Washing method of high-calcium phosphorous-removed silicon

Abstract

The invention discloses a washing method of high-calcium phosphorous-removed silicon. According to the invention, high-calcium metal silicon is crushed into particles; the particles are subject to grinding and sieving, such that powder is obtained; the powder is sampled, and the calcium content is determined; the powder is soaked by using a hydrochloric acid solution; the mixture is stirred, and is subject to solid-liquid separation; the mixture is washed by using deionized water, such that primary mixed powder is obtained; the primary mixed powder is soaked by using an alkali solution; the mixture is stirred, and is subject to solid-liquid separation; the mixture is washed by using deionized water, such that secondary mixed powder is obtained; the secondary mixed powder is soaked by using a mixed acid solution of sulfuric acid and hydrofluoric acid; the mixture is stirred, and is subject to solid-liquid separation; the mixture is washed by using deionized water, such that tertiary mixed powder is obtained; the tertiary mixed powder is soaked by using a mixed acid solution of hydrochloric acid and hydrofluoric acid; the mixture is stirred, and is subject to solid-liquid separation; the mixture is washed by using deionized water, such that quaternary mixed powder is obtained; the quaternary mixed powder is subject to vacuum drying, such that low-phosphorous silicon powder is obtained. With the washing method provided by the invention, on a basis that impurities such as calcium and phosphorous are effectively removed, the generations of flammable and combustible gases are reduced, such that production can be safely preceded.

Description

technical field [0001] The invention relates to the field of polysilicon purification, in particular to a method for cleaning silicon with high calcium and phosphorus removal. Background technique [0002] At present, the requirements for the impurity content of the solar-grade silicon raw materials used in international monocrystalline manufacturing or polycrystalline foundries are as follows according to the application: [0003] use Boron (ppm) Phosphorus (ppm) TMI (ppm) Czochralski / Zone Fusion Single Crystal ≤0.06 ≤0.01 ≤0.01 Polycrystalline ingot ≤0.16 ≤0.01 ≤0.01 [0004] Note: TMI is the total metal content [0005] It can be seen from the above table that phosphorus and boron elements are of great significance to solar grade silicon. When manufacturing high-purity silicon by the Siemens method or the modified Siemens method, the removal of phosphorus and boron is very thorough, so the Siemens method or the modified Siemens method ...

AI Technical Summary

Problems solved by technology

Studies have shown that the more calcium is added, the higher the calcium content of the solidified metal silicon, the more obvious the effect of phosphorus extraction, but the silicon with high calcium content is very dangerous. This kind of high calcium metal silicon often has A large amount of silane and hydrogen are produced, and silane will spontaneously ignite when it encounters oxygen at room temperature, and a large amount of silane and hydrogen will explode immediately. Therefore, a suitable cleaning process is necessary

[0007] A method disclosed in U.S. Patent No. 4,539,194, the calcium content in the silicon is 10,000 to 100,000 ppmw, and it is cleaned in two steps, first using FeCl 3 and HCl aqueous solution for leaching, and then HF and HNO 3 Cleaning with aqueous solution, this method fails to control the production of silane and hydrogen well, and it is easy to cause spontaneous combustion and explosion

[0008] Chin