Crucible with impurity-discharge function and applied in polysilicon purification or ingot casting link, and polysilicon purification or ingot casting method

Abstract

The invention relates to a crucible with an impurity-discharge function, which is applied in a polysilicon purification or ingot casting link. The crucible comprises a columnar crucible body. Overflow holes are arranged on a side wall of the crucible body. A collection tank is arranged on the outer side of the crucible body and below the overflow holes. The height H from the bottom edges of the overflow holes to the inner bottom side of the crucible body equals H liquid+(H solid-H liquid)20%, wherein H liquid is the liquid level of liquid-state polysilicon in the crucible body, and H solid is the height of crystallized polysilicon in the crucible body. The method has the following steps: a polysilicon material is added into the crucible body; the crucible body is mounted in a furnace, and vacuum pre-pumping is carried out; first-stage heating is carried out, and polysilicon is completely molten; crystal growth is carried out; annealing is carried out, such that internal stress in the crystals is eliminated; cooling is carried out, wherein the polysilicon ingot is cooled to a temperature of 400 DEG C with the furnace; the ingot is fetched from the furnace and is cooled to room temperature; the silicon ingot is fetched; and overflown silicon material is collected. During an operation process, a top-layer impurity-rich zone is removed under a liquid state, such that impurity-rich zone reverse osmosis after the silicon ingot is formed is reduced, and silicon ingot overall utilization rate is improved.

Description

technical field [0001] The invention relates to a crucible used in polycrystalline silicon purification or ingot casting and a method for purifying polycrystalline silicon or ingot casting using the crucible. Background technique [0002] At present, the devices used in polysilicon ingot casting include crucibles. Most of the crucibles are in the shape of a cuboid, that is, a box surrounded by four sides and a bottom surface. On the graphite base, a program-controlled heating element is arranged around the crucible in the furnace body. The polysilicon material turns into a liquid when heated, and then crystallizes to form an ingot. When polysilicon is in a liquid state, the top silicon material is an impurity-intensive area. After the silicon ingot is solidified and formed, the impurities will diffuse from the top high-concentration area to the bottom concentration area, thereby affecting the utilization rate of the silicon ingot. The usual method is to use a professional ...

AI Technical Summary

Problems solved by technology

When polysilicon is in a liquid state, the top silicon material is an impurity-intensive area. After the silicon ingot is solidified and formed, the impurities will diffuse from the top high-concentration area to the bottom concentration area, thereby affecting the utilization rate of the silicon ingot.

The usual method is to use a professional cutting machine to cut off the high impurity area on the top after the silicon ingot is formed. It also increases, and the utilization rate decreases accordingly; 2. Professional equipment is required to remove the high-concentration area of ​​top impurities, which increases production and operation costs; 3. At this stage, there are also methods to remove liquid top impurities, but the large amount of equipment transformation is not easy to achieve

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