Columnar polycrystalline silicon ingot casting equipment and ingot casting method

Abstract

The columnar polycrystalline silicon ingot casting equipment comprises an upper furnace body, a lower furnace body, a heat insulation cage, a heat exchange platform, a quartz crucible, an argon flow guide pipe, a stirring mechanism and a control mechanism, the stirring mechanism comprises a fixing frame, and the bottom end of the fixing frame is fixedly connected with the top cover of the upper furnace body; the lifting driving assembly and the rotating driving assembly are arranged on the fixing frame; the rotary driving assembly is connected with the lifting driving assembly; the lifting driving assembly and the rotating driving assembly are both in communication connection with the control mechanism. The top end of the stirring assembly is detachably connected with the rotary driving assembly, and the bottom end of the stirring assembly penetrates through the top cover of the upper furnace body, then extends into the argon flow guide pipe and extends into the quartz crucible; under the control of the control mechanism, the lifting driving assembly drives the rotating driving assembly to further drive the stirring assembly to lift, and the rotating driving assembly drives the stirring assembly to rotate and stir; a columnar polycrystalline silicon ingot casting method adopts the columnar polycrystalline silicon ingot casting equipment, and a stirring process is added after material melting and in a crystal growth process.

Description

Technical Field

[0001] The present invention relates to the technical field of polysilicon manufacturing equipment, and in particular to a columnar polysilicon ingot casting equipment and an ingot casting method. Background Art

[0002] With the rapid development of integrated circuits in the 21st century, silicon component materials are widely used in the chip manufacturing process. The targets commonly used in the production of silicon components are single crystal silicon and polycrystalline silicon. Among them, single crystal silicon has higher intrinsic quality and better structure, but due to the limitations of manufacturing equipment and manufacturing processes, single crystal silicon cannot meet the requirements of large size, and the energy consumption of single crystal silicon manufacturing equipment is high, and the manufacturing cost is also high; while the manufacture of polycrystalline silicon mostly adopts the heat exchange method, the furnace structure used for manufacturing is simple, safe and easy to operate, so it has the advantages of low energy consumption, low cost, high yield rate and large product cross-sectional size; but in the manufacturing process of polycrystalline silicon ingots, due to the large size of the crucible, the center and edge of the molten silicon are heated unevenly, the lateral temperature gradient is large, and the supercooling degree of the center and edge is different. On the one hand, it will bring about the problem of different nucleation density and small number of nucleations. In order to increase the number of nucleations, the existing technology mostly adopts the semi-melting process, that is, at the bottom of the crucible, the molten silicon is heated unevenly, the lateral temperature gradient is large, and the supercooling degree of the center and edge is different. On the one hand, it will bring about the problem of different nucleation density and small number of nucleations. In order to increase the number of nucleations, the existing technology mostly adopts the semi-melting process, that is, at the bottom of the crucible, the semi-melting process is used to heat the molten silicon. Laying seed crystals 10mm high and 0-5mm in size as nucleation points for crystal growth increases the number of nuclei, but will make the bottom 20mm of the polysilicon ingot unusable and need to be cut off and scrapped, resulting in waste and increased costs; on the other hand, the large temperature difference between the center and the edge causes coarse and uneven crystal structure, severe macro-segregation, poor uniformity of horizontal impurities or resistivity during crystal condensation, and large thermal stress in the silicon ingot, which makes it easy to produce hidden cracks during subsequent silicon ingot processing; therefore, in order to make large-sized polysilicon ingots better used in chip manufacturing and meet the high quality requirements of modern technology for target materials for silicon components, it is urgently necessary to provide a polysilicon ingot casting equipment and ingot casting method that can make the center and edge of the molten silicon heated more evenly and have a smaller lateral temperature gradient during the production process. Summary of the invention

[0003] In view of this, it is necessary to provide a columnar polycrystalline silicon ingot casting device and a casting method that can make the center and edge of the molten silicon heated more evenly and have a smaller lateral temperature gradient during the production process.

[0004] A columnar polysilicon ingot casting equipment, comprising: an upper furnace body, a lower furnace body, an insulation cage, a heat exchange platform, a quartz crucible, an argon gas guide tube, a stirring mechanism and a control mechanism; the stirring mechanism comprises: a fixed frame, a stirring assembly, a rotary drive assembly, a connecting seat and a lifting drive assembly; the bottom end of the fixed frame is fixedly connected to the top cover of the upper furnace body; the lifting drive assembly and the rotary drive assembly are both arranged on the fixed frame; the rotary drive assembly is connected to the lifting drive assembly through the connecting seat, and the lifting drive assembly drives the rotary drive assembly to perform lifting and lowering movements; the lifting drive assembly and the rotary drive assembly are both communicatively connected to the control mechanism; the top end of the stirring assembly is detachably connected to the rotary drive assembly, and the bottom end penetrates through the upper furnace body top cover and extends into the argon gas guide tube, and extends into the quartz crucible; under the control of the control mechanism, the lifting drive assembly drives the rotary drive assembly to rise and fall, and then drives the stirring assembly to rise and fall, and the rotary drive assembly drives the stirring assembly to perform rotation and stirring in the quartz crucible.

