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Method for producing high purity silicon

A high-purity, molten silicon technology, applied in chemical instruments and methods, silicon compounds, inorganic chemistry, etc., can solve problems such as reducing the percent yield of silicon, and achieve the effect of low cost and high quality

Inactive Publication Date: 2008-03-05
NIPPON STEEL MATERIALS CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In addition, due to the strong oxidizing power of all these techniques, they may over-oxidize silicon when oxidizing boron, which will significantly reduce the percent yield of silicon

Method used

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  • Method for producing high purity silicon
  • Method for producing high purity silicon
  • Method for producing high purity silicon

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0052] Silicon purification is performed using a purification furnace as shown in FIG. 1 . 50 kg of metallic silicon particles, which have a boron concentration of 12 mass ppm and an average particle diameter of 5 mm, were added to a graphite crucible with a diameter of 500 mm and placed in a purification furnace. The crucible is heated to 1500°C in an argon atmosphere, maintaining the state of molten silicon. In the second heating furnace, add 20kg high-purity quartz sand and 5kg powdered sodium carbonate (Na 2 CO 3 ) mixture, wherein the boron concentration of quartz sand is 1.5 mass ppm, and the average particle size is 10mm, the boron concentration of sodium carbonate is 0.3 mass ppm, the mixture is heated to 1600 ° C and kept warm to form slag. Then, 15 kg of pulverized sodium carbonate (Na 2 CO 3 ), which has a boron concentration of 0.3 mass ppm, the slag prepared in the second heating furnace is transferred to the purification furnace together with the crucible, an...

Embodiment 2

[0054] In this example, sodium hydroxide was used as the oxidizing agent. All other materials and methods were the same as in Example 1. The boron concentration in the finally obtained sample was 0.08 mass ppm, which satisfies the boron concentration requirement of silicon used for solar cells.

Embodiment 3

[0056] In this example, using MgCO 3 as an oxidizing agent. All other materials and methods were the same as in Example 1. The boron concentration in the finally obtained sample was 0.2 mass ppm, which satisfies the boron concentration requirement of silicon used for solar cells.

[0057] Additional Numeral Symbol Table

[0058] 1: Purification furnace

[0059] 2: Crucible

[0060] 3: Heater

[0061] 4: Molten Silicon

[0062] 5: Oxidizing agent

[0063] 6: Slag

[0064] 7: Oxidant feed pipe

[0065] 8: Slag feed pipe

[0066] 9: Waste receiver

[0067] 10: Air intake line

[0068] 11: exhaust line

[0069] 12: Crucible tilting device

[0070] 13: Raw material of slag

[0071] 14: Slag formed on molten silicon

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Abstract

An object of the present invention is to provide a method for producing a great deal of inexpensive high purity silicon useful in a solar battery. Disclosed is a method for producing the high purity silicon by migrating impurities in molten silicon to slag including the step of feeding an oxidizing agent to the molten silicon together with slag, wherein the oxidizing agent is a material comprising as a primary component at least one of the following materials: alkali metal carbonate, hydrate of alkali metal carbonate, alkali metal hydroxide, alkaline-earth metal carbonate, hydrate of alkaline-earth metal carbonate or alkaline-earth metal hydroxide.

Description

[0001] This application claims the benefit of Japanese Patent Application No. 2005-062556 filed in Japan on March 7, 2005 and Japanese Patent Application No. 2006-034342 filed in Japan on February 10, 2006, which are incorporated by reference The entire content of is added to this article. technical field [0002] The invention relates to a method for preparing high-purity silicon. The high-purity silicon is used in solar cells. Background technique [0003] For silicon used in solar cells, its purity must be 99.9999% by mass or higher, and the content of each metal impurity in silicon is required to be not more than 0.1 ppm by mass. In particular, the content of impurity boron (B) is required to be not more than 0.3 mass ppm. Although silicon for semiconductors prepared by the Siemens method can meet the above requirements, it is not suitable for use in solar cells. This is due to the high production cost of silicon prepared by the Siemens method, which requires the sola...

Claims

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Application Information

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IPC IPC(8): C01B33/027
Inventor 伊藤信明近藤次郎冈泽健介冈岛正树
Owner NIPPON STEEL MATERIALS CO LTD