CN110106546B - High-yield casting monocrystalline silicon growth method and thermal field structure - Google Patents
High-yield casting monocrystalline silicon growth method and thermal field structure Download PDFInfo
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- CN110106546B CN110106546B CN201910439879.2A CN201910439879A CN110106546B CN 110106546 B CN110106546 B CN 110106546B CN 201910439879 A CN201910439879 A CN 201910439879A CN 110106546 B CN110106546 B CN 110106546B
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/02—Elements
- C30B29/06—Silicon
Abstract
The invention discloses a method for growing cast monocrystalline silicon with high yield, which comprises the following steps: fixing seed crystals on a seed crystal clamping mechanism, heating and melting the silicon material in the thermal field, and keeping the height of the seed crystals and the height of the top molding heater above the liquid level of the silicon material solution; after the silicon material is melted, the seed crystal clamping framework guides the seed crystal to be immersed below the liquid level of the silicon material melt; when the seed crystal part under the liquid level of the silicon material melt is melted to form a new solid-liquid interface, the seed crystal clamping mechanism is lifted upwards, and the silicon material melt is crystallized downwards from the seed crystal surface to form a crystal ingot; in the process of upwards pulling the seed crystal clamping mechanism, the top heat dissipation door of the thermal field is opened towards two sides, and the top molding heater moves downwards along with the liquid level of the silicon material melt; after the crystallization process is finished, keeping the top heat dissipation door as the maximum opening, separating the seed crystal, and taking out the crystal ingot. The invention also discloses a thermal field structure adopting the method. The method and the thermal field structure can reduce the cutoff amount of the low minority carrier red region of the head, the tail and the edge of the cast monocrystalline silicon ingot and improve the product percent of pass.
Description
Technical Field
The invention relates to the technical field of solar silicon materials, in particular to a high-yield casting monocrystalline silicon growth method and a thermal field structure.
Background
The solar energy has abundant resources and wide distribution, and is the renewable energy with the most development potential. Solar photovoltaic power generation is one of the most important solar energy utilization modes due to the advantages of environmental friendliness, high conversion efficiency, convenience in installation and the like. Under the common efforts of the photovoltaic industry in China, the electricity consumption cost of photovoltaic power generation in nearly ten years is basically close to the grid electricity price of traditional firepower. The market for the application of photovoltaic power generation will further expand rapidly in the foreseeable future.
Monocrystalline silicon wafers and polycrystalline silicon wafers are two basic carriers for photovoltaic cell fabrication. The single crystal silicon wafer grown and cut by the Cz method is favored by a high-efficiency battery process production line due to less crystal defects, long minority carrier lifetime and stable quality. Although the crystal quality of the polycrystalline silicon wafer is lower than that of a monocrystalline silicon wafer, the polycrystalline silicon wafer has the characteristics of large ingot productivity, low unit energy consumption, low requirement on silicon materials, high silicon wafer cost performance and the like, occupies more than half of market share in the past years and is the most main photovoltaic cell base material.
In order to reduce the performance difference between the polycrystalline silicon wafer and the monocrystalline silicon wafer, in the past years, an ingot semi-melting process is developed through the adjustment of a thermal field and the process, and the process is characterized in that a seed crystal for guiding the growth of the crystal is firstly paved at the bottom of a crucible, and other silicon is fed into the crucible. In the stage of melting the silicon material, the seed crystal is kept partially molten by a thermal field and a process, and then the crystal is directionally solidified from the top to the bottom of the seed crystal. The use of granules as seeds produces a highly efficient multicrystalline process characterized by small grains, and the use of monocrystalline silicon blocks as seeds produces cast monocrystalline silicon with an appearance similar to that of a single crystal.
The high-efficiency polycrystal with small crystal grains as characteristics is applied to the large batch from now, although the middle part of the high-efficiency polycrystal is continuously developed by the size of a thermal field (G5 is upgraded to the current G8), the overall performance is basically stable, the high-efficiency polycrystal is always 1-1.5% (absolute value) different from the battery conversion efficiency of a monocrystalline silicon wafer, and the high-efficiency polycrystal is difficult to break through. The cast monocrystalline silicon process integrating the ingot casting and the Cz monocrystalline is considered to be the most important development direction of the next generation of solar silicon materials because a part of silicon wafers can adopt the alkaline texturing cell process which is the same as the Cz monocrystalline silicon wafers due to low defect density and consistent crystal orientation, and the cell conversion efficiency (difference is less than 0.5%) which is basically equivalent to the Cz monocrystalline silicon is obtained.