[0005] Preferably, the stirring assembly comprises: a stirring rod and a plurality of stirring blades; the top end of the stirring rod is detachably connected to the rotary drive assembly, and the bottom end of the stirring rod penetrates through the upper furnace body cover and extends into the argon gas guide tube and extends into the quartz crucible; the plurality of stirring blades are evenly arranged around the circumference of the bottom end of the stirring rod; under the control of the control mechanism, the lifting drive assembly drives the rotary drive assembly to lift and lower, thereby driving the stirring rod and the stirring blades to lift and lower in the quartz crucible, and the rotary drive assembly drives the stirring rod and the stirring blades to rotate and stir in the quartz crucible.

[0006] Preferably, the stirring rod and the stirring blade are made of materials that are stable at high temperatures and do not react with carbon, silicon, carbon monoxide, carbon dioxide and silicon oxides; each stirring blade is in the shape of a fan. For example, the stirring rod and the stirring blade are made of silicon carbide.

[0007] Preferably, the lifting drive assembly includes: a linear guide, a lead screw, a lifting motor, a worm gear reducer and a position encoder; the linear guide is arranged on one side of the fixed frame; the connecting seat is arranged horizontally, and one side end is slidably connected to the linear guide; the lifting motor is fixedly arranged on the fixed frame, and is located on the upper back side of the linear guide; the worm gear reducer is fixedly arranged on the fixed frame, and is located on the upper side of the linear guide opposite to the lifting motor; the output end of the lifting motor is connected to the input end of the worm gear reducer; the top end of the lead screw is fixedly connected to the output end of the worm gear reducer, and the ball nut of the lead screw is sleeved on the connecting seat; the position encoder is connected to the bottom end of the lead screw through a coupling; the lifting motor and the position encoder are both communicatively connected to the control mechanism.

[0008] Preferably, the rotary drive assembly comprises: a bearing, a rotary motor, a reducer, a rotary shaft and a rotary encoder; a center hole is vertically opened on the upper edge of the connecting seat; the bearing is fixedly sleeved in the center hole of the connecting seat; the top of the stirring rod is sleeved in the bearing; the output end of the rotary motor is connected to the input end of the reducer; the output end of the reducer is fixedly connected to the rotary shaft; the bottom end of the rotary shaft is connected to the top end of the stirring rod through a coupling; the rotary encoder is connected to the top end of the rotary shaft through a coupling; the rotary motor and the rotary encoder are both communicatively connected to the control mechanism.

[0009] Preferably, the stirring mechanism further includes: a sealing ring, which is arranged at the intersection of the stirring rod and the upper furnace body and furnace cover.

[0010] Preferably, the lower furnace body supports the quartz crucible through a heat exchange platform; an insulating cage connected to the upper furnace body is provided outside the quartz crucible; an argon gas guide tube extends downward from the upper furnace body top cover, passes through the top cover plate of the quartz crucible and then extends to the top of the quartz crucible.

[0011] A columnar polycrystalline silicon ingot casting method adopts the columnar polycrystalline silicon ingot casting device, and adds a stirring process after the material is quenched and during the crystal growth process, specifically comprising the following steps: S1. After mixing, initial stirring: After the material is molten, the stirring rod is extended into the molten silicon. The height h between the bottom of the stirring blade and the bottom of the quartz crucible is 1 / 3-1 / 2 of the total height H of the molten silicon. The stirring rod and the stirring blade rotate for stirring. S2. Stirring at the initial stage of crystal growth: After the initial stage of crystal growth is completed, the stirring rod is immediately lowered in the molten silicon to a height h of 1 / 7-1 / 5 of the total height H of the molten silicon from the bottom of the stirring blade to the bottom of the quartz crucible, and the stirring rod and the stirring blade rotate for stirring; after the stirring is completed, the stirring rod and the stirring blade stop stirring and remain in place, waiting for the crystal height to grow again to the height required when the initial stage of crystal growth is completed; S3. Stirring in the early stage of crystal growth: During the early stage of the entire crystal growth process, the stirring rod is slowly rotated upward from the bottom of the stirring blade to the bottom of the quartz crucible at a height h of 1 / 7-1 / 5 of the total height H of the molten silicon; S4. Stirring during the middle and late stages of crystal growth: During the entire middle and late stages of crystal growth, the stirring rod slowly rotates and rises upward from the position at the end of the early middle stages of crystal growth; S5, at the end of crystal growth, remove the molten silicon: The stirring rod and stirring blades are moved out of the molten silicon from the position at the end of the middle and late stages of crystal growth.

[0012] Preferably, in S1, during the initial stirring, the speed of the stirring rod and the stirring blade is 8-10 r / min, and the stirring time is 30 min; In S2, during the initial stirring of crystal growth, the stirring rod and stirring blade rotate at a speed of 10-12 r / min, and the stirring time is 10-15 min; In S3, in the early stage of crystal growth, the lifting speed of the stirring rod and stirring blade is 10mm / h-12mm / h, and the rotation speed is 5-7r / min; In S4, in the middle and late stages of crystal growth, the lifting speed of the stirring rod and stirring blade is 9mm / h-11mm / h, and the rotation speed is 1-3r / min; In S5, at the end of the crystal growth, the lifting speed of the stirring rod and the stirring blade is 10-15 mm / h.

