Polycrystalline silicon ingot and its preparation method, polycrystalline silicon chip and crucible for polycrystalline silicon ingot casting

Abstract

The invention provides a method for preparing a polycrystalline silicon ingot, comprising the following steps: setting a nucleation source at the bottom of a crucible to form a nucleation source layer; setting molten silicon material on the nucleation source layer; controlling the temperature in the crucible A temperature gradient is formed by gradually rising in a direction perpendicular to the bottom of the crucible, so that the silicon material in the molten state is nucleated and crystallized by the nucleation source to produce a polycrystalline silicon ingot. The invention also provides a high-quality polysilicon ingot obtained by the preparation method, a polysilicon slice and a crucible for polysilicon ingot prepared by using the polysilicon ingot. The polycrystalline silicon ingot prepared by the preparation method has uniform and regular crystal grains, low dislocation density and no obvious dendrites and twins.

Description

technical field [0001] The invention relates to the field of polycrystalline silicon ingots, in particular to polycrystalline silicon ingots and a preparation method thereof, polycrystalline silicon slices and a crucible for polycrystalline silicon ingots. Background technique [0002] 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, which usually includes the steps of heating, melting, solidification growth, annealing and cooling. During the process of solidification and crystal growth, with the continuous cooling of the bottom of the crucible, the silicon material in molten state spontaneously forms random nucleation and the random nucleation gradually grows. However, since the initial nucleation is not controlled, dislocations are prone to occur during the nucleation process, resulting in irregular crystal orientation, irreg...

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Problems solved by technology

Although the polycrystalline silicon ingot produced by this method has few initial dislocations and slow proliferation, it has the following disadvantages: (1) The crystal grains grow rapidly in the form of dendrites, and different dendrites are easy to squeeze each other, resulting in stress and defects; (2) The grown grains are relatively large, and once there are dislocations inside the large grains, it is easy to expand inside the entire large grains and occupy the entire grain; (3) The growth of dendrites exothermic, relatively The heat released by large grains during the growth process is likely to affect the supercooling required for the growth of other grains around them, making it difficult for other grains to grow, so this method is not suitable for large-scale industrial

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