Compared with high-efficiency polycrystal which also adopts a semi-melting process, the difficulty of the monocrystalline silicon casting process is as follows: 1) in the melting stage, partial melting of the seed crystal (Cz single crystal) is realized through a thermal field and a process design; 2) through the optimization design of the thermal field, the difference value between the center and the edge of a solid-liquid interface is reduced, and the usage amount of the Cz single crystal is reduced so as to reduce the cost; 3) the seed crystal treatment foundation reduces the generation and proliferation of crystal defects at the joints of the seed crystals; 4) the optimization of the thermal field structure reduces the crystal grain nucleation of the crucible wall and the growth to the inside of the crystal, destroys the crystal structure of the quasi-single crystal and reduces the qualification rate of the cast single crystal silicon; 5) in the growth process of the cast monocrystalline silicon, the generation and proliferation of internal defects of the crystal are controlled; 6) the product yield is reduced by cutting off the bottom, the head and the red region with low minority carriers at the edge of the ingot. To obtain a 100% appearance of single crystal-like silicon wafers, manufacturers typically employ large crucibles, increasing the amount of truncation of the ingot edge, which further contributes to a reduction in the yield of cast single crystal silicon. According to measurement and calculation, the yield of the cast monocrystalline silicon product is only between 45% and 60% without considering the reduction of the yield of the crystal caused by defects in the crystal growth process, and is reduced by 10% to 20% compared with the common high-efficiency polycrystal, so that the processing cost of the cast monocrystalline silicon is obviously increased, and the method is one of important reasons for restricting the large-scale application of the cast monocrystalline silicon process.
Patent CN 102732947B proposes a structural design of adding a side heater during movement on the basis of a thermal field structure adopted in the traditional semi-melting process of casting monocrystalline silicon, aiming at inhibiting the formation of new crystal nuclei on the crucible wall and the inward growth of crystals. In the growth process of casting monocrystalline silicon, the truncation amount of the side edge of the crystal ingot is reduced, and the benefit of the crystal ingot is improved. However, the low minority carrier red areas at the head and the tail of the ingot, the mass of which accounts for about 25 percent of the total material loading amount, cannot be improved, and the technical problem that the ingot casting process by the traditional method cannot avoid is solved.
Disclosure of Invention
The invention aims to provide a high-yield casting monocrystalline silicon growth method and a thermal field structure, which can reduce the cutting amount of low minority carrier red regions of a head, a tail and side pieces of a casting monocrystalline silicon ingot and improve the product yield (or yield) of the casting monocrystalline silicon.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a high yield cast single crystal silicon growth method, comprising the steps of:
(1) fixing seed crystals on a seed crystal clamping mechanism, heating and melting the silicon material in the thermal field, and keeping the heights of the seed crystals and the top molding heater above the liquid level of the silicon material solution in the heating and melting stage;
(2) after the silicon material is melted, the seed crystal clamping framework guides the seed crystal to contact the melt liquid level, so that the seed crystal is immersed below the melt liquid level of the silicon material; when the seed crystal part under the liquid level of the silicon material melt is melted to form a new solid-liquid interface, the seed crystal clamping mechanism is lifted upwards, and the silicon material melt is crystallized downwards from the seed crystal surface to form a crystal ingot; in the process of upwards pulling the seed crystal clamping mechanism, the top heat dissipation door of the thermal field is opened towards two sides, and the top molding heater moves downwards along with the liquid level of the silicon material melt and is positioned below the liquid level of the silicon material melt;
(3) and after the crystallization process is finished, keeping the top heat dissipation door as the maximum opening, separating the seed crystal clamping and holding mechanism from the seed crystal, and taking out the crystal ingot.
In the step (1), the silicon material in the thermal field is heated and melted by a program temperature, and protective gas is introduced.