[0013] Preferably, in step S1, during the initial stirring, the height h of the stirring blade from the bottom of the quartz crucible is 1 / 2 of the total height H of the molten silicon; In step S2, during the initial stirring of crystal growth, the height h of the stirring blade from the bottom of the quartz crucible is 1 / 6 of the total height of the molten silicon; In step S3, in the early stage of crystal growth, the lifting speed of the stirring rod and the stirring blade is 10 mm / h; In step S4, in the middle and late stages of crystal growth, the lifting speed of the stirring rod and the stirring blade is 9 mm / h.

[0014] Compared with the polycrystalline silicon ingot casting technology in the prior art, the columnar polycrystalline silicon ingot casting equipment and method reduce the lateral temperature gradient of the molten silicon and improve the heating uniformity of the center and edge of the molten silicon during the casting process through the following aspects: first, by arranging a stirring assembly in the ingot casting equipment, and by arranging a rotating drive assembly and a lifting drive assembly, the stirring rod is driven to drive the stirring blade to stir in the molten silicon, so that the temperature of the molten silicon thermal field is more uniform; second, during the casting process, after the material is quenched, the stirring blade is used to perform initial stirring at 1 / 3-1 / 2 of the total height of the molten silicon, so that the dopant in the molten silicon is evenly distributed; third, after the initial crystal growth is completed, the stirring blade is used to perform initial stirring at 1 / 7 of the total height of the molten silicon. -1 / 5 is stirred to break up the crystals grown in the early stage of crystal growth, refine the grains, and form new nucleation points. After the stirring is completed, the crystals are waited to grow again to the height when the initial growth is completed. The new nucleation points formed after the grain refinement improve the uniformity of the crystal flowers and reduce the segregation phenomenon during the crystal regrowth process. Fourthly, the stirring rod is kept in a slowly rotating upward lifting posture during the early and late stages of crystal growth, thereby increasing horizontal heat convection and reducing the horizontal lateral temperature difference between the center and edge of the molten silicon caused by the large size of the quartz crucible, so that the solid-liquid interface remains planar, reducing thermal stress and improving the mechanical properties and resistivity uniformity of the multicrystalline silicon ingot. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1It is a schematic diagram of the overall structure of the columnar polysilicon ingot casting equipment in a specific embodiment of the present invention.

[0016] Figure 2 It is a schematic diagram of the three-dimensional structure of the stirring mechanism in which the stirring blades are omitted in a specific embodiment of the present invention.

[0017] Figure 3 It is a schematic diagram of the three-dimensional structure of the stirring assembly in a specific embodiment of the present invention.

[0018] Figure 4 These are the specific steps of the method for casting a columnar polycrystalline silicon ingot in a specific embodiment of the present invention.

[0019] Figure 5 The figure is a comparison result of the elastic modulus of the polycrystalline silicon ingots obtained by the comparative example and the example in the specific implementation manner of the present invention.

[0020] Figure 6 The resistivity comparison result of the polycrystalline silicon ingots obtained by the comparative example and the example in the specific implementation manner of the present invention is shown in FIG.

[0021] Figure 7 The figure is a comparison result of the bending strength of the polycrystalline silicon ingots obtained by the comparative example and the example in the specific implementation manner of the present invention.

[0022] Figure 8 The Vickers strength comparison results of the polycrystalline silicon ingots obtained by the comparative example and the example in the specific implementation manner of the present invention are shown in FIG.

[0023] Fig. 9 The horizontal cross-sectional crystal flower morphology of the multicrystalline silicon ingot obtained in the comparative example in the specific implementation manner of the present invention.

[0024] Fig.10 This is the crystal flower morphology of a horizontal cross section of a multicrystalline silicon ingot obtained in an example in a specific implementation manner of the present invention.

[0025] In the figure: upper furnace body 1; lower furnace body 2; insulation cage 3; heat exchange platform 4; quartz crucible 5; argon gas guide tube 6; fixed frame 70; stirring rod 710; stirring blade 711; sealing ring 712; bearing 720; rotating motor 721; reducer 722; rotating shaft 723; rotary encoder 724; connecting seat 73; linear guide rail 740; screw rod 741; lifting motor 742; worm gear reducer 743; position encoder 744; connecting seat 73; molten silicon 9. DETAILED DESCRIPTION

[0026] The technical solutions and technical effects of the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings of the present invention.

[0027] In a typical embodiment of the present invention, please refer to Figure 1-3As shown, a columnar polysilicon ingot casting device is provided, comprising: an upper furnace body 1, a lower furnace body 2, an insulation cage 3, a heat exchange platform 4, a quartz crucible 5, an argon gas guide tube 6, a stirring mechanism and a control mechanism; the stirring mechanism comprises: a fixed frame 70, a stirring component, a rotation drive component, a connecting seat 73 and a lifting drive component; the bottom end of the fixed frame 70 is fixedly connected to the top cover of the upper furnace body 1; the lifting drive component and the rotation drive component are both arranged on the fixed frame 1; the rotation drive component is connected to the lifting drive component through the connecting seat 73, and the lifting drive component drives the rotation drive component to perform lifting and lowering movements; the lifting drive component and the rotation drive component are both communicated and connected with the control mechanism; the top end of the stirring component is detachably connected to the rotation drive component, and the bottom end penetrates through the top cover of the upper furnace body 1 and then extends into the argon gas guide tube 6, and extends into the quartz crucible 5; under the control of the control mechanism, the lifting drive component drives the rotation drive component to rise and fall, and then drives the stirring component to rise and fall, and the rotation drive component drives the stirring component to perform rotation and stirring in the quartz crucible 5.

