Polycrystalline silicon ingot and casting method thereof

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...

AI Technical Summary

Problems solved by technology

[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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