In the invention, the seed crystal is fixed on the seed crystal clamping mechanism, and in the step (1), namely, during the melting process of the silicon material, the seed crystal does not contact with the silicon material or the silicon material melt in the crucible. In the step (2), namely, in the crystallization process, after the silicon material in the crucible is melted, the seed crystal clamping mechanism can drive the seed crystal to move downwards to be contacted with the liquid level of the melt; after the seed crystal is partially melted, gradually opening a top heat dissipation door, forming temperature gradient distribution of upper cold and lower heat in a thermal field, and under the induction of the seed crystal, starting directional crystallization of the melt in the crucible from top to bottom along the seed crystal; in the crystallization process, the crystal is driven by the seed crystal clamping mechanism to be lifted upwards, finally, the melt is completely crystallized and is loaded at the lower part of the seed crystal clamping mechanism, and the formed crystal is not contacted with the crucible all the time; in the crystallization process, the top molding heater descends along with the descending of the liquid level of the melt and is maintained below the liquid level of the melt, and finally the melt is completely solidified or only a small part of high-metal impurity pot bottom materials are remained. In the whole ingot growing process, the ingot is not contacted with the crucible, so that the influence on the quality of the ingot caused by the diffusion of metal impurities in the crucible to the ingot is avoided.
In the step (2), the seed crystal is immersed below 5mm of the liquid level of the silicon material melt.
In the step (2), after 10-30 minutes, the seed crystal part under the liquid level of the silicon material melt is melted to form a new solid-liquid interface.
In the step (2), the seed crystal clamping mechanism is lifted upwards at a speed of 5-25 mm/h. The speed of the seed crystal clamping mechanism which is lifted upwards is the crystallization speed of the silicon material melt.
In the step (2), the distance between the top molding heater and the liquid level of the silicon material melt is 20-50 mm. The growth trend of the crystal ingot towards the periphery can be controlled by controlling the position and the heating power of the top molding heater.
The seed crystal is formed by a monocrystalline silicon block processed by Cz monocrystalline, the shape of the seed crystal block can be a cube or a cuboid, and the crystal direction in the vertical direction is the <100> direction. The seed crystals are spliced into a square structure and fixed on the seed crystal clamping mechanism, and the seed crystal blocks are connected seamlessly.
The seed crystal is formed by cutting and splicing Czochralski single crystals, the thickness is 20-30 mm, the cross section is square, and the side length is 500-1500 mm. The thickness of the monocrystalline silicon block is selected to be 20 mm-30 mm by comprehensively considering the cost and the actual operation.
Preferably, the side length is 960mm (G6).
The invention also provides a thermal field structure of the cast monocrystalline silicon growth method with high yield, the thermal field structure comprises a furnace body, a crucible, a seed crystal clamping mechanism which is positioned right above the crucible and can move up and down, and a top heat dissipation door which can move transversely are arranged in the furnace body; a heater and a heat preservation frame are arranged on the outer sides of the side part and the bottom part of the crucible, and the heater is positioned between the crucible and the heat preservation frame; a top molding heater capable of moving up and down is arranged around the seed crystal clamping mechanism, and the top cooling doors are positioned at two sides of the seed crystal clamping mechanism; the heat preservation frame and the top heat dissipation door form a closed space.
The furnace body adopts an upper furnace cover opening mode to carry out loading and unloading work of materials.
In the thermal field structure provided by the invention, the seed crystal clamping mechanism is a moving part which can move up and down, and the seed crystal is separated from the liquid level in the melting process of the silicon material in the crucible. In the crystallization process: firstly, seeding is carried out, the seed crystal is driven to be partially soaked below the liquid level of the high-temperature silicon material melt, after the seed crystal is partially melted, the top heat dissipation door is opened, the crystal grows downwards from the seed crystal surface, the seed crystal clamping mechanism is slowly lifted upwards, and finally the melt in the crucible is kept to be completely solidified or only a small amount of high-concentration metal impurity pot bottom materials are left.
The heaters arranged on the lateral part and the outer side of the bottom of the crucible and the top molding heater respectively adopt independent temperature control and power supply units.
The crucible has dimensions of 1200mm by 540mm (G7) or 1350mm by 540mm (G8).
