Method for removing phosphorus impurities in silicon by vacuum induction melting

A technology of vacuum induction smelting and impurity, applied in the field of silicon purification, to achieve the effect of simple and easy process, considerable market prospect and convenient operation

Inactive Publication Date: 2010-01-20
XIAMEN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

The optimal design of these process parameters has not yet been reported in the literature

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0035] Use a graphite crucible with a height-to-diameter ratio of 0.5, put 50kg of polysilicon (block or powder) into the graphite crucible, close the vacuum chamber, and turn on the mechanical rotary vane pump for vacuuming. When the vacuum in the vacuum chamber reaches below 15Pa , turn on the power of the oil diffusion pump for preheating. The preheating time is about 40 minutes. After the preheating is completed, close the rough pumping valve, open the diffusion pump valve to draw a high vacuum, and at the same time turn on the intermediate frequency induction heating power supply, and the induction coil is connected with alternating current with a power of 20kW. The graphite crucible starts to generate heat by induction, and the silicon raw material in the crucible is heated Low temperature preheating, when the vacuum reaches 4.0×10 -3 When Pa is below, gradually increase the intermediate frequency heating power to 100kW, and when the temperature reaches above 1415°C, si...

Embodiment 2

[0037] Technological process is with embodiment 1. A graphite crucible with a height-to-diameter ratio of 0.7 is used, and the low-temperature preheating power of 100kg polysilicon (block or powder) is 50kW. When the vacuum degree reaches 4.0×10 -3 When Pa is below, gradually increase the intermediate frequency heating power to 150kW, and when the temperature reaches above 1415°C, silicon begins to melt. After the silicon is completely melted, adjust the intermediate frequency heating power to control the temperature of the silicon liquid at 1750°C. After the temperature stabilizes, control the vacuum at 6.7×10 -2 Pa, start timing, and the holding time is 60min. Then pour the smelted silicon liquid into a mold for rapid solidification, and the P content of the polysilicon is 0.1 ppmw as measured by a plasma inductively coupled mass spectrometer (ICP-MS).

Embodiment 3

[0039] Technological process is with embodiment 1. A graphite crucible with a height-to-diameter ratio of 1 is used, and the low-temperature preheating power of 100kg polysilicon (block or powder) is 30kW. When the vacuum degree reaches 4.0×10 -3 When Pa is below, gradually increase the intermediate frequency heating power to 150kW, and when the temperature reaches above 1415°C, silicon begins to melt. After the silicon is completely melted, adjust the intermediate frequency heating power to control the temperature of the silicon liquid at 1850°C. After the temperature stabilizes, control the vacuum at 1.0×10 -1 Pa, start timing, and the holding time is 45min. Then the smelted silicon liquid was poured into the mold for rapid solidification, and the P content of the polysilicon was measured as 0.37ppmw by a plasma inductively coupled mass spectrometer (ICP-MS).

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Abstract

The invention relates to a silicon-extracting method, in particular provides a method for removing phosphorus impurities in silicon by vacuum induction melting. The silicon-extracting method comprises the following steps: putting polysilicon into a crucible; vacuumizing and preheating the crucible; closing a roughing valve; starting a diffuser pump valve to be vacuumized; switching on a mid-frequency induction heating power supply so that crucible heat is heated by induction; preheating silicon raw materials in the crucible at a low temperature so that silicon is self heated by induction when the temperature rises to 600 DEG C; increasing mid-frequency heating power to 50-200kW so that the silicon starts to melt when the temperature reaches over 1415 DEG C; adjusting the mid-frequency heating power after the silicon is melted so that the temperature of silicon liquid is controlled at 1550-1850 DEG C; controlling a vacuum degree to 1.2*10<-2>-1.0*10<-1> Pa after the temperature is stabilized; starting timing while holding time is 45-120 min; adding circulating water in a water-cooled copper tray; and pouring the melt silicon liquid in a die to rapidly solidify.

Description

technical field [0001] The invention relates to a method for purifying silicon, in particular to a method for removing phosphorus impurities in silicon by vacuum induction melting. Background technique [0002] The so-called "purification" refers to removing the impurity elements in the matrix by appropriate physical or chemical methods according to the physical and chemical properties of the matrix elements or impurity elements. [0003] Industrial silicon (MG-Si) with a purity of 98.5% to 99.5% is mainly obtained by reducing quartz with carbon. To make electronic grade silicon (11N), the impurity content must be reduced by 9 orders of magnitude on the basis of industrial silicon. To meet this requirement, only the chemical method is easier to achieve. At present, the most mature and large-scale production process is the Siemens method or the improved Siemens method. This type of process first reduces silica through C to obtain industrial silicon with a purity of at leas...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01B33/037
Inventor 罗学涛郑淞生蔡靖陈文辉李锦堂陈朝
Owner XIAMEN UNIV
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