeding cylinder, and it is lifted to the inside of the external recharging cylinder at a speed of 800 - 1500 mm / min through the lifting mechanism at the upper part of the external recharging cylinder. The lifting arm places the external recharging device above the valve 6. After evacuating and cleaning the furnace of the external recharging device and meeting the vacuum degree requirement, the valve 6 is opened at this time, and the quartz feeding cylinder is started to descend at a speed of 600 - 1200 mm / min. After reaching the bottom, the quartz umbrella at the bottom of the quartz feeding cylinder opens, and the polysilicon material inside the quartz feeding cylinder automatically falls into the crucible 13. The quartz feeding cylinder is taken out, and the auxiliary furnace chamber 1 is rotated back to complete the recharging. Adjust the heating power to melt the silicon material in the crucible 13 to achieve repeated drawing; In practical applications, the crucible 13 can be lifted upward through the crucible lifting component. The seed crystal can be driven to rotate by the rotating motor on the crystal rod lifting device 3 through the gear transmission system. Electrical components such as the rotating motor and the heater are controlled and powered by the electric control cabinet.

[0026] The CCD imaging system 7 can not only be used to measure the surface temperature of the molten liquid 12 in the crucible 13, but also adjust the power according to the feedback of the pulling speed, thereby changing the temperature of the molten liquid 12 in the furnace. At the same time, it can also be used to collect the state images of crystal growth when the silicon core contacts the liquid surface of the solution, measure the actual diameter of the silicon core through the size and diameter of the gray scale, and increase or decrease the pulling speed according to the change of the silicon core diameter to make the diameters of the front and rear silicon cores consistent. At the same time, according to the size of the whole rod pulling speed, the heater power is adjusted so that the heater power is always within the temperature range for crystal growth. Automatic adjustment reduces the dependence on humans during crystal pulling, reduces the demand for process personnel, and increases the yield of silicon cores.

[0027] The measurement of the silicon core diameter is a real-time communication detection, and the pulling speed is adjusted through the difference between the actual and the set diameters. When the growth speed of the silicon core changes due to the temperature field or other factors at a certain growth stage, the PID automatic adjustment is carried out inside the CCD imaging system 7 to increase or decrease the pulling speed so that the diameter of the silicon core is consistent with the set value.

[0028] The advantages of the present invention are as follows: 1. The present invention can produce more than 20 cylindrical silicon cores with a diameter of more than 8 mm at one time, improving the production efficiency (the specific number can be increased or decreased according to the actual needs of users, that is, two or more silicon cores can be pulled simultaneously); 2. The present invention is applicable to the silicon core furnace for preparing silicon cores by the pulling method, with a wide range of materials, and raw polycrystalline materials, powders, edge skin materials or head and tail materials can all be used, consuming a large amount of broken powder inventory and saving energy and reducing consumption for enterprises; 3. The present invention is applicable to the silicon core furnace for preparing silicon cores by the pulling method. The obtained silicon cores can be directly used in the polysilicon reduction furnace without further cutting and pickling operations, with high production efficiency, stable resistivity at the head and tail of the produced silicon cores, good uniformity of the silicon core diameter in the same group at the head and tail, and no introduction of external impurities; 4. By introducing the CCD imaging system 7, automatic crystal pulling is realized, reducing the dependence on process personnel, reducing human errors, improving efficiency, and reducing labor costs.

[0029] The parts not described in detail above are prior arts and thus are not described in detail.

[0030] The embodiments selected herein for the purpose of disclosing the present invention are currently considered suitable. However, it should be understood that the present invention is intended to cover all variations and improvements of all embodiments falling within the scope of this concept and invention.

Claims

1. A method for simultaneously drawing multiple single crystal rods, characterized in that: The method specifically includes the following steps: First step, loading materials: Load silicon materials into the crucible (13). Install multiple single crystal seeds on the upper crystal rod lifting device (3). The upper lifting steel wire rope drives the crystal rod lifting device (3) to move up and down. After the furnace is closed, evacuate and detect leaks. Second step, melting materials: Start the side heater (11) and the lower heater (14) simultaneously or start the side heater (11) and the lower heater (14) at intervals. Start the lower shaft rotation mechanism to drive the crucible (13) to rotate, and uniformly melt the silicon materials into a melt (12). After all the materials are melted, reduce the power of the side heater (11) to the seeding power. Third step, slag removal: Synchronously lower the seed crystal and the crystal cooling mechanism (8) so that the surface impurities are welded to the bottom of the seed crystal. Adjust the power of the side heater (11) to gradually crystallize the surface of the melting zone. After reaching an appropriate diameter, lift out the crystallized impurities. Fourth step, melting and seeding: Adjust the power of the side heater (11). Measure the liquid surface temperature of the melt (12) by the CCD imaging system (7). When the liquid surface temperature reaches the welding temperature, start the rotation motor on the crystal rod lifting device (3) to rotate the seed crystal. Lower the seed crystal to contact the surface of the melt (12) to weld the seed crystal and the melt (12). After welding, the crystal rod lifting device (3) drives the seed crystal to rise, and the crucible (13) rises synchronously to draw a silicon core with a diameter basically equal to the outer diameter of the seed crystal at a certain speed. Fifth step, shoulder broadening: Lift the seed crystal upward at a certain speed so that the diameter of each seed crystal gradually becomes the diameter of the silicon core. Sixth step, equal-diameter growth: After shoulder broadening is completed, measure the diameter of the drawn silicon core (4) by the CCD imaging system (7). Give the best drawing speed through internal analysis of the CCD imaging system (7), and at the same time perform power and temperature compensation to achieve continuous and stable drawing. Keep the diameters of multiple silicon cores consistent through the crystal cooling mechanism (8) placed above the melt (12) and increase the crystal pulling speed. Seventh step, crystal lifting: After the silicon core (4) grows to a predetermined length with an equal diameter, start to lift the crystal. The silicon core (4) and the crystal cooling mechanism (8) are synchronously lifted into the upper auxiliary furnace chamber (1). Close the valve (6), lift and rotate the auxiliary furnace chamber (1) to the crystal taking position, lower the silicon core to the welding position and then perform a shearing process. Eighth step, recharging: Suspend the external recharging cylinder by the lifting arm. Drive the quartz charging cylinder loaded with polycrystalline silicon recharging materials through the upper lifting mechanism. After evacuating and washing the external recharging device, open the valve (6), lower the quartz charging cylinder to add the polycrystalline silicon recharging materials into the crucible (13). After remelting, the drawing of multiple groups of silicon cores can be realized without stopping the furnace.

