A secondary annealing process for polysilicon ingot

Abstract

The invention provides a double annealing technology of polycrystalline silicon ingot casting. The technology comprises the following steps that silicon raw materials are subjected to first annealing after being subjected to heating, melting and crystal growth working procedure treatment in the ingot casting technology, wherein the annealing temperature is 1330-1380 DEG C, and the temperature is kept for 1-2.5 h; a silicon ingot subjected to first annealing is cooled by lowering the heating power and closing a heat insulation plate, and second annealing is carried out, wherein the second annealing temperature is 1150-1250 DEG C, and the temperature is kept for 0.5-1.5 h; follow-up working procedures are carried out. One in-furnace medium-high temperature annealing is added in the polycrystalline silicon ingot casting technological procedure, head and tail temperature difference and heat stress can be effectively lowered, heat stress is sufficiently released, and the mechanical property of the silicon ingot is effectively improved. Compared with the prior art, the quality of the silicon ingot can be effectively improved, the fragmenting, corner lack, edge breakage, the cracking rate in the segmentation process is lowered, the silicon slice output is improved, and the production cost is saved.

Description

technical field [0001] The invention belongs to the technical field of polycrystalline silicon ingots, and in particular relates to a secondary annealing process for polycrystalline silicon ingots. Background technique [0002] The competition in the solar cell market is fierce. In the case of global solar cell overcapacity, cost is particularly important to maintain a competitive advantage in the market. At present, in order to reduce costs and increase production capacity, more and more ingot manufacturers continue to increase the charging capacity, gradually increasing it from 700kg to nearly 900kg. Due to the increase in the amount of charge, the height of the silicon ingot also increases. During the crystal growth process, the temperature difference between the top and the bottom increases. At the same time, during the cooling process, the temperature difference between the center temperature and the edge of the silicon ingot increases, resulting in a lower thermal stre...

AI Technical Summary

Problems solved by technology

[0003] The technical problem to be solved by the present invention is to provide a secondary annealing process for polycrystalline silicon ingots that can effectively reduce the temperature difference between the head and tail and thermal stress, improve the mechanical properties of silicon ingots, and reduce the internal defects of silicon ingots.