Double annealing process for reducing back diffusion of impurity in polysilicon ingot

Abstract

The invention belongs to the field of polysilicon purification, and particularly relates to a double annealing process for reducing back diffusion of impurities in a polysilicon ingot. The secondary annealing process includes the steps of (1) first annealing after crystal growth in polysilicon ingot process; (2) cooling the polysilicon ingot to room temperature; (3) dividing the polysilicon ingot to obtain a square ingot; (4) placing the square ingot into an annealing oven for second annealing, and then cooling the square ingot to room temperature; and (5) polishing the square ingot. The double annealing process has the advantages that: (1) leftover materials with high content of impurities has been removed during dividing, thus reverse diffusion can be reduced in later annealing and yield is improved; (2) the size of a silicon block is relatively small, so the internal temperature distribution in the annealing step is uniform and the annealing effect can be improved; and (3) production cycle is reduced, production efficiency is improved, and production cost is reduced by 5%.

Description

technical field [0001] The invention belongs to the field of polysilicon purification, and in particular relates to a secondary annealing process for reducing impurity back-diffusion in 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 increas...

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