Study On Detection Methods Of Gas Impurities And Metal Impurities In SiF 4 Gas

Highly purified silicon tetra-fluoride?SiF₄? gas, is an important raw material for the preparation of high purity silane, crystalline silicon, and fiber and so on. SiF₄ gas is an important natural source for fluorine and an important by-product from fluorite and phosphate rocks, which are abundant resouces in China. SiF₄ gas as an accompanying of the product, it 's an important fluorine resource. A high purity of at least 99.99% is required for production of high performance amorphous silicon,mono-crystaline silicon, poly-crystalline silicon and optical fiber. The production technology of highly purity SiF₄ gas is well developed in a few developed countries,such as the United States, Japan, Russia, etc. The study of inductrial prepration process of process of high purity SiF₄ gas in China has just started. Some companies even higher than that of foreign standard,however the detection method of SiF₄ gas has been less reported in China.In this paper,fluorosilicic acid solution and concentrated sulfuric acid were used as raw materials to produce SiF₄. GC, FAB and FIRS were involved to analyze impurity of SiF₄.Standard SiF₄ gas with different impurities?H₂,O₂,N₂,CH4,CO,PH₃,CO₂? added,which concentration of 5 ppm and 10 ppm, was analyzed by GC to establish the characterization protocol. The detection test results showed that, GC column will adsorb small amount of oxygen,uncertainty of all other standard impurities is around 10%. Analyzing CO₂, the detection error is small, and relatively stable. Using Standard gas as reference standard establish the detection method,measure sample gas, the purity range between 99.9% and 99.99%. Most impurities components are no non-condensable gas, every component about 100 ppm, but excluding CH4. For high purity SiF₄ contains only H₂ and N₂ gas, there may be a small amount of oxygen, adsorb by chromatographic column. Secondly, using high pure water as the absorbent to absorb SiF₄ gas, eliminate absorbing liquid, and use flame atomic absorption spectroscopy to detect it. Experimental process, preparing metals standard solution of Mg, Ca, Fe, Zn, Cu, Pb,Cd, concentration range in 0.1 ¹0 ppm, detecting standard curve, and establishing the measuring method.Configuration standard curve measured by standard solution, the correlation coefficient is above 99.99%, except zinc element, the correlation coefficient is above99.9%, accuracy is better. Detecting Mg, Ca, Fe, Zn, Cu, Pb, Cd in the samples,absorbing liquid of SiF₄ gas, determination more times in parallel,measurements of the relative standard deviation has a certain range, but are less than10%, show that the measured precision metal impurity content is feasible. Standard addition recovery experiments found that the metal content of sample recovery is between 98.0% 103%, the accuracy is better. Using the method of Fourier infrared spectrum to detect HF, found that only 10 meters optical path sample pool can detect it, the peak position of HF are 3920cm-1, 4039cm-1, 4001cm-1, 4110cm-1, 4075cm-1.