CN110777425A - Casting silicon single crystal furnace with seed crystal lifting unit and silicon single crystal growth method - Google Patents
Casting silicon single crystal furnace with seed crystal lifting unit and silicon single crystal growth method Download PDFInfo
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- CN110777425A CN110777425A CN201911161271.4A CN201911161271A CN110777425A CN 110777425 A CN110777425 A CN 110777425A CN 201911161271 A CN201911161271 A CN 201911161271A CN 110777425 A CN110777425 A CN 110777425A
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- 239000013078 crystal Substances 0.000 title claims abstract description 237
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 109
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 109
- 239000010703 silicon Substances 0.000 title claims abstract description 109
- 238000002109 crystal growth method Methods 0.000 title claims abstract description 6
- 238000005266 casting Methods 0.000 title abstract description 14
- 238000000034 method Methods 0.000 claims abstract description 24
- 238000001816 cooling Methods 0.000 claims description 58
- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims description 13
- 238000002844 melting Methods 0.000 claims description 12
- 230000008018 melting Effects 0.000 claims description 12
- 230000003028 elevating effect Effects 0.000 claims description 11
- 239000003638 chemical reducing agent Substances 0.000 claims description 10
- 238000002425 crystallisation Methods 0.000 claims description 10
- 230000008025 crystallization Effects 0.000 claims description 10
- 239000010453 quartz Substances 0.000 claims description 9
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 9
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 8
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 7
- 239000000843 powder Substances 0.000 claims description 7
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 7
- 239000011248 coating agent Substances 0.000 claims description 6
- 238000000576 coating method Methods 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 claims description 6
- 239000007788 liquid Substances 0.000 claims description 6
- 239000000463 material Substances 0.000 claims description 5
- 230000000087 stabilizing effect Effects 0.000 claims description 5
- 229910052786 argon Inorganic materials 0.000 claims description 4
- 239000000919 ceramic Substances 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 4
- 238000001035 drying Methods 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 3
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 claims description 3
- 238000005245 sintering Methods 0.000 claims description 3
- 238000011049 filling Methods 0.000 claims 1
- 238000006243 chemical reaction Methods 0.000 abstract description 4
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 239000003513 alkali Substances 0.000 abstract description 2
- 235000012431 wafers Nutrition 0.000 description 12
- 210000004027 cell Anatomy 0.000 description 9
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 8
- 239000000155 melt Substances 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- LBZRRXXISSKCHV-UHFFFAOYSA-N [B].[O] Chemical class [B].[O] LBZRRXXISSKCHV-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 210000003850 cellular structure Anatomy 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
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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
- C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
- C30B11/02—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method without using solvents
-
- 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
- C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
- C30B11/006—Controlling or regulating
-
- 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
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
Abstract
The invention discloses a casting silicon single crystal furnace with a seed crystal lifting unit and a silicon single crystal growth method. The casting silicon single crystal furnace comprises a furnace body, a crystal seed lifting unit, a temperature control unit and a crystal growth unit; the crystal growth unit is positioned in the furnace body; the crystal seed lifting unit is positioned above the furnace body, penetrates into the furnace body to the crystal growth unit and is used for inserting the crystal seed into the crystal growth unit; the temperature control unit is used for providing the temperature required by the crystal growth in the crystal growth unit. The seed crystal lifting unit comprises a corrugated pipe, a seed crystal lifting rod and a lifting mechanism, and the lifting mechanism is used for lifting the seed crystal lifting rod. The silicon crystal grown by the method has good quality, less dislocation multiplication, less crystal boundary and less seed crystal consumption, the silicon single crystal volume ratio in the same direction with the seed crystal is more than 90 percent, and the alkali texturing process can be applied to the process of manufacturing the solar cell by using the silicon wafer manufactured by the ingot casting method to obtain the silicon solar cell with low light attenuation and high solar energy conversion efficiency.
Description
Technical Field
The invention relates to a casting silicon single crystal furnace with a seed crystal lifting unit and a silicon single crystal growth method.
Background
Solar energy is currently utilized primarily by the generation of electricity from silicon solar cells, which account for over 90% of the market share. The silicon solar cell component is mainly based on silicon crystal materials, and the silicon crystal materials used by the silicon solar cell comprise monocrystalline silicon wafers and polycrystalline silicon wafers.