The invention has the beneficial effects that: different from the traditional directional solidification mode, in the whole crystal growth process, the crystal ingot grown and formed in the method provided by the invention is not contacted with the crucible, so that the diffusion of metal impurities to the interior of the crystal ingot can be avoided, the low minority carrier red areas at the head, the tail and the edge of the traditional polycrystalline cast ingot can be greatly reduced, and the qualification rate of products can be greatly improved. The ingot is not contacted with the crucible, so that the growth of anisotropic crystal grains on the side wall of the crucible to the inside of the ingot is fundamentally avoided, the problem of the growth of anisotropic crystal grains of the traditional cast monocrystalline silicon is avoided, and the yield of the cast monocrystalline silicon is further improved.
On the other hand, compared with the traditional method for casting the monocrystalline silicon, the seed crystal is not contacted with the melt in the whole melting stage, so that the problem of seed crystal protection in the traditional monocrystalline silicon casting process is not needed, the melting temperature can be increased, the melting time of the silicon material is reduced, and the production capacity is improved.
On the other hand, the method is different from the traditional method for growing the cast monocrystalline silicon with the seed crystal laid at the bottom of the crucible, the invention avoids the pollution of the seed crystal by the metal from the crucible and other silicon materials in the whole melting stage, and the seed crystal is more convenient to reuse after being cut off after being used, thereby reducing the cost of casting the Cz monocrystalline seed crystal in the monocrystalline silicon.
On the other hand, the method is different from the traditional Cz method for growing the monocrystalline silicon, the crystal of the cast monocrystalline silicon grown by the method provided by the invention completely grows under the induction of seed crystals, the processes of necking and shouldering which are necessary for the Cz method are avoided, the Cz method crystal and the crucible are circular, the crystal and the crucible have certain rotation requirements in the crystal growing process, and the cast monocrystalline silicon grown by the method has the advantages that the crystal ingot is square, the crucible is square or circular, and the crystal and the crucible do not need to rotate in the whole crystal growing stage. The process of crystal growth of the invention does not have the shouldering process in the Cz single crystal, and the ingot casting high single crystal which grows out is all crystallized under the induction of seed crystals. In addition, the crystal of silicon of Cz method grown crystal is dislocation-free, and the crystal grown by the present invention contains dislocations because there is no necking process in Cz method.
Therefore, the growth method and the thermal field structure of the cast monocrystalline silicon provided by the invention can fundamentally solve the problem of low yield of the cast monocrystalline silicon caused by the truncation of the head, the tail and the periphery of the cast monocrystalline silicon, and greatly improve the yield of the cast monocrystalline silicon.
Drawings
FIG. 1 is a schematic diagram of the cross-sectional centrosymmetric right half of a thermal field structure provided by the present invention;
FIG. 2 is a schematic structural diagram of a thermal field structure provided by the present invention during seeding;
FIG. 3 is a schematic structural view of a thermal field structure provided by the present invention when crystallization is completed;
the device comprises a heat dissipation door 1, a side heat preservation frame 2, a top molding heater 3, a side heater 4, a bottom heater 5, a furnace body 6, a seed crystal clamping mechanism 7, a seed crystal 8, a crystal ingot 9, a melt 10, a crucible and a supporting component 11, and a bottom heat preservation plate 12.
Detailed Description
In order that those skilled in the art will better understand the disclosure, the invention will be described in further detail with reference to the accompanying drawings and specific embodiments. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1-3, the thermal field structure of the method for growing cast monocrystalline silicon provided by the invention comprises a furnace body 6, a crucible 11 (also comprising a crucible supporting component), a seed crystal clamping mechanism 7 which is positioned right above the crucible 11 and can move up and down, and a top heat dissipation door 1 which can move transversely are arranged in the furnace body 6; heaters (comprising a side heater 4 and a bottom heater 5) and heat-insulating frames (such as a side heat-insulating frame 2 and a bottom heat-insulating plate 12) are arranged on the outer sides of the side part and the bottom of the crucible 11, and the side heater 4 and the bottom heater 5 are positioned between the crucible 11 and the side heat-insulating frame 2 or the bottom heat-insulating plate 12; a top molding heater 3 which can move up and down is arranged around the seed crystal clamping mechanism 7, and top heat dissipation doors 1 are positioned at two sides of the seed crystal clamping mechanism 7; the heat preservation frame and the top heat dissipation door 1 form a closed space.
