Tungsten Hexafluoride Simple Purification Method

The tungsten hexafluoride gas used in the microelectronic industry VLSI requires high purity, generally not less than 99.999%. The purity of industrial synthesis of tungsten hexafluoride is relatively low, does not meet the needs of electronic products, therefore, the industrial synthesis of primary tungsten hexafluoride must be purified.

On the purification process of tungsten hexafluoride, many scholars at home and abroad have also proposed a lot of programs. Recently, Xiamen Tungsten Industry Chen et al, also proposed a simple process to purify tungsten hexafluoride and applied for a patent. The patent contains the following steps:

1) First de-hydrogen fluoride column, distillation, distillation column, the former collection tank, finished product collection tank and its connected pipe degreasing, drying and connected after cleaning, and then nitrogen tank pressurized with nitrogen to 0.6MPa, for the purification system, the pressure is 0.6MPa, and the pressure drop of the purification system is less than 0.01MPa. After being qualified, the pressure is released to 1atm, then the water ring vacuum pump is opened to vacuum.

2) Purge the column with hydrogen fluoride to 1atm, the tungsten hexachloride through the filling port into the addition of hydrogen fluoride column, fill the sealed filling port, and then through the first heating tile heated raw material tank of high purity tungsten hexafluoride by pipe directly into the finished product collection tank to replace the finished product collection tank residual gas and tank wall attached to the reaction of water vapor generated hydrogen fluoride, replacement after the product collection tank of impure hexafluoride upside down to the distillation pot for low temperature curing, replacement 3 times;

3) Rectification of the cooling water through the jacket of the autoclave was cooled, the cooling temperature of -30 ~ -20 ℃, the primary tungsten hexafluoride after the first heating watt heating a raw material tank after addition of hydrogen fluoride to the distillation column into autoclave curing at low temperature, the temperature of the de-hydrogen fluoride tower is controlled by the second heating tile to be 40-80 °C., the infiltrated primary tungsten hexafluoride is weighed through the weight loss of the scale, a purifying cycle through the amount of material is 500 ~ 600kg, after the end of the material to continue curing 1 ~ 2h, and then use the water ring vacuum distillation tower vacuum distillation 30 ~ 60min, tail gas to the basic spray tower absorption, and then to the distillation flask jacket through 25 ~ 30 ℃ hot water thawed.

4)Into the normal distillation, to the distillation flask jacket through 25 ~ 30 ℃ hot water, to the distillation tower overhead jacket through 6 ~ 12 ℃ cooling water, the evaporated tungsten hexafluoride gas is gradually condensed and refluxed in the rectification column to further remove nitrogen, oxygen, carbon monoxide, carbon dioxide, carbon tetrafluoride, sulfur hexafluoride, silicon tetrafluoride impurity gas and metal impurities, after the initial distillation of tungsten hexafluoride gas through the mass flow meter into the front collection tank for collection.

The research shows that the purity of the tungsten hexafluoride gas purified by the method reaches above 99.999%, and the equipment is simple, the controllable parameters are less, the recovery rate is high, the cost is low, and the raw material is suitable for a wide range of applications.

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