Vacuum pressure continuous control process for polysilicon ingot casting process and control system thereof

Abstract

The invention discloses a vacuum pressure continuous control method used for a polysilicon ingot casting process. A vacuum mode is adopted in furnace heating step; then the melting, growing, annealing and cooling steps are carried out; the gas voltage regulation mode is adopted; under the voltage regulation mode, two modes of gas inlet regulation and gas outlet regulation are adopted to regulate the furnace pressure. At the same time, the invention also discloses a control system for realizing the control method. The method can be used for the polysilicon ingot casting production, can steadily control the vacuum furnace pressure, can guarantee stable gas inlet and gas outlet at the same time, can save the input gas consumption, and is simple and practical and has ideal control effect.

Description

technical field [0001] The invention relates to a continuous control of vacuum pressure and gas flow of an industrial furnace, and further refers to a continuous vacuum pressure control method and a control system of a polysilicon ingot casting process. Background technique [0002] At present, the production process for preparing silicon ingots for solar cells mainly includes single crystal silicon drawing and polycrystalline silicon ingot casting. Polycrystalline silicon ingot casting technology has become the mainstream method for preparing silicon ingots for solar cells because it can directly melt and cast large-size square silicon ingots suitable for large-scale production, the manufacturing process is relatively simple, and the production cost is greatly reduced. [0003] The process of preparing silicon ingots for solar cells includes five processes: heating of silicon materials, melting of silicon materials, crystal growth, annealing of silicon ingots, and cooling o...

AI Technical Summary

Problems solved by technology

[0014] The first method above: simple, but the vacuum pressure can only be controlled regionally, the fluctuation is large, and the vacuum pressure cannot be continuously adjusted

[0015] The second method above: can continuously adjust the vacuum pressure, but because the butterfly valve is driven by a motor, the reliability is too poor, the fault is too high, and the pressure fluctuates greatly, so it is not suitable for long-term operation

[0016] The third method above: it is widely used and can continuously adjust the vacuum pressure, but the vacuum pressure is prone to overshoot, the adjustment stabilization time is long, the intake flow is difficult to control and the consumption is large, and the operating cost is high

When the pressure setting value has a step change, if the conventional "exhaust pressure regulation" mode is used, if the measured value of vacuum pressure is lower than the set value, the "exhaust regulating valve" will be closed, that is, the vacuum "exhaust gas" will be closed. Exhaust port", the gas residence time in the furnace is too long and the impurities in the furnace will react with polysilicon quickly, affecting the performance of polysilicon

[0017] Also in the "silicon material cooling" cooling stage, since the cooling time is about 11 hours, "exhaust adjustment" is adopted to fix the intake air, which is difficult to ensure stable and smooth exhaust gas discharge, and consumes a lot of process gas

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