The method for growing and casting the monocrystalline silicon by the thermal field structure comprises the following steps:
(1) fixing the seed crystal 8 on the seed crystal clamping mechanism 7, heating and melting the silicon material in the thermal field, and keeping the heights of the seed crystal 7 and the top molding heater 3 above the liquid level of the silicon material solution 10 in the heating and melting stage;
(2) after the silicon material is melted, the seed crystal clamping framework 7 guides the seed crystal 8 to contact the liquid level of the silicon material melt 10, so that the seed crystal 8 is immersed below the liquid level of the silicon material melt 10; after the seed crystal 8 is partially melted, the seed crystal holding mechanism 7 is pulled upwards, and the silicon material melt 10 is crystallized downwards from the surface of the seed crystal 8 to form an ingot; in the process of lifting the seed crystal clamping mechanism 7 upwards, the top heat dissipation door 1 of the thermal field is opened towards two sides, and the top molding heater 3 moves downwards along with the liquid level of the silicon material melt 10 and is positioned below the liquid level of the silicon material melt;
(3) after the crystallization process is finished, the top heat dissipation door is kept as the maximum opening, the seed crystal clamping and holding mechanism 7 and the seed crystal 8 are separated, and the crystal ingot 9 is taken out.
Example 1
In this embodiment, to maintain the ease of subsequent ingot 9 squaring processes, crystal growth is carried out using the current mainstream G6 ingot dimensions. The seed crystal 8 is a Cz single crystal silicon block with a block size of 165mm 25mm and a crystal orientation of <100> direction, and is fixed on the seed crystal clamping mechanism 7, and each seed crystal is closely adjacent to each other without a visible gap. The crucible 11 was a conventional G7 size five-sided high purity crucible containing a seed charge of about 810kg total weight of silicon. The upper furnace cover is opened and the crucible 11 filled with the silicon material is placed in the thermal field. The lower surface of the seed crystal 8 is not in contact with the silicon material in the crucible 11.
As shown in FIG. 1, the top heat-radiating door 1 is closed, the upper lid of the furnace body 6 is closed, and vacuum is applied to a pressure of 10pa or less. And (4) running a program, starting the side heater 4 and the bottom heater 5, gradually raising the temperature to 1520 ℃ according to a process temperature rise curve, and keeping the temperature until the silicon material is completely melted. When the temperature in the furnace body 6 rises to 1200 ℃, protective gas (argon) is introduced, the flow rate is 20-50L/min, and the furnace pressure is controlled to be 400-600 mbar.
After the melting is finished, the seed crystal clamping mechanism 7 drives the seed crystal 7 to move downwards and invade the liquid level of the silicon material melt 10 below 5 mm. After about 30 minutes, the top heat dissipation door 1 is opened 100mm to both sides; the seed crystal clamping mechanism 7 moves upwards at the speed of 5-25 mm/h, the top heat dissipation door 1 is opened towards two sides at the speed of 5-15 mm/h, and the maximum moving distance of a single side is 500 mm. The top molding heater 3 controls heating power for the growing trend of the crystal ingot towards the periphery, and moves downwards according to the lifting distance of the seed crystal 8 to maintain the distance of 30-50 mm from the liquid level of the silicon material melt 10. The crystallization time was 30 h.
After the crystallization process is finished, the heater is gradually cooled and finally closed according to a process set curve, the heat dissipation door at the top 1 is kept as the maximum opening, the temperature is reduced to 350 ℃, and the furnace pressure is increased to 1000 mbar. And opening the upper furnace cover, separating the seed crystal clamping and holding mechanism 7 from the seed crystal 8, and taking out the crystal ingot 9. Ingot 9 had a size of about 980mm 360mm (containing the seed crystal), and about 3kg of silicon material remained at the bottom of crucible 11 for a total production cycle of about 60 hours. After the ingot 9 is cooled to normal temperature, the seed crystal end of the ingot 9 is first cut into 30mm pieces as a whole and recovered as a bulk seed crystal. The other end was cut by 20mm and used as a reclaimed material. The crystal ingot passes through a squarer and is cut into finished product rods of 159mm to 310mm, and the appearance crystal orientation of the crystal rods is consistent and no misoriented crystal grains are generated through detection. The final yield of the cast monocrystalline silicon is 81 percent, and is improved by more than 20 percent compared with the traditional yield of the cast monocrystalline silicon.