[0028] For further information, see Figure 1-3 As shown, the stirring assembly includes: a stirring rod 710 and a three-petal stirring blade 711; the top end of the stirring rod 710 is detachably connected to the rotation drive assembly, and the bottom end penetrates the top cover of the upper furnace body 1 and extends into the argon gas guide tube 6, and extends into the quartz crucible 5; the three-petal stirring blade 711 is evenly arranged around the circumference of the bottom end of the stirring rod 710; under the control of the control mechanism, the lifting drive assembly drives the rotation drive assembly to lift and lower, and then drives the stirring rod 710 and the stirring blade 711 to lift and lower in the quartz crucible 5, and the rotation drive assembly drives the stirring rod 710 and the stirring blade 711 to rotate and stir in the quartz crucible 5.

[0029] Further, see Figure 3 As shown, in order to ensure the stability of the stirring rod 710 and the stirring blade 711 when used in a high-temperature working environment and not to damage the environment for casting the polysilicon ingot, the stirring rod 710 and the stirring blade 711 are made of materials that are stable at high temperatures and do not react with carbon, silicon, carbon monoxide, carbon dioxide and silicon oxides; each stirring blade 711 is in the shape of a wind blade; for example: the stirring rod 710 and the stirring blade 711 are both made of silicon carbide.

[0030] In this embodiment, the stirring blade 711 is configured to be a fan blade, so that the stirring blade 711 can stir the molten silicon 9 more evenly.

[0031] Further, see Figure 1 and 2As shown, the lifting drive assembly includes: a linear guide 740, a lead screw 741, a lifting motor 742, a worm gear reducer 743 and a position encoder 744; the linear guide 740 is arranged on one side of the fixed frame 1; the connecting seat 73 is arranged horizontally, and one side end is slidably connected to the linear guide 740; the lifting motor 742 is fixedly arranged on the fixed frame 1, and is located on the upper back side of the linear guide 740; the worm gear reducer 743 is fixedly arranged on the fixed frame 1, and is located on the upper side of the linear guide 740 opposite to the lifting motor 742; the output end of the lifting motor 742 is connected to the input end of the worm gear reducer 743; the top end of the lead screw 741 is fixedly connected to the output end of the worm gear reducer 743, and the ball nut of the lead screw 741 is sleeved on the connecting seat 73; the position encoder 744 is connected to the bottom end of the lead screw 741 through a coupling; the lifting motor 742 and the position encoder 744 are both connected to the control mechanism for communication.

[0032] In this embodiment, the top end of the screw rod 741 is fixedly connected to the output end of the worm gear reducer 743, so that the rotary motor 721 drives the screw rod 741 to rotate through the worm gear reducer 743; the ball nut of the screw rod 741 is arranged on the connecting seat 73, and at the same time, one side end of the connecting seat 73 is slidably connected to the linear guide rail 740, when the screw rod 741 rotates, the connecting seat 73 can be raised and lowered on the linear guide rail 740, thereby driving the stirring rod 710 and the stirring blade 711 connected to the connecting seat 73 to rise and fall along the linear guide rail 740; In this embodiment, by connecting the position encoder 744 to the bottom end of the screw rod 741 and communicating with the control mechanism, the rotation of the screw rod 741 is monitored, and the lifting speed and position of the connecting seat 73 are monitored and controlled, and the lifting speed of the stirring rod 710 and the stirring blade 711 and the position of the stirring blade 711 in the quartz crucible 5 are monitored.

[0033] Further, see Figure 1 and 2 As shown, the rotary drive assembly includes: a bearing 720, a rotary motor 721, a reducer 722, a rotary shaft 723 and a rotary encoder 724; a center hole is vertically opened on the upper edge of the connecting seat 73; the bearing 720 is fixedly sleeved in the center hole of the connecting seat 73; the top of the stirring rod 710 is sleeved in the bearing 720; the output end of the rotary motor 721 is connected to the input end of the reducer 722; the output end of the reducer 722 is fixedly connected to the rotary shaft 723; the bottom end of the rotary shaft 723 is connected to the top end of the stirring rod 710 through a coupling; the rotary encoder 724 is connected to the top end of the rotary shaft 723 through a coupling; the rotary motor 721 and the rotary encoder 724 are both connected to the control mechanism for communication.

[0034] In this embodiment, the output end of the reducer 722 is fixedly connected to the rotating shaft 723, so that the rotating motor 721 can drive the reducer 722, and then drive the rotating shaft 723 to rotate; by connecting the rotating shaft 723 to the stirring rod 710, and the stirring rod 710 is sleeved in the bearing 720 on the connecting seat 73, so that when the rotating motor 721 drives the rotating shaft 723 to rotate, it drives the stirring rod 710 and the stirring blade 711 to rotate; In this embodiment, the rotary encoder 724 is connected to the control mechanism for communication, and the rotary encoder 724 is set at the top of the rotating shaft 723 to monitor and control the rotation of the rotating shaft 723, thereby monitoring and controlling the rotation speed of the stirring rod 710 and the stirring blade 711.

