Polysilicon directional freezing equipment

Abstract

The invention discloses a directional freezing device for polysilicon, which belongs to the technical field of purifying the polysilicon through physical metallurgy techniques, and particularly relates to a polysilicon smelting device that uses a directional freezing method. An inner chamber of a shell of the directional freezing device for polysilicon is a vacuum chamber, and a closed heat preserving region inside the vacuum chamber is composed of an upper heat resisting and insulating fiber sleeve, a lateral quadrate heat resisting and insulating fiber sleeve and a lower heat resisting and insulating fiber sleeve; the middle part of the lower heat resisting and insulating fiber sleeve is opened with a tapered orifice, and a heat resisting and radiating fiber screen that is fixedly connected with a pull rod is inserted into the tapered orifice; the directional freezing device for polysilicon has a supporting platform which consists of a frame-shaped bracket, and a left slide pull rodand a right slide pull rod that are arranged on the frame-shaped bracket; the shell of the directional freezing device for polysilicon is fixed on the frame-shaped bracket. The directional freezing device for polysilicon effectively controls the radiating methods of the liquid polysilicon, ensures the temperature gradient to be kept in a same direction consistently, leads the liquid polysilicon toradiate in a single direction along the bottom, and finishes the directional freezing of the polysilicon. The directional freezing device for polysilicon has the advantages of low energy consumptionand little environmental pollution.

Description

technical field [0001] The invention belongs to the technical field of purifying polysilicon by physical metallurgy technology, in particular to a device for smelting polysilicon by directional solidification. Background technique [0002] High-purity polysilicon is the main raw material for solar cells. The preparation of high-purity polysilicon abroad mainly uses the Siemens method, specifically the silane decomposition method and the gas-phase hydrogen reduction method of chlorosilane, in which SiHCl 3 The Siemens method is currently the mainstream technology for polysilicon preparation. SiHCl 3 The useful deposition ratio of the method is 1×10 3 , is SiH 4 100 times. The deposition rate of the Siemens method can reach 8-10 μm / min. The conversion efficiency of one pass is 5% to 20%, and the deposition temperature is 1100°C, second only to SiCl 4 (1200°C), the power consumption is about 120kWh / kg, and the power consumption is also relatively high. Domestic SiHCl 3...

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Problems solved by technology

The disadvantage of the Siemens method is that it adopts backward thermal chemical vapor deposition on the core side section of the process. There are too many side sections in the process and the conversion rate at one time is low, which leads to too long process time and increases material consumption and energy consumption. cost

Domestic directional solidification equipment generally pulls the crucible into the high temperature range of the heating element by pulling the ingot, which cannot guarantee that the temperature gradient will always maintain one direction

The German ALD polysilicon directional solidification equipment has two parts, the upper heating body and the side heating body, which constitute the heating area. The bottom is heated by heat transfer and the heat diffusion takes a long time. During the solidification process, the heat dissipation of the lower part cannot be controlled, and the constant solidification cannot be guaranteed. temperature difference

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