The monocrystalline silicon wafer is a cylindrical monocrystalline silicon rod slice grown from silicon melt in a quartz crucible by a Czochralski method, and has the advantages of less defects and lower impurity content. At present, monocrystalline silicon wafers used for manufacturing silicon solar cells are all in a (100) crystal orientation, and pyramid-shaped suede structures uniformly distributed on the whole surfaces are formed on the surfaces of the silicon wafers during alkaline texturing in a cell process, so that the reflectivity of the surfaces of the silicon wafers can be greatly reduced, and the sunlight absorption efficiency of the silicon wafers and the conversion efficiency of the monocrystalline silicon solar cells are remarkably improved. However, the production cost of the monocrystalline silicon wafer is high, and for a commonly produced p-type czochralski monocrystalline silicon solar cell, because the oxygen content is high, a large amount of boron-oxygen complexes can be generated under illumination to cause serious light-induced attenuation effect.
The commonly used polycrystalline silicon slice is obtained by slicing a square polycrystalline silicon ingot obtained by directional solidification growth of silicon melt in a square quartz crucible, and has lower cost and large single-furnace yield compared with a monocrystalline silicon slice. The oxygen content in the polycrystalline silicon wafer is much lower than that of Czochralski silicon, and the influence of light attenuation is much smaller. Because the crystal grain orientation of the surface of the polycrystalline silicon wafer prepared by the conventional ingot casting method is different, the texture can be prepared only by the acid texturing process, and the sunlight absorption efficiency and the sunlight conversion efficiency of the alkaline texturing cell piece are difficult to achieve.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a casting silicon single crystal furnace with a seed crystal lifting unit and a silicon single crystal growth method.
A cast silicon single crystal furnace with a seed crystal lifting unit comprises a furnace body, a seed crystal lifting unit, a temperature control unit and a crystal growth unit; the crystal growth unit is positioned in the furnace body; the crystal seed lifting unit is positioned above the furnace body, penetrates into the furnace body to the crystal growth unit and is used for inserting the crystal seed into the crystal growth unit; the temperature control unit is used for providing the temperature required by the crystal growth in the crystal growth unit.
The crystal seed lifting unit comprises a corrugated pipe, a crystal seed lifting rod and a lifting mechanism, wherein the lifting mechanism is used for lifting the crystal seed lifting rod, and the crystal seed lifting rod penetrates through the corrugated pipe to enter the furnace body.
The seed crystal lifting unit is further provided with a heat shielding pipe for shielding high temperature in the furnace body and is positioned below the corrugated pipe, and the seed crystal lifting rod penetrates through the corrugated pipe and the heat shielding pipe to enter the furnace body.
The lifting mechanism sequentially comprises a motor, a speed reducer, a screw rod, a support and a corrugated pipe lifting block, wherein the motor is installed on the speed reducer, the speed reducer and the screw rod are respectively installed on the support, the corrugated pipe lifting block is installed on the screw rod, and the corrugated pipe and a crystal seed lifting rod are installed below the corrugated pipe lifting block.
The temperature control unit comprises a heater, a temperature sensor and a temperature controller.
The heater comprises a main heater; or
The heater comprises a main heater and a bottom heater; or
The heater comprises a main heater and a side heater; or
The heater comprises a main heater, a side heater and a bottom heater;
the main heater is positioned above the crystal growth unit, the bottom heater is positioned below the crystal growth unit, and the side heater is positioned on the side surface of the crystal growth unit.
The temperature control unit further comprises a cooling mechanism.
The cooling mechanism is arranged below the crystal growth unit;
the cooling mechanism comprises a cooling air supply pipe and a cooling air inlet, and the cooling air supply pipe blows air upwards to cool the lower part of the crystal growth unit; or the cooling mechanism comprises a cooling air supply pipe, a cooling air inlet, a cooling air outlet and a cooling exhaust pipe, wherein the cooling air supply pipe blows air upwards to cool the lower part of the crystal growth unit, and the cooling air blown by the cooling air supply pipe is directly taken away by the cooling exhaust pipe.