[0035] Further, see Figure 1 As shown, in order to improve the safety of the equipment, the stirring mechanism also includes: a sealing ring 712, which is arranged at the intersection of the stirring rod 710 and the furnace cover of the upper furnace body 1.

[0036] Furthermore, the lower furnace body 2 supports the quartz crucible 5 through the heat exchange platform 4; the outside of the quartz crucible 5 is provided with an insulating cage 3 connected to the upper furnace body 1; the argon gas guide tube 6 extends downward from the top cover of the upper furnace body 1, passes through the top cover of the quartz crucible 5 and then extends to the top of the inside of the quartz crucible 5.

[0037] See also Figure 4 As shown, in another typical embodiment of the present invention, a method for casting a columnar polycrystalline silicon ingot is also provided, using the above-mentioned columnar polycrystalline silicon ingot casting equipment, adding a stirring process after the completion of the material mixing and during the crystal growth process, specifically comprising the following steps: S1. After mixing, initial stirring: After the material is oxidized, the stirring rod 710 extends into the molten silicon 9, and the height h between the bottom of the stirring blade 711 and the bottom of the quartz crucible 5 is 1 / 3-1 / 2 of the total height H of the molten silicon 9, and the stirring rod 170 and the stirring blade 711 rotate and stir; By stirring the molten silicon 9 after the completion of the fusion and before the start of crystal growth, the impurities such as dopants in the molten silicon 9 are evenly distributed in the molten silicon, so that the material is more uniform after the crystal grows; at the same time, by setting the stirring time h to 1 / 3-1 / 2 of H, it is easier for the stirring blade 711 to apply stirring force to the molten silicon 9 in the entire quartz crucible 5, and the stirring is more uniform; S2. Stirring at the initial stage of crystal growth: After the initial stage of crystal growth is completed, the stirring rod 710 immediately descends in the molten silicon 9 to a point where the height h of the bottom of the stirring blade 711 from the bottom of the quartz crucible 5 is 1 / 7-1 / 5 of the total height H of the molten silicon 9, and the stirring rod 710 and the stirring blade 711 rotate for stirring; after the stirring is completed, the stirring rod 710 and the stirring blade 711 stop stirring and remain in place, waiting for the crystal height to grow again to the height required when the initial stage of crystal growth is completed; By breaking up the grown crystals and refining the grains after the initial stage of crystal growth, compared with the conventional process of laying 10mm high and 0-5mm seed crystals at the bottom of the quartz crucible 5 as nucleation points for crystal growth, the advantages of this specific implementation are as follows: first, in the conventional process, the bottom 30mm of the polycrystalline silicon ingot formed by the pre-laid seed crystals cannot be used and needs to be cut off and scrapped, resulting in material waste and increased costs, while this specific implementation does not require cutting off the bottom part of the polycrystalline silicon ingot, thereby improving the utilization rate of materials and reducing costs; second, after stirring, these fine grains can improve the uniformity of crystallization and reduce segregation; third, after stirring, these refined grains form new nucleation points. After the stirring is turned off, the molten silicon undergoes the initial growth time and process of crystal growth again on the basis of these new nucleation points, but due to the refinement of the grains, the grain boundary area increases, and the grain boundary free energy is relatively increased, and the atoms at the grain boundary position are relatively unstable, which can absorb and eliminate more stress, thereby ultimately improving the mechanical properties of the polycrystalline silicon ingot; S3. Stirring in the early stage of crystal growth: During the early stage of the entire crystal growth process, the stirring rod 710 is slowly rotated upward from the bottom of the stirring blade 711 at a height h of 1 / 7-1 / 5 of the total height H of the molten silicon 9 from the bottom of the quartz crucible 5; In the early stage of crystal growth, during the entire process of crystal growth, the stirring rod 710 and the stirring blade 711 are slowly rotated and lifted upward, and stirred while being lifted, so that the ungrown molten silicon 9 is in a stirred state before it is about to grow into a crystal. Through stirring, horizontal heat convection is increased, the solid-liquid interface is made flat, and thermal stress is reduced, and finally the mechanical properties of the polycrystalline silicon ingot and the uniformity of the resistivity level are improved, and the problem that in the traditional process, the solid-liquid interface is convex or concave, there is a large thermal stress, and the impurities and the circuit rate level are unevenly distributed due to the large size of the quartz crucible and the large temperature difference between the center and the edge of the molten silicon 9. S4. Stirring during the middle and late stages of crystal growth: During the entire middle and late stages of crystal growth, the stirring rod 710 slowly rotates and rises upward from the position at the end of the early middle stages of crystal growth; S5, at the end of crystal growth, remove the molten silicon: The stirring rod 710 and the stirring blade 711 are moved out of the molten silicon from the position at the end of the middle and late stages of crystal growth.

