Method for manufacturing a polycrystalline silicon ingot

Abstract

A method for manufacturing a polycrystalline silicon ingot includes steps of: A) putting a crucible loaded with a silicon material and having a base and a wall around the base in a thermal field, melting the silicon material in the crucible in the thermal field to form a molten silicon; B) after the step (A), controlling the thermal field to provide heat to the molten silicon from above the crucible and to solidify a portion of the molten silicon contacting a base and at least a portion of the wall proximate to the base of the container to form a solid silicon crystalline isolation layer which surrounds a bottom of the rest of the molten silicon; and C) after the step (B), controlling the thermal field to continuously provide heat to the rest of the molten silicon from above the crucible and to solidify the rest of the molten silicon gradually from a bottom to a top of the rest of the molten silicon to form a polycrystalline silicon ingot. Therefore in the process for manufacturing the polycrystalline silicon, the solid silicon ingot is pre-solidified and formed, and the final oxygen content in the polycrystalline silicon can be reduced.

Description

technical field [0001] The present invention relates to a method for manufacturing a silicon ingot, in particular to a method for manufacturing a polycrystalline silicon ingot. Background technique [0002] It is known that polycrystalline silicon wafers used in polycrystalline silicon solar cells are cut from polycrystalline silicon ingots. The manufacturing method of polycrystalline silicon ingots mainly involves placing silicon material in a crucible, and heating the silicon The material is melted into a silicon molten soup, and then the silicon molten soup is cooled and solidified into a polycrystalline silicon ingot. [0003] When growing polycrystalline silicon ingots, doping boron (B) elements can make solar cell chips with low impedance and high photoelectric conversion efficiency. However, in the process of growing a polycrystalline silicon ingot, if there is a high concentration of oxygen impurities, the solar cell made of it will produce boron-oxygen bond defects...

AI Technical Summary

Problems solved by technology

However, it has been proved by experiments that oxygen will still diffuse through the silicon nitride layer into the silicon melt, and the silicon nitride layer cannot effectively reduce the oxygen impurity concentration in the polysilicon ingot.

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