Method for removing impurities in single crystal rod straight pulling process

Abstract

The invention relates to a method for removing impurities in single crystal rod straight pulling process. The method includes that polycrystalline silicon material is placed into a quartz crucible, gradual warming is carried out until the temperature is equal to or more than the melting point of silicone, and the polycrystalline silicon material starts to be melted; when little polycrystalline silicon material is not melted, temperature in the crucible is reduced to intermediate temperature, so that the melting of residual polycrystalline silicon material is slowed or the residual polycrystalline silicon material can not be melted, then all impurities which are floating on the surface of silicon solution and have melting point higher than silicon can be gradually absorbed on the residual unmelted polycrystalline silicon material, and then seed crystal is inserted and the residual polycrystalline silicon material absorbed with impurities is slung. Compared with the original technology, the method of the invention can reduce 1-2 hours for high temperature volatilization, and all impurities having melting point higher than silicon are not melted into silicon solution, thus greatly improving purity and quality of pulled single crystal rod.

Description

Technical field [0001] The invention relates to a method for removing impurities in the Czochralski process of a single crystal rod. Background technique [0002] In the Czochralski process of single crystal rods, after heating according to the melting point of silicon, we melt the polysilicon material into a silicon melt. Due to the presence of some impurities such as quartz fragments and graphite fragments in the silicon material, its melting point is higher than the melting point of silicon (1420 degrees), therefore, these impurities are floating on the liquid surface. When the silicon melt volatilizes, these infusible impurities will float around the wall of the quartz crucible. They are easy to float out and stick to the The crystal shoulders and crystal rods will cause de-edge and even affect the internal quality and internal parameters of the silicon rods. Usually, the method we use to remove impurities is to continue high-temperature volatilization for 1 to 2 hours after...

AI Technical Summary

Problems solved by technology

[0002] In the process of single crystal ingot straight pulling, we heat the polysilicon material according to the melting point of silicon, and then melt all the polycrystalline silicon material into a silicon melt. Because there are some impurities such as quartz fragments and graphite fragments in the silicon material, its melting point is higher than that of silicon. (1420 degrees), therefore, these impurities are floating on the liquid surface, when the silicon melt volatilizes, these insoluble impurities will float around the wall of the quartz crucible, and are easy to float out and stick to the surface during the process of shouldering and equal diameter. On the crystal shoulder and ingot, it will cause edge-off, and even affect the intrinsic quality and intrinsic parameters of the silicon ingot

Usually, the method we use to remove impurities is to continue to volatilize at high temperature for 1 to 2 hours after the polysilicon material is fully melted, then lower the temperature to the seeding temperature, and start the steps of seeding, shouldering, shoulder turning, and equal diameter. , In this way, the original part of the non-melting impurities is melted in the molten material, which will reduce the purity of the silicon single crystal, and there are still impurities with higher melting points floating on the surface of the silicon liquid, and finally remain in the quartz crucible