The crystal growth unit comprises a crucible, a crucible bottom supporting plate and a crucible side protecting plate; a supporting plate is arranged below the crucible bottom supporting plate or is not arranged; the seed crystal is a silicon single crystal.
A silicon single crystal growing method adopting the cast silicon single crystal furnace with the seed crystal lifting unit comprises the following steps:
1) mixing high-purity silicon nitride powder, silica sol and pure water according to a certain proportion, coating a high-purity silicon nitride powder coating on the inner surface of a crucible with the thickness of 1-2mm, naturally drying and sintering at high temperature; the cross section of the crucible is square, the material is quartz ceramic, and the specific size is determined according to the feeding amount;
2) firstly, seed crystals are arranged at the lower end of a seed crystal lifting rod, a motor 1 is started to lift the seed crystals into a corrugated pipe to reach the highest position, a sintered crucible is placed on a crucible bottom supporting plate, a crucible side protecting plate is arranged, and the crucible is filled with blocky or granular polycrystalline silicon;
3) vacuumizing;
4) melting: vacuumizing, introducing argon, and controlling the power of a heater to completely melt the polycrystalline silicon into silicon melt;
5) controlling the temperature: controlling the power of a heater, stabilizing the temperature of the liquid level of the silicon melt to a range which is 1-50 ℃ higher than the melting point of the silicon melt, controlling the temperatures of the inner surface at the side of the crucible and the inner surface at the bottom of the crucible to a range which is 1-10 ℃ higher than the melting point of the silicon melt, and directly or indirectly measuring the temperatures by a temperature sensor to ensure that the temperatures of the inner surface at the side of the crucible and the inner surface at the bottom of the crucible are as close to the melting point of the silicon as possible on the premise;
6) seed crystal descending: controlling a motor to lower the seed crystal to a position 5-10mm away from the surface of the silicon melt at the lower end, stopping lowering, stabilizing the temperature of the seed crystal, and slowly immersing the seed crystal into the silicon melt until the lower end of the seed crystal is contacted with the inner surface of the bottom of the crucible; controlling the temperature in the process to ensure that the surface of the silicon melt does not generate crystallization and the seed crystal is not fused;
7) and (3) crystallization: controlling the temperature to make the silicon melt crystallize by taking the seed crystal as a center, and the crystal grows to the area between the adjacent seed crystals while growing along the seed crystals from bottom to top;
8) cooling the ingot: stopping heating after the silicon melt is completely crystallized, and taking out the crystal ingot after the crystal ingot is cooled.
The beneficial effect of the invention is that,
the silicon single crystal growing furnace with the seed crystal lifting unit is used for growing the cast silicon single crystal, because the crystal growth process taking the silicon seed crystal as the core is the main process in the whole process of the crystallization of the silicon melt from the bottom of the crucible to the surface of the melt, the silicon crystal growing in most areas in the crucible has good quality, the dislocation multiplication is less, the crystal boundary is less, the silicon single crystal occupying ratio in the same direction with the seed crystal is large, and the seed crystal consumption is less. By using the invention, the volume ratio of the silicon single crystal in the same direction with the seed crystal is more than 90 percent. By making the crystal grain size of the silicon wafer prepared by the ingot casting method sufficiently large and mainly having the (100) crystal orientation, which is called as a cast silicon single crystal, the alkali texturing process can be applied to the process of manufacturing a solar cell using the silicon wafer manufactured by the ingot casting method, and a silicon solar cell with low light attenuation and high solar conversion efficiency can be obtained.