Example 2
To maintain the convenience of the subsequent ingot squaring process, crystal growth was carried out using the current mainstream G6 ingot size. The seed crystal is a Cz single crystal silicon block with the size of 64 blocks being 125mm 25mm and the crystal direction being <100> direction, and is fixed on a seed crystal clamping mechanism, and the seed crystals are closely adjacent to each other without visible gaps. The crucible was a conventional G7 size five-sided high purity crucible containing a seed crystal charged with a total weight of about 810kg of silicon material. Using the same procedure as in example 1, the ingot was about 980mm 360mm (including seed crystal) and about 3kg of silicon material remained at the bottom of the crucible after discharge. After the ingot is cooled to normal temperature, the seed crystal end of the ingot is cut into 30mm in whole and recycled as a large seed crystal. The other end was cut by 20mm and used as a reclaimed material. The crystal ingot passes through a squarer and is cut into finished product rods of 159mm to 310mm, and the appearance crystal orientation of the crystal rods is consistent and no misoriented crystal grains are generated through detection. The final yield of cast single crystal silicon is about 82%.
Example 3
In order to reduce the use cost of the Cz single crystal, the whole seed crystal block recovered in the first embodiment is used and used as a whole seed crystal after being cleaned. First, the seed crystal was held in a seed crystal holder using a G7 crucible containing about 810kg of the total weight of the seed silicon material. And opening the upper furnace cover, and placing the crucible filled with the silicon material in the thermal field. The lower surface of the seed crystal is not contacted with the crucible silicon material. Using the same procedure as in example 1, the total production cycle was about 60 hours, and after removal from the furnace, the ingot size was about 980mm 360mm (containing the seed crystals), and about 3kg of silicon material remained at the bottom of the crucible. After the ingot was cooled to room temperature, the seed crystal end of the ingot was cut into 30mm pieces as a whole and recovered as a large seed crystal. The other end was cut by 20mm and used as a reclaimed material. The crystal ingot passes through a squarer and is cut into finished product rods of 159mm to 310mm, and the appearance crystal orientation of the crystal rods is consistent and no misoriented crystal grains are generated through detection. The final yield of the cast monocrystalline silicon is 80%.
Claims (3)
1. A high yield casting monocrystalline silicon growth method is characterized in that a thermal field structure is adopted, the thermal field structure comprises a furnace body, a crucible, a seed crystal clamping mechanism which is positioned right above the crucible and can move up and down and a top heat dissipation door which can move transversely are arranged in the furnace body; a heater and a heat preservation frame are arranged on the outer sides of the side part and the bottom part of the crucible, and the heater is positioned between the crucible and the heat preservation frame; a top molding heater capable of moving up and down is arranged around the seed crystal clamping mechanism, and the top cooling doors are positioned at two sides of the seed crystal clamping mechanism; the heat-insulating frame and the top heat-radiating door form a closed space;
the growth method of the cast monocrystalline silicon comprises the following steps:
the crystal growth is carried out by adopting the size of the current mainstream G6 ingot, the seed crystal uses 36 pieces of Cz single crystal silicon blocks with the size of 165mm, 165mm and 25mm and the crystal direction of <100> direction, the Cz single crystal silicon blocks are fixed on a seed crystal clamping mechanism, each piece of seed crystal is closely adjacent, no visible gap exists, the crucible adopts a traditional G7 size five-surface high-purity crucible, the total weight of the seed crystal loaded with silicon material is 810kg, an upper furnace cover is opened, the crucible loaded with the silicon material is placed in a thermal field, and the lower surface of the seed crystal is not contacted with the silicon material in the crucible;
closing a top heat dissipation door, closing an upper furnace cover of a furnace body, vacuumizing to below 10Pa, running a program, starting a side heater and a bottom heater, gradually raising the temperature to 1520 ℃ according to a process temperature rise curve, keeping the temperature until silicon materials are completely melted, starting introducing protective gas argon when the temperature in the furnace body rises to 1200 ℃, controlling the flow rate to be 20-50L/min, and controlling the furnace pressure to be 400-600 mbar;
after the melting is finished, the seed crystal clamping mechanism drives the seed crystal to move downwards and invade the liquid level of the silicon material melt by less than 5mm, and after 30 minutes, the top heat dissipation door is opened by 100mm towards two sides; the seed crystal clamping mechanism moves upwards at the speed of 5-25 mm/h, the top heat dissipation door is opened towards two sides at the speed of 5-15 mm/h, the maximum moving distance of a single side is 500mm, the top molding heating is the growth trend of the crystal ingot towards the periphery, the heating power is controlled, the seed crystal moves downwards according to the lifting distance of the seed crystal, the distance between the seed crystal and the liquid level of the silicon material melt is maintained to be 30-50 mm, and the crystallization process is 30 h;
