Method for polycrystalline silicon ingot casting

Abstract

The invention discloses a method for polycrystalline silicon ingot casting. The method comprises a first step of installation of an auxiliary heater, wherein the auxiliary heater is installed in a polycrystalline silicon ingot furnace, the auxiliary heater is a bottom heater below a crucible, and the auxiliary heater forms a six-side heating device together with a top heater and four side heaters; a second step of charging; a third step of preheating; a fourth step of melting: six-side heating melting, fifth-side heating melting and follow-up melting; a fifth step of crystal growth; a sixth step of annealing and cooling which comprise primary annealing, secondary annealing and cooling, wherein during the primary annealing, the heating temperature of the polycrystalline silicon ingot furnace is reduced to T4 and heat insulation is performed for 2-3 h, and T4=1250-1280 DEG C; during the secondary annealing, the heating temperature of the polycrystalline silicon ingot furnace is reduced to T5 and heat insulation is performed for 2-3 h, and T5=900-950 DEG C. The method is simple in steps, reasonable in design, convenient to implement and good in using effect. The six-side heating device is adopted for heating, the oxygen content of the bottom of the crucible can be effectively reduced; the annealing process is adjusted, and the quality of a finished ingot can be effectively improved.

Description

technical field [0001] The invention belongs to the technical field of polycrystalline silicon ingot casting, and in particular relates to a polycrystalline silicon ingot casting method. 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 polycrystalline ingot casting techno...

AI Technical Summary

Problems solved by technology

At present, when annealing polysilicon ingots, there is no unified, standard and standardized method to follow. In actual processing, there are inevitably problems such as relatively random operations, long time-consuming, and poor annealing effects. Therefore, the existing The annealing process also has a great influence on the quality of the finished ingot

[0004] In addition, the heaters used in the existing polysilicon ingot furnaces generally have a five-sided heating structure, that is, heaters are installed on the top of the crucible and outside the four side walls. This five-sided heating method heats up from top to bottom. Radiation, melting efficiency is low, and at the same time, the gas at the bottom of the crucible is difficult to get rid of, so that the oxygen content at the bottom of the finished ingot is relatively high

Images