[0038] Furthermore, in S1, during the initial stirring, the rotation speed of the stirring rod 710 and the stirring blade 711 is 8-10 r / min, and the stirring time is 30 min; In S2, during the initial stage of crystal growth, the stirring rod 710 and the stirring blade 711 rotate at a speed of 10-12 r / min, and the stirring time is 10-15 min; In S3, in the early stage of crystal growth, the lifting speed of the stirring rod 710 and the stirring blade 711 is 10 mm / h-12 mm / h, and the rotation speed is 5-7 r / min; In S4, in the middle and late stages of crystal growth, the lifting speed of the stirring rod 710 and the stirring blade 711 is 9 mm / h-11 mm / h, and the rotation speed is 1-3 r / min; the rotation speed in the middle and late stages of crystal growth is set to be slower than that in the early stages of crystal growth, in order to avoid the stirring blade from rotating too fast in the middle and late stages of crystal growth, which would cause the molten silicon 9 to wash the coating and increase impurities; In S5, at the end of the crystal growth, the stirring rod 170 and the stirring blade 711 are lifted at a speed of 10-15 mm / h.

[0039] Because the impurity content in the crystal is high at the end of crystal growth, the grown crystal needs to be cut off and scrapped. Therefore, on the one hand, stirring is not required. On the other hand, compared with the early and late stages of crystal growth, the lifting speed of the stirring rod 710 and the stirring blade 711 is accelerated, so that the stirring blade 711 can be moved out of the molten silicon more quickly.

[0040] Furthermore, in step S1, during the initial stirring, the height h of the stirring blade 711 from the bottom of the quartz crucible 5 is 1 / 2 of the total height H of the molten silicon 9; In step S2, during the initial stirring of the crystal growth, the height h of the stirring blade 711 from the bottom of the quartz crucible 5 is 1 / 6 of the total height of the molten silicon 9; In step S3, in the early stage of crystal growth, the lifting speed of the stirring rod 170 and the stirring blade 711 is 10 mm / h; In step S4, in the middle and late stages of crystal growth, the lifting speed of the stirring rod 710 and the stirring blade 711 is 9 mm / h.

[0041] Each time the stirring rod 710 and the stirring blade 711 are raised or lowered, the control mechanism controls the lifting drive assembly, which in turn drives the stirring rod 710 and the stirring blade 711 to rise or fall; each time the stirring rod 710 and the stirring blade 711 rotate, the control mechanism controls the rotation drive assembly, which drives the stirring rod 710 and the stirring blade 711 to rotate.

[0042] The following is an example of a G6 quartz crucible, a 940kg feed amount, and a total molten silicon height H of 350mm, and the beneficial effects of the present invention are further described in detail in combination with the comparative examples in the prior art and the specific embodiments of the present invention. In the following comparative examples and embodiments, in the early stage of crystal growth, the growth height of the crystal is from 0 to 15mm; in the middle and early stages of crystal growth, the growth height of the crystal is from 15mm to 200mm; in the middle and late stages of crystal growth, the growth height of the crystal is from 200mm to 340mm; at the end of crystal growth, the growth range of the crystal is from 340mm to a total ingot height of 350mm.

[0043] Comparative Example Using conventional methods in the prior art to cast ingots to obtain polycrystalline silicon ingots; Example

[0044] The columnar polycrystalline silicon ingot casting device and the ingot casting method provided in the specific embodiment of the present invention are used to cast ingots to obtain polycrystalline silicon ingots; Among them, in this embodiment, S1. After mixing, initial stirring: After the material is molten, the stirring rod 710 is extended into the molten silicon. The height h between the bottom of the stirring blade 711 and the bottom of the quartz crucible 5 is 175 mm, that is, 1 / 2 of the total height of the molten silicon 9. The stirring rod 710 and the stirring blade 711 rotate and stir at a speed of 9 r / min for 30 minutes. S2. Stirring at the initial stage of crystal growth: When the crystal grows to 15 mm, after the initial stage of crystal growth is completed, the stirring rod 710 is immediately lowered in the molten silicon 9 to a height h of 60 mm from the bottom of the stirring blade 711 to the bottom of the quartz crucible 5, and the stirring rod 710 and the stirring blade 711 rotate and stir at a speed of 11 r / min for 13 minutes; after the stirring is completed, the stirring rod 710 and the stirring blade 711 stop stirring and remain in place, waiting for the crystal height to grow again to the height required when the initial stage of crystal growth is completed, that is, the crystal grows to 15 mm high; S3. Stirring in the early stage of crystal growth: During the early stage of the entire crystal growth process, that is, the crystal grows from 15 mm to 200 mm, which takes 18 hours, the stirring rod 710 is slowly rotated upward from the bottom of the stirring blade 711 at a height h of 60 mm from the bottom of the quartz crucible 5, and the lifting speed is 10 mm / h and the rotation speed is 6 r / min; S4. Stirring during the middle and late stages of crystal growth: During the middle and late stages of crystal growth, and during the process of the crystal growing from 200 mm to 340 mm, which takes 15 hours, the stirring rod 710 slowly rotates upward from the position at the end of the middle and early stages of crystal growth, with a lifting speed of 9 mm / h and a rotation speed of 2 r / min; S5, at the end of crystal growth, remove the molten silicon: At the end of the crystal growth, the crystal grows from 340 mm to a total ingot height of 350 mm. The stirring rod 710 and the stirring blade 711 are moved out of the molten silicon 9 from the position at the end of the middle and late stages of the crystal growth, and the lifting speed is 15 mm / h.