2. The method for simultaneously drawing multiple single crystal rods according to claim 1, characterized in that: The leak detection during evacuation in the first step includes: start the vacuum pump to evacuate to 3 - 5 Pa and then detect leaks. The overall leak rate is < 0.27 pa / min within 2 - 4 minutes. After passing the test, introduce argon gas.

3. The method for simultaneously drawing multiple single crystal rods according to claim 2, characterized in that: The flow rate of the argon gas is 30 L / min - 150 L / min.

4. The method for simultaneously drawing multiple single crystal rods according to claim 1, wherein: In the second step, when the silicon material is uniformly melted into a melt (12), the power of the side heater (11) is set to rise to 70 - 100 KW within 90 min - 120 min, and the power of the lower heater (14) is set to rise to 30 - 60 KW within 90 min - 120 min and then keep the temperature constant for 4 - 12 h to ensure that all the silicon material is melted.

5. The method for simultaneously drawing multiple single crystal rods according to claim 1, characterized in that: In the third step, slag removal includes: lowering the crystal rod lifting device (3) equipped with a seed crystal and the crystal cooling mechanism (8) to the lower limit position of the crystal cooling mechanism (8) at a speed of 300 - 500 mm / min, and then continuing to lower the crystal rod lifting device (3) equipped with a seed crystal at a speed of 30 - 50 mm / min until the seed crystal contacts the surface of the melt (12). Lower the temperature to cool and crystallize the impurities floating on the surface of the melt (12). After reaching an appropriate diameter, synchronously lift the crystal rod lifting device (3) and the crystal cooling mechanism (8) to remove the crystallized impurities.

6. The method for simultaneously drawing multiple single crystal rods according to claim 1, characterized in that: In the fourth step, the optimal melt-joining crystal-pulling temperature is 1400 °C - 1500 °C; when pulling a section of silicon core with a diameter basically equal to the outer diameter of the seed crystal, the diameter of this section of silicon core is 6 - 15 mm and the length is 10 - 120 mm.

7. The method for simultaneously drawing multiple single crystal rods according to claim 1, characterized in that: In the fifth step, shoulder formation includes: pulling up the seed crystal at a speed of 2 - 10 mm / min, starting the rotation of the seed crystal, and making all the seed crystals rotate at a speed of 0.1 - 15 r / min to gradually enlarge the diameter of the seed crystal to be close to the diameter of the required silicon core, which is 6 - 30 mm.

8. The method for simultaneously drawing multiple single crystal rods according to claim 1, characterized in that: In the sixth step, isodiametric growth includes: pulling up the seed crystal at a speed of 3 - 15 mm / min, rotating the crucible (13) at a speed of 0.1 - 15 r / min, and lifting it upward at a speed of 0.1 - 1 mm / min to keep the crystal growth liquid level unchanged; controlling the furnace pressure within the range of 800 Pa - 2666 Pa.

9. The method for simultaneously drawing multiple single crystal rods according to claim 1, characterized in that: In the seventh step, crystal lifting includes: after the silicon core grows isodiametrically to a predetermined length, start crystal lifting. The lower shaft descends at a speed of 10 - 300 mm / min to separate the silicon core (4) from the surface of the melt (12), and at the same time, the silicon core (4) and the crystal cooling mechanism (8) are synchronously lifted to within the upper auxiliary furnace chamber (1) at a speed of 100 - 800 mm / min.

10. The method for simultaneously drawing multiple single crystal rods according to claim 1, wherein: In the eighth step, recharging includes: loading polycrystalline silicon recharging materials into the quartz charging cylinder, lifting it to the inside of the external recharging cylinder at a speed of 800 - 1500 mm / min through the lifting mechanism at the upper part of the external recharging cylinder. After evacuating and cleaning the external recharging device, open the valve (6) and lower the quartz charging cylinder at a speed of 600 - 1200 mm / min to add the polycrystalline silicon recharging materials into the crucible (13).

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