Method for removing carbon tetrafluoride foreign matter in nitrogen trifluoride gas

Abstract

The invention relates to a method to remove the carbon tetrafluoride in trifluorinated carbon. The invention uses azeotropic rectify to purify the NF3. it inlets the original gas and the entrainer into the rectify tower and go on the gas-liquid contacting continuously, the impurity forms the azeotropic thing with the much different gas steam point which is evaporated from the tower top and go into the second rectify tower to receive the entrainer; the entrainer and the NF3 are collected from the tower bottom and go into the third rectify tower; by using the boil difference if the NF3 and the entrainer, the high purify NF3 is get from the tower top, the entrainer is received from the tower bottom. The invention callbacks the entrainer by setting two towers and save the entrainer. The invention has decreased the CF4 content to 20ppm and decreased the condenser using mass. Also the device is simple and it costs low, has high efficiency.

Description

technical field [0001] The present invention relates to a kind of adopting azeotropic rectification to purify NF 3 gas method, which is suitable for industrial NF 3 Purification of gases, especially for CF contained therein 4 Impurities. Background technique [0002] NF 3 It is a new type of electronic gas that has just been developed in recent years, and it is an excellent plasma etching and cleaning gas in the information industry. NF 3 When the gas is used for dry etching, it can improve the automation level in wafer manufacturing, reduce labor intensity, and increase the safety factor; it has the advantages of high etching rate, high selectivity, and small residual pollutants. For semiconductor materials such as silicon, especially VLSI materials with a line width of less than 100nm, NF 3 Compared with other gases, it has better etching speed and selectivity; when it is used as a gas cleaning agent, it has fast cleaning speed, high efficiency, thorough cleaning an...

AI Technical Summary

Problems solved by technology

[0007] There are many ways to purify NF3 gas. Using the differences in the physical and chemical properties of impurities contained in the product gas, some acidic gas impurities can be directly absorbed by lye; as for the CF4 gas impurities, it has been reported that activated alumina, molecular sieves, silica gel , activated carbon and other adsorbent adsorption removal methods, but in practical applications, the adsorbent must be replaced frequently, and NF3 will also be lost while CF4 is adsorbed, resulting in a decrease in yield

If the method of gas-solid chromatographic separation is adopted, although 99.99% grade NF3 product gas can be obtained, it has the disadvantages of low efficiency, high inert gas consumption, and difficulty in industrial implementation

If the conventional cryogenic distillation method is used, it needs to consume a large amount of condensing agent to convert the CF 4 The content dropped from 500ppm to more than 100ppm, and the cost of the distillation column was also high

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