Polycrystalline silicon ingot casting molten material and impurity removing process

Abstract

The invention discloses a polycrystalline silicon ingot casting molten material and an impurity removing process. The process comprises the following steps: 1, preheating: adopting an ingot furnace to preheat a silicon material filled in a crucible, and gradually raising the heating temperature of the ingot furnace to T1; the preheating time is 6-10h, and T1=1165-1185 DEG C; 2, melting: the melting temperature is T1-T5; T5=1540-1560 DEG C; in the melting process, filling insert gases into the ingot furnace, and keeping air pressure in the furnace in Q1, and Q1=550-650mbar; 3, removing impurities: the process is as follows: the 11th step, reducing pressure: the air pressure of the ingot furnace is reduced from Q1 to Q2, and the pressure reducing time is 8-12min, and Q2=350-450mbar; the 12th step, maintaining pressure; the 13th step, boosting pressure and lowering temperature. The process has the advantages of simple steps, reasonable design, convenience in realization, easiness in grasp and good using effect, can discharge gas containing carbon in the furnace in time, and increases the polycrystalline silicon ingot casting quality.

Description

Technical field [0001] The invention belongs to the technical field of polycrystalline silicon ingots, and particularly relates to a polycrystalline silicon ingot melting material and a process for removing impurities. Background technique [0002] Photovoltaic power generation is one of the most important clean energy sources and has great development potential. The key factors restricting the development of the photovoltaic industry are the low photoelectric conversion efficiency on the one hand, and the high cost on the other. Photovoltaic silicon wafers are the basic material for the production of solar cells and modules. 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 negatively affected. influences. In recent years, polycrystalline silicon wafer production technology has made significant progress. Poly...

AI Technical Summary

Problems solved by technology

However, in the actual melting process, the gas in the ingot furnace cannot immediately discharge the heat field through the gas outlet, but will circulate in the combined structure composed of the crucible, guard plate, cover plate, etc., and enter the surface of the silicon melt, making it The carbon element is adsorbed and dissolved into the silicon melt, correspondingly making SiC, Si 3 N 4 Other impurities enter the silicon ingot, resulting in high carbon content in the grown silicon ingot, resulting in ingot defects, affecting the yield of slicing, and ultimately leading to low efficiency of the cell

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