[0045] The mechanical properties of the polycrystalline silicon ingots obtained by the above comparative example and the embodiment of the columnar polycrystalline silicon ingot device and ingot casting method of the present invention, including elastic modulus, bending strength and Vickers hardness, are compared as follows: Figure 5 , Figure 6 and Figure 7 The comparison results of their resistivity are shown in Figure 8 The crystal flower morphologies on the horizontal cross-sections of the polycrystalline silicon ingots obtained in the comparative example and the example are respectively as shown in Fig. 9 and Fig.10 As shown; Depend on Figure 5 It can be seen that compared with the comparative example, the elastic modulus of the polycrystalline silicon ingot obtained in the embodiment is increased by about 2.5 GPa; Figure 6 It can be seen that compared with the comparative example, the bending strength of the polycrystalline silicon ingot obtained in the embodiment is increased by about 9.5 GPa; Figure 7 It can be seen that, compared with the comparative example, the Vickers hardness of the polycrystalline silicon ingot obtained in the embodiment is increased by about 1.5 GPa; Depend on Figure 8 It can be seen that compared with the comparative example, the resistivity of the polycrystalline silicon ingot obtained in the embodiment is more uniform in different parts; Depend on Fig. 9 and Fig.10 It can be seen that the polycrystalline silicon ingot obtained in the comparative example has different sizes of crystal flowers on the horizontal cross section, and the area of ​​the largest crystal flower is about 20cm 2 , small crystal flower area is about 1.5cm 2 , a difference of 13 times; while the polycrystalline silicon ingot obtained in the embodiment has small and uniform crystal flowers in the horizontal cross section, and the crystal flower area is basically 1-2cm 2 .

[0046] What is disclosed above is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. A person skilled in the art can understand that all or part of the processes of the above embodiments and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A columnar polycrystalline silicon ingot casting device, characterized in that: include: An upper furnace body (1), a lower furnace body (2), an insulation cage (3), a heat exchange platform (4), a quartz crucible (5), an argon gas flow guide tube (6), a stirring mechanism and a control mechanism; the stirring mechanism comprises: a fixed frame (70), a stirring assembly, a rotary drive assembly, a connecting seat (73) and a lifting drive assembly; the bottom end of the fixed frame (70) is fixedly connected to the top cover of the upper furnace body (1); the lifting drive assembly and the rotary drive assembly are both arranged on the fixed frame (70); the rotary drive assembly is connected to the lifting drive assembly through the connecting seat (73), and the lifting drive assembly drives the rotary drive assembly to perform a lifting action; the lifting drive assembly and the rotary drive assembly are both communicated with the control mechanism; the top end of the stirring assembly is detachably connected to the rotary drive assembly, and the bottom end penetrates the top cover of the upper furnace body (1) and extends into the argon gas flow guide tube (6), and extends into the quartz crucible (5); under the control of the control mechanism, the lifting drive assembly drives the rotary drive assembly to lift and lower, thereby driving the stirring assembly to lift and lower, and the rotary drive assembly drives the stirring assembly to perform rotation and stirring in the quartz crucible (5).

2. The columnar polycrystalline silicon ingot casting equipment according to claim 1, wherein: A stirring assembly comprises: a stirring rod (710) and a plurality of stirring blades (711); the top end of the stirring rod (710) is detachably connected to the rotary drive assembly, and the bottom end thereof penetrates the top cover of the upper furnace body (1) and extends into the argon gas guide tube (6), and extends into the quartz crucible (5); the plurality of stirring blades (711) are evenly arranged around the circumference of the bottom end of the stirring rod (710); under the control of the control mechanism, the lifting drive assembly drives the rotary drive assembly to lift and lower, thereby driving the stirring rod (710) and the stirring blades (711) to lift and lower in the quartz crucible (5), and the rotary drive assembly drives the stirring rod (710) and the stirring blades (711) to rotate and stir in the quartz crucible (5).

3. The columnar polycrystalline silicon ingot casting apparatus according to claim 2, wherein: The stirring rod (710) and the stirring blade (711) are made of a material that is stable at high temperatures and does not react with carbon, silicon, carbon monoxide, carbon dioxide, and silicon oxides; each stirring blade (711) is in the shape of a fan blade.

4. The columnar polycrystalline silicon ingot casting apparatus according to claim 2, wherein: The lifting drive assembly comprises: a linear guide rail (740), a screw rod (741), a lifting motor (742), a worm gear reducer (743) and a position encoder (744); the linear guide rail (740) is arranged on one side of the fixed frame (70); the connecting seat (73) is arranged horizontally, and one side end is slidably connected to the linear guide rail (740); the lifting motor (742) is fixedly arranged on the fixed frame (70) and is located on the upper back side of the linear guide rail (740); the worm gear reducer (743) is fixedly arranged on the fixed frame ( 70), located on the upper side of the linear guide rail (740) opposite to the lifting motor (742); the output end of the lifting motor (742) is connected to the input end of the worm gear reducer (743); the top end of the screw rod (741) is fixedly connected to the output end of the worm gear reducer (743), and the ball nut of the screw rod (741) is sleeved on the connecting seat; the position encoder (744) is connected to the bottom end of the screw rod (741) through a coupling; the lifting motor (742) and the position encoder (744) are both connected to the control mechanism for communication.

