Two-step annealing process for polycrystalline silicon ingot

Abstract

The invention discloses a two-step annealing process for a polycrystalline silicon ingot. The two-step annealing process comprises the following steps that silicon raw materials are subjected to procedures of heating, smelting and crystal growing in an ingot casting process and then subjected to primary annealing, the heating temperature of an ingot furnace is gradually reduced to 1230-1285 DEG C from 1395-1405 DEG C, the cooling time is 40-60 min, and the temperature is kept for 90-120 min; the silicon ingot subjected to primary annealing is cooled by reducing the heating power and closing a heat isolation plate, secondary annealing is carried out, the heating temperature of the ingot furnace is gradually reduced to 1100-1130 DEG C from 1230-1285 DEG C, the cooling time is 30-60 min, the temperature is kept for 60-120 min, and then following procedures are carried out. By means of the method, the silicon ingot quality is remarkably improved, the proportions of fragments, unfilled corners, broken edges and cracks in the slicing process are reduced, the number of output silicon wafers is increased, the production period is shortened, the production efficiency is improved, and the production cost is effectively reduced.

Description

【Technical field】 [0001] The invention belongs to the field of polysilicon purification, and in particular relates to a two-step annealing process for polysilicon ingots. 【Background technique】 [0002] At present, my country has become the world's largest energy production and consumption country, but the per capita energy consumption level is still very low. With the continuous development of the economy and society, my country's energy demand will continue to grow. In response to the current energy shortage, countries around the world are thinking deeply, and are working hard to improve energy efficiency, promote the development and application of renewable energy, and reduce the impact on energy consumption. Reliance on imported oil to enhance energy security. [0003] As one of the important development directions of renewable energy, solar photovoltaic power generation has developed rapidly in recent years, and its proportion is increasing. According to the Medium and...

AI Technical Summary

Problems solved by technology

In the existing process, after the crystal growth is completed, the annealing process is carried out through a long-term high-temperature state. Under the high-temperature annealing state, the reverse diffusion of impurities around the ingot is intensified, resulting in a decrease in its yield; long-term annealing makes The ingot production cycle is lengthened and the production efficiency is reduced

At the same time, in the cooling stage after annealing, due to the large size of the ingot, the internal temperature distribution is uneven, which seriously affects the annealing effect

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