Method for improving metallurgical-method polycrystalline silicon growth interface

Abstract

The invention relates to a method for improving a metallurgical-method polycrystalline silicon growth interface. The method comprises the steps: (1) loading polycrystalline-silicon silicon materials to a high-purity quartz crucible, placing the high-purity quartz crucible into a directional solidification furnace, and carrying out vacuumizing until the internal degree of vacuum of the furnace is lower than 10Pa; (2) heating the temperature of the furnace to 1,450 DEG C to 1,550 DEG C so as to melt the silicon materials; (3) carrying out external-field treatment on the silicon materials for 10 to 30 minutes at the magnetic intensity of 0.15T to 0.5T, then, cooling the furnace body at the rate of 5 DEG C / min to 10 DEG C / min, downwards shifting a moving part of the furnace body at the rate of 5mm / h to 10mm / h, enabling silicon melt to be divorced from a heater and start to grow crystals, and closing a magnetic field when the temperature is 1,100 DEG C to 1,200 DEG C; and (4) after crystal growth, enabling the moving part of the furnace body to rise to an initial position in a furnace chamber at the rate of 2mm / s to 4mm / s, then, heating the temperature to 1,250 DEG C to 1,350 DEG C, carrying out heat preservation for 2 to 5 hours, and then, carrying out cooling at the cooling rate lower than 4 DEG C / min. According to the method, the form of a solid-liquid interface in a silicon material growth process is regulated and controlled by adopting an external static magnetic field, so that a smooth solid-liquid interface is obtained, ideal columnar crystal grain tissue is obtained, and the quality of silicon ingots is improved; and the process is more environmentally friendly, is compatible with the existing technologies of enterprises and is applicable to large-scale production.

Description

technical field [0001] The invention belongs to the technical field of silicon material purification, and relates to the preparation of polysilicon materials, in particular to a preparation method for improving the growth interface of polysilicon in metallurgical methods. In particular, it can be used in the purification method of silicon for solar cells. Background technique [0002] Solar power is the best choice to solve energy problems. Compared with other conventional energy sources, it has the characteristics of cleanness, extensive resources, abundance and long life. At present, silicon material is still the most important matrix material of solar cells, occupying an absolute market position, especially crystalline silicon solar cells. Generally, the methods for preparing solar-grade polysilicon materials mainly include metallurgical methods and chemical methods. Compared with chemical purification, metallurgical method is a polysilicon preparation technology with l...

AI Technical Summary

Problems solved by technology

However, the current conventional metallurgical method to prepare polysilicon materials has uneven distribution of impurities and many intragranular defects, which lead to unstable performance indicators of polysilicon.

The reason is that during the crystallization and solidification of crystalline silicon, there are large differences in the solid-liquid interface morphology and propulsion mode along the growth direction, which affects the solidification structure characteristics and properties of metallurgical polysilicon.

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