after the crystallization process is finished, the heater is gradually cooled and finally closed according to a process set curve, a top heat dissipation door is kept as a maximum opening, the temperature is reduced to 350 ℃, the furnace pressure is increased to 1000mbar, an upper furnace cover is opened, a seed crystal clamping and holding mechanism is separated from the seed crystal, a crystal ingot is taken out, the size of the crystal ingot is 980mm 360mm, the crystal ingot contains the seed crystal, 3kg of silicon material is remained at the bottom of a crucible, the total production period is 60 hours, after the crystal ingot is cooled to the normal temperature, firstly, the whole seed crystal end of the crystal ingot is cut into 30mm, the crystal ingot is used as a large-block-shaped seed crystal, the other end of the crystal ingot is cut into 20mm and used as a recovery material, the crystal ingot is cut into 159mm, 310mm finished product rods are used, the appearance and crystal orientation of the crystal ingot are consistent through.
2. A high yield casting monocrystalline silicon growth method is characterized in that a thermal field structure is adopted, the thermal field structure comprises a furnace body, a crucible, a seed crystal clamping mechanism which is positioned right above the crucible and can move up and down and a top heat dissipation door which can move transversely are arranged in the furnace body; a heater and a heat preservation frame are arranged on the outer sides of the side part and the bottom part of the crucible, and the heater is positioned between the crucible and the heat preservation frame; a top molding heater capable of moving up and down is arranged around the seed crystal clamping mechanism, and the top cooling doors are positioned at two sides of the seed crystal clamping mechanism; the heat-insulating frame and the top heat-radiating door form a closed space;
the growth method of the cast monocrystalline silicon comprises the following steps:
the crystal growth is carried out by adopting the size of the current mainstream G6 ingot, the seed crystal uses a 64-block size of 125mm 25mm, the Cz single crystal silicon block with the crystal direction of <100> is fixed on a seed crystal clamping mechanism, each seed crystal is closely adjacent, no visible gap exists, the crucible adopts a traditional G7-size five-surface high-purity crucible, the total weight of the seed crystal loaded with silicon material is 810kg, an upper furnace cover is opened, the crucible loaded with the silicon material is placed in a thermal field, and the lower surface of the seed crystal is not contacted with the silicon material in the crucible;
closing a top heat dissipation door, closing an upper furnace cover of a furnace body, vacuumizing to below 10Pa, running a program, starting a side heater and a bottom heater, gradually raising the temperature to 1520 ℃ according to a process temperature rise curve, keeping the temperature until silicon materials are completely melted, starting introducing protective gas argon when the temperature in the furnace body rises to 1200 ℃, controlling the flow rate to be 20-50L/min, and controlling the furnace pressure to be 400-600 mbar;
after the melting is finished, the seed crystal clamping mechanism drives the seed crystal to move downwards and invade the liquid level of the silicon material melt by less than 5mm, and after 30 minutes, the top heat dissipation door is opened by 100mm towards two sides; the seed crystal clamping mechanism moves upwards at the speed of 5-25 mm/h, the top heat dissipation door is opened towards two sides at the speed of 5-15 mm/h, the maximum moving distance of a single side is 500mm, the top molding heating is the growth trend of the crystal ingot towards the periphery, the heating power is controlled, the seed crystal moves downwards according to the lifting distance of the seed crystal, the distance between the seed crystal and the liquid level of the silicon material melt is maintained to be 30-50 mm, and the crystallization process is 30 h;
after the crystallization process is finished, the heater is gradually cooled and finally closed according to a process set curve, a top heat dissipation door is kept as a maximum opening, the temperature is reduced to 350 ℃, the furnace pressure is increased to 1000mbar, an upper furnace cover is opened, a seed crystal clamping and holding mechanism is separated from the seed crystal, an ingot is taken out, the size of the ingot is 980mm 360mm, the ingot contains the seed crystal, 3kg of silicon material is left at the bottom of a crucible, after the ingot is cooled to the normal temperature, the whole seed crystal end of the ingot is cut into 30mm, the ingot is used as a large block seed crystal for recycling, the other end of the ingot is cut into 20mm, the ingot is cut into 159mm 310mm finished product rods through an squarer, the appearance and crystal orientation of the ingot are consistent, no oriented crystal grains are generated, and the final yield of cast monocrystalline silicon is 82.