Drawings
FIG. 1 is a schematic structural view of a first embodiment of a cast silicon single crystal furnace with a seed crystal lifting unit according to the present invention;
FIG. 2 is a schematic structural view of a second embodiment of the cast silicon single crystal furnace with a seed crystal elevating unit according to the present invention;
FIG. 3 is a schematic structural view of a third embodiment of a single crystal furnace for casting silicon according to the present invention, the furnace having a seed crystal elevating unit;
FIG. 4 is a schematic structural view of a fourth embodiment of the single crystal furnace for casting silicon according to the present invention, the furnace having a seed crystal elevating unit;
FIG. 5 is a schematic structural view of a fifth embodiment of the cast silicon single crystal furnace with a seed crystal lifting unit according to the present invention;
FIG. 6 is a schematic structural view of a sixth embodiment of the cast silicon single crystal furnace with a seed crystal lifting unit according to the present invention;
FIG. 7 is a schematic structural view showing a seventh embodiment of the cast silicon single crystal furnace with a seed crystal elevating unit according to the present invention;
FIG. 8 is a schematic structural view showing an eighth embodiment of the single crystal furnace for casting silicon according to the present invention, which is provided with a seed crystal elevating unit;
FIG. 9 is a schematic structural view showing a ninth embodiment of the cast silicon single crystal growing furnace with a seed crystal elevating unit according to the present invention;
FIG. 10 is a schematic structural view showing a tenth embodiment of the single crystal furnace for casting silicon according to the present invention, which is provided with a seed crystal elevating unit;
FIG. 11 is a schematic view showing the structure of a seed crystal elevating unit according to the present invention (a seed crystal is in a state inside a bellows);
FIG. 12 is a schematic view showing the horizontal distribution of the seed crystal in the quartz crucible;
FIG. 13 is a schematic view of a crystallization of a silicon melt from a seed crystal centered within a quartz crucible;
in the above-mentioned figure, a motor 1, a speed reducer 2, a screw rod 3, a bracket 4, a liquid level temperature sensor 5, a bellows 6, a main heater electrode 7, a heat shield tube 8, a seed crystal lifting rod 9, a top heat insulating layer 10, a main heater 11, a seed crystal 12, a side heat insulating layer 13, a crucible 14, a side heater 15, a crucible bottom support plate 16, a support plate 17, a bottom heater electrode 18, a bottom heater 19, a cooling blast pipe 20, a bottom temperature sensor 21, a vacuum exhaust tube 22, a support rod 23, a furnace body 24, a silicon melt 25, a crucible side protective plate 26, a side temperature sensor 27, a silicon melt liquid level 28, an argon gas inlet 29, a bellows lifting block 30, a cooling mechanism 31, a lifting mechanism 32, a silicon single crystal region 33, a cooling air inlet 34, a cooling air outlet.
Detailed Description
The invention is further elucidated with reference to the figures and embodiments.
In fig. 1, a cast silicon single crystal furnace with a seed crystal lifting unit comprises a furnace body 24, a seed crystal lifting unit, a temperature control unit and a crystal growth unit; the crystal growth unit is positioned in the furnace body 24; the seed crystal lifting unit is positioned above the furnace body 24, penetrates into the furnace body 24 to reach the crystal growth unit and is used for inserting the seed crystal 12 into the crystal growth unit; the temperature control unit is used for providing the temperature required by the crystal growth in the crystal growth unit.
The seed crystal lifting unit comprises a corrugated pipe 6, a seed crystal lifting rod 9 and a lifting mechanism 32, wherein the lifting mechanism 32 is used for lifting the seed crystal lifting rod 9, and the seed crystal lifting rod 9 penetrates through the corrugated pipe 6 to enter the furnace body. The bellows 6 is used to ensure that the vacuum state in the furnace body 24 is not changed when the seed crystal lifting rod 9 is lifted.
In fig. 2, the seed crystal elevating unit is further provided with a heat shielding tube 8 for shielding a high temperature in the furnace body, below the bellows 6, and a seed crystal elevating rod 9 is inserted into the furnace body through the bellows 6 and the heat shielding tube 8.
In fig. 9, 10 and 11, the lifting mechanism sequentially includes a motor 1, a speed reducer 2, a screw rod 3, a support 4, a bellows lifting block 30, and the motor 1 is installed on the speed reducer 2, the speed reducer 2 and the screw rod 3 are respectively installed on the support 4, the bellows lifting block 30 is installed on the screw rod 3, and the seed crystal lifting rod 9 is installed below the bellows lifting block 30.
The temperature sensor can be arranged outside the furnace body and used for directly or indirectly measuring the temperature of the crystal growth unit. The heater is positioned in the furnace body and arranged outside the crystal growth unit and used for directly heating the crystal growth unit. The temperature controller is arranged outside the furnace body and is used for processing the temperature signal and controlling the input of the heating power to the heater.
