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Polycrystalline silicon ingot and casting method thereof
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A technology of polycrystalline silicon ingots and silicon liquid is applied in the field of solar cells to achieve the effects of improving performance, reducing energy consumption and reducing production costs
Active Publication Date: 2015-05-13
YINGLI ENERGY CHINA
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[0004] In view of this, the present invention provides a polysilicon ingot and its casting method, which is applied to an ingot casting furnace with only a top heater and a heat preservation bottom plate around the bottom of the cooling table. By changing the process of polysilicon directional growth, the silicon The problem of the scattered distribution of impurities around the ingot improves the performance of polycrystalline silicon ingots, prepares polycrystalline silicon ingots with good quality and high yield, improves the utilization rate of silicon materials, and reduces the production cost of silicon ingots
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Embodiment 1
[0042] This embodiment provides a polysilicon ingot furnace, such as figure 2 As shown, the ingot casting furnace only has a top heater 1, which is characterized in that the ingot casting furnace includes a heat insulation layer 2, a water-cooled copper plate 4 located below the louver 3, a crucible 5 located inside the heat insulation layer 2, and a The heat dissipation platform 6 at the bottom of the crucible 5, and the thermal insulation bottom plate 7 arranged on the periphery of the bottom of the heat dissipation platform 6 and inside the heat insulation layer 2, the thermal insulation bottom plate 7 is directly in contact with the bottom of the heat dissipation platform 6; wherein the heat insulation The bottom of layer 2 has a louver 3 comprising a plurality of louvers, each openable to an angle of 90°;
[0043] Wherein, the shape of the thermal insulation bottom plate 7 arranged on the periphery of the bottom of the heat dissipation platform 6 and inside the heat insula...
Embodiment 2
[0049] This embodiment provides a polysilicon ingot casting method, using the polysilicon ingot furnace provided in Example 1, the specific process is as follows Figure 4 shown, including:
[0050] Step 401: Load the silicon material into the crucible, and heat the silicon material to a molten state.
[0051] After loading the silicon material in the crucible, close the insulation layer, and use the top heater to heat the silicon material in the crucible until the silicon material is in a molten state. In order to melt all the silicon material in the crucible and make the impurities in the silicon liquid more volatile, it is necessary to keep the top of the crucible at a high temperature, and the temperature of the silicon liquid surface is higher than the melting point of the silicon liquid at 1420°C.
[0052] Step 402: Reduce the power of the heater at the top of the polysilicon ingot furnace, and at the same time gradually open the louvers to an angle of 25°-35° to lower ...
Embodiment 3
[0063] This embodiment discloses a polysilicon ingot produced by the methods of the above embodiments. Impurity residues and dark spots around the polycrystalline silicon ingot are significantly reduced, even without impurity residues and dark spots. The infrared flaw detection scan of the polycrystalline silicon ingot is shown in Figure 5 As shown, the quality of the polycrystalline silicon ingot is good and the production rate is high.
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Abstract
The invention discloses a polycrystalline silicon ingot and a casting method thereof, and applies to an ingot furnace which is provided with a top heater, and a thermal insulation bottom plate is arranged at the bottom periphery of a heat radiation platform. The casting method comprises the following steps of: loading a silicon material in a crucible, and heating the silicon material to a molten state; reducing the power of the top heater on the polysilicon ingot furnace, simultaneously opening a shutter to the angle of 25 degrees to 35 degrees gradually, and reducing the surface temperature of a silicone fluid in the molten state to 1400 DEG C-1450 DEG C so that the silicone fluid at the bottom starts crystallizing; continuing gradually opening the shutter to the maximum opening vertical angle, and keeping a stable silicone fluid crystallization rate, wherein the opening speed rate of the shutter is less than the opening speed rate of the shutter in the second step, and the opening speed rate of the shutter is gradually reduced; and maintaining the maximum opening of the shutter until crystallization is finished. The polycrystalline silicon ingot and the casting method thereof provided by the invention solve the problem that the peripheral impurities of the silicon ingot are distributed in a scattering manner through changing a oriented polycrystalline silicon crystallizing process, the property of the polycrystalline silicon ingot is improved, the polycrystalline silicon ingot with good quality and high compound output rate is prepared, the utilization ratio of the silicon material is improved, and the manufacturing cost of the silicon ingot is reduced.
Description
technical field [0001] The invention relates to the technical field of solar cells, in particular to a polycrystalline silicon ingot and a casting method thereof. Background technique [0002] At present, in the manufacture of solar photovoltaic cells, about 90% of the silicon substrates used are polycrystalline silicon wafers, and the ingot furnaces for preparing polycrystalline silicon ingots mostly use directional solidification technology. Taking an ingot furnace with only a top heater as an example, this type of ingot furnace includes a heat insulation layer, which forms a closed heat insulation space with the heat preservation step and the closed louvers below the heat preservation step. The top heater, crucible, The cooling tables are all placed in the heat insulation space, and the top heater is located above the crucible to heat and melt the silicon material in the crucible, while the cooling table is located below the crucible and contacts the bottom of the crucibl...
Claims
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