Polycrystalline silicon ingot preparation technology

Abstract

The invention discloses a polycrystalline silicon ingot preparation technology. The polycrystalline silicon ingot preparation technology comprises the steps as follows: step 1, in a thermal insulationcage provided with a bottom plate, a crucible containing a silicon material is heated by a top heater and side heaters, so that the silicon material in the crucible is melted to form silicon melt; step 2, the bottom plate of the thermal insulation cage is opened, and the silicon melt comes out polycrystalline silicon crystals from bottom to top to form a polycrystalline silicone ingot; step 3, the power of the side heaters and the top heater is reduced quickly to cool the middle and the top of the polycrystalline silicone ingot; step 4, when the difference between the top temperature of the polycrystalline silicone ingot and the bottom temperature of the polycrystalline silicone ingot is smaller than or equal to 50 DEG C, the top heater and the side heaters are turned off, the bottom plate of the thermal insulation cage is closed, and then, the polycrystalline silicone ingot is cooled to the room temperature in the thermal insulation cage. The polycrystalline silicon ingot preparationtechnology can suppress dislocation multiplication by reducing thermal stress produced by thermal shock during annealing.

Description

technical field [0001] The invention relates to a process for preparing polycrystalline silicon ingots. Background technique [0002] During the manufacturing process of polycrystalline silicon ingots, because the ingots require relatively high temperatures, the polycrystalline silicon ingots that have just grown crystals need to be annealed and cooled. In the prior art, after the polysilicon ingot is cast, annealing and cooling are carried out according to the conventional cooling process, that is, by closing the bottom plate of the heat insulation cage, the heat insulation cage becomes a closed space, and at this time the opening of the heat insulation cage is reduced to 0 (i.e. The distance between the heat cage and the bottom plate is 0), to achieve the purpose of quickly closing the heat insulation cage and annealing. Generally speaking, at the end of crystal growth, there is a temperature difference between the top and bottom of the polysilicon ingot, the top is usual...

AI Technical Summary

Problems solved by technology

[0003] Moreover, during annealing, since the oxygen concentration inside the crucible body is much higher than that inside the polysilicon ingot, there is solid-phase diffusion of oxygen donors between the crucible and the polysilicon ingot (diffusion of oxygen from high concentration to low concentration under molecular thermal motion), Therefore, if the temperature of the bottom of the polysilicon ingot rises, the oxygen impurities in the bottom crucible will intensify the solid-phase diffusion to the middle, and the oxygen content at the bottom of the polysilicon ingot will increase, and oxygen will form thermal donors, new donors, oxygen precipitation and induce other crystals Defects will also attract metal elements such as iron, resulting in electrical activity, which will significantly reduce the minority carrier lifetime value of the polycrystalline silicon ingot, and will eventually increase the length of the poor lifetime region at the bottom; and the higher the temperature, the more serious the solid phase diffusion, and the lifetime of the bottom. The longer the length of the bad area, the poorer the quality of the polysilicon ingot

[0004] In general, in the existing process, after the polycrystalline silicon ingot is grown, the bottom plate of the thermal insulation cage is closed for heating and annealing. The top of the polycrystalline silicon ingot is less cooled, and the thermal shock is small; Thermal shock, which will generate dislocation propagation

Moreover, during annealing, the oxygen at the bottom diffuses to the solid phase in the middle under high temperature, which will increase the length of the poor life area at the bottom; the higher the temperature, the more serious the solid phase diffusion, and the longer the poor life area at the bottom of the silicon ingot. The worse the quality of the ingot

Images