The crystal growth unit is positioned in the furnace body and comprises a crucible, a crucible bottom supporting plate and a crucible side protecting plate, wherein the crucible side protecting plate is used for containing polycrystalline silicon and silicon melt, after the polycrystalline silicon is melted, a seed crystal is inserted, and a single crystal with a larger size is grown in the crucible from the silicon melt.
The temperature control unit comprises a heater, a temperature sensor and a temperature controller. The heater is positioned in the furnace body and arranged outside the growth unit. The temperature controller is typically located outside the furnace body and includes temperature signal processing and delivery of heating power to the heater.
In fig. 2, 3, 6, 7, or 8, the heater includes a main heater 11; or
The heater comprises a main heater 11 and a bottom heater 19; or
The heater comprises a main heater 11 and a side heater 15; or
The heater comprises a main heater 11, a side heater 15 and a bottom heater 19;
the main heater 11 is positioned above the crystal growth unit, the bottom heater 19 is positioned below the crystal growth unit, and the side heater 15 is positioned on the side surface of the crystal growth unit.
In fig. 1, the temperature sensor is located on the outer surface of the furnace body 24. The location and number of temperature sensors can be determined as desired and can be readily varied by one skilled in the art. The temperature sensor includes the liquid surface temperature sensor 5, and may include one or both of the bottom temperature sensor 21 and the side temperature sensor 27.
In fig. 3, the temperature control unit further includes a cooling mechanism 31. The cooling mechanism 21 may control the melt crystallization process within the crystal growth unit by one or more of radiation, heat conduction, convection, etc. (e.g., air cooling, water cooling). The cooling mechanism 31 is generally installed below the crystal growth unit, and the installation position and the operation of the cooling mechanism can be easily changed by those skilled in the art.
In fig. 3, the cooling mechanism 31 is disposed below the crystal growth unit. The crystal growth unit includes a crucible 14, a crucible bottom support plate 16, and a crucible side guard plate 26. A supporting plate 17 is arranged below the crucible bottom supporting plate.
In fig. 4, the cooling mechanism 31 includes a cooling air supply pipe 20 and a cooling air inlet 34, and the cooling air supply pipe 20 blows air upwards to cool the lower surface of the crystal growth unit.
In fig. 5, the cooling mechanism 31 includes a cooling air supply pipe 20, a cooling air inlet 34, a cooling air outlet 35, and a cooling exhaust pipe 36, the cooling air supply pipe 20 blows air upwards to cool the lower surface of the crystal growth unit, and the cooling air blown by the cooling air supply pipe 20 is directly taken away by the cooling exhaust pipe 36.
The crucible 14 adopted by the crystal growth unit is made of quartz, the cross section of the crucible can be square, the crucible is made of quartz ceramic, and a high-purity silicon nitride powder coating is coated on the inner surface in advance before use; the seed crystal is a silicon single crystal, the section of the seed crystal can be square, the side length is 5-50mm, and the length is 30-100mm larger than the depth of the silicon melt in the crucible.
Application examples
The cast silicon single crystal furnace with the seed crystal lifting unit used in the embodiment is shown in fig. 10, the distribution of the seed crystal is shown in fig. 12, and the main steps are as follows: (1) mixing high-purity silicon nitride powder, silica sol and pure water according to a certain proportion, coating the high-purity silicon nitride powder on the inner surface of the crucible 14 to a thickness of 1-2mm, naturally drying, and sintering at 1000 ℃. The cross section of the crucible 14 is square, the material is quartz ceramic, and the specific size is determined according to the feeding amount. (2) Firstly, a seed crystal 12 with a (100) crystal orientation is arranged at the lower end of the seed crystal lifting rod 9, and the motor 1 is started to lift the seed crystal 12 into the corrugated pipe 6 and reach the highest position, as shown in fig. 11. The crucible bottom plate 16 is placed on the support plate 17, the sintered crucible 14 is placed on the crucible bottom plate 16, the crucible side guard plate 26 is mounted, and the crucible 14 is filled with chunk-like or granular-like polycrystalline silicon. (3) And (6) vacuumizing. (4) Melting: vacuumizing, introducing argon, and controlling the power of a heater to completely melt the polycrystalline silicon into silicon melt. (5) Controlling the temperature: the power of the heater is controlled to stabilize the temperature of the liquid