3. A high yield casting monocrystalline silicon growth method is characterized in that a thermal field structure is adopted, the thermal field structure comprises a furnace body, a crucible, a seed crystal clamping mechanism which is positioned right above the crucible and can move up and down and a top heat dissipation door which can move transversely are arranged in the furnace body; a heater and a heat preservation frame are arranged on the outer sides of the side part and the bottom part of the crucible, and the heater is positioned between the crucible and the heat preservation frame; a top molding heater capable of moving up and down is arranged around the seed crystal clamping mechanism, and the top cooling doors are positioned at two sides of the seed crystal clamping mechanism; the heat-insulating frame and the top heat-radiating door form a closed space;
the growth method of the cast monocrystalline silicon comprises the following steps:
the whole seed crystal block recovered by the method of claim 1 is used as a whole seed crystal after being washed, and is firstly fixed on a seed crystal holding mechanism, a G7 crucible containing 810kg of the total weight of seed crystal silicon materials is used, an upper furnace cover is opened, the crucible containing the silicon materials is placed in a thermal field, and the lower surface of the seed crystal is not contacted with the silicon materials in the crucible;
closing a top heat dissipation door, closing an upper furnace cover of a furnace body, vacuumizing to below 10Pa, running a program, starting a side heater and a bottom heater, gradually raising the temperature to 1520 ℃ according to a process temperature rise curve, keeping the temperature until silicon materials are completely melted, starting introducing protective gas argon when the temperature in the furnace body rises to 1200 ℃, controlling the flow rate to be 20-50L/min, and controlling the furnace pressure to be 400-600 mbar;
after the melting is finished, the seed crystal clamping mechanism drives the seed crystal to move downwards and invade the liquid level of the silicon material melt by less than 5mm, and after 30 minutes, the top heat dissipation door is opened by 100mm towards two sides; the seed crystal clamping mechanism moves upwards at the speed of 5-25 mm/h, the top heat dissipation door is opened towards two sides at the speed of 5-15 mm/h, the maximum moving distance of a single side is 500mm, the top molding heating is the growth trend of the crystal ingot towards the periphery, the heating power is controlled, the seed crystal moves downwards according to the lifting distance of the seed crystal, the distance between the seed crystal and the liquid level of the silicon material melt is maintained to be 30-50 mm, and the crystallization process is 30 h;
after the crystallization process is finished, the heater is gradually cooled and finally closed according to a process set curve, a top heat dissipation door is kept as a maximum opening, the temperature is reduced to 350 ℃, the furnace pressure is increased to 1000mbar, an upper furnace cover is opened, a seed crystal clamping and holding mechanism is separated from the seed crystal, a crystal ingot is taken out, the size of the crystal ingot is 980mm 360mm, the crystal ingot contains the seed crystal, 3kg of silicon material is remained at the bottom of a crucible, the total production period is 60 hours, after the crystal ingot is cooled to the normal temperature, firstly, the whole seed crystal end of the crystal ingot is cut into 30mm, the crystal ingot is used as a large-block-shaped seed crystal, the other end of the crystal ingot is cut into 20mm and used as a recovery material, the crystal ingot is cut into 159mm, 310mm finished product rods are used, the appearance and crystal orientation of the crystal ingot are consistent through.
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