5. The columnar polycrystalline silicon ingot casting apparatus according to claim 2, wherein: A rotary drive assembly comprises: a bearing (720), a rotary motor (721), a reducer (722), a rotary shaft (723) and a rotary encoder (724); a central hole is vertically provided on the upper edge of the connecting seat (73); the bearing (720) is fixedly sleeved in the central hole of the connecting seat (73); the top of the stirring rod (710) is sleeved in the bearing (720); the output end of the rotary motor (721) is connected to the input end of the reducer (722); the output end of the reducer (722) is fixedly connected to the rotary shaft (723); the bottom end of the rotary shaft (723) is connected to the top end of the stirring rod (710) through a coupling; the rotary encoder (724) is connected to the top end of the rotary shaft (723) through a coupling; the rotary motor (721) and the rotary encoder (724) are both communicatively connected to a control mechanism.

6. The columnar polycrystalline silicon ingot casting equipment according to claim 2, wherein: The stirring mechanism further comprises: a sealing ring (712) arranged at the intersection of the stirring rod (710) and the furnace cover of the upper furnace body (1).

7. The columnar polycrystalline silicon ingot casting apparatus according to claim 1, wherein: The lower furnace body (2) supports the quartz crucible (5) through the heat exchange platform (4); the outside of the quartz crucible (5) is provided with a heat insulation cage (3) connected to the upper furnace body (1); the argon gas guide tube (6) extends downward from the top cover of the upper furnace body (1), passes through the top cover of the quartz crucible (5), and then extends to the upper part of the quartz crucible (5).

8. A method for casting a columnar polycrystalline silicon ingot, using the columnar polycrystalline silicon ingot casting apparatus according to any one of claims 1 to 7, characterized in that: After the material is quenched and during the crystal growth process, a stirring process is added, which specifically includes the following steps: S1. After mixing, stir for the first time: After the material is molten, the stirring rod is extended into the molten silicon, and the height h between the bottom of the stirring blade (711) and the bottom of the quartz crucible (5) is 1 / 3-1 / 2 of the total height H of the molten silicon (9), and the stirring rod (710) and the stirring blade (711) rotate and stir; S2. Stirring during the initial stage of crystal growth: After the initial stage of crystal growth is completed, the stirring rod (710) is immediately lowered in the molten silicon (9) to a position where the height h between the bottom of the stirring blade (711) and the bottom of the quartz crucible (5) is 1 / 7-1 / 5 of the total height H of the molten silicon (9), and the stirring rod (710) and the stirring blade (711) rotate and stir; after the stirring is completed, the stirring rod (710) and the stirring blade (711) stop stirring and remain in place, waiting for the crystal height to grow again to the height required when the initial stage of crystal growth is completed; S3. Stirring in the early stage of crystal growth: During the entire early stage of crystal growth, the stirring rod (710) is slowly rotated upward and lifted from the bottom of the stirring blade (711) to a height h of 1 / 7 to 1 / 5 of the total height H of the molten silicon (9) from the bottom of the quartz crucible (5); S4. Stirring during the middle and late stages of crystal growth: During the entire middle and late stages of crystal growth, the stirring rod (710) slowly rotates and rises from the position at the end of the early stages of crystal growth; S5, at the end of crystal growth, remove the molten silicon (9): The stirring rod (710) and the stirring blade (711) are moved out of the molten silicon from the position at the end of the middle and late stages of crystal growth.

9. The method for casting a columnar polycrystalline silicon ingot according to claim 8, wherein: In S1, during the initial stirring, the stirring rod (710) and the stirring blade (711) rotate at a speed of 8-10 r / min, and the stirring time is 30 min; In S2, during the initial stirring of the crystal growth, the stirring rod (710) and the stirring blade (711) rotate at a speed of 10-12 r / min, and the stirring time is 10-15 min; In S3, in the early stage of crystal growth, the lifting speed of the stirring rod (710) and the stirring blade (711) is 10 mm / h-12 mm / h, and the rotation speed is 5-7 r / min; In S4, in the middle and late stages of crystal growth, the lifting speed of the stirring rod (710) and the stirring blade (711) is 9 mm / h-11 mm / h, and the rotation speed is 1-3 r / min; In S5, at the end of the crystal growth, the lifting speed of the stirring rod (710) and the stirring blade (711) is 10-15 mm / h.

10. The method for casting a columnar polycrystalline silicon ingot according to claim 8, wherein: In step S1, during the initial stirring, the height h of the stirring blade (711) from the bottom of the quartz crucible (5) is 1 / 2 of the total height H of the molten silicon (9); In step S2, during the initial stirring of the crystal growth, the height h between the stirring blade (711) and the bottom of the quartz crucible (5) is 1 / 6 of the total height of the molten silicon (9); In step S3, in the early stage of crystal growth, the lifting speed of the stirring rod (710) and the stirring blade (711) is 10 mm / h; In step S4, in the middle and late stages of crystal growth, the lifting speed of the stirring rod (710) and the stirring blade (711) is 9 mm / h.

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