level 28 of the silicon melt to a range of 1-50 ℃ higher than the melting point (1420 ℃), the temperatures of the inner surface on the side of the crucible 14 and the inner surface on the bottom are controlled to a range of 1-10 ℃ higher than the melting point of silicon, and the temperatures are directly or indirectly measured by the temperature sensor, so that the temperatures of the inner surface on the side of the crucible 14 and the inner surface on the bottom are as close as possible to the melting point of silicon on the premise that the silicon melt does not crystallize. (6) Seed crystal descending: controlling the motor 1 to lower the seed crystal 12 to a position 5-10mm away from the surface of the silicon melt, stopping lowering, stabilizing the temperature of the seed crystal, and slowly immersing the seed crystal 12 into the silicon melt until the lower end of the seed crystal 12 contacts with the inner surface of the bottom of the crucible 14. The temperature is controlled in the process, so that the surface of the silicon melt does not generate crystallization, and the seed crystal 12 is not fused. (7) And (3) crystallization: the temperature is controlled so that the silicon melt is crystallized around the seed crystal 12, and the crystal grows from the bottom to the top along the seed crystal 12 and also grows to the region between the adjacent seed crystals, as shown in fig. 13. (8) Cooling the ingot: stopping heating power after the silicon melt is completely crystallized, cooling the crystal ingot and taking out the crystal ingot.
Because the crystal growth process taking the silicon seed crystal as the core is the main process in the whole process of the crystallization of the silicon melt from the crucible bottom to the melt surface, the silicon crystal growing in most areas in the crucible has good quality, the dislocation multiplication is less, the crystal boundary is less, the silicon single crystal occupying ratio in the same direction with the seed crystal is large, and the seed crystal consumption is less. By using the invention, the volume ratio of the silicon single crystal in the same direction with the seed crystal is more than 90 percent.
Claims (10)
1. A cast silicon single crystal furnace with a seed crystal lifting unit is characterized in that: comprises a furnace body (24), a crystal seed lifting unit, a temperature control unit and a crystal growth unit;
the crystal growth unit is positioned in the furnace body (24);
the seed crystal lifting unit is positioned above the furnace body (24), penetrates into the furnace body (24) to the crystal growth unit and is used for inserting the seed crystal (12) into the crystal growth unit;
the temperature control unit is used for providing the temperature required by the crystal growth in the crystal growth unit.
2. The cast silicon single crystal furnace of claim 1 wherein:
the seed crystal lifting unit comprises a corrugated pipe (6), a seed crystal lifting rod (9) and a lifting mechanism (32), wherein the lifting mechanism (32) is used for lifting the seed crystal lifting rod (9), and the seed crystal lifting rod (9) penetrates through the corrugated pipe (6) to enter the furnace body (24).
3. The cast silicon single crystal furnace as claimed in claim 2, wherein:
the seed crystal lifting unit is further provided with a heat shielding pipe (8) for shielding high temperature in the furnace body (24), and is positioned below the corrugated pipe (6), and the seed crystal lifting rod (9) penetrates through the corrugated pipe (6) and the heat shielding pipe (8) to enter the furnace body (24).
4. The cast silicon single crystal furnace as claimed in claim 2, wherein: the lifting mechanism comprises a motor (1), a speed reducer (2), a screw rod (3), a bracket (4) and a corrugated pipe lifting block (30) in sequence, the motor (1) is arranged on the speed reducer (2),
the speed reducer (2) and the screw rod (3) are respectively installed on the support (4), the corrugated pipe lifting block (30) is installed on the screw rod (3), and the corrugated pipe (6) and the crystal seed lifting rod (9) are installed below the corrugated pipe lifting block (30).
5. The cast silicon single crystal furnace of claim 1 wherein: the temperature control unit comprises a heater, a temperature sensor and a temperature controller.
6. The cast silicon single crystal furnace as claimed in claim 5, wherein: the heater comprises a main heater (11); or
The heater comprises a main heater (11) and a bottom heater (19); or
The heater comprises a main heater (11) and a side heater (15); or
The heater comprises a main heater (11), a side heater (15) and a bottom heater (19);
the main heater (11) is positioned above the crystal growth unit, the bottom heater (19) is positioned below the crystal growth unit, and the side heater (15) is positioned on the side surface of the crystal growth unit.
