Method for purifying tungsten hexafluoride

Abstract

The invention relates to a kind of purification method of tungsten hexafluoride gas. First, put impure tungsten hexafluoride gas in the storage tank of crude product into the bottom of absorption column where there are multihole spherical filling of sodium fluoride or potassium fluoride, remove the most impurity of hydrogen fluoride under temperature of 10-80 degree C,put it into rectifying column through pipe and fluidify it, stop entering tungsten hexafluoride gas after fluidifing it for 5kg-50kg, put helium gas of high purity into bottom of tungsten hexafluoride liquid and keep it boiling under temperature between 3 degree C and 20 degree C,the vaporized gas enter rectification column and rises, it gradually gets into condensation and circumfluence during the process of rising ,continues to rectify it to remove impurity, check it with gas chromatography, when concentration of impurity of gas discharged from tower top whose boiling point is higher than that of tungsten hexafluoride gas reduce to the request index, stop entering helium gas of high purity, and when helium gas's index reaches the request, collect tungsten hexafluoride gas of high purity into storage tank of quality product.

Description

technical field [0001] The invention relates to a method for purifying tungsten hexafluoride gas. Background technique [0002] In tungsten fluoride, WF 6 It is the only variety that is stable and industrially produced. Its main use is as a raw material for metal tungsten chemical vapor deposition (CVD) process in the electronics industry, especially WSi made of it 2 Can be used as wiring material in large scale integration (LSI). The composite coating of tungsten and rhenium is prepared by mixed metal CVD process, which can be used in the manufacture of X-ray emitting electrodes and solar absorbers. In addition, WF6 is also mainly used as a raw material for semiconductor electrodes and conductive pastes in the electronics industry. WF 6 There are also many non-electronic applications. For example, tungsten can generate hard tungsten carbide on the surface of steel by CVD technology, which can be used to improve the surface properties of steel. It can also be used to m...

AI Technical Summary

Problems solved by technology

[0006] Since both tungsten powder and nitrogen trifluoride contain impurities, the tungsten hexafluoride produced by the above reaction usually contains some impurities, mainly including nitrogen, oxygen, carbon monoxide, carbon dioxide, nitrogen trifluoride, carbon tetrafluoride, hexafluoride Volatile impurities such as sulfur and hydrogen fluoride and non-volatile impurities such as metal fluoride, the existence of these impurities will seriously affect the performance of tungsten hexafluoride in VLSI, so it must be removed

For reaction (1), nitrogen trifluoride neutralizes the presence of trace moisture on the inner wall of the system, resulting in a certain amount of hydrogen fluoride in the crude product of tungsten hexafluoride, and the boiling point of hydrogen fluoride (19 ° C) is very close to that of tungsten hexafluoride, and then Coupled with their strong corrosiveness, it is difficult to separate them by conventional methods

The melting and boiling points of other impurities are quite different from those of tungsten hexafluoride. The solubility and vapor pressure in liquid and solid tungsten hexafluoride are different. Most of them can be removed by crystallization and evaporation, but it is time-consuming and difficult. Obtain high purity products

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