A kind of polycrystalline silicon ingot and its preparation method and polycrystalline silicon chip

Abstract

The invention provides a preparation method of a polycrystalline silicon ingot. The preparation method includes the following steps that 1, seed crystals are laid at the bottom of a crucible, and a seed crystal layer is formed; 2, a blocking layer is arranged above the seed crystal layer, and the melting point of the blocking layer is smaller than or equal to that of silicon; 3, the upper portion of the blocking layer is filled with a silicon material, heating is conducted to melt the silicon material, molten silicon bodies are formed, in the melting process of the silicon material, the blocking layer is used for blocking the molten silicon bodies from making contact with the seed crystal layer, when a solid-liquid interface formed after the silicon material and the blocking layer are totally melted is just located or stretches deeply into the seed crystal layer, a thermal field is adjusted, an supercooling state is formed, and crystals begin to grow on the molten silicon bodies on the basis of the seed crystal layer; 4, after all the molten silicon bodies are crystallized, annealing and cooling are conducted, and the polycrystalline silicon ingot is obtained. According to the preparation method, the blocking layer is arranged above the seed crystal layer, nucleation interface dislocation of seed crystals is reduced, and dislocation multiplication in the subsequent crystal growth process can be reduced, so that the quality of the whole polycrystalline silicon ingot is improved, and efficiency of manufacturing polycrystalline silicon cells through casting silicon pieces is improved.

Description

technical field [0001] The invention relates to the field of polycrystalline silicon ingots, in particular to a polycrystalline silicon ingot, a preparation method thereof and a polycrystalline silicon wafer. Background technique [0002] In recent years, solar energy, as an emerging renewable green energy, has become a hotspot of development and research. With the rapid development of the solar cell industry, polysilicon, which is low in cost and suitable for large-scale production, has become one of the most important photovoltaic materials in the industry, and has gradually replaced the traditional Czochralski monocrystalline silicon in the solar cell material market. [0003] At present, the preparation method of polycrystalline silicon ingot mainly adopts the directional solidification system method (DSS for short) furnace crystal growth technology provided by GT Solar, and this method usually includes steps such as heating, melting, solidification growth, annealing and...

AI Technical Summary

Problems solved by technology

However, this method has the following disadvantages: (1) The silicon melt formed during the melting process of the silicon material will flow down from the top of the crucible along the through gap between the silicon materials into the gap of the seed crystal and solidify to form crystals, resulting in the shape of the seed crystal. The nuclei are not easy to control, which affects the seeding effect of the seed crystal; (2) there are many through gaps between the silicon materials, and the gas in the gaps contains some particulate impurities. In addition, the crucible body and the silicon materials also contain some impurities. During the material melting process, on the one hand, the gas in the crucible will entrain particulate impurities and move to the bottom seed crystal to contaminate the seed crystal; on the other hand, the silicon melt will also carry impurities diffused from the crucible and silicon material itself into the seed crystal. The gap between the crystals and solidification occurs, and the impurities will contaminate the seed crystal, which will eventually cause dislocation diffusion, resulting in a decrease in the performance of the silicon crystal

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