7. The cast silicon single crystal furnace as claimed in claim 5, wherein: the temperature control unit further comprises a cooling mechanism (31).
8. The cast silicon single crystal furnace as claimed in claim 7, wherein: the cooling mechanism (31) is arranged below the crystal growth unit;
the cooling mechanism (31) comprises a cooling blast pipe (20) and a cooling air inlet (34), and the cooling blast pipe (20) blows air upwards to cool the lower part of the crystal growth unit;
or the cooling mechanism (31) comprises a cooling air supply pipe (20), a cooling air inlet (34), a cooling air outlet (35) and a cooling exhaust pipe (36), the cooling air supply pipe (20) blows air upwards to cool the lower part of the crystal growth unit, and the cooling air blown by the cooling air supply pipe (20) is directly taken away by the cooling exhaust pipe (36).
9. The cast silicon single crystal furnace of claim 1 wherein: the crystal growth unit comprises a crucible (14), a crucible bottom supporting plate (16) and a crucible side protecting plate (26); a support plate (17) is arranged below the crucible bottom supporting plate (16) or is not arranged; the seed crystal (12) is a silicon single crystal.
10. A silicon single crystal growth method using the cast silicon single crystal furnace with the seed crystal elevating unit according to claim 1, characterized in that: the method comprises the following steps:
1) mixing high-purity silicon nitride powder, silica sol and pure water according to a certain proportion, coating a high-purity silicon nitride powder coating on the inner surface of a crucible with the thickness of 1-2mm, naturally drying and sintering at high temperature; the cross section of the crucible is square, the material is quartz ceramic, and the specific size is determined according to the feeding amount;
2) firstly, mounting a seed crystal at the lower end of a seed crystal lifting rod, starting a motor to lift the seed crystal into a corrugated pipe to reach the highest position, placing a sintered crucible on a crucible bottom supporting plate, mounting a crucible side protecting plate, and filling the crucible with blocky or granular polycrystalline silicon;
3) vacuumizing;
4) melting: vacuumizing, introducing argon, and controlling the power of a heater to completely melt the polycrystalline silicon into silicon melt;
5) controlling the temperature: controlling the power of a heater, stabilizing the temperature of the liquid level of the silicon melt to a range which is 1-50 ℃ higher than the melting point of the silicon melt, controlling the temperatures of the inner surface at the side of the crucible and the inner surface at the bottom of the crucible to a range which is 1-10 ℃ higher than the melting point of the silicon melt, and directly or indirectly measuring the temperatures by a temperature sensor to ensure that the temperatures of the inner surface at the side of the crucible and the inner surface at the bottom of the crucible are as close to the melting point of the silicon as possible on the premise;
6) seed crystal descending: controlling a motor to lower the seed crystal to a position 5-10mm away from the surface of the silicon melt at the lower end, stopping lowering, stabilizing the temperature of the seed crystal, and slowly immersing the seed crystal into the silicon melt until the lower end of the seed crystal is contacted with the inner surface of the bottom of the crucible; controlling the temperature in the process to ensure that the surface of the silicon melt does not generate crystallization and the seed crystal is not fused;
7) and (3) crystallization: controlling the temperature to make the silicon melt crystallize by taking the seed crystal as a center, and the crystal grows to the area between the adjacent seed crystals while growing along the seed crystals from bottom to top;
8) cooling the ingot: stopping heating after the silicon melt is completely crystallized, and taking out the crystal ingot after the crystal ingot is cooled.
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| CN202090092U (en) * | 2010-05-20 | 2011-12-28 | 张志坚 | Single-crystal ingot casting furnace with temperature control seed crystal device |
| CN103194794A (en) * | 2012-01-10 | 2013-07-10 | 徐传兴 | Quasi monocrystalline silicon casting device and method |
| CN211522362U (en) * | 2019-11-24 | 2020-09-18 | 田达晰 | Casting silicon single crystal furnace with seed crystal lifting unit |
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| US20110002835A1 (en) * | 2008-12-30 | 2011-01-06 | Memc Electronic Materials, Inc. | Methods For Pulling A Multicrystalline Silicon Ingot From A Silicon Melt |
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