A device and method for improving polysilicon purification yield by lateral solidification superimposed electric field

Abstract

The invention discloses equipment for improving a purification yield of polycrystalline silicon through transversely solidifying and overlapping an electric field. The equipment is characterized by comprising a water-cooling column, wherein a graphite sleeve is arranged at the outer side of a side wall of the water-cooling column; a graphite crucible is arranged at the outer side of the side wall of the graphite sleeve; axes of the water-cooling column, the graphite sleeve and the graphite crucible are located on the same straight line; an annular heating element is arranged at the outer side of the side wall of the graphite crucible; an annular heating body is arranged at the outer side of the side wall of the annular heating element; a rotary tray is arranged at the bottom of the graphite crucible; a circulating flow channel is arranged in the water-cooling column; and the graphite sleeve and the graphite crucible are connected with positive and negative electrodes of a power supply respectively. According to the equipment disclosed by the invention, the manner of transversely solidifying and overlapping the electric field is adopted, the thickness of a diffusion layer of a solid-liquid interface is reduced through adopting a centrifugal force and an electric field force and a fractional solidification effect is increased.

Description

technical field [0001] The invention relates to a device and a method for increasing the polysilicon purification yield by lateral solidification and superimposed electric field. Background technique [0002] Directional solidification purification is the main technology to remove metal impurities in polysilicon, and it is widely used in the process of polysilicon ingot casting and metallurgical purification. [0003] Directional solidification purification utilizes the segregation behavior of impurities at the solid-liquid interface: during the directional solidification process, due to the different solubility of impurity elements in the solid phase and liquid phase, the solute will redistribute at the solid-liquid interface, redistribution The degree of segregation is determined by the segregation coefficient and the solidification rate. The segregation coefficient k0<<1 of metal impurities in silicon will continuously enrich in liquid silicon, the impurity content...

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Problems solved by technology

[0004] However, the traditional directional solidification technology solidifies from the bottom to the top, and the removal rate of impurities is low. The final solidified impurity area is prone to reverse solidification, which reduces the yield of the product.

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