A kind of impurity removal method for semi-melted ingot of polycrystalline silicon

Abstract

The invention discloses a polycrystalline silicon semi-casting ingot impurity removing method, which comprises: 1, melting and impurity removing, wherein the process comprises: 101, melting: melting a silicon material loaded in a crucible by using a polycrystalline silicon ingot casting furnace, and introducing an inert gas into the polycrystalline silicon ingot casting furnace to carry out pressure maintaining, 102, pressure reducing impurity removing, and 103, impurity removing at late melting stage: increasing the pressure of the polycrystalline silicon ingot casting furnace, continuously melting the silicon material, and adjusting the heating powers of a top portion heater and / or four side portion heaters to make the top side ratio coefficient c of the polycrystalline silicon ingot casting furnace be more than or equal to 0.8 and less than 1; and 2, crystal growing and synchronous impurity removing, wherein the heating powers of the top portion heater and / or the four side portion heaters are adjusted to make the top side ratio coefficient c of the polycrystalline silicon ingot casting furnace be more than or equal to 0.3 and less than 0.9. According to the present invention, the method has characteristics of simple steps, reasonable design, convenient achieving, and good use effect; and with the synchronous impurity removing at the late material melting stage, the pressure reducing impurity removing and the crystal growing and synchronous impurity removing, the hard points of the casting finished product are effectively reduced, and the quality of the casting finished product can be effectively increased.

Description

technical field [0001] The invention belongs to the technical field of polycrystalline silicon ingots, and in particular relates to a method for removing impurities for semi-melted polycrystalline silicon ingots. Background technique [0002] Photovoltaic power generation is one of the most important clean energy sources with great development potential. The key factors restricting the development of photovoltaic industry are low photoelectric conversion efficiency on the one hand and high cost on the other hand. Photovoltaic silicon wafers are the basic material for the production of solar cells and components. The purity of polysilicon used to produce photovoltaic silicon wafers must be above 6N (that is, the total content of non-silicon impurities is below 1ppm), otherwise the performance of photovoltaic cells will be greatly negative influences. In recent years, the production technology of polycrystalline silicon wafers has made remarkable progress, and the polycrysta...

AI Technical Summary

Problems solved by technology

At present, the semi-melted ingot casting process of solar polysilicon ingots has been unanimously promoted by the market due to its advantages such as good crystal flowers. However, in the semi-melted ingot casting process, the impurities and oxygen in the raw materials have not been effectively melted because the silicon material on the side of the crucible has not been melted. The impurity removal will cause these impurities to form hard spots in the ingot casting process, which will have a great impact on the quality of the product

The existing semi-melted ingot casting process can control the hard point of the finished ingot at 3% to 5%, with a large fluctuation range, and this data is the data of the rough square flaw detection, the quasi-square data is higher and hard The point ratio is more than 5%

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